Light quenching and depolarization of fluorescence observed with laser pulses. A new experimental opportunity in time-resolved fluorescence spectroscopy.
We report the first time-resolved studies of quenching of fluorescence by light, i.e., "light quenching". The dye 4-(dicyanomethylene)-2-methyl-6-(p-dimethamino)-4H-pyrane (DCM) was excited in the anti-Stokes region from 560-600 nm. At high illumination power the intensities of DCM were sub-linear with incident power. The extent of light quenching was proportional to the emission spectrum at the incident wavelength, as expected for light-stimulated decay from the excited state. The frequency-domain intensity decays indicated the effect was not due to heating or other photochemical effects. Importantly, the decay time was unchanged, as expected for light quenching with a single pulsed laser beam, while the time-zero anisotropy was decreased due to orientation-dependent quenching of the excited state population. Light quenching of fluorescence provides a new method to control the excited state population and orientation of fluorophores, and offers new experimental opportunities for biophysical applications of time-resolved fluorescence.
Department of Biological Chemistry, University of Maryland at Baltimore, School of Medicine 21201.
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I
Gryczyński
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V
Bogdanov
J R
JR
Lakowicz
D016880:Anisotropy; D005453:Fluorescence; D005456:Fluorescent Dyes; D007834:Lasers; D008027:Light; D013050:Spectrometry, Fluorescence
D005456:Fluorescent Dyes