title: Phosphorescence study of chlorophyll d photophysics. Determination of the energy and lifetime of the photo-excited triplet state. Evidence of singlet oxygen photosensitization.
abstract: Chlorophyll d (Chl d) is the major pigment in both photosystems (PSI and II) of the cyanobacterium Acaryochloris marina, whose pigment composition represents an interesting alternative in oxygenic photosynthesis. While abundant information is available relative to photophysical properties of Chl a , the understanding of Chl d photophysics is still incomplete. In this paper, we present for the first time a characterization of Chl d phosphorescence, which accompanies radiative deactivation of the photoexcited triplet state of this pigment. Reliable information was obtained on the energy and lifetime of the Chl d triplet state in frozen solutions at 77 K using diethyl ether and aqueous dispersions of Triton X100 as solvents. It is shown that triplet Chl d is effectively populated upon photoexcitation of pigment molecules and efficiently sensitizes singlet oxygen phosphorescence in aerobic solutions under ambient conditions. The data obtained are compared with the previous results of the phosphorescence studies of Chl a and Pheo a, and their possible biological implications are discussed.
authors.affiliation: A.N. Bach Institute of Biochemistry, Russian Academy of Science, Leninskii pr., 33, Moscow, 119071, Russian Federation.
authors.forename: Konstantin V
authors.initials: KV
authors.lastname: Neverov
authors.forename: Stefano
authors.initials: S
authors.lastname: Santabarbara
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Krasnovsky
mesh_terms: D002734:Chlorophyll / Q000378:metabolism*; D000077194:Chlorophyll A; D000458:Cyanobacteria / Q000378:metabolism* / Q000528:radiation effects*; D008027:Light; D008163:Luminescent Measurements / Q000379:methods*; D010100:Oxygen / Q000378:metabolism; D026082:Singlet Oxygen / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D002734:Chlorophyll; D026082:Singlet Oxygen; C107509:chlorophyll d; D010100:Oxygen; D000077194:Chlorophyll A