s-Block metallabenzene: aromaticity and hydrogen adsorption

Second group metal dimers can replace the carbon atom in benzene to form metallabenzene (C₅H₆M₂) compounds. These complexes possess some aromatic character and promising hydrogen adsorption properties. In this study, we investigated the aromatic character of these compounds using aromaticity indices and molecular orbital analysis. To determine the nature of interactions between hydrogen and the metallic center, variation-perturbational decomposition of interaction energy was applied together with ETS-NOCV analysis. The results obtained suggest that the aromatic character comes from three π orbitals located mainly on the C₅H₅ ^? fragment. The high hydrogen adsorption energy (up to 6.5 kcal mol^?1) results from two types of interaction. In C₅H₆Be₂, adsorption is controlled by interactions between the empty metal orbital and the σ orbital of the hydrogen molecule (Kubas interaction) together with corresponding back-donation interactions. Other C₅H₆M₂ compounds adsorb H₂ due to Kubas interactions enhanced by H₂–π interactions.

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Graphical Abstract First π orbital in C₅H₆Be₂

     

Evolution of the Selfing Syndrome in Arabis alpina (Brassicaceae)

Introduction

The transition from cross-fertilisation (outcrossing) to self-fertilisation (selfing) frequently coincides with changes towards a floral morphology that optimises self-pollination, the selfing syndrome. Population genetic studies have reported the existence of both outcrossing and selfing populations in Arabis alpina (Brassicaceae), which is an emerging model species for studying the molecular basis of perenniality and local adaptation. It is unknown whether its selfing populations have evolved a selfing syndrome.

Methods

Using macro-photography, microscopy and automated cell counting, we compared floral syndromes (size, herkogamy, pollen and ovule numbers) between three outcrossing populations from the Apuan Alps and three selfing populations from the Western and Central Alps (Maritime Alps and Dolomites). In addition, we genotyped the plants for 12 microsatellite loci to confirm previous measures of diversity and inbreeding coefficients based on allozymes, and performed Bayesian clustering.

Results and Discussion

Plants from the three selfing populations had markedly smaller flowers, less herkogamy and lower pollen production than plants from the three outcrossing populations, whereas pistil length and ovule number have remained constant. Compared to allozymes, microsatellite variation was higher, but revealed similar patterns of low diversity and high Fis in selfing populations. Bayesian clustering revealed two clusters. The first cluster contained the three outcrossing populations from the Apuan Alps, the second contained the three selfing populations from the Maritime Alps and Dolomites.

Conclusion

We conclude that in comparison to three outcrossing populations, three populations with high selfing rates are characterised by a flower morphology that is closer to the selfing syndrome. The presence of outcrossing and selfing floral syndromes within a single species will facilitate unravelling the genetic basis of the selfing syndrome, and addressing which selective forces drive its evolution.     

Shedding of Infectious Borna Disease Virus-1 in Living Bicolored White-Toothed Shrews

Background

Many RNA viruses arise from animal reservoirs, namely bats, rodents and insectivores but mechanisms of virus maintenance and transmission still need to be addressed. The bicolored white-toothed shrew (Crocidura leucodon) has recently been identified as reservoir of the neurotropic Borna disease virus 1 (BoDV-1).

Principal Findings

Six out of eleven wild living bicoloured white-toothed shrews were trapped and revealed to be naturally infected with BoDV-1. All shrews were monitored in captivity in a long-term study over a time period up to 600 days that differed between the individual shrews. Interestingly, all six animals showed an asymptomatic course of infection despite virus shedding via various routes indicating a highly adapted host-pathogen interaction. Infectious virus and viral RNA were demonstrated in saliva, urine, skin swabs, lacrimal fluid and faeces, both during the first 8 weeks of the investigation period and for long time shedding after more than 250 days in captivity.

Conclusions

The various ways of shedding ensure successful virus maintenance in the reservoir population but also transmission to accidental hosts such as horses and sheep. Naturally BoDV-1-infected living shrews serve as excellent tool to unravel host and pathogen factors responsible for persistent viral co-existence in reservoir species while maintaining their physiological integrity despite high viral load in many organ systems.     

Microcolonial fungi from antique marbles in Perge/Side/Termessos (Antalya/Turkey)

In this study rock surfaces of archaeological sites in Antalya were investigated with a focus on black fungi for the first time. Black, meristematic fungi were isolated from surfaces of antique marble monuments in Antalya (Side, Perge, Termessos). Their morphology was characterized, their diversity was documented and the taxonomy and phylogeny of new isolates was clarified based on molecular methods, that is, by sequencing parts of the small ribosomal subunit (18S) and internal transcribed spacer (ITS) regions. From a total of around 250 samples 99 different fungal strains were isolated. In most of 99 strains the rDNA sequencing data and the lack of homologies in “Genbank” gave strong evidence that these strains have to be described as new species/subspecies and/or genera. All of them, however, clustered within the ascomycete orders of Dothideales, Chaetothyriales, and Pleosporales. Field studies show that these organisms cause color changes, black spots, crater shaped lesions as well as chipping and exfoliation of the rock surfaces in Antalya and thus they have to be regarded as a serious threat to the antique cultural heritage in Turkey.     

pH Tolerance in Freshwater Bacterioplankton: Trait Variation of the Community as Measured by Leucine Incorporation

pH is an important factor determining bacterial community composition in soil and water. We have directly determined the community tolerance (trait variation) to pH in communities from 22 lakes and streams ranging in pH from 4 to 9 using a growth-based method not relying on distinguishing between individual populations. The pH in the water samples was altered to up to 16 pH values, covering in situ pH ± 2.5 U, and the tolerance was assessed by measuring bacterial growth (Leu incorporation) instantaneously after pH adjustment. The resulting unimodal response curves, reflecting community tolerance to pH, were well modeled with a double logistic equation (mean R² = 0.97). The optimal pH for growth (pH_opt) among the bacterial communities was closely correlated with in situ pH, with a slope (0.89 ± 0.099) close to unity. The pH interval, in which growth was ≥90% of that at pH_opt, was 1.1 to 3 pH units wide (mean 2.0 pH units). Tolerance response curves of communities originating from circum-neutral pH were symmetrical, whereas in high-pH (8.9) and especially in low-pH (<5.5) waters, asymmetric tolerance curves were found. In low-pH waters, decreasing pH was more detrimental for bacterial growth than increasing pH, with a tendency for the opposite for high-pH waters. A pH tolerance index, using the ratio of growth at only two pH values (pH 4 and 8), was closely related to pH_opt (R² = 0.83), allowing for easy determination of pH tolerance during rapid changes in pH.     

The levels of melatonin and its metabolites in conditioned corn (<Emphasis Type="Italic">Zea mays</Emphasis> L.) and cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.) seeds during storage

The efficiency of pre-sowing conditioning/priming methods used to apply melatonin into seeds was verified: osmopriming in the case of dicot Cucumis sativus and hydropriming of monocot Zea mays seeds. Both priming techniques were selected experimentally as optimal for the studied plant species. Four different seed variants were compared: control non-treated ones, and seeds conditioned with water or with 50 or 500 μM melatonin water solutions. The HPLC–MS quantitative and qualitative analyses were used to determine the content of melatonin and of its potential metabolites in the seeds during 1 year following the conditioning. The control seeds and those conditioned with water contained small amount of endogenous melatonin in both species. However, the level of this indoleamine increased markedly in cucumber and corn seeds primed with exogenous melatonin and it was always correlated with the concentration of melatonin applied. It was noted that melatonin was metabolized during seed storage by its gradual oxidation, thus it protects dry seeds against oxidative stress, prevents potential injuries and significantly increases seeds quality. Interestingly, in the control and water-primed seeds, seasonal fluctuations of endogenous melatonin concentration were noted and significant increase in this indoleamine in the winter month was observed. This suggests that in seeds endogenous melatonin could play a crucial role in seasonal rhythms independently of environmental conditions.     

Similar hypotensive responses to resistance exercise with and without blood flow restriction

Low intensity resistance exercise (RE) with blood flow restriction (BFR) has gained attention in the literature due to the beneficial effects on functional and morphological variables, similar to those observed during traditional RE without BFR, while the effects of BFR on post-exercise hypotension remain unclear. The aim of the present study was to compare the blood pressure (BP) response of trained normotensive individuals to RE with and without BFR. In this cross-over randomized trial, eight male subjects (23.8 ± 4 years, 74 ± 3 kg, 174 ± 4 cm) completed two exercise protocols: traditional RE (3 x 10 repetitions at 70% one-repetition maximum [1-RM]) and low intensity RE (3 x 15 repetitions at 20% 1-RM) with BFR. Blood pressure measurements were performed after 15 min of seated rest (0), immediately after and 10 min, 20 min, 30 min, 40 min, 50 min and 60 min after the experimental sessions. Similar hypotensive effects for systolic BP (SBP) were observed for both protocols (P < 0.05) after exercise, with no differences between groups (P > 0.05) and no statistically significant difference for diastolic BP (P > 0.05). These results suggest that in normotensive trained individuals, both traditional RE and RE with BFR induce hypotension for SBP, which is important to prevent cardiovascular disturbances.