Study on the interaction between promethazine hydrochloride and bovine serum albumin by fluorescence spectroscopy

The interaction between promethazine hydrochloride (PMT) and bovine serum albumin (BSA) in vitro was investigated by means of fluorescence spectroscopy and absorption spectroscopy The fluorescence of BSA was quenched remarkably by PMT and the quenching mechanism was considered as static quenching by forming a complex The association constants K-a and the number of binding sites n were calculated at different temperatures The BSA-PMT binding distance was determined to be less than 8 nm suggesting that energy transfer from BSA to PMT may occur The thermodynamic parameters of the interaction between PMT and BSA were measured according to the van t Hoff equation The enthalpy change (Delta H) and entropy change (Delta S) were calculated to be -23 62 kJ mol(-1) and -0 10 J mol(-1) K 1 respectively which indicated that the interaction of PMT with BSA was driven mainly by van der Waals forces and hydrogen bonds The binding process was a spontaneous process in which Gibbs free energy change (Delta G) was negative In addition the results of synchronous fluorescence pectra and three dimensional fluorescence pectra showed that binding of PMT with BSA can induce conformational changes in BSA (C) 2010 Elsevier B V All rights reserved