PICOSECOND RESOLUTION OF INDOLE ANISOTROPY DECAYS AND SPECTRAL RELAXATION BY 2 GHz FREQUENCY‐DOMAIN FLUOROMETRY

Abstract

Abstract— We used frequency‐domain fluorescence spectroscopy to measure rotational diffusion and time‐resolved emission spectra of indole in methanol on the picosecond timescale. The indole emission was quenched by acrylamide to allow measurements to the instrumental limit of 2 GHz and to eliminate emission from the longer‐lived indole molecules, which can no longer provide information on the picosecond (ps) processes. The resolution was adequate to measure rotational correlation times as short as 8 ps at 80†C, and spectral relaxation times as short as 16 ps at 5†C.

Fluorescence Quenching: Theory and Applications

“…The picosecond rotational correlation times certainly exist in the absence of quencher, but the accurate determination of these small values on unquenched samples is difficult. Lakowicz and co-workers (246,249) have also used this quenching/differential phase method to aid in the evaluation of the rotational correlation time of smaller molecules, such as indole and Y base. This strategy of using solute quenchers to lower the mean decay time can also be useful with pulsed single-photon counting anisotropy decay measurements.…”

Intramolecular Fluorescence Quenching in Covalent Acrylamide‐indole Adducts

“…For differential polarized phase measurements, Glans-Thompson polarizers were used and the excitation wavelength was 300 nm. Using the fluoroscence decay parameters, these anisotropy decay data were analyzed, via non-linear least squares, to obtain the rotational correlation time and limiting anisotropy for the fluorophore (Lakowicz et al, 1987a(Lakowicz et al, , 1988.…”

“…We performed differential polarized phase/modulation measurements (Lakowicz et al, 1987a(Lakowicz et al, , 1988 in order to determine the rotational correlation time, +, for acrylyl-TA and acrylyl-THPI. For 'normal' indole and tryptophan derivatives, which have lifetimes in the 1-10 ns range, such differential phaselmodulation measurements are of little value.…”

<title>Fluorescence-lifetime-based sensing of blood gases and cations</title>

“…There are many more possibilities for analytes to alter the decay time than for analytes to induce spectral shifts. For [11,12] .…”