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PubMed2002

Femtosecond coherent Raman spectroscopy and its application to porphyrins.

The results on femtosecond time-resolved coherent anti-Stokes Raman scattering (CARS) experiments for the analysis and control of ground state vibrational dynamics of porphyrin systems are briefly reviewed. By detecting the spectrum of the transient CARS signal, a detailed mapping of the dynamics initiated by the stimulated Raman pump process is achieved. The method yields the dephasing behavior and spectral information of the investigated system at the same time. The different contributions to the ground state vibrational dynamics are selected by changing the direction of the CARS signal analyzer in the polarization arrangement used.

Binding Sites↗
PubMed1988

Raman spectroscopy.

Explore the source record for details and available documents.

Spectrum Analysis, Raman↗
PubMed2006

New method for the microscopic, nondestructive acquisition of ultraviolet resonance Raman spectra from plant cell walls.

Raman spectroscopy has long been used for the chemical analysis of organic matter, including natural products, using excitation wavelengths in the visible, infrared, or ultraviolet portions of the spectrum. The use of ultraviolet resonance Raman spectroscopy (UVRR) to study bulk samples of plant tissue has typically been carried out by rotating homogeneous macro-samples beneath the laser beam in order to minimize the amount of UV radiation impinging on any one spot, thereby avoiding its potentially damaging effects on the organic matter analyzed. This paper extends the use of UVRR to the study on a microscopic scale of individual plant cell walls by use of the controlled micro-displacement of a sample.

Cell Wall↗
PubMed2005

In situ simultaneous analysis of polyacetylenes, carotenoids and polysaccharides in carrot roots.

This paper presents an approach to simultaneously analyze polyacetylenes, carotenoids, and polysaccharides in carrot (Daucus carota L.) roots by means of Raman spectroscopy. The components were measured in situ in the plant tissue without any preliminary sample preparation. The analysis is based on the intensive and characteristic key bands observed in the Raman spectrum of carrot root. The molecular structures of the main carrot polyacetylenes, falcarinol and falcarindiol, are similar, but their Raman spectra exhibit specific differences demonstrated by the shift of their -C[triple bond]C- mode from 2258 to 2252 cm(-)(1), respectively. Carotenoids can be identified by -C=C- stretching vibrations (about 1520 and 1155 cm(-)(1)) of the conjugated system of their polyene chain, whereas the characteristic Raman band at 478 cm(-)(1) indicates the skeletal vibration mode of starch molecule. The other polysaccharide, pectin, can be identified by the characteristic band at 854 cm(-)(1), which is due to the -C-O-C- skeletal mode of alpha-anomer carbohydrates. The Raman mapping technique applied here has revealed detailed information regarding the relative distribution of polyacetylenes, carotenoids, starch, and pectin in the investigated plant tissues. The distribution of these components varies among various carrot cultivars, and especially a significant difference can be seen between cultivated carrot and the wild relative D. carota ssp. maritimus.

Acetylene↗
PubMed1984

Structural analysis of myeloperoxidase by resonance Raman spectroscopy.

Soret excitation of canine myeloperoxidase (MPO) gives rise to a complex resonance Raman (RR) spectrum characterized by multiple bands in the core size and oxidation state marker regions. Relative intensities of the bands obtained by 406- and 454-nm laser excitation were nearly identical and were temperature independent from 77 to 273 K. Spectra of dithionite-reduced and cyanide-coordinated derivatives are also reported. In the native and dithionite-reduced enzyme, there are no detectable bands between 1620 and 1700 cm-1, indicating that the hemes do not contain formyl substituents in conjugation with the macrocyclic ring. Excitation of the visible absorption band at 568 nm gave rise to only very weakly resonance-enhanced spectra. The RR spectra are interpreted within the context of other physical measurements to indicate that MPO contains two equivalent or nearly equivalent chlorin prosthetic groups. Possible mechanistic consequences of these structural features are discussed.

Animals↗
PubMed2006

Theoretical investigation of the structure and vibrational spectra of carbamoyl azide.

Molecular structure and vibrational frequencies of carbamoyl azide NH2CO-NNN have been investigated with ab initio and density functional theory (DFT) methods. The molecular geometries for all the possible conformers of the molecule were optimized using DFT-B3LYP, DFT-BLYP and MP2 applying the standard 6-311++G** basis set. From the calculations, the molecule was predicted to exist predominantly in cis conformation with the cis-trans rotational barrier of about 7.91-9.10 kcal/mol depending on the level of theory applied. The vibrational frequencies and the corresponding vibrational assignments of carbamoyl azide in Cs symmetry were examined theoretically and the calculated Infrared and Raman spectra of the molecule in the cis conformation were plotted. Observed frequencies for normal modes were compare 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.

Azides↗
PubMed2004

Vibrational frequencies and structural determination of digermyl ether.

The normal mode frequencies and corresponding vibrational assignments of digermyl ether in C(2v) symmetry are examined theoretically using the Gaussian 98 set of quantum chemistry codes. All normal modes were successfully assigned to one of six types of motion (Ge-H stretch, Ge-O stretch, Ge-O-Ge bend, H-Ge-H bend, GeH(3) wag, and GeH(3) twist) 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. Predicted infrared and Raman intensities are reported.

Ethers↗
PubMed2003

[Raman spectra and XPS analyses of the diamond-like carbon film deposited by surface wave plasma].

Raman spectrum and X-ray photoelectron spectroscopy (XPS) were used for the structural analysis of diamond-like carbon (DLC) film deposited by surface wave plasma. Decomposition methods were used respectively to achieve the quantitative measurement of sp3 content of the films deposited under different working times. We obtained the result that the sp3 bonding of the films was in the range of 20%-40% and increased with the depositing time by using both analysis methods.

Carbon↗
PubMed2000

[Analysis of poly(dA).poly(dT) structure by Raman spectroscopy and lattice dynamics].

Poly(dA).poly(dT) is a kind of DNA which one strand contains adenine(A) bases, and the other only thymine(T) bases. This DNA possesses flexible structure and the X-ray diffraction for poly(dA).poly(dT) fiber gives three different structures. So it is of interest to study poly(dA).poly(dT) structure in solution. In this paper, Raman spectrum of poly(dA).poly(dT) in 0.2 mol.L-1 NaCl solution was recorded over the spectral range 750-1000 cm-1. The Raman bands at 817 cm-1 and 843 cm-1 exist simultaneously. This implied that the secondary structure of poly(dA).poly(dT) is neither A-conformation nor B-conformation. Normal mode analysis of heteronomous secondary structure from poly(dA).poly(dT) fibers was carried out by the lattice dynamics. Normal modes were assigned by potential energy distribution (PED). The calculated frequencies are good agreement with the observed Raman spectrum. This indicated that poly(dA).poly(dT) in solution probably has the same structure as poly(dA).poly(dT) fiber, namely the poly(dA) chain has the C-3'-endo ring pucker while the poly(dT) chain has the C-2'-endo ring pucker.

DNA↗
PubMed2004

Vibrational frequencies and structural determination of triethynylmethylstannane.

The normal mode frequencies and corresponding vibrational assignments of Triethynylmethylstannane (SnCH(3)(CCH)(3)) are examined theoretically using the Gaussian 98 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 (Sn-C stretch, C[triple bond]C stretch, C-H stretch, C[triple bond]C-H bend, Sn-C[triple bond]C bend, C-Sn-C bend, H-C-H bend, CH(3) wag, and CH(3) twist) utilizing the C(3v) symmetry of the molecule. A set of uniform scaling factors was derived for each type of motion. Predicted infrared and Raman intensities are reported.

Spectrophotometry, Infrared↗
PubMed1997

Raman microspectroscopy of intracellular cholesterol crystals in cultured bovine coronary artery endothelial cells.

Raman microspectroscopy is presented as a promising technique for the in situ characterization of intracellular cholesterol crystals. Crystal characterization is the first step in investigating the effects of various stimuli on their formation and in determining their role in the development of atherosclerosis. Treatment of cultured bovine coronary artery endothelial cells with 22-hydroxycholesterol (220HC) stimulated the production of intracellular crystals, a phenomenon that did not occur in the absence of viable cells. These crystals were identified as a combination of the 220HC starting material and cholesterol. The best fit to the average Raman spectrum of the microscopic crystals was achieved with a combination of 70% Raman contribution from 220HC and 30% from cholesterol. GC/MS analysis of the crystals confirmed the presence of both compounds. These results demonstrate the potential of Raman microspectroscopy as a powerful tool in lipid research, particularly for the in situ characterization of intracellular crystals.

Animals↗