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PubMed1991

Isolation, crystallization, crystal structure analysis and refinement of constitutive C-phycocyanin from the chromatically adapting cyanobacterium Fremyella diplosiphon at 1.66 A resolution.

Constitutive phycocyanin from cyanobacterium Fremyella diplosiphon (Calothrix sp. PCC 7601) grown in green light, has been isolated and crystallized. The crystals belong to the space group R3 with cell constants a = b = 180.26 A, c = 61.24 A, alpha = beta = 90 degrees, gamma = 120 degrees. The crystal structure has been determined by Patterson search techniques using the molecular model of C-phycocyanin from the cyanobacterium Agmenellum quadruplicatum. The asymmetric unit of the crystal cell consists of two (alpha beta)-monomers related by a local dyad. Three asymmetric units are arranged around a crystallographic triad and form an (alpha beta)6-hexamer, the functional unit in the native antenna rod. The initial structure has been refined in a cyclic manner by energy-restrained crystallographic refinement and modelling until the conventional crystallographic R-factor converged at 18.1% with data to a resolution of 1.66 A. The molecular structure resembles closely the C-phycocyanins of Mastigocladus laminosus and A. quadruplicatum. The conformation and configuration of the alpha-84 and beta-84 chromophores is very similar to the corresponding chromophores in the trimeric C-phycocyanin of M. laminosus, whereas the beta-155 chromophore differs in configuration with C(4)-Z, C(10)-Z and C(15)-Z compared to C(4)-Z, C(10)-Z, C(15)-Z,E. The stereochemistry of the beta-155 chiral centres is C(2)-RC(3)-R and C(31)-S, respectively, whereas alpha-84 and beta-84 have C(2)-RC(3)-R and C(31)-R. The amino acid sequences of constitutive and inducible phycocyanin differ mainly in residues located on the surface of the beta-subunits that mediate the inter-hexameric contacts.

Amino Acid Sequence↗
PubMed1992

Crystal packing in six crystal forms of pancreatic ribonuclease.

We compare the molecular packing of bovine pancreatic ribonuclease A (RNase A) in six crystal forms, two grown with alcohol, three with high salt and one with polyethylene glycol as a precipitant. The six packings differ in the number of molecules in contact and in the extent of the contacts, which bury 1570 A2 to 2790 A2 of the RNase surface. Regions of the protein surface involved in the six packings cover almost the whole RNase molecule. The abundance of polar interactions, about one per 200 A2, is the same in all types of precipitants. All molecule-to-molecule contacts are different in the six crystal forms, except for the one that forms a RNase dimer. The dimer has a large interface covering 1800 A2 and eight to ten polar interactions. Its presence in the three salt-grown crystal forms suggests that it is an intermediate in salt induced crystallization. In contrast, the two alcohol-grown forms contain only small interfaces, implying a different mechanism of nucleation.

Animals↗
PubMed1994

Crystallization and preliminary X-ray crystallographic studies of thermostable xylanase crystals isolated from Paecilomyces varioti.

A highly thermostable xylanase isolated from the thermophilic fungus Paecilomyces varioti has been crystallized by the vapour diffusion method. The isolation of this enzyme by crystallization directly from the culture filtrate projects this fungus as an important source for large-scale production of pure xylanase. The crystals belong to orthorhombic space group P2(1)2(1)2(1) with the unit cell dimensions a = 38.48 A, b = 53.87 A and c = 90.23 A. Four molecules occupy a volume of 187,039.4 A3 along with 34% of solvent. The data collected with an area detector to the resolution of 2.7 A were used to calculate the unit cell parameters and Matthews' constant. The optical behaviour of the crystal was studied at different temperatures to understand its thermal stability.

Computer Simulation↗
PubMed1995

Crystallization and X-ray investigation of vitamin D-binding protein from human serum. Identification of the crystal content.

Vitamin D-binding protein (DBP), a multifunctional, highly polymorphic glycoprotein responsible for the transport of vitamin D and for sequestering extracellular actin, was isolated from human serum and crystallized using vapour diffusion methods. The crystals were grown from 7.5% v/v polyethylene glycol 400 and 0.1 M acetate buffer at pH 4.6. These crystals show diffraction patterns consistent with the tetragonal space groups P4(1) and P4(3) with unit cell dimensions a = b = 135.5(4) A and c = 75.9(4) A. They diffract to 2.3 A. Using polyacrylamide gel electrophoresis it was shown that according to their electrophoretic mobility the O-glycosylated isoforms, with a terminal sialic acid residue, are absent in the crystals.

Crystallization↗
PubMed2006

Electron transfer from NADH bound to horse liver alcohol dehydrogenase (NAD+ dependent dehydrogenase): visualisation of the activity in the enzyme crystals and adsorption of formazan derivatives by these crystals.

The crystals of holoenzyme from native and cross-linked alcohol dehydrogenase exhibit electron transfer from NADH to phenazinium methosulfate (PMS), and then to the tetrazolium salt sodium 3,3'-{1-[(phenylamino)carbonyl]-3,4-tetrazolium}-bis(4-methoxy-6-nitro)benzenesulfonate (XXT). The slow dissociation of the cofactor and/or the conformational change associated can now be bypassed. The reduction product, formazan, did not diffuse out of the crystals in buffer and the crystals turned colored. In the presence of dimethyl sulfoxide or dimethoxyethane, the formazan diffused out to the solution. The reaction rates were found to be, respectively, 18% and 15% of the redox reaction rate of ethanol with cinnamaldehyde, close to the activity determined for the enzyme in solution in the presence of dimethoxyethane. The use of system PMS-tetrazolium salt is a useful tool to visualize the activity of dehydrogenases and other electron transferring systems in the crystalline state. The adsorption of formazan by the alcohol dehydrogenase crystals occurs in solution.

Acrolein↗
PubMed2006

Studies on induction of L-aspartic acid modified chitosan to crystal growth of the calcium phosphate in supersaturated calcification solution by quartz crystal microbalance.

Acidic amino acids, such as aspartic acid (L-Asp) and glutamic acid, are the primary bioactive molecules of the glycoprotein on the organic/inorganic interface of biomineralized tissues. In this study, the induction of chitosan film modified with L-Asp on the crystal growth of hydroxyapatite (HAP) was investigated by a novel in situ analysis approach, quartz crystal microbalance (QCM), associated with the dynamically structural and morphological characterization of precipitation products on various phases by X-ray diffraction (XRD), Fourier-transformed infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The natural chitosan exhibited no inducing ability on the crystal growth of HAP. However, the growth rate of induced HAP was dramatically accelerated by the L-Asp modification of chitosan film and increased with the increase of the concentration of L-Asp in the chitosan substrate. It was shown that the chelation of calcium ion with L-Asp provided a nucleation centre and the cluster nuclei was formed by adsorbing further PO(4)(3-), Ca(2+), and then HAP deposited on the original HAP coating in the supersaturated calcification solution (SCS). The developed method allows a kinetic evaluation of the induction of organic film on crystal nucleation and the growth of HAP in vitro.

Aspartic Acid↗
PubMed2004

Crystallization kinetics of homopolymers: overall crystallization: a review.

This paper is a brief review of the overall crystallization kinetics of synthetic homopolymers. The basic experimental results are presented and compared with theory that is currently available. It is found, surprisingly, that the more sophisticated theories do no better in explaining experimental results than does the free-growth approximation. This is contrary to what is observed for the crystallization of low molecular weight substances. The reason can be attributed to entanglements and other topological defects that are present in the pure melt and are relegated to the non-crystalline regions as crystallization progresses. This results in a more protracted crystallization than is predicted and is yet to be included in theory.

Crystallization↗
PubMed2005

Crystal structure of methyl 3-amino-2,3-dideoxy-beta-D-arabino-hexopyranoside. Stabilization of the crystal lattice by a double network of N-H...O, O-H...N and O-H...O interactions.

The structure, conformation and configuration of methyl 3-amino-2,3-dideoxy-beta-D-arabino-hexopyranoside were investigated by (1)H NMR, (13)C NMR and IR spectroscopy, as well as by optical rotation. The crystal structure was confirmed by single-crystal X-ray crystallographic analysis at 293 K and R = 0.0434 based on 910 independent reflections. The crystal belongs to the monoclinic system, space group of P2(1) with cell dimensions a = 6.050(1) Angstroms, b = 7.284(1) Angstroms, c = 10.289(2) Angstroms, beta = 104.69(3) degrees, D(c) = 1.341 Mg cm(-3) and V = 438.9(1) Angstroms(3) for Z = 2. Furthermore, the molecule has a typical (4)C(1) chair conformation. Hydrogen bonds between sugar molecules are responsible for stabilizing the crystal lattice.

Carbohydrate Conformation↗
PubMed2004

Nano-crystal glass-ceramics obtained by crystallization of vitrified red mud.

Glass has been obtained by melting red mud from Shandong Province in China with different additives. Suitable thermal treatments were employed to convert the obtained glass into nano-crystal glass-ceramics. X-ray diffraction (XRD) patterns showed that the main crystalline phase in both the glass-ceramics is wollastonite (CaSiO3). These crystals are homogeneously dispersed within the parent glass, with an average crystal size of less than 100 nm. The size of nano-crystals varies when different thermal processes were used. Physical and mechanical properties, such as density, thermal expansion coefficient, hardness, and bending strength, of the two glasses have been examined and the corresponding microstructures are discussed. These results demonstrate that both glass-ceramics have potential for a wide range of construction application.

Aluminum↗
PubMed2006

Crystal growth and vibrational spectroscopic studies of the semiorganic non-linear optical crystal--bisthiourea magnesium sulphate.

The semiorganic non-linear optical crystal bisthiourea magnesium sulphate (BTMS) was grown by slow evaporation technique using water as solvent. Vibrational spectra were recorded to determine the symmetries of molecular vibrations. The observed Raman and infrared bands were also assigned and discussed. The optical transmission spectral study was carried out to test the transmitting ability of the crystal in the visible range. The second harmonic generation test of BTMS revealed the non-linear nature of the crystal. The TGA/DTA curve was also recorded for the experimental crystal.

Chemistry, Organic↗
PubMed1998

Low-frequency Raman spectra of lysozyme crystals and oriented DNA films: dynamics of crystal water.

We observed low-frequency Raman spectra of tetragonal lysozyme crystals and DNA films, with varying water content of the samples. The spectra are fitted well by sums of relaxation modes and damped harmonic oscillators in the region from approximately 1 cm(-1) to 250 cm(-1). The relaxation modes are due to crystal water, and the distribution of relaxation times is determined. In wet samples, the relaxation time of a small part of the water molecules is a little longer than that of bulk water. The relaxation time of a considerable part of the crystal water, which belongs mainly to the secondary hydration shell, is an order of magnitude longer than that of bulk water. Furthermore, the relaxation time of some water molecules in the primary hydration shell of semidry samples is shorter than we expected. Thus we have shown that low-frequency Raman measurements combined with properly oriented samples can give specific information on the dynamics of hydration water in the ps range. On the other hand, we concluded, based on polarized Raman spectra of lysozyme crystals, that the damped oscillators correspond to essentially intramolecular vibrational modes.

Crystallization↗
PubMed1990

Crystallization of the reovirus type 3 Dearing core. Crystal packing is determined by the lambda 2 protein.

Core particles of reovirus type 3 Dearing (T3D) crystallized in the face-centered cubic space group F432 with dimensions of 1270 A along each edge of the unit cell. Core particles of reovirus type 1 Lang (T1L) did not crystallize. Experiments with core particles derived from 27 different T1L x T3D reassortant viruses indicated that the L2 genome segment determined the capacity of cores to crystallize. This finding indicates important differences in the surface topography of the L2-translation product, the lambda 2 protein, of these two isolates, and suggests that important crystal contacts are mediated by this protein. These data are used to generate a model of the packing of reovirus core particles within the unit cell.

Crystallization↗
PubMedDate not supplied

Crystallization and preliminary crystal structure of the complex of 17beta-hydroxysteroid dehydrogenase with a dual-site inhibitor.

Human estrogenic 17beta-hydroxysteroid dehydrogenase (17beta-HSD1) catalyzes the synthesis of 17beta-estradiol (E2) from estrone, in the ovary and peripheral tissues. While the structures of 17beta-HSD1 alone and in complex with E2 have been determined (D. Ghosh, V. Pletnev, D.-W. Zhu, Z. Wawrzak, W.-L. Duax, W. Pangborn, F. Labrie, S.-X. Lin, Structure of human 17beta-hydroxysteroid dehydrogenase at 2.20 A resolution, Structure 3 (1995) 503-513), no structures of inhibitor/enzyme complex, either modeled or from crystallography, have been reported before the submission of the present paper. The best available inhibitors are among the 'dual-site inhibitors', blocking estrogenic 17beta-HSD and the estrogen receptor. These compounds belong to a family of estradiol analogues having an halogen atom at the 16alpha position and an extended alkyl-amide chain at the 7alpha position (C. Labrie, G. Martel, J.M. Dufour, G. Levesque, Y. Merand, F. Labrie, Novel compounds inhibit estrogen formation and action, Cancer Res. 52 (1992) 610-615). We now report the crystallization of this enzyme/inhibitor complex. The complex of the best available dual-site inhibitor, EM-139, with 17beta-HSD1 has been crystallized using both cocrystallization and soaking methods. Crystals are isomorphous to the native crystals grown in the presence of 0.06% beta-octyl-glucoside and polyethyleneglycol 4000, with a monoclinic space group C2. Data at 1.8 A have been collected from a synchrotron source. Even though the size of the inhibitor is greater than that of the substrate, our preliminary X-ray-diffraction study shows that EM-139 fits into the active site in a position similar to that of estrogen. The availability of such structural data will help design more potent inhibitors of estrogenic 17beta-HSD.

Apoenzymes↗
PubMed2001

Crystal cataracts: human genetic cataract caused by protein crystallization.

Several human genetic cataracts have been linked recently to point mutations in the gammaD crystallin gene. Here we provide a molecular basis for lens opacity in two genetic cataracts and suggest that the opacity occurs because of the spontaneous crystallization of the mutant proteins. Such crystallization of endogenous proteins leading to pathology is an unusual event. Measurements of the solubility curves of crystals of the Arg-58 to His and Arg-36 to Ser mutants of gammaD crystallin show that the mutations dramatically lower the solubility of the protein. Furthermore, the crystal nucleation rate of the mutants is enhanced considerably relative to that of the wild-type protein. It should be noted that, although there is a marked difference in phase behavior, there is no significant difference in protein conformation among the three proteins.

Cataract↗
PubMed1983

Crystallization of a common cold virus, human rhinovirus 14: "isomorphism" with poliovirus crystals.

Crystals of rhinovirus 14 have been grown reproducibly. They diffract x-rays to a resolution of at least 3.5 A. The orthorhombic crystal unit cell contains two virions, each situated on a crystallographic twofold axis. At less than 30-A resolution, the space group approximates to 1222 with the particles possessing 222 pseudo crystallographic symmetry. The crystals are "isomorphous" with type I polio crystals [Finch, J. T. & Klug, A. (1959) Nature (London) 183, 1709-1714; Hogle, J. M. (1982) J. Mol. Biol. 160, 663-668], suggesting some similarities of structure between enteroviruses and rhinoviruses.

Crystallization↗
PubMed2004

A comparative study of seed crystals for the phosphorus crystallization process.

This study was performed to select a preferred seed crystal material for the phosphorus crystallization process through a comparative study of four materials: electron arc furnace, blast furnace and converter slag, and phosphate rock. Leaching and phosphorus removal tests were conducted to evaluate the efficacy of the four materials as seeding agents. Converter slag demonstrated a much larger leaching capacity with respect to calcium and hydroxide ions than did either electron arc furnace or blast furnace slag. The average phosphorus removal efficiencies of phosphorus rock, and the electron arc furnace, blast furnace and converter slag were 35.9%, 74.2%, 99.1%, and 94.5% following 20, 17, 32, and 175 days of leach time, respectively. Consideration of both technical and cost factors suggests that converter slag may have competitive advantages over the other three seed materials. X-ray diffraction (XRD) analysis showed that peak patterns for hydroxyapatite increased slightly as the hydrous flow time was extended. Scanning electron micrograph (SEM) images revealed that finely distributed cubic crystals were deposited on the surfaces of converter slag. When analyzed by energy dispersive x-ray spectrometer (EDS) mapping, the crystals gave a composition mole ratio (Ca/P) of 1.97 and they were determined to be hydroxyapatite.

Crystallization↗
PubMed2001

Effects of different post-crystallization soaking conditions on the diffraction of Mtcp1 crystals.

The crystal structure of human Mtcp1 was determined at 2 A resolution after the X-ray diffraction limit was improved by post-crystallization soaking in 2.0 M ammonium sulfate for 1-5 months. The effects of varying the ammonium sulfate concentration and addition of polyethylene glycol to the soaking solution were examined in order to understand the phenomenon and to reduce the soaking time. Soaking the crystal for one week in a solution of 1.5 M ammonium sulfate and 2% PEG 3400 gave the desired improvement in diffraction quality. Therefore, different soaking conditions should be explored when crystals show disordered and low-resolution diffraction.

Crystallization↗
PubMed2001

Crystallization and preliminary characterization of crystals of the C-terminal half fragment of tropomodulin.

Tropomodulin (40 kDa) stabilizes the actin-tropomyosin filament by capping the P end (slow-growing end). The C-terminal half (C20, 20 kDa), an independently folded domain that is believed to be responsible for the P-end capping, has been crystallized. Crystals grew in the presence of Zn(2+) as the solution pH was increased from 3 towards the pI of the protein. The crystals belong to the trigonal space group R3. They have unit-cell parameters a = b = 69.6, c = 101.3 A (mean values, with a estimated standard deviation of 0.009 A) and diffract to 1.9 A resolution when the frozen crystals were measured at 120 K on a rotating-anode X-ray source at 120 K.

Carrier Proteins↗