L-amino acids are the only isomers used in proteins as a result of evolution. The CORN law states that when the hydrogen atom is placed behind the alpha-carbon, the carboxyl group (CO) is followed by the R group (the specific side chain) and finally the amine group (N) in an anticlockwise direction .
- ↑ Jeremy M. Berg, John L. Tymoczko, Lubert Stryer (2011). Biochemsitry. 7th. ed. New York: WH Freeman and Company.