isoform: <biochemistry> A protein having the same function and similar (or identical sequence), but the product of a different gene and usually) tissue specific. Rather stronger in implication than homologous.

Fluorescence results from a process that occurs when certain molecules (generally polyaromatic hydrocarbons or heterocycles) called fluorophores, fluorochromes, or fluorescent dyes absorb light. The absorption of light by a population of these molecules raises their energy level to a brief excited state. As they decay from this excited state, they emit fluorescent light. The process responsible for fluorescence is illustrated by a simple electronic state diagram (Fig 2). Excitation When a photon of energy, h&#957;EX, supplied by an external source such as a lamp or a laser, is absorbed by a fluorophore, it creates an excited, unstable electronic singlet state (S1). This process is distinct from chemiluminescence, in which the excited state is created by a chemical reaction.
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