Interaction between Surface Active Agents and Proteins. I. Precipitations formed by Mixing Sodium Alkyl Sulfates and Egg Albumin

Abstract

Abstract (1) Precipitation reactions between SDS and egg albumin, SOS and egg albumin, and SBS and egg albumin were studied. There was an instant precipitation when SDS and egg albumin solutions were mixed, and when SOS and egg albumin solutions were mixed, but not when SBS and egg albumin solutions were mixed. Comparing the precipitation curve of the SDS-egg albumin system and that of the SOS-egg albumin system, we can find that both detergents form a complex having the same formula AD40 (A : albumin, D: detergent) in the region of protein excess, and therefore we can conclude that there is no difference between the reactivities of SDS and SOS toward egg albumin. On the contrary, in the region where redissolution of precipitate occurs, the precipitation curves do not coincide. This means that the two detergents have different powers to dissolve precipitate. In addition, when the concentration of SOS differs, the power to dissolve precipitate differs. (2) It was found electrophoretically that the complex is formed in turbid supernatants after centrifugation and also in transparent solutions the composition of which is in the region where no precipitation occurs. (3) Observing the precipitation curves of the system horse serum albumin-SDS and the system egg albumin-SDS, we can see that there is a region where no precipitation occurs when a great excess of serum albumin is used; but there is not such a region when a great excess of egg albumin is used. (4) We measured the lowering of the CMC of SDS and of SOS caused by the increase in the concentration of buffer solution. The lowering does not depend upon the kinds and pH’s of buffer solutions but upon the ionic strength of buffer solution which dissolves detergent.