retinalin

Retinalin is a synthetic organic chromophore used as an analogue of retinal in vision research. It is designed to resemble the extended polyene chromophore of retinal while incorporating substituents that allow tuning of absorption properties and interaction with protein scaffolds.

It consists of a conjugated polyene chain linked to a terminal ring system and an adjustable functional group for protein attachment. The conjugation length and substitution pattern confer visible-light absorption, with spectra that can be tuned toward the green to yellow region, and support photoisomerization, analogous to the cis–trans isomerization observed for retinal.

Retinalin is employed in in vitro experiments to probe chromophore–protein interactions and to model the photochemical steps of vision. It has been used to study isomerization-driven conformational changes in opsin-like proteins and to benchmark spectroscopic methods. Derivatives of retinalin are explored as tools for optogenetics and as light-activated switches in biomolecular systems.

Retinalin is synthesized via modular assembly of polyene fragments and a functionalized terminus enabling attachment to proteins or lipids. Its synthesis is described in contemporary reviews on chromophore analogues, and access is generally limited to research laboratories with appropriate safety protocols.

As a synthetic analogue, retinalin may not fully replicate the photophysics of native retinal and results should be interpreted with caution. Ongoing work aims to map structure–property relationships to improve binding specificity and spectral tunability.