Photophysical Processes in Molecules of Halogenated Fluorescein Derivatives in Anionic Reverse Micelles

Optics and Spectroscopy - We studied the photophysical processes of halogenated fluorescein derivatives (eosin (E), erythrosine (ER), and Rose Bengal (RB)) in aqueous micellar solutions using...     

Effect of finely dispersed platinum on the structure of luminescence spectra of the adsorbates of magnesium phthalocyanine on silicon dioxide

The luminescence and excitation spectra and kinetic characteristics of the luminescence of the adsorbates of magnesium phthalocyanine (MgPhc) on SiO₂ and the effect on them of surface hydration and finely dispersed platinum are studied. It is found that a structure that improves hydration of the adsorbent surface appears on the platinized surface in the luminescence and excitation spectra. It is assumed that the spectral structure is due to the complexes of MgPhc formed with water molecules, the hydroxyl cover of the surface, and the surface centers of SiO₂ modified by a Pt-catalyst. Reported at the VIIIth International Conference on Spectroscopy of Porphyrins and Their Analogs, Minsk, September 22–26, 1998. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 552–555, July–August, 1999.     

Role Played by Water–Protein Surrounding of Cofactors in Picosecond Electron Transport Steps in Photosynthesis Reaction Centers

Effect of the water–protein environment of cofactors on the rates and efficiency of conversion of light energy into the energy of a photochemical potential in reaction centers of purple bacterium Rhodobacter sphaeroides is studied. The environment is modified by isotopic replacement D₂O H₂O or by adding glycerol and dimethyl sulfoxide (DMSO). The replacement D H is shown to makes no impact on the midpoint potential E _m of the electron donor, whereas addition of 70 vol % of glycerol or 35 vol % of DMSO raises E _m by 30 and 45 mV, respectively. Rate constants of charge separation k _e and electron transport onto quinone k _Q remained unchanged following glycerol addition, while deuteration and DMSO addition diminished k _e and k _Q by two to three times. In addition to the known component with a characteristic time of about 10 ns, a component with a duration of 0.5–0.8 ns appears in the recombination kinetics of charges of deuterated and DMSO-treated preparations of reaction centers. The mechanism of the environment response on the emergence of nonequilibrium states of cofactors is analyzed theoretically. The energy model proposed for primary processes of photosynthesis accounts for the contribution made by the environment in the realization of a highly effective electron transport.