bluuebunny/crossref_metadata_2025_split huggingface dataset:
Three sources of CO2 efflux from soil partitioned by 13C natural abundance in an incubation study
Authors: Kuzyakov Yakov , Bol Roland 
Published: May 2005

AbstractThis study describes a novel approach to separate three soil carbon (C) sources by one tracer method (here 13C natural abundance). The approach is based on the combination of C3 and C4 sources in different treatments, identical decomposition of C3 and C4 substances in soil, and subsequent calculation of their contribution to the total CO2 efflux. We used the temporal dynamics of the CO2 efflux from a C3 grassland soil amended with added C3 or C4 slurry and/or C3 or C4 sugar to estimate contributions of three separate C sources: native soil organic matter (SOM), slurry and sugar, to CO2 efflux. Soil with slurry and/or sugar was incubated under controlled conditions, and concentration and δ13C values of evolved CO2 were measured over a 2‐week period. The main assumption needed for separation of three C sources in CO2 efflux, i.e. identical decomposition of applied C3 and C4 sugars in soil, was investigated and proven. The relative contribution to the CO2 efflux increased, but its duration decreased with an increased microbial availability of the C source, i.e. sugar > slurry > SOM. The microorganisms used the C sources according to their availability. The contribution of sugar to the CO2 efflux was finished after 2–4 days. Separation of three CO2 sources and comparison of CO2 from different treatments tracing the changes of SOM and slurry decomposition induced by addition of sugar were investigated. During the sugar decomposition (the first 2–4 days), the SOM decomposition strongly decreased. At the same time the contribution of slurry‐C to CO2 increased. The shortcomings and limitations as well as possible future applications of the suggested method including FACE (Free Air Carbon dioxide Enrichments) and continuous labelling experiments are discussed. Copyright © 2005 John Wiley & Sons, Ltd.
Denaturant sensitive regions in creatine kinase identified by hydrogen/deuterium exchange
Authors: Mazon Hortense , Marcillat Olivier , Forest Eric , Vial Christian 
Published: May 2005

AbstractThe GdmHCl‐induced unfolding of creatine kinase (CK) has been studied by hydrogen/deuterium (H/D) exchange combined with mass spectrometry. MM‐CK unfolded for various periods in different denaturant concentrations was pulsed‐labeled with deuterium to identify different conformational intermediate states. For all denaturation times or GdmHCl concentrations, we observed variable proportions of only two species. The low‐mass envelope of isotope peaks corresponds to a species that has gained about 10 deuteriums more than native CK, and the high‐mass envelope to a completely deuterated species. To localize precisely the unfolded regions in the states highly populated during denaturation, the protein was digested with two proteases (pepsin and type XIII protease) after H/D exchange and rapid quenching of the reaction. The two sets of fragments obtained were analyzed by liquid chromatography coupled to mass spectrometry to determine the deuterium level in each fragment. Bimodal distributions of deuterium were found for most peptides, indicating that these regions were either folded or unfolded. This behavior is consistent with cooperative, localized unfolding. However, we observed a monomodal distribution of deuterium in two regions (1–12 and 162–186). We conclude that the increment of mass observed in the low‐mass species of the intact protein (+10 Da) has its origin in these two segments. These regions, which are very sensitive to low GdmHCl concentrations, are involved in the monomer–monomer interface of CK and their perturbation is likely to weaken the dimeric structure. At higher denaturant concentration, this would induce dissociation of the dimer. Copyright © 2005 John Wiley & Sons, Ltd.
Rapid screening of drugs of abuse and their metabolites by gas chromatography/mass spectrometry: application to urinalysis
Authors: Strano‐Rossi Sabina , Molaioni Francesco , Rossi Francesca , Botrè Francesco 
Published: May 2005

AbstractThis paper describes a rapid gas chromatographic/mass spectrometric (GC/MS) screening method for the detection of drugs of abuse and/or their metabolites in urine. Synthetic stimulants, opiates, cocaine metabolites, cannabinoids—and specifically the acid metabolite of tetrahydrocannabinol (THC‐COOH)—can be simultaneously extracted by a single liquid/liquid separation step, at alkaline pH, and assayed as trimethylsilyl derivatives by GC/MS in SIM (selected ion monitoring) mode. All the analytes show a good linearity (R2 > 0.99 for most of the considered substances) in the range 25–1000 ng/mL, with a good reproducibility of both the retention times (CV% <0.7) and the relative abundances of the characteristic diagnostic ions (CV% <13). The limit of detection (LOD) of the method is 25 ng/mL of target compound in human urine for most of the substances investigated, 3 ng/mL for THC‐COOH, and 10 ng/mL for norbuprenorphine. Validation of the method allows its application to different fields of forensic analytical toxicology, including antidoping analysis. Copyright © 2005 John Wiley & Sons, Ltd.
Characterization of phenolic compounds in the Chinese herbal drug Tu‐Si‐Zi by liquid chromatography coupled to electrospray ionization mass spectrometry
Authors: Ye Min , Yan Yuning , Guo De‐an 
Published: May 2005

AbstractPhenolic compounds are the major bioactive constituents of the Chinese herbal drug Tu‐Si‐Zi, which is prepared from the seeds of Cuscuta chinensis. However, seeds of C. australis also are offered under the name of this drug in the herb market. In order to make a comparison of their chemical constituents, the phenolic compounds of these two Cuscuta species were analyzed by high‐performance liquid chromatography/diode‐array detection/electrospray ion trap tandem mass spectrometry (HPLC/DAD/ESI‐MSn). A total of 50 compounds were observed in the methanol extracts, including 23 flavonoids, 20 lignans and 7 quinic acid derivatives. These compounds were separated on a C18 column and identified or tentatively characterized based on UV spectra and MS fragmentation behavior. In contrast to previous reports, the phenolic patterns of these two Cuscuta species were found to be very different. Kaempferol and astragalin were the predominant constituents of C. australis, while hyperoside was the major compound in C. chinensis. Most of the identified compounds, especially the acylated flavonoid glycosides, have not previously been reported from Cuscuta species. In addition, a 30 Da neutral loss observed for flavonols was investigated and could be used to differentiate flavonoid isomers such as kaempferol and luteolin. The ESI‐MS fragmentation behavior of furofuran lignans was also investigated, and a characteristic pathway is proposed. The large differences observed between the phenolic constituents of C. chinensis and C. australis strongly encouraged further comparison of the bioactivities of these two species. Copyright © 2005 John Wiley & Sons, Ltd.
Dual linear ion trap/orthogonal acceleration time‐of‐flight mass spectrometer with improved precursor ion selectivity
Authors: Hashimoto Yuichiro , Hasegawa Hideki , Waki Izumi 
Published: May 2005

AbstractA new hybrid mass spectrometer based on dual linear ion traps (LITs) and an orthogonal acceleration time‐of‐flight mass spectrometer (oaTOF), that can achieve MSn analysis and high‐mass‐accuracy detection with high sensitivity, has been developed. Dual‐LIT was necessary because, in a single LIT plus oaTOF combination, the LIT pressure favorable for high precursor selectivity in MSn analysis (less than 1 mTorr) was far different from an optimum damping pressure (50–100 mTorr) for efficient connection to the TOF mass spectrometer. A dual‐LIT solved this problem of inconsistency of the optimum pressures by using the first LIT for MSn analysis and the second LIT for collisional damping. This dual‐LIT/TOF instrument achieved high‐sensitivity MSn analysis with high precursor‐ion selectivity. Copyright © 2005 John Wiley & Sons, Ltd.
An application of electrospray ionization tandem mass spectrometry to probe the interaction of Ca2+/Mg2+/Zn2+ and Cl− with gramicidin A
Authors: Sudhir Putty‐Reddy , Wu Hui‐Fen , Zhou Zi‐Cong 
Published: May 2005

AbstractThe peptide, gramicidin A (GrA), has been demonstrated to interact with divalent salts (CaCl2, MgCl2, and ZnCl2) using electrospray ionization mass spectrometry (ESI‐MS). The ESI‐MS analysis revealed different complexes formed due to the interaction of Val‐GrA and Ile‐GrA with divalent salts: [Val or Ile‐GrA‐H+M]+, [Val or Ile‐GrA+MCl]+ and [Val or Ile‐GrA+M]2+, where M is Ca or Mg or Zn. All these complexes have been subjected to collisionally activated dissociation (CAD). CAD of singly and doubly charged GrA and metal complexes exhibited the losses of water molecules, indicating the ligand preference of GrA. MS/MS and MS3 of [Val or Ile‐GrA+MCl]+ resulted in the elimination of chloride ion and water, respectively. The tandem mass spectrometry data of the complex [Val‐GrA+MCl]+ suggest that chloride interaction is stronger in the presence of Ca than of Mg and Zn. This study reveals that GrA could interact with Ca, Mg, and Zn in metal ion form as well as in ion pair (MCl) form. The interactions of GrA with Ca support the proposal of a physical basis for the messenger role of Ca (Urry et al., J. Biol. Chem. 1982, 257: 6659–6661). Copyright © 2005 John Wiley & Sons, Ltd.
Rapid determination of urinary globotriaosylceramide isoform profiles by electrospray ionization mass spectrometry using stearoyl‐d35‐globotriaosylceramide as internal standard
Authors: Fauler Guenter , Rechberger Gerald N. , Devrnja Danijela , Erwa Wolfgang , Plecko Barbara , Kotanko Peter , Breunig Frank , Paschke Eduard 
Published: May 2005

AbstractGlobotriaosylceramide is a neutral glycolipid containing the trihexoside Gal(α1‐4)Gal(ß1‐4)Glc(ß1‐1′) covalently bound to N‐acylsphingosine. It was identified as the main storage substance in the kidney of patients with Fabry disease, an X‐linked deficiency of lysosomal α‐galactosidase A which can significantly be ameliorated by enzyme replacement therapy. Unlike hemizygote males, affected heterozygote females cannot be identified by enzyme assays and therefore may remain untreated. A quantitation of urinary globotriaosylceramides was proposed as an alternative method for their diagnosis. However, the required studies on physiological and pathological variations in the excretion of trihexosides so far have been prevented by a lack of suitable methods. A validated, robust and quick high‐throughput method for the quantitative analysis of globotriaosylceramide isoforms using stable‐isotope‐dilution/internal standardization and electrospray ionization mass spectrometry (ESI‐MS) was developed. An internal standard, stearoyl‐d35‐globotriaosylceramide, was synthesized by enzymatic coupling of d35‐stearic acid to the corresponding lyso‐ceramidetrihexoside. Glycolipid isoforms of high purity were obtained from a 5‐mL urine portion by extraction on C18 solid‐phase columns and a novel washing protocol. ESI‐MS analysis was performed in full and neutral loss scan modes. Urinary trihexosyl‐ and some of the di‐ and monohexosylceramide isoforms can be quantified within a single experiment. All glycolipid isoforms were above detection limit in healthy male and female subjects (n = 63). Prominent elevations of tetracosanoyl‐(C24:0 plus C24:1)‐globotriaosylceramides were found in urines from female (>2.5‐fold above normals) or male Fabry patients (>5.8‐fold above normals), but not among controls. Globotriaosylceramide isoforms shall now be analyzed in Fabry patients, non‐genetic kidney disease and healthy subjects to define the conditions for a safe diagnosis of heterozygotes. Copyright © 2005 John Wiley & Sons, Ltd.
Photoionization of CH3I mediated by the C state in the visible and ultraviolet regions
Authors: Sharma P. , Vatsa R. K. , Rajasekhar B. N. , Das N. C. , Ghanty T. K. , Kulshreshtha S. K. 
Published: May 2005

AbstractThree/two‐photon resonant multiphoton ionization (MPI) of the CH3I monomer has been studied in the gas phase at 532 and 355 nm using time‐of‐flight mass spectrometry. Under low laser intensity (∼109 W/cm2) the mass spectra showed peaks at m/z 15, 127 and 142, corresponding to [CH3]+, [I]+ and [CH3I]+ species, at both these wavelengths. The laser power dependence for [CH3I]+, [I]+ and [CH3]+ ions showed a three‐photon dependence at 532 nm. For the same three ions, photoionization studies at 355 nm gave a power dependence of 2. Both these results suggest that a vibronic energy level at ∼7 eV, lying in the Rydberg C state, acts as a resonant intermediate level in ionization of CH3I. In the case of 355 nm, with increasing intensity additional peaks at m/z 139 and 141 were observed which could be assigned to [CI]+ and [CH2I]+ fragments. In contrast, for high intensity radiation at 532 nm (∼2 × 1010 W/cm2), only the [CI]+ fragment was observed. At these wavelengths, fragment ions observed in mass spectra mainly arise from photodissociation of the parent ion. Experiments at another wavelength in the visible region (564.2 nm) confirmed the results obtained at 532 nm. In order to assess the role of the Ã state in these MPI experiments, additional experiments were performed at 266 and 282.1 nm, which access the Ã state directly via a one‐photon transition, and showed absence of a surviving precursor ion. Reaction energies for various possible dissociation channels of CH3I/[CH3I]+/[CH2I]+ were calculated theoretically at the MP2 level using the GAMESS electronic structure program. Copyright © 2005 John Wiley & Sons, Ltd.
Electrospray ionization studies of transition‐metal complexes of 2‐acetylbenzimidazolethiosemicarbazone using collision‐induced dissociation and ion‐molecule reactions
Authors: Bhaskar G. , Chary M. Adharvana , Kumar M. Kiran , Syamasundar K. , Vairamani M. , Prabhakar S. 
Published: May 2005

AbstractThe complexes of transition‐metal ions (M2+, where M = Fe, Co, Ni, Cu, Zn, Cd, and Hg) with 2‐acetylbenzimidazolethiosemicarbazone (L) are studied under electrospray ionization (ESI) conditions. The ESI mass spectra of Fe and Co complexes showed the complex ions corresponding to [M+2L–2H]+, and those of Ni and Zn complexes showed [M+2L–H]+ ions, wherein the metal/ligand ratio is 1:2 and the oxidation state of the central metal ion is +3 in the case of Fe and Co and +2 in the case of Ni and Zn. The Cd and Cu complexes showed preferentially 1:1 complex ions, i.e., [M+L–H]+ or [M+L+Cl]+, whereas Hg formed both 1:1 and 1:2 complex ions. During formation of the above complex ions one or two ligands are deprotonated after keto‐enol tautomerism, depending on the nature and oxidation state of central metal ion. The structures and coordination numbers of the metal ions in the complex ions were studied by their collision‐induced dissociation spectra and ion‐molecule reactions with acetonitrile or propylamine in the collision cell. Based on these results it is concluded that Fe, Co, Ni and Zn form stable octahedral complexes, whereas tetrahedral or square planar complexes are formed preferentially for other metals. In addition, the Cu complex showed a [2L+2Cu–3H]+ ion with a CuCu bond. Copyright © 2005 John Wiley & Sons, Ltd.
Comparison of inductively coupled plasma mass spectrometry techniques in the determination of platinum in urine: quadrupole vs. sector field
Authors: Spezia Sandro , Bocca Beatrice , Forte Giovanni , Gatti Anna , Mincione Giovanna , Ronchi Anna , Bavazzano Paolo , Alimonti Alessandro , Minoia Claudio 
Published: May 2005

AbstractIn recent years the increasing use of platinum (Pt) both in medical and in industrial applications has caused its growing anthropogenic emission and spread in the environment. Pt is released into the atmosphere by exhaust catalytic converters, and Pt compounds are often used in antitumour therapies. As a consequence, significant amounts of Pt can be detected in hospital wastewaters. This can lead to an increase in the exposure levels to Pt, especially in urban areas. It is therefore necessary to determine Pt reference values in the general population, by using suitable procedures able to achieve adequate analytical performances. Several measurements of Pt in biological fluids have been reported, but the analytical methods used for the determination of Pt often lack information about the uncertainty of the results, especially for low concentrations of urinary Pt in non‐occupationally exposed subjects. The present paper considers the measurement of urinary Pt levels in a general population group from central Italy, by both quadrupole (Q) and sector field (SF) inductively coupled plasma mass spectrometry (ICP‐MS). The two procedures were validated and their expanded uncertainties were evaluated. The limits of detection (LODs), calculated taking into account dilution factors, were 0.18 and 0.05 ng L−1 of Pt for the Q and SF procedures, respectively. The median value observed was 4.13 ng L−1 of Pt in urine, while the relative combined uncertainty at 5 ng L−1 was below 20% with both ICP‐MS techniques. These data are in good agreement with those reported in the literature for similar studies. Copyright © 2005 John Wiley & Sons, Ltd.
Factors influencing success in introductory college chemistry
Authors: Tai Robert H. , Sadler Philip M. , Loehr John F. 
Published: May 2005

AbstractPrevious research has found a wide range of predictors of student performance in introductory college chemistry. These predictors are associated with both the students' backgrounds and their high school learning experiences. The purpose of this research study was to examine the link between high school chemistry pedagogical experiences and performance in introductory college chemistry while accounting for individual educational and demographic differences. The researchers surveyed 1531 students enrolled in first‐semester introductory college chemistry courses for science and engineering majors at 12 different U.S. colleges and universities. Using multiple regression analysis, the researchers uncovered several interesting high school pedagogical experiences that appeared to be linked with varying levels of performance in college chemistry. Most notably, the researchers found that repeating chemistry labs for understanding was associated with higher student grades, whereas overemphasis on lab procedure in high school chemistry was associated with lower grades in college. These results suggest that high school teachers' pedagogical choices may have a link to future student performance. © 2005 Wiley Periodicals, Inc. J Res Sci Teach 42: 987–1012, 2005
Gestational sac volume measured by three‐dimensional ultrasound at 11 to 13 + 6 weeks of gestation: relation to chromosomal defects
Authors: Falcon O. , Wegrzyn P. , Faro C. , Peralta C. F. A. , Nicolaides K. H. 
Published: May 2005

AbstractObjectiveTo determine the potential value of measuring the gestational sac volume (GSV) at 11 to 13 + 6 weeks of gestation in screening for chromosomal defects.MethodsThe GSV was measured using three‐dimensional (3D) ultrasound in 500 consecutive singleton pregnancies immediately before chorionic villus sampling (CVS) for fetal karyotyping at 11 to 13 + 6 (median 12) weeks of gestation.ResultsThe fetal karyotype was normal in 417 pregnancies and abnormal in 83. In the chromosomally normal group, the mean GSV increased significantly with gestational age from a mean of 69 mL at 11 weeks to 144 mL at 13 + 6 weeks (the standard deviation was 27 mL). In the chromosomally abnormal group, the mean GSV for gestational age was not significantly different from normal in fetuses with trisomy 21, trisomy 18 and Turner syndrome, but it was smaller in those with triploidy and trisomy 13. However, the mean GSV for crown–rump length (CRL) was significantly larger in trisomy 18, smaller in triploidy and trisomy 13, and not different from normal in trisomy 21 and Turner syndrome. The mean CRL for gestational age was significantly smaller than normal in trisomy 18, triploidy and trisomy 13.ConclusionsThe measurement of the GSV at 11 to 13 + 6 weeks of gestation is unlikely to provide useful prediction of the major chromosomal defects. In trisomy 13 and triploidy, the small GSV may be due to early onset fetal growth restriction and reduced amniotic fluid volume. In trisomy 18, the increase in GSV is probably due to the presence of associated fetal abnormalities that interfere with fetal swallowing. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.
Application of PIXE and PIGE under variable ion beam incident angle to several fields of archaeometry
Authors: Weber G. , Martinot L. , Strivay D. , Garnir H. P. , George P. 
Published: May 2005

AbstractFor several years, the specific features of PIXE and PIGE have made them very attractive in the field of archaeometry. Among them, non‐destructivity is one of the most important. The possibility of working under atmospheric pressure is also important because of the very different shapes and sizes of the artefacts concerned. However, these ion beam techniques suffer from the same disadvantage: the information coming from x‐rays or γ‐rays produced at different places along the charged particle path is integrated. That prevents one from taking into account the possible element concentration gradients due to multi‐layered systems or diffusion processes. This paper presents several applications of PIXE and PIGE applied under variable ion beam incident angle. PIGE has been mainly used for studying ancient glass items or glass windows in order to detect or evaluate the glass corrosion process. The examples given for PIGE deal with Roman and Merovingian glass objects and cathedral glass windows and PIXE applications concern studies for resolving the multilayered structure of easel paintings. The set‐up allowing one to perform the measurements should be very stable, the rotation axis should pass through the beam axis and the detector should follow the sample movement. Copyright © 2005 John Wiley & Sons, Ltd.
Contribution of atomic bremsstrahlung in PIXE spectra and screening effect in atomic bremsstrahlung
Authors: Ishii K. , Yamazaki H. , Matsuyama S. , Galster W. , Satoh T. , Budnar M. 
Published: May 2005

AbstractThe continuous background appearing in PIXE spectra has been studied in detail and is understood to comprise three main components: secondary electron bremsstrahlung (SEB), atomic bremsstrahlung (AB) and nuclear bremsstrahlung (NB). Here, studies on continuous x‐rays in PIXE are reviewed and a new phenomenon is discussed, the screening effect of the projectile by target electrons in AB. Copyright © 2005 John Wiley & Sons, Ltd.