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PubMed2001

Detection of natural abundance nitrogen-15 through phosphorus-31 using pulsed field gradients.

NMR characterization of natural abundance (15)N in phosphorus-nitrogen compounds can be performed through (31)P using inverse detection methods. When the (31)P-(15)N scalar coupling is small, its observation is greatly disturbed by the residual signal coming from the 99.6% abundant (14)N isotopomer that usually is not completely suppressed by the phase cycle of the sequence. The combined use of pulsed field gradients to suppress this residual signal and the enhanced sensitivity (31)P, (15)N[(1)H]-esHSQC experiment affords artifact-free spectra with good signal-to-noise ratio, which allows the accurate measurement of (15)N NMR parameters such as chemical shifts and coupling constants with the benefits of phosphorus detection.

Journal Article↗

PubMedDate not supplied

Synthesis of the star-shaped copolymer of epsilon-caprolactone and L-lactide from a cyclotriphosphazene core.

Hexakis[p-(hydroxylmethyl)phenoxy]cyclotriphosphazene was synthesized by the reaction of hexachlorocyclotriphosphazene with the sodium salt of 4-hydroxybenzaldehyde and subsequent reduction of aldehyde groups to alcohol groups by using sodium borohydride. This compound was employed in initiating the ring-opening polymerization of epsilon-caprolactone and L-lactide to produce star-shaped poly(L-lactide) (PLA), poly(epsilon-caprolactone) (PCL), and their block copolymer with cyclophosphazene cores. 1H NMR and GPC analysis showed narrow-distributed star-shaped polyesters were successfully synthesized with high yields.

Magnetic Resonance Spectroscopy↗

PubMed1999

Cloning, sequencing, and expression of an Escherichia coli acid phosphatase/phytase gene (appA2) isolated from pig colon.

Bacterial strains were isolated from the pig colon to screen for phytase and acid phosphatase activities. Among 93 colonies, Colony 88 had the highest activities for both enzymes and was identified as an Escherichia coli strain. Using primers derived from the E. coli pH 2.5 acid phosphatase appA sequence (Dassa et al. (1990), J. Bacteriol. 172, 5497-5500), we cloned a 1482 bp DNA fragment from the isolate. In spite of 95% homology between the sequenced gene and the appA, 7 amino acids were different in their deduced polypeptides. To characterize the properties and functions of the encoded protein, we expressed the coding region of the isolated DNA fragment and appA in Pichia pastoris, respectively, as r-appA2 and r-appA. The recombinant protein r-appA2, like r-appA and the r-phyA phytase expressed in Aspergillus niger, was able to hydrolyze phosphorus from sodium phytate and p-nitrophenyl phosphate. However, there were distinct differences in their pH profiles, Km and Vmax for the substrates, specific activities of the purified enzymes, and abilities to release phytate phosphorus in soybean meal. In conclusion, the DNA fragment isolated from E. coli in pig colon seems to encode for a new acid phosphatase/phytase and is designated as E. coli appA2.

6-Phytase↗

PubMed2006

Aminopeptidase p mediated detoxification of organophosphonate analogues of sarin: mechanistic and stereochemical study at the phosphorus atom of the substrate.

The activity of the aminopeptidase P from Escherichia coli in hydrolyzing a series of organophosphonate sarin analogues (1-6) was evaluated. The enzymatic rates of hydrolysis for methylphosphonate 1 with a methoxy group attached to the phosphorus center were 7- to 15-fold higher than those for the corresponding analogues 2-6. Double mutant R153W/R370L was able to hydrolyze the S(p) enantiomer of racemic 1 at a considerable rate. This mutant allowed the preparation of the R(p) isomer of the sarin analogue 1. All the mutants, R370L, R153A, W88L, R153L/R370L, and R153W/R370L, preferred the formation of (S(p))-8 to that of the corresponding (R(p))-8 enantiomer and displayed a better enantiomeric excess of products, by 1.4- to 2-fold as compared to the wild-type enzyme. Enzymatic hydrolysis of O,O-diisopropyl-p-nitrophenyl phosphate (9) in H(2) (18)O led to the formation of the (18)O-labeled O,O-diisopropyl phosphate product and confirmed that the catalytic reaction starts with cleavage of the P--O bond. From chemical and kinetic studies, the utilization of an optically pure S(p) enantiomer of O-methyl-p-nitrophenyl methylphosphonothioate (S(p))-MNMPT, 7) has demonstrated that the enzymatic reaction proceeds through a displacement mechanism and generates a chiral product in situ with an inversion of stereochemical configuration at the phosphorus atom. The results also lead to the conclusion that alteration of the active site through site-directed mutagenesis can result in a preference for (S(p))-MNMPT (7) rather than the R(p) isomer.

Aminopeptidases↗

PubMed2005

Negative magnetoresistance in a magnetic semiconducting Zintl phase: Eu(3)In(2)P(4).

A new rare earth metal Zintl phase, Eu(3)In(2)P(4), was synthesized by utilizing a metal flux method. The compound crystallizes in the orthorhombic space group Pnnm with the cell parameters a = 16.097(3) A, b = 6.6992(13) A, c = 4.2712(9) A, and Z = 2 (T = 90(2) K, R1 = 0.0159, wR2 = 0.0418 for all data). It is isostructural to Sr(3)In(2)P(4). The structure consists of tetrahedral dimers, [In(2)P(2)P(4/2)](6-), that form a one-dimensional chain along the c axis. Three europium atoms interact via a Eu-Eu distance of 3.7401(6) A to form a straight line triplet. Single-crystal magnetic measurements show anisotropy at 30 K and a magnetic transition at 14.5 K. High-temperature data give a positive Weiss constant, which suggests ferromagnetism, while the shape of susceptibility curves (chi vs T) suggests antiferromagnetism. Heat capacity shows a magnetic transition at 14.5 K that is suppressed with field. This compound is a semiconductor according to the temperature-dependent resistivity measurements with a room-temperature resistivity of 0.005(1) Omega m and E(g) = 0.452(4) eV. It shows negative magnetoresistance below the magnetic ordering temperature. The maximum magnetoresistance (Deltarho/rho(H)) is 30% at 2 K with H = 5 T.

Crystallography, X-Ray↗

PubMed2003

Investigation of the effect of soil herbicides on the growth and nutrient uptake of potato.

In our experiments the effect of three preemergent herbicides was examined on potato varieties. The experiments were carried out under greenhouse conditions in pots with six Hungarian potato varieties. The following herbicides were applied: PATORAN 50 WP (metobromuron), SENCOR 70 WG (metribuzin) and COMMAND 48 EC (chlomazon). The results indicate that the variety Góliát showed the slowest growth. In the case of Lilla fresh and dry shoot weight was decreased by the application of PATORAN 50 WP and SENCOR 70 WG. Tuber weight showed a decrease with the application of SENCOR 70 WG in all varieties. The least tuber weight appeared with the varieties Kánkán and Szózszorszép. Nutrient concentration of potato and N, P and K uptake by potato were examined. In the case of White Lady, Százszorszép and Kánkán N concentration and uptake increase significantly because of SENCOR 70 WG. There was a significant increase in phosphorus concentration and uptake in White Lady, Hópehely and Kánkán varieties in all herbicide treatments. Potassium concentration increased in the case of all the six varieties because of herbicide treatments. Based on these experiments all varieties showed susceptibility against the used herbicides. The results show that important differences occur in the sensitivity and tolerance of varieties against herbicides, which are consequently significant for practical crop protection.

Herbicides↗

PubMed2000

High-pressure ion source combined with an in-axis ion trap mass spectrometer. 1. Instrumentation and applications

A new combination of a dual EI/CI ion source with a quadrupole ion trap mass spectrometer has been realized in order to efficiently produce negative ions in the reaction cell. Analysis of volatile compounds was performed under negative ion chemical ionization (NICI) during a reaction period where selected reactant negative ions, previously produced in the external ion source, were allowed to interact with molecules, introduced by hyphenated techniques such as gas chromatography. The O2*-, CH3O-, and Cl- reactant ions were used in this study to ensure specific ion/molecule interactions such as proton transfer, nucleophilic displacement, or charge exchange processes, respectively leading to even-electron species, i.e., deprotonated [M - H]- molecules, diagnostic [M - R]- ions, or odd-electron M*- molecular species. The reaction orientation depends on the thermochemistry of reactions within kinetic controls. First analytical results are presented here for the trace-level detection of several contaminants under NICI/Cl- conditions. Phosphorus-containing compounds (malathion, ethyl parathion, and methyl parathion as representative for pesticides) and nitro-containing compounds (2,4,6-trinitrotoluene for explosive material) have been chosen in order to explore the analytical ability of this promising instrumental coupling.

Journal Article↗

PubMed2004

Regioselective silylphosphination of methyl vinyl ketone with complexes containing cyclic and linear iron-silicon-phosphorus reacting sites.

Treatment of Cp*(CO)Fe{kappa2(Si,P)-SiMe2PPh2} with methyl vinyl ketone gave a 1,2-addition product, Cp*(CO)Fe{kappa2(Si,P)-SiMe2OCMe(CH=CH2)PPh2}. A linear-type Cp*(CO)2FeSiMe2PPh2 also reacted with the ketone to yield a 1,4-addition product, Cp*(CO)2Fe{kappa1(Si)-SiMe2OC(Me=CHCH2PPh2}, which was further converted to a seven-membered metallacycle, Cp*(CO)Fe{kappa2(Si,P)-SiMe2OC(Me)=CHCH2PPh2}, upon photolysis.

Butanones↗

PubMed1990

Ageing of procaryotes. Acholeplasma laidlawii as an object for cell ageing studies: a brief note.

It was established that A. laidlawii cell viability in the stationary phase of culture development decreases according to the Gompertz law. It was shown that the "stationary" ageing of A. laidlawii cells is accompanied by the lower intensity of phosphorus-containing compounds biosynthesis, decreased rate of membrane proteins synthesis and degradation and also by accumulation of DNA single-strand breaks. The biochemical changes found in ageing A. laidlawii cells are similar to ageing manifestations of resting eucaryotic cells. According to the authors opinion, the received data show that the A. laidlawii cell culture may be used as an object for investigation of the cell ageing mechanisms.

Acholeplasma laidlawii↗

PubMed1963

Perspectives for the development of exobiology.

In the majority of the papers dealing with the status and prospects of the development of exobiology a theoretical analysis predominates. More attention should be given to the discussion of methods and experiments carried out at the present time or planned for the near future. In investigating life in the cosmos, we attach considerable interest to detection of compounds specific to living beings, in particular, organic compounds of phosphorus, porphyrins, amino nitrogen and others. In searching for microorganisms on other planets and in interplanetary space the greatest danger is that, as a result of errors in technique, the investigator will detect earthly microorganisms which have invaded and reproduced in the nutrient mediums used. Information on the vitality of microbes detected in the ground taken in the zone of eternal frigidity, in big pieces of rock salt, in meteorites, etc. confirms these apprehensions. Initially, search for heterotrophic bacteria should be carried out, then for phototrophic, denitrifying, sulfate-reducing, nitrogen-fixing microorganisms, as well as bacteria oxydizing sulfur, iron, methane and hydrogen. Instruments for detection of cosmobionts can be based on nephelometry, potentiometry, manometry and on the use of carbon labelled compounds and added to the nutrient medium. Investigations elucidating the influence of low and high temperatures, vacuum, and radiation on living cells are possible to carry out on earth and therefore are most accessible to exobiology. They give interesting results and in some degree make it possible to approach the study of the conditions to which life would be exposed in space. The sterilization of space ships is of paramount importance for further exobiological investigations. Under space conditions microbes will not completely perish on the space ship surface and, therefore, careful sterilization is necessary. The assertion that earth microbes, having reached the lunar surface, will not be able to develop is not free of objections. To carry out sterilization so that space ships will not contain dead bodies of microbes is impossible. Therefore, the wish expressed sometimes that "carcasses" of microbes should not be conveyed onto other planets is practically unrealizable.

Containment of Biohazards↗

PubMed1986

31P nuclear magnetic resonance spectroscopy: noninvasive biochemical analysis of the ischemic extremity.

The biochemical effects of peripheral vascular disease on skeletal muscle have not been characterized precisely because of the lack of satisfactory noninvasive analytic methods. 31P nuclear magnetic resonance (NMR) spectroscopy was used to measure the high-energy phosphate compounds, phosphocreatine (PCr) and adenosine triphosphate, as well as metabolic byproducts, such as inorganic phosphates (Pi) and phosphate monoesters in calf muscles of 214 limbs with peripheral vascular disease. Intracellular pH was also measured. The NMR index (Pi[PCr + Pi]) was used to quantitate the impairment of oxidative phosphorylation as a result of ischemia. Studies done at rest documented the impairment of oxidative metabolism only in limbs with severe ischemia (ankle-brachial pressure index (API) less than 0.4). Exercise resulted in a significant elevation of the NMR index in all limbs and the rate of return of this value toward normal following exercise was prolonged even in limbs with moderate ischemia (0.4 less than or equal to API less than or equal to 0.9). Correlation of 31P NMR parameters with arteriograms showed that infrapopliteal occlusions resulted in prolonged recovery times only when the superficial femoral artery was occluded and emphasized the metabolic consequences of multisegmental disease. Accumulation of glycolytic pathway intermediates correlated with the decrease in muscle cell pH observed with exercise. Despite immediate improvement in symptoms and hemodynamic parameters following revascularization, return to normal biochemical function occurs over a prolonged period of time. This study demonstrates that 31P NMR spectroscopy can successfully measure noninvasively the important phosphorus-containing compounds involved in the bioenergetics of skeletal muscle in vivo rapidly enough to permit real-time determination during exercise and recovery.

Adenosine Triphosphatases↗

PubMed2004

Phosphorus-nitrogen donor interaction leading to atrane formation in phosphate and oxyphosphorane compositions. Implications for phosphoryl transfer enzymes(1).

Reaction of aminotriphenols, tris(2-hydroxy-3,5-dimethylbenzyl)amine (E) and tris(2- hydroxy-3-tert-butyl-5-methylbenzyl)amine (F), with triphenylphosphite, tris(p-methoxyphenyl)phosphite, or phenyldiphenoxyphosphane in the presence of N-chlorodiisopropylamine led to the isolation of tetraoxyphosphorane 1, pentaoxyphosphorane 3, phosphate-atrane 2, hexacoordinated pentaoxyphosphorane-atrane 4, and the first hexacoordinated tetraoxyphosphorane-atrane 5. X-ray analysis of 1-3 and 5 were obtained. NMR data is reported and supports that the atrane 4 has the same hexacoordinated structure as 5. Phosphate 2 reveals weak phosphorus-nitrogen donor action whereas the hexacoordinated atranes 4 and 5 have pronounced P-N coordination. The results are used to support amino acid donor action occurring at active sites of phosphoryl transfer enzymes. Increased strength of donor action in the higher-coordinate model activated state compared to that in the substrate phosphate composition should serve as a factor in enhancing enzyme reaction rates.

Catalysis↗

PubMed1986

31P NMR studies of the intact perfused rat heart: a novel analytical approach for determining functional-metabolic correlates, temporal relationships, and intracellular actions of cardiotoxic chemicals nondestructively in an intact organ model.

Intact hearts isolated from adult male, Sprague-Dawley rats were perfused under standardized conditions in an apparatus designed for use in a high-resolution nuclear magnetic resonance (NMR) spectrometer system. Myocardial phosphate metabolite concentrations (ATP, PCr, Pi, and phosphomonoesters) and intracellular pH were determined sequentially at timed intervals coincident with the functional assessments of the intact heart by phosphorus-31 (31P) NMR spectroscopic methods. Myocardial functional and metabolic parameters were unaffected by sustained control perfusion (2 hr). The negative inotropic actions of cadmium were associated with significant changes in the chemical environment of inorganic phosphate (Pi) within the cells. This initial cellular response to cadmium, which correlated with the onset and magnitude of the contractile disturbances, appeared to represent the formation of an acidic, intracellular Pi pool (pH, 6.0). This pH compartment reached a steady state during the period in which maximal changes in contractile function were manifested, and before cellular ATP and PCr concentrations were altered. These findings are consistent with the interpretation that the functional deficits caused by cadmium originated primarily from changes in the chemical environment experienced by intracellular metabolites, rather than changes in the amounts of cellular high energy substrates. In contrast, the time-dependent negative inotropic effects of arsenate were proportional to the loss of cellular ATP stores. Intracellular pH was not affected in these hearts. A distinctive metabolic finding associated with the cardiotoxicity of arsenate was the time-dependent accumulation of previously undetected phosphate metabolites in the arsenate-treated hearts. Efforts to chemically identify these metabolites proved inconclusive; however, existing evidence suggests the possibility that these phosphorus-containing compounds may be arsenophosphate derivatives of naturally occurring cellular metabolites. The present findings provide experimental evidence demonstrating that toxicologic assessments in an intact organ model are feasible using whole organ 31P NMR spectroscopic methods and that meaningful, new insights regarding the biochemical mechanisms responsible for the cardiotoxic actions of xenobiotic agents can be obtained by this analytical approach.

Animals↗

PubMed2006

Comparison of high-performance liquid chromatography of cyclotriphosphazene derivatives with one or two equivalent stereogenic centres.

High-performance liquid chromatographic (HPLC) methods have been developed for investigating the stereogenic properties of two analogous series of dibenzylamino derivatives of cyclotriphosphazene containing either one or two equivalent stereogenic centres. Separation of the enantiomers of all the racemic compounds has been investigated by chiral HPLC using Whelk-01 and Chiralcel OD columns. In all cases, conditions for separation of enantiomers have been found using a Whelk-01 column with different ratios of tetrahydrofuran in n-hexane as the mobile phase. It is found that both the separation factor (alpha) and resolution factor (R(S)) of molecules with two equivalent stereogenic centres are greater than those for analogues with only one centre.

Chromatography, High Pressure Liquid↗

PubMed1976

Influence of the concentration of phosphorus, potassium, calcium and iron compounds on the microbial reduction of sulphates.

In the reduction process of sulphates by Desulfovibrio desulfuricans suitable concentration of mineral salts plays an important role. In particular, different K2HPO4, CaCl2 and Fe(NH4)2(SO4)2 content in the reaction medium has an observable effect on the reduction degree (x'), the induction time (t0) and the reduction rate constant (k). These data were recorded for 9 liquid media characterized by different content of mineral salts. The reaction rate constants were calculated for the reduction process in each medium. Optimal reduction conditions exists at the following element concentration ratios: P/S=0.068, K/S=0.086, Fe/S=0.08, N/S=0.33, C/S=1.80, Ca/S=0.03, Cl/S=0.80.

Calcium↗

PubMed2001

Harmonized protocol and certified reference material for the determination of extractable contents of phosphorus in freshwater sediments--a synthesis of recent works.

An analytical protocol for the determination of the extractable phosphorus contents in freshwater sediments has been harmonized through interlaboratory studies in the frame of the Standards Measurements and Testing Program of the European Commission. A homogeneous and stable sediment reference material has been prepared and certified on the basis of this protocol named SMT protocol, and will be available in spring of 2001. The SMT protocol, together with the reference material, are useful tools in the field of water management, especially at a time when quality assurance and data comparability are of paramount importance in laboratory analysis. The knowledge of the bioavailable forms of phosphorus is important not only for sediments but also for sludge and soils. Therefore, the SMT protocol could be extended to these materials and new CRMs could be prepared. The SMT protocol was used in a study of a reservoir, which allowed to calculate the P stock, therefore helping to predict the restoration delay of the lake. The paper describes the protocol and the CRM, and gives a brief outline of the case study.

Chemistry Techniques, Analytical↗

PubMed2005

Spatial patterning of water quality in Biscayne Bay, Florida as a function of land use and water management.

An objective classification analysis was performed on a water quality data set from 25 sites collected monthly during 1994-2003. The water quality parameters measured included: TN, TON, DIN, NH4+, NO3-, NO2-, TP, SRP, TN:TP ratio, TOC, DO, CHL A, turbidity, salinity and temperature. Based on this spatial analysis, Biscayne Bay was divided into five zones having similar water quality characteristics. A robust nutrient gradient, driven mostly by dissolved inorganic nitrogen, from alongshore to offshore in the main Bay, was a large determinant in the spatial clustering. Two of these zones (Alongshore and Inshore) were heavily influenced by freshwater input from four canals which drain the South Dade agricultural area, Black Point Landfill, and sewage treatment plant. The North Bay zone, with high turbidity, phytoplankton biomass, total phosphorus, and low DO, was affected by runoff from five canals, the Munisport Landfill, and the urban landscape. The South Bay zone, an embayment surrounded by mangrove wetlands with little urban development, was high in dissolved organic constituents but low in inorganic nutrients. The Main Bay was the area most influenced by water exchange with the Atlantic Ocean and showed the lowest nutrient concentrations. The water quality in Biscayne Bay is therefore highly dependent of the land use and influence from the watershed.

Alkaline Phosphatase↗

PubMed1990

Phosphorus-31 nuclear magnetic resonance spectroscopy reveals two conformational forms of chloroacetol phosphate-bound triosephosphate isomerase.

Chloroacetol phosphate covalently reacts with Glu-165 in the catalytic center of triosephosphate isomerase. Reaction of the enzyme with the substrate analogue results in two 31P resonances at 6.8 and 5.5 ppm. Dissociation with guanidinium chloride results in a single resonance at 4.5 ppm. Reassociation and redimerization of the triosephosphate isomerase-chloroacetol phosphate complex restores only the resonance at 5.5 ppm. The two 31P resonances appear to represent different conformations of the enzyme which are trapped upon reaction with the affinity label.

Affinity Labels↗