Biophysical and computational approaches to unravel the molecular interaction mechanism of bromodeoxyuridine, a proliferative marker with human serum albumin

摘要

The interaction of a nucleoside analogue bromodeoxyuridine (BrdU) with human serum albumin (HSA) was studied to investigate the binding phenomenon and analyse the protein conformation upon BrdU binding. Multiple spectroscopic techniques, viz. intrinsic and 3-D fluorescence, UV-Vis absorption, and circular dichroism (CD) spectroscopy along with molecular docking were used. Decrease in the Stern-Volmer constant (K-sv) as well as the association constant (K-a) with increase in temperature suggested BrdU-HSA complex formation. Intermediate binding affinity between BrdU and HSA was evident from the K-a values (2.49-3.97 x 10(4) mol(-1) dm(3)), while BrdU-HSA complex formation was driven by hydrophobic and van der Waals interactions along with hydrogen bonds, as revealed by thermodynamic data (Delta S = + 28.48 J mol(-1) K-1; Delta H = - 17.16 kJ mol(-1)). Minor changes occur in both secondary and tertiary structures as well as in the fluorophores' microenvironment of HSA, as recognized from the CD spectral results in the far-UV and the near-UV regions and 3-D fluorescence spectra, respectively. Use of site markers (warfarin and indomethacin for site I; diazepam for site II) as well as docking results suggested BrdU binding to both site I (more preferred) and site II, located in subdomains IIA and IIIA, respectively, of HSA. Graphic abstract