Peer-Reviewed Journal Details
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Togashi, D.M.; Ryder, A.G.;O'Shaughnessy, D.;
2010
March
Journal Of Fluorescence
Monitoring Local Unfolding of Bovine Serum Albumin During Denaturation Using Steady-State and Time-Resolved Fluorescence Spectroscopy
Published
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Optional Fields
Protein Bovine serum albumin Fluorescence ANS Gaussian lifetime distribution Three-state transition model TRYPTOPHAN FLUORESCENCE GUANIDINE-HYDROCHLORIDE ALPHA-CHYMOTRYPSIN ENERGY-TRANSFER PROTEIN BINDING PROBES SITE STABILITY MECHANISM
20
441
452
In a previous report (J. Fluoresc. 16, 153, 2006) we studied the chaotropiclly induced denaturation of Bovine Serum Albumin (BSA) using the fluorescence decay kinetics at different stages in the denaturation of BSA by guanidinium hydrochloride (GuHCl). In this work, we gain a more detailed insight into the BSA denaturation process by investigating the thermodynamics of the process. Structural changes were monitored spectrophotometrically via the intrinsic protein fluorescence from tryptophan residues, and the extrinsic fluorescence from 1,8-anilinonaphthalene sulphonate (ANS). ANS tends to locate in a variety of binding sites in BSA which are located in different domains, and these can be selectively populated using different, 1:1 and 1:10 molar ratios of BSA to ANS. The data from steady-state and time-resolved fluorescence spectroscopy were analyzed using thermodynamic two-state and three-state models and the lifetime data clearly indicated the presence of an intermediate state during denaturation. A global analysis using non-linear regression gave a Delta G(H2O,D)(0) = 6.7 kcal.mol(-1) for the complete unfolding of the BSA-ANS complexes, and a Delta G(H2O,I)(0) = 0.9 kcal.mol(-1) for the first step to the intermediate. Therefore, the unfolding energy of the intermediate, which appears mostly at intermediate GuHCl concentrations (1.0 to 1.5 M), to the denatured state, is 5.8 kcal.mol(-1). The lifetime analysis of the BSA-ANS complexes also shows clearly that there are differences in stability of the BSA domains, with domain III unfolding first at low GuHCl concentrations (<1.5 M).
DOI 10.1007/s10895-009-0566-8
Grant Details
This work was supported by funding from Science Foundation Ireland (Principal Investigator grant number 02/ IN.1/M231 to AGR) and the National Biophotonics Imaging Platform, an Irish Higher Education Authority Programme for Research in Third Level Institutions supported project.
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