Interactions of a few azole derivatives with a transport protein: role of heteroatoms.

The interaction of a few azole derivatives, 2-(4'-N,N-dimethylaminophenyl)benzimidazole, 2-(4'-N,N-dimethylaminophenyl)benzoxazole, 2-(4'-N,N-dimethylaminophenyl)oxazolo[4,5-b]pyridine with bovine serum albumin (BSA) were examined by absorption and fluorescence spectroscopy. The results were compared with the previously studied imidazopyridine derivative 2-(4'-N,N-dimethylaminophenyl)imidazo[4,5-b]pyridine. Displacement studies were carried out with site selective probes to locate the binding site of these ligands. The spectral shifts and the binding constant vary depending on the nature of the ligand. The fluorescence intensity of both oxazole derivatives 2-(4'-N,N-dimethylaminophenyl)benzoxazole and 2-(4'-N,N-dimethylaminophenyl) oxazolo[4,5-b]pyridine increases substantially in the presence of BSA, whereas the intensity of 2-(4'-N,N-dimethylaminophenyl)benzimidazole decreases. However, hypsochromic shift is observed in presence of BSA. The results obtained from the docking studies are also in good agreement with the experimental results. The location and orientation of binding depend upon the nature of the ligand. The studies revealed that apart from hydrophobic interaction, hydrogen bonding also plays a vital role in the molecular binding. Oxazoles have higher binding affinity than imidazoles and substitution of extra nitrogen further increases the binding affinity.