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Abstract: Wedge‐shaped molecules, such as dendrons, are among the most important building blocks for directed supramolecular self‐assembly. Here we present a new approach aimed at widening the range and complexity of potential mesophases by introducing double‐tapered mesogens. Two series of compounds are presented, both alkali metal salts (Li, Na, Cs) of 3,4,5‐tris‐alkoxybenzoic acid with a second tapered tris‐alkoxyaryl group attached at the end of an alkoxy chain. The double‐tapered compounds all display an unusual hexagonal columnar phase consisting of one ionic and three non‐ionic columns per unit cell. The cation size has an unexpectedly drastic effect on unit cell size. Unlike most columnars, the current phases show unusually high dimensional stability on heating, and high stiffness in spite of being 80‐85% aliphatic, attributed to their molecular topology. The described approach may lead to co‐assemblies of multifunctional materials, e.g. parallel p‐ and n‐semiconducting nanowires or parallel ionic and electronic conductors.

Open Access

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Abstract: Structural and associated biomechanical gradients within biological tissues are important for tissue functionality and preventing damaging interfacial stress concentrations. Articular cartilage possesses an inhomogeneous structure throughout its thickness, driving the associated variation in the biomechanical strain profile within the tissue under physiological compressive loading. However, little is known experimentally about the nanostructural mechanical role of the collagen fibrils and how this varies with depth. Utilising a high-brilliance synchrotron X-ray source, we have measured the depth-wise nanostructural parameters of the collagen network in terms of the periodic fibrillar banding (D-period) and associated parameters. We show that there is a depth dependent variation in D-period reflecting the pre-strain and concurrent with changes in the level of intrafibrillar order. Further, prolonged static compression leads to fibrillar changes mirroring those caused by removal of extrafibrillar proteoglycans (as may occur in aging or disease). We suggest that fibrillar D-period is a sensitive indicator of localised changes to the mechanical environment at the nanoscale in soft connective tissues.

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Abstract: This paper describes the structures created by assembling functionalised entangled polymers and the effect these have on the rheology of the material. A polybutadiene (PBd) linear polymer precursor of sufficient molecular weight to be entangled is used. This is end functionalised with the self-associating group 2-ureido-4pyrimidinone (UPy). Interestingly, despite the relatively high molecular weight of the precursor diluting the UPy concentration, the effect on the material’s properties is significant. To characterise the assembled microstructure we present linear rheology, extensional non-linear rheology and small angle X-ray scattering (SAXS). The linear rheology shows that the functionalised PBd assembles into large macro-structures where the terminal relaxation time is up to seven orders of magnitude larger than the precursor. The non-linear rheology shows strain-hardening over a broad range of strain-rates. We then show by both SAXS and modelling of the extensional data that there must exist clusters of UPy associations and hence assembled polymers with branched architecture. By modelling the supra-molecular structure as an effective linear polymer, we show that this would be insufficient in predicting the strain-hardening behaviour at lower extension-rates. Therefore, in this flow regime the strain-hardening is likely to be caused by branching. This is backed up by SAXS measurements which show that UPy clusters larger than pair-pair groups exist.

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Abstract: Pre-treatments are widely used during tanning processes as to improve the performance of the main tannage. Synchrotron small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) were used to study four common types of pre-treatments, viz. monodentate complexing agent (sodium formate, SF), chelating agent (disodium phthalate, DSP), covalent cross-linker (glutaraldehyde, GA) and nanoclay (sodium montmorillonite, MMT) about their effects on chromium-collagen cross-linking reaction during tanning. Based on the results, the performance of chromium-collagen cross-linking with and without pre-treatments was presented considering five aspects: cross-linking, the level of hydration, hydrothermal stability, uniformity through leather cross-section and the uptake of chrome. Comparing to the original ThruBlu chrome tanning, at the same chrome offers, leather pre-treated using SF, DSP and MMT showed improved hydrothermal stability, uniformity and the level of hydration, while GA showed decreased hydration. All of the pre-treatments reduce surface fixation by decreasing the reactivity of chromium with collagen. Changes in the reaction performance can influence the properties of the leather products as well as the efficiency of the leather manufacturing processes. Insights into the structural changes of collagen during tanning with varied reaction conditions can guide the design of novel, benign tanning processes to reduce environmental impact. Take-Away: 1. Uniformity of the hydrothermal stability through leather cross-section were improved by all of the studied pre-treatments. 2. Reactivity of chromium to cross-link with collagen was reduced as a result of the complexing, covalent cross-linking, or preferential adsorption. 3. Complexing agents and nanoclay pre-treatments tend to retain collagen bound water, while covalent cross-linker causing decrease in the level of hydration of collagen.

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Abstract: The majority of vaccines consist of proteins derived from pathogens that, upon vaccination, provide humans with long-term immunity against infectious disease. Vaccine proteins are susceptible to environmental changes. Fluctuations in temperature are the foremost cause of protein degradation and will result in vaccines being ineffective. In short, many vaccines lack thermal stability. Vaccine manufacturer’s therefore store and transport vaccines under continuous refrigeration (2 – 8 °C), known as the “cold-chain”. This increases the longevity of vaccines but is also a very costly procedure. Studies have shown several operational problems within cold-chain and this is reflected in the high prevalence of vaccine-preventable diseases, especially in developing countries. This project investigated the application of a previously developed method, ensilication, to stabilise vaccine proteins with use of silica to prevent thermal denaturation. This could provide an alternative to freeze-drying (lyophilisation) as some vaccines use excipients to improve efficacy which makes them unsuitable for lyophilisation. The ‘sol-gel’ method on which ensilication is based uses an inorganic compound, tetra-ethyl ortho-silicate (TEOS), to produce a polymer particle which can link around and interact with biomolecules present in buffered aqueous solution. This protects against temporal fluctuations in dry powdered form. After storage, the ensilicated protein can be released using a chemical method that removes the silica shell. Recombinant tetanus toxin c fragment (TTCF) was the model protein (antigen) utilised here to establish the feasibility of vaccine ensilication. Structural and physical analysis of ensilicated TTCF, pre- (native) and post-ensilication (released), showed the retention of protein structure and functional properties. Additionally, in vivo animal experiments confirmed retention of released TTCF immunogenicity in mice. This included ensilicated TTCF that was subjected to extreme heat, displaying the thermal resilience of ensilicated material. Finally, synchrotron small angle x-ray scattering (SAXS) experiments elucidated the mechanism of stabilisation. Overall, this study shows a promising application of ensilication for the development of thermostable vaccines.