Carotenoids fluorescence

When light from all three channels excites the fluorescence of crystalline individual compounds such as allelochemicals flavonoids quercetin and rutin or pigments of plant cells - azulene, chlorophyll and carotenoids fluoresce in different regions of the spectra in yellow and red or blue, red and yellow-orange, respectively (Fig. 7). It compares the light emission of the substances within cellular structures. 

Theoretical calculations have been made for photosynthetic pigments . An extensive review of models of energy and electron transfer events of synthetic molecules for photosynthesis has been prepared by Wasielewski . Other studies have made on tetraphenylporphyrin-polypeptide pigments , photosensitization of triplet carotenoids , fluorescence yields and lifetimes for bacteriochlorophyll c , triplet yields and ESR of chlorophyll 3 8 and quenching processes of pheophytin 539 ... 

Fig. 10. Fluorescence emission and excitation (or absorption) spectra in CSj of p-carotene (A) and fucoxanthin (B). See text for details. Figure source (A) Glllbro and Cogdell (1989) Carotenoid fluorescence. Chem Phys Lett. 158 313. (B) Katoh, Nagashima, and Mimuro (1991) Fluorescence properties of the allenic carotenoid fucoxanthin impiication for energy transfer in photosynthetic pigment systems. Photosynthesis Res 27 223.

Whether carotenoid fluorescence originates from the S2- So or S ->So transition appears to depend on the number of conjugated double bonds, i.e., the chain length, and possibly other molecular-structural factors. For instance, the fluorescence from both (3-carotene and spheroidene, each ofwhich has 10 conjugated double bonds, originates from the S2->So transition, while that of fucoxanthin, which has 8 conjugated double bonds, displays the Stokes-shifted Si- Socmission. 

GillbroTand Cogdell RJ (1989) Carotenoid fluorescence. Chem Phys Lett 158 312-316... 

For carotenoids to function properly they may exist as a protein-pigment complex imbedded within the hydrophobic matrix of cell membranes. The involvement of this complex is partly based on the difficulty in demonstrating carotenoid fluorescence ( ). One of the functions of carotenoids in photosynthesis is the transfer of energy to chlorophylls. Perhaps, DPE s directly or indirectly intercept the electron or energy transfers normally occurring between carotenoids and chlorophylls (, 40). 

In order to compare our in vitro fluorescence data with carotenoid fluorescence in vivo we have studied the fluorescence of spheroide-ne in the B800-850 complex from R, spheroides. The quantum yield was found to be 2 10, in good agreement with results obtained... 

Carotenoid pigments also present other spectroscopic properties such as fluorescence and absorption of energy in the infrared (IR) region. Fluorescence is a property rarely present in the carotenoids, and in fact, only a few carotenoids fluoresce when they are excited at appropriated wavelengths (e.g., phytofluene). Therefore, fluorescence spectroscopy is not frequently used in carotenoid studies. Similarly, the use of... 

More specific methods involve chromatographic separation of the retinoids and carotenoids followed by an appropriate detection method. This subject has been reviewed (57). Typically, hplc techniques are used and are coupled with detection by uv. For the retinoids, fluorescent detection is possible and picogram quantities of retinol in plasma have been measured (58—62). These techniques are particularly powerful for the separation of isomers. Owing to the thermal lability of these compounds, gc methods have also been used but to a lesser extent. Recently, the utiUty of cool-on-column injection methods for these materials has been demonstrated (63). 

The red microalga genus Porphyridium is a source of biochemicals possessing nutritional and therapeutic values. The biochemicals include polysaccharides that have anti-inflammatory and antiviral properties, long-chain polyunsaturated fatty acids, carotenoids such as zeaxanthin, and fluorescent phycobiliproteins. 

NPQ (Rakhimberdieva et al. 2004) exactly matches the absorption spectrum of the carotenoid, 3 -hydrox yech i nenone (Polivka et al. 2005) in the OCP. The OCP is now known to be specifically involved in the phycobilisome-associated NPQ and not in other mechanisms affecting the levels of fluorescence such as state transitions or D1 damage (Wilson et al. 2006). Studies by immunogold labeling and electron microscopy showed that most of the OCP is present in the interthylakoid cytoplasmic region, on the phycobilisome side of the membrane, Figure 1.2 (Wilson et al. 2006). The existence of an interaction between the OCP and the phycobilisomes and thylakoids was supported by the co-isolation of the OCP with the phycobilisome-associated membrane fraction (Wilson et al. 2006, 2007). 

Bailey, S., N. Mann, C. Robinson, and D. J. Scanlan (2005). The occurrence of rapidly reversible non-photochemical quenching of chlorophyll a fluorescence in cyanobacteria. FEBS Lett 579(1) 275-280. Boulay, C., L. Abasova, C. Six, I. Vass, and D. Kirilovsky (2008a). Occurrence and function of the orange carotenoid protein in photoprotective mechanisms in various cyanobacteria. Biochim Biophys Acta 1777(10) 1344-1354. 

Rakhimberdieva, M. G., Y. V. Bolychevtseva, I. V. Elanskaya, and N. V. Karapetyan (2007a). Protein-protein interactions in carotenoid triggered quenching of phycobilisome fluorescence in Synechocystis sp. PCC 6803. FEBS Lett 581(13) 2429-2433. 

Havaux, M. and W.I. Gruszecki. 1993. Heat- and light-induced chlorophyll a fluorescence changes in potato leaves containing high or low levels of the carotenoid zeaxanthin Indications of a regulatory effect of zeaxanthin on thylakoid membrane fluidity. Photochem. Photobiol. 58 607-614. 

The iodine-catalyzed photoisomerization of all-trans- a- and (3-carotenes in hexane solutions produced by illumination with 20 W fluorescence light (2000 lux) and monitored by HPLC with diode-array detection yielded a different isomer distribution (Chen et al. 1994). Four cis isomers of [3-carotene (9-cis, 13-cis, 15-cis, and 13,15-cli-r/.v) and three cis isomers of a-carotene (9-cis, 13-cis, and 15-ri.v) were separated and detected. The kinetic data fit into a reversible first-order model. The major isomers formed during the photosensitized reaction of each carotenoid were 13,15-di-d.v- 3-carotene and 13-ds-a-carotene (Chen et al. 1994). 

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