Introduction to the themed issue on bioluminescence

Bioluminescence, the emission of visible light by living organisms, has attracted the attention of many scientists for centuries. It poses many fundamental questions about energy conversion and exchange of information in biological systems. Bioluminescence results from the efficient conversion of energy of chemical bonds into photons of visible light. In general, the bioluminescent systems involve the oxidation of compounds called luciferins by oxygen or by reactive oxygen species, in reactions catalyzed by enzymes generically known as luciferases. Photoproteins are a special type of luciferases, in which a temporarily stable protein-lumophore is the actual emitter. In addition to the luciferases or photoproteins, some bioluminescent systems are also aided by accessory proteins, such as fluorescent proteins, which are proteins with an endogenous fluorophore that serve as excitation energy acceptors from the excited product of the primary light-generating reaction (luciferase or photoprotein), emitting at a different wavelengths; and luciferin-binding proteins, which may serve as temporary storage and protected forms of luciferins, which are often very oxidisable compounds. During the past 40 years, several luciferins, luciferases and accessory fluorescent proteins were isolated and characterized. Some systems such as those from bacteria, coelenterates, ostracods and beetles have been extensively studied in recent years. The corresponding luciferases have been cloned and their three-dimensional structures determined by X-ray crystallography, allowing studies of the relationship between structure and function. Some of these luciferin–luciferase systems promptly became valuable bioanalytical reagents, and their genes are currently being used as important reporter genes. The cloning and engineering of new luciferases is broadening the range of applications, resulting in new bioluminescent probes and biosensors widely used in the fields of biotechnology, biomedicine and environment, and complementing the emergence of new fields such as bioimaging. Some bioluminescent systems, such as that of fungi still remain largely unstudied, promising new important discoveries and potential biotechnological applications.

This themed issue on bioluminescence provides a current perspective and reports recent advances in the field, some of them recently described in the Symposium “Bioluminescence: from protein structure to biosensing applications” held during the Twelfth Congress of the European Society for Photobiology in Bath, on September 2^nd, 2007. In this issue several topics in the bioluminescent field will be addressed, among them, structure and function relationships of luciferases and other accessory proteins of different bioluminescent systems, mechanisms of bioluminescence of Cypridina and firefly luciferases, and biotechnological applications of multicolor luciferases.

Vadim Viviani

Universidade Federal de São Carlos, Sorocaba, SP, Brazil

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Footnote

† We would like to dedicate these papers to the memory of Prof. Dr Liyun Liu, who passed away in June 2007.

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