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781 items found (0 items not approved), displaying 11 to 20.[First/Prev] 1, 2, 3, 4, 5, 6, 7, 8 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I03-Macromolecular Crystallography	Engineering mutually orthogonal PylRS/tRNA pairs for dual encoding of functional histidine analogues Christopher J. Taylor , Florence J. Hardy , Ashleigh J. Burke , Riley M. Bednar , Ryan A. Mehl , Anthony P. Green , Sarah L. Lovelock Protein Science DOI: 10.1002/pro.4640 Diamond Proposal Number(s): [12788] Open Access Show Abstract ▼ Abstract: The availability of an expanded genetic code opens exciting new opportunities in enzyme design and engineering. In this regard histidine analogues have proven particularly versatile, serving as ligands to augment metalloenzyme function and as catalytic nucleophiles in designed enzymes. The ability to genetically encode multiple functional residues could greatly expand the range of chemistry accessible within enzyme active sites. Here we develop mutually orthogonal translation components to selectively encode two structurally similar histidine analogues. Transplanting known mutations from a promiscuous Methanosarcina mazei pyrrolysyl-tRNA synthetase (MmPylRSIFGFF) into a single domain PylRS from Methanomethylophilus alvus (MaPylRSIFGFF) provided a variant with improved efficiency and specificity for 3-methyl-L-histidine (MeHis) incorporation. The MaPylRSIFGFF clone was further characterized using in vitro biochemical assays and X-ray crystallography. We subsequently engineered the orthogonal MmPylRS for activity and selectivity for 3-(3-pyridyl)-L-alanine (3-Pyr), which was used in combination with MaPylRSIFGFF to produce proteins containing both 3-Pyr and MeHis. Given the versatile roles played by histidine in enzyme mechanisms, we anticipate that the tools developed within this study will underpin the development of enzymes with new and enhanced functions.	Apr 2023
I07-Surface & interface diffraction	Suspended phospholipid bilayers: A new biological membrane mimetic Sophie E. Ayscough , Luke A. Clifton , Maximilian W. A. Skoda , Simon Titmuss Journal Of Colloid And Interface Science 633, 1002 - 1011 DOI: 10.1016/j.jcis.2022.11.148 Diamond Proposal Number(s): [22995] Open Access Show Abstract ▼ Abstract: Hypothesis: The attractive interaction between a cationic surfactant monolayer at the air–water interface and vesicles, incorporating anionic lipids, is sufficient to drive the adsorption and deformation of the vesicles. Osmotic rupture of the vesicles produces a continuous lipid bilayer beneath the monolayer. Experimental: Specular neutron reflectivity has been measured from the surface of a purpose-built laminar flow trough, which allows for rapid adsorption of vesicles, the changes in salt concentration required for osmotic rupture of the adsorbed vesicles into a bilayer, and for neutron contrast variation of the sub-phase without disturbing the monolayer. Findings: The neutron reflectivity profiles measured after vesicle addition are consistent with the adsorption and flattening of the vesicles beneath the monolayer. An increase in the buffer salt concentration results in further flattening and fusion of the adsorbed vesicles, which are ruptured by a subsequent decrease in the salt concentration. This process results in a continuous, high coverage, bilayer suspended 11 Å beneath the monolayer. As the bilayer is not constrained by a solid substrate, this new mimetic is well-suited to studying the structure of lipid bilayers that include transmembrane proteins.	Mar 2023
Krios II-Titan Krios II at Diamond	Diverse cytomotive actins and tubulins share a polymerization switch mechanism conferring robust dynamics James Wagstaff , Vicente J. Planelles-Herrero , Grigory Sharov , Aisha Alnami , Frank Kozielski , Emmanuel Derivery , Jan Lowe Science Advances 9 DOI: 10.1126/sciadv.adf3021 Diamond Proposal Number(s): [23268] Open Access Show Abstract ▼ Abstract: Protein filaments are used in myriads of ways to organize other molecules within cells. Some filament-forming proteins couple the hydrolysis of nucleotides to their polymerization cycle, thus powering the movement of other molecules. These filaments are termed cytomotive. Only members of the actin and tubulin protein superfamilies are known to form cytomotive filaments. We examined the basis of cytomotivity via structural studies of the polymerization cycles of actin and tubulin homologs from across the tree of life. We analyzed published data and performed structural experiments designed to disentangle functional components of these complex filament systems. Our analysis demonstrates the existence of shared subunit polymerization switches among both cytomotive actins and tubulins, i.e., the conformation of subunits switches upon assembly into filaments. These cytomotive switches can explain filament robustness, by enabling the coupling of kinetic and structural polarities required for cytomotive behaviors and by ensuring that single cytomotive filaments do not fall apart.	Mar 2023
	Low-rank flat-field correction for artifact reduction in spectral computed tomography Katrine Ottesen Bangsgaard , Genoveva Burca , Evelina Ametova , Martin Skovgaard Andersen , Jakob Sauer Jørgensen Applied Mathematics In Science And Engineering 31 DOI: 10.1080/27690911.2023.2176000 Open Access Show Abstract ▼ Abstract: Spectral computed tomography has received considerable interest in recent years since spectral measurements contain much richer information about the object of interest. In spectral computed tomography, we are interested in the energy channel-wise reconstructions of the object. However, such reconstructions suffer from a low signal-to-noise ratio and share the challenges of conventional low-dose computed tomography such as ring artifacts. Ring artifacts arise from errors in the flat fields and can significantly degrade the quality of the reconstruction. We propose an extended flat-field model that exploits high correlation in the spectral flat fields to reduce ring artifacts in channel-wise reconstructions. The extended model relies on the assumption that the spectral flat fields can be well-approximated by a low-rank matrix. Our proposed model works directly on the spectral flat fields and can be combined with any existing reconstruction model, e.g. filtered back projection and iterative methods. The proposed model is validated on a neutron data set. The results show that our method successfully diminishes ring artifacts and improves the quality of the reconstructions. Moreover, the results indicate that our method is robust; it only needs a single spectral flat-field image, whereas existing methods need multiple spectral flat-field images to reach a similar level of ring reduction.	Mar 2023
I03-Macromolecular Crystallography I24-Microfocus Macromolecular Crystallography	Structural basis of the inhibition of cystathionine γ‐lyase from Toxoplasma gondii by propargylglycine and cysteine Carmen Fernández-Rodríguez , Carolina Conter , Iker Oyenarte , Filippo Favretto , Iban Quintana , Maria Luz Martinez-Chantar , Alessandra Astegno , Luis Alfonso Martinez-Cruz Protein Science DOI: 10.1002/pro.4619 Diamond Proposal Number(s): [28360] Show Abstract ▼ Abstract: Cystathionine γ-lyase (CGL) is a PLP-dependent enzyme that catalyzes the last step of the reverse transsulfuration route for endogenous cysteine biosynthesis. The canonical CGL-catalyzed process consists of an α,γ-elimination reaction that breaks down cystathionine into cysteine, α-ketobutyrate, and ammonia. In some species, the enzyme can alternatively use cysteine as a substrate, resulting in the production of hydrogen sulfide (H2S). Importantly, inhibition of the enzyme and consequently of its H2S production activity, makes multiresistant bacteria considerably more susceptible to antibiotics. Other organisms, such as Toxoplasma gondii, the causative agent of toxoplasmosis, encode a CGL enzyme (TgCGL) that almost exclusively catalyzes the canonical process, with only minor reactivity to cysteine. Interestingly, the substitution of N360 by a serine (the equivalent amino acid residue in the human enzyme) at the active site changes the specificity of TgCGL for the catalysis of cystathionine, resulting in an enzyme that can cleave both the CγS and the CβS bond of cystathionine. Based on these findings and to deepen the molecular basis underlying the enzyme-substrate specificity, we have elucidated the crystal structures of native TgCGL and the variant TgCGL-N360S from crystals grown in the presence of cystathionine, cysteine, and the inhibitor D,L-propargylglycine (PPG). Our structures reveal the binding mode of each molecule within the catalytic cavity and help explain the inhibitory behavior of cysteine and PPG. A specific inhibitory mechanism of TgCGL by PPG is proposed.	Mar 2023
I15-Extreme Conditions	Relating microstructure to magnetocaloric properties in RE36Tb20Co20Al24 (RE = Gd, Dy or Ho) high-entropy metallic-glass microwires designed by binary eutectic clusters method Hangboce Yin , Jun-Qiang Wang , Yongjiang Huang , Hongxian Shen , Shu Guo , Hongbo Fan , Juntao Huo , Jianfei Sun Journal Of Materials Science & Technology 92 DOI: 10.1016/j.jmst.2022.12.008 Diamond Proposal Number(s): [17412] Show Abstract ▼ Abstract: The new high-entropy metallic glasses (HE-MGs) are designed by using Dy and Ho to replace Gd in Gd36Tb20Co20Al24 alloy based on the binary eutectic clusters method. Compared with the equiatomic Gd25Tb25Co25Al25 HE-MG, the non-equiatomic RE36Tb20Co20Al24 (RE = Gd, Dy, or Ho) alloys show better glass-forming ability, which is attributed to the deep binary eutectic compositions used for alloy design. All RE36Tb20Co20Al24 alloys undergo second-order magnetic transition. An extreme peak value of magnetic entropy change is obtained as 10.3 J kg–1 K–1 (5 T) for the Ho36Tb20Co20Al24 alloy. In-situ high-energy synchrotron X-ray diffraction was conducted to observe the microstructural difference among non-equiatomic samples at cryogenic temperatures. The results indicate that Gd36Tb20Co20Al24 alloy possesses a relatively large average value of the dispersion of local clusters at a low-temperature range. This, combined with the critical exponent β close to 0.5 of Gd36Tb20Co20Al24 alloy, leads to its widest working temperature span among non-equiatomic samples. This work successfully establishes the connection between microstructure and magnetocaloric properties of HE-MGs, which is beneficial for understanding the physical mechanism of the magnetocaloric behaviors of HE-MGs.	Feb 2023
I18-Microfocus Spectroscopy	Observational constraints on the process and products of Martian serpentinization Benjamin M. Tutolo , Nicholas J. Tosca Science Advances 9 DOI: 10.1126/sciadv.add8472 Diamond Proposal Number(s): [15947] Open Access Show Abstract ▼ Abstract: The alteration of olivine-rich rocks to serpentine minerals, (hydr)oxides, and aqueous hydrogen through serpentinization is long thought to have influenced the distribution of habitable environments on early Mars and the evolution of the early Martian hydrosphere and atmosphere. Nevertheless, the planetary importance of Martian serpentinization has remained a matter of debate. To constrain the process and products of Martian serpentinization, we studied serpentinized iron-rich olivines from the 1.1-billion-year Duluth Complex. These data indicate that serpentinized iron-rich olivine would have been accompanied by a fivefold increase in hydrogen production relative to serpentinized terrestrial mantle peridotites. In contrast to previous expectations, this style of serpentinization yields hisingerite as the dominant iron serpentine mineral at comparatively low temperature and pH, consistent with meteorite mineralogy and in situ rover data. The widespread occurrence of oxidized iron-bearing phyllosilicates in highly magnetized regions of the Martian crust supports the hypothesis that serpentinization was more pervasive on early Mars than currently estimated.	Feb 2023
	Torsion angles to map and visualize the conformational space of a protein Helen M. Ginn Protein Science DOI: 10.1002/pro.4608 Open Access Show Abstract ▼ Abstract: Present understanding of protein structure dynamics trails behind that of static structures. A torsion-angle based approach, called representation of protein entities (RoPE), derives an interpretable conformational space which correlates with data collection temperature, resolution and reaction coordinate. For more complex systems, atomic coordinates fail to separate functional conformational states, which are still preserved by torsion angle-derived space. This indicates that torsion angles are often a more sensitive and biologically relevant descriptor for protein conformational dynamics than atomic coordinates.	Feb 2023
I12-JEEP: Joint Engineering, Environmental and Processing	A well-preserved ‘placoderm’ (stem-group Gnathostomata) upper jaw from the Early Devonian of Mongolia clarifies jaw evolution Martin D. Brazeau , Haobo Yuan , Sam Giles , Anna L. Jerve , Enkhtaivan Zorig , Ya. Ariunchimeg , Robert S. Sansom , Robert C. Atwood Royal Society Open Science 10 DOI: 10.1098/rsos.221452 Diamond Proposal Number(s): [29710] Open Access Show Abstract ▼ Abstract: The origin of jaws and teeth remains contentious in vertebrate evolution. ‘Placoderms’ (Silurian-Devonian armoured jawed fishes) are central to debates on the origins of these anatomical structures. ‘Acanthothoracids’ are generally considered the most primitive ‘placoderms’. However, they are so far known mainly from disarticulated skeletal elements that are typically incomplete. The structure of the jaws—particularly the jaw hinge—is poorly known, leaving open questions about their jaw function and comparison with other placoderms and modern gnathostomes. Here we describe a near-complete ‘acanthothoracid’ upper jaw, allowing us to reconstruct the likely orientation and angle of the bite and compare its morphology with that of other known ‘placoderm’ groups. We clarify that the bite position is located on the upper jaw cartilage rather than on the dermal cheek and thus show that there is a highly conserved bite morphology among most groups of ‘placoderms’, regardless of their overall cranial geometry. Incorporation of the dermal skeleton appears to provide a sound biomechanical basis for jaw origins. It appears that ‘acanthothoracid’ dentitions were fundamentally similar in location to that of arthrodire ‘placoderms’, rather than resembling bony fishes. Irrespective of current phylogenetic uncertainty, the new data here resolve the likely general condition for ‘placoderms’ as a whole, and as such, ancestral morphology of known jawed vertebrates.	Feb 2023
I05-ARPES	Observation of Mott instability at the valence transition of f-electron system Haifeng Yang , Jingjing Gao , Yingying Cao , Yuanji Xu , Aiji Liang , Xiang Xu , Yujie Chen , Shuai Liu , Kui Huang , Lixuan Xu , Chengwei Wang , Shengtao Cui , Meixiao Wang , Lexian Yang , Xuan Luo , Yuping Sun , Yi-Feng Yang , Zhongkai Liu , Yulin Chen National Science Review DOI: 10.1093/nsr/nwad035 Open Access Show Abstract ▼ Abstract: Mott physics plays a critical role in materials with strong electronic correlations. Mott insulator-to-metal transition can be driven by chemical doping, external pressure, temperature and gate voltage, which is often seen in transition metal oxides with 3d electrons near the Fermi energy (e.g. cuprate superconductor). In 4f-electron system, however, the insulator-to-metal transition is mostly driven by Kondo hybridization and the Mott physics has rarely been explored in experiments. Here, by combining the angle-resolved photoemission spectroscopy and strongly correlated band structure calculations, we show that an unusual Mott instability exists in YbInCu4 accompanying its mysterious first-order valence transition. This contrasts with the prevalent Kondo picture and demonstrates that YbInCu4 is a unique platform to explore the Mott physics in Kondo lattice systems. Our work provides important insight for the understanding and manipulation of correlated quantum phenomena in the f-electron system.	Feb 2023

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