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Abstract: Clupeine, a cationic antimicrobial peptide found in fish, is of interest as a food additive but non-specific binding of the peptide to anionic molecules reduces its antimicrobial activity. The overall positive charge of clupeine can be reduced by blocking 10% of its arginine residues with 1,2-cyclohexanedione (CHD). The modified peptide retains antimicrobial activity but it is not known if its effect on the structure of Gram-negative model membranes is the same as the native peptide. In the presented paper, neutron reflectometry (NR) and X-ray reflectometry were used to investigate the effect of native and modified clupeine on the structure of model monolayer membranes composed of Phosphatidylethanolamine (PE), Phosphatidylglycerol (PG), and Cardiolipin (CL). The effect of the peptides on the structure of 1,2-dipalmitoyl (d62)-sn-glycero-3-phosphocholine (DPPC)/PE:PG:CL bilayers were also examined by NR. In both model systems, modified clupeine demonstrated a greater effect on the lipid structure. Charge reduction in the modified sample also resulted in improved hydrophobicity, and the formation of thicker peptide layers in the membrane models. Some lipid translocation was observed in the inner tail region (∼69 ± 0.24% DPPC and ∼24 ± 0.02% PE:PG:CL); and in the outer tail region (∼24 ± 0.02% DPPC and ∼56 ± 0.01% PE:PG:CL). Improved hydrophobicity and electrostatic interactions with lipid head groups, strongly suggests that the modified clupeine may use the carpet mechanisms to exert its effect on model membranes. These findings suggest that changing the charge on the native peptide changes the way in which the modified peptide disrupts Gram-negative model membranes.

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Abstract: Excellent conversion efficiencies of over 20% and facile cell production have placed hybrid perovskites at the forefront of novel solar cell materials with CH3NH3PbI3 being its archetypal compound. The question why CH3NH3PbI3 has such extraordinary characteristics, particularly a very efficient power conversion from absorbed light to electrical power, is hotly debated with ferroelectricity being a promising candidate. This does, however, afford the crystal structure to be non‐centrosymmetric and we herein present crystallographic evidence as to how the symmetry breaking occurs on a crystallographic, and therefore long‐scale, level. While the molecular cation CH3NH3+ is intrinsically polar, it is heavily disordered and cannot be the sole reason for ferroelectricity. We show that it, nonetheless, plays an important role as it distorts the neighbouring iodide positions from their centrosymmetric positions.

Open Access

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Abstract: Incorporation of mesopores and active sites into metal-organic framework (MOF) materials to uncover new efficient catalysts is a highly desirable but challenging task. We report the first example of a mesoporous MOF obtained by templated electrosynthesis using an ionic liquid as both electrolyte and template. The mesoporous Cu(II)-MOF MFM-100 has been synthesised in 100 seconds at room temperature, and this material incorporates crystal defects with uncoupled Cu(II) centres as evidenced by confocal fluorescence microscopy and electron paramagnetic resonance spectroscopy. MFM-100 prepared in this way shows exceptional catalytic activity for the aerobic oxidation of alcohols to produce aldehydes in near quantitative yield and selectivity under mild conditions, as well as having excellent stability and reusability over repeated cycles. The catalyst-substrate binding interactions have been probed by inelastic neutron scattering. This study offers a simple strategy to create mesopores and active sites simultaneously via electrochemical formation of crystal defects to promote efficient catalysis using MOFs.

Open Access

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Abstract: Efficient sample delivery is an essential aspect of serial crystallography at both synchrotrons and X-ray free-electron lasers. Rastering fixed target chips through the X-ray beam is an efficient method for serial delivery from the perspectives of both sample consumption and beam time usage. Here, an approach for loading fixed targets using acoustic drop ejection is presented that does not compromise crystal quality, can reduce sample consumption by more than an order of magnitude and allows serial diffraction to be collected from a larger proportion of the crystals in the slurry.

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Abstract: Fluorinated non-fullerene acceptors (NFAs) usually have planar backbone and a higher tendency to crystallize compared to their non-fluorinated counterparts, which leads to enhanced charge mobility in organic solar cells (OSCs). However, this self-organization behavior may result in excessive phase separation with electron donors and thereby deteriorate device efficiency. Herein, we demonstrate an effective approach to tune the molecular organization of a fluorinated NFA (INPIC-4F), and its phase separation with the donor PBDB-T, by varying the casting solvent. A prolonged film drying time encourages the crystallization of INPIC-4F into spherulites and consequently results in excessive phase separation, leading to a low device power conversion efficiency (PCE) of 8.1%. Contrarily, a drying time leads to fine mixed domains with inefficient charge transport properties, resulting in a moderate device PCE of 11.4%. An intermediate film drying time results in the formation of face-on π-π stacked PBDB-T and INPIC-4F domains with continuous phase-separated networks, which facilitates light absorption, exciton dissociation as well as balanced charge transport towards the electrode, and achieves a remarkable PCE of 13.1%. This work provides a rational guide for optimizing the molecular ordering of NFAs and electron donors for high device efficiency.