Probing of possible olanzapine binding site on human serum albumin: Combination of spectroscopic methods and molecular dynamics simulation

Human serum albumin (HSA)-drug binding affinity is one of the major factors that determine the pharmacokinetics, halftime and bioavailability of drugs in various tissues. In the present study, the interaction of olanzapine (OLZ), a thienobenzodiazepine drug, administered for the treatment of schizophrenia and bipolar disorder, with HSA has been studied using spectroscopic methods such as ultraviolet absorbance, fluorescence and FTIR combined with computational procedures. Analyzing of the Stern-Volmer quenching data showed only one primary binding site on HSA with a binding constant of 4.12 x 10(4) M-1 at 298 K. Thermodynamic analyses showed enthalpy change (Delta H degrees) and entropy change (Delta S degrees) were 28.03 +/- 3.42 kJ mol(-1) and -25.52 +/- 11.52J mol(-1) K-1, respectively. Molecular docking results suggested the hydrophobic residues such as Val(216), Leu(327), Ala(350) and polar residues such as Glu(354) play an important role in the drug binding. Decrement in alpha-helix content of the protein upon OLZ binding was also confirmed by evidences provided by molecular dynamics simulation as well as FTIR spectroscopy. (C) 2014 Elsevier B.V. All rights reserved.