Multi-spectroscopic approaches combined with theoretical calculation to explore the intermolecular interaction of telmisartan with bovine serum albumin

Intermolecular interaction of telmisartan (TMST), an angiotensin II receptor antagonist with bovine serum albumin was explored in vitro by the means of multi-spectral approaches such as UV absorption, stead-state fluorescence, synchronous fluorescence, 3-D fluorescence, and infrared spectroscopies in combination with theoretical calculation. The UV absorption and steady-state fluorescence studies manifested that BSA interacted with TMST leading to the fluorescence of both BSA and TMST were quenched through a static quenching manner. It can be found that a TMST-BSA complex with the stoichiometric ratio of 1:1 was formed and the binding constant ( K b ) was 7.26 × 10 3  M −1 at 298 K(close to 10 4  M −1 ), suggesting TMST was a moderate affinity on BSA, and its value diminished with the rising temperature, predicating the binding interaction of TMST with BSA was an exothermic reaction. The results from the competitive exploration and molecular modeling have confirmed that TMST primarily inserted into the hydrophobic cavity between sub-domain IIA and IIB of BSA. The calculated Δ H and Δ S values on the base of van't Hoff equation were −40.02 kJ·mol −1 and −60.46 J·mol −1 ·K −1 , meaning that hydrogen bonds and van der Waals force played dominating roles in the TMST–BSA system. The results of FT-IR spectra suggested that the alteration in the secondary structure of BSA like the decline in the contents of α-helix and β-sheets and the increase in the random coil. Meantime, the obvious variety in the configuration of TMST occurred after binding to fit the configuration of binding pocket.