New fluorescent probes for visual proteins. Part II. 5-(Oxo)penta-2,4-dienyl-p-(N,N-dimethylamino)benzoate.
A new dual-fluorescent compound, 5-(oxo)penta-2,4-dienyl-p-(N,N-dimethylamino)benzoate (1), a derivative of dimethylaminobenzoic acid, has been synthesised and studied photophysically. This compound continues the series of potential fluorescent probes for visual and proton-pumping opsin proteins. The photophysical behaviour of this molecule, including charge-transfer interaction in the ground state and dual-fluorescence emission, is similar to that of the previously studied analogue cis-3-(oxo)propenyl-p-(N,N-dimethylamino)benzoate (cis-2). The presence of several theoretically calculated conformers of compound 2 was suggested to be responsible for the observed strongly red-shifted absorption and excitation wavelength dependence. These photophysical anomalies were also observed for molecule 1, though the models put forward to explain them in the cases of 1 and 2 are rather different. Based on theoretical calculations and experimental results, we propose that some of the stable conformers might be connected with either a charge-transfer complex or mesomeric interactions in the ground state. Upon changing the electronic nature of the oxo-pentadienyl acceptor moiety, e.g. protonation, chemical or biochemical reaction, the charge-transfer absorption disappears, which leads to a dramatic increase in the fluorescence quantum yield.
Papper
Vladislav
V
Institute of Chemistry, Humboldt University, Brook-Taylor Strasse 2, D-12489 Berlin, Germany.
Kharlanov
Vladimir
V
Schädel
Sandra
S
Maretzki
Dieter
D
Rettig
Wolfgang
W
D000818:Animals; D002417:Cattle; D003624:Darkness; D005136:Eye Proteins / Q000032:analysis*; D005456:Fluorescent Dyes; D009682:Magnetic Resonance Spectroscopy; D012160:Retina / Q000166:cytology; D012374:Rod Cell Outer Segment / Q000166:cytology*; D017299:Rod Opsins / Q000302:isolation & purification
D005136:Eye Proteins; D005456:Fluorescent Dyes; D017299:Rod Opsins