Search results for "phosphate"
showing 10 items of 1874 documents
The purification and properties of nucleoside phosphotransferase from mucosa of chicken intestine
1984
Abstract (1) Nucleoside phosphotransferase (nucleotide:3′-deoxynucleoside 5′-phosphotransferase, EC 2.7.1.77) has been purified from chicken intestine mucosa to apparent homogeneity. The enzyme is represented by a multisubunit protein at different degrees of association. It can dissociate into a compoenent with a marked fall in catalytic activity. (2) The associated forms are similar to the enzyme previously purified from chick embryo as regards: substrate specificity both with respect to nucleoside monophosphate donors and to deoxyribonucleoside acceptors; sigmoidicity in the rate curve with a variable phosphate donor; instability to heat, dilution and lowering of pH; the activating and pr…
The mechanism of hydrolysis of beta-glycerophosphate by kidney alkaline phosphatase.
1975
1. To identify the functional groups that are involved in the conversion of β-glycerophosphate by alkaline phosphatase (EC 3.1.3.1) from pig kidney, the kinetics of alkaline phosphatase were investigated in the pH range 6.6-10.3 at substrate concentrations of 3 μM-30 mM. From the plots of log ṼH+ against pH and log ṼH+/KH+m against pH one functional group with pK = 7.0 and two functional groups with pK = 9.1 were identified. These groups are involved in substrate binding. Another group with pK = 8.8 was found, which in its unprotonated form catalyses substrate conversion. 2. GSH inhibits the alkaline phosphatase reversibly and non-competitively by attacking the bound Zn(II). 3. The influenc…
Crystal and molecular structure of tris(mepirizole) copper(II) hexafluorophosphate [mepirizole = 4-methoxy-2-5-methoxy-3-methyl-1h-pyrazol-1-yl)-6-me…
1992
Abstract The X-ray crystal structure of Cu(mep)3(PF6)2 [mep = mepirizole or 4-methoxy-2-(5-methoxy-3-methyl-1H-pyrazol-1-yl)-6 methylpyrimidine], obtained from stoichiometric quantities of mep, Cu(NO3)2 and KPF6 in water/ethanol solution was determined. The trisbidentate Cu(mep)32+ cation is observed for the first time. One of the three mep molecules is disordered over two sets of positions related by crystallographic symmetry. The mep molecules exhibit two different conformations A and B: conformation B, which is observed for the first time, derives from the usual conformation A by rotating the pyrimidine ring by 180° around the central CN bond and rotating by 180° the methoxy group bonde…
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…
The Marine Sponge-Derived Inorganic Polymers, Biosilica and Polyphosphate, as Morphogenetically Active Matrices/Scaffolds for the Differentiation of …
2014
The two marine inorganic polymers, biosilica (BS), enzymatically synthesized from ortho-silicate, and polyphosphate (polyP), a likewise enzymatically synthesized polymer consisting of 10 to >100 phosphate residues linked by high-energy phosphoanhydride bonds, have previously been shown to display a morphogenetic effect on osteoblasts. In the present study, the effect of these polymers on the differential differentiation of human multipotent stromal cells (hMSC), mesenchymal stem cells, that had been encapsulated into beads of the biocompatible plant polymer alginate, was studied. The differentiation of the hMSCs in the alginate beads was directed either to the osteogenic cell lineage by …
REGULATORY ELEMENTS OF THE LEUKAEMIA INHIBITORY FACTOR (LIF) PROMOTER IN MURINE BONE MARROW STROMAL CELLS
1999
Leukaemia inhibitory factor (LIF) plays an important role as a haematopoietically active cytokine. As described earlier in a murine model, interleukin 1 (IL-1) induced LIF mRNA and protein expression. We utilized the murine cell line +/+-1.LDA11 to further define regulatory mechanisms of LIF expression in bone marrow stromal cells. The production of LIF mRNA is stimulated by IL-1beta, TNF-alpha, and the cAMP analogue 8-bromoadenosine 3':5'-monophosphate (8BrcAMP). LIF mRNA expression is controlled at the transcriptional level. Different fragments from -542 to -45 bp 5' upstream of the transcriptional start site of the murine LIF gene were fused to the luciferase gene. All LIF-promoter lucif…
Spatial analysis of plant metabolism: Sucrose imaging within Vicia faba cotyledons reveals specific developmental patterns
2002
During legume embryogenesis the differentiation of the cotyledons proceeds gradually in a wave-like manner. The process is metabolically and genetically controlled and regulated by sugars. In order to perform a spatial and temporal analysis of the sugar distribution pattern a new method was developed to specifically measure sucrose directly in tissues via bioluminescence and single photon counting. This enabled a quantitative sucrose imaging with a resolution close to the single cell level. The procedure was applied on sections of Vicia faba cotyledons covering the main stages of histodifferentiation. Young embryos before the storage phase contained moderate levels of sucrose, which were ev…