Molecular Replacement Studies of Cucurmosin from Cucurbita oschata：Structure Homology with Trichosanthin

High diffraction quality crystals of cucurmosin,a type I ribosome inactivating protein isolated from the sarcocarp of Cucurbita moschata(pumpkin),have been grown under newly optimised conditions.With in-house rotating anode X-ray source,these crystals diffract to 1.65A resolution which is moch higher than that of the previously reported crystals that diffracted only to 3A resolution.The crystals belong to space group P212121with cell parameters a=41.5,b=58.4 and c=99.3A.Molecular replacement studies indicate that the cucurmosin structure is homologous to trichosanthin.The initial structural model has been obtained and the model fitting/refinement is in progress.     

pBPB共价修饰蝮蛇酸性磷脂酶A2的晶体学数据

The Crystals of acidic phospholipase A2 from the venom of Agkistrodon blomhoffii brevicaudus (i.e. Agkistrodon halys pallas) covalently modified with p-bromo-phenacylbromide were obtained by the method of hanging drop vapor diffusion. Crystallization droplet was composed of 0.06mol?L-1 Na(CH3)2AsO2 (pH=6.5), 24.8% (v/v) 1,4-butanediol, and 4.5mg?mL-1 protein. The crystal data are of a=b=82.82?., c=32.85?, space group P61. 8945 unique reflections with 1.93 ? resolution were measured on a Siemens area detector X-ray diffractometor, of which 8069 reflections having F0 >2σ(F). The experimental results show that the crystals are suitable to a structure analysis of high resolution.     

Proton magnetic shielding and susceptibility effects in single crystals of ferrocene

The proton NMR in single crystals of ferrocene has been studied by multiple pulse techniques at room temperature. In crystals of natural shape with plane faces the angular dependence of the resonance frequency due to the anisotropy of the shielding and due to the bulk susceptibility was found to be of about equal size, making analysis of the data practically impossible. By using a single crystal sphere the shape dependent part of the susceptibility contribution could be eliminated. In addition, the resolution obtained by the multiple pulse technique is considerably higher for spheres than for non-spherical crystals. As the ferrocene molecules rotate rapidly about their fivefold axes at room temperature, the shielding tensor σ must be axially symmetric. Having this in mind, the data could be analyzed to yield both the shielding tensor with Δσ = σ₆ - σ_⊥ = ?6.5 ± 0.1 ppm, σ_iso = ?4.2 ± 0.5 ppm from a spherical sample of TMS and the anisotropy of the susceptibility Δ _x = 30 × 10^?6 cgs units.     

High-resolution electron microscopy of crystallographic shear structures in tungsten oxides

Crystallographic shear (CS) structure in reduced crystals of W0₃ has been imaged at a resolution of 3–4A?by a high-resolution electron microscope.A?large distortion of the W0₆ octahedra sharing their edges at the CS planes has been directly recognized in electron micrographs.Crystallographic shear occurs preferentially in a particular crystallographic orientation. The preference may be explained by a different degree of distortion along the principal axes in the W0₆ octahedra of the pseudocubic structure of W03 crystal.A model for growth and ordering of the CS planes is discussed.     

Elektronenmikroskopische Untersuchung der Realstruktur von O?LaTa3O9, M?CeTa3O9 und M2?PrTa3O9 – Nachweis einer neuen M1?CeTa3O9-Modifikation

Electronmicroscopic Investigations on Disordered Crystals of O? LaTa₃O₉, M? CeTa₃O₉, and M2? PrTa₃O₉ – Proof of a New M1? CeTa₃O₉-Modification High resolution electron microscope investigations on O? LaTa₃O₉ and M2? PrTa₃O₉ showed twinned areas in both cases. With the help of electron microscopic pictures and models of the crystal structures, respectively, we obtained informations about the structural imperfections. Furthermore we present images of thin crystals which contain areas of two different modifications M1? PrTa₃O₉ and M2? PrTa₃O₉. By comparing these images with the corresponding computed contrasts we obtained a structure model of the phase boundary. Investigations on crystals of M? CeTa₃O₉ showed small areas of a new modification M1? CeTa₃O₉ which is isotypic to M1? LnTa₃O₉ (Ln=Pr, Nd) according to electron diffraction and high resolution images.     

Modeling the Fractionation Process in TREF Systems. III. Model Validation With Low Molecular Weight Homopolymers

Low molecular weight semicrystalline homopolymers are used as a model system for temperature rising elution fractionation (TREF) analysis. An already proposed thermodynamic model for TREF analysis is used to characterize TREF fractions from low molecular weight polyethylenes M?_n = 500 to 3000 and some of their mixtures. In this molecular weight range it is possible, under appropriate crystallization, conditions, to form extended-chain crystals, and therefore lamellar thicknesses become comparable to extended-chain lengths. Lamellar thicknesses calculated from TREF spectra permit calculations of the molecular weights of the fractions, up to a limit of about 142 CH₂, where partially folded-chain crystallites appear under these operating conditions. Also homopolymers blends are fractionated and the TREF spectra analyzed to test model predictions. It is shown that appearance of chain folding may set a resolution limit to the analysis of commercial copolymers by TREF. © 1996 John Wiley & Sons, Inc.     

From adapted and computerized thermomechanical equipments to modelling and the time-evolution behaviour in Cu−Zn−Al shape memory alloys

Using two similar high resolution computer controlled stress-strain-temperature set-up of equivalent resolution (1 mN, 0.1 μm, 5 mK) the detailed study of the martensitic transformation in single crystals of the Cu?Zn?Al shape memory alloys is realized. The devices can obtain 20 or 150 N in applied force, 2 or 4 mm in length and can be operated near room temperature (between 280 and 360 K). The analysis of the hysteresis domain in single crystals clearly visualises the intrinsic characteristics of the material (pseudoelasticity, nucleation, interface friction) and enables the obtenton of parameters for physical models of the hysteretic behaviour in force—lengthening—temperature and, eventually, time-dependent processes. The observation of time evolution shows the ‘recoverable martensite creep’ associated to a microstabilization process.     

ESR of triplet states in single crystals of photochromic 2,3,4,4-tetrachloro-1-keto-1,4-dihydronaphthalene (β-TKN)

Triplet ESR spectra of irradiated single crystals of β-TKN have been investigated as a function of their orientation with respect to the magnetic field. From the directions of the principal axes of the dipolar coupling tensor and the values of the zero field parameters D = ?96.2 gauss and E = ?2.7 gauss, it follows that the four triplet sites, generated in the crystals, consist of radical pairs. Each pair radicals is formed from two β-TKN molecules, which are nearest neighbours in the lattice. Measurements at the temperatures 4.2 K and 1.2 K show that the triplet state is the ground state of the radical pair.     

Expression,Purification,Crystallization and Preliminary Crystallographic Analysis of Nucleoside Diphosphate Kinase(NDK) from Aspergillus Flavus

Aspergillus flavus causes serious disease on important agriculture crops, and its secondary metabolic products-aflatoxins are most potent toxin and carcinogen for animal and human. Structural and functional studies of A. flavus proteins may provide insights into the identification of potential therapeutic targets and prevention of damage caused by A. flavus. Here, we report the expression, purification, crystallization and preliminary crystallographic analysis of NDK protein from A. flavus. The NDK protein was expressed in E. coli and purified by using a series of chromatographic methods to 98% purity. The recombinant protein was crystallized and the crystals diffracted to 2.4 ? resolution. The crystal of NDK is in space group of C121 with a = 190.84, b = 169.47, c = 146.94 ?. Preliminary data analysis indicated that the NDK molecule assembles into a multimer in the asymmetric unit.     

正交晶型江浙蝮蛇毒碱性磷脂酶A2初步结晶学研究

The basic phospholipase A2 from the venom of Agkistrodon halys pallas possesses the ability to cause hemolysis in contrast to the other two phospholipase A2 from the same venom. A new form of crystals of this enzyme was grown. The crystals belong to space group of P212121 with unit cell parameters of a=9.175nm, b=10.080nm , c=2.287nm.The crystals diffract to high resolution, and are suitable for detailed structural studies. The data were collected up to 0.25nm resolution using synchrotron radiation-imaging plate-Weissenberg camera system. Preliminary analysis reveals the presence of two molecules in the asymmetric uint and the molecule may pack with the smallest dimension approximately parallel to the c axis. The new crystal form is more attractive than the monoclinic one previously reported for crystallographic structure determination as it contains fewer molecules in the asymmetric unit.     

Growth and Dissolution of Organic Crystals with “Tailor-Made” Inhibitors—Implications in Stereochemistry and Materials Science

When crystals of organic compounds are grown in the presence of growth inhibitors, there is a change in crystal morphology. A stereochemical correlation exists between the crystal structure, its modified morphology, and the molecular structure of the inhibitor. This correlation has been successfully exploited for the efficient resolution of conglomerates, the engineering of organic crystals with desired morphologies, the direct and relative assignment of the absolute configurations of chiral molecules and crystals, and for the design of a new model for the spontaneous generation of optical activity. In an analogous way dissolution of organic crystals in the presence of these growth inhibitors induces etch pits at preselected faces. The effect of solvent on crystal growth has been analyzed in some model systems. The experimental results are complemented by atom-atom potential energy calculations.     

Analysis of guest—host and intra-guest transitions for hydronaphthyl radicals in naphthalene crystals

High resolution spectroscopic studies of optical absorption and emission around 539 nm and 636 nm for 1- and 2-hydronaphthyl radicals in naphthalene crystals have been made. For each radical several lines with the same polarization as the intra-guest OO vibrational lines were assigned as the vibrational progression, the separation being explained in terms of the intramolecular vibrations of naphthalene. About 20 other lines for each radical, including completely a- or b-polarized lines, were ascribed to the guest—host charge transfer transitions. Each line was assigned to the transition to specific molecules around the radical taking the polarization into consideration. The energy of the transition to a molecule at a distance r can be described by a coulombic relation with the dielectric constant ?: E = E_∞ ?e²/?r, where E_∞ is a constant. The phonon sidebands of the absorption and emission lines of the most intense charge transfer transition in the 1-hydronaphthyl radical was also analyzed and compared with phonon singularities in naphthalene crystals.     

Effect of alkali metal doping on the properties and crystalline perfection of bis(thiourea)zinc(II) chloride crystals

The influence of sodium doping on the properties of bis(thiourea)zinc(II) chloride crystals has been described. The reduction in the intensity observed in powder X-ray diffraction of doped specimen and slight shifts in vibrational frequencies confirm the lattice stress as a result of doping. The incorporation of Na(I) into the crystal lattice was confirmed by energy dispersive X-ray spectroscopy. Surface morphological changes due to doping of the alkali metal are observed by scanning electron microscopy. The TG?CDTA studies reveal the purity of the material and no decomposition is observed up to the melting point. The high resolution X-ray diffraction studies reveal that the crystalline quality is improved considerably by doping with alkali metal. High transmittance is observed and cut off ?? is ~270?nm.     

Tribochemische und thermische Umwandlungen von LnTa3O9 (Ln = Pr,Nd) – röntgenographische und elektronenmikroskopische Untersuchungen

Tribochemical and Thermal Transitions of LnTa₃O₉ (Ln = Pr, Nd) — X-ray and Electron Microscopic Investigations Upon grinding crystals of M1? LnTa₃O₉ (Ln = Pr, Nd) [3] undergo a tribochemical phase transition. This leads to a new modifikation M2? LnTa₃O₉ with a significant higher density. We tried to find out more about the structure with high resolution electron microscopic investigations. According to electron diffraction and powder patterns the lattice parameters are (CuKα₁, λ = 1,54051 Å): M2? PrTa₃O₉: a = 6.2545(7) Å, b = 7.6736(7) Å, c = 6.5316(8) Å, β = 93.93(9)°; M2? NdTa₃O₉: a = 6.2552(5) Å, b = 7.6598(7) Å, c = 6.5103(4) Å, β = 94.096(7)°; (Z = 2). Using the intensities of powder patterns two structure models were calculated (space group P2₁/m, P2/m; R < 20%, heavy metal positions only). A through focus series of high resolution images was in better agreement with the first model (space group P2₁/m). Both models show a remarkable similarity to the structure of M? CeTa₃O₉ [4]. A thermal phase transition leads to M? PrTa₃O₉ and M? NdTa₃O₉ which are both isostructural to M? CeTa₃O₉.     

Mass Spectrometry and X-ray Diffraction Analysis of Two Crystal Types of Dioclea virgata Lectin: An Antinociceptive Protein Candidate to Structure/Function Analysis

The lectin from seeds of Dioclea virgata (DvirL) was purified in a single step affinity chromatography, sequenced by tandem mass spectrometry and submitted to crystallization and biological experiments. DvirL has a molecular mass of 25,412?±?2 Da and the chains β and γ has 12,817 Da?±?2 and 12,612 Da?±?2, respectively. Primary sequence determination was assigned by tandem mass spectrometry and revealed a protein with 237 amino acids and 87% of identify with ConA. The protein crystals were obtained native and complexed with X-Man using vapor-diffusion method at a constant temperature of 293 K. A complete X-ray dataset was collected at 1.8 ? resolution. DvirL crystals were found to be orthorhombic, belonging to the space group I222, with a unit cell parameters a?=?647.5 ?, b?=?86.6 ?, c?=?90.2 ?. Molecular replacement search found a solution with a correlation coefficient of 77.1% and an R(factor) of 44.6%. The present study also demonstrated that D. virgata lectin presents edematogenic and antinociceptive activities in rodents electing this protein as a candidate to structure/function analysis.     

Preparation and Crystal Structure of a Charge-transfer Complex between an Organic Substrate and Molybdosilicic Acid [(CH_3)_2NH(CH_2)C_6H_5]_4SiMo_(12)O_(40)·2CH_3CN·H_2O

1 INTRODUCTION Photochromism of intermolecular complexes based on polyoxometalates has received increasing attention due to their potential applications in ma- terial science[1～3]. However, most studies of photo- chromism have been made in solution[4～7], and those in solid state are relatively less and only a few with photosenstivity properties have been studied crystal- lographically. The title compound has a light yellow color in the darkness and turns greenish when exposed to sunligh…     

Molecular lattice resolution of single faceted crystals of a thermotropic liquid crystalline poly(aryl ether ketone) using atomic force microscopy

Communication: The surfaces of single faceted crystals of a thermotropic liquid crystalline poly(aryl ether ketone) copolymer containing chloro‐side group are investigated by atomic force microscope. The molecular lattice resolution images of the single faceted crystals indicate that the surfaces of the crystals consist of molecular chain ends of the copolymer, and the crystals exhibit orthorhombic packing with the unit cell dimensions of a = 0.787 ± 0.020 nm and b = 0.625 ± 0.010 nm, respectively. The data are further confirmed by electron diffraction results.     

豆薯种子中一种具有抗植物病毒活性的蛋白质的初步晶体学研究

从豆科植物豆薯 (Pachyrrhizuserosus,Leguminosae)的种子中分离纯化了一种具有抗植物病毒活性的蛋白质 ,分子量约为 1 5kD。在 2 0 % (w/v)PEG60 0 0 ,0 .1mol/L磷酸盐缓冲液 (pH7.4)条件下得到了可供衍射用的单晶 ,在MarResearchIP上进行了衍射数据收集 ,其衍射能力达 2 .3 。经MarDenzo软件包处理 ,确定其空间群为P2 1 2 1 2 1 ,晶胞参数为 :a =2 8.80 8,b =32 .840 ,c=1 40 .397 。根据Matthews常数估算 ,每个不对称单元含 1个分子。     

Crystal Structure of Crotin Ⅱ at 2.5  Resolution

1INTRODUCTIONTheplanttoxin,CrotinIisoneoftheribosomeinactivatingproteins(RIPs)[l3.AccordingtothemolecularmechanismofactiontheRIPscanbedividedintotwokinds[2:.OnebelongstoRNAN-glycosidasewhichisclassifiedastwotypes.TypeIconsistsofasinglepolypeptidechain,forexample,trichosanthinandsaporin-Typellconsistsoftwochains,suchasricinandabrin'ThiskindofRIPshydrolysesasingleN-glycosidicbondbetweenanadenineandriboseatspecificnu-cleotide(A4324)of28SrRNAintheribosomes[3i.ThesecondkindofRIPsbel…     

Polytype phase transition in the series GaSe1−xSx

The structure of crystals GaSe_1?xS_x, grown by the iodine transport method, has been investigated with X-ray diffraction techniques. Between x = 0.2 and 0.3 a phase segregation has been found, which is indicative of the first-order nature of the ? to β polytype transitions, which occur in this composition region with increasing sulfur content.