Investigation on the interaction between a heterocyclic aminal derivative, SBDC, and human serum albumin

The interaction between a novel promising drug (spiro[(2R,3R,4S)-4-benzyloxy-2,3-isopropylidene-dioxy-1-oxa-cyclopentane-5,5′-(2-benzoylmethylene-1,3-diaza-cyclohexane)] (SBDC)) and human serum albumin (HSA) under physiological conditions has been investigated by using fluorescence, absorption, and circular dichroism (CD) spectroscopic techniques in combination with protein–ligand docking study. It was observed that SBDC has a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The association constants of SBDC with HSA were determined at different temperatures based on fluorescence quenching results. The negative ΔH and positive ΔS values in case of SBDC–HSA complex showed that apart from an initial hydrophobic association, both van der Waals interactions and hydrogen bonding play a vital role in the binding of SBDC to HSA. The quantitative analysis data of CD spectra showed that the binding of SBDC to HSA induced conformational changes in HSA and the α-helix of 52.1% in free HSA increased to 55.7% in HSA–SBDC complex. The distance between donor (HSA) and acceptor (SBDC) was obtained according to the Förster's theory of non-radiation energy transfer. Data obtained by spectroscopic techniques and protein–ligand docking study suggested that SBDC binds to residues located in subdomain IIA of HSA.