Calorimetric investigation on the interaction of sodium taurodeoxycholate with human serum albumin

Year: 2013

Authors: Bernazzani L., Ferrari C., Gianni P., Mollica V., Tombari E.

Autors Affiliation: Dipartimento di Chimica e Chimica Industriale, Universitą di Pisa, Via Risorgimento 35, 56126 Pisa, Italy; Istituto Nazionale di Ottica (INO-CNR), Area della Ricerca, via G. Moruzzi 1, 56124 Pisa, Italy; Istituto per i Processi Chimico-Fisici (IPCF-CNR), Area della Ricerca, via G. Moruzzi 1, 56124 Pisa, Italy

Abstract: The interaction between sodium taurodeoxycholate and human serum albumin was investigated in aqueous phosphate buffer at pH 7.2 through ITC titrations at 298.15K and 310.15K and TM-DSC measurements. The analysis of the ITC data required the previous determination of the thermodynamic properties of the self-associated oligomeric species of the bile salt in the buffer solution, according to a literature chemical model. Use of a computer program which allows the simultaneous determination of the stability constants and formation enthalpies of complexes indicated that albumin forms a strong 1-1 (salt to albumin) complex at low bile salt concentration and at least one larger complex at higher concentrations. In these larger complexes the protein seems to cooperatively bind a number of moles of the bile salt which increases with temperature. Thermodynamic data are provided for the formation of the most probable species which include a 4-1 complex at 298.15 K and an additional 9-1 complex at 310.15 K. TM-DSC data, while evidencing the partially reversible nature of the folding unfolding process and the stabilization of the protein by interaction with the bile salt, supported the stoichiometry of the complexes found by analysis of ITC data. (C) 2013 Elsevier B.V. All rights reserved.

Journal/Review: THERMOCHIMICA ACTA

Volume: 555      Pages from: 7  to: 16

More Information: This work was partially supported by the Ministero dell\’Universitą e della Ricerca (COFIN 2006). The authors are indebted to Prof. A. Sabatini and Prof. A. Vacca for making available the computer program, properly adapted, which calculates formation constants and enthalpies of complexes.
KeyWords: albumin; bile salts; self-aggregation; protein-surfactant complexes; isothermal titration calorimetry
DOI: 10.1016/j.tca.2012.12.016

Citations: 12
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