Thioxoethenylidene (CCS) as a bridging ligand

The reaction of [Mo(≡CBr)(CO)2(Tp*)] (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) with [Fe2(μ-SLi)2(CO)6] affords, inter alia, the unsymmetrical binuclear thioxoethenylidene complex [Mo2(μ,σ(C):η2(C′S)-CCS)(CO)4(Tp*)2], which may be more directly obtained from [Mo(≡CBr)(CO)2(Tp*)] and Li2S. The reaction presumably proceeds via the intermediacy of the bis(alkylidynyl)thioether complex S{C≡Mo(CO)2(Tp*)}2, which was, however, not directly observed but explored computationally and found to lie 78.6 kJ mol–1 higher in energy than the final thioxoethenylidene product. Computational interrogation of the molecules [M2(μ-C2S)(CO)2(Tp*)2] (M = Mo, W, Re, Os) reveals three plausible coordination modes for a thioxoethenylidene bridge which involve a progressive strengthening of the C–C bond and weakening of the M–C and M–S bonds, as might be expected from simple effective atomic number considerations.This work was supported by the Australian Research Council (DP130102598 and DP110101611)

Molecular architecture of softwood revealed by solid-state NMR

Economically important softwood from conifers is mainly composed of the polysaccharides cellulose, galactoglucomannan and xylan, and the phenolic polymer, lignin. The interactions between these polymers lead to wood mechanical strength and must be overcome in biorefining. Here, we use 13C multidimensional solid-state NMR to analyse the polymer interactions in never-dried cell walls of the softwood, spruce. In contrast to some earlier softwood cell wall models, most of the xylan binds to cellulose in the two-fold screw conformation. Moreover, galactoglucomannan alters its conformation by intimately binding to the surface of cellulose microfibrils in a semi-crystalline fashion. Some galactoglucomannan and xylan bind to the same cellulose microfibrils, and lignin is associated with both of these cellulose-bound polysaccharides. We propose a model of softwood molecular architecture which explains the origin of the different cellulose environments observed in the NMR experiments. Our model will assist strategies for improving wood usage in a sustainable bioeconomy

Molecular interactions of plant cell wall polymers

Specialised plant cells produce thickened cell walls, called secondary cell walls comprised of lignocellulose. The main polymers in lignocellulose are cellulose, xylan, galactoglucomannan and lignin. Lignocellulose forms the majority of biomass on the planet and its utilization for construction, energy production, materials and pharmaceuticals may be important for a more sustainable future. For each of these applications, the interactions between the polymers in secondary cell walls are important. Previously, it was proposed that glucuronic acid side chains on xylan form ester bonds with lignin, and that this cross-linking might be important for cell wall properties. These bonds have been hypothesized to form if the glucuronic acid substitutions of xylan participate in lignin polymerization reactions and thereby cross-link xylan and lignin. Supporting this potentially important role in cell wall cross-linking, previous investigations in the model plant Arabidopsis showed that the glucuronic acid branches of xylan are crucial to the recalcitrance of lignocellulose to enzymatic digestion. In this thesis the molecular basis of this change in recalcitrance was investigated. The gux1 gux2 mutant, which lacks glucuronic acid in secondary cell walls, was found to be more accessible to hydrolytic enzymes, likely due to an increase in the porosity of the cell wall. Investigations with solid-state NMR revealed a reduction in the interactions between lignin and xylan in the mutant plants. Specific lignin synthesis mutants, which have altered lignification chemistry preventing the xylan-lignin cross-linking, were shown to share enzyme accessibility and lignin-xylan interaction phenotypes with the gux1 gux2 mutant. The presence of ester bonds between lignin and xylan was investigated and introduction of novel xylan-lignin cross-links was attempted. Solid-state NMR was used to extend our understanding of the interactions between the cell wall polymers, in industrially relevant conifer cell walls, which have a significantly higher content of galactoglucomannan than Arabidopsis. It was found that both xylan and galactoglucomannan bind to the cellulose surface and that these polysaccharides interact with lignin. This work demonstrates that some similarities in interactions between lignin and hemicelluloses occur in Angiosperms and Gymnosperms and that these interactions may play roles in the maintenance of plant material properties, such as the recalcitrance to enzymatic digestion

Exploring an Exam-Practice Approach to Teaching Academic Reading and Writing in China: Teacher Perspectives and Materials Analysis

This study explores teacher perceptions of an approach to teaching academic reading and writing that focuses on local English for Academic Purposes (EAP) exams (the Exam-Practice Approach) and presents a textual analysis of the teaching materials. The research context is the EAP component of an international foundation year programme for undergraduate students embarking on Business or Engineering pathways at a British university operating in China. Semi-structured interviews were conducted with English teachers and analysed thematically. This data was enhanced through participant observation, documentary evidence and a survey. Findings indicate concerns regarding the separation of academic reading and writing skills, and a mismatch between course aims and assessment. Contextual factors influencing the development of the local EAP programme are identified and concerns are raised over a perceived lack of purpose in teachers’ professional roles. Corpora were constructed from the reading input in the EAP materials divided according to the students’ disciplinary studies (Business and Engineering) and a keyword analysis conducted using the British Academic Written English (BAWE) reference corpus. This was supported through the manual analysis of rhetorical functions in reading materials. Findings indicate that the reading input does not provide a coherent model of target situation writing and that the local academic reading materials contain language features that directly contradict local writing instruction. The primary implication of the findings of this study for pedagogical and professional practice is that course assessment can greatly influence the development of an English for Academic Purposes programme. Focus on English-language test practice risks alienating teachers and reinforcing a deficit model of Chinese students. The purpose of the EAP programme therefore needs to be clear and assessment should reflect that purpose

Combinatorial peptidomics: a generic approach for protein expression profiling

Traditional approaches to protein profiling were built around the concept of investigating one protein at a time and have long since reached their limits of throughput. Here we present a completely new approach for comprehensive compositional analysis of complex protein mixtures, capable of overcoming the deficiencies of current proteomics techniques. The Combinatorial methodology utilises the peptidomics approach, in which protein samples are proteolytically digested using one or a combination of proteases prior to any assay being carried out. The second fundamental principle is the combinatorial depletion of the crude protein digest (i.e. of the peptide pool) by chemical crosslinking through amino acid side chains. Our approach relies on the chemical reactivities of the amino acids and therefore the amino acid content of the peptides (i.e. their information content) rather than their physical properties. Combinatorial peptidomics does not use affinity reagents and relies on neither chromatography nor electrophoretic separation techniques. It is the first generic methodology applicable to protein expression profiling, that is independent of the physical properties of proteins and does not require any prior knowledge of the proteins. Alternatively, a specific combinatorial strategy may be designed to analyse a particular known protein on the basis of that protein sequence alone or, in the absence of reliable protein sequence, even the predicted amino acid translation of an EST sequence. Combinatorial peptidomics is especially suitable for use with high throughput micro- and nano-fluidic platforms capable of running multiple depletion reactions in a single disposable chip

Covalent interactions between lignin and hemicelluloses in plant secondary cell walls.

The plant secondary cell wall is a complex structure composed of polysaccharides and lignin, and is a key evolutionary innovation of vascular land plants. Although cell wall composition is well understood, the cross-linking of the different polymers is only now yielding to investigation. Cross-linking between hemicelluloses and lignin occurs via two different mechanisms: incorporation into lignin by radical coupling of ferulate substitutions on xylan in commelinid monocots, and incorporation of hemicellulosic glycosyl residues by re-aromatisation of lignification intermediates. Recent genetic evidence indicates that hemicellulose:lignin cross-linking has a substantial impact on plant cell wall recalcitrance. Engineering plant biomass with modified frequencies of cross-links will have significant impacts on biomass utilisation.O.M.T was a recipient of an iCASE studentship from the BBSRC and Novozymes (Reference BB/M015432/1). P.D. was supported by the Leverhulme Trust Centre for Natural Material Innovation and the OpenPlant Synthetic Biology Research Centre BB/L014130/1

Project overview and update on WEAVE: the next generation wide-field spectroscopy facility for the William Herschel Telescope

We present an overview of and status report on the WEAVE next-generation spectroscopy facility for the William Herschel Telescope (WHT). WEAVE principally targets optical ground-based follow up of upcoming ground-based (LOFAR) and space-based (Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2-degree prime focus field of view at the WHT, with a buffered pick-and-place positioner system hosting 1000 multi-object (MOS) fibres, 20 integral field units, or a single large IFU for each observation. The fibres are fed to a single spectrograph, with a pair of 8k(spectral) x 6k (spatial) pixel cameras, located within the WHT GHRIL enclosure on the telescope Nasmyth platform, supporting observations at R~5000 over the full 370-1000nm wavelength range in a single exposure, or a high resolution mode with limited coverage in each arm at R~20000. The project is now in the final design and early procurement phase, with commissioning at the telescope expected in 2017.Comment: 11 pages, 11 Figures, Summary of a presentation to Astronomical Telescopes and Instrumentation 201

Self-assembly of proteins and their nucleic acids

We have developed an artificial protein scaffold, herewith called a protein vector, which allows linking of an in-vitro synthesised protein to the nucleic acid which encodes it through the process of self-assembly. This protein vector enables the direct physical linkage between a functional protein and its genetic code. The principle is demonstrated using a streptavidin-based protein vector (SAPV) as both a nucleic acid binding pocket and a protein display system. We have shown that functional proteins or protein domains can be produced in vitro and physically linked to their DNA in a single enzymatic reaction. Such self-assembled protein-DNA complexes can be used for protein cloning, the cloning of protein affinity reagents or for the production of proteins which self-assemble on a variety of solid supports. Self-assembly can be utilised for making libraries of protein-DNA complexes or for labelling the protein part of such a complex to a high specific activity by labelling the nucleic acid associated with the protein. In summary, self-assembly offers an opportunity to quickly generate cheap protein affinity reagents, which can also be efficiently labelled, for use in traditional affinity assays or for protein arrays instead of conventional antibodies

Spatial navigation, episodic memory, episodic future thinking, and theory of mind in children with autism spectrum disorder: evidence for impairments in mental simulation?

This study explored spatial navigation alongside several other cognitive abilities that are thought to share common underlying neurocognitive mechanisms (e.g., the capacity for self-projection, scene construction, or mental simulation), and which we hypothesized may be impaired in autism spectrum disorder (ASD). Twenty intellectually high-functioning children with ASD (with a mean age of ~8 years) were compared to 20 sex, age, IQ, and language ability matched typically developing children on a series of tasks to assess spatial navigation, episodic memory, episodic future thinking (also known as episodic foresight or prospection), theory of mind (ToM), relational memory, and central coherence. This is the first study to explore these abilities concurrently within the same sample. Spatial navigation was assessed using the “memory island” task, which involves finding objects within a realistic, computer simulated, three-dimensional environment. Episodic memory and episodic future thinking were assessed using a past and future event description task. ToM was assessed using the “animations” task, in which children were asked to describe the interactions between two animated triangles. Relational memory was assessed using a recognition task involving memory for items (line drawings), patterned backgrounds, or combinations of items and backgrounds. Central coherence was assessed by exploring differences in performance across segmented and unsegmented versions of block design. Children with ASD were found to show impairments in spatial navigation, episodic memory, episodic future thinking, and central coherence, but not ToM or relational memory. Among children with ASD, spatial navigation was found to be significantly negatively related to the number of repetitive behaviors. In other words, children who showed more repetitive behaviors showed poorer spatial navigation. The theoretical and practical implications of the results are discussed