Publications

With the aim of developing photostable near-infrared cell imaging probes, a convenient route to the synthesis of heteroleptic OsII complexes containing the Os(TAP)2 fragment is reported. This method was used to synthesize the dinuclear OsII complex, [{Os(TAP)2}2tpphz]4+ (where tpphz = tetrapyrido[3,2-a:2′,3′-c:3″,2′′-h:2‴,3′′′-j]phenazine and TAP = 1,4,5,8- tetraazaphenanthrene). Using a combination of resonance Raman and time-resolved absorption spectroscopy, as well as computational studies, the excited state dynamics of the new complex were dissected. These studies revealed that, although the complex has several close lying excited states, its near-infrared, NIR, emission (λmax = 780 nm) is due to a low-lying Os → TAP based 3MCLT state. Cell-based studies revealed that unlike its RuII analogue, the new complex is neither cytotoxic nor photocytotoxic. However, as it is highly photostable as well as live-cell permeant and displays NIR luminescence within the biological optical window, its properties make it an ideal probe for optical microscopy, demonstrated by its use as a super-resolution NIR STED probe for nuclear DNA.

The first demonstration of laser action in ruby was made in 1960 by T. H. Maiman of Hughes Research Laboratories, USA. Many laboratories worldwide began the search for lasers using different materials, operating at different wavelengths. In the UK, academia, industry and the central laboratories took up the challenge from the earliest days to develop these systems for a broad range of applications. This historical review looks at the contribution the UK has made to the advancement of the technology, the development of systems and components and their exploitation over the last 60 years.

Rechargeable Mg/S batteries have the potential to provide a compelling battery for a range of applications owing to their high capacity and gravimetric energy density, safety, and low-cost construction. However, the Mg/S energy storage is not widely developed and deployed due to technical challenges, which include short cycle lifespan and lack of suitable electrolyte. To study the microstructure degradation of Mg/S batteries, multiscale X-ray tomography, an inherently nondestructive method, is performed on dismantled Swagelok Mg/S cells comprising a graphene–sulfur cathode and a super-P separator. For the first time, 3D microstructure visualization and quantification reveal the dissolution (volume fraction decreases from 13.5% to 0.7%, surface area reduces from 2.91 to 1.74 µm2 µm−3) and agglomeration of sulfur particles, and the carbon binder densification after 10 cycles. Using tomography data, the image-based simulations are then performed. The results show that the insoluble polysulfides can inevitably block the Mg2+ transportation via shuttle effect. The representative volume should exceed 8200 µm3 to represent bulk cathode. This work elucidates that the Mg/S cell performance is significantly affected by microstructural degradation, and moreover demonstrates how multiscale and multimodal characterization can play an indispensable role in developing and optimizing the Mg/S electrode design.

Nature employs high-energy metal-oxo intermediates embedded within enzyme active sites to perform challenging oxidative transformations with remarkable selectivity. Understanding how different local metal-oxo coordination environments control intermediate reactivity and catalytic function is a long-standing objective. However, conducting structure–activity relationships directly in active sites has proven challenging due to the limited range of amino acid substitutions achievable within the constraints of the genetic code. Here, we use an expanded genetic code to examine the impact of hydrogen bonding interactions on ferryl heme structure and reactivity, by replacing the N–H group of the active site Trp51 of cytochrome c peroxidase by an S atom. Removal of a single hydrogen bond stabilizes the porphyrin π-cation radical state of CcP W191F compound I. In contrast, this modification leads to more basic and reactive neutral ferryl heme states, as found in CcP W191F compound II and the wild-type ferryl heme-Trp191 radical pair of compound I. This increased reactivity manifests in a >60-fold activity increase toward phenolic substrates but remarkably has negligible effects on oxidation of the biological redox partner cytc. Our data highlight how Trp51 tunes the lifetimes of key ferryl intermediates and works in synergy with the redox active Trp191 and a well-defined substrate binding site to regulate catalytic function. More broadly, this work shows how noncanonical substitutions can advance our understanding of active site features governing metal-oxo structure and reactivity.

A polymer electrolyte fuel cell (PEFC) has been designed to allow operando X-ray
absorption spectroscopy (XAS) measurements of catalysts. The cell has been developed to
operate under standard fuel cell conditions, with elevated temperatures and humidification of
the gas-phase reactants, both of which greatly impact the catalyst utilisation. X-ray windows
in the endplates of the cell facilitate collection of XAS spectra during fuel cell operation
while maintaining good compression in the area of measurement. Results of polarisation
curves and cyclic voltammograms (CVs) showed that the operando cell performs well as a
fuel cell, while also providing XAS data of suitable quality for robust XANES analysis. The
cell has produced comparable XAS results when performing a cyclic voltammogram to an
established in situ cell when measuring the Pt LIII edge. Similar trends of Pt oxidation, and
reduction of the formed Pt oxide, have been presented with a time resolution of 5 seconds for
each spectrum, paving the way for time-resolved spectral measurements of fuel cell catalysts
in a fully-operating fuel cell

SARS-CoV-2 remains a global threat to human health particularly as escape mutants emerge. There is an unmet need for effective treatments against COVID-19 for which neutralizing single domain antibodies (nanobodies) have significant potential. Their small size and stability mean that nanobodies are compatible with respiratory administration. We report four nanobodies (C5, H3, C1, F2) engineered as homotrimers with pmolar affinity for the receptor binding domain (RBD) of the SARS-CoV-2 spike protein. Crystal structures show C5 and H3 overlap the ACE2 epitope, whilst C1 and F2 bind to a different epitope. Cryo Electron Microscopy shows C5 binding results in an all down arrangement of the Spike protein. C1, H3 and C5 all neutralize the Victoria strain, and the highly transmissible Alpha (B.1.1.7 first identified in Kent, UK) strain and C1 also neutralizes the Beta (B.1.35, first identified in South Africa). Administration of C5-trimer via the respiratory route showed potent therapeutic efficacy in the Syrian hamster model of COVID-19 and separately, effective prophylaxis. The molecule was similarly potent by intraperitoneal injection.

In this work we use high-resolution synchrotron X-ray diffraction for electron density mapping, in conjunction with ab initio modelling, to study short O—H⋯O and O+—H⋯O− hydrogen bonds whose behaviour is known to be tuneable by temperature. The short hydrogen bonds have donor–acceptor distances in the region of 2.45 Å and are formed in substituted urea and organic acid molecular complexes of N,N′-dimethylurea oxalic acid 2[thin space (1/6-em)]:[thin space (1/6-em)]1 (1), N,N-dimethylurea 2,4-dinitrobenzoate 1[thin space (1/6-em)]:[thin space (1/6-em)]1 (2) and N,N-dimethylurea 3,5-dinitrobenzoic acid 2[thin space (1/6-em)]:[thin space (1/6-em)]2 (3). From the combined analyses, these complexes are found to fall within the salt-cocrystal continuum and exhibit short hydrogen bonds that can be characterised as both strong and electrostatic (1, 3) or very strong with a significant covalent contribution (2). An additional charge assisted component is found to be important in distinguishing the relatively uncommon O—H⋯O pseudo-covalent interaction from a typical strong hydrogen bond. The electron density is found to be sensitive to the extent of static proton transfer, presenting it as a useful parameter in the study of the salt–cocrystal continuum. From complementary calculated hydrogen atom potentials, we attribute changes in proton position to the molecular environment. Calculated potentials also show zero barrier to proton migration, forming an ‘energy slide’ between the donor and acceptor atoms. The better fundamental understanding of the short hydrogen bond in the ‘zone of fluctuation’ presented in a salt-cocrystal continuum, enabled by studies like this, provide greater insight into their related properties and can have implications in the regulation of pharmaceutical materials.

Globally, water disinfection is reliant on chlorination, but requires a route that avoids the formation of chemical residues. Hydrogen peroxide, a broad-spectrum biocide, can offer such an alternative, but is typically less effective than traditional approaches to water remediation. Here, we show that the reactive oxygen species—which include hydroxyl, hydroperoxyl and superoxide radicals—formed over a AuPd catalyst during the synthesis of hydrogen peroxide from hydrogen and air are over 107 times more potent than an equivalent amount of preformed hydrogen peroxide and over 108 times more effective than chlorination under equivalent conditions. The key to bactericidal and virucidal efficacy is the radical flux that forms when hydrogen and oxygen are activated on the catalyst. This approach could form the basis of an alternative method for water disinfection, particularly in communities not currently served by traditional means of water remediation or where access to potable water is scarce.

Developing suitable electrolytes with high oxidation decomposition potential, low cost, and good compatibility with electrode materials has been a critical challenge in realizing practical magnesium batteries. The emerging magnesium aluminum chloride complex (MACC) electrolytes based on inorganic chloride salts exhibit high Coulombic efficiencies for magnesium batteries. This review summarizes recent studies of MACC electrolytes, focusing on the synthesis, characterization, and chemical environment of Mg species, electrolytic conditioning of electrolytes, and their application in typical magnesium batteries. The electrolyte evolution and influencing factor of electrolytic conditioning are discussed, and several kinds of conditioning-free MACC electrolytes are further introduced. Finally, future trends and perspectives in this field are discussed.