UMLS:C0847097 - FACTA Search

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Query: UMLS:C0847097 (acidity)
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The effect of natural and controlled fermentation with an inoculum of Lactobacillus plantarum and additional thermal treatment (dry heat at 120 degrees C for 20 min) on the availability of N, P, Fe, Cu, Zn, Ca, and Mg from Phaseolus vulgaris L. var. carrilla was estimated using an in vitro method based on equilibrium dialysis. Natural and controlled fermentations caused significant reductions in the pH and phytate content (36%) of the bean flours, with a concomitant increase in the titratable acidity and free phosphorus content, and had no effect on the other nutrients studied. The percentage of dialyzable N, P, Cu, and Mg was significantly improved by both types of fermentation, whereas Zn dialyzability was significantly reduced. The greatest reduction was observed for the bean flour fermented with an inoculum of L. plantarum. The percentage of dialyzable Fe improved significantly as a result of natural fermentation but was not affected by controlled fermentation. The application of dry heat at 120 degrees C for 20 min caused a significant increase in Fe dialyzability and a further reduction in the percentage of dialyzable Zn in fermented bean flours but did not affect the dialyzability of the other nutrients studied.
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PMID:Effect of natural and controlled fermentation on chemical composition and nutrient dialyzability from beans (Phaseolus vulgaris L.). 1290 82

Animal manure contains partially digested feed fiber and grains where phosphorus (P) is bound in organic compounds that include myo-inositol 1,2,3,5/4,6-hexakis dihydrogenphosphate or phytic acid (IP6). Information is needed on the effects of other (non-IP6) organic ligands (LIGND) on the enzymatic dephosphorylation of IP6, which is a potential source of dissolved orthophosphate P (PO4-P) in the soil-manure-water system. The effects of 1,2-cyclohexane diamino-tetraacetate (CDTA), diethylenetriamine-N,N,N',N'',N''-pentaacetate (DTPA), ethylenediamine-N,N,N',N'-tetraacetate (EDTA), oxalate (OXA), and phthalate (PHTH) and LIGND to IP6 molar ratio and charge concentration ratio on IP6 dephosphorylation were studied to determine controlling mechanisms of IP6 persistence in manure. Solution PO4-P concentrations were analyzed by ion chromatography as the phosphomolybdate-ascorbic acid method partly includes IP6-P. Uncomplexed IP6 dephosphorylation by Aspergillus ficuum (Reichardt) Henn. phytase EC 3.1.3.8 at pH 4.5 and 6 is unaffected by the presence of LIGNDs. As the concentrations of Ca2+, Al3+, or Fe3+ increase, dephosphorylation is reduced. Their inhibitory effect lessens in the presence of LIGNDs, in the following order: CDTA = EDTA > DTPA >> OXA > or = PHTH. Whether CDTA or EDTA is the most effective LIGND depends upon the acidity of the suspension and LIGND charge concentration, reducing the inhibitory effect of polyvalent counterions to the point of promoting the hydrolysis of a manure phytase-hydrolyzable phosphorus (PHP) fraction that is otherwise unavailable. Therefore, ligand-induced changes increase the mobilization and dephosphorylation of complexed organic P, above and beyond the simple dissolution of inorganic phosphates. An analytical method for potentially bioavailable PHP in animal manure should include a LIGND as extracting reagent. Also, potential LIGNDs in an organic carbon-rich dairy wastewater may increase the release of PHP and environmental dispersion of PO4-P.
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PMID:Organic ligand effects on enzymatic dephosphorylation of myo-inositol hexakis dihydrogenphosphate in dairy wastewater. 1496 90

Experiments were undertaken to quantify the mechanisms by which acidity might affect phosphorus movement and uptake by black locust (Robinia pseudoacacia L.). Phosphorus diffusion rates in six forest soils were determined by desorption-isotherm buffer power assays. Changes in diffusion as a function of acidity were measured using pH-adjusted desorption solutions. Depending on soil type and phosphorus source solubility, up to a fivefold increase in phosphorus diffusion rate was observed with an increased acidity of one pH unit. Phosphorus uptake rates of mycorrhizal and non-mycorrhizal black locust at pH 4 and pH 7 were determined from (32)P-labeled nutrient-depletion experiments. In mycorrhizal plants, the rate of phosphorus uptake at pH 4.0 was twice that observed at pH 7.0. Non-mycorrhizal plant uptake rates were similar at both pH 4.0 and pH 7.0. The contribution of soil nutrient supply mechanisms to plant nutrient content increased with rhizosphere acidification. Uptake kinetics were also affected by rhizosphere acidification, but to a lesser extent.
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PMID:Consequences of rhizosphere acidification on delivery and uptake kinetics of soil phosphorus. 1497 90

Analysis of Acer pseudoplatanus L. (sycamore) tree rings using ICP-MS was used to assess the impact of metal deposition on trees growing in the vicinity of a metal refinery at Prescot, north-west England compared to a reference site at Croxteth 6 km distant receiving minimal deposition. No difference in tree growth between sites was recorded. Large reductions in Cu and Cd deposition since the late 1970s was accompanied by a steep decline in Cd concentrations in the outer rings in trees close to the refinery. A similar reduction in Cu concentrations was less apparent due to a tendency for Cu to increase in the outer rings. Zinc and Ni were higher in xylem at Prescot compared to Croxteth. There was no trend in Zn concentrations at either site although Ni concentrations increased in trees close to the refinery after 1982. Manganese concentrations in xylem were much higher at Prescot; Mn levels declined until the late 1970s and then increased slightly in later years interspersed by large concentration peaks within individual years during the 1980s. There was little change in Mn concentrations in trees at Croxteth during this period. Calcium, Mg and Sr concentrations remained steady or declined slightly in rings formed since 1965 in trees at Croxteth. Concentrations of Ca, Mg and Sr were higher in rings formed prior to the mid 1970s in trees at Prescot, but declined steadily after this period, although peaks in concentrations of each element were recorded in individual years during the 1980s. Phosphorous concentrations in rings increased towards the cambium at Croxteth, although P levels decreased in rings formed after 1982 at Prescot. No difference in K concentrations between sites was recorded. Lead concentrations in xylem at both sites declined steadily in rings formed after 1970, although concentrations were higher at the reference site. Analysis of individual sycamore tree rings appears to record short-term changes in pollution episodes, with little lateral movement of elements occurring. It is suggested that changes in element concentrations in trees close to the refinery are a result of reduced metal deposition combined with increased soil acidity due to reduced buffering capacity of metal ions in rainfall.
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PMID:Analysis of tree rings using inductively coupled plasma mass spectrometry to record fluctuations in a metal pollution episode. 1509 73

Water samples draining a disused copper mine (Parys Mountain) in Anglesey, North Wales, were analysed for distribution of acidophilic bacteria (iron oxidising and heterotrophic) and for changes in physicochemical composition along the length of the drainage stream. Ten samples were taken at regular distance intervals along a 1 km stretch from the source of the acid mine drainage. The stream remained highly acidic (pH < 2.8) although a slight decrease (0.6 pH unit) in acidity with distance from source was observed. Concentrations of most metals measured decreased with distance along the length of the stream, although some showed a gradual increase and others peaked at c. 200 m from source. Most dissolved iron was in the ferrous form in the upper reaches of the stream, but ferric iron became increasingly dominant downstream as a result of microbial oxidation. Although concentrations of nutrients such as nitrogen and phosphorus were low in the acid mine drainage, they were not limiting rates of bacterial iron oxidation, which appeared to be limited more by temperature. The iron oxidising bacteria Thiobacillus ferrooxidans and Leptospirillum ferrooxidans were both isolated from all sampling sites, although their relative abundances varied; L. ferrooxidans accounted for 57% of all iron oxidising isolates. Numbers of iron oxidising bacteria decreased with distance from drainage source, in contrast to those of acidophilic heterotrophic bacteria which increased. The diversity of heterotrophic isolates also increased with distance. The relationship between the chemistry and microbiology of the stream is discussed.
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PMID:Microbiological and chemical characteristics of an acidic stream draining a disused copper mine. 1509 99

Following the cropping of Sesbania rostrata, Lolium multiflorum was cropped as the subsequent species on an acidified Pb/Zn tailings site. As the experimental treatments, S. rostrata issues harvested on the site were removed from the site or buried into the tailings as the green manure. Changes of tailings chemical and physical properties, germination, growth and heavy metal accumulation of Lolium multiflorum were investigated. The results showed that cropping of S. rostrata improved the chemical and physical properties of the tailings, especially for the contents of organic matter, total nitrogen, available phosphorus and available potassium. The strong acidity (pH < 3) in the Pb/Zn tailings was the main factor that limited the establishment of L. multiflorum. The tailings acidity was decreased temporarily by lime application and it seemed to be helpful only for the germination because the strong acidity was restituted in the end of the experiment. In the most cases, L. multiflorum succeeded to germinate, grow and establish on the Pb/Zn tailings, and yielded relatively great biomass (DM 1.4-3.2 t.km-2). Compared to CK (without S. rostrata cropping), cropping S. rostrata increased the biomass of subsequent L. multiflorum by 4.8%-39.5% in case without S. rostrata green manure using and by 7.7%-139.5% in case with the green manure using, and the green manure application resulted in 2.7%-75.8% increment of L. multiflorum biomass. The results proved that the artificial vegetation process using S. rostrata and subsequent L. multiflorum would be a successful pioneer stage for restoration of the Pb/Zn tailings.
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PMID:[Establishment and growth of Lolium multiflorum for phyto-remediation of Pb/Zn tailings]. 1514 34

Studies of CO-dissociative substitution reactions of the complexes Ru(CO)4L (L = a wide variety of P-donor ligands) have been extended and analysis of the results by the QALE methodology has been refined (QALE = quantitative analysis of ligand effects). Rates increase substantially with increasing size of L, mainly as a consequence of increasingly favourable activation entropies. These can be associated with increasing Ru-CO bond breaking that is compensated enthalpically by increasing Ru-P bond making allowed by release of steric strain. Explicit allowance for pi-acidity shows that these effects are just significant while sigma-donor and aryl effects are negligible. However, pendent hydrogen atoms, attached directly to the phosphorus atoms, have a pronounced and unique positive effect on the rates, with significant kinetic isotope effects (KIE). This is associated with the novel occurrence of direct Ru-H or incipient Ru-(eta2-P-H) agostic bond making as the CO ligand departs.
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PMID:QALE analysis of CO dissociative kinetics of Ru(CO)4L (L = P-donor ligands): accelerating effects of hydrogen in PHnR(3 - n) ligands (n = 1-2). 1525 7

The scope and limitations of the ruthenium-catalyzed propargylic substitution reaction of propargylic alcohols with heteroatom-centered nucleophiles are presented. Oxygen-, nitrogen-, and phosphorus-centered nucleophiles such as alcohols, amines, amides, and phosphine oxide are available for this catalytic reaction. Only the thiolate-bridged diruthenium complexes can work as catalysts for this reaction. Results of some stoichiometric and catalytic reactions indicate that the catalytic propargylic substitution reaction proceeds via an allenylidene complex formed in situ, whereby the attack of nucleophiles to the allenylidene C(gamma) atom is a key step. Investigation of the relative rate constants for the reaction of propargylic alcohols with several para-substituted anilines reveals that the attack of anilines on the allenylidene C(gamma) atom is not involved in the rate-determining step and rather the acidity of conjugated anilines of an alkynyl complex, which is formed after the attack of aniline on the C(gamma) atom, is considered to be the most important factor to determine the rate of this catalytic reaction. The key point to promote this catalytic reaction by using the thiolate-bridged diruthenium complexes is considered to be the ease of the ligand exchange step between a vinylidene ligand on the diruthenium complexes and another propargylic alcohol in the catalytic cycle. The reason why only the thiolate-bridged diruthenium complexes promote the ligand exchange step more easily with respect to other monoruthenium complexes in this catalytic reaction should be that one Ru moiety, which is not involved in the allenylidene formation, works as an electron pool or a mobile ligand to another Ru site. The catalytic procedure presented here provides a versatile, direct, and one-step method for propargylic substitution of propargylic alcohols in contrast to the so far well-known stoichiometric and stepwise Nicholas reaction.
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PMID:Ruthenium-catalyzed propargylic substitution reactions of propargylic alcohols with oxygen-, nitrogen-, and phosphorus-centered nucleophiles. 1565 Oct 18

The guanine nucleotide-binding protein Ras occurs in solution in two different states, state 1 and state 2, when the GTP analogue GppNHp is bound to the active center as detected by (31)P NMR spectroscopy. Here we show that Ras(wt).Mg(2+).GppCH(2)p also exists in two conformational states in dynamic equilibrium. The activation enthalpy DeltaH(++)(12) and the activation entropy DeltaS(++)(12) for the transition from state 1 to state 2 are 70 kJ mol(-1) and 102 J mol(-1) K(-1), within the limits of error identical to those determined for the Ras(wt).Mg(2+).GppNHp complex. The same is true for the equilibrium constants K(12) = [2]/[1] of 2.0 and the corresponding DeltaG(12) of -1.7 kJ mol(-1) at 278 K. This excludes a suggested specific effect of the NH group of GppNHp on the equilibrium. The assignment of the phosphorus resonance lines of the bound analogues has been done by two-dimensional (31)P-(31)P NOESY experiments which lead to a correction of the already reported assignments of bound GppNHp. Mutation of Thr35 in Ras.Mg(2+).GppCH(2)p to serine leads to a shift of the conformational equilibrium toward state 1. Interaction of the Ras binding domain (RBD) of Raf kinase or RalGDS with Ras(wt) or Ras(T35S) shifts the equilibrium completely to state 2. The (31)P NMR experiments suggest that, besides the type of the side chain of residue 35, a main contribution to the conformational equilibrium in Ras complexes with GTP and GTP analogues is the effective acidity of the gamma-phosphate group of the bound nucleotide. A reaction scheme for the Ras-effector interaction is presented which includes the existence of two conformations of the effector loop and a weak binding state.
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PMID:Conformational states of Ras complexed with the GTP analogue GppNHp or GppCH2p: implications for the interaction with effector proteins. 1569 48

A dynamic 1H NMR study has been carried out on the fluxional motion of the symmetric chelating ligand 2,9-dimethyl-1,10-phenanthroline (Me2-phen) between nonequivalent exchanging sites in a variety of square-planar complexes of the type [Pt(Me)(Me2-phen)(PR3)]BArf, 1-14, (BArf = B[3,5-(CF3)2C6H3]4). In these compounds, the P-donor ligands PR3 encompass a wide range of steric and electronic characteristics [PR3 = P(4-XC6H4)3, X = H 1, F, 2, Cl 3, CF3 4, MeO 5, Me 6; PR3 = PMe(C6H5)2 7, PMe2(C6H5) 8, PMe3 9, PEt3 10, P(i-Pr)3 11, PCy(C6H5)2 12, PCy2(C6H5) 13, PCy3 14]. All complexes have been synthesized and fully characterized through elemental analysis, 1H and 31P{1H} NMR. X-ray crystal structures are reported for the compounds 8, 11, 14, and for [Pt(Me)(phen)(P(C6H5)3)]PF6 (15), all but the last showing loss of planarity and a significant rotation of the Me2-phen moiety around the N1-N2 vector. Steric congestion brought about by the P-donor ligands is responsible for tetrahedral distortion of the coordination plane and significant lengthening of the Pt-N2 (cis to phosphane) bond distances. Application of standard quantitative analysis of ligand effects (QALE) methodology enabled a quantitative separation of steric and electronic contributions of P-donor ligands to the values of the platinum-phosphorus 1J(PtP) coupling constants and of the free activation energies DeltaG++ of the fluxional motion of Me2-phen in 1-14. The steric profiles for both 1J(PtP) and DeltaG++ show the onset of steric thresholds (at cone angle values of 150 degrees and 148 degrees , respectively), that are associated with an overload of steric congestion already evidenced by the crystal structures of 11 and 14. The sharp increase of the fluxional rate of Me2-phen can be assumed as a perceptive kinetic tool for revealing ground-state destabilization produced by the P-donor ligands. The mechanism involves initial breaking of a metal-nitrogen bond, fast interconversion between two 14-electron three-coordinate T-shaped intermediates containing eta1-coordinated Me2-phen, and final ring closure. By use of the results from QALE regression analysis, a free-energy surface has been constructed that represents the way in which any single P-donor ligand can affect the energy of the transition state in the absence of aryl or pi-acidity effects.
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PMID:Structural properties and dissociative fluxional motion of 2,9-dimethyl-1,10-phenanthroline in platinum(II) complexes. 1573 65

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