Editing Gel electrophoresis (section)

==Buffers==
Buffers in gel electrophoresis are used to provide ions that carry a current and to maintain the pH at a relatively constant value.
These buffers have plenty of ions in them, which is necessary for the passage of electricity through them. Something like distilled water or benzene contains few ions, which is not ideal for the use in electrophoresis.<ref>{{Cite book|title=fundamental laboratory approaches for biochemistry and biotechnology|last1=Ninfa|first1=Alexander J.|last2=Ballou|first2=David P.|last3=Benore|first3=Marilee|publisher=Wiley|year=2009|isbn=978-0470087664|location=Hoboken, NJ|pages=161}}</ref> There are a number of buffers used for electrophoresis. The most common being, for nucleic acids [[TAE buffer|Tris/Acetate/EDTA]] (TAE), [[TBE buffer|Tris/Borate/EDTA]] (TBE). Many other buffers have been proposed, e.g. [[LB buffer|lithium borate (LB)]], (which is rarely used based on Pubmed citations), isoelectric histidine, pK matched Good's buffers, etc.; in most cases the purported rationale is lower current (less heat) matched ion mobilities, which leads to longer buffer life. Borate is problematic as borate can polymerize or interact with cis diols such as those found in RNA. TAE has the lowest buffering capacity, but provides the best resolution for larger DNA. This means a lower voltage and more time, but a better product. 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).<ref name="pmid15351274">{{cite journal | author1=Brody JR | author2=Kern SE | title=History and principles of conductive media for standard DNA electrophoresis. | journal=Anal Biochem | year=2004 | volume=333 | issue=1 | pages=1–13 | pmid=15351274 | doi=10.1016/j.ab.2004.05.054 | pmc= | url=https://pubmed.ncbi.nlm.nih.gov/15351274 | access-date=23 March 2022 | archive-date=11 June 2022 | archive-url=https://web.archive.org/web/20220611043438/https://www.sciencedirect.com/science/article/abs/pii/S0003269704004932?via%3Dihub | url-status=live }}</ref>

Most SDS-PAGE protein separations are performed using a [[Gel electrophoresis of proteins#Buffer systems|"discontinuous" (or DISC) buffer system]] that significantly enhances the sharpness of the bands within the gel. During electrophoresis in a discontinuous gel system, an ion gradient is formed in the early stage of electrophoresis that causes all of the proteins to focus on a single sharp band in a process called [[isotachophoresis]]. Separation of the proteins by size is achieved in the lower, "resolving" region of the gel. The resolving gel typically has a much smaller pore size, which leads to a sieving effect that now determines the electrophoretic mobility of the proteins.