Geochemical composition,phosphorus speciation and mass transport of fine-grained sediment in two Lake Erie tributaries

The concentration of major elements (Si, Al, Ca, Mg, Na, K, Fe, Ti, Mn and P), particulate phosphorus forms (NH₄Cl-RP, BD-RP, NaOH-RP, HCl-RP and NaOH₍₈₅₎-RP) and carbon content were determined in six size fractions (<8, 8–12, 12–19, 19–31, 31–42 and 42–<60 µm) of sediment collected at gauging stations located in two Lake Erie tributaries (Big Creek and Big Otter Creek). Concentrations of major elements and phosphorus forms were remarkably similar in sediment size fractions from both rivers. Nonapatite inorganic P (NAIP) and organic P (OP) concentrations increased with decreasing grain size while apatite inorganic P (AIP) content decreased with decreasing grain size. Results of phosphorus fractionation studies were combined with historical (particle size) and hydrometric data to simulate the export of particle P on tributary sediment < 63 µm. AIP represents 67 and 70% of the calculated particulate P mass while NAIP accounts for 26 and 23% of sediment-bound P transported in Big Otter Creek and Big Creek, respectively. The < 8 µm size fraction of tributary sediment is the most significant for the potential release of bioavailable P into the water column.     

Phosphorus-31 nuclear magnetic resonance studies of intracellular pH,phosphate compartmentation and phosphate transport in yeasts

³¹P NMR spectra were obtained from suspensions of Candida utilis, Saccharomyces cerevisiae and Zygosaccharomyces bailii grown aerobically on glucose. Direct introduction of substrate into the cell suspension, without interruption of the measurements, revealed rapid changes in pH upon addition of the energy source. All ³¹P NMR spectra of the yeasts studied indicated the presence of two major intracellular inorganic phosphate pools at different pH environments. The pool at the higher pH was assigned to cytoplasmic phosphate from its response to glucose addition and iodoacetate inhibition of glycolysis. After addition of substrate the pH in the compartment containing the second phosphate pool decreased. A parallel response was observed for a significant fraction of the terminal and penultimate phosphates of the polyphosphate observed by ³¹P NMR. This suggested that the inorganic phosphate fraction at the lower pH and the polyphosphates originated from the same intracellular compartment, most probably the vacuole. In this vacuolar compartment, pH is sensitive to metabolic conditions. In the presence of energy source a pH gradient as large as 0.8 to 1.5 units could be generated across the vacuolar membrane. Under certain conditions net transport of inorganic phosphate across the vacuolar membrane was observed during glycolysis: to the cytoplasm when the cytoplasmic phosphate concentration had become very low due to sugar phosphorylation, and into the vacuole when the former concentration had become high again after glucose exhaustion.Non-Standard Abbreviations NMR nuclear magnetic resonance - ppm parts per million - PP polyphosphate - P_i,c cytoplasmic inorganic phosphate - P_i,v vacuolar inorganic phosphate - pH_in,c cytoplasmic pH - pH_in,v vacuolar pH - FCCP carbonyl p-trifluoromethoxyphenylhydrazone     

Fractionation of sediment phosphate with chelating compounds: a simplification, and comparison with other methods

The NTA/EDTA fractionation of sediment-bound, inorganic phosphate was improved and made more effective. The iron-bound phosphate is now extracted with Ca-EDTA plus dithionite and followed by an extraction of calcium-bound phosphate by Nat-EDTA at pH = 4.5. A comparison is made with two other sequential extraction procedures: the SEDEX and the Hieltjes & Lijklema extractions. The EDTA extractions have an advantage over the other two methods.     

Presence of and phosphate release from polyphosphates or phytate phosphate in lake sediments

NaOH is often used as an extractant for thefractionation of sediment-bound phosphates. Besidesorthophosphate, a certain quantity of phosphate whichis called ‘non-reactive NaOH-extractable phosphate’is also extracted. In recent literature it has beensuggested that this fraction consists of bacterialpolyphosphates and might be responsible for the phosphate release from aquatic sediments under anoxicconditions. In a previous publication we have already shown thatNaOH is not an accurate extractant as both theconcentration of NaOH and the duration of theextraction have an influence on the quantity ofphosphate extracted, due to the hydrolysis of organicphosphates. In this article we show that cold NaOH does not onlyextract iron-bound phosphate but phytate phosphate aswell. Non-reactive phosphate in this extract was notrelated to the presence of polyphosphate, but mainlyto phytate and humic phosphates. As it has been shownthat phytate may disappear from sediments when theybecome anoxic, we suggest that phytate mineralizationmay be an important mechanism for anoxic phosphaterelease from sediments. This revised version was published online in July 2006 with corrections to the Cover Date.     

养分和水添加对弃耕草地土壤无机磷组分的影响

合理的养分和水分管理措施是提高退化草地生产力和生物多样性的有效途径,但养分和水添加对弃耕草地土壤无机磷组分的影响研究较少.本文依托内蒙古多伦县2005年建立的养分(N∶ 10 g·m-2·a-1、P∶ 10g·m-2·a-1)和水分(植物生长季增水180 mm)添加田间试验,研究了表土(0～10 cm)无机磷组分及有效...     

Divalent metal ion, inorganic phosphate, and inorganic phosphate analogue binding to yeast inorganic pyrophosphatase

Four different techniques, equilibrium dialysis, protection of enzymatic activity against chemical inactivation, 31P relaxation rats, and water proton relaxation rates, are used to study divalent metal ion, inorganic phosphate, and inorganic phosphate analogue binding to yeast inorganic pyrophosphatase, EC 3.6.1.1. A major new finding is that the binding of a third divalent metal ion per subunit, which has elsewhere been implicated as being necessary for enzymatic activity [Springs, B., Welsh, K. M., & Cooperman, B. S. (1981) Biochemistry (in press)], only becomes evident in the presence of added inorganic phosphate and that, reciprocally, inorganic phosphate binding to both its high- and low-affinity sites on the enzyme is markedly enhanced in the presence of divalent metal ions, with Mn2+ causing an especially large increase in affinity. The results obtained allow evaluation of all of the relevant equilibrium constants for the binding of Mn2+ and inorganic phosphate or of Co2+ and inorganic phosphate to the enzyme and show that the high-affinity site has greater specificity for inorganic phosphate than the low-affinity site. In addition, they provide. The results obtained allow evaluation of all of the relevant equilibrium constants for the binding of Mn2+ and inorganic phosphate or of Co2+ and inorganic phosphate to the enzyme and show that the high-affinity site has greater specificity for inorganic phosphate than the low-affinity site. In addition, they provide. The results obtained allow evaluation of all of the relevant equilibrium constants for the binding of Mn2+ and inorganic phosphate or of Co2+ and inorganic phosphate to the enzyme and show that the high-affinity site has greater specificity for inorganic phosphate than the low-affinity site. In addition, they provide evidence against divalent metal ion inner sphere binding to phosphate for enzyme subunits having one or two divalent metal ions bound per subunit and evidence for a conformational change restricting active-site accessibility to solvent on the binding of a third divalent metal ion per subunit.     

Regulation of phosphate influx in barley roots: Effects of phosphate deprivation and reduction of influx with provision of orthophosphate

Barley plants were grown in nutrient solutions, which were maintained at either 0 (-P) or 15 μ M orthophosphate (+P). After 11 days phosphate influx into the intact roots of the -P plants began to increase by comparison with +P plants. During this period differences became apparent between the treatments in absolute growth rates, as well as in the root:shoot ratios. Phosphate influx in the -P plants continued to increase as a function of time, to a maximum value of 2.4 μmol (g fresh wt)^-1h^-1 at 16 days after germination. This rate was 6 times higher than influx values for +P plants of the same age. During the period of enhanced uptake phosphate was strongly correlated (r²= 0.77) with root organic phosphate concentration. – The enhancement of inorganic phosphate influx into intact roots of -P plants was rapidly reduced by the provision of 15 μ M orthophosphate. Typically, within 4 h of exposure to this concentration of phosphate, influx values fell from 1.80 ± 0.20 to 0.75 ± 0.03 μmol (g fresh wt)^-1 h^-1, while inorganic phosphate concentrations of the roots increased from 0.12 to 1.15 μmol (g fresh wt)^-1 during the same period. Hill plots of the influx data obtained during this period, treating root inorganic phosphate as an inhibitor of influx, gave Hill coefficients close to 2. The rapidity of the reduction of influx associated with increased root inorganic phosphate together with the Hill plot data provide evidence for an allosteric inhibition of influx by internal inorganic phosphate.     

Phosphate metabolism and foetal growth in the rat. II. Net transfer of 31P and 32P inorganic phosphate from the maternal plasma to the normal foetus

Net transfer of 31P and 32P inorganic phosphate from the maternal plasma to the rat foetus has been studied after intraperitoneal injection of [32P] ortho-phosphate in primigravid females at the 12th day or later stages of gestation. The concentration per unit weight of foetus of the inorganic phosphate (P1) fraction increases markedly with increasing foetal weight; labelling data [inverse relationship between P1 concentration and specific activity, absence of precursor/product relationship between P1 and acid-soluble organic-bound phosphates (POAS)] show this increase to result in part from the formation of a relatively inert metabolic pool, presumably in mineralized tissue. The foetal concentrations of calcium and inorganic phosphate show a strong positive correlation, both increasing markedly with foetal weight. The progressive accumulation of calcium does not, however, account entirely for the rising concentration of inorganic phosphate. The concentration per unit weight of foetus of the POAS fraction remains stable for foetuses smaller than 2 000 mg. In heavier foetuses (greater than 2 000 mg) the POAS concentrations are, with an abrupt transition, distinctly lower, rising however slightly with increasing foetal weight. The concentration per unit weight of foetus of the acid-insoluble organic-bound phosphate (POAIS) fraction decreases slightly with increasing foetal weight. The label uptake per unit weight of foetus of both POAS and POAIS fractions is negatively correlated with increasing foetal weight. The amount and label uptake per whole foetus of the P1, POAS and POAIS fractions are positively correlated with increasing foetal weight. Phosphate transfer to the foetus increases continuously, being maximal at or near birth.     

Stimulation of adenine nucleotide translocation in reconstituted vesicles by phosphate and the phosphate transporter

Highly purified adenine nucleotide transporter from bovine heart mitochondria was reconstituted with phospholipids to form vesicles which catalyzed atractyloside-sensitive adenine nucleotide translocation. When internal ATP was exchanged with external ADP, this reaction was enhanced by agents capable of collapsing a membrane potential, but not by inorganic phosphate. When the purified nucleotide transporter was reconstituted together with a second protein fraction, nucleotide transport was stimulated by inorganic phosphate. The stimulated rate was eliminated by mersalyl or other SH reagents. The second protein fraction could be replaced by preparations of purified phosphate transporter.     

Properties of phosphate bound to cerebral microsomes during adenosine-triphosphatase activity

1. Ox-brain microsomes were incubated with [gamma-(32)P]ATP under various conditions. After the reaction, which was stopped with trichloroacetic acid, a small amount of phosphate remained bound to the washed precipitate. 2. Properties of the bound phosphate were studied by treatment with buffers and solvents. 3. The Na(+)-dependent increment in bound phosphate, predominant at low ATP concentration and features of which suggest involvement in the concomitant adenosine-triphosphatase activity, was rapidly released in both circumstances. 4. In aqueous media the labile phosphate was released entirely as inorganic phosphate at faster rates with increasing alkalinity. 5. In acidified chloroform-alcohol mixtures the released phosphate appeared both as inorganic phosphate and different single (32)P-labelled organic phosphates, which were tentatively identified as the relevant mono-alkyl phosphates, presumably derived by acid-catalysed alcoholysis of a labelled microsomal component, or components. 6. The labile phosphate corresponded to the P exchangeable with non-radioactive ATP added during the enzyme reaction. 7. The possible molecular nature of the labile fraction of the bound phosphate is discussed.     

Mechanisms of phosphate uptake into brush-border membrane vesicles from goat jejunum

This study concerns the uptake of inorganic phosphate into brush-border membrane vesicles prepared from jejunal tissues of either control or Ca-and/or P-depleted goats. The brush-border membrane vesicles showed a time-dependent accumulation of inorganic phosphate with a typical overshoot phenomenon in the presence of an inwardly directed Na⁺ gradient. The Na⁺-dependent inorganic phosphate uptake was completely inhibited by application of 5 mmol·l^-1 sodium arsenate. Half-maximal stimulation of inorganic phosphate uptake into brush-border membrane vesicles was found with Na⁺ concentrations in the order of 5 mmol·l^-1. Inorganic phosphate accumulation was not affected by a K⁺ diffusion potential (inside negative), suggesting an electroneutral transport process. Stoichiometry suggested an interaction of two or more Na ions with one inorganic phosphate ion at pH 7.4. Na⁺-dependent inorganic phosphate uptake into jejunal brush-border membrane vesicles from normal goats as a function of inorganic phosphate concentration showed typical Michaelis-Menten kinetic with V _max=0.42±0.08 nmol·mg^-1 protein per 15 s^-1 and K _m=0.03±0.01 mmol·l^-1 (n=4, x ±SEM). Long-term P depletion had no effect on these kinetic parameters. Increased plasma calcitriol concentrations in Ca-depleted goats, however, were associated with significant increases of V _max by 35–80%, irrespective of the level of P intake. In the presence of an inwardly directed Na⁺ gradient inorganic phosphate uptake was significantly stimulated by almost 60% when the external pH was decreased to 5.4 (pH_out/pH_in=5.4/7.4). The proton gradient had no effect on inorganic phosphate uptake in absence of Na⁺. In summary, in goats Na⁺ and calcitriol-dependent mechanisms are involved in inorganic phosphate transport into jejunal brush-border membrane vesicles which can be stimulated by protons.Abbreviations AP activity of alkaline phosphatase - BBMV brush-border membrane vesicles - EGTA ethyleneglycol-triacetic acid - n _app apparent Hill coefficient - P _i inorganic phosphate - PTH parathyroid hormone     

Elucidation of the cytoplasmic and vacuolar components in the inorganic phosphate region in the 31P NMR spectrum of yeast

Subcellular compartments, such as the vacuole in yeast, play important roles in cell metabolism and in cell response to external conditions. Concentrations of inorganic phosphate and pH values of the vacuole and cytoplasm were determined for anaerobic Saccharomyces cerevisiae cells based upon (31)P NMR spectroscopy. A new approach allows the determination of these values for the vacuole in cases when the resonance for inorganic phosphate in the cytoplasm overlaps with the resonance for inorganic phosphate in the vacuole. The intracellular inorganic phosphate resonance was first decomposed into two components by computer analysis. The assignments of the components were determined from in vivo correlations of P(i) chemical shift and the chemical shifts of the cytoplasmic sugar phosphates, and the pH dependency of the resonance of pyrophosphate and the terminal phosphate of poly-phosphate (PP(1)) which reside in the vacuole. An in vivo correlation relating PP(1) and P(i) (vac) chemical shifts was established from numerous evaluations of intracellular compositions for several strains of S. cerevisiae. This correlation will aid future analysis of (31)P NMR spectra of yeast and will extend NMR studies of compartmentation to cellular suspensions in phosphate-containing medium. Application of this method shows that both vacuolar and extracellular P(i) were phosphate reserves during glycolysis in anaerobic S. cerevisiae. Net transport of inorganic phosphate across the vacuolar membrane was not correlated with the pH gradient across the membrane.     

Effect of flooding and cropping on the changes in the inorganic phosphate fractions in some rice soils

Summary Greenhouse experiments were conducted to evaluate the significance to flooded rice of the various forms of inorganic soil phosphate on Aborlan, Luisiana and Pili soils with and without phosphate. Changes in the various inorganic soil phosphate fractions with time under cropped and uncropped conditions were measured. Results showed that the iron phosphate fraction was the most important source of phosphate to the rice plant. It was also evident that phosphate added to the soils was slowly converted into the iron phosphate form. Transformation of soil phosphate seemed to be greatly affected by the presence of plant roots. Changes in the phosphate fractions were marked in the cropped soils.Data presented in this paper form part of Ph.D. dissertation submitted by the first author to the University of the Philippines, College of Agriculture, Los Banos, The Philippines.Professor of Agr. Chemistry, Dept. of Agr. Chemistry, Univ, of the Philippines, College of Agriculture.Rice Agronomist, Univ. of Agr. Sciences, Regional Research Station, Mandaya, Mysore, India.     

Effects of 5-hydroxytryptamine (serotonin) on the incorporation of 32P-inorganic phosphate into phospholipids in Hymenolepis diminuta (Cestoda)

5-Hydroxytryptamine (5-HT) (1,2 and 5 mM) significantly stimulated the incorporation of radioactive inorganic phosphate (32Pi) into phosphatidylinositol, phosphatidylethanolamine, phosphatidic acid and also total phospholipid fraction of Hymenolepis diminuta after one hour of incubation. Such effect was both time and concentration dependent. In the presence of 5-HT early labelling of phosphatidylinositol was observed. Also, the percentage stimulation by 5-HT was the highest in this fraction under all experimental conditions. The inorganic, organic, total and phosphatidylcholine-bound phosphate of H. diminuta incubated with 5-HT were not significantly different from those of the control under all incubation conditions. Results reported herein suggest that messenger molecules that are derived from phosphoinositides may be involved in the stimulatory mechanism of 5-HT in H. diminuta.     

The energetics of phosphate binding to a protein complex

The heat of binding the serine protease, porcine pancreatic elastase, by the inhibitor, turkey ovomucoid third domain, is dependent on the presence of inorganic phosphate. This dependence is saturable and can be accurately modeled as the phosphate binding to a single site on the protease-inhibitor complex; thus, the elastase-ovomucoid system provides a unique opportunity to study phosphate-protein interactions. We have used isothermal titration calorimetry to investigate this binding, thereby providing one of the few complete thermodynamic characterizations of phosphate interacting with proteins. The binding is characterized by a small favorable deltaG degrees, a large unfavorable deltaH degrees, and a positive deltaCp, thermodynamics consistent with the release of water being linked to phosphate binding. These measurements provide insight into the binding of phosphotyrosine containing peptides to SH2 domains by suggesting the energetic consequences of binding phosphate free from other interactions.     

PHosphate metabolism and foetal growth in the rat. I. Net transfer of 31P and 32P phosphate from the maternal plasma to the normal placenta

Net transfer of 31P and 32P inorganic phosphate form the maternal plasma to the rat chorio-allantoic placenta has been studied after intraperitoneal injection of [32P] ortho-phosphate in primigravid females at the 12th day or late stages of gestation. The concentration and label uptake per unit weight of placenta of the inorganic phosphate (Pi), organic-bound acid-soluble phosphate (POAS) and organic-bound acid-insoluble phosphate (POAIS) fractions are negatively correlated with increasing placental weight, whereas their specific activities are independent of placental weight. The amount and label uptake per whole placenta of the Pi, POAS and POAIS fractions are positively correlated with increasing placental weight. The placental concentrations of inorganic phosphate and calcium are positively related without, however, any marked accumulation of calcium. The growing placenta is thus shown to reduce progressively, on a unit weight basis, both the inorganic phosphate uptake from the maternal plasma and its further incorporation into organic-bound fractions. There is no evidence of a control by the foetal weight, acting per se, on these placental activities.     

Ca2+ and phosphate releases from calcified Chara cell walls in concentrated KCl solution

Ca2+ and P(i) (inorganic phosphate) releases from isolated calcified and uncalcified Chara cell walls were measured with a Ca(2+)-selective electrode and colorimetry, and their ionic relations were analysed on the basis of the electroneutrality rule. The results showed that (1) not only Ca2+ but also P(i) can be released from isolated calcified Chara cell walls into pure deionized water and 100 mM KCl solution, and (2) the positive charge due to the Ca2+ released cannot be neutralized only by the negative charge from the simultaneously released P(i). These findings suggest that calcium bands of calcified Chara cell walls are composed of mainly CaCO(3) and CaHPO(4) and some anions other than P(i) should be released simultaneously with the Ca2+ and P(i). More Ca2+ and P(i) can be solubilized from isolated Chara cell walls in 100 mM KCl solution than in pure deionized water. The pH value of 100 mM KCl solution in which isolated uncalcified young Chara cell walls have been immersed is a little lower than that of pure deionized water in which the same isolated uncalcified young Chara cell walls have been immersed, suggesting that some acidic substances are solubilized by 100 mM KCl. To explain this from the viewpoint of solution chemistry, the solubilities of pure CaCO(3) and pure CaHPO(4) in water and 100 mM KCl solution were measured with a Ca2+ -selective electrode and their pH values with a glass pH electrode. The conclusion reached was that the Ca2+ release from isolated Chara cell walls is accompanied by the release of P(i), CO(2-)(3) and acidic substances. This suggests that the so-called calcium bands and/or ionic relations, including ion exchange, in Chara cell walls are chemically or physicochemically more complex than they are currently considered to be.     

Serum stimulation of phosphate uptake into 3T3 cells.

The stimulation by calf serum of phosphate uptake into 3T3 cells results from a change in maximum velocity of the transport process with no change in the Michaelis constant. Only arsenate among a series of inorganic structural analogs of phosphate inhibited phosphate uptake indicating a high specificity for the process. The arsenate inhibition was competitive in nature. Papaverine, theophylline, and protaglandin E1, drugs known to maintain high intracellular levels of cAMP, had little effect on serum stimulated phosphate uptake. The phosphate uptake stimulating factor(s) in serum could be distinguised from the 3T3 cell survival and migration factors by stability characteristics, but this factor(s) could not be completely separated from a uridine uptake stimulation activity or growth promoting activity using a variety of serum fractionation procedures. Only partial stimulation of the uptake process was achieved with any one serum fraction indicating a multiplicity of serum components is probably involved in this process. Because of the rapidity of serum activation of phosphate uptake and its apparent independence of intracellular cyclic nucleotide levels, it is suggested that serum factors may stimulate phosphate uptake by inducing structural changes in the phosphate carrier system.     

P32 distribution in phosphorus fractions of phosphorus-sensitive and -tolerant soybeans

Summary P³² incorporation into various phosphorylated compounds of roots, stems, and leaves was studied with P-sensitive (Clark) and P-tolerant (L9) varieties of soybeans. With increasing P concentration in the pretreatment solution, more P³² was incorporated into the inorganic phosphate fraction, mainly in which form P seemed to be transported from roots to leaves. P³² percentage of inorganic phosphate also showed a continuous decrease with absorption time. The rate of phosphorylation, as manifested by the ratio of P³² percentage or specific activities of the organic acid-soluble P to that of inorganic-P, was higher with the P-tolerant variety than with the P-sensitive one. The rate of RNA synthesis also seemed to be higher with the tolerant variety. Paper No. 7082, Scientific Journal Series, Minnesota Agricultural Experiment Station.