Peroral Immunization of Rats with Escherichia coli Heat-Labile Enterotoxin Delivered by Microspheres

PubMed Central

Klipstein, Frederick A.; Engert, Richard F.; Sherman, William T.

1983-01-01

The antigenicity of the Escherichia coli heat-labile enterotoxin was not protected against the adverse effect of gastric acidity when the toxin was given together with bicarbonate for peroral immunization to rats, but immunization with the heat-labile enterotoxin encapsulated in pH-dependent microspheres aroused the same strong degree of serum and mucosal antitoxin responses and of protection against challenge as was achieved by peroral immunization after ablation of gastric secretions by pretreatment with cimetidine. PMID:6339378

Characterization of plasma labile heme in hemolytic conditions

PubMed Central

Gouveia, Zélia; Carlos, Ana R.; Yuan, Xiaojing; Aires-da-Silva, Frederico; Stocker, Roland; Maghzal, Ghassan J.; Leal, Sónia S.; Gomes, Cláudio M.; Todorovic, Smilja; Iranzo, Olga; Ramos, Susana; Santos, Ana C.; Hamza, Iqbal; Gonçalves, João; Soares, Miguel P.

2018-01-01

Extracellular hemoglobin, a byproduct of hemolysis, can release its prosthetic heme groups upon oxidation. This produces metabolically active heme that is exchangeable between acceptor proteins, macromolecules and low molecular weight ligands, termed here labile heme. As it accumulates in plasma labile heme acts in a pro-oxidant manner and regulates cellular metabolism while exerting pro-inflammatory and cytotoxic effects that foster the pathogenesis of hemolytic diseases. Here, we developed and characterized a panel of heme-specific single domain antibodies (sdAbs) that together with a cellular-based heme reporter assay, allow for quantification and characterization of labile heme in plasma during hemolytic conditions. Using these approaches, we demonstrate that when generated during hemolytic conditions labile heme is bound to plasma molecules with an affinity higher than 10−7 m and that 2–8% (∼ 2–5 μm) of the total amount of heme detected in plasma can be internalized by bystander cells, termed here bioavailable heme. Acute, but not chronic, hemolysis is associated with transient reduction of plasma heme-binding capacity, that is, the ability of plasma molecules to bind labile heme with an affinity higher than 10−7 m. The heme-specific sdAbs neutralize the pro-oxidant activity of soluble heme in vitro, suggesting that these maybe used to counter the pathologic effects of labile heme during hemolytic conditions. Finally, we show that heme-specific sdAbs can be used to visualize cellular heme. In conclusion, we describe a panel of heme-specific sdAbs that when used with other approaches provide novel insights to the pathophysiology of heme. PMID:28783254

Biogeochemical implications of labile phosphorus in forest soils determined by the Hedley fractionation procedure.

PubMed

Johnson, Arthur H; Frizano, Jaqueline; Vann, David R

2003-05-01

Forest ecologists and biogeochemists have used a variety of extraction techniques to assess labile vs. non-labile soil P pools in chronosequences, the balance between biological vs. geochemical control of P transformations across a wide range of soil orders, the role of plants with either N-fixing or mycorrhizal symbionts in controlling soil P fractions, and to make inferences about plant-available P. Currently, variants of the sequential extraction procedure developed by M. J. Hedley and co-workers afford the greatest discrimination among labile and non-labile organic and inorganic P pools. Results of recent studies that used this technique to evaluate P fractions in forest soils indicate the following: (1) in intact, highly weathered forest soils of the humid tropics, Hedley-labile P values are several times larger than extractable P values resulting from mildly acidic extracting solutions which were commonly used in the past 2 decades; (2) pools of Hedley-labile P are several times larger than the annual forest P requirement and P required from the soil annually in both temperate and tropical forests; (3) long-term trends in non-labile P pools during pedogenesis are adequately represented by the Walker and Syers' model of changes in P fractionation during soil development. However, to better represent trends in pools that can supply plant-available P across forest soils of different age and weathering status, the paradigm should be modified; and (4) across a wide range of tropical and temperate forest soils, organic matter content is an important determinant of Hedley-labile P.

3-Aminoquinoline/p-coumaric acid as a MALDI matrix for glycopeptides, carbohydrates, and phosphopeptides.

PubMed

Fukuyama, Yuko; Funakoshi, Natsumi; Takeyama, Kohei; Hioki, Yusaku; Nishikaze, Takashi; Kaneshiro, Kaoru; Kawabata, Shin-Ichirou; Iwamoto, Shinichi; Tanaka, Koichi

2014-02-18

Glycosylation and phosphorylation are important post-translational modifications in biological processes and biomarker research. The difficulty in analyzing these modifications is mainly their low abundance and dissociation of labile regions such as sialic acids or phosphate groups. One solution in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is to improve matrices for glycopeptides, carbohydrates, and phosphopeptides by increasing the sensitivity and suppressing dissociation of the labile regions. Recently, a liquid matrix 3-aminoquinoline (3-AQ)/α-cyano-4-hydroxycinnamic acid (CHCA) (3-AQ/CHCA), introduced by Kolli et al. in 1996, has been reported to increase sensitivity for carbohydrates or phosphopeptides, but it has not been systematically evaluated for glycopeptides. In addition, 3-AQ/CHCA enhances the dissociation of labile regions. In contrast, a liquid matrix 1,1,3,3-tetramethylguanidium (TMG, G) salt of p-coumaric acid (CA) (G3CA) was reported to suppress dissociation of sulfate groups or sialic acids of carbohydrates. Here we introduce a liquid matrix 3-AQ/CA for glycopeptides, carbohydrates, and phosphopeptides. All of the analytes were detected as [M + H](+) or [M - H](-) with higher or comparable sensitivity using 3-AQ/CA compared with 3-AQ/CHCA or 2,5-dihydroxybenzoic acid (2,5-DHB). The sensitivity was increased 1- to 1000-fold using 3-AQ/CA. The dissociation of labile regions such as sialic acids or phosphate groups and the fragmentation of neutral carbohydrates were suppressed more using 3-AQ/CA than using 3-AQ/CHCA or 2,5-DHB. 3-AQ/CA was thus determined to be an effective MALDI matrix for high sensitivity and the suppression of dissociation of labile regions in glycosylation and phosphorylation analyses.

Biologically labile photoproducts from riverine non-labile dissolved organic carbon in the coastal waters

NASA Astrophysics Data System (ADS)

Kasurinen, V.; Aarnos, H.; Vähätalo, A.

2015-06-01

In order to assess the production of biologically labile photoproducts (BLPs) from non-labile riverine dissolved organic carbon (DOC), we collected water samples from ten major rivers, removed labile DOC and mixed the residual non-labile DOC with artificial seawater for microbial and photochemical experiments. Bacteria grew on non-labile DOC with a growth efficiency of 11.5% (mean; range from 3.6 to 15.3%). Simulated solar radiation transformed a part of non-labile DOC into BLPs, which stimulated bacterial respiration and production, but did not change bacterial growth efficiency (BGE) compared to the non-irradiated dark controls. In the irradiated water samples, the amount of BLPs stimulating bacterial production depended on the photochemical bleaching of chromophoric dissolved organic matter (CDOM). The apparent quantum yields for BLPs supporting bacterial production ranged from 9.5 to 76 (mean 39) (μmol C mol photons-1) at 330 nm. The corresponding values for BLPs supporting bacterial respiration ranged from 57 to 1204 (mean 320) (μmol C mol photons-1). According to the calculations based on spectral apparent quantum yields and local solar radiation, the annual production of BLPs ranged from 21 (St. Lawrence) to 584 (Yangtze) mmol C m-2 yr-1 in the plumes of the examined rivers. Complete photobleaching of riverine CDOM in the coastal ocean was estimated to produce 10.7 Mt C BLPs yr-1 from the rivers examined in this study and globally 38 Mt yr-1 (15% of riverine DOC flux from all rivers), which support 4.1 Mt yr-1 of bacterial production and 33.9 Mt yr-1 bacterial respiration.

Amino Acid Enantiomeric Ratios in Semi-Labile vs. Refractory Dissolved Organic Matter: Implications for a Microbial N Pump

NASA Astrophysics Data System (ADS)

Bour, A. L.; Broek, T.; Gier, E. J.; Mccarthy, M. D.

2016-02-01

Microbes are key moderators in the cycling of marine dissolved organic matter (DOM), most of which remains unidentifiable at the molecular level. A major current question, however, is to what degree heterotrophic bacteria directly mediate C and N sequestration in the deep sea. Amino acids (AA) represent almost all organic N that can be identified at the molecular level, while D-AA enantiomers represent unique source-specific biomarkers for prokaryotes, known to be highly enriched in ocean DOM. If increasing bacterial-sourced material ultimately leads to millennial scale sequestration of refractory DOM (RDOM), then one would expect a clear correlation between bacterial biomarkers and DOM radiocarbon (Δ14C) ages, in particular in the deep sea. Here we directly test this idea for the first time, by measuring D-AA abundance and distribution in isolated Δ14C young vs. old DOM from the central north pacific gyre. We used a coupled ultrafiltration/solid phase extraction approach to isolate semi-labile vs. RDOM, based on known molecular weight and Δ14C age correlations. The Δ14C ages of isolated material ranged from 205-275 ybp for surface semi-labile DOM, to 6680-6740 ybp for deep ocean RDOM. We measured enantiomeric (D/L) AA ratios, as well as AA molar percentages to estimate traditional degradation parameters (DI and RI), in semi-labile vs. RDOM fractions from the surface to deep ocean at HOT, Station ALOHA. We interpret our results in terms of the hypothesis of a microbial N pump, examining the similarity of microbial source signatures (D/L distributions) and calculated organic N contributions from heterotrophic bacteria, in the context of the Δ14C age of each fraction. Finally, we also evaluate these data vs. common AA molar percentage based indices of degradation.

Quantification and characterization of chemically-and thermally-labile and recalcitrant biochar fractions.

PubMed

Bakshi, Santanu; Banik, Chumki; Laird, David A

2018-03-01

The C:N ratios of biochar labile fractions is important for assessing biochar stability and N cycling in soil. Here we compare chemically and thermally labile fractions for nine biochars produced from five biomass feedstocks using four production techniques. Biochar fractionation methods included proximate analysis, hot water extraction, acid and base extractions (0.05 M, 0.5 M, 1 M, 2 M, 3 M, and 6 M of either H 2 SO 4 or NaOH), and oxidation with 15% H 2 O 2 and 0.33 M KMnO 4 (pH 7.2). Results show chemical addition reactions cause underestimation of mass of the labile fraction for chemical extraction and oxidation procedures but not the thermal procedure. Estimates of C and N in labile and recalcitrant fractions were not adversely affected by addition reactions, because solvents were independent of C or N. Results indicate that herbaceous biochars may be a source of N fertility while hardwood biochars may immobilize N during the first few years after biochar application to soils. Copyright © 2017 Elsevier Ltd. All rights reserved.

Maternal emotion socialization differentially predicts third-grade children's emotion regulation and lability.

PubMed

Rogers, Megan L; Halberstadt, Amy G; Castro, Vanessa L; MacCormack, Jennifer K; Garrett-Peters, Patricia

2016-03-01

Numerous parental emotion socialization factors have been implicated as direct and indirect contributors to the development of children's emotional competence. To date, however, no study has combined parents' emotion-related beliefs, behaviors, and regulation strategies in one model to assess their cumulative-as well as unique-contributions to children's emotion regulation. We considered the 2 components that have recently been distinguished: emotion regulation and emotional lability. We predicted that mothers' beliefs about the value of and contempt for children's emotions, mothers' supportive and nonsupportive reactions to their children's emotions, as well as mothers' use of cognitive reappraisal and suppression of their own emotions would each contribute unique variance to their children's emotion regulation and lability, as assessed by children's teachers. The study sample consisted of an ethnically and socioeconomically diverse group of 165 mothers and their third-grade children. Different patterns emerged for regulation and lability: Controlling for family income, child gender, and ethnicity, only mothers' lack of suppression as a regulatory strategy predicted greater emotion regulation in children, whereas mothers' valuing of children's emotions, mothers' lack of contempt for children's emotions, mothers' use of cognitive reappraisal to reinterpret events, and mothers' lack of emotional suppression predicted less lability in children. These findings support the divergence of emotion regulation and lability as constructs and indicate that, during middle childhood, children's lability may be substantially and uniquely affected by multiple forms of parental socialization. (c) 2016 APA, all rights reserved).

Light availability affects sex lability in a gynodioecious plant.

PubMed

Varga, Sandra; Kytöviita, Minna-Maarit

2016-11-01

Sex lability (i.e., gender diphasy) in plants is classically linked to the larger resource needs associated with the female sexual function (i.e., seed production) compared to the male function (i.e., pollen production). Sex lability in response to the environment is extensively documented in dioecious species, but has been largely overlooked in gynodioecious plants. Here, we tested whether environmental conditions induce sex lability in the gynodioecious Geranium sylvaticum. We conducted a transplantation experiment in the field where plants with different sex expression were reciprocally transplanted between high light and low light habitats. We measured plants' reproductive output and sex expression over four years. Our results show that sex expression was labile over the study period. The light level at the destination habitat had a significant effect on sexual expression and reproductive output, because plants decreased their reproductive output when transplanted to the low light habitat. Transplantation origin did not affect any parameter measured. This study shows that sex expression in Geranium sylvaticum is labile and related to light availability. Sexually labile plants did not produce more seeds or pollen, and thus, there was no apparent fitness gain in sexually labile individuals. Sex lability in gynodioecious plants may be more common than previously believed because detection of sex lability necessitates data on the same individuals over time, which is rare in sexually dimorphic herbaceous plants. © 2016 Botanical Society of America.

Hemorrhagic shock and surgical stress alter distribution of labile zinc within high- and low-molecular-weight plasma fractions.

PubMed

Kelly, Edward; Mathew, Jeff; Kohler, Jonathan E; Blass, Amy L; Soybel, And David I

2012-08-01

Zinc ions (Zn) are essential for tissue repair following injury or stress. We hypothesize that during such stresses Zn is redistributed to labile pools in plasma components. Here we tested this hypothesis using a novel assay to monitor labile Zn in plasma in hemorrhagic shock. Adult rats in the shock group (S group) underwent hemorrhage and resuscitation. Blood samples were drawn at baseline and at 1, 4, and 24 h. The surgical control group (SC group) was anesthetized and instrumented, but not bled. Albumin, total Zn, and labile Zn levels were assayed in plasma. Binding capacity for Zn was assessed in high- and low-molecular-weight pools. Significant decreases in total Zn were observed by 24 h, in both S and SC groups. Albumin levels were significantly reduced in the S group at 1 and 4 h but restored at 24 h; significant changes were not observed in other groups. In whole plasma, labile Zn levels were stable initially in the S and SC groups, but declined at 24 h. In the high-molecular-weight pool, marked and significant impairment of binding was noted throughout all time periods following the shock period in the S group. Such changes were observed in the SC group of less intensity and duration. These experiments suggest that shock alters affinity of plasma proteins for Zn, promoting delivery to peripheral tissues during periods of increased Zn utilization.

Hemorrhagic Shock and Surgical Stress Alter Distribution of Labile Zinc within High and Low Molecular Weight Plasma Fractions

PubMed Central

Kelly, Edward; Mathew, Jeff; Kohler, Jonathan E.; Blass, Amy L.; Soybel, David I.

2012-01-01

Zinc ions (Zn2+) are essential for tissue repair following injury or stress. We hypothesize that during such stresses Zn2+ is redistributed to labile pools in plasma components. Here we tested this hypothesis utilizing a novel assay to monitor labile Zn2+ in plasma in hemorrhagic shock. Adult rats in the Shock (S) group underwent hemorrhage and resuscitation. Blood samples were drawn at baseline, 1 hr, 4 hrs and 24 hrs. The Surgical Control (SC) group was anesthetized and instrumented, but not bled. Albumin, total Zn2+, and labile Zn2+ levels were assayed in plasma. Binding capacity for Zn2+ was assessed in high (HMW) and low (LMW) molecular weight pools. Significant decreases in total Zn2+ were observed by 24 hrs, in both S and SC groups. Albumin levels were significantly reduced in the S group at 1 hr and 4 hr but restored at 24 hrs; significant changes were not observed in other groups. In whole plasma, labile Zn2+ levels were stable initially in the S and SC groups, but declined at 24 hrs. In the HMW pool, marked and significant impairment of binding was noted throughout all time periods following the shock period in the S group. Such changes were observed in the SC group of less intensity and duration. These experiments suggest that Shock alters affinity of plasma proteins for Zn2+, promoting delivery to peripheral tissues during periods of increased Zn2+ utilization. PMID:22744307

[Character of brain interhemispheric relation in children at forming labile arterial hypertension].

PubMed

Koroleva, N V; Kolesnikov, S I; Bugun, O V; Dolgikh, V V

2010-01-01

Electroencephalography investigations were carried out twice in 26 schoolchildren in the age of 7-8 years and in the age of 9-10 years. The control group included healthy children: the research group included children in whom in the age of 7-8 years the normal level of arterial pressure was registered, and in whom in the age of 9-10 years labile arterial hypertension was revealed. It is revealed, that in children of younger school age forming of the labile form of arterial hypertension is connected whit infringement of processes of age changes of intercortical and cortical-subcortical interrelations and forming of rigidly integrated system of interhemispheric relations. Its mechanism of realization is carried out due to hyperactivation of the right hemisphere and it is incorporated on preclinical stage.

Functionalities of chitosan conjugated with stearic acid and gallic acid and application of the modified chitosan in stabilizing labile aroma compounds in an oil-in-water emulsion.

PubMed

Yang, Tsung-Shi; Liu, Tai-Ti; Lin, I-Hwa

2017-08-01

The aims of this research were to conjugate chitosan (CT) with stearic acid (SA) and gallic acid (GA), and apply the modified chitosan to stabilize labile aroma compounds such as allyl isothiocyanate (AITC) and limonene in oil-in-water emulsions. Generally, the antioxidant activity of CT-SA-GA increased as the GA content in the conjugate increased. In most assays, GA had a lower IC 50 value than that of CT-SA-GA; however, CT-SA-GA exhibited better performance than GA in the Fe 2+ -chelating activity. In accelerated tests (heating or illumination) for evaluating the chemical stability of AITC and limonene during storage, CT-SA and CT-SA-GA were used to prepare AITC and limonene O/W emulsions, respectively. Tween 80 and Span 80 (T-S-80), an emulsifier mixture, were used as a control in both emulsions for comparison. The results show that CT-SA or CT-SA-GA could protect AITC or limonene from degradation or oxidation more effectively than T-S-80. Copyright © 2017 Elsevier Ltd. All rights reserved.

Estimating labile particulate iron concentrations in coastal waters from remote sensing data

NASA Astrophysics Data System (ADS)

McGaraghan, Anna R.; Kudela, Raphael M.

2012-02-01

Owing to the difficulties inherent in measuring trace metals and the importance of iron as a limiting nutrient for biological systems, the ability to monitor particulate iron concentration remotely is desirable. This study examines the relationship between labile particulate iron, described here as weak acid leachable particulate iron or total dissolvable iron, and easily obtained bio-optical measurements. We develop a bio-optical proxy that can be used to estimate large-scale patterns of labile iron concentrations in surface waters, and we extend this by including other environmental variables in a multiple linear regression statistical model. By utilizing a ratio of optical backscatter and fluorescence obtained by satellite, we identify patterns in iron concentrations confirmed by traditional shipboard sampling. This basic relationship is improved with the addition of other environmental parameters in the statistical linear regression model. The optical proxy detects known temporal and spatial trends in average surface iron concentrations in Monterey Bay. The proxy is robust in that similar performance was obtained using two independent particulate iron data sets, but it exhibits weaker correlations than the full statistical model. This proxy will be a valuable tool for oceanographers seeking to monitor iron concentrations in coastal regions and allows for better understanding of the variability of labile particulate iron in surface waters to complement direct measurement of leachable particulate or total dissolvable iron.

Improving release completeness from PLGA-based implants for the acid-labile model protein ovalbumin.

PubMed

Duque, Luisa; Körber, Martin; Bodmeier, Roland

2018-03-01

The objectives of this study were to assess the feasibility of hot melt extrusion (HME) for the preparation of PLGA-based ovalbumin-loaded implants as well as to characterize and improve protein release from the implants. Ovalbumin (OVA) was stable during extrusion, which was attributed to a protective effect of the biodegradable matrix. OVA release was characterized by a low burst, a slow release up to day 21, which plateaued thereafter resulting in incomplete release for all evaluated protein loadings. Release incompleteness was accompanied by the formation of an insoluble residual mass. Further characterization of this mass indicated that it consisted of non-covalent protein aggregates and polymer, where ovalbumin was ionically bound as the pH inside the degrading matrix decreased below the pI of the protein. Although higher protein release was obtained with the inclusion of weak bases because of their neutralizing effect, OVA aggregation and release incompleteness were not fully avoided. With the use of shellac, a well-known enteric and biocompatible polymer, as protective excipient, a distinct late release phase occurred and release completeness was increased to more than 75% cumulative release. Shellac apparently protected the protein against the acidic microclimate due to its low solubility at low pH. Protected OVA was thus released once the pH increased due to a declining PLGA-oligomer formation. The result was a triphasic release profile consisting of an initial burst, a slow diffusion phase over about 7 weeks, and an erosion-controlled dissolution phase over the next 3 weeks. An acid-labile protein like OVA was thus feasibly protected from interactions with PLGA and its degradation products, resulting in a controlled delivery of more than 85% of the original payload. Copyright © 2018 Elsevier B.V. All rights reserved.

Chemical leaching methods and measurements of marine labile particulate Fe

NASA Astrophysics Data System (ADS)

Revels, B. N.; John, S.

2012-12-01

Iron (Fe) is an essential nutrient for life. Yet its low solubility and concentration in the ocean limits marine phytoplankton productivity in many regions of the world. Dissolved phase Fe (<0.4μm) has traditionally been considered the most biologically accessible form, however, the particulate phase (>0.4μm) may contain an important, labile reservoir of Fe that may also be available to phytoplankton. However, concentration data alone cannot elucidate the sources of particulate Fe to the ocean and to what extent particulate iron may support phytoplankton growth. Isotopic analysis of natural particles may help to elucidate the biogeochemical cycling of Fe, though it is important to find a leaching method which accesses bioavailable Fe. Thirty-three different chemical leaches were performed on a marine sediment reference material, MESS-3. The combinations included four different acids (25% acetic acid, 0.01M HCl, 0.5M HCl, 0.1M H2SO4 at pH2), various redox conditions (0.02M hydroxylamine hydrochloride or 0.02M H2O2), three temperatures (25°C, 60°C, 90°C), and three time points (10 minutes, 2 hours, 24 hours). Leached Fe concentrations varied from 1mg/g to 35mg/g, with longer treatment times, stronger acids, and hotter temperatures generally associated with an increase in leached Fe. δ56Fe in these leaches varied from -1.0‰ to +0.2‰. Interestingly, regardless of leaching method used, there was a very similar relationship between the amount of Fe leached from the particles and the δ56Fe of this iron. Isotopically lighter δ56Fe values were associated with smaller amounts of leached Fe whereas isotopically heavier δ56Fe values were associated with larger amounts of leached Fe. Two alternate hypotheses could explain these data. Either, the particles may contain pools of isotopically light Fe that are easily accessed early in dissolution, or isotopically light Fe may be preferentially leached from the particle due to a kinetic isotope effect during dissolution

Using solvent-free sample preparation to promote protonation of poly(ethylene oxide)s with labile end-groups in matrix-assisted laser desorption/ionisation.

PubMed

Mazarin, Michael; Phan, Trang N T; Charles, Laurence

2008-12-01

Protonation is usually required to observe intact ions during matrix-assisted laser desorption/ionization (MALDI) of polymers containing fragile end-groups while cation adduction induces chain-end degradation. These polymers, generally obtained via living free radical polymerization techniques, are terminated with a functionality in which a bond is prone to homolytic cleavage, as required by the polymerization process. A solvent-free sample preparation method was used here to avoid salt contaminant from the solvent traditionally used in the dried-droplet MALDI procedure. Solvent-based and solvent-free sample preparations were compared for a series of three poly(ethylene oxide) polymers functionalized with a labile end-group in a nitroxide-mediated polymerization reaction, using 2,4,6-trihydroxyacetophenone (THAP) as the matrix without any added salt. Intact oligomer ions could only be produced as protonated molecules in solvent-free MALDI while sodium adducts of degraded polymers were formed from the dried-droplet samples. Although MALDI analysis was performed at the laser threshold, fragmentation of protonated macromolecules was still observed to occur. However, in contrast to sodiated molecules, dissociation of protonated oligomers does not involve the labile C--ON bond of the end-group. As the macromolecule size increased, protonation appeared to be less efficient and sodium adduction became the dominant ionization process, although no sodium salt was added in the preparation. Formation of sodiated degraded macromolecules would be dictated by increasing cation affinity as the size of the oligomers increases and would reveal the presence of salts at trace levels in the MALDI samples.

Pharmacological ascorbate and ionizing radiation (IR) increase labile iron in pancreatic cancer☆

PubMed Central

Moser, Justin C.; Rawal, Malvika; Wagner, Brett A.; Du, Juan; Cullen, Joseph J.; Buettner, Garry R.

2013-01-01

Labile iron, i.e. iron that is weakly bound and is relatively unrestricted in its redox activity, has been implicated in both the pathogenesis as well as treatment of cancer. Two cancer treatments where labile iron may contribute to their mechanism of action are pharmacological ascorbate and ionizing radiation (IR). Pharmacological ascorbate has been shown to have tumor-specific toxic effects due to the formation of hydrogen peroxide. By catalyzing the oxidation of ascorbate, labile iron can enhance the rate of formation of hydrogen peroxide; labile iron can also react with hydrogen peroxide. Here we have investigated the magnitude of the labile iron pool in tumor and normal tissue. We also examined the ability of pharmacological ascorbate and IR to change the size of the labile iron pool. Although a significant amount of labile iron was seen in tumors (MIA PaCa-2 cells in athymic nude mice), higher levels were seen in murine tissues that were not susceptible to pharmacological ascorbate. Pharmacological ascorbate and irradiation were shown to increase the labile iron in tumor homogenates from this murine model of pancreatic cancer. As both IR and pharmacological ascorbate may rely on labile iron for their effects on tumor tissues, our data suggest that pharmacological ascorbate could be used as a radio-sensitizing agent for some radio-resistant tumors. PMID:24396727

An ultrahigh-resolution mass spectrometry index to estimate natural organic matter lability

PubMed Central

D'Andrilli, Juliana; Cooper, William T; Foreman, Christine M; Marshall, Alan G

2015-01-01

Rationale Determining the chemical constituents of natural organic matter (NOM) by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICRMS) remains the ultimate measure for probing its source material, evolution, and transport; however, lability and the fate of organic matter (OM) in the environment remain controversial. FTICRMS-derived elemental compositions are presented in this study to validate a new interpretative method to determine the extent of NOM lability from various environments. Methods FTICRMS data collected over the last decade from the same 9.4 tesla instrument using negative electrospray ionization at the National High Magnetic Field Laboratory in Tallahassee, Florida, was used to validate the application of a NOM lability index. Solid-phase extraction cartridges were used to isolate the NOM prior to FTICRMS; mass spectral peaks were calibrated internally by commonly identified NOM homologous series, and molecular formulae were determined for NOM composition and lability analysis. Results A molecular lability boundary (MLB) was developed from the FTICRMS molecular data, visualized from van Krevelen diagrams, dividing the data into more and less labile constituents. NOM constituents above the MLB at H/C ≥1.5 correspond to more labile material, whereas NOM constituents below the MLB, H/C <1.5, exhibit less labile, more recalcitrant character. Of all marine, freshwater, and glacial environments considered for this study, glacial ecosystems were calculated to contain the most labile OM. Conclusions The MLB extends our interpretation of FTICRMS NOM molecular data to include a metric of lability, and generally ranked the OM environments from most to least labile as glacial > marine > freshwater. Applying the MLB is useful not only for individual NOM FTICRMS studies, but also provides a lability threshold to compare and contrast molecular data with other FTICRMS instruments that survey NOM from around the world. Copyright © 2015

Block copolymer micelles with acid-labile ortho ester side-chains: Synthesis, characterization, and enhanced drug delivery to human glioma cells.

PubMed

Tang, Rupei; Ji, Weihang; Panus, David; Palumbo, R Noelle; Wang, Chun

2011-04-10

A new type of block copolymer micelles for pH-triggered delivery of poorly water-soluble anticancer drugs has been synthesized and characterized. The micelles were formed by the self-assembly of an amphiphilic diblock copolymer consisting of a hydrophilic poly(ethylene glycol) (PEG) block and a hydrophobic polymethacrylate block (PEYM) bearing acid-labile ortho ester side-chains. The diblock copolymer was synthesized by atom transfer radical polymerization (ATRP) from a PEG macro-initiator to obtain well-defined polymer chain-length. The PEG-b-PEYM micelles assumed a stable core-shell structure in aqueous buffer at physiological pH with a low critical micelle concentration as determined by proton NMR and pyrene fluorescence spectroscopy. The hydrolysis of the ortho ester side-chain at physiological pH was minimal yet much accelerated at mildly acidic pHs. Doxorubicin (Dox) was successfully loaded into the micelles at pH 7.4 and was released at a much higher rate in response to slight acidification to pH 5. Interestingly, the release of Dox at pH 5 followed apparently a biphasic profile, consisting of an initial fast phase of several hours followed by a sustained release period of several days. Dox loaded in the micelles was rapidly taken up by human glioma (T98G) cells in vitro, accumulating in the endolysosome and subsequently in the nucleus in a few hours, in contrast to the very low uptake of free drug at the same dose. The dose-dependent cytotoxicity of the Dox-loaded micelles was determined by the MTT assay and compared with that of the free Dox. While the empty micelles themselves were not toxic, the IC(50) values of the Dox-loaded micelles were approximately ten-times (by 24h) and three-times (by 48h) lower than the free drug. The much enhanced potency in killing the multi-drug-resistant human glioma cells by Dox loaded in the micelles could be attributed to high intracellular drug concentration and the subsequent pH-triggered drug release. These results

Effect of warming on the degradation and production of low-molecular-weight labile organic carbon in an Arctic tundra soil

DOE PAGES

Yang, Ziming; Wullschleger, Stan D.; Liang, Liyuan; ...

2016-01-16

The fate of soil organic carbon (SOC) stored in the Arctic permafrost is a key concern as temperatures continue to rise in the northern hemisphere. Studies and conceptual models suggest that SOC degradation is affected by the composition of SOC, but it is unclear exactly what portions of SOC are vulnerable to rapid breakdown and what mechanisms may be controlling SOC degradation upon permafrost thaw. Here, we examine the dynamic consumption and production of labile SOC in an anoxic incubation experiment using soil samples from the active layer at the Barrow Environmental Observatory, Barrow, Alaska, USA. Free-reducing sugars, alcohols, andmore » low-molecular-weight (LMW) organic acids were analyzed during incubation at either –2 or 8 °C for up to 240 days. Results show that simple sugar and alcohol SOC largely account for the initial rapid release of CO 2 and CH 4 through anaerobic fermentation, whereas the fermentation products, acetate and formate, are subsequently utilized as primary substrates for methanogenesis. Iron(III) reduction is correlated to acetate production and methanogenesis, suggesting its important role as an electron acceptor in tundra SOC respiration. These observations are further supported in a glucose addition experiment, in which rapid CO 2 and CH 4 production occurred concurrently with rapid production and consumption of labile organics such as acetate. However, addition of tannic acid, as a more complex organic substrate, showed little influence on the overall production of CO 2 and CH 4 and organic acids. Together our study shows that LMW labile organics in SOC control the initial rapid release of green-house gases upon warming. We thus present a conceptual framework for the labile SOC transformations and their relations to fermentation, iron reduction and methanogenesis, thereby providing the basis for improved model prediction of climate feedbacks in the Arctic.« less

Efficacy and pharmacokinetics of a modified acid-labile docetaxel-PRINT(®) nanoparticle formulation against non-small-cell lung cancer brain metastases.

PubMed

Sambade, Maria; Deal, Allison; Schorzman, Allison; Luft, J Christopher; Bowerman, Charles; Chu, Kevin; Karginova, Olga; Swearingen, Amanda Van; Zamboni, William; DeSimone, Joseph; Anders, Carey K

2016-08-01

Particle Replication in Nonwetting Templates (PRINT(®)) PLGA nanoparticles of docetaxel and acid-labile C2-dimethyl-Si-Docetaxel were evaluated with small molecule docetaxel as treatments for non-small-cell lung cancer brain metastases. Pharmacokinetics, survival, tumor growth and mice weight change were efficacy measures against intracranial A549 tumors in nude mice. Treatments were administered by intravenous injection. Intracranial tumor concentrations of PRINT-docetaxel and PRINT-C2-docetaxel were 13- and sevenfold greater, respectively, than SM-docetaxel. C2-docetaxel conversion to docetaxel was threefold higher in intracranial tumor as compared with nontumor tissues. PRINT-C2-docetaxel increased median survival by 35% with less toxicity as compared with other treatments. The decreased toxicity of the PRINT-C2-docetaxel improved treatment efficacy against non-small-cell lung cancer brain metastasis.

Evaluation of Insulin-Like Growth Factor Acid-Labile Subunit as a Potential Biomarker of Effect for Deoxynivalenol-Induced Proinflammatory Cytokine Expression

PubMed Central

Flannery, Brenna M.; Amuzie, Chidozie J.; Pestka, James J.

2013-01-01

Consumption of the trichothecene deoxynivalenol (DON) suppresses growth in experimental animals - an adverse effect that was used to establish the tolerable daily intake for this toxin. DON ingestion has been recently found to suppress plasma insulin-like growth factor acid-labile subunit (IGFALS), a protein essential for growth. Studies were conducted to explore the feasibility of using plasma IGFALS as a biomarker of effect for DON. In the first study, weanling mice were fed 0, 1, 2.5, 5 and 10 ppm DON and weight and plasma IGFALS determined at intervals over 9 wk. Reduced body weight gains were detectable beginning at wk 5 in the 10 ppm dose and wk 7 at the 5 ppm dose. Plasma IGFALS was significantly depressed at wk 5 in the 5 and 10 ppm groups at wk 9 in the 10 ppm group. Depressed IGFALS significantly correlated with reduced body weight at wk 5 and 9. Benchmark dose modeling revealed the BMDL and BMD for plasma IGFALS reduction were 1.1 and 3.0 ppm DON and for weight reduction were 2.1 and 4.5 ppm DON. In the second study, it was demonstrated that mice fed 15 ppm DON diet had significantly less plasma IGFALS than mice fed identical amounts of control diet. Thus DON’s influence on IGFALS likely reflects the combined effects of reduced food intake as well as its physiological action involving suppressors of cytokine signaling. Taken together, these findings suggest that plasma IGFALS might be a useful biomarker for DON’s adverse effects on growth. PMID:23298694

Mayolenes: Labile defensive lipids from the glandular hairs of a caterpillar (Pieris rapae)

PubMed Central

Smedley, Scott R.; Schroeder, Frank C.; Weibel, Douglas B.; Meinwald, Jerrold; Lafleur, Katie A.; Renwick, J. Alan; Rutowski, Ronald; Eisner, Thomas

2002-01-01

Larvae of the European cabbage butterfly, Pieris rapae (Pieridae), are beset with glandular hairs, bearing droplets of a clear oily secretion at their tip. The fluid consists primarily of a series of chemically labile, unsaturated lipids, the mayolenes, which are derived from 11-hydroxylinolenic acid. In bioassays with the ant Crematogaster lineolata, the secretion was shown to be potently deterrent, indicating that the fluid plays a defensive role in nature. PMID:11997469

In situ Identification of Labile Precursor Compounds and their Short-lived Intermediates in Plants using in vivo Nanospray High-resolution Mass Spectrometry.

PubMed

Chang, Qing; Peng, Yue'e; Shi, Bin; Dan, Conghui; Yang, Yijun; Shuai, Qin

2016-05-01

Many secondary metabolites in plants are labile compounds which under environmental stress, are difficult to detect and track due to the lack of rapid in situ identification techniques, making plant metabolomics research difficult. Therefore, developing a reliable analytical method for rapid in situ identification of labile compounds and their short-lived intermediates in plants is of great importance. To develop under atmospheric pressure, a rapid in situ method for effective identification of labile compounds and their short-lived intermediates in fresh plants. An in vivo nanospray high-resolution mass spectrometry (HR-MS) method was used for rapid capture of labile compounds and their short-lived intermediates in plants. A quartz capillary was partially inserted into fresh plant tissues, and the liquid flowed out through the capillary tube owing to the capillary effect. A high direct current (d.c.) voltage was applied to the plant to generate a spray of charged droplets from the tip of the capillary carrying bioactive molecules toward the inlet of mass spectrometer for full-scan and MS/MS analysis. Many labile compounds and short-lived intermediates were identified via this method: including glucosinolates and their short-lived intermediates (existing for only 10 s) in Raphanus sativus roots, alliin and its conversion intermediate (existing for 20 s) in Allium sativum and labile precursor compound chlorogenic acid in Malus pumila Mill. The method is an effective approach for in situ identification of internal labile compounds and their short-lived intermediates in fresh plants and it can be used as an auxiliary tool to explore the degradation mechanisms of new labile plant compounds. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Purification and characterization of an oxygen-labile, NAD-dependent alcohol dehydrogenase from Desulfovibrio gigas.

PubMed Central

Hensgens, C M; Vonck, J; Van Beeumen, J; van Bruggen, E F; Hansen, T A

1993-01-01

A NAD-dependent, oxygen-labile alcohol dehydrogenase was purified from Desulfovibrio gigas. It was decameric, with subunits of M(r) 43,000. The best substrates were ethanol (Km, 0.15 mM) and 1-propanol (Km, 0.28 mM). N-terminal amino acid sequence analysis showed that the enzyme belongs to the same family of alcohol dehydrogenases as Zymomonas mobilis ADH2 and Bacillus methanolicus MDH. Images PMID:8491707

Detection of a variable intracellular acid-labile carbon pool in Thalassiosira weissflogii (Heterokontophyta) and Emiliania huxleyi (Haptophyta) in response to changes in the seawater carbon system.

PubMed

Isensee, Kirsten; Erez, Jonathan; Stoll, Heather M

2014-02-01

Accumulation of an intracellular pool of carbon (C(i) pool) is one strategy by which marine algae overcome the low abundance of dissolved CO2 (CO2 (aq) ) in modern seawater. To identify the environmental conditions under which algae accumulate an acid-labile C(i) pool, we applied a (14) C pulse-chase method, used originally in dinoflagellates, to two new classes of algae, coccolithophorids and diatoms. This method measures the carbon accumulation inside the cells without altering the medium carbon chemistry or culture cell density. We found that the diatom Thalassiosira weissflogii [(Grunow) G. Fryxell & Hasle] and a calcifying strain of the coccolithophorid Emiliania huxleyi [(Lohmann) W. W. Hay & H. P. Mohler] develop significant acid-labile C(i) pools. C(i) pools are measureable in cells cultured in media with 2-30 µmol l(-1) CO2 (aq), corresponding to a medium pH of 8.6-7.9. The absolute C(i) pool was greater for the larger celled diatoms. For both algal classes, the C(i) pool became a negligible contributor to photosynthesis once CO2 (aq) exceeded 30 µmol l(-1) . Combining the (14) C pulse-chase method and (14) C disequilibrium method enabled us to assess whether E. huxleyi and T. weissflogii exhibited thresholds for foregoing accumulation of DIC or reduced the reliance on bicarbonate uptake with increasing CO2 (aq) . We showed that the C(i) pool decreases with higher CO2 :HCO3 (-) uptake rates. © 2013 Scandinavian Plant Physiology Society.

Anger induced by interferon-alpha is moderated by ratio of arachidonic acid to omega-3 fatty acids.

PubMed

Lotrich, Francis E; Sears, Barry; McNamara, Robert K

2013-11-01

Anger worsens in some patients during interferon-alpha (IFN-α) therapy. Elevated anger has also been associated with lower long-chain omega-3 (LCn-3) fatty acid levels. We examined whether fatty acids could influence vulnerability to anger during IFN-α exposure. Plasma arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) levels were determined prior to IFN-α therapy by mass spectroscopy. Repeated-measure analyses examined the relationship between AA/EPA+DHA and the subsequent development of labile anger and irritability in 82 subjects who prospectively completed the Anger, Irritability, and Assault Questionnaire (AIAQ) during the first eight weeks of IFN-α therapy. Prior to IFN-α therapy, AA/EPA+DHA did not correlate with either labile anger or irritability. Pre-treatment AA/EPA+DHA did correlate with the subsequent maximal increase in labile anger during IFN-α therapy (r=0.33; p=0.005). Over time, labile anger increased more in subjects with above median AA/EPA+DHA ratios (p<0.05). Of the 17 subjects ultimately requiring psychiatric intervention for anger, 14/17 had above-median AA/EPA+DHA ratios (p=0.009). There was also an interaction with the tumor necrosis factor-alpha (TNF-α) promoter polymorphism (A-308G), such that only those with both elevated AA/EPA+DHA and the A allele had increased labile anger (p=0.001). In an additional 18 subjects, we conversely observed that selective serotonin reuptake inhibitor treatment was associated with increased irritability during IFN-α therapy. LCn-3 fatty acid status may influence anger development during exposure to elevated inflammatory cytokines, and may interact with genetic risk for increased brain TNF-α. LCn-3 supplements may be one strategy for minimizing this adverse side effect of IFN-α. © 2013.

Repeated Labilization-Reconsolidation Processes Strengthen Declarative Memory in Humans

PubMed Central

Forcato, Cecilia; Rodríguez, María L. C.; Pedreira, María E.

2011-01-01

The idea that memories are immutable after consolidation has been challenged. Several reports have shown that after the presentation of a specific reminder, reactivated old memories become labile and again susceptible to amnesic agents. Such vulnerability diminishes with the progress of time and implies a re-stabilization phase, usually referred to as reconsolidation. To date, the main findings describe the mechanisms associated with the labilization-reconsolidation process, but little is known about its functionality from a biological standpoint. Indeed, two functions have been proposed. One suggests that destabilization of the original memory after the reminder allows the integration of new information into the background of the original memory (memory updating), and the other suggests that the labilization-reconsolidation process strengthens the original memory (memory strengthening). We have previously reported the reconsolidation of human declarative memories, demonstrating memory updating in the framework of reconsolidation. Here we deal with the strengthening function attributed to the reconsolidation process. We triggered labilization-reconsolidation processes successively by repeated presentations of the proper reminder. Participants learned an association between five cue-syllables and their respective response-syllables. Twenty-four hours later, the paired-associate verbal memory was labilized by exposing the subjects to one, two or four reminders. The List-memory was evaluated on Day 3 showing that the memory was improved when at least a second reminder was presented in the time window of the first labilization-reconsolidation process prompted by the earlier reminder. However, the improvement effect was revealed on Day 3, only when at least two reminders were presented on Day2 and not as a consequence of only retrieval. Therefore, we propose central concepts for the reconsolidation process, emphasizing its biological role and the parametrical constrains

Effects of dissolved organic matter (DOM) sources and nature of solid extraction sorbent on recoverable DOM composition: Implication into potential lability of different compound groups.

PubMed

Chen, Meilian; Kim, Sunghwan; Park, Jae-Eun; Kim, Hyun Sik; Hur, Jin

2016-07-01

Noting the source-dependent properties of dissolved organic matter (DOM), this study explored the recoverable compounds by solid phase extraction (SPE) of two common sorbents (C18 and PPL) eluted with methanol solvent for contrasting DOM sources via fluorescence excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Fresh algae and leaf litter extracts DOM, one riverine DOM, and one upstream lacustrine DOM were selected for the comparison. C18 sorbent was generally found to extract more diverse molecular formula, relatively higher molecular weight, and more heteroatomic DOM compounds within the studied mass range than PPL sorbent except for the leaf litter extract. Even with the same sorbent, the main molecular features of the two end member DOM were distributed on different sides of the axes of a multivariate ordination, indicating the source-dependent characteristics of the recoverable compounds by the sorbents. In addition, further examination of the molecular formula uniquely present in the two end members and the upstream lake DOM suggested that proteinaceous, tannin-like, and heteroatomic DOM constituents might be potential compound groups which are labile and easily degraded during their mobilization into downstream watershed. This study provides new insights into the sorbent selectivity of DOM from diverse sources and potential lability of various compound groups.

Non-labile silver species in biosolids remain stable throughout ...

EPA Pesticide Factsheets

Increasing commercial use of nanosilver has focussed attention on the fate of silver (Ag) in the wastewater release pathway. This paper reports the speciation and lability of Ag in archived, stockpiled, and contemporary biosolids from the UK, USA and Australia, and indicates that biosolids Ag concentrations have decreased significantly over recent decades. XANES revealed the importance of reduced-sulfur binding environments for Ag speciation in materials ranging from freshly produced sludge to biosolids weathered under ambient environmental conditions for more than 50 years. Isotopic dilution with 110mAg showed that Ag was predominantly non-labile in both fresh and aged biosolids (13.7% mean lability), with E-values ranging from 0.3 to 60 mg/kg and 5 mM CaNO3 extractable Ag from 1.2 to 609 µg/kg (0.002 - 3.4% of the total Ag). This study indicates that at the time of soil application, biosolids Ag will be predominantly Ag-sulfides and characterised by low isotopic lability. This paper presents an overview of biosolids Ag chemistry in historic and contemporary biosolids sourced from the UK, USA and Australia from the 1950s until today by drawing on a unique collection of archived, stockpiled and contemporary biosolids samples. Characteristics of biosolids Ag chemistry determined in this study included total Ag measurement by neutron activation analysis (NAA); the assessment of Ag lability by 110mAg isotopic dilution (E-values); and Ag speciation by X-ray Absorp

Fate and lability of silver in soils: Effect of ageing

EPA Science Inventory

The fate and lability of added soluble Ag in soils over time was examined by measurement of labile metal (E-value) by isotopic dilution using the ^110mAg radioactive isotope and the solid-phase speciation of Ag by X-ray absorption near edge structure (XANES) spectrosco...

Hydroxytyrosol inhibits hydrogen peroxide-induced apoptotic signaling via labile iron chelation.

PubMed

Kitsati, Natalia; Mantzaris, Michalis D; Galaris, Dimitrios

2016-12-01

Although it is known that Mediterranean diet plays an important role in maintaining human health, the underlying molecular mechanisms remain largely unknown. The aim of this investigation was to elucidate the potential role of ortho-dihydroxy group containing natural compounds in H 2 O 2 -induced DNA damage and apoptosis. For this purpose, the main phenolic alcohols of olive oil, namely hydroxytyrosol and tyrosol, were examined for their ability to protect cultured cells under conditions of oxidative stress. A strong correlation was observed between the ability of hydroxytyrosol to mitigate intracellular labile iron level and the protection offered against H 2 O 2 -induced DNA damage and apoptosis. On the other hand, tyrosol, which lacks the ortho-dihydroxy group, was ineffective. Moreover, hydroxytyrosol (but not tyrosol), was able to diminish the late sustained phase of H 2 O 2 -induced JNK and p38 phosphorylation. The derangement of intracellular iron homeostasis, following exposure of cells to H 2 O 2 , played pivotal role both in the induction of DNA damage and the initiation of apoptotic signaling. The presented results suggest that the protective effects exerted by ortho-dihydroxy group containing dietary compounds against oxidative stress-induced cell damage are linked to their ability to influence changes in the intracellular labile iron homeostasis. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Initial cloning and sequencing of hydHG, an operon homologous to ntrBC and regulating the labile hydrogenase activity in Escherichia coli K-12.

PubMed Central

Stoker, K; Reijnders, W N; Oltmann, L F; Stouthamer, A H

1989-01-01

To isolate genes from Escherichia coli which regulate the labile hydrogenase activity, a plasmid library was used to transform hydL mutants lacking the labile hydrogenase. A single type of gene, designated hydG, was isolated. This gene also partially restored the hydrogenase activity in hydF mutants (which are defective in all hydrogenase isoenzymes), although the low hydrogenase 1 and 2 levels were not induced. Therefore, hydG apparently regulates, specifically, the labile hydrogenase activity. Restoration of this latter activity in hydF mutants was accompanied by a proportional increase of the H2 uptake activity, suggesting a functional relationship. H2:fumarate oxidoreductase activity was not restored in complemented hydL mutants. These latter strains may therefore lack, in addition to the labile hydrogenase, a second component (provisionally designated component R), possibly an electron carrier coupling H2 oxidation to the anerobic respiratory chain. Sequence analysis showed an open reading frame of 1,314 base pairs for hydG. It was preceded by a ribosome-binding site but apparently lacked a promoter. Minicell experiments revealed a single polypeptide of approximately 50 kilodaltons. Comparison of the predicted amino acid sequence with a protein sequence data base revealed strong homology to NtrC from Klebsiella pneumoniae, a DNA-binding transcriptional activator. The 411 base pairs upstream from pHG40 contained a second open reading frame overlapping hydG by four bases. The deduced amino acid sequence showed considerable homology with the C-terminal part of NtrB. This sequence was therefore assumed to be part of a second gene, encoding the NtrB-like component, and was designated hydH. The labile hydrogenase activity in E. coli is apparently regulated by a multicomponent system analogous to the NtrB-NtrC system. This conclusion is in agreement with the results of Birkmann et al. (A. Birkmann, R. G. Sawers, and A. Böck, Mol. Gen. Genet. 210:535-542, 1987), who

Protective Effect of Active Immunization with Purified Escherichia coli Heat-Labile Enterotoxin in Rats

PubMed Central

Klipstein, Frederick A.; Engert, Richard F.

1979-01-01

The protective effect of active immunization by different routes with a purified preparation of the polymyxin-release form of Escherichia coli heat-labile toxin was evaluated in rats. Immunized animals were challenged by placing toxin into ligated ileal loops at dosages which produced either 50% or the maximum secretory response in unimmunized rats. Immunization exclusively by the parenteral route yielded significant protection. Rats were also protected when parenteral priming was followed by boosting given either directly into the duodenum or perorally 2 h after intragastric cimetidine, but not when the peroral boosts were given with bicarbonate. Immunization administered entirely by the peroral route with cimetidine yielded protection but only when the immunizing dosage was fivefold greater than that found effective in the parenteral-peroral approach. Rats immunized exclusively by the parenteral route and those boosted perorally with cimetidine were also tested, and found to be protected, against challenge with viable organisms of strains that produce either heat-labile toxin alone or both heat-labile and heat-stable toxin, but they were not protected against a strain which produces just heat-stable toxin. Geometric mean serum antibody titers were increased by 16-fold or more over control values in those groups of rats in which protection was achieved, with the exception of those immunized exclusively by the peroral route. These observations demonstrate that (i) active immunization with purified E. coli heat-labile toxin results in significant protection against both this toxin as well as viable organisms which produce it, but not against viable strains which produce heat-stable toxin only, and (ii) concomitant ablation of gastric secretion by the use of cimetidine renders the peroral route of immunization effective. They suggest that prophylactic immunization against diarrheal disease caused by heat-labile toxin-producing strains of E. coli may be feasible in

Distribution and origin of major and trace elements (particularly REE, U and Th) into labile and residual phases in an acid soil profile (Vosges Mountains, France)

NASA Astrophysics Data System (ADS)

Aubert, D.; Probst, A.; Stille, P.

2003-04-01

Physical and chemical weathering of rocks and minerals lead to soil formation and allow the removal of chemical elements from these systems to ground- or surface waters. But most of the time the determination of element concentrations in soils is not sufficient to estimate whether they are being accumulated or what is their ability to be released in the environment. Thus, the distribution and chemical binding for a given element is very important because it determines its mobility and potential bioavailability throughout a soil profile. Heavy metals and REE (Rare Earth Elements) are particularly of environmental concern because of their potential toxicity. For most of them, their chemical form strongly depends on the evolution of physico-chemical parameters like pH or redox conditions that will induce adsorption-desorption, complexation or co-precipitation phenomena in the material. The purpose of this study is to determine the distribution of several major and trace elements (especially REE, Th and U) in an acidic forested podzolic soil profile from the Vosges Mountains (France). To achieve this goal we use a 7 step sequential extraction procedure that allows determining precisely the origin and the behaviour of particular elements in the environment (Leleyter et al., 1999). In addition we performed leaching experiments using very dilute acetic and hydrochloric acid in order to establish the origin of REE in this soil. The results of the sequential extraction indicate that most of the metals, Th and U are mainly bound to Fe oxides. Organic matter appears also to be a great carrier of P, Ca, Fe and REE even if its content is very low in the deep horizons of the soil. Moreover, we show that in each soil horizon, middle REE (MREE) to heavy REE (HREE) are more labile than light REE (LREE). Leaching experiments using dilute acid solution further suggest that in the shallowest horizons REE largely derive from atmospheric deposition whereas at greater depth, weathering

Memory expression is independent of memory labilization/reconsolidation.

PubMed

Barreiro, Karina A; Suárez, Luis D; Lynch, Victoria M; Molina, Víctor A; Delorenzi, Alejandro

2013-11-01

There is growing evidence that certain reactivation conditions restrict the onset of both the destabilization phase and the restabilization process or reconsolidation. However, it is not yet clear how changes in memory expression during the retrieval experience can influence the emergence of the labilization/reconsolidation process. To address this issue, we used the context-signal memory model of Chasmagnathus. In this paradigm a short reminder that does not include reinforcement allows us to evaluate memory labilization and reconsolidation, whereas a short but reinforced reminder restricts the onset of such a process. The current study investigated the effects of the glutamate antagonists, APV (0.6 or 1.5 μg/g) and CNQX (1 μg/g), prior to the reminder session on both behavioral expression and the reconsolidation process. Under conditions where the reminder does not initiate the labilization/reconsolidation process, APV prevented memory expression without affecting long-term memory retention. In contrast, APV induced amnesic effects in the long-term when administered before a reminder session that triggers reconsolidation. Under the present parametric conditions, the administration of CNQX prior to the reminder that allows memory to enter reconsolidation impairs this process without disrupting memory expression. Overall, the present findings suggest that memory reactivation--but not memory expression--is necessary for labilization and reconsolidation. Retrieval and memory expression therefore appear not to be interchangeable concepts. Copyright © 2013 Elsevier Inc. All rights reserved.

Impact of Labile Zinc on Heart Function: From Physiology to Pathophysiology

PubMed Central

Turan, Belma; Tuncay, Erkan

2017-01-01

Zinc plays an important role in biological systems as bound and histochemically reactive labile Zn2+. Although Zn2+ concentration is in the nM range in cardiomyocytes at rest and increases dramatically under stimulation, very little is known about precise mechanisms controlling the intracellular distribution of Zn2+ and its variations during cardiac function. Recent studies are focused on molecular and cellular aspects of labile Zn2+ and its homeostasis in mammalian cells and growing evidence clarified the molecular mechanisms underlying Zn2+-diverse functions in the heart, leading to the discovery of novel physiological functions of labile Zn2+ in parallel to the discovery of subcellular localization of Zn2+-transporters in cardiomyocytes. Additionally, important experimental data suggest a central role of intracellular labile Zn2+ in excitation-contraction coupling in cardiomyocytes by shaping Ca2+ dynamics. Cellular labile Zn2+ is tightly regulated against its adverse effects through either Zn2+-transporters, Zn2+-binding molecules or Zn2+-sensors, and, therefore plays a critical role in cellular signaling pathways. The present review summarizes the current understanding of the physiological role of cellular labile Zn2+ distribution in cardiomyocytes and how a remodeling of cellular Zn2+-homeostasis can be important in proper cell function with Zn2+-transporters under hyperglycemia. We also emphasize the recent investigations on Zn2+-transporter functions from the standpoint of human heart health to diseases together with their clinical interest as target proteins in the heart under pathological condition, such as diabetes. PMID:29137144

Impact of Labile Zinc on Heart Function: From Physiology to Pathophysiology.

PubMed

Turan, Belma; Tuncay, Erkan

2017-11-12

Zinc plays an important role in biological systems as bound and histochemically reactive labile Zn 2+ . Although Zn 2+ concentration is in the nM range in cardiomyocytes at rest and increases dramatically under stimulation, very little is known about precise mechanisms controlling the intracellular distribution of Zn 2+ and its variations during cardiac function. Recent studies are focused on molecular and cellular aspects of labile Zn 2+ and its homeostasis in mammalian cells and growing evidence clarified the molecular mechanisms underlying Zn 2+ -diverse functions in the heart, leading to the discovery of novel physiological functions of labile Zn 2+ in parallel to the discovery of subcellular localization of Zn 2+ -transporters in cardiomyocytes. Additionally, important experimental data suggest a central role of intracellular labile Zn 2+ in excitation-contraction coupling in cardiomyocytes by shaping Ca 2+ dynamics. Cellular labile Zn 2+ is tightly regulated against its adverse effects through either Zn 2+ -transporters, Zn 2+ -binding molecules or Zn 2+ -sensors, and, therefore plays a critical role in cellular signaling pathways. The present review summarizes the current understanding of the physiological role of cellular labile Zn 2+ distribution in cardiomyocytes and how a remodeling of cellular Zn 2+ -homeostasis can be important in proper cell function with Zn 2+ -transporters under hyperglycemia. We also emphasize the recent investigations on Zn 2+ -transporter functions from the standpoint of human heart health to diseases together with their clinical interest as target proteins in the heart under pathological condition, such as diabetes.

DNA lability induced by nimustine and ramustine in rat glioma cells.

PubMed Central

Mineura, K; Fushimi, S; Itoh, Y; Kowada, M

1988-01-01

The DNA labile sites induced by two nitrosoureas, nimustine (ACNU) and ramustine (MCNU) synthesised in Japan, have been examined in highly reiterated DNA sequences of rat glioma cells. Reiterated fragments of 167 and 203 base pairs (bp), obtained after Hind III and Hae III restriction endonuclease digestion of rat glioma cells DNA, were used as target DNA sequences to determine the labile sites. In vitro reaction with ACNU and MCNU resulted in scission products corresponding to the locations of guanine. Subsequent piperidine hydrolysis produced more frequent breaks of the phosphodiester bonds at guanine positions, thus forming alkali-labile sites. Images PMID:3236017

Comparison of methods for acid quantification: impact of resist components on acid-generating efficiency

NASA Astrophysics Data System (ADS)

Cameron, James F.; Fradkin, Leslie; Moore, Kathryn; Pohlers, Gerd

2000-06-01

Chemically amplified deep UV (CA-DUV) positive resists are the enabling materials for manufacture of devices at and below 0.18 micrometer design rules in the semiconductor industry. CA-DUV resists are typically based on a combination of an acid labile polymer and a photoacid generator (PAG). Upon UV exposure, a catalytic amount of a strong Bronsted acid is released and is subsequently used in a post-exposure bake step to deprotect the acid labile polymer. Deprotection transforms the acid labile polymer into a base soluble polymer and ultimately enables positive tone image development in dilute aqueous base. As CA-DUV resist systems continue to mature and are used in increasingly demanding situations, it is critical to develop a fundamental understanding of how robust these materials are. One of the most important factors to quantify is how much acid is photogenerated in these systems at key exposure doses. For the purpose of quantifying photoacid generation several methods have been devised. These include spectrophotometric methods, ion conductivity methods and most recently an acid-base type titration similar to the standard addition method. This paper compares many of these techniques. First, comparisons between the most commonly used acid sensitive dye, tetrabromophenol blue sodium salt (TBPB) and a less common acid sensitive dye, Rhodamine B base (RB) are made in several resist systems. Second, the novel acid-base type titration based on the standard addition method is compared to the spectrophotometric titration method. During these studies, the make up of the resist system is probed as follows: the photoacid generator and resist additives are varied to understand the impact of each of these resist components on the acid generation process.

Non-labile Soil Nitrogen Retention beneath Three Tree Species in a Tropical Plantation

Treesearch

Jason P. Kaye; Dan Binkley; Xiaoming Zou

2002-01-01

Soil organic matter is the largest sink for N additions to forests. Species composition may affect soilNretention by altering the amount or proportion of added N stored in non-labile organic pools. We measured 15N tracer retention in labile and non-labile pools of surface (0–20 cm) mineral soils, 7 yr after the tracer was applied to a 9 yr-old Puerto Rican tree...

Brushed block copolymer micelles with pH-sensitive pendant groups for controlled drug delivery.

PubMed

Lee, Hyun Jin; Bae, Younsoo

2013-08-01

To investigate the effects of small aliphatic pendent groups conjugated through an acid-sensitive linker to the core of brushed block copolymer micelles on particle properties. The brushed block copolymers were synthesized by conjugating five types of 2-alkanone (2-butanone, 2-hexanone, 2-octanone, 2-decanone, and 2-dodecanone) through an acid-labile hydrazone linker to poly(ethylene glycol)-poly(aspartate hydrazide) block copolymers. Only block copolymers with 2-hexanone and 2-octanone (PEG-HEX and PEG-OCT) formed micelles with a clinically relevant size (< 50 nm in diameter), low critical micelle concentration (CMC, < 20 μM), and drug entrapment yields (approximately 5 wt.%). Both micelles degraded in aqueous solutions in a pH-dependent manner, while the degradation was accelerated in an acidic condition (pH 5.0) in comparison to pH 7.4. Despite these similar properties, PEG-OCT micelles controlled the entrapment and pH-dependent release of a hydrophobic drug most efficiently, without altering particle size, shape, and stability. The molecular weight of PEG (12 kDa vs 5 kDa) induced no change in pH-controlled drug release rates of PEG-OCT micelles. Acid-labile small aliphatic pendant groups are useful to control the entrapment and release of a hydrophobic drug physically entrapped in the core of brushed block copolymer micelles.

Molecular insights into the microbial formation of marine dissolved organic matter: recalcitrant or labile?

NASA Astrophysics Data System (ADS)

Koch, B. P.; Kattner, G.; Witt, M.; Passow, U.

2014-08-01

The degradation of marine dissolved organic matter (DOM) is an important control variable in the global carbon cycle. For our understanding of the kinetics of organic matter cycling in the ocean, it is crucial to achieve a mechanistic and molecular understanding of its transformation processes. A long-term microbial experiment was performed to follow the production of non-labile DOM by marine bacteria. Two different glucose concentrations and dissolved algal exudates were used as substrates. We monitored the bacterial abundance, concentrations of dissolved and particulate organic carbon (DOC, POC), nutrients, amino acids and transparent exopolymer particles (TEP) for 2 years. The molecular characterization of extracted DOM was performed by ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) after 70 days and after ∼2 years of incubation. Although glucose quickly degraded, a non-labile DOC background (5-9% of the initial DOC) was generated in the glucose incubations. Only 20% of the organic carbon from the algal exudate degraded within the 2 years of incubation. The degradation rates for the non-labile DOC background in the different treatments varied between 1 and 11 μmol DOC L-1 year-1. Transparent exopolymer particles, which are released by microorganisms, were produced during glucose degradation but decreased back to half of the maximum concentration within less than 3 weeks (degradation rate: 25 μg xanthan gum equivalents L-1 d-1) and were below detection in all treatments after 2 years. Additional glucose was added after 2 years to test whether labile substrate can promote the degradation of background DOC (co-metabolism; priming effect). A priming effect was not observed but the glucose addition led to a slight increase of background DOC. The molecular analysis demonstrated that DOM generated during glucose degradation differed appreciably from DOM transformed during the degradation of the algal exudates. Our

Effects of labile carbon addition on a headwater stream food web

Treesearch

Heidi S. Wilcox; J. Bruce Wallace; Judy L. Meyer; Jonathan P. Benstead

2005-01-01

We added dextrose for two 8-week periods (summer and autumn) to a highly heterotrophic headwater stream in North Carolina, U.S.A., to examine the responses of its benthic food web to increased labile carbon. We hypothesized that addition of labile carbon would elevate microbial abundance and activity, resulting in greater resource availability and higher...

Oxygen consumption and labile dissolved organic carbon uptake by benthic biofilms

NASA Astrophysics Data System (ADS)

de Falco, Natalie; Boano, Fulvio; Arnon, Shai

2015-04-01

Biogeochemical activity in streams is often magnified at interfaces, such as in the case of biofilm growth near the surface of the stream sediments. The objective of this study was to evaluate the relative importance of surficial biofilms versus the biofilm in the hyporheic zone to the processes of biodegradation of a labile dissolved organic carbon (DOC) and to oxygen consumption. Experiments were conducted in a recirculating flume, equipped with a drainage system that enables the control on losing and gaining fluxes. A surficial biofilm was developed over a sandy streambed with dune-shaped bed forms, by providing labile DOC (sodium benzoate) and nitrate. Homogeneously distributed biofilm was obtained by the same feeding strategy but with mixing the sediments manually on a daily basis. After the biofilm growth period, transformation of the labile DOC under different overlying velocities and losing or gaining fluxes was studied after spiking with sodium benzoate and by monitoring the decrease in DOC concentration in the bulk water over time using an online UV/Vis spectrophotometer. In addition, oxygen profiles across the water-streambed interface were measured at different locations along the bed form using oxygen microelectrodes. Preliminary results showed that the rate of labile DOC degradation increased exponentially with increasing overlying water velocity, regardless of the type of biofilm. Gaining and losing conditions did not play a critical role in the DOC degradation regardless of the type of biofilm, because the labile DOC was quickly utilized close to the surface. Under losing conditions, complete depletion of oxygen was observed within the top 5 millimeters, regardless of the biofilm type. In contrast, oxygen profiles under gaining condition showed an incomplete consumption of oxygen followed by an increase in the concentration of oxygen deeper in the sediments due to the upward flow of oxygenated groundwater. The results suggest that the transformation

The five-factor model of impulsivity-like traits and emotional lability in aggressive behavior.

PubMed

Dvorak, Robert D; Pearson, Matthew R; Kuvaas, Nicholas J

2013-01-01

Factors that increase automatic psychological processes may result in impulsive action and, consequently, aggressive behavior. The current cross-sectional study examined the association between the five-factor model of impulsivity-like traits (negative urgency, positive urgency, premeditation, perseverance, and sensation seeking), emotional lability, and physically aggressive behaviors among college students (n = 481) in a negative binomial hurdle model. In the logistic portion of the model, emotional lability was related to a higher likelihood of engaging in aggressive acts in the past 6 months. The association between emotional lability and the likelihood of aggressive behavior was moderated by two impulsivity-like traits: negative urgency and positive urgency. Specifically, emotional lability was related to engaging in aggressive acts among those with high negative urgency, and among those with low positive urgency. In the count portion of the model, emotional lability was uniquely related to the number of aggressive acts in the past 6 months. Our results indicate that emotional lability and facets of impulsivity interactively relate to engagement in aggressive behavior, suggesting that these variables be integrated into models of aggression. © 2013 Wiley Periodicals, Inc.

Quantification of Labile Soil Mercury by Stable Isotope Dilution Techniques

NASA Astrophysics Data System (ADS)

Shetaya, Waleed; Huang, Jen-How; Osterwalder, Stefan; Alewell, Christine

2016-04-01

Mercury (Hg) is a toxic element that can cause severe health problems to humans. Mercury is emitted to the atmosphere from both natural and anthropogenic sources and can be transported over long distances before it is deposited to aquatic and terrestrial environments. Aside from accumulation in soil solid phases, Hg deposited in soils may migrate to surface- and ground-water or enter the food chain, depending on its lability. There are many operationally-defined extraction methods proposed to quantify soil labile metals. However, these methods are by definition prone to inaccuracies such as non-selectivity, underestimation or overestimation of the labile metal pool. The isotopic dilution technique (ID) is currently the most promising method for discrimination between labile and non-labile metal fractions in soil with a minimum disturbance to soil-solid phases. ID assesses the reactive metal pool in soil by defining the fraction of metal both in solid and solution phases that is isotopically-exchangeable known as the 'E-value'. The 'E-value' represents the metal fraction in a dynamic equilibrium with the solution phase and is potentially accessible to plants. This is carried out by addition of an enriched metal isotope to soil suspensions and quantifying the fraction of metal that is able to freely exchange with the added isotope by measuring the equilibrium isotopic ratio by ICP-MS. E-value (mg kg-1) is then calculated as follows: E-Value = (Msoil/ W) (CspikeVspike/ Mspike) (Iso1IAspike -Iso2IAspikeRss / Iso2IAsoil Rss - Iso1IAsoil) where M is the average atomic mass of the metal in the soil or the spike, W is the mass of soil (kg), Cspike is the concentration of the metal in the spike (mg L-1), Vspike is the volume of spike (L), IA is isotopic abundance, and Rss is the equilibrium ratio of isotopic abundances (Iso1:Iso2). Isotopic dilution has been successfully applied to determine E-values for several elements. However, to our knowledge, this method has not yet

Affect lability predicts occurrence of suicidal ideation in bipolar patients: a two-year prospective study.

PubMed

Ducasse, D; Jaussent, I; Guillaume, S; Azorin, J M; Bellivier, F; Belzeaux, R; Bougerol, T; Etain, B; Gard, S; Henry, C; Kahn, J P; Leboyer, M; Loftus, J; Passerieux, C; Olié, E; Courtet, P

2017-05-01

The aim of our study was to investigate, in bipolar patients, whether affect lability was associated with suicidal ideation incidence during 2-year follow-up, and which subtype of affect lability was associated with suicidal ideation. A total of 319 euthymic or mildly depressed bipolar outpatients recruited in the French FondaMental Advanced Centres of Expertise for Bipolar Disorder were divided into two subgroups according to the occurrence of suicidal ideation during a 2-year follow-up. Affect lability was assessed by the French version of the Affect Lability Scale. Bipolar patients with high affect lability were more likely to report suicidal ideation during follow-up, even after adjustment for age, study level, rapid cycling, current depression level, anxiety disorder, and lifetime history SA (OR = 2.47; 95% CI [1.15-5.30], P = 0.01). The risk of suicidal ideation increased with the level of affect lability. More specifically, the propensity to switch from neutral to elation affect, from anxious to depressive affect (or inversely), and from neutral to anger affect predicted suicidal ideation. Reducing affective lability could become a new therapeutic target of suicidal prevention in bipolar disorder. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Non-labile Soil 15Nitrogen Retention beneath Three Tree Species in a Tropical Plantation

Treesearch

Jason P. Kaye; Dan Binkley; Xiaoming Zou

2002-01-01

Soil organic matter is the largest sink for N additions to forests.Species composition may affect soilNretention by altering the amount or proportion of added N stored in non-labile organic pools. We measured 15N tracer retention in labile and non-labile pools of surface (0–20 cm) mineral soils, 7 yr after the tracer was applied to a 9 yr-old Puerto Rican tree...

Radiation-induced heat-labile sites that convert into DNA double-strand breaks

NASA Technical Reports Server (NTRS)

Rydberg, B.; Chatterjee, A. (Principal Investigator)

2000-01-01

The yield of DNA double-strand breaks (DSBs) in SV40 DNA irradiated in aqueous solution was found to increase by more than a factor of two as a result of postirradiation incubation of the DNA at 50 degrees C and pH 8.0 for 24 h. This is in agreement with data from studies performed at 37 degrees C that were published previously. Importantly, similar results were also obtained from irradiation of mammalian DNA in agarose plugs. These results suggest that heat-labile sites within locally multiply damaged sites are produced by radiation and are subsequently transformed into DSBs. Since incubation at 50 degrees C is typically employed for lysis of cells in commonly used pulsed-field gel assays for detection of DSBs in mammalian cells, the possibility that heat-labile sites are present in irradiated cells was also studied. An increase in the apparent number of DSBs as a function of lysis time at 50 degrees C was found with kinetics that was similar to that for irradiated DNA, although the magnitude of the increase was smaller. This suggests that heat-labile sites are also formed in the cell. If this is the case, a proportion of DSBs measured by the pulsed-field gel assays may occur during the lysis step and may not be present in the cell as breaks but as heat-labile sites. It is suggested that such sites consist mainly of heat-labile sugar lesions within locally multiply damaged sites. Comparing rejoining of DSBs measured with short and long lysis procedure indicates that the heat-labile sites are repaired with fast kinetics in comparison with repair of the bulk of DSBs.

In Situ, High-Resolution Profiles of Labile Metals in Sediments of Lake Taihu

PubMed Central

Wang, Dan; Gong, Mengdan; Li, Yangyang; Xu, Lv; Wang, Yan; Jing, Rui; Ding, Shiming; Zhang, Chaosheng

2016-01-01

Characterizing labile metal distribution and biogeochemical behavior in sediments is crucial for understanding their contamination characteristics in lakes, for which in situ, high-resolution data is scare. The diffusive gradient in thin films (DGT) technique was used in-situ at five sites across Lake Taihu in the Yangtze River delta in China to characterize the distribution and mobility of eight labile metals (Fe, Mn, Zn, Ni, Cu, Pb, Co and Cd) in sediments at a 3 mm spatial resolution. The results showed a great spatial heterogeneity in the distributions of redox-sensitive labile Fe, Mn and Co in sediments, while other metals had much less marked structure, except for downward decreases of labile Pb, Ni, Zn and Cu in the surface sediment layers. Similar distributions were found between labile Mn and Co and among labile Ni, Cu and Zn, reflecting a close link between their geochemical behaviors. The relative mobility, defined as the ratio of metals accumulated by DGT to the total contents in a volume of sediments with a thickness of 10 mm close to the surface of DGT probe, was the greatest for Mn and Cd, followed by Zn, Ni, Cu and Co, while Pb and Fe had the lowest mobility; this order generally agreed with that defined by the modified BCR approach. Further analyses showed that the downward increases of pH values in surface sediment layer may decrease the lability of Pb, Ni, Zn and Cu as detected by DGT, while the remobilization of redox-insensitive metals in deep sediment layer may relate to Mn cycling through sulphide coprecipitation, reflected by several corresponding minima between these metals and Mn. These in situ data provided the possibility for a deep insight into the mechanisms involved in the remobilization of metals in freshwater sediments. PMID:27608033

Phaeochromocytoma presenting with labile blood pressures following coronary artery bypass grafting.

PubMed

Roy, James; Akhunji, Zakir; Kushwaha, Virag; Mackie, James; Jepson, Nigel

2016-12-01

Pheochromocytomas have been reported prior to and during coronary artery bypass surgery. We present a patient with an undiagnosed pheochromocytoma who presented with labile hypertension following coronary artery bypass surgery. This case calls attention to the inclusion of an undiagnosed pheochromocytoma in the differential diagnosis for all patients who develop labile hypertension in the postoperative period following cardiac surgery. © 2016 Wiley Periodicals, Inc.

Mechanism of Stabilization of Labile Compounds by Silk Fibroin Proteins

DTIC Science & Technology

2017-04-05

AFRL-AFOSR-VA-TR-2017-0076 Mechanism of Stabilization of Labile Compounds by Silk Fibroin Proteins David Kaplan TRUSTEES OF TUFTS COLEGE INC 169... Proteins 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA9550-14-1-0015 5c.  PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) David Kaplan 5d.  PROJECT NUMBER 5e...objective of this research was to elucidate the fundamental mechanisms by which labile compounds are entrapped and stabilized by silk fibroin protein . The

Rhizosphere Environment and Labile Phosphorus Release from Organic Waste-Amended Soils.

NASA Astrophysics Data System (ADS)

Dao, Thanh H.

2015-04-01

Crop residues and biofertilizers are primary sources of nutrients for organic crop production. However, soils treated with large amounts of nutrient-enriched manure have elevated phosphorus (P) levels in regions of intensive animal agriculture. Surpluses occurred in these amended soils, resulting in large pools of exchangeable inorganic P (Pi) and enzyme-labile organic P (Po) that averaging 30.9 and 68.2 mg kg-1, respectively. Organic acids produced during crop residue decomposition can promote the complexation of counter-ions and decouple and release unbound Pi from metal and alkali metal phosphates. Animal manure and cover crop residues also contain large amounts of soluble organic matter, and likely generate similar ligands. However, a high degree of heterogeneity in P spatial distribution in such amended fields, arising from variances in substrate physical forms ranging from slurries to dried solids, composition, and diverse application methods and equipment. Distinct clusters of Pi and Po were observed, where accumulation of the latter forms was associated with high soil microbial biomass C and reduced phosphomonoesterases' activity. Accurate estimates of plant requirements and lability of soil P pools, and real-time plant and soil P sensing systems are critical considerations to optimally manage manure-derived nutrients in crop production systems. An in situ X-ray fluorescence-based approach to sensing canopy and soil XRFS-P was developed to improve the yield-soil P relationship for optimal nutrient recommendations in addition to allowing in-the-field verification of foliar P status.

How to Compute Labile Metal-Ligand Equilibria

ERIC Educational Resources Information Center

de Levie, Robert

2007-01-01

The different methods used for computing labile metal-ligand complexes, which are suitable for an iterative computer solution, are illustrated. The ligand function has allowed students to relegate otherwise tedious iterations to a computer, while retaining complete control over what is calculated.

Effect of exogenous phosphate on the lability and phytoavailability of arsenic in soils.

PubMed

Wang, Jinjin; Zeng, Xibai; Zhang, Hao; Li, Yongtao; Zhao, Shizhen; Su, Shiming; Bai, Lingyu; Wang, Yanan; Zhang, Tuo

2018-04-01

The effect of exogenous phosphate (P, 200 mg⋅kg -1 soil) on the lability and phytoavailability of arsenic (As) was studied using the diffusive gradients in thin films (DGT) technique. Lettuce were grown on the As-amended soils following the stabilization of soil labile As after 90 days incubation. Phosphate (P) application generally facilitated plant growth except one grown on P-sufficient soil. Soil labile As concentration increased in all the soils after P application due to a competition effect. Plant As concentration increased in red soils collected from Hunan Province, while decreases were observed in the other soils. Even though, an overall trend of decrease was obtained in As phytoavailability along with the increase of DGT-measured soil labile P/As molar ratio. The functional equation between P/As and As phytoavailability provided a critical value of 1.7, which could be used as a guidance for rational P fertilization, thus avoiding overfertilization. Copyright © 2018 Elsevier Ltd. All rights reserved.

Lability and Basicity of Bipyridine-Carboxylate-Phosphonate Ligand Accelerate Single-Site Water Oxidation by Ruthenium-Based Molecular Catalysts

DOE PAGES

Shaffer, David W.; Xie, Yan; Szalda, David J.; ...

2017-09-24

Here, a critical step in creating an artificial photosynthesis system for energy storage is designing catalysts that can thrive in an assembled device. Single-site catalysts have an advantage over bimolecular catalysts because they remain effective when immobilized. Hybrid water oxidation catalysts described here, combining the features of single-site bis-phosphonate catalysts and fast bimolecular bis-carboxylate catalysts, have reached turnover frequencies over 100 s –1, faster than both related catalysts under identical conditions. The new [(bpHc)Ru(L) 2] (bpH 2cH = 2,2'-bipyridine-6-phosphonic acid-6'-carboxylic acid, L = 4-picoline or isoquinoline) catalysts proceed through a single-site water nucleophilic attack pathway. The pendant phosphonate base mediatesmore » O–O bond formation via intramolecular atom-proton transfer with a calculated barrier of only 9.1 kcal/mol. Additionally, the labile carboxylate group allows water to bind early in the catalytic cycle, allowing intramolecular proton-coupled electron transfer to lower the potentials for oxidation steps and catalysis. That a single-site catalyst can be this fast lends credence to the possibility that the oxygen evolving complex adopts a similar mechanism.« less

Lability and Basicity of Bipyridine-Carboxylate-Phosphonate Ligand Accelerate Single-Site Water Oxidation by Ruthenium-Based Molecular Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaffer, David W.; Xie, Yan; Szalda, David J.

Here, a critical step in creating an artificial photosynthesis system for energy storage is designing catalysts that can thrive in an assembled device. Single-site catalysts have an advantage over bimolecular catalysts because they remain effective when immobilized. Hybrid water oxidation catalysts described here, combining the features of single-site bis-phosphonate catalysts and fast bimolecular bis-carboxylate catalysts, have reached turnover frequencies over 100 s –1, faster than both related catalysts under identical conditions. The new [(bpHc)Ru(L) 2] (bpH 2cH = 2,2'-bipyridine-6-phosphonic acid-6'-carboxylic acid, L = 4-picoline or isoquinoline) catalysts proceed through a single-site water nucleophilic attack pathway. The pendant phosphonate base mediatesmore » O–O bond formation via intramolecular atom-proton transfer with a calculated barrier of only 9.1 kcal/mol. Additionally, the labile carboxylate group allows water to bind early in the catalytic cycle, allowing intramolecular proton-coupled electron transfer to lower the potentials for oxidation steps and catalysis. That a single-site catalyst can be this fast lends credence to the possibility that the oxygen evolving complex adopts a similar mechanism.« less

Using isotopic dilution to assess chemical extraction of labile Ni, Cu, Zn, Cd and Pb in soils.

PubMed

Garforth, J M; Bailey, E H; Tye, A M; Young, S D; Lofts, S

2016-07-01

Chemical extractants used to measure labile soil metal must ideally select for and solubilise the labile fraction, with minimal solubilisation of non-labile metal. We assessed four extractants (0.43 M HNO3, 0.43 M CH3COOH, 0.05 M Na2H2EDTA and 1 M CaCl2) against these requirements. For soils contaminated by contrasting sources, we compared isotopically exchangeable Ni, Cu, Zn, Cd and Pb (EValue, mg kg(-1)), with the concentrations of metal solubilised by the chemical extractants (MExt, mg kg(-1)). Crucially, we also determined isotopically exchangeable metal in the soil-extractant systems (EExt, mg kg(-1)). Thus 'EExt - EValue' quantifies the concentration of mobilised non-labile metal, while 'EExt - MExt' represents adsorbed labile metal in the presence of the extractant. Extraction with CaCl2 consistently underestimated EValue for Ni, Cu, Zn and Pb, while providing a reasonable estimate of EValue for Cd. In contrast, extraction with HNO3 both consistently mobilised non-labile metal and overestimated the EValue. Extraction with CH3COOH appeared to provide a good estimate of EValue for Cd; however, this was the net outcome of incomplete solubilisation of labile metal, and concurrent mobilisation of non-labile metal by the extractant (MExtEValue). The Na2H2EDTA extractant mobilised some non-labile metal in three of the four soils, but consistently solubilised the entire labile fraction for all soil-metal combinations (MExt ≈ EExt). Comparison of EValue, MExt and EExt provides a rigorous means of assessing the underlying action of soil chemical extraction methods and could be used to refine long-standing soil extraction methodologies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Labile pools of Pb in vegetable-growing soils investigated by an isotope dilution method and its influence on soil pH.

PubMed

Xie, Hong; Huang, Zhi-Yong; Cao, Ying-Lan; Cai, Chao; Zeng, Xiang-Cheng; Li, Jian

2012-08-01

Pollution of Pb in the surface of agricultural soils is of increasing concern due to its serious impact on the plant growth and the human health through the food chain. However, the mobility, activity and bioavailability of Pb rely mainly on its various chemical species in soils. In the present study, E and L values, the labile pools of isotopically exchangeable Pb, were estimated using the method of isotope dilution in three vegetable-growing soils. The experiments involved adding a stable enriched isotope ((206)Pb > 96%) to a soil suspension and to soils in which plants are subsequently grown, the labile pools of Pb were then estimated by measuring the isotopic composition of Pb in soil solutions and in the plant tissues, respectively. In addition, the correlation of E values and soil pH was investigated at the ranges of pH 4.5-7.0. The amount of labile Pb in soils was also estimated using different single chemical extractants and a modified BCR approach. The results showed that after spiking the enriched isotopes of (206)Pb (>96%) for 24 hours an equilibration of isotopic exchanges in soil suspensions was achieved, and the isotope ratios of (208)Pb/(206)Pb measured at that time was used for calculating the E(24 h) values. The labile pools of Pb by %E(24 h) values, ranging from 53.2% to 61.7% with an average 57%, were found to be significantly higher (p < 0.05) than the values estimated with L values, single chemical extractants and the Σ(BCR) values obtained with the BCR approach, respectively. A strong negative correlation (R(2) = 0.984) between E(24 h) values and soil pH was found in the tested soil sample. The results indicate that the %E(24 h) value can more rapidly and easily predict the labile pools of Pb in soils compared with L values, but it might be readily overestimated because of the artificial soil acidity derived from the spiked isotopic tracer and the excess of spiked enriched isotopes. The results also suggest that the amounts of Pb extracted

Modeling Effects of Lability on Microbial Uptake of DOM in River Reaches

NASA Astrophysics Data System (ADS)

Li, A.; Drummond, J. D.; Bowen, J. C.; Cory, R. M.; Kaplan, L.; Packman, A. I.

2017-12-01

Rivers are hotspots for biological degradation of dissolved organic matter (DOM), contributing to 1.8 petagrams of carbon emissions per year. DOM represents approximately 60% of the total mass of organic carbon transported within river networks, fueling stream ecosystem metabolism. Not all DOM is biodegradable, biodegradation rates vary based on lability, and lability decreases with reaction time. Fluorescent fractions of DOM (FDOM) are often used as proxies of DOM lability. Humic-like FDOM, previously considered recalcitrant and thought to contribute minimally to the biodegradable DOM pools, has recently been shown to contribute more than 50% to DOM uptake in bioreactor columns colonized by bacteria in stream water. Protein-like FDOM, a proxy for the biodegradable DOM pool, also contributes to the recalcitrant DOM pool in bioreactors. However, the contribution of different lability pools to DOM uptake at the reach scale remains elusive. Here we combine local-scale results from a bioreactor study and measures of stream geomorphology parameters to model reach-scale DOM uptake in White Clay Creek, a Pennsylvania piedmont stream with an intact, forested riparian zone and inputs from upland agriculture. Steady state modeling of a point-source, continuous injection of FDOM shows that humic-like FDOM contributes up to 80% of the total removal of FDOM at the reach scale, suggesting its importance to in-stream DOM uptake. Tryptophan-like FDOM, a protein-like FDOM, contributes to 80% of the remaining fraction of FDOM at the reach scale that incorporates longer timescales of transport and retention. This is consistent with recent local-scale findings that the lability of tryptophan-like FDOM decreases substantially with reaction time in bioreactors, such that it becomes much more recalcitrant as it travels downstream. Steady state modeling of a distributed source, continuous injection of FDOM shows that contributing sources distribute differently along the river reach for

Characterization of labile organic carbon in coastal wetland soils of the Mississippi River deltaic plain: relationships to carbon functionalities.

PubMed

Dodla, Syam K; Wang, Jim J; Delaune, Ronald D

2012-10-01

Adequate characterization of labile organic carbon (LOC) is essential to the understanding of C cycling in soil. There has been very little evaluation about the nature of LOC characterizations in coastal wetlands, where soils are constantly influenced by different redox fluctuations and salt water intrusions. In this study, we characterized and compared LOC fractions in coastal wetland soils of the Mississippi River deltaic plain using four different methods including 1) aerobically mineralizable C (AMC), 2) cold water extractable C (CWEC), 3) hot water extractable C (HWEC), and 4) salt extractable C (SEC), as well as acid hydrolysable C (AHC) which includes both labile and slowly degradable organic C. Molecular organic C functional groups of these wetland soils were characterized by (13)C solid-state nuclear magnetic resonance (NMR). The LOC and AHC increased with soil organic C (SOC) regardless of wetland soil type. The LOC estimates by four different methods were positively and significantly linearly related to each other (R(2)=0.62-0.84) and with AHC (R(2)=0.47-0.71). The various LOC fractions accounted for ≤4.3% of SOC whereas AHC fraction represented 16-49% of SOC. AMC was influenced positively by O/N-alkyl and carboxyl C but negatively by alkyl C, whereas CWEC and SEC fractions were influenced only positively by carboxyl C but negatively by alkyl C in SOC. On the other hand, HWEC fraction was found to be only influenced positively by carbonyl C, and AHC positively by O/N-alkyl and alkyl C but negatively by aromatic C groups in SOC. Overall these relations suggested different contributions of various molecular organic C moieties to LOC in these wetlands from those often found for upland soils. The presence of more than 50% non-acid hydrolysable C suggested the dominance of relatively stable SOC pool that would be sequestered in these Mississippi River deltaic plain coastal wetland soils. The results have important implications to the understanding of the

Childhood Maltreatment, Emotional Lability, and Alcohol Problems in Young Adults At-Risk for ADHD: Testing Moderation and Moderated Moderation.

PubMed

Bunford, Nóra; Wymbs, Brian T; Dawson, Anne E; Shorey, Ryan C

2017-01-01

Childhood maltreatment and alcohol problems are common among young adults with attention-deficit hyperactivity disorder (ADHD). However, little is known about the degree to which maltreatment and alcohol problems are associated; potential pertinent mediating or moderating mechanisms, such as emotional lability; and whether this association varies by sex. We examined, in a sample of adults at risk for ADHD (N = 122, 37% male), the association between childhood maltreatment and alcohol problems, whether emotional lability mediated or moderated this association, and whether either role of emotional lability differed between men and women. Emotional lability moderated the association between emotional neglect and alcohol problems; maltreatment increased risk for alcohol problems for those scoring high tovery high on emotional lability, but not for those with very low-moderate levels. The association between emotional abuse and alcohol problems depended both on emotional lability and sex; emotional abuse decreased the risk for alcohol problems among men very low/low on emotional lability, but not for men who were moderate to very high on emotional lability, or for women. These findings have implications for the way in which targeting maltreatment and emotional lability may be incorporated into prevention and intervention programs to prevent alcohol problems among men and women at risk for ADHD.

A Longitudinal Study of Emotion Regulation, Emotion Lability/Negativity, and Internalizing Symptomatology in Maltreated and Nonmaltreated Children

PubMed Central

Kim-Spoon, Jungmeen; Cicchetti, Dante; Rogosch, Fred A.

2013-01-01

The longitudinal contributions of emotion regulation and emotion lability/negativity to internalizing symptomatology were examined in a low-income sample (171 maltreated and 151 nonmaltreated children, from age 7 to 10 years). Latent difference score models indicated that, for both maltreated and nonmaltreated children, emotion regulation was a mediator between emotion lability/negativity and internalizing symptomatology, whereas emotion lability/negativity was not a mediator between emotion regulation and internalizing symptomatology. Early maltreatment was associated with high emotion lability/negativity (age 7) that contributed to poor emotion regulation (age 8), which in turn was predictive of increases in internalizing symptomatology (from age 8 to 9). The results imply important roles of emotion regulation in the development of internalizing symptomatology, especially for children with high emotion lability/negativity. PMID:23034132

'Inconstant males' and the maintenance of labile sex expression in subdioecious plants.

PubMed

Ehlers, Bodil K; Bataillon, Thomas

2007-01-01

* Here, we evaluate the role of pollen limitation and selfing in the maintenance of labile sex expression in subdioecious plant species. * We used a literature survey to explore which factors correlated with a significant occurrence of hermaphrodites in dioecious species. We developed models to explore the selective maintenance of labile sex expression. The models had similar ecological assumptions but differed in the genetic basis of sex lability. * We found that a significant frequency of hermaphrodites was associated with animal pollination, and that hermaphrodites were 'inconstant' males with perfect flowers, suggesting evolution through the gynodioecious pathway. Models showed that a modifier converting pure males into inconstant males could be maintained under a wide range of reduction in both male and female fitness. Pollen limitation and self-fertilization facilitated invasion of the modifier. Depending on the genetics of sex determination, we found pure dioecy, stable subdioecy (trioecy), and situations where inconstant males coexisted with either pure females or pure males. Under selfing and pollen limitation, certain conditions selected for inconstant males which will drive populations to extinction. * We discuss our results in relation to the evolution towards, and the breakdown of, dioecy, and the ecological and evolutionary implications of labile sex expression.

Submillimeter-scale heterogeneity of labile phosphorus in sediments characterized by diffusive gradients in thin films and spatial analysis.

PubMed

Meng, Yuting; Ding, Shiming; Gong, Mengdan; Chen, Musong; Wang, Yan; Fan, Xianfang; Shi, Lei; Zhang, Chaosheng

2018-03-01

Sediments have a heterogeneous distribution of labile redox-sensitive elements due to a drastic downward transition from oxic to anoxic condition as a result of organic matter degradation. Characterization of the heterogeneous nature of sediments is vital for understanding of small-scale biogeochemical processes. However, there are limited reports on the related specialized methodology. In this study, the monthly distributions of labile phosphorus (P), a redox-sensitive limiting nutrient, were measured in the eutrophic Lake Taihu by Zr-oxide diffusive gradients in thin films (Zr-oxide DGT) on a two-dimensional (2D) submillimeter level. Geographical information system (GIS) techniques were used to visualize the labile P distribution at such a micro-scale, showing that the DGT-labile P was low in winter and high in summer. Spatial analysis methods, including semivariogram and Moran's I, were used to quantify the spatial variation of DGT-labile P. The distribution of DGT-labile P had clear submillimeter-scale spatial patterns with significant spatial autocorrelation during the whole year and displayed seasonal changes. High values of labile P with strong spatial variation were observed in summer, while low values of labile P with relatively uniform spatial patterns were detected in winter, demonstrating the strong influences of temperature on the mobility and spatial distribution of P in sediment profiles. Copyright © 2017 Elsevier Ltd. All rights reserved.

High Sensitivity Combined with Extended Structural Coverage of Labile Compounds via Nanoelectrospray Ionization at Subambient Pressures

DOE PAGES

Cox, Jonathan T.; Kronewitter, Scott R.; Shukla, Anil K.; ...

2014-09-15

Subambient pressure ionization with nanoelectrospray (SPIN) has proven to be effective in producing ions with high efficiency and transmitting them to low pressures for high sensitivity mass spectrometry (MS) analysis. Here we present evidence that not only does the SPIN source improve MS sensitivity but also allows for gentler ionization conditions. The gentleness of a conventional heated capillary electrospray ionization (ESI) source and the SPIN source was compared by the liquid chromatography mass spectrometry (LC-MS) analysis of colominic acid. Colominic acid is a mixture of sialic acid polymers of different lengths containing labile glycosidic linkages between monomer units necessitating amore » gentle ion source. By coupling the SPIN source with high resolution mass spectrometry and using advanced data processing tools, we demonstrate much extended coverage of sialic acid polymer chains as compared to using the conventional ESI source. Additionally we show that SPIN-LC-MS is effective in elucidating polymer features with high efficiency and high sensitivity previously unattainable by the conventional ESI-LC-MS methods.« less

Labile dissolved organic carbon supply limits hyporheic denitrification

Treesearch

Jay P. Zarnetske; Roy Haggerty; Steven M. Wondzell; Michelle A. Baker

2012-01-01

We used an in situ steady state 15N-labeled nitrate and acetate well-to-wells injection experiment to determine how the availability of labile dissolved organic carbon as acetate influences microbial denitrification in the hyporheic zone of an upland (third-order) agricultural stream.

Characteristic constants of 2,2',4'-trihydroxyazobenzene-5-sulfonic acid, a reagent for spectrophotometric analysis

USGS Publications Warehouse

Fletcher, Mary H.

1960-01-01

The dye 2,2',4'-trihydroxyazobenzene-5-sulfonic acid, has shown promise as a reagent for the determination of zirconium. As the literature contains very little information about this dye, basic data pertinent to its use as a reagent were determined. The sulfonic acid group and all three of the hydroxy groups show acidic characteristics. Apparent dissociation constants were determined for the three more labile protons and the approximate order of magnitude for the fourth constant was estimated. Absorption spectra for the different ionization species are given. A curve is also included which shows the fraction of dye in the different ionization forms at acidities from 10.35M hydrochloric acid to pH 11.9. A sixth dye species was found in 1.0 to 8.4M potassium hydroxide solutions, but its nature is unknown.

Lability of Cd, Cu, and Zn in polluted soils treated with lime, beringite, and red mud and identification of a non-labile colloidal fraction of metals using istopic techniques.

PubMed

Lombi, Enzo; Hamon, Rebecca E; McGrath, Steve P; McLaughlin, Mike J

2003-03-01

The use of soil amendments has been proposed as a low input alternative for the remediation of metal polluted soils. However, little information is available concerning the stability, and therefore the longevity, of the remediation treatments when important soil parameters change. In this paper we investigate the effect of pH changes on the lability of heavy metals in soils treated with lime, beringite, and red mud using a modified isotopic dilution technique in combination with a stepwise acidification procedure. Significant amounts of nonlabile (fixed) Cu and Zn were found to be associated with colloids <0.2 microm in the solution phase. The results obtained indicated that the mobility of fixed colloidal metals is significant and increases with soil pH. This must be considered because most of the soil amendments are alkaline and increase soil pH. All the soil amendments significantly decreased the lability of Cd, Zn, and Cu in the soils as a whole. However, when the soils were re-acidified, the labile pool of metals increased sharply and in the case of lime and beringite, the lability of the metals was similar, at equal pH, to the untreated soil. In contrast the lability of metals in the red mud treated soils was always smaller than that in the untreated soils across the range of pH values tested. These results suggest that the mechanism of action of lime and beringite is similar and probably related to increased metal adsorption and precipitation of metal hydroxides and carbonates at high pH. In the case of red mud, a combination of pH dependent and independent mechanisms (possibly solid-phase diffusion or migration into micropores) may be responsible for the metal fixation observed.

PTSD, alcohol dependence, and conduct problems: Distinct pathways via lability and disinhibition.

PubMed

Simons, Jeffrey S; Simons, Raluca M; O'Brien, Carol; Stoltenberg, Scott F; Keith, Jessica A; Hudson, Jaime A

2017-01-01

This study tested the role of affect lability and disinhibition in mediating associations between PTSD symptoms and two forms of alcohol-related problems, dependence syndrome symptoms (e.g., impaired control over consumption) and conduct problems (e.g., assault, risk behaviors). Genotype at the serotonin transporter linked polymorphic region (5-HTTLPR) was hypothesized to moderate associations between traumatic stress and PTSD symptoms. In addition, the study tested whether childhood traumatic stress moderated associations between combat trauma and PTSD symptoms. Participants were 270 OIF/OEF/OND veterans. The hypothesized model was largely supported. Participants with the low expression alleles of 5-HTTLPR (S or L G ) exhibited stronger associations between childhood (but not combat) traumatic stress and PTSD symptoms. Affect lability mediated the associations between PTSD symptoms and alcohol dependence symptoms. Behavioral disinhibition mediated associations between PTSD symptoms and conduct related problems. Conditional indirect effects indicated stronger associations between childhood traumatic stress and lability, behavioral disinhibition, alcohol consumption, AUD symptoms, and associated conduct problems via PTSD symptoms among those with the low expression 5-HTTLPR alleles. However, interactions between combat trauma and either childhood trauma or genotype were not significant. The results support the hypothesis that affect lability and behavioral disinhibition are potential intermediate traits with distinct associations with AUD and associated externalizing problems. Copyright © 2016 Elsevier Ltd. All rights reserved.

Hmb(off/on) as a switchable thiol protecting group for native chemical ligation.

PubMed

Qi, Yun-Kun; Tang, Shan; Huang, Yi-Chao; Pan, Man; Zheng, Ji-Shen; Liu, Lei

2016-05-04

A new thiol protecting group Hmb(off/on) is described, which has a switchable activity that may be useful in the chemical synthesis of proteins. When placed on the side chain of Cys, Cys(Hmb(off)) is stable to trifluoroacetic acid (TFA) in the process of solid-phase peptide synthesis. When Cys(Hmb(off)) is treated with neutral aqueous buffers, it is cleanly converted to acid-labile Cys(Hmb(on)), which can later be fully deprotected by TFA to generate free Cys. The utility of Cys(Hmb(off/on)) is demonstrated by the chemical synthesis of an erythropoietin segment, EPO[Cys(98)-Arg(166)]-OH through native chemical ligation.

Assessment of Affect Lability: Psychometric Properties of the ALS-18.

PubMed

Contardi, Anna; Imperatori, Claudio; Amati, Italia; Balsamo, Michela; Innamorati, Marco

2018-01-01

Affect lability, an important aspect of emotion dysregulation, characterizes several psychiatric conditions. The short Affective Lability Scales (ALS-18) measures three aspects of changeability between euthymia and affect states (Anxiety/Depression, AD; Depression/Elation, DE; and Anger, Ang). The aim of our study was to investigate the psychometric characteristics of an Italian version of the ALS-18 in a sample of adults recruited from the general population. The sample was composed of 494 adults (343 women and 151 men) aged 18 and higher (mean age = 31.73 years, SD = 12.6). All participants were administered a checklist assessing socio-demographic variables, the ALS-18 and measures of depression and difficulties in emotion regulation. Confirmatory factor analyses indicated adequate fit of the three-factor model (RMSEA = 0.061, 95% CI = 0.054/0.069; CFI = 0.99; SRMR = 0.055), and the presence of a higher-order general factor. Internal consistency was satisfactory for all the lower-order dimensions and the general factor (ordinal α > 0.70). The ALS-18 was significantly associated with concurrent measures of depression and difficulties in emotion regulation. These findings indicate that the ALS-18 is a valid and reliable instrument for measuring affect lability, although discriminant validity of subdimensions scores could be problematic.

Strong-acid, carboxyl-group structures in fulvic acid from the Suwannee River, Georgia. 1. Minor structures

USGS Publications Warehouse

Leenheer, J.A.; Wershaw, R. L.; Reddy, M.M.

1995-01-01

An investigation of the strong-acid characteristics (pKa 3.0 or less) of fulvic acid from the Suwannee River, Georgia, was conducted. Quantitative determinations were made for amino acid and sulfur-containing acid structures, oxalate half-ester structures, malonic acid structures, keto acid structures, and aromatic carboxyl-group structures. These determinations were made by using a variety of spectrometric (13C-nuclear magnetic resonance, infrared, and ultraviolet spectrometry) and titrimetric characterizations on fulvic acid or fulvic acid samples that were chemically derivatized to indicate certain functional groups. Only keto acid and aromatic carboxyl-group structures contributed significantly to the strong-acid characteristics of the fulvic acid; these structures accounted for 43% of the strong-acid acidity. The remaining 57% of the strong acids are aliphatic carboxyl groups in unusual and/or complex configurations for which limited model compound data are available.

Ligand lability and chirality inversion in yb heterobimetallic catalysts.

PubMed

Di Bari, Lorenzo; Lelli, Moreno; Salvadori, Piero

2004-09-20

We have investigated the exchange dynamics between the free and bound ligand in K3[Yb[(R)-binol]3], the most active heterobimetallic lanthanoid catalyst for cyclic imine hydrophosphonylation; we found that the Yb-binol bond is labile. The rate constant for this exchange was determined through NMR saturation transfer experiments. Upon addition of (S)-binaphthol, ligand exchange leads to the formation of a small quantity of heterochiral complexes and, in the presence of a molar excess of (S)-binaphthol, to chirality inversion of the whole complex. This demonstrates that, in contrast to other analogous systems, K3[Yb(binol)3] displays a strong chiral discrimination, with the overwhelming preference for ligands of the same configuration. The lability of Yb-binol bond in THF may suggest a ligand-to-substrate exchange as a key step in the catalytic process.

Effects of acidity and aluminim on the physiology and migratory behavior of Atlantic salmon smolts in Maina, USA

USGS Publications Warehouse

Magee, J.A.; Haines, T.A.; Kocik, J.F.; Beland, K.F.; McCormick, S.D.

2001-01-01

Atlantic salmon, Salmo salar, smolts of hatchery origin were held for 5 to 16 days in ambient (pH 6.35, labile Al = 60 ??g L-1), limed (pH 6.72, labile Al = 58.4 ??g L-1), or acidified (pH 5.47, labile Al=96 ??g L-1) water from the Narraguagus River in Maine, USA. Wild smolts were captured in the same river in rotary traps and held for up to two days in ambient river water. Osmoregulatory ability was assessed by measuring Na+/K+ ATPase activity, hematocrit, and blood Cl concentration in freshwater, and after 24-hr exposure to seawater. Hatchery smolts exposed to acidic water and wild smolts displayed sub-lethal ionoregulatory stress both in fresh and seawater, with mortalities of wild smolts in seawater. Using ultrasonic telemetry, hatchery-reared ambient and acid-exposed, and wild smolts were tracked as they migrated through freshwater and estuarine sections of the river. The proportion of wild smolts migrating during daylight hours was higher than for hatchery-reared smolts. Wild smolts remained in the freshwater portions of the river longer than either group of hatchery smolts, although survival during migration to seawater was similar for all three treatments. Acid-exposed hatchery-origin and wild Narraguagus River smolts were both under ionoregulatory stress that may have affected their migratory behavior, but not their survival for the time and area in which we tracked them.

The evolution of labile traits in sex- and age-structured populations.

PubMed

Childs, Dylan Z; Sheldon, Ben C; Rees, Mark

2016-03-01

Many quantitative traits are labile (e.g. somatic growth rate, reproductive timing and investment), varying over the life cycle as a result of behavioural adaptation, developmental processes and plastic responses to the environment. At the population level, selection can alter the distribution of such traits across age classes and among generations. Despite a growing body of theoretical research exploring the evolutionary dynamics of labile traits, a data-driven framework for incorporating such traits into demographic models has not yet been developed. Integral projection models (IPMs) are increasingly being used to understand the interplay between changes in labile characters, life histories and population dynamics. One limitation of the IPM approach is that it relies on phenotypic associations between parents and offspring traits to capture inheritance. However, it is well-established that many different processes may drive these associations, and currently, no clear consensus has emerged on how to model micro-evolutionary dynamics in an IPM framework. We show how to embed quantitative genetic models of inheritance of labile traits into age-structured, two-sex models that resemble standard IPMs. Commonly used statistical tools such as GLMs and their mixed model counterparts can then be used for model parameterization. We illustrate the methodology through development of a simple model of egg-laying date evolution, parameterized using data from a population of Great tits (Parus major). We demonstrate how our framework can be used to project the joint dynamics of species' traits and population density. We then develop a simple extension of the age-structured Price equation (ASPE) for two-sex populations, and apply this to examine the age-specific contributions of different processes to change in the mean phenotype and breeding value. The data-driven framework we outline here has the potential to facilitate greater insight into the nature of selection and its

Reaction of the thermo-labile triazenide Na[tBu3SiNNNSiMe3] with CO2: formation of the imido carbonate (tBu3SiO)(Me3SiO)C[double bond, length as m-dash]N-SitBu3 and carbamine acid (tBu3SiO)CONH2.

PubMed

Lerner, H-W; Bolte, M; Wagner, M

2017-07-11

The thermo-labile triazenide Na[tBu 3 SiNNNSiMe 3 ] was prepared by the reaction of Me 3 SiN 3 with Na(thf) 2 [SitBu 3 ] in pentane at -78 °C. Treatment of Na[tBu 3 SiNNNSiMe 3 ] with an excess of carbon dioxide in pentane at -78 °C yielded the imido carbonate (tBu 3 SiO)(Me 3 SiO)C[double bond, length as m-dash]N-SitBu 3 and the carbamine acid (tBu 3 SiO)CONH 2 along with other products. From the reaction solution we could isolate the imido carbonate (tBu 3 SiO)(Me 3 SiO)C[double bond, length as m-dash]N-SitBu 3 and carbamine acid (tBu 3 SiO)CONH 2 . At first single crystals of the carbamine acid (tBu 3 SiO)CONH 2 (triclinic, space group P1[combining macron]) were grown from this solution at room temperature. A second crop of crystals were obtained by concentrating the solution. The second charge consisted of the imido carbonate (tBu 3 SiO)(Me 3 SiO)C[double bond, length as m-dash]N-SitBu 3 (monoclinic, space group P2 1 /n).

Upregulation of transferrin receptor-1 induces cholangiocarcinoma progression via induction of labile iron pool.

PubMed

Jamnongkan, Wassana; Thanan, Raynoo; Techasen, Anchalee; Namwat, Nisana; Loilome, Watcharin; Intarawichian, Piyapharom; Titapun, Attapol; Yongvanit, Puangrat

2017-07-01

Labile iron pool is a cellular source of ions available for Fenton reactions resulting in oxidative stress. Living organisms avoid an excess of free irons by a tight control of iron homeostasis. We investigated the altered expression of iron regulatory proteins and iron discrimination in the development of liver fluke-associated cholangiocarcinoma. Additionally, the levels of labile iron pool and the functions of transferrin receptor-1 on cholangiocarcinoma development were also identified. Iron deposition was determined using the Prussian blue staining method in human cholangiocarcinoma tissues. We investigated the alteration of iron regulatory proteins including transferrin, transferrin receptor-1, ferritin, ferroportin, hepcidin, and divalent metal transporter-1 in cholangiocarcinoma tissues using immunohistochemistry. The clinicopathological data of cholangiocarcinoma patients and the expressions of proteins were analyzed. Moreover, the level of intracellular labile iron pool in cholangiocarcinoma cell lines was identified by the RhoNox-1 staining method. We further demonstrated transferrin receptor-1 functions on cell proliferation and migration upon small interfering RNA for human transferrin receptor 1 transfection. Results show that Iron was strongly stained in tumor tissues, whereas negative staining was observed in normal bile ducts of healthy donors. Interestingly, high iron accumulation was significantly correlated with poor prognosis of cholangiocarcinoma patients. The expressions of iron regulatory proteins in human cholangiocarcinoma tissues and normal liver from cadaveric donors revealed that transferrin receptor-1 expression was increased in the cancer cells of cholangiocarcinoma tissues when compared with the adjacent normal bile ducts and was significantly correlated with cholangiocarcinoma metastasis. Labile iron pool level and transferrin receptor-1 expression were significantly increased in KKU-214 and KKU-213 when compared with cholangiocyte

Characterization and diagenesis of strong-acid carboxyl groups in humic substances

USGS Publications Warehouse

Leenheer, J.A.; Wershaw, R. L.; Brown, G.K.; Reddy, M.M.

2003-01-01

A small fraction of carboxylic acid functional groups in humic substances are exceptionally acidic with pKa values as low as 0.5. A review of acid-group theory eliminated most models and explanations for these exceptionally acidic carboxyl groups. These acidic carboxyl groups in Suwannee River fulvic acid were enriched by a 2-stage fractionation process and the fractions were characterized by elemental, molecular-weight, and titrimetric analyses, and by infrared and 13C- and 1H-nuclear magnetic resonance spectrometry. An average structural model of the most acidic fraction derived from the characterization data indicated a high density of carboxyl groups clustered on oxygen-heterocycle alicyclic rings. Intramolecular H-bonding between adjacent carboxyl groups in these ring structures enhanced stabilization of the carboxylate anion which results in low pKa1 values. The standard, tetrahydrofuran tetracarboxylic acid, was shown to have similar acidity characteristics to the highly acidic fulvic acid fraction. The end products of 3 known diagenetic pathways for the formation of humic substances were shown to result in carboxyl groups clustered on oxygen-heterocycle alicyclic rings.

Electrodermal lability as an indicator for subjective sleepiness during total sleep deprivation.

PubMed

Michael, Lars; Passmann, Sven; Becker, Ruth

2012-08-01

The present study addresses the suitability of electrodermal lability as an indicator of individual vulnerability to the effects of total sleep deprivation. During two complete circadian cycles, the effects of 48h of total sleep deprivation on physiological measures (electrodermal activity and body temperature), subjective sleepiness (measured by visual analogue scale and tiredness symptom scale) and task performance (reaction time and errors in a go/no go task) were investigated. Analyses of variance with repeated measures revealed substantial decreases of the number of skin conductance responses, body temperature, and increases for subjective sleepiness, reaction time and error rates. For all changes, strong circadian oscillations could be observed as well. The electrodermal more labile subgroup reported higher subjective sleepiness compared with electrodermal more stable participants, but showed no differences in the time courses of body temperature and task performance. Therefore, electrodermal lability seems to be a specific indicator for the changes in subjective sleepiness due to total sleep deprivation and circadian oscillations, but not a suitable indicator for vulnerability to the effects of sleep deprivation per se. © 2011 European Sleep Research Society.

Investigation of acyl migration in mono- and dicaffeoylquinic acids under aqueous basic, aqueous acidic, and dry roasting conditions.

PubMed

Deshpande, Sagar; Jaiswal, Rakesh; Matei, Marius Febi; Kuhnert, Nikolai

2014-09-17

Acyl migration in chlorogenic acids describes the process of migration of cinnamoyl moieties from one quinic acid alcohol group to another, thus interconverting chlorogenic acid regioisomers. It therefore constitutes a special case of transesterification reaction. Acyl migration constitutes an important reaction pathway in both coffee roasting and brewing, altering the structure of chlorogenic acid initially present in the green coffee bean. In this contribution we describe detailed and comprehensive mechanistic studies comparing inter- and intramolecular acyl migration involving the seven most common chlorogenic acids in coffee. We employe aqueous acidic and basic conditions mimicking the brewing of coffee along with dry roasting conditions. We show that under aqueous basic conditions intramolecular acyl migration is fully reversible with basic hydrolysis competing with acyl migration. 3-Caffeoylquinic acid was shown to be most labile to basic hydrolysis. We additionally show that the acyl migration process is strongly pH dependent with increased transesterification taking place at basic pH. Under dry roasting conditions acyl migration competes with dehydration to form lactones. We argue that acyl migration precedes lactonization, with 3-caffeoylquinic acid lactone being the predominant product.

Cytotoxic effects of polybasic acids, poly(alkenoic acid)s, and the monomers with various functional groups on human pulp fibroblasts.

PubMed

Kurata, Shigeaki; Morishita, Kumiko; Kawase, Toshio; Umemoto, Kozo

2011-01-01

This study evaluated the cytotoxicity of various polybasic acids, poly(alkenoic acid)s, and the monomers with various acidic functional groups such as carboxyl, phosphoryl, and sulfo group. The cell growth of fibroblasts cultivated in medium containing polybasic acids and polymers up to the concentration to 5 mmol/L was not significantly different compared with that of control without their acids. On the other hand, the cell growth fibroblasts cultivated in medium containing 1 mmol/L of the monomers with acryloyloxy and phosphoryl or carboxyl group decreased remarkably compared with that of the control and the cells were probably lifeless. Those exposed to the monomers with a ether bond and a carboxyl group or a amide bond and a sulfo group was not significantly different compared with that of control.

Comparison of folic acid levels in schizophrenic patients and control groups

NASA Astrophysics Data System (ADS)

Arthy, C. C.; Amin, M. M.; Effendy, E.

2018-03-01

Folic acid deficiency is a risk factor for schizophrenia through epidemiology, biochemistry and gene-related studies. Compared with healthy people, schizophrenic patients may have high homocysteine plasma values and homocysteine or low levels of folic acid, which seems to correlate with extrapyramidal motor symptoms caused by neuroleptic therapy and with symptoms of schizophrenia. In this present study, we focus on the difference of folic acid level between schizophrenic patient and control group. The study sample consisted of schizophrenic patients and 14 people in the control group and performed blood sampling to obtain the results of folic acid levels. The folic acid level in both groups was within normal range, but the schizophrenic patient group had lower mean folic acid values of 5.00 ng/ml (sb 1.66), compared with the control group with mean folic acid values of 10.75 ng/ml (sb 4.33). there was the group of the control group had a higher value of folic acid than the schizophrenic group.

Chemical Glucosylation of Labile Natural Products Using a (2-Nitrophenyl)acetyl-Protected Glucosyl Acetimidate Donor.

PubMed

Weber, Julia; Schwarz, Markus; Schiefer, Andrea; Hametner, Christian; Häubl, Georg; Fröhlich, Johannes; Mikula, Hannes

2018-06-07

The synthesis of (2-nitrophenyl)acetyl (NPAc)-protected glucosyl donors is described that were designed for the neighboring-group assisted glucosylation of base-labile natural products also being sensitive to hydrogenolysis. Glycosylation conditions were optimized using a trichloroacetimidate glucosyl donor, and cyclohexylmethanol and (+)-menthol as model acceptors. The approach was then extended to a one-pot procedure for the synthesis of 1,2- trans -glycosides. This method was finally applied for improved synthesis of the masked mycotoxin T2- O -β,d-glucoside.

Estimating soil labile organic carbon and potential turnover rates using a sequential fumigation–incubation procedure.

Treesearch

X.M. Zoua; H.H. Ruanc; Y. Fua; X.D. Yanga; L.Q. Sha

2005-01-01

Labile carbon is the fraction of soil organic carbon with most rapid turnover times and its oxidation drives the flux of CO2 between soils and atmosphere. Available chemical and physical fractionation methods for estimating soil labile organic carbon are indirect and lack a clear biological definition. We have modified the well-established Jenkinson and Powlson’s...

Ablation of Hepatic Production of the Acid-Labile Subunit in Bovine-GH Transgenic Mice: Effects on Organ and Skeletal Growth.

PubMed

Liu, Zhongbo; Han, Tianzhen; Fishman, Shannon; Butler, James; Zimmermann, Tracy; Tremblay, Frederic; Harbison, Carole; Agrawal, Nidhi; Kopchick, John J; Schaffler, Mitchell B; Yakar, Shoshana

2017-08-01

Growth hormone (GH) and insulinlike growth factor 1 (IGF-1) are anabolic hormones that facilitate somatic and skeletal growth and regulate metabolism via endocrine and autocrine/paracrine mechanisms. We hypothesized that excess tissue production of GH would protect skeletal growth and integrity in states of reduction in serum IGF-1 levels. To test our hypothesis, we used bovine GH (bGH) transgenic mice as a model of GH hypersecretion and ablated the liver-derived acid-labile subunit, which stabilizes IGF-1 complexes with IGF-binding protein-3 and -5 in circulation. We used a genetic approach to create bGH/als gene knockout (ALSKO) mice and small interfering RNA (siRNA) gene-silencing approach to reduce als or igf-1 gene expression. We found that in both models, decreased IGF-1 levels in serum were associated with decreased body and skeletal size of the bGH mice. Excess GH produced more robust bones but compromised mechanical properties in male mice. Excess GH production in tissues did not protect from trabecular bone loss in response to reductions in serum IGF-1 (in bGH/ALSKO or bGH mice treated with siRNAs). Reduced serum IGF-1 levels in the bGH mice did not alleviate the hyperinsulinemia and did not resolve liver or kidney pathologies that resulted from GH hypersecretion. We concluded that reduced serum IGF-1 levels decrease somatic and skeletal growth even in states of excess GH. Copyright © 2017 Endocrine Society.

Biotic and abiotic controls on diurnal fluctuations in labile soil phosphorus of a wet tropical forest.

PubMed

Vandecar, Karen L; Lawrence, Deborah; Wood, Tana; Oberbauer, Steven F; Das, Rishiraj; Tully, Katherine; Schwendenmann, Luitgard

2009-09-01

The productivity of many tropical wet forests is generally limited by bioavailable phosphorus (P). Microbial activity is a key regulator of P availability in that it determines both the supply of P through organic matter decomposition and the depletion of bioavailable P through microbial uptake. Both microbial uptake and mineralization occur rapidly, and their net effect on P availability varies with soil moisture, temperature, and soil organic matter quantity and quality. Exploring the mechanisms driving P availability at fine temporal scales can provide insight into the coupling of carbon, water, and nutrient cycles, and ultimately, the response of tropical forests to climate change. Despite the recognized importance of P cycling to the dynamics of wet tropical forests and their potential sensitivity to short-term fluctuations in bioavailable P, the diurnal pattern of P remains poorly understood. This study quantifies diurnal fluctuations in labile soil P and evaluates the importance of biotic and abiotic factors in driving these patterns. To this end, measurements of labile P were made every other hour in a Costa Rican wet tropical forest oxisol. Spatial and temporal variation in Bray-extractable P were investigated in relation to ecosystem carbon flux, soil CO2 efflux, soil moisture, soil temperature, solar radiation, and sap-flow velocity. Spatially averaged bi-hourly (every two hours) labile P ranged from 0.88 to 2.48 microg/g across days. The amplitude in labile P throughout the day was 0.61-0.82 microg/g (41-54% of mean P concentrations) and was characterized by a bimodal pattern with a decrease at midday. Labile P increased with soil CO2 efflux and soil temperature and declined with increasing sap flow and solar radiation. Together, soil CO2 efflux, soil temperature, and sap flow explained 86% of variation in labile P.

Strong-acid, carboxyl-group structures in fulvic acid from the Suwannee River, Georgia. 2. Major structures

USGS Publications Warehouse

Leenheer, J.A.; Wershaw, R. L.; Reddy, M.M.

1995-01-01

Polycarboxylic acid structures that account for the strong-acid characteristics (pKa1 near 2.0) were examined for fulvic acid from the Suwannee River. Studies of model compounds demonstrated that pKa values near 2.0 occur only if the ??-ether or ??-ester groups were in cyclic structures with two to three additional electronegative functional groups (carboxyl, ester, ketone, aromatic groups) at adjacent positions on the ring. Ester linkage removal by alkaline hydrolysis and destruction of ether linkages through cleavage and reduction with hydriodic acid confirmed that the strong carboxyl acidity in fulvic acid was associated with polycarboxylic ??-ether and ??-ester structures. Studies of hypothetical structural models of fulvic acid indicated possible relation of these polycarboxylic structures with the amphiphilic and metal-binding properties of fulvic acid.

Effect of inorganic and organic copper fertilizers on copper nutrition in Spinacia oleracea and on labile copper in soil.

PubMed

Obrador, Ana; Gonzalez, Demetrio; Alvarez, Jose M

2013-05-22

To ensure an optimal concentration of Cu in food crops, the effectiveness of eight liquid Cu fertilizers was studied in a spinach ( Spinacia oleracea L.) crop grown on Cu-deficient soil under greenhouse conditions. Plant dry matter yields, Cu concentrations in spinach plants (total and morpholino acid (MES)- and ethylenediaminedisuccinic acid (EDDS)-extractable), and Cu uptakes were studied. The behavior of Cu in soil was evaluated by both single and sequential extraction procedures. The highest quantities of Cu in labile forms in the soil, total uptakes, and Cu concentrations in the plants were associated with the application of the two sources that contained Cu chelated by EDTA and/or DTPA. The fertilizers containing these Cu chelates represent a promising approach to achieve high levels of agronomic biofortification. The stronger correlations obtained between low-molecular-weight organic acid-extractable Cu in soil and the Cu concentrations and Cu uptakes by the plants show the suitability of this soil extraction method for predicting Cu available to spinach plants.

Nutritional Requirements for Synthesis of Heat-Labile Enterotoxin by Enterotoxigenic Strains of Escherichia coli

PubMed Central

Gilligan, Peter H.; Robertson, Donald C.

1979-01-01

Optimal growth conditions have been established for production of heat-labile enterotoxin (LT) by both porcine and human strains of enterotoxigenic (ENT+) Escherichia coli. There were no unusual growth factor requirements, and some strains produced fairly high levels of LT in a basal salts medium containing 0.5% glucose if the pH was carefully controlled. Several amino acids markedly stimulated LT synthesis when added to the basal salts-glucose medium. Methionine and lysine were the most stimulatory for both human and porcine strains. Either aspartic acid or glutamic acid further enhanced LT synthesis in the presence of methionine and lysine, with aspartic acid being more stimulatory for porcine strains and glutamic acid more stimulatory for human strains. There were no apparent vitamin requirements and no unusual cations needed for toxin synthesis except that Fe3+ was slightly stimulatory for porcine strains. The stimulation by Fe3+ was observed only in the presence of the three amino acids, suggesting that the effect was indirect rather than on toxin synthesis. The carbon source also influenced the yield of LT. Glucose supported maximal synthesis, but other carbon sources which exhibit a high degree of catabolite repression also supported high levels of synthesis. Little or no LT was released below pH 7.0; therefore, because the pH drops during growth from 7.5 to 6.8, even in highly buffered media, it was necessary to adjust the pH to 8.0 to effect complete release of cell-associated toxin. The defined medium containing three amino acids reduced the amount of UV-absorbing material in culture supernatants about fivefold and increased LT activity for various strains from two- to fivefold over a complex Casamino Acids-yeast extract medium. Conditions found to be optimal for synthesis of LT were inhibitory for the heat-stable enterotoxin. PMID:33900

Assessment of the labile fractions of copper and zinc in marinas and port areas in Southern Brazil.

PubMed

Costa, Luiza Dy Fonseca; Wallner-Kersanach, Mônica

2013-08-01

The dissolved labile and labile particulate fractions (LPF) of Cu and Zn were analyzed during different seasons and salinity conditions in estuarine waters of marina, port, and shipyard areas in the southern region of the Patos Lagoon (RS, Brazil). The dissolved labile concentration was determined using the diffusive gradients in thin films technique (DGT). DGT devices were deployed in seven locations of the estuary for 72 h and the physicochemical parameters were also measured. The LPF of Cu and Zn was determined by daily filtering of water samples. Seasonal variation of DGT-Cu concentrations was only significant (p < 0.05) at one shipyard area, while DGT-Zn was significant (p < 0.05) in every locations. The LPF of Cu and Zn concentrations demonstrated seasonal and spatial variability in all locations, mainly at shipyard areas during high salinity conditions. In general, except the control location, the sampling locations showed mean variations of 0.11-0.45 μg L(-1) for DGT-Cu, 0.89-9.96 μg L(-1) for DGT-Zn, 0.65-3.69 μg g(-1) for LPF-Cu, and 1.35-10.87 μg g(-1) for LPF-Zn. Shipyard areas demonstrated the most expressive values of labile Cu and Zn in both fractions. Strong relationship between DGT-Zn and LPF-Zn was found suggesting that the DGT-Zn fraction originates from the suspended particulate matter. Water salinity and suspended particulate matter content indicated their importance for the control of the labile concentrations of Cu and Zn in the water column. These parameters must be taken into consideration for comparison among labile metals in estuaries.

Comparison of metal lability in air-dried and fresh dewatered drinking water treatment residuals.

PubMed

Wang, Changhui; Pei, Yuansheng; Zhao, Yaqian

2015-01-01

In this work, the labilities of Al, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sr, V and Zn in air-dried (for 60 days) and fresh dewatered WTRs were compared using the Toxicity Characteristic Leaching Procedure (TCLP), fractionation, in vitro digestion and a plant enrichment test. The results showed that the air-dried and fresh dewatered WTRs had different properties, e.g., organic matter composition and available nutrients. The air-dried and fresh dewatered WTRs were non-haf zardous according to the TCLP assessment method used in the United States; however, the metals in the two types of WTRs had different lability. Compared with the metals in the fresh dewatered WTRs, those in the air-dried WTRs tended to be in more stable fractions and also exhibited lower bioaccessibility and bioavailability. Therefore, air-drying can decrease the metal lability and thereby reduce the potential metal pollution risk of WTRs.

Impact of temperamental mood lability on depressive mixed state.

PubMed

Benazzi, Franco

2006-01-01

Cyclothymic temperament (which includes mood lability) is common in bipolar II disorder (BP-II). Depressive mixed state (DMX), a major depressive episode (MDE) mixed with intra-episode hypomanic symptoms (3 or more, according to a recently validated definition), was found to be common in BP-II and not uncommon in major depressive disorder (MDD). The study aim was to find the impact of temperamental mood lability (TML) on DMX. Consecutive 148 BP-II and 117 MDD outpatients presenting for MDE treatment were interviewed by the Structured Clinical Interview for DSM-IV as modified by Benazzi and Akiskal to reduce the false negative BP-II. Intra-MDE hypomanic symptoms were systematically assessed. Kraepelin, Angst, and Akiskal's definitions of temperamental mood lability (i.e., frequent up and down fluctuations of mood between major mood episodes since young age) were followed. DMX was present in 61.5%, TML in 52.8%. In the DMX sample, TML was present in 57.6%, and in the non-DMX sample TML was present in 45.0% (OR = 1.6, 95% CI = 1.0-2.7). In the DMX sample, independent predictors of DMX with TML were BP-II and young age at onset. Intra-MDE hypomanic symptoms, and MDE, melancholic and atypical symptoms were not significantly different between DMX patients with TML and DMX patients without TML, apart from more temperamental interpersonal sensitivity in DMX patients with TML (OR = 2.0, 95% CI = 1.0-3.8). DMX patients with TML had a younger onset age, suggesting that TML may facilitate the onset of DMX or that it may be a precursor of DMX. The association of BP-II with DMX, TML, and interpersonal sensitivity can make the course of BP-II more unstable and its treatment more complex.

Differential interaction of Escherichia coli heat-labile toxin and cholera toxin with pig intestinal brush border glycoproteins depending on their ABH and related blood group antigenic determinants.

PubMed

Balanzino, L E; Barra, J L; Monferran, C G; Cumar, F A

1994-04-01

The ability of glycoproteins from pig intestinal brush border membranes (BBM) to bind cholera toxin (CT) or heat-labile toxins from strains of Escherichia coli isolated from human (LTh) or pig (LTp) intestines was studied. Glycoproteins capable of binding the toxins are also recognized by antibodies or lectins specific for ABO(H) blood group and related antigens. Pigs expressing A, H, or I antigenic determinants were used for comparison. The toxin-binding capacity of a glycoprotein depends on the toxin type and the blood group epitope borne by the glycoprotein. LTh and LTp preferably bound to several blood group A-active glycoproteins rather than H-active glycoproteins. By contrast, CT practically did not recognize either blood group A- or blood group H-active glycoproteins, while glycoproteins from pigs expressing I antigenic determinants were able to interact with LTh, LTp, and CT. LTh, LTp, or CT glycoprotein binding was selectively inhibited by specific lectins or monosaccharides. Affinity purification of the toxin binding brush border glycoproteins on the basis of their blood group reactivity suggests that such glycoproteins are hydrolytic enzymes. BBM from A+ pigs contain about 27 times more LTh binding sites, in addition to those recognized by CT, than an equivalent membrane preparation from H+ pigs. The present findings may help clarify some previous unclear results on LTh binding to intestinal BBM glycoproteins obtained by use of animals not typed by their ABO(H) blood group phenotype.

Stabilized liquid membrane device (SLMD) for the passive, integrative sampling of labile metals in water

USGS Publications Warehouse

Brumbaugh, W.G.; Petty, J.D.; Huckins, J.N.; Manahan, S.E.

2002-01-01

A stabilized liquid membrane device (SLMD) is described for potential use as an in situ, passive, integrative sampler for cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) in natural waters. The SLMD (patent pending) consists of a 2.5-cm-wide by 15-cm-long strip of low-density polyethylene (LDPE) layflat tubing containing 1 mL of an equal mixture (v/v) of oleic acid (cis-9-octadecenoic acid) and EMO-8Q (7-[4-ethyl-1-methyloctyl]-8-quinolinol). The reagent mixture continuously diffuses to the exterior surface of the LDPE membrane, and provides for sequestration of several divalent metals for up to several weeks. Depending on sampler configuration, concentration factors of several thousand can be realized for these metal ions after just a few days. In addition to in situ deployment, the SLMD may be useful for laboratory determination of labile metal species in grab samples. Methods for minimizing the effects of water flow on the sampling rate are currently under investigation.

Measurement of labile copper in wine by medium exchange stripping potentiometry utilising screen printed carbon electrodes.

PubMed

Clark, Andrew C; Kontoudakis, Nikolaos; Barril, Celia; Schmidtke, Leigh M; Scollary, Geoffrey R

2016-07-01

The presence of copper in wine is known to impact the reductive, oxidative and colloidal stability of wine, and techniques enabling measurement of different forms of copper in wine are of particular interest in understanding these spoilage processes. Electrochemical stripping techniques developed to date require significant pretreatment of wine, potentially disturbing the copper binding equilibria. A thin mercury film on a screen printed carbon electrode was utilised in a flow system for the direct analysis of labile copper in red and white wine by constant current stripping potentiometry with medium exchange. Under the optimised conditions, including an enrichment time of 500s and constant current of 1.0μA, the response range was linear from 0.015 to 0.200mg/L. The analysis of 52 red and white wines showed that this technique generally provided lower labile copper concentrations than reported for batch measurement by related techniques. Studies in a model system and in finished wines showed that the copper sulfide was not measured as labile copper, and that loss of hydrogen sulfide via volatilisation induced an increase in labile copper within the model wine system. Copyright © 2016 Elsevier B.V. All rights reserved.

Detection and formation scenario of citric acid, pyruvic acid, and other possible metabolism precursors in carbonaceous meteorites

PubMed Central

Cooper, George; Reed, Chris; Nguyen, Dang; Carter, Malika; Wang, Yi

2011-01-01

Carbonaceous meteorites deliver a variety of organic compounds to Earth that may have played a role in the origin and/or evolution of biochemical pathways. Some apparently ancient and critical metabolic processes require several compounds, some of which are relatively labile such as keto acids. Therefore, a prebiotic setting for any such individual process would have required either a continuous distant source for the entire suite of intact precursor molecules and/or an energetic and compact local synthesis, particularly of the more fragile members. To date, compounds such as pyruvic acid, oxaloacetic acid, citric acid, isocitric acid, and α-ketoglutaric acid (all members of the citric acid cycle) have not been identified in extraterrestrial sources or, as a group, as part of a “one pot” suite of compounds synthesized under plausibly prebiotic conditions. We have identified these compounds and others in carbonaceous meteorites and/or as low temperature (laboratory) reaction products of pyruvic acid. In meteorites, we observe many as part of three newly reported classes of compounds: keto acids (pyruvic acid and homologs), hydroxy tricarboxylic acids (citric acid and homologs), and tricarboxylic acids. Laboratory syntheses using 13C-labeled reactants demonstrate that one compound alone, pyruvic acid, can produce several (nonenzymatic) members of the citric acid cycle including oxaloacetic acid. The isotopic composition of some of the meteoritic keto acids points to interstellar or presolar origins, indicating that such compounds might also exist in other planetary systems. PMID:21825143

Detection and formation scenario of citric acid, pyruvic acid, and other possible metabolism precursors in carbonaceous meteorites.

PubMed

Cooper, George; Reed, Chris; Nguyen, Dang; Carter, Malika; Wang, Yi

2011-08-23

Carbonaceous meteorites deliver a variety of organic compounds to Earth that may have played a role in the origin and/or evolution of biochemical pathways. Some apparently ancient and critical metabolic processes require several compounds, some of which are relatively labile such as keto acids. Therefore, a prebiotic setting for any such individual process would have required either a continuous distant source for the entire suite of intact precursor molecules and/or an energetic and compact local synthesis, particularly of the more fragile members. To date, compounds such as pyruvic acid, oxaloacetic acid, citric acid, isocitric acid, and α-ketoglutaric acid (all members of the citric acid cycle) have not been identified in extraterrestrial sources or, as a group, as part of a "one pot" suite of compounds synthesized under plausibly prebiotic conditions. We have identified these compounds and others in carbonaceous meteorites and/or as low temperature (laboratory) reaction products of pyruvic acid. In meteorites, we observe many as part of three newly reported classes of compounds: keto acids (pyruvic acid and homologs), hydroxy tricarboxylic acids (citric acid and homologs), and tricarboxylic acids. Laboratory syntheses using (13)C-labeled reactants demonstrate that one compound alone, pyruvic acid, can produce several (nonenzymatic) members of the citric acid cycle including oxaloacetic acid. The isotopic composition of some of the meteoritic keto acids points to interstellar or presolar origins, indicating that such compounds might also exist in other planetary systems.

Simultaneous quantification of soil phosphorus labile pool and desorption kinetics using DGTs and 3D-DIFS

NASA Astrophysics Data System (ADS)

Menezes-Blackburn, Daniel; Sun, Jiahui; Lehto, Niklas; Zhang, Hao; Stutter, Marc; Giles, Courtney D.; Darch, Tegan; George, Timothy S.; Shand, Charles; Lumsdon, David; Blackwell, Martin; Wearing, Catherine; Cooper, Patricia; Wendler, Renate; Brown, Lawrie; Haygarth, Philip M.

2017-04-01

The phosphorus (P) labile pool and desorption kinetics were simultaneously evaluated in ten representative UK soils using the technique of Diffusive gradients in thin films (DGT). The DGT-induced fluxes in soil and sediments model (DIFS) was fitted to the time series of DGT deployment (1h to 240h). The desorbable P concentration (labile P) was obtained by multiplying the fitted Kd by the soil solution P concentration obtained using Diffusive Equilibration in Thin Films (DET) devices. The labile P was then compared to several soil P extracts including Olsen P, Resin P, FeO-P and water extractable P, in order to assess if these analytical procedures can be used to represent the labile P across different soils. The Olsen P, commonly used as a representation of the soil labile P pool, overestimated the desorbable P concentration by a seven fold factor. The use of this approach for the quantification of soil P desorption kinetics parameters was somewhat unprecise, showing a wide range of equally valid solutions for the response of the system P equilibration time (Tc). Additionally, the performance of different DIFS model versions (1D, 2D and 3D) was compared. Although these models had a good fit to experimental DGT time series data, the fitted parameters showed a poor agreement between different model versions. The limitations of the DIFS model family are associated with the assumptions taken in the modelling approach and the 3D version is here considered to be the most precise among them.

Comparing Amino Acid Abundances and Distributions Across Carbonaceous Chondrite Groups

NASA Technical Reports Server (NTRS)

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

2012-01-01

Meteorites are grouped according to bulk properties such as chemical composition and mineralogy. These parameters can vary significantly among the different carbonaceous chondrite groups (CI, CM, CO, CR, CH, CB, CV and CK). We have determined the amino acid abundances of more than 30 primary amino acids in meteorites from each of the eight groups, revealing several interesting trends. There are noticeable differences in the structural diversity and overall abundances of amino acids between meteorites from the different chondrite groups. Because meteorites may have been an important source of amino acids to the prebiotic Earth and these organic compounds are essential for life as we know it, the observed variations of these molecules may have been important for the origins of life.

Development and Lability in the Parent-Child Relationship During Adolescence: Associations With Pubertal Timing and Tempo

PubMed Central

Marceau, Kristine; Ram, Nilam; Susman, Elizabeth

2014-01-01

Adolescents' and parents' reactions to pubertal development are hypothesized to contribute to changes in family dynamics. Using 7-year longitudinal data from the NICHD-SECCYD (488 boys, 475 girls) we examined relations between pubertal development (timing, tempo) and trajectories (developmental change and year-to-year lability) of parent-child conflict and closeness from age 8.5 to 15.5 years. Changes were mostly characterized by year-to-year fluctuations – lability. Parent-child conflict increased and closeness decreased some with age. Pubertal timing and tempo were more consistently associated with lability in parent-child relationships than with long-term trends, although faster tempo was associated with steeper decreases in parent-child closeness. Findings provide a platform for examining how puberty contributes to both long-term and transient changes in adolescents' relationships and adjustment. PMID:26321856

Immunogenicity of recombinant Lactobacillus casei-expressing F4 (K88) fimbrial adhesin FaeG in conjunction with a heat-labile enterotoxin A (LTAK63) and heat-labile enterotoxin B (LTB) of enterotoxigenic Escherichia coli as an oral adjuvant in mice.

PubMed

Yu, M; Qi, R; Chen, C; Yin, J; Ma, S; Shi, W; Wu, Y; Ge, J; Jiang, Y; Tang, L; Xu, Y; Li, Y

2017-02-01

The aims of this study were to develop an effective oral vaccine against enterotoxigenic Escherichia coli (ETEC) infection and to design new and more versatile mucosal adjuvants. Genetically engineered Lactobacillus casei strains expressing F4 (K88) fimbrial adhesin FaeG (rLpPG-2-FaeG) and either co-expressing heat-labile enterotoxin A (LTA) subunit with an amino acid mutation associated with reduced virulence (LTAK63) and a heat-labile enterotoxin B (LTB) subunit of E. coli (rLpPG-2-LTAK63-co-LTB) or fused-expressing LTAK63 and LTB (rLpPG-2-LTAK63-fu-LTB) were constructed. The immunogenicity of rLpPG-2-FaeG in conjunction with rLpPG-2-LTAK63-co-LTB or rLpPG-2-LTAK63-fu-LTB as an orally administered mucosal adjuvant in mice was evaluated. Results showed that the levels of FaeG-specific serum IgG and mucosal sIgA, as well as the proliferation of lymphocytes, were significantly higher in mice orally co-administered rLpPG-2-FaeG and rLpPG-2-LTAK63-fu-LTB compared with those administered rLpPG-2-FaeG alone, and were lower than those co-administered rLpPG-2-FaeG and rLpPG-2-LTAK63-co-LTB. Moreover, effective protection was observed after challenge with F4+ ETEC strain CVCC 230 in mice co-administered rLpPG-2-FaeG and rLpPG-2-LTAK63-co-LTB or rLpPG-2-FaeG and rLpPG-2-LTAK63-fu-LTB group compared with those that received rLpPG-2-FaeG alone. rLpPG-2-FaeG showed greater immunogenicity in combination with LTAK63 and LTB as molecular adjuvants. Recombinant Lactobacillus provides a promising platform for the development of vaccines against F4+ ETEC infection. © 2016 The Society for Applied Microbiology.

Diagnostic interest of acid-labile subunit measurement in relationship to other components of the IGF system in pediatric patients with growth or eating disorders.

PubMed

Barrios, V; Argente, J; Muñoz, M T; Pozo, J; Chowen, J A; Hernández, M

2001-03-01

To analyze the possible utility of measuring acid-labile subunit (ALS) in some types of pathologies in which the IGF system is altered and to compare it with the clinical implications of measurements of other components of this axis. We studied serum ALS concentrations in 20 children with normal variants of short stature (NVSS) at diagnosis and 24 with growth hormone deficiency (GHD), 18 obese patients and 18 girls with anorexia nervosa at diagnosis and during a follow-up period. In patients with GHD and anorexia nervosa, mean ALS concentrations were significantly reduced, but there was a high percentage of overlap with control values. At diagnosis, ALS concentrations were normal in obese patients and children with NVSS. During follow-up, these values normalized in children with GHD who were treated with GH, tended to normalize in those with anorexia nervosa who showed weight gain, and did not change in obese children upon weight loss. However, ALS measurement was less accurate than that of IGF-I or IGF binding protein (IGFBP)-3 in diagnosis of GHD. The correlations found between ALS and some IGF system components at diagnosis either decreased or were non-significant during follow-up of these clinical conditions. ALS adds little information to that obtained with IGF-I and IGFBP-3 determinations.

Use of an exchange method to estimate the association and dissociation rate constants of cadmium complexes formed with low-molecular-weight organic acids commonly exuded by plant roots.

PubMed

Schneider, André; Nguyen, Christophe

2011-01-01

Organic acids released from plant roots can form complexes with cadmium (Cd) in the soil solution and influence metal bioavailability not only due to the nature and concentration of the complexes but also due to their lability. The lability of a complex influences its ability to buffer changes in the concentration of free ions (Cd); it depends on the association (, m mol s) and dissociation (, s) rate constants. A resin exchange method was used to estimate and (m mol s), which is the conditional estimate of depending on the calcium (Ca) concentration in solution. The constants were estimated for oxalate, citrate, and malate, three low-molecular-weight organic acids commonly exuded by plant roots and expected to strongly influence Cd uptake by plants. For all three organic acids, the and estimates were around 2.5 10 m mol s and 1.3 × 10 s, respectively. Based on the literature, these values indicate that the Cd- low-molecular-weight organic acids complexes formed between Cd and low-molecular-weight organic acids may be less labile than complexes formed with soil soluble organic matter but more labile than those formed with aminopolycarboxylic chelates. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Sensitivity-enhanced detection of non-labile proton and carbon NMR spectra on water resonances.

PubMed

Novakovic, Mihajlo; Martinho, Ricardo P; Olsen, Gregory L; Lustig, Michael S; Frydman, Lucio

2017-12-20

Chemical exchange saturation transfer (CEST) experiments enhance the NMR signals of labile protons by continuously transferring these protons' saturation to an abundant solvent pool like water. The present study expands these principles by fusing into these experiments homonuclear isotropic mixing sequences, enabling the water-enhanced detection of non-exchangeable species. Further opportunities are opened by the addition of coupling-mediated heteronuclear polarization transfers, which then impose on the water resonance a saturation stemming from non-labile heteronuclear species like 13 C. To multiplex the ensuing experiments, these relayed approaches are combined with time-domain schemes involving multiple Ramsey-labeling experiments imparting the frequencies of the non-labile sites on the water resonance, via chemical exchange. 13 C and 1 H NMR spectra were detected in this fashion with about two-fold SNR amplification vis-à-vis conventionally detected spectroscopies. When combined with non-uniform sampling principles, this methodology thus becomes a sensitive alternative to detect non-exchangeable species in biomolecules. Still, multiple parameters including the scalar couplings and solvent exchange rates, will affect the efficiency and consequently the practicality of the overall experiment.

Substrate lability and plant activity controls greenhouse gas release from Neotropical peatland

NASA Astrophysics Data System (ADS)

Sjogersten, Sofie; Hoyos, Jorge; Lomax, Barry; Turner, Ben; Wright, Emma

2014-05-01

Almost one third of global CO2 emissions resulting from land use change and substantial CH4 emissions originate from tropical peatlands. However, our understanding of the controls of CO2 and CH4 release from tropical peatlands are limited. The aim of this study was to investigate the role of peat lability and the activity of the vegetation on gas release using a combination of field and laboratory experiments. We demonstrated that peat lability constrained CH4 production to the surface peat under anaerobic conditions. The presence of plants shifted the C balance from a C source to a C sink with respect to CO2 while the activity of the root system strongly influenced CH4 emissions through its impact on soil O2 inputs. Both field and laboratory data suggest a coupling between the photosynthetic activity of the vegetation and the release of both CO2 and CH4 following the circadian rhythm of the dominant plant functional types. Forest clearance for agriculture resulted in elevated CH4 release, which we attribute in part to the cessation of root O2 inputs to the peat. We conclude that high emissions of CO2 and CH4 from forested tropical peatlands are likely driven by labile C inputs from the vegetation but that root O2 release may limit CH4 emissions.

Oxidation of indole-3-acetic acid to oxindole-3-acetic acid by an enzyme preparation from Zea mays

NASA Technical Reports Server (NTRS)

Reinecke, D. M.; Bandurski, R. S.

1988-01-01

Indole-3-acetic acid is oxidized to oxindole-3-acetic acid by Zea mays tissue extracts. Shoot, root, and endosperm tissues have enzyme activities of 1 to 10 picomoles per hour per milligram protein. The enzyme is heat labile, is soluble, and requires oxygen for activity. Cofactors of mixed function oxygenase, peroxidase, and intermolecular dioxygenase are not stimulatory to enzymic activity. A heat-stable, detergent-extractable component from corn enhances enzyme activity 6- to 10-fold. This is the first demonstration of the in vitro enzymic oxidation of indole-3-acetic acid to oxindole-3-acetic acid in higher plants.

Evaluating Multiple Drivers of Soil Organic Matter Lability and Structure in a Sub-Alpine Forest Ecosystem

NASA Astrophysics Data System (ADS)

Hall, E.; Fegel, T. S., II; Boot, C. M.

2014-12-01

Aeolian deposition of reactive nitrogen (N) is reaching even the most remote ecosystems. There has been an abundance of research investigating how these subsidies of reactive N may alter fundamental ecosystem characteristics such as soil organic matter (SOM) pool size. Previous studies have reported that additions of reactive N have the potential to both increase and decrease SOM content. While there are a series of different variables that may affect the size of the SOM pool it has been suggested that the lability or recalcitrance of the SOM may be related to its chemical composition (kind and relative abundance of constituent molecules). To address this we sampled 6 experimental plots in a sub-alpine forest in Rocky Mountain National Park (3 control and 3 treated with reactive N for 18 years) during two months in the summers of 2011 and 2012. We found the SOM content of the control plots was greater than that of the experimental plots. To assess lability of each SOM sample we extracted the SOM from each plot with water and incubated the dissolved organic carbon with a common aquatic microbial community from a lake within the watershed. To assess structure of the SOM pool we used ultra performance liquid chromatography (UPLC) coupled with MS of each extract before incubation with the bacterial community. The dissolved component of the SOM showed clear differences in lability both in total quantity and rate of decomposition during incubation with aquatic microorganisms. Principle components analysis indicated season was a stronger driver of DOM composition than fertilization, describing the majority of the variability between July and September 2012. When samples were considered within a season and year there were additional differences in both lability and composition of DOM. Here we evaluate the relative influence of inter- and intra-annual variability and reactive N on both the characteristics and composition of SOM. By linking UPLC-MS with a functional assay of

Capturing Labile Sulfenamide and Sulfinamide Serum Albumin Adducts of Carcinogenic Arylamines by Chemical Oxidation

PubMed Central

Peng, Lijuan; Turesky, Robert J.

2013-01-01

Aromatic amines and heterocyclic aromatic amines (HAAs) are a class of structurally related carcinogens that are formed during the combustion of tobacco or during the high temperature cooking of meats. These procarcinogens undergo metabolic activation by N-oxidation of the exocyclic amine group to produce N-hydroxylated metabolites, which are critical intermediates implicated in toxicity and DNA damage. The arylhydroxylamines and their oxidized arylnitroso derivatives can also react with cysteine (Cys) residues of glutathione or proteins to form, respectively, sulfenamide and sulfinamide adducts. However, sulfur-nitrogen linked adducted proteins are often difficult to detect because they are unstable and undergo hydrolysis during proteolytic digestion. Synthetic N-oxidized intermediates of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a carcinogenic HAA produced in cooked meats, and 4-aminobiphenyl, a carcinogenic aromatic amine present in tobacco smoke were reacted with human serum albumin (SA) and formed labile sulfenamide or sulfinamide adducts at the Cys34 residue. Oxidation of the carcinogen-modified SA with m-chloroperoxybenzoic acid (m-CPBA) produced the arylsulfonamide adducts, which were stable to heat and the chemical reduction conditions employed to denature SA. The sulfonamide adducts of PhIP and 4-ABP were identified, by liquid chromatography/mass spectrometry, in proteolytic digests of denatured SA. Thus, selective oxidation of arylamine-modified SA produces stable arylsulfonamide-SA adducts, which may serve as biomarkers of these tobacco and dietary carcinogens. PMID:23240913

Genetic analysis of groups of mid-infrared predicted fatty acids in milk.

PubMed

Narayana, S G; Schenkel, F S; Fleming, A; Koeck, A; Malchiodi, F; Jamrozik, J; Johnston, J; Sargolzaei, M; Miglior, F

2017-06-01

The objective of this study was to investigate genetic variability of mid-infrared predicted fatty acid groups in Canadian Holstein cattle. Genetic parameters were estimated for 5 groups of fatty acids: short-chain (4 to 10 carbons), medium-chain (11 to 16 carbons), long-chain (17 to 22 carbons), saturated, and unsaturated fatty acids. The data set included 49,127 test-day records from 10,029 first-lactation Holstein cows in 810 herds. The random regression animal test-day model included days in milk, herd-test date, and age-season of calving (polynomial regression) as fixed effects, herd-year of calving, animal additive genetic effect, and permanent environment effects as random polynomial regressions, and random residual effect. Legendre polynomials of the third degree were selected for the fixed regression for age-season of calving effect and Legendre polynomials of the fourth degree were selected for the random regression for animal additive genetic, permanent environment, and herd-year effect. The average daily heritability over the lactation for the medium-chain fatty acid group (0.32) was higher than for the short-chain (0.24) and long-chain (0.23) fatty acid groups. The average daily heritability for the saturated fatty acid group (0.33) was greater than for the unsaturated fatty acid group (0.21). Estimated average daily genetic correlations were positive among all fatty acid groups and ranged from moderate to high (0.63-0.96). The genetic correlations illustrated similarities and differences in their origin and the makeup of the groupings based on chain length and saturation. These results provide evidence for the existence of genetic variation in mid-infrared predicted fatty acid groups, and the possibility of improving milk fatty acid profile through genetic selection in Canadian dairy cattle. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Sources and Fates of Carbamyl Phosphate: A Labile Energy-Rich Molecule with Multiple Facets.

PubMed

Shi, Dashuang; Caldovic, Ljubica; Tuchman, Mendel

2018-06-12

Carbamyl phosphate (CP) is well-known as an essential intermediate of pyrimidine and arginine/urea biosynthesis. Chemically, CP can be easily synthesized from dihydrogen phosphate and cyanate. Enzymatically, CP can be synthesized using three different classes of enzymes: (1) ATP-grasp fold protein based carbamyl phosphate synthetase (CPS); (2) Amino-acid kinase fold carbamate kinase (CK)-like CPS (anabolic CK or aCK); and (3) Catabolic transcarbamylase. The first class of CPS can be further divided into three different types of CPS as CPS I, CPS II, and CPS III depending on the usage of ammonium or glutamine as its nitrogen source, and whether N -acetyl-glutamate is its essential co-factor. CP can donate its carbamyl group to the amino nitrogen of many important molecules including the most well-known ornithine and aspartate in the arginine/urea and pyrimidine biosynthetic pathways. CP can also donate its carbamyl group to the hydroxyl oxygen of a variety of molecules, particularly in many antibiotic biosynthetic pathways. Transfer of the carbamyl group to the nitrogen group is catalyzed by the anabolic transcarbamylase using a direct attack mechanism, while transfer of the carbamyl group to the oxygen group is catalyzed by a different class of enzymes, CmcH/NodU CTase, using a different mechanism involving a three-step reaction, decomposition of CP to carbamate and phosphate, transfer of the carbamyl group from carbamate to ATP to form carbamyladenylate and pyrophosphate, and transfer of the carbamyl group from carbamyladenylate to the oxygen group of the substrate. CP is also involved in transferring its phosphate group to ADP to generate ATP in the fermentation of many microorganisms. The reaction is catalyzed by carbamate kinase, which may be termed as catabolic CK (cCK) in order to distinguish it from CP generating CK. CP is a thermally labile molecule, easily decomposed into phosphate and cyanate, or phosphate and carbamate depending on the pH of the solution

Protein degradation by ubiquitin–proteasome system in formation and labilization of contextual conditioning memory

PubMed Central

Sol Fustiñana, María; de la Fuente, Verónica; Federman, Noel; Freudenthal, Ramiro

2014-01-01

The ubiquitin–proteasome system (UPS) of protein degradation has been evaluated in different forms of neural plasticity and memory. The role of UPS in such processes is controversial. Several results support the idea that the activation of this system in memory consolidation is necessary to overcome negative constrains for plasticity. In this case, the inhibition of the UPS during consolidation impairs memory. Similar results were reported for memory reconsolidation. However, in other cases, the inhibition of UPS had no effect on memory consolidation and reconsolidation but impedes the amnesic action of protein synthesis inhibition after retrieval. The last finding suggests a specific action of the UPS inhibitor on memory labilization. However, another interpretation is possible in terms of the synthesis/degradation balance of positive and negative elements in neural plasticity, as was found in the case of long-term potentiation. To evaluate these alternative interpretations, other reconsolidation-interfering drugs than translation inhibitors should be tested. Here we analyzed initially the UPS inhibitor effect in contextual conditioning in crabs. We found that UPS inhibition during consolidation impaired long-term memory. In contrast, UPS inhibition did not affect memory reconsolidation after contextual retrieval but, in fact, impeded memory labilization, blocking the action of drugs that does not affect directly the protein synthesis. To extend these finding to vertebrates, we performed similar experiments in contextual fear memory in mice. We found that the UPS inhibitor in hippocampus affected memory consolidation and blocked memory labilization after retrieval. These findings exclude alternative interpretations to the requirement of UPS in memory labilization and give evidence of this mechanism in both vertebrates and invertebrates. PMID:25135196

A Double Blind Trial of Divalproex Sodium for Affective Lability and Alcohol Use Following Traumatic Brain Injury

DTIC Science & Technology

2010-10-01

comparable to lithium in treating acutely manic bipolar patients, and the FDA approved it in 1995 for this indication. Also, it is used in conjunction with...A Double Blind Trial of Divalproex Sodium for Affective Lability and Alcohol Use Following Traumatic Brain Injury PRINCIPAL INVESTIGATOR...Lability and Alcohol Use Following Traumatic Brain Injury 5b. GRANT NUMBER W81XWH-08-2-0652 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S

An anaerobic incubation study of metal lability in drinking water treatment residue with implications for practical reuse.

PubMed

Wang, Changhui; Yuan, Nannan; Pei, Yuansheng

2014-06-15

Drinking water treatment residue (WTR) is an inevitable by-product generated during the treatment of drinking water with coagulating agents. The beneficial reuse of WTR as an amendment for environmental remediation has attracted growing interest. In this work, we investigated the lability of Al, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sr, V and Zn in Fe/Al hydroxide-comprised WTR based on a 180-day anaerobic incubation test using fractionation, in vitro digestion and a toxicity characteristic leaching procedure. The results indicated that most metals in the WTR were stable during anaerobic incubation and that the WTR before and after incubation could be considered non-hazardous in terms of leachable metal contents according to US EPA Method 1311. However, the lability of certain metals in the WTR after incubation increased substantially, especially Mn, which may be due to the reduction effect. Therefore, although there is no evidence presented to restrict the use of WTR in the field, the lability of metals (especially Mn) in WTR requires further assessment prior to field application. In addition, fractionation (e.g., BCR) is recommended for use to determine the potential lability of metals under various conditions. Copyright © 2014 Elsevier B.V. All rights reserved.

The interactive effects of affect lability, negative urgency, and sensation seeking on young adult problematic drinking.

PubMed

Karyadi, Kenny; Coskunpinar, Ayca; Dir, Allyson L; Cyders, Melissa A

2013-01-01

Prior studies have suggested that affect lability might reduce the risk for problematic drinking among sensation seekers by compensating for their deficiencies in emotional reactivity and among individuals high on negative urgency by disrupting stable negative emotions. Due to the high prevalence of college drinking, this study examined whether affect lability interacted with sensation seeking and negative urgency to influence college student problematic drinking. 414 college drinkers (mean age: 20, 77% female, and 74% Caucasian) from a US Midwestern University completed self-administered questionnaires online. Consistent with our hypotheses, our results indicated that the effects of sensation seeking and negative urgency on problematic drinking weakened at higher levels of affect lability. These findings emphasize the importance of considering specific emotional contexts in understanding how negative urgency and sensation seeking create risk for problematic drinking among college students. These findings might also help us better understand how to reduce problematic drinking among sensation seekers and individuals high on negative urgency.

The Interactive Effects of Affect Lability, Negative Urgency, and Sensation Seeking on Young Adult Problematic Drinking

PubMed Central

Karyadi, Kenny; Coskunpinar, Ayca; Dir, Allyson L.; Cyders, Melissa A.

2013-01-01

Prior studies have suggested that affect lability might reduce the risk for problematic drinking among sensation seekers by compensating for their deficiencies in emotional reactivity and among individuals high on negative urgency by disrupting stable negative emotions. Due to the high prevalence of college drinking, this study examined whether affect lability interacted with sensation seeking and negative urgency to influence college student problematic drinking. 414 college drinkers (mean age: 20, 77% female, and 74% Caucasian) from a US Midwestern University completed self-administered questionnaires online. Consistent with our hypotheses, our results indicated that the effects of sensation seeking and negative urgency on problematic drinking weakened at higher levels of affect lability. These findings emphasize the importance of considering specific emotional contexts in understanding how negative urgency and sensation seeking create risk for problematic drinking among college students. These findings might also help us better understand how to reduce problematic drinking among sensation seekers and individuals high on negative urgency. PMID:24826366

Effect of Acid on Surface Hydroxyl Groups on Kaolinite and Montmorillonite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sihvonen, Sarah K.; Murphy, Kelly A.; Washton, Nancy M.

Mineral dust aerosol participates in heterogeneous chemistry in the atmosphere. In particular, the hydroxyl groups on the surface of aluminosilicate clay minerals are important for heterogeneous atmospheric processes. These functional groups may be altered by acidic processing during atmospheric transport. In this study, we exposed kaolinite (KGa-1b) and montmorillonite (STx-1b) to aqueous sulfuric acid and then rinsed the soluble reactants and products off in order to explore changes to functional groups on the mineral surface. To quantify the changes due to acid treatment of edge hydroxyl groups, we use 19F magic angle spinning nuclear magnetic resonance spectroscopy and a probemore » molecule, 3,3,3-trifluoropropyldimethylchlorosilane. We find that the edge hydroxyl groups (OH) increase in both number and density with acid treatment. Chemical reactions in the atmosphere may be impacted by the increase in OH at the mineral edge.« less

Analysis and modeling of heat-labile enterotoxins of Escherichia coli suggests a novel space with insights into receptor preference.

PubMed

Krishna Raja, M; Ghosh, Asit Ranjan; Vino, S; Sajitha Lulu, S

2015-01-01

Features of heat-labile enterotoxins of Escherichia coli which make them fit to use as novel receptors for antidiarrheals are not completely explored. Data-set of 14 different serovars of enterotoxigenic Escherichia coli producing heat-labile toxins were taken from NCBI Genbank database and used in the study. Sequence analysis showed mutations in different subunits and also at their interface residues. As these toxins lack crystallography structures, homology modeling using Modeller 9.11 led to the structural approximation for the E. coli producing heat-labile toxins. Interaction of modeled toxin subunits with proanthocyanidin, an antidiarrheal showed several strong hydrogen bonding interactions at the cost of minimized energy. The hits were subsequently characterized by molecular dynamics simulation studies to monitor their binding stabilities. This study looks into novel space where the ligand can choose the receptor preference not as a whole but as an individual subunit. Mutation at interface residues and interaction among subunits along with the binding of ligand to individual subunits would help to design a non-toxic labile toxin and also to improve the therapeutics.

Protection of Pyruvate,Pi Dikinase from Maize against Cold Lability by Compatible Solutes 1

PubMed Central

Krall, John P.; Edwards, Gerald E.; Andreo, Carlos S.

1989-01-01

Most C4 species are chilling sensitive and certain enzymes like pyruvate,Pi dikinase of the C4 pathway are also cold labile. The ability of cations and compatible solutes to protect maize (Zea mays) dikinase against cold lability was examined. The enzyme in desalted extracts at pH 8 from preilluminated leaves could be protected against cold lability (at 0°C) by the divalent cations Mn2+, Mg2+, and Ca2+. There was substantial protection by sulfate based salts but little protection by chloride based salts of potassium or ammonium (concentration 250 millimolar). The degree of protection against cold lability under limiting MgCl2 (5 millimolar) was pH sensitive (maximum protection at pH 8), but independent of ionic strength (up to 250 millimolar by addition of KCl). In catalysis Mg2+ is required and Mn2+ could not substitute as a cofactor. Several compatible solutes reduced or prevented the cold inactivation of dikinase (in desalted extracts and the partially purified enzyme), including glycerol, proline, glycinebetaine and trimethylamine-N-oxide (TMAO). TMAO and Mg2+ had an additive effect in protecting dikinase against cold inactivation. TMAO could largely substitute for the divalent cation and addition of TMAO during cold treatment prevented further inactivation. Cold inactivation was partially reversed by incubation at room temperature; with addition of TMAO reversal was complete. The temperature dependence of inactivation at pH 8 and 3 millimolar MgCl2 was evaluated by incubation at 2 to 17°C for 45 minutes, followed by assay at room temperature. At preincubation temperatures below 11°C there was a progressive inactivation which could be prevented by TMAO (450 millimolar). The results are discussed relative to possible effects of the solutes on the quaternary structure of this enzyme, which is known to dissociate at low temperatures. PMID:16666527

Characteristics of labile organic carbon fractions in reclaimed mine soils: Evidence from three reclaimed forests in the Pingshuo opencast coal mine, China.

PubMed

Yuan, Ye; Zhao, Zhongqiu; Li, Xuezhen; Wang, Yangyang; Bai, Zhongke

2018-02-01

The reclamation of discarded spoils has the potential to stimulate carbon (C) sequestration in reclaimed mine soils (RMSs). Nevertheless, to date the temporal dynamics of labile organic C fractions have not been sufficiently elucidated in RMSs. In this study, soil organic carbon (SOC) and labile organic C fractions, including microbial biomass organic C (MBC), easily oxidizable organic C (EOC) and dissolved organic C (DOC), were determined in Robinia pseudoacacia monoculture forests (reclamation periods of 0, 8, 10, 13, 15, 18 and 30years), Pinus tabuliformis forests (reclamation periods of 0, 10, 19, 23 and 25years) and Ulmus pumila forests (reclamation periods of 0, 18, 20 and 22years) situated on RMSs in the Pingshuo opencast coal mine, China. Changes in labile organic C fractions within the soil profiles (0-100cm) were also identified at the 18- or 19-year plots under the three monoculture forests. Our results showed that, SOC and labile organic C fractions, together with soil microbial quotient (SMQ) and C management index (CMI), increased with time since reclamation, indicating that the quality of RMSs improved over time after initial reclamation under the three forest types. R. pseudoacacia significantly increased the accretion of SOC and EOC in the early stage of reclamation while P. tabuliformis accelerated the accumulation of the MBC fraction. Results for U. pumila indicated that this species had a better ability to store C in RMSs 10years or more after reclamation. SOC and labile organic C fractions both had S-shaped distributions within the soil profiles (0-100cm), with the 0-20cm layer recording the highest values (P<0.05). Labile organic C fractions were closely associated and correlated with soil physicochemical properties; our results also showed that nitrogen played an important role in the development of labile organic C fractions. Overall, reclamation accelerated the accretion of both SOC and labile organic C fractions, results of which varied

Host-Pathogen interactions. 25. Endopolygalacturonic acid lyase from Erwinia carotovora elicits phytoalexin accumulation by releasing plant cell wall fragments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, K.R.; Lyon, G.D.; Darvill, A.G.

1984-01-01

Heat-labile elicitors of phytoalexin accumulation in soybeans (Glycine max L. Merr. cv Wayne) were detected in culture filtrates of Erwinia carotovora grown on a defined medium containing citrus pectin as the sole carbon source. The heat-labile elicitors were highly purified by cation-exchange chromatography on a CM-Sephadex (C-50) column, followed by agarose-affinity chromatography on a Bio-Gel A-0.5m gel filtration column. The heat-labile elicitor activity co-purified with two ..cap alpha..-1,4-endopolygalacturonic acid lyases (EC 4 x 2 x 2 x 2). Endopolygalacturonic acid lyase activity appeared to be necessary for elicitor activity because heat-inactivated enzyme preparations did not elicit phytoalexins. The purified endopolygalacturonicmore » acid lyases elicited pterocarpan phytoalexins at microbial-inhibitory concentrations in the soybean-cotyledon bioassay when applied at a concentration of 55 nanograms per milliliter (1 x 10/sup -9/ molar). One of these lyases released heat-stable elicitors from soybean cell walls, citrus pectin, and sodium polypectate. The heat-stable elicitor-active material solubilized from soybean cell walls by the lyase was composed of at least 90% (w/v) uronosyl residues. These results demonstrate that endopolygalacturonic acid lyase elicits phytoalexin accumulation by releasing fragments from pectic polysaccharides in plant cell walls.« less

Mechanism-based design of labile precursors for chromium(I) chemistry

DOE PAGES

Akturk, Eser S.; Yap, Glenn P. A.; Theopold, Klaus H.

2015-08-27

Here, we report that dinitrogen complexes of the type Tp R,RCr–N 2–CrTp R,R are not the most labile precursors for Cr(I) chemistry, as they are sterically protected from obligatory associative ligand substitution. A mononuclear alkyne complex – Tp tBu,MeCr(η 2-C 2(SiMe 3) 2) – proved to be much more reactive.

Immunologic Interrelationships of Coliform Heat-Labile and Heat-Stable Enterotoxins

DTIC Science & Technology

1980-01-15

PUBLICATIONS Supported by Contract No. DAMD 17-77-C-7032 1. Klipstein FA, Engert RF: Immunological interrelationships between cholera toxin and the...heat-labile and heat-stable enterotoxins of coliform bacteria. Infec Immun 18:110, 1977 2. Klipstein FA, Engert RF: Immunological relationship of...different preparations of coliform enterotoxins. Infec Immun 21:771, 1978 3. Klipstein FA, Engert RF: Reversal of jejunal water secretion by glucose in

Immunological Interrelationships of Coliform Heat-Labile and Heat-Stable Enterotoxins

DTIC Science & Technology

1981-01-01

FA, Engert RF: Immunological interrelationships between cholera toxin and the heat-labile and heat-stable enterotoxins of coliforn, bacteria. Infec...Irnmun 18:110, 1977 2. Klipstein FA, Engert RF: Immunological relaticnsh~p of different preparations of coliform enterotoxins. Infec Immun 21:771, 1918...3 Klipstein FA, Engert RF: Reversal of jejunal water secretion by glucose in rats exposed to coliform enterotoxcins. Gastroenterology 75:255, 1978 4

Immunological Interrelationships of Coliform Heat-Labile and Heat-Stable Enterotoxins

DTIC Science & Technology

1981-09-01

FA, Engert RF: Immunological interrelationships between cholera toxin and the heat -labile and hoat-stable enterotoxins of coliform bacteria. Infec...Immun 18:110, 1977 2. Klipstein FA, Engert RF: Immunological relationship of different preparations of coliform enterotoxins. Infec Immun 21:771, 1978...3. Klipstein FA, Engert RF: Reversal of jejunal water secretion by glucose in rats exposed to coliform enterotoxins. Gastroenteroloj y 75:255, 1978 4

Microbial control of soil organic matter mineralization responses to labile carbon in subarctic climate change treatments.

PubMed

Rousk, Kathrin; Michelsen, Anders; Rousk, Johannes

2016-12-01

Half the global soil carbon (C) is held in high-latitude systems. Climate change will expose these to warming and a shift towards plant communities with more labile C input. Labile C can also increase the rate of loss of native soil organic matter (SOM); a phenomenon termed 'priming'. We investigated how warming (+1.1 °C over ambient using open top chambers) and litter addition (90 g m -2  yr -1 ) treatments in the subarctic influenced the susceptibility of SOM mineralization to priming, and its microbial underpinnings. Labile C appeared to inhibit the mineralization of C from SOM by up to 60% within hours. In contrast, the mineralization of N from SOM was stimulated by up to 300%. These responses occurred rapidly and were unrelated to microbial successional dynamics, suggesting catabolic responses. Considered separately, the labile C inhibited C mineralization is compatible with previously reported findings termed 'preferential substrate utilization' or 'negative apparent priming', while the stimulated N mineralization responses echo recent reports of 'real priming' of SOM mineralization. However, C and N mineralization responses derived from the same SOM source must be interpreted together: This suggested that the microbial SOM-use decreased in magnitude and shifted to components richer in N. This finding highlights that only considering SOM in terms of C may be simplistic, and will not capture all changes in SOM decomposition. The selective mining for N increased in climate change treatments with higher fungal dominance. In conclusion, labile C appeared to trigger catabolic responses of the resident microbial community that shifted the SOM mining to N-rich components; an effect that increased with higher fungal dominance. Extrapolating from these findings, the predicted shrub expansion in the subarctic could result in an altered microbial use of SOM, selectively mining it for N-rich components, and leading to a reduced total SOM-use. © 2016 John Wiley

Genetic correlations of mid-infrared-predicted milk fatty acid groups with milk production traits.

PubMed

Fleming, A; Schenkel, F S; Malchiodi, F; Ali, R A; Mallard, B; Sargolzaei, M; Jamrozik, J; Johnston, J; Miglior, F

2018-05-01

The objective of this research was to estimate the genetic correlations between milk mid-infrared-predicted fatty acid groups and production traits in first-parity Canadian Holsteins. Contents of short-chain, medium-chain, long-chain, saturated, and unsaturated fatty acid groupings in milk samples can be predicted using mid-infrared spectral data for cows enrolled in milk recording programs. Predicted fatty acid group contents were obtained for 49,127 test-day milk samples from 10,029 first-parity Holstein cows in 810 herds. Milk yield, fat and protein yield, fat and protein percentage, fat-to-protein ratio, and somatic cell score were also available for these test days. Genetic parameters were estimated for the fatty acid groups and production traits using multiple-trait random regression test day models by Bayesian methods via Gibbs sampling. Three separate 8- or 9-trait analyses were performed, including the 5 fatty acid groups with different combinations of the production traits. Posterior standard deviations ranged from <0.001 to 0.01. Average daily genetic correlations were negative and similar to each other for the fatty acid groups with milk yield (-0.62 to -0.59) and with protein yield (-0.32 to -0.25). Weak and positive average daily genetic correlations were found between somatic cell score and the fatty acid groups (from 0.25 to 0.36). Stronger genetic correlations with fat yield, fat and protein percentage, and fat-to-protein ratio were found with medium-chain and saturated fatty acid groups compared with those with long-chain and unsaturated fatty acid groups. Genetic correlations were very strong between the fatty acid groups and fat percentage, ranging between 0.88 for unsaturated and 0.99 for saturated fatty acids. Daily genetic correlations from 5 to 305 d in milk with milk, protein yield and percentage, and somatic cell score traits showed similar patterns for all fatty acid groups. The daily genetic correlations with fat yield at the beginning

Versatile Synthesis of Amino Acid Functional Polymers without Protection Group Chemistry.

PubMed

Brisson, Emma R L; Xiao, Zeyun; Franks, George V; Connal, Luke A

2017-01-09

The copolymerization of N-isopropylacrylamide (NiPAm) with aldehyde functional monomers facilitates postpolymerization functionalization with amino acids via reductive amination, negating the need for protecting groups. In reductive amination, the imine formed from the condensation reaction between an amine and an aldehyde is reduced to an amine. In this work, we categorize amino acids into four classes based on the functionality of their side chains (acidic, polar neutral, neutral, and basic) and use their amine groups in condensation reactions with aldehyde functional polymers. The dynamic nature of the imine as well as the versatility of reductive amination to functionalize a polymer with a range of amino acids is highlighted. In this manner, amino acid functional polymers are synthesized without the use of protecting groups with high yields, demonstrating the high functional group tolerance of carbonyl condensation chemistry and the subsequent reduction of the imine. Prior to the reduction of the imine bond, transimination reactions are used to demonstrate dynamic polymers that shuffle from a glycine- to a histidine-functional polymer.

Trauma exposure and heavy drinking and drug use among college students: Identifying the roles of negative and positive affect lability in a daily diary study.

PubMed

Weiss, Nicole H; Bold, Krysten W; Contractor, Ateka A; Sullivan, Tami P; Armeli, Stephen; Tennen, Howard

2018-04-01

Trauma exposure is linked to heavy drinking and drug use among college students. Extant research reveals positive associations between negative affect lability and both trauma exposure and alcohol use. This study aimed to extend past research by using daily diary methods to test whether (a) individuals with (versus without) trauma exposure experience greater negative and positive affect lability, (b) negative and positive affect lability are associated with heavy drinking and drug use, and (c) negative and positive affect lability mediate the relations between trauma exposure and heavy drinking and drug use. Participants were 1640 college students (M age=19.2, 54% female, 80% European American) who provided daily diary data for 30days via online surveys. Daily diaries assessed negative and positive affect and substance use (i.e., percent days of heavy drinking, percent days of drug use, total number of drugs used). Individuals with (versus without) a history of trauma exposure demonstrated higher levels of negative and positive affect lability. Negative, but not positive, affect lability was associated with percent days of heavy drinking, percent days of drug use, and total number of drugs used, and mediated the associations between trauma exposure and heavy drinking and drug use outcomes. Findings provide support for the underlying role of negative affect lability in the relations between trauma exposure and heavy drinking and drug use among college students, suggesting that treatments targeting negative affect lability may potentially serve to reduce heavy drinking and drug use among trauma-exposed college students. Copyright © 2017 Elsevier Ltd. All rights reserved.

DETERMINATION OF APPARENT QUANTUM YIELD SPECTRA FOR THE FORMATION OF BIOLOGICALLY LABILE PHOTOPRODUCTS

EPA Science Inventory

Quantum yield spectra for the photochemical formation of biologically labile photoproducts from dissolved organic matter (DOM) have not been available previously, although they would greatly facilitate attempts to model photoproduct formation rates across latitudinal, seasonal, a...

Dual-therapy with αvβ3-targeted Sn2 lipase-labile fumagillin-prodrug nanoparticles and zoledronic acid in the Vx2 rabbit tumor model.

PubMed

Esser, Alison K; Schmieder, Anne H; Ross, Michael H; Xiang, Jingyu; Su, Xinming; Cui, Grace; Zhang, Huiying; Yang, Xiaoxia; Allen, John S; Williams, Todd; Wickline, Samuel A; Pan, Dipanjan; Lanza, Gregory M; Weilbaecher, Katherine N

2016-01-01

Fumagillin, an unstable anti-angiogenesis mycotoxin, was synthesized into a stable lipase-labile prodrug and incorporated into integrin-targeted lipid-encapsulated nanoparticles (αvβ3-Fum-PD NP). Dual anti-angiogenic therapy combining αvβ3-Fum-PD NP with zoledronic acid (ZA), a long-acting osteoclast inhibitor with proposed anti-angiogenic effects, was evaluated. In vitro, αvβ3-Fum-PD NP reduced (P<0.05) endothelial cell viability without impacting macrophage viability. ZA suppressed (P<0.05) macrophage viability at high dosages but not endothelial cell proliferation. 3D MR neovascular imaging of rabbit Vx2 tumors showed no effect with ZA, whereas αvβ3-Fum-PD NP alone and with ZA decreased angiogenesis (P<0.05). Immunohistochemistry revealed decreased (P<0.05) microvascularity with αvβ3-Fum-PD NP and ZA and further microvascular reduction (P<0.05) with dual-therapy. In vivo, ZA did not decrease tumor macrophage numbers nor cancer cell proliferation, whereas αvβ3-Fum-PD-NPs reduced both measures. Dual-therapy with ZA and αvβ3-Fum-PD-NP may provide enhanced neo-adjuvant utility if macrophage ZA uptake is increased. From the Clinical Editor: Although anti-angiogenesis is one of the treatment modalities in the fight against cancer, many cancers become resistant to VEGF pathway inhibitors. In this article, the authors investigated the use of dual therapy using fumagillin, integrin-targeted lipid-encapsulated nanoparticles (αvβ3- Fum-PD NP) and zoledronic acid (ZA), in both in-vitro and in-vivo experiments. This combination approach may provide an insight to the design of future drugs against cancers. Copyright © 2015 Elsevier Inc. All rights reserved.

Molecular imaging of labile iron(II) pools in living cells with a turn-on fluorescent probe.

PubMed

Au-Yeung, Ho Yu; Chan, Jefferson; Chantarojsiri, Teera; Chang, Christopher J

2013-10-09

Iron is an essential metal for living organisms, but misregulation of its homeostasis at the cellular level can trigger detrimental oxidative and/or nitrosative stress and damage events. Motivated to help study the physiological and pathological consequences of biological iron regulation, we now report a reaction-based strategy for monitoring labile Fe(2+) pools in aqueous solution and living cells. Iron Probe 1 (IP1) exploits a bioinspired, iron-mediated oxidative C-O bond cleavage reaction to achieve a selective turn-on response to Fe(2+) over a range of cellular metal ions in their bioavailable forms. We show that this first-generation chemical tool for fluorescence Fe(2+) detection can visualize changes in exchangeable iron stores in living cells upon iron supplementation or depletion, including labile iron pools at endogenous, basal levels. Moreover, IP1 can be used to identify reversible expansion of labile iron pools by stimulation with vitamin C or the iron regulatory hormone hepcidin, providing a starting point for further investigations of iron signaling and stress events in living systems as well as future probe development.

Microbially driven export of labile organic carbon from the Greenland ice sheet

NASA Astrophysics Data System (ADS)

Musilova, Michaela; Tranter, Martyn; Wadham, Jemma; Telling, Jon; Tedstone, Andrew; Anesio, Alexandre M.

2017-04-01

Glaciers and ice sheets are significant sources of dissolved organic carbon and nutrients to downstream subglacial and marine ecosystems. Climatically driven increases in glacial runoff are expected to intensify the impact of exported nutrients on local and regional downstream environments. However, the origin and bioreactivity of dissolved organic carbon from glacier surfaces are not fully understood. Here, we present simultaneous measurements of gross primary production, community respiration, dissolved organic carbon composition and export from different surface habitats of the Greenland ice sheet, throughout the ablation season. We found that microbial production was significantly correlated with the concentration of labile dissolved organic species in glacier surface meltwater. Further, we determined that freely available organic compounds made up 62% of the dissolved organic carbon exported from the glacier surface through streams. We therefore conclude that microbial communities are the primary driver for labile dissolved organic carbon production and recycling on glacier surfaces, and that glacier dissolved organic carbon export is dependent on active microbial processes during the melt season.

Labile dissolved organic carbon supply limits hyporheic denitrification

NASA Astrophysics Data System (ADS)

Zarnetske, Jay P.; Haggerty, Roy; Wondzell, Steven M.; Baker, Michelle A.

2011-12-01

We used an in situ steady state 15N-labeled nitrate (15NO3-) and acetate (AcO-) well-to-wells injection experiment to determine how the availability of labile dissolved organic carbon (DOC) as AcO-influences microbial denitrification in the hyporheic zone of an upland (third-order) agricultural stream. The experimental wells receiving conservative (Cl- and Br) and reactive (15NO3-) solute tracers had hyporheic median residence times of 7.0 to 13.1 h, nominal flowpath lengths of 0.7 to 3.7 m, and hypoxic conditions (<1.5 mg O2 L-1). All receiving wells demonstrated 15N2 production during ambient conditions, indicating that the hyporheic zone was an environment with active denitrification. The subsequent addition of AcO- stimulated more denitrification as evidenced by significant δ15N2 increases by factors of 2.7 to 26.1 in receiving wells and significant decreases of NO3- and DO in the two wells most hydrologically connected to the injection. The rate of nitrate removal in the hyporheic zone increased from 218 kg ha-1 yr-1 to 521 kg ha-1 yr-1 under elevated AcO- conditions. In all receiving wells, increases of bromide and 15N2 occurred without concurrent increases in AcO-, indicating that 100% of AcO- was retained or lost in the hyporheic zone. These results support the hypothesis that denitrification in anaerobic portions of the hyporheic zone is limited by labile DOC supply.

An electromyographic analysis of shoulder muscle activation during push-up variations on stable and labile surfaces.

PubMed

Sandhu, Jaspal S; Mahajan, Shruti; Shenoy, Shweta

2008-04-01

Numerous exercises are used to strengthen muscles around the shoulder joint including the push-up and the push-up plus. An important consideration is the addition of surface instability in the form of swiss ball for rehabilitation and strength. The justification for the use of the swiss ball is based on its potential for increasing muscular demand required to maintain postural stability and for improving joint proprioception. Evidence for this is lacking in literature. To compare the myoelectric amplitude of shoulder muscles during push-ups on labile and stable surface. Same subject experimental study. Thirty healthy male subjects in the age group 20-30 years with a mean height of 173.65 cm (+/- SD 2.56) and a mean weight of 69.9 kg (+/-SD 0.2) were taken. Surface electromyogram was recorded from triceps, pectoralis major, serratus anterior and upper trapezius while performing push-up and push-up plus exercises, both on labile and stable surface. Significant increase in muscle activity was observed in pectoralis major and triceps muscle (only during eccentric phase of elbow pushups), while serratus anterior and upper trapezius showed no change in activation level on swiss ball. The addition of a swiss ball is capable of influencing shoulder muscle activity during push-up variations, although the effect is task and muscle dependent.

The effect of flood events on the partitioning of labile and refractory carbon in the Missouri-Mississippi River system

NASA Astrophysics Data System (ADS)

Roe, K. M.; Rosenheim, B. E.; Kolker, A.; Allison, M. A.; Nittrouer, J. A.; Duncan, D. D.; Nyman, J. A.; Butcher, K. A.; Adamic, J. F.

2009-12-01

The Missouri-Mississippi River system (MMRS) transports over 40% (4.0 x 109 kg) of the United States's annual input of total organic carbon (OC) from land to the marine environment, yet it is challenging to assess the MMRS’s exact role in the global carbon cycle because of the system’s complexity and temporal variability (i.e. high discharge events and low flow regimes). Determining the relative proportion of labile OC to refractory OC entrained in the MMRS during high and mean flow conditions would lend to the understanding of the MMRS’s role in the flux of carbon between the biospheric and atmospheric reservoirs, which is central to determining the role of anthropogenic CO2 in the global carbon cycle and in climate change. In this study, we investigate the relative proportion of labile OC to refractory OC in the lower MMRS during high and near-mean flow conditions in the springs of 2008 and 2009, respectively. The 2008 spring flood discharged 105 km3 of water, the maximum amount of water ever allowed out of the main channel, at a maximum rate of 4.3 x 104 m3s-1. Events of this scale have occurred only nine times in the past 80 years. Additionally, during the spring 2008 flood, bedload sand and large particulate OC transport rates were observed to increase exponentially. The following spring, high discharge rates returned to near-mean values with a peak discharge of 3.6 x 103 m3s-1. Using radiocarbon age and the thermal stability of organic matter (OM) as a proxy for lability, we evaluate the spectra of ages of particulate OM transported in the lower MMRS during these two flow regimes using a programmed-temperature pyrolysis/combustion system (PTP/CS) coupled with 14C determination. The PTP/CS utilizes the differences in thermal stability of acid insoluble particulate organic matter (AIPOM) to separate different components from the bulk. Employing PTP/CS on bulk AIPOM can complement experiments measuring small proportions of total OM such as compound

[Impact of Land Utilization Pattern on Distributing Characters of Labile Organic Carbon in Soil Aggregates in Jinyun Mountain].

PubMed

Li, Rui; Jiang, Chang-sheng; Hao, Qing-ju

2015-09-01

Four land utilization patterns were selected for this study in Jinyun mountain, including subtropical evergreen broad-leaved forest (abbreviation: forest), sloping farmland, orchard and abandoned land. Soil samples were taken every 10 cm in the depth of 60 cm soil and proportions of large macroaggregates (> 2 mm), small macroaggregates (0. 25-2 mm), microaggregates (0. 053 - 0. 25 mm) and silt + clay (<0. 053 mm) were obtained by wet sieving method to measure the content of organic carbon and labile organic carbon in each aggregate fraction and analyze impacts of land uses on organic carbon and labile organic carbon of soil aggregates. LOC content of four soil aggregates were significantly reduced with the increase of soil depth; in layers of 0-60 cm soil depth, our results showed that LOC contents of forest and abandoned land were higher than orchard and sloping farmland. Reserves of labile organic carbon were estimated by the same soil quality, it revealed that forest (3. 68 Mg.hm-2) > abandoned land (1. 73 Mg.hm-2) > orchard (1. 43 Mg.hm-2) >sloping farmland (0.54 Mg.hm-2) in large macroaggregates, abandoned land (7.77, 5. 01 Mg.hm-2) > forest (4. 96, 2.71 Mg.hm-2) > orchard (3. 33, 21. 10 Mg.hm-2) > sloping farmland (1. 68, 1. 35 Mg.hm-2) in small macroaggregates and microaggregates, and abandoned land(4. 32 Mg.hm-2) > orchard(4. 00 Mg.hm-2) > forest(3. 22 Mg.hm-2) > sloping farmland (2.37 Mg.hm-2) in silt + clay, forest and abandoned land were higher than orchard and sloping farmland in other three soil aggregates except silt + clay. It was observed that the level of organic carbon and labile organic carbon were decreased when bringing forest under cultivation to orchard or farmland, and augments on organic carbon and labile organic carbon were found after exchanging farmland to abandoned land. The most reverses of forest and abandoned land emerged in small macroaggregates, orchard and sloping farmland were in microaggregates. That was, during the

Effect of Oxalic Acid Treatment on Sediment Arsenic Concentrations and Lability under Reducing Conditions

PubMed Central

Sun, Jing; Bostick, Benjamin C.; Mailloux, Brian J.; Ross, James M.; Chillrud, Steven N.

2016-01-01

Oxalic acid enhances arsenic (As) mobilization by dissolving As host minerals and competing for sorption sites. Oxalic acid amendments thus could potentially improve the efficiency of widely used pump-and-treat (P&T) remediation. This study investigates the effectiveness of oxalic acid on As mobilization from contaminated sediments with different As input sources and redox conditions, and examines whether residual sediment As after oxalic acid treatment can still be reductively mobilized. Batch extraction, column, and microcosm experiments were performed in the laboratory using sediments from the Dover Municipal Landfill and the Vineland Chemical Company Superfund sites. Oxalic acid mobilized As from both Dover and Vineland sediments, although the efficiency rates were different. The residual As in both Dover and Vineland sediments after oxalic acid treatment was less vulnerable to microbial reduction than before the treatment. Oxalic acid could thus improve the efficiency of P&T. X-ray absorption spectroscopy analysis indicated that the Vineland sediment samples still contained reactive Fe(III) minerals after oxalic acid treatment, and thus released more As into solution under reducing conditions than the Dover samples. Therefore, the efficacy of P&T must consider sediment Fe mineralogy when evaluating its overall potential for remediating groundwater As. PMID:26970042

The effect of acidification on the bioavailability and electrochemical lability of zinc in seawater

PubMed Central

Kim, Ja-Myung; Baars, Oliver

2016-01-01

A poorly studied but potentially important consequence of the CO2-induced acidification of the surface ocean is a possible change in the bioavailability of trace metals, which play a critical role in the productivity and population dynamics of marine ecosystems. We report laboratory and field experiments designed to compare quantitatively the effects of acidification on the bioavailability of Zn, a metal essential to the growth of phytoplankton and on the extent of its complexation by model and natural ligands. We observed a good correspondence between the effects of pH on the rate of Zn uptake by a model diatom and the chemical lability of Zn measured by anodic stripping voltammetry (ASV). In model laboratory systems, the chemical lability and the bioavailability of Zn could either increase or decrease at low pH depending on the mix of complexing ligands. In a sample of coastal surface water, we observed similar increases in the ASV-labile and bioavailable Zn concentrations upon acidification, a result contrary to previous observations. These results, which can likely be generalized to other bioactive trace metals, mutatis mutandis, demonstrate the intricacy of the effects of ocean acidification on the chemistry and the ecology of surface seawater. This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element chemistry’. PMID:29035261

The effect of acidification on the bioavailability and electrochemical lability of zinc in seawater.

PubMed

Kim, Ja-Myung; Baars, Oliver; Morel, François M M

2016-11-28

A poorly studied but potentially important consequence of the CO 2 -induced acidification of the surface ocean is a possible change in the bioavailability of trace metals, which play a critical role in the productivity and population dynamics of marine ecosystems. We report laboratory and field experiments designed to compare quantitatively the effects of acidification on the bioavailability of Zn, a metal essential to the growth of phytoplankton and on the extent of its complexation by model and natural ligands. We observed a good correspondence between the effects of pH on the rate of Zn uptake by a model diatom and the chemical lability of Zn measured by anodic stripping voltammetry (ASV). In model laboratory systems, the chemical lability and the bioavailability of Zn could either increase or decrease at low pH depending on the mix of complexing ligands. In a sample of coastal surface water, we observed similar increases in the ASV-labile and bioavailable Zn concentrations upon acidification, a result contrary to previous observations. These results, which can likely be generalized to other bioactive trace metals, mutatis mutandis , demonstrate the intricacy of the effects of ocean acidification on the chemistry and the ecology of surface seawater.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'. © 2016 The Author(s).

Synthesis of the very acid-sensitive Fmoc-Cys(Mmt)-OH and its application in solid-phase peptide synthesis.

PubMed

Barlos, K; Gatos, D; Hatzi, O; Koch, N; Koutsogianni, S

1996-03-01

S-4-methoxytrityl cysteine was synthesized and converted into the corresponding Fmoc-Cys(Mmt)-OH by its reaction with Fmoc-OSu. As compared to the corresponding Fmoc-Cys(Trt)-OH, the S-Mmt-function was found to be considerably more acid labile. Quantitative S-Mmt-removal occurs selectively in the presence of groups of the tert butyl type and S-Trt by treatment with 0.5-1.0% TFA. The new derivative was successfully utilized in the SPPS of Tyr1-somatostatin on 2-chlorotrityl resin. In this synthesis groups of the Trt-type were exclusively used for amino acid side-chain protection. Quantitative cleavage from the resin and complete deprotection was performed by treatment with 3% TFA in DCM-TES (95:5) for 30 min at RT. We observed no reduction of tryptophan under these conditions.

Affective lability mediates the association between childhood trauma and suicide attempts, mixed episodes and co-morbid anxiety disorders in bipolar disorders.

PubMed

Aas, M; Henry, C; Bellivier, F; Lajnef, M; Gard, S; Kahn, J-P; Lagerberg, T V; Aminoff, S R; Bjella, T; Leboyer, M; Andreassen, O A; Melle, I; Etain, B

2017-04-01

Many studies have shown associations between a history of childhood trauma and more severe or complex clinical features of bipolar disorders (BD), including suicide attempts and earlier illness onset. However, the psychopathological mechanisms underlying these associations are still unknown. Here, we investigated whether affective lability mediates the relationship between childhood trauma and the severe clinical features of BD. A total of 342 participants with BD were recruited from France and Norway. Diagnosis and clinical characteristics were assessed using the Diagnostic Interview for Genetic Studies (DIGS) or the Structured Clinical Interview for DSM-IV Axis I disorders (SCID-I). Affective lability was measured using the short form of the Affective Lability Scale (ALS-SF). A history of childhood trauma was assessed using the Childhood Trauma Questionnaire (CTQ). Mediation analyses were performed using the SPSS process macro. Using the mediation model and covariation for the lifetime number of major mood episodes, affective lability was found to statistically mediate the relationship between childhood trauma experiences and several clinical variables, including suicide attempts, mixed episodes and anxiety disorders. No significant mediation effects were found for rapid cycling or age at onset. Our data suggest that affective lability may represent a psychological dimension that mediates the association between childhood traumatic experiences and the risk of a more severe or complex clinical expression of BD.

Synthesis of copolymers containing diazoketo groups and their application as DUV resists

NASA Astrophysics Data System (ADS)

Kim, Jin-Baek; Kim, Kyoung-Seon

2005-05-01

We synthesized a new type of polymers that have diazoketo groups instead of acid-labile protecting groups. The polymers do not need a photoacid generator for formulation of resists. That is, the new matrix polymers absorb UV light and produce carboxylic groups. Also, there is no necessity for a post-exposure bake step, which is the cause of post-exposure delay effects. New monomer, ethyl 2-diazo-4-methyl-3-oxo-pent-4-enoate was synthesized. This monomer was copolymerized with hydroxystyrene and adamantyl methacrylate. After UV exposure, the polymers became soluble in an aqueous base developer. The polymers showed bleaching effect after UV exposure. Thermal properties of the polymers were measured by TGA and DSC. Characterization of the polymers has been done using other techniques such as FT-IR, NMR, GPC, and UV. The resist patterns of 0.8 μm feature size were resolved using a DUV contact printer and with a tetramethylammonium hydroxide aqueous solution.

Relationship between the lability of sediment-bound Cd and its bioaccumulation in edible oyster.

PubMed

Chakraborty, Parthasarathi; Ramteke, Darwin; Chakraborty, Sucharita; Chennuri, Kartheek; Bardhan, Pratirupa

2015-11-15

A linkage between Cd speciation in sediments and its bioaccumulation in edible oyster (Crassostrea sp.) from a tropical estuarine system was established. Bioaccumulation of Cd in edible oyster increased with the increasing lability and dissociation rate constants of Cd-sediment complexes in the bottom sediments. Total Cd concentration in sediment was not a good indicator of Cd-bioavailability. Increasing trace metal competition in sediments increased lability and bioavailability of Cd in the tropical estuarine sediment. Low thermodynamic stability and high bioavailability of Cd in the estuarine sediment were responsible for high bioaccumulation of Cd in edible oysters (3.2-12.2mgkg(-1)) even though the total concentration of Cd in the bottom sediment was low (0.17-0.49mgkg(-1)). Copyright © 2015 Elsevier Ltd. All rights reserved.

Chemical characterization of ambient aerosol collected during the southwest monsoon and intermonsoon seasons over the Arabian Sea: Labile-Fe(II) and other trace metals

NASA Astrophysics Data System (ADS)

Siefert, Ronald L.; Johansen, Anne M.; Hoffmann, Michael R.

1999-02-01

Atmospheric deposition of iron (Fe) to certain regions of the oceans is an important nutrient source of Fe to the biota, and the ability of the biota to uptake Fe is dependent on the speciation of the Fe. Therefore understanding the speciation of Fe in the atmosphere is critical to understanding the role of Fe as a nutrient source in surface ocean waters. Labile ferrous iron (Fe(II)) concentrations as well as total concentrations for Fe and other important trace metals, cations, and anions were determined over the Arabian Sea for two nonconsecutive months during 1995. Ambient aerosol samples were collected during the Indian Ocean intermonsoon and southwest monsoon seasons over the Arabian Sea. Sampling took place aboard the German research vessel Meteor in the months of May (leg M32/3; intermonsoon) and July/August (leg M32/5; southwest monsoon). Both cruise tracks followed the 65th east meridian, traveling for 30 days each (from north to south during leg M32/3 and from south to north during leg M32/5). A high-volume dichotomous virtual impactor with an aerodynamic cutoff size of 3 μm was used to collect the fine and coarse aerosol fractions for metal analysis. A low volume collector was used to collect aerosol samples for anion and cation analysis. The analysis for labile-Fe(II) was done immediately after sample collection to minimize any possible Fe redox reactions which might occur during sample storage. The analytical procedure involved filter extraction in a formate/formic acid buffered solution at pH 4.2 followed by colorimetric quantification of soluble Fe(II). Metals, anions, and cations were analyzed after the cruise. Total atmospheric aqueous-labile-Fe(II) concentrations during the intermonsoon were between 4.75 and <0.4 ng m-3, of which most (>80%) was present in the fine fraction (<3.0 μm). During the southwest monsoon, atmospheric aqueous-labile-Fe(II) concentrations were consistently below the detection limit (<0.34 to <0.089 ng m-3, depending on

Stand-scale correspondence in empirical and simulated labile carbohydrates in loblolly pine

Treesearch

David A. Sampson; Kurt H. Johnsen; Kim H. Ludovici; Timothy J. Albaugh; Chris A. Maier

2001-01-01

As investment into intensive forestry increases, the potential trade-offs between productivity and sustainability should be scrutinized. Because of their important role in internal carbon (C) budgets, labile C pools may provide a measure of the potential ability of trees and stands to respond to stress. We modified the process model BIOMASS to...

In vivo bioluminescence imaging of labile iron accumulation in a murine model of Acinetobacter baumannii infection.

PubMed

Aron, Allegra T; Heffern, Marie C; Lonergan, Zachery R; Vander Wal, Mark N; Blank, Brian R; Spangler, Benjamin; Zhang, Yaofang; Park, Hyo Min; Stahl, Andreas; Renslo, Adam R; Skaar, Eric P; Chang, Christopher J

2017-11-28

Iron is an essential metal for all organisms, yet disruption of its homeostasis, particularly in labile forms that can contribute to oxidative stress, is connected to diseases ranging from infection to cancer to neurodegeneration. Iron deficiency is also among the most common nutritional deficiencies worldwide. To advance studies of iron in healthy and disease states, we now report the synthesis and characterization of iron-caged luciferin-1 (ICL-1), a bioluminescent probe that enables longitudinal monitoring of labile iron pools (LIPs) in living animals. ICL-1 utilizes a bioinspired endoperoxide trigger to release d-aminoluciferin for selective reactivity-based detection of Fe 2+ with metal and oxidation state specificity. The probe can detect physiological changes in labile Fe 2+ levels in live cells and mice experiencing iron deficiency or overload. Application of ICL-1 in a model of systemic bacterial infection reveals increased iron accumulation in infected tissues that accompany transcriptional changes consistent with elevations in both iron acquisition and retention. The ability to assess iron status in living animals provides a powerful technology for studying the contributions of iron metabolism to physiology and pathology.

Affective lability and difficulties with regulation are differentially associated with amygdala and prefrontal response in women with Borderline Personality Disorder

PubMed Central

Silvers, Jennifer A.; Hubbard, Alexa D.; Biggs, Emily; Shu, Jocelyn; Fertuck, Eric; Chaudhury, Sadia; Grunebaum, Michael F.; Weber, Jochen; Kober, Hedy; Chesin, Megan; Brodsky, Beth S.; Koenigsberg, Harold; Ochsner, Kevin N.; Stanley, Barbara

2016-01-01

The present neuroimaging study investigated two aspects of difficulties with emotion associated with Borderline Personality Disorder (BPD1): affective lability and difficulty regulating emotion. While these two characteristics have been previously linked to BPD symptomology, it remains unknown whether individual differences in affective lability and emotion regulation difficulties are subserved by distinct neural substrates within a BPD sample. To address this issue, sixty women diagnosed with BPD were scanned while completing a task that assessed baseline emotional reactivity as well as top-down emotion regulation. More affective instability, as measured by the Affective Lability Scale (ALS2), positively correlated with greater amygdala responses on trials assessing emotional reactivity. Greater difficulties with regulating emotion, as measured by the Difficulties with Emotion Regulation Scale (DERS3), was negatively correlated with left inferior frontal gyrus (IFG4) recruitment on trials assessing regulatory ability. These findings suggest that, within a sample of individuals with BPD, greater bottom-up amygdala activity is associated with heightened affective lability. By contrast, difficulties with emotion regulation are related to reduced IFG recruitment during emotion regulation. These results point to distinct neural mechanisms for different aspects of BPD symptomology. PMID:27379614

Protein covalent immobilization via its scarce thiol versus abundant amine groups: Effect on orientation, cell binding domain exposure and conformational lability.

PubMed

Ba, O M; Hindie, M; Marmey, P; Gallet, O; Anselme, K; Ponche, A; Duncan, A C

2015-10-01

Quantity, orientation, conformation and covalent linkage of naturally cell adhesive proteins adsorbed or covalently linked to a surface, are known to influence the preservation of their subsequent long term cell adhesion properties and bioactivity. In the present work, we explore two different strategies for the covalent linking of plasma fibronectin (pFN) - used as a cell adhesive model protein, onto a polystyrene (PS) surface. One is aimed at tethering the protein to the surface in a semi-oriented fashion (via one of the 4 free thiol reactive groups on the protein) with a heterofunctional coupling agent (SSMPB method). The other aims to immobilize the protein in a more random fashion by reaction between the abundant pendant primary amine bearing amino acids of the pFN and activated carboxylic surface functions obtained after glutaric anhydride surface treatment (GA method). The overall goal will be to verify the hypothesis of a correlation between covalent immobilization of a model cell adhesive protein to a PS surface in a semi-oriented configuration (versus randomly oriented) with promotion of enhanced exposure of the protein's cell binding domain. This in turn would lead to enhanced cell adhesion. Ideally the goal is to elaborate substrates exhibiting a long term stable protein monolayer with preserved cell adhesive properties and bioactivity for biomaterial and/or cell adhesion commercial plate applications. However, the initial restrictive objective of this paper is to first quantitatively and qualitatively investigate the reversibly (merely adsorbed) versus covalently irreversibly bound protein to the surface after the immobilization procedure. Although immobilized surface amounts were similar (close to the monolayer range) for all immobilization approaches, covalent grafting showed improved retention and stronger "tethering" of the pFN protein to the surface (roughly 40%) after SDS rinsing compared to that for mere adsorption (0%) suggesting an added value

Fast and Facile Synthesis of 4-Nitrophenyl 2-Azidoethylcarbamate Derivatives from N-Fmoc-Protected α-Amino Acids as Activated Building Blocks for Urea Moiety-Containing Compound Library.

PubMed

Chen, Ying-Ying; Chang, Li-Te; Chen, Hung-Wei; Yang, Chia-Ying; Hsin, Ling-Wei

2017-03-13

A fast and facile synthesis of a series of 4-nitrophenyl 2-azidoethylcarbamate derivatives as activated urea building blocks was developed. The N-Fmoc-protected 2-aminoethyl mesylates derived from various commercially available N-Fmoc-protected α-amino acids, including those having functionalized side chains with acid-labile protective groups, were directly transformed into 4-nitrophenyl 2-azidoethylcarbamate derivatives in 1 h via a one-pot two-step reaction. These urea building blocks were utilized for the preparation of a series of urea moiety-containing mitoxantrone-amino acid conjugates in 75-92% yields and parallel solution-phase synthesis of a urea compound library consisted of 30 members in 38-70% total yields.

Feasibility of labile Zn phytoextraction using enhanced tobacco and sunflower: results of five- and one-year field-scale experiments in Switzerland.

PubMed

Herzig, Rolf; Nehnevajova, Erika; Pfistner, Charlotte; Schwitzguebel, Jean-Paul; Ricci, Arturo; Keller, Charles

2014-01-01

Phytoextraction with somaclonal variants of tobacco and sunflower mutant lines (non-GMs) with enhanced metal uptake and tolerance can be a sustainable alternative to conventional destructive decontamination methods, especially for stripping bioavailable zinc excess in topsoil. The overall results of a 5-year time series experiment at field scale in north-eastern Switzerland confirm that the labile Zn pool in soil can be lowered by 45-70%, whereas subplots without phytoextraction treatment maintained labile Zn concentrations. In 2011, the phytoextraction experiment site was enlarged by a factor of 3, and the labile 0.1 M NaNO3 extractable Zn concentration in the soil was reduced up to 58% one period after harvest. A Mass Balance Analysis confirmed soil Zn decontamination in line with plant Zn uptake. The plants partially take Zn from the non-labile pool of the totaL The sustainability of Zn phytoextraction in subplots that no longer exceed the Swiss trigger value is now assessed over time. In contrary to the phytoextraction of total soil Zn which needs a long cleaning up time, the bioavailable Zn stripping is feasible within a few years period.

Lability of Secondary Organic Particulate Matter

DOE PAGES

Liu, Pengfei; Li, Yong Jie; Wang, Yan; ...

2016-10-24

Accurate simulations of the consenctrations of atmospheric organic particulate matter (PM) are needed for predicting energy flow in the Earth’s climate system. In the past, simulations of organic PM widely assume equilibrium partitioning of semivolatile organic compounds (SVOCs) between the PM and surrounding vapor. Herein, we test this assumption by measuring evaporation rates and associated vapor mass concentration of organic films representative of atmospheric PM. For films representing anthropogenic PM, evaporation rates and vapor mass concentrations increased above a threshold relative humidity (RH), indicating equilibrium partitioning above a transition RH but not below. In contrast for films representing biogenic PM,more » no threshold was observed, indicating equilibrium partitioning at all RHs. The results suggest that the mass lability of atmospheric organic PM can differ in consequential ways among Earth’s natural biomes, polluted regions, and regions of land-use change, and these differences need to be considered when simulating atmospheric organic PM.« less

Assessing SOC labile fractions through respiration test, density-size fractionation and thermal analysis - A comparison of methods

NASA Astrophysics Data System (ADS)

Soucemarianadin, Laure; Cécillon, Lauric; Chenu, Claire; Baudin, François; Nicolas, Manuel; Savignac, Florence; Barré, Pierre

2017-04-01

Soil organic matter (SOM) is the biggest terrestrial carbon reservoir, storing 3 to 4 times more carbon than the atmosphere. However, despite its major importance for climate regulation SOM dynamics remains insufficiently understood. For instance, there is still no widely accepted method to assess SOM lability. Soil respiration tests and particulate organic matter (POM) obtained by different fractionation schemes have been used for decades and are now considered as classical estimates of very labile and labile soil organic carbon (SOC), respectively. But the pertinence of these methods to characterize SOM turnover can be questioned. Moreover, they are very time-consuming and their reproducibility might be an issue. Alternate ways of determining the labile SOC component are thus well-needed. Thermal analyses have been used to characterize SOM among which Rock-Eval 6 (RE6) analysis of soil has shown promising results in the determination of SOM biogeochemical stability (Gregorich et al., 2015; Barré et al., 2016). Using a large set of samples of French forest soils representing contrasted pedoclimatic conditions, including deep samples (up to 1 m depth), we compared different techniques used for SOM lability assessment. We explored whether results from soil respiration test (10-week laboratory incubations), SOM size-density fractionation and RE6 thermal analysis were comparable and how they were correlated. A set of 222 (respiration test and RE6), 103 (SOM fractionation and RE6) and 93 (respiration test, SOM fractionation and RE6) forest soils samples were respectively analyzed and compared. The comparison of the three methods (n = 93) using a principal component analysis separated samples from the surface (0-10 cm) and deep (40-80 cm) layers, highlighting a clear effect of depth on the short-term persistence of SOC. A correlation analysis demonstrated that, for these samples, the two classical methods of labile SOC determination (respiration and SOM fractionation

The role of labile sulfur compounds in thermochemical sulfate reduction

USGS Publications Warehouse

Amrani, A.; Zhang, T.; Ma, Q.; Ellis, G.S.; Tang, Y.

2008-01-01

The reduction of sulfate to sulfide coupled with the oxidation of hydrocarbons to carbon dioxide, commonly referred to as thermochemical sulfate reduction (TSR), is an important abiotic alteration process that most commonly occurs in hot carbonate petroleum reservoirs. In the present study we focus on the role that organic labile sulfur compounds play in increasing the rate of TSR. A series of gold-tube hydrous pyrolysis experiments were conducted with n-octane and CaSO4 in the presence of reduced sulfur (e.g. H2S, S??, organic S) at temperatures of 330 and 356 ??C under a constant confining pressure. The in-situ pH was buffered to 3.5 (???6.3 at room temperature) with talc and silica. For comparison, three types of oil with different total S and labile S contents were reacted under similar conditions. The results show that the initial presence of organic or inorganic sulfur compounds increases the rate of TSR. However, organic sulfur compounds, such as 1-pentanethiol or diethyldisulfide, were significantly more effective in increasing the rate of TSR than H2S or elemental sulfur (on a mole S basis). The increase in rate is achieved at relatively low concentrations of 1-pentanethiol, less than 1 wt% of the total n-octane, which is comparable to the concentration of organic S that is common in many oils (???0.3 wt%). We examined several potential reaction mechanisms to explain the observed reactivity of organic LSC. First, the release of H2S from the thermal degradation of thiols was discounted as an important mechanism due to the significantly greater reactivity of thiol compared to an equivalent amount of H2S. Second, we considered the generation of olefines in association with the elimination of H2S during thermal degradation of thiols because olefines are much more reactive than n-alkanes during TSR. In our experiments, olefines increased the rate of TSR, but were less effective than 1-pentanethiol and other organic LSC. Third, the thermal decomposition of

The role of labile sulfur compounds in thermochemical sulfate reduction

NASA Astrophysics Data System (ADS)

Amrani, Alon; Zhang, Tongwei; Ma, Qisheng; Ellis, Geoffrey S.; Tang, Yongchun

2008-06-01

The reduction of sulfate to sulfide coupled with the oxidation of hydrocarbons to carbon dioxide, commonly referred to as thermochemical sulfate reduction (TSR), is an important abiotic alteration process that most commonly occurs in hot carbonate petroleum reservoirs. In the present study we focus on the role that organic labile sulfur compounds play in increasing the rate of TSR. A series of gold-tube hydrous pyrolysis experiments were conducted with n-octane and CaSO4 in the presence of reduced sulfur (e.g. H2S, S°, organic S) at temperatures of 330 and 356 °C under a constant confining pressure. The in-situ pH was buffered to 3.5 (∼6.3 at room temperature) with talc and silica. For comparison, three types of oil with different total S and labile S contents were reacted under similar conditions. The results show that the initial presence of organic or inorganic sulfur compounds increases the rate of TSR. However, organic sulfur compounds, such as 1-pentanethiol or diethyldisulfide, were significantly more effective in increasing the rate of TSR than H2S or elemental sulfur (on a mole S basis). The increase in rate is achieved at relatively low concentrations of 1-pentanethiol, less than 1 wt% of the total n-octane, which is comparable to the concentration of organic S that is common in many oils (∼0.3 wt%). We examined several potential reaction mechanisms to explain the observed reactivity of organic LSC. First, the release of H2S from the thermal degradation of thiols was discounted as an important mechanism due to the significantly greater reactivity of thiol compared to an equivalent amount of H2S. Second, we considered the generation of olefines in association with the elimination of H2S during thermal degradation of thiols because olefines are much more reactive than n-alkanes during TSR. In our experiments, olefines increased the rate of TSR, but were less effective than 1-pentanethiol and other organic LSC. Third, the thermal decomposition of

Suppression of inflammation in a mouse model of rheumatoid arthritis using targeted lipase-labile fumagillin prodrug nanoparticles.

PubMed

Zhou, Hui-Fang; Yan, Huimin; Senpan, Angana; Wickline, Samuel A; Pan, Dipanjan; Lanza, Gregory M; Pham, Christine T N

2012-11-01

Nanoparticle-based therapeutics are emerging technologies that have the potential to greatly impact the treatment of many human diseases. However, drug instability and premature release from the nanoparticles during circulation currently preclude clinical translation. Herein, we use a lipase-labile (Sn 2) fumagillin prodrug platform coupled with a unique lipid surface-to-surface targeted delivery mechanism, termed contact-facilitated drug delivery, to counter the premature drug release and overcome the inherent photo-instability of fumagillin, an established anti-angiogenic agent. We show that α(v)β(3)-integrin targeted fumagillin prodrug nanoparticles, administered at 0.3 mg of fumagillin prodrug/kg of body weight suppress the clinical disease indices of KRN serum-mediated arthritis in a dose-dependent manner when compared to treatment with the control nanoparticles with no drug. This study demonstrates the effectiveness of this lipase-labile prodrug nanocarrier in a relevant preclinical model that approximates human rheumatoid arthritis. The lipase-labile prodrug paradigm offers a translatable approach that is broadly applicable to many targeted nanosystems and increases the translational potential of this platform for many diseases. Copyright © 2012 Elsevier Ltd. All rights reserved.

NSAID-derived γ-secretase modulation requires an acidic moiety on the carbazole scaffold.

PubMed

Zall, Andrea; Kieser, Daniel; Höttecke, Nicole; Naumann, Eva C; Thomaszewski, Binia; Schneider, Katrin; Steinbacher, Dirk T; Schubenel, Robert; Masur, Stefan; Baumann, Karlheinz; Schmidt, Boris

2011-08-15

Modulation of γ-secretase activity holds potential for the treatment of Alzheimer's disease. Most NSAID-derived γ-secretase modulators feature a carboxylic acid, which may impair blood-brain barrier permeation. The structure activity relationship of 33 carbazoles featuring diverse carboxylic acid isosteres or metabolic precursors thereof was established in a cellular amyloid secretion assay. The modulatory activity was observed for acidic moieties and metabolically labile esters only, which supports our hypothesis of an acid-lysine interaction to be relevant for this type of γ-secretase modulators. Copyright © 2011 Elsevier Ltd. All rights reserved.

Synthesis of norbornene copolymers with diazo groups and their application as DUV resists

NASA Astrophysics Data System (ADS)

Kim, Jin-Baek; Kim, Kyoung Seon

2003-06-01

We synthesized a new type of norbornene-maleic anhydride copolymer which as diazoketo groups instead of acid labile protecting groups. The matrix polymer does not need a photoacid generator for the lithographic evaluation. And there is no necessity for the post-exposure bake step that is the cause of PED effects. Methyl 5-norbornenyl-3-oxopropionate was prepared by the reaction of acetyl norbornene with dimethyl carbonate in the presence of sodium hydride. And methyl 5-norbornenyl-2-diazo-3-oxopropionate was synthesized from the reaction between methyl 5-norbornenyl-3-oxopropionate and p-carboxybenzenesulfonyl azide. The polymer was prepared by free radical polymerization. Upon exposure to DUV light, diazoketo groups undergo a series of reactions that culminate in the formation of a carboxylic acid. The matrix polymer in the exposed region becomes soluble in the aqueous base developer. The polymer showed bleaching effect after exposure. Thermal stability of the polymer is measured by TGA and DSC. Characterization of the polymer is achieved using other techniques such as FT-IR, NMR, GPC, and UV. The resist patterns of 0.6 μm feature size were resolved using a KrF exposure tool and with a conventional developer, 2.38 wt% TMAH aqueous solution.

Combined use of UV-labile calcium chelators and calcium-sensitive dyes in a microscope with two light sources influencing different regions in a group of coordinated contracting cardiac myocytes

NASA Astrophysics Data System (ADS)

Pilarczyk, Goetz; Greulich, Karl-Otto

1997-12-01

The coordination of excitation in a biological system of cells such as cardiac myocytes in heart tissue has crucial influence on the function of the entire organ. This coordinated behavior can be visualized in a small group of embryonic cardiac myocytes derived from the hearts of unborn chicken. Loaded with a calcium sensitive dye the excitation can be imaged via the occurring transient rise in cytosolic calcium concentration. It can be shown that in regions with physiological or morphological restrictions the transient rise in cytosolic calcium occurs with a temporal delay compared to the ordinary array of coupled myocytes. The height of the transient rise of cytosolic calcium is related to the ability of the individual cell to participate in the coordinated contraction. The free cytosolic calcium concentration is decreased with the UV-labile calcium, chelator diazo-2. Our setup allows to decrease the free cytosolic calcium in a single cell of the contracting array of cells. This allows us to introduce mismatches in selected regions of the coordinated contraction and to visualize the effects simultaneously.

Fate of microbial nitrogen, carbon, hydrolysable amino acids, monosaccharides, and fatty acids in sediment

NASA Astrophysics Data System (ADS)

Veuger, Bart; van Oevelen, Dick; Middelburg, Jack J.

2012-04-01

The fate of microbial carbon, nitrogen, hydrolysable amino acids (HAAs), monosaccharides, and fatty acids in sediment was investigated experimentally. The microbial community of a tidal flat sediment was labeled with 13C-enriched glucose and 15N-enriched ammonium, and sediment was incubated for up to 371 days. Analysis of total concentrations and 13C- and 15N content of bulk sediment, hydrolysable amino acids (including D-alanine), monosaccharides, total fatty acids (TFAs), and phospholipid-derived fatty acids (PLFAs) allowed us to trace the fate of microbial biomass and -detritus and the major biochemical groups therein (proteins, carbohydrates, and lipids) over intermediate time scales (weeks-months). Moreover, the unidentified fraction of the labeled material (i.e. not analyzed as HAA, FA, or carbohydrate) provided information on the formation and fate of molecularly uncharacterizable organic matter. Loss of 13C and 15N from the sediment was slow (half live of 433 days) which may have been due to the permanently anoxic conditions in the experiment. Loss rates for the different biochemical groups were also low with the following order of loss rate constants: PLFA > TFA > HAA > monosaccharides. The unidentified 13C-pool was rapidly formed (within days) and then decreased relatively slowly, resulting in a gradual relative accumulation of this pool over time. Degradation and microbial reworking of the labeled material resulted in subtle, yet consistent, diagenetic changes within the different biochemical groups. In the HAA pool, glycine, lysine, and proline were lost relatively slowly (i.e. best preserved) while there was no accumulation of D-alanine relative to L-alanine, indicating no relative accumulation of bacterial macromolecules rich in D-alanine. In the fatty acid pool, there was very little difference between PLFAs and TFAs, indicating a very similar lability of these pools. Differences between individual fatty acids included a relatively slow loss of i15

Labile Dissolved Organic Carbon Availability Controls Hyporheic Denitrification: a 15N Tracer Study

NASA Astrophysics Data System (ADS)

Zarnetske, J. P.; Haggerty, R.; Wondzell, S. M.; Baker, M. A.

2009-12-01

We used an in situ 15N-labeled nitrate (15NO3-) and acetate injection experiment to determine how the availability of labile dissolved organic carbon (DOC) as acetate influences microbial denitrification in the hyporheic zone (HZ) of an upland (3rd-order) agricultural stream. A 48 h steady-state injection of a conservative tracer, chloride, and 15NO3- was used to quantify ambient HZ denitrification via 15N2 production. Following ambient plateau measurements of denitrification during the first 24 h, a second conservative tracer, bromide, and labile DOC source, acetate, were co-injected for an additional 24 h to measure HZ denitrification under increased DOC supply. Conservative tracers were observed at 4 of the 6 down gradient wells. Receiving wells represented HZ median residence times of 7.0 to 13.1 h, nominal flowpath lengths of 0.7 to 3.7 m, and hypoxic conditions (7.5 to 9.3 mg-O2 L-1 deficit). All 4 receiving wells demonstrated 15N2 production during ambient conditions indicating that the HZ was an active denitrification environment. Acetate addition stimulated significant increases in 15N2 production by factors of 2.7 to 26.1 in all receiving wells, and significant decreases of NO3- and DOC aromaticity (via SUVA254) in the two wells most hydrologically connected to the injection. In all receiving wells, increases of bromide and 15N2 production occurred without concurrent increases in acetate indicating that 100% of acetate was retained in the HZ, a portion of which is due to biological consumption. These results support our hypothesis that microbial denitrification in anaerobic portions of the hyporheic zone is limited by labile DOC supply.

Novel diffusive gradients in thin films technique to assess labile sulfate in soil.

PubMed

Hanousek, Ondrej; Mason, Sean; Santner, Jakob; Chowdhury, Md Mobaroqul Ahsan; Berger, Torsten W; Prohaska, Thomas

2016-09-01

A novel diffusive gradients in thin films (DGT) technique for sampling labile soil sulfate was developed, based on a strong basic anion exchange resin (Amberlite IRA-400) for sulfate immobilization on the binding gel. For reducing the sulfate background on the resin gels, photopolymerization was applied instead of ammonium persulfate-induced polymerization. Agarose cross-linked polyacrylamide (APA) hydrogels were used as diffusive layer. The sulfate diffusion coefficient in APA gel was determined as 9.83 × 10(-6) ± 0.35 × 10(-6) cm(2) s(-1) at 25 °C. The accumulated sulfate was eluted in 1 mol L(-1) HNO3 with a recovery of 90.9 ± 1.6 %. The developed method was tested against two standard extraction methods for soil sulfate measurement. The obtained low correlation coefficients indicate that DGT and conventional soil test methods assess differential soil sulfate pools, rendering DGT a potentially important tool for measuring labile soil sulfate.

Evolutionary lability of a complex life cycle in the aphid genus Brachycaudus.

PubMed

Emmanuelle, Jousselin; Gwenaelle, Genson; Armelle, Coeur d'acier

2010-09-28

Most aphid species complete their life cycle on the same set of host-plant species, but some (heteroecious species) alternate between different hosts, migrating from primary (woody) to secondary (herbaceous) host plants. The evolutionary processes behind the evolution of this complex life cycle have often been debated. One widely accepted scenario is that heteroecy evolved from monoecy on woody host plants. Several shifts towards monoecy on herbaceous plants have subsequently occurred and resulted in the radiation of aphids. Host alternation would have persisted in some cases due to developmental constraints preventing aphids from shifting their entire life cycle to herbaceous hosts (which are thought to be more favourable). According to this scenario, if aphids lose their primary host during evolution they should not regain it. The genus Brachycaudus includes species with all the types of life cycle (monoecy on woody plants, heteroecy, monoecy on herbs). We used this genus to test hypotheses concerning the evolution of life cycles in aphids. Phylogenetic investigation and character reconstruction suggest that life cycle is evolutionary labile in the genus. Though ancestral character states can be ambiguous depending on optimization methods, all analyses suggest that transitions from monoecy on herbs towards heteroecy have occurred several times. Transitions from heteroecy towards monoecy, are also likely. There have been many shifts in feeding behaviour but we found no significant correlation between life cycle changes and changes in diet. The transitions from monoecy on herbs towards heteroecy observed in this study go against a widely accepted evolutionary scenario: aphids in the genus Brachycaudus seem to be able to recapture their supposedly ancestral woody host. This suggests that the determinants of host alternation are probably not as complicated as previously thought. Definitive proofs of the lability of life cycle in Brachycaudus will necessitate

Acid Stress Response Mechanisms of Group B Streptococci

PubMed Central

Shabayek, Sarah; Spellerberg, Barbara

2017-01-01

Group B streptococcus (GBS) is a leading cause of neonatal mortality and morbidity in the United States and Europe. It is part of the vaginal microbiota in up to 30% of pregnant women and can be passed on to the newborn through perinatal transmission. GBS has the ability to survive in multiple different host niches. The pathophysiology of this bacterium reveals an outstanding ability to withstand varying pH fluctuations of the surrounding environments inside the human host. GBS host pathogen interations include colonization of the acidic vaginal mucosa, invasion of the neutral human blood or amniotic fluid, breaching of the blood brain barrier as well as survival within the acidic phagolysosomal compartment of macrophages. However, investigations on GBS responses to acid stress are limited. Technologies, such as whole genome sequencing, genome-wide transcription and proteome mapping facilitate large scale identification of genes and proteins. Mechanisms enabling GBS to cope with acid stress have mainly been studied through these techniques and are summarized in the current review PMID:28936424

Fraction of organic carbon predicts labile desorption rates of chlorinated organic pollutants in laboratory-spiked geosorbents.

PubMed

Ginsbach, Jake W; Killops, Kato L; Olsen, Robert M; Peterson, Brittney; Dunnivant, Frank M

2010-05-01

The resuspension of large volumes of sediments that are contaminated with chlorinated pollutants continues to threaten environmental quality and human health. Whereas kinetic models are more accurate for estimating the environmental impact of these events, their widespread use is substantially hampered by the need for costly, time-consuming, site-specific kinetics experiments. The present study investigated the development of a predictive model for desorption rates from easily measurable sorbent and pollutant properties by examining the relationship between the fraction of organic carbon (fOC) and labile release rates. Duplicate desorption measurements were performed on 46 unique combinations of pollutants and sorbents with fOC values ranging from 0.001 to 0.150. Labile desorption rate constants indicate that release rates predominantly depend upon the fOC in the geosorbent. Previous theoretical models, such as the macro-mesopore and organic matter (MOM) diffusion model, have predicted such a relationship but could not accurately predict the experimental rate constants collected in the present study. An empirical model was successfully developed to correlate the labile desorption rate constant (krap) to the fraction of organic material where log(krap)=0.291-0.785 . log(fOC). These results provide the first experimental evidence that kinetic pollution releases during resuspension events are governed by the fOC content in natural geosorbents. Copyright (c) 2010 SETAC.

Organic matter degradation in surface sediments of the Changjiang estuary: Evidence from amino acids.

PubMed

Wang, Kui; Chen, Jianfang; Jin, Haiyan; Li, Hongliang; Zhang, Weiyan

2018-05-12

Organic matter degradation is a key component of the processes of carbon preservation and burial in seafloor sediments. The aim of this study was to explore organic matter degradation state within the open-shelf Changjiang Estuary of the East China Sea, using an amino acids-based degradation index (DI) in conjunction with information about organic matter source (marine versus terrestrial), bottom water oxygenation state, and sediment grain size. The relative molar percentages of 17 individual amino acids (characterized using principal component analysis) in surface sediments indicate that organic matter is degraded to varying extents across the estuary seabed. Sediments with DI >0 (relatively labile) were found mostly within a coastal hypoxic area. Sediments of DI less than -1 (relatively refractory) were found near the Changjiang River mouth and the northern and southern parts of the central shelf. We consider DI to be a more reliable indicator of degradation than simple ratios of AAs. DI was inversely correlated with the proportion of terrestrial organic material (F t ) in the sediments, indicating that relatively fresh/labile organic matter was generally associated with marine sources. DI was significantly correlated with F t and bottom water apparent oxygen utilization (AOU bot ) together. The parameter DI and the (labile) amino acid tyrosine were highest in hypoxic areas, suggesting the presence of relatively fresh organic matter, probably due to a combination of marine-source inputs and better preservation of organic matter in the silt and clay sediments of these areas (as compared to sandy sediments). Less degraded organic matter with high amino acids was also favorable to benthic animals. Overall, sedimentary estuarine organic matter was least degraded in areas characterized by marine sources of organic matter, low-oxygen conditions, and fine-grained sediments. Copyright © 2018 Elsevier B.V. All rights reserved.

Orbitrap-MS and FT-ICR-MS of Free and Labile Organic Matter from Carbonaceous Chondrites

NASA Astrophysics Data System (ADS)

Orthous-Daunay, F.-R.; Thissen, R.; Vuitton, V.; Somogyi, A.; Mespoulede, M.; Beck, P.; Bonnet, J.-Y.; Dutuit, O.; Schmitt, B.; Quirico, E.

2011-03-01

We used two types of high-resolution FT-MS to analyze the free and labile organic matter in carbonaceous chondrites of type 1 and 2. The methanol extraction and laser desorption gave access to highly and poorly functionalized molecules respectively.

Main-group compounds selectively oxidize mixtures of methane, ethane, and propane to alcohol esters.

PubMed

Hashiguchi, Brian G; Konnick, Michael M; Bischof, Steven M; Gustafson, Samantha J; Devarajan, Deepa; Gunsalus, Niles; Ess, Daniel H; Periana, Roy A

2014-03-14

Much of the recent research on homogeneous alkane oxidation has focused on the use of transition metal catalysts. Here, we report that the electrophilic main-group cations thallium(III) and lead(IV) stoichiometrically oxidize methane, ethane, and propane, separately or as a one-pot mixture, to corresponding alcohol esters in trifluoroacetic acid solvent. Esters of methanol, ethanol, ethylene glycol, isopropanol, and propylene glycol are obtained with greater than 95% selectivity in concentrations up to 1.48 molar within 3 hours at 180°C. Experiment and theory support a mechanism involving electrophilic carbon-hydrogen bond activation to generate metal alkyl intermediates. We posit that the comparatively high reactivity of these d(10) main-group cations relative to transition metals stems from facile alkane coordination at vacant sites, enabled by the overall lability of the ligand sphere and the absence of ligand field stabilization energies in systems with filled d-orbitals.

[Correlation Between Functional Groups and Radical Scavenging Activities of Acidic Polysaccharides from Dendrobium].

PubMed

Liao, Ying; Yuan, Wen-yu; Zheng, Wen-ke; Luo, Ao-xue; Fan, Yi-jun

2015-11-01

To compare the radical scavenging activity of five different acidic polysaccharides, and to find the correlation with the functional groups. Alkali extraction method and Stepwise ethanol precipitation method were used to extract and concentrate the five Dendrobium polysaccharides, and to determine the contents of sulfuric acid and uronic acid of each kind of acidic polysaccharides, and the scavenging activity to ABTS+ radical and hydroxyl radical. Functional group structures were examined by FTIR Spectrometer. Five kinds of Dendrobium polysaccharides had different ability of scavenging ABTS+ free radical and hydroxyl free radical. Moreover, the study had shown that five kinds of antioxidant activity of acidic polysaccharides had obvious correlation withuronic acid and sulfuric acid. The antioxidant activity of each sample was positively correlated with the content of uronic acid, and negatively correlated with the content of sulfuric acid. Sulfuric acid can inhibit the antioxidant activity of acidic polysaccharide but uronic acid can enhance the free radical scavenging activity. By analyzing the structure characteristics of five acidic polysaccharides, all samples have similar structures, however, Dendrobium denneanum, Dendrobium devonianum and Dendrobium officinale which had β configuration have higher antioxidant activity than Dendrobium nobile and Dendrobium fimbriatum which had a configuration.

The influence of maternal ethnic group and diet on breast milk fatty acid composition.

PubMed

Su, Lin Lin; S K, Thamarai Chelvi; Lim, Su Lin; Chen, Yuming; Tan, Elizabeth A T; Pai, Namratha Narayan; Gong, Yin Han; Foo, Janie; Rauff, Mary; Chong, Yap Seng

2010-09-01

Breast milk fatty acids play a major role in infant development. However, no data have compared the breast milk composition of different ethnic groups living in the same environment. We aimed to (i) investigate breast milk fatty acid composition of three ethnic groups in Singapore and (ii) determine dietary fatty acid patterns in these groups and any association with breast milk fatty acid composition. This was a prospective study conducted at a tertiary hospital in Singapore. Healthy pregnant women with the intention to breastfeed were recruited. Diet profile was studied using a standard validated 3-day food diary. Breast milk was collected from mothers at 1 to 2 weeks and 6 to 8 weeks postnatally. Agilent gas chromatograph (6870N) equipped with a mass spectrometer (5975) and an automatic liquid sampler (ALS) system with a split mode was used for analysis. Seventy-two breast milk samples were obtained from 52 subjects. Analysis showed that breast milk ETA (Eicosatetraenoic acid) and ETA:EA (Eicosatrienoic acid) ratio were significantly different among the races (P = 0.031 and P = 0.020), with ETA being the highest among Indians and the lowest among Malays. Docosahexaenoic acid was significantly higher among Chinese compared to Indians and Malays. No difference was demonstrated in n3 and n6 levels in the food diet analysis among the 3 ethnic groups. Differences exist in breast milk fatty acid composition in different ethnic groups in the same region, although no difference was demonstrated in the diet analysis. Factors other than maternal diet may play a role in breast milk fatty acid composition.

Soft antimicrobial agents: synthesis and activity of labile environmentally friendly long chain quaternary ammonium compounds.

PubMed

Thorsteinsson, Thorsteinn; Másson, Már; Kristinsson, Karl G; Hjálmarsdóttir, Martha A; Hilmarsson, Hilmar; Loftsson, Thorsteinn

2003-09-11

A series of soft quaternary ammonium antimicrobial agents, which are analogues to currently used quaternary ammonium preservatives such as cetyl pyridinium chloride and benzalkonium chloride, were synthesized. These soft analogues consist of long alkyl chain connected to a polar headgroup via chemically labile spacer group. They are characterized by facile nonenzymatic and enzymatic degradation to form their original nontoxic building blocks. However, their chemical stability has to be adequate in order for them to have antimicrobial effects. Stability studies and antibacterial and antiviral activity measurements revealed relationship between activity, lipophilicity, and stability. Their minimum inhibitory concentration (MIC) was as low as 1 microg/mL, and their viral reduction was in some cases greater than 6.7 log. The structure-activity studies demonstrate that the bioactive compounds (i.e., MIC for Gram-positive bacteria of <10 microg/mL) have an alkyl chain length between 12 and 18 carbon atoms, with a polar headgroup preferably of a small quaternary ammonium group, and their acquired inactivation half-life must be greater than 3 h at 60 degrees C.

A new class of high-contrast Fe(II) selective fluorescent probes based on spirocyclized scaffolds for visualization of intracellular labile iron delivered by transferrin.

PubMed

Niwa, Masato; Hirayama, Tasuku; Okuda, Kensuke; Nagasawa, Hideko

2014-09-14

Iron is an essential metal nutrient that plays physiologically and pathologically important roles in biological systems. However, studies on the trafficking, storage, and functions of iron itself in living samples have remained challenging due to the lack of efficient methods for monitoring labile intracellular iron. Herein, we report a new class of Fe(2+)-selective fluorescent probes based on the spirocyclization of hydroxymethylrhodamine and hydroxymethylrhodol scaffolds controlled by using our recently established N-oxide chemistry as a Fe(2+)-selective switch of fluorescence response. By suppressing the background signal, the spirocyclization strategy improved the turn-on rate dramatically, and reducing the size of the substituents of the N-oxide group enhanced the reaction rate against Fe(2+), compared with the first generation N-oxide based Fe(2+) probe, RhoNox-1. These new probes showed significant enhancements in the fluorescence signal against not only the exogenously loaded Fe(2+) but also the endogenous Fe(2+) levels. Furthermore, we succeeded in monitoring the accumulation of labile iron in the lysosome induced by transferrin-mediated endocytosis with a turn-on fluorescence response.

Non-labile silver species in biosolids remain stable throughout 50 years of weathering and ageing.

EPA Science Inventory

Increasing commercial use of nanosilver has focussed attention on the fate of silver (Ag) in the wastewater release pathway. This paper reports the speciation and lability of Ag in archived, stockpiled, and contemporary biosolids from the UK, USA and Australia, and indicates that...

Caged molecular beacons: controlling nucleic acid hybridization with light.

PubMed

Wang, Chunming; Zhu, Zhi; Song, Yanling; Lin, Hui; Yang, Chaoyong James; Tan, Weihong

2011-05-28

We have constructed a novel class of light-activatable caged molecular beacons (cMBs) that are caged by locking two stems with a photo-labile biomolecular interaction or covalent bond. With the cMBs, the nucleic acid hybridization process can be easily controlled with light, which offers the possibility for a high spatiotemporal resolution study of intracellular mRNAs. © The Royal Society of Chemistry 2011

Impact of labile metal nanoparticles on cellular homeostasis. Current developments in imaging, synthesis and applications.

PubMed

Chevallet, Mireille; Veronesi, Giulia; Fuchs, Alexandra; Mintz, Elisabeth; Michaud-Soret, Isabelle; Deniaud, Aurélien

2017-06-01

The use of nanomaterials is constantly increasing in electronics, cosmetics, food additives, and is emerging in advanced biomedical applications such as theranostics, bio-imaging and therapeutics. However their safety raises concerns and requires appropriate methods to analyze their fate in vivo. In this review, we describe the current knowledge about the toxicity of labile metal (ZnO, CuO and Ag) nanoparticles (NPs) both at the organism and cellular levels, and describe the pathways that are triggered to maintain cellular homeostasis. We also describe advanced elemental imaging approaches to analyze intracellular NP fate. Finally, we open the discussion by presenting recent developments in terms of synthesis and applications of Ag and CuO NPs. Labile metal nanoparticles (MeNPs) release metal ions that trigger a cellular response involving biomolecules binding to the ions followed by regulation of the redox balance. In addition, specific mechanisms are set up by the cell in response to physiological ions such as Cu(I) and Zn(II). Among all types of NPs, labile MeNPs induce the strongest inflammatory responses which are most probably due to the combined effects of the NPs and of its released ions. Interestingly, recent developments in imaging technologies enable the intracellular visualization of both the NPs and their ions and promise new insights into nanoparticle fate and toxicity. The exponential use of nanotechnologies associated with the difficulties of assessing their impact on health and the environment has prompted scientists to develop novel methodologies to characterize these nanoobjects in a biological context. Copyright © 2016 Elsevier B.V. All rights reserved.

Metal speciation and potential bioavailability changes during discharge and neutralisation of acidic drainage water.

PubMed

Simpson, Stuart L; Vardanega, Christopher R; Jarolimek, Chad; Jolley, Dianne F; Angel, Brad M; Mosley, Luke M

2014-05-01

The discharge of acid drainage from the farm irrigation areas to the Murray River in South Australia represents a potential risk to water quality. The drainage waters have low pH (2.9-5.7), high acidity (up to 1190 mg L(-1) CaCO3), high dissolved organic carbon (10-40 mg L(-1)), and high dissolved Al, Co, Ni and Zn (up to 55, 1.25, 1.30 and 1.10 mg L(-1), respectively) that represent the greatest concern relative to water quality guidelines (WQGs). To provide information on bioavailability, changes in metal speciation were assessed during mixing experiments using filtration (colloidal metals) and Chelex-lability (free metal ions and weak inorganic metal complexes) methods. Following mixing of drainage and river water, much of the dissolved aluminium and iron precipitated. The concentrations of other metals generally decreased conservatively in proportion to the dilution initially, but longer mixing periods caused increased precipitation or adsorption to particulate phases. Dissolved Co, Mn and Zn were typically 95-100% present in Chelex-labile forms, whereas 40-70% of the dissolved nickel was Chelex-labile and the remaining non-labile fraction of dissolved nickel was associated with fine colloids or complexed by organic ligands that increased with time. Despite the different kinetics of precipitation, adsorption and complexation reactions, the dissolved metal concentrations were generally highly correlated for the pooled data sets, indicating that the major factors controlling the concentrations were similar for each metal (pH, dilution, and time following mixing). For dilutions of the drainage waters of less than 1% with Murray River water, none of the metals should exceed the WQGs. However, the high concentrations of metals associated with fine precipitates within the receiving waters may represent a risk to some aquatic organisms. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Effects of lability of metal complex on free ion measurement using DMT.

PubMed

Weng, Liping; Van Riemsdijk, Willem H; Temminghoff, Erwin J M

2010-04-01

Very low concentrations of free metal ion in natural samples can be measured using the Donnan membrane technique (DMT) based on ion transport kinetics. In this paper, the possible effects of slow dissociation of metal complexes on the interpretation of kinetic DMT are investigated both theoretically and experimentally. The expressions of the lability parameter, Lgrangian , were derived for DMT. Analysis of new experimental studies using synthetic solution containing NTA as the ligand and Cu(2+) ions shows that when the ionic strength is low (labile species measured using other dynamic sensors (DGT, GIME) in several freshwaters, it is concluded that in most waters ion transport in DMT is controlled by diffusion in the membrane. Only in very soft waters (<0.7 mM Ca+Mg), the dissociation rate of natural metal complex may influence ion transport in DMT. In this case, neglecting this effect may lead to an underestimation of the free metal ion concentration measured.

Following The Money: Characterizing the Dynamics of Microbial Ecosystems and Labile Organic Matter in Grassland Soils

NASA Astrophysics Data System (ADS)

Herbert, B. E.; McNeal, K. S.

2006-12-01

The dynamics of soil microbial ecosystems and labile fractions of soil organic matter in grasslands have important implications for the response of these critical ecosystems to perturbations. Organic, inorganic and genetic biomarkers in the solid (e.g. lipids, microbial DNA), liquid (e.g. porewater ions) or gaseous phases (e.g. carbon dioxide) have been used to characterize carbon cycling and soil microbial ecology. These proxies are generally limited in the amount of temporal information that they can provide (i.e., solid-phase proxies) or the amount of specific information they can provide about carbon sources or microbial community processes (e.g. inorganic gases). It is the aim of this research to validate the use of soil volatile organic carbon emissions (VOCs) as useful indicators of subsurface microbial community shifts and processes as a function of ecosystem perturbations. We present results of method validation using laboratory microcosm, where VOC metabolites as characterized by gas chromatography and mass spectrometry (GC-MS), were related to other proxies including carbon dioxide (CO2) via infra-red technology, and microbial community shifts as measured by Biolog© and fatty acid methyl ester (FAME) techniques. Experiments with soil collected from grasslands along the coastal margin region in southern Texas were preformed where environmental factors such as soil water content, soil type, and charcoal content are manipulated. Results indicate that over fifty identifiable VOC metabolites are produced from the soils, where many (~15) can be direct indicators of microbial ecology. Principle component analysis (PCA) evidences these trends through similar cluster patterns for the VOC results, the Biolog© results, and FAME. Regression analysis further shows that VOCs are significant (p < 0.05) indicators of microbial stress. Our results are encouraging that characterizing VOCs production in grassland soils are easy to measure, relatively inexpensive method

Evaluation of the New MALDI Matrix 4-Chloro-α-Cyanocinnamic Acid

PubMed Central

Leszyk, John D.

2010-01-01

MALDI-TOF continues to be an important tool for many proteomic studies. Recently, a new rationally designed matrix 4-chloro-α-cyanocinnamic acid was introduced, which is reported to have superior performance as compared with the “gold standard” α-cyano-4-hydroxycinnamic acid (CHCA).1 In this study, the performance of this new matrix, using the Shimadzu Biotech Axima TOF2 (Shimadzu Biotech, Manchester, UK), was investigated. The overall sequence coverage as well as sensitivity of this matrix were compared with CHCA using standard protein tryptic digests. The performance of this matrix with labile peptides, such as phosphopeptides and 4-sulfophenyl isothiocynate-derivatized peptides, to facilitate de novo sequencing was also explored. This matrix was found to be better performing than CHCA in overall sensitivity and showed better sequence coverage at low-digest levels, partly as a result of less of a bias for arginine-containing peptides. It also showed as much as a tenfold improvement in sensitivity with labile peptides on standard stainless-steel targets. In addition, as a result of the much cooler nature of this matrix, labile peptides are readily seen intact with much less fragmentation in mass spectrometry (MS) mode. This matrix was also evaluated in the MS/MS fragmentation modes of post-source decay (PSD) and collisional-induced dissociation (CID). It was found that fragmentation occurs readily in CID, however as a result of the very cool nature of this new matrix, the PSD fragments were quite weak. This matrix promises to be an important addition to the already extensive array of MALDI matrices. PMID:20592871

4-Mercaptophenylboronic acid SAMs on gold: comparison with SAMs derived from thiophenol, 4-mercaptophenol, and 4-mercaptobenzoic acid.

PubMed

Barriet, David; Yam, Chi Ming; Shmakova, Olga E; Jamison, Andrew C; Lee, T Randall

2007-08-14

We report the formation and characterization of self-assembled monolayers (SAMs) derived from the adsorption of 4-mercaptophenylboronic acid (MPBA) on gold. For comparison, SAMs derived from the adsorption of thiophenol (TP), 4-mercaptophenol (MP), and 4-mercaptobenzoic acid (MBA) were also examined. The structure and properties of the SAMs were evaluated by ellipsometry, contact-angle goniometry, polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS). Specifically, ellipsometry was used to assess the formation of monolayer films, and contact angle measurements were used to determine the surface hydrophilicity and homogeneity. Separately, PM-IRRAS was used to evaluate the molecular composition and orientation as well as the intermolecular hydrogen bonding within the SAMs. Finally, XPS was used to evaluate the film composition and surface coverage (i.e., packing density), which was observed to increase in the following order: TP < MP < MPBA < MBA. A rationalization for the observed packing differences is presented. The XPS data indicate further that ultrahigh vacuum conditions induce the partial dehydration of MPBA SAMs with the concomitant formation of surface boronic anhydride species. Overall, the analytical data collectively show that the MPBA moieties in the SAMs exist in the acid form rather than the anhydride form under ambient laboratory conditions. Furthermore, stability studies find that MPBA SAMs are surprisingly labile in basic solution, where the terminal B-C bonds are cleaved by the attack of hydroxide ion and strongly basic amine nucleophiles. The unanticipated lability observed here should be considered by those wishing to use MPBA moieties in carbohydrate-sensing applications.

A Reexamination of Amino Acids in Lunar Soils: Implications for the Survival of Exogenous Organic Material During Impact Delivery

NASA Technical Reports Server (NTRS)

Brinton, Karen L. F.; Bada, Jeffrey L.

1996-01-01

Using a sensitive high performance liquid chromatography technique, we have analyzed both the hot water extract and the acid hydrolyzed hot water extract of lunar soil collected during the Apollo 17 mission. Both free amino acids and those derived from acid labile precursors are present at a level of roughly 15 ppb. Based on the D/L amino acid ratios, the free alanine and aspartic acid observed in the hot water extract can be entirely attributed to terrestrial biogenic contamination. However, in the acid labile fraction, precursors which yield amino acids are apparently present in the lunar soil. The amino acid distribution suggests that the precursor is probably solar wind implanted HCN. We have evaluated our results with regard to the meteoritic input of intact organic compounds to the moon based on an upper limit of less than or equal to 0.3 ppb for alpha-aminoisobutyric acid, a non-protein amino acid which does not generally occur in terrestrial organisms and which is not a major amino acid produced from HCN, but which is a predominant amino acid in many carbonaceous chondrites. We find that the survival of exogenous organic compounds during lunar impact is less than or equal to 0.8%. This result represents an example of minimum organic impact survivability. This is an important first step toward a better understanding of similar processes on Earth and on Mars, and their possible contribution to the budget of prebiotic organic compounds on the primitive Earth.

Dual, differential isotope labeling shows the preferential movement of labile plant constituents into mineral-bonded soil organic matter.

PubMed

Haddix, Michelle L; Paul, Eldor A; Cotrufo, M Francesca

2016-06-01

The formation and stabilization of soil organic matter (SOM) are major concerns in the context of global change for carbon sequestration and soil health. It is presently believed that lignin is not selectively preserved in soil and that chemically labile compounds bonding to minerals comprise a large fraction of the SOM. Labile plant inputs have been suggested to be the main precursor of the mineral-bonded SOM. Litter decomposition and SOM formation are expected to have temperature sensitivity varying with the lability of plant inputs. We tested this framework using dual (13) C and (15) N differentially labeled plant material to distinguish the metabolic and structural components within a single plant material. Big Bluestem (Andropogon gerardii) seedlings were grown in an enriched (13) C and (15) N environment and then prior to harvest, removed from the enriched environment and allowed to incorporate natural abundance (13) C-CO2 and (15) N fertilizer into the metabolic plant components. This enabled us to achieve a greater than one atom % difference in (13) C between the metabolic and structural components within the plant litter. This differentially labeled litter was incubated in soil at 15 and 35 °C, for 386 days with CO2 measured throughout the incubation. After 14, 28, 147, and 386 days of incubation, the soil was subsequently fractionated. There was no difference in temperature sensitivity of the metabolic and structural components with regard to how much was respired or in the amount of litter biomass stabilized. Only the metabolic litter component was found in the sand, silt, or clay fraction while the structural component was exclusively found in the light fraction. These results support the stabilization framework that labile plant components are the main precursor of mineral-associated organic matter. © 2016 John Wiley & Sons Ltd.

Constraints on Transport and Emplacement Mechanisms of Labile Fractions in Lunar Cold Traps

NASA Technical Reports Server (NTRS)

Rickman, D.; Gertsch, L.

2014-01-01

Sustaining the scientific exploration of the Solar System will require a significant proportion of the necessary fuels and propellants, as well as other bulk commodities, to be produced from local raw materials [1]. The viability of mineral production depends on the ability to locate and characterize mineable deposits of the necessary feedstocks. This requires, among other things, a workable understanding of the mechanisms by which such deposits form, which is the subject of Economic Geology. Multiple deposition scenarios are possible for labile materials on the Moon. This paper suggests labile fractions moved diffusely through space; deposits may grow richer with depth until low porosity rock; lateral transport is likely to have occurred with the regolith, at least for short distances; crystalline ice may not exist; the constituent phases could be extremely complex. At present we can constrain the sources only mildly; once on the Moon, the transport mechanisms inherently mix and therefore obscure the origins. However, the importance of expanding our understanding of ore-forming processes on the Moon behooves us to make the attempt. Thus begins a time of new inquiry for Economic Geology.

Interspecific variations in mangrove leaf litter decomposition are related to labile nitrogenous compounds

NASA Astrophysics Data System (ADS)

Nordhaus, Inga; Salewski, Tabea; Jennerjahn, Tim C.

2017-06-01

Mangrove leaves form a large pool of carbon, nitrogen and energy that is a major driver of element cycles and detrital food webs inside mangrove forests as well as in adjacent coastal waters. However, there are large gaps in knowledge on the transformation pathways and ultimate fate of leaf nitrogen. Therefore, the main objective of this study was to determine the amount and composition of nitrogenous organic matter and possible species-specific differences during the decomposition of mangrove leaf litter. For that purpose a three month decomposition experiment with litterbags was conducted using leaves of Aegiceras corniculatum, Avicennia alba, Ceriops decandra, Rhizophora apiculata, and Sonneratia caseolaris in the mangrove forest of the Segara Anakan Lagoon, Java, Indonesia. Detrital leaves were analyzed for bulk carbon and total nitrogen (N), stable carbon and nitrogen isotope composition (δ13C, δ15N), total hydrolyzable amino acids (THAA) and total hydrolyzable hexosamines (THHA). Decomposition rates (k d-1) were highest and tM50 values (when 50% of the original mass had been degraded) lowest in S. caseolaris (k = 0.0382 d-1; tM50 = 18 days), followed by A. alba, C. decandra, A. corniculatum, and R. apiculata (k = 0.0098 d-1; tM50 = 71 days). The biochemical composition of detrital leaves differed significantly among species and over time. S. caseolaris and A. alba had higher concentrations of N, THAA and THHA and a lower C/N ratio than the other three species. For most of the species concentrations of N, THAA and THHA increased during decomposition. The hexosamine galactosamine, indicative of bacterial cell walls, was first found in leaves after 5-7 days of decomposition and increased afterwards. Our findings suggest an increasing, but species-specific varying, portion of labile nitrogenous OM and total N in decomposing leaves over time that is partly related to the activity of leaf-colonizing bacteria. Despite a higher relative nitrogen content in the

Developing cellulosic waste products as platform chemicals: protecting group chemistry of α-glucoisosaccharinic acid.

PubMed

Almond, Michael; Suleiman, Mustapha G; Hawkins, Matthew; Winder, Daniel; Robshaw, Thomas; Waddoups, Megan; Humphreys, Paul N; Laws, Andrew P

2018-01-02

Alpha and beta-glucoisosaccharinic acids ((2S,4S)-2,4,5-trihydroxy-2-(hydroxymethyl)pentanoic acid and (2R,4S)-2,4,5-trihydroxy-2-(hydroxymethyl)pentanoic acid) which are produced when cellulosic materials are treated with aqueous alkali are potentially valuable platform chemicals. Their highly functionalised carbon skeleton, with fixed chirality at C-2 and C-4, makes them ideal starting materials for use in synthesis. In order to assess the potential of these saccharinic acids as platform chemicals we have explored the protecting group chemistry of the lactone form of alpha-glucoisosaccharinic acid (α-GISAL). We report here the use of single and multiple step reaction pathways leading to the regioselective protection of the three different hydroxyl groups of α-GISAL. We report strategies for protecting the three different hydroxyl groups individually or in pairs. We also report the synthesis of a range of tri-O-protected α-GISAL derivatives where a number of the products contain orthogonal protecting groups. Copyright © 2017 Elsevier Ltd. All rights reserved.

Enterotoxigenic Escherichia coli blood group A interactions intensify diarrheal severity.

PubMed

Kumar, Pardeep; Kuhlmann, F Matthew; Chakroborty, Subhra; Bourgeois, A Louis; Foulke-Abel, Jennifer; Tumala, Brunda; Vickers, Tim J; Sack, David A; DeNearing, Barbara; Harro, Clayton D; Wright, W Shea; Gildersleeve, Jeffrey C; Ciorba, Matthew A; Santhanam, Srikanth; Porter, Chad K; Gutierrez, Ramiro L; Prouty, Michael G; Riddle, Mark S; Polino, Alexander; Sheikh, Alaullah; Donowitz, Mark; Fleckenstein, James M

2018-05-17

Enterotoxigenic Escherichia coli (ETEC) infections are highly prevalent in developing countries where clinical presentations range from asymptomatic colonization to severe cholera-like illness. The molecular basis for these varied presentations, that may involve strain-specific virulence features as well as host factors, have not been elucidated. We demonstrate that when challenged with ETEC strain H10407, originally isolated from a case of cholera-like illness, blood group A human volunteers developed severe diarrhea more frequently than individuals from other blood groups. Interestingly, a diverse population of ETEC strains, including H10407, secrete a novel adhesin molecule, EtpA. As many bacterial adhesins also agglutinate red blood cells, we combined the use of glycan arrays, biolayer inferometry, and non-canonical amino acid labeling with hemagglutination studies to demonstrate that EtpA is a dominant ETEC blood group A specific lectin/hemagglutinin. Importantly, we also show that EtpA interacts specifically with glycans expressed on intestinal epithelial cells from blood group A individuals, and that EtpA-mediated bacterial-host interactions accelerate bacterial adhesion and the effective delivery both heat-labile and heat-stable toxins of ETEC. Collectively, these data provide additional insight into the complex molecular basis of severe ETEC diarrheal illness that may inform rational design of vaccines to protect those at highest risk.

Glaciers as a source of ancient and labile organic matter to the marine environment.

Treesearch

Eran Hood; Jason Fellman; Robert G.M. Spencer; Peter J. Hernes; Rick Edwards; David D' Amore; Durelle Scott

2009-01-01

Riverine organic matter supports of the order of one-fifth of estuarine metabolism. Coastal ecosystems are therefore sensitive to alteration of both the quantity and lability of terrigenous dissolved organic matter (DOM) delivered by rivers. Here we characterize streamwater DOM from 11 coastal watersheds on the Gulf of Alaska that vary widely in glacier coverage. In...

IN-VITRO FORMATION OF PYROMORPHITE VIA REACTION OF PB SOURCES WITH SOFT-DRINK PHOSPHORIC ACID

EPA Science Inventory

The risk of Pb adsorption into the body may be greatly diminished when accompanied by a phosphate sink. One of the most labile, albeit not healthiest, forms of phosphate consumed in the human diet is derived from cola soft drinks that use phosphoric acid as a preservative and als...

Experimental evidence for an effect of early-diagenetic interaction between labile and refractory marine sedimentary organic matter on nitrogen dynamics

NASA Astrophysics Data System (ADS)

Turnewitsch, Robert; Domeyer, Bettina; Graf, Gerhard

2007-05-01

In most natural sedimentary systems labile and refractory organic material (OM) occur concomitantly. Little, however, is known on how different kinds of OM interact and how such interactions affect early diagenesis in sediments. In a simple sediment experiment, we investigated how interactions of OM substrates of different degradability affect benthic nitrogen (N) dynamics. Temporal evolution of a set of selected biogeochemical parameters was monitored in sandy sediment over 116 days in three experimental set-ups spiked with labile OM (tissue of Mytilus edulis), refractory OM (mostly aged Zostera marina and macroalgae), and a 1:1 mixture of labile and refractory OM. The initial amounts of particulate organic carbon (POC) were identical in the three set-ups. To check for non-linear interactions between labile and refractory OM, the evolution of the mixture system was compared with the evolution of the simple sum of the labile and refractory systems, divided by two. The sum system is the experimental control where labile and refractory OM are virtually combined but not allowed to interact. During the first 30 days there was evidence for net dissolved-inorganic-nitrogen (DIN) production followed by net DIN consumption. (Here 'DIN' is the sum of ammonium, nitrite and nitrate.) After ˜ 30 days a quasi steady state was reached. Non-linear interactions between the two types of OM were reflected by three main differences between the early-diagenetic evolutions of nitrogen dynamics of the mixture and sum (control) systems: (1) In the mixture system the phases of net DIN production and consumption commenced more rapidly and were more intense. (2) The mixture system was shifted towards a more oxidised state of DIN products [as indicated by increased (nitrite + nitrate)/(ammonium) ratios]. (3) There was some evidence that more OM, POC and particulate nitrogen were preserved in the mixture system. That is, in the mixture system more particulate OM was preserved while a higher

Labile rhizosphere soil solution fraction for prediction of bioavailability of heavy metals and rare earth elements to plants.

PubMed

Shan, Xiao-Quan; Wang, Zhongwen; Wang, Weisheng; Zhang, Shuzhen; Wen, Bei

2003-02-01

A labile rhizosphere soil solution fraction has been recommended to predict the bioavailability of heavy metals and rare earth elements to plants. This method used moist rhizosphere soil in combination with a mixture of 0.01 mol L(-1) of low-molecular-weight organic acids (LMWOAs) as extractant. The extracted soil solutions were fractionated into two colloidal fractions of <0.45 microm (F(3)) and <0.2 microm (F(2)), and one truly dissolved fraction including free metal ions and inorganic and organic complexes (fractionlabile rhizosphere soil solution fraction, F(lrss). For the soil solutions extracted with a mixture of LMWOAs the concentrations of heavy metals and rare earth elements in F(2) and F(3) were quite similar. However, the mean concentrations of Cr, Ni, Zn, Cu, Pb, Cd, La, Ce, Pr, and Nd in F(lrss) accounted for 79.9%, 91.3%, 90.8%, 60.1%, 77.5%, 75.3%, 81.2%, 77.2%, 80.3%, and 79.5%, respectively, of their concentrations in F(2). In contrast, there were no differences in the extractable metal concentrations between the three fractions while the first step of the method recommended by the European Community of Reference (BCR), where 0.1 mol L(-1) acetic acid was used as an extractant. The single correlation analysis was made between metal concentrations in the different fractions of soil solutions and their concentrations in wheat. If the first step of BCR method was used there was no good correlation between heavy metals in soil pools and that in wheat shoots and roots. When LMWAOs were used a good correlation was obtained between the concentrations of heavy metals in soil pools and that in wheat roots, which followed a general order of r(1 kD, LMWOAs) >r(0.2 microm, LMWOAs) approximately r(0.45 microm, LMWOAs). In the case of rare earth elements the good correlation was obtained for both the wheat roots and shoots. Generally, the correlation coefficients

Hydroxycinnamic acids in cooked potato tubers from Solanum tuberosum group Phureja.

PubMed

Piñeros-Niño, Clara; Narváez-Cuenca, Carlos-Eduardo; Kushalappa, Ajjamada C; Mosquera, Teresa

2017-05-01

Hydroxycinnamic acids are phenolic compounds and are considered to have health promotion properties due to their antioxidant activity. Potato tubers of 113 genotypes of Solanum tuberosum group Phureja belonging to the Colombian Central Collection, landraces of potatoes, and commercial cultivars were evaluated for their hydroxycinnamic acids content. The composition of these compounds was analyzed using cooked tubers in two different agro-climatic conditions. The genotypes were analyzed for chlorogenic acid, neo -chlorogenic acid, crypto -chlorogenic acid, and caffeic acid by ultrahigh-performance liquid chromatography (UHPLC). Chlorogenic acid was the major representative and varied between 0.77 to 7.98 g kg -1  DW (dry weight) followed by crypto -chlorogenic acid (from 0.09 to 1.50 g kg -1  DW). Under moorland agro-climatic conditions even though the chlorogenic acid levels increased with respect to flatland agro-climatic conditions, the related isomer neo -chlorogenic acid decreased as compared to flatland conditions. The correlation between chlorogenic acid with the isomers, and with caffeic acid was positive. This study demonstrated that there is a wide variation in hydroxycinnamic acids contents in the germplasm studied, which can be exploited in breeding programs to contribute to human health.

Changes in labile soil organic matter fractions following land use change from monocropping to poplar-based agroforestry systems in a semiarid region of Northeast China.

PubMed

Mao, Rong; Zeng, De-Hui; Li, Lu-Jun; Hu, Ya-Lin

2012-11-01

Labile fractions of soil organic matter (SOM) respond rapidly to land management practices and can be used as a sensitive indicator of changes in SOM. However, there is little information about the effect of agroforestry practices on labile SOM fractions in semiarid regions of China. In order to test the effects of land use change from monocropping to agroforestry systems on labile SOM fractions, we investigated soil microbial biomass C (MBC) and N, particulate organic matter C (POMC) and N (POMN), as well as total organic C (TOC) and total N (TN) in the 0- to 15-cm and the 15- to 30-cm layers in 4-year-old poplar-based agroforestry systems and adjoining monocropping systems with two different soil textures (sandy loam and sandy clay loam) in a semiarid region of Northeast China. Our results showed that poplar-based agroforestry practices affected soil MBC, POMC, and POMN, albeit there was no significant difference in TOC and TN. Agroforestry practices increased MBC, POMC, and POMN in sandy clay loam soils. However, in sandy loam soils, agroforestry practices only increased MBC and even decreased POMC and POMN at the 0- to 15-cm layer. Our results suggest that labile SOM fractions respond sensitively to poplar-based agroforestry practices and can provide early information about the changes in SOM in semiarid regions of Northeast China and highlight that the effects of agroforestry practices on labile SOM fractions vary with soil texture.

Type II Heat-labile Enterotoxins: Structure, Function, and Immunomofdulatory Properties

PubMed Central

Hajishengallis, George; Connell, Terry D.

2012-01-01

The heat-labile enterotoxins (HLTs) of Escherichia coli and Vibrio cholerae are classified into two major types on the basis of genetic, biochemical, and immunological properties. Type I and Type II HLT have been intensively studied for their exceptionally strong adjuvant activities. Despite general structural similarities, these molecules, in intact or derivative (non-toxic) forms, display notable differences in their mode of immunomodulatory action. The molecular basis of these differences has remained largely uncharacterized until recently. This review focuses on the Type II HLTs and their immunomodulatory properties which depend largely on interactions with unique gangliosides and Toll-like receptors that are not utilized by the Type I HLTs. PMID:23137790

Evolution of phenotypic plasticity and environmental tolerance of a labile quantitative character in a fluctuating environment.

PubMed

Lande, R

2014-05-01

Quantitative genetic models of evolution of phenotypic plasticity are used to derive environmental tolerance curves for a population in a changing environment, providing a theoretical foundation for integrating physiological and community ecology with evolutionary genetics of plasticity and norms of reaction. Plasticity is modelled for a labile quantitative character undergoing continuous reversible development and selection in a fluctuating environment. If there is no cost of plasticity, a labile character evolves expected plasticity equalling the slope of the optimal phenotype as a function of the environment. This contrasts with previous theory for plasticity influenced by the environment at a critical stage of early development determining a constant adult phenotype on which selection acts, for which the expected plasticity is reduced by the environmental predictability over the discrete time lag between development and selection. With a cost of plasticity in a labile character, the expected plasticity depends on the cost and on the environmental variance and predictability averaged over the continuous developmental time lag. Environmental tolerance curves derived from this model confirm traditional assumptions in physiological ecology and provide new insights. Tolerance curve width increases with larger environmental variance, but can only evolve within a limited range. The strength of the trade-off between tolerance curve height and width depends on the cost of plasticity. Asymmetric tolerance curves caused by male sterility at high temperature are illustrated. A simple condition is given for a large transient increase in plasticity and tolerance curve width following a sudden change in average environment. © 2014 The Author. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

Determination of labile copper, cobalt, and chromium in textile mill wastewater

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crain, J.S.; Essling, A.M.; Kiely, J.T.

1997-01-01

Copper, chromium, and cobalt species present in filtered wastewater effluent were separated by cation exchange and reverse phase chromatography. Three sample fractions were obtained: one containing metal cations (i.e., trivalent Cr, divalent Cu, and divalent Co), one containing organic species (including metallized dyes), and one containing other unretained species. The metal content of each fraction was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The sum of the corrected data was compared to the metal content of a filtered effluent aliquot digested totally with fuming sulfuric acid. Other aliquots of the filtered effluent were spiked with the metals ofmore » interest and digested to confirm chemical yield and accuracy. Method detection limits were consistently below 20 {mu}g L{sup -1} for Cu, 30 {mu}g L{sup -1} for Co, and 10 {mu}g L{sup -1} for Cr. Spike recoveries for undifferentiated Cu and Cr were statistically indistinguishable from unity; although Co spike recoveries were slightly low ({approximately}95%), its chemical yield was 98%. Copper retention on the sodium sulfonate cation exchange resin was closely correlated with the [EDTA]/[Cu] ratio, suggesting that metals retained upon the cation exchange column were assignable to labile metal species; however, mass balances for all three elements, though reasonable ({approximately}90%), were significantly different from unity. Mechanical factors may have contributed to the material loss, but other data suggest that some metal species reacted irreversibly with the reverse phase column. 3 refs., 2 figs., 4 tabs.« less

Distribution of dissolved labile and particulate iron and copper in Terra Nova Bay polynya (Ross Sea, Antarctica) surface waters in relation to nutrients and phytoplankton growth

NASA Astrophysics Data System (ADS)

Rivaro, Paola; Ianni, Carmela; Massolo, Serena; Abelmoschi, M. Luisa; De Vittor, Cinzia; Frache, Roberto

2011-05-01

The distribution of the dissolved labile and of the particulate Fe and Cu together with dissolved oxygen, nutrients, chlorophyll a and total particulate matter was investigated in the surface waters of Terra Nova Bay polynya in mid-January 2003. The measurements were conducted within the framework of the Italian Climatic Long-term Interactions of the Mass balance in Antarctica (CLIMA) Project activities. The labile dissolved fraction was operationally defined by employing the chelating resin Chelex-100, which retains free and loosely bound trace metal species. The dissolved labile Fe ranges from below the detection limit (0.15 nM) to 3.71 nM, while the dissolved labile Cu from below the detection limit (0.10 nM) to 0.90 nM. The lowest concentrations for both metals were observed at 20 m depth (the shallowest depth for which metals were measured). The concentration of the particulate Fe was about 5 times higher than the dissolved Fe concentration, ranging from 0.56 to 24.83 nM with an average of 6.45 nM. The concentration of the particulate Cu ranged from 0.01 to 0.71 nM with an average of 0.17 nM. The values are in agreement with the previous data collected in the same area. We evaluated the role of the Fe and Cu as biolimiting metals. The N:dissolved labile Fe ratios (18,900-130,666) would or would not allow a complete nitrate removal, on the basis of the N:Fe requirement ratios that we calculated considering the N:P and the C:P ratios estimated for diatoms. This finding partially agrees with the Si:N ratio that we found (2.29). Moreover we considered a possible influence of the dissolved labile Cu on the Fe uptake process.

Fusion of Escherichia coli heat-stable enterotoxin and heat-labile enterotoxin B subunit.

PubMed

Guzman-Verduzco, L M; Kupersztoch, Y M

1987-11-01

The 3' terminus of the DNA coding for the extracellular Escherichia coli heat-stable enterotoxin (ST) devoid of transcription and translation stop signals was fused to the 5' terminus of the DNA coding for the periplasmic B subunit of the heat-labile enterotoxin (LTB) deleted of ribosomal binding sites and leader peptide. By RNA-DNA hybridization analysis, it was shown that the fused DNA was transcribed in vivo into an RNA species in close agreement with the expected molecular weight inferred from the nucleotide sequence. The translation products of the fused DNA resulted in a hybrid molecule recognized in Western blots (immunoblots) with antibodies directed against the heat-labile moiety. Anti-LTB antibodies coupled to a solid support bound ST and LTB simultaneously when incubated with ST-LTB cellular extracts. By [35S]cysteine pulse-chase experiments, it was shown that the fused ST-LTB polypeptide was converted from a precursor with an equivalent electrophoretic mobility of 20,800 daltons to an approximately 18,500-dalton species, which accumulated within the cell. The data suggest that wild-type ST undergoes at least two processing steps during its export to the culture supernatant. Blocking the natural carboxy terminus of ST inhibited the second proteolytic step and extracellular delivery of the hybrid molecule.

Facile conversion of a coordinated nitro group into an aqua group: acid-induced nitro-to-nitro rearrangement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, W.G.

1987-11-18

The nitro complex (NH/sub 3/)/sub 5/CoNO/sub 2//sup 2 +/ reacts rapidly and completely with neat anhydrous trifluoromethanesulfonic acid to generate the aqua species (NH/sub 3/)/sub 5/CoOH/sub 2//sup 3 +/. Oxygen-17 NMR results show that the oxygen in the bound water is derived from the original nitro group. A mechanism involving acid-catalyzed nitrogen-to-oxygen nitrite rearrangement is considered. The relationship between the mechanisms for oxygen scrambling and acid-catalyzed loss of NO/sup +/ from the nitrito linkage isomer is discussed, together with the mechanism for the present reaction. 20 references, 1 figure.

Collagenase-labile polyurethane urea synthesis and processing into hollow fiber membranes.

PubMed

Fu, Hui-Li; Hong, Yi; Little, Steven R; Wagner, William R

2014-08-11

As a means to stimulate wound healing, a hollow fiber membrane system might be placed within a wound bed to provide local and externally regulated controlled delivery of regenerative factors. After sufficient healing, it would be desirable to triggerably degrade these fibers as opposed to pulling them out. Accordingly, a series of enzymatically degradable thermoplastic elastomers was developed as potential hollow fiber base material. Polyurethane ureas (PUUs) were synthesized based on 1, 4-diisocyanatobutane, polycaprolactone (PCL) diol and polyethylene glycol (PEG) at different molar fractions as soft segments, and collagenase-sensitive peptide GGGLGPAGGK-NH2 as a chain extender (defined as PUU-CLxEGy-peptide, where x and y are the respective molar percents). In these polymers, PEG in the polymer backbone decreased tensile strengths and initial moduli of solvent-cast films in the wet state, while increasing water absorption. Collagenase degradation was observed at 75% relative PEG content in the soft segment. Control PUUs with putrescine or nonsense peptide chain extenders did not degrade acutely in collagenase. Conduits electrospun from PUU-CL25EG75-peptide and PUU-CL50EG50-peptide exhibited appropriate mechanical strength and sustained release of a model protein from the tube lumen for 7 days. Collapse of PUU-CL25EG75-peptide tubes occurred after collagenase degradation for 3 days. In conclusion, through molecular design, synthesis and characterization, a collagenase-labile PUU-CL25EG75-peptide polymer was identified that exhibited the desired traits of triggerable lability, processability, and the capacity to act as a membrane to facilitate controlled protein release.

Simultaneous experimental determination of labile proton fraction ratio and exchange rate with irradiation radio frequency power-dependent quantitative CEST MRI analysis.

PubMed

Sun, Phillip Zhe; Wang, Yu; Xiao, Gang; Wu, Renhua

2013-01-01

Chemical exchange saturation transfer (CEST) imaging is sensitive to dilute proteins/peptides and microenvironmental properties, and has been increasingly evaluated for molecular imaging and in vivo applications. However, the experimentally measured CEST effect depends on the CEST agent concentration, exchange rate and relaxation time. In addition, there may be non-negligible direct radio-frequency (RF) saturation effects, particularly severe for diamagnetic CEST (DIACEST) agents owing to their relatively small chemical shift difference from that of the bulk water resonance. As such, the commonly used asymmetry analysis only provides CEST-weighted information. Recently, it has been shown with numerical simulation that both labile proton concentration and exchange rate can be determined by evaluating the RF power dependence of DIACEST effect. To validate the simulation results, we prepared and imaged two CEST phantoms: a pH phantom of serially titrated pH at a fixed creatine concentration and a concentration phantom of serially varied creatine concentration titrated to the same pH, and solved the labile proton fraction ratio and exchange rate per-pixel. For the concentration phantom, we showed that the labile proton fraction ratio is proportional to the CEST agent concentration with negligible change in the exchange rate. Additionally, we found the exchange rate of the pH phantom is dominantly base-catalyzed with little difference in the labile proton fraction ratio. In summary, our study demonstrated quantitative DIACEST MRI, which remains promising to augment the conventional CEST-weighted MRI analysis. Copyright © 2013 John Wiley & Sons, Ltd.

Labile Low-Molecular-Mass Metal Complexes in Mitochondria: Trials and Tribulations of a Burgeoning Field.

PubMed

Lindahl, Paul A; Moore, Michael J

2016-08-02

Iron, copper, zinc, manganese, cobalt, and molybdenum play important roles in mitochondrial biochemistry, serving to help catalyze reactions in numerous metalloenzymes. These metals are also found in labile "pools" within mitochondria. Although the composition and cellular function of these pools are largely unknown, they are thought to be comprised of nonproteinaceous low-molecular-mass (LMM) metal complexes. Many problems must be solved before these pools can be fully defined, especially problems stemming from the lability of such complexes. This lability arises from inherently weak coordinate bonds between ligands and metals. This is an advantage for catalysis and trafficking, but it makes characterization difficult. The most popular strategy for investigating such pools is to detect them using chelator probes with fluorescent properties that change upon metal coordination. Characterization is limited because of the inevitable destruction of the complexes during their detection. Moreover, probes likely react with more than one type of metal complex, confusing analyses. An alternative approach is to use liquid chromatography (LC) coupled with inductively coupled plasma mass spectrometry (ICP-MS). With help from a previous lab member, the authors recently developed an LC-ICP-MS approach to analyze LMM extracts from yeast and mammalian mitochondria. They detected several metal complexes, including Fe580, Fe1100, Fe1500, Cu5000, Zn1200, Zn1500, Mn1100, Mn2000, Co1200, Co1500, and Mo780 (numbers refer to approximate masses in daltons). Many of these may be used to metalate apo-metalloproteins as they fold inside the organelle. The LC-based approach also has challenges, e.g., in distinguishing artifactual metal complexes from endogenous ones, due to the fact that cells must be disrupted to form extracts before they are passed through chromatography columns prior to analysis. Ultimately, both approaches will be needed to characterize these intriguing complexes and to

Quantifying Functional Group Interactions that Determine Urea Effects on Nucleic Acid Helix Formation

PubMed Central

Guinn, Emily J.; Schwinefus, Jeffrey J.; Cha, Hyo Keun; McDevitt, Joseph L.; Merker, Wolf E.; Ritzer, Ryan; Muth, Gregory W.; Engelsgjerd, Samuel W.; Mangold, Kathryn E.; Thompson, Perry J.; Kerins, Michael J.; Record, Thomas

2013-01-01

Urea destabilizes helical and folded conformations of nucleic acids and proteins, as well as protein-nucleic acid complexes. To understand these effects, extend previous characterizations of interactions of urea with protein functional groups, and thereby develop urea as a probe of conformational changes in protein and nucleic acid processes, we obtain chemical potential derivatives (μ23 = dμ2/dm3) quantifying interactions of urea (component 3) with nucleic acid bases, base analogs, nucleosides and nucleotide monophosphates (component 2) using osmometry and hexanol-water distribution assays. Dissection of these μ23 yields interaction potentials quantifying interactions of urea with unit surface areas of nucleic acid functional groups (heterocyclic aromatic ring, ring methyl, carbonyl and phosphate O, amino N, sugar (C,O)); urea interacts favorably with all these groups, relative to interactions with water. Interactions of urea with heterocyclic aromatic rings and attached methyl groups (as on thymine) are particularly favorable, as previously observed for urea-homocyclic aromatic ring interactions. Urea m-values determined for double helix formation by DNA dodecamers near 25°C are in the range 0.72 to 0.85 kcal mol−1 m−1 and exhibit little systematic dependence on nucleobase composition (17–42% GC). Interpretation of these results using the urea interaction potentials indicates that extensive (60–90%) stacking of nucleobases in the separated strands in the transition region is required to explain the m-value. Results for RNA and DNA dodecamers obtained at higher temperatures, and literature data, are consistent with this conclusion. This demonstrates the utility of urea as a quantitative probe of changes in surface area (ΔASA) in nucleic acid processes. PMID:23510511

Hydrodehalogenation of alkyl iodides with base-mediated hydrogenation and catalytic transfer hydrogenation: application to the asymmetric synthesis of N-protected α-methylamines.

PubMed

Mandal, Pijus K; Birtwistle, J Sanderson; McMurray, John S

2014-09-05

We report a very mild synthesis of N-protected α-methylamines from the corresponding amino acids. Carboxyl groups of amino acids are reduced to iodomethyl groups via hydroxymethyl intermediates. Reductive deiodination to methyl groups is achieved by hydrogenation or catalytic transfer hydrogenation under alkaline conditions. Basic hydrodehalogenation is selective for the iodomethyl group over hydrogenolysis-labile protecting groups, such as benzyloxycarbonyl, benzyl ester, benzyl ether, and 9-fluorenyloxymethyl, thus allowing the conversion of virtually any protected amino acid into the corresponding N-protected α-methylamine.

Hydrodehalogenation of Alkyl Iodides with Base-Mediated Hydrogenation and Catalytic Transfer Hydrogenation: Application to the Asymmetric Synthesis of N-Protected α-Methylamines

PubMed Central

2015-01-01

We report a very mild synthesis of N-protected α-methylamines from the corresponding amino acids. Carboxyl groups of amino acids are reduced to iodomethyl groups via hydroxymethyl intermediates. Reductive deiodination to methyl groups is achieved by hydrogenation or catalytic transfer hydrogenation under alkaline conditions. Basic hydrodehalogenation is selective for the iodomethyl group over hydrogenolysis-labile protecting groups, such as benzyloxycarbonyl, benzyl ester, benzyl ether, and 9-fluorenyloxymethyl, thus allowing the conversion of virtually any protected amino acid into the corresponding N-protected α-methylamine. PMID:25116734

Occurrence and abundance of carbohydrates and amino compounds in sequentially extracted labile soil organic matter fractions.

USDA-ARS?s Scientific Manuscript database

This study aimed to investigate the content of carbohydrates and amino compounds in three labile fraction of soil organic matter (SOM). Soil samples were collected from two agricultural fields in southern Italy and the light fraction (LF), the 500–53-µm particulate organic matter (POM) and the mobil...

The Preparation of an Ultrastable Mesoporous Cr(III)-MOF via Reductive Labilization

DTIC Science & Technology

2015-09-02

of metal clusters from a template MOF with a known structure. Fe(III)-MOFs can serve as practical structural templates because iron resembles chromium ...clusters in PCN-333 are able to accommodate both di- and trivalent metal ions by varying the charges of the terminal ligands, the bridging oxygen atoms, and...molecules in trivalent aqua complexes27 Inert complexes Labile complexes M(OH2) Cr(OH2)6 3+ Ir(OH2)6 3+ V(OH2)6 3+ Fe(OH2)6 3+ Ti(OH2)6 3+ k (s1) 2.4 10

Analysis of Photosynthetic Antenna Function in a Mutant of Arabidopsis thaliana (L.) Lacking trans-Hexadecenoic Acid 1

PubMed Central

McCourt, Peter; Browse, John; Watson, Jan; Arntzen, Charles J.; Somerville, Chris R.

1985-01-01

Several lines of evidence support the proposal that the unusual chloroplast-specific lipid acyl group Δ3,trans-hexadecenoic acid (trans-C16:1) stimulates the formation or maintenance of the oligomeric form of the light-harvesting chlorophyll a/b complex (LHCP). To assess the functional significance of this apparent association we have analyzed LHCP structure and function in a mutant of Arabidopsis thaliana (L.) which lacks trans-C16:1 by electrophoretic analysis of the protein-chlorophyll complexes and by measurements of chlorophyll fluorescence under a variety of conditions. By these criteria the putative oligomeric form of LHCP appears to be slightly more labile to detergent-mediated dissociation in the mutant. The oligomeric PSI chlorophyll-protein complex, associated with PSI, was also more labile to detergent-mediated dissociation in the mutant, suggesting a previously unsuspected association of trans-C16:1 with the PSI complex. However, no significant effect of the mutation on the efficiency of energy transfer from LHCP to the photochemical reaction centers was observed under any of the various conditions imposed. Also, the stability of the chlorophyll-protein complexes to temperature-induced dissociation was unaffected in the mutant. The role of trans-C16:1 is very subtle or is only conditionally expressed. Images Fig. 1 PMID:16664340

Using solid 13C NMR coupled with solution 31P NMR spectroscopy to investigate molecular species and lability of organic carbon and phosphorus from aquatic plants in Tai Lake, China.

PubMed

Liu, Shasha; Zhu, Yuanrong; Wu, Fengchang; Meng, Wei; Wang, Hao; He, Zhongqi; Guo, Wenjing; Song, Fanhao; Giesy, John P

2017-01-01

Forms and labilities of plant-derived organic matters (OMs) including carbon (C) and phosphorus (P) were fundamental for understanding their release, degradation and environmental behaviour in lake ecosystems. Thus, solid 13 C and solution 31 P nuclear magnetic resonance (NMR) spectroscopy were used to characterize biomass of six aquatic plants in Tai Lake, China. The results showed that carbohydrates (61.2% of the total C) were predominant C functional group in the solid 13 C NMR spectra of plant biomass, which may indicate high lability and bioavailability of aquatic plants-derived organic matter in lakes. There was 72.6-103.7% of the total P in aquatic plant biomass extracted by NaOH-EDTA extracts. Solution 31 P NMR analysis of these NaOH-EDTA extracts further identified several molecular species of P including orthophosphate (50.1%), orthophosphate monoesters (46.8%), DNA (1.6%) and pyrophosphate (1.4%). Orthophosphate monoesters included β-glycerophosphate (17.7%), hydrolysis products of RNA (11.7%), α-glycerophosphate (9.2%) and other unknown monoesters (2.1%). Additionally, phytate, the major form of organic P in many lake sediments, was detected in floating plant water poppy. These inorganic P (e.g. orthophosphate and pyrophosphate) and organic P (e.g. diester and its degradation products) identified in plant biomass were all labile and bioavailable P, which would play an important role in recycling of P in lakes. These results increased knowledge of chemical composition and bioavailability of OMs derived from aquatic plants in lakes.

Microwave-assisted extraction performed in low temperature and in vacuo for the extraction of labile compounds in food samples.

PubMed

Xiao, Xiaohua; Song, Wei; Wang, Jiayue; Li, Gongke

2012-01-27

In this study, low temperature vacuum microwave-assisted extraction, which simultaneous performed microwave-assisted extraction (MAE) in low temperature and in vacuo environment, was proposed. The influencing parameters including solid/liquid ratio, extraction temperature, extraction time, degree of vacuum and microwave power were discussed. The predominance of low temperature vacuum microwave-assisted extraction was investigated by comparing the extraction yields of vitamin C, β-carotene, aloin A and astaxanthin in different foods with that in MAE and solvent extraction, and 5.2-243% increments were obtained. On the other hand, the chemical kinetics of vitamin C and aloin A, which composed two different steps including the extraction step of analyte transferred from matrix into solvent and the decomposition step of analyte degraded in the extraction solvent, were proposed. All of the decomposition rates (K(2)) for the selected analyte in low temperature, in vacuo and in nitrogen atmosphere decreased significantly comparing with that in conventional MAE, which are in agreement with that obtained from experiments. Consequently, the present method was successfully applied to extract labile compound from different food samples. These results showed that low temperature and/or in vacuo environment in microwave-assisted extraction system was especially important to prevent the degradation of labile components and have good potential on the extraction of labile compound in foods, pharmaceutical and natural products. Copyright © 2011 Elsevier B.V. All rights reserved.

Evaluation of Adsorption Characteristics of a Fibrous Adsorbent Containing Zwitter-Ionic Functional Group, Targeting Organic Acids.

PubMed

Nakazawa, Akira; Tang, Ning; Inoue, Yoshinori; Kamichatani, Waka; Katoh, Toshifumi; Saito, Mitsuru; Obara, Kenji; Toriba, Akira; Hayakawa, Kazuichi

2017-01-01

Diallylamine-maleic acid copolymer (DAM)-nonwoven fabric (DAM-f), a fibrous adsorbent, contains DAM with zwitter-ionic functional groups and forms a hydration layer on the surface. The aim of this report was to evaluate the adsorption selectivity of DAM-f to semi-volatile organic acid (C1-C5). In the aqueous phase, formic acid dissolved in the hydration layer bound to the imino group of DAM-f due to anion exchange interaction. In the gas phase, the adsorption amounts of organic acids increased with the exposure time. Moreover, the adsorption rate constants correlated with the air/water partition coefficients (log K aw ) for formic acid, propionic acid, butyric acid, valeric acid and isovaleric acid, except for acetic acid. These results indicate that DAM-f is highly selective to hydrophilic compounds which easily move from the air to the hydration layer of DAM-f.

Analysis of mycolic acids from a group of corynebacteria by capillary gas chromatography and mass spectrometry.

PubMed

Gailly, C; Sandra, P; Verzele, M; Cocito, C

1982-06-15

The cell wall of leprosy-derived corynebacteria (a group of 'diphtheroids' isolated from human leprosy lesions and patients' blood) was previously shown to contain, in addition to peptidoglycan and arabinogalactan, mycolic acids. These alpha-branched beta-hydroxy fatty acids were attributed to the corynomycolic group, according to their RF in monodimensional thin-layer chromatography. In the present work, mycolic acids from leprosy-derived and reference corynebacteria have been fractionated by monodimensional and bidimensional thin-layer chromatography and by gas chromatography. Pyrolyzed mycolic acids have been analyzed on conventional packed columns, whereas intact methyl esters of mycolic acids with free and silylated beta-hydroxyl group have been analyzed on capillary columns, and their structure has been established by mass spectrometry. In all leprosy-derived corynebacteria, some 20 components containing 24-36 carbon atoms and 0-4 double bonds were obtained. The three major groups had 32, 34 and 36 carbons, and the frequency of unsaturated versus saturated chains increased proportionally to the molecular weight. For comparison, the main components of a reference corynebacterium. Corynebacterium diphtheriae PW8, had 30 and 32 carbons, and their hydrocarbon chains were essentially saturated. This work confirms the relative chemical homogeneity of different leprosy-derived corynebacteria and describes some peculiar traits in the chemical structure of this group of organisms. In addition, it shows the complexity of the mycolic acid fraction of corynebacterial cell wall and suggests that the mycolic acid pattern is a sort of fingerprint of each bacterial strain grown under standard conditions. Finally, the fractionation of intact corynomycolic acid methyl esters with free or silylated beta-hydroxyl group by capillary gas chromatography proved to be the best analytical procedure at present available for resolving this complex mixture of corynomycolate isomers

Cytosolic labile zinc: a marker for apoptosis in the developing rat brain.

PubMed

Lee, Joo-Yong; Hwang, Jung Jin; Park, Mi-Ha; Koh, Jae-Young

2006-01-01

Cytosolic zinc accumulation was thought to occur specifically in neuronal death (necrosis) following acute injury. However, a recent study demonstrated that zinc accumulation also occurs in adult rat neurons undergoing apoptosis following target ablation, and in vitro experiments have shown that zinc accumulation may play a causal role in various forms of apoptosis. Here, we examined whether intraneuronal zinc accumulation occurs in central neurons undergoing apoptosis during development. Embryonic and newborn Sprague-Dawley rat brains were double-stained for terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling (TUNEL) detection of apoptosis and immunohistochemical detection of stage-specific neuronal markers, such as nestin, proliferating cell nuclear antigen (PCNA), TuJ1 and neuronal nuclear specific protein (NeuN). The results revealed that apoptotic cell death occurred in neurons of diverse stages (neural stem cells, and dividing, young and adult neurons) throughout the brain during the embryonic and early postnatal periods. Further staining of brain sections with acid fuchsin or zinc-specific fluorescent dyes showed that all of the apoptotic neurons were acidophilic and contained labile zinc in their cell bodies. Cytosolic zinc accumulation was also observed in cultured cortical neurons undergoing staurosporine- or sodium nitroprusside (SNP)-induced apoptosis. In contrast, zinc chelation with CaEDTA or N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) reduced SNP-induced apoptosis but not staurosporine-induced apoptosis, indicating that cytosolic zinc accumulation does not play a causal role in all forms of apoptosis. Finally, the specific cytosolic zinc accumulation may have a practical application as a relatively simple marker for neurons undergoing developmental apoptosis.

Localization of alkali-labile sites in donkey (Equus asinus) and stallion (Equus caballus) spermatozoa.

PubMed

Cortés-Gutiérrez, Elva I; Dávila-Rodríguez, Martha I; López-Fernández, Carmen; Fernández, José Luis; Crespo, Francisco; Gosálvez, Jaime

2014-01-15

The presence of constitutive alkali-labile sites (ALS) has been investigated using a protocol of DNA breakage detection-fluorescence in situ hybridization and comet assay in spermatozoa of donkey (Equus asinus) and stallion (Equus caballus). These results were compared with those obtained using a similar experimental approach using somatic cells. The relative abundance of ALS was of the order of four times more in spermatozoa than in somatic cells. Alkali-labile sites showed a tendency to cluster localized at the equatorial-distal regions of the sperm. The amount of hybridized signal in the ALS in the sperm of donkey (Equus asinus) was 1.3 times greater than in stallion (Equus caballus), and the length of the comet tail obtained in donkey sperm was 1.6 times longer than that observed in stallion (P < 0.05); however, these differences were not appreciated in somatic cells. In conclusion, ALS localization in sperm is not a randomized event and a different pattern of ALS distribution occurs for each species. These results suggest that ALS represents a species-specific issue related to chromatin organization in sperm and somatic cells in mammalian species, and they might diverge even with very short phylogenetic distances. Copyright © 2014 Elsevier Inc. All rights reserved.

Synthesis and characterization of new poly(ortho ester amidine) copolymers for nonviral gene delivery

PubMed Central

Tang, Rupei; Ji, Weihang; Wang, Chun

2011-01-01

A new type of pH-labile cationic polymers, poly(ortho ester amidine) (POEAmd) copolymers, has been synthesized and characterized with potential future application as gene delivery carriers. The acid-labile POEAmd copolymer was synthesized by polycondensation of a new ortho ester diamine monomer with dimethylaliphatimidates, and a non-acid-labile polyamidine (PAmd) copolymer was also synthesized for comparison using a triethylene glycol diamine monomer. Both copolymers were easily dissolved in water, and can efficiently bind and condense plasmid DNA at neutral pH, forming nano-scale polyplexes. The physico-chemical properties of the polyplexes have been studied using dynamic light scattering, gel electrophoresis, ethidium bromide exclusion, and heparin competition. The average size of the polyplexes was dependent on the amidine: phosphate (N:P) ratio of the polymers to DNA. Polyplexes containing the acid-labile POEAmd or the non-acid-labile PAmd showed similar average particle size, comparable strength of condensing DNA, and resistance to electrostatic destabilization. They also share similar metabolic toxicity to cells as measured by MTT assay. Importantly, the acid-labile polyplexes undergo accelerated polymer degradation at mildly-acid-pHs, resulting in increasing particle size and the release of intact DNA plasmid. Polyplexes from both types of polyamidines caused distinct changes in the scattering properties of Baby Hamster Kidney (BHK-21) cells, showing swelling and increasing intracellular granularity. These cellular responses are uniquely different from other cationic polymers such as polyethylenimine and point to stress-related mechanisms specific to the polyamidines. Gene transfection of BHK-21 cells was evaluated by flow cytometry. The positive yet modest transfection efficiency by the polyamidines (acid-labile and non-acid-labile alike) underscores the importance of balancing polymer degradation and DNA release with endosomal escape. Insights gained from

A Longitudinal Study of Emotion Regulation, Emotion Lability-Negativity, and Internalizing Symptomatology in Maltreated and Nonmaltreated Children

ERIC Educational Resources Information Center

Kim-Spoon, Jungmeen; Cicchetti, Dante; Rogosch, Fred A.

2013-01-01

The longitudinal contributions of emotion regulation and emotion lability-negativity to internalizing symptomatology were examined in a low-income sample (171 maltreated and 151 nonmaltreated children, from age 7 to 10 years). Latent difference score models indicated that for both maltreated and nonmaltreated children, emotion regulation was a…

Estimating rates and patterns of morphological evolution from phylogenies: lessons in limb lability from Australian Lerista lizards

PubMed Central

Wiens, John J

2009-01-01

Squamates (lizards and snakes) offer an exciting model system for research on the evolution of body form. A new phylogenetic study in BMC Evolutionary Biology of Australian lizards shows remarkable evolutionary lability in digit numbers among closely related species, but also highlights important challenges in this area. PMID:19291259

Amino acid and hexosamine in the equatorial western Pacific: vertical fluxes and individual preservation through water column to surface sediments

NASA Astrophysics Data System (ADS)

Kawahata, H.; Gupta, L. P.; Ishizuka, T.

2002-12-01

Amino acids (AA) and hexosamines (HA) are major constituents for all living organisms, constituting important fractions of labile organic carbon and nitrogen. They usually decompose rapidly than bulk OM and must be expected to be closely linked to biogeochemical processes. In spite of such importance, our understanding of degradation processes of labile components is still limited. Therefore vertical fluxes and preservation of AA and HA from water column to surface sediments are investigated at the western equatorial Pacific. The settling particles were composed of fairly fresh AA, which could be derived from siliceous diatom with less amount of calcareous plankton. In contrast, AA were degraded in sediments and porewaters. Each AA showed highly variable preservation ratio from settling to sedimentary particles. Compared with glycine, the calculated preservation ratio was the lowest (0%) for cysteine, followed by phenylalanine (6%), tyrosine (17%), methionine (47%), leucine (60%), isoleucine (65%), proline (67%), valine (91%), serine (99%), arginine (107%), threonine (112%), alanine (115%), glutamic acid (114%), aspartic acid (150%), lysine (166%) and histidine (186%). Beta-alanine and gamma-aminobutyric acid were the least labile AA. Probably they are so difficult to degrade for bacteria to get biochemical energy that the degradation proceeds fairly slowly. In contrast, after burial, even most labile, aromatic and sulfur-containing AA, degrade at a rate similar to the other protein AA. In spite of complicated reactions, most of the AA showed first-order reaction kinetics during the degradation in the sediments. The decomposition rate constant k (kyr-1) in this study was 2-3 orders lower than those in coastal marine environments. Better preservation of HA over AA in the sediments was probably due to the general incorporation of HA into structural biopolymer matrices, such as bacterial cell-walls and chitinous material. Abundant glycine in the AA in the sediments is

Export of pre-aged, labile DOM from a central California coastal upwelling system: Insights from D/L amino acids and Δ14C signatures

NASA Astrophysics Data System (ADS)

Walker, B. D.; Shen, Y.; Benner, R. H.; Druffel, E. R. M.

2014-12-01

Coastal upwelling zones are among the most productive regions in the world and play a major role in global carbon and nitrogen cycles. Recent research suggests that a substantial fraction of newly fixed organic matter is exported offshore in the form of dissolved organic matter (DOM). However, to date only a few studies have examined DOM composition in the context of production and export from upwelling systems. The ultimate fate and geochemical impact of coastal DOM exported to offshore and mesopelagic ecosystems also remains largely unknown. Between 2007-2009 we conducted a high-resolution biogeochemical time series at the Granite Canyon Marine Pollution Studies Lab in part to evaluate the seasonal production and export of DOM from the Central CA coast. Our previous work demonstrated substantial, albeit disparate, seasonal production of dissolved organic carbon and nitrogen (DOC, DON) - with high DON (and low C:N ratios) produced during upwelling and high DOC produced during summer/fall water column stratification (Walker and McCarthy, 2012). Here we present new total dissolved D/L amino acid (TDAA) and UV-oxidizable DOC radiocarbon (Δ14C) data with the goal of determining the relative sources (heterotrophic vs. autotrophic), bioavailability, microbial processing and 14C-ages of C-rich vs. N-rich DOM exported from this upwelling system. Our results suggest that C-rich DOM produced during water column stratification carries a large microbial signature (i.e. high D/L AA ratios and non-protein AA abundance), whereas N-rich DOM produced during upwelling appears to be fresh, autotrophic DOM (i.e. lowest D/L AA ratios and highest TDAA abundance). DOM Δ14C signatures also did not approximate in situ dissolved inorganic carbon (DIC), and instead were far more negative and highly correlated to water mass density. Together our results indicate a previously unrecognized source of highly labile yet pre-aged DOM potentially impacting offshore and mesopelagic ecosystems.

Differences in dissolved organic matter lability between alpine glaciers and alpine rock glaciers of the American West

NASA Astrophysics Data System (ADS)

Hall, E.; Fegel, T. S., II; Baron, J.; Boot, C. M.

2015-12-01

While alpine glaciers in montane regions represent the largest flux of dissolved organic matter (DOM) from global ice melt no research has examined the bioavailability of DOM melted out of glacial ice in the western continental United States. Furthermore, rock glaciers are an order of magnitude more abundant than ice glaciers in U.S., yet are not included in budgets for perennial ice carbon stores. Our research aims to understand differences in the bioavailability of carbon from ice glaciers and rock glaciers along the Central Rocky Mountains of Colorado. Identical microbial communities were fed standardized amounts of DOM from four different ice glacier-rock glaciers pairs. Using laboratory incubations, paired with mass spectrometry based metabolomics and 16S gene sequencing; we were able to examine functional definitions of DOM lability in glacial ice. We hypothesized that even though DOM quantities are similar in the outputs of both glacial types in our study area, ice glacial DOM would be more bioavailable than DOM from rock glaciers due to higher proportions of byproducts from microbial metabolism than rock glacier DOM, which has higher amounts of "recalcitrant" plant material. Our results show that DOM from ice glaciers is more labile than DOM from geologically and geographically similar paired rock glaciers. Ice glacier DOM represents an important pool of labile carbon to headwater ecosystems of the Rocky Mountains. Metabolomic analysis shows numerous compounds from varying metabolite pathways, including byproducts of nitrification before and after incubation, meaning that, similar to large maritime glaciers in Alaska and Europe, subglacial environments in the mountain ranges of the United States are hotspots for biological activity and processing of organic carbon.

Efficient catalysis of Nazarov cyclization using a cationic iridium complex possessing adjacent labile coordination sites.

PubMed

Janka, Mesfin; He, Wei; Frontier, Alison J; Eisenberg, Richard

2004-06-09

The dicationic Ir(III) complex [IrMe(CO)(dppe)(DIB)](BARF)2 having adjacent labile sites has been found to be a very effective catalyst for promoting the Nazarov cyclization of aryl vinyl and divinyl ketones. Spectroscopic evidence for a substate-catalyst complex before cyclization is presented. The efficiency of the cyclization is attributed to the electrophilicity of the Ir(III) complex and substrate activation via chelation.

The structural study of acetohydroxamic and oxalodihydroxamic acids in DMSO solution based on the DFT calculations of NMR spectra

NASA Astrophysics Data System (ADS)

Kaczor, Agnieszka; Proniewicz, Leonard M.

2004-10-01

The 1H and 13C NMR spectra of acetohydroxamic (aha) and oxalodihydroxamic (oxha) acids were measured in DMSO- d6 solution. The atoms chemical shifts of chosen stable entgegen and zusammen conformers of monomeric acids were computed along with some clusters of the compounds with the solvent molecules [B3LYP/6-311++G(d,p), GIAO]. The latter were proposed to explain the differences between the theoretical and experimental resonances of the protons of the N-H and O-H groups. The computed chemical shifts of aha-(DMSO) 2 and oxha-(DMSO) 2 models are in good agreement with experimental data proving that the compounds existing in solution form aggregates with DMSO. The acids are H-bonded via all the labile protons to the oxygen atoms of the solvent molecules. aha exists in the zusammen and entgegen (relative to C-N bond) forms with the relative intensities of 8:1 while the sole z, E, z-conformers (notation refers to C-N, C-C and C-N bonds, respectively) were found for oxha.

The unique fold and lability of the [2Fe-2S] clusters of NEET proteins mediate their key functions in health and disease.

PubMed

Karmi, Ola; Marjault, Henri-Baptiste; Pesce, Luca; Carloni, Paolo; Onuchic, Jose' N; Jennings, Patricia A; Mittler, Ron; Nechushtai, Rachel

2018-02-12

NEET proteins comprise a new class of [2Fe-2S] cluster proteins. In human, three genes encode for NEET proteins: cisd1 encodes mitoNEET (mNT), cisd2 encodes the Nutrient-deprivation autophagy factor-1 (NAF-1) and cisd3 encodes MiNT (Miner2). These recently discovered proteins play key roles in many processes related to normal metabolism and disease. Indeed, NEET proteins are involved in iron, Fe-S, and reactive oxygen homeostasis in cells and play an important role in regulating apoptosis and autophagy. mNT and NAF-1 are homodimeric and reside on the outer mitochondrial membrane. NAF-1 also resides in the membranes of the ER associated mitochondrial membranes (MAM) and the ER. MiNT is a monomer with distinct asymmetry in the molecular surfaces surrounding the clusters. Unlike its paralogs mNT and NAF-1, it resides within the mitochondria. NAF-1 and mNT share similar backbone folds to the plant homodimeric NEET protein (At-NEET), while MiNT's backbone fold resembles a bacterial MiNT protein. Despite the variation of amino acid composition among these proteins, all NEET proteins retained their unique CDGSH domain harboring their unique 3Cys:1His [2Fe-2S] cluster coordination through evolution. The coordinating exposed His was shown to convey the lability to the NEET proteins' [2Fe-2S] clusters. In this minireview, we discuss the NEET fold and its structural elements. Special attention is given to the unique lability of the NEETs' [2Fe-2S] cluster and the implication of the latter to the NEET proteins' cellular and systemic function in health and disease.

Multivariate Statistical Analysis of Labile Trace Elements in H Chondrites: Evidence for Meteoroid Streams

NASA Astrophysics Data System (ADS)

Wolf, S. F.; Lipschutz, M. E.

1992-07-01

Differences have been observed between meteorite populations with vastly different terrestrial ages, i.e. Antarctic and non-Antarctic meteorite populations (Koeberl and Cassidy, 1991 and references therein). Comparisons of labile trace element contents (Wolf and Lipschutz, 1992) and induced TL parameters (Benoit and Sears, 1992) in samples from Victoria Land and Queen Maud Land, populations which also differ in mean terrestrial age (Nishiizumi et al, 1989), show significant differences consistent with different average thermal histories. These differences are consistent with the proposition that the flux of meteoritic material to Earth varied temporally. Variations in the flux of meteoritic material over time scales of 10^5 10^6 y require the existence of undispersed streams of meteoroids of asteroidal origin which were initially disputed by Wetherill ( 1986) but have since been observed (Olsson-Steele, 1988; Oberst, 1989; Halliday et al. 1990). Orbital evidence for meteoroid and asteroid streams has been independently obtained by others, particularly Halliday et al.(1990) and Drummond (1991). A group of H chondrites of various petrographic types and diverse CRE ages that yielded 16 falls from 1855 until 1895 in the month of May has been proposed to be two co-orbital meteoroid streams with a common source (R. T. Dodd, personal communication). Compositional evidence of a preterrestrial association of the proposed stream members, if it exists, might be observed in the most sensitive indicators of genetic thermal history, the labile trace elements. We report RNAA data for the concentrations of 14 trace elements, mostly labile ones, (Ag, Au, Bi, Cd, Cs, Co, Ga, In, Rb, Sb, Se, Te, Tl, and Zn) in H4-6 ordinary chondrites. Variance of elemental concentrations within a subpopulation, the members of a proposed co-orbital meteorite stream for example, could be expected to be smaller than the variance for the entire population. We utilize multivariate linear regression and

Assessing the Selectivity of Extractant Solutions for Recovering Labile Arsenic Associated with Iron (Hydr)oxides and Sulfides in Sediments

EPA Science Inventory

Sequential extractions can provide analytical constraints on the identification of mineral phases that control arsenic speciation in sediments. Model solids were used in this study to evaluate different solutions designed to extract arsenic from relatively labile solid phases. ...

Unravelling the bioherbicide potential of Eucalyptus globulus Labill: Biochemistry and effects of its aqueous extract

PubMed Central

Reigosa, Manuel J.; Valentão, Patrícia; Andrade, Paula B.

2018-01-01

In the worldwide search for new strategies in sustainable weed management, the use of plant species able to produce and release phytotoxic compounds into the environment could be an effective alternative to synthetic herbicides. Eucalyptus globulus Labill. is known to be a source of biologically active compounds responsible for its phytotoxic and allelopathic properties. Our previous results demonstrated the bioherbicide potential of eucalyptus leaves incorporated into the soil as a green manure, probably through the release of phytotoxins into the soil solution. Thus, the aims of this study were to understand the phytotoxicity of the eucalyptus leaves aqueous extract applied in pre- and post-emergence, and to identify and quantify its potentially phytotoxic water-soluble compounds. The effects were tested on the germination and early growth of the model target species Lactuca sativa and Agrostis stolonifera, and on physiological parameters of L. sativa adult plants after watering or spraying application. Dose-response curves and ED50 and ED80 values for eucalyptus aqueous extracts revealed pre-emergence inhibitory effects on both target species, effects being comparable to the herbicide metolachlor. While spraying treatment reduced the aerial and root biomass and increased the dry weight/fresh weight ratio of lettuce adult plants, watering application reduced protein contents and chlorophyll concentrations with respect to control, reflecting different modes of action depending on the site of phytotoxin entry. Via HPLC analyses, a total of 8 phenolic compounds (chlorogenic, two ρ-coumaric derivatives, ellagic, hyperoside, rutin, quercitrin, and kaempferol 3-O-glucoside) and other 5 low weight organic acids (citric, malic, shikimic, succinic and fumaric acids) were obtained from aqueous extract, the latter being identified for the first time in E. globulus. Despite some phytotoxic effects were found on lettuce adult plants, the use of eucalyptus aqueous extract

Unravelling the bioherbicide potential of Eucalyptus globulus Labill: Biochemistry and effects of its aqueous extract.

PubMed

Puig, Carolina G; Reigosa, Manuel J; Valentão, Patrícia; Andrade, Paula B; Pedrol, Nuria

2018-01-01

In the worldwide search for new strategies in sustainable weed management, the use of plant species able to produce and release phytotoxic compounds into the environment could be an effective alternative to synthetic herbicides. Eucalyptus globulus Labill. is known to be a source of biologically active compounds responsible for its phytotoxic and allelopathic properties. Our previous results demonstrated the bioherbicide potential of eucalyptus leaves incorporated into the soil as a green manure, probably through the release of phytotoxins into the soil solution. Thus, the aims of this study were to understand the phytotoxicity of the eucalyptus leaves aqueous extract applied in pre- and post-emergence, and to identify and quantify its potentially phytotoxic water-soluble compounds. The effects were tested on the germination and early growth of the model target species Lactuca sativa and Agrostis stolonifera, and on physiological parameters of L. sativa adult plants after watering or spraying application. Dose-response curves and ED50 and ED80 values for eucalyptus aqueous extracts revealed pre-emergence inhibitory effects on both target species, effects being comparable to the herbicide metolachlor. While spraying treatment reduced the aerial and root biomass and increased the dry weight/fresh weight ratio of lettuce adult plants, watering application reduced protein contents and chlorophyll concentrations with respect to control, reflecting different modes of action depending on the site of phytotoxin entry. Via HPLC analyses, a total of 8 phenolic compounds (chlorogenic, two ρ-coumaric derivatives, ellagic, hyperoside, rutin, quercitrin, and kaempferol 3-O-glucoside) and other 5 low weight organic acids (citric, malic, shikimic, succinic and fumaric acids) were obtained from aqueous extract, the latter being identified for the first time in E. globulus. Despite some phytotoxic effects were found on lettuce adult plants, the use of eucalyptus aqueous extract

Emotional Lability in Children and Adolescents with Attention Deficit/Hyperactivity Disorder (ADHD): Clinical Correlates and Familial Prevalence

ERIC Educational Resources Information Center

Sobanski, Esther; Banaschewski, Tobias; Asherson, Philip; Buitelaar, Jan; Chen, Wai; Franke, Barbara; Holtmann, Martin; Krumm, Bertram; Sergeant, Joseph; Sonuga-Barke, Edmund; Stringaris, Argyris; Taylor, Eric; Anney, Richard; Ebstein, Richard P.; Gill, Michael; Miranda, Ana; Mulas, Fernando; Oades, Robert D.; Roeyers, Herbert; Rothenberger, Aribert; Steinhausen, Hans-Christoph; Faraone, Stephen V.

2010-01-01

Background: The goal of this study was to investigate the occurrence, severity and clinical correlates of emotional lability (EL) in children with attention deficit/hyperactivity disorder (ADHD), and to examine factors contributing to EL and familiality of EL in youth with ADHD. Methods: One thousand, one hundred and eighty-six children with ADHD…

A nitrous acid biosynthetic pathway for diazo group formation in bacteria.

PubMed

Sugai, Yoshinori; Katsuyama, Yohei; Ohnishi, Yasuo

2016-02-01

Although some diazo compounds have bioactivities of medicinal interest, little is known about diazo group formation in nature. Here we describe an unprecedented nitrous acid biosynthetic pathway responsible for the formation of a diazo group in the biosynthesis of the ortho-diazoquinone secondary metabolite cremeomycin in Streptomyces cremeus. This finding provides important insights into the biosynthetic pathways not only for diazo compounds but also for other naturally occurring compounds containing nitrogen-nitrogen bonds.

A novel amino acid analysis method using derivatization of multiple functional groups followed by liquid chromatography/tandem mass spectrometry.

PubMed

Sakaguchi, Yohei; Kinumi, Tomoya; Yamazaki, Taichi; Takatsu, Akiko

2015-03-21

We have developed a novel amino acid analysis method using derivatization of multiple functional groups (amino, carboxyl, and phenolic hydroxyl groups). The amino, carboxyl, and phenolic hydroxyl groups of the amino acids were derivatized with 1-bromobutane so that the hydrophobicities and basicities of the amino acids were improved. The derivatized amino acids, including amino group-modified amino acids, could be detected with high sensitivity using liquid chromatography/tandem mass spectrometry (LC-MS/MS). In this study, 17 amino acids obtained by hydrolyzing proteins and 4 amino group-modified amino acids found in the human body (N,N-dimethylglycine, N-formyl-L-methionine, L-pyroglutamic acid, and sarcosine) were selected as target compounds. The 21 derivatized amino acids could be separated using an octadecyl-silylated silica column within 20 min and simultaneously detected. The detection limits for the 21 amino acids were 5.4-91 fmol, and the calibration curves were linear over the range of 10-100 nmol L(-1) (r(2) > 0.9984) with good repeatability. A confirmatory experiment showed that our proposed method could be applied to the determination of a protein certified reference material using the analysis of 12 amino acids combined with isotope dilution mass spectrometry. Furthermore, the proposed method was successfully applied to a stable isotope-coded derivatization method using 1-bromobutane and 1-bromobutane-4,4,4-d3 for comparative analysis of amino acids in human serum.

Crystallization and X-ray diffraction analysis of an 'all-locked' nucleic acid duplex derived from a tRNA(Ser) microhelix.

PubMed

Behling, Katja; Eichert, André; Fürste, Jens P; Betzel, Christian; Erdmann, Volker A; Förster, Charlotte

2009-08-01

Modified nucleic acids are of great interest with respect to their nuclease resistance and enhanced thermostability. In therapeutical and diagnostic applications, such molecules can substitute for labile natural nucleic acids that are targeted against particular diseases or applied in gene therapy. The so-called 'locked nucleic acids' contain modified sugar moieties such as 2'-O,4'-C-methylene-bridged beta-D-ribofuranose and are known to be very stable nucleic acid derivatives. The structure of locked nucleic acids in single or multiple LNA-substituted natural nucleic acids and in LNA-DNA or LNA-RNA heteroduplexes has been well investigated, but the X-ray structure of an ;all-locked' nucleic acid double helix has not been described to date. Here, the crystallization and X-ray diffraction data analysis of an 'all-locked' nucleic acid helix, which was designed as an LNA originating from a tRNA(Ser) microhelix RNA structure, is presented. The crystals belonged to space group C2, with unit-cell parameters a = 77.91, b = 40.74, c = 30.06 A, beta = 91.02 degrees . A high-resolution and a low-resolution data set were recorded, with the high-resolution data showing diffraction to 1.9 A resolution. The crystals contained two double helices per asymmetric unit, with a Matthews coefficient of 2.48 A(3) Da(-1) and a solvent content of 66.49% for the merged data.

Processing thermally labile drugs by hot-melt extrusion: The lesson with gliclazide.

PubMed

Huang, Siyuan; O'Donnell, Kevin P; Delpon de Vaux, Sophie M; O'Brien, John; Stutzman, John; Williams, Robert O

2017-10-01

The formation of molecularly dispersed amorphous solid dispersions by the hot-melt extrusion technique relies on the thermal and mechanical energy inputs, which can cause chemical degradation of drugs and polymeric carriers. Additionally, drug degradation may be exacerbated as drugs convert from a more stable crystalline form to a higher energy amorphous form. Therefore, it is imperative to study how drug degrades and evaluate methods to minimize drug degradation during the extrusion process. In this work, gliclazide was used as a model thermally labile drug for the degradation kinetics and process optimization studies. Preformulation studies were conducted using thermal analyses, and liquid chromatography-mass spectroscopy to identify drug degradation pathways and to determine initial extrusion conditions. Formulations containing 10% drug and 90% AFFINISOL™ HPMC HME 100LV were then extruded using a twin screw extruder, and the extrudates were characterized using X-ray powder diffraction, modulated dynamic scanning calorimetry, and potency testing to evaluate physicochemical properties. The energies of activation for both amorphous gliclazide, crystalline gliclazide, and gliclazide solution were calculated using the Arrhenius equation to further guide the extrusion optimization process. Preformulation studies identify two hydrolysis degradation pathways of gliclazide at elevated temperatures. The activation energy study indicates a significantly higher degradation rate for the amorphous gliclazide compared to the crystalline form. After optimization of the hot-melt extrusion process, including improved screw designs, machine setup, and processing conditions, gliclazide amorphous solid dispersion with ∼95% drug recovery was achieved. The ability to process thermally labile drugs and polymers using hot-melt extrusion will significantly expand the possible applications of this manufacturing process. Copyright © 2017 Elsevier B.V. All rights reserved.

Quantitative chemical exchange saturation transfer (qCEST) MRI--RF spillover effect-corrected omega plot for simultaneous determination of labile proton fraction ratio and exchange rate.

PubMed

Sun, Phillip Zhe; Wang, Yu; Dai, ZhuoZhi; Xiao, Gang; Wu, Renhua

2014-01-01

Chemical exchange saturation transfer (CEST) MRI is sensitive to dilute proteins and peptides as well as microenvironmental properties. However, the complexity of the CEST MRI effect, which varies with the labile proton content, exchange rate and experimental conditions, underscores the need for developing quantitative CEST (qCEST) analysis. Towards this goal, it has been shown that omega plot is capable of quantifying paramagnetic CEST MRI. However, the use of the omega plot is somewhat limited for diamagnetic CEST (DIACEST) MRI because it is more susceptible to direct radio frequency (RF) saturation (spillover) owing to the relatively small chemical shift. Recently, it has been found that, for dilute DIACEST agents that undergo slow to intermediate chemical exchange, the spillover effect varies little with the labile proton ratio and exchange rate. Therefore, we postulated that the omega plot analysis can be improved if RF spillover effect could be estimated and taken into account. Specifically, simulation showed that both labile proton ratio and exchange rate derived using the spillover effect-corrected omega plot were in good agreement with simulated values. In addition, the modified omega plot was confirmed experimentally, and we showed that the derived labile proton ratio increased linearly with creatine concentration (p < 0.01), with little difference in their exchange rate (p = 0.32). In summary, our study extends the conventional omega plot for quantitative analysis of DIACEST MRI. Copyright © 2014 John Wiley & Sons, Ltd.

Heat-labile Enterotoxins as Adjuvants or Anti-Inflammatory Agents

PubMed Central

Liang, Shuang; Hajishengallis, George

2010-01-01

Escherichia coli and Vibrio cholerae produce structurally related AB5-type heat-labile enterotoxins which are classified into two major types. The Type I subfamily includes cholera toxin and E. coli LT-I, whereas the Type II subfamily comprises LT-IIa and LT-IIb. In addition to their roles in microbial pathogenesis, the enterotoxins are widely and intensively studied for their exceptionally strong adjuvant and immunomodulatory activities, which are not necessarily dependent upon their abilities to elevate intracellular cAMP levels. Despite general structural similarities, these molecules, in intact or derivative form, display notable differences in their interactions with gangliosides or Toll-like receptors. This divergence results in differential immune response outcomes, the underlying mechanisms of which remain largely uncharacterized. Whereas the study of these molecules has been pivotal in understanding basic mechanisms of immune regulation, a formidable challenge is to dissociate toxicity from useful properties that can be exploited in vaccine development or for the treatment of autoimmune inflammatory diseases. PMID:20461887

Heat-labile enterotoxins as adjuvants or anti-inflammatory agents.

PubMed

Liang, Shuang; Hajishengallis, George

2010-01-01

Escherichia coli and Vibrio cholerae produce structurally related AB5-type heat-labile enterotoxins, which are classified into two major types. The Type I subfamily includes cholera toxin and E. coli LT-I, whereas the Type II subfamily comprises LT-IIa and LT-IIb. In addition to their roles in microbial pathogenesis, the enterotoxins are widely and intensively studied for their exceptionally strong adjuvant and immunomodulatory activities, which are not necessarily dependent upon their abilities to elevate intracellular cAMP levels. Despite general structural similarities, these molecules, in intact or derivative form, display notable differences in their interactions with gangliosides or Toll-like receptors. This divergence results in differential immune response outcomes, the underlying mechanisms of which remain largely uncharacterized. Whereas the study of these molecules has been pivotal in understanding basic mechanisms of immune regulation, a formidable challenge is to dissociate toxicity from useful properties that can be exploited in vaccine development or for the treatment of autoimmune inflammatory diseases.

[Escherichia coli heat-labile enterotoxin B subunit enhances the immune response against canine parvovirus VP2 in mice immunized by VP2 DNA vaccine].

PubMed

Han, Dongmei; Zhong, Fei; Li, Xiujin; Wang, Wei; Wang, Xingxing; Pan, Sumin

2011-01-01

To investigate the effect of Escherichia coli heat-labile enterotoxin (LT) B subunit (LTB) gene on canine parvovirus (CPV) VP2 gene vaccine. The LTB gene was amplified by PCR from genomic DNA of E. coli 44815 strain. The VP2-70 fragment (210 bp) encoding major epitope of VP2 (70 amino acids) was amplified by PCR from a plasmid encoding VP2 gene. VP2-70 and LTB genes were inserted into the eukaryotic vector to construct VP2-70 gene,LTB gene and VP2-70-LTB fused gene vectors. The mice were immunized with VP2-70 vector, VP2-70-LTB fused vector, or VP2-70 vector plus LTB vector, respectively. The antibody titers at the different time were measured by using ELISA method. The spleen lymphocyte proliferation activity was analyzed by 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. The sequence of VP2-70 and LTB genes was identified. The recombinant VP2-70 and LTB proteins could be expressed in HEK293T cells in a secretory manner. The mice immunized with VP2-70 vector, VP2-70-LTB vector or VP2-70 vector plus LTB vector could generate the specific antibody against VP2 protein. The antibody titer immunized with VP2-70-LTB vector reached 1:5120 at 35 d post immunization, significantly higher than that of other two groups (P < 0.01). For antibody isotype analysis, the IgG1 isotype antibody titers in all test groups were significantly higher than of IgG2a (P < 0.01). The high-level spleen lymphocyte stimulation index was observed in the three test groups under the stimulation with Con A, higher than that in control groups (P < 0.01). LTB gene could enhance the humoral immune response of CPV VP2 gene vaccine in mice.

Influence of some DNA-alkylating drugs on thermal stability, acid and osmotic resistance of the membrane of whole human erythrocytes and their ghosts.

PubMed

Ivanov, I T; Gadjeva, V

2000-09-01

Human erythrocytes and their resealed ghosts were alkylated under identical conditions using three groups of alkylating antitumor agents: mustards, triazenes and chloroethyl nitrosoureas. Osmotic fragility, acid resistance and thermal stability of membranes were changed only in alkylated ghosts in proportion to the concentration of the alkylating agent. All the alkylating agents decreased acid resistance in ghosts. The clinically used drugs sarcolysine, dacarbazine and lomustine all decreased osmotic fragility and thermal stability of ghost membranes depending on their lipophilicity. DM-COOH did not decrease osmotic fragility and thermal stability of ghost membranes, while NEM increased thermal stability of membranes. The preliminary but not subsequent treatment of ghosts with DM-COOH fully abolished the alkylation-induced thermal labilization of ghost membrane proteins while NEM had a partial effect only. The present study gives direct evidence that alkylating agents, having a high therapeutic activity against malignant growth, bind covalently to proteins of cellular membranes.

Lability landscape and protease resistance of human insulin amyloid: a new insight into its molecular properties.

PubMed

Malisauskas, Mantas; Weise, Christoph; Yanamandra, Kiran; Wolf-Watz, Magnus; Morozova-Roche, Ludmilla

2010-02-12

Amyloid formation is a universal behavior of proteins central to many important human pathologies and industrial processes. The extreme stability of amyloids towards chemical and proteolytic degradation is an acquired property compared to the precursor proteins and is a major prerequisite for their accumulation. Here, we report a study on the lability of human insulin amyloid as a function of pH and amyloid ageing. Using a range of methods such as atomic force microscopy, thioflavin T fluorescence, circular dichroism, and gas-phase electrophoretic mobility macromolecule analysis, we probed the propensity of human insulin amyloid to propagate or dissociate in a wide span of pH values and ageing in a low concentration regime. We generated a three-dimensional amyloid lability landscape in coordinates of pH and amyloid ageing, which displays three distinctive features: (i) a maximum propensity to grow near pH 3.8 and an age corresponding to the inflection point of the growth phase, (ii) an abrupt cutoff between growth and disaggregation at pH 8-10, and (iii) isoclines shifted towards older age during the amyloid growth phase at pH 4-9, reflecting the greater stability of aged amyloid. Thus, lability of amyloid strongly depends on the ionization state of insulin and on the structure and maturity of amyloid fibrils. The stability of insulin amyloid towards protease K was assessed by using real-time atomic force microscopy and thioflavin T fluorescence. We estimated that amyloid fibrils can be digested both from the free ends and within the length of the fibril with a rate of ca 4 nm/min. Our results highlight that amyloid structures, depending on solution conditions, can be less stable than commonly perceived. These results have wide implications for understanding the propagation of amyloids via a seeding mechanism as well as for understanding their natural clearance and dissociation under solution conditions unfavorable for amyloid formation in biological systems and

Hemodynamic changes in systolic and diastolic function during isoproterenol challenge predicts symptomatic response to myectomy in hypertrophic cardiomyopathy with labile obstruction.

PubMed

Prasad, Megha; Geske, Jeffrey B; Sorajja, Paul; Ommen, Steve R; Schaff, Hartzell V; Gersh, Bernard J; Nishimura, Rick A

2016-11-15

We aimed to assess the utility of changes in systolic and diastolic function by isoproterenol challenge in predicting symptom resolution post-myectomy in selected patients with hypertrophic cardiomyopathy (HCM) and labile obstruction. In a subset of symptomatic HCM patients without resting/provocable obstruction on noninvasive assessment, isoproterenol challenge during hemodynamic catheterization may elicit labile left ventricular outflow tract (LVOT) obstruction, and demonstrate the effect of obstruction on diastolic function. These changes may determine whether patients achieve complete symptom resolution post-myectomy. Between February 2003 and April 2009, 18 symptomatic HCM patients without LVOT obstruction on noninvasive testing underwent isoproterenol provocation and septal myectomy due to presence of provocable gradient and were followed for 4 (IQR 3-7) years. Thirteen (72.2%) had complete symptom resolution, while 5 (27.8%) had improved, but persistent symptoms. Those with provoked gradient >100 mm Hg or increase in left atrial pressure (LAP) with isoproterenol had symptom resolution. Symptomatic HCM patients without LVOT gradient on noninvasive testing may demonstrate labile obstruction with isoproterenol. With isoproterenol, patients with high LVOT gradient or increase in LAP concomitant with an increase in gradient achieved complete symptom resolution post-myectomy. Thus, improved diastolic filling as well as outflow gradient production in patients with HCM may predict symptom response to myectomy. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Measuring the concentration of carboxylic acid groups in torrefied spruce wood.

PubMed

Khazraie Shoulaifar, Tooran; Demartini, Nikolai; Ivaska, Ari; Fardim, Pedro; Hupa, Mikko

2012-11-01

Torrefaction is moderate thermal treatment (∼200-300°C) to improve the energy density, handling and storage properties of biomass fuels. In biomass, carboxylic sites are partially responsible for its hygroscopic. These sites are degraded to varying extents during torrefaction. In this paper, we apply methylene blue sorption and potentiometric titration to measure the concentration of carboxylic acid groups in spruce wood torrefied for 30min at temperatures between 180 and 300°C. The results from both methods were applicable and the values agreed well. A decrease in the equilibrium moisture content at different humidity was also measured for the torrefied wood samples, which is in good agreement with the decrease in carboxylic acid sites. Thus both methods offer a means of directly measuring the decomposition of carboxylic groups in biomass during torrefaction as a valuable parameter in evaluating the extent of torrefaction which provides new information to the chemical changes occurring during torrefaction. Copyright © 2012 Elsevier Ltd. All rights reserved.

Cytoplasmic Delivery of Liposomal Contents Mediated by an Acid-Labile Cholesterol-Vinyl Ether-PEG Conjugate

PubMed Central

Boomer, Jeremy A.; Qualls, Marquita M.; Inerowicz, H. Dorota; Haynes, Robert H.; Patri, G.V. Srilaksmi; Kim, Jong-Mok; Thompson, David H.

2009-01-01

An acid-cleavable PEG lipid, 1′-(4′-cholesteryloxy-3′-butenyl)-ω-methoxy-polyethylene[112] glycolate (CVEP), has been developed that produces stable liposomes when dispersed as a minor component (0.5–5 mol%) in 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE). Cleavage of CVEP at mildly acidic pH’s results in dePEGylation of the latently fusogenic DOPE liposomes, thereby triggering the onset of contents release. This paper describes the synthesis of CVEP via a six step sequence starting from the readily available precursors 1,4-butanediol, cholesterol, and mPEG acid. The hydrolysis rates and release kinetics from CVEP:DOPE liposome dispersions as a function of CVEP loading, as well as the cryogenic transmission electron microscopy and pH-dependent monolayer properties of 9:91 CVEP:DOPE mixtures, also are reported. When folate-receptor positive KB cells were exposed to calcein-loaded 5:95 CVEP:DOPE liposomes containing 0.1 mol% folate-modified 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-polyethylene[76] glycolamide (folate-PEG-DSPE), efficient delivery of the calcein cargo to the cytoplasm of the cells was observed as determined by fluorescence microscopy and flow cytometry. Fluorescence resonance energy transfer analysis of lipid mixing in these cells was consistent with membrane-membrane fusion between the liposome and endosomal membranes. PMID:19072698

Peptide and protein quantitation by acid-catalyzed 18O-labeling of carboxyl groups.

PubMed

Haaf, Erik; Schlosser, Andreas

2012-01-03

We have developed a new method that applies acidic catalysis with hydrochloric acid for (18)O-labeling of peptides at their carboxyl groups. With this method, peptides get labeled at their C-terminus, at Asp and Glu residues, and at carboxymethylated cysteine residues. Oxygen atoms at phosphate groups of phosphopeptide are not exchanged. Our elaborated labeling protocol is easy to perform, fast (5 h and 30 min), and results in 95-97 atom % incorporation of (18)O at carboxyl groups. Undesired side reactions, such as deamidation or peptide hydrolysis, occur only at a very low level under the conditions applied. In addition, data analysis can be performed automatically using common software tools, such as Mascot Distiller. We have demonstrated the capability of this method for the quantitation of peptides as well as for phosphopeptides. © 2011 American Chemical Society

Seasonal Dynamics of Soil Labile Organic Carbon and Enzyme Activities in Relation to Vegetation Types in Hangzhou Bay Tidal Flat Wetland

PubMed Central

Shao, Xuexin; Yang, Wenying; Wu, Ming

2015-01-01

Soil labile organic carbon and soil enzymes play important roles in the carbon cycle of coastal wetlands that have high organic carbon accumulation rates. Soils under three vegetations (Phragmites australis, Spartina alterniflora, and Scirpusm mariqueter) as well as bare mudflat in Hangzhou Bay wetland of China were collected seasonally. Seasonal dynamics and correlations of soil labile organic carbon fractions and soil enzyme activities were analyzed. The results showed that there were significant differences among vegetation types in the contents of soil organic carbon (SOC) and dissolved organic carbon (DOC), excepting for that of microbial biomass carbon (MBC). The P. australis soil was with the highest content of both SOC (7.86 g kg-1) and DOC (306 mg kg-1), while the S. mariqueter soil was with the lowest content of SOC (6.83 g kg-1), and the bare mudflat was with the lowest content of DOC (270 mg kg-1). Soil enzyme activities were significantly different among vegetation types except for urease. The P. australis had the highest annual average activity of alkaline phosphomonoesterase (21.4 mg kg-1 h-1), and the S. alterniflora had the highest annual average activities of β-glycosidase (4.10 mg kg-1 h-1) and invertase (9.81mg g-1 24h-1); however, the bare mudflat had the lowest activities of alkaline phosphomonoesterase (16.2 mg kg-1 h-1), β-glycosidase (2.87 mg kg-1 h-1), and invertase (8.02 mg g-1 24h-1). Analysis also showed that the soil labile organic carbon fractions and soil enzyme activities had distinct seasonal dynamics. In addition, the soil MBC content was significantly correlated with the activities of urease and β-glucosidase. The DOC content was significantly correlated with the activities of urease, alkaline phosphomonoesterase, and invertase. The results indicated that vegetation type is an important factor influencing the spatial-temporal variation of soil enzyme activities and labile organic carbon in coastal wetlands. PMID:26560310

A Chemical Biology Solution to Problems with Studying Biologically Important but Unstable 9-O-Acetyl Sialic Acids.

PubMed

Khedri, Zahra; Xiao, An; Yu, Hai; Landig, Corinna Susanne; Li, Wanqing; Diaz, Sandra; Wasik, Brian R; Parrish, Colin R; Wang, Lee-Ping; Varki, Ajit; Chen, Xi

2017-01-20

9-O-Acetylation is a common natural modification on sialic acids (Sias) that terminate many vertebrate glycan chains. This ester group has striking effects on many biological phenomena, including microbe-host interactions, complement action, regulation of immune responses, sialidase action, cellular apoptosis, and tumor immunology. Despite such findings, 9-O-acetyl sialoglycoconjugates have remained largely understudied, primarily because of marked lability of the 9-O-acetyl group to even small pH variations and/or the action of mammalian or microbial esterases. Our current studies involving 9-O-acetylated sialoglycans on glycan microarrays revealed that even the most careful precautions cannot ensure complete stability of the 9-O-acetyl group. We now demonstrate a simple chemical biology solution to many of these problems by substituting the oxygen atom in the ester with a nitrogen atom, resulting in sialic acids with a chemically and biologically stable 9-N-acetyl group. We present an efficient one-pot multienzyme method to synthesize a sialoglycan containing 9-acetamido-9-deoxy-N-acetylneuraminic acid (Neu5Ac9NAc) and compare it to the one with naturally occurring 9-O-acetyl-N-acetylneuraminic acid (Neu5,9Ac 2 ). Conformational resemblance of the two molecules was confirmed by computational molecular dynamics simulations. Microarray studies showed that the Neu5Ac9NAc-sialoglycan is a ligand for viruses naturally recognizing Neu5,9Ac 2 , with a similar affinity but with much improved stability in handling and study. Feeding of Neu5Ac9NAc or Neu5,9Ac 2 to mammalian cells resulted in comparable incorporation and surface expression as well as binding to 9-O-acetyl-Sia-specific viruses. However, cells fed with Neu5Ac9NAc remained resistant to viral esterases and showed a slower turnover. This simple approach opens numerous research opportunities that have heretofore proved intractable.

Ammonia IRMS-TPD measurements and DFT calculation on acidic hydroxyl groups in CHA-type zeolites.

PubMed

Suzuki, Katsuki; Sastre, German; Katada, Naonobu; Niwa, Miki

2007-12-07

Brønsted acidity of H-chabazite (CHA) zeolites (Si : Al(2) = 4.2) was investigated by means of ammonia infrared-mass spectrometry/temperature-programmed desorption (IRMS-TPD) methods and density functional calculations. Four IR bands were observed at 3644, 3616, 3575 and 3538 cm(-1), and they were ascribable to the acidic OH groups on four nonequivalent oxygen sites in the CHA structure. The absorption band at 3538 cm(-1) was attributed to the O(4)H in the 6-membered ring (MR), and ammonia adsorption energy (DeltaU) of this OH group was the lowest among the 4 kinds of OH groups. The other 3 bands were assigned to the acidic OH groups in 8MR. It was observed that the DeltaU in 8 and 6MR were 131 (+/-3) and 101 kJ mol(-1), respectively. On the other hand, the density functional theory (DFT) calculations within periodic boundary conditions yielded the adsorption energies on these OH groups in 8 and 6MR to be ca. 130 and 110 kJ mol(-1), respectively, in good agreement with the experimentally-observed values.

Optimal conjugation of catechol group onto hyaluronic acid in coronary stent substrate coating for the prevention of restenosis.

PubMed

Lih, Eugene; Choi, Seul Gi; Ahn, Dong June; Joung, Yoon Ki; Han, Dong Keun

2016-01-01

Although endovascular stenting has been used as an interventional therapy to treat cardio- and cerebro-vascular diseases, it is associated with recurrent vascular diseases following stent thrombosis and in-stent restenosis. In this study, a metallic stent was coated with dopamine-conjugated hyaluronic acid with different ratios of catechol group to improve hemocompatibility and re-endothelialization. Especially, we were interested in how much amount of catechol group is appropriate for the above-mentioned purposes. Therefore, a series of dopamine-conjugated hyaluronic acid conjugates with different ratios of catechol group were synthesized via a carbodiimide coupling reaction. Dopamine-conjugated hyaluronic acid conjugates were characterized with 1 H-nuclear magnetic resonance and Fourier transform infrared spectroscopy, and the amount of catechol group in dopamine-conjugated hyaluronic acid was measured by ultraviolet spectrometer. Co-Cr substrates were polished and coated with various dopamine-conjugated hyaluronic acid conjugates under pH 8.5. Dopamine-conjugated hyaluronic acid amounts on the substrate were quantified by micro-bicinchoninic acid assay. Surface characteristics of dopamine-conjugated hyaluronic-acid-coated Co-Cr were evaluated by water contact angle, scanning electron microscopy, and atomic force microscopy. The hemocompatibility of the surface-modified substrates was assessed by protein adsorption and platelet adhesion tests. Adhesion and activation of platelets were confirmed with scanning electron microscopy and lactate dehydrogenase assay. Human umbilical vein endothelial cells were cultured on the substrates, and the viability, adhesion, and proliferation were investigated through cell counting kit-8 assay and fluorescent images. Obtained results demonstrated that optimal amounts of catechol group (100 µmol) in the dopamine-conjugated hyaluronic acid existed in terms of various properties such as hemocompatibility and cellular responses.

Enantiomer analysis of chiral carboxylic acids by AIE molecules bearing optically pure aminol groups.

PubMed

Zheng, Yan-Song; Hu, Yu-Jian; Li, Dong-Mi; Chen, Yi-Chang

2010-01-15

Pure enantiomers of carboxylic acids are a class of important biomolecules, chiral drugs, chiral reagents, etc. Analysis of the enantiomers usually needs expensive instrument or complex chiral receptors. However, to develop simple and reliable methods for the enantiomer analysis of acids is difficult. In this paper, chiral recognition of 2,3-dibenzoyltartaric acid and mandelic acid was first carried out by aggregation-induced emission molecules bearing optically pure aminol group, which was easily synthesized. The chiral recognition is not only seen by naked eyes but also measured by fluorophotometer. The difference of fluorescence intensity between the two enantiomers of the acids aroused by the aggregation-induced emission molecules was up to 598. The chiral recognition could be applied to quantitative analysis of enantiomer content of chiral acids. More chiral AIE amines need to be developed for enantiomer analysis of more carboxylic acids.

A Double Blind Trial of Divalproex Sodium for Affective Lability and Alcohol Use Following Traumatic Brain Injury

DTIC Science & Technology

2009-10-01

SUBJECT TERMS Traumatic Brain Injury, Alcohol Use , Mood , Mood Stabilization 16. SECURITY CLASSIFICATION OF: U 17. LIMITATION OF ABSTRACT 18...1995 for this indication. Also, it is used in conjunction with lithium or carbamazepine to prevent recurrent manic or depressive episodes during long...0652 TITLE: A Double Blind Trial of Divalproex Sodium for Affective Lability and Alcohol Use Following Traumatic Brain Injury PRINCIPAL

Comparison of hamstring and quadriceps femoris electromyographic activity between men and women during a single-limb squat on both a stable and labile surface.

PubMed

Youdas, James W; Hollman, John H; Hitchcock, James R; Hoyme, Gregory J; Johnsen, Jeremiah J

2007-02-01

The purpose of this study was to determine if women are quadriceps dominant and men are hamstring dominant during the performance of a partial single-leg squat (SLS) on both a stable and labile ground surface against body weight resistance. Thirty healthy participants (15 men and 15 women) performed an SLS on both a stable surface and a 6.4-cm-thick vinyl pad. Surface electromyographic (EMG) recordings were obtained from the quadriceps femoris and hamstring muscles during the extension phase of the SLS. Statistical analysis revealed that women produced 14% more EMG activity (p = 0.04) in their quadriceps than the men during the SLS on a stable surface, whereas the men generated 18% more EMG activity (p = 0.04) in their hamstrings than the women during the SLS on a labile surface. Additionally, we found a statistically significant sex effect (p = 0.048) for the hamstring/quadriceps (H/Q) EMG ratio, which was 2.25 and 0.62, respectively, for men and women on the stable surface and 2.52 and 0.71, respectively, on the labile surface. We concluded that women are quadriceps dominant and men are hamstring dominant during the performance of SLS against body weight resistance on either a stable or labile surface condition. During an SLS, men showed an H/Q ratio approximately 3.5 times larger than their female counterparts, suggesting that men activate their hamstrings more effectively than women during an SLS. According to our data, the SLS may not be an ideal exercise for activating the hamstring muscles in women without additional neuromuscular training techniques, because women are quadriceps dominant during the SLS.

Human Protein and Amino Acid Requirements.

PubMed

Hoffer, L John

2016-05-01

Human protein and amino acid nutrition encompasses a wide, complex, frequently misunderstood, and often contentious area of clinical research and practice. This tutorial explains the basic biochemical and physiologic principles that underlie our current understanding of protein and amino acid nutrition. The following topics are discussed: (1) the identity, measurement, and essentiality of nutritional proteins; (2) the definition and determination of minimum requirements; (3) nutrition adaptation; (4) obligatory nitrogen excretion and the minimum protein requirement; (5) minimum versus optimum protein intakes; (6) metabolic responses to surfeit and deficient protein intakes; (7) body composition and protein requirements; (8) labile protein; (9) N balance; (10) the principles of protein and amino acid turnover, including an analysis of the controversial indicator amino acid oxidation technique; (11) general guidelines for evaluating protein turnover articles; (12) amino acid turnover versus clearance; (13) the protein content of hydrated amino acid solutions; (14) protein requirements in special situations, including protein-catabolic critical illness; (15) amino acid supplements and additives, including monosodium glutamate and glutamine; and (16) a perspective on the future of protein and amino acid nutrition research. In addition to providing practical information, this tutorial aims to demonstrate the importance of rigorous physiologic reasoning, stimulate intellectual curiosity, and encourage fresh ideas in this dynamic area of human nutrition. In general, references are provided only for topics that are not well covered in modern textbooks. © 2016 American Society for Parenteral and Enteral Nutrition.

Bicyclic tetrapeptide histone deacetylase inhibitors with methoxymethyl ketone and boronic acid zinc-binding groups.

PubMed

Islam, Md Nurul; Islam, Md Shahidul; Hoque, Md Ashraful; Kato, Tamaki; Nishino, Norikazu; Ito, Akihiro; Yoshida, Minoru

2014-12-01

Histone deacetylase (HDAC) inhibitors are a class of potential therapeutics for the treatment of cancer. Bicyclic tetrapeptides equipped with methoxymethyl ketone and boronic acid as zinc-binding group were designed and synthesized. The inhibitory activities of these compounds were evaluated against HDAC enzymes. The cell-free and cell-based assay data showed that both potency and selectivity changed with the change in zinc-binding group. Boronic acid-based compound showed poor activity whereas methoxymethyl ketone-based compound displayed impressive activity in both cell-free and cell-based conditions. Copyright © 2014 Elsevier Inc. All rights reserved.

Quantitative chemical exchange saturation transfer (qCEST) MRI - omega plot analysis of RF-spillover-corrected inverse CEST ratio asymmetry for simultaneous determination of labile proton ratio and exchange rate.

PubMed

Wu, Renhua; Xiao, Gang; Zhou, Iris Yuwen; Ran, Chongzhao; Sun, Phillip Zhe

2015-03-01

Chemical exchange saturation transfer (CEST) MRI is sensitive to labile proton concentration and exchange rate, thus allowing measurement of dilute CEST agent and microenvironmental properties. However, CEST measurement depends not only on the CEST agent properties but also on the experimental conditions. Quantitative CEST (qCEST) analysis has been proposed to address the limitation of the commonly used simplistic CEST-weighted calculation. Recent research has shown that the concomitant direct RF saturation (spillover) effect can be corrected using an inverse CEST ratio calculation. We postulated that a simplified qCEST analysis is feasible with omega plot analysis of the inverse CEST asymmetry calculation. Specifically, simulations showed that the numerically derived labile proton ratio and exchange rate were in good agreement with input values. In addition, the qCEST analysis was confirmed experimentally in a phantom with concurrent variation in CEST agent concentration and pH. Also, we demonstrated that the derived labile proton ratio increased linearly with creatine concentration (P < 0.01) while the pH-dependent exchange rate followed a dominantly base-catalyzed exchange relationship (P < 0.01). In summary, our study verified that a simplified qCEST analysis can simultaneously determine labile proton ratio and exchange rate in a relatively complex in vitro CEST system. Copyright © 2015 John Wiley & Sons, Ltd.

Amino Acid Derivatives as Palmitoylethanolamide Prodrugs: Synthesis, In Vitro Metabolism and In Vivo Plasma Profile in Rats

PubMed Central

Vacondio, Federica; Bassi, Michele; Silva, Claudia; Castelli, Riccardo; Carmi, Caterina; Scalvini, Laura; Lodola, Alessio; Vivo, Valentina; Flammini, Lisa; Barocelli, Elisabetta; Mor, Marco; Rivara, Silvia

2015-01-01

Palmitoylethanolamide (PEA) has antinflammatory and antinociceptive properties widely exploited in veterinary and human medicine, despite its poor pharmacokinetics. Looking for prodrugs that could progressively release PEA to maintain effective plasma concentrations, we prepared carbonates, esters and carbamates at the hydroxyl group of PEA. Chemical stability (pH 7.4) and stability in rat plasma and liver homogenate were evaluated by in vitro assays. Carbonates and carbamates resulted too labile and too resistant in plasma, respectively. Ester derivatives, prepared by conjugating PEA with various amino acids, allowed to modulate the kinetics of PEA release in plasma and stability in liver homogenate. L-Val-PEA, with suitable PEA release in plasma, and D-Val-PEA, with high resistance to hepatic degradation, were orally administered to rats and plasma levels of prodrugs and PEA were measured at different time points. Both prodrugs showed significant release of PEA, but provided lower plasma concentrations than those obtained with equimolar doses of PEA. Amino-acid esters of PEA are a promising class to develop prodrugs, even if they need further chemical optimization. PMID:26053855

Lability of secondary organic particulate matter

PubMed Central

Liu, Pengfei; Li, Yong Jie; Wang, Yan; Gilles, Mary K.; Zaveri, Rahul A.; Bertram, Allan K.

2016-01-01

The energy flows in Earth’s natural and modified climate systems are strongly influenced by the concentrations of atmospheric particulate matter (PM). For predictions of concentration, equilibrium partitioning of semivolatile organic compounds (SVOCs) between organic PM and the surrounding vapor has widely been assumed, yet recent observations show that organic PM can be semisolid or solid for some atmospheric conditions, possibly suggesting that SVOC uptake and release can be slow enough that equilibrium does not prevail on timescales relevant to atmospheric processes. Herein, in a series of laboratory experiments, the mass labilities of films of secondary organic material representative of similar atmospheric organic PM were directly determined by quartz crystal microbalance measurements of evaporation rates and vapor mass concentrations. There were strong differences between films representative of anthropogenic compared with biogenic sources. For films representing anthropogenic PM, evaporation rates and vapor mass concentrations increased above a threshold relative humidity (RH) between 20% and 30%, indicating rapid partitioning above a transition RH but not below. Below the threshold, the characteristic time for equilibration is estimated as up to 1 wk for a typically sized particle. In contrast, for films representing biogenic PM, no RH threshold was observed, suggesting equilibrium partitioning is rapidly obtained for all RHs. The effective diffusion rate Dorg for the biogenic case is at least 103 times greater than that of the anthropogenic case. These differences should be accounted for in the interpretation of laboratory data as well as in modeling of organic PM in Earth’s atmosphere. PMID:27791063

Lability of secondary organic particulate matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Pengfei; Li, Yong Jie; Wang, Yan

2016-10-24

We report the energy flows in Earth’s natural and modified climate systems are strongly influenced by the concentrations of atmospheric particulate matter (PM). For predictions of concentration, equilibrium partitioning of semivolatile organic compounds (SVOCs) between organic PM and the surrounding vapor has widely been assumed, yet recent observations show that organic PM can be semisolid or solid for some atmospheric conditions, possibly suggesting that SVOC uptake and release can be slow enough that equilibrium does not prevail on timescales relevant to atmospheric processes. Herein, in a series of laboratory experiments, the mass labilities of films of secondary organic material representativemore » of similar atmospheric organic PM were directly determined by quartz crystal microbalance measurements of evaporation rates and vapor mass concentrations. There were strong differences between films representative of anthropogenic compared with biogenic sources. For films representing anthropogenic PM, evaporation rates and vapor mass concentrations increased above a threshold relative humidity (RH) between 20% and 30%, indicating rapid partitioning above a transition RH but not below. Below the threshold, the characteristic time for equilibration is estimated as up to 1 wk for a typically sized particle. In contrast, for films representing biogenic PM, no RH threshold was observed, suggesting equilibrium partitioning is rapidly obtained for all RHs. The effective diffusion rate D org for the biogenic case is at least 10 3 times greater than that of the anthropogenic case. In conclusion, these differences should be accounted for in the interpretation of laboratory data as well as in modeling of organic PM in Earth’s atmosphere.« less

Bipolar Mass Spectrometry of Labile Coordination Complexes, Redox Active Inorganic Compounds, and Proteins Using a Glass Nebulizer for Sonic-Spray Ionization

NASA Astrophysics Data System (ADS)

Antonakis, Manolis M.; Tsirigotaki, Alexandra; Kanaki, Katerina; Milios, Constantinos J.; Pergantis, Spiros A.

2013-08-01

In this study, we report on the development of a novel nebulizer configuration for sonic-spray ionization (SSI) mass spectrometry (MS), more specifically for a version of SSI that is referred to as Venturi easy ambient sonic-spray ionization (V-EASI) MS. The developed nebulizer configuration is based on a commercially available pneumatic glass nebulizer that has been used extensively for aerosol formation in atomic spectrometry. In the present study, the nebulizer was modified in order to achieve efficient V-EASI-MS operation. Upon evaluating this system, it has been demonstrated that V-EASI-MS offers some distinct advantages for the analysis of coordination compounds and redox active inorganic compounds over the predominantly used electrospray ionization (ESI) technique. Such advantages, for this type of compounds, are demonstrated here for the first time. More specifically, a series of labile heptanuclear heterometallic [CuII 6LnIII] clusters held together with artificial amino acid ligands, in addition to easily oxidized inorganic oxyanions of selenium and arsenic, were analyzed. The observed advantages pertain to V-EASI appearing to be a "milder" ionization source than ESI, not requiring electrical potentials for gas phase ion formation, thus eliminating the possibility of unwanted redox transformations, allowing for the "simultaneous" detection of negative and positive ions (bipolar analysis) without the need to change source ionization conditions, and also not requiring the use of syringes and delivery pumps. Because of such features, especially because of the absence of ionization potentials, EASI can be operated with minimal requirements for source parameter optimization. We observed that source temperature and accelerating voltage do not seem to affect labile compounds to the extent they do in ESI-MS. In addition, bipolar analysis of proteins was demonstrated here by acquiring both positive and negative ion mass spectra from the same protein solutions

Bipolar mass spectrometry of labile coordination complexes, redox active inorganic compounds, and proteins using a glass nebulizer for sonic-spray ionization.

PubMed

Antonakis, Manolis M; Tsirigotaki, Alexandra; Kanaki, Katerina; Milios, Constantinos J; Pergantis, Spiros A

2013-08-01

In this study, we report on the development of a novel nebulizer configuration for sonic-spray ionization (SSI) mass spectrometry (MS), more specifically for a version of SSI that is referred to as Venturi easy ambient sonic-spray ionization (V-EASI) MS. The developed nebulizer configuration is based on a commercially available pneumatic glass nebulizer that has been used extensively for aerosol formation in atomic spectrometry. In the present study, the nebulizer was modified in order to achieve efficient V-EASI-MS operation. Upon evaluating this system, it has been demonstrated that V-EASI-MS offers some distinct advantages for the analysis of coordination compounds and redox active inorganic compounds over the predominantly used electrospray ionization (ESI) technique. Such advantages, for this type of compounds, are demonstrated here for the first time. More specifically, a series of labile heptanuclear heterometallic [Cu(II) 6Ln(III)] clusters held together with artificial amino acid ligands, in addition to easily oxidized inorganic oxyanions of selenium and arsenic, were analyzed. The observed advantages pertain to V-EASI appearing to be a "milder" ionization source than ESI, not requiring electrical potentials for gas phase ion formation, thus eliminating the possibility of unwanted redox transformations, allowing for the "simultaneous" detection of negative and positive ions (bipolar analysis) without the need to change source ionization conditions, and also not requiring the use of syringes and delivery pumps. Because of such features, especially because of the absence of ionization potentials, EASI can be operated with minimal requirements for source parameter optimization. We observed that source temperature and accelerating voltage do not seem to affect labile compounds to the extent they do in ESI-MS. In addition, bipolar analysis of proteins was demonstrated here by acquiring both positive and negative ion mass spectra from the same protein solutions

Labile, dissolved and particulate PAHs and trace metals in wastewater: passive sampling, occurrence, partitioning in treatment plants.

PubMed

Gourlay-Francé, C; Bressy, A; Uher, E; Lorgeoux, C

2011-01-01

The occurrence and the partitioning of polycyclic aromatic hydrocarbons (PAHs) and seven metals (Al, Cd, Cr, Cu, Ni, Pb and Zn) were investigated in activated sludge wastewater treatment plants by means of passive and active sampling. Concentrations total dissolved and particulate contaminants were determined in wastewater at several points across the treatment system by means of grab sampling. Truly dissolved PAHs were sampled by means of semipermeable membrane devices. Labile (inorganic and weakly complexed) dissolved metals were also sampled using the diffusive gradient in thin film technique. This study confirms the robustness and the validity of these two passive sampling techniques in wastewater. All contaminant concentrations decreased in wastewater along the treatment, although dissolved and labile concentrations sometimes increased for substances with less affinity with organic matter. Solid-liquid and dissolved organic matter/water partitioning constants were estimated. The high variability of both partitioning constants for a simple substance and the poor relation between K(D) and K(OW) shows that the binding capacities of particles and organic matter are not uniform within the treatment and that other process than equilibrium sorption affect contaminant repartition and fate in wastewater.

The temperature sensitivity of soil organic carbon decomposition is not related to labile and recalcitrant carbon.

PubMed

Tang, Jie; Cheng, Hao; Fang, Changming

2017-01-01

The response of resistant soil organic matter to temperature change is crucial for predicting climate change impacts on C cycling in terrestrial ecosystems. However, the response of the decomposition of different soil organic carbon (SOC) fractions to temperature is still under debate. To investigate whether the labile and resistant SOC components have different temperature sensitivities, soil samples were collected from three forest and two grass land sites, along with a gradient of latitude from 18°40'to 43°17'N and elevation from 600 to 3510 m across China, and were incubated under changing temperature (from 12 to 32 oC) for at least 260 days. Soil respiration rates were positively related to the content of soil organic carbon and soil microbial carbon. The temperature sensitivity of soil respiration, presented as Q10 value, varies from 1.93 ± 0.15 to 2.60 ± 0.21. During the incubation, there were no significant differences between the Q10 values of soil samples from different layers of the same site, nor a clear pattern of Q10 values along with the gradient of latitude. The result of this study does not support current opinion that resistant soil carbon decomposition is more sensitive to temperature change than labile soil carbon.

Comparative degradation of [14C]-2,4-dichlorophenoxyacetic acid in wheat and potato after Foliar application and in wheat, radish, lettuce, and apple after soil application.

PubMed

Hamburg, A; Puvanesarajah, V; Burnett, T J; Barnekow, D E; Premkumar, N D; Smith, G A

2001-01-01

The fate of 2,4-dichlorophenoxyacetic acid (2,4-D) applied foliarly as the 2-ethylhexyl ester (EHE) to wheat and potatoes, to the soil as the dimethylamine (DMA) salt under apple tree canopies, and preplant as the free acid for wheat, lettuce, and radish was studied to evaluate metabolic pathways. Crop fractions analyzed for (14)C residues included wheat forage, straw, and grain; potato vine and tubers; and apple fruit. The primary metabolic pathway for foliar application in wheat is ester hydrolysis followed by the formation of base-labile 2,4-D conjugates. A less significant pathway for 2,4-D in wheat was ring hydroxylation to give NIH-shift products 2,5-dichloro-4-hydroxyphenoxyacetic acid (4-OH-2,5-D), 4-OH-2,3-D, and 5-OH-2,4-D both free and as acid-labile conjugates. The primary metabolic pathway in potato was again ester hydrolysis. 2,4-D acid was further transformed to 4-chlorophenoxyacetic acid and 4-OH-2,5-D. For the soil applications, (14)C residues in the crops were low, and characterization of the (14)C residues indicated association with or incorporation into the biochemical matrix of the tissue. The degradative pathways observed in wheat are similar to those characterized in other intact plant studies but differ from those in studies in wheat cell suspension culture in that no amino acid conjugates were observed.

Carboxylic acid functional group analysis using constant neutral loss scanning-mass spectrometry.

PubMed

Dron, Julien; Eyglunent, Gregory; Temime-Roussel, Brice; Marchand, Nicolas; Wortham, Henri

2007-12-12

The present study describes the development of a new analytical technique for the functional group determination of the carboxylic moiety using atmospheric pressure chemical ionization-mass spectrometry (APCI-MS/MS) operated in the constant neutral loss scanning (CNLS) mode. Carboxylic groups were first derivatized into their corresponding methyl esters by reacting with BF3/methanol mix and the reaction mixture was then directly injected into the APCI chamber. The loss of methanol (m/z = 32 amu) resulting from the fragmentation of the protonated methyl esters was then monitored. Applying this method together with a statistical approach to reference mixtures containing 31 different carboxylic acids at randomly calculated concentrations demonstrated its suitability for quantitative functional group measurements with relative standard deviations below 15% and a detection limit of 0.005 mmol L(-1). Its applicability to environmental matrices was also shown through the determination of carboxylic acid concentrations inside atmospheric aerosol samples. To the best of our knowledge, it is the first time that the tandem mass spectrometry was successfully applied to functional group analysis, offering great perspectives in the characterization of complex mixtures which are prevailing in the field of environmental analysis as well as in the understanding of the chemical processes occurring in these matrices.

Effect of angiotensin II on iron-transporting protein expression and subsequent intracellular labile iron concentration in human glomerular endothelial cells.

PubMed

Tajima, Soichiro; Tsuchiya, Koichiro; Horinouchi, Yuya; Ishizawa, Keisuke; Ikeda, Yasumasa; Kihira, Yoshitaka; Shono, Masayuki; Kawazoe, Kazuyoshi; Tomita, Shuhei; Tamaki, Toshiaki

2010-07-01

Angiotensin II (Ang II)-induced endothelial injury, which is associated with atherosclerosis, is believed to be mediated by intracellular reactive oxygen species (ROS) through stimulation of nicotinamide adenine dinucleotide phosphate oxidase (NOX). Iron is essential for the amplification of oxidative stress. In this study, we investigated whether Ang II altered iron metabolism and whether the Ang II-induced endothelial injury is attributable to changes in iron metabolism of human glomerular endothelial cells (HGECs). When 90% iron-saturated human transferrin (90% Tf) was applied to HGECs without Ang II, the labile ferrous iron level was same as the effect of control in spite of a significant increase in the total cellular iron concentration. Treatment with Ang II and 30% Tf or 90% Tf significantly (P<0.01) increased the intracellular iron concentration, as well as labile ferrous iron and protein oxidation levels, compared with the effect of separate administration of each compound. Ang II treatment facilitated the protein expression of the Tf receptor, divalent metal transporter 1, and ferroportin 1 in a dose- and time-dependent manner. It was also found that simultaneous exposure of HGECs to Ang II and 90% Tf accelerated hydroxyl radical production, as shown by using an electron paramagnetic resonance spectrometer. These results suggest that Ang II not only induces production of ROS by NOX activation but also iron incorporation followed by an increase in labile iron in HGECs. Both of these events may participate in the progression of oxidative stress because of endothelial cell dysfunction through ferrous iron-mediated ROS generation.

Forms and lability of phosphorus in algae and aquatic macrophytes characterized by solution 31P NMR coupled with enzymatic hydrolysis

USDA-ARS?s Scientific Manuscript database

Increased information on forms and lability of phosphorus (P) in aquatic macrophytes and algae is crucial for better understanding of P biogeochemical cycling in eutrophic lakes. In this work, solution 31P nuclear magnetic resonance (NMR) spectroscopy coupled with enzymatic hydrolysis (EH) was used ...

Labile and recalcitrant organic matter utilization by river biofilm under increasing water temperature.

PubMed

Ylla, Irene; Romaní, Anna M; Sabater, Sergi

2012-10-01

Microbial biofilms in rivers contribute to the decomposition of the available organic matter which typically shows changes in composition and bioavailability due to their origin, seasonality, and watershed characteristics. In the context of global warming, enhanced biofilm organic matter decomposition would be expected but this effect could be specific when either a labile or a recalcitrant organic matter source would be available. A laboratory experiment was performed to mimic the effect of the predicted increase in river water temperature (+4 °C above an ambient temperature) on the microbial biofilm under differential organic matter sources. The biofilm microbial community responded to higher water temperature by increasing bacterial cell number, respiratory activity (electron transport system) and microbial extracellular enzymes (extracellular enzyme activity). At higher temperature, the phenol oxidase enzyme explained a large fraction of respiratory activity variation suggesting an enhanced microbial use of degradation products from humic substances. The decomposition of hemicellulose (β-xylosidase activity) seemed to be also favored by warmer conditions. However, at ambient temperature, the enzymes highly responsible for respiration activity variation were β-glucosidase and leu-aminopeptidase, suggesting an enhanced microbial use of polysaccharides and peptides degradation products. The addition of labile dissolved organic carbon (DOC; dipeptide plus cellobiose) caused a further augmentation of heterotrophic biomass and respiratory activity. The changes in the fluorescence index and the ratio Abs(250)/total DOC indicated that higher temperature accelerated the rates of DOC degradation. The experiment showed that the more bioavailable organic matter was rapidly cycled irrespective of higher temperature while degradation of recalcitrant substances was enhanced by warming. Thus, pulses of carbon at higher water temperature might have consequences for DOC

A Hydroxamic Acid Anchoring Group for Durable Dye-Sensitized Solar Cells Incorporating a Cobalt Redox Shuttle.

PubMed

Higashino, Tomohiro; Kurumisawa, Yuma; Cai, Ning; Fujimori, Yamato; Tsuji, Yukihiro; Nimura, Shimpei; Packwood, Daniel M; Park, Jaehong; Imahori, Hiroshi

2017-09-11

A hydroxamic acid group has been employed for the first time as an anchoring group for cobalt-based dye-sensitized solar cells (DSSCs). The porphyrin dye YD2-o-C8HA including a hydroxamic acid anchoring group exhibited a power conversion efficiency (η) of 6.4 %, which is close to that of YD2-o-C8, a representative porphyrin dye incorporating a conventional carboxylic acid. More importantly, YD2-o-C8HA was found to be superior to YD2-o-C8 in terms of both binding ability to TiO 2 and durability of cobalt-based DSSCs. Notably, YD2-o-C8HA photocells revealed a higher η-value (4.1 %) than YD2-o-C8 (2.8 %) after 500 h illumination. These results suggest that the hydroxamic acid can be used for DSSCs with other transition-metal-based redox shuttle to ensure high cell durability as well as excellent photovoltaic performance. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Acidity enhancement of unsaturated bases of group 15 by association with borane and beryllium dihydride. Unexpected boron and beryllium Brønsted acids.

PubMed

Martín-Sómer, Ana; Mó, Otilia; Yáñez, Manuel; Guillemin, Jean-Claude

2015-01-21

The intrinsic acidity of CH2[double bond, length as m-dash]CHXH2, HC[triple bond, length as m-dash]CXH2 (X = N, P, As, Sb) derivatives and of their complexes with BeH2 and BH3 has been investigated by means of high-level density functional theory and molecular orbital ab initio calculations, using as a reference the ethyl saturated analogues. The acidity of the free systems steadily increases down the group for the three series of derivatives, ethyl, vinyl and ethynyl. The association with both beryllium dihydride and borane leads to a very significant acidity enhancement, being larger for BeH2 than for BH3 complexes. This acidity enhancement, for the unsaturated compounds, is accompanied by a change in the acidity trends down the group, which do not steadily decrease but present a minimum value for both the vinyl- and the ethynyl-phosphine. When the molecule acting as the Lewis acid is beryllium dihydride, the π-type complexes in which the BeH2 molecules interact with the double or triple bond are found, in some cases, to be more stable, in terms of free energies, than the conventional complexes in which the attachment takes place at the heteroatom, X. The most important finding, however, is that P, As, and Sb ethynyl complexes with BeH2 do not behave as P, As, or Sb Brønsted acids, but unexpectedly as Be acids.

Protodeboronation of ortho- and para-phenol boronic acids and application to ortho and meta functionalization of phenols using boronic acids as blocking and directing groups.

PubMed

Lee, Chun-Young; Ahn, Su-Jin; Cheon, Cheol-Hong

2013-12-06

The first metal-free thermal protodeboronation of ortho- and para-phenol boronic acids in DMSO was developed. The protodeboronation was successfully applied to the synthesis of ortho- and meta-functionalized phenols using the boronic acid moiety as a blocking group and a directing group, respectively. Mechanistic studies suggested that this protodeboronation proceeds through the coordination of water to the boron atom followed by σ-bond metathesis.

Exogenous sialic acid transport contributes to group B streptococcus infection of mucosal surfaces.

PubMed

Pezzicoli, Alfredo; Ruggiero, Paolo; Amerighi, Fulvia; Telford, John L; Soriani, Marco

2012-09-15

By sequence analysis of available group B streptococcus (GBS) genomes, we discovered a conserved putative operon involved in the catabolism of sialic acid, containing a tripartite transporter formed by two integral membrane components and a sugar-binding unit, named SAL0039. Expression analysis in the presence of different substrates revealed that SAL0039 was specifically upregulated by the presence of sialic acid and downregulated when bacteria were grown in human blood or in the presence of a high concentration of glucose. The role of SAL0039 in sugar transport was supported by the inability of the sal0039 deletion mutant strain to import exogenous sialic acid and to grow in semidefined medium supplemented with this sugar. Furthermore, in vivo evidence showed that the presence of exogenous sialic acid significantly increased the capacity of GBS to infect mice at the mucosal level. These findings suggest that transport of sialic acid may also contribute to GBS infections.

The DIRT on Q10: In situ depletion of labile-inputs does not increase temperature sensitivity in a laboratory incubation (Invited)

NASA Astrophysics Data System (ADS)

Reynolds, L. L.; Lajtha, K.; Bowden, R.; Johnson, B. R.; Bridgham, S. D.

2013-12-01

The decomposition of soil organic matter is expected to increase with global warming and has been commonly described by kinetic models with at least two pools with differing turnover times. Pools characterized by rapid turnover are thought to consist of labile substrates. Meanwhile, slower turnover is attributed, in part, to greater chemical complexity and a necessarily higher activation energy which should in turn lead to a higher sensitivity (Q10) to temperature and a proportionally larger response to warming. Experimental tests of the relative Q10 of these pools have been inconclusive and contradictory in part due the fact that all pools are decomposing simultaneously and soils kept under differing conditions over long periods of time diverge in more than the Q10 response making them less comparable over time. We present here a test of the temperature response on soils from a 20 yr litter manipulation experiment incubated under an experimental regime that minimizes divergence among the soils. We hypothesize that 1) if exclusion of inputs has depleted labile substrates and 2) the remaining carbon is more chemically complex, then the input exclusion treatments should show a higher Q10 compared to the ambient or increased input treatments. The soils are taken from the Detritus Input and Removal Treatment (DIRT) plots in the Bousson Forest, Pennsylvania, US. The DIRT treatments consist of litter and root exclusion (no inputs = NI), no roots (NR), no litter (NL), double litter (DL), and ambient conditions (C). Soils were incubated at 25oC for 525 days. Periodically, replicate sets were rotated into 15oC, 35oC or remained at 25oC for 24 hr. The headspace CO2 concentration was measured before and after the 24 hr temperature treatments, and then all replicate sets were returned to 25oC. Twenty years of input exclusion decreased respiration rate, with NI < NR = NL < C = DL, and total carbon content, and thus, we conclude, labile substrates. The respiration rate at 25o

Characterization of acid functional groups of carbon dots by nonlinear regression data fitting of potentiometric titration curves

NASA Astrophysics Data System (ADS)

Alves, Larissa A.; de Castro, Arthur H.; de Mendonça, Fernanda G.; de Mesquita, João P.

2016-05-01

The oxygenated functional groups present on the surface of carbon dots with an average size of 2.7 ± 0.5 nm were characterized by a variety of techniques. In particular, we discussed the fit data of potentiometric titration curves using a nonlinear regression method based on the Levenberg-Marquardt algorithm. The results obtained by statistical treatment of the titration curve data showed that the best fit was obtained considering the presence of five Brønsted-Lowry acids on the surface of the carbon dots with constant ionization characteristics of carboxylic acids, cyclic ester, phenolic and pyrone-like groups. The total number of oxygenated acid groups obtained was 5 mmol g-1, with approximately 65% (∼2.9 mmol g-1) originating from groups with pKa < 6. The methodology showed good reproducibility and stability with standard deviations below 5%. The nature of the groups was independent of small variations in experimental conditions, i.e. the mass of carbon dots titrated and initial concentration of HCl solution. Finally, we believe that the methodology used here, together with other characterization techniques, is a simple, fast and powerful tool to characterize the complex acid-base properties of these so interesting and intriguing nanoparticles.

Dilute acid hydrolysis of paper birch : kinetics studies of xylan and acetyl-group hydrolysis

Treesearch

Mark T. Maloney; Thomas W. Chapman; Andrew J. Baker

1985-03-01

Batch hydrolysis kinetics of paper birch (Betula papyrifera) xylan and its associated acetyl groups in dilute sulfuric acid have been measured for acid concentrations of between 0.04 and 0.18 M and temperatures of between 100 and 170°C. Only 5% of the cellulose was hydrolyzed for up to 85% xylan removal. Rate data were correlated well by a parallel reaction model based...

Development of Acid Functional Groups and Lactones During the Thermal Degradation of Wood and Wood Components

USGS Publications Warehouse

Rutherford, David W.; Wershaw, Robert L.; Reeves, James B.

2008-01-01

Black carbon (pyrogenic materials including chars) in soils has been recognized as a substantial portion of soil organic matter, and has been shown to play a vital role in nutrient cycling; however, little is known concerning the properties of this material. Previous studies have largely been concerned with the creation of high-surface-area materials for use as sorbents. These materials have been manufactured at high temperature and have often been activated. Chars occurring in the environment can be formed over a wide range of temperature. Because it is extremely difficult to isolate black carbon once it has been incorporated in soils, chars produced in the laboratory under controlled conditions can be used to investigate the range of properties possible for natural chars. This report shows that charring conditions (temperature and time) have substantial impact on the acid functional group and lactone content of chars. Low temperatures (250?C) and long charring times (greater than 72 hours) produce chars with the highest acid functional group and lactone content. The charring of cellulose appears to be responsible for the creation of the acid functional group and lactones. The significance of this study is that low-temperature chars can have acid functional group contents comparable to humic materials (as high as 8.8 milliequivalents per gram). Acid functional group and lactone content decreases as charring temperature increases. The variation in formation conditions expected under natural fire conditions will result in a wide range of sorption properties for natural chars which are an important component of soil organic matter. By controlling the temperature and duration of charring, it is possible to tailor the sorption properties of chars, which may be used as soil amendments.

Effects of composition of labile organic matter on biogenic production of methane in the coastal sediments of the Arabian Sea.

PubMed

Gonsalves, Maria-Judith; Fernandes, Christabelle E G; Fernandes, Sheryl Oliveira; Kirchman, David L; Bharathi, P A Loka

2011-11-01

Coastal regions are potential zones for production of methane which could be governed by ecological/environmental differences or even sediment properties of a niche. In order to test the hypothesis that methanogenesis in most marine sediments could be driven more by proteins than by carbohydrates and lipid content of labile organic matter (LOM), incubation experiments were carried out with sediments from different environmental niches to measure methane production. The methane production rates were examined in relationship to the sediment biochemistry, i.e., carbohydrates, proteins, and lipids. The gas production measured by head space method ranged from 216 ng g( -1) day( -1) in the mangrove sediments to 3.1 μg g( -1) day( -1) in the shallow Arabian Sea. LOM ranged from 1.56 to 2.85 mg g( -1) in the shallow Arabian Sea, from 3.35 to 5.43 mg g( -1) in the mangrove estuary, and from 0.66 to 0.70 mg g( -1) in the sandy sediments with proteins contributing maximum to the LOM pool. Proteins influenced methane production in the clayey sediments of shallow depths of the Arabian Sea (r = 0.933, p < 0.001) and mangrove estuary (r = 0.981, p < 0.001) but in the sandy beach sediments, carbohydrates (r = 0.924, p < 0.001) governed the net methane production. The gas production was more pronounced in shallow and surface sediments and it decreased with depth apparently governed by the decrease in lability index. Thus, the lability index and protein content are important factors that determine methane production rates in these coastal ecosystems.

Catabolism of Naphthalenesulfonic Acids by Pseudomonas sp. A3 and Pseudomonas sp. C22

PubMed Central

Brilon, C.; Beckmann, W.; Knackmuss, H.-J.

1981-01-01

Naphthalene and two naphthalenesulfonic acids were degraded by Pseudomonas sp. A3 and Pseudomonas sp. C22 by the same enzymes. Gentisate is a major metabolite. Catabolic activities for naphthalene, 1-naphthalenesulfonic acid, and 2-naphthalenesulfonic acid are induced by growth with naphthalene, 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, methylnaphthalene, or salicylate. Gentisate is also an inducer in strain A3. Inhibition kinetics show that naphthalene and substituted naphthalenes are hydroxylated by the same naphthalene dioxygenase. Substrates with nondissociable substituents such as CH3, OCH3, Cl, or NO2 are hydroxylated in the 7,8-position, and 4-substituted salicylates are accumulated. If CO2H, CH2CO2H, or SO3H are substituents, hydroxylation occurs with high regioselectivity in the 1,2-position. Thus, 1,2-dihydroxy-1,2-dihydronaphthalene-2-carboxylic acids are formed quantitatively from the corresponding naphthalenecarboxylic acids. Utilization of naphthalenesulfonic acids proceeds by the same regioselective 1,2-dioxygenation which labilizes the C—SO3− bond and eliminates sulfite. PMID:16345814

A simple approach to estimate daily loads of total, refractory, and labile organic carbon from their seasonal loads in a watershed

Treesearch

Ying Ouyang; Johnny M. Grace; Wayne C. Zipperer; Jeff Hatten; Janet Dewey

2018-01-01

Loads of naturally occurring total organic carbons (TOC), refractory organic carbon (ROC), and labile organic carbon (LOC) instreams control the availability of nutrients and the solubility and toxicity of contaminants and affect biological activities throughabsorption of light and complex metals with production of carcinogenic compounds....

[Nocturnal continuous subcutaneous insulin infusion--a therapeutic possibility in labile type I diabetes under exceptional conditions].

PubMed

Bruns, W; Steinborn, F; Menzel, R; Staritz, B; Bibergeil, H

1990-03-15

The whole-day continuous subcutaneous insulin infusion (CSII) with portable pumps in daily blood glucose autocontrol guarantees a more stabile and favourable glycaemia than multiple injections in labile type I diabetics. The success is mainly to be traced back to the continuous replacement of the basal secretion, particularly to the nocturnal fasting phase. In this study the effect on the glycaemia is investigated with exclusively nocturnal administration of the CSII under maintenance of multiple insulin injections during this day. In a group of 18 type I diabetics the nocturnal CSII in comparison to intermediate insulin administrations in the evening led to a significant improvement of glycaemia (p less than 0.01), in particular to the decrease of the fasting blood sugars (p less than 0.05). In two casuistic observations in comparison to all the other conventional methods for the compensation of the nocturnal glycaemia (depot insulin, nocturnal injection of normal insulin) the nocturnal CSII proved to be superior. Therefore, the nocturnal CSII is an--though more rarely to be used--alternative, which may be taken into consideration, of a whole-day CSII is temporarily unwished for.

Using amino acids for the chromatofocusing of metal ions on silica with bonded tetraethylenepentamine groups

NASA Astrophysics Data System (ADS)

Ivanov, A. V.

2014-09-01

Amino acid-based eluents are used for the chromatofocusing of metal ions on Tetren-SiO2 chelating sorbent (silica with bonded tetraethylenepentamine groups) for the first time. The smoothest quasilinear pH gradients form for eluents based on glutamic and aspartic acids. The separation of Mn2+, Cr3+, Co2+, Ni2+, and Cu2+ is achieved.

A Double Blind Trial of Divalproex Sodium for Affective Lability and Alcohol Use Following Traumatic Brain Injury

DTIC Science & Technology

2013-10-01

acutely manic bipolar patients, and the FDA approved it in 1995 for this indication. Also, it is used in conjunction with lithium or carbamazepine to...0652 TITLE: A Double Blind Trial of Divalproex Sodium for Affective Lability and Alcohol Use Following Traumatic Brain Injury...and Alcohol Use Following Traumatic Brain Injury 5a. CONTRACT NUMBER 5b. GRANT NUMBER W81XWH-08-2-0652 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR

Diffusive Milli-Gels (DMG) for in situ assessment of metal bioavailability: A comparison with labile metal measurement using Chelex columns and acute toxicity to Ceriodaphnia dubia for copper in freshwaters.

PubMed

Perez, Magali; Simpson, Stuart L; Lespes, Gaëtane; King, Josh J; Adams, Merrin S; Jarolimek, Chad V; Grassl, Bruno; Schaumlöffel, Dirk

2016-12-01

Fluctuations in concentrations of bioavailable metals occur in most natural waters. In situ measurements are desirable to predict risks of adverse effects to aquatic organisms. We evaluated Diffusive Milli-Gels (DMG), a new in situ passive sampler, for assessing the bioavailability and toxicity of copper in waters exhibiting a wide range of characteristics. The performance was compared to an established Chelex-column method that measures labile copper concentrations by discrete sampling, and the ability to predict acute toxicity to the cladoceran, Ceriodaphnia dubia. The labile copper concentrations measured by the DMG and Chelex-column methods decreased with increasing dissolved organic carbon (DOC) (1.9-15 mg L -1 ) and hardness (21-270 mg CaCO 3  L -1 hardness), with 20-70% of total dissolved copper being present as labile copper. Toxicity decreased with increasing DOC and hardness. Strong linear relationships existed between the EC50 for C. dubia and DOC, and when the EC50 was related to either the labile copper concentrations measured by DMG (r 2  = 0.874) or the Chelex column (0.956) methods. The study demonstrates that the DMG passive sampler is a relevant tool for the in situ assessment of environmental risks posed by metals whose toxicity is strongly influenced by speciation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Intermediate temperature proton conductors for PEM fuel cells based on phosphonic acid as protogenic group: a progress report.

PubMed

Steininger, H; Schuster, M; Kreuer, K D; Kaltbeitzel, A; Bingöl, B; Meyer, W H; Schauff, S; Brunklaus, G; Maier, J; Spiess, H W

2007-04-21

The melting behaviour and transport properties of straight chain alkanes mono- and difunctionalized with phosphonic acid groups have been investigated as a function of their length. The increase of melting temperature and decrease of proton conductivity with increasing chain length is suggested to be the consequence of an increasing ordering of the alkane segments which constrains the free aggregation of the phosphonic acid groups. However, the proton mobility is reduced to a greater extent than the proton diffusion coefficient indicating an increasing cooperativity of proton transport with increasing length of the alkane segment. The results clearly indicate that the "spacer concept", which had been proven successful in the optimization of the proton conductivity of heterocycle based systems, fails in the case of phosphonic acid functionalized polymers. Instead, a very high concentration of phosphonic acid functional groups forming "bulky" hydrogen bonded aggregates is suggested to be essential for obtaining very high proton conductivity. Aggregation is also suggested to reduce condensation reactions generally observed in phosphonic acid containing systems. On the basis of this understanding, the proton conductivities of poly(vinyl phosphonic acid) and poly(meta-phenylene phosphonic acid) are discussed. Though both polymers exhibit a substantial concentration of phosphonic acid groups, aggregation seems to be constrained to such an extent that intrinsic proton conductivity is limited to values below sigma = 10(-3) S cm(-1) at T = 150 degrees C. The results suggest that different immobilization concepts have to be developed in order to minimize the conductivity reduction compared to the very high intrinsic proton conductivity of neat phosphonic acid under quasi dry conditions. In the presence of high water activities, however, (as usually present in PEM fuel cells) the very high ion exchange capacities (IEC) possible for phosphonic acid functionalized ionomers (IEC

Acid-degradable lactobionic acid-modified soy protein nanogels crosslinked by ortho ester linkage for efficient antitumor in vivo.

PubMed

Cheng, Xu; Qin, Jiejie; Wang, Xin; Zha, Qian; Yao, Weijing; Fu, Shengxiang; Tang, Rupei

2018-05-03

It remains a crucial challenge to achieve efficient cellular uptake and intracellular drug release in tumor cells for the nanoscale drug delivery systems. Herein, acid-degradable nanogels were prepared by cross-linking methacrylated soy protein with an acid-labile ortho ester cross-linker (NG1), and then modified with lactobionic acid (LA) to give tumor-targeted nanogels (NG2). Both NG1 and NG2 displayed excellent stability in neutral environment, while showed pH-triggered degradation behaviors under mildly acidic conditions resulting from the breakage of ortho ester bonds. Doxorubicin (DOX) was successfully loaded into nanogels, which exhibited an accelerated release at low pH. In vitro cell studies demonstrated that LA-modified nanogels could effectively improve cellular internalization, show higher cytotoxicity and apoptosis toward asialoglycoprotein receptor (ASGPR) over-expressed HepG2 cells. In vivo antitumor experimentproved that LA modification could significantly enhance the tumor-targeting ability of nanogels and increase DOX concentration in tumor site, leading to better therapeutic efficacy. Histological analysis further demonstrated that soy protein-based nanogels did not cause any damage to normal organs. Overall, these pH-sensitive and tumor-targeting soy protein-based nanogels can be potential drug carriers for efficient tumor treatment. Copyright © 2018. Published by Elsevier B.V.

FTIR-PAS: a powerful tool for characterising the chemical composition and predicting the labile C fraction of various organic waste products.

PubMed

Bekiaris, Georgios; Bruun, Sander; Peltre, Clément; Houot, Sabine; Jensen, Lars S

2015-05-01

Fourier transform infrared (FT-IR) spectroscopy has been used for several years as a fast, low-cost, reliable technique for characterising a large variety of materials. However, the strong influence of sample particle size and the inability to measure the absorption of very dark and opaque samples have made FTIR unsuitable for many waste materials. FTIR-photoacoustic spectroscopy (FTIR-PAS) can eliminate some of the shortcomings of traditional FTIR caused by scattering effects and reflection issues, and recent advances in PAS technology have made commercial instruments available. In this study, FTIR-PAS was used to characterise a wide range of organic waste products and predict their labile carbon fraction, which is normally determined from time-consuming assays. FTIR-PAS was found to be capable of predicting the labile fraction of carbon as efficiently as near infrared spectroscopy (NIR) and furthermore of identifying the compounds that are correlated with the predicted parameter, thus facilitating a more mechanistic interpretation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effects of low molecular weight organic acids on (137)Cs release from contaminated soils.

PubMed

Chiang, Po Neng; Wang, Ming Kuang; Huang, Pan Ming; Wang, Jeng Jong

2011-06-01

Radio pollutant removal is one of several priority restoration strategies for the environment. This study assessed the effect of low molecular weight organic acid on the lability and mechanisms for release of (137)Cs from contaminated soils. The amount of (137)Cs radioactivity released from contaminated soils reacting with 0.02 M low molecular weight organic acids (LMWOAs) specifically acetic, succinic, oxalic, tartaric, and citric acid over 48 h were 265, 370, 760, 850, and 1002 Bq kg(-1), respectively. The kinetic results indicate that (137)Cs exhibits a two-step parabolic diffusion equation and a good linear relationship, indicating that the parabolic diffusion equation describes the data quite well, as shown by low p and high r(2) values. The fast stage, which was found to occur within a short period of time (0.083-3 h), corresponds to the interaction of LMWOAs with the surface of clay minerals; meanwhile, during the slow stage, which occurs over a much longer time period (3-24 h), desorption primarily is attributed to inter-particle or intra-particle diffusion. After a fifth renewal of the LMWOAs, the total levels of (137)Cs radioactivity released by acetic, succinic, oxalic, tartaric, and citric acid were equivalent to 390, 520, 3949, 2061, and 4422 Bq kg(-1) soil, respectively. H(+) can protonate the hydroxyl groups and oxygen atoms at the broken edges or surfaces of the minerals, thereby weakening Fe-O and Al-O bonds. After protonation of H(+), organic ligands can attack the OH and OH(2) groups in the minerals easily, to form complexes with surface structure cations, such as Al and Fe. The amounts of (137)Cs released from contaminated soil treated with LMWOAs were substantially increased, indicating that the LMWOAs excreted by the roots of plants play a critical role in (137)Cs release. Copyright © 2011 Elsevier Ltd. All rights reserved.

Acid-Group-Content-Dependent Proton Conductivity Mechanisms at the Interlayer of Poly(N-dodecylacrylamide-co-acrylic acid) Copolymer Multilayer Nanosheet Films.

PubMed

Sato, Takuma; Tsukamoto, Mayu; Yamamoto, Shunsuke; Mitsuishi, Masaya; Miyashita, Tokuji; Nagano, Shusaku; Matsui, Jun

2017-11-14

The effect of the content of acid groups on the proton conductivity at the interlayer of polymer-nanosheet assemblies was investigated. For that purpose, amphiphilic poly(N-dodecylacrylamide-co-acrylic acid) copolymers [p(DDA/AA)] with varying contents of AA were synthesized by free radical polymerization. Surface pressure (π)-area (A) isotherms of these copolymers indicated that stable polymer monolayers are formed at the air/water interface for AA mole fraction (n) ≤ 0.49. In all cases, a uniform dispersion of the AA groups in the polymer monolayer was observed. Subsequently, polymer monolayers were transferred onto solid substrates using the Langmuir-Blodgett (LB) technique. X-ray diffraction (XRD) analyses of the multilayer films showed strong Bragg diffraction peaks, suggesting a highly uniform lamellar structure for the multilayer films. The proton conductivity of the multilayer films parallel to the direction of the layer planes were measured by impedance spectroscopy, which revealed that the conductivity increased with increasing values of n. Activation energies for proton conduction of ∼0.3 and 0.42 eV were observed for n ≥ 0.32 and n = 0.07, respectively. Interestingly, the proton conductivity of a multilayer film with n = 0.19 did not follow the Arrhenius equation. These results were interpreted in terms of the average distance between the AA groups (l AA ), and it was concluded that, for n ≥ 0.32, an advanced 2D hydrogen bonding network was formed, while for n = 0.07, l AA is too long to form such hydrogen bonding networks. The l AA for n = 0.19 is intermediate to these extremes, resulting in the formation of hydrogen bonding networks at low temperatures, and disruption of these networks at high temperatures due to thermally induced motion. These results indicate that a high proton conductivity with low activation energy can be achieved, even under weakly acidic conditions, by arranging the acid groups at an optimal distance.

Effect of a labile methyl donor on the transformation of 5-demethyltangeretin and the related implication on bioactivity.

PubMed

Ting, Yuwen; Li, Colin C; Pan, Min-Hsiung; Ho, Chi-Tang; Huang, Qingrong

2013-08-28

Polymethoxyflavones (PMFs) belong to a subgroup of flavonoids that particularly exist in the peels of citrus fruits. Despite their many health-beneficial biofunctionalities, the lipophilic nature of PMFs limits their water solubility and oral bioavailability. To investigate the effect of the delivery system on the improvement of PMF bioavailibility, a lecithin-based emulsion was formulated for the delivery of two PMF compounds, tangeretin and 5-demethyltangeretin. While the emulsion system improved the digestion kinetics and the total solubilized PMF concentrations in in vitro lipolysis studies, the concentration of 5-demethyltangeretin decreased due to chemical transformation to its permethoxylated counterpart, tangeretin. The emulsifier lecithin used in this emulsion formulation contained a choline headgroup as a labile methyl group donor. The presence of a methyl donor potentially caused the transformation of 5-demethyltangeretin and reduced its anti-cancer-cell-proliferation activities. Moreover, this is the first report in the literature of the transformation from 5-demethyltangeretin to tangeretin in a lecithin-based emulsion during lipolysis, and the mechanism underlying this phenomenon has also been proposed for the first time.

Organoboron compounds as Lewis acid receptors of fluoride ions in polymeric membranes.

PubMed

Jańczyk, Martyna; Adamczyk-Woźniak, Agnieszka; Sporzyński, Andrzej; Wróblewski, Wojciech

2012-07-06

Newly synthesized organoboron compounds - 4-octyloxyphenylboronic acid (OPBA) and pinacol ester of 2,4,6-trifluorophenylboronic acid (PE-PBA) - were applied as Lewis acid receptors of fluoride anions. Despite enhanced selectivity, the polymer membrane electrodes containing the lipophilic receptor OPBA exhibited non-Nernstian slopes of the responses toward fluoride ions in acidic conditions. Such behavior was explained by the lability of the B-O bond in the boronic acids, and the OH(-)/F(-) exchange at higher fluoride content in the sample solution. In consequence, the stoichiometry of the OPBA-fluoride complexes in the membrane could vary during the calibration, changing the equilibrium concentration of the primary anion in membrane and providing super-Nernstian responses. The proposed mechanism was supported by (19)F NMR studies, which indicated that the fluoride complexation proceeds more effectively in acidic solution leading mainly to PhBF(3)(-) species. Finally, the performances of the membranes based on the phenylboronic acid pinacol ester, with a more stable B-O bond, were tested. As it was expected, Nernstian fluoride responses were recorded for such membranes with worsened fluoride selectivity. Copyright © 2012 Elsevier B.V. All rights reserved.

Changes in lead and zinc lability during weathering-induced acidification of desert mine tailings: Coupling chemical and micro-scale analyses.

PubMed

Hayes, Sarah M; White, Scott A; Thompson, Thomas L; Maier, Raina M; Chorover, Jon

2009-12-01

Desert mine tailings may accumulate toxic metals in the near surface centimeters because of low water through-flux rates. Along with other constraints, metal toxicity precludes natural plant colonization even over decadal time scales. Since unconsolidated particles can be subjected to transport by wind and water erosion, potentially resulting in direct human and ecosystem exposure, there is a need to know how the lability and form of metals change in the tailings weathering environment. A combination of chemical extractions, X-ray diffraction, micro-X-ray fluorescence spectroscopy, and micro-Raman spectroscopy were employed to study Pb and Zn contamination in surficial arid mine tailings from the Arizona Klondyke State Superfund Site. Initial site characterization indicated a wide range in pH (2.5 to 8.0) in the surficial tailings pile. Ligand-promoted (DTPA) extractions, used to assess plant-available metal pools, showed decreasing available Zn and Mn with progressive tailings acidification. Aluminum shows the inverse trend, and Pb and Fe show more complex pH dependence. Since the tailings derive from a common source and parent mineralogy, it is presumed that variations in pH and "bioavailable" metal concentrations result from associated variation in particle-scale geochemistry. Four sub-samples, ranging in pH from 2.6 to 5.4, were subjected to further characterization to elucidate micro-scale controls on metal mobility. With acidification, total Pb (ranging from 5 - 13 g kg(-1)) was increasingly associated with Fe and S in plumbojarosite aggregates. For Zn, both total (0.4 - 6 g kg(-1)) and labile fractions decreased with decreasing pH. Zinc was found to be primarily associated with the secondary Mn phases manjiroite and chalcophanite. The results suggest that progressive tailings acidification diminishes the overall lability of the total Pb and Zn pools.

Changes in lead and zinc lability during weathering-induced acidification of desert mine tailings: Coupling chemical and micro-scale analyses

PubMed Central

Hayes, Sarah M.; White, Scott A.; Thompson, Thomas L.; Maier, Raina M.; Chorover, Jon

2009-01-01

Desert mine tailings may accumulate toxic metals in the near surface centimeters because of low water through-flux rates. Along with other constraints, metal toxicity precludes natural plant colonization even over decadal time scales. Since unconsolidated particles can be subjected to transport by wind and water erosion, potentially resulting in direct human and ecosystem exposure, there is a need to know how the lability and form of metals change in the tailings weathering environment. A combination of chemical extractions, X-ray diffraction, micro-X-ray fluorescence spectroscopy, and micro-Raman spectroscopy were employed to study Pb and Zn contamination in surficial arid mine tailings from the Arizona Klondyke State Superfund Site. Initial site characterization indicated a wide range in pH (2.5 to 8.0) in the surficial tailings pile. Ligand-promoted (DTPA) extractions, used to assess plant-available metal pools, showed decreasing available Zn and Mn with progressive tailings acidification. Aluminum shows the inverse trend, and Pb and Fe show more complex pH dependence. Since the tailings derive from a common source and parent mineralogy, it is presumed that variations in pH and “bioavailable” metal concentrations result from associated variation in particle-scale geochemistry. Four sub-samples, ranging in pH from 2.6 to 5.4, were subjected to further characterization to elucidate micro-scale controls on metal mobility. With acidification, total Pb (ranging from 5 – 13 g kg−1) was increasingly associated with Fe and S in plumbojarosite aggregates. For Zn, both total (0.4 – 6 g kg−1) and labile fractions decreased with decreasing pH. Zinc was found to be primarily associated with the secondary Mn phases manjiroite and chalcophanite. The results suggest that progressive tailings acidification diminishes the overall lability of the total Pb and Zn pools. PMID:20161492

Disruption of Human Plasma High Density Lipoproteins by Streptococcal Serum Opacity Factor Requires Labile Apolipoprotein A-I

PubMed Central

Han, Mikyung; Gillard, Baiba K.; Courtney, Harry S.; Ward, Kathryn; Rosales, Corina; Khant, Htet; Ludtke, Steven J.; Pownall, Henry J.

2010-01-01

Human plasma high density lipoproteins (HDL), the primary vehicle for reverse cholesterol transport, are the target of serum opacity factor (SOF), a virulence determinant of Streptococcus pyogenes that turns serum opaque. HDL comprise a core of neutral lipids–cholesteryl esters and some triglyceride–surrounded by a surface monolayer of cholesterol, phospholipids, and specialized proteins–apolipoproteins (apos) A-I and A-II. HDL is an unstable particle residing in a kinetic trap from which it can escape via chaotropic, detergent or thermal perturbation. Recombinant (r) SOF catalyzes the transfer of nearly all neutral lipids of ~100,000 HDL particles (D ~ 8.5 nm) into a single, large cholesteryl ester-rich microemulsion (CERM; D >100 nm) leaving a new HDL-like particle–neo HDL (D ~5.8 nm) while releasing lipid-free (LF) apo A-I. CERM formation and apo A-I release have similar kinetics suggesting parallel or rapid consecutive steps. By using complementary physico-chemical methods, we have refined the mechanistic model for HDL opacification. According to size exclusion chromatography, HDL containing non-labile apo A-I resists rSOF-mediated opacification. Based on kinetic cryo electron microscopy, rSOF (10 nM) catalyzes the conversion of HDL (4 μM) to neo HDL via a step-wise mechanism in which intermediate-size particles are seen. Kinetic turbidimetry revealed opacification as a rising exponential reaction with a rate constant k = (4.400 ± 0.004) × 10−2 min−1. Analysis of the kinetic data using transition state theory gave an enthalpy, entropy and free energy of activation of ΔH‡ = 73.9 kJ/mol, ΔS‡ = −66.87 J/°K, and ΔG‡ = 94.6 kJ/mol respectively. The free energy of activation for opacification is nearly identical to that for the displacement of apo A-I from HDL by guanidine hydrochloride. We conclude that apo A-I lability is required for HDL opacification, LF apo A-I desorption is the rate-limiting step, and nearly all HDL particles contain

Alteration of Labile Trace Element Concentrations in Antarctic Meteorites by Weathering: A Five-Year Assessment

NASA Astrophysics Data System (ADS)

Wang, M.-S.; Xiao, X.; Lipschutz, M. E.

1992-07-01

Numerous studies since 1987 demonstrate that, on average, Antarctic populations of specific meteorite groups differ from non-Antarctic falls. Some differences could conceivably reflect alteration during the meteorites' residence in Antarctica while others clearly are preterrestrial origin, predating fall on Earth. Concentrations of certain trace elements (Ag, Au, Bi, Cd, Co, Cs, Ga, In, Rb, Sb, Se, Te, Tl, Zn) determined by RNAA in 45 H4-6 chondrites first provided evidence for Antarctic/non-Antarctic meteorite population differences [1]. Most of these elements are thermally labile (easily lost during extended chondritic heating chondrites) so that their concentrations give important information on the thermal history of meteoritic material. Refractory elements cannot give such information. Factors possibly complicating establishment of compositional differences as preterrestrial--meteorite pairing, population reproducibility, analyst bias, and statistical modeling--are of demonstrated in consequence [1-4]. Indeed, compositional differences exist [3,4] between Antarctic meteorite populations (Victoria Land vs. Queen Maud Land) and among observed falls (Cluster 1 vs. other falls). Possibilities for meteorite compositional alteration during Antarctic weathering must be re-assessed as new data are obtained: here, we summarize the current status of this problem. 1. Highly weathered meteorites: Ten of our suite of trace elements have significantly lower mean concentrations (presumably because of leaching) in H5 chondrites of weathering types B/C and C, than in types A, A/B, and B [1]. Meteorites of types A to B-- whether exhibiting efflorescence or not--seem uncompromised [5]. 2. Antarctic meteorites of high weathering susceptibility: Carbonaceous chondrites and lunar meteorites are essentially unaltered by weathering. For example, data for LEW 90500 C(1?) chondrite reported here demonstrate that the 8 most volatile elements (Se, Cs, Te, Zn, Cd, Bi, Tl, In) have a mean

A sensitive method for measuring protein turnover based on the measurement of 2-3H-labelled amino acids in protein.

PubMed Central

Humphrey, T J; Davies, D D

1976-01-01

A method for measuring the rate of protein degradation is described. The method measures the change in 2-3H content of protein with time by racemization of the protein hydrolysate with acetic anhydride. The 3H on C-2 of amino acids is stable in proteins but becomes labile, owing to the action of transaminases, once the amino acids are released by proteolysis. The specific measurement of 2-3H in amino acids largely overcomes problems due to compartmentation and isotope recycling and evidence to support this claim is presented. Values for the half-life of Lemna minor (duckweed) protein determined by the new method are compared with values obtained by other methods. PMID:949338

Utility of DSM-5 section III personality traits in differentiating borderline personality disorder from comparison groups.

PubMed

Bach, B; Sellbom, M; Bo, S; Simonsen, E

2016-09-01

Borderline Personality Disorder (BPD) is a highly prevalent diagnosis in mental health care and includes a heterogeneous constellation of symptoms. As the field of personality disorder (PD) research moves to emphasize dimensional traits in its operationalization, it is important to determine how the alternative DSM-5 Section III personality trait dimensions differentiates such features in BPD patients versus comparison groups. To date, no study has attempted such validation. The current study examined the utility of the DSM-5 trait dimensions in differentiating patients with the categorical DSM-IV/5 diagnosis of BPD (n=101) from systematically matched samples of other PD patients (n=101) and healthy controls (n=101). This was investigated using one-way ANOVA and multinomial logistic regression analyses. Results indicated that Emotional Lability, Risk Taking, and Suspiciousness uniquely differentiated BPD patients from other PD patients, whereas Emotional Lability, Depressivity, and Suspiciousness uniquely differentiated BPD patients from healthy controls. Emotional Lability is in particular a key BPD feature of the proposed Section III model, whereas Suspiciousness also augments essential BPD features. Provided that these findings are replicated cross-culturally in forthcoming research, a more parsimonious traits operationalization of BPD features is warranted. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Polymers functionalized with bronsted acid groups

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Humbeck, Jeffrey; Long, Jeffrey R.; McDonald, Thomas M.

Porous aromatic framework polymers functionalized with Bronsted acid moieties are prepared by polymerization of a three-dimensional organic aryl or heteroaryl monomer and its copolymerization with a second aryl or heteroaryl monomer functionalized with one or more Bronsted acid moiety. The polymers are characterized by a stable three-dimensional structure, which, in exemplary embodiments, includes interpenetrating subunits within one or more domain of the bulk polymer structure. The polymers are of use in methods of adsorbing ammonia and amines and in devices and systems configured for this purpose.

The relation between gastric acid secretion and body habitus, blood groups, smoking, and the subsequent development of dyspepsia and duodenal ulcer

PubMed Central

Novis, B. H.; Marks, I. N.; Bank, S.; Sloan, A. W.

1973-01-01

One hundred and seventy-six students free of gastrointestinal disease were studied to establish normal acid secretion values for healthy male and female students by the augmented histamine test and to re-examine the relationship between gastric acid secretion and ABO blood groups, body weight, fat-free body mass, height, degree of ectomorphy and mesomorphy, the number of cigarettes smoked per day, and serum cholesterol. A prospective study was then carried out on gastric acid secretion and the subsequent development after 10 years of duodenal ulcers or dyspepsia. Young, healthy medical students have a fairly high mean basal and maximal acid output. There was very little difference in the mean acid outputs of the various ABO blood groups. A significant correlation was shown between acid output and body weight and fat-free body mass, but not with the other measurements of body build. Basal acid output was also related to the number of cigarettes smoked per day. Three students who subsequently developed duodenal ulcers all had a preexistent high level of acid secretion. The acid output was, however, similar in the groups who developed significant or minor dyspepsia or who remained asymptomatic. PMID:4696532

A universal fluorogenic switch for Fe(ii) ion based on N-oxide chemistry permits the visualization of intracellular redox equilibrium shift towards labile iron in hypoxic tumor cells.

PubMed

Hirayama, Tasuku; Tsuboi, Hitomi; Niwa, Masato; Miki, Ayaji; Kadota, Satoki; Ikeshita, Yukie; Okuda, Kensuke; Nagasawa, Hideko

2017-07-01

Iron (Fe) species play a number of biologically and pathologically important roles. In particular, iron is a key element in oxygen sensing in living tissue where its metabolism is intimately linked with oxygen metabolism. Regulation of redox balance of labile iron species to prevent the generation of iron-catalyzed reactive oxygen species (ROS) is critical to survival. However, studies on the redox homeostasis of iron species are challenging because of a lack of a redox-state-specific detection method for iron, in particular, labile Fe 2+ . In this study, a universal fluorogenic switching system is established, which is responsive to Fe 2+ ion based on a unique N-oxide chemistry in which dialkylarylamine N-oxide is selectively deoxygenized by Fe 2+ to generate various fluorescent probes of Fe 2+ -CoNox-1 (blue), FluNox-1 (green), and SiRhoNox-1 (red). All the probes exhibited fluorescence enhancement against Fe 2+ with high selectivity both in cuvette and in living cells. Among the probes, SiRhoNox-1 showed an excellent fluorescence response with respect to both reaction rate and off/on signal contrast. Imaging studies were performed showing the intracellular redox equilibrium shift towards labile iron in response to reduced oxygen tension in living cells and 3D tumor spheroids using SiRhoNox-1, and it was found that the hypoxia induction of labile Fe 2+ is independent of iron uptake, hypoxia-induced signaling, and hypoxia-activated enzymes. The present studies demonstrate the feasibility of developing sensitive and specific fluorescent probes for Fe 2+ with refined photophysical characteristics that enable their broad application in the study of iron in various physiological and pathological conditions.

Total and labile metals in surface sediments of the tropical river-estuary system of Marabasco (Pacific coast of Mexico): Influence of an iron mine.

PubMed

Marmolejo-Rodríguez, Ana Judith; Prego, Ricardo; Meyer-Willerer, Alejandro; Shumilin, Evgueni; Cobelo-García, Antonio

2007-01-01

Marabasco is a tropical river-estuary system comprising the Marabasco river and the Barra de Navidad Lagoon. The river is impacted by the Peña Colorada iron mine, which produces 3.5 million tons of pellets per year. Thirteen surface sediment samples were collected in May 2005 (dry season) in order to establish background levels of Al, Cd, Co, Cu, Fe, Ni, Pb, and Zn in the system and to ascertain the potential mobility of metals in the sediments. Analyses were carried out in the fraction finer than 63 microm, and labile metals extracted according the BCR procedure. Certified reference materials were used for validation of methods. Total concentrations of Cd, Co, Cu, Ni, Pb, and Zn were in the range of 0.05-0.34, 6-95, 0.7-31, 9-26, 2-18, and 53-179 mgkg(-1), respectively; Al and Fe ranges of 24-127, and 26-69 mgg(-1) correspondingly. Cadmium was found to be significantly labile in the sediments (20-100%), followed by Co (0-35%), Ni (3-16%) and Zn (0-25%), whereas the labile fraction for Cu, Fe and Pb was almost negligible (<4%). According with the total metal concentrations, background levels and normalised enrichment factors (NEF) of the metals studied, the impact of the Peña Colorada iron mine on the Marabasco system is lower than expected when compared with other similar World systems influenced by mining activities.

On the Labile Memory Buffer in the Attentional Blink: Masking the T2 Representation by Onset Transients Mediates the AB

ERIC Educational Resources Information Center

Jannati, Ali; Spalek, Thomas M.; Di Lollo, Vincent

2011-01-01

Report of a second target (T2) is impaired when presented within 500 ms of the first (T1). This attentional blink (AB) is known to cause a delay in T2 processing during which T2 must be stored in a labile memory buffer. We explored the buffer's characteristics using different types of masks after T2. These characteristics were inferred by…

Peculiarities of one-carbon metabolism in the strict carnivorous cat and the role in feline hepatic lipidosis.

PubMed

Verbrugghe, Adronie; Bakovic, Marica

2013-07-19

Research in various species has indicated that diets deficient in labile methyl groups (methionine, choline, betaine, folate) produce fatty liver and links to steatosis and metabolic syndrome, but also provides evidence of the importance of labile methyl group balance to maintain normal liver function. Cats, being obligate carnivores, rely on nutrients in animal tissues and have, due to evolutionary pressure, developed several physiological and metabolic adaptations, including a number of peculiarities in protein and fat metabolism. This has led to specific and unique nutritional requirements. Adult cats require more dietary protein than omnivorous species, maintain a consistently high rate of protein oxidation and gluconeogenesis and are unable to adapt to reduced protein intake. Furthermore, cats have a higher requirement for essential amino acids and essential fatty acids. Hastened use coupled with an inability to conserve certain amino acids, including methionine, cysteine, taurine and arginine, necessitates a higher dietary intake for cats compared to most other species. Cats also seemingly require higher amounts of several B-vitamins compared to other species and are predisposed to depletion during prolonged inappetance. This carnivorous uniqueness makes cats more susceptible to hepatic lipidosis.

Peculiarities of One-Carbon Metabolism in the Strict Carnivorous Cat and the Role in Feline Hepatic Lipidosis

PubMed Central

Verbrugghe, Adronie; Bakovic, Marica

2013-01-01

Research in various species has indicated that diets deficient in labile methyl groups (methionine, choline, betaine, folate) produce fatty liver and links to steatosis and metabolic syndrome, but also provides evidence of the importance of labile methyl group balance to maintain normal liver function. Cats, being obligate carnivores, rely on nutrients in animal tissues and have, due to evolutionary pressure, developed several physiological and metabolic adaptations, including a number of peculiarities in protein and fat metabolism. This has led to specific and unique nutritional requirements. Adult cats require more dietary protein than omnivorous species, maintain a consistently high rate of protein oxidation and gluconeogenesis and are unable to adapt to reduced protein intake. Furthermore, cats have a higher requirement for essential amino acids and essential fatty acids. Hastened use coupled with an inability to conserve certain amino acids, including methionine, cysteine, taurine and arginine, necessitates a higher dietary intake for cats compared to most other species. Cats also seemingly require higher amounts of several B-vitamins compared to other species and are predisposed to depletion during prolonged inappetance. This carnivorous uniqueness makes cats more susceptible to hepatic lipidosis. PMID:23877091

EFFECTS OF CLIMATE CHANGE ON LABILE AND STRUCTURAL CARBON IN DOUGLAS-FIR NEEDLES AS ESTIMATED BY DELTA 13C AND C AREA MEASUREMENTS

EPA Science Inventory

Isotopic measurements may provide new insights into levels in leaves of labile and structural carbon (C) under climate change. In a 4-year climate change experiment using Pseudotsuga menziesii (Douglas-fir) seedlings and a 2x2 factorial design in enclosed chambers (n=3), atmosph...

[Effects of the different land use on soil labile organic matter and carbon management index in Junyun Mountain].

PubMed

Xu, Peng; Jiang, Chang-Sheng; Hao, Qing-Ju; Zhu, Tao

2013-10-01

The impacts of different land use on soil organic matter (SOM), soil labile organic matter (SLOM) and their efficiency ratios (ER), and soil carbon management index (CMI) were studied in this study. Subtropical evergreen broad-leaved forest (abbreviation: forest) , sloping farmland, orchard and abandoned land were selected and soils at the depths of 0-10, 10-20, 20-30, 30-40, 40-50 and 50-60 cm were sampled in the spring of 2011 to determine the contents of soil organic matter and labile organic matter. The results showed that the contents of soil organic matter and soil labile organic matter both decreased with the increase of soil depth under all four land use types; however, forest and orchard enriched SOM and SLOM contents in the 0-10 cm and 0-20 cm soil layers, respectively, while the contents of SOM and SLOM decreased evenly in sloping farmland and abandoned land. In the whole soil layer (0-60 cm) , the order of SOM and SLOM contents was abandoned land > forest > orchard > sloping farmland, indicating that at the conversion from forest into orchard or sloping farmland, SOM was reduced by 21.56% (P >0.05) and 55.90% (P <0.05), respectively, and at the conversion from sloping farmland into abandoned land, the low SLOM, middle SLOM and high SLOM increased by 144.2% (P<0.05) , 153.3% (P <0.05) and 242.7% (P <0.05), respectively. There was no significant difference in low ER, middle ER and high ER among the four land uses as suggested by ANOVA which showed that SRs were not sensible to the change of land use. All three CMis were in the order of abandoned land > forest > orchard > sloping farmland, revealing that forest reclamation resulted in the reduction of soil organic carbon storage and the decline of soil quality, and the abandonment of sloping farmland would increase soil carbon sink and improve soil quality. Three kinds of SLOM were all positively correlated with soil total nitrogen, available phosphorus and available potassium, while negatively correlated

Ultrafast photochemistry of polyatomic molecules containing labile halogen atoms in solution

NASA Astrophysics Data System (ADS)

Mereshchenko, Andrey S.

Because breaking and making of chemical bonds lies at the heart of chemistry, this thesis focuses on dynamic studies of labile molecules in solutions using ultrafast transient absorption spectroscopy. Specifically, my interest is two-fold: (i) novel reaction intermediates of polyhalogenated carbon, boron and phosphorus compounds; (ii) photophysics and photochemistry of labile copper(II) halide complexes. Excitation of CH2Br2, CHBr3, BBr 3, and PBr3 into n(Br)sigma*(X-Br) states, where X=C, B, or P, leads to direct photoisomerization with formation of isomers having Br-Br bonds as well as rupture of one of X-Br bonds with the formation of a Br atom and a polyatomic radical fragment, which subsequently recombine to form similar isomer products. Nonpolar solvation stabilizes the isomers, consistent with intrinsic reaction coordinate calculations of the isomer ground state potential energy surfaces at the density functional level of theory, and consequently, the involvement of these highly energetic species on chemically-relevant time scales needs to be taken into account. Monochlorocomplexes in methanol solutions promoted to the ligand-to-metal charge transfer (LMCT) excited state predominantly undergo internal conversion via back electron transfer, giving rise to vibrationally hot ground-state parent complexes. Copper-chloride homolitical bond dissociation yielding the solvated copper(I) and Cl- atom/solvent CT complexes constitutes a minor pathway. Insights into ligand substitution mechanisms were acquired by monitoring the recovery of monochloro complexes at the expense of two unexcited dichloro- and unsubstituted forms of Cu(II) complexes also present in the solution. Detailed description of ultrafast excited-state dynamics of CuCl 42- complexes in acetonitrile upon excitation into all possible Ligand Field (LF) excited states and two most intense LMCT transitions is reported. The LF states were found to be nonreactive with lifetimes remarkably longer than those

[Variations of soil labile organic carbon along an altitude gradient in Wuyi Mountain].

PubMed

Xu, Xia; Chen, Yue-Qin; Wang, Jia-She; Fang, Yan-Hong; Quan, Wei; Ruan, Hong-Hua; Xu, Zi-Kun

2008-03-01

By using sequential fumigation-incubation method, this paper determined the soil labile organic carbon (LOC) content under evergreen broadleaf forest, coniferous forest, sub-alpine dwarf forest, and alpine meadow along an altitude gradient in Wuyi Mountain National Nature Reserve in Fujian Province of China, with its relations to soil microbial biomass carbon (MBC), total organic carbon (TOC), total nitrogen (TN), and fine root biomass (FRB) analyzed. The results showed that soil LOC occupied 3.40%-7.46% of soil TOC, and soil MBC occupied 26.87%-80.38% of the LOC. The LOC under different forest stands increased significantly with altitude, and decreased with soil depth. Soil LOC had very significant correlations with soil MBC, TOC, TN and FRB, and its content was obviously higher at higher altitudes than at lower altitudes.

Effects of Fatty Liver Induced by Excess Orotic Acid on B-Group Vitamin Concentrations of Liver, Blood, and Urine in Rats.

PubMed

Shibata, Katsumi; Morita, Nobuya; Kawamura, Tomoyo; Tsuji, Ai; Fukuwatari, Tsutomu

2015-01-01

Fatty liver is caused when rats are given orotic acid of the pyrimidine base in large quantities. The lack of B-group vitamins suppresses the biosynthesis of fatty acids. We investigated how orotic acid-induced fatty liver affects the concentrations of liver, blood, and urine B-group vitamins in rats. The vitamin B6 and B12 concentrations of liver, blood, and urine were not affected by orotic acid-induced fatty liver. Vitamin B2 was measured only in the urine, but was unchanged. The liver, blood, and urine concentrations of niacin and its metabolites fell dramatically. Niacin and its metabolites in the liver, blood, and urine were affected as expected. Although the concentrations of vitamin B1, pantothenic acid, folate, and biotin in liver and blood were decreased by orotic acid-induced fatty liver, these urinary excretion amounts showed a specific pattern toward increase. Generally, as for the typical urinary excretion of B-group vitamins, these are excreted when the body is saturated. However, the ability to sustain vitamin B1, pantothenic acid, folate, and biotin decreased in fatty liver, which is hypothesized as a specific phenomenon. This metabolic response might occur to prevent an abnormally increased biosynthesis of fatty acids by orotic acid.

Evaluation of the Flavor Contribution of Products of the Maillard Reaction

DTIC Science & Technology

the Maillard - type reaction between the products of autoxidized polyunsaturated fatty acids and free amino groups of phospholipids and within meat...intermolecular browning-type reaction with free amino groups, polymerization, etc., are liable to occur. Changes in these labile substances are known...proteins, and between the free amino groups of phospholipids and the monosaccharides present in meat. The reaction was elucidated and its products characterized and evaluated for its contribution to meat flavor.

Overexpression of Lactobacillus casei D-hydroxyisocaproic acid dehydrogenase in cheddar cheese.

PubMed

Broadbent, Jeffery R; Gummalla, Sanjay; Hughes, Joanne E; Johnson, Mark E; Rankin, Scott A; Drake, Mary Anne

2004-08-01

Metabolism of aromatic amino acids by lactic acid bacteria is an important source of off-flavor compounds in Cheddar cheese. Previous work has shown that alpha-keto acids produced from Trp, Tyr, and Phe by aminotransferase enzymes are chemically labile and may degrade spontaneously into a variety of off-flavor compounds. However, dairy lactobacilli can convert unstable alpha-keto acids to more-stable alpha-hydroxy acids via the action of alpha-keto acid dehydrogenases such as d-hydroxyisocaproic acid dehydrogenase. To further characterize the role of this enzyme in cheese flavor, the Lactobacillus casei d-hydroxyisocaproic acid dehydrogenase gene was cloned into the high-copy-number vector pTRKH2 and transformed into L. casei ATCC 334. Enzyme assays confirmed that alpha-keto acid dehydrogenase activity was significantly higher in pTRKH2:dhic transformants than in wild-type cells. Reduced-fat Cheddar cheeses were made with Lactococcus lactis starter only, starter plus L. casei ATCC 334, and starter plus L. casei ATCC 334 transformed with pTRKH2:dhic. After 3 months of aging, the cheese chemistry and flavor attributes were evaluated instrumentally by gas chromatography-mass spectrometry and by descriptive sensory analysis. The culture system used significantly affected the concentrations of various ketones, aldehydes, alcohols, and esters and one sulfur compound in cheese. Results further indicated that enhanced expression of d-hydroxyisocaproic acid dehydrogenase suppressed spontaneous degradation of alpha-keto acids, but sensory work indicated that this effect retarded cheese flavor development.

Organic biomarkers in deep-sea regions affected by bottom trawling: pigments, fatty acids, amino acids and carbohydrates in surface sediments from the La Fonera (Palamós) Canyon, NW Mediterranean Sea

NASA Astrophysics Data System (ADS)

Sañé, E.; Martín, J.; Puig, P.; Palanques, A.

2012-12-01

Deep-sea ecosystems are in general adapted to a limited variability of physical conditions, resulting in high vulnerability and slow recovery rates from anthropogenic perturbations such as bottom trawling. Commercial trawling is the most recurrent and pervasive of human impacts on the deep-sea floor, but studies on its consequences on the biogeochemistry of deep-sea sediments are still scarce. Pigments, fatty acids, amino acids and carbohydrates were analyzed in sediments from the flanks of the La Fonera (Palamós) submarine canyon (NW Mediterranean Sea), where a commercial bottom trawling fishery has been active for more than 70 yr. More specifically, we investigated how trawling-induced sediment reworking affects the quality of sedimentary organic matter which reaches the seafloor and accumulates in the sediment column, which is fundamental for the development of benthic communities. Sediment samples were collected during two oceanographic cruises in spring and autumn 2011. The sampled sites included trawl fishing grounds as well as pristine (control) areas. We report that bottom trawling in the flanks of the La Fonera Canyon has caused an alteration of the quality of the organic matter accumulated in the upper 5 cm of the seafloor. The use of a wide pool of biochemical tracers characterized by different reactivity to degradation allowed us to discriminate the long-term effects of trawled-induced sediment reworking from the natural variability caused by the seasonal cycle of production and sinking of biogenic particles. Differences between untrawled and trawled areas were evidenced by labile amino acids, while differences between spring and autumn samples were detected only by the more labile indicators chlorophyll a and mono-unsaturated fatty acids. These results suggest that changes in the biochemical composition of the sedimentary organic matter caused by bottom trawling can be more relevant than those associated with natural seasonality and pose serious

Organic biomarkers in deep-sea regions affected by bottom trawling: pigments, fatty acids, amino acids and carbohydrates in surface sediments from the La Fonera (Palamós) Canyon, NW Mediterranean Sea

NASA Astrophysics Data System (ADS)

Sañé, E.; Martín, J.; Puig, P.; Palanques, A.

2013-12-01

Deep-sea ecosystems are in general adapted to a limited variability of physical conditions, resulting in high vulnerability and slow recovery rates from anthropogenic perturbations such as bottom trawling. Commercial trawling is the most recurrent and pervasive of human impacts on the deep-sea floor, but studies on its consequences on the biogeochemistry of deep-sea sediments are still scarce. Pigments, fatty acids, amino acids and carbohydrates were analysed in sediments from the flanks of the La Fonera (Palamós) submarine canyon (NW Mediterranean Sea), where a commercial bottom trawling fishery has been active for more than 70 yr. More specifically, we investigated how trawling-induced sediment reworking affects the quality of sedimentary organic matter which reaches the seafloor and accumulates in the sediment column, which is fundamental for the development of benthic communities. Sediment samples were collected during two oceanographic cruises in spring and autumn 2011. The sampled sites included trawl fishing grounds as well as pristine (control) areas. We report that bottom trawling in the flanks of the La Fonera Canyon has caused an alteration of the quality of the organic matter accumulated in the upper 5 cm of the seafloor. The use of a wide pool of biochemical tracers characterized by different reactivity to degradation allowed for us to discriminate the long-term effects of trawl-induced sediment reworking from the natural variability caused by the seasonal cycle of production and sinking of biogenic particles. Differences between untrawled and trawled areas were evidenced by labile amino acids, while differences between spring and autumn samples were detected only by the more labile indicators chlorophyll a and monounsaturated fatty acids. These results suggest that changes in the biochemical composition of the sedimentary organic matter caused by bottom trawling can be more relevant than those associated with natural seasonality and pose serious

Predicting the solubility and lability of Zn, Cd, and Pb in soils from a minespoil-contaminated catchment by stable isotopic exchange

NASA Astrophysics Data System (ADS)

Marzouk, E. R.; Chenery, S. R.; Young, S. D.

2013-12-01

The Rookhope catchment of Weardale, England, has a diverse legacy of contaminated soils due to extensive lead mining activity over four centuries. We measured the isotopically exchangeable content of Pb, Cd and Zn (E-values) in a large representative subset of the catchment soils (n = 246) using stable isotope dilution. All three metals displayed a wide range of %E-values (c. 1-100%) but relative lability followed the sequence Cd > Pb > Zn. A refinement of the stable isotope dilution approach also enabled detection of non-reactive metal contained within suspended sub-micron (<0.22 μm) colloidal particles (SCP-metal). For most soils, the presence of non-labile SCP-metal caused only minor over-estimation of E-values (<2%) but the effect was greater for soils with particularly large humus or carbonate contents. Approximately 80%, 53% and 66% of the variability in Zn, Cd and Pb %E-values (respectively) could be explained by pH, loss on ignition and total metal content. E-values were affected by the presence of ore minerals at high metal contents leading to an inconsistent trend in the relationship between %E-value and soil metal concentration. Metal solubility, in the soil suspensions used to measure E-values, was predicted using the WHAM geochemical speciation model (versions VI and VII). The use of total and isotopically exchangeable metal as alternative input variables was compared; the latter provided significantly better predictions of solubility, especially in the case of Zn. Lead solubility was less well predicted by either version of WHAM, with over-prediction at low pH and under-prediction at high soil pH values. Quantify the isotopically exchangeable fractions of Zn, Cd and Pb (E-values), and assess their local and regional variability, using multi-element stable isotope dilution, in a diverse range of soil ecosystems within the catchment of an old Pb/Zn mining area. Assess the controlling influences of soil properties on metal lability and develop

Valence Focus and Self-Esteem Lability: Reacting to Hedonic Cues in the Social Environment

PubMed Central

Pietromonaco, Paula R.; Barrett, Lisa Feldman

2010-01-01

Individuals differ in the extent to which they emphasize feelings of pleasure or displeasure in their verbal reports of emotional experience, termed valence focus (VF). Two event-contingent, experience-sampling studies examined the relationship between VF and sensitivity to pleasant and unpleasant social cues. It was predicted, and found, that individuals with greater VF (i.e., who emphasized feelings of pleasure/displeasure in reports of emotional experience) demonstrated greater self-esteem lability (i.e., larger changes in self-esteem) to pleasant and unpleasant information contained in social interactions than did those lower in VF. These effects held even after statistically controlling for possible confounding variables (neuroticism, affect intensity). Implications for understanding the psychological impact of valenced interpersonal events are discussed. PMID:19485618

Salmonella enterica Serovar Enteritidis Ghosts Carrying the Escherichia coli Heat-Labile Enterotoxin B Subunit Are Capable of Inducing Enhanced Protective Immune Responses

PubMed Central

Jawale, Chetan V.

2014-01-01

The Escherichia coli heat-labile enterotoxin B subunit (LTB) is a potent vaccine adjuvant. Salmonella enterica serovar Enteritidis ghosts carrying LTB (S. Enteritidis-LTB ghosts) were genetically constructed using a novel plasmid, pJHL187-LTB, designed for the coexpression of the LTB and E lysis proteins. S. Enteritidis-LTB ghosts were characterized using scanning electron microscopy to visualize their transmembrane tunnel structures. The expression of LTB in S. Enteritidis-LTB ghost preparations was confirmed by immunoblot and enzyme-linked immunosorbent assays. The parenteral adjuvant activity of LTB was demonstrated by immunizing chickens with either S. Enteritidis-LTB ghosts or S. Enteritidis ghosts. Chickens were intramuscularly primed at 5 weeks of age and subsequently boosted at 8 weeks of age. In total, 60 chickens were equally divided into three groups (n = 20 for each): group A, nonvaccinated control; group B, immunized with S. Enteritidis-LTB ghosts; and group C, immunized with S. Enteritidis ghosts. Compared with the nonimmunized chickens (group A), the immunized chickens (groups B and C) exhibited increased titers of plasma IgG and intestinal secretory IgA antibodies. The CD3+ CD4+ subpopulation of T cells was also significantly increased in both immunized groups. Among the immunized chickens, those in group B exhibited significantly increased titers of specific plasma IgG and intestinal secretory IgA (sIgA) antibodies compared with those in group C, indicating the immunomodulatory effects of the LTB adjuvant. Furthermore, both immunized groups exhibited decreased bacterial loads in their feces and internal organs. These results indicate that parenteral immunization with S. Enteritidis-LTB ghosts can stimulate superior induction of systemic and mucosal immune responses compared to immunization with S. Enteritidis ghosts alone, thus conferring efficient protection against salmonellosis. PMID:24671556

Study of UltraHigh Performance Supercritical Fluid Chromatography to measure free fatty acids with out fatty acid ester preparation.

PubMed

Ashraf-Khorassani, M; Isaac, G; Rainville, P; Fountain, K; Taylor, L T

2015-08-01

Most lipids are best characterized by their fatty acids which may differ in (a) chain length, (b) degree of unsaturation, (c) configuration and position of the double bonds, and (d) the presence of other functionalities. Thus, a fast, simple, and quantitative analytical technique to determine naturally occurring free fatty acids (FFA) in different samples is very important. Just as for saponified acylglycerols, the determination of FFA's has generally been carried out by high resolution gas chromatography (HRGC). The use of an open tubular capillary column coupled with a flame ionization or mass spectrometric detector provides for both high resolution and quantification of FFA's but only after conversion of all free fatty acids to fatty acid methyl esters (FAME) or pentafluorobenzyl esters. Unfortunately, volatilization of labile ester derivatives of mono- and poly-unsaturated FFA's can cause both thermal degradation and isomerization of the fatty acid during HRGC. The employment of a second generation instrument (here referred to as UltraHigh Performance Supercritical Fluid Chromatograph, UHPSFC) with high precision for modified flow and repeated back pressure adjustment in conjunction with sub-2μm various bonded silica particles (coupled with evaporative light scattering, ELSD, and mass spectrometric, MS, detection) for separation and detection of the following mixtures is described: (a) 31 free fatty acids, (b) isomeric FFA's, and (c) lipophilic materials in two real world fish oil samples. Limits of detection for FFA's via UHPSFC/MS and UHPSFC/ELSD versus detection of FAME's via HRGC/MS are quantitatively compared. Copyright © 2015 Elsevier B.V. All rights reserved.

Temporal Changes in Photochemically Labile DOM and Implications for Carbon Budgets in Peatland Aquatic Systems

NASA Astrophysics Data System (ADS)

Pickard, A.

2015-12-01

Aquatic systems in peatland catchments are subject to high loading of dissolved organic matter (DOM) from surrounding terrestrial environments. However the significance of photochemical transformation of DOM in peatland carbon budgets remains poorly constrained. In this study UV irradiation experiments were conducted on water samples collected over one year from two contrasting systems in Scotland: a stream draining a peatland with high levels of DOM and a reservoir draining a peat catchment with low levels of DOM. Further samples were collected from the high DOM system during two storm events. After experimental exposure, optical and chemical analyses were employed to determine photochemical lability of the DOM pool. At both sites irradiation-induced decreases in dissolved organic carbon (DOC) as a percentage of the total carbon pool were greatest in winter, suggesting that DOM was depleted in photo-reactive molecules in summer. Seasonal variability in DOC was high at the stream site and was positively correlated with CO₂ and CO photoproduction (r2 = 0.81 and 0.83, respectively; p<0.05). Lignin phenol analyses indicate considerable contribution of peat to the DOM pool at the stream site, particularly during summer. Whilst DOC concentrations did not vary greatly during storm events, UV-Vis absorbance indicators did, signifying changing DOM source material from activation of different hydrological pathways. The most photo-reactive DOM occurred 5-10 hours after peak discharge, suggesting that storms replenish photochemically labile DOM in headwater streams. Conservative estimates using data from this study suggest that up to 7% of the DOM pool of peatland streams can be lost (primarily as CO₂ and CO) upon exposure to 8 hours of environmentally representative UV irradiation. Further investigation in field campaigns under natural UV exposure are underway to assess the importance of photodegradation of DOM as a loss pathway of carbon based gases from aquatic systems.

Survival of Acetate in Biodegraded Stream Water DOM: New Insights Based on NMR Spectroscopy

NASA Astrophysics Data System (ADS)

Whitty, S.; Waggoner, D. C.; Bowen, J. C.; Cory, R. M.; Kaplan, L.; Hatcher, P.

2017-12-01

DOM is a complex chemical mixture of high- (HMW) and low-molecular-weight (LMW) organic molecules that serve as the primary energy sources for heterotrophic bacteria in freshwater environments. However, there are still large uncertainties on the composition of DOM that is labile and thus rapidly metabolized. The current thinking is that labile DOM is primarily composed of monosaccharides, amino acids, and other LMW organic acids such as formic, acetic, or propionic among others, although some humic substances also are biologically labile. To test the contribution of LMW organic acids to the labile fraction of DOM, freshwater samples were collected from five streams within the Rio Tempisquito watershed in Costa Rica and subjected to differing degrees of biodegradation using a series of plug-flow bioreactors with residence times ranging from 0.5-150 min. Varying the residence times of bioreactors allows for separation and identification of labile from less labile to more recalcitrant DOM. The stream water fed into the bioreactors had DOC concentrations that ranged from 0.7-1.2 ppm C and the GF/F-filtered stream water as well as the bioreactor effluents were analyzed directly without pre-treatment using proton nuclear magnetic resonance spectroscopy (1H NMR). Small molecules dominated the 1H NMR spectra with the greatest changes, as a function of bioreactor residence time, in the carbohydrate, terminal methyl, and long-chain methylene structures. In contrast, acetate remained relatively constant after 150 min of bioreactor residence time, thus raising the question of why this inherently labile volatile fatty acid was not consumed by stream microbes colonizing bioreactors that otherwise metabolized approximately 35% of the total dissolved organic carbon present in the stream water. We suggest that acetate may resist biodegradation because it is complexed strongly with inorganic cations.

The safety and efficacy of salicylic acid chemical peels in darker racial-ethnic groups.

PubMed

Grimes, P E

1999-01-01

There is a dearth of published data regarding chemical peels in darker racial-ethnic groups. The purpose of the present investigation was to assess the clinical efficacy and safety of a new superficial salicylic acid peel in individuals of skin types V and VI. Twenty-five patients were included in this pilot investigation. Nine had acne vulgaris, 5 had post-inflammatory hyperpigmentation, 6 had melasma, and 5 had rough, oily skin with enlarged pores. The patients were pre-treated for 2 weeks with hydroquinone 4% prior to undergoing a series of five salicylic acid chemical peels. The concentrations of salicylic acid were 20% and 30%. The peels were performed at 2 week intervals. RESULTS. Moderate to significant improvement was observed in 88% of the patients. Minimal to mild side effects occurred in 16%. The results of this study suggest that superficial salicylic acid peels are both safe and efficacious for treatment of acne vulgaris, oily skin, textural changes, melasma, and post-inflammatory hyperpigmentation in patients with skin types V and VI.

The effects of n-3 fatty acid deficiency and repletion upon the fatty acid composition and function of the brain and retina.

PubMed

Connor, W E; Neuringer, M

1988-01-01

It is now apparent that both n-6 and n-3 fatty acids are essential for normal development in mammals, and that each has specific functions in the body. N-6 fatty acids are necessary primarily for growth, reproduction, and the maintenance of skin integrity, whereas n-3 fatty acids are involved in the development and function of the retina and cerebral cortex and perhaps other organs such as the testes. Fetal life and infancy are particularly critical for the nervous tissue development. Therefore, with respect to human nutrition, adequate amounts of omega-3 fatty acids should be provided during pregnancy, lactation and infancy, but probably throughout life. We estimate that adequate levels are provided by diets containing 6-8% kcals from linoleic acid and 1% from n-3 fatty acids (alpha-linolenic acid, EPA and DHA), resulting in a ratio of n-6 to n-3 fatty acids of 4:1 to 10:1. The essentiality of n-3 fatty acids resides in their presence as DHA in vital membranes of the photoreceptors of the retina and the synaptosomes and other subcellular membranes of the brain. The replacement of DHA in deficient animals by the n-6 fatty acid, 22:5, results in abnormal functioning of the membranes for reasons as yet to be ascertained. Most significant is the lability of fatty acid composition in the retinal and brain of deficient animals. Dietary fish oil, which contains EPA and DHA, will readily lead to a change in the composition of the membrane of retina and brain, fatty acids, with DHA replacing the n-6 fatty acid, 22:5. The interrelationships between the chemistry of neural and retinal membranes as affected by diet and their biological functioning provides an exciting prospect for future investigations.

Peracetic Acid: A Practical Agent for Sterilizing Heat-Labile Polymeric Tissue-Engineering Scaffolds

PubMed Central

Yoganarasimha, Suyog; Trahan, William R.; Best, Al M.; Bowlin, Gary L.; Kitten, Todd O.; Moon, Peter C.

2014-01-01

Advanced biomaterials and sophisticated processing technologies aim at fabricating tissue-engineering scaffolds that can predictably interact within a biological environment at the cellular level. Sterilization of such scaffolds is at the core of patient safety and is an important regulatory issue that needs to be addressed before clinical translation. In addition, it is crucial that meticulously engineered micro- and nano- structures are preserved after sterilization. Conventional sterilization methods involving heat, steam, and radiation are not compatible with engineered polymeric systems because of scaffold degradation and loss of architecture. Using electrospun scaffolds made from polycaprolactone, a low melting polymer, and employing spores of Bacillus atrophaeus as biological indicators, we compared ethylene oxide, autoclaving and 80% ethanol to a known chemical sterilant, peracetic acid (PAA), for their ability to sterilize as well as their effects on scaffold properties. PAA diluted in 20% ethanol to 1000 ppm or above sterilized electrospun scaffolds in 15 min at room temperature while maintaining nano-architecture and mechanical properties. Scaffolds treated with PAA at 5000 ppm were rendered hydrophilic, with contact angles reduced to 0°. Therefore, PAA can provide economical, rapid, and effective sterilization of heat-sensitive polymeric electrospun scaffolds that are used in tissue engineering. PMID:24341350

Protein methylation in pea chloroplasts. [Pisum sativum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niemi, K.J.; Adler, J.; Selman, B.R.

1990-07-01

The methylation of chloroplast proteins has been investigated by incubating intact pea (Pisum sativum) chloroplasts with ({sup 3}H-methyl)-S-adenosylmethionine. Incubation in the light increases the amount of methylation in both the thylakoid and stromal fractions. Numerous thylakoid proteins serve as substrates for the methyltransfer reactions. Three of these thylakoid proteins are methylated to a significantly greater extent in the light than in the dark. The primary stromal polypeptide methylated is the large subunit of ribulose bisphosphate carboxylase/oxygenase. One other stromal polypeptide is also methylated much more in the light than in the dark. Two distinct types of protein methylation occur. Onemore » methylinkage is stable to basic conditions whereas a second type is base labile. The base-stable linkage is indicative of N-methylation of amino acid residues while base-lability is suggestive of carboxymethylation of amino acid residues. Labeling in the light increases the percentage of methylation that is base labile in the thylakoid fraction while no difference is observed in the amount of base-labile methylations in light-labeled and dark-labeled stromal proteins. Also suggestive of carboxymethylation is the detection of volatile ({sup 3}H)methyl radioactivity which increases during the labeling period and is greater in chloroplasts labeled in the light as opposed to being labeled in the dark; this implies in vivo turnover of the ({sup 3}H)methyl group.« less

The use of amino acid indices for assessing organic matter quality and microbial abundance in deep-sea Antarctic sediments of IODP Expedition 318

USGS Publications Warehouse

Carr, Stephanie A; Mills, Christopher T.; Mandernack, Kevin W

2016-01-01

The Adélie Basin, located offshore of the Wilkes Land margin, experiences unusually high sedimentation rates (~ 2 cm yr− 1) for the Antarctic coast. This study sought to compare depthwise changes in organic matter (OM) quantity and quality with changes in microbial biomass with depth at this high-deposition site and an offshore continental margin site. Sediments from both sites were collected during the International Ocean Drilling (IODP) Program Expedition 318. Viable microbial biomass was estimated from concentrations of bacterial-derived phospholipid fatty acids, while OM quality was assessed using four different amino acid degradation proxies. Concentrations of total hydrolysable amino acids (THAA) measured from the continental margin suggest an oligotrophic environment, with THAA concentrations representing only 2% of total organic carbon with relative proportions of non-protein amino acids β-alanine and γ-aminobutyric acid as high as 40%. In contrast, THAA concentrations from the near-shore Adélie Basin represent 40%–60% of total organic carbon. Concentrations of β-alanine and γ-aminobutyric acid were often below the detection limit and suggest that the OM of the basin as labile. DI values in surface sediments at the Adélie and margin sites were measured to be + 0.78 and − 0.76, reflecting labile and more recalcitrant OM, respectively. Greater DI values in deeper and more anoxic portions of both cores correlated positively with increased relative concentrations of phenylalanine plus tyrosine and may represent a change of redox conditions, rather than OM quality. This suggests that DI values calculated along chemical profiles should be interpreted with caution. THAA concentrations, the percentage of organic carbon (CAA%) and total nitrogen (NAA%) represented by amino acids at both sites demonstrated a significant positive correlation with bacterial abundance estimates. These data suggest that the selective degradation of amino acids, as

AZD-3043: A Novel, Metabolically-Labile Sedative/Hypnotic Agent with Rapid and Predictable Emergence from Hypnosis

PubMed Central

Egan, Talmage D.; Obara, Shinju; Jenkins, Thomas E.; Jaw-Tsai, Sarah S.; Amagasu, Shanti; Cook, Daniel R.; Steffensen, Scott C.; Beattie, David T.

2013-01-01

Background Propofol can be associated with delayed awakening after prolonged infusion. The aim of this study was to characterize the preclinical pharmacology of AZD-3043, a positive allosteric modulator of the γ-aminobutyric acidA (GABAA) receptor containing a metabolically-labile ester moiety. We postulated that its metabolic pathway would result in a short acting clinical profile. Methods The effects of AZD-3043, propofol and propanidid were studied on GABAA receptor-mediated chloride currents in embryonic rat cortical neurons. Radioligand binding studies were also performed. The in vitro stability of AZD-3043 in whole blood and liver microsomes was evaluated. The duration of the loss of righting reflex and effects on the electroencephalograph evoked by bolus or infusion intravenous (IV) administration were assessed in rats. A mixed-effects kinetic-dynamic model using minipigs permitted exploration of the clinical pharmacology of AZD-3043. Results AZD-3043 potentiated GABAA receptor-mediated chloride currents and inhibited [35S]tert-butylbicyclophosphorothionate binding to GABAA receptors. AZD-3043 was rapidly hydrolyzed in liver microsomes from humans and animals. AZD-3043 produced hypnosis and electroencephalograph depression in rats. Compared to propofol, AZD-3043 was shorter acting in rats and pigs. Computer simulation using the porcine kinetic-dynamic model demonstrated that AZD-3043 has very short 50 and 80% decrement times independent of infusion duration. Conclusions AZD-3043 is a positive allosteric modulator of the GABAA receptor in vitro and a sedative/hypnotic agent in vivo. The esterase dependent metabolic pathway results in rapid clearance and short duration of action even for long infusions. AZD-3043 may have clinical potential as a sedative/hypnotic agent with rapid and predictable recovery. PMID:22531340

Expression and immunogenicity of enterotoxigenic Escherichia coli heat-labile toxin B subunit in transgenic rice callus.

PubMed

Kim, Tae-Geum; Kim, Bang-Geul; Kim, Mi-Young; Choi, Jae-Kwon; Jung, Eun-Sun; Yang, Moon-Sik

2010-01-01

Enterotoxigenic Escherichia coli is one of the leading causes of diarrhea in developing countries, and the disease may be fatal in the absence of treatment. Enterotoxigenic E. coli heat-labile toxin B subunit (LTB) can be used as an adjuvant, as a carrier of fused antigens, or as an antigen itself. The synthetic LTB (sLTB) gene, optimized for plant codon usage, has been introduced into rice cells by particle bombardment-mediated transformation. The integration and expression of the sLTB gene were observed via genomic DNA PCR and western blot analysis, respectively. The binding activity of LTB protein expressed in transgenic rice callus to G(M1)-ganglioside, a receptor for biologically active LTB, was confirmed by G(M1)-ELISA. Oral inoculation of mice with lyophilized transgenic rice calli containing LTB generated significant IgG antibody titers against bacterial LTB, and the sera of immunized mice inhibited the binding of bacterial LTB to G(M1)-ganglioside. Mice orally immunized with non-transgenic rice calli failed to generate detectable anti-LTB IgG antibody titers. Mice immunized with plant-produced LTB generated higher IgG1 antibody titers than IgG2a, indicating a Th2-type immune response. Mice orally immunized with lyophilized transgenic rice calli containing LTB elicited higher fecal IgA antibody titers than mice immunized with non-transgenic rice calli. These experimental results demonstrate that LTB proteins produced in transgenic rice callus and given to mice by oral administration induce humoral and secreted antibody immune responses. We suggest that transgenic rice callus may be suitable as a plant-based edible vaccine to provide effective protection against enterotoxigenic E. coli heat-labile toxin.

Stress-induced resistance to the fear memory labilization/reconsolidation process. Involvement of the basolateral amygdala complex.

PubMed

Espejo, Pablo Javier; Ortiz, Vanesa; Martijena, Irene Delia; Molina, Victor Alejandro

2016-10-01

Consolidated memories can enter into a labile state after reactivation followed by a restabilization process defined as reconsolidation. This process can be interfered with Midazolam (MDZ), a positive allosteric modulator of the GABA-A receptor. The present study has evaluated the influence of prior stress on MDZ's interfering effect. We also assessed the influence of both systemic and intra-basolateral amygdala (BLA) infusion of d-cycloserine (DCS), a partial agonist of the NMDA receptors, on the MDZ effect in previously stressed rats. Furthermore, we analyzed the effect of stress on the expression of Zif-268 and the GluN2B sites, two molecular markers of the labilization/reconsolidation process, following reactivation. The results revealed that prior stress resulted into a memory trace that was insensitive to the MDZ impairing effect. Both systemic and intra-BLA DCS administration previous to reactivation restored MDZ's disruptive effect on memory reconsolidation in stressed animals. Further, reactivation enhanced Zif-268 expression in the BLA in control unstressed rats, whereas no elevation was observed in stressed animals. In agreement with the behavioral findings, DCS restored the increased level of Zif-268 expression in the BLA in stressed animals. Moreover, memory reactivation in unstressed animals elevated GluN2B expression in the BLA, thus suggesting that this effect is involved in memory destabilization, whereas stressed animals did not reveal any changes. These findings are consistent with resistance to the MDZ effect in these rats, indicating that stress exposure prevents the onset of destabilization following reactivation. In summary, prior stress limited both the occurrence of the reactivation-induced destabilization and restabilization. Copyright © 2016 Elsevier Ltd. All rights reserved.

THE SMALL ACID SOLUBLE PROTEINS (SASP α and SASP β) OF BACILLUS WEIHENSTEPHANENSIS AND B. MYCOIDES GROUP 2 ARE THE MOST DISTINCT AMONG THE B. CEREUS GROUP

PubMed Central

Callahan, Courtney; Fox, Karen; Fox, Alvin

2009-01-01

The Bacillus cereus group includes Bacillus anthracis, Bacillus cereus, Bacillus thuringiensis, Bacillus mycoides and Bacillus weihenstephanensis. The small acid-soluble spore protein (SASP) β has been previously demonstrated to be among the biomarkers differentiating B. anthracis and B. cereus; SASP β of B. cereus most commonly exhibits one or two amino acid substitutions when compared to B. anthracis. SASP α is conserved in sequence among these two species. Neither SASP α nor β for B. thuringiensis, B. mycoides and B. weihenstephanensis have been previously characterized as taxonomic discriminators. In the current work molecular weight (MW) variation of these SASPs were determined by matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS) for representative strains of the 5 species within the B. cereus group. The measured MWs also correlate with calculated MWs of translated amino acid sequences generated from whole genome sequencing projects. SASP α and β demonstrated consistent MW among B. cereus, B. thuringiensis, and B. mycoides strains (group 1). However B. mycoides (group 2) and B. weihenstephanensis SASP α and β were quite distinct making them unique among the B. cereus group. Limited sequence changes were observed in SASP α (at most 3 substitutions and 2 deletions) indicating it is a more conserved protein than SASP β (up to 6 substitutions and a deletion). Another even more conserved SASP, SASP α-β type, was described here for the first time. PMID:19616612

Treatment of PCR products with exonuclease I and heat-labile alkaline phosphatase improves the visibility of combined bisulfite restriction analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watanabe, Kousuke; Emoto, Noriko; Sunohara, Mitsuhiro

2010-08-27

Research highlights: {yields} Incubating PCR products at a high temperature causes smears in gel electrophoresis. {yields} Smears interfere with the interpretation of methylation analysis using COBRA. {yields} Treatment with exonuclease I and heat-labile alkaline phosphatase eliminates smears. {yields} The elimination of smears improves the visibility of COBRA. -- Abstract: DNA methylation plays a vital role in the regulation of gene expression. Abnormal promoter hypermethylation is an important mechanism of inactivating tumor suppressor genes in human cancers. Combined bisulfite restriction analysis (COBRA) is a widely used method for identifying the DNA methylation of specific CpG sites. Here, we report that exonucleasemore » I and heat-labile alkaline phosphatase can be used for PCR purification for COBRA, improving the visibility of gel electrophoresis after restriction digestion. This improvement is observed when restriction digestion is performed at a high temperature, such as 60 {sup o}C or 65 {sup o}C, with BstUI and TaqI, respectively. This simple method can be applied instead of DNA purification using spin columns or phenol/chloroform extraction. It can also be applied to other situations when PCR products are digested by thermophile-derived restriction enzymes, such as PCR restriction fragment length polymorphism (RFLP) analysis.« less

Coupling in the absence of tertiary amines.

PubMed

Bodanszky, M; Bednarek, M A; Bodanszky, A

1982-10-01

In order to avoid base catalyzed side reactions during coupling, attempts were made to render superfluous the addition of tertiary amines to the reaction mixture. Weak acids were applied for the removal of acid labile protecting groups. Acetic acid and other carboxylic acids were considered unsuitable for this purpose coupling step. Pentachlorophenol and 2,4-dinitrophenol cleaved the Bpoc, Nps and Trt groups but more practical rates were reached with solutions of 1-hydroxybenzotriazole (HOBt) in trifluoroethanol, in acetic acid, or in a mixture of phenol and p-cresol. In addition to acidolysis, HOBt salts of amino components could also be obtained through hydrogenolysis of the Z group or thiolysis of the Nps group in the presence of HOBt, or by the displacement of acetic acid from acetate salts with HOBt. Acylation of HOBt salts of amino components with symmetrical or mixed anhydrides or with active esters did not require the addition of tertiary amine.

Stereoselective Syntheses of Soman Analog

DTIC Science & Technology

1993-04-28

only one pseudorotatomer cycle exists. Surprisingly. la-f are hydrolytically stable in the absence of acid ; phosphorane lb, for example, remained...unchanged in CDCl3 for at least 2 weeks even in the presence of water or 0.1 N NaOH at room temperature. However, la-f are extremely labile to aqueous acids ...1 and 2 are hydrolytically stable in neutral and basic conditions, but extremely labile to aqueous acids : they remained unchanged for at least 3 days

Characterizing The Microbial Lability And Isotopic (14C, 13C) Signatures Of Marine Organic Matter With A Novel Culture Vessel System

NASA Astrophysics Data System (ADS)

Beaupre, S. R.; Mahmoudi, N.; Pearson, A.

2016-02-01

The rate at which non-living organic matter is respired in the ocean is an unconstrained and important property of the marine carbon cycle. Studies of inherent mineralization rates are complicated by the fact that marine organic matter is a mixture of compounds that vary in reactivity and concentration. While natural radiocarbon ages (14C, half-life = 5730 yr) have served as proxies for lability, they have not been used extensively to characterize that fraction of marine organic matter that is biologically accessible. To address this problem, we developed a novel batch culture system to monitor the time-dependent production rates and isotopic signatures of CO2 released during microbial degradation of natural organic matter. The system simulated a nepheloid layer by maintaining a slurry of decarbonated sediment and minimal media (M9) in a custom 2-liter culture vessel. The natural microbial community was allowed to develop within the sediment, and respired CO2 was continuously sparged from the medium with helium and oxygen, quantified in real time with an infrared gas analyzer, and isolated as a series of contiguous fractions for subsequent isotopic (∆14C, d13C) characterization. Control experiments indicated the accumulation of just 4.5 mg of background carbon per hour of continuous gas flow, which constituted ≤ 10 % of the respired carbon mass in each fraction. Since ∆14C values are conserved during molecular transformations, this low-blank system enables the detection of subtle shifts in the "age" of organic matter respired during the course of a culture experiment. Analyses of sediments from Falmouth, MA revealed both a variable CO2 production rate and an increase in post-bomb ∆14C values during a 10-day incubation. This suggests that the microbial lability of organic matter at this site decreased non-linearly with apparent 14C age, and that the least labile fraction observed was not more than 50 years old. These results underscore the complex

Exploring the in vitro formation of trimethylarsine sulfide from dimethylthioarsinic acid in anaerobic microflora of mouse cecum using HPLC-ICP-MS and HPLC-ESI-MS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kubachka, Kevin M.; Kohan, Michael C.; Herbin-Davis, Karen

Although metabolism of arsenicals to form methylated oxoarsenical species has been extensively studied, less is known about the formation of thiolated arsenical species that have recently been detected as urinary metabolites. Indeed, their presence suggests that the metabolism of ingested arsenic is more complex than previously thought. Recent reports have shown that thiolated arsenicals can be produced by the anaerobic microflora of the mouse cecum, suggesting that metabolism prior to systemic absorption may be a significant determinant of the pattern and extent of exposure to various arsenic-containing species. Here, we examined the metabolism of {sup 34}S labeled dimethylthioarsinic acid ({supmore » 34}S-DMTA{sup V}) by the anaerobic microflora of the mouse cecum using HPLC-ICP-MS and HPLC-ESI-MS/MS to monitor for the presence of various oxo- and thioarsenicals. The use of isotopically enriched {sup 34}S-DMTA{sup V} made it possible to differentiate among potential metabolic pathways for production of the trimethylarsine sulfide (TMAS{sup V}). Upon in vitro incubation in an assay containing anaerobic microflora of mouse cecum, {sup 34}S-DMTA{sup V} underwent several transformations. Labile {sup 34}S was exchanged with more abundant {sup 32}S to produce {sup 32}S-DMTA{sup V}, a thiol group was added to yield DMDTA{sup V}, and a methyl group was added to yield {sup 34}S-TMAS{sup V}. Because incubation of {sup 34}S-DMTA{sup V} resulted in the formation of {sup 34}S-TMAS{sup V}, the pathway for its formation must preserve the arsenic-sulfur bond. The alternative metabolic pathway postulated for formation of TMAS{sup V} from dimethylarsinic acid (DMA{sup V}) would proceed via a dimethylarsinous acid (DMA{sup III}) intermediate and would necessitate the loss of {sup 34}S label. Structural confirmation of the metabolic product was achieved using HPLC-ESI-MS/MS. The data presented support the direct methylation of DMTA{sup V} to TMAS{sup V}. Additionally, the

In vitro incorporation of nonnatural amino acids into protein using tRNACys-derived opal, ochre, and amber suppressor tRNAs

PubMed Central

Gubbens, Jacob; Kim, Soo Jung; Yang, Zhongying; Johnson, Arthur E.; Skach, William R.

2010-01-01

Amber suppressor tRNAs are widely used to incorporate nonnatural amino acids into proteins to serve as probes of structure, environment, and function. The utility of this approach would be greatly enhanced if multiple probes could be simultaneously incorporated at different locations in the same protein without other modifications. Toward this end, we have developed amber, opal, and ochre suppressor tRNAs derived from Escherichia coli, and yeast tRNACys that incorporate a chemically modified cysteine residue with high selectivity at the cognate UAG, UGA, and UAA stop codons in an in vitro translation system. These synthetic tRNAs were aminoacylated in vitro, and the labile aminoacyl bond was stabilized by covalently attaching a fluorescent dye to the cysteine sulfhydryl group. Readthrough efficiency (amber > opal > ochre) was substantially improved by eRF1/eRF3 inhibition with an RNA aptamer, thus overcoming an intrinsic hierarchy in stop codon selection that limits UGA and UAA termination suppression in higher eukaryotic translation systems. This approach now allows concurrent incorporation of two different modified amino acids at amber and opal codons with a combined apparent readthrough efficiency of up to 25% when compared with the parent protein lacking a stop codon. As such, it significantly expands the possibilities for incorporating nonnative amino acids for protein structure/function studies. PMID:20581130

Microbial formation of labile organic carbon in Antarctic glacial environments

USGS Publications Warehouse

Smith, H.J.; Foster, R.; McKnight, D.M.; Lisle, John T.; Littmann, S.; Kuypers, M.M.M.; Foreman, C.M.

2017-01-01

Roughly six petagrams of organic carbon are stored within ice worldwide. This organic carbon is thought to be of old age and highly bioavailable. Along with storage of ancient and new atmospherically deposited organic carbon, microorganisms may contribute substantially to the glacial organic carbon pool. Models of glacial microbial carbon cycling vary from net respiration to net carbon fixation. Supraglacial streams have not been considered in models although they are amongst the largest ecosystems on most glaciers and are inhabited by diverse microbial communities. Here we investigate the biogeochemical sequence of organic carbon production and uptake in an Antarctic supraglacial stream in the McMurdo Dry Valleys using nanometre-scale secondary ion mass spectrometry, fluorescence spectroscopy, stable isotope analysis and incubation experiments. We find that heterotrophic production relies on highly labile organic carbon freshly derived from photosynthetic bacteria rather than legacy organic carbon. Exudates from primary production were utilized by heterotrophs within 24 h, and supported bacterial growth demands. The tight coupling of microbially released organic carbon and rapid uptake by heterotrophs suggests a dynamic local carbon cycle. Moreover, as temperatures increase there is the potential for positive feedback between glacial melt and microbial transformations of organic carbon.

Influence of the aqueous film coating process on the properties and stability of tablets containing a moisture-labile drug.

PubMed

Ruotsalainen, Mirja; Heinämäki, Jyrki; Taipale, Krista; Yliruusi, Jouko

2003-01-01

The effects of an aqueous film coating process on the morphology and storage stability of hydroxypropyl methylcellulose-coated tablets containing a moisture-labile model drug (acetylsalicylic acid, ASA) were evaluated using an instrumented side-vented tablet pan coater. Coating parameters studied were inlet air absolute humidity 5 g/m3 and 12 g/m3, spraying air pressure 100 kPa and 500 kPa, pan air temperature 35 degrees C and 55 degrees C, and coating solution flow rate 2.2 g/min and 7.8 g/min. The surface roughness of the coatings was measured with a laser profilometer and the chemical hydrolysis of the model drug ASA with an UV-spectrophotometer. The film-coated tablets were stored at 25 degrees C/60% RH and 40 degrees C/75% RH for three months. The high absolute humidity of the inlet air increased the residual water content and surface roughness of the coated tablets. Using a lower coating solution flow rate, higher spraying air pressure and pan temperature the coatings were smooth and homogeneous. In both ambient and accelerated storage conditions, the roughness of the coatings and the hydrolysis of ASA increased, but this was independent of the film coating process. Uniform and smooth hydroxypropyl methylcellulose coatings can be achieved by improved control of process parameters related to the application of the coating solution and water evaporation of the tablet surface.

Analytical methods for determination of free metal ion concentration, labile species fraction and metal complexation capacity of environmental waters: a review.

PubMed

Pesavento, Maria; Alberti, Giancarla; Biesuz, Raffaela

2009-01-12

Different experimental approaches have been suggested in the last few decades to determine metal species in complex matrices of unknown composition as environmental waters. The methods are mainly focused on the determination of single species or groups of species. The more recent developments in trace elements speciation are reviewed focusing on methods for labile and free metal determination. Electrochemical procedures with low detection limit as anodic stripping voltammetry (ASV) and the competing ligand exchange with adsorption cathodic stripping voltammetry (CLE-AdCSV) have been widely employed in metal distribution studies in natural waters. Other electrochemical methods such as stripping chronopotentiometry and AGNES seem to be promising to evaluate the free metal concentration at the low levels of environmental samples. Separation techniques based on ion exchange (IE) and complexing resins (CR), and micro separation methods as the Donnan membrane technique (DMT), diffusive gradients in thin-film gels (DGT) and the permeation liquid membrane (PLM), are among the non-electrochemical methods largely used in this field and reviewed in the text. Under appropriate conditions such techniques make possible the evaluation of free metal ion concentration.

Acetylated sialic acid residues and blood group antigens localise within the epithelium in microvillous atrophy indicating internal accumulation of the glycocalyx

PubMed Central

Phillips, A D; Brown, A; Hicks, S; Schüller, S; Murch, S H; Walker-Smith, J A; Swallow, D M

2004-01-01

Background: Microvillous atrophy, a disorder of intractable diarrhoea in infancy, is characterised by the intestinal epithelial cell abnormalities of abnormal accumulation of periodic acid-Schiff (PAS) positive secretory granules within the apical cytoplasm and the presence of microvillous inclusions. The identity of the PAS positive material is not known, and the aim of this paper was to further investigate its composition. Methods: Formaldehyde fixed sections were stained with alcian blue/PAS to identify the acidic or neutral nature of the material, phenylhydrazine blocking was employed to stain specifically for sialic acid, and saponification determined the presence of sialic acid acetylation. The specificity of sialic acid staining was tested by digestion with mild sulphuric acid. Expression of blood group related antigens was tested immunochemically. Results: Alcian blue/PAS staining identified a closely apposed layer of acidic material on the otherwise neutral (PAS positive) brush border in controls. In microvillous atrophy, a triple layer was seen with an outer acidic layer, an unstained brush border region, and accumulation within the epithelium of a neutral glycosubstance that contained acetylated sialic acid. Blood group antigens were detected on the brush border, in mucus, and within goblet cells in controls. In microvillous atrophy they were additionally expressed within the apical cytoplasm of epithelial cells mirroring the PAS abnormality. Immuno electron microscopy localised expression to secretory granules. Conclusions: A neutral, blood group antigen positive, glycosubstance that contains acetylated sialic acid accumulates in the epithelium in microvillous atrophy. Previous studies have demonstrated that the direct and indirect constitutive pathways are intact in this disorder and it is speculated that the abnormal staining pattern reflects accumulation of glycocalyx related material. PMID:15542511

Effect of Strong Acid Functional Groups on Electrode Rise Potential in Capacitive Mixing by Double Layer Expansion

DOE PAGES

Hatzell, Marta C.; Raju, Muralikrishna; Watson, Valerie J.; ...

2014-11-03

We report that the amount of salinity-gradient energy that can be obtained through capacitive mixing based on double layer expansion depends on the extent the electric double layer (EDL) is altered in a low salt concentration (LC) electrolyte (e.g., river water). We show that the electrode-rise potential, which is a measure of the EDL perturbation process, was significantly (P = 10 –5) correlated to the concentration of strong acid surface functional groups using five types of activated carbon. Electrodes with the lowest concentration of strong acids (0.05 mmol g –1) had a positive rise potential of 59 ± 4 mVmore » in the LC solution, whereas the carbon with the highest concentration (0.36 mmol g –1) had a negative rise potential (₋31 ± 5 mV). Chemical oxidation of a carbon (YP50) using nitric acid decreased the electrode rise potential from 46 ± 2 mV (unaltered) to ₋6 ± 0.5 mV (oxidized), producing a whole cell potential (53 ± 1.7 mV) that was 4.4 times larger than that obtained with identical electrode materials (from 12 ± 1 mV). Changes in the EDL were linked to the behavior of specific ions in a LC solution using molecular dynamics and metadynamics simulations. The EDL expanded in the LC solution when a carbon surface (pristine graphene) lacked strong acid functional groups, producing a positive-rise potential at the electrode. In contrast, the EDL was compressed for an oxidized surface (graphene oxide), producing a negative-rise electrode potential. In conclusion, these results established the linkage between rise potentials and specific surface functional groups (strong acids) and demonstrated on a molecular scale changes in the EDL using oxidized or pristine carbons.« less

Amide Neighbouring-Group Effects in Peptides: Phenylalanine as Relay Amino Acid in Long-Distance Electron Transfer.

PubMed

Nathanael, Joses G; Gamon, Luke F; Cordes, Meike; Rablen, Paul R; Bally, Thomas; Fromm, Katharina M; Giese, Bernd; Wille, Uta

2018-05-04

In nature, proteins serve as media for long-distance electron transfer (ET) to carry out redox reactions in distant compartments. This ET occurs either by a single-step superexchange or through a multi-step charge hopping process, which uses side chains of amino acids as stepping stones. In this study we demonstrate that Phe can act as a relay amino acid for long-distance electron hole transfer through peptides. The considerably increased susceptibility of the aromatic ring to oxidation is caused by the lone pairs of neighbouring amide carbonyl groups, which stabilise the Phe radical cation. This neighbouring-amide-group effect helps improve understanding of the mechanism of extracellular electron transfer through conductive protein filaments (pili) of anaerobic bacteria during mineral respiration. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Assessing the concentration, speciation, and toxicity of dissolved metals during mixing of acid-mine drainage and ambient river water downstream of the Elizabeth Copper Mine, Vermont, USA

USGS Publications Warehouse

Balistrieri, L.S.; Seal, R.R.; Piatak, N.M.; Paul, B.

2007-01-01

The authors determine the composition of a river that is impacted by acid-mine drainage, evaluate dominant physical and geochemical processes controlling the composition, and assess dissolved metal speciation and toxicity using a combination of laboratory, field and modeling studies. Values of pH increase from 3.3 to 7.6 and the sum of dissolved base metal (Cd + Co + Cu + Ni + Pb + Zn) concentrations decreases from 6270 to 100 ??g/L in the dynamic mixing and reaction zone that is downstream of the river's confluence with acid-mine drainage. Mixing diagrams and PHREEQC calculations indicate that mixing and dilution affect the concentrations of all dissolved elements in the reach, and are the dominant processes controlling dissolved Ca, K, Li, Mn and SO4 concentrations. Additionally, dissolved Al and Fe concentrations decrease due to mineral precipitation (gibbsite, schwertmannite and ferrihydrite), whereas dissolved concentrations of Cd, Co, Cu, Ni, Pb and Zn decrease due to adsorption onto newly formed Fe precipitates. The uptake of dissolved metals by aquatic organisms is dependent on the aqueous speciation of the metals and kinetics of complexation reactions between metals, ligands and solid surfaces. Dissolved speciation of Cd, Cu, Ni and Zn in the mixing and reaction zone is assessed using the diffusive gradients in thin films (DGT) technique and results of speciation calculations using the Biotic Ligand Model (BLM). Data from open and restricted pore DGT units indicate that almost all dissolved metal species are inorganic and that aqueous labile or DGT available metal concentrations are generally equal to total dissolved concentrations in the mixing zone. Exceptions occur when labile metal concentrations are underestimated due to competition between H+ and metal ions for Chelex-100 binding sites in the DGT units at low pH values. Calculations using the BLM indicate that dissolved Cd and Zn species in the mixing and reaction zone are predominantly inorganic

Thermally labile components of aqueous humor potently induce osteogenic potential in adipose-derived mesenchymal stem cells

PubMed Central

Morgan, Joshua T.; Kwon, Heung Sun; Wood, Joshua A.; Borjesson, Dori L.; Tomarev, Stanislav I.; Murphy, Christopher J.; Russell, Paul

2015-01-01

Adipose-derived mesenchymal stem cells (ASCs) hold promise for use in cell-based therapies. Their intrinsic anti-inflammatory properties are potentially useful for treatments of inflammatory conditions such as uveitis, while their ability to differentiate along multiple cell lineages suggests use in regenerating damaged or degenerated tissue. However, how ASCs will respond to the intraocular environment is poorly studied. We have recently reported that aqueous humor (AH), the fluid that nourishes the anterior segment of the eye, potently increases alkaline phosphatase (ALP) activity of ASCs, indicating osteogenic differentiation. Here, we expand on our previous findings to better define the nature of this response. To this end, we cultured ASCs in the presence of 0, 5, 10, and 20% AH and assayed them for ALP activity. We found ALP activity correlates with increasing AH concentrations from 5 to 20%, and that longer treatments result in increased ALP activity. By using serum free media and pretreating AH with dextran-coated charcoal, we found that serum and charcoal-adsorbable AH components augment but are not required for this response. Further, by heat-treating the AH, we established that thermally labile components are required for the osteogenic response. Finally, we showed myocilin, a protein present in AH, could induce ALP activity in ASCs. However, this was to a lesser extent than untreated 5% AH, and myocilin could only partially rescue the effect after heat treatment, documenting there were additional thermally labile constituents of AH involved in the osteogenic response. Our work adds to the understanding of the induction of ALP in ASCs following exposure to AH, providing important insight in how ASCs will be influenced by the ocular environment. In conclusion, increased osteogenic potential upon exposure to AH represents a potential challenge to developing ASC cell-based therapies directed at the eye. PMID:25720657

Equilibrium adsorption of caffeic, chlorogenic and rosmarinic acids on cationic cross-linked starch with quaternary ammonium groups.

PubMed

Simanaviciute, Deimante; Klimaviciute, Rima; Rutkaite, Ramune

2017-02-01

In the present study, the equilibrium adsorption of caffeic acid (CA) and its derivatives, namely, chlorogenic (CGA) and rosmarinic (RA) acids on cationic cross-linked starch (CCS) with degree of substitution of quaternary ammonium groups of 0.42 have been investigated in relation to the structure and acidity of phenolic acids. The Langmuir, Freundlich and Dubinin-Radushkevich adsorption models have been used to describe the equilibrium adsorption of CA, CGA and RA from their initial solutions and solutions having the equimolar amount of NaOH at different temperatures. In the case of adsorption from the initial solutions of acids the values of adsorption parameters were closely related to the dissociation constants of investigated acids. According to the increasing effectiveness of adsorption, phenolic acids could be arranged in the following order: CAacids solutions changed their sorption properties which became mostly related to the acids structure. Copyright © 2016 Elsevier B.V. All rights reserved.

THz and mid-IR spectroscopy of interstellar ice analogs: methyl and carboxylic acid groups.

PubMed

Ioppolo, S; McGuire, B A; Allodi, M A; Blake, G A

2014-01-01

A fundamental problem in astrochemistry concerns the synthesis and survival of complex organic molecules (COMs) throughout the process of star and planet formation. While it is generally accepted that most complex molecules and prebiotic species form in the solid phase on icy grain particles, a complete understanding of the formation pathways is still largely lacking. To take full advantage of the enormous number of available THz observations (e.g., Herschel Space Observatory, SOFIA, and ALMA), laboratory analogs must be studied systematically. Here, we present the THz (0.3-7.5 THz; 10-250 cm(-1)) and mid-IR (400-4000 cm(-1)) spectra of astrophysically-relevant species that share the same functional groups, including formic acid (HCOOH) and acetic acid (CH3COOH), and acetaldehyde (CH3CHO) and acetone ((CH3)2CO), compared to more abundant interstellar molecules such as water (H2O), methanol (CH3OH), and carbon monoxide (CO). A suite of pure and mixed binary ices are discussed. The effects on the spectra due to the composition and the structure of the ice at different temperatures are shown. Our results demonstrate that THz spectra are sensitive to reversible and irreversible transformations within the ice caused by thermal processing, suggesting that THz spectra can be used to study the composition, structure, and thermal history of interstellar ices. Moreover, the THz spectrum of an individual species depends on the functional group(s) within that molecule. Thus, future THz studies of different functional groups will help in characterizing the chemistry and physics of the interstellar medium (ISM).

Eco-friendly combination of the immobilized PGA enzyme and the S-Phacm protecting group for the synthesis of Cys-containing peptides.

PubMed

Góngora-Benítez, Miriam; Basso, Alessandra; Bruckdorfer, Thomas; Royo, Miriam; Tulla-Puche, Judit; Albericio, Fernando

2012-12-07

Enzyme-labile protecting groups have emerged as a green alternative to conventional protecting groups. These groups introduce a further orthogonal dimension and eco-friendliness into protection schemes for the synthesis of complex polyfunctional organic molecules. S-Phacm, a Cys-protecting group, can be easily removed by the action of a covalently immobilized PGA enzyme under very mild conditions. Herein, the versatility and reliability of an eco-friendly combination of the immobilized PGA enzyme and the S-Phacm protecting group has been evaluated for the synthesis of diverse Cys-containing peptides. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Argon direct analysis in real time mass spectrometry in conjunction with makeup solvents: a method for analysis of labile compounds.

PubMed

Yang, Hongmei; Wan, Debin; Song, Fengrui; Liu, Zhiqiang; Liu, Shuying

2013-02-05

Helium direct analysis in real time (He-DART) mass spectrometry (MS) analysis of labile compounds usually tends to be challenging because of the occurrence of prominent fragmentation, which obscures the assigning of an ion to an independent species or merely a fragment in a mixture. In the present work, argon DART (Ar-DART) MS in conjunction with makeup solvents has been demonstrated to analyze a variety of labile compounds including nucleosides, alkaloids, glucose, and other small molecules. The results presented here confirm that Ar-DART can generate significantly less energetic ions than conventional He-DART and is able to produce the intact molecular ions with little or no fragmentation in both positive and negative ion modes. Adding a makeup solvent (absolute ethyl alcohol, methanol, fluorobenzene, or acetone) to the argon gas stream at the exit of the DART ion source can result in 1-2 orders of magnitude increase in detection signals. The sensitivity attainable by Ar-DART was found to be comparable to that by He-DART. The investigation of influence of solvents improves our understanding of the fundamental desorption and ionization processes in DART. The practical application of this rapid and high throughput method is demonstrated by the successful analysis of a natural product (Crude Kusnezoff Monkshood) extract, demonstrating the great potential in mixture research.

Determination of the total cadmium, copper, lead and zinc concentrations and their labile species fraction in apple beverages by flow-through anodic stripping chronopotentiometry.

PubMed

Jedryczko, Dominika; Pohl, Paweł; Welna, Maja

2017-06-15

An analytical procedure for operationally defined speciation of Cd, Cu, Pb and Zn in apple beverages by anodic stripping chronopotentiometry (ASCP) is presented. Optimal measurement conditions were set down to reliably determine the fraction of the labile metals species. The mean total concentrations of Cu, Pb and Zn were 69±20, 7.3±3.3, and 129±59μgL -1 in apple juices, and 18±3, 4.2±0.1, 53±5μgL -1 in apple drinks, respectively. The contributions of the fraction of the ASCP-labile species varied from 43 to 63% (Cu), from 32 to 42% (Pb) and from 38 to 58% (Zn). The Cd content in all analyzed samples was below 0.02μgL -1 . The detection limits (DLs) achieved for Cu, Pb and Zn were 0.04μgL -1 (Cu), 0.02μgL -1 (Pb), and 0.10μgL -1 (Zn). Copyright © 2016 Elsevier Ltd. All rights reserved.

Spectroscopic and first principles investigation on 4-[(4-pyridinylmethylene)amino]-benzoic acid bearing pyridyl and carboxyl anchoring groups

NASA Astrophysics Data System (ADS)

Zhang, Lei; Wang, Qiaoyi

2018-03-01

We report a combined experimental and computational investigation on the structure and photophysics of 4-[(4-pyridinylmethylene)amino]-benzoic acid, a functional molecule bearing two anchoring groups for attachment onto a TiO2 surface and perovskite surface, for potential solar cell application. This molecule possesses interesting adsorption properties in perovskite solar cell because the pyridyl group serves as the Lewis base and targets Lewis acidic sites in the perovskite surface, while the carboxyl group targets TiO2 surface, improving the coupling between the perovskite surface and the TiO2 surface. The electronic structures of the molecule and its photochemistry are revealed by the UV-vis absorption spectra and the fluorescence spectra under visible light irradiation, which are combined with density functional theory (DFT) and time-dependent density functional theory (TDDFT) analysis. Considering the bi-anchoring groups and the conjugated π system embedded in the molecule, we anticipate it can molecular engineer the TiO2/perovskite interface in perovskite solar cell.

Speciation and Lability of Ag-, AgCl- and Ag2S-Nanoparticles in Soil Determined by X-ray Absorption Spectroscopy and Diffusive Gradients in Thin Films

EPA Science Inventory

Long-term speciation and lability of silver (Ag-), silver chloride (AgCl-) and silver sulfide nanoparticles (Ag₂S-NPs) in soil were studied by X-ray absorption spectroscopy (XAS), and newly developed "nano" Diffusive Gradients in Thin Films (DGT) devices. These nano-D...

Metabolism of vertebrate amino sugars with N-glycolyl groups: mechanisms underlying gastrointestinal incorporation of the non-human sialic acid xeno-autoantigen N-glycolylneuraminic acid.

PubMed

Banda, Kalyan; Gregg, Christopher J; Chow, Renee; Varki, Nissi M; Varki, Ajit

2012-08-17

Although N-acetyl groups are common in nature, N-glycolyl groups are rare. Mammals express two major sialic acids, N-acetylneuraminic acid and N-glycolylneuraminic acid (Neu5Gc). Although humans cannot produce Neu5Gc, it is detected in the epithelial lining of hollow organs, endothelial lining of the vasculature, fetal tissues, and carcinomas. This unexpected expression is hypothesized to result via metabolic incorporation of Neu5Gc from mammalian foods. This accumulation has relevance for diseases associated with such nutrients, via interaction with Neu5Gc-specific antibodies. Little is known about how ingested sialic acids in general and Neu5Gc in particular are metabolized in the gastrointestinal tract. We studied the gastrointestinal and systemic fate of Neu5Gc-containing glycoproteins (Neu5Gc-glycoproteins) or free Neu5Gc in the Neu5Gc-free Cmah(-/-) mouse model. Ingested free Neu5Gc showed rapid absorption into the circulation and urinary excretion. In contrast, ingestion of Neu5Gc-glycoproteins led to Neu5Gc incorporation into the small intestinal wall, appearance in circulation at a steady-state level for several hours, and metabolic incorporation into multiple peripheral tissue glycoproteins and glycolipids, thus conclusively proving that Neu5Gc can be metabolically incorporated from food. Feeding Neu5Gc-glycoproteins but not free Neu5Gc mimics the human condition, causing tissue incorporation into human-like sites in Cmah(-/-) fetal and adult tissues, as well as developing tumors. Thus, glycoproteins containing glycosidically linked Neu5Gc are the likely dietary source for human tissue accumulation, and not the free monosaccharide. This human-like model can be used to elucidate specific mechanisms of Neu5Gc delivery from the gut to tissues, as well as general mechanisms of metabolism of ingested sialic acids.

ON THE NATURE OF THE HEAT-LABILE SUBSTANCE ("V") REQUIRED FOR THE GROWTH OF THE BACILLUS OF PFEIFFER

PubMed Central

Thjötta, Th.

1924-01-01

It has been shown in several experiments that the heat-labile, growth-promoting factor "V" found in the blood of animals does not diminish or disappear when the animals are kept on vitamine B-free diet. The titer of the "V" substance present in the blood of normal animals is undiminished in animals showing severe signs of polyneuritis even to the time of their death. The antipolyneuritic factor of vegetable food, designated as vitamine B, is found to be considerably more heat-stable than is the "V" substance concerned in promoting the growth of Pfeiffer's bacillus. PMID:19868950

Facile regio- and stereoselective hydrometalation of alkynes with a combination of carboxylic acids and group 10 transition metal complexes: selective hydrogenation of alkynes with formic acid.

PubMed

Shen, Ruwei; Chen, Tieqiao; Zhao, Yalei; Qiu, Renhua; Zhou, Yongbo; Yin, Shuangfeng; Wang, Xiangbo; Goto, Midori; Han, Li-Biao

2011-10-26

A facile, highly stereo- and regioselective hydrometalation of alkynes generating alkenylmetal complex is disclosed for the first time from a reaction of alkyne, carboxylic acid, and a zerovalent group 10 transition metal complex M(PEt(3))(4) (M = Ni, Pd, Pt). A mechanistic study showed that the hydrometalation does not proceed via the reaction of alkyne with a hydridometal generated by the protonation of a carboxylic acid with Pt(PEt(3))(4), but proceeds via a reaction of an alkyne coordinate metal complex with the acid. This finding clarifies the long proposed reaction mechanism that operates via the generation of an alkenylpalladium intermediate and subsequent transformation of this complex in a variety of reactions catalyzed by a combination of Brϕnsted acid and Pd(0) complex. This finding also leads to the disclosure of an unprecedented reduction of alkynes with formic acid that can selectively produce cis-, trans-alkenes and alkanes by slightly tuning the conditions.

Acid-functionalized polyolefin materials and their use in acid-promoted chemical reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oyola, Yatsandra; Tian, Chengcheng; Bauer, John Christopher

An acid-functionalized polyolefin material that can be used as an acid catalyst in a wide range of acid-promoted chemical reactions, wherein the acid-functionalized polyolefin material includes a polyolefin backbone on which acid groups are appended. Also described is a method for the preparation of the acid catalyst in which a precursor polyolefin is subjected to ionizing radiation (e.g., electron beam irradiation) of sufficient power and the irradiated precursor polyolefin reacted with at least one vinyl monomer having an acid group thereon. Further described is a method for conducting an acid-promoted chemical reaction, wherein an acid-reactive organic precursor is contacted inmore » liquid form with a solid heterogeneous acid catalyst comprising a polyolefin backbone of at least 1 micron in one dimension and having carboxylic acid groups and either sulfonic acid or phosphoric acid groups appended thereto.« less

The remarkable stability of chimeric, sialic acid-derived alpha/delta-peptides in human blood plasma.

PubMed

Saludes, Jonel P; Natarajan, Arutselvan; DeNardo, Sally J; Gervay-Hague, Jacquelyn

2010-05-01

Peptides are labile toward proteolytic enzymes, and structural modifications are often required to prolong their metabolic half-life and increase resistance. One modification is the incorporation of non-alpha-amino acids into the peptide to deter recognition by hydrolytic enzymes. We previously reported the synthesis of chimeric alpha/delta-peptides from glutamic acids (Glu) and the sialic acid derivative Neu2en. Conformational analyses revealed these constructs adopt secondary structures in water and may serve as conformational surrogates of polysialic acid. Polysialic acid is a tumor-associated polysaccharide and is correlated with cancer metastasis. Soluble polysialic acid is rapidly cleared from the blood limiting its potential for vaccine development. One motivation in developing structural surrogates of polysialic acid was to create constructs with increased bioavailability. Here, we report plasma stability profiles of Glu/Neu2en alpha/delta-peptides. DOTA was conjugated at the peptide N-termini by solid phase peptide synthesis, radiolabeled with (111)In, incubated in human blood plasma at 37 degrees C, and their degradation patterns monitored by cellulose acetate electrophoresis and radioactivity counting. Results indicate that these peptides exhibit a long half-life that is two- to three-orders of magnitude higher than natural alpha-peptides. These findings provide a viable platform for the synthesis of plasma stable, sialic acid-derived peptides that may find pharmaceutical application.

Transformation kinetics of corn and clover residues in mineral substrates of different composition

NASA Astrophysics Data System (ADS)

Pinskii, D. L.; Maltseva, A. N.; Zolotareva, B. N.; Dmitrieva, E. D.

2017-06-01

Mineralization kinetics of corn and clover residues in quartz sand, loam, sand + 15% bentonite, and sand + 30% kaolinite have been studied. A scheme has been proposed for the transformation of plant residues in mineral substrates. Kinetic parameters of mineralization have been calculated with the use of a first-order two-term exponential polynomial. It has been shown that the share of labile organic carbon pool in the clover biomass is higher (57-63%) than in the corn biomass (47-49%), which is related to the biochemical composition of plant residues. The mineralization constants of clover residues generally significantly exceed those of corn because of the stronger stabilization of the decomposition products of corn residues. The turnover time of the labile clover pool (4-9 days) in all substrates and that of the labile corn pool (8-10 days) in sands and substrates containing kaolinites and bentonite are typical for organic acids, amino acids, and simple sugars. In the loamy substrate, the turnover time of labile corn pool is about 46 days due to the stronger stabilization of components of the labile pool containing large amounts of organic acids. The turnover time of the stable clover pool (0.95 years) is significantly lower than that of the stable corn pool (1.60 years) and largely corresponds to the turnover time of plant biomass.

Developmental Change and Intraindividual Variability: Relating Cognitive Aging to Cognitive Plasticity, Cardiovascular Lability, and Emotional Diversity

PubMed Central

Ram, Nilam; Gerstorf, Denis; Lindenberger, Ulman; Smith, Jacqui

2010-01-01

Repeated assessments obtained over years can be used to measure individuals’ developmental change, whereas repeated assessments obtained over a few weeks can be used to measure individuals’ dynamic characteristics. Using data from a burst of measurement embedded in the Berlin Aging Study (BASE: Baltes & Mayer, 1999), we illustrate and examine how long-term changes in cognitive ability are related to short-term changes in cognitive performance, cardiovascular function, and emotional experience. Our findings suggest that “better” cognitive aging over approximately13 years was associated with greater cognitive plasticity, less cardiovascular lability, and less emotional diversity over approximately 2 weeks at age 90 years. The study highlights the potential benefits of multi-time scale longitudinal designs for the study of individual function and development. PMID:21443355

[Effects of Chinese prickly ash orchard on soil organic carbon mineralization and labile organic carbon in karst rocky desertification region of Guizhou province].

PubMed

Zhang, Wen-Juan; Liao, Hong-Kai; Long, Jian; Li, Juan; Liu, Ling-Fei

2015-03-01

Taking 5-year-old Chinese prickly ash orchard (PO-5), 17-year-old Chinese prickly ash orchard (PO- 17), 30-year-old Chinese prickly ash orchard (PO-30) and the forest land (FL, about 60 years) in typical demonstration area of desertification control test in southwestern Guizhou as our research objects, the aim of this study using a batch incubation experiment was to research the mineralization characteristics of soil organic carbon and changes of the labile soil organic carbon contents at different depths (0-15 cm, 15-30 cm, and 30-50 cm). The results showed that: the cumulative mineralization amounts of soil organic carbon were in the order of 30-year-old Chinese prickly ash orchard, the forest land, 5-year-old Chinese prickly ash orchard and 17-year-old Chinese prickly ash orchard at corresponding depth. Distribution ratios of CO2-C cumulative mineralization amount to SOC contents were higher in Chinese prickly ash orchards than in forest land at each depth. Cultivation of Chinese prickly ash in long-term enhanced the mineralization of soil organic carbon, and decreased the stability of soil organic carbon. Readily oxidized carbon and particulate organic carbon in forest land soils were significantly more than those in Chinese prickly ash orchards at each depth (P < 0.05). With the increasing times of cultivation of Chinese prickly ash, the contents of readily oxidized carbon and particulate organic carbon first increased and then declined at 0-15 cm and 15-30 cm depth, respectively, but an opposite trend was found at 30-50 cm depth. At 0-15 cm and 15-30 cm, cultivation of Chinese prickly ash could be good for improving the contents of labile soil organic carbon in short term, but it was not conducive in long-term. In this study, we found that cultivation of Chinese prickly ash was beneficial for the accumulation of labile organic carbon at the 30-50 cm depth.

Restriction point control of cell growth by a labile protein: evidence for increased stability in transformed cells.

PubMed Central

Campisi, J; Medrano, E E; Morreo, G; Pardee, A B

1982-01-01

It has been proposed that animal cells must accumulate a labile protein(s) before they can pass the restriction (R) point in the G1 phase of the cell cycle [Rossow, P. W., Riddle, V. G. H. & Pardee, A. B. (1979) Proc. Natl. Acad. Sci. USA 76, 4446--4450]. Here, we present evidence that this R protein acquires increased stability in transformed 3T3 cells, thereby allowing these cells to continue growth under conditions that arrest untransformed cells. Low doses of cycloheximide or histidinol drastically reduced the rate at which normal 3T3 (A31) fibroblasts in early G1 could enter DNA synthesis. These drugs had less effect on entry of two tumorigenic A31 derivatives, BPA31 and SVA31, in S, although measurement of [3H]leucine incorporation showed that the inhibitors were equally effective in the three cell lines. The hypothesis is that the transformed lines are less sensitive because moderate inhibition of their R protein synthesis is compensated by lower rates of protein degradation. To test this idea, we completely inhibited cytoplasmic protein synthesis for several hours shortly before A31 and BPA31 cells had reached the R point. After removal of inhibitor, A31 cells showed delays in the onset of S that were in excess of the inhibitor pulse, consistent with decay of labile protein during the pulse. BPA31 cells showed no excess delays, suggesting a much more stable R protein. The half-life of the R protein was estimated as 2.5 hr in A31 cells, indicating that, in these cells, R protein synthesis starts at the beginning of G1. In the BPA31 cells the R protein showed no signs of decay for at least 8 hr. PMID:6952194

Ammonia oxidation-dependent growth of group I.1b Thaumarchaeota in acidic red soil microcosms.

PubMed

Wu, Yucheng; Conrad, Ralf

2014-07-01

Accumulating evidence suggests that Thaumarchaeota may control nitrification in acidic soils. However, the composition of the thaumarchaeotal communities and their functioning is not well known. Therefore, we studied nitrification activity in relation to abundance and composition of Thaumarchaeota in an acidic red soil from China, using microcosms incubated with and without cellulose amendment. Cellulose was selected to simulate the input of crop residues used to increase soil fertility by local farming. Accumulation of NO3-(-N) was correlated with the growth of Thaumarchaeota as determined by qPCR of 16S rRNA and ammonia monooxygenase (amoA) genes. Both nitrification activity and thaumarchaeotal growth were inhibited by acetylene. They were also inhibited by cellulose amendment, possibly due to the depletion of ammonium by enhanced heterotrophic assimilation. These results indicated that growth of Thaumarchaeota was dependent on ammonia oxidation. The thaumarchaeotal 16S rRNA gene sequences in the red soil were dominated by a clade related to soil fosmid clone 29i4 within the group I.1b, which is widely distributed but so far uncultured. The archaeal amoA sequences were mainly related to the Nitrososphaera sister cluster. These observations suggest that fosmid clone 29i4 and Nitrososphaera sister cluster represent the same group of Thaumarchaeota and dominate ammonia oxidation in acidic red soil. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

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

Agricultural management and labile carbon additions affect soil microbial community structure and interact with carbon and nitrogen cycling.

PubMed

Berthrong, Sean T; Buckley, Daniel H; Drinkwater, Laurie E

2013-07-01

We investigated how conversion from conventional agriculture to organic management affected the structure and biogeochemical function of soil microbial communities. We hypothesized the following. (1) Changing agricultural management practices will alter soil microbial community structure driven by increasing microbial diversity in organic management. (2) Organically managed soil microbial communities will mineralize more N and will also mineralize more N in response to substrate addition than conventionally managed soil communities. (3) Microbial communities under organic management will be more efficient and respire less added C. Soils from organically and conventionally managed agroecosystems were incubated with and without glucose ((13)C) additions at constant soil moisture. We extracted soil genomic DNA before and after incubation for TRFLP community fingerprinting of soil bacteria and fungi. We measured soil C and N pools before and after incubation, and we tracked total C respired and N mineralized at several points during the incubation. Twenty years of organic management altered soil bacterial and fungal community structure compared to continuous conventional management with the bacterial differences caused primarily by a large increase in diversity. Organically managed soils mineralized twice as much NO3 (-) as conventionally managed ones (44 vs. 23 μg N/g soil, respectively) and increased mineralization when labile C was added. There was no difference in respiration, but organically managed soils had larger pools of C suggesting greater efficiency in terms of respiration per unit soil C. These results indicate that the organic management induced a change in community composition resulting in a more diverse community with enhanced activity towards labile substrates and greater capacity to mineralize N.

Pepsi® or Coke®? Influence of acid on dasatinib absorption.

PubMed

Knoebel, Randall W; Larson, Richard A

2018-03-01

Dasatinib is a second generation ABL kinase inhibitor used in the management of chronic myeloid leukemia or Philadelphia chromosome positive acute lymphoblastic leukemia (Ph+ ALL). Dasatinib's bioavailability is highly dependent on gastric pH. When proton-pump inhibitors (PPIs) are co-administered with dasatinib, absorption is significantly reduced. Cola intake at the time of drug administration has been demonstrated to lead to relevant increases in the bioavailability for other acid labile drugs during PPI treatment. This manuscript reviews the relevant literature supporting a strategy of temporarily lowering the gastric pH with a carbonated beverage at the time of drug administration. The use of cola provides an easy to implement way to significantly improve dasatinib bioavailability, especially during concomitant use of a PPI.

Using High Performance Computing to Understand Roles of Labile and Nonlabile U(VI) on Hanford 300 Area Plume Longevity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lichtner, Peter C.; Hammond, Glenn E.

Evolution of a hexavalent uranium [U(VI)] plume at the Hanford 300 Area bordering the Columbia River is investigated to evaluate the roles of labile and nonlabile forms of U(VI) on the longevity of the plume. A high fidelity, three-dimensional, field-scale, reactive flow and transport model is used to represent the system. Richards equation coupled to multicomponent reactive transport equations are solved for times up to 100 years taking into account rapid fluctuations in the Columbia River stage resulting in pulse releases of U(VI) into the river. The peta-scale computer code PFLOTRAN developed under a DOE SciDAC-2 project is employed inmore » the simulations and executed on ORNL's Cray XT5 supercomputer Jaguar. Labile U(VI) is represented in the model through surface complexation reactions and its nonlabile form through dissolution of metatorbernite used as a surrogate mineral. Initial conditions are constructed corresponding to the U(VI) plume already in place to avoid uncertainties associated with the lack of historical data for the waste stream. The cumulative U(VI) flux into the river is compared for cases of equilibrium and multirate sorption models and for no sorption. The sensitivity of the U(VI) flux into the river on the initial plume configuration is investigated. The presence of nonlabile U(VI) was found to be essential in explaining the longevity of the U(VI) plume and the prolonged high U(VI) concentrations at the site exceeding the EPA MCL for uranium.« less

Comparative Evaluation of Efficacy and Tolerability of Glycolic Acid, Salicylic Mandelic Acid, and Phytic Acid Combination Peels in Melasma.

PubMed

Sarkar, Rashmi; Garg, Vijay; Bansal, Shivani; Sethi, Sumit; Gupta, Chitra

2016-03-01

Melasma is acquired symmetric hypermelanosis characterized by light-to-deep brown pigmentation over cheeks, forehead, upper lip, and nose. Treatment of this condition is difficult and associated with high recurrence rates. Chemical peels have become a popular modality in the treatment of melasma. To compare the therapeutic efficacy and tolerability of glycolic acid (35%) versus salicylic-mandelic (SM) acid (20% salicylic/10% mandelic acid) versus phytic combination peels in Indian patients with melasma. Ninety patients diagnosed with melasma were randomly assigned into 3 groups of 30 patients each. Group A received glycolic acid (GA-35%) peel, Group B received SM acid, and Group C received phytic combination peels. Each group was primed with 4% hydroquinone and 0.05% tretinoin cream for 4 weeks before treatment. Chemical peeling was done after every 14 days in all groups until 12 weeks. Clinical evaluation using melasma area and severity index (MASI) score and photography was recorded at every visit and follow-up was done until 20 weeks. There was a decrease in MASI score in all 3 groups but it was statistically significantly lower in Group A than Group C (p = .00), and it was also statistically significantly lower in Group B than Group C (p = .00) but there was no statistically significant difference between Groups A and B (p = .876). Objective response to treatment evaluated by reduction in MASI scoring after 12 weeks was 62.36% reduction in GA group, 60.98% reduction in SM group, and 44.71% in phytic acid group. It is concluded that GA (35%) and SM acid peels are both equally efficacious and a safe treatment modality for melasma in Indian skin, and are more effective than phytic acid peels. Salicylic-mandelic peels are better tolerated and more suitable for Indian skin.

Expression of Chlamydophila psittaci MOMP heat-labile toxin B subunit fusion gene in transgenic rice.

PubMed

Zhang, Xiuxiang; Yuan, Ziguo; Guo, Xuejun; Li, Jingwen; Li, Zhaonan; Wang, Qingyu

2008-09-01

A DNA fragment encoding the MOMP gene of Chlamydophila psittaci was fused to the heat-labile toxin B subunit gene (LTB-MOMP) and transferred into rice callus by Agrobacterium tumefaciens-mediated transformation. The LTB-MOMP fusion gene was detected in genomic DNA from transformed rice leaves by Southern blot and RT-PCR amplification. Synthesis and assembly of the LTB-MOMP fusion protein into pentamers was detected in transformed leaf extracts by immunoblot analysis. Binding of the pentamers to intestinal epithelial cell membrane glycolipid receptors was quantified by GM1-ganglioside enzyme-linked immunosorbent assay (GM1-ELISA). The ELISA results indicated that LTB-MOMP fusion protein made up 0.0033-0.0054% of the total soluble leaf protein. Meanwhile, this suggested that the fusion protein retained both its native antigenicity and the ability to form pentamers.

Studies of the prevalence and significance of radiolabeled bile acid malabsorption in a group of patients with idiopathic chronic diarrhea

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schiller, L.R.; Hogan, R.B.; Morawski, S.G.

1987-01-01

We studied radiolabeled fecal bile acid excretion in 11 normal subjects and 17 patients with idiopathic chronic diarrhea for three major purposes: to establish normal values for this test in the presence of increased stool volumes (induced in normal subjects by ingestion of poorly absorbable solutions); to test for bile acid malabsorption in the patients and to correlate this with an independent test of ileal function, the Schilling test; and to compare the results of the bile acid excretion test with the subsequent effect of a bile acid binding agent (cholestyramine) on stool weight. In normal subjects fecal excretion ofmore » the radiolabel was increased with increasing stool volumes. As a group, patients with idiopathic chronic diarrhea excreted radiolabeled bile acid more rapidly than normal subjects with induced diarrhea (t1/2 56 +/- 8 vs. 236 +/- 60 h, respectively, p less than 0.005). There was a statistically significant positive correlation between t1/2 of radiolabeled bile acid and Schilling test results in these patients. Although 14 of 17 patients absorbed labeled taurocholic acid less well than any of the normal subjects with comparable volumes of induced diarrhea, cholestyramine had no statistically significant effect on stool weight in the patient group, and in none of the patients was stool weight reduced to within the normal range. In summary, most patients with idiopathic chronic diarrhea have bile acid malabsorption (as measured by fecal excretion of labeled bile acid), but they do not respond to cholestyramine therapy with a significant reduction in stool weight. Although the significance of these findings was not clearly established, the most likely interpretation is that bile acid malabsorption is a manifestation of an underlying intestinal motility or absorptive defect rather than the primary cause of diarrhea.« less

Influence of an iron-rich amendment on chemical lability and plant (Raphanus sativus L.) availability of two metallic elements (As and Pb) on mine-impacted agricultural soils.

PubMed

Kim, Juhee; Kim, Yong-Seong; Hyun, Seunghun; Moon, Deok Hyun; Chang, Jun Young

2016-10-01

Variation of the chemical extractability and phytoavailability of two metallic elements (e.g., As and Pb) on amendment-treated soils was investigated. Four mine-impacted agricultural soils contaminated with both As (174-491 mg kg -1 ) and Pb (116-357 mg kg -1 ) were amended with an iron-rich sludge at the rate of 5 % (w/w). After a 4-, 8-, and 16-week incubation, the extractability of metallic elements was assessed by sequential extraction procedure (SEP; F1-F5). The control without amendment was also run. In amended soils, the labile element mass (i.e., F1 + F2) promptly decreased (15-48 % of As and 5-10 % of Pb) in 4 weeks, but the decrement was continued over 16 weeks up to 70 and 28 % for As and Pb, respectively. The labile mass decrement was quantitatively corresponded with the increment of F3 (bound to amorphous metal oxides). In plant test assessed by radish (Raphanus sativus) grown on the 16-week soils, up to 57 % of As and 28 % of Pb accumulation was suppressed and 10-43 % of growth (i.e., shoot/root elongation and fresh weight) was improved. For both the control and amended soils, element uptake by plant was well correlated with their labile soil concentrations (r 2  = 0.799 and 0.499 for As and Pb, respectively). The results confirmed that the iron-rich material can effectively suppress element uptake during R. sativus seedling growth, most likely due to the chemical stabilization of metallic elements in growth medium.

Expression of non-toxic mutant of Escherichia coli heat-labile enterotoxin in tobacco chloroplasts.

PubMed

Kang, Tae-Jin; Han, So-Chon; Kim, Mi-Young; Kim, Young-Sook; Yang, Moon-Sik

2004-11-01

Chloroplast transformation systems offer unique advantages in biotechnology, including high level of foreign gene expression, maternal inheritance, and polycistronic expression. We studied chloroplast expression of LTK63 (change Ser-->Lys at position 63 in the A subunit) which is the mutant of Escherichia coli heat-labile toxin. LTK63 is devoid of any toxic activity, but still retains its mucosal adjuvanticity. The LTK63 was cloned into chloroplast targeting vector and transformed to tobacco chloroplasts by particle bombardment. PCR and Southern blot analyses confirmed stable homologous recombination of the LTK63 gene into the chloroplast genome. The amount of LTK63 protein detected in tobacco chloroplasts was approximately 3.7% of the total soluble protein. The GM1-ganglioside binding assay confirmed that chloroplast-synthesized LTB of LTK63 binds to the intestinal membrane GM1-ganglioside receptor. Thus, the expression of LTK63 in chloroplasts provides a potential route toward the development of a plant-based edible vaccine for high expression system and environmentally friendly approach.

Plant regulation of greenhouse gas emissions and carbon lability in a Neotropical peatland

NASA Astrophysics Data System (ADS)

Girkin, Nicholas; Vane, Christopher; Turner, Benjamin; Ostle, Nicholas; Sjogersten, Sofie

2017-04-01

Tropical peatlands are under significant threat from land use changes but there remains a significant knowledge gap regarding the influences of contrasting plant types on greenhouse gas emissions and belowground carbon dynamics. We investigated differences in surface CO2 and CH4 fluxes and differences in soil organic carbon chemistry under contrasting surface vegetation types, a palm (Raphia taedigera) and a broadleaved evergreen tree (Campnosperma panamensis), in a Neotropical peatland. CO2 and CH4 production differed significantly between species, with higher fluxes measured under R. taedigera. There were significant differences in peat carbon properties under each species as revealed by Rock-Eval pyrolysis. Peat from under each species showed contrasting trends in degradation inside and outside the rooting zone, and strong differences in the presence of the most labile fractions of carbon. These results highlight the strong impacts that surface vegetation can have on surface gas emissions as well as the influences exerted on peat carbon chemistry within a tropical forested peatland, with implications for our understanding of changes in land use type across the tropics.

Recent advances in nontoxic Escherichia coli heat-labile toxin and its derivative adjuvants.

PubMed

Ma, Yongping

2016-11-01

The nontoxic heat-labile enterotoxin (LT) of Escherichia coli and the B subunit of LT (LTB) have been extensively studied as potent vaccine adjuvants. Areas covered: This review covers the area of enterotoxin based vaccine adjuvant and summarizes the development of nontoxic LT mutant (mLT) and LTB and their potency as oral, parenteral and injection adjuvants. Recent evidences indicated that the mechanism of LTB adjuvanticity was to enhance the turnover of dendritic cells (DCs) in spleen and increase DCs capacity to perform as antigen presentation cells (APCs) encountered with T cells. LTB also induces B and T cells clustering and delay/arrest in T-cell division following endocytosis or B-cell receptor (BCR) uptaking of antigen in a ganglioside-mediated manner. Expert commentary: It is pointed out that the immunogenicity of LTB (or LT) is more important than the receptor binding property (or ADP-ribosylation activity) for the adjuvanticity of LT toxoid. The immunogenicity of LTB (or LT) might confer unknown characteristics to maintain LT toxoid adjuvanticity.

Repair of radiation-induced heat-labile sites is independent of DNA-PKcs, XRCC1 or PARP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stenerlöw, Bo; Karlsson, Karin H.; Radulescu, Irina

2008-04-29

Ionizing radiation induces a variety of different DNA lesions: in addition to the most critical DNA damage, the DSB, numerous base alterations, SSBs and other modifications of the DNA double-helix are formed. When several non-DSB lesions are clustered within a short distance along DNA, or close to a DSB, they may interfere with the repair of DSBs and affect the measurement of DSB induction and repair. We have previously shown that a substantial fraction of DSBs measured by pulsed-field gel electrophoresis (PFGE) are in fact due to heat-labile sites (HLS) within clustered lesions, thus reflecting an artifact of preparation ofmore » genomic DNA at elevated temperature. To further characterize the influence of HLS on DSB induction and repair, four human cell lines (GM5758, GM7166, M059K, U-1810) with apparently normal DSB rejoining were tested for bi-phasic rejoining after gamma irradiation. When heat-released DSBs were excluded from the measurements the fraction of fast rejoining decreased to less than 50% of the total. However, neither the half-times of the fast (t{sub 1/2} = 7-8 min) or slow (t{sub 1/2} = 2.5 h) DSB rejoining were changed significantly. At t=0 the heat-released DSBs accounted for almost 40% of the DSBs, corresponding to 10 extra DSB/cell/Gy in the initial DSB yield. These heat-released DSBs were repaired within 60-90 min in all tested cells, including M059K cells treated with wortmannin or DNA-PKcs defect M059J cells. Furthermore, cells lacking XRCC1 or Poly(ADP-ribose) polymerase-1 (PARP-1) rejoined both total DSBs and heat-released DSBs similar to normal cells. In summary, the presence of heat-labile sites have a substantial impact on DSB induction yields and DSB rejoining rates measured by pulsed-field gel electrophoresis, and HLS repair is independent of DNA-PKcs, XRCC1 and PARP.« less

New Chemistry with Old Functional Groups: On the Reaction of Isonitriles with Carboxylic Acids - A Route to Various Amide Types

PubMed Central

Li, Xuechen; Danishefsky, Samuel J.

2008-01-01

Thermolysis of isonitriles with carboxylic acids provides, in one step, N-formyl imides (see, for example 8 + 19 → 21). The resultant N-formyl group can be converted to N-H, NCH2OH or NCH3. This chemistry allows for a new route for synthesizing β-N (asparagine) linked glycosyl amino acids. PMID:18370392

Mass production of somatic embryos expressing Escherichia coli heat-labile enterotoxin B subunit in Siberian ginseng.

PubMed

Kang, Tae-Jin; Lee, Won-Seok; Choi, Eun-Gyung; Kim, Jae-Whune; Kim, Bang-Geul; Yang, Moon-Sik

2006-01-24

The B subunit of Escherichia coli heat-labile toxin (LTB) is a potent mucosal immunogen and immunoadjuvant for co-administered antigens. In order to produce large scale of LTB for the development of edible vaccine, we used transgenic somatic embryos of Siberian ginseng, which is known as medicinal plant. When transgenic somatic embryos were cultured in 130L air-lift type bioreactor, they were developed to mature somatic embryos through somatic embryogenesis and contained approximately 0.36% LTB of the total soluble protein. Enzyme-linked immunosorbent assay indicated that the somatic embryo-synthesized LTB protein bound specifically to GM1-ganglioside, suggesting the LTB subunits formed active pentamers. Therefore, the use of the bioreactor system for expression of LTB proteins in somatic embryos allows for continuous mass production in a short-term period.

What's Hot and What's Not: Multivariate Statistical Analysis of Ten Labile Trace Elements in H-Chondrite Population Pairs

NASA Astrophysics Data System (ADS)

Wolf, S. F.; Lipschutz, M. E.

1993-07-01

Dodd et al. [1] found that, from their circumstances of fall, 17 H chondrites ("H Cluster 1") which fell in May, from 1855 to 1895, are distinguishable from other H chondrite falls and apparently derive from a co-orbital stream of meteoroids. From data for 10 moderately to highly labile trace elements (Rb, Ag, Se, Cs, Te, Zn, Cd, Bi, Tl, In), they used two multivariate statistical techniques--linear discriminant analysis and logistic regression--to demonstrate that 1. 13 H Cluster 1 chondrites are compositionally distinguishable from 45 other H chondrite falls, probably because of differences in thermal histories of the meteorites' parent materials; 2. The reality of the compositional differences between the populations of falls are beyond any reasonable statistical doubt. 3. The compositional differences are inconsistent with the notion that the results reflect analytical bias. We have used these techniques to assess analogous data for various H chondrite populations [2-4] with results that are listed in Table 1. These data indicate that 1. There is no statistical reason to believe that random populations from Victoria Land, Antarctica, differ compositionally from each other. 2. There is significant statistical reason to believe that the H chondrite population recovered from Victoria Land, Antarctica, differs compositionally from that from Queen Maud Land, Antarctica, and from falls. 3. There is no reason to believe that the H chondrite population recovered from Queen Maud Land, Antarctica, differs compositionally from falls. 4. These observations can be made either by data obtained by one analyst or several. These results, coupled with earlier ones [5], demonstrate that trivial explanations cannot explain compositional differences involving labile trace elements in pairs of H chondrite populations. These differences must then reflect differences of preterrestrial thermal histories of the meteorites' parent materials. Acceptance of these differences as

Natural abundance 17O DNP NMR provides precise O–H distances and insights into the Brønsted acidity of heterogeneous catalysts

DOE PAGES

Perras, Frederic A.; Wang, Zhuoran; Naik, Pranjali; ...

2017-05-12

Heterogeneous Brønsted acid catalysts are tremendously important in industry, particularly in catalytic cracking processes. Here we show that these Brønsted acid sites can be directly observed at natural abundance by 17O DNP surface-enhanced NMR spectroscopy (SENS). We additionally show that the O–H bond length in these catalysts can be measured with sub-picometer precision, to enable a direct structural gauge of the lability of protons in a given material, which is correlated with the pH of the zero point of charge of the material. As a result, experiments performed on materials impregnated with pyridine also allow for the direct detection ofmore » intermolecular hydrogen bonding interactions through the lengthening of O–H bonds.« less

Natural abundance 17O DNP NMR provides precise O–H distances and insights into the Brønsted acidity of heterogeneous catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perras, Frederic A.; Wang, Zhuoran; Naik, Pranjali

Heterogeneous Brønsted acid catalysts are tremendously important in industry, particularly in catalytic cracking processes. Here we show that these Brønsted acid sites can be directly observed at natural abundance by 17O DNP surface-enhanced NMR spectroscopy (SENS). We additionally show that the O–H bond length in these catalysts can be measured with sub-picometer precision, to enable a direct structural gauge of the lability of protons in a given material, which is correlated with the pH of the zero point of charge of the material. As a result, experiments performed on materials impregnated with pyridine also allow for the direct detection ofmore » intermolecular hydrogen bonding interactions through the lengthening of O–H bonds.« less

Structural analysis by reductive cleavage with LiAlH4 of an allyl ether choline-phospholipid, archaetidylcholine, from the hyperthermophilic methanoarchaeon Methanopyrus kandleri

PubMed Central

Nishihara, Masateru; Morii, Hiroyuki; Matsuno, Koji; Ohga, Mami; Stetter, Karl O.; Koga, Yosuke

2002-01-01

A choline-containing phospholipid (PL-4) in Methanopyrus kandleri cells was identified as archaetidylcholine, which has been described by Sprott et al. (1997). The PL-4 consisted of a variety of molecular species differing in hydrocarbon composition. Most of the PL-4 was acid-labile because of its allyl ether bond. The identity of PL-4 was confirmed by thin-layer chromatography (TLC) followed by positive staining with Dragendorff-reagent and fast-atom bombardment–mass spectrometry. A new method of LiAlH4 hydrogenolysis was developed to cleave allyl ether bonds and recover the corresponding hydrocarbons. We confirmed the validity of the LiAlH4 method in a study of the model compound synthetic unsaturated archaetidic acid (2,3-di-O-geranylgeranyl-sn-glycerol-1-phosphate). Saturated ether bonds were not cleaved by the LiAlH4 method. The hydrocarbons formed following LiAlH4 hydrogenolysis of PL-4 were identified by gas–liquid chromatography and mass spectrometry. Four kinds of hydrocarbons with one to four double bonds were detected: 47% of the hydrocarbons had four double bonds; 11% had three double bonds; 14% had two double bonds; 7% had one double bond; and 6% were saturated species. The molecular species composition of PL-4 was also estimated based on acid lability: 77% of the molecular species had two acid-labile hydrocarbons; 11% had one acid-labile and one acid-stable hydrocarbon; and 11% had two acid-stable hydrocarbons. To our knowledge, this is the first report of a specific chemical degradation method for the structural analysis of allyl ether phospholipid in archaea. PMID:15803650

NMR experiments for the rapid identification of P=O···H-X type hydrogen bonds in nucleic acids.

PubMed

Duchardt-Ferner, Elke; Wöhnert, Jens

2017-10-01

Hydrogen bonds involving the backbone phosphate groups occur with high frequency in functional RNA molecules. They are often found in well-characterized tertiary structural motifs presenting powerful probes for the rapid identification of these motifs for structure elucidation purposes. We have shown recently that stable hydrogen bonds to the phosphate backbone can in principle be detected by relatively simple NMR-experiments, providing the identity of both the donor hydrogen and the acceptor phosphorous within the same experiment (Duchardt-Ferner et al., Angew Chem Int Ed Engl 50:7927-7930, 2011). However, for imino and hydroxyl hydrogen bond donor groups rapidly exchanging with the solvent as well as amino groups broadened by conformational exchange experimental sensitivity is severely hampered by extensive line broadening. Here, we present improved methods for the rapid identification of hydrogen bonds to phosphate groups in nucleic acids by NMR. The introduction of the SOFAST technique into 1 H, 31 P-correlation experiments as well as a BEST-HNP experiment exploiting 3h J N,P rather than 2h J H,P coupling constants enables the rapid and sensitive identification of these hydrogen bonds in RNA. The experiments are applicable for larger RNAs (up to ~ 100-nt), for donor groups influenced by conformational exchange processes such as amino groups and for hydrogen bonds with rather labile hydrogens such as 2'-OH groups as well as for moderate sample concentrations. Interestingly, the size of the through-hydrogen bond scalar coupling constants depends not only on the type of the donor group but also on the structural context. The largest coupling constants were measured for hydrogen bonds involving the imino groups of protonated cytosine nucleotides as donors.

Preservation of labile organic matter in soils of drained thaw lakes in Northern Alaska

NASA Astrophysics Data System (ADS)

Mueller, Carsten W.; Rethemeyer, Janet; Kao-Kniffin, Jenny; Löppmann, Sebastian; Hinkel, Kenneth; Bockheim, James

2014-05-01

A large number of studies predict changing organic matter (OM) dynamics in arctic soils due to global warming. In contrast to rather slowly altering bulk soil properties, single soil organic matter (SOM) fractions can provide a more detailed picture of the dynamics of differently preserved SOM pools in climate sensitive arctic regions. By the study of the chemical composition of such distinctive SOM fractions using nuclear magnetic resonance spectroscopy (NMR) together with radiocarbon analyses it is possible to evaluate the stability of the major OM pools. Approximately 50-75% of Alaska's Arctic Coastal Plain is covered with thaw lakes and drained thaw lakes that follow a 5,000 yr cycle of development (between creation and final drainage), thus forming a natural soil chronosequence. The drained thaw lakes offer the possibility to study SOM dynamics affected by permafrost processes over millennial timescales. In April 2010 we sampled 16 soil cores (including the active and permanent layer) reaching from young drained lakes (0-50 years since drainage) to ancient drained lakes (3000-5500 years since drainage). Air dried soil samples from soil horizons of the active and permanent layer were subjected to density fractionation in order to differentiate particulate OM and mineral associated OM. The chemical composition of the SOM fractions was analyzed by 13C CPMAS NMR spectroscopy. For a soil core of a young and an ancient drained thaw lake basin we also analyzed the 14C content. For the studied soils we can show that up to over 25 kg OC per square meter are stored mostly as labile, easily degradable organic matter rich in carbohydrates. In contrast only 10 kg OC per square meter were sequestered as presumably more stable mineral associated OC dominated by aliphatic compounds. Comparable to soils of temperate regions, we found small POM (< 20 µm) occluded in aggregated soil structures which differed in the chemical composition from larger organic particles. This was

Phosphine-free Stille-Migita chemistry for the mild and orthogonal modification of DNA and RNA.

PubMed

Krause, André; Hertl, Alexander; Muttach, Fabian; Jäschke, Andres

2014-12-08

An optimized catalyst system of [Pd2 (dba)3 ] and AsPh3 efficiently catalyzes the Stille reaction between a diverse set of functionalized stannanes and halogenated mono-, di- and oligonucleotides. The methodology allows for the facile conjugation of short and long nucleic acid molecules with moieties that are not compatible with conventional chemical or enzymatic synthesis, among them acid-, base-, or fluoride-labile protecting groups, fluorogenic and synthetically challenging moieties with good to near-quantitative yields. Notably, even azides can be directly introduced into oligonucleotides and (deoxy)nucleoside triphosphates, thereby giving direct access to "clickable" nucleic acids. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanoparticulated heat-stable (STa) and heat-labile B subunit (LTB) recombinant toxin improves vaccine protection against enterotoxigenic Escherichia coli challenge in mouse.

PubMed

Deng, Guangcun; Zeng, Jin; Jian, Minjie; Liu, Wenmiao; Zhang, Zhong; Liu, Xiaoming; Wang, Yujiong

2013-02-01

Enterotoxigenic Escherichia coli (ETEC) remains a major cause of diarrheic disease in developing areas, for which there is no effective vaccine available. In this study, we genetically engineered a recombinant heat-stable enterotoxin (STa) coupled to the subunit B of heat-labile enterotoxin (LTB). This fusion protein, STa-LTB, possesses a single amino acid substitution at position 14 of STa. Our data demonstrates that the enterotoxicity of STa in STa-LTB was dramatically reduced. A gelatin nanovaccine candidate was prepared using the purified STa-LTB fusion protein characterized with an entrapment efficiency of 84.88 ± 6.37% and smooth spheres size ranges of 80-200 nm. Antigen-specific antibody responses against STa-LTB and STa in the sera and the intestinal mucus respectively were used to test the immunogenicity of the nanovaccine. This vaccine was further screened in mice by its ability to elicit neutralizing antibodies against STa and protect animals from the challenge with ETEC in mice. The STa-LTB nanoparticles delivered demonstrated a capacity to induce significantly higher and long-lasting antibody responses and increased immune protection against ETEC challenge relative to the control STa-LTB vaccine absorbed in conventional aluminum hydrate salt (p < 0.01). These results warrant the further studies of the development of a novel nanoparticulate vaccine as a broad-spectrum vaccine against ETEC infection. Copyright © 2012 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Functional Group Analysis.

ERIC Educational Resources Information Center

Smith, Walter T., Jr.; Patterson, John M.

1984-01-01

Literature on analytical methods related to the functional groups of 17 chemical compounds is reviewed. These compounds include acids, acid azides, alcohols, aldehydes, ketones, amino acids, aromatic hydrocarbons, carbodiimides, carbohydrates, ethers, nitro compounds, nitrosamines, organometallic compounds, peroxides, phenols, silicon compounds,…

Exploring alternative Zn-binding groups in the design of HDAC inhibitors: squaric acid, N-hydroxyurea, and oxazoline analogues of SAHA.

PubMed

Hanessian, Stephen; Vinci, Valerio; Auzzas, Luciana; Marzi, Mauro; Giannini, Giuseppe

2006-09-15

Analogues of suberoylanilide hydroxamic acid (SAHA) were prepared by replacing the Zn-binding group with squaric acid, N-hydroxyurea, and 4-hydroxymethyl oxazoline units, also varying the length of the aliphatic chain. No inhibitory activity on HDAC was observed below 1.0 microM and no cytotoxic activity on different tumor cell lines was seen below 20.0 microM.

The application of "double isolation" in Fourier transform ion cyclotron resonance sustained off-resonance irradiation collisionally-induced dissociation tandem mass spectrometry to remove labile isobaric impurities.

PubMed

Gates, Paul J; Lopes, Norberto P; Pinto, Emani; Colepicolo, Pio; Cardozo, Karina H M

2011-01-01

This study reports the application of "double isolation" in sustained off-resonance irradiation collisionally-induced dissociation tandem mass spectrometry (SORI-CID-MS/MS) to remove radio- frequency (RF) fragment ions of very close mass isobaric ions (0.02 m/z apart). Analyses were performed with a fraction of a biological extract isolated from a macroalgae containing the mycosporine-like amino acid asterina-330. Direct isolation of the precursor ion by narrowing the isolation window proved ineffective as it impinged upon the required ion thus substantially reducing its intensity. By increasing the correlated sweep time, ejection efficiency of the isolation was improved, but caused the unwanted side-effect of RF fragmentation of labile ions. Finally, by skipping the ion activation step and performing a second isolation (in the MS(3) module) the RF fragments from the first isolation were removed leaving a very pure isolation of the required precursor ion and allowed a very clean CID fragmentation. We demonstrated that the m/z 272.1351 ion is derived from the loss of NH(3) from m/z 289.1620 isobaric impurity and is not related to asterina-330. This application represents a powerful tool to remove unwanted ions in the MS/MS spectrum that result from fragmentation of isobaric ions.

Tannin structural elucidation and quantitative ³¹P NMR analysis. 2. Hydrolyzable tannins and proanthocyanidins.

PubMed

Melone, Federica; Saladino, Raffaele; Lange, Heiko; Crestini, Claudia

2013-10-02

An unprecedented analytical method that allows simultaneous structural and quantitative characterization of all functional groups present in tannins is reported. In situ labeling of all labile H groups (aliphatic and phenolic hydroxyls and carboxylic acids) with a phosphorus-containing reagent (Cl-TMDP) followed by quantitative ³¹P NMR acquisition constitutes a novel fast and reliable analytical tool for the analysis of tannins and proanthocyanidins with significant implications for the fields of food and feed analyses, tannery, and the development of natural polyphenolics containing products.

Structural Alterations of Lignins in Transgenic Poplars with Depressed Cinnamyl Alcohol Dehydrogenase or Caffeic Acid O-Methyltransferase Activity Have an Opposite Impact on the Efficiency of Industrial Kraft Pulping1

PubMed Central

Lapierre, Catherine; Pollet, Brigitte; Petit-Conil, Michel; Toval, Gabriel; Romero, Javier; Pilate, Gilles; Leplé, Jean-Charles; Boerjan, Wout; Ferret, Valérie; De Nadai, Véronique; Jouanin, Lise

1999-01-01

We evaluated lignin profiles and pulping performances of 2-year-old transgenic poplar (Populus tremula × Populus alba) lines severely altered in the expression of caffeic acid/5-hydroxyferulic acid O-methyltransferase (COMT) or cinnamyl alcohol dehydrogenase (CAD). Transgenic poplars with CAD or COMT antisense constructs showed growth similar to control trees. CAD down-regulated poplars displayed a red coloration mainly in the outer xylem. A 90% lower COMT activity did not change lignin content but dramatically increased the frequency of guaiacyl units and resistant biphenyl linkages in lignin. This alteration severely lowered the efficiency of kraft pulping. The Klason lignin level of CAD-transformed poplars was slightly lower than that of the control. Whereas CAD down-regulation did not change the frequency of labile ether bonds or guaiacyl units in lignin, it increased the proportion of syringaldehyde and diarylpropane structures and, more importantly with regard to kraft pulping, of free phenolic groups in lignin. In the most depressed line, ASCAD21, a substantially higher content in free phenolic units facilitated lignin solubilization and fragmentation during kraft pulping. These results point the way to genetic modification of lignin structure to improve wood quality for the pulp industry. PMID:9880356

Trivalent chromium removal from aqueous solutions by a sol–gel synthesized silica adsorbent functionalized with sulphonic acid groups

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gomez-Gonzalez, Sergio Efrain; Carbajal-Arizaga, Gregorio Guadalupe; Manriquez-Gonzalez, Ricardo

Highlights: • Corpuscular sulphonic acid-functionalized silica holds improved uptake of chromium. • Mesopores on adsorbent facilitate (CH{sub 3}COO){sub 2}Cr{sup +} ion uptake on sulphonate sites. • Formation of chromium acetate sulphonate complex proposed from XPS results. • Fixed bed chromium uptake results suggest potential industrial use. - Abstract: A high capacity hybrid silica adsorbent was synthesized via sol–gel processing with sulphonic acid groups as trivalent chromium complex ions chelators from aqueous solutions. The synthesis included co-condensation of tetraethoxysilane (TEOS) with 3-(mercaptopropyl)trimethoxysilane (MPS), and oxidation of thiol to sulphonic acid groups. Chromium uptake kinetic, batch and fixed-bed experiments were performed tomore » assess the removal of this metal from aqueous solutions. {sup 13}C, {sup 29}Si CPMAS NMR, FTIR, XPS were used to characterize the adsorbent structure and the nature of chromium complexes on the adsorbent surface. Chromium maximum uptake was obtained at pH 3 (72.8 mg/g). Elemental analysis results showed ligand density of 1.48 mmol sulphonic groups/g. About 407 mL of Cr(III) solution (311 mg/L) were treated to breakthrough point reaching ≤0.06 mg/L at the effluent. These results comply with USEPA regulation for chromium concentration in drinking water (≤0.1 mg/L). The adsorbent shows potential to be used in chromium separations to the industrial level.« less

Chlorogenic Acid Attenuates High Mobility Group Box 1 (HMGB1) and Enhances Host Defense Mechanisms in Murine Sepsis

PubMed Central

Lee, Chan-Ho; Yoon, Seong-Jin; Lee, Sun-Mee

2012-01-01

Sepsis is a complex, multifactorial, rapidly progressive disease characterized by an overwhelming activation of the immune system and the countervailing antiinflammatory response. In the current study in murine peritoneal macrophages, chlorogenic acid suppressed endotoxin-induced high mobility group box 1 (HMGB1) release in a concentration-dependent manner. Administration of chlorogenic acid also attenuated systemic HMGB1 accumulation in vivo and prevented mortality induced by endotoxemia and polymicrobial sepsis. The mechanisms of action of chlorogenic acid included attenuation of the increase in toll-like receptor (TLR)-4 expression and suppression of sepsis-induced signaling pathways, such as c-Jun NH2-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-κB, which are critical for cytokine release. The protection conferred by chlorogenic acid was achieved through modulation of cytokine and chemokine release, suppression of immune cell apoptosis and augmentation of bacterial elimination. Chlorogenic acid warrants further evaluation as a potential therapeutic agent for the treatment of sepsis and other potentially fatal systemic inflammatory disorders. PMID:23168580

Multivariate Analysis of Electron Detachment Dissociation and Infrared Multiphoton Dissociation Mass Spectra of Heparan Sulfate Tetrasaccharides Differing Only in Hexuronic acid Stereochemistry

NASA Astrophysics Data System (ADS)

Oh, Han Bin; Leach, Franklin E.; Arungundram, Sailaja; Al-Mafraji, Kanar; Venot, Andre; Boons, Geert-Jan; Amster, I. Jonathan

2011-03-01

The structural characterization of glycosaminoglycan (GAG) carbohydrates by mass spectrometry has been a long-standing analytical challenge due to the inherent heterogeneity of these biomolecules, specifically polydispersity, variability in sulfation, and hexuronic acid stereochemistry. Recent advances in tandem mass spectrometry methods employing threshold and electron-based ion activation have resulted in the ability to determine the location of the labile sulfate modification as well as assign the stereochemistry of hexuronic acid residues. To facilitate the analysis of complex electron detachment dissociation (EDD) spectra, principal component analysis (PCA) is employed to differentiate the hexuronic acid stereochemistry of four synthetic GAG epimers whose EDD spectra are nearly identical upon visual inspection. For comparison, PCA is also applied to infrared multiphoton dissociation spectra (IRMPD) of the examined epimers. To assess the applicability of multivariate methods in GAG mixture analysis, PCA is utilized to identify the relative content of two epimers in a binary mixture.

Biotransformation of linoleic acid and bile acids by Eubacterium lentum.

PubMed Central

Eyssen, H; Verhulst, A

1984-01-01

Eubacterium lentum is a gram-positive, nonsporeforming, nonmotile, asaccharolytic anaerobe. In the present investigations, 3 E. lentum strains (group E) isolated from rat feces were compared with 30 E. lentum strains (groups A, B, C, and D) previously studied by Macdonald et al. (I. A. Macdonald, J. F. Jellet, D. E. Mahony, and L. V. Holdeman, Appl. Environ. Microbiol. 37:992-1000, 1979). All strains alkalized (pH 8 to 8.5) arginine-containing (2 to 15 mg/ml) culture media, and growth of the majority of the strains was stimulated by arginine. All strains converted linoleic acid into transvaccenic acid by shifting the 12,13-cis double bond of linoleic acid into an 11,12-trans(?) double bond followed by biohydrogenation of the 9,10-cis double bond. Hence, biohydrogenation of linoleic acid is a new general characteristic of E. lentum. The 33 strains were also studied for bile acid deconjugase and hydroxysteroid dehydrogenase (HSDH) activities. The 6 strains in group D were steroid inactive; the 27 strains in groups A, B, C, and E were steroid active. The steroid-active group contained bile acid deconjugase-producing strains (groups C and E, plus strain 116 in group A) and nondeconjugating strains. All nondeconjugating strains of groups A and B developed 7 alpha- and 12 alpha-HSDH activities and contained 3 alpha-HSDH-positive strains and 3 alpha-HSDH-negative strains. Deconjugating strains varied in HSDH activities. PMID:6582800

Assay of free and glycine- and taurine-conjugated bile acids in serum by high-pressure liquid chromatography by using post-column reaction after group separation.

PubMed Central

Onishi, S; Itoh, S; Ishida, Y

1982-01-01

An accurate and sensitive method that involves the group separations of serum bile acids (i.e. free and glycine- and taurine-conjugated bile acid fractions) by ion-exchange chromatography on piperidinohydroxypropyl-Sephadex LH-20 is described. Each group was then analysed by high-pressure liquid chromatography by using the post-column reaction technique with immobilized 3 alpha-hydroxy steroid dehydrogenase. The bile acid patterns in the umbilical venous serum samples were analysed by this method. Taurochenodeoxycholate predominated in the umbilical blood. PMID:6956336

A self-crosslinking thermosetting monomer with both epoxy and anhydride groups derived from tung oil fatty acids: Synthesis and properties

USDA-ARS?s Scientific Manuscript database

A self-crosslinking compound with epoxy groups and anhydride groups (GEMA) has been successfully synthesized from tung oil fatty acid by reacting with maleic anhydride via the Diels-Alder reaction. GEMA has very good storage stability and could be cured with trace amounts of tertiary amine. This ad...

A self-crosslinking thermosetting monomer with both epoxy and anhydride groups derived from Tung oil fatty acids: Synthesis and properties

USDA-ARS?s Scientific Manuscript database

A self-crosslinking compound with epoxy groups and anhydride groups (GEMA) has been successfully synthesized from Tung oil fatty acid by reacting with maleic anhydride via the Diels-Alder reaction. GEMA has very good storage stability and can be cured with trace amounts of tertiary amine. This advan...

Classification of group B streptococci with reduced β-lactam susceptibility (GBS-RBS) based on the amino acid substitutions in PBPs.

PubMed

Kimura, Kouji; Nagano, Noriyuki; Arakawa, Yoshichika

2015-01-01

All clinical isolates of group B Streptococcus (GBS; Streptococcus agalactiae) are considered uniformly susceptible to β-lactams, including penicillins. However, GBS with reduced penicillin susceptibility (PRGBS) were first identified by our group in Japan and have also been reported from North America. PRGBS are non-susceptible to penicillin because of acquisition of amino acid substitutions near the conserved active-site motifs in PBP2X. In particular, V405A and Q557E are considered the key amino acid substitutions responsible for penicillin non-susceptibility. We revealed that in addition to the substitutions in PBP2X, an amino acid substitution in PBP1A confers high-level cephalosporin resistance in GBS. As the number of publications on GBS with reduced β-lactam susceptibility (GBS-RBS), especially PRGBS, and concomitantly the need for a systematic classification of GBS-RBS is increasing, we propose here a classification of GBS-RBS based on the amino acid substitutions in their PBPs. © The Author 2015. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Chronic Arachidonic Acid Administration Decreases Docosahexaenoic Acid- and Eicosapentaenoic Acid-Derived Metabolites in Kidneys of Aged Rats.

PubMed

Katakura, Masanori; Hashimoto, Michio; Inoue, Takayuki; Mamun, Abdullah Al; Tanabe, Yoko; Arita, Makoto; Shido, Osamu

2015-01-01

Arachidonic acid (ARA) metabolites produced by cyclo-oxygenase and lipoxygenase are important mediators maintaining physiological renal function. However, the effects of exogenous ARA on kidney function in vivo remain unknown. This study examined the effects of long-term oral ARA administration on normal renal function as well as inflammation and oxidative stress in aged rats. In addition, we measured levels of renal eicosanoids and docosanoids using liquid chromatography-tandem mass spectrometry. Control or ARA oil (240 mg/kg body weight/day) was orally administered to 21-month-old Wistar rats for 13 weeks. Levels of plasma creatinine, blood urea nitrogen, inflammatory and anti-inflammatory cytokines, reactive oxygen species, and lipid peroxidation were not significantly different between the two groups. The ARA concentration in the plasma, kidney, and liver increased in the ARA-administered group. In addition, levels of free-form ARA, prostaglandin E2, and 12- and 15-hydroxyeicosatetraenoic acid increased in the ARA-administered group, whereas renal concentration of docosahexaenoic acid and eicosapentaenoic acid decreased in the ARA-administered group. Levels of docosahexaenoic acid-derived protectin D1, eicosapentaenoic acid-derived 5-, and 18-hydroxyeicosapentaenoic acids, and resolvin E2 and E3 decreased in the ARA-administered group. Our results indicate that long-term ARA administration led to no serious adverse reactions under normal conditions and to a decrease in anti-inflammatory docosahexaenoic acid- and eicosapentaenoic acid-derived metabolites in the kidneys of aged rats. These results indicate that there is a possibility of ARA administration having a reducing anti-inflammatory effect on the kidney.

Chronic Arachidonic Acid Administration Decreases Docosahexaenoic Acid- and Eicosapentaenoic Acid-Derived Metabolites in Kidneys of Aged Rats

PubMed Central

Katakura, Masanori; Hashimoto, Michio; Inoue, Takayuki; Mamun, Abdullah Al; Tanabe, Yoko; Arita, Makoto; Shido, Osamu

2015-01-01

Arachidonic acid (ARA) metabolites produced by cyclo-oxygenase and lipoxygenase are important mediators maintaining physiological renal function. However, the effects of exogenous ARA on kidney function in vivo remain unknown. This study examined the effects of long-term oral ARA administration on normal renal function as well as inflammation and oxidative stress in aged rats. In addition, we measured levels of renal eicosanoids and docosanoids using liquid chromatography–tandem mass spectrometry. Control or ARA oil (240 mg/kg body weight/day) was orally administered to 21-month-old Wistar rats for 13 weeks. Levels of plasma creatinine, blood urea nitrogen, inflammatory and anti-inflammatory cytokines, reactive oxygen species, and lipid peroxidation were not significantly different between the two groups. The ARA concentration in the plasma, kidney, and liver increased in the ARA-administered group. In addition, levels of free-form ARA, prostaglandin E2, and 12- and 15-hydroxyeicosatetraenoic acid increased in the ARA-administered group, whereas renal concentration of docosahexaenoic acid and eicosapentaenoic acid decreased in the ARA-administered group. Levels of docosahexaenoic acid-derived protectin D1, eicosapentaenoic acid-derived 5-, and 18-hydroxyeicosapentaenoic acids, and resolvin E2 and E3 decreased in the ARA-administered group. Our results indicate that long-term ARA administration led to no serious adverse reactions under normal conditions and to a decrease in anti-inflammatory docosahexaenoic acid- and eicosapentaenoic acid-derived metabolites in the kidneys of aged rats. These results indicate that there is a possibility of ARA administration having a reducing anti-inflammatory effect on the kidney. PMID:26485038

An intermetallic Au24Ag20 superatom nanocluster stabilized by labile ligands.

PubMed

Wang, Yu; Su, Haifeng; Xu, Chaofa; Li, Gang; Gell, Lars; Lin, Shuichao; Tang, Zichao; Häkkinen, Hannu; Zheng, Nanfeng

2015-04-08

An intermetallic nanocluster containing 44 metal atoms, Au24Ag20(2-SPy)4(PhC≡C)20Cl2, was successfully synthesized and structurally characterized by single-crystal analysis and density funtional theory computations. The 44 metal atoms in the cluster are arranged as a concentric three-shell Au12@Ag20@Au12 Keplerate structure having a high symmetry. For the first time, the co-presence of three different types of anionic ligands (i.e., phenylalkynyl, 2-pyridylthiolate, and chloride) was revealed on the surface of metal nanoclusters. Similar to thiolates, alkynyls bind linearly to surface Au atoms using their σ-bonds, leading to the formation of two types of surface staple units (PhC≡C-Au-L, L = PhC≡C(-) or 2-pyridylthiolate) on the cluster. The co-presence of three different surface ligands allows the site-specific surface and functional modification of the cluster. The lability of PhC≡C(-) ligands on the cluster was demonstrated, making it possible to keep the metal core intact while removing partial surface capping. Moreover, it was found that ligand exchange on the cluster occurs easily to offer various derivatives with the same metal core but different surface functionality and thus different solubility.

A Tetrazine-Labile Vinyl Ether Benzyloxycarbonyl Protecting Group (VeZ): An Orthogonal Tool for Solid-Phase Peptide Chemistry.

PubMed

Staderini, Matteo; Gambardella, Alessia; Lilienkampf, Annamaria; Bradley, Mark

2018-06-01

The vinyl ether benzyloxycarbonyl (VeZ) protecting group is selectively cleaved by treatment with tetrazines via an inverse electron-demand Diels-Alder reaction. This represents a new orthogonal protecting group for solid-phase peptide synthesis, with Fmoc-Lys(VeZ)-OH as a versatile alternative to Fmoc-Lys(Alloc)-OH and Fmoc-Lys(Dde)-OH, as demonstrated by the synthesis of two biologically relevant cyclic peptides.

Sediment amino acids as indicators of anthropogenic activities and potential environmental risk in Erhai Lake, Southwest China.

PubMed

Ni, Zhaokui; Wang, Shengrui; Zhang, Mianmian

2016-05-01

Total hydrolysable amino acids (THAAs) constitute the most important fraction of labile nitrogen. Anthropogenic activities directly influence various biogeochemical cycles and then accelerate lake ecosystem deterioration. This is the first study that has established the relationship between sediment THAAs and anthropogenic activities using dated sediment cores, and evaluated the possibility of THAAs release at the sediment interface based on changes in environmental conditions in Erhai Lake. The results showed that historical distribution and fractions of THAAs could be divided into three stages: a stable period before the 1970s, a clear increasing period from the 1970s to 1990s, and a gradually steady period that started after the 1990s. The chemical fraction, aromatic and sulfur amino acids (AAs) accounted for only ≤3% of THAAs. Basic AAs accounted for 5-17% of THAAs, and remained at a relatively stable level. However, acidic and neutral AAs, which accounted for 19-44% and 35-69% of THAAs, respectively, were the predominant factors causing THAAs to increase due to rapid agricultural intensification and intensification of contemporary sedimentation of phytoplankton or macrophytes since the 1970s. These trends were closely related to both anthropogenic activities and natural processes, which implied that sediment THAAs could act as an effective indicator that reflects anthropogenic activities and aquatic environmental characteristics. The current contributions of sediment THAAs on TN and TOC were <5% and 1.5%, respectively. However, the dramatic increase in THAAs in the sediment cores indicated that there was a huge potential source of labile nitrogen for the overlying water under certain environmental conditions. Correlation analysis suggested that the release of THAAs was negatively correlated with pH, whereas positively correlated with bacterial number and degree of OM mineralization, which particularly depend on the stability of HFOM. Therefore, the risk of

Application of poly (ethyleneimine) solution as a binding agent in DGT technique for measurement of heavy metals in water.

PubMed

Sui, Dian-Peng; Fan, Hong-Tao; Li, Jing; Li, You; Li, Qiong; Sun, Ting

2013-09-30

A 0.050 mol L(-1) solution of poly (ethyleneimine) (PEI), had been used as a novel binding agent of diffusive gradients in thin-films (DGT) technique (PEI-DGT) for measuring the concentrations of labile Cu(2+), Cd(2+) and Pb(2+) in waters. The binding capacities of the PEI-DGT for Cu(2+), Cd(2+) and Pb(2+) were 11.8, 10.2 and 10.6 μmol L(-1), respectively. The performance of PEI-DGT was independence of pH in the range of 4-8 and ionic strength in the range from 1×10(-4) to 0.1 mol L(-1) (as NaNO3). PEI-DGT could measure 104.7±5.2% of the total concentration of Cd(2+) (0.500 mg L(-1)), 95.2±4.3% of the total Cu(2+) (0.500 mg L(-1)) and 99.2±3.4% of the total Pb(2+) (0.500 mg L(-1)) in synthetic solution. Effects of the ligands on the measurement of labile metals were also investigated in synthetic solutions containing the various concentrations of EDTA and humic acid. In EDTA solution, the concentrations of labile metals measured by PEI-DGT showed good agreement with the theoretical concentrations of free metal ions. In humic acid solution, the concentrations of labile metals measured by PEI-DGT decreased with the increase of the concentrations of humic acid. Several DGT devices with various binding agents, including PEI, sodium polyacrylate and poly(4-styrenesulfonate) solution, were used for the measurement of labile fractions of Cu(2+), Cd(2+) and Pb(2+) in the spiked waters and in mine wastewaters. The results showed that the concentrations of labile metal measured by DGT devices with different binding agents could be significantly different, indicating that the labile fractions of metals were dependent on the binding strength of the binding agents with metals. By choosing binding agents, the useful information on the speciation and bioavailability of the analytes can be provided. Copyright © 2013 Elsevier B.V. All rights reserved.

The influence of labile dietary methyl donors on the arginine requirement of young broiler chicks.

PubMed

Chamruspollert, M; Pesti, G M; Bakalli, R I

2002-08-01

Two experiments were conducted with Ross x Ross boiler chicks in battery brooders from 1 to 14 d of age to determine the influence of dietary methyl donors on the Arg requirement of young broiler chicks. Experiment 1 had a 6 x 2 factorial design, with six levels of Arg supplementation (0, 0.1, 0.2, 0.3, 0.4, and 0.5%) and two levels of DL-Met supplementation (0 and 0.2% of the diet). The design of Experiment 2 was identical to Experiment 1, except that a second source of labile methyl groups was added, 0.2% betaine (6 x 3 factorial arrangement). Both experiments had four replicate pens of 10 chicks each per treatment. The basal diet was based on corn (34.52%), whey (26.96%), corn gluten meal (16.53%), soybean meal (11.74%), and poultry fat (23% CP and 3.20 kcal/g of ME). At 14 d, three chicks per replicate were randomly killed, and breast muscle was collected and pooled for creatine analysis. The broken-line linear model was used to estimate the Arg requirements of the chicks. There were no differences in Arg requirements due to methyl source so the data were pooled. In Experiment 1, the Arg requirements were 1.17 +/- 0.04% for gain, 1.23 +/- 0.03% for feed conversion ratio (FCR), and 1.18 +/- 0.03% for muscle creatine, when the diet contained 0.45 or 0.65% Met. In Experiment 2, the Arg requirements were 1.20 +/- 0.05% for gain, 1.23 +/- 0.03% for FCR, and 1.26 +/- 0.02% for muscle creatine. There was no apparent difference in the Arg requirement of young broilers due to methyl donor supplementation.

Sources, transformation and fate of particulate amino acids and hexosamines under varying hydrological regimes in the tropical Wenchang/Wenjiao Rivers and Estuary, Hainan, China

NASA Astrophysics Data System (ADS)

Unger, Daniela; Herbeck, Lucia S.; Li, Min; Bao, Hongyan; Wu, Ying; Zhang, Jing; Jennerjahn, Tim

2013-04-01

The small tropical Wenchang and Wenjiao Rivers on the island of Hainan, tropical China, are affected by effluents from municipal sewage, aquaculture and agriculture, and by contrasting hydrological regimes related to monsoon and tropical storms. In order to obtain information on the sources, transformation and fate of organic matter (OM) we investigated the amount and composition of amino acids and hexosamines as well as the carbon isotope composition in suspended particulate matter (SPM) from the Wenchang/Wenjiao Estuary. SPM was collected along the salinity gradient starting from the river sites, along the lagoon-shaped Bamen Bay to coastal waters during four sampling campaigns between 2006 and 2009. SPM concentrations ranged between 4.7 and 58.2 mg L-1. Apart from highest values after heavy rain events in spring and summer, SPM showed little seasonal variation, but increased with salinity. From SPM POC% (1.2-20.9%), C/N (4.9-16.5) and δ13Corg (-31.5 to -19.5‰), the molar composition and content of amino acids and hexosamines (8.2-156.2 mg g-1 dry weight) and by comparison with sediments, mangroves, soils and plants we are able to show that soil-derived material, freshwater and marine plankton were the major sources of suspended OM. High POC and amino acid contents were related to primary production sustained by dissolved nutrients to a large extent stemming from municipal and aquaculture effluents. Factor analysis showed that the suite of biogeochemical parameters measured clearly depict the terrestrial vs. marine origin and the freshness/reactivity of OM. The four groups of samples resulting from cluster analysis were basically related to varying hydrological regimes. With respect to the sources, degradation and fate of particulate OM the major factors were: (i) the year round input of labile, amino acid rich riverine OM matter at the freshwater dominated sites, (ii) high input of degraded soil OM after heavy rains with dispersal throughout the estuary and

Pharmacokinetics and metabolic rates of acetyl salicylic acid and its metabolites in an Otomi ethnic group of Mexico.

PubMed

Lares-Asseff, Ismael; Juárez-Olguín, Hugo; Flores-Pérez, Janett; Guillé-Pérez, Adrian; Vargas, Arturo

2004-05-01

The objective of this study was to determine pharmacokinetic differences of acetyl salicylic acid (ASA) and its metabolites: gentisic acid (GA), salicylic acid (SA) and salicyluric acid (SUA) between Otomies and Mesticians healthy subjects. Design. Ten Otomies and 10 Mesticians were included. After a single dose of aspirin given orally (15 mg/kg), blood and urine samples were collected at different times. Results. Pharmacokinetic parameters of salicylates showed significant differences, except distribution volume of SA, and elimination half-life of SUA. Metabolic rates of ASA showed significant differences for all rates between both groups. On the other hand, percentages of dose excreted were more reduced for SA and SUA for the Otomies than for the Mesticians. Conclusion. Results reflect differences in the hydrolysis way i.e. from ASA to SA and aromatic hydroxylation i.e. from SA to GA, which were slower in Otomies subjects, showing a possible pharmacokinetic differences about the capabilities of ASA biotransformation as a consequence of ethnic differences.

Improving Phosphorus Availability in an Acid Soil Using Organic Amendments Produced from Agroindustrial Wastes

PubMed Central

Ch'ng, Huck Ywih; Ahmed, Osumanu Haruna; Majid, Nik Muhamad Ab.

2014-01-01

In acid soils, soluble inorganic phosphorus is fixed by aluminium and iron. To overcome this problem, acid soils are limed to fix aluminium and iron but this practice is not economical. The practice is also not environmentally friendly. This study was conducted to improve phosphorus availability using organic amendments (biochar and compost produced from chicken litter and pineapple leaves, resp.) to fix aluminium and iron instead of phosphorus. Amending soil with biochar or compost or a mixture of biochar and compost increased total phosphorus, available phosphorus, inorganic phosphorus fractions (soluble inorganic phosphorus, aluminium bound inorganic phosphorus, iron bound inorganic phosphorus, redundant soluble inorganic phosphorus, and calcium bound phosphorus), and organic phosphorus. This was possible because the organic amendments increased soil pH and reduced exchangeable acidity, exchangeable aluminium, and exchangeable iron. The findings suggest that the organic amendments altered soil chemical properties in a way that enhanced the availability of phosphorus in this study. The amendments effectively fixed aluminium and iron instead of phosphorus, thus rendering phosphorus available by keeping the inorganic phosphorus in a bioavailable labile phosphorus pool for a longer period compared with application of Triple Superphosphate without organic amendments. PMID:25032229

Structures of chloralide, ?-lactic acid chloralide, malic acid chloralide and citric acid chloralide

NASA Astrophysics Data System (ADS)

Koh, L. L.; Huang, H. H.; Chia, L. H. L.; Liang, E. P.

1995-06-01

The crystal and molecular structures of chloralide ( 1), D-lactic acid chloralide ( 2), malic acid chloralide ( 3) and citric acid chloralide ( 4) have been determined by X-ray diffraction methods. Compound 1 crystallizes in the monoclinic space group, {P2 1}/{c}, a = 6.201(2), b = 17.11(2), c = 10.357(6) Å, β = 95.21(4)°, Z = 4; compound 2 in the monoclinic space group P2 1, a = 7.600(4), b = 5.902(4), c = 9.743(6) Å, β = 99.20(5), Z = 2; compound 3 in the monoclinic space group {P2 1}/{c}, a = 16.500(6), b = 5.819(3), c = 10.120(4) Å, β = 91.41(3), Z = 4; compound 4 in the monoclinic space group {P2 1}/{c}, a = 12.041(3), b = 6.1190(10), c = 17.259(4) Å, β = 101.85(2), Z = 4. The five-membered ring systems of all the compounds are slightly twisted out-of-plane, that of compound 4 being the most puckered. The CCl 3 group is trans to the second CCl 3 group in 1, to the CH 3 group in 2 and to the CH 2COOH group in 3. The two CH 2COOH groups in 4 are disposed axially with respect to the ring. Dipole moment and Kerr constant data for D-lactic acid chloralide suggest a structure in solution which is consistent with the X-ray results. The IR spectra of 2, 3 and 4 are discussed in relation to the structures of these compounds.

Effects of supplementary folic acid and vitamin B(12) on hepatic metabolism of dairy cows according to methionine supply.

PubMed

Preynat, A; Lapierre, H; Thivierge, M C; Palin, M F; Cardinault, N; Matte, J J; Desrochers, A; Girard, C L

2010-05-01

The present experiment was undertaken to study the interactions between dietary supplements of rumen-protected methionine (RPM) and intramuscular injections of folic acid and vitamin B(12), given from 3 wk before calving to 16 wk of lactation, on hepatic metabolism of lactating dairy cows. Sixty multiparous Holstein cows were assigned to 10 blocks of 6 cows each according to their previous milk production. Within each block, 3 cows were fed a diet calculated to supply Met as 1.83% of metabolizable protein, whereas the 3 other cows were fed the same diet supplemented with 18g of RPM calculated to provide Met as 2.23% of metabolizable protein. Within each level of Met, the cows received no vitamin supplement or weekly intramuscular injections of 160mg of folic acid alone or combined with 10mg of vitamin B(12). Liver biopsies were taken at 2, 4, 8, and 16 wk of lactation. Liver concentrations of folates and vitamin B(12) were increased by their respective supplements but this response to vitamin supplements was altered by methionine supply. Concentrations of total lipids and triglycerides increased in livers of cows fed RPM, whereas concentrations of cholesterol ester, cholesterol, diglycerides, phosphatidylethanolamine, and phosphatidylcholine were not affected. Folic acid, alone or combined with vitamin B(12), tended to increase the ratio of phosphatidylcholine to phosphatidylethanolamine. Gene expression of 5,10-methylene-tetrahydrofolate reductase, microsomal transfer protein, and phosphatidylethanolamine methyltransferase were higher in liver of cows fed RPM supplements. The relative mRNA abundance of 5,10-methylene-tetrahydrofolate reductase and methylmalonyl-CoA mutase were increased by the combined injections of folic acid and vitamin B(12), whereas those of methionine synthase and methionine synthase reductase were not affected by treatments. These results suggest that increasing supply of methyl groups, as preformed labile methyl groups or through

Isolation and evolution of labile sulfur allotropes via kinetic encapsulation in interactive porous networks

PubMed Central

Kitagawa, Hakuba; Ohtsu, Hiroyoshi; Cruz-Cabeza, Aurora J.; Kawano, Masaki

2016-01-01

The isolation and characterization of small sulfur allotropes have long remained unachievable because of their extreme lability. This study reports the first direct observation of disulfur (S2) with X-ray crystallography. Sulfur gas was kinetically trapped and frozen into the pores of two Cu-based porous coordination networks containing interactive iodide sites. Stabilization of S2 was achieved either through physisorption or chemisorption on iodide anions. One of the networks displayed shape selectivity for linear molecules only, therefore S2 was trapped and remained stable within the material at room temperature and higher. In the second network, however, the S2 molecules reacted further to produce bent-S3 species as the temperature was increased. Following the thermal evolution of the S2 species in this network using X-ray diffraction and Raman spectroscopy unveiled the generation of a new reaction intermediate never observed before, the cyclo-tri­sulfur dication (cyclo-S3 2+). It is envisaged that kinetic guest trapping in interactive crystalline porous networks will be a promising method to investigate transient chemical species. PMID:27437110

Cell Motility by Labile Association of Molecules

PubMed Central

Inoué, Shinya; Sato, Hidemi

1967-01-01

This article summarizes our current views on the dynamic structure of the mitotic spindle and its relation to mitotic chromosome movements. The following statements are based on measurements of birefringence of spindle fibers in living cells, normally developing or experimentally modified by various physical and chemical agents, including high and low temperatures, antimitotic drugs, heavy water, and ultraviolet microbeam irradiation. Data were also obtained concomitantly with electron microscopy employing a new fixative and through measurements of isolated spindle protein. Spindle fibers in living cells are labile dynamic structures whose constituent filaments (microtubules) undergo cyclic breakdown and reformation. The dynamic state is maintained by an equilibrium between a pool of protein molecules and their linearly aggregated polymers, which constitute the microtubules or filaments. In living cells under physiological conditions, the association of the molecules into polymers is very weak (absolute value of ΔF 25°C < 1 kcal), and the equilibrium is readily shifted to dissociation by low temperature or by high hydrostatic pressure. The equilibrium is shifted toward formation of polymer by increase in temperature (with a large increase in entropy: ΔS 25°C ≃ 100 eu) or by the addition of heavy water. The spindle proteins tend to polymerize with orienting centers as their geometrical foci. The centrioles, kinetochores, and cell plate act as orienting centers successively during mitosis. Filaments are more concentrated adjacent to an orienting center and yield higher birefringence. Astral rays, continuous fibers, chromosomal fibers, and phragmoplast fibers are thus formed by successive reorganization of the same protein molecules. During late prophase and metaphase, polymerization takes place predominantly at the kinetochores; in metaphase and anaphase, depolymerization is prevalent near the spindle poles. When the concentration of spindle protein is high

Accurate Analysis and Evaluation of Acidic Plant Growth Regulators in Transgenic and Nontransgenic Edible Oils with Facile Microwave-Assisted Extraction-Derivatization.

PubMed

Liu, Mengge; Chen, Guang; Guo, Hailong; Fan, Baolei; Liu, Jianjun; Fu, Qiang; Li, Xiu; Lu, Xiaomin; Zhao, Xianen; Li, Guoliang; Sun, Zhiwei; Xia, Lian; Zhu, Shuyun; Yang, Daoshan; Cao, Ziping; Wang, Hua; Suo, Yourui; You, Jinmao

2015-09-16

Determination of plant growth regulators (PGRs) in a signal transduction system (STS) is significant for transgenic food safety, but may be challenged by poor accuracy and analyte instability. In this work, a microwave-assisted extraction-derivatization (MAED) method is developed for six acidic PGRs in oil samples, allowing an efficient (<1.5 h) and facile (one step) pretreatment. Accuracies are greatly improved, particularly for gibberellin A3 (-2.72 to -0.65%) as compared with those reported (-22 to -2%). Excellent selectivity and quite low detection limits (0.37-1.36 ng mL(-1)) are enabled by fluorescence detection-mass spectrum monitoring. Results show the significant differences in acidic PGRs between transgenic and nontransgenic oils, particularly 1-naphthaleneacetic acid (1-NAA), implying the PGRs induced variations of components and genes. This study provides, for the first time, an accurate and efficient determination for labile PGRs involved in STS and a promising concept for objectively evaluating the safety of transgenic foods.

Amino group of salicylic acid exhibits enhanced inhibitory potential against insulin amyloid fibrillation with protective aptitude toward amyloid induced cytotoxicity.

PubMed

Zaman, Masihuz; Khan, Mohsin Vahid; Zakariya, Syed Mohammad; Nusrat, Saima; Meeran, Syed Mustapha; Alam, Parvez; Ajmal, Mohammad Rehan; Wahiduzzaman, Wahiduzzaman; Shahein, Yasser E; Abouelella, Amira M; Khan, Rizwan Hasan

2018-05-01

Protein misfolding and aggregation lead to amyloid generation that in turn may induce cell membrane disruption and leads to cell apoptosis. In an effort to prevent or treat amyloidogenesis, large number of studies has been paying attention on breakthrough of amyloid inhibitors. In the present work, we aim to access the effect of two drugs, that is, acetylsalicylic acid and 5-amino salicylic acid on insulin amyloids by using various biophysical, imaging, cell viability assay, and computational approaches. We established that both drugs reduce the turbidity, light scattering and fluorescence intensity of amyloid indicator dye thioflavin T. Premixing of drugs with insulin inhibited the nucleation phase and inhibitory potential was boosted by increasing the concentration of the drug. Moreover, addition of drugs at the studied concentrations attenuated the insulin fibril induced cytotoxicity in breast cancer cell line MDA-MB-231. Our results highlight the amino group of salicylic acid exhibited enhanced inhibitory effects on insulin fibrillation in comparison to acetyl group. It may be due to presence of amino group that helps it to prolong the nucleation phase with strong binding as well as disruption of aromatic and hydrophobic stacking that plays a key role in amyloid progression. © 2017 Wiley Periodicals, Inc.

Hot regions of labile and stable soil organic carbon in Germany - Spatial variability and driving factors

NASA Astrophysics Data System (ADS)

Vos, Cora; Jaconi, Angélica; Jacobs, Anna; Don, Axel

2018-06-01

Atmospheric carbon dioxide levels can be mitigated by sequestering carbon in the soil. Sequestration can be facilitated by agricultural management, but its influence is not the same on all soil carbon pools, as labile pools with a high turnover may be accumulated much faster but are also more vulnerable to losses. The aims of this study were to (1) assess how soil organic carbon (SOC) is distributed among SOC fractions on a national scale in Germany, (2) identify factors influencing this distribution and (3) identify regions with high vulnerability to SOC losses. The SOC content and proportion of two different SOC fractions were estimated for more than 2500 mineral topsoils (< 87 g kg-1 SOC) covering Germany, using near-infrared reflectance spectroscopy. Drivers of the spatial variability in SOC fractions were determined using the machine learning algorithm cforest. The SOC content and proportions of fractions were predicted with good accuracy (SOC content: R2 = 0.87-0.90; SOC proportions: R2 = 0.83; ratio of performance to deviation (RPD): 2.4-3.2). The main explanatory variables for the distribution of SOC among the fractions were soil texture, bulk soil C / N ratio, total SOC content and pH. For some regions, the drivers were linked to the land-use history of the sites. Arable topsoils in central and southern Germany were found to contain the highest proportions and contents of stable SOC fractions, and therefore have the lowest vulnerability to SOC losses. North-western Germany contains an area of sandy soils with unusually high SOC contents and high proportions of light SOC fractions, which are commonly regarded as representing a labile carbon pool. This is true for the former peat soils in this area, which have already lost and are at high risk of losing high proportions of their SOC stocks. Those black sands can, however, also contain high amounts of stable SOC due to former heathland vegetation and need to be treated and discussed separately from non

Amino acid ionic liquids.

PubMed

Ohno, Hiroyuki; Fukumoto, Kenta

2007-11-01

The preparation of ionic liquids derived from amino acids, and their properties, are outlined. Since amino acids have both a carboxylic acid residue and an amino group in a single molecule, they can be used as either anions or cations. These groups are also useful in their ability to introduce functional group(s). Twenty different natural amino acids were used as anions, to couple with the 1-ethyl-3-methylimidazolium cation. The salts obtained were all liquid at room temperature. The properties of the resulting ionic liquids (AAILs) depend on the side groups of the amino acids involved. These AAILs, composed of an amino acid with some functional groups such as a hydrogen bonding group, a charged group, or an aromatic ring, had an increased glass transition (or melting) temperature and/or higher viscosity as a result of additional interactions among the ions. Viscosity is reduced and the decomposition temperature of imidazolium-type salts is improved by using the tetrabutylphosphonium cation. The chirality of AAILs was maintained even upon heating to 150 degrees C after acetylation of the free amino group. The amino group was also modified to introduce a strong acid group so as to form hydrophobic and chiral ionic liquids. Unique phase behavior of the resulting hydrophobic ionic liquids and water mixture is found; the mixture is clearly phase separated at room temperature, but the solubility of water in this IL increases upon cooling, to give a homogeneous solution. This phase change is reversible, and separation occurs again by raising the temperature a few degrees. It is extraordinary for an IL/water mixture to display such behavior with a lower critical solution temperature. Some likely applications are proposed for these amino acid derived ionic liquids.

Immunization with Salmonella Enteritidis secreting mucosal adjuvant labile toxin confers protection against wild type challenge via augmentation of CD3+CD4+ T-cell proliferation and enhancement of IFN-γ, IL-6 and IL-10 expressions in chicken.

PubMed

Lalsiamthara, Jonathan; Lee, John Hwa

2017-02-01

The protective efficacy and immunological profiles of chickens immunized with an attenuated Salmonella Enteritidis (SE) constitutively secreting double mutant heat labile enterotoxin (dmLT) were investigated. The dmLT is a detoxified variant of Escherichia coli heat labile toxin and is a potent mucosal adjuvant capable of inducing both humoral and cell-mediated immunity. In this study, four-week-old chickens were inoculated with SE-dmLT strain JOL1641, parental SE strain JOL1087 or phosphate buffered saline control. Peripheral blood mononuclear cells of SE-dmLT inoculated birds showed significant proliferation upon stimulation with SE antigens as compared to the control and JOL1087 groups (P⩽0.05). One week post-challenge, the ratio of CD3 + CD4 + to CD3 + CD8 + T-cells showed a significant increase in the immunized groups. Significant increases in IFN-γ levels were observed in JOL1641 birds immunized via oral and intramuscular routes. While immunizations with the JOL1087 strain via the intramuscular route also induced significant increases in IFN-γ, immunization via the oral route did not trigger significant changes. Pro-inflammatory cytokine IL-6 was also elevated significantly in immunized birds; a significant elevation of IL-10 was observed only in oral immunization with JOL1641 (P⩽0.05). JOL1641 immunized birds showed significant reduction of challenge bacterial-organ recovery as compared to JOL1087 and non-immunized birds. Collectively, our results revealed that immunization with the adjuvant-secreting S. Enteritidis confers protection against wild type SE challenge via induction of strong cell proliferative response, augmentation of CD3 + CD4 + : CD3 + CD8 + T-cells ratio and enhancement of IFN-γ, IL-6 and IL-10 cytokine secretion. Copyright © 2016 Elsevier Ltd. All rights reserved.

Acetic acid bacteria: A group of bacteria with versatile biotechnological applications.

PubMed

Saichana, Natsaran; Matsushita, Kazunobu; Adachi, Osao; Frébort, Ivo; Frebortova, Jitka

2015-11-01

Acetic acid bacteria are gram-negative obligate aerobic bacteria assigned to the family Acetobacteraceae of Alphaproteobacteria. They are members of the genera Acetobacter, Gluconobacter, Gluconacetobacter, Acidomonas, Asaia, Kozakia, Swaminathania, Saccharibacter, Neoasaia, Granulibacter, Tanticharoenia, Ameyamaea, Neokomagataea, and Komagataeibacter. Many strains of Acetobacter and Komagataeibacter have been known to possess high acetic acid fermentation ability as well as the acetic acid and ethanol resistance, which are considered to be useful features for industrial production of acetic acid and vinegar, the commercial product. On the other hand, Gluconobacter strains have the ability to perform oxidative fermentation of various sugars, sugar alcohols, and sugar acids leading to the formation of several valuable products. Thermotolerant strains of acetic acid bacteria were isolated in order to serve as the new strains of choice for industrial fermentations, in which the cooling costs for maintaining optimum growth and production temperature in the fermentation vessels could be significantly reduced. Genetic modifications by adaptation and genetic engineering were also applied to improve their properties, such as productivity and heat resistance. Copyright © 2014 Elsevier Inc. All rights reserved.

Stereospecific Palladium-Catalyzed C-H Arylation of Pyroglutamic Acid Derivatives at the C3 Position Enabled by 8-Aminoquinoline as a Directing Group.

PubMed

Verho, Oscar; Maetani, Micah; Melillo, Bruno; Zoller, Jochen; Schreiber, Stuart L

2017-09-01

An efficient and stereospecific Pd-catalyzed protocol for the C-H arylation of pyroglutamic acid derivatives that uses 8-aminoquinoline as a directing group is described. The reaction was shown to proceed efficiently with a variety of aryl and heteroaryl iodides bearing different functional groups, giving C3-arylated cis products in good to high yields. Removal of the 8-aminoquinoline unit from these C-H arylation products enables access to synthetically useful cis and trans pyroglutamic acid-based building blocks.

The Distant Double Bond Determines the Fate of the Carboxylic Group in the Dissociative Photoionization of Oleic Acid.

PubMed

Heringa, Maarten F; Slowik, Jay G; Goldmann, Maximilian; Signorell, Ruth; Hemberger, Patrick; Bodi, Andras

2017-12-15

The valence threshold photoionization of oleic acid has been studied using synchrotron VUV radiation and imaging photoelectron photoion coincidence (iPEPICO) spectroscopy. An oleic acid aerosol beam was impacted on a copper thermodesorber, heated to 130 °C, to evaporate the particles quantitatively. Upon threshold photoionization, oleic acid produces the intact parent ion first, followed by dehydration at higher energies. Starting at ca. 10 eV, a large number of fragment ions slowly rise suggesting several fragmentation coordinates with quasi-degenerate activation energies. However, water loss is the dominant low-energy dissociation channel, and it is shown to be closely related to the unsaturated carbon chain. In the lowest-barrier process, one of the four allylic hydrogen atoms is transferred to the carboxyl group to form the leaving water molecule and a cyclic ketone fragment ion. A statistical model to analyze the breakdown diagram and measured rate constants yields a 0 K appearance energy of 9.77 eV, which can be compared with the density functional theory result of 9.19 eV. Alternative H-transfer steps yielding a terminal C=O group are ruled out based on energetics and kinetics arguments. Some of the previous photoionization mass spectrometric studies also reported 2 amu and 26 amu loss fragment ions, corresponding to hydrogen and acetylene loss. We could not identify such peaks in the mass spectrum of oleic acid. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Studies on interaction of acid-treated nanotube titanic acid and amino acids].

PubMed

Zhang, Huqin; Chen, Xuemei; Jin, Zhensheng; Liao, Guangxi; Wu, Xiaoming; Du, Jianqiang; Cao, Xiang

2010-06-01

Nanotube titanic acid (NTA) has distinct optical and electrical character, and has photocatalysis character. In accordance with these qualities, NTA was treated with acid so as to enhance its surface activity. Surface structures and surface groups of acid-treated NTA were characterized and analyzed by Transmission Electron Microscope (TEM) and Fourier Transform Infrared Spectrometry (FT-IR). The interaction between acid-treated NTA and amino acids was investigated. Analysis results showed that the lengths of acid-treated NTA became obviously shorter. The diameters of nanotube bundles did not change obviously with acid-treating. Meanwhile, the surface of acid-treated NTA was cross-linked with carboxyl or esterfunction. In addition, acid-treated NTA can catch amino acid residues easily, and then form close combination.

Priming effects on labile and stable soil organic carbon decomposition: Pulse dynamics over two years

PubMed Central

Han, Xiaozeng; Yu, Wantai; Wang, Peng; Cheng, Weixin

2017-01-01

Soil organic carbon (SOC) is a major component in the global carbon cycle. Yet how input of plant litter may influence the loss of SOC through a phenomenon called priming effect remains highly uncertain. Most published results about the priming effect came from short-term investigations for a few weeks or at the most for a few months in duration. The priming effect has not been studied at the annual time scale. In this study for 815 days, we investigated the priming effect of added maize leaves on SOC decomposition of two soil types and two treatments (bare fallow for 23 years, and adjacent old-field, represent stable and relatively labile SOC, respectively) of SOC stabilities within each soil type, using a natural 13C-isotope method. Results showed that the variation of the priming effect through time had three distinctive phases for all soils: (1) a strong negative priming phase during the first period (≈0–90 days); (2) a pulse of positive priming phase in the middle (≈70–160 and 140–350 days for soils from Hailun and Shenyang stations, respectively); and (3) a relatively stabilized phase of priming during the last stage of the incubation (>160 days and >350 days for soils from Hailun and Shenyang stations, respectively). Because of major differences in soil properties, the two soil types produced different cumulative priming effects at the end of the experiment, a positive priming effect of 3–7% for the Mollisol and a negative priming effect of 4–8% for the Alfisol. Although soil types and measurement times modulated most of the variability of the priming effect, relative SOC stabilities also influenced the priming effect for a particular soil type and at a particular dynamic phase. The stable SOC from the bare fallow treatment tended to produce a narrower variability during the first phase of negative priming and also during the second phase of positive priming. Averaged over the entire experiment, the stable SOC (i.e., the bare fallow) was at

Discovery and characterization of sialic acid O-acetylation in group B Streptococcus.

PubMed

Lewis, Amanda L; Nizet, Victor; Varki, Ajit

2004-07-27

Group B Streptococcus (GBS) is the leading cause of human neonatal sepsis and meningitis. The GBS capsular polysaccharide is a major virulence factor and the active principle of vaccines in phase II trials. All GBS capsules have a terminal alpha 2-3-linked sialic acid [N-acetylneuraminic acid (Neu5Ac)], which interferes with complement-mediated killing. We show here that some of the Neu5Ac residues of the GBS type III capsule are O-acetylated at carbon position 7, 8, or 9, a major modification evidently missed in previous studies. Data are consistent with initial O-acetylation at position 7, and subsequent migration of the O-acetyl ester at positions 8 and 9. O-acetylation was also present on several other GBS serotypes (Ia, Ib, II, V, and VI). Deletion of the CMP-Neu5Ac synthase gene neuA by precise, in-frame allelic replacement gave intracellular accumulation of O-acetylated Neu5Ac, whereas overexpression markedly decreased O-acetylation. Given the known GBS Neu5Ac biosynthesis pathway, these data indicate that O-acetylation occurs on free Neu5Ac, competing with the CMP-Neu5Ac synthase. O-acetylation often generates immunogenic epitopes on bacterial capsular polysaccharides and can modulate human alternate pathway complement activation. Thus, our discovery has important implications for GBS pathogenicity, immunogenicity, and vaccine design.

[Folic acid fortified foods available in Spain: types of products, level of fortification and target population groups].

PubMed

Samaniego Vaesken, M L; Alonso-Aperte, E; Varela-Moreiras, G

2009-01-01

Folic acid is a potentially relevant factor in the prevention of a number of pathologies (congenital abnormalities, cardiovascular disease, colorectal cancer and neurocognitive decline). This has led to the introduction of different strategies in order to increase folate intake: nutritional education, pharmacological supplementation and mandatory or voluntary fortification of staple foods with folic acid. In Spain there is a growing number of folic acid fortified products on a voluntary basis, but there is also a lack of reliable data to assess their impact on the population's dietary folate intakes. To gather a better knowledge of folic acid food fortification practices in Spain. A Food Composition Database was developed using data from a market study. Also, previously published data of unfortified staple foods from Food Composition Tables was reviewed. The Database included 260 folic acid fortified food items and it was periodically updated. Food groups included were primarily "Cereals and derivatives" (52%) followed by "Dairy products". Most of these foodstuffs lacked a target population for their consumption (37%) or were aimed at "Weight control" (28%) and "Children" (23%), but only 2% targeted women at a reproductive age. Number of unfortified foods included was 690. Fortification levels declared by manufacturers ranged between 15 and 430% of the Recommended Dietary Allowances (RDA) for folic acid per 100 g/ml, and simultaneous addition of B6 and B12 vitamins was observed in 75% of the products. Currently, Spain market offers a significant number of folic acid fortified products on a voluntary basis and at a level > or = 15% of the RDA per 100 g/ml or serving declared by manufacturers.

Affect-based profiles of bulimia nervosa: The utility and validity of indicators assessed in the natural environment.

PubMed

Leraas, Bethany C; Smith, Kathryn E; Utzinger, Linsey M; Cao, Li; Engel, Scott G; Crosby, Ross D; Mitchell, James E; Wonderlich, Stephen A

2018-01-01

Theoretical conceptualizations of bulimia nervosa (BN) emphasize the role of emotion dysregulation in the development and maintenance of symptoms, which has been supported by ecological momentary assessment studies. Given the importance of affective disturbances in BN, this study aimed to classify a sample of adult women with BN (N = 130) based on primarily momentary affective indicators, including negative and positive affect, negative and positive affective lability, and depression. Participants completed baseline assessments followed by a two-week ecological momentary assessment protocol. Latent profile analysis revealed four groups: (1) a "stable normal" group characterized by low affective lability and intensity; (2) a "stable depressed" group characterized by low affective lability and higher affect intensity; (3) an "unstable normal" group characterized by higher affective lability but lower affect intensity; and (4) an "unstable depressed" group characterized by higher affective lability and intensity. The stable depressed group evidenced the highest levels of eating psychopathology, borderline personality traits, and childhood trauma history, while the stable normal group generally evidenced the lowest levels of psychopathology. The findings demonstrate significant heterogeneity in the topography of affect experienced by individuals with BN, and suggest that chronic, intense negative affect may be particularly important to address in treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

Elution of Labile Fluorescent Dye from Nanoparticles during Biological Use

PubMed Central

Tenuta, Tiziana; Monopoli, Marco P.; Kim, JongAh; Salvati, Anna; Dawson, Kenneth A.; Sandin, Peter; Lynch, Iseult

2011-01-01

Cells act as extremely efficient filters for elution of unbound fluorescent tags or impurities associated with nanoparticles, including those that cannot be removed by extensive cleaning. This has consequences for quantification of nanoparticle uptake and sub-cellular localization in vitro and in vivo as a result of the presence of significant amount of labile dye even following extensive cleaning by dialysis. Polyacrylamide gel electrophoresis (PAGE) can be used to monitor the elution of unbound fluorescent probes from nanoparticles, either commercially available or synthesized in-house, and to ensure their complete purification for biological studies, including cellular uptake and sub-cellular localisation. Very different fluorescence distribution within cells is observed after short dialysis times versus following extensive dialysis against a solvent in which the free dye is more soluble, due to the contribution from free dye. In the absence of an understanding of the presence of residual free dye in (most) labeled nanoparticle solutions, the total fluorescence intensity in cells following exposure to nanoparticle solutions could be mis-ascribed to the presence of nanoparticles through the cell, rather than correctly assigned to either a combination of free-dye and nanoparticle-bound dye, or even entirely to free dye depending on the exposure conditions (i.e. aggregation of the particles etc). Where all of the dye is nanoparticle-bound, the particles are highly localized in sub-cellular organelles, likely lysosomes, whereas in a system containing significant amounts of free dye, the fluorescence is distributed through the cell due to the free diffusion of the molecule dye across all cellular barriers and into the cytoplasm. PMID:21998668

A Clostridium Group IV Species Dominates and Suppresses a Mixed Culture Fermentation by Tolerance to Medium Chain Fatty Acids Products

PubMed Central

Andersen, Stephen J.; De Groof, Vicky; Khor, Way Cern; Roume, Hugo; Props, Ruben; Coma, Marta; Rabaey, Korneel

2017-01-01

A microbial community is engaged in a complex economy of cooperation and competition for carbon and energy. In engineered systems such as anaerobic digestion and fermentation, these relationships are exploited for conversion of a broad range of substrates into products, such as biogas, ethanol, and carboxylic acids. Medium chain fatty acids (MCFAs), for example, hexanoic acid, are valuable, energy dense microbial fermentation products, however, MCFA tend to exhibit microbial toxicity to a broad range of microorganisms at low concentrations. Here, we operated continuous mixed population MCFA fermentations on biorefinery thin stillage to investigate the community response associated with the production and toxicity of MCFA. In this study, an uncultured species from the Clostridium group IV (related to Clostridium sp. BS-1) became enriched in two independent reactors that produced hexanoic acid (up to 8.1 g L−1), octanoic acid (up to 3.2 g L−1), and trace concentrations of decanoic acid. Decanoic acid is reported here for the first time as a possible product of a Clostridium group IV species. Other significant species in the community, Lactobacillus spp. and Acetobacterium sp., generate intermediates in MCFA production, and their collapse in relative abundance resulted in an overall production decrease. A strong correlation was present between the community composition and both the hexanoic acid concentration (p = 0.026) and total volatile fatty acid concentration (p = 0.003). MCFA suppressed species related to Clostridium sp. CPB-6 and Lactobacillus spp. to a greater extent than others. The proportion of the species related to Clostridium sp. BS-1 over Clostridium sp. CPB-6 had a strong correlation with the concentration of octanoic acid (p = 0.003). The dominance of this species and the increase in MCFA resulted in an overall toxic effect on the mixed community, most significantly on the Lactobacillus spp., which resulted in a decrease in total

Toll-Like Receptor 2 Mediates Cellular Activation by the B Subunits of Type II Heat-Labile Enterotoxins

PubMed Central

Hajishengallis, George; Tapping, Richard I.; Martin, Michael H.; Nawar, Hesham; Lyle, Elizabeth A.; Russell, Michael W.; Connell, Terry D.

2005-01-01

The type II heat-labile enterotoxins (LT-IIa and LT-IIb) of Escherichia coli have an AB5 subunit structure similar to that of cholera toxin (CT) and other type I enterotoxins, despite significant differences in the amino acid sequences of their B subunits and different ganglioside receptor specificities. LT-II holotoxins and their nontoxic B subunits display unique properties as immunological adjuvants distinct from those of CT and its B subunits. In contrast to type II holotoxins, the corresponding pentameric B subunits, LT-IIaB and LT-IIbB, stimulated cytokine release in both human and mouse cells dependent upon Toll-like receptor 2 (TLR2). Induction of interleukin-1β (IL-1β), IL-6, IL-8, or tumor necrosis factor alpha in human THP-1 cells by LT-IIaB or LT-IIbB was inhibited by anti-TLR2 but not by anti-TLR4 antibody. Furthermore, transient expression of TLR1 and TLR2 in human embryonic kidney 293 cells resulted in activation of a nuclear factor-κB-dependent luciferase gene in response to LT-IIaB or LT-IIbB. Moreover, peritoneal macrophages from TLR2-deficient mice failed to respond to LT-IIaB or LT-IIbB, in contrast to wild-type or TLR4-deficient cells. These results demonstrate that besides their established binding to gangliosides, the B subunits of type II enterotoxins also interact with TLR2. Although a ganglioside-nonbinding mutant (T34I) of LT-IIaB effectively induced cytokine release, a phenotypically similar point mutation (T13I) in LT-IIbB abrogated cytokine induction, suggesting a variable requirement for gangliosides as coreceptors in TLR2 agonist activity. TLR2-dependent activation of mononuclear cells by type II enterotoxin B subunits appears to be a novel mechanism whereby these molecules may exert their immunomodulatory and adjuvant activities. PMID:15731031

Preparation of the very acid-sensitive Fmoc-Lys(Mtt)-OH. Application in the synthesis of side-chain to side-chain cyclic peptides and oligolysine cores suitable for the solid-phase assembly of MAPs and TASPs.

PubMed

Aletras, A; Barlos, K; Gatos, D; Koutsogianni, S; Mamos, P

1995-05-01

N alpha-9-Fluorenylmethoxycarbonyl-N epsilon-4=methyltrityl-lysine, [Fmoc-Lys(Mtt)-OH], was prepared in two steps from lysine, in 42% overall yield. The N epsilon-Mtt function can be quantitatively removed upon treatment with 1% TFA in dichloromethane or with a 1:2:7 mixture of acetic acid/trifluoroethanol/dichloromethane for 30 min and 1 h at room temperature, respectively. Under these conditions, groups of the tert-butyl type and peptide ester bonds to TFA-labile resins, such as the 2-chlorodiphenylmethyl- and the Wang-resin, remained intact. The utility of the new derivative in peptide synthesis has been exemplified with the synthesis of a cyclic cholecystokinin analog. As an example of further application, five types of lysine cores suitable for the solid-phase synthesis of one, two or three epitopes containing antigenic peptides or template-assembled synthetic proteins have been synthesized on Merrifield, Wang and 2-chlorodiphenylmethyl resin.

Comparative studies on the interaction of caffeic acid, chlorogenic acid and ferulic acid with bovine serum albumin

NASA Astrophysics Data System (ADS)

Li, Shuang; Huang, Kelong; Zhong, Ming; Guo, Jun; Wang, Wei-zheng; Zhu, Ronghua

2010-10-01

The substitution of the hydrogen on aromatic and esterification of carboxyl group of the phenol compounds plays an important role in their bio-activities. In this paper, caffeic acid (CaA), chlorogenic acid (ChA) and ferulic acid (FA) were selected to investigate the binding to bovine serum albumin (BSA) using UV absorption spectroscopy, fluorescence spectroscopy and synchronous fluorescence spectroscopy. It was found that the methoxyl group substituting for the 3-hydroxyl group of CaA decreased the affinity for BSA and the esterification of carboxyl group of CaA with quinic acid increased the affinities. The affinities of ChA and FA with BSA were more sensitive to the temperature than that of CaA with BSA. Synchronous fluorescence spectroscopy and time-resolved fluorescence indicated that the Stern-Volmer plots largely deviated from linearity at high concentrations and were caused by complete quenching of the tyrosine fluorescence of BSA.

Effects of EDTA and low molecular weight organic acids on soil solution properties of a heavy metal polluted soil.

PubMed

Wu, L H; Luo, Y M; Christie, P; Wong, M H

2003-02-01

A pot experiment was conducted to study the effects of EDTA and low molecular weight organic acids (LMWOA) on the pH, total organic carbon (TOC) and heavy metals in the soil solution in the rhizosphere of Brassica juncea grown in a paddy soil contaminated with Cu, Zn, Pb and Cd. The results show that EDTA and LMWOA have no effect on the soil solution pH. EDTA addition significantly increased the TOC concentrations in the soil solution. The TOC concentrations in treatments with EDTA were significantly higher than those in treatments with LMWOA. Adding 3 mmol kg(-1) EDTA to the soil markedly increased the total concentrations of Cu, Zn, Pb and Cd in the soil solution. Compared to EDTA, LMWOA had a very small effect on the metal concentrations. Total concentrations in the soil solution followed the sequence: EDTA > citric acid (CA) approximately oxalic acid (OA) approximately malic acid (MA) for Cu and Pb; EDTA > MA > CA approximately OA for Zn; and EDTA > MA > CA > OA for Cd. The labile concentrations of Cu, Zn, Pb and Cd showed similar trends to the total concentrations.

Characteristics of the surface chemistry of linden pyrochar after removal of labile organic matter

NASA Astrophysics Data System (ADS)

Valeeva, A. A.; Smirnova, E. V.; Giniyatullin, K. G.; Vorobev, V. V.; Biktasheva, L. R.; Grachev, A. N.

2018-01-01

The changes of chemical properties of the pyrochar surface were studied in the laboratory experiment that simulated pedogenic transformation of pyrochar under the influence of soil biota. The native pyrochar samples were obtained by pyrolysis of linden wood residues at the temperature of 250°C, 450°C and 650°C. Their modified samples were obtained by removing an easily degradable pool of organic substances that can be used by microorganisms during the first months after application to the soil. In low-temperature linden pyrochar (250°C and 450°C) dominated carboxylic and phenolic surface groups, in high-temperature (650°C) - lactonic groups. After removal of readily decomposable organic substances the acidity of the phenolic and lactonic groups in pyrochar of low-temperature pyrolysis sharply decreased. Characteristic feature of all studied samples is the presence in IR spectra of absorption bands of gyroxyl, carbonyl, methylene groups and organosilicon polymers. The feature of IR spectra of linden pyrochar (250°C and 450°C) is the presence of absorption bands of the stretching vibrations of the tertiary alcohols and phenols C-O group.

Influence of metal loading and humic acid functional groups on the complexation behavior of trivalent lanthanides analyzed by CE-ICP-MS.

PubMed

Kautenburger, Ralf; Hein, Christina; Sander, Jonas M; Beck, Horst P

2014-03-13

The complexation behavior of Aldrich humic acid (AHA) and a modified humic acid (AHA-PB) with blocked phenolic hydroxyl groups for trivalent lanthanides (Ln) is compared, and their influence on the mobility of Ln(III) in an aquifer is analyzed. As speciation technique, capillary electrophoresis (CE) was hyphenated with inductively coupled plasma mass spectrometry (ICP-MS). For metal loading experiments 25 mg L(-1) of AHA and different concentrations (cLn(Eu+Gd)=100-6000 μg L(-1)) of Eu(III) and Gd(III) in 10mM NaClO4 at pH 5 were applied. By CE-ICP-MS, three Ln-fractions, assumed to be uncomplexed, weakly and strongly AHA-complexed metal can be detected. For the used Ln/AHA-ratios conservative complex stability constants log βLnAHA decrease from 6.33 (100 μg L(-1) Ln(3+)) to 4.31 (6000 μg L(-1) Ln(3+)) with growing Ln-content. In order to verify the postulated weaker and stronger humic acid binding sites for trivalent Eu and Gd, a modified AHA with blocked functional groups was used. For these experiments 500 μg L(-1) Eu and 25 mg L(-1) AHA and AHA-PB in 10mM NaClO4 at pH-values ranging from 3 to 10 have been applied. With AHA-PB, where 84% of the phenolic OH-groups and 40% of the COOH-groups were blocked, Eu complexation was significantly lower, especially at the strong binding sites. The log β-values decrease from 6.11 (pH 10) to 5.61 at pH 3 (AHA) and for AHA-PB from 6.01 (pH 7) to 3.94 at pH 3. As a potential consequence, particularly humic acids with a high amount of strong binding sites (e.g. phenolic OH- and COOH-groups) can be responsible for a higher metal mobility in the aquifer due to the formation of dissolved negatively charged metal-humate species. Copyright © 2014 Elsevier B.V. All rights reserved.

Comparison of histological effects of polydeoxyribonucleic acid and hyaluronic acid in experimentally induced osteoarthritis of the knee joints of rats

PubMed Central

Karahan, Nazım; Arslan, İlyas; Orak, Müfit; Midi, Ahmet; Yücel, İstemi

2017-01-01

Aim: The histological effects of intra-articular polydeoxyribonucleic acid and hyaluronic acid in experimentally induced osteoarthritis of the knee joints of rats were investigated. Methods: Thirty rats were divided into three groups, i.e. polydeoxyribonucleic acid group, hyaluronic acid group and saline group. Osteoarthritis of the knee joints of the rats were induced by acl- transection. The polydeoxyribonucleic group was injected with 100 µg (0.05 cc) polydeoxyribonucleic acid. The hyaluronic acid group was injected with 100 µg (0.05 cc) hyaluronic acid, and the saline group was injected with 50 µl (0.05 cc) of 0.9% sodium chloride solution. All of the rats were sacrificed on day 29 and the right knee joints were prepared, and evaluated histologically by Mankin classification. Findings: The differences in total Mankin scores between the three groups were statistically significant (P < 0.01). The differences in total Mankin scores between the polydeoxyribonucleic acid group and the hyaluronic acid group were statistically significant (P < 0.01). The differences in total Mankin scores between hyaluronic acid group and saline group were statistically significant (P < 0.01). Tidemark continuity in all the specimens of the polydeoxyribonucleic acid group was noteworthy. Conclusion: The present study shows that more chondroprotective effect and less degeneration was observed with intra-articularly delivered polydeoxyribonucleic acid compared to hyaluronic acid and saline solution in the experimentally induced osteoarthritis of the knee joints of rats.

Baseline fatty acids, food groups, a diet score and 50-year all-cause mortality rates. An ecological analysis of the Seven Countries Study.

PubMed

Menotti, Alessandro; Kromhout, Daan; Puddu, Paolo Emilio; Alberti-Fidanza, Adalberta; Hollman, Peter; Kafatos, Anthony; Tolonen, Hanna; Adachi, Hisashi; Jacobs, David R

2017-12-01

This analysis deals with the ecologic relationships of dietary fatty acids, food groups and the Mediterranean Adequacy Index (MAI, derived from 15 food groups) with 50-year all-cause mortality rates in 16 cohorts of the Seven Countries Study. A dietary survey was conducted at baseline in cohorts subsamples including chemical analysis of food samples representing average consumptions. Ecologic correlations of dietary variables were computed across cohorts with 50-year all-cause mortality rates, where 97% of men had died. There was a 12-year average age at death population difference between extreme cohorts. In the 1960s the average population intake of saturated (S) and trans (T) fatty acids and hard fats was high in the northern European cohorts while monounsaturated (M), polyunsaturated (P) fatty acids and vegetable oils were high in the Mediterranean areas and total fat was low in Japan. The 50-year all-cause mortality rates correlated (r= -0.51 to -0.64) ecologically inversely with the ratios M/S, (M + P)/(S + T) and vegetable foods and the ratio hard fats/vegetable oils. Adjustment for high socio-economic status strengthened (r= -0.62 to -0.77) these associations including MAI diet score. The protective fatty acids and vegetable oils are indicators of the low risk traditional Mediterranean style diets. KEY MESSAGES We aimed at studying the ecologic relationships of dietary fatty acids, food groups and the Mediterranean Adequacy Index (MAI, derived from 15 food groups) with 50-year all-cause mortality rates in the Seven Countries Study. The 50-year all-cause mortality rates correlated (r = -0.51 to -0.64) ecologically inversely with the ratios M/S [monounsaturated (M) + polyunsaturated (P)]/[saturated (S) + trans (T)] fatty acids and vegetable foods and the ratio hard fats/vegetable oils. After adjustment for high socio-economic status, associations with the ratios strengthened (r = -0.62 to -0.77) including also the MAI diet score

Theoretical study on the interactions between chlordecone hydrate and acidic surface groups of activated carbon under basic pH conditions.

PubMed

Melchor-Rodríguez, Kenia; Gamboa-Carballo, Juan José; Ferino-Pérez, Anthuan; Passé-Coutrin, Nady; Gaspard, Sarra; Jáuregui-Haza, Ulises Javier

2018-05-01

A theoretical study of the influence of acidic surface groups (SG) of activated carbon (AC) on chlordecone hydrate (CLDh) adsorption is presented, in order to help understanding the adsorption process under basic pH conditions. A seven rings aromatic system (coronene) with a functional group in the edge was used as a simplified model of AC to evaluate the influence of SG in the course of adsorption from aqueous solution at basic pH conditions. Two SG were modeled in their deprotonated form: carboxyl and hydroxyl (COO - and O - ), interacting with CLDh. In order to model the solvation process, all systems under study were calculated with up to three water molecules. Multiple Minima Hypersurface (MMH) methodology was employed to study the interactions of CLDh with SG on AC using PM7 semiempirical Hamiltonian, to explore the potential energy surfaces of the systems and evaluate their thermodynamic association energies. The re-optimization of representative structures obtained from MMH was done using M06-2X Density Functional Theory. The Quantum Theory of Atoms in Molecules (QTAIM) was used to characterize the interaction types. As result, the association of CLDh with acidic SG at basic pH conditions preferentially occurs between the two alcohol groups of CLDh with COO - and O - groups and by dispersive interactions of chlorine atoms of CLDh with the graphitic surface. On the other hand, the presence of covalent interactions between the negatively charged oxygen of SG and one hydrogen atom of CLDh alcohol groups (O - ⋯HO interactions) without water molecules, was confirmed by QTAIM study. It can be concluded that the interactions of CLDh with acidic SG of AC under basic pH conditions confirms the physical mechanisms of adsorption process. Copyright © 2018 Elsevier Inc. All rights reserved.

Docosahexaenoic Acid and Eicosapentaenoic Acid Did not Alter trans-10,cis-12 Conjugated Linoleic Acid Incorporation into Mice Brain and Eye Lipids.

PubMed

Vemuri, Madhuri; Adkins, Yuriko; Mackey, Bruce E; Kelley, Darshan S

2017-09-01

trans 10,cis 12-CLA has been reported to alter fatty acid composition in several non-neurological tissues, but its effects are less known in neurological tissues. Therefore, the purpose of this study was to determine if CLA supplementation would alter brain and eye fatty acid composition and if those changes could be prevented by concomitant supplementation with docosahexaenoic acid (DHA; 22:6n3) or eicosapentaenoic acid (EPA; 20:5n3). Eight-week-old, pathogen-free C57BL/6N female mice (n = 6/group) were fed either the control diet or diets containing 0.5% (w/w) t10,c12-CLA in the presence or absence of either 1.5% DHA or 1.5% EPA for 8 weeks. CLA concentration was significantly (P < 0.05) greater in the eye but not in the brain lipids of the CLA group when compared with the control group. The sums of saturated, monounsaturated, polyunsaturated fatty acids, and n3:n6 ratio did not differ between these two groups for both tissues. The n3:n6 ratio and concentrations of 20:5n3 and 22:5n3 were significantly greater, and those of 20:4n6, 22:4n6, and 22:5n6 were lesser in the CLA + DHA and CLA + EPA groups than in the control and CLA groups for either tissue. DHA concentration was higher in the CLA + DHA group only but not in the CLA + EPA group when compared with the CLA group for both tissues. The dietary fatty acids generally induced similar changes in brain and eye fatty acid concentration and at the concentrations used both DHA and EPA fed individually with CLA were more potent than CLA alone in altering the tissue fatty acid concentration.

Mechanisms of proton transfer in Nafion: elementary reactions at the sulfonic acid groups.

PubMed

Sagarik, Kritsana; Phonyiem, Mayuree; Lao-ngam, Charoensak; Chaiwongwattana, Sermsiri

2008-04-21

Proton transfer reactions at the sulfonic acid groups in Nafion were theoretically studied, using complexes formed from triflic acid (CF3SO3H), H3O+ and H2O, as model systems. The investigations began with searching for potential precursors and transition states at low hydration levels, using the test-particle model (T-model), density functional theory (DFT) and ab initio calculations. They were employed as starting configurations in Born-Oppenheimer molecular dynamics (BOMD) simulations at 298 K, from which elementary reactions were analyzed and categorized. For the H3O+-H2O complexes, BOMD simulations suggested that a quasi-dynamic equilibrium could be established between the Eigen and Zundel complexes, and that was considered to be one of the most important elementary reactions in the proton transfer process. The average lifetime of H3O+ obtained from BOMD simulations is close to the lowest limit, estimated from low-frequency vibrational spectroscopy. It was demonstrated that proton transfer reactions at -SO3H are not concerted, due to the thermal energy fluctuation and the existence of various quasi-dynamic equilibria, and -SO3H could directly and indirectly mediate proton transfer reactions through the formation of proton defects, as well as the -SO3- and -SO3H2+ transition states.

The stability of iso-α-acids and reduced iso-α-acids in stored blood specimens.

PubMed

Rodda, Luke N; Gerostamoulos, Dimitri; Drummer, Olaf H

2014-06-01

The long-term stability of the iso-α-acids, and three structurally similar but chemically altered iso-α-acids (known as 'reduced iso-α-acids' and consisting of the rho-, tetrahydro- and hexahydro-iso-α-acid groups) were investigated in whole blood. Pools of blank blood spiked with the four beer-specific ingredient congener groups at two different concentration levels were stored at 20°C, 4°C and -20°C; and extracted in duplicate in weeks 1, 3, 5 and 8, using a previously published method. A loss of 15% of the initial concentration was considered to indicate possible instability and losses greater than 30% demonstrated significant losses. The individual analytes within the four iso-α-acid groups were also measured to determine which iso-α-acids were subject to greater degradation and were responsible for the overall group instability. All four iso-α-acid groups showed significant losses after 8 weeks of storage under room temperature conditions in particularly the natural iso-α-acid group where major losses were observed (96% and 85% losses for low and high concentrations, respectively). Some degradation in all iso-α-acid groups were seen at 4°C samples predominantly due to the 'n' analogs of the groups showing an increased instability in blood. The -20°C storage conditions resulted in minimal changes in concentrations of all analytes. Higher than frozen storage temperatures can result in substantial changes on the stability of the iso-α-acid type groups in blood. The aim of this study was to highlight the stabilities of the IAA analytes in order to assist in the interpretation of IAA in stored blood specimens. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Further Investigation of a Nickel-Based Homogeneous Water Oxidation Catalyst with Two cis Labile Sites.

PubMed

Luo, Gang-Yi; Huang, Hai-Hua; Wang, Jia-Wei; Lu, Tong-Bu

2016-03-08

The reaction of N,N'-dimethyl-N,N'-bis(pyridin-2-ylmethyl)-1,2-diaminoethane ligand (L) with Ni(ClO4)2 ⋅6 H2O generated a complex of [NiL(H2O)2](ClO4)2 (1) with two cis labile sites occupied by two coordinated H2O molecules, which can homogeneously electrocatalyze water oxidation in pH 6.5 acetate (OAc(-)) buffer at room temperature. The catalytic mechanism was studied by electrochemical experiments and density functional theory calculations to elucidate the following steps: (a) one of two water molecules in 1 is exchanged by OAc(-) to generate [NiL(H2O)(OAc)](+) when dissolved in OAc(-) buffer, (b) Ni(II) is directly oxidized to Ni(IV) and OAc(-) is replaced with OH(-) to form [Ni(IV) L(OH)2 ](2+), and (c) a peroxide intermediate is formed through the intramolecular O-O coupling in the presence of OAc(-), which undergoes further oxidation to release O2. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Diffusive gradients in thin films measurement of sulfur stable isotope variations in labile soil sulfate.

PubMed

Hanousek, Ondrej; Santner, Jakob; Mason, Sean; Berger, Torsten W; Wenzel, Walter W; Prohaska, Thomas

2016-11-01

A diffusive gradient in thin films (DGT) technique, based on a strongly basic anion exchange resin (Amberlite IRA-400), was successfully tested for 34 S/ 32 S analysis in labile soil sulfate. Separation of matrix elements (Na, K, and Ca) that potentially cause non-spectral interferences in 34 S/ 32 S analysis by MC ICP-MS (multi-collector inductively coupled plasma-mass spectrometry) during sampling of sulfate was demonstrated. No isotopic fractionation caused by diffusion or elution of sulfate was observed below a resin gel disc loading of ≤79 μg S. Above this threshold, fractionation towards 34 S was observed. The method was applied to 11 different topsoils and one mineral soil profile (0-100 cm depth) and compared with soil sulfate extraction by water. The S amount and isotopic ratio in DGT-S and water-extractable sulfate correlated significantly (r 2  = 0.89 and r 2  = 0.74 for the 11 topsoils, respectively). The systematically lower 34 S/ 32 S isotope ratios of the DGT-S were ascribed to mineralization of organic S.

Targeted metabolomics analysis reveals the association between maternal folic acid supplementation and fatty acids and amino acids profiles in rat pups.

PubMed

Liu, Zhipeng; Liu, Rui; Chou, Jing; Yu, Jiaying; Liu, Xiaowei; Sun, Changhao; Li, Ying; Liu, Liyan

2018-07-15

Maternal diet during pregnancy can influence offspring's health by affecting development and metabolism. This study aimed to analyze the influence of maternal folic acid (FA) supplementation on the metabolism of rat pups using targeted metabolomics. Twenty female rats were randomly assigned to a FA supplementation (FAS group, n = 10) or control group (n = 10), which were fed AIN93G diet with 2 or 10 mg/kg FA, respectively. We then measured amino acids and their derivatives, biogenic amines, and fatty acids in the female rats and their pups by ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UHPLC/MS-MS) and gas chromatography-mass spectrometry (GC/MS-MS). In maternal rats, the significant changes of three metabolites (proline, γ-aminobutyric acid and esterified octadecatetraenoic acid, P < 0.05) were observed in FAS group. For the rat pups, FAS pups had significantly lower homocysteine and higher FA levels than control pups. The lower levels of amino acids (leucine, isoleucine, serine, proline) were obtained in FAS pups. Furthermore, there were the decreased esterified fatty acids (arachidonic acid, eicosapentaenoic acid, and docosatetraenoic acid) and free fatty acids (oleic acid, linoleic acid, γ-linolenic acid, octadecatetraenoic acid, arachidonic acid, eicosapentaenoic acid and selacholeic acid) in FAS pups. Metabolic changes in the FAS pups were characterized by changes in fatty acids and amino acids. These results suggested that FA supplementation during pregnancy influenced amino acids and fatty acids metabolism in rat pups. This study provides new insights into the regulation of amino acids and fatty acids metabolism during early life. Copyright © 2018 Elsevier B.V. All rights reserved.

Is litter decomposition 'primed' by primary producer-release of labile carbon in terrestrial and aquatic experimental systems?

NASA Astrophysics Data System (ADS)

Soares, A. Margarida P. M.; Kritzberg, Emma S.; Rousk, Johannes

2015-04-01

It is possible that recalcitrant organic matter (ROM) can be 'activated' by inputs of labile organic matter (LOM) through the priming effect (PE). Investigating the PE is of major importance to fully understand the microbial use of ROM and its role on carbon (C) and nutrient cycling in both aquatic and terrestrial ecosystems. In aquatic ecosystems it is thought that the PE is triggered by periphytic algae release of LOM. Analogously, in terrestrial systems it is hypothesized that the LOM released in plant rhizospheres, or from the green crusts on the surface of agricultural soils, stimulate the activity and growth of ROM decomposers. Most previous studies on PE have utilised pulse additions of single substrates at high concentrations. However, to achieve an assessment of the true importance of the PE, it is important to simulate a realistic delivery of LOM. We investigated, in a series of 2-week laboratory experiments, how primary producer (PP)-release of LOM influence litter degradation in terrestrial and aquatic experimental systems. We used soil (terrestrial) and pond water (aquatic) microbial communities to which litter was added under light and dark conditions. In addition, glucose was added at PP delivery rates in dark treatments to test if the putative PE in light systems could be reproduced. We observed an initial peak of bacterial growth rate followed by an overall decrease over time with no treatment differences. In light treatments, periphytic algae growth and increased fungal production was stimulated when bacterial growth declined. In contrast, both fungal growth and algal production were negligible in dark treatments. This reveals a direct positive influence of photosynthesis on fungal growth. To investigate if PP LOM supplements, and the associated fungal growth, translate into a modulated litter decomposition, we are using stable isotopes to track the use of litter and algal-derived carbon by determining the δ13C in produced CO2. Fungi and bacteria

Degradation of L-Ascorbic Acid in the Amorphous Solid State.

PubMed

Sanchez, Juan O; Ismail, Yahya; Christina, Belinda; Mauer, Lisa J

2018-03-01

Ascorbic acid degradation in amorphous solid dispersions was compared to its degradation in the crystalline state. Physical blends and lyophiles of ascorbic acid and polymers (pectins and polyvinylpyrrolidone [PVP]) were prepared initially at 50:50 (w/w), with further studies using the polymer that best inhibited ascorbic acid crystallization in the lyophiles in 14 vitamin : PVP ratios. Samples were stored in controlled environments (25 to 60 °C, 0% to 23% RH) for 1 mo and analyzed periodically to track the physical appearance, change in moisture content, physical state (powder x-ray diffraction and polarized light microscopy), and vitamin loss (high performance liquid chromatography) over time. The glass transition temperatures of select samples were determined using differential scanning calorimetry, and moisture sorption profiles were generated. Ascorbic acid in the amorphous form, even in the glassy amorphous state, was more labile than in the crystalline form in some formulations at the highest storage temperature. Lyophiles stored at 25 and 40 °C and those in which ascorbic acid had crystallized at 60 °C (≥70% ascorbic acid : PVP) had no significant difference in vitamin loss (P > 0.05) relative to physical blend controls, and the length of storage had little effect. At 60 °C, amorphous ascorbic acid lyophiles (≤60% ascorbic acid : PVP) lost significantly more vitamin (P < 0.05) relative to physical blend controls after 1 wk, and vitamin loss significantly increased over time. In these lyophiles, vitamin degradation also significantly increased (P < 0.05) at lower proportions of ascorbic acid, a scenario likely encountered in foods wherein vitamins are naturally present or added at low concentrations and production practices may promote amorphization of the vitamin. Vitamin C is one of the most unstable vitamins in foods. This study documents that amorphous ascorbic acid is less stable than crystalline ascorbic acid in some environments (for example