摘要:

AbstractLe tricyclo[3.3.0.02,8]octadiène‐3,6 (semibullvalène; C8H8) siège d'un réarrangement de Cope intramoléculaire, présente un potentiel à double minimum. Sont enregistrés ses spectres Raman (1) et infra‐rouge (1 et g). 41 fondamentales parmis 42 ont été identifiées et leur attribution proposée. Cette attribution est basée sur la détermination des facteurs de dépolarisation ρp et sur I'analyses des contours rotationnels des bandes en absorption infra‐rouge. Une attention particulière est accordée aux doublets pr

ISSN:0377-0486    

DOI:10.1002/jrs.1250180402

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractResonance inverse Raman spectroscopy was used to examine the interactions between the flavin and surounding protein inL‐lactate oxidase (fromMycobacterium smegmatis) and Old Yellow Enzyme (from brewer's bottom yeast). Spectra were taken of the enzymes both free and bound to various ligands. ForL‐lactate oxidase, the ligands consisted of substrate analogs (acetate, propionate) and inorganic anions (phosphate, sulfate and nitrate). For the inorganic anions, the expected attenuation with detuning was not observed for several bands which are associated with flavin rings II and III. This effect appears to be due to a disruption of ring stacking between the uracil–pyrazine end of the flavin moiety and an aromatic amino acid. A shift in the 1232 cm−1band and changes in the bandwidths of bands in the 1450–1600 cm−1region indicate minor reorganization of the hydrogen bonding structure around the isoalloxazine on ligand binding.For Old Yellow Enzyme, the ligand was chloride. Chloride caused a slight change to the Raman spectrum, indicative of decreased hydrogen bonding to

ISSN:0377-0486    

DOI:10.1002/jrs.1250180403

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractRaman spectra of polycrystalline KVO3have been recorded at various temperatures. Splittings have been observed for most fundamentals and the external mode region contains at least eight bands. The spectra are interpreted in terms of a group theoretical analysis based on the molecular symmetry and the known crystal structure. The frequency versus temperature plots for external modes of KVO3indicate that a single crystal structure exists between 10 and 300 K.

ISSN:0377-0486    

DOI:10.1002/jrs.1250180404

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe surface‐enhanced Raman scattering (SERS) of guanine, guanosine, 2′‐deoxyguanosine, 5′‐dGMP, 5′‐rGMP, 5′‐rGDP and 5′‐rGTP adsorbed on aqueous silver sol has been investigated. The peak position and shape of the guanine ring breathing mode are discussed in terms of sugar conformers, the adsorption geometry, the enol‐to‐keto isomerization and the protonation at the N

ISSN:0377-0486    

DOI:10.1002/jrs.1250180405

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe molecular vibration frequencies of the gallium–chlorine gaseous species were selected. For the known species Ga2Cl6, GaCl3and GaCl selection was performed by comparing previous experimental values with our own Raman spectrometric determinations. For the unidentified species Ga2Cl4, Ga2Cl2and GaCl2frequency values were evaluated from theoretical literature considerations. The Raman spectra of the vapours obtained by heating condensed gallium and chlorine mixtures are discussed using the selected frequencies and taking into account the Ga2Cl6and GaCl3detection limits. With our Raman recording conditions corresponding to well defined spectra, the species are detected up to 5 × 10−3at. Under these conditions, for Cl/Ga = 3 and between 70 and 500 °C, the main gaseous species are GaCl3and Ga2Cl6and the system should be described by the single equilibrium: Ga2Cl6(g)⇌2GaCl3(g). For Cl/Ga = 0.122–3, and between 300 and 800 °C, the representation of the system should be simplified to a single heterogeneous equilibrium between the major species: 2Ga(I)+GaCl3(g)⇌3GaCl(g). In this case, the evolution of the Raman spectra with temperature is explained by taking into account contribution of Ga2Cl4in very s

ISSN:0377-0486    

DOI:10.1002/jrs.1250180406

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractProcedures for the quantitative treatment of Raman spectra are proposed for the investigation of gallium–chlorine gaseous mixtures. They are based on correlations between pressures and Raman band intensities and require a knowledge of reliable entropy and heat capacity data for the main gaseous species. For the ratio Cl/Ga=3 and between 590 and 690 K, the pressure determinations from the band intensity evolution corresponding to the symmetric vibrational modes ‘ν1’ of Ga2Cl6and GaCl3confirm the starting consideration of the single equilibrium Ga2Cl6(g)⇌2GaCl3(g). They lead to an enthalpy of dissociation of Ga2Cl6very close to the literature data. For Cl/Ga3 and between 800 and 950 K, the treatment of the Raman spectra is performed by computation of the GaCl spectrum in order to discriminate between the GaCl3‘ν1’ band intensity and the GaCl ‘νs’ branch intensity. This intensity difference and the GaCl ‘νQ’ branch intensity are used for pressure determinations. The results are consistent with the proposed equilibrium 2Ga(l)+GaCl3(g)⇌3GaCl(g). They lead to a calculated reaction enthalpy that allow one to select a reliable value for the enth

ISSN:0377-0486    

DOI:10.1002/jrs.1250180407

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

Abstract[15N]Tribromoacetonitrile was synthesized with an isotopic content of 99.4% and its Raman spectrum was recorded in the range 4000–50 cm−1; depolarization ratios were also measured. The isotopic shifts arising from15N were determined and interpreted. The fundamental vibrations of Br3CCN and also some overtones, combinations and difference bands were assigned. The molecular structure of tribromoacetonitrile was studied employing GAUSSIAN‐ 82ab initiotheoretical calculations and the Teller‐Redlich isotopic product rule was applied by assuming the following geometrical parameters: CN = 1.163 Å, CC = 1.479Å, BrC = 1.950Å,

ISSN:0377-0486    

DOI:10.1002/jrs.1250180408

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractMounting a sodium nitrate crystal on the surface of a disc made by compacting silver powder and the material to be studied enables Raman spectra of compounds such as zinc and nickel phthalocyanine to be measured in such a way that relative peak inteasities in any one disc can be quantified using the nitrate as a standard. It is a good method for the measurement of low‐temperature spectra of resonant compounds and for the measurement of temperature dependenc

ISSN:0377-0486    

DOI:10.1002/jrs.1250180409

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractA fully computer‐controlled Raman optical activity spectrometer equipped with an intensified diode array detector is described. Despite using a conventional single‐lens light collection system for simplicity, both polarized and depolarized Raman optical activity spectra can be obtained rapidly and routinely. A novel double grating spectrograph design permits good spectra to be obtained down to 50 cm−1in liquids. Natural spectra of the chiral samples (–)‐α‐pinene and (+)‐methylcyclohexanone and magnetic spectra of iridium (IV) hexachloride

ISSN:0377-0486    

DOI:10.1002/jrs.1250180410

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractA simple method for determining the quantitative secondary structure of proteins from their Raman spectra, the reference intensity profiles method, is proposed. This uses as a model the Raman spectral intensities of the backbone amide I vibrations (range 1630–1700 cm−1), corresponding to pure classes of secondary conformations, i.e. α‐helical, β‐sheet and undefined structures. The reference intensity profiles were computed by a step‐by‐step fit of the experimental amide I spectra of a large number of proteins, the secondary structures of which were well known from x‐ray diffraction data in the solid state. The method could be of use in determining the secondary structure of a protein in any state. In the case of a protein in solution, the method solves simultaneously for the secondary structural contents and the subtraction coefficient, thus determining the solvent spectral contribution. The proposed method has been applied with success to a large set of proteins. The correlation coefficient between x‐ray data and the Raman calculated results is close to 0.97 for each class of structure, so accurate estimates of secondary structure may be derived by using the reference intensit

ISSN:0377-0486    

DOI:10.1002/jrs.1250180411

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY