lumirhodopsin


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lumirhodopsin

 [loo″mĭ-ro-dop´sin]
an intermediate product of exposure of rhodopsin to light.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

lu·mi·rho·dop·sin

(lū'mi-rō-dop'sin),
An intermediate between rhodopsin and all-trans-retinal plus opsin during bleaching of rhodopsin by light; formed from bathorhodopsin and converted to metarhodopsin I with a half-life of about 20 μs.
[L. lumen, light, + G. rhodon, rose, + opsis, vision]
Farlex Partner Medical Dictionary © Farlex 2012

lu·mi·rho·dop·sin

(lū'mi-rō-dop'sin)
An intermediate between rhodopsin and all-trans-retinal plus opsin during bleaching of rhodopsin by light; formed from bathorhodopsin and converted to metarhodopsin.
[L. lumen, light, + G. rhodon, rose, + opsis, vision]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

rhodopsin 

Visual pigment contained in the outer segments of the rod cells of the retina and involved in scotopic vision. When light stimulates the retina, the chromophore of the pigment molecule '11-cis' retinal (which is vitamin A aldehyde) isomerizes to 'all-trans' retinal. This leads to other chemical transformations which carry on even in the absence of light. The first stage is prelumirhodopsin, then lumirhodopsin and finally metarhodopsin (of which there are two types). This last transformation may lead to the breakdown of the molecule into retinal and opsin. The molecule is regenerated by recombining retinal and opsin with some enzymes. The absorption spectrum of rhodopsin has a maximum around 498 nm. The isomerization from '11-cis' to 'all-trans' also gives rise to the process of transduction in which the membrane potential covering the pigment molecules in the outer segment changes towards a hyperpolarization of the cell. This is the first step in the nervous response to a light stimulation of the retina. Syn. visual purple (not used any more); erythropsin. See dark adaptation; bleaching; receptor potential; absorption spectrum; transduction.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann