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Transient Effects in Fluorescence Quenching Measured by 2-GHz Frequency-Domain Fluorometry.

Joseph R Lakowicz¹, Michael L Johnson¹, Ignazy Gryczynski¹

¹Department of Biological Chemistry, School of Medicine, University of Maryland, Baltimore, Maryland 21201, and Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908.

The Journal of Physical Chemistry

|January 8, 2020

Summary

This summary is machine-generated.

Frequency-domain fluorometry revealed complex indole fluorescence decays when quenched by iodide and acrylamide. These nonexponential decays, attributed to transient effects, challenge simple models at high quencher concentrations.

Keywords:

KI, 7681-11-0 acyrlamide, 79-06-1 indole, 120-72-9

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Area of Science:

Photochemistry
Physical Chemistry
Biophysical Chemistry

Background:

Indole fluorescence is a sensitive probe in aqueous solutions.
Collisional quenching affects fluorescence decay dynamics.
Understanding quenching mechanisms is crucial for molecular studies.

Purpose of the Study:

To investigate indole fluorescence quenching by iodide and acrylamide using frequency-domain fluorometry.
To analyze time-resolved intensity decays and their deviation from theoretical models.
To determine the applicability of existing models at high quencher concentrations.

Main Methods:

Utilized harmonic-content frequency-domain fluorometry.
Measured fluorescence emission over a frequency range of 10 to 2000 MHz.
Recovered time-resolved intensity decays from frequency response data.

Main Results:

Indole fluorescence decay in water is single exponential without quenching.
Decays became nonexponential with increasing iodide and acrylamide concentrations.
An approximate decay model (exp(-t/τ - 2bt^1/2)) was valid below 0.1 M quencher.
Deviations from the radiation model were observed at high acrylamide concentrations (>0.5 M).

Conclusions:

Frequency-domain fluorometry effectively captures complex subnanosecond decays.
Transient effects significantly influence indole fluorescence quenching at high concentrations.
Existing models require refinement to accurately describe quenching dynamics at high quencher levels.