Multispectral and computational probing of the interactions between sitagliptin and serum albumin

The binding of sitagliptin (SIT), an anti-diabetic drug, to human and bovine serum albumin (HSA and BSA; main serum transport proteins) was investigated using various spectroscopic and molecular docking techniques. The fluorescence data demonstrated that SIT quenched inherent fluorescence of these proteins through the formation of SIT-HSA/BSA complexes. The number of binding sites was obtained (~1) and binding constant (Kb) and effective quenching constant (Ka) were calculated as 104 for both systems. Based on thermodynamic parameters, the van der Waals forces and hydrogen bonding were the most important forces in the interactions between HSA/BSA and SIT, and the complex formation processes were spontaneous. The results of UV–vis absorption and FT-IR spectroscopic revealed that SIT induces small conformational changes in the structure of the proteins (HSA/BSA). The synchronous fluorescence (SF) spectroscopy demonstrated that the binding of SIT with HSA/BSA had no effect on the polarity around Trp and Tyr residues. The CD spectra showed changes in the secondary and tertiary structures of both proteins with a decrease in α-helices contents and an increase in β-turn structures. The molecular docking and spectroscopic data verified the binding mechanisms between SIT and HSA/BSA, and revealed that SIT completely fits into the hydrophobic cavity between domain II and domain III of these proteins. [Display omitted] •Interaction between Sitagliptin (SIT) and serum albumins was investigated by experimental and theoretical methods.•The fluorescence quenching mechanism of HSA/BSA by SIT was static quenching.•van der Waals forces and hydrogen bonding play main role in the complex formation between HSA/BSA and SIT.•Molecular docking studies were in good agreement with experimental analysis.