The Peptide Bond is Planar
The 20 amino acids specified by the genetic code are linked into proteins by the peptide bond, as illustrated here by the dipeptide, alanylserine. Complicated names are avoided by using the three-letter (Ala-Ser) or one-letter (A-S) abbreviations, starting with the N-terminal residue, which is at the left.
the peptide bond. The partial double bond of the peptide bond prevents free rotation around the bond. The atoms are now colored by their formal charge to represent where the charge is delocalized. As a result, the six atoms that make up the peptide group lie in the same plane.