Computational modelling of solvent effects in a prolific solvatomorphic porous organic cage

Crystal structure prediction methods can enable the in silico design of functional molecular crystals, but solvent effects can have a major influence on relative lattice energies, sometimes thwarting predictions. This is particularly true for porous solids, where solvent included in the pores can have an important energetic contribution. We present a Monte Carlo solvent insertion procedure for predicting the solvent filling of porous structures from crystal structure prediction landscapes, tested using a highly solvatomorphic porous organic cage molecule, CC1. Using this method, we can understand why the predicted global energy minimum structure for CC1 is never observed from solvent crystallisation. We also explain the formation of three different solvatomorphs of CC1 from three structurally-similar chlorinated solvents. Calculated solvent stabilisation energies are found to correlate with experimental results from thermogravimetric analysis, suggesting a future computational framework for a priori materials design that factors in solvation effects.

Interference of the T Cell and Antigen-Presenting Cell Costimulatory Pathway Using CTLA4-Ig (Abatacept) Prevents Staphylococcal Enterotoxin B Pathology

Staphylococcal enterotoxin B (SEB) is a bacterial superantigen that binds the receptors in the APC/T cell synapse and causes increased proliferation of T cells and a cytokine storm syndrome in vivo. Exposure to the toxin can be lethal and cause significant pathology in humans. The lack of effective therapies for SEB exposure remains an area of concern, particularly in scenarios of acute mass casualties. We hypothesized that blockade of the T cell costimulatory signal by the CTLA4-Ig synthetic protein (abatacept) could prevent SEB-dependent pathology. In this article, we demonstrate mice treated with a single dose of abatacept 8 h post SEB exposure had reduced pathology compared with control SEB-exposed mice. SEB-exposed mice showed significant reductions in body weight between days 4 and 9, whereas mice exposed to SEB and also treated with abatacept showed no weight loss for the duration of the study, suggesting therapeutic mitigation of SEB-induced morbidity. Histopathology and magnetic resonance imaging demonstrated that SEB mediated lung damage and edema, which were absent after treatment with abatacept. Analysis of plasma and lung tissues from SEB-exposed mice treated with abatacept demonstrated significantly lower levels of IL-6 and IFN-γ (p < 0.0001), which is likely to have resulted in less pathology. In addition, exposure of human and mouse PBMCs to SEB in vitro showed a significant reduction in levels of IL-2 (p < 0.0001) after treatment with abatacept, indicating that T cell proliferation is the main target for intervention. Our findings demonstrate that abatacept is a robust and potentially credible drug to prevent toxic effects from SEB exposure.

Potency of irritation by benzylidenemalononitriles in humans correlates with TRPA1 ion channel activation

We show that the physiological activity of solid aerosolized benzylidenemalononitriles (BMNs) including 'tear gas' (CS) in historic human volunteer trials correlates with activation of the human transient receptor potential ankyrin 1 ion channel (hTRPA1). This suggests that the irritation caused by the most potent of these compounds results from activation of this channel. We prepared 50 BMNs and measured their hTRPA1 agonist potencies. A mechanism of action consistent with their physiological activity, involving their dissolution in water on contaminated body surfaces, cell membrane penetration and reversible thiolation by a cysteine residue of hTRPA1, supported by data from nuclear magnetic resonance experiments with a model thiol, explains the structure-activity relationships. The correlation provides evidence that hTRPA1 is a receptor for irritants on nociceptive neurons involved in pain perception; thus, its activation in the eye, nose, mouth and skin would explain the symptoms of lachrymation, sneezing, coughing and stinging, respectively. The structure-activity results and the use of the BMNs as pharmacological tools in future by other researchers may contribute to a better understanding of the TRPA1 channel in humans (and other animals) and help facilitate the discovery of treatments for human diseases involving this receptor.

On crystal versus fiber formation in dipeptide hydrogelator systems

Naphthalene dipeptides have been shown to be useful low-molecular-weight gelators. Here we have used a library to explore the relationship between the dipeptide sequence and the hydrogelation efficiency. A number of the naphthalene dipeptides are crystallizable from water, enabling us to investigate the comparison between the gel/fiber phase and the crystal phase. We succeeded in crystallizing one example directly from the gel phase. Using X-ray crystallography, molecular modeling, and X-ray fiber diffraction, we show that the molecular packing of this crystal structure differs from the structure of the gel/fiber phase. Although the crystal structures may provide important insights into stabilizing interactions, our analysis indicates a rearrangement of structural packing within the fibers. These observations are consistent with the fibrillar interactions and interatomic separations promoting 1D assembly whereas in the crystals the peptides are aligned along multiple axes, allowing 3D growth. This observation has an impact on the use of crystal structures to determine supramolecular synthons for gelators.

A homochiral three-dimensional zinc aspartate framework that displays multiple coordination modes and geometries

A homochiral three-dimensional zinc aspartate has been synthesised via reflux and solvothermal methods, which due to the coordinative flexibility of zinc displays three distinct coordination geometries and three coordination modes of aspartic acid to zinc.

Porous organic cages

Porous materials are important in a wide range of applications including molecular separations and catalysis. We demonstrate that covalently bonded organic cages can assemble into crystalline microporous materials. The porosity is prefabricated and intrinsic to the molecular cage structure, as opposed to being formed by non-covalent self-assembly of non-porous sub-units. The three-dimensional connectivity between the cage windows is controlled by varying the chemical functionality such that either non-porous or permanently porous assemblies can be produced. Surface areas and gas uptakes for the latter exceed comparable molecular solids. One of the cages can be converted by recrystallization to produce either porous or non-porous polymorphs with apparent Brunauer-Emmett-Teller surface areas of 550 and 23 m2 g(-1), respectively. These results suggest design principles for responsive porous organic solids and for the modular construction of extended materials from prefabricated molecular pores.