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Glycine Transporter 2 (GlyT2) inhibitors have shown considerable potential as analgesics for the treatment of neuropathic pain but also display considerable side effects. One potential source of side effects is irreversible inhibition. In this study, we have characterized the mechanism of ORG25543 inhibition of GlyT2 by first considering three potential ligand binding sites on GlyT2—the substrate site, the vestibule allosteric site and the lipid allosteric site. The three sites were tested using a combination of molecular dynamics simulations and analysis of the inhibition of glycine transport of a series point mutated GlyT2 using electrophysiological methods. We demonstrate that the lipid allosteric site on GlyT2 is the most likely binding site for ORG25543. We also demonstrate that cholesterol derived from the cell membrane can form specific interactions with inhibitor‐bound transporters to form an allosteric network of regulatory sites. These observations will guide the future design of GlyT2 inhibitors with the objective of minimising on‐target side effects and improving the therapeutic window for the treatment of patients suffering from neuropathic pain. [ABSTRACT FROM AUTHOR]

The accumulation of iron in dopaminergic neurons can cause oxidative stress and dopaminergic neuron degeneration. Iron chelation therapy may reduce dopaminergic neurodegeneration, but chelators should be targeted towards dopaminergic cells. In this work, two series of compounds based on 8-hydroxyquinoline and deferiprone, iron chelators that have amphetamine-like structures, have been designed, synthesized and characterized. Each of these compounds chelated iron ions in aqueous solution. The hydroxyquinoline-based compounds exhibited stronger iron-binding constants than those of the deferiprone derivatives. The hydroxyquinoline-based compounds also exhibited greater free radical scavenging activities compared to the deferiprone derivatives. Molecular dynamics simulations showed that the hydroxyquinoline-based compounds generally bound well within human dopamine transporter cavities. Thus, these compounds are excellent candidates for future exploration as drugs against diseases that are affected by iron-induced dopaminergic neuron damage, such as Parkinson's disease. [ABSTRACT FROM AUTHOR]

Hydrazones—consisting of a dynamic imine bond and an acidic NH proton—have recently emerged as versatile photoswitches underpinned by their ability to form thermally bistable isomers, (Z) and (E), respectively. Herein, we introduce two photoresponsive homopolymers containing structurally different hydrazones as main‐chain repeating units, synthesized via head‐to‐tail Acyclic Diene METathesis (ADMET) polymerization. Their key difference lies in the hydrazone design, specifically the location of the aliphatic arm connecting the rotor of the hydrazone photoswitch to the aliphatic polymer backbone. Critically, we demonstrate that their main photoresponsive property, i.e. their hydrodynamic volume, changes in opposite directions upon photoisomerization (λ=410 nm) in dilute solution. Further, the polymers—independent of the design of the individual hydrazone monomer—feature a photoswitchable glass transition temperature (Tg) by close to 10 °C. The herein established design strategy allows to photochemically manipulate macromolecular properties by simple structural changes. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A coarse-grain model of the epithelial plasma membrane was developed from high-resolution lipidomic data and simulated using the MARTINI force field to characterize its biophysical properties. Plasmalogen lipids, Forssman glycosphingolipids, and hydroxylated Forssman glycosphingolipids and sphingomyelin were systematically added to determine their structural effects. Plasmalogen lipids have a minimal effect on the overall biophysical properties of the epithelial plasma membrane. In line with the hypothesized role of Forssman lipids in the epithelial apical membrane, the introduction of Forssman lipids initiates the formation of glycosphingolipid-rich nanoscale lipid domains, which also include phosphatidylethanolamine (PE), sphingomyelin (SM), and cholesterol (CHOL). This decreases the lateral diffusion in the extracellular leaflet, as well as the area per lipid of domain forming lipids, most notably PE. Finally, hydroxylation of the Forssman glycosphingolipids and sphingomyelin further modulates the lateral organization of the membrane. Through comparison to the previously studied average and neuronal plasma membranes, the impact of membrane lipid composition on membrane properties was characterized. Overall, this study furthers our understanding of the biophysical properties of complex membranes and the impact of lipid diversity in modulating membrane properties. [ABSTRACT FROM AUTHOR]

We introduce a single‐chain nanoparticle (SCNP) system capable of catalyzing the photooxidation of nonpolar alkenes up to three times more efficiently than an equivalent small‐molecule photosensitizer at an identical concentration. Specifically, we construct a polymer chain constituted of poly(ethylene glycol) methyl ether methacrylate and glycidyl methacrylate which we compact via multifunctional thiol‐epoxide ligation and functionalize with Rose Bengal (RB) in a one pot reaction, affording SCNPs with a hydrophilic shell and hydrophobic photocatalytic regions. Photooxidation of the internal alkene in oleic acid proceeds under green light. RB confined within the SCNP is three times more effective for nonpolar alkenes than free RB in solution, which we hypothesize is due to the spatial proximity of the photosensitizing units to the substrate in the hydrophobic region. Our approach demonstrates that SCNP based catalysts can afford enhanced photocatalysis via confinement effects in a homogeneous reaction environment. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We report the synthesis of two [2]rotaxanes containing an interlocked three dimensional binding cavity formed from a pyridinium bis(amide) axle component containing two phenol donors, and an isophthalamide based macrocycle. In the competitive solvent mixture 1 : 1 CDCl3 : CD3OD, one of the receptors exhibits a much higher selectivity preference for chloride than an analogous rotaxane without the hydroxy groups. X‐ray crystal structures reveal the chloride anion guest encapsulated within the interlocked binding cavity, though not all of the hydrogen bond donors are utilised. Computational semi‐empirical simulations indicate that secondary intermolecular interactions occur between the axle hydroxy hydrogen bond donors and the [2]rotaxane macrocycle components, contributing to a more preorganised binding pocket, which may be responsible for the observed enhanced selectivity. [ABSTRACT FROM AUTHOR]

Glycine receptors (GlyRs) containing the α2 subunit govern cell fate, neuronal migration and synaptogenesis in the developing cortex and spinal cord. Rare missense variants and microdeletions in the X-linked GlyR α2 subunit gene (GLRA2) have been associated with human autism spectrum disorder (ASD), where they typically cause a loss-of-function via protein truncation, reduced cell-surface trafficking and/or reduced glycine sensitivity (e.g., GLRA2 Δex8-9 and extracellular domain variants p.N109S and p.R126Q). However, the GlyR α2 missense variant p.R323L in the intracellular M3-M4 domain results in a gain-of-function characterized by slower synaptic decay times, longer duration active periods and increases in channel conductance. This study reports the functional characterization of four missense variants in GLRA2 associated with ASD or developmental disorders (p.V-22L, p.N38K, p.K213E, p.T269M) using a combination of bioinformatics, molecular dynamics simulations, cellular models of GlyR trafficking and electrophysiology in artificial synapses. The GlyR α2V–22L variant resulted in altered predicted signal peptide cleavage and a reduction in cell-surface expression, suggestive of a partial loss-of-function. Similarly, GlyR α2N38K homomers showed reduced cell-surface expression, a reduced affinity for glycine and a reduced magnitude of IPSCs in artificial synapses. By contrast, GlyR α2K213E homomers showed a slight reduction in cell-surface expression, but IPSCs were larger, with faster rise/decay times, suggesting a gain-of-function. Lastly, GlyR α2T269M homomers exhibited a high glycine sensitivity accompanied by a substantial leak current, suggestive of an altered function that could dramatically enhance glycinergic signaling. These results may explain the heterogeneity of clinical phenotypes associated with GLRA2 mutations and reveal that missense variants can result in a loss, gain or alteration of GlyR α2 function. In turn, these GlyR α2 missense variants are likely to either negatively or positively deregulate cortical progenitor homeostasis and neuronal migration in the developing brain, leading to changes in cognition, learning, and memory. [ABSTRACT FROM AUTHOR]

There is a concerted attempt to develop self‐assembled metallo‐cages of greater structural complexity, and heteroleptic PdII cages are emerging as prime candidates in these efforts. Most of these are dinuclear: few examples of higher nuclearity have been reported. We demonstrate here a robust method for the formation of tripalladium(II) cages from the 2 : 3 : 3 combination of a tritopic ligand, PdII, and a selection of ditopic ligands of the correct size and geometry. [ABSTRACT FROM AUTHOR]

The proposition of a post-antimicrobial era is all the more realistic with the continued rise of antimicrobial resistance. The development of new antimicrobials is failing to counter the ever-increasing rates of bacterial antimicrobial resistance. This necessitates novel antimicrobials and drug targets. The bacterial cell membrane is an essential and highly conserved cellular component in bacteria and acts as the primary barrier for entry of antimicrobials into the cell. Although previously under-exploited as an antimicrobial target, the bacterial cell membrane is attractive for the development of novel antimicrobials due to its importance in pathogen viability. Bacterial cell membranes are diverse assemblies of macromolecules built around a central lipid bilayer core. This lipid bilayer governs the overall membrane biophysical properties and function of its membrane-embedded proteins. This mini-review will outline the mechanisms by which the bacterial membrane causes and controls resistance, with a focus on alterations in the membrane lipid composition, chemical modification of constituent lipids, and the efflux of antimicrobials by membrane-embedded efflux systems. Thorough insight into the interplay between membrane-active antimicrobials and lipid-mediated resistance is needed to enable the rational development of new antimicrobials. In particular, the union of computational approaches and experimental techniques for the development of innovative and efficacious membrane-active antimicrobials is explored. [ABSTRACT FROM AUTHOR]

Our current knowledge of the structural dynamics and complexity of lipid bilayers is still developing. Computational techniques, especially molecular dynamics simulations, have increased our understanding significantly as they allow us to model functions that cannot currently be experimentally resolved. Here we review available computational tools and techniques, the role of the major lipid species, insights gained into lipid bilayer structure and function from molecular dynamics simulations, and recent progress towards the computational modelling of the physiological complexity of eukaryotic lipid bilayers. Molecular dynamics simulations have increased our understanding of the complexity of the cell membrane from that of a simple lipid barrier to a dynamic system containing hundreds of lipid species. [ABSTRACT FROM AUTHOR]

The recruitment of inhibitory GABAA receptors to neuronal synapses requires a complex interplay between receptors, neuroligins, the scaffolding protein gephyrin and the GDP-GTP exchange factor collybistin (CB). Collybistin is regulated by protein-protein interactions at the N-terminal SH3 domain, which can bind neuroligins 2/4 and the GABAAR α2 subunit. Collybistin also harbors a RhoGEF domain which mediates interactions with gephyrin and catalyzes GDP-GTP exchange on Cdc42. Lastly, collybistin has a pleckstrin homology (PH) domain, which binds phosphoinositides, such as phosphatidylinositol 3-phosphate (PI3P/PtdIns3P) and phosphatidylinositol 4-monophosphate (PI4P/PtdIns4P). PI3P located in early/sorting endosomes has recently been shown to regulate the postsynaptic clustering of gephyrin and GABAA receptors and consequently the strength of inhibitory synapses in cultured hippocampal neurons. This process is disrupted by mutations in the collybistin gene (ARHGEF9), which cause X-linked intellectual disability (XLID) by a variety of mechanisms converging on disrupted gephyrin and GABAA receptor clustering at central synapses. Here we report a novel missense mutation (chrX:62875607C>T, p.R356Q) in ARHGEF9 that affects one of the two paired arginine residues in the PH domain that were predicted to be vital for binding phosphoinositides. Functional assays revealed that recombinant collybistin CB3SH3-R356Q was deficient in PI3P binding and was not able to translocate EGFP-gephyrin to submembrane microaggregates in an in vitro clustering assay. Expression of the PI3P-binding mutants CB3SH3-R356Q and CB3SH3-R356N/R357N in cultured hippocampal neurones revealed that the mutant proteins did not accumulate at inhibitory synapses, but instead resulted in a clear decrease in the overall number of synaptic gephyrin clusters compared to controls. Molecular dynamics simulations suggest that the p.R356Q substitution influences PI3P binding by altering the range of structural conformations adopted by collybistin. Taken together, these results suggest that the p.R356Q mutation in ARHGEF9 is the underlying cause of XLID in the probands, disrupting gephyrin clustering at inhibitory GABAergic synapses via loss of collybistin PH domain phosphoinositide binding. [ABSTRACT FROM AUTHOR]