Effect of detergents on the conformation of proteins. III. Rotatory dispersion and C OTTON effect of relation to α‐helical order

The optical rotatory dispersion of ten proteins was investigated by using ultraviolet (UV) light of 220–250 mμ wave length. The spectropolarimeter had a powerful light source, two monochromators, and a very sensitive signal detecting unit. The effect of sodium decyl‐and dodecyl sulfate on the rotatory dispersion of the proteins was studied. It was found that the non‐helical globular proteins, such as serum γ‐globulin, BENCE‐JONES protein, and pepsin, did not exhibit a definite COTTON effect; and that such effect appeared in the presence of the detergents. Also it was found that the COTTON effect of the a‐helical proteins (serum albumin, insulin, growth hormone, lysozyme, bacterial α‐amylase, lactic dehydrogenase, and glutamic dehydrogenase) was diminished by the detergents to a greater or lesser extent. Dodecyl sulfate was in all instances more potent than decyl sulfate. The disulfide bonded a‐helical proteins were more resistant to the denaturing effect of the detergents than the cystine‐free bacterial amylase.