matched goods buffers, etc.; in most cases the purported rationale is lower current (less heat) and or matched ion mobilities, which leads to longer buffer life. Tris-phosphate buffer has high buffering capacity but cannot be used if DNA extracted is to be used in phosphate sensitive reaction. LB is relatively new and is ineffective in resolving fragments larger than 5 kbp; However, with its low conductivity, a much higher voltage could be used (up to 35 V/cm), which means a shorter analysis time for routine electrophoresis. As low as one base pair size difference could be resolved in 3% agarose gel with an extremely low conductivity medium (1 mM lithium borate). Other buffering system may be used in specific applications, for example, barbituric acid-sodium barbiturate or Tris-barbiturate buffers may be used for in agarose gel electrophoresis of proteins, for example in the detection of abnormal distribution of proteins. Applications Estimation of the size of DNA molecules following digestion with restriction enzymes, e.g., in restriction mapping of cloned DNA. Estimation of the DNA concentration by comparing the intensity of the nucleic acid band with the corresponding band of the size marker. Analysis of products of a polymerase chain reaction (PCR), e.g., in molecular genetic diagnosis or genetic fingerprinting Separation of DNA fragments for extraction and purification. Separation of restricted genomic DNA prior to Southern transfer, or of RNA prior to Northern transfer. Separation of proteins, for example, screening of protein abnormalities in clinical chemistry. Agarose gels are easily cast and handled compared to other matrices and nucleic acids are not chemically altered during electrophoresis. Samples are also easily recovered. After the experiment is finished, the resulting gel can be stored in a plastic bag in a refrigerator. Electrophoresis is performed in buffer solutions to reduce pH changes due to the electric field, which is important because the charge of DNA and RNA depends on pH, but running for too long can exhaust the buffering capacity of the solution. Further, different preparations of genetic material may not migrate consistently with each other, for morphological or other reasons. See also Gel electrophoresis Immunodiffusion, Immunoelectrophoresis SDD-AGE Northern blot SDS-polyacrylamide gel electrophoresis Southern blot References External links How to run a DNA or RNA gel Animation of gel analysis of DNA restriction fragments Video and article of agarose gel electrophoresis Step by step photos of running a gel and extracting DNA Drinking straw electrophoresis! A