title: Spectral and photophysical characteristics of unsymmetric polymethine dyes as model compounds for the colour shift of visual pigments.
abstract: Selectively bridged unsymmetric cyanines (dimethylamino-vinyl-benzothiazolium dyes) have been studied with respect to their photophysical properties using steady-state and time-resolved fluorescence. The nonradiative deactivation channels strongly depend on the bridging pattern and can be enhanced or slowed down, with the changes mainly connected to the Arrhenius pre-exponential factor, reflecting the photochemical pathways. The spectral shifts, on the other hand, are independent of the bridging pattern and are correlated with the compound's position on a donor acceptor axis including ideal polymethines. Using this model, the colour shift of visual pigments can be explained as an effect of the internal (protein-induced) electric field on the retinal Schiff base, likewise an unsymmetric polymethine dye system.
authors.affiliation: Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-str. 2, D-12489 Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Sczepan
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Rettig
authors.forename: Alexei I
authors.initials: AI
authors.lastname: Tolmachev