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At least 397 records · Page 22Linked to original sources
PubMed2000

Crystallization and preliminary characterization of crystals of R-alcohol dehydrogenase from Lactobacillus brevis.

The R-specific alcohol dehydrogenase (RADH) from Lactobacillus brevis is a valuable catalyst for the production of chiral alcohols that can be used as synthons in asymmetric syntheses. RADH is a homotetramer with 222 symmetry and a molecular mass of 107 kDa. The recombinant enzyme has been expressed in Escherichia coli, purified to homogeneity and crystallized. The crystals belong to the orthorhombic space group I222, with unit-cell parameters a = 56.5, b = 85.1, c = 115.4 A, and diffract X-rays to at least 1.8 A resolution. The calculated crystal packing parameter V(M) = 2.59 A(3) Da(-1), corresponding to a solvent content of 52.5% and suggesting that one RADH monomer is contained in the asymmetric unit. The RADH tetramer lies on a special position with its molecular dyads coinciding with the crystallographic twofold axes and with its centre of mass on the origin of the unit cell.

Alcohol Dehydrogenase↗
PubMed2001

Purification, crystallization and preliminary X-ray analysis of two crystal forms of ribonuclease Sa3.

RNase Sa3 produced by Streptomyces aureofaciens strain CCM 3239 belongs to the T1 family of microbial ribonucleases. It is closely related both to RNase Sa, studied in detail earlier, and to RNase Sa2 produced by the same microorganism. The most important property of RNase Sa3 is the relatively high cytotoxic activity, which was not observed for RNase Sa and Sa2. Recombinant RNase Sa3 was overexpressed in Escherichia coli and purified to high homogeneity. The hanging-drop vapour-diffusion method was used for crystallization. The two crystal forms are trigonal P3(1)21 and tetragonal P4(1)2(1)2, with unit-cell parameters a = b = 64.7, c = 69.6 A, gamma = 120 degrees and a = b = 34.0, c = 147.2 A, respectively. They diffract to 2.0 and to 1.7 A resolution, respectively, using synchrotron radiation. The asymmetric units of crystal forms I and II contain one molecule of the enzyme, which corresponds to V(M) = 3.8 A(3) Da(-1) with a solvent content of 68% and V(M) = 1.9 A(3) Da(-1) with a solvent content of 37%, respectively.

Crystallization↗
PubMed2001

Histochemical method for characterization of enzyme crystals: application to crystals of Torpedo californica acetylcholinesterase.

Histochemical methods are employed to detect and localize a wide range of enzymes. Even though protein crystallographers do not commonly use this technique, the extensively used colorimetric reaction of Karnovsky was successfully adapted for easy and quick identification of acetylcholinesterase crystals. The method relies on the reduction of ferricyanide to ferrocyanide by thiocholine, released from acetylthiocholine by enzymatic hydrolysis, followed by formation of a cupric ferrocyanide precipitate, and allows rapid differentiation between salt and enzyme crystals and between native and inhibited crystals of the enzyme.

Acetylcholinesterase↗
PubMed2001

Crystallization of quinohaemoprotein alcohol dehydrogenase from Comamonas testosteroni: crystals with unique optical properties.

Quinohaemoprotein alcohol dehydrogenase from Comamonas testosteroni is a functional electron-transfer protein containing both a haem c and a pyrroloquinoline quinone cofactor. The enzyme has been crystallized at 277 K using polyethylene glycol 6000 as precipitant. The crystals belong to space group C2, with unit-cell parameters a = 98.1, b = 74.3, c = 92.2 A, beta = 105.9 degrees. A native data set with a resolution of 2.44 A resolution has been collected. The approximate orientation of the haem group with respect to the unit-cell axes has been determined from the optical properties of the crystals.

Alcohol Oxidoreductases↗
PubMed2002

Effects of a magnetic field and magnetization force on protein crystal growth. Why does a magnet improve the quality of some crystals?

Probable reasons why some protein crystals grown in a magnet exhibited better quality than control are discussed as follows. (1). Sedimenting three-dimensional nuclei are able to have the same orientation as the underlying, mother crystal into which the nuclei merge. (2). Protein solution may become more viscous, leading to reduction of convection. (3). If an upward force is generated by use of an inhomogeneous magnetic field, the effects of the density differences can be made less significant, causing the reduction of natural convection and the retardation of crystal sedimentation.

Animals↗
PubMed2004

Crystals of the ribonucleotide reductase R2 protein from Chlamydia trachomatis obtained by heavy-atom co-crystallization.

Ribonucleotide reductases (RNRs) catalyse the conversion of ribonucleotides to deoxyribonucleotides, utilizing radical chemistry to carry out the reaction. Class I RNRs consist of R1 and R2 subunits: R1 contains the active site and R2 generates and stores a stable tyrosyl radical. The conserved tyrosine where the radical is stored until needed in R1 has previously been believed to be an absolute requirement for R2 activity. The Chlamydia trachomatis R2 lacks this tyrosine and a phenylalanine is present in its place, but the protein is still active. Here, the crystallization of C. trachomatis R2 is described. A heavy-atom co-crystallization approach was used to obtain crystals. Hopefully, the C. trachomatis R2 structure will provide key clues as to how this enzyme is able to function while lacking the features that have previously been believed to be essential for activity.

Binding Sites↗
PubMed2004

Crystallization of Pseudomonas aeruginosa AHL synthase LasI using beta-turn crystal engineering.

In Gram-negative bacteria, intercellular communication and virulence regulation is mediated by the diffusible chemical signal acyl-homoserine-L-lactone (AHL). The AHL synthase enzymes produce a variety of AHLs from the substrates S-adenosyl-L-methionine and acyl-acyl carrier protein. LasI, the AHL synthase from Pseudomonas aeruginosa, has low solubility and has failed to crystallize despite extensive crystallization trials. Based on the previously determined structure of the AHL synthase EsaI, active soluble LasI was produced by re-engineering residues in a tight turn to produce a type I' beta-turn. The resulting protein is active, more stable than the wild-type LasI and has been crystallized in the cubic space group F23, with unit-cell parameters a = b = c = 154.90 A.

4-Butyrolactone↗
PubMed2004

Expression, purification, crystallization and preliminary crystal structure analysis of the Deinococcus radiodurans organic hydroperoxide-resistance protein.

The organic hydroperoxide-resistance protein (DR1857) from Deinococcus radiodurans has been expressed, purified and crystallized. The crystals are suitable for X-ray analysis, diffract to at least 2.3 A resolution, have unit-cell parameters a = 45.7, b = 59.6, c = 49.7 A, beta = 90.43 degrees and belong to space group P2(1). The calculated Matthews coefficient of 2.1 A(3) Da(-1) coupled with a calculated solvent content of approximately 42% is consistent with the presence of a homodimer in the asymmetric unit. Here, the methods used in the overexpression and purification of the protein are described and details of crystallization conditions and preliminary X-ray diffraction are provided.

Bacterial Proteins↗
PubMed2004

Crystallization of parasporin-2, a Bacillus thuringiensis crystal protein with selective cytocidal activity against human cells.

Bacillus thuringiensis is a valuable source of protein toxins that are specifically effective against certain insects and worms but harmless to mammals. In contrast, a protein toxin obtained from B. thuringiensis strain A1547, designated parasporin-2, is not insecticidal but has a strong cytocidal activity against human cells with markedly divergent target specificity. The 37 kDa inactive protein is proteolytically activated to a 30 kDa active form. The active form of the recombinant protein toxin was crystallized in the presence of ethylene glycol and polyethylene glycol 8000 at neutral pH. The crystals belong to the hexagonal space group P6(1) or P6(5), with unit-cell parameters a = b = 134.37, c = 121.24 A. Diffraction data from a native crystal were collected to 2.75 A resolution using a synchrotron-radiation source.

Bacillus thuringiensis↗
PubMed2005

Crystallization of foot-and-mouth disease virus 3C protease: surface mutagenesis and a novel crystal-optimization strategy.

Foot-and-mouth disease virus (FMDV) 3C protease (3C(pro)) plays a vital role in virus replication by performing most of the cleavages required to divide the viral polyprotein precursor into its functional component proteins. To date, no structural information has been available for FMDV 3C(pro), which is an attractive target for antiviral drugs. Targeted mutagenesis of surface amino acids identified two Cys residues that were detrimental to solubility and contributed to the time-dependent formation of a proteinaceous skin in samples of purified wild-type protein. Substitution of these amino acids, combined with trimming of the N- and C-termini, yielded a 3C(pro) construct that was amenable to crystallization. High-resolution diffraction (1.9 A) was only obtained following 'iterative screening' in which commercial crystal screening solutions were used as additives once initial crystallization conditions had been obtained.

3C Viral Proteases↗
PubMed1999

Crystallization and preliminary analysis of a DNA dodecamer of d(CGCGmo6AATCCGCG) containing 2'-deoxy-N6-methoxyadenosine: change in crystal packing with different humidity.

The DNA dodecamer of (CGCGmo6AATCCGCG) containing 2'-deoxy-N6-methoxyadenosine has been crystallized for X-ray analysis in order to investigate the effects of the modified adenosine on base pairing. It has been found that the crystal changes from one form to another during data collection in a manner similar to a phase transition. The two crystal structures show that this phenomenon, ascribed to differences in humidity, is correlated with a change in the contact angle between the two duplexes.

Crystallization↗
PubMed1999

Crystallization and improvement of crystal quality for x-ray diffraction of maltooligosyl trehalose synthase by reductive methylation of lysine residues.

Maltooligosyl trehalose synthase, one of the two enzymes in the coupled trehalose biosynthesis system in Sulfolobus acidocaldarius, has been purified and crystallized. The chemical modification of this enzyme by reductive methylation of lysine residues significantly improved the crystal quality for X-ray diffraction experiments. The crystals of the modified enzyme belong to orthorhombic space group P212121, with unit-cell parameters a = 56.70, b = 140.1, c = 205.2 A measured at cryo-temperature, and are found to contain two enzyme molecules per asymmetric unit.

Archaeal Proteins↗
PubMed1999

Crystallization and preliminary diffraction data analysis of both single and pseudo-merohedrally twinned crystals of rubredoxin oxygen oxidoreductase from Desulfovibrio gigas.

Crystals of rubredoxin oxygen oxidoreductase have been obtained and characterized. They belong to space group P2(1)2(1)2, with unit-cell dimensions a = 88.24 (15), b = 101.25 (7), c = 90.80 (3) A. The homodimer (86 kDa) in the asymmetric unit is related by a non-crystallographic twofold rotation axis parallel to the ab 'diagonal' direction, as shown by the self-rotation maximum in the section with chi = 180 degrees. This pseudo-crystallographic symmetry element was also found to be the twinning axis of pseudo-merohedrally twinned crystals, leading to apparent pseudo-tetragonal P42(1)2 crystal symmetry.

Cold Temperature↗
PubMed2002

Crystal engineering: from structure to function.

Modern crystal engineering has emerged as a rich discipline whose success requires an iterative process of synthesis, crystallography, crystal structure analysis, and computational methods. By focusing on the molecular recognition events during nucleation and growth, chemists have uncovered new ways of controlling the internal structure and symmetry of crystals and of producing materials with useful chemical and physical properties.

Journal Article↗
PubMed2004

Trapping crystal nucleation of cholesterol monohydrate: relevance to pathological crystallization.

Crystalline nucleation of cholesterol at the air-water interface has been studied via grazing incidence x-ray diffraction using synchrotron radiation. The various stages of cholesterol molecular assembly from monolayer to three bilayers incorporating interleaving hydrogen-bonded water layers in a monoclinic cholesterol.H(2)O phase, has been monitored and their structures characterized to near atomic resolution. Crystallographic evidence is presented that this multilayer phase is similar to that of a reported metastable cholesterol phase of undetermined structure obtained from bile before transformation to the triclinic phase of cholesterol.H(2)O, the thermodynamically stable macroscopic form. According to grazing incidence x-ray diffraction measurements and crystallographic data, a transformation from the monoclinic film structure to a multilayer of the stable monohydrate phase involves, at least initially, an intralayer cholesterol rearrangement in a single-crystal-to-single-crystal transition. The preferred nucleation of the monoclinic phase of cholesterol.H(2)O followed by transformation to the stable monohydrate phase may be associated with an energetically more stable cholesterol bilayer arrangement of the former and a more favorable hydrogen-bonding arrangement of the latter. The relevance of this nucleation process of cholesterol monohydrate to pathological crystallization of cholesterol from cell biomembranes is discussed.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1994

Effect of crystallization on fracture strength of castable glass-ceramics containing two crystals.

The relationship between fracture strength and crystallization in castable glass-ceramics was studied using castable glass-ceramics which contained crystalline apatite and magnesium titanate. Bending strength was increased with increases in crystal phases; 90, 124, 122 and 162 MPa were recorded for as-cast specimens and specimens cerammed at temperatures of 905 degrees, 925 degrees and 945 degrees C, respectively. The results of bending tests suggest that the crystallization of magnesium titanate is more effective than that of apatite in increasing the strength of glass-ceramics. Fracture toughness in specimens reheated at 905 degrees C was doubled compared with as-cast specimens. The apatite particles precipitated during ceramming treatment were thought to be an important factor in increasing both the fracture toughness and crack pinning effect.

Apatites↗
PubMed2005

[Crystal growth and spectroscopy of Er/Yb:KGW crystal].

The Er3 /Yb3+:KGW crystal with the dimensions of 30 mm x 25 mm x 15 mm was grown from K2W2O7 solvent by modified Czochralski method. The absorption spectrum was measured at room temperature and its absorption peaks were assigned. The emission spectrum was obtained under the excitation of 980 nm. There are two broad emission bands at 1024 and 1535 nm, whose FHWM are 60 and 36 nm respectively. It shows that this crystal is suitable for InGaAs LD pumping, and may be a promising laser crystal tunable at near 1 024 and 1 535 nm.

Crystallization↗
PubMed1989

Ultrastructural localization of the Charcot-Leyden crystal protein (lysophospholipase) to granules and intragranular crystals in mature human basophils.

Human blood basophils have been shown to form Charcot-Leyden crystals (CLC) and to contain quantities of CLC protein comparable to the eosinophil (Ackerman SJ, Weil GJ, Gleich GJ, J Exp Med 155:1597, 1982). We examined the subcellular localization of CLC protein in human basophils from peripheral blood using an ultrastructural postembedding immunogold method and affinity chromatography-purified polyclonal primary antibody to purified human eosinophil CLC protein. We found CLC protein to be uniquely associated with the main, large, particle-filled granule population of human basophils and particularly within intragranular Charcot-Leyden crystals in these granules. Rarely, CLC protein was localized within small, smooth perigranular vesicles. Neutrophils, lymphocytes, and monocytes present in preparations stained for the CLC protein were negative as were controls for the specificity of the immunogold staining. Mature eosinophils contained small numbers of positive crystalloid-free primary granules, as previously reported (Dvorak AM, Letourneau L, Login GR, Weler PF, Ackerman SJ, Blood 72:150, 1988). The presence of CLC protein in hexagonal and pyramidal crystals regularly present in activated types II and III basophils suggests two possibilities currently being investigated. Like eosinophils, basophils could synthesize CLC protein, or eosinophil-derived CLC protein could be internalized and stored in basophil granules. Regardless of the mechanism for acquisition of CLC protein (lysophospholipase) by basophils, the identification and subcellular localization of this enzyme in basophils requires that it be considered in basophil cell biology as well as in the pathobiology of basophil-rich reactions.

Basophils↗