bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anionic copper complex fragmentations from enkephalins under low‐energy collision‐induced dissociation in an ion trap mass spectrometer
Authors: Bossée Anne , Afonso Carlos , Fournier Françoise , Tasseau Olivier , Pepe Claude , Bellier Bruno , Tabet Jean‐Claude 
Published: August 2004

AbstractPeptide metallation with Cu2+ was explored in the negative ESI mode using an ion trap mass spectrometer. Under these conditions, the [(M − 3H) + CuII]− species formed were investigated under low‐energy collision‐induced dissociation conditions. MS2 experiments indicate a very different behavior of CuII metallated complexes compared with [M − H]− species. CuII induces an easy loss of CO2 and specific side‐chain cleavages (by radical losses) at the C‐terminal residue, as observed previously by prompt ‘in source’ dissociation experiments. The loss of CO2 yields an unstable carbylide that leads to further dissociations involving the migration of a proton or a hydrogen radical (through the reduction of CuII). Multistage MS3 experiments were carried out to rationalize this behavior. Fragmentation pathways are proposed in order to explain the product ions observed. The side‐chain radical loss at the C‐terminus was demonstrated to be a consecutive process. Finally, evidence is provided that the specific side‐chain cleavages can be used for the differentiation of Leu/Ile and Gln/Lys residues when they are located at the C‐terminus. The existence of a zwitterionic form in the case of the anionic YGGFK–CuII complex is proposed. Copyright © 2004 John Wiley & Sons, Ltd.
Mass spectrometry of N‐linked oligosaccharides using atmospheric pressure infrared laser ionization from solution
Authors: Tan Phillip V. , Taranenko Nelli I. , Laiko Victor V. , Yakshin Mikhail A. , Prasad Coorg R. , Doroshenko Vladimir M. 
Published: August 2004

AbstractAn atmospheric pressure (AP) infrared (IR) laser ionization technique, implemented on a quadrupole ion trap mass spectrometer, was used to analyze underivatized, N‐linked oligosaccharides in solution. Experiments were conducted on an atmospheric pressure infrared ionization from solution (AP‐IRIS) ion source which differed from previous AP IR matrix‐assisted laser desorption/ionization (MALDI) interfaces in that the ion source operated in the absence of an extraction electric field with a higher power 2.94 µm IR laser. The general term ‘IRIS’ is used as the mechanism of ionization differs from that of MALDI, and is yet to be fully elucidated. The AP‐IRIS ion source demonstrated femtomole‐level sensitivity for branched oligosaccharides. AP‐IRIS showed ∼ 16 times improved sensitivity for oligomannose‐6 and the core‐fucosylated glycan M3N2F over optimal results obtainable on a AP UV‐MALDI with a 2,4,6‐trihydroxyacetophenone matrix. Comparison between IR and UV cases also showed less fragmentation in the IR spectrum for a glycan with a conserved trimannosyl core, core‐substituted with fucose. A mixture of complex, high‐mannose and sialylated glycans resulted in positive ion mass spectra with molecular ion peaks for each sugar. Tandem mass spectrometry of the sodiated molecular ions in a mixture of glycans revealed primarily glycosidic (B, Y) cleavages. The reported results show the practical utility of AP‐IRIS while the ionization mechanism is still under investigation. Copyright © 2004 John Wiley & Sons, Ltd.
Atmospheric pressure chemical ionization and atmospheric pressure photoionization for simultaneous mass spectrometric analysis of microbial respiratory ubiquinones and menaquinones
Authors: Geyer Roland , Peacock Aaron D. , White David C. , Lytle Cory , Van Berkel Gary J. 
Published: August 2004

AbstractAn atmospheric pressure photoionization (APPI) source and an atmospheric pressure chemical ionization (APCI) source were compared for the selective detection of microbial respiratory ubiquinone and menaquinone isoprenologues using tandem mass spectrometry. Ionization source‐ and compound mass‐dependent parameters were optimized individually for both sources, using the available quinone standards. Detection levels for the two ion sources were determined with ubiquinone‐6 (UQ6) and menaquinone‐4 (MK4, vitamin K2) standards using flow injection analysis and selected reaction monitoring (SRM). With APPI the calculated lower limit of detection (LLOD) was 1.7 fmol µl−1 for UQ6 and 2.2 fmol µl−1 for MK4 at a signal‐to‐noise ratio of 3. These LLODs were at least three times lower than with APCI. The selectivity of detection afforded by SRM detection reduced complex mixture analysis to 3 min per sample by eliminating the need for chromatographic separations. The detection method was successfully applied to quinone quantification in a variety of environmental samples and cell cultures. Adequate amounts of respiratory quinones can be extracted and quantified from samples containing as low as 2 × 107 cells. Copyright © 2004 John Wiley & Sons, Ltd.
Gas‐phase acidity of D‐glucose. A density functional theory study
Authors: Salpin Jean‐Yves , Tortajada Jeanine 
Published: August 2004

AbstractThe gas‐phase acidity of D‐glucopyranose was studied by means of B3LYP calculations combined with 6–31G(d,p) or 6–31+G(d,p) standard basis sets. For each anomer, deprotonation of the various primary and secondary hydroxyl groups was considered. As in solution, the anomeric hydroxyl is found to be the most acidic for both anomers, but only when the 6–31+G(d,p) basis set is used for geometry optimization. Deprotonation of the anomeric hydroxyl induces an important C(1)O endocyclic bond elongation and subsequently promotes an energetically favored ring‐opening process as attested by the very small calculated activation barriers. The results also suggest that interconversion between the various deprotonated α‐ and β‐anomers may easily occur under slightly energetic conditions. B3LYP/6–311+G(2df,2p) calculations led to the an absolute gas‐phase acidity of ΔacidGo298(α‐D‐glucose) = 1398 kJ mol−1. This estimate matches well the only experimental value available to date. Finally, this study again confirms that the use of diffuse functions on heavy atoms is necessary to describe anionic systems properly and to achieve good relative and absolute gas‐phase acidities. Copyright © 2004 John Wiley & Sons, Ltd.
Open‐access high‐resolution mass spectrometry in early drug discovery
Authors: Thomas Steven R. , Gerhard Ute 
Published: August 2004

AbstractTechniques such as mass spectrometry and NMR spectroscopy form an essential part of the medicinal chemist's toolbox for characterizing and assessing the purity of new molecules. Empowering medicinal chemists to gain early insight into their reaction products has a direct impact on productivity. Devolution of cutting‐edge techniques from the specialist to the bench chemist also frees the specialist to concentrate on solving the more demanding of analytical problems. For open‐access techniques to be taken up, they must be robust and be able to handle differing sample concentrations and varying sample complexities. This paper details the implementation of high‐resolution liquid chromatography/mass spectrometry in open access to aid the medicinal chemist in characterizing desired products and identifying unexpected rearrangements, by‐products and complete unknowns. Copyright © 2004 John Wiley & Sons, Ltd.
Extraribosomal cyclic tetradepsipeptides beauverolides: profiling and modeling the fragmentation pathways
Authors: Jegorov Alexandr , Paizs Bela , Kuzma Marek , Zabka Martin , Landa Zdenek , Sulc Miroslav , Barrow Mark P. , Havlicek Vladimir 
Published: August 2004

AbstractProfiling of cyclic tetradepsipeptides beauverolides was tested as a chemotaxonomic tool for fungal strain identification/discrimination. Two new tetradepsipeptides, beauverolides Q and R, were characterized by tandem mass spectrometry. Specific elimination of 113 atomic mass units from both protonated and sodiated molecules of beauverolides is ubiquitous for all 12 most dominant congeners evaluated in this profiling study. Reconstruction of the total ion chromatogram, according to this neutral fragment release, was used for data filtering and selectivity enhancement. Selective ring opening and fragment ion formation of beauverolide I are discussed in detail utilizing high‐level theoretical modeling of the fragmentation pathways. Copyright © 2004 John Wiley & Sons, Ltd.
Cerebrospinal fluid from patients with dementia contains increased amounts of an unknown factor
Authors: White Linda R. , Gårseth Mari , Aasly Jan , Sonnewald Ursula 
Published: August 2004

AbstractIncreased levels of an unidentified peak have been found in cerebrospinal fluid (CSF) from patients with Alzheimer's disease or vascular dementia compared to the level in healthy controls using proton magnetic resonance spectroscopy. No increase was found in patients with amyotrophic lateral sclerosis. Reexamination of spectra from a study published previously (Gårseth et al. [2000] J. Neurosci. Res. 60:779–782), however, shows that this peak was also elevated significantly in CSF from patients with Huntington's disease compared to that in controls. The level in patients with Parkinson's disease, where dementia develops in up to 40% of patients, was not elevated significantly compared to that in controls. To the best of our knowledge, this peak has not yet been identified and we therefore find it appropriate to temporarily designate the name “dementia associated factor” (DAF), although there is as yet no certainty that this substance is specific for these conditions. Apart from a significantly increased level of glutamine in CSF from patients with vascular dementia compared to that in controls, no other significant difference was found for any other metabolite measured in the patient groups using proton magnetic resonance spectroscopy. © 2004 Wiley‐Liss, Inc.
Activity‐dependent expression of Egr1 mRNA in somatosensory cortex of developing rats
Authors: Patra Ramesh C. , Blue Mary E. , Johnston Michael V. , Bressler Joseph , Wilson Mary Ann 
Published: August 2004

AbstractThe rat barrel field in somatosensory cortex is a well‐characterized model of neocortical development, with activity‐dependent and activity‐independent components. Egr1 encodes an inducible transcription factor that is required for certain forms activity‐dependent plasticity. This study examines Egr1 mRNA expression in the developing barrel field under basal conditions and after short‐term deprivation or stimulation of whiskers. Egr1 mRNA was measured with in situ hybridization at postnatal Day (P) 6, P9, P12, P15, and P21. For short‐term deprivation, whiskers were trimmed close to the skin and Egr1 mRNA was examined 3 hr later. For controlled stimulation of a single whisker, surrounding whiskers were trimmed, a wire was glued to the designated whisker, and animals were placed in an AC magnetic field pulsed at 2 Hz, 10 mT rms for 15 min. Egr1 mRNA was examined 30 min later. At P6, basal Egr1 mRNA in the barrel field was very low and was increased only slightly by stimulation (P < 0.05). At each of the later ages, there was a large increase in Egr1 mRNA in stimulated versus deprived barrels (P < 0.001). Egr1 mRNA expression after whisker stimulation increased exponentially with age through P15 (P < 0.001) and then declined between P15 and P21. The onset of Egr1 responses to whisker stimulation at P9 and the striking increase in activity‐dependent Egr1 mRNA expression in the second postnatal week suggest that this transcription factor may play a role in activity‐dependent processes that occur in this developmental period, such as maturation of barrel cortex circuitry. © 2004 Wiley‐Liss, Inc.
Elevated serotonin is involved in hyperactivity but not in the paradoxical effect of amphetamine in mice neonatally lesioned with 6‐hydroxydopamine
Authors: Avale María Elena , Nemirovsky Sergio Iván , Raisman‐Vozari Rita , Rubinstein Marcelo 
Published: August 2004

AbstractThe neonatal lesion with 6‐hydroxydopamine (6‐OHDA) in rodents induces juvenile hyperactivity and paradoxical hypolocomotor response to psychostimulants, in striking contrast to what is observed when similar lesions are carried out in adults. The early disruption of central dopaminergic pathways is followed by increased striatal serotonin (5‐HT) contents although the functional role of this neurodevelopmental adaptation remains unclear. The aim of the present study is to investigate the participation of this neurochemical imbalance in the main behavioral phenotypes of this model. To this end, mice received a neonatal administration of 6‐OHDA that induced an 80% striatal dopamine depletion together with 70% increase in 5‐HT. Serotoninergic hyperinnervation was evidenced further by increased [3H] citalopram autoradiographic binding and 5‐HT transporter immunohistochemistry in striatal sections. To investigate whether elevated 5‐HT was implicated in hyperactivity, we treated control and 6‐OHDA neonatally lesioned mice with the selective irreversible tryptophan hydroxylase inhibitor p‐chlorophenylalanine (PCPA) to induce 5‐HT depletion. Normalization of striatal 5‐HT in 6‐OHDA neonatally lesioned mice to control levels reversed hyperactivity to normal locomotor scores, whereas the same extent of 5‐HT depletion did not affect spontaneous locomotor activity of control mice. In turn, the paradoxical response to amphetamine in neonatal DA‐depleted mice was not prevented by PCPA treatment. Taken together, our results suggest that the increased striatal 5‐HT that follows neonatal DA depletion is involved in hyperlocomotor behavior but not in the paradoxical calming response to amphetamine observed in this mouse model. © 2004 Wiley‐Liss, Inc.
Human neural stem/progenitor cells, expanded in long‐term neurosphere culture, promote functional recovery after focal ischemia in Mongolian gerbils
Authors: Ishibashi Satoru , Sakaguchi Masanori , Kuroiwa Toshihiko , Yamasaki Mami , Kanemura Yonehiro , Shizuko Ichinose , Shimazaki Takuya , Onodera Masafumi , Okano Hideyuki , Mizusawa Hidehiro 
Published: August 2004

AbstractTransplantation of human neural stem cells (NSCs) is a promising potential therapy for neurologic dysfunctions after the hyperacute stage of stroke in humans, but large amounts of human NSCs must be expanded in long‐term culture for such therapy. To determine their possible therapeutic potential for human stroke, human fetal neural stem/progenitor cells (NSPCs) (i.e., neurosphere‐forming cells) were isolated originally from forebrain tissues of one human fetus, and expanded in long‐term neurosphere culture (exceeding 24 weeks), then xenografted into the lesioned areas in the brains of Mongolian gerbils 4 days after focal ischemia. Sensorimotor and cognitive functions were evaluated during the 4 weeks after transplantation. The total infarction volume in the NSPC‐grafted animals was significantly lower than that in controls. Approximately 8% of the grafted NSPCs survived, mainly in areas of selective neuronal death, and were costained with antibodies against neuronal nuclei antibody (NeuN), microtubule associated protein (MAP‐2), glial fibrillary acidic protein (GFAP), and anti‐2′3′ cyclic nucleotide 3′‐phosphodiesterase (CNPase). Synaptic structures between NSPCs‐derived neurons and host neurons were observed. Furthermore, gradual improvement of neurologic functions was observed clearly in the NSPC‐grafted animals, compared to that in controls. Human NSPCs, even from long‐term culture, remarkably improved neurologic functions after focal ischemia in the Mongolian gerbil, and maintained their abilities to migrate around the infarction, differentiate into mature neurons, and form synapses with host neuronal circuits. These results indicate that in vitro‐expanded human neurosphere cells are a potential source for transplantable material for treatment of stroke. © 2004 Wiley‐Liss, Inc.
5‐HT1A, 5‐HT2, and GABAB receptors interact to modulate neurotransmitter release probability in layer 2/3 somatosensory rat cortex as evaluated by the paired pulse protocol
Authors: Torres‐Escalante José L. , Barral Jaime A. , Ibarra‐Villa María D. , Pérez‐Burgos Azucena , Góngora‐Alfaro José L. , Pineda Juan C. 
Published: August 2004

AbstractActivation of γ‐aminobutyric acid B (GABAB) and 5‐hydroxytryptamine (5‐HT) receptors produces presynaptic inhibition at glutamatergic terminals in the rat neocortex. To evaluate interactions between these metabotropic receptors, field potentials were recorded in layer 2/3 of somatosensory cortex. In addition, the paired pulse (PP) protocol was used to measure changes in the ratio of the second/first extracellular synaptic potentials (S2/S1 ratio) as an index of glutamate release probability in the area. Lowering extracellular [Ca2+]o to 0.5 mM, increased the S2/S1 ratio by 318 ± 134%. 5‐HT (1 μM) increased the S2/S1 ratio by 61 ± 15%. In presence of the GABAA antagonist bicuculline (10 μM), 5‐HT increased the S2/S1 ratio by 98 ± 15%. This effect did not desensitize after two consecutive applications of the amine, and was dose dependent in the concentration range between 0.03–1 μM (EC50 = 2.36 × 10−7 mol/L). The increase of S2/S1 ratio induced by 5‐HT (1 μM) was blocked reversibly by the 5‐HT1A antagonist NAN‐190 (10–30 μM), but was unaffected by the selective GABAB antagonist CGP 52432 (1 μM). The action of 5‐HT was mimicked by the 5‐HT1A/7 agonist 8OH‐DPAT (10 μM), increasing the S2/S1 ratio by 84 ± 2%, a response that was unaffected by the 5‐HT2/7 antagonist ritanserin (2 μM). The 5‐HT1B agonist CP93129 (10 μM) had no effect. The GABAB agonist baclofen (1 μM) increased the S2/S1 ratio up to 308 ± 33%, which is similar to that produced by low [Ca2+]o. When the effect of baclofen was maximal, application of 5‐HT (1 μM) reversed the S2/S1 ratio back to 78 ± 27%, a result that was blocked by the 5‐HT2/7 antagonist ritanserin (100 nM). Notably, the interaction between the GABAB agonist and 5‐HT was order dependent, because enhancement of the S2/S1 ratio elicited by baclofen was not inhibited if 5‐HT was applied first. These results suggest a complex interaction between GABAB, 5‐HT1A, and 5‐HT2 receptors in layer 2/3 of rat somatosensory cortex. Activation of GABAB receptors induces PP facilitation (inhibits glutamate release) more efficiently than does activation of 5‐HT1A receptors. When the effect of GABAB receptor activation is maximal, however, the influence of 5‐HT changes to the opposite direction, inhibiting PP facilitation (increasing glutamate release) through activation of 5‐HT2 receptors. © 2004 Wiley‐Liss, Inc.
Spatial changes of soil solution and mineral composition in the rhizosphere of Norway‐spruce seedlings colonized by Piloderma croceum
Authors: Arocena Joselito M. , Göttlein Axel , Raidl Stefan 
Published: August 2004

AbstractEctomycorrhizae (ECM) or the root‐fungal association in forest ecosystems provide a unique soil microenvironment where soil properties and processes differ from the bulk soil. In this study, we would like to better understand the role of ECM systems in mineral weathering and its implications to soil formation and nutrient cycling in forest ecosystems. Specifically, we would like to document the spatial variations in the composition of soil solution and mineralogy of the rhizosphere as influenced by the ECM of Norway spruce + Piloderma croceum. Two‐month‐old seedlings of Norway spruce (control and colonized by P. croceum) were cultivated in special rhizotrons designed to allow spatial collection of soil solution. We used A and C horizons of a Dystric Cambisol collected from Höglwald forest near Munich. Micro suction cups (5 mm x 1mm) were installed in colonized and control rhizotrons, and soil solution was collected from September to November 2000. Our results show that the concentrations of NH$_4^+$, Ca2+, and Mg2+ in the soil solution were lower in <1.0 cm than in >3.0 cm distance from the roots of Norway spruce, due to the possible range of influence of Piloderma mycelium reaching about 2–3 cm from the surface of the mycorrhizal root. In the rhizotron with soil from the A horizon, a higher phosphorus content in Piloderma‐colonized seedlings was observed. X‐ray diffraction data indicate that chlorite and possibly mica are being transformed to 2:1‐expanding clay minerals (probably smectite) within <1.0 cm distance from roots. The spatial variations in soil solution composition and mineral transformation are likely to be due to Piloderma colonization and concentrated mycelial growth within <1.0 cm distance from the roots. This is also evident in more intricate growth of mycelia on surfaces of micaceous minerals as compared to quartz. We assume that Piloderma modifies soil solution and mineralogy through acquisition of essential elements for its own survival and/or for the uptake by plant roots. However, the presence of spontaneous infection with wildtype ECM in the control plots may have altered the influence of Piloderma and must be taken into consideration when interpreting our results.
Temperature functions of the rate coefficients of net N mineralization in sandy arable soils. Part II. Evaluation via field mineralization measurements
Authors: Heumann Sabine , Böttcher Jürgen 
Published: August 2004

AbstractThe aim of this study was to evaluate experimentally derived temperature functions for the rate coefficients of net N mineralization in sandy arable soils from NW Germany via field measurements. In part I of this paper (Heumann and Böttcher, 2004), different temperature functions for the rate coefficients of a two‐pool first‐order kinetic equation were derived by long‐term laboratory incubations at 3°C to 35°C. In this paper, field net N mineralization during winter of 25 plots was measured in undisturbed soil columns with a diameter of 20 cm to the depth of the Ap horizon. Mean simulated net N mineralization with the most adequate multiple functions corresponded also best with the mean of the measured values despite of an overestimation of about 10%. Distinctly larger deviations under use of other temperature functions (Arrhenius, Q10) were directly related to their deviations from mean, experimentally derived rate coefficients. Simulated net N mineralization in the soil columns was significantly correlated with measured values, regardless of the temperature functions. Yet the goodness of fit was generally relatively low due to the spatial variability of measured net N mineralization within replicate soil columns, although the mean CV (38%) was by far not extraordinary. The pool of slowly mineralizable N contributed considerably to net N mineralization during four to five winter months, on an average 10.0 kg N ha–1, about one third of total simulated N mineralization. Sometimes, it contributed even 21.3 kg N ha–1, which is almost sufficient to reach the EU drinking‐water limit for nitrate in these soils. Simulations with widely used functions that were once derived from loess soils overestimated mineralization from pool Nslow in the studied sandy arable soils by a factor of two.