Fluorescence-detected triplet kinetics study of the specifically solvated chlorophyll a and protochlorophyll in frozen solutions

ROOM TEMPERATURE TIME‐RESOLVED IN μs RANGE DELAYED LUMINESCENCE OF CHLOROPHYLL a AND CHLOROPHYLL‐LUTEIN MIXTURE SOLUTIONS

“…Wrdbel (1987) has shown that in liquid crystalline medium, a model of biological membrane, the Chl Mg atom of Chl a is pentacoordinated. The Chl molecules are easily solvated forming at least three types of ligands (Mauring et al, 1987). The spin-forbidden triplet-singlet transition rate is particularly sensitive to the environmental perturbation of pigment molecules.…”

“…The spin-forbidden triplet-singlet transition rate is particularly sensitive to the environmental perturbation of pigment molecules. This perturbation is different in various solvates and aggregates of pigments (Mauring, 1987). Intersystem crossing efficiency is wavelength dependent even for monomeric forms of porphyrin pigment (Bennett et al, 1989), and this dependence could be very strong when the set of various ligands with strongly overlapped spectra occur in a sample.…”

“…Intersystem crossing efficiency is wavelength dependent even for monomeric forms of porphyrin pigment (Bennett et al, 1989), and this dependence could be very strong when the set of various ligands with strongly overlapped spectra occur in a sample. The interaction of Chl with water is very special and strong (Katz and Hindman, 1982;Mauring et al, 1987). Water has an exceptionally high affinity towards the central metal atom (Mauring et al, 1987), therefore its influence in the Phe case must be lower.…”

“…The interaction of Chl with water is very special and strong (Katz and Hindman, 1982;Mauring et al, 1987). Water has an exceptionally high affinity towards the central metal atom (Mauring et al, 1987), therefore its influence in the Phe case must be lower. From the results presented it follows that bands of DL characterized by various decay times and spectral locations are related to different aggregated forms of pigments.…”

“…Delay in observed emission can also be caused by the trapping and detrapping, with thermal energy participation, of excitation from metastable states related to various Chl clusters or ligands followed by the transfer of energy between these forms. Such aggregated or solvated species can have lower energy levels than those of the monomeric pigment molecules because of exciton splitting (Katz and Hindman, 1982;Netzel, 1982;Boxer, 1983), as a result of the bonding of the pigment to a macromolecule (Uehara et al, 1988), or by ligand formation and the solvation effect (Clarke et al, 1982;Mauring, 1987). The delayed emission is weak and therefore it is not easy to establish which mechanism is responsible for its generation (Goedheer, 1966).…”