Ligand-human serum albumin analysis: the near-UV CD and UV-Vis spectroscopic studies.

Spectroscopic methods offer many new opportunities to study protein-ligand interactions. The aim of this study was to evaluate the possibility of using near-UV CD as well as UV-Vis spectroscopic techniques to study the interaction between human serum albumin (HSA) and markers of Sudlow's site I (warfarin, phenylbutazone) and II (ketoprofen, ibuprofen), as well as prednisolone and indapamide. In order to perform the planned measurements, near-UV CD spectropolarimetry and UV-Vis spectrophotometry have been used. It has been demonstrated that both techniques allow for rapid evaluation of non-covalent interactions between HSA and ligand, as well as identification of the HSA aromatic amino acid residues involved in this process. The near-UV CD spectroscopic data were more valuable than the analysis based on the second derivative of differential UV-Vis absorption spectra, especially for ligands with a non-specified binding site and low affinity towards HSA, such as prednisolone. The combination of both techniques makes it possible for comprehensive analysis of the interaction between HSA and ligands.