Global modelling of H2 mixing ratios and isotopic compositions with the TM5 model

The isotopic composition of molecular hydrogen (H2) contains independent information for constraining the global H2 budget. To explore this, we have implemented hydrogen sources and sinks, including their isotopic composition, into the global chemistry transport model TM5. For the first time, a global model now includes a simplified but explicit isotope reaction scheme for the photochemical production of H2. We present a comparison of modelled results for the H2 mixing ratio and isotope composition with available measurements on the seasonal to inter annual time scales for the years 2001–2007. The base model results agree well with observations for H2 mixing ratios. For dD[H2], modelled values are slightly lower than measurements. A detailed sensitivity study is performed to identify the most important parameters for modelling the isotopic composition of H2. The results show that on the global scale, the discrepancy between model and measurements can be closed by adjusting the default values of the isotope effects in deposition, photochemistry and the stratosphere-troposphere exchange within the known range of uncertainty. However, the available isotope data do not provide sufficient information to uniquely constrain the global isotope budget. Therefore, additional studies focussing on the isotopic composition near the tropopause and on the isotope effects in the photochemistry and deposition are recommended

Characteristics of the nuclear (18S, 5.8S, 28S and 5S) and mitochondrial (12S and 16S) rRNA genes of Apis mellifera (Insecta: Hymenoptera): structure, organization, and retrotransposable elements

As an accompanying manuscript to the release of the honey bee genome, we report the entire sequence of the nuclear (18S, 5.8S, 28S and 5S) and mitochondrial (12S and 16S) ribosomal RNA (rRNA)-encoding gene sequences (rDNA) and related internally and externally transcribed spacer regions of Apis mellifera (Insecta: Hymenoptera: Apocrita). Additionally, we predict secondary structures for the mature rRNA molecules based on comparative sequence analyses with other arthropod taxa and reference to recently published crystal structures of the ribosome. In general, the structures of honey bee rRNAs are in agreement with previously predicted rRNA models from other arthropods in core regions of the rRNA, with little additional expansion in non-conserved regions. Our multiple sequence alignments are made available on several public databases and provide a preliminary establishment of a global structural model of all rRNAs from the insects. Additionally, we provide conserved stretches of sequences flanking the rDNA cistrons that comprise the externally transcribed spacer regions (ETS) and part of the intergenic spacer region (IGS), including several repetitive motifs. Finally, we report the occurrence of retrotransposition in the nuclear large subunit rDNA, as R2 elements are present in the usual insertion points found in other arthropods. Interestingly, functional R1 elements usually present in the genomes of insects were not detected in the honey bee rRNA genes. The reverse transcriptase products of the R2 elements are deduced from their putative open reading frames and structurally aligned with those from another hymenopteran insect, the jewel wasp Nasonia (Pteromalidae). Stretches of conserved amino acids shared between Apis and Nasonia are illustrated and serve as potential sites for primer design, as target amplicons within these R2 elements may serve as novel phylogenetic markers for Hymenoptera. Given the impending completion of the sequencing of the Nasonia genome, we expect our report eventually to shed light on the evolution of the hymenopteran genome within higher insects, particularly regarding the relative maintenance of conserved rDNA genes, related variable spacer regions and retrotransposable elements

Diagnostic tools for early detection of cardiac dysfunction in childhood cancer survivors: Methodological aspects of the Dutch late effects after childhood cancer (LATER) cardiology study

Background: Cancer therapy-related cardiac dysfunction and heart failure are major problems in long-term childhood cancer survivors (CCS). We hypothesize that assessment of more sensitive echo- and electrocardiographic measurements, and/or biomarkers will allow for improved recognition of patients with cardiac dysfunction before heart failure develops, and may also identify patients at lower risk for heart failure. Objective: To describe the methodology of the Dutch LATER cardiology study (LATER CARD). Methods: The LATER CARD study is a cross-sectional study in long-term CCS treated with (potentially) cardiotoxic cancer therapies and sibling controls. We will evaluate 1) the prevalence and associated (treatment related) risk factors of subclinical cardiac dysfunction in CCS compared to sibling controls and 2) the diagnostic value of echocardiography including myocardial strain and diastolic function parameters, blood biomarkers for cardiomyocyte apoptosis, oxidative stress, cardiac remodeling and inflammation and ECG or combinations of them in the surveillance for cancer therapy-related cardiac dysfunction. From 2017 to 2020 we expect to include 1900 CCS and 500 siblings. Conclusions: The LATER CARD study will provide knowledge on different surveillance modalities for detection of cardiac dysfunction in long-term CCS at risk for heart

Global scale observations of atmospheric molecular hydrogen and its stable isotopic composition

With average mixing ratios (χ) around 550 ppb (nmole/mole), molecular hydrogen (H2) is the most abundant reduced gas in our atmosphere after methane (CH4), but considerably less studied. H2 is also a promising energy carrier that might replace fossil fuels in vehicles with great sustainability advantages, but there may be environmental side effects. Large-scale leakage of H2 into the atmosphere might affect the atmosphere’s oxidative capacity and stratospheric ozone chemistry. To assess these risks, a better understanding of the atmospheric H2 cycle is needed. Stable isotopic composition measurements can be used to constrain the source and sink terms in the budgets of atmospheric trace gases, as the different processes affect the stable isotopic composition of the gases in different ways. For H2, the effects are particularly large, due to the large relative mass difference between the isotopes (H and D). The largest source, hydrocarbon oxidation, yields D-enriched H2, whereas the smaller combustion-related sources and the minor microbial sources yield D-depleted and extremely D-depleted H2, respectively. Both sink processes, uptake in soils and reaction with hydroxyl radicals (OH), have a D-enriching effect, but the effect is much stronger for OH. Despite its usefulness, few environmental observations of H2 isotopic composition (δD(H2)) are available. We present three new χ(H2) and δD(H2) datasets to fill this gap. First, we present one- to five-year long time series from six globally distributed, predominantly background stations. As expected, average χ(H2) and δD(H2) values were larger in the southern hemisphere (SH) than in the northern hemisphere (NH). The minimum in δD(H2) was found at the NH midlatitude stations, likely a result of fossil fuel combustion. At the three NH coastal and island stations, seasonal δD(H2)-cycles were observed, which were five to six months out-of-phase with the χ(H2)-cycles. No δD(H2)-cycles were observed at the other sites. For the three coastal/island NH stations, a tentative analysis was made of the relative contribution of the two sink processes. This indicated that the relative contribution of soil uptake increases with latitude. In the next chapter, δD(H2) data are presented from samples collected by the CARIBIC passenger aircraft. This commercial aircraft flies in the upper troposphere (UT) but also regularly crosses into the lowermost stratosphere (LMS). In the LMS, tight correlations are found between δD(H2) and χ(CH4). This correlation has applications in global models of δD(H2). UT samples collected over India during the summer monsoon show a decrease in δD(H2) that is correlated with a CH4 increase, possibly indicating a previously unknown microbial H2-source. Lastly, we present a three-year long time series from the Cabauw tall tower in the Netherlands (200 m), which shows excursions to high χ(H2) and low δD(H2) values, especially in winter. These indicate that the local H2-cycle is under heavy anthropogenic influence, which is confirmed by an analysis of the apparent source signature. In addition, several height profiles (20, 60, 120 and 200 m) were measured. These show that the local soil uptake of H2 is wea

Melittin induces HII phase formation in cardiolipin model membranes

The interaction of melittin with bovine heart cardiolipin model membranes was investigated via binding assays, 31P-NMR, freeze-fracture electron microscopy, small angle X-ray diffraction and fluorescence based fusion assays. A strong binding (Kd < 10−7 M) appeared to be accompanied by the formation of large structures, resulting from a fusion process of extremely fast initial rate. As the melittin content is increased, bilayer structure is gradually lost and from a cardiolipin to melittin ratio of about 6 the lipid starts to organize itself in an hexagonal HII phase. At lower temperatures (T < 40° C) the coexistence of another structure is observed, characterized by a broad isotropic 31P-NMR signal and giving rise to sharp X-ray reflections, most probably a cubic phase, as suggested also by freeze-fracture images, showing orderly stacked particles. The results are discussed in relation to contrasting observations on the structural changes induced by melittin in the zwitterionic phospholipid system of dipalmitoylphosphatidylcholine (Dufourcq, J. et al. (1986) Biochim. Biophys. Acta 859, 33–48). The biological relevance of the observations with respect to the process of protein insertion into membranes is indicated

'Ik kan niet zonder': natuur bevordert mentale gezondheid van ouderen in coronatijd

De COVID-19-epidemie heeft er niet toe geleid dat ouderen minder de natuur opzoeken. Sterker nog, het aantal natuurbezoeken is tijdens de coronacrisis zelfs gestegen. De resultaten van ons onderzoek laten zien hoe contact met de natuur voor vitale en hulpbehoevende ouderen goede kansen biedt om een crisissituatie gezond door te komen. Een belangrijke rol daarin speelt de band die ouderen tijdens de epidemie hebben opgebouwd met de natuur en met plekken in de natuur

Melittin induces HII phase formation in cardiolipin model membranes

The interaction of melittin with bovine heart cardiolipin model membranes was investigated via binding assays, 31P-NMR, freeze-fracture electron microscopy, small angle X-ray diffraction and fluorescence based fusion assays. A strong binding (Kd < 10−7 M) appeared to be accompanied by the formation of large structures, resulting from a fusion process of extremely fast initial rate. As the melittin content is increased, bilayer structure is gradually lost and from a cardiolipin to melittin ratio of about 6 the lipid starts to organize itself in an hexagonal HII phase. At lower temperatures (T < 40° C) the coexistence of another structure is observed, characterized by a broad isotropic 31P-NMR signal and giving rise to sharp X-ray reflections, most probably a cubic phase, as suggested also by freeze-fracture images, showing orderly stacked particles. The results are discussed in relation to contrasting observations on the structural changes induced by melittin in the zwitterionic phospholipid system of dipalmitoylphosphatidylcholine (Dufourcq, J. et al. (1986) Biochim. Biophys. Acta 859, 33–48). The biological relevance of the observations with respect to the process of protein insertion into membranes is indicated

Comprehensive two-dimensional gas chromatography coupled to a rapid-scanning quadrupole mass spectrometer: principles and applications

The principles, practicability and potential of comprehensive two-dimensional (2D) gas chromatography coupled to a rapid-scanning quadrupole mass spectrometer (GC × GC-qMS) for the analysis of complex flavour mixtures in food, allergens in fragrances and polychlorinated biphenyls (PCBs) were studied. With a scan speed of 10,000 amu/s, monitoring over a mass range of up to 200 atomic mass unit (amu) can be achieved at an acquisition frequency of 33 Hz. Extending this mass range and/or increasing the data acquisition frequency results in a loss of spectral quality. Optimal parameter settings allow, next to unambiguous identification/confirmation of target compounds on the basis of high-quality mass spectra, fully satisfactory quantification (three to four modulations per peak) with linear calibration plots and detection limits in the low-pg level. The potential of time-scheduled data acquisition to increase the effective mass range within one GC × GC run was also explored. The analyses, with baseline separation of the flavours, allergens and PCB target compounds, took less than 30 min. © 2004 Elsevier B.V. All rights reserved