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2 January 1995 Photophysics of indoles in polar environments
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Proceedings Volume 2370, 5th International Conference on Laser Applications in Life Sciences; (1995)
Event: Laser Applications in Life Sciences: 5th International Conference, 1994, Minsk, Belarus
The photophysics of indoles is far from being understood, which hampers the application of fluorescence methods in the studies of tryptophan fluorescence emission in proteins. For investigation of effects of dipolar relaxations and formations of specific excited-state complexes in polar environments we applied the combination of time-resolved technique (analysis of excited-state lifetime distributions by maximum entropy method) with site- selective excitation (red-edge) effects. They demonstrate, that in polar protic solvents the relaxational contributions to the distributions of lifetimes are characterized by unexpectedly narrow discrete components. They change their sign if the emission wavelength shifts from the short-wavelength to long-wavelength wing of the spectrum and disappear if the excitation is performed at the red edge (300 nm). They are characterized by significant temperature dependence with activation energy 25 - 30 kJ/mol (in isobutanol). In glycerol the situation is more complex: besides the dipole relaxational components, observed at sub-zero temperatures, other discrete short-living lifetime components are observed at room temperatures and above. They may be attributed to formation or rearrangement of the indole complexes with polar molecules after the dielectric equilibrium has been established.
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Alexander P. Demchenko, Jacques Gallay, and Michel Vincent "Photophysics of indoles in polar environments", Proc. SPIE 2370, 5th International Conference on Laser Applications in Life Sciences, (2 January 1995);

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