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Significant opportunities remain for pharmacologically enhancing the clinical effectiveness of proton and carbon ion-based radiotherapies to achieve both tumor cell radiosensitization and normal tissue radioprotection. We investigated whether pretreatment with the hydroxamate-based histone deacetylase inhibitors (HDACi) SAHA (vorinostat), M344, and PTACH impacts radiation-induced DNA double-strand break (DSB) induction and repair, cell killing, and transformation (acquisition of anchorage-independent growth in soft agar) in human normal and tumor cell lines following gamma ray and light ion irradiation. Treatment of normal NFF28 primary fibroblasts and U2OS osteosarcoma, A549 lung carcinoma, and U87MG glioma cells with 5–10 µM HDACi concentrations 18 h prior to cesium-137 gamma irradiation resulted in radiosensitization measured by clonogenic survival assays and increased levels of colocalized gamma-H2AX/53BP1 foci induction. We similarly tested these HDACi following irradiation with 200 MeV protons, 290 MeV/n carbon ions, and 350 MeV/n oxygen ions delivered in the Bragg plateau region. Unlike uniform gamma ray radiosensitization, effects of HDACi pretreatment were unexpectedly cell type and ion species-dependent with C-12 and O-16 ion irradiations showing enhanced G0/G1-phase fibroblast survival (radioprotection) and in some cases reduced or absent tumor cell radiosensitization. DSB-associated foci levels were similar for proton-irradiated DMSO control and SAHA-treated fibroblast cultures, while lower levels of induced foci were observed in SAHA-pretreated C-12 ion-irradiated fibroblasts. Fibroblast transformation frequencies measured for all radiation types were generally LET-dependent and lowest following proton irradiation; however, both gamma and proton exposures showed hyperlinear transformation induction at low doses (≤25 cGy). HDACi pretreatments led to overall lower transformation frequencies at low doses for all radiation types except O-16 ions but generally led to higher transformation frequencies at higher doses (>50 cGy). The results of these in vitro studies cast doubt on the clinical efficacy of using HDACi as radiosensitizers for light ion-based hadron radiotherapy given the mixed results on their radiosensitization effectiveness and related possibility of increased second cancer induction.

Peroxidase-based reagents that react with whole blood typically undergo internal quality control tests for reactivity prior to their use at a crime scene. This study presents a synthetic polymer alternative to using whole mammalian blood as a luminol reagent control testing material. The luminol-reactive polymer was developed by integrating horseradish peroxidase into a silicon-based sol-gel matrix. Liquid formulations of the polymer were made to simulate forensically relevant luminol reactivity with dried, whole ovine blood at dilutions up to 1:1 × 106. Photoemission from chemiluminescence reactions were characterized as a function of time using a SpectraMax® M3 microplate reader luminometer over a duration of three minutes. The maximum chemiluminescence intensity, time at maxima, reaction half-life, and overall behaviour of the sol-gels and two commercially available materials are reported. The behaviour of each material was statistically compared to the whole blood standards using a two-dimensional Kolmogorov-Smirnov test, which suggests that the sol-gels have a more realistic and statistically similar reactivity to neat (p = 0.835) and diluted (1:1 × 106) blood (p = 0.998) than the commercially available materials (p

RATIONALE To detect the small changes in past pH, the boron isotope ratio of coral carbonates, expressed as the δ11 B value, needs to be both precise and accurate (2sd <

Hydrogels are desirable materials to the field of forensic science and offer many advantages for use as tissue simulants in research and training scenarios. In this work, we demonstrate a proof-of-concept study for our biomaterial described as the Calcium-Alginate Tissue Gel (CATG). CATG biomaterials integrate functional DNA strands designed to amplify with known human primer sets for genetic profiling. Our range of CATG materials demonstrate successful DNA extraction, PCR amplification and genotyping when both fresh and aged for 21 days. The rheological properties of the CATGs were measured and the incorporation of DNA into the CATGs was assessed. Overall, the CATGs demonstrated increased viscoelastic behavior with the addition of DNA. In addition, two methods of sampling were considered, where it was found that cutting a sample of the dried CATG produced higher allele peak heights in the genotype compared to swabbing. Overall, our CATG biomaterials can be designed for multiple applications in forensic science with tunable properties for various training and research needs.

This work investigates the spreading dynamics of three candidate sol-gel solutions, of ranging viscosities, surface tensions and densities, and compares them with water and two commercial blood substitute products. Droplets were created with different sizes (10 to75μL) and impact velocities (1.4 to 6.0m/s) to strike 176gsm cardstock. Over 2200 droplets were created using the six different fluids and their final dried stain diameter was measured. Droplet spread was plotted using the Scheller and Bousfield correlation and uses effective viscosity as a parameter for non-Newtonian fluids. Comparing the results to an expected whole human blood range validated the spread of the candidate FBS sol-gel material in passive drip bloodstain pattern simulation. These findings complement the practical application of the material as a safe substitute for demonstrating droplet spread under controlled conditions on hard paper surfaces.

Solution-gelation chemistry has promising applications in forensic synthetic blood substitute development. This research offers a silicon-based sol-gel approach to creating stable materials that share similar rheological properties to that of whole human blood samples. Room temperature, high water content, silicon sol-gels were created using the organosilane precursors 3-glycidoxypropyltrimethoxysilane and tetraethylorthosilicate along with various concentrations of filler and pigment. Shear-thinning non-Newtonian properties were observed within most formulations of the presented materials. The effects of colloidal concentration, temperature, age and filler addition on the viscosity of the sol-gels were investigated. SEM-EDS analysis was used to identify the behavior of the fillers within the film and support their inclusion for basic bloodstain pattern simulation. A final proposed candidate sol-gel was assessed using a previously reported passive drip simulation test on a hard, dry surface and passed. This works represents encouraging development in providing safe material alternatives to using whole human blood for forensic training and research.

Rationale Monitoring of isomeric analytes using mass spectrometry usually requires a time-consuming chromatographic separation of the analytes before analysis. Selected ion flow tube mass spectrometry (SIFT-MS) can provide rapid direct analysis of ethylbenzene and xylene by utilizing the different reaction chemistry of the isomers. O2 + yields the same product ions from each isomer but in different ratios. OH- yields different product ions. Methods The reaction chemistry of C8 H10 with the reagent ion OH- generated from a microwave discharge of moist air in a commercial SIFT-MS instrument was utilized in this study. The product ion from OH- yielded ions at different masses for each isomer. To gain an understanding of how the product ion from ethylbenzene of HO2 - was generated, a theoretical study of the potential reaction surface was undertaken that accounted for the experimental observations. Results Measurements of OH- with ethylbenzene showed the product ion to be HO2 - at m/z 33. The reaction of OH- with xylene yielded the major product ion at m/z 105, C8 H9 - . HO2 - also underwent a slow secondary reaction with CO2 and O2 present from air in the samples. These findings were supported by calculations of the potential energy surface for the reactions. Measurements made on a certified gas mixture of ethylbenzene and xylene in the concentration range up to 5000 ppbv gave a linear response for each analyte. Conclusions A fast, efficient method was developed for monitoring xylene and ethylbenzene in a mixture without the need for chromatographic separation before analysis using SIFT-MS.

During the Paleocene-Eocene Thermal Maximum (PETM), the carbon isotopic signature (δ13C) of surface carbon-bearing phases decreased abruptly by at least 2.5 to 3.0‰. This carbon isotope excursion (CIE) has been attributed to widespread methane hydrate dissociation in response to rapid ocean warming. We ran a thermohydraulic modeling code to simulate hydrate dissociation due to ocean warming for various PETM scenarios. Our results show that hydrate dissociation in response to such warming can be rapid but suggest that methane release to the ocean is modest and delayed by hundreds to thousands of years after the onset of dissociation, limiting the potential for positive feedback from emission-induced warming. In all of our simulations at least half of the dissociated hydrate methane remains beneath the seabed, suggesting that the pre-PETM hydrate inventory needed to account for all of the CIE is at least double that required for isotopic mass balance.

This study investigates the chemiluminescent reaction of whole ovine blood with a luminol solution in a time and dilution series. Replicate samples of both fresh and dried certified pathogen-free ovine blood were prepared and diluted. Seven dilution conditions from neat to 1:1000000 were created for testing. A luminol solution, created using the standard Weber protocol, was applied to all samples in controlled laboratory conditions. A SpectraMax® M3 microplate reader luminometer was used to quantify the chemiluminescence from the reactions as relative luminescence units (RLUs) every four seconds for three minutes. Trends within and amongst the times series, reaction half-lives, and maximum chemiluminescent intensities are discussed. Our research provides a comprehensive dataset derived from instrumental and visual observations on the chemiluminescence resulting from ovine blood's reaction to luminol. This study has implications in forensic bloodstain pattern analysis as it offers a mixed method approach to characterizing the reaction between blood and a commonly used presumptive testing reagent.

B/Ca ratios in foraminifera have attracted considerable scientific attention as a proxy for past ocean carbonate system. However, the carbonate system controls on B/Ca ratios are not straightforward, with ?[ inline image] ([ inline image]in situ – [ inline image]at saturation) correlating best with B/Ca ratios in benthic foraminifera, rather than pH, inline image, or inline image (as a simple model of boron speciation in seawater and incorporation into CaCO3 would predict). Furthermore, culture experiments have shown that in planktic foraminifera properties such as salinity and [B]sw can have profound effects on B/Ca ratios beyond those predicted by simple partition coefficients. Here, we investigate the controls on B/Ca ratios in G. ruber via a combination of culture experiments and core-top measurements, and add to a growing body of evidence that suggests B/Ca ratios in symbiont-bearing foraminiferal carbonate are not a straightforward proxy for past seawater carbonate system conditions. We find that while B/Ca ratios in culture experiments covary with pH, in open ocean sediments this relationship is not seen. In fact, our B/Ca data correlate best with [ inline image] (a previously undocumented association) and in most regions, salinity. These findings might suggest a precipitation rate or crystallographic control on boron incorporation into foraminiferal calcite. Regardless, our results underscore the need for caution when attempting to interpret B/Ca records in terms of the ocean carbonate system, at the very least in the case of mixed-layer planktic foraminifera.

High-resolution mass spectrometry (HRMS) is a highly effective technique for the analysis of DNA and other biological macromolecules and has the potential to be a valuable tool for forensic chemists. In this work, we introduce concepts of HRMS, discuss benefits of the technique, and outline the steps involved in developing an application utilizing this platform. We examine the importance of optimizing instrumental conditions, selecting an appropriate solvent, and interpreting mass spectra with considerations to determining charge state, mass accuracy and resolution. Specifically, we present a method for the analysis of short single stranded oligonucleotides (26- and 28-base) using Fourier-transform ion cyclotron mass spectrometry (FT-ICR MS), while exploring the importance of sample matrix. Results of this work indicate that analysis of small oligonucleotides with 50:50 water:acteonitrile + 20 mM imidazole (C3H4N2) produced a mass spectrum with the −5 charge state as the base peak. Charge states of −4 up to −15 were also observed, although at much lower ion intensities. Analysis of the oligonucleotides using water and 20 mM imidazole produced a charge state distribution from −5 to −11 over the mass range m/z 200–2500. These two solvents, paired with the optimized HRMS method, produced multiple charge states, high resolution mass spectra, and high ion signal intensity that allowed for unambiguous peak identification. This work serves as a “how-to guide” for forensics scientists who require efficient and accurate HRMS protocols. Our research supports using nucleic acids for diagnostics to analyze oligonucleotides, short DNA fragments and other biological macromolecules using HRMS.

Stable oxygen and carbon isotope (δ18O and δ13C) values measured in foraminiferal calcite are one of the primary tools used in paleoceanography. Diagenetic recrystallisation of foraminiferal calcite can act to reset primary isotopic values but its effects are typically poorly quantified. Here we test the impact of early stage diagenesis on stable isotope records generated from a suite of drill sites in the equatorial Pacific Ocean recovered during Ocean Drilling Program (ODP) Leg 199 and Integrated Ocean Drilling Program (IODP) Expedition 320. Our selected sites form paleowater- and burial-depth transects, with excellent stratigraphic control allowing us to confidently correlate our records. We observe large inter-site differences in the preservation state of benthic foraminiferal calcite, implying very different recrystallisation histories, but negligible inter-site offsets in benthic δ18O and δ13C values. We infer that diagenetic alteration of benthic foraminiferal calcite (in sedimentary oozes) must predominantly occur at shallow burial depths (

Early detection and prevention is an important goal in acute respiratory distress syndrome research. We determined the concentration of the anti-inflammatory 15-deoxy-Δ(12,14)-prostaglandin-J2 (15d-PGJ2) and other components of the cyclopentenone prostaglandin cascade in relation to lung inflammation in cytokine (IL-1/LPS)-insufflated rats. We found that 15d-PGJ2 levels increase in the bronchoalveolar lavage (BAL) fluid of rats insufflated with cytokines 2 h before. BAL 15d-PGJ2 increases preceded neutrophil recruitment, lung injury, and oxidative stress in the lungs of cytokine-insufflated rats. 15d-PGJ2 was localized in alveolar macrophages that decreased following cytokine insufflation. 15d-PGJ2 may constitute an early biomarker of lung inflammation and may reflect an endogenous attempt to regulate ongoing inflammation in macrophages and elsewhere after cytokine insufflation.

International audience; Mg/Ca palaeothermometry in foraminiferal calcite is a widely applied tool in palaeoceanography. However, our understanding of the effects of planktic foraminiferal ecology and early diagenesis on test calcite Mg/Ca is limited. Here we report results of a study designed to shed new light on ecological, size-related and very early (water column) diagenetic controls on Mg/Ca in planktic foraminiferal calcite. We analysed Mg/Ca and stable isotopes of nine modern planktic foraminiferal species across fourteen mostly 50 μm-window sieve fractions in a core-top sample from the North Atlantic Ocean. We also analysed Mg/Ca in four of these nine species from plankton-tow samples collected from 0 to 2500 m water depth in the North Atlantic Ocean and Arabian Sea. Our core-top study confirms that sensitivity of Mg/Ca to change in test size is species-specific but reveals an overall decrease in Mg/Ca with increasing test size in all but one species, Orbulina universa, for which Mg/Ca increases with size. These findings are broadly consistent with known ecological behaviour suggesting that the size-related signal is largely environmentally rather than calcification-rate controlled. Our results underscore the need to undertake Mg/Ca palaeothermometry on narrow size fractions of planktic foraminifers, particularly for shallow-dwelling species such as G. bulloides and G. ruber where Mg/Ca is most sensitive to test size across the size range of 200–350 μm. Our plankton-tow data from the Arabian Sea are in agreement with in-situ temperatures. In contrast, our data from the North Atlantic Ocean reveal large variability and marked offsets (to warmer values) from in-situ temperatures that are interpreted to reflect lateral advection from the south, storm-induced vertical mixing of the water column and/or the influence of surface-water salinity on the Mg/Ca signal. None of our plankton-tow Mg/Ca data shows any evidence of test dissolution in the water column. Our study provides important verification that the Mg/Ca signal recorded during calcification does not undergo diagenetic degradation during test transport to the sea floor, thereby satisfying an important precondition of its palaeo-proxy utility.

One of the most dramatic perturbations to the Earth system during the past 100 million years was the rapid onset of Antarctic glaciation near the Eocene/Oligocene boundary some 34 million years ago. This climate transition was accompanied by a deepening of the calcite compensation depth — the ocean depth at which the rate of calcium carbonate input from surface waters equals the rate of dissolution — but the mechanism linking glaciation to the deepening of calcite compensation depth remains unclear. Merico et al. use a global biogeochemical box model to test competing hypotheses put forward to explain the Eocene/Oligocene transition. They find that only shelf-to-deep-sea carbonate partitioning can explain the observed changes in both carbon isotope composition and calcium carbonate accumulation at the sea floor. This work sheds new light on the mechanisms linking glaciation and ocean acidity change during this important climate transition. A global biogeochemical box model is used to test competing hypotheses put forward to explain the Eocene/Oligocene transition. It is found that only shelf-to-deep-sea carbonate partitioning is capable of explaining the observed changes in both carbon isotope composition and calcium carbonate accumulation at the sea floor. This work sheds new light on the mechanisms linking glaciation and ocean acidity change across the climate transition of the Cenozoic. One of the most dramatic perturbations to the Earth system during the past 100 million years was the rapid onset of Antarctic glaciation near the Eocene/Oligocene epoch boundary1,2,3 (∼34 million years ago). This climate transition was accompanied3 by a deepening of the calcite compensation depth—the ocean depth at which the rate of calcium carbonate input from surface waters equals the rate of dissolution. Changes in the global carbon cycle4, rather than changes in continental configuration5, have recently been proposed as the most likely root cause of Antarctic glaciation, but the mechanism linking glaciation to the deepening of calcite compensation depth remains unclear. Here we use a global biogeochemical box model to test competing hypotheses put forward to explain the Eocene/Oligocene transition. We find that, of the candidate hypotheses, only shelf to deep sea carbonate partitioning is capable of explaining the observed changes in both carbon isotope composition and calcium carbonate accumulation at the sea floor. In our simulations, glacioeustatic sea-level fall associated with the growth of Antarctic ice sheets permanently reduces global calcium carbonate accumulation on the continental shelves, leading to an increase in pelagic burial via permanent deepening of the calcite compensation depth. At the same time, fresh limestones are exposed to erosion, thus temporarily increasing global river inputs of dissolved carbonate and increasing seawater δ13C. Our work sheds new light on the mechanisms linking glaciation and ocean acidity change across arguably the most important climate transition of the Cenozoic era.

Reactions of unsaturated hydrocarbons with fluoroformyl cation (CFO+) and of ketene and diketene with CFO+ and CF3+ have been studied in a Flowing Afterglow-Selected Ion Flow Tube (FA-SIFT) in helium at room temperature. Net F+ transfer from CFO+ to the neutral reactants, which is observed in the majority of cases studied, can be explained in terms of formation of a covalent adduct followed by expulsion of CO. Other product ions include the products of net metathesis, C C + CFO+ → C C O + +F C , which are observed in nearly half of the hydrocarbons investigated. Reaction of cyclopentadiene with CFO+ produces inter alia two isomeric C5H5+ ions, neither of which appears to have the same reactivity, as does the C5H5+ ion produced by reaction of propargyl cation (C3H3+) with acetylene. Given that the number of plausible C5H5+ structures is not very great, one of the ions derived from cyclopentadiene is inferred to have the structure of the cyclopentadienyl cation. The reaction of CFO+ with ketene gives F+ transfer, yielding FCH2C≡O+, as the major product channel. By contrast, the reaction of CFO+ with diketene gives no observable F+ transfer. All observed products can be rationalized as coming from initial adduct ions.

The rate coefficients of the ion–molecule reactions between O2 +, H3O+, and a range of linear saturated hydrocarbons, and between common hydrocarbon product ions from these reactions and water were determined using a flowing afterglow selected ion flow tube mass spectrometer. Using these data, the selected ion flow tube-mass spectrometry (SIFT-MS) technique was applied to the real-time measurement of linear saturated hydrocarbons in dry and moist headspace samples without sample preparation. Using a Voice100 SIFT-MS instrument the Geochemical VOC method (GeoVOC) has been assessed against calibrated standards and found to give an experimental RMS precision to within 2% for dry and 6% for humid hydrocarbon samples in the ppm range. The application of SIFT-MS and development of the GeoVOC method offers a fast convenient means of assessment of hydrocarbon seeps.

Previous studies using rodent cells indicate that a deficiency in XRCC1 results in reduced single-strand break repair, increased sensitivity to DNA-damaging agents, and elevated levels of sister chromatid exchange (SCE). Epidemiological studies have suggested an association of certain human XRCC1 polymorphisms with genetic instability and cancer susceptibility. However, investigations on the molecular functions of XRCC1 in human cells are limited. To determine the contributions of this nonenzymatic scaffold protein, we suppressed XRCC1 levels in several human cell lines using small interfering RNA (siRNA) technology. We report that XRCC1 down-regulation in HeLa cells leads to a concomitant decrease in the DNA ligase 3 protein level and an impaired nick ligation capacity. In addition, depletion of XRCC1 resulted in a significantly increased sensitivity to the alkylating agent methyl methanesulfonate and the thymidine base analog 5-hydroxymethyl-2'-deoxyuridine, a slightly increased sensitivity to ethyl methanesulfonate and 1,3-bis(2-chloroethyl)-1-nitrosourea, and no change in the response to camptothecin. We also discovered that a 70-80% reduction in XRCC1 protein leads to an elevated level of SCE in both HeLa cells and normal human fibroblasts, but does not affect chromosome aberrations in the diploid fibroblasts. Last, XRCC1 siRNA transfection led to an approximately 40% decrease in the survival of BRCA2-deficient cells, supporting a model whereby the accumulation of unrepaired SSBs leads to the accumulation of cytotoxic DNA double strand breaks following replication fork collapse in cells defective in homologous recombination.

Stilbenes are secondary metabolites of a class of non-flavanoid phenolics found in certain species of Vitis. This class of compounds includes resveratrol and a resveratrol glucoside called piceid that exists in trans and cis forms. This study was undertaken to determine the cis and trans forms of both resveratrol and piceid in the skin, pulp, seeds, and juice of nine cultivars of muscadine grapes and three cultivars of Vitis labruscana. Juice samples of the muscadine cultivars ‘Fry’, ‘Hunt’, ‘Magnolia’, ‘Watergate’, ‘Carlos’, ‘Noble’, and ‘Sweet Jenny’, and the V. labruscana cultivars ‘Albermarle’, ‘Miss Blanc’, ‘MidSouth’ and ‘Miss Blue’ were harvested at the full ripe stage and divided into two sub-samples. One subsample was used to extract juice and the other was divided into skins, pulp, and seeds. Sample analysis was performed using HPLC with a UV detector. Sample chromatagrams were compared with those of known standards for quantification. ‘Carlos’ and ‘Magnolia’ had the greatest total stil...

Background: There is some evidence that surgical plume may pose a risk to health professionals, but the risks posed by volatile organic compounds have not been thoroughly investigated. Methods: The composition of volatile organic compounds in diathermy plume produced during surgery was analysed by selected ion flow tube mass spectrometry. Results: Hydrogen cyanide (3–51 parts per million), acetylene (2–8 parts per million), and 1,3-butadiene (0.15–0.69 parts per million) were identified in the plume. Conclusion: Although there is no evidence of adverse health effects from the volatile organic compound in diathermy plume, the evidence that it is safe to breathe this plume is lacking. Therefore, we would recommend the use of smoke evacuators where practical.

Since the correlation between carbon dioxide (CO2) levels and global temperatures was established in the ice core records, quantifying the components of the global carbon cycle has become a priority with a view to constraining models of the climate system. The marine carbonate budget is still not adequately constrained and the quantitative significance of the calcareous green alga Halimeda still remains particularly poorly understood. Previously, it has been suggested that Halimeda bioherms on the shelf of the Great Barrier Reef may contain a volume of carbonate equal to or greater than that contained within the shelf edge coral reefs. This study uses published datasets to test this hypothesis in the Northern Great Barrier Reef (NGBR) province. It is estimated that Halimeda bioherms on the outer shelf of the NGBR contain at least as much (and up to four times more) CaCO3 sediment as the adjacent ribbon reef facies. Globally, if these findings are even only partially applicable, the contribution of shallow water carbonate sediments to the global carbon budget based on coral reefs alone is currently substantially underestimated.

Faecal material has increasingly become an important non-invasive source of DNA for wildlife population genetics. However, DNA from faecal sources can have issues associated with quantity (low-template and/or low target-to-total DNA ratio) and quality (degradation and/or low DNA-to-inhibitor ratio). A number of studies utilizing faecal material assume and compensate for the above properties with minimal characterization of quantity or quality of target DNA, which can unnecessarily increase the risk of downstream technical problems. Here, we present a protocol which quantifies faecal DNA using a two step approach: (1) estimating total DNA concentration using a PicogreenTM fluorescence assay and (2) estimating target nuclear DNA concentration by comparing amplification products of field samples at suspected concentrations to those of control DNA at known concentrations. We applied this protocol to faecal material collected in the field from two species: woodland caribou (Rangifer tarandus) and swift fox (Vulpes velox). Total DNA estimates ranged from 6.5 ng/μl to 28.6 ng/μl (X = 16.2 ng/μl) for the caribou extracts and 1.0–26.1 ng/μl (X = 7.5 ng/μl) for the swift fox extracts. Our results showed high concordance between total and target DNA estimates from woodland caribou faecal extracts, with only 10% of the samples showing relatively lower target-to-total DNA ratios. In contrast, DNA extracts from swift fox scat exhibited low target DNA yields, with only 38% (19 of 50) of the samples showing comparative target DNA amplification of at least 0.1 ng. With this information, we were able to estimate the amount of target DNA entered into PCR amplifications, and identify samples having target DNA below a lower threshold of 0.2 ng and requiring modification to genotyping protocols such as multiple tube amplification. Our results here also show that this approach can easily be adapted to other species where faeces are the primary source of DNA template.

Lithium ion attachment is assessed in this study as a possible means of chemical ionization in the selected ion flow tube-mass spectrometric (SIFT-MS) technique. Measurements using a selected ion flow tube (SIFT) operating at room temperature are reported for lithium ion association reactions with 21 neutral reagents. The reagents ranged from small molecules such as CH 4 and CO, for which the association rate coefficients were very small, to larger organic molecules such as C 6 H 6 and C 5 H 5 N, for which the association rates approached the collision rate coefficient. The bond dissociation energy (BDE) of the (Li–X) + bond was an important factor in deciding whether or not lithium ion association might be used in SIFT-MS. The attached molecule, X, in the LiX + molecular ion is switched out by H 2 O for those species having BDEs −1 . For reactants having BDEs ≥137 kJ mol −1 , some switching out by water occurred in Li(X) n + resulting in Li + ·(H 2 O) n terminal ions. For those reagents having BDEs ≫ 137 kJ mol −1 , mixed LiX m + (H 2 O) n clusters were observed.

The late middle Eocene is marked by accelerated global cooling, representing part of the long transitional interval separating the early Eocene ‘greenhouse’ and later Oligocene ‘icehouse’ climatic regimes. This time interval is also regarded as having witnessed a decline in planktic foraminiferal diversity following the extinction of most of the muricate clade (genera Acarinina and Morozovelloides) at approximately 39 Ma. Here we examine planktic foraminiferal assemblages recovered at ODP Site 1052 (Blake Nose, NW Atlantic) and, by recording a high level of taxonomic diversity including several previously undocumented morphotypes, we suggest that the diversity of late middle Eocene planktic foraminifera may have been underestimated. Depth habitats of every species within these late middle Eocene assemblages are reconstructed using oxygen and carbon stable isotope ratios. Furthermore, because stable isotope analyses suggest that species of Globoturborotalita appear to have generally calcified during winter months, these taxa offer, in combination with predominantly summer surface dwellers such as Morozovelloides, the potential to reconstruct patterns of seasonality during the late Palaeogene. Using extremely well preserved ‘glassy’ planktic foraminiferal calcite from a contemporaneous hemipelagic drill site, detailed SEM imaging of test microstructures and wall textures confirm that many modern features of foraminiferal ecology and test architecture had already evolved by the late middle Eocene. The common occurrence of the cancellate wall texture, combined with the wide variety of reconstructed foraminiferal depth habitats, indicates that there is no necessary relationship between foraminiferal wall textures and habitat and that wall textures are evolutionary conservative features of the foraminiferal test.

The Specific Molecular Identification of Life Experiment (SMILE) instrument (Sims et al. Planet. Space Science 2005, 53, 781-791) proposes to use specific molecular receptors for the detection of organic biomarkers on future astrobiology missions (e.g., to Mars). Such receptors will be used in assays with fluorescently labeled assay reagents. A key uncertainty of this approach is whether the fluorescent labels used in the system will survive exposure to levels of solar and galactic particle radiation encountered during a flight to Mars. Therefore, two fluorescent dyes (fluorescein and Alexa Fluor 633) have been exposed to low-energy proton and alpha radiation with total fluences comparable or exceeding that expected during an unshielded cruise to Mars. The results of these initial experiments are presented, which show that both dyes retain their fluorescent properties after irradiation. No significant alteration in the absorption and emission wavelengths or the quantum yields of the dyes with either radiation exposure was found. These results suggest other structurally similar fluorophores will likely retain their fluorescent properties after exposure to similar levels of proton and alpha radiation. However, more extensive radiation fluorophore testing is needed before their suitability for astrobiology missions to Mars can be fully confirmed.

A fast, efficient, real-time method for the quantitative analysis of the peroxide explosive, TATP, is described. The method utilizes rapid ion-molecule reactions of chemical reagent ions with the vapor above solid TATP. The reactions of three reagent ions (H3O+, O2+, NO+) were examined. Although all three ions exhibited a near-collision-rate reaction with TATP, only NO+ showed product ions that provide unequivocal evidence for a TATP-based explosive. The limit of detection of TATP in the gas phase is 10 ppb (4 x 10(-10) mol L(-1)).

The excitatory amino acid transporters (EAATs) play key roles in the regulation of CNS l -glutamate, especially related to synthesis, signal termination, synaptic spillover, and excitotoxic protection. Inhibitors available to delineate EAAT pharmacology and function are essentially limited to those that non-selectively block all EAATs or those that exhibit a substantial preference for EAAT2. Thus, it is difficult to selectively study the other subtypes, particularly EAAT1 and EAAT3. Structure activity studies on a series of β-substituted aspartate analogues identify l -β-benzyl-aspartate ( l -β-BA) as among the first blockers that potently and preferentially inhibits the neuronal EAAT3 subtype. Kinetic analysis of d -[3H]aspartate uptake into C17.2 cells expressing the hEAATs demonstrate that l -β-threo-BA is the more potent diastereomer, acts competitively, and exhibits a 10-fold preference for EAAT3 compared to EAAT1 and EAAT2. Electrophysiological recordings of EAAT-mediated currents in Xenopus oocytes identify l -β-BA as a non-substrate inhibitor. Analyzing l -β-threo-BA within the context of a novel EAAT2 pharmacophore model suggests: (1) a highly conserved positioning of the electrostatic carboxyl and amino groups; (2) nearby regions that accommodate select structural modifications (cyclopropyl rings, methyl groups, oxygen atoms); and (3) a unique region l -β-threo-BA occupied by the benzyl moieties of l -TBOA, l -β-threo-BA and related analogues. It is plausible that the preference of l -β-threo-BA and l -TBOA for EAAT3 and EAAT2, respectively, could reside in the latter two pharmacophore regions.

We describe a new method, Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS) for the rapid and sensitive real-time detection and quantification of volatile organic compounds from medically important fungi, grown on a range of laboratory media. SIFT-MS utilises the chemical ionisation reactions of mass-selected ions to characterise volatile organic compounds (VOCs) that are produced as metabolites from fungi. This technique has the distinct advantage over others in that it readily detects low molecular weight, reactive volatiles, and allows for real-time, quantitative monitoring. The fungi examined in this study were Aspergillus flavus, Aspergillus fumigatus, Candida albicans, Mucor racemosus, Fusarium solani, and Cryptococcus neoformans grown on or in malt extract agar, Columbia agar, Sabouraud's dextrose agar, blood agar, and brain-heart infusion broth. Common metabolites (ethanol, methanol, acetone, acetaldehyde, methanethiol, and crotonaldehyde) were detected and quantified. We found the fingerprint of volatiles, in terms of presence and quantity of volatiles to be strongly dependent on the culture medium, both in terms of variety and quantity of volatiles produced, but may form the basis for species specific identification of medically important fungi.

Two series of three‐ring heterocyclic liquid crystalline (LC) materials have been synthesized and characterized, one incorporating a thiophene ring and the other containing a thiophene‐pyrimidine moiety. This is the first study to show the effect of a thiophene‐pyrimidine moiety on the thermal and physical properties of a mesogen. The effect on the thermal stability of the mesogen by the introduction of the pyrimidine ring has been dramatic, with the thiophene‐pyrimidine‐containing mesogens exhibiting ferro‐ and antiferro‐electric phases only. The introduction of the pyrimidine ring can be compared to the effect observed by lateral fluorination; a reduction in the melting point and smectic phase thermal stability of mesogens. However, its introduction is also conducive to the formation of the SmC* (ferro‐ and antiferro‐electric) phase. Like the fluoro substituent, the pyrimidine ring could play a key role in tailoring important thermal and physical properties of LC materials. An electro‐optical study not ...

The ocean depth at which the rate of calcium carbonate input from surface waters equals the rate of dissolution is termed the calcite compensation depth. At present, this depth is approximately 4,500 m, with some variation between and within ocean basins. The calcite compensation depth is linked to ocean acidity, which is in turn linked to atmospheric carbon dioxide concentrations and hence global climate. Geological records of changes in the calcite compensation depth show a prominent deepening of more than 1 km near the Eocene/Oligocene boundary (approximately 34 million years ago) when significant permanent ice sheets first appeared on Antarctica, but the relationship between these two events is poorly understood. Here we present ocean sediment records of calcium carbonate content as well as carbon and oxygen isotopic compositions from the tropical Pacific Ocean that cover the Eocene/Oligocene boundary. We find that the deepening of the calcite compensation depth was more rapid than previously documented and occurred in two jumps of about 40,000 years each, synchronous with the stepwise onset of Antarctic ice-sheet growth. The glaciation was initiated, after climatic preconditioning, by an interval when the Earth's orbit of the Sun favoured cool summers. The changes in oxygen-isotope composition across the Eocene/Oligocene boundary are too large to be explained by Antarctic ice-sheet growth alone and must therefore also indicate contemporaneous global cooling and/or Northern Hemisphere glaciation.

Selected ion flow tube mass spectrometry (SIFT-MS) is a technique that is well suited to the realtime analysis of head-space. SIFT-MS gives a non-discriminatory snapshot of the volatiles present and their amounts, and is considered to display less bias than chromatographic techniques as neither sample pre-treatment nor separation are necessary in most cases. The technique has been used for analysis of virgin olive oil head-space on more than 100 different oils. Twenty of these are reported. The results obtained using this technique differ from those normally reported from chromatographic analyses in that the dominant species in the head-space of all oils tested were methanol and ethanol. These volatiles were present in the head-space in the concentration ranges of 2.8‐ 11.3ppm (methanol) and 0.4‐4.9ppm (ethanol). (E)-2-Hexenal, normally reported as the dominant olive oil volatile, is found in significantly lower concentrations and is in the range of 0.02‐1.6ppm. Copyright # 2005 John Wiley & Sons, Ltd. The consumption of olive oil is deeply entrenched in the culture of all countries surrounding the Mediterranean basin. Olives are thought to have been first cultivated around 5000 years ago, mostly for their oil. 1 Only recently, however, has high-quality olive oil become a sought-after product, attaining high prices in markets the world over. The most sought-after oils are those displaying an attractive aroma and flavour, no noticeable oxidation and no fermentation. Unfavourable conditions at any stage immediately begin altering the oil, so it is desirable to analyse oil at various stages in its life to discover if it has been affected by poor storage conditions. Because of the industry’s high value, research into the composition of olive oil has become widespread. One important area of research has been the correlation of volatile organic compounds (VOCs) found in olive oil with the perceived aroma and flavour. The proportion of VOCs in olive oil is very small, less than 0.2%, 2 but they are solely responsible for the aroma, and largely responsible for the taste, of olive oil. The current test used to monitor the VOCs of olive oil is the organoleptic taste panel, which is regulated by the International Olive Oil Council (IOOC). 3 This test is performed by a panel of 8–12 trained and accredited judges who score olive oils based on a defined scale. Their results are then combined to minimise the inevitable differences in perception from person to person. 4 Tasting panels generally

Hydrogen transfer is a major channel in the ionized C2H2+/H2CO and H2CO+/C2H2 reaction systems, producing C2H4+ + CO. Similarly, H2 transfer from H2CO is observed in reactions of the ions C3H3+ (linear), CH3CCH+, H2CCCH2+, C3H5+, and HCCCCH+ with formaldehyde, resulting in hydrogenated hydrocarbon ions. The energetics of these reactions allow a two-step mechanism of H+ or H transfer forming a distonic (BH+·HCO) complex, followed by H transfer to form BH2+. Ab initio calculations on the acetylene/formaldehyde system show that the reaction can proceed through a stable cyclic adduct, dissociating to yield C2H4+ that contains carbon atoms from both acetylene and formaldehyde. Both experiment and theory show that H2CO+ does not react with hydrogen, making it a stable reactant ion in interstellar chemistry. The reactions where either H2+ or H2 is transferred can provide significant pathways for the hydrogenation of unsaturated hydrocarbons in interstellar clouds. The reactions of three C2Hx+ (x = 0, 1, or 2) sp...

Nucleotides (NTPs and dNTPs) have been measured in patient-derived chronic lymphocytic leukaemia (CLL) cells stimulated with TPA plus ionomycin and then exposed to cladribine, fludarabine or deoxycoformycin (1 microM, 16 h). dNTPs were not measurable in 10(8) unstimulated CLL cells which are quiescent. Time-dependent changes in nucleotides in CLL cells showed that the mechanism of action changed as the drug triphosphate accumulated. dCf induced substantial accumulation of dATP in CLL cells in culture, and similar levels of dATP in the same patient during subsequent treatment with dCf. Determination of "metabolic response patterns" of nucleotides in CLL cells treated with drugs might distinguish patients with susceptible and refractory CLL prior to chemotherapy.

The reaction between M2Cl2(NMe2)4, where M = Mo or W, and Hhpp (8 equiv) in a solid-state melt reaction at 150 °C yields the compounds M2(hpp)4Cl2 1a (M = Mo) and 1b (M = W), respectively, by the elimination of HNMe2 [hpp is the anion derived from deprotonation of 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine, Hhpp]. Purification of 1a and 1b is achieved by sublimation of the excess Hhpp and subsequent recrystallization from either CH2Cl2 or CHCl3 (or CDCl3). By single-crystal X-ray crystallography, the structures of 1a and 1b are shown to contain a central paddlewheel-like M2(hpp)4 core with Mo−Mo = 2.1708(8) A (from CH2Cl2), 2.1574(5) A (from CDCl3), W−W = 2.2328(2) A (from CDCl3), and M−N = 2.09(1) (av) A. The Cl ligands are axially ligated (linear Cl−M−M−Cl) with abnormally long M−Cl bond distances that, in turn, depend on the presence or absence of hydrogen bonding to chloroform. The quadruply bonded compounds M2(hpp)4, 2a (M = Mo), and 2b (M = W), can be prepared from the reactions between 1,2-...

Alkynes react with a suspension of [W 2 (OCH 2 tBU) 8 ](M=M) in hydrocarbon solvents to give alkyne adducts W 2 (μ-RCCR')(OCH 2 tBu) 8 , where R = H and R' = Ph, Me, Me 3 Si and R = Me and R' = Me and Ph. For PhC≡CH, there is a μ-perpendicular mode of alkyne bonding, θ = 84°, but for MeC≡CH and MeC≡CMe, the bridging alkyne is distinctly skewed with respect to the W-W axis, 0 = 64° and 67°, respectively. In contrast, the PhC≡CMe adduct has the alkyne bonded to only one tungsten, η 2 -PhC≡CMe, with the alkyne C≡C axis being 30° from the W-W axis. In all of these structures, there are alkoxide bridges, and the dinuclear unit may be viewed as a confacial bioctahedron where either one alkyne and two alkoxides or three alkoxides occupy the bridging face. In toluene-d 8 , NMR spectroscopic studies indicate that certain of these alkyne adducts (MeC≡CH, MeC≡CMe, PhC≡CMe, and Me 3 SiC≡CH) exist as a mixture of alkyne-bridged and η 2 -alkyne-bonded isomers. The isomers are fluxional on the NMR time scale by rapid exchange of terminal and bridging alkoxide groups. However, μ-η 2 alkyne exchange is slow on the NMR time scale. The structural data are compared with electronic structure calculations employing density functional theory on model compounds of formula W 2 (alkyne)(OMe) 8 . The calculations suggest that a μ-parallel mode of bonding is energetically favorable relative to u-perpendicular and, further, that the energy difference between bridge and terminal alkyne adducts is, in all cases, less than 5 kcal mol - 1 .

The new technique of selected ion flow tube-mass spectrometry (SIFT-MS) has been applied to the measurement of Henry's Law constants for the volatile organic chemicals o-xylene and trichloroethylene that both have low solubility in aqueous solvents. The method is validated by measurements in water at 298 K using the equilibrium partitioning in closed systems (EPICS) methodology in which the equilibrium headspace concentrations for the volatile organic compounds (VOCs) are measured in two sealed bottles containing different liquid volumes of very dilute solutions of the VOC. The range of solvents is then extended to human body fluids at 309 K including urine, saline, whole blood, red cells in saline, and plasma. The dimensionless distribution coefficients for these solvents vary markedly in the different fluids. For o-xylene they range from k(H) = 0.12-0.15 for water, saline, and urine; 0.53 for red cells in saline; 1.9 for whole blood; to 2.4 for plasma. For trichloroethylene the distribution coefficients range from k(H) = 0.070-0.091 for water, saline, and urine; 0.28 for red cells in saline; 0.35 for plasma; to 0.48 in whole blood. The very different solubilities of organic solvents in body fluids influence the uptake of solvents in workers exposed to VOCs. Some implications of these measurements are briefly discussed.

We report selected ion flow tube measurements of reaction rate coefficients and branching ratios for the reactions of H3O+, O2+ and NO+ with the small hydrocarbons CH4, C2H2, C2H4, C2H6, C3H4 (allene and propyne), C3H6, c-C3H6, C3H8, C4H2, C4H8 and n,i-C4H10. The relevance of these measurements to quantitative selected ion flow tube mass spectrometry (SIFT-MS) is discussed. An application of the measurements is made to the analysis of the chemical species generated by chemical ionization in the exhaust gases from a petrol combustion engine up to m/z=60. The analysis shows that chemical ionization data are required from more than one precursor ion in order to interpret the data.

In this structure/property study six 2-(4-alkyloxyphenyl)-5-thiophen-2-ylpyrimidines and thirty-six 2-(4-alkyloxyphenyl)-5-(5-alkylthiophen-2-yl) pyrimidines were synthesized to evaluate the effect of the introduction of heterocyclic rings on the liquid crystalline (LC) behaviour of mesogens. The ‘bent’ nature of the structure of the 2-(4-alkyloxyphenyl)-5-thiophen-2-yl-pyrimidines, due to the presence of the thiophene ring, was further exaggerated in the 2-(4-alkyloxyphenyl)-5-(5-alkylthiophen-2-yl) pyrimidines by the incorporation of an alkyl group at the 5-position in the thiophene ring. This simple change in structure led to a remarkable change in the LC behaviour of the mesogens. From a series of mesogens having high melting points and exhibiting monotropic nematic phases, the incorporation of the alkyl group gave a series of three-ring mesogens with relatively low melting points (60–80°C), and exhibiting a range of tilted smectic phases, including SmI, SmC and SmCalt phases.

A Cenozoic multi-species record of benthic foraminiferal calcite Sr/Ca has been produced and is corrected for inter-specific offsets (typically less than 0.3 mmol/mol) and for the linear relationship between decreasing benthic foraminiferal Sr/Ca and increasing water depth. The water depth correction, determined from Holocene, Late Glacial Maximum and Eocene paleowater-depth transects, is not, vert, similar0.1 mmol/mol/km. The corrected Cenozoic benthic foraminiferal Sr/Ca record ranges from 1.2 to 2.0 mmol/mol, and has been interpreted in terms of long-term changes in seawater Sr/Ca, enabling issues related to higher-resolution variability in Sr/Ca to be ignored. We estimate that seawater Sr/Ca was not, vert, similar1.5 times modern values in the late Cretaceous, but declined rapidly into the Paleogene. Following a minimum in the Eocene, seawater Sr/Ca increased gradually through to the present day with a minimum superimposed on this trend centered in the late Miocene. By assuming scenarios for changing seawater calcium concentration, and using published carbonate accumulation rate data combined with suitable values for Sr partition coefficients into carbonates, the seawater Sr/Ca record is used to estimate global average river Sr fluxes. These fluxes are used in conjunction with the seawater strontium isotope curve and estimates of hydrothermal activity/tectonic outgassing to calculate changes in global average river 87Sr/86Sr through the Cenozoic. The absolute magnitude of Sr fluxes and isotopic compositions calculated in this way are subject to relatively large uncertainties. Nevertheless, our results suggest that river Sr flux increased from 35 Ma to the present day (roughly two-fold) accompanied by an overall increase in 87Sr/86Sr (by not, vert, similar0 to 0.001). Between 75 and 35 Ma, river 87Sr/86Sr also increased (by not, vert, similar0.001 to 0.002) but was accompanied by a decrease (two- to three-fold) in river Sr flux.

A polymerase chain reaction–based method was developed for gender determination in a wide variety of marine and terrestrial mammals, including cetaceans, pinnipeds, ungulates, canids, and ursids. An intron within the zinc-finger x (Zfx) and zinc-finger y (Zfy) genes was amplified. Size variation between the Zfx and Zfy introns results in a Y-specific band in males. Size of the Zfy intron varies more across species than that of the Zfx intron. This technique is simple and rapid, requires small amounts of DNA, and can be applied to a variety of mammalian species. In contrast to previous methods, only 1 primer set is needed for both gender determination and internal verification of amplification.

The synthesis and transition temperatures of a series of novel 2-(4-benzyl-oxyphenyl)-5-(5-alkylthiophen-2-yl)pyrimidine liquid crystals is described. Using a palladium-catalysed cross-coupling reaction benzyloxyphenylboronic acid was coupled to 5-bromo-2-iodopyrimidine. A second coupling reaction was then performed using a series of 5-alkyl-2-tri-butylstannyl thiophenes to create the title compounds. These compounds exhibit nematic, smectic A, smectic C and smectic C alt phases, and these phases were identified by a combination of differential scanning calorimetry, and optical microscopy. The most unusual aspect of these compounds is the appearance of a previously undiscovered achiral version of the ferrielectric chiral smectic C phase. To unambiguously identify this phase, further detailed investigation by X-ray analysis is being undertaken.

The compounds [(tBuCO2)3M2(μ-O2CC6F4CO2)M2(O2CtBu)3], M4PFT, where M = Mo or W, are shown by model fitting of the powder X-ray diffraction data to have an infinite “twisted” structure involving M···O intermolecular interactions in the solid state. The dihedral angle between the M2 units of each molecule is 54°. Electronic structure calculations employing density functional theory (Gaussian 98 and ADF2000.01, gradient corrected and time dependent) on the model compounds (HCO2)3M2(μ-O2CC6F4CO2)M2(O2CH)3, where M = Mo or W, reveal that in the gas phase the model compounds adopt planar D2h ground-state structures wherein M2 δ to bridge π* back-bonding is maximized. The calculations predict relatively small HOMO−LUMO gaps of 1.53 eV for M = Mo and 1.22 eV for M = W for this planar structure and that, when the “conjugation” is removed by rotation of the plane of the C6F4 ring to become orthogonal to the M4 plane, this energy gap is nearly doubled to 2.57 eV for M = Mo and 2.18 eV for M = W. The Raman and resona...

The drill core of Funafuti Atoll, collected by The Royal Society Coral Reef Expedition in 1896–1898, has been dated using high–precision 14 C and Sr isotope measurements determined by mass spectrometry. The core top is a Holocene reef deposit, reflecting 26.4 m of reef growth since 8 ka, and is underlaid by Pleistocene reef–lagoonal deposits separated by a series of inferred hiatuses at 26.4 m, ca .30 m, ca .65 m and ca .80 m ( ca .0.1 Ma, ca .0.2 Ma, ca .0.3 Ma and ca .0.6 Ma, respectively), reflecting atoll carbonate deposits associated with late Quaternary sea–level changes. In turn, the underlying sequence below ca .80 m comprises an upper section of additional Pleistocene reef–lagoonal deposits, having a high accumulation rate greater than 100 m Ma −1 , and a heavily dolomitized lower section. Sr isotope data in the lower section provide maximum (oldest) ages for dolomite formation and, depending on the extent of the isotopic memory from precursor CaCO 3 , reflect ongoing diagenetic alteration from ca .2.3 Ma (i.e. the oldest dolomite) or in one or more discrete diagenetic events at ca .1 Ma, and possibly at ca .2 Ma. This sequence reflects interaction between atoll carbonate sedimentation, tectonic subsidence and eustatic sea–level change.

Potent inhibitors of enzymes catalyzing reactions in the de novo pathways for biosynthesis of purine and pyrimidine nucleotides are synthetic or natural-product analogues of pathway intermediates or, more recently, inhibitors rationally designed from a knowledge of the catalytic mechanism. Such inhibitors may be effective drugs against cancer, inflammatory disorders, or various infections. For human cancer, the purine pathway may be a better target for inhibition than the pyrimidine pathway, where toxic side effects are more apparent. Drugs such as methotrexate and 6-mercaptopurine have multiple sites of action, making it difficult to quantitatively predict their effects upon cells. Rational design of inhibitors based upon the X-ray structure of the target enzyme has the prospect of yielding drugs with only one site of action in human cells. Such a drug is VX-497, a potent inhibitor of the purine enzyme, IMP dehydrogenase.

A flowing afterglow-selected ion flow drift tube has been used to measure the rate coefficients and product ion distributions for reactions of H3O+, N2H+, and H3+ with a series of 16 alkanes, alken...

The synthesis and characterisation of a series of novel poly-yne polymers, trans-[–(PnBu3)2Pt(CC–L–CC)-]n (L = 2-(2′-thienyl)-pyridine (L1), 2,5-bis(2′-thienyl)pyridine (L2), 6,6′-bis(2″-thienyl)-3,3′-bipyridine (L3)), and the corresponding platinum dimers trans-[(PEt3)2(Ph)Pt(CCLCC)Pt(Ph)(PEt3)2] are described. The dimers were prepared by the reaction of two equivalents of trans-[Pt(PEt3)2(Ph)Cl] with one equivalent of the diterminal diyne HCC–L–CCH, in CuI catalysed dehydrohalogenation reactions in CH2Cl2–Pri2NH, while the polymers are obtained similarly from the diyne and one equivalent of trans-[Pt(PnBu3)2Cl2]. The optical absorption and photoluminescence spectra of the polymers with L1 and L2 linker groups are reported. The optical gaps are 465 nm (2.67 eV) and 486 nm (2.55 eV), respectively. The photoluminescence spectrum for each polymer exhibits one band at room temperature. At 10 K, low-energy emission bands emerge which are attributed to emission from the triplet excited state. The results of these studies are compared with those obtained for other platinum-containing poly-yne and related organometallic polymers.

Aromatic hydrocarbon solutions of [W 2 (O 2 C t Bu) 4 ] react with alkynes RC≡CR' to give adducts of the formula [W 2 (κ 2 -O 2 C t Bu) 4 (μ-RCCR') 2 ], where R = R' = Me, Et, Ph and R = Me, R' = Ph, as orange to purple air-stable,hydrocarbon-soluble, crystalline solids which have been characterized by infrared, NMR spectroscopy, and mass spectrometry. The single-crystal X-ray structures have also been obtained for R = R' = Me and R = Me, R' = Ph. In both structures, there are a pair of perpendicularly bridged alkyne ligands with central C-C distances of ca. 1.34 A and a W-W bond of ca. 2.5 A. The crystallographically characterized molecules have virtual C 2 h symmetry, and in solution, the NMR data are consistent with the presence of this isomer and a second having D 2 symmetry. The two isomers can be related to meso and Δ/Λ isomers of an edge-bridged octahedral unit containing four chelates: [(chelate) 2 M(μ-X) 2 M(chelate) 2 ], where X represents the central position of the μ-perpendicular alkyne. The isomerization in solution was found to be intramolecular and solvent-assisted, with THF-d 8 > benzene-d 6 toluene-d 8 > CD 2 Cl 2 , and can be catalyzed by the addition of t BuCO 2 H. The electronic structure and bonding in these compounds have been investigated using density functional theory calculations on the model compounds D 2 and C 2 h [W 2 (κ 2 -O 2 -CH) 4 (μ-HCCH) 2 ]. These calculational results lend credence to the notion that there is a W-W bond of order 2.

The compounds ((t)BuCO(2))(3)M(2)(mu-O(2)CCO(2))M(2)(O(2)C(t)Bu)(3) (M(4)OXA), where M = Mo or W, are shown by analysis of powder X-ray diffraction data to have extended lattice structures wherein oxygen atoms from the oxalate and pivalate ligands of one M(4)OXA molecule are linked to metal atoms of neighboring molecules. Raman, resonance Raman, electronic absorption (2-325 K in 2-MeTHF), and emission spectra are reported, together with corresponding spectra of the mu-O(2)(13)C(13)CO(2) isotopomers. To aid in the assignment, the Raman spectra of K(2)C(2)O(4).H(2)O and K(2)(13)C(2)O(4).H(2)O have also been recorded. The visible region of the electronic spectra is dominated by intense, fully allowed MLCT transitions, M(2) delta to oxalate pi*, which show pronounced thermochromism and extensive vibronic progressions associated with the oxalate ligand at low temperatures. With excitation into these charge-transfer bands, strong resonance enhancement is seen for Raman bands assigned to the oxalate nu(1)(a(g)) and, to a lesser extent, nu(2)(a(g)) modes. Electronic structure calculations for the model compounds (HCO(2))(3)M(2)(mu-O(2)CCO(2))M(2)(O(2)CH)(3), employing density functional theory (gradient corrected and time-dependent) with the Gaussian 98 and ADF 2000 packages, predict the planar oxalate D(2h) configuration to be favored, which maximizes M(2) delta to oxalate pi* back-bonding, and indicate low barriers (

A new technique is presented for the rapid, high-resolution identification and quantification of multiple trace gases above soils, at concentrations down to 0.01 microL L(-1) (10 ppb). The technique, selected ion flow tube mass spectrometry (SIFT-MS), utilizes chemical ionization reagent ions that react with trace gases but not with the major air components (N2, O2, Ar, CO2). This allows the real-time measurement of multiple trace gases without the need for preconcentration, trapping, or chromatographic separation. The technique is demonstrated by monitoring the emission of ammonia and nitric oxide, and the search for volatile organics, above containerized soil samples treated with synthetic cattle urine. In this model system, NH3 emissions peaked after 24 h at 2000 nmol m(-2) s(-1) and integrated to approximately 7% of the urea N applied, while NO emissions peaked about 25 d after urine addition at approximately 140 nmol m(-2) s(-1) and integrated to approximately 10% of the applied urea N. The monitoring of organics along with NH3 and NO was demonstrated in soils treated with synthetic urine, pyridine, and dimethylamine. No emission of volatile nitrogen organics from the urine treatments was observed at levels >0.01% of the applied nitrogen. The SIFT method allows the simultaneous in situ measurement of multiple gas components with a high spatial resolution of < 10 cm and time resolution

The signaling mechanisms that specify, guide and coordinate cell behavior during embryonic morphogenesis are poorly understood. We report that a Xenopus homolog of the Drosophila planar cell polarity gene strabismus (stbm) participates in the regulation of convergent extension, a critical morphogenetic process required for the elongation of dorsal structures in vertebrate embryos. Overexpression of Xstbm, which is expressed broadly in early development and subsequently in the nervous system, causes severely shortened trunk structures; a similar phenotype results from inhibiting Xstbm translation using a morpholino antisense oligo. Experiments with Keller explants further demonstrate that Xstbm can regulate convergent extension in both dorsal mesoderm and neural tissue. The specification of dorsal tissues is not affected. The Xstbm phenotype resembles those obtained with several other molecules with roles in planar polarity signaling, including Dishevelled and Frizzled-7 and -8. Unlike these proteins, however, Stbm has little effect on conventional Wnt/beta-catenin signaling in either frog or fly assays. Thus our results strongly support the emerging hypothesis that a vertebrate analog of the planar polarity pathway governs convergent extension movements.