MECHANISM OF DENATURATION OF BOVINE SERUM-ALBUMIN BY DODECYL TRIMETHYLAMMONIUM BROMIDE

Bovine serum albumin (BSA) denaturation has been extensively studied b y different anionic and cationic surfactant. Dodecyl trimethylammonium bromide (DTAB) is a cationic surfactant, and it is suggested that it binds to the C-terminal section of BSA. In the present study, the ther modynamical denaturation of BSA by dodecyl trimethylammonium bromide ( DTAB) has been studied with various experimental techniques. Equilibri um dialysis, thermal denaturation, gel electrophoresis, titration micr ocalorimetry at pH 7, I = 0.005, and different temperatures were all p erformed. The enthalpy obtained from the van't Hoff relation and calor imetry method as well as electrophoresis results were utilized to expl ain the BSA tranistion state. Major findings included: the binding iso therm shifts at a low free concentrations of DTAB and at a higher temp erature suggest endothermicity for enthalpy of interaction; the calori metry enthalpy (Delta H-cal) of interaction was smaller than the van't Hoff enthalpy (Delta H-vH) for BSA-DTAB interaction; and the aggregat ion of BS increased with increasing DTAB concentration. This study sug gests that BSA unfolding induced by DTAB follows a multistate transiti on model and does not follow the two-state mechanism assumed for most single subunit proteins. Copyright (C) 1996 Elsevier Science Ltd