Retinal

• Retinaldehyde
• 11-cis -retinal [ Synonym: ( 11Z ) -retinal ]
• All-trans retinal [ Synonym: (all- E) -retinal ]
• IUPAC: 3,7-dimethyl- 9-( 2,6,6- trimethylcyclohex -1 -en- 1-yl) nona -2 ,4,6,8 - tetraenal (without stereochemistry)

116-31-4 (all- trans)

Orange -red crystals

Fixed

• 61-64 ° C ( all-trans )
• 63.5 to 64.5 (11- cis)

All-trans

Attention

All-trans

Template: Infobox chemical / molecular formula search available

Retinal is one of the carotenoids and provides other related compounds, vitamin a; There is the aldehyde of retinol.

Biological Function

Retinal is coupled to the rods of the retina with the protein opsin. This compound is referred to as rhodopsin or rhodopsin. In it, the retinal is present in a particular configuration as 11-cis- retinal. Eye incident light leads to a change in the retinal in the molecular structure of (11 -cis-retinal is to all - trans-retinal ), after which the opsin is cleaved. Thus, a signaling cascade is initiated that ultimately leads to the optic nerve.

A slight hypovitaminosis manifests itself in reduced night vision. Stronger deficiency leads to quicker fatigue of the eyes, night blindness and a keratinization of the photoreceptor cells of the eye.

Visual process

Two isomeric forms of retinal in vision are important: the 11-cis -retinal and the all-trans - retinal. 11 -cis-retinal is the photosensitive element of the rhodopsin molecule which is decisive for the color-neutral See photosensitive chromophore is in the rods of the eye ( see the retina). By absorption of light, the 11 -cis-retinal is transformed into the all-trans configuration, in which it is different from the protein component of rhodopsin, the Skotopsin separates.

This triggers a signal transduction from, through which the light signal is converted indirectly via uptake by the retinal and the decay of rhodopsin in an electrochemical signal, the receptor potential of the rod cell. The resulting all-trans -retinal, however, then, provided that no further light is incident by an enzyme, the so-called. Retinal isomerase, again converted into the cis form, in which it rhodopsin molecule can combine with the remaining protein component to form a new " ready to receive ".

The importance of the retinal for vision is also the reason why the statement is disseminated in the vernacular, carrots are good for the eyes. The β -carotene in many yellow and red colored vegetables is required for the formation of retinal. all-trans -retinal, the aldehyde of vitamin A1 ( retinol) and is therefore in close structural relationship with it.

Other isomeric forms of retinal are known, but have neither in nature nor in the art appreciable importance.