A novel sample cell with control of temperature and relative humidity permitted collection of data of excellent quality, enabling unrestrained refinement of all atomic parameters. One of the K atoms in the structure is disordered; very strong anisotropy in three of the four water O atoms indicates partial static disorder, which does not involve the bonded H atoms.

UK government's fracking 'ban' has a convenient loophole  The Conversation UK

True North to align with Magnetic North at Greenwich for first time in 360 years  Telegraph.co.uk

Interview: Michael Stephenson, British Geological Survey head of science & technology  The Engineer

Earth's North Magnetic Pole Keeps Drifting towards Siberia, Latest World Magnetic Model Shows | Geophysics, Geoscience  Sci-News.com

Oil workers in North Sea feel effects of earthquake, with platform 'shaking'  Evening Telegraph

Tuning in to a Glacial Symphony  Eos

The transmembrane intracellular lectin ER–Golgi intermediate compartment protein 53 (ERGIC-53) and the soluble EF-hand multiple coagulation factor deficiency protein 2 (MCFD2) form a complex that functions as a cargo receptor, trafficking various glycoproteins between the endoplasmic reticulum (ER) and the Golgi apparatus. It has been demonstrated that the carbohydrate-recognition domain (CRD) of ERGIC-53 (ERGIC-53CRD) interacts with N-linked glycans on cargo glycoproteins, whereas MCFD2 recognizes polypeptide segments of cargo glycoproteins. Crystal structures of ERGIC-53CRD complexed with MCFD2 and mannosyl oligosaccharides have revealed protein–protein and protein–sugar binding modes. In contrast, the polypeptide-recognition mechanism of MCFD2 remains largely unknown. Here, a 1.60 Å resolution crystal structure of the ERGIC-53CRD–MCFD2 complex is reported, along with three other crystal forms. Comparison of these structures with those previously reported reveal that MCFD2, but not ERGIC-53–CRD, exhibits significant conformational plasticity that may be relevant to its accommodation of various polypeptide ligands.

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.

A novel monoclinic phase of human insulin co-crystallized with m-cresol was structurally characterized by means of powder and single-crystal X-ray diffraction.

From the perspective of a young(ish) structural biologist who currently specialises in macromolecular X-ray crystallography, are the best years of crystallography over? Some evidence and hopefully thought-provoking analysis is presented here on the subject.

The title compound [systematic name: 4-(2,3-Dichlorophenyl)benzene-1,2-diol], C12H8Cl2O2, is a putative di­hydroxy­lated metabolite of 2,3-di­chloro­biphenyl (PCB 5). The title structure displays intra­molecular O—H⋯O hydrogen bonding, and the π–π stacking distance between inversion-related chlorinated benzene rings of the title compound is 3.371 (3) Å. The dihedral angle between two benzene rings is 59.39 (8)°.

The structure of the title compound, C24H26S2, an example of a pincer ligand with an SCS-chelation motif, illustrates the steric effects of the methyl groups in the thio­phenyl rings at the 2- and 6-positions, forcing a dissimilar spatial orientation of the thio­phenyl rings relative to the central aryl group [dihedral angles = 33.58 (7) and 40.49 (7)°]. In the crystal, weak S⋯S contacts [3.4009 (7) Å] link the mol­ecules into inversion dimers.

In the complex cation of title compound, [Fe(C56H52N4)(C5H8N2)2]ClO4·1.5C6H5Cl, the ironIII atom is coordinated in a distorted octa­hedral manner by four pyrrole N atoms of the porphyrin ring system in the equatorial plane, and by two N atoms of the 1-ethyl­imidazole ligands in the axial sites. A disordered perchlorate anion and one and a half chloro­benzene solvent mol­ecules are also present. The cationic complex exhibits a highly ruffled porphyrin core. The average Fe—Np (Np is a porphyrin N atom) bond length is 1.988 (5), and the axial Fe—NIm (NIm is an imidazole N atom) bond lengths are 1.962 (3) and 1.976 (3) Å. The two 1-ethyl­imidazole ligands are inclined to each other by a dihedral angle of 68.62 (16)°. The dihedral angles between the 1-ethyl­imidazole planes and the planes of the closest Fe—Np vector are 28.52 (18) and 43.57 (13)°. Inter­molecular C—H⋯Cl inter­actions are observed.

In the crystal structure of the title compound, [Sn(C42H26N6)(C7H5O2)2], the SnIV ion is located on a crystallographic inversion centre and is octa­hedrally coordinated with an N4O2 set. Four N atoms of the porphyrin ring form the equatorial plane while the axial positions are occupied by two O atoms from benzoate anions. The molecular packing of the title complex involves non-classical hydrogen bonds of the types C—H⋯O and C—H⋯N, leading to a three-dimensional network structure.

The title compound, C13H10INO, is not planar as the dihedral angle between the planes of the two aryl rings is 44.5 (9)°. The configuration about the central C=N bond is E, and there is an intra­molecular O—H⋯N hydrogen bond which generates an S(6) ring. The mol­ecular packing is stabilized by weak C—H⋯π inter­actions. The structure was refined as a two-component inversion twin.

6-Methyluracil, C5H6N2O2, exists in two crystalline phases: form (I), monoclinic, space group P21/c [Reck et al. (1988). Acta Cryst. A44, 417–421] and form (II), monoclinic, space group C2/c [Leonidov et al. (1993). Russ. J. Phys. Chem. 67, 2220–2223]. The structure of polymorph (II) has been redetermined providing a significant increase in the precision of the derived geometric parameters. In the crystal, mol­ecules form ribbons approximately running parallel to the c-axis direction through N—H⋯O hydrogen bonds. The radical differences observed between the crystal packing of the two polymorphs may be responsible in form (II) for an increase in the contribution of the polar canonical forms C—(O−)=N—H+ relative to the neutral canonical form C(=O)—N—H induced by hydrogen-bonding inter­actions.

In the mol­ecule of the title N,N'-disubstituted imidazol-2-yl­idene palladium(II) complex, [PdBr2(C21H24N4O)]·CH2Cl2, the palladium(II) atom adopts a slightly distorted square-planar coordination (r.m.s. deviation = 0.0145 Å), and the five-membered chelate ring is almost planar [maximum displacement = 0.015 (8) Å]. The mol­ecular conformation is enforced by intra­molecular C—H⋯Br hydrogen bonds. In the crystal, complex mol­ecules and di­chloro­methane mol­ecules are linked into a three-dimensional network by C—H⋯O and C—H⋯Br hydrogen bonds.

The asymmetric unit of the title sulfodi­imide, C22H22N2OS, consists of two crystallographically independent mol­ecules with similar conformations The environment around each sulfur atom is a slightly distorted tetra­hedron with two S=N bonds and two S—C bonds. The S= N(m-methyl­benzo­yl) and S=N(NEt) bond lengths are 1.584 (3) and 1.528 (2) Å, respectively, for one mol­ecule, and 1.575 (2) and 1.529 (3) Å, respectively, for the other. The dihedral angles between the two phenyl rings in the mol­ecules are 86.76 (8) and 82.49 (8)°. The N—S—N—C(m-methyl­benzo­yl) and N—S—N—C(eth­yl) torsion angles are −60.5 (2) and −50.28 (19)°, respectively, for one mol­ecule, and 62.9 (2) and 44.2 (3)°, respectively, for the other. In the crystal, each independent mol­ecule is linked to its inversion-related mol­ecule via a pair of C—H⋯O hydrogen bonds, forming a dimer.

The title compound, C21H16O2, was isolated from the reaction of 1-(2-meth­oxy­eth­oxy)-1-vinyl­cyclo­propane, 4-ethynylbiphenyl, and CO in a [5 + 1 + 2 + 1] cyclo­addition reaction catalysed by [Rh(CO)2Cl]2. The crystals precipitated directly from the crude reaction mixture. A hydrogen-bonding framework between the hy­droxy and carbonyl groups of a symmetry-related neighbour connects the mol­ecules into chains running parallel to the crystallographic c axis. A minor non-merohedral twin component was included in the refinement.

The mol­ecular structure of the title compound, C18H15ISi, which crystallizes in the space group C2/c, does not exhibit any unusual features. Two weak C—H⋯π inter­actions may help to consolidate the packing. The present structure is not isostructural with the known Ph3SiX (X = F, Cl or Br) compounds.

In the title compound, C14H14ClFN2O2S, the di­hydro­pyrimidine ring adopts a shallow-boat conformation and subtends a dihedral angle of 81.91 (17)° with the phenyl ring. In the crystal, N—H⋯O, N—H⋯S and C—H⋯F hydrogen bonds and C—H⋯π inter­actions are found.

In the title compound, C11H10N2OS, the dihedral angle between the thio­phene and pyridine rings is 77.79 (8)°. In the crystal, inversion dimers linked by pairs of N—H⋯N hydrogen bonds generate R22(10) loops. The dimers are reinforced by pairs of C—H⋯N inter­actions and C—H⋯O inter­actions link the dimers into [010] chains.

In the title compound, [Cd(C10H8O4)(H2O)2)]n, the CdII cation is coordinated in a distorted trigonal–prismatic fashion. 3-(4-Carb­oxy­phen­yl)propionate (cpp) ligands connect the CdII cations into zigzag [Cd(cpp)(H2O)2)]n coordination polymer chains, which are oriented parallel to [101]. The chains aggregate into supra­molecular layers oriented parallel to (10overline{1}) by means of O—H⋯O hydrogen bonding between bound water mol­ecules and ligating cpp carboxyl­ate O atoms. The layers stack in an ABAB pattern along [100] via other O—H⋯O hydrogen-bonding mechanisms also involving the bound water mol­ecules. The crystal studied was an inversion twin.

The title compound, [Ag2(C2H3O2)2(C19H20N2)2] (2), was readily synthesized by treatment of 3-benzyl-1-(2,4,6-tri­methyl­phen­yl)imidazolium chloride with silver acetate. The solution structure of the complex was analyzed by NMR spectroscopy, while the solid-state structure was confirmed by single-crystal X-ray diffraction studies. Compound 2 crystallizes in the triclinic space group Poverline{1}, with a silver-to-carbene bond length (Ag—CNHC) of 2.084 (3) Å. The mol­ecule resides on an inversion center, so that only half of the mol­ecule is crystallographically unique. The planes defined by the two imidazole rings are parallel to each other, but not coplanar [inter­planar distance is 0.662 (19) Å]. The dihedral angles between the imidazole ring and the benzyl and mesityl rings are 77.87 (12) and 72.86 (11)°, respectively. The crystal structure features π–π stacking inter­actions between the benzylic groups of inversion-related (−x + 1, −y + 1, −z + 1) mol­ecules and C—H⋯π inter­actions.

The title complex, [RuCl(C10H14)(C10H8N2)](C24H20B), has monoclinic (P21) symmetry at 100 K. It was prepared by the reaction of the di­chlor­ido[1-methyl-4-(propan-2-yl)benzene]­ruthenium(II) dimer with 2,2'-bi­pyridine, followed by the addition of ammonium tetra­phenyl­borate. The 1-methyl-4-(propan-2-yl)benzene group, the 2,2'-bi­pyridine unit and a chloride ion coordinate the ruthenium(II) atom, with the 1-methyl-4-(propan-2-yl)benzene ring and bi­pyridine moieties trans to each other. In the crystal, the complex cations are linked by C—H⋯Cl hydrogen bonds, forming chains parallel to [010]. These chains are linked by a number of C—H⋯π inter­actions, involving the phenyl rings of the tetra­phenyl­borate anion and a pyridine ring of the bpy ligand, resulting in the formation of layers parallel to (10overline{1}).

The complete mol­ecule of the title compound, C32H22F12N4O2, is generated by a crystallographic twofold axis aligned parallel to [010]. The F atoms of one of the CF3 groups are disordered over three orientations in a 0.6: 0.2: 0.2 ratio. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds, forming zigzag chains propagating along the a-axis direction. In addition, weak C—H⋯O and C—H⋯F bonds are observed. The contribution of the disordered solvent to the scattering was removed using the SQUEEZE routine [Spek (2015). Acta Cryst. C71, 9–18] of PLATON. The solvent contribution is not included in the reported mol­ecular weight and density.

The title compound, C31H30O6, was obtained by protecting the six hy­droxy groups of apogossypol by acetalization with di­chloro­methane. The mol­ecule has a bridging dioxepine unit which hinders the rotation around the 2,2'-inter­naphthyl bond. The dihedral angle between the naphthyl units is 55.73 (3)°. In the crystal, very weak C—H⋯O inter­actions may help to consolidate the packing.

In the title compound, C12H8N4O2, the dihedral angle between the phenanthroline ring system and the nitro group is 23.75 (14)°. The mol­ecule features intra­molecular N—H⋯O and C—H⋯O hydrogen bonds. In the crystal, N—H⋯(N,N), C—H⋯N and C—H⋯O hydrogen bonds link the mol­ecules into [100] chains.

In the title compound, C16H19NSe, the dihedral angle between the benzene rings is 66.49 (12) and a weak intra­molecular N—H⋯Se hydrogen bond generates an S(6) ring. In the crystal, weak N—H⋯N hydrogen bonds link the mol­ecules into [100] chains.

In the title compound, C8H5ClF3NO, the F—C—C=O grouping shows a syn conformation [torsion angle = 1.1 (3)°] and an intra­molecular N—H⋯O hydrogen bond generates an S(6) ring. In the crystal, N—H⋯F and N—H⋯O hydrogen bonds link the mol­ecules into [010] chains.

The title salt, C24H27N2OS+·BF4−, was prepared by an alkyl­ation at the amino N atom attached to the sulfur atom of the corresponding sulfodi­imide. The configuration around the sulfur atom is a slightly distorted tetra­hedral geometry with two S—N bonds and two S—C bonds. The lengths of the S—N(di­ethyl­amine) and S=N(m-methyl­benzoyl­imine) bonds are 1.619 (2) and 1.551 (2) Å, respectively. The two N—S—N—C(eth­yl) and the N—S—N—C(m-methyl­benzoyl­imine) torsion angles are −85.43 (3), 58.94 (17) and 62.03 (16)°, respectively. The dihedral angle between the two phenyl rings is 84.03 (14)°. In the crystal, C—H⋯F hydrogen bonds link the cation and anion, forming a three-dimensional network.

In the title compound, C16H16Cl2N2O2S, the pyrazole ring has an envelope conformation with the C atom bearing the phenyl ring being the flap. The dihedral angles between the central pyrazole ring (all atoms) and pendant thio­phene and phenyl rings are 2.00 (14) and 81.49 (12)°, respectively. In the crystal, weak C—H⋯O, Cl⋯π and π–π stacking inter­actions link the mol­ecules into a three-dimensional network.

The title tetra­nuclear stannoxane, [Sn4(C6H5)8(C6H4NO3)4O2]·1.5CHCl3·solvent, crystallized with two independent complex mol­ecules, A and B, in the asymmetric unit together with 1.5 mol­ecules of chloro­form. There is also a region of disordered electron density, which was corrected for using the SQUEEZE routine [Spek (2015). Acta Cryst. C71, 9–18]. The oxo-tin core of each complex is in a planar `ladder' arrangement and each Sn atom is fivefold SnO3C2 coordinated, with one tin centre having an almost perfect square-pyramidal coordination geometry, while the other three Sn centres have distorted shapes. In the crystal, the complex mol­ecules are arranged in layers, composed of A or B complexes, lying parallel to the bc plane. The complex mol­ecules are linked by a number of C—H⋯O hydrogen bonds within the layers and between the layers, forming a supra­molecular three-dimensional structure.

In the title sulfanilamide derivative, C15H13NO2S, which shows significant activity against Staphylococcus aureus and Escherichia coli, the dihedral angle between the planes of the aromatic rings is 62.15 (19)° and the four-coordinate S atom adopts an almost ideal tetra­hedral geometry. In the crystal, N—H⋯O and C—H⋯O hydrogen bonds link the mol­ecules into a three-dimensional network.

The title structure, C12H8Cl2O2, is a putative metabolite of 3,5-di­chloro­biphenyl (PCB 14). The dihedral angle between the two benzene rings of the title compounds is 58.86 (4)°. In the crystal, it displays intra- and inter­molecular O—H⋯O hydrogen bonding and inter­molecular O—H⋯Cl hydrogen⋯chlorine inter­actions. The inter­molecular inter­actions form a two-dimensional network parallel to (010).

The synthesis and crystal structure of the title PtII complex, [Pt(C23H16N)Cl(CH3CN)], based on the C,N-chelating 2,4,6-tri­phenyl­pyridine as the primary ligand, is described. The central PtII atom is in a distorted square-planar coordination environment. In the crystal, mol­ecules are arranged via a metallophilic inter­action between platinum atoms with a Pt⋯Pt contact of 7.052 (2) Å. In addition, a π–π inter­action occurs.

In the title compound, C34H35NO4, the dihedral angle between the pyridine ring and attached benzene ring is 79.17 (8)°. The meth­oxy­eth­oxy–eth­oxy side chain is disordered over two orientations in a 0.732 (7):0.268 (7) ratio. In the crystal, very weak C—H⋯N and C—H⋯O inter­actions link the mol­ecules.

In the cation of the title mol­ecular salt, C15H19N2+·PF6−, the dihedral angle between the benzene and pyridine rings is 38.21 (10)°. In the crystal, weak C—H⋯F inter­actions arising from methyl and methyl­ene groups adjacent to the quaternary N atom generate (001) sheets.

The asymmetric unit of the title compound, C17H20O5, contains two independent mol­ecules, A and B, with similar geometries [dihedral angles between the phenyl rings = 56.19 (8) and 54.98 (7)°, respectively]. Intra­molecular O—H⋯O hydrogen bonds occur in both mol­ecules. In the crystal, the A mol­ecules form [1overline{1}0] chains linked by O—H⋯O hydrogen bonds from the hydroxyl group to one of the meth­oxy O atoms. The B mol­ecules form O—H⋯O hydrogen bonds to the hydroxyl O atoms of the A mol­ecules and thus act as fixed spacers between the chains of mol­ecule A. Some weak C—H⋯O contacts are also present.

The title two-dimensional coordination polymer, [Zn(C6H5PO3)]n, was synthesized serendipitously by reacting a tetra­phospho­nate cavitand Tiiii[C3H7, CH3, C6H5] and Zn(CH3COO)2·2H2O in a DMF/H2O mixture. The basic conditions of the reaction cleaved the phospho­nate bridges at the upper rim of the cavitand, making them available for reaction with the zinc ions. The coordination polymer can be described as an inorganic layer in which zinc coordinates the oxygen atoms of the phospho­nate groups in a distorted tetra­hedral environment, while the phenyl groups, which are statistically disordered over two orientations, point up and down with respect to the layer. The layers inter­act through van der Waals inter­actions. The crystal studied was refined as a two-component twin.

In the title compound, C21H18O4, the dihedral angle between the naphthelene ring system (r.m.s. deviation = 0.014 Å) and the benzene ring is 9.68 (1)°. The C atom of the meth­oxy group of the naphthalene ring system is almost coplanar with the ring [C—O—C—C = −2.0 (3)°], whereas the C atom of the meth­oxy group of the phenol ring is slightly twisted [C—O—C—C = 6.2 (3)°]. An intra­molecular O—H⋯O hydrogen bond generates an S(6) ring motif.

The title compound, C16H20N4, was synthesized by cyanation of brom­hexine. The compound crystallizes with two unique mol­ecules in the asymmetric unit. The substituted aniline and cyclo­hexane rings are inclined to one another by 37.26 (6)° in one mol­ecule and by 22.84 (7)° in the other. In the crystal packing, intra- and inter­molecular N—H⋯N hydrogen bonds and an inter­molecular C—H⋯N contact were observed.

The title com­pound, C34H24O4S·0.5CH2Cl2, crystallizes with two independent mol­ecules and one di­chloro­methane solvent mol­ecule in the asymmetric unit. The crystal packing is consolidated by C—H⋯O hydrogen bonds.

The molecular salt, C23H26N2O2+·Cl−, was obtained from 1-isobutyl-8,9-dimeth­oxy-3-phenyl-5,6-di­hydro­imidazo[5,1-a]iso­quinoline, which was synthesized by cyclo­condensation of α-benzoyl­amino-γ-methyl-N-[2-(3,4-di­meth­oxy­phen­yl)eth­yl]valeramide in the presence of phosphoryl chloride. The tetra­hydro­pyridine ring adopts a twist–boat conformation. In the crystal structure, centrosymmetric dimers are formed by N—H⋯Cl and C—H⋯Cl hydrogen bonds.

In the title compound, C22H25NO5·H2O, the ten-membered ring displays an approximate chair–chair conformation, whereas the five-membered furan ring has an envelope conformation, with the C atom of the methine group adjacent to the spiro C atom as the flap. The isoxazole ring is almost planar and its plane is slightly inclined to the plane of the attached phenyl ring. The mean plane of the furan ring is nearly perpendicular to that of the isoxazole ring, as indicated by the dihedral angle between them of 89.39 (12)°. In the crystal, the organic mol­ecules are linked into [010] chains by O—H⋯O hydrogen bonds. The water mol­ecule forms O—H⋯O and O—H⋯N hydrogen bonds and a weak C—H⋯O inter­action is also observed. Together, these lead to a three-dimensional network.

The title magnesium complex, [Mg(C21H20NO2)2(C4H8O)]n, exhibits two N,O-bidentate 2-(di­methyl­amino)-α,α-di­phenyl­benzene­methano­late ligands, form­ing two six-membered chelate rings. The distorted square-pyramidal coordination sphere of the MgII atom is completed by the O atom of a tetra­hydro­furan ligand, with its O atom in the apical position. The O and N atoms are in a mutual trans arrangement. Except for two C—H⋯π inter­actions, no significant inter­molecular inter­actions are observed in the crystal.

In the title compound, C17H18N4O2, the dihedral angle between the pyridine and benzene rings is 55.68 (11)°. In the crystal, N—H⋯N hydrogen bonds link the mol­ecules into [010] chains.

The title compound, C26H22O2P+·PF6−·C4H7O, crystallizes as a cation-anion pair with a single solvent mol­ecule in the asymmetric unit. Hydrogen bonding occurs between the carb­oxy­lic acid group on the cation and the oxygen atom of the solvent mol­ecule. Longer hydrogen-bonding inter­actions are observed between fluorine atoms of the anion and H atoms on the phenyl rings of the cation.