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Fluorescence Decay Heterogeneity Model Based on Electron Transfer Processes in an Enzyme-Ligand Complex

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Wlodarczyk J., Kierdaszuk B.

Acta Physica Polonica A

2005

vol. 107

issue 6

883-894

The models are described for complex fluorescence decay of tyrosine in proteins involving continuous distribution of fluorescence lifetimes and electron transfer processes. We introduce the analytical decay function with a power-like term, which provides good fits to highly complex fluorescence decays. Moreover, the power-like term in the proposed decay functions is a manifestation of so-called Tsallis nonextensive statistics and is suitable for description of the systems with long-range interactions, memory effect, as well as with fluctuations of the characteristic lifetime of fluorescence. The proposed decay functions were applied to analysis of fluorescence decays of tyrosine in a protein, i.e. the enzyme purine nucleoside phosphorylase from E. coli, free in aqueous solution and in the complex with formycin A (an inhibitor) and orthophosphate (a co-substrate), and demonstrated that both models reflect the enzyme-ligand interactions. Direct measure of heterogeneity of the enzyme systems is provided by a variance of fluorescence lifetime distribution. The possible number of deactivation channels and excited state mean lifetime can be easily derived without a priori knowledge of the complexity of studied system.

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1 Acta Physica Polonica A

1 2005

1 Kierdaszuk B.

1 Wlodarczyk J.

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Fluorescence Decay Heterogeneity Model Based on Electron Transfer Processes in an Enzyme-Ligand Complex