Spectral Studies on the Conformational Transitions of Bovine Insulin During Denaturant-induced Unfolding

doi:10.1007/s40242-014-3372-z

Abstract

Abstract:

Transitions among various molecule states and conformational changes of bovine insulin were investigated under different denaturing conditions by means of fluorescence phase diagrams, fluorescence quenching, 1-anilinonaphthalene-8-sulfonate(ANS) binding assay and circular dichroism(CD) spectra. In both guanidine hydrochloride(GuHCl)-and urea-denatured procedures, the spatial structure of insulin molecules changed from ordered states to relative unordered ones with the increasing of denaturant concentration. The GuHCl-denatured process followed a four-state model, for there were two intermediates existed in 2.0 and 6.0 mol/L GuHCl, respectively. Intermediate I₁ is more compact than the normal protein. And intermediate I₂ has lost most of the secondary structures. When GuHCl concentration was above 6.0 mol/L, the fluorophores originally existed in the internal of insulin molecules would expose to the surface. However, the urea-denatured process followed a three-state model, only one intermediate existed in 2.5 mol/L urea. During the urea-denatured procedure, the fluorophores originally existed in the internal of insulin molecules didn't expose to the surface.

Key words: Bovine insulin, Unfolding, Intermediate, Guanidine hydrochloride, Urea

JI Xu, MA Xiaojuan, BIAN Liujiao. Spectral Studies on the Conformational Transitions of Bovine Insulin During Denaturant-induced Unfolding[J]. Chemical Research in Chinese Universities, 2014, 30(2): 222-227.

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