RELATION OF AMINO ACID COMPOSITION AND MOFFITT PARAMETERS TO SECONDARY STRUCTURE OF PROTEINS

A statistical analysis of the relation between the amino acid composition of proteins and the amount of helical secondary structure as characterized by the Moffitt b0 parameter has shown a high degree of correlation of the b0 parameter with those amino acids whose homopolymers can form helical structures. Using the data for 107 proteins, a linear relation was found between b0 and the sum of the residue percentages of alanine, arginine, aspartic acid, cysteine, glutamic acid, leucine, andlysine. A statistical analysis of the Moffitt a0 parameter, on the other hand, showed no statistically significant grouping of amino acids in relation to the amount of secondary β structure in a protein. A plot of b0 versus a0–a 0R, where a 0R represents the a0 parameter for a fully denatured protein, for 55 proteins showed distinct nonlinearity. This nonlinearity was postulated to be due to presence of β structure, and a nomagram was constructed which allowed a semiquantitative estimate of the amount of helical and β‐type secondary structures from the b0 versus a0–a R0 plot. Copyright © 1969 John Wiley & Sons, Inc.