The quenching mechanism of flueroscence of human serum albumin by Navirapine was discussed. The distance r between donor (human serum albumin) and acceptor (Navirapine) was obtained according to Forster theory of nonradiation energy transfer. Stern–Volmer plots indicated the presence of static component in the quenching mechanism. Fluorescence results revealed the presence of static type of quenching mechanism in the binding of Navirapine to HSA. The values of binding constant, K of Navirapine -HSA were evaluated at 288, 298 and 308K and were found to be 2.895, 1.935 and 1.586 x 104 L mol-1,respectively. The number of binding sites, n was noticed to be almost equal to unity thereby indicating the presence of a single class of binding site for Navirapine on HSA. The thermodynamic parameters obtained from data at different temperatures were calculated. Based on the thermodynamic parameters, ΔH0and ΔS0 nature of binding forces operating between HSA and Navirapine were proposed. Spectral results revealed the conformational changes in protein upon interaction.
