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PubMed1989

Effects of 2-deoxyglucose on Saccharomyces cerevisiae as observed by in vivo 31P-NMR.

Saccharomyces cerevisiae cells were treated with 2-deoxyglucose (1 mM) and the effects induced in the levels of phosphorus compounds and in the internal pH were monitored using 31P-NMR. Upon incubation with 2-deoxyglucose a strong decrease in the polyphosphate level was observed and the cytoplasmic pH decreased by about 0.4 units. This shows that 2-deoxyglucose strongly interferes with the cell conditions and consequently, the results of experiments in which 2-deoxyglucose was used to obtain deenergized cells should be carefully reanalysed.

Deoxy Sugars↗

PubMed2006

Autotrophic denitrification and chemical phosphate removal of agro-industrial wastewater by filtration with granular medium.

A novel granular medium consisting (1.5-5 mm in diameter) of inert perlite particles as nuclei and an effective surface layer containing sulfur, CaCO3 and Mg(OH)2 was developed for advanced treatment of agro-industrial wastewater. The performance of the medium was examined with a laboratory-scale down-flow fixed-bed column reactor using piggery wastewater, which had been treated by an upflow anaerobic sludge blanket reactor and a trickling filter. The removal efficiency of NOx- -N was more than 70% with a NOx- -N loading rate of less than approximately 0.3 kg Nm(-3) d(-1); the removal efficiency dropped due to the accumulation of nitrite when the loading rate exceeded that value. A significant drop of phosphate and Mg2+ concentrations occurred when the effluent pH exceeded 7.9. Ammonium was removed with an average removal efficiency of 12.4%. These results indicated that the crystalline reaction of PO4(3-), Mg2+ and NH4+ (MAP reaction) under alkaline conditions contributed to the removal of phosphate. This medium could be useful for the simultaneous reduction of nitrogenous and phosphorus compounds in biologically treated agro-industrial wastewater.

Filtration↗

PubMed2026

Phosphatase-mediated mitigation of rare earth element toxicity to Pseudomonas putida.

Anthropogenic activities are driving an increasing flux of rare earth elements (REE) into environmental compartments, raising concerns about their biological impact, particularly on microorganisms that sustain ecosystem functioning. Here, we provide a systematic assessment of the toxicity of all 16 REE toward Pseudomonas putida KT2440, a soil bacterium that can use these metals as enzyme cofactors. Dose-response growth inhibition assays revealed high sensitivity to light REE. Toxicity correlated strongly with ionic radius, with IC50 values ranging from 0.3 µM for lanthanum to 10 µM for scandium. Serial propagation of P. putida under gradually increasing REE stress yielded resistant populations, from which two stably resistant strains were isolated. Genome resequencing showed that both strains carried a single mutation in uxpB, encoding an alkaline phosphatase. Gene deletion and overexpression experiments, together with phosphatase activity measurements, confirmed the involvement of uxpB in REE resistance. Our findings reveal a previously unrecognized mechanism of tolerance to REE, suggesting that mutations enhancing phosphatase activity promote phosphate release from organic phosphorus compounds, thereby reducing REE bioavailability through phosphate-mediated complexation and/or immobilization.

Alkaline phosphatase↗

PubMed2006

Evaluation of methods for the determination of water in substances with unknown chemical and thermal behaviour.

The water content of six different substances was determined by means of five different methods. The methods used were loss on drying, thermogravimetry (coupled with DSC), a new phosphorous-pentoxide method, direct Karl-Fischer titration and the Karl-Fischer oven. A combination of direct Karl-Fischer titration and the KF-oven method was found to be the optimal technique for water determination of substances of unidentified chemical and thermal behaviour based on detailed considerations about selectivity, type of water binding, sample properties and efficiency.

Calorimetry, Differential Scanning↗

PubMed2004

Nutrient enrichment caused by in situ fish farms at Eilat, Red Sea is detrimental to coral reproduction.

Recent studies report conflicting results concerning the effects of eutrophication on coral reproduction. The present study examines reproductive effort in the brooding coral Stylophora pistillata exposed to chronic eutrophication caused by in situ fish cages (FC) in the northern Gulf of Eilat (Aqaba). Histological studies of 20 S. pistillata colonies transplanted to each of two study sites, one close to the nutrient enriched FC site and the other at a reference site (IUI), 8 km southwest of the FC site, show that, overall, corals from the FC site have a significantly higher percentage of polyps containing oocytes and testes than corals from the IUI site. However, average oocyte size and the percentage of oocytes reaching the size at which fertilization occurs (i.e., >200 microm) were both significantly greater in colonies at the IUI site compared to the FC site. As the reproductive season progressed, colonies at the IUI site exhibited a decrease in the percentage of polyps containing oocytes, concomitant with an increase in the number of polyps containing planulae, indicating successful development of oocytes into planulae. In contrast, in colonies at the FC site oocyte numbers were greatest at the end of the reproductive season, and overall, numbers of planulae were significantly lower compared with the IUI colonies, suggesting relative failure of oocyte maturation, fertilization and ensuing larval development. The significantly higher lipid content found during the reproduction season in IUI colonies compared with FC colonies corroborates this assertion. This data strongly suggest that nutrients released from the fish farms have adverse effects on successful production of larvae of S. pistillata. In view of the recent severe deterioration of the coral reefs of Eilat and their present critical state of health, the only chance for their renewal is the use of immediate, prudent and rational protection measures against all man-made perturbations.

Animals↗

PubMed2005

Studies on the structure behavior of triphenyldichlorophosphorane in different solvents.

Triphenyldichlorophosporane, which was prepared according to Appel reaction, was an efficient reagent for alkyl halide synthesis by virtue of having two replaceable groups on "pentavalent" phosphorus. The reaction of triphenylphosphine with hexachloroethane was investigated in different solvents and 31P NMR traced the processes of these reactions. As results, it was found that there was similar high coordinated phosphorus species formed in aromatic solvents and in ring ether type solvents, which had large 1J(P-C) (about 140 Hz) according to 13C NMR experiments. It is indicated that, for some solvent such as benzene or dioxane, solvent molecules might be locked in the high coordinated phosphorus compounds, which in turn would affect the triphenyl groups situated at the equatorial position.

Ethane↗

PubMed1989

Interspecies analysis of corneal phosphate metabolites.

Phosphate metabolite profiles of corneas were determined for human, baboon, monkey, cat, guinea-pig, pig, dog, rabbit, and cow using 31P-nuclear magnetic resonance (NMR) spectroscopy. Metabolites quantitatively measured included the low-energy metabolites: hexose 6-phosphates, alpha-glycerophosphate, unassigned phosphorus compound(s) at 4.26-3.91 delta, ethanolamine phosphate, nucleoside monophosphates, choline phosphate, inorganic orthophosphate, phosphodiesters (glycerol 3-phosphoethanolamine and glycerol 3-phosphocholine), and the high-energy metabolites: phosphocreatine, adenosine triphosphate (ATP), adenosine diphosphate (ADP), nucleoside diphosphosugars and dinucleotides. The number of significant differences in metabolites among the species studied, relative to humans, increased in the following order: baboon less than monkey approximately pig approximately cow less than cat approximately guinea-pig less than rabbit less than dog. The 31P energy modulus (human, 1.3 +/- 0.20 S.D.). ATP:Pi ratio (human, 0.5 +/- 0.05 S.D.). ATP:ADP ratio (human, 0.38 +/- 0.34 S.D.). ATP:ADP plus Pi ratio (human, 0.43 +/- 0.04 S.D.) and SP:Pi ratio (human, 0.37 +/- 0.04 S.D.) were determined for each species. All these ratios are indicators of corneal metabolic status, and their values suggest that, of the common laboratory research animals examined, the baboon and monkey are the most like man, and the rabbit and cow the least like man.

Animals↗

PubMed2000

Multiple-technique analytical characterization of a mixture containing chemical-weapons simulant from a munition.

An amber yellow organic liquid was found in a munition shell at Dugway Proving Grounds, UT, USA, that was likely used as a simulant of chemical weapons. The primary analytical techniques to characterize the mixture were gas chromatography-infrared detection-mass spectral detection (GC-IR-MS); liquid chromatography-mass spectrometry (LC-MS); nuclear magnetic resonance (NMR) using the nuclei 1H, 13C and 31P; and gas chromatography-atomic emission detection (GC-AED). Six major phosphorus-containing components were identified and confirmed by at least three techniques, and several additional phosphorus-containing components of lower concentration have been identified by GC-IR-MS and LC-MS. Five major non-phosphorus components, including ethyl acetate, diethyl sulfide and dibutylamine, have been identified by multiple techniques. The major phosphorus compound (23.9+/-0.4 wt.%) was O,O,O-triethyl phosphorothioate (I) and the second most abundant (14.4+/-0.2 wt.%) was O,O,S-triethyl phosphorothioate (III). No VX, G-agent, or pesticide was observed in the sample, although III may be a cholinesterase inhibitor which produces delayed toxic response. III also produces a false hit for the pesticide cyanthoate when analyzed by GC-MS-EI. The mixture appears to have been formulated as a chemical warfare agent simulant, most likely as a challenge of agent detection techniques.

Chemical Warfare Agents↗

PubMed1984

New thermionic detector utilizing orthogonal nebulization for capillary column liquid chromatography.

A new version of the previously studied phosphorus-sensitive, dual-flame thermionic detector has been developed for microcolumn liquid chromatography. The total column effluent is orthogonally nebulized and aspirated directly into a primary air-hydrogen diffusion flame. Phosphorus compounds with molecular weights extending beyond 500 a.m.u. are then selectively detected by measuring the conductivity of the secondary flame in the presence of a rubidium silicate bead. The sensitivity was found to be 1.36 X 10(-11) g phosphorus/sec at the maximum of a Gaussian peak, and the signal increased linearly with concentration over 2 orders of magnitude for dilute samples. Possible mechanisms accounting for the negative orientation of the signal and for the limited dynamic range are discussed.

Chemical Phenomena↗

PubMed2001

Risk assessment of etofenprox (Vectron) on non-target aquatic fauna compared with other pesticides used as Simulium larvicide in a tropical environment.

Within the rotational scheme developed by the Programme to fight the resistance of Simulium damnosum to chemical larvicides, there was an operational gap at discharges between 5 and 70 m3 s(-1) for the treatment of rivers where resistance to organophosphates was present. The use of permethrin and carbosulfan was precluded because of risk of environmental impact and, Bacillus thuringiensis ser. H-14 treatments were not envisageable due to cost and logistics constraints. Among the possible complementary groups of larvicides tested, the pseudo-pyrethroids, held promise, because of a mode of action similar to that of pyrethroids, but along with a usually lower toxicity for fish. Etofenprox, one of the pseudo-pyrethroids tested, shows a global detachment of non-target insects in 24 h close to that of pyraclofos, an organo-phosphorus compound (27 against 23%). In laboratory conditions, six times the operational dose which is 0.03 mg l(-1) 10 min, is needed to cause 50% mortality of Caridina sp. (a small shrimps species) and 30 times this same dose for 95% mortality. For fish species, a safety margin of 400-800 times the operational dose is observed for Oreochromis niloticus and 200-400 times for Tilapia zillii.

Animals↗

PubMed2003

Whole-cell bacterial sensors for the monitoring of phosphate bioavailability.

A phosphate sensor plasmid was constructed, in which the inducible promoter of the alkaline phosphatase gene (phoA) from Escherichia coli is fused to the bioluminescence genes from Vibrio fischeri. The reporter construct was introduced into E. coli MG1655 and the rhizosphere coloniser Pseudomonas fluorescens DF57, which produced light in a dose-dependent manner when exogenous phosphate concentrations fell below 60 and 40 microM, respectively. These strains also responded to various organic and inorganic phosphorus compounds. Their ability to distinguish the bioavailable portion of phosphate in standard solution was demonstrated using different phosphate ligands. When applying the bioassay to wastewater samples, luminescence patterns correlated with phosphate concentrations determined by standard chemical procedure. These results indicated that phoA::lux-based bacterial sensors may serve as tools for the assessment of phosphate bioavailability.

Alkaline Phosphatase↗

PubMed1999

Metabolic aspects of phosphate replacement therapy for hypophosphatemia after renal transplantation: impact on muscular phosphate content, mineral metabolism, and acid/base homeostasis.

Hypophosphatemia caused by renal phosphate loss occurs frequently after kidney transplantation. In assumption of systemic phosphorus depletion, the presumed deficit commonly is replaced by oral phosphate supplements. However, such treatment is debatable, because intracellular phosphorus stores have not been assessed in this setting and may not be accurately reflected by serum phosphate concentrations. Moreover, disturbances in mineral metabolism from chronic renal failure, such as hypocalcemia and hyperparathyroidism, may be prolonged with oral phosphate supplements. Conversely, a neutral phosphate salt might improve renal acid excretion and systemic acid/base homeostasis for its properties as a urinary buffer and a poorly reabsorbable anion. Twenty-eight patients with mild early posttransplantation hypophosphatemia (0.3-0.75 mmol/L) were randomly assigned to receive either neutral sodium phosphate (Na(2)HPO(4)) or sodium chloride (NaCl) for 12 weeks and examined with regard to (1) correction of serum phosphate concentration and urinary phosphate handling; (2) muscular phosphate content; (3) serum calcium and parathyroid hormone (PTH); and, (4) renal acid handling and systemic acid/base homeostasis. Mean serum phosphate concentrations were similar and normal in both groups after 12 weeks of treatment; however, more patients in the NaCl group remained hypophosphatemic (93% versus 67%). Total muscular phosphorus content did not correlate with serum phosphate concentrations and was 25% below normophosphatemic controls but was completely restored after 12 weeks with and without phosphate supplementation. However, the percentage of the energy-rich phosphorus compound adenosine triphosphate (ATP) was significantly higher in the Na(2)HPO(4) group, as was the relative content of phosphodiesters. Also, compensated metabolic acidosis (hypobicarbonatemia with respiratory stimulation) was detected in most patients, which was significantly improved by neutral phosphate supplements through increased urinary titratable acidity. These benefits of added phosphate intake were not associated with any adverse effects on serum calcium and PTH concentrations. In conclusion, oral supplementation with a neutral phosphate salt effectively corrects posttransplantation hypophosphatemia, increases muscular ATP and phosphodiester content without affecting mineral metabolism, and improves renal acid excretion and systemic acid/base status.

Acid-Base Equilibrium↗

PubMed1991

31P nuclear magnetic resonance spectra of milk from various species.

The 31P nuclear magnetic resonance spectra of milk from goats, sheep, a rabbit, a baboon and a human were examined and compared with the spectrum of cows' milk. Most of the peaks observed could be assigned to phosphorus compounds already known to be present in such milks. However, rabbit milk was found to contain unexpectedly large amounts of phosphate esters, and to have only low levels of alkaline phosphatase (EC 3.1.3.1) activity. In addition, an unknown compound was detected in baboon milk and in some samples of sheep and goat colostrum. This compound was not identified, but may be a mixed anhydride such as 1,3 diphosphoglyceric acid. The results show that changes during lactation may be followed by 31P nuclear magnetic resonance and that the technique may be of value in authentification of samples.

Animals↗

PubMed2002

Resolution of tert-butyl-1-(2-methyinaphthyl)phosphine oxide using selectors identified from a chemical combinatorial library.

Resolution of racemic tert-butyl-1-(2-methylnaphthyl)-phosphine oxide 1, a chiral phosphorus compound, was achieved using selectors developed from a small peptide library. Separation factors as high as 3.2 were observed. The library consists of 81 peptide-based potential chiral selectors on polymeric synthesis resins. The linker needed to immobilize the identified chiral selectors onto silica gel proved important in the chiral separation; a longer linker provided a significantly higher separation factor in this study.

Chromatography, High Pressure Liquid↗

PubMed2005

Intelligent signal processing for detection system optimization.

A wavelet-neural network signal processing method has demonstrated approximately 10-fold improvement over traditional signal processing methods for the detection limit of various nitrogen and phosphorus compounds from the output of a thermionic detector attached to a gas chromatograph. A blind test was conducted to validate the lower detection limit. All 14 of the compound spikes were detected when above the estimated threshold, including all 3 within a factor of 2 above the threshold. In addition, two of six spikes were detected at levels of half the concentration of the nominal threshold. Another two of the six would have been detected correctly if we had allowed human intervention to examine the processed data. One apparent false positive in five nulls was traced to a solvent impurity, whose presence was subsequently identified by analyzing a solvent aliquot evaporated to 1% residual volume, while the other four nulls were properly classified. We view this signal processing method as broadly applicable in analytical chemistry, and we advocate that advanced signal processing methods should be applied as directly as possible to the raw detector output so that less discriminating preprocessing and postprocessing does not throw away valuable signal.

Journal Article↗

PubMed2002

Alkaline phosphatase revisited: hydrolysis of alkyl phosphates.

Escherichia coli alkaline phosphatase (AP) is the prototypical two metal ion catalyst with two divalent zinc ions bound approximately 4 A apart in the active site. Studies spanning half a century have elucidated many structural and mechanistic features of this enzyme, rendering it an attractive model for investigating the potent catalytic power of bimetallic centers. Unfortunately, fundamental mechanistic features have been obscured by limitations with the standard assays. These assays generate concentrations of inorganic phosphate (P(i)) in excess of its inhibition constant (K(i) approximately 1 muM). This tight binding by P(i) has affected the majority of published kinetic constants. Furthermore, binding limits k(cat)/K(m) for reaction of p-nitrophenyl phosphate, the most commonly employed substrate. We describe a sensitive (32)P-based assay for hydrolysis of alkyl phosphates that avoids the complication of product inhibition. We have revisited basic mechanistic features of AP with these alkyl phosphate substrates. The results suggest that the chemical step for phosphorylation of the enzyme limits k(cat)/K(m). The pH-rate profile and additional results suggest that the serine nucleophile is active in its anionic form and has a pK(a) of < or = 5.5 in the free enzyme. An inactivating pK(a) of 8.0 is observed for binding of both substrates and inhibitors, and we suggest that this corresponds to ionization of a zinc-coordinated water molecule. Counter to previous suggestions, inorganic phosphate dianion appears to bind to the highly charged AP active site at least as strongly as the trianion. The dependence of k(cat)/K(m) on the pK(a) of the leaving group follows a Brønsted correlation with a slope of beta(lg) = -0.85 +/- 0.1, differing substantially from the previously reported value of -0.2 obtained from data with a less sensitive assay. This steep leaving group dependence is consistent with a largely dissociative transition state for AP-catalyzed hydrolysis of phosphate monoesters. The new (32)P-based assay employed herein will facilitate continued dissection of the AP reaction by providing a means to readily follow the chemical step for phosphorylation of the enzyme.

Alkaline Phosphatase↗

PubMed1999

Evidence for Nondissociative Ligand Exchange within [4+2]-Coordinate Phosphorus Species in Solution.

[4+2]-Coordinate phosphorus compounds, [bis(8-(dimethylamino)-1-naphthyl)]phenylphosphane, [bis(8-(dimethylamino)-1-naphthyl)]phenylphosphane sulfide, [bis(8-(dimethylamino)-1-naphthyl)]phenylphosphonium bromide, [bis(8-(dimethylamino)-1-naphthyl)]methylphosphane, and [bis(8-(dimethylamino)-1-naphthyl)]phosphane oxide, with two identical bidentate (8-(dimethylamino)-1-naphthyl) ligands have asymmetrical geometries in solution and undergo intramolecular nondissociative ligand exchange as shown by dynamic (1)H NMR studies. The DeltaG() values for this process were found to lie in the range 56.2-61.7 kJ mol(-)(1). The (1)H NMR study for bis[(8-(dimethylamino)-1-naphthyl)]phenylphosphane sulfide has revealed that two hexacoordinate isomers coexist in solution in a solvent dependent ratio. Their interconversion in solution is consistent with an intramolecular 1,2-shift of adjacent ligands.

Journal Article↗

PubMed2004

Alkylating agents stronger than alkyl triflates.

A new class of potent electrophilic "R(+)" alkylating agents has been developed using weakly nucleophilic carborane anions as leaving groups. These reagents, R(CHB(11)Me(5)X(6)) (R = Me, Et, and i-Pr; X = Cl, Br), are prepared via metathesis reactions with conventional alkylating agents such as alkyl triflates, using the high oxophilicity of silylium ion-like species, Et(3)Si(carborane), as the driving force to obtain increased alkyl electrophilicity. The crystal structure of the isopropyl reagent, i-Pr(CHB(11)Me(5)Br(6)), has been determined, revealing covalence in the alkyl-carborane bonding. This contrasts with the free i-Pr(+) carbocation observed when the anion is less coordinating (e.g. Sb(2)F(11)(-)) or with tertiary alkyl centers, as in [tert-butyl][carborane] salts. In solution, the reagents exist as equilibrating isomers with the alkyl group at the 7-11 or 12 halide positions of the CB(11) icosahedral carborane anion. These alkylating agents are so electrophilic that they (a) react with alkanes at or below room temperature via hydride extraction to produce carbenium ions, (b) alkylate benzene without a Friedel-Crafts catalyst to give arenium ions, and (c) alkylate electron-deficient phosphorus compounds that are otherwise inert to conventional alkylating agents such as methyl triflate.

Alkylating Agents↗