The Effect of Silicic Acid on Calcium Phosphate Precipitation

1989 ◽  
Vol 68 (9) ◽  
pp. 1355-1359 ◽  
Author(s):  
J.J.M. Damen ◽  
J.M. Ten Cate
Keyword(s):  
Crystal Growth ◽  
Calcium Phosphate ◽  
Silicic Acid ◽  
Inhibitory Effect ◽  
Polysilicic Acid ◽  
Lag Period ◽  
Additional Support ◽  
Silica Suspensions ◽  
Calcium Phosphate Precipitation

So that a possible involvement in the mineralization of dental plaque could be investigated, the effects of silicic acid on calcium phosphate precipitation were assessed in vitro. By measuring the decrease in Ca2+ concentration (by means of ion-selective electrodes), we determined both spontaneous precipitation and seeded crystal growth from solutions that contained 1 mmol/L calcium, 7.5 mmol/L phosphate, 50 mmol/L Hepes pH 7.2, and various amounts of silicic acid. Polymerized silicic acid, but not its monomer, was found both to cause a 60% reduction in the lag period that precedes spontaneous precipitation and to enhance the growth rate of seeded hydroxyapatite crystals. Silica suspensions showed effects similar to those of polysilicic acid. In all cases, the precipitated material was found to be hydroxyapatite. Whereas seeded brushite crystals grew slowly without silicic acid, hydroxyapatite was the only mineral detected after crystal growth in the presence of silicic acid. Apparently, polysilicic acid acted as a substrate for hydroxyapatite nucleation, inducing secondary nuclei on both hydroxyapatite and brushite crystals. The finding that polysilicic acid could overcome part of the inhibitory effect of a phosphoprotein on calcium phosphate precipitation gave additional support for the idea that polysilicic acid and silica may promote the formation of dental calculus.

Molecular Basis of Salivary Proline-rich Protein and Peptide Synthesis: Cell-free Translations and Processing of Human and Macaque Statherin mRNAs and Partial Amino Acid Sequence of their Signal Peptides

1987 ◽  
Vol 66 (2) ◽  
pp. 462-466 ◽  
Author(s):  
F.G. Oppenheim ◽  
D.I. Hay ◽  
D.J. Smith ◽  
G.D. Offner ◽  
R.F. Troxler
Keyword(s):  
Calcium Phosphate ◽  
Macaca Fascicularis ◽  
Electrophoretic Analysis ◽  
Proteolytic Processing ◽  
Oral Environment ◽  
Reticulocyte Lysate ◽  
Polyprotein Precursor ◽  
Phosphate Salts ◽  
Calcium Phosphate Precipitation

Acidic proline-rich phosphoproteins and phosphopeptides are abundant components of parotid and submandibular salivary secretions in man and in the subhuman primate, Macaca fascicularis. The major acidic proline-rich proteins and the proline-rich phosphopeptide, statherin, of man and macaques have been shown to be potent inhibitors of calcium phosphate precipitation and are thought to function in the oral environment by maintaining saliva supersaturated with respect to calcium phosphate salts. Little is known about the biosynthesis of these proline-rich phosphoproteins and peptides, and the aim of the present work was to determine the structural relationship between statherin precursors and native human and macaque statherin. RNA was isolated from human submandibular gland, and poly(A+) mRNA was selected by affinity chromatography on oligo(dT) cellulose and translated in a reticulocyte lysate. Electrophoretic analysis of the translation products revealed that this mRNA directed the synthesis of a large number of polypeptides with M,s ranging from 5000 to 70,000. Immunoprecipitates, prepared with an antiserum directed against human statherin, contained a single component with a Mr of 7800, approximately 2000 daltons larger than native statherin. Radiosequencing of the in vitro precursor of statherin in immunoprecipitates demonstrated the presence of a 19-residue signal peptide. These results suggest that statherin is derived from a unique structural gene, and does not result from proteolytic processing of a large polyprotein precursor.

scholarly journals Antibodies to synthetic peptide from the residue 33 to 42 domain of c-Ha-ras p21 block reconstitution of the protein with different effectors.

1989 ◽  
Vol 9 (9) ◽  
pp. 3904-3910 ◽  
Author(s):  
I Rey ◽  
P Soubigou ◽  
L Debussche ◽  
C David ◽  
A Morgat ◽  
...  
Keyword(s):  
Synthetic Peptide ◽  
Binding Pocket ◽  
Inhibitory Effect ◽  
Effector Proteins ◽  
Structural Basis ◽  
Ras Proteins ◽  
Ras P21 ◽  
Reduced Rate ◽  
Additional Support

Residues 32 to 40, which are conserved among ras proteins from different species, are likely to participate in interactions with the p21 effector system. With the goal of understanding the structural basis of the regulatory functions of c-Ha-ras p21, we produced rabbit antisera against a synthetic peptide corresponding to amino acids 33 to 42 of the protein. The affinity-purified antibodies interacted specifically with p21 and with the antigenic peptide. The epitope recognized by the antibodies appeared to be centered on threonine 35. The antibodies inhibited both in vitro p21-induced production of cyclic AMP in detergent extracts of RAS-defective yeast membranes and GAP-stimulated GTPase activity. However, monoclonal anti-ras antibodies Y13-259 and Y13-238 were not capable of specifically inhibiting interactions of p21 with these two putative effector proteins. The apparent inhibitory effect of Y13-259 on stimulation of p21 by GAP was due to a greatly reduced rate of exchange of nucleotides in the binding pocket of the protein. These findings provide additional support for the essential role of the residue 32 to 40 domain as the true effector site and further evidence of the involvement of GAP as a cellular effector of ras proteins.

Effects of citrate and NaCl on size, morphology, crystallinity and microstructure of calcium phosphates obtained from aqueous solutions at acidic or near-neutral pH

2012 ◽  
Vol 79 (2) ◽  
pp. 238-248 ◽  
Author(s):  
Omar Mekmene ◽  
Thierry Rouillon ◽  
Sophie Quillard ◽  
Paul Pilet ◽  
Jean-Michel Bouler ◽  
...  
Keyword(s):  
Calcium Phosphate ◽  
Calcium Phosphates ◽  
Octacalcium Phosphate ◽  
Inhibitory Effect ◽  
Particle Sizes ◽  
X Ray Diffraction ◽  
Phosphate Dihydrate ◽  
Constant Ph ◽  
Starting Solutions ◽  
Calcium Phosphate Precipitation

Precipitation of calcium phosphates occurs in dairy products and depending on pH and ionic environment, several salts with different crystallinity can form. The present study aimed to investigate the effects of NaCl and citrate on the characteristics of precipitates obtained from model solutions of calcium phosphate at pH 6·70 maintained constant or left to drift. The ion speciation calculations showed that all the starting solutions were supersaturated with respect to dicalcium phosphate dihydrate (DCPD), octacalcium phosphate (OCP) and hydroxyapatite (HAP) in the order HAP>OCP>DCPD. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses of the precipitates showed that DCPD was formed at drifting pH (acidic final pH) whereas poor crystallised calcium deficient apatite was mainly formed at constant pH (6·70). Laser light scattering measurements and electron microscopy observations showed that citrate had a pronounced inhibitory effect on the crystallisation of calcium phosphates both at drifting and constant pH. This resulted in the decrease of the particle sizes and the modification of the morphology and the microstructure of the precipitates. The inhibitory effect of citrate mainly acted by the adsorption of the citrate molecules onto the surfaces of newly formed nuclei of calcium phosphate, thereby changing the morphology of the growing particles. These findings are relevant for the understanding of calcium phosphate precipitation from dairy byproducts that contain large amounts of NaCl and citrate.

Calcium Phosphate Precipitation in Liposomal Suspensions

1989 ◽  
Vol 174 ◽  
Author(s):  
Edward D. Eanes
Keyword(s):  
Calcium Phosphate ◽  
Lipid Vesicles ◽  
Matrix Vesicles ◽  
Liposomal Membrane ◽  
Liposomal Membranes ◽  
Precipitation Reactions ◽  
Basic Features ◽  
Calcium Phosphate Precipitation

AbstractArtificial lipid vesicles (liposomes) provide an in vitro approach for microencapsulating calcium phosphate precipitation reactions in a manner similar to that which occurs in matrix vesicles, the initial loci for extracellular mineralization in many skeletal tissues. Apatitic precipitates readily form within the aqueous interiors of liposomes prepared from phosphatidylcholine, dicetylphosphate, and cholesterol when the liposomal membranes enclosing pH 7.4 buffered PO4 solutions are made permeable to external Ca2+ with ionophores. If the external Ca solution is rendered metastable with PO4, the apatitic precipitates rapidly expand to outside the liposomes as well. The present paper describes the basic features of liposomal mineralization and presents some specific examples on how compositional alterations in the liposomal membrane and external Ca solution can affect the progress of this mineralization.

Isolation from urine of pyrophosphate, a calcification inhibitor

1962 ◽  
Vol 203 (4) ◽  
pp. 671-675 ◽  
Author(s):  
Herbert Fleisch ◽  
Sylvia Bisaz
Keyword(s):  
Calcium Phosphate ◽  
Inorganic Pyrophosphate ◽  
Minimum Value ◽  
Phosphate Compound ◽  
Apatite Crystals ◽  
Urinary Inhibitors ◽  
The Mean ◽  
Calcium Phosphate Precipitation

The minimum value of the product, Ca X P, necessary for calcium phosphate precipitation to occur, was determined in vitro. The addition of 2.2% urine to the solutions raised the mean product from 53 to 105 (mg/100 ml)2, which shows that the urine contains inhibitors to hydroxyapatite precipitation. One of these was isolated and purified. Its characteristics are those of inorganic pyrophosphate. The mean level of urinary pyrophosphate was 2.24 mg P/liter, sufficient to inhibit precipitation of hydroxyapatite. Pyrophosphate is one of the substances permitting urine to be supersaturated with calcium and phosphate; other urinary inhibitors are still to be identified. It is suggested that the phosphate compound present in the plasma which inhibits hydroxyapatite precipitation is pyrophosphate. In bone, pyrophosphatase would act by locally destroying this calcification inhibitor, thus allowing the apatite crystals to form.

scholarly journals The Release Behavior, Biocompatibility and Physical Properties of Ald-loaded Strontium Doped Calcium Phosphate Cement

2020 ◽  
Vol 17 (6) ◽  
pp. 1209-1223
Author(s):  
Maryam Mohammadi ◽  
Sayed Mahmood Rabiee ◽  
Saeed Hesaraki
Keyword(s):  
Calcium Phosphate ◽  
Calcium Phosphate Cement ◽  
Setting Time ◽  
Inhibitory Effect ◽  
Tartrate Resistant Acid Phosphatase ◽  
Alendronate Sodium ◽  
G Cells ◽  
Alp Activity ◽  
Bone Degradation

AbstractThe effect of concurrent attendance of two inhibitors of bone degradation, namely Alendronate (Ald) sodium trihydrate and Strontium (Sr), on Calcium Phosphate Cement (CPC) characteristics was explored. To this aim, 5 wt% Strontium and 21 mM Alendronate sodium trihydrate were used in calcium phosphate cement and setting time, ion and drug release were analyzed. RAW264.7 and G cell were cultured on cement samples and Tartrate-Resistant Acid Phosphatase (TRAP), Alkaline phosphatase (ALP) activity and MTT assay were studied. The results of structural analysis indicated that 21 mM Ald did not let the cement set. Therefore, colloidal silica was added to the cement formula and successfully decreased the setting time. In vitro tests showed Sr-loaded sample had a greater inhibitory effect on biocompatibility of G cells than Ald-loaded and Sr-Ald-loaded samples. In addition, the findings about osteoblast MTT and ALP activity indicated that Sr was more effective in osteogenic activity of G cells. The simultaneous presence of Ald and Sr in Calcium Phosphate Cement (CPC) was not as effective in its biocompatibility as the presence of Sr alone.

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