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Sample records for acidic lakes ph

  1. Benthic fauna of extremely acidic lakes (pH 2-3)

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, G.G.

    2001-07-01

    The structure of the benthic invertebrate communities were investigated in terms of composition, abundance, and biomass from extremely acidic lakes with pH values from 2 to 3 in areas where coal was intensively mined in the Lusatian region in the eastern region of Germany. Benthic invertebrates colonisation on leaves and the breakdown rate processing of the three deciduous leaf: Betula pendula (birch), Fraxinus excelsior (ash), and Juglans regia (walnut) were investigated. Also, the main key-species of these acidic environments were investigated, in terms of description of pupal exuviae of Chironomus crassimanus and the feeding habit of this acid-resistant species through analysis of their gut content. The benthic food web in extremely acidic mining Lusatian lakes is very short in terms of species richness, trophic relationship, guilds and functional feeding groups. Collector-filters and scraper-grazers were absent in extremely acidic mining lakes (AML 107, AML 111 and AML 117). Shredders as Limnophyes minimus (Diptera, Chironomidae, Orthocladiinae) and Hydrozetes lacustris (Acari, Hydrozetidae) occurred in low abundance in AML 107 and AML 111, and it may be in response to slow leaf breakdown process in these ecosystems, except in AML 117 where the H. lacustris contributed most to ecosystems functioning via the processing of litter. Aquatic insects as Sialis lutaria (Megaloptera, Sialidae), Orectochilus villosus (Coleoptera, Gyrinidae), Coenagrion mercuriale (Odonata, Coenagrionidae), and Phryganeidae (Trichoptera) are the top-predators of these ecosystems. They did not depend on the level of pH in the lakes, but on the availability of food resources. (orig.)

  2. Macroinvertebrate and algal communities in an extremely acidic river and the Kawah Ijen crater lake (pH

    NARCIS (Netherlands)

    Löhr, A.J.; Sluik, R.; Olaveson, M.M.; Ivorra, N.; van Gestel, C.A.M.; van Straalen, N.M.

    2006-01-01

    Acidic aquatic ecosystems are mainly characterized by low pH and high concentrations of metals and other elements with evident effects on local community structure. Acidity effects on benthic communities in one of the world's largest extremely acidic crater lakes, the Kawah Ijen (East Java, Indonesi

  3. Macroinvertebrate and algal communities in an extremely acidic river and the Kawah Ijen crater lake (pH

    NARCIS (Netherlands)

    Löhr, A.J.; Sluik, R.; Olaveson, M.M.; Ivorra, N.; van Gestel, C.A.M.; van Straalen, N.M.

    2006-01-01

    Acidic aquatic ecosystems are mainly characterized by low pH and high concentrations of metals and other elements with evident effects on local community structure. Acidity effects on benthic communities in one of the world's largest extremely acidic crater lakes, the Kawah Ijen (East Java,

  4. Factors determining growth and vertical distribution of planktonic algae in extremely acidic mining lakes (pH 2.7)

    Science.gov (United States)

    Bissinger, Vera

    2003-04-01

    In this thesis, I investigated the factors influencing the growth and vertical distribution of planktonic algae in extremely acidic mining lakes (pH 2-3). In the focal study site, Lake 111 (pH 2.7; Lusatia, Germany), the chrysophyte, Ochromonas sp., dominates in the upper water strata and the chlorophyte, Chlamydomonas sp., in the deeper strata, forming a pronounced deep chlorophyll maximum (DCM). Inorganic carbon (IC) limitation influenced the phototrophic growth of Chlamydomonas sp. in the upper water strata. Conversely, in deeper strata, light limited its phototrophic growth. When compared with published data for algae from neutral lakes, Chlamydomonas sp. from Lake 111 exhibited a lower maximum growth rate, an enhanced compensation point and higher dark respiration rates, suggesting higher metabolic costs due to the extreme physico-chemical conditions. The photosynthetic performance of Chlamydomonas sp. decreased in high-light-adapted cells when IC limited. In addition, the minimal phosphorus (P) cell quota was suggestive of a higher P requirement under IC limitation. Subsequently, it was shown that Chlamydomonas sp. was a mixotroph, able to enhance its growth rate by taking up dissolved organic carbon (DOC) via osmotrophy. Therefore, it could survive in deeper water strata where DOC concentrations were higher and light limited. However, neither IC limitation, P availability nor in situ DOC concentrations (bottom-up control) could fully explain the vertical distribution of Chlamydomonas sp. in Lake 111. Conversely, when a novel approach was adopted, the grazing influence of the phagotrophic phototroph, Ochromonas sp., was found to exert top-down control on its prey (Chlamydomonas sp.) reducing prey abundance in the upper water strata. This, coupled with the fact that Chlamydomonas sp. uses DOC for growth, leads to a pronounced accumulation of Chlamydomonas sp. cells at depth; an apparent DCM. Therefore, grazing appears to be the main factor influencing the

  5. Enrichment of sulfate-reducing bacteria and resulting mineral formation in media mimicking pore water metal ion concentrations and pH conditions of acidic pit lakes.

    Science.gov (United States)

    Meier, Jutta; Piva, Angela; Fortin, Danielle

    2012-01-01

    Acid mine drainage sites are extreme environments with high acidity and metal ion concentrations. Under anoxic conditions, microbial sulfate reduction may trigger the formation of secondary minerals as a result of H2S production and pH increase. This process was studied in batch experiments with enrichment cultures from acidic sediments of a pit lake using growth media set at different pH values and containing elevated concentrations of Fe²⁺ and Al³⁺. At initial pH values of 5 and 6, sulfate reduction occurred shortly after inoculation. Sulfate- reducing bacteria affiliated to the genus Desulfosporosinus predominated the microbial communities as shown by 16S rRNA gene analysis performed at the end of the incubation. At initial pH values of 3 and 4, sulfate reduction and cell growth occurred only after an extended lag phase, however, at a higher rate than in the less acidic assays. At the end of the growth phase, enrichments were dominated by Thermodesulfobium spp. suggesting that these sulfate reducers were better adapted to acidic conditions. Iron sulfides in the bulk phase were common in all assays, but specific aluminum precipitates formed in close association with cell surfaces and may function as a detoxification mechanism of dissolved Al species at low pH.

  6. Acid loading test (pH)

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/003615.htm Acid loading test (pH) To use the sharing features on this page, please enable JavaScript. The acid loading test (pH) measures the ability of the ...

  7. Lake morphometry and wind exposure may shape the plankton community structure in acidic mining lakes.

    Science.gov (United States)

    Weithoff, Guntram; Moser, Michael; Kamjunke, Norbert; Gaedke, Ursula; Weisse, Thomas

    2010-05-01

    Acidic mining lakes (pH web in such lakes. The plankton community structure of mining lakes of different morphometry and mixing type but similar chemical characteristics (Lake 130, Germany and Lake Langau, Austria) was investigated. The focus was laid on the species composition, the trophic relationship between the phago-mixotrophic flagellate Ochromonas sp. and bacteria and the formation of a deep chlorophyll maximum along a vertical pH-gradient. The shallow wind-exposed Lake 130 exhibited a higher species richness than Lake Langau. This increase in species richness was made up mainly by mero-planktic species, suggesting a strong benthic/littoral - pelagic coupling. Based on the field data from both lakes, a nonlinear, negative relation between bacteria and Ochromonas biomass was found, suggesting that at an Ochromonas biomass below 50 μg C L(-1), the grazing pressure on bacteria is low and with increasing Ochromonas biomass bacteria decline. Furthermore, in Lake Langau, a prominent deep chlorophyll maximum was found with chlorophyll concentrations ca. 50 times higher than in the epilimnion which was build up by the euglenophyte Lepocinclis sp. We conclude that lake morphometry, and specific abiotic characteristics such as mixing behaviour influence the community structure in these mining lakes.

  8. Microbial Sulfur Cycling in an Acid Mine Lake

    Science.gov (United States)

    Bernier, L.; Warren, L. A.

    2004-12-01

    Geochemical dynamics of a tailings impacted lake in Northern Ontario were investigated over a three-year period, in which active pyrrhotite slurry disposal was initiated in year two. A strong seasonal trend of decreasing epilimnetic pH with significant diurnal acid production, pre-, during and post slurry deposition was observed with high rates observed compared to pre-slurry. Slurry deposition occurred at the surface of the lake and acted as a reaction stimulant for acid generation. Over the diurnal timescale investigated, the highest rates of acid production occurred not at the lake surface but within the metaliminetic region of the lake. This region was exemplified by strong decreasing oxygen gradients, and thus observed high rates of acid generation are more consistent with microbial pathways of sulfur oxidation than with abiotic, oxygen catalyzed pathways. Consistent with microbial catalysis, metalimnetic rates of acid generation were highest during June and July when microbial populations and metabolic rates were maximal. These results indicate that microbial oxidation of sulfur species play a major role in acid generation in this system. Further, observed rates of acid generation exceed those predicted by published abiotic rates of pyrrhotite oxidation, but are consistent with literature estimates of acid generation catalyzed by microbial activity. Acidithiobacilli accounted for up to 50% of the microbial community pre slurry, but were absent post slurry deposition. These results are the first to demonstrate quantitatively that microbial sulfur oxidation can play a predominant role in acid generation within mine tailings impacted systems. They further highlight the need to evaluate the more complex pathways by which microorganisms process sulfur as the conditions, controls and process rates differ from those observed for abiotic reactions.

  9. Determination of polyfluoroalkyl phosphoric acid diesters, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, perfluoroalkyl carboxylic acids, and perfluoroalkane sulfonic acids in lake trout from the Great Lakes region.

    Science.gov (United States)

    Guo, Rui; Reiner, Eric J; Bhavsar, Satyendra P; Helm, Paul A; Mabury, Scott A; Braekevelt, Eric; Tittlemier, Sheryl A

    2012-11-01

    A comprehensive method to extract perfluoroalkyl carboxylic acids, perfluoroalkane sulfonic acids, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, and polyfluoroalkyl phosphoric acid diesters simultaneously from fish samples has been developed. The recoveries of target compounds ranged from 78 % to 121 %. The new method was used to analyze lake trout (Salvelinus namaycush) from the Great Lakes region. The results showed that the total perfluoroalkane sulfonate concentrations ranged from 0.1 to 145 ng/g (wet weight) with perfluorooctane sulfonate (PFOS) as the dominant contaminant. Concentrations in fish between lakes were in the order of Lakes Ontario ≈ Erie > Huron > Superior ≈ Nipigon. The total perfluoroalkyl carboxylic acid concentrations ranged from 0.2 to 18.2 ng/g wet weight. The aggregate mean perfluorooctanoic acid (PFOA) concentration in fish across all lakes was 0.045 ± 0.023 ng/g. Mean concentrations of PFOA were not significantly different (p > 0.1) among the five lakes. Perfluoroalkyl phosphinic acids were detected in lake trout from Lake Ontario, Lake Erie, and Lake Huron with concentration ranging from non-detect (ND) to 0.032 ng/g. Polyfluoroalkyl phosphoric acid diesters were detected only in lake trout from Lake Huron, at levels similar to perfluorooctanoic acid.

  10. pH dependent dissolution of sediment aluminum in six Danish lakes treated with aluminum

    DEFF Research Database (Denmark)

    Reitzel, Kasper; Jensen, Henning S.; Egemose, Sara

    2013-01-01

    The possible pH dependent dissolution of aluminum hydroxides (Al(OH)(3)) from lake sediments was studied in six lakes previously treated with Al to bind excess phosphorus (P). Surface sediment was suspended for 2 h in lake water of pH 7.5, 8.5, or 9.5 with resulting stepwise increments in dissolved......H water. Release rates of dissolved Al from intact sediment cores at the same three pH values was measured in three of the lakes, and showed increased Al release rates at pH 8.5 in one of the lakes and 9.5 in two of the lakes. Our study demonstrates a risk of dissolution of sediment Al(OH)(3) to form...... aluminate in shallow lakes, where resuspension and high pH in the water occurs frequently. In the worst case dissolved Al may reach toxic levels in lakes treated by Al but also the concomitant release of P and the possible loss of dissolved Al to downstream ecosystems are negative effects that may occur...

  11. Effects of acidic deposition on in-lake phosphorus availability: a lesson from lakes recovering from acidification.

    Science.gov (United States)

    Kopáček, Jiří; Hejzlar, Josef; Kaňa, Jiří; Norton, Stephen A; Stuchlík, Evžen

    2015-03-01

    Lake water concentrations of phosphorus (P) recently increased in some mountain areas due to elevated atmospheric input of P rich dust. We show that increasing P concentrations also occur during stable atmospheric P inputs in central European alpine lakes recovering from atmospheric acidification. The elevated P availability in the lakes results from (1) increasing terrestrial export of P accompanying elevated leaching of dissolved organic carbon and decreasing phosphate-adsorption ability of soils due to their increasing pH, and (2) decreasing in-lake P immobilization by aluminum (Al) hydroxide due to decreasing leaching of ionic Al from the recovering soils. The P availability in the recovering lakes is modified by the extent of soil acidification, soil composition, and proportion of till and meadow soils in the catchment. These mechanisms explain several conflicting observations of the acid rain effects on surface water P concentrations.

  12. Egg fatty acid composition from lake trout fed two Lake Michigan prey fish species.

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    Honeyfield, D.C.; Fitzsimons, J.D.; Tillitt, D.E.; Brown, S.B.

    2009-01-01

    We previously demonstrated that there were significant differences in the egg thiamine content in lake trout Salvelinus namaycush fed two Lake Michigan prey fish (alewife Alosa pseudoharengus and bloater Coregonus hoyi). Lake trout fed alewives produced eggs low in thiamine, but it was unknown whether the consumption of alewives affected other nutritionally important components. In this study we investigated the fatty acid composition of lake trout eggs when females were fed diets that resulted in different egg thiamine concentrations. For 2 years, adult lake trout were fed diets consisting of four combinations of captured alewives and bloaters (100% alewives; 65% alewives, 35% bloaters; 35% alewives, 65% bloaters; and 100% bloaters). The alewife fatty acid profile had higher concentrations of arachidonic acid and total omega-6 fatty acids than the bloater profile. The concentrations of four fatty acids (cis-13, 16-docosadienoic, eicosapentaenoic, docosapentaenoic, and docosahexaenoic acids) were higher in bloaters than in alewives. Although six fatty acid components were higher in lake trout eggs in 2001 than in 2000 and eight fatty acids were lower, diet had no effect on any fatty acid concentration measured in lake trout eggs in this study. Based on these results, it appears that egg fatty acid concentrations differ between years but that the egg fatty acid profile does not reflect the alewife-bloater mix in the diet of adults. The essential fatty acid content of lake trout eggs from females fed alewives and bloaters appears to be physiologically regulated and adequate to meet the requirements of developing embryos.

  13. Egg fatty acid composition from lake trout fed two Lake Michigan prey fish species.

    Science.gov (United States)

    Honeyfield, Dale C; Fitzsimons, John D; Tillitt, Donald E; Brown, Scott B

    2009-12-01

    We previously demonstrated that there were significant differences in the egg thiamine content in lake trout Salvelinus namaycush fed two Lake Michigan prey fish (alewife Alosa pseudoharengus and bloater Coregonus hoyi). Lake trout fed alewives produced eggs low in thiamine, but it was unknown whether the consumption of alewives affected other nutritionally important components. In this study we investigated the fatty acid composition of lake trout eggs when females were fed diets that resulted in different egg thiamine concentrations. For 2 years, adult lake trout were fed diets consisting of four combinations of captured alewives and bloaters (100% alewives; 65% alewives, 35% bloaters; 35% alewives, 65% bloaters; and 100% bloaters). The alewife fatty acid profile had higher concentrations of arachidonic acid and total omega-6 fatty acids than the bloater profile. The concentrations of four fatty acids (cis-13, 16-docosadienoic, eicosapentaenoic, docosapentaenoic, and docosahexaenoic acids) were higher in bloaters than in alewives. Although six fatty acid components were higher in lake trout eggs in 2001 than in 2000 and eight fatty acids were lower, diet had no effect on any fatty acid concentration measured in lake trout eggs in this study. Based on these results, it appears that egg fatty acid concentrations differ between years but that the egg fatty acid profile does not reflect the alewife-bloater mix in the diet of adults. The essential fatty acid content of lake trout eggs from females fed alewives and bloaters appears to be physiologically regulated and adequate to meet the requirements of developing embryos.

  14. Primordial soup or vinaigrette: did the RNA world evolve at acidic pH?

    Directory of Open Access Journals (Sweden)

    Bernhardt Harold S

    2012-01-01

    Full Text Available Abstract Background The RNA world concept has wide, though certainly not unanimous, support within the origin-of-life scientific community. One view is that life may have emerged as early as the Hadean Eon 4.3-3.8 billion years ago with an atmosphere of high CO2 producing an acidic ocean of the order of pH 3.5-6. Compatible with this scenario is the intriguing proposal that life arose within alkaline (pH 9-11 deep-sea hydrothermal vents like those of the 'Lost City', with the interface with the acidic ocean creating a proton gradient sufficient to drive the first metabolism. However, RNA is most stable at pH 4-5 and is unstable at alkaline pH, raising the possibility that RNA may have first arisen in the acidic ocean itself (possibly near an acidic hydrothermal vent, acidic volcanic lake or comet pond. As the Hadean Eon progressed, the ocean pH is inferred to have gradually risen to near neutral as atmospheric CO2 levels decreased. Presentation of the hypothesis We propose that RNA is well suited for a world evolving at acidic pH. This is supported by the enhanced stability at acidic pH of not only the RNA phosphodiester bond but also of the aminoacyl-(tRNA and peptide bonds. Examples of in vitro-selected ribozymes with activities at acid pH have recently been documented. The subsequent transition to a DNA genome could have been partly driven by the gradual rise in ocean pH, since DNA has greater stability than RNA at alkaline pH, but not at acidic pH. Testing the hypothesis We have proposed mechanisms for two key RNA world activities that are compatible with an acidic milieu: (i non-enzymatic RNA replication of a hemi-protonated cytosine-rich oligonucleotide, and (ii specific aminoacylation of tRNA/hairpins through triple helix interactions between the helical aminoacyl stem and a single-stranded aminoacylating ribozyme. Implications of the hypothesis Our hypothesis casts doubt on the hypothesis that RNA evolved in the vicinity of alkaline

  15. Geochemistry, mineralogy, and chemical modeling of the acid crater lake of Kawah Ijen Volcano, Indonesia

    Science.gov (United States)

    Delmelle, Pierre; Bernard, Alain

    1994-06-01

    The Kawah Ijen volcano—with a record of phreatic eruptions—has its 1000 m wide crater filled with a lake that has existed for at least one century. At present, the lake waters are hot ( T ≈ 37° C), strongly mineralized (TDS = 105 g/L) and extremely acidic ( pH ≈ 0.4). By its volume, the Javanese lake is probably the largest accumulation in the world of such acidic waters. Mineralogy of the suspended solids within the lake waters suggests that concentrations of Si, Ca, Ti, and Ba are controlled by precipitation of silica, gypsum, anatase, and barite. Lake sediment is composed of chemical precipitates with composition similar to the suspended solids. Thermodynamic calculations predict that the lake waters have reached equilibrium with respect to α-cristobalite, barite, gypsum, anglesite, celestite, and amorphous silica, in agreement with the analytical observations. Significant concentrations of ferric iron suggest that the current lake waters are fairly oxidized. Sulfides are absent in the water column but are always present in the native S spherules that form porous aggregates which float on the lake. The presence of native S provides direct evidence of more reduced conditions at the lake floor where H 2S is probably being injected into the lake. With progressive addition of H 2S to the acid waters, native S, pyrite, and enargite are theoretically predicted to be saturated. Reactions between upward streaming H 2S-bearing gases discharged by subaqueous fumaroles, and metals dissolved in the acidic waters could initiate precipitation of these sulfides. A model of direct absorption of hot magmatic gases into cool water accounts for the extreme acidity of the crater lake. Results show that strongly acidic, sulfate-rich solutions are formed under oxidizing conditions at high gas/water ratios. Reactions between the acidic fluids and the Ijen andesite were modeled to account for elevated cation concentrations in lake water. Current concentrations of conservative

  16. Reduction of dehydroascorbic acid at low pH.

    Science.gov (United States)

    Wechtersbach, Luka; Cigić, Blaz

    2007-08-01

    Ascorbic acid and dehydroascorbic acid are unstable in aqueous solution in the presence of copper and iron ions, causing problems in the routine analysis of vitamin C. Their stability can be improved by lowering the pH below 2, preferably with metaphosphoric acid. Dehydroascorbic acid, an oxidised form of vitamin C, gives a relatively low response on the majority of chromatographic detectors, and is therefore routinely determined as the increase of ascorbic acid formed after reduction. The reduction step is routinely performed at a pH that is suboptimal for the stability of both forms. In this paper, the reduction of dehydroascorbic acid with tris-[2-carboxyethyl] phosphine (TCEP) at pH below 2 is evaluated. Dehydroascorbic acid is fully reduced with TCEP in metaphosphoric acid in less than 20 min, and yields of ascorbic acid are the same as at higher pH. TCEP and ascorbic acid formed by reduction, are more stable in metaphosphoric acid than in acetate or citrate buffers at pH 5, in the presence of redox active copper ions. The simple experimental procedure and low probability of artefacts are major benefits of this method, over those currently applied in a routine assay of vitamin C, performed on large number of samples.

  17. Chemical hazards from acid crater lakes

    Science.gov (United States)

    van Bergen, M. J.; Sumarti, S.; Heikens, A.; Bogaard, T. A.; Hartiyatun, S.

    2003-04-01

    Acid crater lakes, which are hosted by a considerable number of active volcanoes, form a potential threat for local ecosystems and human health, as they commonly contain large amounts of dissolved chemicals. Subsurface seepage or overflow can lead to severe deterioration of the water quality of rivers and wells, as observations around several of these volcanoes have shown. The Ijen crater lake in East Java (Indonesia) is a striking example, as this reservoir of hyperacid (pHdental fluorosis is widespread among the ca. 100,000 residents of the area. A conspicuous spatial correlation between fluoride concentrations and the irrigation system suggest that long-term (century) infiltration of irrigation water may have affected the quality of groundwater. Fluorosis is also a problem in some villages within the caldera, where well water sources may have a more direct subsurface connection with the lake system. From our observations we conclude that water-quality monitoring is especially needed for health reasons in volcanic areas where volatile elements, derived from passively degassing magma, are intercepted by (sub) surface water bodies.

  18. Recently surveyed lakes in northern Manitoba and Saskatchewan, Canada: characteristics and critical loads of acidity

    Directory of Open Access Journals (Sweden)

    Isaac WONG

    2010-08-01

    Full Text Available Based on minimal information, lakes in the western Canadian provinces of Manitoba (MB and Saskatchewan (SK have long been considered unaffected by acid rain. However, emissions of acidifying pollutants from MB smelters and oil sand processing in Alberta (AB may pose a developing threat. Surveys of 347 lakes located on geologically sensitive terrain in northern MB and SK were conducted to assess their acidification sensitivity and status. The survey domain (~193,000 km2 contained 81,494 lakes ≥1 ha in area. Small lakes dominated the inventory in terms of numbers, and large lakes dominated in terms of area. Survey lakes were selected using a stratified-random sampling design in 10 sampling blocks within the overall survey domain. Few lakes had pH <6, and only three (all in SK were acidic, i.e., Gran Alkalinity (Alk <0 μeq L–1. A broad range in lake sensitivity was apparent, and very sensitive lakes (low specific conductance, base cations and Alk were present in all sampling blocks. Dissolved organic carbon (DOC was an important constituent of many lakes. Critical loads (CL of acidity calculated using the Steady-State Water Chemistry model (SSWC revealed extremely low 5th percentile values for every block (range 1.9 to 52.7 eq ha–1 y–1. Block CL exceedances calculated using estimated S and N deposition for 2002 ranged from 54.5 to 909 eq ha–1 y–1. The largest exceedances were for sampling blocks located near smelter sources or downwind of the oil sands. Lake chemistry revealed by our surveys was compared to others conducted both nearby and outside Canada.

  19. Titratable acidity of beverages influences salivary pH recovery

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    Livia Maria Andaló TENUTA

    2015-01-01

    Full Text Available A low pH and a high titratable acidity of juices and cola-based beverages are relevant factors that contribute to dental erosion, but the relative importance of these properties to maintain salivary pH at demineralizing levels for long periods of time after drinking is unknown. In this crossover study conducted in vivo, orange juice, a cola-based soft drink, and a 10% sucrose solution (negative control were tested. These drinks differ in terms of their pH (3.5 ± 0.04, 2.5 ± 0.05, and 5.9 ± 0.1, respectively and titratable acidity (3.17 ± 0.06, 0.57 ± 0.04 and < 0.005 mmols OH- to reach pH 5.5, respectively. Eight volunteers with a normal salivary flow rate and buffering capacity kept 15 mL of each beverage in their mouth for 10 s, expectorated it, and their saliva was collected after 15, 30, 45, 60, 90, and 120 s. The salivary pH, determined using a mini pH electrode, returned to the baseline value at 30 s after expectoration of the cola-based soft drink, but only at 90 s after expectoration of the orange juice. The salivary pH increased to greater than 5.5 at 15 s after expectoration of the cola drink and at 30 s after expectoration of the orange juice. These findings suggest that the titratable acidity of a beverage influences salivary pH values after drinking acidic beverages more than the beverage pH.

  20. Titratable acidity of beverages influences salivary pH recovery.

    Science.gov (United States)

    Tenuta, Livia Maria Andaló; Fernández, Constanza Estefany; Brandão, Ana Carolina Siqueira; Cury, Jaime Aparecido

    2015-01-01

    A low pH and a high titratable acidity of juices and cola-based beverages are relevant factors that contribute to dental erosion, but the relative importance of these properties to maintain salivary pH at demineralizing levels for long periods of time after drinking is unknown. In this crossover study conducted in vivo, orange juice, a cola-based soft drink, and a 10% sucrose solution (negative control) were tested. These drinks differ in terms of their pH (3.5 ± 0.04, 2.5 ± 0.05, and 5.9 ± 0.1, respectively) and titratable acidity (3.17 ± 0.06, 0.57 ± 0.04 and pH 5.5, respectively). Eight volunteers with a normal salivary flow rate and buffering capacity kept 15 mL of each beverage in their mouth for 10 s, expectorated it, and their saliva was collected after 15, 30, 45, 60, 90, and 120 s. The salivary pH, determined using a mini pH electrode, returned to the baseline value at 30 s after expectoration of the cola-based soft drink, but only at 90 s after expectoration of the orange juice. The salivary pH increased to greater than 5.5 at 15 s after expectoration of the cola drink and at 30 s after expectoration of the orange juice. These findings suggest that the titratable acidity of a beverage influences salivary pH values after drinking acidic beverages more than the beverage pH.

  1. Metabolism of nonparticulate phosphorus in an acid bog lake

    Energy Technology Data Exchange (ETDEWEB)

    Koenings, J. P.

    1977-01-01

    In North Gate Lake, an acid bog lake located on the northern Michigan-Wisconsin border, U.S.A., the algal nutrient inorganic phosphate (FRP) is not detectable by chemical means. Organic phosphorus (FUP) represents 100% of the detectable filterable phosphorus. The availability and cycling of this organic fraction are of considerable interest in regard to the primary productivity of this system. To clarify these relationships, the cycling of nonparticulate forms of phosphorus found in the epilimnion of this lake was studied.

  2. The complementary power of pH and lake-water organic carbon reconstructions for discerning the influences on surface waters across decadal to millennial time scales

    Directory of Open Access Journals (Sweden)

    P. Rosén

    2011-09-01

    Full Text Available Lysevatten, a lake in southwest Sweden, has experienced both acidification and recent changes in the amount of lake-water organic carbon (TOC, both causing concern across Europe and North America. A range of paleolimnological tools – diatom-inferred pH, inferred lake-water TOC from visible-near-infrared spectroscopy (VNIRS, multi-element geochemistry and pollen analysis, combined with geochemical modeling were used to reconstruct the lake's chemistry and surroundings back to the most recent deglaciation 12 500 years ago. The results reveal that the recent anthropogenic impacts are similar in magnitude to the long-term variation driven by natural catchment changes and early agricultural land use occurring over centuries and millennia. The combined reconstruction of both lake-water TOC and lithogenic element delivery can explain the major changes in lake-water pH and modeled acid neutralizing capacity during the past 12 500 years. The results raise important questions regarding what precisely comprises "reference" conditions (i.e., free from human impacts as defined in the European Water Framework Directive.

  3. Characterization of three acid strip mine lakes in Grundy County, Illinois

    Energy Technology Data Exchange (ETDEWEB)

    Master, W. A.

    1979-09-01

    Three small lakes with acid water and one with circumneutral water at an abandoned strip mine site were characterized to identify factors limiting biological productivity. Dissolved oxygen, specific conductance, and temperature profiles were determined. Water samples were analyzed for 23 parameters, and the lakes were examined for the presence of aquatic vascular plants and benthic inhabitants. The acid lakes ranged from 0.9 ha to 2.7 ha in surface area and from 3.1 m to 6.7 m in maximum depth. The mean pH of the acid lakes ranged from 3.1 to 3.9. Chemicals found at concentrations higher than Illinois surface water standards or federal criteria for the protection of aquatic life included Cd, Cu, Fe, Mn, SO/sub 4/=, and Zn. A number of these chemicals were at sufficiently high concentrations to limit the survival and productivity of most aquatic fauna. The lake with the poorest water quality had the least diversity of aquatic vascular plants and benthic invertebrates, while the circumneutral lake had the greatest diversity of species.

  4. TRPV1 senses both acidic and basic pH

    OpenAIRE

    Dhaka, Ajay; Uzzell, Valerie; Dubin, Adrienne; Mathur, Jayanti; Petrus, Matt; Bandell, Michael; Patapoutian, Ardem

    2009-01-01

    Maintaining physiological pH is required for survival, and exposure to alkaline chemicals such as ammonia (smelling salts) elicits severe pain and inflammation through unknown mechanisms. TRPV1, the capsaicin receptor, is an integrator of noxious stimuli including heat and extracellular acidic pH. Here we report that ammonia activates TRPV1, TRPA1 (another polymodal nocisensor), and other unknown receptor(s) expressed in sensory neurons. Ammonia and intracellular alkalization activate TRPV1 t...

  5. Geochemistry of highly acidic mine water following disposal into a natural lake with carbonate bedrock

    Energy Technology Data Exchange (ETDEWEB)

    Wisskirchen, Christian, E-mail: ChristianWisskirchen@web.de [Institute of Mineralogy and Geochemistry, University of Lausanne, CH-1015 Lausanne (Switzerland); Dold, Bernhard [Institute of Mineralogy and Geochemistry, University of Lausanne, CH-1015 Lausanne (Switzerland)] [Instituto de Geologia Economica Aplicada, Universidad de Concepcion, Concepcion (Chile); Friese, Kurt [UFZ - Helmholtz Centre for Environmental Research, Department of Lake Research, D-39114 Magdeburg (Germany); Spangenberg, Jorge E. [Institute of Mineralogy and Geochemistry, University of Lausanne, CH-1015 Lausanne (Switzerland); Morgenstern, Peter [UFZ - Helmholtz Centre for Environmental Research, Department of Analytical Chemistry, D-04318 Leipzig (Germany); Glaesser, Walter [Institute of Geophysics and Geology, University of Leipzig, D-04211 Leipzig (Germany)

    2010-08-15

    Research highlights: {yields} Mean lake water element composition did not differ greatly from discharged AMD. {yields} Most elements showed increasing concentrations from the surface to lake bottom. {yields} Jarosite formed in the upper part, settled, and dissolved in the deeper part of the lake. {yields} Elements migrated into the underlying carbonates in the sequence As< Pb {approx} Cu < Cd < Zn = Mn. {yields} Gypsum and hydroxide precipitation had not resulted in complete clogging of the lake bedrocks. - Abstract: Acid mine drainage (AMD) from the Zn-Pb(-Ag-Bi-Cu) deposit of Cerro de Pasco (Central Peru) and waste water from a Cu-extraction plant has been discharged since 1981 into Lake Yanamate, a natural lake with carbonate bedrock. The lake has developed a highly acidic pH of {approx}1. Mean lake water chemistry was characterized by 16,775 mg/L acidity as CaCO{sub 3}, 4330 mg/L Fe and 29,250 mg/L SO{sub 4}. Mean trace element concentrations were 86.8 mg/L Cu, 493 mg/L Zn, 2.9 mg/L Pb and 48 mg/L As, which did not differ greatly from the discharged AMD. Most elements showed increasing concentrations from the surface to the lake bottom at a maximal depth of 41 m (e.g. from 3581 to 5433 mg/L Fe and 25,609 to 35,959 mg/L SO{sub 4}). The variations in the H and O isotope compositions and the element concentrations within the upper 10 m of the water column suggest mixing with recently discharged AMD, shallow groundwater and precipitation waters. Below 15 m a stagnant zone had developed. Gypsum (saturation index, SI {approx} 0.25) and anglesite (SI {approx} 0.1) were in equilibrium with lake water. Jarosite was oversaturated (SI {approx} 1.7) in the upper part of the water column, resulting in downward settling and re-dissolution in the lower part of the water column (SI {approx} -0.7). Accordingly, jarosite was only found in sediments from less than 7 m water depth. At the lake bottom, a layer of gel-like material ({approx}90 wt.% water) of pH {approx}1 with a

  6. Impacts on water quality and biota from natural acid rock drainage in Colorado's Lake Creek watershed

    Science.gov (United States)

    Bird, D.A.; Sares, Matthew A.; Policky, Greg A.; Schmidt, Travis S.; Church, Stanley E.

    2006-01-01

    Colorado's Lake Creek watershed hosts natural acid rock drainage that significantly impacts surface water, streambed sediment, and aquatic life. The source of the ARD is a group of iron-rich springs that emerge from intensely hydrothermally altered, unexploited, low-grade porphyry copper mineralization in the Grizzly Peak Caldera. Source water chemistry includes pH of 2.5 and dissolved metal concentrations of up to 277 mg/L aluminum, 498 mg/L iron, and 10 mg/L copper. From the hydrothermally altered area downstream for 27 kilometers to Twin Lakes Reservoir, metal concentrations in streambed sediment are elevated and the watershed experiences locally severe adverse impacts to aquatic life due to the acidic, metal-laden water. The water and sediment quality of Twin Lakes Reservoir is sufficiently improved that the reservoir supports a trout fishery, and remnants of upstream ARD are negligible.

  7. Testing the steady-state water chemistry model predictions of pre-industrial lake pH with paleolimnological data from northern Sweden.

    Science.gov (United States)

    Bishop, K; Rapp, L; Köhler, S; Korsman, T

    2008-12-15

    Criteria are needed for distinguishing naturally acid water from that acidified by air pollution, especially in the organic-rich waters of northern Sweden. The Steady-State Water Chemistry Model (SSWC) was augmented to include organic acidity so that it could predict pre-industrial pH in organic-rich waters. The resulting model predictions of pre-industrial ANC and pH were then tested against diatom predictions of pre-industrial pH and alkalinity in 58 lakes from N. Sweden (after alkalinity was converted to ANC using the CBALK method). The SSWC Model's predictions of pre-industrial lake pH in N. Sweden did not correspond well with the diatom predictions, even when accounting for the uncertainty in the diatom model. This was due to the SSWC's sensitivity to short-term fluctuations in contemporary water chemistry. Thus the SSWC Model is not suitable for judging the acidification of individual lakes in areas such as northern Sweden where the degree of chronic acidification is small, or without a good average value of contemporary water chemistry. These results should be considered when assessing the accuracy of critical loads calculated using SSWC.

  8. Sulfate Reduction at Low Ph To Remediate Acid Mine Drainage

    NARCIS (Netherlands)

    Sánchez-Andrea, I.; Sanz, J.L.; Bijmans, M.F.M.; Stams, A.J.M.

    2014-01-01

    Industrial activities and the natural oxidation of metallic sulfide-ores produce sulfate-rich waters with low pH and high heavy metals content, generally termed acid mine drainage (AMD). This is of great environmental concern as some heavy metals are highly toxic. Within a number of possibilities,

  9. Sulfate Reduction at Low Ph To Remediate Acid Mine Drainage

    NARCIS (Netherlands)

    Sánchez-Andrea, I.; Sanz, J.L.; Bijmans, M.F.M.; Stams, A.J.M.

    2014-01-01

    Industrial activities and the natural oxidation of metallic sulfide-ores produce sulfate-rich waters with low pH and high heavy metals content, generally termed acid mine drainage (AMD). This is of great environmental concern as some heavy metals are highly toxic. Within a number of possibilities, b

  10. Epilithic algae as indicators of biological recovery in acid-stresed lakes

    Energy Technology Data Exchange (ETDEWEB)

    Vinebrooke, R.D.

    1993-01-01

    The responsiveness of benthic algae to lake acidification and chemical recovery prompted a survey of epilithic algae along an acid-stressed lake gradient. A primary acid-stress recovery gradient, best defined by increasing dissolved inorganic carbon, was characterized by increasing epilithic algal production, and a shift from an Actinotaenium cucurbita/Fragilaria acidobiontica/Homoeothrix juliana/Zygogonium ericetorum to an Achnanthes minutissima/Cymbella spp./Gomphonema spp. indicator assemblage. Increased total, filamentous green, and desmid production, and a shift towards a placoderm desmid-dominated community, typified a secondary recovery gradient defined by increasing water colour. A reciprocal transplant experiment indicated that physiological tolerance of acid-stress was the primary ecological mechanism regulating epilithic algal production and community structure. Macrograzing was of secondary importance, affecting community architecture and species composition only in low acid-stressed habitats. Tadpoles reduced the growth of metaphyton-forming epilithic algae by selective removal of loosely attached filaments of zygnematacean genera. Metaphytic algae from two lakes of different acid-stress levels had contrasting acidity and aluminium tolerance ranges. Z. ericetorum had both a low pH optimum and relative growth rate, along with high aluminium resistance, while a less acidophilic Z. tunetanum exhibited faster growth over a broader range of acidities, but also sensitivity to aluminium concentrations in excess of naturally occurring background levels. 172 refs., 30 figs., 11 tabs.

  11. Detecting acid precipitation impacts on lake water quality

    Science.gov (United States)

    Loftis, Jim C.; Taylor, Charles H.

    1989-09-01

    The United States Environmental Protection Agency is planning to expand its long-term monitoring of lakes that are sensitive to acid deposition effects. Effective use of resources will require a careful definition of the statistical objectives of monitoring, a network design which balances spatial and temporal coverage, and a sound approach to data analysis. This study examines the monitoring objective of detecting trends in water quality for individual lakes and small groups of lakes. Appropriate methods of trend analysis are suggested, and the power of trend detection under seasonal (quarterly) sampling is compared to that of annual sampling. The effects of both temporal and spatial correlation on trend detection ability are described.

  12. Water pH and temperature in Lake Biwa from MBT'/CBT indices during the last 280 000 years

    Science.gov (United States)

    Ajioka, T.; Yamamoto, M.; Takemura, K.; Hayashida, A.; Kitagawa, H.

    2014-10-01

    We generated a 280 000 yr record of water pH and temperature in Lake Biwa, central Japan, by analysing the methylation index (MBT') and cyclisation ratio (CBT) of branched tetraethers in sediments from piston and borehole cores. Our aim was to understand the responses of precipitation and air temperature in central Japan to the East Asian monsoon variability on orbital timescales. Because the water pH in Lake Biwa is determined by phosphorus and alkali cation inputs, the record of water pH should indicate the changes in precipitation and temperature in central Japan. Comparison with a pollen assemblage in a Lake Biwa core suggests that lake water pH was determined by summer temperature in the low-eccentricity period before 55 ka, while it was determined by summer precipitation in the high-eccentricity period after 55 ka. From 130 to 55 ka, the variation in lake pH (summer precipitation) lagged behind that in summer temperature by several thousand years. This perspective is consistent with the conclusions of previous studies (Igarashi and Oba, 2006; Yamamoto, 2009), in that the temperature variation preceded the precipitation variation in central Japan.

  13. Critical loads of acidity for 90,000 lakes in northern Saskatchewan: A novel approach for mapping regional sensitivity to acidic deposition

    Science.gov (United States)

    Cathcart, H.; Aherne, J.; Jeffries, D. S.; Scott, K. A.

    2016-12-01

    Atmospheric emissions of sulphur dioxide (SO2) from large point sources are the primary concern for acidic deposition in western Canada, particularly in the Athabasca Oil Sands Region (AOSR) where prevailing winds may potentially carry SO2 over acid-sensitive lakes in northern Saskatchewan. A novel catchment-scale regression kriging approach was used to assess regional sensitivity and critical loads of acidity for the total lake population of northern Saskatchewan (89,947 lakes). Lake catchments were delineated using Thiessen polygons, and surface water chemistry was predicted for sensitivity indicators (calcium, pH, alkalinity, and acid neutralizing capacity). Critical loads were calculated with the steady state water chemistry model using regression-kriged base cations, sulphate, and dissolved organic carbon concentrations modelled from surface water observations (n > 800) and digital landscape-scale characteristics, e.g., climate, soil, vegetation, landcover, and geology maps. A large region (>13,726 km2) of two or more indicators of acid sensitivity (pH acid neutralizing capacity, alkalinity, calcium acidic deposition in excess of their critical loads and many of them may be at risk of ecosystem damage owing to their sensitivity.

  14. Effects of pH and Eh on release of nitrogen and phosphorus from sediments of West Lake

    Institute of Scientific and Technical Information of China (English)

    胡勤海; 朱荫湄; 宋静; 李震宇; 温军杰

    2003-01-01

    The effects of pH and Eh on release of nitrogen and phosphorus from sediments of West Lake under different conditions were investigated by simulation test. Results showed that the net flux of NH4+-N release from sediments increased with pH, but NO3--N showed negative-going release at all tested pH levels. The net flux of NH4+-N release from sediments was higher under anaerobic or aerobic condition of the overlying water, but only under aerobic condition would net release of NO3--N occur. It was also shown that phosphorus released was mainly in its inorganic form, higher pH and anaerobic conditions of overlying water greatly stimulated release of phosphorus. In situ measurement at several West Lake locations indicated that sediment resuspension induced by boat propeller stimulated nutrients release from sediment into overlying water.

  15. Thiamine and fatty acid content of Lake Michigan Chinook salmon

    Science.gov (United States)

    Honeyfield, D.C.; Peters, A.K.; Jones, M.L.

    2008-01-01

    Nutritional status of Lake Michigan Chinook salmon (Oncorhynchus tshawytscha) is inadequately documented. An investigation was conducted to determine muscle and liver thiamine content and whole body fatty acid composition in small, medium and large Chinook salmon. Muscle and liver thiamine concentrations were highest in small salmon, and tended to decrease with increasing fish size. Muscle thiamine was higher in fall than spring in large salmon. The high percentage of Chinook salmon (24-32% in fall and 58-71% in spring) with muscle thiamine concentration below 500 pmol/g, which has been associated with loss of equilibrium and death in other Great Lake salmonines, suggest that Chinook appear to rely less on thiamine than other Great Lakes species for which such low concentrations would be associated with thiamine deficiency (Brown et al. 2005b). A positive correlation was observed between liver total thiamine and percent liver lipids (r = 0.53, P salmon, liver lipids were observed to be low in fish with less than 4,000 pmol/g liver total thiamine. In individuals with greater than 4,000 pmol/g liver thiamine, liver lipid increased with thiamine concentration. Individual fatty acids declined between fall and spring. Essential omega-3 fatty acids appear to be conserved as lipid content declined. Arachidonic acid (C20:4n6), an essential omega-6 fatty acid was not different between fall and spring, although the sum of omega-6 (Sw6) fatty acids declined over winter. Elevated concentrations of saturated fatty acids (sum) were observed in whole body tissue lipid. In summary, thiamine, a dietary essential vitamin, and individual fatty acids were found to vary in Lake Michigan Chinook salmon by fish size and season of the year.

  16. Analysis and solution of abnormal PH in Shang Lake%尚湖原水pH异常原因分析及应对

    Institute of Scientific and Technical Information of China (English)

    狄春华; 施学峰

    2011-01-01

    目的:调查研究尚湖原水pH异常原因,采取相应的措施予以应对.方法:分析2007年-2008年期间尚湖原水pH值与气候、溶解氧、总硬度、总碱度以及藻类之间关系,并结合现场调杳.结果:尚湖东部水域沉水植物大量繁殖,强烈的光合作用导致取水口原水pH值异常升高,并抑制了藻类的生长.结论:沉水植物大量繁殖有利于净化原水水质,在水厂投加盐酸可以将原水pH调节到适当的范围,确保饮用水安全.%Objective:To find out the reasons of abnormal pH value of raw water in Shang lake, and to deal with them by proper measures. Methods; Based on the field investigation, the relation of pH value with climate, dissolved oxygen, total hardness, total alkalinity, the number of algae of Shang Lake during 2007 and 2008 were analyzed. Results: In the east areas of Shang Lake, the strong photosynthesis of multiplying submerged plants led raw water pH value to increase abnormally, and restrained the growth of algaes. Conclusion: The multiplying of submerged plants purified the raw water quality. In water plant, the raw water pH value was adjusted to normal level by adding hydrochloric acid, to make sure the safety of drinking water.

  17. Composite Biofilms grown in Acidic Mining Lakes and assessed by Electron Microscopy and Molecular Techniques

    Energy Technology Data Exchange (ETDEWEB)

    Luensdorf, Heinrich; Wenderoth, Dirk F.; Abraham, Wolf-Rainer [GBF, German Research Center for Biotechnology, Department Environmental Microbiology (Germany)], E-mail: wab@gbf.de

    2002-05-15

    Microbial consortia of composite biofilms, grown in surface water of acidicmining lakes near Lauchhammer, Germany, were investigated. The red-brown colored lake water was acidic (pH 2.5), had high concentrations of Fe(III), Al(III), and sulphate and low concentrations of dissolved organic matter. As a result the abundance of bacteria in the lake is with 10{sup 4} cells mL{sup -1} rather low. One input of organic material into the lake are autumnal leaves from trees, growing in the lakeside area. From aliquots of unfixed birch leave biofilms the 16S rRNA genes were amplified by PCR and community fingerprints were determined by single-strand conformation polymorphism (SSCP) analysis. Specific bands within the fingerprints were extracted from SSCP gels and sequenced for the taxonomical affiliation.These results were compared with those from the second type of biofilms which were grown on sterile substrata, floating submersed in surface waters of the lakes. By excising the bands from the gel and sequencing the individual bands bacterial taxa, common to both types of biofilms, were found but also some, which were only present in one type of biofilm. Ultrathin sectioned biofilms often showed bacteria associated with electron dense particles as main inorganic constituents. Elemental microanalysis by energy dispersive X-ray analysis (EDX) revealed them to contain iron, sulfur and oxygen as main elemental fractions and electron diffraction ring pattern analysis classified them to be schwertmannite. These bacteria and their interactions with each other as well as with the inorganic minerals formed in this lake generally is of great interest, in order to use these results for bioremediation applications.

  18. Spatial and spectral characterization of acid rain stress in Canadian Shield lakes

    Science.gov (United States)

    Marshall, Elizabeth J.; Tanis, Frederick J.

    1989-01-01

    Results from this study demonstrate that a remote sensor can discriminate lake clarity based upon reflection. The basic hypothesis was that seasonal and multiyear changes in lake optical transparency are indicative of sensitivity to acidic deposition. In many acid-sensitive lakes optical transparency is controlled by the amount of dissolved organic carbon (DOC) present. DOC is a strong absorbing, nonscattering material which has the greatest impact at short visible wavelengths, including Thematic Mapper band 1. Acid-sensitive lakes have high concentrations of aluminum which have been mobilized by acidic components contained in the runoff. Aluminum complexing with DOC is considered to be the primary mechanism to account for observed increases in lake transparency in acid-sensitive lakes. Thus seasonal changes in the optical transparency of lakes should provide an indication of the stress due to acid deposition and loading.

  19. Effect of pH, sulphate concentration and total organic carbon on mercury accumulation in sediments in the Volta Lake at Yeji, Ghana.

    Science.gov (United States)

    Kwaansa-Ansah, E E; Voegborlo, R B; Adimado, A A; Ephraim, J H; Nriagu, J O

    2012-03-01

    In this study, pH, total organic carbon, sulphate concentration and mercury concentrations of sediment samples from the Volta Lake at Yeji in the northern part of Ghana were determined. The results indicate that pH ranged from 6.32 to 8.21, total organic carbon ranged from 0.17 to 3.02 g/kg and sulphate concentration from 10.00 to 57.51 mg/kg. Total mercury concentrations ranged from 32.61 to 700 ng/g which is below the International Atomic Energy Agency recommended value of 810 ng/g. Humic substance-bound mercury ranged from 81.15 to 481.31 mg/kg in sediments and its two fractions existed as humic acid-bound mercury > fulvic acid-bound mercury with the ratio of humic substance-bound mercury to fulvic acid-bound mercury as 1.62 on the average. Humic substance-bound mercury and the two fractions fulvic acid-bound mercury and humic substance-bound mercury in sediments were favorably determined and found to correlate significantly positive with total organic carbon (r = 0.538) and total mercury (r = 0.574). However, there were poor correlations between SO(4) (2-) concentrations and humic substance-bound mercury (r = -0.391) as well as the two fractions; fulvic acid (r = -0.406) and humic acid (r = -0.381). By assuming that methyl mercury is mostly formed in sediments, these significant relations suggest that the efficiency of mercury being methylated from a given inorganic form depends on the amount, and most likely biochemical composition of total organic carbon in the lake sediment but not the SO(4) (2-) concentration.

  20. Water pH and temperature in Lake Biwa from MBT'/CBT indices during the last 282 000 years

    Science.gov (United States)

    Ajioka, T.; Yamamoto, M.; Takemura, K.; Hayashida, A.

    2014-03-01

    We generated a 282 000-year record of water pH and temperature in Lake Biwa, central Japan, by analysing the methylation index (MBT') and cyclisation ratio (CBT) of branched tetraethers in sediments from piston and borehole cores to understand the responses of precipitation and air temperature in central Japan to the East Asian monsoon variability on the orbital timescale. Because water pH in Lake Biwa is determined by phosphorus input driven by precipitation, the record of water pH should indicate changes in summer precipitation in central Japan. The estimated pH showed significant periodicity at 19 and 23 ka (precession) and at 41 ka (obliquity). The variation in the estimated pH agrees with variation in the pollen temperature index. This indicates synchronous variation in summer air temperature and precipitation in central Japan, which contradicts the conclusions of previous studies. The variation in estimated pH was also synchronous with the variation of oxygen isotopes in stalagmites in China, suggesting that East Asian summer monsoon precipitation was governed by Northern Hemisphere summer insolation on orbital timescales. However, the estimated winter temperatures were higher during interglacials and lower during glacials, showing an eccentricity cycle. This suggests that the temperature variation reflected winter monsoon variability.

  1. An overview of a uranium acidic mining lake (Caldas, Brazil): composition of the zooplankton community and limno-chemical aspects

    Energy Technology Data Exchange (ETDEWEB)

    Nascimento, H.; Ferrari, C.; Roque, C.V.; Nascimento, M.R. [Brazilian Nuclear Energy Commission/Pocos de Caldas Laboratory (Brazil); Wisniewski, M.J. [Alfenas Federal University/Limnology Laboratory (Brazil); Rodgher, S. [Universidade Estadual Paulista Julio de Mesquita Filho/Science and Technology Laboratory (Brazil)

    2014-07-01

    This research represents an attempt to fill a gap in the information on the zooplankton composition and limno-chemical aspects of the uranium pit lake (Osamu Utsumi Pit, Brazil), affected by acid mine drainage. In the present study water samples were collected three-monthly, for a period of one year (2008-2009). The water samples from the uranium pit lake showed moderately acidic pH values (3.6 to 4.1), high values of the electrical conductivity, sulfate, uranium, fluoride, zinc, manganese and aluminum concentrations. The Rotifera cephalodella sp., Keratella americana, K. cochlearis, Bdelloidea order and the Cladocera Bosminopsis deitersi, Bosmina sp., were registered in the samples from the uranium pit lake with ADM. Of the species registered the Bdelloidea order was the most important in terms of density (17,500 - 77,778 ind m{sup -3}), since it occurred throughout the whole sampling period. In this study, probably the combined effect of moderately acid pH values and other potentially co-stressors factors, for example the high concentrations of stable and radioactive chemical species, could have influenced this richness and also the composition of the zooplankton species in the water samples from the uranium pit lake. Document available in abstract form only. (authors)

  2. Using Australian Acidic Playa Lakes as Analogs for Phyllosilicate and Sulfate Depositional Environments on Mars

    Science.gov (United States)

    Baldridge, A. M.; Michalski, J.; Kargel, J.; Hook, S.; Marion, G.; Crowley, J.; Bridges, N.; Brown, A.; Ribeiro da Luz, B.; de Souza Filho, C. R.; Thomson, B.

    2008-12-01

    Recent work on the origin of martian sulfates and their relationship to phyllosilicate deposits suggest that these deposits formed in different eras of Mars' history, under distinct environmental conditions. In southwestern Meridiani Planum phyllosilicates exist in close proximity to sulfate deposits. One possible explanation for this relationship is that it is an unconformable stratigraphic sequence, representing a significant change in aqueous geochemical conditions over time. Specifically, it may be interpreted to record a change in environment from neutral pH aqueous alteration in the Noachian to an acidic evaporitic system in the late Noachian to the Hesperian. On Earth, two different geochemical systems need not be evoked to explain such chemical variation. Acidic playa lakes in Western Australia have large pH differences separated by only a few tens of meters and demonstrate how highly variable chemistries can coexist over short distances in natural environments. Playa lakes on Earth tend to be dominated by lateral flow of water and salts leading to lateral chemical variation. Heterogeneity of playa mineralogy in Australia is due to the varied source rocks of brines and the mixing of dilute oxidizing brines and freshwater with the saturated evaporitic brines. This is evidenced by the ferricretes in the near-shore environment and more soluble phases in basin interiors. Playa lakes on Mars would be much larger than their terrestrial counterparts, leading to the prevalence of large-scale surface and crustal advection of water and salt rather than short-distance lateral flow, except at lake boundaries. Little or no influx of freshwater would preclude the formation of playa rim (e.g., crater rim) ferricretes and silcretes. Instead, we expect to see mainly vertical facies changes, and any diachronous lateral facies changes are expected to occur on very large spatial scales. Comparison of high spatial resolution, hyperspectral airborne data for Australian playa

  3. Gas flushing through hyper-acidic crater lakes: the next steps within a reframed monitoring time window

    Science.gov (United States)

    Rouwet, Dmitri

    2016-04-01

    Tracking variations in the chemical composition, water temperature and pH of brines from peak-activity crater lakes is the most obvious way to forecast phreatic activity. Volcano monitoring intrinsically implies a time window of observation that should be synchronised with the kinetics of magmatic processes, such as degassing and magma intrusion. To decipher "how much time ago" a variation in degassing regime actually occurred before eventually being detected in a crater lake is key, and depends on the lake water residence time. The above reasoning assumes that gas is preserved as anions in the lake water (SO4, Cl, F anions), in other words, that scrubbing of acid gases is complete and irreversible. Less is true. Recent work has confirmed, by direct MultiGas measurement from evaporative plumes, that even the strongest acid in liquid medium (i.e. SO2) degasses from hyper-acidic crater lakes. The less strong acid HCl has long been recognised as being more volatile than hydrophyle in extremely acidic solutions (pH near 0), through a long-term steady increase in SO4/Cl ratios in the vigorously evaporating crater lake of Poás volcano. We now know that acidic gases flush through hyper-acidic crater lake brines, but we don't know to which extend (completely or partially?), and with which speed. The chemical composition hence only reflects a transient phase of the gas flushing through the lake. In terms of volcanic surveillance this brings the advantage that the monitoring time window is definitely shorter than defined by the water chemistry, but yet, we do not know how much shorter. Empirical experiments by Capaccioni et al. (in press) have tried to tackle this kinetic problem for HCl degassing from a "lab-lake" on the short-term (2 days). With this state of the art in mind, two new monitoring strategies can be proposed to seek for precursory signals of phreatic eruptions from crater lakes: (1) Tracking variations in gas compositions, fluxes and ratios between species in

  4. The 2005 catastrophic acid crater lake drainage, lahar, and acidic aerosol formation at Mount Chiginagak volcano, Alaska, USA: Field observations and preliminary water and vegetation chemistry results

    Science.gov (United States)

    Schaefer, J.R.; Scott, W.E.; Evans, William C.; Jorgenson, J.; McGimsey, R.G.; Wang, B.

    2008-01-01

    A mass of snow and ice 400-m-wide and 105-m-thick began melting in the summit crater of Mount Chiginagak volcano sometime between November 2004 and early May 2005, presumably owing to increased heat flux from the hydrothermal system, or possibly from magma intrusion and degassing. In early May 2005, an estimated 3.8??106 m3 of sulfurous, clay-rich debris and acidic water, with an accompanying acidic aerosol component, exited the crater through a tunnel at the base of a glacier that breaches the south crater rim. Over 27 km downstream, the acidic waters of the flood inundated an important salmon spawning drainage, acidifying Mother Goose Lake from surface to depth (approximately 0.5 km3 in volume at a pH of 2.9 to 3.1), killing all aquatic life, and preventing the annual salmon run. Over 2 months later, crater lake water sampled 8 km downstream of the outlet after considerable dilution from glacial meltwater was a weak sulfuric acid solution (pH = 3.2, SO4 = 504 mg/L, Cl = 53.6 mg/L, and F = 7.92 mg/L). The acid flood waters caused severe vegetation damage, including plant death and leaf kill along the flood path. The crater lake drainage was accompanied by an ambioructic flow of acidic aerosols that followed the flood path, contributing to defoliation and necrotic leaf damage to vegetation in a 29 km2 area along and above affected streams, in areas to heights of over 150 m above stream level. Moss species killed in the event contained high levels of sulfur, indicating extremely elevated atmospheric sulfurcontent. The most abundant airborne phytotoxic constituent was likely sulfuric acid aerosols that were generated during the catastrophic partial crater lake drainage event. Two mechanisms of acidic aerosol formation are proposed: (1) generation of aerosol mist through turbulent flow of acidic water and (2) catastrophic gas exsolution. This previously undocumented phenomenon of simultaneous vegetationdamaging acidic aerosols accompanying drainage of an acidic crater

  5. Effects of pH and acetic acid on homoacetic fermentation of lactate by Clostridium formicoaceticum.

    Science.gov (United States)

    Tang, I C; Okos, M R; Yang, S T

    1989-10-20

    Clostridium formicoaceticum homofermentatively converts lactate to acetate at 37 degrees C and pH 6.6-9.6. However, this fermentation is strongly inhibited by acetic acid at acidic pH. The specific growth rate of this organism decreased from a maximum at pH 7.6 to zero at pH 6.6. This inhibition effect was found to be attributed to both H(+) and undissociated acetic acid. At pH values below 7.6, the H(+) inhibited the fermentation following non-competitive inhibition kinetics. The acetic acid inhibition was found to be stronger at a lower medium pH. At pH 6.45-6.8, cell growth was found to be primarily limited by a maximum undissociated acetic acid concentration of 0.358 g/L (6mM). This indicates that the undissociated acid, not the dissociated acid, is the major acid inhibitor. At pH 7.6 or higher, this organism could tolerate acetate concentrations of higher than 0.8M, but salt (Na(+)) became a strong inhibitor at concentrations of higher than 0.4M. Acetic acid inhibition also can be represented by noncompetitive inhibition kinetics. A mathematical model for this homoacetic fermentation was also developed. This model can be used to simulate batch fermentation at any pH between 6.9 and 7.6.

  6. The PH gene determines fruit acidity and contributes to the evolution of sweet melons.

    Science.gov (United States)

    Cohen, Shahar; Itkin, Maxim; Yeselson, Yelena; Tzuri, Galil; Portnoy, Vitaly; Harel-Baja, Rotem; Lev, Shery; Sa'ar, Uzi; Davidovitz-Rikanati, Rachel; Baranes, Nadine; Bar, Einat; Wolf, Dalia; Petreikov, Marina; Shen, Shmuel; Ben-Dor, Shifra; Rogachev, Ilana; Aharoni, Asaph; Ast, Tslil; Schuldiner, Maya; Belausov, Eduard; Eshed, Ravit; Ophir, Ron; Sherman, Amir; Frei, Benedikt; Neuhaus, H Ekkehard; Xu, Yimin; Fei, Zhangjun; Giovannoni, Jim; Lewinsohn, Efraim; Tadmor, Yaakov; Paris, Harry S; Katzir, Nurit; Burger, Yosef; Schaffer, Arthur A

    2014-06-05

    Taste has been the subject of human selection in the evolution of agricultural crops, and acidity is one of the three major components of fleshy fruit taste, together with sugars and volatile flavour compounds. We identify a family of plant-specific genes with a major effect on fruit acidity by map-based cloning of C. melo PH gene (CmPH) from melon, Cucumis melo taking advantage of the novel natural genetic variation for both high and low fruit acidity in this species. Functional silencing of orthologous PH genes in two distantly related plant families, cucumber and tomato, produced low-acid, bland tasting fruit, showing that PH genes control fruit acidity across plant families. A four amino-acid duplication in CmPH distinguishes between primitive acidic varieties and modern dessert melons. This fortuitous mutation served as a preadaptive antecedent to the development of sweet melon cultigens in Central Asia over 1,000 years ago.

  7. Influence of bioturbation on the biogeochemistry of littoral sediments of an acidic post-mining pit lake

    Directory of Open Access Journals (Sweden)

    S. Lagauzère

    2011-02-01

    Full Text Available In the last decades, the mining exploitation of large areas in Lusatia (Eastern Germany but also in other mining areas worldwide has led to the formation of hundreds of pit lakes. Pyrite oxidation in the surrounding dumps makes many such lakes extremely acidic (pH < 3. The biogeochemical functioning of these lakes is mainly governed by cycling of iron. This represents a relevant ecological problem and intensive research has been conducted to understand the involved biogeochemical processes and develop bioremediation strategies. Despite some studies reporting the presence of living organisms (mostly bacteria, algae, and macro-invertebrates under such acidic conditions, and their trophic interactions, their potential impact on the ecosystem functioning was poorly investigated. The present study aimed to assess the influence of chironomid larvae on oxygen dynamics and iron cycle in the sediment of acidic pit lakes. In the Mining Lake 111, used as a study case since 1996, Chironomus crassimanus (Insecta, Diptera is the dominant benthic macro-invertebrate species and occurs at relatively high abundances in shallow water. A 16-day laboratory experiment using microcosms combined with high resolution measurements (DET gel probes and O2 microsensors was carried out. The burrowing activity of C. crassimanus larvae induced a 3-fold increase of the diffusive oxygen uptake by sediment, indicating a stimulation of the mineralization of organic matter in the upper layers of the sediment. The iron cycle was also impacted (e.g. lower rates of reduction and oxidation, increase of iron-oxidizing bacteria abundance, stimulation of mineral formation but with no significant effect on the iron flux at the sediment-water interface, and thus on the water acidity budget. This work provides the first assessment of bioturbation in an acidic mining lake and shows that its influence on biogeochemistry cannot be neglected.

  8. Influence of bioturbation on the biogeochemistry of the sediment in the littoral zone of an acidic mine pit lake

    Directory of Open Access Journals (Sweden)

    S. Lagauzère

    2010-10-01

    Full Text Available In the last decades, the mining exploitation of large areas in Lusatia (South-eastern Germany but also in other mining areas worldwide has led to the formation of hundreds of pit lakes. Pyrite oxidation in the surrounding dumps makes many such lakes extremely acidic (pH < 3. The biogeochemical functioning of these lakes is mainly governed by cycling of iron. This represents a relevant ecological problem and intensive research has been conducted to understand the involved biogeochemical processes and develop bioremediation strategies. Despite some studies reporting the presence of living organisms (mostly bacteria, algae, and macro-invertebrates under such acidic conditions, and their trophic interactions, their potential impact on the ecosystem functioning was poorly investigated. The present study aimed to assess the influence of chironomid larvae on oxygen dynamics and iron cycle in the sediment of acidic pit lakes. In the Mining Lake 111, used as a study case since 1996, Chironomus crassimanus (Insecta, Diptera is the dominant benthic macro-invertebrate species and occurs at relatively high abundances in shallow water. A 16-day laboratory experiment using microcosms combined with high resolution measurements (DET gel probes and O2 microsensors was carried out. The burrowing activity of C. crassimanus larvae induced a 3-fold increase of the oxygen consumption by sediment, and stimulated the mineralization of organic matter in the upper layers of the sediment. The iron cycle was also impacted (e.g. lower rates of reduction and oxidation, increase of iron-oxidizing bacteria abundance, stimulation of mineral formation but with no significant effect on the iron flux at the sediment-water interface, and thus on the water acidity budget. This work provides the first assessment of bioturbation in an acidic mining lake and shows that its influence on biogeochemistry cannot be neglected.

  9. Geochemical characterization of acid mine lakes in northwest Turkey and their effect on the environment.

    Science.gov (United States)

    Yucel, Deniz Sanliyuksel; Baba, Alper

    2013-04-01

    Mining activity generates a large quantity of mine waste. The potential hazard of mine waste depends on the host mineral. The tendency of mine waste to produce acid mine drainage (AMD) containing potentially toxic metals depends on the amounts of sulfide, carbonate minerals, and trace-element concentrations found in ore deposits. The acid mine process is one of the most significant environmental challenges and a major source of water pollution worldwide. AMD and its effects were studied in northwest Turkey where there are several sedimentary and hydrothermal mineral deposits that have been economically extracted. The study area is located in Can county of Canakkale province. Canakkale contains marine, lagoon, and lake sediments precipitated with volcanoclastics that occurred as a result of volcanism, which was active during various periods from the Upper Eocene to Plio-Quaternary. Can county is rich in coal with a total lignite reserve >100 million tons and contains numerous mines that were operated by private companies and later abandoned without any remediation. As a result, human intervention in the natural structure and topography has resulted in large open pits and deterioration in these areas. Abandoned open pit mines typically fill with water from runoff and groundwater discharge, producing artificial lakes. Acid drainage waters from these mines have resulted in the degradation of surface-water quality around Can County. The average pH and electrical conductivity of acid mine lakes (AMLs) in this study were found to be 3.03 and 3831.33 μS cm(-1), respectively. Total iron (Fe) and aluminum (Al) levels were also found to be high (329.77 and 360.67 mg L(-1), respectively). The results show that the concentration of most elements, such as Fe and Al in particular, exceed national and international water-quality standards.

  10. Yeast diversity in the acidic Rio Agrio-Lake Caviahue volcanic environment (Patagonia, Argentina).

    Science.gov (United States)

    Russo, Gabriel; Libkind, Diego; Sampaio, José P; van Broock, Maria R

    2008-09-01

    The Rio Agrio and Lake Caviahue system (RAC), in Northwestern Patagonia, is a natural acidic environment. The aims of this study were to characterize the yeast community and to provide the first ecological assessment of yeast diversity of this extreme aquatic environment. Yeast occurrence and diversity were studied at seven sites where the water pH varied between 1.8 and 6.7. Yeast CFU counts in the river ranged from 30 to 1200 CFU L(-1), but in the Lake the values were lower (30-60 CFU L(-1)). A total of 25 different yeast species were found, 11 of which belonged to undescribed taxa. Among these was an unusual strongly acidophilic Cryptococcus species. The RAC yeast community resembles that of acidic aquatic environments resulting from anthropic activities such as the São Domingos mines in Portugal and the Rio Tinto in Spain, respectively. The isolated yeast species were organized into different grades of adaptation to the RAC aquatic system. Based on the proposed grades, Rhodotorula mucilaginosa, Rhodosporidium toruloides and two novel Cryptococcus species were the most adapted species. These Cryptococcus species are apparently specialists of acidic aquatic environments, and might bear physiological features that possibly account for their ability to thrive in such extreme environments.

  11. Chemical, crystallographic and stable isotopic properties of alunite and jarosite from acid-Hypersaline Australian lakes

    Science.gov (United States)

    Alpers, C.N.; Rye, R.O.; Nordstrom, D.K.; White, L.D.; King, B.-S.

    1992-01-01

    reflect a minor contribution of sulfate from pyrite oxidation in the Parilla Sand or a reservoir effect from removal of gypsum enriched in 34S. ??18OSO4-values for alunite from three Western Australia lakes (+17.8 to +18.3??? V-SMOW), for alunite and jarosite from Lake Tyrrell (+22.6 to +24.9???) and for aqueous sulfate from Lake Tyrrell (+17.3 to +19.0???) are much larger than the average value for seawater (+9.6???). The data suggest an approach to 18O-16O equilibrium between aqueous sulfate and groundwater, which is known from experimental studies to be possible at low pH and low temperatures, but has not been previously documented in nature. A residence time of ???0.1-1 kyr for sulfate in acidic water (pH 3-4) is needed to achieve the apparent partial oxygen exchange, using previously published data of R.M. Lloyd. ?? 1992.

  12. Clustering chlorine reactivity of haloacetic acid precursors in inland lakes.

    Science.gov (United States)

    Zeng, Teng; Arnold, William A

    2014-01-01

    Dissolved organic matter (DOM) represents the major pool of organic precursors for harmful disinfection byproducts, such as haloacetic acids (HAAs), formed during drinking water chlorination, but much of it remains molecularly uncharacterized. Knowledge of model precursors is thus a prerequisite for understanding the more complex whole water DOM. The utility of HAA formation potential data from model DOM precursors, however, is limited due to the lack of comparability to water samples. In this study, the formation kinetics of dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), the two predominant HAA species, were delineated upon chlorination of seventeen model DOM precursors and sixty-eight inland lake water samples collected from the Upper Midwest region of the United States. Of particular interest was the finding that the DCAA and TCAA formation rate constants could be grouped into four statistically distinct clusters reflecting the core structural features of model DOM precursors (i.e., non-β-diketone aliphatics, β-diketone aliphatics, non-β-diketone phenolics, and β-diketone phenolics). A comparative approach built upon hierarchical cluster analysis was developed to gain further insight into the chlorine reactivity patterns of HAA precursors in inland lake waters as defined by the relative proximity to four model precursor clusters. This work highlights the potential for implementing an integrated kinetic-clustering approach to constrain the chlorine reactivity of DOM in source waters.

  13. Oxidation in fish oil enriched mayonnaise : Ascorbic acid and low pH increase oxidative deterioration

    DEFF Research Database (Denmark)

    Jacobsen, Charlotte; Timm Heinrich, Maike; Meyer, Anne S.

    2001-01-01

    The effect of ascorbic acid (0-4000 ppm) and pH (3.8-6.2) on oxidation and levels of iron and copper in various fractions of mayonnaise enriched with 16% fish oil was investigated. Ascorbic acid induced release of iron from the assumed oil- water interface into the aqueous phase at all pH levels......, but this effect of ascorbic acid was strongest at low pH (pH 3.8- 4.2). Ascorbic acid generally promoted formation of volatile oxidation compounds and reduced the peroxide value in mayonnaises. Peroxide values and total volatiles generally increased with decreasing pH values, suggesting that low pH promoted...... due to the reduction of Fe3+ to Fe2+ that rapidly catalyzes lipid oxidation via lipid hydroperoxide decomposition at the oil-water interface in mayonnaise...

  14. Acid skim milk gels: The gelation process as affected by preheated pH

    NARCIS (Netherlands)

    Lakemond, C.M.M.; Vliet, van T.

    2008-01-01

    The effect of preheating milk (10 min 80 [degree sign]C) at pH values from 6.20 to 6.90 on formation of acid skim milk gels was studied by dynamic oscillation measurements. Up to pH 6.65 a higher pH of heating (pHheating) resulted in a higher G'. Since below pH 4.9 the development of G'(pH)/G'(pH=4.

  15. Weak-acid preservatives: pH and proton movements in the yeast Saccharomyces cerevisiae.

    Science.gov (United States)

    Stratford, Malcolm; Nebe-von-Caron, Gerhard; Steels, Hazel; Novodvorska, Michaela; Ueckert, Joerg; Archer, David B

    2013-02-15

    Weak-acid preservatives commonly used to prevent fungal spoilage of low pH foods include sorbic and acetic acids. The "classical weak-acid theory" proposes that weak acids inhibit spoilage organisms by diffusion of undissociated acids through the membrane, dissociation within the cell to protons and anions, and consequent acidification of the cytoplasm. Results from 25 strains of Saccharomyces cerevisiae confirmed inhibition by acetic acid at a molar concentration 42 times higher than sorbic acid, in contradiction of the weak-acid theory where all acids of equal pK(a) should inhibit at equimolar concentrations. Flow cytometry showed that the intracellular pH fell to pH 4.7 at the growth-inhibitory concentration of acetic acid, whereas at the inhibitory concentration of sorbic acid, the pH only fell to pH 6.3. The plasma membrane H⁺-ATPase proton pump (Pma1p) was strongly inhibited by sorbic acid at the growth-inhibitory concentration, but was stimulated by acetic acid. The H⁺-ATPase was also inhibited by lower sorbic acid concentrations, but later showed recovery and elevated activity if the sorbic acid was removed. Levels of PMA1 transcripts increased briefly following sorbic acid addition, but soon returned to normal levels. It was concluded that acetic acid inhibition of S. cerevisiae was due to intracellular acidification, in accord with the "classical weak-acid theory". Sorbic acid, however, appeared to be a membrane-active antimicrobial compound, with the plasma membrane H⁺-ATPase proton pump being a primary target of inhibition. Understanding the mechanism of action of sorbic acid will hopefully lead to improved methods of food preservation. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. Influence of bioturbation on the biogeochemistry of littoral sediments of an acidic post-mining pit lake

    Science.gov (United States)

    Lagauzère, S.; Moreira, S.; Koschorreck, M.

    2011-02-01

    In the last decades, the mining exploitation of large areas in Lusatia (Eastern Germany) but also in other mining areas worldwide has led to the formation of hundreds of pit lakes. Pyrite oxidation in the surrounding dumps makes many such lakes extremely acidic (pH bioremediation strategies. Despite some studies reporting the presence of living organisms (mostly bacteria, algae, and macro-invertebrates) under such acidic conditions, and their trophic interactions, their potential impact on the ecosystem functioning was poorly investigated. The present study aimed to assess the influence of chironomid larvae on oxygen dynamics and iron cycle in the sediment of acidic pit lakes. In the Mining Lake 111, used as a study case since 1996, Chironomus crassimanus (Insecta, Diptera) is the dominant benthic macro-invertebrate species and occurs at relatively high abundances in shallow water. A 16-day laboratory experiment using microcosms combined with high resolution measurements (DET gel probes and O2 microsensors) was carried out. The burrowing activity of C. crassimanus larvae induced a 3-fold increase of the diffusive oxygen uptake by sediment, indicating a stimulation of the mineralization of organic matter in the upper layers of the sediment. The iron cycle was also impacted (e.g. lower rates of reduction and oxidation, increase of iron-oxidizing bacteria abundance, stimulation of mineral formation) but with no significant effect on the iron flux at the sediment-water interface, and thus on the water acidity budget. This work provides the first assessment of bioturbation in an acidic mining lake and shows that its influence on biogeochemistry cannot be neglected.

  17. Influence of bioturbation on the biogeochemistry of the sediment in the littoral zone of an acidic mine pit lake

    Science.gov (United States)

    Lagauzère, S.; Moreira, S.; Koschorreck, M.

    2010-10-01

    In the last decades, the mining exploitation of large areas in Lusatia (South-eastern Germany) but also in other mining areas worldwide has led to the formation of hundreds of pit lakes. Pyrite oxidation in the surrounding dumps makes many such lakes extremely acidic (pH bioremediation strategies. Despite some studies reporting the presence of living organisms (mostly bacteria, algae, and macro-invertebrates) under such acidic conditions, and their trophic interactions, their potential impact on the ecosystem functioning was poorly investigated. The present study aimed to assess the influence of chironomid larvae on oxygen dynamics and iron cycle in the sediment of acidic pit lakes. In the Mining Lake 111, used as a study case since 1996, Chironomus crassimanus (Insecta, Diptera) is the dominant benthic macro-invertebrate species and occurs at relatively high abundances in shallow water. A 16-day laboratory experiment using microcosms combined with high resolution measurements (DET gel probes and O2 microsensors) was carried out. The burrowing activity of C. crassimanus larvae induced a 3-fold increase of the oxygen consumption by sediment, and stimulated the mineralization of organic matter in the upper layers of the sediment. The iron cycle was also impacted (e.g. lower rates of reduction and oxidation, increase of iron-oxidizing bacteria abundance, stimulation of mineral formation) but with no significant effect on the iron flux at the sediment-water interface, and thus on the water acidity budget. This work provides the first assessment of bioturbation in an acidic mining lake and shows that its influence on biogeochemistry cannot be neglected.

  18. Organic acid excretion in Penicillium ochrochloron increases with ambient pH

    Directory of Open Access Journals (Sweden)

    Pamela eVrabl

    2012-04-01

    Full Text Available Despite being of high biotechnological relevance, many aspects of organic acid excretion in filamentous fungi like the influence of ambient pH are still insufficiently understood. While the excretion of an individual organic acid may peak at a certain pH value, the few available studies investigating a broader range of organic acids indicate that total organic acid excretion rises with increasing external pH.We hypothesized that this phenomenon might be a general response of filamentous fungi to increased ambient pH. If this is the case, the observation should be widely independent of the organism, growth conditions or experimental design and might therefore be a crucial key point in understanding the function and mechanisms of organic acid excretion in filamentous fungi.In this study we explored this hypothesis using ammonium limited chemostat cultivations (pH 2-7, and ammonium or phosphate limited bioreactor batch cultivations (pH 5 and 7. Two strains of Penicillium ochrochloron were investigated differing in the spectrum of excreted organic acids.Confirming our hypothesis, the main result demonstrated that organic acid excretion in P. ochrochloron was enhanced at high external pH levels compared to low pH levels independent of the tested strain, nutrient limitation and cultivation method. We discuss these findings against the background of three hypotheses explaining organic acid excretion in filamentous fungi, i.e. overflow metabolism, charge balance and aggressive acidification hypothesis.

  19. Thermal and Trophic Stability of Deeper Maine Lakes in Granite Watersheds Impacted by Acid Deposition

    Science.gov (United States)

    Stauffer, Robert E.; Wittchen, Bruce D.

    1990-09-01

    Acid deposition can lead to lake and watershed acidification, increases in lake transparency, and reductions in thermal stability and hypolimnetic oxygen deficits. On the basis of lake surveys during August-September 1985, we determined to what extent the deeper (maximum depth zm > 17 m) Maine lakes in acid-sensitive granitic watersheds have registered changes in temperature and oxygen stratification, as compared to 1938-1942, when G. P. Cooper performed the earliest scientific surveys of the state's lakes. After correcting for small but geographically consistent interannual differences in summer hypolimnetic temperatures related to spring turnover, and weather-dependent differences in mixed layer depth, there has been no significant change in thermal stratification in these Maine lakes over approximately 43 years. On the basis of specific historical contrasts in the late summer metalimnetic, hypolimnetic, and bathylimnetic oxygen concentrations there has been no significant change in lake trophic state or transparency.

  20. Thermal and trophic stability of deeper Maine lakes in granite waterhsheds implacted by acid deposition

    Energy Technology Data Exchange (ETDEWEB)

    Stauffer, R.E.; Wittchen, B.D. (Univ. of Maine, Orono (USA))

    1990-09-01

    Acid deposition can lead to lake and watershed acidification, increases in lake transparency, and reduction in thermal stability and hypolimnetic oxygen deficits. On the basis of lake surveys during August-September 1985, we determined to what extent the deeper (maximum depth z{sub m}{gt}17 m) Maine lakes in acid-sensitive granitic watersheds have registered changes in temperature and oxygen stratification, as compared to 1938-1942, when G.P. Cooper performed the earliest scientific surveys of the state's lakes. After correcting for small but geographically consistent interannual differences in summer hypolimnetic temperatures related to spring turnover, and weather-dependent differences in mixed layer depth, there has been no significant change in thermal stratification in these Maine lakes over approximately 43 years. On the basis of specific historical contrasts in the late summer metalimnetic, hypolimnetic, and bathylimnetic oxygen concentrations there has been no significant change in lake trophic state or transparency.

  1. A Demonstration of Acid Rain and Lake Acidification: Wet Deposition of Sulfur Dioxide.

    Science.gov (United States)

    Goss, Lisa M.

    2003-01-01

    Introduces a science demonstration on the dissolution of sulfuric oxide emphasizing the concept of acid rain which is an environmental problem. Demonstrates the acidification from acid rain on two lake environments, limestone and granite. Includes safety information. (YDS)

  2. Negative pH and extremely acidic mine waters from Iron Mountain, California

    Science.gov (United States)

    Nordstrom, D.K.; Alpers, C.N.; Ptacek, C.J.; Blowes, D.W.

    2000-01-01

    Extremely acidic mine waters with pH values as low as -3.6, total dissolved metal concentrations as high as 200 g/L, and sulfate concentrations as high as 760 g/L, have been encountered underground in the Richmond Mine at Iron Mountain, CA. These are the most acidic waters known. The pH measurements were obtained by using the Pitzer method to define pH for calibration of glass membrane electrodes. The calibration of pH below 0.5 with glass membrane electrodes becomes strongly nonlinear but is reproducible to a pH as low as -4. Numerous efflorescent minerals were found forming from these acid waters. These extreme acid waters were formed primarily by pyrite oxidation and concentration by evaporation with minor effects from aqueous ferrous iron oxidation and efflorescent mineral formation.

  3. Summit crater lake observations, and the location, chemistry, and pH of water samples near Mount Chiginagak volcano, Alaska: 2004-2012

    Science.gov (United States)

    Schaefer, Janet R.; Scott, William E.; Evans, William C.; Wang, Bronwen; McGimsey, Robert G.

    2013-01-01

    maximum depth of 45 m (resulting pH ~2.9), and preventing the annual salmon run in the King Salmon River. A simultaneous release of gas and acidic aerosols from the crater caused widespread vegetation damage along the flow path. Since 2005, we have been monitoring the crater lake water that continues to flow into Mother Goose Lake by collecting surface water samples for major cation and anion analysis, measuring surface-water pH of affected drainages, and photo-documenting the condition of the summit crater lake. This report describes water sampling locations, provides a table of chemistry and pH measurements, and documents the condition of the summit crater between 2004 and 2011. In September 2013, the report was updated with results of water-chemistry samples collected in 2011 and 2012, which were added as an addendum.

  4. Decomposition of Alternative Chirality Amino Acids by Alkaliphilic Anaerobe from Owens Lake, California

    Science.gov (United States)

    Townsend, Alisa; Pikuta, Elena V.; Guisler, Melissa; Hoover, Richard B.

    2009-01-01

    The study of alkaliphilic microbial communities from anaerobic sediments of Owens and Mono Lakes in California led to the isolation of a bacterial strain capable of metabolizing amino acids with alternative chirality. According to the phylogenetic analysis, the anaerobic strain BK1 belongs to the genus Tindallia; however, despite the characteristics of other described species of this genus, the strain BK1 was able to grow on D-arginine and Dlysine. Cell morphology of this strain showed straight, motile, non-spore-forming rods with sizes 0.45 x 1.2-3 microns. Physiological characteristics of the strain showed that it is catalase negative, obligately anaerobic, mesophilic, and obligately alkaliphilic. This isolate is unable to grow at pH 7 and requires CO3 (2-) ions for growth. The strain has chemo-heterotrophic metabolism and is able to ferment various proteolysis products and some sugars. It plays the role of a primary anaerobe within the trophic chain of an anaerobic microbial community by the degradation of complex protein molecules to smaller and less energetic molecules. The new isolate requires NaCl for growth, and can grow within the range of 0.5-13 %, with the optimum at 1 % NaCl (w/v). The temperature range for the growth of the new isolate is 12-40 C with optimum at 35 C. The pH range for the growth of strain BK1 occurs between 7.8 and 11.0 with optimum at 9.5. This paper presents detailed physiological characteristics of the novel isolate from Owens Lake, a unique relic ecosystem of Astrobiological significance, and makes an accent on the ability of this strain to utilize L-amino acids.

  5. Continuous intra-arterial blood pH monitoring in rabbits with acid-base disorders.

    Science.gov (United States)

    Jin, Weizhong; Jiang, Jinjun; Wang, Xun; Zhu, Xiaodan; Wang, Guifang; Song, Yuanlin; Bai, Chunxue

    2011-07-31

    The acid-base balance of arterial blood is important for the clinical management of seriously ill patients, especially patients with acute lung injury or acute respiratory distress syndrome. We developed a novel fluorosensor for continuous blood pH monitoring and evaluated its performance both in vitro and in vivo in rabbits with acid-base disorders. The pH sensor is made of N-allyl-4-piperazinyl-1, 8-napthalimide and 2-hydroxyethyl methacrylate, which were bonded at the distal end of the optical fiber. The fluorescence intensity increased as the pH decreased with good reproducibility, selectivity and linearity in the pH range of 6-8. The pH measurement precision was 0.03 ± 0.03 pH units with a bias of -0.02 ± 0.04 (n = 105) and -0.00 ± 0.05 pH units (n=189) in rabbits with metabolic and respiratory acid-base orders, respectively. The optical pH sensor can accurately measure pH fluctuations with a fast response and is a promising candidate for continuous in-line measurements of blood pH in critical care patients.

  6. Composition of Humic Acids of the Lake Baikal Sediments

    Science.gov (United States)

    Vishnyakova, O.; Chimitdorzhieva, G.; Andreeva, D.

    2012-04-01

    Humic substances are the final stage of the biogeochemical transformation of organic matter in the biosphere. Its natural compounds are found not only in soil, peat, coal, and sediments of basins. Chemical composition and properties of humic substances are determined by the functioning of the ecosystem as a whole. Therefore the study of the unique Lake Baikal sediments can provide information about their genesis, as well as the processes of organic matter transformation. For this purpose, preparations of humic acids (HA) were isolated by alkaline extraction method. The composition of HA was investigated by the elemental analyzer CHNS/O PerkinElmer Series II. Various located sediments of the Lake Baikal were the objects of the study: 1 - Chivyrkuisky Bay, 2 - Kotovo Bay, 3 - Selenga river delta near Dubinino village, 4 - Selenga river delta near Murzino village. Data on the elemental composition of HA in terms of ash-free portion show that the carbon content (CC) is of 50-53% with a maximum value in a sample 3, and minimum - in a sample 2. Such values are characteristic also for the soils with low biochemical activity. The hydrogen content is of 4,2-5,3%, a maximum value is in a sample 1. Data recalculation to the atomic percentages identified following regularities. The CC of HA is of 35-39 at. %. Hydrogen content is of 37-43 at. %. According to the content of these elements investigated substances are clearly divided into two groups: HA of the sediments of the Lake Baikal and river Selenga delta. The magnitude of the atomic ratio H/C can be seen varying degrees of condensation of the molecules of humic acids. The high atomic ratio H/C in HA of the former group indicates the predominance of aliphatic structures in the molecules. Humic acids of the later group are characterized by a low value H/C (organic matter of terrigenous origin, the remains of higher plants are the most source of it. In the bays of the Lake Baikal the remains of aquatic animal organisms, other

  7. Acid rain recovery may help to mitigate the impacts of climate change on thermally sensitive fish in lakes across eastern North America.

    Science.gov (United States)

    Warren, Dana R; Kraft, Clifford E; Josephson, Daniel C; Driscoll, Charles T

    2016-12-15

    From the 1970s to 1990s, more stringent air quality regulations were implemented across North America and Europe to reduce chemical emissions that contribute to acid rain. Surface water pH slowly increased during the following decades, but biological recovery lagged behind chemical recovery. Fortunately, this situation is changing. In the past few years, northeastern US fish populations have begun to recover in lakes that were historically incapable of sustaining wild fish due to acidic conditions. As lake ecosystems across the eastern United States recover from acid deposition, the stress to the most susceptible populations of native coldwater fish appears to be shifting from acidification effects to thermal impacts associated with changing climate. Extreme summer temperature events - which are expected to occur with increasing frequency in the coming century - can stress and ultimately kill native coldwater fish in lakes where thermal stratification is absent or highly limited. Based on data from northeastern North America, we argue that recovery from acid deposition has the potential to improve the resilience of coldwater fish populations in some lakes to impacts of climate change. This will occur as the amount of dissolved organic carbon (DOC) in the water increases with increasing lake pH. Increased DOC will reduce water clarity and lead to shallower and more persistent lake thermoclines that can provide larger areas of coldwater thermal refuge habitat. Recovery from acidification will not eliminate the threat of climate change to coldwater fish, but secondary effects of acid recovery may improve the resistance of coldwater fish populations in lakes to the effects of elevated summer temperatures in historically acidified ecosystems. This analysis highlights the importance of considering the legacy of past ecosystem impacts and how recovery or persistence of those effects may interact with climate change impacts on biota in the coming decades.

  8. Nucleic acid induced unfolding of recombinant prion protein globular fragment is pH dependent.

    Science.gov (United States)

    Bera, Alakesh; Nandi, Pradip K

    2014-12-01

    Nucleic acid can catalyze the conversion of α-helical cellular prion protein to β-sheet rich Proteinase K resistant prion protein oligomers and amyloid polymers in vitro and in solution. Because unfolding of a protein molecule from its ordered α-helical structure is considered to be a necessary step for the structural conversion to its β-sheet rich isoform, we have studied the unfolding of the α-helical globular 121-231 fragment of mouse recombinant prion protein in the presence of different nucleic acids at neutral and acid pH. Nucleic acids, either single or double stranded, do not have any significant effect on the secondary structure of the protein fragment at neutral pH; however the protein secondary structure is modified by the nucleic acids at pH 5. Nucleic acids do not show any significant effect on the temperature induced unfolding of the globular prion protein domain at neutral pH which, however, undergoes a gross conformational change at pH 5 as evidenced from the lowering of the midpoint of thermal denaturation temperatures, Tm, of the protein. The extent of Tm decrease shows a dependence on the nature of nucleic acid. The interaction of nucleic acid with the nonpolar groups exposed from the protein interior at pH 5 probably contributes substantially to the unfolding process of the protein. © 2014 The Protein Society.

  9. A novel acidic pH fluorescent probe based on a benzothiazole derivative.

    Science.gov (United States)

    Ma, Qiujuan; Li, Xian; Feng, Suxiang; Liang, Beibei; Zhou, Tiqiang; Xu, Min; Ma, Zhuoyi

    2017-04-15

    A novel acidic pH fluorescent probe 1 based on a benzothiazole derivative has been designed, synthesized and developed. The linear response range covers the acidic pH range from 3.44 to 6.46, which is valuable for pH researches in acidic environment. The evaluated pKa value of the probe 1 is 4.23. The fluorescence enhancement of the studied probe 1 with an increase in hydrogen ions concentration is based on the hindering of enhanced photo-induced electron transfer (PET) process. Moreover, the pH sensor possesses a highly selective response to H(+) in the presence of metal ions, anions and other bioactive small molecules which would be interfere with its fluorescent pH response. Furthermore, the probe 1 responds to acidic pH with short response time that was less than 1min. The probe 1 has been successfully applied to confocal fluorescence imaging in live HeLa cells and can selectively stain lysosomes. All of such good properties prove it can be used to monitoring pH fluctuations in acidic environment with high sensitivity, pH dependence and short response time.

  10. The evolution of a mining lake - From acidity to natural neutralization

    Energy Technology Data Exchange (ETDEWEB)

    Sienkiewicz, Elwira, E-mail: esienkie@twarda.pan.pl; Gąsiorowski, Michał, E-mail: mgasior@twarda.pan.pl

    2016-07-01

    Along the border of Poland and Germany (central Europe), many of the post-mining lakes have formed “an anthropogenic lake district”. This study presents the evolution of a mining lake ecosystem (TR-33) based on subfossil phyto- and zooplankton, isotopic data (δ{sup 13}C, δ{sup 15}N), elemental analyses of organic carbon and nitrogen (C/N ratio and TOC) and sedimentological analyses. Recently, lake TR-33 became completely neutralized from acidification and an increase in eutrophication began a few years ago. However, the lake has never been neutralized by humans; only natural processes have influenced the present water quality. From the beginning of the existence of the lake (1920s) to the present, we can distinguish four stages of lake development: 1) very shallow reservoir without typical lake sediments but with a sand layer containing fine lignite particles and very poor diatom and cladoceran communities; 2) very acidic, deeper water body with increasing frequencies of phyto- and zooplankton; 3) transitional period (rebuilding communities of diatoms and Cladocera), meaning a deep lake with benthic and planktonic fauna and flora with wide ecological tolerances; and 4) a shift to circumneutral conditions with an essential increase in planktonic taxa that prefer more fertile waters (eutrophication). In the case of lake TR-33, this process of natural neutralization lasted approximately 23 years. - Highlights: • Originally acid water lake had poor phyto- and zooplankton populations. • Process of natural neutralization lasted approximately 23 years. • Presently, lake's ecosystem is similar to other shallow lakes in the region. • Changes in the lake are representative for other mine lakes.

  11. Perfluorinated acids in air, rain, snow, surface runoff, and lakes: relative importance of pathways to contamination of urban lakes.

    Science.gov (United States)

    Kim, Seung-Kyu; Kannan, Kurunthachalam

    2007-12-15

    Concentrations of perfluorinated acids (PFAs) were measured in various environmental matrices (air, rain, snow, surface runoff water, and lake water) in an urban area, to enable identification of sources and pathways of PFAs to urban water bodies. Total PFA concentrations ranged from 8.28 to 16.0 pg/ m3 (mean 11.3) in bulk air (sum of vapor and particulate phases), 0.91 to 13.2 ng/L (6.19) in rainwater, 0.91 to 23.9 ng/L (7.98) in snow, 1.11-81.8 ng/L (15.1 ng/L) in surface runoff water (SRW), and 9.49 to 35.9 ng/L (21.8) in lake water. Perfluorooctanoic acid (PFOA) was the predominant compound, accounting for > 35% of the total PFA concentrations, in all environmental matrices analyzed. Concentrations and relative compositions of PFAs in SRW were similar to those found for urban lakes. SRW contributes to contamination by PFOA in urban lakes. The measured concentration ratios of FTOH to PFOA in air were 1-2 orders of magnitude lower than the ratios calculated based on an assumption of exclusive atmospheric oxidation of FTOHs. Nevertheless, the mass balance analysis suggested the presence of an unknown input pathway that could contribute to a significant amount of total PFOA loadings to the lake. Flux estimates of PFOA at the air-water interface in the urban lake suggest net volatilization from water.

  12. Acidic pit lakes. The legacy of coal and metal surface mines

    Energy Technology Data Exchange (ETDEWEB)

    Geller, Walter; Schultze, Martin [Helmholtz Centre for Environmental Research - UFZ, Magdeburg (Germany); Wolkersdorfer, Christian (eds.) [Cape Breton Univ., Sydney, NS (Canada). Industrial Research Chair in Mine Water Remediation and Management; International Mine Water Association, Wendelstein (Germany). General Secretary; Kleinmann, Robert

    2013-07-01

    This monograph provides an international perspective on pit lakes in post-mining landscapes, including the problem of geogenic acidification. Much has been learned during the last decade through research and practical experience on how to mitigate or remediate the environmental problems of acidic pit lakes. In the first part of the book, general scientific issues are presented in 21 contributions from the fields of geo-environmental science, water chemistry, lake physics, lake modeling, and on the peculiar biological features that occur in the extreme habitats of acidic pit lakes. Another chapter provides an overview of methods currently used to remediate acidic pit lakes and treat outflowing acidic water. The second part of the book is a collection of regional surveys of pit lake problems from three European countries and Australia, and case studies of various individual representative lakes. A final case study provides an innovative approach to assessing the economic value of new pit lakes and balancing the costs and benefits, a valuable tool for decision makers.

  13. pH shift protein recovery with organic acids on texture and color of cooked gels.

    Science.gov (United States)

    Paker, Ilgin; Beamer, Sarah; Jaczynski, Jacek; Matak, Kristen E

    2015-01-01

    Isoelectric solubilization and precipitation (ISP) processing uses pH shifts to separate protein from fish frames, which may increase commercial interest for silver carp. Texture and color properties of gels made from silver carp protein recovered at different pH strategies and organic acid types were compared. ISP was applied to headed gutted silver carp using 10 mol L(-1) sodium hydroxide (NaOH) and either glacial acetic acid (AA) or a (1:1) formic and lactic acid combination (F&L). Protein gels were made with recovered protein and standard functional additives. Texture profile analysis and the Kramer shear test showed that protein gels made from protein solubilized at basic pH values were firmer, harder, more cohesive, gummier and chewier (P proteins solubilized under acidic conditions. Acidic solubilization led to whiter (P protein using organic acids show potential for use as a functional ingredient in restructured foods. © 2014 Society of Chemical Industry.

  14. Dual effect of organic acids as a function of external pH in Oenococcus oeni.

    Science.gov (United States)

    Augagneur, Yoann; Ritt, Jean-François; Linares, Daniel M; Remize, Fabienne; Tourdot-Maréchal, Raphaëlle; Garmyn, Dominique; Guzzo, Jean

    2007-08-01

    In this study we analyzed under various pH conditions including low pH, the effects of L-malic acid and citric acid, combined or not, on the growth, the proton motive force components and the transcription level of selected genes of the heterolactic bacterium Oenococcus oeni. It is shown here that L-malate enhanced the growth yield at pH equal or below 4.5 while the presence of citrate in media led to a complete and unexpected inhibition of the growth at pH 3.2. Nevertheless, whatever the growth conditions, both L-malate and citrate participated in the enhancement of the transmembrane pH gradient, whereas the membrane potential decreased with the pH. These results suggested that it was not citrate that was directly responsible for the inhibition observed in cultures done at low pH, but probably its end products. This was confirmed since, in media containing L-malate, the addition of acetate substantially impaired the growth rate of the bacterium and slightly the membrane potential and pH gradient. Finally, study of the expression of genes involved in the metabolism of organic acids showed that at pH 4.5 and 3.2 the presence of L-malate led to an increased amount of mRNA of mleP encoding a malate transporter.

  15. Oxidation in fish oil enriched mayonnaise : Ascorbic acid and low pH increase oxidative deterioration

    DEFF Research Database (Denmark)

    Jacobsen, Charlotte; Timm Heinrich, Maike; Meyer, Anne S.

    2001-01-01

    oxidation. It is proposed that iron bridges between the egg yolk proteins low-density lipoproteins, lipovitellin, and phosvitin at the oil-water interface are broken at low pH values, whereby iron ions become accessible as oxidation initiators. In the presence of ascorbic acid, oxidation is further enhanced......The effect of ascorbic acid (0-4000 ppm) and pH (3.8-6.2) on oxidation and levels of iron and copper in various fractions of mayonnaise enriched with 16% fish oil was investigated. Ascorbic acid induced release of iron from the assumed oil- water interface into the aqueous phase at all pH levels......, but this effect of ascorbic acid was strongest at low pH (pH 3.8- 4.2). Ascorbic acid generally promoted formation of volatile oxidation compounds and reduced the peroxide value in mayonnaises. Peroxide values and total volatiles generally increased with decreasing pH values, suggesting that low pH promoted...

  16. Oxidation in fish oil enriched mayonnaise: ascorbic acid and low pH increase oxidative deterioration.

    Science.gov (United States)

    Jacobsen, C; Timm, M; Meyer, A S

    2001-08-01

    The effect of ascorbic acid (0-4000 ppm) and pH (3.8-6.2) on oxidation and levels of iron and copper in various fractions of mayonnaise enriched with 16% fish oil was investigated. Ascorbic acid induced release of iron from the assumed oil-water interface into the aqueous phase at all pH levels, but this effect of ascorbic acid was strongest at low pH (pH 3.8-4.2). Ascorbic acid generally promoted formation of volatile oxidation compounds and reduced the peroxide value in mayonnaises. Peroxide values and total volatiles generally increased with decreasing pH values, suggesting that low pH promoted oxidation. It is proposed that iron bridges between the egg yolk proteins low-density lipoproteins, lipovitellin, and phosvitin at the oil-water interface are broken at low pH values, whereby iron ions become accessible as oxidation initiators. In the presence of ascorbic acid, oxidation is further enhanced due to the reduction of Fe(3+) to Fe(2+) that rapidly catalyzes lipid oxidation via lipid hydroperoxide decomposition at the oil-water interface in mayonnaise.

  17. Volatile fatty acids distribution during acidogenesis of algal residues with pH control.

    Science.gov (United States)

    Li, Yan; Hua, Dongliang; Zhang, Jie; Zhao, Yuxiao; Xu, Haipeng; Liang, Xiaohui; Zhang, Xiaodong

    2013-06-01

    The anaerobic acidification of protein-rich algal residues with pH control (4, 6, 8, 10) was studied in batch reactors, which was operated at mesophilic(35 °C) condition. The distribution of major volatile fatty acids (VFAs) during acidogenesis was emphasized in this paper. The results showed that the acidification efficiency and VFAs distribution in the acid reactor strongly depended on the pH. The main product for all the runs involved acetic acid except that the proportion of butyric acid acidified at pH 6 was relatively higher. The other organic acids remained at lower levels. The VFAs yield reached the maximum value with about 0.6 g VFAs/g volatile solid (VS) added as pH was 8, and also the content of total ammonia nitrogen (TAN) reached the highest values of 9,629 mg/l. Low acidification degrees were obtained under the conditions at pH 4 and 10, which was not suitable for the metabolism of acidogens. Hydralic retention time (HRT) required for different conditions varied. As a consequence, it was indicated that pH was crucial to the acidification efficiency and products distribution. The investigation of acidogenesis process, which was producing the major substrates, short-chain fatty acids, would play the primary role in the efficient operation of methanogenesis.

  18. Change of pH during excess sludge fermentation under alkaline, acidic and neutral conditions.

    Science.gov (United States)

    Yuan, Yue; Peng, Yongzhen; Liu, Ye; Jin, Baodan; Wang, Bo; Wang, Shuying

    2014-12-01

    The change in pH during excess sludge (ES) fermentation of varying sludge concentrations was investigated in a series of reactors at alkaline, acidic, and neutral pHs. The results showed that the changes were significantly affected by fermentative conditions. Under different conditions, pH exhibited changing profiles. When ES was fermented under alkaline conditions, pH decreased in a range of (10±1). At the beginning of alkaline fermentation, pH dropped significantly, at intervals of 4h, 4h, and 5h with sludge concentrations of 8665.6mg/L, 6498.8mg/L, and 4332.5mg/L, then it would become moderate. However, under acidic conditions, pH increased from 4 to 5. Finally, under neutral conditions pH exhibited a decrease then an increase throughout entire fermentation process. Further study showed short-chain fatty acids (SCFAs), ammonia nitrogen and cations contributed to pH change under various fermentation conditions. This study presents a novel strategy based on pH change to predict whether SCFAs reach their stable stage.

  19. The cell transmembrane pH gradient in tumors enhances cytotoxicity of specific weak acid chemotherapeutics.

    Science.gov (United States)

    Kozin, S V; Shkarin, P; Gerweck, L E

    2001-06-15

    The extracellular pH is lower in tumor than in normal tissue, whereas their intracellular pH is similar. In this study, we show that the tumor-specific pH gradient may be exploited for the treatment of cancer by weak acid chemotherapeutics. i.v.-injected glucose substantially decreased the electrode estimated extracellular pH in a xenografted human tumor while its intracellular pH, evaluated by (31)P magnetic resonance spectroscopy, remained virtually unchanged. The resulting increase in the average cell pH gradient caused a parallel increase in tumor growth delay by the weak acid chlorambucil (CHL). Regardless of glucose administration, the effect of CHL was significantly greater in tumors preirradiated with a large dose of ionizing radiation. This suggests that CHL was especially pronounced in radioresistant hypoxic cells possessing a larger transmembrane pH gradient. These results indicate that the naturally occurring cell pH gradient difference between tumor and normal tissue is a major and exploitable determinant of the uptake of weak acids in the complex tumor microenvironment. The use of such drugs may be especially effective in combination with radiation.

  20. Molecular Dynamics Simulations Capture the Misfolding of the Bovine Prion Protein at Acidic pH

    Directory of Open Access Journals (Sweden)

    Chin Jung Cheng

    2014-02-01

    Full Text Available Bovine spongiform encephalopathy (BSE, or mad cow disease, is a fatal neurodegenerative disease that is transmissible to humans and that is currently incurable. BSE is caused by the prion protein (PrP, which adopts two conformers; PrPC is the native innocuous form, which is α-helix rich; and PrPSc is the β-sheet rich misfolded form, which is infectious and forms neurotoxic species. Acidic pH induces the conversion of PrPC to PrPSc. We have performed molecular dynamics simulations of bovine PrP at various pH regimes. An acidic pH environment induced conformational changes that were not observed in neutral pH simulations. Putative misfolded structures, with nonnative β-strands formed in the flexible N-terminal domain, were found in acidic pH simulations. Two distinct pathways were observed for the formation of nonnative β-strands: at low pH, hydrophobic contacts with M129 nucleated the nonnative β-strand; at mid-pH, polar contacts involving Q168 and D178 facilitated the formation of a hairpin at the flexible N-terminus. These mid- and low pH simulations capture the process of nonnative β-strand formation, thereby improving our understanding of how PrPC misfolds into the β-sheet rich PrPSc and how pH factors into the process.

  1. [Application of a pH feedback-controlled substrate feeding method in glutamic acid fermentation].

    Science.gov (United States)

    Xing, Yu; Zhang, Liye; Cong, Wei; Yue, Lei; Chen, Chongan; Ma, Jiyin

    2011-10-01

    A novel method based on pH value was proposed to simplify the substrate feeding method for glutamic acid fermentation. The linear relationship between the consumption amounts of ammonia (x) and that of glucose (y) was established (y = 7.4744x, R2 = 0.9989) which could be used as the ratio of the amount of ammonia and that of glucose in the feeding broth. Thus the concentration of glucose could be controlled through the adjustment of pH automatically. In the glutamic acid fermentation using the pH feedback-controlled glucose feeding method, the glucose concentration in fermentation broth was maintained between 12 and 21 g/L. Compare with the constant glucose concentration feeding method, the glucose conversion rate and glutamic acid productivity increased by 9.06% and 17.5% respectively, when the pH feedback-controlled glucose feeding method was employed, and fermentation period was shorten above 2 h.

  2. Life at acidic pH imposes an increased energetic cost for a eukaryotic acidophile.

    Science.gov (United States)

    Messerli, Mark A; Amaral-Zettler, Linda A; Zettler, Erik; Jung, Sung-Kwon; Smith, Peter J S; Sogin, Mitchell L

    2005-07-01

    Organisms growing in acidic environments, pHpH. We begin to investigate this premise by determining the magnitude of the transmembrane electrochemical H+ gradient in an acidophilic Chlamydomonas sp. (ATCC PRA-125) isolated from the Rio Tinto, a heavy metal laden, acidic river (pH 1.7-2.5). This acidophile grows most rapidly at pH 2 but is capable of growth over a wide pH range (1.5-7.0), while Chlamydomonas reinhardtii is restricted to growth at pH>or=3 with optimal growth between pH 5.5 and 8.5. With the fluorescent H+ indicator, 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF), we show that the acidophilic Chlamydomonas maintains an average cytosolic pH of 6.6 in culture medium at both pH 2 and pH 7 while Chlamydomonas reinhardtii maintains an average cytosolic pH of 7.1 in pH 7 culture medium. The transmembrane electric potential difference of Chlamydomonas sp., measured using intracellular electrodes at both pH 2 and 7, is close to 0 mV, a rare value for plants, animals and protists. The 40,000-fold difference in [H+] could be the result of either active or passive mechanisms. Evidence for active maintenance was detected by monitoring the rate of ATP consumption. At the peak, cells consume about 7% more ATP per second in medium at pH 2 than at pH 7. This increased rate of consumption is sufficient to account for removal of H+ entering the cytosol across a membrane with relatively high permeability to H+ (7x10(-8) cm s-1). Our results indicate that the small increase in the rate of ATP consumption can account for maintenance of the transmembrane H+ gradient without the imposition of cell surface H+ barriers.

  3. pH effects of the addition of three biochars to acidic Indonesian mineral soils

    DEFF Research Database (Denmark)

    Martinsen, V; Alling, V; Nurida, N L

    2015-01-01

    Soil acidity may severely reduce crop production. Biochar (BC) may increase soil pH and cation exchange capacity (CEC) but reported effects differ substantially. In a systematic approach, using a standardized protocol on a uniquely large number set of 31 acidic soils, we quantified the effect of ...

  4. The pH ruler: a Java applet for developing interactive exercises on acids and bases.

    Science.gov (United States)

    Barrette-Ng, Isabelle H

    2011-07-01

    In introductory biochemistry courses, it is often a struggle to teach the basic concepts of acid-base chemistry in a manner that is relevant to biological systems. To help students gain a more intuitive and visual understanding of abstract acid-base concepts, a simple graphical construct called the pH ruler Java applet was developed. The applet allows students to visualize the abundance of different protonation states of diprotic and triprotic amino acids at different pH values. Using the applet, the student can drag a widget on a slider bar to change the pH and observe in real time changes in the abundance of different ionization states of this amino acid. This tool provides a means for developing more complex inquiry-based, active-learning exercises to teach more advanced topics of biochemistry, such as protein purification, protein structure and enzyme mechanism.

  5. Determination of the corrosive power of acid pH brines

    Energy Technology Data Exchange (ETDEWEB)

    Duhalt K., A.; Mendoza C., M.; Cortes M., C.

    1970-03-01

    The basic function of hydrochloric acid (aqueous solution 15 to 28% by wt) when injected into an oil well is to react with the carbonates which make up the formation, to improve the interconnection between pores (permeability), and create drainage channels for the fluids contained in the rock. However, this chemical reaction creates brines which may be damaging to tools, tubing, and surface equipment, if they are not withdrawn immediately. The present study presents the results (in graphical representations) of a study of the corrosive aggressiveness of different brines with acid pH. From the results of this study and of the technical discussion included, the following conclusions were reached: (1) at ambient temperatures (40/sup 0/C), the corrosion is acceptable in case of fluids with a pH of 3; (2) at a subsurface temperature of 80/sup 0/C, corrosion is acceptable when the fluid has a pH of 5; (3) there is no economic justification to look for a pH of 7 in the spent acid, because the aggressiveness does not greatly decrease between pH 5 and pH 7; and (4) in view of the above, it is considered necessary to clean out the well until the fluid reaches a pH of 5, with the consequent saving of time in operation of equipment.

  6. Effect of pH on conjugated linoleic acid (CLA) formation of linolenic acid biohydrogenation by ruminal microorganisms.

    Science.gov (United States)

    Lee, Yongjae

    2013-08-01

    Conventional beliefs surrounding the linolenic acid (LNA; cis-9 cis-12 cis-15 C18:3) biohydrogenation (BH) pathway propose that it converts to stearic acid (SA) without the formation of conjugated linoleic acid (CLA) as intermediate isomers. However, an advanced study (Lee and Jenkins, 2011) verified that LNA BH yields multiple CLAs. This study utilized the stable isotope tracer to investigate the BH intermediates of (13)C-LNA with different pH conditions (5.5 and 6.5). The (13)C enrichment was calculated as a (13)C/(12)C ratio of labeled minus unlabeled. After 24 h, eight CLA isomers were significantly enriched on both pH treatment, this result verifies that these CLAs originated from (13)C-LNA BH which supports the results of Lee and Jenkins (2011). The enrichment of cis-cis double bond CLAs (cis-9 cis-11 and cis-10 cis-12 CLA) were significantly higher at low pH conditions. Furthermore, the concentration of cis-10 cis-12 CLA at low pH was four times higher than at high pH conditions after a 3 h incubation. These differences support the LNA BH pathways partial switch under different pH conditions, with a strong influence on the cis-cis CLA at low pH. Several mono-, di-, and tri-enoic fatty acid isomers were enriched during 24 h of incubation, but the enrichment was decreased or restricted at low pH treatment. Based on these results, it is proposed that low pH conditions may cause a changed or limited capacity of the isomerization and reduction steps in BH.

  7. Acidic Food pH Increases Palatability and Consumption and Extends Drosophila Lifespan.

    Science.gov (United States)

    Deshpande, Sonali A; Yamada, Ryuichi; Mak, Christine M; Hunter, Brooke; Soto Obando, Alina; Hoxha, Sany; Ja, William W

    2015-12-01

    Despite the prevalent use of Drosophila as a model in studies of nutrition, the effects of fundamental food properties, such as pH, on animal health and behavior are not well known. We examined the effect of food pH on adult Drosophila lifespan, feeding behavior, and microbiota composition and tested the hypothesis that pH-mediated changes in palatability and total consumption are required for modulating longevity. We measured the effect of buffered food (pH 5, 7, or 9) on male gustatory responses (proboscis extension), total food intake, and male and female lifespan. The effect of food pH on germfree male lifespan was also assessed. Changes in fly-associated microbial composition as a result of food pH were determined by 16S ribosomal RNA gene sequencing. Male gustatory responses, total consumption, and male and female longevity were additionally measured in the taste-defective Pox neuro (Poxn) mutant and its transgenic rescue control. An acidic diet increased Drosophila gustatory responses (40-230%) and food intake (5-50%) and extended survival (10-160% longer median lifespan) compared with flies on either neutral or alkaline pH food. Alkaline food pH shifted the composition of fly-associated bacteria and resulted in greater lifespan extension (260% longer median survival) after microbes were eliminated compared with flies on an acidic (50%) or neutral (130%) diet. However, germfree flies lived longer on an acidic diet (5-20% longer median lifespan) compared with those on either neutral or alkaline pH food. Gustatory responses, total consumption, and longevity were unaffected by food pH in Poxn mutant flies. Food pH can directly influence palatability and feeding behavior and affect parameters such as microbial growth to ultimately affect Drosophila lifespan. Fundamental food properties altered by dietary or drug interventions may therefore contribute to changes in animal physiology, metabolism, and survival. © 2015 American Society for Nutrition.

  8. Monascus ruber as cell factory for lactic acid production at low pH.

    Science.gov (United States)

    Weusthuis, Ruud A; Mars, Astrid E; Springer, Jan; Wolbert, Emil Jh; van der Wal, Hetty; de Vrije, Truus G; Levisson, Mark; Leprince, Audrey; Houweling-Tan, G Bwee; Pha Moers, Antoine; Hendriks, Sjon Na; Mendes, Odette; Griekspoor, Yvonne; Werten, Marc Wt; Schaap, Peter J; van der Oost, John; Eggink, Gerrit

    2017-07-01

    A Monascus ruber strain was isolated that was able to grow on mineral medium at high sugar concentrations and 175g/l lactic acid at pH 2.8. Its genome and transcriptomes were sequenced and annotated. Genes encoding lactate dehydrogenase (LDH) were introduced to accomplish lactic acid production and two genes encoding pyruvate decarboxylase (PDC) were knocked out to subdue ethanol formation. The strain preferred lactic acid to glucose as carbon source, which hampered glucose consumption and therefore also lactic acid production. Lactic acid consumption was stopped by knocking out 4 cytochrome-dependent LDH (CLDH) genes, and evolutionary engineering was used to increase the glucose consumption rate. Application of this strain in a fed-batch fermentation resulted in a maximum lactic acid titer of 190g/l at pH 3.8 and 129g/l at pH 2.8, respectively 1.7 and 2.2 times higher than reported in literature before. Yield and productivity were on par with the best strains described in literature for lactic acid production at low pH. Copyright © 2017 International Metabolic Engineering Society. Published by Elsevier Inc. All rights reserved.

  9. Natively unfolded human prothymosin alpha adopts partially folded collapsed conformation at acidic pH.

    Science.gov (United States)

    Uversky, V N; Gillespie, J R; Millett, I S; Khodyakova, A V; Vasiliev, A M; Chernovskaya, T V; Vasilenko, R N; Kozlovskaya, G D; Dolgikh, D A; Fink, A L; Doniach, S; Abramov, V M

    1999-11-09

    Prothymosin alpha has previously been shown to be unfolded at neutral pH, thus belonging to a growing family of "natively unfolded" proteins. The structural properties and conformational stability of recombinant human prothymosin alpha were characterized at neutral and acidic pH by gel filtration, SAXS, circular dichroism, ANS fluorescence, (1)H NMR, and resistance to urea-induced unfolding. Interestingly, prothymosin alpha underwent a cooperative transition from the unfolded state into a partially folded conformation on lowering the pH. This conformation of prothymosin alpha is a compact denatured state, with structural properties different from those of the molten globule. The formation of alpha-helical structure by the glutamic acid-rich elements of the protein accompanied by the partial hydrophobic collapse is expected at lower pH due to the neutralization of the negatively charged residues. It is possible that such conformational changes may be associated with the protein function.

  10. Photoionization of aromatic amino acid at different pH values

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The photoioization of aromatic amino acid in solutions of different pH values were investigated by 248 nm laser flash photolysis. The results showed that the photoionizations of tyrosine and tryptophan were affected by pH value of solution, but phenylalanine was not. The ionization was in favor of monophotonic process at high pH value and of biphotonic process at low pH value. The mechanisms of pH effect on photoionization of tyrosine and tryptophan were the deprotonation of phenolic hydroxyl group and the deprotonation of>NH on the indole ring respectively. Our results explain the discrepancy of values for the yield of hydrated electron obtained by other investigators.

  11. Initial pH of medium affects organic acids production but do not affect phosphate solubilization

    Directory of Open Access Journals (Sweden)

    Leandro M. Marra

    2015-06-01

    Full Text Available The pH of the culture medium directly influences the growth of microorganisms and the chemical processes that they perform. The aim of this study was to assess the influence of the initial pH of the culture medium on the production of 11 low-molecular-weight organic acids and on the solubilization of calcium phosphate by bacteria in growth medium (NBRIP. The following strains isolated from cowpea nodules were studied: UFLA03-08 (Rhizobium tropici, UFLA03-09 (Acinetobacter sp., UFLA03-10 (Paenibacillus kribbensis, UFLA03-106 (Paenibacillus kribbensis and UFLA03-116 (Paenibacillus sp.. The strains UFLA03-08, UFLA03-09, UFLA03-10 and UFLA03-106 solubilized Ca3(PO42 in liquid medium regardless of the initial pH, although without a significant difference between the treatments. The production of organic acids by these strains was assessed for all of the initial pH values investigated, and differences between the treatments were observed. Strains UFLA03-09 and UFLA03-10 produced the same acids at different initial pH values in the culture medium. There was no correlation between phosphorus solubilized from Ca3(PO42 in NBRIP liquid medium and the concentration of total organic acids at the different initial pH values. Therefore, the initial pH of the culture medium influences the production of organic acids by the strains UFLA03-08, UFLA03-09, UFLA03-10 and UFLA03-106 but it does not affect calcium phosphate solubilization.

  12. Long-term temporal trends and spatial patterns in the acid-base chemistry of lakes in the Adirondack region of New York in response to decreases in acidic deposition

    Science.gov (United States)

    Driscoll, Charles T.; Driscoll, Kimberley M.; Fakhraei, Habibollah; Civerolo, Kevin

    2016-12-01

    We examined the response of lake water chemistry in the Adirondack Mountains of New York State, USA to decreases in acid deposition. Striking declines in the concentrations and fluxes of sulfate and hydrogen ion in wet deposition have been observed since the late 1970s, while significant decreases in nitrate have been evident since the early 2000s. Decreases in estimated dry sulfur and nitrate deposition have also occurred in the Adirondacks, but with no change in dry to wet deposition ratios. These patterns follow long-term decreases in anthropogenic emissions of sulfur dioxide and nitrogen oxides in the U.S. over the same interval. All of the 48 lakes monitored through the Adirondack Long-Term Monitoring program since 1992 have exhibited significant declines in sulfate concentrations, consistent with reductions in atmospheric deposition of sulfur. Nitrate concentrations have also significantly diminished at variable rates in many (33 of 48) lakes. Decreases in concentrations of sulfate plus nitrate (48 of 48) in lakes have driven widespread increases in acid neutralizing capacity (ANC; 42 of 48) and lab pH (33 of 48), and decreases in the toxic fraction, inorganic monomeric Al (45 of 48). Coincident with decreases in acid deposition, concentrations of dissolved organic carbon (DOC) have also increased in some (29 of 48) lakes. While recovery from elevated acid deposition is evident across Adirondack lakes, highly sensitive and impacted mounded seepages lakes and thin till drainage lakes are recovering most rapidly. Future research might focus on how much additional recovery could be achieved given the current deposition relative to future deposition anticipated under the Clean Power Plan, ecosystem effects of increased mobilization of dissolved organic matter, and the influence of changing climate on recovery from acidification.

  13. Sensing and adaptation to low pH mediated by inducible amino acid decarboxylases in Salmonella.

    Directory of Open Access Journals (Sweden)

    Julie P M Viala

    Full Text Available During the course of infection, Salmonella enterica serovar Typhimurium must successively survive the harsh acid stress of the stomach and multiply into a mild acidic compartment within macrophages. Inducible amino acid decarboxylases are known to promote adaptation to acidic environments. Three low pH inducible amino acid decarboxylases were annotated in the genome of S. Typhimurium, AdiA, CadA and SpeF, which are specific for arginine, lysine and ornithine, respectively. In this study, we characterized and compared the contributions of those enzymes in response to acidic challenges. Individual mutants as well as a strain deleted for the three genes were tested for their ability (i to survive an extreme acid shock, (ii to grow at mild acidic pH and (iii to infect the mouse animal model. We showed that the lysine decarboxylase CadA had the broadest range of activity since it both had the capacity to promote survival at pH 2.3 and growth at pH 4.5. The arginine decarboxylase AdiA was the most performant in protecting S. Typhimurium from a shock at pH 2.3 and the ornithine decarboxylase SpeF conferred the best growth advantage under anaerobiosis conditions at pH 4.5. We developed a GFP-based gene reporter to monitor the pH of the environment as perceived by S. Typhimurium. Results showed that activities of the lysine and ornithine decarboxylases at mild acidic pH did modify the local surrounding of S. Typhimurium both in culture medium and in macrophages. Finally, we tested the contribution of decarboxylases to virulence and found that these enzymes were dispensable for S. Typhimurium virulence during systemic infection. In the light of this result, we examined the genomes of Salmonella spp. normally responsible of systemic infection and observed that the genes encoding these enzymes were not well conserved, supporting the idea that these enzymes may be not required during systemic infection.

  14. Controls on the pH of hyper-saline lakes - A lesson from the Dead Sea

    Science.gov (United States)

    Golan, Rotem; Gavrieli, Ittai; Ganor, Jiwchar; Lazar, Boaz

    2016-01-01

    The pH of aqueous environments is determined by the dominant buffer systems of the water, defined operationally as total alkalinity (TA). The major buffer systems in the modern ocean are carbonic and boric acids of which the species bicarbonate, carbonate and borate make up about 77%, 19% and 4% of the TA, respectively. During the course of seawater evaporation (e.g. lagoons) the residual brine loses considerable portion of the dissolved inorganic carbon (DIC) and carbonate alkalinity (CA) already at the early stages of evaporation. DIC and CA decrease due to massive precipitation of CaCO3, while total boron (TB) increases conservatively, turning borate to the dominant alkalinity species in marine derived brines. In the present work we assess the apparent dissociation constant value of boric acid (KB‧) in saline and hypersaline waters, using the Dead Sea (DS) as a case study. We explain the DS low pH (∼6.3) and the effect of the boric and carbonic acid pK‧-s on the behavior of the brine's buffer system, including the pH increase that results from brine dilution.

  15. Acidic duodenal pH alters gene expression in the cystic fibrosis mouse pancreas.

    Science.gov (United States)

    Kaur, Simran; Norkina, Oxana; Ziemer, Donna; Samuelson, Linda C; De Lisle, Robert C

    2004-08-01

    The duodenum is abnormally acidic in cystic fibrosis (CF) due to decreased bicarbonate ion secretion that is dependent on the CF gene product CFTR. In the CFTR null mouse, the acidic duodenum results in increased signaling from the intestine to the exocrine pancreas in an attempt to stimulate pancreatic bicarbonate ion secretion. Excess stimulation is proposed to add to the stress/inflammation of the pancreas in CF. DNA microarray analysis of the CF mouse revealed altered pancreatic gene expression characteristic of stress/inflammation. When the duodenal pH was corrected genetically (crossing CFTR null with gastrin null mice) or pharmacologically (use of the proton pump inhibitor omeprazole), expression levels of genes measured by quantitative RT-PCR were significantly normalized. It is concluded that the acidic duodenal pH in CF contributes to the stress on the exocrine pancreas and that normalizing duodenal pH reduces this stress.

  16. Kinetics of salivary pH after acidic beverage intake by patients undergoing orthodontic treatment.

    Science.gov (United States)

    Turssi, Cecilia P; Silva, Carolina S; Bridi, Enrico C; Amaral, Flavia Lb; Franca, Fabiana Mg; Basting, Roberta T

    2015-01-01

    The saliva of patients undergoing orthodontic treatment with fixed appliances can potentially present a delay in the diluting, clearing, and buffering of dietary acids due to an increased number of retention areas. The aim of this clinical trial was to compare salivary pH kinetics of patients with and without orthodontic treatment, following the intake of an acidic beverage. Twenty participants undergoing orthodontic treatment and 20 control counterparts had their saliva assessed for flow rate, pH, and buffering capacity. There was no significant difference between salivary parameters in participants with or without an orthodontic appliance. Salivary pH recovery following acidic beverage intake was slower in the orthodontic subjects compared to controls. Patients with fixed orthodontic appliances, therefore, seem to be at higher risk of dental erosion, suggesting that dietary advice and preventive care need to be implemented during orthodontic treatment.

  17. Influence of acidic pH on hydrogen and acetate production by an electrosynthetic microbiome.

    Directory of Open Access Journals (Sweden)

    Edward V LaBelle

    Full Text Available Production of hydrogen and organic compounds by an electrosynthetic microbiome using electrodes and carbon dioxide as sole electron donor and carbon source, respectively, was examined after exposure to acidic pH (∼ 5. Hydrogen production by biocathodes poised at -600 mV vs. SHE increased >100-fold and acetate production ceased at acidic pH, but ∼ 5-15 mM (catholyte volume/day acetate and >1,000 mM/day hydrogen were attained at pH ∼ 6.5 following repeated exposure to acidic pH. Cyclic voltammetry revealed a 250 mV decrease in hydrogen overpotential and a maximum current density of 12.2 mA/cm2 at -765 mV (0.065 mA/cm2 sterile control at -800 mV by the Acetobacterium-dominated community. Supplying -800 mV to the microbiome after repeated exposure to acidic pH resulted in up to 2.6 kg/m3/day hydrogen (≈ 2.6 gallons gasoline equivalent, 0.7 kg/m3/day formate, and 3.1 kg/m3/day acetate ( = 4.7 kg CO2 captured.

  18. The effects of extracellular pH and hydroxycinnamic acids influence the intracellular pH of Brettanomyces bruxellensis DSM 7001

    DEFF Research Database (Denmark)

    Campolongo, Simona; Siegumfeldt, Henrik; Aabo, Thomas Ask

    2014-01-01

    and intracellular pH changes in B. bruxellensis DSM 7001, in response to extracellular pH, as well as to the presence of an energy source and hydroxycinnamic acids, have been investigated in this paper by means of Fluorescent Ratio Imaging Microscopy (FRIM). The results show that B. bruxellensis DSM 7001 is able...

  19. NAADP induces pH changes in the lumen of acidic Ca2+ stores

    OpenAIRE

    2006-01-01

    Abstract NAADP-induced Ca 2+} release has been proposed to occur selectively from acidic stores in several cell types including sea urchin eggs. Using fluorescence measurements, we have investigated whether NAADP-induced Ca 2+} release alters the luminal pH (pHL) within these acidic stores in egg homogenates and observed their prompt, concentration-dependent alkalinization by NAADP (but not {beta}-NAD +} or NADP). Like Ca 2+} release, the pH L} change was desensitized by low concen...

  20. Lake

    Science.gov (United States)

    Wien, Carol Anne

    2008-01-01

    The lake is blue black and deep. It is a glaciated finger lake, clawed out of rock when ice retracted across Nova Scotia in a northerly direction during the last ice age. The lake is narrow, a little over a mile long, and deep, 90 to 190 feet in places according to local lore, off the charts in others. The author loves to swim there, with a sense…

  1. Development of Online Spectroscopic pH Monitoring for Nuclear Fuel Reprocessing Plants: Weak Acid Schemes.

    Science.gov (United States)

    Casella, Amanda J; Ahlers, Laura R H; Campbell, Emily L; Levitskaia, Tatiana G; Peterson, James M; Smith, Frances N; Bryan, Samuel A

    2015-05-19

    In nuclear fuel reprocessing, separating trivalent minor actinides and lanthanide fission products is extremely challenging and often necessitates tight pH control in TALSPEAK (Trivalent Actinide-Lanthanide Separation by Phosphorus reagent Extraction from Aqueous Komplexes) separations. In TALSPEAK and similar advanced processes, aqueous pH is one of the most important factors governing the partitioning of lanthanides and actinides between an aqueous phase containing a polyaminopolycarboxylate complexing agent and a weak carboxylic acid buffer and an organic phase containing an acidic organophosphorus extractant. Real-time pH monitoring would significantly increase confidence in the separation performance. Our research is focused on developing a general method for online determination of the pH of aqueous solutions through chemometric analysis of Raman spectra. Spectroscopic process-monitoring capabilities, incorporated in a counter-current centrifugal contactor bank, provide a pathway for online, real-time measurement of solution pH. The spectroscopic techniques are process-friendly and can be easily configured for online applications, whereas classic potentiometric pH measurements require frequent calibration/maintenance and have poor long-term stability in aggressive chemical and radiation environments. Raman spectroscopy discriminates between the protonated and deprotonated forms of the carboxylic acid buffer, and the chemometric processing of the Raman spectral data with PLS (partial least-squares) regression provides a means to quantify their respective abundances and therefore determine the solution pH. Interpretive quantitative models have been developed and validated under a range of chemical composition and pH conditions using a lactic acid/lactate buffer system. The developed model was applied to new spectra obtained from online spectral measurements during a solvent extraction experiment using a counter-current centrifugal contactor bank. The model

  2. THE IMPACT OF CONJUGATED LINOLEIC ACID ADDITION ON PH VALUE OF LONGISSIMUS DORSI MUSCLE

    Directory of Open Access Journals (Sweden)

    Przemysław WASILEWSKI

    2009-08-01

    Full Text Available The subject of research was 60 crossbred gilts, divided into 6 groups, fed the fodder with addition of conjugated linoleic acid (CLA or sunflower oil (SFO in amount: 0.5; 1.0; and 2.0 %, respectively. Animals were slaughtered with the body weight ca. 95 kg. The aim of research was to determine pH value of loin meat tissue (Longissimus dorsi of right half-carcass in 45 minutes, 2, 3, 4, 5, 6 hours and 24 hours after slaughter. Results were statistically elaborated using one-way variance analysis. Longissimus dorsi muscle pH values measured 45 minutes after slaughter in case of all groups of pigs were in range from 6.34 up to 6.47, what shows good meat quality. The lowest pH1 (measured 45 minutes after slaughter had meat of fatteners where addition of 2 % sunflower oil was given into fodder and the highest value of this trait was in group of individuals where also was given sunflower oil in 1 % amount. Statistical significant differences in pH value measured in different time after slaughter i.e. after 45 minutes, 2, 3, 4, 6 and 24 hours between tested groups of pigs were not stated. The exception is the result of pH measurement 5 hours after slaughter. Statistical significant differences were between group of pigs getting 0.5 % addition of conjugated linoleic acid characterized by the highest pH value of meat and group of animals fed the fodder with 1 % addition of conjugated linoleic acid (P≤0.01. On the basis of the results obtained in presented paper may be stated that feeding pigs with addition of conjugated linoleic acid in amounts 0.5; 1.0 and 2.0 % did not impact negatively on meat quality defined by pH value.

  3. Nestedness in Arbuscular Mycorrhizal Fungal Communities along Soil pH Gradients in Early Primary Succession: Acid-Tolerant Fungi Are pH Generalists.

    Science.gov (United States)

    Kawahara, Ai; An, Gi-Hong; Miyakawa, Sachie; Sonoda, Jun; Ezawa, Tatsuhiro

    2016-01-01

    Soil acidity is a major constraint on plant productivity. Arbuscular mycorrhizal (AM) fungi support plant colonization in acidic soil, but soil acidity also constrains fungal growth and diversity. Fungi in extreme environments generally evolve towards specialists, suggesting that AM fungi in acidic soil are acidic-soil specialists. In our previous surveys, however, some AM fungi detected in strongly acidic soils could also be detected in a soil with moderate pH, which raised a hypothesis that the fungi in acidic soils are pH generalists. To test the hypothesis, we conducted a pH-manipulation experiment and also analyzed AM fungal distribution along a pH gradient in the field using a synthesized dataset of the previous and recent surveys. Rhizosphere soils of the generalist plant Miscanthus sinensis were collected both from a neutral soil and an acidic soil, and M. sinensis seedlings were grown at three different pH. For the analysis of field communities, rhizosphere soils of M. sinensis were collected from six field sites across Japan, which covered a soil pH range of 3.0-7.4, and subjected to soil trap culture. AM fungal community compositions were determined based on LSU rDNA sequences. In the pH-manipulation experiment the acidification of medium had a significant impact on the compositions of the community from the neutral soil, but the neutralization of the medium had no effect on those of the community from the acidic soil. Furthermore, the communities in lower -pH soils were subsets of (nested in) those in higher-pH soils. In the field communities a significant nestedness pattern was observed along the pH gradient. These observations suggest that the fungi in strongly acidic soils are pH generalists that occur not only in acidic soil but also in wide ranges of soil pH. Nestedness in AM fungal community along pH gradients may have important implications for plant community resilience and early primary succession after disturbance in acidic soils.

  4. Patterns of nutrient dynamics in Adirondack lakes recovering from acid deposition.

    Science.gov (United States)

    Gerson, Jacqueline R; Driscoll, Charles T; Roy, Karen M

    2016-09-01

    With decreases in acid deposition, nitrogen : phosphorus (N:P) ratios in lakes are anticipated to decline, decreasing P limitation of phytoplankton and potentially changing current food web dynamics. This effect could be particularly pronounced in the Adirondack Mountains of New York State, a historic hotspot for effects of acid deposition. In this study, we evaluate spatial patterns of nutrient dynamics in Adirondack lakes and use these to infer potential future temporal trends. We calculated Mann-Kendall tau correlations among total phosphorus (TP), chlorophyll a, dissolved organic carbon (DOC), acid neutralizing capacity (ANC), and nitrate (NO3(-) ) concentrations in 52 Adirondack Long Term Monitoring (ALTM) program lakes using samples collected monthly during 2008-2012. We evaluated the hypothesis that decreased atmospheric N and S deposition will decrease P limitation in freshwater ecosystems historically impacted by acidification. We also compared these patterns among lake watershed characteristics (i.e., seepage or lacking a surface outlet, chain drainage, headwater drainage, thin glacial till, medium glacial till). We found that correlations (P lakes. Differentiations among watershed till depth were also important in determining correlations due to water interaction with surficial geology. Additionally, we found low NO3(-) :TP (N:P mass) values in seepage lakes (2.0 in winter, 1.9 in summer) compared to chain drainage lakes (169.4 in winter, 49.5 in summer) and headwater drainage lakes (97.0 in winter, 10.9 in summer), implying a high likelihood of future shifts in limitation patterns for seepage lakes. With increasing DOC and decreasing NO3(-) concentrations coinciding with decreases in acid deposition, there is reason to expect changes in nutrient dynamics in Adirondack lakes. Seepage lakes may become N-limited, while drainage lakes may become less P-limited, both resulting in increased productivity. Long-term measurements of TP and chlorophyll a from

  5. A new fluorescent pH probe for extremely acidic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yu [School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Taishan College, Shandong University, Jinan 250100 (China); Jiang, Zheng [School of Life Science, Shandong University, Jinan 250100 (China); Taishan College, Shandong University, Jinan 250100 (China); Xiao, Yu [School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Taishan College, Shandong University, Jinan 250100 (China); Bi, Fu-Zhen [School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Miao, Jun-Ying, E-mail: miaojy@sdu.edu.cn [School of Life Science, Shandong University, Jinan 250100 (China); Zhao, Bao-Xiang, E-mail: bxzhao@sdu.edu.cn [School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China)

    2014-04-01

    A new coumarin-based fluorescent probe can detect highly acidic conditions in both solution and bacteria with high selectivity and sensitivity. Highlights: • A new fluorescence probe for very low pH was synthesized and characterized. • The probe can monitor pH in solution and bacteria. • The two-step protonation of N atoms of the probe leads to fluorescence quenching. Abstract: A novel turn-off fluorescent probe based on coumarin and imidazole moiety for extremely acidic conditions was designed and developed. The probe with pKa = 2.1 is able to respond to very low pH value (below 3.5) with high sensitivity relying on fluorescence quenching at 460 nm in fluorescence spectra or the ratios of absorbance maximum at 380 nm to that at 450 nm in UV–vis spectra. It can quantitatively detect pH value based on equilibrium equation, pH = pKa -log[(Ix - Ib)/(Ia - Ix)]. It had very short response time that was less than 1 min, good reversibility and nearly no interference from common metal ions. Moreover, using ¹H NMR analysis and theoretical calculation of molecular orbital, we verified that a two-step protonation process of two N atoms of the probe leaded to photoinduced electron transfer (PET), which was actually the mechanism of the fluorescence quenching phenomenon under strongly acidic conditions. Furthermore, the probe was also applied to imaging strong acidity in bacteria, E.coli and had good effect. This work illustrates that the new probe could be a practical and ideal pH indicator for strongly acidic conditions with good biological significance.

  6. A new boronic acid fluorescent sensor based on fluorene for monosaccharides at physiological pH

    Science.gov (United States)

    Hosseinzadeh, Rahman; Mohadjerani, Maryam; Pooryousef, Mona; Eslami, Abbas; Emami, Saeed

    2015-06-01

    Fluorescent boronic acids are very useful fluorescent sensor for detection of biologically important saccharides. Herein we synthesized a new fluorene-based fluorescent boronic acid that shows significant fluorescence changes upon addition of saccharides at physiological pH. Upon addition of fructose, sorbitol, glucose, galactose, ribose, and maltose at different concentration to the solution of 7-(dimethylamino)-9,9-dimethyl-9H-fluoren-2-yl-2-boronic acid (7-DMAFBA, 1), significant decreases in fluorescent intensity were observed. It was found that this boronic acid has high affinity (Ka = 3582.88 M-1) and selectivity for fructose over glucose at pH = 7.4. The sensor 1 showed a linear response toward D-fructose in the concentrations ranging from 2.5 × 10-5 to 4 × 10-4 mol L-1 with the detection limit of 1.3 × 10-5 mol L-1.

  7. Dicarboxy-dichlorofluorescein: a new fluorescent probe for measuring acidic intracellular pH.

    Science.gov (United States)

    Nedergaard, M; Desai, S; Pulsinelli, W

    1990-05-15

    Derivatives of fluorescein sensitive to pH are extensively utilized for the determination of intracellular pH (pHi). Available dyes have pKa values of approximately 7.0, and are not well suited for measuring acidic pHi. We examined the fluorescein derivative, 5 (and 6)-carboxy-2',7'-dichlorofluorescein (CDCF) for its potential in the microspectrofluorometric measurement of pHi during acidic conditions. CDCF showed intense fluorescence and pH sensitivity near its "effective" pKa value of 4.2, using a 495/440 nm dual excitation wave-length ratio method. Protein interactions caused fluorescence ratio deviations which were most pronounced at the extremes of pH, whereas calcium and magnesium concentrations had little effect on the fluorescent ratio intensity. Intracellular calibration performed using nigericin in the presence of high potassium eliminated the need to correct for protein interactions, and the ratio method minimized any variations due to dye concentration differences or instrument fluctuation. Intracellular retention of the dye was high, and 95% of the initial signal remained after 1 h. Fluorescence bleaching was 14.5% after 1 h of continuous excitation and cell survival was not affected by dye loading. We conclude that CDCF is an excellent intracellular pH indicator in the pH range of 4-5.

  8. Polyamine/salt-assembled microspheres coated with hyaluronic acid for targeting and pH sensing.

    Science.gov (United States)

    Zhang, Pan; Yang, Hui; Wang, Guojun; Tong, Weijun; Gao, Changyou

    2016-06-01

    The poly(allylamine hydrochloride)/trisodium citrate aggregates were fabricated and further covalently crosslinked via the coupling reaction of carboxylic sites on trisodium citrate with the amine groups on polyamine, onto which poly-L-lysine and hyaluronic acid were sequentially assembled, forming stable microspheres. The pH sensitive dye and pH insensitive dye were further labeled to enable the microspheres with pH sensing property. Moreover, these microspheres could be specifically targeted to HeLa tumor cells, since hyaluronic acid can specifically recognize and bind to CD44, a receptor overexpressed on many tumor cells. Quantitative pH measurement by confocal laser scanning microscopy demonstrated that the microspheres were internalized into HeLa cells, and accumulated in acidic compartments. By contrast, only a few microspheres were adhered on the NIH 3T3 cells surface. The microspheres with combined pH sensing property and targeting ability can enhance the insight understanding of the targeted drug vehicles trafficking after cellular internalization.

  9. Membrane growth can generate a transmembrane pH gradient in fatty acid vesicles.

    Science.gov (United States)

    Chen, Irene A; Szostak, Jack W

    2004-05-25

    Electrochemical proton gradients are the basis of energy transduction in modern cells, and may have played important roles in even the earliest cell-like structures. We have investigated the conditions under which pH gradients are maintained across the membranes of fatty acid vesicles, a model of early cell membranes. We show that pH gradients across such membranes decay rapidly in the presence of alkali-metal cations, but can be maintained in the absence of permeable cations. Under such conditions, when fatty acid vesicles grow through the incorporation of additional fatty acid, a transmembrane pH gradient is spontaneously generated. The formation of this pH gradient captures some of the energy released during membrane growth, but also opposes and limits further membrane area increase. The coupling of membrane growth to energy storage could have provided a growth advantage to early cells, once the membrane composition had evolved to allow the maintenance of stable pH gradients.

  10. Dissolved Divalent Metal and pH Effects on Amino Acid Polymerization: A Thermodynamic Evaluation

    Science.gov (United States)

    Kitadai, Norio

    2016-06-01

    Polymerization of amino acids is a fundamentally important step for the chemical evolution of life. Nevertheless, its response to changing environmental conditions has not yet been well understood because of the lack of reliable quantitative information. For thermodynamics, detailed prediction over diverse combinations of temperature and pH has been made only for a few amino acid-peptide systems. This study used recently reported thermodynamic dataset for the polymerization of the simplest amino acid "glycine (Gly)" to its short peptides (di-glycine and tri-glycine) to examine chemical and structural characteristics of amino acids and peptides that control the temperature and pH dependence of polymerization. Results showed that the dependency is strongly controlled by the intramolecular distance between the amino and carboxyl groups in an amino acid structure, although the side-chain group role is minor. The polymerization behavior of Gly reported earlier in the literature is therefore expected to be a typical feature for those of α-amino acids. Equilibrium calculations were conducted to examine effects of dissolved metals as a function of pH on the monomer-polymer equilibria of Gly. Results showed that metals shift the equilibria toward the monomer side, particularly at neutral and alkaline pH. Metals that form weak interaction with Gly (e.g., Mg2+) have no noticeable influence on the polymerization, although strong interaction engenders significant decrease of the equilibrium concentrations of Gly peptides. Considering chemical and structural characteristics of Gly and Gly peptides that control their interactions with metals, it can be expected that similar responses to the addition of metals are applicable in the polymerization of neutral α-amino acids. Neutral and alkaline aqueous environments with dissolved metals having high affinity with neutral α-amino acids (e.g., Cu2+) are therefore not beneficial places for peptide bond formation on the primitive

  11. Dissolved Divalent Metal and pH Effects on Amino Acid Polymerization: A Thermodynamic Evaluation.

    Science.gov (United States)

    Kitadai, Norio

    2017-03-01

    Polymerization of amino acids is a fundamentally important step for the chemical evolution of life. Nevertheless, its response to changing environmental conditions has not yet been well understood because of the lack of reliable quantitative information. For thermodynamics, detailed prediction over diverse combinations of temperature and pH has been made only for a few amino acid-peptide systems. This study used recently reported thermodynamic dataset for the polymerization of the simplest amino acid "glycine (Gly)" to its short peptides (di-glycine and tri-glycine) to examine chemical and structural characteristics of amino acids and peptides that control the temperature and pH dependence of polymerization. Results showed that the dependency is strongly controlled by the intramolecular distance between the amino and carboxyl groups in an amino acid structure, although the side-chain group role is minor. The polymerization behavior of Gly reported earlier in the literature is therefore expected to be a typical feature for those of α-amino acids. Equilibrium calculations were conducted to examine effects of dissolved metals as a function of pH on the monomer-polymer equilibria of Gly. Results showed that metals shift the equilibria toward the monomer side, particularly at neutral and alkaline pH. Metals that form weak interaction with Gly (e.g., Mg(2+)) have no noticeable influence on the polymerization, although strong interaction engenders significant decrease of the equilibrium concentrations of Gly peptides. Considering chemical and structural characteristics of Gly and Gly peptides that control their interactions with metals, it can be expected that similar responses to the addition of metals are applicable in the polymerization of neutral α-amino acids. Neutral and alkaline aqueous environments with dissolved metals having high affinity with neutral α-amino acids (e.g., Cu(2+)) are therefore not beneficial places for peptide bond formation on the primitive

  12. Dissolved Divalent Metal and pH Effects on Amino Acid Polymerization: A Thermodynamic Evaluation

    Science.gov (United States)

    Kitadai, Norio

    2017-03-01

    Polymerization of amino acids is a fundamentally important step for the chemical evolution of life. Nevertheless, its response to changing environmental conditions has not yet been well understood because of the lack of reliable quantitative information. For thermodynamics, detailed prediction over diverse combinations of temperature and pH has been made only for a few amino acid-peptide systems. This study used recently reported thermodynamic dataset for the polymerization of the simplest amino acid "glycine (Gly)" to its short peptides (di-glycine and tri-glycine) to examine chemical and structural characteristics of amino acids and peptides that control the temperature and pH dependence of polymerization. Results showed that the dependency is strongly controlled by the intramolecular distance between the amino and carboxyl groups in an amino acid structure, although the side-chain group role is minor. The polymerization behavior of Gly reported earlier in the literature is therefore expected to be a typical feature for those of α-amino acids. Equilibrium calculations were conducted to examine effects of dissolved metals as a function of pH on the monomer-polymer equilibria of Gly. Results showed that metals shift the equilibria toward the monomer side, particularly at neutral and alkaline pH. Metals that form weak interaction with Gly (e.g., Mg2+) have no noticeable influence on the polymerization, although strong interaction engenders significant decrease of the equilibrium concentrations of Gly peptides. Considering chemical and structural characteristics of Gly and Gly peptides that control their interactions with metals, it can be expected that similar responses to the addition of metals are applicable in the polymerization of neutral α-amino acids. Neutral and alkaline aqueous environments with dissolved metals having high affinity with neutral α-amino acids (e.g., Cu2+) are therefore not beneficial places for peptide bond formation on the primitive

  13. Unusual Nonterrestrial L-proteinogenic Amino Acid excesses in the Tagish Lake Meteorite

    Science.gov (United States)

    Glavin, Daniel P.; Elsila, Jamie E.; Burton, Aaron S.; Callahan, Michael P.; Dworkin, Jason P.; Hilts, Robert W.; Herd, D. K.

    2012-01-01

    The distribution and isotopic and enantiomeric compositions of amino acids found in three distinct fragments of the Tagish Lake C2-type carbonaceous chondrite were investigated via liquid chromatography with fluorescence detection and time-of-flight mass spectrometry and gas chromatography isotope ratio mass spectrometry. Large L-enantiomeric excesses (L(sub ee) approximately 43-59%) of the alpha-hydrogen aspartic and glutamic amino acids were measured in Tagish Lake, whereas alanine, another alpha hydrogen protein amino acid, was found to be nearly racemic (D much approximately L) using both techniques. Carbon isotope measurements of D- and L-aspartic acid and 1)- and L-alanine in Tagish Lake fall well outside of the terrestrial range and indicate that the measured aspartic acid enantioenrichment is indigenous to the meteorite. Alternate explanations for the L-excesses of aspartic acid such as interference from other compounds present in the sample, analytical biases, or terrestrial amino acid contamination were investigated and rejected. These results can be explained by differences in the solid-solution phase behavior of aspartic acid, which can form conglomerate enantiopure solids during crystallization, and alanine, which can only form racemic crystals. Amplification of a small initial L-enantiomer excess during aqueous alteration on the meteorite parent body could have led to the large L-enrichments observed for aspartic acid and other conglomerate amino acids in Tagish Lake. The detection of non terrestrial L-proteinogenic amino acid excesses in the Tagish Lake meteorite provides support for the hypothesis that significant enantiomeric enrichments for some amino acids could form by abiotic processes prior to the emergence of life.

  14. Unusual nonterrestrial L-proteinogenic amino acid excesses in the Tagish Lake meteorite

    Science.gov (United States)

    Glavin, Daniel P.; Elsila, Jamie E.; Burton, Aaron S.; Callahan, Michael P.; Dworkin, Jason P.; Hilts, Robert W.; Herd, Christopher D. K.

    2012-08-01

    The distribution and isotopic and enantiomeric compositions of amino acids found in three distinct fragments of the Tagish Lake C2-type carbonaceous chondrite were investigated via liquid chromatography with fluorescence detection and time-of-flight mass spectrometry and gas chromatography isotope ratio mass spectrometry. Large L-enantiomeric excesses (Lee ˜ 43-59%) of the α-hydrogen aspartic and glutamic amino acids were measured in Tagish Lake, whereas alanine, another α-hydrogen protein amino acid, was found to be nearly racemic (D ≈ L) using both techniques. Carbon isotope measurements of D- and L-aspartic acid and D- and L-alanine in Tagish Lake fall well outside of the terrestrial range and indicate that the measured aspartic acid enantioenrichment is indigenous to the meteorite. Alternate explanations for the L-excesses of aspartic acid such as interference from other compounds present in the sample, analytical biases, or terrestrial amino acid contamination were investigated and rejected. These results can be explained by differences in the solid-solution phase behavior of aspartic acid, which can form conglomerate enantiopure solids during crystallization, and alanine, which can only form racemic crystals. Amplification of a small initial L-enantiomer excess during aqueous alteration on the meteorite parent body could have led to the large L-enrichments observed for aspartic acid and other conglomerate amino acids in Tagish Lake. The detection of nonterrestrial L-proteinogenic amino acid excesses in the Tagish Lake meteorite provides support for the hypothesis that significant enantiomeric enrichments for some amino acids could form by abiotic processes prior to the emergence of life.

  15. Molecular Weight Distributions of Cotton Cellulose Treated with a Polycarboxylic Acid at Different pH

    Institute of Scientific and Technical Information of China (English)

    MAO Zhi-ping; Charles Q. Yang

    2004-01-01

    In last paper, the average molecular weight of a control cotton fabric and cotton fabrics treated with the polycarboxylic acid at different pH were measured. The result doesn't support the hypothesis that the pH of the finishing bath can affect the depolymerization of the finished cotton fabric. In order to understand more about it, the molecular weight distributions of the control and finished cotton fabrics were measured and the reason was fund. From the ratio and the molecular weight of the low molecular part one can see that the pH of the finishing bath can affect the depolymerization of the finished cotton fabrics. The phenomenon that the average molecular weights of the cotton fabric crosslinked with BTCA at different pH are almost same is attributed to that the crosslinks are not broken completely when treated with 0.5M NaOH solution at 50℃ for 144h.

  16. Effect of pH on Physicochemical Properties and Encapsulation Efficiency of PEGylated Linolenic Acid Vesicles

    Directory of Open Access Journals (Sweden)

    Yin Yin Teo

    2012-01-01

    Full Text Available The preparation of vesicle from a mixture of linolenic acid and 1,2-dipalmitoyl-sn-glycerol-3-phosphoethanolamine-N-[methoxy-(polyethylene glycol -2000] (DPPE-PEG2000 has been successfully carried out by using dry lipid hydration method. The effect of pH on particle size, zeta potential, encapsulation efficiency and critical vesiculation concentration (CVC of the prepared vesicle suspensions in aqueous were studied. Macroscopic stability of the vesicles was also evaluated through their particle size and zeta potential for a period of 30 days. We found that CVC vary according to the pH, with higher pH of the bulk solution, CVC is higher. Vesicles formed at pH 8.5 were the most stable suspension throughout a period of 30 days compared to those at pH 7.5 and pH 9.0. Addition of DPPE-PEG2000 into the preparation of vesicle at pH 8.5 caused a reduction of the vesicle size to the scale of nanometer which is an advantage to their application. On the other hand, encapsulation of calcein and vitamin E were carried out. Certain amount of these compounds could be successfully loaded into the resulting liposomes under this experimental condition.

  17. Acidic pH induced STM1485 gene is essential for intracellular replication of Salmonella.

    Science.gov (United States)

    Allam, Uday Sankar; Krishna, M Gopala; Sen, Minakshi; Thomas, Rony; Lahiri, Amit; Gnanadhas, Divya Prakash; Chakravortty, Dipshikha

    2012-01-01

    During the course of infection, Salmonella has to face several potentially lethal environmental conditions, one such being acidic pH. The ability to sense and respond to the acidic pH is crucial for the survival and replication of Salmonella. The physiological role of one gene (STM1485) involved in this response, which is upregulated inside the host cells (by 90- to 113-fold) is functionally characterized in Salmonella pathogenesis. In vitro, the ΔSTM1485 neither exhibited any growth defect at pH 4.5 nor any difference in the acid tolerance response. The ΔSTM1485 was compromised in its capacity to proliferate inside the host cells and complementation with STM1485 gene restored its virulence. We further demonstrate that the surface translocation of Salmonella pathogenicity island-2 (SPI-2) encoded translocon proteins, SseB and SseD were reduced in the ΔSTM1485. The increase in co-localization of this mutant with lysosomes was also observed. In addition, the ΔSTM1485 displayed significantly reduced competitive indices (CI) in spleen, liver and mesenteric lymph nodes in murine typhoid model when infected by intra-gastric route. Based on these results, we conclude that the acidic pH induced STM1485 gene is essential for intracellular replication of Salmonella.

  18. Dynamics of fatty acid vesicles in response to pH stimuli

    DEFF Research Database (Denmark)

    Ikari, Keita; Sakuma, Yuka; Jimbo, Takehiro

    2015-01-01

    We investigate the dynamics of decanoic acid/decanoate (DA) vesicles in response to pH stimuli. Two types of dynamic processes induced by the micro injection of NaOH solutions are sequentially observed: deformations and topological transitions. In the deformation stage, DA vesicles show a series...

  19. Structure of Acidic pH Dengue Virus Showing the Fusogenic Glycoprotein Trimers

    NARCIS (Netherlands)

    Zhang, Xinzheng; Sheng, Ju; Austin, S. Kyle; Hoornweg, Tabitha E.; Smit, Jolanda M.; Kuhn, Richard J.; Diamond, Michael S.; Rossmann, Michael G.

    2015-01-01

    Flaviviruses undergo large conformational changes during their life cycle. Under acidic pH conditions, the mature virus forms transient fusogenic trimers of E glycoproteins that engage the lipid membrane in host cells to initiate viral fusion and nucleocapsid penetration into the cytoplasm. However,

  20. Sensitization of Listeria monocytogenes to Low pH, Organic Acids, and Osmotic Stress by Ethanol

    Science.gov (United States)

    Barker, Clive; Park, Simon F.

    2001-01-01

    The killing of Listeria monocytogenes following exposure to low pH, organic acids, and osmotic stress was enhanced by the addition of 5% (vol/vol) ethanol. At pH 3, for example, the presence of this agent stimulated killing by more than 3 log units in 40 min of exposure. The rate of cell death at pH 3.0 was dependent on the concentration of ethanol. Thus, while the presence 10% (vol/vol) ethanol at pH 3.0 stimulated killing by more than 3 log units in just 5 min, addition of 1.25% (vol/vol) ethanol resulted in less than 1 log unit of killing in 10 min. The ability of 5% (vol/vol) ethanol to stimulate killing at low pH and at elevated osmolarity was also dependent on the amplitude of the imposed stress, and an increase in the pH from 3.0 to 4.0 or a decrease in the sodium chloride concentration from 25 to 2.5% led to a marked reduction in the effectiveness of 5% (vol/vol) ethanol as an augmentative agent. Combinations of organic acids, low pH, and ethanol proved to be particularly effective bactericidal treatments; the most potent combination was pH 3.0, 50 mM formate, and 5 % (vol/vol) ethanol, which resulted in 5 log units of killing in just 4 min. Ethanol-enhanced killing correlated with damage to the bacterial cytoplasmic membrane. PMID:11282610

  1. Autoinducer-2 detection among commensal oral streptococci is dependent on pH and boric acid.

    Science.gov (United States)

    Cuadra, Giancarlo A; Frantellizzi, Ashley J; Gaesser, Kimberly M; Tammariello, Steven P; Ahmed, Anika

    2016-07-01

    Autoinducer-2, considered a universal signaling molecule, is produced by many species of bacteria; including oral strains. Structurally, autoinducer-2 can exist bound to boron (borated autoinducer-2). Functionally, autoinducer-2 has been linked to important bacterial processes such as virulence and biofilm formation. In order to test production of autoinducer-2 by a given bacterial strain, a bioassay using marine bioluminescent bacteria Vibrio harveyi as a reporter for autoinducer-2 has been designed. We hypothesize that pH adjustment and addition of boron are required for optimal bioluminescence and accurate autoinducer-2 detection. Using this reporter strain we tested autoinducer-2 activity from two oral commensal species, Streptococcus gordonii DL1 and Streptococcus oralis 34. Spent broth was collected and adjusted to pH 7.5 and supplemented with boric acid prior to measuring autoinducer- 2 activity. Results show that low pH inhibits bioluminescence of the reporter strain, but pH 7.5 allows for bioluminescence induction and proper readings of autoinducer-2 activity. Addition of boric acid also has a positive effect on bioluminescence allowing for a more sensitive detection of autoinducer-2 activity. Our data suggests that although autoinducer-2 is present in spent broth, low pH and/or low levels of boric acid become an obstacle for proper autoinducer-2 detection. For proper autoinducer-2 detection, we propose a protocol using this bioassay to include pH adjustment and boric acid addition to spent broth. Studies on autoinducer-2 activity in several bacteria species represent an important area of study as this universal signaling molecule is involved in critical bacterial phenotypes such as virulence and biofilm formation.

  2. ESTIMATION OF pH, TOTAL ACID AND ETHANOL CONTENT OF COMMERCIALLY AVAILABLE ALCOHOL-CONTAINING MOUTHWASHES AND ITS EFFECT ON SALIVARY pH

    Directory of Open Access Journals (Sweden)

    Rafi Shaik

    2017-07-01

    Full Text Available BACKGROUND Use of mouthwash has become widespread as a part of routine oral hygiene. Mouthwashes may have deleterious effects on oral tissues because of its low pH, high acid content and use of ethanol as an antiseptic agent. MATERIALS AND METHODS A cross-sectional experimental study was conducted among 48 undergraduate dental students. Eight commercially available alcohol-containing mouthwashes, which are available in Indian market were selected for which the pH, total acid and ethanol content was estimated. 48 subjects were randomly divided into 8 groups. Unstimulated salivary samples were collected before rinsing, then subjects were asked to rinse with 10 mL mouthwash for 60 seconds and salivary samples were collected immediately after rinsing. Salivary pH before and after rinsing was estimated using digital pH meter. RESULTS Listerine original mouthwash was found to have lowest pH (3.84 and highest acid content (26.8%. High alcohol content was seen in Listerine fresh burst mouthwash (26%. Mean salivary pH before and after rinsing showed a significant difference among all the groups with highest mean salivary pH difference for Listerine fresh burst mouthwash (1.21. Post-hoc Turkey’s analysis to compare the change in mean salivary pH between study groups showed a significant difference between Listerine original, Listerine fresh burst and Listerine cool mint mouthwash with other mouthwashes. CONCLUSION There was a significant reduction in salivary pH after rinsing with low pH, high acid and high alcohol-containing mouthwashes.

  3. Syntrophic associations from hypersaline soda lakes converting organic acids and alcohols to methane at extremely haloalkaline conditions.

    Science.gov (United States)

    Sorokin, Dimitry Y; Abbas, Ben; Geleijnse, Mitchell; Kolganova, Tatjana V; Kleerebezem, Robbert; van Loosdrecht, Mark C M

    2016-09-01

    Until now anaerobic oxidation of VFA at high salt-pH has been demonstrated only at sulfate-reducing conditions. Here, we present results of a microbiological investigation of anaerobic conversion of organic acids and alcohols at methanogenic conditions by syntrophic associations enriched from hypersaline soda lakes in Central Asia. Sediment incubation experiments showed active, albeit very slow, methane formation from acetate, propionate, butyrate and C2 C4 alcohols at pH 10 and various levels of salinity. Enrichments of syntrophic associations using hydrogenotrophic members of the genus Methanocalculus from soda lakes as partners resulted in several highly enriched cultures converting acetate, propionate, butyrate, benzoate and EtOH to methane. Most syntrophs belonged to Firmicutes, while the propionate-oxidizer formed a novel lineage within the family Syntrophobacteraceae in the Deltaproteobacteria. The acetate-oxidizing syntroph was identified as 'Ca. Syntrophonatronum acetioxidans' previously found to oxidize acetate at sulfate-reducing conditions up to salt-saturating concentrations. Butyrate and a benzoate-degrading syntrophs represent novel genus-level lineages in Syntrophomonadales which are proposed as Candidatus taxons 'Syntrophobaca', 'Syntrophocurvum' and 'Syntropholuna'. Overall, despite very slow growth, the results indicated the presence of a functionally competent syntrophic community in hypersaline soda lakes, capable of efficient oxidation of fermentation products to methane at extremely haloalkaline conditions.

  4. Bilayers and wormlike micelles at high pH in fatty acid soap systems.

    Science.gov (United States)

    Xu, Wenlong; Liu, Huizhong; Song, Aixin; Hao, Jingcheng

    2016-03-01

    Bilayers at high pH in the fatty acid systems of palmitic acid/KOH/H2O, palmitic acid/CsOH/H2O, stearic acid/KOH/H2O and stearic acid/CsOH/H2O can form spontaneously (Xu et al., 2014, 2015). In this work, the bilayers can still be observed at 25°C with an increase of the concentration of fatty acids. We found that wormlike micelles can also be prepared in the fatty acid soap systems at high pH, even though the temperature was increased to be 50°C. The viscoelasticity, apparent viscosity, yield stress of the bilayers were determined by the rheological measurements. Wormlike micelles were identified by cryogenic transmission electron microscopy (cryo-TEM) and emphasized by the rheological characterizations, which are in accordance with the Maxwell fluids with good fit of Cole-Cole plots. The phase transition temperature was determined by differential scanning calorimetry (DSC) and the transition process was recorded. The regulating role of counterions of fatty acids were discussed by (CH3)4N(+), (C2H5)4N(+), (C3H7)4N(+), and (C4H9)4N(+) as comparison, concluding that counterions with appropriate hydrated radius were the vital factor in the formation wormlike micelles.

  5. Binding characteristics of Cu(2+) to natural humic acid fractions sequentially extracted from the lake sediments.

    Science.gov (United States)

    He, En; Lü, Changwei; He, Jiang; Zhao, Boyi; Wang, Jinghua; Zhang, Ruiqing; Ding, Tao

    2016-11-01

    Humic acids (HAs) determine the distribution, toxicity, bioavailability, and ultimate fate of heavy metals in the environment. In this work, ten HA fractions (F1-F10) were used as adsorbent, which were sequentially extracted from natural sediments of Lake Wuliangsuhai, to investigate the binding characteristics of Cu(2+) to HA. On the basis of the characterization results, differences were found between the ten extracted HA fractions responding to their elemental compositions and acidic functional groups. The characterization results reveal that the responses of ten extracted HA fractions to their elemental compositions and acidic functional groups were different. The O/C and (O + N)/C ratio of F1-F8 approximately ranged from 0.66 to 0.53 and from 0.72 to 0.61, respectively; the measured results showed that the contents of phenolic groups and carboxyl groups decreased from 4.46 to 2.60 mmol/g and 1.60 to 0.58 mmol/g, respectively. The binding characteristics of Cu(2+) to the ten HA fractions were well modeled by the bi-Langmuir model; the binding behavior of Cu(2+) to all the ten HA fractions were strongly impacted by pH and ionic strength. The FTIR and SEM-EDX image of HA fractions (pre- and post-adsorption) revealed that carboxyl and phenolic groups were responsible for the Cu(2+) sorption on the ten sequentially extracted HA fractions process, which is the same with the analysis of the ligand binding and bi-Langmuir models Accordingly, the adsorption capacity of the former HA fractions on Cu(2+) were higher than the latter ones, which may be attributed to the difference of carboxyl and phenolic group contents between the former and latter extracted HA fractions. Additionally, the functional groups with N and S should not be neglected. This work is hopeful to understand the environmental effect of humic substances, environmental geochemical behavior, and bioavailability of heavy metals in lakes.

  6. Modeling aluminum-silicon chemistries and application to Australian acidic playa lakes as analogues for Mars

    Science.gov (United States)

    Marion, G. M.; Crowley, J. K.; Thomson, B. J.; Kargel, J. S.; Bridges, N. T.; Hook, S. J.; Baldridge, A.; Brown, A. J.; Ribeiro da Luz, B.; de Souza Filho, C. R.

    2009-06-01

    Recent Mars missions have stimulated considerable thinking about the surficial geochemical evolution of Mars. Among the major relevant findings are the presence in Meridiani Planum sediments of the mineral jarosite (a ferric sulfate salt) and related minerals that require formation from an acid-salt brine and oxidizing environment. Similar mineralogies have been observed in acidic saline lake sediments in Western Australia (WA), and these lakes have been proposed as analogues for acidic sedimentary environments on Mars. The prior version of the equilibrium chemical thermodynamic FREZCHEM model lacked Al and Si chemistries that are needed to appropriately model acidic aqueous geochemistries on Earth and Mars. The objectives of this work were to (1) add Al and Si chemistries to the FREZCHEM model, (2) extend these chemistries to low temperatures (lateral salt patterns in WA lakes. The WA playa lakes display significant lateral variations in mineralogy and water chemistry over short distances, reflecting the interaction of acid ground waters with neutral to alkaline lake waters derived from ponded surface runoff. Meridiani Planum observations indicate that such lateral variations are much less pronounced, pointing to the dominant influence of ground water chemistry, vertical ground water movements, and aeolian processes on the Martian surface mineralogy.

  7. Distribution and Variation of Ribonucleic Acid (RNA) and Protein and Its Hydrolysis Products in Lake Sediments

    Institute of Scientific and Technical Information of China (English)

    梁小兵; 万国江; 黄荣贵

    2002-01-01

    Protein and RNA in lake sediments tend to be decomposed progressively with time and sedimentation depth. Their concentrations tend to decrease starting from the sedimentation depth of 17 cm and that of 19 cm, respectively. However, the products of their decomposition-amino acids and nucleotides show different rules of variation. At the depth from 27 cm to 30 cm the amino acids are most abundant in the pore waters of lake sediments. Such variation tendency seems to be related to the extent to which microbes utilize amino acids and nucleotides. Due to polymerization in the geological processes and the adsorption of protein on minerals and organic polymers, below the sedimentation depth of 17 cm there is still a certain amount of protein in the sediments. With the time passing by, protein has been well preserved in various sediment layers, indicating that its decomposition is relatively limited. The peak values of protein content in the sediments of the two lakes are produced in the surface layers at the depth of 10 cm, implicating that the surface sediments are favorable to the release of protein.The contents of amino acids in the pore waters of lake sediments are closely related to the activities of microbes. Below the depth of 27 cm, the amino acids are significantly accumulated in Lake Aha sediments, probably indicating the weakening of microbial activities.

  8. Modeling aluminum-silicon chemistries and application to Australian acidic playa lakes as analogues for Mars

    Science.gov (United States)

    Marion, G.M.; Crowley, J.K.; Thomson, B.J.; Kargel, J.S.; Bridges, N.T.; Hook, S.J.; Baldridge, A.; Brown, A.J.; Ribeiro da Luz, B.; de Souza, Filho C.R.

    2009-01-01

    Recent Mars missions have stimulated considerable thinking about the surficial geochemical evolution of Mars. Among the major relevant findings are the presence in Meridiani Planum sediments of the mineral jarosite (a ferric sulfate salt) and related minerals that require formation from an acid-salt brine and oxidizing environment. Similar mineralogies have been observed in acidic saline lake sediments in Western Australia (WA), and these lakes have been proposed as analogues for acidic sedimentary environments on Mars. The prior version of the equilibrium chemical thermodynamic FREZCHEM model lacked Al and Si chemistries that are needed to appropriately model acidic aqueous geochemistries on Earth and Mars. The objectives of this work were to (1) add Al and Si chemistries to the FREZCHEM model, (2) extend these chemistries to low temperatures (patterns in WA lakes. The WA playa lakes display significant lateral variations in mineralogy and water chemistry over short distances, reflecting the interaction of acid ground waters with neutral to alkaline lake waters derived from ponded surface runoff. Meridiani Planum observations indicate that such lateral variations are much less pronounced, pointing to the dominant influence of ground water chemistry, vertical ground water movements, and aeolian processes on the Martian surface mineralogy. ?? 2009 Elsevier Ltd.

  9. Polymethylene-interrupted fatty acids: Biomarkers for native and exotic mussels in the Laurentian Great Lakes

    Science.gov (United States)

    Mezek, Tadej; Sverko, Ed; Ruddy, Martina D.; Zaruk, Donna; Capretta, Alfredo; Hebert, Craig E.; Fisk, Aaron T.; McGoldrick, Daryl J.; Newton, Teresa J.; Sutton, Trent M.; Koops, Marten A.; Muir, Andrew M.; Johnson, Timothy B.; Ebener, Mark P.; Arts, Michael T.

    2011-01-01

    Freshwater organisms synthesize a wide variety of fatty acids (FAs); however, the ability to synthesize and/or subsequently modify a particular FA is not universal, making it possible to use certain FAs as biomarkers. Herein we document the occurrence of unusual FAs (polymethylene-interrupted fatty acids; PMI-FAs) in select freshwater organisms in the Laurentian Great Lakes. We did not detect PMI-FAs in: (a) natural seston from Lake Erie and Hamilton Harbor (Lake Ontario), (b) various species of laboratory-cultured algae including a green alga (Scenedesmus obliquus), two cyanobacteria (Aphanizomenon flos-aquae and Synechococystis sp.), two diatoms (Asterionella formosa, Diatoma elongatum) and a chrysophyte (Dinobryon cylindricum) or, (c) zooplankton (Daphnia spp., calanoid or cyclopoid copepods) from Lake Ontario, suggesting that PMI-FAs are not substantively incorporated into consumers at the phytoplankton–zooplankton interface. However, these unusual FAs comprised 4-6% of total fatty acids (on a dry tissue weight basis) of native fat mucket (Lampsilis siliquoidea) and plain pocketbook (L. cardium) mussels and in invasive zebra (Dreissena polymorpha) and quagga (D. bugensis) mussels. We were able to clearly partition Great Lakes' mussels into three separate groups (zebra, quagga, and native mussels) based solely on their PMI-FA profiles. We also provide evidence for the trophic transfer of PMI-FAs from mussels to various fishes in Lakes Ontario and Michigan, further underlining the potential usefulness of PMI-FAs for tracking the dietary contribution of mollusks in food web and contaminant-fate studies.

  10. Recovery of carboxylic acids at pH greater than pK{sub a}

    Energy Technology Data Exchange (ETDEWEB)

    Tung, L.A.

    1993-08-01

    Economics of producing carboxylic acids by fermentation is often dominated, not by the fermentation cost, but by the cost of recovering and purifying the acids from dilute aqueous solutions. Experiments were performed to measure uptakes of lactic and succinic acids as functions of pH by basic polymeric sorbents; sorbent regeneration was also tested. Performance at pH > pK{sub a} and regenerability depend on sorbent basicity; apparent pK{sub a} and monomer pK{sub a} can be used to predict sorbent performance. Two basic amine extractants, Alamine 336 and Amberlite LA-2, in were also studied; they are able to sustain capacity to higher pH in diluents that stabilize the acid-amine complex through H bonding. Secondary amines perform better than tert-amines in diluents that solvate the additional proton. Competitive sulfate and phosphate, an interference in fermentation, are taken up by sorbents more strongly than by extractants. The third step in the proposed fermentation process, the cracking of the trimethylammonium (TMA) carboxylate, was also examined. Because lactic acid is more soluble and tends to self-esterify, simple thermal cracking does not remove all TMA; a more promising approach is to esterify the TMA lactate by reaction with an alcohol.

  11. Pirla Project (paleoecological investigation of recent lake acidification): preliminary results for the Adirondacks, New England, Great Lakes States, and N. Florida

    Energy Technology Data Exchange (ETDEWEB)

    Charles, D.F.; Whitehead, D.R.; Anderson, D.S.; Bienert, R.; Camburn, K.E.; Cook, R.B.; Crisman, T.L.; Davis, R.B.; Ford, J.; Fry, B.D.; Hites, R.A.

    1986-01-01

    The PIRLA project is an interdisciplinary paleoecological study designed to provide reconstructions of the recent acidification histories of a representative set of lakes in four acid-sensitive regions in North America. We are trying to determine if lakes in the study regions have acidified, and if so, to what extent, over what time period and why. Sediment cores from 5 to 15 lakes in each region are being analyzed for several characteristics. Diatoms and chrysophytes are being used to reconstruct lake water pH. Results for three Adirondack lakes with current pH of 4.8 to 5.0 indicate a decrease in pH beginning in the 1930's-1950's. Increased atmospheric deposition of strong acids appears to be the primary factor responsible for the pH decline. Two lakes (pH 4.4 and 4.7) in New England show clear evidence of acidification probably due to acidic deposition. Preliminary reconstruction for two lakes in Michigan (pH 4.4 and 5.6), one in Wisconsin (pH 5.3), and one in Minnesota (pH 6.8) suggest no recent pH decrease. For the one Florida lake (pH 4.4) analyzed, inferred pH decreases by about 0.5 unit, beginning in the 1950s; the cause has not been determined.

  12. Variation in Lake Michigan alewife (Alosa pseudoharengus) thiaminase and fatty acids composition

    Science.gov (United States)

    Honeyfield, D.C.; Tillitt, D.E.; Fitzsimons, J.D.; Brown, S.B.

    2010-01-01

    Thiaminase activity of alewife (Alosa pseudoharengus) is variable across Lake Michigan, yet factors that contribute to the variability in alewife thiaminase activity are unknown. The fatty acid content of Lake Michigan alewife has not been previously reported. Analysis of 53 Lake Michigan alewives found a positive correlation between thiaminase activity and the following fatty acid: C22:ln9, sum of omega-6 fatty acids (Sw6), and sum of the polyunsaturated fatty acids. Thiaminase activity was negatively correlated with C15:0, C16:0, C17:0, C18:0, C20:0, C22:0, C24:0, C18:ln9t, C20:3n3, C22:2, and the sum of all saturated fatty acids (SAFA). Multi-variant regression analysis resulted in three variables (C18:ln9t, Sw6, SAFA) that explained 71% (R2=0.71, P<0.0001) of the variation in thiaminase activity. Because the fatty acid content of an organism is related is food source, diet may be an important factor modulating alewife thiaminase activity. These data suggest there is an association between fatty acids and thiaminase activity in Lake Michigan alewife.

  13. Calcite growth-rate inhibition by fulvic acids isolated from Big Soda Lake, Nevada, USA, The Suwannee River, Georgia, USA and by polycarboxylic acids

    Science.gov (United States)

    Reddy, Michael M.; Leenheer, Jerry

    2011-01-01

    Calcite crystallization rates are characterized using a constant solution composition at 25°C, pH=8.5, and calcite supersaturation (Ω) of 4.5 in the absence and presence of fulvic acids isolated from Big Soda Lake, Nevada (BSLFA), and a fulvic acid from the Suwannee River, Georgia (SRFA). Rates are also measured in the presence and absence of low-molar mass, aliphatic-alicyclic polycarboxylic acids (PCA). BSLFA inhibits calcite crystal-growth rates with increasing BSLFA concentration, suggesting that BSLFA adsorbs at growth sites on the calcite crystal surface. Calcite growth morphology in the presence of BSLFA differed from growth in its absence, supporting an adsorption mechanism of calcite-growth inhibition by BSLFA. Calcite growth-rate inhibition by BSLFA is consistent with a model indicating that polycarboxylic acid molecules present in BSLFA adsorb at growth sites on the calcite crystal surface. In contrast to published results for an unfractionated SRFA, there is dramatic calcite growth inhibition (at a concentration of 1 mg/L) by a SRFA fraction eluted by pH 5 solution from XAD-8 resin, indicating that calcite growth-rate inhibition is related to specific SRFA component fractions. A cyclic PCA, 1, 2, 3, 4, 5, 6-cyclohexane hexacarboxylic acid (CHXHCA) is a strong calcite growth-rate inhibitor at concentrations less than 0.1 mg/L. Two other cyclic PCAs, 1, 1 cyclopentanedicarboxylic acid (CPDCA) and 1, 1 cyclobutanedicarboxylic acid (CBDCA) with the carboxylic acid groups attached to the same ring carbon atom, have no effect on calcite growth rates up to concentrations of 10 mg/L. Organic matter ad-sorbed from the air onto the seed crystals has no effect on the measured calcite crystal-growth rates.

  14. Geochemical behavior and dissolved species control in acid sand pit lakes, Sepetiba sedimentary basin, Rio de Janeiro, SE - Brazil

    Science.gov (United States)

    Marques, Eduardo D.; Sella, Sílvia M.; Bidone, Edison D.; Silva-Filho, Emmanoel V.

    2010-12-01

    This work shows the influence of pluvial waters on dissolved components and mineral equilibrium of four sand pit lakes, located in the Sepetiba sedimentary basin, SE Brazil. The sand mining activities promote sediment oxidation, lowering pH and increasing SO 4 contents. The relatively high acidity of these waters, similar to ore pit lakes environment and associated acid mine drainage, increases weathering rate, especially of silicate minerals, which produces high Al concentrations, the limiting factor for fish aquaculture. During the dry season, basic cations (Ca, Mg, K and Na), SiO 2 and Al show their higher values due to evapoconcentration and pH are buffered. In the beginning of the wet season, the dilution factor by rainwater increases SO 4 and decreases pH values. The aluminum monomeric forms (Al(OH) 2+ and Al(OH) 2+), the most toxic species for aquatic organisms, occur during the dry season, while AlSO 4+ species predominate during the wet season. Gibbsite, allophane, alunite and jurbanite are the reactive mineral phases indicated by PHREEQC modeling. During the dry season, hydroxialuminosilicate allophane is the main phase in equilibrium with the solution, while the sulphate salts alunite and jurbanite predominate in the rainy season due to the increasing of SO 4 values. Gibbsite is also in equilibrium with sand pit lakes waters, pointing out that hydrolysis reaction is a constant process in the system. Comparing to SiO 2, sulphate is the main Al retriever in the pit waters because the most samples (alunite and jurbanite) are in equilibrium with the solution in both seasons. This Al hydrochemical control allied to some precaution, like pH correction and fertilization of these waters, allows the conditions for fishpond culture. Equilibrium of the majority samples with kaolinite (Ca, Mg, Na diagrams) and primary minerals (K diagram) points to moderate weathering rate in sand pit sediments, which cannot be considered for the whole basin due to the anomalous

  15. Stability of uncoated and fulvic acids coated manufactured CeO2 nanoparticles in various conditions: From ultrapure to natural Lake Geneva waters.

    Science.gov (United States)

    Oriekhova, Olena; Stoll, Serge

    2016-08-15

    Understanding the behavior of engineered nanoparticles in natural water and impact of water composition in changing conditions is of high importance to predict their fate once released into the environment. In this study we investigated the stability of uncoated and Suwannee River fulvic acids coated CeO2 manufactured nanoparticles in various environmental conditions. The effect of pH changes on the nanoparticle and coating stability was first studied in ultrapure water as well as the variation of zeta potentials and sizes with time in presence of fulvic acids at environmental pH. Then the stability of CeO2 in synthetic and natural Lake Geneva waters was investigated as a function of fulvic acids concentration. Our results indicate that the adsorption of environmentally relevant concentrations of Suwannee River fulvic acids promotes CeO2 stabilization in ultrapure water as well as synthetic water and that the coating stability is high upon pH variations. On the other hand in natural Lake Geneva water CeO2 NPs are found in all cases aggregated due to the effect of heterogeneous organic and inorganic compounds.

  16. Contributions of Cell Metabolism and H+ Diffusion to the Acidic pH of Tumors

    Directory of Open Access Journals (Sweden)

    Paul A. Schornack

    2003-03-01

    Full Text Available The tumor microenvironment is hypoxic and acidic. These conditions have a significant impact on tumor progression and response to therapies. There is strong evidence that tumor hypoxia results from inefficient perfusion due to a chaotic vasculature. Consequently, some tumor regions are well oxygenated and others are hypoxic. It is commonly believed that hypoxic regions are acidic due to a stimulation of glycolysis through hypoxia, yet this is not yet demonstrated. The current study investigates the causes of tumor acidity by determining acid production rates and the mechanism of diffusion for H+ equivalents through model systems. Two breast cancer cell lines were investigated with divergent metabolic profiles: nonmetastatic MCF-7/s and highly metastatic MDA-mb-435 cells. Glycolysis and acid production are inhibited by oxygen in MCF-7/s cells, but not in MDA-mb-435 cells. Tumors of MDAmb-435 cells are significantly more acidic than are tumors of MCF-7/s cells, suggesting that tumor acidity is primarily caused by endogenous metabolism, not the lack of oxygen. Metabolically produced protons are shown to diffuse in association with mobile buffers, in concordance with previous studies. The metabolic and diffusion data were analyzed using a reaction-diffusion model to demonstrate that the consequent pH profiles conform well to measured pH values for tumors of these two cell lines.

  17. Total alcoholic acidity and pH tests as quality parameters in stored soybean grains

    Directory of Open Access Journals (Sweden)

    Maicon Marinho Vieira Araujo

    2016-06-01

    Full Text Available Despite the technology available to agriculture, qualitative and quantitative losses occurring during post-harvest are still not controlled, and stored grains may undergo changes in their composition, due to storage conditions. This study aimed at determining the sensitivity of the alcoholic acidity and pH tests in soybean (GB 874RR cultivar grains with different quality standards obtained during storage. A completely randomized design, in a 3 x 6 x 5 (3 storage conditions x 6 storage times x 5 methods factorial scheme, was used. A correlation was observed among pH, total acidity content (r = 0.888 and grain quality parameters. Deterioration was identified based on the total acidity content, showing a high correlation with fungal incidence (r = 0.864, ether extract (r = -0.781 and electrical conductivity (r = 0.923. The use of phenolphthalein as indicator is more sensitive than pH 8.8. Among the pH determination methods, AOAC was the most suitable for assessing the quality loss during storage.

  18. Is Your Drinking Water Acidic? A Comparison of the Varied pH of Popular Bottled Waters

    National Research Council Canada - National Science Library

    Wright, Kellie F

    2015-01-01

    .... However, water is not typically categorized as acidic. The purpose of this in-vitro study was to investigate the pH levels of several popular brands of bottled water and compare them to various other acidic beverages...

  19. Interaction of Whey Proteins with Phenolic Derivatives Under Neutral and Acidic pH Conditions.

    Science.gov (United States)

    Cao, Yanyun; Xiong, Youling L

    2017-02-01

    Integration of gallic acid (GA) and its derivative epigallocatechin gallate (EGCG; 20, 120, and 240 μmol/g, protein basis) into whey protein isolate (WPI) at room temperature and pH 3.0 and pH 7.0 was investigated. At pH 7.0, both phenolics caused significant structural changes and EGCG induced greater digestibility of WPI. Total sulfhydryl in WPI decreased from 28.6 to 7.6 μmol/g and surface hydrophobicity declined by nearly 50% with 240 μmol/g EGCG at pH 7.0. Similar but less appreciable changes were produced by GA and at pH 3.0. Isothermal titration and fluorescence quenching tests showed moderately weak binding of WPI with GA but strong binding with EGCG at pH 7.0. Both phenolics at high concentrations lowered the thermal transition temperature of β-lactoglobulin by 0.5 °C to 1.4 °C and promoted its digestion. The phenolics also displayed a remarkable synergism with peptides in the WPI digest exerting radical scavenging activity. © 2017 Institute of Food Technologists®.

  20. Response of fish assemblages to declining acidic deposition in Adirondack Mountain lakes, 1984-2012

    Science.gov (United States)

    Baldigo, B. P.; Roy, K. M.; Driscoll, C. T.

    2016-12-01

    Adverse effects of acidic deposition on the chemistry and fish communities were evident in Adirondack Mountain lakes during the 1980s and 1990s. Fish assemblages and water chemistry in 43 Adirondack Long-Term Monitoring (ALTM) lakes were sampled by the Adirondack Lakes Survey Corporation and the New York State Department of Environmental Conservation during three periods (1984-87, 1994-2005, and 2008-12) to document regional impacts and potential biological recovery associated with the 1990 amendments to the 1963 Clean Air Act (CAA). We assessed standardized data from 43 lakes sampled during the three periods to quantify the response of fish-community richness, total fish abundance, and brook trout (Salvelinus fontinalis) abundance to declining acidity that resulted from changes in U.S. air-quality management between 1984 and 2012. During the 28-year period, mean acid neutralizing capacity (ANC) increased significantly from 3 to 30 μeq/L and mean inorganic monomeric Al concentrations decreased significantly from 2.22 to 0.66 μmol/L, yet mean species richness, all species or total catch per net night (CPNN), and brook trout CPNN did not change significantly in the 43 lakes. Regression analyses indicate that fishery metrics were not directly related to the degree of chemical recovery and that brook trout CPNN may actually have declined with increasing ANC. While the richness of fish communities increased with increasing ANC as anticipated in several Adirondack lakes, observed improvements in water quality associated with the CAA have generally failed to produce detectable shifts in fish assemblages within a large number of ALTM lakes. Additional time may simply be needed for biological recovery to progress, or else more proactive efforts may be necessary to restore natural fish assemblages in Adirondack lakes in which water chemistry is steadily recovering from acidification.

  1. The influence of pH adjusted with different acids on the dyeability of polyester fabric

    Directory of Open Access Journals (Sweden)

    Miljkovic Milena N.

    2014-12-01

    Full Text Available The influence of using formic, oxalic, citric, tartaric, hydrochloric, nitric, sulphuric and phosphoric acid for dyebath pH adjustment was investigated upon the dyeing of polyester fabric with CI Disperse Yellow 60. The positions of colour in CIELab coordinates of the samples dyed with the addition of tested acids were assessed and compared to those dyed with the addition of acetic acid. It was found that the differences in dyeabilities obtained with the addition of citric, oxalic, hydrochloric, nitric and sulphuric acid are entirely acceptable according to both M&S 83A and CMC (2:1 standards in comparison to the dyeability obtained with the addition of acetic acid.

  2. [Effects of thiourea on pH and availability of metal ions in acid red soil].

    Science.gov (United States)

    Yang, Bo; Wang, Wen; Zeng, Qing-Ru; Zhou, Xi-Hong

    2014-03-01

    Through the simulation research, the effects of application of thiourea and urea on pH and availability of metal ions in acid red soil were studied, and the results showed that after applying urea, the soil pH increased in the first experimental stage and then reduced gradually to a low level, however, decreased trends of soil pH values were inhibited by the application of thiourea, especially when the concentration of thiourea reached to 5.0 mmol x kg(-1) dry soil, the soil pH was stable at high level, which exceeded to 6.0. It proved that the application of thiourea could inhibit the soil acidification due to urea application. After applying urea with different concentrations of thiourea, the available contents of Zn and Al decreased with the increasing concentration of thiourea, nevertheless, when the concentration of thiourea reached to 5.0 mmol x kg(-1), the available content of Mn was stable at high level which was over 110 mg x kg(-1). In addition, the results showed a highly significant negative correlation between the soil pH and the available content of Cu, Zn and Al, but for Mn, no discipline was found between the soil pH and the availability after applying thiourea. Moreover, the soil pH became higher after applying urea with thiourea compared to add urea only, which led to the decreasing of available content of Al, and it was benefited for the control of the phytotoxic effect of Al. The available content of Mn in the soil not only depended on soil pH but also the content of thiourea due to its redox and complexing reaction with Mn.

  3. Studies on mountain streams in the English lake district I. PH, calcium and the distribution of invertebrates in the River Duddon

    Energy Technology Data Exchange (ETDEWEB)

    Sutcliffe, D.W.; Carrick, T.R.

    1973-01-01

    The River Duddon and its tributaries rarely exceed pH 7.0. There are three types of acid regime; pH>5.7 and pH<5.7 independent of season or rainfall, and fluctuating acidity with pH<5.7 in winter and wet periods, pH>5.7 in summer or dry periods. PH in the River Duddon fluctuates for most of its length. Ph>5.7 is characteristic of tributaries in the lower drainage basin, but pH<5.7 occurs in the headwaters of two of these tributaries. With five exceptions, pH<5.7 or fluctuating pH are characteristic of tributaries in the upper drainage basin. A very close relationship exists between the pH regime of stream water and the benthis cauna. Apart from oligochaetes and flatworms, streams with pH<5.7 or fluctuating pH are characterized by thirteen common or abundant taxa; six plecoptera, four trichoptera and three diptera. These taxa are also common in streams with pH>5.7 but in addition these streams contain ephemeroptera, the trichopterans wormaldia and hydropsyche, the mollusc Ancylus and the amphipod gammarus. It is concluded that the calcium concentration is less important than the pH-bicarbonate concentrations in limiting the qualitative distribution of benthic invertebrates. The limiting effect of pH<5.7 on an extensive range of taxa in the duddon also occurs in other areas. The affected taxa are generally herbivores. It is suggested that in the case of insects the limiting effects of low pH may indirectly operate through changes in food supply.

  4. Sulfur acidic mining lakes in Germany: ways of controlling geogenic acidification

    Energy Technology Data Exchange (ETDEWEB)

    Klapper, H.; Schultze, M. [UFZ GmbH Centre for Environmental Research Leipzig-Halle, Magdeburg (Germany). Section of Inland Water Research

    1997-12-31

    The main cause of the sulphurous acidity found in about 100 mining lakes in eastern Germany is oxidation of pyrite from surface lignite mining. Methods for neutralization of these lakes into well functioning ecosystems are described, in particular, water pollution abatement and the related problems of salinization, contamination, eutrophication, saprobization, and infection. The chemical characteristics and life conditions of the acidic environment and acidification control are discussed. Several ways to foster alkalinity production by microbial processes are outlined. 25 refs., 6 figs., 1 tab.

  5. Development of melamine modified urea formaldehyde resins based o nstrong acidic pH catalyzed urea formaldehyde polymer

    Science.gov (United States)

    Chung-Yun Hse

    2009-01-01

    To upgrade the performance of urea-formaldehyde (UF) resin bonded particleboards, melamine modified urea-formaldehyde (MUF) resins based on strong acidic pH catalyzed UF polymers were investigated. The study was conducted in a series of two experiments: 1) formulation of MUF resins based on a UF polymer catalyzed with strong acidic pH and 2) determination of the...

  6. Monomeric banana lectin at acidic pH overrules conformational stability of its native dimeric form.

    Directory of Open Access Journals (Sweden)

    Javed M Khan

    Full Text Available Banana lectin (BL is a homodimeric protein categorized among jacalin-related family of lectins. The effect of acidic pH was examined on conformational stability of BL by using circular dichroism, intrinsic fluorescence, 1-anilino-8-napthalene sulfonate (ANS binding, size exclusion chromatography (SEC and dynamic light scattering (DLS. During acid denaturation of BL, the monomerization of native dimeric protein was found at pH 2.0. The elution profile from SEC showed two different peaks (59.65 ml & 87.98 ml at pH 2.0 while single peak (61.45 ml at pH 7.4. The hydrodynamic radii (R h of native BL was 2.9 nm while at pH 2.0 two species were found with R h of 1.7 and 3.7 nm. Furthermore at, pH 2.0 the secondary structures of BL remained unaltered while tertiary structure was significantly disrupted with the exposure of hydrophobic clusters confirming the existence of molten globule like state. The unfolding of BL with different subunit status was further evaluated by urea and temperature mediated denaturation to check their stability. As inferred from high Cm and ΔG values, the monomeric form of BL offers more resistance towards chemical denaturation than the native dimeric form. Besides, dimeric BL exhibited a Tm of 77°C while no loss in secondary structures was observed in monomers even up to 95°C. To the best of our knowledge, this is the first report on monomeric subunit of lectins showing more stability against denaturants than its native dimeric state.

  7. Stabilization of T4 bacteriophage at acidic and basic pH by adsorption on paper.

    Science.gov (United States)

    Meyer, Abigail; Greene, Melissa; Kimmelshue, Chad; Cademartiri, Rebecca

    2017-09-05

    Bacteriophages find applications in agriculture, medicine, and food safety. Many of these applications can expose bacteriophages to stresses that inactivate them including acidic and basic pH. Bacteriophages can be stabilized against these stresses by materials including paper, a common material in packaging and consumer products. Combining paper and bacteriophages creates antibacterial materials, which can reduce the use of antibiotics. Here we show that adsorption on paper protects T4, T5, and T7 bacteriophage from acidic and basic pH. We added bacteriophages to filter paper functionalized with carboxylic acid (carboxyl methyl cellulose) or amine (chitosan) groups, and exposed them to pH from 5.6 to 14. We determined the number of infective bacteriophages after exposure directly on the paper. All papers extended the lifetime of infective bacteriophage by at least a factor of four with some papers stabilizing bacteriophages for up to one week. The degree of stabilization depended on five main factors (i) the family of the bacteriophage, (ii) the charge of the paper and bacteriophages, (iii) the location of the bacteriophages within the paper, (iv) the ability of the paper to prevent bacteriophage-bacteriophage aggregation, and (v) the sensitivity of the bacteriophage proteins to the tested pH. Even when adsorbed on paper the bacteriophages were able to remove E. coli in milk. Choosing the right paper modification or material will protect bacteriophages adsorbed on that material against detrimental pH and other environmental challenges increasing the range of applications of bacteriophages on materials. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. The Synthesis of [gamma]-Aminobutyric Acid in Response to Treatments Reducing Cytosolic pH.

    Science.gov (United States)

    Crawford, L. A.; Bown, A. W.; Breitkreuz, K. E.; Guinel, F. C.

    1994-03-01

    [gamma]-Aminobutyric acid (GABA) synthesis (L-glutamic acid + H+ -> GABA + CO2) is rapidly stimulated by a variety of stress conditions including hypoxia. Recent literature suggests that GABA production and concomitant H+ consumption ameliorates the cytosolic acidification associated with hypoxia or other stresses. This proposal was investigated using isolated asparagus (Asparagus sprengeri Regel) mesophyll cells. Cell acidification was promoted using hypoxia, H+/L-glutamic acid symport, and addition of butyrate or other permeant weak acids. Sixty minutes of all three treatments stimulated the levels of both intracellular and extracellular GABA by values ranging from 100 to 1800%. At an external pH of 5.0, addition of 5 mM butyrate stimulated an increase in overall GABA level from 3.86 (0.56 [plus or minus] SE) to 20.4 (2.16 [plus or minus] SE) nmol of GABA/106 cell. Butyrate stimulated GABA levels by 200 to 300% within 15 s, and extracellular GABA was observed after 10 min. The acid load due to butyrate addition was assayed by measuring [14C]butyrate uptake. After 45 s of butyrate treatment, H+-consuming GABA production accounted for 45% of the imposed acid load. The cytosolic location of a fluorescent pH probe was confirmed using fluorescent microscopy. Spectrofluorimetry indicated that butyrate addition reduced cytosolic pH by 0.60 units with a half-time of approximately 2 s. The proposal that GABA synthesis ameliorates cytosolic acidification is supported by the data. The possible roles of H+ and Ca2+ in stimulating GABA synthesis are discussed.

  9. Anoxic Biodegradation of Isosaccharinic Acids at Alkaline pH by Natural Microbial Communities.

    Directory of Open Access Journals (Sweden)

    Simon P Rout

    Full Text Available One design concept for the long-term management of the UK's intermediate level radioactive wastes (ILW is disposal to a cementitious geological disposal facility (GDF. Under the alkaline (10.013.0 anoxic conditions expected within a GDF, cellulosic wastes will undergo chemical hydrolysis. The resulting cellulose degradation products (CDP are dominated by α- and β-isosaccharinic acids (ISA, which present an organic carbon source that may enable subsequent microbial colonisation of a GDF. Microcosms established from neutral, near-surface sediments demonstrated complete ISA degradation under methanogenic conditions up to pH 10.0. Degradation decreased as pH increased, with β-ISA fermentation more heavily influenced than α-ISA. This reduction in degradation rate was accompanied by a shift in microbial population away from organisms related to Clostridium sporosphaeroides to a more diverse Clostridial community. The increase in pH to 10.0 saw an increase in detection of Alcaligenes aquatilis and a dominance of hydrogenotrophic methanogens within the Archaeal population. Methane was generated up to pH 10.0 with acetate accumulation at higher pH values reflecting a reduced detection of acetoclastic methanogens. An increase in pH to 11.0 resulted in the accumulation of ISA, the absence of methanogenesis and the loss of biomass from the system. This study is the first to demonstrate methanogenesis from ISA by near surface microbial communities not previously exposed to these compounds up to and including pH 10.0.

  10. Is Your Drinking Water Acidic? A Comparison of the Varied pH of Popular Bottled Waters.

    Science.gov (United States)

    Wright, Kellie F

    2015-06-01

    Dental professionals continually educate patients on the dangers of consuming acidic foods and beverages due to their potential to contribute to dental erosion and tooth decay. Excess acid in the diet can also lead to acidosis, which causes negative systemic side effects. However, water is not typically categorized as acidic. The purpose of this in-vitro study was to investigate the pH levels of several popular brands of bottled water and compare them to various other acidic beverages. Two different brands of marketed alkaline water (with a pH of 8.8 or higher) were also studied, tested for acidity and described. A pilot in-vitro study was conducted to determine the pH levels of a convenience sample of popular brands of bottled water, tap water and other known acidic beverages in comparison with the pH values reported on the respective manufacturers' website. Each beverage was tested in a laboratory using a calibrated Corning pH meter model 240, and waters were compared to the corresponding company's testified pH value. Waters were also compared and contrasted based on their process of purification. The data was then compiled and analyzed descriptively. The pH values for the tested beverages and bottled waters were found to be predominantly acidic. Ten out of the 14 beverages tested were acidic (pHwaters were neutral (pH=7) and 2 bottled waters were alkaline (pH>7). The majority of waters tested had a more acidic pH when tested in the lab than the value listed in their water quality reports. It is beneficial for the health care provider to be aware of the potential acidity of popular bottled drinking waters and educate patients accordingly. Copyright © 2015 The American Dental Hygienists’ Association.

  11. Chlorogenic acid increased 5-hydroxymethylfurfural formation when heating fructose alone or with aspartic acid at two pH levels.

    Science.gov (United States)

    Zhang, Zhenhua; Zou, Yueyu; Wu, Taigang; Huang, Caihuan; Pei, Kehan; Zhang, Guangwen; Lin, Xiaohua; Bai, Weibin; Ou, Shiyi

    2016-01-01

    Chlorogenic acid (CGA) is a phenolic acid that ubiquitously exists in fruits. This work aims to investigate whether and how CGA influences HMF formation during heating fructose alone, or with an amino acid. The results showed that that CGA increased 5-hydroxymethylfurfural (HMF) formation. At pH 5.5 and 7.0, the addition of 5.0 μmol/ml CGA increased HMF formation by 49.4% and 25.2%, respectively when heating fructose alone, and by 9.0% and 16.7%, respectively when heating fructose with aspartic acid. CGA significantly increased HMF formation by promoting 3-deoxosone formation, and its conversion to HMF by inhibiting HMF elimination, especially in the Maillard reaction system. A comparison of the catalytic capacity of CGA with its six analogous compounds showed that both its di-hydroxyphenyl and carboxyl groups function in increasing HMF formation.

  12. Fluorene-based boronic acids as fluorescent chemosensor for monosaccharides at physiological pH.

    Science.gov (United States)

    Hosseinzadeh, Rahman; Mohadjerani, Maryam; Pooryousef, Mona

    2015-08-01

    Two fluorene-based boronic acids, 9,9-dimethyl-9H-fluoren-2-yl-2-boronic acid (1) and 9,9-dimethyl-9H-fluoren-2,7-diyl-2,7-diboronic acid (2), were synthesized and their sensing abilities for detection of D-monosaccharides were investigated by fluorescence at physiological pH. It was found that both boronic acids 1 and 2 have high selectivity and sensitivity for D-fructose with stability constant of 47.2 and 412.9, respectively. The sensor 2 showed a linear response toward D-fructose in the concentration range from 5 × 10(-5) to 10(-1) mol L(-1) with the detection limit of 2 × 10(-5) mol L(-1). Copyright © 2014 John Wiley & Sons, Ltd.

  13. Effects of Oxygen Availability on Acetic Acid Tolerance and Intracellular pH in Dekkera bruxellensis.

    Science.gov (United States)

    Capusoni, Claudia; Arioli, Stefania; Zambelli, Paolo; Moktaduzzaman, M; Mora, Diego; Compagno, Concetta

    2016-08-01

    The yeast Dekkera bruxellensis, associated with wine and beer production, has recently received attention, because its high ethanol and acid tolerance enables it to compete with Saccharomyces cerevisiae in distilleries that produce fuel ethanol. We investigated how different cultivation conditions affect the acetic acid tolerance of D. bruxellensis We analyzed the ability of two strains (CBS 98 and CBS 4482) exhibiting different degrees of tolerance to grow in the presence of acetic acid under aerobic and oxygen-limited conditions. We found that the concomitant presence of acetic acid and oxygen had a negative effect on D. bruxellensis growth. In contrast, incubation under oxygen-limited conditions resulted in reproducible growth kinetics that exhibited a shorter adaptive phase and higher growth rates than those with cultivation under aerobic conditions. This positive effect was more pronounced in CBS 98, the more-sensitive strain. Cultivation of CBS 98 cells under oxygen-limited conditions improved their ability to restore their intracellular pH upon acetic acid exposure and to reduce the oxidative damage to intracellular macromolecules caused by the presence of acetic acid. This study reveals an important role of oxidative stress in acetic acid tolerance in D. bruxellensis, indicating that reduced oxygen availability can protect against the damage caused by the presence of acetic acid. This aspect is important for optimizing industrial processes performed in the presence of acetic acid. This study reveals an important role of oxidative stress in acetic acid tolerance in D. bruxellensis, indicating that reduced oxygen availability can have a protective role against the damage caused by the presence of acetic acid. This aspect is important for the optimization of industrial processes performed in the presence of acetic acid. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

  14. Water quality of selected lakes in Mount Rainier National Park, Washington, with respect to lake acidification

    Energy Technology Data Exchange (ETDEWEB)

    Turney, G.L.; Dion, N.P.; Sumioka, S.S.

    1986-01-01

    Thirteen lakes in Mount Rainier National park were evaluated for general chemical characteristics, sensitivity to acidification by acidic precipitation, and degree of existing acidification. The lakes studies were Allen, one of the Chenuis group, Crescent, Crystal, Eleanor, Fan, one of the Golfen group, Marsh, Mowich, Mystic, Shriner, and two unnamed lakes. The lakes were sampled in August 1983. The major cations were calcium and sodium, and the major anion was bicarbonate. Alkalinity concentrations ranged from 2.1 to 9.0 mg/L in 12 of the lakes. Allen Lake was the exception, having an alkalinity concentration of 27 mg/L. The pH values for all of the lakes ranged from 5.8 to 6.5. In most of the lakes, vertical profiles of temperature, dissolved oxygen, pH, and specific conductance were relatively uniform. Exceptions to general water quality patterns were observed in three lakes. Allen Lake had a specific conductance value of 58 Microsiemens/cm. The lake of the Golfen group was anaerobic at the bottom and had relatively high concentrations of dissolved organic carbon and dissolved metals, and a lower light transmission than the other lakes studied. One of the unnamed lakes had relatively high concentrations of phytoplankton and dissolved organic carbon and relatively low levels of light transmission. Comparisons of lake data to acid-sensitivity thresholds for specific conductance and alkalinity indicated that all of the lakes except Allen would be sensitive to acidic precipitation. The small sizes of the lakes, and their locations in basins of high precipitation and weathering-resistant rock types, enhance their sensitivity. None of the lakes in this study appeared to be presently acidified.

  15. The PIRLA project (Paleoecological investigation of recent lake acidification). Preliminary results for the Adirondacks, New England, N. Great Lakes States, and N. Florida

    Energy Technology Data Exchange (ETDEWEB)

    Charles, D.F.; Whitehead, D.R.; Anderson, D.S.; Bienert, R.; Camburn, K.E.; Cook, R.B.; Crisman, T.L.; Davis, R.B.; Ford, J.; Fry, B.D.

    1986-09-01

    The PIRLA project is an interdisciplinary paleoecological study designed to provide reconstructions of the recent acidification histories of a representative set of lakes in four acid-sensitive regions in North America. We are trying to determime if lakes in the study regions have acidified, and if so, to what extent, over what time period and why. Sediment cores from 5 to 15 lakes in each region are being analyzed for several characteristics. Diatoms and chrysophytes are being used to reconstruct lakewater pH. Results for three Adirondack lakes with current pH of 4.8 to 5.0 indicate a decrease in pH beginning in the 1930's-1950's. Increased atmospheric deposition of strong acids appears to be the primary factor responsible for the pH decline. Two lakes (pH 4.4 and 4.7) in New England show clear evidence of acidification probably due to acidic deposition. Preliminary reconstructions for two lakes in Michigan (pH 4.4 and 5.6), one in Wisconsin (pH 5.3), and one in Minnesota (pH 6.8) suggest no recent pH decrease. For the one Florida lake (pH 4.4) analyzed, inferred pH decreases by about 0.5 unit, beginning in the 1950's; the cause has not been determined. 26 refs.

  16. Growth of Mycobacterium tuberculosis in a Defined Medium Is Very Restricted by Acid pH and Mg2+ Levels

    OpenAIRE

    Piddington, Debra L.; Kashkouli, Ali; Buchmeier, Nancy A.

    2000-01-01

    Mycobacterium tuberculosis grows within the phagocytic vacuoles of macrophages, where it encounters a moderately acidic and possibly nutrient-restricted environment. Other mycobacterial species encounter acidic conditions in soil and aquatic environments. We have evaluated the influence of pH and divalent cation levels on the growth of M. tuberculosis and seven other mycobacterial species. In a defined medium, the growth of M. tuberculosis was very restricted by acidic pH. Higher levels of Mg...

  17. Preferential intracellular pH regulation represents a general pattern of pH homeostasis during acid-base disturbances in the armoured catfish, Pterygoplichthys pardalis.

    Science.gov (United States)

    Harter, T S; Shartau, R B; Baker, D W; Jackson, D C; Val, A L; Brauner, C J

    2014-08-01

    Preferential intracellular pH (pHi) regulation, where pHi is tightly regulated in the face of a blood acidosis, has been observed in a few species of fish, but only during elevated blood PCO2. To determine whether preferential pHi regulation may represent a general pattern for acid-base regulation during other pH disturbances we challenged the armoured catfish, Pterygoplichthys pardalis, with anoxia and exhaustive exercise, to induce a metabolic acidosis, and bicarbonate injections to induce a metabolic alkalosis. Fish were terminally sampled 2-3 h following the respective treatments and extracellular blood pH, pHi of red blood cells (RBC), brain, heart, liver and white muscle, and plasma lactate and total CO2 were measured. All treatments resulted in significant changes in extracellular pH and RBC pHi that likely cover a large portion of the pH tolerance limits of this species (pH 7.15-7.86). In all tissues other than RBC, pHi remained tightly regulated and did not differ significantly from control values, with the exception of a decrease in white muscle pHi after anoxia and an increase in liver pHi following a metabolic alkalosis. Thus preferential pHi regulation appears to be a general pattern for acid-base homeostasis in the armoured catfish and may be a common response in Amazonian fishes.

  18. Effects of acidic pH on voltage-gated ion channels in rat trigeminal mesencephalic nucleus neurons.

    Science.gov (United States)

    Han, Jin-Eon; Cho, Jin-Hwa; Choi, In-Sun; Kim, Do-Yeon; Jang, Il-Sung

    2017-03-01

    The effects of acidic pH on several voltage-dependent ion channels, such as voltage-dependent K(+) and Ca(2+) channels, and hyperpolarization-gated and cyclic nucleotide-activated cation (HCN) channels, were examined using a whole-cell patch clamp technique on mechanically isolated rat mesencephalic trigeminal nucleus neurons. The application of a pH 6.5 solution had no effect on the peak amplitude of voltage-dependent K(+) currents. A pH 6.0 solution slightly, but significantly inhibited the peak amplitude of voltage-dependent K(+) currents. The pH 6.0 also shifted both the current-voltage and conductance-voltage relationships to the depolarization range. The application of a pH 6.5 solution scarcely affected the peak amplitude of membrane currents mediated by HCN channels, which were profoundly inhibited by the general HCN channel blocker Cs(+) (1 mM). However, the pH 6.0 solution slightly, but significantly inhibited the peak amplitude of HCN-mediated currents. Although the pH 6.0 solution showed complex modulation of the current-voltage and conductance-voltage relationships, the midpoint voltages for the activation of HCN channels were not changed by acidic pH. On the other hand, voltage-dependent Ca(2+) channels were significantly inhibited by an acidic pH. The application of an acidic pH solution significantly shifted the current-voltage and conductance-voltage relationships to the depolarization range. The modulation of several voltage-dependent ion channels by an acidic pH might affect the excitability of mesencephalic trigeminal nucleus neurons, and thus physiological functions mediated by the mesencephalic trigeminal nucleus could be affected in acidic pH conditions.

  19. The Cytosolic pH of Individual Saccharomyces cerevisiae Cells Is a Key Factor in Acetic Acid Tolerance

    Science.gov (United States)

    Fernández-Niño, Miguel; Marquina, Maribel; Swinnen, Steve; Rodríguez-Porrata, Boris

    2015-01-01

    It was shown recently that individual cells of an isogenic Saccharomyces cerevisiae population show variability in acetic acid tolerance, and this variability affects the quantitative manifestation of the trait at the population level. In the current study, we investigated whether cell-to-cell variability in acetic acid tolerance could be explained by the observed differences in the cytosolic pHs of individual cells immediately before exposure to the acid. Results obtained with cells of the strain CEN.PK113-7D in synthetic medium containing 96 mM acetic acid (pH 4.5) showed a direct correlation between the initial cytosolic pH and the cytosolic pH drop after exposure to the acid. Moreover, only cells with a low initial cytosolic pH, which experienced a less severe drop in cytosolic pH, were able to proliferate. A similar correlation between initial cytosolic pH and cytosolic pH drop was also observed in the more acid-tolerant strain MUCL 11987-9. Interestingly, a fraction of cells in the MUCL 11987-9 population showed initial cytosolic pH values below the minimal cytosolic pH detected in cells of the strain CEN.PK113-7D; consequently, these cells experienced less severe drops in cytosolic pH. Although this might explain in part the difference between the two strains with regard to the number of cells that resumed proliferation, it was observed that all cells from strain MUCL 11987-9 were able to proliferate, independently of their initial cytosolic pH. Therefore, other factors must also be involved in the greater ability of MUCL 11987-9 cells to endure strong drops in cytosolic pH. PMID:26341199

  20. Substituent effects and pH profiles for stability constants of arylboronic acid diol esters.

    Science.gov (United States)

    Martínez-Aguirre, Mayte A; Villamil-Ramos, Raul; Guerrero-Alvarez, Jorge A; Yatsimirsky, Anatoly K

    2013-05-17

    Stability constants of boronic acid diol esters in aqueous solution have been determined potentiometrically for a series of meta-, para-substituted phenylboronic acids and diols of variable acidity. The constants β(11-1) for reactions between neutral forms of reactants producing the anionic ester plus proton follow the Hammett equation with ρ depending on pKa of diol and varying from 2.0 for glucose to 1.29 for 4-nitrocatechol. Observed stability constants (K(obs)) measured by UV-vis and fluorometric titrations at variable pH for esters of 4,5-dihydroxy-1,3-benzenedisulfonate (Tiron) generally agree with those expected on the basis of β(11-1) values, but the direct fitting of K(obs) vs pH profiles gives shifted pKa values both for boronic acids and diol as a result of significant interdependence of fitting parameters. The subsituent effects on absorption and fluorescence spectra of Tiron arylboronate esters are characterized. The K(obs) for Tiron determined by (11)B NMR titrations are approximately 1 order of magnitude smaller than those determined by UV-vis titrations under identical conditions. A general equation, which makes possible an estimate of β(11-1) for any pair of boronic acid and diol from their pKa values, is proposed on the basis of established Brönsted-type correlation of Hammett parameters for β(11-1) with acidity of diols. The equation allows one to calculate stability constants expected only on basis of acid-base properties of the components, thus permitting more strict evaluation of contributions of additional factors such as steric or charge effects to the ester stability.

  1. Response of DOC in acid-sensitive Maine lakes to decreasing sulfur deposition (1993 - 2009)

    Science.gov (United States)

    In response to the Clean Air Act Amendments of 1990, sulfur deposition has decreased across the northeastern United States. As a result, sulfate concentrations in lakes and streams have also decreased and many surface waters have become less acidic. Over the same time period, th...

  2. [Short-term changes of pH value and Al activity in acid soils after urea fertilization].

    Science.gov (United States)

    Zeng, Qingru; Liao, Bohan; Jiang, Zhaohui; Zhou, Xihong; Tang, Can; Zhong, Ning

    2005-02-01

    Acidic soils are widely distributed in South China, and their acidity is the major environmental stress factor limiting the growth of most crops. It is well known that soil Al solubilized at low pH is a main toxic factor for plant growth. Our study with three acidic soils showed that soil pH increased quickly, while soil exchangeable Al decreased sharply with the increasing concentrations of applied urea. The time-course experiment revealed that the increase of soil pH was short-lived, with a subsequently slow drop after reached its maximum. Urea fertilization caused a drastic change of soil pH during 2-4 weeks of the experimental period. There was a negative relationship between soil pH and soil exchangeable Al. Biological toxicity test demonstrated that applying urea to acidic soils could obviously decrease the aluminum toxicity of maize in a short-term period.

  3. Effect of pH and lactic or acetic acid on ethanol productivity by Saccharomyces cerevisiae in corn mash.

    Science.gov (United States)

    Graves, Tara; Narendranath, Neelakantam V; Dawson, Karl; Power, Ronan

    2006-06-01

    The effects of lactic and acetic acids on ethanol production by Saccharomyces cerevisiae in corn mash, as influenced by pH and dissolved solids concentration, were examined. The lactic and acetic acid concentrations utilized were 0, 0.5, 1.0, 2.0, 3.0 and 4.0% w/v, and 0, 0.1, 0.2, 0.4, 0.8 and 1.6% w/v, respectively. Corn mashes (20, 25 and 30% dry solids) were adjusted to the following pH levels after lactic or acetic acid addition: 4.0, 4.5, 5.0 or 5.5 prior to yeast inoculation. Lactic acid did not completely inhibit ethanol production by the yeast. However, lactic acid at 4% w/v decreased (Plactic acid at 3% w/v reduced (Pacid increased as the concentration of solids in the mash increased and the pH of the medium declined. Ethanol production was completely inhibited in all mashes set at pH 4 in the presence of acetic acid at concentrations > or =0.8% w/v. In 30% solids mash set at pH 4, final ethanol levels decreased (Pacid. These results suggest that the inhibitory effects of lactic acid and acetic acid on ethanol production in corn mash fermentation when set at a pH of 5.0-5.5 are not as great as that reported thus far using laboratory media.

  4. Influence of aggregated particles on biodegradation activities for dimethylarsinic acid (DMA) in Lake Kahokugata.

    Science.gov (United States)

    Maki, Teruya; Hirota, Wakana; Motojima, Hiroyuki; Hasegawa, Hiroshi; Rahman, Mohammad Azizur

    2011-06-01

    Aquatic arsenic cycles mainly depend on microbial activities that change the arsenic chemical forms and influence human health and organism activities. The microbial aggregates degrading organic matter are significantly related to the turnover between inorganic arsenic and organoarsenic compounds. We investigated the effects of microbial aggregates on organoarsenic mineralization in Lake Kahokugata using lake water samples spiked with dimethylarsinic acid (DMA). The lake water samples converted 1 μmol L(-1) of DMA to inorganic arsenic for 28d only under anaerobic and dark conditions in the presence of microbial activities. During the DMA mineralization process, organic aggregates >5.0 μm with bacterial colonization increased the densities. When the organic aggregates >5.0 μm were eliminated from the lake water samples using filters, the degradation activities were reduced. DMA in the lake water would be mineralized by the microbial aggregates under anaerobic and dark conditions. Moreover, DMA amendment enhanced the degradation activities in the lake water samples, which mineralized 50 μmol L(-1) of DMA. The DMA-amended aggregates >5.0 μm completely degraded 1 μmol L(-1) of DMA with a shorter incubation time of 7d. The supplement of KNO(3) and NaHCO(3) to lake water samples also shortened the DMA-degradation period. Presumably, the bacterial aggregates involved in the chemical heterotrophic process would contribute to the DMA-biodegradation process in Lake Kahokugata, which is induced by the DMA amendment. Copyright © 2011 Elsevier Ltd. All rights reserved.

  5. Iron mineralogy across the oxycline of a lignite mine lake

    OpenAIRE

    Miot, Jennyfer; Lu, Shipeng; Morin, Guillaume; Adra, Areej,; Benzerara, Karim; Küsel, Kirsten

    2016-01-01

    International audience; Iron-rich pelagic aggregates of microbial origin named “iron snow” are formed in the water column of some acidic lignite mine lakes. We investigated the evolution of Fe mineralogy across the oxycline of the Lusatian lake 77, Germany at two sampling sites differing by their pH and mixing profiles. The central basin (CB) of this lake shows a dimictic water regime with a non-permanent anoxic deep layer and a homogeneous acidic pH all over the water column (pH 3). In contr...

  6. Thermodynamic Solubility Profile of Carbamazepine-Cinnamic Acid Cocrystal at Different pH.

    Science.gov (United States)

    Keramatnia, Fatemeh; Shayanfar, Ali; Jouyban, Abolghasem

    2015-08-01

    Pharmaceutical cocrystal formation is a direct way to dramatically influence physicochemical properties of drug substances, especially their solubility and dissolution rate. Because of their instability in the solution, thermodynamic solubility of cocrystals could not be determined in the common way like other compounds; therefore, the thermodynamic solubility is calculated through concentration of their components in the eutectic point. The objective of this study is to investigate the effect of an ionizable coformer in cocrystal with a nonionizable drug at different pH. Carbamazepine (CBZ), a nonionizable drug with cinnamic acid (CIN), which is an acidic coformer, was selected to prepare CBZ-CIN cocrystal and its thermodynamic solubility was studied in pH range 2-7. Instead of HPLC that is a costly and time-consuming method, a chemometric-based approach, net analyte signal standard addition method, was selected for simultaneous determination of CBZ and CIN in solution. The result showed that, as pH increases, CIN ionization leads to change in CBZ-CIN cocrystal solubility and stability in solution. In addition, the results of this study indicated that there is no significant difference between intrinsic solubility of CBZ and cocrystal despite the higher ideal solubility of cocrystal. This verifies that ideal solubility is not good parameter to predict cocrystal solubility.

  7. Connections between hyper-acid crater lakes and flank springs: new evidence from Rincón de la Vieja volcano (Costa Rica)

    Science.gov (United States)

    Martínez, M.; Fernández, E.; Sáenz, W.; van Bergen, M. J.; Ayres, G.; Pacheco, J. F.; Brenes, J.; Avard, G.; Malavassi, E.

    2012-04-01

    Rincón de la Vieja, a complex andesitic stratovolcano in NW Costa Rica, shows various hydrothermal surface manifestations that comprise: (1) A hyper-acid crater lake and subaerial fumaroles receiving direct input of fluids of magmatic origin, (2) Acid thermal discharges along the northeastern slopes of the volcano that feed the headwaters of the Cucaracho river, and (3) Small lakes and a geothermal field with bubbling-boiling mud pools, acid-sulfate springs, steaming ground and fumarolic emissions in a region on the western flank. Here the streams are of relatively low flow rate and their chemical signatures correspond to that of deep fluids from an extensive geothermal reservoir mixed with shallow meteoric water. Physico-chemical properties of the sulfate-chloride hyper-acid lake (T=28-58 °C; pH between 1.2 and water body supplied by a significant input of chemical components derived from hydrolysis of magmatic volatiles and from intense rock leaching. The Cucaracho catchment receives input from warm acid brines with no free-gas phase but carrying a high load of hydrolyzed magmatic volatiles and rock-forming elements. One of these brines (Spring 4) is characterized by a sulfate-chloride chemical signature, medium temperatures of 27-38 °C, pH between 2 and 4 and TDS values between 780 and 1300 mg/L. Based on water and heat-balance considerations, chemical and stable-isotope signatures and groundwater transport modeling, it has been proposed that these acid springs represent brine water from the lake-hydrothermal system that is diluted by shallow groundwater permeating tephra layers (Kempter and Rowe, 2000). Since Rincóńs latest phreatomagmatic activity in 1983, episodes of phreatic eruptions from the crater lake have been registered in 1983-87, 1991, 1995, 1998 and 2011. Some of these eruptions (VEI 1) have expelled large quantities of lake water, triggering small to medium- sized fast-moving acidic lahars running along effluents of the Cucaracho River. They

  8. A combined CaO/electrochemical treatment of the acid mine drainage from the "Robule" Lake.

    Science.gov (United States)

    Orescanin, Visnja; Kollar, Robert

    2012-01-01

    The purpose of this work was development and application of the purification system suitable for the treatment of the acid mine drainage (AMD) accumulated in the "Robule" Lake, which represents the part of the Bor copper mining and smelting complex, Serbia. The study was undertaken in order to minimize adverse effect on the environment caused by the discharge of untreated AMD, which was characterized with low pH value (2.63) and high concentration of heavy metals (up to 610 mg/L) and sulfates (up to 12,000 mg/L). The treatment of the effluent included pretreatment/pH adjustment with CaO followed by electrocoagulation using iron and aluminum electrode sets. Following the final treatment, the decrease in the concentration of heavy metals ranged from 40 up to 61000 times depending on the metal and its initial concentration. The parameters, color and turbidity were removed completely in the pretreatment step, while the removal efficiencies for other considered parameters were as follows: EC = 55.48%, SO(4) (2-) = 70.83%, Hg = 98.36%, Pb = 97.50%, V = 98.43%, Cr = 99.86%, Mn = 97.96%, Fe = 100.00%, Co = 99.96%, Ni = 99.78%, Cu = 99.99% and Zn = 99.94%. Because the concentrations of heavy metals in the electrochemically treated AMD (ranging from 0.001 to 0.336 mg/L) are very low, the negative impact of this effluent on the aquatic life and humans is not expected. The sludge generated during the treatment of AMD is suitable for reuse for at least two purposes (pretreatment of AMD and covering of the flotation waste heap). From the presented results, it could be concluded that electrochemical treatment is a suitable approach for the treatment of AMD.

  9. Role of Low-Molecule-Weight Organic Acids and Their Salts in Regulating Soil pH

    Institute of Scientific and Technical Information of China (English)

    LI Zhi-An; ZOU Bi; XIA Han-Ping; DING Yong-Zhen; TAN Wan-Neng; FU Sheng-Lei

    2008-01-01

    The process of organic materials increasing soil pH has not yet been fully understood.This study examined the role of cations and organic anions in regulating soil pH using organic compounds.Calcareous soil,acid soil,and paddy soil were incubated with different simple organic compounds,pH was determined periodically and CO2 emission was also measured.Mixing organic acids with the soil caused an instant decrease of soil pH.The magnitude of pH decrease depended on the initial soil acidity and dissociation degree of the acids.Decomposition of organic acids could only recover the soil pH to about its original level.Mixing organic salts with soil caused an instant increase of soil pH.Decomposition of organic salts of sodium resulted in a steady increase of soil pH,with final soil pH being about 2.7-3.2 pH units over the control.Organic salts with the same anions (citrate) but different cations led to different magnitudes of pH increase,while those having the same cations but different anions led to very similar pH increases.Organic salts of sodium and sodium carbonate caused very similar pH increases of soil when they were added to the acid soil at equimolar concentrations of Na+.The results suggested that cations played a central role in regulating soil pH.Decarboxylation might only consume a limited number of protons.Conversion of organic salts into inorganic salts (carbonate) was possibly responsible for pH increase during their decomposition,suggesting that only those plant residues containing high excess base cations could actually increase soil pH.

  10. Study of metabolic profile of Rhizopus oryzae to enhance fumaric acid production under low pH condition.

    Science.gov (United States)

    Liu, Ying; Xu, Qing; Lv, Chunwei; Yan, Caixia; Li, Shuang; Jiang, Ling; Huang, He; Ouyang, Pingkai

    2015-12-01

    Ensuring a suitable pH is a major problem in industrial organic acid fermentation. To circumvent this problem, we used a metabolic profiling approach to analyze metabolite changes in Rhizopus oryzae under different pH conditions. A correlation between fumaric acid production and intracellular metabolic characteristics of R. oryzae was revealed by principal component analysis. The results showed that to help cell survival in the presence of low pH, R. oryzae altered amino acid and fatty acid metabolism and promoted sugar or sugar alcohol synthesis, corresponding with a suppressing of energy metabolism, phenylalanine, and tyrosine synthesis and finally resulting in the low performance of fumaric acid production. Based on this observation, 1 % linoleic acid was added to the culture medium in pH 3.0 to decrease the carbon demand for cell survival, and the fumaric acid titer was enhanced by 39.7 % compared with the control (pH 3.0 without linoleic acid addition), reaching 18.3 g/L after 84 h of fermentation. These findings provide new insights into the mechanism by which R. oryzae responds to acidic stress and would be helpful for the development of efficient strategies for fumaric acid production at low pH.

  11. Biogenic precipitation of manganese oxides and enrichment of heavy metals at acidic soil pH

    Science.gov (United States)

    Mayanna, Sathish; Peacock, Caroline L.; Schäffner, Franziska; Grawunder, Anja; Merten, Dirk; Kothe, Erika; Büchel, Georg

    2014-05-01

    The precipitation of biogenic Mn oxides at acidic pH is rarely reported and poorly understood, compared to biogenic Mn oxide precipitation at near neutral conditions. Here we identified and investigated the precipitation of biogenic Mn oxides in acidic soil, and studied their role in the retention of heavy metals, at the former uranium mining site of Ronneburg, Germany. The site is characterized by acidic pH, low carbon content and high heavy metal loads including rare earth elements. Specifically, the Mn oxides were present in layers identified by detailed soil profiling and within these layers pH varied from 4.7 to 5.1, Eh varied from 640 to 660 mV and there were enriched total metal contents for Ba, Ni, Co, Cd and Zn in addition to high Mn levels. Using electron microprobe analysis, synchrotron X-ray diffraction and X-ray absorption spectroscopy, we identified poorly crystalline birnessite (δ-MnO2) as the dominant Mn oxide in the Mn layers, present as coatings covering and cementing quartz grains. With geochemical modelling we found that the environmental conditions at the site were not favourable for chemical oxidation of Mn(II), and thus we performed 16S rDNA sequencing to isolate the bacterial strains present in the Mn layers. Bacterial phyla present in the Mn layers belonged to Firmicutes, Actinobacteria and Proteobacteria, and from these phyla we isolated six strains of Mn(II) oxidizing bacteria and confirmed their ability to oxidise Mn(II) in the laboratory. The biogenic Mn oxide layers act as a sink for metals and the bioavailability of these metals was much lower in the Mn layers than in adjacent layers, reflecting their preferential sorption to the biogenic Mn oxide. In this presentation we will report our findings, concluding that the formation of natural biogenic poorly crystalline birnessite can occur at acidic pH, resulting in the formation of a biogeochemical barrier which, in turn, can control the mobility and bioavailability of heavy metals in

  12. Life in acid: interactive effects of pH and natural organic acids on growth, development and locomotor performance of larval striped marsh frogs (Limnodynastes peronii).

    Science.gov (United States)

    Barth, B J; Wilson, R S

    2010-04-01

    The low pH of naturally acidic aquatic environments is the result of soft-water with low buffering capacity and high concentrations of natural organic acids. Our current understanding of the influence of pH on aquatic organisms is largely limited to laboratory studies conducted under controlled conditions with little incorporation of these organic acids. Recent studies suggest natural organic acids may influence the physiology of aquatic species independent of low pH. We examined the effects of pH and varying concentrations of natural wallum water, which is high in organic acids on the hatching success, growth and locomotor performance of larval striped marsh frogs (Limnodynastes peronii). Based on previous studies, we predicted that the detrimental effects of low pH would be further exacerbated by higher concentrations of naturally occurring organic acids (high concentrations of wallum water). In artificial soft-water, embryos experienced both reduced growth and reduced survival when exposed to low pH. However, greater concentrations of natural organic acids did not exacerbate these effects of low pH on growth and development. Instead, we found some evidence that the natural organic acids within wallum water improved growth and swimming performance across all pH treatments. Using path analyses to investigate the effects of pH and natural organic acid concentration on burst swimming performance, we found performance was directly affected by both body length and organic acid concentration. Our data further highlight our limited understanding of the importance of natural organic acids for aquatic organisms and the need to incorporate greater ecological relevance into these studies.

  13. Anacardic acid-mediated changes in membrane potential and pH gradient across liposomal membranes.

    Science.gov (United States)

    Toyomizu, Masaaki; Okamoto, Katsuyuki; Akiba, Yukio; Nakatsu, Tetsuo; Konishi, Tetsuya

    2002-01-01

    We have previously shown that anacardic acid has an uncoupling effect on oxidative phosphorylation in rat liver mitochondria using succinate as a substrate (Life Sci. 66 (2000) 229-234). In the present study, for clarification of the physicochemical characteristics of anacardic acid, we used a cyanine dye (DiS-C3(5)) and 9-aminoacridine (9-AA) to determine changes of membrane potential (DeltaPsi) and pH difference (DeltapH), respectively, in a liposome suspension in response to the addition of anacardic acid to the suspension. The anacardic acid quenched DiS-C3(5) fluorescence at concentrations higher than 300 nM, with the degree of quenching being dependent on the log concentration of the acid. Furthermore, the K(+) diffusion potential generated by the addition of valinomycin to the suspension decreased for each increase in anacardic acid concentration used over 300 nM, but the sum of the anacardic acid- and valinomycin-mediated quenching was additively increasing. This indicates that the anacardic acid-mediated quenching was not due simply to increments in the K(+) permeability of the membrane. Addition of anacardic acid in the micromolar range to the liposomes with DeltaPsi formed by valinomycin-K(+) did not significantly alter 9-AA fluorescence, but unexpectedly dissipated DeltaPsi. The DeltaPsi preformed by valinomycin-K(+) decreased gradually following the addition of increasing concentrations of anacardic acid. The DeltaPsi dissipation rate was dependent on the pre-existing magnitude of DeltaPsi, and was correlated with the logarithmic concentration of anacardic acid. Furthermore, the initial rate of DeltapH dissipation increased with logarithmic increases in anacardic acid concentration. These results provide the evidence for a unique function of anacardic acid, dissimilar to carbonylcyanide p-trifluoromethoxyphenylhydrazone or valinomycin, in that anacardic acid behaves as both an electrogenic (negative) charge carrier driven by DeltaPsi, and a 'proton

  14. Influence of pH, bleaching agents, and acid etching on surface wear of bovine enamel

    Directory of Open Access Journals (Sweden)

    Ana Flávia Soares

    2016-02-01

    Full Text Available ABSTRACT Development of new materials for tooth bleaching justifies the need for studies to evaluate the changes in the enamel surface caused by different bleaching protocols. Objective The aim of this study was to evaluate the bovine dental enamel wear in function of different bleaching gel protocols, acid etching and pH variation. Material and Methods Sixty fragments of bovine teeth were cut, obtaining a control and test areas. In the test area, one half received etching followed by a bleaching gel application, and the other half, only the bleaching gel. The fragments were randomly divided into six groups (n=10, each one received one bleaching session with five hydrogen peroxide gel applications of 8 min, activated with hybrid light, diode laser/blue LED (HL or diode laser/violet LED (VHL (experimental: Control (C; 35% Total Blanc Office (TBO35HL; 35% Lase Peroxide Sensy (LPS35HL; 25% Lase Peroxide Sensy II (LPS25HL; 15% Lase Peroxide Lite (LPL15HL; and 10% hydrogen peroxide (experimental (EXP10VHL. pH values were determined by a pHmeter at the initial and final time periods. Specimens were stored, subjected to simulated brushing cycles, and the superficial wear was determined (μm. ANOVA and Tukey´s tests were applied (α=0.05. Results The pH showed a slight decrease, except for Group LPL15HL. Group LPS25HL showed the highest degree of wear, with and without etching. Conclusion There was a decrease from the initial to the final pH. Different bleaching gels were able to increase the surface wear values after simulated brushing. Acid etching before bleaching increased surface wear values in all groups.

  15. Disruption of bovine oocytes and preimplantation embryos by urea and acidic pH.

    Science.gov (United States)

    Ocon, O M; Hansen, P J

    2003-04-01

    Feeding cattle diets high in degradable crude protein (CP) or in excess of requirements can reduce fertility and lower uterine pH. Objectives were to determine direct effects of urea and acidic pH during oocyte maturation and embryonic development. For experiment 1, oocytes were matured in medium containing 0, 5, 7.5, or 10 mM urea (0, 14, 21, or 28 mg/dl urea nitrogen, respectively). Cleavage rate was not reduced by any concentration of urea. However, the proportion of oocytes developing to the blastocyst stage at d 8 after insemination was reduced by 7.5 mM urea. In addition, the proportion of cleaved oocytes becoming blastocysts was decreased by 5 and 7.5 mM urea. For experiment 2, putative zygotes were collected -9 h after insemination and cultured in modified Potassium Simplex Optimized Medium (KSOM). Urea did not reduce the proportion of oocytes developing to the blastocyst stage, although 10 mM urea reduced cleavage rate slightly. For experiment 3, dimethadione (DMD), a weak nonmetabolizable acid, was used to decrease culture medium pH. Putative zygotes were cultured in modified KSOM containing 0, 10, 15, or 20 mM DMD for 8 d. DMD reduced cleavage rate at 15 and 20 mM and development to the blastocyst stage at all concentrations. Results support the idea that feeding diets rich in highly degradable CP compromises fertility through direct actions of urea on the oocyte and through diet-induced alterations in uterine pH.

  16. Mycorrhizal response to experimental pH and P manipulation in acidic hardwood forests.

    Directory of Open Access Journals (Sweden)

    Laurel A Kluber

    Full Text Available Many temperate forests of the Northeastern United States and Europe have received significant anthropogenic acid and nitrogen (N deposition over the last century. Although temperate hardwood forests are generally thought to be N-limited, anthropogenic deposition increases the possibility of phosphorus (P limiting productivity in these forest ecosystems. Moreover, inorganic P availability is largely controlled by soil pH and biogeochemical theory suggests that forests with acidic soils (i.e., <pH 5 are particularly vulnerable to P limitation. Results from previous studies in these systems are mixed with evidence both for and against P limitation. We hypothesized that shifts in mycorrhizal colonization and community structure help temperate forest ecosystems overcome an underlying P limitation by accessing mineral and organic P sources that are otherwise unavailable for direct plant uptake. We examined arbuscular mycorrhizal (AM and ectomycorrhizal (EcM communities and soil microbial activity in an ecosystem-level experiment where soil pH and P availability were manipulated in mixed deciduous forests across eastern Ohio, USA. One year after treatment initiation, AM root biomass was positively correlated with the most available P pool, resin P, while AM colonization was negatively correlated. In total, 15,876 EcM root tips were identified and assigned to 26 genera and 219 operational taxonomic units (97% similarity. Ectomycorrhizal richness and root tip abundance were negatively correlated with the moderately available P pools, while the relative percent of tips colonized by Ascomycetes was positively correlated with soil pH. Canonical correspondence analysis revealed regional, but not treatment, differences in AM communities, while EcM communities had both treatment and regional differences. Our findings highlight the complex interactions between mycorrhizae and the soil environment and further underscore the fact that mycorrhizal communities do

  17. Sulfate reduction at low pH to remediate acid mine drainage

    Energy Technology Data Exchange (ETDEWEB)

    Sánchez-Andrea, Irene, E-mail: irene.sanchezandrea@wur.nl [Departamento de Biología Molecular, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Laboratory of Microbiology, Wageningen University, Dreijenplein 10, 6703 HB Wageningen (Netherlands); Sanz, Jose Luis [Departamento de Biología Molecular, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Bijmans, Martijn F.M. [Wetsus, Centre of Sustainable Water Technology, P.O. Box 1113, 8900 CC Leeuwarden (Netherlands); Stams, Alfons J.M. [Laboratory of Microbiology, Wageningen University, Dreijenplein 10, 6703 HB Wageningen (Netherlands); IBB – Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, 4710-057 Braga (Portugal)

    2014-03-01

    Highlights: • Acid mine drainage (AMD) is an important environmental concern. • Remediation through biological sulfate reduction and metal recovery can be applied for AMD. • Microbial community composition has a major impact on the performance of bioreactors to treat AMD. • Acidophilic SRB are strongly influenced by proton, sulfide and organic acids concentration. - Abstract: Industrial activities and the natural oxidation of metallic sulfide-ores produce sulfate-rich waters with low pH and high heavy metals content, generally termed acid mine drainage (AMD). This is of great environmental concern as some heavy metals are highly toxic. Within a number of possibilities, biological treatment applying sulfate-reducing bacteria (SRB) is an attractive option to treat AMD and to recover metals. The process produces alkalinity, neutralizing the AMD simultaneously. The sulfide that is produced reacts with the metal in solution and precipitates them as metal sulfides. Here, important factors for biotechnological application of SRB such as the inocula, the pH of the process, the substrates and the reactor design are discussed. Microbial communities of sulfidogenic reactors treating AMD which comprise fermentative-, acetogenic- and SRB as well as methanogenic archaea are reviewed.

  18. Intracellular pH regulation by acid/base transporters in mammalian neurons

    Directory of Open Access Journals (Sweden)

    Vernon A. Ruffin

    2014-02-01

    Full Text Available Intracellular pH (pHi regulation in the brain is important in both physiological and physiopathological conditions because changes in pHi generally result in altered neuronal excitability. In this review, we will cover 4 major areas: [1] The effect of pHi on cellular processes in the brain, including channel activity and neuronal excitability. [2] pHi homeostasis and how it is determined by the balance between rates of acid loading (JL and extrusion (JE. The balance between JE and JL determine steady-state pHi, as well as the ability of the cell to defend pHi in the face of extracellular acid-base disturbances (e.g. metabolic acidosis. [3] The properties and importance of members of the SLC4 and SLC9 families of acid-base transporters expressed in the brain that contribute to JL (namely the Cl-HCO3 exchanger AE3 and JE (the Na-H exchangers NHE1, NHE3 and NHE5 as well as the Na+- coupled HCO3- transporters NBCe1, NBCn1, NDCBE, and NBCn2. [4] The effect of acid-base disturbances on neuronal function and the roles of acid-base transporters in defending neuronal pHi under physiopathologic conditions.

  19. Geochemical evolution of the acid crater lake of Poas volcano (Costa Rica): Insights into volcanic-hydrothermal processes

    NARCIS (Netherlands)

    Martínez Cruz, María

    2008-01-01

    This thesis describes the evolution of Laguna Caliente, an acid crater lake at the summit of Po:is, a persistently active volcano in central Costa Rica. The appearance, volume, temperature and chemical composition of the lake have continuously changed over the entire known period of its existence. O

  20. Influence of amino acids, buffers, and ph on the γ-irradiation-induced degradation of alginates.

    Science.gov (United States)

    Ulset, Ann-Sissel T; Mori, Hideki; Dalheim, Marianne Ø; Hara, Masayuki; Christensen, Bjørn E

    2014-12-08

    Alginate-based biomaterials and medical devices are commonly subjected to γ-irradiation as a means of sterilization, either in the dry state or the gel (hydrated) state. In this process the alginate chains degrade randomly in a dose-dependent manner, altering alginates' material properties. The addition of free radical scavenging amino acids such as histidine and phenylalanine protects the alginate significantly against degradation, as shown by monitoring changes in the molecular weight distributions using SEC-MALLS and determining the pseudo first order rate constants of degradation. Tris buffer (0.5 M), but not acetate, citrate, or phosphate buffers had a similar effect on the degradation rate. Changes in pH itself had only marginal effects on the rate of alginate degradation and on the protective effect of amino acids. Contrary to previous reports, the chemical composition (M/G profile) of the alginates, including homopolymeric mannuronan, was unaltered following irradiation up to 10 kGy.

  1. A pH dependent Raman and surface enhanced Raman spectroscopic studies of citrazinic acid aided by theoretical calculations

    Science.gov (United States)

    Sarkar, Sougata; Chowdhury, Joydeep; Dutta, Soumen; Pal, Tarasankar

    2016-12-01

    A pH dependent normal Raman scattering (NRS) and surface enhanced Raman scattering (SERS) spectral patterns of citrazinic acid (CZA), a biologically important molecule, have been investigated. The acid, with different pKa values (~ 4 and ~ 11) for the two different functional groups (-COOH and -OH groups), shows interesting range of color changes (yellow at pH ~ 14 and brown at pH ~ 2) with the variation in solution pH. Thus, depending upon the pH of the medium, CZA molecule can exist in various protonated and/or deprotonated forms. Here we have prescribed the existence different possible forms of CZA at different pH (Forms "C", "H" and "Dprot" at pH ~ 14 and Forms "A", "D", and "P" at pH ~ 2 respectively). The NRS spectra of these solutions and their respective SERS spectra over gold nanoparticles were recorded. The spectra clearly differ in their spectral profiles. For example the SERS spectra recorded with the CZA solution at pH ~ 2 shows blue shift for different bands compared to its NRS window e.g. 406 to 450 cm- 1, 616 to 632 cm- 1, 1332 to 1343 cm- 1 etc. Again, the most enhanced peak at ~ 1548 cm- 1 in NRS while in the SERS window this appears at ~ 1580 cm- 1. Similar observation was also made for CZA at pH ~ 14. For example, the 423 cm- 1 band in the NRS profile experience a blue shift and appears at ~ 447 cm- 1 in the SERS spectrum as well as other bands at ~ 850, ~ 1067 and ~ 1214 cm- 1 in the SERS window are markedly enhanced. It is also worth noting that the SERS spectra at the different pH also differ from each other. These spectral differences indicate the existence of various adsorptive forms of the CZA molecule depending upon the pH of the solution. Therefore based on the experimental findings we propose different possible molecular forms of CZA at different pH (acidic and alkaline) conditions. For example forms 'A', 'D' and 'P' existing in acidic pH (pH ~ 2) and three other deprotonated forms 'C', 'H' and 'Dprot' in alkaline pH (pH ~ 14). The DFT

  2. Association of the pr Peptides with Dengue Virus at Acidic pH Blocks Membrane Fusion

    Energy Technology Data Exchange (ETDEWEB)

    Yu, I.-M.; Holdaway, H.A.; Chipman, P.R.; Kuhn, R.J.; Rossmann, M.G.; Chen, J.; Purdue

    2010-07-27

    Flavivirus assembles into an inert particle that requires proteolytic activation by furin to enable transmission to other hosts. We previously showed that immature virus undergoes a conformational change at low pH that renders it accessible to furin (I. M. Yu, W. Zhang, H. A. Holdaway, L. Li, V. A. Kostyuchenko, P. R. Chipman, R. J. Kuhn, M. G. Rossmann, and J. Chen, Science 319:1834-1837, 2008). Here we show, using cryoelectron microscopy, that the structure of immature dengue virus at pH 6.0 is essentially the same before and after the cleavage of prM. The structure shows that after cleavage, the proteolytic product pr remains associated with the virion at acidic pH, and that furin cleavage by itself does not induce any major conformational changes. We also show by liposome cofloatation experiments that pr retention prevents membrane insertion, suggesting that pr is present on the virion in the trans-Golgi network to protect the progeny virus from fusion within the host cell.

  3. Influence of pH and heat treatment on β-lactolobulin-oleic acid complex

    Directory of Open Access Journals (Sweden)

    Ana-Maria SIMION (CIUCIU

    2015-12-01

    Full Text Available One of the major concerns of food technologists is to produce healthier products with specific functionalities. The potential use of β-lactoglobulin as a supplement for new functional products is encouraging due to its nutritional and functional characteristics. The aim of this work was to obtain β-lactoglobulin-oleic acid complexes at different pH values (5.0, 6.0, and 7.0 and to test their stability at different temperatures (25-85°C such as to allow identifying their potential use in a variety of food products. The complexes were characterized through different fluorescence spectroscopy based techniques: phase diagram, intrinsic and extrinsic fluorescence, along with fluorescence quenching experiments. Results showed the presence of more than two structurally distinct species with intermediates as induced by thermal treatment. The heat treatment at temperatures higher than 70°C caused an increase in both intrinsic and ANS fluorescence intensity. Acrylamide quenching showed no significant differences between the values of Stern-Volmer constants as function of temperature for pH 5.0, suggesting that no significant changes occurred in the Trp microenvironments. Quenching experiments with KI lead to decreases in Stern-Volmer constants in the temperature range 25-70°C, suggesting protein folding, whereas at higher temperatures a small increase was observed suggesting unfolding and an increased accessibility of the fluorophore to the quencher for all pH values.

  4. The effect of pH on the toxicity of fatty acids and fatty acid amides to rainbow trout gill cells.

    Science.gov (United States)

    Bertin, Matthew J; Voronca, Delia C; Chapman, Robert W; Moeller, Peter D R

    2014-01-01

    Harmful algal blooms (HABs) expose aquatic organisms to multiple physical and chemical stressors during an acute time period. Algal toxins themselves may be altered by water chemistry parameters affecting their bioavailability and resultant toxicity. The purpose of this study was to determine the effects of two abiotic parameters (pH, inorganic metal salts) on the toxicity of fatty acid amides and fatty acids, two classes of lipids produced by harmful algae, including the golden alga, Prymnesium parvum, that are toxic to aquatic organisms. Rainbow trout gill cells were used as a model of the fish gill and exposed to single compounds and mixtures of compounds along with variations in pH level and concentration of inorganic metal salts. We employed artificial neural networks (ANNs) and standard ANOVA statistical analysis to examine and predict the effects of these abiotic parameters on the toxicity of fatty acid amides and fatty acids. Our results demonstrate that increasing pH levels increases the toxicity of fatty acid amides and inhibits the toxicity of fatty acids. This phenomenon is reversed at lower pH levels. Exposing gill cells to complex mixtures of chemical factors resulted in dramatic increases in toxicity compared to tests of single compounds for both the fatty acid amides and fatty acids. These findings highlight the potential of physicochemical factors to affect the toxicity of chemicals released during algal blooms and demonstrate drastic differences in the effect of pH on fatty acid amides and fatty acids.

  5. Estimated net acid excretion inversely correlates with urine pH in vegans, lacto-ovo vegetarians, and omnivores.

    Science.gov (United States)

    Ausman, Lynne M; Oliver, Lauren M; Goldin, Barry R; Woods, Margo N; Gorbach, Sherwood L; Dwyer, Johanna T

    2008-09-01

    Diet affects urine pH and acid-base balance. Both excess acid/alkaline ash (EAA) and estimated net acid excretion (NAE) calculations have been used to estimate the effects of diet on urine pH. This study's goal was to determine if free-living vegans, lacto-ovo vegetarians, and omnivores have increasingly acidic urine, and to assess the ability of EAA and estimated NAE calculations to predict urine pH. This study used a cross-sectional design. This study assessed urine samples of 10 vegan, 16 lacto-ovo vegetarian, and 16 healthy omnivorous women in the Boston metropolitan area. Six 3-day food records from each dietary group were analyzed for EAA content and estimated NAE, and correlations with measured urine pH were calculated. The mean (+/- SD) urine pH was 6.15 +/- 0.40 for vegans, 5.90 +/- 0.36 for lacto-ovo vegetarians, and 5.74 +/- 0.21 for omnivores (analysis of variance, P = .013). Calculated EAA values were not significantly different among the three groups, whereas mean estimated NAE values were significantly different: 17.3 +/- 14.5 mEq/day for vegans, 31.3 +/- 8.5 mEq/day for lacto-ovo vegetarians, and 42.6 +/- 13.2 mEq/day for omnivores (analysis of variance, P = .01). The average deattenuated correlation between urine pH and EAA was 0.333; this value was -0.768 for estimated NAE and urine pH, with a regression equation of pH = 6.33 - 0.014 NAE (P = .02, r = -0.54). Habitual diet and estimated NAE calculations indicate the probable ranking of urine pH by dietary groups, and may be used to determine the likely acid-base status of an individual; EAA calculations were not predictive of urine pH.

  6. Do pH and flavonoids influence hypochlorous acid-induced catalase inhibition and heme modification?

    Science.gov (United States)

    Krych-Madej, Justyna; Gebicka, Lidia

    2015-09-01

    Hypochlorous acid (HOCl), highly reactive oxidizing and chlorinating species, is formed in the immune response to invading pathogens by the reaction of hydrogen peroxide with chloride catalyzed by the enzyme myeloperoxidase. Catalase, an important antioxidant enzyme, catalyzing decomposition of hydrogen peroxide to water and molecular oxygen, hampers in vitro HOCl formation, but is also one of the main targets for HOCl. In this work we have investigated HOCl-induced catalase inhibition at different pH, and the influence of flavonoids (catechin, epigallocatechin gallate and quercetin) on this process. It has been shown that HOCl-induced catalase inhibition is independent on pH in the range 6.0-7.4. Preincubation of catalase with epigallocatechin gallate and quercetin before HOCl treatment enhances the degree of catalase inhibition, whereas catechin does not affect this process. Our rapid kinetic measurements of absorption changes around the heme group have revealed that heme modification by HOCl is mainly due to secondary, intramolecular processes. The presence of flavonoids, which reduce active catalase intermediate, Compound I to inactive Compound II have not influenced the kinetics of HOCl-induced heme modification. Possible mechanisms of the reaction of hypochlorous acid with catalase are proposed and the biological consequences are discussed.

  7. Swelling characteristics of hydroxyethylmethacrylate/ methacrylic acid pH -sensitive hydrogel as a drug delivery system

    Directory of Open Access Journals (Sweden)

    M. Falamarzian- J. Varshosaz

    1996-08-01

    Full Text Available Hydroxyethyl methacrylate /methacrylic acid (HEMA/MAA copolymer cross-linked with ethylenglycol dimethacrylate was prepared by a bulk.free radical polymerization method. The results indicate that this polymer is a pH -sensitive hydrogel which is collapsed in the acidic medium but completely swollen in the alkaline and neutral pH . it was determined that a proportion of 40% of MAA, the ionizing monomer of this hydrogel, was the best concentration among the different percentages used which showed a non-Fickian water transport mechanism. Increasing MAA content from 20 to 70% was accompanied with a change in water transport mechanism from Fickian to non-Fickian. However, increasing the percentage of MAA from 40 to 70 didn't improve the swelling capacity of this polymer. Pore size determination by a solute exclusion technique, showed the greatest distribution in the hydrogel with 40% MAA compared to other percentages of this monomer used. About 75% of the pores were less than 16.5 A in diameter in this polymer which is important specially in loading the hydrogel with macromoiecular drugs like proteines.

  8. Poly methacrylic acid modified CDHA nanocomposites as potential pH responsive drug delivery vehicles.

    Science.gov (United States)

    Victor, Sunita Prem; Sharma, Chandra P

    2013-08-01

    The objective of this study was to prepare pH sensitive polymethacrylic acid-calcium deficient hydroxyapatite (CDHA) nanocomposites. The CDHA nanoparticles were prepared by coprecipitation method. The modification of CDHA by methacrylic acid (MA) was achieved by AIBN initiated free radical polymerization with sodium bisulphite as catalyst followed by emulsion technique. These nanocomposites with a half life of 8h consisted of high aspect ratio, needle like particles and exhibited an increase in swelling behaviour with pH. The in vivo potential of the nanocomposites was evaluated in vitro by the results of cell aggregation, protein adsorption, MTT assay and haemolytic activity. The invitro loading and release studies using albumin as a model drug indicate that the nanocomposites gave better loading when compared to the CDHA nanoparticles and altered the drug release rates. The nanocomposites also exhibited good uptake on C6 glioma cells as studied by fluorescence microscopy. The results obtained suggest that these nanocomposites have great potential for oral controlled protein delivery and can be extended further for intracellular drug delivery applications.

  9. Acidic pH retards the fibrillization of human islet amyloid polypeptide due to electrostatic repulsion of histidines

    Science.gov (United States)

    Li, Yang; Xu, Weixin; Mu, Yuguang; Zhang, John Z. H.

    2013-08-01

    The human Islet Amyloid Polypeptide (hIAPP) is the major constituent of amyloid deposits in pancreatic islets of type-II diabetes. IAPP is secreted together with insulin from the acidic secretory granules at a low pH of approximately 5.5 to the extracellular environment at a neutral pH. The increased accumulation of extracellular hIAPP in diabetes indicates that changes in pH may promote amyloid formation. To gain insights and underlying mechanisms of the pH effect on hIAPP fibrillogenesis, all-atom molecular dynamics simulations in explicit solvent model were performed to study the structural properties of five hIAPP protofibrillar oligomers, under acidic and neutral pH, respectively. In consistent with experimental findings, simulation results show that acidic pH is not conducive to the structural stability of these oligomers. This provides a direct evidence for a recent experiment [L. Khemtemourian, E. Domenech, J. P. F. Doux, M. C. Koorengevel, and J. A. Killian, J. Am. Chem. Soc. 133, 15598 (2011)], 10.1021/ja205007j, which suggests that acidic pH inhibits the fibril formation of hIAPP. In addition, a complementary coarse-grained simulation shows the repulsive electrostatic interactions among charged His18 residues slow down the dimerization process of hIAPP by twofold. Besides, our all-atom simulations reveal acidic pH mainly affects the local structure around residue His18 by destroying the surrounding hydrogen-bonding network, due to the repulsive interactions between protonated interchain His18 residues at acidic pH. It is also disclosed that the local interactions nearby His18 operating between adjacent β-strands trigger the structural transition, which gives hints to the experimental findings that the rate of hIAPP fibril formation and the morphologies of the fibrillar structures are strongly pH-dependent.

  10. Influence of glutamic acid residues and pH on the properties of transmembrane helices.

    Science.gov (United States)

    Rajagopalan, Venkatesan; Greathouse, Denise V; Koeppe, Roger E

    2017-03-01

    Negatively charged side chains are important for the function of particular ion channels and certain other membrane proteins. To investigate the influence of single glutamic acid side chains on helices that span lipid-bilayer membranes, we have employed GWALP23 (acetyl-GGALW(5)LALALALALALALW(19)LAGA-amide) as a favorable host peptide framework. We substituted individual Leu residues with Glu residues (L12E or L14E or L16E) and incorporated specific (2)H-labeled alanine residues within the core helical region or near the ends of the sequence. Solid-state (2)H NMR spectra reveal little change for the core labels in GWALP23-E12, -E14 and -E16 over a pH range of 4 to 12.5, with the spectra being broader for samples in DOPC compared to DLPC bilayers. The spectra for samples with deuterium labels near the helix ends on alanines 3 and 21 show modest pH-dependent changes in the extent of unwinding of the helix terminals in DLPC and DOPC bilayers. The combined results indicate minor overall responses of these transmembrane helices to changes in pH, with the most buried residue E12 showing no pH dependence. While the Glu residues E14 and E16 may have high pKa values in the lipid bilayer environment, it is also possible that a paucity of helix response is masking the pKa values. Interestingly, when E16 is present, spectral changes at high pH report significant local unwinding of the core helix. Our results are consistent with the expectation that buried carboxyl groups aggressively hold their protons and/or waters of hydration.

  11. Microbial sulfate reduction and metal attenuation in pH 4 acid mine water

    Directory of Open Access Journals (Sweden)

    Alpers Charles N

    2007-10-01

    Full Text Available Abstract Sediments recovered from the flooded mine workings of the Penn Mine, a Cu-Zn mine abandoned since the early 1960s, were cultured for anaerobic bacteria over a range of pH (4.0 to 7.5. The molecular biology of sediments and cultures was studied to determine whether sulfate-reducing bacteria (SRB were active in moderately acidic conditions present in the underground mine workings. Here we document multiple, independent analyses and show evidence that sulfate reduction and associated metal attenuation are occurring in the pH-4 mine environment. Water-chemistry analyses of the mine water reveal: (1 preferential complexation and precipitation by H2S of Cu and Cd, relative to Zn; (2 stable isotope ratios of 34S/32S and 18O/16O in dissolved SO4 that are 2–3 ‰ heavier in the mine water, relative to those in surface waters; (3 reduction/oxidation conditions and dissolved gas concentrations consistent with conditions to support anaerobic processes such as sulfate reduction. Scanning electron microscope (SEM analyses of sediment show 1.5-micrometer, spherical ZnS precipitates. Phospholipid fatty acid (PLFA and denaturing gradient gel electrophoresis (DGGE analyses of Penn Mine sediment show a high biomass level with a moderately diverse community structure composed primarily of iron- and sulfate-reducing bacteria. Cultures of sediment from the mine produced dissolved sulfide at pH values near 7 and near 4, forming precipitates of either iron sulfide or elemental sulfur. DGGE coupled with sequence and phylogenetic analysis of 16S rDNA gene segments showed populations of Desulfosporosinus and Desulfitobacterium in Penn Mine sediment and laboratory cultures.

  12. Microbial sulfate reduction and metal attenuation in pH 4 acid mine water

    Science.gov (United States)

    Church, C.D.; Wilkin, R.T.; Alpers, C.N.; Rye, R.O.; Blaine, R.B.

    2007-01-01

    Sediments recovered from the flooded mine workings of the Penn Mine, a Cu-Zn mine abandoned since the early 1960s, were cultured for anaerobic bacteria over a range of pH (4.0 to 7.5). The molecular biology of sediments and cultures was studied to determine whether sulfate-reducing bacteria (SRB) were active in moderately acidic conditions present in the underground mine workings. Here we document multiple, independent analyses and show evidence that sulfate reduction and associated metal attenuation are occurring in the pH-4 mine environment. Water-chemistry analyses of the mine water reveal: (1) preferential complexation and precipitation by H2S of Cu and Cd, relative to Zn; (2) stable isotope ratios of 34S/32S and 18O/16O in dissolved SO4 that are 2-3 ??? heavier in the mine water, relative to those in surface waters; (3) reduction/oxidation conditions and dissolved gas concentrations consistent with conditions to support anaerobic processes such as sulfate reduction. Scanning electron microscope (SEM) analyses of sediment show 1.5-micrometer, spherical ZnS precipitates. Phospholipid fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) analyses of Penn Mine sediment show a high biomass level with a moderately diverse community structure composed primarily of iron- and sulfate-reducing bacteria. Cultures of sediment from the mine produced dissolved sulfide at pH values near 7 and near 4, forming precipitates of either iron sulfide or elemental sulfur. DGGE coupled with sequence and phylogenetic analysis of 16S rDNA gene segments showed populations of Desulfosporosinus and Desulfitobacterium in Penn Mine sediment and laboratory cultures. ?? 2007 Church et al; licensee BioMed Central Ltd.

  13. Acidez potencial pelo método do pH SMP no Estado do Amazonas Potential acidity by pH SMP method in Amazonas State, Brazil

    Directory of Open Access Journals (Sweden)

    Adônis Moreira

    2004-01-01

    Full Text Available O objetivo deste trabalho foi definir um modelo matemático que estime o H+Al a partir do pH SMP medido em água e em solução de CaCl2 0,01 mol L-1 nas condições edafoclimáticas locais. Foram utilizadas 246 amostras de solo provenientes de diversas localidades. Mesmo apresentando menor coeficiente da correlação (r = 0,89*, a equação H+Al = 30,646 - 3,848pH SMP obtida em H2O foi mais eficiente que a obtida em solução CaCl2 (H+Al = 30,155 - 3,834pH SMP, r = 0,91*, a qual subestima os valores da acidez potencial.The objective of this work was to determine a mathematic model that estimates the potential acidity with pH SMP measured in water and in solution of CaCl2 0.01 mol L-1. Two hundred and forty six soil samples from several localities were utilized. Despite presenting a lower correlation coefficient (r = 0.89*, the equation H+Al = 30.646 - 3.848pH SMP, obtained in H2O, was more efficient than in the CaCl2 solution (H+Al = 30.155 -3.834pH SMP, r = 0.91*, since this last one underestimates the values of the potential acidity.

  14. Is it possible to produce succinic acid at a low pH?

    Science.gov (United States)

    Yuzbashev, Tigran V; Yuzbasheva, Evgeniya Y; Laptev, Ivan A; Sobolevskaya, Tatiana I; Vybornaya, Tatiana V; Larina, Anna S; Gvilava, Ilia T; Antonova, Svetlana V; Sineoky, Sergey P

    2011-01-01

    Bio-based succinate is still a matter of special emphasis in biotechnology and adjacent research areas. The vast majority of natural and engineered producers are bacterial strains that accumulate succinate under anaerobic conditions. Recently, we succeeded in obtaining an aerobic yeast strain capable of producing succinic acid at low pH. Herein, we discuss some difficulties and advantages of microbial pathways producing "succinic acid" rather than "succinate." It was concluded that the peculiar properties of the constructed yeast strain could be clarified in view of a distorted energy balance. There is evidence that in an acidic environment, the majority of the cellular energy available as ATP will be spent for proton and anion efflux. The decreased ATP:ADP ratio could essentially reduce the growth rate or even completely inhibit growth. In the same way, the preference of this elaborated strain for certain carbon sources could be explained in terms of energy balance. Nevertheless, the opportunity to exclude alkali and mineral acid waste from microbial succinate production seems environmentally friendly and cost-effective.

  15. [Effects of simulated acid rain on respiration rate of cropland system with different soil pH].

    Science.gov (United States)

    Zhu, Xue-zhu; Zhang, Gao-chuan; Li, Hui

    2009-10-15

    To evaluate the effects of acid rain on the respiration rate of cropland system, an outdoor pot experiment was conducted with paddy soils of pH 5.48 (S1), pH 6.70 (S1) and pH 8.18 (S3) during the 2005-2007 wheat-growing seasons. The cropland system was exposed to acid rain by spraying the wheat foliage and irrigating the soil with simulated rainwater of T1 (pH 6.0), T2 (pH 6.0, ionic concentration was twice as rainwater T1), and T3 (pH 4.4, ionic concentration was twice as rainwater T1), respectively. The static opaque chamber-gas chromatograph method was used to measure CO2 fluxes from cropland system. The results showed that acid rain affected the respiration rate of cropland system through crop plant, and the cropland system could adapt to acid rain. Acid rainwater significantly increased the average respiration rate in alkaline soil (S3) cropland system, while it had no significant effects on the average respiration rate in neutral soil (S2) and acidic soil (S1) cropland systems. During 2005-2006, after the alkaline soil cropland system was treated with rainwater T3, the average respiration rate was 23.6% and 27.6% higher than that of alkaline soil cropland system treated with rainwater T1 and T2, respectively. During March to April, the respiration rate was enhanced with the increase of rainwater ionic concentration, while it was dropped with the decrease of rainwater pH value in acidic soil cropland system. It was demonstrated that soil pH and crop plant played important roles on the respiration rate of cropland system.

  16. Predicting Thermodynamic Behaviors of Non-Protein Amino Acids as a Function of Temperature and pH.

    Science.gov (United States)

    Kitadai, Norio

    2016-03-01

    Why does life use α-amino acids exclusively as building blocks of proteins? To address that fundamental question from an energetic perspective, this study estimated the standard molal thermodynamic data for three non-α-amino acids (β-alanine, γ-aminobutyric acid, and ε-aminocaproic acid) and α-amino-n-butyric acid in their zwitterionic, negative, and positive ionization states based on the corresponding experimental measurements reported in the literature. Temperature dependences of their heat capacities were described based on the revised Helgeson-Kirkham-Flowers (HKF) equations of state. The obtained dataset was then used to calculate the standard molal Gibbs energies (∆G (o)) of the non-α-amino acids as a function of temperature and pH. Comparison of their ∆G (o) values with those of α-amino acids having the same molecular formula showed that the non-α-amino acids have similar ∆G (o) values to the corresponding α-amino acids in physiologically relevant conditions (neutral pH, acidic and alkaline pH, the non-α-amino acids are thermodynamically more stable than the corresponding α-ones over a broad temperature range. These results suggest that the energetic cost of synthesis is not an important selection pressure to incorporate α-amino acids into biological systems.

  17. Ru-η(6) -arene cations [{(Ph2 PC6 H4 )2 B(η(6) -Ph)}RuX](+) (X=Cl, H) as Lewis acids.

    Science.gov (United States)

    Boone, Michael P; Stephan, Douglas W

    2014-03-17

    The reactivity of [{(Ph2 PC6 H4 )2 B(η(6) -Ph)}RuCl][B(C6 F5 )4 ] (1) as a Lewis acid was investigated. Treatment of 1 with mono and multidentate phosphorus Lewis bases afforded the Lewis acid-base adducts with the ortho-carbon atom of the coordinated arene ring. Similar reactivity was observed upon treatment with N-heterocyclic carbenes; however, adduct formation occurred at both ortho- and para-carbon atoms of the bound arene with the para-position being favoured by increased steric demands. Interestingly treatment with isocyanides resulted in adduct formation with the B-centre of the ligand framework. The hydride-cation [{(Ph2 PC6 H4 )2 B(η(6) -Ph)}RuH] [B(C6 F5 )4 ] was prepared via reaction of 1 with silane. This species in the presence of a bulky phosphine behaves as a frustrated Lewis pair (FLP) to activate H2 between the phosphorus centre and the ortho-carbon atom of the η(6) -arene ring. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Anthropogenically driven changes in chloride complicate interpretation of base cation trends in lakes recovering from acidic deposition.

    Science.gov (United States)

    Rosfjord, Catherine H; Webster, Katherine E; Kahl, Jeffrey S; Norton, Stephen A; Fernandez, Ivan J; Herlihy, Alan T

    2007-11-15

    Declines in Ca and Mg in low ANC lakes recovering from acidic deposition are widespread across the northern hemisphere. We report overall increases between 1984 and 2004 in the concentrations of Ca + Mg and Cl in lakes representing the statistical population of nearly 4000 low ANC lakes in the northeast U.S. Increases in Cl occurred in nearly all lakes in urbanized southern New England, but only 18% of lakes in more remote Maine had Cl increases. This spatial pattern implicates road salt application as the major source of the increased Cl salts. Among the 48% of the lake population classified as salt-affected, the median changes in Cl (+133 microeq/L) and Ca + Mg (+47 microeq/ L) were large and positive in direction over the 20 years. However, in the unaffected lakes, Cl remained stable and Ca + Mg decreased (-3 microeq/L), consistent with reported long-term trends in base cations of acid-sensitive lakes. This discrepancy between the Cl groups suggests that changes in ion exchange processes in salt-affected watersheds have altered the geochemical cycling of Ca and Mg. One policy-relevant implication is that waters influenced by Cl salts complicate regional assessments of surface water recovery from "acid rain" related to the passage of the Clean Air Act.

  19. Growth of Avena Coleoptiles and pH Drop of Protoplast Suspensions Induced by Chlorinated Indoleacetic Acids

    DEFF Research Database (Denmark)

    Engvild, Kjeld Christensen; Doll, Hans; Böttger, M.

    1978-01-01

    -auxins. Some of the derivatives were compared for their effect on pH decline in stem protoplast suspensions of Helianthus annuus L. and Pisum sativum L. The change of pH occurs without a lag period or with only a very short one. Derivatives which are very active in the Avena straight growth assay cause......Several indoleacetic acids, substituted in the benzene ring, were compared in the Avena straight growth bioassay. 4-Chloroindoleacetic acid, a naturally occurring plant hormone, is one of the strongest hormones in this bioassay. With an optimum at 10-6 mol l-1, it is more active than indoleacetic...... acid, 2,4-dichlorphenoxyacetic acid and naphthaleneacetic acid. 5-Chloro- and 6-chloroindoleacetic acids are very strong auxins as well. Other derivatives tested have a lower activity. 5,7-Dichloro- and 5-hydroxyindoleacetic acids have very low auxin activity at 10-4 mol l-1 and may be anti...

  20. Iron buffer system in the water column and partitioning in the sediments of the naturally acidic Lake Caviahue, Neuquén, Argentina

    Science.gov (United States)

    Cabrera, J. M.; Diaz, M. M.; Schultz, S.; Temporetti, P.; Pedrozo, F.

    2016-05-01

    Sedimentary iron partitioning was studied for five sediment strata (16 cm depth) at three sampling sites of the naturally-occurring acidic Lake Caviahue (Patagonia, Argentina). Additionally, water column iron was modeled based on five-year period input loadings to study a possible iron buffer system. The partition coefficient between the water column and the total iron content of the sediments was also addressed. Sedimentary iron was found to be distributed, on average, in the following forms: exchangeable (6%), iron oxides (4%), pyrite and reactive organic matter (38%) and residual (non-andesitic) materials with a high content of humic acids (52%). Furthermore, we found that the dissolved iron in the lake was nearly constant throughout the five year period we studied. This is consistent with the existence of an iron buffer system in the lake at pH between 2.0 and 3.0, which may cause differential iron precipitation at the delta of the volcanic river with respect to the deeper northern and southern arms. Sedimentary iron measurements taken at the delta further support the existence of a buffer system, where it was found that the iron content in the sub-superficial stratum (2 cm) was double that of the remainder of the vertical profile at the same site.

  1. Responses of 20 lake-watersheds in the Adirondack region of New York to historical and potential future acidic deposition.

    Science.gov (United States)

    Zhou, Qingtao; Driscoll, Charles T; Sullivan, Timothy J

    2015-04-01

    Critical loads (CLs) and dynamic critical loads (DCLs) are important tools to guide the protection of ecosystems from air pollution. In order to quantify decreases in acidic deposition necessary to protect sensitive aquatic species, we calculated CLs and DCLs of sulfate (SO4(2-))+nitrate (NO3-) for 20 lake-watersheds from the Adirondack region of New York using the dynamic model, PnET-BGC. We evaluated lake water chemistry and fish and total zooplankton species richness in response to historical acidic deposition and under future deposition scenarios. The model performed well in simulating measured chemistry of Adirondack lakes. Current deposition of SO4(2-)+NO3-, calcium (Ca2+) weathering rate and lake acid neutralizing capacity (ANC) in 1850 were related to the extent of historical acidification (1850-2008). Changes in lake Al3+ concentrations since the onset of acidic deposition were also related to Ca2+ weathering rate and ANC in 1850. Lake ANC and fish and total zooplankton species richness were projected to increase under hypothetical decreases in future deposition. However, model projections suggest that lake ecosystems will not achieve complete chemical and biological recovery in the future. Copyright © 2014. Published by Elsevier B.V.

  2. Changes in composition and enamel demineralization inhibition activities of gallic acid at different pH values

    NARCIS (Netherlands)

    Zhang, J.; Huang, X.; Huang, S.; Deng, M.; Xie, X.; Liu, M.; Liu, H.; Zhou, X.; Li, J.; ten Cate, J.M.

    2015-01-01

    Background. Gallic acid (GA) has been shown to inhibit demineralization and enhance remineralization of enamel; however, GA solution is highly acidic. This study was to investigate the stability of GA solutions at various pH and to examine the resultant effects on enamel demineralization. Methods. T

  3. Microenvironmental pH measurement during sodium naproxenate dissolution in acidic medium by UV/vis imaging

    DEFF Research Database (Denmark)

    Ostergaard, Jesper; Jensen, Henrik; Larsen, Susan W;

    2014-01-01

    Variable dissolution from sodium salts of drugs containing a carboxylic acid group after passing the acidic environment of the stomach may affect oral bioavailability. The aim of the present proof of concept study was to investigate pH effects in relation to the dissolution of sodium naproxenate ...

  4. Effects of urea and acetic acid on the heme axial ligation structure of ferric myoglobin at very acidic pH.

    Science.gov (United States)

    Droghetti, Enrica; Sumithran, Suganya; Sono, Masanori; Antalík, Marián; Fedurco, Milan; Dawson, John H; Smulevich, Giulietta

    2009-09-01

    The heme iron coordination of ferric myoglobin (Mb) in the presence of 9.0M urea and 8.0M acetic acid at acidic pH values has been probed by electronic absorption, magnetic circular dichroism and resonance Raman spectroscopic techniques. Unlike Mb at pH 2.0, where heme is not released from the protein despite the acid denaturation and the loss of the axial ligand, upon increasing the concentration of either urea or acetic acid, a spin state change is observed, and a novel, non-native six-coordinated high-spin species prevails, where heme is released from the protein.

  5. PH metric method for the determination of nicotinic acid in plasma.

    Science.gov (United States)

    Gravesen, J

    1977-04-01

    The acidimetric method for the determination of nicotinic acid (NA) using Lactobacillus plantarum ATCC 8014 (Lactobacillus arabinosus 17-5) has been simplified and thus made less time consuming, and the sensitivity has been increased fivefold by replacement of the titration by a pH determination. As the regression of the decrease in pH on the amount of NA was found linear within a range of 1 to 4 ng of NA per ml, the calculations were performed according to the slope-ratio principle. The NA concentration of plasma was determined with a coefficient of variation of 5 to 7%, which rose to about 10% at low NA concentrations. Assays of fasting plasma samples from 13 hyperlipidemic male patients showed a group mean NA concentration of 80 +/- 55 ng/ml (mean +/- 2 standard deviation), before treatment, and 705 +/- 544 ng/ml (mean +/- 2 standard deviation) during therapy with sustained release NA preparations, of which a single dose, ingested during steady-state conditions, doubled or tripled the plasma concentration within 1 to 3 h.

  6. Reactions of Cr3+ with aspartic acid within a wide pH range

    Directory of Open Access Journals (Sweden)

    Yahia Z. Hamada

    2014-12-01

    Full Text Available Formation of the metal complexes of aspartic acid (Asp with the chromium metal ion (Cr3+ in solutions using potentiometric titrations is presented within a wide pH range (∼3.5 to ∼10.5 at 25°C and I=0.10 M NaNO3. Concentration distribution diagrams revealed that the main complex formed within this pH range is the bis Cr 3+ complex. Literature stability constant values for the Cr–Asp complexes were used to construct concentration distribution diagrams. Complexes taken into consideration were the simple one-to-one complex, the bis-complex, and the bis-mono-protonated complex, namely, Cr–Asp, Cr(Asp2, and Cr(Asp2H. The corresponding Log β values of these complexes were 12.46, 21.86, and 24.30, respectively. UV–Vis spectra demonstrate Cr 3+–Asp binding. The UV–Vis spectra were collected from a system that reached a high level of equilibrium state (50 days’ equilibrium time.

  7. Charge-transfer-based terbium MOF nanoparticles as fluorescent pH sensor for extreme acidity.

    Science.gov (United States)

    Qi, Zewan; Chen, Yang

    2017-01-15

    Newly emerged metal organic frameworks (MOFs) have aroused the great interest in designing functional materials by means of its flexible structure and component. In this study, we used lanthanide Tb(3+) ions and small molecular ligands to design and assemble a kind of pH-sensitive MOF nanoparticle based on intramolecular-charge-transfer effect. This kind of made-to-order MOF nanoparticle for H(+) is highly specific and sensitive and could be used to fluorescently indicate pH value of strong acidic solution via preset mechanism through luminescence of Tb(3+). The long luminescence lifetime of Tb(3+) allows eliminating concomitant non-specific fluorescence by time-revised fluorescence techniques, processing an advantage in sensing H(+) in biological media with strong autofluorescence. Our method showed a great potential of MOF structures in designing and constructing sensitive sensing materials for specific analytes directly via the assembly of functional ions/ligands.

  8. Can A Denaturant Stabilize DNA? Pyridine Reverses DNA Denaturation in Acidic pH.

    Science.gov (United States)

    Portella, Guillem; Terrazas, Montserrat; Villegas, Núria; González, Carlos; Orozco, Modesto

    2015-09-01

    The stability of DNA is highly dependent on the properties of the surrounding solvent, such as ionic strength, pH, and the presence of denaturants and osmolytes. Addition of pyridine is known to unfold DNA by replacing π-π stacking interactions between bases, stabilizing conformations in which the nucleotides are solvent exposed. We show here experimental and theoretical evidences that pyridine can change its role and in fact stabilize the DNA under acidic conditions. NMR spectroscopy and MD simulations demonstrate that the reversal in the denaturing role of pyridine is specific, and is related to its character as pseudo groove binder. The present study sheds light on the nature of DNA stability and on the relationship between DNA and solvent, with clear biotechnological implications.

  9. Temporal-spatial distributions and ecological risks of perfluoroalkyl acids (PFAAs) in the surface water from the fifth-largest freshwater lake in China (Lake Chaohu)

    DEFF Research Database (Denmark)

    Liu, Wen-Xiu; He, Wei; Qin, Ning

    2015-01-01

    To investigate the residues, compositions, distributions and potential ecological risks of perfluoroalkyl acids (PFAAs), water samples were collected seasonally between August 2011 and November 2012 from 20 sites in Lake Chaohu and its tributary rivers. The mean concentration of total PFAAs (TPFA...

  10. Alteration of the phospho- or neutral lipid content and fatty acid composition in Listeria monocytogenes due to acid adaptation mechanisms for hydrochloric, acetic and lactic acids at pH 5.5 or benzoic acid at neutral pH.

    Science.gov (United States)

    Mastronicolis, Sofia K; Berberi, Anita; Diakogiannis, Ioannis; Petrova, Evanthia; Kiaki, Irene; Baltzi, Triantafillia; Xenikakis, Polydoros

    2010-10-01

    This study provides a first approach to observe the effects on Listeria monocytogenes of cellular exposure to acid stress at low or neutral pH, notably how phospho- or neutral lipids are involved in this mechanism, besides the fatty acid profile alteration. A thorough investigation of the composition of polar and neutral lipids from L. monocytogenes grown at pH 5.5 in presence of hydrochloric, acetic and lactic acids, or at neutral pH 7.3 in presence of benzoic acid, is described relative to cells grown in acid-free medium. The results showed that only low pH values enhance the antimicrobial activity of an acid. We suggest that, irrespective of pH, the acid adaptation response will lead to a similar alteration in fatty acid composition [decreasing the ratio of branched chain/saturated straight fatty acids of total lipids], mainly originating from the neutral lipid class of adapted cultures. Acid adaptation in L. monocytogenes was correlated with a decrease in total lipid phosphorus and, with the exception of cells adapted to benzoic acid, this change in the amount of phosphorus reflected a higher content of the neutral lipid class. Upon acetic or benzoic acid stress the lipid phosphorus proportion was analysed in the main phospholipids present: cardiolipin, phosphatidylglycerol, phosphoaminolipid and phosphatidylinositol. Interestingly only benzoic acid had a dramatic effect on the relative quantities of these four phospholipids.

  11. Reactive solute transport in an acidic stream: Experimental pH increase and simulation of controls on pH, aluminum, and iron

    Science.gov (United States)

    Broshears, R.E.; Runkel, R.L.; Kimball, B.A.; McKnight, Diane M.; Bencala, K.E.

    1996-01-01

    Solute transport simulations quantitatively constrained hydrologic and geochemical hypotheses about field observations of a pH modification in an acid mine drainage stream. Carbonate chemistry, the formation of solid phases, and buffering interactions with the stream bed were important factors in explaining the behavior of pH, aluminum, and iron. The precipitation of microcrystalline gibbsite accounted for the behavior of aluminum; precipitation of Fe(OH)3 explained the general pattern of iron solubility. The dynamic experiment revealed limitations on assumptions that reactions were controlled only by equilibrium chemistry. Temporal variation in relative rates of photoreduction and oxidation influenced iron behavior. Kinetic limitations on ferrous iron oxidation and hydrous oxide precipitation and the effects of these limitations on field filtration were evident. Kinetic restraints also characterized interaction between the water column and the stream bed, including sorption and desorption of protons from iron oxides at the sediment-water interface and post-injection dissolution of the precipitated aluminum solid phase.

  12. Influence of in ovo mercury exposure, lake acidity, and other factors on common loon egg and chick quality in Wisconsin

    Science.gov (United States)

    We conducted a field study in Wisconsin to characterize in ovo mercury (Hg) exposure in common loons (Gavia immer). Total Hg mass fractions ranged from 0.17 to 1.23 ìg/g wet weight (ww) in eggs collected from nests on lakes representing a wide range of pH (5.0 - 8.1) and ...

  13. Boronate-Phenolic Network Capsules with Dual Response to Acidic pH and cis-Diols.

    Science.gov (United States)

    Guo, Junling; Sun, Huanli; Alt, Karen; Tardy, Blaise L; Richardson, Joseph J; Suma, Tomoya; Ejima, Hirotaka; Cui, Jiwei; Hagemeyer, Christoph E; Caruso, Frank

    2015-08-26

    Dual-responsive boronate-phenolic network (BPN) capsules are fabricated by the complexation of phenylborate and phenolic materials. The BPN capsules are stable in the presence of competing carbohydrates, but dissociate at acidic pH or in the presence of competing cis-diols at physiological pH. This engineered capsule system provides a platform for a wide range of biological and biomedical applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Fermentation of liquid coproducts and liquid compound diets: Part 2. Effects on pH, acid-binding capacity, organic acids and ethanol during a 6-day period

    NARCIS (Netherlands)

    Scholten, R.H.J.; Rijnen, M.M.J.A.; Schrama, J.W.; Boer, H.; Peet-Schwering, van der C.M.C.; Hartog, den L.A.; Vesseur, P.C.

    2001-01-01

    The effects of a 6-day storage period on changes in pH, acid-binding capacity, level of organic acids and ethanol of three liquid coproducts [liquid wheat starch (LWS), mashed potato steam peel (PSP) and cheese whey (CW)] and two liquid compound diets [liquid grower diet (LGD) and liquid finisher

  15. Lactic acid fermentation from food waste with indigenous microbiota: Effects of pH, temperature and high OLR.

    Science.gov (United States)

    Tang, Jialing; Wang, Xiaochang; Hu, Yisong; Zhang, Yongmei; Li, Yuyou

    2016-06-01

    The effects of pH, temperature and high organic loading rate (OLR) on lactic acid production from food waste without extra inoculum addition were investigated in this study. Using batch experiments, the results showed that although the hydrolysis rate increased with pH adjustment, the lactic acid concentration and productivity were highest at pH 6. High temperatures were suitable for solubilization but seriously restricted the acidification processes. The highest lactic acid yield (0.46g/g-TS) and productivity (278.1mg/Lh) were obtained at 37°C and pH 6. In addition, the lactic acid concentration gradually increased with the increase in OLR, and the semi-continuous reactor could be stably operated at an OLR of 18g-TS/Ld. However, system instability, low lactic acid yield and a decrease in VS removal were noticed at high OLRs (22g-TS/Ld). The concentrations of volatile fatty acids (VFAs) in the fermentation mixture were relatively low but slightly increased with OLR, and acetate was the predominant VFA component. Using high-throughput pyrosequencing, Lactobacillus from the raw food waste was found to selectively accumulate and become dominant in the semi-continuous reactor.

  16. Fatty Acid Composition of the Muscle Lipids of Five Fish Species in Işıklı and Karacaören Dam Lake, Turkey

    Directory of Open Access Journals (Sweden)

    Ozcan Baris Citil

    2014-01-01

    Full Text Available Total fatty acid composition of muscle lipids in some fish species (Cyprinus carpio (Işıklı Dam Lake, Tinca tinca (Işıklı Dam Lake, Scardinius erythrophthalmus (Işıklı Dam Lake, Cyprinus carpio (Karacaören Dam Lake, and Carassius carassius (Karacaören Dam Lake was determined by gas chromatography. Polyunsaturated fatty acids (PUFAs of Cyprinus carpio (Işıklı Dam Lake were found higher than PUFA of other species. Palmitic acid was the highest saturated fatty acid (SFA in Tinca tinca (24.64%. Oleic acid was the highest monounsaturated fatty acid (MUFAs in Cyprinus carpio (Işıklı Dam Lake (19.25%. The most abundant polyunsaturated fatty acid in Scardinius erythrophthalmus was docosahexaenoic acid (DHA (17.94%. Total ω3 fatty acid composition was higher than the total ω6 fatty acids of Cyprinus carpio in both dam lakes. ω3/ω6 rates in Cyprinus carpio (Işıklı Dam Lake, Tinca tinca, Scardinius erythrophthalmus, Cyprinus carpio (Karacaören, and Carassius carassius were 2.12, 1.19, 2.15, 2.87, and 2.82, respectively.

  17. Zooplankton community composition of high mountain lakes in the Tatra Mts., the Alps in North Tyrol, and Scotland: relationship to pH, depth, organic carbon, and chlorophyll-a concentration

    Directory of Open Access Journals (Sweden)

    Skála Ivan

    2015-10-01

    Full Text Available The European EMERGE (European Mountain lake Ecosystems: Regionalisation, diaGnostic & socio-economic Evaluation project was a survey of high mountain lakes (above treeline across Europe using unified methods of sampling and analysis. The sampling was carried out in summer or autumn 2000, and comprised biological samples, and samples for chemical analysis. Data from three lake districts are used in this paper: the Tatra Mts. in Slovakia and Poland (45 lakes, the Alps in Tyrol in Austria (22 lakes, and Scotland (30 lakes. As it is shown by multiple regression analysis, DTOC (dissolved or total organic carbon is the key variable for most groups of zooplankton. With increasing DTOC and mostly with chlorophyll-a decreasing, pH increasing and depth decreasing, macrofitrators with coarse filter meshes are replaced by microfiltrators with fine filter meshes. Higher DTOC may increase bacterioplankton production and advantage species able to consume bacteria (microfiltrators. Other zooplankton species also differ in their preference for DTOC, chlorophyll-a, pH and depth, but DTOC being positively correlated with chlorophyll-a and pH positively correlated with depth. It may be caused by their different preference for food quality in terms of C:P ratio.

  18. X-ray absorption and resonance raman spectroscopy of human myeloperoxidase at neutral and acid pH.

    Science.gov (United States)

    Yue, K T; Taylor, K L; Kinkade, J M; Sinclair, R B; Powers, L S

    1997-04-01

    Myeloperoxidase (MPO), an important enzyme in the oxygen-dependent host defense system of human polymorphonuclear leukocytes, utilizes hydrogen peroxide to catalyze the production of hypochlorous acid, an oxidizing bactericidal agent. While MPO shows significant sequence homology with other peroxidases and this homology is particularly striking among the active-site residues, MPO exhibits unusual spectral features and the unique ability to catalyze the oxidation of chloride ions. We have investigated the MPO active-site with X-ray absorption (XAS) and resonance Raman (RRS) spectroscopies at neutral pH and also at the physiological acidic pH (pH approximately 3) and have compared these results with those of horseradish peroxidase (HRP). At pH 7.5, XAS results show that the iron heme active site is 6-coordinate where the distal ligand is likely nitrogen or oxygen, but not sulfur. The heme is distorted compared to HRP, other peroxidases, and heme compounds, but at pH approximately 3, the distal ligand is lost and the heme is less distorted. RRS results under identical pH conditions show that the skeletal core-size sensitive modes and v3 are shifted to higher frequency at pH approximately 3 indicating a 6- to 5-coordination change of high spin ferric heme. In addition, a new band at 270 cm(-1) is observed at pH approximately 3 which is consistent with the loss of the sixth ligand. The higher symmetry of the heme at pH approximately 3 is reflected by a single v4 mode in the (RRS) spectrum. HRP also loses its loosely associated distal water at this pH, but little change in heme distortion is observed. This change suggests that loss of the distal ligand in MPO releases stress on the heme which may facilitate binding of chloride ion.

  19. Development of On-Line Spectroscopic pH Monitoring for Nuclear Fuel Reprocessing Plants: Weak Acid Schemes

    Energy Technology Data Exchange (ETDEWEB)

    Casella, Amanda J.; Hylden, Laura R.; Campbell, Emily L.; Levitskaia, Tatiana G.; Peterson, James M.; Smith, Frances N.; Bryan, Samuel A.

    2015-05-19

    Knowledge of real-time solution properties and composition is a necessity for any spent nuclear fuel reprocessing method. Metal-ligand speciation in aqueous solutions derived from the dissolved commercial spent fuel is highly dependent upon the acid concentration/pH, which influences extraction efficiency and the resulting speciation in the organic phase. Spectroscopic process monitoring capabilities, incorporated in a counter current centrifugal contactor bank, provide a pathway for on-line real-time measurement of solution pH. The spectroscopic techniques are process-friendly and can be easily configured for on-line applications, while classic potentiometric pH measurements require frequent calibration/maintenance and have poor long-term stability in aggressive chemical and radiation environments. Our research is focused on developing a general method for on-line determination of pH of aqueous solutions through chemometric analysis of Raman spectra. Interpretive quantitative models have been developed and validated under the range of chemical composition and pH using a lactic acid/lactate buffer system. The developed model was applied to spectra obtained on-line during solvent extractions performed in a centrifugal contactor bank. The model predicted the pH within 11% for pH > 2, thus demonstrating that this technique could provide the capability of monitoring pH on-line in applications such as nuclear fuel reprocessing.

  20. [Characteristics of soil pH and exchangeable acidity in red soil profile under different vegetation types].

    Science.gov (United States)

    Ji, Gang; Xu, Ming-gang; Wen, Shi-lin; Wang, Bo-ren; Zhang, Lu; Liu, Li-sheng

    2015-09-01

    The characteristics of soil pH and exchangeable acidity in soil profile under different vegetation types were studied in hilly red soil regions of southern Hunan Province, China. The soil samples from red soil profiles within 0-100 cm depth at fertilized plots and unfertilized plots were collected and analyzed to understand the profile distribution of soil pH and exchangeable acidity. The results showed that, pH in 0-60 cm soil from the fertilized plots decreased as the following sequence: citrus orchard > Arachis hypogaea field > tea garden. As for exchangeable acidity content, the sequence was A. hypogaea field ≤ citrus orchard soil (0-40 cm), compared with the deep soil (60-100 cm), and soil pH decreased by 0.55 and 0.17 respectively, but such changes did not occur in citrus orchard. Soil pH in 0-40 cm soil from the natural recovery vegetation unfertilized plots decreased as the following sequence: Imperata cylindrica land > Castanea mollissima garden > Pinus elliottii forest ≥ Loropetalum chinensis forest. As for exchangeable acidity content, the sequence was L cylindrica land Soil pH in surface soil (0-20 cm) from natural forest plots, secondary forest and Camellia oleifera forest were significantly lower than that from P. massoniana forest, decreased by 0.34 and 0.20 respectively. For exchangeable acidity content in 0-20 cm soil from natural forest plot, P. massoniana forest and secondary forest were significantly lower than C. oleifera forest. Compared with bare land, surface soil acidification in unfertilized plots except I. cylindrica land had been accelerated, and the natural secondary forest was the most serious among them, with surface soil pH decreasing by 0.52. However, the pH increased in deep soils from unfertilized plots except natural secondary forest, and I. cylindrica land was the most obvious among them, with soil pH increasing by 0.43. The effects of fertilization and vegetation type on pH and exchangeable acidity decreased with the

  1. Acidic pH and divalent cation sensing by PhoQ are dispensable for systemic salmonellae virulence.

    Science.gov (United States)

    Hicks, Kevin G; Delbecq, Scott P; Sancho-Vaello, Enea; Blanc, Marie-Pierre; Dove, Katja K; Prost, Lynne R; Daley, Margaret E; Zeth, Kornelius; Klevit, Rachel E; Miller, Samuel I

    2015-05-23

    Salmonella PhoQ is a histidine kinase with a periplasmic sensor domain (PD) that promotes virulence by detecting the macrophage phagosome. PhoQ activity is repressed by divalent cations and induced in environments of acidic pH, limited divalent cations, and cationic antimicrobial peptides (CAMP). Previously, it was unclear which signals are sensed by salmonellae to promote PhoQ-mediated virulence. We defined conformational changes produced in the PhoQ PD on exposure to acidic pH that indicate structural flexibility is induced in α-helices 4 and 5, suggesting this region contributes to pH sensing. Therefore, we engineered a disulfide bond between W104C and A128C in the PhoQ PD that restrains conformational flexibility in α-helices 4 and 5. PhoQ(W104C-A128C) is responsive to CAMP, but is inhibited for activation by acidic pH and divalent cation limitation. phoQ(W104C-A128C) Salmonella enterica Typhimurium is virulent in mice, indicating that acidic pH and divalent cation sensing by PhoQ are dispensable for virulence.

  2. Effect of Temperature and pH on Formulating the Kinetic Growth Parameters and Lactic Acid Production of Lactobacillus bulgaricus

    Directory of Open Access Journals (Sweden)

    Marzieh Aghababaie

    2014-09-01

    Results: Second order model for Xmax, μmax, P and K was significant but product formation parameters were almost constant. The optimum values of temperature and pH for attaining maximum biomass, maximum specific growth rate, and maximum acid production were obtained at 44 °C and 5.7, respectively. Conclusions: The attained empirical mathematical correlations of RSM alongside the kinetic equations could be used to determine growth conditions under predefined temperature and pH in the fermentation process. Keywords: Lactobacillus bulgaricus, Richards model, Response surface methodology, Lactic acid production, Luedeking-Piret model

  3. Extracellular pH defense against lactic acid in untrained and trained altitude residents.

    Science.gov (United States)

    Böning, D; Rojas, J; Serrato, M; Reyes, O; Coy, L; Mora, M

    2008-05-01

    The assumption that buffering at altitude is deteriorated by bicarbonate (bi) reduction was investigated. Extracellular pH defense against lactic acidosis was estimated from changes (Delta) in lactic acid ([La]), [HCO3-], pH and PCO2 in plasma, which equilibrates with interstitial fluid. These quantities were measured in earlobe blood during and after incremental bicycle exercise in 10 untrained (UT) and 11 endurance-trained (TR) highlanders (2,600 m). During exercise the capacity of non-bicarbonate buffers (betanbi=-Delta[La]. DeltapH(-1)-Delta[HCO3-]. DeltapH(-1)) amounted to 40+/-2 (SEM) and 28+/-2 mmol l(-1) in UT and TR, respectively (P<0.01). During recovery beta (nbi) decreased to 20 (UT) and 16 (TR) mmol l(-1) (P<0.001) corresponding to values expected from hemoglobin, dissolved protein and phosphate concentrations related to extracellular fluid (ecf). This was accompanied by a larger decrease of base excess after than during exercise for a given Delta[La]. betabi amounted to 37-41 mmol l(-1) being lower than at sea level. The large exercise betanbi was mainly caused by increasing concentrations of buffers due to temporary shrinking of ecf. Tr has lower betanbi in spite of an increased Hb mass mainly because of an expanded ecf compared to UT. In highlanders betanbi is higher than in lowlanders because of larger Hb mass and reduced ecf and counteracts the decrease in [HCO3-]. The amount of bicarbonate is probably reduced by reduction of the ecf at altitude but this is compensated by lower maximal [La] and more effective hyperventilation resulting in attenuated exercise acidosis at exhaustion.

  4. Influence of Neutral Salts and pH on Exchangeable Acidity of Red Soil and Latosol Colloids

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In the present work, the exchangeable acidity of a red soil colloid and a latosol colloid at different pH during reacting with four neutral salts was measured. The results show that the exchangeable acidity increased with increasing amounts of the neutral salts added, and the relation between them was almost linear. When the amount of the neutral salt added was lower than a certain value, the slope of the line was high, and the slope turned low when the amount exceeded that value, so there was a turning point in each line. The addition amounts of the neutral salts for the turning points were affected by the cation species of the neutral salts, but pH had less effect on them. After the turning points occurred, the exchangeable acidity of the red soil colloid still gradually increased with the addition amounts of the neutral salts, but that of the latosol colloid did not increase any more.The exchangeable acidity in NaClO4, KClO4 and NaCl solutions increased at first, and then decreased with increasing pH, that is to say, peak values appeared. The peak positions of the exchangeable acidity in relation to pH changed with neutral salt solutions and were affected by the surface characteristics of the soil colloids, but not affected by the amounts of the neutral salts added. The exchangeable acidity in the Ba(NO3)2 solution increased continuously with increasing pH. The exchangeable acidity of the red soil colloid was obviously larger than that of the latosol colloid.``

  5. Viability of Lactic Acid Bacteria Isolated from Kombucha Tea Against Low pH and Bile Salt

    Directory of Open Access Journals (Sweden)

    Ni Nyoman Puspawati

    2016-03-01

    Full Text Available Kombucha tea is a functional drink fermented by various types of microbes. Kombucha tea is also a source of lactic acid bacteria that can maintain the balance of the microflora of the digestive tract which can improve the health of the human body. Lactic acid bacteria can act as a probiotic if it is able to survive to the human gastrointestinal tract, where in order to reach the digestive tract, lactic acid bacteria has to be resistant to the low pH in the stomach and bile salts. The purpose of this study was to determine the level of resistance of lactic acid bacteria in kombucha tea against low pH and bile salts. This study uses 20 isolates, each of these isolates were tested to the resistance of low pH 2.0 and 0.5 % bile salts with incubation time of 4 hours. The results indicated that from 20 isolates of lactic acid bacteria that were obtained from kombucha tea, 15 isolates were resistant to low pH and 13 isolates were resistant to bile salts. The isolates have a huge potential to be developed as a probiotic candidate that can contribute greatly to the health of the digestive tract.

  6. Effect of acid rain pH on leaching behavior of cement stabilized lead-contaminated soil.

    Science.gov (United States)

    Du, Yan-Jun; Wei, Ming-Li; Reddy, Krishna R; Liu, Zhao-Peng; Jin, Fei

    2014-04-30

    Cement stabilization is a practical approach to remediate soils contaminated with high levels of lead. However, the potential for leaching of lead out of these stabilized soils under variable acid rain pH conditions is a major environmental concern. This study investigates the effects of acid rain on the leaching characteristics of cement stabilized lead contaminated soil under different pH conditions. Clean kaolin clay and the same soil spiked with 2% lead contamination are stabilized with cement contents of 12 and 18% and then cured for 28 days. The soil samples are then subjected to a series of accelerated leaching tests (or semi-dynamic leaching tests) using a simulated acid rain leachant prepared at pH 2.0, 4.0 or 7.0. The results show that the strongly acidic leachant (pH ∼2.0) significantly altered the leaching behavior of lead as well as calcium present in the soil. However, the differences in the leaching behavior of the soil when the leachant was mildly acidic (pH ∼4.0) and neutral (pH ∼7.0) prove to be minor. In addition, it is observed that the lead contamination and cement content levels can have a considerable impact on the leaching behavior of the soils. Overall, the leachability of lead and calcium is attributed to the stability of the hydration products and their consequent influence on the soil buffering capacity and structure.

  7. Evaluation of the effects of water hardness and chemical pollutants on the zooplankton community in uranium mining lakes with acid mine drainage

    Energy Technology Data Exchange (ETDEWEB)

    Nascimento, H.; Ferrari, C.; Nascimento, M.R. [Brazilian Nulcear Energy Commission/Pocos de Caldas Laboratory (Brazil); Rodgher, S. [Universidade Estadual Paulista Julio de Mesquita Filho/Science and Technology Institute (Brazil); Wisniewski, M.J. [Alfenas Federal University/Limnology Laboratory (Brazil)

    2014-07-01

    Several mining lakes are characterized by the inorganic pollution of its waters, known as acid mine drainage (AMD). The current study was developed in order to evaluate the effect of water hardness and chemical pollutants on the richness and density of the zoo-planktonic community species. A seasonal study was conducted in a uranium mining lake affected by AMD. In environmental conditions of extremely high hardness water values (960.3 to 1284,9 mg/l), zoo-planktonic species have indicated resistance to the combined effect of elevated average concentrations of chemical pollutants such as Al (81.9 mg/l), Zn (15.5 mg/l), Mn (102.8 mg/l), U (2.9 mg/l) and low pH values (average = 3.8). Thus, in environments of extreme chemical conditions, such as a uranium mining lake affected by AMD, the hardness showed to be the best predictor of the zoo-planktonic community richness, indicating a protective effect of ions Ca{sup +2} over in special to Bosminopsis deitersi, Bosmina sp., Keratella americana and K. cochlearis. Document available in abstract form only. (authors)

  8. Long-term recovery of lakes in the Adirondack region of New York to decreases in acidic deposition

    Science.gov (United States)

    Waller, Kristin; Driscoll, Charles; Lynch, Jason; Newcomb, Dani; Roy, Karen

    2012-01-01

    After years of adverse impacts to the acid-sensitive ecosystems of the eastern United States, the Acid Rain Program and Nitrogen Budget Program were developed to control sulfur dioxide (SO 2) and nitrogen oxide (NO x) emissions through market-based cap and trade systems. We used data from the National Atmospheric Deposition Program's National Trends Network (NTN) and the U.S. EPA Temporally Integrated Monitoring of Ecosystems (TIME) program to evaluate the response of lake-watersheds in the Adirondack region of New York to changes in emissions of sulfur dioxide and nitrogen oxides resulting from the Acid Rain Program and the Nitrogen Budget Program. TIME is a long-term monitoring program designed to sample statistically selected subpopulations of lakes and streams across the eastern U.S. to quantify regional trends in surface water chemistry due to changes in atmospheric deposition. Decreases in wet sulfate deposition for the TIME lake-watersheds from 1991 to 2007 (-1.04 meq m -2-yr) generally corresponded with decreases in estimated lake sulfate flux (-1.46 ± 0.72 meq m -2-yr), suggesting declines in lake sulfate were largely driven by decreases in atmospheric deposition. Decreases in lake sulfate and to a lesser extent nitrate have generally coincided with increases in acid neutralizing capacity (ANC) resulting in shifts in lakes among ANC sensitivity classes. The percentage of acidic Adirondack lakes (ANC Budget Program. Two measures of ANC were considered in our analysis: ANC determined directly by Gran plot analysis (ANC G) and ANC calculated by major ion chemistry (ANC calc = CB - CA). While these two metrics should theoretically show similar responses, ANC calc (+2.03 μeq L -1-yr) increased at more than twice the rate as ANC G (+0.76 μeq L -1-yr). This discrepancy has important implications for assessments of lake recovery and appears to be due to compensatory increases in concentrations of naturally occurring organic acids coincident with decreases in

  9. THE BIOENERGETICS OF AMMONIA AND HYDROXYLAMINE OXIDATION IN NITROSOMONAS-EUROPAEA AT ACID AND ALKALINE PH

    NARCIS (Netherlands)

    FRIJLINK, MJ; ABEE, T; LAANBROEK, HJ; DEBOER, W; KONINGS, WN

    1992-01-01

    Autotrophic ammonia oxidizers depend on alkaline or neutral conditions for optimal activity. Below pH 7 growth and metabolic activity decrease dramatically. Actively oxidizing cells of Nitrosomonas europaea do not maintain a constant internal pH when the external pH is varied from 5 to 8. Studies of

  10. Effects of acetic acid and arginine on pH elevation and growth of Bacillus licheniformis in an acidified cucumber juice medium.

    Science.gov (United States)

    Yang, Zhenquan; Meng, Xia; Breidt, Frederick; Dean, Lisa L; Arritt, Fletcher M

    2015-04-01

    Bacillus licheniformis has been shown to cause pH elevation in tomato products having an initial pH below 4.6 and metabiotic effects that can lead to the growth of pathogenic bacteria. Because of this, the organism poses a potential risk to acidified vegetable products; however, little is known about the growth and metabolism of this organism in these products. To clarify the mechanisms of pH change and growth of B. licheniformis in vegetable broth under acidic conditions, a cucumber juice medium representative of a noninhibitory vegetable broth was used to monitor changes in pH, cell growth, and catabolism of sugars and amino acids. For initial pH values between pH 4.1 to 6.0, pH changes resulted from both fermentation of sugar (lowering pH) and ammonia production (raising pH). An initial pH elevation occurred, with starting pH values of pH 4.1 to 4.9 under both aerobic and anaerobic conditions, and was apparently mediated by the arginine deiminase reaction of B. licheniformis. This initial pH elevation was prevented if 5 mM or greater acetic acid was present in the brine at the same pH. In laboratory media, under favorable conditions for growth, data indicated that growth of the organism was inhibited at pH 4.6 with protonated acetic acid concentrations of 10 to 20 mM, corresponding to 25 to 50 mM total acetic acid; however, growth inhibition required greater than 300 mM citric acid (10-fold excess of the amount in processed tomato products) products under similar conditions. The data indicate that growth and pH increase by B. licheniformis may be inhibited by the acetic acid present in most commercial acidified vegetable products but not by the citric acid in many tomato products.

  11. Demineralization of root canal dentine with EDTA and citric acid in different concentrations, pH and application times

    Directory of Open Access Journals (Sweden)

    Mr.Sc. Nexhmije Ajeti

    2011-12-01

    Full Text Available Abstract The aims of the study are: 1. Determination of the amount of extracted Ca ions from den-tine using 17% and 10% EDTA, at pH 7 and pH 9. 2. Determination of the amount of extracted Ca ions from  den-tine using citric acid 5% and 1%, at pH 7 and pH 9.  Methodology 30 extracted, single rooted, human teeth were tested. Their crowns were sectioned at CEJ using diamond disks. The root canals were manually prepared with K-files #50-60. After each instrument 2.5 ml of 5.25% NaOCl was used and 0.9 NaCl as final irrigation. All teeth were longitudinally sectioned and 8 samples of dentine taken from each sample. EDTA 10% and 17 % and citric acid 1% and 5% in neutral and alkaline pH were used.  Each sample was immersed in acid and then exposure time was evaluated after 1, 5, 10, 15 and 25 min. The release rate of calcium ions from root dentine was evaluated by atomic absorption spectrometer.  Results There were significant differences in the amount of extracted Ca by citric acid 1% and 5% or EDTA 10% and 17% in human teeth.  Conclusions It may be concluded that EDTA is a better chelating agent than citric acid. The decalcifying activity of these solutions is related to the duration of exposure, pH and their concentrations.

  12. Gallic Acid as a Complexing Agent for Copper Chemical Mechanical Polishing Slurries at Neutral pH

    Science.gov (United States)

    Kim, Yung Jun; Kang, Min Cheol; Kwon, Oh Joong; Kim, Jae Jeong

    2011-05-01

    Gallic acid was investigated as a new complexing agent for copper (Cu) chemical mechanical polishing slurries at neutral pH. Addition of 0.03 M gallic acid and 1.12 M H2O2 at pH 7 resulted in a Cu removal rate of 560.73±17.49 nm/min, and the ratio of the Cu removal rate to the Cu dissolution rate was 14.8. Addition of gallic acid improved the slurry performance compared to glycine addition. X-ray photoelectron spectroscopy analysis and contact angle measurements showed that addition of gallic acid enhanced the Cu polishing behavior by suppressing the formation of surface Cu oxide.

  13. Acid precipitation and other possible sources for acidification of rivers and lakes

    Energy Technology Data Exchange (ETDEWEB)

    Seip, H.M.; Tollan, A.

    1978-01-01

    The trends in the recent acidification of rivers and lakes in South Norway are reviewed, and the evidence for a causal relationship between acid precipitation and acidification of surface water is critically examined. Results from regional surveys, studies in small catchment areas and from percolation experiments are presented. Several sources may contribute to the acidification. However, changes in the composition of the precipitation during the recent decades, mainly because of increased combustion of fossil fuels, seem to be a dominant cause at least in some of the most affected areas.

  14. Influence of copper recovery on the water quality of the acidic Berkeley Pit lake, Montana, U.S.A.

    Science.gov (United States)

    Tucci, Nicholas J; Gammons, Christopher H

    2015-04-07

    The Berkeley Pit lake in Butte, Montana, formed by flooding of an open-pit copper mine, is one of the world's largest accumulations of acidic, metal-rich water. Between 2003 and 2012, approximately 2 × 10(11) L of pit water, representing 1.3 lake volumes, were pumped from the bottom of the lake to a copper recovery plant, where dissolved Cu(2+) was precipitated on scrap iron, releasing Fe(2+) back to solution and thence back to the pit. Artificial mixing caused by this continuous pumping changed the lake from a meromictic to holomictic state, induced oxidation of dissolved Fe(2+), and caused subsequent precipitation of more than 2 × 10(8) kg of secondary ferric compounds, mainly schwertmannite and jarosite, which settled to the bottom of the lake. A large mass of As, P, and sulfate was also lost from solution. These unforeseen changes in chemistry resulted in a roughly 25-30% reduction in the lake's calculated and measured total acidity, which represents a significant potential savings in the cost of lime treatment, which is not expected to commence until 2023. Future monitoring is needed to verify that schwertmannite and jarosite in the pit sediment do not convert to goethite, a process which would release stored acidity back to the water column.

  15. Mineralogy of evaporite deposits on Mars: Constraints from laboratory, field, and remote measurements of analog terrestrial acid saline lakes

    Science.gov (United States)

    Bridges, N.; Núñez, J. I.; Seelos, F. P., IV; Hook, S. J.; Baldridge, A. M.; Thomson, B. J.

    2015-12-01

    Remote compositional data from imaging spectrometers such as CRISM, OMEGA, and TES, and high-resolution imagery from MOC, CTX, and HiRISE have provided invaluable information for improving our understanding of the composition and geologic history of the martian surface and identifying potential past and present habitable environments on Mars. Simulated CRISM spectra and summary parameter maps and HiRISE color images were generated using airborne hyperspectral data of two acid-saline lakes in Western Australia. These locations are applicable to Mars, as they contain a suite of clays, sulfates, and salts formed under variable pH and salinity - mineralogies similar to those observed in Noachian and Hesperian terrain. The remote datasets were used to make surface composition predictions which were then verified through field study and sample analysis. We find phyllosilicates intermixed with sulfates in sulfate-rich surfaces exhibit variable spectral responses, even for similar conditions and abundances seen in the field. Where sulfates, such as gypsum and alunite, are found, phyllosilicates are intermixed or reside beneath the surface yet are not always detected. This suggests that geologic complexities may mask phyllosilicate detection at or near the surface on Mars where only sulfates have so far been found.

  16. Influence of acidic pH on the formulation of TiO2 nanocrystalline powders with enhanced photoluminescence property

    Directory of Open Access Journals (Sweden)

    Moges Tsega

    2017-02-01

    Full Text Available Titanium dioxide (TiO2 nanoparticles were prepared by the sol-gel method at different pH values (3.2–6.8 with a hydrochloric acid (HCl solution. Raw samples were calcined at 500 °C for 2 h. The effects of pH on the structural, morphological and optical properties of TiO2 nanoparticles were investigated. At pH 4.4–6.8, only the anatase phase of TiO2 was observed. Under strong acidic condition at pH 3.2 rutile, brookite and anatase co-exist, but rutile is the predominant phase. The strain value increased and the crystallite size decreased as the HCl content increased. The increased crystallite sizes in the range 21–24 nm and enhanced blue emission intensity around 432 nm was obtained for the sample at pH 5.0. Experimental results showed that TiO2 nanoparticles synthesized at pH 5.0 exhibited the best luminescence property with pure anatase phase.

  17. Chemical crosslinking of acrylic acid to form biocompatible pH sensitive hydrogel reinforced with cellulose nanocrystals (CNC)

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Lim Sze; Ahmad, Ishak; Lazim, Mohd Azwani Shah Mat [Faculty of Science and Technology, University Kebangsaan Malaysia, 43600 UKM, Bangi, Selangor (Malaysia); Amin, Mohd. Cairul Iqbal Mohd [Faculty of Pharmacy, University Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur (Malaysia)

    2014-09-03

    The purpose of this study is to produce a novel pH and temperature sensitive hydrogel, composed of poly(acrylic acid) (PAA) and cellulose nanocrystal (CNC). CNC was extracted from kenaf fiber through a series of alkali and bleaching treatments followed by acid hydrolysis. The PAA was then subjected to chemical cross-linking using the cross-linking agent (N,N-methylenebisacrylamide) with CNC entrapped in PAA matrix. The mixture was casted onto petri dish to obtain disc shape hydrogel. The effects of reaction conditions such as the ratio of PAA and CNC on the swelling behavior of the hydrogel obtained towards pH and temperature were studied. The obtained hydrogel was further subjected to different tests such swelling test for swelling behaviour at different pH and temperature along with scanning electron microscopy (SEM) for morphology analysis. The hydrogel obtained showed excellent pH sensitivity and obtained maximum swelling at pH 7. Besides that, hydrogel obtained showed significant increase in swelling ratio when temperature of swelling medium was increased from 25°C to 37°C. SEM micrograph showed that the pore size of the hydrogel decreases with increase of CNC content proving that the hydrogel structure became more rigid with addition of CNC. The PAA/CNC hydrogel with such excellent sensitivity towards pH and temperature can be developed further as drug carrier.

  18. Influence of acidic pH on the formulation of TiO2 nanocrystalline powders with enhanced photoluminescence property.

    Science.gov (United States)

    Tsega, Moges; Dejene, F B

    2017-02-01

    Titanium dioxide (TiO2) nanoparticles were prepared by the sol-gel method at different pH values (3.2-6.8) with a hydrochloric acid (HCl) solution. Raw samples were calcined at 500 °C for 2 h. The effects of pH on the structural, morphological and optical properties of TiO2 nanoparticles were investigated. At pH 4.4-6.8, only the anatase phase of TiO2 was observed. Under strong acidic condition at pH 3.2 rutile, brookite and anatase co-exist, but rutile is the predominant phase. The strain value increased and the crystallite size decreased as the HCl content increased. The increased crystallite sizes in the range 21-24 nm and enhanced blue emission intensity around 432 nm was obtained for the sample at pH 5.0. Experimental results showed that TiO2 nanoparticles synthesized at pH 5.0 exhibited the best luminescence property with pure anatase phase.

  19. Determination of critical pH and Al concentration of acidic Ultisols for wheat and canola crops

    Science.gov (United States)

    Abdulaha-Al Baquy, M.; Li, Jiu-Yu; Xu, Chen-Yang; Mehmood, Khalid; Xu, Ren-Kou

    2017-02-01

    Soil acidity has become a principal constraint in dry land crop production systems of acidic Ultisols in tropical and subtropical regions of southern China, where winter wheat and canola are cultivated as important rotational crops. There is little information on the determination of critical soil pH as well as aluminium (Al) concentration for wheat and canola crops. The objective of this study is to determine the critical soil pH and exchangeable aluminium concentration (AlKCl) for wheat and canola production. Two pot cultures with two Ultisols from Hunan and Anhui (SE China) were conducted for wheat and canola crops in a controlled growth chamber. Aluminium sulfate (Al2(SO4)3) and hydrated lime (Ca(OH)2) were used to obtain the target soil pH levels from 3.7 (Hunan) and 3.97 (Anhui) to 6.5. Plant height, shoot dry weight, root dry weight, and chlorophyll content (SPAD value) of wheat and canola were adversely affected by soil acidity in both locations. The critical soil pH and AlKCl of the Ultisol from Hunan for wheat were 5.29 and 0.56 cmol kg-1, respectively. At Anhui, the threshold soil pH and AlKCl for wheat were 4.66 and 1.72 cmol kg-1, respectively. On the other hand, the critical soil pH for canola was 5.65 and 4.87 for the Ultisols from Hunan and Anhui, respectively. The critical soil exchangeable Al for canola cannot be determined from the experiment of this study. The results suggested that the critical soil pH and AlKCl varied between different locations for the same variety of crop, due to the different soil types and their other soil chemical properties. The critical soil pH for canola was higher than that for wheat for both Ultisols, and thus canola was more sensitive to soil acidity. Therefore, we recommend that liming should be undertaken to increase soil pH if it falls below these critical soil pH levels for wheat and canola production.

  20. Acidic intracellular pH shift during Caenorhabditis elegans larval development

    Energy Technology Data Exchange (ETDEWEB)

    Wadsworth, W.G.; Riddle, D.L. (Univ. of Missouri, Columbia (USA))

    1988-11-01

    During recovery from the developmentally arrested, nonfeeding dauer stage of the nemotode Caenorhabditis elegans, metabolic activation is accompanied by a decrease in intracellular pH (pH{sub i}). Phosphorus-31 nuclear magnetic resonance ({sup 31}P NMR) analyses of perchloric acid extracts show that inorganic phosphate predominates in dauer larvae, whereas ATP and other high-energy metabolites are abundant within 6 hr after dauer larvae have been placed in food to initiate development. Although metabolic activation has been associated with an alkaline pH{sub i} shift in other organisms, in vivo {sup 31}P NMR analysis of recovering dauer larvae shows a pH{sub i} decrease from {approx} 7.3 to {approx} 6.3 within 3 hr after the animals encounter food. This shift occurs before feeding begins, and it coincides with, or soon follows, the developmental commitment to recover from the dauer stage, suggesting that control of pH{sub i} may be important in the regulation of larval development in nematodes.

  1. Biophysical implications of sphingosine accumulation in membrane properties at neutral and acidic pH.

    Science.gov (United States)

    Zupancic, Eva; Carreira, Ana C; de Almeida, Rodrigo F M; Silva, Liana C

    2014-05-08

    Sphingosine (Sph) is a simple lipid involved in the regulation of several biological processes. When accumulated in the late endosomal/lysosomal compartments, Sph causes changes in ion signaling and membrane trafficking, leading to the development of Niemann-Pick disease type C. Little is known about Sph interaction with other lipids in biological membranes; however, understanding the effect of Sph in the physical state of membranes might provide insights into its mode of action. Using complementary established fluorescence approaches, we show that Sph accumulation leads to the formation of Sph-enriched gel domains in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and POPC/sphingomyelin (SM)/cholesterol (Chol) model membranes. These domains are more easily formed in membrane models mimicking the neutral pH plasma membrane environment (PM) as compared to the acidic lysosomal membrane environment (LM), where higher Sph concentrations (or lower temperatures) are required. Electrophoretic light scattering measurements further revealed that in PM-raft models (POPC/SM/Chol), Sph is mainly neutral, whereas in LM models, the positive charge of Sph leads to electrostatic repulsion, reducing the Sph ability to form gel domains. Thus, formation of Sph-enriched domains in cellular membranes might be strongly regulated by Sph charge.

  2. Tolerance of upland rice cultivars to aluminum and acidic pH

    Directory of Open Access Journals (Sweden)

    Lucas B. de Freitas

    Full Text Available ABSTRACT Although the upland rice has been known by its moderate tolerance to aluminum, the presence of exchangeable aluminum in acidic soils may inhibit and compromise the adequate plant growth. However, there are few reports detailing modern cultivars used by Brazilian farmers with respect to their susceptibility to aluminum toxicity. This study aimed to characterize the cultivars currently used in the upland rice production with respect to their tolerance to aluminum and their growth under low pH conditions without aluminum. The treatments were arranged in a randomized block design, in a 2 x 9 factorial scheme: presence and absence of aluminum in the nutrient solution and nine upland rice cultivars (BRS Monarca, BRS Pepita, BRS Bonança, BRS Primavera, BRS Sertaneja, Maravilha, IAC 202, ANCambará and ANa7007, with four replicates. Based on the distribution of upland rice cultivars in quartiles, they were divided into two groups; aluminum-tolerant group: BRS Pepita, BRS Primavera and ANa7007; and aluminum-susceptible group: BRS Monarca, BRS Bonança, BRS Sertaneja, Maravilha, IAC 202 and ANCambará.

  3. Tyramine biosynthesis is transcriptionally induced at low pH and improves the fitness of Enterococcus faecalis in acidic environments.

    Science.gov (United States)

    Perez, Marta; Calles-Enríquez, Marina; Nes, Ingolf; Martin, Maria Cruz; Fernandez, Maria; Ladero, Victor; Alvarez, Miguel A

    2015-04-01

    Enterococcus faecalis is a commensal bacterium of the human gut that requires the ability to pass through the stomach and therefore cope with low pH. E. faecalis has also been identified as one of the major tyramine producers in fermented food products, where they also encounter acidic environments. In the present work, we have constructed a non-tyramine-producing mutant to study the role of the tyramine biosynthetic pathway, which converts tyrosine to tyramine via amino acid decarboxylation. Wild-type strain showed higher survival in a system that mimics gastrointestinal stress, indicating that the tyramine biosynthetic pathway has a role in acid resistance. Transcriptional analyses of the E. faecalis V583 tyrosine decarboxylase cluster showed that an acidic pH, together with substrate availability, induces its expression and therefore the production of tyramine. The protective role of the tyramine pathway under acidic conditions appears to be exerted through the maintenance of the cytosolic pH. Tyramine production should be considered important in the adaptability of E. faecalis to acidic environments, such as fermented dairy foods, and to survive passage through the human gastrointestinal tract.

  4. Effect of pH on acid production from sorbitol in washed cell suspensions of oral bacteria.

    Science.gov (United States)

    Kalfas, S; Maki, Y; Birkhed, D; Edwardsson, S

    1990-01-01

    The acid production from sorbitol and glucose was studied under anaerobic conditions in resting cell suspensions of bacteria from the predominant sorbitol-fermenting human dental plaque flora, belonging to the genera Streptococcus, Lactobacillus and Actinomyces. The acid production activity of the bacterial cells was followed by titration with alkali, at environmental pH 7.0, 6.0 and 5.0 after addition of carbohydrate solution. The metabolic end products formed in the suspensions were analyzed thereafter by isotachophoretic and enzymatic methods. The results showed that sorbitol was fermented at a slower rate than glucose. Lowering the environmental pH decreased the acid production activity from the two carbohydrates. Compared with glucose, the catabolism of sorbitol was affected to greater extent by the pH conditions. The total amount of acids formed from sorbitol was considerably less than from glucose. Lactic acid, which was the major end product in glucose-challenged suspensions, was produced only in low concentrations from sorbitol by all strains tested. The ratio strong (formic + lactic)/weak acids was moreover lower for sorbitol than for glucose. The present results further illustrate some of the mechanisms behind the low cariogenic potential of this sugar substitute.

  5. Acid-coated Textiles (pH 5.5-6.5)--a New Therapeutic Strategy for Atopic Eczema?

    Science.gov (United States)

    Jaeger, Teresa; Rothmaier, Markus; Zander, Holger; Ring, Johannes; Gutermuth, Jan; Anliker, Mark D

    2015-07-01

    Increased transepidermal water loss (TEWL) and decreased skin capacitance are characteristic features of the disturbed epidermal barrier in atopic eczema (AE). The "acid mantle", which is a slightly acidic film on the surface of the skin has led to the development of acidic emollients for skin care. In this context, the effect of citric acid-coated textiles on atopic skin has not been examined to date. A textile carrier composed of cellulose fibres was coated with a citric acid surface layer by esterification, ensuring a constant pH of 5.5-6.5. Twenty patients with AE or atopic diathesis were enrolled in the study. In a double-blind, half-side experiment, patients had to wear these textiles for 12 h a day for 14 days. On day 0 (baseline), 7 and 14, tolerability (erythema, pruritus, eczema, wearing comfort) and efficacy on skin barrier were assessed by TEWL skin hydration (corneometry/capacitance), pH and clinical scoring of eczema (SCORAD). Citric acid-coated textiles were well tolerated and improved eczema and objective parameters of skin physiology, including barrier function and a reduced skin surface pH, with potential lower pathogenic microbial colonisation.

  6. Hyaluronic Acid Immobilized Polyacrylamide Nanoparticle Sensors for CD44 Receptor Targeting and pH Measurement in Cells

    DEFF Research Database (Denmark)

    Sun, Honghao; Benjaminsen, Rikke Vicki; Almdal, Kristoffer

    2012-01-01

    distribution profile in cells was measured for nanosensors with HA, cationic, and noncharged NP surface coatings giving a clear indication of the intracellular pH environment that the different NPs experience after internalization. The pH profile of cationic nanosensors in comparison to HA conjugated...... the CD44 receptor, which is overexpressed on the surface of a broad variety of cancer cells, we have synthesized an NP pH sensor system that targets CD44. We used a polyacrylamide nanoparticle matrix bearing hyaluronic acid (HA) on the surface as a CD44 targeting ligand. The HA-coated NPs were prepared...... by radical polymerization followed by post functionalization with sensor fluorophores and physically absorbed or chemically conjugated HA. Cell uptake studies showed significant uptake of HA-coated nanosensors in HeLa cells and no uptake under the same conditions without the HA targeting ligand. The pH...

  7. Lactobacillus plantarum as source of conjugated linoleic acid: Effect of pH, incubation Temperature and inulin incorporation.

    Directory of Open Access Journals (Sweden)

    Carmen Soto

    2013-07-01

    Full Text Available The effect of pH and temperature, and inulin use, on the growth andthe fatty acid profile of Lactobacillus plantarum strain wereevaluated. The best results were obtained at 6.5 pH broth, producing3.2 g/L of biomass and about 20% of conjugated linoleic acid(CLA in the cell lipids. Similar growth was observed with 37 and45ºC, but a low CLA content (10.6% was achieved at 45°C. In thecase of inulin incorporation, a low biomass concentration (1 g/Land low production of CLA (12.4% were observed. These resultssuggest a pH and temperature dependence on CLA production bythe microorganism.

  8. Fatty acid composition of freshwater wild fish in subalpine lakes: a comparative study.

    Science.gov (United States)

    Vasconi, Mauro; Caprino, Fabio; Bellagamba, Federica; Busetto, Maria Letizia; Bernardi, Cristian; Puzzi, Cesare; Moretti, Vittorio Maria

    2015-03-01

    In this study, the proximate and fatty acid compositions of the muscle tissue of 186 samples of fish belonging to fifteen species of freshwater fish harvested in subalpine lakes (bleak, shad, crucian carp, whitefish, common carp, pike, black bullhead, burbot, perch, Italian roach, roach, rudd, wels catfish, chub and tench) were investigated. Most of the fish demonstrated a lipid content in the fillet lower than 2.0 g 100 g(-1) wet weight (range 0.6-9.7). A strong relationship between feeding behavior and fatty acid composition of the muscle lipids was observed. Planktivorous fish showed the lowest amounts of n-3 fatty acids (p < 0.05), but the highest monounsaturated fatty acid (MUFA) contents, in particular 18:1n-9. Conversely, carnivorous fish showed the highest amounts of saturated fatty acids and n-3 fatty acids (p < 0.05), but the lowest MUFA contents. Omnivorous fish showed substantial proportions of n-3 fatty acids and the highest contents of n-6 fatty acids. Principal component analysis showed a distinct separation between fish species according to their feeding habits and demonstrated that the most contributing trophic markers were 18:1n-9, 18:3n-3, 22:6n-3 and 20:4n-6. The quantitative amounts n-3 polyunsaturated fatty acid in muscle tissues varied depending on the fish species, the lipid content and the feeding habits. Some species were very lean, and therefore would be poor choices for human consumption to meet dietary n-3 fatty acid requirements. Nevertheless, the more frequently consumed and appreciated fish, shad and whitefish, had EPA and DHA contents in the range 900-1,000 mg 100 g(-1) fresh fillet.

  9. Denitrification potential in stream sediments impacted by acid mine drainage: effects of pH, various electron donors, and iron.

    Science.gov (United States)

    Baeseman, J L; Smith, R L; Silverstein, J

    2006-02-01

    Acid mine drainage (AMD) contaminates thousands of kilometers of stream in the western United States. At the same time, nitrogen loading to many mountain watersheds is increasing because of atmospheric deposition of nitrate and increased human use. Relatively little is known about nitrogen cycling in acidic, heavy-metal-laden streams; however, it has been reported that one key process, denitrification, is inhibited under low pH conditions. The objective of this research was to investigate the capacity for denitrification in acidified streams. Denitrification potential was assessed in sediments from several Colorado AMD-impacted streams, ranging from pH 2.60 to 4.54, using microcosm incubations with fresh sediment. Added nitrate was immediately reduced to nitrogen gas without a lag period, indicating that denitrification enzymes were expressed and functional in these systems. First-order denitrification potential rate constants varied from 0.046 to 2.964 day(-1). The pH of the microcosm water increased between 0.23 and 1.49 pH units during denitrification. Additional microcosm studies were conducted to examine the effects of initial pH, various electron donors, and iron (added as ferrous and ferric iron). Decreasing initial pH decreased denitrification; however, increasing pH had little effect on denitrification rates. The addition of ferric and ferrous iron decreased observed denitrification potential rate constants. The addition of glucose and natural organic matter stimulated denitrification potential. The addition of hydrogen had little effect, however, and denitrification activity in the microcosms decreased after acetate addition. These results suggest that denitrification can occur in AMD streams, and if stimulated within the environment, denitrification might reduce acidity.

  10. Denitrification potential in stream sediments impacted by acid mine drainage: Effects of pH, various electron donors, and iron

    Science.gov (United States)

    Baeseman, J.L.; Smith, R.L.; Silverstein, J.

    2006-01-01

    Acid mine drainage (AMD) contaminates thousands of kilometers of stream in the western United States. At the same time, nitrogen loading to many mountain watersheds is increasing because of atmospheric deposition of nitrate and increased human use. Relatively little is known about nitrogen cycling in acidic, heavy-metal-laden streams; however, it has been reported that one key process, denitrification, is inhibited under low pH conditions. The objective of this research was to investigate the capacity for denitrification in acidified streams. Denitrification potential was assessed in sediments from several Colorado AMD-impacted streams, ranging from pH 2.60 to 4.54, using microcosm incubations with fresh sediment. Added nitrate was immediately reduced to nitrogen gas without a lag period, indicating that denitrification enzymes were expressed and functional in these systems. First-order denitrification potential rate constants varied from 0.046 to 2.964 day-1. The pH of the microcosm water increased between 0.23 and 1.49 pH units during denitrification. Additional microcosm studies were conducted to examine the effects of initial pH, various electron donors, and iron (added as ferrous and ferric iron). Decreasing initial pH decreased denitrification; however, increasing pH had little effect on denitrification rates. The addition of ferric and ferrous iron decreased observed denitrification potential rate constants. The addition of glucose and natural organic matter stimulated denitrification potential. The addition of hydrogen had little effect, however, and denitrification activity in the microcosms decreased after acetate addition. These results suggest that denitrification can occur in AMD streams, and if stimulated within the environment, denitrification might reduce acidity. ?? Springer Science+Business Media, Inc. 2006.

  11. Significance of pH on the Cytotoxic Potential of the Water Disinfection By-Product Iodoacetic Acid

    Science.gov (United States)

    Significance of pH on the Cytotoxic Potential of the Water Disinfection By-Product Iodoacetic Acid Vicki Richardson1, Susan D. Richardson2, Mary Moyer3, Jane Ellen Simmons1, and Anthony DeAngelo1, 1U.S. Environmental Protection Agency, Research Triangle Park, NC, 2University of...

  12. Microwave synthesis of delaminated acid saponites using quaternary ammonium salt or polymer as template. Study of pH influence

    NARCIS (Netherlands)

    Gebretsadik, Fiseha B.; Mance, Deni; Baldus, Marc; Salagre, Pilar; Cesteros, Yolanda

    2015-01-01

    Mesoporous saponites were prepared at pH8 and 13 without and with template (surfactant or polymer) at 453K and autogenic pressure using microwaves or conventional oven during the hydrothermal ageing treatment. Acidity was obtained by calcination of the NH4-form. The effect of dilution (H<

  13. CA2+-INDUCED FUSION OF PHOSPHOLIPID-VESICLES CONTAINING FREE FATTY-ACIDS - MODULATION BY TRANSMEMBRANE PH GRADIENTS

    NARCIS (Netherlands)

    WILSCHUT, J; SCHOLMA, J; EASTMAN, SJ; HOPE, MJ; CULLIS, PR

    1992-01-01

    The influence of a transmembrane pH gradient on the Ca2+-induced fusion of phospholipid vesicles, containing free fatty acids, has been investigated. Large unilamellar vesicles composed of an equimolar mixture of cardiolipin, dioleoylphosphatidylcholine, and cholesterol, containing 20 mol % oleic ac

  14. Microwave synthesis of delaminated acid saponites using quaternary ammonium salt or polymer as template. Study of pH influence

    NARCIS (Netherlands)

    Gebretsadik, Fiseha B.; Mance, Deni; Baldus, Marc; Salagre, Pilar; Cesteros, Yolanda

    2015-01-01

    Mesoporous saponites were prepared at pH8 and 13 without and with template (surfactant or polymer) at 453K and autogenic pressure using microwaves or conventional oven during the hydrothermal ageing treatment. Acidity was obtained by calcination of the NH4-form. The effect of dilution

  15. Extreme drought causes distinct water acidification and eutrophication in the Lower Lakes (Lakes Alexandrina and Albert), Australia

    Science.gov (United States)

    Li, Siyue; Bush, Richard T.; Mao, Rong; Xiong, Lihua; Ye, Chen

    2017-01-01

    Droughts are set to increase in frequency and magnitude with climate change and water extraction, and understanding their influence on ecosystems is urgent in the Holocene. Low rainfall across the Murray-Darling Basin (MDB) of Australia resulted in an unprecedented water level decline in the Lower Lakes (Lakes Alexandrina and Albert) at the downstream end of the river system. A comprehensive data covering pre-drought (2004-2006), drought (2007-2010) and post-drought (2010-2013) was firstly used to unravel drought effects on water quality in the contrasting main parts and margins of the two Lakes, particularly following water acidification resulting from acid sulfate soil oxidation. Salinity, nutrients and Chl-a significantly increased during the drought in the Lake main waterbody, while pH remained stable or showed minor shifts. In contrast to the Lake Alexandrina, total dissolved solid (TDS) and electrical conductivity (EC) during the post-drought more than doubled the pre-drought period in the Lake Albert as being a terminal lake system with narrow and shallow entrance. Rewetting of the exposed pyrite-containing sediment resulted in very low pH (below 3) in Lake margins, which positively contributed to salinity increases via SO42- release and limestone dissolution. Very acidic water (pH 2-3) was neutralised naturally by lake refill, but aerial limestone dosing was required for neutralisation of water acidity during the drought period. The Lower Lakes are characterized as hypereutrophic with much higher salinity, nutrient and algae concentrations than guideline levels for aquatic ecosystem. These results suggest that, in the Lower Lakes, drought could cause water quality deterioration through water acidification and increased nutrient and Chl-a concentrations, more effective water management in the lake catchment is thus crucial to prevent the similar water quality deterioration since the projected intensification of droughts. A comparative assessment on lake

  16. Embryonic common snapping turtles (Chelydra serpentina) preferentially regulate intracellular tissue pH during acid-base challenges.

    Science.gov (United States)

    Shartau, Ryan B; Crossley, Dane A; Kohl, Zachary F; Brauner, Colin J

    2016-07-01

    The nests of embryonic turtles naturally experience elevated CO2 (hypercarbia), which leads to increased blood PCO2  and a respiratory acidosis, resulting in reduced blood pH [extracellular pH (pHe)]. Some fishes preferentially regulate tissue pH [intracellular pH (pHi)] against changes in pHe; this has been proposed to be associated with exceptional CO2 tolerance and has never been identified in amniotes. As embryonic turtles may be CO2 tolerant based on nesting strategy, we hypothesized that they preferentially regulate pHi, conferring tolerance to severe acute acid-base challenges. This hypothesis was tested by investigating pH regulation in common snapping turtles (Chelydra serpentina) reared in normoxia then exposed to hypercarbia (13 kPa PCO2 ) for 1 h at three developmental ages: 70% and 90% of incubation, and yearlings. Hypercarbia reduced pHe but not pHi, at all developmental ages. At 70% of incubation, pHe was depressed by 0.324 pH units while pHi of brain, white muscle and lung increased; heart, liver and kidney pHi remained unchanged. At 90% of incubation, pHe was depressed by 0.352 pH units but heart pHi increased with no change in pHi of other tissues. Yearlings exhibited a pHe reduction of 0.235 pH units but had no changes in pHi of any tissues. The results indicate common snapping turtles preferentially regulate pHi during development, but the degree of response is reduced throughout development. This is the first time preferential pHi regulation has been identified in an amniote. These findings may provide insight into the evolution of acid-base homeostasis during development of amniotes, and vertebrates in general.

  17. Conformational changes in human serum albumin studied by fluorescence and absorption spectroscopy. Distance measurements as a function of pH and fatty acids

    DEFF Research Database (Denmark)

    Honoré, B; Pedersen, A O

    1989-01-01

    pH- and fatty acid-induced conformational changes in human serum albumin were investigated by fluorescence-energy transfer, determining the distance between Trp-214 and bound bilirubin at 25 degrees C. This distance changes significantly with the pH, being 2.52 +/- 0.01 nm at pH 6, 2.31 +/- 0.04 ...... chromophores. The contraction of the protein carrying long-chain saturated fatty acids is even more pronounced at pH 9. Udgivelsesdato: 1989-Feb-15......pH- and fatty acid-induced conformational changes in human serum albumin were investigated by fluorescence-energy transfer, determining the distance between Trp-214 and bound bilirubin at 25 degrees C. This distance changes significantly with the pH, being 2.52 +/- 0.01 nm at pH 6, 2.31 +/- 0.04 nm...... at pH 9, 2.13 +/- 0.07 nm at pH 11.0 and 2.77 nm at pH 11.9. The influence of different fatty acids on the distance was also determined. At pH 7.4 medium-chain fatty acids seem to increase this distance, whereas long-chain fatty acids, at low concentrations, decrease the distance between the two...

  18. Copper availability and bioavailability are controlled by rhizosphere pH in rape grown in an acidic Cu-contaminated soil.

    Science.gov (United States)

    Chaignon, Valérie; Quesnoit, Marie; Hinsinger, Philippe

    2009-12-01

    We evaluated how root-induced changes in rhizosphere pH varied and interacted with Cu availability and bioavailability in an acidic soil. Rape was grown on a Cu-contaminated acidic soil, which had been limed at 10 rates. Soil Cu bioavailability was not influenced by liming. However, liming significantly decreased CaCl(2)-extracted Cu for pH between 3.7 and 5.1. Little effect was found for pH above 5.1. For soil pH soil. Rhizosphere alkalisation occurred at pH pH. This explained the changes of CaCl(2)-Cu in the rhizosphere at low pH and the absence of pH dependency of Cu bioavailability to rape. In addition, apoplastic Cu in roots increased with increasing soil pH, most probably as a result of increased dissociation and affinity of cell wall compounds for Cu.

  19. Effecf of pH and some cations on activity of acid phosphatase secreted from Ustilago sp. isolated from acid sulphate soil

    Directory of Open Access Journals (Sweden)

    Chairatana Nilnond

    2007-03-01

    Full Text Available Acid phosphatase secreted from Ustilago sp. is able to hydrolyze organic phosphorus. These soil yeast microorganisms were isolated from rice roots grown in acid sulphate soil that generally contains highamount of aluminum (Al, iron (Fe and manganese (Mn ions. Therefore, the objectives of this study were to examine the effect of pH and some cations on acid phosphatase activity. Two isolates of Ustilago sp., AR101and AR102, were cultured in 100 mL of modified Pikovskaya's broth containing Na-phytate, pH 4, and acid phosphatase activity was determined at pH 2.0-7.0. Effect of Al, Fe, and Mn, including calcium (Ca ions,on growth of AR101 and AR102, secreted acid phosphatase activity, and the ability of acid phosphatase on the phosphorus release from Na-phytate by Ustilago sp. were investigated. It was found that the optimum pH for acid phosphatase activity was 3.5-4.5. The activity of acid phosphatase secreted from AR101 (3,690nmol min-1 mL-1 was remarkably higher than that from AR102 (956 nmol min-1 mL-1. Aluminum, iron, manganese and calcium ions in the medium did not affect the growth of either isolate. The activity of secretedacid phosphatase of AR101 was inhibited by Al and Ca ion, and synthesis of acid phosphatase of Ustilago sp. AR102 was possibly stimulated by Fe ion. Both AR101 and AR102 solubilized Na-phytate, resulting in therelease of P. However, some amount of released P was then precipitated with Al and Fe ions as the highly insoluble Fe- or Al- phosphate.

  20. Determination of Sulfuric Acid in Anodizing and Hardcoating Solutions by Acid-Base Titration Using a pH Meter

    Science.gov (United States)

    1989-10-01

    6.99 5 6.95 6 6.95 X(avg) 6.99 Sn 0.04 *The pH values are standardized against primary standard buffer solutions in the potentiometry chapter of...Sn 0.02 *The pH values are standardized against primary standard buffer solutions in the potentiometry chapter of Reference 3 using a pH meter. 9

  1. Influence of salts and pH on growth and activity of a novel facultatively alkaliphilic, extremely salt-tolerant, obligately chemolithoautotrophic sufur-oxidizing Gammaproteobacterium Thioalkalibacter halophilus gen. nov., sp. nov. from South-Western Siberian soda lakes

    NARCIS (Netherlands)

    Banciu, H.L.; Sorokin, D.Y.; Tourova, T.P.; Galinski, E.A.; Muntyan, M.S.; Kuenen, J.G.; Muyzer, G.

    2008-01-01

    A chemolithoautotrophic sulfur-oxidizing bacterium (SOB) strain ALCO 1 capable of growing at both near-neutral and extremely alkaline pH was isolated from hypersaline soda lakes in S-W Siberia (Altai, Russia). Strain ALCO 1 represents a novel separate branch within the halothiobacilli in the Gammapr

  2. Influence of salts and pH on growth and activity of a novel facultatively alkaliphilic, extremely salt-tolerant, obligately chemolithoautotrophic sufur-oxidizing Gammaproteobacterium Thioalkalibacter halophilus gen. nov., sp. nov. from South-Western Siberian soda lakes

    NARCIS (Netherlands)

    Banciu, H.L.; Sorokin, D.Y.; Tourova, T.P.; Galinski, E.A.; Muntyan, M.S.; Kuenen, J.G.; Muyzer, G.

    2008-01-01

    A chemolithoautotrophic sulfur-oxidizing bacterium (SOB) strain ALCO 1 capable of growing at both near-neutral and extremely alkaline pH was isolated from hypersaline soda lakes in S-W Siberia (Altai, Russia). Strain ALCO 1 represents a novel separate branch within the halothiobacilli in the

  3. Addition of formic acid or starter cultures to liquid feed. Effect on pH, microflora composition, organic acid concentration and ammonia concentration.

    Science.gov (United States)

    Canibe, N; Miquel, N; Miettinen, H; Jensen, B B

    2001-01-01

    Some of the charateristics of good quality fermented liquid feed (FLF) are low pH, high numbers of lactic acid bacteria, and low numbers of enterobacteria. In order to test strategies to avoid a proliferation of enterobacteria during the initial phase of FLF elaboration, two in vitro studies were carried out. Addition of various doses of formic acid or two different starter cultures were tested. Adding 0.1% formic acid or L. plantarum VTT E-78076 to the liquid feed seemed to be addecuate ways of inhibiting the growth of enterobacteria, without depleting the growth of lactic acid bacteria.

  4. The acid test of fluoride: how pH modulates toxicity.

    Directory of Open Access Journals (Sweden)

    Ramaswamy Sharma

    Full Text Available BACKGROUND: It is not known why the ameloblasts responsible for dental enamel formation are uniquely sensitive to fluoride (F(-. Herein, we present a novel theory with supporting data to show that the low pH environment of maturating stage ameloblasts enhances their sensitivity to a given dose of F(-. Enamel formation is initiated in a neutral pH environment (secretory stage; however, the pH can fall to below 6.0 as most of the mineral precipitates (maturation stage. Low pH can facilitate entry of F(- into cells. Here, we asked if F(- was more toxic at low pH, as measured by increased cell stress and decreased cell function. METHODOLOGY/PRINCIPAL FINDINGS: Treatment of ameloblast-derived LS8 cells with F(- at low pH reduced the threshold dose of F(- required to phosphorylate stress-related proteins, PERK, eIF2alpha, JNK and c-jun. To assess protein secretion, LS8 cells were stably transduced with a secreted reporter, Gaussia luciferase, and secretion was quantified as a function of F(- dose and pH. Luciferase secretion significantly decreased within 2 hr of F(- treatment at low pH versus neutral pH, indicating increased functional toxicity. Rats given 100 ppm F(- in their drinking water exhibited increased stress-mediated phosphorylation of eIF2alpha in maturation stage ameloblasts (pH<6.0 as compared to secretory stage ameloblasts (pH approximately 7.2. Intriguingly, F(--treated rats demonstrated a striking decrease in transcripts expressed during the maturation stage of enamel development (Klk4 and Amtn. In contrast, the expression of secretory stage genes, AmelX, Ambn, Enam and Mmp20, was unaffected. CONCLUSIONS: The low pH environment of maturation stage ameloblasts facilitates the uptake of F(-, causing increased cell stress that compromises ameloblast function, resulting in dental fluorosis.

  5. Alteration of chemical behavior of L-ascorbic acid in combination with nickel sulfate at different pH solutions in vitro

    Institute of Scientific and Technical Information of China (English)

    Shaheen A Maniyar; Jameel G Jargar; Swastika N Das; Salim A Dhundasi; Kusal K Das

    2012-01-01

    Objective: To evaluate the alteration of chemical behavior of L-ascorbic acid (vitamin C) with metal ion (nickel) at different pH solutions in vitro. Methods: Spectra of pure aqueous solution of L-ascorbic acid (E mark) compound and NiSO4 (H2O) (sigma USA) were evaluated by UV visible spectrophotometer. Spectral analysis of L-ascorbic acid and nickel at various pH (2.0, 7.0, 7.4 and 8.6) at room temperature of 29℃ was recorded. In this special analysis, combined solution of L-ascorbic acid and nickel sulfate at different pH was also recorded. Results: The result revealed that λmax (peak wavelength of spectra) of L-ascorbic acid at pH 2.0 was 289.0 nm whereas at neutral pH 7.0, λmax was 295.4 nm. In alkaline pH 8.6, λmax was 295.4 nm and at pH 7.4 the λmax of L-ascorbic acid remained the same as 295.4 nm. Nickel solution at acidic pH 2.0 was 394.5 nm, whereas at neutral pH 7.0 and pH 7.4 were the same as 394.5 nm. But at alkaline pH 8.6, λmax value of nickel sulfate became 392.0 nm. The combined solution of L-ascorbic acid and nickel sulfate (6 mg/mL each) at pH 2.0 showed 292.5 nm and 392.5 nm, respectively whereas at pH 7.0, L-ascorbic acid showed 296.5 nm and nickel sulfate showed 391.5 nm. At pH 7.4, L-ascorbic acid showed 297.0 nm and nickel sulfate showed 394.0 nm in the combined solution whereas at pH 8.6 (alkaline) L-ascorbic acid and nickel sulfate were showing 297.0 and 393.5 nm, respectively.Conclusions:alone or in combination with nickel sulfate in vitro at different pH. Perhaps oxidation of L-ascorbic acid to L-dehydro ascorbic acid via the free radical (HSc*) generation from the reaction of H2ASc+ Ni (II) is the cause of such alteration of λmax value of L-ascorbic acid in the presence of metal Results clearly indicate an altered chemical behavior of L-ascorbic acid either nickel.

  6. Effect of low pH start-up on continuous mixed-culture lactic acid fermentation of dairy effluent.

    Science.gov (United States)

    Choi, Gyucheol; Kim, Jaai; Lee, Changsoo

    2016-12-01

    Mixed-culture fermentation that does not require an energy-intensive sterilization process is a viable approach for the economically feasible production of lactic acid (LA) due to the potential use of organic waste as feedstock. This study investigated mixed-culture LA fermentation of whey, a high-strength organic wastewater, in continuous mode. Variations in the hydraulic retention time (HRT) from 120 to 8 h under different pH regimes in two thermophilic reactors (55 °C) were compared for their fermentation performance. One reactor was maintained at a low pH (pH 3.0) during operation at HRTs of 120 to 24 h and then adjusted to pH 5.5 in the later phases of fermentation at HRTs of 24 to 8 h (R1), while the second reactor was maintained at pH 5.5 throughout the experiment (R2). Although the LA production in R1 was negligible at low pH, it increased dramatically after the pH was raised to 5.5 and exceeded that in R2 when stabilized at HRTs of 8 and 12 h. The maximum yield (0.62 g LA/g substrate fed as the chemical oxygen demand (COD) equivalent), the production rate (11.5 g/L day), and the selectivity (95 %) of LA were all determined at a 12-h HRT in R1. Additionally, molecular and statistical analyses revealed that changes in the HRT and the pH significantly affected the bacterial community structure and thus the fermentation characteristics of the experimental reactors. Bacillus coagulans was likely the predominant LA producer in both reactors. The overall results suggest that low pH start-up has a positive effect on yield and selectivity in mixed-culture LA fermentation.

  7. The effect of alginates on deoxycholic-acid-induced changes in oesophageal mucosal biology at pH 4.

    Science.gov (United States)

    Dettmar, Peter W; Strugala, Vicki; Tselepis, Chris; Jankowski, Janusz A

    2007-01-01

    Long-standing gastro-oesophageal reflux disease (GORD) can give rise to Barrett's oesophagus (BM), a metaplastic condition and precursor to oesophageal adenocarcinoma (AC). Oesophageal cancer was once rare but is now the 5th biggest cancer killer in the U.K. Reflux of bile acids into the oesophagus is implicated in the progression to BM as bile acids at pH 4 have been shown to induce c-myc expression, an oncogene upregulated in BM and AC. In the present study we investigated the role of the biopolymer alginate on bile acid induced molecular changes in oesophageal cell lines. OE21, OE33 and TE-7 oesophageal cell lines were exposed to 100 microM deoxycholic acid at pH 4 in the presence or absence of alginates. Levels of c-myc, E-cadherin, beta-catenin and Tcf signalling were determined by Real-Time PCR, Western blotting, immunofluoresence and reporter assays. All alginates tested were able to prevent the induction of c-myc by acidified deoxycholic acid in vitro. The upstream effects of acidified deoxycholic acid on E-cadherin, beta-catenin and Tcf signalling were also suppressed by alginate. Therefore, we have demonstrated that reflux of bile acids into the oesophagus initiates a potentially damaging molecular cascade of events using an in vitro model and that a biopolymer, alginate, can protect against these effects.

  8. Water quality of selected lakes in Mount Rainier National Park, Washington with respect to lake acidification

    Science.gov (United States)

    Turney, G.L.; Dion, N.P.; Sumioka, S.S.

    1986-01-01

    Thirteen lakes in Mount Rainier National Park were evaluated for general chemical characteristics, sensitivity to acidification by acidic precipitation, and degree of existing acidification. The lakes studies were Allen, one of the Chenuis group, Crescent , Crystal, Eleanor, Fan, one of the Golden group, Marsh, Mowich, Mystic, Shriner, and two unnamed lakes. The lakes were sampled in August 1983. Specific conductance values were generally 21 microsiemens/cm at 25 C or less, and dissolved solids concentrations were generally 20 mg/L or less. The major cations were calcium and sodium, and the major anion was bicarbonate. Alkalinity concentrations ranged from 2.1 to 9.0 mg/L in 12 of the lakes. Allen Lake was the exception, having an alkalinity concentration of 27 mg/L. The pH values for all of the lakes ranged from 5.8 to 6.5. In most of the lakes, vertical profiles of temperature, dissolved oxygen, pH, and specific conductance were relatively uniform. In the deeper lakes, temperature decreased with depth and dissolved-oxygen concentrations increased to about 20 feet, remained constant to 80 ft, then decreased with increasing depth. Exceptions to general water quality patterns were observed in three lakes. Allen Lake had a specific conductance value of 58 Microsiemens/cm. The lake of the Golden group was anaerobic at the bottom and had relatively high concentrations of dissolved organic carbon and dissolved metals, and a lower light transmission than the other lakes studied. One of the unnamed lakes had relatively high concentrations of phytoplankton and dissolved organic carbon and relatively low levels of light transmission. Comparisons of lake data to acid-sensitivity thresholds for specific conductance and alkalinity indicated that all of the lakes except Allen would be sensitive to acidic precipitation. The small sizes of the lakes, and their locations in basins of high precipitation and weathering-resistant rock types, enhance their sensitivity. None of the

  9. Potentiometric pH Measurements of Acidity Are Approximations, Some More Useful than Others

    Science.gov (United States)

    de Levie, Robert

    2010-01-01

    A recent article by McCarty and Vitz "demonstrating that it is not true that pH = -log[H+]" is examined critically. Then, the focus shifts to underlying problems with the IUPAC definition of pH. It is shown how the potentiometric method can provide "estimates" of both the IUPAC-defined hydrogen activity "and" the hydrogen ion concentration, using…

  10. Kinetic analysis of waste activated sludge hydrolysis and short-chain fatty acids production at pH 10

    Institute of Scientific and Technical Information of China (English)

    FENG Leiyu; YAN Yuanyuan; CHEN Yinguang

    2009-01-01

    The accumulation of short-chain fatty acids (SCFAs), a preferred carbon source for enhanced biological phosphorus removal microbes, was significantly improved when waste activated sludge (WAS) was fermented at pH 10. The kinetics of WAS hydrolysis and SCFAs production at pH 10 were investigated. It was observed that during WAS anaerobic fermentation at pH 10 the accumulation of SCFAs was limited by the hydrolysis process, and both the hydrolysis of WAS particulate COD and the accumulation of SCFAs followed first-order kinetics. The hydrolysis and SCFAs accumulation rate constants increased with a increasing of temperature from 10 to 35℃, which could be described by the Arrhenius equation. The kinetic data further indicated that SCFAs production at pH 10 was a biological process. Compared with the experiment of pH uncontrolled (blank test), both the rate constants of WAS hydrolysis and SCFAs accumulation at 20℃ were significantly improved when WAS was fermented at pH 10.

  11. Effect of pH Value on Stress Corrosion Cracking of X70 Pipeline Steel in Acidic Soil Environment

    Institute of Scientific and Technical Information of China (English)

    Zhiyong LIU; Cuiwei DU; Xin ZHANG; Fuming WANG; Xiaogang LI

    2013-01-01

    The effect of pH value on the stress corrosion cracking (SCC) of API X70 pipeline steel in simulated acidic soil solutions was investigated by using slow strain rate test,electrochemical polarization curves,electrochemical impedance spectroscopy,and scanning electron microscopy.pH plays an important role in the susceptibility and electrochemical mechanism of SCC.The pH higher than 5 has no significant effect on electrochemical processes.By contrast,the pH lower than 5 intensifies cathodic hydrogen evolution reactions,thus increasing the cathodic current and corrosion potential.Under different pH values,the SCC mechanism of X70 pipeline steel varies among anodic dissolution (AD),hydrogen embrittlement (HE),and the combination of AD and HE (AD + HE) with variations of applied potential.At-850 mVSCE,the SCC mechanism is HE if pH is less than 4 or AD + HE if pH value is more positive.

  12. Demonstration of in situ product recovery of butyric acid via CO2 -facilitated pH swings and medium development in two-phase partitioning bioreactors.

    Science.gov (United States)

    Peterson, Eric C; Daugulis, Andrew J

    2014-03-01

    Production of organic acids in solid-liquid two-phase partitioning bioreactors (TPPBs) is challenging, and highly pH-dependent, as cell growth occurs near neutral pH, while acid sorption occurs only at low pH conditions. CO2 sparging was used to achieve acidic pH swings, facilitating undissociated organic acid uptake without generating osmotic stress inherent in traditional acid/base pH control. A modified cultivation medium was formulated to permit greater pH reduction by CO2 sparging (pH 4.8) compared to typical media (pH 5.3), while still possessing adequate nutrients for extensive cell growth. In situ product recovery (ISPR) of butyric acid (pKa = 4.8) produced by Clostridium tyrobutyricum was achieved through intermittent CO2 sparging while recycling reactor contents through a column packed with absorptive polymer Hytrel® 3078. This polymer was selected on the basis of its composition as a polyether copolymer, and the use of solubility parameters for predicting solute polymer affinity, and was found to have a partition coefficient for butyric acid of 3. Total polymeric extraction of 3.2 g butyric acid with no CO2 mediated pH swings was increased to 4.5 g via CO2 -facilitated pH shifting, despite the buffering capacity of butyric acid, which resists pH shifting. This work shows that CO2 -mediated pH swings have an observable positive effect on organic acid extraction, with improvements well over 150% under optimal conditions in early stage fermentation compared to CO2 -free controls, and this technique can be applied other organic acid fermentations to achieve or improve ISPR.

  13. Disruption of the transmembrane pH gradient--a possible mechanism for the antibacterial action of azelaic acid in Propionibacterium acnes and Staphylococcus epidermidis.

    Science.gov (United States)

    Bojar, R A; Cunliffe, W J; Holland, K T

    1994-09-01

    The effect of the topical acne treatment azelaic acid on the transmembrane proton gradient (delta pH) of Propionibacterium acnes and Staphylococcus epidermidis was studied in vitro at external pH values found on human skin (pH 4.0-6.0). Bacteria were grown in defined media using continuous culture and delta pH was estimated by measuring the accumulation of [14C] benzoic by the cells using flow dialysis. In both P. acnes and S. epidermidis the addition of 30 mM azelaic acid and the membrane active inhibitors nigericin (150 microM) and CCCP (150 microM) resulted in a rapid release of [14C] label into the dialysate indicating the dissipation of delta pH between external pH values of 4.0-6.0. The addition of 60 mM NaCl as an iso-osmotic control and 150 microM valinomycin did not induce the release of [14C] label. The addition of 30 mM azelaic acid reduced the delta pH of P. acnes by 44% at external pH 4.0 and 28% at external pH 6.0. In S. epidermidis 30 mM azelaic acid reduced delta pH by 88% at external pH 5.0 and 20% at external pH 6.0. Rapid loss of viability occurred in suspensions of P. acnes and S. epidermidis containing 30 mM azelaic acid at pH 4.0 with no viable cells recovered after 60 min incubation. At pH 6.0 little change in viable numbers of P. acnes and S. epidermidis were observed over a 2 h incubation period. The results indicate that the antibacterial activity of azelaic acid is associated with the perturbation of intracellular pH.

  14. Urea Fertilizer and pH Influence on Sorption Process of Flumetsulam and MCPA Acidic Herbicides in a Volcanic Soil.

    Science.gov (United States)

    Palma, Graciela; Jorquera, Milko; Demanet, Rolando; Elgueta, Sebastian; Briceño, Gabriela; de la Luz Mora, María

    2016-01-01

    The aim of this study was to evaluate the influence of urea fertilizer and pH on the sorption process of two acidic herbicides, flumetsulam (2',6'-difluoro-5-methyl[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonanilide) and MCPA (4-chloro--tolyloxyacetic acid), on an Andisol. Urea reduced the adsorption of MCPA but not that of flumetsulam. The Freundlich parameter of MCPA decreased from 8.5 to 5.1 mg L kg. This finding could be attributed to an increase in dissolved organic C due to an initial increase in soil pH for urea application. The higher acidic character of MCPA compared with that of flumetsulam produced a greater hydrolysis of urea, leading to a further pH increase. A marked effect of pH on the adsorption of both herbicides was observed. The organic C distribution coefficient () values for flumetsulam were in the range of 74 to 10 L kg, while those of MCPA were in the range of 208 to 45 L kg. In the kinetic studies, the pseudo-second-order model appeared to fit the data best ( > 0.994). The initial adsorption rates () ranged from 20.00 to 4.59 mg kg h for flumetsulam and from 125.00 to 25.60 mg kg hfor MCPA. Both herbicides were adsorbed rapidly during the first stage of the sorption process, and the rates of sorption were dependent on pH. The application of the Elovich and Weber-Morris models led us to conclude that mass transfer through the boundary layer and, to a lesser degree, intraparticle diffusion were influenced by the chemical character of the herbicide. These results suggest that urea application could increase leaching of acid herbicides in soils.

  15. Investigations on the "Extreme" Microbial Arsenic Cycle within the Sediments of an Acidic Impoundment of the Former Sulfur Bank Mercury Mine: Herman Pit, Clear Lake, California.

    Science.gov (United States)

    Blum, J. S.; Hoeft McCann, S. E.; Bennett, S.; Miller, L. G.; Stoneburner, B.; Saltikov, C.; Oremland, R. S.

    2014-12-01

    The involvement of prokaryotes in the redox reactions of arsenic occurring between this element's +5 [arsenate; As(V)] and + 3 [arsenite; As(III)] oxidation states has been well established. Most research has focused upon circum-neutral pH environments, such as freshwater lake and aquifer sediments, and extreme environments like hot springs and hypersaline soda lakes have also been well investigated. In contrast, little work has been conducted on acidic environments. The azure-hued, clear waters of the Herman Pit are acidic (pH 2-4), and overlie oxidized sediments that have a distinctive red/orange coloration indicative of the presence of ferrihydrites and other Fe(III) minerals. There is extensive ebullitive release of geothermal gases from the lake bottom in the form of numerous continuous-flow seeps which are composed primarily of mixtures of CO2, CH4, and H2S. We collected near-shore surface sediments with an Eckman grab, and stored the "soupy" material in filled mason jars kept at 4˚C. Initial experiments were conducted using 3:1 mixtures of lake water: sediment so as to generate dilute slurries which were amended with mM levels of electron acceptors (arsenate, nitrate, oxygen), electron donors (arsenite, acetate, lactate, hydrogen), and incubated under N2, air, or H2. Owing to the large adsorptive capacity of the Fe(III)-rich slurries, we were unable to detect As(V) or As(III) in the aqueous phase of either live or autoclaved controls, although the former consumed lactate, acetate, nitrate, or hydrogen, while the latter did not. This prompted us to conduct a series of further diluted slurry experiments using the live materials from the first as a 10 % addition to lakewater. In these experiments we observed reduction of As(V) to As(III) in anoxic slurries and that rates were enhanced by addition of electron donors (H2, acetate, or lactate). We also observed oxidation of As(III) to As(V) in oxic slurries and in anoxic slurries amended with nitrate. These

  16. Cholic acid is accumulated spontaneously, driven by membrane Delta pH, in many lactobacilli

    NARCIS (Netherlands)

    Kurdi, P; van Veen, HW; Tanaka, H; Mierau, [No Value; Konings, WN; Tannock, GW; Tomita, F; Yokota, A

    2000-01-01

    Many lactobacilli from various origins were found to apparently lack cholic acid extrusion activity. Cholic acid was accumulated spontaneously, driven by the transmembrane proton gradient. Accumulation is a newly identified kind of interaction between intestinal microbes and unconjugated bile acids

  17. The time course of the transcriptomic response of Sinorhizobium meliloti 1021 following a shift to acidic pH

    Directory of Open Access Journals (Sweden)

    Pühler Alfred

    2009-02-01

    Full Text Available Abstract Background The symbiotic soil bacterium Sinorhizobium meliloti often has to face low pH in its natural habitats. To identify genes responding to pH stress a global transcriptional analysis of S. meliloti strain 1021 following a pH shift from pH 7.0 to pH 5.75 was carried out. In detail, oligo-based whole genome microarrays were used in a time course experiment. The monitoring period covered a time span of about one hour after the pH shift. The obtained microarray data was filtered and grouped by K-means clustering in order to obtain groups of genes behaving similarly concerning their expression levels throughout the time course. Results The results display a versatile response of S. meliloti 1021 represented by distinct expression profiles of subsets of genes with functional relation. The eight generated clusters could be subdivided into a group of four clusters containing genes that were up-regulated and another group of four clusters containing genes that were down-regulated in response to the acidic pH shift. The respective mean expression progression of the four up-regulated clusters could be described as (i permanently and strong, (ii permanently and intermediate, (iii permanently and progressive, and (iv transiently up-regulated. The expression profile of the four down-regulated clusters could be characterized as (i permanently, (ii permanently and progressive, (iii transiently, and (iv ultra short down-regulated. Genes coding for proteins with functional relation were mostly cumulated in the same cluster, pointing to a characteristic expression profile for distinct cellular functions. Among the strongest up-regulated genes lpiA, degP1, cah, exoV and exoH were found. The most striking functional groups responding to the shift to acidic pH were genes of the exopolysaccharide I biosynthesis as well as flagellar and chemotaxis genes. While the genes of the exopolysaccharide I biosynthesis (exoY, exoQ, exoW, exoV, exoT, exoH, exoK exo

  18. Dissolution kinetics of a lunar glass simulant at 25 degrees C: the effect of pH and organic acids

    Science.gov (United States)

    Eick, M. J.; Grossl, P. R.; Golden, D. C.; Sparks, D. L.; Ming, D. W.

    1996-01-01

    The dissolution kinetics of a simulated lunar glass were examined at pH 3, 5, and 7. Additionally, the pH 7 experiments were conducted in the presence of citric and oxalic acid at concentrations of 2 and 20 mM. The organic acids were buffered at pH 7 to examine the effect of each molecule in their dissociated form. At pH 3, 5, and 7, the dissolution of the synthetic lunar glass was observed to proceed via a two-stage process. The first stage involved the parabolic release of Ca, Mg, Al, and Fe, and the linear release of Si. Dissolution was incongruent, creating a leached layer rich in Si and Ti which was verified by transmission electron microscopy (TEM). During the second stage the release of Ca, Mg, Al, and Fe was linear. A coupled diffusion/surface dissolution model was proposed for dissolution of the simulated lunar glass at pH 3, 5, and 7. During the first stage the initial release of mobile cations (i.e., Ca, Mg, Al, Fe) was limited by diffusion through the surface leached layer of the glass (parabolic release), while Si release was controlled by the hydrolysis of the Si-O-Al bonds at the glass surface (linear release). As dissolution continued, the mobile cations diffused from greater depths within the glass surface. A steady-state was then reached where the diffusion rate across the increased path lengths equalled the Si release rate from the surface. In the presence of the organic acids, the dissolution of the synthetic lunar glass proceeded by a one stage process. The release of Ca, Mg, Al, and Fe followed a parabolic relationship, while the release of Si was linear. The relative reactivity of the organic acids used in the experiments was citrate > oxalate. A thinner leached layer rich in Si/Ti, as compared to the pH experiments, was observed using TEM. Rate data suggest that the chemisorption of the organic anion to the surface silanol groups was responsible for enhanced dissolution in the presence of the organic acids. It is proposed that the increased

  19. Enrichment of Non-Terrestrial L-Proteinogenic Amino Acids by Aqueous Alteration on the Tagish Lake Meteorite Parent Body

    Science.gov (United States)

    Glavin, Daniel P.; Elsila, Jamie E.; Burton, Aaron S.; Callahan, Michael P.; Dworkin, Jason P.; Herd, Christopher D. K.

    2012-01-01

    The distribution and isotopic and enantiomeric compositions of amino acids found in three distinct fragments of the Tagish Lake C2-type carbonaceous chondrite were investigated via liquid chromatography fluorescence detection time-of-flight mass spectrometry and gas chromatography isotope ratio mass spectrometry. Large L-enantiomeric excesses (L(sub ee) approx. 43 to 59%) of the a-hydrogen aspartic and glutamic amino acids were measured in Tagish Lake, whereas alanine, another alpha-hydrogen protein amino acid, was found to be nearly racemic (D approx. L) using both techniques. Carbon isotope measurements of D- and L-aspartic acid and D- and L-alanine in Tagish Lake fall well outside of the terrestrial range and indicate that the measured aspartic acid enantioenrichment is indigenous to the meteorite. Alternate explanations for the Lexcesses of aspartic acid such as interference from other compounds present in the sample, analytical biases, or terrestrial amino acid contamination were investigated and rejected. These results can be explained by differences in the solid-solution phase behavior of aspartic acid, which can form conglomerate enantiopure solids during crystallization, and alanine, which can only form racemic crystals.

  20. Influence of Bath Composition at Acidic pH on Electrodeposition of Nickel-Layered Silicate Nanocomposites for Corrosion Protection

    Directory of Open Access Journals (Sweden)

    Jeerapan Tientong

    2013-01-01

    Full Text Available Nickel-layered silicates were electrochemically deposited from acidic bath solutions. Citrate was used as a ligand to stabilize nickel (II ions in the plating solution. The silicate, montmorillonite, was exfoliated by stirring in aqueous solution over 24 hours. The plating solutions were analyzed for zeta-potential, particle size, viscosity, and conductivity to investigate the effects of the composition at various pHs. The solution particles at pH 2.5 (−22.2 mV and pH 3.0 (−21.9 mV were more stable than at pH 1.6 (−10.1 mV as shown by zeta-potential analysis of the nickel-citrate-montmorillonite plating solution. Ecorr for the films ranged from −0.32 to −0.39 V with varying pH from 1.6 to 3.0. The films were immersed in 3.5% NaCl and the open circuit potential monitored for one month. The coatings deposited at pH 3.0 were stable 13 days longer in the salt solution than the other coatings. X-ray diffraction showed a change in the (111/(200 ratio for the coatings at the various pHs. The scanning electron microscopy and hardness results also support that the electrodeposition of nickel-montmorillonite at pH 3.0 (234 GPa had improved hardness and morphology compared to pH 2.5 (174 GPa and pH 1.6 (147 GPa.

  1. STABILITY OF BETACYANIN PIGMENTS FROM RED PURPLE PITAYA FRUIT (Hylocereus polyrhizus : INFLUENCE OF PH, TEMPERATURE, METAL IONS AND ASCORBIC ACID

    Directory of Open Access Journals (Sweden)

    Tang, C.S Tang, C.S

    2010-06-01

    Full Text Available Betacyanin pigments from red-purple pitaya fruit (Hylocereus polyrhizus could be an attractive source of red colourant for food application. This paper presents results on the extraction of betacyanin pigments from pitaya fruits grown locally in Malaysia. Both the flesh of the fruit and its mesocarp were investigated and it was found that the flesh had higher pigment contents compared to its peel component. The concentration of betacyanins expressed as betanin equivalents per 100 g of flesh and peel were 10.1 ± 0.6 mg and 6.7 ± 0.2 mg, respectively when 80% methanol was used.  The stability of betacyanin pigments were investigated at different pH, temperature and in presence of different concentrations of metal ions (Cu2+ and Fe2+ and ascorbic acid. The results showed that the pigment was most stable at pH range between 5 and 6. However, it forfeited its stability to the heat induced at elevated temperatures. Metal ions (Cu2+ and Fe2+ proved to be capable of accelerating betacyanin degradation, with Cu2+ exhibiting the greatest effect. By contrast, supplementation with ascorbic acid could enhance the pigment stability against the detrimental effects caused by pH, temperature and metal ions. Nevertheless, if the concentration of ascorbic acid exceeds 0.7 %, it may change its role from pigment stabilizer to become a pro-oxidant.    Keywords: Betacyanin, pigments, pitaya fruit, Hylocereus polyrhizus, ascorbic acid

  2. The effect of pH on hydrolysis, cross-linking and barrier properties of starch barriers containing citric acid.

    Science.gov (United States)

    Olsson, Erik; Menzel, Carolin; Johansson, Caisa; Andersson, Roger; Koch, Kristine; Järnström, Lars

    2013-11-01

    Citric acid cross-linking of starch for e.g. food packaging applications has been intensely studied during the last decade as a method of producing water-insensitive renewable barrier coatings. We managed to improve a starch formulation containing citric acid as cross-linking agent for industrial paper coating applications by adjusting the pH of the starch solution. The described starch formulations exhibited both cross-linking of starch by citric acid as well as satisfactory barrier properties, e.g. fairly low OTR values at 50% RH that are comparable with EVOH. Furthermore, it has been shown that barrier properties of coated papers with different solution pH were correlated to molecular changes in starch showing both hydrolysis and cross-linking of starch molecules in the presence of citric acid. Hydrolysis was shown to be almost completely hindered at solution pH≥4 at curing temperatures≤105 °C and at pH≥5 at curing temperatures≤150 °C, whereas cross-linking still occurred to some extent at pH≤6.5 and drying temperatures as low as 70 °C. Coated papers showed a minimum in water vapor transmission rate at pH 4 of the starch coating solution, corresponding to the point where hydrolysis was effectively hindered but where a significant degree of cross-linking still occurred.

  3. Effect of pH on lactic acid production from acidogenic fermentation of food waste with different types of inocula.

    Science.gov (United States)

    Tang, Jialing; Wang, Xiaochang C; Hu, Yisong; Zhang, Yongmei; Li, Yuyou

    2017-01-01

    Effect of acidic pH (4, 5, 6 and uncontrolled) on lactic acid (LA) fermentation from food waste was investigated by batch fermentation experiments using methanogenic sludge, fresh food waste and anaerobic activated sludge as inocula. Results showed that due to the increase of hydrolysis, substrate degradation rate and enzyme activity, the optimal LA concentration and yield were obtained at pH 5, regardless of the inoculum used. The highest LA concentration (28.4g/L) and yield (0.46g/g-TS) were obtained with fresh food waste as inoculum. Moreover, after the substrate was completely utilized, the lactic acid bacteria population sharply decreased, and the LA produced was converted to volatile fatty acids (VFAs) at pH 6 within a short period. The VFA components varied with the inoculum supplied. Microbial community analysis using high-throughput pyrosequencing revealed that diversity decreased and a high abundance of Lactobacillus (83.4-98.5%) accumulated during fermentation with all inocula.

  4. The influence of pH, polyethylene glycol and polyacrylic acid on the stability of stem bromelain

    Directory of Open Access Journals (Sweden)

    Letícia Celia de Lencastre Novaes

    2014-04-01

    Full Text Available Enzyme stability is critical in biotechnology, pharmaceutical and cosmetic industries. Investigations on this subject have drawn attention because of its practical application. Bromelain is a thiol-endopeptidase, obtained from pineapple (Ananas comosus, known for its clinical and therapeutic applications, particularly to selective burn debridement and improvement of antibiotic action and anti-inflammatory activities. To date, the use of bromelain in pharmacological or industrial applications is limited, due to commercial availability, costs, and sensitivity to pH and temperature. Therefore, a better understanding of enzyme stability would be of great interest. The aim of this study was to evaluate bromelain activity and stability in several pH (2.0 to 8.0 and in polyethylene glycol and polyacrylic acid solutions. We observed that bromelain was able to maintain its stability at pH 5.0 for the temperatures studied. PEG solutions increased bromelain stability, but PAA solutions had the opposite effect.

  5. Electrochemically-driven large amplitude pH cycling for acid-base driven DNA denaturation and renaturation.

    Science.gov (United States)

    Wang, Yong-Chun; Lin, Cong-Bin; Su, Jian-Jia; Ru, Ying-Ming; Wu, Qiao; Chen, Zhao-Bin; Mao, Bing-Wei; Tian, Zhao-Wu

    2011-06-15

    In this paper, we present an electrochemically driven large amplitude pH alteration method based on a serial electrolytic cell involving a hydrogen permeable bifacial working electrode such as Pd thin foil. The method allows solution pH to be changed periodically up to ±4~5 units without additional alteration of concentration and/or composition of the system. Application to the acid-base driven cyclic denaturation and renaturation of 290 bp DNA fragments is successfully demonstrated with in situ real-time UV spectroscopic characterization. Electrophoretic analysis confirms that the denaturation and renaturation processes are reversible without degradation of the DNA. The serial electrolytic cell based electrochemical pH alteration method presented in this work would promote investigations of a wide variety of potential-dependent processes and techniques.

  6. Acidic pH shock induces the expressions of a wide range of stress-response genes

    Directory of Open Access Journals (Sweden)

    Hong Soon-Kwang

    2008-12-01

    Full Text Available Abstract Background Environmental signals usually enhance secondary metabolite production in Streptomycetes by initiating complex signal transduction system. It is known that different sigma factors respond to different types of stresses, respectively in Streptomyces strains, which have a number of unique signal transduction mechanisms depending on the types of environmental shock. In this study, we wanted to know how a pH shock would affect the expression of various sigma factors and shock-related proteins in S. coelicolor A3(2. Results According to the results of transcriptional and proteomic analyses, the major number of sigma factor genes were upregulated by an acidic pH shock. Well-studied sigma factor genes of sigH (heat shock, sigR (oxidative stress, sigB (osmotic shock, and hrdD that play a major role in the secondary metabolism, were all strongly upregulated by the pH shock. A number of heat shock proteins including the DnaK family and chaperones such as GroEL2 were also observed to be upregulated by the pH shock, while their repressor of hspR was strongly downregulated. Oxidative stress-related proteins such as thioredoxin, catalase, superoxide dismutase, peroxidase, and osmotic shock-related protein such as vesicle synthases were also upregulated in overall. Conclusion From these observations, an acidic pH shock was considered to be one of the strongest stresses to influence a wide range of sigma factors and shock-related proteins including general stress response proteins. The upregulation of the sigma factors and shock proteins already found to be related to actinorhodin biosynthesis was considered to have contributed to enhanced actinorhodin productivity by mediating the pH shock signal to regulators or biosynthesis genes for actinorhodin production.

  7. EFFECT OF NITRITE AND CITRIC ACID ON THE CHEMICAL COMPOSITION AND pH OF THE CANNED BEEF SAUSAGES

    Directory of Open Access Journals (Sweden)

    M.M.A. MAHA

    2015-01-01

    Full Text Available The effects of nitrite and citric acid as preservatives on the chemical composition and pH of the canned beef sausage were investigated after three months storage at room temperature (35±5ºc. Two experiments were conducted in this study, the first, was undertaken to determine the effect of nitrite as a preservative on the chemical composition and pH of the canned beef sausages retorted at 107.2°C (225ºF for 80 minutes, and at 115.5°C (240ºF for 40 minutes. The second experiment, which was based on the results of the first one, was conducted to determine the effects of the absence of nitrite on the canned beef sausage processed with meat treated by immersion in 1% citric acid before processing at (80 and 30ºc for one minute and drained, then the product retorted at 107.2°C for 80 minutes. The evaluation of percentages of the dry matter, ash, crude protein, fat and also pH were done monthly. The results in experiment 1 indicated that, percentages of the dry matter, ash and crude protein before and after canning of sausages were not significantly different (P>0.05. The fat (% was significantly different among treatments (P0.05 for the raw, cooked and canned sausages. Generally it was observed a decrease in moisture content (increases in dry matter content, ash%, crude protein fat (% and pH value with increasing of storage period. Citric acid had no clear effect on chemical properties and pH value.

  8. The effect of copper and zinc at neutral and acidic pH on the general ...

    African Journals Online (AJOL)

    In general, at neutral pH copper and zinc caused blood acidosis, increases in ... as an adaptation to altered respiratory homeostasis caused by copper and zinc. ... concentrations usually caused blood alkalosis and decreases in white blood ...

  9. pH dependence of iron photoreduction in a rocky mountain stream affected by acid mine drainage

    Science.gov (United States)

    McKnight, Diane M.; Kimball, B.A.; Runkel, R.L.

    2001-01-01

    The redox speciation of dissolved iron and the transport of iron in acidic, metal-enriched streams is controlled by precipitation and dissolution of iron hydroxides, by photoreduction of dissolved ferric iron and hydrous iron oxides, and by oxidation of the resulting dissolved ferrous iron. We examined the pH dependence of these processes in an acidic mine-drainage stream, St Kevin Gulch, Colorado, by experimentally increasing the pH of the stream from about 4.0 to 6.5 and following the downstream changes in iron species. We used a solute transport model with variable flow to evaluate biogeochemical processes controlling downstream transport. We found that at pH 6.4 there was a rapid and large initial loss of ferrous iron concurrent with the precipitation of aluminium hydroxide. Below this reach, ferrous iron was conservative during the morning but there was a net downstream loss of ferrous iron around noon and in the afternoon. Calculation of net oxidation rates shows that the noontime loss rate was generally much faster than rates for the ferrous iron oxidation at pH 6 predicted by Singer and Stumm (1970. Science 167: 1121). The maintenance of ferrous iron concentrations in the morning is explained by the photoreduction of photoreactive ferric species, which are then depleted by noon. Copyright ?? 2001 John Wiley & Sons, Ltd.

  10. Chemical equilibrium modeling of organic acids, pH, aluminum, and iron in Swedish surface waters.

    Science.gov (United States)

    Sjöstedt, Carin S; Gustafsson, Jon Petter; Köhler, Stephan J

    2010-11-15

    A consistent chemical equilibrium model that calculates pH from charge balance constraints and aluminum and iron speciation in the presence of natural organic matter is presented. The model requires input data for total aluminum, iron, organic carbon, fluoride, sulfate, and charge balance ANC. The model is calibrated to pH measurements (n = 322) by adjusting the fraction of active organic matter only, which results in an error of pH prediction on average below 0.2 pH units. The small systematic discrepancy between the analytical results for the monomeric aluminum fractionation and the model results is corrected for separately for two different fractionation techniques (n = 499) and validated on a large number (n = 3419) of geographically widely spread samples all over Sweden. The resulting average error for inorganic monomeric aluminum is around 1 µM. In its present form the model is the first internally consistent modeling approach for Sweden and may now be used as a tool for environmental quality management. Soil gibbsite with a log *Ks of 8.29 at 25°C together with a pH dependent loading function that uses molar Al/C ratios describes the amount of aluminum in solution in the presence of organic matter if the pH is roughly above 6.0.

  11. Effect of urine pH changed by dietary intervention on uric acid clearance mechanism of pH-dependent excretion of urinary uric acid

    Directory of Open Access Journals (Sweden)

    Kanbara Aya

    2012-06-01

    Full Text Available Abstract Background The finding reported in a previous paper - alkalization of urine facilitates uric acid excretion - is contradictory to what one might expect to occur: because food materials for the alkalization of urine contain fewer purine bodies than those for acidification, less uric acid in alkaline urine should have been excreted than in acid urine. To make clear what component of uric acid excretion mechanisms is responsible for this unexpected finding, we simultaneously collected data for the concentration of both creatinine and uric acid in serum as well as in urine, in order to calculate both uric acid and creatinine clearances. Methods Within the framework of the Japanese government’s health promotion program, we made recipes which consisted of protein-rich and less vegetable-fruit food materials for H + -load (acidic diet and others composed of less protein and more vegetable-fruit rich food materials (alkaline diet. This is a crossover study within some limitations. Healthy female students, who had no medical problems at the regular physical examination provided by the university, were enrolled in this consecutive 5-day study for each test. From whole-day collected urine, total volume, pH, organic acid, creatinine, uric acid, titratable acid and all cations (Na+,K+,Ca2+,Mg2+,NH4+ and anions (Cl−,SO42−,PO4− necessary for the estimation of acid–base balance were measured. In the early morning before breakfast of the 1st, 3rd and 5th experimental day, we sampled 5 mL of blood to estimate the creatinine and uric acid concentration in serum. Results and discussion Urine pH reached a steady state 3 days after switching from ordinary daily diets to specified regimens. The amount of acid generated ([SO42−] + organic acid − gut alkaliwas linearly related with the excretion of acid (titratable acid + [NH4+] − [HCO3−], indicating that H + in urine is generated by the metabolic degradation of

  12. Investigation of the microbial diversity of an extremely acidic, metal-rich water body (Lake Robule, Bor, Serbia

    Directory of Open Access Journals (Sweden)

    Stanković Srđan

    2014-01-01

    Full Text Available An investigation of the microbial diversity of the extremely acidic, metal-rich Lake Robule was carried out using culture-dependant and culture-independent (T-RFLP methods, and the ability of indigenous bacteria from the lake water to leach copper from a mineral concentrate was tested. T-RFLP analysis revealed that the dominant bacteria in lake water samples were the obligate heterotroph Acidiphilium cryptum (~50% of total bacteria and the iron-oxidizing autotroph Leptospirillum ferrooxidans (~40% The iron/sulfur-oxidizing autotroph Acidithiobacillus ferrooxidans had been reported to be the most abundant bacteria in the lake in an earlier study by other authors, but it was not detected in the present study using T-RFLP. Although it was isolated on solid media and detected in enrichment (bioleaching cultures. The presence of the two bacterial species detected by T-RFLP (L. ferrooxidans and A. cryptum was also confirmed by cultivation on solid media. The presence and relative abundance of bacteria inhabiting Lake Robule was explained by the physiological characteristics of the bacteria and the physico-chemical characteristics of the lake water. [Projekat Ministarstva nauke Republike Srbije, br. 176016 i br.173048

  13. Tyramine biosynthesis is transcriptionally induced at low pH and improves the fitness of Enterococcus faecalis in acidic environments

    OpenAIRE

    Pérez, Marta M.; Calles-Enríquez, Marina; Nes, Ingolf F.; Martín, M. Cruz; Fernández García, María; Ladero Losada, Víctor Manuel; Álvarez González, Miguel Ángel

    2015-01-01

    © 2014, Springer-Verlag Berlin Heidelberg. Enterococcus faecalis is a commensal bacterium of the human gut that requires the ability to pass through the stomach and therefore cope with low pH. E. faecalis has also been identified as one of the major tyramine producers in fermented food products, where they also encounter acidic environments. In the present work, we have constructed a non-tyramine-producing mutant to study the role of the tyramine biosynthetic pathway, which converts tyrosine ...

  14. α-Cyclodextrin/aminobenzoic acid binding in salt solutions at different pH: dependence on guest structure.

    Science.gov (United States)

    Romanova, Anastasia; Chibunova, Ekaterina; Kumeev, Roman; Fedorov, Maxim; Terekhova, Irina

    2013-06-01

    Influence of Na(+) and K(+) cations on α-cyclodextrin guest-host complex formation with isomeric aminobenzoic acids was examined at different pH and temperature of 298.15 K by (1)H NMR and calorimetry methods. More pronounced influence of Na(+) on inclusion complex formation of α-CD with aminobenzoic acid anions compare to the effects of Na(+) on α-CD complex formation with zwitterionic aminobenzoic acid molecules was revealed. For the first time, the dependence of salt effects on the structure, ionization and the hydration state of the guest molecule was demonstrated and analysed on the basis of the obtained thermodynamic parameters of complex formation and calculated free energy of hydration of different ionized forms of aminobenzoic acids.

  15. Influence of ionic strength and pH on the limitation of latex microsphere deposition sites on iron-oxide coated sand by humic acid

    Energy Technology Data Exchange (ETDEWEB)

    Yang, X. [School of Planning, Architecture and Civil Engineering, Queen' s University Belfast, David Keir Building, Stranmillis Road, Belfast BT9 5AG, N. Ireland (United Kingdom); Flynn, R., E-mail: r.flynn@qub.ac.uk [School of Planning, Architecture and Civil Engineering, Queen' s University Belfast, David Keir Building, Stranmillis Road, Belfast BT9 5AG, N. Ireland (United Kingdom); Kammer, F. von der, E-mail: frank.von.der.kammer@univie.ac.at [Department of Environmental Geosciences, University of Vienna, Althanstrasse 14, 1090 Vienna (Austria); Hofmann, T. [Department of Environmental Geosciences, University of Vienna, Althanstrasse 14, 1090 Vienna (Austria)

    2011-07-15

    This study, for the first time, investigates and quantifies the influence of slight changes in solution pH and ionic strength (IS) on colloidal microsphere deposition site coverage by Suwannee River Humic Acid (SRHA) in a column matrix packed with saturated iron-oxide coated sand. Triple pulse experimental (TPE) results show adsorbed SRHA enhances microsphere mobility more at higher pH and lower IS and covers more sites than at higher IS and lower pH. Random sequential adsorption (RSA) modelling of experimental data suggests 1 {mu}g of adsorbed SRHA occupied 9.28 {+-} 0.03 x 10{sup 9} sites at pH7.6 and IS of 1.6 mMol but covered 2.75 {+-} 0.2 x 10{sup 9} sites at pH6.3 and IS of 20 mMol. Experimental responses are suspected to arise from molecular conformation changes whereby SRHA extends more at higher pH and lower ionic strength but is more compact at lower pH and higher IS. Results suggest effects of pH and IS on regulating SRHA conformation were additive. - Highlights: > We quantified the coupled role of pH and IS and humic acid on colloid deposition. > Humic acid enhances microsphere mobility more at higher pH and lower IS. > pH and IS may control the behaviour of humic acid by regulating its conformation. > The effect of pH and IS on regulating humic acid conformation is additive. - This paper quantifies the impact of pH and ionic strength on the transient deposition behaviour of colloids in porous medium in the presence of humic acid.

  16. Spring flood pH decline in northern Sweden: Towards an operational model separating natural acidity from anthropogenic acidification

    Energy Technology Data Exchange (ETDEWEB)

    Laudon, H.

    1999-10-01

    The spring flood is a defining feature of the ecosystem in northern Sweden. In this region, spring flood is an occasion for dramatic hydrochemical changes that profoundly effect the biodiversity of the aquatic ecosystem. Spring flood is also the period most susceptible to anthropogenic acidification. A belief in the anthropogenic component to pH decline during spring flood has been an important factor in spending over half a billion crowns to lime surface waters in Northern Sweden during the last decade. The natural component of episodic pH decline during spring flood, however, has received less attention. The main objective of this work is to present an operational model for separating and quantifying the anthropogenic and natural contributions of episodic acidification during high flow events in Northern Sweden. The key assumptions in this model are that baseflow ANC has not been affected by anthropogenic acidification, that DOC has not changed due to modern land-use practice and that natural dilution during hydrological episodes can be quantified. The limited data requirements of 10-15 stream water samples before and during spring flood make the model suitable for widespread use in environmental monitoring programs. This makes it possible to distinguish trends of human impact as well as natural pH decline in space and time. Modeling results from northern Sweden demonstrate that the natural driving mechanisms of dilution and organic acidity were the dominant factors in the episodic acidification of spring flood in the region. The anthropogenic contribution to spring pH decline was similar in size to the natural contribution in only two of the more than 30 events where this model was applied. Natural factors alone were found to cause pH values below 4.5 in some streams. Anthropogenic sources of acidity can be superimposed on this natural dynamics. In the sites studied, the magnitude of the anthropogenic ANC decline was correlated to the winter deposition of

  17. Effect of pH and ionic strength on the spectrophotometric assessment of nucleic acid purity.

    Science.gov (United States)

    Wilfinger, W W; Mackey, K; Chomczynski, P

    1997-03-01

    The ratio of absorbance at 260 and 280 nm (the A260/280 ratio) is frequently used to assess the purity of RNA and DNA preparations. Data presented in this report demonstrate significant variability in the RNA A260/280 ratio when different sources of water were used to perform the spectrophotometric determinations. Adjusting the pH of water used for spectrophotometric analysis from approximately 5.4 to a slightly alkaline pH of 7.5-8.5 significantly increased RNA A260/280 ratios from approximately 1.5 to 2.0. Our studies revealed that changes in both the pH and ionic strength of the spectrophotometric solution influenced the A260/280 ratios. In addition, the ability to detect protein contamination was significantly improved when RNA was spectrophotometrically analyzed in an alkaline solution. UV spectral scans showed that the 260-nm RNA absorbance maximum observed in water was shifted by 2 nm to a lower wavelength when determinations were carried out in Na2HPO4 buffer at a pH of 8.5. We found RNA A260/280 ratios to be more reliable and reproducible when these spectrophotometric measurements were performed at pH 8.0-8.5 in 1-3 mM Na2HPO4 buffer.

  18. Characterization of a recombinant flocculent Saccharomyces cerevisiae strain that co-ferments glucose and xylose: II. influence of pH and acetic acid on ethanol production.

    Science.gov (United States)

    Matsushika, Akinori; Sawayama, Shigeki

    2012-12-01

    The inhibitory effects of pH and acetic acid on the co-fermentation of glucose and xylose in complex medium by recombinant flocculent Saccharomyces cerevisiae MA-R4 were evaluated. In the absence of acetic acid, the fermentation performance of strain MA-R4 was similar between pH 4.0-6.0, but was negatively affected at pH 2.5. The addition of acetic acid to batch cultures resulted in negligible inhibition of several fermentation parameters at pH 6.0, whereas the interactive inhibition of pH and acetic acid on the maximum cell and ethanol concentrations, and rates of sugar consumption and ethanol production were observed at pH levels below 5.4. The inhibitory effect of acetic acid was particularly marked for the consumption rate of xylose, as compared with that of glucose. With increasing initial acetic acid concentration, the ethanol yield slightly increased at pH 5.4 and 6.0, but decreased at pH values lower than 4.7. Notably, ethanol production was nearly completely inhibited under low pH (4.0) and high acetic acid (150-200 mM) conditions. Together, these results indicate that the inhibitory effects of acetic acid and pH on ethanol fermentation by MA-R4 are highly synergistic, although the inhibition can be reduced by increasing the medium pH.

  19. Decrease of intracellular pH as possible mechanism of embryotoxicity of glycol ether alkoxyacetic acid metabolites.

    Science.gov (United States)

    Louisse, Jochem; Bai, Yanqing; Verwei, Miriam; van de Sandt, Johannes J M; Blaauboer, Bas J; Rietjens, Ivonne M C M

    2010-06-01

    Embryotoxicity of glycol ethers is caused by their alkoxyacetic acid metabolites, but the mechanism underlying the embryotoxicity of these acid metabolites is so far not known. The present study investigates a possible mechanism underlying the embryotoxicity of glycol ether alkoxyacetic acid metabolites using the methoxyacetic acid (MAA) metabolite of ethylene glycol monomethyl ether as the model compound. The results obtained demonstrate an MAA-induced decrease of the intracellular pH (pH(i)) of embryonic BALB/c-3T3 cells as well as of embryonic stem (ES)-D3 cells, at concentrations that affect ES-D3 cell differentiation. These results suggest a mechanism for MAA-mediated embryotoxicity similar to the mechanism of embryotoxicity of the drugs valproic acid and acetazolamide (ACZ), known to decrease the pH(i)in vivo, and therefore used as positive controls. The embryotoxic alkoxyacetic acid metabolites ethoxyacetic acid, butoxyacetic acid and phenoxyacetic acid also caused an intracellular acidification of BALB/c-3T3 cells at concentrations that are known to inhibit ES-D3 cell differentiation. Two other embryotoxic compounds, all-trans-retinoic acid and 5-fluorouracil, did not decrease the pH(i) of embryonic cells at concentrations that affect ES-D3 cell differentiation, pointing at a different mechanism of embryotoxicity of these compounds. MAA and ACZ induced a concentration-dependent inhibition of ES-D3 cell differentiation, which was enhanced by amiloride, an inhibitor of the Na(+)/H(+)-antiporter, corroborating an important role of the pH(i) in the embryotoxic mechanism of both compounds. Together, the results presented indicate that a decrease of the pH(i) may be the mechanism of embryotoxicity of the alkoxyacetic acid metabolites of the glycol ethers.

  20. DETERMINATION OF URINE PH AND AMMONIA EMISSION AFTER ADDITION OF BENZOIC ACID AND DRIED BEET PULP IN GROWING PIGS

    Directory of Open Access Journals (Sweden)

    Peter Patráš

    2013-02-01

    Full Text Available Twelve crossbred gilts (initial BW 29.9 ± 1.7 kg were used for evalution of the effect of benzoic acid and the fiber in diets on the urinary pH, ammonia of the slurry and redistribution of nitrogen between faeces and urinary. For the pigs there were randomly allotted three dietary treatments according to a replicated 3 x 3 Latin square design. The dietary treatments included: Diet control (C was supplemented with isoleucine, lysine, methionine, threonine, tryptophan, and valine to fulfill the requirements of ideal amino acid profile; diet (BA was similar to diet (C with 10g.kg-1 benzoic acid; diet (BABP was similar to diet (C with 10g.kg-1 benzoic acid and 150 g.kg-1 dried beet pulp, all of them with equal ME content (13.3 MJ/kg and supplemented with rapeseed oil. The pigs were housed in metabolic cages and fed with two equal doses at 7 a.m. and 5 p.m. at a daily rate of 90 g. kg0.75. Water was offered ad libitum. Each experimental period consisted of a 6-d adaptation phase and was followed by a 4-d collection phase. During collection phase the feces and the urine (using bladder catheters were collected. The experimental data were subjected to ANOVA and when significant value for treatment effect (P<0.05 was observed, the differences between means were assessed with using Fisher's LSD procedure. Nitrogen and dry matter intake was not significantly affected by any of the feed additives. Nitrogen and dry matter intake was not significantly affected by any of supplemented additives. Fecal N excretion was increased (P <0.02 in pigs fed with added fiber (BABP, in the same group there was detected the reduction of urinary N excretion (P< 0.04. There was significant decrease of urine pH, concretely by three quarters of pH point in the both experimental groups fed with bonzoic acid diets, regardless of the fiber content in the diet. The coefficients of excretion determination between hippuric acid and urine pH were R2 = 0.298. The same decrease of

  1. Sources of acid and metals from the weathering of the Dinero waste pile, Lake Fork watershed, Leadville, Colorado

    Science.gov (United States)

    Diehl, S.F.; Hageman, Phil L.; Smith, Kathleen S.; Herron, J.T.; Desborough, G.A.

    2005-01-01

    Two trenches were dug into the south Dinero mine-waste pile near Leadville, Colorado, to study the weathering of rock fragments and the mineralogic sources of metal contaminants in the surrounding wetland and Lake Fork Watershed. Water seeping from the base of the south Dinero waste-rock pile was pH 2.9, whereas leachate from a composite sample of the rock waste was pH 3.3. The waste pile was mostly devoid of vegetation, open to infiltration of precipitation, and saturated at the base because of placement in the wetland. The south mine-waste pile is composed of poorly sorted material, ranging from boulder-size to fine-grained rock fragments. The trenches showed both matrix-supported and clast-supported zones, with faint horizontal color banding, suggesting zonation of Fe oxides. Secondary minerals such as jarosite and gypsum occurred throughout the depth of the trenches. Infiltration of water and transport of dissolved material through the pile is evidenced by optically continuous secondary mineral deposits that fill or line voids. Iron-sulfate material exhibits microlaminations with shrinkage cracking and preferential dissolution of microlayers that evidence drying and wetting events. In addition to fluids, submicron-sized to very fine-grained particles such as jarosite are transported through channel ways in the pile. Rock fragments are coated with a mixture of clay, jarosite, and manganese oxides. Dissolution of minerals is a primary source of metals. Skeletal remnants of grains, outlined by Fe-oxide minerals, are common. Potassium jarosite is the most abundant jarosite phase, but Pb-and Ag-bearing jarosite are common. Grain-sized clusters of jarosite suggest that entire sulfide grains were replaced by very fine-grained jarosite crystals. The waste piles were removed from the wetland and reclaimed upslope in 2003. This was an opportunity to test methods to identify sources of acid and metals and metal transport processes within a waste pile. A series of

  2. Humic Acid Complexation of Th, Hf and Zr in Ligand Competition Experiments: Metal Loading and Ph Effects

    Science.gov (United States)

    Stern, Jennifer C.; Foustoukos, Dionysis I.; Sonke, Jeroen E.; Salters, Vincent J. M.

    2014-01-01

    The mobility of metals in soils and subsurface aquifers is strongly affected by sorption and complexation with dissolved organic matter, oxyhydroxides, clay minerals, and inorganic ligands. Humic substances (HS) are organic macromolecules with functional groups that have a strong affinity for binding metals, such as actinides. Thorium, often studied as an analog for tetravalent actinides, has also been shown to strongly associate with dissolved and colloidal HS in natural waters. The effects of HS on the mobilization dynamics of actinides are of particular interest in risk assessment of nuclear waste repositories. Here, we present conditional equilibrium binding constants (Kc, MHA) of thorium, hafnium, and zirconium-humic acid complexes from ligand competition experiments using capillary electrophoresis coupled with ICP-MS (CE- ICP-MS). Equilibrium dialysis ligand exchange (EDLE) experiments using size exclusion via a 1000 Damembrane were also performed to validate the CE-ICP-MS analysis. Experiments were performed at pH 3.5-7 with solutions containing one tetravalent metal (Th, Hf, or Zr), Elliot soil humic acid (EHA) or Pahokee peat humic acid (PHA), and EDTA. CE-ICP-MS and EDLE experiments yielded nearly identical binding constants for the metal- humic acid complexes, indicating that both methods are appropriate for examining metal speciation at conditions lower than neutral pH. We find that tetravalent metals form strong complexes with humic acids, with Kc, MHA several orders of magnitude above REE-humic complexes. Experiments were conducted at a range of dissolved HA concentrations to examine the effect of [HA]/[Th] molar ratio on Kc, MHA. At low metal loading conditions (i.e. elevated [HA]/[Th] ratios) the ThHA binding constant reached values that were not affected by the relative abundance of humic acid and thorium. The importance of [HA]/[Th] molar ratios on constraining the equilibrium of MHA complexation is apparent when our estimated Kc, MHA values

  3. Humic Acid Complexation of Th, Hf and Zr in Ligand Competition Experiments: Metal Loading and Ph Effects

    Science.gov (United States)

    Stern, Jennifer C.; Foustoukos, Dionysis I.; Sonke, Jeroen E.; Salters, Vincent J. M.

    2014-01-01

    The mobility of metals in soils and subsurface aquifers is strongly affected by sorption and complexation with dissolved organic matter, oxyhydroxides, clay minerals, and inorganic ligands. Humic substances (HS) are organic macromolecules with functional groups that have a strong affinity for binding metals, such as actinides. Thorium, often studied as an analog for tetravalent actinides, has also been shown to strongly associate with dissolved and colloidal HS in natural waters. The effects of HS on the mobilization dynamics of actinides are of particular interest in risk assessment of nuclear waste repositories. Here, we present conditional equilibrium binding constants (Kc, MHA) of thorium, hafnium, and zirconium-humic acid complexes from ligand competition experiments using capillary electrophoresis coupled with ICP-MS (CE- ICP-MS). Equilibrium dialysis ligand exchange (EDLE) experiments using size exclusion via a 1000 Damembrane were also performed to validate the CE-ICP-MS analysis. Experiments were performed at pH 3.5-7 with solutions containing one tetravalent metal (Th, Hf, or Zr), Elliot soil humic acid (EHA) or Pahokee peat humic acid (PHA), and EDTA. CE-ICP-MS and EDLE experiments yielded nearly identical binding constants for the metal- humic acid complexes, indicating that both methods are appropriate for examining metal speciation at conditions lower than neutral pH. We find that tetravalent metals form strong complexes with humic acids, with Kc, MHA several orders of magnitude above REE-humic complexes. Experiments were conducted at a range of dissolved HA concentrations to examine the effect of [HA]/[Th] molar ratio on Kc, MHA. At low metal loading conditions (i.e. elevated [HA]/[Th] ratios) the ThHA binding constant reached values that were not affected by the relative abundance of humic acid and thorium. The importance of [HA]/[Th] molar ratios on constraining the equilibrium of MHA complexation is apparent when our estimated Kc, MHA values

  4. Effects of Oxygen Availability on Acetic Acid Tolerance and Intracellular pH in Dekkera bruxellensis

    OpenAIRE

    Capusoni, C.; Arioli, S.; Zambelli, P.; Moktaduzzaman, M.; Mora, D. de; Compagno, C.

    2016-01-01

    The yeast Dekkera bruxellensis, associated with wine and beer production, has recently received attention, because its high ethanol and acid tolerance enables it to compete with Saccharomyces cerevisiae in distilleries that produce fuel ethanol. We investigated how different cultivation conditions affect the acetic acid tolerance of D. bruxellensis. We analyzed the ability of two strains (CBS 98 and CBS 4482) exhibiting different degrees of tolerance to grow in the presence of acetic acid und...

  5. Effect of Aging Temperature on Corrosion Behavior of Sintered 17-4 PH Stainless Steel in Dilute Sulfuric Acid Solution

    Science.gov (United States)

    Szewczyk-Nykiel, Aneta; Kazior, Jan

    2017-07-01

    The general corrosion behavior of sintered 17-4 PH stainless steel processed under different processing conditions in dilute sulfuric acid solution at 25 °C was studied by open-circuit potential measurement and potentiodynamic polarization technique. The corrosion resistance was evaluated based on electrochemical parameters, such as polarization resistance, corrosion potential, corrosion current density as well as corrosion rate. The results showed that the precipitation-hardening treatment could significantly improve the corrosion resistance of the sintered 17-4 PH stainless steel in studied environment. As far as the influence of aging temperature on corrosion behavior of the sintered 17-4 PH stainless steel is concerned, polarization resistance and corrosion rate are reduced with increasing aging temperature from 480 up to 500 °C regardless of the temperature of solution treatment. It can be concluded that the highest corrosion resistance in 0.5 M H2SO4 solution exhibits 17-4 PH after solution treatment at 1040 °C followed by aging at 480 °C.

  6. Bicelle-based liquid crystals for NMR-measurement of dipolar couplings at acidic and basic pH values

    Energy Technology Data Exchange (ETDEWEB)

    Ottiger, Marcel; Bax, Ad [National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Laboratory of Chemical Physics (United States)

    1999-02-15

    It is demonstrated that mixtures of ditetradecyl- phosphatidylcholine or didodecyl-phoshatidylcholine and dihexyl- phosphatidylcholine in water form lyotropic liquid crystalline phases under similar conditions as previously reported for bicelles consisting of dimyristoyl-phosphatidylcholine (DMPC) and dihexanoyl- phosphatidylcholine (DHPC). The carboxy-ester bonds present in DMPC and DHPC are replaced by ether linkages in their alkyl analogs, which prevents acid- or base-catalyzed hydrolysis of these compounds. 15N-1H dipolar couplings measured for ubiquitin over the 2.3-10.4pH range indicate that this protein retains a backbone conformation which is very similar to its structure at pH 6.5 over this entire range.

  7. A Model pH Induced Drug-Delivery System Based on Poly(methacrylic acid) and its Interpolymer complex

    CERN Document Server

    Murugan, K Durai; Natarajan, P

    2015-01-01

    The dynamics and structural aspects of polymethacrylic acid bound rhodamine-123 (PMAA-R123) and its interpolymer complex with poly(vinylpyrrolidone) were investigated and the results show that these complexes have potential for use as drug-delivery system under physiological conditions. The time resolved fluorescence anisotropy decay of PMAA-R123 at different pH exhibits an associated anisotropy decay behavior characteristic of two different environments experienced by the fluorophore and decays with one shorter and another longer lifetime components. The anisotropy decay retains normal bi-exponential behavior under neutral pH. Fluorescence correlation spectroscopic investigation reveals that the attached fluorophore undergoes hydrolysis under basic condition which results in the release of the fluorophore from the polymer backbone. Shrinkage in the hydrodynamic radius of PMAA is observed on addition of the complementary polymer PVP which is attributed to the formation compact solubilised nanoparticle like ag...

  8. Interactions of Zn(II) Ions with Humic Acids Isolated from Various Type of Soils. Effect of pH, Zn Concentrations and Humic Acids Chemical Properties.

    Science.gov (United States)

    Boguta, Patrycja; Sokołowska, Zofia

    2016-01-01

    The main aim of this study was the analysis of the interaction between humic acids (HAs) from different soils and Zn(II) ions at wide concentration ranges and at two different pHs, 5 and 7, by using fluorescence and FTIR spectroscopy, as well as potentiometric measurements. The presence of a few areas of HAs structures responsible for Zn(II) complexing was revealed. Complexation at α-sites (low humified structures of low-molecular weight and aromatic polycondensation) and β-sites (weakly humified structures) was stronger at pH 7 than 5. This trend was not observed for γ-sites (structures with linearly-condensed aromatic rings, unsaturated bonds and large molecular weight). The amount of metal complexed at pH5 and 7 by α and γ-structures increased with a decrease in humification and aromaticity of HAs, contrary to β-areas where complexation increased with increasing content of carboxylic groups. The stability of complexes was higher at pH 7 and was the highest for γ-structures. At pH 5, stability decreased with C/N increase for α-areas and -COOH content increase for β-sites; stability increased with humification decrease for γ-structures. The stability of complexes at α and β-areas at pH 7 decreased with a drop in HAs humification. FTIR spectra at pH 5 revealed that the most-humified HAs tended to cause bidentate bridging coordination, while in the case of the least-humified HAs, Zn caused bidentate bridging coordination at low Zn additions and bidentate chelation at the highest Zn concentrations. Low Zn doses at pH 7 caused formation of unidentate complexes while higher Zn doses caused bidentate bridging. Such processes were noticed for HAs characterized by high oxidation degree and high oxygen functional group content; where these were low, HAs displayed bidentate bridging or even bidentate chelation. To summarize, the above studies have showed significant impact of Zn concentration, pH and some properties of HAs on complexation reactions of humic

  9. Novel membrane concept of internal pH control in electrodiaylis of amino acids using a segmented bipolar membrane (sBPM)

    NARCIS (Netherlands)

    Kattan-Readi, O.M.; Kuenen, H.J.; Zwijnenberg, H.J.; Nijmeijer, D.C.

    2013-01-01

    In electrodialysis of amino acids, pH-changes play an important role in terms of the efficiency of the process. Due to the zwitterionic character of amino acids, small pH changes may result in significant changes in the charge of the amino acids. This decreases either the recovery of the target ions

  10. Acidic deposition ("acid rain")

    Science.gov (United States)

    Schreiber, R. Kent; LaRoe, Edward T.; Farris, Gaye S.; Puckett, Catherine E.; Doran, Peter D.; Mac, Michael J.

    1995-01-01

    Acidic deposition, or "acid rain," describes any form of precipitation, including rain, snow, and fog, with a pH of 5.5 or below (Note: pH values below 7 are acidic; vinegar has a pH of 3). It often results when the acidity of normal precipitation is increased by sulfates and nitrates that are emitted into the atmosphere from burning fossil fuels. This form of airborne contamination is considered harmful, both directly and indirectly, to a host of plant and animal species.Although acid rain can fall virtually anywhere, ecological damages in environmentally sensitive areas downwind of industrial and urban emissions are a major concern. This includes areas that have a reduced capacity to neutralize acid inputs because of low alkalinity soils and areas that contain species with a low tolerance to acid conditions. To determine the distribution of acidic deposition and evaluate its biological effects, research and monitoring are being conducted by the federal government with support from states, universities, and private industry.            The national extent of the acid rain problem has been estimated by sampling water from 3,000 lakes and 500 streams (Irving 1991), representing more than 28,000 lakes and 56,000 stream reaches with a total of 200,000 km (125,000 mi). Some particularly sensitive areas, such as the Adirondack Mountain region, have been more intensively sampled and the biota examined in detail for effects from acidity.         To identify trends in aquatic ecosystems, present and historical survey data on water chemistry and associated biota are compared. In lakes, the chemical and biological history and pH trends may be inferred or reconstructed in some cases by examining assemblages of fossil diatoms and aquatic invertebrates in the sediment layers. In terrestrial ecosystems, vegetation damage is surveyed and effects of acidic deposition to plants and animals are determined from laboratory and field exposure experiments. Natural

  11. Poly-dopamine-beta-cyclodextrin: A novel nanobiopolymer towards sensing of some amino acids at physiological pH.

    Science.gov (United States)

    Hasanzadeh, Mohammad; Sadeghi, Sattar; Bageri, Leyla; Mokhtarzadeh, Ahad; Karimzadeh, Ayub; Shadjou, Nasrin; Mahboob, Soltanali

    2016-12-01

    A novel nanobiopolymer film was electrodeposited on the surface of glassy carbon through cyclic voltammetry from dopamine, β-cyclodextrin, and phosphate buffer solution in physiological pH (7.40). The electrochemical behavior of polydopamine-Beta-cyclodextrin modified glassy carbon electrode was investigated for electro-oxidation and determination of some amino acids (l-Cysteine, l-Tyrosine, l-Glycine, and l-Phenylalanine). The modified electrode was applied for selected amino acid detection at physiological pH using cyclic voltammetry, differential pulse voltammetry and chronoamperometry, chronocoulometery. The linear concentration range of the proposed sensor for the l-Glycine, l-Cysteine, l-Tyrosine, and l-Phenylalanine were 0.2-70, 0.06-0.2, 0.01-0.1, and 0.2-10μM, while low limit of quantifications were 0.2, 0.06, 0.01, and 0.2μM, respectively. The modified electrode shows many advantages as an amino acid sensor such as simple preparation method without using any specific electron transfer mediator or specific reagent, good sensitivity, short response time, and long term stability. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Human tooth enamel dissolution in citric acid as a function of degree of saturation and pH

    CERN Document Server

    Barbour, M E

    2002-01-01

    There is increasing concern among the dental community regarding the damage caused to teeth by the acids in soft drinks. Enamel dissolution in acidic solution can be reduced by addition of calcium and/or phosphate salts to increase the degree of saturation with respect to hydroxyapatite (DS sub H sub A), or by an increase in pH. In soft drinks, however, both of these approaches are associated with a reduced taste quality. The separate effects of each parameter are not known. In the work presented here, enamel dissolution was studied in citric acid solutions with compositions typical of soft drinks. Nanoindentation and atomic force microscopy (AFM) were used to investigate very early stages of enamel dissolution, with typical exposure times of 30-600 s. Preliminary investigations of the application of SIMS, ESEM and XPS to enamel dissolution studies are also reported. The individual effects of DS sub H sub A , pH and calcium and phosphate concentrations on enamel dissolution have been investigated. It was show...

  13. AN HPLC METHOD WITH UVDETECTION, PH CONTROL, AND REDUCTIVE ASCORBIC ACID FOR CYANURIC ACID ANALYSIS IN WATER

    Science.gov (United States)

    Every year over 250 million pounds of cyanuric acid (CA) and chlorinated isocyanurates are produced industrially. These compounds are standard ingredients in formulations for household bleaches, industrial cleansers, dishwasher compounds, general sanitizers, and chlorine stabiliz...

  14. Two distinct etiologies of gastric cardia adenocarcinoma: interactions among pH, Helicobacter pylori, and bile acids

    Directory of Open Access Journals (Sweden)

    Ken-ichi eMukaisho

    2015-05-01

    Full Text Available Gastric cancer can be classified as cardia and noncardia subtypes according to the anatomic site. Although the gastric cancer incidence has decreased steadily in several countries over the past 50 years, the incidence of cardia cancers and esophageal adenocarcinoma (EAC continue to increase. The etiological factors involved in the development of both cardia cancers and EACs are associated with high animal fat intake, which causes severe obesity. Central obesity plays roles in cardiac-type mucosa lengthening and partial hiatus hernia development. There are two distinct etiologies of cardia cancer subtypes: one associated with gastroesophageal reflux (GER, which predominantly occurs in patients without Helicobacter pylori (H. pylori infection and resembles EAC, and the other associated with H. pylori atrophic gastritis, which resembles noncardia cancer. The former can be developed in the environment of high volume duodenal content reflux, including bile acids and a higher acid production in H. pylori–negative patients. N-nitroso compounds, which are generated from the refluxate that includes a large volume of bile acids and are stabilized in the stomach (which has high levels of gastric acid, play a pivotal role in this carcinogenesis. The latter can be associated with the changing colonization of H. pylori from the distal to the proximal stomach with atrophic gastritis because a high concentration of soluble bile acids in an environment of low acid production is likely to act as a bactericide or chemorepellent for H. pylori in the distal stomach with H. pylori infection. The manuscript introduces new insights in causative factors of adenocarcinoma of the cardia about the role of bile acids in gastro-esophageal refluxate based upon robust evidences supporting interactions among pH, H. pylori, and bile acids.

  15. Microfiltration membranes prepared from polyethersulfone powder grafted with acrylic acid by simultaneous irradiation and their pH dependence

    Science.gov (United States)

    Deng, Bo; Li, Jingye; Hou, Zhengchi; Yao, Side; Shi, Liuqing; Liang, Guoming; Sheng, Kanglong

    2008-07-01

    Polyethersulfone (PES) powder was grafted with acrylic acid (AAc) by simultaneous γ-ray irradiation. The kinetics of the radiation induced graft polymerization was studied and the grafted PES powder was characterized. Then, microfiltration (MF) membranes were prepared from PES-g-PAAc powder with different degrees of grafting (DG) under phase inversion method. The swelling behavior and the mean pore size of MF membranes were measured, and the filtration property was tested. The results showed that the pore size and the flux of MF membranes increased with the increase in DG. And, MF membranes' properties were dependent on the pH value.

  16. Short Peptide Nucleic Acids Bind Strongly to Homopurine Tract of Double Helical RNA at pH 5.5

    OpenAIRE

    Li, Ming; Zengeya, Thomas; Rozners, Eriks

    2010-01-01

    The important role that non-coding RNA plays in cell biology makes it an attractive target for molecular recognition. However, the discovery of small molecules that bind double helical RNA selectively and may serve as biochemical probes and potential drug leads has been relatively slow. Herein, we show that peptide nucleic acids, as short as six nucleobases, bind very strongly (Ka > 107) and sequence selectively to a homopurine tract of double helical RNA at pH 5.5. The isothermal titration c...

  17. Response of alpine lakes and soils to changes in acid deposition: the MAGIC model applied to the Tatra Mountain region, Slovakia-Poland

    Directory of Open Access Journals (Sweden)

    Josef VESELÝ

    2004-02-01

    Full Text Available A dynamic process-based model of surface water acidification, MAGIC, was applied to 31 representative alpine lakes in the Tatra Mountains (~50% of all alpine lakes >0.3 ha in the lake-district. The model was calibrated to observed lake chemistry for the period 1980-2002. Surface water and soil chemistry were reconstructed from 1860 to 2002, given estimates of historical acid deposition, and forecast to 2020 based on the reduction in sulphur and nitrogen emissions presupposed by the Gothenburg Protocol. In the 1860s, all lakes were buffered by the carbonate system and only ~6% of lakes had acid neutralising capacity (ANC 50% of the SAA change in sensitive lakes with intermediate weathering rates and little soils (low BC exchangeable capacity and elevated terrestrial export of nitrate and (3 by parallel changes in concentrations of protons and aluminium (each ~20% of the SAA change in extremely sensitive lakes, with the lowest weathering rates and soil base saturation. The full implementation of the Gothenburg Protocol will not be sufficient to allow recovery of the latter group of lakes, which will remain acidified after 2020.

  18. The impact of acid deposition and forest harvesting on lakes and their forested catchments in south central Ontario: a critical loads approach

    Directory of Open Access Journals (Sweden)

    S. A. Watmough

    2002-01-01

    Full Text Available The impact of acid deposition and tree harvesting on three lakes and their representative sub-catchments in the Muskoka-Haliburton region of south-central Ontario was assessed using a critical loads approach. As nitrogen dynamics in forest soils are complex and poorly understood, for simplicity and to allow comparison among lakes and their catchments, CLs (A for both lakes and forest soils were calculated assuming that nitrate leaching from catchments will not change over time (i.e. a best case scenario. In addition, because soils in the region are shallow, base cation weathering rates for the representative sub-catchments were calculated for the entire soil profile and these estimates were also used to calculate critical loads for the lakes. These results were compared with critical loads obtained by the Steady State Water Chemistry (SSWC model. Using the SSWC model, critical loads for lakes were between 7 and 19 meq m-2yr-1 higher than those obtained from soil measurements. Lakes and forests are much more sensitive to acid deposition if forests are harvested, but two acid-sensitive lakes had much lower critical loads than their respective forested sub-catchments implying that acceptable acid deposition levels should be dictated by the most acid-sensitive lakes in the region. Under conditions that assume harvesting, the CL (A is exceeded at two of the three lakes and five of the six sub-catchments assessed in this study. However, sulphate export from catchments greatly exceeds input in bulk deposition and, to prevent lakes from falling below the critical chemical limit, sulphate inputs to lakes must be reduced by between 37% and 92% if forests are harvested. Similarly, sulphate leaching from forested catchments that are harvested must be reduced by between 16 and 79% to prevent the ANC of water draining the rooting zone from falling below 0 μeq l-1. These calculations assume that extremely low calcium leaching losses (9–27 μeq l-1 from

  19. Effect of salt and acidic pH on the stability of virulence plasmid (pYV) in Yersinia enterocolitica and expression of virulence-associated characteristics

    Science.gov (United States)

    The stability of the Yersinia enterocolitica virulence plasmid (pYV) under different NaCl concentrations and under acidic pH conditions was investigated. Exposure of five strains representing five serotypes of pYV-bearing virulent Y. enterocolitica to 0.5, 2 and 5% NaCl and under conditions of pH 4...

  20. Acidic pH triggers conformational changes at the NH2-terminal propeptide of the precursor of pulmonary surfactant protein B to form a coiled coil structure.

    Science.gov (United States)

    Bañares-Hidalgo, A; Pérez-Gil, J; Estrada, P

    2014-07-01

    Pulmonary surfactant protein SP-B is synthesized as a larger precursor, proSP-B. We report that a recombinant form of human SP-BN forms a coiled coil structure at acidic pH. The protonation of a residue with pK=4.8±0.06 is the responsible of conformational changes detected by circular dichroism and intrinsic fluorescence emission. Sedimentation velocity analysis showed protein oligomerisation at any pH condition, with an enrichment of the species compatible with a tetramer at acidic pH. Low 2,2,2,-trifluoroethanol concentration promoted β-sheet structures in SP-BN, which bind Thioflavin T, at acidic pH, whereas it promoted coiled coil structures at neutral pH. The amino acid stretch predicted to form β-sheet parallel association in SP-BN overlaps with the sequence predicted by several programs to form coiled coil structure. A synthetic peptide ((60)W-E(85)) designed from the sequence of the amino acid stretch of SP-BN predicted to form coiled coil structure showed random coil conformation at neutral pH but concentration-dependent helical structure at acidic pH. Sedimentation velocity analysis of the peptide indicated monomeric state at neutral pH (s20, w=0.55S; Mr~3kDa) and peptide association (s20, w=1.735S; Mr=~14kDa) at acidic pH, with sedimentation equilibrium fitting to a Monomer-Nmer-Mmer model with N=6 and M=4 (Mr=14692Da). We propose that protein oligomerisation through coiled-coil motifs could then be a general feature in the assembly of functional units in saposin-like proteins in general and in the organization of SP-B in a functional surfactant, in particular. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. The effects of temperature, pH and redox state on the stability of glutamic acid in hydrothermal fluids

    Science.gov (United States)

    Lee, Namhey; Foustoukos, Dionysis I.; Sverjensky, Dimitri A.; Cody, George D.; Hazen, Robert M.

    2014-06-01

    Natural hydrothermal vent environments cover a wide range of physicochemical conditions involving temperature, pH and redox state. The stability of simple biomolecules such as amino acids in such environments is of interest in various fields of study from the origin of life to the metabolism of microbes at the present day. Numerous previous experimental studies have suggested that amino acids are unstable under hydrothermal conditions and decompose rapidly. However, previous studies have not effectively controlled the redox state of the hydrothermal fluids. Here we studied the stability of glutamate with and without reducing hydrothermal conditions imposed by 13 mM aqueous H2 at temperatures of 150, 200 and 250 °C and initial (25 °C) pH values of 6 and 10 in a flow-through hydrothermal reactor with reaction times from 3 to 36 min. We combined the experimental measurements with theoretical calculations to model the in situ aqueous speciation and pH values. As previously observed under hydrothermal conditions, the main reaction involves glutamate cyclizing to pyroglutamate through a simple dehydration reaction. However, the amounts of decomposition products of the glutamate detected, including succinate, formate, carbon dioxide and ammonia depend on the temperature, the pH and particularly the redox state of the fluid. In the absence of dissolved H2, glutamate decomposes in the sequence glutamate, glutaconate, α-hydroxyglutarate, ketoglutarate, formate and succinate, and ultimately to CO2 and micromolar quantities of H2(aq). Model speciation calculations indicate the CO2, formate and H2(aq) are not in metastable thermodynamic equilibrium. However, with 13 mM H2(aq) concentrations, the amounts of decomposition products are suppressed at all temperatures and pH values investigated. The small amounts of CO2 and formate present are calculated to be in metastable equilibrium with the H2. It is further proposed that there is a metastable equilibrium between glutamate

  2. Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA): emerging contaminants of increasing concern in fish from Lake Varese, Italy.

    Science.gov (United States)

    Squadrone, S; Ciccotelli, V; Prearo, M; Favaro, L; Scanzio, T; Foglini, C; Abete, M C

    2015-07-01

    Perfluoroalkylated substances (PFASs) are highly fluorinated aliphatic compounds with high thermal and chemical stability, used in a range of industrial applications. Extensive screening analyses in biota samples from all over the world have shown the bioaccumulation of PFAS into higher trophic levels in the food chain. Perfluorooctane sulfonic acid (PFOS) and perfluoroctanoic acid (PFOA) are potential reproductive and developmental toxicants and are considered to be emerging endocrine disrupters. Ingestion of fish and other seafood is considered the main source of exposure of these contaminants. Here, we quantified PFOS and PFOA by LC-MS/MS in muscle samples of European perch from Lake Varese, Italy. PFOS was detected in all samples with concentrations of up to 17.2 ng g(-1). Although the reported values were lower than the recommended total daily intake (TDI) proposed by the European Food Safety Authority (EFSA), fish from Lake Varese may be a significant source of dietary PFOS exposure.

  3. Copper availability and bioavailability are controlled by rhizosphere pH in rape grown in an acidic Cu-contaminated soil

    Energy Technology Data Exchange (ETDEWEB)

    Chaignon, Valerie; Quesnoit, Marie [INRA, UMR 1222 Eco and Sols Ecologie fonctionnelle and Biogeochimie des Sols (INRA-IRD-SupAgro), Place Viala, F-34060 Montpellier (France); Hinsinger, Philippe, E-mail: philippe.hinsinger@supagro.inra.f [INRA, UMR 1222 Eco and Sols Ecologie fonctionnelle and Biogeochimie des Sols (INRA-IRD-SupAgro), Place Viala, F-34060 Montpellier (France)

    2009-12-15

    We evaluated how root-induced changes in rhizosphere pH varied and interacted with Cu availability and bioavailability in an acidic soil. Rape was grown on a Cu-contaminated acidic soil, which had been limed at 10 rates. Soil Cu bioavailability was not influenced by liming. However, liming significantly decreased CaCl{sub 2}-extracted Cu for pH between 3.7 and 5.1. Little effect was found for pH above 5.1. For soil pH < 4.4, CaCl{sub 2}-Cu contents were smaller in rhizosphere than uncropped soil. Rhizosphere alkalisation occurred at pH < 4.8, while acidification occurred at greater pH. This explained the changes of CaCl{sub 2}-Cu in the rhizosphere at low pH and the absence of pH dependency of Cu bioavailability to rape. In addition, apoplastic Cu in roots increased with increasing soil pH, most probably as a result of increased dissociation and affinity of cell wall compounds for Cu. - Root-induced increase in pH reduces Cu availability in the rhizosphere and Cu bioavailability to rape.

  4. Survival of lactic acid and chlorine dioxide treated Campylobacter jejuni under suboptimal conditions of pH, temperature and modified atmosphere

    DEFF Research Database (Denmark)

    Smigic, Nada; Rajkovic, Andreja; Nielsen, Dennis Sandris;

    2010-01-01

    Campylobacter jejuni cells treated with lactic acid (LA, 3% lactic acid, pH 4.0, 2 min) or chlorine dioxide (ClO(2), 20 ppm, 2 min) were inoculated in Bolton broth (pH 6.0) and incubated under 80% O(2)/20% N(2), 80% CO(2)/20% N(2), air or micro-aerophilic (10% CO(2)/85% N(2)/5% O(2)) atmosphere, at 4 degrees C...

  5. Intracellular pH as an indicator of viability and resuscitation of Campylobacter jejuni after decontamination with lactic acid

    DEFF Research Database (Denmark)

    Smigic, Nada; Rajkovic, Andreja; Nielsen, Dennis Sandris;

    2009-01-01

    The aim of the study was to determine intracellular pH (pH(i)) as an indicator of the physiological state of two Campylobacter jejuni strains (603 and 608) at the single cell level after bactericidal treatment with lactic acid (3% v/v lactic acid, pH 4.0, 0.85% w/v NaCl) and during recovery and s...

  6. Silica precipitation in acidic solutions: mechanism, pH effect, and salt effect.

    Science.gov (United States)

    Gorrepati, Elizabeth A; Wongthahan, Pattanapong; Raha, Sasanka; Fogler, H Scott

    2010-07-06

    This study is the first to show that silica precipitation under very acidic conditions ([HCl] = 2-8 M) proceeds through two distinct steps. First, the monomeric form of silica is quickly depleted from solution as it polymerizes to form primary particles approximately 5 nm in diameter. Second, the primary particles formed then flocculate. A modified Smoluchowski equation that incorporates a geometric population balance accurately describes the exponential growth of silica flocs. Variation of the HCl concentration between 2 and 8 M further showed that polymerization to form primary particles and subsequent particle flocculation become exponentially faster with increasing acid concentration. The effect of salt was also studied by adding 1 M chloride salts to the solutions; it was found that salts accelerated both particle formation and growth rates in the order: AlCl(3) > CaCl(2) > MgCl(2) > NaCl > CsCl > no salt. It was also found that ionic strength, over cation identity, determines silica polymerization and particle flocculation rates. This research reveals that precipitation of silica products from acid dissolution of minerals can be studied apart from the mineral dissolution process. Thus, silica product precipitation from mineral acidization follows a two-step process--formation of 5 nm primary particles followed by particle flocculation--which becomes exponentially faster with increasing HCl concentration and with salts accelerating the process in the above order. This result has implications for any study of acid dissolution of aluminosilicate or silicate material. In particular, the findings are applicable to the process of acidizing oil-containing rock formations, a common practice of the petroleum industry where silica dissolution products encounter a low-pH, salty environment within the oil well.

  7. Continuous intragastric pH monitoring in the evaluation of ebrotidine, cimetidine and placebo on gastric acidity in healthy volunteers.

    Science.gov (United States)

    Muñoz-Navas, M; Honorato, J; Reina-Ariño, M; Márquez, M; Herrero, E; Villamayor, F; Torres, J; Roset, P N; Fíllat, O; Camps, F; Ortiz, J A

    1997-04-01

    This study was conducted to determine the efficacy and tolerance of ebrotidine (N-[(E)-[[2-[[[2-[(diaminomethylene)amino]-4-thiazolyl) methyl]thio]ethyl]amino]methylene]-4-bromo-benzenesulfonamide, CAS 100981-43.9, FI-3542), a new H2-receptor antagonist, on reducing gastric acidity after a single 800 mg dose, compared with cimetidine 800 mg once daily and placebo by means of a continuous intragastric pH monitoring. A total of 30 healthy volunteers were allocated to receive in a double blind, parallel design the study medication. Clinical observations, physical examinations and visual analogue scales (VAS) were performed during the study to assess the tolerability of the three treatments. Ebrotidine and cimetidine caused a greater and longer-lasting gastric acid inhibition than placebo. With ebrotidine, significantly (p < 0.05) higher median pH values (and interquartile range, IQR) were reached in the post-administration (2.61, IQR 2.02-3.93), postprandial (3.38, IQR 2.82-3.91) and nocturnal (2.83, IQR 1.69-3.77) periods than with placebo: 1.82 (IQR, 1.66-2.09), 2.81 (IQR, 2.02-3.28), and 1.89 (IQR, 1.44-2.13), respectively. Cimetidine showed significant differences compared to placebo in the post-administration (2.36, IQR 1.89-3.46) and nocturnal (2.46, IQR 1.88-4.33) periods. No statistical differences were observed between the active treatments. Ebrotidine caused a significantly higher percentage of time above pH 2.0 in the post-administration and nocturnal periods compared to placebo (p < 0.05), and above pH 3.0 in the post-administration, postprandial and nocturnal periods. No serious adverse effects, or disturbances in the VAS or in the vital signs were reported, and all medications were well tolerated. It is concluded that a single dose of ebrotidine 800 mg is as effective as cimetidine 800 mg in reducing total and nocturnal intragastric acidity. The study also confirms the excellent safety profile of the new drug.

  8. Lake Sediments from Dianchi Lake:A Phosphorus Sink or Source?

    Institute of Scientific and Technical Information of China (English)

    GAO Li; YANG Hao; ZHOU Jian-Min; Lü Jun-Jie

    2004-01-01

    Dianchi Lake is a highly eutrophic lake in southwestern China where phosphorus (P) is the limiting element for eutrophication and where lake sediments play an important role in the P cycle. One hundred and eighteen sites were sampled throughout Dianchi Lake in 2002 to investigate the P loading of the lake sediments, while fresh surface sediments were studied in the laboratory to clarify its role for phosphorus. The results showed that concentrations of total phosphorus (TP) in sediments were very high, with a maximum value of 6.66 g kg-1, and decreased with sediment depth. P adsorption on surface sediments was rapid with adsorption amounts higher in acidic than in alkaline conditions. The release experiments showed that P release increased as pH rose from 7.0 to 10.5. Additionally, compared with aerobic conditions, P release was much higher under anaerobic conditions, especially with low P content in the lake water. At present, the sediments in Dianchi Lake still function as a sink for phosphorus at high P levels in lake water. However, if the external P load was reduced and P content in lake water became low, the sediment would have a large potential for P release under anaerobic conditions.

  9. Phosphatidic acid is a pH biosensor that links membrane biogenesis to metabolism

    NARCIS (Netherlands)

    Young, B.P.; Shin, J.J.H.; Orij, R.; Chao, J.T.; Li, S.C.; Guan, X.L.; Khong, A.; Jan, E.; Wenk, M.R.; Prinz, W.A.; Smits, G.J.; Loewen, C.J.R.

    2010-01-01

    Recognition of lipids by proteins is important for their targeting and activation in many signaling pathways, but the mechanisms that regulate such interactions are largely unknown. Here, we found that binding of proteins to the ubiquitous signaling lipid phosphatidic acid (PA) depended on intracell

  10. The volume-regulated anion channel (LRRC8) in nodose neurons is sensitive to acidic pH

    Science.gov (United States)

    Wang, Runping; Lu, Yongjun; Gunasekar, Susheel; Zhang, Yanhui; Benson, Christopher J.; Chapleau, Mark W.; Sah, Rajan; Abboud, François M.

    2017-01-01

    The leucine rich repeat containing protein 8A (LRRC8A), or SWELL1, is an essential component of the volume-regulated anion channel (VRAC) that is activated by cell swelling and ionic strength. We report here for the first time to our knowledge its expression in a primary cell culture of nodose ganglia neurons and its localization in the soma, neurites, and neuronal membrane. We show that this neuronal VRAC/SWELL1 senses low external pH (pHo) in addition to hypoosmolarity. A robust sustained chloride current is seen in 77% of isolated nodose neurons following brief exposures to extracellular acid pH. Its activation involves proton efflux, intracellular alkalinity, and an increase in NOX-derived H2O2. The molecular identity of both the hypoosmolarity-induced and acid pHo–conditioned VRAC as LRRC8A (SWELL1) was confirmed by Cre-flox–mediated KO, shRNA-mediated knockdown, and CRISPR/Cas9-mediated LRRC8A deletion in HEK cells and in primary nodose neuronal cultures. Activation of VRAC by low pHo reduces neuronal injury during simulated ischemia and N-methyl-D-aspartate–induced (NMDA-induced) apoptosis. These results identify the VRAC (LRRC8A) as a dual sensor of hypoosmolarity and low pHo in vagal afferent neurons and define the mechanisms of its activation and its neuroprotective potential. PMID:28289711

  11. The volume-regulated anion channel (LRRC8) in nodose neurons is sensitive to acidic pH.

    Science.gov (United States)

    Wang, Runping; Lu, Yongjun; Gunasekar, Susheel; Zhang, Yanhui; Benson, Christopher J; Chapleau, Mark W; Sah, Rajan; Abboud, François M

    2017-03-09

    The leucine rich repeat containing protein 8A (LRRC8A), or SWELL1, is an essential component of the volume-regulated anion channel (VRAC) that is activated by cell swelling and ionic strength. We report here for the first time to our knowledge its expression in a primary cell culture of nodose ganglia neurons and its localization in the soma, neurites, and neuronal membrane. We show that this neuronal VRAC/SWELL1 senses low external pH (pHo) in addition to hypoosmolarity. A robust sustained chloride current is seen in 77% of isolated nodose neurons following brief exposures to extracellular acid pH. Its activation involves proton efflux, intracellular alkalinity, and an increase in NOX-derived H2O2. The molecular identity of both the hypoosmolarity-induced and acid pHo-conditioned VRAC as LRRC8A (SWELL1) was confirmed by Cre-flox-mediated KO, shRNA-mediated knockdown, and CRISPR/Cas9-mediated LRRC8A deletion in HEK cells and in primary nodose neuronal cultures. Activation of VRAC by low pHo reduces neuronal injury during simulated ischemia and N-methyl-D-aspartate-induced (NMDA-induced) apoptosis. These results identify the VRAC (LRRC8A) as a dual sensor of hypoosmolarity and low pHo in vagal afferent neurons and define the mechanisms of its activation and its neuroprotective potential.

  12. A comparison of three pH control methods for revealing effects of undissociated butyric acid on specific butanol production rate in batch fermentation of Clostridium acetobutylicum

    Science.gov (United States)

    2013-01-01

    pH control has been essential for butanol production with Clostridium acetobutylicum. However, it is not very clear at what pH level the acid crash will occur, at what pH level butanol production will be dominant, and at what pH level butyric acid production will be prevailing. Furthermore, contradictory results have been reported about required acidic conditions for initiation of solventogenesis. In this study, with the aim of further understanding the role of undissociated butyric acid in butanol production, we investigated the correlation between undissociated butyric acid concentration and specific butanol production rate in batch fermentation of Clostridium acetobutylicum by comparing three pH control approaches: NaOH neutralization (at 12, 24 or 36 h), CaCO3 supplementation (2, 5, or 8 g/l) and NaOAc buffering (pH 4.6, 5.0 or 5.6). By neutralizing the fermentation pH to ~5.0 at different time, we observed that neutralization should take place at the beginning of exponential phase (12 h), and otherwise resulting in lower concentrations of undissociated butyric acid, cell biomass and final butanol. CaCO3 supplementation extended cell growth to 36 h and resulted in higher butyrate yield under 8 g/L of CaCO3. In the NaOAc buffering, the highest specific butanol rate (0.58 h−1) was associated with the highest undissociated butyric acid (1.92 g/L). The linear correlation of the undissociated butyric acid with the specific butanol production rates suggested the undissociated butyric acid could be the major driving force for butanol production. PMID:23294525

  13. Effects of Humic Acid and Solution pH on Dispersion of Na—and Ca—Soil Clays

    Institute of Scientific and Technical Information of China (English)

    LANYEQING; HUQIONGYING; 等

    1996-01-01

    Dispersed soil clays have a negative impact on soil structure and contribute to soil erosion and contaminant movement.In this study,two typical soils from the south of China were chosen for investigating roles of pH and humic acid(HA) on dispersion of soil clays.Critical flocculation concentration (CFC) of the soil clay suspension was determined by using light transmission at a wavelength of 600 nm.The results indicated that effects of pH and HA on dispersion of the soil clays were closely related to the type of the major minerals makin up the soil and to the valence of the exchangeable cations as well.At four rates of pH(4,6,8and 10),the CFC for the Na-yellow-brown soil treated with H2O2 was increased from 0.32 to 0.56,6.0 to 14.0,10.0 to 24.6 and 26.0 to 52.0mmol L-1 NaCl,respectively when Na-HA was added at the rate of from 0 to 40mgL-1,With the same Na-HA addition and three pH(6,8and 10)treatments,the CFC for the Na-red soil was incresed from 0.5 to 20.0,1.0 to 40.0 and 6.0 to 141.0mmol L-1 NaCl,respectively.Obviously,pH and HA has greater effects on clay dispersion of the red soil(dominated by 1:1 minerals and oxides) than on that of the yellow-brown soil(dominated by 2:1minerals).However,at three rates of pH(6,8and 10) and with the addition of Ca-HA from 0 to 40mg L-1,the CFC of the Ca-yellow-brown soil and Ca-red soil treated with H2O2 was increased from 0.55 to 0.81,0.75 to 1.28,0.55 to 1.45and 0.038 to 0.266.0.25 to 0.62,0.7to 1.6mmol CaCl2 L-1,respectively.So,Na-soil claye are more sensitive to pH and HA than Ca-soil clays.

  14. Effects of solids concentration, pH and carbon addition on the production rate and composition of volatile fatty acids in prefermenters using primary sewage sludge

    DEFF Research Database (Denmark)

    Zeng, Raymond Jianxiong; Yuan, Z.; Keller, J.

    2006-01-01

    in prefermenters. In this study, a series of controlled batch experiments were conducted with sludge from a full-scale prefermenter to determine the impact of solids concentration, pH and addition of molasses on prefermentation processes. It was found that an increase in solids concentration enhanced total VFA...... production with an increased propionic acid fraction. The optimal pH for prefermentation was in the range of 6-7 with significant productivity loss when pH was below 5.5. Molasses addition significantly increased the production of VFAs particularly the propionic acid. However, the fermentation rate...

  15. Microbial Diversity and Its Relationship to Physicochemical Characteristics of the Water in Two Extreme Acidic Pit Lakes from the Iberian Pyrite Belt (SW Spain.

    Directory of Open Access Journals (Sweden)

    Esther Santofimia

    Full Text Available The Iberian Pyrite Belt (IPB hosts one of the world's largest accumulations of acidic mine wastes and pit lakes. The mineralogical and textural characteristics of the IPB ores have favored the oxidation and dissolution of metallic sulfides, mainly pyrite, and the subsequent formation of acidic mining drainages. This work reports the physical properties, hydrogeochemical characteristics, and microbial diversity of two pit lakes located in the IPB. Both pit lakes are acidic and showed high concentrations of sulfate and dissolved metals. Concentrations of sulfate and heavy metals were higher in the Nuestra Señora del Carmen lake (NSC by one order of magnitude than in the Concepción (CN lake. The hydrochemical characteristics of NSC were typical of acid mine waters and can be compared with other acidic environments. When compared to other IPB acidic pit lakes, the superficial water of CN is more diluted than that of any of the others due, probably, to the strong influence of runoff water. Both pit lakes showed chemical and thermal stratification with well defined chemoclines. One particular characteristic of NSC is that it has developed a chemocline very close to the surface (2 m depth. Microbial community composition of the water column was analyzed by 16S and 18S rRNA gene cloning and sequencing. The microorganisms detected in NSC were characteristic of acid mine drainage (AMD, including iron oxidizing bacteria (Leptospirillum, Acidithiobacillus ferrooxidans and facultative iron reducing bacteria and archaea (Acidithiobacillus ferrooxidans, Acidiphilium, Actinobacteria, Acidimicrobiales, Ferroplasma detected in the bottom layer. Diversity in CN was higher than in NSC. Microorganisms known from AMD systems (Acidiphilium, Acidobacteria and Ferrovum and microorganisms never reported from AMD systems were identified. Taking into consideration the hydrochemical characteristics of these pit lakes and the spatial distribution of the identified

  16. Novel Halomonas sp. B15 isolated from Larnaca Salt Lake in Cyprus that generates vanillin and vanillic acid from ferulic acid.

    Science.gov (United States)

    Vyrides, Ioannis; Agathangelou, Maria; Dimitriou, Rodothea; Souroullas, Konstantinos; Salamex, Anastasia; Ioannou, Aristostodimos; Koutinas, Michalis

    2015-08-01

    Vanillin is a high value added product with many applications in the food, fragrance and pharmaceutical industries. A natural and low-cost method to produce vanillin is by microbial bioconversions through ferulic acid. Until now, limited microorganisms have been found capable of bioconverting ferulic acid to vanillin at high yield. This study aimed to screen halotolerant strains of bacteria from Larnaca Salt Lake which generate vanillin and vanillic acid from ferulic acid. From a total of 50 halotolenant/halophilic strains 8 grew in 1 g/L ferulic acid and only 1 Halomonas sp. B15 and 3 Halomonas elognata strains were capable of bioconverting ferulic acid to vanillic acid at 100 g NaCl/L. The highest vanillic acid (365 mg/L) at these conditions generated by Halomonas sp. B15 which corresponds to ferulic acid bioconversion yield of 36.5%. Using the resting cell technique with an initial ferulic acid concentration of 0.5 g/L at low salinity, the highest production of vanillin (245 mg/L) took place after 48 h, corresponding to a bioconversion yield of 49%. This is the first reported Halomonas sp. with high yield of vanillin production from ferulic acid at low salinity.

  17. Atmospheric oxalic acid and related secondary organic aerosols in Qinghai Lake, a continental background site in Tibet Plateau

    Science.gov (United States)

    Meng, Jingjing; Wang, Gehui; Li, Jianjun; Cheng, Chunlei; Cao, Junji

    2013-11-01

    Summertime PM2.5 aerosols collected from Qinghai Lake (3200 m a.s.l.), a remote continental site in the northeastern part of Tibetan Plateau, were analyzed for dicarboxylic acids (C2-C11), ketocarboxylic acids and α-dicarbonyals. Oxalic acid (C2) is the dominant dicarboxylic acid in the samples, followed by malonic, succinic and azelaic acids. Total dicarboxylic acids (231 ± 119 ng m-3), ketocarboxylic acids (8.4 ± 4.3 ng m-3), and α-dicarbonyls (2.7 ± 2.1 ng m-3) at the Tibetan background site are 2-5 times less than those detected in lowland areas such as 14 Chinese megacities. Compared to those in other urban and marine areas enhancements in relative abundances of C2/total diacids and diacids-C/WSOC of the PM2.5 samples suggest that organic aerosols in the region are more oxidized due to strong solar radiation. Molecular compositions and air mass trajectories demonstrate that the above secondary organic aerosols in the Qinghai Lake atmosphere are largely derived from long-range transport. Ratios of oxalic acid, glyoxal and methylglyoxal to levoglucosan in PM2.5 aerosols emitted from household burning of yak dung, a major energy source for Tibetan in the region, are 30-400 times lower than those in the ambient air, which further indicates that primary emission from biomass burning is a negligible source of atmospheric oxalic acid and α-dicarbonyls at this background site.

  18. Immune factors and fatty acid composition in human milk from river/lake, coastal and inland regions of China.

    Science.gov (United States)

    Urwin, Heidi J; Zhang, Jian; Gao, Yixiong; Wang, Chunrong; Li, Lixiang; Song, Pengkun; Man, Qingqing; Meng, Liping; Frøyland, Livar; Miles, Elizabeth A; Calder, Philip C; Yaqoob, Parveen

    2013-06-01

    Breast milk fatty acid composition may be affected by the maternal diet during gestation and lactation. The influence of dietary and breastmilk fatty acids on breast milk immune factors is poorly defined. We determined the fatty acid composition and immune factor concentrations of breast milk from women residing in river/lake, coastal and inland regions of China, which differ in their consumption of lean fish and oily fish. Breast milk samples were collected on days 3–5 (colostrum), 14 and 28 post-partum (PP) and analysed for soluble CD14 (sCD14), transforming growth factor (TGF)-b1, TGF-b2, secretory IgA (sIgA) and fatty acids. The fatty acid composition of breast milk differed between the regions and with time PP. The concentrations of all four immune factors in breast milk decreased over time, with sCD14, sIgA and TGF-b1 being highest in the colostrum in the river and lake region. Breast milk DHA and arachidonic acid (AA) were positively associated, and g-linolenic acid and EPA negatively associated, with the concentrations of each of the four immune factors. In conclusion, breast milk fatty acids and immune factors differ between the regions in China characterised by different patterns of fish consumption and change during the course of lactation. A higher breast milk DHA and AA concentration is associated with higher concentrations of immune factors in breast milk, suggesting a role for these fatty acids in promoting gastrointestinal and immune maturation of the infant.

  19. Silicification and biosilicification Part 5. An investigation of the silica structures formed at weakly acidic pH and neutral pH as facilitated by cationically charged macromolecules

    Energy Technology Data Exchange (ETDEWEB)

    Patwardhan, Siddharth V.; Clarson, Stephen J

    2003-06-10

    Biosilicification in diatoms has been reported to occur at (or close to) neutral pH and it has been shown that protein molecules can act as catalysts/templates/scaffolds for this elegant materials chemistry. Here we report the formation of silica spheres from an aqueous silica precursor as facilitated by both poly-L-lysine (PLL) and poly(allylamine hydrochloride) (PAH) at pH 6.0 and under ambient conditions. It was observed by scanning electron microscopy (SEM) that there were morphological differences in the silica formed at pH 6 when compared to the silica morphologies formed using the same macromolecules at neutral pH. Notably, a bimodal distribution of silica particles was seen for both the PLL and PAH systems at pH 6. These results are compared and contrasted with those previously reported for the pH dependence of silicification and biosilicification and in particular, those obtained for the pH dependence of silica formation in the presence silaffin proteins isolated form the diatom C. fusiformis. The findings for these cationically charged macromolecules suggest that lysine may be an important amino acid in the primary sequence of proteins that catalyze the formation of silica structures in vivo.

  20. Influence of lactic acid bacteria, probiotic cultures and pH value in fermented yoghurt drink to sensory quality

    Directory of Open Access Journals (Sweden)

    Hana Šulcerová

    2009-01-01

    Full Text Available Nowadays, we can see on market mainly fermented milk products with addition of probiotic microorganisms, especially strains of Lactobacillus and Bifidobacterium. We can meet also other types of pro­bio­tic products. It is recommended to consume at least 100 grams of fermented milk products with mi­ni­mal concentration of 106 of probiotics in one gram or mililitr of product daily for reaching positive effect on men’s health. During fermentation of the carbohydrates, proteins and lipids are disunite and many of aromatic compounds ane compose. They give a typical sensory characteristic to fermented milk products. For quality and quantity level of probiotics, changes of pH value and sensory qua­li­ty of five kinds of fermented milk product Yoghurt Drink with different flavour were analyzed during the whole expiration period (28 days. Obtained results were statistically evaluated via the analysis of variance and the method of multiple comparison according to Tukey test (P < 0,010 and (P < 0,001. During the minimal endurance time lactic acid bacteria and Bifidobacterium sp. were evaluated and changes of descriptors and pH value were detected. Number of LAB was up to 107 CFU/ml in all samples during 28 days of analysis. Only at sample 2 the number of LAB was 106 CFU/ml. Bifidobacterium sp. grew about degree. The number of LAB and Bifidobacterium sp. of yoghurt drink correspond with public notice number 77/2003 Sb, LAB 107 nad Bifidobacterium sp. 106 KTJ / ml. During 28 days of storage the pH value decreased. The biggest pH drop was recorded between 21. and 28. days of sto­ra­ge in all samples. The beginning pH value was 4.03–4.07 and the final value was between 3.80–3.95.The results of sensory evaluation processed by analysis of dispersion according to type were statistically conlusive in descriptors thickness, texture, intensity of smell, pleasantness of taste and general impression. The results of sensory evaluation processed by

  1. Spatial patterns of mercury in biota of Adirondack, New York lakes.

    Science.gov (United States)

    Yu, Xue; Driscoll, Charles T; Montesdeoca, Mario; Evers, David; Duron, Melissa; Williams, Kate; Schoch, Nina; Kamman, Neil C

    2011-10-01

    We studied the spatial distribution patterns of mercury (Hg) in lake water, littoral sediments, zooplankton, crayfish, fish, and common loons in 44 lakes of the Adirondacks of New York State, USA, a region that has been characterized as a "biological Hg hotspot". Our study confirmed this pattern, finding that a substantial fraction of the lakes studied had fish and loon samples exceeding established criteria for human and wildlife health. Factors accounting for the spatial variability of Hg in lake water and biota were lake chemistry (pH, acid neutralizing capacity (ANC), percent carbon in sediments), biology (taxa presence, trophic status) and landscape characteristics (land cover class, lake elevation). Hg concentrations in zooplankton, fish and common loons were negatively associated with the lake water acid-base status (pH, ANC). Bioaccumulation factors (BAF) for methyl Hg (MeHg) increased from crayfish (mean log(10) BAF = 5.7), to zooplankton (5.9), to prey fish (6.2), to larger fish (6.3), to common loons (7.2). MeHg BAF values in zooplankton, crayfish, and fish (yellow perch equivalent) all increased with increasing lake elevation. Our findings support the hypothesis that bioaccumulation of MeHg at the base of the food chain is an important controller of Hg concentrations in taxa at higher trophic levels. The characteristics of Adirondack lake-watersheds (sensitivity to acidic deposition; significant forest and wetland land cover; and low nutrient inputs) contribute to elevated Hg concentrations in aquatic biota.

  2. Lysozyme stability and amyloid fibrillization dependence on Hofmeister anions in acidic pH.

    Science.gov (United States)

    Poniková, Slavomíra; Antošová, Andrea; Demjén, Erna; Sedláková, Dagmar; Marek, Jozef; Varhač, Rastislav; Gažová, Zuzana; Sedlák, Erik

    2015-09-01

    We have explored an effect of Hofmeister anions, Na2SO4, NaCl, NaBr, NaNO3, NaSCN and NaClO4, on stability and amyloid fibrillization of hen egg white lysozyme at pH 2.7. The stability of the protein was analyzed by differential scanning calorimetry. The Hofmeister effect of the anions was assessed by the parameter dT trs/d[anion] (T trs, transition temperature). We show that dT trs/d[anion] correlates with anion surface tension effects and anion partition coefficients indicating direct interactions between anions and lysozyme. The kinetic of amyloid fibrillization of lysozyme was followed by Thioflavin T (ThT) fluorescence. Negative correlation between dT trs/d[anion] and the nucleation rate of fibrillization in the presence of monovalent anions indicates specific effect of anions on fibrillization rate of lysozyme. The efficiency of monovalent anions to accelerate fibrillization correlates with inverse Hofmeister series. The far-UV circular dichroism spectroscopy and atomic force microscopy findings show that conformational properties of fibrils depend on fibrillization rate. In the presence of sodium chloride, lysozyme forms typical fibrils with elongated structure and with the secondary structure of the β-sheet. On the other hand, in the presence of both chaotropic perchlorate and kosmotropic sulfate anions, the fibrils form clusters with secondary structure of β-turn. Moreover, the acceleration of fibril formation is accompanied by decreased amount of the formed fibrils as indicated by ThT fluorescence. Taken together, our study shows Hofmeister effect of monovalent anions on: (1) lysozyme stability; (2) ability to accelerate nucleation phase of lysozyme fibrillization; (3) amount, and (4) conformational properties of the formed fibrils.

  3. Electrolytic extraction drives volatile fatty acid chain elongation through lactic acid and replaces chemical pH control in thin stillage fermentation.

    Science.gov (United States)

    Andersen, Stephen J; Candry, Pieter; Basadre, Thais; Khor, Way Cern; Roume, Hugo; Hernandez-Sanabria, Emma; Coma, Marta; Rabaey, Korneel

    2015-01-01

    Volatile fatty acids (VFA) are building blocks for the chemical industry. Sustainable, biological production is constrained by production and recovery costs, including the need for intensive pH correction. Membrane electrolysis has been developed as an in situ extraction technology tailored to the direct recovery of VFA from fermentation while stabilizing acidogenesis without caustic addition. A current applied across an anion exchange membrane reduces the fermentation broth (catholyte, water reduction: H2O + e(-) → ½ H2 + OH(-)) and drives carboxylate ions into a clean, concentrated VFA stream (anolyte, water oxidation: H2O → 2e(-) + 2 H(+) + O2). In this study, we fermented thin stillage to generate a mixed VFA extract without chemical pH control. Membrane electrolysis (0.1 A, 3.22 ± 0.60 V) extracted 28 ± 6 % of carboxylates generated per day (on a carbon basis) and completely replaced caustic control of pH, with no impact on the total carboxylate production amount or rate. Hydrogen generated from the applied current shifted the fermentation outcome from predominantly C2 and C3 VFA (64 ± 3 % of the total VFA present in the control) to majority of C4 to C6 (70 ± 12 % in the experiment), with identical proportions in the VFA acid extract. A strain related to Megasphaera elsdenii (maximum abundance of 57 %), a bacteria capable of producing mid-chain VFA at a high rate, was enriched by the applied current, alongside a stable community of Lactobacillus spp. (10 %), enabling chain elongation of VFA through lactic acid. A conversion of 30 ± 5 % VFA produced per sCOD fed (60 ± 10 % of the reactive fraction) was achieved, with a 50 ± 6 % reduction in suspended solids likely by electro-coagulation. VFA can be extracted directly from a fermentation broth by membrane electrolysis. The electrolytic water reduction products are utilized in the fermentation: OH(-) is used for pH control without added chemicals, and H2 is

  4. Effect of ph on the Electrodeposition of Cu(In, Al)Se2 from Aqueous Solution in Presence of Citric Acid as Complexing Agent

    Science.gov (United States)

    Ganjkhanlou, Yadolah; Ebadzadeh, Touradj; Kazemzad, Mahmood; Maghsoudipour, Amir; Kianpour-Rad, Mansoor

    2015-05-01

    Effect of pH on the one-step electrodeposition of Cu(In, Al)Se2 chalcopyrite layer in the presence of citric acid has been investigated by applying different electrochemical and characterization techniques. It has been observed that at pH of 1.5, nanocrystalline phase of chalcopyrite and small amount of binary phase of Cu2Se with overall composition of Cu0.91In0.32Al0.39Se2 have been deposited. On the other hand, at pH of 4, the film composition changed to Cu1.9In0.05Al0.21Se2 and an additional binary phase of copper selenide (CuSe) has also been formed. Morphological investigation illustrated that smooth and compact layer with fine spherical particles having the size of 20 nm has been obtained at pH of 1.5 whereas mixture of planar and spherical particles with size of 450-550 nm have been formed at pH of 4. In alkaline environment (pH 9), the deposition current has been noticeably decreased and no deposition occurred due to the formation of a stable complex of citric acid with metal ions. The mechanism of citric acid interaction with metal ions at different pH has also been studied by cyclic voltammetry measurement.

  5. The precipitation of indium at elevated pH in a stream influenced by acid mine drainage.

    Science.gov (United States)

    White, Sarah Jane O; Hussain, Fatima A; Hemond, Harold F; Sacco, Sarah A; Shine, James P; Runkel, Robert L; Walton-Day, Katherine; Kimball, Briant A

    2017-01-01

    Indium is an increasingly important metal in semiconductors and electronics and has uses in important energy technologies such as photovoltaic cells and light-emitting diodes (LEDs). One significant flux of indium to the environment is from lead, zinc, copper, and tin mining and smelting, but little is known about its aqueous behavior after it is mobilized. In this study, we use Mineral Creek, a headwater stream in southwestern Colorado severely affected by heavy metal contamination as a result of acid mine drainage, as a natural laboratory to study the aqueous behavior of indium. At the existing pH of ~3, indium concentrations are 6-29μg/L (10,000× those found in natural rivers), and are completely filterable through a 0.45μm filter. During a pH modification experiment, the pH of the system was raised to >8, and >99% of the indium became associated with the suspended solid phase (i.e. does not pass through a 0.45μm filter). To determine the mechanism of removal of indium from the filterable and likely primarily dissolved phase, we conducted laboratory experiments to determine an upper bound for a sorption constant to iron oxides, and used this, along with other published thermodynamic constants, to model the partitioning of indium in Mineral Creek. Modeling results suggest that the removal of indium from the filterable phase is consistent with precipitation of indium hydroxide from a dissolved phase. This work demonstrates that nonferrous mining processes can be a significant source of indium to the environment, and provides critical information about the aqueous behavior of indium. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. The precipitation of indium at elevated pH in a stream influenced by acid mine drainage

    Science.gov (United States)

    White, Sarah Jane O.; Hussain, Fatima A.; Hemond, Harold F.; Sacco, Sarah A.; Shine, James P.; Runkel, Robert L.; Walton-Day, Katherine; Kimball, Briant A.

    2017-01-01

    Indium is an increasingly important metal in semiconductors and electronics and has uses in important energy technologies such as photovoltaic cells and light-emitting diodes (LEDs). One significant flux of indium to the environment is from lead, zinc, copper, and tin mining and smelting, but little is known about its aqueous behavior after it is mobilized. In this study, we use Mineral Creek, a headwater stream in southwestern Colorado severely affected by heavy metal contamination as a result of acid mine drainage, as a natural laboratory to study the aqueous behavior of indium. At the existing pH of ~ 3, indium concentrations are 6–29 μg/L (10,000 × those found in natural rivers), and are completely filterable through a 0.45 μm filter. During a pH modification experiment, the pH of the system was raised to > 8, and > 99% of the indium became associated with the suspended solid phase (i.e. does not pass through a 0.45 μm filter). To determine the mechanism of removal of indium from the filterable and likely primarily dissolved phase, we conducted laboratory experiments to determine an upper bound for a sorption constant to iron oxides, and used this, along with other published thermodynamic constants, to model the partitioning of indium in Mineral Creek. Modeling results suggest that the removal of indium from the filterable phase is consistent with precipitation of indium hydroxide from a dissolved phase. This work demonstrates that nonferrous mining processes can be a significant source of indium to the environment, and provides critical information about the aqueous behavior of indium.

  7. Eukaryotic diversity at pH extremes

    Directory of Open Access Journals (Sweden)

    Linda A. Amaral-Zettler

    2013-01-01

    Full Text Available Extremely acidic (pH<3 and extremely alkaline (pH>9 environments support a diversity of single-cell and to a lesser extent, multicellular eukaryotic life. This study compared alpha and beta diversity in eukaryotic communities from 7 diverse aquatic environments with pH values ranging from 2 to 11 using massively-parallel pyrotag sequencing targeting the V9 hypervariable region of the 18S ribosomal RNA (rRNA gene. A total of 946 Operational Taxonomic Units (OTUs were recovered at a 6% cut-off level (94% similarity across the sampled environments. Hierarchical clustering of the samples segregated the communities into acidic and alkaline groups. Similarity Percentage Analysis (SIMPER followed by Indicator OTU Analysis (IOA and Non-metric Multidimensional Scaling (NMDS were used to determine which characteristic groups of eukaryotic taxa typify acidic or alkaline extremes and the extent to which pH explains eukaryotic community structure in these environments. Spain’s Rio Tinto yielded the fewest observed OTUs while Nebraska Sandhills alkaline lakes yielded the most. Distinct OTUs, including metazoan OTUs, numerically dominated pH extreme sites. Indicator OTUs included the diatom Pinnularia and unidentified opisthokonts (Fungi and Filasterea in the extremely acidic environments, and the ciliate Frontonia across the extremely alkaline sites. Inferred from NMDS, pH explained only a modest fraction of the variation across the datasets, indicating that other factors influence the underlying community structure in these environments. The findings from this study suggest that the ability for eukaryotes to adapt to pH extremes over a broad range of values may be rare, but further study of taxa that can broadly adapt across diverse acidic and alkaline environments respectively present good models for understanding adaptation and should be targeted for future investigations.

  8. Flavianate, an amino acid precipitant, is a competitive inhibitor of trypsin at pH 3.0

    Directory of Open Access Journals (Sweden)

    J.M. Schneedorf

    1998-09-01

    Full Text Available Textile dyes bind to proteins leading to selective co-precipitation of a complex involving one protein molecule and more than one dye molecule of opposite charge in acid solutions, in a process of reversible denaturation that can be utilized for protein fractionation. In order to understand what occurs before the co-precipitation, a kinetic study using bovine ß-trypsin and sodium flavianate was carried out based on reaction progress curve techniques. The experiments were carried out using a-CBZ-L-Lys-p-nitrophenyl ester as substrate which was added to 50 mM sodium citrate buffer, pH 3.0, containing varying concentrations of ß-trypsin and dye. The reaction was recorded spectrophotometrically at 340 nm for 30 min, and the families of curves obtained were analyzed simultaneously by fitting integrated Michaelis-Menten equations. The dye used behaved as a competitive inhibitor of trypsin at pH 3.0, with Ki = 99 µM; kinetic parameters for the substrate hydrolysis were: Km = 32 µM, and kcat = 0.38/min. The competitive character of the inhibition suggests a specific binding of the first dye molecule to His-57, the only positively charged residue at the active site of the enzyme.

  9. Volatile fatty acids production from food waste: effects of pH, temperature, and organic loading rate.

    Science.gov (United States)

    Jiang, Jianguo; Zhang, Yujing; Li, Kaimin; Wang, Quan; Gong, Changxiu; Li, Menglu

    2013-09-01

    The effects of pH, temperature, and organic loading rate (OLR) on the acidogenesis of food waste have been determined. The present study investigated their effects on soluble chemical oxygen demand (SCOD), volatile fatty acids (VFAs), volatile solids (VS), and ammonia nitrogen (NH4(+)-N). Both the concentration and yield of VFAs were highest at pH 6.0, acetate and butyrate accounted for 77% of total VFAs. VFAs concentration and the VFA/SCOD ratio were highest, and VS levels were lowest, at 45 °C, but the differences compared to the values at 35 °C were slight. The concentrations of VFAs, SCOD, and NH4(+)-N increased as OLR increased, whereas the yield of VFAs decreased from 0.504 at 5 g/Ld to 0.306 at 16 g/Ld. Acetate and butyrate accounted for 60% of total VFAs. The percentage of acetate and valerate increased as OLR increased, whereas a high OLR produced a lower percentage of propionate and butyrate.

  10. TEMPERATURE AND pH RESPONSE, AND SWELLING BEHAVIOR OF POROUS ACRYLONITRILE-ACRYLIC ACID COPOLYMER HYDROGELS

    Institute of Scientific and Technical Information of China (English)

    Jian Huang; Zhi-ming Huang; Yong-zhong Bao; Zhi-xue Weng

    2006-01-01

    Macroporous acrylonitrile-acrylic acid (AN-AA) copolymer hydrogels were synthesized by free-radical solution polymerizations, using ammonium persulfate (APS)/N,N,N',N'-tetramethylethylenediamine (TEMED) redox initiator system and alcohols porogens. The morphology, temperature and pH sensitive swelling behavior, and swelling kinetics of the resulting hydrogels were investigated. It was found that alcohol type and concentration had great influences on the pore structure and porosity of hydrogels. The pore size of hydrogel increases with the moderate increase of the length of alcohol alkyl chain. However, a further increase of alkyl length would result in the formation of cauliflower-like structure and the decrease of pore size. The porosity of hydrogels increases with the increase of porogen concentration in the polymerization medium. The hydrogels with macroporous structure swell or shrink much faster in response to the change of pH in comparison with the conventional hydrogel without macroporous structure. Furthermore, the response rate is closely related to the porosity of the hydrogels, which could be easily controlled by modulating the concentration of the porogen in the medium. The circular swelling behavior of hydrogels indicated the formation of a relaxing three-dimensional network.

  11. The effect of antioxidants on quantitative changes of lysine and methionine in linoleic acid emulsions at different pH conditions

    Directory of Open Access Journals (Sweden)

    Marzanna Hęś

    2017-03-01

    Full Text Available Background. Plants are an important source of phenolic compounds. The antioxidant capacities of green tea, thyme and rosemary extracts that contain these compounds have been reported earlier. However, there is a lack of accessible information about their activity against lipid oxidation in emulsions and inhibit the interaction of lipid oxidation products with amino acids. Therefore, the influence of green tea, thyme and rosemary extracts and BHT (butylated hydroxytoluene on quantitative changes in lysine and methionine in linoleic acid emulsions at a pH of isoelectric point and a pH lower than the isoelectric point of amino acids was investigated. Material and methods. Total phenolic contents in plant extracts were determined spectrophotometrically by using Folin-Ciocalteu’s reagent, and individual phenols by using HPLC. The level of oxidation of emulsion was determined using the measurement of peroxides and TBARS (thiobarbituric acid reactive substances. Methionine and lysine in the system were reacted with sodium nitroprusside and trinitrobenzenesulphonic acid respectively, and the absorbance of the complexes was measured. Results. Extract of green tea had the highest total polyphenol content. The system containing antioxidants and amino acid protected linoleic acid more efficiently than by the addition of antioxidants only. Lysine and methionine losses in samples without the addition of antioxidants were lower in their isoelectric points than below these points. Antioxidants decrease the loss of amino acids. The protective properties of antioxidants towards methionine were higher in a pH of isoelectric point whereas towards lysine in pH below this point. Conclusion. Green tea, thyme and rosemary extracts exhibit antioxidant activity in linoleic acid emulsions. Moreover, they can be utilized to inhibit quantitative changes in amino acids in lipid emulsions. However, the antioxidant efficiency of these extracts seems to depend on pH

  12. The effect of antioxidants on quantitative changes of lysine and methionine in linoleic acid emulsions at different pH conditions.

    Science.gov (United States)

    Hęś, Marzanna; Gliszczyńska-Świgło, Anna; Gramza-Michałowska, Anna

    2017-01-01

    Plants are an important source of phenolic compounds. The antioxidant capacities of green tea, thyme and rosemary extracts that contain these compounds have been reported earlier. However, there is a lack of accessible information about their activity against lipid oxidation in emulsions and inhibit the interaction of lipid oxidation products with amino acids. Therefore, the influence of green tea, thyme and rosemary extracts and BHT (butylated hydroxytoluene) on quantitative changes in lysine and methionine in linoleic acid emulsions at a pH of isoelectric point and a pH lower than the isoelectric point of amino acids was investigated. Total phenolic contents in plant extracts were determined spectrophotometrically by using Folin-Ciocalteu's reagent, and individual phenols by using HPLC. The level of oxidation of emulsion was determined using the measurement of peroxides and TBARS (thiobarbituric acid reactive substances). Methionine and lysine in the system were reacted with sodium nitroprusside and trinitrobenzenesulphonic acid respectively, and the absorbance of the complexes was measured. Extract of green tea had the highest total polyphenol content. The system containing antioxidants and amino acid protected linoleic acid more efficiently than by the addition of antioxidants only. Lysine and methionine losses in samples without the addition of antioxidants were lower in their isoelectric points than below these points. Antioxidants decrease the loss of amino acids. The protective properties of antioxidants towards methionine were higher in a pH of isoelectric point whereas towards lysine in pH below this point. Green tea, thyme and rosemary extracts exhibit antioxidant activity in linoleic acid emulsions. Moreover, they can be utilized to inhibit quantitative changes in amino acids in lipid emulsions. However, the antioxidant efficiency of these extracts seems to depend on pH conditions. Further investigations should be carried out to clarify this issue.

  13. Comparing peracetic acid and hypochlorite for disinfection of combined sewer overflows: Effects of suspended-solids and pH.

    Science.gov (United States)

    McFadden, M; Loconsole, J; Schockling, A J; Nerenberg, R; Pavissich, J P

    2017-12-01

    Peracetic acid (PAA) is an alternative disinfectant that may be effective for combined sewer overflow (CSO) disinfection, but little is known about the effect of particle size on PAA disinfection efficiency. In this work, PAA and hypochlorite were compared as disinfectants, with a focus on the effect of wastewater particles. Inactivation experiments were conducted on suspended cultures of Escherichia coli and wastewater suspended solids. Tested size fractions included particle diameters solids size. However, solids size had little effect on PAA disinfection. The PAA disinfection efficiency decreased at pH values above 7.5. Live/dead staining revealed that PAA disinfection leaves most cells in a viable but non-culturable condition. Fourier transform infrared spectroscopy (FTIR) analyses suggests that PAA and hypochlorite may inactivate E. coli bacteria by similar mechanisms. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Short peptide nucleic acids bind strongly to homopurine tract of double helical RNA at pH 5.5.

    Science.gov (United States)

    Li, Ming; Zengeya, Thomas; Rozners, Eriks

    2010-06-30

    The important role that noncoding RNA plays in cell biology makes it an attractive target for molecular recognition. However, the discovery of small molecules that bind double helical RNA selectively and may serve as biochemical probes and potential drug leads has been relatively slow. Herein, we show that peptide nucleic acids, as short as six nucleobases, bind very strongly (K(a) > 10(7)) and sequence selectively to a homopurine tract of double helical RNA at pH 5.5. The isothermal titration calorimetry and circular dichroism experiments suggest that the binding mode may be a sequence selective triple helix formation. Our results have implications for development of biochemical probes to study function of noncoding RNAs and design of compounds with potential antibacterial and antiviral activity.

  15. Quantification of 15 bile acids in lake charr feces by ultra-high performance liquid chromatography–tandem mass spectrometry

    Science.gov (United States)

    Li, Ke; Buchinger, Tyler J.; Bussy, Ugo; Fissette, Skye D; Johnson, Nicholas; Li, Weiming

    2015-01-01

    Many fishes are hypothesized to use bile acids (BAs) as chemical cues, yet quantification of BAs in biological samples and the required methods remain limited. Here, we present an UHPLC–MS/MS method for simultaneous, sensitive, and rapid quantification of 15 BAs, including free, taurine, and glycine conjugated BAs, and application of the method to fecal samples from lake charr (Salvelinus namaycush). The analytes were separated on a C18 column with acetonitrile–water (containing 7.5 mM ammonium acetate and 0.1% formic acid) as mobile phase at a flow rate of 0.25 mL/min for 12 min. BAs were monitored with a negative electrospray triple quadrupole mass spectrometer (Xevo TQ-S™). Calibration curves of 15 BAs were linear over the concentration range of 1.00–5,000 ng/mL. Validation revealed that the method was specific, accurate, and precise. The method was applied to quantitative analysis of feces extract of fry lake charr and the food they were eating. The concentrations of analytes CA, TCDCA, TCA, and CDCA were 242.3, 81.2, 60.7, and 36.2 ng/mg, respectively. However, other taurine conjugated BAs, TUDCA, TDCA, and THDCA, were not detected in feces of lake charr. Interestingly, TCA and TCDCA were detected at high concentrations in food pellets, at 71.9 and 38.2 ng/mg, respectively. Application of the method to feces samples from lake charr supported a role of BAs as chemical cues, and will enhance further investigation of BAs as chemical cues in other fish species.

  16. Increasing the Brønsted acidity of Ph2PO2H by the Lewis acid B(C6F5)3. Formation of an eight-membered boraphosphinate ring [Ph2POB(C6F5)2O]2.

    Science.gov (United States)

    Kather, Ralf; Rychagova, Elena; Sanz Camacho, Paula; Ashbrook, Sharon E; Woollins, J Derek; Robben, Lars; Lork, Enno; Ketkov, Sergey; Beckmann, Jens

    2016-09-21

    Autoprotolysis of the metastable acid (C6F5)3BOPPh2OH, prepared in situ by the reaction of the rather weak Brønsted acid Ph2PO2H with the strong Lewis acid B(C6F5)3, gave rise to the formation of the eight-membered ring [Ph2POB(C6F5)2O]2 and C6F5H. The conjugate base was isolated as stable sodium crown ether salt [Na(15-crown-5)][Ph2PO2B(C6F5)3].

  17. Novel PH Sensitive Nanocarrier Agents Based on Citric Acid Dendrimers Containing Conjugated β-Cyclodextrins

    Directory of Open Access Journals (Sweden)

    Hassan Namazi

    2011-06-01

    Full Text Available Introduction: In this work, the use of β-cyclodextrine (β-CD-modified dendrimers as a nanocapsule with a biocompatible shell have studied. β-CD-modified dendrimers have designed and synthesized to enhance the loading capacity of the final dendrimers with encapsulation properties. Methods: To achieve β-CD-modified dendrimers, first citric acid dendrimers were synthesized and then the end functional groups of dendrimers were grafted to β-CD through ester linkages. The molecular structures of resulted dendrimers were verified using common spectroscopic methods such as 1H NMR, FT-IR and the diameters of obtained nanocarriers were evaluated with using dynamic light scattering (DLS experiments. The isolated dendrimers were utilized as the drug delivery agents and the encapsulation and the controlled release of guest drug molecule Naltrexone (NLX was investigated in different pH’s using UV spectroscopy method. Results: It was established that the loading capacity of dendrimers depend on several factors such as their generation and the structure and number of conjugated modifier end groups. Conclusion: Increasing in the number of branches and the size of interior voids and number of conjugated β-CDs cause to enhance the loading capacity.

  18. Encapsulation of quercetin and myricetin in cyclodextrins at acidic pH.

    Science.gov (United States)

    Lucas-Abellán, Carmen; Fortea, Isabel; Gabaldón, José Antonio; Núñez-Delicado, Estrella

    2008-01-09

    The in vitro formation of quercetin- and myricetin-cyclodextrin inclusion complexes in acidic medium has been characterized using the enzymatic system horseradish peroxidase, which oxidizes those flavonols in the presence of H2O2. The presence of cyclodextrins (CDs) in the reaction medium inhibited flavonol oxidation due to the complexation of the flavonol in the hydrophobic cavity of CDs. This inhibitory effect depends on the complexation constant Kc between flavonol and the CD type used. The Kc for quercetin and myricetin with the different types of CD used was calculated by nonlinear regression of the inhibition curves obtained in the presence of CDs. In both cases (quercetin and myricetin), the Kc values obtained followed the order hydroxypropyl-beta-CDs > maltosyl-beta-CDs > beta-CDs, reflecting the greater affinity of modified cyclodextrins for the studied flavonols compared with their parental beta-CDs. Moreover, the complexation efficiency (CE) values for HP-beta-CDs and quercetin or myricetin were calculated (267.4 and 5.3, respectively), indicating that HP-beta-CDs are more efficient for the complexation of quercetin than myricetin in the studied conditions, despite of the K c values being very similar in both cases.

  19. Bilayers at High pH in the Fatty Acid Soap Systems and the Applications for the Formation of Foams and Emulsions.

    Science.gov (United States)

    Xu, Wenlong; Zhang, Heng; Zhong, Yingping; Jiang, Liwen; Xu, Mengxin; Zhu, Xionglu; Hao, Jingcheng

    2015-08-20

    In our previous work, we reported bilayers at high pH in the stearic acid/CsOH/H2O system, which was against the traditional viewpoint that fatty acid (FA) bilayers must be formed at the pKa of the fatty acid. Herein, the microstructures at high pH of several fatty acid soap systems were investigated systematically. We found that palmitic acid/KOH/H2O, palmitic acid/CsOH/H2O, stearic acid/KOH/H2O, and stearic acid/CsOH/H2O systems can form bilayers at high pH. The bilayer structure was demonstrated by cryogenic transmission electron microscopy (cryo-TEM) and deuterium nuclear magnetic resonance ((2)H NMR), and molecular dynamics simulation was used to confirm the formation of bilayers. The influence of fatty acids with different chain lengths (n = 10, 12, 14, 16, and 18) and different counterions including Li(+), Na(+), K(+), Cs(+), (CH3)4N(+), (C2H5)4N(+), (C3H7)4N(+), and (C4H9)4N(+) on the formation of bilayers was discussed. The stability of foam and emulsification properties were compared between bilayers and micelles, drawing the conclusion that bilayer structures possess a much stronger ability to foam and stronger emulsification properties than micelles do.

  20. Oxidizing dissolution mechanism of an irradiated MOX fuel in underwater aerated conditions at slightly acidic pH

    Science.gov (United States)

    Magnin, M.; Jégou, C.; Caraballo, R.; Broudic, V.; Tribet, M.; Peuget, S.; Talip, Z.

    2015-07-01

    The (U,Pu)O2 matrix behavior of an irradiated MIMAS-type (MIcronized MASter blend) MOX fuel, under radiolytic oxidation in aerated pure water at pH 5-5.5 was studied by combining chemical and radiochemical analyses of the alteration solution with Raman spectroscopy characterizations of the surface state. Two leaching experiments were performed on segments of irradiated fuel under different conditions: with or without an external γ irradiation field, over long periods (222 and 604 days, respectively). The gamma irradiation field was intended to be representative of the irradiation conditions for a fuel assembly in an underwater interim storage situation. The data acquired enabled an alteration mechanism to be established, characterized by uranium (UO22+) release mainly controlled by solubility of studtite over the long-term. The massive precipitation of this phase was observed for the two experiments based on high uranium oversaturation indexes of the solution and the kinetics involved depended on the irradiation conditions. External gamma irradiation accelerated the precipitation kinetics and the uranium concentrations (2.9 × 10-7 mol/l) were lower than for the non-irradiated reference experiment (1.4 × 10-5 mol/l), as the quantity of hydrogen peroxide was higher. Under slightly acidic pH conditions, the formation of an oxidized UO2+x phase was not observed on the surface and did not occur in the radiolysis dissolution mechanism of the fuel matrix. The Raman spectroscopy performed on the heterogeneous MOX fuel matrix surface, showed that the fluorite structure of the mainly UO2 phase surrounding the Pu-enriched aggregates had not been particularly impacted by any major structural change compared to the data obtained prior to leaching. For the plutonium, its behavior in solution involved a continuous release up to concentrations of approximately 3 × 10-6 mol L-1 with negligible colloid formation. This data appears to support a predominance of the +V oxidation

  1. Adirondack lakes survey: An interpretive analysis of fish communities and water chemistry, 1984--1987

    Energy Technology Data Exchange (ETDEWEB)

    Baker, J.P. (Baker (Joan P.), Raleigh, NC (USA)); Gherini, S.A.; Munson, R.K. (Tetra Tech, Inc., Pasadena, CA (USA)); Christensen, S.W. (Oak Ridge National Lab., TN (USA)); Driscoll, C.T. (Syracuse Univ., NY (USA)); Gallagher, J. (Adirondack Lakes Survey Corp., Ray Brook, NY (USA)); Newton, R.M. (Smith Coll., Northampton, MA (USA)); Reckhow, K.H. (Duke Univ., Durham, NC (USA)); Schofield, C.L. (Co

    1990-01-01

    The Adirondack Lakes Survey Corporation (ALSC) was formed as a cooperative effort of the New York State Department of Environmental Conservation and the Empire State Electric Energy Research Corporation to better characterize the chemical and biological status of Adirondack lakes. Between 1984 and 1987, the ALSC surveyed 1469 lakes within the Adirondack ecological zone. As a follow-up to the survey, the ALSC sponsored a series of interpretive analyses of the ALSC data base. The primary objectives of these analyses were as follows: Evaluate the influence of mineral acids (from acidic deposition) and nonmineral acids (natural organic acids) on lake pH levels; classify Adirondack lakes according to lake and watershed features expected to influence their responsiveness to changes in acidic deposition; evaluate the sensitivity of Adirondack lakes to changes in environmental conditions, such as changes in mineral acids or dissolved organic carbon concentrations; identify lake characteristics important in explaining the observed present-day status of fish communities in Adirondack lakes, in particular the relative importance of lake acidity; evaluate changes that have occurred over time in Adirondack fish communities and probable causes for these trends by using the available historical data on fish communities in the Adirondacks and the ALSC data base; and determine the degree to which the existing fish resource might be at risk from continued acidic deposition, or might recover if acidity levels were reduced. The basic approach examined relationships observed in the ALSC data base among watershed characteristics, lake chemistry, and fish status. Individual reports are processed separately for the data bases.

  2. A new class of fluorescent boronic acids that have extraordinarily high affinities for diols in aqueous solution at physiological pH.

    Science.gov (United States)

    Cheng, Yunfeng; Ni, Nanting; Yang, Wenqian; Wang, Binghe

    2010-12-03

    The boronic acid group is an important recognition moiety for sensor design. Herein, we report a series of isoquinolinylboronic acids that have extraordinarily high affinities for diol-containing compounds at physiological pH. In addition, 5- and 8-isoquinolinylboronic acids also showed fairly high binding affinities towards D-glucose (K(a)=42 and 46 M(-1), respectively). For the first time, weak but encouraging binding of cis-cyclohexanediol was found for these boronic acids. Such binding was coupled with significant fluorescence changes. Furthermore, 4- and 6-isoquinolinylboronic acids also showed the ability to complex methyl α-D-glucopyranose (K(a)=3 and 2 M(-1), respectively).

  3. Transient responses of phosphoric acid fuel cell power plant system. Ph.D. Thesis

    Science.gov (United States)

    Lu, Cheng-Yi

    1983-01-01

    An analytical and computerized study of the steady state and transient response of a phosphoric acid fuel cell (PAFC) system was completed. Parametric studies and sensitivity analyses of the PAFC system's operation were accomplished. Four non-linear dynamic models of the fuel cell stack, reformer, shift converters, and heat exchangers were developed based on nonhomogeneous non-linear partial differential equations, which include the material, component, energy balance, and electrochemical kinetic features. Due to a lack of experimental data for the dynamic response of the components only the steady state results were compared with data from other sources, indicating reasonably good agreement. A steady state simulation of the entire system was developed using, nonlinear ordinary differential equations. The finite difference method and trial-and-error procedures were used to obtain a solution. Using the model, a PAFC system, that was developed under NASA Grant, NCC3-17, was improved through the optimization of the heat exchanger network. Three types of cooling configurations for cell plates were evaluated to obtain the best current density and temperature distributions. The steady state solutions were used as the initial conditions in the dynamic model. The transient response of a simplified PAFC system, which included all of the major components, subjected to a load change was obtained. Due to the length of the computation time for the transient response calculations, analysis on a real-time computer was not possible. A simulation of the real-time calculations was developed on a batch type computer. The transient response characteristics are needed for the optimization of the design and control of the whole PAFC system. All of the models, procedures and simulations were programmed in Fortran and run on IBM 370 computers at Cleveland State University and the NASA Lewis Research Center.

  4. Fatty acid composition and Ω3/Ω6 ratios of the muscle lipids of six fish species in Sugla Lake, Turkey

    Directory of Open Access Journals (Sweden)

    Cakmak Selim Yavuz

    2012-01-01

    Full Text Available Fatty acid composition of the muscle lipids of Carassius gibelio, Pseudophoxinus anatolicus, Sander lucioperca, Tinca tinca, Vimba vimba tenella and Capoeta capoeta in Sugla Lake were determined. In all species, palmitic acid (13.25- 18.54% of total fatty acids and oleic acid (11.93-34.23% of total fatty acids were identified as major saturated fatty acid (SFA and monounsaturated fatty acid (MUFA, respectively. Docosahexaenoic acid (DHA was found to be the major polyunsaturated fatty acid (PUFA in T. tinca, C. capoeta, C. gibelio, P. anatolicus and S. lucioperca while the predominant PUFA of V. vimba tenella was eicosapentaenoic acid (EPA. S. lucioperca contained more ω3 fatty acids than the other fish species. The percentages of total ω3 fatty acids were higher than those of total ω6 fatty acids in all species. Since P. anatolicus is endemic and endangered, this species should be protected and produced for future marketing.

  5. A mathematical model of pH, based on the total stoichiometric concentration of acids, bases and ampholytes dissolved in water.

    Science.gov (United States)

    Mioni, Roberto; Mioni, Giuseppe

    2015-10-01

    In chemistry and in acid-base physiology, the Henderson-Hasselbalch equation plays a pivotal role in studying the behaviour of the buffer solutions. However, it seems that the general function to calculate the valence of acids, bases and ampholytes, N = f(pH), at any pH, has only been provided by Kildeberg. This equation can be applied to strong acids and bases, pluriprotic weak acids, bases and ampholytes, with an arbitrary number of acid strength constants, pKA, including water. By differentiating this function with respect to pH, we obtain the general equation for the buffer value. In addition, by integrating the titration curve, TA, proposed by Kildeberg, and calculating its Legendre transform, we obtain the Gibbs free energy of pH (or pOH)-dependent titratable acid. Starting from the law of electroneutrality and applying suitable simplifications, it is possible to calculate the pH of the buffer solutions by numerical methods, available in software packages such as Excel. The concept of buffer capacity has also been clarified by Urbansky, but, at variance with our approach, not in an organic manner. In fact, for each set of monobasic, dibasic, tribasic acids, etc., various equations are presented which independently fit each individual acid-base category. Consequently, with the increase in acid groups (pKA), the equations become more and more difficult, both in practice and in theory. Some examples are proposed to highlight the boundary that exists between acid-base physiology and the thermodynamic concepts of energy, chemical potential, amount of substance and acid resistance.

  6. Suppress or not to suppress gastric acid?Intra-gastric pH monitoring Vs. Litmus paper in critically ill patients

    Directory of Open Access Journals (Sweden)

    Mojtaba Mojtahedzadeh

    2007-06-01

    Full Text Available Stress ulceration and gastrointestinal bleeding complicates many clinical illnesses in patients in the intensive care unit (ICU.  We hypothesized that suppression of gastric acid and monitoring of gastric pH using intra-gastric pH monitoring can be beneficial to critically ill patients. To test this idea we have performed a pilot study to compare the accuracy of litmus paper to determine gastric pH to a nasogastric platin-antimony pH probe in a teaching hospital in Tehran. Twenty critically ill patients in intensive care unit who required stress ulcer prophylaxis, by using a crossover design the patients randomized to initially received ranitidine by continuous infusion or intravenous bolus and subsequently were crossed over to the other arm of the study. Gastric pH was determined using pH sensitive litmus paper at the initiation of each arm of the study and at 1, 2, 4 and 8 hours after the initiation of ranitidine. In addition, gastric pH was continuously determined over the same time utilizing a platin-antimony pH probe made in Iran. Pilot Results of gastric pH measurement determined with litmus paper and intra-gastric pH probes demonstrated by regression analysis comparing these two methods showed a good correlation between the two methods (r=0.7. The pH probe technique for intra-gastric pH measurement appears to be technically simple and clinically applicable for use on patients at risk for stress ulcer bleeding.  It may be more accurate than litmus paper in patient receiving H2 antagonists. Further investigations are needed to validate this idea.

  7. Improving clarity and stability of skim milk powder dispersions by dissociation of casein micelles at pH 11.0 and acidification with citric acid.

    Science.gov (United States)

    Pan, Kang; Zhong, Qixin

    2013-09-25

    Casein micelles in milk cause turbidity and have poor stability at acidic conditions. In this study, skim milk powder dispersions were alkalized to pH 10.0 or 11.0, corresponding to reduced particle mass. In the following acidification with hydrochloric or citric acid, the re-formation of casein particles was observed. The combination of treatment at pH 11.0 and acidification with citric acid resulted in dispersions with the lowest turbidity and smallest particles, which enabled translucent dispersions at pH 5.5-7.0, corresponding to discrete nanoparticles. The concentration of ionic calcium was lower when acidified with citric acid than hydrochloric acid, corresponding to smaller particles with less negative zeta potential. The pH 11.0 treatment followed by acidification with citric acid also resulted in smaller particles than the simple chelating effects (directly implementing sodium citrate). The produced casein nanoparticles with reduced dimensions can be used for beverage and other novel applications.

  8. Sediment amino acids as indicators of anthropogenic activities and potential environmental risk in Erhai Lake, Southwest China.

    Science.gov (United States)

    Ni, Zhaokui; Wang, Shengrui; Zhang, Mianmian

    2016-05-01

    Total hydrolysable amino acids (THAAs) constitute the most important fraction of labile nitrogen. Anthropogenic activities directly influence various biogeochemical cycles and then accelerate lake ecosystem deterioration. This is the first study that has established the relationship between sediment THAAs and anthropogenic activities using dated sediment cores, and evaluated the possibility of THAAs release at the sediment interface based on changes in environmental conditions in Erhai Lake. The results showed that historical distribution and fractions of THAAs could be divided into three stages: a stable period before the 1970s, a clear increasing period from the 1970s to 1990s, and a gradually steady period that started after the 1990s. The chemical fraction, aromatic and sulfur amino acids (AAs) accounted for only ≤3% of THAAs. Basic AAs accounted for 5-17% of THAAs, and remained at a relatively stable level. However, acidic and neutral AAs, which accounted for 19-44% and 35-69% of THAAs, respectively, were the predominant factors causing THAAs to increase due to rapid agricultural intensification and intensification of contemporary sedimentation of phytoplankton or macrophytes since the 1970s. These trends were closely related to both anthropogenic activities and natural processes, which implied that sediment THAAs could act as an effective indicator that reflects anthropogenic activities and aquatic environmental characteristics. The current contributions of sediment THAAs on TN and TOC were environment continuously changes. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Determining D/L Ratios of Amino Acids Found in Ice Above Lake Vostok Using ESI/CIT Mass Spectroscopy

    Science.gov (United States)

    Tsapin, A.; Kanik, I.; Beegle, L. W.; Wu, L.; Cooks, R. G.

    2003-01-01

    Astrobiology is an area where longevity of (micro) organisms is of great interest. Cryospheres are common phenomena in the solar system, particularly on satellites, comets and asteroids, as well as at least some of the planets. Recent data from the Mars Global Surveyor mission suggest the possibility of permafrost or perhaps even liquid water under the Martian surface [2]. These environments may be the areas in which the probability of finding life is the highest. This issue is of concern due to the probable evolution of planetary environments such as that of Mars from more hospitable to less hospitable conditions over the history of the solar system. In addition, evaluation of the possible transfer of living organisms between planets via impact ejecta [3] is dependent on knowledge of the maximum time periods over which microorganisms can remain dormant and subsequently revive and reproduce.Amino acid racemization dating, or aminostratigraphy, has been used for many years to date biological systems, and has been examined as a possible biosignature detection technique for Mars. We have suggested using amino acid racemization as one of the most indicative biosignatures [4]. Only life systems produce preferential synthesis of L-amino acids versus D-amino acids. Almost all amino acids in terrestrial organisms can be found only in the L-enantiomeric form.We studied the level of amino acid racemization, specifically of aspartic acid, in permafrost samples from eastern Siberia. Also we analyzed samples of ice from borehole drilled to lake Vostok, Antarctica.

  10. Effect of pH on sulfite oxidation by Thiobacillus thiooxidans cells with sulfurous acid or sulfur dioxide as a possible substrate.

    Science.gov (United States)

    Takeuchi, T L; Suzuki, I

    1994-02-01

    The oxidation of sulfite by Thiobacillus thiooxidans was studied at various pH values with changing concentrations of potassium sulfite. The optimal pH for sulfite oxidation by cells was a function of sulfite concentrations, rising with increasing substrate concentrations, while that by the cell extracts was unaffected. The sulfite oxidation by cells was inhibited at high sulfite concentrations, particularly at low pH values. The results from kinetic studies show that the fully protonated form of sulfite, sulfurous acid or sulfur dioxide, is the form which penetrates the cells for the oxidation.

  11. Diet of yellow-billed loons (Gavia adamsii) in Arctic lakes during the nesting season inferred from fatty acid analysis

    Science.gov (United States)

    Haynes, T B; Schmutz, Joel A.; Bromaghin, Jeffrey; Iverson, S J; Padula, V. M.; Rosenberger, A E

    2015-01-01

    Understanding the dietary habits of yellow-billed loons (Gavia adamsii) can give important insights into their ecology, however, studying the diet of loons is difficult when direct observation or specimen collection is impractical. We investigate the diet of yellow-billed loons nesting on the Arctic Coastal Plain of Alaska using quantitative fatty acid signature analysis. Tissue analysis from 26 yellow-billed loons and eleven prey groups (nine fish species and two invertebrate groups) from Arctic lakes suggests that yellow-billed loons are eating high proportions of Alaska blackfish (Dallia pectoralis), broad whitefish (Coregonus nasus) and three-spined stickleback (Gasterosteus aculeatus) during late spring and early summer. The prominence of blackfish in diets highlights the widespread availability of blackfish during the early stages of loon nesting, soon after spring thaw. The high proportions of broad whitefish and three-spined stickleback may reflect a residual signal from the coastal staging period prior to establishing nesting territories on lakes, when loons are more likely to encounter these species. Our analyses were sensitive to the choice of calibration coefficient based on data from three different species, indicating the need for development of loon-specific coefficients for future study and confirmation of our results. Regardless, fish that are coastally distributed and that successfully overwinter in lakes are likely key food items for yellow-billed loons early in the nesting season.

  12. The most acidified Austrian lake in comparison to a neutralized mining lake.

    Science.gov (United States)

    Moser, Michael; Weisse, Thomas

    2011-12-01

    This study investigated two mining lakes located in the north of Lower Austria. These lakes arose 45 years ago when open cast lignite mining ceased. The lakes are separated by a 7-m wide dam. Due to the oxidation of pyrite, both lakes have been acidified and exhibit iron, sulphate, and heavy metal concentrations several orders of magnitude higher than in circumneutral lakes. The water column of both lakes is divided into two layers by a pronounced chemocline. The smaller mining lake (AML), with pH close to of 2.6, is the most acidic lake in Austria, whereas flooding with stream water and by drainage from the surrounding fields neutralized the adjacent larger pit lake. The goal of our study was to investigate the effect of flooding on its physical, chemical and biological properties, in comparison to the pristine AML. Even relative to other extremely acidic lakes, the flora and fauna in the AML was reduced and composed of only two flagellate, one ciliate, and one rotifer species. The simplified pelagic food web in the mixolimnion consisted of heterotrophic bacteria, the mixotrophic flagellates Chlamydomonas acidophila and Ochromonas sp., the ciliate Oxytricha sp., and the rotifer Cephalodella sp. The latter two are as yet undescribed new species. The heliozoan Actinophrys sp. that may act as top predator occurred only in low abundance. The euglenid Lepocinclis buetschlii formed a stable deep chlorophyll maximum (DCM) at 7 m depth. Highest cell numbers of L. buetschlii in the DCM exceeded 10(8) L(-1). The neutralized mining lake harboured higher plankton diversity similar to that of natural circumneutral lakes. A peak of at least 16 different phytoplankton taxa was observed during summer. The zooplankton consisted of several copepod species, daphnids and other cladocerans, and at least six different rotifer species. Several fish species occurred in the neutralized lake. Although the effect of non-permanent flooding was largely sustainable, interannual fluctuations

  13. A two-component micelle with emergent pH responsiveness by mixing dilauroyl phosphocholine and deoxycholic acid and its delivery of proteins into the cytosol.

    Science.gov (United States)

    Miyamoto, Noriko; Fujii, Shota; Mochizuki, Shinichi; Sakurai, Kazuo; Sakaguchi, Naoki; Koiwai, Kazunori

    2017-06-01

    Providing appropriate pH responsiveness for drug delivery nanoparticles is one of the major issues in developing a new generation of delivery systems. This paper reports that, when phosphocholine and a bile acid were mixed, the resultant two-component micelle gained pH responsiveness, while the individual components did not show any such responsiveness. The pH responsiveness was shown to be determined by the chemical structure, especially the positions and chirality of the OH groups, of the bile acid, and the sensitivity was determined by the alkyl chain length of the phosphocholine. The best combination for evading endocytosis was dilauroyl phosphocholine (DLPC) and deoxycholic acid (DA). Small-angle X-ray scattering revealed that the pH responsiveness was related to the change of surface hydrophobicity, namely, decreasing pH led to protonation of the carboxylic acid, resulting in aggregation of the preceding micelles. We assume that particles that become hydrophobic in this way can start interacting with the endocytotic bilayer, which eventually leads to rupture of the endocytotic vesicle. This mechanism is well supported by the finding that fluorescein-conjugated ovalbumin proteins were transported into the cytosol when they were co-administered with DLPC/DA. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Evaluation of NaCl, pH, and lactic acid on the growth of Shiga toxin-producing Escherichia coli in a liquid Cheddar cheese extract.

    Science.gov (United States)

    Oh, Jee-Hwan; Vinay-Lara, Elena; McMinn, Russell; Glass, Kathleen A; Johnson, Mark E; Steele, James L

    2014-11-01

    A Cheddar cheese model system, Cheddar cheese extract, was used to examine how different levels of known microbial hurdles (NaCl, pH, and lactic acid) in Cheddar cheese contribute to inhibition of bacterial pathogens. This knowledge is critical to evaluate the safety of Cheddar varieties with altered compositions. The range of levels used covered the lowest and highest level of these factors present in low-sodium, low-fat, and traditional Cheddar cheeses. Four pathogens were examined in this model system at 11 °C for 6 wk, with the lowest levels of these inhibitory factors that would be encountered in these products. The 4 pathogens examined were Salmonella enterica, Staphylococcus aureus, Listeria monocytogenes, and Shiga toxin-producing Escherichia coli (STEC). None of these organisms were capable of growth under these conditions. The STEC exhibited the highest survival and hence was used to examine which of these inhibitory factors (NaCl, pH, and lactic acid) was primarily responsible for the observed inhibition. The STEC survival was examined in Cheddar cheese extract varying in NaCl (1.2 vs. 4.8%), lactic acid (2.7 vs. 4.3%), and pH (4.8 vs. 5.3) at 11 °C for 6 wk. The microbial hurdle found to have the greatest effect on STEC survival was pH. The interactions between pH and levels of protonated lactic acid and anionic lactic acid with STEC survival was also evaluated; only the concentration of protonated lactic acid was determined to have a significant effect on STEC survival. These results indicate that, of the pathogens examined, STEC is of the greatest concern in Cheddar varieties with altered compositions and that pH is the microbial hurdle primarily responsible for controlling STEC in these products.

  15. Low pH, aluminum, and phosphorus coordinately regulate malate exudation through GmALMT1 to improve soybean adaptation to acid soils.

    Science.gov (United States)

    Liang, Cuiyue; Piñeros, Miguel A; Tian, Jiang; Yao, Zhufang; Sun, Lili; Liu, Jiping; Shaff, Jon; Coluccio, Alison; Kochian, Leon V; Liao, Hong

    2013-03-01

    Low pH, aluminum (Al) toxicity, and low phosphorus (P) often coexist and are heterogeneously distributed in acid soils. To date, the underlying mechanisms of crop adaptation to these multiple factors on acid soils remain poorly understood. In this study, we found that P addition to acid soils could stimulate Al tolerance, especially for the P-efficient genotype HN89. Subsequent hydroponic studies demonstrated that solution pH, Al, and P levels coordinately altered soybean (Glycine max) root growth and malate exudation. Interestingly, HN89 released more malate under conditions mimicking acid soils (low pH, +P, and +Al), suggesting that root malate exudation might be critical for soybean adaptation to both Al toxicity and P deficiency on acid soils. GmALMT1, a soybean malate transporter gene, was cloned from the Al-treated root tips of HN89. Like root malate exudation, GmALMT1 expression was also pH dependent, being suppressed by low pH but enhanced by Al plus P addition in roots of HN89. Quantitative real-time PCR, transient expression of a GmALMT1-yellow fluorescent protein chimera in Arabidopsis protoplasts, and electrophysiological analysis of Xenopus laevis oocytes expressing GmALMT1 demonstrated that GmALMT1 encodes a root cell plasma membrane transporter that mediates malate efflux in an extracellular pH-dependent and Al-independent manner. Overexpression of GmALMT1 in transgenic Arabidopsis, as well as overexpression and knockdown of GmALMT1 in transgenic soybean hairy roots, indicated that GmALMT1-mediated root malate efflux does underlie soybean Al tolerance. Taken together, our results suggest that malate exudation is an important component of soybean adaptation to acid soils and is coordinately regulated by three factors, pH, Al, and P, through the regulation of GmALMT1 expression and GmALMT1 function.

  16. Eukaryotic diversity at pH extremes.

    Science.gov (United States)

    Amaral-Zettler, Linda A

    2012-01-01

    Extremely acidic (pH 9) environments support a diversity of single-cell and to a lesser extent, multicellular eukaryotic life. This study compared alpha and beta diversity in eukaryotic communities from seven diverse aquatic environments with pH values ranging from 2 to 11 using massively-parallel pyrotag sequencing targeting the V9 hypervariable region of the 18S ribosomal RNA (rRNA) gene. A total of 946 operational taxonomic units (OTUs) were recovered at a 6% cut-off level (94% similarity) across the sampled environments. Hierarchical clustering of the samples segregated the communities into acidic and alkaline groups. Similarity percentage (SIMPER) analysis followed by indicator OTU analysis (IOA) and non-metric multidimensional scaling (NMDS) were used to determine which characteristic groups of eukaryotic taxa typify acidic or alkaline extremes and the extent to which pH explains eukaryotic community structure in these environments. Spain's Rio Tinto yielded the fewest observed OTUs while Nebraska Sandhills alkaline lakes yielded the most. Distinct OTUs, including metazoan OTUs, numerically dominated pH extreme sites. Indicator OTUs included the diatom Pinnularia and unidentified opisthokonts (Fungi and Filasterea) in the extremely acidic environments, and the ciliate Frontonia across the extremely alkaline sites. Inferred from NMDS, pH explained only a modest fraction of the variation across the datasets, indicating that other factors influence the underlying community structure in these environments. The findings from this study suggest that the ability for eukaryotes to adapt to pH extremes over a broad range of values may be rare, but further study of taxa that can broadly adapt across diverse acidic and alkaline environments, respectively present good models for understanding adaptation and should be targeted for future investigations.

  17. PhTX-II a Basic Myotoxic Phospholipase A2 from Porthidium hyoprora Snake Venom, Pharmacological Characterization and Amino Acid Sequence by Mass Spectrometry

    Directory of Open Access Journals (Sweden)

    Salomón Huancahuire-Vega

    2014-10-01

    Full Text Available A monomeric basic PLA2 (PhTX-II of 14149.08 Da molecular weight was purified to homogeneity from Porthidium hyoprora venom. Amino acid sequence by in tandem mass spectrometry revealed that PhTX-II belongs to Asp49 PLA2 enzyme class and displays conserved domains as the catalytic network, Ca2+-binding loop and the hydrophobic channel of access to the catalytic site, reflected in the high catalytic activity displayed by the enzyme. Moreover, PhTX-II PLA2 showed an allosteric behavior and its enzymatic activity was dependent on Ca2+. Examination of PhTX-II PLA2 by CD spectroscopy indicated a high content of alpha-helical structures, similar to the known structure of secreted phospholipase IIA group suggesting a similar folding. PhTX-II PLA2 causes neuromuscular blockade in avian neuromuscular preparations with a significant direct action on skeletal muscle function, as well as, induced local edema and myotoxicity, in mice. The treatment of PhTX-II by BPB resulted in complete loss of their catalytic activity that was accompanied by loss of their edematogenic effect. On the other hand, enzymatic activity of PhTX-II contributes to this neuromuscular blockade and local myotoxicity is dependent not only on enzymatic activity. These results show that PhTX-II is a myotoxic Asp49 PLA2 that contributes with toxic actions caused by P. hyoprora venom.

  18. Diel behavior of rare earth elements in a mountain stream with acidic to neutral pH

    Science.gov (United States)

    Gammons, C.H.; Wood, S.A.; Nimick, D.A.

    2005-01-01

    Diel (24-h) changes in concentrations of rare earth elements (REE) were investigated in Fisher Creek, a mountain stream in Montana that receives acid mine drainage in its headwaters. Three simultaneous 24-h samplings were conducted at an upstream station (pH = 3.3), an intermediate station (pH = 5.5), and a downstream station (pH = 6.8). The REE were found to behave conservatively at the two upstream stations. At the downstream station, REE partitioned into suspended particles to a degree that varied with the time of day, and concentrations of dissolved REE were 2.9- to 9.4-fold (190% to 830%) higher in the early morning vs. the late afternoon. The decrease in dissolved REE concentrations during the day coincided with a corresponding increase in the concentration of REE in suspended particles, such that diel changes in the total REE concentrations were relatively minor (27% to 55% increase at night). Across the lanthanide series, the heavy REE partitioned into the suspended solid phase to a greater extent than the light REE. Filtered samples from the downstream station showed a decrease in shale-normalized REE concentration across the lanthanide series, with positive anomalies at La and Gd, and a negative Eu anomaly. As the temperature of the creek increased in the afternoon, the slope of the REE profile steepened and the magnitude of the anomalies increased. The above observations are explained by cyclic adsorption of REE onto suspended particles of hydrous ferric and aluminum oxides (HFO, HAO). Conditional partition coefficients for each REE between the suspended solids and the aqueous phase reached a maximum at 1700 hours and a minimum at 0700 hours. This pattern is attributed to diel variations in stream temperature, possibly reinforced by kinetic factors (i.e., slower rates of reaction at night than during the day). Estimates of the enthalpy of adsorption of each REE onto suspended particles based on the field results averaged +82 kJ/mol and are similar in

  19. Diel behavior of rare earth elements in a mountain stream with acidic to neutral pH

    Science.gov (United States)

    Gammons, Christopher H.; Wood, Scott A.; Nimick, David A.

    2005-08-01

    Diel (24-h) changes in concentrations of rare earth elements (REE) were investigated in Fisher Creek, a mountain stream in Montana that receives acid mine drainage in its headwaters. Three simultaneous 24-h samplings were conducted at an upstream station (pH = 3.3), an intermediate station (pH = 5.5), and a downstream station (pH = 6.8). The REE were found to behave conservatively at the two upstream stations. At the downstream station, REE partitioned into suspended particles to a degree that varied with the time of day, and concentrations of dissolved REE were 2.9- to 9.4-fold (190% to 830%) higher in the early morning vs. the late afternoon. The decrease in dissolved REE concentrations during the day coincided with a corresponding increase in the concentration of REE in suspended particles, such that diel changes in the total REE concentrations were relatively minor (27% to 55% increase at night). Across the lanthanide series, the heavy REE partitioned into the suspended solid phase to a greater extent than the light REE. Filtered samples from the downstream station showed a decrease in shale-normalized REE concentration across the lanthanide series, with positive anomalies at La and Gd, and a negative Eu anomaly. As the temperature of the creek increased in the afternoon, the slope of the REE profile steepened and the magnitude of the anomalies increased. The above observations are explained by cyclic adsorption of REE onto suspended particles of hydrous ferric and aluminum oxides (HFO, HAO). Conditional partition coefficients for each REE between the suspended solids and the aqueous phase reached a maximum at 1700 hours and a minimum at 0700 hours. This pattern is attributed to diel variations in stream temperature, possibly reinforced by kinetic factors (i.e., slower rates of reaction at night than during the day). Estimates of the enthalpy of adsorption of each REE onto suspended particles based on the field results averaged +82 kJ/mol and are similar in

  20. Influence of different acids for adjusting the dyebath ph value on the dyeability of polyester knitwear dyed with disperse yellow 23

    Directory of Open Access Journals (Sweden)

    Miljković Milena N.

    2011-01-01

    Full Text Available In this paper the influence of the formic and oxalic acids, as substances for dyebath pH adjusting, on the dyeability of polyester fabric dyed with disperse dye Disperse Yellow 23 was examined. The polyester undyed knitwear samples were dyed in baths containing the acids under the same dyeing conditions. Color differences of the samples were assessed using the reflectiometry technique and expressed in terms of CIELcoordinates. The influence of the tested acids on the surface structure of dyed polyester fibers was examined using the scanning electron microscopy (SEM. It was found that the differences in obtained dyeabilities, in the presence of both formic and oxalic acid, are acceptable according to both M&S 83A and CMC (2:1 standards which was not the case with acetic acid. Therefore, acetic acid can be replaced with either formic or oxalic acid as substances for dyebath pH adjusting in the dyeing process described in this paper. SEM micrographs showed small differences in the surface structure of dyed fibers, as well as differences in the shape of undyed samples’ reflectance curves in presence of the acids. Since all of the color differences were quite small, it can be concluded that the influence of formic and oxalic acids on the polyester knitwear dyeability is not significantly different than that of acetic acid.

  1. Production and stability of chlorine dioxide in organic acid solutions as affected by pH, type of acid, and concentration of sodium chlorite, and its effectiveness in inactivating Bacillus cereus spores.

    Science.gov (United States)

    Kim, Hoikyung; Kang, Youngjee; Beuchat, Larry R; Ryu, Jee-Hoon

    2008-12-01

    We studied the production and stability of chlorine dioxide (ClO(2)) in organic acid solutions and its effectiveness in killing Bacillus cereus spores. Sodium chlorite (5000, 10,000, or 50,000 microg/ml) was added to 5% acetic, citric, or lactic acid solution, adjusted to pH 3.0, 4.0, 5.0, or 6.0, and held at 21 degrees C for up to 14 days. The amount of ClO(2) produced was higher as the concentration of sodium chlorite was increased and as the pH of the acid solutions was decreased. However, the stability in production of ClO(2) was enhanced by increasing the pH of the organic acid solutions. To evaluate the lethal activity of ClO(2) produced in various acid solutions as affected by acidulant and pH, suspensions of B. cereus spores were treated at 21 degrees C for 1, 3, 5, or 10 min in hydrochloric acid or organic acid solutions (pH 3.0, 4.0, 5.0, or 6.0) containing ClO(2) at concentrations of 100, 50, or 25 microg/ml. Populations of viable spores treated with ClO(2) at concentrations of 100 or 50 microg/ml in organic acid solutions decreased more rapidly than populations treated with the same concentrations of ClO(2) in HCl. Rates of inactivation tended to increase with higher pH of ClO(2) solutions. Results show that ClO(2) formed in organic acid solutions has higher stability and is more lethal to B. cereus spores than ClO(2) formed at the same concentration in HCl solution. This finding emphasizes the benefits of using organic acid solutions to prepare ClO(2) intended for use as an antimicrobial.

  2. Increased precipitation acidity in the central Sierra Nevada

    Science.gov (United States)

    Byron, Earl R.; Axler, Richard P.; Goldman, Charles R.

    Between 1979 and 1986, precipitation acidity increased significantly on the crest of the central Sierra Nevada. Variation in precipitation pH was closely associated with change in nitrate concentrations but not to sulfate. This area of the Sierra Nevada crest contains many acid-sensitive, poorly buffered lakes and ponds which can be adversely affected by increasing precipitation acidity.

  3. Effect of pH and oxygen atom of the hydrophobic chain on the self-assembly property and morphology of the pyridyl boronic acid based amphiphiles.

    Science.gov (United States)

    Maiti, Monali; Roy, Aparna; Roy, Sumita

    2013-11-05

    The surface activity and aggregation behavior of two synthesized boronic acid based anionic surfactants, sodium salt of 2-dodecyl pyridine-5-boronic acid (SDDPB) and sodium salt of 2-oxydodecyl pyridine-5-boronic acid (SODDPB), were studied in buffer solution at pH 9 and 13 containing carbohydrates. The self-assembly formation was investigated by use of a number of techniques including surface tension, conductivity, fluorescence spectroscopy, dynamic light scattering, X-ray diffraction, and transmission electron microscopy (TEM). Both of the amphiphiles exhibit a single break in the surface tension vs log(concentration) plots, indicating existence of one critical aggregation concentration. Steady state fluorescence spectroscopy was used to determine the polarity indexes using pyrene and the rigidity of the microenvironments of the aggregates using 1,6-diphenyl-1,3,5-hexatriene (DPH) as fluorescence probe molecules. The pKa's of both amphiphiles were determined in buffer solutions of different pH's. XRD studies were performed to shed light on the morphology of the self-assemblies. TEM micrographs revealed the existence of vesicles for both the amphiphiles in buffer solution of pH 9, but at pH 13, TEM pictures indicate the existence of closed vesicles in SDDPB solution and at concentrated solution the vesicles are fused to form sponge-like micelles. After aging the vesicular solution of pH 13 of SDDPB, the closed vesicles are destroyed. In contrast, for SODDPB at pH 13, TEM pictures suggest the existence of spherical and complex micelles in solution which were further transformed into crystal-like structure upon aging. The average hydrodynamic radii were determined by dynamic light scattering measurement. Therefore, for the first time, we have successfully synthesized two new surfactants containing pyridyl-boronic acid as a headgroup which shows remarkable tuning of morphology in two different pH's and in the presence of two different carbohydrates.

  4. Optimization of Initial pH and Total Sugar Concentration Variables on Citric Acid Production from Pineapple Waste with Aspergillus niger Yeast by Using Response Surface Methodology

    Directory of Open Access Journals (Sweden)

    Widayat Widayat

    2011-06-01

    Full Text Available Citric acid can be produced from pineapple waste by using fermentation process. This process is done in bubble column reactor with Aspergillus niger yeast. The objective of this research is to find the optimum conditions of initial pH and total sugar concentration. The optimization method used was response surface methodology. This research was carried out at a temperature of 30 oC, spore concentration of 1.23 x 109 spore/ml, total volume 2.0 liter, flow rate of air 58.07 cc/sec and a 5% antifoam concentration. The fermentation process lasted 7 days and the citric acid concentration was analyzed by High Pressure Liquid Cromatography (HPLC method. Statistica 6 software was used for the data treatment. The mathematical model for the optimization citric acid fermentation in bubble column reactor is Y = 54.507 + 2.9851X - 8.987X12 - 2.581X2 - 15.446X22 - 7.989X1X2 The parameter of Y is citric acid yield, X1 is a coding initial pH and X2 is a coding total sugar concentration. The results has given an initial pH optimum 3.61 and total sugar concentration 19,285% w/v with optimum an yield of 55.03 % . Keywords: Bubble column bioreactor, Citric acid fermentation, Initial pH, Total sugar concentration, Response surface methodology

  5. Evaluation of acidity and total sugar content of children′s popular beverages and their effect on plaque pH

    Directory of Open Access Journals (Sweden)

    Saeed S

    2010-09-01

    Full Text Available Background: In the developing countries, dental caries has increased with the increased exposure to dietary sugars. There is no data on the cariogenicity and acidogenicity of popular beverages in the Syrian market. Aims: To investigate the endogenous pH, titratable acidity, and total sugar content of popular beverages (cola, orange juice, and full-fat milk, and assess plaque pH drop after consumption. Settings and Design: Twenty-five healthy children with a mean age of 11.8 ± 0.6 years were recruited for this single blinded study. Materials and Methods: The pH of beverages was measured by a digital pH meter and the titratable acidity was expressed as the volume of 0.1 N sodium hydroxide required to neutralize the beverage. The total sugar content was estimated using High Performance Liquid Chromatography. Children rinsed with 15 mL of each of the beverages for 1 min. The controls used were 10% sucrose and 10% sorbitol solutions. The plaque pH was assessed before and after rinsing. Statistical Analysis: Statistical analysis was performed using analysis of variance followed by Bonferroni test to assess minimum pH, maximum pH drop, and the area under curve. P value was set as 0.05. Results: Both cola and orange juice had a low pH and similar total sugar content in contrast to the high pH and low sugar content of milk. Cola and orange juice were not statistically different from 10% sucrose (P > 0.05, but different from 10% sorbitol (P < 0.05, in contrast to milk, for all the parameters studied. Conclusion: Cola and orange juice are cariogenic/acidogenic and frequent intake should be discouraged. A reasonable intake of unsweetened milk may be advised safely.

  6. Acidic digestion in a teleost: postprandial and circadian pattern of gastric pH, pepsin activity, and pepsinogen and proton pump mRNAs expression.

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    Manuel Yúfera

    Full Text Available Two different modes for regulation of stomach acid secretion have been described in vertebrates. Some species exhibit a continuous acid secretion maintaining a low gastric pH during fasting. Others, as some teleosts, maintain a neutral gastric pH during fasting while the hydrochloric acid is released only after the ingestion of a meal. Those different patterns seem to be closely related to specific feeding habits. However, our recent observations suggest that this acidification pattern could be modified by changes in daily feeding frequency and time schedule. The aim of this study was to advance in understanding the regulation mechanisms of stomach digestion and pattern of acid secretion in teleost fish. We have examined the postprandial pattern of gastric pH, pepsin activity, and mRNA expression for pepsinogen and proton pump in white seabream juveniles maintained under a light/dark 12/12 hours cycle and receiving only one morning meal. The pepsin activity was analyzed according to the standard protocol buffering at pH 2 and using the actual pH measured in the stomach. The results show how the enzyme precursor is permanently available while the hydrochloric acid, which activates the zymogen fraction, is secreted just after the ingestion of food. Results also reveal that analytical protocol at pH 2 notably overestimates true pepsin activity in fish stomach. The expression of the mRNA encoding pepsinogen and proton pump exhibited almost parallel patterns, with notable increases during the darkness period and sharp decreases just before the morning meal. These results indicate that white seabream uses the resting hours for recovering the mRNA stock that will be quickly used during the feeding process. Our data clearly shows that both daily illumination pattern and feeding time are involved at different level in the regulation of the secretion of digestive juices.

  7. Propagated fixed-bed mixed-acid fermentation: Part I: Effect of volatile solid loading rate and agitation at high pH.

    Science.gov (United States)

    Golub, Kristina W; Forrest, Andrea K; Mercy, Kevin L; Holtzapple, Mark T

    2011-11-01

    Countercurrent fermentation is a high performing process design for mixed-acid fermentation. However, there are high operating costs associated with moving solids, which is an integral component of this configuration. This study investigated the effect of volatile solid loading rate (VSLR) and agitation in propagated fixed-bed fermentation, a configuration which may be more commercially viable. To evaluate the role of agitation on fixed-bed configuration performance, continuous mixing was compared with periodic mixing. VSLR was also varied and not found to affect acid yields. However, increased VSLR and liquid retention time did result in higher conversions, productivity, acid concentrations, but lower selectivities. Agitation was demonstrated to be important for this fermentor configuration, the periodically-mixed fermentation had the lowest conversion and yields. Operating at a high pH (∼9) contributed to the high selectivity to acetic acid, which might be industrially desirable but at the cost of lower yield compared to a neutral pH.

  8. Insights from the metagenome of an acid salt lake: the role of biology in an extreme depositional environment.

    Science.gov (United States)

    Johnson, Sarah Stewart; Chevrette, Marc Gerard; Ehlmann, Bethany L; Benison, Kathleen Counter

    2015-01-01

    The extremely acidic brine lakes of the Yilgarn Craton of Western Australia are home to some of the most biologically challenging waters on Earth. In this study, we employed metagenomic shotgun sequencing to generate a microbial profile of the depositional environment associated with the sulfur-rich sediments of one such lake. Of the 1.5 M high-quality reads generated, 0.25 M were mapped to protein features, which in turn provide new insights into the metabolic function of this community. In particular, 45 diverse genes associated with sulfur metabolism were identified, the majority of which were linked to either the conversion of sulfate to adenylylsulfate and the subsequent production of sulfide from sulfite or the oxidation of sulfide, elemental sulfur, and thiosulfate via the sulfur oxidation (Sox) system. This is the first metagenomic study of an acidic, hypersaline depositional environment, and we present evidence for a surprisingly high level of microbial diversity. Our findings also illuminate the possibility that we may be meaningfully underestimating the effects of biology on the chemistry of these sulfur-rich sediments, thereby influencing our understanding of past geobiological conditions that may have been present on Earth as well as early Mars.

  9. Preparation of Layer-by-Layer Films Composed of Polysaccharides and Poly(Amidoamine Dendrimer Bearing Phenylboronic Acid and Their pH- and Sugar-Dependent Stability

    Directory of Open Access Journals (Sweden)

    Kentaro Yoshida

    2016-05-01

    Full Text Available Layer-by-layer films composed of polysaccharides and poly(amidoamine dendrimer bearing phenylboronic acid (PBA-PAMAM were prepared to study the deposition behavior of the films and their stability in buffer solutions and in sugar solutions. Alginic acid (AGA and carboxymethylcellulose (CMC were employed as counter-polymers in constructing LbL films. AGA/PBA-PAMAM films were successfully prepared at pH 6.0–9.0, whereas the preparation of CMC/PBA-PAMAM film was unsuccessful at pH 8.0 and 9.0. The results show that the LbL films formed mainly through electrostatic affinity between PBA-PAMAM and polysaccharides, while, for AGA/PBA-PAMAM films, the participation of boronate ester bonds in the films was suggested. AGA/PBA-PAMAM films were stable in the solutions of pH 6.0–9.0. In contrast, CMC/PBA-PAMAM films decomposed at pH 7.5–9.0. The AGA/PBA-PAMAM films decomposed in response to 5–30 mM fructose at pH 7.5, while the films were stable in glucose solutions. Thus, AGA is useful as a counter-polymer for constructing PBA-PAMAM films that are stable at physiological pH and decompose in response to fructose.

  10. The pH sensibility of actin-bundling LIM proteins is governed by the acidic properties of their C-terminal domain.

    Science.gov (United States)

    Moes, Danièle; Hoffmann, Céline; Dieterle, Monika; Moreau, Flora; Neumann, Katrin; Papuga, Jessica; Furtado, Angela Tavares; Steinmetz, André; Thomas, Clément

    2015-08-19

    Actin-bundling Arabidopsis LIM proteins are subdivided into two subfamilies differing in their pH sensitivity. Widely-expressed WLIMs are active under low and high physiologically-relevant pH conditions, whereas pollen-enriched PLIMs are inactivated by pH values above 6.8. By a domain swapping approach we identified the C-terminal (Ct) domain of PLIMs as the domain responsible for pH responsiveness. Remarkably, this domain conferred pH sensitivity to LIM proteins, when provided "in trans" (i.e., as a single, independent, peptide), indicating that it operates through the interaction with another domain. An acidic 6xc-Myc peptide functionally mimicked the Ct domain of PLIMs and efficiently inhibited LIM actin bundling activity under high pH conditions. Together, our data suggest a model where PLIMs are regulated by an intermolecular interaction between their acidic Ct domain and another, yet unidentified, domain. Copyright © 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  11. Relative Abundance of Nitrotoga spp. in a Biofilter of a Cold-Freshwater Aquaculture Plant Appears To Be Stimulated by Slightly Acidic pH

    Science.gov (United States)

    Hüpeden, Jennifer; Wegen, Simone; Off, Sandra; Lücker, Sebastian; Bedarf, Yvonne; Daims, Holger; Kühn, Carsten

    2016-01-01

    The functioning of recirculation aquaculture systems (RAS) is essential to maintain water quality for fish health, and one crucial process here is nitrification. The investigated RAS was connected to a rainbow trout production system and operated at an average temperature of 13°C and pH 6.8. Community analyses of the nitrifying biofilm revealed a coexistence of Nitrospira and Nitrotoga, and it is hypothesized that a slightly acidic pH in combination with lower temperatures favors the growth of the latter. Modification of the standard cultivation approach toward lower pH values of 5.7 to 6.0 resulted in the successful enrichment (99% purity) of Nitrotoga sp. strain HW29, which had a 16S rRNA sequence similarity of 99.0% to Nitrotoga arctica. Reference cultures of Nitrospira defluvii and the novel Nitrotoga sp. HW29 were used to confirm differentiation of these nitrite oxidizers in distinct ecological niches. Nitrotoga sp. HW29 revealed pH and temperature optima of 6.8 and 22°C, respectively, whereas Nitrospira defluvii displayed the highest nitrite oxidation rate at pH 7.3 and 32°C. We report here the occurrence of Nitrotoga as one of the main nitrite-oxidizing bacteria in freshwater aquaculture systems and indicate that a slightly acidic pH, in addition to temperatures below 20°C, can be applied as a selective isolation criterion for this microorganism. PMID:26746710

  12. Novel Technique to improve the pH of Acidic Barren Soil using Electrokinetic-bioremediation with the application of Vetiver Grass

    Science.gov (United States)

    Azhar, A. T. S.; Nabila, A. T. A.; Nurshuhaila, M. S.; Zaidi, E.; Azim, M. A. M.; Zahin, A. M. F.

    2016-11-01

    Residual acidic slopes which are not covered by vegetation greatly increases the risk of soil erosion. In addition, low soil pH can bring numerous problems such as Al and Fe toxicity, land degradation issues and some problems related to vegetation. In this research, a series of electrokinetic bioremediation (EK-Bio) treatments using Bacillus sphaericus, Bacillus subtilis and Pseudomonas putida with a combination of Vetiver grass were performed in the laboratory. Investigations were conducted for 14 days and included the observation of changes in the soil pH and the mobilization of microorganism cells through an electrical gradient of 50 V/m under low pH. Based on the results obtained, this study has successfully proven that the pH of soil increases after going through electrokinetic bioremediation (EK-Bio). The treatment using Bacillus sphaericus increases the pH from 2.95 up to 4.80, followed by Bacillus subtilis with a value of 4.66. Based on the overall performance, Bacillus sphaericus show the highest number of bacterial cells in acidic soil with a value of 6.6 × 102 cfu/g, followed by Bacillus subtilis with a value of 5.7 × 102 cfu/g. In conclusion, Bacillus sphaericus and Bacillus subtilis show high survivability and is suitable to be used in the remediation of acidic soil.

  13. Effect of pH on percutaneous absorption of glycyrrhetinic acid%pH对甘草次酸经皮渗透性的影响

    Institute of Scientific and Technical Information of China (English)

    王森; 闫明; 严新安; 管咏梅; 陈丽华; 朱卫丰

    2012-01-01

    目的 考察介质的pH对甘草次酸经皮渗透性的影响.方法 采用HPLC法测定甘草次酸在不同pH介质中的饱和溶解度,采用摇瓶法测定其在不同pH正辛醇/PBS缓冲液中的表观油水分配系数,采用体外Franz扩散池法考察不同pH的甘草次酸饱和溶液在离体小鼠皮上的经皮渗透性.结果 pH5.0~10.8时,甘草次酸饱和溶液的稳态透皮速率随pH升高而增大,而表观渗透系数随pH升高而减小.结论 甘草次酸在介质中饱和时,可通过调节pH来改善甘草次酸的稳态透皮速率.%OBJECTIVE To study the effect of pH on penetration of glycyrrhetinic acid through skin. METHODS The apparent solubilities of glycyrrhetinic acid in media with different pH values were determined. The apparent distribution coefficients of glycyrrhetinic acid were determined using shake - flask method. The penetration parameteres of glycyrrhetinic acid through rat skin in vitro were measured using Franz diffusion cell. RESULTS With increase of pH within 5.0- 10.8 ,the steady state flux of glycyrrhetinic acid was increased, but the apparent permeability coefficient was decreased. CONCLUSION At saturation status, changing the pH may modify the penetration rate of glycyrrhetinic acid.

  14. In silico prediction of drug dissolution and absorption with variation in intestinal pH for BCS class II weak acid drugs: ibuprofen and ketoprofen.

    Science.gov (United States)

    Tsume, Yasuhiro; Langguth, Peter; Garcia-Arieta, Alfredo; Amidon, Gordon L

    2012-10-01

    The FDA Biopharmaceutical Classification System guidance allows waivers for in vivo bioavailability and bioequivalence studies for immediate-release solid oral dosage forms only for BCS class I. Extensions of the in vivo biowaiver for a number of drugs in BCS class III and BCS class II have been proposed, in particular, BCS class II weak acids. However, a discrepancy between the in vivo BE results and in vitro dissolution results for BCS class II acids was recently observed. The objectives of this study were to determine the oral absorption of BCS class II weak acids via simulation software and to determine if the in vitro dissolution test with various dissolution media could be sufficient for in vitro bioequivalence studies of ibuprofen and ketoprofen as models of carboxylic acid drugs. The oral absorption of these BCS class II acids from the gastrointestinal tract was predicted by GastroPlus™. Ibuprofen did not satisfy the bioequivalence criteria at lower settings of intestinal pH of 6.0. Further the experimental dissolution of ibuprofen tablets in a low concentration phosphate buffer at pH 6.0 (the average buffer capacity 2.2 mmol l (-1) /pH) was dramatically reduced compared with the dissolution in SIF (the average buffer capacity 12.6 mmol l (-1) /pH). Thus these predictions for the oral absorption of BCS class II acids indicate that the absorption patterns depend largely on the intestinal pH and buffer strength and must be considered carefully for a bioequivalence test. Simulation software may be a very useful tool to aid the selection of dissolution media that may be useful in setting an in vitro bioequivalence dissolution standard.

  15. Oxidizing dissolution mechanism of an irradiated MOX fuel in underwater aerated conditions at slightly acidic pH

    Energy Technology Data Exchange (ETDEWEB)

    Magnin, M., E-mail: magali.magnin@cea.fr; Jégou, C.; Caraballo, R.; Broudic, V.; Tribet, M.; Peuget, S.; Talip, Z.

    2015-07-15

    Highlights: • Oxidizing dissolution mechanism of MOX fuel. • Effect of the influence of the interim storage conditions. • Raman spectroscopy characterizations. • Precipitation of Studtite-type secondary phases. • Heterogeneous microstructure of the (U,Pu)O{sub 2} oxide. - Abstract: The (U,Pu)O{sub 2} matrix behavior of an irradiated MIMAS-type (MIcronized MASter blend) MOX fuel, under radiolytic oxidation in aerated pure water at pH 5–5.5 was studied by combining chemical and radiochemical analyses of the alteration solution with Raman spectroscopy characterizations of the surface state. Two leaching experiments were performed on segments of irradiated fuel under different conditions: with or without an external γ irradiation field, over long periods (222 and 604 days, respectively). The gamma irradiation field was intended to be representative of the irradiation conditions for a fuel assembly in an underwater interim storage situation. The data acquired enabled an alteration mechanism to be established, characterized by uranium (UO{sub 2}{sup 2+}) release mainly controlled by solubility of studtite over the long-term. The massive precipitation of this phase was observed for the two experiments based on high uranium oversaturation indexes of the solution and the kinetics involved depended on the irradiation conditions. External gamma irradiation accelerated the precipitation kinetics and the uranium concentrations (2.9 × 10{sup −7} mol/l) were lower than for the non-irradiated reference experiment (1.4 × 10{sup −5} mol/l), as the quantity of hydrogen peroxide was higher. Under slightly acidic pH conditions, the formation of an oxidized UO{sub 2+x} phase was not observed on the surface and did not occur in the radiolysis dissolution mechanism of the fuel matrix. The Raman spectroscopy performed on the heterogeneous MOX fuel matrix surface, showed that the fluorite structure of the mainly UO{sub 2} phase surrounding the Pu-enriched aggregates had

  16. Acidic pH strongly enhances in vitro biofilm formation by a subset of hypervirulent ST-17 Streptococcus agalactiae strains.

    Science.gov (United States)

    D'Urzo, Nunzia; Martinelli, Manuele; Pezzicoli, Alfredo; De Cesare, Virginia; Pinto, Vittoria; Margarit, Immaculada; Telford, John Laird; Maione, Domenico

    2014-04-01

    Streptococcus agalactiae, also known as group B Streptococcus (GBS), is a primary colonizer of the anogenital mucosa of up to 40% of healthy women and an important cause of invasive neonatal infections worldwide. Among the 10 known capsular serotypes, GBS type III accounts for 30 to 76% of the cases of neonatal meningitis. In recent years, the ability of GBS to form biofilm attracted attention for its possible role in fitness and virulence. Here, a new in vitro biofilm formation protocol was developed to guarantee more stringent conditions, to better discriminate between strong-, low-, and non-biofilm-forming strains, and to facilitate interpretation of data. This protocol was used to screen the biofilm-forming abilities of 366 GBS clinical isolates from pregnant women and from neonatal infections of different serotypes in relation to medium composition and pH. The results identified a subset of isolates of serotypes III and V that formed strong biofilms under acidic conditions. Importantly, the best biofilm formers belonged to serotype III hypervirulent clone ST-17. Moreover, the abilities of proteinase K to strongly inhibit biofilm formation and to disaggregate mature biofilms suggested that proteins play an essential role in promoting GBS biofilm initiation and contribute to biofilm structural stability.

  17. The effect of degradation on κ-carrageenan/locust bean gum/konjac glucomannan gels at acidic pH.

    Science.gov (United States)

    Yang, Kun; Wang, Zheng; Nakajima, Tetsuya; Nishinari, Katsuyoshi; Brenner, Tom

    2013-10-15

    The feasibility of textural and rheological modification of gels containing κ-carrageenan (KC) and locust bean gum (LBG) by addition of konjac glucomannan (KGM) was investigated. Special attention was paid to the effect of polysaccharide degradation during heating at acidic pH. The general effect of polysaccharide degradation was to decrease the Young's modulus, while the fracture strain in extension was scarcely affected unless the degradation was very severe. Differential scanning calorimetry showed that the melting peak corresponding to dissociation of KC-KGM bonds decreased faster than the melting peak of KC-only bonds with increasing degree of polysaccharide degradation. The implication is that as degradation proceeds, fewer KGM molecules can interact with KC to form elastic bonds, and the excess of KGM which reinforces the existing elastic network and increases the fracture strain actually increases. For this reason, the fracture strain remains nearly unchanged with increasing degradation levels. A decrease in fracture strain is thus observed only at very severe degradations, where KC no longer forms a self-supporting gel by itself.

  18. A paleolimnological assessment of acidification and liming effects on diatom assemblages in a Swedish lake

    Energy Technology Data Exchange (ETDEWEB)

    Renberg, I. (Umea Univ. (Sweden)); Hultberg, H. (Swedish Environmental Research Inst., Goteborg (Sweden))

    1992-01-01

    In Sweden, ca 6000 lakes have been limed to mitigate acidification. Lysevatten in southwestern Sweden was limed in 1974 and 1986 and has better historical pH and fish records than most other, similar forest lakes. Historical data were compared with diatom analyses of a sediment core to assess to what extent diatom-inferred pH reflects the known pH history. The diatom-inferred pH history agrees well with the development known from documentary sources, although the sediment record is slightly smoothed. Both the historical and sediment records show that the acidification, with acid episodes that caused severe damage to lake biota, began during the 1940s and became acute in the 1960s, with pH values of 4.5-4.9. Prior to acidification, the lake water pH was between 6 and 7, and the lake had a planktonic Cyclotella flora. The liming increased pH to 7.5 and resulted in the expansion of Achnanthes minutissima, Cymbella microcephala, and Synedra acus. The reacidification is reflected by a decrease in abundance of these species. Neither the liming in 1974 or the liming in 1986 restored the preacidification diatom flora; there was no recovery of Cyclotella. 20 refs., 3 figs., 2 tabs.

  19. An evaluation of MES (2(N-Morpholino)ethanesulfonic acid) and Amberlite IRC-50 as pH buffers for nutrient solution studies

    Science.gov (United States)

    Bugbee, B. G.; Salisbury, F. B.

    1985-01-01

    All buffering agents used to stabilize pH in hydroponic research have disadvantages. Inorganic buffers are absorbed and may become phytotoxic. Solid carbonate salts temporarily mitigate decreasing pH but provide almost no protection against increasing pH, and they alter nutrient absorption. Exchange resins are more effective, but we find that they remove magnesium and manganese from solution. We have tested 2(N-Morpholino)ethanesulfonic acid (MES) as a buffering agent at concentrations of 1 and 10 mol m-3 (1 and 10 mM) with beans, corn, lettuce, tomatoes, and wheat. MES appears to be biologically inert and does not interact significantly with other solution ions. Relative growth rates among controls and MES treatments were nearly identical for each species during the trial period. The pH was stabilized by 1 mol m-3 MES. This buffer warrants further consideration in nutrient research.

  20. Antimicrobial activity of human hepcidin 20 and 25 against clinically relevant bacterial strains: effect of copper and acidic pH.

    Science.gov (United States)

    Maisetta, Giuseppantonio; Petruzzelli, Raffaele; Brancatisano, Franca Lisa; Esin, Semih; Vitali, Alberto; Campa, Mario; Batoni, Giovanna

    2010-11-01

    Hepcidin 25 (hep-25) is a peptide primarily produced by human liver with a central role in iron homeostasis. Its isoform, hepcidin 20 (hep-20), has an unknown function and lacks the first five aminoacids of the amino-terminal portion. This sequence is crucial for iron regulation by hep-25 and contains a molecular motif able to bind metals. Aim of this study, was to evaluate the antibacterial properties of both peptides in vitro, against a wide range of bacterial clinical isolates and in different experimental conditions. Although both peptides were found to be bactericidal against a variety of clinical isolates with different antibiotic resistance profiles, hep-20 was active at lower concentrations than hep-25, in most of the cases. Killing kinetics, carried on in sodium-phosphate buffer at pH 7.4, demonstrated that bactericidal activity occurred not earlier than 30-90 min of incubation. Bactericidal activity of hep-25 was slightly enhanced in the presence of copper, while the same metal did not affect the activity of hep-20. Interestingly, bactericidal activity of both hepcidins was highly enhanced at acidic pH. Acidic pH (pH 5.0 and 6.6) not only reduced the microbicidal concentrations of hepcidins, but also shortened the killing times of both peptides, as compared to pH 7.4. Combining hep-20 and hep-25 at pH 5.0 a bactericidal effect could be obtained at very low concentrations of both peptides. These results render hepcidins interesting for the design of new drugs for the treatment of infections occurring in body districts with physiologic acidic pH. Copyright © 2010 Elsevier Inc. All rights reserved.

  1. Contrasting Effects of Acidic pH on the Extracellular and Intracellular Activities of the Anti-Gram-Positive Fluoroquinolones Moxifloxacin and Delafloxacin against Staphylococcus aureus ▿ †

    Science.gov (United States)

    Lemaire, Sandrine; Tulkens, Paul M.; Van Bambeke, Françoise

    2011-01-01

    In contrast to currently marketed fluoroquinolones, which are zwitterionic, delafloxacin is an investigational fluoroquinolone with an anionic character that is highly active against Gram-positive bacteria. We have examined the effect of acidic pH on its accumulation in Staphylococcus aureus and in human THP-1 cells, in parallel with its activity against extracellular and intracellular S. aureus. Moxifloxacin was used as a comparator. Delafloxacin showed MICs 3 to 5 log2 dilutions lower than those of moxifloxacin for a collection of 35 strains with relevant resistance mechanisms and also proved to be 10-fold more potent against intracellular S. aureus ATCC 25923. In medium at pH 5.5, this difference was further enhanced, with the MIC decreasing by 5 log2 dilutions. In infected cells incubated in acidic medium, the relative potency was 10-fold higher than that at neutral pH and the maximal relative efficacy reached a bactericidal effect at 24 h. These results can be explained by a 10-fold increase in delafloxacin accumulation in both bacteria and cells at acidic pH, making delafloxacin one of the most efficient drugs tested in this model. Opposite effects were seen for moxifloxacin with respect to both activity and accumulation. As reported for zwitterionic fluoroquinolones, delafloxacin was found associated with the soluble fraction in homogenates of eukaryotic cells. Taken together, these properties may confer to delafloxacin an advantage for the eradication of S. aureus in acidic environments, including intracellular infections. PMID:21135179

  2. Influence of pH on Inhibitory Activity of Acetic Acid on Osmophilic Yeasts Used in Brine Fermentation of Soy Sauce

    OpenAIRE

    Noda, Fumio; Hayashi, Kazuya; Mizunuma, Takeji

    1982-01-01

    The inhibitory activity of acetic acid on osmophilic yeasts (Saccharomyces rouxii and Torulopsis versatilis) used for the brine fermentation of soy sauce increased remarkably as the pH of the medium was lowered. This increased toxicity could not be attributed to a hydrogen ion effect alone.

  3. Influence of pH and lactic acid concentration on Clostridium tyrobutyricum during continuous growth in a pH-auxostat

    NARCIS (Netherlands)

    Thylin, I; Schuisky, P; Lindgren, S; Gottschal, J.C

    1995-01-01

    The aim of this project was to establish the minimal inhibitory concentration (MIC) of lactic acid for growth of Clostridium tyrobutyricum. A pH-auxostat was used to maintain a constant pH and to allow continuous growth at the highest possible rates at fixed, but adjustable concentrations of

  4. Influence of pH and lactic acid concentration on Clostridium tyrobutyricum during continuous growth in a pH-auxostat

    NARCIS (Netherlands)

    Thylin, I; Schuisky, P; Lindgren, S; Gottschal, J.C

    1995-01-01

    The aim of this project was to establish the minimal inhibitory concentration (MIC) of lactic acid for growth of Clostridium tyrobutyricum. A pH-auxostat was used to maintain a constant pH and to allow continuous growth at the highest possible rates at fixed, but adjustable concentrations of lactate

  5. Simultaneous removal of As, Cd, Cr, Cu, Ni and Zn from stormwater using high-efficiency industrial sorbents: Effect of pH, contact time and humic acid

    DEFF Research Database (Denmark)

    Genc-Fuhrman, Hülya; Mikkelsen, Peter Steen; Ledin, Anna

    2016-01-01

    The effect of contact time, solution pH, and the presence of humic acid (HA) on the combined removal of As, Cd, Cr, Cu, Ni and Zn is investigated in batch tests using alumina, granulated activated carbon (GAC), and bauxsol coated sand (BCS) as sorbents. It is found that the equilibrium time for Cd...

  6. Transport and Retention of TiO2 Rutile Nanoparticles in Saturated Porous Media: Influence of Solution pH, Ionic Strength, and the Presence of Humic Acid

    Science.gov (United States)

    The influence of solution pH, ionic strength, and varying concentrations of the Suwannee River Humic Acid (SRHA) on the transport of titanium dioxide (TiO2, rutile) nanoparticle aggregates (nTiO2) in saturated porous media was investigated through systematically examining the tra...

  7. The effect of linoleic acid on pH inside sodium bis(2-ethylhexyl)sulfosuccinate reverse micelles in isooctane and on the enzymic activity of soybean lipoxygenase.

    Science.gov (United States)

    Rodakiewicz-Nowak, J; Maślakiewicz, P; Haber, J

    1996-06-01

    The effective pH of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles (pHrm), containing buffers of different pH (pHst) and various amounts of linoleic acid, was studied within the range of compositions used to study the activity of soybean lipoxygenase in reverse micelles. Significant shifts of pHrm versus pHst were observed for the solutions of relatively higher pHst, dependent on linoleic acid and buffer concentrations. The effect diminished as pHst became closer to 7. When low-ionic-strength buffers were added to AOT solutions in isooctane, a significant buffering effect of linoleic acid in reverse micelles was observed. Solubilization of > 3 mM linoleic acid in micellar solutions containing 25 mM buffers gave the observed pHrm values almost independent of pHst. This effect diminished with the ionic strength of the buffering solution, but did not vanish even at 200 mM buffer. The observed effects result from the balance between ionization of linoleic acid and its partition between the water pool and the micellar interface. The enzymic activity of soybean lipoxygenase in the AOT reverse micellar solutions of the determined pHrm values was also studied. A significant reduction of the kinetics of the enzymic activity was observed, for all studied reverse micellar solutions. Changes of pHrm, caused by the presence of acidic substrate (linoleic acid) do not explain the observed reduction of activity directly through the effect on the enzyme. Due to unfavourable partition of the substrate between the microphases present in the systems, enhanced by reduction of pH at higher total concentrations of linoleic acid, the saturation of the enzyme with the substrate was not observed in the system and is difficult to attain experimentally in reverse micelles. A shift of the lipoxygenase activity/pHrm profile but negligible shift of the activity/pHst profile, with respect to aqueous buffer solutions, were observed. This indicates that either the information given

  8. In-Lake Processes Offset Increased Terrestrial Inputs of Dissolved Organic Carbon and Color to Lakes

    Science.gov (United States)

    Köhler, Stephan J.; Kothawala, Dolly; Futter, Martyn N.; Liungman, Olof; Tranvik, Lars

    2013-01-01

    Increased color in surface waters, or browning, can alter lake ecological function, lake thermal stratification and pose difficulties for drinking water treatment. Mechanisms suggested to cause browning include increased dissolved organic carbon (DOC) and iron concentrations, as well as a shift to more colored DOC. While browning of surface waters is widespread and well documented, little is known about why some lakes resist it. Here, we present a comprehensive study of Mälaren, the third largest lake in Sweden. In Mälaren, the vast majority of water and DOC enters a western lake basin, and after approximately 2.8 years, drains from an eastern basin. Despite 40 years of increased terrestrial inputs of colored substances to western lake basins, the eastern basin has resisted browning over this time period. Here we find the half-life of iron was far shorter (0.6 years) than colored organic matter (A420 ; 1.7 years) and DOC as a whole (6.1 years). We found changes in filtered iron concentrations relate strongly to the observed loss of color in the western basins. In addition, we observed a substantial shift from colored DOC of terrestrial origin, to less colored autochthonous sources, with a substantial decrease in aromaticity (-17%) across the lake. We suggest that rapid losses of iron and colored DOC caused the limited browning observed in eastern lake basins. Across a wider dataset of 69 Swedish lakes, we observed greatest browning in acidic lakes with shorter retention times (< 1.5 years). These findings suggest that water residence time, along with iron, pH and colored DOC may be of central importance when modeling and projecting changes in brownification on broader spatial scales. PMID:23976946

  9. The Use of Response Surface Methodology in Optimization of Lactic Acid Production: Focus on Medium Supplementation, Temperature and pH Control

    Directory of Open Access Journals (Sweden)

    Cristian J. B. de Lima

    2010-01-01

    Full Text Available Two response surface methodologies involving central composite designs have been successfully applied to evaluate the effect of cheese whey, corn steep liquor, ammonium sulphate, temperature and pH control on lactic acid fermentation by Lactobacillus sp. LMI8 isolated from cassava flour wastewater. In the first central composite design, corn steep liquor and ammonium sulphate were investigated as low-cost nitrogen sources in combination with other components to substitute yeast extract for economical production. The best results were obtained with 55 g/L of lactose, 15 g/L of corn steep liquor and 5.625 g/L of ammonium sulphate. At the maximum point, the lactic acid concentration reached 18.68 g/L. After defining the optimal nutritional conditions for lactic acid production, a second central composite design was performed to determine the extent to which temperature and pH influence the lactic acid production with the aim of improving the fermentation process. The second-order polynomial regression model determined that the maximum lactic acid production of 52.37 g/L would be obtained when the optimum temperature and pH were 39.6 °C and 5.9, respectively. Comparing the lactic acid production in shake flask fermentation, there was an increase of 180 % after 30 h of processing, with a conversion efficiency of about 86.12 % of the initial lactose. In addition, lactic acid produced from whey lactose by Lactobacillus sp. LMI8 was optically almost pure D-lactic acid (over 98 % of total lactic acid produced.

  10. Factors affecting the environmental carrying capacity of a freshwater tropical lake system.

    Science.gov (United States)

    Mullakkezhil Reghunathan, Vishnuprasad; Joseph, Sabu; Warrier, C Unnikrishnan; Hameed, A Shahul; Albert Moses, Sheela

    2016-11-01

    Environmental carrying capacity is a measure of competence of a lake to accommodate pollution inputs without degrading water quality. In the research reported here, we identified the factors influencing the environmental carrying capacity of Vellayani Lake or VL (a typical tropical freshwater lake), Thiruvananthapuram, Kerala State, India. R-mode factor analysis is used to identify the factors controlling the carrying capacity of the lake, whereas hierarchical cluster analysis (HCA) helped to classify the lake. The carrying capacity of the lake is low with respect to alkalinity, due to ion deficiency, and is potentially reactive to sudden changes in pH. Eutrophic condition exists in the entire lake system. Acidic factor, mineralization factor, fertilizer factor (P & K), evaporation factor and organic pollution factor are the controllers of VL water quality during the pre-monsoon period. The same factors (but not evaporation factor) and an additional runoff factor control the water quality during monsoon. In the post-monsoon, the aforesaid factors (other than runoff, alkalinity) and soil erosion factor influence the water quality. Hence, managers of the lake system need to also focus on combating acidic factor during pre- and post-monsoons and runoff during monsoon. Smaller areal extent and shallow depth of VL, reduced outflow from it, less rainfall, presence of lateritic rock and soil and absence of limestone strata in the catchment are the chief elements affecting the acidic factor of Vellayani Lake.

  11. Bravo capsule system optimizes intragastric pH monitoring over prolonged time: Effects of ghrelin on gastric acid and hormone secretion in the rat

    Institute of Scientific and Technical Information of China (English)

    Tobias Rudholm; Per Mikael Hellstrom; Elvar Theodorsson; Colin Allan Campbell; Peter Geoffrey McLean; Erik Naslund

    2008-01-01

    AIM: To evaluate measurements of intragastric pH with the Bravo capsule system over a prolonged time. METHODS: A Bravo capsule was placed inside the rat gastric body and pH was studied for periods up to five consecutive days. For comparison, a gastric fistula model was used. Effects of ghrelin and esomeprazole, with or without pentagastrin, on gastric pH were studied. In addition, effects of esomeprazole on plasma ghrelin, gastrin and somatostatin were analyzed. RESULTS: All rats recovered after surgery. The average 24-h pH during free feeding was 2.3±0.1 (η = 20) with a variation of 18%±6% over 5 d. Ghrelin, 2400 pmol/kg, t.i.d, increased pH from 1.7± 0.1 to 3.1±0.3 (P<0.01) as recorded with the Bravo system. After esomeprazole (1 mg/kg, 3 mg/kg and 5 mg/kg) there was a dose-dependent pH increase of maximally 3.4±0.1, with day-to-day variation over the entire period of 8%±3%. The fistula and pH studies generated similar results. Acid inhibition with esomeprazole increased plasma ghrelin from 10±2 pmol/L to 65±26 pmol/L (P<0.001), and somatostatin from 10±2 pmol/L to 67±18 pmol/L (P <0.001). CONCLUSION: pH measurements with the Bravo capsule are reliable, and comparable to those of the gastric fistula model. The Bravo system optimizes accurate intragastric pH monitoring over prolonged periods and allows both short- and long-term evaluation of effects of drugs and hormones.

  12. Impacts of changing food webs in Lake Ontario: Implications of dietary fatty acids on growth of alewives

    Science.gov (United States)

    Snyder, R.J.; Demarche, C.J.; Honeyfield, D.C.

    2011-01-01

    Declines in the abundance and condition of Great Lakes Alewives have been reported periodically during the last two decades, and the reasons for these declines remain unclear. To better understand how food web changes may influence Alewife growth and Wisconsin growth model predictions, we fed Alewives isocaloric diets high in omega-6 fatty acids (corn oil) or high in omega-3 fatty acids (fish oil). Alewives were fed the experimental diets at either 1% ("low ration") or 3% ("high ration") of their wet body weight per day. After six weeks, Alewives maintained on the high ration diets were significantly larger than those fed the low ration diets. Moreover, Alewives given the high ration fish oil diet were significantly larger than those maintained on the high ration corn oil diet after six weeks of growth. Body lipid, energy density and total body energy of Alewives on the high ration diets were significantly higher than those fed the low ration diets, and total body energy was significantly higher in Alewives given the high ration fish oil diet compared to those on the high ration corn oil diet. The current Wisconsin bioenergetics model underestimated growth and overestimated food consumption by Alewives in our study. Alewife thiaminase activity was similar among treatment groups. Overall, our results suggest that future food web changes in Lake Ontario, particularly if they involve decreases in the abundance of lipid rich prey items such as Mysis, may reduce Alewife growth rates and total body energy due to reductions in the availability of dietary omega-3 fatty acids. ?? 2011 AEHMS.

  13. Preservation of glutamic acid-iron chelate into montmorillonite to efficiently degrade Reactive Blue 19 in a Fenton system under sunlight irradiation at neutral pH

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Zhujian [College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642 (China); Wu, Pingxiao, E-mail: pppxwu@scut.edu.cn [School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006 (China); The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006 (China); Gong, Beini; Yang, Shanshan; Li, Hailing [School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006 (China); Zhu, Ziao; Cui, Lihua [College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642 (China)

    2016-05-01

    Graphical abstract: - Highlights: • G–Fe chelate molecules were well preserved into montmorillonite. • The product shows an excellent catalytic activity under sunlight at neutral pH value. • G–Fe–Mt is a promising catalyst for advanced oxidation processes. - Abstract: To further enhance the visible light responsive property and the chemical stability of Fe/clay mineral catalysts, glutamic acid-iron chelate intercalated montmorillonite (G–Fe–Mt) was developed. The physiochemical properties of G–Fe–Mt were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), etc. The results showed that glutamic acid-iron chelates were successfully intercalated into the gallery of montmorillonite and the intercalated glutamic acid-iron chelate molecules were well preserved. The product G–Fe–Mt displayed excellent catalytic performance in heterogeneous photo-Fenton reaction under sunlight irradiation at acidic and neutral pH values. The chelation and the visible light responsiveness of glutamic acid produce a synergistic effect leading to greatly enhanced sunlight-Fenton reaction catalyzed by the heterogeneous G–Fe–Mt under neutral pH. G–Fe–Mt is a promising catalyst for advanced oxidation processes.

  14. Empirical Relationships Between Watershed Attributes and Headwater Lake Chemistry in the Adirondack Region

    Energy Technology Data Exchange (ETDEWEB)

    Hunsaker, C.T.

    1987-01-01

    Surface water acidification may be caused or influenced by both natural watershed processes and anthropogenic actions. Empirical models and observational data can be useful for identifying watershed attributes or processes that require further research or that should be considered in the development of process models. This study focuses on the Adirondack region of New York and has two purposes: to (1) develop empirical models that can be used to assess the chemical status of lakes for which no chemistry data exist and (2) determine on a regional scale watershed attributes that account for variability in lake pH and acid-neutralizing capacity (ANC). Headwater lakes, rather than lakes linked to upstream lakes, were selected for initial analysis. The Adirondacks Watershed Data Base (AWDB), part of the Acid Deposition Data Network maintained at Oak Ridge National Laboratory (ORNL), integrates data on physiography, bedrock, soils, land cover, wetlands, disturbances, beaver activity, land use, and atmospheric deposition with the water chemistry and morphology for the watersheds of 463 headwater lakes. The AWD8 facilitates both geographic display and statistical analysis of the data. The report, An Adirondack Watershed Data Base: Attribute and Mapping Information for Regional Acidic Deposition Studies (ORNL/TM--10144), describes the AWDB. Both bivariate (correlations and Wilcoxon and Kruskal-Wallis tests) and multivariate analyses were performed. Fifty-seven watershed attributes were selected as input variables to multiple linear regression and discriminant analysis. For model development -200 lakes for which pH and ANC data exist were randomly subdivided into a specification and a verification data set. Several indices were used to select models for predicting lake pH (31 variables) and ANC (27 variables). Twenty-five variables are common to the pH and ANC models: four lake morphology, nine soil/geology, eight land cover, three disturbance, and one watershed aspect. An

  15. Acidic pH conditions induce dissociation of the haem from the protein and destabilise the catalase isolated from Aspergillus terreus.

    Science.gov (United States)

    Vatsyayan, Preety; Goswami, Pranab

    2011-02-01

    The stability (half-life, t(½)) of the large catalase (CAT) isolated from Aspergillus terreus was decreased under acidic conditions (maximum t(½) approximately 8.5 months at pH ≤ 6) versus alkaline conditions (t(½) approximately 15 months at pH 8-12). Acidic conditions induce the dissociation of haem from CAT, as revealed from a reduction in the Soret peak intensity at 405 nm and an increase in the peak current at Fe(3+)/Fe(2+) redox potentials. This increase in current is attributed to the facile electron transfer from the free haem generated on the electrode surface as a result of its disintegration from the insulating protein matrix. The haem isolated from CAT at acidic condition was reconstituted with apo-CAT at alkaline denaturing conditions to regenerate the CAT activity.

  16. Short-term adaptation improves the fermentation performance of Saccharomyces cerevisiae in the presence of acetic acid at low pH.

    Science.gov (United States)

    Sànchez i Nogué, Violeta; Narayanan, Venkatachalam; Gorwa-Grauslund, Marie F

    2013-08-01

    The release of acetic acid due to deacetylation of the hemicellulose fraction during the treatment of lignocellulosic biomass contributes to the inhibitory character of the generated hydrolysates. In the present study, we identified a strain-independent adaptation protocol consisting of pre-cultivating the strain at pH 5.0 in the presence of at least 4 g L⁻¹ acetic acid that enabled aerobic growth and improved fermentation performance of Saccharomyces cerevisiae cells at low pH (3.7) and in the presence of inhibitory levels of acetic acid (6 g L⁻¹). During anaerobic cultivation with adapted cells of strain TMB3500, the specific ethanol production rate was increased, reducing the fermentation time to 48 %.

  17. pH effects on the complexation, miscibility and radiation-induced crosslinking in poly(acrylic acid)-poly(vinyl alcohol) blends.

    Science.gov (United States)

    Nurkeeva, Zauresh S; Mun, Grigoriy A; Dubolazov, Artem V; Khutoryanskiy, Vitaliy V

    2005-05-23

    The effect of pH on the complexation of poly(acrylic acid) with poly(vinyl alcohol) in aqueous solution, the miscibility of these polymers in the solid state and the possibility for crosslinking the blends using gamma radiation has been studied. It is demonstrated that the complexation ability of poly(vinyl alcohol) with respect to poly(acrylic acid) is relatively low in comparison with some other synthetic non-ionic polymers. The precipitation of interpolymer complexes was observed below the critical pH of complexation (pH(crit1)), which characterizes the transition between a compact hydrophobic polycomplex and an extended hydrophilic interpolymer associate. Films prepared by casting from aqueous solutions at different pH values exhibited a transition from miscibility to immiscibility at a certain critical pH, pH(crit2), above which hydrogen bonding is prevented. It is shown here that gamma radiation crosslinking of solid blends is efficient and only results in the formation of hydrogel films for blends prepared between pH(crit1) and pH(crit2). The yield of the gel fraction and the swelling properties of the films depended on the absorbed radiation dose and the polymer ratio. [Diagram: see text] SEM image of an equimolar PAA-PVA blend cast from a pH 4.6 solution.

  18. Acidic oral moisturizers with pH below 6.7 may be harmful to teeth depending on formulation: a short report

    Directory of Open Access Journals (Sweden)

    Delgado AJ

    2017-08-01

    Full Text Available Alex J Delgado,1 Vilhelm G Olafsson2,3 1Department of Restorative Dental Sciences, University of Florida, Gainesville, FL, USA; 2Department of Operative Dentistry, Faculty of Odontology, University of Iceland and Private Practice, Reykjavic, Iceland; 3Department of Operative Dentistry, School of Dentistry at the University of North Carolina, Chapel Hill, NC, USA Abstract: Xerostomia affects 30% of the population and manifests as a side effect of medications, systemic diseases, or cancer therapy. Oral moisturizers are prescribed to overcome the ailments of dry mouth and its symptoms. It is imperative that these products help to restore hyposalivation and that they do not present any secondary effect that can harm oral health. It has been shown in the literature that some oral moisturizers may have an erosive potential due to their acidic pH, which is below the critical pH of dentin and enamel. The purpose of this paper was to make clinicians aware of the erosive potential of these products and make recommendations to manufactures for future formulations avoiding acidic pH. For this reason, care should be taken to formulate these products with safe pH values for both enamel and root dentin which, based on specific formulation should be around 6.7 or higher. Keywords: oral moisturizers, pH, erosion, caries, xerostomia, dry mouth

  19. Jack bean (Canavalia ensiformis) urease. Probing acid-base groups of the active site by pH variation.

    Science.gov (United States)

    Krajewska, Barbara; Ciurli, Stefano

    2005-07-01

    A pH-variation study of jack bean (Canavalia ensiformis) urease steady-state kinetic parameters and of the inhibition constant of boric acid, a urease competitive inhibitor, was performed using both noninhibitory organic (MES, HEPES and CHES) and inhibitory inorganic (phosphate) buffers, in an effort to elucidate the functions exercised in the catalysis by the ionizable groups of the enzyme active site. The results obtained are consistent with the requirement for three groups utilized by urease with pK(a)s equal to 5.3+/-0.2, 6.6+/-0.2 and 9.1+/-0.4. Based on the appearance of the ionization step with pK(a)=5.3 in v(max)-pH, K(M)-pH and K(i)-pH profiles, we assigned this group as participating both in the substrate binding and catalytic reaction. As shown by its presence in v(max)-pH and K(M)-pH curves, the obvious role of the group with pK(a)=9.1 is the participation in the catalytic reaction. One function of the group featuring pK(a)=6.6, which was derived from a two-maxima v(max)-pH profile obtained upon increasing phosphate buffer concentration, an effect the first time observed for urease-phosphate systems, is the substrate binding, another possible function being modulation of the active site structure controlled by the ionic strength. It is also possible that the pK(a)=6.6 is a merger of two pK(a)s close in value. The study establishes that regular bell-shaped activity-pH profiles, commonly reported for urease, entail more complex pH-dependent behavior of the urease active site ionizable groups, which could be experimentally derived using species interacting with the enzyme, in addition to changing solution pH and ionic strength.

  20. Preparation and characterization of gelatin-poly(methacrylic acid interpenetrating polymeric network hydrogels as a ph-sensitive delivery system for glipizide

    Directory of Open Access Journals (Sweden)

    Gupta N

    2007-01-01

    Full Text Available In the present study, interpenetrating polymeric network hydrogels of glipizide were prepared using gelatin and methacrylic acid. Methacrylic acid was polymerized using potassium persulfate. Methacrylic acid was crosslinked with methylene bisacrylamide and gelatin was crosslinked using glutaraldehyde. Four formulations were prepared by varying the concentrations of methacrylic acid, methylene bisacrylamide and glutaraldehyde. The amounts of gelatin and potassium persulfate were kept constant in all the formulations. The interpenetrating polymeric network hydrogels were characterized by fourier transform infrared analysis, differential scanning calorimetry and evaluated for swelling and deswelling properties, drug loading and in vitro drug release. All the formulations showed no interaction between drug and polymer as confirmed by fourier transform infrared analysis and differential scanning calorimetric studies. The interpenetrating polymeric network hydrogels swelled only in alkaline pH and swelling was minimal in acidic pH. It was found that as the concentration of cross-linking agents is increased, there is a decrease in swelling and, as the concentration of methacrylic acid is increased, there is an increase in swelling. The release data shows that, as the concentration of methacrylic acid was increased, swelling increased resulting in increased release of the drug.

  1. A global assessment of precipitation chemistry and deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity and pH, and phosphorus

    Science.gov (United States)

    Vet, Robert; Artz, Richard S.; Carou, Silvina

    2014-08-01

    Investigating and assessing the chemical composition of precipitation and atmospheric deposition is essential to understanding how atmospheric pollutants contribute to contemporary environmental concerns including ecosystem acidification and eutrophication, loss of biodiversity, air pollution and global climate change. Evidence of the link between atmospheric deposition and these environmental issues is well established. The state of scientific understanding of this link is that present levels of atmospheric deposition of sulfur and nitrogen adversely affect terrestrial and aquatic ecosystems, putting forest sustainability and aquatic biodiversity at risk. Nitrogen and phosphorus loadings are linked to impacts on the diversity of terrestrial and aquatic vegetation through biological cycling, and atmospheric deposition plays a major role in the emission-transport-conversion-loss cycle of chemicals in the atmosphere as well as the formation of particulate matter and ozone in the troposphere. Evidence also shows that atmospheric constituents are changing the earth's climate through direct and indirect atmospheric processes. This Special Issue, comprising a single article titled "A global assessment of precipitation chemistry and deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity and pH, and phosphorus", presents a recent comprehensive review of precipitation chemistry and atmospheric deposition at global and regional scales. The information in the Special Issue, including all supporting data sets and maps, is anticipated to be of great value not only to the atmospheric deposition community but also to other science communities including those that study ecosystem impacts, human health effects, nutrient processing, climate change, global and hemispheric modeling and biogeochemical cycling. Understanding and quantifying pollutant loss from the atmosphere is, and will remain, an important component of each of these scientific fields as they

  2. Heavy metals removal from acid mine drainage water using biogenic hydrogen sulphide and effluent from anaerobic treatment: Effect of pH

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez-Rodriguez, A.M. [Departamento de Sistemas Fisicos, Quimicos y Naturales, Facultad de Ciencias Ambientales, Universidad Pablo de Olavide. Carretera de Utrera, km 1. 41013 Sevilla (Spain); Duran-Barrantes, M.M. [Departamento de Ingenieria Quimica, Facultad de Quimica, Universidad de Sevilla, C/Profesor Garcia Gonzalez, s/n, 41071 Sevilla (Spain); Borja, R., E-mail: rborja@cica.es [Consejo Superior de Investigaciones Cientificas (CSIC), Instituto de la Grasa, Avda. Padre Garcia Tejero 4, 41012 Sevilla (Spain); Sanchez, E.; Colmenarejo, M.F. [Consejo Superior de Investigaciones Cientificas (CSIC), Centro de Ciencias Medioambientales, C/Serrano, 115-duplicado, 28006 Madrid (Spain); Raposo, F. [Consejo Superior de Investigaciones Cientificas (CSIC), Instituto de la Grasa, Avda. Padre Garcia Tejero 4, 41012 Sevilla (Spain)

    2009-06-15

    Four alternatives (runs A, B, C and D) for heavy metals removal (Fe, Cu, Zn and Al) from acid mine drainage water (AMDW) produced in the mining areas of the Huelva Province, Spain, were evaluated. In run A, the anaerobic effluent from the treatment of acid mine drainage water (cheese whey added as a source of carbon) was mixed with the raw AMDW. The pH increased to 3.5 with the addition of KOH. In run B, biogas with around 30% of hydrogen sulphide obtained in the anaerobic reactor was sparged to the mixture obtained in run A, but in this case at a pH of 5.5. In run C, the pH of the raw AMDW was increased to 3.5 by the addition of KOH solution. Finally, in run D, the pH of the raw AMDW was increased to 5.5 by the addition of KOH solution and further biogas was sparged under the same conditions as in run A. It was found that heavy metal removal was a function of pH. At a pH of 3.5 most of the iron was removed while Zn and Cu were partially removed. At a pH of 5.5 the removal of all metals increased considerably. The best results were obtained in run B where the percentages of removal of Fe, Cu, Zn and Al achieved values of 91.3, 96.1, 79.0 and 99.0%, respectively. According to the experimental results obtained tentative schemas of the flow diagram of the processes were proposed.

  3. pH shift assembly of adenoviral serotype 5 capsid protein nanosystems for enhanced delivery of nanoparticles, proteins and nucleic acids.

    Science.gov (United States)

    Rao, Vidhya R; Upadhyay, Arun K; Kompella, Uday B

    2013-11-28

    Empty adenovirus serotype 5 (Ad5) capsids devoid of viral genome were developed as a novel delivery system for nanoparticles, proteins, and nucleic acids. Ad5 capsids of 110 nm diameter undergo an increase in particle size to 1637 nm in 1mM acetic acid at pH4.0 and then shrink to 60 nm, following pH reversal to 7.4. These pH shifts induced reversible changes in capsid zeta potential and secondary structure and irreversible changes in tertiary structure of capsid proteins. Using pH shift dependent changes in capsid size and structure, 20 nm fluorescent nanoparticles, FITC-BSA, and Alexa Fluor® 488 conjugated siRNA were encapsulated with high efficiency in Ad5 capsids, as confirmed by electron microscopy and/or flow cytometry. HEK cell uptake with capsid delivery system was 7.8-, 7.4-, and 2.9-fold greater for nanoparticles, FITC-BSA, and Alexa-siRNA, respectively, when compared to plain solutes. Physical mixtures of capsids and fluorescent solutes exhibited less capsid associated fluorescence intensity and cell uptake. Further, unlike physical mixture, pH shift assembled Ad5 capsids protected siRNA from RNase degradation. Ad5 capsids before and after pH shift exhibited endolysosomal escape. Thus, empty Ad5 capsids can encapsulate a variety of solutes based on pH shift assembly, resulting in enhanced cellular delivery. © 2013. Published by Elsevier B.V. All rights reserved.

  4. Synthesis and Characterization of Chemically Cross-Linked Acrylic Acid/Gelatin Hydrogels: Effect of pH and Composition on Swelling and Drug Release

    Directory of Open Access Journals (Sweden)

    Syed Majid Hanif Bukhari

    2015-01-01

    Full Text Available This present work was aimed at synthesizing pH-sensitive cross-linked AA/Gelatin hydrogels by free radical polymerization. Ammonium persulfate and ethylene glycol dimethacrylate (EGDMA were used as initiator and as cross-linking agent, respectively. Different feed ratios of acrylic acid, gelatin, and EGDMA were used to investigate the effect of monomer, polymer, and degree of cross-linking on swelling and release pattern of the model drug. The swelling behavior of the hydrogel samples was studied in 0.05 M USP phosphate buffer solutions of various pH values pH 1.2, pH 5.5, pH 6.5, and pH 7.5. The prepared samples were evaluated for porosity and sol-gel fraction analysis. Pheniramine maleate used for allergy treatment was loaded as model drug in selected samples. The release study of the drug was investigated in 0.05 M USP phosphate buffer of varying pH values (1.2, 5.5, and 7.5 for 12 hrs. The release data was fitted to various kinetic models to study the release mechanism. Hydrogels were characterized by Fourier transformed infrared (FTIR spectroscopy which confirmed formation of structure. Surface morphology of unloaded and loaded samples was studied by surface electron microscopy (SEM, which confirmed the distribution of model drug in the gel network.

  5. Kinetics of an acid-base catalyzed reaction (aspartame degradation) as affected by polyol-induced changes in buffer pH and pK values.

    Science.gov (United States)

    Chuy, S; Bell, L N

    2009-01-01

    The kinetics of an acid-base catalyzed reaction, aspartame degradation, were examined as affected by the changes in pH and pK(a) values caused by adding polyols (sucrose, glycerol) to phosphate buffer. Sucrose-containing phosphate buffer solutions had a lower pH than that of phosphate buffer alone, which contributed, in part, to reduced aspartame reactivity. A kinetic model was introduced for aspartame degradation that encompassed pH and buffer salt concentrations, both of which change with a shift in the apparent pK(a) value. Aspartame degradation rate constants in sucrose-containing solutions were successfully predicted using this model when corrections (that is, lower pH, lower apparent pK(a) value, buffer dilution from the polyol) were applied. The change in buffer properties (pH, pK(a)) from adding sucrose to phosphate buffer does impact food chemical stability. These effects can be successfully incorporated into predictive kinetic models. Therefore, pH and pK(a) changes from adding polyols to buffer should be considered during food product development.

  6. Copper release kinetics from a long-term contaminated acid soil using a stirred flow chamber: effect of ionic strength and pH.

    Science.gov (United States)

    Fernández-Calviño, David; Bermúdez-Couso, Alipio; Garrido-Rodríguez, Beatriz; Peña Rodríguez, Susana; Arias-Estévez, Manuel

    2012-02-01

    The effect of pH and ionic strength on copper release in a long-term Cu-polluted soil was studied using a stirred flow chamber. The presence of Ca(2+) and Na(+) was also evaluated. More copper was released as the ionic strength increased, and it was significantly higher in the presence of Ca(2+) than in the presence of Na(+). The maximum amount of Cu that could be released under experimental conditions increased logarithmically as the ionic strength increased, and the release rate parameters were not significantly correlated with ionic strength values. The maximum amount of Cu that could be released was similar for solutions with pH values between 5.5 and 8.5. For solutions with a pH value below 4.5, the amount of Cu released increased exponentially as the pH decreased. The release rate parameters and Cu release pattern were affected by pH, especially for more acidic solutions (pH values of 2.5 and 3.5).

  7. pH- and Electro-Responsive Properties of Poly(acrylic acid) and Poly(acrylic acid)-block-poly(acrylic acid-grad-styrene) Brushes Studied by Quartz Crystal Microbalance with Dissipation Monitoring.

    Science.gov (United States)

    Borisova, O V; Billon, L; Richter, R P; Reimhult, E; Borisov, O V

    2015-07-14

    We report on the synthesis of novel pH- and electro-responsive polyelectrolyte brushes from a gold substrate by direct one-step nitroxide-mediated polymerization of acrylic acid (AA) or copolymerization of AA and styrene (S). In the latter case, amphiphilic brushes of block-gradient copolymers PAA-b-(PAA-grad-PS) comprising one PAA block and one block with the gradient sequence of AA and S were obtained. The block-gradient copolymers are initiated from the surface by the start of the PAA block. The brushes were characterized by XPS and ellipsometry. (1)H NMR confirmed the gradient sequence of the PAA-grad-PS copolymer block. The pH- and electro-responsive properties of the brushes were studied by quartz crystal microbalance with dissipation monitoring (QCM-D) in combination with electrochemistry. This method provides evidence of swelling of the PAA brushes proportional to the contour length of the chains at elevated pH, whereas the response functions of the block-gradient copolymers are more complex and point to intermolecular aggregation in the brush at low pH. Monitoring of the changes in resonance frequency and dissipation of the QCM-D also demonstrates that application of negative voltage to the substrate leads to swelling of the brush; application of a positive voltage provokes only a transient collapse of the brush in proportion to the applied voltage.

  8. Evaluation of buffers toxicity in tobacco cells: Homopiperazine-1,4-bis (2-ethanesulfonic acid) is a suitable buffer for plant cells studies at low pH.

    Science.gov (United States)

    Borgo, Lucélia

    2017-06-01

    Low pH is an important environmental stressor of plant root cells. Understanding the mechanisms of stress and tolerance to acidity is critical; however, there is no widely accepted pH buffer for studies of plant cells at low pH. Such a buffer might also benefit studies of Al toxicity, in which buffering at low pH is also important. The challenge is to find a buffer with minimal cellular effects. We examined the cytotoxicity and possible metabolic disturbances of four buffers that have adequate pKa values and potential use for studies in the pH range of 4.0-5.0. These were homopipes (homopiperazine-1,4-bis (2-ethanesulfonic acid); pKa1 4.4), 3,3-dimethylglutaric acid (pKa1 3.73), β-alanine (pKa1 3.70) and potassium biphthalate (pKa1 2.95; pKa2 5.41). First, tobacco BY-2 cells were grown in a rich medium containing 10 mM of each buffer or MES (2-(N-morpholino) ethanesulfonic acid) as a control, with the pH initially adjusted to 5.7. β-alanine was clearly toxic and dimethylgluturate and biphthalate were found to be cytostatic, in which no culture growth occurred but cell viability was either unaffected or decreased only after 5 days. Only homopipes allowed normal culture growth and cell viability. Homopipes (10 mM) was then tested in cell cultures with an initial pH of 4.3 ± 0.17 in minimal medium to examine whether its undissociated species (H2A) displayed any cellular effects and no cytotoxic effects were observed. It is possible to conclude that among tested buffers, homopipes is the most suitable for studies at low pH, and may be especially useful for aluminum toxicity experiments. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  9. Effectiveness of the bran media and bacteria inoculum treatments in increasing pH and reducing sulfur-total of acid sulfate soils

    Science.gov (United States)

    Taufieq, Nur Anny Suryaningsih; Rahim, Sahibin Abdul; Jamil, Habibah

    2013-11-01

    This study was carried out to determine the effectiveness ofsulfate reducing bacteria (SRB) in using bran as a source of food and energy, and to see the effectiveness of the bran media and bacteria inoculums treatments for pH and sulfur-total of acid sulfate reduction insoils. This study used two factors in group random designs with four treatments for bacteria inoculum of B1 (1%), B2 (5%), B3 (10%), B4 (15%) and two treatments for organic media (bran) of D1 (1:1) and D2 (1:19). Based on three replications, the combination resulted in a total of 24 treatments. Soil pH was measured using the Duddridge and Wainright method and determination of sulfate content in soil was conducted by the spectrophotometry method. The data obtained was analyzed for significance by Analysis of Variance and the Least Significant Difference Test. The pH of the initial acid sulfate soils ranged from 3 to 4 and the soil sulfur-total ranged from 1.4% to 10%. After mixing sulfate reducing bacteria with the bran mediaand incubated for four days, the pH of the acid sulfate soils increased from 3.67 to 4.20, while the soil sulfur-total contents had been reduced by 2.85% to 0.35%. This experiment has proven that an acid sulfate soil with low pH is a good growth medium for the sulfate reducing bacteria. The bestincubation period to achieve an effective bioremediation resultthrough sulfate percentage reduction by sulfate reducing bacteria was 10 days, while the optimum bran media dose was 1:19, and the bacteria inoculums dose was 10%.

  10. Amino Acids and Stable Carbon Isotope Distributions in Taihu Lake, China, Over the Last 15,000 Years, and Their Paleoecological Implications

    Science.gov (United States)

    Jinquan, Wang; Jinling, Liu

    2000-03-01

    Amino acid, organic nitrogen, and stable carbon isotope (13C/12C) profiles through a core from East Taihu Lake are interpreted in terms of paleoecology and paleoclimate over the last ca. 15,000 yr. Lower amino acid contents and higher δ13C values at the base of the core represent a cool and arid climate, and coincide with low organic productivity. A marked increase in total amino acids and organic nitrogen, with a decrease in δ13C values from 193 to 90 cm (ca. 6500-6000 yr B.P.), indicates a warmer and moist climate, and greater organic productivity. Amino acids then decrease in abundance, while δ13C values increase progressively, beginning at 73 cm (ca. 6000 yr B.P.), reflecting cooling and lower organic productivity. The average δ13C values from a core from West Taihu Lake are evidently higher than values from East Taihu Lake. The latter may reflect a stream environment, whereas the high δ13C values from West Taihu Lake likely reflect autotrophic carbon sources and a lacustrine environment since 11,000 yr B.P.

  11. Lake Granbury and Lake Whitney Assessment Initiative Final Scientific/Technical Report Summary

    Energy Technology Data Exchange (ETDEWEB)

    Harris, B. L. [Texas AgriLife Research, College Station, TX (United States); Roelke, Daniel [Texas AgriLife Research, College Station, TX (United States); Brooks, Bryan [Texas AgriLife Research, College Station, TX (United States); Grover, James [Texas AgriLife Research, College Station, TX (United States)

    2010-10-11

    blooms. Our numerical modeling results support the idea that cyanobacteria, through allelopathy, control the timing of golden algae blooms in Lake Granbury. The in-lake experiments in Lake Whitney and Lake Waco also revealed that as golden algae blooms develop, there are natural enemies (a species of rotifer, and a virus) that help slow the population growth. Again, better characterization of these organisms is a high priority as it may be key to managing golden algae blooms. Our laboratory and in-lake experiments and field monitoring have shown that nutrient additions will remove toxicity and prevent golden algae from blooming. In fact, other algae displace the golden algae after nutrient additions. Additions of ammonia are particularly effective, even at low doses (much lower than what is employed in fish hatchery ponds). Application of ammonia in limited areas of lakes, such as in coves, should be explored as a management option. The laboratory experiments and field monitoring also show that the potency of toxins produced by P. parvum is greatly reduced when water pH is lower, closer to neutral levels. Application of mild acid to limited areas of lakes (but not to a level where acidic conditions are created), such as in coves, should be explored as a management option. Finally, our field monitoring and mathematical modeling revealed that flushing/dilution at high enough levels could prevent P. parvum from forming blooms and/or terminate existing blooms. This technique could work using deeper waters within a lake to flush the surface waters of limited areas of the same lakes, such as in coves and should be explored as a management option. In this way, water releases from upstream reservoirs would not be necessary and there would be no addition of nutrients in the lake.

  12. Reactivity and acid-base behavior of ring-methoxylated arylalkanoic acid radical cations and radical zwitterions in aqueous solution. Influence of structural effects and pH on the benzylic C-H deprotonation pathway.

    Science.gov (United States)

    Bietti, Massimo; Capone, Alberto

    2006-07-07

    A product and time-resolved kinetic study of the one-electron oxidation of ring-methoxylated phenylpropanoic and phenylbutanoic acids (Ar(CH2)nCO2H, n = 2, 3) has been carried out at different pH values. Oxidation leads to the formation of aromatic radical cations (Ar.+(CH2)nCO2H) or radical zwitterions (Ar.+(CH2)nCO2-) depending on pH, and pKa values for the corresponding acid-base equilibria have been measured. In the radical cation, the acidity of the carboxylic proton decreases by increasing the number of methoxy ring substituents and by increasing the distance between the carboxylic group and the aromatic ring. At pH 1.7 or 6.7, the radical cations or radical zwitterions undergo benzylic C-H deprotonation as the exclusive side-chain fragmentation pathway, as clearly shown by product analysis results. At pH 1.7, the first-order deprotonation rate constants measured for the ring-methoxylated arylalkanoic acid radical cations are similar to those measured previously in acidic aqueous solution for the alpha-C-H deprotonation of structurally related ring-methoxylated alkylaromatic radical cations. In basic solution, the second-order rate constants for reaction of the radical zwitterions with (-)OH (k-OH)) have been obtained. These values are similar to those obtained previously for the (-)OH-induced alpha-C-H deprotonation of structurally related ring-methoxylated alkylaromatic radical cations, indicating that under these conditions the radical zwitterions undergo benzylic C-H deprotonation. Very interestingly, with 3,4-dimethoxyphenylethanoic acid radical zwitterion, that was previously observed to undergo exclusive decarboxylation up to pH 10, competition between decarboxylation and benzylic C-H deprotonation is observed above pH 11.

  13. The disintegration of populations of underwater plants in soft water lakes enriched with acidic organic matter

    Directory of Open Access Journals (Sweden)

    Józef Szmeja

    2011-01-01

    Full Text Available The characteristics of habitats, individuals and populations of four submerged macrophytes, Lobelia dortmanna L., Isoetes lacustris L., Sphagnum denticulatum Brid. and Fontinalis antipyretica Hedw., were studied in 12 soft water oligohumic lakes which had no inflow of allochtonic DOM and the DOC concentration in the water was <4.0 mg C dm-3 and 13 humic lakes enriched with allochthonous dissolved organic matter (DOM from drained peat bogs and ranging in DOC water concentration from 4.1 to 44.0 mg C dm-3. The analyses of population disintegration were conducted basing on characteristics of individuals (size, habitat, fertility and populations (aggregation density index, settlement index of the population area. The settlement index of the population area for Lobelia, Fontinalis, Isoetes, Sphagnum decreased from 8.4 to 6.2 g d.w. m-2, 4.6 to 0.01 g d.w. m-2, 85.4 to <0.001 g d.w. m-2 and 39.3 to 7.2 g d.w. m-2, respectively. Similar trends were observed in aggregation density. The general pattern of the disintegration of populations of these species was always similar. It was independent of the source macrophytes drew resources from or their susceptibility to environmental changes. Individuals began to be eliminated from the deep and central parts of the population area. The remainder of the populations, which persist in the shallowest, best-illuminated part of the area, are themselves endangered by disturbances caused by wavy motion. The only populations of submerged macrophytes which can survive in polyhumic lakes under such conditions are those which are resistant to disturbances common in the shallow littoral (Lobelia dortmanna, Fontinalis antipyretica.

  14. The use of high pressure CO2 -facilitated pH swings to enhance in situ product recovery of butyric acid in a two-phase partitioning bioreactor.

    Science.gov (United States)

    Peterson, Eric C; Daugulis, Andrew J

    2014-11-01

    Through the use of high partial pressures of CO2 (pCO2 ) to facilitate temporary pH reductions in two-phase partitioning bioreactors (TPPBs), improved pH dependent partitioning of butyric acid was observed which achieved in situ product recovery (ISPR), alleviating end-product inhibition (EPI) during the production of butyric acid by Clostridium tyrobutyricum (ATCC 25755). Through high pressure pCO2 studies, media buffering effects were shown to be substantially overcome at 60 bar pCO2 , resulting in effective extraction of the organic acid by the absorptive polymer Pebax® 2533, yielding a distribution coefficient (D) of 2.4 ± 0.1 after 1 h of contact at this pressure. Importantly, it was also found that C. tyrobutyricum cultures were able to withstand 60 bar pCO2 for 1 h with no decrease in growth ability when returned to atmospheric pressure in batch reactors after several extraction cycles. A fed-batch reactor with cyclic high pCO2 polymer extraction recovered 92 g of butyric acid to produce a total of 213 g compared to 121 g generated in a control reactor. This recovery reduced EPI in the TPPB, resulting in both higher productivity (0.65 vs. 0.33 g L(-1)  h(-1) ) and yield (0.54 vs. 0.40). Fortuitously, it was also found that repeated high pCO2 -facilitated polymer extractions of butyric acid during batch growth of C. tyrobutyricum lessened the need for pH control, and reduced base requirements by approximately 50%. Thus, high pCO2 -mediated absorptive polymer extraction presents a novel method for improving process performance in butyric acid fermentation, and this technique could be applied to the bioproduction of other organic acids as well.

  15. TiO2 Nanoparticles Aggregation and Disaggregation in Presence of Alginates and Humic Acids: pH and Concentration Effects on Suspension Stability

    Science.gov (United States)

    Loosli, Frédéric; Le Coustumer, Philippe; Stoll, Serge

    2013-04-01

    The behavior of manufactured TiO2 nanoparticles is studied here in a systematic way as a function of pH and in the presence of Suwannee river humic acids and alginate, at variable concentrations, which represent two major components found in aquatic systems. TiO2 nanoparticles aggregation, disaggregation and stabilization are investigated using dynamic light scattering and electrophoretic experiments allowing the measurement and evolution determination of z-average hydrodynamic diameters and zeta potential values. Stability of the TiO2 nanoparticles is carried out by considering three pH-dependent electrostatic scenarios (below the point of zero charge of the nanoparticles, at the point of zero charge and above it). In the first scenario, when pH is below the point of zero charge of the TiO2 nanoparticles, nanoparticles exhibit a positively charged surface whereas alginate and Suwannee river humic acids are negatively charged. Fast adsorption at the TiO2 nanoparticles occurs, promotes surface charge neutralization and aggregation and, by increasing further Alginate and Suwannee river humic acids, results in charge inversion and thus stabilization of TiO2 nanoparticles. In the second electrostatic scenario, at the pH of the TiO2 surface charge neutralization, TiO2 nanoparticles are rapidly forming aggregates and adsorption of alginate and Suwannee river humic acid on aggregates surface leads to the partial disaggregation of aggregates. In the third electrostatic scenario, when nanoparticles, alginates and Suwannee river humic acids are negatively charged a small amount of Suwannee river humic acids is adsorbed via hydrophobic interactions. It is found that the fate and behavior of individual and aggregated TiO2 nanoparticles in presence of environmental compounds are strongly dependent on the electrostatic, concentration ratio, and to a less extend to the amphiphilic compounds character and that environmental aquatic concentration ranges of humic acids and

  16. Sorption of Am(Ⅲ) on Na-bentonite: Effect of pH, ionic strength,temperature and humic acid

    Institute of Scientific and Technical Information of China (English)

    Tao Yu; Wang Suo Wu; Qiao Hui Fan

    2012-01-01

    Sorption of Am(Ⅲ) on Na-bentonite as a function of contact time,pH,ionic strength,humic acid (HA) and temperature was investigated under ambient conditions.The results showed that the sorption was strongly dependent on pH and ionic strength.Am(Ⅲ) sorption can be described well by pseudo-second-order model.The presence of HA takes a positive effect at low pH; but a negative influence under high pH range.Enthalpy,entropy and Gibbs free energy (i.e.,AH0,AS0 and AG0) calculated from sorption isotherms suggested that sorption process of Am(Ⅲ) was spontaneous and endothermic.

  17. Fatty acid fouling of forward osmosis membrane: Effects of pH, calcium, membrane orientation, initial permeate flux and foulant composition.

    Science.gov (United States)

    Zhao, Pin; Gao, Baoyu; Yue, Qinyan; Liu, Pan; Shon, Ho Kyong

    2016-08-01

    Octanoic acid (OA) was selected to represent fatty acids in effluent organic matter (EOM). The effects of feed solution (FS) properties, membrane orientation and initial permeate flux on OA fouling in forward osmosis (FO) were investigated. The undissociated OA formed a cake layer quickly and caused the water flux to decline significantly in the initial 0.5hr at unadjusted pH3.56; while the fully dissociated OA behaved as an anionic surfactant and promoted the water permeation at an elevated pH of 9.00. Moreover, except at the initial stage, the sudden decline of water flux (meaning the occurrence of severe membrane fouling) occurred in two conditions: 1. 0.5mmol/L Ca(2+), active layer facing draw solution (AL-DS) and 1.5mol/L NaCl (DS); 2. No Ca(2+), active layer-facing FS (AL-FS) and 4mol/L NaCl (DS). This demonstrated that cake layer compaction or pore blocking occurred only when enough foulants were absorbed into the membrane surface, and the water permeation was high enough to compact the deposit inside the porous substrate. Furthermore, bovine serum albumin (BSA) was selected as a co-foulant. The water flux of both co-foulants was between the fluxes obtained separately for the two foulants at pH3.56, and larger than the two values at pH9.00. This manifested that, at pH3.56, BSA alleviated the effect of the cake layer caused by OA, and OA enhanced BSA fouling simultaneously; while at pH9.00, the mutual effects of OA and BSA eased the membrane fouling.

  18. Effect of weak acid preservatives on growth of bakery product spoilage fungi at different water activities and pH values.

    Science.gov (United States)

    Suhr, K I; Nielsen, P V

    2004-08-15

    Inhibition of spoilage organisms from bakery products by weak acid preservatives in concentrations of 0%, 0.003%, 0.03% and 0.3% (w/v) was investigated experimentally on a substrate media with water activity (a(w)) and pH ranging from sourdough-fermented acidic rye bread to alkaline intermediate moisture sponge cake types (a(w) 0.80-0.95, pH 4.7-7.4). Initially, rye bread conditions (a(w) 0.94-0.97 and pH 4.4-4.8) in combination with calcium propionate were investigated. Results showed that the highest concentration of propionate (0.3%) at all conditions apart from high a(w) (0.97) and high pH (4.8) totally inhibited fungal growth for a 2-week period, with the exception of Penicillium roqueforti, Penicillium commune and Eurotium rubrum. Characteristically for the major spoiler of rye bread, P. roqueforti, all three isolates tested were stimulated by propionate and the stimulation was significantly enhanced at high water activity levels. The effect of propionate on production of secondary metabolites (mycophenolic acid, rugulovasine, echinulin, flavoglaucin) was also studied, and variable or isolate dependent results were found. Subsequently, a screening experiment representing a wider range of bakery products was conducted using calcium propionate, potassium sorbate and sodium benzoate. The obtained data was modelled using survival analysis to determine 'spoilage-free time' for the fungi. At the low a(w) level (0.80) only Eurotium species grew within the test period of 30 days. Higher water activity levels as well as higher pH values decreased spoilage-free times of the fungi. The preservative calcium propionate was less effective than potassium sorbate and sodium benzoate.

  19. Fatty Acid Composition and Levels of Selected Polyunsaturated Fatty Acids in Four Commercial Important Freshwater Fish Species from Lake Victoria, Tanzania

    Directory of Open Access Journals (Sweden)

    Agnes Robert

    2014-01-01

    Full Text Available Fatty acids (FAs particularly ω3 and ω6 polyunsaturated fatty acids (PUFAs play important role in human health. This study aimed to investigate the composition and levels of selected ω3 PUFAs in four commercial fish species, Nile perch (Lates niloticus, Nile tilapia (Oreochromis niloticus, Tilapia zillii, and dagaa (Rastrineobola argentea from Mwanza Gulf in Lake Victoria. The results indicated that 36 types of FAs with different saturation levels were detected. These FAs were dominated by docosahexaenoic (DHA, eicosapentaenoic (EPA, docosapentaenoic (DPA, and eicosatetraenoic acids. O. niloticus had the highest composition of FAs (34 compared to L. niloticus (27, T. zillii (26, and R. argentea (21. The levels of EPA differed significantly among the four commercial fish species (F=6.19,  P=0.001. The highest EPA levels were found in R. argentea followed by L. niloticus and O. niloticus and the lowest in T. zillii. The DPA levels showed no significant difference among the four fish species studied (F=0.652,  P=0.583. The study concluded that all four commercial species collected from Mwanza Gulf are good for human health, but R. argentea is the best for consumption because it contains higher levels of ω3 FAs, mainly EPA.

  20. Pluriannual evolution of the hydrochemistry of two Alpine lakes (Lake Paione Inferiore and Lake Paione Superiore, Ossola Valley in relation to atmospheric loads.

    Directory of Open Access Journals (Sweden)

    Gabriele A. TARTARI

    1999-02-01

    Full Text Available Lakes Paione Inferiore and Paione Superiore (LPI, LPS are extremely sensitive to acidification, so they are useful as indicators in studying changes in atmospheric pollutant fluxes on waterbodies. Regular trends observed in the last 3-4 years cannot merely be a consequence of seasonal or interannual variations. Increasing pH and alkalinity are mainly driven by a decrease in acidic inputs from the atmosphere, which have been halved over the last 10 years. This trend of atmospheric deposition chemistry has emerged in several sampling stations in the subalpine and Alpine area, in the watershed of Lake Maggiore. The decrease in deposition acidity is mainly related to a decrease in sulphate, while nitrate and ammonium deposition is still high, resulting in high nitrate concentrations in lake waters.

  1. Characterization of the acidic and basic limbs of a bell-shaped pH profile in the inhibitory activity of bromelain inhibitor VI.

    Science.gov (United States)

    Hatano, Ken-ichi; Sawano, Yoriko; Miyakawa, Takuya; Tanokura, Masaru

    2006-03-01

    Bromelain inhibitor VI (BI-VI) is a cysteine proteinase inhibitor from pineapple stem and a unique two-chain inhibitor composed of two distinct domains. BI-VI's inhibitory activity toward the target enzyme bromelain is maximal at pH 4 and shows a bell-shaped pH profile with pKa values of about 2.5 and 5.3. This pH profile is quite different from that of bromelain, which is optimally active around pH 7. In the present article, to characterize the acidic limb, we first expressed the recombinant inhibitors designed to lose two putative hydrogen bonds of Ser7(NH)-Asp28(beta-CO2H) and Lys38(NH)-Asp51(beta-CO2H) and confirmed the existence of the hydrogen bonds by two-dimensional nuclear magnetic resonance (NMR). Moreover, it was revealed that these hydrogen bonds are not the essential electrostatic factor and some ionizable groups would be responsible for the acidic limb in the pH-inhibition profile. On the other hand, to characterize the basic limb, we examined the pH-dependent inhibition using the cysteine proteinase papain, some of whose properties differ from those of bromelain, and compared the data with the corresponding data for bromelain. The result suggests that the basic limb would be affected by some electrostatic factors, probably some carboxyl groups in the target proteinase.

  2. Matching phosphate and maleate buffer systems for dissolution of weak acids: Equivalence in terms of buffer capacity of bulk solution or surface pH?

    Science.gov (United States)

    Cristofoletti, Rodrigo; Dressman, Jennifer B

    2016-06-01

    The development of in vitro dissolution tests able to anticipate the in vivo fate of drug products has challenged pharmaceutical scientists over time, especially in the case of ionizable compounds. In the seminal model proposed by Mooney et al. thirty-five years ago, the pH at the solid-liquid interface (pH0) was identified as a key parameter in predicting dissolution rate. In the current work it is demonstrated that the in vitro dissolution of the weak acid ibuprofen in maleate and phosphate buffer systems is a function of the pH0, which in turn is affected by properties of the drug and the medium. The reported pH0 for ibuprofen dissolution in bicarbonate buffer, the predominant buffer species in the human small intestine under fasting conditions, can be achieved by reducing the phosphate buffer concentration to 5.0mM or the maleate buffer concentration to 2.2mM. Using this approach to identify the appropriate buffer/buffer capacity combination for in vitro experiments in FaSSIF-type media, it would be possible to increase the physiological relevance of this important biopharmaceutics tool. However, the necessity of monitoring and adjusting the bulk pH during the experiments carried out in 5.0mM phosphate or 2.2mM maleate buffers must also be taken into consideration. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Compartment-specific pH monitoring in Bacillus subtilis using fluorescent sensor proteins; a tool to analyse the antibacterial effect of weak organic acids.

    Directory of Open Access Journals (Sweden)

    Johan W.A. van Beilen

    2013-06-01

    Full Text Available The internal pH (pHi of a living cell is one of its most important physiological parameters. To monitor the pH inside B. subtilis during various stages of its life cycle, we constructed an improved version (IpHluorin of the ratiometric, pH-sensitive fluorescent protein pHluorin by extending it at the 5’ end with the first 24 bp of comGA. The new version, which showed an approximate 40% increase in fluorescence intensity, was expressed from developmental phase-specific, native promoters of B. subtilis that are specifically active during vegetative growth on glucose (PptsG or during sporulation (PspoIIA, PspoIIID and PsspE. Our results show strong, compartment-specific expression of IpHluorin that allowed accurate pHi measurements of live cultures during exponential growth, early and late sporulation, spore germination, and during subsequent spore outgrowth. Dormant spores were characterised by an internal pH of 6.0 ± 0.3. Upon full germination the internal pH rose dependent on the medium to 7.0-7.4. The presence of sorbic acid in the germination medium inhibited a rise in the intracellular pH of germinating spores and inhibited germination. Such effects were absent when acetic was added at identical concentrations.

  4. A Two-stage pH and Temperature Control with Substrate Feeding Strategy for Production of Gamma-aminobutyric Acid by Lactobacillus brevis CGMCC 1306

    Institute of Scientific and Technical Information of China (English)

    彭春龙; 黄俊; 胡升; 赵伟睿; 姚善泾; 梅乐和

    2013-01-01

    Methods to optimize the production of gamma-aminobutyric acid (GABA) by Lactobacillus brevis CGMCC 1306 were investigated. Results indicated that cell growth was maximal at pH 5.0, while pH 4.5 was pref-erable to GABA formation. The optimal temperature for cell growth (35 °C) was lower than that for GABA forma-tion (40 °C). In a two-stage pH and temperature control fermentation, cultures were maintained at pH 5.0 and 35 °C for 32 h, then adjusted to pH 4.5 and 40 °C, GABA production increased remarkably and reached 474.79 mmol·L-1 at 72 h, while it was 398.63 mmol·L-1 with one stage pH and temperature control process, in which cultivation con-ditions were constantly controlled at pH 5.0 and 35 °C. In order to avoid the inhibition of cell growth at higher L-monosodium glutamate (L-MSG) concentrations, the two-stage control fermentation with substrate feeding strat-egy was applied to GABA production, with 106.87 mmol (20 g) L-MSG supplemented into the shaking-flask at 32 h and 56 h post-