Conformations of amino acids in proteins

Ramachandran plots for all 20 amino acids were produced from 1042 protein subunits from the PDB, separately for those in SHEET, HELIX and Random coil. The classical Ramachandran plot needs to be revised in every detail. Most amino acids have two distinct conformations in the β-sheet region – one more frequent when the amino acids are really parts of SHEET and the other more typical for those occurring in Random coil. Amino acids in parallel and antiparallel β-strands have nearly the same conformations.