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PubMed1998

Development of calcium oxalate crystals on urothelium: effect of free radicals.

The effects of free radicals on the development of crystals attached to the living epithelium have been studied using an experimental model that enables close simulation of the conditions prevailing in the kidney. The results obtained clearly demonstrate that free radical-damaged cells produce a favorable environment for crystal development. At low free radical concentrations, crystals develop on calcium-enriched zones, whereas at higher concentrations, crystals develop on areas with a destroyed monolayer of superficial cells. Evaluation of the action of some products with antioxidant action and/or crystallization-inhibitory capacity is also included. Antioxidants, such as ascorbic acid and mannitol, exerted the most remarkable effects in avoiding calcium oxalate crystal development, whereas crystal inhibitors, such as citric acid, did not produce any remarkable reduction in calcium oxalate crystallization. Phytic acid notably decreased calcium oxalate crystal development. The ability of phytic acid to diminish calcium oxalate crystallization must be attributed to the combination of its inhibitory capacity of calcium oxalate crystallization and its preventive antioxidant action.

Animals↗

PubMed2006

Convection effects on crystallinity in the growth of In0.3Ga0.7 as crystals by the traveling liquidus zone method.

The influence of convection in a melt on the crystallinity of the TLZ-grown In(0.3)Ga(0.7)As crystals has been investigated by growing crystals with various shapes and dimensions on the ground. No single crystals have been grown when the crystal diameter was 10 mm, but we were successful in growing single crystals by reducing crystal diameter to 2 mm. These results suggested the importance of suppressing convection in the melt during alloy crystal growth because constitutional supercooling tends to occur at the freezing interface or ahead of the interface by the segregation effect. Large area is required for substrate use in various applications. This requirement can be fulfilled by the crystal growth in microgravity because density difference-induced convection is suppressed in microgravity. Another means for suppressing convection without deteriorating area is plate-shape crystal growth with reduced thickness. The latter can be applied on the ground and we succeeded in growing single crystals of plate-shaped In(0.3)Ga(0.7)As by the traveling liquidus zone (TLZ) method. Dimensions of obtained single crystals were 10 mm in width and 2 mm in thickness and lengths ranged from 20 to 40 mm. Compositional uniformity was good and 0.3 +/- 0.02 in InAs mole fraction was achieved.

Journal Article↗

PubMed1998

Tetragonal Crystal Structure of Mung Bean Inhibitor-porcine Trypsin Complex.

Crystal structure of the mung bean inhibitor-porcine trypsin (1:2) ternary complex in the tetragonal crystal with space group I422 was determined at 0.25nm resolution. 56 residues of the mung bean inhibitor were resolved among which one more residue Pro11 was determined than the previously reported structure in the trigonal crystal of the same complex. The structure of the inhibitor in the tetragonal crystal is similar to that in the trigonal crystal and the complexes in tetragonal crystal is also in packing disorder as in trigonal crystal, i.e., the complexes pack in two orientations Ta : MaMb : Tb and Tb : MbMa : Ta(Ta, Tb=trypsin, Ma, Mb=loop I and loop II of mung bean inhibitor respectively). But there are some differences in the two crystal forms. First, the inhibitor in the tetragonal crystal has no pseudo- beta-sheet structure which the trigonal crystal has. Second, its conformation is somewhat different from that in the trigonal crystal.Analysis showed that the linkage peptides between the two regid domains of the inhibitor were flexible, which also accounted for the formation of different crystal forms of this complex. Moreover, comparing mung bean inhibitor to other Bowman-Birk inhibitors showed that the two double-stranded antiparallel beta-sheets and the reactive binding loops were highly conservative.

Journal Article↗

PubMed1998

Nucleation and growth of microbial lipase crystals from clarified concentrated fermentation broths.

Bulk crystallization is emerging as a new industrial operation for protein recovery. Characterization of bulk protein crystallization is more complex than protein crystallization for structural study where single crystals are grown in flow cells. This is because both nucleation and crystal growth processes are taking place while the supersaturation falls. An algorithm is presented to characterize crystallization using the rates of the two kinetic processes, nucleation and growth. The values of these rates allow ready comparison of the crystallization process under different operating conditions. The crystallization, via adjustment to the isoelectric pH of a fungal lipase from clarified fermentation broth, is described for a batch stirred reactor. A maximum nucleation rate of five to six crystals formed per microliter of suspension per second and a high power dependency ( approximately 11) on the degree of supersaturation were found. The suspended protein crystals were found to grow at a rate of up to 15-20 nm/s and also to exhibit a high power dependency ( approximately 6) of growth rate on the degree of supersaturation.

Crystallization↗

PubMed1984

Mitogenic effects of hydroxyapatite and calcium pyrophosphate dihydrate crystals on cultured mammalian cells.

Synthetic hydroxyapatite (HA) crystals in 1% serum stimulated 3H thymidine uptake into quiescent canine synovial fibroblasts and human foreskin fibroblast cultures, as did 10% serum. The onset of stimulation and peak uptake of thymidine after crystal addition were delayed by 2-3 hours as compared with the effects produced by 10% serum. Stimulation of 3H thymidine uptake was proportional to the serum concentration used. HA crystals (50 micrograms/ml) stimulated nuclide uptake at each serum concentration used. 3H thymidine uptake was also proportional to the dose of HA or calcium pyrophosphate dihydrate crystals, although larger doses of the latter crystal were required to produce equivalent effects. Not all particulates were effective mitogenic agents. Latex beads and diamond crystals had no effect. Monosodium urate crystals modestly stimulated and calcium urate crystals markedly stimulated nuclide uptake. The more complex crystals found in a naturally occurring condition (calcinosis) were as mitogenic as the pure synthetic HA. The synovial cell hyperplasia sometimes associated with crystals might be explained in part by their mitogenic activity.

Animals↗

PubMed2004

Basic calcium phosphate crystal-induced prostaglandin E2 production in human fibroblasts: role of cyclooxygenase 1, cyclooxygenase 2, and interleukin-1beta.

OBJECTIVE: To elucidate the mechanism of basic calcium phosphate (BCP) crystal-induced prostaglandin E(2) (PGE(2)) production in human foreskin fibroblasts (HFFs), to identify the signaling pathway involved in the induction of cyclooxygenase 2 (COX-2) messenger RNA (mRNA) by BCP crystals, to examine the effect of BCP crystals on interleukin-1beta (IL-1beta) mRNA expression, and to investigate the potential of phosphocitrate to abrogate the BCP crystal-induced effects. METHODS: PGE(2) levels were quantified using a commercial enzyme immunoassay kit. COX-2 and COX-1 transcript levels were quantified using real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Induction of IL-1beta and COX-2 mRNA was examined by end-point RT-PCR. COX-2 protein expression was assessed by Western blotting. RESULTS: PGE(2) production measured 4 and 30 hours after BCP crystal treatment was higher in BCP crystal-treated (mean +/- SEM 1,891 +/- 273 pg/microg and 1,792 +/- 233 pg/microg, respectively) than in untreated (88 +/- 5 pg/microg and 205 +/- 93 pg/microg, respectively) HFFs. The PGE(2) produced after 4 hours was sensitive to inhibition with NS398, a selective COX-2 inhibitor, implying that it was COX-2 mediated, whereas the PGE(2) produced at 30 hours could not be completely inhibited by NS398. Real-time RT-PCR demonstrated a 23-fold increase in COX-2 mRNA that was maximal at 4 hours, whereas analysis of mRNA for COX-1 showed up-regulation of transcript peaking at 24 hours poststimulation (1.75-fold increase). The protein kinase C and phosphatidylinositol 3-kinase signal-transduction inhibitors bisindolylmaleimide I and LY294002, respectively, blocked BCP crystal-induced COX-2 mRNA in HFFs. In addition, BCP crystals were found to up-regulate the proinflammatory cytokine IL-1beta (maximal at 8 hours). The induction of both COX-2 and IL-1beta by BCP crystals was attenuated when the cells were treated with phosphocitrate. CONCLUSION: These findings indicate that BCP crystals may be an important amplifier of PGE(2) production through induction of the COX enzymes and the proinflammatory cytokine IL-1beta.

Calcium Phosphates↗

PubMed2004

Central role of complement membrane attack complex in monosodium urate crystal-induced neutrophilic rabbit knee synovitis.

OBJECTIVE: Monosodium urate monohydrate (MSU) crystals promote gouty inflammation that is critically mediated by neutrophil recruitment and activation. Interleukin-8 (IL-8) and closely related chemokines are major neutrophil chemotaxins in experimental gout. But MSU crystals also activate the classical and alternative pathways of complement, and MSU crystals directly cleave C5 on the crystal surface. Unlike IL-8, the roles in acute gout of individual complement-derived peptides and of the terminal C5b-9 complement components that comprise the membrane attack complex (MAC) are unclear. Hence, we studied rabbits deficient in the MAC component C6 to determine if MAC mediated urate crystal-induced arthritis. METHODS: We injected C6-deficient and C6-sufficient rabbit knee joints with 10 mg of pyrogen-free urate crystals and analyzed IL-8 levels, leukocyte influx, and joint inflammation 24 hours later. RESULTS: There was a significant decrease (>60%) in swelling in MSU crystal-injected knees of C6-deficient animals as compared with C6-sufficient animals (P < 0.05). An attenuated rise in MSU crystal-induced joint effusion levels of IL-8 also was observed, which was concordant with diminished numbers of neutrophils (P < 0.05) but not monocytes in MSU crystal-induced knee synovial fluid from C6-deficient animals. Synovial tissue analysis confirmed mononuclear leukocyte infiltration in response to MSU crystal injection in all animals, but substantial neutrophil infiltration only in C6-sufficient animals. CONCLUSION: MAC activation appears to play a major role in intraarticular IL-8 generation and in neutrophil recruitment in experimental acute gouty arthritis of the rabbit knee. C6 and MAC activation may represent novel therapeutic targets for suppression of neutrophil-mediated joint inflammation in gout.

Animals↗

PubMed2005

Evaluation of a model for seeded isothermal batch protein crystallization.

Bulk protein crystallization, unlike small molecule crystallization, has found very limited use in biopharmaceutical manufacture. Most work in this area targets obtaining single large crystals for molecular structure determination by crystallography. Design and optimization of bulk crystallization for protein recovery and purification is much less common, and requires a mathematical model for analysis of laboratory data suitable for scale-up purposes. Traditionally, the crystal size distribution and method of moments is used to characterize the crystallization process. A simpler method is presented in this paper that utilizes the desupersaturation curve. The method uses an approach that does not require expensive instrumentation or characterization of the seed crystal size distribution. The method is extended to allow determination of both the mass deposition rate constant and the growth rate order from a single desuperaturation curve. Experimental data for the bulk crystallization of ovalbumin are used to validate the method. The rate constants and rate order obtained using the new method compare well with literature values. Scale-up is illustrated by prediction of the impact of changes in seed mass on protein crystallization. This new method offers a straightforward and low-cost alternative to traditional methods for the analysis and scale-up of protein crystallization data.

Computer Simulation↗

PubMed1995

Isolation of calcium-phosphate crystals of bone by non-aqueous methods at low temperature.

We have developed low temperature nonaqueous solution methods as well as low power plasma ashing for the degradation of the organic matrix of bone power which have permitted us to obtain bone crystals essentially free of organic matrix constituents without any significant change in their composition, overall structure, or internal short-range order. We have also been able to disperse the crystals, which has made it possible to examine the isolated crystals by X-ray diffraction and resolution-enhanced Fourier transform infrared (FTIR) spectroscopy and isolated single crystals by high resolution transmission electron microscopy (TEM) and electron diffraction. TEM of isolated single crystals of fish, chicken, mouse and bovine bone have clearly demonstrated that the crystals are very thin plates. No rod or needle-like crystals were observed in any of the bone samples in the four species studied including the earliest crystals deposited. Although there were variations in the size distribution of the crystals in the different species studied, in general the average crystal dimensions were very similar.

Animals↗

PubMedDate not supplied

Comparison of the three-dimensional structures of a human Bence-Jones dimer crystallized on Earth and aboard US Space Shuttle Mission STS-95.

Crystals of a human (Sea) Bence-Jones dimer were produced in a capillary by vapor diffusion under microgravity conditions in the 9 day US Space Shuttle Mission STS-95. In comparison to ground-based experiments, nucleation was facile and spontaneous in space. Appearance of a very large (8 x 1.6 x 1.0 mm) crystal in a short time period is a strong endorsement for the use of microgravity to produce crystals sufficiently large for neutron diffraction studies. The Sea dimer crystallized in the orthorhombic space group P2(1)2(1)2(1), with a = 48.9 A, b = 85.2 A, and c = 114.0 A. The crystals grown in microgravity exhibited significantly lower mosaicities than those of ground-based crystals and the X-ray diffraction data had a lower overall B factor. Three-dimensional structures determined by X-ray analysis at two temperatures (100 and 293 K) were indistinguishable from those obtained from ground-based crystals. However, both the crystallographic R factor and the free R factor were slightly lower in the models derived from crystals produced in microgravity. The major difference between the two crystal growth systems is a lack of convection and sedimentation in a microgravity environment. This environment resulted in the growth of much larger, higher-quality crystals of the Sea Bence-Jones protein. Structurally, heretofore unrecognized grooves on the external surfaces of the Sea and other immunoglobulin-derived fragments are regular features and may offer supplementary binding regions for super antigens and other elongated ligands in the bloodstream and perivascular tissues.

Bence Jones Protein↗

PubMed1995

Influence of divalent cations in protein crystallization.

We have tested the effect of several cations in attempts to crystallize the ligand-bound forms of the leucine/isoleucine/valine-binding protein (LIVBP) (M(r) = 36,700) and leucine-specific binding protein (LBP) (M(r) = 37,000), which act as initial periplasmic receptors for the high-affinity osmotic-shock-sensitive active transport system in bacterial cells. Success was achieved with Cd2+ promoting the most dramatic improvement in crystal size, morphology, and diffraction quality. This comes about 15 years after the ligand-free proteins were crystallized. Nine other different divalent cations were tried as additives in the crystallization of LIVBP with polyethylene glycol 8000 as precipitant, and each showed different effects on the crystal quality and morphology. Cd2+ produced large hexagonal prism crystals of LIVBP, whereas a majority of the cations resulted in less desirable needle-shaped crystals. Zn2+ gave crystals that are long rods with hexagonal cross sections, a shape intermediate between the hexagonal prism and needle forms. The concentration of Cd2+ is critical. The best crystals of the LIVBP were obtained in the presence of 1 mM CdCl2, whereas those of LBP, with trigonal prism morphology, were obtained at a much higher concentration of 100 mM. Both crystals diffract to at least 1.7 A resolution using a conventional X-ray source.

Bacterial Proteins↗

PubMed2003

Predictive crystallization of ribonuclease A via rapid screening of osmotic second virial coefficients.

Important progress has been made in recent years toward developing a molecular-level understanding of protein phase behavior in terms of the osmotic second virial coefficient, a thermodynamic parameter that characterizes pairwise protein interactions. Yet there has been little practical application of this knowledge to the field of protein crystallization, largely because of the difficult and time-consuming nature of traditional techniques for characterizing protein interactions. Self-interaction chromatography has recently been proposed as a highly efficient method for measuring the osmotic second virial coefficient. The utility of the technique is examined in this work by characterizing virial coefficients for ribonuclease A under 59 solution conditions using several crystallization additives, including PEG, sodium chloride, ammonium sulfate, and propanol. The virial coefficient measurements show some counterintuitive trends and shed light on the previous difficulties in crystallizing ribonuclease A. Crystallization experiments at the corresponding solution conditions were conducted by using ultracentrifugal crystallization. Using this methodology, ribonuclease A crystals were obtained under conditions for which the virial coefficients fell within the "crystallization slot." Crystallographic characterization showed that the crystals diffract to high resolution. Metastable crystals were also obtained for conditions outside, but near, the "crystallization slot," and they could also be frozen and used to collect structural information.

1-Propanol↗

PubMed1991

Comparison of the crystal structure of bacteriophage T4 lysozyme at low, medium, and high ionic strengths.

Crystals of bacteriophage T4 lysozyme used for structural studies are routinely grown from concentrated phosphate solutions. It has been found that crystals in the same space group can also be grown from solutions containing 0.05 M imidazole chloride, 0.4 M sodium choride, and 30% polyethylene glycol 3500. These crystals, in addition, can also be equilibrated with a similar mother liquor in which the sodium chloride concentration is reduced to 0.025 M. The availability of these three crystal variants has permitted the structure of T4 lysozyme to be compared at low, medium, and high ionic strength. At the same time the X-ray structure of phage T4 lysozyme crystallized from phosphate solutions has been further refined against a new and improved X-ray diffraction data set. The structures of T4 lysozyme in the crystals grown with polyethylene glycol as a precipitant, regardless of the sodium chloride concentration, were very similar to the structure in crystals grown from concentrated phosphate solutions. The main differences are related to the formation of mixed disulfides between cysteine residues 54 and 97 and 2-mercaptoethanol, rather than to the differences in the salt concentration in the crystal mother liquor. Formation of the mixed disulfide at residue 54 resulted in the displacement of Arg-52 and the disruption of the salt bridge between this residue and Glu-62. Other than this change, no obvious alterations in existing salt bridges in T4 lysozyme were observed. Neither did the reduction in the ionic strength of the mother liquor result in the formation of new salt bridge interactions. These results are consistent with the ideas that a crystal structure determined at high salt concentrations is a good representation of the structure at lower ionic strengths, and that models of electrostatic interactions in proteins that are based on crystal structures determined at high salt concentrations are likely to be relevant at physiological ionic strengths.

Crystallization↗

PubMed1993

A DNA dodecamer containing an adenine tract crystallizes in a unique lattice and exhibits a new bend.

The structure of d(CGCGAAAAAACG)/d(CGTTTTTTCGCG) was determined at 2.3 A resolution in order to deduce the local structural features that give rise to DNA bending by adenine tracts. Whereas all previously reported B-DNA dodecamers have crystallized isomorphously (spacegroup P2(1)2(1)2(1) with unit cell dimensions of a = 24.5 A, b = 40.3 A, c = 65.9 A), the duplex reported here crystallizes in a different lattice (spacegroup P2(1)2(1)2 with unit cell dimensions of a = 44.8 A, b = 66.1 A, c = 42.9 A). The DNA exhibits a 30 degree bend in the helix axis that is 180 degrees away from the 20 degree bend exhibited by the adenine tract DNA crystal structures that have been previously determined. This bend is 90 degrees away from the bend predicted for an adenine tract by solution and gel experiments. The adenine tract is straight and bending occurs in the G+C-rich regions. Comparison of the various adenine tract DNA crystal structures reveals that in all cases the adenine tracts have nearly identical structures, even though the overall bends of the helix axes are quite different. This implies that the structure of the adenine tract is robust, at least under the conditions of crystallization. The base-pairs in the adenine tracts exhibit a large propeller twist that leads to the formation of bifurcated hydrogen bonds and a narrow minor groove. In the crystal structure of d(CGCGAAAAAACG)/d(CGTTTTTTCGCG), a minor groove spine of hydration is observed that probably stabilizes the straight structure of the adenine tract. This straight structure of the A-tract is not consistent with the results of fiber diffraction, gel experiments, and NMR studies. Although this may imply that the results of solution experiments need to be reinterpreted, the conditions under which the crystals were grown are different from those under which the solution experiments were done. The possibility remains that the 2-methyl-2,4-pentanediol necessary for crystal growth may facilitate formation of the spine of hydration that stabilizes the straight A-tract, although recent NMR results show the presence of the spine of hydration in aqueous solution. We have also extended our previously reported observation that non-self-complementary DNA structures can exist in the crystal lattice in two orientations. A dodecamer brominated on one strand provides experimental evidence that d(CGCAAAAAAGCG)/d(CGCTTTTTTG CG) is positioned in two orientations in the crystal lattice that are related by a 180 degree rotation around the pseudo-dyad axis of the sequence.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenine↗

PubMed2000

Protein crystallization by design: chymotrypsinogen without precipitants.

Protein crystals are usually obtained by an empirical approach based on extensive screening to identify suitable crystallization conditions. In contrast, we have used a systematic predictive procedure to produce data-quality crystals of bovine chymotrypsinogen A and used them to obtain a refined X-ray structure to 3 A resolution. Measurements of the osmotic second virial coefficient of chymotrypsinogen solutions were used to identify suitable solvent conditions, following which crystals were grown for approximately 30 hours by ultracentrifugal crystallization, without the use of any precipitants. Existing structures of chymotrypsinogen were obtained in solutions including 10-30 % ethanol, whereas simple buffered NaCl solutions were used here. The protein crystallized in the tetragonal space group P4(1)2(1)2, with one molecule per asymmetric unit. The quality of the refined map was very high throughout, with the main-chain atoms of all but four residues clearly defined and with nearly all side-chains also defined. Although only minor differences are seen compared to the structures previously reported, they indicate the possibility of structural changes due to the crystallization conditions used in those studies. Our results show that more systematic crystallization of proteins is possible, and that the procedure can expand the range of conditions under which crystals can be grown successfully and can make new crystal forms available.

Animals↗

PubMed1998

Parameters for the two-dimensional crystallization of the membrane protein microsomal glutathione transferase.

Various crystallization parameters were investigated to obtain two-dimensional crystals of the detoxification enzyme microsomal glutathione transferase for structural analysis by electron crystallography. The protein was crystallized by reconstitution of the solubilized trimer into proteoliposomes. Crystallization occurs when minimal amounts of lipid in the range of three lipid molecules per protein trimer are added to the dialysate. Once crystals were obtained, the effect of several parameters on the crystallization was determined. The temperature and initial detergent concentration were found to be crucial parameters in influencing the size of the crystals, and conclusions could be drawn about the rate dependence of the crystallization process. Two highly ordered crystal forms, which are suitable for structural analysis by electron crystallography, were obtained under the two-dimensional crystallization conditions described here.

Animals↗

PubMed1996

Association of urinary macromolecules with calcium oxalate crystals induced in vitro in normal human and rat urine.

This study was undertaken to identify proteins which are found associated with calcium oxalate crystals induced in vitro in normal human and rat urine. Crystallization was initiated by adding sodium oxalate individually to each urine sample without centrifugation and filtration. Crystals were collected and analyzed by scanning electron microscopy and X-ray diffraction. Crystal matrix proteins (CMPs) were obtained by demineralization of the crystals with ethylenediaminetetra-acetic acid (EDTA) and analyzed by western blotting technique for immunological identification. Crystals produced in human urine were found to be a mixture of calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) while those produced in rat urine were exclusively COD. CMPs extracted from crystals in human urine comprised, in addition to prothrombin-related proteins, osteopontin and albumin. However, CMPs extracted from crystals in rat urine contained only osteopontin and albumin. Prothrombin-related proteins were found only in trace amounts. In a separate experiment, rat urine samples were supplemented with COM before inducing crystallization. Similar results were observed showing that CMP contained osteopontin, albumin and trace amounts of prothrombin-related proteins. We conclude that several urinary macromolecules including not only prothrombin-related proteins, but also osteopontin and albumin, become associated with CaOx crystals. The incorporation of these proteins in growing stones is not only due to the presence of gamma-carboxyglutamic acid as it was suggested for prothrombin-related proteins, but may be due to other factors such as urinary chemistry, presence of glutamic and aspartic acid residues, and calcium-binding sites.

Albuminuria↗

PubMed1996

Is citrate an inhibitor of calcium oxalate crystal growth in high concentrations of urine?

The effect of citrate on calcium oxalate (CaOx) crystal growth was studied in a system in which series of samples containing [45Ca]calcium chloride were brought to different levels of supersaturation with various concentrations of oxalate. The crystallization was assessed by measuring the amount of isotope remaining in solution 30 min after the addition of CaOx seed crystals to samples containing citrate in concentrations corresponding to those in final urine. The experiments were carried out both in pure salt solutions and in solutions with dialysed urine. Increased concentrations of citrate resulted in a reduced crystallization of CaOx in both the presence and absence of dialysed urine, but with the lowest rate of crystallization in the samples containing urine. The increased concentration of 45Ca remaining in solution reflected a reduced crystallization, which could possibly be explained both by a reduced supersaturation and by an increased inhibition of CaOx crystal growth. The direct effects of citrate on CaOx crystal growth were assessed by calculating the ion-activity product of CaOx (APCaOx) at corresponding degrees of crystallization. The APCaOx recorded at a 30% reduction of the amount of isotope in solution increased with increasing concentrations of citrate between 1.0 and 1.5 mmol/l samples both with and without dialysed urine. These findings indicate that citrate has a weak direct inhibitory effect on CaOx crystal growth, which adds to the reduced growth rate brought about by urinary macromolecules and a decreased supersaturation.

Antacids↗