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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: Improvement of pain management strategies after arthroscopic surgery by multimodal analgesia may include the use of long-acting amide local anesthetics. Among these anesthetics, the low molecular weight local anesthetic agent bupivacaine (BUP) is attractive for use in postoperative pain management. However, it has relatively a short duration of action and imposes higher risk of systemic toxicity at relatively large bolus doses. Bupivacaine encapsulation in lipid-based delivery systems is an attractive strategy for prolonging its local anaesthetic effect and reducing the associated undesirable systemic side effects. Here, we discuss the potential development of liquid crystalline nanocarriers by using a binary lipid mixture of citrem and soy phosphatidylcholine (SPC) at different weight ratios. The produced safe-by-design family of citrem/SPC nanoparticles are attractive for use in the development of nanocarriers owing to the previously reported hemocompatibility. BUP encapsulation efficiency (EE), depending on the lipid composition , was in the range of 65-77%. In this study, nanoparticle tracking analysis (NTA) and synchrotron small-angle X-ray scattering (SAXS) were employed to gain insight into the effect of BUP solubilization and lipid composition on the size and structural characteristics of the produced citrem/SPC nanodispersions. BUP loading led to a slight change in the mean sizes (diameters) and size distributions of citrem/SPC nanoparticles. However, we found that BUP accommodation into the nanoparticles’ self-assembled interiors, triggers in BUP concentration- and lipid composition-dependent manners significant structural alterations that involve vesicles-cubosomes and vesicles-hexosomes transitions. The structural tunability of citrem/SPC nanoparticles and the implications for a potential use for intra-articular BUP delivery are discussed.

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Abstract: The modular building principle of metal–organic frameworks (MOFs) presents an excellent platform to explore and establish structure–property relations that tie microscopic to macroscopic properties. Negative thermal expansion (NTE) is a common phenomenon in MOFs and is often ascribed to collective motions that can move through the structure at sufficiently low energies. Here, we show that the introduction of additional linkages in a parent framework, retrofitting, is an effective approach to access lattice dynamics experimentally, in turn providing researchers with a tool to alter the NTE behavior in MOFs. By introducing TCNQ (7,7,8,8-tetracyanoquinodimethane) into the prototypical MOF Cu3BTC2 (BTC = 1,3,5-benzenetricarboxylate; HKUST-1), NTE can be tuned between αV = −15.3 × 10–6 K–1 (Cu3BTC2) and αV = −8.4 × 10–6 K–1 (1.0TCNQ@Cu3BTC2). We ascribe this phenomenon to a general stiffening of the framework as a function of TCNQ loading due to additional network connectivity, which is confirmed by computational modeling and far-infrared spectroscopy. Our findings imply that retrofitting is generally applicable to MOFs with open metal sites, opening yet another way to fine-tune properties in this versatile class of materials.

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Abstract: Many insects have triplets of camera type eyes, called ocelli, whose function remains unclear for most species. Here, we investigate the ocelli of the bumblebee, Bombus terrestris, using reconstructed 3D data from X-ray microtomography scans combined with computational ray-tracing simulations. This method enables us, not only to predict the visual fields of the ocelli, but to explore for the first time the effect that hair has on them as well as the difference between worker female and male ocelli. We find that bumblebee ocellar fields of view are directed forward and dorsally, incorporating the horizon as well as the sky. There is substantial binocular overlap between the median and lateral ocelli, but no overlap between the two lateral ocelli. Hairs in both workers and males occlude the ocellar field of view, mostly laterally in the worker median ocellus and dorsally in the lateral ocelli. There is little to no sexual dimorphism in the ocellar visual field, suggesting that in B. terrestris they confer no advantage to mating strategies. We compare our results with published observations for the visual fields of compound eyes in the same species as well as with the ocellar vision of other bee and insect species.

Open Access

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Abstract: Autophagy is an essential recycling and quality control pathway. Mammalian ATG8 proteins drive autophagosome formation and selective removal of protein aggregates and organelles by recruiting autophagy receptors and adaptors that contain a LC3-interacting region (LIR) motif. LIR motifs can be highly selective for ATG8 subfamily proteins (LC3s/GABARAPs), however the molecular determinants regulating these selective interactions remain elusive. Here we show that residues within the core LIR motif and adjacent C-terminal region as well as ATG8 subfamily-specific residues in the LIR docking site are critical for binding of receptors and adaptors to GABARAPs. Moreover, rendering GABARAP more LC3B-like impairs autophagy receptor degradation. Modulating LIR binding specificity of the centriolar satellite protein PCM1, implicated in autophagy and centrosomal function, alters its dynamics in cells. Our data provides new mechanistic insight into how selective binding of LIR motifs to GABARAPs is achieved, and elucidate the overlapping and distinct functions of ATG8 subfamily proteins.