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PubMed1995

Magic-angle spinning nuclear magnetic resonance study of the structure of some PbO-Al2O3-P2O5 glasses.

Some PbO-Al2O3-P2O5 glasses have been investigated using 31P and 27Al magic-angle spinning nuclear magnetic resonance. The observed spectra could be divided into two groups. In the first, Al(IV), Al(V) and Al(VI) are observed, the 31P linewidths are large and the chemical shift range (-30 to -36 ppm) is typical of network phosphate. In the second group, only Al(VI) is observed, the 31P linewidths are much narrower and the shifts are less negative (-18 to -28 ppm).

Aluminum Oxide↗
PubMed1995

Nuclear magnetic resonance investigation of the structures of phosphate and phosphate-containing glasses: a review.

This paper presents a review of the nuclear magnetic resonance (NMR) data for phosphate and phosphate-containing glasses obtained primarily within the past 10 years and of the structural interpretations based on those data. Compositions discussed include P2O5, alkali and alkaline earth phosphates, aluminophosphates, borophosphates, fluorophosphates, and phosphate-containing silicate and aluminosilicate glasses. 31P NMR data, in conjunction with 27Al, 29Si, 11B, 7Li, and 23Na data if appropriate, have proven very powerful in providing direct evidence about the local structural environments present in the these materials and in many cases have allowed interpretation of the physical and chemical behavior of these glasses in terms of polyhedral structures.

Alkalies↗
PubMed2004

Important amino acids in the phosphohydrolase module of Escherichia coli Orf135.

The Escherichia coli Orf135 protein, a MutT-type enzyme, hydrolyzes 2-hydroxy-dATP and 8-hydroxy-dGTP, in addition to dCTP and 5-methyl-dCTP, and its deficiency causes increases in both the spontaneous and H(2)O(2)-induced mutation frequencies. In this study, the Gly-36, Gly-37, Lys-38, Glu-43, Arg-51, Glu-52, Leu-53, Glu-55, and Glu-56 residues of Orf135, which are conserved in the three MutT-type proteins (Orf135, MutT, and MTH1), were substituted, and the enzymatic activity of these mutant proteins was examined. The mutant proteins with a substitution at the 36th, 37th, 52nd, and 56th amino acid residues completely lost their activity. On the other hand, the mutant proteins with a substitution at the 38th, 43rd, 51st, 53rd, and 55th residues could hydrolyze 5-methyl-dCTP. Some mutants with detectable activity for 5-methyl-dCTP did not hydrolyze dCTP. Activities for known substrates (5-methyl-dCTP, dCTP, 2-hydroxy-dATP, and 8-hydroxy-dGTP) were examined in detail with the four mutants, K38R, E43A, L53A, and E55Q. These results indicate the essential residues for the activity of the Orf135 protein.

Amino Acid Sequence↗
PubMed2004

Unfolding and inactivation during thermal denaturation of an enzyme that exhibits phytase and acid phosphatase activities.

The thermostability of an enzyme that exhibits phytase and acid phosphatase activities was studied. Kinetics of inactivation and unfolding during thermal denaturation of the enzyme were compared. The loss of phytase activity on thermal denaturation is most suggestive of a reversible process. As for acid phosphatase activities, an interesting phenomenon was observed; there are two phases in thermal inactivation: when the temperature was between 45 and 50 degrees C, the thermal inactivation could be characterized as an irreversible inactivation which had some residual activity and when the temperature was above 55 degrees C, the thermal inactivation could be characterized as an irreversible process which had no residual activity. The microscopic rate constants for the free enzyme and substrate-enzyme complex were determined by Tsou's method [Adv. Enzymol. Relat. Areas Mol. Biol. 61 (1988) 381]. Fluorescence analyses indicate that when the enzyme was treated at temperatures below 60 degrees C for 60 min, the conformation of the enzyme had no detectable change; when the temperatures were above 60 degrees C, some fluorescence red-shift could be observed with a decrease in emission intensity. The inactivation rates (k(+0)) of free enzymes were faster than those of conformational changes during thermal denaturation at the same temperature. The rapid inactivation and slow conformational changes of phytase during thermal denaturation suggest that inactivation occurs before significant conformational changes of the enzyme, and the active site of this enzyme is situated in a relatively fragile region which makes the active site more flexible than the molecule as a whole.

6-Phytase↗
PubMed2005

Geographical determinants and environmental implications of livestock production intensification in Asia.

Under growing and urbanizing demand, livestock production is rapidly evolving in South, East and South-east Asia, with both an increase of production and a shift to intensive production systems. These changes infer impacts on the environment, on public health and on rural development. Environmental impacts are mainly associated with a mismanagement of animal excreta, leading to pollution of surface water, ground water and soils by nutrients, organic matter, and heavy metals. In the framework of the Livestock Environment and Development Initiative, this research aims at assessing, on a regional scale, the impacts of livestock production on nutrient fluxes. Phosphate (P(2)O(5)) mass balances were chosen as an indicator and were calculated on the basis of spatially modelled livestock densities, estimated excretion values and crop uptake. The results show a strong West--East gradient regarding the distribution of monogastrics, with clear concentration in densely populated areas and around urban centres. P(2)O(5) overloads are estimated on 23.6% of the study area's agricultural land, mainly located in eastern China, the Ganges basin and around urban centres such as Bangkok, Ho Chi Minh City and Manila. On average, livestock manure is estimated to account for 39.4% of the agricultural P(2)O(5) supply (the remaining share being supplied by chemical fertilisers). Livestock is the dominant agricultural source of P(2)O(5) around urban centres and in livestock specialised areas (southern and north-eastern China), while chemical fertilisers are dominant in crop (rice) intensive areas.

Agriculture↗
PubMed2004

The fertilizer value of pig slurry. I. Values depending on the type of operation.

151 samples of pig slurries were taken from 83 operations in the Castile-Leon region of Spain. Analysis of them enabled comparison of slurries coming from pig farming operations located in different Spanish and European regions. These operations were classified into three groups, namely maternity (64 samples), closed cycle (35 samples) and fattening (52 samples). For each sample 27 parameters were analysed. Data obtained from each kind of operation were compared. Finally, the fertilizer value of slurries was determined with regard to the relationship between their major elements, N/P2O5/K2O (1/0.6/0.4).

Agriculture↗
PubMed2006

Potential nitrification in alum-treated soil slurries amended with poultry manure.

Alum is used to reduce environmental pollutants in poultry production. Alum decreases NH3 volatilization and increases total N and NH4+-N compared to untreated poultry manure. Nitrification in poultry wastes could therefore be stimulated due to higher NH4+ concentrations or could be inhibited because the soil environment is acidified. A 10-day laboratory study was conducted to study potential nitrification rates in soil slurries (20 g soil in 150 ml water) amended with 2.0 g alum-treated poultry manure. Fecal bacteria, NH4+, NO2-, NO3-, orthophosphate, pH, and NH3 were measured at 2-day intervals. Alum significantly reduced fecal bacteria concentrations through day 6. Water-soluble P was reduced 82% by day 10. Alum-treated manure had significantly increased NH4+ concentrations by day 8 and 10, and significantly decreased NO2- and NO3- concentrations by days 6-10. Alum's effect on potential nitrification was inhibitory in the soil environment. Slurries with alum-treated poultry manure had reduced nitrification rates, fecal bacteria, and soluble P. Therefore, in addition to reducing P loss, alum could temporarily reduce the risk for environmental pollution from land-applied manures in terms of both NO3- and fecal bacteria loss.

Alum Compounds↗
PubMed2005

A macromolecular prodrug of doxorubicin conjugated to a biodegradable cyclotriphosphazene bearing a tetrapeptide.

A new biodegradable water-soluble phosphazene trimer-doxorubicin conjugate was synthesized, in which equimolar hydrophilic methoxy-poly(ethylene glycol) with a molecular weight of 350 (MPEG350) and a tumor-specific tetrapeptide (Gly-Phe-Leu-Gly) were grafted to cyclotriphosphazene. The present conjugate exhibited cytotoxicity lower than that of free doxorubicin (IC50=0.10 microM) but a reasonably higher in vitro cytotoxicity (IC50=1.1 microM) against the leukemia L1210 cell line probably due to its enzymatically controlled release.

Animals↗
PubMed2005

Synthesis and structural analysis of 6-deoxy-6-hydroxyphosphinyl-D-fructopyranose derivatives.

3,4-Di-O-benzyl-6-deoxy-6-diethoxyphosphinyl-1,2-O-isopropylidene-beta-D-fructofuranose (13) was prepared from the known 1,2-O-isopropylidene-6-O-tosyl-beta-D-fructofuranose in five steps. Reduction of 13 with sodium dihydrobis(2-methoxyethoxy)aluminate, followed by the action of hydrochloric acid and then hydrogen peroxide, afforded the 6-deoxy-6-hydroxyphosphinyl-D-fructopyranose derivative. This was converted into the 1,2,3,4,5-penta-O-acetyl-6-deoxy-6-methoxyphosphinyl-D-fructopyranoses, whose structure and conformation were established by 1H NMR spectroscopy.

Fructose↗
PubMed2005

Regioselective phosphorylation of branched cyclodextrins with cyclo-mono-mu-imidotriphosphate.

The phosphorylation of the branched cyclodextrins, mono-6-O-(alpha-D-glucopyranosyl)cyclomaltohexaose, mono-6-O-(alpha-D-maltosyl)cyclomaltohexaose, mono-6-O-(alpha-D-glucopyranosyl)cyclomaltoheptaose, and mono-6-O-(alpha-D-maltosyl)cyclomaltoheptaose, in aqueous solution by sodium cyclo-mono-mu-imidotriphosphate (cMITP) was examined. In these reactions, only the 2-OH group of a single alpha-D-glucopyranosyl residue of the cyclodextrin ring was phosphorylated, in a maximum yield of 67%. A possible mechanism for the phosphorylation is discussed.

Carbohydrate Conformation↗
PubMed2004

Assessment of the effectiveness of different phosphorus fertilizers to remediate Pb-contaminated soil using in vitro test.

The addition of P-containing amendments was found to effectively reduce the bioaccessibility of Pb in soils to the human, using an in vitro test. For all treatments with P additions, the removal of soluble Pb in the small intestinal phase was observed. The effectiveness of various P treatments in the small intestinal phase generally followed this order at the equivalent P addition level: hydroxyapatite (HA)>phosphate rock (PR)>HA+single super-phosphate (SSP)>SSP. The relatively low effectiveness of P amendments at the gastric phase may be explained by the high solubility of pyromorphite at relatively low pH of 1.7, compared with that at the neutral small intestinal pH. Single super-phosphate showed the best performance in minimizing the bioaccessibility of Pb in the gastric phase, possibly due to its highest solubility at pH 1.7. Single super-phosphate showed the best performance in minimizing the bioaccessibility of Pb in gastric phase, possibly due its highest solubility at pH 1.7. However, in the small intestinal phase, SSP appears to be the least effective amendment, possibly due to its lowest Ca supply level to replace Pb form exchangeable sites, as reflected by its lowest molar Ca/P ratio of 1:2. The disagreement of the sequential extraction results with that of the in vitro test results indicated that the sequential extraction was not suitable for the assessment of the effect of P addition on minimizing the bioaccessibility of Pb to human due to the formation of pyromorphite during the extraction procedure. Results from this study also suggested that the time required for the in vitro test might be shortened for fast screening.

Biological Availability↗
PubMed2004

Intra- and intercellular variations in the repair efficiency of O6-methylguanine, and their contribution to kinetic complexity.

Following administration to rats of various doses of N-nitrosodimethylamine (NDMA), O(6)-methylguanine (O(6)-meG) was lost from the DNA of four tissues (liver, white blood cells, lymph nodes, bone marrow) over two, sharply demarcated phases with substantially differing repair rates. Repair during each phase followed approximately first-order kinetics in O(6)-meG, even after a high dose of NDMA which caused substantial depletion of O(6)-alkylguanine-DNA alkyltransferase (AGT), a suicide repair protein. This is compatible with rate-determining adduct repair being brought about by a distinct, minor pool of AGT molecules which is rapidly replenished by de novo AGT synthesis. Similar biphasic repair kinetics were also observed in HepG2 cells treated in vitro with NDMA. In this case, the first phase of repair was inhibited by alpha-amanitin, an inhibitor of RNA polymerase II-mediated transcription. However, no dependence on transcriptional activity was found when O(6)-meG repair in specific gene sequences with different transcriptional status in rat liver was examined, suggesting that the effects of alpha-amanitin in HepG2 cells did not reflect inhibition of preferential repair of transcribed sequences. Repair was also examined in rat liver hepatocytes and non-parenchymal cells separately after administration of NDMA at non-AGT depleting doses. Within each cell-population, the repair followed single phase, first-order kinetics, with adduct loss from AGT-rich hepatocytes being significantly faster than from the relatively AGT-deficient non-parenchymal cells. In conclusion, differences in the AGT content of different cell subpopulations in the liver (and probably in other tissues), as well as additional cellular factors affecting repair efficiency, appear to determine the observed variation in the kinetics of repair of O(6)-meG. The additional cellular factors involved appear not to be related to the transcriptional state of the sequences being repaired, but may reflect different states of chromatin condensation.

Alkyl and Aryl Transferases↗
PubMed2004

A theoretical study of P4O10: vibrational analysis, infrared and Raman spectra.

The normal mode frequencies and the corresponding vibrational assignments of tetraphosphorus decaoxide (P4O10) in tetrahedral (Td) symmetry are examined theoretically and experimentally. The Gaussian 98 set of quantum chemistry codes at the HF/6-311G*, MP2/6-311G*, and DFT/B3LYP/6-311G* levels of theory are used. By comparison to experimental normal mode frequencies deduced by Gilliam et al. [J. Phys. Chem. B 107 (2003) 2892], Chapman [Spectrochim. Acta A, 24 (1968) 1687], Beattie et al. [J. Chem. Soc. A (1970) 449], Konings et al. [J. Mol. Spectrosc. 152 (1992) 29] and the present work, correction factors for predominant vibrational motions are determined and compared. Normal modes were decomposed into five non-redundant motions (P-O stretch, P=O stretch, P-O-P bend, P-O-P wag, and P=O wag). Standard deviations found for the HF, MP2, and DFT corrected frequencies compared to experiment are 9, 5, and 4 cm(-1), respectively. Electron distribution for selected molecular orbitals is considered.

Electrons↗
PubMed2004

Vibrational frequencies and structural determination of phosphorous tricyanide.

The normal mode frequencies and corresponding vibrational assignments of phosphorous tricyanide (P(CN)(3)) are examined theoretically using the Gaussian98 set of quantum chemistry codes. Each of the vibrational modes was assigned to one of four types of motion predicted by a group theoretical analysis P-C stretch, CN stretch, P-C[triple bond]C bend, and C-P-C bend) utilizing the C(3v) symmetry of the molecule. A uniform scaling factor was derived for each type of motion. Predicted infrared and Raman intensities are reported.

Cyanides↗
PubMed2007

Temporal and spatial variation of phosphate distribution in the sediment of a free water surface constructed wetland.

This study was aimed at determining the spatial and temporal variation of P distribution in sediment of an artificial wetland for sewage and industrial wastewater treatment, and the fraction that is potentially involved in the P exchange processes. Influent, effluent, macrophytes and sediment at the inlet, middle and outlet areas were sampled over 24 months. The P-fractionation in sediment was performed following the EDTA method. Eichhornia crassipes and Typha domingensis removed P efficiently when cover was high, but E. crassipes caused anoxic conditions. The increase in cover of T. domingensis may contribute to attain oxic conditions and to improve P removal. When macrophytes are not present or when cover is low, sediment seems to increase removal efficiency. A significant increase in the concentration of the fraction of Fe(OOH) approximately P and mainly that of CaCO(3) approximately P can be observed at the inlet. High pH, Ca(2+) and CO(3)(-)(2) concentrations in the influent suggest that P co-precipitates together with CaCO(3). Therefore, it seems that CaCO(3) approximately P represents the main precipitating mechanism. However, mineralization of organic matter maintained the sediment at a pH range lower than the high values prevailing in the influent. CO(3)(-)(2) could undergo partial dissolution and the released i-P(diss) could be readsorbed onto the Fe(OOH) approximately P fraction. Since the environment for P retention (high pH, Fe, Ca and ionic concentrations) is largely provided by the influent, the wetland may be expected to continue retaining P as far as the composition of the influent is maintained and there are available adsorption sites in the sediment.

Adsorption↗
PubMed2004

Origins and implications of drinking water odours in lakes and reservoirs of British Columbia, Canada.

The relationship between commonly measured limnological parameters and odours was examined in 16 reservoirs and lakes used as sources for drinking water and three reference lakes. Odour analysis was conducted using flavour profile analysis (FPA) and, on select lakes, gas chromatography ion-trap mass spectrometry (GC-ITMS) for target compounds. Total phosphorus (TP) was the best single predictor of FPA intensity and multiple regression models accounted for 37-39% of intensity variance in the epilimnion and metalimnion, respectively. Earthy odours were more prevalent in reservoirs and lakes with higher TP, whereas decomposing vegetation and green vegetation+grassy odours almost exclusively occurred when TP was lower (<13 microg P/L). Only geosmin was identified with GC-ITMS, and it was found to occur in lakes and reservoirs of higher trophic status (e.g. more algal biomass). Infrequent episodic events in the Greater Victoria's principal reservoir (e.g. algal blooms) have previously been linked with taste and odour problems in their tap water. However, analysis of odours under the conditions of this study (i.e. no strong odour episodes in the source reservoir) suggest that typical odours prevalent in tap water originating from Sooke Lake Reservoir are derived from treatment processes or the distribution system, not directly from the reservoir. This study demonstrates the utility of employing relatively simple and established methods to better understand management issues of a drinking water system.

British Columbia↗