bluuebunny/crossref_metadata_2025 huggingface dataset:
The conformations adopted by the octamer peptide (AAKA)2 in aqueous solution probed by FTIR and polarized Raman spectroscopy
Authors: Measey Thomas , Schweitzer‐Stenner Reinhard
Published: January 2006

In an effort to further elucidate the chain length dependence of the poly‐L‐proline 31 helical structure (PPII) in short alanine‐based polypeptides, we utilize FTIR, isotropic and anisotropic Raman, and electronic circular dichroism (ECD) spectroscopies to probe the amide I′ band of the unblocked octamer H‐Ala‐Ala‐Lys‐Ala‐Ala‐Ala‐Lys‐Ala‐OD in D2O. Our results are in disagreement with recent notions suggesting that the 31 helical structure increases with an increase in the number of alanine residues.1, 2 Simulations of the spectra were carried out and found to best reproduce experimental spectra using parameters that suggest a 40/60% PPII/β‐strand (ßs) mixture. The amount of PPII in the octamer is found to be significantly lower than what was determined for unblocked alanine‐based peptides of comparable or even larger size. This is confirmed by the relatively weak ECD minimum and maximum at ∼195 and ∼220 nm, respectively, for the octamer relative to tri‐ and tetraalanine.3 In this paper we also address a recent issue concerning the validity of the delocalized character of the amide I mode in unfolded polypeptides containing a significant amount of PPII structure. We conclude that experimental evidence strongly supports the vibrational coupling model used to interpret the amide I mode in unfolded polypeptides. Copyright © 2006 John Wiley & Sons, Ltd.
Polarized Raman spectra of Gd2(MoO4)3 in its orthorhombic structure
Authors: Guy Lucazeau , Denis Machon
Published: January 2006

Polarized Raman spectra of a single crystal of gadolinium molybdate, Gd2(MoO4)3 were obtained between 400 and 80 K. Tentative assignments of high‐wavenumber bands of symmetric and antisymmetric MoO4 stretching modes to the three types of tetrahedra present in the ferroelectric phase described by the C2v8 space group are made on the oriented gas model. A careful analysis of the low‐wavenumber spectra allowed identification of new bands compared to those in the literature. The evolution of wavenumbers in the investigated temperature range indicates that a small structural change takes place at about 200 K. Some modes soften when approaching the ferroelectric–paraelectric transition at 159 °C. Copyright © 2006 John Wiley & Sons, Ltd.
Single‐beam CARS spectroscopy applied to low‐wavenumber vibrational modes
Authors: von Vacano Bernhard , Wohlleben Wendel , Motzkus Marcus
Published: January 2006

In single‐beam coherent anti‐Stokes Raman scattering (CARS) spectroscopy, a complete CARS scheme is accomplished with tailored pulses from a fs‐oscillator by coherent control of the nonlinear signal generation. Here, the application of single‐beam CARS to low‐wavenumber vibrational modes in the range of 50–400 cm−1 is demonstrated by investigating pure liquid‐phase samples and molecules in solution. The spectral resolution (17 cm−1) achieved by coherent control of the CARS process is an order of magnitude better than the spectral width of the excitation pulses (150 cm−1 FWHM). At the same time, nonresonant background is suppressed by more than 1 order of magnitude. It is shown that spectral shaping of the excitation spectrum can drastically extend the accessible range of vibrational modes in single‐beam CARS. The implemented scheme is very well suited for CARS microscopy because of its conceptual simplicity and flexibility, and presents the opportunity for spatially resolved studies of conformational modes in biological samples. Copyright © 2006 John Wiley & Sons, Ltd.
Evaluation of Raman spectroscopy and application of chemometric methods for the differentiation of contemporary ivory specimens I: elephant and mammalian species
Authors: Edwards H. G. M. , Hassan N. F. Nik , Arya N.
Published: January 2006

Specimens of mammoth, African and Asian ivory dentine, and other mammalian species were examined using Fourier–Transform (FT), conventional dispersive (confocal) and remote‐sensing portable Raman spectroscopy, all with near‐infrared laser excitation (1064 and 785 nm). FT‐Raman spectroscopy produced the best quality spectra for differentiation purposes and the application of a fibre probe coupled to a portable Raman spectrometer has also been demonstrated and proposed for the in situ characterization of suspected contraband ivories at airports. In addition to the visual comparison of spectral features, chemometric methods are used to discriminate between African and Asian elephant dentine by analyzing normalized integrated band areas in ten selected wavenumber regions. Principal component analysis separates the spectra of both species into two well‐defined groups based upon their organic and inorganic composition. By means of stepwise discriminant analysis almost 98% of the spectra are correctly classified to their species group memberships. Copyright © 2006 John Wiley & Sons, Ltd.
Time‐resolved resonance Raman spectroscopy of sensory rhodopsin II in the micro‐ and millisecond time range using gated cw excitation
Authors: Naumann Hendrik , Murgida Daniel H. , Engelhard Martin , Klare Johann P. , Hildebrandt Peter
Published: January 2006

A time‐resolved resonance Raman (RR) spectroscopic approach is presented that allows probing the dynamics of photoconvertible systems in a wide dynamics range covering more than six decades. It is based on an external opto‐electronic gating of continuous wave (cw) pump and probe lasers. Pump and probe events, the delay time as well as the repetition of this sequence can be varied from the nanosecond to the second time scale and thus adjusted to the desired time‐resolution and the recovery of the photoreversible system. Upon combination with the rotating cell technique, the approach offers several additional advantages, particularly for studying biological photoreceptors. Unlike in capillary flow systems, only small amounts of sample (ca 10 nmol) are required and no harmful mechanical stress is exerted on the proteins. External gating of cw lasers does not only provide freely adjustable pump and probe times but also avoids high pulse energies with pulsed laser excitation, thereby reducing the risk of unwanted photoinduced processes. The high potential of this approach is demonstrated by studying the formation and decay of a long‐lived intermediate (M400) of the sensory photoreceptor NpSRII from Natronobacterium pharaonis. The results are in very good agreement with the kinetic data derived from transient UV–vis absorption spectroscopy and demonstrate that this technique represents a powerful tool for studying the cofactor dynamics of biological photoreceptors in general. Copyright © 2006 John Wiley & Sons, Ltd.
Raman investigation of pigmentary molecules in the molluscan biogenic matrix
Authors: Barnard W. , de Waal D.
Published: January 2006

Raman spectra of the pigments of several marine mollusc shells have been obtained using the 514.5 nm laser line of an Ar+laser. Shell species were chosen to obtain a variety of colour. The spectra obtained for the molluscan pigments indicated that they are polyacetylenic in nature, and, from the spectral features, it was deduced that the pigments were carotenoids, with unmethylated polyacetylenic backbones of various conjugation lengths. A logarithmic relationship was established between the number of conjugated double bonds (N) and the CC vibration (ν1) of previous reported data for finite polyacetylenic systems, and this relationship was used to evaluate the data obtained in this study. The aragonite and calcite phases of CaCO3were also identified to be present in different species of molluscs. Copyright © 2006 John Wiley & Sons, Ltd.
Quantitative diagnostics of a methane/air mini‐flame by Raman spectroscopy
Authors: Fernández J. M. , Punge A. , Tejeda G. , Montero S.
Published: January 2006

We present a quantitative investigation by linear Raman spectroscopy of a methane/air premixed flame from a commercial burner. Rotational temperatures and absolute densities of the major species, N2, O2, CH4, CO2, and H2O have been measured in a grid of points across the flame section. Axial and radial profiles of temperature and densities are reported, and mass balances along the flame axis are discussed. We show the capabilities of this technique for combustion studies by using currently available standard detectors and spectrometers. Copyright © 2006 John Wiley & Sons, Ltd.
Indole ring orientations of Trp189 in the ground and M intermediate states of bacteriorhodopsin as studied by polarized UV resonance Raman spectroscopy
Authors: Asakawa Kazuhiro , Masuda Satoshi , Takeuchi Hideo
Published: January 2006

Polarized resonance Raman spectroscopy provides a means for orientation analysis of proteins in aligned samples. Previously, we developed a Raman linear intensity difference (RLID) method to determine the orientations of aromatic amino acid side chains in flow‐oriented or membrane‐bound proteins. In this study, we have applied the RLID method to Trp189 in bacteriorhodopsin (BR), a transmembrane protein that acts as a light‐driven proton pump. Among the eight Trp residues in BR, the Raman spectrum of Trp189 has been extracted by subtracting the spectrum of the Trp189 → Phe mutant from that of wild‐type BR. By examining the 251.3‐nm‐exited polarized resonance Raman intensities of two indole ring vibrations of Trp189, the directions of the La and Bb transition moments have been determined with respect the membrane normal in the light‐adapted ground state (BR568) and a photo‐excited intermediate (M). Comparison of the orientations of the Trp189 indole ring derived from the La and Bb inclination angles has shown that the indole ring slightly but significantly reorients toward the ionone ring of the retinal chromophore in the M intermediate. The reorientation of Trp189 is consistent with the previous observation that helix F, on which Trp189 is located, undergoes an outward tilt and the hydrophobic interaction of Trp189 increases in the M intermediate. The RLID method combined with 251.3 nm excitation and point mutation is useful for detecting even a small reorientation of a targeted Trp residue. Copyright © 2006 John Wiley & Sons, Ltd.
Raman and SERS investigations of potassium benzylpenicillin
Authors: Iliescu T. , Baia M. , Pavel I.
Published: January 2006

Raman spectroscopic investigations in combination with density‐functional theory (DFT) calculations were performed on the potassium benzylpenicillin (KBP) molecule. The theoretical values of the geometrical parameters and the vibrational wavenumbers were compared with the experimental X‐ray diffraction and Raman data and a fairly good agreement was obtained. The SER spectrum of the KBP molecule on silver colloid at pH value of 6 was recorded and analyzed. The adsorbed molecule is bonded to the silver surface through the carboxylate group. The comparison between KBP aqueous solution Raman spectrum and SERS data demonstrates that benzene, beta‐lactam, and thiazolidine rings are situated at a relatively large distance to the silver surface and for these rings the electromagnetic mechanism of enhancement can be implied. Copyright © 2006 John Wiley & Sons, Ltd.
Vibrational spectra, conformational stability, structural parameters and ab initio calculations of 2,2,5,5‐tetramethyl‐2,5‐disila‐1‐oxacyclopentane
Authors: Zheng Chao , Yazdi Mehdi R. , Kalasinsky Victor F. , Durig James R.
Published: January 2006

The Raman spectrum (4000–200 cm−1) of liquid and infrared spectra (4000–400 cm−1) of gaseous and liquid 2,2,5,5‐tetramethyl‐2,5‐disila‐1‐oxacyclopentane, c‐OSi(CH3)2CH2CH2Si(CH3)2, have been recorded. Ab initio and density functional theory (DFT) calculations with several different basis sets including diffuse functions have been carried out to predict the conformational stabilities with comparisons to disiloxane (H3SiOSiH3)and 2,5‐disila‐1‐oxacyclopentane (c‐OSiH2CH2CH2SiH2). These calculations predict the twisted C2 conformer as the most stable form of the ring compounds, with the planar C2v conformer a transition state and the envelope Cs conformer not a stable form. These predicted stabilities are supported by the vibrational data. Additionally, force constants, infrared intensities, Raman activities, depolarization ratios and scaled vibrational wavenumbers have been determined from MP2(full)/6–31G(d) calculations for all three molecules and compared with experimental values when available. Predicted r0 structural parameters have been obtained for dimethyl ether, methyl silyl ether and disiloxane, which are compared with the experimentally determined values. On the basis of these data, estimated r0 parameters are provided for both five‐membered rings with the expectation that these values are as accurate as could be measured experimentally in the gas phase. The results are discussed and compared with corresponding quantities for some similar molecules. Copyright © 2006 John Wiley & Sons, Ltd.
Micro‐Raman spectroscopic investigations of graphite in the carbonaceous meteorites Allende, Axtell and Murchison
Authors: Larsen K. L. , Nielsen O. F.
Published: January 2006

The graphite content of the carbonaceous meteorites Allende, Axtell and Murchison was investigated by Raman microscopy. Laser excitation wavelengths at 514.5 (2.43 eV), 785 (1.59 eV) and 1064 nm (1.17 eV) were used for Allende and Axtell. Owing to severe background problems, Raman spectra of Murchison were only recorded at 785 nm. The wavenumber of the order G‐band was independent of the excitation laser wavelength. A linear dependence on the laser excitation energy of the wavenumber for the disorder D‐band was found with an increasing wavenumber for increasing laser energy. The intensity ratios of the D‐band and G‐band for Allende at 514.5 nm were used to find the graphite order diameter (La) for the graphite sheets. This value was used to find correlation factors between the D/G intensity ratios and La in the NIR region at 785 and 1064 nm. La values for Axtell and Murchison were calculated from D/G‐band intensity ratios. The C3‐type meteorites Allende and Axtell show very similar La values around 45 Å, whereas the C2 meteorite Murchison has La around 70 Å. This difference is consistent with different environments during the formation process of the graphite. Copyright © 2006 John Wiley & Sons, Ltd.
Surface‐enhanced resonance Raman and hyper‐Raman spectroscopy of water‐soluble substituted stilbene and distyrylbenzene chromophores
Authors: Leng Weinan , Woo Han Young , Vak Doojin , Bazan Guillermo C. , Myers Kelley Anne
Published: January 2006

Surface‐enhanced Raman spectra (SERS) are presented for two water‐soluble, donor–donor‐ or donor–acceptor‐substituted phenylene vinylene derivatives adsorbed on the surfaces of colloidal silver nanoparticles. The normally water‐insoluble, substituted stilbene and distyrylbenzene chromophores have been modified by attaching trimethylammoniumalkyl chains to the amino donor group, creating both aqueous solubility and a net positive charge that facilitates binding to citrate‐ or borohydride‐reduced silver colloids. A symmetrically donor‐substituted distyrylbenzene exhibits strong electronically pre‐resonant SERS spectra that are not highly dependent on excitation wavelength and are qualitatively similar to the solution‐phase resonance Raman (RR) spectra. A donor–acceptor‐substituted stilbene exhibits weaker SERS enhancement despite being fully electronically resonant. The spectra vary considerably with excitation wavelength and show new lines not present in the solution‐phase spectra, which are attributed to a photoproduct formed on the surface. Two‐photon resonant hyper‐Raman spectra are also presented for the donor–acceptor stilbene, both with and without surface enhancement. Copyright © 2006 John Wiley & Sons, Ltd.
Molecular interactions between the penetration enhancer 1,8‐cineole and human skin
Authors: Williams A. C. , Edwards H. G. M. , Lawson E. E. , Barry B. W.
Published: January 2006

Penetration enhancers are chemicals that temporarily and reversibly diminish the barrier function of the outermost layer of skin, the stratum corneum, to facilitate drug delivery to and through the tissue. In the current study, the complex mechanisms by which 1,8‐cineole, a potent terpene penetration enhancer, disrupts the stratum corneum barrier is investigated using post‐mortem skin samples. In order to validate the use of excised tissue for these and related studies, a fibre optical probe coupled to an FT‐Raman spectrometer compared spectroscopic information for human skin recorded from in vivo and in vitro sampling arrangements. Spectra from full‐thickness (epidermis and dermis) post‐mortem skin samples presented to the spectrometer with minimal sample preparation (cold acetone rinse) were compared with the in vivo system (the forearms of human volunteers). No significant differences in the Raman spectra between the in vivo and in vitro samples were observed, endorsing the use of post‐mortem or surgical samples for this investigational work. Treating post‐mortem samples with the penetration enhancer revealed some unexpected findings: while evidence for enhancer‐induced disruption of the barrier lipid packing in the stratum corneum was detected in some samples, spectra from other samples revealed an increase in lipid order on treatment with the permeation promoter. These findings are consistent with phase‐separation of the enhancer within the barrier lipid domains as opposed to homogeneous disruption of the lipid lamellae. Copyright © 2006 John Wiley & Sons, Ltd.
Study by Raman microscopy of nine variants of the green–blue pigment verdigris
Authors: Chaplin Tracey D. , Clark Robin J. H. , Scott David A.
Published: January 2006

The Raman spectra of nine variants of ‘verdigris’ (organo‐copper complexes) synthesized recently by different methods have been measured at room temperature and at 150 K. The spectra are all characterized by a strong band atca2935 cm−1and weaker bands at 3010, 2985, 2935, 1550, 1445, 1415, 1350 and 940 cm−1at both temperatures; the majority of spectra also feature bands at 220 and 140 cm−1. The features in the 3000–4000 cm−1and 900–50 cm−1regions of the spectra show the greatest differences from sample to sample: those in the high wavenumber region relate directly to the nature of the hydrogen bonding in each sample, while those in the lower region reflect the variations in the Cu–O bonding and crystal structures of each sample. The characteristic bands present in the 900–3000 cm−1region are sufficient for the identification of a sample as a particular form of verdigris. Copyright © 2006 John Wiley & Sons, Ltd.
Introduction of a high‐pressure cell for use with Raman microscopy
Authors: Uhlemann Ute , Schmitt Michael , Oehme Karl‐Ludwig , Notni Johannes , Anders Ernst , Popp Jürgen
Published: January 2006

A high‐pressure cell for Raman spectroscopical applications has been developed. By using this cell, it is possible to investigate reactions between solids and gases, applying pressures up to 3000 bar. The cell has been successfully tested on the reaction between ferrocene and carbon monoxide. The results point towards a multi‐step reaction mechanism. Furthermore, first results are presented for the investigation of the reaction path of CO2 with a zinc thiolate complex. Copyright © 2006 John Wiley & Sons, Ltd.
FT‐Raman and NIR‐SERS characterization of the antimalarial drugs chloroquine and mefloquine and their interaction with hematin
Authors: Cîntǎ‐Pînzaru S. , Peica N. , Küstner B. , Schlücker S. , Schmitt M. , Frosch T. , Faber J. H. , Bringmann G. , Popp J.
Published: January 2006

Raman and surface‐enhanced Raman scattering (SERS) spectroscopies were employed to probe the interaction of the antimalarial drugs chloroquine (CQ) and mefloquine (MQ) with hematin. NIR‐SERS spectra of both quinoline derivatives were obtained from a colloidal gold surface. Strong chemical interactions of each drug with the Au particles are observed and the similarities of the two NIR‐SERS spectra allowed to predict a similar orientation geometry for both of the drugs on the colloidal surface, namely through the quinoline skeletal part of each molecular structure.

Separately, the adsorption behavior of hematin on the Au colloid was studied under nonresonant conditions. In addition, both hematin–antimalarial drug systems (CQ and MQ) were prepared and investigated by NIR‐SERS. Copyright © 2006 John Wiley & Sons, Ltd.
Time‐resolved resonance Raman, time‐resolved UV–visible absorption and DFT calculation study on photo‐oxidation of the reduced form of nicotinamide adenine dinucleotide
Authors: Takahashi Noriko , Shinno Takaaki , Tachikawa Masanori , Yuzawa Tetsuro , Takahashi Hiroaki
Published: January 2006

Photochemical reaction of the reduced form of nicotinamide adenine dinucleotide (NADH) was studied in aqueous solutions using nanosecond time‐resolved resonance Raman and UV–visible absorption spectroscopies combined with DFT/B3LYP calculations. Four transients were detected. A transient exhibiting absorption bands at 370 and 560 nm was assigned to the cation radical NADH+•. A transient having an absorption band at 394 nm was assigned to the deprotonated neutral radical NAD•. A transient exhibiting an absorption band at 493 nm was considered to be attributable to the anion radical NADH−•. The broad and strong band at about 700 nm was assigned to hydrated electrons. It was concluded that the photo‐oxidation of NADH to NAD+ proceeded stepwise via NADH+• and NAD•. The Raman band at 1627 cm−1 of NADH+• was assigned to the CC symmetric stretch of the protonated pyridyl ring of the dihydronicotinamide moiety. It was shown that the CC symmetric stretch of the protonated pyridyl ring exhibited a low‐wavenumber shift from 1688 cm−1 to 1627 cm−1 on going from the ground state to NADH+•. This implies that the protonated pyridyl ring is weakened considerably on ionization in good accord with the DFT calculations. Copyright © 2006 John Wiley & Sons, Ltd.
Identification of the pigments on a sixteenth century Persian book of poetry by Raman microscopy
Authors: Clark Robin J. H. , Mirabaud Sigrid
Published: January 2006

A Persian book of poetry—a poetic history of Shah Isma'il—by Mirza Kasim, dating to A.D. 1541, has been studied by Raman microscopy in order to explore the palette used at this time in Persia. The palette was found to include lazurite, indigo, red lead, vermilion, haematite, carbon black, orpiment, lead white and gold. The palette thus differs from that of another contemporary book of Persian poetry, most notably by the inclusion of indigo, and from that of a 1537–1538 Persian codex by the use of an intimate orpiment/indigo mixture for green rather than the copper‐based mineral malachite. The palette also differs in a few respects from that of a Persian Herati manuscript of A.D. 1530 in that the latter uses an intimate mixture of orpiment and lazurite for green and does not include either haematite or indigo. Copyright © 2006 John Wiley & Sons, Ltd.
Study of vibrational dephasing of CCl stretching mode of 2Cl‐pyridine and 3Cl‐pyridine in methanol environment by polarized Raman study and DFT calculations
Authors: Singh Ranjan K. , Srivastava Sunil K. , Ojha Animesh K. , Arvind U. , Asthana B. P.
Published: January 2006

Raman spectra of [2Cl‐pyridine (2Cl‐p) + methanol] and [3Cl‐pyridine (3Cl‐p) + methanol] mixtures were recorded in the region 360–480 cm−1 and the concentration dependence of linewidths and peak positions of the isotropic part of the Raman scattered radiation for the CCl stretching mode were studied in the light of the existing models. The analysis of the results revealed that concentration fluctuation and diffusion simultaneously play a role in the dephasing of the CCl stretching mode. The optimized structures of the reference systems, 2Cl‐p and 3‐Cl‐p, and their various complexes with methanol were calculated by density functional theory (DFT) geometry optimization technique using B3LYP functional and 6–31 + G(d,p) basis set. On the basis of the results of geometry optimization and energy minimization calculation, we propose that the complex formed as a result of hydrogen bonding of one 3Cl‐p molecule with three methanol molecules is more stable than the one formed by one 3Cl‐p molecule and two methanol molecules. This study presents an explanation of changes in spectral features of ortho/meta Cl‐substituted pyridines supported by DFT derived optimized geometries. Equilibrium constants have been obtained from the spectral data for one of the systems (2Cl‐pyridine + methanol). Copyright © 2006 John Wiley & Sons, Ltd.
Estimating the influence of experimental parameters on the prediction error of PLS calibration models based on Raman spectra
Authors: Wolthuis Rolf , Tjiang Gilbert C. H. , Puppels Gerwin J. , Bakker Schut Tom C.
Published: January 2006

Partial least squares (PLS) calibration is often the method of choice for making multivariate calibration models to predict analyte concentrations from Raman spectral measurements. In the development of such models, it is often difficult to assess beforehand what the prediction error will be, and whether instrumental or model factors limit the lower limit of the prediction error. Here, we present a method to assess the influence of experimental errors such as power fluctuations and spectral shifts, on the PLS prediction errors using simulated datasets. Assumptions that are implicit to PLS calibration and their implications with respect to the choice of experimental parameters for collecting a proper set of Raman spectra are discussed. The influence of various experimental parameters and signal pre‐processing steps on PLS prediction error is demonstrated by means of simulations. The results of simulations are compared with the outcome of PLS calibrations of an experimental dataset. Copyright © 2006 John Wiley & Sons, Ltd.
The electrosorption of 1,2,3‐triazole on gold as studied with surface‐enhanced Raman spectroscopy
Authors: Jbarah Abdel Aziz , Ihle Andreas , Banert Klaus , Holze Rudolf
Published: January 2006

The electrosorption of 1,2,3‐triazole on a polycrystalline gold electrode has been studied with surface‐enhanced Raman spectroscopy (SERS) and cyclic voltammetry. Vibrational wavenumbers were calculated for the 1H‐ and 2H‐1,2,3‐triazole at the B3LYP and MP2 levels using 6–31G* basis set. The data obtained from vibrational wavenumber calculations are used to analyze the SERS spectra. Results imply a tilted orientation of the triazole molecule both from acidic and neutral perchlorate solution with a nitrogen atom interacting directly with the gold surface. Strong adsorption in both cases is also evident from cyclic voltammograms of polycrystalline gold electrodes, indicating strong inhibition of gold hydroxide formation. Copyright © 2006 John Wiley & Sons, Ltd.
4‐Aminobenzonitrile: ab initio calculations, FTIR and Raman spectra
Authors: Palafox M. Alcolea , Rastogi V. K. , Vats J. K.
Published: January 2006

The experimental IR (in different matrices) and Raman spectra of 4‐aminobenzonitrile molecule were recorded. The results were compared with theoretical values. Geometry, vibrational wavenumbers and thermodynamic parameters were calculated using DFT quantum chemical methods. With the help of specific scaling procedures, the experimentally observed FTIR and Raman vibrational wavenumbers were analyzed and assigned to different normal modes of the molecule. The error obtained was, in general, very low. The contributions of the different modes to each wavenumber were determined using potential energy distributions (PEDs). Other general conclusions were also deduced. Copyright © 2006 John Wiley & Sons, Ltd.
Surface‐enhanced Raman spectroscopy of imidazole adsorbed on electrode and colloidal surfaces of Cu, Ag, and Au
Authors: Loo B. H. , Tse Y. , Parsons K. , Adelman C. , El‐Hage A. , Lee Y. G.
Published: January 2006

Surface‐enhanced Raman spectra have been obtained from imidazole adsorbed on Cu and Ag electrodes, and on Cu, Ag, and Au colloids at pH ranging from 5.6 to 11.0. For these pHs, the imidazole molecule is coordinated through its unshared electron pair on its ‘pyridine’ nitrogen to the metal surfaces. On the Cu and Au colloidal systems, the imidazole molecule adsorbs with the ring perpendicular to the metal surface since only in‐plane vibrations are observed. On the other hand, both the in‐plane and out‐of‐plane vibrations are observed on the Cu and Ag electrodes, and on the Ag colloid, therefore the adsorbed imidazole is tilted at an angle with respect to the surface normal. Copyright © 2006 John Wiley & Sons, Ltd.
Construction of picosecond time‐resolved Raman spectrometers with near‐infrared excitation
Authors: Sakamoto A. , Matsuno S. , Tasumi M.
Published: January 2006

We have constructed two types of picosecond time‐resolved Raman spectrometers with near‐infrared excitation. One system is based on a step‐scan Fourier transform (FT) interferometer equipped with a Ge detector, and the other system is based on a dispersive spectrometer equipped with an InGaAs array detector. For the former system with pulsed Raman excitation, we have developed a new method of signal processing. This method does not require synchronization among laser pulses for Raman excitation, the stepping of the step‐scan interferometer, and the sampling of the analog‐to‐digital converter. In spite of large fluctuation in the probe‐pulse energy, the ordinary FT‐Raman spectra of samples in the ground electronic state can be obtained with satisfactory signal‐to‐noise ratios by the former system. By the latter system, picosecond transient Raman spectra have been obtained from the first excited singlet (S1) state of 9‐phenylanthracene and the second excited singlet (S2) state of all‐trans‐β‐carotene by using 388‐nm light for photoexcitation and 1064‐nm light for Raman excitation. Copyright © 2006 John Wiley & Sons, Ltd.
Surface‐ and tip‐enhanced Raman scattering of DNA components
Authors: Rasmussen A. , Deckert V.
Published: January 2006

While surface‐enhanced Raman scattering (SERS) is an established technique to significantly enhance the Raman signal from samples bound to metal surfaces, a quantitative interpretation is very difficult because of the rough and arbitrary nature of the substrate. A distinction between concentration and enhancement effects is virtually impossible. Tip‐enhanced Raman scattering (TERS), a scattering type of near‐field optical microscopy technique, circumvents the problem of random enhancement by concentrating the roughness to only a small region directly at the apex of a scanning probe tip. In this paper, TERS spectra of DNA pyrimidine bases have been collected and compared with standard SERS and Raman measurements of the nucleotides and the pure bases. The results are discussed in terms of electromagnetic and chemical effects of the SERS enhancement of the TERS probes. Copyright © 2006 John Wiley & Sons, Ltd.
Nondegenerate hard‐mode Raman studies of phase transition in antiferroelectric lead ytterbium niobate‐based perovskite compound
Authors: Ahn Sang‐Jin , Kim Jong‐Jean , Kim Jai‐Hyun , Choo Woong‐Kil
Published: January 2006

By using Slater's phenomenological theory of atomic lattice dynamics, general results for the nondegenerate hard mode of phase transition are rederived in a simpler form. The change in inverse dielectric susceptibility (χ−1) associated with the phase transition is related to the hard‐mode frequency shift (ωQ) as ${\Delta}(\chi^{-1}) = R\omega_{\rm Q}^{2}$, where the proportionality constant R can be determined from the experimental data. This relation ${\Delta}(\chi^{-1}) = R\omega_{\rm Q}^{2}$ between the changes in χ−1 and $\omega_{\rm Q}^{2}$ was verified for the antiferroelectric phase transition observed in 0.94PYN [Pb(Yb1/2Nb1/2)O3]–0.06PT[PbTiO3], with the proportionality constant R as −1.6 × 10−7 cm2 in the antiferroelectric phase. Copyright © 2006 John Wiley & Sons, Ltd.
Femtosecond CARS of methanol–water mixtures
Authors: Pestov Dmitry , Zhi Miaochan , Sariyanni Zoe‐Elizabeth , Kalugin Nikolai G. , Kolomenskii Alexander , Murawski Robert , Rostovtsev Yuri V. , Sautenkov Vladimir A. , Sokolov Alexei V. , Scully Marlan O.
Published: January 2006

We utilize femtosecond time‐resolved coherent anti‐Stokes Raman spectroscopy (CARS) to study the vibrational dynamics of methanol–water solutions. We measure the beat wavenumbers between Raman modes and coherence decay rates of CH stretch modes (at 2835 cm−1 and 2943 cm−1) in methanol. We observe a qualitative dependence of the coherence relaxation rate on the concentration of methanol in its water solution. This may be linked to the formation of the recently observed supramolecular structures in methanol–water mixtures. Copyright © 2006 John Wiley & Sons, Ltd.
Raman spectroscopy at the beginning of the twenty‐first century
Authors: Schmitt M. , Popp J.
Published: January 2006

This paper gives a summary of the Wolfgang Kiefer Honorary Issue of the Journal of Raman Spectroscopy. The contributions in this special issue convincingly demonstrate the great applicability of Raman spectroscopy for almost all natural sciences, making this technique one of the most essential laser spectroscopic methods. Copyright © 2006 John Wiley & Sons, Ltd.
Sensitive capillary GC‐MS‐SIM determination of selective serotonin reuptake inhibitors: Reliability evaluation by validation and robustness study
Authors: Berzas Nevado Juan José , Villaseñor Llerena María Jesús , Guiberteau Cabanillas Carmen , Rodríguez Robledo Virginia , Buitrago Sierra
Published: January 2006

A simple, fast, selective and very sensitive capillary GC‐MS method for the simultaneous determination of five antidepressant drugs is described. Fluoxetine, fluvoxamine, citalopram, sertraline and paroxetine belong to the newest and most important drug group termed selective serotonin reuptake inhibitors. Imipramine was used in this method as an internal standard for quantification. Optimum parameters for GC separation were investigated, i. e., flow rate, column head pressure, injector temperature, injection splitless conditions and oven temperature program. MS detection was performed in SIM mode to increase the sensitivity. Stability of the solutions, linear concentration range, accuracy, precision, LOD, LOQ (3.6–41.5 mg/L) and specificity were examined in the presence of excipients for checking the reliability of this method. The robustness was evaluated with a matrix of 15 experiments (seven factors and three levels) using Plackett‐Burman fractional factorial experimental design, and Youden and Steiner statistical treatment. The method was applied to the analysis of these antidepressants in nearly all their pharmaceutical formulations, obtaining recoveries between 98.1% and 102.7% with regard to the claimed values.
Application of LC/MS and ICP/MS for establishing the fingerprint spectrum of the traditional Chinese medicinal preparation Gan‐Lu‐Yin
Authors: Lin I‐Hsin , Lee Ming‐Chung , Chuang Wu‐Chang
Published: January 2006

We developed a method to analyze the fingerprint spectrum qualitatively and quantitatively for the traditional Chinese herbal medicinal preparation Gan‐Lu‐Yin with HPLC combined with photodiode array detection, and MS, and to identify the preparation's 14 main components including baicalin, baicalein, oroxylin A‐7‐O‐glucuronide, wogonin‐7‐O‐glucuronide, wogonin, and oroxylin A in Radix Scutellariae; naringin and neohesperidin in Aurantii fructus; liquiritigenin, liquiritin, and glycyrrhizic acid in Radix Glycyrrhizae. In LC/UV assay, a Cosmosil 5C18‐MS‐II column was used as the stationary phase, and a gradient of potassium dihydrogen phosphate, ACN, and water as the elute solution. The UV detection wavelengths were 250 and 280 nm. In LC/MS assay, a gradient of phosphoric acid, ACN, and water was used as the elute solution, and electrospray positive ion mode ((+)‐ESI) as the analytic mode. In order to explore the distribution of trace metal elements effectively in Gan‐Lu‐Yin, a microwave digestion method was used for sample treatment, and an inductively coupled plasma MS assay was used to analyze fingerprint spectra of the inorganic metals in Gan‐Lu‐Yin. Combined with fingerprint spectra of organic compounds by LC/UV and LC/MS, it was expected to provide effective quality control in the production of Gan‐Lu‐Yin.
A simple and inexpensive “solvent in silicone tube extraction” approach and its evaluation in the gas chromatographic analysis of pesticides in fruits and vegetables
Authors: Jánská Marie , Lehotay Steven J. , Ma�tovská Katerina , Haj�lová Jana , Alon Tal , Amirav Aviv
Published: January 2006

A novel, simple, and inexpensive approach to sorptive extraction, which we call solvent in silicone tube extraction (SiSTEx), was applied to pesticide residue analysis and its effectiveness and efficiency were evaluated. In SiSTEx, which is a form of open tubular sorptive extraction, a piece of silicone tubing (4 cm long, 1.47 mm ID, 1.96 mm OD in this study) is attached to the cap of a 20 mL glass vial that contains the aqueous sample. The tubing is plugged at the end dangling in the sample solution, and MeCN (e. g., 40 μL) added by syringe to the inner tube volume through a septum in the cap. A stir‐bar is used to mix the sample for a certain time (e. g., 60 min), which allows chemicals to partition into the tubing where they diffuse across the silicone and partition into the MeCN. The final MeCN extract is then analyzed for the concentrated analytes. In this study, the SiSTEx approach was evaluated for the analysis of organophosphorus (OP) and organochlorine (OC) pesticides in fruits and vegetables using GC/pulsed flame photometric (PFPD) and halogen specific (XSD) detectors for analysis. The produced samples were initially extracted by a rapid MeCN procedure, and 5 mL of the initial extract was diluted four‐fold with water to undergo sorptive extraction for 60 min. The final extract was analyzed by GC/PFPD + XSD for 14 OP and 22 OC pesticides. This simple approach was able to detect 26 of the 36 pesticides at 10 ng/g or less original equivalent sample concentration with average reproducibility of 11 %RSD. For those 26 pesticides, a 44‐fold lower detection limit on average was achieved in matrix extracts using SiSTEx despite the four‐fold dilution with water.
Analysis of lorazepam and its 3O‐glucuronide in human urine by capillary electrophoresis: Evidence for the formation of two distinct diastereoisomeric glucuronides
Authors: Baldacci Andrea , Thormann Wolfgang
Published: January 2006

Lorazepam (LOR) is a 3‐hydroxy‐1,4‐benzodiazepine that is chiral and undergoes enantiomerization at room temperature. In humans, about 75% of the administered dose of LOR is excreted in the urine as its 3O‐glucuronide. CE‐MS with negative ESI was used to confirm the presence of LOR‐3O‐glucuronide in urines that stemmed from a healthy individual who ingested 1 or 2 mg LOR, whereas free LOR could be detected in extracts prepared from enzymatically hydrolyzed urines. As the 3O‐glucuronidation reaction occurs at the chiral center of the molecule, two diastereoisomers can theoretically be formed, molecules that can no longer interconvert. The stereoselective formation of LOR glucuronides in humans and in vitro was investigated. MEKC analysis of extracts of the nonhydrolyzed urines suggested the presence of the two different LOR glucuronides in the urine. The formation of the same two diastereoisomers was also observed in vitro employing incubations of LOR with human liver microsomes in the presence of uridine 5′‐diphospho‐glucuronic acid as coenzyme. The absence of other coenzymes excluded the formation of phase I or other phase II metabolites of LOR. Both results revealed a stereoselectivity, one diastereoisomer being formed in a higher amount than the other. After enzymatic hydrolysis using β‐glucuronidase, these peaks could not be detected any more. Instead, LOR was monitored. Analysis of the extracts prepared from enzymatically hydrolyzed urines by MEKC in the presence of 2‐hydroxypropyl‐β‐CD revealed the enantiomerization process of LOR (observation of two peaks of equal magnitude connected with a plateau zone). The data presented provide for the first time the evidence of the stereoselectivity of the LOR glucuronidation in humans.
A study of surface modification and anchoring techniques used in the preparation of monolithic microcolumns in fused silica capillaries
Authors: Courtois Julien , Szumski Michal , Byström Emil , Iwasiewicz Agnieszka , Shchukarev Andrei , Irgum Knut
Published: January 2006

Based on a survey of the literature on pretreatment of fused silica capillaries, 3 etching procedures and 11 silanization protocols based on the vinylic silane 3‐((trimethoxysilyl)propyl) methacrylate (γ‐MAPS) were found to be most representative as a means of ensuring attachment of in situ prepared vinylic polymers. These techniques were applied to fused silica capillaries and the success in establishing the intended surface modification was assessed. X‐ray photoelectron spectroscopy (XPS) was used to characterize the chemical state of the surface, providing information regarding presence of the reagent bound to the capillary. Wetting angles were measured and correlated with the XPS results. An adherence test was done by photopolymerization of a 2 mm long plug of 1,6‐butanediol dimethacrylate in the prepared capillaries and evaluation of its ability to withstand applied hydraulic pressure. SEM was also performed in cases where the plug was released or other irregularities were observed. Finally, the roughness of the etched surface, considered to be of importance, was assessed by atomic force microscopy. Alkaline etching at elevated temperature provided a surface roughness promoting adhesion. The commonly used silanization protocols involving water in the silanization or washing steps gave inadequate surface treatment. The best silanization procedure was based on toluene as a solvent.
Reliable assessment of high temperature oxidation resistance by the development of a comprehensive code of practice for thermocycling oxidation testing – European COTEST project –
Authors: Schütze M. , Malessa M.
Published: January 2006

The cyclic oxidation test is the most often used tool in industry to characterise the high temperature oxidation/corrosion resistance of technical materials in the laboratory. In the past, however, there has been the problem of a lack of intercomparability of data from different laboratories and sometimes even from different test runs in the same lab since no general guidelines or standards were existing for this type of test. Being aware of this situation the European COTEST research project was started with 23 participants from 11 countries including representatives from industry, universities, private institutes and national research labs. The present paper reports about the outcome of this project after three years. The project consisted of 8 work packages including literature search on the state‐of‐the‐art at the beginning of the work, experimental investigations supported by a statistics approach in order to quantify the impact of the different test parameters on the test results, a validation testing phase and the development of a comprehensive set of guidelines. The latter is available on the internet and serves as a basis for a future ISO standard for this type of test.
Variation in cyclic oxidation testing practice and data: The European situation before COTEST
Authors: Osgerby S. , Pettersson R.
Published: January 2006

A survey of existing testing practice and pre‐existing data was conducted to provide a starting point for the COTEST project on cyclic oxidation testing. The main parameters within the test that need to be controlled were identified as: control of test environment; temperature stability during hold periods; heating and cooling rates; specimen preparation; and post test evaluation. Existing experimental facilities were surveyed to establish the full range of variability within these parameters.
Designing experiments for maximum information from cyclic oxidation tests and their statistical analysis using half Normal plots
Authors: Coleman S. Y. , Nicholls J. R.
Published: January 2006

Cyclic oxidation testing at elevated temperatures requires careful experimental design and the adoption of standard procedures to ensure reliable data. This is a major aim of the ‘COTEST’ research programme. Further, as such tests are both time consuming and costly, in terms of human effort, to take measurements over a large number of cycles, it is important to gain maximum information from a minimum number of tests (trials). This search for standardisation of cyclic oxidation conditions leads to a series of tests to determine the relative effects of cyclic parameters on the oxidation process. Following a review of the available literature, databases and the experience of partners to the COTEST project, the most influential parameters, upper dwell temperature (oxidation temperature) and time (hot time), lower dwell time (cold time) and environment, were investigated in partners' laboratories. It was decided to test upper dwell temperature at 3 levels, at and equidistant from a reference temperature; to test upper dwell time at a reference, a higher and a lower time; to test lower dwell time at a reference and a higher time and wet and dry environments. Thus an experiment, consisting of nine trials, was designed according to statistical criteria. The results of the trial were analysed statistically, to test the main linear and quadratic effects of upper dwell temperature and hot time and the main effects of lower dwell time (cold time) and environment. The nine trials are a quarter fraction of the 36 possible combinations of parameter levels that could have been studied. The results have been analysed by half Normal plots as there are only 2 degrees of freedom for the experimental error variance, which is rather low for a standard analysis of variance. Half Normal plots give a visual indication of which factors are statistically significant. In this experiment each trial has 3 replications, and the data are analysed in terms of mean mass change, oxidation kinetics (up to the onset of spall), the onset of spalling, spallation rate and also the variation between the 3 replications. The method is illustrated by cyclic oxidation of alloy 800 undertaken as part of the COTEST project.
Influence of cycling parameter variation on thermal cyclic oxidation testing of high temperature materials (COTEST)
Authors: Niewolak L. , Malessa M. , Coleman S. Y. , Quadakkers W. J. , Schütze M.
Published: January 2006

The effect of cycling parameter variation (i.e. oxidation temperature, upper and lower dwell time, humidity in test gas) of the oxidation/spallation kinetics on four alloys was investigated within the framework of an EC funded research project (COTEST). For this purpose, specimens of AISI 441, Alloy 800H, CM 247 and P91 were subjected to thermocyclic testing in dry or humidified air. It was found that a minimum of 300 h accumulated hot dwell time is required for meaningful test results. Detailed characterisation of the corrosion products was performed using OM, SEM/EDX and XRD. The net weight change curves were evaluated with regards to the characteristic quantitative parameters describing oxide growth rate, time to onset of spallation/breakaway and weight of spalled oxide. Analysis of these values was made by the ANOVA method, which allows assessment of the significance of the roles of different test parameters and parameter variations on the oxidation/spallation kinetics from a limited number of experiments.