The water molecules in 25 (21 high-resolution and four atomic resolution) crystal structures of bovine pancreatic phospholipase A(2) have been analyzed in order to identify the invariant water molecules and their possible roles. A total of 24 water molecules have been identified that are invariant in all 25 crystal structures examined. These include the catalytic water molecule, which is direct...

Extended microscale crystal defects, including dislocations and stacking faults, can radically alter the properties of technologically important materials. Determining the atomic structure and the influence of defects on properties remains a major experimental and computational challenge. Using a newly developed simulation technique, the structure of the 1/2a <100> screw dislocation in nanoporo...

Single crystals of NbF4, niobium(IV) tetra-fluoride, were synthesized by disproportionation of Nb2F5 at 1273 K in a sealed niobium tube, extracted and studied by single-crystal X-ray diffraction. Previous reports on the crystal structure of NbF4 were based on X-ray powder diffraction data and the observed isotypicity to SnF4 [Gortsema & Didchenko (1965 ▸). Inorg. Chem. 4, 182-186; Schäfer et al...

Defect sites on bone minerals play a critical role in bone remodeling processes. We investigated single crystal hydroxyapatite (100) surfaces bearing crystal defects under acidic dissolution conditions using real-time in situ atomic force microscopy. At defect sites, surface structure-dependent asymmetric hexagonal etch pits were formed, which dominated the overall dissolution rate. Meanwhile, ...

We propose a new type of crystal growth phenomenon—structure-dependent attachment kinetics—to explain the growth of thin ice plates from the vapor phase at temperatures near 15 C. In particular, we propose that the condensation coefficient for growth of ice prism facets increases dramatically when the width of the facet approaches atomic dimensions. This model reconciles several conflicting mea...

The concept of a crystal is that of a solid body in which the atomic or molecular units are so arranged as to form an array having three dimensional periodicity. Because of the periodicity, it is possible to describe the arrangements of the atomic composition by means of Fourier series. The type of Fourier series that is used in crystal structure analysis represents the electron density distrib...

Crystal structure prediction for organic molecules requires both the fast assessment of thousands to millions of crystal structures and the greatest possible accuracy in their relative energies. We describe a crystal lattice simulation program, DMACRYS, emphasizing the features that make it suitable for use in crystal structure prediction for pharmaceutical molecules using accurate anisotropic ...

single-walled carbon nanotubes (swcnt) and multi-walled carbon nanotubes(mwcnt) were melt-blended with polyvinylidene fluoride (pvdf).ft-ir technique revealed that swcnt has insignificant effect on the crystalline structure of pvdf and at 3wt% modification only 14% beta crystal isformed. this observation was accounted for by the chair structure of swcnt. in mwcnt nancomposites it was found that...

the zinc(ii) complex [zn2(dmdtc)2(μ-dmdtc)2] has been synthesized directly from thiram ligand, containing a disulfide bond {dmdtc = n,n-dimethyldithiocarbamate; thiram = n,n-tetramethylthiuram disulfide}, and characterized by elemental analysis and spectroscopic methods. surprisingly thiram, undergoes a reductive disulfide bond scission upon reaction with zn2+ in methanolic media to give the [z...