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Proceedings Paper

Phosphorescence from tryptophan and tryptophan analogs in the solid state
Author(s): Colin McCaul; Richard D. Ludescher
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Paper Abstract

Tryptophan phosphorescence provides a long-lived optical signal whose lifetime and quantum yield are sensitive to the local environment of the protein The phosphorescence from tryptophan analogs, however, has not been studied. We report here data on the room temperature phosphorescence of tryptophan, 4-, 5-, and 6-fluorotryptophan, and 5- bromotryptophan embedded in sucrose glasses. The absorption of the analogs was either blue-shifted (4-F-trp), markedly red- shifted (5-F-trp and 5-Br-trp), or not shifted (6-F-trp) with respect to tryptophan. The phosphorescence emission spectra of all analogs were red-shifted compared to trp (442 nm) with maxima at 446 nm (5-F), 451 nm (6-F), 452 nm (5-Br), and 469 nm (4-F). The 5-F and 6-F analogs had emission intensities similar to tryptophan (relative quantum yields of 0.68 and 0.91, respectively), while the emission intensities of the 4-F and 5-Br analogs were much lower (relative quantum yields of 0.039 and 0.022, respectively). All analogs exhibited complex decay behavior which required several exponentials for an adequate fit. The average lifetimes were all significantly lower than that of trp (2109 ms). The average lifetimes of the fluorinated analogs (5-F: 1496 ms, 6-F: 1004 ms, and 4-F: 87 ms) scaled approximately with the relative quantum yields while that of 5-Br (1.03 ms) was significantly lower.

Paper Details

Date Published: 1 May 1998
PDF: 6 pages
Proc. SPIE 3256, Advances in Optical Biophysics, (1 May 1998); doi: 10.1117/12.307068
Show Author Affiliations
Colin McCaul, Rutgers Univ. (United States)
Richard D. Ludescher, Rutgers Univ. (United States)

Published in SPIE Proceedings Vol. 3256:
Advances in Optical Biophysics
Joseph R. Lakowicz; J. B. Alexander Ross, Editor(s)

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