摘要:

AbstractThe Raman spectra of violuric acid [2,4,6(1H,3H)‐pyrimidinetrione‐5‐oxime, H3V] and sodium violurate (NaH2V) were investigated as solids and in aqueous solution at different pH. A tentative vibrational assignment is presented. From the Raman spectra obtained in solution it was possible to identify some characteristic Raman shifts for H3V, H2V−and HV2−(violurate dianion). The surface‐enhanced Raman (SER) spectra of the H2V−ion adsorbed on a silver electrode in borate buffer solution (pH 8.4) was also investigated. For potentials less negative than −0.5 V the H2V−anion adsorbs with the nitrogen atom of the oxime group and the oxygen atom of a neighbouring carbonyl group towards the surface. For potentials more negative the surface species undergoes reduction, with the oximate group ( NO−) being reduced to form an NH2group. The SER spectra of this new species are enhanced for potentials mo

ISSN:0377-0486    

DOI:10.1002/jrs.1250220402

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractRaman spectra are reported for ribonuclease and its complexes with the dideoxynucleotides dCpdC, dCpdA and dCpdG, using 240–250‐nm excitation to enhance the purine and pyrimidine modes, as well as tyrosine and phenylalanine modes of the protein. Spectral perturbations associated with binding were examined via difference spectroscopy. Consistent with the crystal structure of CpA* bound to RNase, the 3′‐cytidine was inferred to be hydrogen bonded to a protein donor via the N‐3 ring atom, but not via the carbonyl O atom, since the 1526 cm−1band shifts up on binding, as it does when aqueous CMP is protonated, and the CO stretch shifts from 1655 to 1670 cm−1, an effect attributable to polarization via the N‐3 hydrogen bond. The effect of binding on the spectra of the 5′‐purine rings is limited to intensity changes, an augmentation of the adenine 1578 cm−1band and a diminution of the guanine 1330 cm−1band, consistent with only weak interactions with the protein. Binding of dCpdC intensifies the 1615 cm−1protein band, suggesting environmental changes for tyrosine or phenylalanine residues. No spectral perturbation was observed on mixing RNase with dGpdC or dGpdG, consistent with weak or non‐specific binding of dinucleotides lacking a

ISSN:0377-0486    

DOI:10.1002/jrs.1250220403

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractA method is proposed for calculating the resonance Raman excitation profiles in the case of degenerate excited electronic levels strongly coupled to non‐totally symmetric degenerate vibrations, based on the semi‐classical approach. General equations have been obtained and model calculations with the Monte Carlo method for systems of cubic symmetry have been carried out. There is a simple transform relationship between the absorption spectrum and the Raman amplitude of the non‐totally symmetric mode which prevails. All the equations obtained can also be used for pre‐resonance Raman scattering regardless of the strength of the vibronic c

ISSN:0377-0486    

DOI:10.1002/jrs.1250220404

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractA confocal Raman microspectrometer was developed for the study of small biological objects such as single living cells and metaphase and polytene chromosomes. It employs a confocal detection scheme, well known from confocal fluorescence microscopes, in order to avoid signal contributions from the environment of the samples. The resolution is 0.45 ± 0.05 μm in the lateral direction and 1.3 ± 0.1 μm in the axial direction. The laser excitation wavelength is 660 nm. At this wavelength biological samples do not degrade in the laser radiation as was the case when laser radiation of 514.5 nm was used. The signal throughput from the sample position to the detector was optimized to the extent that in the spectral region around a 1000 cm−1Raman shift 15% of the Raman scattered light collected by the microscope objective is detected. For signal detection a liquid nitrogen‐cooled slow‐scan CCD camera is used. Laser powers of 5–10 mW suffice to obtain high‐quality Raman spectra, with signal integration times of the order of minutes. As an example, spectra obtained from the nucleus and the cytoplasm of an intact human lymphoc

ISSN:0377-0486    

DOI:10.1002/jrs.1250220405

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractRaman spectral examinations of water‐alcohol interactions with various types of polyhydric alcohols at different levels of concentration were conducted. The parameters chosen for study seem to indicate that, at the concentrations used, polyols have little or no effect on the molecular structure of water. Further, the new band in the isotropic spectra of salt solutions reported for various alkali metal halides is absent from the spectra of polyhydric alcohols. It is concluded that polyols have less effect on the molecular organization of water than small but charged entities such as ion

ISSN:0377-0486    

DOI:10.1002/jrs.1250220406

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractRaman spectra were measured for five crystals containingN‐deuterated histidinium and their C2‐deuterated analogues. The spectra showed strong bands assignable to the C4C5stretching mode, ν(C4C5), and the NτC2Nπsymmetric stretching mode, ν(NτC2Nπ), characteristic of theN‐deuterated imidazolium ring. By comparison with the crystal structures, the ν(C4C5) and ν(NτC2Nπ) frequencies are found to increase linearly with increase of the absolute value of the CαCβC4C5torsional angle (χ2, 1), which determines the ring orientation relative to the amino acid backbone. Exceptionally, the ν(NτC2Nπ) frequency of the C2‐deuterated imidazolium ring does not depend on the conformation but shows a correlation with the ND stretching frequency of the ring, indicating that ν(NτC2Nπ) becomes a marker of hydrogen‐bonding strength when the imidazolium ring is deuterated at C2. These marker bands may be useful in studying the conformation and hydrogen‐bonding state

ISSN:0377-0486    

DOI:10.1002/jrs.1250220407

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe IR and Raman spectra of two hydrated molybdates, MgMoO4· H2O and MgMoO4· 5H2O, were recorded and analysed. In both the compounds, bands indicating MoO octahedral coordination are observed. Three crystallographically different water molecules exist in MgMoO4· 5H2O. MgMoO4· H2O exhibits weak hydrogen bonds and MgMoO4· 5H2O hydrogen bonds of medium st

ISSN:0377-0486    

DOI:10.1002/jrs.1250220408

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractBased on group vibrations, a vibrational assignment is proposed for the (P4W8O40)12−ion in Na12P4W8O40· 20H2O. The WO6octahedra and the PO4tetrahedra are found to be distorted in the crystal. Multiple bands observed for the stretching and bending modes of water are due to different strongly hydrogen‐bonded water molec

ISSN:0377-0486    

DOI:10.1002/jrs.1250220409

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe infrared and Raman spectra of M6P6O18· 6H2O (M = Cs, Rb) were recorded and analysed. The frequencies were assigned on the basis of characteristic vibrations of PO 22−‐and POP groups. The P6O 186−anion is found to haveCisymmetry with considerable distortion. The compounds are found to have a structure intermediate between those of chain polyphosphate and cyclic tetra‐ and trimetaphosphates. The presence of three different water molecu

ISSN:0377-0486    

DOI:10.1002/jrs.1250220410

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

ISSN:0377-0486    

DOI:10.1002/jrs.1250220401

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY