Aggregation, dissociation and denaturation of sesame (Sesamum indicum L.) alpha-globulin in cetyl trimethyl ammonium...

The behaviour of the major protein of sesame seed (Sesamum indicum L.) alpha-globulin has been studied in a cationic detergent, cetyl trimethyl ammonium bromide solution. Up to a critical detergent concentration the protein is precipitated from solution, above which redissolution of the protein is observed. Sedimentation velocity patterns indicate the presence of higher aggregates in the detergent concentration range 5 X 10(-5)--1 X 10(-3) M. These are considered to be the soluble precursors of the insoluble aggregates. Fluorescence measurements show that tryptophanyl groups of the protein which are in contact with the aqueous phase are perturbed by the detergent. The difference spectra of the protein in higher concentration of detergent indicate considerable red shift in the spectrum. Spectrophotometric titration of phenolic groups in 1 X 10(-2) M CTAB indicate that a conformational change in the protein has taken place.