Classification of proteins according to conformation

On the basis of optical rotatory dispersion data and other evidence, it was attempted to classify the proteins according to the conformation of their polypeptide chains. Three large groups of globular proteins emerge: 1. proteins with a high α‐helix content, 2. proteins with a low α‐helix content, and 3. the nonhelical globular proteins. Recent optical rotatory dispersion data have revealed that the nonhelical proteins can be subdivided into three subgroups: (a) proteins with an unknown order of type I (chymotrypsinogen, elastase, the luteinizing hormone, soyabean trypsin inhibitor, etc. ), (b) proteins with an unknown non‐helical order of type II (serum γ‐globulin, the B ENCE J ONES proteins), and (c) disordered proteins (phosvitin, histones in aqueous solutions). New results on the following proteins are reported: adenosine deaminase, arginase, bacterial α‐amylase, collagenase, conalbumin, glucose‐6‐phosphate dehydrogenase, glyoxalase, 20‐β‐hydroxysteroid dehydrogenase, isocitric dehydrogenase, nucleoside phosphorylase, ovalbumin, peroxidase, α‐phosphorylase, phosphotransacetylase, phosphoglycerate mutase, transferrin, triose phosphate isomerase, and xanthine oxidase. The M OFFITT constants (b 0 ) were determined, and the far ultraviolet C OTTON effects were studied. Since the rotatory power of completely disordered proteins at the wave length of 198 mμ is now known, the α‐helix content of the proteins exhibiting the positive maximum in the curves at 198 mμ can be calculated from the amplitude of the maximum using the poly‐α‐ L ‐glutamic acid as standard.