Reaction mechanism of organoselenium-catalyzed <Emphasis Type="Italic">syn</Emphasis>-dichlorination of alkenes: a DFT study

A new method for the syn-dichlorination of alkenes at room temperature has been proposed by Denmark et al. The method uses diselenide (PhSeSePh) as the precatalyst, benzyltriethylammonium chloride (BnEt₃NCl) as the source of chlorine, and an N-fluoropyridinium salt as the oxidant to recover the catalyst. This approach has achieved exquisite diastereocontrol on a number of alkene substrates. In this paper, we report the results of DFT calculations we performed to study the mechanism of this reaction. We were able to identify a reasonable reaction path, including the intermediate and transition-state structures. The results also indicate that PhSeCl₃, rather than PhSeCl, is the active catalyst.     

Targeted Gene Deletion in <Emphasis Type="Italic">Cordyceps militaris</Emphasis> Using the Split-Marker Approach

The macrofungus Cordyceps militaris contains many kinds of bioactive ingredients that are regulated by functional genes, but the functions of many genes in C. militaris are still unknown. In this study, to improve the frequency of homologous integration, a genetic transformation system based on a split-marker approach was developed for the first time in C. militaris to knock out a gene encoding a terpenoid synthase (Tns). The linear and split-marker deletion cassettes were constructed and introduced into C. militaris protoplasts by PEG-mediated transformation. The transformation of split-marker fragments resulted in a higher efficiency of targeted gene disruption than the transformation of linear deletion cassettes did. The color phenotype of the Tns gene deletion mutants was different from that of wild-type C. militaris. Moreover, a PEG-mediated protoplast transformation system was established, and stable genetic transformants were obtained. This method of targeted gene deletion represents an important tool for investigating the role of C. militaris genes.     

Single‐Crystalline Nanomesh Tantalum Nitride Photocatalyst with Improved Hydrogen‐Evolving Performance

Tantalum nitride (Ta₃N₅) with a suitable bandgap (≈2 eV) is regarded as one of the most promising photocatalysts for efficient solar energy harvesting and conversion. However, Ta₃N₅ suffers from low hydrogen production activity due to the low carrier mobility and fast carrier recombination. Thus, the design of Ta₃N₅ nanostructures to facilitate charge carrier transport and improve photocatalytic performance remains a challenge. This study reports a new type of ultrathin (≈2 nm) Ta₃N₅ nanomesh with high specific surface area (284.6 m² g^?1) and excellent crystallinity by an innovative bottom‐up graphene oxide templated strategy. The resulting Ta₃N₅ nanomeshes demonstrate drastically improved electron transport ability and prolonged lifetime of charge carriers, due to the nature of high surface area and excellent crystallinity. As a result, when used as photocatalysts, the Ta₃N₅ nanomeshes exhibit a greater than tenfold improvement in solar hydrogen production compared to bulk counterparts. This work provides an effective and generic strategy for designing 2D ultrathin nanomesh structures for nonlayered materials with improved catalytic activity.     

A 55 K SNP array-based genetic map and its utilization in QTL mapping for productive tiller number in common wheat

Key message

A high-density genetic map constructed with a wheat 55 K SNP array was highly consistent with the physical map of this species and it facilitated the identification of a novel major QTL for productive tiller number.

Abstract

Productive tiller number (PTN) plays a key role in wheat grain yield. In this study, a recombinant inbred line population with 199 lines derived from a cross between ‘20828’ and ‘Chuannong16’ was used to construct a high-density genetic map using wheat 55 K single nucleotide polymorphism (SNP) array. The constructed genetic map contains 12,109 SNP markers spanning 3021.04 cM across the 21 wheat chromosomes. The orders of the genetic and physical positions of these markers are generally in agreement, and they also match well with those based on the 660 K SNP array from which the one used in this study was derived. The ratios of SNPs located in each of the wheat deletion bins were similar among the wheat 9 K, 55 K, 90 K, 660 K and 820 K SNP arrays. Based on the constructed maps, a novel major quantitative trait locus QPtn.sau-4B for PTN was detected across multi-environments in a 0.55 cM interval on 4B and it explained 17.23–45.46% of the phenotypic variance. Twenty common genes in the physical interval between the flanking markers were identified on chromosome 4B of ‘Chinese Spring’ and wild emmer. These results indicate that wheat 55 K SNP array could be an ideal tool in primary mapping of target genes and the identification of QPtn.sau-4B laid a foundation for the following fine mapping and cloning work.

     

Migration and wintering strategies in vulnerable Mediterranean Osprey populations

A broad range of migration strategies exist in avian species, and different strategies can occur in different populations of the same species. For the breeding Osprey Pandion haliaetus populations of the Mediterranean, sporadic observations of ringed birds collected in the past suggested variations in migratory and wintering behaviour. We used GPS tracking data from 41 individuals from Corsica, the Balearic Islands and continental Italy to perform the first detailed analysis of the migratory and wintering strategies of these Osprey populations. Ospreys showed heterogeneous migratory behaviour, with 73% of the individuals migrating and the remaining 27% staying all year round at breeding sites. For migratory individuals, an extremely short duration of migration (5.2 ± 2.6 days) was recorded. Mediterranean Ospreys were able to perform long non‐stop flights over the open sea, sometimes overnight. They also performed pre‐ and post‐migratory trips to secondary sites, before or after crossing the sea during both autumn and spring migration. Ospreys spent the winter at temperate latitudes and showed high plasticity in habitat selection, using marine bays, coastal lagoons/marshland and inland freshwater sites along the coasts of different countries of the Mediterranean basin. Movements and home‐range areas were restricted during the wintering season. The short duration of trips and high levels of variability in migratory routes and wintering grounds revealed high behavioural plasticity among individuals, probably promoted by the relatively low seasonal variability in ecological conditions throughout the year in the Mediterranean region, and weak competition for non‐breeding sites. We stress the importance of considering the diversity in migration strategies and the particular ecology of these vulnerable populations, especially in relation to proactive management measures for the species at the scale of the Mediterranean region.     

Assessing global range expansion in a cryptic species complex: insights from the red seaweed genus Asparagopsis (Florideophyceae)

The mitochondrial genetic diversity, distribution and invasive potential of multiple cryptic operational taxonomic units (OTUs) of the red invasive seaweed Asparagopsis were assessed by studying introduced Mediterranean and Hawaiian populations. Invasive behavior of each Asparagopsis OTU was inferred from phylogeographic reconstructions, past historical demographic dynamics, recent range expansion assessments and future distributional predictions obtained from demographic models. Genealogical networks resolved Asparagopsis gametophytes and tetrasporophytes into four A. taxiformis and one A. armata cryptic OTUs. Falkenbergia isolates of A. taxiformis L3 were recovered for the first time in the western Mediterranean Sea and represent a new introduction for this area. Neutrality statistics supported past range expansion for A. taxiformis L1 and L2 in Hawaii. On the other hand, extreme geographic expansion and an increase in effective population size were found only for A. taxiformis L2 in the western Mediterranean Sea. Distribution models predicted shifts of the climatically suitable areas and population expansion for A. armata L1 and A. taxiformis L1 and L2. Our integrated study confirms a high invasive risk for A. taxiformis L1 and L2 in temperate and tropical areas. Despite the differences in predictions among modelling approaches, a number of regions were identified as zones with high invasion risk for A. taxiformis L2. Since range shifts are likely climate‐driven phenomena, future invasive behavior cannot be excluded for the rest of the lineages.     

Multiscale Persistent Functions for Biomolecular Structure Characterization

In this paper, we introduce multiscale persistent functions for biomolecular structure characterization. The essential idea is to combine our multiscale rigidity functions (MRFs) with persistent homology analysis, so as to construct a series of multiscale persistent functions, particularly multiscale persistent entropies, for structure characterization. To clarify the fundamental idea of our method, the multiscale persistent entropy (MPE) model is discussed in great detail. Mathematically, unlike the previous persistent entropy (Chintakunta et al. in Pattern Recognit 48(2):391–401, 2015; Merelli et al. in Entropy 17(10):6872–6892, 2015; Rucco et al. in: Proceedings of ECCS 2014, Springer, pp 117–128, 2016), a special resolution parameter is incorporated into our model. Various scales can be achieved by tuning its value. Physically, our MPE can be used in conformational entropy evaluation. More specifically, it is found that our method incorporates in it a natural classification scheme. This is achieved through a density filtration of an MRF built from angular distributions. To further validate our model, a systematical comparison with the traditional entropy evaluation model is done. It is found that our model is able to preserve the intrinsic topological features of biomolecular data much better than traditional approaches, particularly for resolutions in the intermediate range. Moreover, by comparing with traditional entropies from various grid sizes, bond angle-based methods and a persistent homology-based support vector machine method (Cang et al. in Mol Based Math Biol 3:140–162, 2015), we find that our MPE method gives the best results in terms of average true positive rate in a classic protein structure classification test. More interestingly, all-alpha and all-beta protein classes can be clearly separated from each other with zero error only in our model. Finally, a special protein structure index (PSI) is proposed, for the first time, to describe the “regularity” of protein structures. Basically, a protein structure is deemed as regular if it has a consistent and orderly configuration. Our PSI model is tested on a database of 110 proteins; we find that structures with larger portions of loops and intrinsically disorder regions are always associated with larger PSI, meaning an irregular configuration, while proteins with larger portions of secondary structures, i.e., alpha-helix or beta-sheet, have smaller PSI. Essentially, PSI can be used to describe the “regularity” information in any systems.     

<Emphasis Type="Italic">Ponticoccus alexandrii</Emphasis> sp. nov., a novel bacterium isolated from the marine toxigenic dinoflagellate <Emphasis Type="Italic">Alexandrium minutum</Emphasis>

During an investigation of the biodiversity of the cultivable bacterial community associated with paralytic shellfish poisoning toxin-producing marine dinoflagellate, Alexandrium minutum a novel algal-associated bacterium, designated strain AT2-A^T was isolated. 16S rRNA gene sequence similarity analysis showed that the strain is a member of the genus Ponticoccus, with high sequence similarity to Ponticoccus litoralis DSM 18986^T (97.9%) and Ponticoccus lacteus JCM 30379^T (96.0%). However, based on the data obtained for the physiological and biochemical characteristics, and low level of DNA–DNA relatedness analysis, the strain could be genotypically and phenotypically differentiated from two type strains of the genus Ponticoccus. Therefore, this algal-associated bacterial strain is concluded to represent a novel species of the genus Ponticoccus, for which the name Ponticoccus alexandrii sp. nov. is proposed. The type strain is AT2-A^T (CCTCC AB 2017228 ^T = KCTC 52626 ^T ).