Abstract
The interactions of 3-carboxyphenoxathiin with Bovine Serum Albumin (BSA) and Human Serum Albumin (HSA) have been studied by fluorescence and circular dichroism spectroscopy. The binding of 3-carboxyphenoxathiin quenches the BSA and HSA fluorescence, revealing a 1:1 interaction with a binding constant of about 105 M-1. In addition, according to the synchronous fluorescence spectra of BSA and HSA in presence of 3-carboxyphenoxathiin, the tryptophan residues of the proteins are most perturbed by the binding process. Finally, the distance between the acceptor, 3-carboxyphenoxathiin, and the donor, BSA or HSA, was estimated on the basis of the Förster resonance energy transfer (FRET). The fluorescence results are correlated with those obtained from the circular dichroism spectra, which reveal the change of the albumin conformation during the interaction process.
Highlights
Especially bovine (BSA) and human (HSA), labeled with fluorescent probes are commonly used for the investigation of surface induced conformational changes in protein interfaces
In this paper we report the experimental study using steady state fluorescence and circular dichroism spectroscopy of the interaction of Bovine Serum Albumin (BSA)/Human Serum Albumin (HSA) with a carboxylic acid, 3-carboxyphenoxathiin (I, Figure 1)
When the concentrations of BSA/HSA were fixed at 3×10-6 M, and the concentration of I was gradually increased, the fluorescence intensity of the protein bands, BSA and HSA, decreased
Summary
Especially bovine (BSA) and human (HSA), labeled with fluorescent probes are commonly used for the investigation of surface induced conformational changes in protein interfaces. From a biopharmaceutical point of view, one of the most important biological functions of albumins is their ability to carry drugs, endogenous and exogenous substances. Numerous experiments with the Molecules 2010, 15 aim of characterizing the binding capacity and binding sites of albumins have been carried out. The spectral changes observed on the binding of fluorophores with proteins are important tools for the investigations of the topology of the binding sites, of the conformational changes and for the characterization of substrate to ligand binding [1]. Serum albumin being the major transporters binding protein for the drugs and other physiological substances, it is considered as a model for studying drug–protein interaction in vitro. Among the fluorophores, the aromatic or heteroaromatic carboxylic acids have been found suitable for this purpose [4]
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