Carotenoid triplet state

Rodgers, M.A.J. and Bates A.L. 1980. Kinetic and spectroscopic features of some carotenoid triplet states Sensitization by singlet oxygen. Photochem. Photobiol. 31 533-537. 

Table II. Attempts to Detect Carotenoid Triplet-state by ESE ...

Then, the carotenoid triplet state decays via non-radiative intersystem crossing ... 

The decay of the carotenoid radical cation absorption of C +-P-C6o occurs on the micro second time scale in the frozen glass. It is accompanied by the rise of C-P-Ceo generated by charge recombination of the C -P-Ceo biradical, which is formed with a quantum yield of 0.07. The major component of the decay of the - C-P-Ceo transient has a time constant of 10 ps, which is a typical lifetime for a carotenoid triplet state. The absorption of C -P-Ceo " at 77 K does not decay exponentially, but an average decay rate of 7.5 x 10 s may be calculated from the data [155]. Time-resolved experiments have allowed detection of the EPR resonances of the C +-P-C6o biradical and C-P-Ceo- The spin-polarization of the carotenoid triplet spectrum verifies formation of this state by the radical pair... 

Again, in order to establish that conclusions can be transferred from porphyrin to chlorophyll-based systems we measured the triplet-triplet energy transfer rate in carotenopyropheophorbide 28 [58]. The rise time of the carotenoid triplet state was faster than the 50 ns response time of the spectrometer, and is likely limited by k, g. 

Miscellaneous Physical Chemistry. Various aspects of the physical chemistry of /3-carotene and related carotenoids have been reported, including several theoretical calculations related to spectroscopic properties,investigations of carotenoid triplet states and triplet energies,studies of carotenoid radical ions, and examination of electron-transfer reactions between carotenoids and chlorophyll Two reviews offer brief surveys of the year s literature on the photochemistry of... 

Cogdell RJ, Monger TG and Parson WW (1975) Carotenoid triplet states in reaction centers from Rhodopseudomonas sphaeroides and Rhodospirillum rubrum. Biochim Biophys Acta 408 189-199... 

Resonance Raman spectra of the RC-bound carotenoid in its triplet state were firstrecorded using pulsed lasers (Lutz et al, 1983). Later on, it was shown that it was possible to accumulate the carotenoid triplet state in the reaction centers with continuous illumination, by making use of the fact that this triplet state is usually produced in these proteins with a high yield when the electron transfer is blocked (Robert et al, 1989 see Fig. 4). From these experiments it was concluded that the particular, 15-15"-dx, twisted, structure of the carotenoid is conserved when these molecules are in the triplet state. In particular, resonance Raman spectra of the RC-bound carotenoid in their triplet states exhibit an unusuallyintense 4, which likely reveals that the molecule is not planar (Lutz et al., 1983, Robert et al, 1989). 

A. Carotenoid Triplet States in Photosynthetic Antenna Complexes.204... 

The spin polarization of the anteima carotenoid triplet state has been observed by Frank et al. (1980 1982a 1987) in quite a number of different purple bacterial strains, and under all conditions shows an eae aea pattern (where e means emission and a absorption of microwaves) that can be explained with intersystem crossing in a BChl molecule with subsequent triplet energy transfer to the carotenoid. This seems to contradict the additional triplet formation pathway by hetero-fission of a carotenoid singlet excitation and it would therefore be of great interest to revisit the earlier time-resolved optical... 

Aust V, Angerhofer A, Ullrich J, von Schiitz JU, Wolf HC and Cogdell RJ (1991) ADMR of carotenoid triplet states in bacterial photosynthetic antenna and reaction center complexes. Chem Phys Lett 181 213-221... 

Carbonera D, Di Valentin M, Agostini G, Giacometti G, Liddell PA, Gust D, Moore AL and Moore TA (1997b) Energy transfer and spin polarization ofthe carotenoid triplet state in synthetic carotenoporphyrin dyads and in natural antenna complexes. Appl Magn Res 13 487-504... 

Frank HA and Violette CA (1989) MonomericbacteriochlorophyU is required for the triplet energy transfer between the primary donor and the carotenoid in photosynthetic bacterial reaction centers. Biochim Biophys Acta 976 222-232 Frank HA, Bolt JD, de B. Costa SM and Sauer K (1980) Electron paramagnetic resonance detection of carotenoid triplet states. J Am Chem Soc 102 4893 898 Frank HA, Machniki J and Felber M (1982a) Carotenoid triplet states in photosynthetic bacteria. Photochem Photobiol 35 713-718... 

Kramer H (1980) Quantum yield and rate of formation ofthe carotenoid triplet state in photo synthetic structures. Biochim Biophys Acta 593 319-329... 

Kung MC and DeVault D (1976) Carotenoid triplet state in R. spheroides GA Chromatophores. Photochem Photobiol 24 87-91... 

McGann WJ and Frank HA (1985) Transient electron spin resonance spectroscopy of the carotenoid triplet state in Rhodopseudomonas sphaeroides wild type, Chem Phys Lett 121 253-261... 

Peterman EJG, DukkerFM, van Grondelle Rand van Amerongen H (1995) Chlorophyll a and carotenoid triplet states in lightharvesting complex 11 of higher plants. Biophys J 69 2670-2678... 

RJ (1989) Carotenoid triplet states in pigment-protein complexes from photosynthetic bacteria Absorption-detected magnetic resonance from 4 to 225 K. Chem Phys Lett 155 363-370... 

The first demonstration that /3-carotene could inhibit photosensitized oxidation and was, therefore, an efficient quencher of O was reported by Foote and Denny (1968). Wilkinson and Ho (1978) showed that quenching by electron exchange energy transfer to produce the carotenoid triplet state ( CAR) is the principal mechanism of carotenoid photoprotection against O ... 

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