Carotenoids absorption spectroscopy

In good electron acceptor solvents, such as carbon tetrachloride and chloroform, the photodegradation of carotenoids is significantly increased as compared to other solvents (Christophersen et al. 1991, Mortensen and Skibsted 1999), because of a direct photoinduced electron-transfer reaction from the excited singlet state of the carotenoids to the solvent, as determined by transient absorption spectroscopy (Jeevarajan et al. 1996, Mortensen and Skibsted 1996,1997a,b, El-Agamey et al. 2005), Equation 12.2 ... 

Cells are typically concentrated by filtration and extracted into an organic solvent (usually acetone) after which, pigments are detected by fluorescence or absorption spectroscopy, sometimes after chromatographic separation (Bidigare and Trees, 2000). The application of HPLC to phytoplankton pigment analysis has lowered the uncertainty in the measurement of Chi a and accessory carotenoids, since compounds are physically separated and individually quantified. 

Electronic Absorption Spectroscopy. Absorption spectra have been obtained for radical cations and anions generated from a number of carotenoids [phytoene (7,8,ll,12,7, 8, ll, 12 -octahydro-i//,i/ -carotene) (135) and canthaxanthin ()3,/3-carotene-4,4 -dione) (130)] and related polyenes [7,7 -dihydro- -carotene (131),... 

The intense colors of the chlorophylls and carotenoids make them ideal candidates for absorption spectroscopy studies (Tan and Soderstrom, 1989). In fact, each plant pigment studied in this experiment has a unique visible spectrum that can provide a positive identification. As shown in Figure E8.3, chlorophylls a and b have absorption maxima in the 600-675 and... 

Degraded Carotenoids Physical Methods Separation and Assay N.M.R. Spectroscopy Mass Spectrometry Chiroptical Methods Electronic Absorption Spectroscopy Infrared and Resonance Raman Spectroscopy Other Spectroscopic Techniques Miscellaneous Physical Chemistry Photoreceptor Pigments Biosynthesis and Metabolism Stereochemistry Enzyme Systems Inhibition and Regulation... 

The absorption spectrum of 22 is nearly identical to the sum of the spectra of unlinked model compounds. The long wavelength band of the free base porphyrin is observed at 650nm in chloroform, whereas that of the zinc porphyrin is at 590nm. Excitation of a chloroform solution of 22 with a 15 ns pulse of 650 nm laser light leads to the formation of a carotenoid radical cation which can be detected by transient absorption spectroscopy (Figure 14). This ion arises from the charge separated state C -Pzh-P-Qa-Qb, and is formed with a quantum yield of 0.83. The lifetime of the species is 55/iS. 

Electronic Absorption Spectroscopy. Extensive tables of light absorption maxima and extinction coefficients for naturally occurring carotenoids are included in the review by Davies. ... 

The importance of carotenoids in photobiology is well known and there is a continuing interest in their photochemistry. Although they do not normally participate in PET processes because of the short lifetimes of their singlet states, incorporation into organized systems with suitable electron acceptors can lead to photoactivity. The dynamics of photoinduced electron injection and recombination between all-trans-8 -apo-p-caroten-8 -oic acid (125) and a Ti02 colloidal nanoparticle have been studied by means of transient absorption spectroscopy. " " An ultrafast ( 360 fs) electron injection from the initially excited S2 state of the carotenoic acid into the Ti02 conduction band with a quantum... 

Electronic Absorption Spectroscopy. A review has been published of the absorption spectra of a range of natural carotenoids." A model has been presented which attributes the widths of carotenoid absorption bands to conformational... 

Two bacteriochlorophyll monomers, and Bg, are located next to the primary donor D, but they are buried deeper in the membrane. Their positions are fixed by helices B, C, D, and de of the L- and M-subunits, respectively. How these so-called accessory bacteriochlorphylls are involved in the ET has been the subject of a long debate (Holzapfel et al., 1990 Kirmaier and Holten, 1991). Some evidence for their function as true electron carriers has been provided by subpicosecond absorption spectroscopy (Arlt et al., 1993 Zinth et al., 1996). The Bg molecule facilitates the triplet energy transfer between D and the carotenoid (Frank and Violette, 1989). B and Bg follow the local Cj symmetry. Their tetrapyrrole rings are superimposed by a rotation (M on L) of -175.8 (Deisenhofer and Michel, 1989a,b) which is not as perfect as for the D /Dgpair. As in the case of Dg,the phytyl side chain of Bg interacts with the M-subunit... 

Hudson BS and Kohler BE (1973) Polyene spectroscopy the lowest energy excited singlet state ofdiphenyloctatetraene and other linear polyenes. J Chem Phys 59 4984-5002 Hudson BS and Kohler BE (1974) Linear polyene electronic structure and spectroscopy. Ann Rev Phys Chem 25 437-460 Hudson BS and Kohler BE (1984) Electronic stmcture and spectra of finite linear polyenes. Synthetic Metals 9 241-253 Hudson BS, Ridyard JN and Diamond J (1976) Polyene spectroscopy. Photoelectron spectra of the diphenylpolyenes. J Am Chem Soc 98 1126-1129 Hudson BS, Kohler BE and Schulten K (1982) Linear polyene electronic structure and potential surfaces. In Lim EC (ed) Excited States, Vol 6, pp 1-95. Academic Press, New York Jones PF, Jones WJ and Davies B (1992) Direct observation of the 2 Ag electronic state of carotenoid molecules by consecutive two-photon absorption spectroscopy. Photochem Photohiol A Chem, 68 59-75... 

Jones PF, Jones WJ and Davies BH (1992) Direct observation of the 2. Ag electronic state of carotenoid molecules by consecutive two-photon absorption spectroscopy./. Photochem Photobiol A Chem. 68 59-75... 

Electronic Absorption Spectroscopy. Doping with iodine and SO3 had a significant effect on the absorption spectrum of /3-carotene. Triplet-triplet absorption spectra have been obtained for six carotenoids, e.g. canthaxanthin carotene-4,4 -dione (181)] in benzene, " and bimolecular rate constants for energy transfer from singlet oxygen to carotenoids evaluated. U.v. spectra of retinal, retinyl acetate, and axerophtene (182) in solid films have been determined. Several papers discuss the light absorption spectra of retinal derivatives as rhodopsin models. ... 

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