EFFECT OF SODIUM DODECYL SULFATE, ACID, ALKALI, UREA AND GUANIDINE HYDROCHLORIDE ON THE CIRCULAR DICHROISM OF α‐GLOBULIN OF SESAMUM INDICUM L

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Abstract
The circular dichroic spectra of .alpha.-globulin [the major storage protein of sesame seed, S. indicum L.] were obtained under various solution conditions of sodium dodecyl sulfate [SDS], acid, alkali, urea and guanidine hydrochloride. The protein in phosphate buffer pH 7.4, 0.2 M has .apprx. 25% .beta.-structure and 5% .alpha.-helix, the rest being aperiodic or irregular structure. SDS induced more .alpha.-helical structure in the protein. The protein had nearly 20% .alpha.-helix at 1 .times. 10-2 M SDS. At extreme acid or alkaline pH, the protein had no .alpha.-helix, with .beta.-structure decreasing with further extremes of pH. The protein is represented by 100% aperiodic structure in 6.6 M urea and in 6.0 M guanidine hydrochloride solutions. The above results are discussed in view of some of the earlier results with regard to the association-dissociation and denaturation behavior of .alpha.-globulin under various solution conditions.