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Proceedings Paper

On the origin of non-exponential fluorescence decays in enzyme-ligand complex
Author(s): Jakub Wlodarczyk; Borys Kierdaszuk
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Paper Abstract

Complex fluorescence decays have usually been analyzed with the aid of a multi-exponential model, but interpretation of the individual exponential terms has not been adequately characterized. In such cases the intensity decays were also analyzed in terms of the continuous lifetime distribution as a consequence of an interaction of fluorophore with environment, conformational heterogeneity or their dynamical nature. We show that non-exponential fluorescence decay of the enzyme-ligand complexes may results from time dependent energy transport. The latter, to our opinion, may be accounted for by electron transport from the protein tyrosines to their neighbor residues. We introduce the time-dependent hopping rate in the form v(t)~(a+bt)-1. This in turn leads to the luminescence decay function in the form I(t)=Ioexp(-t1)(1+lt/γτ2). Such a decay function provides good fits to highly complex fluorescence decays. The power-like tail implies the time hierarchy in migration energy process due to the hierarchical energy-level structure. Moreover, such a power-like term is a manifestation of so called Tsallis nonextensive statistic and is suitable for description of the systems with long-range interactions, memory effect as well as with fluctuations of characteristic lifetime of fluorescence. The proposed decay function was applied in analysis of fluorescence decays of tyrosine protein, i.e. the enzyme purine nucleoside phosphorylase from E. coli in a complex with formycin A (an inhibitor) and orthophosphate (a co-substrate).

Paper Details

Date Published: 28 May 2004
PDF: 9 pages
Proc. SPIE 5330, Complex Dynamics, Fluctuations, Chaos, and Fractals in Biomedical Photonics, (28 May 2004); doi: 10.1117/12.535329
Show Author Affiliations
Jakub Wlodarczyk, Univ. of Warsaw (Poland)
Borys Kierdaszuk, Univ. of Warsaw (Poland)

Published in SPIE Proceedings Vol. 5330:
Complex Dynamics, Fluctuations, Chaos, and Fractals in Biomedical Photonics
Valery V. Tuchin, Editor(s)

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