| Abstract: | Dielectric relaxation and viscosity measurements were performed on delipidated and relipidated samples of bovine serum albumin (BSA) at urea concentrations between O and 6M. By the combined interpretation of these two hydrodynamic methods the characterization of conformational changes of the molecule during urea denaturation is possible. The denaturation of delipidated BSA results from two mechanisms. The first one is a slow, time-dependent elongation of the molecule; the second one is a rapid swelling which becomes most pronounced at urea concentrations higher than 4M. For relipidated albumin, the slow elongation mechanism occurs but the presence of fatty acids protects the protein aganist molecular swelling. In both cases these conformational changes are accompanied by an increased disymmetry of charge repartition and a concomitant increase of the dipole moment. From these results it follows that lipidated albumin (as occurs under physiological conditions) is less sensitive to denaturation than delipidated albumin. |
