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Results for “Spectrum Analysis, Raman”

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At least 703 records · Page 39Linked to original sources

PubMed1984

The structure of crystalline and membrane-bound gramicidin A by vibrational analysis.

The results of normal mode calculations on the beta 4.4, beta 6.3, beta 5.6, and beta 7.2 structures of gramicidin A are compared with infrared and Raman spectra of crystalline native, crystalline Cs+-bound, and vesicle-bound gramicidin A. The observed frequencies and frequency splittings are in good agreement with an assignment of beta 5.6, beta 7.2, and beta 6.3 structures, respectively, to the gramicidin A molecules in the above three systems.

Crystallization↗

PubMed1997

Raman spectroscopy in dental research: a short review of recent studies.

The Raman spectroscopic technique enables us to obtain vibrational (IR and far-IR) spectra of minerals by analyzing scattered light caused by (visible or near-visible) monochromatic laser excitation. The method possesses several advantages over IR absorption, including simple sample preparation, easy spectral/band analysis, and linear-response to mineral/chemical concentrations. In micro-Raman spectrometer systems, samples are positioned under an optical microscope, and specimens can be scanned with a lateral resolution (approximately 1 mm). In this paper, recent applications of micro-Raman spectroscopy and near-infrared Fourier transform Raman spectroscopy in the study of dental hard tissues and of calculus are reviewed. Special attention is given to mineral components in enamel, dentin, and calculus, and to calcium fluoride formed in/on enamel. The results from the use of an Ar(+)-laser/grating-based micro-Raman spectrometer show that: CaF2 formed in/on enamel by APF treatment is detectable and different from pure CaF2; and with the technique, the crystallite orientation in enamel can be determined. A Raman spectrometer based on Fourier transform and a diode-laser-pumped Nd:YAG laser (1.06 mm) can be used to obtain fluorescence-free Raman signals from biological materials, and identification of mineral components present in dental calculus is possible.

Calcium Fluoride↗

PubMed1996

Calcium oxalate crystals in human pathology. Molecular analysis with the laser Raman microprobe.

OBJECTIVE: Calcium oxalate crystals in pathologic specimens were examined by the laser Raman microprobe, a nondestructive spectroscopic technique. Although research focused on the identification of calcium oxalate deposits in tissue sections, kidney stones were also studied to determine the in situ structural specificity of the technique. DESIGN: Paraffin-embedded tissue specimens were cut into sections of 2 to 6 microns. The unstained sections were placed on metal (aluminum)-plated slides and excited with the 514.5-nm line of an argon-ion laser, which was focused to a 1-micron spot size using a high-resolution optical microscope. MAIN OUTCOME MEASURE: The laser Raman microprobe technique generates spectra that differentiate the monohydrate (CaC2O4.H2O, whewellite) and the dihydrate (CaC2O4.2H2O, weddellite) forms of calcium oxalate inclusions in tissue sections. RESULTS: Characteristic spectra were generated and provided unequivocal evidence for the identification of the dihydrate oxalate form of calcium oxalate crystals in cases of oxalosis of the myocardium and for the monohydrate oxalate structure in a case of oxalosis of the pituitary. Finally, the combined occurrence of both oxalate structures was confirmed in kidney stone specimens. CONCLUSION: The results obtained in this investigation demonstrate the efficacy of the laser Raman microprobe as a useful adjunct in diagnostic pathology.

Calcium Oxalate↗

PubMed1998

The quantitative analysis of crystallinity using FT-Raman spectroscopy.

PURPOSE: To establish if FT-Raman spectroscopy can be used to quantitate the degree of crystallinity in a model compound. METHODS: Mixtures containing different proportions of amorphous and crystalline indomethacin were prepared. Using the peak intensity ratio 1698 cm(-1) (crystalline) to 1680 cm(-1) (amorphous), a correlation curve was prepared. This correlation curve was validated by testing further samples of known composition. Partially crystalline indomethacin was prepared by milling crystalline indomethacin. RESULTS: A linear correlation curve was obtained across the entire range of 0-100% crystallinity. Using this method, it was possible to detect down to either 1% amorphous or crystalline content. The largest errors were found to result from inhomogeneities in the mixing of the calibration and validation samples. The spectra of the mechanically processed samples were similar to the spectra of the calibration samples, and the degree of crystallinity could be estimated in these samples. CONCLUSIONS: FT-Raman spectroscopy is a potentially useful method to complement existing techniques for the quantitative determination of crystallinity.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2005

[Application of depth-analysis of confocal Raman micro-spectroscopy to chirography identification].

Depth analysis of confocal Raman micro-spectroscopy was applied to chirography identification. The result indicated that depth analysis has potential application to forensic science field, especially in longitudinal identification of ink and inkpad. No matter what the spatial distributions of the signature pen and inkpad are, confocal Raman micro-spectroscopy can longitudinally distinguish those spatial differences. All those suggested that confocal Raman micro-spectroscopy is a fast, simple, high sensitive and non-destructive technique.

Forensic Medicine↗

PubMed2006

Single seed Raman measurements allow taxonomical discrimination of Apiaceae accessions collected in gene banks.

NIR-FT-Raman spectroscopy was applied for a nondestructive analysis of single seeds (fruit mericarps) of 36 accessions belonging to various species of the Apiaceae family. Main seed components such as fatty acids, polysaccharides, proteins, and lignin were identified based on the obtained Raman spectra. Variation at the species and genus level was related to differences observed between spectra. The application of cluster analysis discriminated among most of the species evaluated and grouped them according to their taxonomical classification. The spectroscopically analyzed seeds germinated and developed into normal seedlings to demonstrate the additional advantage that Raman spectroscopy is nondestructive and can be applied to living seed without harm. These results indicate that Raman spectroscopy is a valuable tool for the rational evaluation and management of genetic resources in ex situ seed collections by providing useful information for taxonomical validation of the accessions.

Apiaceae↗

PubMed1983