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Instruments / Technical Area	Publication Details	Published
I03-Macromolecular Crystallography I04-1-Macromolecular Crystallography (fixed wavelength)	Structure of the imine reductase from Ajellomyces dermatitidis in three crystal forms Mahima Sharma , Anibal Cuetos , Adam Williamson , Daniel González-Martínez , Gideon Grogan Acta Crystallographica Section F Structural Biology Communications 79 DOI: 10.1107/S2053230X23006672 Diamond Proposal Number(s): [9948] Open Access Show Abstract ▼ Abstract: The NADPH-dependent imine reductase from Ajellomyces dermatitidis (AdRedAm) catalyzes the reductive amination of certain ketones with amine donors supplied in an equimolar ratio. The structure of AdRedAm has been determined in three forms. The first form, which belongs to space group P3121 and was refined to 2.01 Å resolution, features two molecules (one dimer) in the asymmetric unit in complex with the redox-inactive cofactor NADPH4. The second form, which belongs to space group C21 and was refined to 1.73 Å resolution, has nine molecules (four and a half dimers) in the asymmetric unit, each complexed with NADP+. The third form, which belongs to space group P3121 and was refined to 1.52 Å resolution, has one molecule (one half-dimer) in the asymmetric unit. This structure was again complexed with NADP+ and also with the substrate 2,2-difluoroacetophenone. The different data sets permit the analysis of AdRedAm in different conformational states and also reveal the molecular basis of stereoselectivity in the transformation of fluorinated acetophenone substrates by the enzyme.	Sep 2023
B18-Core EXAFS	Biogeochemical cycling of 99Tc in alkaline sediments Adam J. Williamson , Jonathan R. Lloyd , Christopher Boothman , Gareth T. W. Law , Samuel Shaw , Joe S. Small , Gianni F. Vettese , Heather A. Williams , Katherine Morris Environmental Science & Technology 14 DOI: 10.1021/acs.est.1c04416 Diamond Proposal Number(s): [7367, 7593] Show Abstract ▼ Abstract: 99Tc will be present in significant quantities in radioactive wastes including intermediate-level waste (ILW). The internationally favored concept for disposing of higher activity radioactive wastes including ILW is via deep geological disposal in an underground engineered facility located ∼200–1000 m deep. Typically, in the deep geological disposal environment, the subsurface will be saturated, cement will be used extensively as an engineering material, and iron will be ubiquitous. This means that understanding Tc biogeochemistry in high pH, cementitious environments is important to underpin safety case development. Here, alkaline sediment microcosms (pH 10) were incubated under anoxic conditions under “no added Fe(III)” and “with added Fe(III)” conditions (added as ferrihydrite) at three Tc concentrations (10–11, 10–6, and 10–4 mol L–1). In the 10–6 mol L–1 Tc experiments with no added Fe(III), ∼35% Tc(VII) removal occurred during bioreduction. Solvent extraction of the residual solution phase indicated that ∼75% of Tc was present as Tc(IV), potentially as colloids. In both biologically active and sterile control experiments with added Fe(III), Fe(II) formed during bioreduction and >90% Tc was removed from the solution, most likely due to abiotic reduction mediated by Fe(II). X-ray absorption spectroscopy (XAS) showed that in bioreduced sediments, Tc was present as hydrous TcO2-like phases, with some evidence for an Fe association. When reduced sediments with added Fe(III) were air oxidized, there was a significant loss of Fe(II) over 1 month (∼50%), yet this was coupled to only modest Tc remobilization (∼25%). Here, XAS analysis suggested that with air oxidation, partial incorporation of Tc(IV) into newly forming Fe oxyhydr(oxide) minerals may be occurring. These data suggest that in Fe-rich, alkaline environments, biologically mediated processes may limit Tc mobility.	Nov 2021
B18-Core EXAFS	Microbial reduction of U(VI) under alkaline conditions: implications for radioactive waste geodisposal Adam Williamson , Katherine Morris , Gareth Law , Athanasios Rizoulis , John Charnock , Jonathan R. Lloyd Environmental Science & Technology 48 (22), 13549 - 13556 DOI: 10.1021/es5017125 Diamond Proposal Number(s): [7367, 7593, 8070] Open Access Show Abstract ▼ Abstract: Although there is consensus that microorganisms significantly influence uranium speciation and mobility in the subsurface under circumneutral conditions, microbiologically mediated U(VI) redox cycling under alkaline conditions relevant to the geological disposal of cementitious intermediate level radioactive waste, remains unexplored. Here, we describe microcosm experiments that investigate the biogeochemical fate of U(VI) at pH 1010.5, using sediments from a legacy lime working site, stimulated with an added electron donor, and incubated in the presence and absence of added Fe(III) as ferrihydrite. In systems without added Fe(III), partial U(VI) reduction occurred, forming a U(IV)-bearing non-uraninite phase which underwent reoxidation in the presence of air (O2) and to some extent nitrate. By contrast, in the presence of added Fe(III), U(VI) was first removed from solution by sorption to the Fe(III) mineral, followed by bioreduction and (bio)magnetite formation coupled to formation of a complex U(IV)-bearing phase with uraninite present, which also underwent air (O2) and partial nitrate reoxidation. 16S rRNA gene pyrosequencing showed that Gram-positive bacteria affiliated with the Firmicutes and Bacteroidetes dominated in the post-reduction sediments. These data provide the first insights into uranium biogeochemistry at high pH and have significant implications for the long-term fate of uranium in geological disposal in both engineered barrier systems and the alkaline, chemically disturbed geosphere.	Nov 2014
B18-Core EXAFS	Geomicrobiology of cementitious nuclear waste Adam Williamson , Katherine Morris , Gareth Law , Sam Shaw , Chris Boothman , Jonathan Lloyd Migration 2013	Sep 2013
B18-Core EXAFS	Microbial reduction of U(VI) at alkaline pH relevant to geological disposal Adam Williamson , Katherine Morris , Gareth Law , Sam Shaw , Jonathan Lloyd Goldschmidt 2012 Show Abstract ▼ Abstract: The UK’s intermediate level radioactive wastes (ILW) will be disposed of in a deep geological disposal facility (GDF) [1]. Here, one likely scenario for disposal in the UK GDF is mixing ILW with cement, grouting into stainless steel canisters followed by further backfilling with cement. Post-closure, re-saturation of the cementitious GDF over time will form a hyperalkaline chemically disturbed zone (CDZ) within the host rock. Microbial processes, especially Fe(III) reduction, may immobilise redox active radioactive contaminants in the waste either through direct enzymatic reduction or via interactions with biogenic Fe(II) [2]. Here, we explore the extent of microbiologically- mediated U(VI) reduction under GDF relevant alkaline conditions. Microcosms were set up using sediments taken from legacy lime works, adjusted to pH 10, augmented with electron donor (organic acids with yeast extract) and systems were run with and without added Fe(III) oxyhydroxides. Systems were established with lower (20 ppm) and higher (100 ppm) concentrations of UO22+ and allowed to progress through a series of redox processes, potentially including metal reduction, and to assess sorption of U(VI), uranium biotransformations and to prepare samples for XAS analysis. A cascade of microbial redox processes occurred at high pH in all microbially active systems with U(VI)-removal occurring in sediments with and without added Fe(III) oxyhydroxides. In Fe(III) augmented systems, which displayed high levels of Fe(III)-reduction, magnetite was the dominant Fe(II) bearing bio-mineral product. XANES analyses of all microbially active sediment end-members confirmed reduction of U(VI) to U(IV). Interestingly, controls using pre-reduced, autoclaved sediments showed no sign of U(VI) reduction, suggesting that U(VI) reduction in these systems is predominantly enzymatic. Overall, these results show that microbial metal reduction can occur in a high pH environment analogous to that of an evolved GDF and demonstrates the reductive removal of U(VI) from solution in such systems is likely mediated by direct enzymatic processes.	Jun 2012
B18-Core EXAFS	Microbial transformation of radionuclides - the radionuclide biomineral interface Katherine Morris , Diana Brookshaw , Victoria Evans , Clare Thorpe , Adam Williamson , Gareth Law , Athanasios Rizoulis , Francis Livens , Jon Lloyd Goldshmidt 2012	Jun 2012

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