Fluorescence quenching kinetics in short polymer chains: Dependence on chain length |
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Authors: | X Wang E N Bodunov W M Nau |
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Institution: | 1.Departement Chemie,Universit?t Basel,Basel,Switzerland;2.Physics Department,Russian State Hydrometeorological University,St. Petersburg,Russia;3.School of Engineering and Science,International University Bremen,Bremen,Germany |
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Abstract: | Monte Carlo simulations of chain conformations and the diffusion equation were used to analyze the fluorescence kinetics of short polymer chains labeled with a probe and a quencher at opposite ends. In simulations, three chain models were considered: an ideal chain (without volume interactions); a self-avoiding chain taking into account the exclusive volume effect; and a self-avoiding chain with limited flexibility between nearest segments. For each model, end-to-end distance distribution functions were obtained, which were different from Gaussian ones. The distribution functions were used in a diffusion equation to simulate the fluorescence kinetics of the probe affected by intramolecular end-to-end collisions of short chains. The kinetics has been numerically calculated for a representative experimental system in a nonviscous solution. The simulated time-resolved fluorescence decays were monoexponential except at very short times (<2 ns). Diffusion coefficients were calculated for different chain models and different chain lengths. The experimental data could be reproduced by assuming systematically smaller end-to-end diffusion coefficients for the shorter chains. |
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