Electron-Donating Strengths of Side Chains in the Determination of Protein Structure

摘要

It is well established that the structure of proteins is determined by their amino acid sequences. A hypothesis for the presence of an induction component in the short range interaction that determines protein secondary structure was suggested in 1964 and now further extended. This hypothesis is based on the assumptions: (1) that peptide-amide to peptide-amide H bonds in alpha-helical( and Beta-structure) segments of globular proteins are stronger than peptide-amide to water H bonds; (2) that the amide C -O double bond group is much more polarizable than the amide NH groups; (3) that is is primarily the basicity of the C-O double bond groups rather than the acidity of the NH groups that determine the strength of the peptide-amide to peptide-amide H bonds; and (4) that the electron-donating strength of each amino acid side chain determines the basicity of its own backbone peptide C - 0 double bond group and hence its preferred secondary structure (as well as the secondary structures of near neighboring peptide chains).