Retinal
Systematic name	(all-E)-3,7-Dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,4,6,8-nonatetraenal
Molecular formula	C20H28O
Molar mass	284.436
CAS number	[116-31-4]
Melting point	63 °C Image File history File links Download high-resolution version (1546x504, 11 KB) Chemical structure of retinal created with ChemDraw. ... IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ... A chemical formula (also called molecular formula) is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... The melting point of a crystalline solid is the temperature at which it changes state from solid to liquid. ...
PubChem	1070
SMILES	CC1=C(/C=C/C(C)=C/C=C/C(C)=C/C=O)C(C)(C)CCC1
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Retinal, technically called retinene₁ or "retinaldehyde", is a light-sensitive retinene molecule found in the photoreceptor cells of the retina. Retinal is the fundamental chromophore involved in the transduction of light into visual signals, i.e. nerve impulses, in the visual system of the central nervous system. PubChem is a database of chemical molecules. ... The simplified molecular input line entry specification or SMILES is a specification for unambiguously describing the structure of chemical molecules using short ASCII strings. ... In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals) and 25 degrees Celsius (298. ... The Retinenes (Retinene1 and Retinene2) are chemical derivatives of the dietary supplement vitamin A (see retinol) formed through oxidation reactions. ... Photoreceptor cells are contained in the retina and are responsible for transducing, or converting, light into signals that can be ultimately transmitted to the brain via the optic nerve. ... Human eye cross-sectional view. ... A chromophore is part (or moiety) of a molecule responsible for its color. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific context, electromagnetic radiation of any wavelength[1]. The elementary particle that defines light is the photon. ... The visual system is the part of the nervous system which allows organisms to see. ... A diagram showing the CNS: 1. ...

Overview

The molecule that takes part in the initial step in the vision process, rhodopsin, has two components called 11-cis retinal and opsin. Retinal is a light-sensitive derivative of vitamin A, and opsin is a protein molecule. Rhodopsin is found in the rod cells of the eye. 11-cis retinal is a powerful absorber of light because it is a polyene; its 6 alternating slml'l'kllingle and double bonds make up a long unsaturated electron network. When no light is present, the 11-cis retinal molecule is found in a "bent configuration" (fig A), and as such it is attached to the opsin molecule in a stable arrangement. When light strikes the retina, within 200 femtoseconds, after the retinal molecule absorbs a photon into one of the pi bonds found between the eleventh and twelfth carbon atoms, the 11-cis retinal is transformed into the all-trans retinal (fig B) in a straightened configuration.^[1] A rhodopsin molecule (yellow) with bound retinal (orange), embedded in a cell membrane (lipids shown as green, head groups as red/blue). ... A rhodopsin molecule in the cell membrane. ... It has been suggested that Retinol be merged into this article or section. ... Normalised absoption spectra of human rod (R) and cone (S,M,L) cells. ... A femtosecond is the SI unit of time equal to 10-15 of a second. ... The word light is defined here as electromagnetic radiation of any wavelength; thus, X-rays, gamma rays, ultraviolet light, microwaves, radio waves, and visible light are all forms of light. ... Electron atomic and molecular orbitals, showing a Pi-bond at the bottom right of the picture In chemistry, pi bonds (Ï€ bonds) are bonds with a single nodal plane containing the line segment between the two atoms. ...

Retinal molecule - straightens in response to a photon γ (light), of the correct wavelength

The all-trans retinal configuration, subsequently, does not fit into the binding site of the opsin molecule; as a result, upon isomerization, the trans isomer separates from the protein, which triggers a G protein signaling pathway' including transducin, that results in the generation of an electrical impulse, which is transmitted through the optic nerve to the brain for processing. It takes a minimum of five photons to trigger a nerve impulse.^[2] In the absence of light, enzymes mediate the isomerization of all-trans back to the 11-cis configuration, and rhodopsin is regenerated by a new formation of a Schiff base linkage, which actuates the binding of the cis isomer to opsin. This is the basic mechanism of the vision cycle. Image File history File links Download high-resolution version (1040x555, 9 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Photon Retinal User talk:V8rik History of the molecule User:Sadi Carnot/Sandbox2 ... Image File history File links Download high-resolution version (1040x555, 9 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Photon Retinal User talk:V8rik History of the molecule User:Sadi Carnot/Sandbox2 ... The word light is defined here as electromagnetic radiation of any wavelength; thus, X-rays, gamma rays, ultraviolet light, microwaves, radio waves, and visible light are all forms of light. ... In chemistry, isomerization is the transformation of a molecule into a different isomer. ... G-proteins, short for guanine nucleotide binding proteins, are a family of proteins involved in second messenger cascades. ... Transducin is the name given to the G-protein alpha-subunits that are naturally expressed in vertebrate retina rods and cones. ... The article on electrical energy is located elsewhere. ... MRI scan of human eye showing optic nerve. ... In animals, the brain, or encephalon (Greek for in the head), is the control center of the central nervous system. ... a mixture of 4,4-diaminodiphenyl ether 1 (1. ...

All-trans-retinal is also an essential component of type I, or microbial, opsins such as bacteriorhodopsin, channelrhodopsin, and halorhodopsin. In these molecules, light causes the all-trans-retinal to become 13-cis retinal, which then cycles back to all-trans-retinal in the dark state. Bacteriorhodopsin is a photosynthetic pigment used by archaea, most notably halobacteria. ... Channelrhodopsins are ion channels that are directly opened by light. ... Halorhodopsin is a light-driven ion pump, specific for chloride ions, and found in phylogenetically ancient bacteria (archaea), known as halobacteria. ...

History

This photon induced retinal-bending mechanism was discovered in 1958 by the American biochemist George Wald and his co-workers. For his work, Wald won a share of the 1967 Nobel Prize in Physiology or Medicine with Haldan Keffer Hartline and Ragnar Granit.^[3] George Wald (November 18, 1906–April 12, 1997) was an American scientist who is best known for his work with pigments in the retina. ... 1967 (MCMLXVII) was a common year starting on Sunday of the Gregorian calendar (the link is to a full 1967 calendar). ... List of Nobel Prize laureates in Physiology or Medicine from 1901 to the present day. ... Haldan Keffer Hartline (December 22, 1903 - March 17, 1983) was an American physiologist who was a cowinner (with George Wald and Ragnar Granit) of the 1967 Nobel Prize in Physiology or Medicine for his work in analyzing the neurophysiological mechanisms of vision. ... Ragnar Arthur Granit (October 30, 1900, Helsinki, Finland - March 12, 1991, Stockholm, Sweden) was a Finnish scientist who won the Nobel Prize in Physiology or Medicine in 1967, along with Haldan Keffer Hartline and George Wald. ...

See also

• Sensory system
• Vision

This article or section may be confusing for some readers, and should be edited to be clearer or more simplified. ... This article or section does not cite its references or sources. ...

References

External links

• First Steps of Vision - National Health Museum
• Vision and Light-Induced Molecular Changes
• Retinal Anatomy and Visual Capacities
• Retinal

J Photochem Photobiol B. 2002 Apr;66(3):188-94.