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Proceedings Paper

Fluorescence studies with conformationally constrained tryptophan analogs: implications on the mechanisms of intramolecular quenching
Author(s): Maurice R. Eftink; D. Hu; Y. W. Jia
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Paper Abstract

The fluorescence properties of a set of tryptophan analogs, including several that are conformationally restricted, is reported. The conformationally restricted analogs include tetrahydrocarboline-3-carboxylic acid, 3-amino-3-carboxytetrahydrocarbazole, 3- aminotetrahydrocarbazole, and 3-carboxytetrahydrocarbazole. Steady-state and time-resolved measurements were made. The fluorescence decay of most of the conformationally restricted analogs is a bi-exponential. The fluorescence quantum yield and average lifetime of the restricted analogs is a bi-exponential. The fluorescence quantum yield and average lifetime of the restricted analogs are higher than the values for tryptophan and corresponding flexible tryptophan analogs. This indicates that the effective rate constant for intramolecular non- radiative (quenching) processes, knx, is smaller for the restricted tryptophan analogs than for the flexible analogs. For a series of flexible analogs, having a bifunctional side chain, there is synergism between the two functional groups (i.e., (alpha) -NH3+ and (alpha) -CO2- groups) in determining the effective knx. Potential mechanisms for intramolecular quenching mechanisms, which contribute to knx, include proton transfer from a side chain ammonium group to position four of the excited indole ring and charge transfer from the excited indole ring to a side chain acceptor group. By measuring the rate of photo-induced isotope exchange into position four of an analog's indole ring, we have estimated the contribution of proton transfer quenching to the total intramolecular quenching rate constant for several flexible tryptophan derivatives.

Paper Details

Date Published: 1 April 1992
PDF: 6 pages
Proc. SPIE 1640, Time-Resolved Laser Spectroscopy in Biochemistry III, (1 April 1992); doi: 10.1117/12.58198
Show Author Affiliations
Maurice R. Eftink, Univ. of Mississippi (United States)
D. Hu, Univ. of Mississippi (United States)
Y. W. Jia, Univ. of Chicago (United States)

Published in SPIE Proceedings Vol. 1640:
Time-Resolved Laser Spectroscopy in Biochemistry III
Joseph R. Lakowicz, Editor(s)

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