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PubMed1978

A vibrational analysis of rhodopsin and bacteriorhodopsin chromophore analogues: resonance Raman and infrared spectroscopy of chemically modified retinals and Schiff bases.

Resonance Raman spectroscopy has been used to study chemically modified retinal analogues involving chain substitutions, ring substitutions, or Schiff-base linkages. In addition, retinal fragments and fully deuterated retinals were investigated, and infrared spectra of the four isomers of retinal were obtained. Low-frequency resonance Raman spectra are also reported for all of the isomers of retinal, for the protonated and unprotonated Schiff bases of trans-retinal, for beta-ionone, and for trans-3-dehydroretinal. Band assignments were made to specific vibrational motions, and these assignments have led to a detailed understanding of the spectral features observed in the resonance raman spectra of the retinylidene chromophore in rhodopsin and bacteriorhodopsin.

Bacteriorhodopsins↗
PubMed2006

Combined FT-Raman spectroscopic and mass spectrometric study of ancient Egyptian sarcophagal fragments.

The application of combined Raman spectroscopic and GC-MS analytical techniques for the characterisation of organic varnish residues from Egyptian Dynastic funerary sarcophagal and cartonnage fragments from the Graeco-Roman period, ca. 2200 BP, is described. The nondestructive use of Raman spectroscopy was initially employed to derive information about the specific location of organic material on the specimens, which were then targeted in specific areas using minimal sampling for GC-MS analysis. In the case of the sarcophagal fragment, a degraded yellow-brown surface treatment was identified as a Pistacia spp. resin; this provides additional evidence for the use of this resin, which has previously been identified in Canaanite transport amphorae, varnishes and "incense" bowls in an Egyptian Late Bronze Age archaeological context. The cartonnage fragment also contained an organic coating for which the Raman spectrum indicated a degradation that was too severe to facilitate identification, but the GC-MS data revealed that it was composed of a complex mixture of fatty acid residues. The combined use of GC-MS and Raman spectroscopy for the characterisation of organic materials in an archaeological context is advocated for minimisation of sampling and restriction to specifically identified targets for museum archival specimens.

Archaeology↗
PubMed2005

Structural characterization of tellurite glasses doped with transition metal oxides using Raman spectra and ab initio calculations.

Systems of iron tellurite glasses were prepared by melt quenching with compositions of [85%TeO2+5%Fe2O3+10%TMO], where transition metal oxides (TMO) are TiO2, V2O5, MnO, CoO, NiO and CuO. Furthermore, the main structural units of these samples have been characterized by means of Raman spectra (150-1200 cm(-1)) as well as wavenumber predictions by means of Gaussian 98 ab initio calculations for the proposed site symmetries of TeO4(4-) triagonal bipyramid (C2v) and Te2O7(6-) bridged tetrahedra (Cs and C1). Aided by normal coordinate analysis, calculated vibrational frequencies, Raman scattering activities, force constants in internal coordinates and potential energy distributions (PEDs), revised vibrational assignments for the fundamental modes have been proposed. The main structural features are correlated to the dominant units of triagonal bipyramid (tbp) or bridged tetrahedral (TeO3+1 binds to TeO3 through TeOTe bridge; corner sharing). Moreover, the Raman spectra of the investigated tellurites reflect a structural change from tbp (coordination number is four) to triagonal pyramidal (coordination number is three).

Glass↗
PubMed2006

In situ monitoring by quantitative Raman spectroscopy of alcoholic fermentation by Saccharomyces cerevisiae under high pressure.

We monitored alcoholic fermentation in Saccharomyces cerevisiae as a function of high hydrostatic pressure. Ethanol production from 0.15 M glucose was measured by Raman spectroscopy in situ in a diamond-anvil cell. At 10 MPa, fermentation proceeds three times faster than at ambient pressure and the fermentation yield is enhanced by 5% after 24 h. Above 20 MPa, the reaction kinetics slows down with increasing pressure. The pressure above which no more ethanol is produced is calculated to be 87 +/- 7 MPa. These results indicate that the activity of one or several enzymes of the glycolytic pathway is enhanced at low pressure up to 10 MPa. At higher pressures, they become progressively repressed, and they are completely inhibited above 87 MPa. Although fermentation was predicted to stop at ca. 50 MPa, due to the loss of activity of phosphofructokinase, the present study demonstrates that there is still an activity of ca. 30% of that measured at ambient pressure at 65 MPa. This study also validates the use of Raman spectroscopy for monitoring the metabolism of living microorganisms.

Ethanol↗
PubMed1983

Laser Raman studies of the 5 S rRNA-protein L5 complex of rat liver ribosomes.

The effects of ribosomal protein L5 on the conformation of 5 S rRNA in the 5 S rRNA-protein L5 complex extracted from rat liver ribosomes have been studied by laser Raman spectroscopy. A comparison of the spectra shows small protein-induced conformational changes in the 5 S rRNA, but most of the base-paired regions appear to be present in the complex with protein L5 as well as in the free 5 S rRNA. Furthermore specific interactions between 5 S rRNA and protein L5 are indicated. Cytosine (and/or uracil) residues in single-stranded regions and the N(7) of guanine are engaged in interactions with the protein as suggested by the Raman data.

Animals↗
PubMed2005

Hydration properties of N-(alpha-hydroxyacyl)-sphingosine: X-ray powder diffraction and FT-Raman spectroscopic studies.

The thermotropic properties of N-(alpha-hydroxyacyl)-sphingosine (CER[AS]) in dry and hydrated state were studied by means of X-ray powder diffraction and FT-Raman spectroscopy. The polymorphic states of the CER[AS]/water mixture (lamellar crystalline, lamellar hexagonal gel, liquid crystalline) depend on the thermal pre-treatment of the sample. Only by heating the CER[AS]/water mixture above the melting chain transition can the system be hydrated. At room temperature, both dry and hydrated states form lamellar structures, which differ in their repeat distance and packing of hydrocarbon chains. Above the melting chain transition, hydrated CER[AS] forms a liquid crystalline hexagonal phase, whereas anhydrous CER[AS] forms an isotropic liquid phase. The various phases of hydrated CER[AS] are distinguished on the basis of the corresponding Raman spectra.

Ceramides↗
PubMed2004

An infrared and Raman spectroscopic study of natural zinc phosphates.

Zinc phosphates are important in the study of the phosphatisation of metals. Raman spectroscopy in combination with infrared spectroscopy has been used to characterise the zinc phosphate minerals. The minerals may be characterised by the patterns of the hydroxyl stretching vibrations in both the Raman and infrared spectra. Spencerite is characterised by a sharp Raman band at 3516 cm(-1) and tarbuttite by a single band at 3446 cm(-1). The patterns of the Raman spectra of the hydroxyl stretching region of hopeite and parahopeite are different in line with their differing crystal structures. The Raman spectrum of the PO4 stretching region shows better band separated peaks than the infrared spectra which consist of a complex set of overlapping bands. The position of the PO4 symmetric stretching mode can be used to identify the zinc phosphate mineral. It is apparent that Raman spectroscopy lends itself to the fundamental study of the evolution of zinc phosphate films.

Crystallization↗
PubMed2005

FT-Raman spectroscopic study of calcium-rich and magnesium-rich carbonate minerals.

Calcium and magnesium carbonates are important minerals found in sedimentary environments. Although sandstones are the most common rock colonized by endolith organisms, the production of calcium and magnesium carbonates is important in survival strategies of organisms and as a source for the removal of oxalate ions. Extremophile organisms in some situations may convert or destroy carbonates of calcium and magnesium, which gives important information about the conditions under which these organisms can survive. The identification on the surface of Mars of 'White Rock' formations, in Juventae Chasma or Sabaea Terra, as possibly carbonate rocks makes the study of these minerals a prerequisite of remote Martian exploration. Here, we show the protocol for the identification by Raman spectroscopy of different calcium and magnesium carbonates and we present a database of relevance in the search for life, extinct or extant, on Mars; this will be useful for the assessment of data obtained from remote, miniaturized Raman spectrometers now proposed for Mars exploration.

Calcium Carbonate↗
PubMed2006

Laser induced fluorescence bands in the FT-Raman spectra of bioceramics.

A new fluorescence band at about 1930cm-1 has been observed in the FT-Raman spectra of some bioceramics. While a fluorescence band at about 760cm-1 has been already reported in the FT-Raman spectra of hydroxyapatite and related calcium phosphates, this new band is observed for the first time. This strong band is totally absent in the anti-Stokes side of the FT-Raman spectra and therefore has been assigned as a laser induced fluorescence band. It has been concluded that in recording FT-Raman spectra of minerals, all precautions about fluorescence bands should be considered, otherwise the FT-Raman spectra may well be misinterpreted.

Biocompatible Materials↗