Gating ring

Johnson JP, Jr., Zagotta WN. The carboxyl-terminal region of cyclic nucleotide-modulated channels is a gating ring, not a permeation path. Proc Natl Acad Sci USA 2005 102 2742-7. 

A steroid very closely related structurally to cholesterol is its 7 dehydro derivative 7 Dehydrocholesterol is formed by enzymatic oxidation of cholesterol and has a conju gated diene unit m its B ring 7 Dehydrocholesterol is present m the tissues of the skin where it is transformed to vitamin D3 by a sunlight induced photochemical reaction... 

Gate valves are used to minimize pressure drop in the open position and to stop the flow of fluid rather than to regulate it. The problem, when the valve is closed, of pressure buildup in the bonnet from cold liquids expanding or chemical action between fluid and bonnet should be solved oy a relief valve or by notching the upstream seat ring. 

Gates, M. (1950) The Synthesis of Ring Systems Related to Morphine. III. 5,6-Dimethoxy-4-cyanomethyl-1,2-naphthoquinone and its Condensation with Dienes. Journal of the American Chemical Society, 72, 228-234. 

Figure 13.12. Images and electrical measurements of integrated circuits that use semiconductor wires and ribbons on plastic, (a) Silicon ribbon five-stage ring oscillator and (b) differential amplifier. (Reprinted with permission from Ref. 87. Copyright 2007 American Institute of Physics.) (c) GaAs logic gates. (Reprinted with permission from Ref. 86. Copyright 2006 Wiley-VCH Verlag.)...

As noted with the reactions between terpenes and dihalocarbenes, mono-insertion adducts at the more electron-rich sites can be isolated from the reaction of non-conju-gated acyclic and cyclic dienes although, depending on the reaction conditions, the bis-adducts may also be formed. Norbomadiene produces both 1,2-endo and 1,2-exo mono-insertion adducts with dichlorocarbene, as well as a 1,4-addition product (Scheme 7.4) [67]. The mono adduct produced from the reaction with dimethylvinylidene carbene rearranges thermally to yield the ring-expanded product (Scheme 7.4) [157] a similar ring-expanded product is produced with cyclo-hexylidene carbene [149]. 

We recently examined a two-state case that represents the simplest model for any gated reaction [10a, b]. Consider a donor-acceptor pair, [d, a], as part of a system that exhibits two conformations, B(boat) and C(chair). For concreteness, we may imagine d and a as attached at the 1,4 positions on a cyclohexane ring the same formal situation will be realized in far more interesting ways with protein complexes. In this case, each of the three system states shown in Scheme... 

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