PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Spectrum Analysis, Raman”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6Linked to original sources
PubMed2005

Rapid epidemiological analysis of Acinetobacter strains by Raman spectroscopy.

From earlier publications, we noticed that Raman spectra could potentially be used for subspecies identification of microorganisms. Here we evaluated the technique for its use as a typing tool of Acinetobacter species, using a collection of well-characterised strains from five hospital outbreaks. The strains were previously analysed using molecular techniques as cell envelope protein profiling and ribotyping. In this study, we have typed the strains by AFLP analysis and Raman spectroscopy. We compared the results using hierarchical cluster analysis, which showed highly similar groupings by both techniques. There seemed to be some misclassification between two sets of outbreak strains in the Raman analysis. We ascribe this to the clonal relationship between the strains of both outbreaks, described earlier. This results from a highly similar biochemical composition of the strains involved, and hence a highly similar Raman spectrum. We conclude that Raman spectroscopy could be an easy-to-use alternative in epidemiological studies of Acinetobacter strains and a promising starting point for the development of epidemiological studies in general.

Acinetobacter↗
PubMed1999

Molecular structure of 5-methyl thiophene acryloyl ethyl thiolester: a vibrational spectroscopic and density functional theory study.

Enzyme-substrate intermediates involving the acyl group 5-methyl thiophene acryloyl (5-MTA) bound to the active site of an enzyme via a sulfur or selenium atom have been characterized by Raman spectroscopy (e.g., J. D. Doran and P. R. Carey, Biochemistry 1996, 35, 12495-12502, and M. J. O'Connor et al., J Amer Chem Soc 1996, 118, 239-240). Raman difference spectra reveal the Raman spectrum of the acyl group in the active site and, in turn, these can be used to probe acyl group conformation and active site forces and interactions. In order to improve the understanding of the relationship between conformational states and vibrational spectra of 5-MTA thiolesters, calculations based on a density functional theory analysis are undertaken for 5-methyl thiophene acryloyl ethyl ester. The calculations provide the precise geometries and energies of rotomers of 5-MTA ethyl thiolester involving rotational isomerism about the C--C single bonds flanking the ethylenic linkage and the S--C bond linking the ethyl group to the sulfur atom. The calculations also provide the vibrational spectrum for each conformer and these predictions are compared with the experimental Raman an IR data for the thiolester in carbon tetrachloride. Modes are identified that can act as conformational markers for isomerism about the C--C and S--C2H5 single bonds. These findings are used to identify the two conformational states giving rise to the Raman spectrum of the 5-MTA-S-enzyme formed by the viral cysteine protease HAV-3C.

Acrylates↗
PubMed2006

Surface-enhanced Raman scattering and the adsorption behavior of (RS)-phenylsuccinic acid.

The surface geometry of (RS)-phenylsuccinic acid molecule was studied by analysis of the SERS spectra of aromatic dicarboxylic acid adsorbed on silver colloid surfaces. For a reliable analysis of the SERS spectrum, we also performed density functional theoretical calculations. The SERS spectral features indicated that the RSPSA molecules should bound to the silver as dicarboxylate, with a strongly tilted orientation with respect to the normal to the surface. Such a tilted orientation was presumed to occur by the simultaneous sigma and pi-type coordination of carboxylate groups to silver surface caused by the steric hindrance and electrostatic repulsion between the two carboxylate groups, and thereby RSPSA on silver was easily displaced with aromatic carboxylic acids. A sigma-type coordination therefore seemed to be more important than a pi-type coordination for aromatic carboxylic acid derivatives to assemble on a silver surface. The large enhancement of in-plane bending, out of plane bending and ring breathing modes in the surface-enhanced Raman scattering spectrum indicates that the molecule is adsorbed on the silver surface in a 'at least vertical' configuration, with the ring perpendicular to the silver surface.

Adsorption↗
PubMed2004

Vibrational frequencies and structural determination of digermylcarbodiimide.

The vibrational frequencies and corresponding normal mode assignments of digermylcarbodiimide are examined theoretically using the Gaussian98 set of quantum chemistry codes. All normal modes were successfully assigned to one of eight types of motion (N=C=N asymmetric stretch, N=C=N symmetric stretch, Ge-H stretch, Ge-N stretch, H-Ge-H bend, GeH(3) wag, GeH(3) twist, and Ge-N. . .N-Ge torsion) utilizing the C(2) symmetry of the molecule. Uniform scaling factors were derived for each type of motion. Predicted infrared and Raman intensities are reported.

Carbodiimides↗
PubMed2000

Anomalous temperature dependence of peptide films at air-water interface.

The tetrapeptide derivative Tyr-Gly-Phe-Ala-OBz (1) forms monolayers as confirmed by compressibility studies carried out at various temperatures. Peptide 1 monolayer exhibits an anomalous structural transition at 40 degrees C as evidenced by pi-A isotherms recorded at different temperatures. The structural transition is also observed in aqueous solution of trifluoroacetate of peptide 1 as evidenced by fluorescence and Raman scattering intensity measurements.

Air↗
PubMed2004

[Raman spectroscopy study of 1,3-dimethyluracil and its ab initio (DFT) calculation].

The Raman spectrum of polycrystal 1,3-dimethyluracil (DMU) was obtained and investigated. Ab initio (DFT) calculation (B3PW91/6-31G method) of DMU was performed. And the vibration modes of DMU molecular were analyzed. The results suggest that DMU molecule, as a model compound of bio-base, has some advantages in Raman analysis, such as stronger intensity of marker bands and sharper, clearer bands of double band stretching than uracil's. The ultimate goal of this research is to get large quantity of spectral information of DMU and its cyclobutane dimers, use them as model compounds to research on the Raman characteristics of DNA's or RNA's photodamage. And this work is also an essential supplement to the 1,3-dimethyluracil's Raman study.

Calcium Phosphates↗
PubMed2004

Vibrational frequencies and structural determinations of tetrachlorobutatriene.

The normal mode frequencies and corresponding vibrational assignments of tetrachlorobutatriene in D2h symmetry are examined theoretically using the Gaussian 98 set of quantum chemistry codes. All normal modes were successfully assigned to one of the six types of motion (C=C stretch, CCl2 scissors, CCl2 twist, CCl2 wag, CCl2 rock, and C=C=C bend) predicted by a group theoretical analysis. By comparing the vibrational frequencies with IR and Raman spectra available in the literature, a set of scaling factors is derived.

Chlorine↗
PubMed2006

Ab initio and DFT studies of the molecular structures and vibrational spectra of succinonitrile.

The Molecular structure, conformational stability and vibrational frequencies of succinonitrile NCCH2CH2CN have been investigated with ab initio and density functional theory (DFT) methods implementing the standard 6-311++G* basis set. The potential energy surfaces (PES) have been explored at DFT-B3LYP, HF and MP2 levels of theory. In agreements with previous experimental results, the molecule was predicted to exist in equilibrium mixture of trans and gauche conforms with the trans form being slightly lower in energy. The vibrational frequencies and the corresponding vibrational assignments of succinonitrile in both C2h and C2 symmetry were examined theoretically and the calculated Infrared and Raman spectra of the molecule were plotted. Observed frequencies for normal modes were compared with those calculated from normal mode coordinate analysis carried out on the basis of ab initio and DFT force fields using the standard 6-311++G* basis set of the theoretical optimized geometry. Theoretical IR intensities and Raman activities are reported.

Models, Chemical↗
PubMed1991

Young Investigator Award. Raman spectroscopy of human atherosclerotic plaque: implications for laser angioplasty.

Raman spectroscopy is a specialized technique that permits highly specific identification of specimens, in contrast to fluorescence spectroscopy with which analysis of arterial tissues generates spectra that are broad and featureless, with little difference seen between normal artery and atheroma. Various plaque types and the contributions of different arterial fluorophores were studied to determine if Raman spectroscopy could function as a potential guidance modality for laser angioplasty. Arterial specimens obtained at atherectomy and post mortem were studied in air and while immersed in blood. One hundred fifty-six Raman spectra were collected from arterial specimens and chromatographic samples of collagen, elastin, cholesterol, beta-carotene, and L-tryptophan. Analysis showed both fatty and fibrous atherosclerotic plaques to have characteristic spectral peaks at 1,002, 1,154, and 1,516 cm-1, while the Raman spectrum of normal vessel was featureless. Spectral peaks of beta-carotene were nearly identical to those of fatty plaque. The arterial fluorophores collagen, elastin, cholesterol, and L-tryptophan were non-contributory. The Raman spectrum of fatty plaque immersed in a blood field was also detectable, suggesting that this technique may be useful for in vivo plaque recognition.

Angioplasty, Laser↗
PubMedDate not supplied

Spectroscopic analysis of the oxygenation state of hemoglobin using coherent anti-Stokes Raman scattering.

A method for noninvasively determining blood oxygenation in individual vessels inside bulk tissue would provide a powerful tool for biomedical research. We explore the potential of coherent anti-Stokes Raman scattering (CARS) spectroscopy to provide this capability. Using the multiplex CARS approach, we measure the vibrational spectrum in hemoglobin solutions as a function of the oxygenation state and observe a clear dependence of the spectral shape on oxygenation. The direct extraction of the Raman line shape from the CARS data using a maximum entropy method phase retrieval algorithm enables quantitative analysis. The CARS spectra associated with intermediate oxygenation saturation levels can be accurately described by a weighted sum of the fully oxygenated and fully deoxygenated spectra. We find that the degree of oxygenation determined from the CARS data agrees well with that determined by optical absorption. As a nonlinear optical technique, CARS inherently provides the 3-D imaging capability and tolerance to scattering necessary for biomedical applications. We discuss the challenges in extending the proof of principle demonstrated to in vivo applications.

Algorithms↗
PubMed2006

Structural heterogeneity of wheat arabinoxylans revealed by Raman spectroscopy.

A set of arabinoxylan samples differing in their arabinose composition and various samples of arabino-xylo-oligosaccharide samples were analysed by Raman spectroscopy. Specific signatures for arabinose substitution were found in several spectral regions, that is, 400-600, 800-950 and 1030-1100 cm(-1). A linear relationship was observed between the peak ratio 855/895 cm(-1) of the second derivative spectra and the A/X ratio determined by chemical analysis. Moreover, spectral changes were observed in the 400-600 cm(-1) region assigned to the coupled vibrations mode in the skeleton: while the intensity of the band at 570 cm(-1) increased with the degree of substitution, that at 494 cm(-1) decreased. Similarly, a linear relationship was observed between the peak intensity ratio 570/494 cm(-1) calculated on the second derivative spectra and the composition data. Analysis of Raman spectra of arabino-xylo-oligosaccharides allowed to identify specific spectral features of disubstitution.

Spectrum Analysis, Raman↗
PubMed2004

Vibrational frequencies and structural determination of triethynylmethylgermane.

The normal mode frequencies and corresponding vibrational assignments of triethynylmethylgermane are examined theoretically using the Gaussian98 set of quantum chemistry codes. Each of the vibrational modes was assigned to one of nine types of motion predicted by a group theoretical analysis Ge-C stretch, C[triple bond]C stretch, C-H stretch, C[triple bond]C-H bend, Ge-C[triple bond]C bend, C-Ge-C bend, H-C-H bend, CH3 wag, and CH3 twist) utilizing the C3v symmetry of the molecule. Uniform scaling factors were derived for each type of motion. Predicted infrared and Raman intensities are reported.

Germanium↗
PubMed2006

Raman spectrum, quantum mechanical calculations and vibrational assignments of (95% alpha-TeO2/5% Sm2O3) glass.

Chozen system of tellurite glasses doped with rare earth oxides (95% alpha-TeO(2)+5% Sm2O3) was prepared by melt quenching. Consequently, the Raman spectrum (150-1250 cm(-1)) of the modified tellurite have been recorded. As a continuation to our normal coordinate analysis, force constants and quantum mechanical (QM) calculations for tbp TeO4(4-) (triagonal bipyramid, C(2v)) and TeO(3+1); Te2O7(6-) (bridged tetrahedral), we have carried out ab initio frequency calculations for tpy TeO3(2-) (triagonal pyramidal, C(3v) and C(s)) and tp TeO3(2-) (triagonal planar, D(3h)) ions. The quantum mechanical calculations at the levels of RHF, B3LYP and MP2 allow confident vibrational assignments and structural identification in the binary oxide glass (95% alpha-TeO2 +5% Sm2O3). The dominant three-dimensional network structures in the modified glass are triagonal pyramidal TeO3 with minor features of short range distorted tbp TeO4 and bridged tetrahedral unit of TeO(3+1), leading to a structure of infinite chain. Therefore, alpha-TeO2/Sm2O3 (95/5%) glass experience structural changes from TeO4 (tbp); Te2O7 (TeO(3+1))-->TeO3 (tpy).

Ceramics↗
PubMed1989

Raman microspectroscopy of fixed rabbit and human lenses and lens slices: new potentialities.

Raman spectroscopy is a non-invasive, non-destructive technique for the study of the macromolecular composition of tissues. Raman spectra were obtained from intact fresh and paraformaldehyde fixed rabbit lenses and from thin slices prepared from these lenses. In addition the Raman spectrum of an intact 82-yr-old human lens was compared with a slice of the same lens. It appeared that fixation with paraformaldehyde had only a minor qualitative effect on the Raman spectra and that Raman spectra of intact lenses and lens slices were comparable. It was also shown that in the slice of the old human lens the fluorescence, due to chromophores, could be reduced so that a reliable Raman spectrum could be obtained. The use of slices improves the accuracy of the position at which Raman spectra are recorded and fixation extends the time available for Raman analysis which is particularly important for the study of human lenses. Moreover, slicing enables Raman analysis of old human lenses, which up to now was thought to be impossible due to the overwhelming fluorescence of the chromophores present in these lenses.

Aged↗