Abstract

Mechanism of interaction of antipsychotic drug trifluoperazine dihydrochloride with bovine serum albumin (BSA) has been reported. Association constant for drug-protein binding showed that the interactions are non-covalent in nature and there are two independent binding sites. Binding studies in the presence of hydrophobic probe, 8-anilino-1-naphthalene sulphonic acid, sodium salt (ANS) showed that there is hydrophobic interaction between drug and ANS and they do not share common sites in BSA. Small decrease in critical micellar concentration (CMC) of anionic surfactant, sodium dodecyl sulphate (SDS) in the presence of drug showed that the ionic character of drug also contributes to binding. Stern-Volmer analysis of fluorescence quenching data showed that the fraction of fluorophore (protein) accessible to the quencher (drug), was close to unity indicating thereby that both tryptophan residues of BSA are involved in drug-protein interaction. The rate constant for quenching, greater than 1010M-1S-1, indicated that the TFP binding site is in close proximity to tryptophan residues of BSA.