Interaction of benzodiazepine derivatives with bovine serum albumin-II. Circular dichroism studies.

Abstract The interaction of benzodiazepine derivatives with bovine serum albumin (BSA) was studied by circular dichroism (CD) measurements. Most of the investigated benzoidiazepines show biphasic extrinsic Cotton effects, which are largely influenced by raising pH from 6.60 to 8.20. Quantitative estimation of the CD data pointed out that there are several binding sites on the BSA molecule. The CD data do not differ very much from those found for the interaction of the drugs with human serum albumin (HSA). Therefore it is suggested that at least a part of the benzodiazepine binding sites on the BSA molecule has similar properties to the single binding site on the HSA molecule. The extrinsic Cotton effects of the benzodiazepines in the presence of BSA are influenced by fatty acids and sodium dodecyl sulfate in a similar way as by the pH-value of the solution. This is explained by a similar influence of the substances and of pH on the protein conformation.