title: Thermodynamics of the interaction of the food additive tartrazine with serum albumins: a microcalorimetric investigation.
abstract: The thermodynamics of the interaction of the food colourant tartrazine with two homologous serum proteins, HSA and BSA, were investigated, employing microcalorimetric techniques. At T=298.15K the equilibrium constants for the tartrazine-BSA and HSA complexation process were evaluated to be (1.92 ± 0.05) × 10(5)M(-1) and (1.04 ± 0.05) × 10(5)M(-1), respectively. The binding was driven by a large negative standard molar enthalpic contribution. The binding was dominated essentially by non-polyelectrolytic forces which remained largely invariant at all salt concentrations. The polyelectrolytic contribution was weak at all salt concentrations and accounted for only 6-18% of the total standard molar Gibbs energy change in the salt concentration range 10-50mM. The negative standard molar heat capacity values, in conjunction with the enthalpy-entropy compensation phenomenon observed, established the involvement of dominant hydrophobic forces in the complexation process. Tartrazine enhanced the stability of both serum albumins against thermal denaturation.
authors.affiliation: Biophysical Chemistry Laboratory, Chemistry Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700 032, India.
authors.forename: Anirban
authors.initials: A
authors.lastname: Basu
authors.affiliation: Biophysical Chemistry Laboratory, Chemistry Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700 032, India. Electronic address: gskumar@iicb.res.in.
authors.forename: Gopinatha Suresh
authors.initials: GS
authors.lastname: Kumar
mesh_terms: D002151:Calorimetry; D005503:Food Additives / Q000737:chemistry*; D005505:Food Coloring Agents / Q000009:adverse effects*; D012709:Serum Albumin / Q000737:chemistry*; D013645:Tartrazine / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D005503:Food Additives; D005505:Food Coloring Agents; D012709:Serum Albumin; D013645:Tartrazine
keywords: Polyelectrolytic forces; Serum albumins; Standard molar heat capacity; Tartrazine; Thermodynamics