Novel retinylidene iminium salts for defining opsin shifts: synthesis and intrinsic chromophoric properties.
Retinal Schiff bases serve as chromophores in many photoactive proteins that carry out functions such as signalling and light-induced ion translocation. The retinal Schiff base can be found as neutral or protonated, as all-trans, 11-cis or 13-cis isomers and can adopt different conformations in the protein binding pocket. Here we present the synthesis and characterisation of isomeric retinylidene iminium salts as mimics blocked towards isomerisation at the C11 position and conformationally restrained. The intrinsic chromophoric properties are elucidated by gas phase absorption studies. These studies reveal a small blue-shift in the S0-->S1 absorption for the 11-locked derivative as compared to the unlocked one. The gas phase absorption spectra of all the cationic mimics so far investigated show almost no absorption in the blue region. This observation stresses the importance of protein interactions for colour tuning, which allows the human eye to perceive blue light.
Petersen
Michael Axman
MA
Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100, Copenhagen Ø, Denmark.
Nielsen
Iben B
IB
Kristensen
Michael B
MB
Kadziola
Anders
A
Lammich
Lutz
L
Andersen
Lars H
LH
Nielsen
Mogens Brøndsted
MB
D003198:Computer Simulation; D018360:Crystallography, X-Ray; D007097:Imines / Q000138:chemical synthesis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D012172:Retinaldehyde / Q000031:analogs & derivatives / Q000138:chemical synthesis* / Q000737:chemistry*; D012176:Retinoids / Q000737:chemistry*; D017299:Rod Opsins / Q000737:chemistry*; D012545:Schiff Bases / Q000737:chemistry
D007097:Imines; D012176:Retinoids; D017299:Rod Opsins; D012545:Schiff Bases; C121835:retinylidene chromophore; D012172:Retinaldehyde