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Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with colored visible light. The color of the light emitted depends on the chemical composition of the substance.
Biofluorescence is fluorescence exhibited by a living organism: part of the organism absorbs light or other radiation at one wavelength and emits visible light at another, usually longer. The absorbed radiation is often blue or ultraviolet , while the light emitted is typically green, red, or anything in between.
A simplified Jablonski diagram illustrating the change of energy levels.. The principle behind fluorescence is that the fluorescent moiety contains electrons which can absorb a photon and briefly enter an excited state before either dispersing the energy non-radiatively or emitting it as a photon, but with a lower energy, i.e., at a longer wavelength (wavelength and energy are inversely ...
In fluorescence, the species is first excited, by absorbing a photon, from its ground electronic state to one of the various vibrational states in the excited electronic state. Collisions with other molecules cause the excited molecule to lose vibrational energy until it reaches the lowest vibrational state from the excited electronic state.
The observed change in fluorescence is based on two distinct effects. On the one hand it is based on a temperature related intensity change (TRIC) of the fluorescent probe, which can be affected by binding events. On the other hand, it is based on thermophoresis, the directed movement of particles in a microscopic temperature gradient.
Fluorescence of different substances under UV light. Green is a fluorescein, red is Rhodamine B, yellow is Rhodamine 6G, blue is quinine, purple is a mixture of quinine and rhodamine 6g. Solutions are about 0.001% concentration in water. Fluorophore molecules could be either utilized alone, or serve as a fluorescent motif of a functional system.
The rings make it impossible for left-handed people to lay their hands flat on the page and write normally. Notebooks with spirals on the top or right side are much easier to use.
To study structures within living cells, in combination with fluorescence, one can utilize recombinant proteins containing fluorescent protein domains, e.g., green fluorescent protein (GFP). The GFP-technique involves altering the genetic information of the cells. [18] [19]