
pii helix

proteinukalil kaanapedunna oru tharam dvitheeya gadanayaanu paii helix (allengil π-helix). 1952-ll chrystallographer barbara loow kandethiyathum orikkal apoorvamaayi karuthappettirunnathumaaya hrasvamaaya π-helikkukal ariyappedunna protein gadanakalil 15 sathamaanathil kaanapedunnu, koodaathe orotta amino assid oru α-helixil ulppeduthunnathiloode uruthirinja parinamaparamaaya poruthappeduthalaannenna vishwasikkappedunnu. atharam ulppeduthalukal valare asthirappeduthunnathil, proteinu chila pravarthanaparamaaya nettangal nalkiyillengil π-helixukalude roopeekaranam thiranjedukkaan saadhyathayund. athinaal π-helikkukal saadhaaranayaayi proteinukalude pravartthana sthalangalkku sameepamaan kaanappedunnath.
staanderd ghadana.
oru staanderd π-helixile amino aasidukal valamkaiyyan helical gadanayilaanu krameekarichirikkunnathu. oro amino assid helixile 87° thirivumayi poruthappedunnu (i.iii.helixil oro thirivinum 4.1 avashishtangalundu), koodaathe helical aaksisil oru vivarthanavum undu. ettavum pradhanamaayi, oru amino aasidinte n-h group neratthe amino aasidinte "anchu" avashishtangalude c = o grouppumaayi oru hydrajan boond roopappeduthunnu; ithu aavarthichulla "i" + 5 "i" hydrajan bonting oru π-helix nirvachikkunnu. samanamaaya gadanakalil 310 helix ("i" + 3 "i" hydrajan bonting), α-helix ("i" + 4 "i" hydrajan bonting) enniva ulppedunnu.
π-helikkukalil bhooribhaagavum 7 avashishtangal maathramaan, avaa α-helikkukal allengil β-sheettukal pole muzhuvan ghadanayilum pathivayi aavarthikkunna ("φ", "si") dihedral konukal sweekarikkunnilla. ekkaaranathaal, π-helixile ellah avashishtangalkkum orotta dihedral moolyangal nalkunna paatapusthakangal thettidharippikkunnava. ennirunnaalum, chila saamaanyavalkkaranangal nadatthaam. onnaamatheyum avasaanatheyum avashishta jodikale ozhivaakkumbol, oru avashishtatthinte "si" dihedral konum "adutha" avashishtatthinte "φ" dihedral konum ekadesham −125° aayi vyathyaasappedunna vidhathil dihedral konukal nilanilkkunnu. aadyathethum avasaanathethumaaya avashishta jodikal yathaakramam −95°, −105° enninganeyaanu. thaarathamyathinu, oru 310 helixinte dihedral konukalude aakethuka ekadesham −75° aanu, athesamayam α-helixinte aakethuka ekadesham − 105° aanu. π-helixukalude avasaanathinu thottupinnaleyaanu prolin palappozhum kaanappedunnath. trans" isomerukalulla eathenkilum polypeptide helixinte avashishtangalkk ω enna bhramana koninulla pothuvaaya soothravaakyam samavaakyam nalkunnu.
idathu kaii ghadana.
thathwathil, ("φ", "si") dihedral konukalude adayaalam (55°, 70°) lake vipareethamaakkunnathiloode π-helixinte idathu kaii pathipp saadhyamaan. eee kapada-"mirror-imej" helixil oro teninum ekadesham ore ennam avashishtangalum (4.1) helical pichum () undu. amino assid avashishtangalkk ippozhum idathu kaii kairality ullathinaal ithu oru yadhaartha kannaadi chithramalla. swaabhaavikamaayi undaakunna amino aasidukalil glycine maathrame 55° polulla positteev "φ" dihedral konukal sweekarikkaan saadhyathayulloo ennathinaal proteinukalil neelamulla idathu kaii π-helix nireekshikkaan saadhyathayilla.
prakrithiyil π-helikkukal.
saadhaaranayaayi upayogikkunna dii. ezz. ezz. pii polulla automated secondary structure assainment prograamukal soochippikkunnathu <1 sathamaanam proteinukalil π-helix adangiyirikkunnu ennaanu. swaabhaavikamaayi sambhavikkunna π-helikkukal saadhaaranayaayi neelatthil cheruthaanu (7 muthal 10 vare avashishtangal), mikkavarum ellaayppozhum (i.iii. iruvashathum) α-helikkukal kondu chuttappettirikkunnu. athinaal mikkavarum ellah π-helixukalum nigoodamaanu, kaaranam π-helical avashishtangal α-helical allengil "tains" aayi thettayi nalkiyirikkunnu. protein gadanakalile π-helixukale shariyaayi vyaakhyaanikkunnathinaayi aduthide vikasippicha prograamukal ezhuthiyittundu, koodaathe 6 proteinukalil 1 (ekadesham 15 sathamaanam) ll kuranjathu oru π-helical segmentengilum adangiyittundennu avar kandethi.
swaabhaavika π-helixukale oru ghadanayil neelamulla α-helixinullil oru "balj" aayi eluppathil thirichariyaan kazhiyum. atharam helical baljukale munbu α-anyoorisangal, α-baljukal, π-baljukal, wide-tains, looping aouttukal, π-tains ennu vilichirunnu, ennaal vaasthavathil avayude aavarthanamaaya "i" + 5 → "i" hydrajan bondukal nirnnayikkunnathupole π-helixukalaanu. munpu nilavilundaayirunna oru α-helixil orotta adhika amino assid cherkkunnathiloodeyaanu eee baljukal allengil π-helikkukal srishtikkappedunnathenna thelivukal soochippikkunnu. athinaal, orotta amino assid ulppeduthunnathiloodeyum illaathaakkunnathiloodeyum α-helixukalum π-helixukalum parasparam parivartthanam cheyyaan kazhiyum. π-helixukalude thaarathamyena uyarnna thothum pravartthana sittukalumaayulla avayude sradheyamaaya bandhavum (i.iii. proteinukalude sajeevamaaya sittukal), α-helixukalum π-helixukalum thammil parasparam parivartthanam cheyyaanulla eee kazhivu parinaamatthinte kaalaghattatthil protein pravarthanakshamathayil maattam varuthunnathinum vaividyavalkkarikkunnathu oru pradhana samvidaanamaanu.
ferrittinukal, bacteria ferrittinukal, ruberithrinukal, klaas I raibo nucleotide reductaseukal, layikkunna meedhane monoxygenesukal enniva ulppedunna ferritin polulla suuppar faamiliyaan atharam oru parinaama samvidaanathaal valareyadhikam swaadheenikkappettathaayi thonnunna proteinukalude ettavum sradheyamaaya grouppukalil onnu. 13 (pii. dii. bii coode 1emdiai) ulla orotta ensaimil ettavum kooduthal π-helixukalude nilavile record holderanu layikkunna meedhane monoxygenase. ennirunnaalum, oru naa +/klu-dependent neuro traansmittar transporterinte (pii. dii. bii coode 2a65) baakteeriyal homologue 8 ulla orotta pepttaid shringalayil ettavum kooduthal π-helikkukalude record kaivasham vaykkunnu.

