Search results for " PHOSPHATE"
showing 10 items of 293 documents
Electrostatic Contribution to the Surface Pressure of Charged Monolayers Containing Polyphosphoinositides
2008
Structural and functional studies of lateral heterogeneity in biological membranes have underlined the importance of membrane organization in biological function. Most inquiries have focused on steric determinants of membrane organization, such as headgroup size and acyl-chain saturation. This manuscript reports a combination of theory and experiment that shows significant electrostatic contributions to surface pressures in monolayers of phospholipids where the charge spacing is smaller than the Bjerrum length. For molecules with steric cross sections typical of phospholipids in the cell membrane (approximately 50 A(2)), only polyphosphoinositides achieve this threshold. The most abundant s…
Self-assembly in surfactant-based mixtures driven by acid–base reactions: bis(2-ethylhexyl) phosphoric acid–n-octylamine systems
2013
Structural and dynamic features of bis(2-ethylhexyl) phosphoric acid (HDEHP)-n-octylamine (NOA) mixtures as a function of the NOA mole fraction (X-NOA) have been investigated by SAXS, WAXS, IR, dielectric spectroscopy and polarized optical microscopy. In the 0 <= X-NOA < 0.5 range, mixtures are transparent liquids, while the abrupt formation of a waxy solid characterized by an hexagonal bidimensional structure occurs at X-NOA = 0.5. Such a composition-induced phase transition results from the synergetic effect of the progressive increase in number density of ordered HDEHP-NOA nanodomains with X-NOA. Mainly driven by an HDEHP to NOA proton transfer, the increase of structural order with X-NO…
In-Situ DRIFT Spectroscopic Investigation on the Chemical Evolution of Zinc Phosphate Acid−Base Cement
2000
Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy has been used to follow the chemical evolution of zinc phosphate acid−base cement (ZPC), which has been prepared from unmodified, as well as from aluminum- and zinc-modified orthophosphoric acid. For the first time, amorphous dizinc cyclotetraphosphate octahydrate, Zn2P4O12·8H2O, although hydrolytically instable, has been observed as precursor phase prior to crystallization of α-hopeite, α-Zn3(PO4)2·4H2O, in both systems. Within minutes from onset of mixing the infrared spectrum of unmodified ZPC is dominated by the characteristic vibrations of α-hopeite, due to matrix crystallization. Setting of modified ZPC is strongly af…
Molecular association of small amphiphiles: Origin of ionic liquid properties in dibutyl phosphate/propylamine binary mixtures
2018
Abstract Binary mixtures of liquid surfactants, owing to the amphiphilic nature of the molecules involved, can exhibit nano-segregation and peculiar transport properties. The amphiphilicity, and consequently the resulting self-assembly, can be tuned by changing the length of the alkyl chains and the nature of the polar head group. So, in the present study, the structural and dynamic properties of dibutyl phosphate/propylamine liquid mixtures at various compositions have been investigated by Wide Angle X-ray Scattering (WAXS), FT-IR, rheometry and dielectric spectroscopy in order to study the intermolecular association taking place when alkylphosphates and alkylamines with a small apolar par…
Recovery of zinc from spent pickling solutions by liquid–liquid extraction using TBP
2019
In this paper, recovery of zinc from real spent pickling solutions by liquid–liquid extraction with tributyl phosphate (TBP) was studied. In particular, the effects of some parameters were investigated, such as the volume ratio between the organic phase and real spent pickling liquor (O/A) (1:2, 1:1, 2:1, 4:1), the stirring time (5–20–30 min) and the TBP concentration (10%–55%–100%), in order to determine the conditions leading to higher zinc extraction efficiency, as well as selectivity in relationships to other metals such as iron. After zinc extraction, TBP was successfully regenerated. Among several tested solutions, water allows zinc recovery higher than 90%, especially at 10% diluted …
Radiation-Induced Stable Radicals in Calcium Phosphates: Results of Multifrequency EPR, EDNMR, ESEEM, and ENDOR Studies
2021
This article presents the results of a study of radiation-induced defects in various synthetic calcium phosphate (CP) powder materials (hydroxyapatite—HA and octacalcium phosphate—OCP) by electron paramagnetic resonance (EPR) spectroscopy at the X, Q, and W-bands (9, 34, 95 GHz for the microwave frequencies, respectively). Currently, CP materials are widely used in orthopedics and dentistry owing to their high biocompatibility and physico-chemical similarity with human hard tissue. It is shown that in addition to the classical EPR techniques, other experimental approaches such as ELDOR-detected NMR (EDNMR), electron spin echo envelope modulation (ESEEM), and electronnuclear double resonance…
Synthesis and characterization of α-hopeite, Zn3(PO4)2·4H2O
1999
Orthorhombic α-Zn3(PO4)2·4H2O, α-hopeite, was synthesized from an aqueous solution of zinc acetate and orthophosphoric acid. The synthesis from these starting materials yielded best results with respect to purity and crystallinity. Structural characteristics of the compound were investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), and thermogravimetric/differential thermal analysis (TG/DTA). Supplemental data came from surface area, particle size distribution, and density measurements. The obtained compound proved to be highly crystalline and stoichiometric. Dehydration of α-hopeite is accompanied by at least two endothermic effect…
FC 079HIGH SERUM PHOSPHATE, A NOVEL POTENTIAL RISK FACTOR FOR BONE FRAGILITY FRACTURES IN THE COSMOS STUDY
2021
Abstract Background and Aims Bone fragility fractures (bone fractures) are extremely frequent in haemodialysis (HD) patients. Serum phosphate (P) has been suggested as a risk factor for bone fracture, nonetheless, evidence is poor. The aim of this study was to assess the association between incidence of bone fractures and serum phosphate (P), calcium (Ca) and parathyroid hormone (PTH) in patients from the COSMOS study. Method COSMOS is an observational, prospective, open cohort study with 3 years of follow-up including 6797 haemodialysis patients from 227 centres randomly selected from 20 European countries. At baseline, demographics, comorbidities, treatments, serum biochemical parameters …
Synthesis and luminescent properties of Mn-doped alpha-tricalcium phosphate
2021
This project has received funding from European Social Fund (project No 09.3.3-LMT-K-712-19-0069) under grant agreement with the Research Council of Lithuania (LMTLT). Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART². The World Federation of Scientists is highly acknowledged for the National Scholarship to AZ. © 2021. This work is licensed under a CC BY-NC-ND 4.0 license.
The quantitative determination of metabolites of 6-mercaptopurine in biological materials. VII. Chemical synthesis by phosphorylation of 6-thioguanos…
1990
Abstract A fast and reliable two-step method has been established for the chemical synthesis of 6-thioguanosine 5′-monophosphate, 6-thioguanosine 5′-diphosphate and 6-thioguanosine 5′-triphosphate starting from the ribonucleoside. In the first step, 6-thioguanosine dissolved in triethyl phosphate, at high yield reacts with phosphorus oxide trichloride to 6-thioguanosine 5′-monophosphate which is purified by anion-exchange chromatography on DEAE-Sephadex using a step gradient of hydrochloric acid. In the second step, 6-thioguanosine 5′-monophosphate dissolved in water, reacts with phosphoric acid in the presence of pyridine/dicyclohexyl carbodiimide and is converted to 6-thioguanosine 5′-dip…