title: Study on the interaction of the toxic food additive carmoisine with serum albumins: a microcalorimetric investigation.
abstract: The interaction of the synthetic azo dye and food colorant carmoisine with human and bovine serum albumins was studied by microcalorimetric techniques. A complete thermodynamic profile of the interaction was obtained from isothermal titration calorimetry studies. The equilibrium constant of the complexation process was of the order of 10(6)M(-1) and the binding stoichiometry was found to be 1:1 with both the serum albumins. The binding was driven by negative standard molar enthalpy and positive standard molar entropy contributions. The binding affinity was lower at higher salt concentrations in both cases but the same was dominated by mostly non-electrostatic forces at all salt concentrations. The polyelectrolytic forces contributed only 5-8% of the total standard molar Gibbs energy change. The standard molar enthalpy change enhanced whereas the standard molar entropic contribution decreased with rise in temperature but they compensated each other to keep the standard molar Gibbs energy change almost invariant. The negative standard molar heat capacity values suggested the involvement of a significant hydrophobic contribution in the complexation process. Besides, enthalpy-entropy compensation phenomenon was also observed in both the systems. The thermal stability of the serum proteins was found to be remarkably enhanced on binding to carmoisine.
authors.affiliation: Biophysical Chemistry Laboratory, Chemistry Division, CSIR-Indian Institute of Chemical Biology Kolkata, 4, Raja S.C. Mullick Road Jadavpur, Kolkata 700 032, West Bengal, India.
authors.forename: Anirban
authors.initials: A
authors.lastname: Basu
authors.affiliation: Biophysical Chemistry Laboratory, Chemistry Division, CSIR-Indian Institute of Chemical Biology Kolkata, 4, Raja S.C. Mullick Road Jadavpur, Kolkata 700 032, West Bengal, India. Electronic address: gskumar@iicb.res.in.
authors.forename: Gopinatha Suresh
authors.initials: GS
authors.lastname: Kumar
mesh_terms: D002152:Calorimetry, Differential Scanning; D019277:Entropy; D005503:Food Additives / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D009282:Naphthalenesulfonates / Q000378:metabolism*; D011485:Protein Binding; D012709:Serum Albumin / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000378:metabolism*; D000075462:Serum Albumin, Human; D013816:Thermodynamics
chemical_list: C422455:ALB protein, human; D005503:Food Additives; D009282:Naphthalenesulfonates; D012709:Serum Albumin; D012710:Serum Albumin, Bovine; C006671:azo rubin S; D000075462:Serum Albumin, Human
keywords: Calorimetry; Carmoisine; Enthalpy–entropy compensation; Serum proteins