Asymmetrically substituted 5,5 `-bistriazoles - nitrogen-rich materials with various energetic functionalities

In this contribution the synthesis and full structural and spectroscopic characterization of three asymmetrically substituted bis-1,2,4-triazoles, along with different energetic moieties like amino, nitro, nitrimino and azido moieties, is presented. Additionally, selected nitrogen-rich ionic derivatives have been prepared and characterized. This comparative study on the influence of these energetic moieties on structural and energetic properties constitutes a complete characterization including IR, Raman and multinuclear NMR spectroscopy. Single crystal X-ray crystallographic measurements were performed and provide insight into structural characteristics as well as inter-and intramolecular interactions. The standard enthalpies of formation were calculated for all compounds at the CBS-4M level of theory, revealing highly positive heats of formation for all compounds. The detonation parameters were calculated using the EXPLO5 program and compared to the common secondary explosive RDX as well as recently published symmetric bistriazoles. As expected, the measured sensitivities to mechanical stimuli and decomposition temperatures strongly depend on the energetic moiety of the triazole ring. All compounds were characterized in terms of sensitivities (impact, friction, electrostatic) and thermal stabilities, the ionic derivatives were found to be thermally stable, insensitive compounds

Turnover of soil monosaccharides: Recycling versus Stabilization

Soil organic matter (SOM) represents a mixture of differently degradable compounds. Each of these compounds are characterised by different dynamics due to different chemical recalcitrance, transformation or stabilisation processes in soil. Carbohydrates represent one of these compounds and contribute up to 25 % to the soil organic matter. Vascular plants are the main source of pentose sugars (Arabinose and Xylose), whereas hexoses (Galactose and Mannose) are primarily produced by microorganisms. Several studies suggest that the mean turnover times of the carbon in soil sugars are similar to the turnover dynamics of the bulk carbon in soil. The aim of the study is to characterise the influence of stabilisation and turnover of soil carbohydrates. Soil samples are collected from (i)a continuous maize cropping experiment (“Höhere Landbauschule” Rotthalmünster, Bavaria) established 1979 on a Stagnic Luvisol and (ii) from a continuous wheat cropping, established 1969, as reference site. The effect of stabilisation is estimated by the comparison of turnover times of microbial and plant derived soil carbohydrates. As the dynamics of plant derived carbohydrate are solely influenced by stabilisation processes, whereas the dynamics of microbial derived carbohydrates are affected by recycling of organic carbon compounds derived from C3 plant substrate as well as stabilisation processes. The compound specific isotopic analysis (CSIA) of soil carbohydrates was performed using a HPLC/o/IRMS system. The chromatographic and mass spectrometric subunits were coupled with a LC–Isolink interface. Soil sugars were extracted after mild hydrolysis using 4 M trifluoroacetic acid (TFA)

Effects of climate and land use on carbon and nutrients cycles control soil organic matter pools at Mount Kilimanjaro

Ecosystem functions of tropical mountain ecosystems and their ability to provide ecosystem services are particularly threatened by the combined impact of climate and land-use change. Soils, as the linkage between abiotic and biotic components of an ecosystem, are strongly affected by these changes. To understand impacts of climate and land use changes on biodiversity and accompanying ecosystem stability and services at Mt. Kilimanjaro, detailed understanding and description of the current biotic and abiotic controls on ecosystem Carbon (C) and nutrient fluxes are needed. Therefore, we quantitatively described cycles of C and major nutrients (N, P, K, Ca, Mg, Mn, Na, S) on pedon and stand level scale along a 3500 m elevation gradient and in up to three stages of land-use intensification. Qualitative indicators (composition of soil organic matter and microbial communities) were used to relate pool changes to underlying processes. Annual pattern of litterfall and decomposition were closely related to rainfall seasonality and temperature. Several factors, such as decomposition rate, C & N contents, microbial biomass (MBC) and leaf litter quality, increased at mid elevation. This was reflected in shifts of soil organic matter composition and microbial communities controlling soil C stability. Land-use intensification led to 40-80% losses in topsoil C and MBC contents as well as an increased turnover through higher microbial demand for new C sources. In ecosystems with strong seasonal variations (savanna and alpine helichrysum cushion) the effectiveness of C storage and N turnover was strongly affected by spatial vegetation heterogeneity. Ecosystems at mid elevation (~2000 m) represent the interception zone of optimal moisture and temperature conditions. High inputs and fast turnover control the C sequestration in these ecosystems, while climatic restrains on input and decomposition limit the C turnover in soils at lower and higher elevation. Land-use intensification increases C and nutrient cycling, decreases stabilization from new C inputs through increased microbial C demand and thus decreases soil C storage

Turnover of microbial groups and cell components in soil: ¹³C analysis of cellular biomarkers

© 2017 The Author(s).Microorganisms regulate the carbon (C) cycle in soil, controlling the utilization and recycling of organic substances. To reveal the contribution of particular microbial groups to C utilization and turnover within the microbial cells, the fate of 13C-labelled glucose was studied under field conditions. Glucose-derived 13C was traced in cytosol, amino sugars and phospholipid fatty acid (PLFA) pools at intervals of 3, 10 and 50 days after glucose addition into the soil. 13C enrichment in PLFAs (∼1.5% of PLFA C at day 3) was an order of magnitude greater than in cytosol, showing the importance of cell membranes for initial C utilization. The 13C enrichment in amino sugars of living microorganisms at day 3 accounted for 0.57% of total C pool; as a result, we infer that the replacement of C in cell wall components is 3 times slower than that of cell membranes. The C turnover time in the cytosol (150 days) was 3 times longer than in PLFAs (47 days). Consequently, even though the cytosol pool has the fastest processing rates compared to other cellular compartments, intensive recycling of components here leads to a long C turnover time. Both PLFA and amino-sugar profiles indicated that bacteria dominated in glucose utilization. 13C enrichment decreased with time for bacterial cell membrane components, but it remained constant or even increased for filamentous microorganisms. 13C enrichment of muramic acid was the 3.5 times greater than for galactosamine, showing a more rapid turnover of bacterial cell wall components compared to fungal. Thus, bacteria utilize a greater proportion of low-molecular-weight organic substances, whereas filamentous microorganisms are responsible for further C transformations. Thus, tracing 13C in cellular compounds with contrasting turnover rates elucidated the role of microbial groups and their cellular compartments in C utilization and recycling in soil. The results also reflect that microbial C turnover is not restricted to the death or growth of new cells. Indeed, even within living cells, highly polymeric cell compounds are constantly replaced and renewed. This is especially important for assessing C fluxes in soil and the contribution of C from microbial residues to soil organic matter

Fate of low molecular weight organic substances in an arable soil: From microbial uptake to utilisation and stabilisation

Microbial uptake and utilisation are the main transformation pathways of low molecular weight organic substances (LMWOS) in soil, but details on transformations are strongly limited. As various LMWOS classes enter biochemical cycles at different steps, we hypothesize that the percentage of their carbon (C) incorporation into microbial biomass and consequently stabilisation in soil are different. Representatives of the three main groups of LMWOS: amino acids (alanine, glutamate), sugars (glucose, ribose) and carboxylic acids (acetate, palmitate) - were applied at naturally-occurring concentrations into a loamy arable Luvisol in a field experiment. Incorporation of 13C from these LMWOS into extractable microbial biomass (EMB) and into phospholipid fatty acids (PLFAs) was investigated 3d and 10d after application. The microbial utilisation of LMWOS for cell membrane construction was estimated by replacement of PLFA-C with 13C.35-80% of initially applied LMWOS-13C was still present in the composition of soil organic matter after 10 days of experiment, with 10-24% of 13C incorporation into EMB at day three and 1-15% at day 10. Maximal incorporation of 13C into EMB was observed from sugars and the least from amino acids. Strong differences in microbial utilisation between LMWOS were observed mainly at day 10. Thus, despite similar initial rapid uptake by microorganisms, further metabolism within microbial cells accounts for the specific fate of C from various LMWOS in soils.13C from each LMWOS was incorporated into each PLFA. This reflects the ubiquitous utilisation of all LMWOS by all functional microbial groups. The preferential incorporation of palmitate into PLFAs reflects its role as a direct precursor for fatty acids. Higher 13C incorporation from alanine and glucose into specific PLFAs compared to glutamate, ribose and acetate reflects the preferential use of glycolysis-derived substances in the fatty acids synthesis.Gram-negative bacteria (16:1ω7c and 18:1ω7c) were the most abundant and active in LMWOS utilisation. Their high activity corresponds to a high demand for anabolic products, e.g. to dominance of pentose-phosphate pathway, i.e. incorporation of ribose-C into PLFAs. The 13C incorporation from sugars and amino acids into filamentous microorganisms was lower than into all prokaryotic groups. However, for carboxylic acids, the incorporation was in the same range (0.1-0.2% of the applied carboxylic acid 13C) as that of gram-positive bacteria. This may reflect the dominance of fungi and other filamentous microorganisms for utilisation of acidic and complex organics.Thus, we showed that despite similar initial uptake, C from individual LMWOS follows deviating metabolic pathways which accounts for the individual fate of LMWOS-C over 10 days. Consequently, stabilisation of C in soil is mainly connected with its incorporation into microbial compounds of various stability and not with its initial microbial uptake. © 2014 Elsevier Ltd

Detection of the DCC gene product in normal and malignant colorectal tissues and its relation to a codon 201 mutation.

Protein expression of the putative tumour-suppressor gene DCC on chromosome 18q was evaluated in a panel of 16 matched colorectal cancer and normal colonic tissue samples together with DCC mRNA expression and allelic deletions (loss of heterozygosity, LOH). Determined by a polymerase chain reaction (PCR)-LOH assay, 12 of the 16 (75%) cases were informative with LOH occurring in 2 of the 12 cases. For DCC mRNA, transcripts could be detected in all analysed normal tissues (eight out of eight) by RT-PCR, whereas 6 of the 15 tumours were negative. DCC protein expression, investigated by immunohistochemistry using the monoclonal antibody 15041 A directed against the intracellular domain, was homogeneously positive in all normal tissue samples. In tumour tissues, no DCC protein was seen in 11 out of 16 samples (69%). For the DCC codon 201, we found a loss of a wild-type codon sequence caused by mutation or LOH in at least 8 out of 15 cases (53%) compared with the corresponding normal tissue. DCC protein expression was undetectable in eight of the nine tumours missing both wild-type codons. Only one of the five tumours with retained DCC protein expression had no detectable wild-type codon 201. In addition, 9 out of 15 normal tissue specimens were mutated in codon 201. In two out of three cases with homozygous wild-type codons in peripheral blood lymphocyte (PBL) DNA, mutations were already observed in the tumour adjacent normal colonic mucosa. We conclude that DCC immunostaining should be introduced in the clinicopathological routine because of its strong correlation with the known prognostic markers 18q LOH and mutation of codon 201

The tree species matters: Belowground carbon input and utilization in the myco-rhizosphere

© 2017 Elsevier Masson SAS Rhizodeposits act as major carbon (C) source for microbial communities and rhizosphere-driven effects on forest C cycling receive increasing attention for maintaining soil biodiversity and ecosystem functions. By in situ 13 CO 2 pulse labeling we investigated C input and microbial utilization of rhizodeposits by analyzing 13 C incorporation into phospholipid fatty acids (PLFA) of beech- (Fagus sylvatica) and ash-associated (Fraxinus excelsior) rhizomicrobial communities. Plant compartments and soil samples were analyzed to quantify the allocation of assimilates. For 1 m high trees, ash assimilated more of the applied 13 CO 2 (31%) than beech (21%), and ash allocated twice as much 13 C belowground until day 20. Approximately 0.01% of the applied 13 C was incorporated into total PLFAs, but incorporation varied significantly between microbial groups. Saprotrophic and ectomycorrhizal fungi under beech and ash, but also arbuscular mycorrhizal fungi and Gram negative bacteria under ash, incorporated most 13 C. PLFA allowed differentiation of C fluxes from tree roots into mycorrhiza: twice as much 13 C was incorporated into the fungal biomarker 18:2ω6,9 under beech than under ash. Within 5 days, 30% of the fungal PLFA-C was replaced by rhizodeposit-derived 13 C under beech but only 10% under ash. None of the other microbial groups reached such high C replacement, suggesting direct C allocation via ectomycorrhizal symbioses dominates the C flux under beech. Based on 13 CO 2 labeling and 13 C tracing in PLFA we conclude that ash allocated more C belowground and has faster microbial biomass turnover in the rhizosphere compared to beech

Einfluss räumlicher Heterogenität von Phosphor auf die mikrobielle P‑Aufnahme und die Zusammensetzung der mikrobiellen Gemeinschaft in Waldböden

Neben Stickstoff ist Phosphor (P) das wichtigste wachstumslimitierende Nährelement in Böden. Dennoch gibt es wenig Information über die räumliche Heterogenität des P-Gehaltes in Waldböden. Darüber hinaus ist der Effekt einer homogenen versus heterogenen P‑Verteilung im Boden auf die mikrobielle P‑Akquirierung und Zusammensetzung der mikrobiellen Gemeinschaft weitgehend unbekannt. Ein Rhizotronexperiment mit P-armem Waldboden wurde durchgeführt um konkurrierende P‑Aufnahmestrategien von Mikroorganismen zu untersuchen. Um den Effekt räumlicher P‑Heterogenität auf pflanzliche und mikrobielle P‑Aufnahme zu eruieren wurden mit F.sylvatica bepflanzte Rhizotrone mit P‑33‑Eisen(III)phosphat, einer relativ immobilen P Quelle, in verschiedenen räumlichen Verteilungen markiert. Die P‑Mobilisierung durch Mikroorganismen wurde mittels einer verbesserten P-33-PLFA-Methode verfolgt, welche die P‑33‑Inkorporierung in Mikroorganismen mit Änderungen in der Zusammensetzung mikrobieller Gemeinschaften in situ verbindet. Die mikrobielle P-Aufnahme war erhöht in Rhizotronen mit hoher P‑Verfügbarkeit, sowie in solchen mit heterogener P‑Verteilung. Charakteristische PLFA weisen auf eine Akkumulation von Ektomykorrhizapilzen, typischerweise assoziiert mit Buchenwurzeln, in P‑reichen Arealen hin. Diese Ektomykorrhizzapilze führen wahrscheinlich zu einer starken Zunahme der P‑Mobilisierung des ausgebrachten P‑33‑Eisen(III)phosphats in stark P-haltigen Habitaten. Im Gegensatz hierzu benötigen Habitate mit niedriger P-Verfügbarkeit eine komplexer zusammengesetzte mikrobielle Gemeinschaft um unzugängliche P-Quellen zu mobilisieren. Entsprechend fördern hohe P‑Vorkommen die Bildung von Pilzhyphen zur P-Mobilisierung – ein Effekt, der mit sinkendem P-Gehalt abnimmt. Des Weiteren zeigen grampositive und ‑negative Bakterien eine massiv erhöhte P‑Aufnahme unter zunehmend heterogenen P-Verteilungen. Sie stellen jedoch einen kleineren Anteil der mikrobiellen Gemeinschaft als in homogen P‑angereicherten Rhizotronen, was auf einen Vorteil filamentöser Organismen bei heterogener P-Verteilung hindeutet. Entsprechend fördert eine heterogene P-Verteilung in Waldböden die P-Aufnahme mikrobieller Gemeinschaften aus mineralischen P-Quellen mit geringer biologischer Verfügbarkeit in Waldböden

Klima und Wurzelabstand bestimmen die Enzymaktivitäten und den Umsatz der organischen Bodensubstanz

In der chilenischen Küstenkordillera wurden entlang eines klimatischen Gradienten von 1500 km, von arid bis mäßig humid, natürliche Ökosysteme ausgewählt, um den Abbau der organischen Bodensubstanz (OBS) sowie die Nährstofffreisetzung zu untersuchen. Mikroorganismen können mithilfe extrazellulärer Enzyme organische Verbindungen aufspalten und Nährstoffe für Pflanzen bereitstellen. Es stellt sich die Frage, welchen Einfluss die Bodenfeuchte und der Kohlenstoffeintrag über das Wurzelsystem auf den mikrobiellen Abbau haben. Es wurde die Hypothese geprüft, dass feuchte Bodenbedingungen und Wurzelnähe den enzymatischen OBS-Abbau und die Nährstofffreisetzung fördern. In zwei Klimaregionen, einem humid gemäßigtem und einem semiariden Waldgebiet, wurden entlang vertikaler (Bodentiefe) und horizontaler (Wurzelabstand) Gradienten folgende Parameter bestimmt: Bodenfeuchte, C- und N-Gehalte, d13C- und d15N-Werte sowie die Aktivitäten von sechs extrazellulären Enzymen, beteiligt in den C-, N- und P-Kreisläufen. Höhere C- und N-Gehalte in Böden des humiden Ökosystems spiegeln dessen höhrere Produktivität gegenüber dem semiariden System wieder. Die Regressionen von d13C und –[ln(%C)] zeigen eine starke Isotopenfraktionierung von Ober- zu Unterboden im semiariden Ökosystem und weisen auf einen schnelleren OBS-Umsatz als im humiden Ökosystem hin. Die d15N-Tiefentrends lassen auf eine N-Limitierung in beiden Böden schließen, mit einer stärkeren Ausprägung im humiden Ökosystem. Die Aktivitäten der Enzyme, die für C-, N- und P-Kreisläufe zuständig sind, stiegen mit dem C-Gehalt an und nahmen von Ober- zu Unterboden und mit zunehmender Entfernung von der Wurzel ab. Nur die Tyrosin‑aminopeptidase Aktivitäten stiegen mit dem N-Gehalt und deuten zudem auf eine schnellere Substratumsetzung unter semiariden gegenüber humiden Klimabedingungen hin. Die Aktivitäten von Chitiniase und Phosphatase weisen dagegen auf einen schnelleren Umsatz unter humiden Bedingungen hin. Wir schließen daraus, dass die N-Verfügbarkeit und der OBS-Umsatz im semiariden Ökosystem höher als im humiden System ist. Die Enzymaktivitäten zeigten nur einen indirekten Zusammenhang mit der Bodentiefe und werden vorwiegend von dem C-Gehalt bestimmt, der direkt über den C‑Eintrag der Wurzel beeinflusst wird