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Rétinal

Rétinal
Image illustrative de l’article Rétinal
Tout-trans-rétinal
Identification
Nom UICPA (2E,4E,6E,8E)-3,7-diméthyl-9-(2,6,6-triméthylcyclohexén-1-yl)nona-2,4,6,8-tétraénal
Synonymes

rétinaldéhyde

No CAS 116-31-4
No ECHA 100.003.760
Apparence cristaux orange[1]
Propriétés chimiques
Formule C20H28O
Masse molaire[2] 284,435 7 ± 0,018 3 g/mol
C 84,45 %, H 9,92 %, O 5,62 %,
Propriétés physiques
T° fusion
  • 61–64 °C (tout-trans)[3]
  • 63,5–64,5 °C (11-cis)[3]
Solubilité Liposoluble, pratiquement insoluble dans l'eau
Précautions
Directive 67/548/EEC
Nocif
Xn
Unités du SI et CNTP, sauf indication contraire.
modifier 

Le rétinal, appelé aussi rétinaldéhyde, est l'une des trois formes de la vitamine A. Le rétinal est un aldéhyde polyinsaturé capable d'absorber la lumière et qui présente une couleur orangée. Il se lie à des protéines, les opsines, et constitue la base moléculaire de la vision.

En effet, le cycle de la vision est régi par la photoisomérisation du rétinal : lorsque le rétinal 11-cis absorbe un photon, il passe de l'état 11-cis à l'état tout-trans ; cette isomérisation est à l'origine d'une hyperpolarisation du photorécepteur par phototransduction (en).

Lié à des rhodopsines de type 1, le rétinal permet à certains microorganismes de convertir la lumière en énergie métabolique. Chez les animaux, le rétinal peut être obtenu à partir des autres formes de vitamine A, le rétinol, ainsi que ses esters et l'acide rétinoïque, qui se trouvent dans les produits d'origines animales ou par scission oxydative du carotène végétal. Le rétinal est sensible à l'oxygène de l'air, ainsi qu'à la lumière et à la chaleur.

Absorption d'un photon par le rétinal 11-cis et isomérisation en tout-trans.

Notes et références

  1. ↑ Merck Index, 13th Edition, 8249.
  2. ↑ Masse molaire calculée d’après « Atomic weights of the elements 2007 », sur www.chem.qmul.ac.uk.
  3. ↑ a et b Jutta Möseneder, in: Römpp Online - Version 3.5, 2009, Georg Thieme Verlag, Stuttgart.

Annexes

Bibliographie

v · m
Liposolubles
A
D
E
K
Hydrosolubles
B
C

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