bluuebunny/crossref_metadata_2025_split huggingface dataset:
Liquid chromatography/electrospray tandem mass spectrometry of terpenoid lactones in Ginkgo biloba
Authors: Sun Yongkai , Li Wenkui , Fitzloff John F. , van Breemen Richard B. 
Published: February 2005

AbstractGinkgo biloba (ginkgo) is one of most frequently used botanical dietary supplements. The bioactive constituents include the terpenoid lactones consisting of bilobalide and the ginkgolides A, B, C and J. A new assay based on high‐performance liquid chromatography/electrospray tandem mass spectrometry (LC/MS/MS) was developed for the measurement of the terpenoid lactones in ginkgo products such as leaf powder and extracts. Initially, the MS/MS fragmentation pathways of ginkgolides were investigated to identify abundant fragment ions that might be useful for the sensitive and selective detection of ginkgolides and bilobalide during LC/MS/MS. Then, sample preparation and clean‐up procedures were streamlined to maximize throughput by taking advantage of the selectivity of LC/MS/MS detection. Analyte recoveries exceeded 90%, the intra‐assay and inter‐assay relative standard deviations were <5%, the relative error was <8% and the limits of detection and quantification were 3.6–120 and 11–350 fmol, depending on the analyte that was injected on to the LC column. Therefore, this LC/MS/MS assay facilitated the rapid quantitative analysis of ginkgolides A, B, C and J and bilobalide in ginkgo dietary supplements with excellent recovery, reproducibity, accuracy and sensitivity. Copyright © 2005 John Wiley & Sons, Ltd.
Mass spectrometric determination of selenenylsulfide linkages in rat selenoprotein P
Authors: Ma Shuguang , Hill Kristina E. , Burk Raymond F. , Caprioli Richard M. 
Published: February 2005

AbstractThe reversible formation of a selenenylsulfide linkage in mammalian thioredoxin reductase was identified as having a key role in its activity. Identification of selenenylsulfide and/or diselenide linkages is therefore critical to the determination of the structure and function of selenoproteins. A selenopeptide, 298SGSAITUQCAENLPSLCSUQGLFAEEK324 (U = selenocysteine), was isolated from a tryptic digest of rat selenoprotein P. Its two cysteine residues and two selenocysteine (Sec) residues were determined to be present in oxidized form by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). The selenopeptide was subjected to partial reduction by dithiothreitol with immediate alkylation by iodoacetamide. This process was monitored by MALDI‐TOFMS to determine the number of alkylations that had taken place. The partially reduced and alkylated peptides were then analyzed by nano‐electrospray ionization tandem mass spectrometry and the results indicated that selenenylsulfide linkages Sec304–Cys314 and Cys306–Sec316 were present. It is concluded that selenoprotein P contains these two selenenylsulfide bonds. Copyright © 2005 John Wiley & Sons, Ltd.
Purification and initial characterization of a novel protein with factor Xa activity from Lonomia obliqua caterpillar spicules
Authors: Lilla S. , Pereira R. , Hyslop S. , Donato J. L. , Le Bonniec B. F. , de Nucci G. 
Published: February 2005

AbstractA novel protein with factor Xa‐like activity was isolated from Lonomia obliqua caterpillar spicules by gel filtration chromatography and reversed‐phase high‐performance liquid chromatography. The protein had a mass of 20745.7 Da, as determined by mass spectrometry, and contained four Cys residues. Enzymatic hydrolysis followed by de novo sequencing by tandem mass spectrometry was used to determine the primary structure of the protein and the cysteine residues linked by disulfide bridges. The positions of 24 sequenced tryptic peptides, including the N‐terminal, were deduced by comparison with a homologous protein from the superfamily Bombycoidea. Approximately 90% of the primary structure of the active protein was determined. Copyright © 2005 John Wiley & Sons, Ltd.
Gas‐phase reactivity of the OP(OCH3)2+ phosphonium ion towards α,β‐unsaturated esters in a quadrupole ion trap
Authors: Leclerc Eric , Leon Emmanuelle , Taphanel Marie‐Hélène , Morizur Jean‐Pierre 
Published: February 2005

AbstractIon–molecule reactions between the OP(OCH3)2+ phosphonium ions and eight α,β‐unsaturated esters (methyl acrylate, ethyl acrylate, methyl crotonate, ethyl crotonate, methyl 3,3‐dimethylacrylate, ethyl 3,3‐dimethylacrylate, methyl methacrylate and ethyl methacrylate) were performed in a quadrupole ion trap mass spectrometer. The OP(OCH3)2+ phosphonium ions, formed by electron ionization from neutral trimethyl phosphite, were found to react with α,β‐unsaturated esters to give an adduct [RR′CCR″COOR″′, OP(OCH3)2]+, which lose spontaneously a molecule of trimethyl phosphate (R″′CH3) or dimethyl ethyl phosphate (R″′C2H5). An ion corresponding to a protonated trialkyl phosphate is also observed when substituent R″H. To confirm the experimental results, and to elucidate the mechanism for the formation of the ionic species, a theoretical study using the density functional theory (DFT) approach was carried out. The potential energy surface obtained from B3LYP/6–31G(d,p) calculations for the reaction between OP(OCH3)2+ and methyl acrylate is described. Copyright © 2005 John Wiley & Sons, Ltd.
Characterization of chemically modified steroids for doping control purposes by electrospray ionization tandem mass spectrometry
Authors: Thevis Mario , Bommerich Ute , Opfermann Georg , Schänzer Wilhelm 
Published: February 2005

AbstractThe discovery of the designer steroid tetrahydrogestrinone (THG) in elite athletes' doping control samples in 2003 demonstrated the availability of steroid derivatives prepared solely for doping purposes. Modern mass spectrometers utilizing electrospray ionization and collisionally activated dissociation (CAD) of analytes allow the structural characterization of steroids and their derivatization sites by the elucidation of fragmentation behaviors. A total of 21 steroids comprising either a 4,9,11‐triene, a 3‐keto‐4‐ene or a 3‐keto‐1‐ene nucleus were investigated regarding their dissociation pathways, deuterated analogues were synthesized and fragmentation routes were postulated, permitting the identification of steroidal structures and modifications. Compounds based on a 4,9,11‐triene steroid with an ethyl residue at C‐13 (gestrinone analogues) generate abundant fragment ions at m/z 241 and 199, whereas the substitution of the C‐13 ethyl group by a methyl residue (trenbolone analogues) results in a shift of m/z 241 to 227. Substances related to testosterone with a 3‐keto‐4‐ene structure give rise to abundant fragment ions at m/z 109 and 97 whereas steroids with a 3‐keto‐1‐ene nucleus eliminate the A‐ring including the carbons C‐1–C‐4, in addition to C‐19 that is proposed to migrate from C‐10 to C‐1 under CAD conditions. Copyright © 2005 John Wiley & Sons, Ltd.
Testing the role of solvent surface tension in protein ionization by electrospray
Authors: Šamalikova Maria , Grandori Rita 
Published: February 2005

AbstractThis work was aimed at probing the influence of solvent surface tension on protein ionization by electrospray. In particular, we were interested in testing the previously suggested hypothesis that the charge‐state distributions (CSDs) of proteins in electrospray ionization mass spectrometry (ESI‐MS) are controlled by the surface tension of the least volatile solvent component. In the attempt to minimize uncontrolled conformational effects, we used acid‐sensitive proteins (cytochrome c and myoglobin) at low pH or highly stable proteins (ubiquitin and lysozyme) in the presence of low concentrations of organic solvents. A first set of experiments compared the effect of 1‐ and 2‐propanol. These two alcohols have similar chemico‐physical properties but values of vapor pressure below and above that of water, respectively. Both compounds have much lower surface tension than water. The solvents employed allowed testing of the influence of surface tension on protein spectra obtained from similarly denaturing solutions. The compared solvent conditions gave rise to very similar spectra for each tested protein. We then investigated the effect of the addition of dimethyl sulfoxide to acid‐unfolded proteins. We observed enhanced ionization in the presence of acetic or formic acid, consistent with the previously described supercharging effect, but almost no shift of the CSD in the presence of HCl. Finally, we analyzed thermally denatured cytochrome c, to obtain reference spectra of the unfolded protein in high‐surface‐tension solutions. Also in this case, the CSD of the unfolded protein was shifted towards lower m/z values relative to low‐surface‐tension systems. In contrast to the other results reported here, this effect is consistent with an influence of solvent surface tension on CSD. The magnitude of the effect, however, is much smaller than predicted by the Rayleigh equation. The results presented here are not easy to reconcile with the hypothesis that the maximum charge state exhibited by proteins in ESI‐MS reflects the Rayleigh‐limit charge of the precursor droplet. The data are discussed with reference to models for the mechanism of electrospray ionization. Copyright © 2005 John Wiley & Sons, Ltd.
Analysis of amphetamines and fentanyls by atmospheric pressure desorption/ionization on silicon mass spectrometry and matrix‐assisted laser desorption/ionization mass spectrometry and its application to forensic analysis of drug seizures
Authors: Pihlainen Katja , Grigoras Kestutis , Franssila Sami , Ketola Raimo , Kotiaho Tapio , Kostiainen Risto 
Published: February 2005

AbstractThe suitability of atmospheric pressure desorption/ionization on silicon mass spectrometry (AP‐DIOS‐MS) and matrix‐assisted laser desorption ionization mass spectrometry (AP‐MALDI‐MS) for the identification of amphetamines and fentanyls in forensic samples was studied. With both ionization techniques, the mass spectra recorded showed abundant protonated molecules, and the background did not disturb the analysis. The use of tandem mass spectrometry (MS/MS) allowed unambiguous identification of the amphetamines and fentanyls. AP‐DIOS‐MS/MS and AP‐MALDI‐MS/MS were also successfully applied to the identification of authentic compounds from drug seizures. Common diluents and tablet materials did not disturb the analysis and compounds were unequivocally identified. The limits of detection (LODs) for amphetamines and fentanyls with AP‐DIOS‐MS/MS were 1–3 pmol, indicating excellent sensitivity of the method. The LODs with AP‐MALDI‐MS/MS were about 5–10 times higher. Copyright © 2005 John Wiley & Sons, Ltd.
A novel rearrangement in electrospray ionization multistage tandem mass spectrometry of amino acid ester cyclohexyl phosphoramidates of AZT
Authors: Chen Yi , Yin Yingwu , Sun Xiaobin , Liu Xiaohong , Wang Haiyan , Zhao Yufen 
Published: February 2005

AbstractSeveral amino acid ester cyclohexyl phosphoramidates of AZT as anti‐HIV prodrugs were synthesized and investigated by electrospray ionization tandem mass spectrometry (ESI‐MSn). A novel methoxy group migration from the carbonyl group to the phosphoryl group was observed in ESI‐MS2. This migration is believed to be a general pathway for ions with a methyl ester moiety at the γ‐position to a phosphoric acid moiety, which is assisted with metal ions such as Li+, Na+ and K+. Coordination between metal ions with both the carbonyl oxygen and phosphoryl oxygen might be a key factor responsible for this migration. Copyright © 2005 John Wiley & Sons, Ltd.
Wavenumber‐resolved interaction‐induced Raman scattering by a gaseous atomic mixture
Authors: Dixneuf S. , Chrysos M. , Rachet F. 
Published: February 2005

AbstractA preliminary joint experimental and theoretical study of the depolarized, I||(ν), binary interaction‐induced Raman scattering profile by a gaseous atomic mixture is reported for the first time. An absolute‐unit calibration of the recorded scattering cross‐sections of the mixture permitted a straightforward comparison of the data with cross‐sections obtained with quantum mechanics. As a working system the Ne–Ar mixture was chosen, for which modern interatomic potential and incremental anistropy models are available for all the atomic pairs involved. Copyright © 2005 John Wiley & Sons, Ltd.
Theoretical introduction to nanoCARS: a local probing of nanocomposite materials with spectral profiles of coherent anti‐Stokes Raman scattering
Authors: Zheltikov A. M. 
Published: February 2005

AbstractA theoretical introduction to coherent anti‐Stokes Raman scattering (CARS) as a local probe for nanocomposite materials is given. The interference nature of CARS spectra and the high spatial resolution make this non‐linear process an ideal local probe for the metrology of nanostructures and nanocomposites (nanoCARS). Local field enhancement of CARS in nanostructures allows the creation of efficient nanoCARS sensors. Copyright © 2005 John Wiley & Sons, Ltd.
Experimental demonstration of nanoCARS: coherent anti‐Stokes Raman scattering in mesoporous silica aerogels infiltrated with condensed‐ and gas‐phase Raman‐active materials
Authors: Konorov S. O. , Mitrokhin V. P. , Smirnova I. V. , Sidorov‐Biryukov D. A. , Fedotov A. B. , Zheltikov A. M. 
Published: February 2005

AbstractCoherent anti‐Stokes Raman scattering (CARS) is shown to allow the reliable detection of Raman‐active modes of gas‐phase molecular nitrogen, and also toluene molecules in the condensed and gas phases infiltrated into mesoporous silica aerogels. We experimentally demonstrate a nanoscale extension of CARS methodology, referred to as nanoCARS, adapting CARS for local probing of nanostructures and nanocomposite materials, and also for the sensing of Raman‐active species in the liquid and gas phases in a nanocomposite host. Copyright © 2005 John Wiley & Sons, Ltd.
Collisional line broadening in the atmosphere of light particles: problems and solutions in the framework of semiclassical treatment
Authors: Buldyreva J. , Ivanov S. V. , Nguyen L. 
Published: February 2005

AbstractFor the case of perturbation by light particles, the computation of spectral line parameters by traditional semiclassical approaches reveals the problem of translational energy conservation. The rototranslational energy balance is, however, easily maintained within classical molecular dynamics. The line broadening of two ‘problematic’ systems, C2H2–He and CO2–He, is addressed from these two different points of view. In the framework of a traditional semiclassical approach, the non‐validity of the translational energy conservation hypothesis leads to a significant overestimation of the linebroadening for both systems. This overestimation is, however, substantially reduced for the ensemble of C2H2–He and CO2–He linewidths when a non‐perturbative completely classical method is employed. Used with caution, this latter approach therefore seems thus to be more appropriate for linewidth computations in the case of molecular systems of the type ‘heavy radiator + light perturber’. Copyright © 2005 John Wiley & Sons, Ltd.
Accurate pair‐anisotropy models out of a set of input experimental moments via a novel non‐linear inversion method
Authors: Chrysos M. , Dixneuf S. 
Published: February 2005

AbstractWe report a useful multiparameter Newton–Raphson method, yielding accurate pair‐anisotropy models from a set of low‐order experimental spectral moments. The method is applied to the depolarized binary collision‐induced scattering spectrum of argon. Its reliability is established through comparison between the (Ar)2 experimental spectrum, previously recorded by our group over a broad wavenumber domain, and quantum‐mechanical profiles whose inputs are various pair‐anisotropy models. Copyright © 2005 John Wiley & Sons, Ltd.
Four‐photon coherent spectroscopy of orientational motion of H2O molecules in liquid water
Authors: Bunkin A. F. , Nurmatov A. A. , Pershin S. M. , Vigasin A. A. 
Published: February 2005

AbstractThe unexpectedly narrow structure of Rayleigh wing spectra from 5 to 50 cm−1 was detected using four‐photon coherent laser spectroscopy. The observed features were compared with the IR water vapor absorption (from the HITRAN database) and with the spontaneous Raman spectrum in the vapor phase. The fairly good resemblance between our recorded four‐photon spectrum and the pure rotational spectra of H2O molecules in the gas phase allows the suggestion that a discernible proportion of water molecules may exhibit virtually free rotation in the liquid phase. Copyright © 2005 John Wiley & Sons, Ltd.
Characterization of nonlinear optical superlattices by means of ω‐k spectroscopy
Authors: Kitaeva G. Kh. , Tishkova V. V. , Penin A. N. 
Published: February 2005

AbstractA method for measuring the spatial profiles of the second‐order non‐linear susceptibility χ(2)(z) in the bulk of periodically poled crystals and other structures was developed. The method is based on the general relation between the Fourier harmonics of χ(2)(z) and the parametric signal lineshape in the ω− k space which is governed by the dependence of the output signal intensity on the phase mismatch. The special cases of non‐linear interferometers, periodically poled crystals with stepwise or smoothed space χ(2)(z) profiles and Fibonacci‐type non‐linear superlattices were considered. Experimental schemes based on spontaneous parametric down‐conversion and the second harmonic generation were compared and discussed. Copyright © 2005 John Wiley & Sons, Ltd.
Single‐shot high‐resolution dual‐broadband CARS interferometric lineshape spectroscopy
Authors: Vereschagin K. A. , Smirnov V. V. , Stel'makh O. M. , Fabelinsky V. I. , Clauss W. , Klimenko D. N. , Oschwald M. , Vereschagin A. K. 
Published: February 2005

AbstractA high‐resolution spectroscopic method that allows single‐shot spectra of Raman‐active molecular transitions in non‐stationary media to be obtained with a resolution of ∼0.1 cm−1 was developed. The method is based on application of a Fabry–Pérot interferometer to spectral analysis of the CARS signal from Raman transitions with further detection of an interference pattern by a two‐dimensional photo‐matrix. The implementation of a dual‐broadband (DBB) CARS configuration for effective spectral averaging over pump and Stokes laser spectra together with angular averaging of CARS intensities along the complete circumference of Fabry–Pérot interference patterns leads to a significant improvement of interferogram quality, so that nearly all of the single‐shot interference patterns obtained for Q‐branch lines of the hydrogen molecule in a gas probe volume became suitable for linewidth measurements. Copyright © 2005 John Wiley & Sons, Ltd.
Improved species concentration measurements using a species‐specific weighting procedure on rotational CARS spectra
Authors: Vestin Fredrik , Afzelius Mikael , Bengtsson Per‐Erik 
Published: February 2005

AbstractRotational coherent anti‐Stokes Raman spectroscopy (CARS) is used for measurements of temperatures and relative species concentrations. The evaluation of a rotational CARS spectrum is normally performed using a least‐squares fitting algorithm to find the best‐fit theoretical spectrum in a library of spectra calculated at different temperatures and relative concentrations. A general problem is that species with weak spectral features have a minor influence on the results in the standard evaluation procedure. A species‐specific weighting (SSW) procedure enhancing the influence of weak spectral features in the spectral fitting algorithm has therefore been developed. The SSW procedure was tested on the evaluation of low concentrations of O2 in mixtures with N2, and it is shown that both the accuracy and precision of single‐shot spectra concentration measurements are improved by use of the SSW evaluation procedure. Also, a comparison with previously used weighting procedures shows that this approach is superior. The application of the technique to oxygen concentration measurements in the product gas of a fuel‐lean flame is demonstrated. In addition, a test was made using the developed weighting procedure for thermometry, by applying spectral weighting to the rotational spectrum originating from the first thermally excited vibrational state. The precision of the temperature measurements was then slightly improved. Copyright © 2005 John Wiley & Sons, Ltd.
Phase‐matched coherent anti‐Stokes Raman scattering in isolated air‐guided modes of hollow photonic‐crystal fibers
Authors: Konorov S. O. , Fedotov A. B. , Serebryannikov E. E. , Mitrokhin V. P. , Sidorov‐Biryukov D. A. , Zheltikov A. M. 
Published: February 2005

AbstractHollow‐core photonic‐crystal fibers with a specially designed dispersion profile offer unique phase‐matching solutions for gas‐phase coherent anti‐Stokes Raman scattering (CARS) in isolated guided modes with a transverse radius of only a few micrometers. Efficient single‐mode CARS tuned to a Raman resonance with 2331 cm−1 Q‐branch vibrations of molecular nitrogen filling the hollow core of the photonic crystal fiber is demonstrated using the second‐harmonic output of a Q‐switched Nd:YAG laser and wavelength‐tunable dye‐laser radiation as pump fields. Copyright © 2005 John Wiley & Sons, Ltd.
Non‐linear Raman spectroscopy 75 years after the Nobel Prize for the discovery of Raman scattering and 40 years after the first CARS experiments
Authors: Zheltikov A. M. , Radi P. 
Published: February 2005

AbstractWe give a brief overview of the Proceedings of the European Conference on Non‐linear Optical Spectroscopy (ECONOS2004), held at the University of Erlangen, Germany, 4–6 April 2004. Conceptual and technical advances in non‐linear Raman techniques and interesting research results and engineering applications reported in this issue are in many ways representative of the state of the art in the field of non‐linear Raman spectroscopy 75 years after the Nobel Prize for the discovery of Raman scattering and 40 years after the first experiments on coherent anti‐Stokes Raman scattering (CARS), providing, at the same time, new and interesting perspectives on recent trends in this field. Copyright © 2005 John Wiley & Sons, Ltd.
Pathophysiology of spastic paresis. I: Paresis and soft tissue changes
Authors: Gracies Jean‐Michel 
Published: February 2005

AbstractSpastic paresis follows chronic disruption of the central execution of volitional command. Motor function in patients with spastic paresis is subjected over time to three fundamental insults, of which the last two are avoidable: (1) the neural insult itself, which causes paresis, i.e., reduced voluntary motor unit recruitment; (2) the relative immobilization of the paretic body part, commonly imposed by the current care environment, which causes adaptive shortening of the muscles left in a shortened position and joint contracture; and (3) the chronic disuse of the paretic body part, which is typically self‐imposed in most patients. Chronic disuse causes plastic rearrangements in the higher centers that further reduce the ability to voluntarily recruit motor units, i.e., that aggravate baseline paresis. Part I of this review focuses on the pathophysiology of the first two factors causing motor impairment in spastic paresis: the vicious cycle of paresis–disuse–paresis and the contracture in soft tissues. Muscle Nerve, 2005