Denaturation study of bovine serum albumin induced by guanidine chloride or urea by microcalorimetry

Abstract

The denaturation of bovine serum albumin (BSA) induced by guanidine chloride or urea at different pH values was studied by isothermal microcalorimetry measurements at 30°C. The simple bonding model, which was developed by Privalov, was employed to obtain the apparent bonding constant K, the apparent singular bonding Gibbs bonding energy ΔG and the total Gibbs energy ΔG(a) between the protein and denaturant, from analysis of the calorimetric data. Furthermore, linear extrapolation at the midpoint of transition was employed to determine the apparent denaturation enthalpy ΔH_d. The results showed that for guanidine chloride, the bonding between BSA and guanidine chloride could proceed more easily in an alkaline condition, and the apparent denaturation enthalpy ΔH_d of BSA due to guanidine chloride was 350 kJ·mol^–1 at pH 6.97 and 7.05, while it was 275 kJ·mol^–1 at pH 9.30, which indicated that BSA was more stabilized in a neutral condition. However, for urea, the bonding between BSA and urea could proceed more easily in an acidic condition, and the apparent denaturation enthalpy ΔH_d of BSA due to urea was 295 kJ·mol^–1 at pH 6.97, while it was 230 kJ·mol^–1 at pH 7.05 and 9.30. The results indicate that the degree of expansion of BSA in the two denaturants is different.

Keywords

bovine serum albumin / isothermal microcalorimetry / guanidine chloride / urea / denaturation

References

[1] Chilom G, Chilom O, Telea C, Visan T. A calorimetric study of bovine serum albumin interaction with urea. Rev Roumaine Chim, 2000, 45(11): 989–993

[2] Watlaufer D B, Malik S K, Stoller L, Coffin R L. Nonpolar group participation in the denaturation of proteins by urea and guanidinium salts. Model compound studies. J Am Chem Soc,1964, 86(3): 508–514

[3] Vanzi F, Madan B, Sharp K. Effect of protein denaturants urea and guanidinium on water structure: a structural and thermodynamic study. J Am Chem Soc, 1998, 120(41): 10748–10753

[4] Zou Q, Habermann-Rottinghaus S M, Murphy K P. Urea effects on protein stability: Hydrogen bonding and hydrophobic effect. Proteins: Structure, Function and Genetics, 1998, 31(2): 107–115

[5] Schellman J A. The thermodynamics of solvent exchange. Biopolymers, 1994, 34(8): 1015–1026

[6] Privalov P L, Khechinashvili N N. A thermodynamic approach to the problem of stabilization of globular protein structure: a calorimetric study. J Mol Biol, 1974, 86(3): 665–684

[7] Kinsella J E, Whitehead D M. Protein in whey: chemical, physical, and functional properties. Advances in Food and Nutrition Research, 1989, 33: 343–348

[8] Moosavi-Movahedi A A, Bordbar A K, Taleshi A A, Naderimanesh H M, Ghadam P. Mechanism of denaturation of bovine serum albumin by dodecyl trimethylammonium bromide. Biochem Cell Biol, 1996, 28(9): 991–998

[9] Yamasaki M, Yano H, Aoki K. Differential scanning calorimetric studies on bovine serum albumin: I. Effects of pH and ionic strength. BioMacromolecules, 1990, 12(4): 263–268

[10] Chen D, Lu Y, Xie G, Zhang S. Study on the interactions of bovine serum albumin in aqueous NaCl solution by osmotic. Chemical Research and Application, 2004, 16 (3): 327–329 (in Chinese)

[11] Stokes R H. Thermodynamics of aqueous urea solutions. Aust J Chem, 1967, 20(10): 2087–2100

[12] Barone G, Delvecchio P, Fessas D, Giancola C, Graziano G. The deconvolution of multi-state transition DSC curves of biological macromolecules: bovine serum albumin and bovine seminal ribonuclease, Thermochim Acta, 1993, 227(38): 185–195

[13] Fang Y Y, Hu X G, Yu L, Li W B, Lin R S. Study on Thermal Denaturation of Lysozyme by DSC. Acta Physico-Chimica Sinica, 2007, 23(1): 84–87 (in Chinese)

RIGHTS & PERMISSIONS

Higher Education Press and Springer-Verlag Berlin Heidelberg