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At least 433 records · Page 24Linked to original sources
PubMed2006

Validation of the drop coating deposition Raman method for protein analysis.

Drop coating deposition Raman (DCDR) spectroscopy is critically evaluated to establish the limits to which it may be used to detect changes in protein conformation, binding, and purity. Difference spectroscopy is used to evaluate the reproducibility of the DCDR spectra under various experimental conditions. The results indicate (i) the absence of thermal/photochemical laser damage induced by the Raman excitation laser under typical DCDR data collection conditions, (ii) the reproducibility of DCDR spectra from samples with different volumes or concentrations, (iii) the water content of DCDR protein deposits and associated spectral signatures, and (iv) the degree of similarity between solution Raman spectra and DCDR spectra.

Deuterium Oxide↗
PubMed2005

Detection of meningioma in dura mater by Raman spectroscopy.

Radical tumor resection is the treatment of choice for patients suffering from meningioma. However, recurrence of these tumors is a problem. Tumor recurrences are attributed to residual nests of meningioma within the regional dura. Therefore, complete removal of all tumor-infiltrated dura is important. Meningioma and normal dura were studied by Raman microspectroscopy to assess the possibility of developing an in vivo Raman method for guidance of meningioma resections. Pseudocolor Raman maps were constructed of cryosections of dura and meningioma, obtained from 20 patients. Comparison of these maps with histopathology enabled assignment of the spectra to either meningioma or dura. Large differences exist between the Raman spectra of dura and meningioma, because of the high collagen content of dura and the increased lipid content of tumors. A classification model for dura and tumor tissue based on linear discriminant analysis of Raman spectra yielded an accuracy of 100%. A first attempt was made to determine the minimum amount of meningioma in dura that is detectable by Raman spectroscopy. It is concluded that Raman spectra enable meningioma to be distinguished from dura, which makes Raman spectroscopy a viable candidate for guidance of surgical resection of meningioma.

Dura Mater↗
PubMed2004

A Raman spectroscopic study of thermally treated glushinskite--the natural magnesium oxalate dihydrate.

Raman spectroscopy has been used to study the thermal transformations of natural magnesium oxalate dihydrate known in mineralogy as glushinskite. The data obtained by Raman spectroscopy was supplemented with that of infrared emission spectroscopy. The vibrational spectroscopic data was complimented with high resolution thermogravimetric analysis combined with evolved gas mass spectrometry. TG-MS identified two mass loss steps at 146 and 397 degrees C. In the first mass loss step water is evolved only, in the second step carbon dioxide is evolved. The combination of Raman microscopy and a thermal stage clearly identifies the changes in the molecular structure with thermal treatment. Glushinskite is the dihydrate phase in the temperature range up to the pre-dehydration temperature of 146 degrees C. Above 397 degrees C, magnesium oxide is formed. Infrared emission spectroscopy shows that this mineral decomposes at around 400 degrees C. Changes in the position and intensity of the CO and CC stretching vibrations in the Raman spectra indicate the temperature range at which these phase changes occur.

Hot Temperature↗
PubMed2002

Quantitative analysis of mannitol polymorphs. FT-Raman spectroscopy.

Mannitol is a polymorphic excipient which is usually used in pharmaceutical products as the beta form, although other polymorphs (alpha and delta) are common contaminants. Binary mixtures containing beta and delta mannitol were prepared to quantify the concentration of the beta form using FT-Raman spectroscopy. Spectral regions characteristic of each form were selected and peak intensity ratios of beta peaks to delta peaks were calculated. Using these ratios, a correlation curve was established which was then validated by analysing further samples of known composition. The results indicate that levels down to 2% beta could be quantified using this novel, non-destructive approach. Potential errors associated with quantitative studies using FT-Raman spectroscopy were also researched. The principal source of variability arose from inhomogeneities on mixing of the samples; a significant reduction of these errors was observed by reducing and controlling the particle size range. The results show that FT-Raman spectroscopy can be used to rapidly and accurately quantitate polymorphic mixtures.

Excipients↗
PubMed2003

Evaluating the potential of fluorinated tyrosines as spectroscopic probes of local protein environments: a UV resonance Raman study.

Ultraviolet resonance Raman (UVRR) studies designed to test the utility of fluorinated tyrosines as spectroscopic probes of the local environment are presented. Specifically, resonance Raman spectra of 2-fluoro-L-tyrosine and 3-fluoro-L-tyrosine (3-Y(f)) obtained with 229 nm excitation are reported. In contrast to the modest environmental dependence of the tyrosine resonance Raman spectrum, the spectrum of 3-Y(f) is found to be extremely dependent on the hydrogen bonding strength of the surrounding environment. Preliminary ab initio studies suggest that this behavior is due to normal modes having dominant contributions from the C-OH and C-F internal coordinates. Hydrogen bonding to the solvent perturbs the internal coordinate energetics and/or couplings, thereby altering the character of the normal modes and the corresponding transition frequencies and/or intensities. In addition to the solvent studies, 3-Y(f) is site specifically incorporated into the influenza hemagglutinin (HA) 100-107 peptide which binds to the Fv fragment of the 17/9 anti-HA(98-108) peptide antibody. These studies demonstrate that the spectrum of 3-Y(f) can be monitored in the presence of native tyrosine. In summary, the studies presented here demonstrate that 3-Y(f) holds exceptional promise as a probe of the protein environment.

Cresols↗
PubMed2006

Orientation-insensitive spectra for Raman microspectroscopy.

Separating effects due to molecular conformation from those due to orientation in the spectra of oriented samples obtained by Raman microspectroscopy is a complex issue. To solve this problem, we propose a procedure to calculate an orientation-insensitive spectrum (so-called isotropic spectrum) from polarized spectra obtained by Raman microspectroscopy that is valid for systems that exhibit a uniaxial symmetry. The method has first been tested on highly oriented samples of high-density polyethylene (HDPE). Polarized and isotropic spectra of a highly oriented HDPE cylindrical rod and an isotropic HDPE sample have been compared. The differences in the relative intensities, which occur in the polarized spectra and are due to orientation of the polyethylene chains, are nearly cancelled in the isotropic spectra, showing that the orientation-insensitive spectrum adequately represents the molecular conformation without contributions of orientation. Second, spectra of silk fibroins have been compared in the amide I region for Bombyx mori cocoon silk fibers and methanol-treated regenerated fibroin films. The similarity of the shape of the amide I band of the isotropic spectra indicates that the secondary structure of the fibroins is very close in both samples. These experimental results support the conclusion that the molecular conformation can be efficiently characterized from the intensity and the shape of Raman bands in the orientation-insensitive spectrum.

Animals↗
PubMed2005

Effect of excitation wavelength on the Raman spectroscopy of the porcine photoreceptor layer from the area centralis.

PURPOSE: Raman microscopy, based upon the inelastic scattering (Raman) of light by molecular species, has been applied as a specific structural probe in a wide range of biomedical samples. The purpose of the present investigation was to assess the potential of the technique for spectral characterization of the porcine outer retina derived from the area centralis, which contains the highest proportion of cone:rod cell ratio in the pig retina. METHODS: Retinal cross-sections, immersion-fixed in 4% (w/v) PFA and cryoprotected, were placed on salinized slides and air-dried prior to direct Raman microscopic analysis at three excitation wavelengths, 785 nm, 633 nm, and 514 nm. RESULTS: Raman spectra of each of the photoreceptor inner and outer segments (PIS, POS) and of the outer nuclear layer (ONL) of the retina acquired at 785 nm were dominated by vibrational features characteristic of proteins and lipids. There was a clear difference between the inner and outer domains in the spectroscopic regions, amide I and III, known to be sensitive to protein conformation. The spectra recorded with 633 nm excitation mirrored those observed at 785 nm excitation for the amide I region, but with an additional pattern of bands in the spectra of the PIS region, attributed to cytochrome c. The same features were even more enhanced in spectra recorded with 514 nm excitation. A significant nucleotide contribution was observed in the spectra recorded for the ONL at all three excitation wavelengths. A Raman map was constructed of the major spectral components found in the retinal outer segments, as predicted by principal component analysis of the data acquired using 633 nm excitation. Comparison of the Raman map with its histological counterpart revealed a strong correlation between the two images. CONCLUSIONS: It has been demonstrated that Raman spectroscopy offers a unique insight into the biochemical composition of the light-sensing cells of the retina following the application of standard histological protocols. The present study points to the considerable promise of Raman microscopy as a component-specific probe of retinal tissue.

Animals↗
PubMed2004

Technical note: comparison of Raman, mid, and near infrared spectroscopy for predicting the amino acid content in animal meals.

The objective of this study was to compare three infrared spectroscopy techniques for routine evaluation of AA in animal meals. Animal meals (n = 54) with known AA contents were scanned with a near (NIRS), mid (FTIR), and Raman infrared spectrometer. For NIRS and Raman, samples were scanned "as is", whereas for FTIR, samples had to be finely ground before scanning to obtain reasonable spectra. Both FTIR and Raman data suffered from noise; for Raman, this prevented the development of calibrations. Using derivatized spectral data and a standardized outlier removal procedure, calibrations for nutritionally relevant AA could be developed that were equivalent for both NIRS and FTIR. The variation across AA tested explained (r2) by these calibrations was 70% for NIRS and 68 + 3% for FTIR. Removing spectral data between 4,000 and 2,000 cm(-1) from the FTIR data improved calibrations (P = 0.09) and explained an average of 77% of the variation with prediction errors lower than obtained with NIRS (P < 0.01). However, FTIR calibrations based on the entire or the shortened spectrum contained fewer samples than did NIRS calibrations (41 and 39 vs. 48, respectively; P < 0.01) because more samples were removed as outliers. In conclusion, Raman did not yield acceptable spectra for animal meals. For FTIR, sample preparation was more time-consuming because the samples required grinding before analysis. Using the entire mid-infrared range, FTIR calibrations were comparable to NIRS calibrations. Calibrations for FTIR were improved by eliminating wave numbers that exhibited more noise, resulting in prediction errors better than those for NIRS. Thus, FTIR has the potential to yield better calibrations for AA in animal meals than NIRS, but it requires greater care in sample preparation and scanning.

Amino Acids↗