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I Like Foreign Tv
Personal Stories, Advice, and Support 3 People
With Shows Like This Who Wouldn't???Bounce Bounce Bounce Bounce Bounce Bounce Bounce http://www.liveleak.com/view?i=2db_1226039141
0 Jan 19, 2013
I enjoy watching foreign TVHello everyone, I am in Georgia, USA but I enjoy watching TV online from foreign countries. Some of my favorite channels are. ACC religion - Austraila. Silt & light - Canada Anime - Japan Peace TV religion - India Good TV - Taiwan And where I am learning Mandarin Chinese I like...
Haoran 31-35, M 0 Dec 20, 2010


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If you have never fucked a black tranny before you are missing out. I don't know if these sluts attend tranny-school or something but they know how to fuck like professionals. I mean, this tranny not only has an awesome face, tits, and cock she also has the right attitude. The type of style that can challenge even straight men. Watch her jerk off and play. She knows you are watching and wants to show you what she can do. Trannies this hot should be illegal. They've been known to end marriages.
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|12 Sep 2011
No pop-up when clicking system tray network icon?
Hi guys,
Here's a goofy problem that's eventually happened to me on every Windows 7 install I've done. Has it happened to you?:
You want to connect to a wireless network, so you click the "network" icon in the system tray. But nothing happens; the usual network list doesn't appear. To see the menu, you have to open the Network and Sharing Center and click "Connect to a network". You must now do this each timeto connect or disconnect.
I realize this is more like basic Windows functionality than actual network stuffbut any idea what causes it, and how to fix it? Thanks, Ander
|My System Specs
|12 Aug 2014
No one could answer this? The same thing has happened to me, with every Windows 7 install I've done. No fix available?
|My System Specs
|Thread Tools
|Similar help and support threads
Network icon missing from system tray
Sometimes when i reboot my PC the Network system tray icon would go missing, checking the notifications at control panel shows that network icon is unselectable and is at off, rebooting several times fixes the problem though, anyone know whats causing this ?
|Network & Sharing
Wireless network - System Tray icon wrong
Hi, I have a Netgear WN111 USB wireless adaptor on my PC (802.11n NIC). It works fine with my WiFi network, but it always displays the wrong icon in the System Tray when connected. It shows the signal bars greyed out, with a yellow star on top. I have tried a Windows update on the...
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Yellow triangle over system tray network icon
Hi all, Just a minor issue. When I boot up (or restart) my PC, all my system icons appear as they should, but a yellow triangle appears over the network icon (it is a wired connection). It goes away after a few seconds and internet access is normal. It never used to do this until a few days...
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I currently have the "window screen with the power plug." I would like to change it to the Wi-fi icon (the three bars). Is there a way?
Wrong Network Icon in system tray
hi, i am connect to internet by LAN network correctly but the network icon show disconnect! click image to large. http://up98.org/upload/server1/01/s/gojk9ii47ttik854kev.jpg i try dial-up and wireless internet connection, and have same problem with them. please help me... thanks.
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Question on network icon in system tray
Hi everyone, I'm running Windows 7 Home Premium (with Service Pack 1 installed) on a standalone laptop at home with access to the internet via a cable modem. Very occasionally after booting up, the "blue circle" sign, indicating "busy", does not clear from the network icon in the system tray,...
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Limit of Love: Umizaru Trailer (2006)
"Limit of Love" 06 May 2006 Drama, Action 117 mins
A small team of Coast Guard divers, including Daisuke, rappels onto the ship from a helicopter and begins to evacuate the panicked passengers. Then Daisuke finds a familiar face - Kanna. They had a tiff the night before about their wedding plans - Kanna had already made her dress, while Daisuke was still reluctant to propose - and she left for Tokyo, feeling like a fool. Now she see Daisuke in a different, more heroic light - but before they can properly reconcile, she has to evacuate, while Daisuke searches for stray passengers.
Watch the official Limit of Love: Umizaru 2006 trailer in HD below or find more Limit of Love: Umizaru videos on Vidimovie.


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West Hempstead NY Weight Loss
The popular W8MD Medical Weight Loss Centers of America's insurance physician weight loss program in West Hempstead (Long Island) New York at Dr. M. A. Rahman's office.
Call us for more information on the
weight loss program in West Hempstead NY
151 Hempstead Turnpike, West Hempstead, New York 11552
(516) 483-1100
- Physician supervised
- Accept most insurances
- Meal replacements
- Fast weight loss*
- $50.00 biweekly with insurance*
- Sleep disorder management
- Appetite suppressants
- Limited acceptance
- Primary Care Services
W8MD's West Hempstead Physician Weight Loss Program*
Our evidence based physician supervised insurance medical weight loss program is unique in many ways.
- Accept most insurances - unlike the many cash only weight loss programs, the W8MD medical weight loss program accepts most health insurances for weight loss physician visits.
- Delicious, and affordable optional W8MD protein meal replacement weight loss supplements - using the Very Low Calorie and Low Calorie Diet methods of 800-1400 calories using evidence based low carbohydrate, and low calorie partial meal replacement supplements for faster weight loss results
- For those that want to use their self prepared low calorie meals, we offer printed nutritional instructions
- Nutritional counseling on the right food choices for best weight loss results
- Minimal biweekly program cost of $50.00 includes up to two week supply of diet pills if dispensed in office, or 3 boxes of W8MD protein meal replacements with a total of 21 meals replaced.
- No surgery or invasive procedures for weight loss.
- Careful physician supervision for safe and effective weight loss
- Correction of underlying factors causing weight gain such as insulin resistance, sleep problems, eating disorders, medications etc.
- Evidence based medicine and not fad diets for long term weight loss success
- Appetite suppressant prescription diet pills - In order to help reduce hunger, increase metabolism and to help with weight, we offer prescription diet pills or appetite suppressant medications.
We also offer FDA approved prescription diet pills when appropriate in addition to a low calorie diet and increased physical activity!
Contrave (Bupropion and Naltrexone) - Brand new weight loss medication
The latest weight loss drug FDA approved in December of 2014, Saxenda
Phentermine and Topiramate (Qsymia)
(Phentermine and Topiramate is one of the most popular and most effective weight loss medications) for fast weight loss, almost twice as effective as some of the other weight loss medications!
Lorcaserin (Belviq) - New weight loss medication FDA approved in June of 2012.
Phentermine (Adipex) also called Ionamin, one of the most commonly used prescription diet pill.
Topiramate (Topamax) most commonly used along with Phentermine for faster weight loss results
Phendimetrazine (Bontril)
Diethylpropion (Tenuate)
Xenical and others
Review of thebest weight loss medications!
Check out the amazing weight loss success stories!
About our weight loss physicians
Weight loss doctor in West Hempstead
Dr. M. A. Rahman M.D
Professional Experience
As the Medical Director and founder, Magnum Physicians PC, a W8MD Medical Weight Loss Center, Dr M.A. Rahman has been in private practice since April 2012 along with his physician partner and wife, Dr. Sultana Rahman, MD.
West Hempstead W8MD Weight Loss Center Address: 151 Hempstead Turnpike, West Hempstead, NY, 11552
Dr. M.A. Rahman is a board certifiled internal medicine physician with extensive practice experience in both in patient, out patient and preventive medicine with special interest in helping patients lose weight, get healthier and live longer.
Brief summary of qualifications of our West Hempstead weight loss physician, Dr. M.A. Rahman
▪Board Certified in Internal Medicine (By ABIM)
▪Certified in ACLS, ATLS, PALS
▪Certified instructor in BLS and ACLS
Physician Specialist June 2005- Present
Department of Medicine, Kings County Hospital Center ▪ 451 Clarkson Avenue, Brooklyn, NY 11203
Physician Specialist June 1997-June 2004
Department of Emergency Medicine Kings County Hospital Center ▪ 451 Clarkson Avenue, Brooklyn, NY 11203
Attending Physician July 1989-May 1997
Department of Emergency Medicine Kings County Hospital Center ▪ 451 Clarkson Avenue, Brooklyn, NY 11203
Resident Physician July 1986-June 1989
Department of Medicine, SUNY Downstate Medical Center ▪ 450 Clarkson Avenue, Brooklyn NY, 11203
House Physician February 1985- June 1986
Department of Surgery Brookdale Hospital Center ▪ Linden Boulevard, Brooklyn, NY 11212
Resident Physician April 1978-June 1983
General Surgery, Chittagong Medical College Hospital ▪ Chittagong, Bangladesh
Academic Experience
Faculty member - Department of Medicine, State University of New York Downstate Medical Center
Associate Professor - St. George's University
Research and Publication
Silverberg, M.A., Rahman, M.Z. (2003) Axillary Breast Tissue Mistaken for Supportive Hidradenitis: An Avoidable Error. Journey of Emergency Medicine, 25, 51-55.
Harsh D Patel, BS/BA, Mohammed A. Rahman, MD, et al. A Patient with Gardner's Syndrome and Familial Adenomatous Polyposis Presenting with Extra-abdominal Desmoid Tumors and Diffuse Intestinal Polyposis. ACG Case Reports Journal, J2-2015;2(3):133-134.
Honors and Awards
Received Distinction in Final MBBS Examination - 1977
Merit Scholarship, Government of Bangladesh 1971-1976
List of insurances we accept - all major insurances accepted include
Blue Cross Blue Shield and affiliates
1199 insurance benefit fund
Tricare etc.
Hours of operation for Dr. M.A. Rahman, MD
Monday 5 P to 9P
Friday 5 P to 9 P
Sat 10 A to 4P
By appointment only
List of other services provided at this location in addition to medical weight loss
- Complete physical exam
- Immigration physicals
- Adult Immunization
- Immigration Physical ( USCIS Civil Surgeon )
- Prevetive Medicine
- Bariatric Medicine
- Treatment of Hypertension, Diabetes, Asthma, COPD , Sexually transmitted diseases, Skin conditions etc
- Minor wound repair, removal of small cyst & drainage of small abscess.
- Blood drawn at the premise
- Spirometry
- Parking is free
- We offer evening and weekend hours for your convenience
- Within the same week weight loss physician appointments
Cities served for weight loss by our West Hempstead Long Island weight loss center
- Franklin Square, NY
- Hempstead, NY
- Garden City, NY
- New Hyde Park, NY
- Uniondale, NY
- North Valley Stream, NY
- Mineola, NY
- Floral Park, NY
- Elmont, NY
- North New Hyde Park, NY
- Lynbrook, NY
- Roosevelt, NY
- Baldwin, NY
- Valley Stream, NY
- East Rockaway, NY
If you have tried everything else and need real help from experienced, physicians specializing in non-surgical weight loss using evidence based measures as opposed to fad diets, contact us today at
(516) 483-1100
to schedule your weight loss consultation.
We also offer primary care services for all adults, immigration physicals, preventive health visits and women's health.With over 27 years of Experience in Internal Medicine & Emergency Medicine, Dr. Rahman, specializes in Acute & chronic illness management & preventive care to help adults avoid medical issues before they begin. I aim to keep all patients in the best health while providing welcoming & empathic care.
W8MD's Insurance Physician Weight Loss Services
Having realized the association of obesity with over 50 different medical problems and realizing the preventive health benefits offered by physician supervised medical weight loss, Dr. Rahman offers the popular W8MD's insurance physician weight loss program at his office in West Hempstead, NY.
Office Hours For Dr. Sultana Rahman, MD
Dr Sultana Rahman is a board certified family medicine physician
Services offered by Dr. Sultana Rahman, MD
- Complete Physical exam
- Adult & Children immunization
- School Physical
- Bariatric Medicine
- Preventine Medicine
- Treatment of Hypertension, Diabetes, Asthma, COPD , Sexually transmitted diseases, Skin conditions etc
- Minor wound repair, removal of small cyst & drainage of small abscess.
- Blood drawn at the premise
- Spirometry
All Major Insurances including Medicaid & Medicare are accepted.
Office Hours
Monday 5 P to 9P
Tuesday 2 P to 8 P
Thursday 2 P to 8P
Friday 5 P to 9 P
By appointment only
Credentials for Dr. Sultana Rahman, MD
As an attending physician at many local hospitals, board certified in Family Medicine, Dr. Sultana brings in unique bring blend of experience and professional care with a focus on prevention rather than cure.
Realizing the association of being overweight or obese with many diseases including diabetes, high blood pressure, sleep apnea, metabolic syndrome, cardiovascular disease to name few, Dr. Sultana can help you lose weight fast and safe under careful physician supervision using the popular W8MD Medical Weight Loss Centers of America's insurance physician weight loss program.
Professional Experience
Attending Physician ▪ 04/06 - Present
Brookdale University Hospital Family Center ▪ 2554 Linden Boulevard, Brooklyn, NY 11208
Private Practice ▪ 4/12 - Present
Magnum Physicians▪ 151 Hempstead Turnpike, West Hempstead, NY 11552
Attending Physician ▪ 10/05 – 02/06
Brooklyn Hospital Center, Arbor We Care TBHC ▪ 100 Parkside Avenue Brooklyn, NY 11208
Physician ▪ 5/05 – 09/05
Bedford Medical Group ▪ 176 Fenimore Street, Brooklyn, NY 11215
Resident Physician ▪ 7/02 – 6/05
Department of Family Medicine ▪ SUNY Downstate Medical Center, 450 Clarkson Avenue Brooklyn, NY 11203
Conditions treated for weight loss
Unlike most other programs, W8MD Medical Weight Loss Centers physician weight loss program is focussed on understanding the true causes of weight gain including metabolic, nutritional, sleep related factors, genetic factors, hormonal imbalances, medications, stress, eating disorders!
- Metabolic syndrome
- Acanthosis Nigricans
- Insulin resistance
- Eating disorders
- Bulemia
- Food addiction
- Carb addiction
- Food cravings
- Belly fat
- Diabetes
- High blood pressure
- High cholesterol
- Elevated triglycerides
- Sleep apnea
- Osteoarthritis
- Headache
- Fibromyalgia
- Chronic back pain
- Depression
What patients are saying?
Anonymous Verified Patient On Patient Fusion May 16th, 2015
I felt that Dr. Rahman and his coworkers were very communicative, comfortable to be around. The addressed my concerns in a gentle but thorough manner.
Anonymous Verified Patient On Patient Fusion August 8th, 2015
151 Hempstead Turnpike West Hempstead, New York 11552
Phone:(516) 483-1100


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THERE'S one vista many of us hanker after when house hunting - a sea view, ideally with a beach thrown in for good measure.
Philippe and Florence Grelon rent a three-floor house in Chung Hom Kok, Hong Kong Island. This is a rare luxury in Hong Kong, where living conditions for most local residents would described as cramped, at best.
However, the view was a decisive criteria in the choice of this house, explained to the French couple. "It's this view - with no neighbors in sight, only birds and the constant procession of cargo ships in the distance - that we find amazing," Florence said.
"The fact that the house is on three floors with a terrace is great, too. It reminds us of some London houses and it keeps you fit, even without going to the gym."
Even though the house was not in a great condition when the family moved in, that didn't worry Florence too much. Like many French women, she has a talent for combining colors and styles to create a good mood and foster an optimistic outlook. Her talents have created a soothing and cheerful vibe here.
Each corner of the house exerts an aesthetic appeal at once comfortable and tasteful.
"I was never into a typical 'deco' style that you see in every magazine and that everyone seems to try and imitate. We haven't changed sofas for 20 years and now I would buy a very different one, with more straight and simple lines," she said.
"I want people to feel they are coming into a real family house. The inside of your home should tell a bit about the inside of your heart. If you want it warm and welcoming, it is natural to have wood and warm colors, such as deep red."
Florence says she never buys items from home decor shops. Having been a newspaper correspondent for almost two decades, she has travelled the world. Each object in the house has its own story.
In the living room, you will find a collection of objects from countries including Papua New Guinea, India, the Solomon Islands, China, Malaysia, Indonesia, Thailand, Myanmar, Cambodia, Vietnam, Colombia, Italy and France.
"But you don't want to have a house looking like the Cairo Museum," Florence said. "The only thing that creates unity between many different objects from different cultures is your own taste."
Florence has carried her love of mixing, matching and adapting to her furniture. The coffee table that has pride of place in the living room started life as Indian bed.
"We loved the color of the wood but it was too high. Looking at the legs, we realized that the shape would allow for a straight cut. We decided to try that and it worked perfectly.
"Many people notice the table and wonder where it comes from, as you don't find antique Indian coffee tables," she added.
The Chinese wedding cabinet has had quite an incredible life too, said Florence.
"Long before we ever thought we would end up in China, we were living in New Zealand. I had spotted this red lacquered cabinet from a distance in the auction place and decided to go to the auction night. I had never placed a bid in an auction before and felt a bit intimidated but fought for this cabinet and got it," she said.
Some Chinese furniture ended up in New Zealand in the second half of the 19th century, when Chinese attracted by a small gold rush settled and sent for their furniture.
"It is funny to think that this wedding cabinet traveled from China to New Zealand more than a century ago and came back to Hong Kong with us. I wish objects could talk sometime as they carry fascinating stories."
Talking about her favorite furniture style, Florence said that "simplicity is the utmost elegance. It is tempting to add, but it is often much better to remove."
Colors, materials and artworks are essential to create a cozy and welcoming look. "I don't mind things getting a bit old and damaged. Cushions get damaged by the light, but that's OK as I don't like things to be perfect."
Florence firmly believes that home is a safe haven where a family can rejuvenate and rest.
Florence Grelon
Q: What's the best thing about living in Hong Kong?
A: The energy of the city.
Q: Describe your home in three words.
A: Homy, warm and personal.
Q: What's the first thing you do when you get home?
A: Go and check the view and the sea on the balcony.
Q: How do you unwind?
A: I rarely do …
Q: Where do you spend most of the time at home?
A: At my desk …
Q: What's the best view from your window?
A: I can see the sea from most of the windows, a little island called Round Island and further away Lamma Island. But it changes all the time.
Q: How do you scent your home?
A: Good cooking, first of all! And the occasional home fragrance when I feel like it.
Q: What's your favorite object at home?
A: Too hard to tell. I like some for their beauty, others for their symbolic value, others for their stories, others because of where they come from or who gave them to us … It's impossible to establish a ranking.
Q: Where do you source furniture in Hong Kong?
A: The dark red armchair, covered in Italian velvet, was purchased at Pure. Some lights were purchased at Lane Crawford. But all our previous houses in other countries were larger, so there is little space for more.
Pekka Salminen
Who is he?
Pekka Salminen is the founder, president and senior partner of PES-Architects. Fellow partners are Tuomas Silvennoinen and Jarkko Salminen. They have their main office in Helsinki, Finland, and a studio in Shanghai. PES-Architects has undertaken more than 60 projects since 2003.
Tell us about some of your works, and say which you are most proud of.
My main work in Finland is Helsinki Airport, and in Germany I built St Mary's Concert Hall in Neubrandenburg. Both projects received many international awards.
I am most proud of the Wuxi Grand Theatre, in Wuxi, Jiangsu Province, in China, because with it I realized an old dream of combining an opera house and the language of form. I admire the beauty of organic forms found in nature. These were my inspiration for the Wuxi Grand Theatre.
Are you currently involved in any projects?
Yes. Xidong New City Cultural Center; Xiehe International School; and the hanging "Dancing Pedestrian Bridge" - all in Wuxi. In Finland, I'm designing a small studio apartment as an annex to my home. I am also busy with publishing projects related to the Wuxi Grand Theatre. My hometown Helsinki is appointed World Design Capital this year and I participated in Shanghai Radical Design Week.
Describe your design style.
It can be described as Scandinavian style: modest, clean, functional and user-friendly. It was great that I could create some Finnish features for Wuxi Grand Theatre public lobby area. It has a large wall with almost 20,000 specially designed glass bricks, giving a feeling of Finnish lakes.
Are there any designer you look up to?
Architect IM Pei who designed Suzhou Museum. As as student, I was drawn to the work of Danish architect J?rn Utzon.
Who and what inspires you?
Nelson Mandela and old Chinese poetry.
What do you collect?
I'm interested in Mediterranean citrus plants and modern yachts, so I collect info about these things.
What does your home mean to you?
My home means a building I have designed and where I can live and work. I have designed six small private houses of this type for myself. This is also a hobby.
Where would you like to go most in Shanghai?
I always first take my Finnish friends to the Jinmao Tower in Pudong. It is a fine skyscraper from where you can admire the rapid growth of Shanghai. I also stayed with my wife in the hotel in Jinmao, when signing the design contract for the Wuxi Grand Theatre. It was a memorable time.
What will be the next big design trend?
In China, it's to understand the value of bamboo as an important local and sustainable interior material. Bamboo is neglected in China, perhaps because it's become known as a "poor man's timber." Technology makes it possible to use it in many ways.
I believe that the bamboo interior of Main Opera Auditorium in Wuxi Grand Theatre has started sort of "bamboo boom" in China.
Another trend is green roofs and green facades, which both embody sustainable design.
From ¥280
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Study Hall
Study Hall
- For the convenience of parents and students, Schola provides a limited number of seats in study hall ONLY for registered Schola students who are 12 years old and above on or before September 1 of the current school year during free periods between classes or while waiting for siblings or car-pool partners in class.
- No fee is charged for the use of the study hall; however, our facilities are limited, and we ask that study hall be used only when necessary.
- To use the study hall, Schola students must be registered for its use.
- To apply for a study hall seat, print and complete a Study Hall Application. Be sure to include the reason why you are requesting a seat in study hall. Applications that do not state a reason will not be considered. Study Hall seats will be assigned on a first-come-first-served basis.
- Mail form with your Registration Form.


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Catalytic Proteins - Enzymes
Junichi Fujii
Learning objectives
After reading this chapter you should be able to:
Describe the characteristics of enzymatic reactions from the viewpoint of free energy, equilibrium and kinetics.
Discuss the structure and composition of enzymes, including the role of cofactors, and conditions that affect enzymatic reactions.
Describe enzyme kinetics based on the Michaelis–Menten equation and the significance of the Michaelis constant (Km).
Describe the elements of enzyme structure that explain their substrate specificity and catalytic activity.
Describe regulatory mechanisms affecting enzymatic reactions, including regulation by allosteric effectors and covalent modification.
Differentiate among the major types of enzyme inhibition from the viewpoint of enzyme kinetics.
Discuss the therapeutic use of enzyme inhibitors and the diagnostic utility of clinical enzyme assays.
Almost all biological functions are supported by chemical reactions catalyzed by biological catalysts, called enzymes
Efficient metabolism is controlled by orderly, sequential, and branching metabolic pathways. Enzymes accelerate chemical reactions under physiologic conditions. However, an enzyme cannot alter the equilibrium for a reaction; it can only accelerate the reaction rate, by decreasing the activation energy of the reaction (Fig. 6.1). Regulation of enzymatic activities allows metabolism to adapt to rapidly changing conditions. Nearly all enzymes are proteins, although some ribonucleic acid molecules, termed ribozymes, also have catalytic activity (Chapter 32). Based on analysis of the human genome, it is estimated that about a quarter of human genes encode for enzymes that catalyze metabolic reactions.
FIG. 6.1 Reaction profile for enzymatic and nonenzymatic reactions.
The basic principles of an enzyme-catalyzed reaction are the same as any chemical reaction. When a chemical reaction proceeds, the substrate must gain activation energy to reach a point called the transition state of the reaction, at which the energy level is maximum. Since the transition state of the enzyme-catalyzed reaction has a lower energy than that of the uncatalyzed reaction, the reaction can proceed faster. ES complex, enzyme–substrate complex; EP complex, enzyme–product complex.
Enzymatic Reactions
Factors affecting enzymatic reactions
Effect of temperature
Enzymes have an optimum temperature at which they function most efficiently
In the case of an inorganic catalyst, the reaction rate increases with the temperature of the system, and high temperature may be used to accelerate a reaction. In contrast, enzymes normally function as catalysts at constant (ambient or body) temperature. In in vitro assays, however, enzyme activity increases with temperature, but then declines at higher temperature. This happens because enzymes, like all proteins, denature at high temperature and lose activity.
Effect of pH
Every enzyme has a pH optimum because ionizable amino acids, such as histidine, glutamate, and cysteine, participate in the catalytic reactions
Cytosolic enzymes have pH optima in the pH 7–8 range. Pepsin, which is secreted by gastric cells and functions in gastric juice, has a pH optimum of 1.5–2.0; trypsin and chymotrypsin have alkaline pH optima, consistent with their digestive activity in alkaline pancreatic juice; lysosomal enzymes typically have acidic pH optima. The pH sensitivity of enzymes results from the effect of pH on the ionic charge of amino acid side chains of enzymes. Various solutes, including substrates, products, metal ions and regulatory molecules, also affect the rate of enzymatic reactions.
Definition of enzyme activity
One international unit (IU) of enzyme catalyzes conversion of 1 µmol of substrate to product per minute
For the purposes of standardization, the activity of an enzyme is measured under defined conditions (temperature, pH, buffer, substrate and coenzyme concentration). The rate or velocity (v) of an enzymatic reaction under these conditions is defined as the rate of conversion of substrate to product per unit of time. A unit of enzyme is a measure of the amount of enzyme. The commonly used international unit (IU) is the amount of enzyme that catalyzes conversion of one micromole of substrate to product per min (1 IU = 1 µmol/min). The katal is an international unit for the amount of enzyme that catalyzes conversion of 1 mole of substrate into 1 mole of product per second (1 kat = 1 mol/s). Because the katal is generally a very small number, the much larger international unit is more commonly used as the standard unit of activity.
The specific activity of an enzyme is a measure of the number of IU/mg protein
The specific activity of an enzyme, a measure of activity per amount of protein, is expressed as µmol/min/mg of protein or IU/mg of protein. The specific activity of enzymes varies greatly among tissues, depending on the metabolic function of the tissue. The enzymes for cholesterol synthesis, for example, have a higher specific activity (IU/mg tissue) in liver than in muscle, consistent with the role of liver in biosynthesis of cholesterol. The specific activity of an enzyme is useful for estimating its purity – the higher the specific activity of an enzyme, the higher its purity or homogeneity.
Reaction and substrate specificity
Most enzymes are highly specific for both the type of reaction catalyzed and the nature of the substrate(s)
The reaction that the enzyme catalyzes, is determined chemically by the amino acid residues in the catalytic center of the enzyme. In general, the active site of the enzyme is composed of the substrate binding site and the catalytic site. Substrate specificity is determined by the size, structure, charges, polarity, and hydrophobicity of the substrate binding site. This is because the substrate must bind in the active site as the first step in the reaction, setting the stage for catalysis. Highly specific enzymes such as catalase and urease, which degrade H2O2 and urea, respectively, catalyze only one specific chemical reaction, but some enzymes have broader substrate specificity. The serine proteases are a typical example of such a group of enzymes. These are a family of closely related enzymes, such as the pancreatic enzymes, chymotrypsin, trypsin, and elastase, which contain a reactive serine residue in the catalytic site. They catalyze the hydrolysis of peptide bonds on the carboxyl side of a limited range of amino acids in protein. Although they have similar structures and catalytic mechanisms, their substrate specificities are quite different because of structural features of the substrate binding site (Fig. 6.2).
FIG. 6.2 Characteristics of the substrate binding sites in the serine proteases chymotrypsin, trypsin, and elastase.
In chymotrypsin a hydrophobic pocket binds aromatic amino acid residues such as phenyl-alanine (Phe). In trypsin, the negative charge of the aspartate residue in the substrate binding site promotes cleavage to the carboxyl side of positively charged lysine (Lys) and arginine (Arg) residues. In elastase, side chains of valine and threonine block the substrate binding site and permit binding of amino acids with small or no side chains, such as glycine (Gly). ▼ site of hydrolysis by enzyme.
All enzymes are assigned a four-digit enzyme classification (EC) number to organize the different enzymes that catalyze the many thousands of reactions. The first digit indicates membership of one of the six major classes of enzymes shown in Table 6.1. The next two digits indicate substrate subclasses and sub-subclasses; the fourth digit indicates the serial number of the specific enzyme. Isozymes are enzymes that catalyze the same reaction, but differ in their primary structure and/or subunit composition. The activities of some tissue-specific enzymes and isozymes are measured in serum for diagnostic purposes (Fig. 6.3 and Table 6.2).
Table 6.1
Enzyme classification
1. Oxidoreductases
Ared + Box→Aox + Bred
Dehydrogenases, peroxidases
2. Transferases
Hexokinase, transaminases
3. Hydrolases
Alkaline phosphatase, trypsin
4. Lyases (synthases)
fumarase, dehydratases
5. Isomerases
A isoA
Triose phosphate isomerase, phosphogluco-mutase
6. Ligases (synthetases)
A + B + ATP→A-B + ADP + Pi
Pyruvate carboxylase, DNA ligases
Table 6.2
Some enzymes used for clinical diagnosis
Tissue source(s)
Diagnostic use
Heart, skeletal muscle, liver, brain
Liver disease
Liver disease, e.g. hepatitis
Pancreas, salivary gland
Acute pancreatitis, biliary obstruction
Skeletal muscle, heart, brain
Muscular dystrophy, myocardial infarction
Hepatitis, cirrhosis
Heart, liver, erythrocytes
Lymphoma, hepatitis
Acute pancreatitis, biliary obstruction
Alkaline phosphatase
Bone disease, bone tumors
Acid phosphatase
Prostate cancer
AST, aspartate aminotransferase, formerly known as serum glutamate oxaloacetate transaminase (SGOT); ALT, alanine aminotransferase, formerly known as serum glutamate pyruvate transaminase (SGPT) CK, creatine phosphokinase; GGT, γ-glutamyl transpeptidase; LDH, lactate dehydrogenase; PSA, prostate-specific antigen (kallikrein 3).
FIG. 6.3 Densitometric patterns of the lactate dehydrogenase (LDH) isozymes in serum of patients diagnosed with myocardial infarction or acute hepatitis.
Isozymes, differing slightly in charge, are separated by electrophoresis on cellulose acetate, visualized using a chromogenic substrate, and quantified by densitometry. Total serum LDH activity is also increased in these patients. Since hemolysis releases LDH from red blood cells and affects isozyme distribution and differential diagnosis, blood samples should be treated with care. The LDH measurements for the diagnosis of myocardial infarction have now been superseded by assay of plasma troponin and other biomarkers.
Roles of coenzymes
Helper molecules, referred to as coenzymes, play an essential part in many enzyme-catalyzed reactions
Enzymes with covalently or noncovalently bound coenzymes are referred to as holoenzymes. A holoenzyme without a coenzyme is termed an apoenzyme. Coenzymes are divided into two categories. Soluble coenzymes bind reversibly to the protein moiety of the enzyme. They are often modified during the enzymatic reaction, then dissociate from the enzyme and are recycled by another enzyme; oxidoreductases, discussed in Chapter 9, have coenzymes that may be oxidized by one enzyme, then reduced and recycled by another. Coenzymes, such as coenzyme A, assist in the transport of intermediates from one enzyme to another during a sequence of reactions. Most coenzymes are vitamin derivatives. Derivatives of the B vitamins, niacin and riboflavin, act as coenzymes for oxidoreductase reactions. The structure and function of coenzymes will be described in later chapters. Prosthetic groups are tightly bound, often covalently linked, to an enzyme and remain associated with the enzyme during the entire catalytic cycle. Some enzymes require inorganic (metal) ions, frequently termed cofactors, for their activity, e.g. blood-clotting enzymes that require Ca2+, and oxidoreductases, which use iron, copper, and manganese.
Clinical test box Tissue specificity of lactate dehydrogenase isozymes
A 56-year-old female was admitted to an intensive care unit. The patient had suffered from a slight fever for 1 week, and had some chest pain, and difficulty breathing for the past 24 h. No abnormality was found on chest X-ray or by electrocardiography. However, a blood test showed white blood cells 12,100/mm3 (normal: 4000–9000/mm3), red blood cells 240 × 104/mm3 (normal: 380–500 × 104/mm3), hemoglobin 8.6 g/dL (normal: 11.8–16.0 g/dL), lactate dehydrogenase (LDH) 1400 IU/L (normal: 200–400 IU/L). Levels of other enzymes were normal. Based on the blood tests, the LDH isozyme profile and other data, the patient was eventually diagnosed with malignant lymphoma.
LDH is a tetrameric enzyme, and oxidoreductases composed of two different 35 kDa subunits. The heart contains mainly the H type, and skeletal muscle and the liver the M type subunit, which are encoded by different genes. Five types of tetrameric isozymes can be formed from these subunits: H4 (LDH1), H3M1 (LDH2), H2M2 (LDH3), H1M3(LDH4), and M4 (LDH5). Since isozyme distributions differ among tissues, it is possible to diagnose tissue damage by assaying total LDH activity and then by isozyme profiling (Fig. 6.3).
For hematological reference values, see Table 5.2 and appendix 1.
Advanced concept box Proportion of enzyme genes in whole human genome
Original data (Venter et al., Science 291:1335, 2001) are quoted here, and so classification does not exactly match nomenclature in Table 6.2. About a quarter of genes encode enzymes. Names of enzyme groups with number and proportion (percentage in parenthesis) in a total of 26,383 human genes were as follows: transferase, 610 (2.0); synthase and synthetase, 313 (1.0); oxidoreductase, 656 (2.1); lyase, 117 (0.4); ligase, 56 (0.2); isomerase, 163 (0.5); hydrolase, 1227 (4.0); kinase, 868 (2.8); nucleic acid enzyme, 2308 (7.5).
Clinical test box Isozymes
Isozyme profiles are often performed in the clinical laboratory for diagnostic purposes (see Fig. 6.3). The definition of isozymes is often operational, i.e. based on simple and reproducible substrate-specific assay methods that sometimes do not require precise knowledge of enzyme structure.
The term isozyme is commonly used to refer to: (1) genetic variants of an enzyme; (2) genetically independent proteins with little homology; (3) heteropolymers of two or more noncovalently bound polypeptide chains; (4) unrelated enzymes that catalyze similar reactions, e.g. enzymes conjugated with different prosthetic groups or requiring different coenzymes or cofactors; (5) different forms of a single polypeptide chain, e.g. varying in carbohydrate composition, deamination of amino acids, or proteolytic modification.
Enzyme Kinetics
The Michaelis–Menten equation: a simple model of an enzymatic reaction
Enzyme reactions are multistep in nature and comprise several partial reactions
In 1913, long before the structure of proteins was known, Leonor Michaelis and Maud Leonora Menten developed a simple model for the kinetics of enzyme-catalyzed reactions (Fig. 6.4). The Michaelis–Menten model assumes that the substrate S binds to the enzyme E, forming an essential intermediate, the enzyme-substrate complex (ES), which then undergoes reaction on the enzyme surface and decomposes to E + P (product). The model assumes that E, S, and ES are all in rapid equilibrium with one another, so that a steady-state concentration of ES is rapidly achieved, and that decomposition of the ES complex to E + P is the rate-limiting step in catalysis. The rate of this reaction is directly dependent on the activation energy of the enzyme-catalyzed reaction (Fig. 6.1).
FIG. 6.4 Properties of glucokinase and hexokinase.
Glucokinase and hexokinase catalyze the same reaction, phosphorylation of glucose to glucose 6-phosphate (Glc-6-P). They exhibit different kinetic properties and have different tissue distributions and physiologic functions.
The catalytic constant, kcat, also known as the turnover number, is a rate constant which describes how quickly an enzyme can catalyze a reaction. The kcat is defined as the number of substrate molecules converted to product per enzyme molecule per unit time. The proportion of ES, in relation to the total number of enzyme molecules [E]t, i.e. the ratio [ES]/[E]t, limits the velocity of an enzyme (v) so that:
Since E, S, and ES are all in chemical equilibrium, the enzyme achieves maximal velocity, Vmax, at very high (saturating) substrate concentrations [S], when [ES] ≈ [E]t (total enzyme). Thus:
For the dissociation of the ES complex, the law of mass action yields:
Given that:
it can be shown that:
Consequently, the velocity of the enzymatic reaction, v, is given by:
Since kcat [E]t corresponds to the maximum velocity, Vmax, that is attained at high (saturating) substrate concentrations, we obtain the Michaelis–Menten equation:
Analysis of the above equations indicates that the Michaelis constant, Km, is expressed in units of concentration and corresponds to the substrate concentration at which v is 50% of the maximum velocity, i.e. [ES] = ½ [E]t and v = Vmax/2 (Fig. 6.4)
Km is a useful constant for estimating the affinity of an enzyme for its substrate. Enzymes with a high Km require high substrate concentration for efficient activity, while those with low Kmoperate efficiently on trace levels of substrate.The Michaelis–Menten model is based on the assumptions that:
E, S, and ES are in rapid equilibrium.
There are no forms of the enzyme present other than E and ES.
The conversion of ES into E + P is a rate-limiting, irreversible step. While all enzyme-catalyzed reactions are theoretically reversible, initial velocities are normally measured, i.e. when product concentration, and therefore the rate of the reverse reaction, is negligible.
Importantly, similar types of kinetic models have been developed for describing the kinetics of multisubstrate, multiproduct enzymes.
Advanced concept box glucokinase and hexokinase
Hexokinase catalyzes the first step in glucose metabolism in all cells, namely the phosphorylation reaction of glucose by adenosine triphosphate (ATP) to form glucose 6-phosphate (Glc-6-P):
This enzyme has a low Km for glucose (0.2 mmol/L) and is inhibited allosterically by its product, Glc-6-P. Since normal glucose levels in blood are about 5 mmol/L and intracellular levels are 0.2–2 mmol/L, hexokinase efficiently catalyzes this reaction (50–90% of Vmax) under normal conditions, e.g. in muscle.
Hepatocytes, which store glucose as glycogen, and pancreatic β-cells, which regulate glucose consumption in tissues and its storage in liver by secreting insulin, contain an isozyme called glucokinase.
Glucokinase catalyzes the same reaction as hexokinase, but has a higher Km for glucose (10 mmol/L) and is not inhibited by the product, Glc-6-P. Since glucokinase has a much higher Km than hexokinase, glucokinase phosphorylates glucose with increasing efficiency as blood glucose levels increase following a meal (see Fig. 6.4). One of the physiologic roles of glucokinase in the liver is to provide Glc-6-P for the synthesis of glycogen, a storage form of glucose. In the pancreatic β-cell, glucokinase functions as the glucose sensor, determining the threshold for insulin secretion. Mice lacking glucokinase in the pancreatic β-cell die within 3 days of birth of profound hyperglycemia, because of failure to secrete insulin.
Use of the Lineweaver–Burk and Eadie–Hofstee plots
Alternative graphical analyses permit more accurate determination of the Km and Vmax of an enzyme
In a plot of reaction rate versus substrate concentration, the rate of the reaction approaches the maximum velocity (Vmax) asymptotically (Fig. 6.5A), so that it is difficult to obtain accurate values for Vmax and, as a result, Km (substrate concentration required for half-maximal activity), by simple extrapolation. To solve this problem, several linear transformations of the Michaelis–Menten equation have been developed.
FIG. 6.5 Enzyme kinetics plot.
Kinetic representations of the properties of enzymes. (A) Michaelis–Menten plot of velocity (v) versus substrate concentration ([S]). (B) Lineweaver–Burk plot. (C) Eadie–Hofstee plot.
Lineweaver–Burk plot
The Lineweaver–Burk, or double reciprocal, plot is obtained by taking the reciprocal of the Michaelis–Menten equation (Fig. 6.5B). By rearranging the equation, we obtain:
This equation yields a straight line (y = mx + b), with y = 1/v, x = 1/[S], m = slope, b = y intercept. Therefore, a graph of 1/v versus 1/[S] (Fig. 6.5B) has a slope of Km/Vmax, a 1/v intercept of 1/Vmax and a 1/[S] intercept of –1/Km. Although the Lineweaver–Burk plot is widely used for kinetic analysis of enzyme reactions, because reciprocals of the data are calculated, a small experimental error, especially at low substrate concentration, can result in a large error in the graphically determined values of Km and Vmax. An additional disadvantage is that important data obtained at high substrate concentrations are concentrated into a narrow region near the 1/v axis.
Eadie–Hofstee plot
A second, widely used linear form of the Michaelis–Menten equation is the Eadie–Hofstee plot (Fig. 6.5C), described by the equation:
In this case, a plot of v versus v/[S] has a y axis (v-intercept) of Vmax, an x axis (v/[S]) intercept of Vmax/Km, and a slope of −Km. The Eadie–Hofstee plot does not compress the data at high substrate concentrations.
Clinical test box Measurement of enzyme activity in clinical samples
In clinical laboratories, enzyme activity is measured in the presence of saturating substrate(s) and coenzyme concentrations. Initial rates are recorded to minimize errors resulting from the reverse reaction. Under these conditions v ≈ Vmax, and enzyme activity is directly proportional to enzyme concentration. The amount of enzyme (enzyme activity) is commonly expressed in IU/mL of plasma, serum, cerebrospinal fluid, rather than per mg protein. For interlaboratory comparisons, the conditions for the enzyme assay must be standardized, e.g. by specifying the substrate and coenzyme concentrations used, the buffer, buffer concentration, ionic species and ionic strength, pH and temperature.
Most clinical samples are collected under fasting conditions; this assures consistency in measurement of analytes whose concentration may vary diurnally or others, such as glucose or lipids, which vary in response to food intake. Lipemic samples are cloudy and may yield unreliable data by spectrophotometric or fluorometric methods. To avoid such problems, clinical samples must be delipidated, commonly by extraction with organic solvent.
Mechanism of Enzyme Action
Enzymatic reactions involve functional groups on enzymes, coenzymes, substrates and products
Enzymes vary significantly in their mechanism of action. In some cases catalysis is carried out on the substrate, non-covalently, reversibly bound to the enzyme. In other cases, a covalent intermediate is formed on, and then released from, the enzyme and, in others, all the action takes place on a coenzyme which forms a covalent bond with substrate. The mechanisms of action of many enzymes are discussed in later chapters in this text.
The serine proteases, introduced in Figure 6.2, are representative of enzymes that form a covalent intermediate with their substrates. These enzymes cleave peptide bonds in proteins and, as in all enzymatic reactions, functional groups on amino acid side chains participate in the enzyme-catalyzed reaction. In the serine protease family, an active site serine residue catalyzes cleavage of the peptide bond. The functional group on serine, a primary alcohol, is not among the more reactive functional groups in organic chemistry. To enhance its activity in serine proteases, this serine residue is part of a 'catalytic triad', in the case of chymotrypsin: Asp102, His57 and Ser195 (Fig. 6.6). Concerted hydrogen bonding interactions between these amino acids increase the nucleophilicity of the serine residue, so that it can attack the carbonyl carbon atom of the peptide bond in the substrate. Chymotrypsin is specific for cleavage on the carboxyl side of peptide bonds containing aromatic amino acids, such as phenylalanine. The mechanism of the enzymatic reaction is outlined in Figure 6.7, showing the formation and cleavage of an enzyme-bound intermediate.
FIG. 6.6 A schematic model of a catalytic triad of serine protease.
FIG. 6.7 Mechanism of action of chymotrypsin.
The active site serine residue attacks the carbonyl group of the peptide bond on the carboxyl side of a phenylalanine residue. The carboxy-terminal peptide is released and the amino-terminal peptide remains an enzyme-bound intermediate – the amino-terminal peptide linked covalently through its carboxy-terminal phenylalanine esterified to the active site serine residue. The ester bond is hydrolyzed in the second step of the reaction to release the amino-terminal peptide and regenerate active enzyme.
Trypsin and elastase, two other digestive enzymes with different amino acid specificities (Fig. 6.2), are similar to chymotrypsin in many respects. About 40% of the amino acid sequences of these three enzymes are identical, and their three-dimensional structures are very similar. All three enzymes contain the aspartate-histidine-serine catalytic triad, and are inactivated by reaction of fluorophosphates with the active serine residue. The nerve gas, diisopropylfluorophosphate, forms a sterically hindered, very slowly hydrolyzed serine-diisopropylphospate ester and inhibits serine proteases.
Enzyme Inhibition
Among numerous substances affecting metabolic processes, enzyme inhibitors are particularly important. Many drugs, either naturally occurring or synthetic, act as enzyme inhibitors. Metabolites of these compounds may also inhibit enzyme activity. Most enzyme inhibitors act reversibly, but there are also irreversible inhibitors that permanently modify the target enzyme. Using the Lineweaver–Burk plots, it is possible to distinguish three forms of reversible inhibition: competitive, uncompetitive, and noncompetitive inhibition.
Competitive inhibitors cause an apparent increase in Km, without changing Vmax
An enzyme can be inhibited competitively by substances that are similar in chemical structure to the substrate. These compounds bind in the active site and compete with substrate for the active site of the enzyme; they cause an apparent increase in Km, but no change in Vmax (Fig. 6.8). The inhibition is not the result of an effect on enzyme activity, but on substrate access to the active site. The reaction scheme for competitive inhibition is:
FIG. 6.8 Competitive enzyme inhibition.
(A) Plot of velocity versus substrate concentration. (B) Mechanism of competitive inhibition. (C) Lineweaver–Burk plot in the presence of a competitive inhibitor. (D) Eadie–Hofstee plot in the presence of a competitive inhibitor. K′m is the apparent Km in presence of inhibitor.
The inhibition constant (Ki) is the dissociation constant of the enzyme–inhibitor complex (EI) and the lower the Ki, the more efficient the inhibition of enzyme activity. Regardless of theKi, however, the rate of the enzyme-catalyzed reaction in the presence of a competitive inhibitor can be increased by increasing the substrate concentration, since substrate, at higher concentration, competes more effectively with the inhibitor.
Clinical box Treatment with an inhibitor of angiotensin-converting enzyme (ACE)
A 50-year-old man was admitted to hospital suffering from general fatigue, a stiff shoulder, and headache. The patient was 1.8 m tall and weighed 84 kg. His blood pressure was 196/98 mmHg (normal below 140/90 mmHg; optimal below 120/80 mmHg) and his pulse was 74. He was diagnosed as hypertensive. The patient was given captopril, an angiotensin-converting enzyme (ACE) inhibitor. After 5 days' treatment, his blood pressure returned to near-normal levels.
Renin in the kidney converts angiotensinogen into angiotensin I, which is then proteolytically cleaved to angiotensin II by ACE. Angiotensin II increases renal fluid and electrolyte retention, contributing to hypertension. Inhibition of ACE activity is therefore an important target for hypertension treatment. Captopril inhibits ACE competitively, decreasing blood pressure. (See also Chapter 23.)
Clinical box Methanol poisoning can be treated by ethanol administration
A 46-year-old male presented to the emergency room 7 h after consuming a large quantity of bootleg alcohol. He could not see clearly and complained of abdominal and back pain. Laboratory results indicated severe metabolic acidosis, a serum osmolality of 465 mmol/kg (reference range 285–295 mmol/kg), and serum methanol level of 4.93 g/L (156 mmol/L!). By aggressive treatment, including an ethanol drip, bicarbonate, and hemodialysis, he survived and regained his eyesight.
Methanol poisoning is uncommon but extremely hazardous. Ethylene glycol poisoning is more common and exhibits similar clinical characteristics. The most important initial symptom of methanol poisoning is visual disturbance. Laboratory evidence of methanol poisoning includes severe metabolic acidosis and increased plasma solute (methanol) concentration. Methanol is slowly metabolized to formaldehyde, which is then rapidly metabolized to formate by alcohol dehydrogenase. Formate accumulates during methanol intoxication and is responsible for the metabolic acidosis in the early stage of intoxication. In later stages lactate may also accumulate as a result of formate inhibition of respiration. Ethanol is metabolized by alcohol dehydrogenase, which binds ethanol with much higher affinity than either methanol or ethylene glycol. Ethanol is therefore a useful agent to inhibit competitively the metabolism of methanol and ethylene glycol to toxic metabolites. The unmetabolized methanol and ethylene glycol are gradually excreted in urine. Early treatment with ethanol, together with bicarbonate to combat acidosis and hemodialysis to remove methanol and its toxic metabolites, yields a good prognosis.
Noncompetitive inhibitors cause an apparent decrease in Vmax
An uncompetitive inhibitor binds only to the enzyme–substrate complex and not to the free enzyme. The equation below shows the reaction scheme for uncompetitive inhibition. In this case, the Ki is the dissociation constant for the enzyme–substrate–inhibitor complex (ESI).
The inhibitor causes a decrease in Vmax because a fraction of the enzyme–substrate complex is diverted by the inhibitor to the inactive ESI complex. Binding of the inhibitor and the increase in the ESI complex may also affect the dissociation of substrate, causing an apparent decrease in Km, i.e. an apparent increase in substrate affinity.
Non-competitive inhibitors may bind to sites outside the active site and alter both the Km and Vmax of the enzyme
An uncompetitive inhibitor can bind either to the free enzyme or to the enzyme–substrate complex, e.g. at an allosteric site. Uncompetitive inhibitors exhibit more complex effects and may alter both the Km and Vmax of an enzymatic reaction. The equation below shows the reaction scheme observed for noncompetitive inhibition.
Many drugs and poisons irreversibly inhibit enzymes
Prostaglandins are key inflammatory mediators. Their synthesis is initiated by cyclooxygenase-mediated oxidation and cyclization of arachidonate under inflammatory conditions (Chapter 40). Compounds that suppress cyclooxygenase have anti-inflammatory activity. Aspirin (acetylsalicylic acid) inhibits cyclooxygenase activity by acetylating Ser530, which blocks access of arachidonate to the active site of the enzyme. Other nonsteroidal anti-inflammatory drugs (NSAIDs), such as indomethacin, inhibit cyclooxygenase activity by reversibly blocking the arachidonate binding site.
Disulfiram (Antabuse®) is a drug used for the treatment of alcoholism. Alcohol is metabolized in two steps to acetic acid. The first enzyme, alcohol dehydrogenase, yields acetaldehyde, which is then converted into acetic acid by aldehyde dehydrogenase. The latter enzyme has an active site cysteine residue that is irreversibly modified by disulfiram, resulting in accumulation of alcohol and acetaldehyde in the blood. People who take disulfiram become sick because of the accumulation of acetaldehyde in blood and tissues, leading to alcohol avoidance.
Alkylating agents, such as iodoacetamide (ICH2CONH2), irreversibly inhibit the catalytic activity of some enzymes by modifying essential cysteine residues. Heavy metals, such as mercury and lead salts, also inhibit enzymes with active site sulfhydryl residues. The mercury adducts are often reversible by thiol compounds. Eggs or egg white are sometimes administered as an antidote for accidental ingestion of heavy metals The egg white protein, ovalbumin, is rich in sulfhydryl groups; it traps the free metal ions and prevents their absorption from the gastrointestinal tract.
In many cases, irreversible inhibitors are used to identify active-site residues involved in enzyme catalysis, and to gain insight into the mechanism of enzyme action. By sequencing or mass spectrometric analysis of the modified peptide, it is possible to identify the specific amino acid residue modified by the inhibitor and involved in catalysis.
Advanced concept box Enzyme inhibition: transition-state inhibition and suicide substrate
Enzymes catalyze reactions by inducing the transition state of the reaction. It should therefore be possible to construct molecules that bind very tightly to the enzyme by mimicking the transition state of the substrate. Transition states themselves cannot be isolated, because they are not a stable arrangement of atoms, and some bonds are only partially formed or broken. But for some enzymes, analogues can be synthesized that are stable, but still have some of the structural features of the transition state.
Penicillin (Fig. 6.9) is a good example of a transition state analogue. It inhibits the transpeptidase that crosslinks bacterial cell-wall peptidoglycan strands, the last step in cell-wall synthesis in bacteria. It has a strained 4-membered lactam ring that mimics the transition state of the normal substrate. When penicillin binds to the active site of the enzyme, its lactam ring opens, forming a covalent bond with a serine residue at the active site. Penicillin is a potent irreversible inhibitor of bacterial cell-wall synthesis, making the bacterium osmotically fragile and unable to survive in the body.
FIG. 6.9 Structure of penicillin showing the reactive peptide bond in the β-lactam ring and core structure of cephalosporins.
Penicillins contain a β-lactam ring fused to a thiazolidine ring. Cephalosporins are another class of compounds containing the β-lactam ring fused to a six-membered dihydrothiazine ring. Because of their effectiveness and lack of toxicity, β-lactam compounds are widely used antibiotics. Bacteria with β-lactamase, which breaks the β-lactam ring, are resistant to these antibiotics.
Regulation of Enzyme Activity
In multistep metabolic pathways, the slowest step limits the overall rate of the reaction
It is most efficient to regulate a metabolic pathway by controlling key enzymes that are involved in the 'rate-limiting' step. Generally, five independent mechanisms are involved in the regulation of enzyme activity.
The expression of the enzyme protein from the corresponding gene changes in response to the cell's changing environment or metabolic demands.
Enzymes may be irreversibly activated or inactivated by proteolytic enzymes.
Enzymes may be reversibly activated or inactivated by covalent modification, such as phosphorylation.
Allosteric regulation modulates the activity of key enzymes through reversible binding of small molecules at sites distinct from the active site in a process that is relatively rapid and, hence, the first response of cells to changing conditions.
The degradation of enzymes by intracellular proteases in the lysosome or by proteasomes in the cytosol also determines the lifetimes of the enzymes and consequently enzyme activity over a much longer period of time.
Despite extensive studies it is still impossible to deduce precisely the activity of specific enzymes in the body; many factors including substrate concentrations, pH and allosteric effectors change with time under physiologic conditions. Advances in technology now permit the measurement of thousands of metabolites quantitatively and simultaneously in tissues – a developing field known as metabolomics (Chapter 36). Using the tools of basic enzymology and metabolomics, it may eventually be possible to measure the endogenous flux through complex metabolic pathways in vivo.
Proteolytic activation of digestive enzymes
Some enzymes are stored in subcellular organelles or compartments in an inactive precursor form
Several digestive enzymes are stored as inactive zymogens or proenzymes in secretory vesicles in the pancreas. The zymogens are secreted in pancreatic juice following a meal and are activated in the gastrointestinal tract. Trypsinogen is converted into trypsin by the action of intestinal enteropeptidase. Enteropeptidase, located on the inner surface of the duodenum, hydrolyzes an N-terminal peptide from the inactive trypsinogen. Rearrangement of the tertiary structure yields the proteolytically active form of trypsin. The active trypsin then digests other zymogens, such as procarboxypeptidase, proelastase and chymotrypsinogen, as well as other trypsinogen molecules (Chapter 10). Similar proteolytic cascades are observed in blood clotting and fibrinolysis (dissolution of clots) (Chapter 7).
Allosteric regulation of rate-limiting enzymes in metabolic pathways
Allosteric enzymes display sigmoidal, rather than hyperbolic, plots of reaction rate vs. substrate concentration
The substrate saturation curve for an 'isosteric' (single shape) enzyme is hyperbolic (see Fig. 6.5A). In contrast, allosteric enzymes show sigmoidal plots of reaction velocity versus substrate concentration [S] (Fig. 6.10). An allosteric (other site) effector molecule binds to the enzyme at a site that is distinct and physically separate from the substrate binding site, and affects substrate binding (Km) and/or kcat. In some cases, the substrate may exert allosteric effects; this is referred to as a homotropic effect. If the allosteric effector is different from the substrate, it is referred to as a heterotropic effect. Homotropic effects are observed when the reaction of one substrate molecule with a multimeric enzyme affects the binding of a second substrate molecule at a different active site on the enzyme. The interaction between subunits makes the binding of substrate cooperative and results in a sigmoidal curve in the plot of vversus [S]. This effect is essentially identical with that described for the binding of O2 to hemoglobin (Chapter 5), except that in the case of enzymes, substrate binding leads to an enzyme-catalyzed reaction.
FIG. 6.10 Allosteric regulation of aspartate transcarbamoylase (ATCase).
Plot of velocity (v) versus substrate concentration in the presence of an allosteric activator or allosteric inhibitor ATCase is an example of an allosteric enzyme. Aspartate (substrate) homotropically regulates ATCase activity, providing sigmoidal kinetics. CTP, an end product, heterotropically inhibits, but ATP, a precursor, heterotropically activates ATCase.
Clinical box Hemophilia is caused by a defect in zymogen activation
A child was admitted to hospital with muscle bleeding affecting the femoral nerve. Laboratory findings indicated a blood-clotting disorder, hemophilia A, resulting from deficiency of factor VIII. Factor VIII was administered to the patient to restore blood-clotting activity.
Formation of a blood clot results from a cascade of zymogen-activation reactions. Over a dozen different proteins, known as blood-clotting factors, are involved. In the final step, the blood clot is formed by conversion of a soluble protein, fibrinogen (factor I), into an insoluble, fibrous product, fibrin, which forms the matrix of the clot. This last step is catalyzed by the serine protease, thrombin (factor IIa). Hemophilia is a disorder of blood clotting caused by a defect in one of the sequence of clotting factors. Hemophilia A, the major (85%) form of hemophilia, is caused by a defect of clotting Factor VIII (see Chapter 7).
Advanced concept box Nucleoside analogues as ANTIVIRAL agents
Nucleoside analogues such as acyclovir and ganciclovir have been used for treatment of herpes simplex virus (HSV), varicella-zoster (VZV), and cytomegalovirus (CMV). They are pro-drugs that are activated by phosphorylation and terminate viral DNA synthesis by inhibiting the viral DNA polymerase reaction. The thymidine kinase (TK), more properly a nucleoside kinase, of the viruses phosphorylate these compounds to their monophosphate form. Cellular kinases next add phosphates to form the active triphosphate compounds, which are competitive inhibitors of the viral DNA polymerase during DNA replication (Chapter 32).
While viral TK has low substrate specificity and efficiently phosphorylates nucleoside analogues, cellular nucleoside kinases have high substrate specificity and barely phosphorylate the nucleoside analogues. Thus, virus-infected cells are prone to be arrested at specific cell cycle stage, G2-M checkpoint (Chapter 42), but uninfected cells are resistant to the nucleoside analogues.
Positive and negative cooperativity
Positive cooperativity indicates that the reaction of a substrate with one active site makes it easier for another substrate to react at another active site. Negative cooperativity means that the reaction of a substrate with one active site makes it more difficult for a substrate to react at the other active site. Since the affinity of the enzyme changes with substrate concentration, it cannot be described by simple Michaelis–Menten kinetics. Instead, it is characterized by the substrate concentration giving a half-maximal rate, [S]0.5, and the Hill coefficient (H) (Chapter 5). The H-values are larger than 1 for enzymes with positive cooperativity and less than 1 for those with negative cooperativity. For most allosteric enzymes, intracellular substrate concentrations are poised near the [S]0.5, so that the enzyme's activity responds to slight changes in substrate concentration.
The model most often invoked to rationalize allosteric behavior was established by Monod, Wyman and Changeaux, the so-called concerted model (Fig. 6.11). As with O2 binding to Hb, in the absence of substrate, the enzyme has a low affinity for substrate and is in the T state (tense state). The other conformation of the enzyme is the R state (relaxed state). Binding of allosteric effector molecules shifts the fraction of enzyme from one state to the other. In this model, all the active sites in the R state are the same and all have higher substrate affinity than in the T state. Because the transition between the T and R states occurs at the same time for all subunits, this is called the concerted (two-state) model. An alternative model, the so-calledsequential (multistate) model, was proposed by Koshland, Nèmethy and Filmer. It postulates that each subunit changes independently to a different conformation and that different subunits may have different affinities for substrate. It is now recognized that both models are applicable to different enzymes.
FIG. 6.11 Schematic representation of allosteric regulation.
(A) In homotropic regulation, the substrate acts as an allosteric effector. Two models are presented. In the concerted model, all of the subunits convert from the T (tense; low affinity for substrate) – into the R (relaxed; high affinity for substrate) – state at the same time; in the sequential model, they change one by one, with each substrate binding reaction. (B) In heterotropic regulation, the effector is distinct from the substrate, and binds at a structurally different site on the enzyme. Positive and negative effectors stabilize the enzyme in R and T state, respectively.
Clinical box Insecticide poisoning
A 55-year-old man was spraying an insecticide containing organic fluorophosphates in a rice field. He suddenly developed a frontal headache, eye pain, and tightness in his chest, typical signs of over-exposure to toxic organic fluorophosphates. He was taken to hospital and treated with an intravenous injection of 2 mg of atropine sulfate, and gradually recovered.
Organic fluorophosphates form covalent phosphoryl-enzyme complexes with both serine proteases and esterases, such as acetylcholinesterase. irreversibly inhibiting the enzymes. Acetylcholinesterase terminates the action of acetylcholine during neuromuscular activity (Chapter 41) by hydrolyzing the acetylcholine to acetate and choline. Inhibition of this enzyme prolongs the action of acetylcholine, leading to constant neuromuscular stimulation. Atropine competitively blocks acetylcholine binding and muscle stimulation at the neuromuscular junction.
Enzymatic Measurement of Blood Glucose
The glucose oxidase/peroxidase assay
In clinical laboratories, most compounds are measured by automated enzymatic methods
The most common assay procedure uses a mixture of glucose oxidase and peroxidase (Fig. 6.12). Glucose oxidase is highly specific for glucose, but oxidizes only the β-anomer of the sugar, which represents ~64% of glucose in solution. The assay mixture is therefore supplemented with mutarotase, which rapidly catalyzes the interconversion of the anomers, enhancing assay sensitivity by ~50%. The H2O2 produced in the oxidase reaction is then used in a peroxidase reaction to oxidize a chromogen to yield a colored chromophore. The color yield is directly proportional to the glucose content of the sample. There are fluorometric versions of this assay for high sensitivity, and one commercial analyzer uses an oxygen electrode to measure the rate of decrease in oxygen concentration in the sample, which is also directly proportional to the glucose concentration.
FIG. 6.12 The glucose oxidase/peroxidase assay for blood glucose.
The color produced in this assay is directly proportional to blood glucose concentration.
Reagent strips and glucometers
People with diabetes normally monitor their blood glucose several times a day using reagent strips or glucose meters
The glucose reagent strips are impregnated with a glucose oxidase/peroxidase (GOP) reagent. In the manual version of this assay, the extent of color change on a dipstick is related to glucose concentration – typically on a 1–4 scale. Modern glucometers use a small drop of blood (~1 µL) and amperometric electrodes to measure the current produced by the redox reaction catalyzed by glucose dehydrogenase (GDH), which oxidizes glucose to gluconic acid, but reduces a coenzyme rather than oxygen. These assays are commonly used where rapid or frequent measurements of blood glucose are required. When the GOP and GDH assays were compared at high altitude on a trek up Mount Kilimanjaro, the GOP assay, which depends on ambient oxygen, had a greater error. Both methods were less accurate at the low temperatures at high altitude.
Kinetic assays
Kinetic assays are more rapid than end-point assays
In the assay described in Figure 6.12 and plotted for several glucose concentrations in Figure 6.13A, the reaction is allowed to proceed to its endpoint, i.e. until all the glucose has been oxidized; then the color change is measured. The color yield is then plotted against a standard to determine blood glucose concentration (Fig. 6.13B). High-throughput kinetic analyzers estimate the glucose concentration in a sample by measuring the initial rate of the reaction. Analysis of the kinetic plots in Figure 6.13A, for example, indicates that both the endpoint and the initial rate of the glucose oxidase assay are dependent on glucose concentration. Thus, the analyzer can measure the change in absorbance (or some other parameter) during the early stages of the reaction and compare this rate to that of a standard solution to estimate the glucose concentration (Fig. 6.13C). These assays are performed on flow-injection or centrifugal analyzers to insure rapid mixing of reagents and sample.
FIG. 6.13 Glucose oxidase/peroxidase assays – endpoint versus kinetic assays.
(A) Graphical analysis of an endpoint assay. (B) The final (endpoint) absorbances are plotted as a function of glucose concentration, yielding a straight line. (C) Initial rates of reactions are estimated by multiple measurements early in the assay (dotted lines in frame A), and plotted versus glucose concentration. Nonlinear plots, when obtained, are analyzed by computer.
Kinetic analyzers are inherently faster than endpoint assays because they estimate glucose concentration before the assay reaches its endpoint. These assays work because glucose oxidase and glucose dehydrogenase have a high Km for glucose. At the concentrations of glucose found in blood, the rate of the oxidase reaction is proportional to glucose concentration, i.e. in the first-order region of the Michaelis–Menten equation where the substrate concentration is less than the Km (see Fig. 6.4).
Most metabolism is catalyzed by biological catalysts called enzymes. Their catalytic activities are apparent at body temperature, and they are strictly regulated by several mechanisms.
Both covalent and noncovalent modifications are involved in this regulation and allow for efficient metabolic control. Enzyme activity can be inhibited (or activated) by synthetic compounds (drugs), exogenous compounds (toxins), and endogenous compounds (allosteric effectors).
Kinetic analyses of enzymatic reaction are beneficial for evaluating the biological role of enzymes and for elucidating their reaction mechanisms.
Assays of enzymes in blood are useful for diagnosis and monitoring of many clinical conditions.
Active learning
1. In a multistep sequence of enzymatic reactions, where is the most effective site for controlling the flux of substrate through the pathway? What effect will an inhibitor of a rate-limiting enzyme have on the concentration of substrates in a multistep pathway?
2. Most drugs are designed to inhibit specific enzymes in biological systems. The drug Prozac has had a profound effect on the medical treatment of depression. Review the history of development of Prozac, illustrating the importance of specificity in the mechanism of drug action.
3. Discuss some examples of reversible and irreversible enzyme inhibitors used in medical practice.
4. Knock-out mice are mice that lack a specific gene. Discuss the impact of KO mice on the direction of drug development in the pharmaceutical industry.
Further reading
Androutsopoulos, VP, Hernandez, AF, Liesivuori, J, et al. A mechanistic overview of health associated effects of low levels of organochlorine and organophosphorous pesticides. Toxicology. 2012.
Christenson, RH, Duh, SH. Methodological and analytic considerations for blood biomarkers. Prog Cardiovasc Dis. 2012; 55:25–33.
Claudino, WM, Goncalves, PH, di Leo, A, et al. Metabolomics in cancer: A bench-to-bedside intersection. Crit Rev Oncol Hematol. 2012.
DeFeo, EM, Wu, CL, McDougal, WS, et al. A decade in prostate cancer: from NMR to metabolomics. Nat Rev Urol. 2011; 8(6):301–311.
Lippi, G, Valentino, M, Cervellin, G. Laboratory diagnosis of acute pancreatitis: in search of the Holy Grail. Crit Rev Clin Lab Sci. 2012; 49:18–31.
Lopez-Otin, C, Matrisian, LM. Emerging roles of proteases in tumour suppression. Nat Rev Cancer. 2007; 7:800–808.
Niemela, O, Alatalo, P. Biomarkers of alcohol consumption and related liver disease. Scand J Clin Lab Invest. 2010; 70:305–312.
Öberg, D, Östenson, C-G. Performance of glucose dehydrogenase-and glucose oxidase-based blood glucose meters at high altitude and low temperature. Diabetes Care. 2005; 28:1261.
Spratt, BG. The 2011 Garrod Lecture: From penicillin-binding proteins to molecular endocrinology. J Antimicrob Chemother. 2012; 67:1578–1588.
Teicher, BA, Linehan, WM, Helman, LJ. Targeting cancer metabolism. Clin Cancer Res. 2012; 18:5537–5545.
Zhang, GF, Sadhukhan, S, Tochtrop, GP, et al. Metabolomics, pathway regulation, and pathway discovery. J Biol Chem. 2011; 286:23631–23635.
Clinical Enzymology. www.labtestsonline.org/.
International Federation of Clinical Chemistry and Laboratory Medicin. www.ifcc.org/
Chymotrypsin, mechanism of action. www.chembio.uoguelph.ca/educmat/chm258/lecture12.pdf.
Serine proteases. www.med.unibs.it/~marchesi/pps97/course/section12/serprot1.html.
Enzyme classification. www.chem.qmul.ac.uk/iubmb/enzyme/rules.html.
The Comprehensive Enzyme Information Syste. www.brenda-enzymes.info/
A Database of Enzyme Catalytic Mechanism. http://mbs.cbrc.jp/EzCatDB/
The Enzyme Databas. www.enzyme-database.org/
Enzyme nomenclature. www.chem.qmul.ac.uk/iubmb/enzyme/.
Enzyme nomenclature database. http://enzyme.expasy.org/.
Enzyme structures database. www.ebi.ac.uk/thornton-srv/databases/enzymes/.
IntEnz (Integrated relational Enzyme database). www.ebi.ac.uk/intenz/.
A resource portal for enzymes. www.enzymedirectory.com/.


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Joseph A.
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How do you write the perfect dating profile? Is there even such a thing? There are plenty of websites that let you know what or what not to put on your profile. On Reddit, women were asked about what they considered immediate deal breakers when scrolling through a man's dating profile.
Some of the top 25 deal breakers include:
-Being "too good" for dating sites
-Overuse of emojis
-Grossly Sexual Usernames
-Badmouthing your exes
-Having a weird obsession with your vehicle
-Using bad grammar
-Listing what you don't want
-Posting only shirtless or group pics
-Saying you don't read
-Referring to yourself as a "nice guy."
You can check out the rest of the instant deal breakers HERE.
Via Bustle


text:
Bandwidth is primarily a memory bandwidth benchmark, but it can also measure network bandwidth. It measures the maximum memory bandwidth of each part of the memory system, including main memory, L1, L2, and L3 caches, framebuffer memory, and register-to-register. For many tests, it performs both sequential memory accesses as well as random memory accesses to provide a more real-world performance estimate. The tests support Linux (Intel), Windows/Cygwin, and Mac OS X. Its core routines are in assembly for x86 and x86-64 architectures with both SSE4 and AVX support. Bandwidth also includes automatic graphing of the results, stored to a BMP image file. The network bandwidth tests support Linux, Mac OS X, and Windows/Cygwin.
AntiJOP is an anti-malware solution that recodes assembly language to remove JOP attack gadgets. JOP attacks on x86 often hinge on the availability of 0xFF bytes in preexisting code, which can be co-opted to serve as register-indirect call instructions. AntiJOP removes instances of 0xFF bytes that may exist, for example, in immediate values, MOD/RM bytes, etc.
A tool for securing DNS communications between a client and a DNS resolver.
A polyhedral extraction tool (PET).


text:
Pak calls in Army to protect diplomatic zone from protesters
Pakistan deployed Army in the sensitive diplomatic enclave after a protest over an anti-Islam film turned violent, leaving 86 people injured.
Islamabad: Pakistan on Thursday deployed Army in the sensitive diplomatic enclave after a protest over an anti-Islam film turned violent, leaving 86 people injured, including 36 policemen, as angry demonstrators tried to breach the high security area to reach the US embassy.
Members of student groups, including the Islami Jamiat-e-Talaba, began gathering outside the Red Zone in the heart of Islamabad, which includes the US embassy, Indian High Commission and missions of other countries as also sensitive government buildings, at around 2 pm in large numbers to protest against the anti-Islam film `Innocence of Muslims`.
The crowds swelled about two hours later as thousands of members of hardline religious groups, including Ahl-e-Sunnat Wal Jamaat and Jamaat-ud-Dawah, came to Islamabad from Rawalpindi in a rally.
The Indian High Commission is located less than a kilometre from the gate of the diplomatic enclave.
All Indians in the diplomatic area are safe and they are inside the country`s mission, sources said.
The protesters fought running battles with riot police for almost three hours. They lobbed stones at police, who used tear gas, rubber bullets and batons while trying to disperse them.
At least 36 policemen and 50 protesters were injured.
After police failed to bring the situation under control, the Interior Ministry called in the army to quell the protest.
The unrest lasted for five hours and came to an end after sunset.
The Army has taken over the security of the diplomatic area. More protests are expected to take place tomorrow.
About 25 protesters were arrested for trying to breach security barriers and scaling the walls of the diplomatic enclave.
The protesters burnt at least two police posts.
They gathered in large numbers near the five-star Serena Hotel, located a short distance from the diplomatic enclave.
Clerics held talks with top security officials and finalised a "deal" under which they will end the protest and the police will release the arrested people.


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A good wedding photographer captures timeless, beautiful images that you will have for life. Before signing a contract for your engagement and wedding albums, consider the following:
Determine the wedding photographer's aesthetic style
Search the wedding photographer's website to determine their photo style. Then, if you discover a photographer whose aesthetic syncs with yours, have a face to face meeting. Finally, view a wedding album that the photographer shot from start to finish to gauge his or her style.
Verify important wedding photography experience
Has the photographer shot a wedding like yours? If the photographer's portfolio features only sunny outdoor celebrations, he or she might not be a great fit for your Christmas-themed indoor wedding reception in December.
If you want a test run before the wedding with your favorite photographer, hire him or her for an engagement shoot. A pre wedding shoot is an opportunity to work out any kinks as well as test the photographer's shooting style and disposition.
Ask about the photographer's wedding photo packages and day rates
Some wedding packages cover everything from wedding albums and prints t0 a video; other are à la carte. Ask how many hours the photographer will spend with you shooting the wedding and the reception — nine hours is ideal.
If you have a large wedding party, ask if there will be a second shooter to give more detailed shots of your family and wedding party.
Determine your ideal wedding photo timeline
Wedding album planning requires a detailed timeline to execute properly. You will want to know when you can expect to receive everything from prints (average wait: three months) to your wedding album( up to a year.)
Since some wedding photographers limit the number of years that they keep wedding photos, check to see if your bridal photographer offers a CD of all the images in your wedding photo package.
The surefire way to get all the photos that you want is to choose the right photographer for your wedding — and have a detailed and comprehensive wedding photo plan.
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what to have when we are out...
Discussion in 'Slimming World' started by jade-h, 10 March 2009 Social URL.
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MiniMins.com is a weight loss support community helping each other on their weight loss journey. We have a multitude of forums, from Slimming World and Exante, to Success Stories. Click the logo at the top right to return to the forum home page at any time.


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Guide Price £197,000
3 Bedroom House Ref: EAXML398_1270724
Stanton Mortimer - Residential
80-81 High Street
North Yorkshire
United Kingdom
Tel: 01609 firstname.lastname@example.com
A substantial three storey mid terrace townhouse offering spacious, well appointed three bedroom, two bathroom accommodation in this popular residential area situated just off the Green in the sought after Romanby area of town convenient for local, shops, primary school and the main line rail station. Gas central heating is installed together with upvc double glazing whilst outside there is an attractive rear garden and integral Garage. An internal inspection is recommended. EPC Rating C 76
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1. Re: Error in accessing SQL DeveloperGary Graham-Oracle Dec 7, 2012 1:29 AM (in response to 978497)Hi Mahesh,
Make sure you point at a 32-bit 1.6 JDK in the SetJavaHome line of your
<SQLDev_Home>\sqldeveloper\sqldeveloper\bin\sqldeveloper.conffile. Alternately, delete that SetJavaHome line so you will get prompted to browse for it on next SQL Developer start-up.
If you had downloaded the Windows 32-bit - zip file includes the JDK1.6.0_35 from
you would never get prompted -- the default SetJavaHome line points at the JDK included in the download.
Hope this helps,
SQL Developer Team
2. Re: Error in accessing SQL Developer978497 Dec 7, 2012 10:33 AM (in response to Gary Graham-Oracle)Thanks for the help Gary.


text: Just so you are aware, if you are having any problems with Facebook it is because it is broken. No, its not your phone, your rom, or anything you are doing wrong, Facebook won't sync until HTC/Facebook fix it. That said, please no more new threads about how your facebook contacts wont sync as there are currently about a hundred on these forums alone.


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Ask a four year old "Where is space?" and they will likely reply "Up there!" Look in the Outer Space Treaty or virtually any other US law relating to space for a definition of "where is space?" and you're not going to do much better than the four year old's answer. Obviously the Earth ends and space begins somewhere but today, as it has been for the entirety of humanity's manned and unmanned exploration of "up there", there is no international legal definition of space; no clear indication of where space law applies! This ambiguity is a potential source of confusion and unease for aerospace companies and space farers because different nations (or the same nation) may apply different laws to the physically identical vehicles and flight profiles and may attempt to apply their laws to satellites in orbits that overfly their soil.
Within a year of the first ballooners taking to the skies, governments began applying the rule of law to flying vehicles. Long standing international law recognizes that all countries have the right to control the airspace above their lands, but somewhere above all nations airspace ends and space (or outer space, if you prefer) begins. Different laws apply which assert that this area "shall be free for exploration and use by all."
Internationally, there is not yet an established boundary marking where space begins. International efforts to define where space begins take three different approaches. The first approach seeks to define where space law applies from a physical prospective. The secod approach is functional, applying space law based on the characteristics of the vehicle involved. The third approach is to legally define space from an arbitrary standpoint that serves one or more sovereign nations' interests, or definition by fiat.
Physically defined "space"
Physical boundary layers for space are typically defined in terms of physical laws. The most famous "line in the sky" is the Kármán Line. Hungarian physicist Theodore von Kármán determined that at an altitude of approximately 100 km above sea level, the atmosphere becomes so thin that a vehicle would have to travel faster than orbital velocity to generate sufficient aerodynamic lift to be self supporting. But then it would be essentially orbiting the planet already, so why would it worry about generating enough lift to stay aloft? It's in orbit!
So, let's define space as the point where you can stay aloft only by achieving orbital velocity and call it a day; simple, right? Wrong. Even Kármán pointed out that his 100 km high line in the sky was approximate. The atmosphere is a dynamic system, thickening and thinning in response to myriad factors like solar output, local chemical composition, temperatures, and air currents. Depending on atmospheric conditions, a lifting body at altitudes significantly higher than 100 km might generate sufficient lift to stay aloft at sub-orbital velocities. And that's for a craft designed to be a lifting body! Not all spacecraft are lifting bodies, a lot of their physical profiles more closely resemble rocks, rather than 747s.
Another approach would be to define space at an altitude above which satellite orbits don't rapidly decay. At approximately 200 km, well above the planned apogee of SpaceShipTwo, the atmosphere is so thin that air resistance is almost negligible, but satellite orbits still rapidly decay without boosts from on board thrusters. Even at 300 to 400 km altitudes, where the Shuttle and the International Space Station orbit, regular station keeping thruster firings are required to avoid orbital decay due to atmospheric drag but it would seem ludicrous to define space in a manner that did not include the orbit of the International Space Station!
As far back as 1979, defining space at an altitude in the multi-hundreds of kilometers above sea level was discouraged from many quarters. The USSR proposed that future UN treaties addressing issues of space indicate that space start "at an altitude not exceeding 110 km above sea level." Others have suggested setting the boundary of space at an astonishing 1500 km above the Earth's surface. That would include virtually all of low Earth orbit!
Come back tomorrow when we'll explore two more approaches to legally defining space: the functional approach and the fiat approach.
Happy creating!
Update: Read part 2 here!


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DW Tournament: Round 4
My fictitious Deadliest Warrior tournament marches on and we get closer to the imaginary conclusion of an imaginary battle to see who is the greatest warrior of all time!
Round 4
Round 4 is upon us! After the bloody massacres and surprising upsets of round 3 it seems like armored warriors and those with the best long ranged weapons are rising to the top.
This tournament isn't seeded and the competitors aren't locked into place like an NCAA bracket which means the match ups can change from round to round. However, there are two distinct brackets (winner's and loser's) and within each bracket there are two divisions (modern and ancient).
-Loser's Bracket (Modern)
1-1 British Royal Gurkhas (c1984)
1-1 U.S. Rough Riders (c1895)
-Loser's Bracket (Ancient)
1-1 Mongol Warrior (c1220)
1-1 Aztec Jaguar (c1520)
2-1 Japanese Samurai (c1000)
-Winner's Bracket (Modern)
2-0 Boer Commandos (c1898)
2-0 Irish Republican Army (c1990)
1-1 Russian Spetsnaz (c2000)
2-0 U.S. Navy Seals (c1989)
-Winner's Bracket (Ancient)
2-0 Scottish Highlander (1297)
2-0 Persian Immortal (c500 BC)
2-0 Spanish Conquistador (c1520)
2-0 Spartan Warrior (c500 BC)
2-1 European Knight (c1200)
1-1 Egyptian Charioteer (c1400 BC)
2-0 Apache Warrior (1800)
-Loser's Bracket
Round 3 was a massacre as 8 more warriors were booted from the tournament, bringing the tally of defeated contestants up to 12: Yakuza, Maori, Ninja, Gladiator, Mafia, Zhou Warrior, Green Beret, Pirate, Shaolin Monk, Zulu, Taliban and Viking.
The Loser's bracket is nearing the end with only 5 contestants remaining. The Samurai gets a bye into round 5 seeing as he is the only warrior in the loser's bracket who has fought in all three rounds. That leaves only 2 match ups for this round.
Gurkha vs. Rough Riders: Fearsome B.A.F. infantry against hard-fighting U.S. volunteers.
Aztec Jaguar vs. Mongol Warrior: Elite warrior against unstoppable conqueror.
-Winner's Bracket
Three warriors were knocked out of the winner's bracket last round but 4 others return from their bye in round 3.
There's still a long way to go in the winner's bracket as 11 warriors remain, with 9 of those being undefeated. The Knight gets a bye into round 5 seeing as he is the only warrior in the winner's bracket who fought in all three rounds. That leaves 5 match ups for this round.
Boer Commandos vs. Navy SEALs: Turn of the century Militia against modern Special Forces.
Immortal vs. Apache: Persian Imperial Guard against Native American scalp hunter.
Spartan vs. Highlander: Perfect warrior of ancient Greece against powerful Scottish warrior.
Spetsnaz vs. IRA: Feared Russian anti-terrorist unit against determined Irish terrorist cell.
Conquistadors vs Egyptian Warrior: Spanish cavalry against Egyptian war chariot.
-Watch for Loser's Bracket results next week!
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GraphicRiver Car Interface Symbols 7550563
Category: Stock Vector | Comment: ( 0 )
GraphicRiver Car Interface Symbols 7550563
Stock Vector \ Web Element
Interface \ Icon \ Generation \ Fuel \ Gasoline \ Odometer \ Pump \ Safety \ Pressure
Stock Vector - Car Interface Symbols 7550563 by panyamail @ GraphicRiver
Stock Vector \ Web Element
Graphics Files Included: JPG Image, Vector EPS; Layered: No; Minimum Adobe CS Version: CS.
Vector illustration. Car interface symbols
Blank Ancient Parchment; Christmas Card; Vector Ticket; Abstract Layered Background; Wooden Plate with British flag; Wooden Plate; Old Ticket.
Keywords: airbag, alertness, and, battery, belt, brake, computer, connection, control, coupling, danger, dashboard, drop, electricity, engine, equipment, fuel, gasoline, generation, icon, interface, led, odometer, oil, panel, physical, power, pressure, pump, safety.


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Cassettes are rigid holders used in conventional and computed radiography (CR) for the screen film system and imaging plate respectively.
The back side of the cassette has a rubber or felt for adequate contact between screen film system or with the imaging plate. The front is made of low atomic number material (e.g. plastic or carbon) and the back is made of high atomic number material (e.g. lead) to reduce back scatter.
In case of conventional radiography, two screens are mounted on each side of the cassette, except in mammography, where a single screen is mounted on the back side. These cassettes have to loaded with film in dark room unlike the cassettes used in CR which can be loaded with imaging plate in light.
No cassette is used in direct digital radiography.
- 1. Curry TS, Dowdey JE, Murry RE. Christensen ́s physics of diagnostic radiology 4 Ed. Lippincott Williams & Wilkins. (1990) ISBN:0812113101. Read it at Google Books - Find it at Amazon
Related articles
X-ray physics
- x-ray production
- x-ray tubes
- tube rating
- interaction with matter
- filters
- beam collimators
- grids
- air gap technique
- cassette
- intensifying screen
- x-ray film
- image intensifier
- digital radiography
- digital image
- mammography
- x-ray artifacts
- radiation units
- radiation safety
- radiation detectors


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Pisos de obra nueva en Volpelleres
Appartment - Flat in RENT in BARCELONA situated in SANT CUGAT DEL VALLES in the zone of Vollpelleres.
Appartment - Flat Obra nueva of 91m2 with 3 bedrooms and with 2 bathrooms.
Dispose of: Terrace, Pool, Parking,
1.600 € / month
Brand new flat of 2 rooms and 1 bathroom, with terrace. Fully exterior, with semi open kitchen, 1 double bedroom and 1 single, 1 complete bathroom. High quality aluminum carpentry, lacquered interior doors, armored access door and video intercom, with heating and air conditioning by air-therm and LED lighting. Pre-installation of telephone and internet wiring and security measures. With saline treatment pool, a single garage, direct lift and community area. Community with concierge. Located in the Volpelleres area, near FFCC, motorways, shops and shopping center.