Changes in protein stability upon chemical modification of lysine residues of bovine serum albumin by different reagents.

Using acetic anhydride, potassium cyanate and O-methyl isourea six chemically modified derivatives of bovine serum albumin with chemical modification on lysine side chains have been prepared. All the modified preparations were found to be homogeneous with respect to size and charge. Size exclusion chromatography on a calibrated Sephacryl S-300 column revealed that whereas acetylation and carbamylation produce significant increase in Stokes' radius, guanidination produces a slight decrease in Stokes' radius. Stability of native and different modified preparations was studied by following urea induced denaturation using the technique of uv difference spectroscopy and by measuring delta GDH2O and delta delta GD(urea)50% from these data. The order of stability of different preparations was found to be guanidinated > native > carbamylated > acetylated.