Chlorpromazine interactions to sera albumins - A study by the quenching of fluorescence

Binding of chlorpromazine (CPZ) and hemin (Hmn) to human (HSA) and bovine (BSA) serum albumin was studied by fluorescence quenching technique. Intrinsic fluorescences of BSA and HSA were measured by selectively exciting their tryptophan residues. Gradual quenching was observed by titration of both proteins with CPZ and Hum. CPZ is a widely used anti-psychosis drug that causes severe side effects and strongly interacts with biomembranes, both in its lipidic and proteic regions. CPZ also interacts with blood components, influences bioavailability, and affects the function of several biomolecules. Albumin plays an important role in the transport and storage of hormones, ions, fatty acids and others substances, including CPZ, affecting the regulation of their plasmatic concentration. Hum is an important ferric residue of hemoglobin that binds within the hydrophobic region of albumin with great specificity. Hmn added to HSA and BSA solutions at a molar ratio of 1:1 quenched about half of their fluorescence. Stern-Volmer plots obtained from experiments carried out at 25 and 35 degreesC showed the quenching of fluorescence of HSA and BSA by CPZ to be a collisional phenomenon. Hum quenches fluorescence by a static process, which specifically indicates the formation of a complex. Our results suggest the prime binding site for CPZ and Hum on both HSA and BSA to be near tryptophan residues. (C) 2003 Elsevier B.V. All rights reserved.