Science.gov

Sample records for acid site strength

  1. Number and strength of surface acidic sites on porous aluminosilicates of the MCM-41 type inferred from a combined microcalorimetric and adsorption study

    SciTech Connect

    Meziani, M.J.; Zajac, J.; Jones, D.J.; Partyka, S.; Roziere, J.

    2000-03-07

    A combined microcalorimetry and adsorption study has been used to characterize the surface acidity of two series of MCM-41 aluminosilicates (referred to as SiAlxCn, where x is the mole Si:Al ration and n the chain length of the surfactant template). {sup 29}Si magic angle spinning NMR spectra of a selected sample (SiAl32C16) indicates the presence of siloxane groups, Si(OSi){sub 4}, and three types of silanol groups, that is, single (SiO){sub 3}-Si-OH, hydrogen-bonded (SiO){sub 3}-SiOH{hor{underscore}ellipsis}HO-Si-(SiO){sub 3}, and germinal (SiO){sub 2}-Si(OH){sub 2}. It is also possible to detect the contributions from Si(3Si, 1Al) and Si(2Si,2Al) sites. The volumetric and calorimetric measurements of gas ammonia adsorption at 353 K were used to determine the number and strength of surface acidic sites. With the exception of H{sup +}-SiAl32C14 and SiAl8C14, all samples have low surface acidity. Following the pyridine-TPD study on SiAl9C14 sample, Lewis acid sites producing surface pyridine complexes constitute the strongest acidic site.

  2. College Chemistry Students' Mental Models of Acids and Acid Strength

    ERIC Educational Resources Information Center

    McClary, LaKeisha; Talanquer, Vicente

    2011-01-01

    The central goal of this study was to characterize the mental models of acids and acid strength expressed by advanced college chemistry students when engaged in prediction, explanation, and justification tasks that asked them to rank chemical compounds based on their relative acid strength. For that purpose we completed a qualitative research…

  3. Residual Strength Prediction of Fuselage Structures with Multiple Site Damage

    NASA Technical Reports Server (NTRS)

    Chen, Chuin-Shan; Wawrzynek, Paul A.; Ingraffea, Anthony R.

    1999-01-01

    This paper summarizes recent results on simulating full-scale pressure tests of wide body, lap-jointed fuselage panels with multiple site damage (MSD). The crack tip opening angle (CTOA) fracture criterion and the FRANC3D/STAGS software program were used to analyze stable crack growth under conditions of general yielding. The link-up of multiple cracks and residual strength of damaged structures were predicted. Elastic-plastic finite element analysis based on the von Mises yield criterion and incremental flow theory with small strain assumption was used. A global-local modeling procedure was employed in the numerical analyses. Stress distributions from the numerical simulations are compared with strain gage measurements. Analysis results show that accurate representation of the load transfer through the rivets is crucial for the model to predict the stress distribution accurately. Predicted crack growth and residual strength are compared with test data. Observed and predicted results both indicate that the occurrence of small MSD cracks substantially reduces the residual strength. Modeling fatigue closure is essential to capture the fracture behavior during the early stable crack growth. Breakage of a tear strap can have a major influence on residual strength prediction.

  4. Solvation and Acid Strength Effects on Catalysis by Faujasite Zeolites

    SciTech Connect

    Gounder, Rajamani P.; Jones, Andrew J.; Carr, Robert T.; Iglesia, Enrique

    2012-02-01

    Kinetic, spectroscopic, and chemical titration data indicate that differences in monomolecular isobutane cracking and dehydrogenation and methanol dehydration turnover rates (per H+) among FAU zeolites treated thermally with steam (H-USY) and then chemically with ammonium hexafluorosilicate (CDHUSY) predominantly reflect differences in the size and solvating properties of their supercage voids rather than differences in acid strength. The number of protons on a given sample was measured consistently by titrations with Na+, with CH3 groups via reactions of dimethyl ether, and with 2,6-di-tert-butylpyridine during methanol dehydration catalysis; these titration values were also supported by commensurate changes in acidic OH infrared band areas upon exposure to titrant molecules. The number of protons, taken as the average of the three titration methods, was significantly smaller than the number of framework Al atoms (Alf) obtained from X-ray diffraction and 27Al magic angle spinning nuclear magnetic resonance spectroscopy on H-USY (0.35 H+/Alf) and CD-HUSY (0.69 H+/Alf). These data demonstrate that the ubiquitous use of Alf sites as structural proxies for active H+ sites in zeolites can be imprecise, apparently because distorted Al structures that are not associated with acidic protons are sometimes detected as Alf sites. Monomolecular isobutane cracking and dehydrogenation rate constants, normalized non-rigorously by the number of Alf species, decreased with increasing Na+ content on both H-USY and CD-HUSY samples and became undetectable at sub-stoichiometric exchange levels (0.32 and 0.72 Na+/Alf ratios, respectively), an unexpected finding attributed incorrectly in previous studies to the presence of minority ‘‘super-acidic’’ sites. These rate constants, when normalized rigorously by the number of residual H+ sites were independent of Na+ content on both H-USY and CD-HUSY samples, reflecting the stoichiometric replacement of protons that are uniform in

  5. Of Mental Models, Assumptions and Heuristics: The Case of Acids and Acid Strength

    ERIC Educational Resources Information Center

    McClary, LaKeisha Michelle

    2010-01-01

    This study explored what cognitive resources (i.e., units of knowledge necessary to learn) first-semester organic chemistry students used to make decisions about acid strength and how those resources guided the prediction, explanation and justification of trends in acid strength. We were specifically interested in the identifying and…

  6. Effects of acid diffusibility and affinity to cellulose on strength loss of polycarboxylic acid crosslinked fabrics.

    PubMed

    Ji, Bolin; Zhao, Cunyi; Yan, Kelu; Sun, Gang

    2016-06-25

    1,2,3,4-Butanetetracarboxylic acid (BTCA) imparts good anti-wrinkle property to cotton fabrics and results in significant strength loss due to cross-linking and acid degradation of cellulose simultaneously. However, benzophenone-3,3',4,4'- tetracarboxylic acid (BPTCA), an aromatic acid, crosslinks cellulose effectively but causes less strength loss to the products under similar conditions. The difference in damages to cellulose fibers was analyzed by using diffusibility and corresponding affinity of the acids to cellulose fibers, which were estimated by their molecular sizes and Hansen solubility parameters (HSP). Both experimental results and theoretical speculations revealed consistent agreement, indicating that smaller acid molecules could diffuse into cellulose fiber more rapidly and deeply, resulting in more acid degradation. Besides, the aliphatic acid such as BTCA has higher molecular affinity than BPTCA to cellulose, causing additional more degradation of cellulose. Both factors are potential reasons of the observed more severe tensile strength loss of the BTCA treated cotton fabrics.

  7. The influence of dicarboxylic acids: Oxalic acid and tartaric acid on the compressive strength of glass ionomer cements

    NASA Astrophysics Data System (ADS)

    Permana, Ahmadi Jaya; Setyawati, Harsasi; Hamami, Murwani, Irmina Kris

    2016-03-01

    Glass ionomer cement (GIC) has limitation on the mechanical properties especially compressive strength. The change of compressive strength of GIC by adding oxalic acid and tartaric acid has been investigated. Oxalic acid and tartaric acid was added to the liquid components at concentrations of 0 - 15% (w/w). Powder component of GIC was made from optimum experimental powder glass SiO2-Al2O3-CaF2. GIC was characterized by compressive strength test, SEM-EDX and FTIR. The addition of tartaric acid to GIC has greater improvement than addition of oxalic acid. The addition of tartaric acid at 10 % (w/w) to GIC has greatest value of compressive strength.

  8. Age and sex differences in estimated tibia strength: influence of measurement site.

    PubMed

    Sherk, Vanessa D; Bemben, Debra A

    2013-01-01

    Variability in peripheral quantitative computed tomography (pQCT) measurement sites and outcome variables limit direct comparisons of results between studies. Furthermore, it is unclear what estimates of bone strength are most indicative of changes due to aging, disease, or interventions. The purpose of this study was to examine age and sex differences in estimates of tibia strength. An additional purpose of this study was to determine which tibia site or sites are most sensitive for detecting age and sex differences in tibia strength. Self-identifying Caucasian men (n=55) and women (n=59) aged 20-59yr had their tibias measured with pQCT from 5% to 85% of limb length in 10% increments distal to proximal. Bone strength index, strength strain index (SSI), moments of inertia (Ip, Imax, and Imin), and strength-to-mass ratios (polar moment of inertia to total bone mineral content [BMC] ratio [Ip:Tot.BMC] and strength strain index to total BMC ratio [SSI:Tot.BMC]) were quantified. There were significant (p<0.01) site effects for all strength variables and strength-to-mass ratios. Site×sex interaction effects were significant (p<0.05) for all strength variables. Men had greater (p<0.01) values than women for all strength variables. Sex differences in Ip, Imax, Ip:Tot.BMC, SSI, and SSI:Tot.BMC ratios were the smallest at the 15% site and peaked at various sites, depending on variable. Site×age interactions existed for Imax, Ip:Tot.BMC, and SSI:Tot.BMC. There were significant age effects, Imax, Ip:Tot.BMC, and SSI:Tot.BMC, as values were the lowest in the 20-29 age group. Age and sex differences varied by measurement site and variable, and larger sex differences existed for moments of inertia than SSI. Strength-to-mass ratios may reflect efficiency of the whole bone architecture.

  9. Modeling lanthanide series binding sites on humic acid.

    PubMed

    Pourret, Olivier; Martinez, Raul E

    2009-02-01

    Lanthanide (Ln) binding to humic acid (HA) has been investigated by combining ultrafiltration and ICP-MS techniques. A Langmuir-sorption-isotherm metal-complexation model was used in conjunction with a linear programming method (LPM) to fit experimental data representing various experimental conditions both in HA/Ln ratio (varying between 5 and 20) and in pH range (from 2 to 10) with an ionic strength of 10(-3) mol L(-1). The LPM approach, not requiring prior knowledge of surface complexation parameters, was used to solve the existing discrepancies in LnHA binding constants and site densities. The application of the LPM to experimental data revealed the presence of two discrete metal binding sites at low humic acid concentrations (5 mg L(-1)), with log metal complexation constants (logK(S,j)) of 2.65+/-0.05 and 7.00 (depending on Ln). The corresponding site densities were 2.71+/-0.57x10(-8) and 0.58+/-0.32x10(-8) mol of Ln(3+)/mg of HA (depending on Ln). Total site densities of 3.28+/-0.28x10(-8), 4.99+/-0.02x10(-8), and 5.01+/-0.01x10(-8) mol mg(-1) were obtained by LPM for humic acid, for humic acid concentrations of 5, 10, and 20 mg L(-1), respectively. These results confirm that lanthanide binding occurs mainly at weak sites (i.e., ca. 80%) and second at strong sites (i.e., ca. 20%). The first group of discrete metal binding sites may be attributed to carboxylic groups (known to be the main binding sites of Ln in HA), and the second metal binding group to phenolic moieties. Moreover, this study evidences heterogeneity in the distribution of the binding sites among Ln. Eventually, the LPM approach produced feasible and reasonable results, but it was less sensitive to error and did not require an a priori assumption of the number and concentration of binding sites.

  10. Consequences of acid strength for isomerization and elimination catalysis on solid acids.

    PubMed

    Macht, Josef; Carr, Robert T; Iglesia, Enrique

    2009-05-13

    We address here the manner in which acid catalysis senses the strength of solid acids. Acid strengths for Keggin polyoxometalate (POM) clusters and zeolites, chosen because of their accurately known structures, are described rigorously by their deprotonation energies (DPE). Mechanistic interpretations of the measured dynamics of alkane isomerization and alkanol dehydration are used to obtain rate and equilibrium constants and energies for intermediates and transition states and to relate them to acid strength. n-Hexane isomerization rates were limited by isomerization of alkoxide intermediates on bifunctional metal-acid mixtures designed to maintain alkane-alkene equilibrium. Isomerization rate constants were normalized by the number of accessible protons, measured by titration with 2,6-di-tert-butylpyridine during catalysis. Equilibrium constants for alkoxides formed by protonation of n-hexene increased slightly with deprotonation energies (DPE), while isomerization rate constants decreased and activation barriers increased with increasing DPE, as also shown for alkanol dehydration reactions. These trends are consistent with thermochemical analyses of the transition states involved in isomerization and elimination steps. For all reactions, barriers increased by less than the concomitant increase in DPE upon changes in composition, because electrostatic stabilization of ion-pairs at the relevant transition states becomes more effective for weaker acids, as a result of their higher charge density at the anionic conjugate base. Alkoxide isomerization barriers were more sensitive to DPE than for elimination from H-bonded alkanols, the step that limits 2-butanol and 1-butanol dehydration rates; the latter two reactions showed similar DPE sensitivities, despite significant differences in their rates and activation barriers, indicating that slower reactions are not necessarily more sensitive to acid strength, but instead reflect the involvement of more unstable organic

  11. Strengths of hydrogen bonds involving phosphorylated amino acid side chains.

    PubMed

    Mandell, Daniel J; Chorny, Ilya; Groban, Eli S; Wong, Sergio E; Levine, Elisheva; Rapp, Chaya S; Jacobson, Matthew P

    2007-01-31

    Post-translational phosphorylation plays a key role in regulating protein function. Here, we provide a quantitative assessment of the relative strengths of hydrogen bonds involving phosphorylated amino acid side chains (pSer, pAsp) with several common donors (Arg, Lys, and backbone amide groups). We utilize multiple levels of theory, consisting of explicit solvent molecular dynamics, implicit solvent molecular mechanics, and quantum mechanics with a self-consistent reaction field treatment of solvent. Because the approximately 6 pKa of phosphate suggests that -1 and -2 charged species may coexist at physiological pH, hydrogen bonds involving both protonated and deprotonated phosphates for all donor-acceptor pairs are considered. Multiple bonding geometries for the charged-charged interactions are also considered. Arg is shown to be capable of substantially stronger salt bridges with phosphorylated side chains than Lys. A pSer hydrogen-bond acceptor tends to form more stable interactions than a pAsp acceptor. The effect of phosphate protonation state on the strengths of the hydrogen bonds is remarkably subtle, with a more pronounced effect on pAsp than on pSer.

  12. Evaporative properties and pinning strength of laser-ablated, hydrophilic sites on lotus-leaf-like, nanostructured surfaces.

    PubMed

    McLauchlin, Melissa L; Yang, Dongqing; Aella, P; Garcia, Antonio A; Picraux, S T; Hayes, Mark A

    2007-04-24

    Wetting, evaporative, and pinning strength properties of hydrophilic sites on superhydrophobic, nanostructured surfaces were examined. Understanding these properties is important for surface characterization and designing features in self-cleaning, lotus-leaf-like surfaces. Laser-ablated, hydrophilic spots between 250 mum and 2 mm in diameter were prepared on silicon nanowire (NW) superhydrophobic surfaces. For larger circumference pinning sites, initial contact angle measurements resemble the contact angle of the surface within the pinning site: 65-69 degrees . As the drop volume is increased, the contact angles approach the contact angle of the NW surface without pinning sites: 171-176 degrees . The behavior of water droplets on the pinning sites is governed by how much of the water droplet is being influenced by the superhydrophobic NW surfaces versus the hydrophilic areas. During the evaporation of sinapic acid solution, drops are pinned by the spots except for the smaller circumference sites. Pinning strengths of the hydrophilic sites are a linear function of the pinning spot circumference. Protein samples prepared and deposited on the pinning sites for analysis by matrix-assisted laser desorption ionization indicate an improvement in sensitivity from that of a standard plate analysis by a factor of 5.

  13. Support Effects on Bronsted acid site densities and alcohol dehydration turnover rates on tungsten oxide domains

    SciTech Connect

    Macht, Josef; Baertsch, Chelsey D.; May-Lozano, Marcos; Soled, Stuart L.; Wang, Yong; Iglesia, Enrique

    2005-03-01

    Initial activity and acid site density of several WAl, WSi (MCM41) and one WSn sample were determined. Trans/cis 2-butene selectivity is dependent on the support. Presumably, these differences are due to subtle differences in base strengths. 2-Butanol dehydration rates (per W-atom) reached maximum values at intermediate WOx surface densities on WAl, as reported for 2-butanol dehydration reactions on WZr. Titration results indicate that Bronsted acid sites are required for 2-butanol dehydration on WAl, WSi and WSn. UV-visible studies suggest that WAl is much more difficult to reduce than WZr. The detection of reduced centers on WAl, the number of which correlates to Bronsted acid site density and catalyst activity, as well as the temperature dependence of Bronsted acid site density indicate the in-situ formation of these active sites. We infer that this mechanism is common among all supported WOx samples described in this study. Turnover rates are a function of Bronsted acid site density only. High acid site densities lead to high turnover rates. Higher active site densities may cause stronger conjugate bases, as a higher electron density has to be stabilized, and thus weaker acidity, enabling a faster rate of product desorption. The maximum achievable active site density is dependent on the support. WZr reaches a higher active site density than WAl.

  14. Fracture Strength of Fused Silica From Photonic Signatures Around Collision Sites

    NASA Technical Reports Server (NTRS)

    Yost, William T.; Cramer, K Elliott

    2015-01-01

    Impact sites in glass affect its fracture strength. An analytical model that predicts fracture strength from grey-field polariscope (GFP) readings (photoelastic retardations) has been developed and reported in the literature. The model is suggestive that stress fields, resulting from impact damage, destablizes sites within the glass, which lead to pathways that cause strength degradation. Using data collected from fused silica specimens fabricated from outer window panes that were designed for the space shuttle, the model was tested against four categories of inflicted damage. The damage sites were cored from the window carcasses, examined with the GFP and broken using the ASTM Standard C1499-09 to measure the fracture strength. A correlation is made between the fracture strength and the photoelastic retardation measured at the damage site in each specimen. A least-squares fit is calculated. The results are compared with the predictions from the model. A plausible single-sided NDE damage site inspection method (a version of which is planned for glass inspection in the Orion Project) that relates photoelastic retardation in glass components to its fracture strength is presented.

  15. Heuristic Reasoning in Chemistry: Making decisions about acid strength

    NASA Astrophysics Data System (ADS)

    McClary, LaKeisha; Talanquer, Vicente

    2011-07-01

    The characterization of students' reasoning strategies is of central importance in the development of instructional strategies that foster meaningful learning. In particular, the identification of shortcut reasoning procedures (heuristics) used by students to reduce cognitive load can help us devise strategies to facilitate the development of more analytical ways of thinking. The central goal of this qualitative study was thus to investigate heuristic reasoning as used by organic chemistry college students, focusing our attention on their ability to predict the relative acid strength of chemical compounds represented using explicit composition and structural features (i.e., structural formulas). Our results indicated that many study participants relied heavily on one or more of the following heuristics to make most of their decisions: reduction, representativeness, and lexicographic. Despite having visual access to reach structural information about the substances included in each ranking task, many students relied on isolated composition features to make their decisions. However, the specific characteristics of the tasks seemed to trigger heuristic reasoning in different ways. Although the use of heuristics allowed students to simplify some components of the ranking tasks and generate correct responses, it often led them astray. Very few study participants predicted the correct trends based on scientifically acceptable arguments. Our results suggest the need for instructional interventions that explicitly develop college chemistry students' abilities to monitor their thinking and evaluate the effectiveness of analytical versus heuristic reasoning strategies in different contexts.

  16. SITE demonstration of the Zenogem{trademark} technology to treat high strength wastewaters

    SciTech Connect

    Sullivan, D.; Merdinger, M.; Kosco, W.

    1995-10-01

    High strength organic wastewaters are encountered at hazardous waste sites in the form of leachate and in some cases groundwater. The ZenoGem{trademark} Process is designed to remove biodegradable materials, including most organic contaminants, from wastewater to produce a high quality effluent. This technology was accepted into EPA`s Superfund Innovative Technology Evaluation (SITE) program in summer 1992; this paper summarizes the technology demonstration performed at a Superfund site in 1994.

  17. The Correlation of Binary Acid Strengths with Molecular Properties in First-Year Chemistry

    ERIC Educational Resources Information Center

    Fridgen, Travis D.

    2008-01-01

    This article deals with the rather complicated if not incorrect way that the strengths of binary acids are rationalized to students in many classrooms owing to the way it is presented in first-year chemistry textbooks. The common explanations, which use the homolytic bond dissociation energy as a rationalization of the trend in acid strengths when…

  18. Students' Understandings of Acid Strength: How Meaningful Is Reliability When Measuring Alternative Conceptions

    ERIC Educational Resources Information Center

    Bretz, Stacey Lowery; McClary, LaKeisha

    2015-01-01

    Most organic chemistry reactions occur by a mechanism that includes acid-base chemistry, so it is important that students develop and learn to use correct conceptions of acids and acid strength. Recent studies have described undergraduate organic chemistry students' cognitive resources related to the Brønsted-Lowry acid model and the Lewis acid…

  19. Trimethylamine as a probe molecule to differentiate acid sites in Y-FAU zeolite: FTIR study.

    PubMed

    Sarria, Francisca Romero; Blasin-Aubé, Vanessa; Saussey, Jacques; Marie, Olivier; Daturi, Marco

    2006-07-06

    In heterogeneous catalysis acidity has a very important influence on activity and selectivity: correct determination of acidic properties is a base to improve industrial processes. The aim of this work was to study trimethylamine (TMA) as a probe molecule able to distinguish between the different Brønsted acid sites in zeolitic frameworks. Our work mainly focused on faujasite-type zeolites because the HY zeolite is one of the most used acidic catalysts in industrial processes. In this paper, typical IR bands assigned to TMA-protonated species (formed in supercages) are detected in the HY zeolite. TMA interacting by hydrogen bonding with the acid sites located in the sodalite units is also observed. The wavenumbers of some typical IR bands assigned to TMA-protonated species appear to depend on the acidic strength, and a complementary study with ZSM-5 and X-FAU samples confirms this proposition.

  20. Emergence, Learning Difficulties, and Misconceptions in Chemistry Undergraduate Students' Conceptualizations of Acid Strength

    NASA Astrophysics Data System (ADS)

    Tümay, Halil

    2016-03-01

    Philosophical debates about chemistry have clarified that the issue of emergence plays a critical role in the epistemology and ontology of chemistry. In this article, it is argued that the issue of emergence has also significant implications for understanding learning difficulties and finding ways of addressing them in chemistry. Particularly, it is argued that many misconceptions in chemistry may derive from students' failure to consider emergence in a systemic manner by taking into account all relevant factors in conjunction. Based on this argument, undergraduate students' conceptions of acids, and acid strength (an emergent chemical property) were investigated and it was examined whether or not they conceptualized acid strength as an emergent chemical property. The participants were 41 third- and fourth-year undergraduate students. A concept test and semi-structured interviews were used to probe students' conceptualizations and reasoning about acid strength. Findings of the study revealed that the majority of the undergraduate students did not conceptualize acid strength as an emergent property that arises from interactions among multiple factors. They generally focused on a single factor to predict and explain acid strength, and their faulty responses stemmed from their failure to recognize and consider all factors that affect acid strength. Based on these findings and insights from philosophy of chemistry, promoting system thinking and epistemologically sound argumentative discourses among students is suggested for meaningful chemical education.

  1. Effect of soil acidity, soil strength and macropores on root growth and morphology of perennial grass species differing in acid-soil resistance.

    PubMed

    Haling, Rebecca E; Simpson, Richard J; Culvenor, Richard A; Lambers, Hans; Richardson, Alan E

    2011-03-01

    It is unclear whether roots of acid-soil resistant plants have significant advantages, compared with acid-soil sensitive genotypes, when growing in high-strength, acid soils or in acid soils where macropores may allow the effects of soil acidity and strength to be avoided. The responses of root growth and morphology to soil acidity, soil strength and macropores by seedlings of five perennial grass genotypes differing in acid-soil resistance were determined, and the interaction of soil acidity and strength for growth and morphology of roots was investigated. Soil acidity and strength altered root length and architecture, root hair development, and deformed the root tip, especially in acid-soil sensitive genotypes. Root length was restricted to some extent by soil acidity in all genotypes, but the adverse impact of soil acidity on root growth by acid-soil resistant genotypes was greater at high levels of soil strength. Roots reacted to soil acidity when growing in macropores, but elongation through high-strength soil was improved. Soil strength can confound the effect of acidity on root growth, with the sensitivity of acid-resistant genotypes being greater in high-strength soils. This highlights the need to select for genotypes that resist both acidity and high soil strength.

  2. Adverse experiences with nitric acid at the Savannah River Site

    SciTech Connect

    Durant, W.S.; Craig, D.K.; Vitacco, M.J.; McCormick, J.A.

    1991-06-01

    Nitric acid is used routinely at the Savannah River Site (SRS) in many processes. However, the site has experienced a number of adverse situations in handling nitric acid. These have ranged from minor injuries to personnel to significant explosions. This document compiles many of these events and includes discussions of process upsets, fires, injuries, and toxic effects of nitric acid and its decomposition products. The purpose of the publication is to apprise those using the acid that it is a potentially dangerous material and can react in many ways as demonstrated by SRS experience. 10 refs.

  3. Mapping the natural variation in whole bone stiffness and strength across skeletal sites.

    PubMed

    Schlecht, Stephen H; Bigelow, Erin M R; Jepsen, Karl J

    2014-10-01

    Traits of the skeletal system are coordinately adjusted to establish mechanical homeostasis in response to genetic and environmental factors. Prior work demonstrated that this 'complex adaptive' process is not perfect, revealing a two-fold difference in whole bone stiffness of the tibia across a population. Robustness (specifically, total cross-sectional area relative to length) varies widely across skeletal sites and between sexes. However, it is unknown whether the natural variation in whole bone stiffness and strength also varies across skeletal sites and between men and women. We tested the hypotheses that: 1) all major long bones of the appendicular skeleton demonstrate inherent, systemic constraints in the degree to which morphological and compositional traits can be adjusted for a given robustness; and 2) these traits covary in a predictable manner independent of body size and robustness. We assessed the functional relationships among robustness, cortical area (Ct.Ar), cortical tissue mineral density (Ct.TMD), and bone strength index (BSI) across the long bones of the upper and lower limbs of 115 adult men and women. All bones showed a significant (p<0.001) positive regression between BSI and robustness after adjusting for body size, with slender bones being 1.7-2.3 times less stiff and strong in men and 1.3-2.8 times less stiff and strong in women compared to robust bones. Our findings are the first to document the natural inter-individual variation in whole bone stiffness and strength that exist within populations and that is predictable based on skeletal robustness for all major long bones. Documenting and further understanding this natural variation in strength may be critical for differentially diagnosing and treating skeletal fragility.

  4. Mapping the natural variation in whole bone stiffness and strength across skeletal sites

    PubMed Central

    Schlecht, Stephen H.; Bigelow, Erin M.R.; Jepsen, Karl J.

    2016-01-01

    Traits of the skeletal system are coordinately adjusted to establish mechanical homeostasis in response to genetic and environmental factors. Prior work demonstrated that this `complex adaptive' process is not perfect, revealing a two-fold difference in whole bone stiffness of the tibia across a population. Robustness (specifically, total cross-sectional area relative to length) varies widely across skeletal sites and between sexes. However, it is unknown whether the natural variation in whole bone stiffness and strength also varies across skeletal sites and between men and women. We tested the hypotheses that: 1) all major long bones of the appendicular skeleton demonstrate inherent, systemic constraints in the degree to which morphological and compositional traits can be adjusted for a given robustness; and 2) these traits covary in a predictable manner independent of body size and robustness. We assessed the functional relationships among robustness, cortical area (Ct.Ar), cortical tissue mineral density (Ct.TMD), and bone strength index (BSI) across the long bones of the upper and lower limbs of 115 adult men and women. All bones showed a significant (p < 0.001) positive regression between BSI and robustness after adjusting for body size, with slender bones being 1.7–2.3 times less stiff and strong in men and 1.3–2.8 times less stiff and strong in women compared to robust bones. Our findings are the first to document the natural inter-individual variation in whole bone stiffness and strength that exist within populations and that is predictable based on skeletal robustness for all major long bones. Documenting and further understanding this natural variation in strength may be critical for differentially diagnosing and treating skeletal fragility. PMID:24999223

  5. Influence of previous acid etching on bond strength of universal adhesives to enamel and dentin.

    PubMed

    Torres, Carlos Rocha Gomes; Zanatta, Rayssa Ferreira; Silva, Tatiane Josefa; Huhtala, Maria Filomena Rocha Lima; Borges, Alessandra Bühler

    2017-01-01

    The objective of this study was to evaluate the effect of acid pretreatment on the bond strength of composite resin bonded to enamel and dentin with 2 different universal self-etching adhesives. The null hypothesis was that the acid treatment performed prior to adhesive application would not significantly change the bond strength to enamel or dentin for either universal adhesive tested. A sample of 112 bovine incisors were selected and embedded in acrylic resin. Half were ground until a flat enamel surface was obtained, and the other half were polished until a 6 × 6-mm area of dentin was exposed, resulting into 2 groups (n = 56). The enamel and dentin groups were divided into 2 subgroups according to the adhesive system applied: Futurabond U or Scotchbond Universal. Each of these subgroups was divided into 2 additional subgroups (n = 14); 1 subgroup received phosphoric acid pretreatment, and 1 subgroup did not. The bond strength was assessed with a microtensile test. Data from enamel and dentin specimens were analyzed separately using 1-way analysis of variance. The acid pretreatment did not significantly change the bond strength of the adhesives tested, either to enamel (P = 0.4161) or to dentin (P = 0.4857). The acid etching pretreatment did not affect the bond strength to dentin and enamel when the tested universal multipurpose adhesive systems were used.

  6. Shear bond strength of resin to acid/pumice-microabraded enamel.

    PubMed

    Royer, M A; Meiers, J C

    1995-01-01

    The effect of enamel microabrasion techniques consisting of either 18% hydrochloric acid in pumice or a commercially available abrasive/10% hydrochloric acid mixture, PREMA, on composite/enamel shear bond strengths was investigated. Sixty extracted third molars had the bonding surface flattened and were divided into six treatment groups (n=10) with the enamel treated prior to bonding as follows: Group 1-- untreated; Group 2--37% phosphoric acid etched for 30 seconds; Group 3--18% hydrochloric acid/pumice mixture applied for five 20-second treatments; Group 4--similar to Group 3 with additional 37% phosphoric acid etch; Group 5--treated with PREMA compound applied for five 20-second treatments; Group 6--similar to Group 5 treatment with additional 37% phosphoric acid. Herculite XR composite resin was then bonded to all samples using a VLC unit. Samples were tested in shear, and fractured enamel surfaces were evaluated using light microscopy to determine the enamel-to-resin failures. Resin bond strengths to microabraded and H3PO4-etched enamel were similar to bond strengths of untreated H3PO4-etched enamel and were significantly better than bond strengths to PREMA-treated or unetched enamel.

  7. Synthesis of Site-Specifically (13)C Labeled Linoleic Acids.

    PubMed

    Offenbacher, Adam R; Zhu, Hui; Klinman, Judith P

    2016-10-12

    Soybean lipoxygenase-1 (SLO-1) catalyzes the C-H abstraction from the reactive carbon (C-11) in linoleic acid as the first and rate-determining step in the formation of alkylhydroperoxides. While previous labeling strategies have focused on deuterium labeling to ascertain the primary and secondary kinetic isotope effects for this reaction, there is an emerging interest and need for selectively enriched (13)C isotopologues. In this report, we present synthetic strategies for site-specific (13)C labeled linoleic acid substrates. We take advantage of a Corey-Fuchs formyl to terminal (13)C-labeled alkyne conversion, using (13)CBr4 as the labeling source, to reduce the number of steps from a previous fatty acid (13)C synthetic labeling approach. The labeled linoleic acid substrates are useful as nuclear tunneling markers and for extracting active site geometries of the enzyme-substrate complex in lipoxygenase.

  8. Site-selective Alkane Dehydrogenation of Fatty Acids

    DTIC Science & Technology

    2011-12-14

    dehydrogenation of fatty acids Contract/Grant#: FA9550-10-1-0532 Final Reporting Period: 15 September 2011 to 14 September 2011...directly incorporate fatty acids into the ligand. The preparation of the acyl phosphines (1-5) was easily accomplished starting from the corresponding...AFOSR Final Report Final Report 
 The proposed research examines the site-selective dehydrogenation of alkanes. The alkanes employed were fatty

  9. Bacterial Diversity at an Acid Mine Drainage Site in Maine

    NASA Astrophysics Data System (ADS)

    Gaynor, J.; Sawyer, T.; Riley, F. E.; Moulton, K. D.; Rothschild, L. J.; Duboise, S. M.

    2010-04-01

    Bacterial diversity in acidic mine drainage at a historic Maine iron mining site was investigated by isolation of environmental DNA, PCR amplification of the V3 region of the 16S rRNA gene, denaturing gradient gel electrophoresis, and DNA sequencing.

  10. Evaluating Variability and Uncertainty of Geological Strength Index at a Specific Site

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Aladejare, Adeyemi Emman

    2016-09-01

    Geological Strength Index (GSI) is an important parameter for estimating rock mass properties. GSI can be estimated from quantitative GSI chart, as an alternative to the direct observational method which requires vast geological experience of rock. GSI chart was developed from past observations and engineering experience, with either empiricism or some theoretical simplifications. The GSI chart thereby contains model uncertainty which arises from its development. The presence of such model uncertainty affects the GSI estimated from GSI chart at a specific site; it is, therefore, imperative to quantify and incorporate the model uncertainty during GSI estimation from the GSI chart. A major challenge for quantifying the GSI chart model uncertainty is a lack of the original datasets that have been used to develop the GSI chart, since the GSI chart was developed from past experience without referring to specific datasets. This paper intends to tackle this problem by developing a Bayesian approach for quantifying the model uncertainty in GSI chart when using it to estimate GSI at a specific site. The model uncertainty in the GSI chart and the inherent spatial variability in GSI are modeled explicitly in the Bayesian approach. The Bayesian approach generates equivalent samples of GSI from the integrated knowledge of GSI chart, prior knowledge and observation data available from site investigation. Equations are derived for the Bayesian approach, and the proposed approach is illustrated using data from a drill and blast tunnel project. The proposed approach effectively tackles the problem of how to quantify the model uncertainty that arises from using GSI chart for characterization of site-specific GSI in a transparent manner.

  11. Effects of different silanes and acid concentrations on bond strength of brackets to porcelain surfaces.

    PubMed

    Trakyali, Göksu; Malkondu, Ozlem; Kazazoğlu, Ender; Arun, Tülin

    2009-08-01

    The aim of this study was to determine the optimum silane-coupling agent and the optimum concentration of acid agent when bonding to porcelain surfaces. Eighty deglazed feldspathic porcelain discs with a diameter of 10 mm and a thickness of 2 mm mounted in acrylic resin blocks were randomly divided into four groups. In groups 1 and 2, the porcelain surfaces were etched with 9.6 per cent hydrofluoric (HF) acid and in groups 3 and 4 with 5 per cent HF acid. In groups 1 and 3, the Dynalock maxillary central incisor brackets were bonded with Pulpdent silane and Unite bonding adhesive and in groups 2 and 4 with Reliance silane and Unite. Shear forces were applied to the samples using an Instron universal test machine. The non-parametric Kruskal-Wallis test was used to determine significant differences in bond strengths between the four groups and Dunn's multiple comparison test to compare subgroups. The mean bond strengths and standard deviations of groups 1 to 4 were 5.51 +/- 1.19, 6.54 +/- 0.002, 4.55 +/- 1.93, and 6.39 +/- 0.45 MPa, respectively. Specimens bonded with Reliance showed a statistically significantly higher in vitro bond strength than those bonded with Pulpdent. The concentration of etching gels did not result in any statistically significant difference on the in vitro bond strength when evaluated separately.

  12. Acid precipitation at 3 sites in the Klang Valley, Malaysia

    SciTech Connect

    Philip, E.; Yap, S.K.; Azimi, S.

    1996-12-31

    A study which examined spatial variation, dust and chemical composition factors associated with precipitation pH in the Klang Valley had been conducted. Precipitation samples were collected on a monthly basis at 3 different locations during the periods of 1993-1995. These long term sites were situated at varying distance from the industrial zone of the Klang Valley. Data were collected on a monthly basis and where possible after every rainfall. This included the field pH, electrical conductivity (EC) and analysis of chemical components. To date, the general pH trend at these stations is decreasing towards the acid range. The site furthest from the industrial zone had the highest pH values while site closest to the industrial zone had the lowest pH. There appeared to be a correlation between the precipitation pH and electrical conductivity (EC), the EC readings increased with increased acidity. Variations in precipitation pH was closely associated with the changes in sulfate concentration. The pH of precipitation is determined not only by the anions, but also by the concentration of cations in the atmosphere which neutralized the acidity by forming salts. The main cause for the decrease in the pH values is the significant increase of acidic components and decrease of soil-oriented components (Mg and Ca) in the rain water.

  13. C-H bond strengths and acidities in aromatic systems: effects of nitrogen incorporation in mono-, di-, and triazines.

    PubMed

    Wren, Scott W; Vogelhuber, Kristen M; Garver, John M; Kato, Shuji; Sheps, Leonid; Bierbaum, Veronica M; Lineberger, W Carl

    2012-04-18

    The negative ion chemistry of five azine molecules has been investigated using the combined experimental techniques of negative ion photoelectron spectroscopy to obtain electron affinities (EA) and tandem flowing afterglow-selected ion tube (FA-SIFT) mass spectrometry to obtain deprotonation enthalpies (Δ(acid)H(298)). The measured Δ(acid)H(298) for the most acidic site of each azine species is combined with the EA of the corresponding radical in a thermochemical cycle to determine the corresponding C-H bond dissociation energy (BDE). The site-specific C-H BDE values of pyridine, 1,2-diazine, 1,3-diazine, 1,4-diazine, and 1,3,5-triazine are 110.4 ± 2.0, 111.3 ± 0.7, 113.4 ± 0.7, 107.5 ± 0.4, and 107.8 ± 0.7 kcal mol(-1), respectively. The application of complementary experimental methods, along with quantum chemical calculations, to a series of nitrogen-substituted azines sheds light on the influence of nitrogen atom substitution on the strength of C-H bonds in six-membered rings.

  14. The effect of elevated temperature on the strength parameters of silica acid ester consolidated porous limestones

    NASA Astrophysics Data System (ADS)

    Pápay, Zita; Török, Ákos

    2013-04-01

    The porous limestone is one of the most widespread construction materials of the monuments in Central Europe, with emblematic buildings in Vienna, Bratislava, Budapest and many other cities of Austria, Slovakia, Czech Republic and Hungary. The restoration of these monuments very often requires the consolidation of the porous limestone material, where various types of consolidants are used to strengthen the highly weathered stone. Our research focused on the understanding of the behaviour of consolidated porous limestone when the material is subjected to higher temperatures. Test procedure included the preparation of cylindrical test specimens from the Miocene porous limestone which was followed by consolidation by four various types of silica acid ester. The samples after consolidation were heated to 300 and 600 °C in electric oven. The material properties such as ultrasonic pulse velocity, density were tested before and after the treatment. Indirect tensile strength (Brazilian test) was used to compare the strength parameters of non treated and consolidated samples. Silica acid ester treated samples after heating were also measured in terms of strength, density and ultrasonic pulse velocity. The results show that there are significant changes in strength of various pre-treated samples after heating indicating the sensitivity of the materials to temperature changes and accidental fire.

  15. Multi-site study of diffusion metric variability: effects of site, vendor, field strength, and echo time on regions-of-interest and histogram-bin analyses

    NASA Astrophysics Data System (ADS)

    Helmer, K. G.; Chou, M.-C.; Preciado, R. I.; Gimi, B.; Rollins, N. K.; Song, A.; Turner, J.; Mori, S.

    2016-03-01

    It is now common for magnetic-resonance-imaging (MRI) based multi-site trials to include diffusion-weighted imaging (DWI) as part of the protocol. It is also common for these sites to possess MR scanners of different manufacturers, different software and hardware, and different software licenses. These differences mean that scanners may not be able to acquire data with the same number of gradient amplitude values and number of available gradient directions. Variability can also occur in achievable b-values and minimum echo times. The challenge of a multi-site study then, is to create a common protocol by understanding and then minimizing the effects of scanner variability and identifying reliable and accurate diffusion metrics. This study describes the effect of site, scanner vendor, field strength, and TE on two diffusion metrics: the first moment of the diffusion tensor field (mean diffusivity, MD), and the fractional anisotropy (FA) using two common analyses (region-of-interest and mean-bin value of whole brain histograms). The goal of the study was to identify sources of variability in diffusion-sensitized imaging and their influence on commonly reported metrics. The results demonstrate that the site, vendor, field strength, and echo time all contribute to variability in FA and MD, though to different extent. We conclude that characterization of the variability of DTI metrics due to site, vendor, field strength, and echo time is a worthwhile step in the construction of multi-center trials.

  16. Multi-site study of diffusion metric variability: effects of site, vendor, field strength, and echo time on regions-of-interest and histogram-bin analyses

    PubMed Central

    Helmer, K. G.; Chou, M-C.; Preciado, R. I.; Gimi, B.; Rollins, N. K.; Song, A.; Turner, J.; Mori, S.

    2016-01-01

    It is now common for magnetic-resonance-imaging (MRI) based multi-site trials to include diffusion-weighted imaging (DWI) as part of the protocol. It is also common for these sites to possess MR scanners of different manufacturers, different software and hardware, and different software licenses. These differences mean that scanners may not be able to acquire data with the same number of gradient amplitude values and number of available gradient directions. Variability can also occur in achievable b-values and minimum echo times. The challenge of a multi-site study then, is to create a common protocol by understanding and then minimizing the effects of scanner variability and identifying reliable and accurate diffusion metrics. This study describes the effect of site, scanner vendor, field strength, and TE on two diffusion metrics: the first moment of the diffusion tensor field (mean diffusivity, MD), and the fractional anisotropy (FA) using two common analyses (region-of-interest and mean-bin value of whole brain histograms). The goal of the study was to identify sources of variability in diffusion-sensitized imaging and their influence on commonly reported metrics. The results demonstrate that the site, vendor, field strength, and echo time all contribute to variability in FA and MD, though to different extent. We conclude that characterization of the variability of DTI metrics due to site, vendor, field strength, and echo time is a worthwhile step in the construction of multi-center trials. PMID:27330240

  17. Electrophysiological evidence for acidic, basic, and neutral amino acid olfactory receptor sites in the catfish

    PubMed Central

    1984-01-01

    Electrophysiological experiments indicate that olfactory receptors of the channel catfish, Ictalurus punctatus, contain different receptor sites for the acidic (A), basic (B), and neutral amino acids; further, at least two partially interacting neutral sites exist, one for the hydrophilic neutral amino acids containing short side chains (SCN), and the second for the hydrophobic amino acids containing long side chains (LCN). The extent of cross-adaptation was determined by comparing the electro-olfactogram (EOG) responses to 20 "test" amino acids during continuous bathing of the olfactory mucosa with water only (control) to those during each of the eight "adapting" amino acid regimes. Both the adapting and test amino acids were adjusted in concentrations to provide approximately equal response magnitudes in the unadapted state. Under all eight adapting regimes, the test EOG responses were reduced from those obtained in the unadapted state, but substantial quantitative differences resulted, depending upon the molecular structure of the adapting stimulus. Analyses of the patterns of EOG responses to the test stimuli identified and characterized the respective "transduction processes," a term used to describe membrane events initiated by a particular subset of amino acid stimuli that are intricately linked to the origin of the olfactory receptor potential. Only when the stimulus compounds interact with different transduction processes are the stimuli assumed to bind to different membrane "sites." Four relatively independent L-alpha-amino acid transduction processes (and thus at least four binding sites) identified in this report include: (a) the A process for aspartic and glutamic acids; (b) the B process for arginine and lysine; (c) the SCN process for glycine, alanine, serine, glutamine, and possibly cysteine; (d) the LCN process for methionine, ethionine, valine, norvaline, leucine, norleucine, glutamic acid-gamma-methyl ester, histidine, phenylalanine, and also

  18. Effect of phytic acid used as etchant on bond strength, smear layer, and pulpal cells.

    PubMed

    Nassar, Mohannad; Hiraishi, Noriko; Islam, Md Sofiqul; Aizawa, Mamoru; Tamura, Yukihiko; Otsuki, Masayuki; Kasugai, Shohei; Ohya, Keiichi; Tagami, Junji

    2013-10-01

    This study aimed to evaluate the effect of phytic acid (IP6), used as etchant, on resin-dentin bond strength, smear layer removal, and the viability of pulpal cells. Flat dentin surfaces with smear layer were etched with 1% IP6 for 60, 30, or 15 s; in the control group 37% phosphoric acid (PA) was used. Dentin surfaces were rinsed, blot-dried, and bonded with an etch-and-rinse adhesive, followed by composite build-ups. The specimens were subjected to tensile testing after 24 h of water storage at 37°C, and failure modes were determined using scanning electron microscopy. The effectiveness of IP6 to remove the smear layer was observed using scanning electron microscopy. To evaluate the effect on pulpal cells, solutions of 0.1 and 0.01% IP6 and of 3.7 and 0.37% PA were prepared and rat pulpal cells were treated with these solutions for 6 and 24 h. Cell viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The results demonstrated that all application times of IP6 produced bond-strength values that were significantly higher than that of the control. Phytic acid effectively removed the smear layer and plugs, thus exposing the collagen network. Phytic acid had a minimal effect on pulpal cells, whereas PA resulted in a marked decrease in their viability.

  19. Acidity of edge surface sites of montmorillonite and kaolinite

    NASA Astrophysics Data System (ADS)

    Liu, Xiandong; Lu, Xiancai; Sprik, Michiel; Cheng, Jun; Meijer, Evert Jan; Wang, Rucheng

    2013-09-01

    Acid-base chemistry of clay minerals is central to their interfacial properties, but up to now a quantitative understanding on the surface acidity is still lacking. In this study, with first principles molecular dynamics (FPMD) based vertical energy gap technique, we calculate the acidity constants of surface groups on (0 1 0)-type edges of montmorillonite and kaolinite, which are representatives of 2:1 and 1:1-type clay minerals, respectively. It shows that tbnd Si-OH and tbnd Al-OH2OH groups of kaolinite have pKas of 6.9 and 5.7 and those of montmorillonite have pKas of 7.0 and 8.3, respectively. For each mineral, the calculated pKas are consistent with the experimental ranges derived from fittings of titration curves, indicating that tbnd Si-OH and tbnd Al-OH2OH groups are the major acidic sites responsible to pH-dependent experimental observations. The effect of Mg substitution in montmorillonite is investigated and it is found that Mg substitution increases the pKas of the neighboring tbnd Si-OH and tbnd Si-OH2 groups by 2-3 pKa units. Furthermore, our calculation shows that the pKa of edge tbnd Mg-(OH2)2 is as high as 13.2, indicating the protonated state dominates under common pH. Together with previous adsorption experiments, our derived acidity constants suggest that tbnd Si-O- and tbnd Al-(OH)2 groups are the most probable edge sites for complexing heavy metal cations.

  20. Inorganic Nitrogen Cycling in an Extreme Acid Mine Drainage Site

    NASA Astrophysics Data System (ADS)

    Kalnejais, L. H.; Smith, R. L.; Nordstrom, D. K.; Banfield, J. F.

    2006-12-01

    Weathering of the massive sulfide ore body at Iron Mountain, northern California has generated sulfuric acid solutions with pH values ranging from 0.5 to 1, temperatures up to 50°C and high concentrations of toxic metals. Communities of microorganisms catalyze the oxidation of iron and sulfur that generates this extreme environment. The nitrogen requirements of these organisms and the nitrogen cycling within these waters are not understood. By adapting the chemiluminescence detection method of Baeseman (2004) we have constrained the stability of nitrate and nitrite species in acidic, high ferrous iron solutions and have measured a time series of the nitrate concentrations at sites within Iron Mountain. The half-life of nitrite is less than an hour due to reactions with ferrous ions, while nitrate is found at concentrations of up to 10 μM within the mine. By coupling this information with geochemical and microbial community information at each site together with culture enrichment studies using various nitrogen sources we hope to gain insight into the pathways of nitrogen utilization in this extreme environment. References Baeseman, J.L. (2004) Denitrification in acid-impacted mountain stream sediments. Ph.D. Dissertation, University of Colorado, Department of Civil, Environmental, and Architectural Engineering.

  1. Active site amino acid sequence of human factor D.

    PubMed

    Davis, A E

    1980-08-01

    Factor D was isolated from human plasma by chromatography on CM-Sephadex C50, Sephadex G-75, and hydroxylapatite. Digestion of reduced, S-carboxymethylated factor D with cyanogen bromide resulted in three peptides which were isolated by chromatography on Sephadex G-75 (superfine) equilibrated in 20% formic acid. NH2-Terminal sequences were determined by automated Edman degradation with a Beckman 890C sequencer using a 0.1 M Quadrol program. The smallest peptide (CNBr III) consisted of the NH2-terminal 14 amino acids. The other two peptides had molecular weights of 17,000 (CNBr I) and 7000 (CNBr II). Overlap of the NH2-terminal sequence of factor D with the NH2-terminal sequence of CNBr I established the order of the peptides. The NH2-terminal 53 residues of factor D are somewhat more homologous with the group-specific protease of rat intestine than with other serine proteases. The NH2-terminal sequence of CNBr II revealed the active site serine of factor D. The typical serine protease active site sequence (Gly-Asp-Ser-Gly-Gly-Pro was found at residues 12-17. The region surrounding the active site serine does not appear to be more highly homologous with any one of the other serine proteases. The structural data obtained point out the similarities between factor D and the other proteases. However, complete definition of the degree of relationship between factor D and other proteases will require determination of the remainder of the primary structure.

  2. Relative strengths of axial and equatorial bonds and site preferences for ligand substitution on σ complexes

    NASA Astrophysics Data System (ADS)

    Su, Ming-Der

    An analytical LCAO MO perturbation approach has been developed for treating the electronic structure and some properties of Y-shaped EL3 compounds where E is a main group element A or a transition metal M. Three problems have been considered: (i) the relative strengths of E-L(1,2) (1 and 2 stand for the paired ligands) and E-L(3) (3 stands for the unique ligand) bonds; (ii) the mutual influence of ligands in substituted complexes EL2L'; (iii) the site preference of the stronger donor (or acceptor) of substituents L', L''. Ratios of overlap populations T=NE-L(3)/NE-L(1) were estimated for ns, np and (n-1)d contributions. For 6-10 valence electron AL3 we found T(s)>1, T(p)>1. These contributions all reinforce to make the A-L(3) bond relatively stronger than A-L(1,2) bonds. The ML3 d0-d8 case was also examined and it was found that T(s+p+d)>1, while the T(p) contribution dominates in ML3 (d10) complexes to make M-L(3)>M-L(1,2). The perturbing influence on ligand σ orbital energies δα'=α(L')-α(L), where δα'>0(<0) corresponds to a better donor (acceptor) substituent L', and all changes in overlap populations of different E-L bonds, δN(E-L)/δα', were obtained in terms of the ns, np and (n-1)d contributions. In addition, there are three kinds of substitution type: sub-L(3)-cis-L(1), sub-L(1)-cis-L(2) and sub-L(1)-cis-L(3) effects. It was found that both the nature of E, L', L and steric factors may play important roles in determining the relative bond strengthening of E-L(1,2) and E-L(3) for unsubstituted and substituted EL3 compounds. Y-shaped substituents were examined using first-order perturbation theory, with the finding that the most electronegative atom prefers to substitute at the L(3) site in AL3 and d0-d10 ML3 complexes. The role of π bonding effects is briefly discussed. The results obtained agree with the available experimental and computational data and permit a number of predictions to be made.

  3. Binding sites of retinol and retinoic acid with serum albumins.

    PubMed

    Belatik, A; Hotchandani, S; Bariyanga, J; Tajmir-Riahi, H A

    2012-02-01

    Retinoids are effectively transported in the bloodstream via serum albumins. We report the complexation of bovine serum albumin (BSA) with retinol and retinoic acid at physiological conditions, using constant protein concentration and various retinoid contents. FTIR, CD and fluorescence spectroscopic methods and molecular modeling were used to analyze retinoid binding site, the binding constant and the effects of complexation on BSA stability and secondary structure. Structural analysis showed that retinoids bind BSA via hydrophilic and hydrophobic interactions with overall binding constants of K(Ret)(-BSA) = 5.3 (±0.8) × 10(6) M(-1) and K(Retac-BSA) = 2.3 (±0.4) × 10(6) M(-1). The number of bound retinoid molecules (n) was 1.20 (±0.2) for retinol and 1.8 (±0.3) for retinoic acid. Molecular modeling showed the participation of several amino acids in retinoid-BSA complexes stabilized by H-bonding network. The retinoid binding altered BSA conformation with a major reduction of α-helix from 61% (free BSA) to 36% (retinol-BSA) and 26% (retinoic acid-BSA) with an increase in turn and random coil structures indicating a partial protein unfolding. The results indicate that serum albumins are capable of transporting retinoids in vitro and in vivo.

  4. Shear bond strength of resin cement to an acid etched and a laser irradiated ceramic surface

    PubMed Central

    Motro, Pelin Fatma Karagoz; Yurdaguven, Haktan

    2013-01-01

    PURPOSE To evaluate the effects of hydrofluoric acid etching and Er,Cr:YSGG laser irradiation on the shear bond strength of resin cement to lithium disilicate ceramic. MATERIALS AND METHODS Fifty-five ceramic blocks (5 mm × 5 mm × 2 mm) were fabricated and embedded in acrylic resin. Their surfaces were finished with 1000-grit silicon carbide paper. The blocks were assigned to five groups: 1) 9.5% hydrofluoric-acid etching for 60 s; 2-4), 1.5-, 2.5-, and 6-W Er,Cr:YSGG laser applications for 60 seconds, respectively; and 5) no treatment (control). One specimen from each group was examined using scanning electron microscopy. Ceramic primer (Rely X ceramic primer) and adhesive (Adper Single Bond) were applied to the ceramic surfaces, followed by resin cement to bond the composite cylinders, and light curing. Bonded specimens were stored in distilled water at 37℃ for 24 hours. Shear bond strengths were determined by a universal testing machine at 1 mm/min crosshead speed. Data were analyzed using Kruskal-Wallis and Mann-Whitney U-tests (α=0.05). RESULTS Adhesion was significantly stronger in Group 2 (3.88 ± 1.94 MPa) and Group 3 (3.65 ± 1.87 MPa) than in Control group (1.95 ± 1.06 MPa), in which bonding values were lowest (P<.01). No significant difference was observed between Group 4 (3.59 ± 1.19 MPa) and Control group. Shear bond strength was highest in Group 1 (8.42 ± 1.86 MPa; P<.01). CONCLUSION Er,Cr:YSGG laser irradiation at 1.5 and 2.5 W increased shear bond strengths between ceramic and resin cement compared with untreated ceramic surfaces. Irradiation at 6 W may not be an efficient ceramic surface treatment technique. PMID:23755333

  5. Multi-site Study of Diffusion Metric Variability: Characterizing the Effects of Site, Vendor, Field Strength, and Echo Time using the Histogram Distance

    PubMed Central

    Helmer, K. G.; Chou, M-C.; Preciado, R. I.; Gimi, B.; Rollins, N. K.; Song, A.; Turner, J.; Mori, S.

    2016-01-01

    MRI-based multi-site trials now routinely include some form of diffusion-weighted imaging (DWI) in their protocol. These studies can include data originating from scanners built by different vendors, each with their own set of unique protocol restrictions, including restrictions on the number of available gradient directions, whether an externally-generated list of gradient directions can be used, and restrictions on the echo time (TE). One challenge of multi-site studies is to create a common imaging protocol that will result in a reliable and accurate set of diffusion metrics. The present study describes the effect of site, scanner vendor, field strength, and TE on two common metrics: the first moment of the diffusion tensor field (mean diffusivity, MD), and the fractional anisotropy (FA). We have shown in earlier work that ROI metrics and the mean of MD and FA histograms are not sufficiently sensitive for use in site characterization. Here we use the distance between whole brain histograms of FA and MD to investigate within- and between-site effects. We concluded that the variability of DTI metrics due to site, vendor, field strength, and echo time could influence the results in multi-center trials and that histogram distance is sensitive metrics for each of these variables. PMID:27350723

  6. Solvent effects on the electronic absorption spectra and acid strength of some substituted pyridinols

    NASA Astrophysics Data System (ADS)

    Hashem, Elham Y.; Saleh, Magda S.

    2002-01-01

    The electronic absorption spectra of some substituted pyridinols in organic solvents of different polarities are studied. Also, the solvent effects on the intramolecular charge transfer bands are discussed using various solvent parameters. The acid-base equilibria of the compounds used are studied spectrophotometrically in various mixed aqueous solvents at 25 °C and 0.1 M ionic strength (NaClO 4). Furthermore, the influence of the solvents on the dissociation constants and tautomeric equilibria of a pyridinol derivatives are discussed. The effect of molecular structure of the pyridinols on the p K's is also examined.

  7. Effect of aluminum anodizing in phosphoric acid electrolyte on adhesion strength and thermal performance

    NASA Astrophysics Data System (ADS)

    Lee, Sulki; Kim, Donghyun; Kim, Yonghwan; Jung, Uoochang; Chung, Wonsub

    2016-01-01

    This study examined the adhesive bond strength and thermal performance of the anodized aluminum 6061 in phosphoric acid electrolyte to improve the adhesive bond strength and thermal performance for use in metal core printed circuit boards (MCPCB). The electrolyte temperature and applied voltage were altered to generate varied pore structures. The thickness, porosity and pore diameter of the anodized layer were measured. The pore morphologies were affected most by temperature, which was the driving force for ion transportation. The mechanism of adhesive bond was penetration of the epoxy into the pores. The optimal anodization conditions for maximum adhesive bond strength, 27 MPa, were 293 K and 100V. The maximum thermal conductivity of the epoxy-treated anodized layer was 1.6 W/m·K at 273 K. Compared with the epoxy-treated Al layer used for conventional MCPCBs, the epoxy-treated anodized layer showed advanced thermal performance due to a low difference of thermal resistance and high heat dissipation.

  8. Analysis of the strengths and weaknesses of acid rain electronic data reports

    SciTech Connect

    Schott, J.

    1997-12-31

    Entergy Corporation is a Phase II utility with a fossil generation base composed primarily of natural gas and low sulfur coal. This paper presents an analysis of a large Phase II utility`s continuous emissions monitoring data reported to EPA under Title IV Acid Rain. Electric utilities currently report hourly emissions of NO{sub x}, SO{sub 2}, CO{sub 2}, fuel use, and generation through electronic data reports to EPA. This paper describes strengths and weaknesses of the data reported to EPA as determined through an analysis of 1995 data. Emissions reported by this company under acid rain for SO{sub 2} and NO{sub x} are very different from emissions reported to state agencies for annual emission inventory purposes in past years and will represent a significant break with historic trends. A comparison of emissions has been made of 1995 emissions reported under Electronic Data Reports to the emissions that would have been reported using emission factors and fuel data in past years. In addition, the paper examines the impacts of 40 CFR Part 75 Acid Rain requirements such as missing data substitution and monitor bias adjustments. Measurement system errors including stack flow measurement and false NO{sub x}Lb/MMBtu readings at very low loads are discussed. This paper describes the implications for public policy, compliance, emissions inventories, and business decisions of Part 75 acid rain monitoring and reporting requirements.

  9. BOND STRENGTH AND MORPHOLOGY OF ENAMEL USING SELF-ETCHING ADHESIVE SYSTEMS WITH DIFFERENT ACIDITIES

    PubMed Central

    Moura, Sandra Kiss; Reis, Alessandra; Pelizzaro, Arlete; Dal-Bianco, Karen; Loguercio, Alessandro Dourado; Arana-Chavez, Victor Elias; Grande, Rosa Helena Miranda

    2009-01-01

    Objectives: To assess the bond strength and the morphology of enamel after application of self-etching adhesive systems with different acidities. The tested hypothesis was that the performance of the self-etching adhesive systems does not vary for the studied parameters. Material and methods: Composite resin (Filtek Z250) buildups were bonded to untreated (prophylaxis) and treated (burcut or SiC-paper) enamel surfaces of third molars after application of four self-etching and two etch-and-rinse adhesive systems (n=6/condition): Clearfil SE Bond (CSE); OptiBond Solo Plus Self-Etch (OP); AdheSe (AD); Tyrian Self Priming Etching (TY), Adper Scotchbond Multi-Purpose Plus (SBMP) and Adper Single Bond (SB). After storage in water (24 h/37°C), the bonded specimens were sectioned into sticks with 0.8 mm2 cross-sectional area and the microtensile bond strength was tested at a crosshead speed of 0.5 mm/min. The mean bond strength values (MPa) were subjected to two-way ANOVA and Tukey's test (α=0.05). The etching patterns of the adhesive systems were also observed with a scanning electron microscope. Results: The main factor adhesive system was statistically significant (p<0.05). The mean bond strength values (MPa) and standard deviations were: CSE (20.5±3.5), OP (11.3±2.3), AD (11.2±2.8), TY (11.1±3.0), SBMP (21.9±4.0) and SB (24.9±3.0). Different etching patterns were observed for the self-etching primers depending on the enamel treatment and the pH of the adhesive system. Conclusion: Although there is a tendency towards using adhesive systems with simplified application procedures, this may compromise the bonding performance of some systems to enamel, even when the prismless enamel is removed. PMID:19668991

  10. Development and Assessment of a Diagnostic Tool to Identify Organic Chemistry Students' Alternative Conceptions Related to Acid Strength

    ERIC Educational Resources Information Center

    McClary, LaKeisha M.; Bretz, Stacey Lowery

    2012-01-01

    The central goal of this study was to create a new diagnostic tool to identify organic chemistry students' alternative conceptions related to acid strength. Twenty years of research on secondary and college students' conceptions about acids and bases has shown that these important concepts are difficult for students to apply to qualitative problem…

  11. High ionic strength narrows the population of sites participating in protein ion-exchange adsorption: a single-molecule study.

    PubMed

    Kisley, Lydia; Chen, Jixin; Mansur, Andrea P; Dominguez-Medina, Sergio; Kulla, Eliona; Kang, Marci K; Shuang, Bo; Kourentzi, Katerina; Poongavanam, Mohan-Vivekanandan; Dhamane, Sagar; Willson, Richard C; Landes, Christy F

    2014-05-23

    The retention and elution of proteins in ion-exchange chromatography is routinely controlled by adjusting the mobile phase salt concentration. It has repeatedly been observed, as judged from adsorption isotherms, that the apparent heterogeneity of adsorption is lower at more-eluting, higher ionic strength. Here, we present an investigation into the mechanism of this phenomenon using a single-molecule, super-resolution imaging technique called motion-blur Points Accumulation for Imaging in Nanoscale Topography (mbPAINT). We observed that the number of functional adsorption sites was smaller at high ionic strength and that these sites had reduced desorption kinetic heterogeneity, and thus narrower predicted elution profiles, for the anion-exchange adsorption of α-lactalbumin on an agarose-supported, clustered-charge ligand stationary phase. Explanations for the narrowing of the functional population such as inter-protein interactions and protein or support structural changes were investigated through kinetic analysis, circular dichroism spectroscopy, and microscopy of agarose microbeads, respectively. The results suggest the reduction of heterogeneity is due to both electrostatic screening between the protein and ligand and tuning the steric availability within the agarose support. Overall, we have shown that single molecule spectroscopy can aid in understanding the influence of ionic strength on the population of functional adsorbent sites participating in the ion-exchange chromatographic separation of proteins.

  12. High ionic strength narrows the population of sites participating in protein ion-exchange adsorption: A single-molecule study

    PubMed Central

    Kisley, Lydia; Chen, Jixin; Mansur, Andrea P.; Dominguez-Medina, Sergio; Kulla, Eliona; Kang, Marci; Shuang, Bo; Kourentzi, Katerina; Poongavanam, Mohan-Vivekanandan; Dhamane, Sagar; Willson, Richard C.; Landes, Christy F.

    2014-01-01

    The retention and elution of proteins in ion-exchange chromatography is routinely controlled by adjusting the mobile phase salt concentration. It has repeatedly been observed, as judged from adsorption isotherms, that the apparent heterogeneity of adsorption is lower at more-eluting, higher ionic strength. Here, we present an investigation into the mechanism of this phenomenon using a single-molecule, super-resolution imaging technique called motion-blur Points Accumulation for Imaging in Nanoscale Topography (mbPAINT). We observed that the number of functional adsorption sites was smaller at high ionic strength and that these sites had reduced desorption kinetic heterogeneity, and thus narrower predicted elution profiles, for the anion-exchange adsorption of α-lactalbumin on an agarose-supported, clustered-charge ligand stationary phase. Explanations for the narrowing of the functional population such as inter-protein interactions and protein or support structural changes were investigated through kinetic analysis, circular dichroism spectroscopy, and microscopy of agarose microbeads, respectively. The results suggest the reduction of heterogeneity is due to both electrostatic screening between the protein and ligand and tuning the steric availability within the agarose support. Overall, we have shown that single molecule spectroscopy can aid in understanding the influence of ionic strength on the population of functional adsorbent sites participating in the ion-exchange chromatographic separation of proteins. PMID:24751557

  13. Comparison of bond strength and surface morphology of dental enamel for acid and Nd-YAG laser etching

    NASA Astrophysics Data System (ADS)

    Parmeswearan, Diagaradjane; Ganesan, Singaravelu; Ratna, P.; Koteeswaran, D.

    1999-05-01

    Recently, laser pretreatment of dental enamel has emerged as a new technique in the field of orthodontics. However, the changes in the morphology of the enamel surface is very much dependent on the wavelength of laser, emission mode of the laser, energy density, exposure time and the nature of the substance absorbing the energy. Based on these, we made a comparative in vitro study on laser etching with acid etching with reference to their bond strength. Studies were conducted on 90 freshly extracted, non carious, human maxillary or mandibular anteriors and premolars. Out of 90, 60 were randomly selected for laser irradiation. The other 30 were used for conventional acid pretreatment. The group of 60 were subjected to Nd-YAG laser exposure (1060 nm, 10 Hz) at differetn fluences. The remaining 30 were acid pretreated with 30% orthophosphoric acid. Suitable Begg's brackets were selected and bound to the pretreated surface and the bond strength were tested using Instron testing machine. The bond strength achieved through acid pretreatment is found to be appreciably greater than the laser pretreated tooth. Though the bond strength achieved through the acid pretreated tooth is found to be significantly greater than the laser pretreated specimens, the laser pretreatement is found to be successful enough to produce a clinically acceptable bond strength of > 0.60 Kb/mm. Examination of the laser pre-treated tooth under SEM showed globule formation which may produce the mechanical interface required for the retention of the resin material.

  14. A computer program for geochemical analysis of acid-rain and other low-ionic-strength, acidic waters

    USGS Publications Warehouse

    Johnsson, P.A.; Lord, D.G.

    1987-01-01

    ARCHEM, a computer program written in FORTRAN 77, is designed primarily for use in the routine geochemical interpretation of low-ionic-strength, acidic waters. On the basis of chemical analyses of the water, and either laboratory or field determinations of pH, temperature, and dissolved oxygen, the program calculates the equilibrium distribution of major inorganic aqueous species and of inorganic aluminum complexes. The concentration of the organic anion is estimated from the dissolved organic concentration. Ionic ferrous iron is calculated from the dissolved oxygen concentration. Ionic balances and comparisons of computed with measured specific conductances are performed as checks on the analytical accuracy of chemical analyses. ARCHEM may be tailored easily to fit different sampling protocols, and may be run on multiple sample analyses. (Author 's abstract)

  15. Effects of salicylic-lactic acid conditioner on the shear bond strength of brackets and enamel surfaces.

    PubMed

    Chang, W-G; Lim, B-S; Yoon, T-H; Lee, Y-K; Kim, C-W

    2005-04-01

    The purpose of this study was to evaluate the effects of salicylic-lactic (SL) acid conditioner on the shear bond strength of brackets. Fluoride releasing (Light-bond) and non-fluoride releasing (Enlight) composite adhesives were used after conditioning with 0.22% salicylic + 9% lactic acid or 34% phosphoric acid. Composite adhesives were light cured with either a halogen light curing (HLC) unit for 30-50 s or a plasma arc curing (PAC) unit for 4 s. The shear bond strength was measured with an Instron. Failure modes of debonded brackets were identified based on adhesive remnants on the bracket and tooth. Salicylic-lactic acid conditioning was found to provide adequate shear bond strength. Groups conditioned with SL acid were debonded mainly at the enamel-resin interface and comparatively clean enamel surface after debonding was observed than those conditioned with phosphoric acid. Using confocal laser scanning microscopic examinations, it was found that demineralization patterns between SL acid and phosphoric acid conditioned groups were not different when the same adhesive was used. The SL acid conditioner did not reduce the demineralization. Light-bond adhesive showed less demineralization than Enlight adhesive. The PAC unit can be recommended as an alterative to the HLC unit because it significantly reduces the irradiation time.

  16. A glial amino-acid transporter controls synapse strength and courtship in Drosophila.

    PubMed

    Grosjean, Yael; Grillet, Micheline; Augustin, Hrvoje; Ferveur, Jean-François; Featherstone, David E

    2008-01-01

    Mate choice is an evolutionarily critical decision that requires the detection of multiple sex-specific signals followed by central integration of these signals to direct appropriate behavior. The mechanisms controlling mate choice remain poorly understood. Here, we show that the glial amino-acid transporter genderblind controls whether Drosophila melanogaster males will attempt to mate with other males. Genderblind (gb) mutant males showed no alteration in heterosexual courtship or copulation, but were attracted to normally unappealing male species-specific chemosensory cues. As a result, genderblind mutant males courted and attempted to copulate with other Drosophila males. This homosexual behavior could be induced within hours using inducible RNAi, suggesting that genderblind controls nervous system function rather than its development. Consistent with this, and indicating that glial genderblind regulates ambient extracellular glutamate to suppress glutamatergic synapse strength in vivo, homosexual behavior could be turned on and off by altering glutamatergic transmission pharmacologically and/or genetically.

  17. Chemical characteristics and sources of organic acids in precipitation at a semi-urban site in Southwest China

    NASA Astrophysics Data System (ADS)

    Zhang, Y. L.; Lee, X. Q.; Cao, F.

    2011-01-01

    In order to investigate the chemical characteristics and sources of organic acids in precipitation in Southwest China, 105 rainwater samples were collected at a semi-urban site in Anshun from June 2007 to June 2008. Organic acids and major anions were analyzed along with pH and electrical conductivity. The pH values varied from 3.57 to 7.09 for all the rainfall events sampled, with an average of 4.67 which was typical acidic value. Formic, acetic and oxalic acids were found to be the predominant carboxylic acids and their volume weighted average (VWA) concentrations were 8.77, 6.93 and 2.84 μmol l -1, respectively. These organic acids were estimated to account for 8.1% to the total free acidity (TFA) in precipitation. The concentrations of the majority organic acids at studied site had a clear seasonal pattern, reaching higher levels during the non-growing season than those in growing season, which was attributed to dilution effect of heavy rainfall during the growing season. The seasonal variation of wet deposition flux of these organic acids confirmed higher source strength of biogenic emissions from vegetation during the growing season. Formic-to-acetic acids ratio (F/A), an indicator of primary versus secondary sources of these organic acids, suggested that primary sources from vehicular emission, biomass burning, soil and vegetation emissions were dominant sources. In addition, the lowest concentrations of organic acids were found under type S, when air masses originated from the marine (South China Sea) during Southern Asian Monsoon period. And the highest concentrations were observed in precipitation events from Northeast China (type NE), prevailing mostly during winter with the lowest rainfall.

  18. Ursolic Acid-Induced Elevation of Serum Irisin Augments Muscle Strength During Resistance Training in Men

    PubMed Central

    Bang, Hyun Seok; Seo, Dae Yun; Chung, Yong Min; Oh, Kyoung-Mo; Park, Jung Jun; Arturo, Figueroa; Jeong, Seung-Hun; Kim, Nari

    2014-01-01

    Ursolic acid (UA), a type of pentacyclic triterpenoid carboxylic acid purified from natural plants, can promote skeletal muscle development. We measured the effect of resistance training (RT) with/without UA on skeletal muscle development and related factors in men. Sixteen healthy male participants (age, 29.37±5.14 years; body mass index=27.13±2.16 kg/m2) were randomly assigned to RT (n=7) or RT with UA (RT+UA, n=9) groups. Both groups completed 8 weeks of intervention consisting of 5 sets of 26 exercises, with 10~15 repetitions at 60~80% of 1 repetition maximum and a 60~90-s rest interval between sets, performed 6 times/week. UA or placebo was orally ingested as 1 capsule 3 times/day for 8 weeks. The following factors were measured pre-and post-intervention: body composition, insulin, insulin-like growth factor-1 (IGF-1), irisin, and skeletal muscle strength. Body fat percentage was significantly decreased (p<0.001) in the RT+UA group, despite body weight, body mass index, lean body mass, glucose, and insulin levels remaining unchanged. IGF-1 and irisin were significantly increased compared with baseline levels in the RT+UA group (p<0.05). Maximal right and left extension (p<0.01), right flexion (p<0.05), and left flexion (p<0.001) were significantly increased compared with baseline levels in the RT+UA group. These findings suggest that UA-induced elevation of serum irisin may be useful as an agent for the enhancement of skeletal muscle strength during RT. PMID:25352765

  19. Direct inference of site strength in basic solids upon CO2 adsorption: enthalpy-entropy compensation effects.

    PubMed

    Pera-Titus, M

    2016-08-10

    The adsorption of CO2 coupled to calorimetry is a state-of-the-art technique for characterizing the basic properties of solids. In this paper, we show that the differential heat and entropy curves measured upon CO2 adsorption on a basic solid can be reasonably estimated from a single CO2 isotherm with no need for any independent heat (calorimetric) measurement. Our method relies on two important observations: (1) formulation of generalized F-H-TS thermodynamic isotherms, the former (F) being directly generated from the raw CO2 isotherms, and (2) the presence of unexpected enthalpy-entropy compensation effects upon CO2 adsorption linking the integral enthalpy and entropy of adsorption until saturation for different solids. Our thermodynamic method has been validated using a broad library of basic solids with variable site strength and heterogeneity. Finally, a new scale of basicity is proposed using the parameters fitted from the thermodynamic isotherm (free energy basis) as descriptors of basic strength. This method opens an avenue to the inference of site strength of basic solids without the need for expensive calorimeters.

  20. Effects of phosphatidic acid supplementation on muscle thickness and strength in resistance-trained men.

    PubMed

    Gonzalez, Adam M; Sell, Katie M; Ghigiarelli, Jamie J; Kelly, Christopher F; Shone, Edward W; Accetta, Matthew R; Baum, Jamie B; Mangine, Gerald T

    2017-04-01

    The purpose of this study was to investigate the effects of phosphatidic acid (PA) supplementation on muscle thickness and strength following an 8 week supervised resistance-training program. Fifteen resistance trained men (22.8 ± 3.5 years; 80.6 ± 8.7 kg; 178.1 ± 5.6 cm; 14.6% ± 8.8% body fat) were randomly assigned to a group that either consumed 750 mg of PA or a placebo (PL). Testing was carried out before (PRE) and after (POST) training/supplementation for muscle thickness and strength. Muscle thickness of the rectus femoris (RF), vastus lateralis (VL), biceps brachii (BB), and triceps brachii (TB) muscles were measured via ultrasonography, along with 1 repetition maximum (1RM) of squat, deadlift, and bench press. Analysis of covariance (ANCOVA), using PRE values as the covariate, did not reveal any group differences for measures of muscle thickness in the RF (PA: 3.6% ± 5.2%; PL: 3.2% ± 4.2%, p = 0.97), VL (PA: 23.4% ± 18.1%, PL: 12.5% ± 15.4%, p = 0.37), BB (PA: 3.7% ± 6.4%, PL: 9.6% ± 12.4%, p = 0.86), or TB (PA: 15.1% ± 17.9%, PL: 10.7% ± 19.3%, p = 0.79). Likewise, no group differences were observed in changes in squat (PA: 8.4% ± 4.1%, PL: 8.1% ± 4.2%, p = 0.79), deadlift (PA: 10.1% ± 10.1%, PL: 8.9% ± 9.5%, p = 0.66), or bench press (PA: 5.7% ± 5.5%, PL: 5.1% ± 3.0%, p = 0.76) exercises. Collectively, however, all participants experienced significant (p < 0.05) improvements in each measure of muscle thickness and strength. Results of this study suggest that PA supplementation, in combination with a 3 days·week(-1) resistance-training program for 8 weeks, did not have a differential effect compared with PL on changes in muscle thickness or 1RM strength.

  1. Promoter strength of folic acid synthesis genes affects sulfa drug resistance in Saccharomyces cerevisiae.

    PubMed

    Iliades, Peter; Berglez, Janette; Meshnick, Steven; Macreadie, Ian

    2003-01-01

    The enzyme dihydropteroate synthase (DHPS) is an important target for sulfa drugs in both prokaryotic and eukaryotic microbes. However, the understanding of DHPS function and the action of antifolates in eukaryotes has been limited due to technical difficulties and the complexity of DHPS being a part of a bifunctional or trifunctional protein that comprises the upstream enzymes involved in folic acid synthesis (FAS). Here, yeast strains have been constructed to study the effects of FOL1 expression on growth and sulfa drug resistance. A DHPS knockout yeast strain was complemented by yeast vectors expressing the FOL1 gene under the control of promoters of different strengths. An inverse relationship was observed between the growth rate of the strains and FOL1 expression levels. The use of stronger promoters to drive FOL1 expression led to increased sulfamethoxazole resistance when para-aminobenzoic acid (pABA) levels were elevated. However, high FOL1 expression levels resulted in increased susceptibility to sulfamethoxazole in pABA free media. These data suggest that up-regulation of FOL1 expression can lead to sulfa drug resistance in Saccharomyces cerevisiae.

  2. The Effect of Omega-3 Fatty Acid Supplementation on the Inflammatory Response to eccentric strength exercise

    PubMed Central

    Jouris, Kelly B.; McDaniel, Jennifer L.; Weiss, Edward P.

    2011-01-01

    adverse response to exercise. Our research demonstrates that 3000 mg·d-1 omega-3 fatty acid supplementation minimizes the severe, delayed-onset muscle soreness that results from strenuous eccentric strength exercise. This information, along with a plethora of information showing that omega-3 fatty acid supplementation has other health benefits, demonstrates that a readily available over the counter nutritional supplement (i.e. omega-3 fatty acids) reduces delayed-onset soreness caused by strenuous strength exercise. This information has obvious relevance to athletic populations but also to other groups such as physical therapy patients and newly admitted cardiac rehabilitation patients, as muscle soreness, if left unchecked, can slow the progress in adapting to a new exercise program. Furthermore, as inflammation is known to be involved in the pathogenesis if numerous diseases, including heart disease, cancer, and diabetes, it is likely prudent for individuals to use inflammation-attenuating interventions, such as omega-3 supplementation, to keep inflammatory responses to physical activity at a minimum. PMID:24150614

  3. A Sialic Acid Binding Site in a Human Picornavirus

    PubMed Central

    Frank, Martin; Hähnlein-Schick, Irmgard; Ekström, Jens-Ola; Arnberg, Niklas; Stehle, Thilo

    2014-01-01

    The picornaviruses coxsackievirus A24 variant (CVA24v) and enterovirus 70 (EV70) cause continued outbreaks and pandemics of acute hemorrhagic conjunctivitis (AHC), a highly contagious eye disease against which neither vaccines nor antiviral drugs are currently available. Moreover, these viruses can cause symptoms in the cornea, upper respiratory tract, and neurological impairments such as acute flaccid paralysis. EV70 and CVA24v are both known to use 5-N-acetylneuraminic acid (Neu5Ac) for cell attachment, thus providing a putative link between the glycan receptor specificity and cell tropism and disease. We report the structures of an intact human picornavirus in complex with a range of glycans terminating in Neu5Ac. We determined the structure of the CVA24v to 1.40 Å resolution, screened different glycans bearing Neu5Ac for CVA24v binding, and structurally characterized interactions with candidate glycan receptors. Biochemical studies verified the relevance of the binding site and demonstrated a preference of CVA24v for α2,6-linked glycans. This preference can be rationalized by molecular dynamics simulations that show that α2,6-linked glycans can establish more contacts with the viral capsid. Our results form an excellent platform for the design of antiviral compounds to prevent AHC. PMID:25329320

  4. First-principles study of He effects in a bcc Fe grain boundary: site preference, segregation and theoretical tensile strength.

    PubMed

    Zhang, Lei; Shu, Xiaolin; Jin, Shuo; Zhang, Ying; Lu, Guang-Hong

    2010-09-22

    We perform a first-principles calculation to investigate the effects of He in an Fe Σ5(310)/[001] grain boundary (GB) with the SIESTA code, for which the reliability of the pseudopotential and the basis set are systematically tested. We calculate the formation and segregation energies for different substitutional and interstitial cases in order to determine the site preference and the segregation properties of He in the Fe GB. It is demonstrated that the He segregation either breaks (substitution) or weakens (interstitial) the surrounding interfacial Fe-Fe bonds, leading to the GB tensile strength reduction.

  5. Nitrous Acid at Concordia (Inland Site) and Dumont d'Urville (Costal Site), East Antarctica

    NASA Astrophysics Data System (ADS)

    Kerbrat, M.; Legrand, M.; Preunkert, S.; Gallée, H.; Kleffman, J.

    2012-04-01

    One of the most recent important finding made in Antarctica after the discovery of the appearance of the Antarctic ozone hole in the early 80's was the discovery of a very oxidizing canopy over the South Pole region in relation with unexpected high levels of NO. There is a strong need however to extend investigations of the oxidation capacity of the lower atmosphere at the scale of the whole Antarctic continent, and in particular, over East Antarctica. That motivated the OPALE (Oxidant Production over Antarctic Land and its Export) project. Indeed the limited data gained by using aircraft sampling during ANTCI 2003 suggest that over the East Antarctic plateau even higher NO emissions persist. Among several not yet resolved questions related to the high level of oxidants over Antarctica is the role of nitrous acid (HONO). During the austral summer 2010/2011 the levels of nitrous acid (HONO) were for the first time investigated at Concordia (75°06'S, 123°33'E) and Dumont D'Urville (66°40'S, 140°01'E), two stations located in East Antarctica. Also for the first time in Antarctica, HONO was measured by deploying a long path absorption photometer (LOPAP). At Concordia, from the end of December 2010 to mid January 2011 HONO mixing ratios at 1 m above the snow surface ranged between 5 and 60 pptv. Diurnal cycles were observed with levels peaking in the morning (06:30 to 07:30) and the evening (19:00 to 20:00). At Dumont d'Urville, background mixing ratios close to 2 pptv were observed in February 2011. No clear diurnal cycles were observed at that site but several events of air masses export from inland Antarctica were encountered with enhanced HONO levels reaching 10 pptv at night. These first HONO data gained in East Antarctica are discussed in terms of sources and sinks along with synoptic weather conditions.

  6. Effect of ascorbic acid on bond strength between the hydrogen peroxide-treated fiber posts and composite resin cores

    PubMed Central

    Talebian, Reza; Khamverdi, Zahra; Nouri, Maryam; Kasraei, Shahin

    2014-01-01

    Aim: This study evaluated the effect of 10% ascorbic acid on the bond strength between fiber post and composite resin core after applying 24% hydrogen peroxide. Materials and Methods: Twenty-four hydrogen peroxide-treated fiber posts were divided into 4 groups (n = 6). Group 1 was the control group with no treatment. In groups 2-4, post surfaces were treated with 10% v ascorbic acid solution for 10, 30 and 60 minutes, respectively. Cores were built up using flowable composite resin. Two sticks were prepared from each specimen. Microtensile bond strength test was performed for each stick. Failure modes of sticks were evaluated under a stereomicroscope (×20). Surface morphologies of two fractured sticks from each group were assessed by SEM. Statistical analysis: Data were analyzed using one-way ANOVA and Tukey HSD tests (α = 0.05). Results: The highest microtensile bond strength was observed in Group 4 (20.55 ± 2.09) and the lowest in Group 1 (10.10 ± 0.55). There were significant differences in microtensile bond strength between all the groups (P < 0.05). Conclusion: It is concluded that ascorbic acid application increased the microtensile bond strength between the hydrogen peroxide treated fiber post and composite resin core. The increase is dependent on the duration of exposure to the antioxidant. PMID:24944443

  7. Layered materials with coexisting acidic and basic sites for catalytic one-pot reaction sequences.

    PubMed

    Motokura, Ken; Tada, Mizuki; Iwasawa, Yasuhiro

    2009-06-17

    Acidic montmorillonite-immobilized primary amines (H-mont-NH(2)) were found to be excellent acid-base bifunctional catalysts for one-pot reaction sequences, which are the first materials with coexisting acid and base sites active for acid-base tamdem reactions. For example, tandem deacetalization-Knoevenagel condensation proceeded successfully with the H-mont-NH(2), affording the corresponding condensation product in a quantitative yield. The acidity of the H-mont-NH(2) was strongly influenced by the preparation solvent, and the base-catalyzed reactions were enhanced by interlayer acid sites.

  8. Ionic Strength Effect on the Rate of Reduction of Hexacyanoferrate (III) by Ascorbic Acid: A Physical Chemistry Laboratory Experiment.

    ERIC Educational Resources Information Center

    Watkins, Kenneth W.; Olson, June A.

    1980-01-01

    Describes a physical chemistry experiment that allows students to test the effect of ionic strength on the rates of a reaction between ions. The reduction of hexacyanoferrate III by ascorbic acid is detailed. Comparisons with the iodine clock reaction are made. (CS)

  9. EFFECTS OF PH, SOLID/SOLUTION RATIO, IONIC STRENGTH, AND ORGANIC ACIDS ON PB AND CD SOPRTION ON KAOLINITE

    EPA Science Inventory

    Potentiometric and ion-selective electrode titrations together with batch sorption/desorption experiments, were performed to explain the aqueous and surface complexation reactions between kaolinite, Pb, Cd and three organic acids. Variables included pH, ionic strength, metal conc...

  10. Characterization of the binding sites for dicarboxylic acids on bovine serum albumin.

    PubMed Central

    Tonsgard, J H; Meredith, S C

    1991-01-01

    Dicarboxylic acids are prominent features of several diseases, including Reye's syndrome and inborn errors of mitochondrial and peroxisomal fatty acid oxidation. Moreover, dicarboxylic acids are potentially toxic to cellular processes. Previous studies [Tonsgard, Mendelson & Meredith (1988) J. Clin. Invest. 82, 1567-1573] demonstrated that long-chain dicarboxylic acids have a single high-affinity binding site and between one and three lower-affinity sites on albumin. Medium-chain-length dicarboxylic acids have a single low-affinity site. We further characterized dicarboxylic acid binding to albumin in order to understand the potential effects of drugs and other ligands on dicarboxylic acid binding and toxicity. Progesterone and oleate competitively inhibit octadecanedioic acid binding to the single high-affinity site. Octanoate inhibits binding to the low-affinity sites. Dansylated probes for subdomain 2AB inhibit dodecanedioic acid binding whereas probes for subdomain 3AB do not. In contrast, low concentrations of octadecanedioic acid inhibit the binding of dansylated probes to subdomain 3AB and 2AB. L-Tryptophan, which binds in subdomain 3AB, inhibits hexadecanedioic acid binding but has no effect on dodecanedioic acid. Bilirubin and acetylsalicylic acid, which bind in subdomain 2AB, inhibit the binding of medium-chain and long-chain dicarboxylic acids. Our results suggest that long-chain dicarboxylic acids bind in subdomains 2C, 3AB and 2AB. The single low-affinity binding site for medium-chain dicarboxylic acids is in subdomain 2AB. These studies suggest that dicarboxylic acids are likely to be unbound in disease states and may be potentially toxic. PMID:2064600

  11. Highly selective Lewis acid sites in desilicated MFI zeolites for dihydroxyacetone isomerization to lactic acid.

    PubMed

    Dapsens, Pierre Y; Mondelli, Cecilia; Pérez-Ramírez, Javier

    2013-05-01

    Desilication of commercial MFI-type (ZSM-5) zeolites in solutions of alkali metal hydroxides is demonstrated to generate highly selective heterogeneous catalysts for the aqueous-phase isomerization of biobased dihydroxyacetone (DHA) to lactic acid (LA). The best hierarchical ZSM-5 sample attains a LA selectivity exceeding 90 %, which is comparable to that of the state-of-the-art catalyst (i.e., the Sn-beta zeolite); this optimized hierarchical catalyst is recyclable over three runs. The Lewis acid sites, which are created through desilication along with the introduction of mesoporosity, are shown to play a crucial role in the formation of the desired product; these cannot be achieved by using other post-synthetic methods, such as steaming or impregnation of aluminum species. Desilication of other metallosilicates, such as Ga-MFI, also leads to high LA selectivity. In the presence of a soluble aluminum source, such as aluminum nitrate, alkaline-assisted alumination can introduce these unique Lewis acid centers in all-silica MFI zeolites. These findings highlight the potential of zeolites in the field of biomass-to-chemical conversion, and expand the applicability of desilication for the generation of selective catalytic centers.

  12. Transient kinetics of electron transfer reactions of flavodoxin: ionic strength dependence of semiquinone oxidation by cytochrome c, ferricyanide, and ferric ethylenediaminetetraacetic acid and computer modeling of reaction complexes.

    PubMed

    Simondsen, R P; Weber, P C; Salemme, F R; Tollin, G

    1982-12-07

    Electron transfer reactions between Clostridum pasteurianum flavodoxin semiquinone and various oxidants [horse heart cytochrome c, ferricyanide, and ferric ethylenediaminetetraacetic [horse heart cytochrome c, ferricyanide, and ferric ethylenediaminetetraacetic acid (EDTA)] have been studied as a function of ionic strength by using stopped-flow spectrophotometry. The cytochrome c reaction is complicated by the existence of two cytochrome species which react at different rates and whose relative concentrations are ionic strength dependent. Only the faster of these two reactions is considered here. At low ionic strength, complex formation between cytochrome c and flavodoxin is indicated by a leveling off of the pseudo-first-order rate constant at high cytochrome c concentration. This is not observed for either ferricyanide or ferric EDTA. For cytochrome c, the rate and association constants for complex formation were found to increase with decreasing ionic strength, consistent with negative charges on flavodoxin interacting with the positively charged cytochrome electron transfer site. Both ferricyanide and ferric EDTA are negatively charged oxidants, and the rate data respond to ionic strength changes as would be predicted for reactants of the same charge sign. These results demonstrate that electrostatic interactions involving negatively charged groups are important in orienting flavodoxin with respect to oxidants during electron transfer. We have also carried out computer modeling studies of putative complexes of flavodoxin with cytochrome c and ferricyanide, which relate their structural properties to both the observed kinetic behavior and some more general features of physiological electron transfer processes. The results of this study are consistent with the ionic strength behavior described above.

  13. Effect of Peracetic Acid as A Final Rinse on Push Out Bond Strength of Root Canal Sealers to Root Dentin

    PubMed Central

    Gaddala, Naresh; Veeramachineni, Chandrasekhar

    2015-01-01

    Background Smear layer which was formed during the instrumentation of root canals hinders the penetration of root canal sealers to root dentin and affect the bond strength of root canal sealers to root dentin. Final irrigant such as demineralizing agents are used to remove the inorganic portion of the smear layer. In the present study, peracetic acid used as a final rinse, to effect the bond strength of root canal sealers to root dentin. Aim The purpose of the present study was to evaluate the efficacy of peracetic acid as a final irrigant on bond strength of root canal sealers to root dentin. Materials and Methods Sixty six freshly extracted human single rooted mandibular premolars were used for this study. After decoronation the samples were instrumented with Protaper upto F3 and irrigated with 5.25% NaOcl. The teeth were then divided into three groups based on final irrigant used: Group-1(control group) Canals were irrigated with distilled water. Group-2: Canals were irrigated with peracetic acid. Group-3: Canals were irrigated with smear clear. Each group was further divided into three subgroups (n=30) based on the sealer used to obturate the canals. Subgroup-1: kerr, Subgroup-2: Apexit plus, Subgroup-3: AH PLUS. Each sealer was mixed and coated to master cone and placed in the canal. The bonding between sealer and dentin surface was evaluated using push out bond strength by universal testing machine. The mean bond strength values of each group were statistically evaluated using Two-way ANOVA followed by Tukey post-hoc test. Results Significant difference was found among the bond strength of the sealers. But, there is no statistically significant difference between the groups irrigated with peracetic acid and smear clear compared to control group. AH Plus showed highest bond strength irrespective of the final irrigant used. Conclusion Peracetic acid when employed as final irrigant improved the bond strength of root canal sealers compared to control group but

  14. N2O Source Strength of Tropical Rain Forests: From the Site to the Global Scale

    NASA Astrophysics Data System (ADS)

    Kiese, R.; Werner, C.; Butterbach-Bahl, K.

    2006-12-01

    In contrast to the significant importance of tropical rain forest ecosystems as one of the major single sources within the global atmospheric N2O budget (2.2 3.7 Tg N y-1, regional and global estimates of their N2O source strength are still limited and highly uncertain. However, accurate quantification of sources and sinks of greenhouse gases like CO2, N2O and CH4 for natural, agricultural and forest ecosystems is crucial to our understanding of land use change effects on global climate change. At present, up-scaling approaches which link detailed geographic information systems (GIS) to mechanistic biochemical models are seen as a promising tool to contribute towards more reliable estimates of biogenic sources of N2O, e.g. tropical rain forest ecosystems. In our study we further developed and tested the PnET-N-DNDC model using Bayesian calibration techniques based on detailed N2O emission data of two recently conducted field campaigns in African (Kenya) and Asian (SE-China) tropical forest ecosystems and additional datasets from earlier own field campaigns or the literature. For global upscaling of N2O emissions an extensive GIS database was constructed holding all necessary parameters (climate ECWMF ERA 40; soil: FAO, vegetation: LPJ-DGVM simulation) in spatial and temporal resolution for initializing and driving the further developed biogeochemical model at a grid size of 0.25°x0.25°. We calculated global N2O emissions inventories for the years 1991 to 2001, and found a general agreement of the simulated flux ranges with reported N2O emissions from tropical forest ecosystems worldwide. According to our simulations, tropical rainforest soils are indeed a significant source of atmospheric N2O ranging from 1.1 2.2 Tg in dependence from the simulated year. Notably, related to differences in environmental conditions, N2O emissions varied considerably within the tropical belt. Furthermore, our simulations revealed a pronounced inter-annual variability of N2O

  15. Site specific incorporation of keto amino acids into proteins

    DOEpatents

    Schultz, Peter G [La Jolla, CA; Wang, Lei [San Diego, CA

    2011-12-06

    Compositions and methods of producing components of protein biosynthetic machinery that include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, and orthogonal pairs of tRNAs/synthetases, which incorporate keto amino acids into proteins are provided. Methods for identifying these orthogonal pairs are also provided along with methods of producing proteins with keto amino acids using these orthogonal pairs.

  16. Site specific incorporation of keto amino acids into proteins

    DOEpatents

    Schultz, Peter G [La Jolla, CA; Wang, Lei [San Diego, CA

    2012-02-14

    Compositions and methods of producing components of protein biosynthetic machinery that include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, and orthogonal pairs of tRNAs/synthetases, which incorporate keto amino acids into proteins are provided. Methods for identifying these orthogonal pairs are also provided along with methods of producing proteins with keto amino acids using these orthogonal pairs.

  17. Site specific incorporation of keto amino acids into proteins

    DOEpatents

    Schultz, Peter G [La Jolla, CA; Wang, Lei [San Diego, CA

    2011-03-22

    Compositions and methods of producing components of protein biosynthetic machinery that include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, and orthogonal pairs of tRNAs/synthetases, which incorporate keto amino acids into proteins are provided. Methods for identifying these orthogonal pairs are also provided along with methods of producing proteins with keto amino acids using these orthogonal pairs.

  18. Site specific incorporation of keto amino acids into proteins

    DOEpatents

    Schultz, Peter G.; Wang, Lei

    2008-10-07

    Compositions and methods of producing components of protein biosynthetic machinery that include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, and orthogonal pairs of tRNAs/synthetases, which incorporate keto amino acids into proteins are provided. Methods for identifying these orthogonal pairs are also provided along with methods of producing proteins with keto amino acids using these orthogonal pairs.

  19. Site specific incorporation of keto amino acids into proteins

    DOEpatents

    Schultz, Peter G.; Wang, Lei

    2009-04-28

    Compositions and methods of producing components of protein biosynthetic machinery that include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, and orthogonal pairs of tRNAs/synthetases, which incorporate keto amino acids into proteins are provided. Methods for identifying these orthogonal pairs are also provided along with methods of producing proteins with keto amino acids using these orthogonal pairs.

  20. Effect of acid etching on bond strength of nanoionomer as an orthodontic bonding adhesive

    PubMed Central

    Khan, Saba; Verma, Sanjeev K.; Maheshwari, Sandhya

    2015-01-01

    Aims: A new Resin Modified Glass Ionomer Cement known as nanoionomer containing nanofillers of fluoroaluminosilicate glass and nanofiller 'clusters' has been introduced. An in-vitro study aimed at evaluating shear bond strength (SBS) and adhesive remnant index (ARI) of nanoionomer under etching/unetched condition for use as an orthodontic bonding agent. Material and Methods: A total of 75 extracted premolars were used, which were divided into three equal groups of 25 each: 1-Conventional adhesive (Enlight Light Cure, SDS, Ormco, CA, USA) was used after and etching with 37% phosphoric acid for 30 s, followed by Ortho Solo application 2-nanoionomer (Ketac™ N100, 3M, ESPE, St. Paul, MN, USA) was used after etching with 37% phosphoric acid for 30 s 3-nanoionomer was used without etching. The SBS testing was performed using a digital universal testing machine (UTM-G-410B, Shanta Engineering). Evaluation of ARI was done using scanning electron microscopy. The SBS were compared using ANOVA with post-hoc Tukey test for intergroup comparisons and ARI scores were compared with Chi-square test. Results: ANOVA (SBS, F = 104.75) and Chi-square (ARI, Chi-square = 30.71) tests revealed significant differences between groups (P < 0.01). The mean (SD) SBS achieved with conventional light cure adhesive was significantly higher (P < 0.05) (10.59 ± 2.03 Mpa, 95% CI, 9.74-11.41) than the nanoionomer groups (unetched 4.13 ± 0.88 Mpa, 95% CI, 3.79-4.47 and etched 9.32 ± 1.87 Mpa, 95% CI, 8.58-10.06). However, nanoionomer with etching, registered SBS in the clinically acceptable range of 5.9–7.8 MPa, as suggested by Reynolds (1975). The nanoionomer groups gave significantly lower ARI values than the conventional adhesive group. Conclusion: Based on this in-vitro study, nanoionomer with etching can be successfully used as an orthodontic bonding agent leaving less adhesive remnant on enamel surface, making cleaning easier. However, in-vivo studies are needed to confirm the validity

  1. Effects of ultraviolet irradiation on bonding strength between Co-Cr alloy and citric acid-crosslinked gelatin matrix.

    PubMed

    Inoue, Motoki; Sasaki, Makoto; Katada, Yasuyuki; Taguchi, Tetsushi

    2014-02-01

    Novel techniques for creating a strong bond between polymeric matrices and biometals are required. We immobilized polymeric matrices on the surface of biometal for drug-eluting stents through covalent bond. We performed to improve the bonding strength between a cobalt-chromium alloy and a citric acid-crosslinked gelatin matrix by ultraviolet irradiation on the surface of cobalt-chromium alloy. The ultraviolet irradiation effectively generated hydroxyl groups on the surface of the alloy. The bonding strength between the gelatin matrix and the alloy before ultraviolet irradiation was 0.38 ± 0.02 MPa, whereas it increased to 0.48 ± 0.02 MPa after ultraviolet irradiation. Surface analysis showed that the citric acid derivatives occurred on the surface of the cobalt-chromium alloy through ester bond. Therefore, ester bond formation between the citric acid derivatives active esters and the hydroxyl groups on the cobalt-chromium alloy contributed to the enhanced bonding strength. Ultraviolet irradiation and subsequent immobilization of a gelatin matrix using citric acid derivatives is thus an effective way to functionalize biometal surfaces.

  2. Improvement of enamel bond strengths for conventional and resin-modified glass ionomers: acid-etching vs. conditioning*

    PubMed Central

    Zhang, Ling; Tang, Tian; Zhang, Zhen-liang; Liang, Bing; Wang, Xiao-miao; Fu, Bai-ping

    2013-01-01

    Objective: This study deals with the effect of phosphoric acid etching and conditioning on enamel micro-tensile bond strengths (μTBSs) of conventional and resin-modified glass ionomer cements (GICs/RMGICs). Methods: Forty-eight bovine incisors were prepared into rectangular blocks. Highly-polished labial enamel surfaces were either acid-etched, conditioned with liquids of cements, or not further treated (control). Subsequently, two matching pre-treated enamel surfaces were cemented together with one of four cements [two GICs: Fuji I (GC), Ketac Cem Easymix (3M ESPE); two RMGICs: Fuji Plus (GC), RelyX Luting (3M ESPE)] in preparation for μTBS tests. Pre-treated enamel surfaces and cement-enamel interfaces were analyzed by scanning electron microscopy (SEM). Results: Phosphoric acid etching significantly increased the enamel μTBS of GICs/RMGICs. Conditioning with the liquids of the cements produced significantly weaker or equivalent enamel μTBS compared to the control. Regardless of etching, RMGICs yielded stronger enamel μTBS than GICs. A visible hybrid layer was found at certain enamel-cement interfaces of the etched enamels. Conclusions: Phosphoric acid etching significantly increased the enamel μTBSs of GICs/RMGICs. Phosphoric acid etching should be recommended to etch the enamel margins before the cementation of the prostheses such as inlays and onlays, using GICs/RMGICs to improve the bond strengths. RMGICs provided stronger enamel bond strength than GICs and conditioning did not increase enamel bond strength. PMID:24190447

  3. PTH(1-34) and zoledronic acid have differing longitudinal effects on juvenile mouse femur strength and morphology.

    PubMed

    Bartlow, Christopher M; Oest, Megan E; Mann, Kenneth A; Zimmerman, Nicholas D; Butt, Bilal B; Damron, Timothy A

    2016-09-21

    Treatment of secondary pediatric osteoporosis-particularly that due to chronic diseases, immobilization, and necessary medical treatments-is currently limited by a poor understanding of the long-term efficacy and safety of skeletal metabolism modifying drugs. This study aimed to characterize longitudinal effects of representative anabolic (parathyroid hormone, PTH) and anti-catabolic (zoledronic acid, ZA) drugs on skeletal morphology, mechanical strength, and growth in juvenile mice. BALB/cJ mice aged 4 weeks were given PTH(1-34) or vehicle (control) daily for 8 weeks, or 4 weekly doses of ZA, and evaluated at time points 0-26 weeks after treatment initiation. There were no enduring differences in body length or mass between treatment groups. ZA increased femur size as early as week 0, including increased distal femur bone volume and diaphyseal cross-sectional area, persisting through week 26. PTH treatment only transiently increased bone size, including distal femur volume at weeks 4-12. ZA decreased diaphyseal cortical tissue mineral density (TMD) at 12-26 weeks versus controls; PTH decreased TMD only at 2 weeks (vs. controls). ZA increased bending strength at 0-12 weeks and flexural strength at week 4 (vs. controls), but decreased flexural strength and modulus at week 26. PTH treatment increased bending strength only at 4 weeks, and did not affect flexural strength. Overall, ZA rapidly and persistently increased femur strength and size, but compromised bone material quality long-term. In healthy juvenile mice, limited-duration PTH treatment did not exert a strong anabolic effect, and had no adverse effects on femur strength, morphology, or growth. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

  4. Comparative Evaluation of Shear Bond Strength of Luting Cements to Different Core Buildup Materials in Lactic Acid Buffer Solution

    PubMed Central

    Patil, Siddharam M.; Desai, Raviraj G.; Arabbi, Kashinath C.; Prakash, Ved

    2015-01-01

    Aim and Objectives The core buildup material is used to restore badly broken down tooth to provide better retention for fixed restorations. The shear bond strength of a luting agent to core buildup is one of the crucial factors in the success of the cast restoration. The aim of this invitro study was to evaluate and compare the shear bond strength of luting cements with different core buildup materials in lactic acid buffer solution. Materials and Methods Two luting cements {Traditional Glass Ionomer luting cement (GIC) and Resin Modified Glass Ionomer luting cement (RMGIC)} and five core buildup materials {Silver Amalgam, Glass ionomer (GI), Glass Ionomer Silver Reinforced (GI Silver reinforced), Composite Resin and Resin Modified Glass Ionomer(RMGIC)} were selected for this study. Total 100 specimens were prepared with 20 specimens for each core buildup material using a stainless steel split metal die. Out of these 20 specimens, 10 specimens were bonded with each luting cement. All the bonded specimens were stored at 370c in a 0.01M lactic acid buffer solution at a pH of 4 for 7days. Shear bond strength was determined using a Universal Testing Machine at a cross head speed of 0.5mm/min. The peak load at fracture was recorded and shear bond strength was calculated. The data was statistically analysed using Two-way ANOVA followed by HOLM-SIDAK method for pair wise comparison at significance level of p<0.05. Results Two-Way ANOVA showed significant differences in bond strength of the luting cements (p<0.05) and core materials (p<0.05) and the interactions (p<0.05). Pairwise comparison of luting cements by HOLM-SIDAK test, showed that the RMGIC luting cement had higher shear bond strength values than Traditional GIC luting cement for all the core buildup materials. RMGIC core material showed higher bond strength values followed by Composite resin, GI silver reinforced, GI and silver amalgam core materials for both the luting agents. Conclusion Shear bond strength of

  5. Characterization of the binding strengths between boronic acids and cis-diol-containing biomolecules by affinity capillary electrophoresis.

    PubMed

    Lü, Chenchen; Liu, Zhen

    2015-01-01

    The affinity of boronic acids toward cis-diol-containing biomolecules has found wide applications in many fields, such as sensing, separation, drug delivery, and functional materials. A sound understanding of the binding interactions will greatly facilitate exquisite applications of this chemistry. Traditional techniques are associated with some apparent drawbacks, so they are only applicable to a limited range of boronic acids and cis-diol-containing biomolecules. This chapter describes an affinity capillary electrophoresis (ACE) method for the characterization of the binding strengths between boronic acids and cis-diol-containing biomolecules. As compared with existing approaches, such as (11)B NMR, the ACE method exhibits several significant advantages: (1) possibility of simultaneous study of multiple interactions, (2) low requirement on the purity of the binding species, (3) widely applicable to almost all types of cis-diol-containing compounds and boronic acids, and (4) high accuracy and precision.

  6. Interaction of metal ions with acid sites of biosorbents peat moss and Vaucheria and model substances alginic and humic acids

    SciTech Connect

    Crist, R.H.; Martin, J.R.; Crist, D.R.

    1999-07-01

    The interaction between added metal ions and acid sites of two biosorbents, peat moss and the alga Vaucheria, was studied. Results were interpreted in terms of two model substances, alginic acid, a copolymer of guluronic and mannuronic acids present in marine algae, and humic acid in peat moss. For peat moss and Vaucheria at pH 4--6, two protons were displaced per Cd sorbed, after correction for sorbed metals also displaced by the heavy metal. The frequent neglect of exchange of heavy metals for metals either sorbed on the native material or added for pH adjustment leads to erroneous conclusions about proton displacement stoichiometry. Proton displacement constants K{sub ex}{sup H} decreased logarithmically with pH and had similar slopes for alginic acid and biosorbents. This pH effect was interpreted as an electrostatic effect of increasing anionic charge making proton removal less favorable. The maximum number of exchangeable acid sites (capacity C{sub H}) decreased with pH for alginic acid but increased with pH for biosorbents. Consistent with titration behavior, this difference was explained in terms of more weak acid sites in the biosorbents.

  7. Locating the binding sites of folic acid with milk α- and β-caseins.

    PubMed

    Bourassa, P; Tajmir-Riahi, H A

    2012-01-12

    We located the binding sites of folic acid with milk α- and β-caseins at physiological conditions, using constant protein concentration and various folic acid contents. FTIR, UV-visible, and fluorescence spectroscopic methods as well as molecular modeling were used to analyze folic acid binding sites, the binding constant, and the effect of folic acid interaction on the stability and conformation of caseins. Structural analysis showed that folic acid binds caseins via both hydrophilic and hydrophobic contacts with overall binding constants of K(folic acid-α-caseins) = 4.8 (±0.6) × 10(4) M(-1) and K(folic acid-β-caseins) = 7.0 (±0.9) × 10(4) M(-1). The number of bound acid molecules per protein was 1.5 (±0.4) for α-casein and 1.4 (±0.3) for β-casein complexes. Molecular modeling showed different binding sites for folic acid on α- and β-caseins. The participation of several amino acids in folic acid-protein complexes was observed, which was stabilized by hydrogen bonding network and the free binding energy of -7.7 kcal/mol (acid-α-casein) and -8.1 kcal/mol (acid-β-casein). Folic acid complexation altered protein secondary structure by the reduction of α-helix from 35% (free α-casein) to 33% (acid-complex) and 32% (free β-casein) to 26% (acid-complex) indicating a partial protein destabilization. Caseins might act as carriers for transportation of folic acid to target molecules.

  8. Biodegradable poly-lactic acid based-composite reinforced unidirectionally with high-strength magnesium alloy wires.

    PubMed

    Li, X; Chu, C L; Liu, L; Liu, X K; Bai, J; Guo, C; Xue, F; Lin, P H; Chu, Paul K

    2015-05-01

    Biodegradable poly-lactic acid (PLA)--based composites reinforced unidirectionally with high-strength magnesium alloy wires (MAWs) are fabricated by a heat-compressing process and the mechanical properties and degradation behavior are studied experimentally and theoretically. The composites possess improved strengthening and toughening properties. The bending strength and impact strength of the composites with 40 vol% MAWs are 190 MPa and 150 kJ/m(2), respectively, although PLA has a low viscosity and an average molecular weight of 60,000 g/mol. The mechanical properties of the composites can be further improved by internal structure modification and interface strengthening and a numerical model incorporating the equivalent section method (ESM) is proposed for the bending strength. Micro arc oxidization (MAO) of the MAWs is an effective interfacial strengthening method. The composites exhibit high strength retention during degradation and the PLA in the composite shows a smaller degradation rate than pure PLA. The novel biodegradable composites have large potential in bone fracture fixation under load-bearing conditions.

  9. A study of the source-receptor relationships influencing the acidity of precipitation collected at a rural site in France

    NASA Astrophysics Data System (ADS)

    Charron, Aurélie; Plaisance, Hervé; Sauvage, Stéphane; Coddeville, Patrice; Galloo, Jean-Claude; Guillermo, René

    In order to examine the qualitative and quantitative source-receptor relationships responsible for acid rains at a background site in France, a receptor-oriented model was applied to the precipitation data collected from 1992 to 1995. Origins of acidic and alkaline species in precipitations have been investigated. The methodology combines precipitation chemical data with air parcel backward trajectories to establish concentration field maps of likely contributing sources. Highest acidities and concentrations of sulfate and nitrate in precipitation were associated with transport from the high emission areas of central Europe. Alkaline events were associated with air masses originating from Mediterranean basin or northern Africa. The quantitative relationships between the maps of potential sources and the European emissions of SO 2 and NO x were examined performing a correlation analysis. Good correlations were found between computed concentrations of acidic species and emissions of SO 2 and NO x. Substantial seasonal variations of acidic species were revealed. The highest concentrations occurred during the warm season. These seasonal variations are the effect of change of meteorological conditions and of the strength atmospheric processes according to the season.

  10. Effect of a fluoride-releasing self-etch acidic primer on the shear bond strength of orthodontic brackets.

    PubMed

    Bishara, Samir E; Ajlouni, Raed; Laffoon, John F; Warren, John J

    2002-06-01

    Conventional adhesive systems use three different agents--an enamel conditioner, a primer solution, and an adhesive resin--during the bonding of orthodontic brackets to enamel. A unique characteristic of some new bonding systems in operative dentistry is that they combine the conditioning and priming agents into a single application. Combining conditioning and priming saves time and should be more cost-effective to the clinician and indirectly to the patient. The purpose of this study was to assess and compare the effects of self-etching primers, including a fluoride-releasing primer, on the shear bond strength of orthodontic brackets. The brackets were bonded to extracted human teeth according to one of four protocols. In group 1 (control), teeth were etched with 37% phosphoric acid; after the sealant was applied, the brackets were bonded with Transbond XT (3M Unitek, Monrovia, Calif) and light cured for 20 seconds. In group 2, a self-etch acidic primer (3M ESPE, St Paul, Minn) was applied as suggested by the manufacturer, and the brackets were then bonded with Transbond XT as in the first group. In group 3, an experimental self-etch primer EXL #547 (3M ESPE) was applied to the teeth as suggested by the manufacturer, and the brackets were then bonded as in groups 1 and 2. In group 4, a fluoride-releasing self-etch primer, One-Up Bond F (J. Mortia, USA Inc. Irvine, Calif) that also has a novel dye-sensitized photo polymerization initiator system was applied as suggested by the manufacturer, and the brackets were then bonded as in the other groups. The present in vitro findings indicated that the shear bond strengths of the four groups were significantly different (P = .001). Duncan multiple range tests indicated that One-Up Bond F (mean +/- SD strength, 5.1+/-2.5 MPa) and Prompt L-Pop (strength, 7.1+/-4.4 MPa) had significantly lower shear bond strengths than both the EXL #547 self-etch primer (strength, 9.7+/-3.7 MPa) or the phosphoric acid etch and the

  11. Resident and Faculty Perceptions of Program Strengths and Opportunities for Improvement: Comparison of Site Visit Reports and ACGME Resident Survey Data in 5 Surgical Specialties.

    PubMed

    Caniano, Donna A; Yamazaki, Kenji; Yaghmour, Nicholas; Philibert, Ingrid; Hamstra, Stanley J

    2016-05-01

    Background Resident and faculty views of program strengths and opportunities for improvement (OFIs) offer insight into how stakeholders assess key elements of the learning environment. Objective This study sought (1) to assess the degree to which residents and faculty in 359 programs in 5 surgical specialties (obstetrics and gynecology, orthopaedic surgery, otolaryngology, plastic surgery, and surgery) were aligned or divergent in their respective views of program strengths and OFIs; and (2) to evaluate whether responses to selected questions on the Accreditation Council for Graduate Medical Education (ACGME) Resident Survey correlated with strengths or OFIs identified by the residents during the site visit. Methods Faculty and resident lists of program strengths and OFIs in site visit reports for 2012 and 2013 were aggregated, analyzed, and compared to responses on the Resident Survey. Results While there was considerable alignment in resident and faculty perceptions of program strengths and OFIs, some attributes were more important to one or the other group. Collegiality was valued highly by both stakeholder groups. Responses to 2 questions on the ACGME Resident Survey were associated with resident-identified OFIs in site visit reports pertaining to aspects of the didactic program and responsiveness to resident suggestions for improvement. Conclusions The findings offer program leadership additional insight into how 2 key stakeholder groups view elements of the learning environment as program strengths or OFIs and may serve as useful focal areas for ongoing improvement activities.

  12. The effect of topical fluorides, after acid etching of enamel, on the bond strength of directly bonded orthodontic brackets.

    PubMed

    Hirce, J D; Sather, A H; Chao, E Y

    1980-10-01

    This study tests the hypothesis that the beneficial effects of topical fluoride can be realized without reducing the bond strength of the resin adhesive. Twenty-eight groups of four teeth (third molars and premolars) were extracted from twenty-eight patients and stored in distilled water. Twin brackets on Ormesh pads were bonded to all teeth with Endur adhesive. One tooth from each group was bonded according to the manufacturer's instructions. These teeth, Subgroup I, served as controls. Subgroup II teeth were etched for 4 minutes with 50% phosphoric acid containing 2 percent sodium fluoride. Subgroup III teeth received a 3-minute application of a basic phosphate fluoride solution (10(-2)M NA3PO4, 10(3) ppm F) after 1 minute of etching with 50 percent phosphoric acid. Subgroup IV teeth received a 4-minute application of 8 percent stannous fluoride solution after 1 minute of etching with 50 percent phosphoric acid. Each tooth was mounted in a block of improved dental stone; guide wires were used to reproduce bracket orientation. The M.T.S. materials-testing apparatus was used to generate a torsional moment on the bracket at a rate of 1 degree per second. Fluoride uptake by enamel has been shown to be greater in an acid medium or after acid etching. The application of directly bonded orthodontic brackets and pit-and-fissure sealants requires acid etching of the enamel surface. This study supports the use of topical fluoride after acid etching, a procedure that achieves the benefits of increased fluoride uptake without changing the bond strength of the resin adhesive.

  13. Brønsted-Lowry Acid Strength of Metal Hydride and Dihydrogen Complexes.

    PubMed

    Morris, Robert H

    2016-08-10

    Transition metal hydride complexes are usually amphoteric, not only acting as hydride donors, but also as Brønsted-Lowry acids. A simple additive ligand acidity constant equation (LAC for short) allows the estimation of the acid dissociation constant Ka(LAC) of diamagnetic transition metal hydride and dihydrogen complexes. It is remarkably successful in systematizing diverse reports of over 450 reactions of acids with metal complexes and bases with metal hydrides and dihydrogen complexes, including catalytic cycles where these reactions are proposed or observed. There are links between pKa(LAC) and pKa(THF), pKa(DCM), pKa(MeCN) for neutral and cationic acids. For the groups from chromium to nickel, tables are provided that order the acidity of metal hydride and dihydrogen complexes from most acidic (pKa(LAC) -18) to least acidic (pKa(LAC) 50). Figures are constructed showing metal acids above the solvent pKa scales and organic acids below to summarize a large amount of information. Acid-base features are analyzed for catalysts from chromium to gold for ionic hydrogenations, bifunctional catalysts for hydrogen oxidation and evolution electrocatalysis, H/D exchange, olefin hydrogenation and isomerization, hydrogenation of ketones, aldehydes, imines, and carbon dioxide, hydrogenases and their model complexes, and palladium catalysts with hydride intermediates.

  14. One-dimensional alignment of strong Lewis acid sites in a porous coordination polymer.

    PubMed

    Kajiwara, Takashi; Higuchi, Masakazu; Yuasa, Akihiro; Higashimura, Hideyuki; Kitagawa, Susumu

    2013-11-18

    A new lanthanoid porous coordination polymer, La-BTTc (BTTc = benzene-1,3,5-tris(2-thiophene-5-carboxylate)), was synthesized and structurally characterized to have densely aligned one-dimensional open metal sites, which were found to act as strong Lewis acid sites after the removal of the coordinated solvent.

  15. Effect of Acidic Environment on the Push-Out Bond Strength of Calcium-Enriched Mixture Cement

    PubMed Central

    Sobhnamayan, Fereshte; Sahebi, Safoora; Naderi, Misagh; Shojaee, Nooshin Sadat; Shanbezadeh, Najmeh

    2014-01-01

    Introduction: This laboratory study was performed to evaluate the effect of different acidic pH values on the push-out bond strength of calcium-enriched mixture (CEM) cement. Methods and Materials: Forty-eight root dentin slices were obtained from freshly extracted single rooted human teeth and their lumen were instrumented to achieve a diameter of 1.3 mm. Then, CEM cement was mixed according to manufacturers’ instruction and placed in the lumens with minimal pressure. The specimens were randomly divided into four groups (n=12) which were wrapped in pieces of gauze soaked in either synthetic tissue fluid (STF) (pH=7.4) or butyric acid which was buffered at pH values of 4.4, 5.4 and 6.4. They were then incubated for 4 days at 37°C. The push-out test was performed by means of the universal testing machine. Specimens were then examined under a digital light microscope at 20× magnification to determine the nature of the bond failure. The data were analyzed using the Kruskal-Wallis test followed by Dunn’s test for pairwise comparisons. Results: The highest push-out bond strength (10.19±4.39) was seen in the pH level of 6.4, which was significantly different from the other groups (P<0.05). The values decreased to 2.42±2.25 MPa after exposure to pH value of 4.4. Conclusion: Lower pH value of highly acidic environments (pH=4.4), adversely affects the force needed for displacement of CEM cement; while in higher pH values (pH=6.4) the bond-strength was not affected. CEM cement is recommended in clinical situations where exposure to acidic environment is unavoidable. PMID:25386207

  16. Sorption of triclosan onto activated carbon, kaolinite and montmorillonite: effects of pH, ionic strength, and humic acid.

    PubMed

    Behera, Shishir Kumar; Oh, Seok-Young; Park, Hung-Suck

    2010-07-15

    Sorption of triclosan on three sorbents, viz., activated carbon, kaolinite and montmorillonite was studied as a function of pH, ionic strength and humic acid (HA) concentration through controlled batch experiments. Triclosan sorption was found to be higher in the acidic pH range, as varying pH showed significant influence on the surface charge of the sorbents and degree of ionization of the sorbate. Sorption capacity of the sorbents increased with an increase in the ionic strength of solution. At low pH (pH 3), the overall increase in triclosan sorption was 1.2, approximately 4 and 3.5 times, respectively for activated carbon, kaolinite and montmorillonite when ionic strength was increased from 1x10(-3) to 5x10(-1) M. Triclosan sorption onto activated carbon decreased from 31.4 to 10.6 mg g(-1) by increasing the HA concentration to 200 mg C L(-1). However, during sorption onto kaolinite and montmorillonite, the effect of HA was very complex probably due to (i) hydrophobicity (log K(ow)=4.76) of triclosan; and (ii) complexation of HA with triclosan. Though triclosan sorption onto activated carbon is higher, the potential of kaolinite and montmorillonite in controlling the transport of triclosan in subsurface environment can still be appreciable.

  17. Influence of different forms of acidities on soil microbiological properties and enzyme activities at an acid mine drainage contaminated site.

    PubMed

    Sahoo, Prafulla Kumar; Bhattacharyya, Pradip; Tripathy, Subhasish; Equeenuddin, Sk Md; Panigrahi, M K

    2010-07-15

    Assessment of microbial parameters, viz. microbial biomass, fluorescence diacetate, microbial respiration, acid phosphatase, beta-glucosidase and urease with respect to acidity helps in evaluating the quality of soils. This study was conducted to investigate the effects of different forms of acidities on soil microbial parameters in an acid mine drainage contaminated site around coal deposits in Jainta Hills of India. Total potential and exchangeable acidity, extractable and exchangeable aluminium were significantly higher in contaminated soil compared to the baseline (p<0.01). Different forms of acidity were significantly and positively correlated with each other (p<0.05). Further, all microbial properties were positively and significantly correlated with organic carbon and clay (p<0.05). The ratios of microbial parameters with organic carbon were negatively correlated with different forms of acidity. Principal component analysis and cluster analyses showed that the microbial activities are not directly influenced by the total potential acidity and extractable aluminium. Though acid mine drainage affected soils had higher microbial biomass and activities due to higher organic matter content than those of the baseline soils, the ratios of microbial parameters/organic carbon indicated suppression of microbial growth and activities due to acidity stress.

  18. Effect of salicylhydroxamic acid on endosperm strength and embryo growth of Lactuca sativa L. cv Waldmann's Green seeds

    NASA Technical Reports Server (NTRS)

    Brooks, C. A.; Mitchell, C. A.

    1988-01-01

    Salicylhydroxamic acid (SHAM) stimulated germination of photosensitive lettuce (Lactuca sativa L. cv Waldmann's Green) seeds in darkness. To determine whether SHAM acts on the embryo or the endosperm, we investigated separately effects of SHAM on growth potential of isolated embryos as well as on endosperm strength. Embryo growth potential was quantified by incubating decoated embryos in various concentrations of osmoticum and measuring subsequent radicle elongation. Growth potential of embryos isolated from seeds pretreated with 4 millimolar SHAM was equal to that of untreated controls. Rupture strength of endosperm tissue excised from seeds pretreated with SHAM was 33% less than that of controls in the micropylar region. To determine if the embryo must be in contact with the endosperm of SHAM to weaken the endosperm, some endosperms were incubated with SHAM only after dissection from seeds. Rupture strength of SHAM-treated, isolated endosperms in the micropylar region was 25% less than that of untreated controls. There was no difference in rupture strength in the cotyledonary region of endosperm isolated from seeds treated with SHAM in buffer or buffer alone. SHAM therefore stimulates germination not by enhancing embryo growth potential, but by weakening the micropylar region of the endosperm enclosing the embryo.

  19. Modeling and predicting the tensile strength of poly (lactic acid)/graphene nanocomposites by using support vector regression

    NASA Astrophysics Data System (ADS)

    Cheng, W. D.; Cai, C. Z.; Luo, Y.; Li, Y. H.; Zhao, C. J.

    2016-04-01

    According to an experimental dataset under different process parameters, support vector regression (SVR) combined with particle swarm optimization (PSO) for its parameter optimization was employed to establish a mathematical model for prediction of the tensile strength of poly (lactic acid) (PLA)/graphene nanocomposites. Four variables, while graphene loading, temperature, time and speed, were employed as input variables, while tensile strength acted as output variable. Using leave-one-out cross validation test of 30 samples, the maximum absolute percentage error does not exceed 1.5%, the mean absolute percentage error (MAPE) is only 0.295% and the correlation coefficient (R2) is as high as 0.99. Compared with the results of response surface methodology (RSM) model, it is shown that the estimated errors by SVR are smaller than those achieved by RSM. It revealed that the generalization ability of SVR is superior to that of RSM model. Meanwhile, multifactor analysis is adopted for investigation on significances of each experimental factor and their influences on the tensile strength of PLA/graphene nanocomposites. This study suggests that the SVR model can provide important theoretical and practical guide to design the experiment, and control the intensity of the tensile strength of PLA/graphene nanocomposites via rational process parameters.

  20. Predicting Protein–Protein Interaction Sites Using Sequence Descriptors and Site Propensity of Neighboring Amino Acids

    PubMed Central

    Kuo, Tzu-Hao; Li, Kuo-Bin

    2016-01-01

    Information about the interface sites of Protein–Protein Interactions (PPIs) is useful for many biological research works. However, despite the advancement of experimental techniques, the identification of PPI sites still remains as a challenging task. Using a statistical learning technique, we proposed a computational tool for predicting PPI interaction sites. As an alternative to similar approaches requiring structural information, the proposed method takes all of the input from protein sequences. In addition to typical sequence features, our method takes into consideration that interaction sites are not randomly distributed over the protein sequence. We characterized this positional preference using protein complexes with known structures, proposed a numerical index to estimate the propensity and then incorporated the index into a learning system. The resulting predictor, without using structural information, yields an area under the ROC curve (AUC) of 0.675, recall of 0.597, precision of 0.311 and accuracy of 0.583 on a ten-fold cross-validation experiment. This performance is comparable to the previous approach in which structural information was used. Upon introducing the B-factor data to our predictor, we demonstrated that the AUC can be further improved to 0.750. The tool is accessible at http://bsaltools.ym.edu.tw/predppis. PMID:27792167

  1. UV irradiation enhances the bonding strength between citric acid-crosslinked gelatin and stainless steel.

    PubMed

    Inoue, Motoki; Sasaki, Makoto; Katada, Yasuyuki; Taguchi, Tetsushi

    2011-11-01

    The effect of ultraviolet ray (UV) irradiation on the bonding strength between low carbon stainless steel 316 (SUS316L) and trisuccinimidyl citrate (TSC)-crosslinked alkali-treated gelatin (AlGelatin-TSC) was investigated. The UV irradiation effectively generated hydroxyl groups on the surface of SUS316L. The bonding strength between AlGelatin-TSC and SUS316L before UV irradiation was 0.345±0.007 MPa, and upon UV irradiation it increased to 0.750±0.069 MPa. In order to explain this enhanced bonding strength, the surface of SUS316L was examined using its water contact angle and X-ray photoelectron spectroscopy. Furthermore, the N 1s peaks derived from the TSC succinimidyl group were assigned to the surface of SUS316L after the immobilization of the TSC. This indicates that ester bond formation between the TSC active esters and the SUS316L hydroxyl groups contributed to the enhanced bonding strength. Therefore, UV irradiation and subsequent TSC immobilization is a simple way to functionalize biometal surfaces with various structures. This has practical applications for medical devices such as drug-eluting stents, dental implants, and metallic artificial bone.

  2. Organic acids in cloud water and rainwater at a mountain site in acid rain areas of South China.

    PubMed

    Sun, Xiao; Wang, Yan; Li, Haiyan; Yang, Xueqiao; Sun, Lei; Wang, Xinfeng; Wang, Tao; Wang, Wenxing

    2016-05-01

    To investigate the chemical characteristics of organic acids and to identify their source, cloud water and rainwater samples were collected at Mount Lu, a mountain site located in the acid rain-affected area of south China, from August to September of 2011 and March to May of 2012. The volume-weighted mean (VWM) concentration of organic acids in cloud water was 38.42 μeq/L, ranging from 7.45 to 111.46 μeq/L, contributing to 2.50 % of acidity. In rainwater samples, organic acid concentrations varied from 12.39 to 68.97 μeq/L (VWM of 33.39 μeq/L). Organic acids contributed significant acidity to rainwater, with a value of 17.66 %. Formic acid, acetic acid, and oxalic acid were the most common organic acids in both cloud water and rainwater. Organic acids had an obviously higher concentration in summer than in spring in cloud water, whereas there was much less discrimination in rainwater between the two seasons. The contribution of organic acids to acidity was lower during summer than during spring in both cloud water (2.20 % in summer vs 2.83 % in spring) and rainwater (12.24 % in summer vs 19.89 % in spring). The formic-to-acetic acid ratio (F/A) showed that organic acids were dominated by primary emissions in 71.31 % of the cloud water samples and whole rainwater samples. Positive matrix factorization (PMF) analysis determined four factors as the sources of organic acids in cloud water, including biogenic emissions (61.8 %), anthropogenic emissions (15.28 %), marine emissions (15.07 %) and soil emissions (7.85 %). The findings from this study imply an indispensable role of organic acids in wet deposition, but organic acids may have a limited capacity to increase ecological risks in local environments.

  3. Effects of ionic strength and fulvic acid on adsorption of Tb(III) and Eu(III) onto clay

    NASA Astrophysics Data System (ADS)

    Poetsch, Maria; Lippold, Holger

    2016-09-01

    High salinity and natural organic matter are both known to facilitate migration of toxic or radioactive metals in geochemical systems, but little is known on their combined effect. We investigated complexation of Tb(III) and Eu(III) (as analogues for trivalent actinides) with fulvic acid and their adsorption onto a natural clay in the presence of NaCl, MgCl2 and CaCl2 up to very high ionic strengths. 160Tb, 152Eu and 14C-labelled fulvic acid were employed as radiotracers, allowing investigations at very low concentrations according to probable conditions in far-field scenarios of nuclear waste repositories. A combined Kd approach (Linear Additive Model) was tested for suitability in predicting solid-liquid distribution of metals in the presence of organic matter based on the interactions in the constituent subsystems. In this analysis, it could be shown that high ionic strength does not further enhance the mobilizing potential of humic matter. A quantitative reproduction of the influence of fulvic acid failed for most systems under study. Assumptions and limitations of the model are discussed.

  4. Phosphatidic acid: biosynthesis, pharmacokinetics, mechanisms of action and effect on strength and body composition in resistance-trained individuals.

    PubMed

    Bond, Peter

    2017-01-01

    The mechanistic target of rapamycin complex 1 (mTORC1) has received much attention in the field of exercise physiology as a master regulator of skeletal muscle hypertrophy. The multiprotein complex is regulated by various signals such as growth factors, energy status, amino acids and mechanical stimuli. Importantly, the glycerophospholipid phosphatidic acid (PA) appears to play an important role in mTORC1 activation by mechanical stimulation. PA has been shown to modulate mTOR activity by direct binding to its FKBP12-rapamycin binding domain. Additionally, it has been suggested that exogenous PA activates mTORC1 via extracellular conversion to lysophosphatidic acid and subsequent binding to endothelial differentiation gene receptors on the cell surface. Recent trials have therefore evaluated the effects of PA supplementation in resistance-trained individuals on strength and body composition. As research in this field is rapidly evolving, this review attempts to provide a comprehensive overview of its biosynthesis, pharmacokinetics, mechanisms of action and effect on strength and body composition in resistance-trained individuals.

  5. Characterization of a domoic acid binding site from Pacific razor clam.

    PubMed

    Trainer, Vera L; Bill, Brian D

    2004-08-10

    The Pacific razor clam, Siliqua patula, is known to retain domoic acid, a water-soluble glutamate receptor agonist produced by diatoms of the genus Pseudo-nitzschia. The mechanism by which razor clams tolerate high levels of the toxin, domoic acid, in their tissues while still retaining normal nerve function is unknown. In our study, a domoic acid binding site was solubilized from razor clam siphon using a combination of Triton X-100 and digitonin. In a Scatchard analysis using [3H]kainic acid, the partially-purified membrane showed two distinct receptor sites, a high affinity, low capacity site with a KD (mean +/- S.E.) of 28 +/- 9.4 nM and a maximal binding capacity of 12 +/- 3.8 pmol/mg protein and a low affinity, high capacity site with a mM affinity for radiolabeled kainic acid, the latter site which was lost upon solubilization. Competition experiments showed that the rank order potency for competitive ligands in displacing [3H]kainate binding from the membrane-bound receptors was quisqualate > ibotenate > iodowillardiine = AMPA = fluorowillardiine > domoate > kainate > L-glutamate. At high micromolar concentrations, NBQX, NMDA and ATPA showed little or no ability to displace [3H]kainate. In contrast, Scatchard analysis using [3H]glutamate showed linearity, indicating the presence of a single binding site with a KD and Bmax of 500 +/- 50 nM and 14 +/- 0.8 pmol/mg protein, respectively. These results suggest that razor clam siphon contains both a high and low affinity receptor site for kainic acid and may contain more than one subtype of glutamate receptor, thereby allowing the clam to function normally in a marine environment that often contains high concentrations of domoic acid.

  6. Comparison of shear bond strength and surface structure between conventional acid etching and air-abrasion of human enamel.

    PubMed

    Olsen, M E; Bishara, S E; Damon, P; Jakobsen, J R

    1997-11-01

    Recently, air-abrasion technology has been examined for potential applications within dentistry, including the field of orthodontics. The purpose of this study was to compare the traditional acid-etch technique with an air-abrasion surface preparation technique, with two different sizes of abrading particles. The following parameters were evaluated: (a) shear bond strength, (b) bond failure location, and (c) enamel surface preparation, as viewed through a scanning electron microscope. Sixty extracted human third molars were pumiced and divided into three groups of 20. The first group was etched with a 37% phosphoric acid gel for 30 seconds, rinsed for 30 seconds, and dried for 20 seconds. The second and third groups were air-abraded with (a) a 50 microm particle and (b) a 90 microm particle of aluminum oxide, with the Micro-etcher microabrasion machine (Danville Engineering Inc.). All three groups had molar stainless steel orthodontic brackets bonded to the buccal surface of each tooth with Transbond XT bonding system (3M Unitek). A Zwick Universal Testing Machine (Calitek Corp.) was used to determine shear bond strengths. The analysis of variance was used to compare the three groups. The Adhesive Remnant Index (ARI) was used to evaluate the residual adhesive on the enamel after bracket removal. The chi square test was used to evaluate differences in the ARI scores among the groups. The significance for all tests was predetermined at p < or = 0.05. The results indicated that there was a significant difference in shear bond strength among the three groups (p = 0.0001). The Duncan Multiple Range test showed a significant decrease in shear bond strength in the air-abraded groups. The chi square test revealed significant differences among the ARI scores of the acid-etched group and the air-abraded groups (chi(2) = 0.0001), indicating no adhesive remained on the enamel surface after debonding when air-abrasion was used. In conclusion, the current findings indicate that

  7. Site specific incorporation of heavy atom-containing unnatural amino acids into proteins for structure determination

    DOEpatents

    Xie, Jianming; Wang, Lei; Wu, Ning; Schultz, Peter G.

    2008-07-15

    Translation systems and other compositions including orthogonal aminoacyl tRNA-synthetases that preferentially charge an orthogonal tRNA with an iodinated or brominated amino acid are provided. Nucleic acids encoding such synthetases are also described, as are methods and kits for producing proteins including heavy atom-containing amino acids, e.g., brominated or iodinated amino acids. Methods of determining the structure of a protein, e.g., a protein into which a heavy atom has been site-specifically incorporated through use of an orthogonal tRNA/aminoacyl tRNA-synthetase pair, are also described.

  8. Ranking relative hydrogen-bond strengths in hydroxybenzoic acids for crystal-engineering purposes.

    PubMed

    Aakeröy, Christer B; Epa, Kanishka; Forbes, Safiyyah; Schultheiss, Nathan; Desper, John

    2013-10-25

    Systematic co-crystallizations resulting in a total of six new crystal structures involving either 3-hydroxy- or 4-hydroxybenzoic acid, complemented by calculated molecular electrostatic potential surfaces and existing structural data, have shown that in a competitive molecular recognition situation, the -OH moiety is a more effective hydrogen-bond donor than the -COOH moiety which, in turn, highlights that electrostatic charge can offer more useful guidance than acidity for predicting competitive hydrogen-bond preferences.

  9. Atmospheric geochemistry of formic and acetic acids at a mid-latitude temperate site

    NASA Technical Reports Server (NTRS)

    Talbot, R. W.; Beecher, K. M.; Harriss, R. C.; Cofer, R. W., III

    1988-01-01

    Tropospheric concentrations of formic and acetic acids in the gas, the aerosol, and the rainwater phases were determined in samples collected 1-2 m above ground level at an open field site in eastern Virginia. These acids were found to occur principally (98 percent or above) in the gas phase, with a marked annual seasonality, averaging 1890 ppt for formate and 1310 ppt for acetate during the growing season, as compared to 695 ppt and 700 ppt, respectively, over the nongrowing season. The data support the hypothesis that biogenic emissions from vegatation are important sources of atmospheric formic and acetic acid during the local growing season. The same time trends were observed for precipitation, although with less defined seasonality. The relative increase of the acetic acid/formic acid ratio during the nongrowing season points to the dominance of anthropogenic inputs of acetic acid from motor vehicles and biomass combustion in the wintertime.

  10. Binding of coumarins to site I of human serum albumin. Effect of the fatty acids.

    PubMed

    Zatón, A M; Ferrer, J M; Ruiz de Gordoa, J C; Marquínez, M A

    1995-07-14

    It is known that binding site I on human serum albumin (HSA) consists of a zone of two overlapping regions: the specific binding region represented by warfarin binding and the specific binding region represented by azapropazone and phenylbutazone binding. In this paper binding parameters to defatted HSA and to HSA with fatty acids (molar ratio of fatty acid/HSA = 4) were compared. High-affinity binding sites for warfarin, 4-chromanol, 4-hydroxycoumarin, coumarin, 3-acetylcoumarin and phenylbutazone (759,549 M-1 > Ka > 67,024 M-1) constitute binding site I on HSA. In this binding area defatted HSA can bind two molecules of warfarin, but the presence of fatty acids diminish the binding capacity of warfarin to HSA (2 > n > 1).

  11. Lots of data, how do we use it? Strengths and inaccuracies of utility acid rain electronic data reports

    SciTech Connect

    Schott, J.

    1996-12-31

    Entergy Corporation is a Phase II utility with a fossil generation base composed primarily natural gas and low sulfur coal. This paper presents an analysis of a large Phase II utility`s continuous emissions monitoring data reported to EPA under Title IV Acid Rain. Electric utilities currently report hourly emissions of NOx, SO{sub 2}, CO{sub 2}, fuel use, and generation through electronic data reports to EPA. This paper describes strengths and weaknesses of the data reported to EPA as determined through an analysis of 1995 data. Emissions reported by this company tinder acid rain for SO{sub 2} and NOx are very different from emissions reported to state agencies for annual emission inventory purposes in past years and will represent a significant break with historic trends. A comparison of emissions has been made of 1995 emissions reported under Electronic Data Reports to the emissions that would have been reported using emission factors and fuel data in past years. In addition, the paper examines the impacts of 40 CFR Part 75 Acid Rain requirements such as missing data substitution and monitor bias adjustments. Measurement system errors including stack flow measurement and false NOx Lb/MMBtu readings at very low loads are discussed. This paper describes the implications for public policy, compliance, emissions inventories, and business decisions of Part 75 acid rain monitoring and reporting requirements.

  12. High melt strength, tear resistant blown film based on poly(lactic acid)

    NASA Astrophysics Data System (ADS)

    Edmonds, Neil R.; Plimmer, Peter N.; Tanner, Chris

    2015-05-01

    A major problem associated with the commercial manufacture of thin films from PLA is inferior processing characteristics on blown film lines compared to low density polyethylene. PLA has poor melt strength (leading to bubble instability) and develops a permanent crease in the flattened film as it exits the tower of the film line. In addition, the thin film product has poor tear strength and an unacceptable `noise' level when converted into flexible packaging. Furthermore, fabricated articles based on PLA are known to show an unattractive tendency toward dimensional instability. This behaviour is associated with `cold crystallization', a phenomenon which also causes exudation of any plasticizer added for improving flexibility. Blow moulded articles based on PLA also exhibit dimensional sensitivity above 60°C. All of these issues have been overcome by the technology described in this paper. This has been accomplished without loss of the valuable compostability characteristic of PLA; this was confirmed by evaluation of film in a commercial composting operation. These results have been achieved through novel reactive compounding technology which: (a) Creates a PLA-rich structure containing long chain crosslinks, (b) generates a low glass transition temperature phase covalently bonded to the PLA structure, and (c) provides a material which performs like LDPE in a blown film manufacturing operation. The technology developed is covered by NZ Patent 580231 (3). The patent is held by UniServices Ltd, The University of Auckland, New Zealand.

  13. A bidentate Lewis acid with a telluronium ion as an anion-binding site

    NASA Astrophysics Data System (ADS)

    Zhao, Haiyan; Gabbaï, François P.

    2010-11-01

    The search for receptors that can selectively capture small and potentially toxic anions in protic media has sparked a renewed interest in the synthesis and anion-binding properties of polydentate Lewis acids. Seeking new paradigms to enhance the anion affinities of such systems, we synthesized a bidentate Lewis acid that contains a boryl and a telluronium moiety as Lewis acidic sites. Anion-complexation studies indicate that this telluronium borane displays a high affinity for fluoride in methanol. Structural and computational studies show that the unusual fluoride affinity of this bidentate telluronium borane can be correlated with the formation of a B-F --> Te chelate motif supported by a strong lone-pair(F) --> σ*(Te-C) donor-acceptor interaction. These results, which illustrate the viability of heavier chalcogenium centres as anion-binding sites, allow us to introduce a novel strategy for the design of polydentate Lewis acids with enhanced anion affinities.

  14. A bidentate Lewis acid with a telluronium ion as an anion-binding site.

    PubMed

    Zhao, Haiyan; Gabbaï, François P

    2010-11-01

    The search for receptors that can selectively capture small and potentially toxic anions in protic media has sparked a renewed interest in the synthesis and anion-binding properties of polydentate Lewis acids. Seeking new paradigms to enhance the anion affinities of such systems, we synthesized a bidentate Lewis acid that contains a boryl and a telluronium moiety as Lewis acidic sites. Anion-complexation studies indicate that this telluronium borane displays a high affinity for fluoride in methanol. Structural and computational studies show that the unusual fluoride affinity of this bidentate telluronium borane can be correlated with the formation of a B-F → Te chelate motif supported by a strong lone-pair(F) → σ*(Te-C) donor-acceptor interaction. These results, which illustrate the viability of heavier chalcogenium centres as anion-binding sites, allow us to introduce a novel strategy for the design of polydentate Lewis acids with enhanced anion affinities.

  15. Site-specific fatty acid-conjugation to prolong protein half-life in vivo

    PubMed Central

    Lim, Sung In; Mizuta, Yukina; Takasu, Akinori; Hahn, Young S.; Kim, Yong Hwan; Kwon, Inchan

    2015-01-01

    Therapeutic proteins are indispensable in treating numerous human diseases. However, therapeutic proteins often suffer short serum half-life. In order to extend the serum half-life, a natural albumin ligand (a fatty acid) has been conjugated to small therapeutic peptides resulting in a prolonged serum half-life via binding to patients' serum albumin in vivo. However, fatty acid-conjugation has limited applicability due to lack of site-specificity resulting in the heterogeneity of conjugated proteins and a significant loss in pharmaceutical activity. In order to address these issues, we exploited the site-specific fatty acid-conjugation to a permissive site of a protein, using copper-catalyzed alkyne-azide cycloaddition, by linking a fatty acid derivative to p-ethynylphenylalanine incorporated into a protein using an engineered pair of yeast tRNA/aminoacyl tRNA synthetase. As a proof-of-concept, we show that single palmitic acid conjugated to superfolder green fluorescent protein (sfGFP) in a site-specific manner enhanced a protein's albumin-binding in vitro about 20 times and the serum half-life in vivo 5 times when compared to those of the unmodified sfGFP. Furthermore, the fatty acid conjugation did not cause a significant reduction in the fluorescence of sfGFP. Therefore, these results clearly indicate that the site-specific fatty acid-conjugation is a very promising strategy to prolong protein serum half-life in vivo without compromising its folded structure and activity. PMID:23735573

  16. Effect of Acid Etching, Silane and Thermal Cycling on the Bond Strength of Metallic Brackets to Ceramic.

    PubMed

    Matos, Natália Regina Santos de; Costa, Ana Rosa; Valdrighi, Heloísa Cristina; Correr, Américo Bortolazzo; Vedovello, Silvia Amélia; Santamaria, Milton; Correr-Sobrinho, Lourenço

    2016-01-01

    The aim of this study was to evaluate the effect of silanes, thermal cycling and acid etching on the shear bond strength (SBS) of metallic brackets to feldspathic ceramic. Feldspathic ceramic cylinders (Groups 1, 2, 5 and 6) were etched for 60 s with 10% hydrofluoric acid and Groups 3, 4, 7 and 8, without acid etching. Two layers of silane Clearfil Ceramic Primer (CCP, Groups 1 to 4) and two layers of RelyX Ceramic Primer (RCP, groups 5 to 8) were applied and dried for 60 s. Brackets were bonded to the cylinders with Transbond XT and light-activated for 40 s with Bluephase G2. All specimens were stored in deionized water at 37 °C for 24 h, and the specimens of groups 1, 3, 5 and 7 were submitted to 7,000 thermal cycles (5 °C/55 °C). After storage, the SBS test was performed at a crosshead speed of 1 mm/min. Data were subjected to three-way ANOVA and Tukey's post hoc test (α=0.05). The adhesive remnant index (ARI) was evaluated at 8x magnification. The SBS of CCP was significantly greater than of RCP (p<0.05), with or without thermal cycling. Thermal cycling significantly reduced the SBS (p<0.05). The groups submitted to acid etching showed significantly higher SBS than those without acid etching (p<0.05). In conclusion, thermal cycling reduced SBS for all groups. The best ceramic surface treatment for bracket bonding was achieved by acid etching and CCP silane. The ARI results showed predominance of score 0 for all groups.

  17. Functional site profiling and electrostatic analysis of cysteines modifiable to cysteine sulfenic acid.

    PubMed

    Salsbury, Freddie R; Knutson, Stacy T; Poole, Leslie B; Fetrow, Jacquelyn S

    2008-02-01

    Cysteine sulfenic acid (Cys-SOH), a reversible modification, is a catalytic intermediate at enzyme active sites, a sensor for oxidative stress, a regulator of some transcription factors, and a redox-signaling intermediate. This post-translational modification is not random: specific features near the cysteine control its reactivity. To identify features responsible for the propensity of cysteines to be modified to sulfenic acid, a list of 47 proteins (containing 49 known Cys-SOH sites) was compiled. Modifiable cysteines are found in proteins from most structural classes and many functional classes, but have no propensity for any one type of protein secondary structure. To identify features affecting cysteine reactivity, these sites were analyzed using both functional site profiling and electrostatic analysis. Overall, the solvent exposure of modifiable cysteines is not different from the average cysteine. The combined sequence, structure, and electrostatic approaches reveal mechanistic determinants not obvious from overall sequence comparison, including: (1) pKaS of some modifiable cysteines are affected by backbone features only; (2) charged residues are underrepresented in the structure near modifiable sites; (3) threonine and other polar residues can exert a large influence on the cysteine pKa; and (4) hydrogen bonding patterns are suggested to be important. This compilation of Cys-SOH modification sites and their features provides a quantitative assessment of previous observations and a basis for further analysis and prediction of these sites. Agreement with known experimental data indicates the utility of this combined approach for identifying mechanistic determinants at protein functional sites.

  18. Effect of the acidic strength on the vapor phase Beckmann rearrangement of cyclohexanone oxime over the MFI zeolite: an embedded ONIOM study.

    PubMed

    Sirijaraensre, Jakkapan; Limtrakul, Jumras

    2009-01-21

    The mechanism and energetic profile of the Beckmann rearrangement reaction of cyclohexanone oxime to epsilon-caprolactam catalyzed by the H-[Al]-MFI and H-[B]-MFI zeolites were investigated by both the bare cluster and the ONIOM models at the B3LYP/6-31G(d,p) and the B3LYP/6-31G(d,p):MNDO levels of theory, respectively. In order to improve the energetic properties and take into account the whole zeolite framework effect, single point calculations are undertaken at the embedded ONIOM2 schemes; MP2/6-311G(d,p):HF/6-31G(d) with an additional long-range electrostatic potential from the extended zeolite framework. The reaction mechanism of the Beckmann rearrangement over the acid site of zeolites consists of three steps: the 1,2 H shift, the rearrangement and the tautomerization. The activation energies for the Beckmann rearrangement of cyclohexanone oxime on the H-[Al]-MFI zeolite are calculated to be 31.46, 16.15 and 18.95 kcal mol(-1), for the first, second and third steps, respectively, whereas in the H-[B]-MFI zeolite, the energy barriers for each step of the reaction are 24.33, 7.46 and 20.43 kcal mol(-1), respectively. The rate-determining step of the reaction is the first step, which is the transformation from the N-ended cyclohexanone oxime adsorption complex and the O-ended one. These results signify the important role that the acid strength of zeolites plays in altering the energy profile of the reaction. The results further indicate that the weak Brønsted acid sites in the [B]-MFI zeolite could better catalyze the Beckmann rearrangement of cyclohexanone oxime than the strong acid sites in the [Al]-MFI zeolite, as compared with the quantitatively low activation energy of most steps. However, the turnover reaction of the H-[B]-MFI zeolite might be delayed by the quantitatively high desorption energy of the product as compared to the adsorption energy of the reactant.

  19. Interaction morphology and bond strength of nanofilled simplified-step adhesives to acid etched dentin

    PubMed Central

    Di Hipólito, Vinicius; Reis, André Figueiredo; Mitra, Sumita B.; de Goes, Mario Fernando

    2012-01-01

    Objective: To evaluate the effect of nanofillers incorporated into adhesives on the microtensile bond strength (μ-TBS) and interfacial micromorphology to dentin. Methods: The occlusal enamel of 5 human molars was removed and each tooth sectioned into four quarters. The exposed dentin was treated with one of the following adhesives: Adper Single Bond (SB-unfilled), OptiBond Solo Plus (OS-barium aluminoborosilicate, 400nm Ø), Prime & Bond NT (NT-colloidal silica, 7–40 nm Ø) and Adper Single Bond 2 (SB2-colloidal silica, 5nm Ø). Cylinders of resin-based composite were constructed on the adhesive layers. After 24-hour storage, the restored tooth-quadrants were sectioned to obtain stick-shaped specimens (0.8 mm2, cross-sectional area) and submitted to μ-TBS at a cross-speed of 0.5 mm/min. Data were analyzed using one-way ANOVA and Tukey’s test (alpha = .05). Twenty-eight additional teeth were used for interfacial micro-morphologic analysis by SEM (16-teeth) and TEM (12-teeth). The dentin surfaces of 32 discs were treated with the adhesives (8 discs for adhesive) and laminated to form disc-pairs using a flowable resin composite for SEM/EDS analysis. For TEM, 90nm-thick nondemineralized unstained sections were processed. Results: SB2 showed significant higher bond strength than SB, OS and NT. The SEM/EDS and TEM analysis revealed nanofillers infiltrated within the interfibrillar spaces of the SB2-hybrid layer. Fillers were concentrated around patent tubular orifices and in the adhesive layer for OS and NT. Conclusion: The presence of nanofillers within the interfibrillar spaces of the SB2-hybrid layer suggests its importance in the improvement of the μ-TBS. PMID:23077413

  20. A comparative study of shear bond strength of orthodontic bracket after acid-etched and Er:YAG treatment on enamel surface

    NASA Astrophysics Data System (ADS)

    Leão, Juliana C.; Mota, Cláudia C. B. O.; Cassimiro-silva, Patricia F.; Gomes, Anderson S. L.

    2016-02-01

    This study aimed to evaluate the shear bond strength (SBS) of teeth prepared for orthodontic bracket bonding with 37% phosphoric acid and Er:YAG laser. Forty bovine incisors were divided into two groups. In Group I, the teeth were conditioned with 37% phosphoric acid and brackets were bonded with Transbond XT; in Group II, the teeth were irradiated with Er:YAG and bonding with Transbond XT. After SBS test, the adhesive remnant index was determined. Adhesion to dental hard tissues after Er:YAG laser etching was inferior to that obtained after acid etching but exceeded what is believed to be clinically sufficient strength, and therefore can be used in patients.

  1. Effect of sun elevation upon remote sensing of ocean color over an acid waste dump site

    NASA Technical Reports Server (NTRS)

    Bressette, W. E.

    1978-01-01

    Photographic flights were made over an ocean acid waste dump site while dumping was in progress. The flights resulted in wide angle, broadband, spectral radiance film exposure data between the wavelengths of 500 to 900 nanometers for sun elevation angles ranging from 26 to 42 degrees. It is shown from densitometer data that the spectral signature of acid waste discharged into ocean water can be observed photographically, the influence of sun elevation upon remotely sensed apparent color can be normalized by using a single spectral band ratioing technique, and photographic quantification and mapping of acid waste through its suspended iron precipitate appears possible.

  2. In Situ Oxalic Acid Injection to Accelerate Arsenic Remediation at a Superfund Site in New Jersey.

    PubMed

    Wovkulich, Karen; Stute, Martin; Mailloux, Brian J; Keimowitz, Alison R; Ross, James; Bostick, Benjamin; Sun, Jing; Chillrud, Steven N

    2014-09-25

    Arsenic is a prevalent contaminant at a large number of US Superfund sites; establishing techniques that accelerate As remediation could benefit many sites. Hundreds of tons of As were released into the environment by the Vineland Chemical Co. in southern New Jersey during its manufacturing lifetime (1949-1994), resulting in extensive contamination of surface and subsurface soils and sediments, groundwater, and the downstream watershed. Despite substantial intervention at this Superfund site, sufficient aquifer cleanup could require many decades if based on traditional pump and treat technologies only. Laboratory column experiments have suggested that oxalic acid addition to contaminated aquifer solids could promote significant As release from the solid phase. To evaluate the potential of chemical additions to increase As release in situ and boost treatment efficiency, a forced gradient pilot scale study was conducted on the Vineland site. During spring/summer 2009, oxalic acid and bromide tracer were injected into a small portion (~50 m(2)) of the site for 3 months. Groundwater samples indicate that introduction of oxalic acid led to increased As release. Between 2.9 and 3.6 kg of As were removed from the sampled wells as a result of the oxalic acid treatment during the 3-month injection. A comparison of As concentrations on sediment cores collected before and after treatment and analyzed using X-ray fluorescence spectroscopy suggested reduction in As concentrations of ~36% (median difference) to 48% (mean difference). While further study is necessary, the addition of oxalic acid shows potential for accelerating treatment of a highly contaminated site and decreasing the As remediation time-scale.

  3. In Situ Oxalic Acid Injection to Accelerate Arsenic Remediation at a Superfund Site in New Jersey

    PubMed Central

    Wovkulich, Karen; Stute, Martin; Mailloux, Brian J.; Keimowitz, Alison R.; Ross, James; Bostick, Benjamin; Sun, Jing; Chillrud, Steven N.

    2015-01-01

    Arsenic is a prevalent contaminant at a large number of US Superfund sites; establishing techniques that accelerate As remediation could benefit many sites. Hundreds of tons of As were released into the environment by the Vineland Chemical Co. in southern New Jersey during its manufacturing lifetime (1949–1994), resulting in extensive contamination of surface and subsurface soils and sediments, groundwater, and the downstream watershed. Despite substantial intervention at this Superfund site, sufficient aquifer cleanup could require many decades if based on traditional pump and treat technologies only. Laboratory column experiments have suggested that oxalic acid addition to contaminated aquifer solids could promote significant As release from the solid phase. To evaluate the potential of chemical additions to increase As release in situ and boost treatment efficiency, a forced gradient pilot scale study was conducted on the Vineland site. During spring/summer 2009, oxalic acid and bromide tracer were injected into a small portion (~50 m2) of the site for 3 months. Groundwater samples indicate that introduction of oxalic acid led to increased As release. Between 2.9 and 3.6 kg of As were removed from the sampled wells as a result of the oxalic acid treatment during the 3-month injection. A comparison of As concentrations on sediment cores collected before and after treatment and analyzed using X-ray fluorescence spectroscopy suggested reduction in As concentrations of ~36% (median difference) to 48% (mean difference). While further study is necessary, the addition of oxalic acid shows potential for accelerating treatment of a highly contaminated site and decreasing the As remediation time-scale. PMID:25598701

  4. Shear bond strength of metal brackets to feldspathic porcelain treated by Nd:YAG laser and hydrofluoric acid.

    PubMed

    Hosseini, Mohammad Hashem; Sobouti, Farhad; Etemadi, Ardavan; Chiniforush, Nasim; Shariati, Mahsa

    2015-02-01

    Adult orthodontic treatment requires bonding orthodontic attachment to dental restorations. Ceramics are commonly used as esthetic restorative materials for the crowns and bridges. The present study evaluated the shear bond strength of metal orthodontic brackets to the feldspathic porcelain surfaces following conditioning by different powers of neodymium-doped yttrium aluminum garnet (Nd:YAG) laser and hydrofluoric acid as a conventional method. Seventy-two glazed porcelain samples were prepared and randomly attributed to six equal groups of 12. In the conventional hydrofluoric (HF) group, the specimens were etched by 9.6% hydrofluoric acid for 4 min. In laser groups, samples were conditioned by 0.75-, 1-, 1.25-, 1.5-, and 2-W Nd:YAG laser for 10 s. Metal brackets were bonded to porcelain samples and after being stored in distilled water for 24 h, they were subjected to thermocycling for 500 cycles. The debonding was carried out by a Zwick testing machine. The data were statistically analyzed by ANOVA and Tamhane multiple comparisons tests. The mean ± SD of the shear bond strength in the laser group 0.75, 1, 1.25, 1.5, and 2 W and HF group was 2.2 ± 0.9, 4.2 ± 1.1, 4.9 ± 2.4, 7 ± 1.7, 9.6 ± 2.7, and 9.4 ± 2.5, respectively. Together with the increased power of laser, the mean shear bond strength was increased continuously and no significant differences were found between the HF group and the laser groups with power of 1.5 or 2 W. Also, there was no significant difference between all test groups in ARI scores. There was no significant difference between bond strength of laser groups with power of 1.5 and 2 W and HF-etched group. So, Nd:YAG laser with appropriate parameters can be used as an alternative method for porcelain etching.

  5. Effective and site-specific phosphoramidation reaction for universally labeling nucleic acids.

    PubMed

    Su, Yu-Chih; Chen, Hsing-Yin; Ko, Ni Chien; Hwang, Chi-Ching; Wu, Min Hui; Wang, Li-Fang; Wang, Yun-Ming; Chang, Sheng-Nan; Wang, Eng-Chi; Wang, Tzu-Pin

    2014-03-15

    Here we report efficient and selective postsynthesis labeling strategies, based on an advanced phosphoramidation reaction, for nucleic acids of either synthetic or enzyme-catalyzed origin. The reactions provided phosphorimidazolide intermediates of DNA or RNA which, whether reacted in one pot (one-step) or purified (two-step), were directly or indirectly phosphoramidated with label molecules. The acquired fluorophore-labeled nucleic acids, prepared from the phosphoramidation reactions, demonstrated labeling efficacy by their F/N ratio values (number of fluorophores per molecule of nucleic acid) of 0.02-1.2 which are comparable or better than conventional postsynthesis fluorescent labeling methods for DNA and RNA. Yet, PCR and UV melting studies of the one-step phosphoramidation-prepared FITC-labeled DNA indicated that the reaction might facilitate nonspecific hybridization in nucleic acids. Intrinsic hybridization specificity of nucleic acids was, however, conserved in the two-step phosphoramidation reaction. The reaction of site-specific labeling nucleic acids at the 5'-end was supported by fluorescence quenching and UV melting studies of fluorophore-labeled DNA. The two-step phosphoramidation-based, effective, and site-specific labeling method has the potential to expedite critical research including visualization, quantification, structural determination, localization, and distribution of nucleic acids in vivo and in vitro.

  6. Efficient solid acid catalyst containing Lewis and Brønsted Acid sites for the production of furfurals.

    PubMed

    Mazzotta, Michael G; Gupta, Dinesh; Saha, Basudeb; Patra, Astam K; Bhaumik, Asim; Abu-Omar, Mahdi M

    2014-08-01

    Self-assembled nanoparticulates of porous sulfonated carbonaceous TiO2 material that contain Brønsted and Lewis acidic sites were prepared by a one-pot synthesis method. The material was characterized by XRD, FTIR spectroscopy, NH3 temperature-programmed desorption, pyridine FTIR spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, N2 -sorption, atomic absorbance spectroscopy, and inductively coupled plasma optical emission spectroscopy. The carbonaceous heterogeneous catalyst (Glu-TsOH-Ti) with a Brønsted-to-Lewis acid density ratio of 1.2 and more accessible acid sites was effective to produce 5-hydroxymethylfurfural and furfural from biomass-derived mono- and disaccharides and xylose in a biphasic solvent that comprised water and biorenewable methyltetrahydrofuran. The catalyst was recycled in four consecutive cycles with a total loss of only 3 % activity. Thus, Glu-TsOH-Ti, which contains isomerization and dehydration catalytic sites and is based on a cheap and biorenewable carbon support, is a sustainable catalyst for the production of furfurals, platform chemicals for biofuels and chemicals.

  7. Absolute acidity of clay edge sites from ab-initio simulations

    NASA Astrophysics Data System (ADS)

    Tazi, Sami; Rotenberg, Benjamin; Salanne, Mathieu; Sprik, Michiel; Sulpizi, Marialore

    2012-10-01

    We provide a microscopic understanding of the solvation structure and reactivity of the edges of neutral clays. In particular we address the tendency to deprotonation of the different reactive groups on the (0 1 0) face of pyrophyllite. Such information cannot be inferred directly from titration experiments, which do not discriminate between different sites and whose interpretation resorts to macroscopic models. The determination of the corresponding pKa then usually relies on bond valence models, sometimes improved by incorporating some structural information from ab-initio simulations. Here we use density functional theory based molecular dynamics simulations, combined with thermodynamic integration, to compute the free energy of the reactions of water with the different surface groups, leading to a deprotonated site and an aqueous hydronium ion. Our approach consistently describes the clay and water sides of the interface and includes naturally electronic polarization effects. It also allows to investigate the structure and solvation of all sites separately. We find that the most acidic group is SiOH, due to its ability to establish strong hydrogen bonds with adsorbed water, as it also happens on the quartz and amorphous silica surfaces. The acidity constant of AlOH2 is only 1 pKa unit larger. Finally, the pKa of AlOH is outside the possible range in water and this site should not deprotonate in aqueous solution. We show that the solvation of surface sites and hence their acidity is strongly affected by the proximity of other sites, in particular for AlOH and AlOH2 which share the same Al. We discuss the implications of our findings on the applicability of bond valence models to predict the acidity of edge sites of clays.

  8. Effect of acidic amino acids engineered into the active site cleft of Thermopolyspora flexuosa GH11 xylanase.

    PubMed

    Li, He; Turunen, Ossi

    2015-01-01

    Thermopolyspora flexuosa GH11 xylanase (XYN11A) shows optimal activity at pH 6-7 and 75-80 °C. We studied how mutation to aspartic acid (N46D and V48D) in the vicinity of the catalytic acid/base affects the pH activity of highly thermophilic GH11 xylanase. Both mutations shifted the pH activity profile toward acidic pH. In general, the Km values were lower at pH 4-5 than at pH 6, and in line with this, the rate of hydrolysis of xylotetraose was slightly faster at pH 4 than at pH 6. The N46D mutation and also lower pH in XYN11A increased the hydrolysis of xylotriose. The Km value increased remarkably (from 2.5 to 11.6 mg/mL) because of V48D, which indicates the weakening of binding affinity of the substrate to the active site. Xylotetraose functioned well as a substrate for other enzymes, but with lowered reaction rate for V48D. Both N46D and V48D increased the enzyme inactivation by ionic liquid [emim]OAc. In conclusion, the pH activity profile could be shifted to acidic pH due to an effect from two different directions, but the tightly packed GH11 active site can cause steric problems for the mutations.

  9. Are carboxyl groups the most acidic sites in amino acids? Gas-phase acidities, photoelectron spectra, and computations on tyrosine, p-hydroxybenzoic acid, and their conjugate bases.

    PubMed

    Tian, Zhixin; Wang, Xue-Bin; Wang, Lai-Sheng; Kass, Steven R

    2009-01-28

    Deprotonation of tyrosine in the gas phase was found to occur preferentially at the phenolic site, and the conjugate base consists of a 70:30 mixture of phenoxide and carboxylate anions at equilibrium. This result was established by developing a chemical probe for differentiating these two isomers, and the presence of both ions was confirmed by photoelectron spectroscopy. Equilibrium acidity measurements on tyrosine indicated that deltaG(acid)(o) = 332.5 +/- 1.5 kcal mol(-1) and deltaH(acid)(o) = 340.7 +/- 1.5 kcal mol(-1). Photoelectron spectra yielded adiabatic electron detachment energies of 2.70 +/- 0.05 and 3.55 +/- 0.10 eV for the phenoxide and carboxylate anions, respectively. The H/D exchange behavior of deprotonated tyrosine was examined using three different alcohols (CF3CH2OD, C6H5CH2OD, and CH3CH2OD), and incorporation of up to three deuterium atoms was observed. Two pathways are proposed to account for these results, and all of the experimental findings are supplemented with B3LYP/aug-cc-pVDZ and G3B3 calculations. In addition, it was found that electrospray ionization of tyrosine from a 3:1 (v/v) CH3OH/H2O solution using a commercial source produces a deprotonated [M-H]- anion with the gas-phase equilibrium composition rather than the structure of the ion that exists in aqueous media. Electrospray ionization from acetonitrile, however, leads largely to the liquid-phase (carboxylate) structure. A control molecule, p-hydroxybenzoic acid, was found to behave in a similar manner. Thus, the electrospray conditions that are employed for the analysis of a compound can alter the isomeric composition of the resulting anion.

  10. Strength determination of periodontal splints fabricated from acid-etched retained materials.

    PubMed

    Compton, F H; Beagrie, G S; Chernecky, R

    1977-07-01

    Six systems (one polycarboxylate, one polymethyl methacrylate, one unfilled BIS-GMA resin, two combinations of methyl cyanoacrylate and polymethyl methacrylate, and one combination of unfilled BIS-GMA and filled composite resin) were evaluated for in vitro retention to acid-etched human enamel. Also tested were one unfilled-filled resin combination backed by perforated orthodontic band metal and another unfilled resin backed by stainless steel wire mesh. Significant differences in retention were found. Results show that retention depends pril surface and to resist subsequent chemical degradation.

  11. LIME TREATMENT LAGOONS TECHNOLOGY FOR TREATING ACID MINE DRAINAGE FROM TWO MINING SITES

    EPA Science Inventory

    Runoff and drainage from active and inactive mines are someof the most environmentally damaging land uses i the US. Acid Mine drainage (AMD) from mining sites across the country requires treatment because of high metal concentrations that exceed regulatory standards for safe disc...

  12. Positive Darwinian selection at single amino acid sites conferring plant virus resistance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Explicit evaluation of the accuracy and power of Maximum Likelihood and Bayesian methods for detecting site-specific positive Darwinian selection presents a challenge because selective consequences of single amino acid changes are generally unknown. We exploit extensive molecular and functional cha...

  13. PHYSICAL SOLUTIONS FOR ACID ROCK DRAINAGE AT REMOTE SITES DEMONSTRATION PROJECT

    EPA Science Inventory

    This report summarizes the results of Mine Waste Technology Program, Activity III, Project 42, Physical Solutions for Acid Rock Drainage at Remote Sites, funded by the U.S. Environmental Protection Agency (EPA) and jointly administered by EPA and the U.S. Department of Energy. A...

  14. Comparative Evaluation of Tensile – Bond Strength of An Orthodontic Adhesive with and without Fluoride Application, After Acid Etching -An Invitro Study

    PubMed Central

    Yugandhar, G; Ramana, I Venkata; Srinivas, K; Yadav, S. Sarjeev Singh

    2015-01-01

    Background Fixed appliances hinder the effective control of plaque accumulation and white spot lesions may develop under the ill fitting bands or adjacent to the stainless steel brackets during orthodontic treatment particularly the etching process. Aims and Objectives Comparative study of tensile bond strength of an orthodontic adhesive with and without fluoride application after acid etching to know the effect of fluoride on bond strength. Materials and Methods This study is carried out on 90 non carious human premolar teeth, and divided in 6 groups with each group of 15 specimens. In those Groups I and IV were control group acid etch treatment, Group II and V is 1.23% APF gel (acid etch plus APF gel treatment,) and group III and VI is 8% SnF2 (acid etch plus SnF2 treatment). Samples of Group I, II and III bond strength were tested after 24 h and groups IV, V and VI after one month on microtechtensometer machine. The scanning electron microscope (SEM) investigation was carried out for the 2 specimens for the control group after acid etch and 4 specimens after acid etch with fluoride application for fluoride groups. Results Control and SnF2 treated groups was found to be nearly similar to the control group whereas APF treated group showed less focal holes than the other 2 groups. Conclusion Fluoride application after acid etching without having an adverse effect on bond strength but we can prevent the white spot lesions and caries. PMID:26023648

  15. Enzymatic digestion of corncobs pretreated with low strength of sulfuric acid for bioethanol production.

    PubMed

    Kahar, Prihardi; Taku, Kazuo; Tanaka, Shuzo

    2010-10-01

    In this study, the effect and the optimum pretreatment condition of corncobs using low strength of H2SO4 were investigated, in which H2SO4 was used to improve the enzymatic digestibility of corncobs for saccharification without degradation of sugars released. The optimum pretreatment condition was found to be the addition of 0.5% (vol./vol.) H2SO4 and autoclaving at 122°C for 20 min. Under this condition, the structural integrity of corncob was altered to make cellulose microfibrils more accessible for cellulase enzymes, and the enzymatic digestion of corncobs could be significantly enhanced. A high yield of sugar, 80% (wt./wt.), could be obtained at a low enzyme dosage of 0.024 g enzymes/g cobs, when pretreated. As a result, the ethanol production was obviously improved by the pretreatment, i.e., the ethanol yield of 77% (wt./wt.) was obtained within 36 h in the SSF fermentation using Saccharomyces cerevisiae NBRC2114.

  16. Brønsted acid sites based on penta-coordinated aluminum species

    NASA Astrophysics Data System (ADS)

    Wang, Zichun; Jiang, Yijiao; Lafon, Olivier; Trébosc, Julien; Duk Kim, Kyung; Stampfl, Catherine; Baiker, Alfons; Amoureux, Jean-Paul; Huang, Jun

    2016-12-01

    Zeolites and amorphous silica-alumina (ASA), which both provide Brønsted acid sites (BASs), are the most extensively used solid acid catalysts in the chemical industry. It is widely believed that BASs consist only of tetra-coordinated aluminum sites (AlIV) with bridging OH groups in zeolites or nearby silanols on ASA surfaces. Here we report the direct observation in ASA of a new type of BAS based on penta-coordinated aluminum species (AlV) by 27Al-{1H} dipolar-mediated correlation two-dimensional NMR experiments at high magnetic field under magic-angle spinning. Both BAS-AlIV and -AlV show a similar acidity to protonate probe molecular ammonia. The quantitative evaluation of 1H and 27Al sites demonstrates that BAS-AlV co-exists with BAS-AlIV rather than replaces it, which opens new avenues for strongly enhancing the acidity of these popular solid acids.

  17. Brønsted acid sites based on penta-coordinated aluminum species

    PubMed Central

    Wang, Zichun; Jiang, Yijiao; Lafon, Olivier; Trébosc, Julien; Duk Kim, Kyung; Stampfl, Catherine; Baiker, Alfons; Amoureux, Jean-Paul; Huang, Jun

    2016-01-01

    Zeolites and amorphous silica-alumina (ASA), which both provide Brønsted acid sites (BASs), are the most extensively used solid acid catalysts in the chemical industry. It is widely believed that BASs consist only of tetra-coordinated aluminum sites (AlIV) with bridging OH groups in zeolites or nearby silanols on ASA surfaces. Here we report the direct observation in ASA of a new type of BAS based on penta-coordinated aluminum species (AlV) by 27Al-{1H} dipolar-mediated correlation two-dimensional NMR experiments at high magnetic field under magic-angle spinning. Both BAS-AlIV and -AlV show a similar acidity to protonate probe molecular ammonia. The quantitative evaluation of 1H and 27Al sites demonstrates that BAS-AlV co-exists with BAS-AlIV rather than replaces it, which opens new avenues for strongly enhancing the acidity of these popular solid acids. PMID:27976673

  18. Improve the Strength of PLA/HA Composite Through the Use of Surface Initiated Polymerization and Phosphonic Acid Coupling Agent

    PubMed Central

    Wang, Tongxin; Chow, Laurence C.; Frukhtbeyn, Stanislav A.; Ting, Andy Hai; Dong, Quanxiao; Yang, Mingshu; Mitchell, James W.

    2011-01-01

    Bioresorbable composite made from degradable polymers, e.g., polylactide (PLA), and bioactive calcium phosphates, e.g., hydroxyapatite (HA), are clinically desirable for bone fixation, repair and tissue engineering because they do not need to be removed by surgery after the bone heals. However, preparation of PLA/HA composite from non-modified HA usually results in mechanical strength reductions due to a weak interface between PLA and HA. In this study, a calcium-phosphate/phosphonate hybrid shell was developed to introduce a greater amount of reactive hydroxyl groups onto the HA particles. Then, PLA was successfully grafted on HA by surface-initiated polymerization through the non-ionic surface hydroxyl groups. Thermogravimetric analysis indiated that the amount of grafted PLA on HA can be up to 7 %, which is about 50 % greater than that from the literature. PLA grafted HA shows significantly different pH dependent ζ-potential and particle size profiles from those of uncoated HA. By combining the phosphonic acid coupling agent and surface initiated polymerization, PLA could directly link to HA through covalent bond so that the interfacial interaction in the PLA/HA composite can be significantly improved. The diametral tensile strength of PLA/HA composite prepared from PLA-grafted HA was found to be over twice that of the composite prepared from the non-modified HA. Moreover, the tensile strength of the improved composite was 23 % higher than that of PLA alone. By varying additional variables, this approach has the potential to produce bioresorbable composites with improved mechanical properties that are in the range of natural bones, and can have wide applications for bone fixation and repair in load-bearing areas. PMID:22399838

  19. Molecular Design of a Chiral Brønsted Acid with Two Different Acidic Sites: Regio-, Diastereo-, and Enantioselective Hetero-Diels-Alder Reaction of Azopyridinecarboxylate with Amidodienes Catalyzed by Chiral Carboxylic Acid-Monophosphoric Acid.

    PubMed

    Momiyama, Norie; Tabuse, Hideaki; Noda, Hirofumi; Yamanaka, Masahiro; Fujinami, Takeshi; Yamanishi, Katsunori; Izumiseki, Atsuto; Funayama, Kosuke; Egawa, Fuyuki; Okada, Shino; Adachi, Hiroaki; Terada, Masahiro

    2016-09-07

    A chiral Brønsted acid containing two different acidic sites, chiral carboxylic acid-monophosphoric acid 1a, was designed to be a new and effective concept in catalytic asymmetric hetero-Diels-Alder reactions of azopyridinecarboxylate with amidodienes. The multipoint hydrogen-bonding interactions among the carboxylic acid, monophosphoric acid, azopyridinecarboxylate, and amidodiene achieved high catalytic and chiral efficiency, producing substituted 1,2,3,6-tetrahydropyridazines with excellent stereocontrol in a single step. This constitutes the first example of regio-, diastereo-, and enantioselective azo-hetero-Diels-Alder reactions by chiral Brønsted acid catalysis.

  20. Simultaneous determination of Ca, Cu, Ni, Zn and Cd binding strengths with fulvic acid fractions by Schubert's method

    USGS Publications Warehouse

    Brown, G.K.; MacCarthy, P.; Leenheer, J.A.

    1999-01-01

    The equilibrium binding of Ca2+, Ni2+, Cd2+, Cu2+ and Zn2+ with unfractionated Suwannee river fulvic acid (SRFA) and an enhanced metal binding subfraction of SRFA was measured using Schubert's ion-exchange method at pH 6.0 and at an ionic strength (??) of 0.1 (NaNO3). The fractionation and subfractionation were directed towards obtaining an isolate with an elevated metal binding capacity or binding strength as estimated by Cu2+ potentiometry (ISE). Fractions were obtained by stepwise eluting an XAD-8 column loaded with SRFA with water eluents of pH 1.0 to pH 12.0. Subfractions were obtained by loading the fraction eluted from XAD-8 at pH 5.0 onto a silica gel column and eluting with solvents of increasing polarity. Schuberts ion exchange method was rigorously tested by measuring simultaneously the conditional stability constants (K) of citric acid complexed with the five metals at pH 3.5 and 6.0. The logK of SRFA with Ca2+, Ni2+, Cd2+, Cu2+ and Zn2+ determined simultaneously at pH 6.0 follow the sequence of Cu2+>Cd2+>Ni2+>Zn2+>Ca2+ while all logK values increased for the enhanced metal binding subfraction and followed a different sequence of Cu2+>Cd2+>Ca2+>Ni2+>Zn2+. Both fulvic acid samples and citric acid exhibited a 1:1 metal to ligand stochiometry under the relatively low metal loading conditions used here. Quantitative 13C nuclear magnetic resonance spectroscopy showed increases in aromaticity and ketone content and decreases in aliphatic carbon for the elevated metal binding fraction while the carboxyl carbon, and elemental nitrogen, phosphorus, and sulfur content did not change. The more polar, elevated metal binding fraction did show a significant increase in molecular weight over the unfractionated SRFA. Copyright (C) 1999 Elsevier Science B.V.

  1. Bacterial periplasmic sialic acid-binding proteins exhibit a conserved binding site

    SciTech Connect

    Gangi Setty, Thanuja; Cho, Christine; Govindappa, Sowmya; Apicella, Michael A.; Ramaswamy, S.

    2014-07-01

    Structure–function studies of sialic acid-binding proteins from F. nucleatum, P. multocida, V. cholerae and H. influenzae reveal a conserved network of hydrogen bonds involved in conformational change on ligand binding. Sialic acids are a family of related nine-carbon sugar acids that play important roles in both eukaryotes and prokaryotes. These sialic acids are incorporated/decorated onto lipooligosaccharides as terminal sugars in multiple bacteria to evade the host immune system. Many pathogenic bacteria scavenge sialic acids from their host and use them for molecular mimicry. The first step of this process is the transport of sialic acid to the cytoplasm, which often takes place using a tripartite ATP-independent transport system consisting of a periplasmic binding protein and a membrane transporter. In this paper, the structural characterization of periplasmic binding proteins from the pathogenic bacteria Fusobacterium nucleatum, Pasteurella multocida and Vibrio cholerae and their thermodynamic characterization are reported. The binding affinities of several mutations in the Neu5Ac binding site of the Haemophilus influenzae protein are also reported. The structure and the thermodynamics of the binding of sugars suggest that all of these proteins have a very well conserved binding pocket and similar binding affinities. A significant conformational change occurs when these proteins bind the sugar. While the C1 carboxylate has been identified as the primary binding site, a second conserved hydrogen-bonding network is involved in the initiation and stabilization of the conformational states.

  2. KDP crystal doped with L-arginine amino acid: growth, structure perfection, optical and strength characteristics

    NASA Astrophysics Data System (ADS)

    Pritula, I. M.; Kostenyukova, E. I.; Bezkrovnaya, O. N.; Kolybaeva, M. I.; Sofronov, D. S.; Dolzhenkova, E. F.; Kanaev, A.; Tsurikov, V.

    2016-07-01

    Potassium Dihydrogen Phosphate (KDP) crystal doped with L-arginine (L-arg) amino acid with 1.4 wt% concentration in the solution was grown onto a point seed by the method of temperature reduction. For the first time an attempt was made to grow large-size (7 × 6 × 8 cm3) optically transparent crystals, which allowed to analyze the effect of L-arg additive on the physical properties of the different growth sectors ({100} and {101}) of KDP. The incorporation of L-arg into both growth sectors of the crystal was confirmed by the methods of optical and IR spectroscopy and found to be caused by the ability of the amino acid to form hydrogen bonds with the face {100} and electrostatically interact with the positively charged face {101} of KDP crystal. A slight variation in the unit cell parameters was reported, the elementary cell volume of KDP:L-arg crystal increased in comparison with the one of pure KDP by 2·10-2 and 2.07·10-2 Å3 in the sectors {100} and {101}, respectively. It was found that the doping of L-arg enhanced the SHG efficiency of KDP and depended on the crystal growth sectors. The SHG efficiency of KDP:L-arg was by a factor 2.53 and 3.95 higher in comparison with those of pure KDP for {101} and {100} growth sector, respectively. The doping was found to lead to softening of both faces by ∼3-10% and ∼14-17% in the sectors {101} and {100}, respectively. Investigation of the influence of L-arg molecules on the bulk laser damage threshold of the crystals showed that the bulk laser damage threshold of the samples of KDP:L-arg crystal was higher than the one of the pure crystal in the sector {101} and lower in the sector {100}. The correlation between microhardness and laser damage threshold were discussed. The study is helpful for further searching, designing and simulation of hybrid NLO materials.

  3. Doxycycline as a matrix metalloproteinase inhibitor to prevent bond degradation: the effect of acid and neutral solutions on dentin bond strength.

    PubMed

    Oliveira, Hellen de Lacerda; Tedesco, Tamara Kerber; Rodrigues-Filho, Leonardo Eloy; Soares, Fabio Zovico Maxnuck; Rocha, Rachel de Oliveira

    2016-01-01

    The aim of this in vitro study was to evaluate the pH effect of doxycycline solutions on the immediate dentin bond strength of a total-etch adhesive system. Twenty human molars were divided into 4 groups (n = 5) after acid etching according to surface treatment: 10% acidic doxycycline, 10% neutral doxycycline, 2% chlorhexidine, and control. Composite resin blocks were made and subjected to microtensile testing. Mean bond strength values were submitted to a 1-way analysis of variance and a Tukey test (α = 0.05). No statistically significant differences between the experimental groups were found (P = 0.093). The chlorhexidine group showed the highest number of pretesting failures. The application of either acidic or neutral doxycycline solution prior to the dentin adhesive did not influence the bond strength of the total-etch adhesive system evaluated.

  4. Three Dimensional Structure Prediction of Fatty Acid Binding Site on Human Transmembrane Receptor CD36.

    PubMed

    Tarhda, Zineb; Semlali, Oussama; Kettani, Anas; Moussa, Ahmed; Abumrad, Nada A; Ibrahimi, Azeddine

    2013-01-01

    CD36 is an integral membrane protein which is thought to have a hairpin-like structure with alpha-helices at the C and N terminals projecting through the membrane as well as a larger extracellular loop. This receptor interacts with a number of ligands including oxidized low density lipoprotein and long chain fatty acids (LCFAs). It is also implicated in lipid metabolism and heart diseases. It is therefore important to determine the 3D structure of the CD36 site involved in lipid binding. In this study, we predict the 3D structure of the fatty acid (FA) binding site [127-279 aa] of the CD36 receptor based on homology modeling with X-ray structure of Human Muscle Fatty Acid Binding Protein (PDB code: 1HMT). Qualitative and quantitative analysis of the resulting model suggests that this model was reliable and stable, taking in consideration over 97.8% of the residues in the most favored regions as well as the significant overall quality factor. Protein analysis, which relied on the secondary structure prediction of the target sequence and the comparison of 1HMT and CD36 [127-279 aa] secondary structures, led to the determination of the amino acid sequence consensus. These results also led to the identification of the functional sites on CD36 and revealed the presence of residues which may play a major role during ligand-protein interactions.

  5. Three Dimensional Structure Prediction of Fatty Acid Binding Site on Human Transmembrane Receptor CD36

    PubMed Central

    Tarhda, Zineb; Semlali, Oussama; Kettani, Anas; Moussa, Ahmed; Abumrad, Nada A.; Ibrahimi, Azeddine

    2013-01-01

    CD36 is an integral membrane protein which is thought to have a hairpin-like structure with alpha-helices at the C and N terminals projecting through the membrane as well as a larger extracellular loop. This receptor interacts with a number of ligands including oxidized low density lipoprotein and long chain fatty acids (LCFAs). It is also implicated in lipid metabolism and heart diseases. It is therefore important to determine the 3D structure of the CD36 site involved in lipid binding. In this study, we predict the 3D structure of the fatty acid (FA) binding site [127–279 aa] of the CD36 receptor based on homology modeling with X-ray structure of Human Muscle Fatty Acid Binding Protein (PDB code: 1HMT). Qualitative and quantitative analysis of the resulting model suggests that this model was reliable and stable, taking in consideration over 97.8% of the residues in the most favored regions as well as the significant overall quality factor. Protein analysis, which relied on the secondary structure prediction of the target sequence and the comparison of 1HMT and CD36 [127–279 aa] secondary structures, led to the determination of the amino acid sequence consensus. These results also led to the identification of the functional sites on CD36 and revealed the presence of residues which may play a major role during ligand-protein interactions. PMID:24348024

  6. Adsorption of Carbon Dioxide on Unsaturated Metal Sites in M2 (dobpdc) Frameworks with Exceptional Structural Stability and Relation between Lewis Acidity and Adsorption Enthalpy.

    PubMed

    Yoo, Ga Young; Lee, Woo Ram; Jo, Hyuna; Park, Joonho; Song, Jeong Hwa; Lim, Kwang Soo; Moon, Dohyun; Jung, Hyun; Lim, Juhyung; Han, Sang Soo; Jung, Yousung; Hong, Chang Seop

    2016-05-23

    A series of metal-organic frameworks (MOFs) M2 (dobpdc) (M=Mn, Co, Ni, Zn; H4 dobpdc=4,4'-dihydroxy-1,1'-biphenyl-3,3'-dicarboxylic acid), with a highly dense arrangement of open metal sites along hexagonal channels were prepared by microwave-assisted or simple solvothermal reactions. The activated materials were structurally expanded when guest molecules including CO2 were introduced into the pores. The Lewis acidity of the open metal sites varied in the order MnZn, as confirmed by C=O stretching bands in the IR spectra, which are related to the CO2 adsorption enthalpy. DFT calculations revealed that the high CO2 binding affinity of transition-metal-based M2 (dobpdc) is primarily attributable to the favorable charge transfer from CO2 (oxygen lone pair acting as a Lewis base) to the open metal sites (Lewis acid), while electrostatic effects, the underlying factor responsible for the particular order of binding strength observed across different transition metals, also play a role. The framework stability against water coincides with the order of Lewis acidity. In this series of MOFs, the structural stability of Ni2 (dobpdc) is exceptional; it endured in water vapor, liquid water, and in refluxing water for one month, and the solid remained intact on exposure to solutions of pH 2-13. The DFT calculations also support the experimental finding that Ni2 (dobpdc) has higher chemical stability than the other frameworks.

  7. Evidence of sulphur and nitrogen deposition signals at the United Kingdom Acid Waters Monitoring Network sites.

    PubMed

    Cooper, D M

    2005-09-01

    Some recent studies of trends in sulphate in surface waters have alluded to possible lag effects imposed by catchment soils, resulting in discrepancies between trends in deposition and run-off. To assess the extent of these possible effects in the UK, sulphate concentration data from the United Kingdom Acid Waters Monitoring Network (AWMN) sites are compared with estimates of sulphur deposition at each site. From these data, input-output budgets are computed at an annual time scale. The estimated budgets suggest a close association between catchment sulphur inputs and outputs at an annual scale, with well-balanced annual budgets at most sites, indicative of only minor lag effects. A similar analysis of the AWMN site nitrogen budget shows little evidence of an association between nitrogen inputs and outputs at this time scale.

  8. Lipid Classes and Fatty Acids in Ophryotrocha cyclops, a Dorvilleid from Newfoundland Aquaculture Sites.

    PubMed

    Salvo, Flora; Dufour, Suzanne C; Hamoutene, Dounia; Parrish, Christopher C

    2015-01-01

    A new opportunistic annelid (Ophryotrocha cyclops) discovered on benthic substrates underneath finfish aquaculture sites in Newfoundland (NL) may be involved in the remediation of organic wastes. At those aquaculture sites, bacterial mats and O. cyclops often coexist and are used as indicators of organic enrichment. Little is known on the trophic strategies used by these annelids, including whether they might consume bacteria or other aquaculture-derived wastes. We studied the lipid and fatty acid composition of the annelids and their potential food sources (degraded flocculent organic matter, fresh fish pellets and bacterial mats) to investigate feeding relationships in these habitats and compared the lipid and fatty acid composition of annelids before and after starvation. Fish pellets were rich in lipids, mainly terrestrially derived C18 fatty acids (18:1ω9, 18:2ω6, 18:3ω3), while bacterial samples were mainly composed of ω7 fatty acids, and flocculent matter appeared to be a mixture of fresh and degrading fish pellets, feces and bacteria. Ophryotrocha cyclops did not appear to store excessive amounts of lipids (13%) but showed a high concentration of ω3 and ω6 fatty acids, as well as a high proportion of the main fatty acids contained in fresh fish pellets and bacterial mats. The dorvilleids and all potential food sources differed significantly in their lipid and fatty acid composition. Interestingly, while all food sources contained low proportions of 20:5ω3 and 20:2ω6, the annelids showed high concentrations of these two fatty acids, along with 20:4ω6. A starvation period of 13 days did not result in a major decrease in total lipid content; however, microscopic observations revealed that very few visible lipid droplets remained in the gut epithelium after three months of starvation. Ophryotrocha cyclops appears well adapted to extreme environments and may rely on lipid-rich organic matter for survival and dispersal in cold environments.

  9. Characterization of Naphthaleneacetic Acid Binding to Receptor Sites on Cellular Membranes of Maize Coleoptile Tissue 1

    PubMed Central

    Ray, Peter M.; Dohrmann, Ulrike; Hertel, Rainer

    1977-01-01

    Characteristics of and optimum conditions for saturable (“specific”) binding of [14C]naphthaleneacetic acid to sites located on membranous particles from maize (Zea mays L.) coleoptiles are described. Most, if not all, of the specific binding appears to be due to a single kinetic class of binding sites having a KD of 5 to 7 × 10−7m for naphthalene-1-acetic acid (NAA). Binding of NAA is insensitive to high monovalent salt concentrations, indicating that binding is not primarily ionic. However, specific binding is inhibited by Mg2+ or Ca2+ above 5 mm. Specific binding is improved by organic acids, especially citrate. Binding is heat-labile and is sensitive to agents that act either on proteins or on lipids. Specific binding is reversibly inactivated by reducing agents such as dithioerythritol; a reducible group, possibly a disulfide group, may be located at the binding site and required for its function. The affinity of the specific binding sites for auxins is modified by an unidentified dialyzable, heat-stable, apparently amphoteric, organic factor (“supernatant factor”) found in maize tissue. PMID:16659851

  10. Zinc-induced oligomerization of zinc α2 glycoprotein reveals multiple fatty acid-binding sites.

    PubMed

    Zahid, Henna; Miah, Layeque; Lau, Andy M; Brochard, Lea; Hati, Debolina; Bui, Tam T T; Drake, Alex F; Gor, Jayesh; Perkins, Stephen J; McDermott, Lindsay C

    2016-01-01

    Zinc α2 glycoprotein (ZAG) is an adipokine with a class I MHC protein fold and is associated with obesity and diabetes. Although its intrinsic ligand remains unknown, ZAG binds the dansylated C11 fatty acid 11-(dansylamino)undecanoic acid (DAUDA) in the groove between the α1 and α2 domains. The surface of ZAG has approximately 15 weak zinc-binding sites deemed responsible for precipitation from human plasma. In the present study the functional significance of these metal sites was investigated. Analytical ultracentrifugation (AUC) and CD showed that zinc, but not other divalent metals, causes ZAG to oligomerize in solution. Thus ZAG dimers and trimers were observed in the presence of 1 and 2 mM zinc. Molecular modelling of X-ray scattering curves and sedimentation coefficients indicated a progressive stacking of ZAG monomers, suggesting that the ZAG groove may be occluded in these. Using fluorescence-detected sedimentation velocity, these ZAG-zinc oligomers were again observed in the presence of the fluorescent boron dipyrromethene fatty acid C16-BODIPY (4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-hexadecanoic acid). Fluorescence spectroscopy confirmed that ZAG binds C16-BODIPY. ZAG binding to C16-BODIPY, but not to DAUDA, was reduced by increased zinc concentrations. We conclude that the lipid-binding groove in ZAG contains at least two distinct fatty acid-binding sites for DAUDA and C16-BODIPY, similar to the multiple lipid binding seen in the structurally related immune protein CD1c. In addition, because high concentrations of zinc occur in the pancreas, the perturbation of these multiple lipid-binding sites by zinc may be significant in Type 2 diabetes where dysregulation of ZAG and zinc homoeostasis occurs.

  11. Later Age at Onset of Independent Walking Is Associated with Lower Bone Strength at Fracture-Prone Sites in Older Men.

    PubMed

    Ireland, Alex; Muthuri, Stella; Rittweger, Joern; Adams, Judith E; Ward, Kate A; Kuh, Diana; Cooper, Rachel

    2017-02-09

    Later age at onset of independent walking is associated with lower leg bone strength in childhood and adolescence. However it is unknown whether these associations persist into older age, or whether they are evident at axial (central) or upper limb sites. Therefore we examined walking age obtained at 2y and bone outcomes obtained by dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT) scans at 60-64y in a nationally-representative cohort study of British people, the MRC National Survey of Health and Development. It was hypothesised that later walking age would be associated with lower bone strength at all sites. Later independent walking age was associated with lower height-adjusted hip (standardised regression coefficients with 95%CI) [-0.179(-0.251,-0.107)], spine [-0.157(-0.232,-0.082)] and distal radius [-0.159(-0.245,-0.073)] bone mineral content (BMC, indicating bone compressive strength) in men (all P < 0.001). Adjustment for covariates partially attenuated these associations, primarily due to lower lean mass and adolescent sporting ability in later walkers. These associations were also evident for a number of hip geometric parameters (including cross-sectional moment of inertia (CSMI), indicating bone bending/torsional strength) assessed by Hip Structural Analysis (HSA) from DXA scans. Similar height-adjusted associations were also observed in women for several hip, spine and upper limb outcomes, although adjustment for fat or lean mass led to complete attenuation for most outcomes, with the exception of femoral shaft CSMI and spine bone area (BA). In conclusion, later independent walking age appears to have a lifelong association with bone strength across multiple skeletal sites in men. These effects may result from direct effects of early life loading on bone growth, and mediation by adult body composition. Results suggest that late walking age may represent a novel risk factor for subsequent low bone strength

  12. Effective treatment of PAH contaminated Superfund site soil with the peroxy-acid process.

    PubMed

    Scott Alderman, N; N'Guessan, Adeola L; Nyman, Marianne C

    2007-07-31

    Peroxy-organic acids are formed by the chemical reaction between organic acids and hydrogen peroxide. The peroxy-acid process was applied to two Superfund site soils provided by the U.S. Environmental Protection Agency (EPA). Initial small-scale experiments applied ratios of 3:5:7 (v/v/v) or 3:3:9 (v/v/v) hydrogen peroxide:acetic acid:deionized (DI) water solution to 5g of Superfund site soil. The experiment using 3:5:7 (v/v/v) ratio resulted in an almost complete degradation of the 14 EPA regulated polycyclic aromatic hydrocarbons (PAHs) in Bedford LT soil during a 24-h reaction period, while the 3:3:9 (v/v/v) ratio resulted in no applicable degradation in Bedford LT lot 10 soil over the same reaction period. Specific Superfund site soil characteristics (e.g., pH, total organic carbon content and particle size distribution) were found to play an important role in the availability of the PAHs and the efficiency of the transformation during the peroxy-acid process. A scaled-up experiment followed treating 150g of Bedford LT lot 10 soil with and without mixing. The scaled-up processes applied a 3:3:9 (v/v/v) solution resulting in significant decrease in PAH contamination. These findings demonstrate the peroxy-acid process as a viable option for the treatment of PAH contaminated soils. Further work is necessary in order to elucidate the mechanisms of this process.

  13. Site-Specific Characterization of d-Amino Acid Containing Peptide Epimers by Ion Mobility Spectrometry

    PubMed Central

    2013-01-01

    Traditionally, the d-amino acid containing peptide (DAACP) candidate can be discovered by observing the differences of biological activity and chromatographic retention time between the synthetic peptides and naturally occurring peptides. However, it is difficult to determine the exact position of d-amino acid in the DAACP candidates. Herein, we developed a novel site-specific strategy to rapidly and precisely localize d-amino acids in peptides by ion mobility spectrometry (IMS) analysis of mass spectrometry (MS)-generated epimeric fragment ions. Briefly, the d/l-peptide epimers were separated by online reversed-phase liquid chromatography and fragmented by collision-induced dissociation (CID), followed by IMS analysis. The epimeric fragment ions resulting from d/l-peptide epimers exhibit conformational differences, thus showing different mobilities in IMS. The arrival time shift between the epimeric fragment ions was used as criteria to localize the d-amino acid substitution. The utility of this strategy was demonstrated by analysis of peptide epimers with different molecular sizes, [d-Trp]-melanocyte-stimulating hormone, [d-Ala]-deltorphin, [d-Phe]-achatin-I, and their counterparts that contain all-l amino acids. Furthermore, the crustacean hyperglycemia hormones (CHHs, 8.5 kDa) were isolated from the American lobster Homarus americanus and identified by integration of MS-based bottom-up and top-down sequencing approaches. The IMS data acquired using our novel site-specific strategy localized the site of isomerization of l- to d-Phe at the third residue of the CHHs from the N-terminus. Collectively, this study demonstrates a new method for discovery of DAACPs using IMS technique with the ability to localize d-amino acid residues. PMID:24328107

  14. Mutation-selection models of coding sequence evolution with site-heterogeneous amino acid fitness profiles

    PubMed Central

    Rodrigue, Nicolas; Philippe, Hervé; Lartillot, Nicolas

    2010-01-01

    Modeling the interplay between mutation and selection at the molecular level is key to evolutionary studies. To this end, codon-based evolutionary models have been proposed as pertinent means of studying long-range evolutionary patterns and are widely used. However, these approaches have not yet consolidated results from amino acid level phylogenetic studies showing that selection acting on proteins displays strong site-specific effects, which translate into heterogeneous amino acid propensities across the columns of alignments; related codon-level studies have instead focused on either modeling a single selective context for all codon columns, or a separate selective context for each codon column, with the former strategy deemed too simplistic and the latter deemed overparameterized. Here, we integrate recent developments in nonparametric statistical approaches to propose a probabilistic model that accounts for the heterogeneity of amino acid fitness profiles across the coding positions of a gene. We apply the model to a dozen real protein-coding gene alignments and find it to produce biologically plausible inferences, for instance, as pertaining to site-specific amino acid constraints, as well as distributions of scaled selection coefficients. In their account of mutational features as well as the heterogeneous regimes of selection at the amino acid level, the modeling approaches studied here can form a backdrop for several extensions, accounting for other selective features, for variable population size, or for subtleties of mutational features, all with parameterizations couched within population-genetic theory. PMID:20176949

  15. Moleculary imprinted polymers with metalloporphyrin-based molecular recognition sites coassembled with methacrylic acid.

    PubMed

    Takeuchi, T; Mukawa, T; Matsui, J; Higashi, M; Shimizu, K D

    2001-08-15

    A diastereoselective molecularly imprinted polymer (MIP) for (-)-cinchonidine, PPM(CD), was prepared by the combined use of methacrylic acid and vinyl-substituted zinc(II) porphyrin as functional monomers. Compared to MIPs using only methacrylic acid or zinc porphyrin as a functional monomer, PM(CD) and PP(CD), respectively, PPM(CD) showed higher binding ability for (-)-cinchonidine in chromatographic tests using the MIP-packed columns. Scatchard analysis gave a higher association constant of PPM(CD) for (-)-cinchonidine (1.14 x 10(7) M(-1)) than those of PP(CD) (1.45 x 10(6) M(-1)) and PM(CD) (6.78 x 10(6) M(-1)). The affinity distribution of binding sites estimated by affinity spectrum analysis showed a higher percentage of high-affinity sites and a lower percentage of low-affinity sites in PPM(CD). The MIPs containing a zinc(II) porphyrin in the binding sites, PPM(CD) and PP(CD), showed fluorescence quenching according to the binding of (-)-cinchonidine, and the quenching was significant in the low-concentration range, suggesting that the high-affinity binding sites contain the porphyrin residue. The correlation of the relative fluorescence intensity against log of (-)-cinchonidine concentrations showed a linear relationship. These results revealed that the MIP having highly specific binding sites was assembled by the two functional monomers, vinyl-substituted zinc(II) porphyrin and methacrylic acid, and they cooperatively worked to yield the specific binding. In addition, the zinc(II) porphyrin-based MIPs appeared to act as fluorescence sensor selectively responded by binding events of the template molecule.

  16. Generation of Food-Grade Recombinant Lactic Acid Bacterium Strains by Site-Specific Recombination

    PubMed Central

    Martín, M. Cruz; Alonso, Juan C.; Suárez, Juan E.; Alvarez, Miguel A.

    2000-01-01

    The construction of a delivery and clearing system for the generation of food-grade recombinant lactic acid bacterium strains, based on the use of an integrase (Int) and a resolvo-invertase (β-recombinase) and their respective target sites (attP-attB and six, respectively) is reported. The delivery system contains a heterologous replication origin and antibiotic resistance markers surrounded by two directly oriented six sites, a multiple cloning site where passenger DNA could be inserted (e.g., the cI gene of bacteriophage A2), the int gene, and the attP site of phage A2. The clearing system provides a plasmid-borne gene encoding β-recombinase. The nonreplicative vector-borne delivery system was transformed into Lactobacillus casei ATCC 393 and, by site-specific recombination, integrated as a single copy in an orientation- and Int-dependent manner into the attB site present in the genome of the host strain. The transfer of the clearing system into this strain, with the subsequent expression of the β-recombinase, led to site-specific DNA resolution of the non-food-grade DNA. These methods were validated by the construction of a stable food-grade L. casei ATCC 393-derived strain completely immune to phage A2 infection during milk fermentation. PMID:10831443

  17. Effects of pH, dissolved oxygen, and ionic strength on the survival of Escherichia coli O157:H7 in organic acid solutions.

    PubMed

    Kreske, Audrey C; Bjornsdottir, Kristin; Breidt, Fred; Hassan, Hosni

    2008-12-01

    The ability of Escherichia coli O157:H7 to survive in acidified vegetable products is of concern because of previously documented outbreaks associated with fruit juices. A study was conducted to determine the survival of E. coli O157:H7 in organic acids at pH values typical of acidified vegetable products (pH 3.2 and 3.7) under different dissolved oxygen conditions (< or = 0.05 and 5 mg/liter) and a range of ionic strengths (0.086 to 1.14). All solutions contained 20 mM gluconic acid, which was used as a noninhibitory low pH buffer to compare the individual acid effect to that of pH alone on the survival of E. coli O157:H7. E. coli O157:H7 cells challenged in buffered solution with ca. 5-mg/liter dissolved oxygen (present in tap water) over a range of ionic strengths at pH 3.2 exhibited a decrease in survival over 6 h at 30 degrees C as the ionic strength was increased. Cells challenged in 40 mM protonated L-lactic and acetic acid solutions with ionic strength of 0.684 achieved a > 4.7-log CFU/ml reduction at pH 3.2. However, under oxygen-limiting conditions in an anaerobic chamber, with < or = 0.05-mg/ liter oxygen, E. coli O157:H7 cells showed < or = 1.55-log CFU/ml reduction regardless of pH, acid type, concentration, or ionic strength. Many acid and acidified foods are sold in hermetically sealed containers with oxygen-limiting conditions. Our results demonstrate that E. coli O157:H7 may survive better than previously expected from studies with acid solutions containing dissolved oxygen.

  18. An In Vitro Comparison of the Bond Strength of Composite to Superficial and Deep Dentin, Treated With Er:YAG Laser Irradiation or Acid-Etching.

    PubMed

    Alaghehmand, Homayoon; Nezhad Nasrollah, Fatemeh; Nokhbatolfoghahaei, Hanieh; Fekrazad, Reza

    2016-01-01

    Introduction: The aim of this study was to compare the micro-shear bond strength of composite resin on superficial and deep dentin after conditioning with phosphoric acid and Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser. Methods: Thirty human molars were selected, roots were removed and crowns were bisected to provide a total of 60 half-crowns. Specimens were ground to expose superficial and deep dentin. Samples were assigned to six groups: (1) AS (acid etching of superficial dentin); (2) AD (acid etching of deep dentin); (3) LS (Er:YAG laser irradiation on superficial dentin); (4) LD (Er:YAG laser irradiation on deep dentin); (5) LAS (Er:YAG laser irradiation on superficial dentin followed by acid etching); (6) LAD (Er:YAG laser irradiation on deep dentin followed by acid etching) The adhesive protocol was performed. Samples were thermocycled and micro-shear bond strength was tested to failure. The data were submitted to statistical analysis with one-way analysis of variance (ANOVA) and Tukey post hoc test. Results: The AS group, demonstrated the greatest amount of micro-shear bond strength. Statistical analysis showed a decrease in bond strength in laser-treated groups which was more significant for deep dentin. Conclusion: Preparation of dentin with laser did not improve bonding to superficial and deep dentin.

  19. An In Vitro Comparison of the Bond Strength of Composite to Superficial and Deep Dentin, Treated With Er:YAG Laser Irradiation or Acid-Etching

    PubMed Central

    Alaghehmand, Homayoon; Nezhad Nasrollah, Fatemeh; Nokhbatolfoghahaei, Hanieh; Fekrazad, Reza

    2016-01-01

    Introduction: The aim of this study was to compare the micro-shear bond strength of composite resin on superficial and deep dentin after conditioning with phosphoric acid and Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser. Methods: Thirty human molars were selected, roots were removed and crowns were bisected to provide a total of 60 half-crowns. Specimens were ground to expose superficial and deep dentin. Samples were assigned to six groups: (1) AS (acid etching of superficial dentin); (2) AD (acid etching of deep dentin); (3) LS (Er:YAG laser irradiation on superficial dentin); (4) LD (Er:YAG laser irradiation on deep dentin); (5) LAS (Er:YAG laser irradiation on superficial dentin followed by acid etching); (6) LAD (Er:YAG laser irradiation on deep dentin followed by acid etching) The adhesive protocol was performed. Samples were thermocycled and micro-shear bond strength was tested to failure. The data were submitted to statistical analysis with one-way analysis of variance (ANOVA) and Tukey post hoc test. Results: The AS group, demonstrated the greatest amount of micro-shear bond strength. Statistical analysis showed a decrease in bond strength in laser-treated groups which was more significant for deep dentin. Conclusion: Preparation of dentin with laser did not improve bonding to superficial and deep dentin. PMID:28144437

  20. The strength of an Ig switch region is determined by its ability to drive R loop formation and its number of WGCW sites.

    PubMed

    Zhang, Zheng Z; Pannunzio, Nicholas R; Han, Li; Hsieh, Chih-Lin; Yu, Kefei; Lieber, Michael R

    2014-07-24

    R loops exist at the murine IgH switch regions and possibly other locations, but their functional importance is unclear. In biochemical systems, R loop initiation requires DNA sequence regions containing clusters of G nucleotides, but cellular studies have not been done. Here, we vary the G-clustering, total switch region length, and the number of target sites (WGCW sites for the activation-induced deaminase) at synthetic switch regions in a murine B cell line to determine the effect on class switch recombination (CSR). G-clusters increase CSR regardless of their immediate proximity to the WGCW sites. This increase is accompanied by an increase in R loop formation. CSR efficiency correlates better with the absolute number of WGCW sites in the switch region rather than the total switch region length or density of WGCW sites. Thus, the overall strength of the switch region depends on G-clusters, which initiate R loop formation, and on the number of WGCW sites.

  1. Novel ionic liquid with both Lewis and Brønsted acid sites for Michael addition.

    PubMed

    Jiang, Xiaoyue; Ye, Weidong; Song, Xiaohua; Ma, Wenxin; Lao, Xuejun; Shen, Runpu

    2011-01-01

    Ionic liquid with both Lewis and Brønsted acid sites has been synthesized and its catalytic activities for Michael addition were carefully studied. The novel ionic liquid was stable to water and could be used in aqueous solution. The molar ratio of the Lewis and Brønsted acid sites could be adjusted to match different reactions. The results showed that the novel ionic liquid was very efficient for Michael addition with good to excellent yields within several min. Operational simplicity, high stability to water and air, small amount used, low cost of the catalyst used, high yields, chemoselectivity, applicability to large-scale reactions and reusability are the key features of this methodology, which indicated that this novel ionic liquid also holds great potential for environmentally friendly processes.

  2. Site-directed spin labeling studies on nucleic acid structure and dynamics

    PubMed Central

    Sowa, Glenna Z.; Qin, Peter Z.

    2009-01-01

    Site-directed spin labeling (SDSL) uses electron paramagnetic resonance (EPR) spectroscopy to monitor the behavior of a stable nitroxide radical attached at specific locations within a macromolecule such as protein, DNA, or RNA. Parameters obtained from EPR measurements, such as internitroxide distances and descriptions of the rotational motion of a nitroxide, provide unique information on features near the labeling site. With recent advances in solid-phase synthesis of nucleic acids and developments in EPR methodologies, particularly pulsed EPR technologies, SDSL has been increasingly used to study the structure and dynamics of DNA and RNA at the level of the individual nucleotides. This chapter summarizes the current SDSL studies on nucleic acids, with discussions focusing on literature from the last decade. PMID:18929141

  3. Disulfide bridge regulates ligand-binding site selectivity in liver bile acid-binding proteins.

    PubMed

    Cogliati, Clelia; Tomaselli, Simona; Assfalg, Michael; Pedò, Massimo; Ferranti, Pasquale; Zetta, Lucia; Molinari, Henriette; Ragona, Laura

    2009-10-01

    Bile acid-binding proteins (BABPs) are cytosolic lipid chaperones that play central roles in driving bile flow, as well as in the adaptation to various pathological conditions, contributing to the maintenance of bile acid homeostasis and functional distribution within the cell. Understanding the mode of binding of bile acids with their cytoplasmic transporters is a key issue in providing a model for the mechanism of their transfer from the cytoplasm to the nucleus, for delivery to nuclear receptors. A number of factors have been shown to modulate bile salt selectivity, stoichiometry, and affinity of binding to BABPs, e.g. chemistry of the ligand, protein plasticity and, possibly, the formation of disulfide bridges. Here, the effects of the presence of a naturally occurring disulfide bridge on liver BABP ligand-binding properties and backbone dynamics have been investigated by NMR. Interestingly, the disulfide bridge does not modify the protein-binding stoichiometry, but has a key role in modulating recognition at both sites, inducing site selectivity for glycocholic and glycochenodeoxycholic acid. Protein conformational changes following the introduction of a disulfide bridge are small and located around the inner binding site, whereas significant changes in backbone motions are observed for several residues distributed over the entire protein, both in the apo form and in the holo form. Site selectivity appears, therefore, to be dependent on protein mobility rather than being governed by steric factors. The detected properties further establish a parallelism with the behaviour of human ileal BABP, substantiating the proposal that BABPs have parallel functions in hepatocytes and enterocytes.

  4. Minodronic acid (ONO-5920/YM529) prevents decrease in bone mineral density and bone strength, and improves bone microarchitecture in ovariectomized cynomolgus monkeys.

    PubMed

    Mori, Hiroshi; Tanaka, Makoto; Kayasuga, Ryoji; Masuda, Taisei; Ochi, Yasuo; Yamada, Hiroyuki; Kishikawa, Katsuya; Ito, Masako; Nakamura, Toshitaka

    2008-11-01

    This study examined the effect of the highly potent nitrogen-containing bisphosphonate, minodronic acid (ONO-5920/YM529), on bone mineral density (BMD), bone turnover, bone microarchitecture and bone strength in ovariectomized (OVX) cynomolgus monkeys. Skeletally mature female cynomolgus monkeys, aged 9-17 years, were ovariectomized or sham-operated. Minodronic acid was administered orally once a day in doses of 0, 0.015, and 0.15 mg/kg from the day after surgery for 17 months. Bone resorption markers (urinary N-terminal cross-linking telopeptide of type I collagen and deoxypyridinoline), bone formation markers (serum osteocalcin and bone alkaline phosphatase) and lumbar vertebral BMD were measured at baseline and at 4, 8, 12 and 16 months after surgery. Treatment with minodronic acid dose-dependently inhibited OVX-induced increase in bone turnover markers and decrease in lumbar vertebral BMD, and minodronic acid at 0.15 mg/kg completely prevented these changes. At 17 months after surgery, minodronic acid also suppressed bone resorption (Oc.S/BS and N.Oc/BS) and bone formation (OS/BS, MS/BS, MAR, BFR/BS, and BFR/BV) in the lumbar vertebral bodies and tibia. In the mechanical tests, ultimate load on lumbar vertebral bodies and femoral neck of the OVX-control animals were significantly reduced compared to the sham animals. Minodronic acid prevented these reductions in bone strength at 0.15 mg/kg. There was significant correlation between BMD and bone strength, suggesting that the increase in bone strength was associated with the increase in BMD produced by minodronic acid. In micro-CT analysis of the lumbar vertebral bodies, minodronic acid improved trabecular architecture, converting rod structures into plate structures, and preventing the increase in trabecular disconnectivity at 0.15 mg/kg. In conclusion, similar to patients with postmenopausal osteoporosis, reduction in bone strength of lumbar vertebral bodies and femoral neck was clearly demonstrated in OVX

  5. Remaining Sites Verification Package for the 120-B-1, 105-B Battery Acid Sump, Waste Site Reclassification Form 2006-057

    SciTech Connect

    L. M. Dittmer

    2006-09-25

    The 120-B-1 waste site, located in the 100-BC-1 Operable Unit of the Hanford Site, consisted of a concrete battery acid sump that was used from 1944 to 1969 to neutralize the spent sulfuric acid from lead cell batteries of emergency power packs and the emergency lighting system. The battery acid sump was associated with the 105-B Reactor Building and was located adjacent to the building's northwest corner. The results of verification sampling demonstrated that residual contaminant concentrations do not preclude any future uses and allow for unrestricted use of shallow zone soils. The results also showed that residual contaminant concentrations are protective of groundwater and the Columbia River.

  6. Evaluation of the effect of surface preparation using phosphoric acid and luting cement on the flexural strength of porcelain laminate veneering material

    PubMed Central

    Guruprasada; Rivankar, N.; Dhiman, R.K.; Viswambaran, M.

    2015-01-01

    Background Conventionally HF acid has been used for etching ceramic veneer restorations before their cementation. Studies are lacking regarding the effectiveness of phosphoric acid as a substitute for HF acid for etching the ceramic veneers. The purpose of this study was to evaluate the effectiveness of surface preparation of porcelain laminate veneers using phosphoric acid, as compared to HF acid etching in providing the necessary surface roughness conducive to development of an effective bond between the ceramic laminate and the resin luting cement. Methods 210 porcelain discs of 15 mm diameter and 0.9 mm thickness were prepared. These study samples were divided into seven groups of thirty samples each. Surfaces of the first (control) and the second group of samples were not prepared. The surfaces of other five groups were prepared with different surface treatments. Further all the groups of specimens were coated with a layer of resin luting cement. Flexural strength of each specimen was determined using universal testing machine and the results were compared. Results The combination surface treatment using alumina surface abrasion followed by etching with phosphoric acid provided the highest flexural strength with the mean flexural strength of 101.11 MPa, followed by alumina surface abrasion (95.41 MPa), and phosphoric acid surface etching (81.68 MPa). Conclusion Laminate veneers surface treated using 50 μm alumina abrasion followed by etching with phosphoric acid showed the highest flexural strengths after resin coating compared to other groups. PMID:26843743

  7. Cellular Site in Bacillus subtilis of a Nuclease Which Preferentially Degrades Single-Stranded Nucleic Acids

    PubMed Central

    Birnboim, H. C.

    1966-01-01

    Birnboim, H. C. (Albert Einstein College of Medicine, New York, N.Y.). Cellular site in Bacillus subtilis of a nuclease which preferentially degrades single-stranded nucleic acids. J. Bacteriol. 91:1004–1011. 1966.—A nuclease, identified by a marked preference for single-stranded nucleic acids, has been demonstrated in extracts of Bacillus subtilis. The enzyme was associated with the cell wall-membrane fraction of mechanically disrupted cells and was released from cells which had been converted to protoplasts by lysozyme. The nuclease activity prepared by the latter procedure was found to be activated and solubilized by treatment with trypsin. The enzyme had about 2% activity on native deoxyribonucleic acid (DNA) as compared with denatured DNA. By use of CsCl analytical density gradient ultracentrifugation, this preparation was shown to degrade denatured DNA selectively in mixtures of native and denatured DNA. PMID:4956329

  8. Multiple site-selective insertions of non-canonical amino acids into sequence-repetitive polypeptides

    PubMed Central

    Wu, I-Lin; Patterson, Melissa A.; Carpenter Desai, Holly E.; Mehl, Ryan A.; Giorgi, Gianluca

    2013-01-01

    A simple and efficient method is described for introduction of non-canonical amino acids at multiple, structurally defined sites within recombinant polypeptide sequences. E. coli MRA30, a bacterial host strain with attenuated activity for release factor 1 (RF1), is assessed for its ability to support the incorporation of a diverse range of non-canonical amino acids in response to multiple encoded amber (TAG) codons within genetic templates derived from superfolder GFP and an elastin-mimetic protein polymer. Suppression efficiency and isolated protein yield were observed to depend on the identity of the orthogonal aminoacyl-tRNA synthetase/tRNACUA pair and the non-canonical amino acid substrate. This approach afforded elastin-mimetic protein polymers containing non-canonical amino acid derivatives at up to twenty-two positions within the repeat sequence with high levels of substitution. The identity and position of the variant residues was confirmed by mass spectrometric analysis of the full-length polypeptides and proteolytic cleavage fragments resulting from thermolysin digestion. The accumulated data suggest that this multi-site suppression approach permits the preparation of protein-based materials in which novel chemical functionality can be introduced at precisely defined positions within the polypeptide sequence. PMID:23625817

  9. Impact of oxalate desensitizer combined with ethylene-diamine tetra acetic acid-conditioning on dentin bond strength of one-bottle adhesives during dry bonding

    PubMed Central

    Shafiei, Fereshteh; Doozandeh, Maryam

    2013-01-01

    Background: Elimination of water entrapment in hybrid layer during bonding procedure would increase bonding durability. Aims: This study evaluated the effect of oxalate desensitizer (OX) pretreatment on bond strength of three one-bottle adhesives to ethylene-diamine tetra acetic acid (EDTA)-conditioned dentin under dry bonding. Materials and Methods: Three adhesive systems, One-Step Plus (OS), Optibond Solo Plus (OP) and Adper Single Bond (SB) were bonded on dentin surfaces under four bonding conditions: (1) Wet-bonding on acid-etched dentin, (2) wet bonding on EDTA-conditioned dentin, (3) dry bonding on EDTA-conditioned dentin, (4) dry bonding associated with OX on the EDTA-conditioned dentin. After storage and thermo cycling, shear bond strength test was performed. Data were analyzed using two-way analysis of variance and Tukey tests. Results: Wet bonding with EDTA or acid etching showed similar bond strength for test adhesives. Dry bonding with EDTA significantly decreased the bond strength of OS, but it had no effect on the bonding of OP and SB. OX application in the forth bonding condition, in comparison with the third condition, had a negative effect on the bond strength of OP, but not influence on OS and SB. Conclusions: The use of an OX on EDTA-conditioned dentin compromised the bonding efficacy of OS and OP under dry bonding but compatible for SB. PMID:23833461

  10. Fatty acid binding sites of human and bovine albumins: Differences observed by spin probe ESR

    NASA Astrophysics Data System (ADS)

    Muravsky, Vladimir; Gurachevskaya, Tatjana; Berezenko, Stephen; Schnurr, Kerstin; Gurachevsky, Andrey

    2009-09-01

    Bovine and human serum albumins and recombinant human albumin, all non-covalently complexed with 5- and 16-doxyl stearic acids, were investigated by ESR spectroscopy in solution over a range of pH values (5.5-8.0) and temperatures (25-50 °C), with respect to the allocation and mobility of fatty acid (FA) molecules bound to the proteins and conformation of the binding sites. In all proteins bound FA undergo a permanent intra-albumin migration between the binding sites and inter-domain residence. Nature identity of the recombinant human albumin to its serum-derived analog was observed. However, the binding sites of bovine albumin appeared shorter in length and wider in diameter than those of human albumin. Presumably, less tightly folded domains in bovine albumin allow better penetration of water molecules in the interior of the globule that resulted in higher activation energy of FA dissociation from the binding site. Thus, the sensitive technique based on ESR non-covalent spin labeling allowed quantitative analysis and reliable comparison of the fine features of binding proteins.

  11. Remedial action at the Acid/Pueblo Canyon site, Los Alamos, New Mexico. Final report

    SciTech Connect

    1984-10-01

    The Acid/Pueblo Canyon site (TA-45) was designated in 1976 for remedial action under the Formerly Utilized Sites Remedial Action Program (FUSRAP). During the period 1943 to 1964 untreated and treated liquid wastes generated by nuclear weapons research activities at the Los Alamos Scientific Laboratory (LASL) were discharged into the two canyons. A survey of the site conducted by LASL in 1976 to 1977 identified two areas where radiological contamination exceeded criteria levels. The selected remedial action was based on extensive radiological characterization and comprehensive engineering assessments and comprised the excavation and disposal of 390 yd/sup 3/ of contaminated soil and rock. This document describes the background to the remedial action, the parties involved in administering and executing it, the chronology of the work, verification of the adequacy of the remedial action, and the cost incurred. 14 references, 5 figures, 5 tables.

  12. Resistance training and timed essential amino acids protect against the loss of muscle mass and strength during 28 days of bed rest and energy deficit

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Space flight and bed rest (BR) result in losses of muscle mass and strength. Resistance training (RT) and amino acid (AA) supplementation are potential countermeasures to minimize these losses. However, it is unknown if timing of supplementation with exercise can optimize benefits, particularly with...

  13. Transport and Retention of TiO2 Rutile Nanoparticles in Saturated Porous Media: Influence of Solution pH, Ionic Strength, and the Presence of Humic Acid

    EPA Science Inventory

    The influence of solution pH, ionic strength, and varying concentrations of the Suwannee River Humic Acid (SRHA) on the transport of titanium dioxide (TiO2, rutile) nanoparticle aggregates (nTiO2) in saturated porous media was investigated through systematically examining the tra...

  14. Is There a Need to Discuss Atomic Orbital Overlap When Teaching Hydrogen-Halide Bond Strength and Acidity Trends in Organic Chemistry?

    ERIC Educational Resources Information Center

    Devarajan, Deepa; Gustafson, Samantha J.; Bickelhaupt, F. Matthias; Ess, Daniel H.

    2015-01-01

    Undergraduate organic chemistry textbooks and Internet websites use a variety of approaches for presenting and explaining the impact of halogen atom size on trends in bond strengths and/or acidity of hydrogen halides. In particular, several textbooks and Internet websites explain these trends by invoking decreasing orbital overlap between the…

  15. Transparent indium oxide films doped with high Lewis acid strength Ge dopant for phosphorescent organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Kang, Sin-Bi; Lim, Jong-Wook; Lee, Sunghun; Kim, Jang-Joo; Kim, Han-Ki

    2012-08-01

    We report on Ge-doped In2O3(IGO) films prepared by co-sputtering GeO2 and In2O3 targets for anode of phosphorescent organic light-emitting diodes (POLEDs). Under optimized annealing conditions, the IGO film exhibited a low sheet resistance of 14.0 Ω/square, a high optical transmittance of 86.9% and a work function of 5.2 eV, comparable to conventional Sn-doped In2O3 (ITO) films. Due to the higher Lewis acid strength of the Ge4+ ion (3.06) than that of Sn3+(1.62), the IGO film showed higher transparency in the near infrared and higher carrier mobility of 39.16 cm2 V-1 s-1 than the ITO films. In addition, the strongly preferred (2 2 2) orientation of the IGO grains, caused by Zone II grain growth during rapid thermal annealing, increased the carrier mobility and improved the surface morphology of the IGO film. POLEDs fabricated on IGO anodes showed identical current density-voltage-luminance curves and efficiencies to POLEDs with ITO electrodes due to the low sheet resistance and high transmittance of the IGO anode.

  16. Microbial Communities in Biofilms of an Acid Mine Drainage Site Determined by Phospholipid Analysis

    NASA Astrophysics Data System (ADS)

    Das Gupta, S.; Fang, J.

    2008-12-01

    Phospholipids were extracted to determine the microbial biomass and community structure of biofims from an acid mine drainage (AMD) at the Green Valley coal mine site (GVS) in western Indiana. The distribution of specific biomarkers indicated the presence of a variety of microorganisms. Phototrophic microeukaryotes, which include Euglena mutabilis, algae, and cyanobacteria were the most dominant organisms, as indicated by the presence of polyunsaturated fatty acids. The presence of terminally methyl branched fatty acids suggests the presence of Gram-positive bacteria, and the mid-methyl branched fatty acids indicates the presence of sulfate-reducing bacteria. Fungi appear to also be an important part of the AMD microbial communities as suggested by the presence of 18:2 fatty acid. The acidophilic microeukaryotes Euglena dominated the biofilm microbial communities. These microorganisms appear to play a prominent role in the formation and preservation of stromatolites and in releasing oxygen to the atmosphere by oxygenic photosynthesis. Thus, the AMD environment comprises a host of microorganisms spreading out within the phylogenetic tree of life. Novel insights on the roles of microbial consortia in the formation and preservation of stromatolites and the production of oxygen through photosynthesis in AMD systems may have significance in the understanding of the interaction of Precambrian microbial communities in environments that produced microbially-mediated sedimentary structures and that caused oxygenation of Earth's atmosphere.

  17. Characterizing Surface Acidic Sites in Mesoporous-Silica-Supported Tungsten Oxide Catalysts Using Solid State NMR and Quantum Chemistry Calculations

    SciTech Connect

    Hu, Jian Z.; Kwak, Ja Hun; Wang, Yong; Hu, Mary Y.; Turcu, Romulus VF; Peden, Charles HF

    2011-10-18

    The acidic sites in dispersed tungsten oxide supported on SBA-15 mesoporous silica were investigated using a combination of pyridine titration, both fast-, and slow-MAS {sup 15}N NMR, static {sup 2}H NMR, and quantum chemistry calculations. It is found that the bridged acidic -OH groups in surface adsorbed tungsten dimers (i.e., W-OH-W) are the Broensted acid sites. The unusually strong acidity of these Broensted acid sites is confirmed by quantum chemistry calculations. In contrast, terminal W-OH sites are very stable and only weakly acidic as are terminal Si-OH sites. Furthermore, molecular interactions between pyridine molecules and the dimer Broensted and terminal W-OH sites for dispersed tungsten oxide species is strong. This results in restricted molecular motion for the interacting pyridine molecules even at room temperature, i.e., a reorientation mainly about the molecular 2-fold axis. This restricted reorientation makes it possible to estimate the relative ratio of the Broensted (tungsten dimer) to the weakly acidic terminal W-OH sites in the catalyst using the slow-MAS {sup 1}H-{sup 15}N CP PASS method.

  18. Skeletal site-specific effects of endurance running on structure and strength of tibia, lumbar vertebrae, and mandible in male Sprague-Dawley rats.

    PubMed

    Bott, Kirsten N; Sacco, Sandra M; Turnbull, Patrick C; Longo, Amanda B; Ward, Wendy E; Peters, Sandra J

    2016-06-01

    Bone microarchitecture, bone mineral density (BMD), and bone strength are affected positively by impact activities such as running; however, there are discrepancies in the magnitude of these effects. These inconsistencies are mainly a result of varying training protocols, analysis techniques, and whether or not the skeletal sites measured are weight bearing. This study's purpose was to determine the effects of endurance running on sites that experience different weight bearing and load. Eight-week-old male Sprague-Dawley rats (n = 20) were randomly assigned to either a group with a progressive treadmill running protocol (25 m/min for 1 h, incline of 10%) or a nontrained control group for 8 weeks. The trabecular structure of the tibia, lumbar vertebra (L3), and mandible and the cortical structure at the tibia midpoint were measured using microcomputed tomography to quantify bone volume fraction (i.e., bone volume divided by total volume (BV/TV)), trabecular number (Tb.N), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), and cortical thickness. BMD at the proximal tibia, lumbar vertebrae (L1-L3), and mandible was measured using dual energy X-ray absorptiometry. The tibia midpoint strength was measured by 3-point bending using a materials testing system. Endurance running resulted in superior bone structure at the proximal tibia (12% greater BV/TV (p = 0.03), 14% greater Tb.N (p = 0.01), and 19% lower Tb.Sp (p = 0.05)) but not at other sites. Contrary to our hypothesis, mandible bone structure was altered after endurance training (8% lower BV/TV (p < 0.01) and 15% lower Tb.Th (p < 0.01)), which may be explained by a lower food intake, resulting in less mechanical loading from chewing. These results highlight the site-specific effects of loading on the skeleton.

  19. Fatty acid composition differences between adipose depot sites in dairy and beef steer breeds.

    PubMed

    Liu, T; Lei, Z M; Wu, J P; Brown, M A

    2015-03-01

    The objective of the study was to compare fatty acid composition of longissimus dorsi (LD) and kidney fat (KF) in Holstein steers (HS), Simmental steers (SS) and Chinese LongDong Yellow Cattle steers (CLD). All steers received the same nutrition and management but in different locations. Cattle were harvested at approximately 550 kg and fatty acid composition of longissimus dorsi and kidney fat was analyzed in samples taken after 3 days of aging. There was evidence (P < 0.05) that C18:3n6 was greater in KF than LD in CLD cattle but not in HS or SS cattle. Percentage C18:1n9, C18:2n6, C18:3n3, and n6 fatty acids were greater in LD than KF for all breeds (P < 0.05), but the difference between fat sources for n6 in CLD cattle was smaller than the other two breeds. The LD had greater percentage of polyunsaturated fatty acids (PUFA), monounsaturated fatty acids (MUFA), and a greater ratio of n6:n3 PUFAs compared to the KF in each breed (P < 0.05). The △(9)-desaturase catalytic activity index was greater in LD than in KF in each breed group (P < 0.05). Percentage cis-9, trans-11 CLA was greater in KF than LD in HS (P < 0.05) but not SS or CLD cattle. These results indicate fatty acid percentages generally differed between longissimus dorsi fat and kidney fat. Further, there was some indication that some of these differences between fatty acid deposition sites were not consistent across breed group.

  20. Comparison of shear bond strength of reattached incisor fragment using Er,Cr:YSGG laser etching and conventional acid etching: An in vitro study

    PubMed Central

    Kumar, Gyanendra; Goswami, Mridula; Dhillon, Jatinder Kaur

    2016-01-01

    Aim: The aim of this invitro study is to evaluate the shear bond strength of reattached fractured incisor fragments using Er,Cr:YSGG laser and conventional acid etching without additional tooth preparation. Materials and methods: Forty extracted human teeth were divided in two groups of 20 each (Groups A and B). In Group A, fractured surface was treated by an Er, Cr: YSGG laser system (Waterlase MD, Biolase Technology Inc., San Clemente, CA, USA) operating at a wavelength of 2,780 nm and frequency of 20 Hz. In Group B, fractured surface was etched using 37% phosphoric acid (Scotchbond, 3M). In both the groups, further subdivision with 10 sample each was made based on horizontal and oblique fracture. After laser or acid etching, all the samples were reattached using flowable composite resin and light cured. The samples were tested for shear bond strength. Results: Mean shear bond strength for Group A (94.70±39.158) was lower as compared to Group B (121.25±49.937), although the difference was not statistically significant(p value=0.121). Similarly no statistical significant difference was observed amongst the subgroups. (p>0.05) Conclusion: Er,Cr:YSGG laser etching in reattachment of fractured incisor fragment is a good alternative to conventional acid etching. Er,Cr:YSGG showed comparable efficiency in rebonding of fractured teeth fragment as acid etching. PMID:27721563

  1. Effects of Short-Term Docosahexaenoic Acid Supplementation on Markers of Inflammation after Eccentric Strength Exercise in Women

    PubMed Central

    Corder, Katherine E.; Newsham, Katherine R.; McDaniel, Jennifer L.; Ezekiel, Uthayashanker R.; Weiss, Edward P.

    2016-01-01

    The omega-3 fatty acid docosahexaenoic acid (DHA) has anti-inflammatory and anti-nociceptive (pain inhibiting) effects. Because strenuous exercise often results in local inflammation and pain, we hypothesized that DHA supplementation attenuates the rise in markers of local muscle inflammation and delayed onset muscle soreness (DOMS) that occur after eccentric strength exercise. Twenty-seven, healthy women (33 ± 2 y, BMI 23.1±1.0 kg·m-2) were randomized to receive 9d of 3000 mg/d DHA or placebo in a double-blind fashion. On day 7 of the supplementation period, the participants performed 4 sets of maximal-effort eccentric biceps curl exercise. Before and 48h after the eccentric exercise, markers of inflammation were measured including measures of muscle soreness (10-point visual analog pain scale, VAS), swelling (arm circumference), muscle stiffness (active and passive elbow extension), skin temperature, and salivary C-reactive protein (CRP) concentrations. As expected, muscle soreness and arm circumference increased while active and passive elbow extension decreased. The increase in soreness was 23% less in the DHA group (48h increase in VAS soreness ratings: 4.380.4 vs. 5.600.5, p=0.02). Furthermore, the number of subjects who were able to achieve full active elbow extension 48h after eccentric exercise was greater in the DHA group (71% vs. 15%, p = 0.006), indicating significantly less muscle stiffness. No between-group differences were observed for passive elbow extension (p = 0.78) or arm swelling (p = 0.75). Skin temperature and salivary CRP concentrations did not change from baseline to 48h after exercise in either group. These findings indicate that short-term DHA supplementation reduces exercise-induced muscle soreness and stiffness. Therefore, in addition to other health benefits that n-3 fatty acids have been associated with, DHA supplementation could be beneficial for improving tolerance to new and/or strenuous exercise programs and thereby might

  2. Effects of Short-Term Docosahexaenoic Acid Supplementation on Markers of Inflammation after Eccentric Strength Exercise in Women.

    PubMed

    Corder, Katherine E; Newsham, Katherine R; McDaniel, Jennifer L; Ezekiel, Uthayashanker R; Weiss, Edward P

    2016-03-01

    The omega-3 fatty acid docosahexaenoic acid (DHA) has anti-inflammatory and anti-nociceptive (pain inhibiting) effects. Because strenuous exercise often results in local inflammation and pain, we hypothesized that DHA supplementation attenuates the rise in markers of local muscle inflammation and delayed onset muscle soreness (DOMS) that occur after eccentric strength exercise. Twenty-seven, healthy women (33 ± 2 y, BMI 23.1±1.0 kg·m(-2)) were randomized to receive 9d of 3000 mg/d DHA or placebo in a double-blind fashion. On day 7 of the supplementation period, the participants performed 4 sets of maximal-effort eccentric biceps curl exercise. Before and 48h after the eccentric exercise, markers of inflammation were measured including measures of muscle soreness (10-point visual analog pain scale, VAS), swelling (arm circumference), muscle stiffness (active and passive elbow extension), skin temperature, and salivary C-reactive protein (CRP) concentrations. As expected, muscle soreness and arm circumference increased while active and passive elbow extension decreased. The increase in soreness was 23% less in the DHA group (48h increase in VAS soreness ratings: 4.380.4 vs. 5.600.5, p=0.02). Furthermore, the number of subjects who were able to achieve full active elbow extension 48h after eccentric exercise was greater in the DHA group (71% vs. 15%, p = 0.006), indicating significantly less muscle stiffness. No between-group differences were observed for passive elbow extension (p = 0.78) or arm swelling (p = 0.75). Skin temperature and salivary CRP concentrations did not change from baseline to 48h after exercise in either group. These findings indicate that short-term DHA supplementation reduces exercise-induced muscle soreness and stiffness. Therefore, in addition to other health benefits that n-3 fatty acids have been associated with, DHA supplementation could be beneficial for improving tolerance to new and/or strenuous exercise programs and thereby might

  3. An improved thermodynamic model for the complexation of trivalent actinides and lanthanide with oxalic acid valid to high ionic strength.

    DOE PAGES

    Xiong, Yongliang; Thakur, Punam; Borkowski, Marian

    2015-07-30

    The dissociation constants of oxalic acid (Ox), and the stability constants of Am3+, Cm3+ and Eu3+ with Ox2– have been determined at 25 °C, over a range of concentration varying from 0.1 to 6.60 m NaClO4 using potentiometric titration and extraction techniques, respectively. The experimental data support the formation of complexes, M(Ox)n3 – 2n, where (M = Am3+, Cm3+ and Eu3+ and n = 1 and 2). The dissociation constant and the stability constant values measured as a function of NaClO4 concentration were used to estimate the Pitzer parameters for the respective interactions of Am3+, Cm3+ and Eu3+ with Ox.more » Furthermore, the stability constants data of Am3+ –Ox measured in NaClO4 and in NaCl solutions from the literature were simultaneously fitted in order to refine the existing actinide–oxalate complexation model that can be used universally in the safety assessment of radioactive waste disposal. The thermodynamic stability constant: log β0101 = 6.30 ± 0.06 and log β0102 = 10.84 ± 0.06 for Am3+ was obtained by simultaneously fitting data in NaCl and NaClO4 media. Additionally, log β0101 = 6.72 ± 0.08 and log β0102 = 11.05 ± 0.09 for the Cm3+ and log β0101 = 6.67 ± 0.08 and log β0102 = 11.15 ± 0.09 for the Eu3+ were calculated by extrapolation of data to zero ionic strength in NaClO4 medium only. For all stability constants, the Pitzer model gives an excellent representation of the data using interaction parameters β(0), β(1), and CΦ determined in this work. The thermodynamic model developed in this work will be useful in accurately modeling the potential solubility of trivalent actinides and early lanthanides to ionic strength of 6.60 m in low temperature environments in the presence of Ox. Furthermore, the work is also applicable to the accurate modeling transport of rare earth elements in various environments under the surface conditions.« less

  4. Shear Bond Strength of an Etch-and-rinse Adhesive to Er:YAG Laser- and/or Phosphoric Acid-treated Dentin

    PubMed Central

    Davari, Abdolrahim; Sadeghi, Mostafa; Bakhshi, Hamid

    2013-01-01

    Background and aims. Er:YAG laser irradiation has been claimed to improve the adhesive properties of dentin; therefore, it has been proposed as an alternative to acid etching. The aim of this in vitro study was to investigate the shear bond strength of an etch-and-rinse adhesive system to dentin surfaces following Er:YAG laser and/or phosphoric acid etching. Materials and methods. The roots of 75 sound maxillary premolars were sectioned below the CEJ and the crowns were embedded in auto-polymerizing acrylic resin with the buccal surfaces facing up. The buccal surfaces were ground using a diamond bur and polished until the dentin was exposed; the samples were randomly divided into five groups (n=15) according to the surface treatment: (1) acid etching; (2) laser etching; (3) laser etching followed by acid etching; (4) acid etching followed by laser etching and (5) no acid etching and no laser etching (control group). Composite resin rods (Point 4, Kerr Co) were bonded to treated dentin surfaces with an etch-and-rise adhesive system (Optibond FL, Kerr Co) and light-cured.After storage for two weeks at 37°C and 100% humidity and then thermocycling, bond strength was measured with a Zwick Universal Testing Machine at a crosshead speed of 1 mm/min. Data was analyzed using parametric and non-parametric tests (P<0.05). Results. Mean shear bond strength for acid etching (20.1±1.8 MPa) and acid+laser (15.6±3.5 MPa) groups were significantly higher than those for laser+acid (15.6±3.5 MPa), laser etching (14.1±3.4 MPa) and control (8.1±2.1 MPa) groups. However, there were no significant differences between acid etching and acid+laser groups, and between laser+acid and laser groups. Conclusion. When the cavity is prepared by bur, it is not necessary to etch the dentin surface by Er:YAG laser following acid etching and acid etching after laser etching. PMID:23875083

  5. Effect of acid etching duration on tensile bond strength of composite resin bonded to erbium:yttrium-aluminium-garnet laser-prepared dentine. Preliminary study.

    PubMed

    Chousterman, M; Heysselaer, D; Dridi, S M; Bayet, F; Misset, B; Lamard, L; Peremans, A; Nyssen-Behets, C; Nammour, S

    2010-11-01

    The purpose of this study was to compare the tensile bond strength of composite resin bonded to erbium:yttrium-aluminium-garnet (Er:YAG) laser-prepared dentine after different durations of acid etching. The occlusal third of 68 human third molars was removed in order to expose the dentine surface. The teeth were randomly divided into five groups: group B (control group), prepared with bur and total etch system with 15 s acid etching [37% orthophosphoric acid (H(3)PO(4))]; group L15, laser photo-ablated dentine (200 mJ) (laser irradiation conditions: pulse duration 100 micros, air-water spray, fluence 31.45 J/ cm(2), 10 Hz, non-contact hand pieces, beam spot size 0.9 mm, irradiation speed 3 mm/s, and total irradiation time 2 x 40 s); group L30, laser prepared, laser conditioned and 30 s acid etching; group L60, laser prepared, laser conditioned and 60 s acid etching; group L90, laser prepared, laser conditioned and 90 s acid etching. A plot of composite resin was bonded onto each exposed dentine and then tested for tensile bond strength. The values obtained were statistically analysed by analysis of variance (ANOVA) coupled with the Tukey-Kramer test at the 95% level. A 90 s acid etching before bonding showed the best bonding value (P < 0.05) when compared with all the other groups including the control group. There is no significance difference between other groups, nor within each group and the control group. There was a significant increase in tensile bond strength of the samples acid etched for 90 s.

  6. Effect of experimental acid/base conditioner on microtensile bond strength of 4-META/MMA-TBB resin to dentin after long-term water immersion.

    PubMed

    Soeno, Kohyoh; Taira, Yohsuke; Ito, Shuichi

    2012-01-01

    An experimental conditioner (Exp), which was an aqueous solution of 10% ascorbic acid and 5% ferric chloride, was prepared in this study. This study evaluated the effect of Exp on the microtensile bond strength between a self-curing resin and dentin after long-term water immersion. Flat human dentin surfaces were sequentially pretreated with 40% phosphoric acid, 10% sodium hypochlorite, and Exp. Surface pretreatment with an aqueous solution of 10% citric and 3% ferric chloride (10-3) was used as a control. Composite resin rods were bonded to pretreated dentin surfaces using 4-META/MMA-TBB resin. Microtensile bond strengths were evaluated after water immersion at 24 h, 12 months, 24 months, and 36 months. At each immersion period, the bond strength of Exp was significantly higher than that of 10-3. After 36 months, Exp showed no significant decrease in microtensile bond strength, but 10-3 showed significant reductions. Pretreatment with experimental acid/base conditioner markedly improved the bonding durability of 4-META/MMA-TBB resin to human dentin when compared against the conventional 10-3 treatment.

  7. Characterization of an intracellular hyaluronic acid binding site in isolated rat hepatocytes

    SciTech Connect

    Frost, S.J.; Raja, R.H.; Weigel, P.H. )

    1990-11-13

    125I-HA, prepared by chemical modification at the reducing sugar, specifically binds to rat hepatocytes in suspension or culture. Intact hepatocytes have relatively few surface 125I-HA binding sites and show low specific binding. However, permeabilization of hepatocytes with the nonionic detergent digitonin results in increased specific 125I-HA binding (45-65%) and a very large increase in the number of specific 125I-HA binding sites. Scatchard analysis of equilibrium 125I-HA binding to permeabilized hepatocytes in suspension at 4 degrees C indicates a Kd = 1.8 x 10(-7) M and 1.3 x 10(6) molecules of HA (Mr approximately 30,000) bound per cell at saturation. Hepatocytes in primary culture for 24 h show the same affinity but the total number of HA molecules bound per cell at saturation decreases to approximately 6.2 x 10(5). Increasing the ionic strength above physiologic concentrations decreases 125I-HA binding to permeable cells, whereas decreasing the ionic strength above causes an approximately 4-fold increase. The divalent cation chelator EGTA does not prevent binding nor does it release 125I-HA bound in the presence of 2 mM CaCl2, although higher divalent cation concentrations stimulate 125I-HA binding. Ten millimolar CaCl2 or MnCl2 increases HA binding 3-6-fold compared to EGTA-treated cells. Ten millimolar MgCl2, SrCl2, or BaCl2 increased HA binding by 2-fold. The specific binding of 125I-HA to digitonin-treated hepatocytes at 4{degrees}C increased greater than 10-fold at pH 5.0 as compared to pH 7.

  8. Mutational Studies on Resurrected Ancestral Proteins Reveal Conservation of Site-Specific Amino Acid Preferences throughout Evolutionary History

    PubMed Central

    Risso, Valeria A.; Manssour-Triedo, Fadia; Delgado-Delgado, Asunción; Arco, Rocio; Barroso-delJesus, Alicia; Ingles-Prieto, Alvaro; Godoy-Ruiz, Raquel; Gavira, Jose A.; Gaucher, Eric A.; Ibarra-Molero, Beatriz; Sanchez-Ruiz, Jose M.

    2015-01-01

    Local protein interactions (“molecular context” effects) dictate amino acid replacements and can be described in terms of site-specific, energetic preferences for any different amino acid. It has been recently debated whether these preferences remain approximately constant during evolution or whether, due to coevolution of sites, they change strongly. Such research highlights an unresolved and fundamental issue with far-reaching implications for phylogenetic analysis and molecular evolution modeling. Here, we take advantage of the recent availability of phenotypically supported laboratory resurrections of Precambrian thioredoxins and β-lactamases to experimentally address the change of site-specific amino acid preferences over long geological timescales. Extensive mutational analyses support the notion that evolutionary adjustment to a new amino acid may occur, but to a large extent this is insufficient to erase the primitive preference for amino acid replacements. Generally, site-specific amino acid preferences appear to remain conserved throughout evolutionary history despite local sequence divergence. We show such preference conservation to be readily understandable in molecular terms and we provide crystallographic evidence for an intriguing structural-switch mechanism: Energetic preference for an ancestral amino acid in a modern protein can be linked to reorganization upon mutation to the ancestral local structure around the mutated site. Finally, we point out that site-specific preference conservation naturally leads to one plausible evolutionary explanation for the existence of intragenic global suppressor mutations. PMID:25392342

  9. In situ detection of salicylic acid binding sites in plant tissues.

    PubMed

    Liu, Jing-Wen; Deng, Da-Yi; Yu, Ying; Liu, Fang-Fei; Lin, Bi-Xia; Cao, Yu-Juan; Hu, Xiao-Gang; Wu, Jian-Zhong

    2015-02-01

    The determination of hormone-binding sites in plants is essential in understanding the mechanisms behind hormone function. Salicylic acid (SA) is an important plant hormone that regulates responses to biotic and abiotic stresses. In order to label SA-binding sites in plant tissues, a quantum dots (QDs) probe functionalized with a SA moiety was successfully synthesized by coupling CdSe QDs capped with 3-mercaptopropionic acid (MPA) to 4-amino-2-hydroxybenzoic acid (PAS), using 1-ethyl-3-(3-dimethyllaminopropyl) carbodiimide (EDC) as the coupling agent. The probe was then characterized by dynamic light scattering and transmission electron microscopy, as well as UV/vis and fluorescence spectrophotometry. The results confirmed the successful conjugation of PAS to CdSe QDs and revealed that the conjugates maintained the properties of the original QDs, with small core diameters and adequate dispersal in solution. The PAS-CdSe QDs were used to detect SA-binding sites in mung bean and Arabidopsis thaliana seedlings in vitro and in vivo. The PAS-CdSe QDs were effectively transported into plant tissues and specifically bound to SA receptors in vivo. In addition, the effects of the PAS-CdSe QDs on cytosolic Ca(2+) levels in the tips of A. thaliana seedlings were investigated. Both SA and PAS-CdSe QDs had similar effects on the trend in cytosolic-free Ca(2+) concentrations, suggesting that the PAS-CdSe QDs maintained the bioactivity of SA. To summarize, PAS-CdSe QDs have high potential as a fluorescent probe for the in vitro/in vivo labeling and imaging of SA receptors in plants.

  10. The species- and site-specific acid-base properties of penicillamine and its homodisulfide

    NASA Astrophysics Data System (ADS)

    Mirzahosseini, Arash; Szilvay, András; Noszál, Béla

    2014-08-01

    Penicillamine, penicillamine disulfide and 4 related compounds were studied by 1H NMR-pH titrations and case-tailored evaluation methods. The resulting acid-base properties are quantified in terms of 14 macroscopic and 28 microscopic protonation constants and the concomitant 7 interactivity parameters. The species- and site-specific basicities are interpreted by means of inductive and shielding effects through various intra- and intermolecular comparisons. The thiolate basicities determined this way are key parameters and exclusive means for the prediction of thiolate oxidizabilities and chelate forming properties in order to understand and influence chelation therapy and oxidative stress at the molecular level.

  11. Site Specific Incorporation of Amino Acid Analogues into Proteins In Vivo

    DTIC Science & Technology

    2010-08-11

    Positions in CCR5 ( ) and rhodopsin ( ) subjected to site-specific incorporation of unnatural amino acids are indicated. Figure 15. Expression...of functional CCR5 mutants containing Acp or Bzp at positions 28, 96, or 260. HEK293T cells were transfected with plasmids carrying the genes for... CCR5 -wt or CCR5 mutant with an amber mutation at position I28, F96, or F260. Plasmids encoding Bst-Yam and E. coli TyrRS (AcpRS or BzpRS) were co

  12. REMOVING SLUDGE HEELS FROM SAVANNAH RIVER SITE WASTE TANKS BY OXALIC ACID DISSOLUTION

    SciTech Connect

    Poirier, M; David Herman, D; Fernando Fondeur, F; John Pareizs, J; Michael Hay, M; Bruce Wiersma, B; Kim Crapse, K; Thomas Peters, T; Samuel Fink, S; Donald Thaxton, D

    2009-03-01

    The Savannah River Site (SRS) will remove sludge as part of waste tank closure operations. Typically the bulk sludge is removed by mixing it with supernate to produce a slurry, and transporting the slurry to a downstream tank for processing. Experience shows that a residual heel may remain in the tank that cannot be removed by this conventional technique. In the past, SRS used oxalic acid solutions to disperse or dissolve the sludge heel to complete the waste removal. To better understand the actual conditions of oxalic acid cleaning of waste from carbon steel tanks, the authors developed and conducted an experimental program to determine its effectiveness in dissolving sludge, the hydrogen generation rate, the generation rate of other gases, the carbon steel corrosion rate, the impact of mixing on chemical cleaning, the impact of temperature, and the types of precipitates formed during the neutralization process. The test samples included actual SRS sludge and simulated SRS sludge. The authors performed the simulated waste tests at 25, 50, and 75 C by adding 8 wt % oxalic acid to the sludge over seven days. They conducted the actual waste tests at 50 and 75 C by adding 8 wt % oxalic acid to the sludge as a single batch. Following the testing, SRS conducted chemical cleaning with oxalic acid in two waste tanks. In Tank 5F, the oxalic acid (8 wt %) addition occurred over seven days, followed by inhibited water to ensure the tank contained enough liquid to operate the mixer pumps. The tank temperature during oxalic acid addition and dissolution was approximately 45 C. The authors analyzed samples from the chemical cleaning process and compared it with test data. The conclusions from the work are: (1) Oxalic acid addition proved effective in dissolving sludge heels in the simulant demonstration, the actual waste demonstration, and in SRS Tank 5F. (2) The oxalic acid dissolved {approx} 100% of the uranium, {approx} 100% of the iron, and {approx} 40% of the manganese

  13. The effect of the distance between acidic site and basic site immobilized on mesoporous solid on the activity in catalyzing aldol condensation

    SciTech Connect

    Yu Xiaofang; Yu Xiaobo; Wu Shujie; Liu Bo; Liu Heng; Guan Jingqi; Kan Qiubin

    2011-02-15

    Acid-base bifunctional heterogeneous catalysts containing carboxylic and amine groups, which were immobilized at defined distance from one another on the mesoporous solid were synthesized by immobilizing lysine onto carboxyl-SBA-15. The obtained materials were characterized by X-ray diffraction (XRD), N{sub 2} adsorption, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron micrographs (SEM), transmission electron micrographs (TEM), elemental analysis, and back titration. Proximal-C-A-SBA-15 with a proximal acid-base distance was more active than maximum-C-A-SBA-15 with a maximum acid-base distance in aldol condensation reaction between acetone and various aldehydes. It appears that the distance between acidic site and basic site immobilized on mesoporous solid should be an essential factor for catalysis optimization. -- Graphical abstract: Proximal-C-A-SBA-15 with a proximal acid-base distance and maximum-C-A-SBA-15 with a maximum acid-base distance were synthesized by immobilizing lysine onto carboxyl-SBA-15. Display Omitted Research highlights: {yields} Proximal-C-A-SBA-15 with a proximal acid-base distance. {yields} Maximum-C-A-SBA-15 with a maximum acid-base distance. {yields} Compared to maximum-C-A-SBA-15, proximal-C-A-SBA-15 was more active toward aldol condensation reaction between acetone and various aldehydes.

  14. The Structure and Density of Mo and Acid Sites in Mo-ExchangedH-ZSMZ Catalysts

    SciTech Connect

    Borry III, Richard W.; Kim, Young Ho; Huffsmith, Anne; Reimer,Jeffrey A.; Iglesia, Enrique

    1999-03-01

    Mo/H-ZSM5 (1.0-6.3 wt percent Mo; Mo/Al = 0.11-0.68) catalysts for CH4 aromatization were prepared from physical mixtures of MoO3 and H-ZSM5 (Si/Al= 14.3). X-ray diffraction and elemental analysis of physical mixtures treated in air indicate that MoOx species migrate onto the external ZSM5 surface at about 623 K. Between 773 and 973 K, MoOx species migrate inside zeolite channels via surface and gas phase transport, exchange at acid sites, and react to form H2O. The amount of H2O evolved during exchange and the amount of residual OH groups detected by isotopic equilibration with D2 showed that each Mo atom replaces one H+ during exchange. This stoichiometry and the requirement for charge compensation suggest that exchanged species consist of (Mo2O5)2+ditetrahedral structures interacting with two cation exchange sites. The proposed mechanism may provide a general framework to describe the exchange of multivalent cations onto Al sites in zeolites. As the Mo concentration exceeds that required to form a MoOx monolayer on the external zeolite surface ({approx}4 wt percent Mo for the H-ZSM5 used), Mo species sublime as (MoO3)n oligomers or extract Al from the zeolite framework to form inactive Al2(MoO4)3 domains detectable by 27Al NMR. These (Mo2O5)2+ species reduce to form the active MoCx species during the initial stages of CH4 conversion reactions. Optimum CH4 aromatization rates were obtained on catalysts with intermediate Mo contents ({approx}0.4Mo/Al), because both MoCx and acid sites are required to activate CH4 and to convert the initial C2H4 products into C6+ aromatics favored by thermodynamics.

  15. Characterization of the Adeno-Associated Virus 1 and 6 Sialic Acid Binding Site

    PubMed Central

    Huang, Lin-Ya; Patel, Ami; Ng, Robert; Miller, Edward Blake; Halder, Sujata; McKenna, Robert; Asokan, Aravind

    2016-01-01

    ABSTRACT The adeno-associated viruses (AAVs), which are being developed as gene delivery vectors, display differential cell surface glycan binding and subsequent tissue tropisms. For AAV serotype 1 (AAV1), the first viral vector approved as a gene therapy treatment, and its closely related AAV6, sialic acid (SIA) serves as their primary cellular surface receptor. Toward characterizing the SIA binding site(s), the structure of the AAV1-SIA complex was determined by X-ray crystallography to 3.0 Å. Density consistent with SIA was observed in a pocket located at the base of capsid protrusions surrounding icosahedral 3-fold axes. Site-directed mutagenesis substitution of the amino acids forming this pocket with structurally equivalent residues from AAV2, a heparan sulfate binding serotype, followed by cell binding and transduction assays, further mapped the critical residues conferring SIA binding to AAV1 and AAV6. For both viruses five of the six binding pocket residues mutated (N447S, V473D, N500E, T502S, and W503A) abolished SIA binding, whereas S472R increased binding. All six mutations abolished or decreased transduction by at least 50% in AAV1. Surprisingly, the T502S substitution did not affect transduction efficiency of wild-type AAV6. Furthermore, three of the AAV1 SIA binding site mutants—S472R, V473D, and N500E—escaped recognition by the anti-AAV1 capsid antibody ADK1a. These observations demonstrate that common key capsid surface residues dictate both virus binding and entry processes, as well as antigenic reactivity. This study identifies an important functional capsid surface “hot spot” dictating receptor attachment, transduction efficiency, and antigenicity which could prove useful for vector engineering. IMPORTANCE The adeno-associated virus (AAV) vector gene delivery system has shown promise in several clinical trials and an AAV1-based vector has been approved as the first gene therapy treatment. However, limitations still exist with respect

  16. Metal retention on pine bark and blast furnace slag--on-site experiment for treatment of low strength landfill leachate.

    PubMed

    Nehrenheim, Emma; Waara, Sylvia; Johansson Westholm, Lena

    2008-03-01

    Treatment of landfill leachate using blast furnace slag and pine bark as reactive sorbents was studied in an in situ column experiment at the Lilla Nyby landfill site in Eskilstuna, Sweden. The columns were filled with approximately 101 of each sorbent and leachate was supplied at three different flow rates during a period of 4 months. Samples of inflow and outflow were collected three times a week and were analyzed for physical and chemical parameters, including concentrations of some metals, and toxicity. It was found that pine bark removed metals more efficiently than did the blast furnace slags; that Zn was most efficiently retained in the filters and that both retention time and initial concentration played an important role in the sorption process. It was also observed that the pine bark column did not release COD. No toxicity of the untreated or the treated leachate was found with the test organisms and test responses used.

  17. Micro-shear bond strength and surface micromorphology of a feldspathic ceramic treated with different cleaning methods after hydrofluoric acid etching

    PubMed Central

    STEINHAUSER, Henrique Caballero; TURSSI, Cecília Pedroso; FRANÇA, Fabiana Mantovani Gomes; do AMARAL, Flávia Lucisano Botelho; BASTING, Roberta Tarkany

    2014-01-01

    Objective The aim of this study was to evaluate the effect of feldspathic ceramic surface cleaning on micro-shear bond strength and ceramic surface morphology. Material and Methods Forty discs of feldspathic ceramic were prepared and etched with 10% hydrofluoric acid for 2 minutes. The discs were randomly distributed into five groups (n=8): C: no treatment, S: water spray + air drying for 1 minute, US: immersion in ultrasonic bath for 5 minutes, F: etching with 37% phosphoric acid for 1 minute, followed by 1-minute rinse, F+US: etching with 37% phosphoric acid for 1 minute, 1-minute rinse and ultrasonic bath for 5 minutes. Composite cylinders were bonded to the discs following application of silane and hydrophobic adhesive for micro-shear bond strength testing in a universal testing machine at 0.5 mm/min crosshead speed until failure. Stereomicroscopy was used to classify failure type. Surface micromorphology of each treatment type was evaluated by scanning electron microscopy at 500 and 2,500 times magnification. Results One-way ANOVA test showed no significant difference between treatments (p=0.3197) and the most common failure types were cohesive resin cohesion followed by adhesive failure. Micro-shear bond strength of the feldspathic ceramic substrate to the adhesive system was not influenced by the different surface cleaning techniques. Absence of or less residue was observed after etching with hydrofluoric acid for the groups US and F+US. Conclusions Combining ceramic cleaning techniques with hydrofluoric acid etching did not affect ceramic bond strength, whereas, when cleaning was associated with ultrasound, less residue was observed. PMID:24676577

  18. SAVANNAH RIVER SITE TANK CLEANING: CORROSION RATE FOR ONE VERSUS EIGHT PERCENT OXALIC ACID SOLUTION

    SciTech Connect

    Ketusky, E.; Subramanian, K.

    2011-01-20

    Until recently, the use of oxalic acid for chemically cleaning the Savannah River Site (SRS) radioactive waste tanks focused on using concentrated 4 and 8-wt% solutions. Recent testing and research on applicable dissolution mechanisms have concluded that under appropriate conditions, dilute solutions of oxalic acid (i.e., 1-wt%) may be more effective. Based on the need to maximize cleaning effectiveness, coupled with the need to minimize downstream impacts, SRS is now developing plans for using a 1-wt% oxalic acid solution. A technology gap associated with using a 1-wt% oxalic acid solution was a dearth of suitable corrosion data. Assuming oxalic acid's passivation of carbon steel was proportional to the free oxalate concentration, the general corrosion rate (CR) from a 1-wt% solution may not be bound by those from 8-wt%. Therefore, after developing the test strategy and plan, the corrosion testing was performed. Starting with the envisioned process specific baseline solvent, a 1-wt% oxalic acid solution, with sludge (limited to Purex type sludge-simulant for this initial effort) at 75 C and agitated, the corrosion rate (CR) was determined from the measured weight loss of the exposed coupon. Environmental variations tested were: (a) Inclusion of sludge in the test vessel or assuming a pure oxalic acid solution; (b) acid solution temperature maintained at 75 or 45 C; and (c) agitation of the acid solution or stagnant. Application of select electrochemical testing (EC) explored the impact of each variation on the passivation mechanisms and confirmed the CR. The 1-wt% results were then compared to those from the 8-wt%. The immersion coupons showed that the maximum time averaged CR for a 1-wt% solution with sludge was less than 25-mils/yr for all conditions. For an agitated 8-wt% solution with sludge, the maximum time averaged CR was about 30-mils/yr at 50 C, and 86-mils/yr at 75 C. Both the 1-wt% and the 8-wt% testing demonstrated that if the sludge was removed from

  19. Enhanced concentrations of citric acid in spring aerosols collected at the Gosan background site in East Asia

    NASA Astrophysics Data System (ADS)

    Jung, Jinsang; Kawamura, Kimitaka

    2011-09-01

    In order to investigate water-soluble dicarboxylic acids and related compounds in the aerosol samples under the Asian continent outflow, total suspended particle (TSP) samples ( n = 32) were collected at the Gosan site in Jeju Island over 2-5 days integration during 23 March-1 June 2007 and 16-24 April 2008. The samples were analyzed for water-soluble dicarboxylic acids, ketocarboxylic acids, and α-dicarbonyls using a capillary gas chromatography technique. We found elevated concentrations of atmospheric citric acid (range: 20-320 ng m -3) in the TSP samples during mid- to late April of 2007 and 2008. To specify the sources of citric acid, dicarboxylic acids and related compounds were measured in the pollen sample collected at the Gosan site (Pollen_Gosan), authentic pollen samples from Japanese cedar ( Cryptomeria) (Pollen_cedar) and Japanese cypress ( Chamaecyparis obtusa) (Pollen_cypress), and tangerine fruit produced from Jeju Island. Citric acid (2790 ng in unit mg of pollen mass) was found as most abundant species in the Pollen_Gosan, followed by oxalic acid (2390 ng mg -1). Although citric acid was not detected in the Pollen_cedar and Pollen_cypress as major species, it was found as a dominant species in the tangerine juice while malic acid was detected as major species in the tangerine peel, followed by oxalic and citric acids. Since Japanese cedar trees are planted around tangerine farms to prevent strong winds from the Pacific Ocean, citric acid that may be directly emitted from tangerine is likely adsorbed on pollens emitted from Japanese cedar and then transported to the Gosan site. Much lower malic/citric acid ratios obtained under cloudy condition than clear condition suggest that malic acid may rapidly decompose to lower molecular weight compounds such as oxalic and malonic acids (

  20. Hatching success in salamanders and chorus frogs at two sites in Colorado, USA: Effects of acidic deposition and climate

    USGS Publications Warehouse

    Muths, E.; Campbell, D.H.; Corn, P.S.

    2003-01-01

    The snowpack in the vicinity of the Mount Zirkel Wilderness Area is among the most acidic in the western United States. We analyzed water chemistry and examined hatching success in tiger salamanders and chorus frogs at ponds there and at nearby Rabbit Ears Pass (Dumont) to determine whether acid deposition affects amphibians or their breeding habitats at these potentially sensitive locations. We found a wide range of acid neutralizing capacity among ponds within sites; the minimum pH recorded during the experiment was 5.4 at one of 12 ponds with all others at pH ??? 5.7. At Dumont, hatching success for chorus frogs was greater in ponds with low acid neutralizing capacity; however, lowest pHs were >5.8. At current levels of acid deposition, weather and pond characteristics are likely more important than acidity in influencing hatching success in amphibian larvae at these sites.

  1. Site-directed mutagenesis of an alkaline phytase: influencing specificity, activity and stability in acidic milieu.

    PubMed

    Tran, Thuy T; Mamo, Gashaw; Búxo, Laura; Le, Nhi N; Gaber, Yasser; Mattiasson, Bo; Hatti-Kaul, Rajni

    2011-07-10

    Site-directed mutagenesis of a thermostable alkaline phytase from Bacillus sp. MD2 was performed with an aim to increase its specific activity and activity and stability in an acidic environment. The mutation sites are distributed on the catalytic surface of the enzyme (P257R, E180N, E229V and S283R) and in the active site (K77R, K179R and E227S). Selection of the residues was based on the idea that acid active phytases are more positively charged around their catalytic surfaces. Thus, a decrease in the content of negatively charged residues or an increase in the positive charges in the catalytic region of an alkaline phytase was assumed to influence the enzyme activity and stability at low pH. Moreover, widening of the substrate-binding pocket is expected to improve the hydrolysis of substrates that are not efficiently hydrolysed by wild type alkaline phytase. Analysis of the phytase variants revealed that E229V and S283R mutants increased the specific activity by about 19% and 13%, respectively. Mutation of the active site residues K77R and K179R led to severe reduction in the specific activity of the enzyme. Analysis of the phytase mutant-phytate complexes revealed increase in hydrogen bonding between the enzyme and the substrate, which might retard the release of the product, resulting in decreased activity. On the other hand, the double mutant (K77R-K179R) phytase showed higher stability at low pH (pH 2.6-3.0). The E227S variant was optimally active at pH 5.5 (in contrast to the wild type enzyme that had an optimum pH of 6) and it exhibited higher stability in acidic condition. This mutant phytase, displayed over 80% of its initial activity after 3h incubation at pH 2.6 while the wild type phytase retained only about 40% of its original activity. Moreover, the relative activity of this mutant phytase on calcium phytate, sodium pyrophosphate and p-nitro phenyl phosphate was higher than that of the wild type phytase.

  2. Shear Bond Strength of Acidic Primer, Light-Cure Glass Ionomer, Light-Cure and Self Cure Composite Adhesive Systems - An In Vitro Study

    PubMed Central

    D, Krishnakanth Reddy; V, Kishore M S; Safeena, Safeena

    2013-01-01

    Background: The purpose of this study was to determine shear bond strength and the effect on the bracket/ adhesive failure mode when an acidic primer and other etchants were used to condition the enamel surface before bonding. Materials & Methods: Group I: Brackets bonded with Ultimate cure-on-light Light-cure composite adhesive system. Group II: Brackets bonded with Ortho-one no-mix. Self-cure composite adhesive system. Group III: Brackets bonded with Light-cure glass ionomer adhesive system. Group IV: Brackets bonded with Transbond plus self etching primer. Results: The results of this study indicated that the shear bond strength when using Transbond plus self etching primer showed the highest bond strength Group- IV(8.69 2.54 MPa) followed by Ultimate cure-on-light Group-I (8.62 1.84 MPa), Ortho-one no-mix (Bisco Inc. USA)Group-II (8.07 1.72 MPa), and least bond strength was seen in G.C. Fuji Ortho L.C. Group-III (6.01 1.6) MPa Conclusion: Use of self etching primer saves chairside time and satisfactory high bond strength was obtained. Care should be taken during debonding of ceramic brackets How to cite this article: Reddy K D, Kishore M S V, Safeena S. Shear Bond Strength of Acidic Primer, Light-Cure Glass Ionomer, Light-Cure and Self Cure Composite Adhesive Systems - An In Vitro Study. J Int Oral Health 2013; 5(3):73-78. PMID:24155606

  3. Composite active site of chondroitin lyase ABC accepting both epimers of uronic acid

    SciTech Connect

    Shaya, D.; Hahn, Bum-Soo; Bjerkan, Tonje Marita; Kim, Wan Seok; Park, Nam Young; Sim, Joon-Soo; Kim, Yeong-Shik; Cygler, M.

    2008-03-19

    Enzymes have evolved as catalysts with high degrees of stereospecificity. When both enantiomers are biologically important, enzymes with two different folds usually catalyze reactions with the individual enantiomers. In rare cases a single enzyme can process both enantiomers efficiently, but no molecular basis for such catalysis has been established. The family of bacterial chondroitin lyases ABC comprises such enzymes. They can degrade both chondroitin sulfate (CS) and dermatan sulfate (DS) glycosaminoglycans at the nonreducing end of either glucuronic acid (CS) or its epimer iduronic acid (DS) by a {beta}-elimination mechanism, which commences with the removal of the C-5 proton from the uronic acid. Two other structural folds evolved to perform these reactions in an epimer-specific fashion: ({alpha}/{alpha}){sub 5} for CS (chondroitin lyases AC) and {beta}-helix for DS (chondroitin lyases B); their catalytic mechanisms have been established at the molecular level. The structure of chondroitinase ABC from Proteus vulgaris showed surprising similarity to chondroitinase AC, including the presence of a Tyr-His-Glu-Arg catalytic tetrad, which provided a possible mechanism for CS degradation but not for DS degradation. We determined the structure of a distantly related Bacteroides thetaiotaomicron chondroitinase ABC to identify additional structurally conserved residues potentially involved in catalysis. We found a conserved cluster located {approx}12 {angstrom} from the catalytic tetrad. We demonstrate that a histidine in this cluster is essential for catalysis of DS but not CS. The enzyme utilizes a single substrate-binding site while having two partially overlapping active sites catalyzing the respective reactions. The spatial separation of the two sets of residues suggests a substrate-induced conformational change that brings all catalytically essential residues close together.

  4. Heterogeneous ceria catalyst with water-tolerant Lewis acidic sites for one-pot synthesis of 1,3-diols via Prins condensation and hydrolysis reactions.

    PubMed

    Wang, Yehong; Wang, Feng; Song, Qi; Xin, Qin; Xu, Shutao; Xu, Jie

    2013-01-30

    The use of a heterogeneous Lewis acid catalyst, which is insoluble and easily separable during the reaction, is a promising option for hydrolysis reactions from both environmental and practical viewpoints. In this study, ceria showed excellent catalytic activity in the hydrolysis of 4-methyl-1,3-dioxane to 1,3-butanediol in 95% yield and in the one-pot synthesis of 1,3-butanediol from propylene and formaldehyde via Prins condensation and hydrolysis reactions in an overall yield of 60%. In-depth investigations revealed that ceria is a water-tolerant Lewis acid catalyst, which has seldom been reported previously. The ceria catalysts showed rather unusual high activity in hydrolysis, with a turnover number (TON) of 260, which is rather high for bulk oxide catalysts, whose TONs are usually less than 100. Our conclusion that ceria functions as a Lewis acid catalyst in hydrolysis reactions is firmly supported by thorough characterizations with IR and Raman spectroscopy, acidity measurements with IR and (31)P magic-angle-spinning NMR spectroscopy, Na(+)/H(+) exchange tests, analyses using the in situ active-site capping method, and isotope-labeling studies. A relationship between surface vacancy sites and catalytic activity has been established. CeO(2)(111) has been confirmed to be the catalytically active crystalline facet for hydrolysis. Water has been found to be associatively adsorbed on oxygen vacancy sites with medium strength, which does not lead to water dissociation to form stable hydroxides. This explains why the ceria catalyst is water-tolerant.

  5. Evaluation Of Sludge Heel Dissolution Efficiency With Oxalic Acid Cleaning At Savannah River Site

    SciTech Connect

    Sudduth, Christie; Vitali, Jason; Keefer, Mark

    2014-01-08

    The chemical cleaning process baseline strategy at the Savannah River Site was revised to improve efficiency during future execution of the process based on lessons learned during previous bulk oxalic acid cleaning activities and to account for operational constraints imposed by safety basis requirements. These improvements were also intended to transcend the difficulties that arise from waste removal in higher rheological yield stress sludge tanks. Tank 12 implemented this improved strategy and the bulk oxalic acid cleaning efforts concluded in July 2013. The Tank 12 radiological removal results were similar to previous bulk oxalic acid cleaning campaigns despite the fact that Tank 12 contained higher rheological yield stress sludge that would make removal more difficult than the sludge treated in previous cleaning campaigns. No appreciable oxalate precipitation occurred during the cleaning process in Tank 12 compared to previous campaigns, which aided in the net volume reduction of 75-80%. Overall, the controls established for Tank 12 provide a template for an improved cleaning process.

  6. Site directed mutagenesis of StSUT1 reveals target amino acids of regulation and stability.

    PubMed

    Krügel, Undine; Wiederhold, Elena; Pustogowa, Jelena; Hackel, Aleksandra; Grimm, Bernhard; Kühn, Christina

    2013-11-01

    Plant sucrose transporters (SUTs) are functional as sucrose-proton-cotransporters with an optimal transport activity in the acidic pH range. Recently, the pH optimum of the Solanum tuberosum sucrose transporter StSUT1 was experimentally determined to range at an unexpectedly low pH of 3 or even below. Various research groups have confirmed these surprising findings independently and in different organisms. Here we provide further experimental evidence for a pH optimum at physiological extrema. Site directed mutagenesis provides information about functional amino acids, which are highly conserved and responsible for this extraordinary increase in transport capacity under extreme pH conditions. Redox-dependent dimerization of the StSUT1 protein was described earlier. Here the ability of StSUT1 to form homodimers was demonstrated by heterologous expression in Lactococcus lactis and Xenopus leavis using Western blots, and in plants by bimolecular fluorescence complementation. Mutagenesis of highly conserved cysteine residues revealed their importance in protein stability. The accessibility of regulatory amino acid residues in the light of StSUT1's compartmentalization in membrane microdomains is discussed.

  7. Pore architecture and ion sites in acid-sensing ion channels and P2X receptors.

    PubMed

    Gonzales, Eric B; Kawate, Toshimitsu; Gouaux, Eric

    2009-07-30

    Acid-sensing ion channels are proton-activated, sodium-selective channels composed of three subunits, and are members of the superfamily of epithelial sodium channels, mechanosensitive and FMRF-amide peptide-gated ion channels. These ubiquitous eukaryotic ion channels have essential roles in biological activities as diverse as sodium homeostasis, taste and pain. Despite their crucial roles in biology and their unusual trimeric subunit stoichiometry, there is little knowledge of the structural and chemical principles underlying their ion channel architecture and ion-binding sites. Here we present the structure of a functional acid-sensing ion channel in a desensitized state at 3 A resolution, the location and composition of the approximately 8 A 'thick' desensitization gate, and the trigonal antiprism coordination of caesium ions bound in the extracellular vestibule. Comparison of the acid-sensing ion channel structure with the ATP-gated P2X(4) receptor reveals similarity in pore architecture and aqueous vestibules, suggesting that there are unanticipated yet common structural and mechanistic principles.

  8. An improved thermodynamic model for the complexation of trivalent actinides and lanthanide with oxalic acid valid to high ionic strength.

    SciTech Connect

    Xiong, Yongliang; Thakur, Punam; Borkowski, Marian

    2015-07-30

    The dissociation constants of oxalic acid (Ox), and the stability constants of Am3+, Cm3+ and Eu3+ with Ox2– have been determined at 25 °C, over a range of concentration varying from 0.1 to 6.60 m NaClO4 using potentiometric titration and extraction techniques, respectively. The experimental data support the formation of complexes, M(Ox)n3 – 2n, where (M = Am3+, Cm3+ and Eu3+ and n = 1 and 2). The dissociation constant and the stability constant values measured as a function of NaClO4 concentration were used to estimate the Pitzer parameters for the respective interactions of Am3+, Cm3+ and Eu3+ with Ox. Furthermore, the stability constants data of Am3+ –Ox measured in NaClO4 and in NaCl solutions from the literature were simultaneously fitted in order to refine the existing actinide–oxalate complexation model that can be used universally in the safety assessment of radioactive waste disposal. The thermodynamic stability constant: log β0101 = 6.30 ± 0.06 and log β0102 = 10.84 ± 0.06 for Am3+ was obtained by simultaneously fitting data in NaCl and NaClO4 media. Additionally, log β0101 = 6.72 ± 0.08 and log β0102 = 11.05 ± 0.09 for the Cm3+ and log β0101 = 6.67 ± 0.08 and log β0102 = 11.15 ± 0.09 for the Eu3+ were calculated by extrapolation of data to zero ionic strength in NaClO4 medium only. For all stability constants, the Pitzer model gives an excellent representation of the data using interaction parameters β(0), β(1), and CΦ determined in this work. The thermodynamic model developed in this work will be useful in accurately modeling the potential solubility of trivalent

  9. Characteristics of fluoride in pore-water at accidental hydrofluoric acid spillage site, Gumi, Korea

    NASA Astrophysics Data System (ADS)

    Kwon, E. H.; Lee, H. A.; Lee, J.; Kim, D.; Lee, S.; Yoon, H. O.

    2015-12-01

    A leakage accident of hydrofluoric acid (HF) occurred in Gumi, South Korea at Sep. 2012. The study site is located in the borderline between a large-scale industrial complex and a rural area. The HF plume was made immediately, and moved toward the rural area through air. After the accident, 212 ha of farm land were influenced and most of crops were withered. To recover the soil, CaO was applied after six months. Although several studies have done to estimate the extension and movement of HF plume in the air and to assess the impact on human health or plant after the incident, the long-term fate of fluoride (F) in the affected soils is not identified clearly. Thus, this study aimed to understand the behavior of F in the soil after HF releasing from accident site through chemical analysis and geochemical modeling. Within the radius of 1 km of accident site, 16 pore-water and soil samples were collected. The semi-quantitative soil composition (i.e., Al, Ca, Fe, K, Mg, Mn, Na, P, Si, Ti), total F, total P, OM contents in soil, and soil pH have already been measured, and pore-water compositions are also identified. From these experimental and modeling data, we could be evaluate if impact of accident exists until now, and also could be select and identify existing form of fluoride in soil and pore-water.

  10. The Effect of an Acidic Food-Simulating Environment on the Shear Bond Strength of Self-Ligating Brackets with Different Base Designs

    PubMed Central

    Sheibaninia, Ahmad; Sepasi, Sepehr; Saghiri, Mohammad Ali; Sepasi, Setareh

    2014-01-01

    Aim. This study aims to evaluate the effect of acidic food simulant and (acetic acid 3%) on the shear bond strength (SBS) and adhesive remnant index (ARI) scores of one conventional and three different self-ligating brackets with different base designs. Materials and Methods. Freshly extracted first maxillary premolars (n = 160) were embedded in resin blocks. A conventional stainless steel bracket, Equilibrium 2, and three types of self-ligating brackets, Speed, In-Ovation R, and Damon 3MX, were bonded to teeth and exposed to distilled water (groups 1, 3, 5, and 7) or acetic acid 3% (groups 2, 4, 6, 8) for 12 weeks. SBS and ARI were calculated and statistical analysis was performed with the analysis of variance (SBS) or χ2 test (ARI) to compare values between the different groups. Results. Equilibrium 2 and In-Ovation R showed a significantly lower SBS in the acidic environment than in distilled water. Significant differences in ARI scores were found for Equilibrium 2 after immersion in an acidic environment, shifting from 0 in distilled water to 2 in an acidic environment. Conclusions. Equilibrium 2 and In-Ovation R brackets showed a significant decrease in SBS after a 12-week immersion in acetic acid 3%, although all groups showed clinically acceptable SBS. Equilibrium 2 showed significant differences in ARI scores when exposed to acetic acid 3%. PMID:25328524

  11. Influence of acid-base conditioning on the bond strength of five luting agents employing self-etching primer to enamel and dentin.

    PubMed

    Yokomichi, Rie; Taira, Yohsuke; Soeno, Kohyoh; Atsuta, Mitsuru

    2005-06-01

    The purpose of this study was to evaluate the effect of multi-step conditioning (PA-AD conditioning) with phosphoric acid and sodium hypochlorite on the bond strength of five luting materials to enamel and dentin. Three commercial self-etching/priming systems (Panavia, Linkmax, and Multibond) and two experimental systems (ED/Super-Bond and EDFe/Super-Bond) were used. The surfaces of bovine enamel or dentin were bonded to a stainless steel rod. Tensile bond strength was determined after 24-hour immersion in water. PA-AD conditioning significantly improved the bond strength between enamel and three of the systems (Panavia, ED/Super-Bond, and EDFe/Super-Bond), but did not have any effect on Linkmax and Multibond. Likewise, PA-AD conditioning did not significantly improve the bond strength of Panavia, Linkmax, Multibond, and ED/Super-Bond to dentin. Highest bond strength to dentin (19.7 MPa) was obtained when self-etching primer containing ferric chloride (EDFe/Super-Bond) was used, but additional PA-AD conditioning significantly weakened the bonding (12.6 MPa).

  12. The effect of humic acid on the aggregation of titanium dioxide nanoparticles under different pH and ionic strengths.

    PubMed

    Zhu, Miao; Wang, Hongtao; Keller, Arturo A; Wang, Tao; Li, Fengting

    2014-07-15

    With the increasingly widespread use of titanium dioxide nanoparticles (TiO2 NPs), the particles' environmental impacts have attracted concern, making it necessary to understand the fate and transport of TiO2 NPs in aqueous media. In this study, we investigated TiO2 NP aggregation caused by the effects of humic acid (HA), ionic strength (IS) and different pH using dynamic light scattering (DLS) to monitor the size distribution of the TiO2 NPs continuously. It was determined that HA can influence the stability of TiO2 NPs through charge neutralization, steric hindrance and bridging effects. In the absence of IS, aggregation was promoted by adding HA only when the pH (pH=4) is less than the point of zero charge for the TiO2 NPs (pHPZC≈6) because HA reduces the zeta potential of the TiO2 NPs via charge neutralization. At pH=4 and when the concentration of HA is 94.5 μg/L, the zeta potential of TiO2 NPs is close to zero, and they reach an aggregation maximum. A higher concentration of HA results in more negatively charged TiO2 NP surfaces, which hinder their aggregation. When the pH is 5.8, HA enhances the negative zeta potential of the TiO2 NPs and increases their stability via electrostatic repulsion and steric hindrance. When the pH (pH=8) is greater than pHpzc, the zeta potential of the TiO2 NPs is high (~40 mV), and it barely changes with increasing HA concentration. Thus, the TiO2 NPs are notably stable, and their size does not grow at pH8. The increase in the critical coagulation concentration (CCC) of TiO2 NPs indicated that there is steric hindrance after the addition of HA. HA can enhance the coagulation of TiO2 NPs, primarily due to bridging effect. These findings are useful in understanding the size change of TiO2 NPs, as well as the removal of TiO2 NPs and HA from aqueous media.

  13. Role of Criegee Intermediates in Formation of Sulfuric Acid at BVOCs-rich Cape Corsica Site

    NASA Astrophysics Data System (ADS)

    Kukui, A.; Dusanter, S.; Sauvage, S.; Gros, V.; Bourrianne, T.; Sellegri, K.; Wang, J.; Colomb, A.; Pichon, J. M.; Chen, H.; Kalogridis, C.; Zannoni, N.; Bonsang, B.; Michoud, V.; Locoge, N.; Leonardis, T.

    2015-12-01

    Oxidation of SO2 in reactions with stabilised Criegee Intermediates (sCI) was suggested as an additional source of gaseous sulfuric acid (H2SO4) in the atmosphere, complementary to the conventional H2SO4 formation in reaction of SO2 with OH radicals. Evaluation of the importance of this additional source is complicated due to large uncertainty in the mechanism and rate constants for the reactions of different sCI with SO2, water vapor and other atmospheric species. Here we present an evaluation of the role of sCI in H2SO4 production at remote site on Cape Corsica near the North tip of Corsica Island (Ersa station, Western Mediterranean). In July 2013 comprehensive field observations including gas phase (OH and RO2 radicals, H2SO4, VOCs, NOx, SO2, others) and aerosol measurements were conducted at this site in the frame of ChArMEx project. During the field campaign the site was strongly influenced by local emissions of biogenic volatile compounds (BVOCs), including isoprene and terpenes, forming different sCI in reactions with ozone and, hence, presenting additional source of H2SO4 via sCI+SO2. However, this additional source of H2SO4 at the Ersa site was found to be insignificant. The observed concentrations of H2SO4 were found to be in good agreement with those estimated from the H2SO4 condensation sink and the production of H2SO4 only in the reaction of OH with SO2, without accounting for any additional H2SO4 source. Using the BVOCs observations we present estimation of the upper limit for the rate constants of H2SO4 production via reactions of different sCI with SO2.

  14. Putative binding sites for arachidonic acid on the human cardiac Kv1.5 channel

    PubMed Central

    Bai, Jia‐Yu; Ding, Wei‐Guang; Kojima, Akiko; Seto, Tomoyoshi

    2015-01-01

    Background and Purpose In human heart, the Kv1.5 channel contributes to repolarization of atrial action potentials. This study examined the electrophysiological and molecular mechanisms underlying arachidonic acid (AA)‐induced inhibition of the human Kv1.5 (hKv1.5) channel. Experimental Approach Site‐directed mutagenesis was conducted to mutate amino acids that reside within the pore domain of the hKv1.5 channel. Whole‐cell patch‐clamp method was used to record membrane currents through wild type and mutant hKv1.5 channels heterologously expressed in CHO cells. Computer docking simulation was conducted to predict the putative binding site(s) of AA in an open‐state model of the Kv1.5 channel. Key Results The hKv1.5 current was minimally affected at the onset of depolarization but was progressively reduced during depolarization by the presence of AA, suggesting that AA acts as an open‐channel blocker. AA itself affected the channel at extracellular sites independently of its metabolites and signalling pathways. The blocking effect of AA was attenuated at pH 8.0 but not at pH 6.4. The blocking action of AA developed rather rapidly by co‐expression of Kvβ1.3. The AA‐induced block was significantly attenuated in H463C, T480A, R487V, I502A, I508A, V512A and V516A, but not in T462C, A501V and L510A mutants of the hKv1.5 channel. Docking simulation predicted that H463, T480, R487, I508, V512 and V516 are potentially accessible for interaction with AA. Conclusions and Implications AA itself interacts with multiple amino acids located in the pore domain of the hKv1.5 channel. These findings may provide useful information for future development of selective blockers of hKv1.5 channels. PMID:26292661

  15. Fabrication of hydrophobic polymer foams with double acid sites on surface of macropore for conversion of carbohydrate.

    PubMed

    Pan, Jianming; Mao, Yanli; Gao, Heping; Xiong, Qingang; Qiu, Fengxian; Zhang, Tao; Niu, Xiangheng

    2016-06-05

    Herein we reported a simple and novel synthetic strategy for the fabrication of two kinds of hydrophobic polymer foam catalysts (i.e. Cr(3+)-HPFs-1-H(+) and HPFs-1-H(+)) with hierarchical porous structure, inhomogeneous acidic composition and Lewis-Brønsted double acid sites distributed on the surface, which was used to one-pot conversion of carbohydrate (such as cellulose, glucose and fructose) to a key chemical platform (i.e. 5-hydroxymethylfurfural, HMF). The water-in-oil (W/O) high internal phase emulsions (HIPEs), stabilized by both Span 80 and acidic prepolymers as analogous particles offered the acidic actives, were used as the template for simultaneous polymerization of oil phase in the presence of divinylbenzene (DVB) and styrene (St). After subsequent ion-exchange process, Lewis and Brønsted acid sites derived from exchanged Cr(3+) and H(+) ion were both fixed on the surface of cell of the catalysts. The HPFs-1-H(+) and Cr(3+)-HPFs-1-H(+) had similar hierarchical porous, hydrophobic surface and acid sites (HPFs-1-H(+) with macropores ranging from 0.1 μm to 20 μm, uniform mesopores in 14.4 nm, water contact angle of 122° and 0.614 mmolg(-1) of Brønsted acid sites, as well as Cr(3+)-HPFs-1-H(+) with macropores ranging from 0.1 μm to 20 μm, uniform mesopores in 13.3 nm, water contact angle of 136° and 0.638 mmolg(-1) of Lewis-Brønsted acid sites). It was confirmed that Lewis acid sites of catalyst had a slight influence on the HMF yield of fructose came from the function of Brønsted acid sites, and Lewis acid sites were in favor of improving the HMF yield from cellulose and glucose. This work opens up a simple and novel route to synthesize multifunctional polymeric catalysts for efficient one-pot conversion of carbohydrate to HMF.

  16. Interaction of Beta-Hydroxy-Beta-Methylbutyrate Free Acid and Adenosine Triphosphate on Muscle Mass, Strength, and Power in Resistance Trained Individuals.

    PubMed

    Lowery, Ryan P; Joy, Jordan M; Rathmacher, John A; Baier, Shawn M; Fuller, John C; Shelley, Mack C; Jäger, Ralf; Purpura, Martin; Wilson, Stephanie M C; Wilson, Jacob M

    2016-07-01

    Lowery, RP, Joy, JM, Rathmacher, JA, Baier, SM, Fuller, JC Jr, Shelley, MC II, Jäger, R, Purpura, M, Wilson, SMC, and Wilson, JM. Interaction of beta-hydroxy-beta-methylbutyrate free acid and adenosine triphosphate on muscle mass, strength, and power in resistance trained individuals. J Strength Cond Res 30(7): 1843-1854, 2016-Adenosine-5'-triphosphate (ATP) supplementation helps maintain performance under high fatiguing contractions and with greater fatigue recovery demands also increase. Current evidence suggests that the free acid form of β-hydroxy-β-methylbutyrate (HMB-FA) acts by speeding regenerative capacity of skeletal muscle after high-intensity or prolonged exercise. Therefore, we investigated the effects of 12 weeks of HMB-FA (3 g) and ATP (400 mg) administration on lean body mass (LBM), strength, and power in trained individuals. A 3-phase double-blind, placebo-, and diet-controlled study was conducted. Phases consisted of an 8-week periodized resistance training program (phase 1), followed by a 2-week overreaching cycle (phase 2), and a 2-week taper (phase 3). Lean body mass was increased by a combination of HMB-FA/ATP by 12.7% (p < 0.001). In a similar fashion, strength gains after training were increased in HMB-FA/ATP-supplemented subjects by 23.5% (p < 0.001). Vertical jump and Wingate power were increased in the HMB-FA/ATP-supplemented group compared with the placebo-supplemented group, and the 12-week increases were 21.5 and 23.7%, respectively. During the overreaching cycle, strength and power declined in the placebo group (4.3-5.7%), whereas supplementation with HMB-FA/ATP resulted in continued strength gains (1.3%). In conclusion, HMB-FA and ATP in combination with resistance exercise training enhanced LBM, power, and strength. In addition, HMB-FA plus ATP blunted the typical response to overreaching, resulting in a further increase in strength during that period. It seems that the combination of HMB-FA/ATP could benefit those who

  17. Methane to acetic acid over Cu-exchanged zeolites: mechanistic insights from a site-specific carbonylation reaction.

    PubMed

    Narsimhan, Karthik; Michaelis, Vladimir K; Mathies, Guinevere; Gunther, William R; Griffin, Robert G; Román-Leshkov, Yuriy

    2015-02-11

    The selective low temperature oxidation of methane is an attractive yet challenging pathway to convert abundant natural gas into value added chemicals. Copper-exchanged ZSM-5 and mordenite (MOR) zeolites have received attention due to their ability to oxidize methane into methanol using molecular oxygen. In this work, the conversion of methane into acetic acid is demonstrated using Cu-MOR by coupling oxidation with carbonylation reactions. The carbonylation reaction, known to occur predominantly in the 8-membered ring (8MR) pockets of MOR, is used as a site-specific probe to gain insight into important mechanistic differences existing between Cu-MOR and Cu-ZSM-5 during methane oxidation. For the tandem reaction sequence, Cu-MOR generated drastically higher amounts of acetic acid when compared to Cu-ZSM-5 (22 vs 4 μmol/g). Preferential titration with sodium showed a direct correlation between the number of acid sites in the 8MR pockets in MOR and acetic acid yield, indicating that methoxy species present in the MOR side pockets undergo carbonylation. Coupled spectroscopic and reactivity measurements were used to identify the genesis of the oxidation sites and to validate the migration of methoxy species from the oxidation site to the carbonylation site. Our results indicate that the Cu(II)-O-Cu(II) sites previously associated with methane oxidation in both Cu-MOR and Cu-ZSM-5 are oxidation active but carbonylation inactive. In turn, combined UV-vis and EPR spectroscopic studies showed that a novel Cu(2+) site is formed at Cu/Al <0.2 in MOR. These sites oxidize methane and promote the migration of the product to a Brønsted acid site in the 8MR to undergo carbonylation.

  18. 36C1 measurements and the hydrology of an acid injection site

    USGS Publications Warehouse

    Vourvopoulos, G.; Brahana, J.V.; Nolte, E.; Korschinek, G.; Priller, A.; Dockhorn, B.

    1990-01-01

    In an area in western Tennessee (United States), an industrial firm is injecting acidic (pH = 0.1) iron chloride into permeable zones of carbonate rocks at depths ranging from 1000 to 2200 m below land surface. Overlying the injection zone at a depth of approximately 500 m below land surface is a regional fresh-water aquifer, the Knox aquifer. A study is currently underway to investigate whether the injection wells are hydraulically isolated from the fresh-water aquifer. Drilling of a test well that will reach a total depth of 2700 m has been initiated. The 36Cl content of 15 samples from the Knox aquifer, from monitor wells in the vicinity of the injection site, and from the test well have been analyzed. ?? 1990.

  19. BTX abatement using Chilean natural zeolite: the role of Brønsted acid sites.

    PubMed

    Alejandro, S; Valdés, H; Manero, M-H; Zaror, C A

    2012-01-01

    In wastewater treatment facilities, air quality is not only affected by conventional unpleasant odour compounds; toxic volatile organic compounds (VOCs) are also found. In this study, the adsorptive capacity of Chilean natural zeolite toward VOC removal was evaluated. Moreover, the influence of zeolite chemical surface properties on VOC elimination was also investigated. Three modified zeolite samples were prepared from a natural Chilean zeolite (53% clinoptilolite, 40% mordenite and 7% quartz). Natural and modified zeolite samples were characterised by nitrogen adsorption at 77 K, elemental analyses and X-ray fluorescence (XRF). Chemical modifications of natural zeolite showed the important role of Brønsted acid sites on the abatement of VOCs. The presence of humidity has a negative effect on zeolite adsorption capacity. Natural zeolites could be an interesting option for benzene, toluene and xylene vapour emission abatement.

  20. Site-Specific Pyrolysis Induced Cleavage at Aspartic Acid Residue in Peptides and Proteins

    PubMed Central

    Zhang, Shaofeng; Basile, Franco

    2011-01-01

    A simple and site-specific non-enzymatic method based on pyrolysis has been developed to cleave peptides and proteins. Pyrolytic cleavage was found to be specific and rapid as it induced a cleavage at the C-terminal side of aspartic acid in the temperature range of 220–250 °C in 10 seconds. Electrospray Ionization (ESI) mass spectrometry (MS) and tandem-MS (MS/MS) were used to characterize and identify pyrolysis cleavage products, confirming that sequence information is conserved after the pyrolysis process in both peptides and protein tested. This suggests that pyrolysis-induced cleavage at aspartyl residues can be used as a rapid protein digestion procedure for the generation of sequence specific protein biomarkers. PMID:17388620

  1. Characterization of lysosomal acid lipase by site-directed mutagenesis and heterologous expression.

    PubMed

    Sheriff, S; Du, H; Grabowski, G A

    1995-11-17

    Lysosomal acid lipase (LAL) is essential for the hydrolysis of cholesterol esters and triglycerides that are delivered to the lysosomes via the low density lipoprotein receptor system. The deficiency of LAL is associated with cholesteryl ester storage disease (CESD) and Wolman's disease (WD). We cloned the human LAL cDNA and expressed the active enzyme in the baculovirus system. Two molecular forms (M(r) approximately 41,000 and approximately 46,000) with different glycosylation were found intracellularly, and approximately 24% of the M(r) approximately 46,000 form was secreted into the medium. Tunicamycin treatment produced only an inactive M(r) approximately 41,000 form. This result implicates glycosylation occupancy in the proper folding for active-site function. Catalytic activity was greater toward cis- than trans-unsaturated fatty acid esters of 4-methylumbelliferone and toward esters with 7-carbon length acyl chains. LAL cleaved cholesterol esters and mono-, tri-, and diglycerides. Heparin had a biphasic effect on enzymatic activity with initial activation followed by inhibition. Inhibition of LAL activity by tetrahydrolipstatin and diethyl p-nitrophenyl phosphate suggested the presence of active serines in binding/catalytic domain(s) of the protein. Site-directed mutagenesis at two putative active centers, GXSXG, showed that Ser153 was important to catalytic activity, whereas Ser99 was not and neither was the catalytic nucleophile. Three reported mutations (L179P, L336P, and delta AG302 deletion) from CESD patients were created and expressed in the Sf9 cell system. None cleaved cholesterol esters, and L179P and L336P cleaved only triolein at approximately 4% of wild-type levels. These results suggest that mechanisms, in addition to LAL defects, may operate in the selective accumulation of cholesterol esters or triglycerides in CESD and WD patients.

  2. Comparison of Shear Bond Strength of Orthodontic Brackets Bonded to Enamel Prepared By Er:YAG Laser and Conventional Acid-Etching

    PubMed Central

    Hosseini, M.H.; Namvar, F.; Chalipa, J.; Saber, K.; Chiniforush, N.; Sarmadi, S.; Mirhashemi, A.H.

    2012-01-01

    Introduction: The purpose of this study was to compare shear bond strength (SBS) of orthodontic brackets bonded to enamel prepared by Er:YAG laser with two different powers and conventional acid-etching. Materials and Methods: Forty-five human premolars extracted for orthodontic purposes were randomly assigned to three groups based on conditioning method: Group 1- conventional etching with 37% phosphoric acid; Group 2- irradiation with Er:YAG laser at 1 W; and Group 3- irradiation with Er:YAG laser at 1.5 W. Metal brackets were bonded on prepared enamel using a light-cured composite. All groups were subjected to thermocycling process. Then, the specimens mounted in auto-cure acryle and shear bond strength were measured using a universal testing machine with a crosshead speed of 0.5 mm per second. After debonding, the amount of resin remaining on the teeth was determined using the adhesive remnant index (ARI) scored 1 to 5. One-way analysis of variance was used to compare shear bond strengths and the Kruskal-Wallis test was performed to evaluate differences in the ARI for different etching types. Results: The mean and standard deviation of conventional acid-etch group, 1W laser group and 1.5W laser group was 3.82 ± 1.16, 6.97 ± 3.64 and 6.93 ± 4.87, respectively. Conclusion: The mean SBS obtained with an Er:YAG laser operated at 1W or 1.5W is approximately similar to that of conventional etching. However, the high variability of values in bond strength of irradiated enamel should be considered to find the appropriate parameters for applying Er:YAG laser as a favorable alternative for surface conditioning. PMID:22924098

  3. Evaluation of modifying the bonding protocol of a new acid-etch primer on the shear bond strength of orthodontic brackets.

    PubMed

    Ajlouni, Raed; Bishara, Samir E; Oonsombat, Charuphan; Denehy, Gerald E

    2004-06-01

    The purpose of the study was to evaluate the shear bond strength of orthodontic brackets when light curing both the self-etch primer and the adhesive in one step. Fourty eight teeth were bonded with self-etch primer Angel I (3M/ESPE, St Paul, Minn) and divided into three groups. In group I (control), 16 teeth were stored in deionized water for 24 hours before debonding. In group II, 16 teeth were debonded within half-an-hour to simulate when the initial archwires were ligated. In group III, 16 additional teeth were bonded using exactly the same procedure as in groups I and II, but the light cure used for 10 seconds after applying the acid-etch primer was eliminated, and the light cure used for 20 seconds after the precoated bracket was placed over the tooth. This saved at least two minutes of the total time of the bonding procedure. The teeth in this group were also debonded within half-an-hour from the time of initial bonding. The teeth debonded after 24 hours of water storage at 37 degrees C had a mean shear bond strength of 6.0 +/- 3.5 MPa, the group that was debonded within half-an-hour of two light exposures had a mean shear bond strength of 5.9 +/- 2.7 MPa, and the mean for the group with only one light cure exposure was 4.3 +/- 2.6 MPa. Light curing the acid-etch primer together with the adhesive after placing the orthodontic bracket did not significantly diminish the shear bond strength as compared with light curing the acid-etch primer and the adhesive separately.

  4. In-situ stress and strength in the Nankai inner accretionary prism at Site C0002, IODP NanTroSEIZE

    NASA Astrophysics Data System (ADS)

    Kitajima, H.; Valdez, R. D.; Kitamura, M.; Sone, H.; Saffer, D. M.; Tobin, H. J.; Hirose, T.; Kuo, S. T.

    2015-12-01

    As a part of the International Ocean Discovery Program (IODP) Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE), a deep riser borehole has been drilled into the Kumano forearc basin and the underlying inner accretionary wedge at Site C0002, located ~35 km landward from the trench. One of the primary objectives of drilling the riser site was to characterize in-situ stress and pore pressure in the hanging wall above the locked plate boundary. Here, we: (1) investigate the mechanical strength and deformation behavior of prism sediment via laboratory experiments on core samples; and (2) quantify in-situ stress (Sv, Sh, and SH), and pore pressure (Pp) in the Kumano basin and the inner prism. We conducted triaxial compression experiments on core samples recovered from ~ 2200 meters below sea floor (mbsf) during IODP Expedition 348, at effective pressures (Pe) ranging from 8 and 36 MPa, and at temperatures of either 25°C or 60°C. Our preliminary results indicate that the prism (20 - 42% porosity) rocks deform brittlely at Pe < 22 MPa, but exhibit strain hardening at Pe = 36 MPa. This pressure-porosity condition for a brittle-ductile transition is consistent with previous work defining yield models for incoming sediments at the Nankai Trough (Kitajima and Saffer, 2012). Combining P-wave velocity logs and downhole measurements of leak-off pressure at Site C0002 with an empirical relationship between P-wave velocity, porosity, and effective stress, we show that the Kumano forearc basin is in a uniaxial-strain loading path, which defines a normal faulting stress regime (Sv>SH>=Sh), whereas the inner accretionary prism is in a triaxial-strain loading path that defines a strike-slip faulting regime (SH>Sv>Sh). We estimate excess pore pressure below ~2000 mbsf ranging from 0-12 MPa, corresponding to a pore pressure ratio λ* of 0 - 0.40.

  5. Identification of Arg-12 in the active site of Escherichia coli K1 CMP-sialic acid synthetase.

    PubMed Central

    Stoughton, D M; Zapata, G; Picone, R; Vann, W F

    1999-01-01

    Escherichia coli K1 CMP-sialic acid synthetase catalyses the synthesis of CMP-sialic acid from CTP and sialic acid. The active site of the 418 amino acid E. coli enzyme was localized to its N-terminal half. The bacterial CMP-sialic acid synthetase enzymes have a conserved motif, IAIIPARXXSKGLXXKN, at their N-termini. Several basic residues have been identified at or near the active site of the E. coli enzyme by chemical modification and site-directed mutagenesis. Only one of the lysines in the N-terminal motif, Lys-21, appears to be essential for activity. Mutation of Lys-21 in the N-terminal motif results in an inactive enzyme. Furthermore, Arg-12 of the N-terminal motif appears to be an active-site residue, based on the following evidence. Substituting Arg-12 with glycine or alanine resulted in inactive enzymes, indicating that this residue is required for enzymic activity. The Arg-12-->Lys mutant was partially active, demonstrating that a positive charge is required at this site. Steady-state kinetic analysis reveals changes in k(cat), K(m) and K(s) for CTP, which implicates Arg-12 in catalysis and substrate binding. PMID:10510306

  6. Site-specific acid-base properties of pholcodine and related compounds.

    PubMed

    Kovács, Z; Hosztafi, S; Noszál, B

    2006-11-01

    The acid-base properties of pholcodine, a cough-depressant agent, and related compounds including metabolites were studied by 1H NMR-pH titrations, and are characterised in terms of macroscopic and microscopic protonation constants. New N-methylated derivatives were also synthesized in order to quantitate site- and nucleus-specific protonation shifts and to unravel microscopic acid-base equilibria. The piperidine nitrogen was found to be 38 and 400 times more basic than its morpholine counterpart in pholcodine and norpholcodine, respectively. The protonation data show that the molecule of pholcodine bears an average of positive charge of 1.07 at physiological pH, preventing it from entering the central nervous system, a plausible reason for its lack of analgesic or addictive properties. The protonation constants of pholcodine and its derivatives are interpreted by comparing with related molecules of pharmaceutical interest. The pH-dependent relative concentrations of the variously protonated forms of pholcodine and morphine are depicted in distribution diagrams.

  7. Purification, enzymatic properties, and active site environment of a novel manganese(III)-containing acid phosphatase.

    PubMed

    Sugiura, Y; Kawabe, H; Tanaka, H; Fujimoto, S; Ohara, A

    1981-10-25

    A new manganese-containing acid phosphatase has been isolated and crystallized from sweet potato tubers. The pure enzyme contains one atom of manganese per Mr = 110,000 polypeptide and shows phosphatase activity toward various phosphate substrates. The pH optimum of the enzyme was 5.8 and the enzyme activity was inhibited by Cu2+, Zn2+, Hg2+, AsO43-, and MoO42-. This stable metalloenzyme is red-violet in color with an intense absorption band at 515 nm (epsilon - 2460). Our electronic, circular dichroism, and electron spin resonance findings strongly indicate that the Mn-valence state of the native enzyme is trivalent. When the Mn-enzyme is excited by the 5145 A line of Ar+ laser, prominent Raman lines at 1230, 1298, 1508, and 1620 cm-1 were detected. This Raman spectrum can probably be interpreted in terms of internal vibration of a coordinated tyrosine phenolate anion. The tryptophan-modified enzyme showed a positive Raman band at 370 cm-1, which is preferentially assigned to a Mn(III)-S streching mode. The modification of the Mn-enzyme by N-bromosuccinimide led to a large decrease in the fluorescence intensity of 335 nm which was dominated by its tryptophan residues within a considerable hydrophobic environment. The acid phosphatase activity was significantly decreased by the tryptophan modification. With respect to the active site donor sets, the Mn(III)-containing acid phosphatase is distinctly different from the Zn(II)-containing alkaline phosphatase. Of interest is also the appreciable similarity of some enzymatic and spectroscopic properties between the present enzyme and uteroferrin.

  8. Effect of cavity preparation method on microtensile bond strength of a self-etching primer vs phosphoric acid etchant to enamel.

    PubMed

    de Souza-Zaroni, Wanessa Christine; Delfino, Carina Sinclér; Ciccone-Nogueira, Juliane Cristina; Palma-Dibb, Regina Guenka; Corona, Silmara Aparecida Milori

    2007-10-01

    This study evaluated the effect of cavity preparation using air abrasion or carbide bur on bond strength to enamel treated with a self-etching primer (Tyrian SPE) or a phosphoric acid etchant. Twenty-four molars were divided into three groups: high-speed; standard handpiece (ST air abrasion) or supersonic handpiece (SP air abrasion) of the same air-abrasive system. The enamel surfaces were treated with one of the two etchants and the same adhesive agent One Step Plus, and then composite buildups were done with Filtek Z250. After 24 h at 37 degrees C, beams (0.8 mm2) were obtained and subjected to tensile stress in a universal testing machine (0.5 mm/min). The data were submitted to analysis of variance and Tukey's test (P < 0.05). For the conditioning agents, it was observed that the specimens conditioned with phosphoric acid presented superior results than the specimens that used Tyrian SPE. For the preparation techniques, it was verified that the SP air abrasion groups showed the highest bond strengths and carbide-bur groups presented the lowest bond strengths when the specimens were conditioned with Tyrian SPE. It can be concluded that the influence of the cavity preparation method was dependent on the conditioning system used, only when using carbide-bur preparation technique.

  9. Copper release kinetics from a long-term contaminated acid soil using a stirred flow chamber: effect of ionic strength and pH.

    PubMed

    Fernández-Calviño, David; Bermúdez-Couso, Alipio; Garrido-Rodríguez, Beatriz; Peña Rodríguez, Susana; Arias-Estévez, Manuel

    2012-02-01

    The effect of pH and ionic strength on copper release in a long-term Cu-polluted soil was studied using a stirred flow chamber. The presence of Ca(2+) and Na(+) was also evaluated. More copper was released as the ionic strength increased, and it was significantly higher in the presence of Ca(2+) than in the presence of Na(+). The maximum amount of Cu that could be released under experimental conditions increased logarithmically as the ionic strength increased, and the release rate parameters were not significantly correlated with ionic strength values. The maximum amount of Cu that could be released was similar for solutions with pH values between 5.5 and 8.5. For solutions with a pH value below 4.5, the amount of Cu released increased exponentially as the pH decreased. The release rate parameters and Cu release pattern were affected by pH, especially for more acidic solutions (pH values of 2.5 and 3.5).

  10. Dual mechanism of activation of plant plasma membrane Ca2+-ATPase by acidic phospholipids: evidence for a phospholipid binding site which overlaps the calmodulin-binding site.

    PubMed

    Meneghelli, Silvia; Fusca, Tiziana; Luoni, Laura; De Michelis, Maria Ida

    2008-09-01

    The effect of phospholipids on the activity of isoform ACA8 of Arabidopsis thaliana plasma membrane (PM) Ca2+-ATPase was evaluated in membranes isolated from Saccharomyces cerevisiae strain K616 expressing wild type or mutated ACA8 cDNA. Acidic phospholipids stimulated the basal Ca2+-ATPase activity in the following order of efficiency: phosphatidylinositol 4-monophosphate > phosphatidylserine > phosphatidylcholine approximately = phosphatidylethanolamine approximately = 0. Acidic phospholipids increased V(max-Ca2+) and lowered the value of K(0.5-Ca2+) below the value measured in the presence of calmodulin (CaM). In the presence of CaM acidic phospholipids activated ACA8 by further decreasing its K(0.5-Ca2+) value. Phosphatidylinositol 4-monophosphate and, with lower efficiency, phosphatidylserine bound peptides reproducing ACA8 N-terminus (aa 1-116). Single point mutation of three residues (A56, R59 and Y62) within the sequence A56-T63 lowered the apparent affinity of ACA8 for phosphatidylinositol 4-monophosphate by two to three fold, indicating that this region contains a binding site for acidic phospholipids. However, the N-deleted mutant Delta74-ACA8 was also activated by acidic phospholipids, indicating that acidic phospholipids activate ACA8 through a complex mechanism, involving interaction with different sites. The striking similarity between the response to acidic phospholipids of ACA8 and animal plasma membrane Ca2+-ATPase provides new evidence that type 2B Ca2+-ATPases share common regulatory properties independently of structural differences such as the localization of the terminal regulatory region at the N- or C-terminal end of the protein.

  11. A class frequency mixture model that adjusts for site-specific amino acid frequencies and improves inference of protein phylogeny

    PubMed Central

    2008-01-01

    Background Widely used substitution models for proteins, such as the Jones-Taylor-Thornton (JTT) or Whelan and Goldman (WAG) models, are based on empirical amino acid interchange matrices estimated from databases of protein alignments that incorporate the average amino acid frequencies of the data set under examination (e.g JTT + F). Variation in the evolutionary process between sites is typically modelled by a rates-across-sites distribution such as the gamma (Γ) distribution. However, sites in proteins also vary in the kinds of amino acid interchanges that are favoured, a feature that is ignored by standard empirical substitution matrices. Here we examine the degree to which the pattern of evolution at sites differs from that expected based on empirical amino acid substitution models and evaluate the impact of these deviations on phylogenetic estimation. Results We analyzed 21 large protein alignments with two statistical tests designed to detect deviation of site-specific amino acid distributions from data simulated under the standard empirical substitution model: JTT+ F + Γ. We found that the number of states at a given site is, on average, smaller and the frequencies of these states are less uniform than expected based on a JTT + F + Γ substitution model. With a four-taxon example, we show that phylogenetic estimation under the JTT + F + Γ model is seriously biased by a long-branch attraction artefact if the data are simulated under a model utilizing the observed site-specific amino acid frequencies from an alignment. Principal components analyses indicate the existence of at least four major site-specific frequency classes in these 21 protein alignments. Using a mixture model with these four separate classes of site-specific state frequencies plus a fifth class of global frequencies (the JTT + cF + Γ model), significant improvements in model fit for real data sets can be achieved. This simple mixture model also reduces the long-branch attraction problem

  12. A decade of monitoring at Swiss Long-Term Forest Ecosystem Research (LWF) sites: can we observe trends in atmospheric acid deposition and in soil solution acidity?

    PubMed

    Pannatier, Elisabeth Graf; Thimonier, Anne; Schmitt, Maria; Walthert, Lorenz; Waldner, Peter

    2011-03-01

    Trends in atmospheric acid deposition and in soil solution acidity from 1995 or later until 2007 were investigated at several forest sites throughout Switzerland to assess the effects of air pollution abatements on deposition and the response of the soil solution chemistry. Deposition of the major elements was estimated from throughfall and bulk deposition measurements at nine sites of the Swiss Long-Term Forest Ecosystem Research network (LWF) since 1995 or later. Soil solution was measured at seven plots at four soil depths since 1998 or later. Trends in the molar ratio of base cations to aluminum (BC/Al) in soil solutions and in concentrations and fluxes of inorganic N (NO(3)-N + NH(4)-N), sulfate (SO(4)-S), and base cations (BC) were used to detect changes in soil solution chemistry. Acid deposition significantly decreased at three out of the nine study sites due to a decrease in total N deposition. Total SO(4)-S deposition decreased at the nine sites, but due to the relatively low amount of SO(4)-S load compared to N deposition, it did not contribute to decrease acid deposition significantly. No trend in total BC deposition was detected. In the soil solution, no trend in concentrations and fluxes of BC, SO(4)-S, and inorganic N were found at most soil depths at five out of the seven sites. This suggests that the soil solution reacted very little to the changes in atmospheric deposition. A stronger reduction in base cations compared to aluminum was detected at two sites, which might indicate that acidification of the soil solution was proceeding faster at these sites.

  13. Suppressive effect of viscous dietary fiber on elevations of uric acid in serum and urine induced by dietary RNA in rats is associated with strength of viscosity.

    PubMed

    Koguchi, Takashi; Nakajima, Hisao; Koguchi, Hiromi; Wada, Masahiro; Yamamoto, Yuji; Innami, Satoshi; Maekawa, Akio; Tadokoro, Tadahiro

    2003-10-01

    This study was performed to clarify how dietary fiber (DF) with different viscosities would be associated with dietary RNA metabolism. Male Wistar strain rats, four weeks old, were fed diets containing a 3% (w/w) yeast RNA and a 5% (w/w) viscous DF for five days. Viscosity of DF samples used, in order of strength, were xanthan gum (XG) > guar gum (GG) > locust bean gum (LBG) > karaya gum (KG) > pectin (PE) = arabic gum (AG) > CM-cellulose (CMC) = inulin (IN). The serum uric acid concentration in the viscous DF groups significantly decreased as compared with that in the cellulose (CL) group. The urinary excretions of uric acid and allantoin in the respective groups given AG, GG, IN, KG, PE, and XG were significantly suppressed as compared with those in the CL group. The fecal RNA excretion was markedly increased in the IN, KG, PE, and XG groups in comparison to the CL group. The DF with high viscosity significantly suppressed RNA digestion by RNase A and decreased uptakes of 14C-labeled adenosine and adenosine 5'-monophosphate (5'-AMP) in rat jejunum. The results reveal that the suppressive effect of DF on elevation of serum uric acid concentration induced by dietary RNA in rats is associated with the strength of DF viscosity. The mechanism by which this is accomplished is suggested to be attributed to the inhibitions of digestion for dietary RNA and/or absorption of the hydrolyzed compounds.

  14. Carboxylic acids in gas and PM2.5 particulate phase at a rural mountain site in northeastern United States

    NASA Astrophysics Data System (ADS)

    Hussain, M. M.; Khan, A. R.; Khwaja, H. A.

    2009-12-01

    Low molecular weight carboxylic acids are important constituents of the organic fraction of atmospheric particulate matter in rural and polluted regions. The knowledge on their source is sparse, however, and organic aerosols in general need to better characterized. Atmospheric gas- and particle-phase carboxylic acids (formic, acetic, pyruvic, glyoxalic, benzoaic, adipic, succinic, malonic, and oxalic) and related compounds were measured during August 2002 at a rural site, Whiteface Mountain, NY. Formic and acetic acids were present in the PM2.5 fraction and in the gas phase. Other seven carboxylic acids were below the detection limit in all samples. Formic and acetic acid were present in the atmosphere mostly in the gaseous form with less than 10% in the PM2.5 fraction. Concentrations of formic acid and acetic acid were in the 0.5 - 2.4 ppbv and 0.6 - 1.9 ppbv ranges, respectively. Formic-to-acetic acid ratios less than one (0.88) were recorded, likely due to an increase in acetic acid contribution from direct emissions. In the fine particulate mode (PM2.5 ) the concentrations for acetic acid and formic acid were 120 - 400 and 10 - 180 ng/m3 , respectively. Backward trajectory data indicate that air mass originated at midwestern region on August 5th and gradually moved towards north on August 9th. Correlation of formic acid with sulfate was investigated to interpret their possible secondary formation pathways. A strong correlation (0.73) was observed between formic acid and sulfate in PM2.5 particulates. Since the source of sulfate found at Whiteface Mountain widely accepted as anthropogenic, its association with formic acid indicated that the later might have anthropogenic source.

  15. Eight Weeks of Phosphatidic Acid Supplementation in Conjunction with Resistance Training Does Not Differentially Affect Body Composition and Muscle Strength in Resistance-Trained Men.

    PubMed

    Andre, Thomas L; Gann, Joshua J; McKinley-Barnard, Sarah K; Song, Joon J; Willoughby, Darryn S

    2016-09-01

    This study attempted to determine the effects of eight weeks of resistance training (RT) combined with phosphatidic acid (PA) supplementation at a dose of either 250 mg or 375 mg on body composition and muscle size and strength. Twenty-eight resistance-trained men were randomly assigned to ingest 375 mg [PA375 (n = 9)] or 250 mg [PA250 (n = 9)] of PA or 375 mg of placebo [PLC (n = 10)] daily for eight weeks with RT. Supplements were ingested 60 minutes prior to RT and in the morning on non-RT days. Participants' body composition, muscle size, and lower-body muscle strength were determined before and after training/supplementation. Separate group x time ANOVAs for each criterion variable were used employing an alpha level of ≤ 0.05. Magnitude- based inferences were utilized to determine the likely or unlikely impact of PA on each criterion variable. A significant main effect for time was observed for improvements in total body mass (p = 0.003), lean mass (p = 0.008), rectus femoris cross-sectional area [RF CSA (p = 0.011)], and lower-body strength (p < 0.001), but no significant interactions were present (p > 0.05). Collectively, magnitude-based inferences determined both doses of PA to have a likely impact of increasing body mass (74.2%), lean mass (71.3%), RF CSA (92.2%), and very likely impact on increasing lower-body strength (98.1% beneficial). When combined with RT, it appears that PA has a more than likely impact on improving lower-body strength, whereas a likely impact exists for increasing muscle size and lean mass.

  16. Atmospheric oxalic acid and related secondary organic aerosols in Qinghai Lake, a continental background site in Tibet Plateau

    NASA Astrophysics Data System (ADS)

    Meng, Jingjing; Wang, Gehui; Li, Jianjun; Cheng, Chunlei; Cao, Junji

    2013-11-01

    Summertime PM2.5 aerosols collected from Qinghai Lake (3200 m a.s.l.), a remote continental site in the northeastern part of Tibetan Plateau, were analyzed for dicarboxylic acids (C2-C11), ketocarboxylic acids and α-dicarbonyals. Oxalic acid (C2) is the dominant dicarboxylic acid in the samples, followed by malonic, succinic and azelaic acids. Total dicarboxylic acids (231 ± 119 ng m-3), ketocarboxylic acids (8.4 ± 4.3 ng m-3), and α-dicarbonyls (2.7 ± 2.1 ng m-3) at the Tibetan background site are 2-5 times less than those detected in lowland areas such as 14 Chinese megacities. Compared to those in other urban and marine areas enhancements in relative abundances of C2/total diacids and diacids-C/WSOC of the PM2.5 samples suggest that organic aerosols in the region are more oxidized due to strong solar radiation. Molecular compositions and air mass trajectories demonstrate that the above secondary organic aerosols in the Qinghai Lake atmosphere are largely derived from long-range transport. Ratios of oxalic acid, glyoxal and methylglyoxal to levoglucosan in PM2.5 aerosols emitted from household burning of yak dung, a major energy source for Tibetan in the region, are 30-400 times lower than those in the ambient air, which further indicates that primary emission from biomass burning is a negligible source of atmospheric oxalic acid and α-dicarbonyls at this background site.

  17. Isotope geochemistry of waters affected by acid mine drainage in old labour sites (SE, Spain).

    NASA Astrophysics Data System (ADS)

    Pérez-Sirvent, Carmen; Martinez-Sanchez, Maria Jose; Garcia-Lorenzo, Maria Luz; Agudo, Ines; Hernandez-Cordoba, Manuel; Recio, Clemente

    2015-04-01

    The ore deposits of this zone have iron, lead and zinc as the main metal components. Iron is present in oxides, hydroxides, sulfides, sulfates, carbonates, and silicates; lead and zinc occur in sulfides (galena and sphalerite, respectively), carbonates, sulfates, and lead or zinc-bearing (manganese, iron) oxides. Mining started with the Romans and activity peaked in the second half of the 19th century and throughout the 20th century until the 1980's. From 1940 to 1957, mineral concentration was made by froth flotation and, prior to this, by gravimetric techniques. The mining wastes, or tailings, with a very fine particle size were deposited inland (tailings dams) and, since 1957, huge releases were made in directly the sea coast. The objective of this work was to evaluate processes affecting waters from abandoned mine sites by way of stable isotopic analysis, particularly H and O stable isotopes from water and S and O from dissolved sulfates. Several common chemical and physical processes, such as evaporation, water-rock interaction and mixing could alter water isotopic composition. Evaporation, which causes an enrichment in δD and δ18O in the residual water, is an important process in semiarid areas. The results obtained indicate that, for sites near the coast, waters are meteoric, and marine infiltration only takes place in the deepest layers near the shore or if water remains stagnated in sediments with low permeability. The main source of sulfate was the oxidation of sulfides, resulting in the liberation of acid, sulfate and metals. In order to assess the mechanism responsible for sulfide oxidation, the stoichiometric isotope balance model and the general isotope balance model were tested, suggesting that the oxidation via Fe3+ was predominant in the surface, and controlled by A. ferrooxidans, while at depth, sulfate reduction occurred.

  18. Trans-gamma-hydroxycrotonic acid binding sites in brain: evidence for a subpopulation of gamma-hydroxybutyrate sites.

    PubMed

    Hechler, V; Schmitt, M; Bourguignon, J J; Maitre, M

    1990-03-02

    Trans-gamma-hydroxycrotonate (THCA), a compound naturally present in rat brain, possesses high-affinity binding sites with a heterogeneous distribution which are superimposable with those for gamma-hydroxybutyrate (GHB). Binding studies of THCA on rat brain membranes revealed two binding components, one of high affinity (Kd1, 7 nM, Bmax1 42 fmol/mg protein) and the other of low affinity (Kd2, 2 microM, Bmax2 13 pmol/mg protein). Displacement curves of [3H]THCA by THCA and GHB or of [3H]GHB by THCA are in favour of the existence of a specific high affinity site for THCA. Quantitative autoradiography with image analysis of [3H]THCA binding in rat brain slices indicated that [3H]THCA high affinity binding was displaced at a lower potency by GHB. THCA showed also some selectivity in displacing [3H]GHB from its high affinity binding site (Kd = 95 nM). This mutual overlap favours a subpopulation of GHB receptors, which have THCA as a natural ligand, showing partial agonistic properties compared to GHB. The functional significance of this result remains unknown.

  19. Iodine 125-lysergic acid diethylamide binds to a novel serotonergic site on rat choroid plexus epithelial cells

    SciTech Connect

    Yagaloff, K.A.; Hartig, P.R.

    1985-12-01

    /sup 125/I-Lysergic acid diethylamide (/sup 125/I-LSD) binds with high affinity to serotonergic sites on rat choroid plexus. These sites were localized to choroid plexus epithelial cells by use of a novel high resolution stripping film technique for light microscopic autoradiography. In membrane preparations from rat choroid plexus, the serotonergic site density was 3100 fmol/mg of protein, which is 10-fold higher than the density of any other serotonergic site in brain homogenates. The choroid plexus site exhibits a novel pharmacology that does not match the properties of 5-hydroxytryptamine-1a (5-HT1a), 5-HT1b, or 5-HT2 serotonergic sites. /sup 125/I-LSD binding to the choroid plexus site is potently inhibited by mianserin, serotonin, and (+)-LSD. Other serotonergic, dopaminergic, and adrenergic agonists and antagonists exhibit moderate to weak affinities for this site. The rat choroid plexus /sup 125/I-LSD binding site appears to represent a new type of serotonergic site which is located on non-neuronal cells in this tissue.

  20. Spectrophotometric determination of acidity constants of salicylaldoxime in aqueous solution at 25 °C and ionic strength of 0.5 M controlled with NaCl

    NASA Astrophysics Data System (ADS)

    Tshuma, Joel; Alarcón-Ángeles, Georgina; Palacios-Beas, Elia; Vargas-García, Roberto; Ramírez-Silva, María Teresa; Rojas-Hernández, Alberto

    2007-04-01

    The equilibrium constants of salicylaldoxime in water at 25 °C, 0.5 M of ionic strength with NaCl and concentration of 1 × 10 -4 M were determined spectrophotometrically. The spectral data were processed using SQUAD program. The salicylaldoxime in acid medium has the value of p Ka1 = 1.224 ± 0.027. In alkaline medium the salicylaldoxime has the values of p Ka2 = 8.551 ± 0.024 and p Ka3 = 11.728 ± 0.016.

  1. Spectrophotometric determination of acidity constants of salicylaldoxime in aqueous solution at 25 degrees C and ionic strength of 0.5 M controlled with NaCl.

    PubMed

    Tshuma, Joel; Alarcón-Angeles, Georgina; Palacios-Beas, Elia; Vargas-García, Roberto; Ramírez-Silva, María Teresa; Rojas-Hernández, Alberto

    2007-04-01

    The equilibrium constants of salicylaldoxime in water at 25 degrees C, 0.5 M of ionic strength with NaCl and concentration of 1x10(-4) M were determined spectrophotometrically. The spectral data were processed using SQUAD program. The salicylaldoxime in acid medium has the value of pKa1=1.224+/-0.027. In alkaline medium the salicylaldoxime has the values of pKa2=8.551+/-0.024 and pKa3=11.728+/-0.016.

  2. Eight Weeks of Phosphatidic Acid Supplementation in Conjunction with Resistance Training Does Not Differentially Affect Body Composition and Muscle Strength in Resistance-Trained Men

    PubMed Central

    Andre, Thomas L.; Gann, Joshua J.; McKinley-Barnard, Sarah K.; Song, Joon J.; Willoughby, Darryn S.

    2016-01-01

    This study attempted to determine the effects of eight weeks of resistance training (RT) combined with phosphatidic acid (PA) supplementation at a dose of either 250 mg or 375 mg on body composition and muscle size and strength. Twenty-eight resistance-trained men were randomly assigned to ingest 375 mg [PA375 (n = 9)] or 250 mg [PA250 (n = 9)] of PA or 375 mg of placebo [PLC (n = 10)] daily for eight weeks with RT. Supplements were ingested 60 minutes prior to RT and in the morning on non-RT days. Participants’ body composition, muscle size, and lower-body muscle strength were determined before and after training/supplementation. Separate group x time ANOVAs for each criterion variable were used employing an alpha level of ≤ 0.05. Magnitude- based inferences were utilized to determine the likely or unlikely impact of PA on each criterion variable. A significant main effect for time was observed for improvements in total body mass (p = 0.003), lean mass (p = 0.008), rectus femoris cross-sectional area [RF CSA (p = 0.011)], and lower-body strength (p < 0.001), but no significant interactions were present (p > 0.05). Collectively, magnitude-based inferences determined both doses of PA to have a likely impact of increasing body mass (74.2%), lean mass (71.3%), RF CSA (92.2%), and very likely impact on increasing lower-body strength (98.1% beneficial). When combined with RT, it appears that PA has a more than likely impact on improving lower-body strength, whereas a likely impact exists for increasing muscle size and lean mass. Key points In response to eight weeks resistance training and PLC and PA (375 mg and 250 mg) supplementation, similar increases in lower-body muscle strength occurred in all three groups; however, the increases were not different between supplement groups. In response to eight weeks resistance training and PLC and PA (375 mg and 250 mg) supplementation, similar increases in lean mass occurred in all three groups; however, the increases were

  3. Elucidating the structure of surface acid sites on {gamma}-Al{sub 2}O{sub 3}.

    SciTech Connect

    Chupas, P. J.; Chapman, K. W.; Halder, G. J.

    2011-05-12

    Differential pair distribution function analysis was applied to resolve, with crystallographic detail, the structure of catalytic sites on the surface of nanoscale {gamma}-Al{sup 2}O{sub 3}. The structure was determined for a basic probe molecule, monomethylamine (MMA), bound at the minority Lewis acid sites. These active sites were found to be five-coordinate, forming distorted octahedra upon MMA binding. This approach could be applied to study the interaction of molecules at surfaces in dye-sensitized solar cells, nanoparticles, sensors, materials for waste remediation, and catalysts.

  4. CHARACTERIZATION OF INDIVIDUAL CHEMICAL REACTIONS CONSUMING ACID DURING NUCLEAR WASTE PROCESSING AT THE SAVANNAH RIVER SITE - 136B

    SciTech Connect

    Koopman, D.; Pickenheim, B.; Lambert, D.; Newell, J.; Stone, M.

    2009-09-02

    Conversion of legacy radioactive high-level waste at the Savannah River Site into a stable glass waste form involves a chemical pretreatment process to prepare the waste for vitrification. Waste slurry is treated with nitric and formic acids to achieve certain goals. The total quantity of acid added to a batch of waste slurry is constrained by the catalytic activity of trace noble metal fission products in the waste that can convert formic acid into hydrogen gas at many hundreds of times the radiolytic hydrogen generation rate. A large block of experimental process simulations were performed to characterize the chemical reactions that consume acid prior to hydrogen generation. The analysis led to a new equation for predicting the quantity of acid required to process a given volume of waste slurry.

  5. Vitamin B12, folic acid, ferritin and haematological variables among Thai construction site workers in urban Bangkok.

    PubMed

    Tungtrongchitr, R; Pongpaew, P; Phonrat, B; Chanjanakitskul, S; Paksanont, S; Migasena, P; Schelp, F P

    1995-01-01

    Serum vitamin B12, folic acid, ferritin and haematological variables were investigated in eighty-seven male and nineteen female construction site workers in Bangkok. Haemoglobin concentration, haematocrit and MCHC were found to be higher in male than in female workers. Serum ferritin was slightly higher in males than in females. Serum B12 was found to be higher in male than in female workers and serum folic acid level were significantly higher in female than in male workers. Vitamin B12 deficiency was found in 2.3 per cent and folic acid deficiency in 6.9 per cent of the male workers. Serum vitamin B12 and folic acid levels were normal for female workers. The adequate serum levels of vitamin B12 and folic acid might be the result of the habit of the workers to consume tonic drinks which contain glucose, caffeine, and vitamins especially vitamins B6, and B12.

  6. High-Temperature Decomposition of Brønsted Acid Sites in Gallium-Substituted Zeolites

    SciTech Connect

    K Al-majnouni; N Hould; W Lonergan; D Vlachos; R Lobo

    2011-12-31

    The dehydroxylation of Broensted acid sites (BAS) in Ga-substituted zeolites was investigated at temperatures up to 850 C using X-ray absorption spectroscopy (XAS), Fourier transform infrared spectroscopy (FTIR), and mass spectrometry-temperature programmed desorption (MS-TPD). X-ray absorption near-edge spectroscopy (XANES) revealed that the majority of gallium has tetrahedral coordination even after complete dehydroxylation. The interatomic gallium-oxygen distance and gallium coordination number determined by extended X-ray absorption fine structure (EXAFS) are consistent with gallium in tetrahedral coordination at low T (< 550 C). Upon heating Ga-Beta and Ga-ZSM5 to 850 C, analysis of the EXAFS showed that 70 and 80% of the gallium was still in tetrahedral coordination. The remainder of the gallium was found to be in octahedral coordination. No trigonal Ga atoms were observed. FTIR measurements carried out at similar temperatures show that the intensity of the OH vibration due to BAS has been eliminated. MS-TPD revealed that hydrogen in addition to water evolved from the samples during dehydroxylation. This shows that dehydrogenation in addition to dehydration is a mechanism that contributes to BAS decomposition. Dehydrogenation was further confirmed by exposing the sample to hydrogen to regenerate some of the BAS as monitored by FTIR and MS-TPD.

  7. Evolution of translation machinery in recoded bacteria enables multi-site incorporation of nonstandard amino acids

    PubMed Central

    Amiram, Miriam; Haimovich, Adrian D; Fan, Chenguang; Wang, Yane-Shih; Aerni, Hans-Rudolf; Ntai, Ioanna; Moonan, Daniel W; Ma, Natalie J; Rovner, Alexis J; Hong, Seok Hoon; Kelleher, Neil L; Goodman, Andrew L; Jewett, Michael C; Söll, Dieter; Rinehart, Jesse; Isaacs, Farren J

    2016-01-01

    Expansion of the genetic code with nonstandard amino acids (nsAAs) has enabled biosynthesis of proteins with diverse new chemistries. However, this technology has been largely restricted to proteins containing a single or few nsAA instances. Here we describe an in vivo evolution approach in a genomically recoded Escherichia coli strain for the selection of orthogonal translation systems capable of multi-site nsAA incorporation. We evolved chromosomal aminoacyl-tRNA synthetases (aaRSs) with up to 25-fold increased protein production for p-acetyl-L-phenylalanine and p-azido-L-phenylalanine (pAzF). We also evolved aaRSs with tunable specificities for 14 nsAAs, including an enzyme that efficiently charges pAzF while excluding 237 other nsAAs. These variants enabled production of elastin-like-polypeptides with 30 nsAA residues at high yields (~50 mg/L) and high accuracy of incorporation (>95%). This approach to aaRS evolution should accelerate and expand our ability to produce functionalized proteins and sequence-defined polymers with diverse chemistries. PMID:26571098

  8. Characterization of excipient and tableting factors that influence folic acid dissolution, friability, and breaking strength of oil- and water-soluble multivitamin with minerals tablets.

    PubMed

    Du, Jianping; Hoag, Stephen W

    2003-11-01

    The goal of this study is to characterize the formulation and processing factors that influence folic acid dissolution from oil- and water-soluble multivitamin with minerals tablet formulations for direct compression. The following parameters were studied: bulk filler solubility, soluble to insoluble bulk filler ratio, triturating agent (preblending carrier) solubility, disintegrant usage, compression pressure, and folic acid particle size. Folic acid particle size was determined by using light microscopy, and surface area was measured by using BET adsorption. The tablets were compressed on an instrumented Stokes B2 tablet press, and the friability, weight variation, and dissolution were measured according to USP methods, along with tablet breaking strength. In summary, we found the following factors to be critical to folic acid dissolution: bulk filler solubility (soluble fillers, such as maltose, increase folic acid dissolution); disintegrant amount (levels less than 0.4% (w/w) are ineffectual, whereas levels greater than 1.2% (w/w) did not further increase dissolution); and compression force (generally, maltose produce harder tablets). In addition, folic acid dissolution was less affected by changes in compaction pressure when a "super" disintegrant and maltose, as a bulk filler, were used. It was determined that the trituration agent did not play a significant role in folic acid dissolution. In the range of parameters studied, statistical analysis found no significant interactions between the parameters studied, which means they act independently in an additive manner. The results also show that no one factor is completely responsible for dissolution failure. Thus, it is the combination of formulation factors and processing conditions that collectively add up to produce dissolution failure; however, the use of a disintegrant and a soluble filler such as maltose can make a formulation more robust to the inevitable changes that can occur during commercial

  9. Site-specific dynamics of amyloid formation and fibrillar configuration of Aβ(1-23) using an unnatural amino acid.

    PubMed

    Liu, Haiyang; Lantz, Richard; Cosme, Patrick; Rivera, Nelson; Andino, Carlos; Gonzalez, Walter G; Terentis, Andrew C; Wojcikiewicz, Ewa P; Oyola, Rolando; Miksovska, Jaroslava; Du, Deguo

    2015-04-25

    We identify distinct site-specific dynamics over the time course of Aβ1-23 amyloid formation by using an unnatural amino acid, p-cyanophenylalanine, as a sensitive fluorescent and Raman probe. Our results also suggest the key role of an edge-to-face aromatic interaction in the conformational conversion to form and stabilize β-sheet structure.

  10. Effect of a self-etching primer and phosphoric acid etching on the bond strength of 4-META/MMA-TBB resin to human enamel.

    PubMed

    Nogawa, Hiroshi; Koizumi, Hiroyasu; Saiki, Osamu; Hiraba, Haruto; Nakamura, Mitsuo; Matsumura, Hideo

    2015-01-01

    The purpose of this study was to evaluate the shear bond strength and durability of 4-META/MMA-TBB resin to human enamel. A self-etching primer that contained 4-META (Teeth Primer, TP) and 35-45% or 60-65% concentrations of phosphoric acid (K-Etchant Gel, KE, and Super Bond C&B Red Activator, RA) were used as the surface treatment agents. A methyl methacrylate (MMA)-based self-polymerizing resin (Super-Bond C&B) was used as a luting agent. The shear bond strength was determined both pre and post thermocycling. The results were statistically analyzed with a non-parametric procedure. The post-thermocycling shear bond strength of the TP group was significantly higher than that of other groups, and that of the KE group was significantly higher compared with the RA group. These results demonstrated that 4-META was effective. Furthermore, when the degree of tooth demineralization was compared, surface treatment with less demineralization using TP was the most effective treatment.

  11. Forced Ambiguity of the Leucine Codons for Multiple-Site-Specific Incorporation of a Noncanonical Amino Acid

    PubMed Central

    Kwon, Inchan; Choi, Eun Sil

    2016-01-01

    Multiple-site-specific incorporation of a noncanonical amino acid into a recombinant protein would be a very useful technique to generate multiple chemical handles for bioconjugation and multivalent binding sites for the enhanced interaction. Previously combination of a mutant yeast phenylalanyl-tRNA synthetase variant and the yeast phenylalanyl-tRNA containing the AAA anticodon was used to incorporate a noncanonical amino acid into multiple UUU phenylalanine (Phe) codons in a site-specific manner. However, due to the less selective codon recognition of the AAA anticodon, there was significant misincorporation of a noncanonical amino acid into unwanted UUC Phe codons. To enhance codon selectivity, we explored degenerate leucine (Leu) codons instead of Phe degenerate codons. Combined use of the mutant yeast phenylalanyl-tRNA containing the CAA anticodon and the yPheRS_naph variant allowed incorporation of a phenylalanine analog, 2-naphthylalanine, into murine dihydrofolate reductase in response to multiple UUG Leu codons, but not to other Leu codon sites. Despite the moderate UUG codon occupancy by 2-naphthylalaine, these results successfully demonstrated that the concept of forced ambiguity of the genetic code can be achieved for the Leu codons, available for multiple-site-specific incorporation. PMID:27028506

  12. Dynamic HypA zinc site is essential for acid viability and proper urease maturation in Helicobacter pylori

    PubMed Central

    Johnson, Ryan C.; Hu, Heidi Q.; Merrell, D. Scott; Maroney, Michael J.

    2015-01-01

    Helicobacter pylori requires urease activity in order to survive in the acid environment of the human stomach. Urease is regulated in part by nickelation, a process that requires the HypA protein, which is a putative nickel metallochaperone that is generally associated with hydrogenase maturation. However, in H. pylori, HypA plays a dual role. In addition to an N-terminal nickel binding site, HypA proteins also contain a structural zinc site that is coordinated by two rigorously conserved CXXC sequences, which in H. pylori are flanked by His residues. These structural Zn sites are known to be dynamic, converting from Zn(Cys)4 centers at pH 7.2 to Zn(Cys)2(His)2 centers at pH 6.3 in the presence of Ni(II) ions. In this study, mutant strains of H. pylori that express zinc site variants of the HypA protein are used to show that the structural changes in the zinc site are important for the acid viability of the bacterium, and that a reduction in acid viability in these variants can be traced in large measure to deficient urease activity. This in turn leads to a model that connects the Zn(Cys)4 coordination to urease maturation. PMID:25608738

  13. The amino acid sequence around the active-site cysteine and histidine residues, and the buried cysteine residue in ficin.

    PubMed

    Husain, S S; Lowe, G

    1970-04-01

    Ficin that had been prepared from the latex of Ficus glabrata by salt fractionation and chromatography on carboxymethylcellulose was completely and irreversibly inhibited with 1,3-dibromo[2-(14)C]acetone and then treated with N-(4-dimethylamino-3,5-dinitrophenyl)maleimide in 6m-guanidinium chloride. After reduction and carboxymethylation of the labelled protein, it was digested with trypsin and alpha-chymotrypsin. Two radioactive peptides and two coloured peptides were isolated chromatographically and their sequences determined. The radioactive peptides revealed the amino acid sequences around the active-site cysteine and histidine residues and showed a high degree of homology with the omino acid sequence around the active-site cysteine and histidine residues in papain. The coloured peptides allowed the amino acid sequence around the buried cysteine residue in ficin to be determined.

  14. Influence of pH, soil humic/fulvic acid, ionic strength, foreign ions and addition sequences on adsorption of Pb(II) onto GMZ bentonite.

    PubMed

    Wang, Suowei; Hu, Jun; Li, Jiaxing; Dong, Yunhui

    2009-08-15

    This work contributed to the adsorption of Pb(II) onto GMZ bentonite in the absence and presence of soil humic acid (HA)/fulvic acid (FA) using a batch technique. The influences of pH from 2 to 12, ionic strengths from 0.004M to 0.05M NaNO(3), soil HA/FA concentrations from 1.6 mg/L to 20mg/L, foreign cations (Li+, Na+, K+), anions (Cl(-), NO(3)(-)), and addition sequences on the adsorption of Pb(II) onto GMZ bentonite were tested. The adsorption isotherms of Pb(II) were determined at pH 3.6+/-0.1 and simulated with the Langmuir, Freundlich, and D-R adsorption models, respectively. The results demonstrated that the adsorption of Pb(II) onto GMZ bentonite increased with increasing pH from 2 to 6. HA was shown to enhance Pb(II) adsorption at low pH, but to reduce Pb(II) adsorption at high pH, whereas FA was shown to decrease Pb(II) adsorption at pH from 2 to 11. The results also demonstrated that the adsorption was strongly dependent on ionic strength and slightly dependent on the concentration of HA/FA. The adsorption of Pb(II) onto GMZ bentonite was dependent on foreign ions in solution. The addition sequences of bentonite/Pb(II)/HA had no effect on the adsorption of Pb(II).

  15. Effects of sex and site on amino acid metabolism enzyme gene expression and activity in rat white adipose tissue

    PubMed Central

    Arriarán, Sofía; Agnelli, Silvia; Remesar, Xavier; Fernández-López, José Antonio

    2015-01-01

    Background and Objectives. White adipose tissue (WAT) shows marked sex- and diet-dependent differences. However, our metabolic knowledge of WAT, especially on amino acid metabolism, is considerably limited. In the present study, we compared the influence of sex on the amino acid metabolism profile of the four main WAT sites, focused on the paths related to ammonium handling and the urea cycle, as a way to estimate the extent of WAT implication on body amino-nitrogen metabolism. Experimental Design. Adult female and male rats were maintained, undisturbed, under standard conditions for one month. After killing them under isoflurane anesthesia. WAT sites were dissected and weighed. Subcutaneous, perigonadal, retroperitoneal and mesenteric WAT were analyzed for amino acid metabolism gene expression and enzyme activities. Results. There was a considerable stability of the urea cycle activities and expressions, irrespective of sex, and with only limited influence of site. Urea cycle was more resilient to change than other site-specialized metabolic pathways. The control of WAT urea cycle was probably related to the provision of arginine/citrulline, as deduced from the enzyme activity profiles. These data support a generalized role of WAT in overall amino-N handling. In contrast, sex markedly affected WAT ammonium-centered amino acid metabolism in a site-related way, with relatively higher emphasis in males’ subcutaneous WAT. Conclusions. We found that WAT has an active amino acid metabolism. Its gene expressions were lower than those of glucose-lipid interactions, but the differences were quantitatively less important than usually reported. The effects of sex on urea cycle enzymes expression and activity were limited, in contrast with the wider variations observed in other metabolic pathways. The results agree with a centralized control of urea cycle operation affecting the adipose organ as a whole. PMID:26587356

  16. Gamma-aminobutyric acid-modulated benzodiazepine binding sites in bacteria

    SciTech Connect

    Lummis, S.C.R.; Johnston, G.A.R. ); Nicoletti, G. ); Holan, G. )

    1991-01-01

    Benzodiazepine binding sites, which were once considered to exist only in higher vertebrates, are here demonstrated in the bacteria E. coli. The bacterial ({sup 3}H)diazepam binding sites are modulated by GABA; the modulation is dose dependent and is reduced at high concentrations. The most potent competitors of E.Coli ({sup 3}H)diazepam binding are those that are active in displacing ({sup 3}H)benzodiazepines from vertebrate peripheral benzodiazepine binding sites. These vertebrate sites are not modulated by GABA, in contrast to vertebrate neuronal benzodiazepine binding sites. The E.coli benzodiazepine binding sites therefore differ from both classes of vertebrate benzodiazepine binding sites; however the ligand spectrum and GABA-modulatory properties of the E.coli sites are similar to those found in insects. This intermediate type of receptor in lower species suggests a precursor for at least one class of vertebrate benzodiazepine binding sites may have existed.

  17. Retinoic acid signalling centres in the avian embryo identified by sites of expression of synthesising and catabolising enzymes.

    PubMed

    Blentic, Aida; Gale, Emily; Maden, Malcolm

    2003-05-01

    Retinoic acid is an important signalling molecule in the developing embryo, but its precise distribution throughout development is very difficult to determine by available techniques. Examining the distribution of the enzymes by which it is synthesised by using in situ hybridisation is an alternative strategy. Here, we describe the distribution of three retinoic acid synthesising enzymes and one retinoic acid catabolic enzyme during the early stages of chick embryogenesis with the intention of identifying localized retinoic acid signalling regions. The enzymes involved are Raldh1, Raldh2, Raldh3, and Cyp26A1. Although some of these distributions have been described before, here we assemble them all in one species and several novel sites of enzyme expression are identified, including Hensen's node, the cardiac endoderm, the presumptive pancreatic endoderm, and the dorsal lens. This study emphasizes the dynamic pattern of expression of the enzymes that control the availability of retinoic acid as well as the role that retinoic acid plays in the development of many regions of the embryo throughout embryogenesis. This strategy provides a basis for understanding the phenotypes of retinoic acid teratology and retinoic acid-deficiency syndromes.

  18. Contrasting microbial functional genes in two distinct saline-alkali and slightly acidic oil-contaminated sites.

    PubMed

    Liang, Yuting; Zhao, Huihui; Zhang, Xu; Zhou, Jizhong; Li, Guanghe

    2014-07-15

    To compare the functional gene structure and diversity of microbial communities in saline-alkali and slightly acidic oil-contaminated sites, 40 soil samples were collected from two typical oil exploration sites in North and South China and analyzed with a comprehensive functional gene array (GeoChip 3.0). The overall microbial pattern was significantly different between the two sites, and a more divergent pattern was observed in slightly acidic soils. Response ratio was calculated to compare the microbial functional genes involved in organic contaminant degradation and carbon, nitrogen, phosphorus, and sulfur cycling. The results indicated a significantly low abundance of most genes involved in organic contaminant degradation and in the cycling of nitrogen and phosphorus in saline-alkali soils. By contrast, most carbon degradation genes and all carbon fixation genes had similar abundance at both sites. Based on the relationship between the environmental variables and microbial functional structure, pH was the major factor influencing the microbial distribution pattern in the two sites. This study demonstrated that microbial functional diversity and heterogeneity in oil-contaminated environments can vary significantly in relation to local environmental conditions. The limitation of nitrogen and phosphorus and the low degradation capacity of organic contaminant should be carefully considered, particularly in most oil-exploration sites with saline-alkali soils.

  19. A study of oleic acid and 2,4-DHB acid aerosols using an IR-VUV-ITMS: insights into the strengths and weaknesses of the technique.

    PubMed

    Hanna, Sarah J; Campuzano-Jost, Pedro; Simpson, Emily A; Burak, Itamar; Blades, Michael W; Hepburn, John W; Bertram, Allan K

    2009-09-28

    An investigation of oleic acid and 2,4-dihydroxybenzoic (DHB) acid aerosols was carried out using an aerosol mass spectrometer with pulsed lasers for vaporization and ionization and an ion trap for mass analysis. The extent of ion fragmentation was studied as a function of both vaporization energy and ionization wavelength. Low CO2 laser energies in the vaporization stage and near-threshold single photon ionization resulted in the least fragmented mass spectra. For DHB, only the molecular ion was observed, but for oleic acid fragmentation could not be eliminated. Tandem MS of the main fragment peak from oleic acid was carried out and provided a tool for compound identification. Photoionization efficiency curves were also collected for both DHB and oleic acid and the appearance energies of both parent and fragment ions were measured. Evidence for fragmentation occurring post-ionization is given by the similar appearance energies for both the parent and fragment ions. The results from this study were compared with those from similar experiments undertaken with time-of-flight (TOF) mass analyzers. The degree of fragmentation in the ion trap was considerably higher than that seen with TOF systems, particularly for oleic acid. This was attributed to the long storage interval in the ion trap which allows time for metastable ions to decay. Differences in the degree of fragmentation between the ion trap and TOF studies also provided further evidence for fragmentation occurring post-ionization. For 2,4-dihydroxybenzoic acid, the long delay prior to mass analysis also allowed time for reactions with background gases, in this case water, to occur.

  20. Effects of acidic recharge on groundwater at the St. Kevin Gulch site, Leadville, Colorado

    USGS Publications Warehouse

    Paschke, S.S.; Harrison, W.J.; Walton-Day, K.

    2001-01-01

    The acid rock drainage-affected stream of St. Kevin Gulch recharges the Quaternary sand and gravel aquifer of Tennessee Park, near Leadville, Colorado, lowering pH and contributing iron, cadmium, copper, zinc and sulphate to the ground-water system. Dissolved metal mobility is controlled by the seasonal spring runoff as well as oxidation/reduction (redox) reactions in the aquifer. Oxidizing conditions occur in the unconfined portions of the aquifer whilst sulphate-reducing conditions are found down gradient where semi-confined groundwater flow occurs beneath a natural wetland. Iron-reducing conditions occur in the transition from unconfined to semi-confined groundwater flow. Dissolved iron concentrations are low to not detectable in the alluvial fan recharge zone and increase in a down gradient direction. The effects of low-pH, metal-rich recharge are pronounced during low-flow in the fall when there is a defined area of low pH groundwater with elevated concentrations of dissolved zinc, cadmium, copper and sulphate adjacent to St. Kevin Gulch. Dissolved metal and sulphate concentrations in the recharge zone are diluted during spring runoff, although the maximum concentrations of dissolved zinc, cadmium, copper and sulphate occur at selected down gradient locations during high flow. Dissolved zinc, cadmium and copper concentrations are low to not detectable, whereas dissolved iron concentrations are greatest, in groundwater samples from the sulphate-reducing zone. Attenuation of zinc, cadmium and copper beneath the wetland suggests sulphide mineral precipitation is occurring in the semi-confined aquifer, in agreement with previous site investigations and saturation index calculations. Adsorption of dissolved zinc, cadmium and copper onto iron hydroxides is a minor attenuation process due to the low pH of the groundwater system.

  1. Acid-Sulfate-Weathering Activity in Shergottite Sites on Mars Recorded in Grim Glasses

    NASA Technical Reports Server (NTRS)

    Rao, M. N.; Nyquist, L. E.; Ross, K.; Sutton, S. R.; Schwandt, C. S.

    2011-01-01

    Based on mass spectrometric studies of sulfur species in Shergotty and EET79001, [1] and [2] showed that sulfates and sulfides occur in different proportions in shergottites. Sulfur speciation studies in gas-rich impact-melt (GRIM) glasses in EET79001 by the XANES method [3] showed that S K-XANES spectra in GRIM glasses from Lith A indicate that S is associated with Ca and Al presumably as sulfides/sulfates whereas the XANES spectra of amorphous sulfide globules in GRIM glasses from Lith B indicate that S is associated with Fe as FeS. In these amorphous iron sulfide globules, [4] found no Ni using FE-SEM and suggested that the globules resulting from immiscible sulfide melt may not be related to the igneous iron sulfides having approximately 1-3% Ni. Furthermore, in the amorphous iron sulfides from 507 GRIM glass, [5] determined delta(sup 34)S values ranging from +3.5%o to -3.1%o using Nano-SIMS. These values plot between the delta(sup 34)S value of +5.25%o determined in the sulfate fraction in Shergotty [6] at one extreme and the value of -1.7%o obtained for igneous sulfides in EET79001 and Shergotty [7] at the other. These results suggest that the amorphous Fe-S globules likely originated by shock reduction of secondary iron sulfate phases occurring in the regolith precursor materials during impact [7]. Sulfates in the regolith materials near the basaltic shergottite sites on Mars owe their origin to surficial acid-sulfate interactions. We examine the nature of these reactions by studying the composition of the end products in altered regolith materials. For the parent material composition, we use that of the host shergottite material in which the impact glasses are situated.

  2. Trace metal biogeochemistry in mangrove ecosystems: a comparative assessment of acidified (by acid sulfate soils) and non-acidified sites.

    PubMed

    Nath, Bibhash; Birch, Gavin; Chaudhuri, Punarbasu

    2013-10-01

    The generation of acidity and subsequent mobilization of toxic metals induced by acid sulfate soils (ASSs) are known to cause severe environmental damage to many coastal wetlands and estuaries of Australia and worldwide. Mangrove ecosystems serve to protect coastal environments, but are increasingly threatened from such ASS-induced acidification due to variable hydrological conditions (i.e., inundation-desiccation cycles). However, the impact of such behaviors on trace metal distribution, bio-availability and accumulation in mangrove tissues, i.e., leaves and pneumatophores, are largely unknown. In this study, we examined how ASS-induced acidifications controlled trace metal distribution and bio-availability in gray mangrove (Avicennia marina) soils and in tissues in the Kooragang wetland, New South Wales, Australia. We collected mangrove soils, leaves and pneumatophores from a part of the wetland acidified from ASS (i.e., an affected site) for detailed biogeochemical studies. The results were compared with samples collected from a natural intertidal mangrove forest (i.e., a control site) located within the same wetland. Soil pH (mean: 5.90) indicated acidic conditions in the affected site, whereas pH was near-neutral (mean: 7.17) in the control site. The results did not show statistically significant differences in near-total and bio-available metal concentrations, except for Fe and Mn, between affected and control sites. Iron concentrations were significantly (p values≤0.001) greater in the affected site, whereas Mn concentrations were significantly (p values≤0.001) greater in the control site. However, large proportions of near-total metals were potentially bio-available in control sites. Concentrations of Fe and Ni were significantly (p values≤0.001) greater in leaves and pneumatophores of the affected sites, whereas Mn, Cu, Pb and Zn were greater in control sites. The degree of metal bio-accumulation in leaves and pneumatophores suggest contrasting

  3. A Mutational Analysis of the Active Site Loop Residues in cis-3-Chloroacrylic Acid Dehalogenase

    PubMed Central

    Schroeder, Gottfried K.; Huddleston, Jamison P.; Johnson, William H.; Whitman, Christian P.

    2013-01-01

    cis -3-Chloroacrylic acid dehalogenase (cis-CaaD) from Pseudomonas pavonaceae 170 and a homologue from Corynebacterium glutamicum designated Cg10062 share 34% sequence identity (54% similarity). The former catalyzes a key step in a bacterial catabolic pathway for the nematocide 1,3-dichloropropene, whereas the latter has no known biological activity. Although Cg10062 has the six active site residues (Pro-1, His-28, Arg-70, Arg-73, Tyr-103, Glu-114) that are critical for cis-CaaD activity, it shows only a low level cis-CaaD activity and lacks the specificity of cis-CaaD: Cg10062 processes both isomers of 3-chloroacrylate with a preference for the cis-isomer. Although the basis for these differences is unknown, a comparison of the crystal structures of the enzymes covalently modified by an adduct resulting from their incubation with the same inhibitor offers a possible explanation. A 6-residue active site loop in cis-CaaD shows a strikingly different conformation from that observed in Cg10062: the loop closes down on the active site of cis-CaaD, but not on that of Cg10062. In order to examine what this loop might contribute to cis-CaaD catalysis and specificity, the residues were changed individually to those found in Cg10062. Subsequent kinetic and mechanistic analysis suggests that the T34A mutant of cis-CaaD is more Cg10062-like. The mutant enzyme shows a 4-fold increase in Km (using cis-3-bromoacrylate), but not to the degree observed for Cg10062 (687-fold). The mutation also causes a 4-fold decrease in the burst rate (compared to the wild type cis-CaaD), whereas Cg10062 shows no burst rate. More telling is the reaction of the T34A mutant of cis-CaaD with the alternate substrate, 2,3-butadienoate. In the presence of NaBH4 and the allene, cis-CaaD is completely inactivated after one turnover due to the covalent modification of Pro-1. The same experiment with Cg10062 does not result in the covalent modification of Pro-1. The different outcomes are attributed to

  4. Amino acid sequence around the active-site serine residue in the acyltransferase domain of goat mammary fatty acid synthetase.

    PubMed Central

    Mikkelsen, J; Højrup, P; Rasmussen, M M; Roepstorff, P; Knudsen, J

    1985-01-01

    Goat mammary fatty acid synthetase was labelled in the acyltransferase domain by formation of O-ester intermediates by incubation with [1-14C]acetyl-CoA and [2-14C]malonyl-CoA. Tryptic-digest and CNBr-cleavage peptides were isolated and purified by high-performance reverse-phase and ion-exchange liquid chromatography. The sequences of the malonyl- and acetyl-labelled peptides were shown to be identical. The results confirm the hypothesis that both acetyl and malonyl groups are transferred to the mammalian fatty acid synthetase complex by the same transferase. The sequence is compared with those of other fatty acid synthetase transferases. PMID:3922356

  5. Thermodynamic and kinetic aspects of surface acidity

    SciTech Connect

    Dumesic, J.A.

    1992-01-01

    Our research in the general area of acid catalysis involves the characterization of solid acidity and the corresponding assessment of catalytic performance of acidic materials. Acid characterization studies are required to provide essential information about the type of acid site (i.e., Lewis versus Bronsted), the strength of the sites, and the mobility of molecules adsorbed on the acid sites. An accurate measure of acid strength is given by the heat of adsorption of a basic probe molecule on the acid site. A thermodynamic representation of the mobility of adsorbed species on these sites is given by the entropy of adsorption. Important techniques used in these acid site characterization studies include microcalorimetry, thermogravimetric measurements, temperature programmed desorption, infrared spectroscopy and solid state nuclear magnetic resonance. The combination of these acid site characterization studies with reaction kinetics measurements of selected catalytic processes allows the elucidation of possible relationships between surface thermodynamic and kinetic properties of acidic sites. Such relationships are important milestones in formulating effective strategies for the effective utilization of solid acid catalysts. Current work in this direction involves methylamine syntheses over various zeolites, and the basic probe molecules employed include ammonia, methanol, water and mono-, di- and tri-methylamines. 31 refs., 18 figs., 1 tab.

  6. Distribution and integrated assessment of lead in an abandoned lead-acid battery site in Southwest China before redevelopment.

    PubMed

    Wang, Mei; Zhang, Chao; Zhang, Zhuo; Li, Fasheng; Guo, Guanlin

    2016-06-01

    Lead-acid battery sites have contributed enormous amounts of lead to the environment, significantly affecting its global biogeochemical cycle and leaving the potential risks to human health. An abandoned lead-acid battery site prepared for redevelopment was selected in order to study the distribution of lead in soils, plants, rhizosphere soils and soil solutions. In total, 197 samples from 77 boreholes were collected and analyzed. Single extractions by acetic acid (HOAc) were conducted to assess the bioavailability and speciation of lead in soils for comparison with the parts of the plants that are aboveground. Health risks for future residential development were evaluated by the integrated exposure uptake biokinetic (IEUBK) model. The results indicated that lead concentrations in 83% of the soil samples exceeded the Chinese Environmental Quality Standard for soil (350 mg/kg for Pb) and mainly occurred at depths between 0 and 1.5 m while accumulating at the surface of demolished construction waste and miscellaneous fill. Lead concentrations in soil solutions and HOAc extraction leachates were linked closely to the contents of aboveground Broussonetia papyrifera and Artemisia annua, two main types of local plants that were found at the site. The probability density of lead in blood (PbB) in excess of 10 µg/dL could overtake the 99% mark in the residential scenario. The findings provided a relatively integrated method to illustrate the onsite investigations and assessment for similar sites before remediation and future development from more comprehensive aspects.

  7. Aceneuramic Acid Extended Release Administration Maintains Upper Limb Muscle Strength in a 48-week Study of Subjects with GNE Myopathy: Results from a Phase 2, Randomized, Controlled Study

    PubMed Central

    Argov, Zohar; Caraco, Yoseph; Lau, Heather; Pestronk, Alan; Shieh, Perry B.; Skrinar, Alison; Koutsoukos, Tony; Ahmed, Ruhi; Martinisi, Julia; Kakkis, Emil

    2016-01-01

    Background: GNE Myopathy (GNEM) is a progressive adult-onset myopathy likely caused by deficiency of sialic acid (SA) biosynthesis. Objective: Evaluate the safety and efficacy of SA (delivered by aceneuramic acid extended-release [Ace-ER]) as treatment for GNEM. Methods: A Phase 2, randomized, double-blind, placebo-controlled study evaluating Ace-ER 3 g/day or 6 g/day versus placebo was conducted in GNEM subjects (n = 47). After the first 24 weeks, placebo subjects crossed over to 3 g/day or 6 g/day for 24 additional weeks (dose pre-assigned during initial randomization). Assessments included serum SA, muscle strength by dynamometry, functional assessments, clinician- and patient-reported outcomes, and safety. Results: Dose-dependent increases in serum SA levels were observed. Supplementation with Ace-ER resulted in maintenance of muscle strength in an upper extremity composite (UEC) score at 6 g/day compared with placebo at Week 24 (LS mean difference +2.33 kg, p = 0.040), and larger in a pre-specified subgroup able to walk ≥200 m at Screening (+3.10 kg, p = 0.040). After cross-over, a combined 6 g/day group showed significantly better UEC strength than a combined 3 g/day group (+3.46 kg, p = 0.0031). A similar dose-dependent response was demonstrated within the lower extremity composite score, but was not significant (+1.06 kg, p = 0.61). The GNEM-Functional Activity Scale demonstrated a trend improvement in UE function and mobility in a combined 6 g/day group compared with a combined 3 g/day group. Patients receiving Ace-ER tablets had predominantly mild-to-moderate AEs and no serious adverse events. Conclusions: This is the first clinical study to provide evidence that supplementation with SA delivered by Ace-ER may stabilize muscle strength in individuals with GNEM and initiating treatment earlier in the disease course may lead to better outcomes. PMID:27854209

  8. Quantitative assessment of the preferences for the amino acid residues flanking archaeal N-linked glycosylation sites.

    PubMed

    Igura, Mayumi; Kohda, Daisuke

    2011-05-01

    Oligosaccharyltransferase (OST) catalyzes the transfer of an oligosaccharide to an asparagine residue in polypeptide chains. Using positional scanning peptide libraries, we assessed the effects of amino acid variations on the in vitro glycosylation efficiency within and adjacent to an N-glycosylation consensus, Asn-X-Ser/Thr, with an archaeal OST from Pyrococcus furiosus. The amino acid variations at the X(-2), X(-1) and X(+1) positions in the sequence X(-2)-X(-1)-Asn-X-Ser/Thr-X(+1) strongly influenced the glycosylation efficiency to a similar extent at position X. The rank orders of the amino acid preferences were unique at each site. We experimentally confirmed that the archaeal OST does not require an acidic residue at the -2 position, unlike the eubacterial OSTs. Pro was disfavored at the -1 and +1 positions, although the exclusion was not as strict as that at X, whereas Pro was the most favored amino acid residue among those studied at the -2 position. The overall amino acid preferences are correlated with a conformational propensity to extend around the sequon. The results of the library experiments revealed that the optimal acceptor sequence was PYNVTK, with a K(m) of 10 µM. The heat-stable, single-subunit OST of P. furiosus is a potential candidate enzyme for the production of recombinant glycoproteins in bacterial cells. Quantitative assessment of the amino acid preferences of the OST enzyme will facilitate the proper design of a production system.

  9. Developing palaeolimnological records of organic content (DOC and POC) using the UK Acid Water Monitoring Network sites

    NASA Astrophysics Data System (ADS)

    Russell, Fiona; Chiverrell, Richard; Boyle, John

    2016-04-01

    Monitoring programmes have shown increases in concentrations of dissolved organic matter (DOM) in the surface waters of northern and central Europe (Monteith et al. 2007), and negative impacts of the browning of river waters have been reported for fish populations (Jonsson et al. 2012; Ranaker et al. 2012) and for ecosystem services such as water treatment (Tuvendal and Elmqvist 2011). Still the exact causes of the recent browning remain uncertain, the main contenders being climate change (Evans et al. 2005) and reduced ionic strength in surface water resulting from declines in anthropogenic sulphur and sea salt deposition (Monteith et al. 2007). There is a need to better understand the pattern, drivers and trajectory of these increases in DOC and POC in both recent and longer-term (Holocene) contexts to improve the understanding of carbon cycling within lakes and their catchments. In Britain there are some ideal sites for testing whether these trends are preserved and developing methods for reconstructing organic fluxes from lake sedimentary archives. There is a suite of lakes distributed across the country, the UK Acid Waters Monitoring Network (UKAWMN) sites, which have been monitored monthly for dissolved organic carbon and other aqueous species since 1988. These 12 lakes have well studied recent and in some case whole Holocene sediment records. Here four of those lakes (Grannoch, Chon, Scoat Tarn and Cwm Mynach) are revisited, with sampling focused on the sediment-water interface and very recent sediments (approx.150 years). At Scoat Tarn (approx. 1000 years) and Llyn Mynach (11.5k years) longer records have been obtained to assess equivalent patterns through the Holocene. Analyses of the gravity cores have focused on measuring and characterising the organic content for comparison with recorded surface water DOC measurements (UKAWMN). Data from pyrolysis measurements (TGA/DSC) in an N atmosphere show that the mass loss between 330-415°C correlates well with

  10. A comparison of copper and acid site zeolites for the production of nitric oxide for biomedical applications.

    PubMed

    Russell, Samantha E; González Carballo, Juan María; Orellana-Tavra, Claudia; Fairen-Jimenez, David; Morris, Russell E

    2017-03-21

    Copper-exchanged and acidic zeolites are shown to produce nitric oxide (NO) from a nitrite source in biologically active (nanomolar) concentrations. Four zeolites were studied; mordenite, ferrierite, ZSM-5 and SSZ-13, which had varying pore size, channel systems and Si/Al ratios. ZSM-5 and SSZ-13 produced the highest amounts of NO in both the copper and acid form. The high activity and regeneration of the copper active sites makes them good candidates for long-term NO production. Initial cytotoxicity tests have shown at least one of the copper zeolites (Cu-SSZ-13) to be biocompatible, highlighting the potential usage within biomedical applications.

  11. Mapping of colicin E2 and colicin E3 plasmid deoxyribonucleic acid EcoR-1-sensitive sites.

    PubMed

    Inselburg, J; Johns, V

    1975-01-01

    Colicin plasmids E2 and E3 (Col E2 and Col E3) deoxyribonucleic acid (DNA) has been shown to contain, respectively, two and three EcoR1 restriction endonuclease-sensitive sites. This was determined by measuring the DNA fragments generated after EcoR1 endonuclease treatment by agarose gel electrophoresis and electron microscopy. The structure of heteroduplex Col E2-col E3 DNA molecules formed from EcoR1-generated fragments permitted a localization of the EcoR1-sensitive sites on the plasmid chromosomes.

  12. Intermittent minodronic acid treatment with sufficient bone resorption inhibition prevents reduction in bone mass and strength in ovariectomized rats with established osteopenia comparable with daily treatment.

    PubMed

    Kimoto, Aishi; Tanaka, Makoto; Nozaki, Kazutoshi; Mori, Masamichi; Fukushima, Shinji; Mori, Hiroshi; Shiroya, Tsutomu; Nakamura, Toshitaka

    2013-07-01

    This study examined and compared the effects of four-week intermittent and daily administrations of minodronic acid, a highly potent nitrogen-containing bisphosphonate, on bone mineral density (BMD), bone strength, bone turnover, and histomorphometry on established osteopenia in ovariectomized (OVX) rats. Fourteen-week-old female F344 rats were OVX or sham-operated. At 12 weeks post surgery, minodronic acid was orally administered once every 4 weeks at 0.2, 1, and 5 mg/kg and once daily at 0.006, 0.03, and 0.15 mg/kg for 12 months. The total dosing amount was comparable between the two dosing regimens. The levels of urinary deoxypyridinoline and serum osteocalcin were measured to assess bone turnover. BMD as assessed via dual-energy X-ray absorptiometry, bone structure and dynamical changes in vertebral trabecula and biomechanical properties were measured ex vivo at 12 months to assess bone content and material properties. Minodronic acid dose-dependently ameliorated the decrease in BMD of lumbar vertebrae and the femur in both treatment regimens similarly. Minodronic acid suppressed elevated urinary levels of deoxypyridinoline, a bone resorption marker, and reduced the serum levels of osteocalcin, a bone formation marker. In the mechanical test at 12 months of treatment, minodronic acid dose-dependently ameliorated the reduction in bone strength in femur and vertebral body. There is no significant difference in parameters between the two regimens except maximal load of lower doses in lumbar vertebral body and absorption energy of middle doses in femur. With these parameters with significant differences, values of the intermittent regimen were significantly lower than that of daily repeated regimen. Bone histomorphometric analysis of the lumbar vertebral body showed that minodronic acid significantly ameliorated the decrease in bone mass, trabecular thickness and number, and the increase in trabecular separation, bone resorption indices (Oc.S/BS and N.Oc/BS), and

  13. Hyperfine and Nuclear Quadrupole Tensors of Nitrogen Donors in the QA Site of Bacterial Reaction Centers: Correlation of the Histidine Nδ Tensors with Hydrogen Bond Strength

    PubMed Central

    2015-01-01

    X- and Q-band pulsed EPR spectroscopy was applied to study the interaction of the QA site semiquinone (SQA) with nitrogens from the local protein environment in natural abundance 14N and in 15N uniformly labeled photosynthetic reaction centers of Rhodobacter sphaeroides. The hyperfine and nuclear quadrupole tensors for His-M219 Nδ and Ala-M260 peptide nitrogen (Np) were estimated through simultaneous simulation of the Q-band 15N Davies ENDOR, X- and Q-band 14,15N HYSCORE, and X-band 14N three-pulse ESEEM spectra, with support from DFT calculations. The hyperfine coupling constants were found to be a(14N) = 2.3 MHz, T = 0.3 MHz for His-M219 Nδ and a(14N) = 2.6 MHz, T = 0.3 MHz for Ala-M260 Np. Despite that His-M219 Nδ is established as the stronger of the two H-bond donors, Ala-M260 Np is found to have the larger value of a(14N). The nuclear quadrupole coupling constants were estimated as e2Qq/4h = 0.38 MHz, η = 0.97 and e2Qq/4h = 0.74 MHz, η = 0.59 for His-M219 Nδ and Ala-M260 Np, respectively. An analysis of the available data on nuclear quadrupole tensors for imidazole nitrogens found in semiquinone-binding proteins and copper complexes reveals these systems share similar electron occupancies of the protonated nitrogen orbitals. By applying the Townes–Dailey model, developed previously for copper complexes, to the semiquinones, we find the asymmetry parameter η to be a sensitive probe of the histidine Nδ–semiquinone hydrogen bond strength. This is supported by a strong correlation observed between η and the isotropic coupling constant a(14N) and is consistent with previous computational works and our own semiquinone-histidine model calculations. The empirical relationship presented here for a(14N) and η will provide an important structural characterization tool in future studies of semiquinone-binding proteins. PMID:25026433

  14. Influence of methoxy-substituents on the strength of Br … Br type II halogen bonds in bromobenzoic acid

    NASA Astrophysics Data System (ADS)

    Raffo, Pablo A.; Marcolongo, Juan P.; Funes, Alejandro V.; Slep, Leonardo D.; Baggio, Ricardo F.; Cukiernik, Fabio D.

    2016-03-01

    4-bromo-3,5-di(methoxy)benzoic acid (I) crystallizes in the monoclinic C2/c space group, a = 22.3405 (6) Å, b = 4.85142 (14) Å, c = 18.1583 (5) Å, β = 93.086 (2)°. The crystal structure shows head-to-head dimeric units linked via type II Br … Br interactions as well as Br … π and weak H-bonding interactions. The whole structure exhibits features similar to those of the parent 4-bromobenzoic acid (II), most notably the overall geometrical features involved in the Br … Br type II interactions. Both structures display comparable C-Br … Br angles (θ1 = 98.3 and 91.6° and θ2 = 163.0 and 163.5° for (I) and (II) respectively), but the Br … Br distance is significantly shorter in (I) (3.58 Å) than in (II) (3.81 Å). QM computations provide the magnitude of the intermolecular interactions present in both (I) and (II), and allow disclosing the individual covalent and electrostatic contributions to the Br⋯Br halogen bond in terms of interaction energies, electrostatic potentials, and a molecular orbital (MO) analysis.

  15. Synthesis, characterization, and reactivity studies of heterodinuclear complexes modeling active sites in purple acid phospatases.

    PubMed

    Jarenmark, Martin; Haukka, Matti; Demeshko, Serhiy; Tuczek, Felix; Zuppiroli, Luca; Meyer, Franc; Nordlander, Ebbe

    2011-05-02

    To model the heterodinuclear active sites in plant purple acid phosphatases, a mononuclear synthon, [Fe(III)(H(2)IPCPMP)(Cl(2))][PF(6)] (1), has been generated in situ from the ligand 2-(N-isopropyl-N-((2-pyridyl)methyl)aminomethyl)-6-(N-(carboxylmethyl)-N-((2-pyridyl)methyl)amino methyl)-4-methylphenol (IPCPMP) and used to synthesize heterodinuclear complexes of the formulas [Fe(III)M(II)(IPCPMP)(OAc)(2)(CH(3)OH)][PF(6)] (M = Zn (2), Co (3), Ni (4), Mn (5)), [Fe(III)Zn(II)(IPCPMP)(mpdp)][PF(6)] (6) (mpdp = meta-phenylene-dipropionate), and [Fe(III)Cu(II)(IPCPMP) (OAc)}(2)(μ-O)][PF(6)] (7). Complexes 2-4, 6, and 7 have been crystallographically characterized. The structure of 6 is a solid state coordination polymer with heterodinuclear monomeric units, and 7 is a tetranuclear complex consisting of two heterodinuclear phenolate-bridged Fe(III)Cu(II) units bridged through a μ-oxido group between the two Fe(III) ions. Mössbauer spectra confirm the presence of high spin Fe(III) in an octahedral environment for 1, 3, and 5 while 2 and 4 display relaxation effects. Magnetic susceptibility measurements indicate weak antiferromagnetic coupling for 3, 4, and 5 and confirm the assignment of the metal centers in 2-5 as high spin Fe(III)-M(II) (M = Zn, Co (high spin), Ni (high spin), Mn (high spin)). Complexes 2-5 are intact in acetonitrile solution as indicated by IR spectroscopy (for 2-4) and electrospray ionization mass spectrometry (ESI-MS) but partly dissociate to hydroxide species and a mononuclear complex in water/acetonitrile solutions. UV-vis spectroscopy reveal pH-dependent behavior, and species that form upon increasing the pH have been assigned to μ-hydroxido-bridged Fe(III)M(II) complexes for 2-5 although 2 and 3 is further transformed into what is propsed to be a μ-oxido-bridged tetranuclear complex similar to 7. Complexes 2-5 enhance phosphodiester cleavage of 2-hydroxy-propyl-p-nitrophenyl phosphate (HPNP) and bis(2,4-dinitrophenyl)phosphate (BDNPP), but

  16. Effects of background electrolytes and ionic strength on enrichment of Cd(II) ions with magnetic graphene oxide-supported sulfanilic acid.

    PubMed

    Hu, Xin-jiang; Liu, Yun-guo; Zeng, Guang-ming; You, Shao-hong; Wang, Hui; Hu, Xi; Guo, Yi-ming; Tan, Xiao-fei; Guo, Fang-ying

    2014-12-01

    To elucidate the influence mechanisms of background electrolytes and ionic strength on Cd(II) removal, the adsorption of Cd(II) onto magnetic graphene oxide-supported sulfanilic acid (MGO-SA) in aqueous solutions containing different types and concentrations of background electrolytes was studied. The results indicate that Cd(II) adsorption was strongly dependent on pH and could be strongly affected by background electrolytes and ionic strength. The Cd(II) removal was decreased with the presence of background electrolyte cations (Na(+), K(+), Ca(2+), Mg(2+), Mn(2+), Zn(2+), and Ni(2+)), and the divalent cations exerted more obvious influences on the Cd(II) uptake than the monovalent cations at pH 6. Both Cl(-) and NO3(-) had negative effects on Cd(II) adsorption because they can form water-soluble metal-anion complexes with Cd(II) ions. The presence of 0.01molL(-1) Na3PO4 reduced the removal percentage of Cd(II) at pH<5 but extremely enhanced the Cd(II) removal when the pH>5. The Cd(II) adsorption was sensitive to changes in the concentration of NaCl, NaNO3, NaClO4, and Na3PO4. Besides, the adsorption isotherm of Cd(II) onto MGO-SA could be well described by the Freundlich model and was also influenced by the type of background electrolyte ions and the ionic strength.

  17. Highly efficient one-step conversion of cyclohexane to adipic acid using single-site heterogeneous catalysts.

    PubMed

    Raja, Robert; Thomas, John Meurig; Xu, Mingcan; Harris, Kenneth D M; Greenhill-Hooper, Michael; Quill, Kieran

    2006-01-28

    A solid source of 'active' oxygen (acetylperoxyborate, APB), when dissolved in aqueous solution in the presence of a single-site microporous catalyst containing redox centres (Fe(III)AlPO-31, Mn(III)AlPO-5, Fe(III)AlPO-5), converts cyclohexane with high efficiency (ca. 88%) and exceptionally high selectivity (ca. 81%) to adipic acid at 383 K; this procedure is also effective in converting styrene to styrene oxide and -pinene and (+)-limonene to their corresponding epoxides.

  18. Identification of protein SUMOylation sites by mass spectrometry using combined microwave-assisted aspartic acid cleavage and tryptic digestion

    PubMed Central

    Osula, Omoruyi; Swatkoski, Stephen; Cotter, Robert J.

    2012-01-01

    SUMO (Small-Ubiquitin-like MOdifier) is a post-translational modifier of protein substrates at lysine residues that conjugates to proteins in response to various changes in the cell. As a result of SUMO modification, marked changes in transcription regulation, DNA repair, subcellular localization, and mitosis, among other cellular processes, are known to occur. However, while the identification of ubiquitylation sites by mass spectrometry is aided in part by the presence of a small di-amino acid GlyGly “tag” that remains on lysine residues following tryptic digestion, SUMOylation poses a particular challenge as the absence of a basic residue near to the SUMO C-terminus results in a significant 27 or 32 amino acid sequence branch conjugated to the substrate peptide. MS/MS analyses of these branch peptides generally reveal abundant fragment ions resulting from cleavage of the SUMO tail, but which obscure those needed for characterizing the target peptide sequence. Other approaches for identifying SUMO substrates exist and include overexpression of the SUMO isoforms using an N-terminal histidine tag, as well as site-directed mutagenesis of the C-terminal end of the SUMO sequence. Here, we employ combined enzymatic/chemical approaches which serve to shorten the SUMO tag, and thus help to simplify SUMO spectra, making interpretation of mass spectra and location of the SUMOylation site easier. As described in this report, we demonstrate a method for identifying SUMOylation sites using three commercially available SUMO- modified isoforms, and by employing acid-only and acid/trypsin cleavage strategies. These approaches were carried out using MALDI-TOF and LC/MS instrumentation, along with CID and ETD fragmentation. PMID:22576878

  19. Fabrication of Poly-l-lactic Acid/Dicalcium Phosphate Dihydrate Composite Scaffolds with High Mechanical Strength-Implications for Bone Tissue Engineering.

    PubMed

    Tanataweethum, Nida; Liu, Wai Ching; Goebel, W Scott; Li, Ding; Chu, Tien Min

    2015-11-04

    Scaffolds were fabricated from poly-l-lactic acid (PLLA)/dicalcium phosphate dihydrate (DCPD) composite by indirect casting. Sodium citrate and PLLA were used to improve the mechanical properties of the DCPD scaffolds. The resulting PLLA/DCPD composite scaffold had increased diametral tensile strength and fracture energy when compared to DCPD only scaffolds (1.05 vs. 2.70 MPa and 2.53 vs. 12.67 N-mm, respectively). Sodium citrate alone accelerated the degradation rate by 1.5 times independent of PLLA. Cytocompatibility of all samples were evaluated using proliferation and differentiation parameters of dog-bone marrow stromal cells (dog-BMSCs). The results showed that viable dog-BMSCs attached well on both DCPD and PLLA/DCPD composite surfaces. In both DCPD and PLLA/DCPD conditioned medium, dog-BMSCs proliferated well and expressed alkaline phosphatase (ALP) activity indicating cell differentiation. These findings indicate that incorporating both sodium citrate and PLLA could effectively improve mechanical strength and biocompatibility without increasing the degradation time of calcium phosphate cement scaffolds for bone tissue engineering purposes.

  20. An Aqueous Thermodynamic Model for the Complexation of Sodium and Strontium with Organic Chelates valid to High Ionic Strength. I. Ethylenedinitrilotetraacetic acid (EDTA)

    SciTech Connect

    Felmy, Andrew R.; Mason, Marvin J.

    2003-04-01

    An aqueous thermodynamic model is developed, which accurately describes the effects of Na+ complexation, ionic strength, carbonate concentration, and temperature on the complexation of Sr2+ by ethylenedinitrilotetraacetic acid (EDTA) under basic conditions. The model is developed from the analysis of literature data on apparent equilibrium constants, enthalpies, and heat capacities; as well as on an extensive set of solubility data on SrCO3(c) in the presence of EDTA obtained as part of this study. The solubility data for SrCO3(c) were obtained in solutions ranging in Na2CO3 concentration from 0.01m to 1.8m, in NaNO3 concentration from 0 to 5m, and at temperatures extending to 75?C. The final aqueous thermodynamic model is based upon the equations of Pitzer and requires the inclusion of a NaEDTA3- species. An accurate model for the ionic strength dependence of the ion-interaction coefficients for the SrEDTA2- and NaEDTA3- aqueous species allows the extrapolation of standard state equilibrium constants for these species which are significantly different from the 0.1m reference state values available in the literature. The final model is tested by application to chemical systems containing competing metal ions (i.e., Ca2+) to further verify the proposed model and indicate the applicability of the model parameters to chemical systems containing other divalent metal-EDTA complexes.

  1. Solubility and modeling acid-base properties of adrenaline in NaCl aqueous solutions at different ionic strengths and temperatures.

    PubMed

    Bretti, Clemente; Cigala, Rosalia Maria; Crea, Francesco; De Stefano, Concetta; Vianelli, Giuseppina

    2015-10-12

    Solubility and acid-base properties of adrenaline were studied in NaCl aqueous solutions at different ionic strengths (0strength was modeled by means of the Debye-Hückel type equation and of the SIT (Specific ion Interaction Theory) approach. The specific interaction parameters of the ion pairs were also reported. For the protonation constants, the following thermodynamic values at infinite dilution were obtained: T=298.15 K, logK1(H0)=10.674±0.018 and logK2(H0)=8.954±0.022; T=310.15K, logK1(H0)=10.355±0.018 and logK2(H0)=8.749±0.030.

  2. Site-specific incorporation of redox active amino acids into proteins

    DOEpatents

    Alfonta; Lital , Schultz; Peter G. , Zhang; Zhiwen

    2010-10-12

    Compositions and methods of producing components of protein biosynthetic machinery that include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, and orthogonal pairs of tRNAs/synthetases, which incorporate redox active amino acids into proteins are provided. Methods for identifying these orthogonal pairs are also provided along with methods of producing proteins with redox active amino acids using these orthogonal pairs.

  3. Site-specific incorporation of redox active amino acids into proteins

    DOEpatents

    Alfonta, Lital; Schultz, Peter G.; Zhang, Zhiwen

    2011-08-30

    Compositions and methods of producing components of protein biosynthetic machinery that include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, and orthogonal pairs of tRNAs/synthetases, which incorporate redox active amino acids into proteins are provided. Methods for identifying these orthogonal pairs are also provided along with methods of producing proteins with redox active amino acids using these orthogonal pairs.

  4. Site-specific incorporation of redox active amino acids into proteins

    DOEpatents

    Alfonta, Lital [San Diego, CA; Schultz, Peter G [La Jolla, CA; Zhang, Zhiwen [San Diego, CA

    2012-02-14

    Compositions and methods of producing components of protein biosynthetic machinery that include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, and orthogonal pairs of tRNAs/synthetases, which incorporate redox active amino acids into proteins are provided. Methods for identifying these orthogonal pairs are also provided along with methods of producing proteins with redox active amino acids using these orthogonal pairs.

  5. Site-specific incorporation of redox active amino acids into proteins

    DOEpatents

    Alfonta, Lital; Schultz, Peter G.; Zhang, Zhiwen

    2009-02-24

    Compositions and methods of producing components of protein biosynthetic machinery that include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, and orthogonal pairs of tRNAs/synthetases, which incorporate redox active amino acids into proteins are provided. Methods for identifying these orthogonal pairs are also provided along with methods of producing proteins with redox active amino acids using these orthogonal pairs.

  6. Shear bond strength and debonding characteristics of metal and ceramic brackets bonded with conventional acid-etch and self-etch primer systems: An in-vivo study

    PubMed Central

    Mirzakouchaki, Behnam; Sharghi, Reza; Shirazi, Samaneh; Moghimi, Mahsan; Shahrbaf, Shirin

    2016-01-01

    Background Different in-vitro studies have reported various results regarding shear bond strength (SBS) of orthodontic brackets when SEP technique is compared to conventional system. This in-vivo study was designed to compare the effect of conventional acid-etching and self-etching primer adhesive (SEP) systems on SBS and debonding characteristics of metal and ceramic orthodontic brackets. Material and Methods 120 intact first maxillary and mandibular premolars of 30 orthodontic patients were selected and bonded with metal and ceramic brackets using conventional acid-etch or self-etch primer system. The bonded brackets were incorporated into the wire during the study period to simulate the real orthodontic treatment condition. The teeth were extracted and debonded after 30 days. The SBS, debonding characteristics and adhesive remnant indices (ARI) were determined in all groups. Results The mean SBS of metal brackets was 10.63±1.42 MPa in conventional and 9.38±1.53 MPa in SEP system, (P=0.004). No statistically significant difference was noted between conventional and SEP systems in ceramic brackets. The frequency of 1, 2 and 3 ARI scores and debonding within the adhesive were the most common among all groups. No statistically significant difference was observed regarding ARI or failure mode of debonded specimens in different brackets or bonding systems. Conclusions The SBS of metal brackets bonded using conventional system was significantly higher than SEP system, although the SBS of SEP system was clinically acceptable. No significant difference was found between conventional and SEP systems used with ceramic brackets. Total SBS of metal brackets was significantly higher than ceramic brackets. Due to adequate SBS of SEP system in bonding the metal brackets, it can be used as an alternative for conventional system. Key words:Shear bond strength, Orthodontic brackets, Adhesive remnant index, self-etch. PMID:26855704

  7. Extending the Diffuse Layer Model of Surface Acidity Behavior: III. Estimating Bound Site Activity Coefficients

    EPA Science Inventory

    Although detailed thermodynamic analyses of the 2-pK diffuse layer surface complexation model generally specify bound site activity coefficients for the purpose of accounting for those non-ideal excess free energies contributing to bound site electrochemical potentials, in applic...

  8. NH3 adsorption on the Lewis and Bronsted acid sites of MoO3 (0 1 0) surface: A cluster DFT study

    NASA Astrophysics Data System (ADS)

    Yan, Zhifeng; Fan, Junyan; Zuo, Zhijun; Li, Zhe; Zhang, Jinshan

    2014-01-01

    The adsorption of NH3 on the Lewis and Bronsted acid sites of MoO3 (0 1 0) surface has been investigated based on the density functional theory (DFT) method using the clusters models. The calculated results indicate that NH3 could strongly adsorb on both the Lewis and Bronsted acid sites in the form of NH3 species and NH4+ respectively, whereas the adsorption on the Lewis acid site is found to be more favorable energetically than that on the Bronsted acid site. For the Lewis acid site Mulliken population analysis shows a donation of lone pairs from NH3 to the surface and activation of N-H bond. The overlaps of N-s, N-p and Mo-d orbitals suggest the strong interaction between N and Mo atoms. For the Bronsted acid site N-H bond is also activated by the formation of NH4+ species. The hybridizations between H and O atoms as well as N and H atoms are the major reasons for strong chemical adsorption of NH3 and the existence of NH4+ species, which partly attributed to the presence of N-H… O hydrogen bonds. Furthermore, the formation of a second Lewis acid site at adjacent or diagonal site results in slight changes of adsorption stability, structural changes and charge redistributions, suggesting its small influence on NH3 adsorption.

  9. Fluorescent amino acid undergoing excited state intramolecular proton transfer for site-specific probing and imaging of peptide interactions.

    PubMed

    Sholokh, Marianna; Zamotaiev, Oleksandr M; Das, Ranjan; Postupalenko, Viktoriia Y; Richert, Ludovic; Dujardin, Denis; Zaporozhets, Olga A; Pivovarenko, Vasyl G; Klymchenko, Andrey S; Mély, Yves

    2015-02-12

    Fluorescent amino acids bearing environment-sensitive fluorophores are highly valuable tools for site-selective probing of peptide/ligand interactions. Herein, we synthesized a fluorescent l-amino acid bearing the 4'-methoxy-3-hydroxyflavone fluorophore (M3HFaa) that shows dual emission, as a result of an excited state intramolecular proton transfer (ESIPT). The dual emission of M3HFaa was found to be substantially more sensitive to hydration as compared to previous analogues. By replacing the Ala30 and Trp37 residues of a HIV-1 nucleocapsid peptide, M3HFaa was observed to preserve the peptide structure and functions. Interaction of the labeled peptides with nucleic acids and lipid vesicles produced a strong switch in their dual emission, favoring the emission of the ESIPT product. This switch was associated with the appearance of long-lived fluorescence lifetimes for the ESIPT product, as a consequence of the rigid environment in the complexes that restricted the relative motions of the M3HFaa aromatic moieties. The strongest restriction and thus the longest fluorescence lifetimes were observed at position 37 in complexes with nucleic acids, where the probe likely stacks with the nucleobases. Based on the dependence of the lifetime values on the nature of the ligand and the labeled position, two-photon fluorescence lifetime imaging was used to identify the binding partners of the labeled peptides microinjected into living cells. Thus, M3HFaa appears as a sensitive tool for monitoring site selectively peptide interactions in solution and living cells.

  10. Conceptual Model of Uranium in the Vadose Zone for Acidic and Alkaline Wastes Discharged at the Hanford Site Central Plateau

    SciTech Connect

    Truex, Michael J.; Szecsody, James E.; Qafoku, Nikolla; Serne, R. Jeffrey

    2014-09-01

    Historically, uranium was disposed in waste solutions of varying waste chemistry at the Hanford Site Central Plateau. The character of how uranium was distributed in the vadose zone during disposal, how it has continued to migrate through the vadose zone, and the magnitude of potential impacts on groundwater are strongly influenced by geochemical reactions in the vadose zone. These geochemical reactions can be significantly influenced by the disposed-waste chemistry near the disposal location. This report provides conceptual models and supporting information to describe uranium fate and transport in the vadose zone for both acidic and alkaline wastes discharged at a substantial number of waste sites in the Hanford Site Central Plateau. The conceptual models include consideration of how co-disposed acidic or alkaline fluids influence uranium mobility in terms of induced dissolution/precipitation reactions and changes in uranium sorption with a focus on the conditions near the disposal site. This information, when combined with the extensive information describing uranium fate and transport at near background pH conditions, enables focused characterization to support effective fate and transport estimates for uranium in the subsurface.

  11. Effects of conventional machining on the high cycle fatigue strength and crack initiation sites of the gamma titanium aluminide alloy Ti-47Al-2Nb-2Cr (at%) at 23 and 760 C

    SciTech Connect

    Jones, P.E.; Eylon, D.

    1999-07-01

    Effects of a deformed surface layer, created by conventional machining, on the high cycle fatigue strength (10e6 cycles) and fatigue initiation sites of Ti-48Al-2Nb-2Cr (at%) were examined above and below the ductile-to-brittle transition temperature. All samples were tested to failure under the same step loading profile. Comparisons were made between samples having the same load history. At room temperature, fatigue strength and initiation sites were equivalent for turned and electropolished surface conditions. At the anticipated service temperature, 760 C, the work hardened layer created by turning quickly recrystallized. This fine recrystallized surface enhanced the fatigue crack initiation resistance of turned specimens when compared to coarse grained electropolished samples which did not recrystallize during the test. The severe surface deformation resulting from conventional machining did not impair the high cycle fatigue behavior of this intermetallic alloy under the conditions evaluated.

  12. In situ fluorescence labelling of jasmonic acid binding sites in plant tissues with cadmium-free quantum dots.

    PubMed

    Liao, Qiumei; Yu, Ying; Cao, Yujuan; Lin, Bixia; Wei, Jingjing

    2015-02-01

    The fluorescence labelling of plant hormone binding sites is an important analytical technique in research on the molecular mechanisms of plant hormone activities. The authors synthesised a jasmonic acid (JA)-conjugated ZnS:Mn quantum dot (QD) probe, with a cubic structure and average hydrodynamic sizes of about 17.0 nm. The maximum fluorescence emission of the probe was recorded at about 585 nm. The probe was used for fluorescence labelling of JA binding sites in mung bean seedling tissues. Analysis revealed that the probe exhibited high selectivity to JA binding sites and good performance in eliminating interference from background fluorescence in plant tissues. In addition, the probe did not exhibit any apparent biotoxicity, and is much more suitable than probes constructed from CdTe QDs for the analysis of biological samples.

  13. The active site sulfenic acid ligand in nitrile hydratases can function as a nucleophile.

    PubMed

    Martinez, Salette; Wu, Rui; Sanishvili, Ruslan; Liu, Dali; Holz, Richard

    2014-01-29

    Nitrile hydratase (NHase) catalyzes the hydration of nitriles to their corresponding commercially valuable amides at ambient temperatures and physiological pH. Several reaction mechanisms have been proposed for NHase enzymes; however, the source of the nucleophile remains a mystery. Boronic acids have been shown to be potent inhibitors of numerous hydrolytic enzymes due to the open shell of boron, which allows it to expand from a trigonal planar (sp(2)) form to a tetrahedral form (sp(3)). Therefore, we examined the inhibition of the Co-type NHase from Pseudonocardia thermophila JCM 3095 (PtNHase) by boronic acids via kinetics and X-ray crystallography. Both 1-butaneboronic acid (BuBA) and phenylboronic acid (PBA) function as potent competitive inhibitors of PtNHase. X-ray crystal structures for BuBA and PBA complexed to PtNHase were solved and refined at 1.5, 1.6, and 1.2 Å resolution. The resulting PtNHase-boronic acid complexes represent a "snapshot" of reaction intermediates and implicate the cysteine-sulfenic acid ligand as the catalytic nucleophile, a heretofore unknown role for the αCys(113)-OH sulfenic acid ligand. Based on these data, a new mechanism of action for the hydration of nitriles by NHase is presented.

  14. Complete amino acid sequence of branched-chain amino acid aminotransferase (transaminase B) of Salmonella typhimurium, identification of the coenzyme-binding site and sequence comparison analysis

    SciTech Connect

    Feild, M.J.

    1988-01-01

    The complete amino acid sequence of the subunit of branched-chain amino acid aminotransferase of Salmonella typhimurium was determined by automated Edman degradation of peptide fragments generated by chemical and enzymatic digestion of S-carboxymethylated and S-pyridylethylated transaminase B. Peptide fragments of transaminase B were generated by treatment of the enzyme with trypsin, Staphylococcus aureus V8 protease, endoproteinase Lys-C, and cyanogen bromide. Protocols were developed for separation of the peptide fragments by reverse-phase high performance liquid chromatography (HPLC), ion-exchange HPLC, and SDS-urea gel electrophoresis. The enzyme subunit contains 308 amino acid residues and has a molecular weight of 33,920 daltons. The coenzyme-binding site was determined by treatment of the enzyme, containing bound pyridoxal 5-phosphate, with tritiated sodium borohydride prior to trypsin digestion. Monitoring radioactivity incorporation and peptide map comparisons with an apoenzyme tryptic digest, allowed identification of the pyridoxylated-peptide which was isolated by reverse-phase HPLC and sequenced. The coenzyme-binding site is a lysyl residue at position 159. Some peptides were further characterized by fast atom bombardment mass spectrometry.

  15. Modular organization of residue-level contacts shape the selection pressure on individual amino acid sites of ribosomal proteins.

    PubMed

    Mallik, Saurav; Kundu, Sudip

    2017-02-22

    Understanding the molecular evolution of macromolecular complexes in the light of their structure, assembly and stability is of central importance. Here we address how the modular organization of native molecular contacts shapes the selection pressure on individual residue sites of ribosomal complexes. The bacterial ribosomal complex is represented as a residue contact network where nodes represent amino acid/nucleotide residues and edges represent their van der Waals interactions. We find statistically overrepresented native amino acid-nucleotide contacts (OaantC, one amino acid contacts one or multiple nucleotides, inter-nucleotide contacts are disregarded). Contact number is defined as the number of nucleotides contacted. Involvement of individual amino acids in OaantCs with smaller contact numbers is more random, while only a few amino acids significantly contribute to OaantCs with higher contact numbers. An investigation of structure, stability and assembly of bacterial ribosome depicts the involvement of these OaantCs in diverse biophysical interactions stabilizing the complex, including high-affinity protein-RNA contacts, inter-protein cooperativity, inter-subunit bridge, packing of multiple ribosomal RNA domains etc. Amino acid-nucleotide constituents of OaantCs with higher contact numbers are generally associated with significantly slower substitution rates compared to that of OaantCs with smaller contact numbers. This evolutionary rate heterogeneity emerges from the strong purifying selection pressure that conserves the respective amino acid physicochemical properties relevant to the stabilizing interaction with OaantC nucleotides. An analysis of relative molecular orientations of OaantC residues and their interaction energetics provides the biophysical ground of purifying selection conserving OaantC amino acid physicochemical properties.

  16. Acid-base strength and acidochromism of some dimethylamino-azinium iodides. An integrated experimental and theoretical study.

    PubMed

    Benassi, Enrico; Carlotti, Benedetta; Fortuna, Cosimo G; Barone, Vincenzo; Elisei, Fausto; Spalletti, Anna

    2015-01-15

    The effects of pH on the spectral properties of stilbazolium salts bearing dimethylamino substituents, namely, trans isomers of the iodides of the dipolar E-[2-(4-dimethylamino)styryl]-1-methylpyridinium, its branched quadrupolar analogue E,E-[2,6-di-(p-dimethylamino)styryl]-1-methylpyridinium, and three analogues, chosen to investigate the effects of the stronger quinolinium acceptor, the longer butadiene π bridge, or both, were investigated through a joint experimental and computational approach. A noticeable acidochromism of the absorption spectra (interesting for applications) was observed, with the basic and protonated species giving intensely colored and transparent solutions, respectively. The acid–base equilibrium constants for the protonation of the dimethylamino group in the ground state (pKa) were experimentally derived. Theoretical calculations according to the thermodynamic Born-Haber cycle provided pKa values in good agreement with the experimental values. The very low fluorescence yield did not allow a direct investigation of the changes in the acid-base properties in the excited state (pKa*) by fluorimetric titrations. Their values were derived by quantum-mechanical calculations and estimated experimentally on the basis of the Förster cycle.

  17. Site-directed mutagenesis of conserved amino acids in the alpha subunit of toluene dioxygenase: potential mononuclear non-heme iron coordination sites.

    PubMed Central

    Jiang, H; Parales, R E; Lynch, N A; Gibson, D T

    1996-01-01

    The terminal oxygenase component of toluene dioxygenase from Pseudomonas putida F1 is an iron-sulfur protein (ISP(TOL)) that requires mononuclear iron for enzyme activity. Alignment of all available predicted amino acid sequences for the large (alpha) subunits of terminal oxygenases showed a conserved cluster of potential mononuclear iron-binding residues. These were between amino acids 210 and 230 in the alpha subunit (TodC1) of ISP(TOL). The conserved amino acids, Glu-214, Asp-219, Tyr-221, His-222, and His-228, were each independently replaced with an alanine residue by site-directed mutagenesis. Tyr-266 in TodC1, which has been suggested as an iron ligand, was treated in an identical manner. To assay toluene dioxygenase activity in the presence of TodC1 and its mutant forms, conditions for the reconstitution of wild-type ISP(TOL) activity from TodC1 and purified TodC2 (beta subunit) were developed and optimized. A mutation at Glu-214, Asp-219, His-222, or His-228 completely abolished toluene dioxygenase activity. TodC1 with an alanine substitution at either Tyr-221 or Tyr-266 retained partial enzyme activity (42 and 12%, respectively). In experiments with [14C]toluene, the two Tyr-->Ala mutations caused a reduction in the amount of Cis-[14C]-toluene dihydrodiol formed, whereas a mutation at Glu-214, Asp-219, His-222, or His-228 eliminated cis-toluene dihydrodiol formation. The expression level of all of the mutated TWO proteins was equivalent to that of wild-type TodC1 as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot (immunoblot) analyses. These results, in conjunction with the predicted amino acid sequences of 22 oxygenase components, suggest that the conserved motif Glu-X3-4,-Asp-X2-His-X4-5-His is critical for catalytic function and the glutamate, aspartate, and histidine residues may act as mononuclear iron ligands at the site of oxygen activation. PMID:8655491

  18. [Identification of rat and human hemoglobin acetilation sites after its interaction with acetylsalicylic acid].

    PubMed

    Shreĭner, E V; Murashko, E A; Dubrovskiĭ, Ia D; Krasnov, N V; Podol'skaia, E P; Babakov, V N

    2012-01-01

    The possibility of interaction of 0.1 mg/mL acetylsalicylic acid with purified human and rat globin in vitro during 24 h at 37 degrees C was investigated. The rat globin can be modified with acetylsalicylic acid on aminoacid residues K-17, K-57, K-91, K-140 in alpha subunit as well as on K-18, K-77 in beta subunit. The human globin can be modified with acetylsalicylic acid on aminoacid residues K-17, K-41, K-57 and K-91 in alpha subunit as well as on K-18, K-96 and K- 133 in beta subunit. We identified of acetetylated lysines K-17 and K-57 in alpha subunit of human hemoglobin after incubation whole blood with 0.1 mg/mL acetylsalicylic acid during 3 h.

  19. Spectrophotometric determination of acidity and tautomeric constants and hydrogen bonding strength for a new Schiff base using hard modeling and multivariate curve resolution alternative least squares methods.

    PubMed

    Afkhami, Abbas; Khajavi, Farzad; Khanmohammadi, Hamid

    2009-02-23

    The equilibria of a new Schiff base derived from 3,6-bis((aminoethyl)thio)pyridazine were studied spectrophotometrically with the aid of factor-analytical methods. Hard modeling program was used for determination of the acidity constants of the Schiff base in dimethylformamide (DMF)/water mixture (30:70 v/v). In this method acidity constant equations act as hard models and the score vectors obtained by decomposing of absorbance data matrix will be linear combinations of equilibrium concentrations of species that exist in the absorption matrix. Two rank annihilation factor analysis (TRAFA) was used as a standard method to investigate the accuracy of the method. The tautomerization constant, K(t), of the Schiff base solution in various DMF/water mixtures has also been determined using spectral variations of the Schiff base solutions in various volume ratios of water with the aid of evolving factor analysis (EFA) and multivariate curve resolution alternative least squares (MCR-ALS) methods. In addition the intramolecular hydrogen bonding strength and its related thermodynamic parameters have been determined using MCR-ALS and spectral variation of the Schiff base solutions in different temperatures.

  20. The impact of acid treatment on soilwater chemistry at the Humex site

    SciTech Connect

    Vogt, R.D.; Ranneklev, S.B.; Mykkelbost, T.C. )

    1994-01-01

    The effects of acid treatment on soil water dissolved organic carbon (DOC) and inorganic chemistry are being monitored at the Humic Lake Acidification Experiment (HUMEX) in western Norway. The HUMEX project involves artificial acidification of half of a dystrophic lake and the corresponding drainage basin. Soil water chemistry data were collected from 30 monitoring lysimeters and 130 grid lysimeters. The samples from the monitoring lysimeters were collected before and, for a period of two years, after the onset of acid treatment. Operationally-defined functional fractions of DOC showed that hydrophilic (HPI) and hydrophobic (HPO) acids account for 60% to 90% of the DOC. In soils rich in DOC, the HPO acids were dominant, whereas in mineral soil horizons low in DOC, the HPI acid fractions were highest. The amount of DOC relative to labile aluminum and iron may determine the HPO/HPI acid ratio. The sulphate concentration has increased more in the treated than in the reference side. Coincident decreases in DOC and organically complexes aluminum (Al[sub 0]) concentrations were observed for surface histosol locations. The temporal and spatial variations in c(Al[sub 0]) were mainly explained by variation in c(DOC). 26 refs., 5 figs., 3 tabs.

  1. Modifying the strength and strain concentration profile within collagen scaffolds using customizable arrays of poly-lactic acid fibers.

    PubMed

    Mozdzen, Laura C; Vucetic, Alan; Harley, Brendan A C

    2017-02-01

    The tendon-to-bone junction is a highly specialized tissue which dissipates stress concentrations between mechanically dissimilar tendon and bone. Upon injury, the local heterogeneities across this insertion are not regenerated, leading to poor functional outcomes such as formation of scar tissue at the insertion and re-failure rates exceeding 90%. Although current tissue engineering methods are moving towards the development of spatially-graded biomaterials to begin to address these injuries, significant opportunities remain to engineer the often complex local mechanical behavior of such biomaterials to enhance their bioactivity. Here, we describe the use of three-dimensional printing techniques to create customizable arrays of poly-lactic acid (PLA) fibers that can be incorporated into a collagen scaffold under development for tendon bone junction repair. Notably, we use additive manufacturing concepts to generate arrays of spatially-graded fibers from biodegradable PLA that are incorporated into collagen scaffolds to create a collagen-PLA composite. We demonstrate the ability to tune the mechanical performance of the fiber-scaffold composite at the bulk scale. We also demonstrate the incorporation of spatially-heterogeneous fiber designs to establish non-uniform local mechanical performance of the composite biomaterial under tensile load, a critical element in the design of multi-compartment biomaterials for tendon-to-bone regeneration applications. Together, this work highlights the capacity to use multi-scale composite biomaterials to control local and bulk mechanical properties, and provides key insights into design elements under consideration for mechanically competent, multi-tissue regeneration platforms.

  2. New amino acid changes in drug resistance sites and HBsAg in hepatitis B virus genotype H.

    PubMed

    Fernández-Galindo, D A; Sánchez-Ávila, F; Bobadilla-Morales, L; Gómez-Quiróz, P; Bueno-Topete, M; Armendáriz-Borunda, J; Sánchez-Orozco, L V

    2015-06-01

    Long-term treatment with retrotranscriptase (RT) inhibitors eventually leads to the development of drug resistance. Drug-related mutations occur naturally and these can be found in hepatitis B virus (HBV) carriers who have never received antiviral therapy. HBsAg are overlapped with RT domain, thus nucleot(s)ide analogues (NAs) resistance mutations and naturally-occurring mutations can cause amino acid changes in the HBsAg. Twenty-two patients with chronic hepatitis B were enrolled; three of them were previously treated with NAs and 19 were NAs-naïve treated. HBV reverse transcriptase region was sequenced; genotyping and analysis of missense mutations were performed in both RT domain and HBsAg. There was predominance of genotype H. Drug mutations were present in 18.2% of patients. Classical lamivudine resistance mutations (rtM204V/rtL180M) were present in one naïve-treatment patient infected with genotype G. New amino acid changes were identified in drug resistance sites in HBV strains from patients infected with genotype H; rtQ215E was present in two naïve-NAs treatment patients and rtI169M was identified in a patient previously treated with lamivudine. Mutations at sites rt169, rt204, and rt215 resulted in the Y161C, I195M, and C206W mutations at HBsAg. Also, new amino acid changes were identified in B-cell and T-cell epitopes and were more frequent in HBsAg compared to RT domain. In conclusion, new amino acid changes at antiviral resistance sites, B-cell and T-cell epitopes in HBV genotype H were identified in Mexican patients.

  3. Extent of the Acidification by N7-Coordinated cis-Diammine-Platinum(II) on the Acidic Sites of Guanine Derivatives

    PubMed Central

    Song, Bin; Oswald, Gerda; Bastian, Matthias

    1996-01-01

    Coordination of two monoprotonated 2'-deoxyguanosine 5'-monophosphate species, H(dGMP)−, via N7 to cis-(NH2)2Pt2+ gives the complex cis-(NH2)2Pt(H·dGMP)2 which is a four-protonic acid. The corresponding acidity constants were measured by potentiometric pH titrations (25℃; I = 0.1 M, NaNO3). The first two protons are released from the two -P(O)2(OH)− groups (PKa/1= 5.57; PKa/2 = 6.29) and the next two protons are from the H(N1) sites of the guanine residues (PKa/3 = 8.73; PKa/4 = 9.48). The micro acidity constants of the various sites are also evaluated. Comparison of these data with those determined for the three-protonic H2(dGMP)± (PKa/1 = 2.69 for the H+(N7) site; PKa/2 = 6.29 for -P(O)2(OH)− ;PKa/3 = 9.56 for H(N1)) shows that on average the N-7-coordinated Pt2+ acidifies the phosphate protons by Δ pKa = 0.36 and the H(N1) sites by Δ pKa = 0.46. These results are further compared with those obtained previously for cis-(NH2)2Pt(L)2, where L = 9-ethylguanine or monoprotonated 2'-deoxycytidine 5'-monophosphate. Conclusions regarding platinated DNA are also presented. PMID:18472808

  4. Evaluation of Shear Strength Threshold of Concern for Retrieval of Interim-Stored K-Basin Sludge in the Hanford Site

    SciTech Connect

    Onishi, Yasuo; Yokuda, Satoru T.; Schmidt, Andrew J.

    2010-11-01

    K-Basin sludge will be recovered into the Sludge Transport and Storage Containers (STSCs) and will be stored in the T Plant for interim storage (at least 10 years). Long-term sludge storage tests conducted by Pacific Northwest National Laboratory show that high uranium content K Basin sludge can self-cement and form a strong sludge with a bulk shear strength of up to 65 kPa. Some of this sludge has "paste" and "chunks" with shear strengths of approximately 3~5 kPa and 380 ~ 770 kPa, respectively. High uranium content sludge samples subjected to hydrothermal testing (e.g., 185°C, 10 h) have been observed to form agglomerates with a shear strength up to 170 kPa. After interim storage at T Plant, the sludge in the STSCs will be mobilized by water jets impinging the sludge. The objective of the evaluation was to determine the range of sludge shear strength for which there is high confidence that a water-jet retrieval system can mobilize stored K-Basin sludge from STSCs. The shear strength at which the sludge can be retrieved is defined as the "shear strength threshold of concern." If the sludge shear strength is greater than the value of the shear strength threshold of concern, a water-jet retrieval system will be unlikely to mobilize the sludge up to the container’s walls. The shear strength threshold of concern can be compared with the range of possible shear strengths of K-Basin stored sludge to determine if the current post interim-storage, water-jet retrieval method is adequate. Fourteen effective cleaning radius (ECR) models were reviewed, and their validity was examined by applying them to Hanford 241-SY-101 and 241-AZ-101 Tanks to reproduce the measured ECR produced by the mixer pumps. The validation test identified that the Powell-3 and Crowe-2 ECR models are more accurate than other ECR models reviewed. These ECR models were used to address a question as to whether the effective cleaning radius of a water jet is sufficient or if it can be readily expanded

  5. Modeling of recognition sites of nucleic acid bases aaand amide side chains of amino acids. Combination of experimental and theoretical approaches

    NASA Astrophysics Data System (ADS)

    Shelkovsky, V. S.; Stepanian, S. G.; Galetich, I. K.; Kosevich, M. V.; Adamowicz, L.

    2002-09-01

    A combined experimental-theoretical approach to modeling of building blocks of recognition complexes formed by nucleic acid bases and the amino-acids side-chain amino group is reviewed. The approach includes the temperature dependent field-ionization mass spectrometry and ab initio quantum chemical calculations. The mass spectrometric technique allows determination of interaction enthalpies of biomolecules in the gas phase, and the results it produces are directly comparable to the results obtained through theoretical modeling. In our works we have analyzed both thermodynamic and structural aspects of the recognition complexes of four canonical nucleic acid bases and acrylamide, which models the side chain of asparagine and glutamine. It has been shown that all bases can interact with amide group of the amino acids via their Watson-Crick sites when being incorporated into a single strand DNA or RNA. Stability of the complexes studied, expressed as -Δ H (kJ mole^{-1}) decreases as: m^9Gua (-59.5) > m^1Cyt (-57.0) > m^9Ade (-52.0) gg m^1Ura (-40.6). We have determined that in the double stranded DNA only purine bases can be recognized.

  6. Computational Identification of Protein Pupylation Sites by Using Profile-Based Composition of k-Spaced Amino Acid Pairs.

    PubMed

    Hasan, Md Mehedi; Zhou, Yuan; Lu, Xiaotian; Li, Jinyan; Song, Jiangning; Zhang, Ziding

    2015-01-01

    Prokaryotic proteins are regulated by pupylation, a type of post-translational modification that contributes to cellular function in bacterial organisms. In pupylation process, the prokaryotic ubiquitin-like protein (Pup) tagging is functionally analogous to ubiquitination in order to tag target proteins for proteasomal degradation. To date, several experimental methods have been developed to identify pupylated proteins and their pupylation sites, but these experimental methods are generally laborious and costly. Therefore, computational methods that can accurately predict potential pupylation sites based on protein sequence information are highly desirable. In this paper, a novel predictor termed as pbPUP has been developed for accurate prediction of pupylation sites. In particular, a sophisticated sequence encoding scheme [i.e. the profile-based composition of k-spaced amino acid pairs (pbCKSAAP)] is used to represent the sequence patterns and evolutionary information of the sequence fragments surrounding pupylation sites. Then, a Support Vector Machine (SVM) classifier is trained using the pbCKSAAP encoding scheme. The final pbPUP predictor achieves an AUC value of 0.849 in 10-fold cross-validation tests and outperforms other existing predictors on a comprehensive independent test dataset. The proposed method is anticipated to be a helpful computational resource for the prediction of pupylation sites. The web server and curated datasets in this study are freely available at http://protein.cau.edu.cn/pbPUP/.

  7. Interaction of P-aminobenzoic acid with normal and sickel erythrocyte membrane: photoaffinity labelling of the binding sites

    SciTech Connect

    Premachandra, B.R.

    1986-03-05

    Electron microscopic studies revealed that P-Amino benzoic acid (PABA) could prevent eichinocytosis of red cells in vitro. Equilibrium binding studies with right side out membrane vesicles (ROV) revealed a similar number of binding sites (1.2-1.4 ..mu..mol/mg) and Kd (1.4-1.6 mM) values for both normal and sickle cell membranes. /sup 14/C-Azide analogue of PABA was synthesized as a photoaffinity label to probe its sites of interaction on the erythrocyte membranes. Competitive binding studies of PABA with its azide indicated that both the compounds share common binding sites on the membrane surface since a 20 fold excess of azide inhibited PABA binding in a linear fashion. The azide was covalently incorporated into the membrane components only upon irradiation (52-35% of the label found in the proteins and the rest in lipids). Electrophoretic analysis of photolabelled ROV revealed that the azide interacts chiefly with Band 3 protein. PABA inhibited both high and low affinity calcium (Ca) binding sites situated on either surface of the membrane in a non-competitive manner; however, Ca binding stimulated by Mg-ATP was not affected. Ca transport into inside out vesicles was inhibited by PABA; but it did not affect the calcium ATP-ase activity. The authors studies suggest that the mechanism of action of PABA is mediated by its interaction with Band 3 protein (anion channel), calcium channel and calcium binding sites of erythrocyte membrane.

  8. MtPAN(3): site-class specific amino acid replacement matrices for mitochondrial proteins of Pancrustacea and Collembola.

    PubMed

    Nardi, Francesco; Liò, Pietro; Carapelli, Antonio; Frati, Francesco

    2014-06-01

    Phylogenetic analyses of Pancrustacea have generally relied on empirical models of amino acid substitution estimated from large reference datasets and applied to the entire alignment. More recently, following the observation that different sites, or groups of sites, may evolve under different evolutionary constraints, methods have been developed to deal with site or site-class specific models. A set of three matrices has been here developed based on an alignment of complete mitochondrial pancrustacean genomes partitioned using an unsupervised clustering procedure acting over per-site physiochemical properties. The performance of the proposed matrix set - named MtPAN(3) - was compared to relevant single matrix models (MtZOA, MtART, MtPAN) under ML and BI. While the application of the new model does not solve some of the topological problems frequently encountered with pancrustacean mitogenomic phylogenetic analyses, MtPAN(3) largely outperforms its competitors based on AIC and Bayes factors, indicating a significantly improved fit to the empirical data. The applicability of the new model, as well as of multiple matrix models in general, is discussed and an R/BioPerl script that implements the procedure is provided.

  9. Counting Active Sites on Titanium Oxide-Silica Catalysts for Hydrogen Peroxide Activation through In Situ Poisoning with Phenylphosphonic Acid

    SciTech Connect

    Eaton, Todd R.; Boston, Andrew M.; Thompson, Anthony B.; Gray, Kimberly A.; Notestein, Justin M.

    2015-06-04

    Quantifying specific active sites in supported catalysts improves our understanding and assists in rational design. Supported oxides can undergo significant structural changes as surface densities increase from site-isolated cations to monolayers and crystallites, which changes the number of kinetically relevant sites. Herein, TiOx domains are titrated on TiOx–SiO2 selectively with phenylphosphonic acid (PPA). An ex situ method quantifies all fluid-accessible TiOx, whereas an in situ titration during cis-cyclooctene epoxidation provides previously unavailable values for the number of tetrahedral Ti sites on which H2O2 activation occurs. We use this method to determine the active site densities of 22 different catalysts with different synthesis methods, loadings, and characteristic spectra and find a single intrinsic turnover frequency for cis-cyclooctene epoxidation of (40±7) h-1. This simple method gives molecular-level insight into catalyst structure that is otherwise hidden when bulk techniques are used.

  10. Strength Testing.

    ERIC Educational Resources Information Center

    Londeree, Ben R.

    1981-01-01

    Postural deviations resulting from strength and flexibility imbalances include swayback, scoliosis, and rounded shoulders. Screening tests are one method for identifying strength problems. Tests for the evaluation of postural problems are described, and exercises are presented for the strengthening of muscles. (JN)

  11. CD44 Binding to Hyaluronic Acid Is Redox Regulated by a Labile Disulfide Bond in the Hyaluronic Acid Binding Site

    PubMed Central

    Kellett-Clarke, Helena; Stegmann, Monika; Barclay, A. Neil; Metcalfe, Clive

    2015-01-01

    CD44 is the primary leukocyte cell surface receptor for hyaluronic acid (HA), a component of the extracellular matrix. Enzymatic post translational cleavage of labile disulfide bonds is a mechanism by which proteins are structurally regulated by imparting an allosteric change and altering activity. We have identified one such disulfide bond in CD44 formed by Cys77 and Cys97 that stabilises the HA binding groove. This bond is labile on the surface of leukocytes treated with chemical and enzymatic reducing agents. Analysis of CD44 crystal structures reveal the disulfide bond to be solvent accessible and in the–LH hook configuration characteristic of labile disulfide bonds. Kinetic trapping and binding experiments on CD44-Fc chimeric proteins show the bond is preferentially reduced over the other disulfide bonds in CD44 and reduction inhibits the CD44-HA interaction. Furthermore cells transfected with CD44 no longer adhere to HA coated surfaces after pre-treatment with reducing agents. The implications of CD44 redox regulation are discussed in the context of immune function, disease and therapeutic strategies. PMID:26379032

  12. Chromatographic analysis of the effects of fatty acids and glycation on binding by probes for Sudlow sites I and II to human serum albumin.

    PubMed

    Anguizola, Jeanethe; Debolt, Erin; Suresh, D; Hage, David S

    2016-05-15

    The primary endogenous ligands of human serum albumin (HSA) are non-esterified fatty acids, with 0.1-2mol of fatty acids normally being bound to HSA. In type II diabetes, fatty acid levels in serum are often elevated, and the presence of high glucose results in an increase in the non-enzymatic glycation of HSA. High-performance affinity chromatography (HPAC) was used to examine the combined effects of glycation and the presence of long chain fatty acids on the binding of HSA with R-warfarin and l-tryptophan (i.e., probes for Sudlow sites I and II, the major sites for drugs on this protein). Zonal elution competition studies were used to examine the interactions of myristic acid, palmitic acid and stearic acid with these probes on HSA. It was found that all these fatty acids had direct competition with R-warfarin at Sudlow site I of normal HSA and glycated HSA, with the glycated HSA typically having stronger binding for the fatty acids at this site. At Sudlow site II, direct competition was observed for all the fatty acids with l-tryptophan when using normal HSA, while glycated HSA gave no competition or positive allosteric interactions between these fatty acids and l-tryptophan. These data indicated that glycation can alter the interactions of drugs and fatty acids at specific binding sites on HSA. The results of this study should lead to a better understanding of how these interactions may change during diabetes and demonstrate how HPAC can be used to examine drug/solute-protein interactions in complex systems.

  13. Subnucleosomes and their relationships to the arrangement of histone binding sites along nucleosome deoxyribonucleic acid

    SciTech Connect

    Nelson, D.A.; Mencke, A.J.; Chambers, S.A.; Oosterhof, D.K.; Rill, R.L.

    1982-01-01

    Micrococcal nuclease cleaves within nucleosomes at sites spaced about 10.4 base pairs (bp) apart. Cleavages at sites equivalent to 30-35 bp from the ends of 146-bp cores cause spontaneous loss of an H2a-H2b pair associated with 30-40 bp length DNA. Cleavages at certain other sites do not affect the nucleosome integrity unless a solvent perturbant such as urea is added. Chromatin moderately digested with micrococcal nuclease, when fractionated by sedimentation or electrophoresis in the presence of 3 M urea, yielded four previously unobserved subnucleosomes with the following histone/DNA compositions: (H3)/sub 2/(H4)/sub 2/(H2a)(H2b)/95-115 bp; (H3)(H4)/70-80 bp DNA; (H2a)(H2b)/50-60 bp DNA; and (H1)/60-70 bp DNA. All but the latter subnucleosome were also obtained upon DNase I digestion of purified nucleosome cores labeled on the 5' ends with /sup 32/P. Only subnucleosomes that retained H2a and H2b also retained labeled ends. These results show that H2a and H2b are paired on the terminal 30-40 bp of core DNA, as suggested from analyses of histone-DNA cross-link products by Mirzabekov and coworkers. Considerations of the orgins and compositions of subnucleosomes and of cross-linking data suggest an expanded model for the locations of histone binding sites along nucleosome core DNA. The principal features of this model are (i) strong electrostatic binding sites of H2a and H2b occur at positions approximately 20-30 bp from the core ends, (ii) strong electrostatic binding sites of H3 and H4 occur primarily on the central 40 bp of core DNA, (iii) strong nonelectrostatic, urea-sensitive binding sites of H3 and H4 occur at positions approximately 30-50 bp from the core ends, and (iv) urea-sensitive binding sites of H2a or H2b may occur on the terminal 10-20 bp of core DNA.

  14. Does physical activity in adolescence have site-specific and sex-specific benefits on young adult bone size, content, and estimated strength?

    PubMed

    Duckham, Rachel L; Baxter-Jones, Adam D G; Johnston, James D; Vatanparast, Hassanali; Cooper, David; Kontulainen, Saija

    2014-02-01

    The long-term benefits of habitual physical activity during adolescence on adult bone structure and strength are poorly understood. We investigated whether physically active adolescents had greater bone size, density, content, and estimated bone strength in young adulthood when compared to their peers who were inactive during adolescence. Peripheral quantitative computed tomography (pQCT) was used to measure the tibia and radius of 122 (73 females) participants (age mean ± SD, 29.3 ± 2.3 years) of the Saskatchewan Pediatric Bone Mineral Accrual Study (PBMAS). Total bone area (ToA), cortical density (CoD), cortical area (CoA), cortical content (CoC), and estimated bone strength in torsion (SSIp ) and muscle area (MuA) were measured at the diaphyses (66% tibia and 65% radius). Total density (ToD), trabecular density (TrD), trabecular content (TrC), and estimated bone strength in compression (BSIc ) were measured at the distal ends (4%). Participants were grouped by their adolescent physical activity (PA) levels (inactive, average, and active) based on mean PA Z-scores obtained from serial questionnaire assessments completed during adolescence. We compared adult bone outcomes across adolescent PA groups in each sex using analysis of covariance followed by post hoc pairwise comparisons with Bonferroni adjustments. When adjusted for adult height, MuA, and PA, adult males who were more physically active than their peers in adolescence had 13% greater adjusted torsional bone strength (SSIp , p < 0.05) and 10% greater adjusted ToA (p < 0.05) at the tibia diaphysis. Females who were more active in adolescence had 10% larger adjusted CoA (p < 0.05), 12% greater adjusted CoC (p < 0.05) at the tibia diaphysis, and 3% greater adjusted TrC (p < 0.05) at the distal tibia when compared to their inactive peers. Benefits to tibia bone size, content, and strength in those who were more active during adolescence seemed to persist into young adulthood

  15. Prediction of posttranslational modification sites from amino acid sequences with kernel methods.

    PubMed

    Xu, Yan; Wang, Xiaobo; Wang, Yongcui; Tian, Yingjie; Shao, Xiaojian; Wu, Ling-Yun; Deng, Naiyang

    2014-03-07

    Post-translational modification (PTM) is the chemical modification of a protein after its translation and one of the later steps in protein biosynthesis for many proteins. It plays an important role which modifies the end product of gene expression and contributes to biological processes and diseased conditions. However, the experimental methods for identifying PTM sites are both costly and time-consuming. Hence computational methods are highly desired. In this work, a novel encoding method PSPM (position-specific propensity matrices) is developed. Then a support vector machine (SVM) with the kernel matrix computed by PSPM is applied to predict the PTM sites. The experimental results indicate that the performance of new method is better or comparable with the existing methods. Therefore, the new method is a useful computational resource for the identification of PTM sites. A unified standalone software PTMPred is developed. It can be used to predict all types of PTM sites if the user provides the training datasets. The software can be freely downloaded from http://www.aporc.org/doc/wiki/PTMPred.

  16. Technology development for phosphoric acid fuel cell powerplant (phase 2). [on site integrated energy systems

    NASA Technical Reports Server (NTRS)

    Christner, L.

    1980-01-01

    Progress is reported in the development of material, cell components, and reformers for on site integrated energy systems. Internal resistance and contact resistance were improved. Dissolved gases (O2, N2, and CO2) were found to have no effect on the electrochemical corrosion of phenolic composites. Stack performance was increased by 100 mV over the average 1979 level.

  17. Experimental and Mechanistic Understanding of Aldehyde Hydrogenation Using Au25 Nanoclusters with Lewis Acids: Unique Sites for Catalytic Reactions.

    PubMed

    Li, Gao; Abroshan, Hadi; Chen, Yuxiang; Jin, Rongchao; Kim, Hyung J

    2015-11-18

    The catalytic activity of Au25(SR)18 nanoclusters (R = C2H4Ph) for the aldehyde hydrogenation reaction in the presence of a base, e.g., ammonia or pyridine, and transition-metal ions M(z+), such as Cu(+), Cu(2+), Ni(2+) and Co(2+), as a Lewis acid is studied. The addition of a Lewis acid is found to significantly promote the catalytic activity of Au25(SR)18/CeO2 in the hydrogenation of benzaldehyde and a number of its derivatives. Matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) mass spectrometry in conjunction with UV-vis spectroscopy confirm the generation of new species, Au25-n(SR)18-n (n = 1-4), in the presence of a Lewis acid. The pathways for the speciation of Au24(SR)17 from its parent Au25(SR)18 nanocluster as well as its structure are investigated via the density functional theory (DFT) method. The adsorption of M(z+) onto a thiolate ligand "-SR-" of Au25(SR)18, followed by a stepwise detachment of "-SR-" and a gold atom bonded to "-SR-" (thus an "Au-SR" unit) is found to be the most likely mechanism for the Au24(SR)17 generation. This in turn exposes the Au13-core of Au24(SR)17 to reactants, providing an active site for the catalytic hydrogenation. DFT calculations indicate that M(z+) is also capable of adsorbing onto the Au13-core surface, producing a possible active metal site of a different kind to catalyze the aldehyde hydrogenation reaction. This study suggests, for the first time, that species with an open metal site like adducts [nanoparticle-M]((z-1)+) or fragments Au25-n(SR)18-n function as the catalysts rather than the intact Au25(SR)18.

  18. Hydrogenation of biofuels with formic acid over a palladium-based ternary catalyst with two types of active sites.

    PubMed

    Wang, Liang; Zhang, Bingsen; Meng, Xiangju; Su, Dang Sheng; Xiao, Feng-Shou

    2014-06-01

    A composite catalyst including palladium nanoparticles on titania (TiO2) and on nitrogen-modified porous carbon (Pd/TiO2@N-C) is synthesized from palladium salts, tetrabutyl titanate, and chitosan. N2 sorption isotherms show that the catalyst has a high BET surface area (229 m(2)  g(-1)) and large porosity. XPS and TEM characterization of the catalyst shows that palladium species with different chemical states are well dispersed across the TiO2 and nitrogen-modified porous carbon, respectively. The Pd/TiO2@N-C catalyst is very active and shows excellent stability towards hydrogenation of vanillin to 2-methoxy-4-methylphenol using formic acid as hydrogen source. This activity can be attributed to a synergistic effect between the Pd/TiO2 (a catalyst for dehydrogenation of formic acid) and Pd/N-C (a catalyst for hydrogenation of vanillin) sites.

  19. Chicoric acid binds to two sites and decreases the activity of the YopH bacterial virulence factor

    PubMed Central

    Kuban-Jankowska, Alicja; Sahu, Kamlesh K.; Gorska, Magdalena; Tuszynski, Jack A.; Wozniak, Michal

    2016-01-01

    Chicoric acid (CA) is a phenolic compound present in dietary supplements with a large spectrum of biological properties reported ranging from antioxidant, to antiviral, to immunostimulatory properties. Due to the fact that chicoric acid promotes phagocytic activity and was reported as an allosteric inhibitor of the PTP1B phosphatase, we examined the effect of CA on YopH phosphatase from pathogenic bacteria, which block phagocytic processes of a host cell. We performed computational studies of chicoric acid binding to YopH as well as validation experiments with recombinant enzymes. In addition, we performed similar studies for caffeic and chlorogenic acids to compare the results. Docking experiments demonstrated that, from the tested compounds, only CA binds to both catalytic and secondary binding sites of YopH. Our experimental results showed that CA reduces activity of recombinant YopH phosphatase from Yersinia enterocolitica and human CD45 phosphatase. The inhibition caused by CA was irreversible and did not induce oxidation of catalytic cysteine. We proposed that inactivation of YopH induced by CA is involved with allosteric inhibition by interacting with essential regions responsible for ligand binding. PMID:26735581

  20. Chicoric acid binds to two sites and decreases the activity of the YopH bacterial virulence factor.

    PubMed

    Kuban-Jankowska, Alicja; Sahu, Kamlesh K; Gorska, Magdalena; Tuszynski, Jack A; Wozniak, Michal

    2016-01-19

    Chicoric acid (CA) is a phenolic compound present in dietary supplements with a large spectrum of biological properties reported ranging from antioxidant, to antiviral, to immunostimulatory properties. Due to the fact that chicoric acid promotes phagocytic activity and was reported as an allosteric inhibitor of the PTP1B phosphatase, we examined the effect of CA on YopH phosphatase from pathogenic bacteria, which block phagocytic processes of a host cell. We performed computational studies of chicoric acid binding to YopH as well as validation experiments with recombinant enzymes. In addition, we performed similar studies for caffeic and chlorogenic acids to compare the results. Docking experiments demonstrated that, from the tested compounds, only CA binds to both catalytic and secondary binding sites of YopH. Our experimental results showed that CA reduces activity of recombinant YopH phosphatase from Yersinia enterocolitica and human CD45 phosphatase. The inhibition caused by CA was irreversible and did not induce oxidation of catalytic cysteine. We proposed that inactivation of YopH induced by CA is involved with allosteric inhibition by interacting with essential regions responsible for ligand binding.

  1. Design of protease-resistant myelin basic protein-derived peptides by cleavage site directed amino acid substitutions.

    PubMed

    Burster, Timo; Marin-Esteban, Viviana; Boehm, Bernhard O; Dunn, Shannon; Rotzschke, Olaf; Falk, Kirsten; Weber, Ekkehard; Verhelst, Steven H L; Kalbacher, Hubert; Driessen, Christoph

    2007-11-15

    Multiple Sclerosis (MS) is considered to be a T cell-mediated autoimmune disease. An attractive strategy to prevent activation of autoaggressive T cells in MS, is the use of altered peptide ligands (APL), which bind to major histocompatibility complex class II (MHC II) molecules. To be of clinical use, APL must be capable of resisting hostile environments including the proteolytic machinery of antigen presenting cells (APC). The current design of APL relies on cost- and labour-intensive strategies. To overcome these major drawbacks, we used a deductive approach which involved modifying proteolytic cleavage sites in APL. Cleavage site-directed amino acid substitution of the autoantigen myelin basic protein (MBP) resulted in lysosomal protease-resistant, high-affinity binding peptides. In addition, these peptides mitigated T cell activation in a similar fashion as conventional APL. The strategy outlined allows the development of protease-resistant APL and provides a universal design strategy to improve peptide-based immunotherapeutics.

  2. Site-Specifically Labeled Immunoconjugates for Molecular Imaging—Part 2: Peptide Tags and Unnatural Amino Acids

    PubMed Central

    Adumeau, Pierre; Sharma, Sai Kiran; Brent, Colleen; Zeglis, Brian M.

    2016-01-01

    Molecular imaging using radioisotope- or fluorophore-labeled antibodies is increasingly becoming a critical component of modern precision medicine. Yet despite this promise, the vast majority of these immunoconjugates are synthesized via the random coupling of amine-reactive bifunctional probes to lysines within the antibody, a process that can result in heterogeneous and poorly defined constructs with suboptimal pharmacological properties. In an effort to circumvent these issues, the last 5 years have played witness to a great deal of research focused on the creation of effective strategies for the site-specific attachment of payloads to antibodies. These chemoselective modification methods yield immunoconjugates that are more homogenous and better defined than constructs created using traditional synthetic approaches. Moreover, site-specifically labeled immunoconjugates have also been shown to exhibit superior in vivo behavior compared to their randomly modified cousins. The over-arching goal of this two-part review is to provide a broad yet detailed account of the various site-specific bioconjugation approaches that have been used to create immunoconjugates for positron emission tomography (PET), single photon emission computed tomography (SPECT), and fluorescence imaging. In Part 1, we covered site-specific bioconjugation techniques based on the modification of cysteine residues and the chemoenzymatic manipulation of glycans. In Part 2, we will detail two families of bioconjugation approaches that leverage biochemical tools to achieve site-specificity. First, we will discuss modification methods that employ peptide tags either as sites for enzyme-catalyzed ligations or as radiometal coordination architectures. And second, we will examine bioconjugation strategies predicated on the incorporation of unnatural or non-canonical amino acids into antibodies via genetic engineering. Finally, we will compare the advantages and disadvantages of the modification

  3. Using Unnatural Amino Acids to Probe the Energetics of Oxyanion Hole Hydrogen Bonds in the Ketosteroid Isomerase Active Site

    PubMed Central

    2015-01-01

    Hydrogen bonds are ubiquitous in enzyme active sites, providing binding interactions and stabilizing charge rearrangements on substrate groups over the course of a reaction. But understanding the origin and magnitude of their catalytic contributions relative to hydrogen bonds made in aqueous solution remains difficult, in part because of complexities encountered in energetic interpretation of traditional site-directed mutagenesis experiments. It has been proposed for ketosteroid isomerase and other enzymes that active site hydrogen bonding groups provide energetic stabilization via “short, strong” or “low-barrier” hydrogen bonds that are formed due to matching of their pKa or proton affinity to that of the transition state. It has also been proposed that the ketosteroid isomerase and other enzyme active sites provide electrostatic environments that result in larger energetic responses (i.e., greater “sensitivity”) to ground-state to transition-state charge rearrangement, relative to aqueous solution, thereby providing catalysis relative to the corresponding reaction in water. To test these models, we substituted tyrosine with fluorotyrosines (F-Tyr’s) in the ketosteroid isomerase (KSI) oxyanion hole to systematically vary the proton affinity of an active site hydrogen bond donor while minimizing steric or structural effects. We found that a 40-fold increase in intrinsic F-Tyr acidity caused no significant change in activity for reactions with three different substrates. F-Tyr substitution did not change the solvent or primary kinetic isotope effect for proton abstraction, consistent with no change in mechanism arising from these substitutions. The observed shallow dependence of activity on the pKa of the substituted Tyr residues suggests that the KSI oxyanion hole does not provide catalysis by forming an energetically exceptional pKa-matched hydrogen bond. In addition, the shallow dependence provides no indication of an active site electrostatic

  4. Introduction of lewis acidic and redox-active sites into a porous framework for ammonia capture with visual color response.

    PubMed

    Tan, Bin; Chen, Cheng; Cai, Li-Xuan; Zhang, Ya-Jun; Huang, Xiao-Ying; Zhang, Jie

    2015-04-06

    Based on the Lewis acidic site and redox ability of bipyridinium ligand, a porous framework with an adsorption advantage for ammonia over water and color response ability has been constructed. The compound is highly stable and flexible to external stimuli, exhibiting reversible single-crystal-to-single-crystal transformations, in response to temperature change and NH3 capture. More attractively, the title compound shows obvious color change from yellow to dark blue when exposed to ammonia vapor within just a few seconds, indicating a strong ability to function as a visual colorimetric absorbent for ammonia.

  5. In healthy elderly postmenopausal women variations in BMD and BMC at various skeletal sites are associated with differences in weight and lean body mass rather than by variations in habitual physical activity, strength or VO2max.

    PubMed

    Schöffl, I; Kemmler, W; Kladny, B; Vonstengel, S; Kalender, W A; Engelke, K

    2008-01-01

    The objective of this study was an integrated cross-sectional investigation for answering the question whether differences in bone mineral density in elderly postmenopausal women are associated with differences in habitual physical activity and unspecific exercise levels. Two hundred and ninety nine elderly women (69-/+3 years), without diseases or medication affecting bone metabolism were investigated. The influence of weight, body composition and physical activity on BMD was measured at multiple sites using different techniques (DXA, QCT, and QUS). Physical activity and exercise level were assessed by questionnaire, maximum strength of the legs and aerobic capacity. Variations in physical activity or habitual exercise had no effect on bone. The only significant univariate relation between strength/VO(2)max and BMD/BMC that remained after adjusting for confounding variables was between arm BMD (DXA) and hand-grip strength. The most important variable for explaining BMD was weight and for cortical BMC of the femur (QCT) lean body mass. Weight and lean body mass emerge as predominant predictors of BMD in normal elderly women, whereas the isolated effect of habitual physical activity, unspecific exercise participation, and muscle strength on bone parameters is negligible. Thus, an increase in the amount of habitual physical activity will probably have no beneficial impact on bone.

  6. Two amino acid sequences direct Aspergillus nidulans protein kinase C (PkcA) localization to hyphal apices and septation sites.

    PubMed

    Jackson-Hayes, Loretta; Hill, Terry W; Loprete, Darlene M; DelBove, Claire E; Shapiro, Justin A; Henley, Jordan L; Dawodu, Omolola O

    2015-01-01

    The Aspergillus nidulans ortholog of protein kinase C (pkcA) is involved in the organism's putative cell wall integrity (CWI) pathway, and PkcA also is highly localized at growing tips and forming septa. In the present work we identify the regions within PkcA that are responsible for its localization to hyphal tips and septation sites. To this end, we used serially truncated pkcA constructs and expressed them as green fluorescent protein (GFP) chimeras and identified two regions that direct PkcA localization. The first region is a 10 amino-acid sequence near the carboxyl end of the C2 domain that is required for localization to hyphal tips. Proteins containing this sequence also localize to septation sites. A second region between C2 and C1B (encompassing C1A) is sufficient for localization to septation sites but not to hyphal tips. We also report that localization to hyphal tips and septation sites alone is not sufficient for truncated constructs to complement hypersensitivity to the cell wall compromising agent calcofluor white in a strain bearing a mutation in the pkcA gene. Taken together, these results suggest that localization and stress response might be independent.

  7. Structure and Mutagenesis of Neural Cell Adhesion Molecule Domains Evidence for Flexibility in the Placement of Polysialic Acid Attachment Sites

    SciTech Connect

    Foley, Deirdre A.; Swartzentruber, Kristin G.; Lavie, Arnon; Colley, Karen J.

    2010-11-09

    The addition of {alpha}2,8-polysialic acid to the N-glycans of the neural cell adhesion molecule, NCAM, is critical for brain development and plays roles in synaptic plasticity, learning and memory, neuronal regeneration, and the growth and invasiveness of cancer cells. Our previous work indicates that the polysialylation of two N-glycans located on the fifth immunoglobulin domain (Ig5) of NCAM requires the presence of specific sequences in the adjacent fibronectin type III repeat (FN1). To understand the relationship of these two domains, we have solved the crystal structure of the NCAM Ig5-FN1 tandem. Unexpectedly, the structure reveals that the sites of Ig5 polysialylation are on the opposite face from the FN1 residues previously found to be critical for N-glycan polysialylation, suggesting that the Ig5-FN1 domain relationship may be flexible and/or that there is flexibility in the placement of Ig5 glycosylation sites for polysialylation. To test the latter possibility, new Ig5 glycosylation sites were engineered and their polysialylation tested. We observed some flexibility in glycosylation site location for polysialylation and demonstrate that the lack of polysialylation of a glycan attached to Asn-423 may be in part related to a lack of terminal processing. The data also suggest that, although the polysialyltransferases do not require the Ig5 domain for NCAM recognition, their ability to engage with this domain is necessary for polysialylation to occur on Ig5 N-glycans.

  8. [Experimental and kinetic modeling of acid/base and redox reactions over oxide catalysts

    SciTech Connect

    Not Available

    1993-01-01

    The research has involved the characterization of catalyst acidity, [sup 2]D NMR studies of Bronsted acid sites, and kinetic, calorimetric, and spectroscopic studies of methylamine synthesis and related reactions over acid catalysts. Approach of this work was to explore quantitative correlations between factors that control the generation, type, strength, and catalytic properties of acid sites on zeolite catalysts. Microcalorimetry, thermogravimetric analysis, IR spectroscopy, and NMR spectroscopy have provided information about the nature and strength of acid sites in zeolites. This was vital in understanding the catalytic cycles involved in methylamine synthesis and related reactions over zeolite catalysts.

  9. Remediation of acid mine drainage at the friendship hill national historic site with a pulsed limestone bed process

    USGS Publications Warehouse

    Sibrell, P.L.; Watten, B.; Boone, T.; ,

    2003-01-01

    A new process utilizing pulsed fluidized limestone beds was tested for the remediation of acid mine drainage at the Friendship Hill National Historic Site, in southwestern Pennsylvania. A 230 liter-per-minute treatment system was constructed and operated over a fourteen-month period from June 2000 through September 2001. Over this period of time, 50,000 metric tons of limestone were used to treat 50 million liters of water. The influent water pH was 2.5 and acidity was 1000 mg/L as CaCO3. Despite the high potential for armoring at the site, effluent pH during normal plant operation ranged from 5.7 to 7.8 and averaged 6.8. As a result of the high influent acidity, sufficient CO2 was generated and recycled to provide a net alkaline discharge with about 50 mg/L as CaCO3 alkalinity. Additions of commercial CO2 increased effluent alkalinity to as high as 300 mg/L, and could be a useful process management tool for transient high flows or acidities. Metal removal rates were 95% for aluminum (60 mg/L in influent), 50 to 90% for iron (Fe), depending on the ratio of ferrous to ferric iron, which varied seasonally (200 mg/L in influent), and <10% of manganese (Mn) (10 mg/L in influent). Ferrous iron and Mn removal was incomplete because of the high pH required for precipitation of these species. Iron removal could be improved by increased aeration following neutralization, and Mn removal could be effected by a post treatment passive settling/oxidation pond. Metal hydroxide sludges were settled in settling tanks, and then hauled from the site for aesthetic purposes. Over 450 metric tons of sludge were removed from the water over the life of the project. The dried sludge was tested by the Toxicity Characteristics Leaching Protocol (TCLP) and was found to be non-hazardous. Treatment costs were $43,000 per year and $1.08 per m 3, but could be decreased to $22,000 and $0.51 per m3 by decreasing labor use and by onsite sludge handling. These results confirm the utility of the new

  10. Amino acid substitutions in the poliovirus maturation cleavage site affect assembly and result in accumulation of provirions.

    PubMed Central

    Ansardi, D C; Morrow, C D

    1995-01-01

    The assembly of infectious poliovirus virions requires a proteolytic cleavage between an asparagine-serine amino acid pair (the maturation cleavage site) in VP0 after encapsidation of the genomic RNA. In this study, we have investigated the effects that mutations in the maturation cleavage site have on P1 polyprotein processing, assembly of subviral intermediates, and encapsidation of the viral genomic RNA. We have made mutations in the maturation cleavage site which change the asparagine-serine amino acid pair to either glutamine-glycine or threonine-serine. The mutations were created by site-directed mutagenesis of P1 cDNAs which were recombined into wild-type vaccinia virus to generate recombinant vaccinia viruses. The P1 polyproteins expressed from the recombinant vaccinia viruses were analyzed for proteolytic processing and assembly defects in cells coinfected with a recombinant vaccinia virus (VV-P3) that expresses the poliovirus 3CD protease. A trans complementation system using a defective poliovirus genome was utilized to assess the capacity of the mutant P1 proteins to encapsidate genomic RNA (D. C. Ansardi, D. C. Porter, and C. D. Morrow, J. Virol. 67:3684-3690, 1993). The mutant P1 proteins containing the glutamine-glycine amino acid pair (VP4-QG) and the threonine-serine pair (VP4-TS) were processed by 3CD provided in trans from VV-P3. The processed capsid proteins VP0, VP3, and VP1 derived from the mutant precursor VP4-QG were unstable and failed to assemble into subviral structures in cells coinfected with VV-P3. However, the capsid proteins derived from VP4-QG did assemble into empty-capsid-like structures in the presence of the defective poliovirus genome. In contrast, the capsid proteins derived from processing of the VP4-TS mutant assembled into subviral intermediates both in the presence and in the absence of the defective genome RNA. By a sedimentation analysis, we determined that the capsid proteins derived from the VP4-TS precursor

  11. Characterization of epoxyeicosatrienoic acid binding site in U937 membranes using a novel radiolabeled agonist, 20-125i-14,15-epoxyeicosa-8(Z)-enoic acid.

    PubMed

    Yang, Wenqi; Tuniki, Venugopal Raju; Anjaiah, Siddam; Falck, J R; Hillard, Cecilia J; Campbell, William B

    2008-03-01

    Epoxyeicosatrienoic acids (EETs) are important regulators of vascular tone and homeostasis. Whether they initiate signaling through membrane receptors is unclear. We developed 20-iodo-14,15-epoxyeicosa-8(Z)-enoic acid (20-I-14,15-EE8ZE), a radiolabeled EET agonist, to characterize EET binding to membranes of U937 cells. 20-I-14,15-EE8ZE stimulated cAMP production in U937 cells with similar potency, but it decreased efficacy compared with 11,12-EET. Maximum cAMP production increased 4.2-fold, with an EC(50) value of 9 muM. Like 14,15-EET, 20-I-14,15-EE8ZE relaxed bovine coronary arteries, with a similar EC(50) value. Both 20-I-14,15-EE8ZE agonist activities were blocked by the EET antagonist 14,15-epoxyeicosa-5(Z)enoic acid (14,15-EE5ZE). Specific 20-(125)I-14,15-EE8ZE binding to U937 membranes reached equilibrium within 10 min and remained unchanged for 30 min at 4 degrees C. The binding was saturable, reversible, and exhibited K(D) and B(max) values of 11.8 +/- 1.1 nM and 5.8 +/- 0.2 pmol/mg protein, respectively. Pretreatment of the membranes with guanosine 5'-O-(3-thio)triphosphate reduced the B(max) in a concentration-related manner. 20-(125)I-14,15-EE8ZE binding was inhibited by eicosanoids with potency order of 11,12-EET >14,15-EE5ZE approximately 14,15-EET > 15-hydroxyeicosatetraenoic acid > 14,15-EET-thiirane >14,15-dihydroxyeicosatrienoic acid. This order is in agreement with the efficacy and potency of cAMP production. In summary, 20-(125)I-14,15-EE8ZE is a radiolabeled EET agonist that is useful to study binding and metabolism. Using this radioligand, we have identified a specific high-affinity and high-abundance EET binding site in U937 cell membranes. This binding site could represent a specific EET receptor, which is probably a G protein-coupled receptor.

  12. Capture and Recycling of Sortase A through Site-Specific Labeling with Lithocholic Acid.

    PubMed

    Rosen, Christian B; Kwant, Richard L; MacDonald, James I; Rao, Meera; Francis, Matthew B

    2016-07-18

    Enzyme-mediated protein modification often requires large amounts of biocatalyst, adding significant costs to the process and limiting industrial applications. Herein, we demonstrate a scalable and straightforward strategy for the efficient capture and recycling of enzymes using a small-molecule affinity tag. A proline variant of an evolved sortase A (SrtA 7M) was N-terminally labeled with lithocholic acid (LA)-an inexpensive bile acid that exhibits strong binding to β-cyclodextrin (βCD). Capture and recycling of the LA-Pro-SrtA 7M conjugate was achieved using βCD-modified sepharose resin. The LA-Pro-SrtA 7M conjugate retained full enzymatic activity, even after multiple rounds of recycling.

  13. Effect of Ascorbic Acid on Shear Bond Strength of Orthodontic Brackets Bonded with Resin-modified Glass-ionomer Cement to Bleached Teeth

    PubMed Central

    Khosravanifard, Behnam; Rakhshan, Vahid; Araghi, Solmaz; Parhiz, Hadi

    2012-01-01

    Background and aims Bleaching can considerably reduce shear bond strength (SBS) of orthodontic brackets bonded with composite adhesives. Application of antioxidants is a method to reverse the negative effect of bleaching on composite-to-enamel bond. However, the efficacy of antioxidants in increasing the SBS of brackets bonded using resin-modified glass-ionomer cement (RMGIC) has not been studied, which was the aim of this study. Materials and methods Fifty freshly extracted human maxillary first premolars were bleached with 35% hydrogen peroxide (Pola Office Bleaching, SDI). Sodium ascorbate 10% was applied to the experimental specimens (n=25). All the specimens were etched with 37% phosphoric acid (Ivoclar/Vivadent) and bonded using RMGIC (Fuji Ortho LC, GC). The specimens were subjected to incubation (37°C, 24h) and thermocycling (1000 cycles, 5-55°C, dwell time = 1 min). The SBS was measured at 0.5 mm/min debonding crosshead speed. The adhesive remnant index (ARI) was scored under ×10 magni-fication. Data were analyzed using Mann-Whitney U test, one- and independent-samples t-test, and Fisher’sexact test (α=0.05). Results The mean SBS of experimental and control groups were 11.97 ± 4.49 and 7.7 ± 3.19 MPa, respectively. The dif-ference was statistically significant (P=0.000 by t-test). SBS of both control (P=0.014) and experimental (P=0.000) groups were significantly higher than the minimum acceptable SBS of 6 MPa, according to one-sample t-test. Conclusion Application of ascorbic acid can guarantee a strong bond when RMGIC is to be used. However, RMGIC might tolerate the negative effect of bleaching with minimum SA treatments (or perhaps without treatments), which de-serves further studies. PMID:22991638

  14. The Effectiveness of Predict-Observe-Explain Technique in Probing Students' Understanding about Acid-Base Chemistry: A Case for the Concepts of pH, pOH, and Strength

    ERIC Educational Resources Information Center

    Kala, Nesli; Yaman, Fatma; Ayas, Alipasa

    2013-01-01

    The present study describes high school students' conceptions about acids and bases in terms of pH, pOH, microscopic level, strength, and concentration. A total of 27 high school students participated in the study. The data was collected using 3 POE tasks and a semi-structured interview. The data analysis demonstrated that most of the students had…

  15. Strength Training

    MedlinePlus

    ... strengthens your heart and lungs. When you strength train with weights, you're using your muscles to ... see there are lots of different ways to train with weights. Try a few good basic routines ...

  16. Treatment of Acid Mine Drainage By A Semipassive Barrier System, The Kristineberg Mine Site, Northern Sweden.

    NASA Astrophysics Data System (ADS)

    Morales, T. A.; Herbert, R.; Hallberg, R.

    The production of acidic mine waters containing high concentrations of sulphate and metals are of great environmental concern. One method for removing metals from leachate waters is by stimulating sulphate reduction in a treatment system, thereby producing alkalinity and hydrogen sulphide. Dissolved metals and hydrogen sulphide may then precipitate as metal sulphides. Laboratory and field studies have been con- ducted for the evaluation of the removal processes in a groundwater treatment system, in which both inorganic and organic materials have been used to neutralize acidity and to promote the growth of sulphate reducing bacteria (SRB). Dissolution of olivine and dolomite was found to be successful in neutralizing acidity, since a continuous pH buffering was obtained from pH 2-3 to pH 5-6. Column studies with olivine indi- cate higher dissolution rates obtained with higher flow rates, where Mg is released at a higher rate than Si. The rate of dolomite dissolution also shows a correlation with acid- ity flux at lower fluxes. At higher acidity fluxes, the Ca release rate appears to reach a constant level, suggesting that there are factors limiting the removal of Ca from the dolomite surface. Electron microscopy studies suggest that gypsum has formed in the columns. Field sampling during two years and laboratory results indicate that at most a limited development of sulphate reducing bacteria is obtained in the organic leaf com- post. The SRB are probably present at near neutral pH that is measured in the system, but they are not very active. One main reason for this may be the complexity of the organic substrate used. In the column studies using unamended compost, sulphate and iron removal is obtained in the organic matter at a range of flow rates, initially due to adsorption and precipitation. After the addition of an easily degradable organic carbon source, a full development of SRB was obtained with an effective removal of both iron and sulphate. Iron sulphide

  17. Corrosion inhibition in 2.0 M sulfuric acid solutions of high strength maraging steel by aminophenyl tetrazole as a corrosion inhibitor

    NASA Astrophysics Data System (ADS)

    Sherif, El-Sayed M.

    2014-02-01

    The corrosion of high strength maraging steel after varied immersion times in concentrated solution, 2.0 M, of sulfuric acid has been investigated. The work was also extended to study the effect of 5-(3-aminophenyl)-tetrazole (APTA) on the inhibition of the steel corrosion. The study has been carried out using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and scanning electron microscope (SEM) along with energy dispersive X-ray analyzer (EDX) investigations. EIS spectra showed that the corrosion and polarization resistances decrease with increasing the immersion time of the steel before measurement and increase in the presence of APTA and the increase of its concentration. Polarization data agreed with the EIS measurements and indicated that the increase of immersion time increases the corrosion of steel by increasing its corrosion current and corrosion rate and lowering its polarization resistance. On the other hand, the addition of APTA and the increase of its concentration minimized the corrosion of steel through decreasing the corrosion current and corrosion rate and increasing the polarization resistance at all exposure test periods. SEM and EDX investigations confirmed that the inhibition of the maraging steel in the 2.0 M H2SO4 solutions is achieved via the adsorption of the APTA molecules onto the steel protecting its surface from being dissolved easily.

  18. Exploring the Strength of the H-Bond in Synthetic Models for Heme Proteins: The Importance of the N-H Acidity of the Distal Base.

    PubMed

    Alberti, Mariza N; Polyhach, Yevhen; Tzirakis, Manolis D; Tödtli, Laura; Jeschke, Gunnar; Diederich, François

    2016-07-11

    The distal hydrogen bond (H-bond) in dioxygen-binding proteins is crucial for the discrimination of O2 with respect to CO or NO. We report the preparation and characterization of a series of Zn(II) porphyrins, with one of three meso-phenyl rings bearing both an alkyl-tethered proximal imidazole ligand and a heterocyclic distal H-bond donor connected by a rigid acetylene spacer. Previously, we had validated the corresponding Co(II) complexes as synthetic model systems for dioxygen-binding heme proteins and demonstrated the structural requirements for proper distal H-bonding to Co(II) -bound dioxygen. Here, we systematically vary the H-bond donor ability of the distal heterocycles, as predicted based on pKa values. The H-bond in the dioxygen adducts of the Co(II) porphyrins was directly measured by Q-band Davies-ENDOR spectroscopy. It was shown that the strength of the hyperfine coupling between the dioxygen radical and the distal H-atom increases with enhanced acidity of the H-bond donor.

  19. An analysis of the shear strength of the bond between enamel and porcelain laminate veneers with different etching systems: acid and Er,Cr:YSGG laser separately and combined.

    PubMed

    Dundar, Berivan; Guzel, Kahraman Gündüz

    2011-11-01

    Conditioning of the enamel surface is now an accepted and widely applied technique used to improve retention in porcelain laminate veneer restorations. The aim of this study was to evaluate strength of the bond between porcelain laminate veneers and tooth surfaces etched with acid and laser, separately and together. The teeth studied comprised 60 incisors extracted for periodontal reasons. These were divided into four groups according to etching method: group 1, acid etching alone; group 2, acid etching followed by laser etching; group 3, laser etching followed by acid etching; group 4, laser etching alone. The teeth were etched with 37% phosphoric acid and a Er,Cr:YSGG laser system. In addition, 60 IPS Empress II cylindrical blocks 2 mm in height and 5 mm in diameter were also prepared for the etched tooth surface. These blocks were bonded to the teeth with dual cured resin cement and shear tests were then performed. After the shear tests, Scanning electron microscopy images of the tooth surfaces were obtained at a magnification of ×3,800. Etching with acid alone yielded the highest mean value of bond shear strength (15.4±3.8 MPa), while laser etching followed by acid etching gave the lowest mean value (11.5±4.6 MPa). The mean values of the bond shear strength for acid etching followed by laser etching and laser etching alone were 13.8±3.9 MPa and 12.8±4.6 MPa, respectively. Statistical analysis revealed no significant differences between the groups. The results suggest that laser etching is easy to apply and less time-consuming. They further suggest that the order in which the acid and laser are applied in combined treatments is important.

  20. Metal ion blockage of tritium incorporation into gamma-carboxyglutamic acid of prothrombin. Stoichiometry of gamma-carboxyglutamic acid to Gd3+ for the high affinity sites

    SciTech Connect

    Bajaj, S.P.; Saini, R.; Katz, A.; Cai, G.Z.; Maki, S.L.; Brodsky, G.L.

    1988-07-15

    Prothrombin possesses two high affinity and four low affinity gamma-carboxyglutamic acid (Gla)-dependent gadolinium binding sites. Earlier work has shown that tritium can be specifically incorporated at the gamma-carbon of Gla in proteins at pH 5. In the present work we show that inclusion of saturating concentrations of Ca2+ in nondenaturing buffer systems ranging from pH 5.5 to 8.5 prevents the exchange of tritium into all 10 Gla residues of prothrombin. Similarly, saturating concentrations of Gd3+ prevent tritium incorporation into Gla at pH 5.5. Positive cooperativity was observed for the binding of Gd3+ to human prothrombin (at pH 5.5) for the two high affinity sites (Kd congruent to 35 nM). The four low affinity sites bind Gd3+ with a Kd congruent to 5 microM. Incubation of prothrombin ranging in concentrations from 10 to 40 microM with 2 eq of Gd3+ at pH 5.5 prevents 5.7 (average of seven determinations) Gla residues from tritium incorporation. Sedimentation velocity experiments conducted at pH 5.5 indicate that prothrombin in the presence of saturating concentrations of Gd3+ polymerizes, most likely, to a trimer. Further, in the presence of 2 eq of Gd3+, calculated percent weight average concentration of monomer prothrombin is congruent to 100% at 10 microM, approximately equal to 95% at 20 microM, and congruento to 80% at 40 microM protein concentration. Thus, it appears that under conditions in which prothrombin primarily exists as a monomer, occupancy of the initial two metal binding sites by Gd3+ involves six Gla residues.

  1. Thermodynamic and kinetic aspects of surface acidity. Progress report

    SciTech Connect

    Dumesic, J.A.

    1992-04-01

    Our research in the general area of acid catalysis involves the characterization of solid acidity and the corresponding assessment of catalytic performance of acidic materials. Acid characterization studies are required to provide essential information about the type of acid site (i.e., Lewis versus Bronsted), the strength of the sites, and the mobility of molecules adsorbed on the acid sites. An accurate measure of acid strength is given by the heat of adsorption of a basic probe molecule on the acid site. A thermodynamic representation of the mobility of adsorbed species on these sites is given by the entropy of adsorption. Important techniques used in these acid site characterization studies include microcalorimetry, thermogravimetric measurements, temperature programmed desorption, infrared spectroscopy and solid state nuclear magnetic resonance. The combination of these acid site characterization studies with reaction kinetics measurements of selected catalytic processes allows the elucidation of possible relationships between surface thermodynamic and kinetic properties of acidic sites. Such relationships are important milestones in formulating effective strategies for the effective utilization of solid acid catalysts. Current work in this direction involves methylamine syntheses over various zeolites, and the basic probe molecules employed include ammonia, methanol, water and mono-, di- and tri-methylamines. 31 refs., 18 figs., 1 tab.

  2. Impact of acid mine drainages on surficial waters of an abandoned mining site.

    PubMed

    García-Lorenzo, M L; Marimón, J; Navarro-Hervás, M C; Pérez-Sirvent, C; Martínez-Sánchez, M J; Molina-Ruiz, José

    2016-04-01

    Weathering of sulphide minerals produces a great variety of efflorescences of soluble sulphate salts. These minerals play an important role for environmental pollution, since they can be either a sink or a source for acidity and trace elements. This paper aims to characterise surface waters affected by mining activities in the Sierra Minera of Cartagena-La Union (SE, Spain). Water samples were analysed for trace metals (Zn, Cd, Pb, Cu, As and Fe), major ions (Na(+), K(+), Ca(2+) and Mg(2+)) and anions (F(-), Cl(-), NO3 (-), CO3 (2-), SO4 (2-)) concentrations and were submitted to an "evaporation-precipitation" experiment that consisted in identifying the salts resulting from the evaporation of the water aliquots sampled onsite. Mineralogy of the salts was studied using X-ray diffraction and compared with the results of calculations using VISUAL MINTEQ. The study area is heavily polluted as a result of historical mining and processing activities that has produced large amount of wastes characterised by a high trace elements content, acidic pH and containing minerals resulting from the supergene alteration of the raw materials. The mineralogical study of the efflorescences obtained from waters shows that magnesium, zinc, iron and aluminium sulphates predominate in the acid mine drainage precipitates. Minerals of the hexahydrite group have been quantified together with minerals of the rozenite group, alunogen and other phases such as coquimbite and copiapite. Calcium sulphates correspond exclusively to gypsum. In a semiarid climate, such as that of the study area, these minerals contribute to understand the response of the system to episodic rainfall events. MINTEQ model could be used for the analysis of waters affected by mining activities but simulation of evaporation gives more realistic results considering that MINTEQ does not consider soluble hydrated salts.

  3. Genetic Incorporation of the Unnatural Amino Acid p-Acetyl Phenylalanine into Proteins for Site-Directed Spin Labeling

    PubMed Central

    Evans, Eric G.B.; Millhauser, Glenn L.

    2016-01-01

    Site-directed spin labeling (SDSL) is a powerful tool for the characterization of protein structure and dynamics; however, its application in many systems is hampered by the reliance on unique and benign cysteine substitutions for the site-specific attachment of the spin label. An elegant solution to this problem involves the use of genetically encoded unnatural amino acids (UAAs) containing reactive functional groups that are chemically orthogonal to those of the 20 amino acids found naturally in proteins. These unique functional groups can then be selectively reacted with an appropriately functionalized spin probe. In this chapter, we detail the genetic incorporation of the ketone-bearing amino acid p-acetyl phenylalanine (pAcPhe) into recombinant proteins expressed in E. coli. Incorporation of pAcPhe is followed by chemoselective reaction of the ketone side chain with a hydroxylamine-functionalized nitroxide to afford the spin-labeled side chain “K1,” and we present two protocols for successful K1 labeling of proteins bearing site-specific pAcPhe. We outline the basic requirements for pAcPhe incorporation and labeling, with an emphasis on practical aspects that must be considered by the researcher if high yields of UAA incorporation and efficient labeling reactions are to be achieved. To this end, we highlight recent advances that have led to increased yields of pAcPhe incorporation, and discuss the use of aniline-based catalysts allowing for facile conjugation of the hydroxylamine spin label under mild reaction conditions. To illustrate the utility of K1 labeling in proteins where traditional cysteine-based SDSL methods are problematic, we site-specifically K1 label the cellular prion protein at two positions in the C-terminal domain and determine the interspin distance using double electron–electron resonance EPR. Recent advances in UAA incorporation and ketone-based bioconjugation, in combination with the commercial availability of all requisite

  4. Interaction of aspartic acid-104 and proline-287 with the active site of m-calpain.

    PubMed Central

    Arthur, J S; Elce, J S

    1996-01-01

    In an ongoing study of the mechanisms of calpain catalysis and Ca(2+)-induced activation, the effects of Asp-104-->Ser and Pro-287-->Ser large subunit mutations on m-calpain activity, the pH-activity profile, Ca(2+)-sensitivity, and autolysis were measured. The importance of these positions was suggested by sequence comparisons between the calpain and papain families of cysteine proteinases. Asp-104 is adjacent to the active-site Cys-105, and Pro-287 is adjacent to the active-site Asn-286 and probably to the active-site His-262; both Asp-104 and Pro-287 are absolutely conserved in the known calpains, but are replaced by highly conserved serine residues in the papains. The single mutants had approx. 10-15% of wild-type activity, due mainly to a decrease in kcat, since Km was only slightly increased. The Pro-287-->Ser mutation appeared to cause a local perturbation of the catalytic Cys-105/His-262 catalytic ion pair, reducing its efficiency without major effect on the conformation and stability of the enzyme. The Asp-104-->Ser mutation caused a marked narrowing of the pH-activity curve, a 9-fold increase in Ca2+ requirement, and an acceleration of autolysis, when compared with the wild-type enzyme. The results indicated that Asp-104 alters the nature of its interaction with the catalytic ion pair during Ca(2+)-induced conformational change in calpain. This interaction may be direct or indirect, but is important in activation of the enzyme. PMID:8912692

  5. Fungal variegatic acid and extracellular polysaccharides promote the site-specific generation of reactive oxygen species.

    PubMed

    Zhu, Yuan; Mahaney, James; Jellison, Jody; Cao, Jinzhen; Gressler, Julia; Hoffmeister, Dirk; Goodell, Barry

    2017-03-01

    This study aims to clarify the role of variegatic acid (VA) in fungal attack by Serpula lacrymans, and also the generation and scavenging of reactive oxygen species (ROS) by the fungus. VA promotes a mediated Fenton reaction to generated ROS after oxalate solubilizes oxidized forms of iron. The fungal extracellular matrix (ECM) β-glucan scavenged ROS, and we propose this as a mechanism to protect the fungal hyphae while ROS generation is promoted to deconstruct the lignocellulose cell wall. A relatively high pH (4.4) also favored Fe(III) transfer from oxalate to VA as opposed to a lower pH (2.2) conditions, suggesting a pH-dependent Fe(III) transfer to VA employed by S. lacrymans. This permits ROS generation within the higher pH of the cell wall, while limiting ROS production near the fungal hyphae, while β-glucan from the fungal ECM scavenges ROS in the more acidic environments surrounding the fungal hyphae.

  6. Characterization of the S1 binding site of the glutamic acid-specific protease from Streptomyces griseus.

    PubMed Central

    Stennicke, H. R.; Birktoft, J. J.; Breddam, K.

    1996-01-01

    The glutamic acid-specific protease from Streptomyces griseus (SGPE) is an 18.4-kDa serine protease with a distinct preference for Glu in the P1 position. Other enzymes characterized by a strong preference for negatively charged residues in the P1 position, e.g., interleukin-1 beta converting enzyme (ICE), use Arg or Lys residues as counterions within the S1 binding site. However, in SGPE, this function is contributed by a His residue (His 213) and two Ser residues (Ser 192 and S216). It is demonstrated that proSGPE is activated autocatalytically and dependent on the presence of a Glu residue in the -1 position. Based on this observation, the importance of the individual S1 residues is evaluated considering that enzymes unable to recognize a Glu in the P1 position will not be activated. Among the residues constituting the S1 binding site, it is demonstrated that His 213 and Ser 192 are essential for recognition of Glu in the P1 position, whereas Ser 216 is less important for catalysis out has an influence on stabilization of the ground state. From the three-dimensional structure, it appears that His 213 is linked to two other His residues (His 199 and His 228), forming a His triad extending from the S1 binding site to the back of the enzyme. This hypothesis has been tested by substitution of His 199 and His 228 with other amino acid residues. The catalytic parameters obtained with the mutant enzymes, as well as the pH dependence, do not support this theory; rather, it appears that His 199 is responsible for orienting His 213 and that His 228 has no function associated with the recognition of Glu in P1. PMID:8931145

  7. Dephosphorylation of microtubule-binding sites at the neurofilament-H tail domain by alkaline, acid, and protein phosphatases.

    PubMed

    Hisanaga, S; Yasugawa, S; Yamakawa, T; Miyamoto, E; Ikebe, M; Uchiyama, M; Kishimoto, T

    1993-06-01

    The dephosphorylation-induced interaction of neurofilaments (NFs) with microtubules (MTs) was investigated by using several phosphatases. Escherichia coli alkaline and wheat germ acid phosphatases increased the electrophoretic mobility of NF-H and NF-M by dephosphorylation, and induced the binding of NF-H to MTs. The binding of NFs to MTs was observed only after the electrophoretic mobility of NF-H approached the exhaustively dephosphorylated level when alkaline phosphatase was used. The number of phosphate remaining when NF-H began to bind to MTs was estimated by measuring phosphate bound to NF-H. NF-H did not bind to MTs even when about 40 phosphates from the total of 51 had been removed by alkaline phosphatase. The removal of 6 further phosphates finally resulted in the association of NF-H with MTs. A similar finding, that the restricted phosphorylation sites in the NF-H tail domain, but not the total amount of phosphates, were important for binding to MTs, was also obtained with acid phosphatases. In contrast to alkaline and acid phosphatases, four classes of protein phosphatases (protein phosphatases 1, 2A, 2B, and 2C) were ineffective for shifting the electrophoretic mobility of NF proteins and for inducing the association of NFs to MTs.

  8. p-Coumaric acid decarboxylase from Lactobacillus plantarum: structural insights into the active site and decarboxylation catalytic mechanism.

    PubMed

    Rodríguez, Héctor; Angulo, Iván; de Las Rivas, Blanca; Campillo, Nuria; Páez, Juan A; Muñoz, Rosario; Mancheño, José M

    2010-05-15

    p-Coumaric acid decarboxylases (PDCs) catalyze the nonoxidative decarboxylation of hydroxycinnamic acids to generate the corresponding vinyl derivatives. Despite the biotechnological relevance of PDCs in food industry, their catalytic mechanism remains largely unknown. Here, we report insights into the structural basis of catalysis for the homodimeric PDC from Lactobacillus plantarum (LpPDC). The global fold of LpPDC is based on a flattened beta-barrel surrounding an internal cavity. Crystallographic and functional analyses of single-point mutants of residues located within this cavity have permitted identifying a potential substrate-binding pocket and also to provide structural evidences for rearrangements of surface loops so that they can modulate the accessibility to the active site. Finally, combination of the structural and functional data with in silico results enables us to propose a two-step catalytic mechanism for decarboxylation of p-coumaric acid by PDCs where Glu71 is involved in proton transfer, and Tyr18 and Tyr20 are involved in the proper substrate orientation and in the release of the CO(2) product.

  9. Site-specific PEGylation of therapeutic proteins via optimization of both accessible reactive amino acid residues and PEG derivatives.

    PubMed

    Zhang, Chun; Yang, Xiao-lan; Yuan, Yong-hua; Pu, Jun; Liao, Fei

    2012-08-01

    Modification of accessible amino acid residues with poly(ethylene glycol) [PEG] is a widely used technique for formulating therapeutic proteins. In practice, site-specific PEGylation of all selected/engineered accessible nonessential reactive residues of therapeutic proteins with common activated PEG derivatives is a promising strategy to concomitantly improve pharmacokinetics, allow retention of activity, alleviate immunogenicity, and avoid modification isomers. Specifically, through molecular engineering of a therapeutic protein, accessible essential residues reactive to an activated PEG derivative are substituted with unreactive residues provided that protein activity is retained, and a limited number of accessible nonessential reactive residues with optimized distributions are selected/introduced. Subsequently, all accessible nonessential reactive residues are completely PEGylated with the activated PEG derivative in great excess. Branched PEG derivatives containing new PEG chains with negligible metabolic toxicity are more desirable for site-specific PEGylation. Accordingly, for the successful formulation of therapeutic proteins, optimization of the number and distributions of accessible nonessential reactive residues via molecular engineering can be integrated with the design of large-sized PEG derivatives to achieve site-specific PEGylation of all selected/engineered accessible reactive residues.

  10. Isolation and properties of the acid site-specific endonuclease from mature eggs of the sea urchin Strongylocentrotus intermedius

    SciTech Connect

    Sibirtsev, Yu.T.; Konechnyi, A.A.; Rasskazov, V.A.

    1986-01-10

    An acid site-specific endonuclease has been detected in mature sea urchin eggs and cells of embryos at early stages of differentiation. Fractionation with ammonium sulfate, followed by chromatography on columns with DEAE, phosphocellulose, and hydroxyapatite resulted in an 18,000-fold purification. The molecular weight of the enzyme was determined at approx. 29,000, the optimum pH 5.5. The activity of the enzyme does not depend on divalent metal ions, EDTA, ATP, and tRNA, but it is modulated to a substantial degree by NaCl. The maximum rate of cleavage of the DNA supercoil (form I) is observed at 100 mM NaCl. Increasing the NaCl concentration to 350 mM only slightly lowers the rate of cleavage of form I, yielding form II, but entirely suppresses the accumulation of form III. Restriction analysis of the products of enzymatic hydrolysis of Co1E1 and pBR322 DNA showed that at the early stages of hydrolysis the enzyme exhibits pronounced specificity for definite sites, the number of which is 12 for Co1 E1 DNA and 8 sites for pBR322 DNA.

  11. One-Tube-Only Standardized Site-Directed Mutagenesis: An Alternative Approach to Generate Amino Acid Substitution Collections

    PubMed Central

    Mingo, Janire; Erramuzpe, Asier; Luna, Sandra; Aurtenetxe, Olaia; Amo, Laura; Diez, Ibai; Schepens, Jan T. G.; Hendriks, Wiljan J. A. J.; Cortés, Jesús M.; Pulido, Rafael

    2016-01-01

    Site-directed mutagenesis (SDM) is a powerful tool to create defined collections of protein variants for experimental and clinical purposes, but effectiveness is compromised when a large number of mutations is required. We present here a one-tube-only standardized SDM approach that generates comprehensive collections of amino acid substitution variants, including scanning- and single site-multiple mutations. The approach combines unified mutagenic primer design with the mixing of multiple distinct primer pairs and/or plasmid templates to increase the yield of a single inverse-PCR mutagenesis reaction. Also, a user-friendly program for automatic design of standardized primers for Ala-scanning mutagenesis is made available. Experimental results were compared with a modeling approach together with stochastic simulation data. For single site-multiple mutagenesis purposes and for simultaneous mutagenesis in different plasmid backgrounds, combination of primer sets and/or plasmid templates in a single reaction tube yielded the distinct mutations in a stochastic fashion. For scanning mutagenesis, we found that a combination of overlapping primer sets in a single PCR reaction allowed the yield of different individual mutations, although this yield did not necessarily follow a stochastic trend. Double mutants were generated when the overlap of primer pairs was below 60%. Our results illustrate that one-tube-only SDM effectively reduces the number of reactions required in large-scale mutagenesis strategies, facilitating the generation of comprehensive collections of protein variants suitable for functional analysis. PMID:27548698

  12. Spectroscopic insights into the nature of active sites in iron–nitrogen–carbon electrocatalysts for oxygen reduction in acid

    SciTech Connect

    Jia, Qingying; Ramaswamy, Nagappan; Tylus, Urszula; Strickland, Kara; Li, Jingkun; Serov, Alexey; Artyushkova, Kateryna; Atanassov, Plamen; Anibal, Jacob; Gumeci, Cenk; Barton, Scott Calabrese; Sougrati, Moulay-Tahar; Jaouen, Frederic; Halevi, Barr; Mukerjee, Sanjeev

    2016-11-01

    Developing efficient and inexpensive catalysts for the sluggish oxygen reduction reaction (ORR) constitutes one of the grand challenges in the fabrication of commercially viable fuel cell devices and metal–air batteries for future energy applications. Despite recent achievements in designing advanced Pt-based and Pt-free catalysts, current progress primarily involves an empirical approach of trial-and-error combination of precursors and synthesis conditions, which limits further progress. Rational design of catalyst materials requires proper understanding of the mechanistic origin of the ORR and the underlying surface properties under operating conditions that govern catalytic activity. Herein, several different groups of iron-based catalysts synthesized via different methods and/or precursors were systematically studied by combining multiple spectroscopic techniques under ex situ and in situ conditions in an effort to obtain a comprehensive understanding of the synthesis-products correlations, nature of active sites, and the reaction mechanisms. These catalysts include original macrocycles, macrocycle-pyrolyzed catalysts, and Fe-N–C catalysts synthesized from individual Fe, N, and C precursors including polymer-based catalysts, metal organic framework (MOF)-based catalysts, and sacrificial support method (SSM)-based catalysts. The latter group of catalysts is most promising as not only they exhibit exceptional ORR activity and/or durability, but also the final products are controllable. We show that the high activity observed for most pyrolyzed Fe-based catalysts can mainly be attributed to a single active site: non-planar Fe–N4 moiety embedded in distorted carbon matrix characterized by a high potential for the Fe2+/3+ redox transition in acidic electrolyte/environment. The high intrinsic ORR activity, or turnover frequency (TOF), of this site is shown to be accounted for by redox catalysis mechanism that highlights the dominant role

  13. Chemical characterization of the surface sites of coal

    SciTech Connect

    Fowkes, F.M.; Lloyd, T.B.; Cole, D.A.

    1990-08-01

    We propose to do experimental studies in four related areas concerning the acid-base properties of coal surfaces; (1) develop high precision flow microcalorimetric methods for determining the concentrations and strengths of the acidic and basic surface sites of coal powders; (2) develop photo-acoustic FTIR and solid-state NMR spectral shift techniques for determination of the concentrations and strengths of acidic and basic surface sites of coal powders; (3) determine the concentrations and strengths of the acidic and basic surface sites of some of the well-characterized coal samples from Argonne National Labs, comparing the coal samples before and after demineralization treatments with HCl and HF; (4) study the effects of surface acidity and basicity on the coal/water interface, with emphasis on the role of interfacial acid-base interactions in the adsorption of ions, surfactants and coal/water slurry stabilizers. A practical application of the new measurements of the acidity and basicity of surface sites will be to exploit acid-base contributions to preferential wettability for optimizing separation of coal pyrites from the organic components. Work this quarter concentrated on flow microcalorimetry for assessing acidity/basicity of coal powders. 8 refs., 9 figs., 1 tab.

  14. Concentrations of nitrous acid, nitric acid, nitrite and nitrate in the gas and aerosol phase at a site in the emission zone during ESCOMPTE 2001 experiment

    NASA Astrophysics Data System (ADS)

    Acker, K.; Möller, D.; Auel, R.; Wieprecht, W.; Kalaß, D.

    2005-03-01

    Ground-based measurements were performed at the "Expérience sur Site pour COntraindre les Modèles de Pollution atmosphérique et de Transport d`Emissions" (ESCOMPTE) field site E3 (Realtor) about 30 km north of the urban environment of Marseille and east of the industrial centre Berre pond to investigate the formation of nitrous and nitric acid and to detect the distribution of reactive N-species between the gas and particle phase during photochemical pollution events. A wet denuder sampling for gases followed by a steam jet collection for aerosols was both coupled to anion chromatographic analysis. The analytical system provided data continuously with 30-min time resolution between June 13 and July 13, 2001. Indications for heterogeneous formation of nitrous acid during nighttime and daytime on ground and aerosol surfaces were found, the average HNO 2/NO 2 ratio was 6%. Highest concentrations were observed during two episodes of strong pollution accumulation when sea breeze transported industrial, traffic and urban pollution land-inwards. After nocturnal heterogeneous formation (about 0.1 ppb v h -1 were estimated corresponding to increasing HNO 2/NO 2 ratios) and accumulation processes up to 1.2 ppb v HNO 2 were observed. Their photolysis produces up to 5-9×10 6 OH cm -3 s -1 and will contribute significantly to initiation of the daily photochemistry in the lowest part of the troposphere. For the key tropospheric species, HNO 3 daily peaks up to 4 ppb v were detected.

  15. Effects of jasmonic acid signalling on the wheat microbiome differ between body sites

    PubMed Central

    Liu, Hongwei; Carvalhais, Lilia C.; Schenk, Peer M.; Dennis, Paul G.

    2017-01-01

    Jasmonic acid (JA) signalling helps plants to defend themselves against necrotrophic pathogens and herbivorous insects and has been shown to influence the root microbiome of Arabidopsis thaliana. In this study, we determined whether JA signalling influences the diversity and functioning of the wheat (Triticum aestivum) microbiome and whether these effects are specific to particular parts of the plant. Activation of the JA pathway was achieved via exogenous application of methyl jasmonate and was confirmed by significant increases in the abundance of 10 JA-signalling-related gene transcripts. Phylogenetic marker gene sequencing revealed that JA signalling reduced the diversity and changed the composition of root endophytic but not shoot endophytic or rhizosphere bacterial communities. The total enzymatic activity and substrate utilisation profiles of rhizosphere bacterial communities were not affected by JA signalling. Our findings indicate that the effects of JA signalling on the wheat microbiome are specific to individual plant compartments. PMID:28134326

  16. Synthesis and Site-Specific Incorporation of Red-Shifted Azobenzene Amino Acids into Proteins.

    PubMed

    John, Alford A; Ramil, Carlo P; Tian, Yulin; Cheng, Gang; Lin, Qing

    2015-12-18

    A series of red-shifted azobenzene amino acids were synthesized in moderate-to-excellent yields via a two-step procedure in which tyrosine derivatives were first oxidized to the corresponding quinonoidal spirolactones followed by ceric ammonium nitrate-catalyzed azo formation with the substituted phenylhydrazines. The resulting azobenzene-alanine derivatives exhibited efficient trans/cis photoswitching upon irradiation with a blue (448 nm) or green (530 nm) LED light. Moreover, nine superfolder green fluorescent protein (sfGFP) mutants carrying the azobenzene-alanine analogues were expressed in E. coli in good yields via amber codon suppression with an orthogonal tRNA/PylRS pair, and one of the mutants showed durable photoswitching with the LED light.

  17. Magic-angle-spinning NMR studies of acid sites in zeolite H-ZSM-5

    SciTech Connect

    Brunner, E.; Ernst, H.; Freude, D.; Froehlich, T.; Hunger, M.; Pfeifer, H. )

    1991-01-01

    {sup 1}H, {sup 13}C, {sup 27}Al, and {sup 29}Si magic-angle-spinning (MAS) NMR was used to elucidate the nature of the catalytic activity of zeolite H-ZSM-5. {sup 1}H MAS NMR of sealed samples after mild hydrothermal dealumination shows that the enhanced activity for n-hexane cracking is not due to an enhanced Bronstead acidity. The concentrations of the various OH groups and aluminous species suggest that the reason for the enhanced catalytic activity is the interaction of the n-hexane molecule with a bridging hydroxyl group and with extra-framework aluminium species, which give rise to the enhanced activity, cannot be easily removed from their positions, and are therefore immobilized by the zeolitic framework.

  18. Site-Selective Binding of Nanoparticles to Double-Stranded DNA via Peptide Nucleic Acid "Invasion"

    SciTech Connect

    Stadler, A.L.; van der Lelie, D.; Sun, D.; Maye, M. M.; Gang, O.

    2011-04-01

    We demonstrate a novel method for by-design placement of nano-objects along double-stranded (ds) DNA. A molecular intercalator, designed as a peptide nucleic acid (PNA)-DNA chimera, is able to invade dsDNA at the PNA-side due to the hybridization specificity between PNA and one of the duplex strands. At the same time, the single-stranded (ss) DNA tail of the chimera, allows for anchoring of nano-objects that have been functionalized with complementary ssDNA. The developed method is applied for interparticle attachment and for the fabrication of particle clusters using a dsDNA template. This method significantly broadens the molecular toolbox for constructing nanoscale systems by including the most conventional not yet utilized DNA motif, double helix DNA.

  19. Lysophosphatidic acid directly activates TRPV1 through a C-terminal binding site.

    PubMed

    Nieto-Posadas, Andrés; Picazo-Juárez, Giovanni; Llorente, Itzel; Jara-Oseguera, Andrés; Morales-Lázaro, Sara; Escalante-Alcalde, Diana; Islas, León D; Rosenbaum, Tamara

    2011-11-20

    Since 1992, there has been growing evidence that the bioactive phospholipid lysophosphatidic acid (LPA), whose amounts are increased upon tissue injury, activates primary nociceptors resulting in neuropathic pain. The TRPV1 ion channel is expressed in primary afferent nociceptors and is activated by physical and chemical stimuli. Here we show that in control mice LPA produces acute pain-like behaviors, which are substantially reduced in Trpv1-null animals. Our data also demonstrate that LPA activates TRPV1 through a unique mechanism that is independent of G protein-coupled receptors, contrary to what has been widely shown for other ion channels, by directly interacting with the C terminus of the channel. We conclude that TRPV1 is a direct molecular target of the pain-producing molecule LPA and that this constitutes, to our knowledge, the first example of LPA binding directly to an ion channel to acutely regulate its function.

  20. Application of geophysics to acid mine drainage investigations. Volume 2. Site investigations

    SciTech Connect

    Custis, K.

    1994-09-01

    The report describes geophysical field investigations undertaken to evaluate the utility of surface geophysical techniques in detecting and monitoring groundwater pollution from mine waste in the Western United States. The document addresses results of investigations at Spenceville Copper Mine, Leviathan Sulfur Mine, Iron Mountain Copper Mine, and Walker Copper Mine. Methods used in the field investigations included conventional D.C. resistivity, electromagnetic, self potential, and magnetic. It was found that the source and extent of acid mine drainage can be identified, known groundwater flow paths correlate well with geophysical anomalies, subsurface layering of mine waste piles can be mapped with some geophysical methods, and leakage from waste impoundments is detectable by some surface geophysical methods. The document includes maps, charts, and tables.

  1. Neurologic syndrome associated with homozygous mutation at MAG sialic acid binding site.

    PubMed

    Roda, Ricardo H; FitzGibbon, Edmond J; Boucekkine, Houda; Schindler, Alice B; Blackstone, Craig

    2016-08-01

    The MAG gene encodes myelin-associated glycoprotein (MAG), an abundant protein involved in axon-glial interactions and myelination during nerve regeneration. Several members of a consanguineous family with a clinical syndrome reminiscent of Pelizaeus-Merzbacher disease and demyelinating leukodystrophy on brain MRI were recently found to harbor a homozygous missense p.Ser133Arg MAG mutation. Here, we report two brothers from a nonconsanguineous family afflicted with progressive cognitive impairment, neuropathy, ataxia, nystagmus, and gait disorder. Exome sequencing revealed the homozygous missense mutation p.Arg118His in MAG. This Arg118 residue in immunoglobulin domain 1 is critical for sialic acid binding, providing a compelling mechanistic basis for disease pathogenesis.

  2. Complete amino acid sequence of Mytilus anterior byssus retractor paramyosin and its putative phosphorylation site.

    PubMed

    Watabe, S; Iwasaki, K; Funabara, D; Hirayama, Y; Nakaya, M; Kikuchi, K

    2000-01-01

    A cDNA encoding the full-length paramyosin molecule was cloned from the mussel Mytilus galloprovincialis, a species closely related to Mytilus edulis. It contained 3,497 nucleotides (nt), with 79 and 826 nt for the 5' and 3' non-coding regions, respectively. The coding region was composed of 2,592 nt for 864 amino acid residues, a size typical of paramyosin. While genomic DNA digests with either HindIII or PstI exhibited a single band when hybridized with a SacI fragment of paramyosin cDNA, the digests with either EcoRV or EcoRI showed two bands, suggesting that the mussel has at least two genes encoding paramyosin. The mRNAs encoding paramyosin were most abundant in muscle tissues from byssus retractor and adductor muscles. Only traces of paramyosin transcripts were found in the tissue of foot, gill, inner mantle, and outer mantle. The same phosphorylatable peptide previously reported for paramyosin from the bivalve Mercenaria mercenaria, Ser-Arg-Ser-Met-Ser(P)-Val-Ser-Arg (Watabe et al. 1989. Comp Biochem Physiol 94B:813-821) was found in the C-terminal non-helical part of this Mytilus paramyosin. We predict that this particular paramyosin has a coiled-coil structure composed of two alpha-helices that show the heptad repeats (a-b-c-d-e-f-g) with further 28-amino acid repeat zones, where a and d tend to be occupied by nonpolar residues.

  3. A Wood-Waste Cover Prevents Sulphide Oxidation and Treats Acid Effluents at the East-Sullivan Mine Site

    NASA Astrophysics Data System (ADS)

    Germain, D.; Tassé, N.; Cyr, J.

    2004-05-01

    At the East Sullivan site, wood wastes covering the abandoned mine tailings impoundment prevent sulphide oxidation by creating an anoxic environment. The addition of coarse ligneous wastes favours infiltration, resulting in a water table rise. This maintains most tailings saturated and thus provides an additional protection against sulphide oxidation. Moreover, high infiltration allows a more rapid flushing of acid prone groundwater generated prior to the cover placement. Finally, the pore-waters under the cover are characterized by a strong reducing potential and high alkalinity. These conditions favour sulphate reduction and base metal precipitation as sulphides and carbonates. The restoration strategy capitalized on the alkaline and reductive properties of the waters underlying the wood-waste cover. An original treatment of acid effluents, based on the recirculation of water discharging around the impoundment through the organic cover, was implemented in 1998. In 2003, the total volume of water treated was 725 000 m3. Data gathered near the dispersal zone show that despite dispersing acid water, the groundwater pH decreases by only one unit from 7 to 6, during the recirculation period: May to October. However, alkalinity decreases from 800 to 100 mg/L-CaCO3. But it is back up to 800 mg/L the following spring, thanks to sulphate reduction. Fe2+ concentrations near the dispersal zone are maintained below 2 mg/L. Evolution of the iron mass in the surface waters suggests that the contaminated groundwater flush is completed in the north and west sectors of the impoundment; the east and south ones are expected to be recovered within 3 to 4 years. A wood-waste cover, besides limiting sulphide oxidation, can fill the role of alkaline reducing barrier for the treatment of these acidogenic waters, until a balance between acidity and alkalinity in the effluent is reached.

  4. Conversion of citrate synthase into citryl-CoA lyase as a result of mutation of the active-site aspartic acid residue to glutamic acid.

    PubMed Central

    Man, W J; Li, Y; O'Connor, C D; Wilton, D C

    1991-01-01

    The active-site aspartic acid residue, Asp-362, of Escherichia coli citrate synthase was changed by site-directed mutagenesis to Glu-362, Asn-362 or Gly-362. Only very low catalytic activity could be detected with the Asp----Asn and Asp----Gly mutations. The Asp----Glu mutation produced an enzyme that expressed about 0.8% of the overall catalytic rate, and the hydrolysis step in the reaction, monitored as citryl-CoA hydrolysis, was inhibited to a similar extent. However, the condensation reaction, measured in the reverse direction as citryl-CoA cleavage to oxaloacetate and acetyl-CoA, was not affected by the mutation, and this citryl-CoA lyase activity was the major catalytic activity of the mutant enzyme. This high condensation activity in an enzyme in which the subsequent hydrolysis step was about 98% inhibited permitted considerable exchange of the methyl protons of acetyl-CoA during catalysis by the mutant enzyme. The Km for oxaloacetate was not significantly altered in the D362E mutant enzyme, whereas the Km for acetyl-CoA was about 5 times lower. A mechanism is proposed in which Asp-362 is involved in the hydrolysis reaction of this enzyme, and not as a base in the deprotonation of acetyl-CoA as recently suggested by others. [Karpusas, Branchaud & Remington (1990) Biochemistry 29, 2213-2219; Alter, Casazza, Zhi, Nemeth, Srere & Evans, (1990) Biochemistry 29, 7557-7563]. PMID:1684105

  5. Direct conversion of bio-ethanol to isobutene on nanosized Zn(x)Zr(y)O(z) mixed oxides with balanced acid-base sites.

    PubMed

    Sun, Junming; Zhu, Kake; Gao, Feng; Wang, Chongmin; Liu, Jun; Peden, Charles H F; Wang, Yong

    2011-07-27

    We report the design and synthesis of nanosized Zn(x)Zr(y)O(z) mixed oxides for direct and high-yield conversion of bio-ethanol to isobutene (~83%). ZnO is addded to ZrO(2) to selectively passivate zirconia's strong Lewis acidic sites and weaken Brönsted acidic sites, while simultaneously introducing basicity. As a result, the undesired reactions of bio-ethanol dehydration and acetone polymerization/coking are suppressed. Instead, a surface basic site-catalyzed ethanol dehydrogenation to acetaldehyde, acetaldehyde to acetone conversion via a complex pathway including aldol-condensation/dehydrogenation, and a Brönsted acidic site-catalyzed acetone-to-isobutene reaction pathway dominates on the nanosized Zn(x)Zr(y)O(z) mixed oxide catalyst, leading to a highly selective process for direct conversion of bio-ethanol to isobutene.

  6. Amino acid polymorphisms in the fibronectin-binding repeats of fibronectin-binding protein A affect bond strength and fibronectin conformation.

    PubMed

    Casillas-Ituarte, Nadia N; Cruz, Carlos H B; Lins, Roberto D; DiBartola, Alex C; Howard, Jessica; Liang, Xiaowen; Höök, Magnus; Viana, Isabelle F T; Sierra-Hernández, M Roxana; Lower, Steven K

    2017-04-11

    The Staphylococcus aureus cell surface contains cell wall-anchored proteins such as fibronectin-binding protein A (FnBPA) that bind to host ligands (e.g. fibronectin; Fn) present in the extracellular matrix of tissue or coatings on cardiac implants. Recent clinical studies have found a correlation between cardiovascular infections caused by S. aureus and nonsynonymous single nucleotide polymorphisms (SNPs) in FnBPA. Atomic force microscopy (AFM), surface plasmon resonance (SPR), and molecular simulations were used to investigate interactions between Fn and each of eight, 20-mer peptide variants containing amino acids A, H, I, K, N, and Q at positions equivalent to 782 and/or 786 in Fn-binding repeat-9 (FnBR-9) of FnBPA. Experimentally measured bond lifetimes (1/koff ) and dissociation constants (Kd = koff / kon ), determined by mechanically dissociating the Fn-peptide complex at loading rates relevant to the cardiovascular system varied from the lowest-affinity H782A+K786A peptide (0.011 sec, 747 µM) to the highest-affinity H782Q+K786N peptide (0.192 sec, 15.7 µM). These AFM results tracked remarkably well to metadynamics simulations in which peptide detachment was defined solely by the free-energy landscape. Simulations and SPR experiments suggested that an Fn conformational change may enhance the stability of the binding complex for peptides with K786I or H782Q+K786I (Kd(app) = 0.2 to 0.5 µM. as determined by SPR) compared with the lowest-affinity double alanine peptide (Kd(app) = 3.8 µM). Together, these findings demonstrate that amino acid substitutions in FnBR-9 can significantly affect bond strength and influence the conformation of Fn upon binding. They provide a mechanistic explanation for the observation of nonsynonymous SNPs in fnbA) among clinical isolates of S. aureus that cause endovascular infections.

  7. Evaluation of muscle strength and motor abilities in children with type II and III spinal muscle atrophy treated with valproic acid

    PubMed Central

    2011-01-01

    Background Spinal muscular atrophy (SMA) is an autosomal recessive disorder that affects the motoneurons of the spinal anterior horn, resulting in hypotonia and muscle weakness. The disease is caused by deletion or mutation in the telomeric copy of SMN gene (SMN1) and clinical severity is in part determined by the copy number of the centromeric copy of the SMN gene (SMN2). The SMN2 mRNA lacks exon 7, resulting in a production of lower amounts of the full-length SMN protein. Knowledge of the molecular mechanism of diseases has led to the discovery of drugs capable of increasing SMN protein level through activation of SMN2 gene. One of these drugs is the valproic acid (VPA), a histone deacetylase inhibitor. Methods Twenty-two patients with type II and III SMA, aged between 2 and 18 years, were treated with VPA and were evaluated five times during a one-year period using the Manual Muscle Test (Medical Research Council scale-MRC), the Hammersmith Functional Motor Scale (HFMS), and the Barthel Index. Results After 12 months of therapy, the patients did not gain muscle strength. The group of children with SMA type II presented a significant gain in HFMS scores during the treatment. This improvement was not observed in the group of type III patients. The analysis of the HFMS scores during the treatment period in the groups of patients younger and older than 6 years of age did not show any significant result. There was an improvement of the daily activities at the end of the VPA treatment period. Conclusion Treatment of SMA patients with VPA may be a potential alternative to alleviate the progression of the disease. Trial Registration ClinicalTrials.gov: NCT01033331 PMID:21435220

  8. Acid mine drainage risks - A modeling approach to siting mine facilities in Northern Minnesota USA

    NASA Astrophysics Data System (ADS)

    Myers, Tom

    2016-02-01

    Most watershed-scale planning for mine-caused contamination concerns remediation of past problems while future planning relies heavily on engineering controls. As an alternative, a watershed scale groundwater fate and transport model for the Rainy Headwaters, a northeastern Minnesota watershed, has been developed to examine the risks of leaks or spills to a pristine downstream watershed. The model shows that the risk depends on the location and whether the source of the leak is on the surface or from deeper underground facilities. Underground sources cause loads that last longer but arrive at rivers after a longer travel time and have lower concentrations due to dilution and attenuation. Surface contaminant sources could cause much more short-term damage to the resource. Because groundwater dominates baseflow, mine contaminant seepage would cause the most damage during low flow periods. Groundwater flow and transport modeling is a useful tool for decreasing the risk to downgradient sources by aiding in the placement of mine facilities. Although mines are located based on the minerals, advance planning and analysis could avoid siting mine facilities where failure or leaks would cause too much natural resource damage. Watershed scale transport modeling could help locate the facilities or decide in advance that the mine should not be constructed due to the risk to downstream resources.

  9. [Experimental and kinetic modeling of acid/base and redox reactions over oxide catalysts]. Technical progress report

    SciTech Connect

    Not Available

    1993-07-01

    The research has involved the characterization of catalyst acidity, {sup 2}D NMR studies of Bronsted acid sites, and kinetic, calorimetric, and spectroscopic studies of methylamine synthesis and related reactions over acid catalysts. Approach of this work was to explore quantitative correlations between factors that control the generation, type, strength, and catalytic properties of acid sites on zeolite catalysts. Microcalorimetry, thermogravimetric analysis, IR spectroscopy, and NMR spectroscopy have provided information about the nature and strength of acid sites in zeolites. This was vital in understanding the catalytic cycles involved in methylamine synthesis and related reactions over zeolite catalysts.

  10. Identification of sites responsible for the potentiating effect of niflumic acid on ClC-Ka kidney chloride channels

    PubMed Central

    Zifarelli, G; Liantonio, A; Gradogna, A; Picollo, A; Gramegna, G; De Bellis, M; Murgia, AR; Babini, E; Conte Camerino, D; Pusch, M

    2010-01-01

    Background and purpose: ClC-K kidney Cl− channels are important for renal and inner ear transepithelial Cl− transport, and are potentially interesting pharmacological targets. They are modulated by niflumic acid (NFA), a non-steroidal anti-inflammatory drug, in a biphasic way: NFA activates ClC-Ka at low concentrations, but blocks the channel above ∼1 mM. We attempted to identify the amino acids involved in the activation of ClC-Ka by NFA. Experimental approach: We used site-directed mutagenesis and two-electrode voltage clamp analysis of wild-type and mutant channels expressed in Xenopus oocytes. Guided by the crystal structure of a bacterial CLC homolog, we screened 97 ClC-Ka mutations for alterations of NFA effects. Key results: Mutations of five residues significantly reduced the potentiating effect of NFA. Two of these (G167A and F213A) drastically altered general gating properties and are unlikely to be involved in NFA binding. The three remaining mutants (L155A, G345S and A349E) severely impaired or abolished NFA potentiation. Conclusions and implications: The three key residues identified (L155, G345, A349) are localized in two different protein regions that, based on the crystal structure of bacterial CLC homologs, are expected to be exposed to the extracellular side of the channel, relatively close to each other, and are thus good candidates for being part of the potentiating NFA binding site. Alternatively, the protein region identified mediates conformational changes following NFA binding. Our results are an important step towards the development of ClC-Ka activators for treating Bartter syndrome types III and IV with residual channel activity. PMID:20649569

  11. Multi-component reactive transport modeling of natural attenuation of an acid groundwater plume at a uranium mill tailings site

    NASA Astrophysics Data System (ADS)

    Zhu, Chen; Hu, Fang Q.; Burden, David S.

    2001-11-01

    Natural attenuation of an acidic plume in the aquifer underneath a uranium mill tailings pond in Wyoming, USA was simulated using the multi-component reactive transport code PHREEQC. A one-dimensional model was constructed for the site and the model included advective-dispersive transport, aqueous speciation of 11 components, and precipitation-dissolution of six minerals. Transport simulation was performed for a reclamation scenario in which the source of acidic seepage will be terminated after 5 years and the plume will then be flushed by uncontaminated upgradient groundwater. Simulations show that successive pH buffer reactions with calcite, Al(OH) 3(a), and Fe(OH) 3(a) create distinct geochemical zones and most reactions occur at the boundaries of geochemical zones. The complex interplay of physical transport processes and chemical reactions produce multiple concentration waves. For SO 42- transport, the concentration waves are related to advection-dispersion, and gypsum precipitation and dissolution. Wave speeds from numerical simulations compare well to an analytical solution for wave propagation.

  12. Multi-component reactive transport modeling of natural attenuation of an acid groundwater plume at a uranium mill tailings site.

    PubMed

    Zhu, C; Hu, F Q; Burden, D S

    2001-11-01

    Natural attenuation of an acidic plume in the aquifer underneath a uranium mill tailings pond in Wyoming, USA was simulated using the multi-component reactive transport code PHREEQC. A one-dimensional model was constructed for the site and the model included advective-dispersive transport, aqueous speciation of 11 components, and precipitation-dissolution of six minerals. Transport simulation was performed for a reclamation scenario in which the source of acidic seepage will be terminated after 5 years and the plume will then be flushed by uncontaminated upgradient groundwater. Simulations show that successive pH buffer reactions with calcite, Al(OH)3(a), and Fe(OH)3(a) create distinct geochemical zones and most reactions occur at the boundaries of geochemical zones. The complex interplay of physical transport processes and chemical reactions produce multiple concentration waves. For SO4(2-) transport, the concentration waves are related to advection-dispersion, and gypsum precipitation and dissolution. Wave speeds from numerical simulations compare well to an analytical solution for wave propagation.

  13. Experimental and computational investigation of acetic acid deoxygenation over oxophilic molybdenum carbide: Surface chemistry and active site identity

    SciTech Connect

    Schaidle, Joshua A.; Blackburn, Jeffrey; Farberow, Carrie A.; Nash, Connor; Steirer, K. Xerxes; Clark, Jared; Robichaud, David J.; Ruddy, Daniel A.

    2016-01-21

    Ex situ catalytic fast pyrolysis (CFP) is a promising route for producing fungible biofuels; however, this process requires bifunctional catalysts that favor C–O bond cleavage, activate hydrogen at near atmospheric pressure and high temperature (350–500 °C), and are stable under high-steam, low hydrogen-to-carbon environments. Recently, early transition-metal carbides have been reported to selectively cleave C–O bonds of alcohols, aldehydes, and oxygenated aromatics, yet there is limited understanding of the metal carbide surface chemistry under reaction conditions and the identity of the active sites for deoxygenation. In this study, we evaluated molybdenum carbide (Mo2C) for the deoxygenation of acetic acid, an abundant component of biomass pyrolysis vapors, under ex situ CFP conditions, and we probed the Mo2C surface chemistry, identity of the active sites, and deoxygenation pathways using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations.

  14. Experimental and computational investigation of acetic acid deoxygenation over oxophilic molybdenum carbide: Surface chemistry and active site identity

    DOE PAGES

    Schaidle, Joshua A.; Blackburn, Jeffrey; Farberow, Carrie A.; ...

    2016-01-21

    Ex situ catalytic fast pyrolysis (CFP) is a promising route for producing fungible biofuels; however, this process requires bifunctional catalysts that favor C–O bond cleavage, activate hydrogen at near atmospheric pressure and high temperature (350–500 °C), and are stable under high-steam, low hydrogen-to-carbon environments. Recently, early transition-metal carbides have been reported to selectively cleave C–O bonds of alcohols, aldehydes, and oxygenated aromatics, yet there is limited understanding of the metal carbide surface chemistry under reaction conditions and the identity of the active sites for deoxygenation. In this study, we evaluated molybdenum carbide (Mo2C) for the deoxygenation of acetic acid, anmore » abundant component of biomass pyrolysis vapors, under ex situ CFP conditions, and we probed the Mo2C surface chemistry, identity of the active sites, and deoxygenation pathways using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations.« less

  15. Multiplex detection of functional G protein-coupled receptors harboring site-specifically modified unnatural amino acids.

    PubMed

    Naganathan, Saranga; Ray-Saha, Sarmistha; Park, Minyoung; Tian, He; Sakmar, Thomas P; Huber, Thomas

    2015-01-27

    We developed a strategy for identifying positions in G protein-coupled receptors that are amenable to bioorthogonal modification with a peptide epitope tag under cell culturing conditions. We introduced the unnatural amino acid p-azido-l-phenylalanine (azF) into human CC chemokine receptor 5 (CCR5) at site-specific amber codon mutations. We then used strain-promoted azide-alkyne [3+2] cycloaddition to label the azF-CCR5 variants with a FLAG peptide epitope-conjugated aza-dibenzocyclooctyne (DBCO) reagent. A microtiter plate-based sandwich fluorophore-linked immunosorbent assay was used to probe simultaneously the FLAG epitope and the receptor using infrared dye-conjugated antibodies so that the extent of DBCO incorporation, corresponding nominally to labeling efficiency, could be quantified ratiometrically. The extent of incorporation of DBCO at the various sites was evaluated in the context of a recent crystal structure of maraviroc-bound CCR5. We observed that labeling efficiency varied dramatically depending on the topological location of the azF in CCR5. Interestingly, position 109 in transmembrane helix 3, located in a hydrophobic cavity on the extracellular side of the receptor, was labeled most efficiently. Because the bioorthogonal labeling and detection strategy described might be used to introduce a variety of different peptide epitopes or fluorophores into engineered expressed receptors, it might prove to be useful for a wide range of applications, including single-molecule detection studies of receptor trafficking and signaling mechanism.

  16. Multiplex Detection of Functional G Protein-Coupled Receptors Harboring Site-Specifically Modified Unnatural Amino Acids

    PubMed Central

    2015-01-01

    We developed a strategy for identifying positions in G protein-coupled receptors that are amenable to bioorthogonal modification with a peptide epitope tag under cell culturing conditions. We introduced the unnatural amino acid p-azido-l-phenylalanine (azF) into human CC chemokine receptor 5 (CCR5) at site-specific amber codon mutations. We then used strain-promoted azide–alkyne [3+2] cycloaddition to label the azF-CCR5 variants with a FLAG peptide epitope-conjugated aza-dibenzocyclooctyne (DBCO) reagent. A microtiter plate-based sandwich fluorophore-linked immunosorbent assay was used to probe simultaneously the FLAG epitope and the receptor using infrared dye-conjugated antibodies so that the extent of DBCO incorporation, corresponding nominally to labeling efficiency, could be quantified ratiometrically. The extent of incorporation of DBCO at the various sites was evaluated in the context of a recent crystal structure of maraviroc-bound CCR5. We observed that labeling efficiency varied dramatically depending on the topological location of the azF in CCR5. Interestingly, position 109 in transmembrane helix 3, located in a hydrophobic cavity on the extracellular side of the receptor, was labeled most efficiently. Because the bioorthogonal labeling and detection strategy described might be used to introduce a variety of different peptide epitopes or fluorophores into engineered expressed receptors, it might prove to be useful for a wide range of applications, including single-molecule detection studies of receptor trafficking and signaling mechanism. PMID:25524496

  17. Vesiculoviral matrix (M) protein occupies nucleic acid binding site at nucleoporin pair (Rae1 • Nup98).

    PubMed

    Quan, Beili; Seo, Hyuk-Soo; Blobel, Günter; Ren, Yi

    2014-06-24

    mRNA export factor 1 (Rae1) and nucleoporin 98 (Nup98) are host cell targets for the matrix (M) protein of vesicular stomatitis virus (VSV). How Rae1 functions in mRNA export and how M protein targets both Rae1 and Nup98 are not understood at the molecular level. To obtain structural insights, we assembled a 1:1:1 complex of M•Rae1•Nup98 and established a crystal structure at 3.15-Å resolution. We found that the M protein contacts the Rae1•Nup98 heterodimer principally by two protrusions projecting from the globular domain of M like a finger and thumb. Both projections clamp to the side of the β-propeller of Rae1, with the finger also contacting Nup98. The most prominent feature of the finger is highly conserved Methionine 51 (Met51) with upstream and downstream acidic residues. The complementary surface on Rae1 displays a deep hydrophobic pocket, into which Met51 fastens like a bolt, and a groove of basic residues on either side, which bond to the acidic residues of the finger. Notably, the M protein competed for in vitro binding of various oligonucleotides to Rae1•Nup98. We localized this competing activity of M to its finger using a synthetic peptide. Collectively, our data suggest that Rae1 serves as a binding protein for the phosphate backbone of any nucleic acid and that the finger of M mimics this ligand. In the context of mRNA export, we propose that a given mRNA segment, after having been deproteinated by helicase, is transiently reproteinated by Nup98-tethered Rae1. We suggest that such repetitive cycles provide cytoplasmic stopover sites required for ratcheting mRNA across the nuclear pore.

  18. Vesiculoviral matrix (M) protein occupies nucleic acid binding site at nucleoporin pair (Rae1∙Nup98)

    SciTech Connect

    Quan, Beili; Seo, Hyuk-Soo; Blobel, Günter; Ren, Yi

    2014-07-01

    mRNA export factor 1 (Rae1) and nucleoporin 98 (Nup98) are host cell targets for the matrix (M) protein of vesicular stomatitis virus (VSV). How Rae1 functions in mRNA export and how M protein targets both Rae1 and Nup98 are not understood at the molecular level. To obtain structural insights, we assembled a 1:1:1 complex of M•Rae1•Nup98 and established a crystal structure at 3.15-Å resolution. We found that the M protein contacts the Rae1•Nup98 heterodimer principally by two protrusions projecting from the globular domain of M like a finger and thumb. Both projections clamp to the side of the β-propeller of Rae1, with the finger also contacting Nup98. The most prominent feature of the finger is highly conserved Methionine 51 (Met51) with upstream and downstream acidic residues. The complementary surface on Rae1 displays a deep hydrophobic pocket, into which Met51 fastens like a bolt, and a groove of basic residues on either side, which bond to the acidic residues of the finger. Notably, the M protein competed for in vitro binding of various oligonucleotides to Rae1•Nup98. We localized this competing activity of M to its finger using a synthetic peptide. Collectively, our data suggest that Rae1 serves as a binding protein for the phosphate backbone of any nucleic acid and that the finger of M mimics this ligand. In the context of mRNA export, we propose that a given mRNA segment, after having been deproteinated by helicase, is transiently reproteinated by Nup98-tethered Rae1. We suggest that such repetitive cycles provide cytoplasmic stopover sites required for ratcheting mRNA across the nuclear pore.

  19. Encapsulating Metal Clusters and Acid Sites within Small Voids: Synthetic Strategies and Catalytic Consequences

    NASA Astrophysics Data System (ADS)

    Goel, Sarika

    The selective encapsulation of metal clusters within zeolites can be used to prepare clusters that are uniform in diameter and to protect them against sintering and contact with feed impurities, while concurrently allowing active sites to select reactants based on their molecular size, thus conferring enzyme-like specificity to chemical catalysis. The apertures in small and medium-pore zeolites preclude the use of post-synthetic protocols to encapsulate the relevant metal precursors because cationic or anionic precursors with their charge-balancing double layer and gaseous complexes cannot diffuse through their windows or channels. We have developed general strategies to encapsulate metal clusters within small-pore zeolites by using metal precursors stabilized by ammonia or organic amine ligands, which stabilize metal precursors against their premature precipitation at the high temperature and pH conditions required for the hydrothermal synthesis of the target zeolite structures and favor interactions between metal precursors and incipient aluminosilicate nuclei during the self-assembly of microporous frameworks. When synthesis temperatures were higher than 400 K, available ligands were unable to prevent the premature precipitation of the metal precursors. In such cases, encapsulation was achieved instead via interzeolite transformations after successfully encapsulating metal precursors or clusters via post-synthesis exchange or ligand protection into parent zeolites and subsequently converting them into the target structures while retaining the encapsulated clusters or precursors. Such strategies led to the successful selective encapsulation of a wide range of metal clusters (Pt, Pd, Ru, Rh, Ir, Re, and Ag) within small-pore (SOD (sodalite), LTA (Linde type A (zeolite A)), GIS (gismondine), and ANA (analcime)) and medium-pore (MFI (ZSM-5)) zeolites. These protocols provide novel and diverse mechanism-based strategies for the design of catalysts with protected

  20. The Association between Elevated Levels of Peripheral Serotonin and Its Metabolite – 5-Hydroxyindoleacetic Acid and Bone Strength and Metabolism in Growing Rats with Mild Experimental Chronic Kidney Disease

    PubMed Central

    Oksztulska-Kolanek, Ewa; Znorko, Beata; Domaniewski, Tomasz; Rogalska, Joanna; Roszczenko, Alicja; Brzóska, Małgorzata Michalina; Pryczynicz, Anna; Kemona, Andrzej

    2016-01-01

    Chronic kidney disease (CKD) is associated with disturbances in bone strength and metabolism. The alterations of the serotonergic system are also observed in CKD. We used the 5/6 nephrectomy model of CKD to assess the impact of peripheral serotonin and its metabolite– 5-hydroxyindoleacetic acid on bone biomechanical properties and metabolism in growing rats. The animals were sacrificed one and three months after nephrectomy. Biomechanical properties were determined on two different bone types: the cortical bone of the femoral diaphysis using three-point bending test and the mixed cortico-trabecular bone by the bending test of the femoral neck. Biomechanical tests revealed preserved cortical bone strength, whereas work to fracture (W) and yield load (Fy) of mixed cortico-trabecular bone were significantly lower in CKD compared to controls. Serum activity of alkaline phosphatase (ALP), a bone formation marker, and tartrate-resistant acid phosphatase (TRACP 5b) reflecting bone resorption, were similar in CKD and controls. ALP was associated with lower femoral stiffness and strength, and higher displacements and W. TRACP 5b was inversely associated with cortical Fu and W. The elevated peripheral serotonergic system in CKD was: inversely associated with stiffness but positively related to the displacements and W; inversely associated with cortical Fy but positively correlated with this parameter in cortico-trabecular bone; inversely associated with ALP in controls but positively correlated with this biomarker in CKD animals. In conclusion, this study demonstrates the distinct effect of mild degree of CKD on bone strength in rapidly growing rats. The impaired renal function affects the peripheral serotonin metabolism, which in turn may influence the strength and metabolism of bones in these rats. This relationship seems to be beneficial on the biomechanical properties of the cortico-trabecular bone, whereas the cortical bone strength can be potentially reduced. PMID

  1. Determination of the positions of aluminum atoms introduced into SSZ-35 and the catalytic properties of the generated Brønsted acid sites.

    PubMed

    Miyaji, Akimitsu; Kimura, Nobuhiro; Shiga, Akinobu; Hayashi, Yoshihiro; Nishitoba, Toshiki; Motokura, Ken; Baba, Toshihide

    2017-03-01

    The positions of aluminum (Al) atoms in SSZ-35 together with the characteristics of the generated protons were investigated by (27)Al multiple quantum magic-angle spinning (MQ-MAS), (29)Si MAS, and (1)H MAS NMR data analyses accompanied by a variable temperature (1)H MAS NMR analysis. The origin of the acidic -OH groups (Brønsted acid sites) generated by introducing Al atoms into the T sites was investigated and the T sites introduced into the Al atoms were revealed. To further determine the catalytic properties of the acidic protons generated in SSZ-35, the influence of the concentration of the Al atoms on the catalytic activity and selectivity during the transformation of toluene was examined.

  2. Hydrogeology and ground-water quality of the Chromic Acid Pit site, US Army Air Defense Artillery Center and Fort Bliss, El Paso, Texas

    USGS Publications Warehouse

    Abeyta, Cynthia G.; Thomas, C.L.

    1996-01-01

    The Chromic Acid Pit site is an inactive waste disposal site that is regulated by the Resource Conservation and Recovery Act of 1976. The 2.2-cubic-yard cement-lined pit was operated from 1980 to 1983 by a contractor to the U.S. Army Air Defense Artillery Center and Fort Bliss. The pit, located on the Fort Bliss military reservation, in El Paso, Texas, was used for disposal and evaporation of chromic acid waste generated from chrome plating operations. The site was certified closed in 1989 and the Texas Natural Resources Conservation Commission issued Permit Number HW-50296 (U.S. Environmental Protection Agency Permit Number TX4213720101), which approved and implemented post-closure care for the Chromic Acid Pit site. In accordance with an approved post-closure plan, the U.S. Geological Survey is cooperating with the U.S. Army in evaluating hydrogeologic conditions and ground- water quality at the site. One upgradient and two downgradient ground-water monitoring wells were installed adjacent to the chromic acid pit by a private contractor. Quarterly ground-water sampling of these wells by the U.S. Geological Survey began in December 1993. The Chromic Acid Pit site is situated in the Hueco Bolson intermontane valley. The Hueco Bolson is a primary source of ground water in the El Paso area. City of El Paso and U.S. Army water-supply wells are located on all sides of the study area and are completed 600 to more than 1,200 feet below land surface. The ground-water level in the area of the Chromic Acid Pit site has declined about 25 feet from 1982 to 1993. Depth to water at the Chromic Acid Pit site in September 1994 was about 284 feet below land surface; ground-water flow is to the southeast. Ground-water samples collected from monitoring wells at the Chromic Acid Pit site contained dissolved-solids concentrations of 442 to 564 milligrams per liter. Nitrate as nitrogen concentrations ranged from 2.1 to 2.7 milligrams per liter; nitrite plus nitrate as nitrogen

  3. Modeling solubility and acid-base properties of some amino acids in aqueous NaCl and (CH3)4NCl aqueous solutions at different ionic strengths and temperatures.

    PubMed

    Bretti, Clemente; Giuffrè, Ottavia; Lando, Gabriele; Sammartano, Silvio

    2016-01-01

    New potentiometric experiments have been performed in NaCl and in (CH3)4NCl media, to determine the protonation constants, the protonation enthalpy changes and the solubility of six natural α-amino acids, namely Glycine (Gly), Alanine (Ala), Valine (Val), Leucine (Leu), Serine (Ser) and Phenylalanine (Phe). The aim of the work is the rationalization of the protonation thermodynamics (log [Formula: see text], solubility and [Formula: see text]) in NaCl, determining recommended, tentative or provisional values in selected experimental conditions and to report, for the first time, data in a weak interacting medium, as (CH3)4NCl. Literature data analysis was performed selecting the most reliable values, analyzed together with new data here reported. Significant trends and similarities were observed in the behavior of the six amino acids, and in some cases it was possible to determine common parameters for the ionic strength and temperature dependence. In general, the first protonation step, relative to the amino group, is significantly exothermic (average value is [Formula: see text] = -44.5 ± 0.4 kJ mol(-1) at infinite dilution and T = 298.15 K), and the second, relative to the carboxylate group, is fairly close to zero ([Formula: see text] = -2.5 ± 1.6, same conditions). In both cases, the main contribution to the proton binding reaction is mainly entropic in nature. For phenylalanine and leucine, solubility measurements at different concentrations of supporting electrolyte allowed to determine total and specific solubility values, then used to obtain the Setschenow and the activity coefficients of all the species involved in the protonation equilibria. The values of the first protonation constant in (CH3)4NCl are lower than the corresponding values in NaCl, due to the weak interaction between the deprotonated amino group and (CH3)4N(+). In this light, differences between the protonation functions in NaCl and (CH3)4NCl were used for the quantification

  4. Impact of ursodeoxycholic acid on a CCK1R cholesterol-binding site may contribute to its positive effects in digestive function

    PubMed Central

    Desai, Aditya J.; Dong, Maoqing; Harikumar, Kaleeckal G.

    2015-01-01

    Dysfunction of the type 1 cholecystokinin (CCK) receptor (CCK1R) as a result of increased gallbladder muscularis membrane cholesterol has been implicated in the pathogenesis of cholesterol gallstones. Administration of ursodeoxycholic acid, which is structurally related to cholesterol, has been shown to have beneficial effects on gallstone formation. Our aims were to explore the possible direct effects and mechanism of action of bile acids on CCK receptor function. We studied the effects of structurally related hydrophobic chenodeoxycholic acid and hydrophilic ursodeoxycholic acid in vitro on CCK receptor function in the setting of normal and elevated membrane cholesterol. We also examined their effects on a cholesterol-insensitive CCK1R mutant (Y140A) disrupting a key site of cholesterol action. The results show that, similar to the impact of cholesterol on CCK receptors, bile acid effects were limited to CCK1R, with no effects on CCK2R. Chenodeoxycholic acid had a negative impact on CCK1R function, while ursodeoxycholic acid had no effect on CCK1R function in normal membranes but was protective against the negative impact of elevated cholesterol on this receptor. The cholesterol-insensitive CCK1R mutant Y140A was resistant to effects of both bile acids. These data suggest that bile acids compete with the action of cholesterol on CCK1R, probably by interacting at the same site, although the conformational impact of each bile acid appears to be different, with ursodeoxycholic acid capable of correcting the abnormal conformation of CCK1R in a high-cholesterol environment. This mechanism may contribute to the beneficial effect of ursodeoxycholic acid in reducing cholesterol gallstone formation. PMID:26138469

  5. The role of outer surface/inner bulk Brønsted acidic sites in the adsorption of a large basic molecule (simazine) on H-Y zeolite.

    PubMed

    Sannino, Filomena; Pansini, Michele; Marocco, Antonello; Bonelli, Barbara; Garrone, Edoardo; Esposito, Serena

    2015-11-21

    The simple means adopted for investigating H-Y zeolite acidity in water is the pH-dependence of the amount of a basic molecule adsorbed under isochoric conditions, a technique capable of yielding, under equilibrium conditions, an estimate of the pKa value of the involved acidic centres: the behaviour with temperature of adsorbed amounts yields instead some information on thermodynamics. Simazine (Sim, 2-chloro-4,6-bis(ethylamino)-s-triazine) was chosen as an adsorbate because its transverse dimension (7.5 Å) is close to the opening of the supercage in the faujasite structure of H-Y (7.4 Å). In short term measurements, Sim adsorption at 25 °C occurs only at the outer surface of H-Y particles. Two types of mildly acidic centres are present (with pKaca. 7 and ca. 8, respectively) and no strong one is observed. Previous adsorption of ammonia from the gas phase discriminates between the two. The former survives, and shows features common with the silanols of amorphous silica. The latter is suppressed: because of this and other features distinguishing this site from silanol species (e.g. the formation of dimeric Sim2H(+) species, favoured by coverage and unfavoured by temperatures of adsorption higher than ambient temperature) a candidate is an Al based site. We propose a Lewis centre coordinating a water molecule, exhibiting acidic properties. This acidic water molecule can be replaced by the stronger base ammonia, also depleting inner strong Brønsted sites. A mechanism for the generation of the two sites from surface Brønsted species is proposed. Long term adsorption measurements at 25 °C already show the onset of the interaction with inner strongly acidic Brønsted sites: because of its size, activation is required for Sim to pass the supercage openings and reach inner acidic sites. When adsorption is run at 40-50 °C, uptake is much larger and increases with temperature. Isochoric measurements suggest a pKa value of ca. 3 compatible with its marked acidic

  6. Site-Directed Mutagenesis of HgcA and HgcB Reveals Amino Acid Residues Important for Mercury Methylation

    PubMed Central

    Smith, Steven D.; Bridou, Romain; Johs, Alexander; Parks, Jerry M.; Elias, Dwayne A.; Hurt, Richard A.; Brown, Steven D.; Podar, Mircea

    2015-01-01

    Methylmercury is a potent neurotoxin that is produced by anaerobic microorganisms from inorganic mercury by a recently discovered pathway. A two-gene cluster, consisting of hgcA and hgcB, encodes two of the proteins essential for this activity. hgcA encodes a corrinoid protein with a strictly conserved cysteine proposed to be the ligand for cobalt in the corrinoid cofactor, whereas hgcB encodes a ferredoxin-like protein thought to be an electron donor to HgcA. Deletion of either gene eliminates mercury methylation by the methylator Desulfovibrio desulfuricans ND132. Here, site-directed mutants of HgcA and HgcB were constructed to determine amino acid residues essential for mercury methylation. Mutations of the strictly conserved residue Cys93 in HgcA, the proposed ligand for the corrinoid cobalt, to Ala or Thr completely abolished the methylation capacity, but a His substitution produced measurable methylmercury. Mutations of conserved amino acids near Cys93 had various impacts on the methylation capacity but showed that the structure of the putative “cap helix” region harboring Cys93 is crucial for methylation function. In the ferredoxin-like protein HgcB, only one of two conserved cysteines found at the C terminus was necessary for methylation, but either cysteine sufficed. An additional, strictly conserved cysteine, Cys73, was also determined to be essential for methylation. This study supports the previously predicted importance of Cys93 in HgcA for methylation of mercury and reveals additional residues in HgcA and HgcB that facilitate the production of this neurotoxin. PMID:25724962

  7. Site-Directed Mutagenesis of HgcA and HgcB Reveals Amino Acid Residues Important for Mercury Methylation

    DOE PAGES

    Smith, Steven D.; Bridou, Romain; Johs, Alexander; ...

    2015-02-27

    Methylmercury is a potent neurotoxin that is produced by anaerobic microorganisms from inorganic mercury by a recently discovered pathway. A two-gene cluster, consisting of hgcA and hgcB, encodes two of the proteins essential for this activity. hgcA encodes a corrinoid protein with a strictly conserved cysteine proposed to be the ligand for cobalt in the corrinoid cofactor, whereas hgcB encodes a ferredoxin-like protein thought to be an electron donor to HgcA. Deletion of either gene eliminates mercury methylation by the methylator Desulfovibrio desulfuricans ND132. Here, site-directed mutants of HgcA and HgcB were constructed to determine amino acid residues essential formore » mercury methylation. Mutations of the strictly conserved residue Cys93 in HgcA, the proposed ligand for the corrinoid cobalt, to Ala or Thr completely abolished the methylation capacity, but a His substitution produced measurable methylmercury. Mutations of conserved amino acids near Cys93 had various impacts on the methylation capacity but showed that the structure of the putative “cap helix” region harboring Cys93 is crucial for methylation function. In the ferredoxin-like protein HgcB, only one of two conserved cysteines found at the C terminus was necessary for methylation, but either cysteine sufficed. An additional, strictly conserved cysteine, Cys73, was also determined to be essential for methylation. Ultimately, this study supports the previously predicted importance of Cys93 in HgcA for methylation of mercury and reveals additional residues in HgcA and HgcB that facilitate the production of this neurotoxin.« less

  8. Site-Directed Mutagenesis of HgcA and HgcB Reveals Amino Acid Residues Important for Mercury Methylation

    SciTech Connect

    Smith, Steven D.; Bridou, Romain; Johs, Alexander; Parks, Jerry M.; Elias, Dwayne A.; Hurt, Richard A.; Brown, Steven D.; Podar, Mircea; Wall, Judy D.

    2015-02-27

    Methylmercury is a potent neurotoxin that is produced by anaerobic microorganisms from inorganic mercury by a recently discovered pathway. A two-gene cluster, consisting of hgcA and hgcB, encodes two of the proteins essential for this activity. hgcA encodes a corrinoid protein with a strictly conserved cysteine proposed to be the ligand for cobalt in the corrinoid cofactor, whereas hgcB encodes a ferredoxin-like protein thought to be an electron donor to HgcA. Deletion of either gene eliminates mercury methylation by the methylator Desulfovibrio desulfuricans ND132. Here, site-directed mutants of HgcA and HgcB were constructed to determine amino acid residues essential for mercury methylation. Mutations of the strictly conserved residue Cys93 in HgcA, the proposed ligand for the corrinoid cobalt, to Ala or Thr completely abolished the methylation capacity, but a His substitution produced measurable methylmercury. Mutations of conserved amino acids near Cys93 had various impacts on the methylation capacity but showed that the structure of the putative “cap helix” region harboring Cys93 is crucial for methylation function. In the ferredoxin-like protein HgcB, only one of two conserved cysteines found at the C terminus was necessary for methylation, but either cysteine sufficed. An additional, strictly conserved cysteine, Cys73, was also determined to be essential for methylation. Ultimately, this study supports the previously predicted importance of Cys93 in HgcA for methylation of mercury and reveals additional residues in HgcA and HgcB that facilitate the production of this neurotoxin.

  9. Rational Design of Fatty Acid Amide Hydrolase Inhibitors that Act by Covalently Bonding to Two Active Site Residues

    PubMed Central

    Otrubova, Katerina; Brown, Monica; McCormick, Michael S.; Han, Gye W.; O’Neal, Scott T.; Cravatt, Benjamin F.; Stevens, Raymond C.; Lichtman, Aron H.; Boger, Dale L.

    2013-01-01

    The design and characterization of α-ketoheterocycle fatty acid amide hydrolase (FAAH) inhibitors are disclosed that additionally and irreversibly target a cysteine (Cys269) found in the enzyme cytosolic port while maintaining the reversible covalent Ser241 attachment responsible for their rapid and initially reversible enzyme inhibition. Two α-ketooxazoles (3 and 4) containing strategically placed electrophiles at the C5 position of the pyridyl substituent of 2 (OL-135) were prepared and examined as inhibitors of FAAH. Consistent with the observed time-dependent non-competitive inhibition, the co-crystal X-ray structure of 3 bound to a humanized variant of rat FAAH revealed that 3 was not only covalently bound to the active site catalytic nucleophile Ser241 as a deprotonated hemiketal, but also to Cys269 through the pyridyl C5-substituent, thus providing an inhibitor with dual covalent attachment in the enzyme active site. In vivo characterization of the prototypical inhibitors in mice demonstrate that they raise endogenous brain levels of FAAH substrates to a greater extent and for a much longer duration (>6 h) than the reversible inhibitor 2, indicating that the inhibitors accumulate and persist in the brain to completely inhibit FAAH for a prolonged period. Consistent with this behavior and the targeted irreversible enzyme inhibition, 3 reversed cold allodynia in the chronic constriction injury model of neuropathic pain in mice for a sustained period (>6 h) beyond that observed with the reversible inhibitor 2, providing effects that were unchanged over the 1–6 h time course monitored. PMID:23581831

  10. In Silico Structure Prediction of Human Fatty Acid Synthase-Dehydratase: A Plausible Model for Understanding Active Site Interactions.

    PubMed

    John, Arun; Umashankar, Vetrivel; Samdani, A; Sangeetha, Manoharan; Krishnakumar, Subramanian; Deepa, Perinkulam Ravi

    2016-01-01

    Fatty acid synthase (FASN, UniProt ID: P49327) is a multienzyme dimer complex that plays a critical role in lipogenesis. Consequently, this lipogenic enzyme has gained tremendous biomedical importance. The role of FASN and its inhibition is being extensively researched in several clinical conditions, such as cancers, obesity, and diabetes. X-ray crystallographic structures of some of its domains, such as β-ketoacyl synthase, acetyl transacylase, malonyl transacylase, enoyl reductase, β-ketoacyl reductase, and thioesterase, (TE) are already reported. Here, we have attempted an in silico elucidation of the uncrystallized dehydratase (DH) catalytic domain of human FASN. This theoretical model for DH domain was predicted using comparative modeling methods. Different stand-alone tools and servers were used to validate and check the reliability of the predicted models, which suggested it to be a highly plausible model. The stereochemical analysis showed 92.0% residues in favorable region of Ramachandran plot. The initial physiological substrate β-hydroxybutyryl group was docked into active site of DH domain using Glide. The molecular dynamics simulations carried out for 20 ns in apo and holo states indicated the stability and accuracy of the predicted structure in solvated condition. The predicted model provided useful biochemical insights into the substrate-active site binding mechanisms. This model was then used for identifying potential FASN inhibitors using high-throughput virtual screening of the National Cancer Institute database of chemical ligands. The inhibitory efficacy of the top hit ligands was validated by performing molecular dynamics simulation for 20 ns, where in the ligand NSC71039 exhibited good enzyme inhibition characteristics and exhibited dose-dependent anticancer cytotoxicity in retinoblastoma cancer cells in vitro.

  11. In Silico Structure Prediction of Human Fatty Acid Synthase–Dehydratase: A Plausible Model for Understanding Active Site Interactions

    PubMed Central

    John, Arun; Umashankar, Vetrivel; Samdani, A.; Sangeetha, Manoharan; Krishnakumar, Subramanian; Deepa, Perinkulam Ravi

    2016-01-01

    Fatty acid synthase (FASN, UniProt ID: P49327) is a multienzyme dimer complex that plays a critical role in lipogenesis. Consequently, this lipogenic enzyme has gained tremendous biomedical importance. The role of FASN and its inhibition is being extensively researched in several clinical conditions, such as cancers, obesity, and diabetes. X-ray crystallographic structures of some of its domains, such as β-ketoacyl synthase, acetyl transacylase, malonyl transacylase, enoyl reductase, β-ketoacyl reductase, and thioesterase, (TE) are already reported. Here, we have attempted an in silico elucidation of the uncrystallized dehydratase (DH) catalytic domain of human FASN. This theoretical model for DH domain was predicted using comparative modeling methods. Different stand-alone tools and servers were used to validate and check the reliability of the predicted models, which suggested it to be a highly plausible model. The stereochemical analysis showed 92.0% residues in favorable region of Ramachandran plot. The initial physiological substrate β-hydroxybutyryl group was docked into active site of DH domain using Glide. The molecular dynamics simulations carried out for 20 ns in apo and holo states indicated the stability and accuracy of the predicted structure in solvated condition. The predicted model provided useful biochemical insights into the substrate–active site binding mechanisms. This model was then used for identifying potential FASN inhibitors using high-throughput virtual screening of the National Cancer Institute database of chemical ligands. The inhibitory efficacy of the top hit ligands was validated by performing molecular dynamics simulation for 20 ns, where in the ligand NSC71039 exhibited good enzyme inhibition characteristics and exhibited dose-dependent anticancer cytotoxicity in retinoblastoma cancer cells in vitro. PMID:27559295

  12. Analysis of diurnal variability of atmospheric halocarbons and CFC replacements to imply emission strength and sources at an urban site of Lukang in central Taiwan

    NASA Astrophysics Data System (ADS)

    Lee, Bing-Sun; Chiou, Chung-Biau; Lin, Chung-Yi

    2014-12-01

    Hourly atmospheric measurements of halocarbons and chlorofluorocarbon (CFC) replacements were conducted at an urban site of Lukang, Changhua, in central Taiwan from May to August, 2013. The temporal distribution of different groups of halocarbons in the Lukang urban atmosphere, including chlorofluorocarbons (CFCs), Chlorodifluoromethane (HCFC-22), Bromochlorodifluoromethane (Halon-1211), and other chlorinated compounds, is presented and discussed. The concentrations (mixing ratios) of HCFC-22, Dichlorodifluoromethane (CFC-12), Halon-1211, Trichlorofluoromethane (CFC-11), Dichloromethane (CH2Cl2), and Trichloroethylene (TCE) were enhanced with respect to the local background levels; the atmospheric mixing ratio of carbon tetrachloride (CCl4) was slightly higher than its local background level; on the other hand, 1,1,2-Trichlorotrifluoroethane (CFC-113) was relatively uniform and not very different from background atmospheric level in non-urban areas. Among these compounds, HCFC-22, Halon-1211 and the halogenated compounds, CH2Cl2 and TCE, used as solvents were strongly enhanced. The average mixing ratio of Halon-1211 was higher than the local background of ∼4.5 ppt by ∼60% although Halon-1211 production had been phased out by 1996. Hourly average mixing ratios of halocarbons (HCFC-22, CFC-12, Halon-1211, CFC-11, CH2Cl2, and TCE) illustrated a distinct diurnal cycle characterized with a pattern of elevated mixing ratio and large mixing ratio variability amplitude at night relative to that in daytime. Although emission sources of these halocarbons were complex, hourly average mixing ratios for most of these high variability halocarbons peaked at ∼5:00 AM when the hourly average wind speed reached the minimum value of the day; by contrast, the hourly average mixing ratio of CO peaked at ∼8:30 AM when the ambient atmospheric wind condition was strongly influenced by sea breezes during the traffic rush hours. This phenomenon revealed that meteorological factors

  13. Chemical characterization of the surface sites of coal

    SciTech Connect

    Fowkes, F.M.; Riddle, F.L. Jr.; Cole, D.A.

    1990-08-01

    We propose to do experimental studies in four related areas concerning the acid-base properties of coal surfaces; (1) develop high precision flow microcalorimetric methods for determining the concentrations and strengths of the acidic and basic surface sites of coal powders; (2) develop photo-acoustic FTIR and solid-state NMR spectral shift techniques for determination of the concentrations and strengths of acidic and basic surface sites of coal powders; (3) determine the concentrations and strengths of the acidic and basic surface sites of some of the well-characterized coal samples from Argonne National Labs, comparing the coal samples before and after demineralization treatments with HCl and HF; (4) study the effects of surface acidity and basicity on the coal/water interface, with emphasis on the role of interfacial acid-base interactions in the adsorption of ions, surfactants and coal/water slurry stabilizers. One of the major goals of this research effort is to identify and characterize acidic and basic molecules which have NMR active nuclei such that through measurements of NMR chemical shifts one can deduce the surface acidity or basicity of solids such as coals. This quarter, triphenylsilanol was investigated as an NMR chemical shift probe molecule. 2 figs., 1 tab.

  14. Chemical repair of base lesions, AP-sites, and strand breaks on plasmid DNA in dilute aqueous solution by ascorbic acid

    SciTech Connect

    Hata, Kuniki; Urushibara, Ayumi; Yamashita, Shinichi; Shikazono, Naoya; Yokoya, Akinari; Katsumura, Yosuke

    2013-05-03

    Highlights: •We report a novel mechanism of radiation protection of DNA by chemical activity of ascorbic acid. •The “chemical repair” of DNA damage was revealed using biochemical assay and chemical kinetics analysis. •We found that ascorbic acid significantly repairs precursors of nucleobase lesions and abasic sites. •However, ascorbic acid seldom repairs precursors of DNA-strand breaks. -- Abstract: We quantified the damage yields produced in plasmid DNA by γ-irradiation in the presence of low concentrations (10–100 μM) of ascorbic acid, which is a major antioxidant in living systems, to clarify whether it chemically repairs radiation damage in DNA. The yield of DNA single strand breaks induced by irradiation was analyzed with agarose gel electrophoresis as conformational changes in closed circular plasmids. Base lesions and abasic sites were also observed as additional conformational changes by treating irradiated samples with glycosylase proteins. By comparing the suppression efficiencies to the induction of each DNA lesion, in addition to scavenging of the OH radicals derived from water radiolysis, it was found that ascorbic acid promotes the chemical repair of precursors of AP-sites and base lesions more effectively than those of single strand breaks. We estimated the efficiency of the chemical repair of each lesion using a kinetic model. Approximately 50–60% of base lesions and AP-sites were repaired by 10 μM ascorbic acid, although strand breaks were largely unrepaired by ascorbic acid at low concentrations. The methods in this study will provide a route to understanding the mechanistic aspects of antioxidant activity in living systems.

  15. Conformational transition of FGFR kinase activation revealed by site-specific unnatural amino acid reporter and single molecule FRET

    PubMed Central

    Perdios, Louis; Lowe, Alan R.; Saladino, Giorgio; Bunney, Tom D.; Thiyagarajan, Nethaji; Alexandrov, Yuriy; Dunsby, Christopher; French, Paul M. W.; Chin, Jason W.; Gervasio, Francesco Luigi; Tate, Edward W.; Katan, Matilda

    2017-01-01

    Protein kinases share significant structural similarity; however, structural features alone are insufficient to explain their diverse functions. Thus, bridging the gap between static structure and function requires a more detailed understanding of their dynamic properties. For example, kinase activation may occur via a switch-like mechanism or by shifting a dynamic equilibrium between inactive and active states. Here, we utilize a combination of FRET and molecular dynamics (MD) simulations to probe the activation mechanism of the kinase domain of Fibroblast Growth Factor Receptor (FGFR). Using genetically-encoded, site-specific incorporation of unnatural amino acids in regions essential for activation, followed by specific labeling with fluorescent moieties, we generated a novel class of FRET-based reporter to monitor conformational differences corresponding to states sampled by non phosphorylated/inactive and phosphorylated/active forms of the kinase. Single molecule FRET analysis in vitro, combined with MD simulations, shows that for FGFR kinase, there are populations of inactive and active states separated by a high free energy barrier resulting in switch-like activation. Compared to recent studies, these findings support diversity in features of kinases that impact on their activation mechanisms. The properties of these FRET-based constructs will also allow further studies of kinase dynamics as well as applications in vivo. PMID:28045057

  16. "Opening" the ferritin pore for iron release by mutation of conserved amino acids at interhelix and loop sites.

    PubMed

    Jin, W; Takagi, H; Pancorbo, B; Theil, E C

    2001-06-26

    Ferritin concentrates, stores, and detoxifies iron in most organisms. The iron is a solid, ferric oxide mineral (< or =4500 Fe) inside the protein shell. Eight pores are formed by subunit trimers of the 24 subunit protein. A role for the protein in controlling reduction and dissolution of the iron mineral was suggested in preliminary experiments [Takagi et al. (1998) J. Biol. Chem. 273, 18685-18688] with a proline/leucine substitution near the pore. Localized pore disorder in frog L134P crystals coincided with enhanced iron exit, triggered by reduction. In this report, nine additional substitutions of conserved amino acids near L134 were studied for effects on iron release. Alterations of a conserved hydrophobic pair, a conserved ion pair, and a loop at the ferritin pores all increased iron exit (3-30-fold). Protein assembly was unchanged, except for a slight decrease in volume (measured by gel filtration); ferroxidase activity was still in the millisecond range, but a small decrease indicates slight alteration of the channel from the pore to the oxidation site. The sensitivity of reductive iron exit rates to changes in conserved residues near the ferritin pores, associated with localized unfolding, suggests that the structure around the ferritin pores is a target for regulated protein unfolding and iron release.

  17. Legume-grass intercropping phytoremediation of phthalic acid esters in soil near an electronic waste recycling site: a field study.

    PubMed

    Ma, Ting Ting; Teng, Ying; Luo, Yong Ming; Christie, Peter

    2013-01-01

    A field experiment was conducted to study the phytoremediation of phthalic acid esters (PAEs) by legume (alfalfa, Medicago sativa L.)-grass (perennial ryegrass, Lolium perenne L. and tall fescue, Festuca arundinacea) intercropping in contaminated agricultural soil at one of the largest e-waste recycling sites in China. Two compounds, DEHP and DnBP, were present in the soil and in the shoots of the test plants at much higher concentrations than the other target PAEs studied. Over 80% of 'total' (i.e., all six) PAEs were removed from the soil across all treatments by the end of the experiment. Alfalfa in monoculture removed over 90% of PAEs and alfalfa in the intercrop of the three plant species contained the highest shoot concentration of total PAEs of about 4.7 mg kg(-1) DW (dry weight). Calculation of phytoextraction efficiency indicated that the most effective plant combinations in eliminating soil PAEs were the three-species intercrop (1.78%) and the alfalfa monocrop (1.41%). Phytoremediation with alfalfa was effective in both monoculture and intercropping. High bioconcentration factors (BCFs) indicated the occurrence of significant extraction of PAEs by plants from soil, suggesting that phytoremediation may have potential for the removal of PAEs from contaminated soils.

  18. Conformational transition of FGFR kinase activation revealed by site-specific unnatural amino acid reporter and single molecule FRET

    NASA Astrophysics Data System (ADS)

    Perdios, Louis; Lowe, Alan R.; Saladino, Giorgio; Bunney, Tom D.; Thiyagarajan, Nethaji; Alexandrov, Yuriy; Dunsby, Christopher; French, Paul M. W.; Chin, Jason W.; Gervasio, Francesco Luigi; Tate, Edward W.; Katan, Matilda

    2017-01-01

    Protein kinases share significant structural similarity; however, structural features alone are insufficient to explain their diverse functions. Thus, bridging the gap between static structure and function requires a more detailed understanding of their dynamic properties. For example, kinase activation may occur via a switch-like mechanism or by shifting a dynamic equilibrium between inactive and active states. Here, we utilize a combination of FRET and molecular dynamics (MD) simulations to probe the activation mechanism of the kinase domain of Fibroblast Growth Factor Receptor (FGFR). Using genetically-encoded, site-specific incorporation of unnatural amino acids in regions essential for activation, followed by specific labeling with fluorescent moieties, we generated a novel class of FRET-based reporter to monitor conformational differences corresponding to states sampled by non phosphorylated/inactive and phosphorylated/active forms of the kinase. Single molecule FRET analysis in vitro, combined with MD simulations, shows that for FGFR kinase, there are populations of inactive and active states separated by a high free energy barrier resulting in switch-like activation. Compared to recent studies, these findings support diversity in features of kinases that impact on their activation mechanisms. The properties of these FRET-based constructs will also allow further studies of kinase dynamics as well as applications in vivo.

  19. Site-specific integration and constitutive expression of key genes into Escherichia coli chromosome increases shikimic acid yields.

    PubMed

    Liu, Xianglei; Lin, Jun; Hu, Haifeng; Zhou, Bin; Zhu, Baoquan

    2016-01-01

    As the key starting material for the chemical synthesis of Oseltamivir, shikimic acid (SA) has captured worldwide attention. Many researchers have tried to improve SA production by metabolic engineering, yet expression plasmids were used generally. In recent years, site-specific integration of key genes into chromosome to increase the yield of metabolites showed considerable advantages. The genes could maintain stably and express constitutively without induction. Herein, crucial genes aroG, aroB, tktA, aroE (encoding 3-deoxy-D-arabinoheptulosonate-7-phosphate synthase, dehydroquinate synthase, transketolase and shikimate dehydrogenase, respectively) of SA pathway and glk, galP (encoding glucokinase and galactose permease) were integrated into the locus of ptsHIcrr (phosphoenolpyruvate: carbohydrate phosphotransferase system operon) in a shikimate kinase genetic defect strain Escherichia coli BW25113 (ΔaroL/aroK, DE3). Furthermore, another key gene ppsA (encoding phosphoenolpyruvate synthase) was integrated into tyrR (encoding Tyr regulator protein). As a result, SA production of the recombinant (SA5/pGBAE) reached to 4.14 g/L in shake flask and 27.41 g/L in a 5-L bioreactor. These data suggested that integration of key genes increased SA yields effectively. This strategy is environmentally friendly for no antibiotic is added, simple to handle without induction, and suitable for industrial production.

  20. Effect of the ionic strength of a mobile phase on the chromatographic retention and thermodynamic characteristics of the adsorption of enantiomers of α-phenylcarboxylic acids on a chiral adsorbent with grafted antibiotic eremomycin

    NASA Astrophysics Data System (ADS)

    Reshetova, E. N.

    2017-01-01

    The effect the ionic strength of an aqueous ethanol mobile phase containing buffer salt has the on retention and thermodynamics of adsorption of optical isomers of some α-phenylcarboxylic acids on chiral adsorbent Nautilus-E with grafted antibiotic eremomycin is investigated. It is shown that ion exchange processes participate in the adsorption of enantiomers of α-phenylcarboxylic acids. It is established that electrostatic interactions contribute to the retention of enantiomers of α-phenylcarboxylic acids and affect selectivity only slightly. The dependences of retention characteristics, selectivity, and thermodynamic parameters on the concentration of the buffer salt in the eluent are determined. A statistical analysis of enthalpy-entropy compensation is performed, and the compensation effect is shown to be true. It is found that the points corresponding to the investigated adsorbates are distributed over the compensation dependence according to the spatial structural characteristics of molecules.

  1. Comparative analysis of amino acid composition in the active site of nirk gene encoding copper-containing nitrite reductase (CuNiR) in bacterial spp.

    PubMed

    Adhikari, Utpal Kumar; Rahman, M Mizanur

    2017-04-01

    The nirk gene encoding the copper-containing nitrite reductase (CuNiR), a key catalytic enzyme in the environmental denitrification process that helps to produce nitric oxide from nitrite. The molecular mechanism of denitrification process is definitely complex and in this case a theoretical investigation has been conducted to know the sequence information and amino acid composition of the active site of CuNiR enzyme using various Bioinformatics tools. 10 Fasta formatted sequences were retrieved from the NCBI database and the domain and disordered regions identification and phylogenetic analyses were done on these sequences. The comparative modeling of protein was performed through Modeller 9v14 program and visualized by PyMOL tools. Validated protein models were deposited in the Protein Model Database (PMDB) (PMDB id: PM0080150 to PM0080159). Active sites of nirk encoding CuNiR enzyme were identified by Castp server. The PROCHECK showed significant scores for four protein models in the most favored regions of the Ramachandran plot. Active sites and cavities prediction exhibited that the amino acid, namely Glycine, Alanine, Histidine, Aspartic acid, Glutamic acid, Threonine, and Glutamine were common in four predicted protein models. The present in silico study anticipates that active site analyses result will pave the way for further research on the complex denitrification mechanism of the selected species in the experimental laboratory.

  2. Acid-Sensitive Sheddable PEGylated PLGA Nanoparticles Increase the Delivery of TNF-α siRNA in Chronic Inflammation Sites

    PubMed Central

    Aldayel, Abdulaziz M; Naguib, Youssef W; O'Mary, Hannah L; Li, Xu; Niu, Mengmeng; Ruwona, Tinashe B; Cui, Zhengrong

    2016-01-01

    There has been growing interest in utilizing small interfering RNA (siRNA) specific to pro-inflammatory cytokines, such as tumor necrosis factor-α ( TNF-α), in chronic inflammation therapy. However, delivery systems that can increase the distribution of the siRNA in chronic inflammation sites after intravenous administration are needed. Herein we report that innovative functionalization of the surface of siRNA-incorporated poly (lactic-co-glycolic) acid (PLGA) nanoparticles significantly increases the delivery of the siRNA in the chronic inflammation sites in a mouse model. The TNF-α siRNA incorporated PLGA nanoparticles were prepared by the standard double emulsion method, but using stearoyl-hydrazone-polyethylene glycol 2000, a unique acid-sensitive surface active agent, as the emulsifying agent, which renders (i) the nanoparticles PEGylated and (ii) the PEGylation sheddable in low pH environment such as that in chronic inflammation sites. In a mouse model of lipopolysaccharide-induced chronic inflammation, the acid-sensitive sheddable PEGylated PLGA nanoparticles showed significantly higher accumulation or distribution in chronic inflammation sites than PLGA nanoparticles prepared with an acid-insensitive emulsifying agent (i.e., stearoyl-amide-polyethylene glycol 2000) and significantly increased the distribution of the TNF-α siRNA incorporated into the nanoparticles in inflamed mouse foot. PMID:27434685

  3. Comparison of the supporting strength of a poly-L-lactic acid sheet and porous polyethylene (Medpor) for the reconstruction of orbital floor fractures.

    PubMed

    Hwang, Kun; Kim, Dong Hyun

    2010-05-01

    The aim of this study was to elucidate the supporting strength of the curved poly-L-lactic acid (PLLA) sheet and porous polyethylene (Medpor) for reconstruction of orbital floor fractures. For one-half and two-thirds orbital floor fractures, reconstruction was performed using the PLLA sheet and Medpor. The PLLA sheet was molded to fit the orbital floor (concavity). The anterior portion (1 cm) was curved to fit the inferior orbital rim and fixed with a screw. Medpor was designed to fit the orbital floor. A screw was fixed 6 mm away from the anterior border of the orbital floor. Each implant was hung by wire, and the degree of sagging of the implant was measured using micrometers by the power of a force gauge. For one-half orbital floor fractures, the power of the PLLA sheet to sag 5 mm was 2.46 (SD, 0.14) N, and that of Medpor was 0.59 (SD, 0.04) N. The power of the PLLA sheet to sag 10 mm was 6.9 (SD, 0.14) N, and that of Medpor was 1.52 (SD, 0.16) N. For two-thirds orbital floor fractures, the power of the PLLA sheet to sag 5 mm was 1.79 (SD, 0.24) N, and that of Medpor was 0.39 (SD, 0.04) N. For 10 mm of sagging, the power of the PLLA sheet was 5.61 (SD, 0.29) N, and that of Medpor was 0.94 (SD, 0.09) N. For sagging of 15 mm, the power of the PLLA sheet was 8.99 (SD, 0.16) N, and that of Medpor was 2.98 (SD, 0.24) N. The PLLA sheet was irreversibly bent when the force reached approximately 8 to 9 N. For Medpor, the degree of sagging during the early stage was larger than at the later stage. In all situations, the supporting power of the PLLA sheet was greater than that of Medpor. The differences were significant in all situations (P = 0.000). The degree of sagging in one-half orbital floor fractures was 2.87 mm for the PLLA sheet and 7.96 mm for Medpor. There was an increased orbital volume of 0.4 mL with the PLLA sheet and 1.19 mL for Medpor. The predicted enophthalmos was 0.41 mm with the PLLA sheet and 1.07 mm with Medpor. The degree of sagging for the two

  4. The cooperative effect between active site ionized groups and water desolvation controls the alteration of acid/base catalysis in serine proteases.

    PubMed

    Shokhen, Michael; Khazanov, Netaly; Albeck, Amnon

    2007-08-13

    What is the driving force that alters the catalytic function of His57 in serine proteases between general base and general acid in each step along the enzymatic reaction? The stable tetrahedral complexes (TC) of chymotrypsin with trifluoromethyl ketone transition state analogue inhibitors are topologically similar to the catalytic transition state. Therefore, they can serve as a good model to study the enzyme catalytic reaction. We used DFT quantum mechanical calculations to analyze the effect of solvation and of polar factors in the active site of chymotrypsin on the pKa of the catalytic histidine in FE (the free enzyme), EI (the noncovalent enzyme inhibitor complex), and TC. We demonstrated that the acid/base alteration is controlled by the charged groups in the active site--the catalytic Asp102 carboxylate and the oxyanion. The effect of these groups on the catalytic His is modulated by water solvation of the active site.

  5. SORPTION OF CU AND ZN TO KAOLINITE AND IRON OXIDE: EFFECTS OF HUMIC ACID AND IONIC STRENGTH AND IMPLICATIONS FOR STORMWATER RUNOFF

    EPA Science Inventory

    Heavy metals are common pollutants in wet weather flows and urban waterways. Changes in ionic strength, whether from mixing with saline waters, road salt, or from the large osmotic adjustment needed for the Microtox toxicity assay, affect the aqueous chemistry of stormwater runof...

  6. Enhancement of the catalytic activity of ferulic acid decarboxylase from Enterobacter sp. Px6-4 through random and site-directed mutagenesis.

    PubMed

    Lee, Hyunji; Park, Jiyoung; Jung, Chaewon; Han, Dongfei; Seo, Jiyoung; Ahn, Joong-Hoon; Chong, Youhoon; Hur, Hor-Gil

    2015-11-01

    The enzyme ferulic acid decarboxylase (FADase) from Enterobacter sp. Px6-4 catalyzes the decarboxylation reaction of lignin monomers and phenolic compounds such as p-coumaric acid, caffeic acid, and ferulic acid into their corresponding 4-vinyl derivatives, that is, 4-vinylphenol, 4-vinylcatechol, and 4-vinylguaiacol, respectively. Among various ferulic acid decarboxylase enzymes, we chose the FADase from Enterobacter sp. Px6-4, whose crystal structure is known, and produced mutants to enhance its catalytic activity by random and site-directed mutagenesis. After three rounds of sequential mutations, FADase(F95L/D112N/V151I) showed approximately 34-fold higher catalytic activity than wild-type for the production of 4-vinylguaiacol from ferulic acid. Docking analyses suggested that the increased activity of FADase(F95L/D112N/V151I) could be due to formation of compact active site compared with that of the wild-type FADase. Considering the amount of phenolic compounds such as lignin monomers in the biomass components, successfully bioengineered FADase(F95L/D112N/V151I) from Enterobacter sp. Px6-4 could provide an ecofriendly biocatalytic tool for producing diverse styrene derivatives from biomass.

  7. Effects of folic acid on overall and site-specific cancer incidence during the randomised trials: meta-analyses of data on 50 000 individuals

    PubMed Central

    Vollset, Stein Emil; Clarke, Robert; Lewington, Sarah; Ebbing, Marta; Halsey, Jim; Lonn, Eva; Armitage, Jane; Manson, JoAnn E; Hankey, Graeme J; Spence, J David; Galan, Pilar; Bønaa, Kaare H; Jamison, Rex; Gaziano, J Michael; Guarino, Peter; Baron, John A; Logan, Richard FA; Giovannucci, Edward L; den Heijer, Martin; Ueland, Per M; Bennett, Derrick; Collins, Rory; Peto, Richard

    2013-01-01

    Summary Background Some countries fortify flour with folic acid to prevent neural tube defects but others do not, partly because of concerns about cancer risks. We aimed to assess the effects of folic acid supplementation on site-specific cancer rates in the randomised trials. Methods Meta-analyses of data on each individual in all placebo-controlled trials of folic acid for prevention of cardiovascular disease (10 trials, n=46,969) or colorectal adenoma (3 trials, n=2652) that recorded cancer incidence and recruited >500 participants. All trials were evenly randomised. Risk ratios (RRs) compare those allocated folic acid vs those allocated placebo, giving cancer incidence rate ratios (among those still free of cancer) during, but not after the scheduled treatment period. Findings During a weighted mean follow-up duration of 5.5 years, allocation to folic acid quadrupled plasma folate, but had no statistically significant effect on overall cancer incidence (1904 vs 1809 cancers, RR=1.06 [95%CI 0.99–1.13], p=0.10; trend with duration of treatment p=0.46). There was no significant heterogeneity between the results of individual trials (p=0.23), or between the cadiovascular prevention trials and the adenoma prevention trials (p=0.13). Moreover, there was no significant effect of folic acid supplementation on the incidence of cancer of the large intestine, prostate, lung, breast or any other specific site. Interpretation Folic acid supplementation does not substantially increase or decrease site-specific cancer incidence during the first 5 years of treatment. Funding British Heart Foundation, Medical Research Council, Cancer Research UK, Food Standards Agency. PMID:23352552

  8. Fatty acid-binding site environments of serum vitamin D-binding protein and albumin are different

    PubMed Central

    Swamy, Narasimha; Ray, Rahul

    2008-01-01

    Vitamin D-binding protein (DBP) and albumin (ALB) are abundant serum proteins and both possess high-affinity binding for saturated and unsaturated fatty acids. However, certain differences exist. We surmised that in cases where serum albumin level is low, DBP presumably can act as a transporter of fatty acids. To explore this possibility we synthesized several alkylating derivatives of 14C-palmitic acid to probe the fatty acid binding pockets of DBP and ALB. We observed that N-ethyl-5-phenylisooxazolium-3′-sulfonate-ester (WRK ester) of 14C-palmitic acid specifically labeled DBP; but p-nitrophenyl- and N-hydroxysuccinimidyl-esters failed to do so. However, p-nitrophenyl ester of 14C-palmitic acid specifically labeled bovine ALB, indicating that the micro-environment of the fatty acid-binding domains of DBP and ALB may be different; and DBP may not replace ALB as a transporter of fatty acids. PMID:18374965

  9. pH-Responsive poly(itaconic acid-co-N-vinylpyrrolidone) hydrogels with reduced ionic strength loading solutions offer improved oral delivery potential for high isoelectric point-exhibiting therapeutic proteins

    PubMed Central

    Koetting, Michael C.; Peppas, Nicholas A.

    2014-01-01

    pH-Responsive hydrogels comprised of itaconic acid copolymerized with N-vinylpyrrolidone (P(IA-co-NVP)) were synthesized and tested as carriers for the oral delivery of high isoelectric point (pI) exhibiting therapeutic proteins. Swelling studies show that P(IA-co-NVP) hydrogels exhibit significantly greater and faster pH-responsive swelling than previously studied methacrylic acid-based hydrogels, achieving up to 68% greater equilibrium swelling and 10.4 times greater swelling in time-limited experiments. Using salmon calcitonin as a model high pI protein therapeutic, we show that P(IA-co-NVP) hydrogels exhibit significantly greater delivery potential than methacrylic acid-based hydrogels. Additionally, we show that utilizing a lower ionic strength solution during drug loading significantly improves drug delivery potential for high pI therapeutics. By using a 1.5 mM PBS buffer rather than the standard 150 mM PBS buffer during loading, up to 83 times as much calcitonin can be delivered in neutral conditions, with up to a 9.6 fold improvement in percent release. Using P(IA-co-NVP) hydrogel microparticles and a low ionic strength loading solution, up to 48 μg calcitonin/mg hydrogel can be delivered in small intestinal conditions. Based on expected absorption in the small intestine, this is sufficient delivery potential for achieving therapeutic dosage via a single, regularly-sized pill taken daily. PMID:24853463

  10. Active Site Dynamical Effects in the Hydrogen Transfer Rate-limiting Step in the Catalysis of Linoleic Acid by Soybean Lipoxygenase-1 (SLO-1): Primary and Secondary Isotope Contributions.

    PubMed

    Phatak, Prasad; Venderley, Jordan; Debrota, John; Li, Junjie; Iyengar, Srinivasan S

    2015-07-30

    Using ab initio molecular dynamics (AIMD) simulations that facilitate the treatment of rare events, we probe the active site participation in the rate-determining hydrogen transfer step in the catalytic oxidation of linoleic acid by soybean lipoxygenase-1 (SLO-1). The role of two different active site components is probed. (a) On the hydrogen atom acceptor side of the active site, the hydrogen bonding propensity between the acceptor side hydroxyl group, which is bound to the iron cofactor, and the backbone carboxyl group of isoleucine (residue number 839) is studied toward its role in promoting the hydrogen transfer event. Primary and secondary (H/D) isotope effects are also probed and a definite correlation with subtle secondary H/D isotope effects is found. With increasing average nuclear kinetic energy, the increase in transfer probability is enhanced due to the presence of the hydrogen bond between the backbone carbonyl of I839 and the acceptor oxygen. Further increase in average nuclear kinetic energy reduces the strength of this secondary hydrogen bond which leads to a deterioration in hydrogen transfer rates and finally embrances an Arrhenius-like behavior. (b) On the hydrogen atom donor side, the coupling between vibrational modes predominantly localized on the donor-side linoleic acid group and the reactive mode is probed. There appears to be a qualitative difference in the coupling between modes that belong to linoleic acid and the hydrogen transfer mode, for hydrogen and deuterium transfer. For example, the donor side secondary hydrogen atom is much more labile (by nearly a factor of 5) during deuterium transfer as compared to the case for hydrogen transfer. This appears to indicate a greater coupling between the modes belonging to the linoleic acid scaffold and the deuterium transfer mode and also provides a new rationalization for the abnormal (nonclassical) secondary isotope effect results obtained by Knapp, Rickert, and Klinman in J. Am. Chem. Soc

  11. Evaluation of Fe(II) oxidation at an acid mine drainage site using laboratory-scale reactors

    NASA Astrophysics Data System (ADS)

    Brown, Juliana; Burgos, William

    2010-05-01

    Acid mine drainage (AMD) is a severe environmental threat to the Appalachian region of the Eastern United States. The Susquehanna and Potomac River basins of Pennsylvania drain to the Chesapeake Bay, which is heavily polluted by acidity and metals from AMD. This study attempted to unravel the complex relationships between AMD geochemistry, microbial communities, hydrodynamic conditions, and the mineral precipitates for low-pH Fe mounds formed downstream of deep mine discharges, such as Lower Red Eyes in Somerset County, PA, USA. This site is contaminated with high concentrations of Fe (550 mg/L), Mn (115 mg/L), and other trace metals. At the site 95% of dissolved Fe(II) and 56% of total dissolved Fe is removed without treatment, across the mound, but there is no change in the concentration of trace metals. Fe(III) oxides were collected across the Red Eyes Fe mound and precipitates were analyzed by X-ray diffraction, electron microscopy and elemental analysis. Schwertmannite was the dominant mineral phase with traces of goethite. The precipitates also contained minor amounts of Al2O3, MgO,and P2O5. Laboratory flow-through reactors were constructed to quantify Fe(II) oxidation and Fe removal over time at terrace and pool depositional facies. Conditions such as residence time, number of reactors in sequence and water column height were varied to determine optimal conditions for Fe removal. Reactors with sediments collected from an upstream terrace oxidized more than 50% of dissolved Fe(II) at a ten hour residence time, while upstream pool sediments only oxidized 40% of dissolved Fe(II). Downstream terrace and pool sediments were only capable of oxidizing 25% and 20% of Fe(II), respectively. Fe(II) oxidation rates measured in the reactors were determined to be between 3.99 x 10-8and 1.94 x 10-7mol L-1s-1. The sediments were not as efficient for total dissolved Fe removal and only 25% was removed under optimal conditions. The removal efficiency for all sediments

  12. Covalent modification of Lys19 in the CTP binding site of cytidine 5'-monophosphate N-acetylneuraminic acid synthetase.

    PubMed Central

    Tullius, M. V.; Vann, W. F.; Gibson, B. W.

    1999-01-01

    Periodate oxidized CTP (oCTP) was used to investigate the importance of lysine residues in the CTP binding site of the cytidine 5'-monophosphate N-acetylneuraminic acid (CMP-NeuAc) synthetase (EC 2.7.7.43) from Haemophilus ducreyi. The reaction of oCTP with the enzyme follows pseudo-first-order saturation kinetics, giving a maximum rate of inactivation of 0.6 min(-1) and a K(I) of 6.0 mM at pH 7.1. Mass spectrometric analysis of the modified enzyme provided data that was consistent with beta-elimination of triphosphate after the reaction of oCTP with the enzyme. A fully reduced enzyme-oCTP conjugate, retaining the triphosphate moiety, was obtained by inclusion of NaBH3CN in the reaction solution. The beta-elimination product of oCTP reacted several times more rapidly with the enzyme compared to equivalent concentrations of oCTP. This compound also formed a stable reduced morpholino adduct with CMP-NeuAc synthetase when the reaction was conducted in the presence of NaBH3CN, and was found to be a useful lysine modifying reagent. The substrate CTP was capable of protecting the enzyme to a large degree from inactivation by oCTP and its beta-elimination product. Lys19, a residue conserved in CMP-NeuAc synthetases, was identified as being labeled with the beta-elimination product of oCTP. PMID:10091669

  13. A cluster DFT study of NH3 and NO adsorption on the (MoO2)2+/HZSM-5 surface: Lewis versus Brønsted acid sites

    NASA Astrophysics Data System (ADS)

    Yan, Zhifeng; Zuo, Zhijun; Li, Zhe; Zhang, Jinshan

    2014-12-01

    A systematic DFT study was carried out to investigate NH3 and NO adsorption on both Lewis and Brønsted acid sites of (MoO2)2+/HZSM-5 catalyst by using cluster models. The adsorption energy results indicate that NH3 could strongly adsorb on both Lewis and Brønsted acid sites in the form of coordinated NH3 and NH4+, respectively, whereas NO represents poorer adsorption ability. It is also found that Lewis and Brønsted acid sites are competitive energetically for NH3 adsorption. According to the difference in the proposed mechanisms for NH3 adsorption on different acid sites, particular attention has been focused on the first dissociation of coordinated NH3 for Lewis acid site and the effect of Mo site on the introduction of NO for Brønsted acid site. For the coordinated NH3 on Lewis acid site, the more electron donation from NH3 is, the greater its adsorption stability is and the higher active its H atoms are. In addition, DOS results show that stability of the H atoms is enhanced by interacting with framework oxygen and especially the H atoms chemical-bonded with framework oxygen. For the NH4+ on Brønsted acid site, reduced-state Mo5+ holds stronger reducibility and oxidizability than terminal oxygen, which is suggested to play a key role in adsorption and activation of NOx together with the adsorbed NH4+.

  14. Guest dynamics in solid acetone-d/sub 6/-DOCA and acetone-d/sub 6/-APA inclusion compounds: correlation between the symmetry of the motion and the site symmetry. [Deoxycholic acid; Apocholic acid

    SciTech Connect

    Meirovitch, E.

    1986-10-23

    The molecular motion of acetone-d/sub 6/ acting as guest in deoxycholic acid and apocholic acid host lattices in the solid state is interpreted in light of a broader concept assessing that very often the motion of the guest proceeds through discrete jumps rather than diffusively and its symmetry is congenial with the site symmetry of the host lattice. In particular, the acetone molecules are engaged in threefold jumps about a unique axis, compatible with the 32 site symmetry of the host lattice. The entire dynamic range of this process is investigated in terms of spectral consequences brought about by variations in jump rates, in the relative population of the three symmetry related sites, and in instrumental parameters such as the time interval between the two 90/sup 0/ pulses in the quadrupole echo sequence and the length of the 90/sup 0/ pulses.

  15. Toughening of poly(lactic acid) without sacrificing stiffness and strength by melt-blending with polyamide 11 and selective localization of halloysite nanotubes

    NASA Astrophysics Data System (ADS)

    Rashmi, Baralu Jagannatha; Prashantha, Kalappa; Lacrampe, Marie-France; Krawczak, Patricia

    2016-03-01

    This paper aims at improving the mechanical behavior of biobased brittle amorphous polylactide (PLA) by extrusion melt-blending with biobased semi-crystalline polyamide 11 (PA 11) and addition of natural halloysite nanotubes (HNT). The structure and properties of PLA/PA11/HNT blends were studied in terms of morphological, thermal and mechanical properties. The morphological analysis of the PLA/PA11/HNT blends shows a strong interface between the two polymeric phases due to hydrogen bonding, and the migration of HNTs towards PA 11 phase inducing their selective localization in one of the polymeric phases of the blend. A "salami-like" structure is formed revealing a HNTs-rich tubular-like (fibrillar) PA11 phase. Moreover, HNTs localized in the dispersed phase acts as nucleating agents for PA11. Blending PLA (80 wt.%) and PA11 (20 wt.%) increases PLA ductility (elongation at break, ɛr, is multiplied by more than 20), however at the slight expense of strength and stiffness. Further addition of HNTs (2 wt.%) further increases ductility (ɛr reaches 155 %, i.e. it is multiplied by more than 40) whereas tensile strength and modulus of PLA are unchanged and impact strength is more than doubled. The toughening mechanism is discussed based on the combined effect of resistance to crack propagation and nanotubes load bearing capacity due to the existence of the fibrillar structure. Thus, blending brittle PLA with PA11 and HNT nanotubes results in tailor-made PLA-based compounds with enhanced ductility without sacrificing stiffness and strength.

  16. Characterization of the N-Acetyl-5-neuraminic Acid-binding Site of the Extracytoplasmic Solute Receptor (SiaP) of Nontypeable Haemophilus influenzae Strain 2019

    SciTech Connect

    Johnston, Jason W.; Coussens, Nathan P.; Allen, Simon; Houtman, Jon C.D.; Turner, Keith H.; Zaleski, Anthony; Ramaswamy, S.; Gibson, Bradford W.; Apicella, Michael A.

    2012-11-14

    Nontypeable Haemophilus influenzae is an opportunistic human pathogen causing otitis media in children and chronic bronchitis and pneumonia in patients with chronic obstructive pulmonary disease. The outer membrane of nontypeable H. influenzae is dominated by lipooligosaccharides (LOS), many of which incorporate sialic acid as a terminal nonreducing sugar. Sialic acid has been demonstrated to be an important factor in the survival of the bacteria within the host environment. H. influenzae is incapable of synthesizing sialic acid and is dependent on scavenging free sialic acid from the host environment. To achieve this, H. influenzae utilizes a tripartite ATP-independent periplasmic transporter. In this study, we characterize the binding site of the extracytoplasmic solute receptor (SiaP) from nontypeable H. influenzae strain 2019. A crystal structure of N-acetyl-5-neuraminic acid (Neu5Ac)-bound SiaP was determined to 1.4 {angstrom} resolution. Thermodynamic characterization of Neu5Ac binding shows this interaction is enthalpically driven with a substantial unfavorable contribution from entropy. This is expected because the binding of SiaP to Neu5Ac is mediated by numerous hydrogen bonds and has several buried water molecules. Point mutations targeting specific amino acids were introduced in the putative binding site. Complementation with the mutated siaP constructs resulted either in full, partial, or no complementation, depending on the role of specific residues. Mass spectrometry analysis of the O-deacylated LOS of the R127K point mutation confirmed the observation of reduced incorporation of Neu5Ac into the LOS. The decreased ability of H. influenzae to import sialic acid had negative effects on resistance to complement-mediated killing and viability of biofilms in vitro, confirming the importance of sialic acid transport to the bacterium.

  17. A comparative IR characterization of acidic sites on HY zeolite by pyridine and CO probes with silica-alumina and γ-alumina references.

    PubMed

    Kondo, Junko N; Nishitani, Ryoko; Yoda, Eisuke; Yokoi, Toshiyuki; Tatsumi, Takashi; Domen, Kazunari

    2010-10-07

    Using IR spectroscopy, three different surface states of HY zeolite were probed by successive adsorption of CO at 143 K followed by evacuation and pyridine adsorption at 523 K: HY zeolite [1] without strong Lewis acid sites (LAS); [2] after high temperature (873 K) evacuation to convert Brønsted acid sites (BAS) to strong LAS; and [3] after water re-adsorption on HY zeolite [2] to recover BAS from LAS. The original surface of HY zeolite [1] seemed to be recovered on HY zeolite [3] after high temperature evacuation and water treatment by CO adsorption, while a part of generated LAS on HY zeolite [2] seemed irreversible on HY zeolite [3] to HY zeolite [1] by pyridine adsorption. To clarify this discrepancy, re-examination of the IR spectra of adsorbed CO and pyridine on γ-alumina and silica-alumina after similar treatments to those on HY zeolite was conducted. Based on the results of CO adsorption on γ-alumina and silica-alumina, the presence of extra-framework aluminium sites on HY zeolite [1] was confirmed. High temperature evacuation of HY zeolite [1] formed very strong LAS, a part of which was irreversible to BAS by water re-adsorption at room temperature. The irreversible sites on HY zeolite [3] were assigned to non-acidic OH groups attributed to silica-alumina. The non-acidic OH groups on HY zeolite [3], which were BAS on HY zeolite [1], hydrogen-bonded to pyridine to show IR spectra similar to those adsorbed on LAS. Thus, LAS on HY zeolite [3] seemed irreversible by pyridine adsorption after water re-adsorption. On the other hand, CO adsorbed on non-acidic OH groups showed a band at only slightly lower frequency (2160 cm(-1)) than that of BAS (2178 cm(-1)), resulting in overlapps and ignoring their presence. Thus, CO adsorption seemed to show that complete recovery of LAS to BAS occurred.

  18. Active site inhibitors of HCV NS5B polymerase. The development and pharmacophore of 2-thienyl-5,6-dihydroxypyrimidine-4-carboxylic acid.

    PubMed

    Stansfield, Ian; Avolio, Salvatore; Colarusso, Stefania; Gennari, Nadia; Narjes, Frank; Pacini, Barbara; Ponzi, Simona; Harper, Steven

    2004-10-18

    5,6-Dihydroxypyrimidine-4-carboxylic acids are a promising series of hepatitis C virus (HCV) NS5B polymerase inhibitors that bind at the active site of the enzyme. Here we report a simple 2-thienyl substituted analogue that shows 10-fold improved activity over the original lead, and which allowed us to further delineate the key elements of the pharmacophore of this class of inhibitor. This work led to the identification of a trifluoromethyl acylsulfonamide group as a viable replacement for the C4 carboxylic acid in this series.

  19. Long-range atmospheric transport of volatile monocarboxylic acids with Asian dust over a high mountain snow site, central Japan

    NASA Astrophysics Data System (ADS)

    Mochizuki, Tomoki; Kawamura, Kimitaka; Aoki, Kazuma; Sugimoto, Nobuo

    2016-11-01

    To understand the long-range transport of monocarboxylic acids from the Asian continent to the Japanese islands, we collected snowpack samples from a pit sequence (depth ca. 6 m) at the Murodo-Daira snowfield near the summit of Mt. Tateyama, central Japan, in 2009 and 2011. Snow samples (n = 16) were analyzed for normal (C1-C10), branched chain (iC4-iC6), aromatic (benzoic and toluic acid isomers), and hydroxyl (glycolic and lactic) monocarboxylic acids, together with inorganic ions and dissolved organic carbon (DOC). Acetic acid (C2) was found to be a dominant species (average 125 ng g-1), followed by formic acid (C1) (85.7 ng g-1) and isopentanoic acid (iC5) (20.0 ng g-1). We found a strong correlation (r = 0.88) between formic plus acetic acids and non-sea-salt Ca2+ that is a proxy of Asian dust. Contributions of total monocarboxylic acids to DOC in 2009 (21.2 ± 11.6 %) were higher than that in 2011 (3.75 ± 2.62 %), being consistent with higher intensity of Asian dust in 2009 than in 2011. Formic plus acetic acids also showed a positive correlation (r = 0.90) with benzoic acid that is a tracer of automobile exhaust, indicating that monocarboxylic acids and their precursors are largely emitted from anthropogenic sources in China and/or secondarily produced in the atmosphere by photochemical processing. In addition, the ratio of formic plus acetic acids to nss-Ca2+ (0.27) was significantly higher than those (0.00036-0.0018) obtained for reference dust materials of Chinese loess deposits from the Tengger and Gobi deserts. This result suggests that volatile and semi-volatile organic acids are adsorbed on the alkaline dust particles during long-range atmospheric transport. Entrainment of organic acids by dusts is supported by a good correlation (r = 0.87) between formic plus acetic acids and pH of melt snow samples. Our study suggests that Asian alkaline dusts may be a carrier of volatile monocarboxylic acids.

  20. Acidic soft drinks effects on the shear bond strength of orthodontic brackets and a scanning electron microscopy evaluation of the enamel.

    PubMed

    Oncag, Gokhan; Tuncer, Ali Vehbi; Tosun, Yahya Serif

    2005-03-01

    This study investigated the effects of acidic soft drinks on the resistance of metal brackets to shear forces in vitro and in vivo. Thirty noncarious maxillary premolar teeth, scheduled for extraction for orthodontic purposes, were used in the in vivo group. Thirty other noncarious maxillary premolar teeth, already extracted for orthodontic purposes, were used in the in vitro group. The teeth in both groups were divided equally in three subgroups, ie, the Coca-Cola, Sprite, and control subgroups. Brackets were bonded using conventional methods. Teeth in the in vivo group were rinsed with the acidic drink three times for five minutes daily and extracted after three months. Teeth in the in vitro group were kept in the acidic drink for five minutes on three equal time intervals within 24 hours. The brackets from both groups were subjected to shearing forces using a Universal test machine. After the shearing tests, a scanning electron microscope was used to determine the amount and the localization of erosion. The results indicated that both acidic soft drink subgroups had a reduced debonding resistance in vivo and in vitro compared with their control subgroups. No statistical difference in debonding resistance was found between the in vivo and in vitro groups. Areas of defect due to erosion were observed on the enamel surface around the brackets in both the in vitro and in vivo groups. Acidic soft drinks such as Coca-Cola and Sprite have a negative effect on bracket retention against shearing forces and enamel erosion.

  1. Optical oscillator strength distribution of amino acids from 3 to 250 eV and examination of the Thomas Reiche Kuhn sum rule

    NASA Astrophysics Data System (ADS)

    Kamohara, Masumi; Izumi, Yudai; Tanaka, Masafumi; Okamoto, Keiko; Tanaka, Masahito; Kaneko, Fusae; Kodama, Yoko; Koketsu, Toshiyuki; Nakagawa, Kazumichi

    2008-10-01

    Absorption spectra of thin films of glycine (Gly), alanine (Ala), valine (Val), serine (Ser), leucine (Leu), phenylalanine (Phe) and methinine (Met) were measured in absolute values of absorption cross section σ( E) for the photon energy E from 3 to 250 eV. We translated σ( E) into the optical oscillator strength distribution df/dE and we examined the Thomas-Reiche-Kuhn sum rule [Hirschfelder, J.O., Curtiss, C.F., Bird, R.B., 1954. Molecular Theory of Gases and Liquids. Wiley, New York, p. 890]. We concluded that T-R-K sum rule was correctly applicable for such relatively large size of biomolecules.

  2. Distribution bias analysis of germline and somatic single-nucleotide variations that impact protein functional site and neighboring amino acids

    PubMed Central

    Pan, Yang; Yan, Cheng; Hu, Yu; Fan, Yu; Pan, Qing; Wan, Quan; Torcivia-Rodriguez, John; Mazumder, Raja

    2017-01-01

    Single nucleotide variations (SNVs) can result in loss or gain of protein functional sites. We analyzed the effects of SNVs on enzyme active sites, ligand binding sites, and various types of post translational modification (PTM) sites. We found that, for most types of protein functional sites, the SNV pattern differs between germline and somatic mutations as well as between synonymous and non-synonymous mutations. From a total of 51,138 protein functional site affecting SNVs (pfsSNVs), a pan-cancer analysis revealed 142 somatic pfsSNVs in five or more cancer types. By leveraging patient information for somatic pfsSNVs, we identified 17 loss of functional site SNVs and 60 gain of functional site SNVs which are significantly enriched in patients with specific cancer types. Of the key pfsSNVs identified in our analysis above, we highlight 132 key pfsSNVs within 17 genes that are found in well-established cancer associated gene lists. For illustrating how key pfsSNVs can be prioritized further, we provide a use case where we performed survival analysis showing that a loss of phosphorylation site pfsSNV at position 105 in MEF2A is significantly associated with decreased pancreatic cancer patient survival rate. These 132 pfsSNVs can be used in developing genetic testing pipelines. PMID:28176830

  3. The relationship between the acidity and the hydrocarbon cracking activity of ultrastable H-Y zeolite

    NASA Astrophysics Data System (ADS)

    Kuehne, Mark Andrew

    Changes in the structural, acidic, and catalytic properties of H-USY (acidic ultrastable Y zeolite) that occur during steam dealumination were investigated. This study focused on three factors that previously have been suggested to cause the enhanced activity of H-USY: (1) increased Bronsted acid strength caused by nonframework Al; (2) increased Bronsted acid strength caused by decreased framework Al content; and (3) direct participation of Lewis acid sites in the cracking reaction. Acidity was characterized by microcalorimetry and FTIR of NH3 adsorption. The 2-methylpentane cracking activity of H-USY at 573 K was 35 times higher than that of H-Y that had not been steamed. With further steaming of H-USY, the cracking activity decreased, although the activity per strong Bronsted acid site remained essentially constant. H-USY, with both Bronsted and Lewis acid sites, had a heterogeneous acid strength and many acid sites with heat of NH3 adsorption >130 kJ/mol. In contrast, zeolites containing only Bronsted acid sites had a rather homogeneous acid strength. The heat of NH3 adsorption did not exceed 130 U/mol for (H,NH4)-USY, in which the strongly acidic Lewis acid sites were covered by NH3, but its activity was equal to that of H-USY. Thus, Lewis acid sites are inactive for hydrocarbon cracking. Dealumination by ammonium hexafluorosilicate, which produces very little nonframework Al, resulted in a zeolite with a low heat of NH3 adsorption equal to that of H-Y, and activity only three times higher than that of H-Y. The mechanism of coke deactivation in H-USY was studied. Coke caused a proportionally larger decrease in n-hexane cracking activity than in the number of acid sites, but did not cause pore blockage or reduced n-hexane diffusivity. The evidence is consistent with a site poisoning deactivation model for a diffusion-limited reaction. In conclusion, the enhanced cracking activity of USY is not caused by Lewis acid sites nor by Bronsted acid sites with a very

  4. N-Glycosylation Improves the Pepsin Resistance of Histidine Acid Phosphatase Phytases by Enhancing Their Stability at Acidic pHs and Reducing Pepsin's Accessibility to Its Cleavage Sites.

    PubMed

    Niu, Canfang; Luo, Huiying; Shi, Pengjun; Huang, Huoqing; Wang, Yaru; Yang, Peilong; Yao, Bin

    2015-12-04

    N-Glycosylation can modulate enzyme structure and function. In this study, we identified two pepsin-resistant histidine acid phosphatase (HAP) phytases from Yersinia kristensenii (YkAPPA) and Yersinia rohdei (YrAPPA), each having an N-glycosylation motif, and one pepsin-sensitive HAP phytase from Yersinia enterocolitica (YeAPPA) that lacked an N-glycosylation site. Site-directed mutagenesis was employed to construct mutants by altering the N-glycosylation status of each enzyme, and the mutant and wild-type enzymes were expressed in Pichia pastoris for biochemical characterization. Compared with those of the N-glycosylation site deletion mutants and N-deglycosylated enzymes, all N-glycosylated counterparts exhibited enhanced pepsin resistance. Introduction of the N-glycosylation site into YeAPPA as YkAPPA and YrAPPA conferred pepsin resistance, shifted the pH optimum (0.5 and 1.5 pH units downward, respectively) and improved stability at acidic pH (83.2 and 98.8% residual activities at pH 2.0 for 1 h). Replacing the pepsin cleavage sites L197 and L396 in the immediate vicinity of the N-glycosylation motifs of YkAPPA and YrAPPA with V promoted their resistance to pepsin digestion when produced in Escherichia coli but had no effect on the pepsin resistance of N-glycosylated enzymes produced in P. pastoris. Thus, N-glycosylation may improve pepsin resistance by enhancing the stability at acidic pH and reducing pepsin's accessibility to peptic cleavage sites. This study provides a strategy, namely, the manipulation of N-glycosylation, for improvement of phytase properties for use in animal feed.

  5. N-Glycosylation Improves the Pepsin Resistance of Histidine Acid Phosphatase Phytases by Enhancing Their Stability at Acidic pHs and Reducing Pepsin's Accessibility to Its Cleavage Sites

    PubMed Central

    Niu, Canfang; Luo, Huiying; Shi, Pengjun; Huang, Huoqing; Wang, Yaru; Yang, Peilong

    2015-01-01

    N-Glycosylation can modulate enzyme structure and function. In this study, we identified two pepsin-resistant histidine acid phosphatase (HAP) phytases from Yersinia kristensenii (YkAPPA) and Yersinia rohdei (YrAPPA), each having an N-glycosylation motif, and one pepsin-sensitive HAP phytase from Yersinia enterocolitica (YeAPPA) that lacked an N-glycosylation site. Site-directed mutagenesis was employed to construct mutants by altering the N-glycosylation status of each enzyme, and the mutant and wild-type enzymes were expressed in Pichia pastoris for biochemical characterization. Compared with those of the N-glycosylation site deletion mutants and N-deglycosylated enzymes, all N-glycosylated counterparts exhibited enhanced pepsin resistance. Introduction of the N-glycosylation site into YeAPPA as YkAPPA and YrAPPA conferred pepsin resistance, shifted the pH optimum (0.5 and 1.5 pH units downward, respectively) and improved stability at acidic pH (83.2 and 98.8% residual activities at pH 2.0 for 1 h). Replacing the pepsin cleavage sites L197 and L396 in the immediate vicinity of the N-glycosylation motifs of YkAPPA and YrAPPA with V promoted their resistance to pepsin digestion when produced in Escherichia coli but had no effect on the pepsin resistance of N-glycosylated enzymes produced in P. pastoris. Thus, N-glycosylation may improve pepsin resistance by enhancing the stability at acidic pH and reducing pepsin's accessibility to peptic cleavage sites. This study provides a strategy, namely, the manipulation of N-glycosylation, for improvement of phytase properties for use in animal feed. PMID:26637601

  6. Bond strength of composite to dentin: effect of acid etching and laser irradiation through an uncured self-etch adhesive system

    NASA Astrophysics Data System (ADS)

    Castro, F. L. A.; Carvalho, J. G.; Andrade, M. F.; Saad, J. R. C.; Hebling, J.; Lizarelli, R. F. Z.

    2014-08-01

    This study evaluated the effect on micro-tensile bond strength (µ-TBS) of laser irradiation of etched/unetched dentin through an uncured self-etching adhesive. Dentinal surfaces were treated with Clearfil SE Bond Adhesive (CSE) either according to the manufacturer’s instructions (CSE) or without applying the primer (CSE/NP). The dentin was irradiated through the uncured adhesive, using an Nd:YAG laser at 0.75 or 1 W power settings. The adhesive was cured, composite crowns were built up, and the teeth were sectioned into beams (0.49 mm2) to be stressed under tension. Data were analyzed using one-way ANOVA and Tukey statistics (α = 5%). Dentin of the fractured specimens and the interfaces of untested beams were observed under scanning electron microscopy (SEM). The results showed that non-etched irradiated surfaces presented higher µ-TBS than etched and irradiated surfaces (p < 0.05). Laser irradiation alone did not lead to differences in µ-TBS (p > 0.05). SEM showed solidification globules on the surfaces of the specimens. The interfaces were similar on irradiated and non-irradiated surfaces. Laser irradiation of dentin through the uncured adhesive did not lead to higher µ-TBS when compared to the suggested manufacturer’s technique. However, this treatment brought benefits when performed on unetched dentin, since bond strengths were higher when compared to etched dentin.

  7. Newly identified essential amino acid residues affecting ^8-sphingolipid desaturase activity revealed by site-directed mutagenesis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In order to identify amino acid residues crucial for the enzymatic activity of ^8-sphingolipid desaturases, a sequence comparison was performed among ^8-sphingolipid desaturases and ^6-fatty acid desaturase from various plants. In addition to the known conserved cytb5 (cytochrome b5) HPGG motif and...

  8. Low molecular weight (C1-C10) monocarboxylic acids, dissolved organic carbon and major inorganic ions in alpine snow pit sequence from a high mountain site, central Japan

    NASA Astrophysics Data System (ADS)

    Kawamura, Kimitaka; Matsumoto, Kohei; Tachibana, Eri; Aoki, Kazuma

    2012-12-01

    Snowpack samples were collected from a snow pit sequence (6 m in depth) at the Murodo-Daira site near the summit of Mt. Tateyama, central Japan, an outflow region of Asian dusts. The snow samples were analyzed for a homologous series of low molecular weight normal (C1-C10) and branched (iC4-iC6) monocarboxylic acids as well as aromatic (benzoic) and hydroxy (glycolic and lactic) acids, together with major inorganic ions and dissolved organic carbon (DOC). The molecular distributions of organic acids were characterized by a predominance of acetic (range 7.8-76.4 ng g-1-snow, av. 34.8 ng g-1) or formic acid (2.6-48.1 ng g-1, 27.7 ng g-1), followed by propionic acid (0.6-5.2 ng g-1, 2.8 ng g-1). Concentrations of normal organic acids generally decreased with an increase in carbon chain length, although nonanoic acid (C9) showed a maximum in the range of C5-C10. Higher concentrations were found in the snowpack samples containing dust layer. Benzoic acid (0.18-4.1 ng g-1, 1.4 ng g-1) showed positive correlation with nitrate (r = 0.70), sulfate (0.67), Na+ (0.78), Ca2+ (0.86) and Mg+ (0.75), suggesting that this aromatic acid is involved with anthropogenic sources and Asian dusts. Higher concentrations of Ca2+ and SO42- were found in the dusty snow samples. We found a weak positive correlation (r = 0.43) between formic acid and Ca2+, suggesting that gaseous formic acid may react with Asian dusts in the atmosphere during long-range transport. However, acetic acid did not show any positive correlations with major inorganic ions. Hydroxyacids (0.03-5.7 ng g-1, 1.5 ng g-1) were more abundant in the granular and dusty snow. Total monocarboxylic acids (16-130 ng g-1, 74 ng g-1) were found to account for 1-6% of DOC (270-1500 ng g-1, 630 ng g-1) in the snow samples.

  9. The reaction mechanism for the SCR process on monomer V(5+) sites and the effect of modified Brønsted acidity.

    PubMed

    Arnarson, Logi; Falsig, Hanne; Rasmussen, Søren B; Lauritsen, Jeppe V; Moses, Poul Georg

    2016-06-22

    The energetics, structures and activity of a monomeric VO3H/TiO2(001) catalyst are investigated for the selective catalytic reduction (SCR) reaction by the use of density functional theory (DFT). Furthermore we study the influences of a dopant substitute in the TiO2 support and its effects on the known properties of the SCR system such as Brønsted acidity and reducibility of vanadium. We find for the reduction part of the SCR mechanism that it involves two Ti-O-V oxygen sites. One is a hydroxyl possessing Brønsted acidity which contributes to the formation of NH4(+), while the other accepts a proton which charge stabilizes the reduced active site. In the reduction the proton is donated to the latter due to a reaction between NH3 and NO that forms a H2NNO molecule which decomposes into N2(g) and H2O(g). A dopant substitution of 10 different dopants: Si, Ge, Se, Zr, Sn, Te, Hf, V, Mo and W at each of the sites, which participate in the reaction, modifies the energetics and therefore the SCR activity. We find that Brønsted acidity is a descriptor for the SCR activity at low temperatures. Based on this descriptor we find that Zr, Hf and Sn have a positive effect as they decrease the activation energy for the SCR reaction.

  10. A quantum chemical study for exploring the inhibitory effect of nitrogen containing species on the adsorption of polynuclear aromatic hydrocarbons over a Bronsted acid site

    NASA Astrophysics Data System (ADS)

    Celis-Cornejo, C. M.; Garnica Mantilla, M. M.; Baldovino-Medrano, V. G.; Ramírez-Caballero, G. E.

    2016-08-01

    The analysis of the inhibitory effect of nitrogenated compounds on the hydroprocessing and hydropurification of oil derived fuels is important to produce cleaner fuels. In this work, density functional theory calculations were performed to investigate the effect of the nitrogen containing molecules on the adsorption of Polynuclear Aromatic Hydrocarbons (PAHs). Mordenite was chosen as a zeolitic structure for simulating a Bronsted acid site. The character of the acid site was confirmed by both a vibrational frequency calculation and a Bader charge analysis. From the adsorption calculations, it was found that the adsorption energy of PAHs increases with the number of aromatic rings in the structure. Also, the nitrogen containing species possibly inhibit more extensively two and three rings PAHs because of their lower adsorption energies. Finally, it was observed that the nitrogen species tend to drag the proton from the mordenite acid site. This explains the inhibitory effect in the adsorption of PAHs and contributes to understanding the dynamics of hydrocarbon hydroprocessing in refineries.

  11. Microbial Community Structure and Physiological Status of Different Types of Biofilms in an Acid Mine Drainage Site Determined by Phospholipid Analysis

    NASA Astrophysics Data System (ADS)

    Fang, J.

    2009-12-01

    A unique aspect of the acid mine drainage (AMD) system at the Green Valley coal mine site (GVS) in western Indiana is the abundance of biofims and biolaminates - stromatolites. Three major types of biofilms have been observed from the AMD site: bright green biofilm dominated by the acidophilic, oxygenic photosynthetic protozoan Euglena mutabilis, olive green biofilm of photosynthetic diatom belonging to the genus Nitzschia, and an olive-green to brownish-green filamentous algae-dominated community. These biofilms are either attached to hard substrata of the effluent channel, or floating at the surface of the effluent with abundant oxygen bubbles, with or without encrusted Fe precipitates. We analyzed lipids (hydrocarbons, wax esters, phospholipids, glycolipids, and neutral lipids) to determine the microbial biomass, community structure and physiological status of biofims collected from the GVS site. Distinctive lipid compositions were observed. The attached, red-crusted biofilms were characterized by abundant wax esters, monounsaturated fatty acids, whereas the floating biofilms by phytadienes, phytanol, polyunsaturated n-alkenes, polyunsaturated fatty acids. The accumulation of abundant wax esters probably reflects the readily available carbon and limitation of nutrients to the biofilm. Alternatively, the wax esters may be the biochemical relics of the anaerobic past of the Earth and the detection of these compounds has important implications for the evolution of eukaryotes and the paleo-environmental conditions on early Earth. This type of biochemical machine may have allowed early eukaryotes to survive recurrent anoxic conditions on early Earth.

  12. D-aspartic acid supplementation combined with 28 days of heavy resistance training has no effect on body composition, muscle strength, and serum hormones associated with the hypothalamo-pituitary-gonadal axis in resistance-trained men.

    PubMed

    Willoughby, Darryn S; Leutholtz, Brian

    2013-10-01

    It was hypothesized that D-aspartic acid (D-ASP) supplementation would not increase endogenous testosterone levels or improve muscular performance associated with resistance training. Therefore, body composition, muscle strength, and serum hormone levels associated with the hypothalamo-pituitary-gonadal axis were studied after 28 days of resistance training and D-ASP supplementation. Resistance-trained men resistance trained 4 times/wk for 28 days while orally ingesting either 3 g of placebo or 3 g of D-ASP. Data were analyzed with 2 × 2 analysis of variance (P < .05). Before and after resistance training and supplementation, body composition and muscle strength, serum gonadal hormones, and serum D-ASP and d-aspartate oxidase (DDO) were determined. Body composition and muscle strength were significantly increased in both groups in response to resistance training (P < .05) but not different from one another (P > .05). Total and free testosterone, luteinizing hormone, gonadotropin-releasing hormone, and estradiol were unchanged with resistance training and D-ASP supplementation (P > .05). For serum D-ASP and DDO, D-ASP resulted in a slight increase compared with baseline levels (P > .05). For the D-ASP group, the levels of serum DDO were significantly increased compared with placebo (P < .05). The gonadal hormones were unaffected by 28 days of D-ASP supplementation and not associated with the observed increases in muscle strength and mass. Therefore, at the dose provided, D-ASP supplementation is ineffective in up-regulating the activity of the hypothalamo-pituitary-gonadal axis and has no anabolic or ergogenic effects in skeletal muscle.

  13. Aspartic Acid 397 in Subunit B of the Na+-pumping NADH:Quinone Oxidoreductase from Vibrio cholerae Forms Part of a Sodium-binding Site, Is Involved in Cation Selectivity, and Affects Cation-binding Site Cooperativity

    PubMed Central

    Shea, Michael E.; Juárez, Oscar; Cho, Jonathan; Barquera, Blanca

    2013-01-01

    The Na+-pumping NADH:quinone complex is found in Vibrio cholerae and other marine and pathogenic bacteria. NADH:ubiquinone oxidoreductase oxidizes NADH and reduces ubiquinone, using the free energy released by this reaction to pump sodium ions across the cell membrane. In a previous report, a conserved aspartic acid residue in the NqrB subunit at position 397, located in the cytosolic face of this protein, was proposed to be involved in the capture of sodium. Here, we studied the role of this residue through the characterization of mutant enzymes in which this aspartic acid was substituted by other residues that change charge and size, such as arginine, serine, lysine, glutamic acid, and cysteine. Our results indicate that NqrB-Asp-397 forms part of one of the at least two sodium-binding sites and that both size and charge at this position are critical for the function of the enzyme. Moreover, we demonstrate that this residue is involved in cation selectivity, has a critical role in the communication between sodium-binding sites, by promoting cooperativity, and controls the electron transfer step involved in sodium uptake (2Fe-2S → FMNC). PMID:24030824

  14. Effects of pH, dissolved oxygen, and ionic strength on the survival of Escherichia coli O157:H7 in organic acid solutions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The ability of Escherichia coli O157:H7 to survive in acidified vegetable products is of concern because of previously documented outbreaks associated with fruit juices. A study was conducted to determine the survival of E. coli O157:H7 in organic acids at pH values typical of acidified vegetable pr...

  15. Influence of synthesis pH and oxidative strength of the catalyzing acid on the morphology and chemical structure of hydrothermal carbon.

    PubMed

    Reiche, Sylvia; Kowalew, Natalia; Schlögl, Robert

    2015-02-23

    A specific control of the morphology and chemical structure of hydrothermal carbon (HTC) is of crucial importance for its application, both in catalyst supports or electrochemical devices. Here we show how the morphology, that is, particles size and homogeneity, and the distribution of functional groups can be controlled by the control of the synthesis pH of the hydrothermal carbonization. A complementary analysis of liquid byproducts by HPLC provides useful information on the nature of the polymeric species produced during the poly-condensation in the hydrothermal process and reveals the potential implementation of the process into the biorefinery concept. The acidic byproducts levulinic acid and formic acid determine the hydrothermal carbonization autocatalytically by additional supply of protons to the reaction medium. Thus, for a starting pH>3, only minor structural differences can be detected for HTC. The use of oxidizing acids favors higher yields of HTC and improves carbonization towards higher condensed carbon domains. Scaling up the process in a stirred 2 L batch reactor favors carbonization leading to higher condensed carbonaceous products. The relative trends of pH variation are maintained.

  16. Exploring the role of putative active site amino acids and pro-region motif of recombinant falcipain-2: a principal hemoglobinase of Plasmodium falciparum.

    PubMed

    Kumar, Amit; Dasaradhi, P V N; Chauhan, Virander S; Malhotra, Pawan

    2004-04-23

    Falcipain-2 is one of the principal hemoglobinases of Plasmodium falciparum, a human malaria parasite. It has a typical papain family cysteine protease structural organization, a large pro-domain, a mature domain with conserved active site amino acids. Pro-domain of falcipain-2 also contains two important conserved motifs, "GNFD" and "ERFNIN." The "GNFD" motif has been shown to be responsible for correct folding and stability in case of many papain family proteases. In the present study, we carried out site-directed mutagenesis to assess the roles of active site residues and pro-domain residues for the activity of falcipain-2. Our results showed that substitutions of putative active site residues; Q36, C42, H174, and N204 resulted in complete loss of falcipain-2 activity, while W206 and D155 mutants retained partial/complete activity in comparison to the wild type falcipain-2. Homology modeling data also corroborate the results of mutagenesis; Q36, C42, H174, N204, and W206 residues form the active site loop of the enzyme and D155 lie outside the active pocket. Substitutions in the pro-region did not affect the activity of falcipain-2. This implies that falcipain-2 shares active site residues with other members of papain family, however pro-region of falcipain-2 does not play any role in the activity of enzyme.

  17. Molecular distribution, seasonal variation, chemical transformation and sources of dicarboxylic acids and related compounds in atmospheric aerosols at remote marine Gosan site, Jeju Island

    NASA Astrophysics Data System (ADS)

    Kundu, S.; Kawamura, K.; Lee, M.

    2009-12-01

    : A homologous series of C2-C12 α, ω-dicarboxylic acids, ω-oxocarboxylic acids (C2-C9), pyruvic acid and α-dicarbonyls (C2-C3) were detected in atmospheric aerosols collected between April 2003 and April 2004 from remote marine Gosan site (33°29‧ N, 126°16‧ E) located in Jeju Island, South Korea. They were determined using a GC-FID and GC/MS. Total diacid concentration ranged from 130 to 1911 ng m-3 (av. 642 ng m-3), whereas total oxoacid concentration ranged from 7 to 155 ng m-3 (av. 43 ng m-3), and pyruvic acid and α-dicarbonyls ranged from 0.5 to 15 ng m-3 (av. 5 ng m-3) and 2-108 ng m-3 (av. 17.3 ng m-3), respectively. Oxalic (C2) acid was the most abundant in all seasons followed by malonic (C3) or succinic (C4) acid, and phthalic (Ph) acid. The concentration of diacids decreased with an increase in carbon number except for azelaic (C9) acid, which was more abundant than suberic (C8) acid. Glyoxylic acid was predominant ω-oxoacid contributing to 92% of total ω-oxoacid. Total diacids, oxoacids and dicarbonyls showed maximum concentrations in spring and occasionally in winter, while minimum concentrations were observed in summer. Air mass trajectory analysis suggests that either spring or winter maxima can be explained by strong continental outflow associated with cold front passages, while summer minima are associated with warm southerly flows, which transport clean marine air from low latitudes to Jeju Island. The comparison between total diacid concentration level of this study and other study results of urban and remote sites of East Asia reveals that Gosan site is more heavily influenced by the continental outflow from China. The seasonal variation of malonic/succinic (C3/C4), malic/succinic (hC4/C4), fumaric/maleic (F/M), oxalic/pyruvic (C2/Py) and oxalic/Glyoxal (C2/Gly) ratios showed maxima in summer due to an enhanced photo-production and degradation of diacids and related compounds. Throughout all seasons C3/C4 ratio at Gosan site, located

  18. Respiratory syncytial virus fusion glycoprotein: nucleotide sequence of mRNA, identification of cleavage activation site and amino acid sequence of N-terminus of F1 subunit.

    PubMed Central

    Elango, N; Satake, M; Coligan, J E; Norrby, E; Camargo, E; Venkatesan, S

    1985-01-01

    The amino acid sequence of respiratory syncytial virus fusion protein (Fo) was deduced from the sequence of a partial cDNA clone of mRNA and from the 5' mRNA sequence obtained by primer extension and dideoxysequencing. The encoded protein of 574 amino acids is extremely hydrophobic and has a molecular weight of 63371 daltons. The site of proteolytic cleavage within this protein was accurately mapped by determining a partial amino acid sequence of the N-terminus of the larger subunit (F1) purified by radioimmunoprecipitation using monoclonal antibodies. Alignment of the N-terminus of the F1 subunit within the deduced amino acid sequence of Fo permitted us to identify a sequence of lys-lys-arg-lys-arg-arg at the C-terminus of the smaller N-terminal F2 subunit that appears to represent the cleavage/activation domain. Five potential sites of glycosylation, four within the F2 subunit, were also identified. Three extremely hydrophobic domains are present in the protein; a) the N-terminal signal sequence, b) the N-terminus of the F1 subunit that is analogous to the N-terminus of the paramyxovirus F1 subunit and the HA2 subunit of influenza virus hemagglutinin, and c) the putative membrane anchorage domain near the C-terminus of F1. Images PMID:2987829

  19. Conserved amino acid motifs from the novel Piv/MooV family of transposases and site-specific recombinases are required for catalysis of DNA inversion by Piv.

    PubMed

    Tobiason, D M; Buchner, J M; Thiel, W H; Gernert, K M; Karls, A C

    2001-02-01

    Piv, a site-specific invertase from Moraxella lacunata, exhibits amino acid homology with the transposases of the IS110/IS492 family of insertion elements. The functions of conserved amino acid motifs that define this novel family of both transposases and site-specific recombinases (Piv/MooV family) were examined by mutagenesis of fully conserved amino acids within each motif in Piv. All Piv mutants altered in conserved residues were defective for in vivo inversion of the M. lacunata invertible DNA segment, but competent for in vivo binding to Piv DNA recognition sequences. Although the primary amino acid sequences of the Piv/MooV recombinases do not contain a conserved DDE motif, which defines the retroviral integrase/transposase (IN/Tnps) family, the predicted secondary structural elements of Piv align well with those of the IN/Tnps for which crystal structures have been determined. Molecular modelling of Piv based on these alignments predicts that E59, conserved as either E or D in the Piv/MooV family, forms a catalytic pocket with the conserved D9 and D101 residues. Analysis of Piv E59G confirms a role for E59 in catalysis of inversion. These results suggest that Piv and the related IS110/IS492 transposases mediate DNA recombination by a common mechanism involving a catalytic DED or DDD motif.

  20. Identification of Active and Spectator Sn Sites in Sn-β Following Solid-State Stannation, and Consequences for Lewis Acid Catalysis

    PubMed Central

    Hammond, Ceri; Padovan, Daniele; Al-Nayili, Abbas; Wells, Peter P; Gibson, Emma K; Dimitratos, Nikolaos

    2015-01-01

    Lewis acidic zeolites are rapidly emerging liquid-phase Lewis acid catalysts. Nevertheless, their inefficient synthesis procedure currently prohibits greater utilization and exploitation of these promising materials. Herein, we demonstrate that SnIV-containing zeolite beta can readily be prepared both selectively and extremely rapidly by solid-state incorporation (SSI) method. Through a combination of spectroscopic (XRD, UV/Vis, X-ray absorption, magic-angle spinning NMR, and diffuse reflectance infrared Fourier transform spectroscopy) studies, we unambiguously demonstrate that site-isolated, isomorphously substituted SnIV sites dominate the Sn population up to a loading of 5 wt % Sn. These sites are identical to those found in conventionally prepared Sn-beta, and result in our SSI material exhibiting identical levels of intrinsic activity (that is, turnover frequency) despite the threefold increase in Sn loading, and the extremely rapid and benign nature of our preparation methodology. We also identify the presence of spectator sites, in the form of SnIV oligomers, at higher levels of Sn loading. The consequences of this mixed population with regards to catalysis (Meerwein–Pondorf–Verley reaction and glucose isomerization) are also identified. PMID:26583051

  1. Application of Strength Diagnosis.

    ERIC Educational Resources Information Center

    Newton, Robert U.; Dugan, Eric

    2002-01-01

    Discusses the various strength qualities (maximum strength, high- and low-load speed strength, reactive strength, rate of force development, and skill performance), noting why a training program design based on strength diagnosis can lead to greater efficacy and better performance gains for the athlete. Examples of tests used to assess strength…

  2. Effect of Ethylene diamine tetra acetic acid and sodium hypochlorite solution conditioning on microtensile bond strength of one-step self-etch adhesives

    PubMed Central

    Kasraei, Shahin; Azarsina, Mohadese; Khamverdi, Zahra

    2013-01-01

    Background: Attempts to improve bond strength of self-etch adhesives can enhance the durability of composite restorations. Aims: The aim of the present study was to evaluate the effect of collagen and smear layer removal with sodium hypochlorite solution (NaOCl) and EDTA on micro-tensile bond strength (μTBS) of self-etch adhesives to dentin. Settings and Design: It was an in-vitro study. Materials and Methods: Seventy-two teeth were divided into eight groups and their crowns were ground perpendicular to their long axis to expose dentin. The teeth were polished with silicon-carbide papers. The groups were treated as follows: No conditioning, 0.5-M EDTA conditioning, 2.5% NaOCl conditioning, NaOCl + EDTA conditioning. The surfaces were rinsed and blot-dried. Clearfil S3 and I-Bond were applied according to manufacturers’ instructions and restored with Z100 composite. After 500 cycles of thermo-cycling between 5°C and 55°C, the samples were sectioned and tested for μTBS. Statistical Analysis: Data were analyzed by two-way ANOVA and Tukey-HSD test. Results: The highest μTBS was recorded with Clearfil S3 + NaOCl + EDTA, and the lowest was recorded with I-Bond without conditioning. μTBS in EDTA-and EDTA + NaOCl-treated groups was significantly higher than the control and NaOCl-conditioned groups. Conclusions: Application of EDTA or EDTA + NaOCl before one-step self-etch adhesives increased μTBS. PMID:23833459

  3. Import of amber and ochre suppressor tRNAs into mammalian cells: A general approach to site-specific insertion of amino acid analogues into proteins

    PubMed Central

    Köhrer, Caroline; Xie, Liang; Kellerer, Susanne; Varshney, Umesh; RajBhandary, Uttam L.

    2001-01-01

    A general approach to site-specific insertion of amino acid analogues into proteins in vivo would be the import into cells of a suppressor tRNA aminoacylated with the analogue of choice. The analogue would be inserted at any site in the protein specified by a stop codon in the mRNA. The only requirement is that the suppressor tRNA must not be a substrate for any of the cellular aminoacyl–tRNA synthetases. Here, we describe conditions for the import of amber and ochre suppressor tRNAs derived from Escherichia coli initiator tRNA into mammalian COS1 cells, and we present evidence for their activity in the specific suppression of amber (UAG) and ochre (UAA) codons, respectively. We show that an aminoacylated amber suppressor tRNA (supF) derived from the E. coli tyrosine tRNA can be imported into COS1 cells and acts as a suppressor of amber codons, whereas the same suppressor tRNA imported without prior aminoacylation does not, suggesting that the supF tRNA is not a substrate for any mammalian aminoacyl–tRNA synthetase. These results open the possibility of using the supF tRNA aminoacylated with an amino acid analogue as a general approach for the site-specific insertion of amino acid analogues into proteins in mammalian cells. We discuss the possibility further of importing a mixture of amber and ochre suppressor tRNAs for the insertion of two different amino acid analogues into a protein and the potential use of suppressor tRNA import for treatment of some of the human genetic diseases caused by nonsense mutations. PMID:11717406

  4. Changes in the Cytoplasmic Composition of Amino Acids and Proteins Observed in Staphylococcus aureus during Growth under Variable Growth Conditions Representative of the Human Wound Site

    PubMed Central

    Alreshidi, Mousa M.; Dunstan, R. Hugh; Gottfries, Johan; Macdonald, Margaret M.; Crompton, Marcus J.; Ang, Ching-Seng; Williamson, Nicholas A.; Roberts, Tim K.

    2016-01-01

    Staphylococcus aureus is an opportunistic pathogen responsible for a high proportion of nosocomial infections. This study was conducted to assess the bacterial responses in the cytoplasmic composition of amino acids and ribosomal proteins under various environmental conditions designed to mimic those on the human skin or within a wound site: pH6-8, temperature 35–37°C, and additional 0–5% NaCl. It was found that each set of environmental conditions elicited substantial adjustments in cytoplasmic levels of glutamic acid, aspartic acid, proline, alanine and glycine (P< 0.05). These alterations generated characteristic amino acid profiles assessed by principle component analysis (PCA). Substantial alterations in cytoplasmic amino acid and protein composition occurred during growth under conditions of higher salinity stress implemented via additional levels of NaCl in the growth medium. The cells responded to additional NaCl at pH 6 by reducing levels of ribosomal proteins, whereas at pH 8 there was an upregulation of ribosomal proteins compared with the reference control. The levels of two ribosomal proteins, L32 and S19, remained constant across all experimental conditions. The data supported the hypothesis that the bacterium was continually responding to the dynamic environment by modifying the proteome and optimising metabolic homeostasis. PMID:27442022

  5. Site-specific solvent exposure analysis of a membrane protein using unnatural amino acids and {sup 19}F nuclear magnetic resonance

    SciTech Connect

    Shi, Pan; Li, Dong; Chen, Hongwei; Xiong, Ying; Tian, Changlin

    2011-10-22

    Highlights: {yields} Solvent isotope shift analysis of {sup 19}F-tfmF in different H{sub 2}O/D{sub 2}O molar ratio. {yields} Correlation between solvent isotope shift of {sup 19}F-spins and solvent exposure analysis. {yields} Solvent exposure analysis of membrane proteins. -- Abstract: Membrane proteins play an essential role in cellular metabolism, transportation and signal transduction across cell membranes. The scarcity of membrane protein structures has thus far prevented a full understanding of their molecular mechanisms. Preliminary topology studies and residue solvent exposure analysis have the potential to provide valuable information on membrane proteins of unknown structure. Here, a {sup 19}F-containing unnatural amino acid (trimethylfluoro-phenylalanine, tfmF) was applied to accomplish site-specific {sup 19}F spin incorporation at different sites in diacylglycerol kinase (DAGK, an Escherichia coli membrane protein) for site-specific solvent exposure analysis. Due to isotope effect on {sup 19}F spins, a standard curve for {sup 19}F-tfmF chemical shifts was drawn for varying solvent H{sub 2}O/D{sub 2}O ratios. Further site-specific {sup 19}F solvent isotope shift analysis was conducted for DAGK to distinguish residues in water-soluble loops, interfacial areas or hydrophobic membrane regions. This site-specific solvent exposure analysis method could be applied for further topological analysis of other membrane proteins.

  6. Genetic correlations among fatty acid compositions in different sites of fat tissues, meat production, and meat quality traits in Duroc pigs.

    PubMed

    Suzuki, K; Ishida, M; Kadowaki, H; Shibata, T; Uchida, H; Nishida, A

    2006-08-01

    This study estimated genetic parameters for fatty acids of different sites of fat tissue, meat production, and meat quality traits of Duroc pigs selected during 7 generations for ADG, LM area, backfat thickness (BF), and intramuscular fat (IMF). For this study, 394 barrows and 153 gilts were slaughtered at 105 kg of BW. High heritabilities for C18:0 of outer and inner subcutaneous fat tissue were estimated, respectively, as 0.54 and 0.51; those of intermuscular and intramuscular fat were 0.40 and 0.51, respectively. Genetic and phenotypic correlations of ADG and BF with saturated fatty acids of outer and inner subcutaneous fat were positive, but those with C16:1 and C18:2 were negative, and those with C18:1 were nearly zero. Genetic and phenotypic correlations between LM area and respective fatty acids showed opposite results. Respective genetic and phenotypic correlations of melting points with C18:0 and C18:1 were positive and high, and negative and high, respectively. Genetic correlations between cooking loss and SFA (C14:0, C16:0, and C18:0) of IMF were positive and moderate: 0.56, 0.47, and 0.47, respectively. On the other hand, monosaturated fatty acid of C18:1 was highly and negatively correlated with cooking loss (-0.61). Moreover, high genetic correlation between meat color (pork color standard and lightness) and fatty acid compositions of IMF suggest that the SFA (C14:0, C16:0, and C18:0) were correlated genetically with meat lightness and that unsaturated fatty acid compositions (C18:1 and C18:2) were correlated with meat darkness. Results of this study suggest that the fatty acid composition of adipose tissue is correlated genetically wi