Time-resolved fluorescence spectra of chlorophyll a dimers and aggregates using selective photochemical bleaching

Abstract

Pulsed laser-induced time-resolved fluorescence spectra for chlorophyll a (Chl a) in benzene are reported. These spectra show that, in addition to the monomeric fluorescence, emission bands are observed at 625 and 690 nm, with a broad spectral feature at -740 nm. Results from selective photochemical bleaching experiments with blue and with red pulsed laser light, together with consideration of theoretical calculations of the energy levels of Chl a dimers and oligomers, permit the assignment of the bands at 625 and 690 nm to the Chl a dimer in benzene. The emission at 740 nm is assigned to higher aggregates of Chl a. IntroductionThe aggregation of chlorophylls in solution is the subject of extensive literature. Much of the information concerning dimeric and aggregated species of chlorophyll a (Chl a) has been obtained by spectroscopic methods,'s2 including absorption and fluorescence measurements at

Anti-Stokes Fluorescence Spectra of Chloroplasts in Parachlorella kessleri and Maize at Room Temperature as Characterized by Near-Infrared Continuous-Wave Laser Fluorescence Microscopy and Absorption Microscopy

“…17 Because the fluorescence quantum yield of Chl aggregates has been reported to be significantly lower than that of monomer Chl a, 17 the fluorescent properties of Chl aggregates have been documented less than their absorption properties. Chl a aggregates in pyridine and dried benzene have also been reported to fluoresce very weakly, but detectably, at around 735 and 740 nm, respectively, 41,42 which is consistent with the values observed here for fluorescence at the latest stage of acetone treatment. Although our microscopic absorption spectra do not clearly indicate components with maxima at around 740 nm, there may be several types of Chl aggregates with a wide distribution of absorption peaks.…”

PHOTOPHYSICS IN LIQUID CRYSTALS. FLUORESCENCE BEHAVIOR OF CHLOROPHYLL‐a IN DODECYLCYANOBIPHENYL

“…The effects of such constraints on the photophysics of chlorophyll have been studied in a variety of model systems: micelles (Levanon and Neta, 1982;Chauvet et al, 1982;Chauvet et a/., 1981;Brown et al, 1980;Kiwi and Graetzel, 1980), vesicles (Ford and Tollin, 1982;Cheddar et al, 1980;Kurihara et al, 1979;Miyasaka et al, 1979;Wong et al , 1979;Toyoshima et al, 1977), monolayers (Ke, 1966;Tweet etal., 1964a and b;Jones et al, 1980;Janzen and Bolton, 1979;Janzen et al, 1979). Among other phenomena, aggregates of chlorophyll (Wilton and Konignstein, 1983;Bucks and Boxer, 1982;Freed, 1980;Clarke et al, 1979) and chlorophyll in microcrystalline form (Alfano, 1982;Fong et al, 1982;Dodelet et a / . , 1979) have been reported in such model systems as evidenced by absorption and emission behavior.…”