bluuebunny/crossref_metadata_2025 huggingface dataset:
In vivo responses of mouse superficial dorsal horn neurones to both current injection and peripheral cutaneous stimulation
Authors: Graham B. A. , Brichta A. M. , Callister R. J.
Published: October 2004

In the superficial dorsal horn (SDH) processing of noxious and innocuous stimuli is critically dependent on the input–output relationship of its component neurones. Such relationships are routinely examined by assessing neuronal responses to somatic current injection or activation of synaptic inputs. A more complete understanding of input–output relationships would be achieved by comparing, in the same neurone, how the two forms of activation contribute to neuronal output. Therefore, we examined how SDH neurones transform depolarizing current injections and synaptic excitation via peripheral cutaneous stimuli (brush and pinch of the hindpaw) into trains of action potentials, in an in vivo preparation of the adult mouse spinal cord. Under whole‐cell current clamp recording conditions four action potential discharge patterns were observed during depolarizing current injection: tonic firing neurones (21/93) discharged spikes throughout the step; initial bursting neurones (35/93) discharged several spikes at step onset; single spiking neurones (16/93) discharged one or two spikes at step onset; and delayed firing neurones (21/93) discharged spikes delayed from the step onset. Four characteristic profiles were observed in response to application of noxious (pinch) and innocuous (brush) cutaneous stimuli: nociceptive neurones (20/37) responded maximally to pinch stimulation; light touch neurones (9/37) responded maximally to brush stimulation; subthreshold neurones (4/37) exhibited depolarizing responses without firing action potentials; and hyperpolarizing neurones (4/37) exhibited a sustained pinch‐induced hyperpolarization. Comparisons of current‐evoked discharge patterns with peripherally evoked responses indicate SDH neurones expressing each of the four discharge patterns could receive, and therefore participate in the processing of information concerning, either noxious or innocuous stimuli. These data suggest that a neurone's response to current injection does not necessarily help identify or predict how the same neurone will respond to physiologically or functionally relevant stimuli.
Muscle pyruvate availability can limit the flux, but not activation, of the pyruvate dehydrogenase complex during submaximal exercise in humans
Authors: Constantin‐Teodosiu Dumitru , Peirce Nicholas S. , Fox John , Greenhaff Paul L.
Published: October 2004

While lowering muscle glycogen availability to an extent that would reduce muscle pyruvate formation during intense exercise, we investigated the importance of muscle pyruvate availability to pyruvate dehydrogenase complex (PDC) activation during intense exercise in human skeletal muscle. The present study demonstrated that regardless of whether pre‐exercise muscle glycogen content was at a habitual resting concentration (412 ± 30 mmol (kg dry muscle)−1) or depleted (60 ± 3 mmol (kg dry muscle)−1), the increase in PDC activation from its resting value (5.46 ± 0.96 and 3.67 ± 0.34 nmol acetyl‐CoA min−1 (mg protein)−1, respectively) during 10 min of exercise at 75% of the maximum rate of oxygen consumption (Δ12.82 ± 1.72 and Δ13.24 ± 1.42 nmol acetyl‐CoA min−1 (mg protein)−1, respectively) was the same, despite pyruvate accumulation during exercise being 3‐fold lower in the glycogen depleted state (Δ0.34 ± 0.04 and Δ0.11 ± 0.06 mmol (kg dry muscle)−1, P < 0.001). However, as a result of the reduction in pyruvate availability, calculated flux through the PDC reaction was at least 2‐fold lower in the glycogen depleted state compared with normal (21.81 ± 2.62 and 9.41 ± 0.63 nmol acetyl‐CoA min−1 (mg protein)−1, respectively; P < 0.001). It is therefore pertinent to conclude that whilst muscle pyruvate availability appears to be important to the rate of flux through the PDC reaction during in vivo contraction, it is not of primary importance to the control of PDC activation under these conditions, which is probably principally regulated by muscle calcium availability. The proposed central role of pyruvate in muscle PDC activation during in vivo contraction may therefore have been over stated.
Heteromeric KCNE2/KCNQ1 potassium channels in the luminal membrane of gastric parietal cells
Authors: Heitzmann Dirk , Grahammer Florian , von Hahn Thomas , Schmitt‐Gräff Annette , Romeo Elisa , Nitschke Roland , Gerlach Uwe , Lang Hans Jochen , Verrey François , Barhanin Jacques , Warth Richard
Published: October 2004

Recently, we and others have shown that luminal K+ recycling via KCNQ1 K+ channels is required for gastric H+ secretion. Inhibition of KCNQ1 by the chromanol 293B strongly diminished H+ secretion. The present study aims at clarifying KCNQ1 subunit composition, subcellular localization, regulation and pharmacology in parietal cells. Using in situ hybridization and immunofluorescence techniques, we identified KCNE2 as the β subunit of KCNQ1 in the luminal membrane compartment of parietal cells. Expressed in COS cells, hKCNE2/hKCNQ1 channels were activated by acidic pH, PIP2, cAMP and purinergic receptor stimulation. Qualitatively similar results were obtained in mouse parietal cells. Confocal microscopy revealed stimulation‐induced translocation of H+,K+‐ATPase from tubulovesicles towards the luminal pole of parietal cells, whereas distribution of KCNQ1 K+ channels did not change to the same extent. In COS cells the 293B‐related substance IKs124 blocked hKCNE2/hKCNQ1 with an IC50 of 8 nm. Inhibition of hKCNE1‐ and hKCNE3‐containing channels was weaker with IC50 values of 370 and 440 nm, respectively. In conclusion, KCNQ1 coassembles with KCNE2 to form acid‐activated luminal K+ channels of parietal cells. KCNQ1/KCNE2 is activated during acid secretion via several pathways but probably not by targeting of the channel to the membrane. IKs124 could serve as a leading compound in the development of subunit‐specific KCNE2/KCNQ1 blockers to treat peptic ulcers.
Nitric oxide is significantly reduced in ex vivo porcine arteries during reverse flow because of increased superoxide production
Authors: Lu X. , Kassab G. S.
Published: October 2004

Oscillatory and negative flows occur normally in the cardiovascular system, which predispose those regions to atherosclerosis. Nitric oxide (NO) production increases in proportion to the magnitude of flow and is known to be athero‐protective. What is not known, however, is the effect of flow reversal on NO concentration ([NO]). The hypothesis of the present study is that [NO] is reduced in reverse flow. An additional hypothesis is that the reduction in [NO] is mediated through an increase in superoxide production during flow reversal. These hypotheses were tested in an ex vivo preparation of porcine elastic and muscular arteries. The flow of a physiological solution through the vessels was regulated in the forward and reverse direction and the effluent was assayed for nitrite levels using a combination of a diazo coupling method and high performance liquid chromatography. Our results show that [NO] is significantly reduced during reverse flow. Furthermore, addition of tempol (superoxide dismutase‐mimetic) which is a superoxide scavenger returns the [NO] during reverse flow to mirror those of forward flow. These results have important implications since the action of superoxide is implicated in many cardiovascular diseases, and the present finding suggests that flow reversal should be added to the list.
Long-Term Aridity Changes in the Western United States
Authors: Cook Edward R. , Woodhouse Connie A. , Eakin C. Mark , Meko David M. , Stahle David W.
Published: October 2004

The western United States is experiencing a severe multiyear drought that is unprecedented in some hydroclimatic records. Using gridded drought reconstructions that cover most of the western United States over the past 1200 years, we show that this drought pales in comparison to an earlier period of elevated aridity and epic drought in AD 900 to 1300, an interval broadly consistent with the Medieval Warm Period. If elevated aridity in the western United States is a natural response to climate warming, then any trend toward warmer temperatures in the future could lead to a serious long-term increase in aridity over western North America.
Femtomolar Sensitivity of a NO Sensor from
Clostridium botulinum
Authors: Nioche Pierre , Berka Vladimir , Vipond Julia , Minton Nigel , Tsai Ah-Lim , Raman C. S.
Published: October 2004

Nitric oxide (NO) is extremely toxic to
Clostridium botulinum
, but its molecular targets are unknown. Here, we identify a heme protein sensor (SONO) that displays femtomolar affinity for NO. The crystal structure of the SONO heme domain reveals a previously undescribed fold and a strategically placed tyrosine residue that modulates heme-nitrosyl coordination. Furthermore, the domain architecture of a SONO ortholog cloned from
Chlamydomonas reinhardtii
indicates that NO signaling through cyclic guanosine monophosphate arose before the origin of multicellular eukaryotes. Our findings have broad implications for understanding bacterial responses to NO, as well as for the activation of mammalian NO-sensitive guanylyl cyclase.
Synthetic Approach to 5α-Pregnanolone 19-[O-(Carboxymethyl)oxime] Derivatives
Authors: Černý Ivan , Havlíková Helena , Hill Martin , Hampl Richard , Pouzar Vladimír
Published: October 2004

Syntheses of 5α-pregnanolone derivatives (3-hydroxy-5α-pregnan-20-ones) with 3α- and 3β-configuration and 19-[O-(carboxymethyl)oxime] group were developed, starting from 19-hydroxy-20-oxopregn-5-en-3β-yl acetate. After catalytic hydrogenation, acetylation and ketone protection, the acetyl in position 3 was removed. To obtain the 3α-derivative, nitrite epimerization of the intermediate tosylate was performed before the introduction of methoxymethyl protecting group, while the 3β-derivative was protected directly. In both series, deacetylation, oxidation to an aldehyde andO-(carboxymethyl)hydroxylamine condenzation followed. Conversion to the methyl ester, simultaneous deprotection of positions 3 and 20, and alkaline hydrolysis gave the corresponding 19-[O-(carboxymethyl)oximes]. The nine- and ten-step syntheses described herein (yields 19.5 and 7.3%, respectively) gave the target compounds, designed as haptens for immunological use.
Inhibition of Biosynthesis and Biochemical Modulation of N-Acylneuraminic Acid (Biochemical Engineering of Sialoconjugates). A Review
Authors: Reutter Werner , Horstkorte Rüdiger
Published: October 2004

The key enzyme of sialic acid biosynthesis is the bifunctional UDP-GlcNAc 2-epimerase/ ManNAc kinase. Novel inhibitors of this enzyme have been synthesized. TheN-acyl side chain of sialic acid can be biochemically engineered by incubating cells with non-naturalN-acylmannosamine analogues such asN-propionylmannosamine and related compounds. These modified sialic acids lead to various biological changes, such as stimulation of T-lymphocyte proliferation, inhibition of the uptake of influenza A virus, stimulation of neuritic growth, increased expression of sialyl-Lewisxand altered adhesion. A review with 41 references.
2-Haloethyl 1-Thioglycosides as New Tools in Glycoside Syntheses. Part 1: Preparation, Characteristics, General Reactions
Authors: Krüger Andreas , Pyplo-Schnieders Jutta , Redlich Hartmut , Winkelmann Pär
Published: October 2004

2-Haloethyl 1-thioglycosides are excellent leaving groups when the 2-haloethyl function is activated with silver salts or Lewis acids. These thioglycosides can be synthesized on the original Černý route or for better compatibility with the needs of a more complex glycoside synthesis, in stepwise procedures via 2-(2-tetrahydropyran-2-yloxy)ethyl glycosides or trityl 1-thioglycosides. The initial step in glycosidation reaction presumably proceeds via a thiiranium ion, which is responsible for their increased reactivity compared with normal thioethers as leaving groups in glycoside syntheses. Basic features of this new system with respect to reactivity and selectivity in disaccharide syntheses are described.
Synthesis of 2-Amino-2-deoxy-β-D-galactopyranosyl-(1→4)-2-amino-2-deoxy-β-D-galactopyranosides: Using Various 2-Deoxy-2-phthalimido-D-galactopyranosyl Donors and Acceptors
Authors: Veselý Jan , Ledvina Miroslav , Jindřich Jindřich , Trnka Tomáš , Šaman David
Published: October 2004

A systematic study is presented of the efficiency of the most common glycosylation methods using standard 2-deoxy-2-phthalimidogalactopyranosyl donors ethyl 4-O-acetyl-3,6-di-O- benzyl-2-deoxy-2-phthalimido-1-thio-β-D-galactopyranoside (3a), 4-O-Acetyl-3,6-di-O-benzyl- 2-deoxy-2-phthalimido-β-D-galactopyranosyl bromide (4), 4-O-acetyl-3,6-di-O-benzyl-2-deoxy-2-phthalimido-β-D-galactopyranosyl fluoride (5b), O-(4-O-acetyl-3,6-di-O-benzyl-2-deoxy-2-phthalimido-β-D-galactopyranosyl) trichloroacetimidate (7) and ethyl 3,6-di-O-benzyl-2-deoxy-2-phthalimido-1-thio-β-D-galactopyranoside (8), pent-4-enyl 3,6-di-O-benzyl- and 3-O-allyl-6-O-benzyl-2-deoxy-2-phthalimido-β-D-galactopyranoside (10a) and (10b) and pent-4-enyl 3,6-di-O-benzyl-2-deoxy-2-phthalimido-4-O-(trimethylsilyl)-β-D-galactopyranoside (11) as glycosyl acceptors in the synthesis of 2-amino-2-deoxy-β-D-galactopyranosyl-(1→4)-2-amino-2-deoxy-β-D-galactopyranosides 12, 16a and 17a. It was found that due to a low reactivity of the axial OH(4) group of glycosyl acceptors, disaccharides 16b and 17b with α(1→4) bond were also formed. The unexpected intermolecular migration of ethylsufanyl group from the reducing end of glycosyl acceptor 8 the reducing end of the activated form of glycosyl donor 4 in the glycosylation step to give ethylsulfanyl derivative 3a was proved. For preparation of the glycosyl donors and glycosyl acceptors with galacto configuration an approach based on epimerization of 4-O-mesyl derivatives of appropriate synthons with gluco configuration 2a and 2b was employed.
Methods for calculating vibrational energy levels
Authors: Carrington Tucker
Published: October 2004

This article reviews new methods for computing vibrational energy levels of small polyatomic molecules. The principal impediment to the calculation of energy levels is the size of the required basis set. If one uses a product basis the Hamiltonian matrix for a four-atom molecule is too large to store in core memory. We discuss iterative methods that enable one to use a product basis to compute energy levels (and spectra) without storing a Hamiltonian matrix. Despite the advantages of iterative methods it is not possible, using product basis functions, to calculate vibrational spectra of molecules with more than four atoms. A very recent method combining contracted basis functions and the Lanczos algorithm with which vibrational energy levels of methane have been computed is described. New ideas, based on exploiting preconditioning, for reducing the number of matrix-vector products required to converge energy levels of interest are also summarized.Key words: vibrational energy levels, kinetic energy operators, Lanczos algorithm, contracted basis functions, preconditioning.
Photoionization dynamics in CS fragmented from CS2 studied by high-resolution photoelectron spectroscopy
Authors: Rijs Anouk M , Backus Ellen HG , de Lange Cornelis A
Published: October 2004

The photoionization dynamics of CS have been studied using high-resolution laser photoelectron spectroscopy. The photodissociation of CS2 at ~308 nm results in highly rotationally excited CS in its X1Σ+ singlet ground state, as well as in rotationally cold CS in the excited a3Π triplet state. The ground-state CS fragments are formed together with sulfur in its 3P, 1D, and 1S electronic states; triplet CS is produced in coincidence with ground-state sulfur (3P). In both channels the photoelectron spectra are dominated by Δv = 0 propensity, but transitions involving Δv = 1 and 2 are also observed. Key words: photoelectron spectroscopy, photoionization, photodissociation, excited states, reactive intermediates.
Electrochemical behaviour of 1-{[(3-halophenyl)imino]methyl}-2-naphthol Schiff bases on graphite electrodes
Authors: Polat Kamran , Uçar Mustafa , Aksu M Levent , Ünver Hüseyin
Published: October 2004

An electrochemical study of the reduction of 1-{[(3-halophenyl)imino]methyl}-2-naphthol compounds on graphite electrodes was carried out. All the compounds were dissolved in a 1:4 (volume fraction) mixture of tetrahydrofuran (THF) and methanol. NaClO4 (0.1 mol L1) was used as the supporting electrolyte. Cyclic voltammetry, chronoamperometry, constant-potential coulometry (bulk electrolysis), and constant-potential preparative electrolysis were employed. The cyclic voltammetric data revealed that the reduction on graphite was irreversible and followed an EC mechanism. The diffusion coefficients and the number of electrons transferred were determined using the chronoamperometric Cottrell slope and the ultramicro electrode steady-state current. The number of electrons was also determined by bulk electrolysis. The products of the electroreduction were synthesized in milligram quantities by the use of constant-potential preparative electrolysis. These products were purified and characterized by spectroscopic methods. Based on these findings, a mechanism for the electroreduction process is proposed.Key words: electrochemical reduction, hydroxynaphthylideneaniline Schiff bases, cyclic voltammetry, ultramicro electrode.
Micellar properties of zwitterionic surfactant - alkoxyethanol mixed micelles
Authors: Mullally Maria K , Marangoni D Gerrard
Published: October 2004

The micelle formation process for a zwitterionic surfactant, N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (ZW3-12), has been investigated in a series of mixed solvents consisting of different concentrations of ethoxylated alcohols and polymers. The critical micelle concentrations (cmc values) of the aggregates were determined by fluorescence spectroscopy, and the surfactant aggregation numbers were obtained from luminescence probing experiments. The cmc values for ZW3-12 changed very little in the presence of increasing amounts of poly(ethyleneoxide) (PEO) in the mixed solvent. In the case of the ethoxylated alcohol  ZW3-12 systems, the cmc values and aggregation numbers decreased systematically with increasing alcohol concentration. However, the cmc values of the mixed micelles showed little dependence on the number of ethylene oxide (EO) groups at constant alcohol concentration. These results are compared with the well-studied sodium dodecylsulfate  ethoxylated alcohol, and dodecyltrimethylammonium bromide  ethoxylated alcohol mixed micellar systems and to SDSPEO systems and are discussed in terms of the contribution of the EO groups to the hydrophobic interactions. Key words: zwitterionic surfactant, alcohols, mixed micelles, luminescence probing.
An ab initio study of the potential energy surfaces for the collision between a Cs atom and an I2molecule
Authors: Sun Xiaomin , Feng Dacheng , Cai Zhengting , Bian Wensheng
Published: October 2004

For the Cs + I2collision system, a systematic theoretical study is first reported using the ab initio method. Three of eight possible channels are considered. The nonadiabatic coupling between the covalent state and the ionic one is calculated from different angles, especially the T-shape collision. The complete ion-pair formation potential energy surfaces of the T-shape collision in two electronic states (ionic2B2state and covalent2A1state) and the reactive surface of the linear collision are constructed at the QCISD(T)/SDD level. The main features of potential energy surfaces, such as the minimum energy reaction path, the crossing radius (Rc), and energy minimum geometries, are analyzed. The cross section of this titled system is calculated based on the harpoon mechanism and compared with the available experimental data and those obtained for the M + I2(M = Li, Na) systems.Key words: ab initio two-state potential energy surfaces, nonadiabatic coupling, ion-pair formation, cross section.
Temperature- and pressure-dependent luminescence spectroscopy on the trans-[ReO2(pyridine)4]+ complex  Analysis of vibronic structure, luminescence energies, and bonding characteristics
Authors: Grey John K , Butler Ian S , Reber Christian
Published: October 2004

Resolved vibronic structure in electronic spectra provides a detailed view into how molecular structure changes after absorption or emission of a photon. We report temperature- and pressure-dependent luminescence spectra of trans-[ReO2(pyridine)4]I. Low-temperature spectra reveal long vibronic progressions in the totally symmetric O=Re=O (907 cm1) and Re-pyridine (211 cm1) stretching modes, indicating large structural displacements along these normal coordinates. The luminescence band maximum is at ca. 15 500 cm1. Room-temperature spectra are somewhat less-resolved; however, intervals closely matching the O=Re=O frequency (~870 cm1) persist at higher temperatures. The variable pressure spectra exhibit distinct changes in the vibronic patterns, and luminescence energies decrease by 16 ± 2 cm1/kbar (1 bar = 100 kPa). Low-temperature spectra are modeled using two-dimensional potential energy surfaces to represent the initial and final electronic states, from which the quantitative normal coordinate offsets can be determined. We then adapt this model to the room-temperature, pressure-dependent data where it is possible to determine how the offsets and other important spectroscopic parameters vary with the pressure-induced changes of the molecular structure. Key words: trans-[ReO2(pyridine)4]I, low-temperature luminescence spectroscopy, high-pressure luminescence spectroscopy, vibronic structure, emitting state distortions.
CN spectroscopy and cosmic background radiation measurements
Authors: Leach Sydney
Published: October 2004

A source of possible error, not previously considered, in the determination of the cosmic background radiation (CBR) temperature Tγ(CN) from interstellar CN absorption is proposed. This concerns the intrinsic assumption of the validity of using HönlLondon rotational line intensity factors to determine the rotational components of the oscillator strengths of the R(0), R(1), and P(1) lines of the CN B2Σ+X2Σ+(0,0) transition. Published data on interstellar CN absorption shows that Tγ(CN) is slightly greater than the standard cosmological CBR temperature, Tγ(COBE) = 2.725 K, determined by the COBE satellite, even when local excitation effects of CN are taken into account. From this difference, an estimation was made of the maximum corrections, a few percent, to the ratio of the line strengths and to the ratio of the HönlLondon factors. Fluorescence lifetime data were shown to give similar values for the corrections as well as providing evidence for intramolecular coupling between the relevant B2Σ+state rotational levels and close-lying levels of the A2Π state, this being responsible for rendering the standard HönlLondon factors invalid. Key words: CN spectroscopy, cosmic background radiation, HönlLondon factors.
Fermi resonance and conformation in glycolaldehyde particles
Authors: Jetzki Martin , Luckhaus David , Signorell Ruth
Published: October 2004

The infrared spectra of gas-phase glycolaldehyde and small glycolaldehyde particles both exhibit a split carbonyl band around 1730 cm1. Ab initio calculations show that this splitting can be traced back to a Fermi resonance involving the C=O-stretching band and the first overtone of the CC-stretching band. The analysis of this resonance leads to detailed information about the conformation of glycolaldehyde in the particles. The results can be summarized as follows. (i) In the particles, monomers with OCCO dihedral angles of 0° and CCOH dihedral angles around 50° are strongly preferred. (ii) The intramolecular hydrogen bond observed in the gas phase is partly replaced by intermolecular hydrogen bonds. (iii) The calculated infrared spectrum and the results from the Fermi resonance analysis are in good agreement with the formation of long chains of monomeric glycolaldehyde. This is in contrast to the solid bulk, which consists of chemically bound dimers. Key words: Fermi resonance, conformation, glycolaldehyde particles, hydroxyacetone particles, Fourier transform infrared spectroscopy.
CH2 revisited
Authors: Kalemos Apostolos , Dunning Jr. Thom H , Mavridis Aristides , Harrison James F
Published: October 2004

The first four states of the CH2 molecule ([Formula: see text]3B1, ã1 A1, [Formula: see text]1A1, and [Formula: see text]1A1) are examined using state-of-the-art ab initio methods and basis sets. The construction of potential energy curves with respect to the C + H2 and CH + H channels provides significant clues to understanding the geometric and electronic structure of the above states. All of our numerical findings are in excellent agreement with the existing experimental data. Key words: CH2, MRCI, potential curves, vbL icons.
Torsional isomers in methylated aminoethanols - A jet-FT-IR study
Authors: Liu Yaqian , Rice Corey A , Suhm Martin A
Published: October 2004

Jet-FT-IR spectra of aminoethanol (AE), N-methylaminoethanol (MAE), and N,N-dimethylaminoethanol (DMAE) are presented and compared to gas-phase and matrix isolation IR, microwave, and quantum chemical data. The intramolecular O-H···N hydrogen bond gives rise to characteristically shifted O-H stretching bands and torsional difference bands in the monomer spectra. It stabilizes one out of 14 diastereomeric monomer conformations of AE and DMAE and two out of 27 diastereomeric MAE conformations. The latter two correspond to torsional or N-inversional isomers, the interconversion of which is hindered by the intramolecular hydrogen bond. Their energy difference is found to be <1.2 kJ/mol. The intermolecular aggregation patterns of the three aminoethanols are quite distinct and non-monotonic, as suggested by their O-H stretching fingerprints.Key words: aminoethanol, IR spectroscopy, conformation, hydrogen bond, supersonic jet.
Conformational stability, infrared and Raman spectra, and vibrational assignment of ethyl bromogermane
Authors: Durig James R , Pan Chunhua , Witkowski Witold , Guirgis Gamil A
Published: October 2004

The infrared spectra (320030 cm1) of ethyl bromogermane, CH3CH2GeH2Br, in the gaseous phase and of amorphous and annealed solid samples as well as the Raman spectrum (3200100 cm1) of the liquid have been recorded. Variable-temperature (105 to 150 °C) studies of the infrared spectra of a sample dissolved in liquid krypton have been carried out. From these data, the enthalpy difference between the gauche and trans conformers has been determined to be 158 ± 16 cm1 (1.89 ± 0.20 kJ/mol), with the gauche conformer being the more stable form. This result is consistent with the prediction from ab initio calculations at both the HartreeFock level and with full electron correlation by the perturbation method to second order. It is estimated that at ambient temperature 81 ± 2% of the sample is in the gauche form. A relatively complete vibrational assignment is proposed for both the gauche and trans conformers based on infrared band contours, relative intensities, depolarization values, and group frequencies which is supported by normal coordinate calculations utilizing the force constants from the ab initio MP2/6-31G(d) calculations. The optimized geometries and conformational stabilities have also been obtained from ab initio calculations utilizing several different basis sets with full electron correlation by the perturbation method up to MP2/6-311+G(2d,2p). Additionally, the potential functions governing the conformation interchange have been estimated from ab initio MP2/6-31G(d) and density functional theory calculations by the B3LYP method, with barriers to conformational interchange of 560, 924, and 852 cm1 from MP2/6-31G(d) and 418, 771, and 606 cm1 from B3LYP/6-31G(d) calculations for the trans to gauche, gauche to gauche, and gauche to trans conformers, respectively. The results are discussed and compared to some corresponding quantities for several related molecules.Key words: conformational stability, Raman spectra, infrared spectra; ab initio calculations, ethyl bromogermane.
A vacuum ultraviolet laser single-photon zero kinetic energy photoelectron spectroscopic study of the 2E3/2 ground electronic state of CH3Br+
Authors: Shi Y J , Wang S , Jakubek Z J , Simard B
Published: October 2004

The vacuum ultraviolet laser single-photon zero kinetic energy (ZEKE) photoelectron spectrum of the [Formula: see text]2E3/2 ground electronic state of the methyl bromide cation is reported. The spectrum is dominated by the origin band 000 of the transition [Formula: see text]2E3/2 ← [Formula: see text]1A1. In addition, the 210 band and the 311 hot band are observed. All observed bands show similar rotational contours. Simulation of the rotational contour of the origin band yields the first ionization energy of methyl bromide (85 031.2 ± 1.0 cm1) and the rotational constants of the cation in its ground electronic state. Key words: methyl bromide, vacuum ultraviolet laser, single-photon excitation, zero kinetic energy photoelectron spectroscopy.
The dependence of thymine and thymidine Raman spectra on solvent
Authors: Beyere L , Arboleda P , Monga V , Loppnow G R
Published: October 2004

Recent work has focused on developing Raman spectroscopy as a noninvasive probe of DNA interactions with solvents, intercalants, proteins, and other ligands. Here, we report the Raman spectra of thymine in eight solvents and thymidine in nine solvents obtained with visible excitation. Raman spectra under acidic, neutral, and basic conditions were also obtained of both thymine and thymidine. Changes in both the frequencies and intensities of several of the vibrational bands in the 8001800 cm1 region are observed. No evidence of deprotonation in the different solvents is observed for either thymine or thymidine. Correlations of the observed frequency shifts of specific vibrational modes with characteristic properties of the solvent for both thymine and thymidine show a significant correlation with acceptor and donor numbers, measures of the hydrogen-bonding ability of the solvent, in both thymine and thymidine. These results are interpreted in terms of hydrogen-bonding interactions between the N-H protons of the thymine base and lone pairs of electrons on the solvent molecules and between the solvent hydrogens and lone pairs on C=O sites. The solvent-dependent intensity in vibrational bands of thymine between 1500 and 1800 cm1 indicates a strong interaction between thymine and solvent at the C=O and N-H sites that leads to separation of the C=O stretches from the C=C stretch. The intensity variations with solvent were much smaller for thymidine than for thymine, perhaps as a result of replacing the N1 proton by the sugar. These results suggest that Raman spectroscopy is uniquely sensitive to specific interactions of thymine and thymidine with their environment.Key words: Raman spectroscopy, thymine, thymidine, solvent effects, hydrogen bonding.
Voltammetric behavior and quantification of the anti-leukemia drug imatinib in bulk form, pharmaceutical formulation, and human serum at a mercury electrode
Authors: Hammam E , El-Desoky H S , Tawfik A , Ghoneim M M
Published: October 2004

Imatinib (GleevecTM, ST1571) exemplifies the successful development of a rationally designed molecularly targeted therapy for treatment of a specific cancer. It is a highly promising new drug for the treatment of chronic myelogenous leukemia in blast crisis, in the accelerated or chronic phase after interferon failure or intolerance. The electrochemical behavior of imatinib was studied in BrittonRobinson (BR) buffers of pH 2 to 11 by means of cyclic voltammetry at a hanging mercury drop electrode. The voltammograms showed a single 2-electron irreversible cathodic peak, which may be attributed to reduction of the C=O double bond of the imatinib molecule. Imatinib exhibited a strong adsorption onto the electrode surface especially in BR buffers of pH 6 and 7. The adsorptive response of the drug was optimized with respect to the pH of the electrolysis medium, accumulation variables, and instrumental parameters using a square-wave stripping voltammetry technique. A fully validated, simple, sensitive, precise, and selective square-wave adsorptive cathodic stripping voltammetric procedure is described for trace determination of imatinib. The limits of detection (LOD) and quantitation (LOQ) of the bulk imatinib, following preconcentration for 150 s onto the hanging mercury drop electrode, were found to be 2.6 × 1010 and 8.7 × 1010 mol/L, respectively. The proposed procedure was successfully applied for quantitation of imatinib in pharmaceutical formulation (Glivec®) and spiked human serum, without the necessity for sample pretreatment or time-consuming extraction or evaporation steps prior to analysis of the drug. LOD and LOQ of 4.6 × 1010 and 1.5 × 109 mol/L, respectively, were achieved after 120 s of preconcentration of the drug spiked in human serum.Key words: imatinib, GleevecTM, Glivec®, ST1571, cyclic voltammetry, square-wave stripping voltammetry, electrochemical behavior, quantification, pharmaceutical formulation, human serum.
Taxol interaction with DNA and RNA  Stability and structural features
Authors: Ouameur A Ahmed , Malonga H , Neault J F , Diamantoglou S , Tajmir-Riahi H A
Published: October 2004

Taxol (paclitaxel) is an anticancer drug that interacts with microtubule proteins in a manner that catalyzes their formation from tubulin and stabilizes the resulting structures. However, in the human lung tumor cell, the concentration of paclitaxel is highest in the nucleus. Therefore, it was of interest to examine the interaction of taxol with DNA and RNA in aqueous solution at physiological pH. Capillary electrophoresis and Fourier transform infrared (FTIR) difference spectroscopic methods were used to characterize the nature of drugDNA and drugRNA interactions and to determine the taxol binding site, the binding constant, the sequence selectivity, the helix stability, and the biopolymer secondary structure in the taxolpolynucleotide complexes in vitro. The FTIR spectroscopic studies were conducted with taxol/polynucleotide (phosphate) ratios of 1/80, 1/40, 1/20, 1/10, 1/4, and 1/2 with a final DNA(P) or RNA(P) concentration of 12.5 mmol/L, and capillary electrophoresis was performed after incubation of taxol with polynucleotides at ratios of 1/200 to 1/12 with a final polynucleotide concentration of 1.25 mmol/L. Taxol was shown to bind to DNA and RNA at GC, AT, or AU bases and the backbone PO2group. Two types of binding were observed for taxolDNA with K1 = 1.3 × 104L mol1and K2 = 3.5 × 103L mol1, whereas taxolRNA complexes showed one type of binding with K = 1.3 × 104L mol1. The taxolpolynucleotide complexation is associated with a partial helix stabilization and no major alterations of B-DNA or A-RNA structure. Key words: DNA, RNA, taxol, binding site, binding constant, conformation, helix stability, electrophoresis, FTIR spectroscopy.
A computational study of a cyano-bridged dinuclear ruthenium complex containing the non-innocent methylpyrazinium ligand
Authors: Lever A BP
Published: October 2004

The properties of a series of complexes trans-[LRu(NH3)4-NC-Ru(NH3)4(methylpyrazinium)]n+ where L is an anion (Cl, F, CN, OH) or neutral ligand (CO, H2O, pyridine, CH3NO2) were analyzed using density functional theory. The objective was to probe the change in electronic coupling between the two ruthenium atoms and between ruthenium and the non-innocent methylpyrazinium ligand as L is varied. Molecular orbital coefficients and optical spectra were derived. The electronic interactions involved are seen to be quite sensitive to the charge on the ruthenium to which the ligand L is attached as L is varied. Exchange (K) and Coulomb (J) energies are also calculated, using the INDO/S model, for the various metal-to-ligand charge-transfer transitions. K correlates well with the energy and intensity of the transitions and specifically with the variation in delocalization induced by variation of L.Key words: DFT, ruthenium, non-innocent ligand, methylpyrazinium, ZINDO.
Temporal evolution of an ultrathin, noncrystalline ice deposit at crystallization near 160 K studied by FT-IR reflection-absorption spectroscopy
Authors: Mitlin S , Leung K T
Published: October 2004

The temporal evolution of the OH stretching modes of a noncrystalline ice deposit upon annealing followed by crystallization near 160 K has been investigated by FT-IR reflectionabsorption spectroscopy. Using the earlier theoretical results from Whalley (E. Whalley. Can. J. Chem. 55, 3429 (1977)) and from Buch and Devlin (V. Buch and J.P. Devlin. J. Chem. Phys. 110, 3437 (1999)), the most prominent changes in these modes have been characterized for the first time. A dynamical picture of the structural transformation during crystallization has been developed, and it supports the observation that crystallization proceeds directly from a noncrystalline to a crystalline state without any long-lived intermediate state structurally different from its noncrystalline predecessor.Key words: crystallization, noncrystalline ice, FT-IR reflectionabsorption spectroscopy, temporary evolution.
Intrachannel vibronic coupling in molecular photoionization
Authors: Rathbone G J , Poliakoff E D , Bozek John D , Lucchese R R
Published: October 2004

We discuss the excitation of forbidden vibrational transitions accompanying photoionization of linear triatomic molecules. Excitation of a single quantum of the antisymmetric stretching vibration is observed for mole cules with inversion symmetry, as is the bending mode. Photoelectron spectra of the N2O+(A2Π), CO2+(C2Σg+), and CS2+(B2Σu+) states obtained over a range of ionization energies exhibit contrasting behavior for the relative intensities of the forbidden vibrations. These energy-dependent vibrational branching ratios are shown to result from an intrachannel vibronic coupling mechanism. Moreover, this intrachannel coupling can be further divided into two cases, one in which the photoionization cross section is sensitive to geometry changes, and a second case in which it is not. These different cases can be distinguished by comparing the experimental and theoretical results for all three molecules.Key words: photoelectron spectroscopy, vibronic coupling, photoionization.PACS Nos.: 33.60.Cv, 33.20.Ni, 33.20.Wr, 33.80.Eh
Transition state dynamics and a QM/MM model for the Cl + C2H5Cl SN2 reaction
Authors: Sun Lipeng , Chang Eunkyung , Song Kihyung , Hase William L
Published: October 2004

A MP2/6-31G* direct dynamics simulation is used to study the dynamics of the central barrier [Cl-C2H5-Cl] for the Cl + C2H5 SN2 reaction. The majority of the trajectories move off the central barrier to form the ClC2H5Cl complex and appear to undergo efficient IVR as assumed by RRKM theory. However, some of the trajectories move directly to products without forming the complex, a non-RRKM result. A hydrogen atom link-atom QM/MM model is described for studying the dynamics of [X-CH2R-Y] central barriers with the -R substituent. The model is used to calculate vibrational frequencies for the [Cl-C2H5-Cl] central barrier.Key words: SN2 reaction dynamics, RRKM theory, QM/MM model, central barrier dynamics, direct dynamics classical trajectories.
Rydberg states of the rare gas dimers
Authors: Ginter Marshall L , Eden J Gary
Published: October 2004

This work is dedicated to Gerhard Herzberg and his prodigious contributions to molecular spectroscopy. Of particular relevance here is Herzberg's seminal 1987 article (Annu. Rev. Phys. Chem. 38, 27 (1987)) in which he discussed the electronic structures of several groups of molecules he termed "Rydberg molecules". Among these are the rare gas dimers (Rg2), a group whose study has benefited significantly from recent advances in laser excitation and synchrotron-based spectroscopies, as well as in theory. Following the spirit of Herzberg's 1987 article, this paper reviews some of the more prominent features of Rydberg states in the Rg2 family as viewed from the current perspective.Key words: rare gas dimers, rare gas dimer excited states, Rg2 electronic structures, Rydberg states of He2, Ne2, Ar2, Kr2, and Xe2, electronic states of He2, Ne2, Ar2, Kr2, and Xe2.
Annual fertilization and interspecific competition control: effects on in situ forest floor nitrogen fluxes of different-aged Pinus taeda stands in southeast Georgia, USA
Authors: Meason Dean F , Markewitz Daniel , Will Rodney E
Published: October 2004

Forest floor organic matter in managed pine forests can accumulate large quantities of N during early stand development. The conversion of the forest floor from a net accumulator to a net source of N as stands age, however, is not well quantified, nor is the effect of management activities on this conversion process. Nitrogen flux from the forest floor of different-aged Pinus taeda L. stands (8, 12, and 14 years old) was measured to understand the impact of annual fertilization (~70 kg N·ha1·year1) and complete interspecific competition control on forest floor N cycling. Throughfall and forest floor leachate solutions were collected for 1 year and N mineralization assays conducted. Volume-weighted mean concentrations were used in conjunction with hydrologic fluxes to estimate the net nitrate (NO3-N), ammonium (NH4+-N), and dissolved organic N flux from the forest floor. Complete competition control had no effect on the inorganic N flux. Changes in inorganic or organic N flux also were not discernable with stand age. Fertilization treatments, excluding fertilizer pulses, significantly increased the forest floor release of N in the fertilized stands compared with the nonfertilized stands (p < 0.05). Overall fluxes of NO3-N and NH4+-N from the forest floor were, respectively, 2.8 and 6.2 kg N·ha1·year1 for fertilized stands and 1.1 and 0.9 kg N·ha1·year1 for nonfertilized stands. Unlike inorganic N, organic N was retained in fertilized stands as a result of large organic throughfall inputs. Nitrogen cycling through the forest floor was ~4 kg·ha1·year1 greater in fertilized stands. This increased N release may account for as much as 6% of average annual pine demand and thus may well enhance productivity in future years.
Resistance of forest songbirds to habitat perforation in a high-elevation conifer forest
Authors: Leupin Ernest E , Dickinson Thomas E , Martin Kathy
Published: October 2004

We examined responses of songbirds breeding in high-elevation Engelmann spruce  subalpine fir (Picea englemannii Parry ex Engelm.  Abies lasiocarpa (Hook.) Nutt.) forests to four perforation harvest patterns near Sicamous, British Columbia. Each treatment removed approximately 30% of the timber volume but varied the size of openings from 10-ha clearcuts to small gaps (<0.01 ha), where individual trees were removed. Abundance and diversity of breeding songbirds were monitored over a 4-year period, including 2 years each of pre- and post-harvest conditions. Two-thirds of the original songbird assemblage consisted of mature forest species that showed only modest changes in relative abundance following harvest. Two species showed significant responses to harvesting: golden-crowned kinglet (Regulus satrapa Lichtensteins) declined significantly postharvest, with the largest declines occurring in single-tree and 10-ha treatments; and dark-eyed junco (Junco hyemalis L.) responded positively to harvest. At high elevations, 30% volume removal allowed much of the songbird community to be accommodated immediately after harvest. Future research should address whether the apparent short-term accommodation of high-elevation birds persists across time and as more of the continuous forest cover is removed.
Insecthost relationships influencing disturbance by the spruce budworm in a boreal mixedwood forest
Authors: Nealis V G , Régnière J
Published: October 2004

Demographic data from a 15-year outbreak of the spruce budworm, Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae), in a boreal mixedwood forest in Ontario, Canada, are used to interpret stand-level ecological disturbance in terms of susceptibility and vulnerability (mortality) of balsam fir (Abies balsamea (L.) Mill.), white spruce (Picea glauca (Moench) Voss), and black spruce (Picea mariana (Mill.) BSP). All three host-tree species are highly susceptible for oviposition by the spruce budworm and all are suitable for completion of the budworm life cycle. Host-related differences in susceptibility arise from the degree of synchrony between spruce budworm phenology during the feeding stages and host-tree phenology. Spruce budworm density was highest on white spruce throughout the budworm's life cycle and over the course of the outbreak, but more rapid flushing and growth of current-year buds in white spruce reduced damage relative to that on balsam fir. Conversely, later flushing of current-year buds on black spruce led to a reduction in budworm density early in the season and a corresponding reduction in defoliation. The combination of high budworm densities and severe defoliation caused mortality first on balsam fir. By the end of the outbreak, 89% of the balsam fir component >10 cm DBH was eliminated compared with 49% of the white spruce in the same size class. The lower susceptibility of black spruce resulted in survival of all but the smallest size classes of that species. Nonhost species such as trembling aspen (Populus tremuloides Michx.) nearly doubled their basal area during the outbreak. The results link processes inherent in the insecthost relationship with the population ecology of the insect and the disturbance ecology of the forest.
Competition and facilitation in mixtures of aspen seedlings, alfalfa, and marsh reedgrass
Authors: Powell George W , Bork Edward W
Published: October 2004

Increasing demand for aspen (Populus tremuloides Michx.) and related poplar species is generating interest in their intensive cultivation. Successful establishment of aspen plantations requires minimizing the negative effects of associated plant species. Competitive and facilitative effects were isolated in field plots containing fixed-density mixtures of aspen seedlings, alfalfa (Medicago sativa L.), and marsh reedgrass (Calamagrostis canadensis (Michx.) Beauv.) in central Alberta. Although aspen survival was unaffected in mixtures, damage to aspen leaf area was lower when grown with either herbaceous species than when grown in monoculture, possibly reflecting facilitation through plant defense guilds. Over the first two growing seasons, net competition was expressed as most aspects of aspen growth were reduced. Herbaceous species reduced photosynthetically active radiation, soil moisture, and soil N available to aspen. Moreover, relative yield totals from the species mixtures examined consistently indicated either neutral effects (combined yields equaled monoculture yields) or underyielding. Despite this, evidence of facilitation was also found when aspen was grown with alfalfa, including increases of overall available soil N and transient increases in soil moisture with pulsed precipitation during drought. These results indicate that short-term facilitative aspects of aspenlegume mixtures may be exploited through an agroforestry scheme by appropriately timed harvest of the herbaceous component. Conversely, aspen establishment has limited potential for integrated production with marsh reedgrass.
CDF RESULTS ON TOP
Authors: BERETVAS ANDREW
Published: October 2004

CDF has established the existence of the top quark. Results from [Formula: see text] collisions at [Formula: see text] TeV are presented. In the dilepton final state we find seven events with a background of 1.3±0.3. In the e, μ+v+jets channel with a b identified via a secondary vertex detector (SVX), we find 21 events with a background of 5.5±1.8. We measure the top quark mass to be 176±8 (stat) ±10 (syst) GeV/c2, and the [Formula: see text] production cross section to be [Formula: see text] . The integrated luminosity for the results presented in this paper is 67 pb−1. The CDF detector needs to be upgraded for our next run. The integrated luminosity for the next run is expected to be more than 1000 pb −1.