Showing papers on "Phosphate published in 1997"
TL;DR: In this in vitro study, CPP-stabilized calcium phosphate solutions were shown to remineralize subsurface lesions in human third-molar enamel and were significantly correlated with the degree of saturation for hydroxyapatite, octacalcium phosphate, or ACP.
Abstract: Casein phosphopeptides (CPP) stabilize amorphous calcium phosphate (ACP), localize ACP in dental plaque, and are anticariogenic in animal and in situ human caries model. In this vitro study, CPP-stabilized calcium phosphate solutions were shown to remineralize subsurface lesions in human third-molar enamel. Solutions were used to examine the effect of CPP-calcium phosphate concentration on remineralization. Other solutions were used to examine the effect of increasing pH, which decreased the concentrations of free calcium and phosphate ions and increased the level of CPP-bound ACP. Although most of the remineralizing solutions were supersaturated with respect to the amorphous and crystalline calcium phosphate phases, the solutions were stabilized by the CPP such that spontaneous precipitation of calcium phosphate did not occur. After a ten-day remineralization period, enamel lesions were sectioned, subjected to microradiography, and the mineral content determined by microdensitometry. All solutions deposited mineral into the bodies of the lesions, with the 1.0% CPP-calcium phosphate (pH 7.0) solution replacing 63.9 +/- 20.1% of mineral lost at an averaged rate of 3.9 +/- 0.8 x 10(-8) mol hydroxyapatite/m2/s. The remineralizing capacity was greater for the solutions with the higher levels of CPP-stabilized free calcium and phosphate ions. Remineralization was not significantly correlated with either the CPP-bound ACP of the degrees of saturation for hydroxyapatite, octacalcium phosphate, or ACP. However, remineralization was significantly correlated with the degree of saturation for dicalcium phosphate dihydrate (CaHPO4.2H2O), but his was attributed to the significant correlation of remineralization with the activity gradients from the solution into the lesion of some calcium phosphate ions and ion pairs, in particular the neutral ion pair CaHPO4(0). The CPP, by stabilizing calcium phosphate in solution, maintain high-concentration gradients of calcium and phosphate ions and ion pairs into the subsurface lesion and thus effect high rates of enamel remineralization.
660 citations
TL;DR: It would appear that ceramic solubility influences osteoclast resorption activity, with osteoclasts resorbed BCP most extensively, with an HA/beta-TCP ratio of 25/75, producing typical lobulated, zig-zag track-like resorptive lacunae.
464 citations
Book•
31 Dec 1997
TL;DR: In this article, the role of metal ions in the growth of calcification of calcined calcium pyrophosphate has been investigated in the presence of Polymeric Inhibitors.
Abstract: Preface. Part I: General. 1. Calcium Phosphates: Structures: Composition, Solubility and Stability M.S. Tung. 2. Amorphous Calcium Phosphate: Thermodynamic and Kinetic Considerations E.D. Eanes. 3. Growth of Calcium Phosphates on Different Substrates: Epitaxial Considerations P.G. Koutsoukos. 4. Physicochemical Properties of Fluorapatite L.C. Chow, M. Markovic. 5. Interfacial Properties of Calcium Phosphates P. Somasundaran, B. Markovic. 6. Nuclear Magnetic Resonance Spectroscopy of Calcium Phosphates J.P. Yesinowski. Part II: Calcium Phosphates in Biological Systems. 7. Influence of Metal Ions on the Crystal Growth of Calcium Phosphates P.G. Koutsoukos. 8. Structure/Performance Relationships of Phosphorous and Carboxyl Containing Additives as Calcium Phosphate Crystal Growth Inhibitors J.D. Sallis. 9. Crystal Growth of Calcium Phosphates in the Presence of Polymeric Inhibitors S. Shimabayashi, T. Uno. 10. Calcium Phosphates for Medical Applications C. Rey. 11. Importance of Calcium Phosphates in the Development of Calcium Urolithiasis S.R. Khan. 12. Calcium Pyrophosphate Crystal Formation and Dissolution K.P.H. Pritzker. 13. Calcium Phosphates in Pharmaceutical Product Development M.A. Khan, I.K. Reddy. 14. Recent Advances in Dentifrice Technologies A. Gaffar, J. Afflitto. 15. Preparation and Application of Calcium Phosphate Fibers K. Ioku. Part III: Calcium Phosphates in Industrial Systems. 16. Development of Calcium Phosphate Inhibiting Polymers for Cooling Water Applications Z. Amjad. 17. Mechanism of Calcium Phosphate Scale Formation and Inhibition in Cooling Systems L.A. Perez. 18. The Role of Calcium Phosphate in Internal Boiler Water Treatment J.S. Gill. 19. Equipment Fouling in the Dairy Application: Problem and Pretreatment G. Daufin, J.-P. Labbe. 20. Phosphate Removal from Waste Water M.M. Seckler, et al. 21. Phosphorous Speciation in Sediments and its Release Control K. Ito, M. Okada. 22. Mechanistic Aspects of Calcium Phosphonates Precipitation L.M. Frostman, et al. Index.
346 citations
TL;DR: Calcium fluoride deposits act in such a way, owing to a surface covering of phosphate and/or proteins, which makes the CaF2 less soluble under in vivo conditions than in a pure form in inorganic solutions.
Abstract: Low concentrations of fluoride have a beneficial effect on enamel and dentin de- and remineralization. After fluoride treatments, such as topical applications, rinses or dentifrices, salivary fluoride concentrations decrease exponentially in a biphasic manner to very low concentrations within a few hours. For treatments to be effective over periods longer than the brushing and the following salivary clearance, fluoride needs to be deposited and slowly released. Calcium fluoride (or like) deposits act in such a way, owing to a surface covering of phosphate and/or proteins, which makes the CaF2 less soluble under in vivo conditions than in a pure form in inorganic solutions. Moreover, due to the phosphate groups on the surface of the calcium fluoride globules, fluoride is assumed to be released with decreasing pH when the phosphate groups are protonated in the dental plaque.
320 citations
TL;DR: Rock phosphate fertilization and inoculation with Glomus constrictum and rock-phosphate-solubilizing fungi (A. niger and P. citrinum) significantly increased dry matter yield of wheat plants under all experimental conditions, but the effect was more evident in non- sterilized pot soils and in the field than in sterilized pots.
Abstract: A total of 36 fungal species isolated from soil were tested for their ability to solubilize rock phosphate (RP) in agar plates. Most of these fungi were non-rock phosphate solubilizers, but two isolates, Aspergillus niger and Penicillium citrinum, had high activity. Liquid culture experiments revealed that both fungi caused a remarkable drop in pH of culture media and solubilized considerable amounts of phosphate. The effects on wheat of inoculation with vesicular–arbuscular mycorrhizal fungi and rock-phosphate-solubilizing fungi and fertilization with rock phosphate were studied in sterilized pot soils, nonsterilized pot trials and in field plot soils. Rock phosphate fertilization and inoculation with Glomus constrictum and rock-phosphate-solubilizing fungi (A. niger and P. citrinum) significantly increased dry matter yield of wheat plants under all experimental conditions. However, the effect was more evident in non- sterilized pot soils and in the field than in sterilized pots. Rock phosphate had no significant effect on the total phosphorus content of plants grown under pot conditions but it was significantly increased in field plots; the effect of inoculation with fungi (G. constrictum, A. niger and P. citrinum) on plant phosphorus was closely related to this in dry matter production. The greatest positive effect on growth and phosphorus contents of wheat plants was recorded in the treatments that received rock phosphate and were inoculated with a mixed inoculum of the three microorganisms used, followed by dual inoculation treatments of G. constrictum plus either A. niger or P. citrinum.
266 citations
TL;DR: It is proposed that plastids contain various phosphate translocators with overlapping substrate specificities to ensure an efficient supply of plastidids with a single substrate, even in the presence of other phosphorylated metabolites.
Abstract: We have purified a plastidic phosphate transport protein from maize endosperm membranes and cloned and sequenced the corresponding cDNAs from maize endosperm, maize roots, cauliflower buds, tobacco leaves, and Arabidopsis leaves. All of these cDNAs exhibit high homology to each other but only approximately 30% identity to the known chloroplast triose phosphate/phosphate translocators. The corresponding genes are expressed in both photosynthetically active tissues and in nongreen tissues, although transcripts were more abundant in nongreen tissues. Expression of the coding region in transformed yeast cells and subsequent transport measurements of the purified recombinant translocator showed that the protein mediates transport of inorganic phosphate in exchange with C3 compounds phosphorylated at C-atom 2, particularly phosphoenolpyruvate, which is required inside the plastids for the synthesis of, for example, aromatic amino acids. This plastidic phosphate transporter is thus different in structure and function from the known triose phosphate/phosphate translocator. We propose that plastids contain various phosphate translocators with overlapping substrate specificities to ensure an efficient supply of plastids with a single substrate, even in the presence of other phosphorylated metabolites.
251 citations
TL;DR: In this article, the oxygen isotope exchange between phosphate and water mediated by bacteria is governed by equilibrium rather than kinetic factors, which has important implications for paleoclimatological and paleoenvironmental studies.
251 citations
TL;DR: In this paper, the corrosion and protection characteristics of zinc and manganese phosphate coatings in aqueous solutions were investigated by means of physical methods and electrochemical measurements, and the results showed that the insulation property of zinc phosphate coating is better than that of mananganese phosphate, but the porosity of the former is inferior to that of the latter.
Abstract: The corrosion and protection characteristics of zinc and manganese phosphate coatings in aqueous solutions are investigated by means of physical methods and electrochemical measurements. The results show that the insulation property of zinc phosphate coating is better than that of manganese phosphate, but the porosity of the former is inferior to that of the latter. The anodic current of coated samples decreases and polarization resistance increases compared to the substrate. The corrosion of phosphated steel exhibits the characteristics of no diffusion in acidic solution, a finite-length diffusion in neutral medium, and a semi-infinite diffusion in alkahne solution. Chemical dissolution is the primary form in the failure of phosphate coatings, which is induced by the electrochemical corrosion of the substrate. The protection ability of phosphate coatings mainly depends on their barrier performance.
201 citations
TL;DR: In this paper, the feasibility of phosphate removal from the supernatant of anaerobically digested sludge by struvite (MAP, MgNH 4 PO 4 ) crystallization in a fluidized-bed reactor (FBR) was studied.
195 citations
TL;DR: In this article, experimental studies on sediment cores from freshwater and marine conditions reveal major differences in the benthic exchange of phosphate across the sediment-water interface when shifting from anoxicto oxic conditions.
Abstract: Comparative, experimental studies on sediment cores from freshwater andbrackish-marine conditions reveal major differences in the benthic exchangeof phosphate across the sediment-water interface when shifting from anoxicto oxic conditions The flux of phosphate to the sediment during this shiftwas found to be mediated mainly by scavenging from newly formed colloidalferric oxohydroxide The capacity of the iron-rich particles to scavengephosphorus depended on the stoichiometric ratio between dissolved iron andphosphorus built up in the supernatant water during reducing conditions Thefreshwater system was characterized by high iron to phosphorus ratios in thedissolved phase and thus most of the phosphate was incorporated into thecolloidal iron oxohydroxide during the oxygenation In contrast, the marinesystems reached lower iron to phosphorus ratios during the anoxic period whichresulted in less efficient phosphate scavenging Consequently, significantamounts of phosphate remained dissolved in the marine systems after the changeto oxic conditions, possibly increasing the proportion of phosphate recycledto the euphotic zone Manganese showed a consistent redox-dependent behaviourin all the investigated systems, but interacted neither with phosphate norwith iron
194 citations
TL;DR: In this paper, it was found that aluminum hydroxide has a significant sorptive capacity for orthophosphate, condensed phosphate and organic phosphate, but not for non-reactive phosphate.
TL;DR: New artificial bone materials were prepared using calcium phosphates, hydroxyapatite and β-tricalicum phosphate, and copoly-L-lactide, CPLA, and scanning electron microscope observations indicated that the composites were homogeneously dispersed and highly adhesive.
Abstract: New artificial bone materials were prepared using calcium phosphates, hydroxyapatite and β-tricalicum phosphate, and copoly-L-lactide, CPLA. Calcium phosphate powder and CPLA were mixed at 453 K for 10 min with various mixing ratios. Scanning electron microscope observations indicated that the composites of β-tricalicum phosphate and CPLA were homogeneously dispersed and highly adhesive. Young’s modulus of the composites was the same as bone, and bending strength was over half that of bone. The improvement of Young’s modulus compared to the original two materials was due to a composite effect. The composites are expected to be usable as artificial bone materials.
TL;DR: In this article, the effects of phosphate rock on chemical associations of Pb in eight Pb-contaminated soils using a sequential extraction procedure were evaluated using an analytical model.
Abstract: Lead contamination is of great concern because of its adverse effects on human health, especially children. This research evaluated the effects of phosphate rock on chemical associations of Pb in eight Pb-contaminated soils using a sequential extraction procedure. The chemical fractions are operationally defined by an extraction sequence in the order of increasing ability to dissolve Pb of lower solubilities. Additionally, more soluble forms of Pb are considered to be potentially more bioavailable than the less soluble forms. Lead in these soils was primarily associated with the carbonate and Fe-Mn oxide fractions (63-85%). Up to 21% of the Pb in these soils was associated with either the organic or the residual fraction and <11% was associated with the water-soluble and the exchangeable fractions. Phosphate rocks effectively converted Pb from the water soluble, exchangeable, carbonate, Fe-Mn oxide, and organic fractions (collectively the nonresidual fraction) to the residual fraction, thus reducing Pb solubility and presumably bioavailability. Lead precipitation as a fluoropyro-morphite-like mineral in these contaminated soils was suggested as the primary mechanism for reduced Pb solubility and Pb reduction in the nonresidual fraction. The effective conversion of Pb from potentially available fractions to the residual fraction suggests that phosphate rock has potential for in-situ immobilization in Pb contaminated soils.
TL;DR: In this paper, the effect of bivalent ions on the structure and relative stability of β-tricalcium phosphate with their ionic radius was investigated, which can be used to interpret the role of ionic composition on the properties of biological phosphates.
TL;DR: In this paper, it was shown that cold NaOH does not only extract iron-bound phosphate but also phytate and humic phosphates from aquatic sediments, which may be an important mechanism for anoxic phosphate release from sediments.
Abstract: NaOH is often used as an extractant for thefractionation of sediment-bound phosphates. Besidesorthophosphate, a certain quantity of phosphate whichis called ‘non-reactive NaOH-extractable phosphate’is also extracted. In recent literature it has beensuggested that this fraction consists of bacterialpolyphosphates and might be responsible for the phosphate release from aquatic sediments under anoxicconditions. In a previous publication we have already shown thatNaOH is not an accurate extractant as both theconcentration of NaOH and the duration of theextraction have an influence on the quantity ofphosphate extracted, due to the hydrolysis of organicphosphates. In this article we show that cold NaOH does not onlyextract iron-bound phosphate but phytate phosphate aswell. Non-reactive phosphate in this extract was notrelated to the presence of polyphosphate, but mainlyto phytate and humic phosphates. As it has been shownthat phytate may disappear from sediments when theybecome anoxic, we suggest that phytate mineralizationmay be an important mechanism for anoxic phosphaterelease from sediments.
TL;DR: Rod-like hydroxyapatite was synthesized by precipitating calcium nitrate tetrahydrate and ammonium dibase phosphate in the presence of polyacrylic acid followed by hydrothermal treatment.
Abstract: Rod-like hydroxyapatite was synthesized by precipitating calcium nitrate tetrahydrate and ammonium dibase phosphate in the presence of polyacrylic acid followed by hydrothermal treatment. Both polyacrylic acid and the hydrothermal treatment stabilised the hydroxyapatite.
TL;DR: The inhibitins effects of the HA and beta-TCP powders on the osteoblast cell cultures possibly are mediated by the increased synthesis of PGE2.
Abstract: With advances in ceramics technology, calcium phosphate bioceramics have been applied as bone substitutes for several decades. The focus of this work is to elucidate the biocompatibility of the particulates of various calcium phosphate cytotoxicities. Four different kinds of calcium phosphate powders, including beta-tricalcium phosphate (beta-TCP), hydroxyapatite (HA), beta-dicalcium pyrophosphate (beta-DCP), and sintered beta-dicalcium pyrophosphate (SDCP), were tested by osteoblast cell culture. The results were analyzed by cell count, concentration of transforming growth factor-beta 1 (TGF-beta 1), alkaline phosphatase (ALP), and prostaglandin E2 (PGE2) in culture media. The changes were most significant when osteoblasts were cultured with beta-TCP and HA bioceramics. The changes in cell population of the beta-TCP and HA were quite low in the first 3 days, then increased gradually toward the seventh day. The changes in TGF-beta 1 concentration in culture medium inversely related to the changes in cell population. The ALP titer in the culture media of the beta-TCP and HA were quite high in the first 3 days, then decreased rapidly between the third and seventh days. The concentrations of PGE2 in the culture media tested were quite high on the first day, decreased rapidly to the third day, and then gradually until the seventh day. The changes in the beta-DCP and SDCP were quite similar to those of HA and beta-TCP but much less significant. We conclude that HA and beta-TCP have an inhibitory effect on the growth of osteoblasts. The inhibitins effects of the HA and beta-TCP powders on the osteoblast cell cultures possibly are mediated by the increased synthesis of PGE2.
TL;DR: In this article, ordered non-lamellar mesoporous aluminophosphates and gallo-aluminoph phosphates have been synthesized by introducing phosphate linking groups to cluster/surfactants salts of prearranged AlO4Al12(OH)24(H2O)127+ (Al13) and GaAl12 (GaAl12) tridecamers.
Abstract: Ordered nonlamellar mesoporous aluminophosphates and galloaluminophosphates have been synthesized by introducing phosphate linking groups to cluster/surfactants salts of prearranged AlO4Al12(OH)24(H2O)127+ (Al13) and GaO4Al12(OH)24(H2O)127+ (GaAl12) tridecamers. The Al13 and GaAl12 polyoxocations form a layered mesoscopic salt with the anionic surfactant sodium dodecylsulfate. Upon the reaction with a buffered hydrogen phosphate/dihydrogen phosphate solution the layers of clusters are transformed into a nonlayered, nearly hexagonal mesoscopic phase. Removal of the surfactant from the alumino- and galloaluminophosphates by anion-exchange results in mesoporous materials with BET surface areas up to 630 and 455 m2/g, respectively. FT-IR and 27Al and 31P MAS−NMR as well as 27Al → 31P cross-polarization experiments indicate that the phosphate treatment results in the formation of new bonds between aluminate and phosphate species. A fraction of the clusters are transformed leading to an increase in the number o...
TL;DR: Nutrient and ancillary chemical changes in a stretch of the Great Ouse river near Brackley in Northamptonshire, UK, were measured on a seasonal basis over one year with an initial pilot study in the spring of 1994.
TL;DR: Results suggest that the difference in the pH of a hydraulic calcium phosphate cement made of monocalcium phosphate monohydrate and β-tricalcium phosphate is much lower than 5.9, the value predicted by calculation, and may be due to the presence of impurities in the cement.
Abstract: The pH of a hydraulic calcium phosphate cement (HCPC) made of monocalcium phosphate monohydrate (Ca(H2PO4)2·H2O; MCPM), β-tricalcium phosphate (β-(Ca3(PO4)2; β-TCP) and water was measured as a function of reaction time and composition at room temperature During setting, the cement pH varies from very acidic pH values, ie, 25, to almost neutral pH values, ie, 6 The cement pH profile significantly depends on the initial cement composition However, all profiles are characterized by a sharp initial decrease of the pH due to the dissolution of MCPM crystals and the precipitation of dicalcium phosphate dihydrate (CaHPO4· 2H2O; DCPD) crystals With an excess of MCPM, the final pH stays low, and its value can be predicted from the initial composition of the cement and solubility data With an excess of β-TCP, the end pH is close to 5, which is much lower than 59, the value predicted by calculation Results suggest that the difference may be due to the presence of impurities in the cement Replacing MCPM by phosphoric acid renders the cement paste very acidic for the initial 30 s, but then the pH profile follows that obtained with MCPM Adding pyrophosphate ions into the cement paste postpones the position of the pH minimum The delay, which is proportional to the concentration of pyrophosphate ions, is thought to be due to the inhibiting action of pyrophosphate ions on the precipitation of DCPD crystals
TL;DR: The distribution pattern and temporal variations of concentrations of phosphorus forms were studied in the sediments of the Bay of Seine in seven cruises over the period of 1992-1994 as mentioned in this paper.
TL;DR: In this paper, the effects of buffer type and concentration on the Maillard reaction were evaluated in phosphate and citrate buffer solutions of various concentrations at pH 7 and 25 °C, respectively.
TL;DR: In this paper, a phosphate-solubilising isolate of Penicillium radicum (sp. nov) was used to inoculate wheat in a glasshouse experiment and a field trial, using low pH soils at 5 levels of phosphate application.
Abstract: A phosphate-solubilising isolate of Penicillium radicum (sp. nov.) was used to inoculate wheat (Triticum aestivum cv. Dollarbird) in a glasshouse experiment and a field trial, using low pH soils at 5 levels of phosphate application. When data for all phosphate application levels were combined, inoculation by P. radicum resulted in 14% increases in wheat yield in the field trial and increases in both phosphate uptake (10%) and yield (9%) in the glasshouse. In the glasshouse, the response to inoculation was higher at the nil phosphate application level (17%) than for the combined phosphate application levels (9%). This negative interaction indicates that growth promotion could be partially due to soil phosphate solubilisation by the fungus, with a greater response for soils with lower available P. However, other plant-growth promotion mechanisms may also be involved.
TL;DR: In this paper, a synthetic goethite, α-Fe(OH)3, with surfaces saturated with Pb2+ was used to represent adsorbed Pb, one of the primary soil Pb species.
Abstract: Conversion of labile soil Pb species into stable Pb minerals is a crucial process in the development of an in situ soil Pb remediation strategy. A complete understanding of the reaction with specific soil Pb species is therefore of fundamental importance. A synthetic goethite, α-Fe(OH)3, with surfaces saturated with Pb2+ was used to represent adsorbed Pb, one of the primary soil Pb species. Hydroxyapatite (Ca5(PO4)3OH) and NaH2PO4 were the source of solid and soluble phosphate, respectively. When stoichiometric concentrations of soluble phosphate were added directly to the suspension of Pb-adsorbed goethite, the thermodynamically stable lead phosphate mineral chloropyromorphite (Pb5(PO4)3Cl) was rapidly precipitated. By contrast, when the same goethite suspension was reacted in a dialysis system in the presence of hydroxyapatite, the formation of chloropyromorphite is slow and appears to be controlled by the rate of dissolution of the hydroxyapatite. Chloropyromorphite minerals produced in these experimen...
TL;DR: The calculated values of the maximum surface density of coprecipitated phosphate are in good agreement with those from abiotic conditions, which indicates that the same mechanism is in operation.
TL;DR: The Humber is a large and complex estuarine system on the east coast of England fed by several rivers and fluxes of nutrients to the system are highly seasonal as discussed by the authors.
1 Aug 1997
TL;DR: The CD-MUSIC model is able to describe data sets of both simultaneous and single adsorption of cadmium and phosphate with the same parameters, and confirmed the idea that only singly coordinated surface groups are reactive for specific ion binding.
Abstract: Interactions between different ions are of importance in understanding chemical processes in natural systems. In this study simultaneous adsorption of phosphate and cadmium on goethite is studied in detail. The charge distribution (CD)-multisite complexation (MUSIC) model has been successful in describing extended data sets of cadmium adsorption and phosphate adsorption on goethite. In this study, the parameters of this model for these two data sets were combined to describe a new data set of simultaneous adsorption of cadmium and phosphate on goethite. Attention is focused on the surface speciation of cadmium. With the extra information that can be obtained from the interaction experiments, the cadmium adsorption model is refined. For a perfect description of the data, the singly coordinated surface groups at the 110 face of goethite were assumed to form both monodentate and bidentate surface species with cadmium. The CD-MUSIC model is able to describe data sets of both simultaneous and single adsorption of cadmium and phosphate with the same parameters. The model calculations confirmed the idea that only singly coordinated surface groups are reactive for specific ion binding.
TL;DR: In this article, α-TCP powder was made and immersed in deionized water and morphology change and phase composition were analyzed before and after immersion, based on the results of hydrolysis, a formula for the converted apatite-TPC phase containing lattice water was put forward and a partial structural model along the hydroxyl column was proposed.