THERMAL-DENATURATION OF BOVINE SERUM-ALBUMIN AND ITS OLIGOMERS AND DERIVATIVES PH-DEPENDENCE

In a previous paper, we report a preliminary DSC study on bovine (BSA) and human (HSA) serum albumins. However, at accurate HPLC analysis th e commercial proteins show three peaks: Fraction V-I, probably globuli ns (as declared by the producers), Fraction V-II (about 15-18% of the product) and Fraction V-III that represents pure BSA or HSA. A hypothe sis is that the Fraction II is a covalent dimer, or trimer or a mixtur e of both, generated during the scalf-life of the commercial product. Denaturation enthalpies of the purified Fraction V-III and Fraction V- II of BSA, have been determined calorimetrically, at changing the pH, and the results of both compared with those obtained on the untreated protein. Few calorimetric experiments have been also carried on a BSA monomer derivative with sulphidril group protected. Computer program h ave been developed for the deconvolution of exo- and endothermic effec ts and for the analysis of thermal denaturation profiles.