Carotenoids resonance

Resonance Raman Spectroscopy and Carotenoid Stereochemistry Resonance Raman Spectroscopy of Excited States of Carotenoids Resonance Raman of Carotenoid Molecules In Vivo Light-Hanresting Proteins... 

Other spectroscopic methods such as infrared (ir), and nuclear magnetic resonance (nmr), circular dichroism (cd), and mass spectrometry (ms) are invaluable tools for identification and stmcture elucidation. Nmr spectroscopy allows for geometric assignment of the carbon—carbon double bonds, as well as relative stereochemistry of ring substituents. These spectroscopic methods coupled with traditional chemical derivatization techniques provide the framework by which new carotenoids are identified and characterized (16,17). 

Resonance states in the excited state carotenoid allowing delocalisation and stabilisation of the excited state. 

Although saponification was found to be unnecessary for the separation and quantification of carotenoids from leafy vegetables by high performance liquid chromatography (HPLC) or open column chromatography (OCC), saponification is usually employed to clean the extract when subsequent purification steps are required such as for nuclear magnetic resonance (NMR) spectroscopy and production of standards from natural sources. 

Because carotenoids are light- and oxygen-sensitive, a closed-loop hyphenated technique such as the on-line coupling of high performance liquid chromatography (HPLC) together with nuclear magnetic resonance (NMR) spectroscopy can be used for the artifact-free structural determination of the different isomers. 

The pattern of the II-NMR spectrum of lycopene differs from the spectra of the other carotenoids because lycopene consists of conjugated double bonds. At 6.6ppm the multiplet of protons 11/11 (6.63ppm) and of proton pairs 15/15 (6.60ppm) resonate adjacent to the doublet of proton pair 7/7 (6.44 ppm), the doublet of proton pair 12/12 (6.29 ppm), the doublet of proton pair 14/14 (6.22 ppm), the doublet of proton pairs 8/8 (6.15ppm), and finally the doublet of proton pair 10/10. The resonance of proton pairs 6/6 and 2/2 are shifted to a higher field at 5.85 and 5.00 ppm due to their position in the conjugated system. 

Putzbach, K., Krucker, M., Grynbaum, M. D., Hentschel, P., Webb, A. G., and Albert, K. 2005. Hyphenation of capillary high-performance liquid chromatography to microcoil magnetic resonance spectroscopy—Determination of various carotenoids in a small-sized spinach sample. J. Pharm. Biomed Anal. 38 910-917. 

When carotenoids such as lutein and zeaxanthin are excited by wavelengths in the -450-550 nm range, they exhibit particularly strong resonance Raman signals that can be used to quantify the amount of carotenoid present. The application of this technique for quantifying the macular carotenoids has been developed, thereby providing another noninvasive physical method for MP measurement. A detailed description of this method is given in Chapter 6. 

Application of Resonance Raman Spectroscopy to the Detection of Carotenoids In Vivo... 

Optical Properties and Resonance Raman Scattering of Carotenoids.89... 

OPTICAL PROPERTIES AND RESONANCE RAMAN SCATTERING OF CAROTENOIDS... 

Bergeson SD, Peatross JB, Eyring NY, Fralick JF, Stevenson DN, and Ferguson SB (2008), Resonance Raman measurements of carotenoids using light emitting diodes, J. Biomed. Opt. 13 044026-1-044026-6. 

Bernstein PS, Zhao DY, Wintch SW, Ermakov IV, and Gellermann W (2002), Resonance Raman measurement of macular carotenoids in normal subjects and in age-related macular degeneration patients, Ophthalmology 109 1780-1787. 

Ermakov IV, Ermakova MR, McClane RW, and Gellermann W (2001a), Resonance Raman detection of carotenoid antioxidants in living human skin, Opt. Lett. 26 1179-1181. 

Gellermann W, Ermakov IV, Ermakova MR, McClane RW, Zhao DY, and Bernstein PS (2002a), In vivo resonant Raman measurement of macular carotenoid pigments in the young and the aging human retina, J. Opt. Soc. Am. A 19 1172-1186. 

Koyama Y (1995), Resonance Raman spectroscopy, in Carotenoids, Vol IB, Spectroscopy, G. Britton, S. Liaaen-Jensen, and H. Pfander, Eds., pp. 135-146, Birkhauser, Basel, Switzerland. 

The resonance Raman spectra are very rich in information. They carry not only a fingerprint of a type of carotenoid and its conformation, but also the information about molecular distortion. Even though the geometric changes are relatively small, resonance Raman can be very useful for the identification and the probing properties of the xanthophyll binding loci. 

In order to obtain nearly absolute purity of the spectra of these xanthophylls, it was necessary to calculate the difference Raman spectra. Therefore, for zeaxanthin, two spectra of samples, one containing violaxanthin and the other enriched in zeaxanthin, were measured at 514.5 nm excitation. After their normalization using chlorophyll a bands at 1354 or 1389 cm-1, a deepoxidized-minus-epoxidized difference spectrum has for the first time been calculated to produce a pure resonance Raman spectrum of zeaxanthin in vivo (Figure 7.10b). A similar procedure was used for the calculation of the pure spectrum for violaxanthin. The only difference is that the 488.0nm excitation wavelength and epoxidized-minus-deepoxidized order of spectra have been applied in the calculation. The spectra produced using this approach have remarkable similarity to the spectra of xanthophyll cycle carotenoids in pure solvents (Ruban et al., 2001). The v, peaks of violaxanthin and zeaxanthin spectra are 7 cm 1 apart and in correspondence to the maxima of this band for isolated zeaxanthin and violaxanthin, respectively. The v3 band for zeaxanthin is positioned at 1003 cm-1, while the one for violaxanthin is upshifted toward 1006 cm-1. 

The v4 region enhancement and structure in the resonance Raman spectra of xanthophylls reviewed in this chapter shows that it can be used for the analysis of carotenoid-protein interactions. Figure 7.8 summarizes the spectra for all four major types of LHCII xanthophylls. Lutein 2 possesses the most intense and well-resolved v4 bands. The spectrum for zeaxanthin is very similar to that of lutein with a slightly more complex structure. This similarity correlates with the structural similarity between these pigments. It is likely that they are both similarly distorted. The richer structure of zeaxanthin spectrum may be explained by the presence of the two flexible P-end rings... 

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