‘Click’ functionalised polymer resins : a new approach to the synthesis of surface attached bipyridinium and naphthalene diimide [2]rotaxanes

Herein we describe the design and synthesis of a series of solid-tethered [2]rotaxanes utilising crown ether-naphthalene diimide or crown ether- bipyridinium host guest interactions. TentaGel polystyrene resins were initially modified in a two-stage procedure to azide functionalised beads before the target supramolecular architectures were attached using a copper catalysed “click” procedure. The final assembly was examined using IR spectroscopy and gel-phase 1H High Resolution Magic Angle Spinning (HR MAS) NMR spectroscopy. The HR MAS technique enabled a direct comparison between the solid-tethered architectures and the synthesis and characterisation of analogous solution-based [2]rotaxanes to be made.

Stabilization of exotic minority phases in a multicomponent self-assembled molecular network

Trimesic acid (TMA) and alcohols were recently shown to self-assemble into a stable, two-component linear pattern at the solution/highly oriented pyrolytic graphite (HOPG) interface. Away from equilibrium, the TMA/alcohol self-assembled molecular network (SAMN) can coexist with pure-TMA networks. Here, we report on some novel characteristics of these non-equilibrium TMA structures, investigated by scanning tunneling microscopy (STM). We observe that both the chicken-wire and flower-structure TMA phases can host 'guest' C60 molecules within their pores, whereas the TMA/alcohol SAMN does not offer any stable adsorption sites for the C60 molecules. The presence of the C60 molecules at the solution/solid interface was found to improve the STM image quality. We have taken advantage of the high-quality imaging conditions to observe unusual TMA bonding geometries at domain boundaries in the TMA/alcohol SAMN. Boundaries between aligned TMA/alcohol domains can give rise to doubled TMA dimer rows in two different configurations, as well as a tripled-TMA row. The boundaries created between non-aligned domains can create geometries that stabilize TMA bonding configurations not observed on surfaces without TMA/alcohol SAMNs, including small regions of the previously predicted 'super flower' TMA bonding geometry and a tertiary structure related to the known TMA phases. These structures are identified as part of a homologic class of TMA bonding motifs, and we explore some of the reasons for the stabilization of these phases in our multicomponent system.

Exploiting the 1,2,3-triazolium motif in anion-templated formation of a bromide-selective rotaxane host assembly

Stimulated by the efficacy of copper (I) catalysed Huisgen-type 1,3-dipolar cycloaddition of terminal alkynes and organic azides to generate 1,4-disubstituted 1,2,3-triazole derivatives, the importance of ‘click’ chemistry in the synthesis of organic and biological molecular systems is ever increasing.[1] The mild reaction conditions have also led to this reaction gaining favour in the construction of interlocked molecular architectures.[2-4] In the majority of cases however, the triazole group simply serves as a covalent linkage with no function in the resulting organic molecular framework. More recently a renewed interest has been shown in the transition metal coordination chemistry of triazole ligands.[3, 5, 6] In addition novel aryl macrocyclic and acyclic triazole based oligomers have been shown to recognise halide anions via cooperative triazole C5-H….anion hydrogen bonds.[7] In light of this it is surprising the potential anion binding affinity of the positively charged triazolium motif has not, with one notable exception,[8] been investigated. With the objective of manipulating the unique topological cavities of mechanically bonded molecules for anion recognition purposes, we have developed general methods of using anions to template the formation of interpenetrated and interlocked structures.[9-13] Herein we report the first examples of exploiting the 1,2,3-triazolium group in the anion templated formation of pseudorotaxane and rotaxane assemblies. In an unprecedented discovery the bromide anion is shown to be a superior templating reagent to chloride in the synthesis of a novel triazolium axle containing [2]rotaxane. Furthermore the resulting rotaxane interlocked host system exhibits the rare selectivity preference for bromide over chloride...

Three-dimensional geological modelling and multivariate statistical analysis of water chemistry data to analyse and visualise aquifer structure and groundwater composition in the Wairau Plain, Marlborough District, New Zealand

Concerns regarding groundwater contamination with nitrate and the long-term sustainability of groundwater resources have prompted the development of a multi-layered three dimensional (3D) geological model to characterise the aquifer geometry of the Wairau Plain, Marlborough District, New Zealand. The 3D geological model which consists of eight litho-stratigraphic units has been subsequently used to synthesise hydrogeological and hydrogeochemical data for different aquifers in an approach that aims to demonstrate how integration of water chemistry data within the physical framework of a 3D geological model can help to better understand and conceptualise groundwater systems in complex geological settings. Multivariate statistical techniques(e.g. Principal Component Analysis and Hierarchical Cluster Analysis) were applied to groundwater chemistry data to identify hydrochemical facies which are characteristic of distinct evolutionary pathways and a common hydrologic history of groundwaters. Principal Component Analysis on hydrochemical data demonstrated that natural water-rock interactions, redox potential and human agricultural impact are the key controls of groundwater quality in the Wairau Plain. Hierarchical Cluster Analysis revealed distinct hydrochemical water quality groups in the Wairau Plain groundwater system. Visualisation of the results of the multivariate statistical analyses and distribution of groundwater nitrate concentrations in the context of aquifer lithology highlighted the link between groundwater chemistry and the lithology of host aquifers. The methodology followed in this study can be applied in a variety of hydrogeological settings to synthesise geological, hydrogeological and hydrochemical data and present them in a format readily understood by a wide range of stakeholders. This enables a more efficient communication of the results of scientific studies to the wider community.

Implantation of osteogenic differentiated donor mesenchymal stem cells causes recruitment of host cells

The interaction between host and donor cells is believed to play an important role in osteogenesis. However, it is still unclear how donor osteogenic cells behave and interact with host cells in vivo. The purpose of this study was to track the interactions between transplanted osteogenic cells and host cells during osteogenesis. In vitro migration assay was carried out to investigate the ability of osteogenic differentiated humanmesenchymal stemcells (O-hMSCs) to recruit MSCs. At the in vivo level, O-hMSCs were implanted subcutaneously or into skull defects in severe combined immunodeficient (SCID) mice. New bone formation was observed bymicro-CT and histological procedures. In situ hybridization (ISH) against human Alu sequences was performed to distinguish donor osteogenic cells from host cells. In vitro migration assay revealed an increased migration potential of MSCs by co-culturing with O-hMSCs. In agreement with the results of in vitro studies, ISH against human Alu sequences showed that host mouse MSCs migrated in large numbers into the transplantation site in response to O-hMSCs. Interestingly, host cells recruited by O-hMSCs were the major cell populations in newly formed bone tissues, indicating that O-hMSCs can trigger and initiate osteogenesis when transplanted in orthotopic sites. The observations fromthis study demonstrated that in vitro induced O-hMSCs were able to attract hostMSCs in vivo andwere involved inosteogenesis togetherwith host cells,whichmay be of importance for bone tissue-engineering applications.

Advances in mesoporous molecular sieve MCM-41

The discovery of mesoporous molecular sieves, MCM-41, which possesses a regular hexagonal array of uniform pore openings, aroused a worldwide resurgence in this field. This is not only because it has brought about a series of novel mesoporous materials with various compositions which may find applications in catalysis, adsorption, and guest-host chemistry, but also it has opened a new avenue for creating zeotype materials. This paper presents a comprehensive overview of recent advances in the field of MCM-41. Beginning with the chemistry of surfactant/silicate solutions, progresses made in design and synthesis, characterization, and physicochemical property evaluation of MCM-41 are enumerated. Proposed formation mechanisms are presented, discussed, and identified. Potential applications are reviewed and projected. More than 100 references are cited.

Size- and orientation-selective Si nanowire growth : thermokinetic effects of naeoscale plasma chemistry

A multiscale, multiphase thermokinetic model is used to show the effective control of the growth orientation of thin Si NWs for nanoelectronic devices enabled by nanoscale plasma chemistry. It is shown that very thin Si NWs with [110] growth direction can nucleate at much lower process temperatures and pressures compared to thermal chemical vapor deposition where [111]-directed Si NWs are predominantly grown. These findings explain a host of experimental results and offer the possibility of energy- and matter-efficient, size- and orientation-controlled growth of [110] Si NWs for next-generation nanodevices.

Room-temperature, atmospheric plasma needle reduces adenovirus gene expression in HEK 293A host cells

Room-temperature, atmospheric-pressure plasma needle treatment is used to effectively minimize the adenovirus (AdV) infectivity as quantified by the dramatic reduction of its gene expression in HEK 293A primary human embryonic kidney cells studied by green fluorescent protein imaging. The AdV titer is reduced by two orders of magnitude within only 8 min of the plasma exposure. This effect is due to longer lifetimes and higher interaction efficacy of the plasma-generated reactive species in confined space exposed to the plasma rather than thermal effects commonly utilized in pathogen inactivation. This generic approach is promising for the next-generation anti-viral treatments and imunotherapies.

Supramolecular assembly of heterocirculenes in 2D and 3D

The results of a high-resolution ambient STM study of ‘sulflower’ (octathio[8]circulene) and ‘selenosulflower’ (sym-tetraselena-tetrathio[8]circulene) molecules, immobilized in a hydrogen-bonded matrix of trimesic acid (TMA) at the solid–liquid interface, are compared with the STM and X-ray structure of separate host and guest 2D and 3D crystals, respectively.

3D numerical simulation of avascular tumour growth: effect of hypoxic micro-environment in host tissue

A three-dimensional (3D) mathematical model of tumour growth at the avascular phase and vessel remodelling in host tissues is proposed with emphasis on the study of the interactions of tumour growth and hypoxic micro-environment in host tissues. The hybrid based model includes the continuum part, such as the distributions of oxygen and vascular endothelial growth factors (VEGFs), and the discrete part of tumour cells (TCs) and blood vessel networks. The simulation shows the dynamic process of avascular tumour growth from a few initial cells to an equilibrium state with varied vessel networks. After a phase of rapidly increasing numbers of the TCs, more and more host vessels collapse due to the stress caused by the growing tumour. In addition, the consumption of oxygen expands with the enlarged tumour region. The study also discusses the effects of certain factors on tumour growth, including the density and configuration of preexisting vessel networks and the blood oxygen content. The model enables us to examine the relationship between early tumour growth and hypoxic micro-environment in host tissues, which can be useful for further applications, such as tumour metastasis and the initialization of tumour angiogenesis.

Influence of host plant structure and microclimate on the abundance and behaviour of Tephritid fly

Microclimate and host plant architecture significantly influence the abundance and behavior of insects. However, most research in this field has focused at the invertebrate assemblage level, with few studies at the single-species level. Using wild Solanum mauritianum plants, we evaluated the influence of plant structure (number of leaves and branches and height of plant) and microclimate (temperature, relative humidity, and light intensity) on the abundance and behavior of a single insect species, the monophagous tephritid fly Bactrocera cacuminata (Hering). Abundance and oviposition behavior were signficantly influenced by the host structure (density of foliage) and associated microclimate. Resting behavior of both sexes was influenced positively by foliage density, while temperature positively influenced the numbers of resting females. The number of ovipositing females was positively influenced by temperature and negatively by relative humidity. Feeding behavior was rare on the host plant, as was mating. The relatively low explanatory power of the measured variables suggests that, in addition to host plant architecture and associated microclimate, other cues (e.g., olfactory or visual) could affect visitation and use of the larval host plant by adult fruit flies. For 12 plants observed at dusk (the time of fly mating), mating pairs were observed on only one tree. Principal component analyses of the plant and microclimate factors associated with these plants revealed that the plant on which mating was observed had specific characteristics (intermediate light intensity, greater height, and greater quantity of fruit) that may have influenced its selection as a mating site.