Synthetic analogs of retinal with spacer arms attached to the seco-ring for the structural probes of retinal proteins: Rhodopsin and bacteriorhodopsin.
Item
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Title
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Synthetic analogs of retinal with spacer arms attached to the seco-ring for the structural probes of retinal proteins: Rhodopsin and bacteriorhodopsin.
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Identifier
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AAI9304686
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identifier
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9304686
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Creator
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Kozak, Wei Xing.
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Contributor
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Advisers: Neil McKelvie | John Lomabardi
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Date
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1992
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Organic | Chemistry, Biochemistry
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Abstract
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Retinal proteins in vertebrates and invertebrates comprise rhodopsin: visual pigments which serve as light detectors for the sensory system; whereas the pigment present in Halobacterium halobium, called bacteriorhodopsin (bR) functions as a photosynthetic energy source. The retinal chromophores in both proteins are the 11-cis isomer with a linkage to Lys-296, and the all-trans isomer with a linkage to Lys-216 of their respective apoproteins via a protonated Schiff base. Incident light causes both to undergo a series of conformational changes of retinal moiety, related to formation of photointermediates. They are responsible for visual transduction coupled with the permeability of the cytoplasmic membrane to sodium ions, and the proton translocation coupled with the synthesis of ATP in the bR photocycle.;In order to understand both processes in molecular detail, the tertiary structures of these photointermediates and the proteins must be precisely established. Synthetic retinal analogs confer great advantages for this purpose. A series of seco-ring spacer armed retinal analogs connected to an ester linkage were synthesized. Up to ten carbons in length, all of these analogs efficiently reacted with bacterioopsin to form bacteriorhodopsin analogs with absorption maxima ranging from 530 nm to 536 nm, indicative that the distance between the ring-binding site and the exterior surface of the membrane is about 11-12 A. Moreover, that these synthetic retinals fully occupy the native binding site is shown by the result of inhibition due to the native chromorphore displacement. These bR analogs function similar to native pigment as shown by the CD spectrum and light-dark adaptation experiments. The all-trans seven-carbon spacer armed retinal was photoisomerized to its cis isomers which were also bound to bovine opsin at maximum absorption of 450 nm. The synthesis of seco-ring retinal analogs with an attached terminal photoactive group has been attempted with great effort using several different methods.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
