Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Crystallization”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources
PubMed1996

Atomic force microscopy of insulin single crystals: direct visualization of molecules and crystal growth.

Atomic force microscopy performed on single crystals of three different polymorphs of bovine insulin revealed molecularly smooth (001) layers separated by steps whose heights reflect the dimensions of a single insulin hexamer. Whereas contact mode imaging caused etching that prevented molecular-scale resolution, tapping mode imaging in solution provided molecular-scale contrast that enabled determination of lattice parameters and polymorph identification while simultaneously enabling real-time examination of growth modes and assessment of crystal quality. Crystallization proceeds layer by layer, a process in which the protein molecules assemble homoepitaxially with nearly perfect orientational and translational commensurism. Tapping mode imaging also revealed insulin aggregates attached to the (001) faces, their incorporation into growing terraces, and their role in defect formation. These observations demonstrate that tapping mode imaging is ideal for real-time in situ investigation of the crystallization of soft protein crystals of relatively small proteins such as insulin, which cannot withstand the lateral shear forces exerted by the scanning probe in conventional imaging modes.

Animals↗
PubMed1993

Crystallization kinetics of calcium oxalate in fresh, minimally diluted urine: comparison of recurrent stone formers and healthy controls in a continuous mixed suspension mixed product removal crystallizer.

A reproducible method has been developed for studying calcium oxalate crystallization from fresh, minimally diluted (92%) urine with the mixed suspension mixed product removal continuous crystallization technique. All samples were adjusted to give the same starting calcium and oxalate concentrations. Twenty-one recurrent male stone formers were compared with twenty-two healthy controls. There was no difference in crystal growth rates but crystal nucleation rates were much higher in the control group (p = 0.003). Using growth rate and nucleation rate results, the amount of crystalline material in suspension was shown to be lower in the urine from stone formers, and therefore the equilibrium supersaturation in the crystallizer was lower in the control group (p = 0.001). We propose that the ability of a healthy person's urine to maintain a lower supersaturation is a crucial protective factor distinguishing non-stone formers from stone formers.

Calcium Oxalate↗
PubMed1994

The sequence, crystal structure determination and refinement of two crystal forms of lipase B from Candida antarctica.

BACKGROUND: Lipases constitute a family of enzymes that hydrolyze triglycerides. They occur in many organisms and display a wide variety of substrate specificities. In recent years, much progress has been made towards explaining the mechanism of these enzymes and their ability to hydrolyze their substrates at an oil-water interface. RESULTS: We have determined the DNA and amino acid sequences for lipase B from the yeast Candida antarctica. The primary sequence has no significant homology to any other known lipase and deviates from the consensus sequence around the active site serine that is found in other lipases. We have determined the crystal structure of this enzyme using multiple isomorphous replacement methods for two crystal forms. Models for the orthorhombic and monoclinic crystal forms of the enzyme have been refined to 1.55 A and 2.1 A resolution, respectively. Lipase B is an alpha/beta type protein that has many features in common with previously determined lipase structures and other related enzymes. In the monoclinic crystal form, lipid-like molecules, most likely beta-octyl glucoside, can be seen close to the active site. The behaviour of these lipid molecules in the crystal structure has been studied at different pH values. CONCLUSION: The structure of Candida antarctica lipase B shows that the enzyme has a Ser-His-Asp catalytic triad in its active site. The structure appears to be in an 'open' conformation with a rather restricted entrance to the active site. We believe that this accounts for the substrate specificity and high degree of stereospecificity of this lipase.

Amino Acid Sequence↗
PubMed2000

Orientations of liquid crystals on mechanically rubbed films of bovine serum albumin: a possible substrate for biomolecular assays based on liquid crystals.

We report the uniform planar anchoring of thermotropic liquid crystals on films of bovine serum albumin (BSA) covalently immobilized on the surface of glass microscope slides and mechanically rubbed using a cloth. The azimuthal orientations of the liquid crystals were measured to be parallel to the direction of rubbing. Following immersion and removal of these rubbed films of BSA from aqueous solutions containing either BSA, fibrinogen, lysozyme, anti-FITC immunoglobulin G (IgG), or antistreptavidin IgG, we measured liquid crystals placed onto these surfaces to largely retain their uniform alignment. In contrast, following immersion of a rubbed film of BSA into an aqueous solution of anti-BSA IgG, we observed liquid crystals on these surfaces to assume nonuniform orientations. We conclude that specific binding of anti-BSA IgG to the film of rubbed BSA erased anisotropy induced within the film of BSA by rubbing. This result suggests that the spatial scale of anisotropy within the rubbed film of BSA is comparable to or smaller than the size of the IgG molecule. Because the anisotropy within a rubbed film of a protein can be erased by specific binding of a second protein, we believe these types of substrates (rubbed films of proteins) have the potential to be useful in a variety of label-free biomolecular assays where specific binding of a target species to its ligand can be imaged through observation of the optical appearance of liquid crystal placed onto the surface.

Adsorption↗
PubMed1994

Preparation of agglomerated crystals for direct tabletting and microencapsulation by the spherical crystallization technique with a continuous system.

Adhesive and cohesive properties of chlorpromazine hydrochloride (CP) crystals were modified to improve their powder processing, e.g., direct tabletting and microencapsulation, by agglomeration. Moreover, sustained-released gelling microcapsules of CP were devised to prolong the pharmacological effect. The spherical crystallization technique was applied to prepare agglomerates for direct tabletting and microencapsulation to use them as core materials. The ethanolic solution dissolving CP was poured into a stirred cyclohexane, yielding spherically agglomerated crystals. The resultant agglomerates were free-flowing and easily packable spheres with average diameters of 200 to 1000 microns. The agglomerates reserved the high compressibility of the original powder having a small particle size (14 microns). The compression behavior represented by Heckel's equation suggested that the agglomerates were disintegrated to individual primary crystals at low compression pressures, and then they were closely repacked and plastically deformed at higher pressures. After agglomeration, microencapsulation was continuously performed in the same batch by a phase separation method. Coacervate droplets produced by pouring cyclohexane into a dichloromethane solution, dissolving polyvinyl acetate as a coating polymer, were added to the crystallization system under stirring, to prepare the microcapsules. By filling the microcapsules in gelatin hard capsules or tabletting them, their drug release rates became retarded compared with the physical mixture treated in the same way, having the same formulation as the microcapsules. This phenomenon was due to the gelation of polyvinyl acetate of the microcapsules in the dissolution medium, whose glass transition temperature is very low. This novel sustained-release dosage form is termed "gelled microcapsules."

Adhesiveness↗
PubMed1965

FORMATION OF CHARCOT-LEYDEN CRYSTALS IN HUMAN EOSINOPHILS AND BASOPHILS AND STUDY OF THE COMPOSITION OF ISOLATED CRYSTALS.

Methods are described for the isolation of human eosinophils and basophils from donor blood. Using these cell preparations Charcot-Leyden crystals were found to originate from both eosinophils and basophils when the cells were suspended in hypotonic saline solution. The crystals formed also when saline extracts of eosinophils and basophils were concentrated by ultrafiltration through dialysis tubing. Fractions of eosinophils were prepared and the crystals were obtained from the cytoplasmic fraction but not from the nuclear or granular fractions. Chemical studies showed the crystals to be protein in nature and some evidence is presented which suggests that RNA may decrease the tendency for the protein to crystallize out of solution.

Basophils↗
PubMed1998

Crystal structure of carboxypeptidase A complexed with an inactivator in two crystal forms.

Two different crystal forms of carboxypeptidase A (CPA) complexed with an inactivator were obtained by the method of hanging drop vapor diffusion. The inactivator, 2-benzyl-3-iodo-propanoic acid (BIPA), binds covalently to an active site residue Glu270 of CPA. The complexes were crystallized in the space group P2(1) (CPA-I) and P2(1)2(1)2(1) (CPA-II), respectively. The structures of both crystal forms were determined by molecular replacement using the native CPA crystal structure as the search model. The final crystallographic residuals are 0.163 for CPA-I and 0.152 for CPA-II. Except for the modification of Glu270, the inactivator exhibits normal binding mode compared with other ligand complexes of CPA. In the final electron density difference maps (2Fo-Fc, Fo-Fc), the density of the iodo ion could not be found in both crystal forms while the conserved water molecule remains coordinated to Zn2+ as in the native CPA. Comparisons of the complexes of CPA-BIPA with the native CPA and the CPA-D-Phe complex are presented. The mechanism of the inactivation of CPA and its implication for catalytic mechanism were discussed.

Animals↗
PubMed2000

A legume lectin from the bark of Robinia pseudoacacia crystallizes in two crystal forms: preliminary diffraction analyses.

The A(4) isoform of the bark lectin RPbAI from Robinia pseudoacacia has been crystallized in two different crystal forms. Crystal form I grows in the P2(1) space group with two tetramers in the asymmetric unit, whereas crystal form II grows in the I222 space group with a monomer in the asymmetric unit. Data sets were collected for both crystal forms to resolution limits of 2.55 and 1.81 A, respectively, which will allow successful structure determinations.

Crystallization↗
PubMed2001

Crystallization of a large single crystal of a B-DNA decamer for a neutron diffraction experiment by the phase-diagram technique.

Crystallization of a large single crystal of a B-DNA decamer, d(CCATTAATGG), for a neutron-diffraction experiment has been accomplished by an analysis of its solubility phase diagram and a large single crystal was successfully crystallized at around the minimum solubility point of the oligonucleotide: 30%(v/v) MPD, 100 mM MgCl(2) pD 6.6 using 0.4 ml D(2)O solutions of the DNA (sample concentration 1.5 mM). It is confirmed that the resulting crystal (dimensions: 1.7 x 1.3 x 0.6 mm) diffracts sufficiently well for neutron data collection.

Base Sequence↗
PubMed2002

Semi-automatic protein crystallization system that allows in situ observation of X-ray diffraction from crystals in the drop.

Semi-automatic protein crystallization device was developed using 96 format Hydra dispenser. Eight extra syringes were added for pipetting protein solution with its own dispensing mechanism. This device allows setting up 96 drops in about three minutes. New crystallization plate has also been developed. The plate allows collecting an oscillation photograph of the crystal directly in the drop. The diffraction quality of the crystals in the drops can be inspected without causing any other physical perturbations to the crystals. With the modified dispenser and this plate, we can perform both hanging and sitting drop vapour diffusion method.

Archaeal Proteins↗
PubMed2003

Optimization of crystals from nanodrops: crystallization and preliminary crystallographic study of a pheromone-binding protein from the honeybee Apis mellifera L.

Pheromone-binding proteins (PBPs) are small helical proteins ( approximately 13-17 kDa) present in various sensory organs from moths and other insect species. They are involved in the transport of pheromones from the sensillar lymph to the olfactory receptors. Here, crystals of a PBP (Amel-ASP1) originating from honeybee (Apis mellifera L.) antennae and expressed as recombinant protein using the yeast Pichia pastoris are reported. Crystals of Amel-ASP1 have been obtained by the sitting-drop vapour-diffusion method using a nanodrop-dispensing robot under the following conditions: 200 nl of 40 mg ml(-1) protein solution in 10 mM Tris, 25 mM NaCl pH 8.0 was mixed with 100 nl of well solution containing 0.15 M sodium citrate, 1.5 M ammonium sulfate pH 5.5. The protein crystallizes in space group C222(1), with unit-cell parameters a = 74.8, b = 85.8, c = 50.2 A. With one molecule in the asymmetric unit, V(M) is 3.05 A(3) Da(-1) and the solvent content is 60%. A complete data set has been collected at 1.6 A resolution on beamline ID14-2 (ESRF, Grenoble). The nanodrop crystallization technique used with a novel optimization procedure made it possible to consume small amounts of protein and to obtain a unique crystal per nanodrop, suitable directly for data collection in-house or at a synchrotron-radiation source.

Amino Acid Sequence↗
PubMed2003

Crystallization of the PX domain of cytokine-independent survival kinase (CISK): improvement of crystal quality for X-ray diffraction with sodium malonate.

Phox homology (PX) domains play critical roles in the intracellular localization of a variety of cell-signaling proteins through interactions with specific phosphoinositides. For cytokine-independent survival kinase (CISK), the PX domain also plays a role in the regulation of CISK activity in response to the activation of phosphatidylinositol-3 (PI-3) kinase. The PX domain of mouse CISK has been purified and crystallized, as well as its complex with a phosphoinositide ligand. The native PX domain was crystallized in space group I4 and the crystals diffracted to a maximum resolution of 1.6 A. Selenomethionine-derivatized PX domain was also prepared and crystallized for MAD phasing. In this study, the use of sodium malonate is the key to both successful crystallization and cryoprotection of the PX domain of CISK.

Animals↗
PubMed2004

Crystals of the beta-subunit of bovine luteinizing hormone and indicators for the involvement of proteolysis in protein crystallization.

The beta-subunit of luteinizing hormone (LH), the subunit responsible for the physiological response, has been crystallized beginning with the intact alphabeta-heterodimeric hormone purified from bovine pituitary glands. The crystals were grown at 310 K in the presence of neutral detergents along with trypsin. The tetragonal bipyramidal crystals diffract to 3 A resolution and belong to space group I4(1)22, with unit-cell parameters a = b = 57, c = 207 A. It is noted that proteins exposed to proteases sometimes yield products that crystallize better than the native molecule and that the beta-subunit of LH represents yet another example. Some indicators of when proteolysis may be a factor in crystallization, as well as some consequences, are described.

Animals↗
PubMed2005

Investigating crystal-growth mechanisms with and without LB template: protein transfer from LB to crystal.

Protein nanocrystallography has recently been introduced as a unique nanotechnology-based approach to forming stable protein crystals and to characterize them down to atomic resolution. In particular, a protein nanostuctured template appears to be capable of stimulating nucleation and crystal growth of so far unsolved proteins. In the present communication, aimed at investigating the lysozyme crystal-growth mechanisms with and without nanotemplate, the lysozymes appear to transfer directly from the nanostructured film into the drop to trigger the formation of the crystal, therefore highlighting the physical interpretation of the mechanism for nanotemplate-induced protein crystallization.

Animals↗
PubMed1999

Crystallization and preliminary x-ray study of two crystal forms of Klebsiella oxytoca diol dehydratase-cyanocobalamin complex.

Two crystal forms of Klebsiella oxytoca diol dehydratase complexed with cyanocobalamin have been obtained and preliminary crystallographic experiments have been performed. The crystals belong to two different space groups, depending on the crystallization conditions. One crystal (form I) belongs to space group P212121 with unit-cell parameters a = 76.2, b = 122.3, c = 209. 6 A, and diffracts to 2.2 A resolution using an X-ray beam from a synchrotron radiation source. The other crystal (form II) belongs to space group P21 with unit-cell parameters a = 75.4, b = 132.7, c = 298.8 A, beta = 91.9 degrees, and diffracts to 3.0 A resolution. For the purpose of structure determination, a heavy-atom derivative search was carried out and some mercuric derivatives were found to be promising. Structure analysis by the multiple isomorphous replacement method is now under way.

Bacterial Proteins↗
PubMed2003

Crystallization of a large single crystal of cubic insulin for neutron protein crystallography.

The growth of a large single crystal of cubic porcine insulin for characterization of hydrogen and hydration in cubic insulin crystals by neutron diffraction analysis is reported. Growth in D2O was investigated based on the phase diagram for cubic insulin to determine appropriate growth conditions, and a large single crystal was then successfully grown by a dialysis method to a size of 4.0 x 4.0 x 1.3 mm3. Neutron diffraction analysis of the cubic insulin crystals was carried out using a single-crystal diffractometer at the JRR-3M reactor of the Japan Atomic Energy Research Institute. In preliminary analysis, Npi appears to be protonated and Ntau deprotonated in His5 in the B-chain, whereas both Npi and Ntau are protonated in His10.

Crystallization↗
PubMed2005

Crystallization and crystal manipulation of a steric chaperone in complex with its lipase substrate.

Bacterial lipases that are secreted via the type II secretion pathway require a lipase-specific foldase in order to obtain their native and biologically active conformation in the periplasmic space. The lipase-foldase complex from Burkholderia glumae (319 and 333 residues, respectively) was crystallized in two crystal forms. One crystal form belongs to space group P3(1)21 (P3(2)21), with unit-cell parameters a = b = 122.3, c = 98.2 A. A procedure is presented which improved the diffraction of these crystals from approximately 5 to 2.95 A. For the second crystal form, which belonged to space group C2 with unit-cell parameters a = 183.0, b = 75.7, c = 116.6 A, X-ray data were collected to 1.85 A.

Bacterial Proteins↗
PubMed1992

The role of crystal polarity in alpha-amino acid crystals for induced nucleation of ice.

The hydrophobic faces of single crystals of a series of pairs of racemic and chiral-resolved hydrophobic alpha-amino acids were used as a substrate, onto which water vapor has been cooled to freezing. The morphologies and molecular packing arrangements within each crystal pair are similar but only one of each pair exhibits a polar axis, parallel to the hydrophobic face exposed to water. Those crystals that have a polar axis induce a freezing point higher by 4 degrees to 5 degrees C than the corresponding crystals that do not have a polar axis. The results are interpreted in terms of an electric field mechanism that helps align the water molecules into ice-like clusters en route to crystallization.

Amino Acids↗