POLARIZATION ANISOTROPY APPLIED TO THE DETERMINATION OF STRUCTURAL-CHANGES IN THE PHOTOISOMERIZATION OF DODCI

The steady-state fluorescence anisotropy of the photoisomerizable dye 3,3'-diethyloxadicarbocyanine iodide (DODCI) in ethanol, was studied a s a function of temperature, in order to determine its molecular confo rmation. Dual laser excitation was used to separate the emission of th e normal species from that of its photoisomer. This permitted us to fo llow separately the fluorescence anisotropy of both species. The resul ts were analyzed with stick-slip hydrodynamic boundary conditions and asymmetric ellipsoids were used to simulate the molecular shape. Resul ts were in agreement with those predicted from with slip hydrodynamic boundary conditions, allowing re, get a possible conformational assign ation to those species of DODCI that take part in the photoisomerizati on process.