Biological chemical reactions bioluminescence

Chemiluminescence is produced when a chemical reaction yields an electronically excited molecule, which emits light as it returns to the ground state. Chemiluminescence reactions are encountered in a number of biological systems, where the process is often termed bioluminescence. Examples of species exhibiting bioluminescence include the firefly, the sea pansy, certain jellyfish, bacteria, protozoa, and Crustacea. 

Chemluminescence occurs when a chemical reaction produces an excited species to emit a photon in order to reach the ground state. These reactions can be encountered in biological systems, known as bioluminescence. 

Luminescence includes phenomena such as fluorescence and phosphorescence. It comes from the radiative deactivation of excited matter following an excitation (the mechanism of the excitation, as well as fluorescence and phosphorescence is explained below). The excitation can come from light (photoliuninescence), electricity (electroluminescence), a chemical reaction (chemoluminescence or bioluminescence, if the reaction takes place in a biological system), or a mechanical stress (triboluminescence). We focus on photoluminescence, because most of the other excitation sources require special conditions and are, with the exception of electroluminescence, quite rare, especially when dealing with the luminescence of the lanthanides. 

Fig. 1 Chemical interaction mechanisms, basic components of the optical sensor instrumentation and their operation. Mechanisms direct measurement of chemical compounds that exhibit spectroscopic properties (1 A) and measurement of light originating from a chemical or a biological reaction in chemiluminescent or bioluminescent phenomena (IB) 2 optodes based on the interaction of indicators and labels with light, which are immobilized in a support and sensors that modify the intrinsic physical or chemical properties of a waveguide (refractive index, phase, etc.) as a result of the presence of the analyte (3A), a recognition element (35), an intermediate analyte (3C) or an indicator (3D)...

Chemiluminescence and bioluminescence are defined as processes in which light is generated during chemical or biological reactions, i.e., exothermic reactions in which part of the reaction energy is converted into photons. In chemiluminescence, an educt molecule is converted to the final stable product upon decay of an unstable chemical intermediate that only exists in an excited electronic state [160, 161]. Bioluminescence includes reactions of photoproteins such as aequorin and of enzymes such as the luciferases (see below). 

Bioluminescence- and Chemiluminescence-Based Biosensors These reactions are the most sensitive chemical probes. The simplest accepted mechanism for the production of light from biological reactions is that of the cmstacean Cypridina hilgendorfii ... 

The most simple photometric method uses the direct detection of the light emitted from chemical and biological changes (chemiluminescence or bioluminescence). These reactions can be catalysed by enzymes immobilized on the end of optical fibers. 

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