Using 7-Azatryptophan To Probe Small Molecule-Protein Interactions on the Picosecond Time Scale: The Complex of Avidin and Biotinylated 7-Azatryptophan

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Date
1995
Authors
Rich, R.
Gai, F.
Lane, J.
Petrich, Jacob
Schwabacher, A.
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Chemistry
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Abstract

The utility of 7-azatryptophan as an alternative to tryptophan for optically probing protein structure and dynamics is demonstrated by investigating the complex of egg-white avidin and biotinylated 7-azatryptophan. We report the synthesis of biotinylated 7-azatryptophan and optical measurements of its complex with avidin. Although there are four biotin binding sites, the emission from the 7-azatryptophan tagged to biotin decays by a single exponential, whereas the tryptophyl emission from avidin requires two exponentials in order to be adequately fit. Fluorescence depolarization measurements of the complex probed by emission from 7-azatryptophan reveal both rapid (-80 ps) and much longer-lived decay. The former component is attributable to the local motion of the probe with respect to the protein; the latter component represents overall protein tumbling. In addition, energy transfer from tryptophan to 7-azatryptophan and a blue-shift in the spectrum of biotinylated 7-azatryptophan are observed upon formation of the complex. Modified strategies of effecting optical selectivity are also discussed.

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Reprinted (adapted) with permission from Journal of the American Chemical Society 117 (1995): 733, doi: 10.1021/ja00107a016. Copyright 1995 American Chemical Society.

Keywords
7 azatryptophan, avidin, tryptophan derivative, fluorescence, protein binding, spectrophotometry
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