Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Thermal analysis has shown that contrary to the case of Zn2+, considerable amounts of water enter in HFO (hydrous ferric oxide), HSO (hydrous stannic oxide), and HMO (hydrous mixed oxide) when Co2+ is adsorbed. A large amount of Co2+ and Zn2+ in all the oxides cannot participate in isotopic exchange, seemingly because of being trapped inside the micropores, a fact hindering oxide capacity determination by isotopic dilution. The % adsorption-pH curves for tracer and 10(-3) M transition metal chloride solutions show a general preference to Zn2+ over Co2+ by all the oxides, in agreement with thermal analysis data. Large shifts of these curves to the left occur with tracer experiments on many samples on adding 0.1 M NaCl, probably due to Cl- adsorption accompanied by a change in the adsorption mechanism. Conclusions from log Kd-pH plots may be erroneous, probably due to changes in the activity coefficients of surface species even at sufficiently low surface coverages. More adsorption of Co2+ and Zn2+ generally occurs on the oxide of lower pHPZC (higher acidity).
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PMID:Adsorption of Co2+ and Zn2+ Ions on Hydrous Fe(III), Sn(IV), and Fe(III)/Sn(IV) Oxides 895 37

EC50s for cadmium, copper, lead and zinc were determined for juvenile production of Folsomia candida at pH6.0, 5.0 and 4.5 in a standard laboratory test system. In contrast to most previous studies where metal toxicity was increased at low pHs, in our experiments there was no clear relationship between soil acidity and EC50-reproduction in this species. The EC50-reproduction values (microgram g-1) for cadmium and zinc were similar at all three pHs (pH6.0: Cd 590, Zn 900; pH5.0: Cd 780, Zn 600; pH4.5: Cd 480, Zn 590). In contaminated field sites adjacent to primary zinc smelters, zinc is invariably present in soils at concentrations of at least 50 times that of cadmium. Thus deleterious effects of mixtures of these metals on populations of Collembola in such sites can be attributed to zinc rather than cadmium.
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PMID:Effects of pH on the toxicity of cadmium, copper, lead and zinc to Folsomia candida Willem, 1902 (Collembola) in a standard laboratory test system. 897 58

Integration and comparison of metal contamination from acid mine drainage and an assessment of the potential for ecological impact was conducted in the aquatic ecosystems of the Le An river. The results indicated low acidity, high levels of suspended solids containing a high content of copper in river water and sediment in the upstream region of the Le An river due to the pollution from the Dexing copper mine, and high concentrations of zinc and copper in surface water and sediments, high release potential and ready bioavailability of heavy metals in sediments downstream (after site A07) due to the pollution from the Jishui river. The pollution from acid mine drainage in the Le An river potentially effects an ecological impact on the aquatic ecosystem, mainly between sites A04 and A08. The management strategy should, therefore be mainly applied to acid mine drainage from the Dexing copper mine and heavy metal discharges from the Jishui river.
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PMID:Spatial and temporal patterns of acidity and heavy metals in predicting the potential for ecological impact on the Le An river polluted by acid mine drainage. 937 91

Tandem pore domain K+ channels represent a new family of ion channels involved in the control of background membrane conductances. We report the structural and functional properties of a TWIK-related acid-sensitive K+ channel (rTASK), a new member of this family cloned from rat cerebellum. The salient features of the primary amino acid sequence include four putative transmembrane domains and, unlike other cloned tandem pore domain channels, a PDZ (postsynaptic density protein, disk-large, zo-1) binding sequence at the C terminal. rTASK has distant overall homology to a putative Caenorhabditis elegans K+ channel and to the mammalian clones TREK-1 and TWIK-1. rTASK expression is most abundant in rat heart, lung, and brain. When exogenously expressed in Xenopus oocytes, rTASK currents activate instantaneously, are noninactivating, and are not gated by voltage. Because rTASK currents satisfy the Goldman-Hodgkin-Katz current equation for an open channel, rTASK can be classified an open rectifier. Activation of protein kinase A produces inhibition of rTASK, whereas activation of protein kinase C has no effect. rTASK currents were inhibited by extracellular acidity. rTASK currents also were inhibited by Zn2+ (IC50 = 175 microM), the local anesthetic bupivacaine (IC50 = 68 microM), and the anti-convulsant phenytoin ( approximately 50% inhibition at 200 microM). By demonstrating open rectification and open probability independent of voltage, we have established that rTASK is a baseline potassium channel.
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PMID:An open rectifier potassium channel with two pore domains in tandem cloned from rat cerebellum. 943 8

Botulinum neurotoxins type A (BoNT/A), the most toxic substance known to man, is produced by Clostridium botulinum type A as a complex with a group of neurotoxin-associated proteins (NAPs), possibly through a polycistronic expression of a clustered group of genes. The botulinum neurotoxin complex is the only known example of a protein complex where a group of proteins (NAPs) protect another protein (BoNT) against acidity and proteases of the GI tract. We now report that NAPs also potentiate the Zn2+ endopeptidase activity of BoNT/A in both in vitro and in vivo assays against its known intracellular target protein, 25 kDa synaptosomal associated protein (SNAP-25). While BoNT/A exhibited no protease activity prior to reduction with dithiothreitol (DTT), the BoNT/A complex exhibited a high protease activity even in its nonreduced form. Our results suggest that the bacterial production of NAPs along with BoNT is designed for the NAPs to play an accessory role in the neurotoxin function, in contrast to their previously known limited role in protecting the neurotoxin in the GI tract and in the external environment. Structural features of BoNT/A change considerably upon disulfide reduction, as revealed by near-UV circular dichroism spectroscopy. BoNT/A in the reduced form adopts a more flexible structure than in the unreduced form, as also indicated by large differences in DeltaH values (155 vs 248 kJ mol-1) of temperature-induced unfolding of BoNT/A.
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PMID:Enhancement of the endopeptidase activity of botulinum neurotoxin by its associated proteins and dithiothreitol. 1034 12

The role of metal ions in the T- to R-allosteric transition is ascertained from the investigation of the T- to R-allosteric transition of transition metal ions substituted-insulin hexamers, as well as from the kinetics of their dissociation. These studies establish that ligand field stabilization energy (LFSE), coordination geometry preference, and the Lewis acidity of the metal ion in the zinc sites modulate the T- to R-state transition. (1)H NMR, (113)Cd NMR, and UV-vis measurements demonstrate that, under suitable conditions, Fe2+/3+, Ni2+, and Cd2+ bind insulin to form stable hexamers, which are allosteric species. (1)H NMR R-state signatures are elicited by addition of phenol alone in the case of Ni(II)- and Cd(II)-substituted insulin hexamers. The Fe(II)-substituted insulin hexamer is converted to the ferric analogue upon addition of phenol. For the Fe(III)-substituted insulin hexamer, appearance of (1)H NMR R-state signatures requires, additionally to phenol, ligands containing a nitrogen that can donate a lone pair of electrons. This is consistent with stabilization of the R-state by heterotropic interactions between the phenol-binding pocket and ligand binding to Fe(III) in the zinc site. UV-vis measurements indicate that the (1)H NMR detected changes in the conformation of the Fe(III)-insulin hexamer are accompanied by a change in the electronic structure of the iron site. Kinetic measurements of the dissociation of the hexamers provide evidence for the modulation of the stability of the hexamer by ligand field stabilization effects. These kinetic studies also demonstrate that the T- to R-state transition in the insulin hexamer is governed by coordination geometry preference of the metal ion in the zinc site and the compatibility between Lewis acidity of the metal ion in the zinc site and the Lewis basicity of the exogenous ligands. Evidence for the alteration of the calcium site has been obtained from (113)Cd NMR measurements. This finding adds to the number of known conformational changes that occur during the T- to R-transition and is an important consideration in the formulation of allosteric mechanisms of the insulin hexamer.
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PMID:Role of metal ions in the T- to R-allosteric transition in the insulin hexamer. 1052 Dec 51

Changes in pH, titratable acidity and mineral content (Ca, Fe, Mg, Zn) were estimated in processed cassava products while the mineral content of raw and blanched amaranthus vegetable was determined. pH of fresh cassava (6.5) decreased as total organic acid (0.07%) increased with fermentation period. Fufu and lafun had the lowest pH and the highest total organic acids contents. Fermentation of cassava increased the total calcium and iron contents, reduced magnesium level while zinc remained fairly constant in grated cassava but was reduced when soaked in water (for the preparation of fufu and lafun). Fermentation also increased the availability of these selected minerals in both cassva products and simulated cassava-vegetable diets. Blanching reduced the mineral content of amaranthus vegetable but increased mineral availability. Fermentation of cassava and blanching of vegetables play an important role in making minerals more available and these processing methods should be encouraged to potentially ameliorate the disease states associated with mineral deficiency.
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PMID:The effect of processing on total organic acids content and mineral availability of simulated cassava-vegetable diets. 1054 Sep 89

/ In Yellowstone National Park, tailings and associated trace metals from past mining have been deposited along 28 km of Soda Butte Creek by large flood events. This study documents grass species diversity, density, and biomass; trace metal concentrations in soils; and soil pH, salinity, and clay content in four selected floodplain meadows contaminated by these tailings. Trace metal levels frequently exceed acceptable concentrations for agricultural soils at sampling points within the meadows. pH levels within flood-deposited tailings are strongly to moderately acid, while pH levels outside of tailings deposits are neutral. The data analysis: (1) shows that metals and acidity associated with tailings affect plant biomass, density, and diversity; (2) documents that the vegetation/metal and vegetation/pH associations are more of a threshold than a linear relationship; and (3) suggests that other factors may be involved in structuring the community. Vegetation diversity, density, and biomass decrease at threshold levels of trace metal concentrations and soil pH in all four meadows. CuSum plots of diversity in relation to trace metal levels show a decrease in mean diversity at 315 ppm copper, 22 ppm arsenic, 4.2% iron, 65 ppm lead, and 170 ppm zinc. Densities of Phleum pratense and Poa pratensis were significantly lower (P </= 0.001) on plots with more than 250 ppm copper. Above-ground biomass of Phleum pratense was also significantly lower on plots with copper levels above 250 ppm. Decreased mean grass density was found on plots with pH < 6.4, but the only statistically significant difference was for Juncus balticus, which had increased density on plots with pH < 6.4. In contrast to the clear impacts of trace metals and pH on vegetation, other site characteristics did not alter measured vegetation characteristics.
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PMID:Persistent Impacts of Trace Metals from Mining on Floodplain Grass Communities Along Soda Butte Creek, Yellowstone National Park. 1062 12

It was established in the experiments determining the influence of the mushroom powder on acidity of the HCl solution by means of ionometrical method that in 15 minutes after introduction 3 gram of the powder pH of the solution increases from 1.62 up to 2.64. The stable meaning of the solution pH (without fall) can be (held) the same in the presence of the powder more than 23 hours. The mushroom powder reduces the high content of the ions Pb2+ and Cu2+ in the solution from 8.8 x 10(-6) up to 3.3 x 10(-6) and from 11.8 x 10(-6) up to 8.6 x 10(-6) mole/ml correspondingly. The trustworthy reduction (fall) of the concentration of the ions Zn2+ and Cd2+ in the filtrate was not discovered (found out). To determine the content of metal in the solution the method of flaming atomic adsorption.
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PMID:[Antacid and sorption properties of mushroom powder made of dried solids (Pleurotus ostreatus)]. 1064 Dec 77

A simple and highly selective flow injection on-line pre-concentration and separation-flame atomic absorption spectrometric method was developed for routine analysis of trace amounts of lead in biological and environmental samples. The selective preconcentration of lead was achieved in a wide range of sample acidity (0.075 to > or = 3 mol L(-1)HNO3) on a microcolumn (145 microL) packed with a macrocycle immobilized on silica gel. The lead retained on the column was effectively eluted with an EDTA solution (0.03 mol L(-1), pH 10.5). Three kinds of potential interferences, i.e., preconcentration inferences from metal ions with an ionic radius similar to that of Pb(II) due to their competition for the cavity of the macrocyle, elution kinetic interferences from ions which form stable complexes with EDTA due to their competition for EDTA, and interferences in the atomizer from residual matrix, were evaluated and compared in view of the read-out mode of the analyte response (peak area vs peak height), column wash step (with vs without), column capacity (50 vs 145 microL), and column shape (conical vs cylindrical). The results showed that a combination of increase in column capacity, quantitation based on peak area, and use of dilute nitric acid for column wash before elution efficiently avoid the above-mentioned potential interferences. With the use of a 145 microL column the present system tolerated up to 0.1 g L(-1) Ba(II), 1 g L(-1) Sr(II), and at least 10 g L(-1) Fe(III), Cu(II), Ni(II), Zn(II), Cd(II), Al(III), K(I), Na(I), CaII), and Mg(II) in the sample digest. Further improvement of the interference tolerance can be achieved by increasing column capacity if more complicated samples need to be analyzed. At a sample loading rate of 3.9 mL min(-1) with 30-s preconcentration, an enrichment factor of 52, a detection limit (3s) of 5 micrograms L(-1) Pb in the digest and a sampling frequency of 63 h(-1) were obtained. The precision (RSD, n = 11) at the 200 micrograms L(-1) level was 1.9%. The enrichment factor and the detection limit can be further improved by increasing sample loading rate without degradation in the efficiency due to the favorable kinetics and low hydrodynamic impedance of the present system. The analytical results obtained by the proposed method for a number of biological and environmental standard reference materials were in good agreement with the certified and recommended values.
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PMID:Application of a macrocycle immobilized silica gel sorbent to flow injection on-line microcolumn preconcentration and separation coupled with flame atomic absorption spectrometry for interference-free determination of trace lead in biological and environmental samples. 1066 Apr 37


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