Photobleaching

Photobleaching is the light-induced loss of color or fluorescence when illumination chemically alters a pigment or fluorescent material.

Photochemistry: The study of chemical reactions initiated by light. Photobleaching is a photochemical process initiated when a molecule absorbs light.
Fluorescence microscopy: Microscopy that forms images from light emitted by fluorescent labels or materials. Bleaching dims labels during image acquisition and can limit observation time.
Quenching: A reduction in fluorescence intensity caused by processes that deactivate excited states. Quenching can dim fluorescence without chemically destroying the fluorophore.
Chromophore: The part of a molecule responsible for absorbing light and producing color. Bleaching often alters the chromophore that gives a pigment or dye its color.
Fluorescence: Light emission by a substance after it absorbs photons, usually at a longer wavelength. Photobleaching is observed as the loss of a fluorophore’s emitted light.
Fluorescence recovery after photobleaching: A microscopy method that measures molecular mobility by tracking fluorescence returning to a bleached region. It deliberately uses localized bleaching as the starting point for measuring molecular movement.
Fluorescence blinking: Intermittent switching of a fluorescent molecule between emitting and nonemitting states. Blinking can resemble bleaching in a short observation but may be reversible.
Absorption spectrum: A representation of how strongly a substance absorbs light at different wavelengths. Changes to absorption reveal how bleaching alters a material’s interaction with light.
Reactive oxygen species: Reactive oxygen-containing molecules, including singlet oxygen and hydroxyl radicals. These species can oxidize dyes and damage fluorescent molecules during illumination.
Single-molecule fluorescence: Methods that detect fluorescence from individual molecules rather than ensemble averages. A single fluorophore’s bleaching often marks the end of its observable signal.

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