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Instruments / Technical Area	Publication Details	Published
I11-High Resolution Powder Diffraction	Crystallisation studies of sodium acetate trihydrate – suppression of incongruent melting and sub-cooling to produce a reliable, high-performance phase-change material David E. Oliver , Andrew J. Bissell , Xiaojiao Liu , Chiu C. Tang , Colin Pulham Crystengcomm 2 DOI: 10.1039/D0CE01454K Diamond Proposal Number(s): [2060] Open Access Show Abstract ▼ Abstract: This study has identified two polymer additives that when added in low concentrations can be used to reliably prevent incongruent melting of sodium acetate trihydrate (SAT) when temperature-cycled over multiple thousands of melting and freezing cycles. The polymers appear to act as crystal-habit modifiers that at sub-optimal concentrations dramatically alter the morphology of any anhydrous sodium acetate that may be formed, and at higher concentrations completely suppress precipitation of anhydrous sodium acetate. In situ X-ray powder diffraction experiments show that the active nucleator for SAT is Na2HPO4·2H2O, and that the mechanism of thermally induced deactivation is dehydration in solution to form anhydrous Na2HPO4. Based on these studies, new formulations of SAT have been developed that demonstrate consistent and reliable performance as phase-change materials for heat-storage applications.	Dec 2020
I15-Extreme Conditions	Experimental and simulation study of the high-pressure behavior of squalane and poly-α-olefins Iain J. Prentice , Xiaojiao Liu , Oleg A. Nerushev , Sashi Balakrishnan , Colin Pulham , Philip J. Camp The Journal Of Chemical Physics 152 DOI: 10.1063/1.5139723 Diamond Proposal Number(s): [193351] Show Abstract ▼ Abstract: The equation of state, dynamical properties, and molecular-scale structure of squalane and mixtures of poly-α-olefins at room temperature are studied with a combination of state-of-the-art, high-pressure experiments and molecular-dynamics simulations. Diamond-anvil cell experiments indicate that both materials are non-hydrostatic media at pressures above ∼1 GPa. The equation of state does not exhibit any sign of a first-order phase transition. High-pressure x-ray diffraction experiments on squalane show that there are no Bragg peaks, and hence, the apparent solidification occurs without crystallization. These observations are complemented by a survey of the equation of state and dynamical properties using simulations. The results show that molecular diffusion is essentially arrested above about 1 GPa, which supports the hypothesis that the samples are kinetically trapped in metastable amorphous-solid states. The shear viscosity becomes extremely large at very high pressures, and the coefficient governing its increase from ambient pressure is in good agreement with the available literature data. Finally, simulated radial distribution functions are used to explore the evolution of the molecular-scale structure with increasing pressure. Subtle changes in the short-range real-space correlations are related to a collapse of the molecular conformations with increasing pressure, while the evolution of the static structure factor shows excellent correlation with the available x-ray diffraction data. These results are of indirect relevance to oil-based lubricants, as the pressures involved are comparable to those found in engines, and hence, the ability of lubricating thin films to act as load-bearing media can be linked to the solidification phenomena studied in this work.	Feb 2020
Krios I-Titan Krios I at Diamond	Structural basis of transcription inhibition by the DNA mimic protein Ocr of bacteriophage T7 Fuzhou Ye , Ioly Kotta-Loizou , Milija Jovanovic , Xiaojiao Liu , David T. F. Dryden , Martin Buck , Xiaodong Zhang Elife 9 DOI: 10.7554/eLife.52125 Diamond Proposal Number(s): [14769] Open Access Show Abstract ▼ Abstract: Bacteriophage T7 infects Escherichia coli and evades the host restriction/modification system. The Ocr protein of T7 was shown to exist as a dimer mimicking DNA and to bind to host restriction enzymes, thus preventing the degradation of the viral genome by the host. Here we report that Ocr can also inhibit host transcription by directly binding to bacterial RNA polymerase (RNAP) and competing with the recruitment of RNAP by sigma factors. Using cryo electron microscopy, we determined the structures of Ocr bound to RNAP. The structures show that an Ocr dimer binds to RNAP in the cleft, where key regions of sigma bind and where DNA resides during transcription synthesis, thus providing a structural basis for the transcription inhibition. Our results reveal the versatility of Ocr in interfering with host systems and suggest possible strategies that could be exploited in adopting DNA mimicry as a basis for forming novel antibiotics.	Feb 2020
I11-High Resolution Powder Diffraction	Influence of crystal packing on the mechanism of decomposition of the acetonitrile-solvated co-crystal of piroxicam and succinic acid Xiaojiao Liu , Chiu C. Tang , Elena V. Boldyreva , Colin R. Pulham Crystal Growth & Design DOI: 10.1021/acs.cgd.9b01189 Diamond Proposal Number(s): [20626] Show Abstract ▼ Abstract: Variable-temperature single-crystal and powder X-ray diffraction techniques have been used to study the thermal and mechanical decomposition of the acetonitrile solvate of the co-crystal formed between piroxicam and succinic acid (PRXSA-ACN). The results show that the thermal expansion behavior of PRXSA-ACN is highly anisotropic and can be correlated with structural features of the crystal lattice. Thermally-induced desolvation of PRXSA-ACN led initially to the formation of the α-form of piroxicam and the 1:1 piroxicam:succinic acid co-crystal (PRXSA), and this can be rationalized on the basis of the crystal structure of PRXSA-ACN and its thermal expansion behavior. Subsequent decomposition of PRXSA produced amorphous succinic acid and the thermodynamically more stable β-form of piroxicam. The α- and β-forms co-existed up until the melting point of the α-form, at which point the sample recrystallized to give the β-form of piroxicam. Mechanical treatment (light grinding) of PRXSA-ACN resulted in mild structural damage to the crystal structure and this led to subsequent desolvation.	Nov 2019

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