The OECD has published fundamental and guiding principles to facilitate the application of QSAR methods to the risk assessment of chemicals. The main focus is on the critical role of mechanistic consideration in improving various (Q)SAR approaches and possible integrative approaches of combining chemoinformatics and bioinformatics.

Latest releases: AOPs are the central element of a toxicological knowledge framework, promoted by member countries through OECD, built to support chemical risk assessment based on mechanistic reasoning. Seven New AOPs have now been published.

After award-winning hits of classics Robert Icke ends his stint as an associate director at the Almeida with a dense but intriguing work that is very much of the moment.

Chloe Lattanzi is unable to see mum Olivia Newton-John this Mother's Day. 

They have been self-isolating together amid the coronavirus pandemic. And Dakota, 26, and Elle Fanning, 22, were glimpsed stepping out together in Los Angeles this Saturday.

The wife of Justin Bieber highlighted her stunning physique while urging her 26.8 million fans to donate to a COVID-19 charity benefiting the World Health Organization.

A National Convention of Nomads and Adivasis was organized last month in Delhi. This was perhaps one of the first attempts to give a unified political voice for Adivasi and Nomadic communities in India. G. N. Devy writes on the efforts to make this convention happen, and its import.

Six-year-old Yunosuke and four-year-old Koujirou can be seen training on the Swedish and Serbian legends in a viral video.

Archives, Room Use Only - TK6015.R64 1904

Archives, Room Use Only - PN6161.P557 1897

Archives, Room Use Only - CS71.V129 1937

Archives, Room Use Only - CS71.V129 1947

Archives, Room Use Only - QC527.T73 1895

Archives, Room Use Only - HE8680.G7 G74 1913

Archives, Room Use Only - KD2885.A26 G78 1868

Archives, Room Use Only - UG582.H4 G78 1920z

The Communist Party of India (Marxist) has opposed a proposal to set up a Tamil Nadu State Marketing Corporation (Tasmac) outlet in the vicinity of Ho

A new Rococo 2 X-ray fluorescence detector was implemented into the cryogenic sample environment at the Hard X-ray Micro/Nano-Probe beamline P06 at PETRA III, DESY, Hamburg, Germany. A four sensor-field cloverleaf design is optimized for the investigation of planar samples and operates in a backscattering geometry resulting in a large solid angle of up to 1.1 steradian. The detector, coupled with the Xspress 3 pulse processor, enables measurements at high count rates of up to 106 counts per second per sensor. The measured energy resolution of ∼129 eV (Mn Kα at 10000 counts s−1) is only minimally impaired at the highest count rates. The resulting high detection sensitivity allows for an accurate determination of trace element distributions such as in thin frozen hydrated biological specimens. First proof-of-principle measurements using continuous-movement 2D scans of frozen hydrated HeLa cells as a model system are reported to demonstrate the potential of the new detection system.

A simple two-spindle based lathe system for the preparation of cylindrical samples intended for X-ray tomography is presented. The setup can operate at room temperature as well as under cryogenic conditions, allowing the preparation of samples down to 20 and 50 µm in diameter, respectively, within minutes. Case studies are presented involving the preparation of a brittle biomineral brachiopod shell and cryogenically fixed soft brain tissue, and their examination by means of ptychographic X-ray computed tomography reveals the preparation method to be mainly free from causing artefacts. Since this lathe system easily yields near-cylindrical samples ideal for tomography, a usage for a wide variety of otherwise challenging specimens is anticipated, in addition to potential use as a time- and cost-saving tool prior to focused ion-beam milling. Fast sample preparation becomes especially important in relation to shorter measurement times expected in next-generation synchrotron sources.

Gluconate 5-dehydrogenase (Ga5DH; EC 1.1.1.69) from Lentibacter algarum (LaGa5DH) was recombinantly expressed in Escherichia coli and purified to homogeneity. The protein was crystallized and the crystal structure was solved at 2.1 Å resolution. The crystal belonged to the monoclinic system, with space group P1 and unit-cell parameters a = 55.42, b = 55.48, c = 79.16 Å, α = 100.51, β = 105.66, γ = 97.99°. The structure revealed LaGaDH to be a tetramer, with each subunit consisting of six α-helices and three antiparallel β-hairpins. LaGa5DH has high structural similarity to other Ga5DH proteins, demonstrating that this enzyme is highly conserved.

The enzyme 4-hydroxy-tetrahydrodipicolinate synthase (DapA) is involved in the production of lysine and precursor molecules for peptidoglycan synthesis. In a multistep reaction, DapA converts pyruvate and l-aspartate-4-semialdehyde to 4-hydroxy-2,3,4,5-tetrahydrodipicolinic acid. In many organisms, lysine binds allosterically to DapA, causing negative feedback, thus making the enzyme an important regulatory component of the pathway. Here, the 2.1 Å resolution crystal structure of DapA from the thermoacidophilic methanotroph Methylacidiphilum fumariolicum SolV is reported. The enzyme crystallized as a contaminant of a protein preparation from native biomass. Genome analysis reveals that M. fumariolicum SolV utilizes the recently discovered aminotransferase pathway for lysine biosynthesis. Phylogenetic analyses of the genes involved in this pathway shed new light on the distribution of this pathway across the three domains of life.

The redetermination of the crystal structure of barium oxidotellurate(IV) monohydrate allowed the localization of the hydrogen atoms that were not determined in the previous study [Nielsen, Hazell & Rasmussen (1971). Acta Chem. Scand. 25, 3037–3042], thus making an unambiguous assignment of the hydrogen-bonding scheme possible. The crystal structure shows a layered arrangement parallel to (001), consisting of edge-sharing [BaO6(H2O)] polyhedra and flanked by isolated [TeO3] trigonal pyramids on the top and bottom. O—H⋯O hydrogen bonds of medium strength link adjacent layers along [001].

In the title compound, C61H15ClN2O3, the heterocyclic ring adopts an envelope conformation, folded across the N⋯N line, with the 2,5-di­meth­oxy­phenyl unit occupying a quasi-axial site. There are two N—H⋯O hydrogen bonds in the structure: one hydrogen bond links mol­ecules related by a 41 screw axis to form a C(6) chain, and the other links inversion-related pairs of mol­ecules to form an R22(8) ring. The ring motif links all of the chains into a continuous three-dimensional framework structure. Comparisons are made with the structures of some related compounds.

The hydro­thermal synthesis and crystal structure of the simple inorganic compound CaHPO3, which crystallizes in the chiral space group P43212, are reported. The structure is built up from distorted CaO7 capped trigonal prisms and HPO3 pseudo pyramids, which share corners and edges to generate a three-dimensional network.

In the crystal structure of the isostructural title compounds, namely {2,6-bis­[(di-tert-butyl­phosphan­yl)­oxy]-4-hy­droxy­phen­yl}chlorido­palladium(II), [Pd(C22H39O3P2)Cl], 1, and {2,6-bis­[(di-tert-butyl­phosphan­yl)­oxy]-4-hy­droxy­phen­yl}chlorido­platinum(II), [Pt(C22H39O3P2)Cl], 2, the metal centres are coordinated in a distorted square-planar fashion by the POCOP pincer fragment and the chloride ligand. Both complexes form strong hydrogen-bonded chain structures through an inter­action of the OH group in the 4-position of the aromatic POCOP backbone with the halide ligand.

The title compound, C12H21NO7, (I), is conformationally unstable; the predominant form present in its solution is the β-pyran­ose form (74.3%), followed by the β- and α-furan­oses (12.1 and 10.2%, respectively), α-pyran­ose (3.4%), and traces of the acyclic carbohydrate tautomer. In the crystalline state, the carbohydrate part of (I) adopts the 2C5 β-pyran­ose conformation, and the amino acid portion exists as a zwitterion, with the side chain cyclo­pentane ring assuming the E9 envelope conformation. All heteroatoms are involved in hydrogen bonding that forms a system of anti­parallel infinite chains of fused R33(6) and R33(8) rings. The mol­ecule features extensive intra­molecular hydrogen bonding, which is uniquely multicentered and involves the carboxyl­ate, ammonium and carbohydrate hy­droxy groups. In contrast, the contribution of inter­molecular O⋯H/H⋯O contacts to the Hirshfeld surface is relatively low (38.4%), as compared to structures of other d-fructose-amino acids. The 1H NMR data suggest a slow rotation around the C1—C2 bond in (I), indicating that the intra­molecular heteroatom contacts survive in aqueous solution of the mol­ecule as well.

Amino­pyridine and phthalic acid are well known synthons for supra­molecular architectures for the synthesis of new materials for optical applications. The 2-amino­pyridinium hydrogen phthalate title salt, C5H7N2+·C8H5O4−, crystallizes in the non-centrosymmetric space group P21. The nitro­gen atom of the –NH2 group in the cation deviates from the fitted pyridine plane by 0.035 (7) Å. The plane of the pyridinium ring and phenyl ring of the anion are oriented at an angle of 80.5 (3)° to each other in the asymmetric unit. The anion features a strong intra­molecular O—H⋯O hydrogen bond, forming a self-associated S(7) ring motif. The crystal packing is dominated by inter­molecular N—H⋯O hydrogen bonds leading to the formation of 21 helices, with a C(11) chain motif. They propagate along the b axis and enclose R22(8) ring motifs. The helices are linked by C—H⋯O hydrogen bonds, forming layers parallel to the ab plane. Hirshfeld surface analysis and two-dimensional fingerprint plots were used to investigate and qu­antify the inter­molecular inter­actions in the crystal.

Charge-assisted hydrogen bonding plays a significant role in the crystal structures of solvates of ionic com­pounds, especially when the cation or cations are primary ammonium salts. We report the crystal structures of four ammonium salts of molybdenum halide cluster solvates where we observe significant hydrogen bonding between the solvent molecules and cations. The crystal structures of bis­(anilinium) octa-μ3-chlorido-hexa­chlorido-octa­hedro-hexa­molybdate N,N-di­­methyl­formamide tetra­solvate, (C6H8N)2[Mo6Cl8Cl6]·4C3H7NO, (I), p-phenyl­enedi­ammonium octa-μ3-chlorido-hexa­chlorido-octa­hedro-hexa­mol­yb­date N,N-di­methyl­formamide hexa­solvate, (C6H10N2)[Mo6Cl8Cl6]·6C3H7NO, (II), N,N'-(1,4-phenyl­ene)bis­(propan-2-iminium) octa-μ3-chlorido-hexa­chlo­rido-octa­hedro-hexa­molybdate acetone tris­olvate, (C12H18N2)[Mo6Cl8Cl6]·3C3H6O, (III), and 1,1'-dimethyl-4,4'-bipyridinium octa-μ3-chlo­rido-hexa­chlorido-octa­hedro-hexa­molybdate N,N-di­methyl­formamide tetra­solvate, (C12H14N2)[Mo6Cl8Cl6]·4C3H7NO, (IV), are reported and described. In (I), the anilinium cations and N,N-di­methyl­formamide (DMF) solvent mol­ecules form a cyclic R42(8) hydrogen-bonded motif centered on a crystallographic inversion center with an additional DMF mol­ecule forming a D(2) inter­action. The p-phenyl­enedi­ammonium cation in (II) forms three D(2) inter­actions between the three N—H bonds and three independent N,N-di­methyl­formamide mol­ecules. The dication in (III) is a protonated Schiff base solvated by acetone mol­ecules. Compound (IV) contains a methyl viologen dication with N,N-di­methyl­formamide mol­ecules forming close contacts with both aromatic and methyl H atoms.

The structures of two isomeric com­pounds of 5-nitro­quinoline with chloro- and nitro-substituted benzoic acid, namely, 2-chloro-4-nitro­benzoic acid–5-nitro­quinoline (1/1), (I), and 5-chloro-2-nitro­benzoic acid–5-nitro­quinoline (1/1), (II), both C7H4ClNO4·C9H6N2O2, have been determined at 190 K. In each com­pound, the acid and base mol­ecules are held together by an O—H⋯N hydrogen bond. In the crystal of (I), the hydrogen-bonded acid–base units are linked by a C—H⋯O hydrogen bond, forming a tape structure along [1overline{2}0]. The tapes are stacked into a layer parallel to the ab plane via N—O⋯π inter­actions between the nitro group of the base mol­ecule and the quinoline ring system. The layers are further linked by other C—H⋯O hydrogen bonds, forming a three-dimensional network. In the crystal of (II), the hydrogen-bonded acid–base units are linked into a wide ribbon structure running along [1overline{1}0] via C—H⋯O hydrogen bonds. The ribbons are further linked via another C—H⋯O hydrogen bond, forming a layer parallel to (110). Weak π–π inter­actions [centroid–centroid distances of 3.7080 (10) and 3.7543 (9) Å] are observed between the quinoline ring systems of adjacent layers. Hirshfeld surfaces for the 5-nitro­quinoline mol­ecules of the two com­pounds mapped over shape index and dnorm were generated to visualize the weak inter­molecular inter­actions.

The title mol­ecular salt, C9H12N3O2S+·HSO4−, was obtained through the protonation of the azomethine N atom in a sulfuric acid medium. The crystal com­prises two entities, a thio­semicarbazide cation and a hydrogen sulfate anion. The cation is essentially planar and is further stabilized by a strong intra­molecular O—H⋯N hydrogen bond. In the crystal, a three-dimensional network is established through O—H⋯O and N—H⋯O hydrogen bonds. A weak intermolecular C—H⋯O hydrogen bond is also observed. The hydrogen sulfate anion exhibits disorder over two sets of sites and was modelled with refined occupancies of 0.501 (6) and 0.499 (6).

The title compound [systematic name: (1R*, 8S)-2-acetamidoocta­hydro­pyrrol­izin-4-ium chloride–N-[(1R, 8S)-hexa­hydro-1H-pyrrolizin-2-yl)acetamide (1/1)], 2(C9H16N2O)·HCl or C9H17N2O+·Cl−·C9H16N2O, arose as an unexpected product when 1-exo-acetamido­pyrrolizidine (AcAP; C9H16N2O) was dissolved in CHCl3. Within the AcAP pyrrolizidine group, the unsubstituted five-membered ring is disordered over two orientations in a 0.897 (5):0.103 (5) ratio. Two AcAP mol­ecules related by a crystallographic twofold axis link to H+ and Cl− ions lying on the rotation axis, thereby forming N—H⋯N and N—H⋯Cl⋯H—N hydrogen bonds. The first of these has an unusually short N⋯N separation of 2.616 (2) Å: refinement of different models against the present data set could not distinguish between a symmetrical hydrogen bond (H atom lying on the twofold axis and equidistant from the N atoms) or static or dynamic disorder models (i.e. N—H⋯N + N⋯H—N). Computational studies suggest that the disorder model is slightly more stable, but the energy difference is very small.

The asymmetric unit of the title 1:1 salt 1,2,4-triazolium hydrogen oxalate, C2H4N3+·C2HO4− (I), comprises one 1,2,4-triazolium cation and one hydrogen oxalate anion. In the crystal, the hydrogen oxalate anions are linked by O—H⋯O hydrogen bonds into chains running parallel to [100]. In turn, the anionic chains are linked through the 1,2,4-triazolium cations by charge-assisted +N—H⋯O− hydrogen bonds into sheets aligned parallel to (01overline{1}). The sheets are further stacked through π–π inter­actions between the 1,2,4-triazolium rings [centroid-to-centroid distance = 3.642 (3) Å, normal distance = 3.225 (3) Å, slippage 1.691 Å], resulting in the formation of a three-dimensional supra­molecular network. Hirshfeld surface analysis of the title salt suggests that the most significant contributions to the crystal packing are by H⋯O/O⋯H and H⋯N/N⋯H contacts involving the hydrogen bonds.

The redetermined structure [for the previous study, see: Godfrey & Waters (1975). Cryst. Struct. Commun. 4, 5–8] of ammonium μ-oxido-μ-[1,5,6-tri­hydroxy­hexane-2,3,4-tris­(olato)]bis­[dioxidomolybdenum(V)] monohydrate, NH4[Mo2(C6H11O6)O5]·H2O, was obtained from an attempt to prepare a glutamic acid complex from the [Co2Mo10H4O38]6− anion. Subsequent study indicated the complex arose from a substantial impurity of mannitol in the glutamic acid sample used. All hydrogen atoms have been located in the present study and the packing displays N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds. A Hirshfeld surface analysis was also performed.

The crystal structures of two salt crystals of 2,2-bis­(4-methyl­phen­yl)hexa­fluoro­propane (Bmphfp) with amines, namely, dipyridinium 4,4'-(1,1,1,3,3,3-hexa­fluoro­propane-2,2-di­yl)dibenzoate 4,4'-(1,1,1,3,3,3-hexa­fluoro­propane-2,2-di­yl)di­benzoic acid, 2C5H6N+·C17H8F6O42−·C17H10F6O4, (1), and a monohydrated ethyl­enedi­ammonium salt ethane-1,2-diaminium 4,4'-(1,1,1,3,3,3-hexa­fluoro­propane-2,2-di­yl)dibenzoate monohydrate, C2H10N22+·C17H8F6O42−·H2O, (2), are reported. Compounds 1 and 2 crystallize, respectively, in space group P21/c with Z' = 2 and in space group Pbca with Z' = 1. The crystals of compound 1 contain neutral and anionic Bmphfp mol­ecules, and form a one-dimensional hydrogen-bonded chain motif. The crystals of compound 2 contain anionic Bmphfp mol­ecules, which form a complex three-dimensional hydrogen-bonded network with the ethyl­enedi­amine and water mol­ecules.

A three-dimensional hydrogen-bonded network based on a rare mok topology has been constructed using an organic molecule synthesized in the solid state. The molecule is obtained using a supramolecular protecting-group strategy that is applied to a solid-state [2+2] photodimerization. The photodimerization affords a novel head-to-head cyclo­butane product. The cyclo­butane possesses tetrahedrally disposed cis-hydrogen-bond donor (phenolic) and cis-hydrogen-bond acceptor (pyridyl) groups. The product self-assembles in the solid state to form a mok network that exhibits twofold interpenetration. The cyclo­butane adopts different conformations to provide combinations of hydrogen-bond donor and acceptor sites to conform to the structural requirements of the mok net.

Radiation damage is the most fundamental limitation for achieving high resolution in electron cryo-microscopy (cryo-EM) of biological samples. The effects of radiation damage are reduced by liquid-helium cooling, although the use of liquid helium is more challenging than that of liquid nitrogen. To date, the benefits of liquid-nitrogen and liquid-helium cooling for single-particle cryo-EM have not been compared quantitatively. With recent technical and computational advances in cryo-EM image recording and processing, such a comparison now seems timely. This study aims to evaluate the relative merits of liquid-helium cooling in present-day single-particle analysis, taking advantage of direct electron detectors. Two data sets for recombinant mouse heavy-chain apoferritin cooled with liquid-nitrogen or liquid-helium to 85 or 17 K were collected, processed and compared. No improvement in terms of resolution or Coulomb potential map quality was found for liquid-helium cooling. Interestingly, beam-induced motion was found to be significantly higher with liquid-helium cooling, especially within the most valuable first few frames of an exposure, thus counteracting any potential benefit of better cryoprotection that liquid-helium cooling may offer for single-particle cryo-EM.

High-resolution single-crystal X-ray measurements of the monoclinic polymorph of bicalutamide and the aspherical atom databank approach have served as a basis for a reconstruction of the charge density distribution of the drug and its androgen receptor (AR) and albumin complexes. The contributions of various types of intermolecular interactions to the total crystal energy or ligand:AR energy were estimated. The cyan and amide groups secured the ligand placement in the albumin (Lys-137) and the AR binding pocket (Leu-704, Asn-705, Arg-752), and also determined the packing of the small-molecule crystals. The total electrostatic interaction energy on average was −230 kJ mol−1, comparable with the electrostatic lattice energy of the monoclinic bicalutamide polymorph. This is the result of similar distributions of electropositive and electronegative regions on the experimental and theoretical molecular electrostatic potential maps despite differences in molecular conformations. In general, bicalutamide interacted with the studied proteins with similar electrostatic interaction energies and adjusted its conformation and electrostatic potential to fit the binding pocket in such a way as to enhance the interactions, e.g. hydrogen bonds and π⋯π stacking.

A large amount of hydrogen circulates inside the Earth, which affects the long-term evolution of the planet. The majority of this hydrogen is stored in deep Earth within the crystal structures of dense minerals that are thermodynamically stable at high pressures and temperatures. To understand the reason for their stability under such extreme conditions, the chemical bonding geometry and cation exchange mechanism for including hydrogen were analyzed in a representative structure of such minerals (i.e. phase E of dense hydrous magnesium silicate) by using time-of-flight single-crystal neutron Laue diffraction. Phase E has a layered structure belonging to the space group R3m and a very large hydrogen capacity (up to 18% H2O weight fraction). It is stable at pressures of 13–18 GPa and temperatures of up to at least 1573 K. Deuterated high-quality crystals with the chemical formula Mg2.28Si1.32D2.15O6 were synthesized under the relevant high-pressure and high-temperature conditions. The nuclear density distribution obtained by neutron diffraction indicated that the O—D dipoles were directed towards neighboring O2− ions to form strong interlayer hydrogen bonds. This bonding plays a crucial role in stabilizing hydrogen within the mineral structure under such high-pressure and high-temperature conditions. It is considered that cation exchange occurs among Mg2+, D+ and Si4+ within this structure, making the hydrogen capacity flexible.

The bacterial flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenase complex derived from Burkholderia cepacia (BcGDH) is a representative molecule of direct electron transfer-type FAD-dependent dehydrogenase complexes. In this study, the X-ray structure of BcGDHγα, the catalytic subunit (α-subunit) of BcGDH complexed with a hitchhiker protein (γ-subunit), was determined. The most prominent feature of this enzyme is the presence of the 3Fe–4S cluster, which is located at the surface of the catalytic subunit and functions in intramolecular and intermolecular electron transfer from FAD to the electron-transfer subunit. The structure of the complex revealed that these two molecules are connected through disulfide bonds and hydrophobic interactions, and that the formation of disulfide bonds is required to stabilize the catalytic subunit. The structure of the complex revealed the putative position of the electron-transfer subunit. A comparison of the structures of BcGDHγα and membrane-bound fumarate reductases suggested that the whole BcGDH complex, which also includes the membrane-bound β-subunit containing three heme c moieties, may form a similar overall structure to fumarate reductases, thus accomplishing effective electron transfer.

Active cathode particles are fundamental architectural units for the composite electrode of Li-ion batteries. The microstructure of the particles has a profound impact on their behavior and, consequently, on the cell-level electrochemical performance. LiCoO2 (LCO, a dominant cathode material) is often in the form of well-shaped particles, a few micrometres in size, with good crystallinity. In contrast to secondary particles (an agglomeration of many fine primary grains), which are the other common form of battery particles populated with structural and chemical defects, it is often anticipated that good particle crystallinity leads to superior mechanical robustness and suppressed charge heterogeneity. Yet, sub-particle level charge inhomogeneity in LCO particles has been widely reported in the literature, posing a frontier challenge in this field. Herein, this topic is revisited and it is demonstrated that X-ray absorption spectra on single-crystalline particles with highly anisotropic lattice structures are sensitive to the polarization configuration of the incident X-rays, causing some degree of ambiguity in analyzing the local spectroscopic fingerprint. To tackle this issue, a methodology is developed that extracts the white-line peak energy in the X-ray absorption near-edge structure spectra as a key data attribute for representing the local state of charge in the LCO crystal. This method demonstrates significantly improved accuracy and reveals the mesoscale chemical complexity in LCO particles with better fidelity. In addition to the implications on the importance of particle engineering for LCO cathodes, the method developed herein also has significant impact on spectro-microscopic studies of single-crystalline materials at synchrotron facilities, which is broadly applicable to a wide range of scientific disciplines well beyond battery research.

Digitonin has long been used as a mild detergent for extracting proteins from membranes for structure and function studies. As supplied commercially, digitonin is inhomogeneous and requires lengthy pre-treatment for reliable downstream use. Glyco-diosgenin (GDN) is a recently introduced synthetic surfactant with features that mimic digitonin. It is available in homogeneously pure form. GDN is proving to be a useful detergent, particularly in the area of single-particle cryo-electron microscopic studies of membrane integral proteins. With a view to using it as a detergent for crystallization trials by the in meso or lipid cubic phase method, it was important to establish the carrying capacity of the cubic mesophase for GDN. This was quantified in the current study using small-angle X-ray scattering for mesophase identification and phase microstructure characterization as a function of temperature and GDN concentration. The data show that the lipid cubic phase formed by hydrated monoolein tolerates GDN to concentrations orders of magnitude in excess of those used for membrane protein studies. Thus, having GDN in a typical membrane protein preparation should not deter use of the in meso method for crystallogenesis.

This paper reports an Fe-added Y2O3 crucible which is capable of balancing the solution spontaneously and is employed to effectively enhance the homogeneity of YBa2(Cu1−xFex)3O7−δ single crystals.

Neutron crystal structure analysis of hen egg-white lysozyme hydrogen/deuterium exchanged before crystallization were performed by the joint X-ray and neutron refinement. The differences in hydrogen/deuterium exchange behavior between this study and previous ones were observed.

Hydrogen is present in almost all of the molecules in living things. It is very reactive and forms bonds with most of the elements, terminating their valences and enhancing their chemistry. X-ray diffraction is the most common method for structure determination. It depends on scattering of X-rays from electron density, which means the single electron of hydrogen is difficult to detect. Generally, neutron diffraction data are used to determine the accurate position of hydrogen atoms. However, the requirement for good quality single crystals, costly maintenance and the limited number of neutron diffraction facilities means that these kind of results are rarely available. Here it is shown that the use of Transferable Aspherical Atom Model (TAAM) instead of Independent Atom Model (IAM) in routine structure refinement with X-ray data is another possible solution which largely improves the precision and accuracy of X—H bond lengths and makes them comparable to averaged neutron bond lengths. TAAM, built from a pseudoatom databank, was used to determine the X—H bond lengths on 75 data sets for organic molecule crystals. TAAM parametrizations available in the modified University of Buffalo Databank (UBDB) of pseudoatoms applied through the DiSCaMB software library were used. The averaged bond lengths determined by TAAM refinements with X-ray diffraction data of atomic resolution (dmin ≤ 0.83 Å) showed very good agreement with neutron data, mostly within one single sample standard deviation, much like Hirshfeld atom refinement (HAR). Atomic displacements for both hydrogen and non-hydrogen atoms obtained from the refinements systematically differed from IAM results. Overall TAAM gave better fits to experimental data of standard resolution compared to IAM. The research was accompanied with development of software aimed at providing user-friendly tools to use aspherical atom models in refinement of organic molecules at speeds comparable to routine refinements based on spherical atom model.