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Sample records for acid base hydrolytic

  1. Synthesis and characterization of hydrolytically degradable copolyester biomaterials based on glycolic acid, sebacic acid and ethylene glycol.

    PubMed

    Simitzis, J; Soulis, S; Triantou, D; Zoumpoulakis, L; Zotali, P

    2011-12-01

    Copolyesters of glycolic acid (G) combined with sebacic acid (S) and ethylene glycol were synthesized in different molar ratios (G: 0-100% and S: 100-0%) and their hydrolytic degradation was studied and correlated with their structures. Based on the FTIR spectra of the homopolyesters and copolyesters and the normalized peak intensity of the I(2918), I(2848) and I(1087) for the corresponding wavenumbers, it is concluded that the I(2918) and the I(2848) are in accordance with the mean number degree of polymerization of ethylene sebacate units and the I(1087) is in accordance with the mean number degree of polymerization of glycolate units. Based on the XRD diffractograms, poly(ethylene sebacate) and poly(glycolic acid) belong to the monoclinic and the orthorhombic crystal system, respectively and both have higher crystallinity than the copolyesters. The experimental data of the hydrolytic degradation were fitted with exponential rise to maximum type functions using two-parameter model and four-parameter model. Three regions can been distinguished for the hydrolytic degradation by decreasing the molar feed ratio of sebacic acid, which are correlated with the changes of crystallinity. Two copolyesters are proposed: first the copolyester with high amount of glycolate units (S10G90) having higher hydrolytic degradation than G100 and second the copolyester with equal amount of glycolate and ethylene sebacate units (S50G50), having lower hydrolytic degradation than G100. These hydrolytically degradable copolyesters are soluble in common organic solvents, opposite to poly(glycolic acid) and could have perspectives for biomedical applications.

  2. Histidine-Based Lipopeptides Enhance Cleavage of Nucleic Acids: Interactions with DNA and Hydrolytic Properties.

    PubMed

    Bélières, M; Déjugnat, C; Chouini-Lalanne, N

    2015-12-16

    Interaction studies and cleavage activity experiments were carried out between plasmid DNA and a series of histidine-based lipopeptides. Specific fluorescent probes (ethidium bromide, Hoechst 33342, and pyrene) were used to monitor intercalation, minor groove binding, and self-assembly of lipopeptides, respectively. Association between DNA and lipopeptides was thus evidenced, highlighting the importance of both histidine and hydrophobic tail in the interaction process. DNA cleavage in the presence of lipopeptides was then detected by gel electrophoresis and quantified, showing the importance of histidine and the involvement of its side-chain imidazole in the hydrolysis mechanism. These systems could then be developed as synthetic nucleases while raising concern of introducing histidine in the design of lipopeptide-based transfection vectors.

  3. Self-reinforcement and hydrolytic degradation of amorphous lactic acid based poly(ester-amide), and of its composite with sol-gel derived fibers.

    PubMed

    Haltia, Anna-Maija; Lähteenkorva, Kimmo; Törmälä, Pertti; Helminen, Antti; Tuominen, Jukka; Seppälä, Jukka; Veittola, Sinikka; Ahvenlammi, Jarno

    2002-10-01

    The self-reinforcing and hydrolytic degradation of an amorphous poly(ester-amide) (PEA) based on lactic acid have been studied and compared with those of poly-L-lactide (PLLA). The studied PEA-rods were self-reinforced (SR) by solid-state die drawing resulting double shear strength. The hydrolytic degradation of PEA was studied during exposure to phosphate buffered saline at pH 7.4 and at 37 degrees C for 18 weeks. The degradation and mechanical properties of PEA were also followed in a self-reinforced composite structure consisting of PEA and sol-gel derived SiO(2)-fibers (SGF, 8 wt %). The hydrolytic degradation of the SR-PEA-rods with and without SG-fibers was significantly faster than that of SR-PLLA-rods. The weight average molecular weight (Mw) of PEA decreased by 90% from the initial Mw during the first 6 weeks in hydrolysis, when the Mw of the PLLA decreased by 10%. PMID:15348182

  4. Influences of acidic reaction and hydrolytic conditions on monosaccharide composition analysis of acidic, neutral and basic polysaccharides.

    PubMed

    Wang, Qing-Chi; Zhao, Xia; Pu, Jiang-Hua; Luan, Xiao-Hong

    2016-06-01

    Monosaccharide composition analysis is important for structural characterization of polysaccharides. To investigate the influences of acidic reaction and hydrolytic conditions on monosaccharide composition analysis of polysaccharides, we chose alginate, starch, chitosan and chondroitin sulfate as representative of acidic, neutral, basic and complex polysaccharides to compare the release degree of monosaccharides under different hydrolytic conditions. The hydrolysis stability of 10 monosaccharide standards was also explored. Results showed that the basic sugars were hard to release but stable, the acidic sugars (uronic acids) were easy to release but unstable, and the release and stability of neutral sugars were in between acidic and basic sugars. In addition, the hydrolysis process was applied to monosaccharide composition analysis of Hippocampus trimaculatus polysaccharide and the appropriate hydrolytic condition was accorded with that of the above four polysaccharides. Thus, different hydrolytic conditions should be used for the monosaccharide composition analysis of polysaccharides based on their structural characteristics. PMID:27083372

  5. Activity-based protein profiling of hydrolytic enzymes induced by gibberellic acid in isolated aleurone layers of malting barley.

    PubMed

    Daneri-Castro, Sergio N; Chandrasekar, Balakumaran; Grosse-Holz, Friederike M; van der Hoorn, Renier A L; Roberts, Thomas H

    2016-09-01

    During barley germination, the aleurone layer secretes most of the enzymes required to degrade the endosperm, many of which are yet to be characterized. We used activity-based protein profiling (ABPP) to detect a range of active enzymes extracted from aleurone layers isolated from grains of a commercial malting barley variety incubated with or without gibberellic acid (GA). Enzymes found to be induced by GA were putative aleurains, cathepsin-B-like proteases and serine hydrolases. By using an inhibitory sugar panel, a specific active retaining β-glycosidase in the barley aleurone was identified as a putative xylanase. Our results show that ABPP can be used rapidly to identify a variety of active enzyme isoforms in cereal aleurone without the need for enzyme purification.

  6. Effects of degree of dissociation of acid used on hydrolytic durability of ceramic primer.

    PubMed

    Aoki, Naoko; Kimoto, Suguru; Tanimura, Hideki; Nishiyama, Norihiro; Aida, Masahiro

    2014-01-01

    In this study, effects of the degree of dissociation of acids on the hydrolysis rate of methoxy group in γ-methacryloxypropyltrimethoxysilane (γ-MPS) and the adsorption characteristics of γ-MPS on ceramic surfaces were studied using acetic, phosphoric, and hydrochloric acids. Hydrolytic stability of γ-MPS adsorption layer at the resin-ceramic interface was thus examined. (29)Si NMR observations of acidactivated γ-MPS and contact angle measurements following ceramic surface silanization were performed. Bond strengths of resin to the silanized ceramic surfaces were measured. Statistical analyses of shear bond strength and contact angle data were performed. Increase in the degree of dissociation of the acid used increased the hydrolysis rate of methoxy group in γ-MPS, but lowered the contact angle to the silanized ceramic surface. Decrease in the contact angle increased the hydrolytic stability of γ-MPS adsorption layer.

  7. HYDROLYTIC BREAKDOWN OF LACTOFERRICIN BY LACTIC ACID BACTERIA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lactoferricin is a 25 amino acid antimicrobial peptide domain that is liberated by pepsin digestion of lactoferrin in bovine milk. Along with its antibacterial properties, lactoferricin has also been reported to have immunostimulatory, antiviral, and anticarcinogenic effects. There is substantial ...

  8. Hydrolytic breakdown of lactoferricin by lactic acid bacteria.

    PubMed

    Paul, Moushumi; Somkuti, George A

    2010-02-01

    Lactoferricin is a 25-amino acid antimicrobial peptide fragment that is liberated by pepsin digestion of lactoferrin present in bovine milk. Along with its antibacterial properties, lactoferricin has also been reported to have immunostimulatory, antiviral, and anticarcinogenic effects. These attributes provide lactoferricin and other natural bioactive peptides with the potential to be functional food ingredients that can be used by the food industry in a variety of applications. At present, commercial uses of these types of compounds are limited by the scarcity of information on their ability to survive food processing environments. We have monitored the degradation of lactoferricin during its incubation with two types of lactic acid bacteria used in the yogurt-making industry, Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus, with the aim of assessing the stability of this milk protein-derived peptide under simulated yogurt-making conditions. Analysis of the hydrolysis products isolated from these experiments indicates degradation of this peptide near neutral pH by lactic acid bacteria-associated peptidases, the extent of which was influenced by the bacterial strain used. However, the data also showed that compared to other milk-derived bioactive peptides that undergo complete degradation under these conditions, the 25-amino acid lactoferricin is apparently more resistant, with approximately 50% of the starting material remaining after 4 h of incubation. These findings imply that lactoferricin, as a natural milk protein-derived peptide, has potential applications in the commercial production of yogurt-like fermented dairy products as a multi-functional food ingredient.

  9. Oligomeric structure of proclavaminic acid amidino hydrolase: evolution of a hydrolytic enzyme in clavulanic acid biosynthesis.

    PubMed Central

    Elkins, Jonathan M; Clifton, Ian J; Hernández, Helena; Doan, Linh X; Robinson, Carol V; Schofield, Christopher J; Hewitson, Kirsty S

    2002-01-01

    During biosynthesis of the clinically used beta-lactamase inhibitor clavulanic acid, one of the three steps catalysed by clavaminic acid synthase is separated from the other two by a step catalysed by proclavaminic acid amidino hydrolase (PAH), in which the guanidino group of an intermediate is hydrolysed to give proclavaminic acid and urea. PAH shows considerable sequence homology with the primary metabolic arginases, which hydrolyse arginine to ornithine and urea, but does not accept arginine as a substrate. Like other members of the bacterial sub-family of arginases, PAH is hexameric in solution and requires Mn2+ ions for activity. Other metal ions, including Co2+, can substitute for Mn2+. Two new substrates for PAH were identified, N-acetyl-(L)-arginine and (3R)-hydroxy-N-acetyl-(L)-arginine. Crystal structures of PAH from Streptomyces clavuligerus (at 1.75 A and 2.45 A resolution, where 1 A=0.1 nm) imply how it binds beta-lactams rather than the amino acid substrate of the arginases from which it evolved. The structures also suggest how PAH selects for a particular alcohol intermediate in the clavam biosynthesis pathway. As observed for the arginases, each PAH monomer consists of a core of beta-strands surrounded by alpha-helices, and its active site contains a di-Mn2+ centre with a bridging water molecule responsible for hydrolytic attack on to the guanidino group of the substrate. Comparison of structures obtained under different conditions reveals different conformations of a flexible loop, which must move to allow substrate binding. PMID:12020346

  10. Polylactide stereocomplexation leads to higher hydrolytic stability but more acidic hydrolysis product pattern.

    PubMed

    Andersson, Sofia Regnell; Hakkarainen, Minna; Inkinen, Saara; Södergård, Anders; Albertsson, Ann-Christine

    2010-04-12

    Poly-l-lactide/poly-d-lactide (PLLA/PDLA) stereocomplex had much higher hydrolytic stability compared to plain PLLA, but at the same time shorter and more acidic degradation products were formed. Both materials were subjected to hydrolytic degradation in water and in phosphate buffer at 37 and 60 degrees C, and the degradation processes were monitored by following mass loss, water uptake, thermal properties, surface changes, and pH of the aging medium. The degradation product patterns were determined by electrospray ionization-mass spectrometry (ESI-MS). The high crystallinity and strong secondary interactions in the stereocomplex prevented water uptake and resulted in lower mass loss and degradation rate. However, somewhat surprisingly, the pH of the aging medium decreased much faster in the case of PLLA/PDLA stereocomplex. In accordance, the ESI-MS results showed that hydrolysis of PLLA/PDLA resulted in shorter and more acidic degradation products. This could be explained by the increased intermolecular crystallization due to stereocomplexation, which results in an increased number of tie chains. Because mainly these short tie chains are susceptible to hydrolysis this leads to formation of shorter oligomers compared to hydrolysis of regular PLLA.

  11. Alkaline and acid hydrolytic processes in aerobic and anaerobic sludges: effect on total EPS and fractions.

    PubMed

    Cassini, S T; Andrade, M C E; Abreu, T A; Keller, R; Gonçalves, R F

    2006-01-01

    Sludge samples from an upflow anaerobic sludge blanket (UASB) reactor and four submerged aerated biofilters (BFs) of a wastewater treatment plant (1,000 inhab.) were processed at bench scale by alkaline and acid hydrolysis with the objective to evaluate the organic matter solubilization, volatile solids (VS) destruction and the effect of hydrolytic processes on the extracellular polymeric substances (EPS) fraction of the sludge samples. The results showed that alkaline hydrolysis of sludge samples treatment with 1.0% total solids (TS) using NaOH 20 meq L(-1) was more efficient on organic matter solubilization and VS destruction than acid hydrolysis. The EPS sludge content was also affected by the alkaline treatment of anaerobic sludge samples. The EPS concentrations (mg EPS/gVSS) on the anaerobic sludge after the alkaline treatment were significantly lowered according to sample height in the UASB reactor. Data indicated that the EPS sludge fraction is the main component affected by the alkaline hydrolytic process of anaerobic sludge samples. PMID:16784189

  12. Identification and Characterization of Two New Degradation Products of Saikosaponin A under Acid Hydrolytic Conditions.

    PubMed

    Li, Jun; Xu, Qiang; Jiang, Hua

    2016-01-01

    Saikosaponin (SS) A is a compound with various pharmacological properties and is easily degraded into SS-B1 and SS-G under acid conditions. In the present work, two new degradation products of SS-A, formed under acid hydrolytic conditions, were detected and isolated using analytical and semi-preparative liquid chromatography technology; furthermore, their structures were characterized as hydroxy-saikosaponin A and SS-B2 by spectral analysis, which is not only essential in stability-indicating method development and validation, but also could be used as a worst case scenario to assess the analytical method performance of SS-A. Moreover, their structural transformation pathways are also proposed. PMID:27649123

  13. Hydrolytic and oxidate stability of L-(+) -ascorbic acid supported in pectin films: Influence of the macromolecular structure and calcium presence

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The hydrolytic and oxidative stability of L-(+)-ascorbic acid (AA) into plasticized pectin films were separately studied in view of preserving vitamin C activity and/or to achieve localized antioxidant activity at pharmaceutical and food interfaces. Films were made with each one of the enzymatically...

  14. Acidic Deep Eutectic Solvents As Hydrolytic Media for Cellulose Nanocrystal Production.

    PubMed

    Sirviö, Juho Antti; Visanko, Miikka; Liimatainen, Henrikki

    2016-09-12

    In this study, a new method to fabricate cellulose nanocrystals (CNCs) based on DES pretreatment of wood cellulose fibers with choline chloride and organic acids are reported. Oxalic acid (anhydrous and dihydrate), p-toluenesulfonic acid monohydrate, and levulinic acid were studied as acid components of DESs. DESs were formed at elevated temperatures (60-100 °C) by combining choline chloride with organic acids and were then used to hydrolyze less ordered amorphous regions of cellulose. All the DES treatments resulted in degradation of wood fibers into microsized fibers and after mechanically disintegrating, CNCs were successfully obtained from choline chloride/oxalic acid dihydrate-treated fibers, whereas no liberation of CNCs was observed with other DESs. The DES-produced CNCs had a width and length of 9-17 and 310-410 nm, respectively. The crystallinity indexes (CrIs) and carboxylic acid content of the CNCs were 66-71% and 0.20-0.28 mmol/g, respectively. CNCs exhibited good thermal stabilities (the onset thermal degradation temperatures ranged from 275-293 °C). The demonstrated acidic DES method exhibits certain advantages over previously reported CNC productions, namely, milder processing conditions and easily obtainable and relatively inexpensive biodegradable solvents with low toxicity (compared, e.g., to ILs).

  15. Acidic Deep Eutectic Solvents As Hydrolytic Media for Cellulose Nanocrystal Production.

    PubMed

    Sirviö, Juho Antti; Visanko, Miikka; Liimatainen, Henrikki

    2016-09-12

    In this study, a new method to fabricate cellulose nanocrystals (CNCs) based on DES pretreatment of wood cellulose fibers with choline chloride and organic acids are reported. Oxalic acid (anhydrous and dihydrate), p-toluenesulfonic acid monohydrate, and levulinic acid were studied as acid components of DESs. DESs were formed at elevated temperatures (60-100 °C) by combining choline chloride with organic acids and were then used to hydrolyze less ordered amorphous regions of cellulose. All the DES treatments resulted in degradation of wood fibers into microsized fibers and after mechanically disintegrating, CNCs were successfully obtained from choline chloride/oxalic acid dihydrate-treated fibers, whereas no liberation of CNCs was observed with other DESs. The DES-produced CNCs had a width and length of 9-17 and 310-410 nm, respectively. The crystallinity indexes (CrIs) and carboxylic acid content of the CNCs were 66-71% and 0.20-0.28 mmol/g, respectively. CNCs exhibited good thermal stabilities (the onset thermal degradation temperatures ranged from 275-293 °C). The demonstrated acidic DES method exhibits certain advantages over previously reported CNC productions, namely, milder processing conditions and easily obtainable and relatively inexpensive biodegradable solvents with low toxicity (compared, e.g., to ILs). PMID:27478001

  16. Effect of blending tricalcium phosphate on hydrolytic degradation of a block polyester containing poly(L-lactic acid) segment.

    PubMed

    Imai, Y; Fukuzawa, A; Watanabe, M

    1999-01-01

    The effect of blending tricalcium phosphate (TCP) on hydrolytic degradation of a new type of poly(L-lactic acid)/poly(ethylene:hexamethylene/sebacate) block polyester (60: 40 wt%) was studied. 100- and 250-microm film specimens blended with 0, 10, and 30 wt% TCP were immersed in phosphate buffered saline (pH 7.4) at 37 degrees C for up to 80-104 weeks. At appropriate intervals, water absorption, dry and wet tensile strength, molecular weight, and thermal properties of the specimens were measured by weighing, tensile strength testing, size exclusion chromatography, and differential scanning calorimetry, respectively. Some samples were characterized by 1H NMR spectroscopy. Blending of TCP with the block polyester was effective in retarding degradation. The blended TCP was thought to retard degradation for the most part by neutralizing the lactic acid oligomers produced by hydrolysis of the poly(lactic acid) part during the initial stage of degradation. PMID:10426231

  17. Biocatalyzed approach for the surface functionalization of poly(L-lactic acid) films using hydrolytic enzymes.

    PubMed

    Pellis, Alessandro; Acero, Enrique Herrero; Weber, Hansjoerg; Obersriebnig, Michael; Breinbauer, Rolf; Srebotnik, Ewald; Guebitz, Georg M

    2015-09-01

    Poly(lactic acid) as a biodegradable thermoplastic polyester has received increasing attention. This renewable polyester has found applications in a wide range of products such as food packaging, textiles and biomedical devices. Its major drawbacks are poor toughness, slow degradation rate and lack of reactive side-chain groups. An enzymatic process for the grafting of carboxylic acids onto the surface of poly(L-lactic acid) (PLLA) films was developed using Candida antarctica lipase B as a catalyst. Enzymatic hydrolysis of the PLLA film using Humicola insolens cutinase in order to increase the number of hydroxyl and carboxylic groups on the outer polymer chains for grafting was also assessed and showed a change of water contact angle from 74.6 to 33.1° while the roughness and waviness were an order of magnitude higher in comparison to the blank. Surface functionalization was demonstrated using two different techniques, (14) C-radiochemical analysis and X-ray photoelectron spectroscopy (XPS) using (14) C-butyric acid sodium salt and 4,4,4-trifluorobutyric acid as model molecules, respectively. XPS analysis showed that 4,4,4-trifluorobutyric acid was enzymatically coupled based on an increase of the fluor content from 0.19 to 0.40%. The presented (14) C-radiochemical analyses are consistent with the XPS data indicating the potential of enzymatic functionalization in different reaction conditions.

  18. Transparent and hard zirconia-based hybrid coatings with excellent dynamic/thermoresponsive oleophobicity, thermal durability, and hydrolytic stability.

    PubMed

    Masheder, Benjamin; Urata, Chihiro; Hozumi, Atsushi

    2013-08-28

    Smooth, transparent, and extremely hard zirconia (ZrO2)-based inorganic-organic hybrid films showing excellent dynamic oleophobicity, thermal durability, and hydrolytic stability were successfully prepared through a simple combination of zirconium tetrapropoxide (Zr(O(CH2)2CH3)4) with stearic acids. In this study, we have particularly focused on the effects of stearic acid molecular architecture (linear-stearic acid (LSA) and branched-stearic acid (BSA)) on surface physical/chemical properties. Although, in each case, the resulting hybrid (Zr:LSA and Zr:BSA) films achieved by a simple spin-coating method were highly smooth and transparent, the final surface properties were markedly dependent on their molecular architectures. Thanks to the thermal stability of BSA, our Zr:BSA hybrid films displayed a greatly improved thermal effective range (maximum of 200 °C), while for Zr:LSA hybrid films, serious thermal damage to surface dewetting behavior was observed at less than 150 °C. The hardness of the Zr:BSA hybrid films were markedly increased by curing at 200 °C for 1 h (from 1.95 GPa to 3.03 GPa), while maintaining their dynamic dewettability toward n-hexadecane, when compared with Zr:LSA hybrid films (0.95-1.19 GPa). Small volume n-hexadecane droplets (5 μL) were easily set in motion, sliding across and off our best Zr:BSA hybrid film surfaces at low substrate tilt angles (<10°) without pinning. Moreover, they also showed thermoresponsive dynamic dewetting behavior, reasonable resistance to hydrolysis in an aqueous environment, and antifingerprint properties.

  19. Tuning the acid/metal balance of carbon nanofiber-supported nickel catalysts for hydrolytic hydrogenation of cellulose.

    PubMed

    Van de Vyver, Stijn; Geboers, Jan; Schutyser, Wouter; Dusselier, Michiel; Eloy, Pierre; Dornez, Emmie; Seo, Jin Won; Courtin, Christophe M; Gaigneaux, Eric M; Jacobs, Pierre A; Sels, Bert F

    2012-08-01

    Carbon nanofibers (CNFs) are a class of graphitic support materials with considerable potential for catalytic conversion of biomass. Earlier, we demonstrated the hydrolytic hydrogenation of cellulose over reshaped nickel particles attached at the tip of CNFs. The aim of this follow-up study was to find a relationship between the acid/metal balance of the Ni/CNFs and their performance in the catalytic conversion of cellulose. After oxidation and incipient wetness impregnation with Ni, the Ni/CNFs were characterized by various analytical methods. To prepare a selective Ni/CNF catalyst, the influences of the nature of oxidation agent, Ni activation, and Ni loading were investigated. Under the applied reaction conditions, the best result, that is, 76 % yield in hexitols with 69 % sorbitol selectivity at 93 % conversion of cellulose, was obtained on a 7.5 wt % Ni/CNF catalyst prepared by chemical vapor deposition of CH(4) on a Ni/γ-Al(2)O(3) catalyst, followed by oxidation in HNO(3) (twice for 1 h at 383 K), incipient wetness impregnation, and reduction at 773 K under H(2). This preparation method leads to a properly balanced Ni/CNF catalyst in terms of Ni dispersion and hydrogenation capacity on the one hand, and the number of acidic surface-oxygen groups responsible for the acid-catalyzed hydrolysis on the other.

  20. Tuning the acid/metal balance of carbon nanofiber-supported nickel catalysts for hydrolytic hydrogenation of cellulose.

    PubMed

    Van de Vyver, Stijn; Geboers, Jan; Schutyser, Wouter; Dusselier, Michiel; Eloy, Pierre; Dornez, Emmie; Seo, Jin Won; Courtin, Christophe M; Gaigneaux, Eric M; Jacobs, Pierre A; Sels, Bert F

    2012-08-01

    Carbon nanofibers (CNFs) are a class of graphitic support materials with considerable potential for catalytic conversion of biomass. Earlier, we demonstrated the hydrolytic hydrogenation of cellulose over reshaped nickel particles attached at the tip of CNFs. The aim of this follow-up study was to find a relationship between the acid/metal balance of the Ni/CNFs and their performance in the catalytic conversion of cellulose. After oxidation and incipient wetness impregnation with Ni, the Ni/CNFs were characterized by various analytical methods. To prepare a selective Ni/CNF catalyst, the influences of the nature of oxidation agent, Ni activation, and Ni loading were investigated. Under the applied reaction conditions, the best result, that is, 76 % yield in hexitols with 69 % sorbitol selectivity at 93 % conversion of cellulose, was obtained on a 7.5 wt % Ni/CNF catalyst prepared by chemical vapor deposition of CH(4) on a Ni/γ-Al(2)O(3) catalyst, followed by oxidation in HNO(3) (twice for 1 h at 383 K), incipient wetness impregnation, and reduction at 773 K under H(2). This preparation method leads to a properly balanced Ni/CNF catalyst in terms of Ni dispersion and hydrogenation capacity on the one hand, and the number of acidic surface-oxygen groups responsible for the acid-catalyzed hydrolysis on the other. PMID:22730195

  1. A fluorescence-based hydrolytic enzyme activity assay for quantifying toxic effects of Roundup® to Daphnia magna.

    PubMed

    Ørsted, Michael; Roslev, Peter

    2015-08-01

    Daphnia magna is a widely used model organism for aquatic toxicity testing. In the present study, the authors investigated the hydrolytic enzyme activity of D. magna after exposure to toxicant stress. In vivo enzyme activity was quantified using 15 fluorogenic enzyme probes based on 4-methylumbelliferyl or 7-amino-4-methylcoumarin. Probing D. magna enzyme activity was evaluated using short-term exposure (24-48 h) to the reference chemical K2 Cr2 O7 or the herbicide formulation Roundup®. Toxicant-induced changes in hydrolytic enzyme activity were compared with changes in mobility (International Organization for Standardization standard 6341). The results showed that hydrolytic enzyme activity was quantifiable as a combination of whole body fluorescence of D. magna and the fluorescence of the surrounding water. Exposure of D. magna to lethal and sublethal concentrations of Roundup resulted in loss of whole body enzyme activity and release of cell constituents, including enzymes and DNA. Roundup caused comparable inhibition of mobility and alkaline phosphatase activity with median effective concentration values at 20 °C of 8.7 mg active ingredient (a.i.)/L to 11.7 mg a.i./L. Inhibition of alkaline phosphatase activity by Roundup was lowest at 14 °C and greater at 20 °C and 26 °C. The results suggest that the fluorescence-based hydrolytic enzyme activity assay (FLEA assay) can be used as an index of D. magna stress. Combining enzyme activity with fluorescence measurements may be applied as a simple and quantitative supplement for toxicity testing with D. magna.

  2. Hydrolytic potential of Trichoderma sp. strains evaluated by microplate-based screening followed by switchgrass saccharification.

    PubMed

    Cianchetta, Stefano; Galletti, Stefania; Burzi, Pier Luigi; Cerato, Claudio

    2012-05-10

    Bioconversion of lignocellulosic biomass to fuel requires a hydrolysis step to obtain fermentable sugars, generally accomplished by fungal enzymes. Large-scale screening of different microbial strains would provide optimal enzyme cocktails for any target feedstock. The aim of this study was to screen a large collection of Trichoderma sp. strains for the hydrolytic potential towards switchgrass (Panicum virgatum L.). Strains were cultivated in a small-scale system and assayed in micro-plates for xylanase and cellulase activities. The population distributions of these traits are reported after growth on switchgrass in comparison with cellulose. The distribution profiles suggest that the growth on switchgrass strongly promotes xylanase production. The IK4 strain displayed the highest xylanase activity after growth on switchgrass (133U/mL). Enzymes (10FPU/g substrate) from IK4 were compared with those from 2 cellulolytic Trichoderma strains and a commercial enzyme in saccharification time-course experiments on untreated and pretreated switchgrass and on an artificial substrate. Samples were analysed by DNS assay and by an oxygraphic method for sugar equivalent or glucose concentration. On the untreated substrate, IK4 enzymes even outperformed a 5-fold load of commercial enzyme, suggesting that xylanase or accessory enzymes are a limiting factor on this type of recalcitrant substrate. On the other substrates, IK4 preparations showed intermediate behaviour if compared with the commercial enzyme at 10FPU/g substrate and at 5-fold load. IK4 also nearly halved the time to release 50% of the hydrolysable sugar equivalents (T(50%)), with respect to the other preparations at the same enzymatic load. DNS assay and oxygraphic method gave highly correlated results for the 3 saccharified substrates. The study suggests that accessory enzymes like xylanase play a key role in improving the performance of cellulase preparations on herbaceous lignocellulosic feedstocks like switchgrass.

  3. A fluorescent hydrogel-based flow cytometry high-throughput screening platform for hydrolytic enzymes.

    PubMed

    Pitzler, Christian; Wirtz, Georgette; Vojcic, Ljubica; Hiltl, Stephanie; Böker, Alexander; Martinez, Ronny; Schwaneberg, Ulrich

    2014-12-18

    Screening throughput is a key in directed evolution experiments and enzyme discovery. Here, we describe a high-throughput screening platform based on a coupled reaction of glucose oxidase and a hydrolase (Yersinia mollaretii phytase [YmPh]). The coupled reaction produces hydroxyl radicals through Fenton's reaction, acting as initiator of poly(ethyleneglycol)-acrylate-based polymerization incorporating a fluorescent monomer. As a consequence, a fluorescent hydrogel is formed around Escherichia coli cells expressing active YmPh. We achieve five times enrichment of active cell population through flow cytometry analysis and sorting of mixed populations. Finally, we validate the performance of the fluorescent polymer shell (fur-shell) technology by directed phytase evolution that yielded improved variants starting from a library containing 10(7) phytase variants. Thus, fur-shell technology represents a rapid and nonlaborious way of identifying the most active variants from vast populations, as well as a platform for generation of polymer-hybrid cells for biobased interactive materials. PMID:25525992

  4. Monitoring the hydrolytic degradation of polyester-based composites by a piezoelectric method

    SciTech Connect

    Sainte-Pierre, N.; Perrissin, I.; Jayet, Y.; Tatiboueet, J.

    1995-10-01

    Theoretical considerations show that the electric impedance of a piezoelectric element depends on the physical and geometrical properties of the element and also on the viscoelastic characteristics of the different media surrounding it. According to a dynamic model, an original technique has been developed by inserting a piezoelectric ceramic in the composite structure when processed. The electric signal, after signal processing and numerical treatments, gives access to the viscoelastic properties of the external medium. This method is an excellent indicator to display the polymerization kinetics of the resin as well as the post-curing phase of the composite structure process. Moreover, a further application of this non-destructive method is the monitoring of the hydrolitic degradation of the composite structure. The evolution of the electric impedance of the piezoelectric sensor is presented here as a function of water exposition time for a polyester-based composite.

  5. Structure-Based Design and Biological Evaluation of Triphenyl Scaffold-Based Hybrid Compounds as Hydrolytically Stable Modulators of a LuxR-Type Quorum Sensing Receptor

    PubMed Central

    2015-01-01

    Many common bacterial pathogens utilize quorum sensing to coordinate group behaviors and initiate virulence at high cell densities. The use of small molecules to block quorum sensing provides a means of abrogating pathogenic phenotypes, but many known quorum sensing modulators have limitations, including hydrolytic instability and displaying non-monotonic dose curves (indicative of additional targets and/or modes of action). To address these issues, we undertook a structure-based scaffold-hopping approach to develop new chemical modulators of the LasR quorum sensing receptor in Pseudomonas aeruginosa. We combined components from a triphenyl derivative known to strongly agonize LasR with chemical moieties known for LasR antagonism and generated potent LasR antagonists that are hydrolytically stable across a range of pH values. Additionally, many of these antagonists do not exhibit non-monotonic dose effects, delivering probes that inhibit LasR across a wider range of assay conditions relative to known lactone-based ligands. PMID:26807436

  6. Designing hydrolytic zinc metalloenzymes.

    PubMed

    Zastrow, Melissa L; Pecoraro, Vincent L

    2014-02-18

    Zinc is an essential element required for the function of more than 300 enzymes spanning all classes. Despite years of dedicated study, questions regarding the connections between primary and secondary metal ligands and protein structure and function remain unanswered, despite numerous mechanistic, structural, biochemical, and synthetic model studies. Protein design is a powerful strategy for reproducing native metal sites that may be applied to answering some of these questions and subsequently generating novel zinc enzymes. From examination of the earliest design studies introducing simple Zn(II)-binding sites into de novo and natural protein scaffolds to current studies involving the preparation of efficient hydrolytic zinc sites, it is increasingly likely that protein design will achieve reaction rates previously thought possible only for native enzymes. This Current Topic will review the design and redesign of Zn(II)-binding sites in de novo-designed proteins and native protein scaffolds toward the preparation of catalytic hydrolytic sites. After discussing the preparation of Zn(II)-binding sites in various scaffolds, we will describe relevant examples for reengineering existing zinc sites to generate new or altered catalytic activities. Then, we will describe our work on the preparation of a de novo-designed hydrolytic zinc site in detail and present comparisons to related designed zinc sites. Collectively, these studies demonstrate the significant progress being made toward building zinc metalloenzymes from the bottom up. PMID:24506795

  7. Designing Hydrolytic Zinc Metalloenzymes

    PubMed Central

    2015-01-01

    Zinc is an essential element required for the function of more than 300 enzymes spanning all classes. Despite years of dedicated study, questions regarding the connections between primary and secondary metal ligands and protein structure and function remain unanswered, despite numerous mechanistic, structural, biochemical, and synthetic model studies. Protein design is a powerful strategy for reproducing native metal sites that may be applied to answering some of these questions and subsequently generating novel zinc enzymes. From examination of the earliest design studies introducing simple Zn(II)-binding sites into de novo and natural protein scaffolds to current studies involving the preparation of efficient hydrolytic zinc sites, it is increasingly likely that protein design will achieve reaction rates previously thought possible only for native enzymes. This Current Topic will review the design and redesign of Zn(II)-binding sites in de novo-designed proteins and native protein scaffolds toward the preparation of catalytic hydrolytic sites. After discussing the preparation of Zn(II)-binding sites in various scaffolds, we will describe relevant examples for reengineering existing zinc sites to generate new or altered catalytic activities. Then, we will describe our work on the preparation of a de novo-designed hydrolytic zinc site in detail and present comparisons to related designed zinc sites. Collectively, these studies demonstrate the significant progress being made toward building zinc metalloenzymes from the bottom up. PMID:24506795

  8. Hydrolytic synthesis of novel lanthanide(III) complexes with pyridine-2,6-dicarboxylic acid: Characterization of the structure and the physical properties

    NASA Astrophysics Data System (ADS)

    Hojnik, Nuša; Kristl, Matjaž; Golobič, Amalija; Jagličić, Zvonko; Drofenik, Miha

    2015-01-01

    The coordination compounds of pyridine-2,6-dicarboxylic acid and two lanthanide(III) ions, Ho3+ and Dy3+, were hydrolytically synthesized in aqueous solutions at a slightly basic pH, and then characterized by thermogravimetric analysis, IR spectroscopy, magnetic measurements as well as X-ray powder and single-crystal diffraction analysis. The elemental analyses were performed to check the purity of the compounds. The formula for these compounds is identified as Na3[Ln(Pydc)3]ṡ14H2O (Ln = Ho, 1; Ln = Dy, 2) in agreement with the X-ray structural analysis and all the other experimental data. The absence of the 1709 cm-1 band corresponding to ν(C dbnd O) in the IR spectra of the compounds evidences the deprotonating of the carboxyl group. The very strong inductive effect of the metal ion that is readily coordinated by the carboxylate group of the zwitterionic ligand is responsible for the formation of the product. The single-crystal X-ray structural analysis revealed that compounds 1 and 2 are isostructural. Their structure can be described as interchanging layers of complex anions [Ln(Pydc)3]3 (Ln = Ho and Dy for 1 and 2, respectively) and layers of hydrated sodium cations. In complex anions the holmium and dysprosium atoms are coordinated by three crystallographically independent pyridinedicarboxylate ligands in tridentate-chelate mode, via one O atom of both carboxylate groups and the ring N atom. The coordination number is nine and the coordination polyhedron is a tricapped trigonal prism with O atoms at the corners.

  9. Hydrolytic Amino Acids Employed as a Novel Organic Nitrogen Source for the Preparation of PGPF-Containing Bio-Organic Fertilizer for Plant Growth Promotion and Characterization of Substance Transformation during BOF Production.

    PubMed

    Zhang, Fengge; Meng, Xiaohui; Feng, Chenglong; Ran, Wei; Yu, Guanghui; Zhang, Yingjun; Shen, Qirong

    2016-01-01

    Opportunity costs seriously limit the large-scale production of bio-organic fertilizers (BOFs) both in China and internationally. This study addresses the utilization of amino acids resulting from the acidic hydrolysis of pig corpses as organic nitrogen sources to increase the density of TrichodermaharzianumT-E5 (a typical plant growth-promoting fungi, PGPF). This results in a novel, economical, highly efficient and environmentally friendly BOF product. Fluorescence excitation-emission matrix (EEM) spectroscopy combined with fluorescence regional integration (FRI) was employed to monitor compost maturity levels, while pot experiments were utilized to test the effects of this novel BOF on plant growth. An optimization experiment, based on response surface methodologies (RSMs), showed that a maximum T-E5 population (3.72 × 108 ITS copies g-1) was obtained from a mixture of 65.17% cattle manure compost (W/W), 19.33% maggot manure (W/W), 15.50% (V/W)hydrolytic amino acid solution and 4.69% (V/W) inoculum at 28.7°C after a 14 day secondary solid fermentation. Spectroscopy analysis revealed that the compost transformation process involved the degradation of protein-like substances and the formation of fulvic-like and humic-like substances. FRI parameters (PI, n, PII, n, PIII, n and PV, n) were used to characterize the degree of compost maturity. The BOF resulted in significantly higher increased chlorophyll content, shoot length, and shoot and root dry weights of three vegetables (cucumber, tomato and pepper) by 9.9%~22.4%, 22.9%~58.5%, 31.0%~84.9%, and 24.2%~34.1%, respectively. In summary, this study presents an operational means of increasing PGPF T-E5 populations in BOF to promote plant growth with a concomitant reduction in production cost. In addition, a BOF compost maturity assessment using fluorescence EEM spectroscopy and FRI ensured its safe field application. PMID:26974549

  10. Hydrolytic Amino Acids Employed as a Novel Organic Nitrogen Source for the Preparation of PGPF-Containing Bio-Organic Fertilizer for Plant Growth Promotion and Characterization of Substance Transformation during BOF Production

    PubMed Central

    Feng, Chenglong; Ran, Wei; Yu, Guanghui; Zhang, Yingjun; Shen, Qirong

    2016-01-01

    Opportunity costs seriously limit the large-scale production of bio-organic fertilizers (BOFs) both in China and internationally. This study addresses the utilization of amino acids resulting from the acidic hydrolysis of pig corpses as organic nitrogen sources to increase the density of TrichodermaharzianumT-E5 (a typical plant growth-promoting fungi, PGPF). This results in a novel, economical, highly efficient and environmentally friendly BOF product. Fluorescence excitation-emission matrix (EEM) spectroscopy combined with fluorescence regional integration (FRI) was employed to monitor compost maturity levels, while pot experiments were utilized to test the effects of this novel BOF on plant growth. An optimization experiment, based on response surface methodologies (RSMs), showed that a maximum T-E5 population (3.72 × 108 ITS copies g−1) was obtained from a mixture of 65.17% cattle manure compost (W/W), 19.33% maggot manure (W/W), 15.50% (V/W)hydrolytic amino acid solution and 4.69% (V/W) inoculum at 28.7°C after a 14 day secondary solid fermentation. Spectroscopy analysis revealed that the compost transformation process involved the degradation of protein-like substances and the formation of fulvic-like and humic-like substances. FRI parameters (PI, n, PII, n, PIII, n and PV, n) were used to characterize the degree of compost maturity. The BOF resulted in significantly higher increased chlorophyll content, shoot length, and shoot and root dry weights of three vegetables (cucumber, tomato and pepper) by 9.9%~22.4%, 22.9%~58.5%, 31.0%~84.9%, and 24.2%~34.1%, respectively. In summary, this study presents an operational means of increasing PGPF T-E5 populations in BOF to promote plant growth with a concomitant reduction in production cost. In addition, a BOF compost maturity assessment using fluorescence EEM spectroscopy and FRI ensured its safe field application. PMID:26974549

  11. Hydrolytic Amino Acids Employed as a Novel Organic Nitrogen Source for the Preparation of PGPF-Containing Bio-Organic Fertilizer for Plant Growth Promotion and Characterization of Substance Transformation during BOF Production.

    PubMed

    Zhang, Fengge; Meng, Xiaohui; Feng, Chenglong; Ran, Wei; Yu, Guanghui; Zhang, Yingjun; Shen, Qirong

    2016-01-01

    Opportunity costs seriously limit the large-scale production of bio-organic fertilizers (BOFs) both in China and internationally. This study addresses the utilization of amino acids resulting from the acidic hydrolysis of pig corpses as organic nitrogen sources to increase the density of TrichodermaharzianumT-E5 (a typical plant growth-promoting fungi, PGPF). This results in a novel, economical, highly efficient and environmentally friendly BOF product. Fluorescence excitation-emission matrix (EEM) spectroscopy combined with fluorescence regional integration (FRI) was employed to monitor compost maturity levels, while pot experiments were utilized to test the effects of this novel BOF on plant growth. An optimization experiment, based on response surface methodologies (RSMs), showed that a maximum T-E5 population (3.72 × 108 ITS copies g-1) was obtained from a mixture of 65.17% cattle manure compost (W/W), 19.33% maggot manure (W/W), 15.50% (V/W)hydrolytic amino acid solution and 4.69% (V/W) inoculum at 28.7°C after a 14 day secondary solid fermentation. Spectroscopy analysis revealed that the compost transformation process involved the degradation of protein-like substances and the formation of fulvic-like and humic-like substances. FRI parameters (PI, n, PII, n, PIII, n and PV, n) were used to characterize the degree of compost maturity. The BOF resulted in significantly higher increased chlorophyll content, shoot length, and shoot and root dry weights of three vegetables (cucumber, tomato and pepper) by 9.9%~22.4%, 22.9%~58.5%, 31.0%~84.9%, and 24.2%~34.1%, respectively. In summary, this study presents an operational means of increasing PGPF T-E5 populations in BOF to promote plant growth with a concomitant reduction in production cost. In addition, a BOF compost maturity assessment using fluorescence EEM spectroscopy and FRI ensured its safe field application.

  12. A one-pot protocol for synthesis of non-noble metal-based core-shell nanoparticles under ambient conditions: toward highly active and cost-effective catalysts for hydrolytic dehydrogenation of NH3BH3.

    PubMed

    Jiang, Hai-Long; Akita, Tomoki; Xu, Qiang

    2011-10-21

    A one-pot synthesis of non-noble transition metal-based core-shell nanoparticles (NPs) has been developed under ambient conditions. The obtained Cu@M (M = Co, Fe, Ni) NPs exhibit superior catalytic activity for hydrolytic dehydrogenation of NH(3)BH(3), compared to the alloy and monometallic counterparts. PMID:21909589

  13. Hydrolytic kinetics of biodegradable polyester monolayers

    SciTech Connect

    Lee, W.K.; Gardella, J.A. Jr.

    2000-04-04

    The rate of hydrolysis of Langmuir monolayer films of a series of biodegradable polyesters was investigated at the air/water interface. The present study investigated parameters such as degradation medium, pH, and time. The hydrolysis of polyester monolayers strongly depended on both the degradation medium used to control subphase pH and the concentration of active ions. Under the conditions studied here, polymer monolayers showed faster hydrolysis when they were exposed to a basic subphase rather than that of acidic or neutral subphase. The basic (pH = 10) hydrolysis of [poly(l-lactide)/polycaprolactone](l-PLA/PCL 1/1 by mole) blend was faster than that of each homopolymer at the initial stage. This result is explained by increasing numbers of base attack sites per unit area owing to the very slow hydrolysis of PCL, a dilution effect on the concentration of l-PLA monolayers. Conversely the hydrolytic behavior of l-lactide-co-caprolactone (1/1 by mole) was similar to that of PCL even though the chemical compositions of the blend and the copolymer are very similar to each other. The resistance of the copolymer to hydrolysis might be attributed to the hydrophobicity and the steric hindrance of caprolactone unit in the copolymer.

  14. [Oxidative and hydrolytic deterioration of palm oil and fat products based on it under various conditions of storage and transportation].

    PubMed

    Bessonov, V V; Zaĭtseva, L V; Stepanova, L I; Baĭkov, V G

    2012-01-01

    Studies have been conducted on the effect of storage conditions for refined deodorized palm oil on the quality and safety: in containers made of ferrous metals (mild steel) at unregulated temperature, in sealed plastic bags at the temperature -20 degrees C in stainless steel under stratification of nitrogen at the temperature of 40+/-1 degrees C. The choice of the objects of study determined by the normative documents of the Russian Federation governing the transportation and storage of vegetable oils and fat products based on them. All samples of palm oil with peroxide value of 1,0 to 1,5 meq O2/kg indicated the presence of a weak foreign taste, is not peculiar impersonalfat, the samples with peroxide value above 1,5 meq O2/kg were observed pronounced off-flavors and odors characteristic of stale oil. Rancidity was observed in samples having peroxide value of 2,0 meq O2/kg or more. Free acid value and anizidin value for the studied period changed to a lesser extent, from 0,06 to 0,1 mg KOH/g and from 1,2 to 1,4 respectively. It is proved that, transportation/storage of palm oil at the temperature above 50 degrees C without stratification of nitrogen greatly accelerates the process of oxidative damage. Based on these data we can recommend transportation/storage and management process with the least possible time of contact of melted palm oil with oxygen to produce high-quality final product (within 2-3 hours from the time of melting).

  15. De novo design, synthesis and spectroscopic characterization of chiral benzimidazole-derived amino acid Zn(II) complexes: Development of tryptophan-derived specific hydrolytic DNA artificial nuclease agent

    NASA Astrophysics Data System (ADS)

    Parveen, Shazia; Arjmand, Farukh

    2012-01-01

    Novel ternary dizinc(II) complexes 1- 3, derived from 1,2-bis(1H-benzimidazol-2-yl)ethane-1,2-diol and L-form of amino acids (viz., tryptophan, leucine and valine) were synthesized and characterized by spectroscopic (IR, 1H NMR, UV-vis, ESI-MS) and other analytical methods. To evaluate the biological preference of chiral drugs for inherently chiral target DNA, interaction of 1- 3 with calf thymus DNA in Tris-HCl buffer was studied by various biophysical techniques which reveal that all these complexes bind to CT DNA non-covalently via electrostatic interaction. The higher Kb value of L-tryptophan complex 1 suggested greater DNA binding propensity. Further, to evaluate the mode of action at the molecular level, interaction studies of complexes 1 and 2 with nucleotides (5'-GMP and 5'-TMP) were carried out by UV-vis titrations, 1H and 31P NMR which implicates the preferential selectivity of these complexes to N3 of thymine rather than N7 of guanine. Furthermore, complex 1 exhibits efficient DNA cleavage with supercoiled pBR322. The complex 1 cleaves DNA efficiently involving hydrolytic cleavage pathway. Such chiral synthetic hydrolytic nucleases with asymmetric centers are gaining considerable attention owing to their importance in biotechnology and drug design, in particular to cleave DNA with sequence selectivity different from that of the natural enzymes.

  16. Srchi24, A Chitinase Homolog Lacking an Essential Glutamic Acid Residue for Hydrolytic Activity, Is Induced during Nodule Development on Sesbania rostrata1

    PubMed Central

    Goormachtig, Sofie; Van de Velde, Willem; Lievens, Sam; Verplancke, Christa; Herman, Sylvia; De Keyser, Annick; Holsters, Marcelle

    2001-01-01

    The interaction between the tropical legume Sesbania rostrata and the bacterium Azorhizobium caulinodans results in the formation of nodules on both stem and roots. Stem nodulation was used as a model system to isolate early markers by differential display. One of them, Srchi24 is a novel early nodulin whose transcript level increased already 4 h after inoculation. This enhancement depended on Nod factor-producing bacteria. Srchi24 transcript levels were induced also by exogenous cytokinins. In situ hybridization and immunolocalization experiments showed that Srchi24 transcripts and proteins were present in the outermost cortical cell layers of the developing nodules. Sequence analyses revealed that Srchi24 is similar to class III chitinases, but lacks an important catalytic glutamate residue. A fusion between a maltose-binding protein and Srchi24 had no detectable hydrolytic activity. A function in nodulation is proposed for the Srchi24 protein. PMID:11553736

  17. The first proton sponge-based amino acids: synthesis, acid-base properties and some reactivity.

    PubMed

    Ozeryanskii, Valery A; Gorbacheva, Anastasia Yu; Pozharskii, Alexander F; Vlasenko, Marina P; Tereznikov, Alexander Yu; Chernov'yants, Margarita S

    2015-08-21

    The first hybrid base constructed from 1,8-bis(dimethylamino)naphthalene (proton sponge or DMAN) and glycine, N-methyl-N-(8-dimethylamino-1-naphthyl)aminoacetic acid, was synthesised in high yield and its hydrobromide was structurally characterised and used to determine the acid-base properties via potentiometric titration. It was found that the basic strength of the DMAN-glycine base (pKa = 11.57, H2O) is on the level of amidine amino acids like arginine and creatine and its structure, zwitterionic vs. neutral, based on the spectroscopic (IR, NMR, mass) and theoretical (DFT) approaches has a strong preference to the zwitterionic form. Unlike glycine, the DMAN-glycine zwitterion is N-chiral and is hydrolytically cleaved with the loss of glycolic acid on heating in DMSO. This reaction together with the mild decarboxylative conversion of proton sponge-based amino acids into 2,3-dihydroperimidinium salts under air-oxygen was monitored with the help of the DMAN-alanine amino acid. The newly devised amino acids are unique as they combine fluorescence, strongly basic and redox-active properties.

  18. The first proton sponge-based amino acids: synthesis, acid-base properties and some reactivity.

    PubMed

    Ozeryanskii, Valery A; Gorbacheva, Anastasia Yu; Pozharskii, Alexander F; Vlasenko, Marina P; Tereznikov, Alexander Yu; Chernov'yants, Margarita S

    2015-08-21

    The first hybrid base constructed from 1,8-bis(dimethylamino)naphthalene (proton sponge or DMAN) and glycine, N-methyl-N-(8-dimethylamino-1-naphthyl)aminoacetic acid, was synthesised in high yield and its hydrobromide was structurally characterised and used to determine the acid-base properties via potentiometric titration. It was found that the basic strength of the DMAN-glycine base (pKa = 11.57, H2O) is on the level of amidine amino acids like arginine and creatine and its structure, zwitterionic vs. neutral, based on the spectroscopic (IR, NMR, mass) and theoretical (DFT) approaches has a strong preference to the zwitterionic form. Unlike glycine, the DMAN-glycine zwitterion is N-chiral and is hydrolytically cleaved with the loss of glycolic acid on heating in DMSO. This reaction together with the mild decarboxylative conversion of proton sponge-based amino acids into 2,3-dihydroperimidinium salts under air-oxygen was monitored with the help of the DMAN-alanine amino acid. The newly devised amino acids are unique as they combine fluorescence, strongly basic and redox-active properties. PMID:26159785

  19. Installing hydrolytic activity into a completely de novo protein framework

    NASA Astrophysics Data System (ADS)

    Burton, Antony J.; Thomson, Andrew R.; Dawson, William M.; Brady, R. Leo; Woolfson, Derek N.

    2016-09-01

    The design of enzyme-like catalysts tests our understanding of sequence-to-structure/function relationships in proteins. Here we install hydrolytic activity predictably into a completely de novo and thermostable α-helical barrel, which comprises seven helices arranged around an accessible channel. We show that the lumen of the barrel accepts 21 mutations to functional polar residues. The resulting variant, which has cysteine-histidine-glutamic acid triads on each helix, hydrolyses p-nitrophenyl acetate with catalytic efficiencies that match the most-efficient redesigned hydrolases based on natural protein scaffolds. This is the first report of a functional catalytic triad engineered into a de novo protein framework. The flexibility of our system also allows the facile incorporation of unnatural side chains to improve activity and probe the catalytic mechanism. Such a predictable and robust construction of truly de novo biocatalysts holds promise for applications in chemical and biochemical synthesis.

  20. Installing hydrolytic activity into a completely de novo protein framework

    NASA Astrophysics Data System (ADS)

    Burton, Antony J.; Thomson, Andrew R.; Dawson, William M.; Brady, R. Leo; Woolfson, Derek N.

    2016-09-01

    The design of enzyme-like catalysts tests our understanding of sequence-to-structure/function relationships in proteins. Here we install hydrolytic activity predictably into a completely de novo and thermostable α-helical barrel, which comprises seven helices arranged around an accessible channel. We show that the lumen of the barrel accepts 21 mutations to functional polar residues. The resulting variant, which has cysteine–histidine–glutamic acid triads on each helix, hydrolyses p-nitrophenyl acetate with catalytic efficiencies that match the most-efficient redesigned hydrolases based on natural protein scaffolds. This is the first report of a functional catalytic triad engineered into a de novo protein framework. The flexibility of our system also allows the facile incorporation of unnatural side chains to improve activity and probe the catalytic mechanism. Such a predictable and robust construction of truly de novo biocatalysts holds promise for applications in chemical and biochemical synthesis.

  1. Installing hydrolytic activity into a completely de novo protein framework.

    PubMed

    Burton, Antony J; Thomson, Andrew R; Dawson, William M; Brady, R Leo; Woolfson, Derek N

    2016-09-01

    The design of enzyme-like catalysts tests our understanding of sequence-to-structure/function relationships in proteins. Here we install hydrolytic activity predictably into a completely de novo and thermostable α-helical barrel, which comprises seven helices arranged around an accessible channel. We show that the lumen of the barrel accepts 21 mutations to functional polar residues. The resulting variant, which has cysteine-histidine-glutamic acid triads on each helix, hydrolyses p-nitrophenyl acetate with catalytic efficiencies that match the most-efficient redesigned hydrolases based on natural protein scaffolds. This is the first report of a functional catalytic triad engineered into a de novo protein framework. The flexibility of our system also allows the facile incorporation of unnatural side chains to improve activity and probe the catalytic mechanism. Such a predictable and robust construction of truly de novo biocatalysts holds promise for applications in chemical and biochemical synthesis. PMID:27554410

  2. Acid-Base Homeostasis.

    PubMed

    Hamm, L Lee; Nakhoul, Nazih; Hering-Smith, Kathleen S

    2015-12-01

    Acid-base homeostasis and pH regulation are critical for both normal physiology and cell metabolism and function. The importance of this regulation is evidenced by a variety of physiologic derangements that occur when plasma pH is either high or low. The kidneys have the predominant role in regulating the systemic bicarbonate concentration and hence, the metabolic component of acid-base balance. This function of the kidneys has two components: reabsorption of virtually all of the filtered HCO3(-) and production of new bicarbonate to replace that consumed by normal or pathologic acids. This production or generation of new HCO3(-) is done by net acid excretion. Under normal conditions, approximately one-third to one-half of net acid excretion by the kidneys is in the form of titratable acid. The other one-half to two-thirds is the excretion of ammonium. The capacity to excrete ammonium under conditions of acid loads is quantitatively much greater than the capacity to increase titratable acid. Multiple, often redundant pathways and processes exist to regulate these renal functions. Derangements in acid-base homeostasis, however, are common in clinical medicine and can often be related to the systems involved in acid-base transport in the kidneys.

  3. Photocurable bioadhesive based on lactic acid.

    PubMed

    Marques, D S; Santos, J M C; Ferreira, P; Correia, T R; Correia, I J; Gil, M H; Baptista, C M S G

    2016-01-01

    Novel photocurable and low molecular weight oligomers based on l-lactic acid with proven interest to be used as bioadhesive were successfully manufactured. Preparation of lactic acid oligomers with methacrylic end functionalizations was carried out in the absence of catalyst or solvents by self-esterification in two reaction steps: telechelic lactic acid oligomerization with OH end groups and further functionalization with methacrylic anhydride. The final adhesive composition was achieved by the addition of a reported biocompatible photoinitiator (Irgacure® 2959). Preliminary in vitro biodegradability was investigated by hydrolytic degradation in PBS (pH=7.4) at 37 °C. The adhesion performance was evaluated using glued aminated substrates (gelatine pieces) subjected to pull-to-break test. Surface energy measured by contact angles is lower than the reported values of the skin and blood. The absence of cytoxicity was evaluated using human fibroblasts. A notable antimicrobial behaviour was observed using two bacterial models (Staphylococcus aureus and Escherichia coli). The cured material exhibited a strong thrombogenic character when placed in contact with blood, which can be predicted as a haemostatic effect for bleeding control. This novel material was subjected to an extensive characterization showing great potential for bioadhesive or other biomedical applications where biodegradable and biocompatible photocurable materials are required. PMID:26478350

  4. Hydrolytic function of Exo1 in mammalian mismatch repair

    PubMed Central

    Shao, Hongbing; Baitinger, Celia; Soderblom, Erik J.; Burdett, Vickers; Modrich, Paul

    2014-01-01

    Genetic and biochemical studies have previously implicated exonuclease 1 (Exo1) in yeast and mammalian mismatch repair, with results suggesting that function of the protein in the reaction depends on both its hydrolytic activity and its ability to interact with other components of the repair system. However, recent analysis of an Exo1-E109K knockin mouse has concluded that Exo1 function in mammalian mismatch repair is restricted to a structural role, a conclusion based on a prior report that N-terminal His-tagged Exo1-E109K is hydrolytically defective. Because Glu-109 is distant from the nuclease hydrolytic center, we have compared the activity of untagged full-length Exo1-E109K with that of wild type Exo1 and the hydrolytically defective active site mutant Exo1-D173A. We show that the activity of Exo1-E109K is comparable to that of wild type enzyme in a conventional exonuclease assay and that in contrast to a D173A active site mutant, Exo1-E109K is fully functional in mismatch-provoked excision and repair. We conclude that the catalytic function of Exo1 is required for its participation in mismatch repair. We also consider the other phenotypes of the Exo1-E109K mouse in the context of Exo1 hydrolytic function. PMID:24829455

  5. Understanding Acid Base Disorders.

    PubMed

    Gomez, Hernando; Kellum, John A

    2015-10-01

    The concentration of hydrogen ions is regulated in biologic solutions. There are currently 3 recognized approaches to assess changes in acid base status. First is the traditional Henderson-Hasselbalch approach, also called the physiologic approach, which uses the relationship between HCO3(-) and Pco2; the second is the standard base excess approach based on the Van Slyke equation. The third approach is the quantitative or Stewart approach, which uses the strong ion difference and the total weak acids. This article explores the origins of the current concepts framing the existing methods to analyze acid base balance.

  6. Hydrolytic Degradation of Estane 5703

    SciTech Connect

    Wrobleski, D.A.; Smith, M.E.; Orler, E.B.

    1999-04-27

    Relative to the unaged Estane{reg_sign} 5703, heating decreases the modulus and ultimate stress for both the dry and humid samples. The sample aged in dry air, quickly recovered to its original mechanical properties. The reversibility of the mechanical properties is a result of the reorganization of the hard segments into domains. For the Estane 5703 samples aged in humid air, the mechanical properties only partially recovered with time. Molecular weight data confirm that differences in the extent of the recovery for the samples aged under humid environments are likely due to the hydrolytic scission of the polyester soft segments. Since the tensile moduli are similar for the samples aged in both the dry and humid environments, it is believed that the phase behavior of the hard domains dictate the mechanical properties at low extensions. However, at higher elongations, the mechanical properties are dominated by the soft segments. Both the influences of morphological changes and chemical changes induced by heating must be considered in multiphase polymers when accelerated aging is utilized to predict long term polymer properties. After accelerated aging experiments, the morphology must be allowed to recover to equilibrium conditions in order to assess the extent of degradation and aging. Also, the effect of different humidities on the rate of hydrolytic degradation are presented.

  7. Microbial biosurfactants and hydrolytic enzymes mediates in situ development of stable supra-molecular assemblies in fatty acids released from triglycerides.

    PubMed

    Gnanamani, Arumugam; Kavitha, V; Radhakrishnan, N; Sekaran, G; Rajakumar, G Suseela; Mandal, A B

    2010-07-01

    The present study demonstrates in situ formation of multilamellar stable vesicles (MLSVs) of fatty acids released during the growth of microorganisms in the presence of triglycerides. Release of lipase during initial phase of growth hydrolyzes the triglycerides and release free fatty acids (mono or diglycerides) and glycerol. By extending the growth and the prevailing composition of media (unspent nutrients, salts, pH of the medium, biosurfactants, fatty acids, glycerol) and agitation transforms free fatty acids to MLSV of both cylindrical and spherical macroscopic structures via micelle formation with in 240h of incubation. Cross-sectional view and SEM analysis of macroscopic structures reveal the existence of continuous multilayering. Thermo-gravimetric analysis illustrates the stability of the vesicles. FT-IR analysis emphasizes the presence of amide linkages, responsible for self-assembly processes. Schematic representation of formation of MLSV demonstrated for further understanding. Additional exploration on MLSV formation in arteries and the relationship between MLSV and in situ plaque formation by the components of blood in the arteries are schematically explained and submitted as supporting information (SI-2).

  8. [Chemical ribonucleases. 2. Design and hydrolytic properties RNase mimetics based on diazabicyclo[2.2.2]octane with various positive charges].

    PubMed

    Zenkova, M A; Vlasov, A V; Konevets, D A; Sil'nikov, V N; Giege, R; Vlasov, V V

    2000-09-01

    A procedure was proposed allowing one to synthesize RNA mimics on the basis of conjugates of diazabicyclo[2.2.2]octane with imidazole bearing a varying number of positive charges (nDm series, where n is the number of positive charges at neutral pH, m is the code of an imidazole-containing fragment of the catalytic domain: 1, histamine; 2, histidine methyl ester). The hydrolytic activity of six compounds of this series was studied under physiological conditions using in vitro transcript of human mitochondrial tRNA(Lys) as a substrate. It was shown that the rate of RNA hydrolysis with nDm conjugates rises with an increase in the number of positive charges: an approximately 30-fold acceleration of hydrolysis was observed with an increase in the total charge of the construct from +2 to +4.

  9. Activity of hydrolytic enzymes in fungi isolated from diabetic pregnant women: is there any relationship between fungal alkaline and acid phosphatase activity and glycemic control?

    PubMed

    Nowakowska, Dorota; Kurnatowska, Alicja; Stray-Pedersen, Babill; Wilczyński, Jan

    2004-06-01

    Ability to respond to environmental changes and secretion of hydrolases are considered to be important for Candida virulence. In this study we determined and compared the activities of 19 different hydrolases of the fungal strains isolated from diabetic and non-diabetic pregnant women. We also looked for the presence of a relationship between hydrolase activities and glycemic control, and, furthermore, evaluated the influence of gestational age on the activity of hydrolases. Mycological examinations were performed for 119 diabetic pregnant women: 47 with diabetes mellitus type I (DM), 72 with gestational diabetes (GDM), and for 132 healthy women (CON). Samples were collected from the vagina, rectum and oral cavity and cultured on Sabouraud media. The fungal hydrolase activities were evaluated using the API ZYM test (bioMerieux). For the 19 different fungal hydrolases tested, 13 activities were present in the isolated fungal strains. The activity of alkaline phosphatase (ALP) in vaginal strains (p=0.028) and acid phosphatase (ACP) in strains from the vagina (p=0.006) and rectum (p=0.049) was significantly lower in DM than in GDM and CON women. In conclusion, we describe for the first time that fungi isolated from pregnant diabetic women have lower activity of both phosphatases compared to fungi isolated from healthy women. Furthermore, similar differences of mean ALP and ACP activities were observed in the course of pregnancy in strains from the vagina and rectum of DM and CON women. However, strains from DM had lower activity at each stage of pregnancy. The highest activity of ALP and ACP was detected at the beginning, then declined, and had the lowest values between the 24(th) and 33(rd) week of gestation. After that period the activity of both phosphatases increased.

  10. Variation in pH optima of hydrolytic enzyme activities in tropical rain forest soils.

    PubMed

    Turner, Benjamin L

    2010-10-01

    Extracellular enzymes synthesized by soil microbes play a central role in the biogeochemical cycling of nutrients in the environment. The pH optima of eight hydrolytic enzymes involved in the cycles of carbon, nitrogen, phosphorus, and sulfur, were assessed in a series of tropical forest soils of contrasting pH values from the Republic of Panama. Assays were conducted using 4-methylumbelliferone-linked fluorogenic substrates in modified universal buffer. Optimum pH values differed markedly among enzymes and soils. Enzymes were grouped into three classes based on their pH optima: (i) enzymes with acidic pH optima that were consistent among soils (cellobiohydrolase, β-xylanase, and arylsulfatase), (ii) enzymes with acidic pH optima that varied systematically with soil pH, with the most acidic pH optima in the most acidic soils (α-glucosidase, β-glucosidase, and N-acetyl-β-glucosaminidase), and (iii) enzymes with an optimum pH in either the acid range or the alkaline range depending on soil pH (phosphomonoesterase and phosphodiesterase). The optimum pH values of phosphomonoesterase were consistent among soils, being 4 to 5 for acid phosphomonoesterase and 10 to 11 for alkaline phosphomonoesterase. In contrast, the optimum pH for phosphodiesterase activity varied systematically with soil pH, with the most acidic pH optima (3.0) in the most acidic soils and the most alkaline pH optima (pH 10) in near-neutral soils. Arylsulfatase activity had a very acidic optimum pH in all soils (pH ≤3.0) irrespective of soil pH. The differences in pH optima may be linked to the origins of the enzymes and/or the degree of stabilization on solid surfaces. The results have important implications for the interpretation of hydrolytic enzyme assays using fluorogenic substrates.

  11. Variation in pH Optima of Hydrolytic Enzyme Activities in Tropical Rain Forest Soils ▿

    PubMed Central

    Turner, Benjamin L.

    2010-01-01

    Extracellular enzymes synthesized by soil microbes play a central role in the biogeochemical cycling of nutrients in the environment. The pH optima of eight hydrolytic enzymes involved in the cycles of carbon, nitrogen, phosphorus, and sulfur, were assessed in a series of tropical forest soils of contrasting pH values from the Republic of Panama. Assays were conducted using 4-methylumbelliferone-linked fluorogenic substrates in modified universal buffer. Optimum pH values differed markedly among enzymes and soils. Enzymes were grouped into three classes based on their pH optima: (i) enzymes with acidic pH optima that were consistent among soils (cellobiohydrolase, β-xylanase, and arylsulfatase), (ii) enzymes with acidic pH optima that varied systematically with soil pH, with the most acidic pH optima in the most acidic soils (α-glucosidase, β-glucosidase, and N-acetyl-β-glucosaminidase), and (iii) enzymes with an optimum pH in either the acid range or the alkaline range depending on soil pH (phosphomonoesterase and phosphodiesterase). The optimum pH values of phosphomonoesterase were consistent among soils, being 4 to 5 for acid phosphomonoesterase and 10 to 11 for alkaline phosphomonoesterase. In contrast, the optimum pH for phosphodiesterase activity varied systematically with soil pH, with the most acidic pH optima (3.0) in the most acidic soils and the most alkaline pH optima (pH 10) in near-neutral soils. Arylsulfatase activity had a very acidic optimum pH in all soils (pH ≤3.0) irrespective of soil pH. The differences in pH optima may be linked to the origins of the enzymes and/or the degree of stabilization on solid surfaces. The results have important implications for the interpretation of hydrolytic enzyme assays using fluorogenic substrates. PMID:20709838

  12. High-buffering capacity, hydrolytically stable, low-pI isoelectric membranes for isoelectric trapping separations.

    PubMed

    Lalwani, Sanjiv; Shave, Evan; Vigh, Gyula

    2004-10-01

    Hydrolytically stable, low-pI isoelectric membranes have been synthesized from low-pI ampholytic components, poly(vinyl alcohol), and a bifunctional cross-linker, glycerol-1,3-diglycidyl ether. The low-pI ampholytic components used contain one amino group and at least two weakly acidic functional groups. The acidic functional groups are selected such that the pI value of the ampholytic component is determined by the pK(a) values of the acidic functional groups. When the concentration of the ampholytic component incorporated into the membrane is higher than a required minimum value, the pI of the membrane becomes independent of variations in the actual incorporation rate of the ampholytic compound. The new, low-pI isoelectric membranes have been successfully used as anodic membranes in isoelectric trapping separations with pH < 1.5 anolytes and replaced the hydrolytically less stable polyacrylamide-based isoelectric membranes. The new low-pI isoelectric membranes have excellent mechanical stability, low electric resistance, good buffering capacity, and long life time, even when used with as much as 50 W power and current densities as high as 33 mA/cm(2) during the isoelectric trapping separations.

  13. High-buffering capacity, hydrolytically stable, low-pI isoelectric membranes for isoelectric trapping separations.

    PubMed

    Lalwani, Sanjiv; Shave, Evan; Vigh, Gyula

    2004-10-01

    Hydrolytically stable, low-pI isoelectric membranes have been synthesized from low-pI ampholytic components, poly(vinyl alcohol), and a bifunctional cross-linker, glycerol-1,3-diglycidyl ether. The low-pI ampholytic components used contain one amino group and at least two weakly acidic functional groups. The acidic functional groups are selected such that the pI value of the ampholytic component is determined by the pK(a) values of the acidic functional groups. When the concentration of the ampholytic component incorporated into the membrane is higher than a required minimum value, the pI of the membrane becomes independent of variations in the actual incorporation rate of the ampholytic compound. The new, low-pI isoelectric membranes have been successfully used as anodic membranes in isoelectric trapping separations with pH < 1.5 anolytes and replaced the hydrolytically less stable polyacrylamide-based isoelectric membranes. The new low-pI isoelectric membranes have excellent mechanical stability, low electric resistance, good buffering capacity, and long life time, even when used with as much as 50 W power and current densities as high as 33 mA/cm(2) during the isoelectric trapping separations. PMID:15490454

  14. Hydrolytic degradation of Kevlar 49 fibers

    SciTech Connect

    Morgan, R.J.; Pruneda, C.O.; Butler, N.; Kong, F.M.; Caley, L.; Moore, R.L.

    1983-12-05

    The hydrolytic degradation of Kevlar 49 fibers and the principal parameters that control this degradation are presented. Hydrolytic chain scission of the amide linkage and corresponding fiber strength deterioration are considered in terms of RH, time, temperature and stress level. The rates of hydrolytic degradation at 100% RH in the 100 to 200/sup 0/C range are reported. The estimated rates of fiber degradation in various service environment conditions are also reported and shown not to be serious. The impurities present in Kevlar 49 fibers and their effect on hydrolytic degradation are also discussed. In addition, the aging of Kevlar 49 fibers as a result of exposure to uv and stress are reviewed.

  15. Urbanised beaches of the Ligurian coastal area (NW Mediterranean): a classification based on organic-matter characteristics and hydrolytic enzymatic activities.

    PubMed

    Misic, Cristina; Covazzi Harriague, Anabella

    2013-01-01

    The beaches of Liguria have been intensively affected by human activities for over a century, transforming nearly the entire coastline from natural to urbanised and significantly upsetting beach ecological properties. The present study aims to investigate 9 Ligurian beaches characterised by different degree of urbanisation, to test if and to what extent the organic-matter (OM) recycling processes can be linked to the human activity. Swash zone sediment, sampled during the spring-summer-autumn period, when the anthropogenic influence is at its maximum due to tourism, was analysed for OM features and recycling processes. Multivariate statistical analyses showed that huge amounts of detrital OM accumulated in the more urbanised sites, where the anthropogenic influence was at its peak, deriving from higher inhabitant number and density, from the presence of crowded roads very near to the swash zone and sewage treatment plants. The presence of torrent outlets on the beaches provided further OM accumulation. Lipids, carbohydrates and degraded autotrophic pigments were the OM fractions mainly responsible of the differentiation, and rather constant, high labile phosphorus contents were found in the more urbanised sites. The high activity values of the hydrolytic enzymes indicate the response of the microbial system to the OM accumulation in the urban sites. However, a decoupling of the trends of some enzymatic activities (namely glucosidase and lipase) and their target OM was observed in the highly urbanised conditions.

  16. Hydrolytic microbial communities in terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Manucharova, Natalia; Chernov, Timofey; Kolcova, Ekaterina; Zelezova, Alena; Lukacheva, Euhenia; Zenova, Galina

    2014-05-01

    Hydrolytic microbial communities in terrestrial ecosystems Manucharova N.A., Chernov T.I., Kolcova E.M., Zelezova A.D., Lukacheva E.G. Lomonosov Moscow State University, Russia Vertical differentiation of terrestrial biogeocenoses is conditioned by the formation of vertical tiers that differ considerably in the composition and structure of microbial communities. All the three tiers, phylloplane, litter and soil, are united by a single flow of organic matter, and are spatially separated successional stages of decomposition of organic substances. Decomposition of organic matter is mainly due to the activity of microorganisms producing enzymes - hydrolase and lyase - which destroy complex organic compounds. Application of molecular biological techniques (FISH) in environmental studies provides a more complete information concerning the taxonomic diversity and potential hydrolytic activity of microbial complexes of terrestrial ecosystems that exist in a wide range of environmental factors (moisture, temperature, redox potential, organic matter). The combination of two molecular biological techniques (FISH and DGGE-analysis of fragments of gene 16S rRNA total amplificate) enables an informative assessment of the differences in the structure of dominant and minor components of hydrolytic complexes formed in different tiers of terrestrial ecosystems. The functional activity of hydrolytic microbial complexes of terrestrial ecosystems is determined by the activity of dominant and minor components, which also have a high gross enzymatic activity. Degradation of biopolymers in the phylloplane is mainly due to the representatives of the Proteobacteria phylogenetic group (classes alpha and beta). In mineral soil horizons, the role of hydrolytic representatives of Firmicutes and Actinobacteria increases. Among the key environmental parameters that determine the functional activity of the hydrolytic (chitinolytic) complex of soil layer (moisture, nutrient supply, successional

  17. Oxidative and hydrolytic stability of a novel acrylic terpolymer for biomedical applications.

    PubMed

    Veleva, Anka N; Khan, Saad A; Cooper, Stuart L

    2005-07-01

    Oxidative and hydrolytic biostability assessment was carried out on a novel acrylic material made of hexamethyl methacrylate (HMA), methyl methacrylate (MMA), and methacrylic acid (MAA). To simulate the in vivo microenvironment, solutions of H2O2/CoCl2 and buffered solutions of cholesterol esterase (CE) and phospholipase A2 (PLA) were used. As controls, film specimens were incubated in deionized water. Samples were incubated in these solutions at 37 degrees C for 10 weeks before physical and mechanical properties were evaluated by size exclusion chromatography (SEC), 1H- nuclear magnetic resonance (1H-NMR), acid-base titration, and Instron tensile testing. The results from this study indicate excellent biostability of HMA-MMA-MAA terpolymers and thus their potential for use in biomedical devices for long-term implantation. PMID:15924302

  18. Screening for hydrolytic enzymes reveals Ayr1p as a novel triacylglycerol lipase in Saccharomyces cerevisiae.

    PubMed

    Ploier, Birgit; Scharwey, Melanie; Koch, Barbara; Schmidt, Claudia; Schatte, Jessica; Rechberger, Gerald; Kollroser, Manfred; Hermetter, Albin; Daum, Günther

    2013-12-13

    Saccharomyces cerevisiae, as well as other eukaryotes, preserves fatty acids and sterols in a biologically inert form, as triacylglycerols and steryl esters. The major triacylglycerol lipases of the yeast S. cerevisiae identified so far are Tgl3p, Tgl4p, and Tgl5p (Athenstaedt, K., and Daum, G. (2003) YMR313c/TGL3 encodes a novel triacylglycerol lipase located in lipid particles of Saccharomyces cerevisiae. J. Biol. Chem. 278, 23317-23323; Athenstaedt, K., and Daum, G. (2005) Tgl4p and Tgl5p, two triacylglycerol lipases of the yeast Saccharomyces cerevisiae, are localized to lipid particles. J. Biol. Chem. 280, 37301-37309). We observed that upon cultivation on oleic acid, triacylglycerol mobilization did not come to a halt in a yeast strain deficient in all currently known triacylglycerol lipases, indicating the presence of additional not yet characterized lipases/esterases. Functional proteome analysis using lipase and esterase inhibitors revealed a subset of candidate genes for yet unknown hydrolytic enzymes on peroxisomes and lipid droplets. Based on the conserved GXSXG lipase motif, putative functions, and subcellular localizations, a selected number of candidates were characterized by enzyme assays in vitro, gene expression analysis, non-polar lipid analysis, and in vivo triacylglycerol mobilization assays. These investigations led to the identification of Ayr1p as a novel triacylglycerol lipase of yeast lipid droplets and confirmed the hydrolytic potential of the peroxisomal Lpx1p in vivo. Based on these results, we discuss a possible link between lipid storage, lipid mobilization, and peroxisomal utilization of fatty acids as a carbon source.

  19. Development of urethane coating and potting material with improved hydrolytic and oxidative stability

    NASA Technical Reports Server (NTRS)

    Morris, D. E.

    1981-01-01

    A series of saturated hydrocarbon based urethanes was prepared and characterized for hydrolytic and oxidative stability. A series of ether based urethanes was used as a basis for comparison. The alkane base urethanes were found to be hydrolytically and oxidatively stable and had excellent electrical properties. The alkane based materials absorbed little or no water and were reversion resistant. There was little loss in hardness or weight when exposed to high temperature and humidity. Dielectric properties were excellent and suffered little adverse effects from the high temperature/humidity conditions. The alkane based urethanes were not degraded by ozone exposure.

  20. Preparation of Dental Resins Resistant to Enzymatic and Hydrolytic Degradation in Oral Environments.

    PubMed

    Gonzalez-Bonet, Andres; Kaufman, Gili; Yang, Yin; Wong, Christopher; Jackson, Abigail; Huyang, George; Bowen, Rafael; Sun, Jirun

    2015-10-12

    The short average service life of traditional dental composite restorative materials and increasing occurrence of secondary caries adjacent to composite restorations and sealants are necessitating the development of new, longer lasting compositions. Novel monomers and their polymers, reinforcing fillers, and adhesive components are needed. The goal of this research is to develop resin systems for use in restorations, sealants, and other dental services that are superior in properties and endurance to currently used bisphenol A glycidyl dimethacrylate/triethylene glycol dimethacrylate (Bis-GMA/TEGDMA) and urethane-dimethacrylate products. Ether-based monomers and their polymers that were not susceptible to enzymatic or hydrolytic degradation were prepared and characterized. They showed no degradation under hydrolytic and enzymatic challenges, whereas the hydrolysis of ester links weakened contemporary resins within 16 days under these challenges. The success of the ether-based materials is promising in making durable systems that are subjected to long-term biochemical and hydrolytic challenges in oral environments.

  1. Comparison of hydrolytic and non-hydrolytic atomic layer deposition chemistries: Interfacial electronic properties at alumina-silicon interfaces

    NASA Astrophysics Data System (ADS)

    Marstell, Roderick J.; Strandwitz, Nicholas C.

    2015-11-01

    We report the differences in the passivation and electronic properties of aluminum oxide (Al2O3) deposited on silicon via traditional hydrolytic atomic layer deposition (ALD) and non-hydrolytic (NH) ALD chemistries. Traditional films were grown using trimethylaluminum (TMA) and water and NHALD films grown using TMA and isopropanol at 300 °C. Hydrolytically grown ALD films contain a smaller amount of fixed charge than NHALD films (oxide fixed charge Qf Traditional = -8.1 × 1011 cm-2 and Qf NHALD = -3.6 × 1012 cm-2), and a larger degree of chemical passivation than NHALD films (density of interface trap states, Dit Traditional = 5.4 × 1011 eV-1 cm-2 and Dit NHALD = 2.9 × 1012 eV-1 cm-2). Oxides grown with both chemistries were found to have a band gap of 7.1 eV. The conduction band offset was 3.21 eV for traditionally grown films and 3.38 eV for NHALD. The increased Dit for NHALD films may stem from carbon impurities in the oxide layer that are at and near the silicon surface, as evidenced by both the larger trap state time constant (τTraditional = 2.2 × 10-9 s and τNHALD = 1.7 × 10-7 s) and the larger carbon concentration. We have shown that the use of alcohol-based oxygen sources in NHALD chemistry can significantly affect the resulting interfacial electronic behavior presenting an additional parameter for understanding and controlling interfacial electronic properties at semiconductor-dielectric interfaces.

  2. Molten fatty acid based microemulsions.

    PubMed

    Noirjean, Cecile; Testard, Fabienne; Dejugnat, Christophe; Jestin, Jacques; Carriere, David

    2016-06-21

    We show that ternary mixtures of water (polar phase), myristic acid (MA, apolar phase) and cetyltrimethylammonium bromide (CTAB, cationic surfactant) studied above the melting point of myristic acid allow the preparation of microemulsions without adding a salt or a co-surfactant. The combination of SANS, SAXS/WAXS, DSC, and phase diagram determination allows a complete characterization of the structures and interactions between components in the molten fatty acid based microemulsions. For the different structures characterized (microemulsion, lamellar or hexagonal phases), a similar thermal behaviour is observed for all ternary MA/CTAB/water monophasic samples and for binary MA/CTAB mixtures without water: crystalline myristic acid melts at 52 °C, and a thermal transition at 70 °C is assigned to the breaking of hydrogen bounds inside the mixed myristic acid/CTAB complex (being the surfactant film in the ternary system). Water determines the film curvature, hence the structures observed at high temperature, but does not influence the thermal behaviour of the ternary system. Myristic acid is partitioned in two "species" that behave independently: pure myristic acid and myristic acid associated with CTAB to form an equimolar complex that plays the role of the surfactant film. We therefore show that myristic acid plays the role of a solvent (oil) and a co-surfactant allowing the fine tuning of the structure of oil and water mixtures. This solvosurfactant behaviour of long chain fatty acid opens the way for new formulations with a complex structure without the addition of any extra compound. PMID:27241163

  3. Cyclic Imide Dioxime: Formation and Hydrolytic Stability

    SciTech Connect

    Kang, S.O.; Vukovic, Sinisa; Custelcean, Radu; Hay, Benjamin

    2012-01-01

    Poly(acrylamidoximes) play an important role in the uranium extraction from seawater. The present work reports solution studies of simple analogs to address the formation and stability of two binding sites present in these polymers, open-chain amidoximes and cyclic imide dioximes, including: 1) conditions that maximize the formation of the cyclic form, 2) existence of a base-induced conversion from open-chain to cyclic form, and 3) degradation under acid and base conditions.

  4. Nucleic acid based logical systems.

    PubMed

    Han, Da; Kang, Huaizhi; Zhang, Tao; Wu, Cuichen; Zhou, Cuisong; You, Mingxu; Chen, Zhuo; Zhang, Xiaobing; Tan, Weihong

    2014-05-12

    Researchers increasingly visualize a significant role for artificial biochemical logical systems in biological engineering, much like digital logic circuits in electrical engineering. Those logical systems could be utilized as a type of servomechanism to control nanodevices in vitro, monitor chemical reactions in situ, or regulate gene expression in vivo. Nucleic acids (NA), as carriers of genetic information with well-regulated and predictable structures, are promising materials for the design and engineering of biochemical circuits. A number of logical devices based on nucleic acids (NA) have been designed to handle various processes for technological or biotechnological purposes. This article focuses on the most recent and important developments in NA-based logical devices and their evolution from in vitro, through cellular, even towards in vivo biological applications.

  5. Radiometric acid-base titrations.

    PubMed

    Erdey, L; Gimesi, O; Szabadváry, F

    1969-03-01

    Acid-base titrations can be performed with radiometric end-point detection by use of labelled metal salts (e.g., ZnCl(2), HgCl(2)). Owing to the formation or dissolution of the corresponding hydroxide after the equivalence point, the activity of the titrated solution linearly increases or decreases as excess of standard solution is added. The end-point of the titration is determined graphically.

  6. Comparison of hydrolytic and non-hydrolytic atomic layer deposition chemistries: Interfacial electronic properties at alumina-silicon interfaces

    SciTech Connect

    Marstell, Roderick J.; Strandwitz, Nicholas C.

    2015-11-14

    We report the differences in the passivation and electronic properties of aluminum oxide (Al{sub 2}O{sub 3}) deposited on silicon via traditional hydrolytic atomic layer deposition (ALD) and non-hydrolytic (NH) ALD chemistries. Traditional films were grown using trimethylaluminum (TMA) and water and NHALD films grown using TMA and isopropanol at 300 °C. Hydrolytically grown ALD films contain a smaller amount of fixed charge than NHALD films (oxide fixed charge Q{sub f} {sub Traditional} = −8.1 × 10{sup 11 }cm{sup −2} and Q{sub f} {sub NHALD} = −3.6 × 10{sup 12 }cm{sup −2}), and a larger degree of chemical passivation than NHALD films (density of interface trap states, D{sub it} {sub Traditional} = 5.4 × 10{sup 11 }eV{sup −1 }cm{sup −2} and D{sub it} {sub NHALD} = 2.9 × 10{sup 12 }eV{sup −1 }cm{sup −2}). Oxides grown with both chemistries were found to have a band gap of 7.1 eV. The conduction band offset was 3.21 eV for traditionally grown films and 3.38 eV for NHALD. The increased D{sub it} for NHALD films may stem from carbon impurities in the oxide layer that are at and near the silicon surface, as evidenced by both the larger trap state time constant (τ{sub Traditional} = 2.2 × 10{sup −9} s and τ{sub NHALD} = 1.7 × 10{sup −7} s) and the larger carbon concentration. We have shown that the use of alcohol-based oxygen sources in NHALD chemistry can significantly affect the resulting interfacial electronic behavior presenting an additional parameter for understanding and controlling interfacial electronic properties at semiconductor-dielectric interfaces.

  7. Identification and Characterization of Hydrolytic Degradation Products of Cefditoren Pivoxil using LC and LC-MS/TOF

    PubMed Central

    Gawande, V. T.; Bothara, K. G.; Singh, A.; Mahajan, A. A.

    2015-01-01

    The present research work was carried out to determine stability of cefditoren pivoxil, an orally absorbed prodrug that is rapidly hydrolysed by intestinal esterases to the active cephalosporin cefditoren. Cefditoren was subjected to stress conditions recommended by the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use guideline Q1A (R2). Cefditoren pivoxil was susceptible for degradation under acidic, alkaline and neutral hydrolytic conditions while it was stable under photolytic and thermal stress conditions. Separation of cefditoren and degradation products were carried out by using HPLC. The unknown degradation products were characterized by liquid chromatography-mass spectrometry/time of flight studies. Structures were proposed for each fragment based on best possible molecular formula and complete degradation pathways were reported for cefditoren and its degradants. PMID:25767321

  8. High-performance liquid chromatography study of the enantiomer separation of chrysanthemic acid and its analogous compounds on a terguride-based stationary phase.

    PubMed

    Dondi, M; Flieger, M; Olsovska, J; Polcaro, C M; Sinibaldi, M

    1999-10-29

    The direct enantioseparation of chrysanthemic acid [2,2-dimethyl-3-(2-methylpropenyl)-cyclopropanecarboxylic acid] and its halogen-substituted analogues was systematically studied by HPLC using a terguride-based chiral stationary phase in combination with a UV diode array and chiroptical detectors. Isomers with (1R) configuration always eluted before those with (IS) configuration. The elution sequence of cis- and trans-isomers was strongly affected by mobile phase pH, whereas the enantioselectivity remained the same. Conditions for the separation of all the enantiomers were also examined. This method was used for monitor the hydrolytic degradation products of Cyfluthrin (Baythroid) in soil under laboratory conditions.

  9. Hydrolytic degradation of electron beam irradiated high molecular weight and non-irradiated moderate molecular weight PLLA.

    PubMed

    Loo, Say Chye Joachim; Tan, Hui Tong; Ooi, Chui Ping; Boey, Yin Chiang Freddy

    2006-05-01

    The purpose of this study is to examine the hydrolytic degradation of electron beam irradiated ring-opening polymerized (ROP) poly(l-lactide) (PLLA-ir) and non-irradiated melt polycondensation polymerized poly(l-lactic acid) (PLLA-pc). It was observed that irradiation increases the hydrolytic degradation rate constant for ROP PLLA. This was due to a more hydrophilic PLLA-ir, as a result of irradiation. The degradation rate constants (k) of PLLA-ir samples were also found to be similar, regardless of the radiation dose, and an empirically formulated equation relating hydrolytic degradation time span to radiation dose was derived. The k value for PLLA-pc was observed to be lower than that for PLLA-ir, though the latter had a higher molecular weight. This was due to the difference in degradation mechanism, in which PLLA-ir undergoes end group scission, through a back- biting mechanism, during hydrolysis and thus a faster hydrolysis rate. Electron beam irradiation, though accelerates the degradation of PLLA, has been shown to be useful in accurately controlling the hydrolytic time span of PLLA. This method of controlling the hydrolytic degradation time was by far an easier task than through melt polycondensation polymerization. This would allow PLLA to be used for drug delivery purposes or as a temporary implant that requires a moderate time span (3-6 months). PMID:16701888

  10. Use of an Acid-Base Table.

    ERIC Educational Resources Information Center

    Willis, Grover; And Others

    1986-01-01

    Identifies several ways in which an acid-base table can provide students with information about chemical reactions. Cites examples of the chart's use and includes a table which indicates the strengths of some common acids and bases. (ML)

  11. The Acid-Base Titration of a Very Weak Acid: Boric Acid

    ERIC Educational Resources Information Center

    Celeste, M.; Azevedo, C.; Cavaleiro, Ana M. V.

    2012-01-01

    A laboratory experiment based on the titration of boric acid with strong base in the presence of d-mannitol is described. Boric acid is a very weak acid and direct titration with NaOH is not possible. An auxiliary reagent that contributes to the release of protons in a known stoichiometry facilitates the acid-base titration. Students obtain the…

  12. Ga(III) complexes as models for the M(III) site of purple acid phosphatase: ligand effects on the hydrolytic reactivity toward bis(2,4-dinitrophenyl) phosphate.

    PubMed

    Coleman, Fergal; Hynes, Michael J; Erxleben, Andrea

    2010-07-19

    The effects of a series of Ga(III) complexes with tripodal ligands on the hydrolysis rate of the activated phosphate diester bis(2,4-dinitrophenyl)phosphate (BDNPP) have been investigated. In particular, the influence of the nature of the ligand donor sites on the reactivity of Ga(III) which represents a mimic of the Fe(III) ion in purple acid phosphatase has been evaluated. It has been shown that replacing neutral nitrogen donor atoms and carboxylate groups by phenolate groups enhanced the reactivity of the Ga complexes. Bell-shaped pH-rate profiles and the measured solvent deuterium isotope effects are indicative of a mechanism that involves nucleophilic attack on the coordinated substrate by Ga-OH. The trend in reactivity found for the different Ga complexes reveals that of the two effects of the metal, Lewis acid activation of the substrate and nucleophile activation, the latter one is more important in determining the intrinsic reactivity of the metal catalyst. The relevance of the present findings for the modulation of the activity of the M(III) ion in purple acid phosphatase whose active site contains a phenolate (tyrosine side chain) is discussed. PMID:20565083

  13. Hydrolytic depolymerization of hydrolysis lignin: Effects of catalysts and solvents.

    PubMed

    Mahmood, Nubla; Yuan, Zhongshun; Schmidt, John; Xu, Chunbao Charles

    2015-08-01

    Hydrolytic depolymerization of hydrolysis lignin (HL) in water and water-ethanol co-solvent was investigated at 250°C for 1h with 20% (w/v) HL substrate concentration with or without catalyst (H2SO4 or NaOH). The obtained depolymerized HLs (DHLs) were characterized with GPC-UV, FTIR, GC-MS, (1)H NMR and elemental analyzer. In view of the utilization of depolymerized HL (DHL) for the preparation of rigid polyurethane foams/resins un-catalyzed depolymerization of HL employing water-ethanol mixture appeared to be a viable route with high yield of DHL ∼70.5wt.% (SR yield of ∼9.8wt.%) and with Mw as low as ∼1000g/mole with suitable aliphatic (227.1mgKOH/g) and phenolic (215mgKOH/g) hydroxyl numbers. The overall % carbon recovery under the selected best route was ∼87%. Acid catalyzed depolymerization of HL in water and water-ethanol mixture lead to slightly increased Mw. Alkaline hydrolysis helped in reducing Mw in water and opposite trend was observed in water-ethanol mixture. PMID:25936442

  14. Gamma-irradiation stability of saturated and unsaturated aliphatic polyanhydrides--ricinoleic acid based polymers.

    PubMed

    Teomim, D; Mäder, K; Bentolila, A; Magora, A; Domb, A J

    2001-01-01

    The effect of terminal sterilization by gamma-irradiation on several ricinoleic acid based polyanhydrides was investigated. The following polymers were used: poly(ricinoleic acid maleate) [P(RAM)], poly(ricinoleic acid succinate) [P(RAS)], poly(hydroxy stearic acid succinate) [P(HSAS)], poly(hydroxy stearic acid maleate) [P(HSAM)], and their copolymers with sebacic acid. The polymers were irradiated with an absorbed dose of 2.5 or 10 Mrad by means of a 60Co source under dry ice or at room temperature. No differences were found between samples irradiated under dry ice and at room temperature. Polymers prepared from monomers containing maleate residues, which contain double bonds adjusted to the anhydride linkage along the polymer chain, decreased in molecular weight, became insoluble, and showed fast hydrolytic degradation. For example, p(RAM), p(HSAM), and their copolymers with sebacic acid decreased in Mw from about 10,000 to about 2000, and from about 30,000 to about 5000, respectively, while polymers based on RAS and HSAS remained stable. This phenomenon was explained by an anhydride interchange-self-depolymerization process of the unsaturated anhydride bonds induced by gamma-irradiation. This explanation was supported by the depolymerization of another class of polymers having an anhydride bond between two double bonds, fumaric acid anhydride polymers. The anhydride bond that lies between two double bonds was found to be more sensitive to gamma-irradiation. This anhydride bond may be cleaved to form two radicals that further react with aliphatic anhydride bonds along the polymer chain to form inter- and/or intracyclization products. PMID:11710004

  15. The Legionella pneumophila GTPase Activating Protein LepB Accelerates Rab1 Deactivation by a Non-canonical Hydrolytic Mechanism*

    PubMed Central

    Mishra, Ashwini K.; Del Campo, Claudia M.; Collins, Robert E.; Roy, Craig R.; Lambright, David G.

    2013-01-01

    GTPase activating proteins (GAPs) from pathogenic bacteria and eukaryotic host organisms deactivate Rab GTPases by supplying catalytic arginine and glutamine fingers in trans and utilizing the cis-glutamine in the DXXGQ motif of the GTPase for binding rather than catalysis. Here, we report the transition state mimetic structure of the Legionella pneumophila GAP LepB in complex with Rab1 and describe a comprehensive structure-based mutational analysis of potential catalytic and recognition determinants. The results demonstrate that LepB does not simply mimic other GAPs but instead deploys an expected arginine finger in conjunction with a novel glutamic acid finger, which forms a salt bridge with an indispensible switch II arginine that effectively locks the cis-glutamine in the DXXGQ motif of Rab1 in a catalytically competent though unprecedented transition state configuration. Surprisingly, a heretofore universal transition state interaction with the cis-glutamine is supplanted by an elaborate polar network involving critical P-loop and switch I serines. LepB further employs an unusual tandem domain architecture to clamp a switch I tyrosine in an open conformation that facilitates access of the arginine finger to the hydrolytic site. Intriguingly, the critical P-loop serine corresponds to an oncogenic substitution in Ras and replaces a conserved glycine essential for the canonical transition state stereochemistry. In addition to expanding GTP hydrolytic paradigms, these observations reveal the unconventional dual finger and non-canonical catalytic network mechanisms of Rab GAPs as necessary alternative solutions to a major impediment imposed by substitution of the conserved P-loop glycine. PMID:23821544

  16. 3-d structure-based amino acid sequence alignment of esterases, lipases and related proteins

    SciTech Connect

    Gentry, M.K.; Doctor, B.P.; Cygler, M.; Schrag, J.D.; Sussman, J.L.

    1993-05-13

    Acetylcholinesterase and butyrylcholinesterase, enzymes with potential as pretreatment drugs for organophosphate toxicity, are members of a larger family of homologous proteins that includes carboxylesterases, cholesterol esterases, lipases, and several nonhydrolytic proteins. A computer-generated alignment of 18 of the proteins, the acetylcholinesases, butyrylcholinesterases, carboxylesterases, some esterases, and the nonenzymatic proteins has been previously presented. More recently, the three-dimensional structures of two enzymes enzymes in this group, acetylcholinesterase from Torpedo californica and lipase from Geotrichum candidum, have been determined. Based on the x-ray structures and the superposition of these two enzymes, it was possible to obtain an improved amino acid sequence alignment of 32 members of this family of proteins. Examination of this alignment reveals that 24 amino acids are invariant in all of the hydrolytic proteins, and an additional 49 are well conserved. Conserved amino acids include those of the active site, the disulfide bridges, the salt bridges, in the core of the proteins, and at the edges of secondary structural elements. Comparison of the three-dimensional structures makes it possible to find a well-defined structural basis for the conservation of many of these amino acids.

  17. "Non-hydrolytic" sol-gel synthesis of molybdenum sulfides

    NASA Astrophysics Data System (ADS)

    Leidich, Saskia; Buechele, Dominique; Lauenstein, Raphael; Kluenker, Martin; Lind, Cora

    2016-10-01

    Non-hydrolytic sol-gel reactions provide a low temperature solution based synthetic approach to solid-state materials. In this paper, reactions between molybdenum chloride and hexamethyldisilthiane in chloroform were explored, which gave access to both MoS2 and Mo2S3 after heat treatment of as-recovered amorphous samples to 600-1000 °C. Interesting morphologies were obtained for MoS2, ranging from fused spherical particles to well-defined nanoplatelets and nanoflakes. Both 2H- and 3R-MoS2 were observed, which formed thin hexagonal and triangular platelets, respectively. The platelets exhibited thicknesses of 10-30 nm, which corresponds to 15-50 MoS2 layers. No attempts to prevent agglomeration were made, however, well separated platelets were observed for many samples. Heating at 1000 °C led to formation of Mo2S3 for samples that showed well-defined MoS2 at lower temperatures, while less crystalline samples had a tendency to retain the MoS2 structure.

  18. Preparation of Dental Resins Resistant to Enzymatic and Hydrolytic Degradation in Oral Environments.

    PubMed

    Gonzalez-Bonet, Andres; Kaufman, Gili; Yang, Yin; Wong, Christopher; Jackson, Abigail; Huyang, George; Bowen, Rafael; Sun, Jirun

    2015-10-12

    The short average service life of traditional dental composite restorative materials and increasing occurrence of secondary caries adjacent to composite restorations and sealants are necessitating the development of new, longer lasting compositions. Novel monomers and their polymers, reinforcing fillers, and adhesive components are needed. The goal of this research is to develop resin systems for use in restorations, sealants, and other dental services that are superior in properties and endurance to currently used bisphenol A glycidyl dimethacrylate/triethylene glycol dimethacrylate (Bis-GMA/TEGDMA) and urethane-dimethacrylate products. Ether-based monomers and their polymers that were not susceptible to enzymatic or hydrolytic degradation were prepared and characterized. They showed no degradation under hydrolytic and enzymatic challenges, whereas the hydrolysis of ester links weakened contemporary resins within 16 days under these challenges. The success of the ether-based materials is promising in making durable systems that are subjected to long-term biochemical and hydrolytic challenges in oral environments. PMID:26358180

  19. Phosphonic acid based exchange resins

    DOEpatents

    Horwitz, E.P.; Alexandratos, S.D.; Gatrone, R.C.; Chiarizia, R.

    1995-09-12

    An ion exchange resin is described for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene. 10 figs.

  20. Phosphonic acid based exchange resins

    DOEpatents

    Horwitz, E. Philip; Alexandratos, Spiro D.; Gatrone, Ralph C.; Chiarizia, Ronato

    1995-01-01

    An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene.

  1. Students' Alternate Conceptions on Acids and Bases

    ERIC Educational Resources Information Center

    Pan, Hanqing; Henriques, Laura

    2015-01-01

    Knowing what students bring to the classroom can and should influence how we teach them. This study is a review of the literature associated with secondary and postsecondary students' ideas about acids and bases. It was found that there are six types of alternate ideas about acids and bases that students hold. These are: macroscopic properties of…

  2. The Kidney and Acid-Base Regulation

    ERIC Educational Resources Information Center

    Koeppen, Bruce M.

    2009-01-01

    Since the topic of the role of the kidneys in the regulation of acid base balance was last reviewed from a teaching perspective (Koeppen BM. Renal regulation of acid-base balance. Adv Physiol Educ 20: 132-141, 1998), our understanding of the specific membrane transporters involved in H+, HCO , and NH transport, and especially how these…

  3. The Conjugate Acid-Base Chart.

    ERIC Educational Resources Information Center

    Treptow, Richard S.

    1986-01-01

    Discusses the difficulties that beginning chemistry students have in understanding acid-base chemistry. Describes the use of conjugate acid-base charts in helping students visualize the conjugate relationship. Addresses chart construction, metal ions, buffers and pH titrations, and the organic functional groups and nonaqueous solvents. (TW)

  4. Poly(ester amide)s based on (L)-lactic acid oligomers and α-amino acids: influence of the α-amino acid side chain in the poly(ester amide)s properties.

    PubMed

    Fonseca, Ana C; Coelho, Jorge F J; Valente, Joana F A; Correia, Tiago R; Correia, Ilídio J; Gil, Maria H; Simões, Pedro N

    2013-01-01

    Novel biodegradable and low cytotoxic poly(ester amide)s (PEAs) based on α-amino acids and (L)-lactic acid (L-LA) oligomers were successfully synthesized by interfacial polymerization. The chemical structure of the new polymers was confirmed by spectroscopic analyses. Further characterization suggests that the α-amino acid plays a critical role on the final properties of the PEA. L-phenylalanine provides PEAs with higher glass transition temperature, whereas glycine enhances the crystallinity. The hydrolytic degradation in PBS (pH = 7.4) at 37 °C also depends on the α-amino acid, being faster for glycine-based PEAs. The cytotoxic profiles using fibroblast human cells indicate that the PEAs did not elicit an acute cytotoxic effect. The strategy presented in this work opens the possibility of synthesizing biodegradable PEAs with low citotoxicity by an easy and fast method. It is worth to mention also that the properties of these materials can be fine-tuned only by changing the α-amino acid.

  5. Evidence of hydrolytic route for anaerobic cyanide degradation.

    PubMed Central

    Fallon, R D

    1992-01-01

    Products observed during anaerobic cyanide transformation are consistent with a hydrolytic pathway (HCN + H2O <--> HCONH2 + H2O <--> HCOOH + NH3). Formate, the most frequently observed product, was generally converted to bicarbonate. Formamide was rapidly hydrolyzed to formate upon exposure to the anaerobic consortium but was not detected as an intermediate of cyanide transformation. PMID:1444430

  6. Sequential injection redox or acid-base titration for determination of ascorbic acid or acetic acid.

    PubMed

    Lenghor, Narong; Jakmunee, Jaroon; Vilen, Michael; Sara, Rolf; Christian, Gary D; Grudpan, Kate

    2002-12-01

    Two sequential injection titration systems with spectrophotometric detection have been developed. The first system for determination of ascorbic acid was based on redox reaction between ascorbic acid and permanganate in an acidic medium and lead to a decrease in color intensity of permanganate, monitored at 525 nm. A linear dependence of peak area obtained with ascorbic acid concentration up to 1200 mg l(-1) was achieved. The relative standard deviation for 11 replicate determinations of 400 mg l(-1) ascorbic acid was 2.9%. The second system, for acetic acid determination, was based on acid-base titration of acetic acid with sodium hydroxide using phenolphthalein as an indicator. The decrease in color intensity of the indicator was proportional to the acid content. A linear calibration graph in the range of 2-8% w v(-1) of acetic acid with a relative standard deviation of 4.8% (5.0% w v(-1) acetic acid, n=11) was obtained. Sample throughputs of 60 h(-1) were achieved for both systems. The systems were successfully applied for the assays of ascorbic acid in vitamin C tablets and acetic acid content in vinegars, respectively.

  7. Electrochemical nanomaterial-based nucleic acid aptasensors.

    PubMed

    Palchetti, Ilaria; Mascini, Marco

    2012-04-01

    Recent progress in the development of electrochemical nanomaterial-aptamer-based biosensors is summarized. Aptamers are nucleic acid ligands that can be generated against amino acids, drugs, proteins, and other molecules. They are isolated from a large random library of synthetic nucleic acids by an iterative process of binding, separation, and amplification, called systematic evolution of ligands by exponential enrichment (SELEX). In this review, different methods of integrating aptamers with different nanomaterials and nanoparticles for electrochemical biosensing application are described.

  8. Base-acid hybrid water electrolysis.

    PubMed

    Chen, Long; Dong, Xiaoli; Wang, Fei; Wang, Yonggang; Xia, Yongyao

    2016-02-21

    A base-acid hybrid electrolytic system with a low onset voltage of 0.78 V for water electrolysis was developed by using a ceramic Li-ion exchange membrane to separate the oxygen-evolving reaction (OER) in a basic electrolyte solution containing the Li-ion and hydrogen-evolving reaction (HER) in an acidic electrolyte solution. PMID:26804323

  9. Effects of lactide monomer on the hydrolytic degradation of poly(lactide-co-glycolide) 85L/15G.

    PubMed

    Paakinaho, K; Heino, H; Väisänen, J; Törmälä, P; Kellomäki, M

    2011-10-01

    The hydrolytic degradation of oriented poly(L-lactide-co-glycolide) 85 L/15 G (PLGA 85/15) sample materials with various amounts of lactide monomer was monitored in vitro at 37 °C. The materials were manufactured from medical grade PLGA 85/15 by a two-step melt extrusion-die drawing process. Results showed that the hydrolytic degradation rate depended highly on the lactide monomer content, which in turn influenced the retention of mechanical properties, mass loss, crystallinity, and dimensional stability. Even small quantities of lactide monomer (0.05-0.20 wt%) affected especially the retention of mechanical properties, which started to decline rapidly upon the inherent viscosity reaching 0.6-0.8 dl/g due to hydrolytic degradation. Based on our hydrolytic degradation data, we constructed a simplified mathematical model of degradation-related strength retention and recommend it as a functional quality control tool for melt-processed biodegradable medical devices manufactured from poly(L-lactide-co-glycolide) 85 L/15 G. PMID:21783137

  10. Jammed acid-base reactions at interfaces.

    PubMed

    Gibbs-Davis, Julianne M; Kruk, Jennifer J; Konek, Christopher T; Scheidt, Karl A; Geiger, Franz M

    2008-11-19

    Using nonlinear optics, we show that acid-base chemistry at aqueous/solid interfaces tracks bulk pH changes at low salt concentrations. In the presence of 10 to 100 mM salt concentrations, however, the interfacial acid-base chemistry remains jammed for hours, until it finally occurs within minutes at a rate that follows the kinetic salt effect. For various alkali halide salts, the delay times increase with increasing anion polarizability and extent of cation hydration and lead to massive hysteresis in interfacial acid-base titrations. The resulting implications for pH cycling in these systems are that interfacial systems can spatially and temporally lag bulk acid-base chemistry when the Debye length approaches 1 nm.

  11. A Direct, Biomass-Based Synthesis of Benzoic Acid: Formic Acid-Mediated Deoxygenation of the Glucose-Derived Materials Quinic Acid and Shikimic Acid

    SciTech Connect

    Arceo, Elena; Ellman, Jonathan; Bergman, Robert

    2010-05-03

    An alternative biomass-based route to benzoic acid from the renewable starting materials quinic acid and shikimic acid is described. Benzoic acid is obtained selectively using a highly efficient, one-step formic acid-mediated deoxygenation method.

  12. Microbial hydrolytic enzyme activities in deep-sea sediments

    NASA Astrophysics Data System (ADS)

    Boetius, A.

    1995-03-01

    The potential hydrolysis rates of five different hydrolytic enzymes were determined in deep-sea sediments from the northeast Atlantic (BIOTRANS area) in March 1992. Fluorogenic substrates were used to assay extracellular α- and β-glucosidase, chitobiase, lipase and aminopeptidase. The potential activity of most of the enzymes investigated decreased to a minimum within the upper two centimetre range, whereas aminopeptidase was high over the upper five centimetre range. Exceptions were found when macrofaunal burrows occurred in the cores, always increasing the activities of some hydrolases, and therefore indicating the impact of bioturbation on degradation rates. The most striking feature of the investigated enzyme spectrum was the 50 2000 times higher specific activity of the aminopeptidase, compared with the other hydrolases. The activity of hydrolytic enzymes most likely reflects the availability of their respective substrates and is not a function of bacterial biomass.

  13. Functional Screening of Hydrolytic Activities Reveals an Extremely Thermostable Cellulase from a Deep-Sea Archaeon

    PubMed Central

    Leis, Benedikt; Heinze, Simon; Angelov, Angel; Pham, Vu Thuy Trang; Thürmer, Andrea; Jebbar, Mohamed; Golyshin, Peter N.; Streit, Wolfgang R.; Daniel, Rolf; Liebl, Wolfgang

    2015-01-01

    Extreme habitats serve as a source of enzymes that are active under extreme conditions and are candidates for industrial applications. In this work, six large-insert mixed genomic libraries were screened for hydrolase activities in a broad temperature range (8–70°C). Among a variety of hydrolytic activities, one fosmid clone, derived from a library of pooled isolates of hyperthermophilic archaea from deep sea vents, displayed hydrolytic activity on carboxymethyl cellulose substrate plates at 70°C but not at lower temperatures. Sequence analysis of the fosmid insert revealed a gene encoding a novel glycoside hydrolase family 12 (GHF12) endo-1,4-β-glucanase, termed Cel12E. The enzyme shares 45% sequence identity with a protein from the archaeon Thermococcus sp. AM4 and displays a unique multidomain architecture. Biochemical characterization of Cel12E revealed a remarkably thermostable protein, which appears to be of archaeal origin. The enzyme displayed maximum activity at 92°C and was active on a variety of linear 1,4-β-glucans like carboxymethyl cellulose, β-glucan, lichenan, and phosphoric acid swollen cellulose. The protein is able to bind to various insoluble β-glucans. Product pattern analysis indicated that Cel12E is an endo-cleaving β-glucanase. Cel12E expands the toolbox of hyperthermostable archaeal cellulases with biotechnological potential. PMID:26191525

  14. Analysis of the extractive and hydrolytic behavior of microthane poly(ester-urethane) foam by high pressure liquid chromatography

    SciTech Connect

    Amin, P.; Wille, J.; Shah, K.; Kydonieus, A. )

    1993-05-01

    Microthane foam, a poly(ester-urethane) (PU) used in the manufacture of Meme/Replicon breast implants, was analyzed by an HPL method to determine whether 2,4- and 2,6-toluenediamine (TDA) were formed under a variety of physiological and nonphysiological extraction and hydrolytic conditions. At the detection limit of 20 ppb, no 2,4- or 2,6-TDA was observed in either methyl tert-butyl ether (MTBE), or aqueous buffer extracts of PU foam. The predominant extractable components identified by HPLC UV-analysis, were a mixture of nonaromatic and aromatic PU fragments. Moreover, no detectable amounts of TDA were found in foam or MTBE extract of foam incubated in phosphate buffer, pH 7.4, at 37 C for 5 days. By contrast, 2,4- and 2,6-TDA were found in foam and foam extracts exposed to low concentrations of either strong mineral acid or base; higher levels were found at higher acidity, treatment temperature, or durations of incubation. Moreover, 2,4- and 2,6-TDA were found in oligomers isolated by preparative HPLC and exposed to alkaline conditions. Finally, 1-2 ppm of 2,4-TDA was detected when PU foam extracts were prepared by the Snyder-Breder method, which employs acidic and alkaline conditions in the work-up procedure. Based on these findings, the authors suggest that published observations of 2,4-TDA formation from in vitro and ex vivo extractions of PU foam are artifacts resulting from pH effects on oligomeric PU fragments present in or extracted from the foam.

  15. [Kidney, Fluid, and Acid-Base Balance].

    PubMed

    Shioji, Naohiro; Hayashi, Masao; Morimatsu, Hiroshi

    2016-05-01

    Kidneys play an important role to maintain human homeostasis. They contribute to maintain body fluid, electrolytes, and acid-base balance. Especially in fluid control, we, physicians can intervene body fluid balance using fluid resuscitation and diuretics. In recent years, one type of fluid resuscitation, hydroxyl ethyl starch has been extensively studied in the field of intensive care. Although their effects on fluid resuscitation are reasonable, serious complications such as kidney injury requiring renal replacement therapy occur frequently. Now we have to pay more attention to this important complication. Another topic of fluid management is tolvaptan, a selective vasopressin-2 receptor antagonist Recent randomized trial suggested that tolvaptan has a similar supportive effect for fluid control and more cost effective compared to carperitide. In recent years, Stewart approach is recognized as one important tool to assess acid-base balance in critically ill patients. This approach has great value, especially to understand metabolic components in acid-base balance. Even for assessing the effects of kidneys on acid-base balance, this approach gives us interesting insight. We should appropriately use this new approach to treat acid-base abnormality in critically ill patients. PMID:27319095

  16. Physicochemical properties and supernucleophilicity of oxime-functionalized surfactants: hydrolytic catalysts toward dephosphorylation of di- and triphosphate esters.

    PubMed

    Singh, Namrata; Karpichev, Yevgen; Gupta, Bhanushree; Satnami, Manmohan L; Marek, Jan; Kuca, Kamil; Ghosh, Kallol K

    2013-04-11

    Aggregation and kinetic studies have been performed to understand the hydrolytic potencies of the series of oxime-functionalized surfactants, viz., 3- hydroxyiminomethyl-1-alkylpyridinium bromide (alkyl = CnH2n+1, n = 10, 12, 14, 16, 18) in the cleavage of phosphate esters, p-nitrophenyl diphenyl phosphate (PNPDPP) and bis(2,4-dinitrophenyl) phosphate (BNDPP), in mixed micelles with cetylpyridinium bromide (CPB). Micellization and surface properties of mixed micelles functional surfactants with CPB were studied by conductivity and surface tension measurements. Acid dissociation constants (pKa) were determined, the effect of functional surfactant alkyl chain length and pH on the observed rate constant (kobs) for phosphate ester cleavage has been discussed, and the effect of substrate on the supernucleophilicities of the studied oximes was monitored. Functionalized oxime-based surfactants were proved to be supernucleophiles to attack on the P═O center of tri- and diphosphate esters. Oximes with hexadecyl alkyl chain length (3-C16) showed maximum micellar effect on the rate constants toward PNPDPP. Micellar effects were analyzed in terms of the pseudophase model.

  17. Hydrolytic ectoenzyme activity associated with suspended and sinking organic particles within the anoxic Cariaco Basin

    NASA Astrophysics Data System (ADS)

    Taylor, Gordon T.; Thunell, Robert; Varela, Ramon; Benitez-Nelson, Claudia; Scranton, Mary I.

    2009-08-01

    Ectohydrolase activities of suspended microbiota were compared to those associated with sinking particles (sed-POM) retrieved from sediment traps deployed in the permanently anoxic Cariaco Basin. In shore-based assays, activities of aminopeptidase, β-glucosidase, chitinase and alkaline phosphatase were measured in samples obtained from oxic and anoxic depths using MUF- and MCA-labeled fluorogenic substrate analogs. Hydrolysis potentials for these enzymes in the seston varied widely over the nine cruises sampled (8 Nov 1996-3 May 2000) and among depths (15-1265 m); from <10 to over 1600 nM d -1 hydrolysate released, generally co-varying with one another and with suspended particulate organic carbon (POC) and particulate nitrogen (PN). Hydrolytic potentials, prokaryotic abundances and POC/PN concentrations in sinking debris were 400-1.3×10 7 times higher than in comparable volumes of seawater. However when normalized to PN, hydrolytic potentials in sediment trap samples were not demonstrably higher than in Niskin bottle samples. We estimate that PN pools in sediment trap samples were turned over 2-1400 times (medians=7-26 x) slower by hydrolysis than were suspended PN pools. Median prokaryotic growth rates (divisions d -1) in sinking debris were also ˜150 times slower than for bacterioplankton. Hydrolytic potentials in surface oxic waters were generally faster than in underlying anoxic waters on a volumetric basis (nM hydrolysate d -1), but were not significantly ( p>0.05) different when normalized to PN or prokaryote abundances. Alkaline phosphatase was consistently the most active ectohydrolase in both sample types, suggesting that Cariaco Basin assemblages were adapted to decomposing phosphate esters in organic polymers. However, phosphorus limitation was not evident from nutrient inventories in the water column. Results support the hypothesis that efficiencies of polymer hydrolysis in anoxic waters are not inherently lower than in oxic waters.

  18. Conversion of lignocellulosic biomass into its molecular components by sequential combination of organic acid and base

    NASA Astrophysics Data System (ADS)

    Noda, Yu

    The primary objective of this research is to explore a new concept of converting lignocellulosic biomass into liquid organic products via hydrolysis by sequentially combining acid and base treatments. The concept was examined by studying two-step hydrolytic reactions of biomass (spruce) using oxialic acid (OA) and tetramethylammonium hydroxide (TMAH) at moderate reaction temperatures below 200 °C. Different selectivity of C-O bond cleavage of hemicellulose, cellulose, and lignin between the reactions with OA and TMAH was demonstrated, and the sequential combination of OA and TMAH treatments exhibited an enhancing effect on conversion of biomass, which proves the promise of the proposed concept. A similar enhancing effect of combination was further confirmed in the reactions with mineral acid and base. Interestingly, characterization of solid residue from reactions of biomass and further investigation of the reactions of commercial cellulose revealed that the A-B sequence (the first reaction with OA and the second with TMAH) enhanced the conversion of cellulose at the second step with TMAH. It was suggested from the NMR and XRD study of solid residues that this enhancement was caused by the reduction of crystallinity of cellulose by the first reaction with OA. This effect was shown to be an interesting feature of A-B treatment sequence for converting lignocellulosic biomass. To improve the yield of monomeric sugars, the effect of adding organic solvents to the system was also studied. No improvement on sugar yield was observed under the explored conditions. However, it was shown that some furans and phenols can be directly formed from the reactions of biomass in the binary solvent system, which may be beneficial for producing more value-added chemicals from biomass.

  19. Polylactic Acid-Based Polymer Blends for Durable Applications

    NASA Astrophysics Data System (ADS)

    Finniss, Adam

    There has been considerable scientific interest in both research and commercial communities as of late in the area of biologically based or sourced plastics. As the consumption of petroleum rises and concerns about climate change increase, this field is likely to grow even larger. One bioplastic that has received a great deal of attention is polylactic acid (PLA). In the past, this material was used mainly in medical or specialty applications, but advancements in manufacturing have led to a desire to use PLA more widely, especially in durable applications. Unfortunately, PLA has several drawbacks that hinder more widespread usage of the material as a durable item: it has low ductility and impact strength in bulk applications, along with poor stability in the face of heat, humidity or liquid media. To combat these deficiencies, a number of techniques were investigated. Samples were annealed to create crystalline domains that would improve mechanical properties and reduce diffusion, blended with graphene to create barriers to diffusion throughout the material, or compounded with a polycarbonate (PC) polymer phase to protect the PLA phase and to enhance the mechanical properties of the blend. If a material containing biologically sourced components with good mechanical properties can be created, it would be desirable for durable uses such as electronics components or as an automotive grade resin. Crystallization experiments were carried out in a differential scanning calorimeter to determine the effects of heat treatment and additives on the rather slow crystallization kinetics of PLA polymer. It was determined that the blending in of the PC phase did not significantly alter the kinetics or mechanism of crystal growth. The addition of graphene to any PC/PLA formulation served as a nucleating agent which speeded up the crystallization kinetics markedly, in some cases by several orders of magnitude. Results obtained from these experiments were internally consistent

  20. Separation of Acids, Bases, and Neutral Compounds

    NASA Astrophysics Data System (ADS)

    Fujita, Megumi; Mah, Helen M.; Sgarbi, Paulo W. M.; Lall, Manjinder S.; Ly, Tai Wei; Browne, Lois M.

    2003-01-01

    Separation of Acids, Bases, and Neutral Compounds requires the following software, which is available for free download from the Internet: Netscape Navigator, version 4.75 or higher, or Microsoft Internet Explorer, version 5.0 or higher; Chime plug-in, version compatible with your OS and browser (available from MDL); and Flash player, version 5 or higher (available from Macromedia).

  1. Jigsaw Cooperative Learning: Acid-Base Theories

    ERIC Educational Resources Information Center

    Tarhan, Leman; Sesen, Burcin Acar

    2012-01-01

    This study focused on investigating the effectiveness of jigsaw cooperative learning instruction on first-year undergraduates' understanding of acid-base theories. Undergraduates' opinions about jigsaw cooperative learning instruction were also investigated. The participants of this study were 38 first-year undergraduates in chemistry education…

  2. The Magic Sign: Acids, Bases, and Indicators.

    ERIC Educational Resources Information Center

    Phillips, Donald B.

    1986-01-01

    Presents an approach that is used to introduce elementary and junior high students to a series of activities that will provide concrete experiences with acids, bases, and indicators. Provides instructions and listings of needed solutions and materials for developing this "magic sign" device. Includes background information and several student…

  3. Student Concept Changes in Acids and Bases.

    ERIC Educational Resources Information Center

    Ye, Renmin; Wells, Raymond R.

    This study focuses on student concept changes in acids and bases. Variables include field dependent level, personal independence level, interest in science or chemistry, teaching strategy, and student gender. This study of Grade 10 students (N=81) provides information relevant to secondary school chemistry learning, teaching, and concept change.…

  4. Drug-induced acid-base disorders.

    PubMed

    Kitterer, Daniel; Schwab, Matthias; Alscher, M Dominik; Braun, Niko; Latus, Joerg

    2015-09-01

    The incidence of acid-base disorders (ABDs) is high, especially in hospitalized patients. ABDs are often indicators for severe systemic disorders. In everyday clinical practice, analysis of ABDs must be performed in a standardized manner. Highly sensitive diagnostic tools to distinguish the various ABDs include the anion gap and the serum osmolar gap. Drug-induced ABDs can be classified into five different categories in terms of their pathophysiology: (1) metabolic acidosis caused by acid overload, which may occur through accumulation of acids by endogenous (e.g., lactic acidosis by biguanides, propofol-related syndrome) or exogenous (e.g., glycol-dependant drugs, such as diazepam or salicylates) mechanisms or by decreased renal acid excretion (e.g., distal renal tubular acidosis by amphotericin B, nonsteroidal anti-inflammatory drugs, vitamin D); (2) base loss: proximal renal tubular acidosis by drugs (e.g., ifosfamide, aminoglycosides, carbonic anhydrase inhibitors, antiretrovirals, oxaliplatin or cisplatin) in the context of Fanconi syndrome; (3) alkalosis resulting from acid and/or chloride loss by renal (e.g., diuretics, penicillins, aminoglycosides) or extrarenal (e.g., laxative drugs) mechanisms; (4) exogenous bicarbonate loads: milk-alkali syndrome, overshoot alkalosis after bicarbonate therapy or citrate administration; and (5) respiratory acidosis or alkalosis resulting from drug-induced depression of the respiratory center or neuromuscular impairment (e.g., anesthetics, sedatives) or hyperventilation (e.g., salicylates, epinephrine, nicotine).

  5. Screening of Marine Actinomycetes from Segara Anakan for Natural Pigment and Hydrolytic Activities

    NASA Astrophysics Data System (ADS)

    Asnani, A.; Ryandini, D.; Suwandri

    2016-02-01

    Marine actinomycetes have become sources of great interest to natural product chemistry due to their new chemical entities and bioactive metabolites. Since April 2010, we have screened actinobacteria from five sites that represent different ecosystems of Segara Anakan lagoon. In this present study we focus on specific isolates, K-2C which covers 1) actinomycetes identification based on morphology observation and 16S rRNA gene; 2) fermentation and isolation of pigment; 3) structure determination of pigment; and 4) hydrolytic enzymes characterization; Methodologies relevant to the studies were implemented accordingly. The results indicated that K-2C was likely Streptomyces fradiae strain RSU15, and the best fermentation medium should contain starch and casein with 21 days of incubation. The isolate has extracellular as well as intracellular pigments. Isolated pigments gave purple color with λmax of 529.00 nm. The pigment was structurally characterized. Interestingly, Streptomyces K-2C was able to produce potential hydrolytic enzymes such as amylase, cellulase, protease, lipase, urease, and nitrate reductase.

  6. Cationic Lipid-Based Nucleic Acid Vectors.

    PubMed

    Jubeli, Emile; Goldring, William P D; Pungente, Michael D

    2016-01-01

    The delivery of nucleic acids into cells remains an important laboratory cell culture technique and potential clinical therapy, based upon the initial cellular uptake, then translation into protein (in the case of DNA), or gene deletion by RNA interference (RNAi). Although viral delivery vectors are more efficient, the high production costs, limited cargo capacity, and the potential for clinical adverse events make nonviral strategies attractive. Cationic lipids are the most widely applied and studied nonviral vectors; however, much remains to be solved to overcome limitations of these systems. Advances in the field of cationic lipid-based nucleic acid (lipoplex) delivery rely upon the development of robust and reproducible lipoplex formulations, together with the use of cell culture assays. This chapter provides detailed protocols towards the formulation, delivery, and assessment of in vitro cationic lipid-based delivery of DNA. PMID:27436310

  7. Polylactic Acid-Based Polymer Blends for Durable Applications

    NASA Astrophysics Data System (ADS)

    Finniss, Adam

    There has been considerable scientific interest in both research and commercial communities as of late in the area of biologically based or sourced plastics. As the consumption of petroleum rises and concerns about climate change increase, this field is likely to grow even larger. One bioplastic that has received a great deal of attention is polylactic acid (PLA). In the past, this material was used mainly in medical or specialty applications, but advancements in manufacturing have led to a desire to use PLA more widely, especially in durable applications. Unfortunately, PLA has several drawbacks that hinder more widespread usage of the material as a durable item: it has low ductility and impact strength in bulk applications, along with poor stability in the face of heat, humidity or liquid media. To combat these deficiencies, a number of techniques were investigated. Samples were annealed to create crystalline domains that would improve mechanical properties and reduce diffusion, blended with graphene to create barriers to diffusion throughout the material, or compounded with a polycarbonate (PC) polymer phase to protect the PLA phase and to enhance the mechanical properties of the blend. If a material containing biologically sourced components with good mechanical properties can be created, it would be desirable for durable uses such as electronics components or as an automotive grade resin. Crystallization experiments were carried out in a differential scanning calorimeter to determine the effects of heat treatment and additives on the rather slow crystallization kinetics of PLA polymer. It was determined that the blending in of the PC phase did not significantly alter the kinetics or mechanism of crystal growth. The addition of graphene to any PC/PLA formulation served as a nucleating agent which speeded up the crystallization kinetics markedly, in some cases by several orders of magnitude. Results obtained from these experiments were internally consistent

  8. Chem I Supplement: Emphasis on Acids and Bases

    ERIC Educational Resources Information Center

    Journal of Chemical Education Staff

    1977-01-01

    Provides supplementary notes on acids and bases suitable for secondary school chemistry instruction, including acidity in solid and natural waters, acidity balance in body chemistry, acid and basic foods, pH values of common fluids, examples of drugs, and commercial preparation of nitric acid. (SL)

  9. Modern quantitative acid-base chemistry.

    PubMed

    Stewart, P A

    1983-12-01

    Quantitative analysis of ionic solutions in terms of physical and chemical principles has been effectively prohibited in the past by the overwhelming amount of calculation it required, but computers have suddenly eliminated that prohibition. The result is an approach to acid-base which revolutionizes our ability to understand, predict, and control what happens to hydrogen ions in living systems. This review outlines that approach and suggests some of its most useful implications. Quantitative understanding requires distinctions between independent variables (in body fluids: pCO2, net strong ion charge, and total weak acid, usually protein), and dependent variables [( HCO-3], [HA], [A-], [CO(2-)3], [OH-], and [H+] (or pH]. Dependent variables are determined by independent variables, and can be calculated from the defining equations for the specific system. Hydrogen ion movements between solutions can not affect hydrogen ion concentration; only changes in independent variables can. Many current models for ion movements through membranes will require modification on the basis of this quantitative analysis. Whole body acid-base balance can be understood quantitatively in terms of the three independent variables and their physiological regulation by the lungs, kidneys, gut, and liver. Quantitative analysis also shows that body fluids interact mainly by strong ion movements through the membranes separating them.

  10. A General Simulator for Acid-Base Titrations

    NASA Astrophysics Data System (ADS)

    de Levie, Robert

    1999-07-01

    General formal expressions are provided to facilitate the automatic computer calculation of acid-base titration curves of arbitrary mixtures of acids, bases, and salts, without and with activity corrections based on the Davies equation. Explicit relations are also given for the buffer strength of mixtures of acids, bases, and salts.

  11. [Study of the hydrolytic degradation of a biodegradable copolymer].

    PubMed

    Sabino, Marco A; Morales, Dayanara; Ronca, Gladys; Feijoo, José Luis

    2003-01-01

    The hydrolytic degradation of bioabsorbable Poliglactin 910 was studied in a phosphate buffer solution, pH = 7.4, at 37 degrees C. The degradation was evaluated by analyzing the changes in weight loss, pH, DSC, mechanical properties and morphological changes. After 10 weeks, the weight loss and pH changes suggested diffusion of low molecular weight chain segments into the reaction medium as a consequence of the breaking of ester bonds in the material. Breaking stress and Young Modulus decrease, indicating that chain scission proceeded in two steps: the first occurring in the amorphous regions within the intermicrofibrillar space; the second in the crystalline regions. Surface morphological changes suggest a heterogeneous degradation mechanism by layers.

  12. Hydrolytic weakening and penetrative deformation within a natural shear zone

    NASA Astrophysics Data System (ADS)

    Kronenberg, Andreas K.; Segall, Paul; Wolf, George H.

    Processes of fluid infiltration, hydrolytic weakening, and penetrative deformation within a small ductile shear zone within granitic rocks of the central Sierra Nevada have been investigated using integrated field observations, strain analysis, infrared spectroscopy, and transmission electron microscopy. Several lines of evidence suggest that tensile fracturing accompanied by fluid infiltration preceded the ductile shearing event and that shear strains have localized on a pre-existing sealed fracture. Finite shear strains within an aplite dike and granodiorite host increase sharply from nominally O outside the shear zone to values of 10±2 near its center. Water contents of quartz grains exhibit similar spatial trends to that of strain, rising from 60 and 2000 ppm within the undeformed aplite and granodiorite, respectively, to 4000 and 11,000 ppm within their highly sheared equivalents. Infrared signatures of absorptions measured at room temperature and at 77 K show that most of the intragranular water within quartz and feldspar resides in fluid inclusions. Two distinct populations of fluid inclusions have been observed by optical and electron microscopy; one decorating healed microcracks and the second decorating dislocations. We interpret these relations to record interactions between fluids and processes of brittle failure and ductile flow. Fluid inclusions, forming planar arrays along the traces of healed microcracks, are relatively large (˜0.4-3 μm in diameter) and irregular in shape. A second set of fluid inclusions consists of extremely fine (20-140 nm in diameter), more nearly spherical inclusions which consistently lie along free dislocations and dislocation nodes, and exhibit relationships with dislocations similar to those observed in hydrolytically-weakened synthetic quartz. These observations suggest that water-related defects gained access to grain interiors and dislocation cores by fluid infiltration along open microcracks followed by pipe

  13. An Introductory Laboratory Exercise for Acids and Bases.

    ERIC Educational Resources Information Center

    Miller, Richard; Silberman, Robert

    1986-01-01

    Discusses an acid-base neutralization exercise requiring groups of students to determine: (1) combinations of solutions giving neutralization; (2) grouping solutions as acids or bases; and (3) ranking groups in order of concentration. (JM)

  14. The Bronsted-Lowery Acid-Base Concept.

    ERIC Educational Resources Information Center

    Kauffman, George B.

    1988-01-01

    Gives the background history of the simultaneous discovery of acid-base relationships by Johannes Bronsted and Thomas Lowry. Provides a brief biographical sketch of each. Discusses their concept of acids and bases in some detail. (CW)

  15. Coronavirus phylogeny based on triplets of nucleic acids bases

    NASA Astrophysics Data System (ADS)

    Liao, Bo; Liu, Yanshu; Li, Renfa; Zhu, Wen

    2006-04-01

    We considered the fully overlapping triplets of nucleotide bases and proposed a 2D graphical representation of protein sequences consisting of 20 amino acids and a stop code. Based on this 2D graphical representation, we outlined a new approach to analyze the phylogenetic relationships of coronaviruses by constructing a covariance matrix. The evolutionary distances are obtained through measuring the differences among the two-dimensional curves.

  16. Mathematical modeling of acid-base physiology

    PubMed Central

    Occhipinti, Rossana; Boron, Walter F.

    2015-01-01

    pH is one of the most important parameters in life, influencing virtually every biological process at the cellular, tissue, and whole-body level. Thus, for cells, it is critical to regulate intracellular pH (pHi) and, for multicellular organisms, to regulate extracellular pH (pHo). pHi regulation depends on the opposing actions of plasma-membrane transporters that tend to increase pHi, and others that tend to decrease pHi. In addition, passive fluxes of uncharged species (e.g., CO2, NH3) and charged species (e.g., HCO3− , NH4+) perturb pHi. These movements not only influence one another, but also perturb the equilibria of a multitude of intracellular and extracellular buffers. Thus, even at the level of a single cell, perturbations in acid-base reactions, diffusion, and transport are so complex that it is impossible to understand them without a quantitative model. Here we summarize some mathematical models developed to shed light onto the complex interconnected events triggered by acids-base movements. We then describe a mathematical model of a spherical cell–which to our knowledge is the first one capable of handling a multitude of buffer reaction–that our team has recently developed to simulate changes in pHi and pHo caused by movements of acid-base equivalents across the plasma membrane of a Xenopus oocyte. Finally, we extend our work to a consideration of the effects of simultaneous CO2 and HCO3− influx into a cell, and envision how future models might extend to other cell types (e.g., erythrocytes) or tissues (e.g., renal proximal-tubule epithelium) important for whole-body pH homeostasis. PMID:25617697

  17. Mathematical modeling of acid-base physiology.

    PubMed

    Occhipinti, Rossana; Boron, Walter F

    2015-01-01

    pH is one of the most important parameters in life, influencing virtually every biological process at the cellular, tissue, and whole-body level. Thus, for cells, it is critical to regulate intracellular pH (pHi) and, for multicellular organisms, to regulate extracellular pH (pHo). pHi regulation depends on the opposing actions of plasma-membrane transporters that tend to increase pHi, and others that tend to decrease pHi. In addition, passive fluxes of uncharged species (e.g., CO2, NH3) and charged species (e.g., HCO3(-), [Formula: see text] ) perturb pHi. These movements not only influence one another, but also perturb the equilibria of a multitude of intracellular and extracellular buffers. Thus, even at the level of a single cell, perturbations in acid-base reactions, diffusion, and transport are so complex that it is impossible to understand them without a quantitative model. Here we summarize some mathematical models developed to shed light onto the complex interconnected events triggered by acids-base movements. We then describe a mathematical model of a spherical cells-which to our knowledge is the first one capable of handling a multitude of buffer reactions-that our team has recently developed to simulate changes in pHi and pHo caused by movements of acid-base equivalents across the plasma membrane of a Xenopus oocyte. Finally, we extend our work to a consideration of the effects of simultaneous CO2 and HCO3(-) influx into a cell, and envision how future models might extend to other cell types (e.g., erythrocytes) or tissues (e.g., renal proximal-tubule epithelium) important for whole-body pH homeostasis.

  18. Bipolar Membranes for Acid Base Flow Batteries

    NASA Astrophysics Data System (ADS)

    Anthamatten, Mitchell; Roddecha, Supacharee; Jorne, Jacob; Coughlan, Anna

    2011-03-01

    Rechargeable batteries can provide grid-scale electricity storage to match power generation with consumption and promote renewable energy sources. Flow batteries offer modular and flexible design, low cost per kWh and high efficiencies. A novel flow battery concept will be presented based on acid-base neutralization where protons (H+) and hydroxyl (OH-) ions react electrochemically to produce water. The large free energy of this highly reversible reaction can be stored chemically, and, upon discharge, can be harvested as usable electricity. The acid-base flow battery concept avoids the use of a sluggish oxygen electrode and utilizes the highly reversible hydrogen electrode, thus eliminating the need for expensive noble metal catalysts. The proposed flow battery is a hybrid of a battery and a fuel cell---hydrogen gas storing chemical energy is produced at one electrode and is immediately consumed at the other electrode. The two electrodes are exposed to low and high pH solutions, and these solutions are separated by a hybrid membrane containing a hybrid cation and anion exchange membrane (CEM/AEM). Membrane design will be discussed, along with ion-transport data for synthesized membranes.

  19. Endophytic filamentous fungi from a Catharanthus roseus: Identification and its hydrolytic enzymes.

    PubMed

    Ayob, Farah Wahida; Simarani, Khanom

    2016-05-01

    This paper reported on the various filamentous fungi strains that were isolated from a wild grown Catharanthus roseus. Based on the morphological characteristics and molecular technique through a Polymerase Chain Reaction and DNA sequencing method using internal transcribed spacer (ITS), these fungi had been identified as a Colletotrichum sp., Macrophomina phaseolina, Nigrospora sphaerica and Fusarium solani. The ultrastructures of spores and hyphae were observed under a Scanning Electron Microscope. The hydrolytic enzyme test showed that all strains were positive in secreting cellulase. Colletotrichum sp. and F. solani strains also gave a positive result for amylase while only F. solani was capable to secrete protease. These fungi were putatively classified as endophytic fungi since they produced extracellular enzymes that allow them to penetrate plant cell walls and colonize with symbiotic properties.

  20. Using quantitative acid-base analysis in the ICU.

    PubMed

    Lloyd, P; Freebairn, R

    2006-03-01

    The quantitative acid-base 'Strong Ion' calculator is a practical application of quantitative acid-base chemistry, as developed by Peter Stewart and Peter Constable. It quantifies the three independent factors that control acidity, calculates the concentration and charge of unmeasured ions, produces a report based on these calculations and displays a Gamblegram depicting measured ionic species. Used together with the medical history, quantitative acid-base analysis has advantages over traditional approaches.

  1. Teaching Acid/Base Physiology in the Laboratory

    ERIC Educational Resources Information Center

    Friis, Ulla G.; Plovsing, Ronni; Hansen, Klaus; Laursen, Bent G.; Wallstedt, Birgitta

    2010-01-01

    Acid/base homeostasis is one of the most difficult subdisciplines of physiology for medical students to master. A different approach, where theory and practice are linked, might help students develop a deeper understanding of acid/base homeostasis. We therefore set out to develop a laboratory exercise in acid/base physiology that would provide…

  2. Using Willie's Acid-Base Box for Blood Gas Analysis

    ERIC Educational Resources Information Center

    Dietz, John R.

    2011-01-01

    In this article, the author describes a method developed by Dr. William T. Lipscomb for teaching blood gas analysis of acid-base status and provides three examples using Willie's acid-base box. Willie's acid-base box is constructed using three of the parameters of standard arterial blood gas analysis: (1) pH; (2) bicarbonate; and (3) CO[subscript…

  3. [Progress in biotransformation of bio-based lactic acid ].

    PubMed

    Gao, Chao; Ma, Cuiqing; Xu, Ping

    2013-10-01

    Fermentative production of lactic acid, an important bio-based chemicals, has made considerable progress. In addition to the food industry and production of polylactic acid, lactic acid also can be used as an important platform chemical for the production of acrylic acid, pyruvic acid, 1,2-propanediol, and lactic acid esters. This article summarizes the recent progress in biocatalytic production of lactic acid derivatives by dehydration, dehydrogenation, reduction, and esterification. Trends in the biotransformation of lactic acid are also discussed. PMID:24432656

  4. Identifying a base in a nucleic acid

    DOEpatents

    Fodor, Stephen P. A.; Lipshutz, Robert J.; Huang, Xiaohua

    2005-02-08

    Devices and techniques for hybridization of nucleic acids and for determining the sequence of nucleic acids. Arrays of nucleic acids are formed by techniques, preferably high resolution, light-directed techniques. Positions of hybridization of a target nucleic acid are determined by, e.g., epifluorescence microscopy. Devices and techniques are proposed to determine the sequence of a target nucleic acid more efficiently and more quickly through such synthesis and detection techniques.

  5. Industrially important hydrolytic enzyme diversity explored in stove ash bacterial isolates.

    PubMed

    Kiran, Tabbassum; Asad, Wajeeha; Siddiqui, Shahla; Ajaz, Munazza; Rasool, Sheikh Ajaz

    2015-11-01

    Extreme environments merit special attention and significance because of the possible existence of thermophilic microorganisms in such ecological niches. Keeping this in mind indigenous stove ash samples were explored for extremophilic bacteria in term of their biodiversity. Accordingly, this study reports 37 bacterial isolates from the local wood run oven (Tandoor) ash samples. All the isolated strains belong to genus Bacillus on the bases of morpho-cultural and biochemical considerations. The average temperature tolerance profile was >45°C thereby, indicating towards the thermophilic nature of the isolated strains. The Bacillus isolates were screened for 10 different hydrolytic enzymes (cellulase, xylanase, amylase, pectinase, caseinase, keratinase, lipase, esterase, dextranase and β-galactosidase) by plate screening method using the medium incorporated with specific substrate(s). It was found that keratinase was produced by all the isolates while, 36 (97.2%) isolates showed caseinase and esterase production. Amylase was produced by 35(94.6%) isolates and 34 (91.8%) isolates were able to degrade Tween-80 and xylan as substrate for lipase and xylanase respectively. The enzyme, β-galactosidase was produced by 31 (89.1%) of the isolates. Cellulase and dextranase were produced by 26 (70.2%) and 22 (59.4%) isolates respectively. None of the isolates could (under the existing conditions) produce pectin-hydrolyzing enzyme. According to the Tukey's post hoc test, significant difference was found between the mean enzyme index of all the (screened) enzymes. Thus, the isolated bacterial strains with diverse hydrolytic potential may be of great value and relevance for the existing (national) industrial setups.

  6. Hydrolytic and oxidative degradation of electrospun supramolecular biomaterials: In vitro degradation pathways.

    PubMed

    Brugmans, M C P; Sӧntjens, S H M; Cox, M A J; Nandakumar, A; Bosman, A W; Mes, T; Janssen, H M; Bouten, C V C; Baaijens, F P T; Driessen-Mol, A

    2015-11-01

    The emerging field of in situ tissue engineering (TE) of load bearing tissues places high demands on the implanted scaffolds, as these scaffolds should provide mechanical stability immediately upon implantation. The new class of synthetic supramolecular biomaterial polymers, which contain non-covalent interactions between the polymer chains, thereby forming complex 3D structures by self assembly. Here, we have aimed to map the degradation characteristics of promising (supramolecular) materials, by using a combination of in vitro tests. The selected biomaterials were all polycaprolactones (PCLs), either conventional and unmodified PCL, or PCL with supramolecular hydrogen bonding moieties (either 2-ureido-[1H]-pyrimidin-4-one or bis-urea units) incorporated into the backbone. As these materials are elastomeric, they are suitable candidates for cardiovascular TE applications. Electrospun scaffold strips of these materials were incubated with solutions containing enzymes that catalyze hydrolysis, or solutions containing oxidative species. At several time points, chemical, morphological, and mechanical properties were investigated. It was demonstrated that conventional and supramolecular PCL-based polymers respond differently to enzyme-accelerated hydrolytic or oxidative degradation, depending on the morphological and chemical composition of the material. Conventional PCL is more prone to hydrolytic enzymatic degradation as compared to the investigated supramolecular materials, while, in contrast, the latter materials are more susceptible to oxidative degradation. Given the observed degradation pathways of the examined materials, we are able to tailor degradation characteristics by combining selected PCL backbones with additional supramolecular moieties. The presented combination of in vitro test methods can be employed to screen, limit, and select biomaterials for pre-clinical in vivo studies targeted to different clinical applications. PMID:26316031

  7. Industrially important hydrolytic enzyme diversity explored in stove ash bacterial isolates.

    PubMed

    Kiran, Tabbassum; Asad, Wajeeha; Siddiqui, Shahla; Ajaz, Munazza; Rasool, Sheikh Ajaz

    2015-11-01

    Extreme environments merit special attention and significance because of the possible existence of thermophilic microorganisms in such ecological niches. Keeping this in mind indigenous stove ash samples were explored for extremophilic bacteria in term of their biodiversity. Accordingly, this study reports 37 bacterial isolates from the local wood run oven (Tandoor) ash samples. All the isolated strains belong to genus Bacillus on the bases of morpho-cultural and biochemical considerations. The average temperature tolerance profile was >45°C thereby, indicating towards the thermophilic nature of the isolated strains. The Bacillus isolates were screened for 10 different hydrolytic enzymes (cellulase, xylanase, amylase, pectinase, caseinase, keratinase, lipase, esterase, dextranase and β-galactosidase) by plate screening method using the medium incorporated with specific substrate(s). It was found that keratinase was produced by all the isolates while, 36 (97.2%) isolates showed caseinase and esterase production. Amylase was produced by 35(94.6%) isolates and 34 (91.8%) isolates were able to degrade Tween-80 and xylan as substrate for lipase and xylanase respectively. The enzyme, β-galactosidase was produced by 31 (89.1%) of the isolates. Cellulase and dextranase were produced by 26 (70.2%) and 22 (59.4%) isolates respectively. None of the isolates could (under the existing conditions) produce pectin-hydrolyzing enzyme. According to the Tukey's post hoc test, significant difference was found between the mean enzyme index of all the (screened) enzymes. Thus, the isolated bacterial strains with diverse hydrolytic potential may be of great value and relevance for the existing (national) industrial setups. PMID:26639497

  8. Hydrolytic and oxidative degradation of electrospun supramolecular biomaterials: In vitro degradation pathways.

    PubMed

    Brugmans, M C P; Sӧntjens, S H M; Cox, M A J; Nandakumar, A; Bosman, A W; Mes, T; Janssen, H M; Bouten, C V C; Baaijens, F P T; Driessen-Mol, A

    2015-11-01

    The emerging field of in situ tissue engineering (TE) of load bearing tissues places high demands on the implanted scaffolds, as these scaffolds should provide mechanical stability immediately upon implantation. The new class of synthetic supramolecular biomaterial polymers, which contain non-covalent interactions between the polymer chains, thereby forming complex 3D structures by self assembly. Here, we have aimed to map the degradation characteristics of promising (supramolecular) materials, by using a combination of in vitro tests. The selected biomaterials were all polycaprolactones (PCLs), either conventional and unmodified PCL, or PCL with supramolecular hydrogen bonding moieties (either 2-ureido-[1H]-pyrimidin-4-one or bis-urea units) incorporated into the backbone. As these materials are elastomeric, they are suitable candidates for cardiovascular TE applications. Electrospun scaffold strips of these materials were incubated with solutions containing enzymes that catalyze hydrolysis, or solutions containing oxidative species. At several time points, chemical, morphological, and mechanical properties were investigated. It was demonstrated that conventional and supramolecular PCL-based polymers respond differently to enzyme-accelerated hydrolytic or oxidative degradation, depending on the morphological and chemical composition of the material. Conventional PCL is more prone to hydrolytic enzymatic degradation as compared to the investigated supramolecular materials, while, in contrast, the latter materials are more susceptible to oxidative degradation. Given the observed degradation pathways of the examined materials, we are able to tailor degradation characteristics by combining selected PCL backbones with additional supramolecular moieties. The presented combination of in vitro test methods can be employed to screen, limit, and select biomaterials for pre-clinical in vivo studies targeted to different clinical applications.

  9. Differences in hydrolytic abilities of two crude lipases from Geotrichum candidum 4013.

    PubMed

    Brabcová, Jana; Zarevúcka, Marie; Macková, Martina

    2010-12-01

    The fungus Geotrichum candidum 4013 produces two types of lipases (extracellular and cell-bound). Both enzymes were tested for their hydrolytic ability to p-nitrophenyl esters and compounds having a structure similar to the original substrate (triacylglycerols). Higher lipolytic activity of extracellular lipase was observed when triacylglycerols of medium- (C12) and long- (C18) chain fatty acids were used as substrates. Cell-bound lipase preferentially hydrolysed trimyristate (C14). The differences in the abilities of these two enzymes to hydrolyse p-nitrophenyl esters were observed as well. The order of extracellular lipase hydrolysis relation velocity was as follows: p-nitrophenyl decanoate > p-nitrophenyl caprylate > p-nitrophenyl laurate > p-nitrophenyl palmitate > p-nitrophenyl stearate. The cell-bound lipase indicates preference for p-nitrophenyl palmitate. The most striking differences in the ratios between the activity of both lipases (extracellular : cell-bound) towards different fatty acid methyl esters were 2.2 towards methyl hexanoate and 0.46 towards methyl stearate (C18). The Michaelis constant (K(m) ) and maximum reaction rate (V(max) ) for p-nitrophenyl palmitate hydrolysis of cell-bound lipase were significantly higher (K(m) 2.462 mM and V(max) 0.210 U/g/min) than those of extracellular lipase (K(m) 0.406 mM and V(max) 0.006 U/g/min).

  10. Facial recognition of heroin vaccine opiates: type 1 cross-reactivities of antibodies induced by hydrolytically stable haptenic surrogates of heroin, 6-acetylmorphine, and morphine.

    PubMed

    Matyas, Gary R; Rice, Kenner C; Cheng, Kejun; Li, Fuying; Antoline, Joshua F G; Iyer, Malliga R; Jacobson, Arthur E; Mayorov, Alexander V; Beck, Zoltan; Torres, Oscar B; Alving, Carl R

    2014-03-14

    Novel synthetic compounds similar to heroin and its major active metabolites, 6-acetylmorphine and morphine, were examined as potential surrogate haptens for the ability to interface with the immune system for a heroin vaccine. Recent studies have suggested that heroin-like haptens must degrade hydrolytically to induce independent immune responses both to heroin and to the metabolites, resulting in antisera containing mixtures of antibodies (type 2 cross-reactivity). To test this concept, two unique hydrolytically stable haptens were created based on presumed structural facial similarities to heroin or to its active metabolites. After conjugation of a heroin-like hapten (DiAmHap) to tetanus toxoid and mixing with liposomes containing monophosphoryl lipid A, high titers of antibodies after two injections in mice had complementary binding sites that exhibited strong type 1 ("true") specific cross-reactivity with heroin and with both of its physiologically active metabolites. Mice immunized with each surrogate hapten exhibited reduced antinociceptive effects caused by injection of heroin. This approach obviates the need to create hydrolytically unstable synthetic heroin-like compounds to induce independent immune responses to heroin and its active metabolites for vaccine development. Facial recognition of hydrolytically stable surrogate haptens by antibodies together with type 1 cross-reactivities with heroin and its metabolites can help to guide synthetic chemical strategies for efficient development of a heroin vaccine.

  11. The phosphate of pyridoxal-5'-phosphate is an acid/base catalyst in the mechanism of Pseudomonas fluorescens kynureninase.

    PubMed

    Phillips, Robert S; Scott, Israel; Paulose, Riya; Patel, Akshay; Barron, Taylor Colt

    2014-02-01

    Kynureninase (L-kynurenine hydrolase, EC 3.7.1.3) catalyzes the hydrolytic cleavage of L-kynurenine to L-alanine and anthranilic acid. The proposed mechanism of the retro-Claisen reaction requires extensive acid/base catalysis. Previous crystal structures showed that Tyr226 in the Pseudomonas fluorescens enzyme (Tyr275 in the human enzyme) hydrogen bonds to the phosphate of the pyridoxal-5'-phosphate (PLP) cofactor. This Tyr residue is strictly conserved in all sequences of kynureninase. The human enzyme complexed with a competitive inhibitor, 3-hydroxyhippuric acid, showed that the ligand carbonyl O is located 3.7 Å from the phenol of Tyr275 (Lima, S., Kumar, S., Gawandi, V., Momany, C. & Phillips, R. S. (2009) J. Med. Chem. 52, 389-396). We prepared a Y226F mutant of P. fluorescens kynureninase to probe the role of this residue in catalysis. The Y226F mutant has approximately 3000-fold lower activity than wild-type, and does not show the pKa values of 6.8 on kcat and 6.5 and 8.8 on k(cat)/K(m) seen for the wild-type enzyme (Koushik, S. V., Moore, J. A. III, Sundararaju, B. & Phillips, R. S. (1998) Biochemistry 37, 1376-1382). Wild-type kynureninase shows a resonance at 4.5 ppm in (31)P-NMR, which is shifted to 5.0, 3.3 and 2.0 ppm when the potent inhibitor 5-bromodihydrokynurenine is added. However, Y226F kynureninase shows resonances at 3.6 and 2.5 ppm, and no change in the peak position is seen when 5-bromodihydrokynurenine is added. Taken together, these results suggest that Tyr226 mediates proton transfer between the substrate and the phosphate, which accelerates formation of external aldimine and gem-diol intermediates. Thus, the phosphate of PLP acts as an acid/base catalyst in the mechanism of kynureninase.

  12. Impact of the diet on net endogenous acid production and acid-base balance.

    PubMed

    Poupin, Nathalie; Calvez, Juliane; Lassale, Camille; Chesneau, Caroline; Tomé, Daniel

    2012-06-01

    Net acid production, which is composed of volatile acids (15,000 mEq/day) and metabolic acids (70-100 mEq/day) is relatively small compared to whole-body H⁺ turnover (150,000 mEq/day). Metabolic acids are ingested from the diet or produced as intermediary or end products of endogenous metabolism. The three commonly reported sources of net acid production are the metabolism of sulphur amino acids, the metabolism or ingestion of organic acids, and the metabolism of phosphate esters or dietary phosphoproteins. Net base production occurs mainly as a result of absorption of organic anions from the diet. To maintain acid-base balance, ingested and endogenously produced acids are neutralized within the body by buffer systems or eliminated from the body through the respiratory (excretion of volatile acid in the form of CO₂) and urinary (excretion of fixed acids and remaining H⁺) pathways. Because of the many reactions involved in the acid-base balance, the direct determination of acid production is complex and is usually estimated through direct or indirect measurements of acid excretion. However, indirect approaches, which assess the acid-forming potential of the ingested diet based on its composition, do not take all the acid-producing reactions into account. Direct measurements therefore seem more reliable. Nevertheless, acid excretion does not truly provide information on the way acidity is dealt with in the plasma and this measurement should be interpreted with caution when assessing acid-base imbalance.

  13. Polymer gel dosimeter based on itaconic acid.

    PubMed

    Mattea, Facundo; Chacón, David; Vedelago, José; Valente, Mauro; Strumia, Miriam C

    2015-11-01

    A new polymeric dosimeter based on itaconic acid and N, N'-methylenebisacrylamide was studied. The preparation method, compositions of monomer and crosslinking agent and the presence of oxygen in the dosimetric system were analyzed. The resulting materials were irradiated with an X-ray tube at 158cGy/min, 226cGymin and 298cGy/min with doses up to 1000Gy. The dosimeters presented a linear response in the dose range 75-1000Gy, sensitivities of 0.037 1/Gyat 298cGy/min and an increase in the sensitivity with lower dose rates. One of the most relevant outcomes in this study was obtaining different monomer to crosslinker inclusion in the formed gel for the dosimeters where oxygen was purged during the preparation method. This effect has not been reported in other typical dosimeters and could be attributed to the large differences in the reactivity among these species.

  14. Enhanced hydrolytic stability of dental composites by use of fluoroalkyltrimethoxysilanes.

    PubMed

    Nihei, T; Kurata, S; Kondo, Y; Umemoto, K; Yoshino, N; Teranaka, T

    2002-07-01

    The hydrolytic stability of a group of experimental composite materials was evaluated. Seven distinct composites were formed by the mixing of a resin monomer mixture with silica filler that had been pre-treated with one of 7 different ethanol solutions. In one case, the filler was treated with an ethanol solution that contained only 3-methacryloyloxypropyltrimethoxysilane. In 5 cases, it was treated with solution containing a mixture of 3-methacryloyloxypropyltrimethoxysilane and one of the following hydrophobic fluoroalkyltrimethoxysilanes: trifluoropropyl-, nonafluorohexyl-, tridecafluorooctyl-, heptadecafluorodecyl-, and henicosafluorododecyl-trimethoxysilane. The tensile strength, after being immersed in water for 1800 days, of 2 of the experimental composites, whose pre-treatment regimen had included a fluoroalkyltrimethoxysilane, was significantly higher than that of the composite whose pre-treatment regimen had not included a fluoroalkyltrimethoxysilane. Moreover, there was no significant difference between the tensile strength of fresh samples of these 2 composites and the tensile strength of identically produced samples that had remained under water for 1800 days or that had been subjected to 30,000 cycles of thermal stress.

  15. Hydrolytic catalysis and structural stabilization in a designed metalloprotein.

    PubMed

    Zastrow, Melissa L; Peacock, Anna F A; Stuckey, Jeanne A; Pecoraro, Vincent L

    2011-11-27

    Metal ions are an important part of many natural proteins, providing structural, catalytic and electron transfer functions. Reproducing these functions in a designed protein is the ultimate challenge to our understanding of them. Here, we present an artificial metallohydrolase, which has been shown by X-ray crystallography to contain two different metal ions-a Zn(II) ion, which is important for catalytic activity, and a Hg(II) ion, which provides structural stability. This metallohydrolase displays catalytic activity that compares well with several characteristic reactions of natural enzymes. It catalyses p-nitrophenyl acetate (pNPA) hydrolysis with an efficiency only ~100-fold less than that of human carbonic anhydrase (CA)II and at least 550-fold better than comparable synthetic complexes. Similarly, CO(2) hydration occurs with an efficiency within ~500-fold of CAII. Although histidine residues in the absence of Zn(II) exhibit pNPA hydrolysis, miniscule apopeptide activity is observed for CO(2) hydration. The kinetic and structural analysis of this first de novo designed hydrolytic metalloenzyme reveals necessary design features for future metalloenzymes containing one or more metals.

  16. Hydrolytic catalysis and structural stabilization in a designed metalloprotein

    NASA Astrophysics Data System (ADS)

    Zastrow, Melissa L.; Peacock, Anna F. A.; Stuckey, Jeanne A.; Pecoraro, Vincent L.

    2012-02-01

    Metal ions are an important part of many natural proteins, providing structural, catalytic and electron transfer functions. Reproducing these functions in a designed protein is the ultimate challenge to our understanding of them. Here, we present an artificial metallohydrolase, which has been shown by X-ray crystallography to contain two different metal ions—a Zn(II) ion, which is important for catalytic activity, and a Hg(II) ion, which provides structural stability. This metallohydrolase displays catalytic activity that compares well with several characteristic reactions of natural enzymes. It catalyses p-nitrophenyl acetate (pNPA) hydrolysis with an efficiency only ~100-fold less than that of human carbonic anhydrase (CA)II and at least 550-fold better than comparable synthetic complexes. Similarly, CO2 hydration occurs with an efficiency within ~500-fold of CAII. Although histidine residues in the absence of Zn(II) exhibit pNPA hydrolysis, miniscule apopeptide activity is observed for CO2 hydration. The kinetic and structural analysis of this first de novo designed hydrolytic metalloenzyme reveals necessary design features for future metalloenzymes containing one or more metals.

  17. Structure, molecular evolution, and hydrolytic specificities of largemouth bass pepsins.

    PubMed

    Miura, Yoko; Suzuki-Matsubara, Mieko; Kageyama, Takashi; Moriyama, Akihiko

    2016-02-01

    The nucleotide sequences of largemouth bass pepsinogens (PG1, 2 and 3) were determined after molecular cloning of the respective cDNAs. Encoded PG1, 2 and 3 were classified as fish pepsinogens A1, A2 and C, respectively. Molecular evolutionary analyses show that vertebrate pepsinogens are classified into seven monophyletic groups, i.e. pepsinogens A, F, Y (prochymosins), C, B, and fish pepsinogens A and C. Regarding the primary structures, extensive deletion was obvious in S'1 loop residues in fish pepsin A as well as tetrapod pepsin Y. This deletion resulted in a decrease in hydrophobic residues in the S'1 site. Hydrolytic specificities of bass pepsins A1 and A2 were investigated with a pepsin substrate and its variants. Bass pepsins preferred both hydrophobic/aromatic residues and charged residues at the P'1 sites of substrates, showing the dual character of S'1 sites. Thermodynamic analyses of bass pepsin A2 showed that its activation Gibbs energy change (∆G(‡)) was lower than that of porcine pepsin A. Several sites of bass pepsin A2 moiety were found to be under positive selection, and most of them are located on the surface of the molecule, where they are involved in conformational flexibility. The broad S'1 specificity and flexible structure of bass pepsin A2 are thought to cause its high proteolytic activity. PMID:26627128

  18. Hydrolytic degradation and morphologic study of poly-p-dioxanone.

    PubMed

    Lin, H L; Chu, C C; Grubb, D

    1993-02-01

    The in vitro hydrolytic degradation of 2-0 size PDS monofilament suture was studied for the purpose of revealing its morphologic structure and degradation mechanism. The sutures were immersed in phosphate buffer of pH 7.44 for up to 120 days at 37 degrees C. These hydrolyzed sutures were examined by the changes in tensile properties, weight, thermal properties, x-ray diffraction structure, surface morphology, and dye diffusion phenomena. It was found that hydrolysis had significant effects on the change of PDS fiber morphology and properties. Hydrolysis, however, had no significant effect on overall molecular orientation of the fiber until the very late stage. PDS suture fibers retained their skeleton throughout the earlier periods of hydrolysis concurrent with mass and tensile strength losses. PDS sutures exhibited an absorption delay of 120 days. Both heat of fusion and melting point exhibited a maximum function of hydrolysis time. Hydrolysis of PDS suture fibers proceeded through two stages: random scission of chain segments located in the amorphous regions of microfibrils and intermicrofibrillar space, followed by stepwise scission of chain segments located in the crystalline regions of microfibrils. Dye diffusion data showed that the passage along the longitudinal direction of the fiber was relatively easier than the lateral direction as evident in the diffusion coefficient, activation energy, and flexibility of chain segments. Swiss-cheese model of fiber structure appears to describe the observed dye diffusion phenomena and their dependence on hydrolysis time and dying temperature. PMID:8436572

  19. SAMHD1, the Aicardi-Goutières syndrome gene and retroviral restriction factor, is a phosphorolytic ribonuclease rather than a hydrolytic ribonuclease.

    PubMed

    Ryoo, Jeongmin; Hwang, Sung-Yeon; Choi, Jongsu; Oh, Changhoon; Ahn, Kwangseog

    2016-09-01

    SAMHD1 plays diverse roles in innate immunity, autoimmune diseases and HIV restriction, but the mechanisms involved are still unclear. SAMHD1 has been reported to have both dNTPase and RNase activities. However, whether SAMHD1 possesses RNase activity remains highly controversial. Here, we found that, unlike conventional hydrolytic exoribonucleases, SAMHD1 requires inorganic phosphate to degrade RNA substrates and produces nucleotide diphosphates rather than nucleoside monophosphates, which indicated that SAMHD1 is a phosphorolytic but not hydrolytic 3'-5' exoribonuclease. Furthermore, SAMHD1 preferentially cleaved single-stranded RNAs comprising A20 or U20, whereas neither C20 nor G20 was susceptible to SAMHD1-mediated degradation. Our findings will facilitate more advanced studies into the role of the SAMHD1 RNase function in the cellular pathogenesis implicated in nucleic acid-triggered inflammatory responses and the anti-retroviral function of SAMHD1. PMID:27387229

  20. Nanocrystalline nickel ferrite particles synthesized by non-hydrolytic sol-gel method and their composite with biodegradable polymer.

    PubMed

    Yin, H; Casey, P S; Chow, G M

    2012-11-01

    Targeted drug delivery has been one of the most important biomedical applications for magnetic particles. Such applications require magnetic particles to have functionalized surfaces/surface coatings that facilitate their incorporation into a polymer matrix to produce a polymer composite. In this paper, nanocrystalline nickel ferrite particles with an oleic acid surface coating were synthesized using a non-hydrolytic sol-gel method and incorporated into a biodegradable polymer matrix, poly(D,L-lactide) PLA prepared using a double emulsion method. As-synthesized nickel ferrite particles had a multi-crystalline structure with chemically adsorbed oleic acid on their surface. After forming the PLA composite, nickel ferrite particles were encapsulated in PLA microspheres. At low nickel ferrite concentrations, composites showed very similar surface charges to that of PLA. The composites were magnetically responsive and increasing the nickel ferrite concentration was found to increase magnetization of the composite. PMID:23421226

  1. On the acid-base properties of humic acid in soil.

    PubMed

    Cooke, James D; Hamilton-Taylor, John; Tipping, Edward

    2007-01-15

    Humic acid was isolated from three contrasting organic-rich soils and acid-base titrations performed over a range of ionic strengths. Results obtained were unlike most humic acid data sets; they showed a greater ionic strength dependency at low pH than at high pH. Forward- and back-titrations with the base and acid revealed hysteresis, particularly at low pH. Previous authors attributed this type of hysteresis to humic acid aggregates-created during the isolation procedure-being redissolved during titration as the pH increased and regarded the results as artificial. However, forward- and back-titrations with organic-rich soils also demonstrated a similar hysteretic behavior. These observations indicate (i) that titrations of humic acid in aggregated form (as opposed to the more usual dissolved form) are more representative of the acid-base properties of humic acid in soil and (ii) that the ionic strength dependency of proton binding in humic acid is related to its degree of aggregation. Thus, the current use of models based on data from dissolved humic substances to predictthe acid-base properties of humic acid in soil under environmental conditions may be flawed and could substantially overestimate their acid buffering capacity.

  2. Renal acid-base metabolism after ischemia.

    PubMed

    Holloway, J C; Phifer, T; Henderson, R; Welbourne, T C

    1986-05-01

    The response of the kidney to ischemia-induced cellular acidosis was followed over the immediate one hr post-ischemia reflow period. Clearance and extraction experiments as well as measurement of cortical intracellular pH (pHi) were performed on Inactin-anesthetized Sprague-Dawley rats. Arteriovenous concentration differences and para-aminohippurate extraction were obtained by cannulating the left renal vein. Base production was monitored as bicarbonate released into the renal vein and urine; net base production was related to the renal handling of glutamine and ammonia as well as to renal oxygen consumption and pHi. After a 15 min control period, the left renal artery was snared for one-half hr followed by release and four consecutive 15 min reflow periods. During the control period, cortical cell pHi measured by [14C]-5,5-Dimethyl-2,4-Oxazolidinedione distribution was 7.07 +/- 0.08, and Q-O2 was 14.1 +/- 2.2 micromoles/min; neither net glutamine utilization nor net bicarbonate generation occurred. After 30 min of ischemia, renal tissue pH fell to 6.6 +/- 0.15. However, within 45 min of reflow, cortical cell pH returned and exceeded the control value, 7.33 +/- 0.06 vs. 7.15 +/- 0.08. This increase in pHi was associated with a significant rise in cellular metabolic rate, Q-O2 increased to 20.3 +/- 6.4 micromoles/min. Corresponding with cellular alkalosis was a net production of bicarbonate and a net ammonia uptake and glutamine release; urinary acidification was abolished. These results are consistent with a nonexcretory renal metabolic base generating mechanism governing cellular acid base homeostasis following ischemia. PMID:3723929

  3. Long-term hydrolytic capacity evaluation of a thermophilic anaerobic digester treating sewage sludge.

    PubMed

    Donoso-Bravo, Andres; Pérez-Elvira, Sara; Wouwer, Alain Vande; Fdz-Polanco, Fernando

    2012-01-01

    This study presents an evaluation of the hydrolytic activity of a continuous thermophilic anaerobic reactor in long-term operation. The hydrolytic coefficient was estimated by fitting a three-reaction model of the anaerobic digestion process with experimental data obtained from a pilot thermophilic digester operated for about 2 years. The model fitting and the cross-validation indicate that this model can represent the behavior of the system in a proper way; moreover, the results show a variation of the hydrolytic capacity of the system throughout the evaluation period. The increase in the hydrolytic coefficient is in agreement with the increase in the organic load applied to the reactor, which shows the capacity of the continuous reactor to select populations according to the input conditions of the system.

  4. Base pairing and base mis-pairing in nucleic acids

    NASA Technical Reports Server (NTRS)

    Wang, A. H. J.; Rich, A.

    1986-01-01

    In recent years we have learned that DNA is conformationally active. It can exist in a number of different stable conformations including both right-handed and left-handed forms. Using single crystal X-ray diffraction analysis we are able to discover not only additional conformations of the nucleic acids but also different types of hydrogen bonded base-base interactions. Although Watson-Crick base pairings are the predominant type of interaction in double helical DNA, they are not the only types. Recently, we have been able to examine mismatching of guanine-thymine base pairs in left-handed Z-DNA at atomic resolution (1A). A minimum amount of distortion of the sugar phosphate backbone is found in the G x T pairing in which the bases are held together by two hydrogen bonds in the wobble pairing interaction. Because of the high resolution of the analysis we can visualize water molecules which fill in to accommodate the other hydrogen bonding positions in the bases which are not used in the base-base interactions. Studies on other DNA oligomers have revealed that other types of non-Watson-Crick hydrogen bonding interactions can occur. In the structure of a DNA octamer with the sequence d(GCGTACGC) complexed to an antibiotic triostin A, it was found that the two central AT base pairs are held together by Hoogsteen rather than Watson-Crick base pairs. Similarly, the G x C base pairs at the ends are also Hoogsteen rather than Watson-Crick pairing. Hoogsteen base pairs make a modified helix which is distinct from the Watson-Crick double helix.

  5. Novel insights in the use of hydrolytic enzymes secreted by fungi with biotechnological potential.

    PubMed

    Pereira, J L; Noronha, E F; Miller, R N G; Franco, O L

    2007-06-01

    Entomopathogenic and mycoparasitic fungi synthesize hydrolytic enzymes such as chitinases, proteinases and beta-glucanases. These enzymes can act synergistically, helping fungi to control insect pests and pathogens that attack productive crops, and offer potential economic benefit to agribusiness. A number of hydrolytic enzymes have also been utilized in industrial applications. This review focuses on biochemical and structural analyses of fungal enzymes, together with current research information on secretion mechanisms.

  6. Enhanced Hydrolytic Stability of Siliceous Surfaces Modified with Pendant Dipodal Silanes

    PubMed Central

    Arkles, Barry; Pan, Youlin; Larson, Gerald L; Singh, Mani

    2014-01-01

    Dipodal silanes possess two silicon atoms that can covalently bond to a surface. They offer a distinct advantage over conventional silanes commonly used for surface modification in terms of maintaining the integrity of surface coatings, adhesive primers, and composites in aqueous environments. New nonfunctional and functional dipodal silanes with structures containing “pendant” rather than “bridged” organofunctionality are introduced. The stability of surfaces in aqueous environments prepared from dipodal silanes with hydrophobic alkyl functionality is compared to the stability of similar surfaces prepared from the conventional silanes. In strongly acidic and brine environments, surfaces modified with dipodal silanes demonstrate markedly improved resistance to hydrolysis compared to surfaces prepared from conventional silanes. Pendant dipodal silanes exhibit greater stability than bridged dipodal silanes. The apparent equilibrium constant for the formation of silanol species by the hydrolysis of a disiloxane bond was determined as Kc=[SiOH]2/[Si-O-Si][H2O]=6±1×10−5 and is helpful in understanding the enhanced hydrolytic stability of surfaces modified with dipodal silanes. PMID:25043315

  7. Canceling effect leads temperature insensitivity of hydrolytic enzymes in soil

    NASA Astrophysics Data System (ADS)

    Razavi, Bahar S.; Blagodatskaya, Evgenia; Kuzyakov, Yakov

    2015-04-01

    Extracellular enzymes are important for decomposition of many macromolecules abundant in soil such as cellulose, hemicelluloses and proteins (Allison et al., 2010; Chen et al., 2012). The temperature sensitivity of enzymes responsible for organic matter decomposition is the most crucial parameter for prediction of the effects of global warming on carbon cycle. Temperature responses of biological systems are often expressed as a Q10 functions; The Q10 describes how the rate of a chemical reaction changes with a temperature increase for 10 °C The aim of this study was to test how the canceling effect will change with variation in temperature interval, during short-term incubation. We additionally investigated, whether canceling effect occurs in a broad range of concentrations (low to high) and whether it is similar for the set of hydrolytic enzymes within broad range of temperatures. To this end, we performed soil incubation over a temperature range of 0-40°C (with 5°C steps). We determined the activities of three enzymes involved in plant residue decomposition: β-glucosidase and cellobiohydrolase, which are commonly measured as enzymes responsible for degrading cellulose (Chen et al., 2012), and xylanase, which degrades xylooligosaccharides (short xylene chain) in to xylose, thus being responsible for breaking down hemicelluloses (German et al., 2011). Michaelis-Menten kinetics measured at each temperature allowed to calculate Q10 values not only for the whole reaction rates, but specifically for maximal reaction rate (Vmax) and substrate affinity (Km). Subsequently, the canceling effect - simultaneous increase of Vmax and Km with temperature was analyzed within 10 and 5 degree of temperature increase. Three temperature ranges (below 10, between 15 and 25, and above 30 °C) clearly showed non-linear but stepwise increase of temperature sensitivity of all three enzymes and allowed to conclude for predominance of psychrophilic, mesophilic and thermophilic

  8. Tuning the hydrolytic aqueous chemistry of osmium arene complexes with N,O-chelating ligands to achieve cancer cell cytotoxicity.

    PubMed

    Peacock, Anna F A; Parsons, Simon; Sadler, Peter J

    2007-03-21

    Potential biological and medical applications of organometallic complexes are hampered by a lack of knowledge of their aqueous solution chemistry. We show that the hydrolytic and aqueous solution chemistry of half-sandwich OsII arene complexes of the type [(eta6-arene)Os(XY)Cl] can be tuned with XY chelating ligands to achieve cancer cell cytoxicity comparable to carboplatin. Complexes containing arene = p-cymene, XY = N,O-chelating ligands glycinate (1), L-alaninate (2), alpha-aminobutyrate (3), beta-alaninate (4), picolinate (5), or 8-hydroxyquinolinate (7) were synthesized. Although, 1-4 and 7 hydrolyzed rapidly (acidic (pKa* = 6.67, 6.33) than the other aqua adducts (pKa* = 7.17-7.71). At biological test concentrations (micromolar), the chelating ligands dissociated from complexes 1-4 to give the inert hydroxo-bridged dinuclear species [(eta6-arene)Os(mu-OH)3Os(eta6-arene)]+ (8), and these complexes were inactive toward human lung A549 and ovarian A2780 cancer cells. In contrast, 5-7 were cytotoxic, especially 6 (IC50 values of 8 and 4.2 microM). The X-ray structures of 9-ethylguanine, [(eta6-p-cym)Os(pico)(9EtG-N7)]PF6, and 9-ethyladenine, [(eta6-p-cym)Os(pico)(9EtA-N7)]PF6, adducts of 5 are reported (the first reported for G or A adducts of OsII). Crystals of the 9EtA complex contain homoadenine base pairing. The 9EtG adduct in particular exhibits remarkable aqueous kinetic stability. This work shows how the rational control of chemical reactivity (hydrolysis, acidity, formation of hydroxo-bridged dinuclear species) can allow the design of cytotoxic anticancer OsII arene complexes.

  9. History of medical understanding and misunderstanding of Acid base balance.

    PubMed

    Aiken, Christopher Geoffrey Alexander

    2013-09-01

    To establish how controversies in understanding acid base balance arose, the literature on acid base balance was reviewed from 1909, when Henderson described how the neutral reaction of blood is determined by carbonic and organic acids being in equilibrium with an excess of mineral bases over mineral acids. From 1914 to 1930, Van Slyke and others established our acid base principles. They recognised that carbonic acid converts into bicarbonate all non-volatile mineral bases not bound by mineral acids and determined therefore that bicarbonate represents the alkaline reserve of the body and should be a physiological constant. They showed that standard bicarbonate is a good measure of acidosis caused by increased production or decreased elimination of organic acids. However, they recognised that bicarbonate improved low plasma bicarbonate but not high urine acid excretion in diabetic ketoacidosis, and that increasing pCO2 caused chloride to shift into cells raising plasma titratable alkali. Both indicate that minerals influence pH. In 1945 Darrow showed that hyperchloraemic metabolic acidosis in preterm infants fed milk with 5.7 mmol of chloride and 2.0 mmol of sodium per 100 kcal was caused by retention of chloride in excess of sodium. Similar findings were made but not recognised in later studies of metabolic acidosis in preterm infants. Shohl in 1921 and Kildeberg in 1978 presented the theory that carbonic and organic acids are neutralised by mineral base, where mineral base is the excess of mineral cations over anions and organic acid is the difference between mineral base, bicarbonate and protein anion. The degree of metabolic acidosis measured as base excess is determined by deviation in both mineral base and organic acid from normal.

  10. Acid-Base Pairs in Lewis Acidic Zeolites Promote Direct Aldol Reactions by Soft Enolization.

    PubMed

    Lewis, Jennifer D; Van de Vyver, Stijn; Román-Leshkov, Yuriy

    2015-08-17

    Hf-, Sn-, and Zr-Beta zeolites catalyze the cross-aldol condensation of aromatic aldehydes with acetone under mild reaction conditions with near quantitative yields. NMR studies with isotopically labeled molecules confirm that acid-base pairs in the Si-O-M framework ensemble promote soft enolization through α-proton abstraction. The Lewis acidic zeolites maintain activity in the presence of water and, unlike traditional base catalysts, in acidic solutions.

  11. Chip-based sequencing nucleic acids

    SciTech Connect

    Beer, Neil Reginald

    2014-08-26

    A system for fast DNA sequencing by amplification of genetic material within microreactors, denaturing, demulsifying, and then sequencing the material, while retaining it in a PCR/sequencing zone by a magnetic field. One embodiment includes sequencing nucleic acids on a microchip that includes a microchannel flow channel in the microchip. The nucleic acids are isolated and hybridized to magnetic nanoparticles or to magnetic polystyrene-coated beads. Microreactor droplets are formed in the microchannel flow channel. The microreactor droplets containing the nucleic acids and the magnetic nanoparticles are retained in a magnetic trap in the microchannel flow channel and sequenced.

  12. Quantitative iTRAQ secretome analysis of Aspergillus niger reveals novel hydrolytic enzymes.

    PubMed

    Adav, Sunil S; Li, An A; Manavalan, Arulmani; Punt, Peter; Sze, Siu Kwan

    2010-08-01

    The natural lifestyle of Aspergillus niger made them more effective secretors of hydrolytic proteins and becomes critical when this species were exploited as hosts for the commercial secretion of heterologous proteins. The protein secretion profile of A. niger and its mutant at different pH was explored using iTRAQ-based quantitative proteomics approach coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). This study characterized 102 highly confident unique proteins in the secretome with zero false discovery rate based on decoy strategy. The iTRAQ technique identified and relatively quantified many hydrolyzing enzymes such as cellulases, hemicellulases, glycoside hydrolases, proteases, peroxidases, and protein translocating transporter proteins during fermentation. The enzymes have potential application in lignocellulosic biomass hydrolysis for biofuel production, for example, the cellulolytic and hemicellulolytic enzymes glucan 1,4-alpha-glucosidase, alpha-glucosidase C, endoglucanase, alpha l-arabinofuranosidase, beta-mannosidase, glycosyl hydrolase; proteases such as tripeptidyl-peptidase, aspergillopepsin, and other enzymes including cytochrome c oxidase, cytochrome c oxidase, glucose oxidase were highly expressed in A. niger and its mutant secretion. In addition, specific enzyme production can be stimulated by controlling pH of the culture medium. Our results showed comprehensive unique secretory protein profile of A. niger, its regulation at different pH, and the potential application of iTRAQ-based quantitative proteomics for the microbial secretome analysis.

  13. Assessment of acid-base balance. Stewart's approach.

    PubMed

    Fores-Novales, B; Diez-Fores, P; Aguilera-Celorrio, L J

    2016-04-01

    The study of acid-base equilibrium, its regulation and its interpretation have been a source of debate since the beginning of 20th century. Most accepted and commonly used analyses are based on pH, a notion first introduced by Sorensen in 1909, and on the Henderson-Hasselbalch equation (1916). Since then new concepts have been development in order to complete and make easier the understanding of acid-base disorders. In the early 1980's Peter Stewart brought the traditional interpretation of acid-base disturbances into question and proposed a new method. This innovative approach seems more suitable for studying acid-base abnormalities in critically ill patients. The aim of this paper is to update acid-base concepts, methods, limitations and applications.

  14. Phosphonic acid based ion exchange resins

    DOEpatents

    Horwitz, E.P.; Alexandratos, S.D.; Gatrone, R.C.; Chiarizia, R.

    1994-01-25

    An ion exchange resin is described for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene. 9 figures.

  15. Phosphonic acid based ion exchange resins

    DOEpatents

    Horwitz, E.P.; Alexandratos, S.D.; Gatrone, R.C.; Chiarizia, R.

    1996-07-23

    An ion exchange resin is described for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene. 10 figs.

  16. Phosphonic acid based ion exchange resins

    DOEpatents

    Horwitz, E. Philip; Alexandratos, Spiro D.; Gatrone, Ralph C.; Chiarizia, Ronato

    1994-01-01

    An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene disphosphonic acid with styrene, acrylonitrile and divinylbenzene.

  17. Phosphonic acid based ion exchange resins

    DOEpatents

    Horwitz, E. Philip; Alexandratos, Spiro D.; Gatrone, Ralph C.; Chiarizia, Ronato

    1996-01-01

    An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene.

  18. Non-hydrolytic Sol-gel Synthesis of Tin Sulfides

    NASA Astrophysics Data System (ADS)

    Kaur, Rajvinder

    The non-hydrolytic sol-gel (NHSG) process is an effective low temperature route well known for preparing homogeneous metal oxides. Thermodynamically as well as kinetically favored products, which cannot be prepared with the traditional solid-state routes, can be produced using NHSG. This project is focused on the exploration of NHSG synthesis of binary tin sulfides. In the past few years, metal sulfides have been the subject of significant interest. Much effort has been devoted to understand these materials because of their potential applications in electronic, optical, and superconductor devices.4 Among these materials, tin sulfides are materials of technological importance, which are being explored as semiconductors, anode materials for Li ion batteries, photoconductors, photocatalysts and absorber layer materials in photovoltaic solar cell devices. All of these applications depend upon features like homogeneity, oxidation state, high surface area and purity of the materials. These properties can be difficult to achieve by employing traditional synthetic routes, which require high temperatures due to slow diffusion, limiting the products to thermodynamically stable phases and prohibiting control over properties like particle size and surface area. A variety of low temperature methods are being explored due to the increased demand for such advanced materials. This project is focused on exploring the NHSG approach to synthesize binary tin sulfides, with the main goal of establishing conditions for the targeted synthesis of different tin sulfide polymorphs with controlled particle size. Being non-oxide materials, tin sulfides can be air sensitive, which requires special attention in handling. All reactions were carried out in absence of oxygen. This project explores the reaction of tin halides with thioethers in a dry solvent medium, leading to the formation of tin sulfides. There are a number of synthetic parameters that can be varied for the NHSG approach. A

  19. Advances in nucleic acid-based detection methods.

    PubMed Central

    Wolcott, M J

    1992-01-01

    Laboratory techniques based on nucleic acid methods have increased in popularity over the last decade with clinical microbiologists and other laboratory scientists who are concerned with the diagnosis of infectious agents. This increase in popularity is a result primarily of advances made in nucleic acid amplification and detection techniques. Polymerase chain reaction, the original nucleic acid amplification technique, changed the way many people viewed and used nucleic acid techniques in clinical settings. After the potential of polymerase chain reaction became apparent, other methods of nucleic acid amplification and detection were developed. These alternative nucleic acid amplification methods may become serious contenders for application to routine laboratory analyses. This review presents some background information on nucleic acid analyses that might be used in clinical and anatomical laboratories and describes some recent advances in the amplification and detection of nucleic acids. PMID:1423216

  20. What is the Ultimate Goal in Acid-Base Regulation?

    ERIC Educational Resources Information Center

    Balakrishnan, Selvakumar; Gopalakrishnan, Maya; Alagesan, Murali; Prakash, E. Sankaranarayanan

    2007-01-01

    It is common to see chapters on acid-base physiology state that the goal of acid-base regulatory mechanisms is to maintain the pH of arterial plasma and not arterial PCO [subscript 2] (Pa[subscript CO[subscript 2

  1. A Closer Look at Acid-Base Olfactory Titrations

    ERIC Educational Resources Information Center

    Neppel, Kerry; Oliver-Hoyo, Maria T.; Queen, Connie; Reed, Nicole

    2005-01-01

    Olfactory titrations using raw onions and eugenol as acid-base indicators are reported. An in-depth investigation on olfactory titrations is presented to include requirements for potential olfactory indicators and protocols for using garlic, onions, and vanillin as acid-base olfactory indicators are tested.

  2. The Roles of Acids and Bases in Enzyme Catalysis

    ERIC Educational Resources Information Center

    Weiss, Hilton M.

    2007-01-01

    Many organic reactions are catalyzed by strong acids or bases that protonate or deprotonate neutral reactants leading to reactive cations or anions that proceed to products. In enzyme reactions, only weak acids and bases are available to hydrogen bond to reactants and to transfer protons in response to developing charges. Understanding this…

  3. A Modern Approach to Acid-Base Chemistry

    ERIC Educational Resources Information Center

    Drago, Russell S.

    1974-01-01

    Summarizes current status of our knowledge about acid-base interactions, including Lewis considerations, experimental design, data about donor-acceptor systems, common misconceptions, and hard-soft acid-base model. Indicates that there is the possibility of developing unifying concepts for chemical reactions of inorganic compounds. (CC)

  4. Hydrolytic Enzyme Activities and Protein Pattern of Avocado Fruit Ripened in Air and in Low Oxygen, with and without Ethylene.

    PubMed

    Kanellis, A K; Solomos, T; Mattoo, A K

    1989-05-01

    The effect of 2.5% O(2) atmosphere with and without ethylene on the activities of hydrolytic enzymes associated with cell walls, and total protein profile during ripening of avocado fruits (Persea americana Mill., cv Hass) were investigated. The low 2.5% O(2) atmosphere prevented the rise in the activities of cellulase, polygalacturonase, and acid phosphatase in avocado fruits whose ripening was initiated with ethylene. Addition of 100 microliters per liter ethylene to low O(2) atmosphere did not alter these suppressive effects of 2.5% O(2). Furthermore, 2.5% O(2) atmosphere delayed the development of a number of polypeptides that appear during ripening of avocado fruits while at the same time new polypeptides accumulated. The composition of the extraction buffer and its pH greatly affected the recovery of cellulase activity and its total immunoreactive protein.

  5. Connecting Acids and Bases with Encapsulation... and Chemistry with Nanotechnology

    ERIC Educational Resources Information Center

    Criswell, Brett

    2007-01-01

    The features and the development of various new acids and bases activity sets that combines chemistry with nanotechnology are being described. These sets lead to the generation of many nanotechnology-based pharmaceuticals for the treatment of various diseases.

  6. MOF-5-Polystyrene: Direct Production from Monomer, Improved Hydrolytic Stability, and Unique Guest Adsorption.

    PubMed

    Gamage, Nipuni-Dhanesha H; McDonald, Kyle A; Matzger, Adam J

    2016-09-19

    An unprecedented mode of reactivity of Zn4 O-based metal-organic frameworks (MOFs) offers a straightforward and powerful approach to polymer-hybridized porous solids. The concept is illustrated with the production of MOF-5-polystyrene wherein polystyrene is grafted and uniformly distributed throughout MOF-5 crystals after heating in pure styrene for 4-24 h. The surface area and polystyrene content of the material can be fine-tuned by controlling the duration of heating styrene in the presence of MOF-5. Polystyrene grafting significantly alters the physical and chemical properties of pristine MOF-5, which is evident from the unique guest adsorption properties (solvatochromic dye uptake and improved CO2 capacity) as well as the dramatically improved hydrolytic stability of composite. Based on the fact that MOF-5 is the best studied member of the structure class, and has been produced at scale by industry, these findings can be directly leveraged for a range of current applications.

  7. Nanostructured Ni2 P as a Robust Catalyst for the Hydrolytic Dehydrogenation of Ammonia-Borane.

    PubMed

    Peng, Cheng-Yun; Kang, Lei; Cao, Shuang; Chen, Yong; Lin, Zhe-Shuai; Fu, Wen-Fu

    2015-12-21

    Ammonia-borane (AB) is a promising chemical hydrogen-storage material. However, the development of real-time, efficient, controllable, and safe methods for hydrogen release under mild conditions is a challenge in the large-scale use of hydrogen as a long-term solution for future energy security. A new class of low-cost catalytic system is presented that uses nanostructured Ni2 P as catalyst, which exhibits excellent catalytic activity and high sustainability toward hydrolysis of ammonia-borane with the initial turnover frequency of 40.4 mol(H2)  mol(Ni2P) (-1)  min(-1) under air atmosphere and at ambient temperature. This value is higher than those reported for noble-metal-free catalysts, and the obtained Arrhenius activation energy (Ea =44.6 kJ mol(-1) ) for the hydrolysis reaction is comparable to Ru-based bimetallic catalysts. A clearly mechanistic analysis of the hydrolytic reaction of AB based on experimental results and a density functional theory calculation is presented. PMID:26545954

  8. MOF-5-Polystyrene: Direct Production from Monomer, Improved Hydrolytic Stability, and Unique Guest Adsorption.

    PubMed

    Gamage, Nipuni-Dhanesha H; McDonald, Kyle A; Matzger, Adam J

    2016-09-19

    An unprecedented mode of reactivity of Zn4 O-based metal-organic frameworks (MOFs) offers a straightforward and powerful approach to polymer-hybridized porous solids. The concept is illustrated with the production of MOF-5-polystyrene wherein polystyrene is grafted and uniformly distributed throughout MOF-5 crystals after heating in pure styrene for 4-24 h. The surface area and polystyrene content of the material can be fine-tuned by controlling the duration of heating styrene in the presence of MOF-5. Polystyrene grafting significantly alters the physical and chemical properties of pristine MOF-5, which is evident from the unique guest adsorption properties (solvatochromic dye uptake and improved CO2 capacity) as well as the dramatically improved hydrolytic stability of composite. Based on the fact that MOF-5 is the best studied member of the structure class, and has been produced at scale by industry, these findings can be directly leveraged for a range of current applications. PMID:27555362

  9. A Computer-Based Simulation of an Acid-Base Titration

    ERIC Educational Resources Information Center

    Boblick, John M.

    1971-01-01

    Reviews the advantages of computer simulated environments for experiments, referring in particular to acid-base titrations. Includes pre-lab instructions and a sample computer printout of a student's use of an acid-base simulation. Ten references. (PR)

  10. First derivative spectrophotometric determination of granisetron hydrochloride in presence of its hydrolytic products and preservative and application to pharmaceutical preparations.

    PubMed

    Hewala, Ismail I; Bedair, Mona M; Shousha, Sherif M

    2013-04-01

    Granisetron is a selective 5-HT3 receptor antagonist used in prevention and treatment of chemotherapy-induced nausea and vomiting. The drug is available in tablet dosage form and parenteral dosage form containing benzyl alcohol as a preservative. The main route of degradation of granisetron is through hydrolysis. The present work describes the development of a simple, rapid, and reliable first derivative spectrophotometric method for the determination of granisetron in presence of its hydrolytic products as well as the formulations adjuvant and benzyl alcohol. The method is based on the measurement of the first derivative response of granisetron at 290 nm where the interference of the hydrolytic products, the co-formulated adjuvant and benzyl alcohol is completely eliminated. The proposed method was validated with respect to specificity, linearity, selectivity, accuracy, precision, robustness, detection, and quantification limits. Regression analysis showed good correlation between the first derivative response and the concentration of granisetron over a range of 8-16 μg ml(-1) . Statistical analysis proved the accuracy of the proposed method compared with a reference stability indicating high performance liquid chromatography method. The described method was successfully applied to the determination of granisetron in different batches of tablets and ampoules. The assay results obtained in this study strongly encourage us to apply the validated method for the quality control and routine analysis of tablets and parenteral preparations containing granisetron.

  11. Nucleic acid duplexes incorporating a dissociable covalent base pair

    NASA Technical Reports Server (NTRS)

    Gao, K.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

    1999-01-01

    We have used molecular modeling techniques to design a dissociable covalently bonded base pair that can replace a Watson-Crick base pair in a nucleic acid with minimal distortion of the structure of the double helix. We introduced this base pair into a potential precursor of a nucleic acid double helix by chemical synthesis and have demonstrated efficient nonenzymatic template-directed ligation of the free hydroxyl groups of the base pair with appropriate short oligonucleotides. The nonenzymatic ligation reactions, which are characteristic of base paired nucleic acid structures, are abolished when the covalent base pair is reduced and becomes noncoplanar. This suggests that the covalent base pair linking the two strands in the duplex is compatible with a minimally distorted nucleic acid double-helical structure.

  12. Nucleic acid duplexes incorporating a dissociable covalent base pair.

    PubMed

    Gao, K; Orgel, L E

    1999-12-21

    We have used molecular modeling techniques to design a dissociable covalently bonded base pair that can replace a Watson-Crick base pair in a nucleic acid with minimal distortion of the structure of the double helix. We introduced this base pair into a potential precursor of a nucleic acid double helix by chemical synthesis and have demonstrated efficient nonenzymatic template-directed ligation of the free hydroxyl groups of the base pair with appropriate short oligonucleotides. The nonenzymatic ligation reactions, which are characteristic of base paired nucleic acid structures, are abolished when the covalent base pair is reduced and becomes noncoplanar. This suggests that the covalent base pair linking the two strands in the duplex is compatible with a minimally distorted nucleic acid double-helical structure. PMID:10611299

  13. Organic acids and bases: Review of toxicological studies

    SciTech Connect

    Leung, H.W.; Paustenbach, D.J. )

    1990-01-01

    Organic acids and bases are among the most frequently used chemicals in the manufacturing industries. However, the toxicology of only a number of them has been fully characterized, and for fewer still have occupational exposure limits been established. This paper reviews the acute and chronic toxicity data of the organic acids and bases, and considers the mechanism by which these chemicals produce their effects. A methodology for establishing preliminary occupational exposure limits based on the physicochemical properties of these chemicals is presented. Workplace exposure limits for 20 organic acids and bases which currently have no exposure guidelines are suggested. Advice regarding appropriate medical treatment of exposure to these materials is discussed. 98 references.

  14. General base-general acid catalysis by terpenoid cyclases.

    PubMed

    Pemberton, Travis A; Christianson, David W

    2016-07-01

    Terpenoid cyclases catalyze the most complex reactions in biology, in that more than half of the substrate carbon atoms often undergo changes in bonding during the course of a multistep cyclization cascade that proceeds through multiple carbocation intermediates. Many cyclization mechanisms require stereospecific deprotonation and reprotonation steps, and most cyclization cascades are terminated by deprotonation to yield an olefin product. The first bacterial terpenoid cyclase to yield a crystal structure was pentalenene synthase from Streptomyces exfoliatus UC5319. This cyclase generates the hydrocarbon precursor of the pentalenolactone family of antibiotics. The structures of pentalenene synthase and other terpenoid cyclases reveal predominantly nonpolar active sites typically lacking amino acid side chains capable of serving general base-general acid functions. What chemical species, then, enables the Brønsted acid-base chemistry required in the catalytic mechanisms of these enzymes? The most likely candidate for such general base-general acid chemistry is the co-product inorganic pyrophosphate. Here, we briefly review biological and nonbiological systems in which phosphate and its derivatives serve general base and general acid functions in catalysis. These examples highlight the fact that the Brønsted acid-base activities of phosphate derivatives are comparable to the Brønsted acid-base activities of amino acid side chains.

  15. Acid-base properties of 2-phenethyldithiocarbamoylacetic acid, an antitumor agent

    NASA Astrophysics Data System (ADS)

    Novozhilova, N. E.; Kutina, N. N.; Petukhova, O. A.; Kharitonov, Yu. Ya.

    2013-07-01

    The acid-base properties of the 2-phenethyldithiocarbamoylacetic acid (PET) substance belonging to the class of isothiocyanates and capable of inhibiting the development of tumors on many experimental models were studied. The acidity and hydrolysis constants of the PET substance in ethanol, acetone, aqueous ethanol, and aqueous acetone solutions were determined from the data of potentiometric (pH-metric) titration of ethanol and acetone solutions of PET with aqueous solidum hydroxide at room temperature.

  16. Hydrolytic Activation Kinetics of the Herbicide Benzobicyclon in Simulated Aquatic Systems.

    PubMed

    Williams, Katryn L; Tjeerdema, Ronald S

    2016-06-22

    Herbicide resistance is a growing concern for weeds in California rice fields. Benzobicyclon (BZB; 3-(2-chloro-4-(methylsulfonyl)benzoyl)-2-phenylthiobicyclo[3.2.1]oct-2-en-4-one) has proven successful against resistant rice field weeds in Asia. A pro-herbicide, BZB forms the active agent, benzobicyclon hydrolysate (BH), in water; however, the transformation kinetics are not understood for aquatic systems, particularly flooded California rice fields. A quantitative experiment was performed to assess the primary mechanism and kinetics of BZB hydrolysis to BH. Complete conversion to BH was observed for all treatments. Basic conditions (pH 9) enhanced the reaction, with half-lives ranging from 5 to 28 h. Dissolved organic carbon (DOC) hindered transformation, which is consistent with other base-catalyzed hydrolysis reactions. BH was relatively hydrolytically stable, with 18% maximum loss after 5 days. Results indicate BZB is an efficient pro-herbicide under aqueous conditions such as those of a California rice field, although application may be best suited for fields with recirculating tailwater systems. PMID:27248841

  17. Hydrolytically degradable poly(ethylene glycol) hydrogel scaffolds with tunable degradation and mechanical properties

    PubMed Central

    Zustiak, Silviya P.

    2011-01-01

    The objective of this work was to create three-dimensional (3D) hydrogel matrices with defined mechanical properties, as well as tunable degradability for use in applications involving protein delivery and cell encapsulation. Thus, we report the synthesis and characterization of a novel hydrolytically degradable poly(ethylene glycol) (PEG) hydrogel composed of PEG vinyl sulfone (PEG-VS) cross-linked with PEG-diester-dithiol. Unlike previously reported degradable PEG-based hydrogels, these materials are homogeneous in structure, fully hydrophilic and have highly specific cross-linking chemistry. We characterized hydrogel degradation and associated trends in mechanical properties, i.e., storage modulus (G′), swelling ratio (QM), and mesh size (ξ). Degradation time and the monitored mechanical properties of the hydrogel correlated with cross-linker molecular weight, cross-linker functionality, and total polymer density; these properties changed predictably as degradation proceeded (G′ decreased, whereas QM and ξ increased) until the gels reached complete degradation. Balb/3T3 fibroblast adhesion and proliferation within the 3D hydrogel matrices were also verified. In sum, these unique properties indicate that the reported degradable PEG hydrogels are well poised for specific applications in protein and cell delivery to repair soft tissue. PMID:20355705

  18. Carbon-based strong solid acid for cornstarch hydrolysis

    NASA Astrophysics Data System (ADS)

    Nata, Iryanti Fatyasari; Irawan, Chairul; Mardina, Primata; Lee, Cheng-Kang

    2015-10-01

    Highly sulfonated carbonaceous spheres with diameter of 100-500 nm can be generated by hydrothermal carbonization of glucose in the presence of hydroxyethylsulfonic acid and acrylic acid at 180 °C for 4 h. The acidity of the prepared carbonaceous sphere C4-SO3H can reach 2.10 mmol/g. It was used as a solid acid catalyst for the hydrolysis of cornstarch. Total reducing sugar (TRS) concentration of 19.91 mg/mL could be obtained by hydrolyzing 20 mg/mL cornstarch at 150 °C for 6 h using C4-SO3H as solid acid catalyst. The solid acid catalyst demonstrated good stability that only 9% decrease in TRS concentration was observed after five repeat uses. The as-prepared carbon-based solid acid catalyst can be an environmentally benign replacement for homogeneous catalyst.

  19. Quorum sensing in marine snow and its possible influence on production of extracellular hydrolytic enzymes in marine snow bacterium Pantoea ananatis B9.

    PubMed

    Jatt, Abdul Nabi; Tang, Kaihao; Liu, Jiwen; Zhang, Zenghu; Zhang, Xiao-Hua

    2015-02-01

    Marine snow is a continuous shower of organic and inorganic detritus, and plays a crucial role in transporting materials from the sea surface to the deep ocean. The aims of the current study were to identify N-acyl homoserine lactone (AHL)-based quorum sensing (QS) signaling molecules directly from marine snow particles and to investigate the possible regulatory link between QS signals and extracellular hydrolytic enzymes produced by marine snow bacteria. The marine snow samples were collected from the surface water of China marginal seas. Two AHLs, i.e. 3OC6-HSL and C8-HSL, were identified directly from marine snow particles, while six different AHL signals, i.e. C4-HSL, 3OC6-HSL, C6-HSL, C10-HSL, C12-HSL and C14-HSL were produced by Pantoea ananatis B9 inhabiting natural marine snow particles. Of the extracellular hydrolytic enzymes produced by P. ananatis B9, alkaline phosphatase activity was highly enhanced in growth medium supplemented with exogenous AHL (C10-HSL), while quorum quenching enzyme (AiiA) drastically reduced the enzyme activity. To our knowledge, this is the first report revealing six different AHL signals produced by P. ananatis B9 and AHL-based QS system enhanced the extracellular hydrolytic enzyme in P. ananatis B9. Furthermore, this study first time revealing 3OC6-HSL production by Paracoccus carotinifaciens affiliated with Alphaproteobacteria. PMID:25764555

  20. Quorum sensing in marine snow and its possible influence on production of extracellular hydrolytic enzymes in marine snow bacterium Pantoea ananatis B9.

    PubMed

    Jatt, Abdul Nabi; Tang, Kaihao; Liu, Jiwen; Zhang, Zenghu; Zhang, Xiao-Hua

    2015-02-01

    Marine snow is a continuous shower of organic and inorganic detritus, and plays a crucial role in transporting materials from the sea surface to the deep ocean. The aims of the current study were to identify N-acyl homoserine lactone (AHL)-based quorum sensing (QS) signaling molecules directly from marine snow particles and to investigate the possible regulatory link between QS signals and extracellular hydrolytic enzymes produced by marine snow bacteria. The marine snow samples were collected from the surface water of China marginal seas. Two AHLs, i.e. 3OC6-HSL and C8-HSL, were identified directly from marine snow particles, while six different AHL signals, i.e. C4-HSL, 3OC6-HSL, C6-HSL, C10-HSL, C12-HSL and C14-HSL were produced by Pantoea ananatis B9 inhabiting natural marine snow particles. Of the extracellular hydrolytic enzymes produced by P. ananatis B9, alkaline phosphatase activity was highly enhanced in growth medium supplemented with exogenous AHL (C10-HSL), while quorum quenching enzyme (AiiA) drastically reduced the enzyme activity. To our knowledge, this is the first report revealing six different AHL signals produced by P. ananatis B9 and AHL-based QS system enhanced the extracellular hydrolytic enzyme in P. ananatis B9. Furthermore, this study first time revealing 3OC6-HSL production by Paracoccus carotinifaciens affiliated with Alphaproteobacteria.

  1. Reactive Distillation for Esterification of Bio-based Organic Acids

    SciTech Connect

    Fields, Nathan; Miller, Dennis J.; Asthana, Navinchandra S.; Kolah, Aspi K.; Vu, Dung; Lira, Carl T.

    2008-09-23

    The following is the final report of the three year research program to convert organic acids to their ethyl esters using reactive distillation. This report details the complete technical activities of research completed at Michigan State University for the period of October 1, 2003 to September 30, 2006, covering both reactive distillation research and development and the underlying thermodynamic and kinetic data required for successful and rigorous design of reactive distillation esterification processes. Specifically, this project has led to the development of economical, technically viable processes for ethyl lactate, triethyl citrate and diethyl succinate production, and on a larger scale has added to the overall body of knowledge on applying fermentation based organic acids as platform chemicals in the emerging biorefinery. Organic acid esters constitute an attractive class of biorenewable chemicals that are made from corn or other renewable biomass carbohydrate feedstocks and replace analogous petroleum-based compounds, thus lessening U.S. dependence on foreign petroleum and enhancing overall biorefinery viability through production of value-added chemicals in parallel with biofuels production. Further, many of these ester products are candidates for fuel (particularly biodiesel) components, and thus will serve dual roles as both industrial chemicals and fuel enhancers in the emerging bioeconomy. The technical report from MSU is organized around the ethyl esters of four important biorenewables-based acids: lactic acid, citric acid, succinic acid, and propionic acid. Literature background on esterification and reactive distillation has been provided in Section One. Work on lactic acid is covered in Sections Two through Five, citric acid esterification in Sections Six and Seven, succinic acid in Section Eight, and propionic acid in Section Nine. Section Ten covers modeling of ester and organic acid vapor pressure properties using the SPEAD (Step Potential

  2. Conventional and modified hydrodistillation method for the extraction of glucosinolate hydrolytic products: a comparative account.

    PubMed

    Arora, Rohit; Singh, Bikram; Vig, Adarsh Pal; Arora, Saroj

    2016-01-01

    Eruca sativa is extensively used as raw and its oil is also used for cooking due to its exceptional flavour. The volatile nature of the hydrolytic products of glucosinolates makes the extraction difficult. The hydrodistillation method used previously yield very less amount of the extract as well as the absence of stirring in the round bottom flask causes burning of both the crushed seeds and the flask. To overcome these drawbacks, a method has been developed using magnetic stirrer and hot plate. The yield and composition of hydrolytic products in the extract with the modified method was increased along with an increase in the amount of major hydrolytic products as seen by GC-MS. This method thus has immense potential in pharmaceutical industries, due to the ease of extraction and isolation. PMID:27217994

  3. Evaluation of wild herbivore faeces from South Africa as a potential source of hydrolytically active microorganisms.

    PubMed

    Ndlela, Luyanda L; Schmidt, Stefan

    2016-01-01

    This study assessed faecal matter from three indigenous South African herbivores-zebra, giraffe and impala-as a potential source for hydrolytically active aerobic and facultatively anaerobic bacteria. Herbivore droppings were collected freshly in a local nature reserve in Pietermaritzburg, South Africa. Soil samples adjacent to faecal collection sites and faeces from a domestic herbivore, the Nguni cow, were included as controls. Hydrolase and dehydrogenase activity in faecal matter and soil samples were measured by the fluorescein diacetate and the triphenyltetrazolium chloride assay. Viable counts and counts for amylase, cellulase, esterase and protease producers were established using plate count agar and solid media containing cellulose, skim milk, starch and Tween 80. Zebra droppings produced the highest hydrolase and dehydrogenase activity. Faecal matter of the three indigenous herbivores generally produced higher hydrolytic activity than Nguni cow faeces and soil controls, thereby confirming that these materials are potential targets for hydrolytic enzyme mining. PMID:26900540

  4. Polymerization of amino acids containing nucleotide bases

    NASA Technical Reports Server (NTRS)

    Ben Cheikh, Azzouz; Orgel, Leslie E.

    1990-01-01

    The nucleoamino acids 1-(3'-amino,3'-carboxypropyl)uracil (3) and 9-(3'-amino,3'-carboxypropyl)adenine (4) have been prepared as (L)-en-antiomers and as racemic mixtures. When 3 or 4 is suspended in water and treated with N,N'-carbon-yldiimidazole, peptides are formed in good yield. The products formed from the (L)-enantiomers are hydrolyzed to the monomeric amino acids by pronase. Attempts to improve the efficiency of these oligomerizations by including a polyuridylate template in the reaction mixture were not successful. Similarly, oligomers derived from the (L)-enantiomer of 3 did not act as templates to facilitate the oligomerization of 4.

  5. Carbon-based strong solid acid for cornstarch hydrolysis

    SciTech Connect

    Nata, Iryanti Fatyasari; Irawan, Chairul; Mardina, Primata; Lee, Cheng-Kang

    2015-10-15

    Highly sulfonated carbonaceous spheres with diameter of 100–500 nm can be generated by hydrothermal carbonization of glucose in the presence of hydroxyethylsulfonic acid and acrylic acid at 180 °C for 4 h. The acidity of the prepared carbonaceous sphere C4-SO{sub 3}H can reach 2.10 mmol/g. It was used as a solid acid catalyst for the hydrolysis of cornstarch. Total reducing sugar (TRS) concentration of 19.91 mg/mL could be obtained by hydrolyzing 20 mg/mL cornstarch at 150 °C for 6 h using C4-SO{sub 3}H as solid acid catalyst. The solid acid catalyst demonstrated good stability that only 9% decrease in TRS concentration was observed after five repeat uses. The as-prepared carbon-based solid acid catalyst can be an environmentally benign replacement for homogeneous catalyst. - Highlights: • Carbon solid acid was successfully prepared by one-step hydrothermal carbonization. • The acrylic acid as monomer was effectively reduce the diameter size of particle. • The solid acid catalyst show good catalytic performance of starch hydrolysis. • The solid acid catalyst is not significantly deteriorated after repeated use.

  6. A review on hydrolytic enzymes in the treatment of wastewater with high oil and grease content.

    PubMed

    Cammarota, M C; Freire, D M G

    2006-11-01

    Wastewater from dairies and slaughterhouses contains high levels of fats and proteins that present low biodegradability. A large number of pretreatment systems are employed to remove oil and grease (O&G) to prevent a host of problems that may otherwise arise in the biological process, and reduce the efficiency of the treatment station. Problems caused by excessive O&G include a reduction in the cell-aqueous phase transfer rates, a sedimentation hindrance due to the development of filamentous microorganisms, development and flotation of sludge with poor activity, clogging and the emergence of unpleasant odors. Therefore the application of a pretreatment to hydrolyze and dissolve lipids may improve the biological degradation of fatty wastewaters, accelerating the process and improving time efficiency. However thus far, only a few studies describing the degradation of fats and oils by alkaline/acid/enzymatic hydrolysis have been reported; the treatment of effluents from several origins is a new and promising application for lipases. Among the strains that produce the hydrolytic enzymes studied, the fungus Penicillium restrictum is a particularly promising one. When cultivated in low-cost solid medium composed of agro-industrial waste, P. restrictum produces a pool of hydrolases capable of degrading the most complex organic compounds. This degradation enables a considerable increase in organic matter removal efficiency to be realized, which results in the attainment of a high-quality effluent in the subsequent biological treatment stage. Consequently, there is presently a wide variety of ongoing scientific investigation in the field of developing enzymatic hydrolysis processes to precede traditional biological treatment.

  7. The acid-base titration of montmorillonite

    NASA Astrophysics Data System (ADS)

    Bourg, I. C.; Sposito, G.; Bourg, A. C.

    2003-12-01

    Proton binding to clay minerals plays an important role in the chemical reactivity of soils (e.g., acidification, retention of nutrients or pollutants). If should also affect the performance of clay barriers for waste disposal. The surface acidity of clay minerals is commonly modelled empirically by assuming generic amphoteric surface sites (>SOH) on a flat surface, with fitted site densities and acidity constant. Current advances in experimental methods (notably spectroscopy) are rapidly improving our understanding of the structure and reactivity of the surface of clay minerals (arrangement of the particles, nature of the reactive surface sites, adsorption mechanisms). These developments are motivated by the difficulty of modelling the surface chemistry of mineral surfaces at the macro-scale (e.g., adsorption or titration) without a detailed (molecular-scale) picture of the mechanisms, and should be progressively incorporated into surface complexation models. In this view, we have combined recent estimates of montmorillonite surface properties (surface site density and structure, edge surface area, surface electrostatic potential) with surface site acidities obtained from the titration of alpha-Al2O3 and SiO2, and a novel method of accounting for the unknown initial net proton surface charge of the solid. The model predictions were compared to experimental titrations of SWy-1 montmorillonite and purified MX-80 bentonite in 0.1-0.5 mol/L NaClO4 and 0.005-0.5 mol/L NaNO3 background electrolytes, respectively. Most of the experimental data were appropriately described by the model after we adjusted a single parameter (silanol sites on the surface of montmorillonite were made to be slightly more acidic than those of silica). At low ionic strength and acidic pH the model underestimated the buffering capacity of the montmorillonite, perhaps due to clay swelling or to the interlayer adsorption of dissolved aluminum. The agreement between our model and the experimental

  8. Differential titration of bases in glacial acetic acid.

    PubMed

    Castellano, T; Medwick, T; Shinkai, J H; Bailey, L

    1981-01-01

    A study of bases in acetic acid and their differential titration was carried out. The overall basicity constants for 20 bases were measured in acetic acid, and the differential titration of five binary mixtures of variable delta pKb values in acetic acid was followed using a glass electrode-modified calomel electrode system. Agreement with literature values was good. A leveling diagram was constructed that indicated that bases stronger than aqueous pKb 10 are leveled to an acetous pKb 5.69, whereas weaker bases are not leveled but instead exhibit their own intrinsic basicity, with the acetous pKb to aqueous pKb values being linearly related (slope 1.18, correlation coefficient 0.962). A minimum acetous delta pKb of four units is required for the satisfactory differential titration of two bases in acetic acid.

  9. Acid-base status in dietary treatment of phenylketonuria.

    PubMed

    Manz, F; Schmidt, H; Schärer, K; Bickel, H

    1977-10-01

    Blood acid-base status, serum electrolytes, and urine pH were examined in 64 infants and children with phenylketonuria (PKU) treated with three different low phenylalanine protein hydrolyzates (Aponti, Cymogran, AlbumaidXP) and two synthetic amino acid mixtures (Aminogran, PAM). The formulas caused significant differences in acid-base status, serum potassium, and chloride, and in urine pH. In acid-base balance studies in two patients with PKU, Aponti, PAM, and two modifications of PAM (P2 + P3) were given. We observed a change from mild alkalosis to increasing metabolic acidosis from Aponti (serum bicarbonate 25,8 mval/liter) to P3 (24,0Y, P2 (19, 3) and PAM (17,0). Urine pH decreased and renal net acid excretion increased. In the formulas PAM, P2 and P3 differences in renal net acid excretion correlated with differences in chloride and sulfur contents of the diets and of the urines. New modifications of AlbumaidXP and of PAM, prepared according to our recommendations, showed normal renal net acid excretion (1 mEq/kg/24 hr) in a balance study performed in one patient with PKU and normal acid base status in 20 further patients.

  10. Potentiometric Acid-Base Titrations with Activated Graphite Electrodes

    NASA Astrophysics Data System (ADS)

    Riyazuddin, P.; Devika, D.

    1997-10-01

    Dry cell graphite (DCG) electrodes activated with potassium permanganate are employed as potentiometric indicator electrodes for acid-base titrations. Special attention is given to an indicator probe comprising activated DCG-non-activiated DCG electrode couple. This combination also proves suitable for the titration of strong or weak acids.

  11. Nucleic acid based fluorescent sensor for mercury detection

    DOEpatents

    Lu, Yi; Liu, Juewen

    2013-02-05

    A nucleic acid enzyme comprises an oligonucleotide containing thymine bases. The nucleic acid enzyme is dependent on both Hg.sup.2+and a second ion as cofactors, to produce a product from a substrate. The substrate comprises a ribonucleotide, a deoxyribonucleotide, or both.

  12. Aqueous solution synthesis of Pt-M (M = Fe, Co, Ni) bimetallic nanoparticles and their catalysis for the hydrolytic dehydrogenation of ammonia borane.

    PubMed

    Wang, Shuai; Zhang, Duo; Ma, Yanyun; Zhang, Hui; Gao, Jing; Nie, Yuting; Sun, Xuhui

    2014-08-13

    Platinum-based bimetallic nanocatalysts have attracted much attention due to their high-efficiency catalytic performance in energy-related applications such as fuel cell and hydrogen storage, for example, the hydrolytic dehydrogenation of ammonia borane (AB). In this work, a simple and green method has been demonstrated to successfully prepare Pt-M (M = Fe, Co, Ni) NPs with tunable composition (nominal Pt/M atomic ratios of 4:1, 1:1, and 1:4) in aqueous solution under mild conditions. All Pt-M NPs with a small size of 3-5 nm show a Pt fcc structure, suggesting the bimetallic formation (alloy and/or partial core-shell), examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray absorption fine structure (XAFS) analysis. The catalytic activities of Pt-M NPs in the hydrolytic dehydrogenation of AB reveal that Pt-Ni NPs with a ratio of 4:1 show the best catalytic activity and even better than that of pure Pt NPs when normalized to Pt molar amount. The Ni oxidation state in Pt-Ni NPs has been suggested to be responsible for the corresponding catalytic activity for hydrolytic dehydrogenation of AB by XAFS study. This strategy for the synthesis of Pt-M NPs is simple and environmentally benign in aqueous solution with the potential for scale-up preparation and the in situ catalytic reaction. PMID:25058566

  13. Hydraulic retention time impact of treated recirculated leachate on the hydrolytic kinetic rate of coffee pulp in an acidogenic reactor.

    PubMed

    Houbron, E; González-López, G I; Cano-Lozano, V; Rustrían, E

    2008-01-01

    This study attempted to investigate the impact of HRT of treated leachate recirculation on hydrolysis solubilization rate of coffee pulp in an acidogenic reactor. Coffee pulp presents more than 70% of organic matter and around of 30% of lignin and cellulose. Five lab scale reactors of 20 litres were used. Each reactor was fed with 5 kg of fresh coffee pulp and anaerobic sludge was used as inoculate. HRT of 0.5, 1, 3 and 10 days were applied. Each experiment shows that Total, Soluble and VFA COD appear rapidly in the removed leachate. HRT have a great impact on hydrolytic rate with an optimal value of 32,000 mg x L(-1) x d(-1).Low HRT increases hydrolysis rate and in consequence reduces duration of the hydrolytic phase. Also composition and concentration of VFA are influenced by HRT. Low ones favour acetic acid production and high ones permit the production of butyric. Low HRT generates leachate more easily fermentable. Efficiency of solubilization and acidification are independent of the HRT and present average values of 78% and 65% respectively. By batch feeding solid and continuous recirculation of treated leachate, HRT and SRT could be dissociated, where solid had a very high retention without problems of load, mixing and inhibition, and liquid could be recirculated with a very high rate. Under these low HRT condition, the first reactor of a two stage anaerobic system could reduces the hydrolysis duration of organic solid waste like coffee pulp and generate an optimal leachate for the methanization process.

  14. Acid-base titration curves for acids with very small ratios of successive dissociation constants.

    PubMed

    Campbell, B H; Meites, L

    1974-02-01

    The shapes of the potentiometric acid-base titration curves obtained in the neutralizations of polyfunctional acids or bases for which each successive dissociation constant is smaller than the following one are examined. In the region 0 < < 1 (where is the fraction of the equivalent volume of reagent that has been added) the slope of the titration curve decreases as the number j of acidic or basic sites increases. The difference between the pH-values at = 0.75 and = 0.25 has (1 j)log 9 as the lower limit of its maximum value.

  15. Renal acidification responses to respiratory acid-base disorders.

    PubMed

    Madias, Nicolaos E

    2010-01-01

    Respiratory acid-base disorders are those abnormalities in acid-base equilibrium that are expressed as primary changes in the arterial carbon dioxide tension (PaCO2). An increase in PaCO2 (hypercapnia) acidifies body fluids and initiates the acid-base disturbance known as respiratory acidosis. By contrast, a decrease in PaCO2 (hypocapnia) alkalinizes body fluids and initiates the acid-base disturbance known as respiratory alkalosis. The impact on systemic acidity of these primary changes in PaCO2 is ameliorated by secondary, directional changes in plasma [HCO3¯] that occur in 2 stages. Acutely, hypercapnia or hypocapnia yields relatively small changes in plasma [HCO3¯] that originate virtually exclusively from titration of the body's nonbicarbonate buffers. During sustained hypercapnia or hypocapnia, much larger changes in plasma [HCO3¯] occur that reflect adjustments in renal acidification mechanisms. Consequently, the deviation of systemic acidity from normal is smaller in the chronic forms of these disorders. Here we provide an overview of the renal acidification responses to respiratory acid-base disorders. We also identify gaps in knowledge that require further research.

  16. An Olfactory Indicator for Acid-Base Titrations.

    ERIC Educational Resources Information Center

    Flair, Mark N.; Setzer, William N.

    1990-01-01

    The use of an olfactory acid-base indicator in titrations for visually impaired students is discussed. Potential olfactory indicators include eugenol, thymol, vanillin, and thiophenol. Titrations performed with each indicator with eugenol proved to be successful. (KR)

  17. Biologist's Toolbox. Acid-base Balance: An Educational Computer Game.

    ERIC Educational Resources Information Center

    Boyle, Joseph, III; Robinson, Gloria

    1987-01-01

    Describes a microcomputer program that can be used in teaching the basic physiological aspects of acid-base (AB) balance. Explains how its game format and graphic approach can be applied in diagnostic and therapeutic exercises. (ML)

  18. Towards lactic acid bacteria-based biorefineries.

    PubMed

    Mazzoli, Roberto; Bosco, Francesca; Mizrahi, Itzhak; Bayer, Edward A; Pessione, Enrica

    2014-11-15

    Lactic acid bacteria (LAB) have long been used in industrial applications mainly as starters for food fermentation or as biocontrol agents or as probiotics. However, LAB possess several characteristics that render them among the most promising candidates for use in future biorefineries in converting plant-derived biomass-either from dedicated crops or from municipal/industrial solid wastes-into biofuels and high value-added products. Lactic acid, their main fermentation product, is an attractive building block extensively used by the chemical industry, owing to the potential for production of polylactides as biodegradable and biocompatible plastic alternative to polymers derived from petrochemicals. LA is but one of many high-value compounds which can be produced by LAB fermentation, which also include biofuels such as ethanol and butanol, biodegradable plastic polymers, exopolysaccharides, antimicrobial agents, health-promoting substances and nutraceuticals. Furthermore, several LAB strains have ascertained probiotic properties, and their biomass can be considered a high-value product. The present contribution aims to provide an extensive overview of the main industrial applications of LAB and future perspectives concerning their utilization in biorefineries. Strategies will be described in detail for developing LAB strains with broader substrate metabolic capacity for fermentation of cheaper biomass.

  19. Towards lactic acid bacteria-based biorefineries.

    PubMed

    Mazzoli, Roberto; Bosco, Francesca; Mizrahi, Itzhak; Bayer, Edward A; Pessione, Enrica

    2014-11-15

    Lactic acid bacteria (LAB) have long been used in industrial applications mainly as starters for food fermentation or as biocontrol agents or as probiotics. However, LAB possess several characteristics that render them among the most promising candidates for use in future biorefineries in converting plant-derived biomass-either from dedicated crops or from municipal/industrial solid wastes-into biofuels and high value-added products. Lactic acid, their main fermentation product, is an attractive building block extensively used by the chemical industry, owing to the potential for production of polylactides as biodegradable and biocompatible plastic alternative to polymers derived from petrochemicals. LA is but one of many high-value compounds which can be produced by LAB fermentation, which also include biofuels such as ethanol and butanol, biodegradable plastic polymers, exopolysaccharides, antimicrobial agents, health-promoting substances and nutraceuticals. Furthermore, several LAB strains have ascertained probiotic properties, and their biomass can be considered a high-value product. The present contribution aims to provide an extensive overview of the main industrial applications of LAB and future perspectives concerning their utilization in biorefineries. Strategies will be described in detail for developing LAB strains with broader substrate metabolic capacity for fermentation of cheaper biomass. PMID:25087936

  20. Synthesis and antimicrobial activities of new higher amino acid Schiff base derivatives of 6-aminopenicillanic acid and 7-aminocephalosporanic acid

    NASA Astrophysics Data System (ADS)

    Özdemir (nee Güngör), Özlem; Gürkan, Perihan; Özçelik, Berrin; Oyardı, Özlem

    2016-02-01

    Novel β-lactam derivatives (1c-3c) (1d-3d) were produced by using 6-aminopenicillanic acid (6-APA), 7-aminocephalosporanic acid (7-ACA) and the higher amino acid Schiff bases. The synthesized compounds were characterized by elemental analysis, IR, 1H/13C NMR and UV-vis spectra. Antibacterial activities of all the higher amino acid Schiff bases (1a-3a) (1b-3b) and β-lactam derivatives were screened against three gram negative bacteria (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Acinetobacter baumannii RSKK 02026), three gram positive bacteria (Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 07005, Bacillus subtilis ATCC 6633) and their drug-resistant isolates by using broth microdilution method. Two fungi (Candida albicans and Candida krusei) were used for antifungal activity.

  1. Acid-base homeostasis in the human system

    NASA Technical Reports Server (NTRS)

    White, R. J.

    1974-01-01

    Acid-base regulation is a cooperative phenomena in vivo with body fluids, extracellular and intracellular buffers, lungs, and kidneys all playing important roles. The present account is much too brief to be considered a review of present knowledge of these regulatory systems, and should be viewed, instead, as a guide to the elements necessary to construct a simple model of the mutual interactions of the acid-base regulatory systems of the body.

  2. Acid Base Titrations in Nonaqueous Solvents and Solvent Mixtures

    NASA Astrophysics Data System (ADS)

    Barcza, Lajos; Buvári-Barcza, Ágnes

    2003-07-01

    The acid base determination of different substances by nonaqueous titrations is highly preferred in pharmaceutical analyses since the method is quantitative, exact, and reproducible. The modern interpretation of the reactions in nonaqueous solvents started in the last century, but several inconsistencies and unsolved problems can be found in the literature. The acid base theories of Brønsted Lowry and Lewis as well as the so-called solvent theory are outlined first, then the promoting (and leveling) and the differentiating effects are discussed on the basis of the hydrogen-bond concept. Emphasis is put on the properties of formic acid and acetic anhydride since their importance is increasing.

  3. Carbonic anhydrase and acid-base regulation in fish.

    PubMed

    Gilmour, K M; Perry, S F

    2009-06-01

    Carbonic anhydrase (CA) is the zinc metalloenzyme that catalyses the reversible reactions of CO(2) with water. CA plays a crucial role in systemic acid-base regulation in fish by providing acid-base equivalents for exchange with the environment. Unlike air-breathing vertebrates, which frequently utilize alterations of breathing (respiratory compensation) to regulate acid-base status, acid-base balance in fish relies almost entirely upon the direct exchange of acid-base equivalents with the environment (metabolic compensation). The gill is the critical site of metabolic compensation, with the kidney playing a supporting role. At the gill, cytosolic CA catalyses the hydration of CO(2) to H(+) and HCO(3)(-) for export to the water. In the kidney, cytosolic and membrane-bound CA isoforms have been implicated in HCO(3)(-) reabsorption and urine acidification. In this review, the CA isoforms that have been identified to date in fish will be discussed together with their tissue localizations and roles in systemic acid-base regulation.

  4. An Acid-Base Chemistry Example: Conversion of Nicotine

    NASA Astrophysics Data System (ADS)

    Summerfield, John H.

    1999-10-01

    The current government interest in nicotine conversion by cigarette companies provides an example of acid-base chemistry that can be explained to students in the second semester of general chemistry. In particular, the conversion by ammonia of the +1 form of nicotine to the easier-to-assimilate free-base form illustrates the effect of pH on acid-base equilibrium. The part played by ammonia in tobacco smoke is analogous to what takes place when cocaine is "free-based".

  5. Swollenin from Trichoderma reesei exhibits hydrolytic activity against cellulosic substrates with features of both endoglucanases and cellobiohydrolases.

    PubMed

    Andberg, Martina; Penttilä, Merja; Saloheimo, Markku

    2015-04-01

    The cellulolytic and hemicellulolytic enzymes of Trichoderma reesei comprise one of the best characterised enzyme systems involved in lignocellulose degradation. In this paper, swollenin (SWOI), a protein recognised based on its sequence similarity with plant expansins, has been characterised. SWOI and its catalytic domain were subjected to analysis of their hydrolytic activity on different soluble carbohydrate polymers. By measuring the production of reducing ends, zymogram-, and viscosity analysis, SWOI was shown to have activity on substrates containing β-1,4 glucosidic bonds, i.e. carboxymethyl cellulose, hydroxyethyl cellulose and β-glucan. The formation of oligosaccharides from β-glucan was analysed by HPLC and showed cellobiose as the main reaction product. SWOI was also able to hydrolyse soluble cello-oligosaccharides and the products formed were all consistent with SWOI cleaving a cellobiose unit off the substrate. In conclusion, the T. reesei swollenin showed a unique mode of action with similarities with action of both endoglucanases and cellobiohydrolases. PMID:25643956

  6. Investigations on hydrolytic activities from Stachybotrys microspora and their use as an alternative in yeast DNA extraction.

    PubMed

    Abdeljalil, Salma; Ben Hmad, Ines; Saibi, Walid; Amouri, Bahia; Maalej, Wiem; Kaaniche, Marwa; Koubaa, Aida; Gargouri, Ali

    2014-02-01

    Stachybotrys microspora is a filamentous fungus characterized by the secretion of multiple hydrolytic activities (cellulolytic and non-cellulolytic enzymes). The production of these biocatalysts was studied under submerged culture using glucose, cellulose, and wheat bran as carbon sources. Endoglucanases, pectinases, xylanases, β-glucanases, chitinases, and proteases were induced on cellulose-based medium and repressed on glucose in both strains with higher amounts produced by the mutant. β-glucosidases were roughly equally produced by both strains under glucose and cellulose conditions. The yield of chitinases, β-glucanases, and proteases produced by Stachybotrys strains was as much higher than the commercialized lysing enzyme called "zymolyase," currently used in yeast DNA extraction. In this context, we showed that S. microspora hydrolases can be successfully applied in the extraction of yeast DNA.

  7. Roles of urea production, ammonium excretion, and amino acid oxidation in acid-base balance.

    PubMed

    Mackenzie, W

    1986-02-01

    Atkinson and colleagues recently proposed several concepts that contrast with traditional views: first, that acid-base balance is regulated chiefly by the reactions leading to urea production in the liver; second, that ammonium excretion by the kidney plays no role in acid-base homeostasis; and third, that ammonium does not stimulate ureagenesis (except indirectly). To examine these concepts, plasma ions other than bicarbonate are categorized as 1) fixed cations (Na+, K+, Ca2+, and Mg2+, symbolized M+) and anions (Cl-), 2) buffer anions (A-), 3) other anions (X-), and 4) ammonium plus charged amino groups (N+). Since electroneutrality dictates that M+ + N+ = Cl- + HCO3- + A- + X-, it follows that delta HCO3- = delta(M+ - Cl-) - delta A- - delta X- + delta N+. Therefore acid-base disturbances (changes in HCO3-) can be categorized as to how they affect bodily content and hence plasma concentration of each of these four types of ions. The stoichiometry of ureagenesis, glutamine hydrolysis, ammonium and titratable acid excretion, oxidation of neutral, acidic, and basic amino acids, and oxidation of methionine, phosphoserine, and protein are examined to see how they alter these quantities. It is concluded that 1) although ureagenesis is pH dependent and also counteracts a tendency of amino acid oxidation to cause alkalosis, this tendency is inherently limited by the hyperammonemia (delta N+) that necessarily accompanies it, 2) ammonium excretion is equivalent to hydrogen excretion in its effects on acid-base balance if, and only if, it occurs in exchange for sodium or is accompanied by chloride excretion and only when the glutamate generated by glutamine hydrolysis is oxidized.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3511732

  8. Role of acids and bases in nanoparticle growth

    NASA Astrophysics Data System (ADS)

    Yli-Juuti, Taina; Barsanti, Kelley; Bzdek, Bryan; Hildebrandt Ruiz, Lea; Jokinen, Tuija; Kieloaho, Antti-Jussi; Makkonen, Ulla; Petäjä, Tuukka; Ruuskanen, Taina; Johnston, Murray; Kulmala, Markku; Riipinen, Ilona

    2014-05-01

    Secondary aerosol particles that are formed in atmosphere by gas-to-particle conversion during new particle formation events have potential to affect climate significantly due to their typically high number concentrations. This, however, requires that the freshly formed nanoparticles of about 1 nm in diameter grow tens of nanometers and reach climatically relevant sizes, i.e. sizes where they can act as cloud condensation nuclei. During the growth towards larger sizes the nanoparticles are subject to coagulational losses, and the rate at which the nanoparticles grow by condensation of vapors is a key factor affecting their probability to survive to climatically relevant sizes. Vapors that condense on the nanoparticles can be produced in the atmosphere from volatile compounds through gas phase chemical reactions, and their volatility can also be further lowered by particle phase processes. Therefore, particle composition and particle phase processes may influence nanoparticle growth. We study the growth of atmospheric nanoparticles and especially the role of particle phase salt formation in the nanoparticle growth using MABNAG model (Model for Acid-Base chemistry in NAnoparticle Growth) and by comparing to atmospheric measurements. MABNAG is a condensation growth model for aqueous solution particles. In MABNAG the dynamics of gas phase mass transport of vapors to particle are coupled with thermodynamics of particle phase acid-base chemistry, and both the composition and size dependence of equilibrium vapor pressures are accounted for. The model is applied especially for boreal forest environment. Here nanoparticle growth is modeled with a system of water, two acids (sulfuric acid and an organic acid) and two bases (ammonia and an amine) as condensing vapors. Focus is on the neutralization of acids by the bases and the related effects on the particle growth. According to the model predictions the enhancement of condensation of organic acid due to salt formation is

  9. In vitro hydrolytic digestion, glycemic response in dogs, and true metabolizable energy content of soluble corn fibers.

    PubMed

    de Godoy, M R C; Knapp, B K; Parsons, C M; Swanson, K S; Fahey, George C

    2014-06-01

    The objective of this research was to measure in vitro hydrolytic digestion, glycemic and insulinemic responses in dogs, and true ME (TMEn) content of select soluble corn fibers (SCF) in roosters. The first generation (G1) SCF included hydrochloric acid-treated corn syrup (G1-CS-HCl), an SCF with an increased total dietary fiber (TDF) content (G1-SCF-HCl), an SCF that was spray-dried (G1-SCF-SD), and a hydrogenated SCF (G1-SCF-hydrog). The second generation (G2) SCF included those prepared using phosphoric acid catalyzation in both a liquid [G2-SCF-phos (Lq)] and powder [G2-SCF-phos (Pw)] form, and SCF that were prepared using hydrochloric acid catalyzation in both a liquid [G2-SCF-HCl (Lq)] and powder [G2-SCF-HCl (Pw)] form. Also, in the G2 set of samples were SCF prepared using the same method, but in 3 separate batches, all of which contained 70% TDF and 15% sugars. Two were in liquid form [G2-SCF-phos+HCl (Lq1)] and [G2-SCF-phos+HCl (Lq2)], and one in powder form ([G2-SCF-phos+HCl (Pw)]. A lower sugar form (80% TDF and 5% sugar) of SCF was also evaluated (G2-SCF-low sugar). Glucose was the major free sugar and bound monosaccharide in all SCF except for G1-SCF-hydrog that had greater concentrations of sorbitol. All SCF had intermediate to low amounts of monosaccharides released as a result of in vitro hydrolytic digestion, with glucose being the primary sugar component released. The G1-SCF were more digestible in vitro (approximately 50%) compared to G2-SCF (approximately 32%). All SCF had attenuated glycemic responses in adult dogs compared to a maltodextrin control (P < 0.05). The G2-SCF, on average, had lower glycemic responses and TMEn values in roosters than G1-SCF. All SCF had low free sugar concentrations with varying degrees of resistance to digestion, reduced caloric content, and attenuated glycemic and insulinemic responses in adult dogs. These ingredients are potential candidates for inclusion in reduced calorie and low glycemic canine diets.

  10. Poly (ricinoleic acid) based novel thermosetting elastomer.

    PubMed

    Ebata, Hiroki; Yasuda, Mayumi; Toshima, Kazunobu; Matsumura, Shuichi

    2008-01-01

    A novel bio-based thermosetting elastomer was prepared by the lipase-catalyzed polymerization of methyl ricinoleate with subsequent vulcanization. Some mechanical properties of the cured carbon black-filled polyricinoleate compounds were evaluated as a thermosetting elastomer. It was found that the carbon black-filled polyricinoleate compounds were readily cured by sulfur curatives to produce a thermosetting elastomer that formed a rubber-like sheet with a smooth and non-sticky surface. The curing behaviors and mechanical properties were dependent on both the molecular weight of the polyricinoleate and the amount of the sulfur curatives. Cured compounds consisting of polyricinoleate with a molecular weight of 100,800 showed good mechanical properties, such as a hardness of 48 A based on the durometer A measurements, a tensile strength at break of 6.91 MPa and an elongation at break of 350%. PMID:18469493

  11. Biocompatible hydrogels based on hyaluronic acid cross-linked with a polyaspartamide derivative as delivery systems for epithelial limbal cells.

    PubMed

    Fiorica, Calogero; Senior, Richard A; Pitarresi, Giovanna; Palumbo, Fabio Salvatore; Giammona, Gaetano; Deshpande, Pallavi; MacNeil, Sheila

    2011-07-29

    The aim of this work was to evaluate the potential use of hydrogels based on hyaluronic acid (HA) chemically cross-linked with α,β-poly(N-2-hydroxyethyl) (2-aminoethylcarbamate)-D,L-aspartamide (PHEA-EDA) as substitutes for the amniotic membrane able to release limbal cells for corneal regeneration. Hydrogels, shaped as films, with three different molar ratios (X) between PHEA-EDA and HA (X = 0.5, 1.0 and 1.5) have been investigated. First, it has been evaluated their swelling ability, hydrolytic resistance in simulated physiological fluid and cell compatibility by using human dermal fibroblasts chosen as a model cell line. Then adhesion studies in comparison with collagen gel, have been performed by using immortalized cells, such as human corneal epithelial cells (HCEC) or primary cells, such as rabbit limbal epithelial cells (RLEC) and/or rabbit limbal fibroblasts (RLF). HA/PHEA-EDA hydrogels allow a moderate/poor adhesion of all investigated cells thus suggesting their potential ability to act as cell delivery systems. Finally, commercial contact lenses have been coated, in their inner surface, with each HA/PHEA-EDA film and it has been found that in these conditions, a greater cell adhesion occurs, particularly when RLEC are in co-culture with RLF. However, this adhesion is only transitory, in fact after three days, viable cells are released in the culture medium thus suggesting a potential application of HA/PHEA-EDA hydrogels, for delivering limbal cells in the treatment of corneal damage.

  12. Study on the effects of heating of virgin olive oil blended with mildly deodorized olive oil: focus on the hydrolytic and oxidative state.

    PubMed

    Bendini, Alessandra; Valli, Enrico; Cerretani, Lorenzo; Chiavaro, Emma; Lercker, Giovanni

    2009-11-11

    In this study, mildly deodorized olive oil (DEO) and its admixtures with extra virgin olive oil (EVOO) have been analyzed after heating treatments by microwave and conventional oven. Different patterns in oxidative and hydrolytic degradation of lipids in genuine and sophisticated olive oils have been evaluated by chromatographic and spectroscopic methods and related to heating treatments. The experimental plan focused on the assessment of the (a) hydrolytic degree of the samples by the free acidity and the 1,2- and 1,3-diacylglycerols (DAG) determinations; (b) oxidative status of the samples by the assessment of the peroxide value (POV) and oxidized fatty acid (OFA), the specific absorption at 270 nm (k(270)), the accelerated aging test (OSI) and volatile compounds. In general, the thermal treatment by conventional oven led to a higher content of 1,3-DAG and secondary oxidation products than microwave heating. A duo-trio sensory test was also performed: tasters were not able to discriminate between EVOO and DEO heated by conventional oven whereas they were when oils were microwaved.

  13. Micellar acid-base potentiometric titrations of weak acidic and/or insoluble drugs.

    PubMed

    Gerakis, A M; Koupparis, M A; Efstathiou, C E

    1993-01-01

    The effect of various surfactants [the cationics cetyl trimethyl ammonium bromide (CTAB) and cetyl pyridinium chloride (CPC), the anionic sodium dodecyl sulphate (SDS), and the nonionic polysorbate 80 (Tween 80)] on the solubility and ionization constant of some sparingly soluble weak acids of pharmaceutical interest was studied. Benzoic acid (and its 3-methyl-, 3-nitro-, and 4-tert-butyl-derivatives), acetylsalicylic acid, naproxen and iopanoic acid were chosen as model examples. Precise and accurate acid-base titrations in micellar systems were made feasible using a microcomputer-controlled titrator. The response curve, response time and potential drift of the glass electrode in the micellar systems were examined. The cationics CTAB and CPC were found to increase considerably the ionization constant of the weak acids (delta pKa ranged from -0.21 to -3.57), while the anionic SDS showed negligible effect and the nonionic Tween 80 generally decreased the ionization constants. The solubility of the acids in aqueous micellar and acidified micellar solutions was studied spectrophotometrically and it was found increased in all cases. Acetylsalicylic acid, naproxen, benzoic acid and iopanoic acid could be easily determined in raw material and some of them in pharmaceutical preparations by direct titration in CTAB-micellar system instead of using the traditional non-aqueous or back titrimetry. Precisions of 0.3-4.3% RSD and good correlation with the official tedious methods were obtained. The interference study of some excipients showed that a preliminary test should be carried out before the assay of formulations.

  14. Soil Studies: Applying Acid-Base Chemistry to Environmental Analysis.

    ERIC Educational Resources Information Center

    West, Donna M.; Sterling, Donna R.

    2001-01-01

    Laboratory activities for chemistry students focus attention on the use of acid-base chemistry to examine environmental conditions. After using standard laboratory procedures to analyze soil and rainwater samples, students use web-based resources to interpret their findings. Uses CBL probes and graphing calculators to gather and analyze data and…

  15. High School Students' Concepts of Acids and Bases.

    ERIC Educational Resources Information Center

    Ross, Bertram H. B.

    An investigation of Ontario high school students' understanding of acids and bases with quantitative and qualitative methods revealed misconceptions. A concept map, based on the objectives of the Chemistry Curriculum Guideline, generated multiple-choice items and interview questions. The multiple-choice test was administered to 34 grade 12…

  16. A computational study of ultrafast acid dissociation and acid-base neutralization reactions. I. The model.

    PubMed

    Maurer, Patrick; Thomas, Vibin; Rivard, Ugo; Iftimie, Radu

    2010-07-28

    Ultrafast, time-resolved investigations of acid-base neutralization reactions have recently been performed using systems containing the photoacid 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) and various Bronsted bases. Two conflicting neutralization mechanisms have been formulated by Mohammed et al. [Science 310, 83 (2005)] and Siwick et al. [J. Am. Chem. Soc. 129, 13412 (2007)] for the same acid-base system. Herein an ab initio molecular dynamics based computational model is formulated, which is able to investigate the validity of the proposed mechanisms in the general context of ground-state acid-base neutralization reactions. Our approach consists of using 2,4,6-tricyanophenol (exp. pKa congruent with 1) as a model for excited-state HPTS( *) (pKa congruent with 1.4) and carboxylate ions for the accepting base. We employ our recently proposed dipole-field/quantum mechanics (QM) treatment [P. Maurer and R. Iftimie, J. Chem. Phys. 132, 074112 (2010)] of the proton donor and acceptor molecules. This approach allows one to tune the free energy of neutralization to any desired value as well as model initial nonequilibrium hydration effects caused by a sudden increase in acidity, making it possible to achieve a more realistic comparison with experimental data than could be obtained via a full-QM treatment of the entire system. It is demonstrated that the dipole-field/QM model reproduces correctly key properties of the 2,4,6-tricyanophenol acid molecule including gas-phase proton dissociation energies and dipole moments, and condensed-phase hydration structure and pKa values.

  17. A computational study of ultrafast acid dissociation and acid-base neutralization reactions. I. The model

    NASA Astrophysics Data System (ADS)

    Maurer, Patrick; Thomas, Vibin; Rivard, Ugo; Iftimie, Radu

    2010-07-01

    Ultrafast, time-resolved investigations of acid-base neutralization reactions have recently been performed using systems containing the photoacid 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) and various Brønsted bases. Two conflicting neutralization mechanisms have been formulated by Mohammed et al. [Science 310, 83 (2005)] and Siwick et al. [J. Am. Chem. Soc. 129, 13412 (2007)] for the same acid-base system. Herein an ab initio molecular dynamics based computational model is formulated, which is able to investigate the validity of the proposed mechanisms in the general context of ground-state acid-base neutralization reactions. Our approach consists of using 2,4,6-tricyanophenol (exp. pKa≅1) as a model for excited-state HPTS∗ (pKa≅1.4) and carboxylate ions for the accepting base. We employ our recently proposed dipole-field/quantum mechanics (QM) treatment [P. Maurer and R. Iftimie, J. Chem. Phys. 132, 074112 (2010)] of the proton donor and acceptor molecules. This approach allows one to tune the free energy of neutralization to any desired value as well as model initial nonequilibrium hydration effects caused by a sudden increase in acidity, making it possible to achieve a more realistic comparison with experimental data than could be obtained via a full-QM treatment of the entire system. It is demonstrated that the dipole-field/QM model reproduces correctly key properties of the 2,4,6-tricyanophenol acid molecule including gas-phase proton dissociation energies and dipole moments, and condensed-phase hydration structure and pKa values.

  18. Acid-base properties of humic and fulvic acids formed during composting.

    PubMed

    Plaza, César; Senesi, Nicola; Polo, Alfredo; Brunetti, Gennaro

    2005-09-15

    The soil acid-base buffering capacity and the biological availability, mobilization, and transport of macro- and micronutrients, toxic metal ions, and xenobiotic organic cations in soil are strongly influenced by the acid-base properties of humic substances, of which humic and fulvic acids are the major fractions. For these reasons, the proton binding behavior of the humic acid-like (HA) and fulvic acid-like (FA) fractions contained in a compost are believed to be instrumental in its successful performance in soil. In this work, the acid-base properties of the HAs and FAs isolated from a mixture of the sludge residue obtained from olive oil mill wastewater (OMW) evaporated in an open-air pond and tree cuttings (TC) at different stages of composting were investigated by a current potentiometric titration method and the nonideal competitive adsorption (NICA)-Donnan model. The NICA-Donnan model provided an excellent description of the acid-base titration data, and pointed out substantial differences in site density and proton-binding affinity between the HAs and FAs examined. With respect to FAs, HAs were characterized by a smaller content of carboxylic- and phenolic-type groups and their larger affinities for proton binding. Further, HAs featured a greater heterogeneity in carboxylic-type groups than FAs. The composting process increased the content and decreased the proton affinity of carboxylic- and phenolic-type groups of HAs and FAs, and increased the heterogeneity of phenolic-type groups of HAs. As a whole, these effects indicated that the composting process could produce HA and FA fractions with greater cation binding capacities. These results suggest that composting of organic materials improves their agronomic and environmental value by increasing their potential to retain and exchange macro- and micronutrients, and to reduce the bioavailability of organic and inorganic pollutants.

  19. Deoxyribonucleic acid base compositions of dermatophytes.

    PubMed

    Davison, F D; Mackenzie, D W; Owen, R J

    1980-06-01

    DNA was extracted and purified from 55 dermatophyte isolates representing 34 species of Trichophyton, Microsporum and Epidermophyton. The base compositions of the chromosomal DNA were determined by CsCl density gradient centrifugation and were found to be in the narrow range of 48.7 to 50.3 mol % G + C. A satellite DNA component assumed to be of mitochondrial origin was present in most strains, with a G + C content ranging from 14.7 to 30.8 mol % G + C. Heterogeneity in microscopic and colonial characteristics was not reflected in differences in the mean G + C content of the chromosomal DNAs. Strains varied in the G + C contents of satelite DNA, but these did not correlate with traditional species concepts.

  20. Hydrolytic polymerization of chromium(III). I. Two dimeric species

    SciTech Connect

    Thompson, M.; Connick, R.E.

    1981-07-01

    In addition to the well-known doubly bridged chromium(III) dimer ((H/sub 2/O)/sub 4/Cr(OH)/sub 2/Cr(H/sub 2/O)/sub 4/)/sup 4 +/, a second dimer of formula ((H/sub 2/O)/sub 5/CrOHCr(H/sub 2/O)/sub 5/)/sup 5 +/ has been found. The formula of the latter was established through equilibrium measurements and freezing point depression. The equilibrium between Cr/sup 3 +/ and the doubly bridged dimer was measured at various ionic strengths and temperatures. The equilibrium between the doubly bridged and singly bridged dimers is shifted strongly toward the latter only at high acidities, with roughly equal concentrations at 2 M acid. Electron spin resonance spectra were taken for both dimers in order to obtain g values. The latter were used with magnetic susceptibility measurements to calculate the spin-spin coupling constants between the two chromiums of these species. Comparison is made with the coupling constants of other bridged chromium(III) compounds, and the results are shown to be in reasonable agreement. The striking difference in magnetic susceptibility between the doubly bridged chromium dimer and the iron(III) dimer of empirical formula Fe/sub 2/(OH)/sub 2//sup 4 +/ is discussed in terms of possible structures and electronic interactions.

  1. Quantitative phase analysis and microstructure characterization of magnetite nanocrystals obtained by microwave assisted non-hydrolytic sol–gel synthesis

    SciTech Connect

    Sciancalepore, Corrado; Bondioli, Federica; Manfredini, Tiziano; Gualtieri, Alessandro

    2015-02-15

    An innovative preparation procedure, based on microwave assisted non-hydrolytic sol–gel synthesis, to obtain spherical magnetite nanoparticles was reported together with a detailed quantitative phase analysis and microstructure characterization of the synthetic products. The nanoparticle growth was analyzed as a function of the synthesis time and was described in terms of crystallization degree employing the Rietveld method on the magnetic nanostructured system for the determination of the amorphous content using hematite as internal standard. Product crystallinity increases as the microwave thermal treatment is increased and reaches very high percentages for synthesis times longer than 1 h. Microstructural evolution of nanocrystals was followed by the integral breadth methods to obtain information on the crystallite size-strain distribution. The results of diffraction line profile analysis were compared with nanoparticle grain distribution estimated by dimensional analysis of the transmission electron microscopy (TEM) images. A variation both in the average grain size and in the distribution of the coherently diffraction domains is evidenced, allowing to suppose a relationship between the two quantities. The traditional integral breadth methods have proven to be valid for a rapid assessment of the diffraction line broadening effects in the above-mentioned nanostructured systems and the basic assumption for the correct use of these methods are discussed as well. - Highlights: • Fe{sub 3}O{sub 4} nanocrystals were obtained by MW-assisted non-hydrolytic sol–gel synthesis. • Quantitative phase analysis revealed that crystallinity up to 95% was reached. • The strategy of Rietveld refinements was discussed in details. • Dimensional analysis showed nanoparticles ranging from 4 to 8 nm. • Results of integral breadth methods were compared with microscopic analysis.

  2. Changes in the cell surface of the dimorphic forms of Candida albicans by treatment with hydrolytic enzymes.

    PubMed

    Chattaway, F W; Shenolikar, S; O'Reilly, J; Barlow, A J

    1976-08-01

    The release of acid phosphatase and polysaccharide-peptide complexes by hydrolytic enzymes from the surface of the blastospore and mycelial forms of Candida albicans has been examined in cells from 4 h and 18 h cultures and the results correlated with the appearance of the treated cells in the electron microscope. Treatment with dithiothreitol was necessary for the degradative action of the enzymes to occur. Material released by all the treatments used had a similar qualitative composition, but the proportions of mannan, glucan, peptide and acid phosphatase varied with different treatments and with the type of cell examined. I,3-beta-Glucanase was required for major changes in the cell wall to be effected, but a significant amount of material was released with a chitinase preparation containing some protease activity. Protoplasts were obtained from all types of cell using Cytophaga lytic enzyme L1 which had I,3-beta-glucanase and protease activity, but the purified I,3-beta-glucanase and protease prepared from Streptomyces violaceus cultures required the presence of a chitinase before protoplasts were released. The bonding association between the major components which comprise the cell wall, and the spatial distribution of these macromolecules, varies appreciably between the two dimorphic forms and with the age of the culture. PMID:784907

  3. Hydrolytic charge-reversal of PEGylated polyplexes enhances intracellular un-packaging and activity of siRNA.

    PubMed

    Werfel, Thomas A; Swain, Corban; Nelson, Christopher E; Kilchrist, Kameron V; Evans, Brian C; Miteva, Martina; Duvall, Craig L

    2016-04-01

    Hydrolytically degrading nano-polyplexes (HDG-NPs) that reverse charge through conversion of tertiary amines to carboxylic acids were investigated to improve intracellular un-packaging of siRNA and target gene silencing compared to a non-degradable analog (non-HDG-NPs). Both NP types comprised reversible addition-fragmentation chain-transfer (RAFT) synthesized diblock copolymers of a poly(ethylene glycol) (PEG) corona-forming block and a cationic block for nucleic acid packaging that incorporated butyl methacrylate (BMA) and either dimethylaminoethyl methacrylate (DMAEMA, non-HDG-NPs) or dimethylaminoethyl acrylate (DMAEA, HDG-NPs). HDG-NPs decreased significantly in size and released significantly more siRNA (∼40%) than non-HDG-NPs after 24 h in aqueous solution. While both HDG-NPs and non-HDG-NPs had comparable uptake and cytotoxicity up to 150 nM siRNA doses, HDG-NPs achieved significantly higher target gene silencing of the model gene luciferase in vitro. High resolution FRET confocal microscopy was used to monitor the intracellular un-packaging of siRNA. Non-HDG-NPs had significantly higher FRET efficiency than HDG-NPs, indicating that siRNA delivered from HDG-NPs was more fully un-packaged and therefore had improved intracellular bioavailability.

  4. Acid-Base Titration of (S)-Aspartic Acid: A Circular Dichroism Spectrophotometry Experiment

    NASA Astrophysics Data System (ADS)

    Cavaleiro, Ana M. V.; Pedrosa de Jesus, Júlio D.

    2000-09-01

    The magnitude of the circular dichroism of (S)-aspartic acid in aqueous solutions at a fixed wavelength varies with the addition of strong base. This laboratory experiment consists of the circular dichroism spectrophotometric acid-base titration of (S)-aspartic acid in dilute aqueous solutions, and the use of the resulting data to determine the ionization constant of the protonated amino group. The work familiarizes students with circular dichroism and illustrates the possibility of performing titrations using a less usual instrumental method of following the course of a reaction. It shows the use of a chiroptical property in the determination of the concentration in solution of an optically active molecule, and exemplifies the use of a spectrophotometric titration in the determination of an ionization constant.

  5. Relativistic effects on acidities and basicities of Brønsted acids and bases containing gold.

    PubMed

    Koppel, Ilmar A; Burk, Peeter; Kasemets, Kalev; Koppel, Ivar

    2013-11-01

    It is usually believed that relativistic effects as described by the Dirac-Schrödinger equation (relative to the classical or time-independent Schrödinger equation) are of little importance in chemistry. A closer look, however, reveals that some important and widely known properties (e.g., gold is yellow, mercury is liquid at room temperature) stem from relativistic effects. So far the influence of relativistic effects on the acid-base properties has been mostly ignored. Here we show that at least for compounds of gold such omission is completely erroneous and would lead to too high basicity and too low acidity values with errors in the range of 25-55 kcal mol(-1) (or 20 to 44 powers of ten in pK(a) units) in the gas-phase. These findings have important implications for the design of new superstrong acids and bases, and for the understanding of gold-catalysed reactions.

  6. Hydrogen generation from hydrolytic dehydrogenation of hydrazine borane by poly(N-vinyl-2-pyrrolidone)-stabilized palladium nanoparticles

    NASA Astrophysics Data System (ADS)

    Tunç, Nihat; Abay, Bayram; Rakap, Murat

    2015-12-01

    Poly(N-vinyl-2-pyrrolidone)-stabilized palladium nanoparticles (3.5 ± 1.0 nm) are efficient catalysts in the hydrolytic dehydrogenation of hydrazine borane to give hydrogen gas. The catalyst, prepared by reduction of palladium metal ion in ethanol/water mixture by an alcohol reduction method, is durable and efficient catalysts for hydrogen generation from the hydrolytic dehydrogenation of hydrazine borane even at very low concentrations and temperature, providing an average turnover frequency of 42.9 min-1 with an activation energy of 54.5 ± 2 kJ mol-1 for the hydrolytic dehydrogenation of hydrazine borane.

  7. Nucleic acid-based nanoengineering: novel structures for biomedical applications

    PubMed Central

    Li, Hanying; LaBean, Thomas H.; Leong, Kam W.

    2011-01-01

    Nanoengineering exploits the interactions of materials at the nanometre scale to create functional nanostructures. It relies on the precise organization of nanomaterials to achieve unique functionality. There are no interactions more elegant than those governing nucleic acids via Watson–Crick base-pairing rules. The infinite combinations of DNA/RNA base pairs and their remarkable molecular recognition capability can give rise to interesting nanostructures that are only limited by our imagination. Over the past years, creative assembly of nucleic acids has fashioned a plethora of two-dimensional and three-dimensional nanostructures with precisely controlled size, shape and spatial functionalization. These nanostructures have been precisely patterned with molecules, proteins and gold nanoparticles for the observation of chemical reactions at the single molecule level, activation of enzymatic cascade and novel modality of photonic detection, respectively. Recently, they have also been engineered to encapsulate and release bioactive agents in a stimulus-responsive manner for therapeutic applications. The future of nucleic acid-based nanoengineering is bright and exciting. In this review, we will discuss the strategies to control the assembly of nucleic acids and highlight the recent efforts to build functional nucleic acid nanodevices for nanomedicine. PMID:23050076

  8. Crystal and molecular structure of eight organic acid-base adducts from 2-methylquinoline and different acids

    NASA Astrophysics Data System (ADS)

    Zhang, Jing; Jin, Shouwen; Tao, Lin; Liu, Bin; Wang, Daqi

    2014-08-01

    Eight supramolecular complexes with 2-methylquinoline and acidic components as 4-aminobenzoic acid, 2-aminobenzoic acid, salicylic acid, 5-chlorosalicylic acid, 3,5-dinitrosalicylic acid, malic acid, sebacic acid, and 1,5-naphthalenedisulfonic acid were synthesized and characterized by X-ray crystallography, IR, mp, and elemental analysis. All of the complexes are organic salts except compound 2. All supramolecular architectures of 1-8 involve extensive classical hydrogen bonds as well as other noncovalent interactions. The results presented herein indicate that the strength and directionality of the classical hydrogen bonds (ionic or neutral) between acidic components and 2-methylquinoline are sufficient to bring about the formation of binary organic acid-base adducts. The role of weak and strong noncovalent interactions in the crystal packing is ascertained. These weak interactions combined, the complexes 1-8 displayed 2D-3D framework structure.

  9. Novel ultra stable silica-based stationary phases for reversed phase liquid chromatography--study of a hydrophobically assisted weak acid cation exchange phase.

    PubMed

    Zhang, Yu; Carr, Peter W

    2011-02-11

    A mixed-mode reversed-phase/weak cation exchange (RP/WCX) phase has been developed by introducing a small amount of carboxylate functionality into a hydrophobic hyper-crosslinked (HC) platform. This silica-based HC platform was designed to form an extensive polystyrene network completely confined to the particle's surface. The fully connected polymer network prevents the loss of bonded phase, which leads to superior hydrolytic stability of the new phase when compared to conventional silica-based phases. Compared to previously introduced HC phases the added carboxylic groups impart a new weak cation exchange selectivity to the base hydrophobic HC platform. The phase thus prepared shows a mixed-mode retention mechanism, allowing for both neutral organic compounds and bases of a wide polarity range to be simultaneously separated on the same phase under the same conditions. In addition, the new phase offers the flexibility that gradients in organic modifier, pH or ionic competitors can be used to affect the separation of a wide range of solutes. Moreover, the inherent weak acid cation exchange groups allow formic and acetic acid buffers to be used as eluents thereby avoiding the mass spectrometric ionization suppression problems concomitant to the use of non-volatile additives such as strong amine modifiers (e.g. triethylamine) or salts (e.g. NaCl) to elute basic solutes from the strong cation exchange phase which was previously developed in this lab. The use of the new phase for achieving strong retention of rather hydrophilic neurotransmitters and drugs of abuse without the need for ion pairing agents is demonstrated.

  10. Catalytic Hydrolytic Cleavage and Oxy-Cleavage of Lignin Linkages

    SciTech Connect

    Xia, Guanguang; Chen, Baowei; Zhang, Rui; Zhang, Z. Conrad

    2014-07-26

    In this work, new strategies involving organic bases were evaluated to depolymerize lignin to reduced molecular fragments in aqueous medium. NaOH as an inorganic base was also investigated as a reference. Full nature lignin samples are used for the study. As research tools to unravel the complexity of the macro lignin structure and bulky molecular size under this study, size exclusion chromatography and high resolution mass spectrometric analysis, typically used for protein characterizations, were used to follow the progress of lignin depolymerisation by measuring the molecular weight distribution of the products and determining the key molecular fingerprints, respectively. The results show that sodium phenoxide and guanidine carbonate are effective catalysts for lignin depolymerization. It is observed that there exists a synergism between H2O2 and the organic base, which is strongest with guanidine carbonate.

  11. Effects of physical training, methandione and their combination on the lysosomal hydrolytic activities in dog heart.

    PubMed

    Takala, T E; Kiviluoma, K; Kihlström, M; Rämö, P; Vihko, V

    1992-01-01

    The effects of endurance training, anabolic steroid (methandione 1.5 mg/kg p.o. daily) and their combination on the activities or aryl sulphatase, B-glucuronidase and cathepsin D, all lysosomal hydrolytic enzymes, were studied in the heart of male beagle dogs. Training caused significant increase in the B-glucuronidase activity in the right ventricular wall. Anabolic steroid as such caused no change in any enzymic activities, whereas exercise combined with steroid treatment resulted in significant increases in the activities of all enzymes studied in the right ventricular wall. The combined effect of exercise training and anabolic steroid on the lysosomal hydrolytic enzymes may reflect and mediate the previous observed degenerative effects of this combination in the heart. PMID:1544733

  12. Synthesis of new poly(ether-urethane-urea)s based on amino acid cyclopeptide and PEG: study of their environmental degradation.

    PubMed

    Rafiemanzelat, Fatemeh; Fathollahi Zonouz, Abolfazl; Emtiazi, Giti

    2013-02-01

    Conventional polyurethanes (PUs) are among biomaterials not intended to degrade but are susceptible to hydrolytic, oxidative and enzymatic degradation in vivo. Biodegradable PUs are typically prepared from polyester polyols, aliphatic diisocyanates and chain extenders. In this work we have developed a degradable monomer based on α-amino acid to accelerate hard segment degradation. Thus a new class of degradable poly(ether-urethane-urea)s (PEUUs) was synthesized via direct reaction of 4,4'-methylene-bis(4-phenylisocyanate) (MDI), L-leucine anhydride (LA) and polyethylene glycol with molecular weight of 1,000 (PEG-1000) as polyether soft segment. The resulting polymers are environmentally biodegradable and thermally stable. Decomposition temperatures for 5 % weight loss occurred above 300 °C by TGA in nitrogen atmospheres. Some structural characterization and physical properties of these polymers before and after degradation in soil, river water and sludge are reported. The environmental degradation of the polymer films was investigated by SEM, FTIR, TGA, DSC, GPC and XRD techniques. A significant rate of degradation occurred in PEUU samples under river water and sludge condition. The polymeric films were not toxic to E. coli (Gram negative), Staphylococcus aureus and Micrococcus (Gram positive) bacteria and showed good biofilm formation on polymer surface. Our results show that hard segment degraded selectively as much as soft segment and these polymers are susceptible to degradation in soil and water. Thus our study shows that new environment-friendly polyurethane, which can degrade in soil, river water and sludge, is synthesized.

  13. Acid-base metabolism: implications for kidney stones formation.

    PubMed

    Hess, Bernhard

    2006-04-01

    The physiology and pathophysiology of renal H+ ion excretion and urinary buffer systems are reviewed. The main focus is on the two major conditions related to acid-base metabolism that cause kidney stone formation, i.e., distal renal tubular acidosis (dRTA) and abnormally low urine pH with subsequent uric acid stone formation. Both the entities can be seen on the background of disturbances of the major urinary buffer system, NH3+ <--> NH4+. On the one hand, reduced distal tubular secretion of H+ ions results in an abnormally high urinary pH and either incomplete or complete dRTA. On the other hand, reduced production/availability of NH4+ is the cause of an abnormally low urinary pH, which predisposes to uric acid stone formation. Most recent research indicates that the latter abnormality may be a renal manifestation of the increasingly prevalent metabolic syndrome. Despite opposite deviations from normal urinary pH values, both the dRTA and uric acid stone formation due to low urinary pH require the same treatment, i.e., alkali. In the dRTA, alkali is needed for improving the body's buffer capacity, whereas the goal of alkali treatment in uric acid stone formers is to increase the urinary pH to 6.2-6.8 in order to minimize uric acid crystallization.

  14. Acid/base account and minesoils: A review

    SciTech Connect

    Hossner, L.R.; Brandt, J.E.

    1997-12-31

    Generation of acidity from the oxidation of iron sulfides (FeS{sub 2}) is a common feature of geological materials exposed to the atmosphere by mining activities. Acid/base accounting (ABA) has been the primary method to evaluate the acid- or alkaline-potential of geological materials and to predict if weathering of these materials will have an adverse effect on terrestrial and aquatic environments. The ABA procedure has also been used to evaluate minesoils at different stages of weathering and, in some cases, to estimate lime requirements. Conflicting assessments of the methodology have been reported in the literature. The ABA is the fastest and easiest way to evaluate the acid-forming characteristics of overburden materials; however, accurate evaluations sometimes require that ABA data be examined in conjunction with additional sample information and results from other analytical procedures. The end use of ABA data, whether it be for minesoil evaluation or water quality prediction, will dictate the method`s interpretive criteria. Reaction kinetics and stoichiometry may vary and are not clearly defined for all situations. There is an increasing awareness of the potential for interfering compounds, particularly siderite (FeCO{sub 3}), to be present in geological materials associated with coal mines. Hardrock mines, with possible mixed sulfide mineralogy, offer a challenge to the ABA, since acid generation may be caused by minerals other than pyrite. A combination of methods, static and kinetic, is appropriate to properly evaluate the presence of acid-forming materials.

  15. Students' Understanding of Acids/Bases in Organic Chemistry Contexts

    ERIC Educational Resources Information Center

    Cartrette, David P.; Mayo, Provi M.

    2011-01-01

    Understanding key foundational principles is vital to learning chemistry across different contexts. One such foundational principle is the acid/base behavior of molecules. In the general chemistry sequence, the Bronsted-Lowry theory is stressed, because it lends itself well to studying equilibrium and kinetics. However, the Lewis theory of…

  16. Turkish Prospective Chemistry Teachers' Alternative Conceptions about Acids and Bases

    ERIC Educational Resources Information Center

    Boz, Yezdan

    2009-01-01

    The purpose of this study was to obtain prospective chemistry teachers' conceptions about acids and bases concepts. Thirty-eight prospective chemistry teachers were the participants. Data were collected by means of an open-ended questionnaire and semi-structured interviews. Analysis of data indicated that most prospective teachers did not have…

  17. Thymine, adenine and lipoamino acid based gene delivery systems.

    PubMed

    Skwarczynski, Mariusz; Ziora, Zyta M; Coles, Daniel J; Lin, I-Chun; Toth, Istvan

    2010-05-14

    A novel class of thymine, adenine and lipoamino acid based non-viral carriers for gene delivery has been developed. Their ability to bind to DNA by hydrogen bonding was confirmed by NMR diffusion, isothermal titration calorimetry and transmission electron microscopy experiments.

  18. Photoresponsive self-assemblies based on fatty acids.

    PubMed

    Fameau, A-L; Arnould, A; Lehmann, M; von Klitzing, R

    2015-02-18

    Photoresponsive surfactant system based on fatty acids has been developed by the introduction in aqueous solution of a photoacid generator (PAG). Self-assembly transitions are triggered by UV irradiation due to a pH change induced by the presence of PAG.

  19. Acid-Base Disorders--A Computer Simulation.

    ERIC Educational Resources Information Center

    Maude, David L.

    1985-01-01

    Describes and lists a program for Apple Pascal Version 1.1 which investigates the behavior of the bicarbonate-carbon dioxide buffer system in acid-base disorders. Designed specifically for the preclinical medical student, the program has proven easy to use and enables students to use blood gas parameters to arrive at diagnoses. (DH)

  20. A Schiff base formed from sulfanilic acid and dimethylformamide.

    PubMed

    Hempel, A; Camerman, N; Mastropaolo, D; Camerman, A

    1999-04-15

    The crystal structure the Schiff base contains one 4-dimethylaminomethyleneaminobenzenesulfonic acid molecule in zwitterionic form [4-(dimethylaminomethyleneammonio)benzenesulfonate], and one water molecule in the asymmetric unit (C9H12N2O3S.H2O). Protonation occurs at nitrogen atom N1, but the charge is delocalized.

  1. Using Spreadsheets to Produce Acid-Base Titration Curves.

    ERIC Educational Resources Information Center

    Cawley, Martin James; Parkinson, John

    1995-01-01

    Describes two spreadsheets for producing acid-base titration curves, one uses relatively simple cell formulae that can be written into the spreadsheet by inexperienced students and the second uses more complex formulae that are best written by the teacher. (JRH)

  2. Hydrolytic degradation and drug release properties of ganciclovir-loaded biodegradable microspheres.

    PubMed

    Chen, Xi; Ooi, Chui Ping

    2008-07-01

    The in vitro hydrolytic degradation of ganciclovir (GCV)-loaded biodegradable microspheres of poly(D,L-lactide) and poly(D,L-lactide-co-glycolide) polymers were studied. Microspheres of size 120+/-40 microm were prepared using an oil-in-water emulsification/solvent evaporation technique. The effects of polymer molecular weight, lactide (LA) to glycolide (GA) ratio and GCV payload on the degradation and drug release profiles were investigated in vitro in phosphate-buffered solution (pH 7.0) at 37 degrees C. GCV accelerated the hydrolysis process of the low (5-7 wt.%) GCV-loaded microspheres due to a basic catalytic effect, giving a larger degradation rate, k', compared with blank and high (18-20 wt.%) GCV-loaded microspheres. In the high GCV-loaded microspheres, hydrolysis of the polymer backbone occurred with little and/or no autocatalytic effect, resulting in a smaller k' compared with low GCV-loaded microspheres. This was due to pores and microchannels created at the surface following the initial burst release, which increased water uptake and the dissolution and diffusion of GCV and degradation products from the matrix. The rate of hydrolytic degradation was also affected by the LA to GA ratio. For polymers of similar LA to GA ratio, those with a higher degree of blockiness had faster hydrolytic degradation rates irrespective of the initial molecular weight. The release profile had a biphasic pattern, which closely followed the degradation profile of the polymer. The time taken for the complete release of GCV was controlled by the diffusion phase and was dependent on the hydrolytic degradation rate of the polymers. PMID:18342589

  3. Novel bioactive polyester scaffolds prepared from unsaturated resins based on isosorbide and succinic acid.

    PubMed

    Smiga-Matuszowicz, Monika; Janicki, Bartosz; Jaszcz, Katarzyna; Łukaszczyk, Jan; Kaczmarek, Marcin; Lesiak, Marta; Sieroń, Aleksander L; Simka, Wojciech; Mierzwiński, Maciej; Kusz, Damian

    2014-12-01

    In this study new biodegradable materials obtained by crosslinking poly(3-allyloxy-1,2-propylene succinate) (PSAGE) with oligo(isosorbide maleate) (OMIS) and small amount of methyl methacrylate were investigated. The porous scaffolds were obtained in the presence of a foaming system consisted of calcium carbonate/carboxylic acid mixture, creating in situ porous structure during crosslinking of liquid formulations. The maximum crosslinking temperature and setting time, the cured porous materials morphology as well as the effect of their porosity on mechanical properties and hydrolytic degradation process were evaluated. It was found that the kind of carboxylic acid used in the foaming system influenced compressive strength and compressive modulus of porous scaffolds. The MTS cytotoxicity assay was carried out for OMIS using hFOB1.19 cell line. OMIS resin was found to be non-toxic in wide range of concentrations. On the ground of scanning electron microscopy (SEM) observations and energy X-ray dispersive analysis (EDX) it was found that hydroxyapatite (HA) formation at the scaffolds surfaces within short period of soaking in phosphate buffer solution occurs. After 3h immersion a compact layer of HA was observed at the surface of the samples. The obtained results suggest potential applicability of resulted new porous crosslinked polymeric materials as temporary bone void fillers. PMID:25491802

  4. Mechanisms of Acid and Base Secretion by the Airway Epithelium

    PubMed Central

    Fischer, Horst; Widdicombe, Jonathan H.

    2010-01-01

    SUMMARY One of the main functions of the airway epithelium is to inactivate and remove infectious particles from inhaled air and thereby prevent infection of the distal lung. This function is achieved by mucociliary and cough clearance and by antimicrobial factors present in the airway surface liquid (ASL). There are indications that airway defenses are affected by the pH of the ASL and historically, acidification of the airway surfaces has been suggested as a measure of airway disease. However, even in health, the ASL is slightly acidic, and this acidity might be part of normal airway defense. Only recently research has focused on the mechanisms responsible for acid and base secretion into the ASL. Advances resulted from research into the airway disease associated with cystic fibrosis (CF) after it was found that the CFTR C1- channel conducts HCO3- and, therefore, may contribute to ASL pH. However, the acidity of the ASL indicated parallel mechanisms for H+ secretion. Recent investigations identified several H+ transporters in the apical membrane of the airway epithelium. These include H+ channels and ATP-driven H+ pumps, including a non-gastric isoform of the H+-K+ ATPase and a vacuolar-type H+ ATPase. Current knowledge of acid and base transporters and their potential roles in airway mucosal pH regulation is reviewed here. PMID:17091214

  5. Isolation of moderately halophilic pseudoalteromonas producing extracellular hydrolytic enzymes from persian gulf.

    PubMed

    Ardakani, M Roayaie; Poshtkouhian, A; Amoozegar, M A; Zolgharnein, H

    2012-03-01

    Extracellular hydrolytic enzymes such as amylases, proteases, lipases and DNases have quite diverse potential usages in different areas such as food industry, biomedical sciences and chemical industries, also it would be of great importance to have available enzymes showing optimal activities at different values of salt concentrations and temperature. Halophiles are the most likely source of such enzymes, because not only their enzymes are salt-tolerant, but many are also thermotolerant. The purpose of this study was isolation of hydrolytic extracellular enzyme producing halophilic bacteria from water and sediment of the Persian Gulf. Isolated bacteria from water and sediment were inoculated in media with concentration of 0-20% NaCl to determine the optimum salt concentration for growth, isolates were also inoculated in 4 types of solid medium containing substrates of 3 extracellular hydrolytic enzymes including amylase, Protease and Lipase, to determine the quantitative detection of enzyme production, selected strains after more accurate physiological and biochemical studies were identified regarding phylogeny and molecular characteristics using 16S rRNA technique. Isolated enzyme producing bacteria belong to Pseudoalteromonas genera. PMID:23450116

  6. Primordial transport of sugars and amino acids via Schiff bases

    NASA Astrophysics Data System (ADS)

    Stillwell, William; Rau, Aruna

    1981-09-01

    Experimental support is given for a model concerning the origin of a primordial transport system. The model is based on the facilitated diffusion of amino acids stimulated by aliphatic aldehyde carriers and sugars stimulated by aliphatic amine carriers. The lipid-soluble diffusing species is the Schiff base. The possible role of this simple transport system in the origin of an early protocell is discussed.

  7. Model for acid-base chemistry in nanoparticle growth (MABNAG)

    NASA Astrophysics Data System (ADS)

    Yli-Juuti, T.; Barsanti, K.; Hildebrandt Ruiz, L.; Kieloaho, A.-J.; Makkonen, U.; Petäjä, T.; Ruuskanen, T.; Kulmala, M.; Riipinen, I.

    2013-03-01

    Climatic effects of newly-formed atmospheric secondary aerosol particles are to a large extent determined by their condensational growth rates. However, all the vapors condensing on atmospheric nanoparticles and growing them to climatically relevant sizes are not identified yet and the effects of particle phase processes on particle growth rates are poorly known. Besides sulfuric acid, organic compounds are known to contribute significantly to atmospheric nanoparticle growth. In this study a particle growth model MABNAG (Model for Acid-Base chemistry in NAnoparticle Growth) was developed to study the effect of salt formation on nanoparticle growth, which has been proposed as a potential mechanism lowering the equilibrium vapor pressures of organic compounds through dissociation in the particle phase and thus preventing their evaporation. MABNAG is a model for monodisperse aqueous particles and it couples dynamics of condensation to particle phase chemistry. Non-zero equilibrium vapor pressures, with both size and composition dependence, are considered for condensation. The model was applied for atmospherically relevant systems with sulfuric acid, one organic acid, ammonia, one amine and water in the gas phase allowed to condense on 3-20 nm particles. The effect of dissociation of the organic acid was found to be small under ambient conditions typical for a boreal forest site, but considerable for base-rich environments (gas phase concentrations of about 1010 cm-3 for the sum of the bases). The contribution of the bases to particle mass decreased as particle size increased, except at very high gas phase concentrations of the bases. The relative importance of amine versus ammonia did not change significantly as a function of particle size. While our results give a reasonable first estimate on the maximum contribution of salt formation to nanoparticle growth, further studies on, e.g. the thermodynamic properties of the atmospheric organics, concentrations of low

  8. An explanation of flocculation using Lewis acid-base theory

    SciTech Connect

    Brown, P.M.; Stanley, D.A.; Scheiner, B.J.

    1988-01-01

    This paper describes a Bureau of Mines-devleoped method of dewatering clay slurries based on flocculation by high-molecular-weight polymers and water removal from the formed flocs using a trommel or hydrosieve. The exchange ion on the clays affects their dewaterability. Metal ions in solution and on the exchange sites of smectite clays are known to act as Lewis acids. Recent work has determined that these ions can be titrated with high-molecular-weight polymers. The relative acidity of the exchange ion and the basicity of the polymer determined by the new method give insight into the dewatering mechanism.

  9. Acid-base transport in pancreas—new challenges

    PubMed Central

    Novak, Ivana; Haanes, Kristian A.; Wang, Jing

    2013-01-01

    Along the gastrointestinal tract a number of epithelia contribute with acid or basic secretions in order to aid digestive processes. The stomach and pancreas are the most extreme examples of acid (H+) and base (HCO−3) transporters, respectively. Nevertheless, they share the same challenges of transporting acid and bases across epithelia and effectively regulating their intracellular pH. In this review, we will make use of comparative physiology to enlighten the cellular mechanisms of pancreatic HCO−3 and fluid secretion, which is still challenging physiologists. Some of the novel transporters to consider in pancreas are the proton pumps (H+-K+-ATPases), as well as the calcium-activated K+ and Cl− channels, such as KCa3.1 and TMEM16A/ANO1. Local regulators, such as purinergic signaling, fine-tune, and coordinate pancreatic secretion. Lastly, we speculate whether dys-regulation of acid-base transport contributes to pancreatic diseases including cystic fibrosis, pancreatitis, and cancer. PMID:24391597

  10. A C69-family cysteine dipeptidase from Lactobacillus farciminis JCM1097 possesses strong Gly-Pro hydrolytic activity.

    PubMed

    Sakamoto, Takuma; Otokawa, Takuya; Kono, Ryosuke; Shigeri, Yasushi; Watanabe, Kunihiko

    2013-11-01

    Dipeptide Gly-Pro, a hard-to-degrade and collagenous peptide, is thought to be hydrolysed by prolidases that can work on various X-Pro dipeptides. Here, we found an entirely different type of dipeptidase from Lactobacillus farciminis JCM1097 that cleaves Gly-Pro far more efficiently and with higher specificity than prolidases, and then investigated its properties by use of a recombinant enzyme. Although L. farciminis dipeptidase was expressed in the form of an inclusion body in Escherichia coli at 37 °C, it was smoothly over-expressed in a soluble form at a lower temperature. The maximal Gly-Pro hydrolytic activity was attained in E. coli at 30 °C. In contrast to prolidases that are metallopeptidases showing the modest or marginal activity toward Gly-Pro, this L. farciminis dipeptidase belongs to the cysteine peptidase family C69. Lactobacillus farciminis dipeptidase occurs in cytoplasm and utilizes the side chain of an amino-terminal cysteine residue to perform the nucleophilic attack on the target amide bond between Gly-Pro after processing eight amino acid residues at the N-terminus. Furthermore, L. farciminis dipeptidase is potent enough to synthesize Gly-Pro from Gly and Pro by a reverse reaction. These novel properties could be revealed by virtue of the success in preparing recombinant enzymes in higher yield and in a stable form.

  11. Long term effect of alkali types on waste activated sludge hydrolytic acidification and microbial community at low temperature.

    PubMed

    Jin, Baodan; Wang, Shuying; Xing, Liqun; Li, Baikun; Peng, Yongzhen

    2016-01-01

    The effect of four alkali reagents (NaOH, KOH, Ca(OH)2, mixed alkali) on waste activated sludge (WAS) hydrolytic acidification and microbial community was studied in semi-continuous fermentation systems at low temperature (15°C) over long term operational time (65day). The results showed that protein and polysaccharide of NaOH (124.26, 11.92) was similar to that of KOH (109.53, 11.30), both were higher than Ca(OH)2 (70.66, 3.74) and mixed alkali (90.66, 8.71). The short chain fatty acids (SCFAs) of NaOH (231.62) was higher than KOH (220.62mg chemical oxygen demand (COD)/g VSS). Although Ca(OH)2 system had strong acidification capacity, the shortage of SCFAs occurred due to the low activity of hydrolase. Illumina MiSeq sequencing revealed that Tissierella and Erysipelothrix were enriched in the NaOH and Ca(OH)2 systems, where Peptostreptococcaceae incertae_sedis was enriched in the NaOH and KOH systems, less Anaerolinea was involved in Ca(OH)2 condition. PMID:26546788

  12. Antifouling gold surfaces grafted with aspartic acid and glutamic acid based zwitterionic polymer brushes.

    PubMed

    Li, Wenchen; Liu, Qingsheng; Liu, Lingyun

    2014-10-28

    We report two new amino acid based antifouling zwitterionic polymers, poly(N(4)-(2-methacrylamidoethyl)asparagine) (pAspAA) and poly(N(5)-(2-methacrylamidoethyl)glutamine) (pGluAA). The vinyl monomers were developed from aspartic acid and glutamic acid. Surface-initiated photoiniferter-mediated polymerization was employed to graft polymer brushes from gold surfaces. Different thickness of polymer brushes was controlled by varying UV irradiation time. The nonspecific adsorption from undiluted human blood serum and plasma was studied by surface plasmon resonance (SPR). With the polymer film as thin as 11-12 nm, the adsorption on pAspAA from serum and plasma was as low as 0.75 and 5.18 ng/cm(2), respectively, and 1.88 and 10.15 ng/cm(2), respectively, for pGluAA. The adsorption amount is comparable to or even better than other amino acid based zwitterionic polymers such as poly(serine methacrylate), poly(lysine methacrylamide), and poly(ornithine methacrylamide) and other widely used antifouling polymers such as poly(sulfobetaine methacrylate), even under thinner polymer film thickness. The pAspAA and pGluAA grafted surfaces also showed strong resistance to endothelial cell attachment. The possession of both zwitterionic structure and hydrophilic amide groups, biomimetic property, and multifunctionality make pAspAA and pGluAA promising candidates for biocompatible antifouling functionalizable materials. PMID:25262768

  13. Antifouling gold surfaces grafted with aspartic acid and glutamic acid based zwitterionic polymer brushes.

    PubMed

    Li, Wenchen; Liu, Qingsheng; Liu, Lingyun

    2014-10-28

    We report two new amino acid based antifouling zwitterionic polymers, poly(N(4)-(2-methacrylamidoethyl)asparagine) (pAspAA) and poly(N(5)-(2-methacrylamidoethyl)glutamine) (pGluAA). The vinyl monomers were developed from aspartic acid and glutamic acid. Surface-initiated photoiniferter-mediated polymerization was employed to graft polymer brushes from gold surfaces. Different thickness of polymer brushes was controlled by varying UV irradiation time. The nonspecific adsorption from undiluted human blood serum and plasma was studied by surface plasmon resonance (SPR). With the polymer film as thin as 11-12 nm, the adsorption on pAspAA from serum and plasma was as low as 0.75 and 5.18 ng/cm(2), respectively, and 1.88 and 10.15 ng/cm(2), respectively, for pGluAA. The adsorption amount is comparable to or even better than other amino acid based zwitterionic polymers such as poly(serine methacrylate), poly(lysine methacrylamide), and poly(ornithine methacrylamide) and other widely used antifouling polymers such as poly(sulfobetaine methacrylate), even under thinner polymer film thickness. The pAspAA and pGluAA grafted surfaces also showed strong resistance to endothelial cell attachment. The possession of both zwitterionic structure and hydrophilic amide groups, biomimetic property, and multifunctionality make pAspAA and pGluAA promising candidates for biocompatible antifouling functionalizable materials.

  14. [Blood acid-base balance of sportsmen during physical activity].

    PubMed

    Petrushova, O P; Mikulyak, N I

    2014-01-01

    The aim of this study was to investigate the acid-base balance parameters in blood of sportsmen by physical activity. Before exercise lactate concentration in blood was normal. Carbon dioxide pressure (рСО2), bicarbonate concentration (НСО3 -), base excess (BE), were increased immediately after physical activity lactate concentration increased, while pH, BE, НСО3 -, рСО2 decreased in capillary blood of sportsmen. These changes show the development of lactate-acidosis which is partly compensated with bicarbonate buffering system and respiratory alkalosis. During postexercise recovery lactate concentration decreased, while рСО2, НСО3 -, BE increased. The results of this study can be used for diagnostics of acid-base disorders and their medical treatment for preservation of sportsmen physical capacity.

  15. PDMS-based gold electrode for sensing ascorbic acid.

    PubMed

    Xu, Qin; Bi, Lianhua; Zheng, Huxiang; Fan, Dahe; Wang, Wei

    2011-11-01

    Electrode with optical shapes is appreciated in microfluidics. In this article, we reported a flexible poly(dimethylsiloxane) (PDMS)-based gold electrode for ascorbic acid detection. Gold nanoparticles were chemically deposited on PDMS and the composite film was applied as working electrode. The electrode could undergo deformation and display good response performance without damage. This biosensor could give quick response to ascorbic acid (AA) (<5s) and the currents were linear with concentrations of AA in range of 0.023-7.00 mM and 30-100 mM, respectively. Limit of detection was 0.008 mM (S/N=3). This biosensor has been applied to determine ascorbic acid content in vitamin C tablets and the results were consistent with traditional iodometric method. PMID:21807485

  16. Food composition and acid-base balance: alimentary alkali depletion and acid load in herbivores.

    PubMed

    Kiwull-Schöne, Heidrun; Kiwull, Peter; Manz, Friedrich; Kalhoff, Hermann

    2008-02-01

    Alkali-enriched diets are recommended for humans to diminish the net acid load of their usual diet. In contrast, herbivores have to deal with a high dietary alkali impact on acid-base balance. Here we explore the role of nutritional alkali in experimentally induced chronic metabolic acidosis. Data were collected from healthy male adult rabbits kept in metabolism cages to obtain 24-h urine and arterial blood samples. Randomized groups consumed rabbit diets ad libitum, providing sufficient energy but variable alkali load. One subgroup (n = 10) received high-alkali food and approximately 15 mEq/kg ammonium chloride (NH4Cl) with its drinking water for 5 d. Another group (n = 14) was fed low-alkali food for 5 d and given approximately 4 mEq/kg NH4Cl daily for the last 2 d. The wide range of alimentary acid-base load was significantly reflected by renal base excretion, but normal acid-base conditions were maintained in the arterial blood. In rabbits fed a high-alkali diet, the excreted alkaline urine (pH(u) > 8.0) typically contained a large amount of precipitated carbonate, whereas in rabbits fed a low-alkali diet, both pH(u) and precipitate decreased considerably. During high-alkali feeding, application of NH4Cl likewise decreased pH(u), but arterial pH was still maintained with no indication of metabolic acidosis. During low-alkali feeding, a comparably small amount of added NH4Cl further lowered pH(u) and was accompanied by a significant systemic metabolic acidosis. We conclude that exhausted renal base-saving function by dietary alkali depletion is a prerequisite for growing susceptibility to NH4Cl-induced chronic metabolic acidosis in the herbivore rabbit.

  17. Acid-base titrations by stepwise addition of equal volumes of titrant with special reference to automatic titrations-II Theory of titration of mixtures of acids, polyprotic acids, acids in mixture with weak bases, and ampholytes.

    PubMed

    Pehrsson, L; Ingman, F; Johansson, S

    A general method for evaluating titration data for mixtures of acids and for acids in mixture with weak bases is presented. Procedures are given that do not require absolute [H]-data, i.e., relative [H]-data may be used. In most cases a very rough calibration of the electrode system is enough. Further, for simple systems, very approximate values of the stability constants are sufficient. As examples, the titration of the following are treated in some detail: a mixture of two acids, a diprotic acid, an acid in presence of its conjugate base, and an ampholyte.

  18. Evidence and characteristics of hydrolytic disproportionation of organic matter during metasomatic processes

    NASA Astrophysics Data System (ADS)

    Price, Leigh C.; DeWitt, Ed

    2001-11-01

    Petroleum-geochemical analyses of carbonaceous regionally metamorphosed rocks, carbonaceous rocks from ore deposits, and alkalic plutonic rocks from diverse settings, demonstrated the presence of very low to moderately low concentrations of solvent-extractable organic matter, this observation in spite of the fact that some of these rocks were exposed to extremely high metamorphic temperatures. Biomarker and δ 13C analyses established that the extractable organic matter originated as sedimentary-derived hydrocarbons. However, the chemistry of the extractable bitumen has been fundamentally transformed from that found in sediment bitumen and oils. Asphaltenes and resins, as defined in the normal petroleum-geochemical sense, are completely missing. The principal aromatic hydrocarbons present in oils and sediment bitumens (especially the methylated naphthalenes) are either in highly reduced concentrations or are missing altogether. Instead, aromatic hydrocarbons typical of sediment bitumens and oils are very minor, and a number of unidentified compounds and oxygen-bearing compounds are dominant. Relatively high concentrations of alkylated benzenes are typical. The polar "resin" fraction, eluted during column chromatography, is the principal compound group, by weight, being composed of six to eight dominant peaks present in all samples, despite the great geologic diversity of the samples. These, and other, observations suggest that a strong drive towards equilibrium exists in the "bitumen." Gas chromatograms of the saturated hydrocarbons commonly have a pronounced hump in both the n-paraffins and naphthenes, centered near the C 19 to C 26 carbon numbers, and a ubiquitous minimum in the n-paraffin distribution near n-C 12 to n-C 14. Multiple considerations dictate that the bitumen in the samples is indigenous and did not originate from either surficial field contamination or from laboratory procedures. Our observations are consistent with the hydrolytic

  19. Evidence and characteristics of hydrolytic disproportionation of organic matter during metasomatic processes

    USGS Publications Warehouse

    Price, L.C.; Dewitt, E.

    2001-01-01

    Petroleum-geochemical analyses of carbonaceous regionally metamorphosed rocks, carbonaceous rocks from ore deposits, and alkalic plutonic rocks from diverse settings, demonstrated the presence of very low to moderately low concentrations of solvent-extractable organic matter, this observation in spite of the fact that some of these rocks were exposed to extremely high metamorphic temperatures. Biomarker and ??13C analyses established that the extractable organic matter originated as sedimentary-derived hydrocarbons. However, the chemistry of the extractable bitumen has been fundamentally transformed from that found in sediment bitumen and oils. Asphaltenes and resins, as defined in the normal petroleum-geochemical sense, are completely missing. The principal aromatic hydrocarbons present in oils and sediment bitumens (especially the methylated naphthalenes) are either in highly reduced concentrations or are missing altogether, Instead, aromatic hydrocarbons typical of sediment bitumens and oils are very minor, and a number of unidentified compounds and oxygen-bearing compounds are dominant. Relatively high concentrations of alkylated benzenes are typical. The polar "resin" fraction, eluted during column chromatography, is the principal compound group, by weight, being composed of six to eight dominant peaks present in all samples, despite the great geologic diversity of the samples. These, and other, observations suggest that a strong drive towards equilibrium exists in the "bitumen." Gas chromatograms of the saturated hydrocarbons commonly have a pronounced hump in both the n-paraffins and naphthenes, centered near the C19 to C26 carbon numbers, and a ubiquitos minimum in the n-paraffin distribution near n-C12 to n-C14. Multiple considerations dictate that the bitumen in the samples is indigenous and did not originate from either surficial field contamination or from laboratory procedures. Our observations are consistent with the hydrolytic disproportion of

  20. Hard and soft acids and bases: structure and process.

    PubMed

    Reed, James L

    2012-07-01

    Under investigation is the structure and process that gives rise to hard-soft behavior in simple anionic atomic bases. That for simple atomic bases the chemical hardness is expected to be the only extrinsic component of acid-base strength, has been substantiated in the current study. A thermochemically based operational scale of chemical hardness was used to identify the structure within anionic atomic bases that is responsible for chemical hardness. The base's responding electrons have been identified as the structure, and the relaxation that occurs during charge transfer has been identified as the process giving rise to hard-soft behavior. This is in contrast the commonly accepted explanations that attribute hard-soft behavior to varying degrees of electrostatic and covalent contributions to the acid-base interaction. The ability of the atomic ion's responding electrons to cause hard-soft behavior has been assessed by examining the correlation of the estimated relaxation energies of the responding electrons with the operational chemical hardness. It has been demonstrated that the responding electrons are able to give rise to hard-soft behavior in simple anionic bases.

  1. Long-term in vitro hydrolytic stability of thermoplastic polyurethanes.

    PubMed

    Mishra, Abhinay; Seethamraju, Kasyap; Delaney, Joseph; Willoughby, Patrick; Faust, Rudolf

    2015-12-01

    Long-term in vitro stability of thermoplastic polyurethanes (TPUs) was studied for up to 52 weeks in phosphate buffer solution at 37, 55, and 80°C. Water uptake, molecular weights, and tensile properties were measured at regular intervals of 4, 8, 16, 32, and 52 weeks. The rate of molecular weight reduction increased with increasing temperature, and after 52 weeks at 80°C, all commercial polycarbonate (Bionate-55D, Quadrathane-80A, and Chronoflex-80A), poly(dimethylsiloxane) (ElastEon-2A) and polyether (Elasthane-55D) TPUs showed significant (43-51%) molecular weight (Mn ) reduction. The polyisobutylene (PIB)-based TPU exhibited a significantly lower decrease in Mn (26%) after 52 weeks at 80°C. For Bionate-55D and ElastEon-2A, at 80°C in dry nitrogen atmosphere substantial thermal degradation was observed, while for the other TPUs the effect of thermal degradation is small. The temperature dependent reduction of molecular weight was interpreted by simple second order kinetics. From the approximately linear Arrhenius plots the activation energies were calculated, which were highest for PIB-PU-020 and lowest for ElastEon-2A. For Elasthane-55D the in vitro molecular weight reduction was compared with that of explanted leads. The molecular weight reduction in vivo was much smaller than that predicted from in vitro data, which may suggest that the in vitro model does not adequately describe the hydrolysis in vivo. In the absence of validation for the other TPUs that in vitro methods closely reproduce in vivo degradation, it is unknown how these results correlate with in vivo performance. PMID:26097127

  2. Long-term in vitro hydrolytic stability of thermoplastic polyurethanes.

    PubMed

    Mishra, Abhinay; Seethamraju, Kasyap; Delaney, Joseph; Willoughby, Patrick; Faust, Rudolf

    2015-12-01

    Long-term in vitro stability of thermoplastic polyurethanes (TPUs) was studied for up to 52 weeks in phosphate buffer solution at 37, 55, and 80°C. Water uptake, molecular weights, and tensile properties were measured at regular intervals of 4, 8, 16, 32, and 52 weeks. The rate of molecular weight reduction increased with increasing temperature, and after 52 weeks at 80°C, all commercial polycarbonate (Bionate-55D, Quadrathane-80A, and Chronoflex-80A), poly(dimethylsiloxane) (ElastEon-2A) and polyether (Elasthane-55D) TPUs showed significant (43-51%) molecular weight (Mn ) reduction. The polyisobutylene (PIB)-based TPU exhibited a significantly lower decrease in Mn (26%) after 52 weeks at 80°C. For Bionate-55D and ElastEon-2A, at 80°C in dry nitrogen atmosphere substantial thermal degradation was observed, while for the other TPUs the effect of thermal degradation is small. The temperature dependent reduction of molecular weight was interpreted by simple second order kinetics. From the approximately linear Arrhenius plots the activation energies were calculated, which were highest for PIB-PU-020 and lowest for ElastEon-2A. For Elasthane-55D the in vitro molecular weight reduction was compared with that of explanted leads. The molecular weight reduction in vivo was much smaller than that predicted from in vitro data, which may suggest that the in vitro model does not adequately describe the hydrolysis in vivo. In the absence of validation for the other TPUs that in vitro methods closely reproduce in vivo degradation, it is unknown how these results correlate with in vivo performance.

  3. Model for acid-base chemistry in nanoparticle growth (MABNAG)

    NASA Astrophysics Data System (ADS)

    Yli-Juuti, T.; Barsanti, K.; Hildebrandt Ruiz, L.; Kieloaho, A.-J.; Makkonen, U.; Petäjä, T.; Ruuskanen, T.; Kulmala, M.; Riipinen, I.

    2013-12-01

    Climatic effects of newly-formed atmospheric secondary aerosol particles are to a large extent determined by their condensational growth rates. However, all the vapours condensing on atmospheric nanoparticles and growing them to climatically relevant sizes are not identified yet and the effects of particle phase processes on particle growth rates are poorly known. Besides sulfuric acid, organic compounds are known to contribute significantly to atmospheric nanoparticle growth. In this study a particle growth model MABNAG (Model for Acid-Base chemistry in NAnoparticle Growth) was developed to study the effect of salt formation on nanoparticle growth, which has been proposed as a potential mechanism lowering the equilibrium vapour pressures of organic compounds through dissociation in the particle phase and thus preventing their evaporation. MABNAG is a model for monodisperse aqueous particles and it couples dynamics of condensation to particle phase chemistry. Non-zero equilibrium vapour pressures, with both size and composition dependence, are considered for condensation. The model was applied for atmospherically relevant systems with sulfuric acid, one organic acid, ammonia, one amine and water in the gas phase allowed to condense on 3-20 nm particles. The effect of dissociation of the organic acid was found to be small under ambient conditions typical for a boreal forest site, but considerable for base-rich environments (gas phase concentrations of about 1010 cm-3 for the sum of the bases). The contribution of the bases to particle mass decreased as particle size increased, except at very high gas phase concentrations of the bases. The relative importance of amine versus ammonia did not change significantly as a function of particle size. While our results give a reasonable first estimate on the maximum contribution of salt formation to nanoparticle growth, further studies on, e.g. the thermodynamic properties of the atmospheric organics, concentrations of low

  4. Acid-base chemical mechanism of aspartase from Hafnia alvei.

    PubMed

    Yoon, M Y; Thayer-Cook, K A; Berdis, A J; Karsten, W E; Schnackerz, K D; Cook, P F

    1995-06-20

    An acid-base chemical mechanism is proposed for Hafnia alvei aspartase in which a proton is abstracted from C-3 of the monoanionic form of L-aspartate by an enzyme general base with a pK of 6.3-6.6 in the absence and presence of Mg2+. The resulting carbanion is presumably stabilized by delocalization of electrons into the beta-carboxyl with the assistance of a protonated enzyme group in the vicinity of the beta-carboxyl. Ammonia is then expelled with the assistance of a general acid group that traps an initially expelled NH3 as the final NH4+ product. In agreement with the function of the general acid group, potassium, an analog of NH4+, binds optimally when the group is unprotonated. The pK for the general acid is about 7 in the absence of Mg2+, but is increased by about a pH unit in the presence of Mg2+. Since the same pK values are observed in the pKi(succinate) and V/K pH profile, both enzyme groups must be in their optimum protonation state for efficient binding of reactant in the presence of Mg2+. At the end of a catalytic cycle, both the general base and general acid groups are in a protonation state opposite that in which they started when aspartate was bound. The presence of Mg2+ causes a pH-dependent activation of aspartase exhibited as a partial change in the V and V/Kasp pH profiles. When the aspartase reaction is run in D2O to greater than 50% completion no deuterium is found in the remaining aspartate, indicating that the site is inaccessible to solvent during the catalytic cycle.

  5. Bio-based production of organic acids with Corynebacterium glutamicum.

    PubMed

    Wieschalka, Stefan; Blombach, Bastian; Bott, Michael; Eikmanns, Bernhard J

    2013-03-01

    The shortage of oil resources, the steadily rising oil prices and the impact of its use on the environment evokes an increasing political, industrial and technical interest for development of safe and efficient processes for the production of chemicals from renewable biomass. Thus, microbial fermentation of renewable feedstocks found its way in white biotechnology, complementing more and more traditional crude oil-based chemical processes. Rational strain design of appropriate microorganisms has become possible due to steadily increasing knowledge on metabolism and pathway regulation of industrially relevant organisms and, aside from process engineering and optimization, has an outstanding impact on improving the performance of such hosts. Corynebacterium glutamicum is well known as workhorse for the industrial production of numerous amino acids. However, recent studies also explored the usefulness of this organism for the production of several organic acids and great efforts have been made for improvement of the performance. This review summarizes the current knowledge and recent achievements on metabolic engineering approaches to tailor C. glutamicum for the bio-based production of organic acids. We focus here on the fermentative production of pyruvate, L- and D-lactate, 2-ketoisovalerate, 2-ketoglutarate, and succinate. These organic acids represent a class of compounds with manifold application ranges, e.g. in pharmaceutical and cosmetics industry, as food additives, and economically very interesting, as precursors for a variety of bulk chemicals and commercially important polymers. PMID:23199277

  6. Bio-based production of organic acids with Corynebacterium glutamicum.

    PubMed

    Wieschalka, Stefan; Blombach, Bastian; Bott, Michael; Eikmanns, Bernhard J

    2013-03-01

    The shortage of oil resources, the steadily rising oil prices and the impact of its use on the environment evokes an increasing political, industrial and technical interest for development of safe and efficient processes for the production of chemicals from renewable biomass. Thus, microbial fermentation of renewable feedstocks found its way in white biotechnology, complementing more and more traditional crude oil-based chemical processes. Rational strain design of appropriate microorganisms has become possible due to steadily increasing knowledge on metabolism and pathway regulation of industrially relevant organisms and, aside from process engineering and optimization, has an outstanding impact on improving the performance of such hosts. Corynebacterium glutamicum is well known as workhorse for the industrial production of numerous amino acids. However, recent studies also explored the usefulness of this organism for the production of several organic acids and great efforts have been made for improvement of the performance. This review summarizes the current knowledge and recent achievements on metabolic engineering approaches to tailor C. glutamicum for the bio-based production of organic acids. We focus here on the fermentative production of pyruvate, L- and D-lactate, 2-ketoisovalerate, 2-ketoglutarate, and succinate. These organic acids represent a class of compounds with manifold application ranges, e.g. in pharmaceutical and cosmetics industry, as food additives, and economically very interesting, as precursors for a variety of bulk chemicals and commercially important polymers.

  7. Acid-Base Balance in Uremic Rats with Vascular Calcification

    PubMed Central

    Peralta-Ramírez, Alan; Raya, Ana Isabel; Pineda, Carmen; Rodríguez, Mariano; Aguilera-Tejero, Escolástico; López, Ignacio

    2014-01-01

    Background/Aims Vascular calcification (VC), a major complication in humans and animals with chronic kidney disease (CKD), is influenced by changes in acid-base balance. The purpose of this study was to describe the acid-base balance in uremic rats with VC and to correlate the parameters that define acid-base equilibrium with VC. Methods Twenty-two rats with CKD induced by 5/6 nephrectomy (5/6 Nx) and 10 nonuremic control rats were studied. Results The 5/6 Nx rats showed extensive VC as evidenced by a high aortic calcium (9.2 ± 1.7 mg/g of tissue) and phosphorus (20.6 ± 4.9 mg/g of tissue) content. Uremic rats had an increased pH level (7.57 ± 0.03) as a consequence of both respiratory (PaCO2 = 28.4 ± 2.1 mm Hg) and, to a lesser degree, metabolic (base excess = 4.1 ± 1 mmol/l) derangements. A high positive correlation between both anion gap (AG) and strong ion difference (SID) with aortic calcium (AG: r = 0.604, p = 0.02; SID: r = 0.647, p = 0.01) and with aortic phosphorus (AG: r = 0.684, p = 0.007; SID: r = 0.785, p = 0.01) was detected. Conclusions In an experimental model of uremic rats, VC showed high positive correlation with AG and SID. PMID:25177336

  8. Origin of D-amino acids detected in the acid hydrolysates of purified Escherichia coli β-galactosidase.

    PubMed

    Miyamoto, Tetsuya; Sekine, Masae; Ogawa, Tetsuhiro; Hidaka, Makoto; Homma, Hiroshi; Masaki, Haruhiko

    2015-12-10

    In previous report, we detected D-amino acids in the acid hydrolysates of purified recombinant β-galactosidase. Here, we employed a deuterium-hydrogen exchange method to discriminate innate D-amino acids from those generated during hydrolytic incubation. After hydrolysis of β-galactosidase in DCl/D2O, amino acids were derivatized with NBD-F and separated on a reverse-phase column, followed by liquid chromatography-tandem mass spectrometry equipped with a chiral column. Our results show an absence of innate D-amino acid residues in the protein and suggest that the protein undergoes isomerization during a very early stage of hydrolytic incubation.

  9. The physiological assessment of acid-base balance.

    PubMed

    Howorth, P J

    1975-04-01

    Acid-base terminology including the sue of SI units is reviewed. The historical reasons why nomograms have been particularly used in acid-base work are discussed. The theoretical basis of the Henderson-Hasselbalch equation is considered. It is emphasized that the solubility of CO2 in plasma and the apparent first dissociation constant of carbonic acid are not chemical constants when applied to media of uncertain and varying composition such as blood plasma. The use of the Henderson-Hasselbalch equation in making hypothermia corrections for PCO2 is discussed. The Astrup system for the in vitro determination of blood gases and derived parameters is described and the theoretical weakness of the base excess concept stressed. A more clinically-oriented approach to the assessment of acid-base problems is presented. Measurement of blood [H+] and PCO2 are considered to be primary data which should be recorded on a chart with in vivo CO2-titration lines (see below). Clinical information and results of other laboratory investigations such as plasma bicarbonate, PO2,P50 are then to be considered together with the primary data. In order to interpret this combined information it is essential to take into account the known ventilatory response to metabolic acidosis and alkalosis, and the renal response to respiratory acidosis and alkalosis. The use is recommended of a chart showing the whole-body CO2-titration points obtained when patients with different initial levels of non-respiratory [H+] are ventilated. A number of examples are given of the use of this [H+] and PCO2 in vivo chart in the interpretation of acid-base data. The aetiology, prognosis and treatment of metabolic alkalosis is briefly reviewed. Treatment with intravenous acid is recommended for established cases. Attention is drawn to the possibility of iatrogenic production of metabolic alkalosis. Caution is expressed over the use of intravenous alkali in all but the severest cases of metabolic acidosis. The role of

  10. Acid and base stress and transcriptomic responses in Bacillus subtilis.

    PubMed

    Wilks, Jessica C; Kitko, Ryan D; Cleeton, Sarah H; Lee, Grace E; Ugwu, Chinagozi S; Jones, Brian D; BonDurant, Sandra S; Slonczewski, Joan L

    2009-02-01

    Acid and base environmental stress responses were investigated in Bacillus subtilis. B. subtilis AG174 cultures in buffered potassium-modified Luria broth were switched from pH 8.5 to pH 6.0 and recovered growth rapidly, whereas cultures switched from pH 6.0 to pH 8.5 showed a long lag time. Log-phase cultures at pH 6.0 survived 60 to 100% at pH 4.5, whereas cells grown at pH 7.0 survived <15%. Cells grown at pH 9.0 survived 40 to 100% at pH 10, whereas cells grown at pH 7.0 survived <5%. Thus, growth in a moderate acid or base induced adaptation to a more extreme acid or base, respectively. Expression indices from Affymetrix chip hybridization were obtained for 4,095 protein-encoding open reading frames of B. subtilis grown at external pH 6, pH 7, and pH 9. Growth at pH 6 upregulated acetoin production (alsDS), dehydrogenases (adhA, ald, fdhD, and gabD), and decarboxylases (psd and speA). Acid upregulated malate metabolism (maeN), metal export (czcDO and cadA), oxidative stress (catalase katA; OYE family namA), and the SigX extracytoplasmic stress regulon. Growth at pH 9 upregulated arginine catabolism (roc), which generates organic acids, glutamate synthase (gltAB), polyamine acetylation and transport (blt), the K(+)/H(+) antiporter (yhaTU), and cytochrome oxidoreductases (cyd, ctaACE, and qcrC). The SigH, SigL, and SigW regulons were upregulated at high pH. Overall, greater genetic adaptation was seen at pH 9 than at pH 6, which may explain the lag time required for growth shift to high pH. Low external pH favored dehydrogenases and decarboxylases that may consume acids and generate basic amines, whereas high external pH favored catabolism-generating acids.

  11. Acid-base properties of bentonite rocks with different origins.

    PubMed

    Nagy, Noémi M; Kónya, József

    2006-03-01

    Five bentonite samples (35-47% montmorillonite) from a Sarmatian sediment series with bentonite sites around Sajóbábony (Hungary) is studied. Some of these samples were tuffogenic bentonite (sedimentary), the others were bentonitized tuff with volcano sedimentary origin. The acid-base properties of the edge sites were studied by potentiometric titrations and surface complexation modeling. It was found that the number and the ratio of silanol and aluminol sites as well as the intrinsic stability constants are different for the sedimentary bentonite and bentonitized tuff. The characteristic properties of the edges sites depend on the origins. The acid-base properties are compared to other commercial and standard bentonites.

  12. Evolution of the Acid-Base Status in Cardiac Arrest

    PubMed Central

    Carrasco G., Hugo A.; Oletta L., José F.

    1973-01-01

    In a study of the evolution of acid-base status in 26 patients who had cardiopulmonary arrest in the operating room, it appeared that: The determination of acid-base status within the first hour post-cardiac arrest is useful in differentiating final survivors from non-survivors. Respiratory or combined acidosis carries a poor prognosis not evidenced for metabolic acidosis. Late respiratory complications are more frequent in patients with initial combined acidosis. Treatment should be instituted on the basis of frequent determinations of acidbase status, since accurate diagnosis of degree and type of acidosis cannot be done on clinical grounds only. Recovery of consciousness is influenced by the type and severity of acidosis, less so by duration of arrest; and that high pCO2 is associated frequently with unconsciousness after recovery of circulatory function. PMID:4709532

  13. Self-glazing ceramic tiles based on acidic igneous glasses

    SciTech Connect

    Merkin, A.P.; Nanazashvili, V.I.

    1988-07-01

    A technology was derived to produce self-glazing ceramic tiles based on single-component systems of acidic igneous (volcanic) glasses. A weakly alkaline solution of NaOH or KOH was used as the sealing water to activate the sintering process. Tests conducted on the self-glazing ceramic tiles showed that their water absorption amounts to 2.5-8%, linear shrinkage is 3.2-7%, and frost resistance amounts to 35-70 cycles. The application of acidic igneous glasses as the main raw material for the production of ceramic facing tiles made it possible to widen the raw material base and simplify the technology for fabricating ceramic facing tiles at lower cost. The use of waste products when processing perlite-bearing rocks, when carrying out mining and cutting of tuffs, slags, and tuff breccia for recovering cut materials was recommended.

  14. [Injuries caused by acids and bases - emergency treatment].

    PubMed

    Reifferscheid, Florian; Stuhr, Markus; Kaiser, Guido; Freudenberg, Matthias; Kerner, Thoralf

    2014-06-01

    Emergency medical care for injuries caused by acids and bases is challenging for rescue services. They have to deal with operational safety, detection of the toxic agent, emergency medical care of the patient and handling of the rescue mission. Because of the rareness of such situations experience and routine are largely missing. This article highlights some basic points for the therapy and provides support for such rescue missions.

  15. Synthesis of bio-based methacrylic acid by decarboxylation of itaconic acid and citric acid catalyzed by solid transition-metal catalysts.

    PubMed

    Le Nôtre, Jérôme; Witte-van Dijk, Susan C M; van Haveren, Jacco; Scott, Elinor L; Sanders, Johan P M

    2014-09-01

    Methacrylic acid, an important monomer for the plastics industry, was obtained in high selectivity (up to 84%) by the decarboxylation of itaconic acid using heterogeneous catalysts based on Pd, Pt and Ru. The reaction takes place in water at 200-250 °C without any external added pressure, conditions significantly milder than those described previously for the same conversion with better yield and selectivity. A comprehensive study of the reaction parameters has been performed, and the isolation of methacrylic acid was achieved in 50% yield. The decarboxylation procedure is also applicable to citric acid, a more widely available bio-based feedstock, and leads to the production of methacrylic acid in one pot in 41% selectivity. Aconitic acid, the intermediate compound in the pathway from citric acid to itaconic acid was also used successfully as a substrate. PMID:25045161

  16. Influence of ions on aqueous acid-base reactions.

    PubMed

    Cox, M Jocelyn; Siwick, Bradley J; Bakker, Huib J

    2009-01-12

    We study the effects of bromide salts on the rate and mechanism of the aqueous proton/deuteron-transfer reaction between the photoacid 8-hydroxy-1,3,6-pyrenetrisulfonic acid (HPTS) and the base acetate. The proton/deuteron release is triggered by exciting HPTS with 400 nm femtosecond laser pulses. Probing the electronic and vibrational resonances of the photoacid, the conjugate photobase, the hydrated proton/deuteron and the accepting base with femtosecond visible and mid-infrared pulses monitors the proton transfer. Two reaction channels are identified: 1) direct long-range proton transfer over hydrogen-bonded water bridges that connect the acid and base and 2) acid dissociation to produce fully solvated protons followed by proton scavenging from solution by acetate. We observe that the addition of salt affects the long-range reaction pathway, and reduces both the rate at which protons are released to solution by HPTS and the rate at which solvated protons are scavenged from solution by acetate. We study the dependence of these effects on the nature and concentration of the dissolved salt.

  17. The normal acid-base status of mice.

    PubMed

    Iversen, Nina K; Malte, Hans; Baatrup, Erik; Wang, Tobias

    2012-03-15

    Rodent models are commonly used for various physiological studies including acid-base regulation. Despite the widespread use of especially genetic modified mice, little attention have been made to characterise the normal acid-base status in these animals in order to reveal proper control values. Furthermore, several studies report blood gas values obtained in anaesthetised animals. We, therefore, decided to characterise blood CO(2) binding characteristic of mouse blood in vitro and to characterise normal acid-base status in conscious BALBc mice. In vitro CO(2) dissociation curves, performed on whole blood equilibrated to various PCO₂ levels in rotating tonometers, revealed a typical mammalian pK' (pK'=7.816-0.234 × pH (r=0.34)) and a non-bicarbonate buffer capacity (16.1 ± 2.6 slyke). To measure arterial acid-base status, small blood samples were taken from undisturbed mice with indwelling catheters in the carotid artery. In these animals, pH was 7.391 ± 0.026, plasma [HCO(3)(-)] 18.4 ± 0.83 mM, PCO₂ 30.3 ± 2.1 mm Hg and lactate concentration 4.6 ± 0.7 mM. Our study, therefore, shows that mice have an arterial pH that resembles other mammals, although arterial PCO₂ tends to be lower than in larger mammals. However, pH from arterial blood sampled from mice anaesthetised with isoflurane was significantly lower (pH 7.239 ± 0.021), while plasma [HCO(3)(-)] was 18.5 ± 1.4 mM, PCO₂ 41.9 ± 2.9 mm Hg and lactate concentration 4.48 ± 0.67 mM. Furthermore, we measured metabolism and ventilation (V(E)) in order to determine the ventilation requirements (VE/VO₂) to answer whether small mammals tend to hyperventilate. We recommend, therefore, that studies on acid-base regulation in mice should be based on samples taken for indwelling catheters rather than cardiac puncture of terminally anaesthetised mice.

  18. Lewis base activation of Lewis acids: development of a Lewis base catalyzed selenolactonization.

    PubMed

    Denmark, Scott E; Collins, William R

    2007-09-13

    The concept of Lewis base activation of Lewis acids has been applied to the selenolactonization reaction. Through the use of substoichiometric amounts of Lewis bases with "soft" donor atoms (S, Se, P) significant rate enhancements over the background reaction are seen. Preliminary mechanistic investigations have revealed the resting state of the catalyst as well as the significance of a weak Brønsted acid promoter.

  19. [Nutrition, acid-base metabolism, cation-anion difference and total base balance in humans].

    PubMed

    Mioni, R; Sala, P; Mioni, G

    2008-01-01

    The relationship between dietary intake and acid-base metabolism has been investigated in the past by means of the inorganic cation-anion difference (C(+)(nm)-A(-)(nm)) method based on dietary ash-acidity titration after the oxidative combustion of food samples. Besides the inorganic components of TA (A(-)(nm)-C(+)(nm)), which are under renal control, there are also metabolizable components (A(-)(nm)-C(+)(nm)) of TA, which are under the control of the intermediate metabolism. The whole body base balance, NBb(W), is obtained only by the application of C(+)(nm)-A(-)(nm) to food, feces and urine, while the metabolizable component (A(-)(nm)-C(+)(nm)) is disregarded. A novel method has been subsequently suggested to calculate the net balance of fixed acid, made up by the difference between the input of net endogenous acid production: NEAP = SO(4)(2-)+A(-)(m)-(C(+)(nm)-A(-)(nm)), and the output of net acid excretion: NAE = TA + NH(4)(+) - HCO(3)(-). This approach has been criticized because 1) it includes metabolizable acids, whose production cannot be measured independently; 2) the specific control of metabolizable acid and base has been incorrectly attributed to the kidney; 3) the inclusion of A-m in the balance input generates an acid overload; 4) the object of measurement in making up a balance has to be the same, a condition not fulfilled as NEAP is different from NAE. Lastly, by rearranging the net balance of the acid equation, the balance of nonmetabolizable acid equation is obtained. Therefore, any discrepancy between these two equations is due to the inaccuracy in the urine measurement of metabolizable cations and/or anions.

  20. Acid Base Equilibrium in a Lipid/Water Gel

    NASA Astrophysics Data System (ADS)

    Streb, Kristina K.; Ilich, Predrag-Peter

    2003-12-01

    A new and original experiment in which partition of bromophenol blue dye between water and lipid/water gel causes a shift in the acid base equilibrium of the dye is described. The dye-absorbing material is a monoglyceride food additive of plant origin that mixes freely with water to form a stable cubic phase gel; the nascent gel absorbs the dye from aqueous solution and converts it to the acidic form. There are three concurrent processes taking place in the experiment: (a) formation of the lipid/water gel, (b) absorption of the dye by the gel, and (c) protonation of the dye in the lipid/water gel environment. As the aqueous solution of the dye is a deep purple-blue color at neutral pH and yellow at acidic pH the result of these processes is visually striking: the strongly green-yellow particles of lipid/water gel are suspended in purple-blue aqueous solution. The local acidity of the lipid/water gel is estimated by UV vis spectrophotometry. This experiment is an example of host-guest (lipid/water gel dye) interaction and is suitable for project-type biophysics, physical chemistry, or biochemistry labs. The experiment requires three, 3-hour lab sessions, two of which must not be separated by more than two days.

  1. Acid-base chemistry of frustrated water at protein interfaces.

    PubMed

    Fernández, Ariel

    2016-01-01

    Water molecules at a protein interface are often frustrated in hydrogen-bonding opportunities due to subnanoscale confinement. As shown, this condition makes them behave as a general base that may titrate side-chain ammonium and guanidinium cations. Frustration-based chemistry is captured by a quantum mechanical treatment of proton transference and shown to remove same-charge uncompensated anticontacts at the interface found in the crystallographic record and in other spectroscopic information on the aqueous interface. Such observations are untenable within classical arguments, as hydronium is a stronger acid than ammonium or guanidinium. Frustration enables a directed Grotthuss mechanism for proton transference stabilizing same-charge anticontacts.

  2. Acid-base chemistry of frustrated water at protein interfaces.

    PubMed

    Fernández, Ariel

    2016-01-01

    Water molecules at a protein interface are often frustrated in hydrogen-bonding opportunities due to subnanoscale confinement. As shown, this condition makes them behave as a general base that may titrate side-chain ammonium and guanidinium cations. Frustration-based chemistry is captured by a quantum mechanical treatment of proton transference and shown to remove same-charge uncompensated anticontacts at the interface found in the crystallographic record and in other spectroscopic information on the aqueous interface. Such observations are untenable within classical arguments, as hydronium is a stronger acid than ammonium or guanidinium. Frustration enables a directed Grotthuss mechanism for proton transference stabilizing same-charge anticontacts. PMID:26762189

  3. Acid-base disorders in calves with chronic diarrhea.

    PubMed

    Bednarski, M; Kupczyński, R; Sobiech, P

    2015-01-01

    The aim of this study was to analyze disorders of acid-base balance in calves with chronic diarrhea caused by mixed, viral, bacterial and Cryptosporydium parvum infection. We compared results ob- tained with the classic model (Henderson-Hasselbalch) and strong ion approach (the Steward model). The study included 36 calves aged between 14 and 21 days. The calves were allocated to three groups: I - (control) non-diarrheic calves, group II - animals with compensated acid-base imbalance and group III calves with compensated acid-base disorders and hypoalbuminemia. Plasma concentrations of Na+, K+, Cl-, C12+, Mg2+, P, albumin and lactate were measured. In the classic model, acid-base balance was determined on the basis of blood pH, pCO2, HCO3-, BE and anion gap. In the strong ion model, strong ion difference (SID), effective strong anion difference, total plasma concentration of nonvolatile buffers (A(Tot)) and strong ion gap (SIG) were measured. The control calves and the animals from groups II and III did not differ significantly in terms of their blood pH. The plasma concentration of HCO3-, BE and partial pressure of CO2 in animals from the two groups with chronic diarrhea were significantly higher than those found in the controls. The highest BE (6.03 mmol/l) was documented in calves from group II. The animals from this group presented compensation resulted from activation of metabolic mechanisms. The calves with hypoal- buminemia (group III) showed lower plasma concentrations of albumin (15.37 g/L), Cl (74.94 mmol/L), Mg2+ (0.53 mmol/L), P (1.41 mmol/L) and higher value of anion gap (39.03 mmol/L). This group III presented significantly higher SID3 (71.89 mmol/L), SID7 (72.92 mmol/L) and SIG (43.53 mmol/L) values than animals from the remaining groups (P < 0.01), whereas A(Tot) (6.82 mmol/L) were significantly lower. The main finding of the correlation study was the excellent relationship between the AGcorr and SID3, SID7, SIG. In conclusion, chronic diarrhea leads

  4. Structural features of lignohumic acids

    NASA Astrophysics Data System (ADS)

    Novák, František; Šestauberová, Martina; Hrabal, Richard

    2015-08-01

    The composition and structure of humic acids isolated from lignohumate, which is produced by hydrolytic-oxidative conversion of technical lignosulfonates, were characterized by chemical and spectral methods (UV/VIS, FTIR, and 13C NMR spectroscopy). As comparative samples, humic acids (HA) were isolated also from lignite and organic horizon of mountain spruce forest soil. When compared with other HA studied, the lignohumate humic acids (LHHA) contained relatively few carboxyl groups, whose role is partly fulfilled by sulfonic acid groups. Distinctive 13C NMR signal of methoxyl group carbons, typical for lignin and related humic substances, was found at the shift of 55.9 ppm. Other alkoxy carbons were present in limited quantity, like the aliphatic carbons. Due to the low content of these carbon types, the LHHA has high aromaticity of 60.6%. Comparison with the natural HA has shown that lignohumate obtained by thermal processing of technical lignosulfonate can be regarded as an industrially produced analog of natural humic substances. Based on the chemical and spectral data evaluation, structural features of lignohumate humic acids were clarified and their hypothetical chemical structure proposed, which described typical "average" properties of the isolated fraction.

  5. Procedure for the quantitative determination of mixtures of nucleic Acid components based on multivariate spectrophotometric Acid-base titrations.

    PubMed

    Saurina, J; Hernández-Cassou, S; Tauler, R; Izquierdo-Ridorsa, A

    1999-01-01

    A new procedure for the quantitative determination of mixtures of nucleic acid components, based on continuous spectrophotometric acid-base titrations and multivariate curve resolution, is proposed. The procedure simultaneously takes into account the spectroscopic and acid-base properties of the compounds, which leads to a higher selectivity. Furthermore, quantitative determination of an analyte in a complex mixture is performed using a synthetic solution as standard containing only the analyte of interest. An intrinsic difficulty in the analysis of spectrometric titration data is the presence of rank deficiency due to closure for the mixtures of two or more compounds. An additional problem can be encountered in some mixtures if species spectra or species concentration profiles are practically identical (rank overlap). However, even in the presence of these rank difficulties, accurate quantitation with prediction errors lower than 5% was obtained. The presence of unknown and uncalibrated interferences in the samples does not affect the quantitative determination of the analyte of interest. The proposed procedure was successfully applied to the analysis of real samples (pharmaceuticals) using synthetic external standards.

  6. Hydrolytic activity of vanadate toward serine-containing peptides studied by kinetic experiments and DFT theory.

    PubMed

    Ho, Phuong Hien; Mihaylov, Tzvetan; Pierloot, Kristine; Parac-Vogt, Tatjana N

    2012-08-20

    Hydrolysis of dipeptides glycylserine (Gly-Ser), leucylserine (Leu-Ser), histidylserine (His-Ser), glycylalanine (Gly-Ala), and serylglycine (Ser-Gly) was examined in vanadate solutions by means of (1)H, (13)C, and (51)V NMR spectroscopy. In the presence of a mixture of oxovanadates, the hydrolysis of the peptide bond in Gly-Ser proceeds under the physiological pH and temperature (37 °C, pD 7.4) with a rate constant of 8.9 × 10(-8) s(-1). NMR and EPR spectra did not show evidence for the formation of paramagnetic species, excluding the possibility of V(V) reduction to V(IV) and indicating that the cleavage of the peptide bond is purely hydrolytic. The pD dependence of k(obs) exhibits a bell-shaped profile, with the fastest hydrolysis observed at pD 7.4. Combined (1)H, (13)C, and (51)V NMR experiments revealed formation of three complexes between Gly-Ser and vanadate, of which only one complex, designated Complex 2, formed via coordination of amide oxygen and amino nitrogen to vanadate, is proposed to be hydrolytically active. Kinetic experiments at pD 7.4 performed by using a fixed amount of Gly-Ser and increasing amounts of Na(3)VO(4) allowed calculation of the formation constant for the Gly-Ser/VO(4)(3-) complex (K(f) = 16.1 M(-1)). The structure of the hydrolytically active Complex 2 is suggested also on the basis of DFT calculations. The energy difference between Complex 2 and the major complex detected in the reaction mixture, Complex 1, is calculated to be 7.1 kcal/mol in favor of the latter. The analysis of the molecular properties of Gly-Ser and their change upon different modes of coordination to the vanadate pointed out that only in Complex 2 the amide carbon is suitable for attack by the hydroxyl group in the Ser side chain, which acts as an effective nucleophile. The origin of the hydrolytic activity of vanadate is most likely a combination of the polarization of amide oxygen in Gly-Ser due to the binding to vanadate, followed by the intramolecular

  7. Fatty acid-based polyurethane films for wound dressing applications.

    PubMed

    Gultekin, Guncem; Atalay-Oral, Cigdem; Erkal, Sibel; Sahin, Fikret; Karastova, Djursun; Tantekin-Ersolmaz, S Birgul; Guner, F Seniha

    2009-01-01

    Fatty acid-based polyurethane films were prepared for use as potential wound dressing material. The polymerization reaction was carried out with or without catalyst. Polymer films were prepared by casting-evaporation technique with or without crosslink-catalyst. The film prepared from uncatalyzed reaction product with crosslink-catalyst gave slightly higher crosslink density. The mechanical tests showed that, the increase in the tensile strength and decrease in the elongation at break is due to the increase in the degree of crosslinking. All films were flexible, and resisted to acid solution. The films prepared without crosslink-catalyst were more hydrophilic, absorbed more water. The highest permeability values were generally obtained for the films prepared without crosslink catalyst. Both the direct contact method and the MMT test were applied for determination of cytotoxicity of polymer films and the polyurethane film prepared from uncatalyzed reaction product without crosslink-catalyst showed better biocompatibility property, closest to the commercial product, Opsite.

  8. Fatty acid-based polyurethane films for wound dressing applications.

    PubMed

    Gultekin, Guncem; Atalay-Oral, Cigdem; Erkal, Sibel; Sahin, Fikret; Karastova, Djursun; Tantekin-Ersolmaz, S Birgul; Guner, F Seniha

    2009-01-01

    Fatty acid-based polyurethane films were prepared for use as potential wound dressing material. The polymerization reaction was carried out with or without catalyst. Polymer films were prepared by casting-evaporation technique with or without crosslink-catalyst. The film prepared from uncatalyzed reaction product with crosslink-catalyst gave slightly higher crosslink density. The mechanical tests showed that, the increase in the tensile strength and decrease in the elongation at break is due to the increase in the degree of crosslinking. All films were flexible, and resisted to acid solution. The films prepared without crosslink-catalyst were more hydrophilic, absorbed more water. The highest permeability values were generally obtained for the films prepared without crosslink catalyst. Both the direct contact method and the MMT test were applied for determination of cytotoxicity of polymer films and the polyurethane film prepared from uncatalyzed reaction product without crosslink-catalyst showed better biocompatibility property, closest to the commercial product, Opsite. PMID:18839285

  9. Carboxylic acid free novel isocyanide-based reactions.

    PubMed

    Soeta, Takahiro; Ukaji, Yutaka

    2014-02-01

    In order to develop a practical method for the construction of drug-like and heterocyclic compounds, we have designed a novel Passerini- or Ugi-type reaction system where a compound (which we write in the general form as Z-X) composed of an electrophilic (Z) and a nucleophilic group (X) could essentially perform the same function as the carboxylic acid. Based on this concept, we have developed the O-silylative Passerini reaction and the borinic acid catalyzed α-addition of isocyanides to aldehydes and water. In addition, we have designed and demonstrated the addition reaction of isocyanides to nitrones in the presence of TMSCl to afford the corresponding 1,2,3,4-tetrahydroisoquinoline-1-carboxyamides. Furthermore, a novel [5 + 1] cycloaddition of isocyanide was explored with C,N-cyclic N'-acyl azomethine imines as a "1,5-dipole" via a strategy involving intramolecular trapping of the isocyanide.

  10. Nucleic acid-based tissue biomarkers of urologic malignancies.

    PubMed

    Dietrich, Dimo; Meller, Sebastian; Uhl, Barbara; Ralla, Bernhard; Stephan, Carsten; Jung, Klaus; Ellinger, Jörg; Kristiansen, Glen

    2014-08-01

    Molecular biomarkers play an important role in the clinical management of cancer patients. Biomarkers allow estimation of the risk of developing cancer; help to diagnose a tumor, ideally at an early stage when cure is still possible; and aid in monitoring disease progression. Furthermore, they hold the potential to predict the outcome of the disease (prognostic biomarkers) and the response to therapy (predictive biomarkers). Altogether, biomarkers will help to avoid tumor-related deaths and reduce overtreatment, and will contribute to increased survival and quality of life in cancer patients due to personalized treatments. It is well established that the process of carcinogenesis is a complex interplay between genomic predisposition, acquired somatic mutations, epigenetic changes and genomic aberrations. Within this complex interplay, nucleic acids, i.e. RNA and DNA, play a fundamental role and therefore represent ideal candidates for biomarkers. They are particularly promising candidates because sequence-specific hybridization and amplification technologies allow highly accurate and sensitive assessment of these biomarker levels over a broad dynamic range. This article provides an overview of nucleic acid-based biomarkers in tissues for the management of urologic malignancies, i.e. tumors of the prostate, testis, kidney, penis, urinary bladder, renal pelvis, ureter and other urinary organs. Special emphasis is put on genomic, transcriptomic and epigenomic biomarkers (SNPs, mutations [genomic and mitochondrial], microsatellite instabilities, viral and bacterial DNA, DNA methylation and hydroxymethylation, mRNA expression, and non-coding RNAs [lncRNA, miRNA, siRNA, piRNA, snRNA, snoRNA]). Due to the multitude of published biomarker candidates, special focus is given to the general applicability of different molecular classes as biomarkers and some particularly promising nucleic acid biomarkers. Furthermore, specific challenges regarding the development and clinical

  11. Bio-based production of organic acids with Corynebacterium glutamicum

    PubMed Central

    Wieschalka, Stefan; Blombach, Bastian; Bott, Michael; Eikmanns, Bernhard J

    2013-01-01

    The shortage of oil resources, the steadily rising oil prices and the impact of its use on the environment evokes an increasing political, industrial and technical interest for development of safe and efficient processes for the production of chemicals from renewable biomass. Thus, microbial fermentation of renewable feedstocks found its way in white biotechnology, complementing more and more traditional crude oil-based chemical processes. Rational strain design of appropriate microorganisms has become possible due to steadily increasing knowledge on metabolism and pathway regulation of industrially relevant organisms and, aside from process engineering and optimization, has an outstanding impact on improving the performance of such hosts. Corynebacterium glutamicum is well known as workhorse for the industrial production of numerous amino acids. However, recent studies also explored the usefulness of this organism for the production of several organic acids and great efforts have been made for improvement of the performance. This review summarizes the current knowledge and recent achievements on metabolic engineering approaches to tailor C. glutamicum for the bio-based production of organic acids. We focus here on the fermentative production of pyruvate, l-and d-lactate, 2-ketoisovalerate, 2-ketoglutarate, and succinate. These organic acids represent a class of compounds with manifold application ranges, e.g. in pharmaceutical and cosmetics industry, as food additives, and economically very interesting, as precursors for a variety of bulk chemicals and commercially important polymers. Funding Information Work in the laboratories of the authors was supported by the Fachagentur Nachwachsende Rohstoffe (FNR) of the Bundesministerium für Ernährung, Landwirtschaft und Verbraucherschutz (BMELV; FNR Grants 220-095-08A and 220-095-08D; Bio-ProChemBB project, ERA-IB programme), by the Deutsche Bundesstiftung Umwelt (DBU Grant AZ13040/05) and the Evonik Degussa AG. PMID

  12. DEOXYRIBONUCLEIC ACID BASE COMPOSITION OF PROTEUS AND PROVIDENCE ORGANISMS

    PubMed Central

    Falkow, Stanley; Ryman, I. R.; Washington, O.

    1962-01-01

    Falkow, Stanley (Walter Reed Army Institute of Research, Washington D.C.), I. R. Ryman, and O. Washington. Deoxyribonucleic acid base composition of Proteus and Providence organisms. J. Bacteriol. 83:1318–1321. 1962.—Deoxyribonucleic acids (DNA) from various species of Proteus and of Providence bacteria have been examined for their guanine + cytosine (GC) content. P. vulgaris, P. mirabilis, and P. rettgeri possess essentially identical mean GC contents of 39%, and Providence DNA has a GC content of 41.5%. In marked contrast, P. morganii DNA was found to contain 50% GC. The base composition of P. morganii is only slightly lower than those observed for representatives of the Escherichia, Shigella, and Salmonella groups. Aerobacter and Serratia differ significantly from the other members of the family by their relatively high GC content. Since a minimal requirement for genetic compatibility among different species appears to be similarity of their DNA base composition, it is suggested that P. morganii is distinct genetically from the other species of Proteus as well as Providence strains. The determination of the DNA base composition of microorganisms is important for its predictive information. This information should prove of considerable value in investigating genetic and taxonomic relationships among bacteria. PMID:13891463

  13. Effect of Chain-Extenders on the Properties and Hydrolytic Degradation Behavior of the Poly(lactide)/Poly(butylene adipate-co-terephthalate) Blends

    PubMed Central

    Dong, Weifu; Zou, Benshu; Yan, Yangyang; Ma, Piming; Chen, Mingqing

    2013-01-01

    Biodegradable poly(lactide)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends were prepared by reactive blending in the presence of chain-extenders. Two chain-extenders with multi-epoxy groups were studied. The effect of chain-extenders on the morphology, mechanical properties, thermal behavior, and hydrolytic degradation of the blends was investigated. The compatibility between the PLA and PBAT was significantly improved by in situ formation of PLA-co-PBAT copolymers in the presence of the chain-extenders, results in an enhanced ductility of the blends, e.g., the elongation at break was increased to 500% without any decrease in the tensile strength. The differential scanning calorimeter (DSC) results reveal that cold crystallization of PLA was enhanced due to heterogeneous nucleation effect of the in situ compatibilized PBAT domains. As known before, PLA is sensitive to hydrolysis and in the presence of PBAT and the chain-extenders, the hydrolytic degradation of the blend was evident. A three-stage hydrolysis mechanism for the system is proposed based on a study of weight loss and molecular weight reduction of the samples and the pH variation of the degradation medium. PMID:24152436

  14. Effect of chain-extenders on the properties and hydrolytic degradation behavior of the poly(lactide)/poly(butylene adipate-co-terephthalate) blends.

    PubMed

    Dong, Weifu; Zou, Benshu; Yan, Yangyang; Ma, Piming; Chen, Mingqing

    2013-10-10

    Biodegradable poly(lactide)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends were prepared by reactive blending in the presence of chain-extenders. Two chain-extenders with multi-epoxy groups were studied. The effect of chain-extenders on the morphology, mechanical properties, thermal behavior, and hydrolytic degradation of the blends was investigated. The compatibility between the PLA and PBAT was significantly improved by in situ formation of PLA-co-PBAT copolymers in the presence of the chain-extenders, results in an enhanced ductility of the blends, e.g., the elongation at break was increased to 500% without any decrease in the tensile strength. The differential scanning calorimeter (DSC) results reveal that cold crystallization of PLA was enhanced due to heterogeneous nucleation effect of the in situ compatibilized PBAT domains. As known before, PLA is sensitive to hydrolysis and in the presence of PBAT and the chain-extenders, the hydrolytic degradation of the blend was evident. A three-stage hydrolysis mechanism for the system is proposed based on a study of weight loss and molecular weight reduction of the samples and the pH variation of the degradation medium.

  15. Superabsorbent biphasic system based on poly(lactic acid) and poly(acrylic acid)

    NASA Astrophysics Data System (ADS)

    Sartore, Luciana; Pandini, Stefano; Baldi, Francesco; Bignotti, Fabio

    2016-05-01

    In this research work, biocomposites based on crosslinked particles of poly(acrylic acid), commonly used as superabsorbent polymer (SAP), and poly-L-lactic acid (PLLA) were developed to elucidate the role of the filler (i.e., polymeric crosslinked particles) on the overall physico-mechanical behavior and to obtain superabsorbent thermoplastic products. Samples prepared by melt-blending of components in different ratios showed a biphasic system with a regular distribution of particles, with diameter ranging from 5 to 10 μm, within the PLLA polymeric matrix. The polymeric biphasic system, coded PLASA i.e. superabsorbent poly(lactic acid), showed excellent swelling properties, demonstrating that cross-linked particles retain their superabsorbent ability, as in their free counterparts, even if distributed in a thermoplastic polymeric matrix. The thermal characteristics of the biocomposites evidence enhanced thermal stability in comparison with neat PLLA and also mechanical properties are markedly modified by addition of crosslinked particles which induce regular stiffening effect. Furthermore, in aqueous environments the particles swell and are leached from PLLA matrix generating very high porosity. These new open-pore PLLA foams, produced in absence of organic solvents and chemical foaming agents, with good physico-mechanical properties appear very promising for several applications, for instance in tissue engineering for scaffold production.

  16. General analytical procedure for determination of acidity parameters of weak acids and bases.

    PubMed

    Pilarski, Bogusław; Kaliszan, Roman; Wyrzykowski, Dariusz; Młodzianowski, Janusz; Balińska, Agata

    2015-01-01

    The paper presents a new convenient, inexpensive, and reagent-saving general methodology for the determination of pK a values for components of the mixture of diverse chemical classes weak organic acids and bases in water solution, without the need to separate individual analytes. The data obtained from simple pH-metric microtitrations are numerically processed into reliable pK a values for each component of the mixture. Excellent agreement has been obtained between the determined pK a values and the reference literature data for compounds studied.

  17. Analytic calculation of physiological acid-base parameters in plasma.

    PubMed

    Wooten, E W

    1999-01-01

    Analytic expressions for plasma total titratable base, base excess (DeltaCB), strong-ion difference, change in strong-ion difference (DeltaSID), change in Van Slyke standard bicarbonate (DeltaVSSB), anion gap, and change in anion gap are derived as a function of pH, total buffer ion concentration, and conditional molar equilibrium constants. The behavior of these various parameters under respiratory and metabolic acid-base disturbances for constant and variable buffer ion concentrations is considered. For constant noncarbonate buffer concentrations, DeltaSID = DeltaCB = DeltaVSSB, whereas these equalities no longer hold under changes in noncarbonate buffer concentration. The equivalence is restored if the reference state is changed to include the new buffer concentrations.

  18. Functional nucleic-acid-based sensors for environmental monitoring.

    PubMed

    Sett, Arghya; Das, Suradip; Bora, Utpal

    2014-10-01

    Efforts to replace conventional chromatographic methods for environmental monitoring with cheaper and easy to use biosensors for precise detection and estimation of hazardous environmental toxicants, water or air borne pathogens as well as various other chemicals and biologics are gaining momentum. Out of the various types of biosensors classified according to their bio-recognition principle, nucleic-acid-based sensors have shown high potential in terms of cost, sensitivity, and specificity. The discovery of catalytic activities of RNA (ribozymes) and DNA (DNAzymes) which could be triggered by divalent metallic ions paved the way for their extensive use in detection of heavy metal contaminants in environment. This was followed with the invention of small oligonucleotide sequences called aptamers which can fold into specific 3D conformation under suitable conditions after binding to target molecules. Due to their high affinity, specificity, reusability, stability, and non-immunogenicity to vast array of targets like small and macromolecules from organic, inorganic, and biological origin, they can often be exploited as sensors in industrial waste management, pollution control, and environmental toxicology. Further, rational combination of the catalytic activity of DNAzymes and RNAzymes along with the sequence-specific binding ability of aptamers have given rise to the most advanced form of functional nucleic-acid-based sensors called aptazymes. Functional nucleic-acid-based sensors (FNASs) can be conjugated with fluorescent molecules, metallic nanoparticles, or quantum dots to aid in rapid detection of a variety of target molecules by target-induced structure switch (TISS) mode. Although intensive research is being carried out for further improvements of FNAs as sensors, challenges remain in integrating such bio-recognition element with advanced transduction platform to enable its use as a networked analytical system for tailor made analysis of environmental

  19. Liquid crystal based biosensors for bile acid detection

    NASA Astrophysics Data System (ADS)

    He, Sihui; Liang, Wenlang; Tanner, Colleen; Fang, Jiyu; Wu, Shin-Tson

    2013-03-01

    The concentration level of bile acids is a useful indicator for early diagnosis of liver diseases. The prevalent measurement method in detecting bile acids is the chromatography coupled with mass spectrometry, which is precise yet expensive. Here we present a biosensor platform based on liquid crystal (LC) films for the detection of cholic acid (CA). This platform has the advantage of low cost, label-free, solution phase detection and simple analysis. In this platform, LC film of 4-Cyano-4'-pentylbiphenyl (5CB) was hosted by a copper grid supported with a polyimide-coated glass substrate. By immersing into sodium dodecyl sulfate (SDS) solution, the LC film was coated with SDS which induced a homeotropic anchoring of 5CB. Addition of CA introduced competitive adsorption between CA and SDS at the interface, triggering a transition from homeotropic to homogeneous anchoring. The detection limit can be tuned by changing the pH value of the solution from 12uM to 170uM.

  20. Paediatric acid-base disorders: A case-based review of procedures and pitfalls.

    PubMed

    Carmody, J Bryan; Norwood, Victoria F

    2013-01-01

    Acid-base disorders occur frequently in paediatric patients. Despite the perception that their analysis is complex and difficult, a straightforward set of rules is sufficient to interpret even the most complex disorders - provided certain pitfalls are avoided. Using a case-based approach, the present article reviews the fundamental concepts of acid-base analysis and highlights common mistakes and oversights. Specific topics include the proper identification of the primary disorder; distinguishing compensatory changes from additional primary disorders; use of the albumin-corrected anion gap to generate a differential diagnosis for patients with metabolic acidosis; screening for mixed disorders with the delta-delta formula; recognizing the limits of compensation; use of the anion gap to identify 'hidden' acidosis; and the importance of using information from the history and physical examination to identify the specific cause of a patient's acid-base disturbance.

  1. Hydrolytic activity of Virgibacillus sp. SK37, a starter culture of fish sauce fermentation, and its cell-bound proteinases.

    PubMed

    Sinsuwan, Sornchai; Rodtong, Sureelak; Yongsawatdigul, Jirawat

    2012-08-01

    Fish sauce production relies on a natural fermentation process requiring 12-18 months for process completion. Virgibacillus sp. SK37 has been shown to be a potential strain for fish sauce acceleration. However, hydrolytic activity of proteinases bound at cell surface of this strain has not been well elucidated. Addition of 0.2 % CaCl(2) (w/w) in conjunction with starter cultures of Virgibacillus sp. SK 37 increased protein hydrolysis as measured by α-amino group content throughout fermentation (P < 0.05). Cell-bound proteinases from Virgibacillus sp. SK 37 were extracted into a free form by incubating the washed cells in Ca(2+)-free buffer at 37 °C for 2 h. Cell-bound proteinases revealed molecular mass of 19, 20, 22, 32, 34, and 44 kDa based on a synthetic peptide zymogram. The proteinases showed subtilisin-like serine characteristics with the highest activity at 50 °C and pH 8 and 11. Activity of the extracted proteinases increased ~4 times at ≥100 mM CaCl(2). In addition, CaCl(2) enhanced thermal stability of the extracted proteinases. Enzymes showed proteolytic activity in either the absence or presence of 10 and 25 % NaCl toward fish muscle, soy protein isolate, and casein substrates. Cell-bound proteinases were likely to play an important role in protein hydrolysis during fish sauce fermentation. PMID:22806191

  2. The comprehensive acid-base characterization of glutathione

    NASA Astrophysics Data System (ADS)

    Mirzahosseini, Arash; Somlyay, Máté; Noszál, Béla

    2015-02-01

    Glutathione in its thiol (GSH) and disulfide (GSSG) forms, and 4 related compounds were studied by 1H NMR-pH titrations and a case-tailored evaluation method. The resulting acid-base properties are quantified in terms of 128 microscopic protonation constants; the first complete set of such parameters for this vitally important pair of compounds. The concomitant 12 interactivity parameters were also determined. Since biological redox systems are regularly compared to the GSH-GSSG pair, the eight microscopic thiolate basicities determined this way are exclusive means for assessing subtle redox parameters in a wide pH range.

  3. Conducting Polymer Based Nucleic Acid Sensor for Environment Monitoring

    NASA Astrophysics Data System (ADS)

    Malhotra, Bansi Dhar; Prabhakar, Nirmal; Solanki, Pratima R.

    Nucleic acid sensor based on polyaniline has been fabricated by covalently immobilizing double stranded calf thymus (dsCT) DNA onto perchlorate (ClO-4) doped polyaniline (PANI) film deposited onto indium-tin-oxide (ITO) glass plate using 1-(3-(dimethylamino) propyl)-3-ethylcarbodiimide hydrochloride (EDC)/N-hydroxyl succinimide (NHS) chemistry. These dsCT-DNA-PANI/ITO and PANI/ITO electrodes have been characterized using square wave voltammetry, electrochemical impedance, and Fourier-transform-infra-red (FTIR) measurements. This disposable dsCT-DNA-PANI/ITO bioelectrode is stable for about four months, can be used to detect arsenic trioxide (0.1ppm) in 30s.

  4. Gallic acid-based indanone derivatives as anticancer agents.

    PubMed

    Saxena, Hari Om; Faridi, Uzma; Srivastava, Suchita; Kumar, J K; Darokar, M P; Luqman, Suaib; Chanotiya, C S; Krishna, Vinay; Negi, Arvind S; Khanuja, S P S

    2008-07-15

    Gallic acid-based indanone derivatives have been synthesised. Some of the indanones showed very good anticancer activity in MTT assay. Compounds 10, 11, 12 and 14 possessed potent anticancer activity against various human cancer cell lines. The most potent indanone (10, IC(50)=2.2 microM), against MCF-7, that is, hormone-dependent breast cancer cell line, showed no toxicity to human erythrocytes even at higher concentrations (100 microg/ml, 258 microM). While, indanones 11, 12 and 14 showed toxicities to erythrocytes at higher concentrations.

  5. Acid-Base Homeostasis: Overview for Infusion Nurses.

    PubMed

    Masco, Natalie A

    2016-01-01

    Acid-base homeostasis is essential to normal function of the human body. Even slight alterations can significantly alter physiologic processes at the tissue and cellular levels. To optimally care for patients, nurses must be able to recognize signs and symptoms that indicate deviations from normal. Nurses who provide infusions to patients-whether in acute care, home care, or infusion center settings-have a responsibility to be able to recognize the laboratory value changes that occur with the imbalance and appreciate the treatment options, including intravenous infusions. PMID:27598068

  6. A fully automatic system for acid-base coulometric titrations.

    PubMed

    Cladera, A; Caro, A; Estela, J M; Cerdà, V

    1990-01-01

    An automatic system for acid-base titrations by electrogeneration of H(+) and OH(-) ions, with potentiometric end-point detection, was developed. The system includes a PC-compatible computer for instrumental control, data acquisition and processing, which allows up to 13 samples to be analysed sequentially with no human intervention.The system performance was tested on the titration of standard solutions, which it carried out with low errors and RSD. It was subsequently applied to the analysis of various samples of environmental and nutritional interest, specifically waters, soft drinks and wines.

  7. [Acid-base equilibrium in sportsmen during physical exercise].

    PubMed

    Brinzak, V P; Kalinskiĭ, M I; Val'tin, A I; Povzhitkova, M S

    1983-01-01

    Acid-base balance in venous blood of basketball players was studied under specific loadings of various intensity by means of the micro-Astrup device. It is established that under acyclic loadings (throwing the ball into the basket) the state of metabolic acidosis is developed in the sportsmen and the more intensive the work, the higher the degree of the state of metabolic acidosis. The efficiency of actions of the persons examined was in inverse dependence on the degree of metabolic disturbances, i.e. the least efficiency was marked under the most profound acidosis.

  8. High throughput screening of hydrolytic enzymes from termites using a natural substrate derived from sugarcane bagasse

    PubMed Central

    2011-01-01

    Background The description of new hydrolytic enzymes is an important step in the development of techniques which use lignocellulosic materials as a starting point for fuel production. Sugarcane bagasse, which is subjected to pre-treatment, hydrolysis and fermentation for the production of ethanol in several test refineries, is the most promising source of raw material for the production of second generation renewable fuels in Brazil. One problem when screening hydrolytic activities is that the activity against commercial substrates, such as carboxymethylcellulose, does not always correspond to the activity against the natural lignocellulosic material. Besides that, the macroscopic characteristics of the raw material, such as insolubility and heterogeneity, hinder its use for high throughput screenings. Results In this paper, we present the preparation of a colloidal suspension of particles obtained from sugarcane bagasse, with minimal chemical change in the lignocellulosic material, and demonstrate its use for high throughput assays of hydrolases using Brazilian termites as the screened organisms. Conclusions Important differences between the use of the natural substrate and commercial cellulase substrates, such as carboxymethylcellulose or crystalline cellulose, were observed. This suggests that wood feeding termites, in contrast to litter feeding termites, might not be the best source for enzymes that degrade sugarcane biomass. PMID:22081987

  9. Carbon Nanotubes as Support in the Platinum-Catalyzed Hydrolytic Dehydrogenation of Ammonia Borane.

    PubMed

    Chen, Wenyao; Duan, Xuezhi; Qian, Gang; Chen, De; Zhou, Xinggui

    2015-09-01

    We report remarkable support effects for carbon nanotubes (CNTs) in the Pt/CNT-catalyzed hydrolytic dehydrogenation of ammonia borane. The origin of the support-dependent activity and durability is elucidated by combining the catalytic and durability testing with characterization by a range of spectroscopy and high-angle annular dark-field scanning transmission electron microscopy techniques and ICP analysis. The effects mainly arise from different electronic properties and different abilities for the adsorption of boron-containing species on platinum surfaces and changes in size and shape of the platinum particles during the reaction. Defect-rich CNTs in particular are a promising support material, as it not only enhances the platinum binding energy, leading to the highest hydrogen generation rate, but also inhibits the adsorption of boron-containing species and stabilizes the platinum nanoparticles to resist the agglomeration during the reaction, leading to the highest durability. The insights revealed herein may pave the way for the rational design of highly active and durable metal/carbon catalysts for the hydrolytic dehydrogenation of ammonia borane.

  10. 78 FR 36698 - Microbiology Devices; Reclassification of Nucleic Acid-Based Systems for Mycobacterium tuberculosis

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-19

    ... Nucleic Acid-Based Systems for Mycobacterium tuberculosis Complex in Respiratory Specimens AGENCY: Food...) is proposing to reclassify nucleic acid-based in vitro diagnostic devices for the detection of... Controls Guideline: Nucleic Acid-Based In Vitro Diagnostic Devices for the Detection of...

  11. Transgalactosylation and hydrolytic activities of commercial preparations of β-galactosidase for the synthesis of prebiotic carbohydrates.

    PubMed

    Guerrero, Cecilia; Vera, Carlos; Conejeros, Raúl; Illanes, Andrés

    2015-03-01

    β-Galactosidases exhibit both hydrolytic and transgalactosylation activities; the former has been used traditionally for the production of delactosed milk and dairies, while the latter is being increasingly used for the synthesis of lactose-derived oligosaccharides: balance between both activities was highly dependent on the enzyme origin: β-galactosidases from Aspegillus oryzae and Bacillus circulans exhibited high transgalactosylation activity, while those from one from Kluyveromyces exhibited high hydrolytic activity but quite low transgalactosylation activity. Also the affinity for the donors (lactose or lactulose) and the acceptors (lactose, lactulose or fructose) of transgalactosylated galactose was dependent on the enzyme origin, as reflected by the Michaelis constants obtained in the synthesis of galacto-oligosaccharides, fructosyl-galacto-oligosaccharides and lactulose. Finally, the balance between transgalactosylation and hydrolytic activities of β-galactosidases could be tuned by changing the concentration of galactose donor.

  12. Effect of temperature on the acid-base properties of the alumina surface: microcalorimetry and acid-base titration experiments.

    PubMed

    Morel, Jean-Pierre; Marmier, Nicolas; Hurel, Charlotte; Morel-Desrosiers, Nicole

    2006-06-15

    Sorption reactions on natural or synthetic materials that can attenuate the migration of pollutants in the geosphere could be affected by temperature variations. Nevertheless, most of the theoretical models describing sorption reactions are at 25 degrees C. To check these models at different temperatures, experimental data such as the enthalpies of sorption are thus required. Highly sensitive microcalorimeters can now be used to determine the heat effects accompanying the sorption of radionuclides on oxide-water interfaces, but enthalpies of sorption cannot be extracted from microcalorimetric data without a clear knowledge of the thermodynamics of protonation and deprotonation of the oxide surface. However, the values reported in the literature show large discrepancies and one must conclude that, amazingly, this fundamental problem of proton binding is not yet resolved. We have thus undertaken to measure by titration microcalorimetry the heat effects accompanying proton exchange at the alumina-water interface at 25 degrees C. Based on (i) the surface sites speciation provided by a surface complexation model (built from acid-base titrations at 25 degrees C) and (ii) results of the microcalorimetric experiments, calculations have been made to extract the enthalpic variations associated respectively to first and second deprotonation of the alumina surface. Values obtained are deltaH1 = 80+/-10 kJ mol(-1) and deltaH2 = 5+/-3 kJ mol(-1). In a second step, these enthalpy values were used to calculate the alumina surface acidity constants at 50 degrees C via the van't Hoff equation. Then a theoretical titration curve at 50 degrees C was calculated and compared to the experimental alumina surface titration curve. Good agreement between the predicted acid-base titration curve and the experimental one was observed.

  13. Design of chitosan-based nanoparticles functionalized with gallic acid.

    PubMed

    Lamarra, J; Rivero, S; Pinotti, A

    2016-10-01

    Active nanoparticles based on chitosan could be applied as a support for the modulation of gallic acid delivery. In this sense, these nanostructures could be employed in different fields such as food, packaging, and pharmaceutical areas. The design parameters of chitosan-based nanoparticles functionalized with gallic acid (GA) were optimized through RSM by means of the analysis of zeta potential (ZP) and percentage encapsulation efficiency (PEE). The nanoparticles were prepared by ionotropic gelation using tripolyphosphate (TPP), at different combinations of chitosan (CH) concentration, CH:TPP ratio and GA. Global desirability methodology allowed finding the optimum formulation that included CH 0.76% (w/w), CH:TPP ratio of 5 and 37mgGA/gCH leading to ZP of +50mV and 82% of PEE. Analysis through QuickScan and turbidity demonstrated that the most stable nanoparticle suspensions were achieved combining concentrations of chitosan ranging between 0.5 and 0.75% with CH:TPP ratios higher than 3. These suspensions had high stability confirmed by means ZP and transmittance values which were higher than +25mV and 0.21 on average, respectively, as well as nanoparticle diameters of about 140nm. FTIR revealed the occurrence of both hydrogen bond and ionic interactions of CH-TPP which allowed the encapsulation and the improvement of the stability of the active agent. PMID:27287172

  14. Sphingoid bases inhibit acid-induced demineralization of hydroxyapatite.

    PubMed

    Valentijn-Benz, Marianne; van 't Hof, Wim; Bikker, Floris J; Nazmi, Kamran; Brand, Henk S; Sotres, Javier; Lindh, Liselott; Arnebrant, Thomas; Veerman, Enno C I

    2015-01-01

    Calcium hydroxyapatite (HAp), the main constituent of dental enamel, is inherently susceptible to the etching and dissolving action of acids, resulting in tooth decay such as dental caries and dental erosion. Since the prevalence of erosive wear is gradually increasing, there is urgent need for agents that protect the enamel against erosive attacks. In the present study we studied in vitro the anti-erosive effects of a number of sphingolipids and sphingoid bases, which form the backbone of sphingolipids. Pretreatment of HAp discs with sphingosine, phytosphingosine (PHS), PHS phosphate and sphinganine significantly protected these against acid-induced demineralization by 80 ± 17%, 78 ± 17%, 78 ± 7% and 81 ± 8%, respectively (p < 0.001). On the other hand, sphingomyelin, acetyl PHS, octanoyl PHS and stearoyl PHS had no anti-erosive effects. Atomic force measurement revealed that HAp discs treated with PHS were almost completely and homogeneously covered by patches of PHS. This suggests that PHS and other sphingoid bases form layers on the surface of HAp, which act as diffusion barriers against H(+) ions. In principle, these anti-erosive properties make PHS and related sphingosines promising and attractive candidates as ingredients in oral care products.

  15. Applications of synchrotron-based spectroscopic techniques in studying nucleic acids and nucleic acid-functionalized nanomaterials.

    PubMed

    Wu, Peiwen; Yu, Yang; McGhee, Claire E; Tan, Li Huey; Lu, Yi

    2014-12-10

    In this review, we summarize recent progress in the application of synchrotron-based spectroscopic techniques for nucleic acid research that takes advantage of high-flux and high-brilliance electromagnetic radiation from synchrotron sources. The first section of the review focuses on the characterization of the structure and folding processes of nucleic acids using different types of synchrotron-based spectroscopies, such as X-ray absorption spectroscopy, X-ray emission spectroscopy, X-ray photoelectron spectroscopy, synchrotron radiation circular dichroism, X-ray footprinting and small-angle X-ray scattering. In the second section, the characterization of nucleic acid-based nanostructures, nucleic acid-functionalized nanomaterials and nucleic acid-lipid interactions using these spectroscopic techniques is summarized. Insights gained from these studies are described and future directions of this field are also discussed.

  16. Applications of synchrotron-based spectroscopic techniques in studying nucleic acids and nucleic acid-functionalized nanomaterials

    PubMed Central

    Wu, Peiwen; Yu, Yang; McGhee, Claire E.; Tan, Li Huey

    2014-01-01

    In this review, we summarize recent progresses in the application of synchrotron-based spectroscopic techniques for nucleic acid research that takes advantage of high-flux and high-brilliance electromagnetic radiation from synchrotron sources. The first section of the review focuses on the characterization of the structure and folding processes of nucleic acids using different types of synchrotron-based spectroscopies, such as X-ray absorption spectroscopy, X-ray emission spectroscopy, X-ray photoelectron spectroscopy, synchrotron radiation circular dichroism, X-ray footprinting and small-angle X-ray scattering. In the second section, the characterization of nucleic acid-based nanostructures, nucleic acid-functionalized nanomaterials and nucleic acid-lipid interactions using these spectroscopic techniques is summarized. Insights gained from these studies are described and future directions of this field are also discussed. PMID:25205057

  17. A comprehensive classification of nucleic acid structural families based on strand direction and base pairing.

    PubMed Central

    Lavery, R; Zakrzewska, K; Sun, J S; Harvey, S C

    1992-01-01

    We propose a classification of DNA structures formed from 1 to 4 strands, based only on relative strand directions, base to strand orientation and base pairing geometries. This classification and its associated notation enable all nucleic acids to be grouped into structural families and bring to light possible structures which have not yet been observed experimentally. It also helps in understanding transitions between families and can assist in the design of multistrand structures. PMID:1383936

  18. Probe kit for identifying a base in a nucleic acid

    DOEpatents

    Fodor, Stephen P. A.; Lipshutz, Robert J.; Huang, Xiaohua

    2001-01-01

    Devices and techniques for hybridization of nucleic acids and for determining the sequence of nucleic acids. Arrays of nucleic acids are formed by techniques, preferably high resolution, light-directed techniques. Positions of hybridization of a target nucleic acid are determined by, e.g., epifluorescence microscopy. Devices and techniques are proposed to determine the sequence of a target nucleic acid more efficiently and more quickly through such synthesis and detection techniques.

  19. Hybridization and sequencing of nucleic acids using base pair mismatches

    DOEpatents

    Fodor, Stephen P. A.; Lipshutz, Robert J.; Huang, Xiaohua

    2001-01-01

    Devices and techniques for hybridization of nucleic acids and for determining the sequence of nucleic acids. Arrays of nucleic acids are formed by techniques, preferably high resolution, light-directed techniques. Positions of hybridization of a target nucleic acid are determined by, e.g., epifluorescence microscopy. Devices and techniques are proposed to determine the sequence of a target nucleic acid more efficiently and more quickly through such synthesis and detection techniques.

  20. Method of Identifying a Base in a Nucleic Acid

    DOEpatents

    Fodor, Stephen P. A.; Lipshutz, Robert J.; Huang, Xiaohua

    1999-01-01

    Devices and techniques for hybridization of nucleic acids and for determining the sequence of nucleic acids. Arrays of nucleic acids are formed by techniques, preferably high resolution, light-directed techniques. Positions of hybridization of a target nucleic acid are determined by, e.g., epifluorescence microscopy. Devices and techniques are proposed to determine the sequence of a target nucleic acid more efficiently and more quickly through such synthesis and detection techniques.

  1. Hydrolytic and pumping activity of H+-ATPase from leaves of sugar beet (Beta vulgaris L.) as affected by salt stress.

    PubMed

    Wakeel, Abdul; Hanstein, Stefan; Pitann, Britta; Schubert, Sven

    2010-06-15

    Cell wall extensibility plays an important role in plant growth. According to the acid-growth theory, lower apoplastic pH allows extension growth by affecting cell wall extensibility. A lowered apoplastic pH is presumed to activate wall-loosening enzymes that control plant growth. Plasma membrane (PM) H(+)-ATPases play a major role in the apoplastic acidification by H(+) transport from cytosol to the apoplast. A salt-induced decrease in H(+)-pumping activity of plasma membrane H(+)-ATPases in salt-sensitive maize plants has previously been found. This led us to formulate the hypothesis that salt-resistant plant species such as sugar beet (Beta vulgaris L.) may have a mechanism to eliminate the effect of higher salt concentrations on plasma membrane H(+)-ATPase activity. In the present study, sugar beet plants were grown in 1mM NaCl (control) or 150 mM NaCl in hydroponics. H(+)-ATPase hydrolytic and pumping activities were measured in plasma membrane vesicles isolated from sugar beet shoots. We found that plasma membrane H(+)-ATPase hydrolytic and pumping activities were not affected by application of 150 mM NaCl. Moreover, apoplastic pH was also not affected under salt stress. However, a decrease in plant growth was observed. We assume that growth reduction was not due to a decrease in PM-H(+)-ATPase activity, but that other factors may be responsible for growth inhibition of sugar beet plants under salt stress.

  2. Biocomposites of pHEMA with HA/β -TCP (60/40) for bone tissue engineering: Swelling, hydrolytic degradation, and in vitro behavior

    PubMed Central

    Huang, Jijun; Ten, Elena; Liu, Gao; Finzen, Matthew; Yu, Wenli; Lee, Janice S.; Saiz, Eduardo; Tomsia, Antoni P.

    2013-01-01

    The field of bone and cartilage tissue engineering has a pressing need for novel, biocompatible, biodegradable biocomposites comprising polymers with bioceramics or bioglasses to meet numerous requirements for these applications. We created hydrolytically degradable hydrogel/bioceramic biocomposites, comprising poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels and 50 wt% biphasic hydroxyapatite/β-tricalcium phosphate (60/40) through in situ polymerization. The hydrolytic degradation starts with hydrolysis of the cross-linker, N, O-dimethacryloyl hydroxylamine, which was synthesized in house. Swelling and degradation were examined in details at a phosphate buffered saline solution at 37 °C over a 12-week period of time. To vary degradability, a co-monomer, acrylic acid (AA) or 2-hydroxypropyl methacrylamide (HPMA), was introduced, coupled with altering the concentration of the cross-linker and of the bioceramic. The co-monomer HPMA was found to be more effective than AA in enhancing degradation, though AA led to greater swelling ratios. 33% of weight loss was achieved in some of the biocomposites containing HPMA. Porous structures were developed during swelling and degradation in biocomposites with AA but not in those containing HPMA, suggesting different degradation mechanisms: bulk erosion vs. bulk degradation. Good biocompatibility, as evidenced by attachment and proliferation of mouse-derived osteoblast precursor cells from the MC3T3-E1 lineage, was observed on these biomaterials, regardless of the type of the co-monomer. The rationale and approaches employed here open up new opportunities for creating novel, complex organic-inorganic biomaterials in orthopedic tissue engineering. PMID:23525522

  3. Attaining control by design over the hydrolytic stability of Fe-TAML oxidation catalysts.

    PubMed

    Polshin, Victor; Popescu, Delia-Laura; Fischer, Andreas; Chanda, Arani; Horner, David C; Beach, Evan S; Henry, Jennifer; Qian, Yong-Li; Horwitz, Colin P; Lente, Gabor; Fabian, Istvan; Münck, Eckard; Bominaar, Emile L; Ryabov, Alexander D; Collins, Terrence J

    2008-04-01

    The iron(III) complexes of tetra amidato macrocyclic ligands (TAMLs) ([Fe{1-X1-2-X2C6H2-4,5-(NCOCMe2NCO)2CR2}(OH2)]- , 1: X1 = X2 = H, R2 = Me2 (a), R2 = (CH2)2 (b); X1 = X2 = Cl, R2 = F2 (c), etc.), which the proton is known to demetalate at pH < 3, are also subject to catalyzed demetalation by Brønsted acid buffer components at pH 4-9 such as H2PO4-, HSO3-, and CH3CO2H, HO2CCH2CO2-. Buffers based on pyridine (py) and tris(hydroxymethyl)aminomethane (TRIS) are catalytically inactive. Where reactions proceed, the products are demetalated TAMLs and iron species of variable composition. Pseudo-first-order rate constants for the demetalation (kobs) are linear functions of the acid concentrations, and the effective second-order rate constants k1,eff have a hyperbolic dependence on [H+] (k1,eff = a1[H+]/(b1+[H+]). The rate of demetalation of 1a in H2PO4-/HPO42- buffer is appreciable, but the kobs values for 1b and 1c are immeasurably low, showing that the rates are strongly affected by the CR2 or "tail" fragments, which are known to potently affect the TAML basicity. The reactivities of 1 depend insignificantly on the aromatic ring or "head" group of 1. The proposed mechanism involves precoordination of the acidic buffer species followed by hydrolysis. The demetalating abilities of buffer species depend on their structures and acidities. Thus, although pyridine-2-carboxylic (picolinic) acid catalyzes the demetalation, its 3- and 4-isomers (nicotinic and isonicotininc acids) are inactive. The difference is rationalized to result from the ability that only coordinated picolinic acid has to deliver a proton to an amidato nitrogen in an intramolecular manner. The reaction order in picolinic acid equals one for 1a and two for 1b. For 1b, "inactive" pyridine and nicotinic acid speed up the demetalation in the presence of picolinic acid, suggesting that the second order arises from the axial binding of two pyridine molecules, one of which must be picolinic acid. The binding

  4. Acid-base titrations using microfluidic paper-based analytical devices.

    PubMed

    Karita, Shingo; Kaneta, Takashi

    2014-12-16

    Rapid and simple acid-base titration was accomplished using a novel microfluidic paper-based analytical device (μPAD). The μPAD was fabricated by wax printing and consisted of ten reservoirs for reaction and detection. The reaction reservoirs contained various amounts of a primary standard substance, potassium hydrogen phthalate (KHPth), whereas a constant amount of phenolphthalein was added to all the detection reservoirs. A sample solution containing NaOH was dropped onto the center of the μPAD and was allowed to spread to the reaction reservoirs where the KHPth neutralized it. When the amount of NaOH exceeded that of the KHPth in the reaction reservoirs, unneutralized hydroxide ion penetrated the detection reservoirs, resulting in a color reaction from the phenolphthalein. Therefore, the number of the detection reservoirs with no color change determined the concentration of the NaOH in the sample solution. The titration was completed within 1 min by visually determining the end point, which required neither instrumentation nor software. The volumes of the KHPth and phenolphthalein solutions added to the corresponding reservoirs were optimized to obtain reproducible and accurate results for the concentration of NaOH. The μPADs determined the concentration of NaOH at orders of magnitude ranging from 0.01 to 1 M. An acid sample, HCl, was also determined using Na2CO3 as a primary standard substance instead of KHPth. Furthermore, the μPAD was applicable to the titrations of nitric acid, sulfuric acid, acetic acid, and ammonia solutions. The μPADs were stable for more than 1 month when stored in darkness at room temperature, although this was reduced to only 5 days under daylight conditions. The analysis of acidic hot spring water was also demonstrated in the field using the μPAD, and the results agreed well with those obtained by classic acid-base titration.

  5. Guanine base stacking in G-quadruplex nucleic acids.

    PubMed

    Lech, Christopher Jacques; Heddi, Brahim; Phan, Anh Tuân

    2013-02-01

    G-quadruplexes constitute a class of nucleic acid structures defined by stacked guanine tetrads (or G-tetrads) with guanine bases from neighboring tetrads stacking with one another within the G-tetrad core. Individual G-quadruplexes can also stack with one another at their G-tetrad interface leading to higher-order structures as observed in telomeric repeat-containing DNA and RNA. In this study, we investigate how guanine base stacking influences the stability of G-quadruplexes and their stacked higher-order structures. A structural survey of the Protein Data Bank is conducted to characterize experimentally observed guanine base stacking geometries within the core of G-quadruplexes and at the interface between stacked G-quadruplex structures. We couple this survey with a systematic computational examination of stacked G-tetrad energy landscapes using quantum mechanical computations. Energy calculations of stacked G-tetrads reveal large energy differences of up to 12 kcal/mol between experimentally observed geometries at the interface of stacked G-quadruplexes. Energy landscapes are also computed using an AMBER molecular mechanics description of stacking energy and are shown to agree quite well with quantum mechanical calculated landscapes. Molecular dynamics simulations provide a structural explanation for the experimentally observed preference of parallel G-quadruplexes to stack in a 5'-5' manner based on different accessible tetrad stacking modes at the stacking interfaces of 5'-5' and 3'-3' stacked G-quadruplexes. PMID:23268444

  6. Structure of six organic acid-base adducts from 6-bromobenzo[d]thiazol-2-amine and acidic compounds

    NASA Astrophysics Data System (ADS)

    Jin, Shouwen; Zhang, Jing; Wang, Daqi; Tao, Lin; Zhou, Mengjian; Shen, Yinyan; Chen, Quan; Lin, Zhanghui; Gao, Xingjun

    2014-05-01

    Six anhydrous organic acid-base adducts of 6-bromobenzo[d]thiazol-2-amine were prepared with organic acids as 2,4,6-trinitrophenol, salicylic acid, 3,5-dinitrobenzoic acid, 3,5-dinitrosalicylic acid, malonic acid and sebacic acid. The compounds 1-6 were characterized by X-ray diffraction analysis, IR, and elemental analysis. The melting points of all the adducts were given. Of the six adducts, 1, 3, 4, and 5 are organic salts, while 2, and 6 are cocrystals. The supramolecular arrangement in the crystals 2-6 is based on the R22(8) synthon. Analysis of the crystal packing of 1-6 suggests that there are strong NH⋯O, OH⋯N, and OH⋯O hydrogen bonds (charge assisted or neutral) between acid and base components in the supramolecular assemblies. When the hydroxyl group is present in the ortho position of the carboxy, the intramolecular S6 synthon is present, as expected. Besides the classical hydrogen bonding interactions, other noncovalent interactions also play important roles in structure extension. Due to the synergetic effect of these weak interactions, compounds 1-6 display 1D-3D framework structure.

  7. Acid-degradable polyurethane particles for protein-based vaccines

    PubMed Central

    Bachelder, Eric M.; Beaudette, Tristan T.; Broaders, Kyle E.; Paramonov, Sergey E.; Dashe, Jesse; Fréchet, Jean M. J.

    2009-01-01

    Acid-degradable particles containing a model protein antigen, ovalbumin, were prepared from a polyurethane with acetal moieties embedded throughout the polymer, and characterized by dynamic light scattering and transmission electron microscopy. The small molecule degradation by-product of the particles was synthesized and tested in vitro for toxicity indicating an LC50 of 12,500 μg/ml. A new liquid chromatography-mass spectrometry technique was developed to monitor the in vitro degradation of these particles. The degradation by-product inside RAW macrophages was at its highest level after 24 hours of culture and was efficiently exocytosed until it was no longer detectable after four days. When tested in vitro, these particles induced a substantial increase in the presentation of the immunodominant ovalbumin-derived peptide SIINFEKL in both macrophages and dendritic cells. In addition, vaccination with these particles generated a cytotoxic T-lymphocyte response that was superior to both free ovalbumin and particles made from an analogous but slower-degrading acid-labile polyurethane polymer. Overall, we present a fully degradable polymer system with non-toxic by-products, which may find use in various biomedical applications including protein-based vaccines. PMID:18710254

  8. Kinetics of acid base catalyzed transesterification of Jatropha curcas oil.

    PubMed

    Jain, Siddharth; Sharma, M P

    2010-10-01

    Out of various non-edible oil resources, Jatropha curcas oil (JCO) is considered as future feedstock for biodiesel production in India. Limited work is reported on the kinetics of transesterification of high free fatty acids containing oil. The present study reports the results of kinetic study of two-step acid base catalyzed transesterification process carried out at an optimum temperature of 65 °C and 50 °C for esterification and transesterification respectively under the optimum methanol to oil ratio of 3:7 (v/v), catalyst concentration 1% (w/w) for H₂SO₄ and NaOH. The yield of methyl ester (ME) has been used to study the effect of different parameters. The results indicate that both esterification and transesterification reaction are of first order with reaction rate constant of 0.0031 min⁻¹ and 0.008 min⁻¹ respectively. The maximum yield of 21.2% of ME during esterification and 90.1% from transesterification of pretreated JCO has been obtained.

  9. Water-wire catalysis in photoinduced acid-base reactions.

    PubMed

    Kwon, Oh-Hoon; Mohammed, Omar F

    2012-07-01

    The pronounced ability of water to form a hyperdense hydrogen (H)-bond network among itself is at the heart of its exceptional properties. Due to the unique H-bonding capability and amphoteric nature, water is not only a passive medium, but also behaves as an active participant in many chemical and biological reactions. Here, we reveal the catalytic role of a short water wire, composed of two (or three) water molecules, in model aqueous acid-base reactions synthesizing 7-hydroxyquinoline derivatives. Utilizing femtosecond-resolved fluorescence spectroscopy, we tracked the trajectories of excited-state proton transfer and discovered that proton hopping along the water wire accomplishes the reaction more efficiently compared to the transfer occurring with bulk water clusters. Our finding suggests that the directionality of the proton movements along the charge-gradient H-bond network may be a key element for long-distance proton translocation in biological systems, as the H-bond networks wiring acidic and basic sites distal to each other can provide a shortcut for a proton in searching a global minimum on a complex energy landscape to its destination.

  10. Fast high-throughput method for the determination of acidity constants by capillary electrophoresis: I. Monoprotic weak acids and bases.

    PubMed

    Fuguet, Elisabet; Ràfols, Clara; Bosch, Elisabeth; Rosés, Martí

    2009-04-24

    A new and fast method to determine acidity constants of monoprotic weak acids and bases by capillary zone electrophoresis based on the use of an internal standard (compound of similar nature and acidity constant as the analyte) has been developed. This method requires only two electrophoretic runs for the determination of an acidity constant: a first one at a pH where both analyte and internal standard are totally ionized, and a second one at another pH where both are partially ionized. Furthermore, the method is not pH dependent, so an accurate measure of the pH of the buffer solutions is not needed. The acidity constants of several phenols and amines have been measured using internal standards of known pK(a), obtaining a mean deviation of 0.05 pH units compared to the literature values. PMID:19168179

  11. Fast high-throughput method for the determination of acidity constants by capillary electrophoresis: I. Monoprotic weak acids and bases.

    PubMed

    Fuguet, Elisabet; Ràfols, Clara; Bosch, Elisabeth; Rosés, Martí

    2009-04-24

    A new and fast method to determine acidity constants of monoprotic weak acids and bases by capillary zone electrophoresis based on the use of an internal standard (compound of similar nature and acidity constant as the analyte) has been developed. This method requires only two electrophoretic runs for the determination of an acidity constant: a first one at a pH where both analyte and internal standard are totally ionized, and a second one at another pH where both are partially ionized. Furthermore, the method is not pH dependent, so an accurate measure of the pH of the buffer solutions is not needed. The acidity constants of several phenols and amines have been measured using internal standards of known pK(a), obtaining a mean deviation of 0.05 pH units compared to the literature values.

  12. Spherical Nucleic Acids as Intracellular Agents for Nucleic Acid Based Therapeutics

    NASA Astrophysics Data System (ADS)

    Hao, Liangliang

    Recent functional discoveries on the noncoding sequences of human genome and transcriptome could lead to revolutionary treatment modalities because the noncoding RNAs (ncRNAs) can be applied as therapeutic agents to manipulate disease-causing genes. To date few nucleic acid-based therapeutics have been translated into the clinic due to challenges in the delivery of the oligonucleotide agents in an effective, cell specific, and non-toxic fashion. Unmodified oligonucleotide agents are destroyed rapidly in biological fluids by enzymatic degradation and have difficulty crossing the plasma membrane without the aid of transfection reagents, which often cause inflammatory, cytotoxic, or immunogenic side effects. Spherical nucleic acids (SNAs), nanoparticles consisting of densely organized and highly oriented oligonucleotides, pose one possible solution to circumventing these problems in both the antisense and RNA interference (RNAi) pathways. The unique three dimensional architecture of SNAs protects the bioactive oligonucleotides from unspecific degradation during delivery and supports their targeting of class A scavenger receptors and endocytosis via a lipid-raft-dependent, caveolae-mediated pathway. Owing to their unique structure, SNAs are able to cross cell membranes and regulate target genes expression as a single entity, without triggering the cellular innate immune response. Herein, my thesis has focused on understanding the interactions between SNAs and cellular components and developing SNA-based nanostructures to improve therapeutic capabilities. Specifically, I developed a novel SNA-based, nanoscale agent for delivery of therapeutic oligonucleotides to manipulate microRNAs (miRNAs), the endogenous post-transcriptional gene regulators. I investigated the role of SNAs involving miRNAs in anti-cancer or anti-inflammation responses in cells and in in vivo murine disease models via systemic injection. Furthermore, I explored using different strategies to construct

  13. Modeling description and spectroscopic evidence of surface acid-base properties of natural illites.

    PubMed

    Liu, W

    2001-12-01

    The acid-base properties of natural illites from different areas were studied by potentiometric titrations. The acidimetric supernatant was regarded as the system blank to calculate the surface site concentration due to consideration of substrate dissolution during the prolonged acidic titration. The following surface complexation model could give a good interpretation of the surface acid-base reactions of the aqueous illites:

  14. Dynamical Approach to Multiequilibria Problems for Mixtures of Acids and Their Conjugated Bases

    ERIC Educational Resources Information Center

    Glaser, Rainer E.; Delarosa, Marco A.; Salau, Ahmed Olasunkanmi; Chicone, Carmen

    2014-01-01

    Mathematical methods are described for the determination of steady-state concentrations of all species in multiequilibria systems consisting of several acids and their conjugated bases in aqueous solutions. The main example consists of a mixture of a diprotic acid H[subscript 2]A, a monoprotic acid HB, and their conjugate bases. The reaction…

  15. Comparative Study of Corn Stover Pretreated by Dilute Acid and Cellulose Solvent-Based Lignocellulose Fractionation: Enzymatic Hydrolysis, Supramolecular Structure, and Substrate Accessibility

    SciTech Connect

    Zhu, Z.; Sathitsuksanoh, N.; Vinzant, T.; Schell, D. J.; McMillian, J. D.; Zhang, Y. H. P.

    2009-07-01

    Liberation of fermentable sugars from recalcitrant biomass is among the most costly steps for emerging cellulosic ethanol production. Here we compared two pretreatment methods (dilute acid, DA, and cellulose solvent and organic solvent lignocellulose fractionation, COSLIF) for corn stover. At a high cellulase loading [15 filter paper units (FPUs) or 12.3 mg cellulase per gram of glucan], glucan digestibilities of the corn stover pretreated by DA and COSLIF were 84% at hour 72 and 97% at hour 24, respectively. At a low cellulase loading (5 FPUs per gram of glucan), digestibility remained as high as 93% at hour 24 for the COSLIF-pretreated corn stover but reached only {approx}60% for the DA-pretreated biomass. Quantitative determinations of total substrate accessibility to cellulase (TSAC), cellulose accessibility to cellulase (CAC), and non-cellulose accessibility to cellulase (NCAC) based on adsorption of a non-hydrolytic recombinant protein TGC were measured for the first time. The COSLIF-pretreated corn stover had a CAC of 11.57 m{sup 2}/g, nearly twice that of the DA-pretreated biomass (5.89 m{sup 2}/g). These results, along with scanning electron microscopy images showing dramatic structural differences between the DA- and COSLIF-pretreated samples, suggest that COSLIF treatment disrupts microfibrillar structures within biomass while DA treatment mainly removes hemicellulose. Under the tested conditions COSLIF treatment breaks down lignocellulose structure more extensively than DA treatment, producing a more enzymatically reactive material with a higher CAC accompanied by faster hydrolysis rates and higher enzymatic digestibility.

  16. Comparative study of corn stover pretreated by dilute acid and cellulose solvent-based lignocellulose fractionation: Enzymatic hydrolysis, supramolecular structure, and substrate accessibility.

    PubMed

    Zhu, Zhiguang; Sathitsuksanoh, Noppadon; Vinzant, Todd; Schell, Daniel J; McMillan, James D; Zhang, Y-H Percival

    2009-07-01

    Liberation of fermentable sugars from recalcitrant biomass is among the most costly steps for emerging cellulosic ethanol production. Here we compared two pretreatment methods (dilute acid, DA, and cellulose solvent and organic solvent lignocellulose fractionation, COSLIF) for corn stover. At a high cellulase loading [15 filter paper units (FPUs) or 12.3 mg cellulase per gram of glucan], glucan digestibilities of the corn stover pretreated by DA and COSLIF were 84% at hour 72 and 97% at hour 24, respectively. At a low cellulase loading (5 FPUs per gram of glucan), digestibility remained as high as 93% at hour 24 for the COSLIF-pretreated corn stover but reached only approximately 60% for the DA-pretreated biomass. Quantitative determinations of total substrate accessibility to cellulase (TSAC), cellulose accessibility to cellulase (CAC), and non-cellulose accessibility to cellulase (NCAC) based on adsorption of a non-hydrolytic recombinant protein TGC were measured for the first time. The COSLIF-pretreated corn stover had a CAC of 11.57 m(2)/g, nearly twice that of the DA-pretreated biomass (5.89 m(2)/g). These results, along with scanning electron microscopy images showing dramatic structural differences between the DA- and COSLIF-pretreated samples, suggest that COSLIF treatment disrupts microfibrillar structures within biomass while DA treatment mainly removes hemicellulose. Under the tested conditions COSLIF treatment breaks down lignocellulose structure more extensively than DA treatment, producing a more enzymatically reactive material with a higher CAC accompanied by faster hydrolysis rates and higher enzymatic digestibility.

  17. Buoyancy-driven instabilities of acid-base fronts

    NASA Astrophysics Data System (ADS)

    Almarcha, Christophe; R'honi, Yasmina; Trevelyan, Philip M. J.; de Wit, Anne

    2010-11-01

    Chemical reactions can produce buoyancy-driven motions in solutions by changing the local density in the gravity field. Starting from a stratification of one given miscible reactant solution on top of another miscible one, convective destabilization influenced by the reaction can emerge as a combination of several non-reactive hydrodynamic instabilities, including Rayleigh-Taylor and double diffusive instabilities. In the specific case of reactions between a strong acid and a strong base, we show that all the possible scenarios reduce to the composition of only two asymptotic situations because products generated at the reactive zone are always less dense and slower diffusing than the reactants. Experiments in a vertically orientated Hele-Shaw cell confirm the theoretical predictions and can be quantitatively compared to numerical simulations of a nonlinear reaction-diffusion-convection model.

  18. Ultrasonic and densimetric titration applied for acid-base reactions.

    PubMed

    Burakowski, Andrzej; Gliński, Jacek

    2014-01-01

    Classical acoustic acid-base titration was monitored using sound speed and density measurements. Plots of these parameters, as well as of the adiabatic compressibility coefficient calculated from them, exhibit changes with the volume of added titrant. Compressibility changes can be explained and quantitatively predicted theoretically in terms of Pasynski theory of non-compressible hydrates combined with that of the additivity of the hydration numbers with the amount and type of ions and molecules present in solution. It also seems that this development could be applied in chemical engineering for monitoring the course of chemical processes, since the applied experimental methods can be carried out almost independently on the medium under test (harmful, aggressive, etc.).

  19. Activity, life time and effect of hydrolytic enzymes for enhanced biogas production from sludge anaerobic digestion.

    PubMed

    Odnell, Anna; Recktenwald, Michael; Stensén, Katarina; Jonsson, Bengt-Harald; Karlsson, Martin

    2016-10-15

    As an alternative to energy intensive physical methods, enzymatic treatment of sludge produced at wastewater treatment plants for increased hydrolysis and biogas production was investigated. Several hydrolytic enzymes were assessed with a focus on how enzyme activity and life time was influenced by sludge environments. It could be concluded that the activity life time of added enzymes was limited (<24 h) in both waste activated sludge and anaerobic digester sludge environments and that this was, for the majority of enzymes, due to endogenous protease activity. In biogas in situ experiments, subtilisin at a 1% mixture on basis of volatile solids, was the only enzyme providing a significantly increased biomethane production of 37%. However, even at this high concentration, subtilisin could not hydrolyze all available substrate within the life time of the enzyme. Thus, for large scale implementation, enzymes better suited to the sludge environments are needed. PMID:27498254

  20. Inhibitors of the Hydrolytic Enzyme Dimethylarginine Dimethylaminohydrolase (DDAH): Discovery, Synthesis and Development.

    PubMed

    Murphy, Rhys B; Tommasi, Sara; Lewis, Benjamin C; Mangoni, Arduino A

    2016-01-01

    Dimethylarginine dimethylaminohydrolase (DDAH) is a highly conserved hydrolytic enzyme found in numerous species, including bacteria, rodents, and humans. In humans, the DDAH-1 isoform is known to metabolize endogenous asymmetric dimethylarginine (ADMA) and monomethyl arginine (l-NMMA), with ADMA proposed to be a putative marker of cardiovascular disease. Current literature reports identify the DDAH family of enzymes as a potential therapeutic target in the regulation of nitric oxide (NO) production, mediated via its biochemical interaction with the nitric oxide synthase (NOS) family of enzymes. Increased DDAH expression and NO production have been linked to multiple pathological conditions, specifically, cancer, neurodegenerative disorders, and septic shock. As such, the discovery, chemical synthesis, and development of DDAH inhibitors as potential drug candidates represent a growing field of interest. This review article summarizes the current knowledge on DDAH inhibition and the derived pharmacokinetic parameters of the main DDAH inhibitors reported in the literature. Furthermore, current methods of development and chemical synthetic pathways are discussed. PMID:27187323

  1. Biogas production from brewery spent grain enhanced by bioaugmentation with hydrolytic anaerobic bacteria.

    PubMed

    Čater, Maša; Fanedl, Lijana; Malovrh, Špela; Logar, Romana Marinšek

    2015-06-01

    Lignocellulosic substrates are widely available but not easily applied in biogas production due to their poor anaerobic degradation. The effect of bioaugmentation by anaerobic hydrolytic bacteria on biogas production was determined by the biochemical methane potential assay. Microbial biomass from full scale upflow anaerobic sludge blanket reactor treating brewery wastewater was a source of active microorganisms and brewery spent grain a model lignocellulosic substrate. Ruminococcus flavefaciens 007C, Pseudobutyrivibrio xylanivorans Mz5(T), Fibrobacter succinogenes S85 and Clostridium cellulovorans as pure and mixed cultures were used to enhance the lignocellulose degradation and elevate the biogas production. P. xylanivorans Mz5(T) was the most successful in elevating methane production (+17.8%), followed by the coculture of P. xylanivorans Mz5(T) and F. succinogenes S85 (+6.9%) and the coculture of C. cellulovorans and F. succinogenes S85 (+4.9%). Changes in microbial community structure were detected by fingerprinting techniques.

  2. Shape and size controlled synthesis of uniform iron oxide nanocrystals through new non-hydrolytic routes

    NASA Astrophysics Data System (ADS)

    Li, Wenlu; Lee, Seung Soo; Wu, Jiewei; Hinton, Carl H.; Fortner, John D.

    2016-08-01

    New, non-hydrolytic routes to synthesize highly crystalline iron oxide nanocrystals (8–40 nm, magnetite) are described in this report whereby particle size and morphology were precisely controlled through reactant (precursor, e.g. (FeO(OH)) ratios, co-surfactant and organic additive, and/or reaction time. Particle size, with high monodispersivity (<10%), is demonstrated to be a function of precursor concentrations and through the addition of different cosurfactants and/or additives, cubic, octahedral, potato-like, and flower-like iron oxide nanocrystals can be reproducibly synthesized through simple one-pot thermal decomposition methods. High resolution transmission electron microscope, x-ray diffraction, and superconducting quantum interference device were used to characterize the size, structure and magnetic properties of the resulting nanocrystals. For aqueous applications, materials synthesized/purified in organic solvents are broadly water dispersible through a variety of phase (aqueous) transfer method(s).

  3. Biogas production from brewery spent grain enhanced by bioaugmentation with hydrolytic anaerobic bacteria.

    PubMed

    Čater, Maša; Fanedl, Lijana; Malovrh, Špela; Logar, Romana Marinšek

    2015-06-01

    Lignocellulosic substrates are widely available but not easily applied in biogas production due to their poor anaerobic degradation. The effect of bioaugmentation by anaerobic hydrolytic bacteria on biogas production was determined by the biochemical methane potential assay. Microbial biomass from full scale upflow anaerobic sludge blanket reactor treating brewery wastewater was a source of active microorganisms and brewery spent grain a model lignocellulosic substrate. Ruminococcus flavefaciens 007C, Pseudobutyrivibrio xylanivorans Mz5(T), Fibrobacter succinogenes S85 and Clostridium cellulovorans as pure and mixed cultures were used to enhance the lignocellulose degradation and elevate the biogas production. P. xylanivorans Mz5(T) was the most successful in elevating methane production (+17.8%), followed by the coculture of P. xylanivorans Mz5(T) and F. succinogenes S85 (+6.9%) and the coculture of C. cellulovorans and F. succinogenes S85 (+4.9%). Changes in microbial community structure were detected by fingerprinting techniques. PMID:25836034

  4. Metagenomics as a Tool for Enzyme Discovery: Hydrolytic Enzymes from Marine-Related Metagenomes.

    PubMed

    Popovic, Ana; Tchigvintsev, Anatoly; Tran, Hai; Chernikova, Tatyana N; Golyshina, Olga V; Yakimov, Michail M; Golyshin, Peter N; Yakunin, Alexander F

    2015-01-01

    This chapter discusses metagenomics and its application for enzyme discovery, with a focus on hydrolytic enzymes from marine metagenomic libraries. With less than one percent of culturable microorganisms in the environment, metagenomics, or the collective study of community genetics, has opened up a rich pool of uncharacterized metabolic pathways, enzymes, and adaptations. This great untapped pool of genes provides the particularly exciting potential to mine for new biochemical activities or novel enzymes with activities tailored to peculiar sets of environmental conditions. Metagenomes also represent a huge reservoir of novel enzymes for applications in biocatalysis, biofuels, and bioremediation. Here we present the results of enzyme discovery for four enzyme activities, of particular industrial or environmental interest, including esterase/lipase, glycosyl hydrolase, protease and dehalogenase. PMID:26621459

  5. The addition of accessory enzymes enhances the hydrolytic performance of cellulase enzymes at high solid loadings.

    PubMed

    Hu, Jinguang; Chandra, Richard; Arantes, Valdeir; Gourlay, Keith; van Dyk, J Susan; Saddler, Jack N

    2015-06-01

    The pretreatment process used and the nature of the biomass feedstock will influence the role that accessory enzymes can play in synergistically interacting with cellulases to effectively deconstruct the substrate. The work reported here assessed the possible boosting effects of the xylanase and lytic polysaccharide monooxygenase (AA9, formerly known as GH61) on the hydrolytic potential of cellulase enzyme mixtures during hydrolysis of steam pretreated poplar and corn stover at high (10-20% w/v) substrate concentrations. A higher proportion of xylanase was required when the substrate had a relatively high xylan content and at high substrate concentrations. In contrast, a relatively small amount of AA9 (about 2 mg/g cellulose) was enough, regardless of the nature or concentration of the substrate. The overall protein loading required to achieve effective hydrolysis of high concentrations of pretreated biomass substrates could be substantially reduced by optimizing the ratio of enzymes in the "cellulase" mixture.

  6. Activity, life time and effect of hydrolytic enzymes for enhanced biogas production from sludge anaerobic digestion.

    PubMed

    Odnell, Anna; Recktenwald, Michael; Stensén, Katarina; Jonsson, Bengt-Harald; Karlsson, Martin

    2016-10-15

    As an alternative to energy intensive physical methods, enzymatic treatment of sludge produced at wastewater treatment plants for increased hydrolysis and biogas production was investigated. Several hydrolytic enzymes were assessed with a focus on how enzyme activity and life time was influenced by sludge environments. It could be concluded that the activity life time of added enzymes was limited (<24 h) in both waste activated sludge and anaerobic digester sludge environments and that this was, for the majority of enzymes, due to endogenous protease activity. In biogas in situ experiments, subtilisin at a 1% mixture on basis of volatile solids, was the only enzyme providing a significantly increased biomethane production of 37%. However, even at this high concentration, subtilisin could not hydrolyze all available substrate within the life time of the enzyme. Thus, for large scale implementation, enzymes better suited to the sludge environments are needed.

  7. Inhibitors of the Hydrolytic Enzyme Dimethylarginine Dimethylaminohydrolase (DDAH): Discovery, Synthesis and Development.

    PubMed

    Murphy, Rhys B; Tommasi, Sara; Lewis, Benjamin C; Mangoni, Arduino A

    2016-01-01

    Dimethylarginine dimethylaminohydrolase (DDAH) is a highly conserved hydrolytic enzyme found in numerous species, including bacteria, rodents, and humans. In humans, the DDAH-1 isoform is known to metabolize endogenous asymmetric dimethylarginine (ADMA) and monomethyl arginine (l-NMMA), with ADMA proposed to be a putative marker of cardiovascular disease. Current literature reports identify the DDAH family of enzymes as a potential therapeutic target in the regulation of nitric oxide (NO) production, mediated via its biochemical interaction with the nitric oxide synthase (NOS) family of enzymes. Increased DDAH expression and NO production have been linked to multiple pathological conditions, specifically, cancer, neurodegenerative disorders, and septic shock. As such, the discovery, chemical synthesis, and development of DDAH inhibitors as potential drug candidates represent a growing field of interest. This review article summarizes the current knowledge on DDAH inhibition and the derived pharmacokinetic parameters of the main DDAH inhibitors reported in the literature. Furthermore, current methods of development and chemical synthetic pathways are discussed.

  8. Plastic-PDMS bonding for high pressure hydrolytically stable active microfluidics.

    PubMed

    Lee, Kevin S; Ram, Rajeev J

    2009-06-01

    We explore the application of organofunctional silanes for bonding plastic substrates to PDMS membranes. Such devices would enable actuated membrane microfluidics in plastic devices. Bond strength degradation in aqueous environments can be reduced by using bis-silanes with larger alkoxy end groups to promote organofunctional bond formation with the plastic substrate. Hydrolytic failure can also result from low silane crosslink density or interface hydrophilicity. A test device consisting of three-valve peristaltic pumps is fabricated out of polycarbonate (PC) and bonded to PDMS through isopropoxy modified bis-trimethoxy-silyl-propyl-amine. Valves operated up to 60 psi in aqueous environments without failure. Solutions of DI water and 1 M HCl were also pumped through the device via peristaltic actuation at 18 psi for 2 weeks without bond failure. 1 M NaOH was also tested but resulted in bond failure after 115 hours.

  9. The ciliate, Troglodytella abrassarti, contributes to polysaccharide hydrolytic activities in the chimpanzee colon.

    PubMed

    Profousová, I; Mihaliková, K; Laho, T; Váradyová, Z; Petrželková, K J; Modrý, D; Kišidayová, S

    2011-07-01

    Entodiniomorphid ciliates are intestinal protists inhabiting the colons of African great apes. The participation of intestinal entodiniomorphid ciliates in ape hindgut digestion has been proposed, but little data have been available to support the hypothesis. We measured the specific activities of carboxymethyl cellulase, xylanase, inulinase, and α-amylase against different polysaccharides in the feces of captive chimpanzees and evaluated the participation of the entodiniomorphid ciliate, Troglodytella abrassarti, in these activities. T. abrassarti contributed to the total fecal hydrolytic activities of CM-cellulase by 16.2%, α-amylase by 5.95%, and xylanase by 0.66%. Inulinase activity in T. abrassarti samples was not measurable at reaction conditions used. The ciliates, T. abrassarti, actively participate in the chimpanzee hindgut fermentation of fiber and starch.

  10. Shape and size controlled synthesis of uniform iron oxide nanocrystals through new non-hydrolytic routes

    NASA Astrophysics Data System (ADS)

    Li, Wenlu; Lee, Seung Soo; Wu, Jiewei; Hinton, Carl H.; Fortner, John D.

    2016-08-01

    New, non-hydrolytic routes to synthesize highly crystalline iron oxide nanocrystals (8-40 nm, magnetite) are described in this report whereby particle size and morphology were precisely controlled through reactant (precursor, e.g. (FeO(OH)) ratios, co-surfactant and organic additive, and/or reaction time. Particle size, with high monodispersivity (<10%), is demonstrated to be a function of precursor concentrations and through the addition of different cosurfactants and/or additives, cubic, octahedral, potato-like, and flower-like iron oxide nanocrystals can be reproducibly synthesized through simple one-pot thermal decomposition methods. High resolution transmission electron microscope, x-ray diffraction, and superconducting quantum interference device were used to characterize the size, structure and magnetic properties of the resulting nanocrystals. For aqueous applications, materials synthesized/purified in organic solvents are broadly water dispersible through a variety of phase (aqueous) transfer method(s).

  11. Metagenomics as a Tool for Enzyme Discovery: Hydrolytic Enzymes from Marine-Related Metagenomes.

    PubMed

    Popovic, Ana; Tchigvintsev, Anatoly; Tran, Hai; Chernikova, Tatyana N; Golyshina, Olga V; Yakimov, Michail M; Golyshin, Peter N; Yakunin, Alexander F

    2015-01-01

    This chapter discusses metagenomics and its application for enzyme discovery, with a focus on hydrolytic enzymes from marine metagenomic libraries. With less than one percent of culturable microorganisms in the environment, metagenomics, or the collective study of community genetics, has opened up a rich pool of uncharacterized metabolic pathways, enzymes, and adaptations. This great untapped pool of genes provides the particularly exciting potential to mine for new biochemical activities or novel enzymes with activities tailored to peculiar sets of environmental conditions. Metagenomes also represent a huge reservoir of novel enzymes for applications in biocatalysis, biofuels, and bioremediation. Here we present the results of enzyme discovery for four enzyme activities, of particular industrial or environmental interest, including esterase/lipase, glycosyl hydrolase, protease and dehalogenase.

  12. Base excess or buffer base (strong ion difference) as measure of a non-respiratory acid-base disturbance.

    PubMed

    Siggaard-Andersen, O; Fogh-Andersen, N

    1995-01-01

    Stewart in 1983 (Can J Physiol Pharmacol 1983: 61: 1444) reintroduced plasma buffer base under the name "strong ion difference" (SID). Buffer base was originally introduced by Singer and Hastings in 1948 (Medicine (Baltimore) 1948: 27: 223). Plasma buffer base, which is practically equal to the sum of bicarbonate and albuminate anions, may be increased due to an excess of base or due to an increased albumin concentration. Singer and Hastings did not consider changes in albumin as acid-base disorders and therefore used the base excess, i.e., the actual buffer base minus the buffer base at normal pH and pCO2, as measure of a non-respiratory acid-base disturbance. Stewart and followers, however, consider changes in albumin concentration to be acid-base disturbances: a patient with normal pH, pCO2, and base excess but with increased plasma buffer base due to increased plasma albumin concentration get the diagnoses metabolic (strong ion) alkalosis (because plasma buffer base is increased) combined with metabolic hyperalbuminaemic acidosis. Extrapolating to whole blood, anaemia and polycytaemia should represent types of metabolic alkalosis and acidosis, respectively. This reveals that the Stewart approach is absurd and anachronistic in the sense that an increase or decrease in any anion is interpreted as indicating an excess or deficit of a specific acid. In other words, a return to the archaic definitions of acids and bases as being the same as anions and cations. We conclude that the acid-base status (the hydrogen ion status) of blood and extracellular fluid is described in terms of the arterial pH, the arterial pCO2, and the extracellular base excess. It is measured with a modern pH-blood gas analyser. The electrolyte status of the plasma is a description of the most important electrolytes, usually measured in venous blood with a dedicated electrolyte analyser, i.e., Na+, Cl-, HCO3-, and K+. Albumin anions contribute significantly to the anions, but calculation

  13. Adansonian Analysis and Deoxyribonucleic Acid Base Composition of Serratia marcescens

    PubMed Central

    Colwell, R. R.; Mandel, M.

    1965-01-01

    Colwell, R. R. (Georgetown University, Washington, D.C.), and M. Mandel. Adansonian analysis and deoxyribonucleic acid base composition of Serratia marcescens. J. Bacteriol. 89:454–461. 1965.—A total of 33 strains of Serratia marcescens were subjected to Adansonian analysis for which more than 200 coded features for each of the organisms were included. In addition, the base composition [expressed as moles per cent guanine + cytosine (G + C)] of the deoxyribonucleic acid (DNA) prepared from each of the strains was determined. Except for four strains which were intermediate between Serratia and the Hafnia and Aerobacter group C of Edwards and Ewing, the S. marcescens species group proved to be extremely homogeneous, and the different strains showed high affinities for each other (mean similarity, ¯S = 77%). The G + C ratio of the DNA from the Serratia strains ranged from 56.2 to 58.4% G + C. Many species names have been listed for the genus, but only a single clustering of the strains was obtained at the species level, for which the species name S. marcescens was retained. S. kiliensis, S. indica, S. plymuthica, and S. marinorubra could not be distinguished from S. marcescens; it was concluded, therefore, that there is only a single species in the genus. The variety designation kiliensis does not appear to be valid, since no subspecies clustering of strains with negative Voges-Proskauer reactions could be detected. The characteristics of the species are listed, and a description of S. marcescens is presented. PMID:14255714

  14. Are carboxyl groups the most acidic sites in amino acids? Gas-phase acidities, photoelectron spectra, and computations on tyrosine, p-hydroxybenzoic acid, and their conjugate bases.

    PubMed

    Tian, Zhixin; Wang, Xue-Bin; Wang, Lai-Sheng; Kass, Steven R

    2009-01-28

    Deprotonation of tyrosine in the gas phase was found to occur preferentially at the phenolic site, and the conjugate base consists of a 70:30 mixture of phenoxide and carboxylate anions at equilibrium. This result was established by developing a chemical probe for differentiating these two isomers, and the presence of both ions was confirmed by photoelectron spectroscopy. Equilibrium acidity measurements on tyrosine indicated that deltaG(acid)(o) = 332.5 +/- 1.5 kcal mol(-1) and deltaH(acid)(o) = 340.7 +/- 1.5 kcal mol(-1). Photoelectron spectra yielded adiabatic electron detachment energies of 2.70 +/- 0.05 and 3.55 +/- 0.10 eV for the phenoxide and carboxylate anions, respectively. The H/D exchange behavior of deprotonated tyrosine was examined using three different alcohols (CF3CH2OD, C6H5CH2OD, and CH3CH2OD), and incorporation of up to three deuterium atoms was observed. Two pathways are proposed to account for these results, and all of the experimental findings are supplemented with B3LYP/aug-cc-pVDZ and G3B3 calculations. In addition, it was found that electrospray ionization of tyrosine from a 3:1 (v/v) CH3OH/H2O solution using a commercial source produces a deprotonated [M-H]- anion with the gas-phase equilibrium composition rather than the structure of the ion that exists in aqueous media. Electrospray ionization from acetonitrile, however, leads largely to the liquid-phase (carboxylate) structure. A control molecule, p-hydroxybenzoic acid, was found to behave in a similar manner. Thus, the electrospray conditions that are employed for the analysis of a compound can alter the isomeric composition of the resulting anion.

  15. Nanoconstructions Based on Spatially Ordered Nucleic Acid Molecules

    NASA Astrophysics Data System (ADS)

    Yevdokimov, Yu. M.

    Different strategies for the design of nanoconstructions whose building blocks are both linear molecules of double-stranded nucleic acids and nucleic acid molecules fixed in the spatial structure of particles of liquid-crystalline dispersions are described.

  16. Amine-based systems for carboxylic acid recovery

    SciTech Connect

    King, C.J.

    1992-05-01

    Several carboxylic acids are prominent commercial products, and their number and importance will probably grow. Getting these acids out of aqueous solution is necessary in petrochemical manufacture, fermentation, and the environmentally and economically important recovery from waste streams. In this paper, the authors discuss the methods possible to extract acids such as citric, lactic, and succinic from complex mixtures. Carboxylic acids are also readily made by fermentation and are among the most attractive substances that could be manufactured from biomass. Branches of this cycle lead to acetic, lactic, propionic, and formic acids, among others. Carboxylic acids are promising intermediates in a bioprocessing complex, because the oxygen of the biomass is placed in a form that is useful for further reaction with many other products. Citric acid is manufactured on a large scale by fermentation, and lactic and fumaric acids, among others, were manufactured that way in the past.

  17. Biotechnological routes based on lactic acid production from biomass.

    PubMed

    Gao, Chao; Ma, Cuiqing; Xu, Ping

    2011-01-01

    Lactic acid, the most important hydroxycarboxylic acid, is now commercially produced by the fermentation of sugars present in biomass. In addition to its use in the synthesis of biodegradable polymers, lactic acid can be regarded as a feedstock for the green chemistry of the future. Different potentially useful chemicals such as pyruvic acid, acrylic acid, 1,2-propanediol, and lactate ester can be produced from lactic acid via chemical and biotechnological routes. Here, we reviewed the current status of the production of potentially valuable chemicals from lactic acid via biotechnological routes. Although some of the reactions described in this review article are still not applicable at current stage, due to their "greener" properties, biotechnological processes for the production of lactic acid derivatives might replace the chemical routes in the future. PMID:21846500

  18. Microgel Tethering For Microarray-Based Nucleic Acid Diagnostics

    NASA Astrophysics Data System (ADS)

    Dai, Xiaoguang

    Molecular diagnostics (MDx) have radically changed the process of clinical microbial identification based on identifying genetic information, MDx approaches are both specific and fast. They can identify microbes to the species and strain level over a time scale that can be as short as one hour. With such information clinicians can administer the most effective and appropriate antimicrobial treatment at an early time point with substantial implications both for patient well-being and for easing the burden on the health-care system. Among the different MDx approaches, such as fluorescence in-situ hybridization, microarrays, next-generation sequencing, and mass spectrometry, point-of-care MDx platforms are drawing particular interest due to their low cost, robustness, and wide application. This dissertation develops a novel MDx technology platform capable of high target amplification and detection performance. For nucleic acid target detection, we fabricate an array of electron-beam-patterned microgels on a standard glass microscope slide. The microgels can be as small as a few hundred nanometers. The unique way of energy deposition during electron-beam lithography provides the microgels with a very diffuse water -gel interface that enables them to not only serve as substrates to immobilize DNA probes but do so while preserving them in a highly hydrated environment that optimizes their performance. Benefiting from the high spatial resolution provided by such techniques as position-sensitive microspotting and dip-pen nanolithography, multiple oligonucleotide probes known as molecular beacons (MBs) can be patterned on microgels. Furthermore, nucleic acid target amplification can be conducted in direct contact with the microgel-tethered detection array. Specifically, we use an isothermal RNA amplification reaction - nucleic acid sequence-based amplification (NASBA). ssRNA amplicons of from the NASBA reaction can directly hybridize with microgel-tethered MBs, and the

  19. Improved physical stability of amorphous state through acid base interactions.

    PubMed

    Telang, Chitra; Mujumdar, Siddharthya; Mathew, Michael

    2009-06-01

    To investigate role of specific interactions in aiding formation and stabilization of amorphous state in ternary and binary dispersions of a weakly acidic drug. Indomethacin (IMC), meglumine (MU), and polyvinyl pyrollidone (PVP) were the model drug, base, and polymer, respectively. Dispersions were prepared using solvent evaporation. Physical mixtures were cryogenically coground. XRPD, PLM, DSC, TGA, and FTIR were used for characterization. MU has a high crystallization tendency and is characterized by a low T(g) (17 degrees C). IMC crystallization was inhibited in ternary dispersion with MU compared to IMC/PVP alone. An amorphous state formed readily even in coground mixtures. Spectroscopic data are indicative of an IMC-MU amorphous salt and supports solid-state proton transfer. IMC-MU salt displays a low T(g) approximately 50 degrees C, but is more physically stable than IMC, which in molecular mixtures with MU, resisted crystallization even when present in stoichiometric excess of base. This is likely due to a disrupted local structure of amorphous IMC due to specific interactions. IMC showed improved physical stability on incorporating MU in polymer, in spite of low T(g) of the base indicating that chemical interactions play a dominant role in physical stabilization. Salt formation could be induced thermally and mechanically.

  20. Acid-base transport by the renal proximal tubule

    PubMed Central

    Skelton, Lara A.; Boron, Walter F.; Zhou, Yuehan

    2015-01-01

    Each day, the kidneys filter 180 L of blood plasma, equating to some 4,300 mmol of the major blood buffer, bicarbonate (HCO3−). The glomerular filtrate enters the lumen of the proximal tubule (PT), and the majority of filtered HCO3− is reclaimed along the early (S1) and convoluted (S2) portions of the PT in a manner coupled to the secretion of H+ into the lumen. The PT also uses the secreted H+ to titrate non-HCO3− buffers in the lumen, in the process creating “new HCO3−” for transport into the blood. Thus, the PT – along with more distal renal segments – is largely responsible for regulating plasma [HCO3−]. In this review we first focus on the milestone discoveries over the past 50+ years that define the mechanism and regulation of acid-base transport by the proximal tubule. Further on in the review, we will summarize research still in progress from our laboratory, work that addresses the problem of how the PT is able to finely adapt to acid–base disturbances by rapidly sensing changes in basolateral levels of HCO3− and CO2 (but not pH), and thereby to exert tight control over the acid–base composition of the blood plasma. PMID:21170887

  1. [Determination of body fluid based on analysis of nucleic acids].

    PubMed

    Korabečná, Marie

    2015-01-01

    Recent methodological approaches of molecular genetics allow isolation of nucleic acids (DNA and RNA) from negligible forensic samples. Analysis of these molecules may be used not only for individual identification based on DNA profiling but also for the detection of origin of the body fluid which (alone or in mixture with other body fluids) forms the examined biological trace. Such an examination can contribute to the evaluation of procedural, technical and tactical value of the trace. Molecular genetic approaches discussed in the review offer new possibilities in comparison with traditional spectrum of chemical, immunological and spectroscopic tests especially with regard to the interpretation of mixtures of biological fluids and to the confirmatory character of the tests. Approaches based on reverse transcription of tissue specific mRNA and their subsequent polymerase chain reaction (PCR) and fragmentation analysis are applicable on samples containing minimal amounts of biological material. Methods for body fluid discrimination based on examination of microRNA in samples provided so far confusing results therefore further development in this field is needed. The examination of tissue specific methylation of nucleotides in selected gene sequences seems to represent a promising enrichment of the methodological spectrum. The detection of DNA sequences of tissue related bacteria has been established and it provides satisfactory results mainly in combination with above mentioned methodological approaches. PMID:26419517

  2. Influence of electron-beam radiation on the hydrolytic degradation behaviour of poly(lactide-co-glycolide) (PLGA).

    PubMed

    Loo, Say Chye Joachim; Ooi, Chui Ping; Boey, Yin Chiang Freddy

    2005-06-01

    The purpose of this study is to examine the effect of electron-beam (e-beam) radiation on the hydrolytic degradation of poly(lactide-co-glycolide) (PLGA) films. PLGA films were irradiated and observed to undergo radiation-induced degradation through chain scission, as observed from a drop in its average molecular weight with radiation dose. Irradiated (5, 10 and 20 Mrad) and non-irradiated (0 Mrad) samples of PLGA were subsequently hydrolytically degraded in phosphate-buffered saline solution at 37.0 degrees C over a span of 12 weeks. It was observed that the natural logarithmic molecular weight (lnMn) of PLGA decreases linearly with hydrolytic degradation time. The rate of water uptake is higher for samples irradiated at higher radiation dose (e.g. 20 Mrad) and subsequently causing an earlier onset of mass loss. It is postulated that the increase in water uptake is due to the presence of more hydrophilic end groups, which results in the formation of microcavities because of an increase in osmotic pressure. A relationship between radiation dose and the rate of hydrolytic degradation of PLGA films, through its molecular weight was also established. This relationship allows a more accurate and precise control of the life span of PLGA through the use of e-beam radiation. PMID:15626429

  3. Methylene-bis[(aminomethyl)phosphinic acids]: synthesis, acid-base and coordination properties.

    PubMed

    David, Tomáš; Procházková, Soňa; Havlíčková, Jana; Kotek, Jan; Kubíček, Vojtěch; Hermann, Petr; Lukeš, Ivan

    2013-02-21

    Three symmetrical methylene-bis[(aminomethyl)phosphinic acids] bearing different substituents on the central carbon atom, (NH(2)CH(2))PO(2)H-C(R(1))(R(2))-PO(2)H(CH(2)NH(2)) where R(1) = OH, R(2) = Me (H(2)L(1)), R(1) = OH, R(2) = Ph (H(2)L(2)) and R(1),R(2) = H (H(2)L(3)), were synthesized. Acid-base and complexing properties of the ligands were studied in solution as well as in the solid state. The ligands show unusually high basicity of the nitrogen atoms (log K(1) = 9.5-10, log K(2) = 8.5-9) if compared with simple (aminomethyl)phosphinic acids and, consequently, high stability constants of the complexes with studied divalent metal ions. The study showed the important role of the hydroxo group attached to the central carbon atom of the geminal bis(phosphinate) moiety. Deprotonation of the hydroxo group yields the alcoholate anion which tends to play the role of a bridging ligand and induces formation of polynuclear complexes. Solid-state structures of complexes [H(2)N=C(NH(2))(2)][Cu(2)(H(-1)L(2))(2)]CO(3)·10H(2)O and Li(2)[Co(4)(H(-1)L(1))(3)(OH)]·17.5H(2)O were determined by X-ray diffraction. The complexes show unexpected geometries forming dinuclear and cubane-like structures, respectively. The dinuclear copper(II) complex contains a bridging μ(2)-alcoholate group with the (-)O-P(=O)-CH(2)-NH(2) fragments of each ligand molecule chelated to the different central ion. In the cubane cobalt(II) complex, one μ(3)-hydroxide and three μ(3)-alcoholate anions are located in the cube vertices and both phosphinate groups of one ligand molecule are chelating the same cobalt(II) ion while each of its amino groups are bound to different neighbouring metal ions. All such three metal ions are bridged by the alcoholate group of a given ligand.

  4. Reaction Mechanism for Direct Proton Transfer from Carbonic Acid to a Strong Base in Aqueous Solution I: Acid and Base Coordinate and Charge Dynamics.

    PubMed

    Daschakraborty, Snehasis; Kiefer, Philip M; Miller, Yifat; Motro, Yair; Pines, Dina; Pines, Ehud; Hynes, James T

    2016-03-10

    Protonation by carbonic acid H2CO3 of the strong base methylamine CH3NH2 in a neutral contact pair in aqueous solution is followed via Car-Parrinello molecular dynamics simulations. Proton transfer (PT) occurs to form an aqueous solvent-stabilized contact ion pair within 100 fs, a fast time scale associated with the compression of the acid-base hydrogen-bond (H-bond), a key reaction coordinate. This rapid barrierless PT is consistent with the carbonic acid-protonated base pKa difference that considerably favors the PT, and supports the view of intact carbonic acid as potentially important proton donor in assorted biological and environmental contexts. The charge redistribution within the H-bonded complex during PT supports a Mulliken picture of charge transfer from the nitrogen base to carbonic acid without altering the transferring hydrogen's charge from approximately midway between that of a hydrogen atom and that of a proton. PMID:26879554

  5. Reaction Mechanism for Direct Proton Transfer from Carbonic Acid to a Strong Base in Aqueous Solution I: Acid and Base Coordinate and Charge Dynamics.

    PubMed

    Daschakraborty, Snehasis; Kiefer, Philip M; Miller, Yifat; Motro, Yair; Pines, Dina; Pines, Ehud; Hynes, James T

    2016-03-10

    Protonation by carbonic acid H2CO3 of the strong base methylamine CH3NH2 in a neutral contact pair in aqueous solution is followed via Car-Parrinello molecular dynamics simulations. Proton transfer (PT) occurs to form an aqueous solvent-stabilized contact ion pair within 100 fs, a fast time scale associated with the compression of the acid-base hydrogen-bond (H-bond), a key reaction coordinate. This rapid barrierless PT is consistent with the carbonic acid-protonated base pKa difference that considerably favors the PT, and supports the view of intact carbonic acid as potentially important proton donor in assorted biological and environmental contexts. The charge redistribution within the H-bonded complex during PT supports a Mulliken picture of charge transfer from the nitrogen base to carbonic acid without altering the transferring hydrogen's charge from approximately midway between that of a hydrogen atom and that of a proton.

  6. Amino acid-bile acid based molecules: extremely narrow surfactant nanotubes formed by a phenylalanine-substituted cholic acid.

    PubMed

    Travaglini, Leana; D'Annibale, Andrea; Schillén, Karin; Olsson, Ulf; Sennato, Simona; Pavel, Nicolae V; Galantini, Luciano

    2012-12-21

    An amino acid-substituted bile acid forms tubular aggregates with inner and outer diameters of about 3 and 6 nm. The diameters are unusually small for surfactant self-assembled tubes. The results enhance the spectrum of applications of supramolecular tubules and open up possibilities for investigating a novel class of biological amphiphiles.

  7. Swelling behaviors of porous lignin based poly (acrylic acid).

    PubMed

    Ma, Yanli; Sun, Yajie; Fu, Yujie; Fang, Guizhen; Yan, Xingru; Guo, Zhanhu

    2016-11-01

    Supramolecular cross-linked porous lignin based poly (acrylic acid) [LBPAA] was lab-synthesized by copolymerizing lignin grafted N, N'-methylene-bisacrylamide (LM) and acrylic acid. LBPAA successfully acted as a water retention agent with salt resistance and biodegradation for agricultural applications. Lignin was found to improve its swelling behaviors with higher water retention, fast swelling and de-swelling rates. The salt tolerance was stronger in the case of LBPAA (60 PAA/40 LM) [60 wt% PAA/40 wt% LM], i.e., 145.79 g·g(-1) higher than PAA at 0.09 mM KCl solution. The effect of ion charges on the LBPAA swelling ratio was greater than that of ionic radius. The weight loss of LBPAA (60 PAA/40 LM) was 5.47%, 4.96%, and 4.56% in the soil of Tangshan, Harbin, and Sian, respectively. The soil moisture content and clay content were observed to decrease gradually with increasing the burial time. The biodegradation test of LBPAA (60 PAA/40 LM) composite exhibited different bacterial colony forming units (CFU), the soil of Tangshan was 2.0 × 10(3) CFU·g(-1) soil, 7.0 × 10(3) CFU·g(-1) soil for Harbin, and 6.10 × 10(4) CFU·g(-1) soil for Sian. However, the organic matter contents in the soils did not have significant changes (Tangshan 6.21 mg·g(-1), Harbin 0.61 mg·g(-1), and Sian 0.405 mg·g(-1)). PMID:27587327

  8. Electrospun poly(lactic acid) based conducting nanofibrous networks

    NASA Astrophysics Data System (ADS)

    Patra, S. N.; Bhattacharyya, D.; Ray, S.; Easteal, A. J.

    2009-08-01

    Multi-functionalised micro/nanostructures of conducting polymers in neat or blended forms have received much attention because of their unique properties and technological applications in electrical, magnetic and biomedical devices. Biopolymer-based conducting fibrous mats are of special interest for tissue engineering because they not only physically support tissue growth but also are electrically conductive, and thus are able to stimulate specific cell functions or trigger cell responses. They are effective for carrying current in biological environments and can thus be considered for delivering local electrical stimuli at the site of damaged tissue to promote wound healing. Electrospinning is an established way to process polymer solutions or melts into continuous fibres with diameter often in the nanometre range. This process primarily depends on a number of parameters, including the type of polymer, solution viscosity, polarity and surface tension of the solvent, electric field strength and the distance between the spinneret and the collector. The present research has included polyaniline (PANi) as the conducting polymer and poly(L-lactic acid) (PLLA) as the biopolymer. Dodecylbenzene sulphonic acid (DBSA) doped PANi and PLLA have been dissolved in a common solvent (mixtures of chloroform and dimethyl formamide (DMF)), and the solutions successfully electrospun. DMF enhanced the dielectric constant of the solvent, and tetra butyl ammonium bromide (TBAB) was used as an additive to increase the conductivity of the solution. DBSA-doped PANi/PLLA mat exhibits an almost bead-free network of nanofibres that have extraordinarily smooth surface and diameters in the range 75 to 100 nm.

  9. Solution influence on biomolecular equilibria - Nucleic acid base associations

    NASA Technical Reports Server (NTRS)

    Pohorille, A.; Pratt, L. R.; Burt, S. K.; Macelroy, R. D.

    1984-01-01

    Various attempts to construct an understanding of the influence of solution environment on biomolecular equilibria at the molecular level using computer simulation are discussed. First, the application of the formal statistical thermodynamic program for investigating biomolecular equilibria in solution is presented, addressing modeling and conceptual simplications such as perturbative methods, long-range interaction approximations, surface thermodynamics, and hydration shell. Then, Monte Carlo calculations on the associations of nucleic acid bases in both polar and nonpolar solvents such as water and carbon tetrachloride are carried out. The solvent contribution to the enthalpy of base association is positive (destabilizing) in both polar and nonpolar solvents while negative enthalpies for stacked complexes are obtained only when the solute-solute in vacuo energy is added to the total energy. The release upon association of solvent molecules from the first hydration layer around a solute to the bulk is accompanied by an increase in solute-solvent energy and decrease in solvent-solvent energy. The techniques presented are expectd to displace less molecular and more heuristic modeling of biomolecular equilibria in solution.

  10. Ligation with nucleic acid sequence-based amplification.

    PubMed

    Ong, Carmichael; Tai, Warren; Sarma, Aartik; Opal, Steven M; Artenstein, Andrew W; Tripathi, Anubhav

    2012-01-01

    This work presents a novel method for detecting nucleic acid targets using a ligation step along with an isothermal, exponential amplification step. We use an engineered ssDNA with two variable regions on the ends, allowing us to design the probe for optimal reaction kinetics and primer binding. This two-part probe is ligated by T4 DNA Ligase only when both parts bind adjacently to the target. The assay demonstrates that the expected 72-nt RNA product appears only when the synthetic target, T4 ligase, and both probe fragments are present during the ligation step. An extraneous 38-nt RNA product also appears due to linear amplification of unligated probe (P3), but its presence does not cause a false-positive result. In addition, 40 mmol/L KCl in the final amplification mix was found to be optimal. It was also found that increasing P5 in excess of P3 helped with ligation and reduced the extraneous 38-nt RNA product. The assay was also tested with a single nucleotide polymorphism target, changing one base at the ligation site. The assay was able to yield a negative signal despite only a single-base change. Finally, using P3 and P5 with longer binding sites results in increased overall sensitivity of the reaction, showing that increasing ligation efficiency can improve the assay overall. We believe that this method can be used effectively for a number of diagnostic assays. PMID:22449695

  11. Studies on the effect of virtual crosslinking on the hydrolytic stability of novel aliphatic polyurethane ureas for blood contact applications.

    PubMed

    Thomas, V; Jayabalan, M

    2001-07-01

    The effect of virtual crosslinking on the hydrolytic stability of completely aliphatic novel poly(urethane ureas), HFL9-PU1 (hard-segment content 57.5%) and HFL13-PU2 (hard-segment content 67.9%) based on 4,4'-methylene bis(cyclohexyl isocyanate) (H(12)MDI)-hydroxy-terminated polybutadiene-1,6-hexamethylene diamine, was studied. Fourier transform infrared-attenuated total reflectance and wide-angle X-ray diffraction studies revealed hydrogen-bonding interaction and microphase separation and formation of crystallites by short- and long-range ordering in hard-segment domains. Three-dimensional networks from hydrogen bonding in the present polymers lead to virtually crosslinking and insolubility. These polymers were noncytotoxic to L929 fibroblast cells. The hemolytic potential is below the accepted limit. The studies on in vitro biostability in Ringer's solution, phosphate buffered saline, and papain enzyme revealed no weight loss. The infrared spectral studies revealed changes in the surface, especially on HFL9-PU1 aged in Ringer's solution and phosphate buffered saline, and no changes when aged in papain. The marginal changes noticed in tensile properties were attributed to the changes in degree of hydrogen bonding and associated rearrangement of molecular structure in the bulk. The results revealed that the lesser the crosslinking in virgin polymer, the higher the crosslinking in aged polymer and vice versa. Increased crosslinking during aging provided increased tensile properties in the aged polymer over the virgin polymer and vice versa. For comparison, an aliphatic polyetherurethane urea (HFL16-PU3) was also synthesized using poly(oxy tetra methylene glycol) in addition to the above reactants. Though both HFL9-PU1 and HFL16-PU3 contained the same hard-segment content, the aged sample of the latter showed decreased tensile properties with increased crosslinking during aging in contrast to the former. This was attributed to less microphase separation in the

  12. Hemolymph acid-base balance of the crayfish Astacus leptodactylus as a function of the oxygenation and the acid-base balance of the ambient water.

    PubMed

    Dejours, P; Armand, J

    1980-07-01

    The acid-base balance of the prebranchial hemolymph of the crayfish Astacus leptodactylus was studied at various acid-base balances and levels of oxygenation of the ambient water at 13 degrees C. The water acid-base balance was controlled automatically by a pH-CO2-stat. Into water of constant titration alkalinity, TA, this device intermittenly injects carbon dioxide to maintain the pH at a preset value. Water pH was reduced to the same value either by hypercapnia (at constant TA) or by adding HCl or H2SO4 to decrease the TA (at constant CO2 tension). Decrease of hemolymph pH and increase of hemolymph PCO2 were similar for the three acidic waters. Water oxygenation changes strongly affected hemolymph ABB. In crayfish living in hyperoxic water (PO2 congruent to 600 Torr) compared to those in hypoxic water (PO2 congruent to 40 Torr), hemolymph pH was 0.3 to 0.4 unit lower and hemolymph PCO2 several times higher, the exact values of pH and PCO2 depending on the controlled ambient acid-base balance. In any study of the hemolymph acid-base balance of the crayfish, it is an important to control ambient water's acid-base balance and oxygenation as it is to control its temperature, a conclusion which probably holds true for studies on all water breathers.

  13. Effect of acid-base alterations on hepatic lactate utilization

    PubMed Central

    Goldstein, Philip J.; Simmons, Daniel H.; Tashkin, Donald P.

    1972-01-01

    1. The effect of acid-base changes on hepatic lactate utilization was investigated in anaesthetized, mechanically ventilated dogs. 2. Portal vein flow and hepatic artery flow were measured with electromagnetic flowmeters, lactate concentration of portal vein, arterial and mixed hepatic venous blood was determined by an enzymatic technique, and hepatic lactate uptake was calculated using the Fick principle. 3. Respiratory alkalosis (Δ pH 0·25 ± 0·02) in four dogs resulted in a significant fall in total hepatic blood flow (-22 ± 4%) and a significant rise in both arterial lactate concentration (2·18 ± 0·32 m-mole/l.) and hepatic lactate utilization (3·9 ± 1·2 μmole/min.kg). 4. 0·6 M-Tris buffer infusion (Δ pH 0·21 ± 0·02) in four dogs produced no significant changes in liver blood flow, arterial lactate concentration or hepatic lactate uptake. 5. Respiratory acidosis (Δ pH -0·20 ± 0·03) in six dogs and metabolic acidosis (Δ pH -0·20 ± 0·02) in four dogs produced no significant changes in liver blood flow, decreases in arterial lactate concentration of 0·38 ± 0·09 m-mole/l. (P < 0·05) and 0·13 ± 0·13 m-mole/l., respectively, and no significant changes in hepatic lactate uptake. 6. A significant correlation (r = 0·63; P < 0·01) was found between hepatic lactate utilization and arterial lactate concentration during the hyperlactataemia associated with respiratory alkalosis. 7. Hyperlactataemia induced in four dogs by infusion of buffered sodium lactate (Δ pH 0·05 ± 0·01;% Δ liver blood flow 29 ± 7%) was also significantly correlated with hepatic lactate utilization (r = 0·70; P < 0·01) and the slope of the regression was similar to that during respiratory alkalosis. 8. These data suggest that the hyperlactataemia of alkalosis is not due to impaired hepatic utilization of lactate and that the principal determinant of hepatic lactate uptake during alkalosis or lactate infusion is blood lactate concentration, rather than liver

  14. Ultrastructural observation of the acid-base resistant zone of all-in-one adhesives using three different acid-base challenges.

    PubMed

    Tsujimoto, Miho; Nikaido, Toru; Inoue, Go; Sadr, Alireza; Tagami, Junji

    2010-11-01

    The aim of this study was to analyze the ultrastructure of the dentin-adhesive interface using two all-in-one adhesive systems (Clearfil Tri-S Bond, TB; Tokuyama Bond Force, BF) after different acid-base challenges. Three solutions were used as acidic solutions for the acid-base challenges: a demineralizing solution (DS), a phosphoric acid solution (PA), and a hydrochloric acid solution (HCl). After the acid-base challenges, the bonded interfaces were examined by scanning electron microscopy. Thickness of the acid-base resistant zone (ABRZ) created in PA and HCl was thinner than in DS for both adhesive systems. For BF adhesive, an eroded area was observed beneath the ABRZ after immersion in PA and HCl, but not in DS. Conversely for TB adhesive, the eroded area was observed only after immersion in PA. In conclusion, although the ABRZ was observed for both all-in-one adhesive systems, its morphological features were influenced by the ingredients of both the adhesive material and acidic solution.

  15. An elementary derivation of the hard/soft-acid/base principle.

    PubMed

    Ayers, Paul W

    2005-04-01

    The hard/soft-acid/base (HSAB) principle indicates that hard acids prefer binding to hard bases (often forming bonds with substantial ionic character) while soft acids prefer binding to soft bases (often forming bonds with substantial covalent character). Though the HSAB principle is a foundational concept of the modern theory of acids and bases, the theoretical underpinnings of the HSAB principle remain murky. This paper examines the exchange reaction, wherein two molecules, one the product of reacting a hard acid and a soft base and the other the product of reacting a soft acid with a hard base, exchange substituents to form the preferred hard-hard and soft-soft product. A simple derivation shows that this reaction is exothermic, proving the validity of the HSAB principle. The analysis leads to the simple and conceptually appealing conclusion that the HSAB principle is a driven by simple electron transfer effects.

  16. ACID-BASE ACCOUNT EFFECTIVENESS FOR DETERMINATION OF MINE WASTE POTENTIAL ACIDITY. (R825549C048)

    EPA Science Inventory

    The oxidation of sulfide minerals in mine waste is a widespread source of resource degradation, often resulting in the generation of acidic water and mobilization of heavy metals. The quantity of acid forming minerals present in mine waste, dominantly as pyrite (FeS2

  17. Design and Characterization of Auxotrophy-Based Amino Acid Biosensors

    PubMed Central

    Bertels, Felix; Merker, Holger; Kost, Christian

    2012-01-01

    Efficient and inexpensive methods are required for the high-throughput quantification of amino acids in physiological fluids or microbial cell cultures. Here we develop an array of Escherichia coli biosensors to sensitively quantify eleven different amino acids. By using online databases, genes involved in amino acid biosynthesis were identified that – upon deletion – should render the corresponding mutant auxotrophic for one particular amino acid. This rational design strategy suggested genes involved in the biosynthesis of arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, threonine, tryptophan, and tyrosine as potential genetic targets. A detailed phenotypic characterization of the corresponding single-gene deletion mutants indeed confirmed that these strains could neither grow on a minimal medium lacking amino acids nor transform any other proteinogenic amino acid into the focal one. Site-specific integration of the egfp gene into the chromosome of each biosensor decreased the detection limit of the GFP-labeled cells by 30% relative to turbidometric measurements. Finally, using the biosensors to determine the amino acid concentration in the supernatants of two amino acid overproducing E. coli strains (i.e. ΔhisL and ΔtdcC) both turbidometrically and via GFP fluorescence emission and comparing the results to conventional HPLC measurements confirmed the utility of the developed biosensor system. Taken together, our study provides not only a genotypically and phenotypically well-characterized set of publicly available amino acid biosensors, but also demonstrates the feasibility of the rational design strategy used. PMID:22829942

  18. Using problem based learning and guided inquiry in a high school acid-base chemistry unit

    NASA Astrophysics Data System (ADS)

    McKinley, Katie

    The purpose of this investigation was to determine if incorporating problem based learning and guided inquiry would improve student achievement in an acid base unit for high school chemistry. The activities and labs in the unit were modified to be centered around the problem of a fish kill that students investigated. Students also participated in guided inquiry labs to increase the amount of critical thinking and problem solving being done in the classroom. The hypothesis was that the implementation of problem based learning and guided inquiry would foster student learning. Students took a pre-test and post-test on questions covering the objectives of the acid base unit. These assessments were compared to determine the effectiveness of the unit. The results indicate that the unit was effective in increasing student performance on the unit test. This study also analyzed the process of problem based learning. Problem based learning can be an effective method of engaging students in inquiry. However, designing an effective problem based learning unit requires careful design of the problem and enough structure to assure students learn the intended content.

  19. Electroreduction and acid-base properties of dipyrrolylquinoxalines.

    PubMed

    Fu, Zhen; Zhang, Min; Zhu, Weihua; Karnas, Elizabeth; Mase, Kentaro; Ohkubo, Kei; Sessler, Jonathan L; Fukuzumi, Shunichi; Kadish, Karl M

    2012-10-18

    The electroreduction and acid-base properties of dipyrrolylquinoxalines of the form H(2)DPQ, H(2)DPQ(NO(2)), and H(2)DPQ(NO(2))(2) were investigated in benzonitrile (PhCN) containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). This study focuses on elucidating the complete electrochemistry, spectroelectrochemistry, and acid-base properties of H(2)DPQ(NO(2))(n) (n = 0, 1, or 2) in PhCN before and after the addition of trifluoroacetic acid (TFA), tetra-n-butylammonium hydroxide (TBAOH), tetra-n-butylammonium fluoride (TBAF), or tetra-n-butylammonium acetate (TBAOAc) to solution. Electrochemical and spectroelectrochemical data provide support for the formation of a monodeprotonated anion after disproportionation of a dipyrrolylquinoxaline radical anion produced initially. The generated monoanion is then further reduced in two reversible one-electron-transfer steps at more negative potentials in the case of H(2)DPQ(NO(2)) and H(2)DPQ(NO(2))(2). Electrochemically monitored titrations of H(2)DPQ(NO(2))(n) with OH(-), F(-), or OAc(-) (in the form of TBA(+)X(-) salts) give rise to the same monodeprotonated H(2)DPQ(NO(2))(n) produced during electroreduction in PhCN. This latter anion can then be reduced in two additional one-electron-transfer steps in the case of H(2)DPQ(NO(2)) and H(2)DPQ(NO(2))(2). Spectroscopically monitored titrations of H(2)DPQ(NO(2))(n) with X(-) show a 1:2 stoichiometry and provide evidence for the production of both [H(2)DPQ(NO(2))(n)](-) and XHX(-). The spectroscopically measured equilibrium constants range from log β(2) = 5.3 for the reaction of H(2)DPQ with TBAOAc to log β(2) = 8.8 for the reaction of H(2)DPQ(NO(2))(2) with TBAOH. These results are consistent with a combined deprotonation and anion binding process. Equilibrium constants for the addition of one H(+) to each quinoxaline nitrogen of H(2)DPQ, H(2)DPQ(NO(2)), and H(2)DPQ(NO(2))(2) in PhCN containing 0.1 M TBAP were also determined via electrochemical and spectroscopic means

  20. A Comparison of Different Teaching Designs of "Acids and Bases" Subject

    ERIC Educational Resources Information Center

    Ültay, Neslihan; Çalik, Muammer

    2016-01-01

    Inability to link the acid-base concepts with daily life phenomena (as contexts) highlights the need for further research on the context-based acid-base chemistry. In this vein, the aim of this study is to investigate the effects of different teaching designs (REACT strategy, 5Es learning model and traditional (existing) instruction) relevant with…

  1. Hands-On Science: Is It an Acid or a Base? These Colorful Tests Tell All!

    ERIC Educational Resources Information Center

    VanCleave, Janice

    1998-01-01

    Two hands-on science activities for K-6 students teach them how to determine if something is an acid or a base. The activities require acid/base indicator juice, testing strips, and a base solution. A recipe for making them in the classroom using red cabbage and baking soda is provided. (SM)

  2. A library of L-tyrosine-derived biodegradable polyarylates for potential biomaterial applications, part I: synthesis, characterization and accelerated hydrolytic degradation.

    PubMed

    Huang, Xia; Shen, Chang-Yu; Chen, Jia-Chang; Li, Qian

    2009-01-01

    A combinatorial library of biodegradable polyarylates derived from L-tyrosine was synthesized and characterized. These polyarylates are A-B-type co-polymers consisting of a cyclic dipeptide and a diacid. General structure-property correlations were established by comparing aryl diacid co-polymers and aliphatic diacid co-polymers. The synthesized polymers were characterized by FT-IR, (1)H-NMR, (13)C-NMR for their chemical structure, by DSC and TGA for their thermal characteristics and by GPC for their molecular weight distribution. The T(g) of polymers decreased and water absorption increased with increasing number of methylene groups in the polymer backbone. Using a cyclic peptide derived from L-tyrosine as co-monomer we obtained optimum bioactivity and biocompatibility. Combinatorial approaches of designing material increased effectively the number of available degradable polymers which can be used in different biomaterials applications. General structure-property correlation makes polymers' properties varied in a predictable and systematic fashion. Accelerated hydrolytic degradation studies of polyarylates were performed at 70 degrees C in acid and alkali medium. The degradation rates of polymers were in accordance with their water absorption. The degradation rates of samples in acid medium were lower than those in alkali medium. PMID:19454161

  3. 77 FR 16126 - Microbiology Devices; Reclassification of Nucleic Acid-Based Systems for Mycobacterium tuberculosis

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-19

    ... Food and Drug Administration 21 CFR Part 866 Microbiology Devices; Reclassification of Nucleic Acid...: Proposed rule. SUMMARY: The Food and Drug Administration (FDA) is proposing to reclassify nucleic acid... effectiveness of the device for its intended use. II. Regulatory Background of the Device Nucleic acid-based...

  4. Evaluation of the number of ionogenic groups of inulinase by acid-base titration.

    PubMed

    Kovaleva, T A; Holyavka, M G; Rezvan, S G; Kozhedub, S V

    2008-06-01

    Acid base titration showed that Aspergillus awamori inulinase includes 178 asparaginic and glutamic acid residues, 20 histidine, 10 serine, and 34 lysine and tyrosine residues. Denaturation temperature for this enzyme was calculated using analysis of the proportion of stabilizing and destabilizing amino acids in the molecule.

  5. [Development of Nucleic Acid-Based Adjuvant for Cancer Immunotherapy].

    PubMed

    Kobiyama, Kouji; Ishii, Ken J

    2015-09-01

    Since the discovery of the human T cell-defined tumor antigen, the cancer immunotherapy field has rapidly progressed, with the research and development of cancer immunotherapy, including cancer vaccines, being conducted actively. However, the disadvantages of most cancer vaccines include relatively weak immunogenicity and immune escape or exhaustion. Adjuvants with innate immunostimulatory activities have been used to overcome these issues, and these agents have been shown to enhance the immunogenicity of cancer vaccines and to act as mono-therapeutic anti-tumor agents. CpG ODN, an agonist for TLR9, is one of the promising nucleic acid-based adjuvants, and it is a potent inducer of innate immune effector functions. CpG ODN suppresses tumor growth in the absence of tumor antigens and peptide administration. Therefore, CpG ODN is expected to be useful as a cancer vaccine adjuvant as well as a cancer immunotherapy agent. In this review, we discuss the potential therapeutic applications and mechanisms of CpG ODN for cancer immunotherapy.

  6. Environmental applications of poly(amic acid)-based nanomaterials.

    PubMed

    Okello, Veronica A; Du, Nian; Deng, Boling; Sadik, Omowunmi A

    2011-05-01

    Nanoscale materials offer new possibilities for the development of novel remediation and environmental monitoring technologies. Different nanoscale materials have been exploited for preventing environmental degradation and pollutant transformation. However, the rapid self-aggregation of nanoparticles or their association with suspended solids or sediments where they could bioaccumulate supports the need for polymeric coatings to improve mobility, allows faster site cleanups and reduces remediation cost. The ideal material must be able to coordinate different nanomaterials functionalities and exhibit the potential for reusability. We hereby describe two novel environmental applications of nanostructured poly (amic acid)-based (nPAA) materials. In the first application, nPAA was used as both reductant and stabilizer during the in situ chemical reduction of chromium(vi) to chromium(iii). Results showed that Cr(vi) species were rapidly reduced within the concentration range of 10(-1) to 10(2) mM with efficiency of 99.9% at 40 °C in water samples and 90% at 40 °C in soil samples respectively. Furthermore, the presence of PdNPs on the PAA-Au electrode was found to significantly enhance the rate of reduction. In the second application, nPAA membranes were tested as filters to capture, isolate and detect nanosilver. Preliminary results demonstrate the capability of the nPAA membranes to quantitatively capture nanoparticles from suspension and quantify their abundance on the membranes. Silver nanoparticles detection at concentrations near the toxic threshold of silver was also demonstrated.

  7. Hyaluronic Acid Based Hydrogels for Regenerative Medicine Applications.

    PubMed

    Borzacchiello, Assunta; Russo, Luisa; Malle, Birgitte M; Schwach-Abdellaoui, Khadija; Ambrosio, Luigi

    2015-01-01

    Hyaluronic acid (HA) hydrogels, obtained by cross-linking HA molecules with divinyl sulfone (DVS) based on a simple, reproducible, and safe process that does not employ any organic solvents, were developed. Owing to an innovative preparation method the resulting homogeneous hydrogels do not contain any detectable residual cross-linking agent and are easier to inject through a fine needle. HA hydrogels were characterized in terms of degradation and biological properties, viscoelasticity, injectability, and network structural parameters. They exhibit a rheological behaviour typical of strong gels and show improved viscoelastic properties by increasing HA concentration and decreasing HA/DVS weight ratio. Furthermore, it was demonstrated that processes such as sterilization and extrusion through clinical needles do not imply significant alteration of viscoelastic properties. Both SANS and rheological tests indicated that the cross-links appear to compact the network, resulting in a reduction of the mesh size by increasing the cross-linker amount. In vitro degradation tests of the HA hydrogels demonstrated that these new hydrogels show a good stability against enzymatic degradation, which increases by increasing HA concentration and decreasing HA/DVS weight ratio. Finally, the hydrogels show a good biocompatibility confirmed by in vitro tests. PMID:26090451

  8. [Development of Nucleic Acid-Based Adjuvant for Cancer Immunotherapy].

    PubMed

    Kobiyama, Kouji; Ishii, Ken J

    2015-09-01

    Since the discovery of the human T cell-defined tumor antigen, the cancer immunotherapy field has rapidly progressed, with the research and development of cancer immunotherapy, including cancer vaccines, being conducted actively. However, the disadvantages of most cancer vaccines include relatively weak immunogenicity and immune escape or exhaustion. Adjuvants with innate immunostimulatory activities have been used to overcome these issues, and these agents have been shown to enhance the immunogenicity of cancer vaccines and to act as mono-therapeutic anti-tumor agents. CpG ODN, an agonist for TLR9, is one of the promising nucleic acid-based adjuvants, and it is a potent inducer of innate immune effector functions. CpG ODN suppresses tumor growth in the absence of tumor antigens and peptide administration. Therefore, CpG ODN is expected to be useful as a cancer vaccine adjuvant as well as a cancer immunotherapy agent. In this review, we discuss the potential therapeutic applications and mechanisms of CpG ODN for cancer immunotherapy. PMID:26469159

  9. Hyaluronic Acid Based Hydrogels for Regenerative Medicine Applications

    PubMed Central

    Borzacchiello, Assunta; Russo, Luisa; Malle, Birgitte M.; Schwach-Abdellaoui, Khadija; Ambrosio, Luigi

    2015-01-01

    Hyaluronic acid (HA) hydrogels, obtained by cross-linking HA molecules with divinyl sulfone (DVS) based on a simple, reproducible, and safe process that does not employ any organic solvents, were developed. Owing to an innovative preparation method the resulting homogeneous hydrogels do not contain any detectable residual cross-linking agent and are easier to inject through a fine needle. HA hydrogels were characterized in terms of degradation and biological properties, viscoelasticity, injectability, and network structural parameters. They exhibit a rheological behaviour typical of strong gels and show improved viscoelastic properties by increasing HA concentration and decreasing HA/DVS weight ratio. Furthermore, it was demonstrated that processes such as sterilization and extrusion through clinical needles do not imply significant alteration of viscoelastic properties. Both SANS and rheological tests indicated that the cross-links appear to compact the network, resulting in a reduction of the mesh size by increasing the cross-linker amount. In vitro degradation tests of the HA hydrogels demonstrated that these new hydrogels show a good stability against enzymatic degradation, which increases by increasing HA concentration and decreasing HA/DVS weight ratio. Finally, the hydrogels show a good biocompatibility confirmed by in vitro tests. PMID:26090451

  10. Improving pharmacy students' understanding and long-term retention of acid-base chemistry.

    PubMed

    Roche, Victoria F

    2007-12-15

    Despite repeated exposure to the principles underlying the behavior of organic acids and bases in aqueous solution, some pharmacy students remain confused about the topic of acid-base chemistry. Since a majority of organic drug molecules have acid-base character, the ability to predict their reactivity and the extent to which they will ionize in a given medium is paramount to students' understanding of essentially all aspects of drug action in vivo and in vitro. This manuscript presents a medicinal chemistry lesson in the fundamentals of acid-base chemistry that many pharmacy students have found enlightening and clarifying.

  11. Acid-base properties of sorbents based on modified zirconium(IV) phosphates

    SciTech Connect

    Bekrenev, A.V.; Pyartman, A.K.

    1995-11-01

    Modifying and doping syntheses are widely used to improve the reproducibility of ion-exchange properties and to increase the capacity of inorganic ion exchangers. Numerous examples of doping zirconium phosphate ion exchangers with cationic or anionic additives are known. The aim of this work was to investigate the acid-base properties of zirconium phosphates modified with anionic additives (phthalate and sulfosalicylate ions) in comparison with unmodified samples.

  12. Polyol and Amino Acid-Based Biosurfactants, Builders, and Hydrogels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This chapter reviews different detergent materials which have been synthesized from natural agricultural commodities. Background information, which gives reasons why the use of biobased materials may be advantageous, is presented. Detergent builders from L-aspartic acid, citric acid and D-sorbitol...

  13. Nitric acid: modeling osmotic coefficients and acid-base dissociation using the BIMSA theory.

    PubMed

    Ruas, Alexandre; Pochon, Patrick; Simonin, Jean-Pierre; Moisy, Philippe

    2010-11-14

    This work is aimed at a description of the thermodynamic properties of highly concentrated aqueous solutions of nitric acid salts at 25 °C within the binding mean spherical approximation (BIMSA) theory. The predictive capability of this model was examined. First, Raman spectroscopy was used to study the proportion of associated nitric acid as a function of concentration. The corresponding apparent association constant values were compared with literature values. Besides, the BIMSA model, taking into account complex formation, was used to represent literature experimental osmotic coefficient variation with concentration. This theoretical description led to an assessment of the degree of association. The so calculated amount of associated nitric acid coincides accurately with our Raman experimental results up to a high concentration of acid.

  14. Production of Jatropha biodiesel fuel over sulfonic acid-based solid acids.

    PubMed

    Chen, Shih-Yuan; Lao-Ubol, Supranee; Mochizuki, Takehisa; Abe, Yohko; Toba, Makoto; Yoshimura, Yuji

    2014-04-01

    Sulfonic acid-functionalized platelet SBA-15 mesoporous silica with an acid capacity of 2.44mmol H(+) g-cat(-1) (shortly termed 15SA-SBA-15-p) was one-pot synthesized by co-condensation method. When applied as solid acid catalyst in synthesis of Jatropha biodiesel fuel (BDF), the 15SA-SBA-15-p catalyst showed higher activity and resistances to water and free fatty acid (FFA) than commercial sulfonic resins of Amberlyst-15 and SAC-13. For the continuous Jatropha BDF production, a steady 75-78wt% of fatty acid methyl ester (FAME) content was obtained over 15SA-SBA-15-p catalyst at 150°C for 75h, whereas the Amberlyst-15 and SAC-13 catalysts were quickly deactivated due to the decomposition of thermally unstable framework and serious leaching of sulfonic acids. More importantly, the quality, stability and cold flow characteristic of Jatropha BDF synthesized by 15SA-SBA-15-p catalyst were better than those synthesized by Amberlyst-15 and SAC-13 catalysts, making the blending with petro-diesel an easy task.

  15. Classification and identification of amino acids based on THz spectroscopy

    NASA Astrophysics Data System (ADS)

    Huang, Ping J.; Ma, Ye H.; Li, Xian; Hou, Di B.; Cai, Jin H.; Zhang, Guang X.

    2015-11-01

    Amino acids are important nutrient substances for life, and many of them have several isomerides, while only L-type amino acids can be absorbed by body as nutrients. So it is certain worth to accurately classify and identify amino acids. In this paper, terahertz time-domain spectroscopy (THz-TDS) was used to detect isomers of various amino acids to obtain their absorption spectra, and their spectral characteristics were analyzed and compared. Results show that not all isomerides of amino acids have unique spectral characteristics, causing the difficulty of classification and identification. To solve this problem, partial least squares discriminant analysis (PLS-DA), firstly, was performed on extracting principal component of THz spectroscopy and classifying amino acids. Moreover, variable selection (VS) was employed to optimize spectral interval of feature extraction to improve analysis effect. As a result, the optimal classification model was determined and most samples can be accurately classified. Secondly, for each class of amino acids, PLS-DA combined with VS was also applied to identify isomerides. This work provides a suggestion for material classification and identification with THz spectroscopy.

  16. Development of polylactic acid-based materials through reactive modification

    NASA Astrophysics Data System (ADS)

    Fowlks, Alison Camille

    2009-12-01

    Polylactic acid (PLA)-based systems have shown to be of great potential for the development of materials requiring biobased content, biodegradation, and sufficient properties. The efforts in this study are directed toward addressing the current research need to overcome some of the inherent drawbacks of PLA. To meet this need, reactive extrusion was employed to develop new materials based on PLA by grafting, compounding, and polymer blending. In the first part of this work, maleic anhydride (MA) was grafted onto PLA by reactive extrusion. Two structurally different peroxides were used to initiate grafting and results were reported on the basis of grafting, molecular weight, and thermal behavior. An inverse relationship between degree of grafting and molecular weight was established. It was also found that, regardless of peroxide type, there is an optimum peroxid-to-MA ratio of 0.5:2 that promotes maximum grafting, beyond which degradation reactions become predominant. Overall, it was found that the maleated copolymer (MAPLA) could be used as an interfacial modifier in PLA-based composites. Therefore, MAPLA was incorporated into PLA-talc composites in varying concentrations. The influence of the MAPLA addition on the mechanical and thermal behavior was investigated. When added in an optimum concentration, MAPLA improved the tensile strength and crystallization of the composite. Furthermore, microscopic observation confirmed the compatibilization effect of MAPLA in PLA-talc composites. Vinyltrimethoxysilane was free-radically grafted onto the backbone of PLA and subsequently moisture crosslinked. The effects of monomer, initiator, and catalyst concentration on the degree of crosslinking and the mechanical and thermal properties were investigated. The presence of a small amount of catalyst showed to be a major contributor to the crosslinking formation in the time frame investigated, shown by an increase in gel content and decrease in crystallinity. Furthermore

  17. Unnatural amino acid mutagenesis-based enzyme engineering.

    PubMed

    Ravikumar, Yuvaraj; Nadarajan, Saravanan Prabhu; Yoo, Tae Hyeon; Lee, Chong-soon; Yun, Hyungdon

    2015-08-01

    Traditional enzyme engineering relies on substituting one amino acid by one of the other 19 natural amino acids to change the functional properties of an enzyme. However, incorporation of unnatural amino acids (UAAs) has been harnessed to engineer efficient enzymes for biocatalysis. Residue-specific and site-specific in vivo incorporation methods are becoming the preferred approach for producing enzymes with altered or improved functions. We describe the contribution of in vivo UAA incorporation methodologies to enzyme engineering as well as the future prospects for the field, including the integration of UAAs with other new advances in enzyme engineering.

  18. Hybride magnetic nanostructure based on amino acids functionalized polypyrrole

    NASA Astrophysics Data System (ADS)

    Nan, Alexandrina; Bunge, Alexander; Turcu, Rodica

    2015-12-01

    Conducting polypyrrole is especially promising for many commercial applications because of its unique optical, electric, thermal and mechanical properties. We report the synthesis and characterization of novel pyrrole functionalized monomers and core-shell hybrid nanostructures, consisting of a conjugated polymer layer (amino acids functionalized pyrrole copolymers) and a magnetic nanoparticle core. For functionalization of the pyrrole monomer we used several amino acids: tryptophan, leucine, phenylalanine, serine and tyrosine. These amino acids were linked via different types of hydrophobic linkers to the nitrogen atom of the pyrrole monomer. The magnetic core-shell hybrid nanostructures are characterized by various methods such as FTIR spectroscopy, transmission electron microscopy (TEM) and magnetic measurements.

  19. Hybride magnetic nanostructure based on amino acids functionalized polypyrrole

    SciTech Connect

    Nan, Alexandrina Bunge, Alexander; Turcu, Rodica

    2015-12-23

    Conducting polypyrrole is especially promising for many commercial applications because of its unique optical, electric, thermal and mechanical properties. We report the synthesis and characterization of novel pyrrole functionalized monomers and core-shell hybrid nanostructures, consisting of a conjugated polymer layer (amino acids functionalized pyrrole copolymers) and a magnetic nanoparticle core. For functionalization of the pyrrole monomer we used several amino acids: tryptophan, leucine, phenylalanine, serine and tyrosine. These amino acids were linked via different types of hydrophobic linkers to the nitrogen atom of the pyrrole monomer. The magnetic core-shell hybrid nanostructures are characterized by various methods such as FTIR spectroscopy, transmission electron microscopy (TEM) and magnetic measurements.

  20. Acid-base site detection and mapping on solid surfaces by Kelvin force microscopy (KFM).

    PubMed

    Gouveia, Rubia F; Bernardes, Juliana S; Ducati, Telma R D; Galembeck, Fernando

    2012-12-01

    Electrostatic potential at the surface of acidic or basic solids changes under higher relative humidity (RH), as determined by using Kelvin force microscopy (KFM). The potential on acid surfaces becomes more negative as the water vapor pressure increases, while it becomes more positive on basic solids. These results verify the following hypothesis: OH(-) or H(+) ions associated with atmospheric water ion clusters are selectively adsorbed on solid surfaces, depending on the respective Brønsted acid or base character. Therefore, Kelvin microscopy, under variable humidity, is a rigorous but convenient alternative to determine the acid-base character of solid surfaces, with a great advantage: it uses only one amphoteric and simple reagent to determine both the acid and base sites. Moreover, this technique provides information on the spatial distribution of acid-base sites, which is currently inaccessible to any other method.

  1. In Vitro Investigation of Self-Assembled Nanoparticles Based on Hyaluronic Acid-Deoxycholic Acid Conjugates for Controlled Release Doxorubicin: Effect of Degree of Substitution of Deoxycholic Acid

    PubMed Central

    Wei, Wen-Hao; Dong, Xue-Meng; Liu, Chen-Guang

    2015-01-01

    Self-assembled nanoparticles based on a hyaluronic acid-deoxycholic acid (HD) chemical conjugate with different degree of substitution (DS) of deoxycholic acid (DOCA) were prepared. The degree of substitution (DS) was determined by titration method. The nanoparticles were loaded with doxorubicin (DOX) as the model drug. The human cervical cancer (HeLa) cell line was utilized for in vitro studies and cell cytotoxicity of DOX incorporated in the HD nanoparticles was accessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. In addition, cellular uptake of fluorescently labeled nanoparticles was also investigated. An increase in the degree of deoxycholic acid substitution reduced the size of the nanoparticles and also enhanced their drug encapsulation efficiency (EE), which increased with the increase of DS. A higher degree of deoxycholic acid substitution also lead to a lower release rate and an initial burst release of doxorubicin from the nanoparticles. In summary, the degree of substitution allows the modulation of the particle size, drug encapsulation efficiency, drug release rate, and cell uptake efficiency of the nanoparticles. The herein developed hyaluronic acid-deoxycholic acid conjugates are a good candidate for drug delivery and could potentiate therapeutic formulations for doxorubicin–mediated cancer therapy. PMID:25837468

  2. Nanoconjugate based on polymalic acid for tumor targeting.

    PubMed

    Ljubimova, Julia Y; Fujita, Manabu; Khazenzon, Natalya M; Lee, Bong-Seop; Wachsmann-Hogiu, Sebastian; Farkas, Daniel L; Black, Keith L; Holler, Eggehard

    2008-01-30

    A new prototype of polymer-derived drug delivery system, the nanoconjugate Polycefin, was tested for its ability to accumulate in tumors based on enhanced permeability and retention (EPR) effect and receptor mediated endocytosis. Polycefin was synthesized for targeted delivery of Morpholino antisense oligonucleotides into certain tumors. It consists of units that are covalently conjugated with poly(beta-l-malic acid) (M(w) 50,000, M(w)/M(n) 1.3) highly purified from cultures of myxomycete Physarum polycephalum. The units are active in endosomal uptake, disruption of endosomal membranes, oligonucleotide release in the cytoplasm, and protection against enzymatic degradation in the vascular system. The polymer is biodegradable, non-immunogenic and non-toxic. Polycefin was also coupled with AlexaFluor 680 C2-maleimide dye for in vivo detection. Nude mice received subcutaneous injections of MDA-MB 468 human breast cancer cells into the left posterior mid-dorsum or intracranial injections of human glioma cell line U87MG. Polycefin at concentration of 2.5mg/kg was injected via the tail vein. In vivo fluorescence tumor imaging was performed at different time points, 0-180 min up to 24h after the drug injection. The custom-made macro-illumination imaging MISTI system was used to examine the in vivo drug accumulation in animals bearing human breast and brain tumors. In breast tumors the fluorescence signal in large blood vessels and in the tumor increased rapidly until 60 min and remained in the tumor at a level 6 times higher than in non-tumor tissue (180 min) (p<0.003). In brain tumors drug accumulated selectively in 24h without any detectable signal in non-tumor areas. The results of live imaging were corroborated histologically by fluorescence microscopic examination of various organs. In addition to tumors, only kidney and liver showed some fluorescent signal.

  3. Highly efficient procedure for the synthesis of fructone fragrance using a novel carbon based acid.

    PubMed

    Hu, Baowei; Li, Chunqing; Zhao, Sheng-Xian; Rong, Lin-Mei; Lv, Shao-Qin; Liang, Xuezheng; Qi, Chenze

    2010-08-01

    The novel carbon based acid has been synthesized via one-step hydrothermal carbonization of furaldehyde and hydroxyethylsulfonic acid. A highly efficient procedure for the synthesis of fructone has been developed using the novel carbon based acid. The results showed that the catalyst possessed high activity for the reaction, giving a yield of over 95%. The advantages of high activity, stability, reusability and low cost for a simple synthesis procedure and wide applicability to various diols and beta-keto esters make this novel carbon based acid one of the best choices for the reaction.

  4. (R,S)-2-chlorophenoxyl pyrazolides as novel substrates for improving lipase-catalyzed hydrolytic resolution.

    PubMed

    Kao, Min-fang; Lu, Pei-yu; Kao, Jou-yan; Wang, Pei-yun; Wu, An-chi; Tsai, Shau-Wei

    2012-01-01

    The best reaction condition of Candida antartica lipase B as biocatalyst, 3-(2-pyridyl)pyrazole as leaving azole, and water-saturated methyl t-butyl ether as reaction medium at 45°C were first selected for performing the hydrolytic resolution of (R,S)-2-(4-chlorophenoxyl) azolides (1-4). In comparison with the kinetic resolution of (R,S)-2-phenylpropionyl 3-(2-pyridyl)pyrazolide or (R,S)-α-methoxyphenylacetyl 3-(2-pyridyl)pyrazolide at the same reaction condition, excellent enantioselectivity with more than two order-of-magnitudes higher activity for each enantiomer was obtained. The resolution was then extended to other (R,S)-3-(2-pyridyl)pyrazolides (5-7) containing 2-chloro, 3-chloro, or 2,4-dichloro substituent, giving good (E > 48) to excellent (E > 100) enantioselectivity. The thermodynamic analysis for 1, 2, and 4-7 demonstrates profound effects of the acyl or leaving moiety on varying enthalpic and entropic contributions to the difference of Gibbs free energies. A thorough kinetic analysis further indicates that on the basis of 6, the excellent enantiomeric ratio for 4 and 7 is due to the higher reactivity of (S)-4 and lower reactivity of (R)-7, respectively. PMID:22012845

  5. In vitro Paracoccidioides brasiliensis biofilm and gene expression of adhesins and hydrolytic enzymes

    PubMed Central

    Sardi, Janaina de Cássia Orlandi; Pitangui, Nayla de Souza; Voltan, Aline Raquel; Braz, Jaqueline Derissi; Machado, Marcelo Pelajo; Fusco Almeida, Ana Marisa; Mendes Giannini, Maria Jose Soares

    2015-01-01

    Paracoccidioides species are dimorphic fungi that initially infect the lungs but can also spread throughout the body. The spreading infection is most likely due to the formation of a biofilm that makes it difficult for the host to eliminate the infection. Biofilm formation is crucial for the development of infections and confines the pathogen to an extracellular matrix. Its presence is associated with antimicrobial resistance and avoidance of host defenses. This current study provides the first description of biofilm formation by Paracoccidioides brasiliensis (Pb18) and an analysis of gene expression, using real-time PCR, associated with 3 adhesins and 2 hydrolytic enzymes that could be associated with the virulence profile. Biofilm formation was analyzed using fluorescence microscopy, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Metabolic activity was determined using the XTT reduction assay. P. brasiliensis was able to form mature biofilm in 144 h with a thickness of 100 μm. The presence of a biofilm was found to be associated with an increase in the expression of adhesins and enzymes. GP43, enolase, GAPDH and aspartyl proteinase genes were over-expressed, whereas phospholipase was down-regulated in biofilm. The characterization of biofilm formed by P. brasiliensis may contribute to a better understanding of the pathogenesis of paracoccidioidomycosis as well as the search for new therapeutic alternatives; while improving the effectiveness of treatment. PMID:26055497

  6. A novel hydrolytic product from flesh of Mactra veneriformis and its bioactivities in calcium supplement

    NASA Astrophysics Data System (ADS)

    Wang, Lingchong; Chen, Shiyong; Liu, Rui; Wu, Hao

    2012-09-01

    To prepare calcium-binding peptides, the flesh residue of Mactra Veneriformis was subjected to enzymatic hydrolysis. By comparing the capability of combining calcium of the hydrolyzates, pepsin was confirmed to be the most suitable enzyme for hydrolyzing the flesh residue to release calcium-binding peptides among the seven tested proteases. The pepsin hydrolyzate (PHM) was divided into three fractions according to the molecule weight of its composition, which ranged from 0.5 to 15 kDa. The low-molecule-weight fraction named PHM-3 had the highest capability in combining calcium. The peptides existing in the PHM-3 fraction consisted of higher contents of Glu, Ala and Leu, and could produce one type of calcium-peptide complex by powerfully chelating calcium ions. PHM-3 products could effectively increase calcium absorption and retention while they decreased the calcium excretion in animal tests. Additionally, symptoms caused by low calcium bioavailability in ovariectomized rats, such as bone mineral density reduction and mechanical strength loss could be significantly ameliorated by the hydrolytic products addition in diet.

  7. Ultrasound-assisted extraction and characterization of hydrolytic and oxidative enzymes produced by solid state fermentation.

    PubMed

    Szabo, Orsolya Erzsebet; Csiszar, Emilia; Toth, Karolina; Szakacs, George; Koczka, Bela

    2015-01-01

    Ligninolytic and hydrolytic enzymes were produced with six selected fungi on flax substrate by solid state fermentation (SSF). The extracellular enzyme production of the organisms in two SSF media was evaluated by measuring the soluble protein concentration and the filter paper, endoxylanase, 1,4-β-d-glucosidase, 1,4-β-d-endoglucanase, polygalacturonase, lignin peroxidase, manganese peroxidase and laccase activities of the clear culture solutions produced by conventional extraction from the SSF materials. The SSF material of the best enzyme producer (Trichoderma virens TUB F-498) was further investigated to enhance the enzyme recovery by low frequency ultrasound treatment. Performance of both the original and ultrasound macerated crude enzyme mixtures was evaluated in degradation of the colored lignin-containing and waxy materials of raw linen fabric. Results proved that sonication (at 40%, 60% and 80% amplitudes, for 60min) did not result in reduction in the filter paper, lignin peroxidase and laccase activities of the crude enzyme solution, but has a significant positive effect on the efficiency of enzyme extraction from the SSF material. Depending on the parameters of sonication, the enzyme activities in the extracts obtained can be increased up to 129-413% of the original activities measured in the control extracts recovered by a common magnetic stirrer. Sonication also has an effect on both the enzymatic removal of the lignin-containing color materials and hydrophobic surface layer from the raw linen.

  8. Particulate retrieval of hydrolytically degraded poly(lactide-co-glycolide) polymers.

    PubMed

    Cordewener, F W; Dijkgraaf, L C; Ong, J L; Agrawal, C M; Zardeneta, G; Milam, S B; Schmitz, J P

    2000-04-01

    This article describes a technique for the retrieval of polymeric particulate debris following advanced hydrolytic in vitro degradation of a biodegradable polymer and presents the results of the subsequent particle analysis. Granular 80/20 poly(L-lactide-co-glycolide) (PLG) was degraded in distilled, deionized water in Pyrextrade mark test tubes at 80 degrees C for 6 weeks. Subsequently, a density gradient was created by layering isopropanol over the water, followed by a 48-h incubation. Two opaque layers formed in the PLG tubes, which were removed and filtered through 0.2-micrometer polycarbonate membrane filters. In addition, Fourier transform IR spectroscopy (FTIR) was performed to confirm the presence of polymer in the removed layers. The filters were gold sputter coated, and scanning electron microscopy (SEM) images were made. FTIR analysis confirmed that the removed material was PLG. SEM images of the extracts from the upper (lowest density) opaque layer showed a fine, powderlike substance and globular structures of 500-750 nm. The SEM images of the lower (highest density) opaque layer showed particles with a crystalline-like morphology ranging in size from 4 to 30 micrometer. Particulate PLG debris generated with the described technique can be useful for further studies of its biological role in complications associated with poly(alpha-hydroxy)ester implants. This study shows the presence of very persistent nano- and microparticles in the degradation pathway of PLG.

  9. (R,S)-2-chlorophenoxyl pyrazolides as novel substrates for improving lipase-catalyzed hydrolytic resolution.

    PubMed

    Kao, Min-fang; Lu, Pei-yu; Kao, Jou-yan; Wang, Pei-yun; Wu, An-chi; Tsai, Shau-Wei

    2012-01-01

    The best reaction condition of Candida antartica lipase B as biocatalyst, 3-(2-pyridyl)pyrazole as leaving azole, and water-saturated methyl t-butyl ether as reaction medium at 45°C were first selected for performing the hydrolytic resolution of (R,S)-2-(4-chlorophenoxyl) azolides (1-4). In comparison with the kinetic resolution of (R,S)-2-phenylpropionyl 3-(2-pyridyl)pyrazolide or (R,S)-α-methoxyphenylacetyl 3-(2-pyridyl)pyrazolide at the same reaction condition, excellent enantioselectivity with more than two order-of-magnitudes higher activity for each enantiomer was obtained. The resolution was then extended to other (R,S)-3-(2-pyridyl)pyrazolides (5-7) containing 2-chloro, 3-chloro, or 2,4-dichloro substituent, giving good (E > 48) to excellent (E > 100) enantioselectivity. The thermodynamic analysis for 1, 2, and 4-7 demonstrates profound effects of the acyl or leaving moiety on varying enthalpic and entropic contributions to the difference of Gibbs free energies. A thorough kinetic analysis further indicates that on the basis of 6, the excellent enantiomeric ratio for 4 and 7 is due to the higher reactivity of (S)-4 and lower reactivity of (R)-7, respectively.

  10. Particulate retrieval of hydrolytically degraded poly(lactide-co-glycolide) polymers.

    PubMed

    Cordewener, F W; Dijkgraaf, L C; Ong, J L; Agrawal, C M; Zardeneta, G; Milam, S B; Schmitz, J P

    2000-04-01

    This article describes a technique for the retrieval of polymeric particulate debris following advanced hydrolytic in vitro degradation of a biodegradable polymer and presents the results of the subsequent particle analysis. Granular 80/20 poly(L-lactide-co-glycolide) (PLG) was degraded in distilled, deionized water in Pyrextrade mark test tubes at 80 degrees C for 6 weeks. Subsequently, a density gradient was created by layering isopropanol over the water, followed by a 48-h incubation. Two opaque layers formed in the PLG tubes, which were removed and filtered through 0.2-micrometer polycarbonate membrane filters. In addition, Fourier transform IR spectroscopy (FTIR) was performed to confirm the presence of polymer in the removed layers. The filters were gold sputter coated, and scanning electron microscopy (SEM) images were made. FTIR analysis confirmed that the removed material was PLG. SEM images of the extracts from the upper (lowest density) opaque layer showed a fine, powderlike substance and globular structures of 500-750 nm. The SEM images of the lower (highest density) opaque layer showed particles with a crystalline-like morphology ranging in size from 4 to 30 micrometer. Particulate PLG debris generated with the described technique can be useful for further studies of its biological role in complications associated with poly(alpha-hydroxy)ester implants. This study shows the presence of very persistent nano- and microparticles in the degradation pathway of PLG. PMID:10644964

  11. Stimulation of the hydrolytic stage for biogas production from cattle manure in an electrochemical bioreactor.

    PubMed

    Samani, Saeed; Abdoli, Mohammad Ali; Karbassi, Abdolreza; Amin, Mohammad Mehdi

    2016-01-01

    Electrical current in the hydrolytic phase of the biogas process might affect biogas yield. In this study, four 1,150 mL single membrane-less chamber electrochemical bioreactors, containing two parallel titanium plates were connected to the electrical source with voltages of 0, -0.5, -1 and -1.5 V, respectively. Reactor 1 with 0 V was considered as a control reactor. The trend of biogas production was precisely checked against pH, oxidation reduction potential and electrical power at a temperature of 37 ± 0.5°C amid cattle manure as substrate for 120 days. Biogas production increased by voltage applied to Reactors 2 and 3 when compared with the control reactor. In addition, the electricity in Reactors 2 and 3 caused more biogas production than Reactor 4. Acetogenic phase occurred more quickly in Reactor 3 than in the other reactors. The obtained results from Reactor 4 were indicative of acidogenic domination and its continuous behavior under electrical stimulation. The results of the present investigation clearly revealed that phasic electrical current could enhance the efficiency of biogas production.

  12. Phytoestrogens in milk: Overestimations caused by contamination of the hydrolytic enzyme used during sample extraction.

    PubMed

    Bláhová, L; Kohoutek, J; Procházková, T; Prudíková, M; Bláha, L

    2016-09-01

    Isoflavones are natural phytoestrogens with antioxidant and endocrine-disrupting potencies. Monitoring of their levels is important to ensure the high quality and safety of food, milk, and dairy products. The efficiency and accuracy of phytoestrogen analyses in complex matrices such as milk depend on the extraction procedure, which often uses hydrolysis by means of the β-glucuronidase/sulfatase enzyme originating from Helix pomatia. The present study reveals that the commercially available hydrolytic enzyme is contaminated by several phytoestrogen isoflavones (genistein, daidzein, formononetin, and biochanin A) and their metabolite equol, as well as flavones (naringenin and apigenin) and coumestrol. We show that the concentrations of daidzein and genistein in the enzyme could have impaired the results of analyses of the main isoflavones in several previously published studies. Of 8 analyzed compounds, only equol was confirmed in the present study and it serves as a reliable marker of phytoestrogens originating from cow feed. Critical reassessment of phytoestrogen concentrations in milk is needed because several previously published studies might have overestimated the concentrations depending on the extraction procedure used. PMID:27394955

  13. Stimulation of the hydrolytic stage for biogas production from cattle manure in an electrochemical bioreactor.

    PubMed

    Samani, Saeed; Abdoli, Mohammad Ali; Karbassi, Abdolreza; Amin, Mohammad Mehdi

    2016-01-01

    Electrical current in the hydrolytic phase of the biogas process might affect biogas yield. In this study, four 1,150 mL single membrane-less chamber electrochemical bioreactors, containing two parallel titanium plates were connected to the electrical source with voltages of 0, -0.5, -1 and -1.5 V, respectively. Reactor 1 with 0 V was considered as a control reactor. The trend of biogas production was precisely checked against pH, oxidation reduction potential and electrical power at a temperature of 37 ± 0.5°C amid cattle manure as substrate for 120 days. Biogas production increased by voltage applied to Reactors 2 and 3 when compared with the control reactor. In addition, the electricity in Reactors 2 and 3 caused more biogas production than Reactor 4. Acetogenic phase occurred more quickly in Reactor 3 than in the other reactors. The obtained results from Reactor 4 were indicative of acidogenic domination and its continuous behavior under electrical stimulation. The results of the present investigation clearly revealed that phasic electrical current could enhance the efficiency of biogas production. PMID:27508365

  14. Phytoestrogens in milk: Overestimations caused by contamination of the hydrolytic enzyme used during sample extraction.

    PubMed

    Bláhová, L; Kohoutek, J; Procházková, T; Prudíková, M; Bláha, L

    2016-09-01

    Isoflavones are natural phytoestrogens with antioxidant and endocrine-disrupting potencies. Monitoring of their levels is important to ensure the high quality and safety of food, milk, and dairy products. The efficiency and accuracy of phytoestrogen analyses in complex matrices such as milk depend on the extraction procedure, which often uses hydrolysis by means of the β-glucuronidase/sulfatase enzyme originating from Helix pomatia. The present study reveals that the commercially available hydrolytic enzyme is contaminated by several phytoestrogen isoflavones (genistein, daidzein, formononetin, and biochanin A) and their metabolite equol, as well as flavones (naringenin and apigenin) and coumestrol. We show that the concentrations of daidzein and genistein in the enzyme could have impaired the results of analyses of the main isoflavones in several previously published studies. Of 8 analyzed compounds, only equol was confirmed in the present study and it serves as a reliable marker of phytoestrogens originating from cow feed. Critical reassessment of phytoestrogen concentrations in milk is needed because several previously published studies might have overestimated the concentrations depending on the extraction procedure used.

  15. Biochar amendment to lead-contaminated soil: Effects on fluorescein diacetate hydrolytic activity and phytotoxicity to rice.

    PubMed

    Tan, Xiaofei; Liu, Yunguo; Gu, Yanling; Zeng, Guangming; Hu, Xinjiang; Wang, Xin; Hu, Xi; Guo, Yiming; Zeng, Xiaoxia; Sun, Zhichao

    2015-09-01

    The amendment effects of biochar on total microbial activity was measured by fluorescein diacetate (FDA) hydrolytic activity, and phytotoxicity in Pb(II)-contaminated soils was examined by the application of 4 different biochars to soil, with rice as a test plant. The FDA hydrolytic activities of biochar-amended soils were much higher than that of the control. The survival rate of rice in lead-contaminated biochar-amended soils showed significant improvement over the control, especially for bamboo biochar-amended soil (93.3%). In addition, rice grown in lead-contaminated control sediment displayed lower biomass production than that in biochar-amended soil. The immobilization of Pb(II) and the positive effects of biochar amendment on soil microorganisms may account for these effects. The results suggest that biochar may have an excellent ability to mitigate the toxic effects of Pb(II) on soil microorganisms and rice.

  16. Evolution and Distribution of Hydrolytic Enzyme Activities during Preharvest Sprouting of Wheat (Triticum aestivum) in the Field.

    PubMed

    Olaerts, Heleen; Roye, Chiara; Derde, Liesbeth J; Sinnaeve, Georges; Meza, Walter R; Bodson, Bernard; Courtin, Christophe M

    2016-07-20

    To date, research on preharvest sprouted (PHS) wheat has mostly been conducted on kernels germinated under laboratory conditions, which differ widely from conditions in the field. To obtain detailed knowledge of the evolution of hydrolytic enzyme activities in PHS wheat (Triticum aestivum), a broad collection of samples from three varieties was obtained by harvesting before, at, and after maturity. Delaying harvest time coupled with periods of heavy rainfall caused sprouting in the kernels, observed as a drop in Falling Number and an increase in α-amylase activity. The appearance of α- and β-amylase, peptidase, and endoxylanase activity during field sprouting was independent from each other. Consequently, Falling Number could not be used to predict activity of other hydrolytic enzymes. When differentiating endogenous from kernel-associated microbial enzymes, results showed that α- and β-amylase and peptidase activity of PHS kernels were predominantly of endogenous origin, whereas endoxylanase activity was largely from microbial origin. PMID:27341479

  17. Evolution and Distribution of Hydrolytic Enzyme Activities during Preharvest Sprouting of Wheat (Triticum aestivum) in the Field.

    PubMed

    Olaerts, Heleen; Roye, Chiara; Derde, Liesbeth J; Sinnaeve, Georges; Meza, Walter R; Bodson, Bernard; Courtin, Christophe M

    2016-07-20

    To date, research on preharvest sprouted (PHS) wheat has mostly been conducted on kernels germinated under laboratory conditions, which differ widely from conditions in the field. To obtain detailed knowledge of the evolution of hydrolytic enzyme activities in PHS wheat (Triticum aestivum), a broad collection of samples from three varieties was obtained by harvesting before, at, and after maturity. Delaying harvest time coupled with periods of heavy rainfall caused sprouting in the kernels, observed as a drop in Falling Number and an increase in α-amylase activity. The appearance of α- and β-amylase, peptidase, and endoxylanase activity during field sprouting was independent from each other. Consequently, Falling Number could not be used to predict activity of other hydrolytic enzymes. When differentiating endogenous from kernel-associated microbial enzymes, results showed that α- and β-amylase and peptidase activity of PHS kernels were predominantly of endogenous origin, whereas endoxylanase activity was largely from microbial origin.

  18. [Effect of Arnica montana tincture on some hydrolytic enzyme activities of rat liver in experimental toxic hepatitis].

    PubMed

    Iaremiĭ, I M; Meshchyshen, I F; Hrihor'ieva, N P; Kostiuk, L S

    1998-01-01

    Effects of tinctura arnica on arginase, adenosine triphosphatase, glucose-6-phosphatase and 5'-nucleotidase activities of rats liver in case of experimental toxic hepatitis have been studied. Toxic hepatitis was caused by 2 times interstomach administration of 0.25 ml oil solution of carbon tetrachloride per 100 g of animal weight. 20 mkl/100 g of tinctura arnica was administered every day per os for 14 days. The enzyme activities have been investigated at 3, 7 and 17 days. A significant demention of a studied hydrolytic enzyme activities in rats liver at intoxication of the body by CCI4 has been shown. It has been established that tinctura arnica administered per os to intoxicated animals sped up the normalization of hydrolytic enzyme activities in rat liver.

  19. Importance of acid-base equilibrium in electrocatalytic oxidation of formic acid on platinum.

    PubMed

    Joo, Jiyong; Uchida, Taro; Cuesta, Angel; Koper, Marc T M; Osawa, Masatoshi

    2013-07-10

    Electro-oxidation of formic acid on Pt in acid is one of the most fundamental model reactions in electrocatalysis. However, its reaction mechanism is still a matter of strong debate. Two different mechanisms, bridge-bonded adsorbed formate mechanism and direct HCOOH oxidation mechanism, have been proposed by assuming a priori that formic acid is the major reactant. Through systematic examination of the reaction over a wide pH range (0-12) by cyclic voltammetry and surface-enhanced infrared spectroscopy, we show that the formate ion is the major reactant over the whole pH range examined, even in strong acid. The performance of the reaction is maximal at a pH close to the pKa of formic acid. The experimental results are reasonably explained by a new mechanism in which formate ion is directly oxidized via a weakly adsorbed formate precursor. The reaction serves as a generic example illustrating the importance of pH variation in catalytic proton-coupled electron-transfer reactions.

  20. K(+)- and HCO3(-)-dependent acid-base transport in squid giant axons. I. Base efflux

    PubMed Central

    1995-01-01

    We used microelectrodes to monitor the recovery (i.e., decrease) of intracellular pH (pHi) after using internal dialysis to load squid giant axons with alkali to pHi values of 7.7, 8.0, or 8.3. The dialysis fluid (DF) contained 400 mM K+ but was free of Na+ and Cl-. The artificial seawater (ASW) lacked Na+, K+, and Cl-, thereby eliminating effects of known acid-base transporters on pHi. Under these conditions, halting dialysis unmasked a slow pHi decrease caused at least in part by acid-base transport we refer to as "base efflux." Replacing K+ in the DF with either NMDG+ or TEA+ significantly reduced base efflux and made membrane voltage (Vm) more positive. Base efflux in K(+)-dialyzed axons was stimulated by decreasing the pH of the ASW (pHo) from 8 to 7, implicating transport of acid or base. Although postdialysis acidifications also occurred in axons in which we replaced the K+ in the DF with Li+, Na+, Rb+, or Cs+, only with Rb+ was base efflux stimulated by low pHo. Thus, the base effluxes supported by K+ and Rb+ appear to be unrelated mechanistically to those observed with Li+, Na+, or Cs+. The combination of 437 mM K+ and 12 mM HCO3- in the ASW, which eliminates the gradient favoring a hypothetical K+/HCO3- efflux, blocked pHi recovery in K(+)-dialyzed axons. However, the pHi recovery was not blocked by the combination of 437 mM Na+, veratridine, and CO2/HCO3- in the ASW, a treatment that inverts electrochemical gradients for H+ and HCO3- and would favor passive H+ and HCO3- fluxes that would have alkalinized the axon. Similarly, the recovery was not blocked by K+ alone or HCO3- alone in the ASW, nor was it inhibited by the K-H pump blocker Sch28080 nor by the Na-H exchange inhibitors amiloride and hexamethyleneamiloride. Our data suggest that a major component of base efflux in alkali-loaded axons cannot be explained by metabolism, a H+ or HCO3- conductance, or by a K-H exchanger. However, this component could be mediated by a novel K/HCO3- cotransporter

  1. Using the Logarithmic Concentration Diagram, Log "C", to Teach Acid-Base Equilibrium

    ERIC Educational Resources Information Center

    Kovac, Jeffrey

    2012-01-01

    Acid-base equilibrium is one of the most important and most challenging topics in a typical general chemistry course. This article introduces an alternative to the algebraic approach generally used in textbooks, the graphical log "C" method. Log "C" diagrams provide conceptual insight into the behavior of aqueous acid-base systems and allow…

  2. Lewis Acid-Base, Molecular Modeling, and Isotopic Labeling in a Sophomore Inorganic Chemistry Laboratory

    ERIC Educational Resources Information Center

    Nataro, Chip; Ferguson, Michelle A.; Bocage, Katherine M.; Hess, Brian J.; Ross, Vincent J.; Swarr, Daniel T.

    2004-01-01

    An experiment to prepare a deuterium labeled adduct of a Lewis acid and Lewis base, to use computational methods allowing students to visualize the LUMO of Lewis acids, the HOMO of Lewis bases and the molecular orbitals of the adduct that is formed is developed. This allows students to see the interplay between calculated and experimental results.

  3. The acid-base resistant zone in three dentin bonding systems.

    PubMed

    Inoue, Go; Nikaido, Toru; Foxton, Richard M; Tagami, Junji

    2009-11-01

    An acid-base resistant zone has been found to exist after acid-base challenge adjacent to the hybrid layer using SEM. The aim of this study was to examine the acid-base resistant zone using three different bonding systems. Dentin disks were applied with three different bonding systems, and then a resin composite was light-cured to make dentin disk sandwiches. After acid-base challenge, the polished surfaces were observed using SEM. For both one- and two-step self-etching primer systems, an acid-base resistant zone was clearly observed adjacent to the hybrid layer - but with differing appearances. For the wet bonding system, the presence of an acid-base resistant zone was unclear. This was because the self-etching primer systems etched the dentin surface mildly, such that the remaining mineral phase of dentin and the bonding agent yielded clear acid-base resistant zones. In conclusion, the acid-base resistant zone was clearly observed when self-etching primer systems were used, but not so for the wet bonding system.

  4. Thai Grade 11 Students' Alternative Conceptions for Acid-Base Chemistry

    ERIC Educational Resources Information Center

    Artdej, Romklao; Ratanaroutai, Thasaneeya; Coll, Richard Kevin; Thongpanchang, Tienthong

    2010-01-01

    This study involved the development of a two-tier diagnostic instrument to assess Thai high school students' understanding of acid-base chemistry. The acid-base diagnostic test (ABDT) comprising 18 items was administered to 55 Grade 11 students in a science and mathematics programme during the second semester of the 2008 academic year. Analysis of…

  5. A Comparative Study of French and Turkish Students' Ideas on Acid-Base Reactions

    ERIC Educational Resources Information Center

    Cokelez, Aytekin

    2010-01-01

    The goal of this comparative study was to determine the knowledge that French and Turkish upper secondary-school students (grades 11 and 12) acquire on the concept of acid-base reactions. Following an examination of the relevant curricula and textbooks in the two countries, 528 students answered six written questions about the acid-base concept.…

  6. High School Students' Understanding of Acid-Base Concepts: An Ongoing Challenge for Teachers

    ERIC Educational Resources Information Center

    Damanhuri, Muhd Ibrahim Muhamad; Treagust, David F.; Won, Mihye; Chandrasegaran, A. L.

    2016-01-01

    Using a quantitative case study design, the "Acids-Bases Chemistry Achievement Test" ("ABCAT") was developed to evaluate the extent to which students in Malaysian secondary schools achieved the intended curriculum on acid-base concepts. Responses were obtained from 260 Form 5 (Grade 11) students from five schools to initially…

  7. Using Conceptual Change Texts with Analogies for Misconceptions in Acids and Bases

    ERIC Educational Resources Information Center

    Cetingul, Ipek; Geban, Omer

    2011-01-01

    This study was conducted to explore the effectiveness of conceptual change oriented instruction over traditional instruction on students' understanding of acids and bases concept. Besides, effects of gender difference and science process skills on students' understanding of acids and bases were also investigated. Analysis of the results showed…

  8. Measuring the Confidence of 8th Grade Taiwanese Students' Knowledge of Acids and Bases

    ERIC Educational Resources Information Center

    Jack, Brady Michael; Liu, Chia-Ju; Chiu, Houn-Lin; Tsai, Chun-Yen

    2012-01-01

    The present study investigated whether gender differences were present on the confidence judgments made by 8th grade Taiwanese students on the accuracy of their responses to acid-base test items. A total of 147 (76 male, 71 female) students provided item-specific confidence judgments during a test of their knowledge of acids and bases. Using the…

  9. Collaborative Strategies for Teaching Common Acid-Base Disorders to Medical Students

    ERIC Educational Resources Information Center

    Petersen, Marie Warrer; Toksvang, Linea Natalie; Plovsing, Ronni R.; Berg, Ronan M. G.

    2014-01-01

    The ability to recognize and diagnose acid-base disorders is of the utmost importance in the clinical setting. However, it has been the experience of the authors that medical students often have difficulties learning the basic principles of acid-base physiology in the respiratory physiology curriculum, particularly when applying this knowledge to…

  10. Canonical Pedagogical Content Knowledge by Cores for Teaching Acid-Base Chemistry at High School

    ERIC Educational Resources Information Center

    Alvarado, Clara; Cañada, Florentina; Garritz, Andoni; Mellado, Vicente

    2015-01-01

    The topic of acid-base chemistry is one of the oldest in general chemistry courses and it has been almost continuously in academic discussion. The central purpose of documenting the knowledge and beliefs of a group of ten Mexican teachers with experience in teaching acid-base chemistry in high school was to know how they design, prepare and…

  11. [Dynamics of blood gases and acid-base balance in patients with carbon monoxide acute poisoning].

    PubMed

    Polozova, E V; Shilov, V V; Bogachova, A S; Davydova, E V

    2015-01-01

    Evaluation of blood gases and acid-base balance covered patients with carbon monoxide acute poisoning, in accordance with inhalation trauma presence. Evidence is that thermochemical injury of respiratory tract induced severe acid-base dysbalance remaining decompensated for a long time despite the treatment.

  12. Students' Understanding of Acid, Base and Salt Reactions in Qualitative Analysis.

    ERIC Educational Resources Information Center

    Tan, Kim-Chwee Daniel; Goh, Ngoh-Khang; Chia, Lian-Sai; Treagust, David F.

    2003-01-01

    Uses a two-tier, multiple-choice diagnostic instrument to determine (n=915) grade 10 students' understanding of the acid, base, and salt reactions involved in basic qualitative analysis. Reports that many students did not understand the formation of precipitates and the complex salts, acid/salt-base reactions, and thermal decomposition involved in…

  13. Red Shoe-Blue Shoe: An Acid-Base Demonstration with a Fashionable Twist.

    ERIC Educational Resources Information Center

    Breyer, Arthur C.; Uzelmeier, Calvin E.

    1998-01-01

    Illustrates that acid-base indicators come in many forms and the reversible effects that acids and bases have on the colors of such indicators. An object is dyed in an indicator, which causes the object to turn dark blue at pH less than 3.0 to 5.0. Suggests using dyeable fabric shoes and other cotton articles. (PVD)

  14. Effects of fatty acid activation on photosynthetic production of fatty acid-based biofuels in Synechocystis sp. PCC6803

    PubMed Central

    2012-01-01

    Background Direct conversion of solar energy and carbon dioxide to drop in fuel molecules in a single biological system can be achieved from fatty acid-based biofuels such as fatty alcohols and alkanes. These molecules have similar properties to fossil fuels but can be produced by photosynthetic cyanobacteria. Results Synechocystis sp. PCC6803 mutant strains containing either overexpression or deletion of the slr1609 gene, which encodes an acyl-ACP synthetase (AAS), have been constructed. The complete segregation and deletion in all mutant strains was confirmed by PCR analysis. Blocking fatty acid activation by deleting slr1609 gene in wild-type Synechocystis sp. PCC6803 led to a doubling of the amount of free fatty acids and a decrease of alkane production by up to 90 percent. Overexpression of slr1609 gene in the wild-type Synechocystis sp. PCC6803 had no effect on the production of either free fatty acids or alkanes. Overexpression or deletion of slr1609 gene in the Synechocystis sp. PCC6803 mutant strain with the capability of making fatty alcohols by genetically introducing fatty acyl-CoA reductase respectively enhanced or reduced fatty alcohol production by 60 percent. Conclusions Fatty acid activation functionalized by the slr1609 gene is metabolically crucial for biosynthesis of fatty acid derivatives in Synechocystis sp. PCC6803. It is necessary but not sufficient for efficient production of alkanes. Fatty alcohol production can be significantly improved by the overexpression of slr1609 gene. PMID:22433663

  15. Unravelling the Interactions between Hydrolytic and Oxidative Enzymes in Degradation of Lignocellulosic Biomass by Sporothrix carnis under Various Fermentation Conditions

    PubMed Central

    Ogunyewo, Olusola A.; Olajuyigbe, Folasade M.

    2016-01-01

    The mechanism underlying the action of lignocellulolytic enzymes in biodegradation of lignocellulosic biomass remains unclear; hence, it is crucial to investigate enzymatic interactions involved in the process. In this study, degradation of corn cob by Sporothrix carnis and involvement of lignocellulolytic enzymes in biodegradation were investigated over 240 h cultivation period. About 60% degradation of corn cob was achieved by S. carnis at the end of fermentation. The yields of hydrolytic enzymes, cellulase and xylanase, were higher than oxidative enzymes, laccase and peroxidase, over 144 h fermentation period. Maximum yields of cellulase (854.4 U/mg) and xylanase (789.6 U/mg) were at 96 and 144 h, respectively. Laccase and peroxidase were produced cooperatively with maximum yields of 489.06 U/mg and 585.39 U/mg at 144 h. Drastic decline in production of cellulase at 144 h (242.01 U/mg) and xylanase at 192 h (192.2 U/mg) indicates that they play initial roles in biodegradation of lignocellulosic biomass while laccase and peroxidase play later roles. Optimal degradation of corn cob (76.6%) and production of hydrolytic and oxidative enzymes were achieved with 2.5% inoculum at pH 6.0. Results suggest synergy in interactions between the hydrolytic and oxidative enzymes which can be optimized for improved biodegradation. PMID:26881077

  16. Unravelling the Interactions between Hydrolytic and Oxidative Enzymes in Degradation of Lignocellulosic Biomass by Sporothrix carnis under Various Fermentation Conditions.

    PubMed

    Ogunyewo, Olusola A; Olajuyigbe, Folasade M

    2016-01-01

    The mechanism underlying the action of lignocellulolytic enzymes in biodegradation of lignocellulosic biomass remains unclear; hence, it is crucial to investigate enzymatic interactions involved in the process. In this study, degradation of corn cob by Sporothrix carnis and involvement of lignocellulolytic enzymes in biodegradation were investigated over 240 h cultivation period. About 60% degradation of corn cob was achieved by S. carnis at the end of fermentation. The yields of hydrolytic enzymes, cellulase and xylanase, were higher than oxidative enzymes, laccase and peroxidase, over 144 h fermentation period. Maximum yields of cellulase (854.4 U/mg) and xylanase (789.6 U/mg) were at 96 and 144 h, respectively. Laccase and peroxidase were produced cooperatively with maximum yields of 489.06 U/mg and 585.39 U/mg at 144 h. Drastic decline in production of cellulase at 144 h (242.01 U/mg) and xylanase at 192 h (192.2 U/mg) indicates that they play initial roles in biodegradation of lignocellulosic biomass while laccase and peroxidase play later roles. Optimal degradation of corn cob (76.6%) and production of hydrolytic and oxidative enzymes were achieved with 2.5% inoculum at pH 6.0. Results suggest synergy in interactions between the hydrolytic and oxidative enzymes which can be optimized for improved biodegradation. PMID:26881077

  17. Fatty acid synthesis in Escherichia coli and its applications towards the production of fatty acid based biofuels

    PubMed Central

    2014-01-01

    The idea of renewable and regenerative resources has inspired research for more than a hundred years. Ideally, the only spent energy will replenish itself, like plant material, sunlight, thermal energy or wind. Biodiesel or ethanol are examples, since their production relies mainly on plant material. However, it has become apparent that crop derived biofuels will not be sufficient to satisfy future energy demands. Thus, especially in the last decade a lot of research has focused on the production of next generation biofuels. A major subject of these investigations has been the microbial fatty acid biosynthesis with the aim to produce fatty acids or derivatives for substitution of diesel. As an industrially important organism and with the best studied microbial fatty acid biosynthesis, Escherichia coli has been chosen as producer in many of these studies and several reviews have been published in the fields of E. coli fatty acid biosynthesis or biofuels. However, most reviews discuss only one of these topics in detail, despite the fact, that a profound understanding of the involved enzymes and their regulation is necessary for efficient genetic engineering of the entire pathway. The first part of this review aims at summarizing the knowledge about fatty acid biosynthesis of E. coli and its regulation, and it provides the connection towards the production of fatty acids and related biofuels. The second part gives an overview about the achievements by genetic engineering of the fatty acid biosynthesis towards the production of next generation biofuels. Finally, the actual importance and potential of fatty acid-based biofuels will be discussed. PMID:24405789

  18. Fatty acid synthesis in Escherichia coli and its applications towards the production of fatty acid based biofuels.

    PubMed

    Janßen, Helge Jans; Steinbüchel, Alexander

    2014-01-01

    The idea of renewable and regenerative resources has inspired research for more than a hundred years. Ideally, the only spent energy will replenish itself, like plant material, sunlight, thermal energy or wind. Biodiesel or ethanol are examples, since their production relies mainly on plant material. However, it has become apparent that crop derived biofuels will not be sufficient to satisfy future energy demands. Thus, especially in the last decade a lot of research has focused on the production of next generation biofuels. A major subject of these investigations has been the microbial fatty acid biosynthesis with the aim to produce fatty acids or derivatives for substitution of diesel. As an industrially important organism and with the best studied microbial fatty acid biosynthesis, Escherichia coli has been chosen as producer in many of these studies and several reviews have been published in the fields of E. coli fatty acid biosynthesis or biofuels. However, most reviews discuss only one of these topics in detail, despite the fact, that a profound understanding of the involved enzymes and their regulation is necessary for efficient genetic engineering of the entire pathway. The first part of this review aims at summarizing the knowledge about fatty acid biosynthesis of E. coli and its regulation, and it provides the connection towards the production of fatty acids and related biofuels. The second part gives an overview about the achievements by genetic engineering of the fatty acid biosynthesis towards the production of next generation biofuels. Finally, the actual importance and potential of fatty acid-based biofuels will be discussed. PMID:24405789

  19. Functional fermented whey-based beverage using lactic acid bacteria.

    PubMed

    Pescuma, Micaela; Hébert, Elvira María; Mozzi, Fernanda; de Valdez, Graciela Font

    2010-06-30

    Whey protein concentrate (WPC) is employed as functional food ingredient because of its nutritional value and emulsifying properties. However, the major whey protein beta-lactoglobulin (BLG) is the main cause of milk allergy. The aim of this study was to formulate a fermented whey beverage using selected lactic acid bacteria and WPC35 (WPC containing 35% of proteins) to obtain a fermented product with low lactose and BLG contents and high essential amino acid concentration. Cell viability, lactose consumption, lactic acid production, proteolytic activity, amino acid release and BLG degradation by the selected strains Lactobacillus acidophilus CRL 636, Lactobacillus delbrueckii subsp. bulgaricus CRL 656 and Streptococcus thermophilus CRL 804, as single or mixed (SLaB) cultures were evaluated in WPC35 (10%, w/v) incubated at 37 degrees C for 24h. Then, the fermented WPC35 was mixed with peach juice and calcium lactate (2%, w/v) and stored at 10 degrees C for 28 days. During fermentation, single cultures grew 1.7-3.1 log CFU/ml and produced 25.1-95.0 mmol/l of lactic acid as consequence of lactose consumption (14.0-41.8 mmol/l) after 12h fermentation. L. delbrueckii subsp. bulgaricus CRL 656 was the most proteolytic strain (626 microg/ml Leu) and released the branched-chain essential amino acids Leu (16 microg/ml), Ile (27 microg/ml) and Val (43 microg/ml). All strains were able to degrade BLG in a range of 41-85% after 12h incubation. The starter culture SLaB grew 3.0 log CFU/ml, showed marked pH reduction, produced 122.0 mmol/l of lactic acid, displayed high proteolytic activity (484 microg/ml Leu) releasing Leu (13 microg/ml), Ile (18 microg/ml) and Val (35 microg/ml), and hydrolyzed 92% of BLG. The addition of calcium lactate to WPC35 maintained the drink pH stable during shelf life; no contamination was detected during this period. After 28 days, a decrease in cell viability of all strains was observed being more pronounced for L. delbrueckii subsp. bulgaricus

  20. [Reaction of bone tissue elements on synthetic bioresorbable materials based on lactic and glycolic acids].

    PubMed

    Kulakov, A A; Grigor'ian, A S

    2014-01-01

    The aim of the study was to evaluate the adverse effects of synthetic polymeric bioresorbable materials based on lactic and glycolic acids on the bone tissue. The study was carried-out on 40 Wister-line rats. Four types of bioresorbable polymeric materials were implanted: PolyLactide Glycolide Acid (PLGA), Poly-L-Lactide Acid (PLLA); Poly-96L/4D-Lactide Acid (96/4 PLDLA); Poly-70L/30D-Lactide Acid (70/30 PLDLA). The results showed connective tissue formation (fibrointegration) bordering bone adjacent to implanted materials. This proved the materials to cause pathogenic influence on the bone which mechanisms are described in the article.

  1. Hydrolytically Stable Nanoporous Thorium Mixed Phosphite and Pyrophosphate Framework Generated from Redox-Active Ionothermal Reactions.

    PubMed

    Gui, Daxiang; Zheng, Tao; Chen, Lanhua; Wang, Yanlong; Li, Yuxiang; Sheng, Daopeng; Diwu, Juan; Chai, Zhifang; Albrecht-Schmitt, Thomas E; Wang, Shuao

    2016-04-18

    The first thorium framework compound with mixed-valent phosphorus-based (phosphite and pyrophosphate) ligands, [BMMim]2[Th3(PO3)4(H2P2O7)3] (ThP-1), was synthesized by ionothermal reactions concurrent with the partial oxidation of phosphoric acid. The overall structural topology of ThP-1 highly resembles that of MOF-5, containing only one type of three-dimensional channels with a window size of 11.32 Å × 11.32 Å. ThP-1 has a free void volume of 50.8%, making it one of the most porous purely inorganic actinide-based framework materials. More importantly, ThP-1 is highly stable in aqueous solutions over an extremely wide pH range from 1 to 14 and thus may find potential applications in selective ion exchange and catalysis. PMID:27015432

  2. Beyond ketonization: selective conversion of carboxylic acids to olefins over balanced Lewis acid-base pairs.

    PubMed

    Baylon, Rebecca A L; Sun, Junming; Martin, Kevin J; Venkitasubramanian, Padmesh; Wang, Yong

    2016-04-11

    We report the direct conversion of mixed carboxylic acids to C-C olefins with up to 60 mol% carbon yield through cascade (cross) ketonization, (cross) aldolization and self-deoxygenation reactions. Co-feeding hydrogen provides an additional ketone hydrogenation/dehydration pathway to a wider range of olefins. PMID:26898532

  3. A novel enzyme-based acidizing system: Matrix acidizing and drilling fluid damage removal

    SciTech Connect

    Harris, R.E.; McKay, D.M.; Moses, V.

    1995-12-31

    A novel acidizing process is used to increase the permeability of carbonate rock cores in the laboratory and to remove drilling fluid damage from cores and wafers. Field results show the benefits of the technology as applied both to injector and producer wells.

  4. Beyond ketonization: selective conversion of carboxylic acids to olefins over balanced Lewis acid-base pairs.

    PubMed

    Baylon, Rebecca A L; Sun, Junming; Martin, Kevin J; Venkitasubramanian, Padmesh; Wang, Yong

    2016-04-11

    We report the direct conversion of mixed carboxylic acids to C-C olefins with up to 60 mol% carbon yield through cascade (cross) ketonization, (cross) aldolization and self-deoxygenation reactions. Co-feeding hydrogen provides an additional ketone hydrogenation/dehydration pathway to a wider range of olefins.

  5. Cross-linked, biodegradable, cytocompatible salicylic acid based polyesters for localized, sustained delivery of salicylic acid: an in vitro study.

    PubMed

    Chandorkar, Yashoda; Bhagat, Rajesh K; Madras, Giridhar; Basu, Bikramjit

    2014-03-10

    In order to suppress chronic inflammation while supporting cell proliferation, there has been a continuous surge toward development of polymers with the intention of delivering anti-inflammatory molecules in a sustained manner. In the above backdrop, we report the synthesis of a novel, stable, cross-linked polyester with salicylic acid (SA) incorporated in the polymeric backbone and propose a simple synthesis route by melt condensation. The as-synthesized polymer was hydrophobic with a glass transition temperature of 1 °C, which increases to 17 °C upon curing. The combination of NMR and FT-IR spectral techniques established the ester linkages in the as-synthesized SA-based polyester. The pH-dependent degradation rate and the rate of release of salicylic acid from the as-synthesized SA-based polymer were studied at physiological conditions in vitro. The polyester underwent surface erosion and exhibited linear degradation kinetics in which a change in degradation rate is observed after 4-10 days and 24% mass loss was recorded after 4 months at 37 °C and pH 7.4. The delivery of salicylic acid also showed a similar change in slopes, with a sustained release rate of 3.5% in 4 months. The cytocompatibility studies of these polyesters were carried out with C2C12 murine myoblast cells using techniques like MTT assay and flow cytometry. Our results strongly suggest that SA-based polyester supports cell proliferation for 3 days in culture and do not cause cell death (<7%), as quantified by propidium iodide (PI) stained cells. Hence, these polyesters can be used as implant materials for localized, sustained delivery of salicylic acid and have applications in adjuvant cancer therapy, chronic wound healing, and as an alternative to commercially available polymers like poly(lactic acid) and poly(glycolic acid) or their copolymers.

  6. Effect of Acid-Base Equilibrium on Absorption Spectra of Humic acid in the Presence of Copper Ions

    NASA Astrophysics Data System (ADS)

    Lavrik, N. L.; Mulloev, N. U.

    2014-03-01

    The reaction between humic acid (HA, sample IHSS) and a metal ion (Cu2+) that was manifested as absorption bands in the range 210-350 nm was recorded using absorption spectroscopy. The reaction was found to be more effective as the pH increased. These data were interpreted in the framework of generally accepted concepts about the influence of acid-base equilibrium on the dissociation of salts, according to which increasing the solution pH increases the concentration of HA anions. It was suggested that [HA-Cu2+] complexes formed.

  7. Separation of thorium and uranium in nitric acid solution using silica based anion exchange resin.

    PubMed

    Chen, Yanliang; Wei, Yuezhou; He, Linfeng; Tang, Fangdong

    2016-09-30

    To separate thorium and uranium in nitric acid solution using anion exchange process, a strong base silica-based anion exchange resin (SiPyR-N4) was synthesized. Batch experiments were conducted and the separation factor of thorium and uranium in 9M nitric acid was about 10. Ion exchange chromatography was applied to separate thorium and uranium in different ratios. Uranium could be eluted by 9M nitric acid and thorium was eluted by 0.1M nitric acid. It was proved that thorium and uranium can be separated and recovered successfully by this method.

  8. Separation of thorium and uranium in nitric acid solution using silica based anion exchange resin.

    PubMed

    Chen, Yanliang; Wei, Yuezhou; He, Linfeng; Tang, Fangdong

    2016-09-30

    To separate thorium and uranium in nitric acid solution using anion exchange process, a strong base silica-based anion exchange resin (SiPyR-N4) was synthesized. Batch experiments were conducted and the separation factor of thorium and uranium in 9M nitric acid was about 10. Ion exchange chromatography was applied to separate thorium and uranium in different ratios. Uranium could be eluted by 9M nitric acid and thorium was eluted by 0.1M nitric acid. It was proved that thorium and uranium can be separated and recovered successfully by this method. PMID:27614730

  9. A field pilot-scale study of biological treatment of heavy oil-produced water by biological filter with airlift aeration and hydrolytic acidification system.

    PubMed

    Zhang, Min; Wang, Junming; Zhang, Zhongzhi; Song, Zhaozheng; Zhang, Zhenjia; Zhang, Beiyu; Zhang, Guangqing; Wu, Wei-Min

    2016-03-01

    Heavy oil-produced water (HOPW) is a by-product during heavy oil exploitation and can cause serious environmental pollution if discharged without adequate treatment. Commercial biochemical treatment units are important parts of HOPW treatment processes, but many are not in stable operation because of the toxic and refractory substances, salt, present. Therefore, pilot-scale experiments were conducted to evaluate the performance of hydrolytic acidification-biological filter with airlift aeration (HA-BFAA), a novel HOPW treatment system. Four strains isolated from oily sludge were used for bioaugmentation to enhance the biodegradation of organic pollutants. The isolated bacteria were evaluated using 3-day biochemical oxygen demand, oil, dodecyl benzene sulfonic acid, and chemical oxygen demand (COD) removals as evaluation indices. Bioaugmentation enhanced the COD removal by 43.5 mg/L under a volume load of 0.249 kg COD/m(3) day and hydraulic retention time of 33.6 h. The effluent COD was 70.9 mg/L and the corresponding COD removal was 75.0 %. The optimum volumetric air-to-water ratio was below 10. The removal ratios of the total extractable organic pollutants, alkanes, and poly-aromatic hydrocarbons were 71.1, 94.4, and 94.0 %, respectively. Results demonstrated that HA-BFAA was an excellent HOPW treatment system.

  10. Influence of polymerization conditions on the hydrolytic degradation of poly(DL-lactide) polymerized in the presence of stannous octoate or zinc-metal.

    PubMed

    Schwach, Grégoire; Coudane, Jean; Engel, Robert; Vert, Michel

    2002-02-01

    Laboratory- and pilot-scale racemic polylactides (PLA50) were synthesized in the presence of stannous octoate (SnOct2) or zinc-metal as initiators in the absence of alcohol. The resulting polymers were processed by compression molding or injection molding depending on the batch scale. The hydrolytic degradation of compression-molded samples selected to be comparable was investigated first in order to show the influence of the initiator system. Differences in water uptake were found between PLA50-Zn (zinc-metal initiation) and PLA50-Sn (SnOct2 initiation). PLA50-Zn being much more hydrophilic. PLA50-Sn exhibited a slower molecular weight decrease and delayed onsets of weight loss, release of acidity and stereocomplex formation, with respect to PLA-Zn. The concentration in residual tin in PLA50-Sn increased from 306 to 795 ppm during aging. In the case of PLA50-Zn the residual metal remains constant at ca. 40 ppm. In a second series of experiments, high molecular weight PLA50 different in characteristics and in initiator, synthesized under pilot-scale, were compared. The effects of the initiator on the degradation of the polymers well agreed with laboratory-scale findings, differences in hydrophobicity being enlarged by the up scaling. PLA50-Sn polymers appeared much more degradation resistant than PLA50-Zn ones. Contributions of the other characteristics (e.g. molecular weight, purity, stereoregularity, processing) were shown to be important as well.

  11. Differences in the effect of phosphatidylinositol 4,5-bisphosphate on the hydrolytic and transphosphatidylation activities of membrane-bound phospholipase D from poppy seedlings.

    PubMed

    Oblozinsky, Marek; Bezakova, Lydia; Mansfeld, Johanna; Heilmann, Ingo; Ulbrich-Hofmann, Renate

    2013-08-01

    The hydrolytic activity of phospholipase D (PLD) yielding phosphatidic acid from phosphatidylcholine and other glycerophospholipids is known to be involved in many cellular processes. In contrast, it is not clear whether the competitive transphosphatidylation activity of PLD catalyzing the head group exchange of phospholipids has a natural function. In poppy seedlings (Papaver somniferum L.) where lipid metabolism and alkaloid synthesis are closely linked, five isoenzymes with different substrate and hydrolysis/transphosphatidylation selectivities have been detected hitherto. A membrane-bound PLD, found in microsomal fractions of poppy seedlings, is active at micromolar concentrations of Ca(2+) ions and needs phosphatidylinositol 4,5-bisphosphate (PIP2) as effector in the hydrolysis of phosphatidylcholine (PC). The optimum PIP2 concentration at 1.2 mol% of the concentration of the substrate PC indicates a specific activation effect. Transphosphatidylation with glycerol, ethanolamine, l-serine, or myo-inositol as acceptor alcohols is also activated by PIP2, however, with an optimum concentration at 0.6-0.9 mol%. In contrast to hydrolysis, a basic transphosphatidylation activity occurs even in the absence of PIP2, suggesting a different fine-tuning of the two competing reactions.

  12. Observation of an organic acid mediated spin state transition in a Co(II)-Schiff base complex: an EPR, HYSCORE, and DFT study.

    PubMed

    Vinck, Evi; Carter, Emma; Murphy, Damien M; Van Doorslaer, Sabine

    2012-08-01

    The interactions of a weak organic acid (acetic acid, HOAc) with a toluene solution of the Co(II)-Schiff base type complex, (R,R')-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexane-diamino Co(II) (labeled [Co(1)]), was investigated using EPR, HYSCORE, and DFT computations. This activated [Co(II)(1)] system is extremely important within the context of asymmetric catalysts (notably the hydrolytic kinetic resolution of epoxides) despite the lack of detailed structural information about the nature of the paramagnetic species present. Under anaerobic conditions, the LS [Co(II)(1)] complex with a |yz, (2)A(2)〉 ground state is converted into a low-spin (LS) and a high-spin (HS) complex in the presence of the acid. The newly formed LS state is assigned to the coordinated [Co(II)(1)]-(HOAc) complex, possessing a |z(2), (2)A(1)〉 ground state (species A; g(x) = 2.42, g(y) = 2.28, g(z) = 2.02, A(x) = 100, A(y) = 120, A(z) = 310 MHz). The newly formed HS state is assigned to an acetate coordinated [Co(II)(1)]-(OAc(-)) complex, possessing an S = 3/2 spin ground state (species B, responsible for a broad EPR signal with g ≈ 4.6). These spin ground states were confirmed with DFT calculations using the hybrid BP86 and B3LYP functionals. Under aerobic conditions, the LS and HS complexes (species A and B) are not observed; instead, a new HS complex (species C) is formed. This complex is tentatively assigned to a paramagnetic superoxo bridged dimer (AcO(-))[Co(II)(1)···O(2)(-)Co(III)(1)](HOAc), as distinct from the more common diamagnetic peroxo bridged dimers. Species C is characterized by a very broad HS EPR signal (g(x) = 5.1, g(y) = 3.9, g(z) = 2.1) and is reversibly formed by oxygenation of the LS [Co(II)(1)]-(HOAc) complex to the superoxo complex [Co(III)(1)O(2)(-)](HOAc), which subsequently forms the association complex C by interaction with the HS [Co(II)(1)](OAc(-)) species. The LS and HS complexes were also identified using other organic acids (benzoic and

  13. Observation of an organic acid mediated spin state transition in a Co(II)-Schiff base complex: an EPR, HYSCORE, and DFT study.

    PubMed

    Vinck, Evi; Carter, Emma; Murphy, Damien M; Van Doorslaer, Sabine

    2012-08-01

    The interactions of a weak organic acid (acetic acid, HOAc) with a toluene solution of the Co(II)-Schiff base type complex, (R,R')-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexane-diamino Co(II) (labeled [Co(1)]), was investigated using EPR, HYSCORE, and DFT computations. This activated [Co(II)(1)] system is extremely important within the context of asymmetric catalysts (notably the hydrolytic kinetic resolution of epoxides) despite the lack of detailed structural information about the nature of the paramagnetic species present. Under anaerobic conditions, the LS [Co(II)(1)] complex with a |yz, (2)A(2)〉 ground state is converted into a low-spin (LS) and a high-spin (HS) complex in the presence of the acid. The newly formed LS state is assigned to the coordinated [Co(II)(1)]-(HOAc) complex, possessing a |z(2), (2)A(1)〉 ground state (species A; g(x) = 2.42, g(y) = 2.28, g(z) = 2.02, A(x) = 100, A(y) = 120, A(z) = 310 MHz). The newly formed HS state is assigned to an acetate coordinated [Co(II)(1)]-(OAc(-)) complex, possessing an S = 3/2 spin ground state (species B, responsible for a broad EPR signal with g ≈ 4.6). These spin ground states were confirmed with DFT calculations using the hybrid BP86 and B3LYP functionals. Under aerobic conditions, the LS and HS complexes (species A and B) are not observed; instead, a new HS complex (species C) is formed. This complex is tentatively assigned to a paramagnetic superoxo bridged dimer (AcO(-))[Co(II)(1)···O(2)(-)Co(III)(1)](HOAc), as distinct from the more common diamagnetic peroxo bridged dimers. Species C is characterized by a very broad HS EPR signal (g(x) = 5.1, g(y) = 3.9, g(z) = 2.1) and is reversibly formed by oxygenation of the LS [Co(II)(1)]-(HOAc) complex to the superoxo complex [Co(III)(1)O(2)(-)](HOAc), which subsequently forms the association complex C by interaction with the HS [Co(II)(1)](OAc(-)) species. The LS and HS complexes were also identified using other organic acids (benzoic and

  14. Improvement of ruthenium based decarboxylation of carboxylic acids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The removal of oxygen atoms from biobased carboxylic acids is an attractive route to provide the drop in replacement feedstocks that industry needs to continue to provide high performance products. Through the use of ruthenium catalysis, an efficient method where this process can be accomplished on ...

  15. Variations in ectoenzymatic hydrolytic activity in an oligotrophic environment (Southern Tyrrhenian Sea, W Mediterranean)

    NASA Astrophysics Data System (ADS)

    Misic, Cristina; Castellano, Michela; Ruggieri, Nicoletta; Harriague, Anabella Covazzi

    2008-09-01

    The variations in the expression of two hydrolytic ectoenzymes (leucine aminopeptidase - LA - and β glucosidase — BG) were studied in the southern Tyrrhenian Sea during spring 2004. This area is characterised by a complex morphology and hydrodynamism, which generate significant differences between different sectors, particularly in the 0-100 m layer. However, the area generally exhibits oligotrophic features such as low autotrophic pigment and organic matter concentrations and a higher bacterial biomass than the phytoplanktonic one. Despite this general bottom-up pressure, adaptations by the microbial consumers were indicated by the ectoenzymatic activities and by the relationships between the enzymes, their organic substrates and their producers (namely the bacteria). In particular, bacteria were able to exploit the inorganic N supply (nitrite + nitrate provided by irregular intrusions of intermediate waters) to escape the bottom-up limitation and produce enzymes such as BG devoted to the degradation of cellulose remnants and, therefore, also able to take advantage on this refractory organic matter. In the 200-800 m layer, where trophic limitation was strong due to the low values of potentially-labile organic matter (namely proteins), the peculiar hydrodynamism led to the formation of nepheloid layers rich in organic matter, which provided the bacteria with substrates and allowed the development of a significant correlation between LA activity and its own organic substrate. Furthermore, a reduction of the bottom-up pressure was also indicated by a higher mean bacteria cell size in the entire water column of the central and eastern sectors, and a significantly increased expression of BG related to the increase in the cell size. The ectoenzymatic activities, therefore, suggested that the southern Tyrrhenian Sea should be considered as a mosaic of subsystems, where the peculiar hydrological features stimulate bacterial adaptations and enhance the channelling of

  16. Optimizing dentin bond durability: strategies to prevent hydrolytic degradation of the hybrid layer

    PubMed Central

    Tjäderhane, Leo; Nascimento, Fabio D.; Breschi, Lorenzo; Mazzoni, Annalisa; Tersariol, Ivarne L.S.; Geraldeli, Saulo; Tezvergil-Mutluay, Arzu; Carrilho, Marcela; Carvalho, Ricardo M.; Tay, Franklin R.; Pashley, David H.

    2014-01-01

    Objectives Endogenous dentin collagenolytic enzymes, matrix metalloproteinases (MMPs) and cysteine cathepsins, are responsible for the time-related hydrolysis of collagen matrix of the hybrid layers. As the integrity of the collagen matrix is essential for the preservation of long-term dentin bond strength, inhibition or inactivation of endogenous dentin proteases is necessary for durable resin-bonded composite resin restorations. Methods Dentin contains collagenolytic enzymes, matrix metalloproteinases (MMPs) and cysteine cathepsins, which are responsible for the hydrolytic degradation of collagen matrix in the bonded interface. Several tentative approaches to prevent enzyme function either directly or indirectly have been proposed in the literature. Results Chlorhexidine, a general inhibitor of both MMPs and cysteine cathepsins, applied before primer/adhesive application is the most tested method. In general, these experiments have shown that enzyme inhibition is a promising scheme to improve hybrid layer preservation and bond strength durability. Other enzyme inhibitors, e.g. enzyme-inhibiting monomers and antimicrobial compounds, may be considered promising alternatives that would allow more simple clinical application than chlorhexidine. Cross-linking collagen and/or dentin organic matrix-bound enzymes could render hybrid layer organic matrix resistant to degradation, and complete removal of water from the hybrid layer with ethanol wet bonding or biomimetic remineralization should eliminate hydrolysis of both collagen and resin components. Significance Identification of the enzymes responsible for the hydrolysis of hybrid layer collagen and understanding their function has prompted several innovative approaches to retain the hybrid layer integrity and strong dentin bonding. The ultimate goal, prevention of collagen matrix degradation with techniques and commercially available materials that are simple and effective in clinical settings may be achievable in

  17. Enzymatic saccharification coupling with polyester recovery from cotton-based waste textiles by phosphoric acid pretreatment.

    PubMed

    Shen, Fei; Xiao, Wenxiong; Lin, Lili; Yang, Gang; Zhang, Yanzong; Deng, Shihuai

    2013-02-01

    In order to recycle the cotton-based waste textiles, a novel process was designed for pretreating waste textiles with phosphoric acid to recover polyester and fermentable sugar. The effects of pretreatment conditions including, phosphoric acid concentration, pretreatment temperature, time, and ratio of textiles and phosphoric acid were thoroughly investigated. Results indicated the mentioned four factors had significant influences on sugar and polyester recovery. Almost complete polyester recovery was achieved by enhancing phosphoric acid concentration, temperature and pretreatment time or reducing the ratio of textiles and phosphoric acid. However, these behaviors decreased the sugar recovery seriously. 100% polyester recovery with a maximum sugar recovery of 79.2% was achieved at the optimized conditions (85% phosphoric acid, 50°C, 7h, and the ratio of 1:15). According to the technical and cost-benefit analysis, it was technically feasible and potentially profitable to recover polyester and sugar from waste textiles by phosphoric acid pretreatment.

  18. Electrodeposited Fe-Co films prepared from a citric-acid-based plating bath

    NASA Astrophysics Data System (ADS)

    Yanai, T.; Uto, H.; Shimokawa, T.; Nakano, M.; Fukunaga, H.; Suzuki, K.

    2013-06-01

    Electrodeposited Fe-Co films are commonly prepared in a boric-acid-based bath. In this research, we applied citric acid instead of boric acid for the plating of Fe-Co films because boron in the waste bath is restricted by environmental-protection regulations in Japan. We evaluated the effect of citric acid on the magnetic and structural properties of the films. The saturation magnetization of the Fe-Co films slightly increased while the Fe content in the Fe-Co films decreased with increasing citric acid concentration. The lowest coercivity value of 240 A/m was obtained at a citric acid concentration of 100 g/L. The plating bath with this citric acid concentration enabled us to obtain Fe-Co films with high saturation magnetizations and smooth surface morphologies.

  19. Acid-base chemical reaction model for nucleation rates in the polluted atmospheric boundary layer.

    PubMed

    Chen, Modi; Titcombe, Mari; Jiang, Jingkun; Jen, Coty; Kuang, Chongai; Fischer, Marc L; Eisele, Fred L; Siepmann, J Ilja; Hanson, David R; Zhao, Jun; McMurry, Peter H

    2012-11-13

    Climate models show that particles formed by nucleation can affect cloud cover and, therefore, the earth's radiation budget. Measurements worldwide show that nucleation rates in the atmospheric boundary layer are positively correlated with concentrations of sulfuric acid vapor. However, current nucleation theories do not correctly predict either the observed nucleation rates or their functional dependence on sulfuric acid concentrations. This paper develops an alternative approach for modeling nucleation rates, based on a sequence of acid-base reactions. The model uses empirical estimates of sulfuric acid evaporation rates obtained from new measurements of neutral molecular clusters. The model predicts that nucleation rates equal the sulfuric acid vapor collision rate times a prefactor that is less than unity and that depends on the concentrations of basic gaseous compounds and preexisting particles. Predicted nucleation rates and their dependence on sulfuric acid vapor concentrations are in reasonable agreement with measurements from Mexico City and Atlanta. PMID:23091030

  20. Acid-base chemical reaction model for nucleation rates in the polluted atmospheric boundary layer.

    PubMed

    Chen, Modi; Titcombe, Mari; Jiang, Jingkun; Jen, Coty; Kuang, Chongai; Fischer, Marc L; Eisele, Fred L; Siepmann, J Ilja; Hanson, David R; Zhao, Jun; McMurry, Peter H

    2012-11-13

    Climate models show that particles formed by nucleation can affect cloud cover and, therefore, the earth's radiation budget. Measurements worldwide show that nucleation rates in the atmospheric boundary layer are positively correlated with concentrations of sulfuric acid vapor. However, current nucleation theories do not correctly predict either the observed nucleation rates or their functional dependence on sulfuric acid concentrations. This paper develops an alternative approach for modeling nucleation rates, based on a sequence of acid-base reactions. The model uses empirical estimates of sulfuric acid evaporation rates obtained from new measurements of neutral molecular clusters. The model predicts that nucleation rates equal the sulfuric acid vapor collision rate times a prefactor that is less than unity and that depends on the concentrations of basic gaseous compounds and preexisting particles. Predicted nucleation rates and their dependence on sulfuric acid vapor concentrations are in reasonable agreement with measurements from Mexico City and Atlanta.

  1. Acid-base accounting assessment of mine wastes using the chromium reducible sulfur method.

    PubMed

    Schumann, Russell; Stewart, Warwick; Miller, Stuart; Kawashima, Nobuyuki; Li, Jun; Smart, Roger

    2012-05-01

    The acid base account (ABA), commonly used in assessment of mine waste materials, relies in part on calculation of potential acidity from total sulfur measurements. However, potential acidity is overestimated where organic sulfur, sulfate sulfur and some sulfide compounds make up a substantial portion of the sulfur content. The chromium reducible sulfur (CRS) method has been widely applied to assess reduced inorganic sulfur forms in sediments and acid sulfate soils, but not in ABA assessment of mine wastes. This paper reports the application of the CRS method to measuring forms of sulfur commonly found in mine waste materials. A number of individual sulfur containing minerals and real waste materials were analyzed using both CRS and total S and the potential acidity estimates were compared with actual acidity measured from net acid generation tests and column leach tests. The results of the CRS analysis made on individual minerals demonstrate good assessment of sulfur from a range of sulfides. No sulfur was measured using the CRS method in a number of sulfate salts, including jarosite and melanterite typically found in weathered waste rocks, or from dibenzothiophene characteristic of organic sulfur compounds common to coal wastes. Comparison of ABA values for a number of coal waste samples demonstrated much better agreement of acidity predicted from CRS analysis than total S analysis with actual acidity. It also resulted in reclassification of most samples tested from PAF to NAF. Similar comparisons on base metal sulfide wastes generally resulted in overestimation of the acid potential by total S and underestimation of the acid potential by CRS in comparison to acidity measured during NAG tests, but did not generally result in reclassification. In all the cases examined, the best estimate of potential acidity included acidity calculated from both CRS and jarositic S. PMID:22444067

  2. Acid-base accounting assessment of mine wastes using the chromium reducible sulfur method.

    PubMed

    Schumann, Russell; Stewart, Warwick; Miller, Stuart; Kawashima, Nobuyuki; Li, Jun; Smart, Roger

    2012-05-01

    The acid base account (ABA), commonly used in assessment of mine waste materials, relies in part on calculation of potential acidity from total sulfur measurements. However, potential acidity is overestimated where organic sulfur, sulfate sulfur and some sulfide compounds make up a substantial portion of the sulfur content. The chromium reducible sulfur (CRS) method has been widely applied to assess reduced inorganic sulfur forms in sediments and acid sulfate soils, but not in ABA assessment of mine wastes. This paper reports the application of the CRS method to measuring forms of sulfur commonly found in mine waste materials. A number of individual sulfur containing minerals and real waste materials were analyzed using both CRS and total S and the potential acidity estimates were compared with actual acidity measured from net acid generation tests and column leach tests. The results of the CRS analysis made on individual minerals demonstrate good assessment of sulfur from a range of sulfides. No sulfur was measured using the CRS method in a number of sulfate salts, including jarosite and melanterite typically found in weathered waste rocks, or from dibenzothiophene characteristic of organic sulfur compounds common to coal wastes. Comparison of ABA values for a number of coal waste samples demonstrated much better agreement of acidity predicted from CRS analysis than total S analysis with actual acidity. It also resulted in reclassification of most samples tested from PAF to NAF. Similar comparisons on base metal sulfide wastes generally resulted in overestimation of the acid potential by total S and underestimation of the acid potential by CRS in comparison to acidity measured during NAG tests, but did not generally result in reclassification. In all the cases examined, the best estimate of potential acidity included acidity calculated from both CRS and jarositic S.

  3. Acid-base chemistry of the blood--a general model.

    PubMed

    Rees, S E; Andreassen, S; Hovorka, R; Summers, R; Carson, E R

    1996-10-01

    This paper describes a general model of acid-base chemistry of the blood which can be used to simulate physiological perturbation of acid-base chemistry on addition or removal of any buffer acid or base. In particular, it is shown how this model can be used to estimate the concentrations of buffer acid or base. In particular, it is shown how this model can be used to estimate the concentrations of buffer acids and bases when blood is equilibrated to a new pCO2, when hydrogen ions H+ are added to the blood, or when two pools of blood with different concentrations of buffer acids and bases are mixed. The ability of the model to represent the addition or removal of any acid or base is a significant increase in functionality above the Siggaard-Andersen nomogram which is limited to simulating the effects of equilibrating the blood to a new pCO2. When used to represent the situation where blood is equilibrated at a new pCO2 the model enables calculation of the amount CO2 removed during equilibration, a further increase in functionality above the Siggaard-Andersen nomogram. In two experimental situations, equilibrating blood to a new pCO2 and addition of H+ ions, the model predictions are shown to be consistent with existing experimental data in the form of the Siggaard-Andersen nomogram. PMID:8894395

  4. Amino acid ratings of different forms of infant formulas based on varying degrees of processing.

    PubMed

    Sarwar, G

    1991-01-01

    Amino acid profiles, protein digestibility and/or amino acid bioavailability for the various forms (powder, liquid concentrate, ready-to-use, etc.) of infant formulas (involving varying degrees of heat processing during preparation) have been determined. Amino acid scores (based on the single most limiting amino acid) were calculated by comparing the essential amino acid data with that of human milk. Amino acid scores were multiplied by total protein (g/100 kcal) to obtain amino acid ratings, which take into account both quality and quantity of protein. Amino acid scores for milk- and soy-based formulas ranged from 49 to 90 and 59 to 81%, respectively, due to deficiencies in methionine plus cystine and/or tryptophan. The deficiency in the limiting amino acids was more marked in liquid concentrate than powder prepared by the same manufacturer. Because of significantly higher total protein contents (g/100 kcal) of soy- (2.65-3.68) and milk-based (2.20-2.95) formulas compared to human milk (1.5), the relative amino acid ratings (human milk = 100) of all formulas except two milk-based liquid concentrates and one ready-to-feed (with values of 77-87%) were greater than 100%. When corrected for protein digestibility, the relative amino acid ratings for all four liquid concentrates were less than 100%. Lower levels of digestible protein and bioavailable amino acids in liquid concentrate compared with powder (prepared by the same manufacturer) would suggest that inferior protein quality of liquid concentrates may be due to more severe heat treatment involved in their preparation.

  5. Influence of pasture-based feeding systems on fatty acids, organic acids and volatile organic flavour compounds in yoghurt.

    PubMed

    Akbaridoust, Ghazal; Plozza, Tim; Trenerry, V Craige; Wales, William J; Auldist, Martin J; Ajlouni, Said

    2015-08-01

    The influence of different pasture-based feeding systems on fatty acids, organic acids and volatile organic flavour compounds in yoghurt was studied. Pasture is the main source of nutrients for dairy cows in many parts of the world, including southeast Australia. Milk and milk products produced in these systems are known to contain a number of compounds with positive effects on human health. In the current study, 260 cows were fed supplementary grain and forage according to one of 3 different systems; Control (a traditional pasture based diet offered to the cows during milking and in paddock), PMR1 (a partial mixed ration which contained the same supplement as Control but was offered to the cows as a partial mixed ration on a feedpad), PMR 2 (a differently formulated partial mixed ration compared to Control and PMR1 which was offered to the cows on a feedpad). Most of the yoghurt fatty acids were influenced by feeding systems; however, those effects were minor on organic acids. The differences in feeding systems did not lead to the formation of different volatile organic flavour compounds in yoghurt. Yet, it did influence the relative abundance of these components. PMID:26143651

  6. Influence of pasture-based feeding systems on fatty acids, organic acids and volatile organic flavour compounds in yoghurt.

    PubMed

    Akbaridoust, Ghazal; Plozza, Tim; Trenerry, V Craige; Wales, William J; Auldist, Martin J; Ajlouni, Said

    2015-08-01

    The influence of different pasture-based feeding systems on fatty acids, organic acids and volatile organic flavour compounds in yoghurt was studied. Pasture is the main source of nutrients for dairy cows in many parts of the world, including southeast Australia. Milk and milk products produced in these systems are known to contain a number of compounds with positive effects on human health. In the current study, 260 cows were fed supplementary grain and forage according to one of 3 different systems; Control (a traditional pasture based diet offered to the cows during milking and in paddock), PMR1 (a partial mixed ration which contained the same supplement as Control but was offered to the cows as a partial mixed ration on a feedpad), PMR 2 (a differently formulated partial mixed ration compared to Control and PMR1 which was offered to the cows on a feedpad). Most of the yoghurt fatty acids were influenced by feeding systems; however, those effects were minor on organic acids. The differences in feeding systems did not lead to the formation of different volatile organic flavour compounds in yoghurt. Yet, it did influence the relative abundance of these components.

  7. Hydrolytic release of bound residues from composted soil contaminated with 2,4,6-trinitrotoluene

    SciTech Connect

    Thorne, P.G.; Leggett, D.C.

    1997-06-01

    The US Army is obligated to restore land previously contaminated with the explosive 2,4,6-trinitrotoluene (TNT). One remediation method that is being tried is composting. In this method, the soil to be treated is mixed with a readily decomposable source of organic carbon, which is usually a mixture of readily available organic material. Samples of composted soil were extracted with solvent, then hydrolyzed with acid or base. The concentrations of extractable, unbound 2,4,6-trinitrotoluene and its mono- and diamino metabolites fell rapidly after the first days of composting. Hydrolysis of the extracted residues released significant quantities of intact metabolites. The objectives of this work were to differentiate between bound and unbound explosives and their transformation products in composted soil, to investigate the time course of metabolite evolution and binding, and to evaluate various hydrolysis methods.

  8. [Practical diagnostics of acid-base disorders: part I: differentiation between respiratory and metabolic disturbances].

    PubMed

    Deetjen, P; Lichtwarck-Aschoff, M

    2012-11-01

    The first part of this overview on diagnostic tools for acid-base disorders focuses on basic knowledge for distinguishing between respiratory and metabolic causes of a particular disturbance. Rather than taking sides in the great transatlantic or traditional-modern debate on the best theoretical model for understanding acid-base physiology, this article tries to extract what is most relevant for everyday clinical practice from the three schools involved in these keen debates: the Copenhagen, the Boston and the Stewart schools. Each school is particularly strong in a specific diagnostic or therapeutic field. Appreciating these various strengths a unifying, simplified algorithm together with an acid-base calculator will be discussed.

  9. Acid-base and chelatometric photo-titrations with photosensors and membrane photosensors.

    PubMed

    Matsuo, T; Masuda, Y; Sekido, E

    1986-08-01

    Photosensors (PS) and membrane photosensors (MPS), which can be immersed in the test solution and facilitate the measurement of concentration, have been developed by miniaturizing an optical system consisting of a light source and a photocell. For use in acid-base or complexometric titrations a poly(vinyl chloride) membrane containing an acid-base or metallochromic indicator can be applied as a coating to the photocell. Spectrophotometric determination of copper(II), and photometric acid-base and chelatometric titrations have been performed with the PS and MPS systems.

  10. Boronic acid-based enzyme inhibitors: a review of recent progress.

    PubMed

    Fu, H; Fang, H; Sun, Jie; Wang, H; Liu, A; Sun, J; Wu, Z

    2014-01-01

    Since Bortezomib was approved by US FDA as the first drug to treat multiple myeloma, various boronic acid compounds have been developed as enzyme inhibitors. This paper reviewed the progress of boronic acid-based inhibitors against enzymes including proteasome, serine protease, HDACs and other enzymes in the past decade.

  11. Surveying Students' Conceptual and Procedural Knowledge of Acid-Base Behavior of Substances

    ERIC Educational Resources Information Center

    Furio-Mas, Carles; Calatayud, Maria-Luisa; Barcenas, Sergio L.

    2007-01-01

    By the end of their high school studies, students should be able to understand macroscopic and sub-microscopic conceptualization of acid-base behavior and the relationship between these conceptual models. The aim of this article is to ascertain whether grade-12 students have sufficient background knowledge to explain the properties of acids,…

  12. Synthesis of novel trivalent amino acid glycoconjugates based on the cyclotriveratrylene ('CTV') scaffold.

    PubMed

    van Ameijde, Jeroen; Liskamp, Rob M J

    2003-08-01

    The convenient synthesis of novel trivalent amino acid glycoconjugates based on cyclotriveratrylene ('CTV') is described. These constructs consist of the CTV scaffold, three oligoethylene glycol spacers of variable length connected to a glyco amino acid residue which can also be varied. The resulting library of trivalent glycoconjugates can be used for studying multivalent interactions. PMID:12948190

  13. EFFECTIVENESS OF USING DILUTE OXALIC ACID TO DISSOLVEHIGH LEVEL WASTE IRON BASED SLUDGE SIMULANT

    SciTech Connect

    Ketusky, E

    2008-07-11

    At the Savannah River Site (SRS), near Aiken South Carolina, there is a crucial need to remove residual quantities of highly radioactive iron-based sludge from large select underground storage tanks (e.g., 19,000 liters of sludge per tank), in order to support tank closure. The use of oxalic acid is planned to dissolve the residual sludge, hence, helping in the removal. Based on rigorous testing, primarily using 4 and 8 wt% oxalic acid solutions, it was concluded that the more concentrated the acid, the greater the amount of residual sludge that would be dissolved; hence, a baseline technology on using 8 wt% oxalic acid was developed. In stark contrast to the baseline technology, reports from other industries suggest that the dissolution will most effectively occur at 1 wt% oxalic acid (i.e., maintaining the pH near 2). The driver for using less oxalic acid is that less (i.e., moles) would decrease the severity of the downstream impacts (i.e., required oxalate solids removal efforts). To determine the initial feasibility of using 1 wt% acid to dissolve > 90% of the sludge solids, about 19,000 liters of representative sludge was modeled using about 530,000 liters of 0 to 8 wt% oxalic acid solutions. With the chemical thermodynamic equilibrium based software results showing that 1 wt% oxalic acid could theoretically work, simulant dissolution testing was initiated. For the dissolution testing, existing simulant was obtained, and an approximate 20 liter test rig was built. Multiple batch dissolutions of both wet and air-dried simulant were performed. Overall, the testing showed that dilute oxalic acid dissolved a greater fraction of the stimulant and resulted in a significantly larger acid effectiveness (i.e., grams of sludge dissolved/mole of acid) than the baseline technology. With the potential effectiveness confirmed via simulant testing, additional testing, including radioactive sludge testing, is planned.

  14. Essentials in the diagnosis of acid-base disorders and their high altitude application.

    PubMed

    Paulev, P E; Zubieta-Calleja, G R

    2005-09-01

    This report describes the historical development in the clinical application of chemical variables for the interpretation of acid-base disturbances. The pH concept was already introduced in 1909. Following World War II, disagreements concerning the definition of acids and bases occurred, and since then two strategies have been competing. Danish scientists in 1923 defined an acid as a substance able to give off a proton at a given pH, and a base as a substance that could bind a proton, whereas the North American Singer-Hasting school in 1948 defined acids as strong non-buffer anions and bases as non-buffer cations. As a consequence of this last definition, electrolyte disturbances were mixed up with real acid-base disorders and the variable, strong ion difference (SID), was introduced as a measure of non-respiratory acid-base disturbances. However, the SID concept is only an empirical approximation. In contrast, the Astrup/Siggaard-Andersen school of scientists, using computer strategies and the Acid-base Chart, has made diagnosis of acid-base disorders possible at a glance on the Chart, when the data are considered in context with the clinical development. Siggaard-Andersen introduced Base Excess (BE) or Standard Base Excess (SBE) in the extracellular fluid volume (ECF), extended to include the red cell volume (eECF), as a measure of metabolic acid-base disturbances and recently replaced it by the term Concentration of Titratable Hydrogen Ion (ctH). These two concepts (SBE and ctH) represent the same concentration difference, but with opposite signs. Three charts modified from the Siggaard-Andersen Acid-Base Chart are presented for use at low, medium and high altitudes of 2500 m, 3500 m, and 4000 m, respectively. In this context, the authors suggest the use of Titratable Hydrogen Ion concentration Difference (THID) in the extended extracellular fluid volume, finding it efficient and better than any other determination of the metabolic component in acid-base

  15. Essentials in the diagnosis of acid-base disorders and their high altitude application.

    PubMed

    Paulev, P E; Zubieta-Calleja, G R

    2005-09-01

    This report describes the historical development in the clinical application of chemical variables for the interpretation of acid-base disturbances. The pH concept was already introduced in 1909. Following World War II, disagreements concerning the definition of acids and bases occurred, and since then two strategies have been competing. Danish scientists in 1923 defined an acid as a substance able to give off a proton at a given pH, and a base as a substance that could bind a proton, whereas the North American Singer-Hasting school in 1948 defined acids as strong non-buffer anions and bases as non-buffer cations. As a consequence of this last definition, electrolyte disturbances were mixed up with real acid-base disorders and the variable, strong ion difference (SID), was introduced as a measure of non-respiratory acid-base disturbances. However, the SID concept is only an empirical approximation. In contrast, the Astrup/Siggaard-Andersen school of scientists, using computer strategies and the Acid-base Chart, has made diagnosis of acid-base disorders possible at a glance on the Chart, when the data are considered in context with the clinical development. Siggaard-Andersen introduced Base Excess (BE) or Standard Base Excess (SBE) in the extracellular fluid volume (ECF), extended to include the red cell volume (eECF), as a measure of metabolic acid-base disturbances and recently replaced it by the term Concentration of Titratable Hydrogen Ion (ctH). These two concepts (SBE and ctH) represent the same concentration difference, but with opposite signs. Three charts modified from the Siggaard-Andersen Acid-Base Chart are presented for use at low, medium and high altitudes of 2500 m, 3500 m, and 4000 m, respectively. In this context, the authors suggest the use of Titratable Hydrogen Ion concentration Difference (THID) in the extended extracellular fluid volume, finding it efficient and better than any other determination of the metabolic component in acid-base

  16. Highly acidic mesostructured aluminosilicates assembled from surfactant-mediated zeolite hydrolysis products.

    PubMed

    Wang, Hui; Liu, Yu; Pinnavaia, Thomas J

    2006-03-16

    The surfactant-mediated hydrolysis of ZSM-5 zeolite affords five-membered ring subunits that can be readily incorporated into the framework walls of a hexagonal mesostructured aluminosilicate, denoted MSU-Z. The five-membered ring subunits, which are identifiable by infrared spectroscopy, impart unprecedented acidity to the mesostructure, as judged by cumene cracking activity at 300 degrees C. Most notably, MSU-Z aluminosilicate made through the base hydrolysis of ZSM-5 in the presence of cetyltrimethylammonium ions exhibits a cumene conversion of 73%, which is 6.7-fold higher than the conversion provided by a conventional MCM-41. This approach to stabilizing zeolitic subunits through surfactant-mediated hydrolysis of zeolites appears to be general. The hydrolysis of USY zeolite under analogous hydrolytic conditions also affords zeolitic fragments that boost the acidity of the mesostructure in comparison to equivalent compositions prepared from conventional aluminosilicate precursors.

  17. The solubilization of fatty acids in systems based on block copolymers and nonionic surfactants

    NASA Astrophysics Data System (ADS)

    Mirgorodskaya, A. B.; Yatskevich, E. I.; Zakharova, L. Ya.

    2010-12-01

    The solubilizing action of micellar, microemulsion, and polymer-colloid systems formed on the basis of biologically compatible amphiphilic polymers and nonionic surfactants on capric, lauric, palmitic, and stearic acids was characterized quantitatively. Systems based on micelle forming oxyethyl compounds increased the solubility of fatty acids by more than an order of magnitude. Acid molecules incorporated into micelles increased their size and caused structural changes. Solubilization was accompanied by complete or partial destruction of intrinsic acid associates and an increase in their p K a by 1.5-2 units compared with water.

  18. Antimicrobial polyurethane thermosets based on undecylenic acid: synthesis and evaluation.

    PubMed

    Lluch, Cristina; Esteve-Zarzoso, Braulio; Bordons, Albert; Lligadas, Gerard; Ronda, Juan C; Galià, Marina; Cádiz, Virginia

    2014-08-01

    In the present study, plant oil-derived surface-modifiable polyurethane thermosets are presented. Polyol synthesis is carried out taking advantage of thiol-yne photopolymerization of undecylenic acid derivatives containing methyl ester or hydroxyl moieties. The prepared methyl ester-containing polyurethanes allow surface modification treatment to enhance their hydrophilicity and impart antimicrobial activity through the following two steps: i) grafting poly(propylene glycol) monoamine (Jeffamine M-600) via aminolysis and ii) Jeffamine M-600 layer complexation with iodine. The antimicrobial activity of the iodine-containing polyurethanes is demonstrated by its capacity to inhibit the growth of Staphylococcus aureus, and Candida albicans in agar media.

  19. Influence of dissolved organic carbon content on modelling natural organic matter acid-base properties.

    PubMed

    Garnier, Cédric; Mounier, Stéphane; Benaïm, Jean Yves

    2004-10-01

    Natural organic matter (NOM) behaviour towards proton is an important parameter to understand NOM fate in the environment. Moreover, it is necessary to determine NOM acid-base properties before investigating trace metals complexation by natural organic matter. This work focuses on the possibility to determine these acid-base properties by accurate and simple titrations, even at low organic matter concentrations. So, the experiments were conducted on concentrated and diluted solutions of extracted humic and fulvic acid from Laurentian River, on concentrated and diluted model solutions of well-known simple molecules (acetic and phenolic acids), and on natural samples from the Seine river (France) which are not pre-concentrated. Titration experiments were modelled by a 6 acidic-sites discrete model, except for the model solutions. The modelling software used, called PROSECE (Programme d'Optimisation et de SpEciation Chimique dans l'Environnement), has been developed in our laboratory, is based on the mass balance equilibrium resolution. The results obtained on extracted organic matter and model solutions point out a threshold value for a confident determination of the studied organic matter acid-base properties. They also show an aberrant decreasing carboxylic/phenolic ratio with increasing sample dilution. This shift is neither due to any conformational effect, since it is also observed on model solutions, nor to ionic strength variations which is controlled during all experiments. On the other hand, it could be the result of an electrode troubleshooting occurring at basic pH values, which effect is amplified at low total concentration of acidic sites. So, in our conditions, the limit for a correct modelling of NOM acid-base properties is defined as 0.04 meq of total analysed acidic sites concentration. As for the analysed natural samples, due to their high acidic sites content, it is possible to model their behaviour despite the low organic carbon concentration.

  20. A novel protease-resistant alpha-galactosidase with high hydrolytic activity from Gibberella sp. F75: gene cloning, expression, and enzymatic characterization.

    PubMed

    Cao, Yanan; Wang, Yaru; Meng, Kun; Bai, Yingguo; Shi, Pengjun; Luo, Huiying; Yang, Peilong; Zhou, Zhigang; Zhang, Zhifang; Yao, Bin

    2009-07-01

    A novel alpha-galactosidase gene (aga-F75) from Gibberella sp. F75 was cloned and expressed in Escherichia coli. The gene codes for a protein of 744 amino acids with a 24-residue putative signal peptide and a calculated molecular mass of 82.94 kDa. The native structure of the recombinant Aga-F75 was estimated to be a trimer or tetramer. The deduced amino acid sequence showed highest identity (69%) with an alpha-galactosidase from Hypocrea jecorina (Trichoderma reesei), a member of the glycoside hydrolase family 36. Purified recombinant Aga-F75 was optimally active at 60 degrees C and pH 4.0 and was stable at pH 3.0-12.0. The enzyme exhibited broad substrate specificity and substantial resistance to neutral and alkaline proteases. The enzyme K (m) values using pNPG, melibiose, stachyose, and raffinose as substrates were 1.06, 1.75, 54.26, and 8.23 mM, respectively. Compared with the commercial alpha-galactosidase (Aga-A) from Aspergillus niger var. AETL and a protease-resistant alpha-galactosidase (Aga-F78) from Rhizopus sp. F78, Aga-F75 released 1.4- and 4.9-fold more galactose from soybean meal alone, respectively, and 292.5- and 8.6-fold more galactose from soybean meal in the presence of trypsin, respectively. The pH and thermal stability and hydrolytic activity of Aga-F75 make it potentially useful in the food and feed industries.

  1. Tuning Acid-Base Properties Using Mg-Al Oxide Atomic Layer Deposition.

    PubMed

    Jackson, David H K; O'Neill, Brandon J; Lee, Jechan; Huber, George W; Dumesic, James A; Kuech, Thomas F

    2015-08-01

    Atomic layer deposition (ALD) was used to coat γ-Al2O3 particles with oxide films of varying Mg/Al atomic ratios, which resulted in systematic variation of the acid and base site areal densities. Variation of Mg/Al also affected morphological features such as crystalline phase, pore size distribution, and base site proximity. Areal base site density increased with increasing Mg content, while acid site density went through a maximum with a similar number of Mg and Al atoms in the coating. This behavior leads to nonlinearity in the relationship between Mg/Al and acid/base site ratio. The physical and chemical properties were elucidated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 physisorption, and CO2 and NH3 temperature-programmed desorption (TPD). Fluorescence emission spectroscopy of samples grafted with 1-pyrenebutyric acid (PBA) was used for analysis of base site proximity. The degree of base site clustering was correlated to acid site density. Catalytic activity in the self-condensation of acetone was dependent on sample base site density and independent of acid site density. PMID:26168188

  2. Tuning Acid-Base Properties Using Mg-Al Oxide Atomic Layer Deposition.

    PubMed

    Jackson, David H K; O'Neill, Brandon J; Lee, Jechan; Huber, George W; Dumesic, James A; Kuech, Thomas F

    2015-08-01

    Atomic layer deposition (ALD) was used to coat γ-Al2O3 particles with oxide films of varying Mg/Al atomic ratios, which resulted in systematic variation of the acid and base site areal densities. Variation of Mg/Al also affected morphological features such as crystalline phase, pore size distribution, and base site proximity. Areal base site density increased with increasing Mg content, while acid site density went through a maximum with a similar number of Mg and Al atoms in the coating. This behavior leads to nonlinearity in the relationship between Mg/Al and acid/base site ratio. The physical and chemical properties were elucidated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 physisorption, and CO2 and NH3 temperature-programmed desorption (TPD). Fluorescence emission spectroscopy of samples grafted with 1-pyrenebutyric acid (PBA) was used for analysis of base site proximity. The degree of base site clustering was correlated to acid site density. Catalytic activity in the self-condensation of acetone was dependent on sample base site density and independent of acid site density.

  3. 2-Keto acids based biosynthesis pathways for renewable fuels and chemicals.

    PubMed

    Tashiro, Yohei; Rodriguez, Gabriel M; Atsumi, Shota

    2015-03-01

    Global energy and environmental concerns have driven the development of biological chemical production from renewable sources. Biological processes using microorganisms are efficient and have been traditionally utilized to convert biomass (i.e., glucose) to useful chemicals such as amino acids. To produce desired fuels and chemicals with high yield and rate, metabolic pathways have been enhanced and expanded with metabolic engineering and synthetic biology approaches. 2-Keto acids, which are key intermediates in amino acid biosynthesis, can be converted to a wide range of chemicals. 2-Keto acid pathways were engineered in previous research efforts and these studies demonstrated that 2-keto acid pathways have high potential for novel metabolic routes with high productivity. In this review, we discuss recently developed 2-keto acid-based pathways.

  4. A poly(γ, L-glutamic acid)-citric acid based nanoconjugate for cisplatin delivery.

    PubMed

    Xiong, Yerong; Jiang, Weiwei; Shen, Yan; Li, Huiyi; Sun, Chunmeng; Ouahab, Ammar; Tu, Jiasheng

    2012-10-01

    A cisplatin-loaded nanoconjugate, poly(γ, L-glutamic acid)-citric acid-cisplatin [γ-PGA-CA-CDDP], as a tumor-targeted drug delivery system with sustained release capacity was successfully synthesized and characterized, and its antitumor activity was evaluated. The particle size (107 ± 6.3 nm) and average molecular weight (66 kDa) were determined by dynamic light scattering (DLS) and gel permeation chromatography (GPC), respectively. The nanoconjugate delivery system released platinum in a sustained manner in PBS at 37 °C with an initial burst release during the first 8 h and 50% cumulative release within 48 h. Both in-vitro and in-vivo studies showed that the toxicity of γ-PGA-CA-CDDP nanoconjugate significantly decreased by comparison to that of unconjugated CDDP. The maximum tolerated dose (MTD) of γ-PGA-CA-CDDP nanoconjugate was about 38 mg/kg versus 8 mg/kg for CDDP. No apathy or acute adverse reactions were observed in γ-PGA-CA-CDDP nanoconjugate groups while mice expressed apathy at all dose levels with CDDP treatment. In ICR mice, the area under the curve and total body clearance values for γ-PGA-CA-CDDP nanoconjugate were 9-fold and one-twentieth of the values for CDDP, respectively. With the aid of near-infrared fluorescence (NIRF) imaging system, it was demonstrated that γ-PGA-CA-CDDP nanoconjugate gradually accumulated at the tumor site within 15 min postinjection and exhibited prolonged retention for more than 8 h. In H22-implanted mice, γ-PGA-CA-CDDP showed a significantly higher antitumor activity versus CDDP. These results reveal that γ-PGA-CA-CDDP nanoconjugate with improved stability, reduced toxicity and prolonged in-vivo retention time holds great potential in terms of clinical application to cancer therapy.

  5. Transition metal cation separations with a resorcinarene-based amino acid stationary phase.

    PubMed

    Li, Na; Allen, Lee J; Harrison, Roger G; Lamb, John D

    2013-03-01

    A resorcinarene-based macrocyclic ligand functionalized with alanine and undecyl groups (AUA) was synthesized and applied to ion chromatographic separations. The selectivity and separation of transition metal ions on a column packed with AUA adsorbed onto 55% cross-linked styrene-divinylbenzene resin are presented. The upper and lower rims of the resorcinarene were modified with amino acids and -C(11)H(23) alkyl chains, respectively. The four carboxylic acid groups on the upper rim act as cation-exchangers while the four -C(11)H(23) alkyl chains serve to anchor the ligand to the resin surface by the hydrophobic effect. A systematic study of the effect of different eluent components including non-metal-chelating (HNO(3)) and chelating acids (oxalic acid, succinic acid, dipicolinic acid, and citric acid) on the retention of transition metal ions was investigated. Six metal ions (Mn(2+), Co(2+), Ni(2+), Cd(2+), Cu(2+), and Zn(2+)) were separated on the AUA column within a reasonable time with a single eluent gradient using oxalic acid. The separation is compared to that obtained using a commercial column containing carboxylic acid functional groups. The AUA column containing four preorganized carboxylic acid groups showed selectivity for Cu(2+) when no chelating eluent was present, a selectivity which was not observed with the comparison column.

  6. Envisioning an enzymatic Diels-Alder reaction by in situ acid-base catalyzed diene generation.

    PubMed

    Linder, Mats; Johansson, Adam Johannes; Manta, Bianca; Olsson, Philip; Brinck, Tore

    2012-06-01

    We present and evaluate a new and potentially efficient route for enzyme-mediated Diels-Alder reactions, utilizing general acid-base catalysis. The viability of employing the active site of ketosteroid isomerase is demonstrated.

  7. An Intuitive and General Approach to Acid-Base Equilibrium Calculations.

    ERIC Educational Resources Information Center

    Felty, Wayne L.

    1978-01-01

    Describes the intuitive approach used in general chemistry and points out its pedagogical advantages. Explains how to extend it to acid-base equilibrium calculations without the need to introduce additional sophisticated concepts. (GA)

  8. A phosphomolybdic acid anion probe-based label-free, stable and simple electrochemical biosensing platform.

    PubMed

    Wei, Tianxiang; Chen, Yuyun; Tu, Wenwen; Lan, Yaqian; Dai, Zhihui

    2014-08-25

    A versatile label-free, stable, low-cost and simple electrochemical biosensing platform has been developed based on a phosphomolybdic acid anion probe by jointly taking advantages of its native electronegativity, electrochemical activity and chemisorption with graphene oxide.

  9. L-shaped benzimidazole fluorophores: synthesis, characterization and optical response to bases, acids and anions.

    PubMed

    Lirag, Rio Carlo; Le, Ha T M; Miljanić, Ognjen Š

    2013-05-14

    Nine L-shaped benzimidazole fluorophores have been synthesized, computationally evaluated and spectroscopically characterized. These "half-cruciform" fluorophores respond to bases, acids and anions through changes in fluorescence that vary from moderate to dramatic.

  10. A room-temperature adenosine-based molecular beacon for highly sensitive detection of nucleic acids.

    PubMed

    Lin, Yen-Hsiu; Tseng, Wei-Lung

    2012-06-25

    This study developed a simple, sensitive, and selective molecular beacon for detecting nucleic acids at room temperature based on coralyne induced conformational change of a MB through A(2)-coralyne-A(2) coordination.

  11. Going Beyond, Going Further: The Preparation of Acid-Base Titration Curves.

    ERIC Educational Resources Information Center

    McClendon, Michael

    1984-01-01

    Background information, list of materials needed, and procedures used are provided for a simple technique for generating mechanically plotted acid-base titration curves. The method is suitable for second-year high school chemistry students. (JN)

  12. Why and How To Teach Acid-Base Reactions without Equilibrium.

    ERIC Educational Resources Information Center

    Carlton, Terry S.

    1997-01-01

    Recommends an approach to the treatment of acid-base equilibria that involves treating each reaction as either going to completion or not occurring at all. Compares the method with the traditional approach step by step. (DDR)

  13. Development of electrochemical folic acid sensor based on hydroxyapatite nanoparticles

    NASA Astrophysics Data System (ADS)

    Kanchana, P.; Sekar, C.

    2015-02-01

    We report the synthesis of hydroxyapatite (HA) nanoparticles (NPs) by a simple microwave irradiation method and its application as sensing element for the precise determination of folic acid (FA) by electrochemical method. The structure and composition of the HA NPs characterized using XRD, FTIR, Raman and XPS. SEM and EDX studies confirmed the formation of elongated spherical shaped HA NPs with an average particle size of about 34 nm. The HA NPs thin film on glassy carbon electrode (GCE) were deposited by drop casting method. Electrocatalytic behavior of FA in the physiological pH 7.0 was investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry. The fabricated HA/GCE exhibited a linear calibration plot over a wide FA concentration ranging from 1.0 × 10-7 to 3.5 × 10-4 M with the detection limit of 75 nM. In addition, the HA NPs modified GCE showed good selectivity toward the determination of FA even in the presence of a 100-fold excess of ascorbic acid (AA) and 1000-fold excess of other common interferents. The fabricated biosensor exhibits good sensitivity and stability, and was successfully applied for the determination of FA in pharmaceutical samples.

  14. Hexafluorozirconic Acid Based Surface Pretreatments: Characterization and Performance Assessment

    SciTech Connect

    Adhikari, Saikat; Unocic, Kinga A; Zhai, Yumei; Frankel, Gerald; Zimmerman, John; Fristad, W

    2010-01-01

    A new phosphate-free pretreatment from Henkel Corp. named TecTalis , was investigated. The treatment bath is composed of dilute hexafluorozirconic acid with small quantities of non-hazardous components containing Si and Cu. The performance of treated steel was compared to samples treated in a phosphate conversion coating bath, in simple hexafluorozirconic acid and in TecTalis without the addition of the Cu containing component. Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) were used to characterize the coating surface morphology, structure and composition. A Quartz Crystal Microbalance (QCM) was used for studying film growth kinetics on thin films of pure Fe, Al and Zn. Electrochemical Impedance Spectroscopy (EIS) was performed on treated and painted steel for studying long-term corrosion performance of the coatings. The phosphate-free coating provided long-term corrosion performance comparable to that of phosphate conversion coatings. The coatings uniformly cover the surface in the form of 10-20 nm sized nodules and clusters of these features up to 500 nm in size. The coatings are usually about 20-30 nm thick and are mostly composed of Zr and O with enrichment of copper at randomly distributed locations and clusters.

  15. Production of cellulase systems by selected mutants of Trichoderma reesei in soild-state fermentation and their hydrolytic potentials

    SciTech Connect

    Awafo, V.A. ||; Chahal, D.S.; Simpson, B.K. |; Le, G.B.B.

    1996-12-31

    Three mutants of Trichoderma reesei were grown in solid-state fermentation (SSF) in flasks and in a pan bioreactor. Mutant strain MCG 80 proved to be the best at producing an optimal cellulose system using lignocellulosic material (wheat straw [WS]) as substrate. This preparation exhibited a {beta}-glucosidase activity (PGA) to FPA (FPA) ratio of about 1.0, which is indicative of a high potential for hydrolysis of cellulose. The yields of cellulose systems and the ratio of PGA to FPA produced in flasks were comparable to that of the pan bioreactor. The cellulose system of T. reesei MCG 80 having a ratio of {beta}GA to FPA close to 1.0 gave the most complete (88-95%) hydrolysis of 5% delignified wheat straw (DWS). On the other hand, the cellulose system of cocultures of T. reesei QMY-1 and Aspergillus phoenicis failed to produce high hydrolytic yields in spite of having a very high ratio of PGA to FPA (3.04). This failure was owing to the fact that coculture contained the relatively poor-quality cellulase system of the dominant organism, A. phoenicis. The resulting fermented WS can be used, as a source of enzyme (unextracted), for hydrolysis of wheat straw, and it gives increased yields of reducing sugars compared to analogous extracted enzyme preparations. The hydrolytic potential of two commercial enzymes tested were considerably lower than those of the cellulose systems produced on WS. It is evident that a complete cellulose system having a {beta}GA-to-FPA ratio close to 1.0 and high hydrolytic potential can be produced on lignocellulosic feedstocks in SSF. 21 refs., 3 figs., 3 tabs.

  16. Production of Oxidative and Hydrolytic Enzymes by Coprinus cinereus (Schaeff.) Gray from Sisal Wastes Supplemented with Cow Dung Manure.

    PubMed

    Raymond, Prosper; Mshandete, Anthony Manoni; Kajumulo Kivaisi, Amelia

    2015-01-01

    The activity of oxidative and hydrolytic enzymes of the edible and medicinal white rot fungi Coprinus cinereus (Schaeff.) Gray mushroom was observed during mycelia growth and fruiting body development in solid substrate fermentation using sisal waste fractions amended with cow dung manure as supplement. Laccase had the highest titre value among the five detected enzymes. Its activity was higher during mycelia growth compared to fruiting phase, with 10% supplemented substrate formulation unmixed sisal leaf decortication residues [abbreviated SL : SB (100 : 0)] displaying the highest activity of 39.45 ± 12.05 Ug(-1). Lignin peroxidase (LiP) exhibited a characteristic wave-like pattern with the highest peaks found either during full mycelia colonization or soon after first flush harvest; the highest activity of 1.93 ± 0.62 Ug(-1) was observed on unsupplemented SL : SB (100 : 0) substrate formulation during mycelia colonization. For hydrolytic enzymes, the highest carboxymethyl cellulase (CMCase) activity of 2.03 ± 0.70 Ug(-1) was observed on 20% supplemented SL : SB (0 : 100) after first flush; that of pectinase (1.90 ± 0.32 Ug(-1)) was revealed after third flush on 10% supplemented SL : SB (0 : 100) substrate formulation while 10% supplemented SL : SB (25 : 75) exhibited the highest xylanase activity (1.23 ± 0.12 Ug(-1)) after first flush. These findings show that the activities of both oxidative and hydrolytic enzymes were regulated in line with developmental phase of growth of Coprinus cinereus.

  17. Production of Oxidative and Hydrolytic Enzymes by Coprinus cinereus (Schaeff.) Gray from Sisal Wastes Supplemented with Cow Dung Manure

    PubMed Central

    Raymond, Prosper; Mshandete, Anthony Manoni; Kajumulo Kivaisi, Amelia

    2015-01-01

    The activity of oxidative and hydrolytic enzymes of the edible and medicinal white rot fungi Coprinus cinereus (Schaeff.) Gray mushroom was observed during mycelia growth and fruiting body development in solid substrate fermentation using sisal waste fractions amended with cow dung manure as supplement. Laccase had the highest titre value among the five detected enzymes. Its activity was higher during mycelia growth compared to fruiting phase, with 10% supplemented substrate formulation unmixed sisal leaf decortication residues [abbreviated SL : SB (100 : 0)] displaying the highest activity of 39.45 ± 12.05 Ug−1. Lignin peroxidase (LiP) exhibited a characteristic wave-like pattern with the highest peaks found either during full mycelia colonization or soon after first flush harvest; the highest activity of 1.93 ± 0.62 Ug−1 was observed on unsupplemented SL : SB (100 : 0) substrate formulation during mycelia colonization. For hydrolytic enzymes, the highest carboxymethyl cellulase (CMCase) activity of 2.03 ± 0.70 Ug−1 was observed on 20% supplemented SL : SB (0 : 100) after first flush; that of pectinase (1.90 ± 0.32 Ug−1) was revealed after third flush on 10% supplemented SL : SB (0 : 100) substrate formulation while 10% supplemented SL : SB (25 : 75) exhibited the highest xylanase activity (1.23 ± 0.12 Ug−1) after first flush. These findings show that the activities of both oxidative and hydrolytic enzymes were regulated in line with developmental phase of growth of Coprinus cinereus. PMID:26664748

  18. Thiazole orange as fluorescent universal base in peptide nucleic acids.

    PubMed

    Köhler, Olaf; Seitz, Oliver

    2003-12-01

    Thiazole orange is shown to possess characteristics of a universal base while maintaining duplex stability. Its fluorescence properties allowed distinction between matched and single mismatched hybridisation.

  19. A non-linear least-squares approach to the refinement of all parameters involved in acid-base titrations.

    PubMed

    Arena, G; Rizzarelli, E; Sammartano, S; Rigano, C

    1979-01-01

    A non-linear least-squares computer program has been written for the refinement of the parameters involved in potentiometric acid-base titrations. The program ACBA (ACid-BAse titrations) is applicable under quite general conditions to solutions containing one or more acids or bases. The method of refinement used gives the program several advantages over the other programs described previously.

  20. Closed cycle ion exchange method for regenerating acids, bases and salts

    DOEpatents

    Dreyfuss, Robert M.

    1976-01-01

    A method for conducting a chemical reaction in acidic, basic, or neutral solution as required and then regenerating the acid, base, or salt by means of ion exchange in a closed cycle reaction sequence which comprises contacting the spent acid, base, or salt with an ion exchanger, preferably a synthetic organic ion-exchange resin, so selected that the counter ions thereof are ions also produced as a by-product in the closed reaction cycle, and then regenerating the spent ion exchanger by contact with the by-product counter ions. The method is particularly applicable to closed cycle processes for the thermochemical production of hydrogen.