Pigment, Raman spectroscopy

Neelam K, O Gorman N, Nolan J, O Donovan O, Wong HB, Eong KGA, Beatty S (2005) Measurement of macular pigment Raman spectroscopy versus heterochromatic flicker photometry. Invest Ophthalmol Vis Sci 46 1023-1032. doi 10.1167/iovs.04-1032... 

Resonance Raman Spectroscopy. If the excitation wavelength is chosen to correspond to an absorption maximum of the species being studied, a 10 —10 enhancement of the Raman scatter of the chromophore is observed. This effect is called resonance enhancement or resonance Raman (RR) spectroscopy. There are several mechanisms to explain this phenomenon, the most common of which is Franck-Condon enhancement. In this case, a band intensity is enhanced if some component of the vibrational motion is along one of the directions in which the molecule expands in the electronic excited state. The intensity is roughly proportional to the distortion of the molecule along this axis. RR spectroscopy has been an important biochemical tool, and it may have industrial uses in some areas of pigment chemistry. Two biological appHcations include the deterrnination of helix transitions of deoxyribonucleic acid (DNA) (18), and the elucidation of several peptide stmctures (19). A review of topics in this area has been pubHshed (20). 

Pigments in stratigraphic section may be analysed by TXRF (elemental composition), x Raman spectroscopy (functional groups) or XRD (structural analysis). At variance to conventional XRD, SR-XRD allows acquisition of patterns on thin stratigraphic sections... 

In ocular applications, Raman spectroscopy can quickly and objectively assess composite lutein and zeaxanthin concentrations of macular pigment using spatially averaged, integral measurements or images that quantify and map the complete MP distribution with high spatial resolution. Importantly, both variants can be validated with HPLC methods in excised human eyecups and in animal models. 

Pure pigments and dyes can be identified from their IR spectrum. Some reference spectra are given in the Hummel and Scholl collection [9]. Other than simple white pigments or solvent soluble types, identification of pigments in finished products is particularly difficult. Raman spectroscopy can aid the positive identification of pigments such as titanium dioxide. 

Bicchieri M., Nardone M., Russo P.A., Sodo A., Corsi M., Cristoforetti G., Palleschi V., Salvetti A., Tognoni E., Characterization of azurite and lazurite based pigments by LIBS and micro-Raman spectroscopy, Spectrochim. Acta B 2001 56 915-922. 

Clark, R. J. H., Curri, L., Henshaw, G. S., and Laganara, C. (1997). Characterization of brown-black and blue pigments in glazed pottery fragments from Castel Fiorentino (Foggia, Italy) by Raman microscopy, X-ray powder diffractometry and X-ray photoelectron spectroscopy. Journal of Raman Spectroscopy 28 105-109. 

F.R. Perez, Applications of IR and Raman spectroscopy to the study of medieval pigments, in Handbook of Raman Spectroscopy From the Research Laboratory to the Process Line, I.R. Lewis and H.G.M. Edwards (Eds), Practical Spectroscopy 28, Marcel Dekker, New York, 2001. 

Resonance Raman Spectroscopy. A review of the interpretation of resonance Raman spectra of biological molecules includes a consideration of carotenoids and retinal derivatives. Another review of resonance Raman studies of visual pigments deals extensively with retinals. Excitation profiles of the coherent anti-Stokes resonance Raman spectrum of j8-carotene have been presented. Resonance Raman spectroscopic methods have been used for the detection of very low concentrations of carotenoids in blood plasma and for the determination of carotenoid concentrations in marine phytoplankton, either in situ or in acetone extracts. ... 

Ramos PM, Eerre J, Ruisanchez I, Andrikopoulos KS (2004) Euzzy logic for identifying pigments studied by Raman spectroscopy. Appl Spectrosc 58 848-854... 

The basis of phenotypic discrimination of closely related species via Raman spectroscopy lies in its sensitivity to the intracellular molecular components including extrachromosomally encoded phenotypes, such as the Bacillus anthracis or B. thuringiensis toxins or polyglutamic acid capsules. Other prominent examples are cell storage materials like the polyhydroxy butyric acid (PHB), carotenoid-based pigments like sarcinaxanthin, hemoproteins like cytochrome or calcium dipicolinate (CaDPA). Raman spectra of single bacteria, in which the latter four intracellular substances occur, are shown in... 

Resonance Raman and NMR Studies. The major support to the protonation hypothesis is presently based on the recent application of resonance-Raman spectroscopy. (For recent reviews, see refs. 217-219.) The method uses an incident beam which is in resonance with the absorption of the retinyl chromophore. This results in the selective enhancement of the Raman cross sections coupled with the chromophore, relative to the very weak, non-resonant, modes of the opsin. Characteristic spectra are shown in Fig. 6. Early evidence for protonation came from the observation of a close similarity between the C=N vibrational frequency in rhodopsin and in a model protonated Schiff base (220). More conclusive arguments were provided by Oseroff and Callender, who carried out experiments at low temperatures in order to control sample photoability (221). It was observed that deuteration shifts the C=N vibration frequency from 1655 cm- to 1630 cm-- -, both in the pigment and in a model protonated Schiff base. 

Joint interpretation of the IR and Raman spectra of biomolecules, which frequently lack symmetry properties, may afford more extensive information concerning the primary, secondary and tertiary structure, than does the interpretation of one type of spectrum only. Many systems can only be investigated in aqueous solution, a good solvent for Raman spectroscopy. The technique of resonance Raman spectroscopy facilitates investigations of pigments and the NIR FT Raman spectroscopy allows the investigation of nearly all samples which has not been possible before due to absorption and fluorescence. Spectra of biomolecules are exhaustively discussed in Sec. 4.7. Here only some general features are discussed. 

Spectrometric methods such as IR spectroscopy give information on the main components of the examined samples (dyes, resins and oily liquids). The main pigments are easily detectable in the IR spectra of inks. Because of its non-destructive nature, Raman spectroscopy is applied in forensic investigations for the identification of inks directly on a document, and for determination of the... 

The coral Allopora californica also contains a purple-blue complex between (3.S,3 5)-astaxanthin and protein." Both these proteins are relatively simple structures, with molecular weight < 80 000 daltons. Photoacoustic spectroscopy has indicated the presence of a variety of carotenoprotein species in lobster shell, the distribution varying with the depth into the shell.Resonance Raman spectroscopy has revealed that the lobster egg pigment ovoverdin contains two astaxanthin molecules at different sites in the protein. "... 

Infrared and Resonance Raman Spectroscopy. Reviewson the uses of resonance Raman spectroscopy in biochemistry and biology include sections on carotenoproteins, visual pigments, and bacteriorhodopsin. The resonance Raman spectrum of the lowest excited triplet state of /3-carotene has been reported.A resonance Raman method has been used for the quantitative analysis of /3-carotene and lutein (20) in tobacco.The mechanism of carotenoid-protein interactions in the carotenoproteins ovoverdin and /3-crustacyanin has been investigated by resonance Raman spectroscopy. " 2 axanthin (24) has been used as a resonance Raman probe of membrane structure. " The resonance Raman spectra have been reported of all-frans-anhydrovitamin A (194), " /3-ionone, retinals, and Schiff bases.The technique has been used extensively to study... 

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... 

We report on application of Ag nanoparticles in high sensitive surface-enhanced Raman spectroscopy to detect low quantity of art pigments. 

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