title: Optical spectroscopic exploration of binding of Cochineal Red A with two homologous serum albumins.
abstract: Cochineal Red A is a negatively charged synthetic azo food colorant and a potential carcinogen. We present here the study of binding of Cochineal Red A with two homologous serum albumins, human (HSA) and bovine (BSA), in aqueous pH 7.4 buffer by optical spectroscopic techniques. Protein intrinsic fluorescence quenching by Cochineal Red A occurs through ground-state static interaction and its binding with BSA is stronger than with HSA. The magnitudes of thermodynamic parameters suggest that dye binding occurs principally via electrostatic complexation. Site-marker competitive binding shows that Cochineal Red A binds primarily to site I of serum albumins. Circular dichroic spectra indicate that dye binding results in some conformational modification of serum albumins. Increased ionic strength of the medium results in lowering of binding. This study provides an important insight into possible means of removal of dye toxicity.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, India.
authors.forename: Priyanka
authors.initials: P
authors.lastname: Bolel
authors.forename: Niharendu
authors.initials: N
authors.lastname: Mahapatra
authors.forename: Mintu
authors.initials: M
authors.lastname: Halder
mesh_terms: D000818:Animals; D001391:Azo Compounds / Q000378:metabolism*; D001665:Binding Sites; D002417:Cattle; D002942:Circular Dichroism; D005505:Food Coloring Agents / Q000378:metabolism*; D006801:Humans; D009282:Naphthalenesulfonates; D009994:Osmolar Concentration; D011487:Protein Conformation; D012709:Serum Albumin / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D055672:Static Electricity; D013816:Thermodynamics
chemical_list: D001391:Azo Compounds; D005505:Food Coloring Agents; D009282:Naphthalenesulfonates; D012709:Serum Albumin; D012710:Serum Albumin, Bovine; C576297:ponceau 4R