Thermodynamic analysis of thymoquinone binding to human serum albumin.

The interaction of thymoquinone (TQ) with human serum albumin (HAS) in physiological buffer (pH=7.0) was studied at four temperatures in the range 25-50 °C using fluorescence quenching study. The binding parameters were determined by Scatchard and Stern-Volmer models. Fluorescence quenching data revealed that the binding constants (Ksc) are 1.71×10(4), 1.08×10(4), 1.03×10(4) and 0.969×10(4) M(-1) at 298, 303, 313 and 323 K, respectively (on the basis of Scatchard model). The thermodynamic parameters ΔG°, ΔH° and ΔS° were calculated the results indicated that the hydrogen bonding and hydrophobic interactions were the predominant intermolecular factors in stabilizing the TQ-HSA complex. The distance between donor (HSA) and acceptor (TQ) was calculated to be 3.26 nm based on Förster's non-radiative energy transfer theory. Published by Elsevier B.V.