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Synthetic biological circuits are an application of synthetic biology where biological parts inside a cell are designed to perform logical functions mimicking those observed in electronic circuits. The applications range from simply inducing production to adding a measurable element, like GFP, to an existing natural biological circuit, to implementing completely new systems of many parts. The goal of synthetic biology is to generate an array of tunable and characterized parts, or modules, with which any desirable synthetic biological circuit can be easily designed and implemented.〔(【引用サイトリンク】url=http://syntheticbiology.org/FAQ.html )〕 These circuits can serve as a method to modify cellular functions, create cellular responses to environmental conditions, or influence cellular development. By implementing rational, controllable logic elements in cellular systems, researchers can use living systems as engineered "machines" to perform a vast range of useful functions.〔 ==History== The first natural gene circuit studied in detail was the lac operon. In studies of diauxic growth of ''E. coli'' on two-sugar media, Jacques Monod and Francois Jacob discovered that ''E.coli'' preferentially consumes the more easily processed glucose before switching to lactose metabolism. They discovered that the mechanism that controlled the metabolic "switching" function was a two-part control mechanism on the lac operon. When lactose is present in the cell the enzyme β-galactosidase is produced to convert lactose into glucose or galactose. When lactose is absent in the cell the lac repressor inhibits the production of the enzyme β-galactosidase to prevent any inefficient processes within the cell. The lac operon is used in the biotechnology industry for production of recombinant proteins for therapeutic use. The gene or genes for producing an exogenous protein are placed on a plasmid under the control of the lac promoter. Initially the cells are grown in a medium that does not contain lactose or other sugars, so the new genes are not expressed. Once the cells reach a certain point in their growth, Isopropyl_β-D-1-thiogalactopyranoside (IPTG) is added. IPTG, a molecule similar to lactose, but with a sulfur bond that is not hydrolyzable so that E. Coli does not digest it, is used to activate or "induce" the production of the new protein. Once the cells are induced, it is difficult to remove IPTG from the cells and therefore it is difficult to stop expression. An early example of a synthetic biological circuit was published in Nature in 2000 by Tim Gardner, Charles Cantor, and Jim Collins working at Boston University. They were able to create a "bistable" switch in E. Coli. The switch is turned on by heating the culture of bacteria and turned off by addition of IPTG. They used GFP as a reporter for their system.〔Gardner, T.s., Cantor, C.R., Collins, J. Construction of a genetic toggle switch in Escherichia coli. ''Nature'' 403, 339-342 (20 January 2000).〕 Currently, synthetic circuits are a burgeoning area of research in systems biology with more publications detailing synthetic biological circuits published every year.〔Priscilla E. M. Purnick & Ron Weis. The second wave of synthetic biology: from modules to systems. Nature Reviews Molecular Cell Biology 10, 410-422 (June 2009) | 〕 There has been significant interest in encouraging education and outreach as well: the International Genetically Engineered Machines Competition〔International Genetically Engineered Machines (iGem) http://igem.org/Main_Page〕 manages the creation and standardization of BioBrick parts as a means to allow undergraduate and high school students to design their own synthetic biological circuits. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Synthetic biological circuit」の詳細全文を読む スポンサード リンク
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