Fluorescence lifetime distribution of folded and unfolded proteins

E Gratton,G Mei,A Finazzi‐Agro,I Savini,N Silva,N Rosato

doi:10.1002/qua.560420522

Abstract

AbstractTime‐resolved fluorescence of single tryptophan proteins have demonstrated the complexity of protein dynamic and protein structure. In particular, for some single tryptophan proteins, their fluorescence decay is best described by a distribution of fluorescence lifetimes rather than one or two lifetimes. Such results have provided further confirmation that the protein system is one which fluctuates between a hierarchy of many conformational substates. With this scenario as a theoretical framework, the correlations between protein dynamic and structure are investigated by studying the time‐resolved fluorescence and anisotropy decay of holo and apo human superoxide dismutase (HSOD) at different denaturant concentrations. As a function of guanidine hydrochloride (GdHCl), the width of the fluorescence lifetime distribution of HSOD displays a maximum which is not coincident with the fully denatured form of HSOD at 6.5M GdHCl. Furthermore, the width of the fluorescence lifetime distribution for the fully denatured forms of holo and apo HSOD is greater than that of the native forms.

Highlights

One of the goals of internal protein dynamics studies is understanding the role of protein motions in determining protein function
There was an attempt to identify the events occurring in a given time scale with some functional property of the protein
We have demonstrated that for some single tryptophan proteins the number of discrete components necessary to describe the fluorescence decay must increase at low temperature

Summary

Introduction

One of the goals of internal protein dynamics studies is understanding the role of protein motions in determining protein function. From the physical point of view, proteins are mesoscopic systems that display unusual properties and provide an unique experimental system. Theoretical studies of internal protein motions center on the physical and chemical basis for the proper description and understanding of internal protein motions, whereas most of the experimental studies focus on the relationship of some specific detectable motion with some functional properties of the macromolecule. One of the most salient properties of protein dynamics is the enormous time scale over which dynamics can be detected. In one of the earlier reviews of protein dynamics [l], it was pointed out that protein time events can occur from picoseconds to several thousand seconds. There was an attempt to identify the events occurring in a given time scale with some functional property of the protein. A large amount of experimental data has accumulated to provide a better insight

Methods

Results

Conclusion