The distribution of the values of the dihedral angles (χj) in the side group conformations of various amino acid residues in the three proteins myoglobin, lysozyme and tosyl‐α.‐chomotrypsin has been analysed. The observations in these protein structures are found to agree well with the theoretical distribution worked out on the basis of contact criteria and the number of allowed conformations of each category. The nature of the conformations are, in general, similar to those observed in simple amino acid structures. Hydrogen‐bonding interactions between side group and backbone seem to play a significant role in determining the conformations of certain polar side groups like serine, threonine, and aspartic acid.
Chanhrasekaran et al. (1970) studied this question.