Quenching of the intrinsic fluorescence of bovine serum albumin by chlorpromazine and hemin

Abstract

The binding of chlorpromazine (CPZ) and hemin to bovine serum albumin was studied by the fluorescence quenching technique. CPZ is a widely used anti-psychotic drug that interacts with blood components, influences bioavailability, and affects function of several biomolecules. Hemin is an important ferric residue of hemoglobin that binds within the hydrophobic region of albumin with high specificity. Quenching of the intrinsic fluorescence of bovine serum albumin (BSA) was observed by selectively exciting tryptophan residues at 290 nm. Emission spectra were recorded in the range from 300 to 450 nm for each quencher addition. Stern-Volmer graphs were plotted, and the quenching constant estimated for BSA solution titrated with hemin at 25ºC was 1.44 (± 0.05) x 10 5 M -1 . Results showed that bovine albumin tryptophans are not equally accessible to CPZ, in agreement with the idea that polar or charged quenchers have more affinity for amino acid residues on the outer wall of the protein. Hemin added to albumin solution at a molar ratio of 1:1 quenched about 25% of their fluorescence. The quenching effect of CPZ on albumin-hemin solution was stronger than on pure BSA. This increase can be the result of combined conformational changes in the structure of albumin caused firstly by hemin and then by CPZ. Our results suggest that the primary binding site for hemin on bovine albumin may be located asymmetrically between the two tryptophans along the sequence formed by subdomains IB and IIA, closer to tryptophan residue 212.

Interaction of N-nitrosodiethylamine/bovine serum albumin complexes with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine monolayers at the air–water interface

“…In this direction, some researchers have been interested in understanding the interaction of BSA and human serum albumin (HSA) with different ligands [27][28][29]. In recent experiments [30], we have investigated the interactions between N -nitrosodiethylamine (NDA) and BSA at the air-water and chloroform-water interfaces using axisymmetric drop tensiometry, fluorescence, and circular dichroism.…”

Interaction of anthracene and its oxidative derivatives with human serum albumin.

“…In a recent paper Epps et al (1999) studied the association constants and found the following values: for high affinity drugs: 0.45 and 2.08 × 10 6 M -1 and for low-affinity 0.054 × 10 6 M -1 . The studies were also conducted with bovine serum albumin and the following values of the constants were obtained for hemin -50 × 10 6 M -1 (Silva et al, 2004) and for the antibiotic Gatifloxacin 0.1 × 10 6 M -1 (Guo et al, 2004).…”

“…: Chloropromazine (three aromatic rings), Ibuprofen (one ring, -COOH), Oxazepan (two rings, =O, -OH), Warfarin (three rings, =O, -OH), Tolmetin (one ring, -COOH) as well as Ochratoxin (two rings -OH, =O) and its derivatives, hydroquinone and on O-methylated derivative. All these drugs were shown to bind either in subdomain IIA or IIIA (Epps et al, 1995;Qiu et al, 1998;Perry et al, 2003;Silva et al, 2004).…”

Purification and physico-chemical study of serum albumins of two neotropical fish species from the São Francisco River Bassin, Brazil

“…Much data about quantity and structure of mammalian albumins, mainly bovine (BSA) and human (HSA) serum albumin, can be found in literature (Silva et al 2004a, 2004b, 2004c, Bertucci and Domenici 2002, Kragh-Hansen 1990, but very few information about fish albumin is available (Silva et al 2009a(Silva et al , 2009b. The shortage of data about fish albumin makes to establish a pattern a difficult task, even so for the same family (Perrier et al 1974, Davidson et al 1989.…”