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PubMed1989

Crystallization and characterization of human chorionic gonadotropin in chemically deglycosylated and enzymatically desialylated states.

Crystals suitable for X-ray diffraction studies at moderate resolution have been grown from two forms of human chorionic gonadotropin (hCG): HF-treated hCG and neuraminidase-treated hCG. The enzymatically desialylated form of hCG produced crystals that diffract to 2.8 A as compared to the HF-treated hCG crystals that diffract to 3.0 A. Although it was assumed that the high and heterogeneous carbohydrate content of the glycoprotein hormones inhibited their crystallization, this report suggests that it is the negatively charged surface sugars and neither the total carbohydrate content nor its heterogeneity which interferes with crystal formation. Chemical deglycosylation resulted in significantly increased protein degradation during crystal growth. Such peptide bond cleavages were observed to a much lesser extent in the crystals grown from neuraminidase-digested hCG. Sequence analysis of the HF-treated hCG crystals suggested that up to 45% of the molecules within the crystal had an acid-labile peptide bond cleaved. In contrast, the neuraminidase-treated hCG exhibited less than 9% of this type of cleavage. The increase in heterogeneity of the polypeptide chains within both crystals over that existent in the starting proteins was apparently due to changes occurring during crystal growth. The manner in which hCG was treated prior to crystallization was found to be a very important factor in the extent of peptide bond cleavages occurring during crystal growth. HF treatment of glycoproteins may render glycoproteins more susceptible to peptide bond cleavages during crystal growth.

Amino Acid Sequence↗
PubMedDate not supplied

Crystal growth and solid-state structure of poly(lactide) Stereocopolymers.

Solid-state structure and melting behavior for random stereocopolymers of L-lactide with meso-lactide (P(L-LA-co-meso-LA)) with different meso-LA compositions of 0, 2, 4, and 10 mol % were investigated under various isothermal crystallization conditions. The crystalline morphology of P(L-LA-co-meso-LA) samples changed from the spherulitic aggregates to hexagonal lamellae stacking with a rise in crystallization temperature. Under each crystallization condition, P(L-LA-co-meso-LA) samples formed alpha-crystal modifications for homopolymer of L-LA. By using the atomic force microscopy and small-angle X-ray scattering, the stacking structure of lamellar crystals was examined for the isothermally crystallized P(L-LA-co-meso-LA) thin films. The lamellar thickness of P(L-LA-co-meso-LA) ranged from 6.2 to 15.5 nm, and the values increased with crystallization temperature. Melting profiles of crystalline regions were examined by the differential scanning calorimetry (DSC) for the P(L-LA-co-meso-LA) samples. Distinct two melting peaks were detected in the DSC thermograms of several samples. Investigations on the time-dependent changes in lamellar structure and melting temperature of the P(L-LA-co-meso-LA) samples under isothermal crystallization conditions provided the evidence that a small amount of D-lactyl units was trapped in the crystalline regions during early stage of crystallization process under the certain crystallization condition. In addition, it was found that the D-lactyl units trapped in crystalline regions were excluded from crystalline lamellae to form the thermally stable crystals without changes in crystal thickness during further isothermal storage at a crystallization temperature. The equilibrium melting temperature (T(m)0) of P(L-LA-co-meso-LA) samples was estimated by using modified Hoffman-Weeks methods, and the obtained values decreased from 215 to 184 degrees C as the meso-LA composition was increased from 0 to 10 mol %. Furthermore, the crystal growth kinetics of the P(L-LA-co-meso-LA) samples was analyzed by using the secondary nucleation theory. Transitions of crystalline regime both from regime III to regime II and from regime II to regime I were detected for each sample. The transition temperature from regime II to regime I of each of the P(L-LA-co-meso-LA) samples was very close to the temperature region revealed the morphological changes in the crystalline aggregates from the spherulitic aggregates to hexagonal lamellae stacking.

Calorimetry, Differential Scanning↗
PubMed2003

Intra-articular corticosteroid preparations: different characteristics and their effect during inflammation induced by monosodium urate crystals in the rat subcutaneous air pouch.

OBJECTIVE: To examine the effects of three commonly used intra-articular depot corticosteroid preparations tested in a rat air pouch model and their effect against monosodium urate (MSU) crystal-induced inflammation. Rheumatologists use intra-articular corticosteroid preparations to relieve pain and inflammation of acute monoarthritis without really knowing their effects on the synovial fluid and membrane or the differences between distinct preparations. This work compares the effect of three commonly used corticosteroid preparations in vivo, showing that they behave differently. METHODS: A subcutaneous air pouch was formed in male Sprague-Dawley rats. A first group of 6-day-old air pouches were injected with 10 ml of 6 mg/ml normal saline solution, 6 mg/ml betamethasone containing both depot betamethasone acetate and soluble betamethasone phosphate (Celestone) in 9 ml of normal saline solution, 20 mg/ml of prednisolone tebutate (Hydeltra) in 9 ml of normal saline solution or 20 mg/ml of triamcinolone hexacetonide (Aristospan) in 9 ml of normal saline solution. A second group (group 2) of air pouches were injected with 15 mg of synthetic MSU crystals and 24 h later they were reinjected with 1 ml of the same three corticosteroid suspensions. For each condition four rats were killed at 6, 24, 48 h and 7 days. Pouch fluid and tissue were analysed. RESULTS: In the first 6 h after normal saline solution or corticosteroid injection into the air pouch there were mildly increased leucocyte counts in the air pouch fluid. Betamethasone-injected pouches showed no cells in the fluid after 6 h and no crystals after 24 h, triamcinolone-injected pouches still showed rare cells at 7 days. Both triamcinolone and prednisolone crystals persisted in higher numbers and lasted longer in the fluid than did betamethasone (P<0.05). In group 2 MSU crystal phagocytosis in the fluid was decreased in the betamethasone- (P<0.01), prednisolone- (P<0.003) and triamcinolone- (P<0.006) injected pouches when compared with the MSU crystal-injected pouches alone. Pouches injected with MSU crystals alone showed the most intense tissue inflammation at all times. After MSU, betamethasone-injected pouches had a rapid but mild decrease in the number of lining cells and inflammation. In contrast, triamcinolone- and prednisolone-injected pouches showed a very thin tissue with few or no vessels and almost no inflammation at 7 days. The pouches injected with MSU crystals and any of the corticoid preparations had three times more tophus-like structures and persistent crystals identified than the ones injected with MSU crystals alone. CONCLUSION: Each of the corticosteroid preparations by themselves produced very mild transient inflammation. The betamethasone preparation with a soluble steroid component had a quicker but milder anti-inflammatory effect on MSU crystal-induced inflammation. In contrast to the doses used, prednisolone tebutate and triamcinolone hexacetonide preparations dramatically suppressed urate crystal-induced inflammation at 7 days, but both produced atrophy and necrosis of the membrane, yielding a very thin membrane with almost no vessels. When used for MSU crystal-induced inflammation these corticosteroid preparations suppressed some aspects of inflammation but may actually promote the persistence of MSU crystals and the formation of tophi.

Animals↗
PubMed2003

Apocrustacyanin C(1) crystals grown in space and on earth using vapour-diffusion geometry: protein structure refinements and electron-density map comparisons.

Models of apocrustacyanin C(1) were refined against X-ray data recorded on Bending Magnet 14 at the ESRF to resolutions of 1.85 and 2 A from a space-grown and an earth-grown crystal, respectively, both using vapour-diffusion crystal-growth geometry. The space crystals were grown in the APCF on the NASA Space Shuttle. The microgravity crystal growth showed a cyclic nature attributed to Marangoni convection, thus reducing the benefits of the microgravity environment, as reported previously [Chayen et al. (1996), Q. Rev. Biophys. 29, 227-278]. A subsequent mosaicity evaluation, also reported previously, showed only a partial improvement in the space-grown crystals over the earth-grown crystals [Snell et al. (1997), Acta Cryst. D53, 231-239], contrary to the case for lysozyme crystals grown in space with liquid-liquid diffusion, i.e. without any major motion during growth [Snell et al. (1995), Acta Cryst. D52, 1099-1102]. In this paper, apocrustacyanin C(1) electron-density maps from the two refined models are now compared. It is concluded that the electron-density maps of the protein and the bound waters are found to be better overall for the structures of apocrustacyanin C(1) studied from the space-grown crystal compared with those from the earth-grown crystal, even though both crystals were grown using vapour-diffusion crystal-growth geometry. The improved residues are on the surface of the protein, with two involved in or nearby crystal lattice-forming interactions, thus linking an improved crystal-growth mechanism to the molecular level. The structural comparison procedures developed should themselves be valuable for evaluating crystal-growth procedures in the future.

Carrier Proteins↗
PubMed2005

Intracrystalline proteins and urolithiasis: a comparison of the protein content and ultrastructure of urinary calcium oxalate monohydrate and dihydrate crystals.

OBJECTIVE: To compare the ultrastructure and protein content, particularly prothrombin fragment 1 and osteopontin, of calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) crystals precipitated from human urine, and their susceptibility to proteolysis, to try to clarify the role of intracrystalline proteins in urolithiasis, as differences between these types of crystal may determine whether calcium oxalate crystals nucleated in urine progress to stone formation. MATERIALS AND METHODS: Sodium dodecyl sulphate gel electrophoresis and Western blotting were used to analyse demineralized extracts of COM and/or COD crystals deposited from the same centrifuged and filtered urine (which contains abundant urinary proteins) by adjusting the calcium concentration to 2 and 7 mmol/L, respectively. Similar analyses were performed on COM and COD crystals deposited from ultrafiltered urine (which contains only proteins of < 10 kDa) and then incubated in centrifuged and filtered urine, as well as crystals generated in the presence of increasing concentrations of proteins derived from the organic matrix of urinary calcium oxalate crystals. Field-emission scanning electron microscopy was used to assess effects of proteinase K and cathepsin D on internal and superficial crystal structure. RESULTS: Osteopontin was undetectable in COM extracts, but clearly visible in COD. Prothrombin fragment 1 was abundant in COM, but present in COD in lesser amounts than osteopontin. The selectivity was also the same with crystals from ultrafiltered urine that were incubated in centrifuged and filtered urine: prothrombin fragment 1 binding was favoured by low calcium concentration, while osteopontin bound at higher levels. Scanning electron microscopy of COM and COD digested with proteinase K and cathepsin D revealed superficial and internal texture, as wells as surface erosion, in crystals from centrifuged and filtered urine, thus confirming the presence of intracrystalline proteins. Such features were absent from crystals precipitated from ultrafiltered urine. CONCLUSION: Binding of osteopontin and prothrombin fragment 1 to calcium oxalate is dictated primarily by ambient calcium concentration. Each protein may inhibit urolithiasis by inhibiting crystallization of its preferred crystal habit, and by facilitating the intracellular disintegration and dissolution of crystals attached to and internalized by renal epithelial cells.

Blotting, Western↗
PubMed1995

Adhesion of calcium oxalate monohydrate crystals to renal epithelial cells is inhibited by specific anions.

Adhesion of urinary crystals to the apical surface of renal tubular cells could be a critical step in the formation of kidney stones. The interaction between renal epithelial cells (BSC-1 line) and the most common crystal in kidney stones, calcium oxalate monohydrate (COM), was studied in a tissue culture model system. COM crystals bound to the cell surface within seconds in a concentration-dependent manner to a far greater extent than did brushite, another calcium-containing crystal found in urine. Adhesion of COM crystals to cells was blocked by the polyanion, heparin. Other glycosaminoglycans including chondroitin sulfate A or B, heparan sulfate, and hyaluronic acid, but not chondroitin sulfate C, prevented binding of COM crystals. Two nonsulfated polyanions, polyglutamic acid and polyaspartic acid, also blocked adherence of COM crystals. Three molecules found in urine, nephrocalcin, uropontin, and citrate, each inhibited binding of COM crystals, whereas Tamm-Horsfall glycoprotein (THP) did not. Prior exposure of crystals but not cells to inhibitory molecules blocked adhesion, suggesting that these agents exert their effect at the crystal surface. Inhibition of crystal binding followed a linear Langmuir adsorption isotherm for each inhibitor identified, suggesting that these molecules bind to a single class of sites on the crystal that are important for adhesion to the cell surface. Inhibition of crystal adhesion by heparin was rapidly overcome by the polycation protamine, suggesting that the glycosaminoglycan regulates cell-crystal interactions in a potentially reversible manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Ultrastructural studies of the reaction of urate crystals with a cultured renal tubular cell line.

Hypotheses concerning the development of uric acid and gouty nephropathy suggest that the initiating disease mechanism involves an interaction between uric acid or monosodium urate monohydrate (MSUM) crystals and renal tubular epithelial cells. We have studied the interaction of these crystals with Madin-Darby canine kidney (MDCK) cells, which exhibit many of the characteristics of cells of the collecting duct epithelium. Addition of MSUM crystals to monolayer cultures of MDCK cells leads to the formation of reaction sites, localised areas which are raised above the monolayer forming a 3-dimensional structure. These reaction sites are evident within 4-8 h and appear to be initiated by the interaction of a single crystal or small number of crystals with a single cell. With time, both cells and crystals accumulate at the site. By 24 h most reaction sites involve 6-12 cells and numerous crystals. Interaction of MSUM crystals and MDCK cells not only involves the attachment of crystals to cells but, by 8 h, some crystals appear to be completely or partially covered by the cell membrane, and MDCK cells appear to react by growing around the crystals. Transmission electron microscopy shows that crystals are found not only within cells, but also within the intercellular spaces. Within the cells, crystals have been shown in vacuoles containing lysosomal enzymes, indicating the formation of a phagolysosome. Ultimately, enzyme release occurs. These studies support the hypothesis that some interstitial deposits of urate and uric acid in the kidney may be derived from intratubular deposits that react with the tubular epithelium and pass into the interstitium; loss of tubular integrity may not be a prerequisite for crystal migration.

Animals↗
PubMed1999

The effect of warfarin therapy on the charge properties of urinary prothrombin fragment 1 and crystallization of calcium oxalate in undiluted human urine.

Urinary prothrombin fragment 1 (UPTF1) is the principal protein in calcium oxalate (CaOx) crystals precipitated from human urine and is a potent inhibitor of CaOx crystallization, a property that should depend, at least in part, upon the extent of gamma-carboxylation of the 10 glutamic residues in its N-terminal region. Warfarin therapy limits full gamma-carboxylation of vitamin K-dependent proteins, including UPTF1. The aims of this study were to determine the effect of warfarin therapy on UPTF1, its occlusion into CaOx urinary crystals, and its influence on the crystallization of CaOx in undiluted human urine. In the first part of the study, urines were collected from six men prior to cardiac surgery and after stabilization on long-term warfarin treatment. Proteins in the urines and in the matrix of CaOx crystals precipitated from them were analyzed by two-dimensional SDS-PAGE and Western blotting. In urine, at least two charge variants of UPTF1 with low isoelectric point (pI) values were detected before and during warfarin therapy, but additional higher pI forms of the protein were also seen during anticoagulation. Nonetheless, the majority of UPTF1 was present in the more fully gamma-carboxylated state. CaOx crystals precipitated from the same urine samples contained only low pI forms of UPTF1. The effect of warfarin treatment on CaOx crystallization in urine was tested by collecting two consecutive 24-h urine samples from 16 men prior to cardiac surgery and during subsequent warfarin treatment. CaOx crystallization was induced in each sample by the addition of sodium oxalate. The size and volume of the particles deposited were determined using a Coulter counter, and the crystals were examined by scanning electron microscopy (SEM). There were no significant differences between the urinary metastable limits before or during warfarin treatment or in the total volume of crystals precipitated. A slight increase in the mean diameter of the crystalline particles precipitated from the urines during anticoagulant therapy was not significant. SEM showed little evidence of changes in overall particle size, although individual crystals of CaOx tended to be larger during warfarin treatment. It was concluded from these studies that the binding of UPTF1 to CaOx crystal surfaces is related to the degree of gamma-carboxylation of its Gla domain, which would also influence the protein's inhibitory effects on CaOx crystallization. However, during warfarin therapy the majority of UPTF1 exists in a highly charged state, indicating that it is completely, or almost completely, gamma-carboxylated, which would explain the lack of any difference between CaOx crystallization parameters in the urine of subjects before and during warfarin administration. We conclude that physiologically significant reductions in the inhibitory potency of UPTF1 would be likely to occur only as a result of proscription of gamma-carboxylation more extensive than that induced by warfarin.

Adult↗
PubMed1994

Crystal-membrane interaction in kidney stone disease.

Urolithiasis is a multifaceted process that initiates with the formation of microcrystals in the urine and terminates with the formation of mature renal calculi. The attachment of crystals by the urothelium is a major event in the successful formation of the mature stone. The papillary tip is the primary site for crystal attachment and stone maturation, and the attachment process appears to be mediated by specific molecular interactions between molecular structures on the surfaces of stone crystals and molecular arrays on the surfaces of cell membranes. Animal models have demonstrated the interaction between cells and crystals, and they have suggested a correlation between cellular damage and crystal interaction, especially when crystals bind to and then break free from the tubular epithelium. Cell culture studies on inner medullary late collecting duct (IMCD) cells have demonstrated that calcium oxalate monohydrate, hydroxyapatite, and uric acid crystals bind to IMCD cells in primary culture. The attachment of these crystals to IMCD cells was crystal structure dependent, saturable, and competitively inhibitable if more than one crystal type was present at the same time. The crystals preferentially attach to cells that have lost partial or complete intercellular junctional integrity. These crystal-attaching cells appear to have altered membrane composition and/or structure. Recent studies on red blood cells and IMCD cells that have been enriched with cholesterol and selected phospholipids suggest that crystal-membrane phospholipid interactions play a major role in crystal attachment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Development and application of image analysis to quantify calcium lactate crystals on the surface of smoked Cheddar cheese.

Calcium lactate crystals that form white specks or haze on the surface of cheese constitute a significant quality problem for producers of Cheddar cheese. Subjective methods to evaluate crystal coverage of cheese surfaces have been reported previously, but objective methods are currently lacking. The objectives of this work were to develop and evaluate an objective method to measure the area occupied by calcium lactate crystals on surfaces of naturally smoked Cheddar cheese samples using digital photography and image analysis. Coefficients of variation ranged from 1.29 to 4.68% for 5 replicate analyses of 3 different cheese surfaces that ranged from approximately 2 to 49% of total surface area occupied by crystals. Thus, results showed a high degree of repeatability for the 3 cheese surfaces, which ranged from very slight and geometrically simple to very heavy and geometrically complex crystal coverage. The method underestimated total area occupied by crystals on the 3 surfaces by 0.24 to 4.83% unless the fainter crystal regions that went undetected during initial thresholding were manually segmented and quantified. The wet weight of crystal substance collected per unit of surface area from 20 different cheese samples increased exponentially as the percentage of total surface area occupied by crystals increased. These data were consistent with subjective observations that crystal regions appeared to grow vertically as well as horizontally as they expanded to occupy greater surface area. Image analysis was well suited for evaluating changes in crystal coverage during cheese aging because measurements were made nondestructively and with minimal disruption to the cheese. The area occupied by crystals on 6 different surfaces from 3 different cheese samples increased linearly (R2 = 0.94 to 0.99) during storage at 4 degrees C for up to 33 wk. However, the rates of increase differed significantly among the 3 cheese samples. Image analysis may serve as a useful tool to quantitatively evaluate the effects of factors such as cheese composition, packaging conditions and storage temperature on rate of crystal growth and time of crystal appearance during storage.

Calcium Compounds↗
PubMed1989

Acceleration of hemoglobin C crystallization by hemoglobin S.

We previously reported that circulating hemoglobin (Hb) CC erythrocytes contain oxygenated HbC crystals with little or no HbF and that HbF inhibits in vitro crystallization of HbC. We now report that HbS accelerates in vitro crystallization of HbC. Crystals were formed in 1.8 mol/L potassium phosphate buffer, pH 7.4, at 30 degrees C and were counted in several time intervals with a hematocytometer. The hemoglobin composition of Millipore-isolated crystals and supernatant were also analyzed. Under the conditions selected, 100% HbS formed needle-shaped crystals only after two hours. Pure HbC does not form crystals within 15 minutes, whereas a ratio of 10% HbS:90% HbC forms 1,100 crystals/mm3, 20% HbS:80% HbC forms 370 crystals/mm3, and 30% HbS:70% HbC forms 5 crystals/mm3. Crystals formed in the presence of HbS are tetragonal, as are pure HbC crystals. As compared with 100% HbC, HbA or albumin mixed with HbC showed a decreased number of crystals as a result of dilution. Analysis of the Hb content of isolated crystals by citrate agar gel electrophoresis showed that HbS was rapidly incorporated into the crystal in the same ratio over time. These results demonstrate that HbS accelerates crystallization of HbC with respect to the rates of crystallization of any of these two Hbs separately, through a mechanism that involves cocrystallization. These results may be significant in understanding SC disease.

Crystallization↗
PubMed1995

Analysis of glycosaminoglycans induced in newly formed calcium oxalate crystals using an undiluted urine system.

The aim of this study was to examine the effect of sodium pentosan polysulfate (SPP) in an undiluted urine system and to study its relative affinity to calcium oxalate (CaOx) crystals in the presence or absence of heparan sulfate (HS). CaOx crystals were induced with an overload of oxalate above the metastable limit in spun and filtered urine (SF) and ultrafiltered urine (UF). Then, the crystals were dissolved with EDTA (ethylenediaminetetraacetic acid), electrodialysed and lyophilized. The polyanions, HS or SPP were added to the UF prior to the addition of oxalate. Polyanions in crystal matrices were examined by cellulose acetate electrophoresis. Crystal volume and size were suppressed according to the increase of the concentration of SPP when compared with those of the UF. Scanning electron microscopy (SEM) showed marked aggregation of the crystals in the UF and no aggregation in the presence of SPP. HS was the only polyanion found in CaOx crystals formed after overload of oxalate in SF. Crystals formed in UF did not contain any polyanions. When SPP was added to UF, SPP appeared in the crystal matrix in accordance with its concentration. Once HS in physiological concentration was added to the UF containing SPP, HS and SPP obtained from crystals were strongly stained with Alcian blue in electrophoretic study, where SPP is stained stronger than HS. These results suggest that SPP strongly binds to CaOx crystals as well as HS and that HS and SPP competitively bind to the crystal, then, as a result, they are incorporated into the crystals. The fact that SPP suppressed the aggregation of CaOx crystals in undiluted urine showed the possibility that SPP might be one of the useful drugs for preventing CaOx urolithiasis.

Adult↗
PubMed1983

Equivalence of the projected structure of thin catalase crystals preserved for electron microscopy by negative stain, glucose or embedding in the presence of tannic acid.

Thin crystals of beef liver catalase have been examined by electron microscopy following various preservation procedures. In the first part of this investigation, micrographs of three principal projections were obtained from thin sections of micro-crystals embedded in the presence of tannic acid. Computer reconstructions confirmed the space group assignment of P2(1)2(1)2(1) and permitted the packing arrangement of the catalase tetramers to be deduced to a resolution of about 20 A. These results corroborate the packing model for this crystal form proposed by Unwin (1975) on the basis of molecular modeling of one projection. In the second part of this investigation, the projected structures of the thin crystals in various preserving media were compared. The negative contrasting of crystals embedded in the presence of tannic acid was confirmed by direct comparison with non-embedded, negatively stained thin platelet crystals. In addition, good agreement at 20 A resolution was observed between the structure of negatively stained crystals and the structure of crystal platelets preserved in glucose and examined by low-dose methods, while moderate agreement was established with the published data of Taylor (1978) for crystals embedded in thin ice films. Tannic acid alone was also found to serve as a suitable medium for preserving catalase crystals to a resolution of 3 X 7 A as judged by electron diffraction. Overall, we demonstrate that projections obtained from thin sections of catalase crystals embedded in the presence of tannic acid can provide a reliable, negatively contrasted representation of the protein structure to 20 A resolution. Examination of sectioned crystals could thus provide a useful adjunct to X-ray crystallographic studies of protein crystals and three-dimensional reconstruction of crystal thin sections should ultimately be possible.

Animals↗
PubMed1999

The effect of temperature and solution pH on the nucleation of tetragonal lysozyme crystals.

Part of the challenge of macromolecular crystal growth for structure determination is obtaining crystals with a volume suitable for x-ray analysis. In this respect an understanding of the effect of solution conditions on macromolecule nucleation rates is advantageous. This study investigated the effects of supersaturation, temperature, and pH on the nucleation rate of tetragonal lysozyme crystals. Batch crystallization plates were prepared at given solution concentrations and incubated at set temperatures over 1 week. The number of crystals per well with their size and axial ratios were recorded and correlated with solution conditions. Crystal numbers were found to increase with increasing supersaturation and temperature. The most significant variable, however, was pH; crystal numbers changed by two orders of magnitude over the pH range 4.0-5.2. Crystal size also varied with solution conditions, with the largest crystals obtained at pH 5.2. Having optimized the crystallization conditions, we prepared a batch of crystals under the same initial conditions, and 50 of these crystals were analyzed by x-ray diffraction techniques. The results indicate that even under the same crystallization conditions, a marked variation in crystal properties exists.

Animals↗
PubMed1996

Crystal Structures and Luminescence Properties of Platinum(II) Complexes Containing 3,3'-Biisoquinoline.

Three new platinum complexes containing 3,3'-biisoquinoline (i-biq), [Pt(CN)(2)(i-biq)] (1), [PtCl(2)(i-biq)] (2), and [Pt(i-biq)(2)](PF(6))(2) (3), have been synthesized as orange-red, yellow, and colorless crystals, respectively. Their crystal structures and luminescence properties are reported. Crystal data: for 1.0.5H(2)O, PtO(0.5)N(4)C(20)H(13), orthorhombic, Pbcm, a = 13.989(2) Å, b = 18.304(1) Å, c = 6.682(3) Å, V = 1710.9(6) Å(3), Z = 4, and final R = 0.039 (R(w) = 0.033) for 970 independent reflections; for 2.DMF.H(2)O, PtCl(2)O(2)N(3)C(21)H(21), triclinic, P&onemacr;, a = 11.047(1) Å, b = 12.397(3) Å, c = 8.000(2) Å, alpha = 106.56(1) degrees, beta = 100.15(1) degrees, gamma = 76.15(1) degrees, V = 1012.8(3) Å(3), Z = 2, and final R = 0.058 (R(w) = 0.077) for 4219 independent reflections; for 3.2DMF, PtP(2)F(12)O(2)N(6)C(42)H(38), triclinic, P&onemacr;, a = 10.795(2) Å, b = 13.511(2) Å, c = 8.281(1) Å, alpha = 105.22(1) degrees, beta = 112.17(1) degrees, gamma = 85.02(1) degrees, V = 1079.2(3) Å(3), Z = 1, and final R = 0.038 (R(w) = 0.042) for 3606 independent reflections. Square-planar complexes of 1 are stacked in the crystal to form a columnar structure with the Pt-Pt distance of 3.34 Å. The crystal emits strongly, even at room temperature, and the emission spectrum is similar to that for the [Pt(CN)(2)(bpy)] crystal (bpy = 2,2'-bipyridine), which is due to a (3)dpi[dsigma(Pt) --> pi(i-biq)] transition. The single crystal emission spectrum at 77 K is, however, observed as a superposition of broad (3)dpi and sharp (3)pipi(i-biq) emissions. The crystal structure of 2 has a completely different stacking structure from that of 1. The stacking occurs on the i-biq ligands, and the Pt atoms are separated more than 6 Å. The complex exhibits only a structured emission component assigned to the (3)pipi(i-biq) transition in the crystal at 77 K, in agreement with the crystal structure with no Pt-Pt interaction. In the crystal of 3, the [Pt(i-biq)(2)](2+) complexes are stacked but offset, being in close contact between parts of adjacent i-biq ligands. There is no Pt-Pt interaction also in this case. Two i-biq ligands in the complex are distorted to adopt the bowed conformation due to the steric crowding of the alpha-hydrogens on opposite ligands. Nevertheless, 3 provides almost the same (3)pipi emission spectrum as 1 and 2 in dilute glassy solution at 77 K. The (3)pipi emission spectra observed in the crystals of these Pt(II) complexes are red-shifted compared with those in dilute glassy solution. The fact is attributable to the pi-pi intermolecular interactions between the ligands in the crystals. The factors controlling the crystal structures for these complexes are also discussed.

Journal Article↗
PubMed2005

Phase-field modeling on morphological landscape of isotactic polystyrene single crystals.

Spatio-temporal growth of isotactic polystyrene single crystals during isothermal crystallization has been investigated theoretically based on the phase field model by solving temporal evolution of a nonconserved phase order parameter coupled with a heat conduction equation. In the description of the total free energy, an asymmetric double-well local free energy density has been adopted to represent the metastable melt and the stable solid crystal. Unlike the small molecule systems, polymer crystallization rarely reaches thermodynamic equilibrium; most polymer crystals are kinetically stabilized in some metastable states. To capture various metastable polymer crystals, the phase field crystal order parameter at the solidification potential has been treated to be supercooling dependent such that it can assume an intermediate value between zero (melt) and unity (perfect crystal), reflecting imperfect polycrystalline nature of polymer crystals. Two-dimensional simulations exhibit various single crystal morphologies of isotactic polystyrene crystals such as faceted hexagonal patterns transforming to nonfaceted snowflakes with increasing supercooling. Of particular interest is that heat liberation from the crystallizing front influences the curvature of the crystal-melt interface, leading to directional growth of lamellar tips and side branches. The landscape of these morphological textures has been established as a function of anisotropy of surface energy and supercooling. With increasing supercooling and decreasing anisotropy, the hexagonal single crystal transforms to the dense lamellar branching morphology in conformity with the experimental findings.

Journal Article↗
PubMed1988

Crystal identification in human synovial fluids. Methods and interpretation.

Gout is largely solved, both from diagnostic and therapeutic standpoints. Acute gout is easily suppressed and joint destruction can be prevented and at least reversed by lowering the serum uric acid level with relatively safe and very effective drugs. But the arthritides associated with the calcium-containing crystals remain untreatable by other than symptomatic or surgical means. If we had a method or a drug to remove CPPD or BCP crystal deposits from joints, would it make any difference in the severity of the arthritis? Which of the paradigms shown in Figure 5 holds for these crystals? If joint damage directly follows crystal deposition as in gout, then crystal removal should prove prophylactic. The unusual pattern of joint degeneration associated with polyarticular CPPD crystal deposition and the initial appearance of CPPD crystals in radiographically normal cartilage favors this idea. But radiologic chondrocalcinosis appearing in knees subjected years before to meniscectomy but not in the contralateral knees suggests that crystal deposition, in these cases at least, is secondary to trauma or surgery. If degeneration of cartilage precedes crystal deposition, as it probably does in the case of BCP crystals, then crystal removal may not be particularly helpful. Dieppe and his colleagues proposed that the calcium crystals provide a positive feedback (amplification) loop. This represents the minimalistic view of their importance. The biologic consequences of the calcium crystal deposition diseases are now being explored at the molecular level. Much more data are needed before more than speculative answers to the questions posed here can be formulated. Calcium crystal deposition is more common in older persons. The degenerative and destructive arthropathies associated with them will predictably become increasingly common as our population ages.

Arthritis↗
PubMed1990

Helix aggregation in peptide crystals: occurrence of either all parallel or antiparallel packing motifs for alpha-helices in polymorphs of Boc-Aib-Ala-Leu-Ala-Leu-Aib-Leu-Ala-Leu-Aib-OMe.

Three crystalline polymorphs of the helical decapeptide, Boc-Aib-Ala-Leu-Ala-Leu-Aib-Leu-Ala-Leu-Aib-OMe, have been obtained. Antiparallel helix aggregation is observed in crystals grown from methanol (A), while completely parallel packing is observed in crystals from isopropanol (B) or an ethylene glycol-ethanol mixture (C). Crystals B and C are very similar in molecular conformation and packing. The packing motifs in crystals A and B consist of rows of parallel molecules, with an almost identical arrangement in both crystals. In crystal A, adjacent rows assemble with the helix axes pointed in opposite directions, whereas in crystal B all rows assemble with helix axes pointed in the same direction. Electrostatic interactions between helix dipoles do not appear to be a major determinant of packing modes. The structures also do not provide a ready rationalization of packing preferences in terms of side-chain interactions or solvation. The alpha-helix of the peptide in crystal A has seven 5----1 hydrogen bonds; the helix in crystal B is a mixed 3(10)/alpha-helix. The crystal parameters are as follows. Crystal A: C51H92N10O13.CH3OH, space group P2(1) with a = 10.498 (1) A, b = 18.189 (3) A, c = 16.475 (3) A, beta = 99.28 (1) degree, Z = 2, R = 9.6% for 1860 data. Crystal B: C51H92N10O13.C3H7OH, space group P2(1) with a = 10.534 (1) A, b = 28.571 (4) A, c = 11.055 (2) A, beta = 95.74 (1) degree, Z = 2, R = 6.5% for 3251 data. Crystal C: C51H92N10O13.C2H5OH, space group P2(1), with a = 10.450 (1) A, b = 28.442 (5) A, c = 11.020 (2) A, beta = 95.44(1) degree, Z = 2, R = 14.8% (isotropic) for 1948 data.

Amino Acid Sequence↗