bluuebunny/crossref_metadata_2025_split huggingface dataset:
Detection of conserved structural elements in ferredoxins and cupredoxins by resonance Raman spectroscopy
Authors: Loehr Thomas M. 
Published: May 2005

AbstractIron‐sulfur proteins and cupredoxins are electron‐transfer proteins containing metal—cysteinate ligation. Both classes of proteins have intense (Cys)S → Mox charge‐transfer bands that are effective for resonance enhancement of Raman‐active modes of vibration of the metal ion chromophores. Resonance Raman (RR) spectroscopy provides a sensitive and powerful method for the investigation of the structural details of the metal clusters. The abundance of normal modes in plant ferredoxins and high‐potential iron proteins has been shown to arise from coupling of the FeS stretching modes with an SCC deformation mode that is at a maximum when the FeSCC dihedral angle is ∼ 180°. X‐ray crystallographic results support these findings. For cupredoxins, the complexity of the RR spectra has been considerably more difficult to understand. However, the availability of several high‐resolution crystal structures of plant and bacterial cupredoxins has shown that the conformation of the cysteinate ligand is highly conserved, and that the five‐atom chain consisting of CuSγCβCαN is coplanar. This coplanarity provides a mechanism for coupling ν(CuS) with δ(CuSC), δ(SCC) and δ(CCN) deformation modes. Experiments with Cu, N and H isotopes have extended these assignments by revealing the extent of the coupled modes of vibrations. Modern molecular biology techniques are now providing site‐specific ligand mutations that are revolutionizing the study of the metal clusters in these electron‐transfer proteins.
Time‐resolved resonance Raman studies of bacteriorhodopsin and its intermediates K590 and L550: Biological implications
Authors: Lohrmann R. , Stockburger M. 
Published: May 2005

AbstractExperiments with a spinning cell and a single continuous‐wave laser beam (514 nm) in reflection geometry were performed to obtain the resonance Raman (RR) spectra of the intermediate K590 of the retinal chromophore of bacteriorhodopsin (bR). Samples of diluted aqueous suspensions of ‘purple membranes’ from Halobacterium halobium were used, which entail bR as an integral protein. K590 is formed photochemically in ca. 5 ps from the parent chromophore BR570 and in H2O decays into the product L550 with a time constant of ca. 1.2 μs (21°C). Using a flow velocity of ca. 20 m s−1 and a beam waist of 40 μm, the integrated relative concentrations of BR570, K590 and L550 in the beam were 58:33:10, respectively. By this method the ‘late’ K intermediate which is accumulated on a time scale of ca. 1 μs was probed. The spectra of the mixture were recorded with a spectral step width of 0.2 cm−1 and a band width of 4 cm−1. Up to 100 scans were accumulated to obtain the high quality which is required for subtraction and band‐fitting procedures. The contributions of BR570 and L550, whose spectra were obtained in separate experiments, were subtracted leaving the pure spectra of K590. Experiments were performed in H2O and D2O suspensions. Structural changes of the chromophore during the transition from K590 to L550 were inferred from the RP spectra in the hydrogen out‐of‐plane, the fingerprint and the CC/CN stretching regions. It was concluded that in this transition the chromophore relaxes from a distorted to a planar conformation and at the same time a positive charge of the protein envelope approaches the β‐ionone ring of retinal. It is proposed that this electrostatic interaction is important for the biological function of bR.
Theoretical analysis of the resonance CARS spectra of diacetylene single crystals
Authors: Materny A. , Kiefer W. 
Published: May 2005

AbstractA theoretical model is presented which describes the excitation and line profiles of resonance CARS spectra obtained from diacetylene single crystals containing few short polymer chains. The model is based on a crude Born‐Oppenheimer approximation. The electronic wavefunctions are calculated by means of an LCAO MO (linear combination of atomic molecular orbital) method in the Hückel approach. The Franck—Condon integrals are calculated under the assumption of harmonic potential functions. The model includes a distribution of polymer chain lengths and inhomogeneous broadening due to distortions of the monomer host lattice. The simulations of the CARS excitation and line profiles taken from FBS and TS/FBS diacetylene crystals are based on results of former calculations of absorption and linear resonance Raman spectra of these materials. Fairly good agreement between model and experimental CARS spectra is obtained. Strong resonance behaviour can be seen by varying the frequency of the pump laser. Interference effects occur for neighbouring lines, which can also be simulated by the theoretical model. Possibilities for applications of diacetylene polymers as non‐linear optical devices are discussed.
High‐pressure Raman study of K and T forms of the octachloro cyclic phosphazene tetramer P4 N4 CI8
Authors: Muthu D. Victor S. , Chandrabhas N. , Sood A. K. , Venkatesan K. , Venugopalan P. , Jayaraman A. 
Published: May 2005

AbstractThe octachloro cyclic phosphazene tetramer P4N4Cl8 was studied by high‐pressure Raman spectroscopy up to 10 GPa in the K form (boat‐shaped molecule) and in the T form (chair‐shaped molecule). There are pressure‐induced phase transitions in the crystal with the K‐form molecules. There is a conformation change from the T to the K form under a non‐hydrostatic pressure of less than 0.7 GPa.
Fourier transform Raman and infrared vibrational study of human skin: Assignment of spectral bands
Authors: Barry B. W. , Edwards H. G. M. , Williams A. C. 
Published: May 2005

AbstractFourier transform (FT) Raman and infrared spectra of the outermost layer of human skin, the stratum corneum, were recorded. Assignments consistent with the FT Raman vibrations were made for the first time and compared with assignments from the FTIR spectrum. The results demonstrate that FT Raman spectroscopy holds several advantages over FTIR in studies of human skin. The molecular and conformational nature of human skin, and modifications induced by drug or chemical treatments, may be assessed by FT Raman spectroscopy.
Low‐temperature Raman spectrum of phase V ammonium nitrate
Authors: Park Y. S. , Reid J. K. , Brown R. J. C. , Shurvell H. F. , Norrby L. J. 
Published: May 2005

AbstractRaman spectra of polycrystalline normal and three 15N isotopic ammonium nitrates (15NH4NO3, NH4 15NO3 and 15NH4 15NO3) were recorded at various temperatures between 10 and 300 K. Isotopic shifts of both internal and external modes of the ammonium ion relative to isotopic normal NH4NO3 were observed. Various components of the hetero‐ionic coupled internal mode (ν3 of the nitrate ion with ν4′ of the ammonium ion) were assigned with more certainty on the basis of the 15N isotopic shifts. Detailed studies of the temperature dependence of one internal mode (ν1) of the NO3 ‐ ion and several external modes were made. The frequency and half band width versus temperature plots for both the internal mode and the external modes of 15NH4NO3 indicate only one crystal structure (phase V) between 10 and 257 K. Comparison of the frequency shifts between various isotopic compounds in the external mode region permitted a more precise assignment of the lattice modes associated with the NH4+ and NO3− ions to be made.
Normal coordinate analysis and MNDO calculations: Assignment of the vibrational spectrum of acridine
Authors: Butler Catherine A. , Cooney Ralph P. 
Published: May 2005

AbstractA combination of normal coordinate analysis (based on a Urey–Bradley–Kekulé force field) (UBFF) and modified neglect of diatomic overlap (MNDO) calculations were employed to determine a qualitative working assignment of the vibrational spectrum of acridine. This assignment was employed in resonance Raman studies of the chromophoric acridine‐based anti‐tumour drug amsacrine. The assignments emerge from the potential energy distribution (PED) calculations in the normal coordinate analysis and from the potential energy minima and optimized geometry in the MNDO calculations. The MNDO frequency parameters were calibrated using the carbon–hydrogen stretching modes.
Skeletal vibrational spectra of LAuCl3 complexes with heterocyclic nitrogen donors
Authors: Shamir J. , Givan A. , Canovese L. , Cattalini L. , Uguagliati P. , Tobe M. L. 
Published: May 2005

AbstractThe low‐frequency Raman and infrared spectra of a series of gold(III) chloride complexes of the type of LAuCl3 (where L is thiazole, oxazole and their derivatives) were studied. The skeletal gold–chlorine and the gold–ligand vibrations were assigned.
Raman and infrared spectra, conformational stability, vibrational assignment, barriers to internal rotation and ab initio calculations of but‐2‐enoyl chloride
Authors: Durig J. R. , Groner Christian U. , Costner T. G. , Wang Aiying 
Published: May 2005

AbstractThe Raman (3500–10 cm−1) and infrared (3200–50 cm−1) spectra were recorded for the fluid and solid phases of but‐2‐enoyl chloride (crotonyl chloride), trans‐CH3CHCHCClO, where the methyl group is trans to the CClO group, and a complete vibrational assignment is proposed. These data were interpreted on the basis that the s‐trans (anti) form (two double bonds oriented trans to one another) is the most stable form in the fluid phases and the only conformer remaining in the solid state. The asymmetric torsional fundamental of the more stable s‐trans and the higher energy s‐cis (syn) form were observed at 97.5 and 86.9 cm−1, respectively. From these data the asymmetric potential function governing the internal rotation about the CC bond was determined. The potential coefficients are V1 = −111 ± 2, V2 = 1860 ± 48, V3 = 6 ± 2, V4, = −43 ± 24 and V6 = −22 ± 6. The s‐trans to s‐cis and s‐cis to s‐trans barriers were determined to be 1890 and 1785 cm−1, respectively, with an enthalpy difference between the conformers of 105 ± 52 cm−1 [300 ± 149 cal mol−1 (1 cal = 4.184 J)]. Similarly, the barrier governing internal rotation of the CH3 group for the s‐trans conformer was also determined to be 912 ± 30 (2.61 ± 0.09 kcal mol−1) from the torsional fundamental observed in the far‐infared spectrum of the gas. All these data were compared with the corresponding quantities obtained from ab initio Hartree–Fock gradient calculations employing the RHF/3–21G*, RHF/6–31G* and/or MP2/6–31G* basis sets. These results were compared with the corresponding quantities for some similar molecules.
Resonance polarization and phase‐mismatched CARS of pheophytinbexcited in theQyband
Authors: De Boeij W. P. , Lucassen G. W. , Otto C. , Greve J. 
Published: May 2005

AbstractResonance polarization and phase‐mismatched coherent anti‐Stokes Raman scattering (CARS) measurements were performed on pheophytinbdissolved in acetone excited in theQyabsorption band, where strong broad fluorescence makes spontaneous Raman spectroscopy impossible. The phase‐mismatching technique was applied to suppress solvent background and used in combination with the polarization‐sensitive CARS technique to measure directly the\documentclass{article}\pagestyle{empty}\begin{document}$ \chi \mathop {1111}\limits^{(3)} $\end{document}and\documentclass{article}\pagestyle{empty}\begin{document}$ \chi \mathop {1221}\limits^{(3)} $\end{document}components to estimate depolarization ratios. The spectra were fitted by a non‐linear least‐squares procedure yielding vibrational band parameters. Some CARS dispersion information on the vibrational amplitudes was obtained by varying the pump wavelength. CARS excitation profiles based on transform theory were calculated and partly explain the observed amplitude dispersion. The application of the combined phase‐mismatched polarization CARS technique may be useful in many other cases of highly fluorescing molecules when resonantly excited.
Femtosecond three‐colour CARS of liquids with magic polarization conditions
Authors: Purucker H.‐G. , Tunkin V. , Laubereau A. 
Published: May 2005

AbstractIt was shown recently that three scattering mechanisms with different time behaviours can be separated in time‐domain CARS simply by varying the polarization of the detected anti‐Stokes signal. In an extension of this work, the magic angle 49.1° for the elimination of the resonant‐anisotropic contribution was verified experimentally. It was also found that the residual non‐resonant scattering component observed at −60° with suppression of the common CARS interaction represents a six‐wave mixing process involving the optical Kerr effect. Using the novel polarization techniques the vibrational dynamics of neat dimethyl sulphoxide was studied in the CH stretching region. Evidence is reported for homogeneous broadening of the symmetric mode at 2913 cm−1 and for a doublet splitting of the asymmetric Raman band of the liquid at 2996 cm−1 not resolved in spontaneous Raman spectroscopy.
Applications of Raman spectroscopy to the study of polymers and polymerization processes
Authors: Edwards H. G. M. , Johnson A. F. , Lewis I. R. 
Published: May 2005

AbstractThe application of Raman spectroscopy to polymers and polymerization processes is surveyed and the advent of recent advances in instrumental techniques to polymer analysis is highlighted. Some of the problems of the more widely‐used infrared spectroscopic methods, for example in microstructural analysis of polydienes and copolymers, are discussed and the advantages of the Raman spectroscopic technique are explained. The use of near‐infrared excitation and Fourier‐transform Raman instrumentation for process monitoring and polymer composite studies is discussed. Raman microscopic and waveguide spectroscopic studies of small samples and polymer coatings on substrates are considered. Other applications are mentioned in the areas of polymer orientation, surface‐enhanced Raman scattering, conducting polymers, biopolymers and time‐resolved studies.
Waveguide Raman spectroscopy of polymers and polymer laminates
Authors: Tait Jonathan K. F. , Dixon N. Michael , Everall Neil , Davies Gerald , McIntyre Robert , Yarwood Jack 
Published: May 2005

AbstractThe Raman waveguide spectra of a series of polymer laminates obtained using a simple optical waveguide coupling device are reported. The optical properties of these polymer films were obtained by measuring the waveguide coupling angles and the resulting electric field calculations were shown to predict (semiquantitatively) the observed spectra as a function of waveguide mode number. A discussion of the practical difficulties encountered with available polymer samples emphasizes why such measurements are not yet to be regarded as ‘routine’. No unequivocal evidence could be found for interfacial effects at the polymer/polymer interface.
Polytypic structure and low‐frequency Raman spectra of long‐chain compounds: Stearic acid E form
Authors: Kaneko Fumitoshi , Kobayashi Masamichi , Sakashita Hirotoshi 
Published: May 2005

AbstractPolarized Raman spectra in the low‐frequency region were measured for single‐layered (Mon) and double‐layered (Orth II) polytypes of stearic acid, E form. In E(Mon) three intense bands due to the longitudinal acoustic modes (LAM) were observed in both the (cc) and (bc) polarizations (which is consistent with the crystal structure), whereas in E(Orth II) the (cc) and (bc) components split at different frequencies. The LAM modes were analysed using a simple coupled oscillator model involving an interaction between the terminal methyls. The LAM modes vibrating in‐phase between successive bimolecular layers appear at higher frequencies than the antiphase modes, because the interlayer interaction acts only on the former modes. The half‐widths of the higher order harmonics of LAM bands are about twice that of the fundamental.
Theory of dispersion of raman scattering by molecules containing two identical chromophores
Authors: Morozov V. A. 
Published: May 2005

AbstractIt is shown that the interaction between identical chromophores of freely orienting rigid bichromophoric molecule described by the non‐diagonal elements of the molecular damping matrix may lead to unusual dispersion of the depolarization ratios of Raman bands. The forms of the predicted dispersion curves depend on the mechanism for the occurrence of a Raman band and on the mutual orientation of the chromophores. The dispersion curves have anomalous extrema at the frequency of the pure electronic transition of the molecule, i.e. at the maxima of the excitation profiles of Raman lines in an examined frequency field, in contrast to known dispersion curves of the depolarization ratio, the extrema of which are often found to coincide with minima rather than maxima in the excitation profile. This circumstance favours the experimental observation of the predicted curves. Also presented is an excitation profile of the vibrational Raman optical activity signal for such randomly oriented molecules with optically inactive chromophores. This profile has one sign only, unlike the double‐signed spectrum of circular dichroism for such molecules. This makes the recording of this profile under conditions of inhomogeneous broadening of spectral lines more convenient than recording the circular dichroism spectrum.
Fourier transform IR, matrix fourier transform IR, Raman, 13C NMR, 1H NMR and mass spectroscopic study of acetyl isocyanate
Authors: Védova C. O. Della , Mack H.‐G. , Altabef A. Ben 
Published: May 2005

AbstractInfrared data for vapour and matrix‐isolated acetyl isocyanate, CH3C(O)NCO, in argon at low temperature, together with the Raman spectrum of the liquid, suggest the existence at room temperature of only one conformer with Cs symmetry and cis with respect to the double bonds. The study was completed with characterization of the compound by mass, 13C NMR and 1H NMR spectra.
Relative intensities in surface‐enhanced Raman spectra of 9‐methoxy‐2‐N‐methylellipticinium chloride studied by potential energy distribution of the vibrational modes
Authors: Aubard J. , Bernard S. , Levi G. , Grosroyat H. , Christensen D. H. , Sorensen G. O. , Nielsen O. Faurskov 
Published: May 2005

AbstractNear‐infrared Fourier transform (NIR‐FT) Raman and surface‐enhanced Raman spectroscopic (SERS) techniques were used in studies of the vibrational spectrum of 9‐methoxy‐2‐N‐methylellipticinium chloride. NIR‐FT‐Raman spectra were obtained on the powder and SER spectra were measured in silver colloids using dilute aqueous solutions of the drug (2 × 10−6 M, pH 7.5). Some Raman bands in the SER spectrum show increased relative intensities compared with the corresponding bands in the NIR‐FT‐Raman spectrum, whereas other bands show decreased relative intensities. A general valence force field was used in the calculation of the potential energy distribution of the vibrational modes. This calculation reveals that bands from the indole moiety of the molecule show intensity enhancements, whereas bands arising from modes localized in the isoquinolinium part of the molecule show decreasing intensities in the SER spectra. These results strongly indicate that the indole part of the molecule is close to or attached to the silver surface.
Combined Raman and 51V NMR spectroscopic study of vanadium (V) oligomerization in aqueous alkaline solutions
Authors: Amado Ana Margarida , Aureliano M. , Riberio‐Claro Paulo J. A. , Teixeira‐Dias J. J. C. 
Published: May 2005

AbstractThe Raman spectra of aqueous vanadium (V) solutions at different pH values, ranging from 13.1 to 7.0, are presented. The dominant bands in the range 700–1100 cm−1 are assigned to the VO symmetrical stretching of the different oligomers, using additional information from 51V NMR spectra and empirical models. The effects of pH, concentration and ionic strength on the oligomerization equilibria are discussed. The ionic strength is found to affect significantly the oligomer composition of vanadate solutions, which is of interest in biochemical and biological studies.
Experimental verification of backscattering CARS spectroscopy on opaque media
Authors: Weippert A. , Funk J.‐M. , Materny A. , Kiefer W. 
Published: May 2005

AbstractThe applicability of a recently suggested coherent anti‐Stokes Raman spectroscopic (CARS) reflection technique to investigations of strongly absorbing materials was tested. Teh underlying principle is that the CARS signal generated in the surface layers of the sample is detected as a beam which is backscattered from the surface of an opaque medium rather than in transmission. A special experimental arrangement was used which allowed CARS spectra to be obtained with reasonable signal strenth. As an example, experimental results for a TS6 (hexa‐2,4‐diynylene di‐p‐toluenesulphonate)polydiacetylene single crystal are presented. Spectra obtained at different angles of incidence are discussed.
Micro Raman study of dislocations in n‐type doped GaAs
Authors: Paetzold O. , Irmer G. , Monecke J. , Griehl S. , Oettel O. 
Published: May 2005

AbstractMicro Raman spectroscopy was used in order to clarify dislocation‐related effects in a GaAs sample Bridgeman‐grown from a slightly As‐rich melt and doped with Si to achieve a free electron concentration of about 1018 cm−3. The specific advantage of the Raman method is demonstrated by the direct observation of an increase in the carrier concentration in the vicinity of dislocations and by the detection of both crystalline and amorphous As in the dislocation core. A defect model is proposed, which is in a agreement with results obtained by other methods such as high spatial resolution photoluminescence. The possibility of determining internal lattice distortions by means of Raman spectroscopy is discussed, but further systematic investigations are necessary to obtain reliable results.
Infrared and Raman studies on calcium, zinc and cadmium hydroxide halides Ca{O(H,D)}Cl, Cd{O(H,D)}Cl, Zn{O(H,D)}F and β‐Zn{O(H,D)}Cl
Authors: Lutz H. D. , Schmidt M. , Weckler B. 
Published: May 2005

AbstractIR and Raman spectra of Zn(OH)F, β‐Zn(OH)Cl and isostructural Ca(OH)Cl and Cd(OH)Cl and of deuterated specimens recorded at ambient and liquid nitrogen temperature are presented and assigned to OH(OD) stretching, librational and translational modes. The spectra obtained are discussed on the basis of the layered crystal structures of these hydroxide halides. The main results are (i) detection and proof of the presence of very weak hydrogen bonds in the case of M(OH)Cl (M = Ca, Cd) and for OH(2) of Zn(OH)F [in addition to ordinary hydrogen bonds in the case of β‐Zn(OH)Cl and OH(1) of Zn(OH)F] with OH stretching wavenumbers of the corresponding hydroxide ions partially greater than that of free, gaseous OH− ions, (ii) a less symmetrical structure of Ca(OH)Cl and Cd(OH)Cl compared with that obtained from the heavy atoms alone and (iii) proof of the presence of two different kinds of hydroxide ions in nearly equal amounts in Zn(OH)F containing two lattice sites each occupied by F− and OH−. The high‐energy shift of the OH modes mentioned above is attributed to the synergetic effect.
Property tensors and tensorial covariants of classical point groups. Applications to Raman effects of higher order and other problems
Authors: Brandmüller J. , Illig D. 
Published: May 2005

AbstractPolar and axial tensorial covariants without intrinsic symmetries have been calculated using the method of representation theory up to rank 4 for the 32 crystallographic, the 5 pentagonal, the 2 icosahedral, the 7 decagonal and the 5 continuous one‐parametric classical point groups (Curie limiting point groups). The full results have been published as tables by the Fachinformationszentrum Karlsruhe. This paper reviews the general method of calculation, which is based on representation theory using an extension of Neumann's principle. The results are compared critically with various complications of special cases in the literature and a number of errors and inconsistencies are pointed out.