bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular evolution of herbicide resistance to phytoene desaturase inhibitors in Hydrilla verticillata and its potential use to generate herbicide‐resistant crops
Authors: Arias Renée S , Netherland Michael D , Scheffler Brian E , Puri Atul , Dayan Franck E 
Published: January 2005

AbstractHydrilla [Hydrilla verticillata (Lf) Royle] is one of the most serious invasive aquatic weed problems in the USA. This plant possesses numerous mechanisms of vegetative reproduction that enable it to spread very rapidly. Management of this weed has been achieved by the systemic treatment of water bodies with the herbicide fluridone. At least three dioecious fluridone‐resistant biotypes of hydrilla with two‐ to fivefold higher resistance to the herbicide than the wild‐type have been identified. Resistance is the result of one of three independent somatic mutations at the arginine 304 codon of the gene encoding phytoene desaturase, the molecular target site of fluridone. The specific activities of the three purified phytoene desaturase variants are similar to the wild‐type enzyme. The appearance of these herbicide‐resistant biotypes may jeopardize the ability to control the spread of this non‐indigenous species to other water bodies in the southern USA. The objective of this paper is to provide general information about the biology and physiology of this aquatic weed in relation to its recent development of resistance to the herbicide fluridone, and to discuss how this discovery might lead to a new generation of herbicide‐resistant crops. Copyright © 2005 Society of Chemical Industry
High‐Tc cuprate superconductivity in a nutshell
Authors: Won Hyekyung , Haas Stephan , Parker David , Maki Kazumi 
Published: January 2005

AbstractThe cover picture shows the quasiparticle spectra of the vortex states of the high‐Tc nodal superconductor PrOs4Sb12: the p+h‐wave of the A‐phase (left) and that of the B‐phase (right).The present issue of physica status solidi (b) contains invited and contributed papers from the 28th International Conference of Theoretical Physics – Electron Correlations in Nano‐ and Macrosystems (ICTP2004) which was held from 2–7 September 2004 in Ustroń, Poland.
Cytotoxic activity of Justicia spicigera is inhibited by bcl‐2 proto‐oncogene and induces apoptosis in a cell cycle dependent fashion
Authors: Cáceres‐Cortés J. R. , Cantú‐Garza F. A. , Mendoza‐Mata M. T. , Chavez‐González M. A. , Ramos‐Mandujano G. , Zambrano‐Ramírez I. R. 
Published: January 2005

AbstractIdentification of organic compounds from plants is of clinical significance because of the effect that they might have in patients with haematopoietic disorders. We studied the effect of the plant extract Justicia spicigera (Acanthaceae) in different haematopoietic cells: human leukaemic cell lines, umbilical cord blood cells, and mouse bone marrow cells.By examining colony formation and performing the MTT (3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide) assay it was shown that the plant extract of Justicia spicigera contains cytotoxic factors for leukaemic cells and has no proliferative activity on normal haematopoietic progenitor cells. Our results show that this plant extract induces apoptosis in the human leukaemia cell line TF‐1, but not in the bcl‐2 transfectant cell line TB‐1. Similar results were obtained using a haemopoietic cell line 32D and 32DBcl2. The cultures of umbilical cord blood cells and mouse bone marrow that contain granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) do not proliferate or become terminally differentiated in the presence of the infusion of Justicia spicigera. GM‐CSF that acts by abrogating programmed cell death is not sufficient to inhibit the apoptotic stimulus in TF‐1 and 32D cells. Moreover mouse fibroblasts (3T3) and two cervical carcinoma cell lines CALO and INBL, undergo apoptosis in the presence of different concentrations of an infusion from the plant. Our data show that there is a strong correlation between the cytotoxic effect and cell proliferation. Together, these results indicate that the plant infusion of Justicia spicigera does not contain any haematopoietic activity, induces apoptosis inhibited by bcl‐2 and is linked to cell proliferation. Copyright © 2001 John Wiley & Sons, Ltd.
Electronic structure of laser dye DCM and its derivatives
Authors: Khohlova S. S. , Lebedev N. G. , Bondarev S. L. , Knyukshto V. N. , Turban A. A. , Mikhailova V. A. , Ivanov A. I. 
Published: January 2005

AbstractThe electron energetic characteristics of laser dye molecules 4‐dicyanomethylene‐2‐methyl‐6‐p‐dimethylamino‐styryl‐4H‐pyran (DCM), (E)‐2‐{2‐[2‐(4‐dimethylaminophenyl)ethynyl]‐6‐threefluoromethyl‐4H‐4‐pyranylidene}‐malonitrile (DCMF3), (E)‐2‐{2‐[2‐(4‐dimethylaminophenyl)ethynyl]‐6‐n‐heptafluoropropyl‐4H‐4‐pyranylidene}‐malonitrile (DCMF7), (E)‐2‐{2‐[2‐(5‐piperidine‐2‐thienyl)ethynyl]‐6‐threefluoromethyl‐4H‐4‐pyranylidene}‐malonitrile (PTFDN) were investigated thoroughly using semiempirical methods ZINDO/1 and ZINDO/S. The geometry optimization was carried out by the method of conjugated gradients. On the basis of the electronic structure and optimum geometry of the molecules, the spectra of electronic transitions to the excited states, the dipole moments, and oscillator strengths of the transitions were calculated by the method of configuration interaction. Typical features of the electronic absorption spectra of these molecules were calculated and compared with the experimental data. The influence of the solvent on the optical absorption spectra was explored. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Development of an analytical system for the simultaneous determination of anabolic macrocyclic lactones in aquatic environmental samples
Authors: Laganá Aldo , Fago Giovanna , Marino Alessandra , Santarelli Daniela 
Published: January 2005

AbstractAn analytical procedure that enables routine analysis for trace determination of six anabolic macrocyclic lactones (zearalenone, α‐ and β‐zearalenol, zearalanone, zeranol, and taleranol) in sewage treatment plant (STP) samples has been developed. The method uses solid‐phase extraction, followed by high‐performance liquid chromatography with on‐line tandem mass spectrometry using atmospheric pressure chemical ionization (LC/APCI‐MS/MS). The extraction of these compounds from filtered water samples was performed off‐line with C18 solid‐phase cartridges. The detection was achieved by isocratic reversed‐phase high‐performance liquid chromatography coupled with an heated nebulizer (HN) APCI interface operating in negative ion mode. Mean recovery of the analytes in STP effluent samples generally exceeded 81%. This method was used to determine the occurrence of target analytes in the aquatic environment. In the selected STP effluent samples, zearalenone and α‐zearalenol were detected in the ng/L range. Copyright © 2001 John Wiley & Sons, Ltd.
The potential of inductively coupled plasma mass spectrometry detection for high‐performance liquid chromatography combined with accurate mass measurement of organic pharmaceutical compounds
Authors: Axelsson B‐O. , Jörnten‐Karlsson M. , Michelsen P. , Abou‐Shakra F. 
Published: January 2005

AbstractQuantification of unknown components in pharmaceutical, metabolic and environmental samples is an important but difficult task. Most commonly used detectors (like UV, RI or MS) require standards of each analyte for accurate quantification. Even if the chemical structure or elemental composition is known, the response from these detectors is difficult to predict with any accuracy. In inductively coupled plasma mass spectrometry (ICP‐MS) compounds are atomised and ionised irrespective of the chemical structure(s) incorporating the element of interest. Liquid chromatography coupled with inductively coupled plasma mass spectrometry (LC/ICP‐MS) has been shown to provide a generic detection for structurally non‐correlated compounds with common elements like phosphorus and iodine. Detection of selected elements gives a better quantification of tested ‘unknowns’ than UV and organic mass spectrometric detection. It was shown that the ultrasonic nebuliser did not introduce any measurable dead volume and preserves the separation efficiency of the system. ICP‐MS can be used in combination with many different mobile phases ranging from 0–100% organic modifier. The dynamic range was found to exceed 2.5 orders of magnitude. The application of LC/ICP‐MS to pharmaceutical drugs and formulations has shown that impurities can be quantified below the 0.1 mol‐% level. Copyright © 2001 John Wiley & Sons, Ltd.
Electrospray tandem mass spectrometry of lexitropsins
Authors: Domingues M. Rosário M. , Domingues Pedro , Gajewski Mariusz , Czuchajowski Leszek , Ferrer‐Correia A. J. 
Published: January 2005

AbstractSeveral compounds, representative of the class of lexitropsins, were analyzed by electrospray tandem mass spectrometry. The study of the fragmentations of the protonated molecular species ([M + H]+) and of selected fragment ions allowed proposals for the main fragmentation pathways of compounds of this type. The interpretation of the fragmentation pathways of these compounds was complicated because of intramolecular hydrogen migration. In order to better understand the fragmentation pathways, the MS/MS/MS spectra of several compounds, and the MS/MS and MS/MS/MS spectra of the deuterated compounds, were obtained. Accurate mass measurements helped elucidate the structures of smaller fragment ions. Low‐energy collision‐induced decomposition (CID) tandem mass spectrometry of lexitropsins with electrospray ionization has proven to be a good method for the structural characterization and identification of this class of compounds. Main fragmentation pathways occur by cleavage of the peptide bond followed by the elimination of the substituted pyrrole ring, and their elucidation will facilitate structural characterization of new lexitropsins. Copyright © 2001 John Wiley & Sons, Ltd.
RNA–RNA noncovalent interactions investigated by microspray ionization mass spectrometry
Authors: Hoyne Paula Rodrigues , Benson Linda M. , Veenstra Timothy D. , Maher L. James , Naylor Stephen 
Published: January 2005

AbstractElectrospray ionization mass spectrometry is playing an increasing role in the study of noncovalent interactions involving biomolecules. RNA–RNA complexes are important in many areas of biology, including RNA catalysis, RNA splicing, ribosome function, and gene regulation. Here, microelectrospray mass spectrometry (µESI‐MS) is used to study noncovalent base‐pairing interactions between RNA oligonucleotides, an area not previously explored by this technique. Using a set of complementary RNA oligonucleotides, we demonstrate the formation of the expected double‐helical RNA complexes composed of three distinct oligonucleotides. The ability to study specific RNA noncovalent interactions by µESI‐MS has the potential to provide a unique method by which to analyze and assign precise molecular masses to RNA–RNA complexes. Copyright © 2001 John Wiley & Sons, Ltd.
Direct coupling of a nano‐high‐performance liquid chromatography column to an ion trap designed for a gas chromatography/mass spectrometry system
Authors: Moneti Gloriano , Pieraccini Giuseppe , Bartolucci Gianluca , Guida Gianni , Seraglia Roberta , Traldi Pietro 
Published: January 2005

AbstractThe possibility of direct liquid injection inside an ion trap, designed for a commercial gas chromatography/mass spectrometry (GC/MS) system, has been tested by continuous solution flow and by loop injection. Instrumental parameters such as solution flows and sample concentration, and temperatures of transfer line, ion trap and ion trap housing, have been optimised. Different configurations of the interface capillary have been also considered, and the best results have been obtained by the injection of the solution coaxially with a helium flow. The experimental arrangement leads to the detection of good quality electron (EI) and chemical (CI) ionisation spectra of low to medium polarity compounds, at µM levels. The direct coupling of a nano‐HPLC column with the modified transfer line led on one hand to EI spectra which were successfully employed for library searches, and on the other to CI data directly comparable to results achieved by a commercial HPLC/MS system operating under ESI conditions. Copyright © 2001 John Wiley & Sons, Ltd.
Laser ablation of Co/Ge mixtures: a new type of endohedral structure, a semiconductor cage trapping a metal atom
Authors: Zhang Xia , Li Guoliang , Gao Zhen 
Published: January 2005

AbstractIn experiments on Co/Ge binary clusters by laser vaporization, a remarkably strong signal in the mass spectrum was presented, which was assigned to the cluster anion consisting of ten germanium atoms and one cobalt atom, [CoGe10]−. For this cluster anion we suggest an endohedral structure – a Ge10 cage trapping a Co atom in its interior. Reactions between cobalt clusters and germanium clusters using a laser double ablation reactor also confirmed the endohedral structure. According to the electronic and geometrical shell closures, a bicapped tetragonal antiprism structure was predicted for this endohedral [CoGe10]− cluster anion. Copyright © 2001 John Wiley & Sons, Ltd.
Ion rotating motion in a gas‐filled radio‐frequency quadrupole ion guide as a new technique for structural and kinetic investigations of ions
Authors: Raznikov Valeri V. , Soulimenkov Ilia V. , Kozlovski Viatcheslav I. , Pikhtelev Alexander R. , Raznikova Marina O. , Horwath Thomas , Kholomeev Alexander A. , Zhou Zhen , Wollnik Herman , Dodonov Alexander F. 
Published: January 2005

AbstractAn ion rotating excitation mode of operation of a segmented gas‐filled radio‐frequency quadrupole (RFQ) ion guide for a high‐resolution orthogonal time‐of‐flight (TOF) mass spectrometer is described. It is shown theoretically, by computer simulation and experimentally, that ion rotating excitation in a gas‐filled RFQ has several advantages over other types of ion oscillation excitation. The main advantages are an approximately twofold increase in average ion kinetic energy for the same maximal deviation from the RFQ axis and therefore an increase of about this factor of average internal excitation energy of ions, and the extended mass range of fragment ions that can be observed. The new method of ion decomposition by ion rotation around the axis of an RFQ ion guide was experimentally implemented and tested using a home‐built ‘SIN‐COS’ generator to supply the excitation voltage. This generator enables control of phase shift and amplitude of excitation voltages applied to quadrupole rods smoothly from the data acquisition program running on a PC. Copyright © 2001 John Wiley & Sons, Ltd.
Studies of the ortho effect in fragmentations of acetyl ion adducts of disubstituted benzenes
Authors: Li Zhili , Song Fengrui , Liu Shuying 
Published: January 2005

AbstractThe ion‐molecule reactions of disubstituted benzenes under chemical ionization conditions with acetyl chloride as reagent gas were examined, and the fragmentation reactions of the adduct ions (mostly proton and acetyl ion adducts) were studied by collision‐induced dissociation. Electron‐releasing substituents favored the adduct reactions, and electron‐withdrawing groups did not. The position and properties of substituting groups had an effect on the relative abundances of the adduct ions. Several examples of the ortho effect were observed. The fragmentation reaction of the adduct ions formed by ortho‐benzenediamine with the acetyl ion was similar to the reductive alkylation reaction of amines in the condensed phase. Copyright © 2001 John Wiley & Sons, Ltd.
Analysis of small organics on planar silica surfaces using surface‐assisted laser desorption/ionization mass spectrometry
Authors: Chen Yu‐Chie , Wu Jia‐Yi 
Published: January 2005

AbstractThis study demonstrates the feasibility of directly obtaining analyte signals from a planar silica gel surface by using laser desorption mass spectrometry (LDMS). The surface of the planar silica gel was pretreated using a line drawn by a soft carbon pencil, and 0.3 µL of a liquid matrix (15% sucrose/glycerol‐methanol 1:1, v/v) was applied to it (width ∼1mm) before sample deposition. The laser was then used to directly irradiate the sample spot on the pencil line (∼2 mm). Carbon powder ablated from the pencil residue is used to couple the laser UV energy into a liquid solution in LDMS. This sample preparation method is related to surface‐assisted laser desorption/ionization (SALDI) mass spectrometry, which uses a suspension of µm‐sized carbon powder (SALDI solid) mixed with a viscous liquid (SALDI matrix) as the matrix. In the present approach, the ablated carbon powder from the pencil drawing on a planar silica gel surface was used as an alternative to the SALDI solid. The liquid matrix was that used in conventional SALDI matrix systems, and the sample preparation applied herein is simpler than conventional SALDI. The matrix background remains quite low in this approach, which significantly assists the analysis of small organics such as methylephedrine and cytosine. PEG (polyethylene glycol) 400 and PEG 2000 were also used for demonstration purposes. Copyright © 2001 John Wiley & Sons, Ltd.
Ion chemistry of chloroethanes in air at atmospheric pressure
Authors: Nicoletti Anna , Paradisi Cristina , Scorrano Gianfranco 
Published: January 2005

AbstractIon chemistry at atmospheric pressure is of major relevance to novel methods for the abatement of volatile organic compounds (VOCs) that employ non‐thermal plasmas. For this reason, positive and negative APCI (atmospheric pressure chemical ionization) mass spectra of all six di‐, tri‐ and tetrachloroethanes diluted in air (500–1500 ppm) at atmospheric pressure were investigated at 30 °C and at 300 °C. Spectral changes due to collisional activation of the ions achieved by increasing ΔV, the potential difference between sampling and skimmer cones, are informative of structures and ion‐molecule reactions. Positive ion chemistry of the chloroethanes (M) can, in general, be ascribed to C‐C and C‐Cl cleavages of the molecular ion, M+·, never detected but likely formed via exothermic charge exchange from primary ions of the APCI plasma. Exceptions to this characteristic pattern were observed for 1,1‐dichloroethane and 1,1,2,2‐tetrachloroethane, which give [M − H]+ and [M − HCl]+· species, respectively. It is suggested that both such species are due to ionization via hydride transfer. Upon increasing ΔV, the [M − HCl]+· ion formed from 1,1,2,2‐tetrachloroethane undergoes the same fragmentation and ion‐molecule reactions previously reported for trichloroethene. A nucleophilic reaction of water within the [C2H4Cl+](H2O)n ionic complexes to displace HCl is postulated to account for the [C2H5O+](H2O)m species observed in the positive APCI spectra of the dichloroethanes. Negative ion spectra are, for all investigated chloroethanes, dominated by Cl− and its ion‐neutral complexes with one, two and, in some cases, three molecules of the neutral precursor and/or water. Another common feature is the formation of species (X−)(M)n where X− is a background ion of the APCI plasma, namely O2−,O3− and, in some cases, (NO)2−. Peculiar to 1,1,1‐trichloroethane are species attributed to Cl− complexes with phosgene, (Cl−)(Cl2C=O)n(n = 1,2). Such complexes, which were not observed for either the isomeric 1,1,2‐trichloroethane or for the tetrachloroethanes, are of interest as oxidation intermediates in the corona‐induced decomposition process. No conclusions can be drawn in the case of the dichloroethanes, since, for these compounds, the ions (Cl−)(Cl2C=O)n and (Cl−)(M)n happen to be isobaric. Copyright © 2001 John Wiley & Sons, Ltd.
Negative ion fragmentations of deprotonated peptides: backbone cleavages directed through both Asp and Glu
Authors: Brinkworth Craig S. , Dua Suresh , McAnoy Andrew M. , Bowie John H. 
Published: January 2005

AbstractThe collision‐induced spectra of [M − H]− ions of a variety of natural and synthetic amphibian peptides containing Asp and/or Glu exhibit characteristic γ backbone cleavage ions that identify the positions of these residues in the peptide. A theoretical study suggests that the Glu cleavage involves an SNi reaction of the carboxylate anion from the Glu α side chain to form a deprotonated cyclic lactone. The presence of either Asp or Glu or other residues that effect pronounced side‐chain cleavages (e.g. Ser or Thr) results in the normal α and β backbone cleavages being reduced in comparison to those cleavages which originate from side chains. Copyright © 2001 John Wiley & Sons, Ltd.
Optimal pressure conditions for unbiased external ion accumulation in a two‐dimensional radio‐frequency quadrupole for Fourier transform ion cyclotron resonance mass spectrometry
Authors: Belov Mikhail E. , Gorshkov Michael V. , Alving Kim , Smith Richard D. 
Published: January 2005

AbstractWhen combined with on‐line separations (e.g., capillary liquid chromatography (LC)), Fourier transform ion cyclotron resonance mass spectrometry (FTICR‐MS) provides a powerful tool for biological applications, and particularly proteomic studies. The sensitivity, dynamic range, and duty cycle provided by FTICR‐MS have been shown to be increased by ion trapping and accumulation in a two‐dimensional (2D) radio‐frequency (rf)‐only multipole positioned externally to an FTICR cell. However, it is important that ions be detected across the desired m/z range without a significant bias. In this work we found that pressure inside the accumulation rf‐quadrupole plays an important role in obtaining ‘unbiased’ ion accumulation. Pressure optimization was performed in both pulsed and continuous modes. It was found that unbiased accumulation in a 2D rf‐only quadrupole could be achieved in the pressure range of 5 × 10−4 to 5 × 10−3 Torr. External ion accumulation performed at the optimal pressure resulted in an increase in both the spectrum acquisition rates and dynamic range. Copyright © 2001 John Wiley & Sons, Ltd.