Stability of bulk metallic glass structure

Energy Technology Data Exchange (ETDEWEB)

Jain, H.; Williams, D.B.

2003-06-18

The fundamental origins of the stability of the (Pd-Ni){sub 80}P{sub 20} bulk metallic glasses (BMGs), a prototype for a whole class of BMG formers, were explored. While much of the properties of their BMGs have been characterized, their glass-stability have not been explained in terms of the atomic and electronic structure. The local structure around all three constituent atoms was obtained, in a complementary way, using extended X-ray absorption fine structure (EXAFS), to probe the nearest neighbor environment of the metals, and extended energy loss fine structure (EXELFS), to investigate the environment around P. The occupied electronic structure was investigated using X-ray photoelectron spectroscopy (XPS). The (Pd-Ni){sub 80}P{sub 20} BMGs receive their stability from cumulative, and interrelated, effects of both atomic and electronic origin. The stability of the (Pd-Ni){sub 80}P{sub 20} BMGs can be explained in terms of the stability of Pd{sub 60}Ni{sub 20}P{sub 20} and Pd{sub 30}Ni{sub 50}P{sub 20}, glasses at the end of BMG formation. The atomic structure in these alloys is very similar to those of the binary phosphide crystals near x=0 and x=80, which are trigonal prisms of Pd or Ni atoms surrounding P atoms. Such structures are known to exist in dense, randomly-packed systems. The structure of the best glass former in this series, Pd{sub 40}Ni{sub 40}P{sub 20} is further described by a weighted average of those of Pd{sub 30}Ni{sub 50}P{sub 20} and Pd{sub 60}Ni{sub 20}P{sub 20}. Bonding states present only in the ternary alloys were found and point to a further stabilization of the system through a negative heat of mixing between Pd and Ni atoms. The Nagel and Tauc criterion, correlating a decrease in the density of states at the Fermi level with an increase in the glass stability, was consistent with greater stability of the Pd{sub x}Ni{sub (80-x)}P{sub 20} glasses with respect to the binary alloys of P. A valence electron concentration of 1.8 e/a, which

Cloning, expression, purification, crystallization and preliminary X-ray diffraction analysis of chlorite dismutase: a detoxifying enzyme producing molecular oxygen

Energy Technology Data Exchange (ETDEWEB)

Geus, Daniël C. de, E-mail: d.de.geus@chem.leidenuniv.nl; Thomassen, Ellen A. J.; Feltz, Clarisse L. van der; Abrahams, Jan Pieter [Biophysical Structural Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden (Netherlands)

2008-08-01

Preliminary X-ray data collection and analysis for crystals of chlorite dismutase, a haem-based enzyme that very effectively reduces chlorite to chloride while producing molecular oxygen, is reported to 2.1 Å resolution. Chlorite dismutase, a homotetrameric haem-based protein, is one of the key enzymes of (per)chlorate-reducing bacteria. It is highly active (< 2 kU mg{sup −1}) in reducing the toxic compound chlorite to the innocuous chloride anion and molecular oxygen. Chlorite itself is produced as the intermediate product of (per)chlorate reduction. The chlorite dismutase gene in Azospira oryzae strain GR-1 employing degenerate primers has been identified and the active enzyme was subsequently overexpressed in Escherichia coli. Chlorite dismutase was purified, proven to be active and crystallized using sitting drops with PEG 2000 MME, KSCN and ammonium sulfate as precipitants. The crystals belonged to space group P2{sub 1}2{sub 1}2 and were most likely to contain six subunits in the asymmetric unit. The refined unit-cell parameters were a = 164.46, b = 169.34, c = 60.79 Å. The crystals diffracted X-rays to 2.1 Å resolution on a synchrotron-radiation source and a three-wavelength MAD data set has been collected. Determination of the chlorite dismutase structure will provide insights into the active site of the enzyme, for which no structures are currently available.

Stability Analysis and Stabilization of Miduk Heap Leaching Structure, Iran

Directory of Open Access Journals (Sweden)

Mehdi Amini

2013-06-01

Full Text Available To construct copper heap leaching structures, a stepped heap of ore is placed over an isolated sloping surface and then washed with sulphuric acid. The isolated bed of such a heap consists of some natural and geosynthetic layers. Shear strength parameters between these layers are low, so they form the possible sliding surfaces of the heaps. Economic and environmental considerations call for studying such slides. In this study, firstly, results of the laboratory tests carried on the materials of the heap leaching structures bed are presented. Then, the instability mechanisms of such structures are investigated and proper approaches are summarized for their stabilization. Finally, stability of the Miduk copper heap is evaluated as a case history, and appropriate approaches and their effects are discussed for its stabilization.

Stability of Benzotriazole Derivatives with Free Cu, Zn, Co and Metal-Containing Enzymes: Binding and Interaction of Methylbenzotriazoles with Superoxide Dismutase and Vitamin B12

Science.gov (United States)

Abudalo, R. A.; AbuDalo, M. A.; Hernandez, M. T.

2018-02-01

Benzotriazole derivatives form very strong bonds with transition metals, and are the most widely used type of industrial corrosion inhibitor. Some benzotriazole derivatives have been implicated as hormone regulators which also carry the ability to induce uncoupling responses or otherwise inhibit respiration processes in some microorganisms. However, the mechanisms associated with benzotriazole toxicity and inhibition are unknown. Using Differential Pulse Polarography, the stability constants of commercially significant corrosion inhibitors, 4-and 5-methylbenzotriazole, coordinated with free Cu (II) and Co (III), were determined to be 1015 and 108, respectively. Polarographic analyses were extended to confirm that methylbenzotriazole also binds the copper center(s) in the ubiquitous enzyme superoxide dismutase, and the Corrin site in the coenzyme cobalamin (vitamin B12). These results suggest that the metal-chelating ability of this unique class of compounds may confer inhibition to certain enzyme systems.

Characterizing Isozymes of Chlorite Dismutase for Water Treatment

Directory of Open Access Journals (Sweden)

Kellen C. Mobilia

2017-12-01

Full Text Available This work investigated the potential for biocatalytic degradation of micropollutants, focusing on chlorine oxyanions as model contaminants, by mining biology to identify promising biocatalysts. Existing isozymes of chlorite dismutase (Cld were characterized with respect to parameters relevant to this high volume, low-value product application: kinetic parameters, resistance to catalytic inactivation, and stability. Maximum reaction velocities (Vmax were typically on the order of 104 μmol min-1 (μmol heme-1. Substrate affinity (Km values were on the order of 100 μM, except for the Cld from Candidatus Nitrospira defluvii (NdCld, which showed a significantly lower affinity for chlorite. NdCld also had the highest susceptibility to catalytic inactivation. In contrast, the Cld from Ideonella dechloratans was least susceptible to catalytic inactivation, with a maximum turnover number of approximately 150,000, more than sevenfold higher than other tested isozymes. Under non-reactive conditions, Cld was quite stable, retaining over 50% of activity after 30 days, and most samples retained activity even after 90–100 days. Overall, Cld from I. dechloratans was the most promising candidate for environmental applications, having high affinity and activity, a relatively low propensity for catalytic inactivation, and excellent stability.

Models of Superoxide Dismutases

Energy Technology Data Exchange (ETDEWEB)

Cabelli, Diane E.; Riley, Dennis; Rodriguez, Jorge A.; Valentine, Joan Selverstone; Zhu, Haining

1998-05-20

In this review we have focused much of our discussion on the mechanistic details of how the native enzymes function and how mechanistic developments/insights with synthetic small molecule complexes possessing SOD activity have influenced our understanding of the electron transfer processes involved with the natural enzymes. A few overriding themes have emerged. Clearly, the SOD enzymes operate at near diffusion controlled rates and to achieve such catalytic turnover activity, several important physical principles must be operative. Such fast electron transfer processes requires a role for protons; i.e., proton-coupled electron transfer (''H-atom transfer'') solves the dilemma of charge separation developing in the transition state for the electron transfer step. Additionally, outer-sphere electron transfer is likely a most important pathway for manganese and iron dismutases. This situation arises because the ligand exchange rates on these two ions in water never exceed {approx}10{sup +7} s{sup -1}; consequently, 10{sup +9} catalytic rates require more subtle mechanistic insights. In contrast, copper complexes can achieve diffusion controlled (>10{sup +9}) exchange rates in water; thus inner-sphere electron transfer processes are more likely to be operative in the Cu/Zn enzymes. Recent studies have continued to expand our understanding of the mechanism of action of this most important class of redox active enzymes, the superoxide dismutases, which have been critical in the successful adaptation of life on this planet to an oxygen-based metabolism. The design of SOD mimic drugs, synthetic models compounds that incorporate this superoxide dismutase catalytic activity and are capable of functioning in vivo, offers clear potential benefits in the control of diseases, ranging from the control of neurodegenerative conditions, such as Parkinson's or Alzheimer's disease, to cancer.

Sensitivity of system stability to model structure

Science.gov (United States)

Hosack, G.R.; Li, H.W.; Rossignol, P.A.

2009-01-01

A community is stable, and resilient, if the levels of all community variables can return to the original steady state following a perturbation. The stability properties of a community depend on its structure, which is the network of direct effects (interactions) among the variables within the community. These direct effects form feedback cycles (loops) that determine community stability. Although feedback cycles have an intuitive interpretation, identifying how they form the feedback properties of a particular community can be intractable. Furthermore, determining the role that any specific direct effect plays in the stability of a system is even more daunting. Such information, however, would identify important direct effects for targeted experimental and management manipulation even in complex communities for which quantitative information is lacking. We therefore provide a method that determines the sensitivity of community stability to model structure, and identifies the relative role of particular direct effects, indirect effects, and feedback cycles in determining stability. Structural sensitivities summarize the degree to which each direct effect contributes to stabilizing feedback or destabilizing feedback or both. Structural sensitivities prove useful in identifying ecologically important feedback cycles within the community structure and for detecting direct effects that have strong, or weak, influences on community stability. The approach may guide the development of management intervention and research design. We demonstrate its value with two theoretical models and two empirical examples of different levels of complexity. ?? 2009 Elsevier B.V. All rights reserved.

Structural stability of nonlinear population dynamics.

Science.gov (United States)

Cenci, Simone; Saavedra, Serguei

2018-01-01

In population dynamics, the concept of structural stability has been used to quantify the tolerance of a system to environmental perturbations. Yet, measuring the structural stability of nonlinear dynamical systems remains a challenging task. Focusing on the classic Lotka-Volterra dynamics, because of the linearity of the functional response, it has been possible to measure the conditions compatible with a structurally stable system. However, the functional response of biological communities is not always well approximated by deterministic linear functions. Thus, it is unclear the extent to which this linear approach can be generalized to other population dynamics models. Here, we show that the same approach used to investigate the classic Lotka-Volterra dynamics, which is called the structural approach, can be applied to a much larger class of nonlinear models. This class covers a large number of nonlinear functional responses that have been intensively investigated both theoretically and experimentally. We also investigate the applicability of the structural approach to stochastic dynamical systems and we provide a measure of structural stability for finite populations. Overall, we show that the structural approach can provide reliable and tractable information about the qualitative behavior of many nonlinear dynamical systems.

Structural stability of nonlinear population dynamics

Science.gov (United States)

Cenci, Simone; Saavedra, Serguei

2018-01-01

In population dynamics, the concept of structural stability has been used to quantify the tolerance of a system to environmental perturbations. Yet, measuring the structural stability of nonlinear dynamical systems remains a challenging task. Focusing on the classic Lotka-Volterra dynamics, because of the linearity of the functional response, it has been possible to measure the conditions compatible with a structurally stable system. However, the functional response of biological communities is not always well approximated by deterministic linear functions. Thus, it is unclear the extent to which this linear approach can be generalized to other population dynamics models. Here, we show that the same approach used to investigate the classic Lotka-Volterra dynamics, which is called the structural approach, can be applied to a much larger class of nonlinear models. This class covers a large number of nonlinear functional responses that have been intensively investigated both theoretically and experimentally. We also investigate the applicability of the structural approach to stochastic dynamical systems and we provide a measure of structural stability for finite populations. Overall, we show that the structural approach can provide reliable and tractable information about the qualitative behavior of many nonlinear dynamical systems.

Immobilization of Superoxide Dismutase on Polyelectrolyte-Functionalized Titania Nanosheets.

Science.gov (United States)

Rouster, Paul; Pavlovic, Marko; Szilagyi, Istvan

2018-02-16

The superoxide dismutase (SOD) enzyme was successfully immobilized on titania nanosheets (TNS) functionalized with the poly(diallyldimethylammonium chloride) (PDADMAC) polyelectrolyte. The TNS-PDADMAC solid support was prepared by hydrothermal synthesis followed by self-assembled polyelectrolyte layer formation. It was found that SOD strongly adsorbed onto oppositely charged TNS-PDADMAC through electrostatic and hydrophobic interactions. The TNS-PDADMAC-SOD material was characterized by light scattering and microscopy techniques. Colloidal stability studies revealed that the obtained nanocomposites possessed good resistance against salt-induced aggregation in aqueous suspensions. The enzyme kept its functional integrity upon immobilization; therefore, TNS-PDADMAC-SOD showed excellent superoxide radical anion scavenging activity. The developed system is a promising candidate for applications in which suspensions of antioxidant activity are required in the manufacturing processes. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evolutionary conservativeness of electric field in the Cu,Zn superoxide dismutase active site. Evidence for co-ordinated mutation of charged amino acid residues.

Science.gov (United States)

Desideri, A; Falconi, M; Polticelli, F; Bolognesi, M; Djinovic, K; Rotilio, G

1992-01-05

Equipotential lines were calculated, using the Poisson-Boltzmann equation, for six Cu,Zn superoxide dismutases with different protein electric charge and various degrees of sequence homology, namely those from ox, pig, sheep, yeast, and the isoenzymes A and B from the amphibian Xenopus laevis. The three-dimensional structures of the porcine and ovine superoxide dismutases were obtained by molecular modelling reconstruction using the structure of the highly homologous bovine enzyme as a template. The three-dimensional structure of the evolutionary distant yeast Cu,Zn superoxide dismutase was recently resolved by us, while computer-modelled structures are available for X. laevis isoenzymes. The six proteins display large differences in the net protein charge and distribution of electrically charged surface residues but the trend of the equipotential lines in the proximity of the active sites was found to be constant in all cases. These results are in line with the very similar catlytic rate constants experimentally measured for the corresponding enzyme activities. This analysis shows that electrostatic guidance for the enzyme-substrate interaction in Cu,Zn superoxide dismutases is related to a spatial distribution of charges, arranged so as to maintain, in the area surrounding the active sites, an identical electrostatic potential distribution, which is conserved in the evolution of this protein family.

Stability patterns for a size-structured population model and its stage-structured counterpart

DEFF Research Database (Denmark)

Zhang, Lai; Pedersen, Michael; Lin, Zhigui

2015-01-01

In this paper we compare a general size-structured population model, where a size-structured consumer feeds upon an unstructured resource, to its simplified stage-structured counterpart in terms of equilibrium stability. Stability of the size-structured model is understood in terms of an equivale...... to the population level....

Stability of Bulk Metallic Glass Structure. Final Report

Energy Technology Data Exchange (ETDEWEB)

Jain, H.; Williams, D. B.

2003-06-01

The fundamental origins of the stability of the (Pd-Ni){sub 80}P{sub 20} bulk metallic glasses (BMGs), a prototype for a whole class of BMG formers, were explored. While much of the properties of their BMGs have been characterized, their glass-stability have not been explained in terms of the atomic and electronic structure. The local structure around all three constituent atoms was obtained, in a complementary way, using extended X-ray absorption fine structure (EXAFS), to probe the nearest neighbor environment of the metals, and extended energy loss fine structure (EXELFS), to investigate the environment around P. The occupied electronic structure was investigated using X-ray photoelectron spectroscopy (XPS). The (Pd-Ni){sub 80}P{sub 20} BMGs receive their stability from cumulative, and interrelated, effects of both atomic and electronic origin. The stability of the (Pd-Ni){sub 80}P{sub 20} BMGs can be explained in terms of the stability of Pd{sub 60}Ni{sub 20}P{sub 20} and Pd{sub 30}Ni{sub 50}P{sub 20}, glasses at the end of BMG formation. The atomic structure in these alloys is very similar to those of the binary phosphide crystals near x=0 and x=80, which are trigonal prisms of Pd or Ni atoms surrounding P atoms. Such structures are known to exist in dense, randomly-packed systems. The structure of the best glass former in this series, Pd{sub 40}Ni{sub 40}P{sub 20} is further described by a weighted average of those of Pd{sub 30}Ni{sub 50}P{sub 20} and Pd{sub 60}Ni{sub 20}P{sub 20}. Bonding states present only in the ternary alloys were found and point to a further stabilization of the system through a negative heat of mixing between Pd and Ni atoms. The Nagel and Tauc criterion, correlating a decrease in the density of states at the Fermi level with an increase in the glass stability, was consistent with greater stability of the Pd{sub x}Ni{sub 80-x}P{sub 20} glasses with respect to the binary alloys of P. A valence electron concentration of 1.8 e/a, which

The activity of catalase and superoxide dismutase in isogenous bacteria strains with different radioresistance

International Nuclear Information System (INIS)

Vasil'eva, E.I.; Goncharenko, E.N.; Yudz, T.I.; Samojlenko, I.I.

1984-01-01

The catalase and superoxide dismutase activity in isogenous bacterial strains with various radiosensitivity is investigated. In micrococcus radiodurans mutants with defects in the DNA repair systems the superoxide dismutase activity is lower than in the wild type cells. In investigated Escherichia coli strains differing in radiosensitivity, no alteration in catalase and superoxide dismutase activity is found. The conclusion is drawn that viability of bacteria subjected to the effect of ionizing radiations is determined by the efficiency of DNA repair systems whose functional reliability is sometimes connected with the catalase and suferoxide dismutase activity

Endogenous superoxide dismutase and catalase activities and radiation resistance in mouse cell lines

International Nuclear Information System (INIS)

Davy, C.A.; Tesfay, Z.; Jones, J.; Rosenberg, R.C.; McCarthy, C.; Ostrand-Rosenberg, S.

1988-01-01

The relationship between the endogenous cytoplasmic levels of the enzymes superoxide dismutase and catalase and the inhibition of cell proliferation by γ-radiation has been studied in 11 mouse cell lines. The resistance of these mouse cell lines to radiation was found to vary by over 25-fold. No correlation was found between the cytoplasmic level of CuZn-superoxide dismutase or catalase and the resistance to radiation as measured by extrapolation number (EN), quasi-threshold dose (Dsub(q)), or Dsub(o). None of the cell lines had detectable cytoplasmic Mn-superoxide dismutase. The apparent Ksub(i) of potassium cyanide for mouse CuZn-superoxide dismutase was determined (Ksub(i) = 6.5 μmol dm -3 ). (author)

Stability and the structure of continuous-time economic models

NARCIS (Netherlands)

Nieuwenhuis, H.J.; Schoonbeek, L.

In this paper we investigate the relationship between the stability of macroeconomic, or macroeconometric, continuous-time models and the structure of the matrices appearing in these models. In particular, we concentrate on dominant-diagonal structures. We derive general stability results for models

Structure of Dynamic, Taxol-Stabilized, and GMPPCP-Stabilized Microtubule.

Science.gov (United States)

Ginsburg, Avi; Shemesh, Asaf; Millgram, Abigail; Dharan, Raviv; Levi-Kalisman, Yael; Ringel, Israel; Raviv, Uri

2017-09-14

Microtubule (MT) is made of αβ-tubulin heterodimers that dynamically assemble into a hollow nanotube composed of straight protofilaments. MT dynamics is facilitated by hydrolysis of guanosine-5'-triphosphate (GTP) and can be inhibited by either anticancer agents like taxol or the nonhydrolyzable GTP analogues like GMPPCP. Using high-resolution synchrotron X-ray scattering, we have measured and analyzed the scattering curves from solutions of dynamic MT (in other words, in the presence of excess GTP and free of dynamic-inhibiting agents) and examined the effect of two MT stabilizers: taxol and GMPPCP. Previously, we have analyzed the structure of dynamic MT by docking the atomic model of tubulin dimer onto a 3-start left handed helical lattice, derived from the PDB ID 3J6F . 3J6F corresponds to a MT with 14 protofilaments. In this paper, we took into account the possibility of having MT structures containing between 12 and 15 protofilaments. MTs with 12 protofilaments were never observed. We determined the radii, the pitch, and the distribution of protofilament number that best fit the scattering data from dynamic MT or stabilized MT by taxol or GMPPCP. We found that the protofilament number distribution shifted when the MT was stabilized. Taxol increased the mass fraction of MT with 13 protofilaments and decreased the mass fraction of MT with 14 protofilaments. GMPPCP reduced the mass fraction of MT with 15 protofilaments and increased the mass fraction of MT with 14 protofilaments. The pitch, however, remained unchanged regardless of whether the MT was dynamic or stabilized. Higher tubulin concentrations increased the fraction of dynamic MT with 14 protofilaments.

Insulin structure and stability.

Science.gov (United States)

Brange, J; Langkjoer, L

1993-01-01

Insulin is composed of 51 amino acids in two peptide chains (A and B) linked by two disulfide bonds. The three-dimensional structure of the insulin molecule (insulin monomer), essentially the same in solution and in solid phase, exists in two main conformations. These differ in the extent of helix in the B chain which is governed by the presence of phenol or its derivatives. In acid and neutral solutions, in concentrations relevant for pharmaceutical formulation, the insulin monomer assembles to dimers and at neutral pH, in the presence of zinc ions, further to hexamers. Many crystalline modifications of insulin have been identified but only those with the hexamer as the basic unit are utilized in preparations for therapy. The insulin hexamer forms a relatively stable unit but some flexibility remains within the individual molecules. The intrinsic flexibility at the ends of the B chain plays an important role in governing the physical and chemical stability of insulin. A variety of chemical changes of the primary structure (yielding insulin derivatives), and physical modifications of the secondary to quaternary structures (resulting in "denaturation," aggregation, and precipitation) are known to affect insulin and insulin preparations during storage and use (Fig. 8). The tendency of insulin to undergo structural transformation resulting in aggregation and formation of insoluble insulin fibrils has been one of the most intriguing and widely studied phenomena in relation to insulin stability. Although the exact mechanism of fibril formation is still obscure, it is now clear that the initial step is an exposure of certain hydrophobic residues, normally buried in the three-dimensional structure, to the surface of the insulin monomer. This requires displacement of the COOH-terminal B-chain residues from their normal position which can only be accomplished via monomerization of the insulin. Therefore, most methods stabilizing insulin against fibrillation share the

Phase stability and electronic structure of transition-metal aluminides

International Nuclear Information System (INIS)

Carlsson, A.E.

1992-01-01

This paper will describe the interplay between die electronic structure and structural energetics in simple, complex, and quasicrystalline Al-transition metal (T) intermetallics. The first example is the Ll 2 -DO 22 competition in Al 3 T compounds. Ab-initio electronic total-energy calculations reveal surprisingly large structural-energy differences, and show that the phase stability of both stoichiometric and ternary-substituted compounds correlates closely with a quasigap in the electronic density of states (DOS). Secondly, ab-initio calculations for the structural stability of the icosahedrally based Al 12 W structure reveal similar quasigap effects, and provide a simple physical explanation for the stability of the complex aluminide structures. Finally, parametrized tight-binding model calculations for the Al-Mn quasicrystal reveal a large spread in the local Mn DOS behavior, and support a two-site model for the quasicrystal's magnetic behavior

Effect of yogic exercise on superoxide dismutase levels in diabetics

Directory of Open Access Journals (Sweden)

Mahapure Hemant

2008-01-01

Full Text Available Context: Reactive oxygen species are known to aggravate disease progression. To counteract their harmful effects, the body produces various antioxidant enzymes, viz , superoxide dismutase, glutathione reductase etc. Literature reviews revealed that exercises help to enhance antioxidant enzyme systems; hence, yogic exercises may be useful to combat various diseases. Aims: This study aims to record the efficacy of yoga on superoxide dismutase, glycosylated hemoglobin (Hb and fasting blood glucose levels in diabetics. Settings and Design: Forty diabetics aged 40-55 years were assigned to experimental (30 and control (10 groups. The experimental subjects underwent a Yoga program comprising of various Asanas (isometric type exercises and Pranayamas (breathing exercises along with regular anti-diabetic therapy whereas the control group received anti-diabetic therapy only. Methods and Material: Heparinized blood samples were used to determine erythrocyte superoxide dismutase (SOD activity and glycosylated Hb levels and fasting blood specimens collected in fluoride Vacutainers were used for assessing blood glucose. Statistical analysis used: Data were analyzed by using 2 x 2 x 3 Factorial ANOVA followed by Scheffe′s posthoc test. Results: The results revealed that Yogic exercise enhanced the levels of Superoxide dismutase and reduced glycosylated Hb and glucose levels in the experimental group as compared to the control group. Conclusion: The findings conclude that Yogic exercises have enhanced the antioxidant defence mechanism in diabetics by reducing oxidative stress.

Superoxide dismutase and catalase conjugated to polyethylene glycol increases endothelial enzyme activity and oxidant resistance

International Nuclear Information System (INIS)

Beckman, J.S.; Minor, R.L. Jr.; White, C.W.; Repine, J.E.; Rosen, G.M.; Freeman, B.A.

1988-01-01

Covalent conjugation of superoxide dismutase and catalase with polyethylene glycol (PEG) increases the circulatory half-lives of these enzymes from 125 I-PEG-catalase or 125 I-PEG-superoxide dismutase produced a linear, concentration-dependent increase in cellular enzyme activity and radioactivity. Fluorescently labeled PEG-superoxide dismutase incubated with endothelial cells showed a vesicular localization. Mechanical injury to cell monolayers, which is known to stimulate endocytosis, further increased the uptake of fluorescent PEG-superoxide dismutase. Addition of PEG and PEG-conjugated enzymes perturbed the spin-label binding environment, indicative of producing an increase in plasma membrane fluidity. Thus, PEG conjugation to superoxide dismutase and catalase enhances cell association of these enzymes in a manner which increases cellular enzyme activities and provides prolonged protection from partially reduced oxygen species

Unifying dynamical and structural stability of equilibria

Science.gov (United States)

Arnoldi, Jean-François; Haegeman, Bart

2016-09-01

We exhibit a fundamental relationship between measures of dynamical and structural stability of linear dynamical systems-e.g. linearized models in the vicinity of equilibria. We show that dynamical stability, quantified via the response to external perturbations (i.e. perturbation of dynamical variables), coincides with the minimal internal perturbation (i.e. perturbations of interactions between variables) able to render the system unstable. First, by reformulating a result of control theory, we explain that harmonic external perturbations reflect the spectral sensitivity of the Jacobian matrix at the equilibrium, with respect to constant changes of its coefficients. However, for this equivalence to hold, imaginary changes of the Jacobian's coefficients have to be allowed. The connection with dynamical stability is thus lost for real dynamical systems. We show that this issue can be avoided, thus recovering the fundamental link between dynamical and structural stability, by considering stochastic noise as external and internal perturbations. More precisely, we demonstrate that a linear system's response to white-noise perturbations directly reflects the intensity of internal white-noise disturbance that it can accommodate before becoming stochastically unstable.

Catalase and Superoxide Dismutase of Root-Colonizing Saprophytic Fluorescent Pseudomonads †

OpenAIRE

Katsuwon, Jirasak; Anderson, Anne J.

1990-01-01

Root-colonizing, saprophytic fluorescent pseudomonads of the Pseudomonas putida-P. fluorescens group express similar levels of catalase and superoxide dismutase activities during growth on a sucrose- and amino acid-rich medium. Increased specific activities of catalase but not superoxide dismutase were observed during growth of these bacteria on components washed from root surfaces. The specific activities of both enzymes were also regulated during contact of these bacteria with intact bean r...

Micropore Structure of Cement-Stabilized Gold Mine Tailings

Directory of Open Access Journals (Sweden)

Joon Kyu Lee

2018-03-01

Full Text Available Mine tailings have often to be stabilized by mixing them with cementing agents. In this study, the pore structure of gold tailings stabilized with Portland cement was evaluated by means of mercury intrusion porosimetry. The investigation was conducted on samples prepared with different fractions of tailings and cement as well as on samples activated with elevated temperature curing and chemical (CaCl2 addition. It was observed that all mixed samples exhibit a mono-modal pore size distribution, indicating that the cement-stabilized tailings are characterized by a single-porosity structure. The results also showed that the higher fraction of tailings and cement leads to a dense and finer pore structure. The total porosity of mixture samples decreases with increasing curing temperature and CaCl2 concentration due to the acceleration of hydration reaction.

Enzymatic Activity Enhancement of Non-Covalent Modified Superoxide Dismutase and Molecular Docking Analysis

Directory of Open Access Journals (Sweden)

Fa-Jun Song

2012-03-01

Full Text Available The enzyme activity of superoxide dismutase was improved in the pyrogallol autoxidation system by about 27%, after interaction between hydroxypropyl-β-cyclo- dextrin and superoxide dismutase. Fluorescence spectrometry was used to study the interaction between hydroxypropyl-β-cyclodextrin and superoxide dismutase at different temperatures. By doing this, it can be found that these interactions increase fluorescence sensitivity. In the meantime, the synchronous fluorescence intensity revealed the interaction sites to be close to the tryptophan (Trp and tyrosine (Tyr residues of superoxide dismutase. Furthermore, molecular docking was applied to explore the binding mode between the ligands and the receptor. This suggested that HP-β-CD interacted with the B ring, G ring and the O ring and revealed that the lysine (Lys residues enter the nanocavity. It was concluded that the HP-β-CD caused specific conformational changes in SOD by non-covalent modification.

Superoxide dismutase 1 is positively selected to minimize protein aggregation in great apes

DEFF Research Database (Denmark)

Dasmeh, Pouria; Kepp, Kasper Planeta

2017-01-01

Positive (adaptive) selection has recently been implied in human superoxide dismutase 1 (SOD1), a highly abundant antioxidant protein with energy signaling and antiaging functions, one of very few examples of direct selection on a human protein product (exon); the molecular drivers...... and SOD1 aggregates and triggered by aging. Our study thus marks an example of direct selection for a particular chemical phenotype (high net charge and stability) in a single human protein with possible implications for the evolution of aging....... of this selection are unknown. We mapped 30 extant SOD1 sequences to the recently established mammalian species tree and inferred ancestors, key substitutions, and signatures of selection during the protein's evolution. We detected elevated substitution rates leading to great apes (Hominidae) at ~1 per 2 million...

Atomistic mechanisms governing structural stability change of zinc antimony thermoelectrics

Energy Technology Data Exchange (ETDEWEB)

Yang, Xiaolong [Frontier Institute of Science and Technology, Xi' an Jiaotong University, Xi' an 710054 (China); Lin, Jianping, E-mail: jaredlin@163.com [School of Materials Science and Engineering, Xiamen University of Technology, Xiamen 361024 (China); Qiao, Guanjun [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Wang, Zhao, E-mail: zwangzhao@gmail.com [Frontier Institute of Science and Technology, Xi' an Jiaotong University, Xi' an 710054 (China); State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China)

2015-01-05

The structural stability of thermoelectric materials is a subject of growing importance for their energy harvesting applications. Here, we study the microscopic mechanisms governing the structural stability change of zinc antimony at its working temperature, using molecular dynamics combined with experimental measurements of the electrical and thermal conductivity. Our results show that the temperature-dependence of the thermal and electrical transport coefficients is strongly correlated with a structural transition. This is found to be associated with a relaxation process, in which a group of Zn atoms migrates between interstitial sites. This atom migration gradually leads to a stabilizing structural transition of the entire crystal framework, and then results in a more stable crystal structure of β–Zn{sub 4}Sb{sub 3} at high temperature.

Advances in Computational Stability Analysis of Composite Aerospace Structures

International Nuclear Information System (INIS)

Degenhardt, R.; Araujo, F. C. de

2010-01-01

European aircraft industry demands for reduced development and operating costs. Structural weight reduction by exploitation of structural reserves in composite aerospace structures contributes to this aim, however, it requires accurate and experimentally validated stability analysis of real structures under realistic loading conditions. This paper presents different advances from the area of computational stability analysis of composite aerospace structures which contribute to that field. For stringer stiffened panels main results of the finished EU project COCOMAT are given. It investigated the exploitation of reserves in primary fibre composite fuselage structures through an accurate and reliable simulation of postbuckling and collapse. For unstiffened cylindrical composite shells a proposal for a new design method is presented.

Extraction of Erythrocyte Enzymes for the Preparation of Polyhemoglobin-catalase-superoxide Dismutase

OpenAIRE

Gu, Jingsong; Chang, Thomas Ming Swi

2009-01-01

In sustained severe ischemia, reperfusion with oxygen carriers may result in ischemia-reperfusion injuries because of the release of damaging oxygen radicals. A nanobiotechnology-based polyhemogloin-calatase-superoxide dismutase can prevent this because the oxygen carrier, polyhemoglobin, is linked to antioxidant enzymes, catalase and superoxide dismutase. However, these antioxidant enzymes come from nonhuman sources and recombinant human enzymes are expensive. This paper describes our study ...

Effects of Ecohydraulic Bank Stabilization Structures on Bank Stability and Macroinvertebrate Community in Surabaya River

Directory of Open Access Journals (Sweden)

Daru Setyo Rini

2018-01-01

Full Text Available There were 18 accelerated erosion sites identified along 7 km of Surabaya River Fishery Sanctuary Area. A model of ecohydraulic bank stabilization was applied to reduce bank erosion in Surabaya River at Gresik Regency Indonesia. The model is combination of reprofiled and revegetated bank with rock toe reinforcement and  addition of log groynes. Various native plant species were planted and naturally grown to establish multi-strata littoral vegetation structure. This study assessed effects of ecohydraulic bank stabilization on bank morphology, near bank velocity and littoral macroinvertebrate community during September 2014 to August 2016. The study found that rock toe enforcement, log groynes and reprofiled bank slope could stabilized the eroded bank, and littoral vegetation formation reduced near bank velocity at restored sites. There were 31 families of macroinvertebrate found in Surabaya River with high abundance of moderately pollution sensitive taxa Atyidae and pollution tolerant taxa Corixidae, Chironomidae and Tubificidae. The taxa richness, diversity index and abundance of sensitive and moderately sensitive macroinvertebrate group were increased after application of ecohydraulic bank stabilization at restored area. The results shown that ecohydraulic bank stabilization structure provides multi-benefits in improving bank stabilization against erosion and providing new micro-habitats for biotic community. Keywords:  ecohydraulic bank stabilization, macroinvertebrates, riparian restoration

Structure stability index allocation theory and measurement of laser prototype facility

International Nuclear Information System (INIS)

Zhang Junwei; China Academy of Engineering Physics, Mianyang; Zhou Hai; Feng Bin; Lin Donghui; Jing Feng; Zhou Yi; Wang Shilong

2008-01-01

Structure stability is an important design index of ICF driver. Based on laser prototype facility(TIL) design characteristic of multi-pass amplifier and frame structure, the optical matrix is used to analyze the single optical element influence on the beam drift and get the mathematic model. Considering all the optical elements influence on the beam drift, the mathematic model of the optical element stability index allocation is built, the parameter relation of the mathematic model is defined according to the structure characteristic of TIL, the stability index of each optical element is got as the support structure design index. Charge-coupled device(CCD) detect technology is used to measure the general beam stability of TIL. The root mean square beam drift in x and y direction are 2.78 μm, the difference between peak and valley values are 14.4 μm and 15.60 μm, respectively. The result indicates that the stability drift of the prototype facility can satisfy the design requirement, the way of the stability allocation is reasonable. (authors)

Stabilization and structural adjustment in Mozambique

DEFF Research Database (Denmark)

Tarp, Finn; Arndt, Channing; Jensen, Henning Tarp

2000-01-01

This paper outlines the complex historical legacy and structural adjustment efforts in Mozambique in addition to reviewing recent economic developments. An in-depth analysis of new and more reliable national accounts data show that macroeconomic stabilization has occurred through recovery from...

Early structure of LPG partially premixed conically stabilized flames

KAUST Repository

Elbaz, Ayman M.

2013-01-01

This paper presents experimental investigation of LPG partially premixed turbulent flames stabilized within a conical nozzle burner under constant degree of partial premixing. The stability limits and mean flame structure are presented based

Interface stability of granular filter structures under currents

NARCIS (Netherlands)

Verheij, H.J.; Hoffmans, G.; Dorst, K.; Van de Sande, S.

2012-01-01

Granular filters are used for protection of structures against scour and erosion. For a proper functioning it is necessary that the interfaces between the filter structure, the subsoil and the water flowing above the filter structure are stable. Stability means that there is no transport of subsoil

Isolation and characterization of Cu/Zn-superoxide dismutase in Fasciola gigantica.

Science.gov (United States)

Lalrinkima, H; Raina, O K; Chandra, Dinesh; Jacob, Siju Susan; Bauri, R K; Chandra, Subhash; Yadav, H S; Singh, M N; Rialch, A; Varghese, A; Banerjee, P S; Kaur, Navneet; Sharma, Arvind

2015-01-01

A full-length complementary DNA (cDNA) encoding Cu/Zn-superoxide dismutase was isolated from Fasciola gigantica that on nucleotide sequencing showed a close homology (98.9%) with Cu/Zn-superoxide dismutase (SOD) of the temperate liver fluke, F. hepatica. Expression of the gene was found in all the three developmental stages of the parasite viz. adult, newly excysted juvenile and metacercaria at transcriptional level by reverse transcription-polymerase chain reaction (RT-PCR) and at the protein level by Western blotting. F. gigantica Cu/Zn-SOD cDNA was cloned and expressed in Escherichia coli. Enzyme activity of the recombinant protein was determined by nitroblue tetrazolium (NBT)-polyacrylamide gel electrophoresis (PAGE) and this activity was inactivated by hydrogen peroxide but not by sodium azide, indicating that the recombinant protein is Cu/Zn-SOD. The enzyme activity was relatively stable at a broad pH range of pH 4.0-10.0. Native Cu/Zn-superoxide dismutase protein was detected in the somatic extract and excretory-secretory products of the adult F. gigantica by Western blotting. NBT-PAGE showed a single Cu/Zn-SOD present in the somatic extract while three SODs are released ex vivo by the adult parasite. The recombinant superoxide dismutase did not react with the serum from buffaloes infected with F. gigantica. The role of this enzyme in defense by the parasite against the host reactive oxygen species is discussed. Copyright © 2015 Elsevier Inc. All rights reserved.

Structural Stability of Low-Crested Breakwaters

DEFF Research Database (Denmark)

Kramer, Morten

equations. New improved design formulae for calculation of static stability of LCS's are developed on the basis of new 2D and 3D laboratory experiments with scale models. The formulae are specially designed for breakwaters subject to shallow water waves and/or depth limited waves, as the majority...... of existing LCS’s are exposed to such conditions. The formulae are validated against prototype experience. Ecological aspects in relation to structural stability are important, and design guidance on how to consider ecology in the design is therefore given. The new design guidance adds practical and helpful...

DNA secondary structures: stability and function of G-quadruplex structures

Science.gov (United States)

Bochman, Matthew L.; Paeschke, Katrin; Zakian, Virginia A.

2013-01-01

In addition to the canonical double helix, DNA can fold into various other inter- and intramolecular secondary structures. Although many such structures were long thought to be in vitro artefacts, bioinformatics demonstrates that DNA sequences capable of forming these structures are conserved throughout evolution, suggesting the existence of non-B-form DNA in vivo. In addition, genes whose products promote formation or resolution of these structures are found in diverse organisms, and a growing body of work suggests that the resolution of DNA secondary structures is critical for genome integrity. This Review focuses on emerging evidence relating to the characteristics of G-quadruplex structures and the possible influence of such structures on genomic stability and cellular processes, such as transcription. PMID:23032257

Early structure of LPG partially premixed conically stabilized flames

KAUST Repository

Elbaz, Ayman M.

2013-01-01

This paper presents experimental investigation of LPG partially premixed turbulent flames stabilized within a conical nozzle burner under constant degree of partial premixing. The stability limits and mean flame structure are presented based on the mean gas temperature and the concentration of CO, O 2, NO, and HC at the flame early region of reaction. The investigation covered the influence of the nozzle cone angle, the jet exit velocity and the jet equivalence ratio. The stability results show that the flames with cone are more stable than those without cone. For conical stabilized flames, the stability results exhibit three different sensitivity regions between the jet velocity and equivalence ratio. The inflame measurements prove that the flame stability could be attributed to the triple flame structure at the flame leading edge. The data show that the triple flame structure is influenced by cone angle, the jet velocity and the equivalence ratio. The flame is believed to be controlled by the recirculation flow inside the cone. Increasing the cone angle induced higher air entrainment to the reaction zone as depicted by a higher O 2 concentration within the flame leading edge. Increasing the jet velocity to a certain limit enhances the intensity of combustion at the flame leading edge, while excessive increase in jet velocity reduces this intensity. At a fixed jet velocity the higher the equivalence ratio, the higher the amount of fuel diffused and engulfed to the reaction zone, the more delay of the combustion completion and the higher the emission concentrations of the flame. © 2012 Elsevier Inc.

Structural Stability Of Detached Low Crested Breakwaters

DEFF Research Database (Denmark)

Burcharth, Hans F.; Kramer, Morten; Lamberti, Alberto

2006-01-01

The aim of the paper is to describe hydraulic stability of rock-armoured low-crested structures on the basis of new experimental tests and prototype observations. Rock armour stability results from earlier model tests under non-depth-limited long-crested head-on waves are reviewed. Results from new...... determining armour stone size in shallow water conditions is given together with a rule of thumb for the required stone size in depth-limited design waves. Rock toe stability is discussed on the basis of prototype experience, hard bottom 2-D tests in depth-limited waves and an existing hydraulic stability...... formula. Toe damage predicted by the formula is in agreement with experimental results. In field sites, damage at the toe induced by scour or by sinking is observed and the volume of the berm is often insufficient to avoid regressive erosion of the armour layer. Stone sinking and settlement in selected...

Structure and stability of spiro-cyclic water clusters

Indian Academy of Sciences (India)

Administrator

Abstract. The structure and stability of spiro-cyclic water clusters containing up to 32 water molecules have been ... due to its importance in various real life systems. 1–8. High level ... It is well-known from the crystal structure data- base that the ...

Characteristics of the Copper,Zinc Superoxide Dismutase of a Hadal Sea Cucumber (Paelopatides sp.) from the Mariana Trench.

Science.gov (United States)

Li, Yanan; Kong, Xue; Chen, Jiawei; Liu, Helu; Zhang, Haibin

2018-05-18

Superoxide dismutases (SODs) are among the most important antioxidant enzymes and show great potential in preventing adverse effects during therapeutic trials. In the present study, cloning, expression, and characterization of a novel Cu,Zn superoxide dismutase (Ps-Cu,Zn-SOD) from a hadal sea cucumber ( Paelopatides sp.) were reported. Phylogenetic analysis showed that Ps-Cu,Zn-SOD belonged to a class of intracellular SOD. Its K m and V max were 0.0258 ± 0.0048 mM and 925.1816 ± 28.0430 units/mg, respectively. The low K m value of this enzyme represents a high substrate affinity and can adapt to the low metabolic rate of deep sea organisms. The enzyme functioned from 0 °C to 80 °C with an optimal temperature of 40 °C. Moreover, the enzyme activity was maintained up to 87.12% at 5 °C. The enzyme was active at pH 4 to 12 with an optimal pH of 8.5. Furthermore, Ps-Cu,Zn-SOD tolerated high concentration of urea and GuHCl, resisted hydrolysis by proteases, and maintained stability at high pressure. All these features demonstrated that the deep sea Ps-Cu,Zn-SOD is a potential candidate for application to the biopharmaceutical field.

Structural stability of DNA origami nanostructures in the presence of chaotropic agents.

Science.gov (United States)

Ramakrishnan, Saminathan; Krainer, Georg; Grundmeier, Guido; Schlierf, Michael; Keller, Adrian

2016-05-21

DNA origami represent powerful platforms for single-molecule investigations of biomolecular processes. The required structural integrity of the DNA origami may, however, pose significant limitations regarding their applicability, for instance in protein folding studies that require strongly denaturing conditions. Here, we therefore report a detailed study on the stability of 2D DNA origami triangles in the presence of the strong chaotropic denaturing agents urea and guanidinium chloride (GdmCl) and its dependence on concentration and temperature. At room temperature, the DNA origami triangles are stable up to at least 24 h in both denaturants at concentrations as high as 6 M. At elevated temperatures, however, structural stability is governed by variations in the melting temperature of the individual staple strands. Therefore, the global melting temperature of the DNA origami does not represent an accurate measure of their structural stability. Although GdmCl has a stronger effect on the global melting temperature, its attack results in less structural damage than observed for urea under equivalent conditions. This enhanced structural stability most likely originates from the ionic nature of GdmCl. By rational design of the arrangement and lengths of the individual staple strands used for the folding of a particular shape, however, the structural stability of DNA origami may be enhanced even further to meet individual experimental requirements. Overall, their high stability renders DNA origami promising platforms for biomolecular studies in the presence of chaotropic agents, including single-molecule protein folding or structural switching.

Extraction of erythrocyte enzymes for the preparation of polyhemoglobin-catalase-superoxide dismutase.

Science.gov (United States)

Gu, Jingsong; Chang, Thomas Ming Swi

2009-01-01

In sustained severe ischemia, reperfusion with oxygen carriers may result in ischemia-reperfusion injuries because of the release of damaging oxygen radicals. A nanobiotechnology-based polyhemogloin-calatase-superoxide dismutase can prevent this because the oxygen carrier, polyhemoglobin, is linked to antioxidant enzymes, catalase and superoxide dismutase. However, these antioxidant enzymes come from nonhuman sources and recombinant human enzymes are expensive. This paper describes our study on extracting these enzymes from red blood cells and analyzing the amount of enzymes needed for adequate protection from ischemia-reperfusion.

Superoxide anion production and superoxide dismutase and catalase activities in Coxiella burnetii.

OpenAIRE

Akporiaye, E T; Baca, O G

1983-01-01

Coxiella burnetii was examined for superoxide anion (O2-) production and superoxide dismutase and catalase activities. The organism generated O2- at pH 4.5 but not at pH 7.4. The rickettsia displayed superoxide dismutase activity distinguishable from that of the host cell (L-929 mouse fibroblast). Catalase activity was maximal at pH 7.0 and diminished at pH 4.5. These enzymes may account, in part, for the ability of this obligate intracellular parasite to survive within phagocytes.

Copper-zinc superoxide dismutase is activated through a sulfenic acid intermediate at a copper ion entry site.

Science.gov (United States)

Fetherolf, Morgan M; Boyd, Stefanie D; Taylor, Alexander B; Kim, Hee Jong; Wohlschlegel, James A; Blackburn, Ninian J; Hart, P John; Winge, Dennis R; Winkler, Duane D

2017-07-21

Metallochaperones are a diverse family of trafficking molecules that provide metal ions to protein targets for use as cofactors. The copper chaperone for superoxide dismutase (Ccs1) activates immature copper-zinc superoxide dismutase (Sod1) by delivering copper and facilitating the oxidation of the Sod1 intramolecular disulfide bond. Here, we present structural, spectroscopic, and cell-based data supporting a novel copper-induced mechanism for Sod1 activation. Ccs1 binding exposes an electropositive cavity and proposed "entry site" for copper ion delivery on immature Sod1. Copper-mediated sulfenylation leads to a sulfenic acid intermediate that eventually resolves to form the Sod1 disulfide bond with concomitant release of copper into the Sod1 active site. Sod1 is the predominant disulfide bond-requiring enzyme in the cytoplasm, and this copper-induced mechanism of disulfide bond formation obviates the need for a thiol/disulfide oxidoreductase in that compartment. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

On Robust Stability of Differential-Algebraic Equations with Structured Uncertainty

Directory of Open Access Journals (Sweden)

A. Kononov

2018-03-01

Full Text Available We consider a linear time-invariant system of differential-algebraic equations (DAE, which can be written as a system of ordinary differential equations with non-invertible coefficients matrices. An important characteristic of DAE is the unsolvability index, which reflects the complexity of the internal structure of the system. The question of the asymptotic stability of DAE containing the uncertainty given by the matrix norm is investigated. We consider a perturbation in the structured uncertainty case. It is assumed that the initial nominal system is asymptotically stable. For the analysis, the original equation is reduced to the structural form, in which the differential and algebraic subsystems are separated. This structural form is equivalent to the input system in the sense of coincidence of sets of solutions, and the operator transforming the DAE into the structural form possesses the inverse operator. The conversion to structural form does not use a change of variables. Regularity of matrix pencil of the source equation is the necessary and sufficient condition of structural form existence. Sufficient conditions have been obtained that perturbations do not break the internal structure of the nominal system. Under these conditions robust stability of the DAE with structured uncertainty is investigated. Estimates for the stability radius of the perturbed DAE system are obtained. The text of the article is from the simpler case, in which the perturbation is present only for an unknown function, to a more complex one, under which the perturbation is also present in the derivative of the unknown function. We used values of the real and the complex stability radii of explicit ordinary differential equations for obtaining the results. We consider the example illustrating the obtained results.

The crystal structure and stability of molybdenum at ultrahigh pressures

International Nuclear Information System (INIS)

Jona, F; Marcus, P M

2005-01-01

Crystal structures and their stabilities for molybdenum under increasing hydrostatic pressures are investigated by first-principles calculations of the Gibbs free energy. Three structures are considered: body-centred cubic (bcc, the ground state at zero pressure), hexagonal close-packed (hcp) and face-centred cubic (fcc). For each structure and each pressure (up to 8 Mbar) the equilibrium states are found from minima of the Gibbs free energy at zero temperature. The stability is tested by calculating the elastic constants and checking whether they satisfy the appropriate stability conditions. The bcc structure is confirmed to be stable at zero pressure and at 6 Mbar. At and above 6.2 M-bar the ground-state structure changes to hcp, which is found to be stable at 7 M-bar. At 7.7 Mbar another transition occurs, and the ground-state structure changes from hcp to fcc. The fcc structure, which is unstable at zero pressure, becomes metastable over the range from 3 to 7.7 M-bar and becomes the ground state at higher pressures (at least up to 8 Mbar). Direct confirmation of these calculated transition pressures with experiment is not now possible, as the maximum static pressure currently reached experimentally is 5.6 Mbar, where Mo is found to be still in the bcc phase

Water stress induces overexpression of superoxide dismutases that ...

African Journals Online (AJOL)

Water stress is known to induce active oxygen species in plants. The accumulation of these harmful species must be prevented by plants as rapidly as possible to maintain growth and productivity. The aim of this study was to determine the effect of water stress on superoxide dismutase isozymes (SOD, EC 1.15.1.1.) in two ...

ACTIVITY OF SUPEROXIDE DISMUTASE ENZYME IN YEAST SACCHAROMYCES CEREVISIAE

Directory of Open Access Journals (Sweden)

Blažena Lavová

2014-02-01

Full Text Available Reactive oxygen species (ROS with reactive nitrogen species (RNS are known to play dual role in biological systems, they can be harmful or beneficial to living systems. ROS can be important mediators of damage to cell structures, including proteins, lipids and nucleic acids termed as oxidative stress. The antioxidant enzymes protect the organism against the oxidative damage caused by active oxygen forms. The role of superoxide dismutase (SOD is to accelerate the dismutation of the toxic superoxide radical, produced during oxidative energy processes, to hydrogen peroxide and molecular oxygen. In this study, SOD activity of three yeast strains Saccharomyces cerevisiae was determined. It was found that SOD activity was the highest (23.7 U.mg-1 protein in strain 612 after 28 hours of cultivation. The lowest SOD activity from all tested strains was found after 56 hours of cultivation of strain Gyöng (0.7 U.mg-1 protein.

Structural stability of interaction networks against negative external fields

Science.gov (United States)

Yoon, S.; Goltsev, A. V.; Mendes, J. F. F.

2018-04-01

We explore structural stability of weighted and unweighted networks of positively interacting agents against a negative external field. We study how the agents support the activity of each other to confront the negative field, which suppresses the activity of agents and can lead to collapse of the whole network. The competition between the interactions and the field shape the structure of stable states of the system. In unweighted networks (uniform interactions) the stable states have the structure of k -cores of the interaction network. The interplay between the topology and the distribution of weights (heterogeneous interactions) impacts strongly the structural stability against a negative field, especially in the case of fat-tailed distributions of weights. We show that apart from critical slowing down there is also a critical change in the system structure that precedes the network collapse. The change can serve as an early warning of the critical transition. To characterize changes of network structure we develop a method based on statistical analysis of the k -core organization and so-called "corona" clusters belonging to the k -cores.

Towards a "Golden Standard" for computing globin stability: Stability and structure sensitivity of myoglobin mutants.

Science.gov (United States)

Kepp, Kasper P

2015-10-01

Fast and accurate computation of protein stability is increasingly important for e.g. protein engineering and protein misfolding diseases, but no consensus methods exist for important proteins such as globins, and performance may depend on the type of structural input given. This paper reports benchmarking of six protein stability calculators (POPMUSIC 2.1, I-Mutant 2.0, I-Mutant 3.0, CUPSAT, SDM, and mCSM) against 134 experimental stability changes for mutations of sperm-whale myoglobin. Six different high-resolution structures were used to test structure sensitivity that may impair protein calculations. The trend accuracy of the methods decreased as I-Mutant 2.0 (R=0.64-0.65), SDM (R=0.57-0.60), POPMUSIC2.1 (R=0.54-0.57), I-Mutant 3.0 (R=0.53-0.55), mCSM (R=0.35-0.47), and CUPSAT (R=0.25-0.48). The mean signed errors increased as SDMMean absolute errors increased as I-Mutant 2.0Structural sensitivity increased as I-Mutant 3.0 (0.05)structures and reveal structure-dependent effects even in the near-atomic resolution limit. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of Low Level Cadmium Exposure on Superoxide Dismutase ...

African Journals Online (AJOL)

Purpose: To investigate the effect of low level cadmium (Cd) exposure on the activity of superoxide dismutase ... cancer, aging and a diversity of diseases [5]. Superoxide .... responsible for the long biological half-life of cadmium [12]. ... indicator of the balance between the damaging effects and the ... Scand J Work Environ.

Oxidative stress and superoxide dismutase activity in brain of rats ...

African Journals Online (AJOL)

JTEkanem

effect of superoxide dismutase (SOD) activity in brain homogenates of Wistar rats. Oxidative stress measured as ..... on the brain and nervous system of humans as handlers and ... environment may be at higher health risk in that their internal ...

Structure, stability and behaviour of nucleic acids in ionic liquids

Science.gov (United States)

Tateishi-Karimata, Hisae; Sugimoto, Naoki

2014-01-01

Nucleic acids have become a powerful tool in nanotechnology because of their conformational polymorphism. However, lack of a medium in which nucleic acid structures exhibit long-term stability has been a bottleneck. Ionic liquids (ILs) are potential solvents in the nanotechnology field. Hydrated ILs, such as choline dihydrogen phosphate (choline dhp) and deep eutectic solvent (DES) prepared from choline chloride and urea, are ‘green’ solvents that ensure long-term stability of biomolecules. An understanding of the behaviour of nucleic acids in hydrated ILs is necessary for developing DNA materials. We here review current knowledge about the structures and stabilities of nucleic acids in choline dhp and DES. Interestingly, in choline dhp, A–T base pairs are more stable than G–C base pairs, the reverse of the situation in buffered NaCl solution. Moreover, DNA triplex formation is markedly stabilized in hydrated ILs compared with aqueous solution. In choline dhp, the stability of Hoogsteen base pairs is comparable to that of Watson–Crick base pairs. Moreover, the parallel form of the G-quadruplex is stabilized in DES compared with aqueous solution. The behaviours of various DNA molecules in ILs detailed here should be useful for designing oligonucleotides for the development of nanomaterials and nanodevices. PMID:25013178

Electrochemical stability of ionic clathrate hydrates and their structural consideration

International Nuclear Information System (INIS)

Lee, Wonhee; Lim, Dongwook; Lee, Huen

2013-01-01

Although electrochemical stability is an essential factor in relation to the potential applications of ionic clathrate hydrates to solid electrolytes, most studies regarding the proton conductors have focused on their ionic conductivity and thermal stability. Solid electrolytes in various electrochemical devices have to endure the applied potentials; thus, we examined the linear sweep voltammograms of various tetraalkylammonium hydroxide hydrates in order to shed light on the trend of electrochemical stability depending on the hydrate structure. We revealed that the electrochemical stability of Me 4 NOH hydrates is mainly affected by both their ionic concentration and cage occupancy. In particular, the true clathrate structures of β-Me 4 NOH hydrates are more electrochemically stable than their α-forms that possess partially broken hydrogen bonds. We also observed that the binary THF–Pr 4 NOH and pure Bu 4 NOH clathrate hydrates exhibit greater electrochemical stability than those of pure Me 4 NOH hydrates having lower or similar ionic concentrations. These results are considered to arise from the fact that each of the Pr 4 N + and Bu 4 N + ions occupies an extended space comprising four cages, which leads to stabilization of the larger unit, whereas a Me 4 N + ion is completely included only in one cage

Structure and stabilization of hydrogen-rich transverse.

Energy Technology Data Exchange (ETDEWEB)

Lyra, Sgouria [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Wilde, B [Georgia Inst. of Technology, Atlanta, GA (United States); Kolla, Hemanth [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Seitzman, J. [Georgia Inst. of Technology, Atlanta, GA (United States); Lieuwen, T. C. [Georgia Inst. of Technology, Atlanta, GA (United States); Chen, Jacqueline H. [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

2014-07-01

This paper reports the results of a joint experimental and numerical study of the ow characteristics and flame stabilization of a hydrogen rich jet injected normal to a turbulent, vitiated cross ow of lean methane combustion products. Simultaneous high-speed stereoscopic PIV and OH PLIF measurements were obtained and analyzed alongside three-dimensional direct numerical simulations of inert and reacting JICF with detailed H₂/CO chemistry. Both the experiment and the simulation reveal that, contrary to most previous studies of reacting JICF stabilized in low-to-moderate temperature air cross ow, the present conditions lead to an autoigniting, burner-attached flame that initiates uniformly around the burner edge. Significant asymmetry is observed, however, between the reaction zones located on the windward and leeward sides of the jet, due to the substantially different scalar dissipation rates. The windward reaction zone is much thinner in the near field, while also exhibiting significantly higher local and global heat release than the much broader reaction zone found on the leeward side of the jet. The unsteady dynamics of the windward shear layer, which largely control the important jet/cross flow mixing processes in that region, are explored in order to elucidate the important flow stability implications arising in the reacting JICF. Vorticity spectra extracted from the windward shear layer reveal that the reacting jet is globally unstable and features two high frequency peaks, including a fundamental mode whose Strouhal number of ~0.7 agrees well with previous non-reacting JICF stability studies. The paper concludes with an analysis of the ignition, ame stabilization, and global structure of the burner-attached flame. Chemical explosive mode analysis (CEMA) shows that the entire windward shear layer, and a large region on the leeward side of the jet, are highly explosive prior to ignition and are dominated by non-premixed flame structures after

Ab initio study on structural stability of uranium carbide

International Nuclear Information System (INIS)

Sahoo, B.D.; Joshi, K.D.; Gupta, Satish C.

2013-01-01

First principles calculations have been performed using plane wave pseudopotential and full potential linearized augmented plane wave (FP-LAPW) methods to analyze structural, elastic and dynamic stability of UC under hydrostatic compression. Our calculations within pseudopotential method suggest that the rocksalt (B1) structure will transform to body centered orthorhombic (bco) structure at ∼21.5 GPa. The FP-LAPW calculations put this transition at 23 GPa. The transition pressures determined from our calculations though agree reasonably with the experimental value of 27 GPa, the high pressure bco structure suggested by theory differs slightly from the experimentally reported pseudo bco phase. The elastic stability analysis of B1 phase suggests that the B1 to bco transition is driven by the failure of C 44 modulus. This finding is further substantiated by the lattice dynamic calculations which demonstrate that the B1 phase becomes dynamically unstable around the transition pressure and the instability is of long wavelength nature

Design criteria development for the structural stability of nuclear waste repository

Energy Technology Data Exchange (ETDEWEB)

Yun, C H [Korea Institute of Nuclear Safety, Taejon (Korea, Republic of); Yu, T S [Daewoo Engineering Company, Sungnam (Korea, Republic of); Ko, H M [Seoul National Univ., Seoul (Korea, Republic of)

1990-11-15

The objective of the present project is to develop design criteria for the structural stability of rock cavity for the underground repository are defined, according to which detailed descriptions for design methodologies, design stages and stability analysis of the cavity are made. The proposed criteria can be used as a guide for the preparation of design codes which are to be established as the site condition and technical emplacement procedure are fixed. The present report first reviews basic safety requirements and criteria of the underground disposal of nuclear wastes for the establishment of design concepts and stability analysis of the rock cavity. Important factors for the design are also described by considering characteristics of the wastes and underground facilities. The present project has investigated technical aspects on the design of underground structures based on the currently established underground construction technologies, and presented a proposal for design criteria for the structural stability of the nuclear waste repository. The proposed criteria consist of general provisions, geological exploration, rock classification, design process and methods, supporting system, analyses and instrumentation.

Cloning and expression of an iron-containing superoxide dismutase in the parasitic protist, Trichomonas vaginalis.

Science.gov (United States)

Viscogliosi, E; Delgado-Viscogliosi, P; Gerbod, D; Dauchez, M; Gratepanche, S; Alix, A J; Dive, D

1998-04-01

A superoxide dismutase (SOD) gene of the parasitic protist Trichomonas vaginalis was cloned, sequenced, expressed in Escherichia coli, and its gene product characterized. It is an iron-containing dimeric protein with a monomeric mass of 22,067 Da. Southern blots analyses suggested the presence of seven iron-containing (FeSOD) gene copies. Hydrophobic cluster analysis revealed some peculiarities in the 2D structure of the FeSOD from T. vaginalis and a strong structural conservation between prokaryotic and eukaryotic FeSODs. Phylogenetic reconstruction of the SOD sequences confirmed the dichotomy between FeSODs and manganese-containing SODs. FeSODs of protists appeared to group together with homologous proteobacterial enzymes suggesting a possible origin of eukaryotic FeSODs through an endosymbiotic event.

Calcium Stabilized And Geogrid Reinforced Soil Structures In Seismic Areas

International Nuclear Information System (INIS)

Rimoldi, Pietro; Intra, Edoardo

2008-01-01

In many areas of Italy, and particularly in high seismic areas, there is no or very little availability of granular soils: hence embankments and retaining structures are often built using the locally available fine soil. For improving the geotechnical characteristics of such soils and/or for building steep faced structures, there are three possible techniques: calcium stabilization, geogrid reinforcement, and the combination of both ones, that is calcium stabilized and reinforced soil. The present paper aims to evaluate these three techniques in terms of performance, design and construction, by carrying out FEM modeling and stability analyses of the same reference embankments, made up of soil improved with each one of the three techniques, both in static and dynamic conditions. Finally two case histories are illustrated, showing the practical application of the above outlined techniques

A new method for evaluating structural stability of bulk metallic glasses

Energy Technology Data Exchange (ETDEWEB)

Zhao, Lei; Jia, Haoling [Key Laboratory of Aerospace Materials and Performance, Ministry of Education, School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Xie, Shenghui; Zeng, Xierong [College of Materials Science and Engineering, Shenzhen University and Shenzhen Key Laboratory of Special Functional Materials, ShenZhen 518060 (China); Zhang, Tao [Key Laboratory of Aerospace Materials and Performance, Ministry of Education, School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Ma, Chaoli, E-mail: machaoli@buaa.edu.c [Key Laboratory of Aerospace Materials and Performance, Ministry of Education, School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)

2010-08-15

This paper proposed a new method for evaluating the structural stability of bulk metallic glasses (BMGs) based on dilatometric measurements. During heating in the dilatometric experiments, the BMGs expanded continuously with increasing temperature. When the temperature reached the glass transition temperature (T{sub g}), viscous shrinkage occurred due to the viscosity of material becoming lower. Since the inhomogeneous nature of the metallic glasses at atomic level, the processes of rigid expansion and the viscous shrinkage co-exist in a certain temperature region. The expansion stopped completely at a temperature (named T{sub p} here) beyond T{sub g}. The values of the temperature region, {Delta}T{sub gp} = T{sub p} - T{sub g}, and the corresponding time interval ({Delta}t{sub gp}) and the activation energy (E{sub p}) corresponding to the expansion processes, are the reflection of the structural stability of BMGs. Investigating the co-existing processes kinetically and thermodynamically, we can make an insight into the structural stability of metallic glasses. Based on this idea, the thermal expansion behaviors of Mg-, Pd-, Zr-, Ti- and Fe-based BMG were studied, and their structural stability was evaluated by the parameters of {Delta}T{sub gp}, {Delta}t{sub gp} and E{sub p}.

Structure and stability of charged colloid-nanoparticle mixtures

Science.gov (United States)

Weight, Braden M.; Denton, Alan R.

2018-03-01

Physical properties of colloidal materials can be modified by addition of nanoparticles. Within a model of like-charged mixtures of particles governed by effective electrostatic interactions, we explore the influence of charged nanoparticles on the structure and thermodynamic phase stability of charge-stabilized colloidal suspensions. Focusing on salt-free mixtures of particles of high size and charge asymmetry, interacting via repulsive Yukawa effective pair potentials, we perform molecular dynamics simulations and compute radial distribution functions and static structure factors. Analysis of these structural properties indicates that increasing the charge and concentration of nanoparticles progressively weakens correlations between charged colloids. We show that addition of charged nanoparticles to a suspension of like-charged colloids can induce a colloidal crystal to melt and can facilitate aggregation of a fluid suspension due to attractive van der Waals interactions. We attribute the destabilizing influence of charged nanoparticles to enhanced screening of electrostatic interactions, which weakens repulsion between charged colloids. This interpretation is consistent with recent predictions of an effective interaction theory of charged colloid-nanoparticle mixtures.

A reliable method for the stability analysis of structures ...

African Journals Online (AJOL)

The detection of structural configurations with singular tangent stiffness matrix is essential because they can be unstable. The secondary paths, especially in unstable buckling, can play the most important role in the loss of stability and collapse of the structure. A new method for reliable detection and accurate computation of ...

Oxidative stability of structured lipids produced from sunflower oil and caprylic acid

DEFF Research Database (Denmark)

Timm Heinrich, Maike; Xu, Xuebing; Nielsen, Nina Skall

2003-01-01

Traditional sunflower oil (SO), randomized lipid (RL) and specific structured lipid (SL), both produced from SO and tricaprylin/caprylic acid, respectively, were stored for up to 12 wk to compare their oxidative stabilities by chemical and sensory analyses. Furthermore, the effect of adding...... a commercial antioxidant blend Grindox 117 (propyl gallate/citric acid/ascorbyl palmitate) or gallic acid to the SL was investigated. The lipid type affected the oxidative stability: SL was less stable than SO and RL. The reduced stability was most likely caused by both the structure of the lipid...

First-principles calculation of the structural stability of 6d transition metals

International Nuclear Information System (INIS)

Oestlin, A.; Vitos, L.

2011-01-01

The phase stability of the 6d transition metals (elements 103-111) is investigated using first-principles electronic-structure calculations. Comparison with the lighter transition metals reveals that the structural sequence trend is broken at the end of the 6d series. To account for this anomalous behavior, the effect of relativity on the lattice stability is scrutinized, taking different approximations into consideration. It is found that the mass-velocity and Darwin terms give important contributions to the electronic structure, leading to changes in the interstitial charge density and, thus, in the structural energy difference.

Oxidative stress and superoxide dismutase activity in brain of rats ...

African Journals Online (AJOL)

The present study was envisaged to investigate the possible role of oxidative stress in permethrin neurotoxicity and to evaluate the protective effect of superoxide dismutase (SOD) activity in brain homogenates of Wistar rats. Oxidative stress measured as thiobarbituric acid reacting substances (TBARS) was found to ...

Purification and characterization of a chlorite dismutase from Pseudomonas chloritidismutans

NARCIS (Netherlands)

Mehboob, F.; Wolterink, A.F.W.M.; Vermeulen, A.J.; Jiang, B.; Hagedoorn, P.L.; Stams, A.J.M.; Kengen, S.W.M.

2009-01-01

The chlorite dismutase (Cld) of Pseudomonas chloritidismutans was purified from the periplasmic fraction in one step by hydroxyapatite chromatography. The enzyme has a molecular mass of 110 kDa and consists of four 31-kDa subunits. Enzyme catalysis followed Michaelis-Menten kinetics, with Vmax and

Recent Advances in Heliogyro Solar Sail Structural Dynamics, Stability, and Control Research

Science.gov (United States)

Wilkie, W. Keats; Warren, Jerry E.; Horta, Lucas G.; Lyle, Karen H.; Juang, Jer-Nan; Gibbs, S. Chad; Dowell, Earl H.; Guerrant, Daniel V.; Lawrence, Dale

2015-01-01

Results from recent NASA sponsored research on the structural dynamics, stability, and control characteristics of heliogyro solar sails are summarized. Specific areas under investigation include coupled nonlinear finite element analysis of heliogyro membrane blade with solar radiation pressure effects, system identification of spinning membrane structures, and solarelastic stability analysis of heliogyro solar sails, including stability during blade deployment. Recent results from terrestrial 1-g blade dynamics and control experiments on "rope ladder" membrane blade analogs, and small-scale in vacuo system identification experiments with hanging and spinning high-aspect ratio membranes will also be presented. A low-cost, rideshare payload heliogyro technology demonstration mission concept is used as a mission context for these heliogyro structural dynamics and solarelasticity investigations, and is also described. Blade torsional dynamic response and control are also shown to be significantly improved through the use of edge stiffening structural features or inclusion of modest tip masses to increase centrifugal stiffening of the blade structure. An output-only system identification procedure suitable for on-orbit blade dynamics investigations is also developed and validated using ground tests of spinning sub-scale heliogyro blade models. Overall, analytical and experimental investigations to date indicate no intractable stability or control issues for the heliogyro solar sail concept.

Profiling of antioxidant superoxide dismutase in saliva of oral submucous fibrosis patients to categorize its diagnosis in varying stages

International Nuclear Information System (INIS)

Sirohi, Y.; Shetty, D.C.; Urs, A.B.; Rai, H.C.

2011-01-01

Background: Oral submucous fibrosis is a pre malignant condition in Indian and South-East Asia. Role of oxidant-antioxidant in causation and progression of cancer and pre cancers is known. Reactive oxygen species are generated in the oral cavity during chewing areca nut, the major etiological agent in oral submucous fibrosis. Objectives: To see the alterations in the salivary superoxide dismutase levels in various clinical and histopathological grades of oral submucous fibrosis. Materials and Methods: Unstimulated saliva was collected from 25 oral submucous fibrosis patients and age and gender matched controls. The saliva was assessed for superoxide dismutase value by spectrophotometric method using assay kit (Bio Vision Catalog number K335-100). The oral submucous fibrosis cases were grouped into clinical stages and histopathological grades and superoxide dismutase values were compared in different clinical stages and histopathological grades. Results: The superoxide dismutase levels were reduced in oral submucous fibrosis as compared to controls. A steady decline in the levels was seen as the clinical stage and histopathological grade of oral submucous fibrosis advanced. Conclusions: Salivary superoxide dismutase levels can be alternatively used as a surrogate marker for the diagnosis of oral submucous fibrosis. Policy message: Oral physicians should advise the pan chewers to regularly check their salivary superoxide dismutase levels so as to ease the early diagnosis of oral submucous fibrosis. (author)

Range and stability of structural colors generated by Morpho-inspired color reflectors.

Science.gov (United States)

Chung, Kyungjae; Shin, Jung H

2013-05-01

The range and stability of structural colors generated by Morpho-inspired color reflectors are investigated. We find that despite the internal randomness of such structures that gives rise to their Morpho-like angle-independent iridescence, their colors under ambient lighting condition can be predicted by simple transfer-matrix calculations of corresponding planar multilayer structures. By calculating the possible range of colors generated by multilayers of different structures and material combinations using such transfer-matrix methods, we find that low-refractive index multilayers with intrastructure absorption, such as the melanin-containing chitin/air multilayer structure from the Morpho butterflies, can provide not only the most pure structural colors with the largest color gamut, but also the highest stability of color against variations in multilayer structure.

Furin proteolytically processes the heparin-binding region of extracellular superoxide dismutase

DEFF Research Database (Denmark)

Bowler, Russell P; Nicks, Mike; Olsen, Dorte Aa

2002-01-01

Extracellular superoxide dismutase (EC-SOD) is an antioxidant enzyme that attenuates brain and lung injury from oxidative stress. A polybasic region in the carboxyl terminus distinguishes EC-SOD from other superoxide dismutases and determines EC-SOD's tissue half-life and affinity for heparin....... There are two types of EC-SOD that differ based on the presence or absence of this heparin-binding region. It has recently been shown that proteolytic removal of the heparin-binding region is an intracellular event (Enghild, J. J., Thogersen, I. B., Oury, T. D., Valnickova, Z., Hojrup, P., and Crapo, J. D...... of intracellular proteases implicate furin as a processing protease. In vitro experiments using furin and purified EC-SOD suggest that furin proteolytically cleaves EC-SOD in the middle of the polybasic region and then requires an additional carboxypeptidase to remove the remaining lysines and arginines...

Absence of superoxide dismutase activity causes nuclear DNA fragmentation during the aging process

International Nuclear Information System (INIS)

Muid, Khandaker Ashfaqul; Karakaya, Hüseyin Çaglar; Koc, Ahmet

2014-01-01

Highlights: • Aging process increases ROS accumulation. • Aging process increases DNA damage levels. • Absence of SOD activity does not cause DNA damage in young cells. • Absence of SOD activity accelerate aging and increase oxidative DNA damages during the aging process. - Abstract: Superoxide dismutases (SOD) serve as an important antioxidant defense mechanism in aerobic organisms, and deletion of these genes shortens the replicative life span in the budding yeast Saccharomyces cerevisiae. Even though involvement of superoxide dismutase enzymes in ROS scavenging and the aging process has been studied extensively in different organisms, analyses of DNA damages has not been performed for replicatively old superoxide dismutase deficient cells. In this study, we investigated the roles of SOD1, SOD2 and CCS1 genes in preserving genomic integrity in replicatively old yeast cells using the single cell comet assay. We observed that extend of DNA damage was not significantly different among the young cells of wild type, sod1Δ and sod2Δ strains. However, ccs1Δ mutants showed a 60% higher amount of DNA damage in the young stage compared to that of the wild type cells. The aging process increased the DNA damage rates 3-fold in the wild type and more than 5-fold in sod1Δ, sod2Δ, and ccs1Δ mutant cells. Furthermore, ROS levels of these strains showed a similar pattern to their DNA damage contents. Thus, our results confirm that cells accumulate DNA damages during the aging process and reveal that superoxide dismutase enzymes play a substantial role in preserving the genomic integrity in this process

Absence of superoxide dismutase activity causes nuclear DNA fragmentation during the aging process

Energy Technology Data Exchange (ETDEWEB)

Muid, Khandaker Ashfaqul; Karakaya, Hüseyin Çaglar; Koc, Ahmet, E-mail: ahmetkoc@iyte.edu.tr

2014-02-07

Highlights: • Aging process increases ROS accumulation. • Aging process increases DNA damage levels. • Absence of SOD activity does not cause DNA damage in young cells. • Absence of SOD activity accelerate aging and increase oxidative DNA damages during the aging process. - Abstract: Superoxide dismutases (SOD) serve as an important antioxidant defense mechanism in aerobic organisms, and deletion of these genes shortens the replicative life span in the budding yeast Saccharomyces cerevisiae. Even though involvement of superoxide dismutase enzymes in ROS scavenging and the aging process has been studied extensively in different organisms, analyses of DNA damages has not been performed for replicatively old superoxide dismutase deficient cells. In this study, we investigated the roles of SOD1, SOD2 and CCS1 genes in preserving genomic integrity in replicatively old yeast cells using the single cell comet assay. We observed that extend of DNA damage was not significantly different among the young cells of wild type, sod1Δ and sod2Δ strains. However, ccs1Δ mutants showed a 60% higher amount of DNA damage in the young stage compared to that of the wild type cells. The aging process increased the DNA damage rates 3-fold in the wild type and more than 5-fold in sod1Δ, sod2Δ, and ccs1Δ mutant cells. Furthermore, ROS levels of these strains showed a similar pattern to their DNA damage contents. Thus, our results confirm that cells accumulate DNA damages during the aging process and reveal that superoxide dismutase enzymes play a substantial role in preserving the genomic integrity in this process.

Formation, structure, and stability of MHD intermediate shocks

International Nuclear Information System (INIS)

Wu, C.C.

1990-01-01

Contrary to the usual belief that MHD intermediate shocks are extraneous, the author has recently shown by numerical solutions of dissipative MHD equations that intermediate shocks are admissible and can be formed through nonlinear wave steepening from continuous waves. In this paper, the formation, structure and stability of intermediate shocks in dissipative MHD are considered in detail. The differences between the conventional theory and his are pointed out and clarified. He shows that all four types of intermediate shocks can be formed from smooth waves. He also shows that there are free parameters in the structure of the intermediate shocks, and that these parameters are related to the shock stability. In addition, he shows that a rotational discontinuity can not exist with finite width, indicate how this is related to the existence of time-dependent intermediate shocks, and show why the conventional theory is not a good approximation to dissipative MHD solutions whenever there is rotation in magnetic field

Structural stability, electronic structure and mechanical properties of actinide carbides AnC (An = U, Np)

International Nuclear Information System (INIS)

Manikandan, M.; Santhosh, M.; Rajeswarapalanichamy, R.

2016-01-01

Ab initio calculations are performed to investigate the structural stability, electronic structure and mechanical properties of actinide carbides AnC (An=U, Np) for three different crystal structures, namely NaCl, CsCl and ZnS. Among the considered structures, NaCl structure is found to be the most stable structure for these carbides at normal pressure. A pressure induced structural phase transition from NaCl to ZnS is observed. The electronic structure reveals that these carbides are metals. The calculated elastic constants indicate that these carbides are mechanically stable at normal pressure.

Structure-activity relationships between sterols and their thermal stability in oil matrix.

Science.gov (United States)

Hu, Yinzhou; Xu, Junli; Huang, Weisu; Zhao, Yajing; Li, Maiquan; Wang, Mengmeng; Zheng, Lufei; Lu, Baiyi

2018-08-30

Structure-activity relationships between 20 sterols and their thermal stabilities were studied in a model oil system. All sterol degradations were found to be consistent with a first-order kinetic model with determination of coefficient (R 2 ) higher than 0.9444. The number of double bonds in the sterol structure was negatively correlated with the thermal stability of sterol, whereas the length of the branch chain was positively correlated with the thermal stability of sterol. A quantitative structure-activity relationship (QSAR) model to predict thermal stability of sterol was developed by using partial least squares regression (PLSR) combined with genetic algorithm (GA). A regression model was built with R 2 of 0.806. Almost all sterol degradation constants can be predicted accurately with R 2 of cross-validation equals to 0.680. Four important variables were selected in optimal QSAR model and the selected variables were observed to be related with information indices, RDF descriptors, and 3D-MoRSE descriptors. Copyright © 2018 Elsevier Ltd. All rights reserved.

Structural Stability and Hydraulic Conductivity Of Nkpologu Sandy ...

African Journals Online (AJOL)

Studies were conducted in the runoff plots at the University of Nigeria Nsukka Teaching and Resesarch Farm in 2010 and 2011 to monitor the changes in structural stability and saturated hydraulic conductivity (Ksat) of Nkpologu sandy loam soil under different cover management practices. The management practices were ...

PH dependence of the spectral and anion binding properties of iron containing superoxide dismutase from E. coli B. An explanation for the azide inhibition of dismutase activity

Energy Technology Data Exchange (ETDEWEB)

Fee, J A; McClune, G J; Lees, A C [Michigan Univ., Ann Arbor (USA). Dept. of Biological Chemistry; Zidovetzki, R; Pecht, I [Weizmann Inst. of Science, Rehovoth (Israel). Dept. of Chemical Immunology

1981-01-01

Examination of the optical and EPR properties of the ferric form of the iron containing superoxide dismutase from E.coli B, at pH values ranging from 4.5 to 10.9, has revealed two reversible structural transitions affecting the Fe/sup 3 +/ ion. The apparent pKsub(a) values of these transitions are 5.1+-0.3 and 9.O+-0.3. The binding of azide has been studied over the pH range 4.5 to 10.7; the affinity of the Fe/sup 3 +/ for N/sub 3//sup -/ is independent of pH from 4.5 to approximately 7.5, after which the dissociation constant decreased by a factor of 10 per unit increase in pH. The apparent pKsub(a) which affects N/sub 3//sup -/ binding to the iron is 8.6+-0.2. The association of N/sub 3//sup -/ with the iron has been examined using the temperature-jump method at pH 7.4 and 9.3. The kinetics of ligand association were shown to conform to the minimal mechanism: P-Fe/sup 3 +/ + N/sub 3//sup -/reversible K/sub 1/N/sub 3//sup -/ - P-Fe/sup 3 +/reversible K/sub 2/P-Fe/sup 3 +/ - N/sub 3//sup -/. K/sub 1/ was found to be essentially unaffected by pH whereas K/sub 2/ was much lower at pH 9.3 than at 7.4. The value of K/sub 1/ at pH 7.4 (100 M/sup -1/) corresponds very closely to that obtained for the inhibition constant of azide, 10mM. A scheme is presented in which N/sub 3//sup -/ inhibits the iron containing dismutase by competing with O/sub 2//sup -/ for an anion binding site near, but not on the Fe/sup 3 +/.

Network structure and thermal stability study of high temperature seal glass

Science.gov (United States)

Lu, K.; Mahapatra, M. K.

2008-10-01

High temperature seal glass has stringent requirement on glass thermal stability, which is dictated by glass network structures. In this study, a SrO-La2O3-Al2O3-B2O3-SiO2 based glass system was studied using nuclear magnetic resonance, Raman spectroscopy, and x-ray diffraction for solid oxide cell application purpose. Glass structural unit neighboring environment and local ordering were evaluated. Glass network connectivity as well as silicon and boron glass former coordination were calculated for different B2O3:SiO2 ratios. Thermal stability of the borosilicate glasses was studied after thermal treatment at 850 °C. The study shows that high B2O3 content induces BO4 and SiO4 structural unit ordering, increases glass localized inhomogeneity, decreases glass network connectivity, and causes devitrification. Glass modifiers interact with either silicon- or boron-containing structural units and form different devitrified phases at different B2O3:SiO2 ratios. B2O3-free glass shows the best thermal stability among the studied compositions, remaining stable after thermal treatment for 200 h at 850 °C.

Structural Stability of Tokamak Equilibrium: Transport Barriers

Energy Technology Data Exchange (ETDEWEB)

Solano, E. R.

2001-07-01

A generalised theory of structural stability of differential equations is introduced and applied to the Grad-Shafranov equation. It is discussed how the formation and loss of transport barrier could be associated with the appearance/disappearance of equilibria. The equilibrium conjecture is presented: transport barriers are associated with locally diamagnetic regions in the plasma, and affected by the paramagnetism of the bootstrap current. (Author) 18 refs.

Differentiable dynamical systems an introduction to structural stability and hyperbolicity

CERN Document Server

Wen, Lan

2016-01-01

This is a graduate text in differentiable dynamical systems. It focuses on structural stability and hyperbolicity, a topic that is central to the field. Starting with the basic concepts of dynamical systems, analyzing the historic systems of the Smale horseshoe, Anosov toral automorphisms, and the solenoid attractor, the book develops the hyperbolic theory first for hyperbolic fixed points and then for general hyperbolic sets. The problems of stable manifolds, structural stability, and shadowing property are investigated, which lead to a highlight of the book, the \\Omega-stability theorem of Smale. While the content is rather standard, a key objective of the book is to present a thorough treatment for some tough material that has remained an obstacle to teaching and learning the subject matter. The treatment is straightforward and hence could be particularly suitable for self-study. Selected solutions are available electronically for instructors only. Please send email to textbooks@ams.org for more informatio...

Structures and Stability of Metal Amidoboranes (MAB): Density Functional Calculations

International Nuclear Information System (INIS)

Li Cailin; Wu Chaoling; Chen Yungui; Zhou Jingjing; Zheng Xin; Pang Lijuan; Deng Gang

2010-01-01

Molecule geometry structures, frequencies, and energetic stabilities of ammonia borane (AB, NH 3 BH 3 ) and metal amidoboranes (MAB, MNH 2 BH 3 ), formed by substituting H atom in AB with one of main group metal atoms, have been investigated by density-functional theory and optimized at the B3LYP levels with 6-311G++ (3df, 3pd) basic set. Their structural parameters and infrared spectrum characteristic peaks have been predicted, which should be the criterion of a successfully synthesized material. Several parameters such as binding energies, vibrational frequencies, and the energy gaps between the HOMO and the LUMO have been adopted to characterize and evaluate their structure stabilities. It is also found that the binding energies and HOMO-LUMO energy gaps of the MAB obviously change with the substitution of the atoms. MgAB has the lowest binding energy and is easier to decompose than any other substitutional structures under same conditions, while CaAB has the highest chemical activity. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

The structure and stability of common mental disorders - The NEMESIS Study

NARCIS (Netherlands)

Vollebergh, W.A.M.; Iedema, J; Bijl, R.V.; de Graaf, R.; Smit, F.; Ormel, J.

Background: We analyzed the underlying latent structure of 12-month DSM-III-R diagnoses of 9 common disorders for the general population in the Netherlands. In addition, we sought to establish (1) the stability of the latent structure underlying mental disorders across a 1-year period (structural

Superoxide dismutase from Trichuris ovis--inhibition by benzimidazoles and pyrimidine derivatives.

Science.gov (United States)

Sanchez-Moreno, M; Garcia-Rejon, L; Salas, I; Osuna, A; Monteoliva, M

1992-01-01

Three superoxide dismutase isoenzymes of different cellular location were detected in an homogenate of Trichuris ovis. Each of these molecular forms was purified by differential centrifugation and precipitation with ammonium sulphate, followed by chromatography on DEAE-cellulose and Sephadex G-75 columns. The activity levels of the two molecular forms detected in the mitochondrial (one cyanide sensitive Cu-Zn-SOD and the other cyanide insensitive Mn-SOD) were higher than that of the superoxide dismutase detected in the cytoplasmic fraction (cyanide sensitive Cu-Zn-SOD). All molecular forms present evident differences to the SODs contained in the host liver. Molecular mass and some of the physical and chemical properties of the enzyme was determined for all three molecular forms. An inhibitory effect on the SOD of the parasite an the host was detected with a series of compounds, some of which markedly inhibited parasite enzyme but not host enzyme.

Structure and Mechanical Properties of Al-Cu-Fe-X Alloys with Excellent Thermal Stability.

Science.gov (United States)

Školáková, Andrea; Novák, Pavel; Mejzlíková, Lucie; Průša, Filip; Salvetr, Pavel; Vojtěch, Dalibor

2017-11-05

In this work, the structure and mechanical properties of innovative Al-Cu-Fe based alloys were studied. We focused on preparation and characterization of rapidly solidified and hot extruded Al-Cu-Fe, Al-Cu-Fe-Ni and Al-Cu-Fe-Cr alloys. The content of transition metals affects mechanical properties and structure. For this reason, microstructure, phase composition, hardness and thermal stability have been investigated in this study. The results showed exceptional thermal stability of these alloys and very good values of mechanical properties. Alloying by chromium ensured the highest thermal stability, while nickel addition refined the structure of the consolidated alloy. High thermal stability of all tested alloys was described in context with the transformation of the quasicrystalline phases to other types of intermetallics.

Rock stream stability structures in the vicinity of bridges.

Science.gov (United States)

2014-10-01

This report was sponsored by the Utah Department of Transportation (UDOT) to determine if rock stream stability structures could be used as : scour countermeasures and to protect streambanks. Traditional scour countermeasures, such as rock riprap, ar...

Superoxide dismutase levels and peak expiratory flow in asthmatic children

Directory of Open Access Journals (Sweden)

Arie Kurniasih

2016-11-01

Full Text Available Background Asthma is a chronic inflammatory process which involve variety of cells such as inflammatory mediators, reactive oxygen species (ROS, and cytokines. The inflammatory process would be exacerbated in the presence of oxidative stress. Superoxide dismutase (SOD is the first important enzyme to protect the respiratory tract against oxidative stress. The decreased of SOD has a correlation with increased of airway obstruction and bronchospasm. Objective To assess for a correlation between superoxide dismutase (SOD levels and peak expiratory flow, as well as to determine the impact of SOD levels for predicting asthma attacks. Methods We conducted a prospective cohort study at Dr. Sardjito Hospital, Yogyakarta, between February and April 2011 involving asthmatic children aged 5-18 years. Subjects’ serum SOD levels and peak expiratory flow were measured at the same time point. We then performed a prospective study following up on the same subjects to find out if they had a recurrent asthma attack within one month of the tests. We also reassessed their peak expiratory flow one month after blood specimens were obtained. Results Thirty-nine patients were enrolled in this study. There was no significant correlation between SOD level and peak expiratory flow [r=0.289; 95%CI -0.025 to 0.47; P=0.074]. However, older age was significantly associated with higher peak expiratory flow (=0.5; 95%CI 3.10 to 11.57; P=0.01. Lower levels of SOD increased the risk of asthma attacks in a month following the initial measurements (RR=5.5; 95%CI 1.6 to 18.9; P=0.009. Conclusion Superoxide dismutase (SOD level is not significantly associated with peak expiratory flow. However, we find a relationship between older age and higher peak expiratory flow and a relationship between lower SOD levels and risk of asthma attacks within one month following the tests.

Experimental study of antiradiation properties of recombinant superoxide dismutase

International Nuclear Information System (INIS)

Derimedvyid', L.V.; Simonova, L.Yi.; Gertman, V.Z.

2003-01-01

The study involved 250 mongrel white male mice weighing 18-22 g. It was shown that the superoxide dismutase had a marked radioprotective effect. The experiments on animals exposed to ionizing radiation at a absolute and mean lethal doses demonstrate considerable increase of survival rate, mean life span of the dead animals, shifts in the peaks of lethality to later terms, reduction in the percentage of animals with intestinal syndrome,

The Cu,Zn Superoxide Dismutase: not only a dismutase enzyme

Directory of Open Access Journals (Sweden)

Paolo Mondola

2016-11-01

Full Text Available The Cu,Zn superoxide dismutase (SOD1 is an ubiquitary cytosolic dimeric carbohydrate free molecule, belonging to a family of isoenzymes involved in the scavenger of superoxide anions. This effect certainly represents the main and well known function ascribed to this enzyme. Here we highlight new aspects of SOD1 physiology that point out some inedited effects of this enzyme in addition to the canonic role of oxygen radical enzymatic dismutation. In the last two decades our research group produced many data obtained in in vitro studies performed in many cellular lines, mainly neuroblastoma SK-N-BE cells, indicating that this enzyme is secreted either constitutively or after depolarization induced by high extracellular K+ concentration. In addition, we gave many experimental evidences showing that SOD1 is able to stimulate, through muscarinic M1 receptor, pathways involving ERK1/2 and AKT activation. These effects are accompanied with an intracellular calcium increase. In the last part of this review we describe researches that link deficient extracellular secretion of mutant SOD1G93A to its intracellular accumulation and toxicity in NSC-34 cells. Alternatively, SOD1G93A toxicity has been attributed to a decrease of Km for H2O2 with consequent OH. radical formation. Interestingly, this last inedited effect of SOD1G93A could represent a gain of function that could be involved in the pathogenesis of familial Amyotrophic Lateral Sclerosis (fALS.

Towards a "Golden Standard" for computing globin stability: Stability and structure sensitivity of myoglobin mutants

DEFF Research Database (Denmark)

Kepp, Kasper Planeta

2015-01-01

Fast and accurate computation of protein stability is increasingly important for e.g. protein engineering and protein misfolding diseases, but no consensus methods exist for important proteins such as globins, and performance may depend on the type of structural input given. This paper reports be...

Structure and Mechanical Properties of Al-Cu-Fe-X Alloys with Excellent Thermal Stability

Directory of Open Access Journals (Sweden)

Andrea Školáková

2017-11-01

Full Text Available In this work, the structure and mechanical properties of innovative Al-Cu-Fe based alloys were studied. We focused on preparation and characterization of rapidly solidified and hot extruded Al-Cu-Fe, Al-Cu-Fe-Ni and Al-Cu-Fe-Cr alloys. The content of transition metals affects mechanical properties and structure. For this reason, microstructure, phase composition, hardness and thermal stability have been investigated in this study. The results showed exceptional thermal stability of these alloys and very good values of mechanical properties. Alloying by chromium ensured the highest thermal stability, while nickel addition refined the structure of the consolidated alloy. High thermal stability of all tested alloys was described in context with the transformation of the quasicrystalline phases to other types of intermetallics.

Correlation between local structure and stability of supercooled liquid state in Zr-based metallic glasses

International Nuclear Information System (INIS)

Saida, Junji; Imafuku, Muneyuki; Sato, Shigeo; Sanada, Takashi; Matsubara, Eiichiro; Inoue, Akihisa

2007-01-01

The correlation between the local structure and stability of supercooled liquid state is investigated in the Zr 70 (Ni, Cu) 30 binary and Zr 70 Al 10 (Ni, Cu) 20 (numbers indicate at.%) ternary metallic glasses. The Zr 70 Ni 30 binary amorphous alloy with a low stability of supercooled liquid state has a tetragonal Zr 2 Ni-like local structure around Ni atom. Meanwhile, the Zr 70 Cu 30 binary metallic glass has a different local structure of tetragonal Zr 2 Cu, where we suggest the icosahedral local structure by the quasicrystallization behavior in addition of a very small amount of noble metals. The effect of Al addition on the local structure in the Zr-Ni alloy is also examined. We have investigated that the dominant local structure changes in the icosahedral-like structure from the tetragonal Zr 2 Ni-like local structure by the Al substitution with Ni accompanying with the significant stabilization of supercooled liquid state. It is concluded that the formation of icosahedral local structure contributes to the enhancement of stability of supercooled liquid state in the Zr-based alloys

Radioprotective effects of bacterial superoxide dismutase on mice

International Nuclear Information System (INIS)

Hu Tianxi

1992-01-01

The radioprotective effects of bacterial superoxide dismutase (b-SOD) on the mice irradiated by 8 Gy γ-ray were investigated. The results showed that when b-SOD was injected before and after irradiation, the survival fraction of mice is increased 50% and 30% respectively. The former treatment could increase the DNA synthesis of the myeloid cells and spleen's lymphocytes, decrease the LPO of tissue homogenates and the hemolysis of erythrocytes significantly. The mechanism that b-SOD can drop the radiation injury of the mice was discussed

Exogenous superoxide dismutase may lose its antidotal ability on rice leaves

Science.gov (United States)

Leaf diffusates of the resistant rice cultivars suppressed spore germination of blast fungus (Magnaporthe grisea). Bovine Cu-Zn superoxide dismutase (SOD) added to the diffusate abolished its toxicity. However, the enzyme added to the inoculum did not affect the toxicity of the diffusate. Even the s...

Structure and stability of warm cores in neutron stars

Energy Technology Data Exchange (ETDEWEB)

Ibanez Cabanell, J M [Departamento de Mecanica y Astronomia, Facultad de Matematicas, Burjasot-Valencia (Spain)

1981-12-01

Relativistic equations of structure are solved using Lamb's equations of state for warm neutron degenerate matter. The stability of isothermal cores in neutron stars is discussed and also the possible compatibility of the results obtained with experimental evidence is shown.

The structure of nuclei far from beta stability

International Nuclear Information System (INIS)

Zganjar, E.F.

1992-01-01

This report discusses: shape coexistence and intruder states; the electric monopole transition in nuclei; gold isotopes; platinum isotopes; iridium isotopes; search for superdeformation in 192 Hg; search for population of superformed states in 194 Pb using 194 Bi β + -decay; detailed nuclear structure studies far from stability; prototype internal pair spectrometer; and picosecond lifetime spectrometer

Superoxide dismutase from Trichuris ovis, inhibiton by benzimidazoles and pyrimidine derivatives

Directory of Open Access Journals (Sweden)

M. Sanchez-Moreno

1992-01-01

Full Text Available Three superoxide dismutase isoenzymes of different cellular location were detected in an homogenate of Thrichuris ovis. Each of these molecular forms was purified by differential centrifugation and precipitation with ammonium sulphate, followed by chromatography on DEAE-cellulose and Sephadex G-75 columns. The activity levels of the two molecular forms detected in the mitochondrial (one cyanide sensitive Cu-Zn-SOD and the other cyanide intensitive Mn-Sod were higher than that of the superoxide dismutase detected in the cytoplasmic fraction (cyanid sensitive Cu-Zn-SOD. All the mollecular forms present evident differences to the SODs contained in the host liver. Molecular mass and some of the physical and chemical aproperties of the enzyme was determined for all three molecular forms. An inhibitory effect on the SOD of the parasite an the host was detected with a series of compounds, some of wich markedly inhibited parasite ensyme but not host enzyme.

A plastic stabilizer dibutyltin dilaurate induces subchronic neurotoxicity in rats☆

OpenAIRE

Jin, Minghua; Song, Peilin; Li, Na; Li, Xuejun; Chen, Jiajun

2012-01-01

Dibutyltin dilaurate functions as a stabilizer for polyvinyl chloride. In this study, experimental rats were intragastrically administered 5, 10, or 20 mg/kg dibutyltin dilaurate to model sub-chronic poisoning. After exposure, our results showed the activities of superoxide dismutase and glutathione peroxidase decreased in rat brain tissue, while the malondialdehyde and nitric oxide content, as well as nitric oxide synthase activity in rat brain tissue increased. The cell cycle in the right p...

Design Formulae for Hydraulic Stability and Structural Integrity of Dolos Breakwater Round-Heads

DEFF Research Database (Denmark)

Burcharth, H. F.; Jensen, Jacob Birk; Liu, Z.

1995-01-01

A rational design of Dolos armour unit should incorporate both the hydraulic stability and the structural integrity. The previous tests performed by Aalborg University (AU) resulted in design formulae for the trunk of a 1:1.5 slope Dolos breakwater without superstructure including both...... the hydraulic stability and the structural integrity. The objective of the round-head tests is to produce similar design formulae for Dolos armour in around-head. The tests will also include examinations of the hydraulic stability and run-up for a trunk section adjacent to the round-head. A run-up formula...

THE ZN-SITE IN BOVINE COPPER, ZINC SUPEROXIDE-DISMUTASE STUDIED BY CD-111 PAC

DEFF Research Database (Denmark)

Kofod, Pauli; Bjerrum, Morten J.; Bauer, Rogert

1991-01-01

The active site in bovine copper, zinc superoxide dismutase (Cu2. Zn2 SOD) has been studied by 111Cd time differential Perturbed Angular Correlation (PAC) on enzyme with Zn2+ replaced by excited 'Cd2+. The PAC spectra obtained for both the oxidized and the reduced form of Cu2Cd2SOD show...... no asymmetry between the two Zn-sites in the dimeric enzyme. The spectv further reveal that a significant change has taken place at the Zn-site in the reduced form compared to the oxidized form. Semi-empirical calculations based on the Angular Overlap Model (AOM) and coordinates from the crystal structure...... of the native enzyme are in agreement with the experimental PAC data of the oxidized enzyme. The results indicate that Cd2+ coordinates in the same manner as Zn2+ and that the crystal structure of SOD is valid for the enzyme in solution. The PAC spectrum of the reduced enzyme can be explained by extending...

Structures, stabilities, and electronic properties for rare-earth lanthanum doped gold clusters

International Nuclear Information System (INIS)

Zhao, Ya-Ru

2015-01-01

The structures, stabilities, and electronic properties of rare-earth lanthanum doped gold La 2 Au n (n = 1-9) and pure gold Au n (n ≤ 11) clusters have been investigated by using density functional theory. The optimized geometries show that the lowest energy structures of La 2 Au n clusters favour the 3D structure at n ≥ 3. The lanthanum atoms can strongly enhance the stabilities of gold clusters and tend to occupy the most highly coordinated position. By analysing the gap, vertical ionization potential, and chemical hardness, it is found that the La 2 Au 6 isomer possesses higher stability for small-sized La 2 Au n clusters (n = 1-9). The charges in the La 2 Au n clusters transfer from La atoms to the Au n host. In addition, Wiberg bond indices analysis reveals that the intensity of different bonds of La 2 Au n clusters exhibits a sequence of La-La bond > La-Au bond > Au-Au bond.

Robust stability analysis of large power systems using the structured singular value theory

Energy Technology Data Exchange (ETDEWEB)

Castellanos, R.; Sarmiento, H. [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico); Messina, A.R. [Cinvestav, Graduate Program in Electrical Engineering, Guadalajara, Jalisco (Mexico)

2005-07-01

This paper examines the application of structured singular value (SSV) theory to analyse robust stability of complex power systems with respect to a set of structured uncertainties. Based on SSV theory and the frequency sweep method, techniques for robust analysis of large-scale power systems are developed. The main interest is focused on determining robust stability for varying operating conditions and uncertainties in the structure of the power system. The applicability of the proposed techniques is verified through simulation studies on a large-scale power system. In particular, results for the system are considered for a wide range of uncertainties of operating conditions. Specifically, the developed technique is used to estimate the effect of variations in the parameters of a major system inter-tie on the nominal stability of a critical inter-area mode. (Author)

New insights into structural determinants of prion protein folding and stability.

Science.gov (United States)

Benetti, Federico; Legname, Giuseppe

2015-01-01

Prions are the etiological agent of fatal neurodegenerative diseases called prion diseases or transmissible spongiform encephalopathies. These maladies can be sporadic, genetic or infectious disorders. Prions are due to post-translational modifications of the cellular prion protein leading to the formation of a β-sheet enriched conformer with altered biochemical properties. The molecular events causing prion formation in sporadic prion diseases are still elusive. Recently, we published a research elucidating the contribution of major structural determinants and environmental factors in prion protein folding and stability. Our study highlighted the crucial role of octarepeats in stabilizing prion protein; the presence of a highly enthalpically stable intermediate state in prion-susceptible species; and the role of disulfide bridge in preserving native fold thus avoiding the misfolding to a β-sheet enriched isoform. Taking advantage from these findings, in this work we present new insights into structural determinants of prion protein folding and stability.

Structural Stability of Light-harvesting Protein LH2 Adsorbed on Mesoporous Silica Supports.

Science.gov (United States)

Shibuya, Yuuta; Itoh, Tetsuji; Matsuura, Shun-ichi; Yamaguchi, Akira

2015-01-01

In the present study, we examined the reversible thermal deformation of the membrane protein light-harvesting complex LH2 adsorbed on mesoporous silica (MPS) supports. The LH2 complex from Thermochromatium tepidum cells was conjugated to MPS supports with a series of pore diameter (2.4 to 10.6 nm), and absorption spectra of the resulting LH2/MPS conjugates were observed over a temperature range of 273 - 313 K in order to examine the structure of the LH2 adsorbed on the MPS support. The experimental results confirmed that a slight ellipsoidal deformation of LH2 was induced by adsorption on the MPS supports. On the other hand, the structural stability of LH2 was not perturbed by the adsorption. Since the pore diameter of MPS support did not influence the structural stability of LH2, it could be considered that the spatial confinement of LH2 in size-matches pore did not improve the structural stability of LH2.

The structure of nuclei far from beta stability

International Nuclear Information System (INIS)

Zganjar, E.F.

1991-01-01

This report discusses the structural of nuclei for from beta stability of the following isotopes: thallium isotopes; mercury isotopes; gold isotopes; platinum isotopes; iridium isotopes; the neutron deficient rare-earth, Z = 57-72 region, and the neutron deficient Z = 50-56 region; also discussed are in-beam spectroscopy in the A = 70 region and shape coexistence, intruder states, and EO transitions

The stability of gabion walls for earth retaining structures

OpenAIRE

Mahyuddin Ramli; T.J.r. Karasu; Eethar Thanon Dawood

2013-01-01

The stability of earth retaining structures in flood prone areas has become a serious problem in many countries. The two most basic causes of failure arising from flooding are scouring and erosion of the foundation of the superstructure. Hence, a number of structures like bridges employ scour-arresting devices, e.g., gabions to acting on the piers and abutments during flooding. Research was therefore undertaken to improve gabion resistance against lateral movement by means of an interlocking ...

[Optimizing synthesis of conjugates of superoxide dismutase and catalase with aldehyde dextrans in surfactant microemulsions in heptane].

Science.gov (United States)

Eremin, A N; Metelitsa, D I

1997-01-01

Stable microemulsions in heptane retaining considerable amounts of the polar phase were obtained by using Aerosol OT (AOT), Triton X-45, and catalase. Conjugates of superoxide dismutase (SOD) and catalase with aldehyde dextrans (AD) were synthesized in surfactant microemulsions in heptane. Effects of the reaction duration, the microemulsion polar phase volume, and concentrations of enzymes and modifiers on the properties of these conjugates were studied. The catalytic properties of conjugates depended on the nature of the surfactants used to stabilize the microemulsions, the initial concentration of protein in the reaction mixture, and the enzyme: modifier ratio. The degree of modification of the enzymes and the stabilities of their conjugates during isolation from microemulsions by a water-acetone solution depended on the concentration of the AD used. The catalytic properties of the conjugates synthesized were compared, and their stabilities in the presence of H2O2 were described. We suggested a simple method of transformation of whole kinetic curves of H2O2 conversion in coordinates 1/ln([H2O2]0/[H2O2]t - 1/t for simultaneous measurement of the constant of the catalase inactivation rate by H2O2 (Cin, S-1) and the rate constant of the catalase complex 1 interaction with the second H2O2 molecule (C2, M-1 S-1). This method was tested experimentally. Values C2 and Cin for catalase and its conjugates with ADs were compared, and these results were discussed.

Frame Stability of Tunnel‐Structured Cryptomelane Nanofibers: The Role of Tunnel Cations

DEFF Research Database (Denmark)

Gao, Tao; Norby, Poul

2013-01-01

precursor to the tunnel‐structured cryptomelane, in which the K+ ions play important roles in templating and stabilizing the tunneled framework. The presence of tunnel K+ ions also enhances the frame stability of the cryptomelane nanofibers at elevated temperatures. The formation of a layered KxMn2O4 (x ≈ 0...

PENGARUH DAUN UBI JALAR UNGU TERHADAP KADAR SUPEROKSID DISMUTASE TIKUS YANG DIPAPAR ASAP ROKOK (EFFECT OF PURPLE SWEET POTATO LEAVES ON SUPEROXIDE DISMUTASE LEVEL ON RATS EXPOSED TO CIGARETTE SMOKE

Directory of Open Access Journals (Sweden)

Inggita Kusumastuty

2014-12-01

Superoxide Dismutase (SOD is an enzymatic antioxidant that protects cells from oxidative stress by catalyzing dismutase from superoxide into O2 and H2O2. The purple sweet potato leave (Ipomoea batatas L. Lam is a kind of vegetable plant that contains  high polyphenol which is about 1805 mgGAE on 100-gram edible portions. This research was aimed to determine the effect of purple sweet potato leaves powder in SOD levels that had been given to an animal model with cigarette smoke exposure. 6-8 week- male Rattus novergicus-wistar’s strain was used in this experiment that weighed about 140-250 gram and the entire rats were in healthy condition and were never exposed to another treatment before. Firstly, the rats were prepared in one week which was then divided into 5 treatment groups, a group that had not been exposed to cigarette smoke (P0, cigarette smoke exposed (P1, and exposed to cigarette smoke with the addition PSPL flour treatment in varying doses: 0.07g (P2, 0.14g (P3, and 0.28g (P4 for 30 days. After that, SOD levels were measured with spectrophotometry method. The result shows that there was obviously a significant difference between the treatment groups (ANOVA, p=0.000. In short, it was found that the given PSPL dosages resulted in higher SOD’s level. Keywords :, purple sweet potato leaves, Superoxide Dismutase level, cigarette smoking

Elastic stability of biaxially loaded longitudinally stiffened composite structures.

Science.gov (United States)

Viswanathan, A. V.; Tamekuni, M.; Tripp, L. L.

1973-01-01

A linear analysis method is presented for the elastic stability of structures of uniform cross section, that may be idealized as an assemblage of laminated plate-strips, flat and curved, and beams. Each plate-strip and beam covers the entire length of the structure and is simply supported on the edges normal to the longitudinal axis. Arbitrary boundary conditions may be specified on any external longitudinal side of plate-strips. The structure or selected plate-strips may be loaded in any desired combination of inplane biaxial loads. The analysis simultaneously considers all modes of instability and is applicable for the buckling of laminated composite structures. Some numerical results are presented to indicate possible applications.

Influences of the Structure of Lipids on Thermal Stability of Lipid Membranes

International Nuclear Information System (INIS)

Hai Nan-Nan; Zhou Xin; Li Ming

2015-01-01

The binding free energy (BFE) of lipid to lipid bilayer is a critical factor to determine the thermal or mechanical stability of the bilayer. Although the molecular structure of lipids has significant impacts on BFE of the lipid, there lacks a systematic study on this issue. In this paper we use coarse-grained molecular dynamics simulation to investigate this problem for several typical phospholipids. We find that both the tail length and tail unsaturation can significantly affect the BFE of lipids but in opposite way, namely, BFE decreases linearly with increasing length, but increases linearly with addition of unsaturated bonds. Inspired by the specific structure of cholesterol which is a crucial component of biomembrane, we also find that introduction of carbo-ring-like structures to the lipid tail or to the bilayer may greatly enhance the stability of the bilayer. Our simulation also shows that temperature can influence the bilayer stability and this effect can be significant when the bilayer undergoes phase transition. These results may be helpful to the design of liposome or other self-assembled lipid systems. (paper)

Double-Layer Structured CO2 Adsorbent Functionalized with Modified Polyethyleneimine for High Physical and Chemical Stability.

Science.gov (United States)

Jeon, Sunbin; Jung, Hyunchul; Kim, Sung Hyun; Lee, Ki Bong

2018-06-18

CO 2 capture using polyethyleneimine (PEI)-impregnated silica adsorbents has been receiving a lot of attention. However, the absence of physical stability (evaporation and leaching of amine) and chemical stability (urea formation) of the PEI-impregnated silica adsorbent has been generally established. Therefore, in this study, a double-layer impregnated structure, developed using modified PEI, is newly proposed to enhance the physical and chemical stabilities of the adsorbent. Epoxy-modified PEI and diepoxide-cross-linked PEI were impregnated via a dry impregnation method in the first and second layers, respectively. The physical stability of the double-layer structured adsorbent was noticeably enhanced when compared to the conventional adsorbents with a single layer. In addition to the enhanced physical stability, the result of simulated temperature swing adsorption cycles revealed that the double-layer structured adsorbent presented a high potential working capacity (3.5 mmol/g) and less urea formation under CO 2 -rich regeneration conditions. The enhanced physical and chemical stabilities as well as the high CO 2 working capacity of the double-layer structured adsorbent were mainly attributed to the second layer consisting of diepoxide-cross-linked PEI.

Metabolic regulation of manganese superoxide dismutase expression via essential amino acid deprivation.

Science.gov (United States)

Aiken, Kimberly J; Bickford, Justin S; Kilberg, Michael S; Nick, Harry S

2008-04-18

Organisms respond to available nutrient levels by rapidly adjusting metabolic flux, in part through changes in gene expression. A consequence of adaptations in metabolic rate is the production of mitochondria-derived reactive oxygen species. Therefore, we hypothesized that nutrient sensing could regulate the synthesis of the primary defense of the cell against superoxide radicals, manganese superoxide dismutase. Our data establish a novel nutrient-sensing pathway for manganese superoxide dismutase expression mediated through essential amino acid depletion concurrent with an increase in cellular viability. Most relevantly, our results are divergent from current mechanisms governing amino acid-dependent gene regulation. This pathway requires the presence of glutamine, signaling via the tricarboxylic acid cycle/electron transport chain, an intact mitochondrial membrane potential, and the activity of both the MEK/ERK and mammalian target of rapamycin kinases. Our results provide evidence for convergence of metabolic cues with nutrient control of antioxidant gene regulation, revealing a potential signaling strategy that impacts free radical-mediated mutations with implications in cancer and aging.

Understanding structure-stability relationships of Candida antartica lipase B in ionic liquids.

Science.gov (United States)

De Diego, Teresa; Lozano, Pedro; Gmouh, Said; Vaultier, Michel; Iborra, José L

2005-01-01

Two different water-immiscible ionic liquids (ILs), 1-ethyl-3-methylimidizolium bis(trifluoromethylsulfonyl)imide and butyltrimethylammonium bis(trifluoromethylsulfonyl)imide, were used for butyl butyrate synthesis from vinyl butyrate catalyzed by Candida antarctica lipase B (CALB) at 2% (v/v) water content and 50 degrees C. Both the synthetic activity and stability of the enzyme in these ILs were enhanced as compared to those in hexane. Circular dichroism and intrinsic fluorescence spectroscopic techniques have been used over a period of 4 days to determine structural changes in the enzyme associated with differences in its stability for each assayed medium. CALB showed a loss in residual activity higher than 75% after 4 days of incubation in both water and hexane media at 50 degrees C, being related to great changes in both alpha-helix and beta-strand secondary structures. The stabilization of CALB, which was observed in the two ILs studied, was associated with both the maintenance of the 50% of initial alpha-helix content and the enhancement of beta-strands. Furthermore, intrinsic fluorescence studies clearly showed how a classical enzyme unfolding was occurring with time in both water and hexane media. However, the structural changes associated with the incubation of the enzyme in both ILs might be attributed to a compact and active enzyme conformation, resulting in an enhancement of the stability in these nonaqueous environments.

Stability analysis and structural rules of titanium dioxide clusters (TiO2)n with n = 1-9

International Nuclear Information System (INIS)

Zhang Weiwei; Han Ye; Yao Shuyu; Sun Haiqing

2011-01-01

Highlights: · We investigated the structure and stability of (TiO 2 ) n clusters with n = 1-9. · Some initial structures are introduced and proved to be the real global minimum. · We summarized the structural rules for small (TiO 2 ) n clusters. · The bonding features for the energy increment or decrement of the clusters are investigated. · A general shift of stability and reactivity with size for (TiO 2 ) n clusters. - Abstract: Atomic clusters have been considered as models for fundamental mechanistic insight into complex surfaces and catalysts. The structure and stability of (TiO 2 ) n clusters with n = 1-9 are investigated using the b3lyp hybrid density functional method in this paper. Some of the clusters are proposed initially and proved to be the real global minima. The stability and band gap of the clusters as a function of size are also investigated. The structural rules of the clusters are first summarized. The lowest-lying (TiO 2 ) n isomers tend to form some compact rather than quasi-linear or circular structures. The oxygen atom in 4-fold coordination and the titanium atom in 4-fold coordination favor the cluster stability. The 5-fold coordinated Ti-atom, the Ti-Ti bond and the terminal Ti-O bond lead to stability penalty for the clusters. No evidence for a regular variation in stability or reactivity with size of the clusters has shown. The structural rules can serve as guiding factors for formation research and structure design of (TiO 2 ) n and other transition metal oxide clusters.

Structural Stability and Vibration

DEFF Research Database (Denmark)

Wiggers, Sine Leergaard; Pedersen, Pauli

This book offers an integrated introduction to the topic of stability and vibration. Strikingly, it describes stability as a function of boundary conditions and eigenfrequency as a function of both boundary conditions and column force. Based on a post graduate course held by the author at the Uni...... and their derivation, thus stimulating them to write interactive and dynamic programs to analyze instability and vibrational modes....

The effect of relativity on stability of Copernicium phases, their electronic structure and mechanical properties

Science.gov (United States)

Čenčariková, Hana; Legut, Dominik

2018-05-01

The phase stability of the various crystalline structures of the super-heavy element Copernicium was determined based on the first-principles calculations with different levels of the relativistic effects. We utilized the Darwin term, mass-velocity, and spin-orbit interaction with the single electron framework of the density functional theory while treating the exchange and correlation effects using local density approximations. It is found that the spin-orbit coupling is the key component to stabilize the body-centered cubic (bcc) structure over the hexagonal closed packed (hcp) structure, which is in accord with Sol. Stat. Comm. 152 (2012) 530, but in contrast to Atta-Fynn and Ray (2015) [11], Gaston et al. (2007) [10], Papaconstantopoulos (2015) [9]. It seems that the main role here is the correct description of the semi-core relativistic 6p1/2 orbitals. The all other investigated structures, i.e. face-centered cubic (fcc) , simple cubic (sc) as well as rhombohedral (rh) structures are higher in energy. The criteria of mechanical stability were investigated based on the calculated elastic constants, identifying the phase instability of fcc and rh structures, but surprisingly confirm the stability of the energetically higher sc structure. In addition, the pressure-induced structural transition between two stable sc and bcc phases has been detected. The ground-state bcc structure exhibits the highest elastic anisotropy from single elements of the Periodic table. At last, we support the experimental findings that Copernicium is a metal.

Cell lysis and superoxide dismutase activities of highly radioresistant bacteria

Energy Technology Data Exchange (ETDEWEB)

Yoshinaka, T; Yano, K; Yamaguchi, H [Tokyo Univ. (Japan). Faculty of Agriculture

1976-01-01

The highly radioresistant bacterium, Arthrobacter radiotolerans, has been isolated from the radioactive hot spring of Misasa, and it does not sporulate, it is Gram-positive, and its color is pink to red. This bacterium shows the highest resistance to gamma-ray among Gram-positive resistants, but the lytic enzyme capable of lysing the cells of strong radioresistants and the surface structure of the cells are little known except those about Micrococcus radiodurans. The cells of the M. radiodurans can be lysed by Achramobacter lyticus enzyme, and electron microscopic observation and chemical analysis revealed the mutilayered surface structure of the cells consisting of an inner membrane, a mucopeptide wall layer and a very outer layer. The superoxide dismutase (SOD) activity of aerobic and anaerobic bacteria was studied, and the relatively high SOD activity of the M. radiodurans was found. The SOD function acts against the threat posed by the reactive superoxide radical being generated biologically, photochemically and radiochemically in the presence of molecular oxygen. In this paper, it is reported that the lytic enzyme No.2 obtained from Cytophaga sp., containing N-acetyl-muramyl-L-alanine amidase, peptidase and endopeptidase, and showing broad lytic spectra, was able to lyse the cells of A. radiotolerans and four radioresistant micrococci, and the radioresistant bacteria showedrelatively high SOD activity except M. sp. 248. It is well known that superoxide anions are generated by aerobic irradiation, and are toxic to microbial cells.

Cell lysis and superoxide dismutase activities of highly radioresistant bacteria

International Nuclear Information System (INIS)

Yoshinaka, Taeko; Yano, Keiji; Yamaguchi, Hikoyuki

1976-01-01

The highly radioresistant bacterium, Arthrobacter radiotolerans, has been isolated from the radioactive hot spring of Misasa, and it does not sporulate, it is Gram-positive, and its color is pink to red. This bacterium shows the highest resistance to gamma-ray among Gram-positive resistants, but the lytic enzyme capable of lysing the cells of strong radioresistants and the surface structure of the cells are little known except those about Micrococcus radiodurans. The cells of the M. radiodurans can be lysed by Achramobacter lyticus enzyme, and electron microscopic observation and chemical analysis revealed the mutilayered surface structure of the cells consisting of an inner membrane, a mucopeptide wall layer and a very outer layer. The superoxide dismutase (SOD) activity of aerobic and anaerobic bacteria was studied, and the relatively high SOD activity of the M. radiodurans was found. The SOD function acts against the threat posed by the reactive superoxide radical being generated biologically, photochemically and radiochemically in the presence of molecular oxygen. In this paper, it is reported that the lytic enzyme No.2 obtained from Cytophaga sp., containing N-acetyl-muramyl-L-alanine amidase, peptidase and endopeptidase, and showing broad lytic spectra, was able to lyse the cells of A. radiotolerans and four radioresistant micrococci, and the radioresistant bacteria showed relatively high SOD activity except M. sp. 248. It is well known that superoxide anions are generated by aerobic irradiation, and are toxic to microbial cells. (Kako, I.)

Monte Carlo analysis of critical phenomenon of the Ising model on memory stabilizer structures

International Nuclear Information System (INIS)

Viteri, C. Ricardo; Tomita, Yu; Brown, Kenneth R.

2009-01-01

We calculate the critical temperature of the Ising model on a set of graphs representing a concatenated three-bit error-correction code. The graphs are derived from the stabilizer formalism used in quantum error correction. The stabilizer for a subspace is defined as the group of Pauli operators whose eigenvalues are +1 on the subspace. The group can be generated by a subset of operators in the stabilizer, and the choice of generators determines the structure of the graph. The Wolff algorithm, together with the histogram method and finite-size scaling, is used to calculate both the critical temperature and the critical exponents of each structure. The simulations show that the choice of stabilizer generators, both the number and the geometry, has a large effect on the critical temperature.

Structural properties and out-of-plane stability of roller bent steel arches

NARCIS (Netherlands)

Spoorenberg, R.C.

2011-01-01

In contemporary architecture the use of steel arches has seen a significant increase. They are applied in buildings and large span bridges, combining structural design with architectural merits. For arches lacking lateral support (or freestanding arches) the out-of-plane structural stability

Structural homeostasis in the nervous system: A balancing act for wiring plasticity and stability

Directory of Open Access Journals (Sweden)

Jun eYin

2015-01-01

Full Text Available Experience-dependent modifications of neural circuits provide the cellular basis for functional adaptation and learning, while presenting significant challenges to the stability of neural networks. The nervous system copes with these perturbations through a variety of compensatory mechanisms with distinct spatial and temporal profiles. Mounting evidence suggests that structural plasticity, through modifications of the number and structure of synapses, or changes in local and long-range connectivity, might contribute to the stabilization of network activity and serve as an important component of the homeostatic regulation of the nervous system. Conceptually similar to the homeostatic regulation of synaptic strength and efficacy, homeostatic structural plasticity has a profound and lasting impact on the intrinsic excitability of the neuron and circuit properties, yet remains largely unexplored. In this review, we examine recent reports describing structural modifications associated with functional compensation in both developing and adult nervous systems, and discuss the potential role for structural homeostasis in maintaining network stability and its implications in physiological and pathological conditions of the nervous systems.

Oxidative stability during storage of structured lipids produced from fish oil and caprylic acid

DEFF Research Database (Denmark)

Nielsen, Nina Skall; Xu, Xuebing; Timm Heinrich, Maike

2004-01-01

Structured lipids produced by enzymatic or chemical methods for different applications have been receiving considerable attention. The oxidative stability of a randomized structured lipid (RFO), produced by chemical interesterification from fish oil (FO) and tricaprylin, and a specific structured...... lipid (SFO), produced by enzymatic interesterification from the same oil and caprylic acid, was compared with the stability of FO. Oils were stored at 2degreesC for 11 wk followed by storage at 20degreesC for 6 wk. In addition, the antioxidative effect of adding the metal chelators EDTA or citric acid...

The essential dynamics of Cu, Zn superoxide dismutase : Suggestion of intersubunit communication

NARCIS (Netherlands)

Chillemi, G; Falconi, M; Amadei, A; Zimatore, G; Desideri, A; DiNola, A

A 300-ps molecular dynamics simulation of the whole Cu, Zn superoxide dismutase dimer has been carried out in water, and the trajectory has been analyzed by the essential dynamics method. The results indicate that the motion is defined by few preferred directions identified by the first four to six

Microflora and structural stability of soils

International Nuclear Information System (INIS)

Guckert, A.; Chone, Therese; Jacquin, F.; Institut National Polytechnique, 54 - Nancy; Centre National de la Recherche Scientifique, 54 - Vandoeuvre-les-Nancy

1975-01-01

Water stable aggregates produced during the incubation of a loamy soil amended with glucose 14 C show a quite differing evolution of their physical properties and their organic matter according to the time of incubation after which they have been isolated from the soil by water sieving. The aggregates, built up during the first week of incubation, therefore during the maximal activity stage of the microflora of the soil, present the highest stability against biodegradation induced by a second incubation process, even if this one has reached six weeks. This evolution of the physical properties of the aggregates, is essentially in relationship with the microbially synthetized organic matter and especially the polysaccharides preferentially incorporated into the humine fraction. This relatively labile microbial humine has a high aggregating effect, the polysaccharide chains forming several bonds between the neighbouring clay surfaces and building up stable structural units. The mechanical strength of these aggregates is related to the stabilization of the humine produced previously and whose evolution towards a relatively stable form seems to be the result of two mechanisms: a secundary biodegradation parallel to a higher humification process of the organic matter and a increase of the bonds between polysaccharides and clay surfaces favoured by the alternation of wetting and drying [fr

Electronic structure and phase stability during martensitic transformation in Al-doped ZrCu intermetallics

International Nuclear Information System (INIS)

Qiu Feng; Shen Ping; Liu Tao; Lin Qiaoli; Jiang Qichuan

2010-01-01

Martensitic transformation, phase stability and electronic structure of Al-doped ZrCu intermetallics were investigated by experiments and first-principles calculations using the pseudopotentials plane wave method. The formation energy calculations indicate that the stability of the ZrCu phase increases with the increasing Al content. Al plays a decisive role in controlling the formation and microstructures of the martensite phases in Zr-Cu-Al alloys. The total energy difference between ZrCu (B2) austenite and ZrCu martensite plays an important role in the martensitic transformation. The phase stability is dependent on its electronic structure. The densities of states (DOS) of the intermetallics were discussed in detail.

Effects of PEG size on structure, function and stability of PEGylated BSA

DEFF Research Database (Denmark)

Plesner, Bitten; Fee, Conan J.; Westh, Peter

2011-01-01

The effects of PEGylation on the structural, thermal and functional stability of bovine serum albumin (BSA) were investigated using BSA and 6 linear mono-PEGylated BSA compounds. The secondary and tertiary structure of BSA measured by circular dichroism (CD) was independent of PEGylation. In cont...

Biochemical properties of Cu/Zn-superoxide dismutase from fungal strain Aspergillus niger 26

Science.gov (United States)

Dolashki, Aleksandar; Abrashev, Radoslav; Stevanovic, Stefan; Stefanova, Lilyana; Ali, Syed Abid; Velkova, Ludmila; Hristova, Rumyana; Angelova, Maria; Voelter, Wolfgang; Devreese, Bart; Van Beeumen, Jozef; Dolashka-Angelova, Pavlina

2008-12-01

The fungal strain Aspergillus niger produces two superoxide dismutases, Cu/Zn-SOD and Mn-SOD. The primary structure of the Cu/Zn-SOD has been determined by Edman degradation of peptide fragments derived from proteolytic digests. A single chain of the protein, consisting of 153 amino acid residues, reveals a very high degree of structural homology with the amino acid sequences of other Aspergillus Cu/Zn-SODs. The molecular mass of ANSOD, measured by MALDI-MS and ESI-MS, and calculated by its amino acid sequence, was determined to be 15 821 Da. Only one Trp residue, at position 32, and one disulfide bridge were identified. However, neither a Tyr residue nor a carbohydrate chain occupying an N-linkage site (-Asn-Ile-Thr-) were found. Studies on the temperature and pH dependence of fluorescence, and on the temperature dependence of CD spectroscopic properties, confirmed that the enzyme is very stable, which can be explained by the stabilising effect of the disulfide bridge. The enzyme retains about 53% of its activity after incubation for a period of 30 min at 60 °C, and 15% at 85 °C.

Developing a high performance superoxide dismutase based electrochemical biosensor for radiation dosimetry of thallium 201

International Nuclear Information System (INIS)

Salem, Fatemeh; Tavakoli, Hassan; Sadeghi, Mahdi; Riazi, Abbas

2014-01-01

To develop a new biosensor for measurement of superoxide free radical generated in radiolysis reaction, three combinations of SOD-based biosensors including Au/Cys/SOD, Au/GNP/Cys/SOD and Au/GNP/Cys/SOD/Chit were fabricated. In these biosensors Au, GNP, Cys, SOD and Chit represent gold electrode, gold nano-particles, cysteine, superoxide dismutase and chitosan, respectively. For biosensors fabrication, SOD, GNP, Cys and Chit were immobilized at the surface of gold electrode. Cyclic voltametry and chronoamperometry were utilized for evaluation of biosensors performances. The results showed that Au/GNP/Cys/SOD/Chit has significantly better responses compared to Au/Cys/SOD and Au/GNP/Cys/SOD. As a result, this biosensor was selected for dosimetry of ionizing radiation. For this purpose, thallium 201 at different volumes was added to buffer phosphate solution in electrochemical cell. To obtain analytical parameters of Au/GNP/Cys/SOD/Chit, calibration curve was sketched. The results showed that this biosensor has a linear response in the range from 0.5 to 4 Gy, detection limit 0.03 μM. It also has a proper sensitivity (0.6038 nA/Gy), suitable long term stability and cost effective as well as high function for radiation dosimetry. - highlights: • Our biosensor is able to measure produced superoxide radical during water radiolysis. • It has suitable linearity range, good detection limit and long term stability. • It also has proper sensitivity and high performance for low LET ionizing radiation. • The electrochemical method is as good as traditional methods for radiation dosimetry

Structure and stability of accretion-disk around a black-hole

Energy Technology Data Exchange (ETDEWEB)

Shibazaki, N; Hoshi, R [Rikkyo Univ., Tokyo (Japan). Dept. of Physics

1975-09-01

Structure and stability of a stationary thin-disk formed around a black-hole are studied using the conventional formula for the viscous stress. The disk is classified into an optically thick case, an optically thin case and an intermediate case in which the comptonization plays an important role. Thermal and secular stabilities are examined in each of the above three cases. High temperatures in excess of 10sup(9 0)K are expected in the optically thin case and in the comptonization dominant case. However, it is shown that in these cases the disk is unstable for the thermal perturbation.

Local chromatin structure of heterochromatin regulates repeated DNA stability, nucleolus structure, and genome integrity

Energy Technology Data Exchange (ETDEWEB)

Peng, Jamy C. [Univ. of California, Berkeley, CA (United States)

2007-01-01

Heterochromatin constitutes a significant portion of the genome in higher eukaryotes; approximately 30% in Drosophila and human. Heterochromatin contains a high repeat DNA content and a low density of protein-encoding genes. In contrast, euchromatin is composed mostly of unique sequences and contains the majority of single-copy genes. Genetic and cytological studies demonstrated that heterochromatin exhibits regulatory roles in chromosome organization, centromere function and telomere protection. As an epigenetically regulated structure, heterochromatin formation is not defined by any DNA sequence consensus. Heterochromatin is characterized by its association with nucleosomes containing methylated-lysine 9 of histone H3 (H3K9me), heterochromatin protein 1 (HP1) that binds H3K9me, and Su(var)3-9, which methylates H3K9 and binds HP1. Heterochromatin formation and functions are influenced by HP1, Su(var)3-9, and the RNA interference (RNAi) pathway. My thesis project investigates how heterochromatin formation and function impact nuclear architecture, repeated DNA organization, and genome stability in Drosophila melanogaster. H3K9me-based chromatin reduces extrachromosomal DNA formation; most likely by restricting the access of repair machineries to repeated DNAs. Reducing extrachromosomal ribosomal DNA stabilizes rDNA repeats and the nucleolus structure. H3K9me-based chromatin also inhibits DNA damage in heterochromatin. Cells with compromised heterochromatin structure, due to Su(var)3-9 or dcr-2 (a component of the RNAi pathway) mutations, display severe DNA damage in heterochromatin compared to wild type. In these mutant cells, accumulated DNA damage leads to chromosomal defects such as translocations, defective DNA repair response, and activation of the G2-M DNA repair and mitotic checkpoints that ensure cellular and animal viability. My thesis research suggests that DNA replication, repair, and recombination mechanisms in heterochromatin differ from those in

Decentralized stabilization of semi-active vibrating structures

Science.gov (United States)

Pisarski, Dominik

2018-02-01

A novel method of decentralized structural vibration control is presented. The control is assumed to be realized by a semi-active device. The objective is to stabilize a vibrating system with the optimal rates of decrease of the energy. The controller relies on an easily implemented decentralized switched state-feedback control law. It uses a set of communication channels to exchange the state information between the neighboring subcontrollers. The performance of the designed method is validated by means of numerical experiments performed for a double cantilever system equipped with a set of elastomers with controlled viscoelastic properties. In terms of the assumed objectives, the proposed control strategy significantly outperforms the passive damping cases and is competitive with a standard centralized control. The presented methodology can be applied to a class of bilinear control systems concerned with smart structural elements.

Strength Analysis of Coconut Fiber Stabilized Earth for Farm Structures

Science.gov (United States)

Enokela, O. S.; P. O, Alada

2012-07-01

Investigation of the strength characteristic of soil from alluvial deposit of River Benue in makurdi stabilized with coconut fiber as a stabilizer was carried as local building material for farm structure. Processed coconut fibers were mixed with the soil at four different mix ratios of 1% fiber, 2% fiber, 3% fiber and 4% fiber by percentage weight with 0% fiber as control. Compaction test and compressive strength were carried out on the various stabilizing ratio. From the compaction test, the correlation between the maximum dry density and optimum moisture content is a second order polynomial with a coefficient of 63% obtained at1.91kg/m3and 20.0% respectively while the compressive strength test shows an optimum failure load of 8.62N/mm2 at 2%fibre:100% soil mix ratio at 2.16 maximum dry density.

Stabilization of structure in near-infrared fluorescent proteins by binding of biliverdin chromophore

Science.gov (United States)

Stepanenko, Olesya V.; Stepanenko, Olga V.; Bublikov, G. S.; Kuznetsova, I. M.; Verkhusha, V. V.; Turoverov, K. K.

2017-07-01

Near-infrared fluorescent proteins (NIR FPs) engineered from bacterial phytochromes and their mutants with different location of Cys residues, which able to bind a biliverdin chromophore, or without these Cys residues were studied using intrinsic tryptophan fluorescence, NIR fluorescence and circular dichroism. It was shown that a covalent binding of the biliverdin chromophore to a Cys residue via thioether group substantially stabilizes the spatial structure of NIR FPs. The stability of the protein structure and the chromophore association strength strongly depends on the location of Cys residues and decreases in the following order: a protein with Cys residues in both domains, a protein with Cys in PAS domains, and a protein with Cys in GAF domains. NIR FPs without Cys residues capable to covalently attach biliverdin have the lowest stability, comparable to NIR FP apoforms.

Attenuation of 6-hydroxydopamine-induced dopaminergic nigrostriatal lesions in superoxide dismutase transgenic mice

International Nuclear Information System (INIS)

Cadet, J.L.; Hirata, H.; Asanuma, M.

1998-01-01

6-Hydroxydopamine is a neurotoxin that produces degeneration of the nigrostriatal dopaminergic pathway in rodents. Its toxicity is thought to involve the generation of superoxide anion secondary to its autoxidation. To examine the effects of the overexpression of Cu,Zn-superoxide dismutase activity on 6-hydroxydopamine-induced dopaminergic neuronal damage, we have measured the effects of 6-hydroxydopamine on striatal and nigral dopamine transporters and nigral tyrosine hydroxylase-immunoreactive neurons in Cu,Zn-superoxide dismutase transgenic mice. Intracerebroventricular injection of 6-hydroxydopamine (50 μg) in non-transgenic mice produced reductions in the size of striatal area and an enlargement of the cerebral ventricle on both sides of the brains of mice killed two weeks after the injection. In addition, 6-hydroxydopamine caused marked decreases in striatal and nigral [ 125 I]RTI-121-labelled dopamine transporters not only on the injected side but also on the non-injected side of non-transgenic mice; this was associated with decreased cell number and size of tyrosine hydroxylase-immunoreactive dopamine neurons in the substantia nigra pars compacta on both sides in these mice. In contrast, superoxide dismutase transgenic mice were protected against these neurotoxic effects of 6-hydroxydopamine, with the homozygous transgenic mice showing almost complete protection.These results provide further support for a role of superoxide anion in the toxic effects of 6-hydroxydopamine. They also provide further evidence that reactive oxygen species may be the main determining factors in the neurodegenerative effects of catecholamines. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

Importance of structural stability to success of mourning dove nests

Science.gov (United States)

Coon, R.A.; Nichols, J.D.; Percival, H.F.

1981-01-01

Studies of nest-site selection and nesting habitats often involve a "characterization" of nests and of habitats in which nests are found. Our objective in the present work is to identify nest-site characteristics that are associated with variation in components of Mourning Dove (Zenaida macroura) fitness (e.g. the probability of a nest succeeding), as opposed to simply "characterizing" dove nest sites. If certain nest- site characteristics affect the probability that a nest will succeed, then we suspect that these characteristics will be associated with either concealment (the probability of detection by certain predators) or structural stability (the probability of eggs or entire nests falling to the ground as a result of wind, rain storms, parental activity, etc.). Although other workers agree that structural stability is an important determinant of Mourning Dove nesting success (e.g. McClure 1944: 384; Woolfenden and Rohwer 1969: 59), we are aware of no actual tests of this hypothesis.

Properties of purified cytosolic isoenzyme I of Cu,Zn-superoxide dismutase from Nicotiana plumbaginifolia leaves.

Science.gov (United States)

Ragusa, S; Cambria, M T; Scarpa, M; Di Paolo, M L; Falconi, M; Rigo, A; Cambria, A

2001-11-01

The isoenzyme I of cytosolic Cu,Zn-superoxide dismutase (SOD) from Nicotiana plumbaginifolia (tobacco) leaves has been purified to apparent homogeneity. The relative molecular mass of the native isoenzyme, determined by gel filtration chromatography, is about 33.2 kDa. SDS-polyacrylamide gel electrophoresis shows that the enzyme is composed of two equal subunits of 16.6 kDa The isolectric point, assayed by isoelectric focusing, in the pH range of 3.5-6.5, is 4.3. The enzyme stability was tested at different temperatures, pH, and concentration of inhibitors (KCN and H(2)O(2)). The catalytic constant (k(cat)) was 1.17 +/- 0.14 x 10(9) M(-1) s(-1) at pH 9.9 and 0.1 M ionic strength. The activation energy of the thermal denaturation process is 263 kJ mol(-1). The electrostatic surface potential of the modeled tobacco Cu,Zn-SOD I was calculated showing that the functional spatial network of charges on the protein surface has been maintained, independently of the amino acid substitution around the active sites. Copyright 2001 Academic Press.

Structure and Mechanical Properties of Al-Cu-Fe-X Alloys with Excellent Thermal Stability

OpenAIRE

Školáková, Andrea; Novák, Pavel; Mejzlíková, Lucie; Průša, Filip; Salvetr, Pavel; Vojtěch, Dalibor

2017-01-01

In this work, the structure and mechanical properties of innovative Al-Cu-Fe based alloys were studied. We focused on preparation and characterization of rapidly solidified and hot extruded Al-Cu-Fe, Al-Cu-Fe-Ni and Al-Cu-Fe-Cr alloys. The content of transition metals affects mechanical properties and structure. For this reason, microstructure, phase composition, hardness and thermal stability have been investigated in this study. The results showed exceptional thermal stability of these allo...

Influence of structured sidewalls on the wetting states and superhydrophobic stability of surfaces with dual-scale roughness

Energy Technology Data Exchange (ETDEWEB)

Wu, Huaping, E-mail: wuhuaping@gmail.com [Key Laboratory of E& M (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014 (China); State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024 (China); Zhu, Kai; Wu, Bingbing [Key Laboratory of E& M (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014 (China); Lou, Jia [Piezoelectric Device Laboratory, Department of Mechanics and Engineering Science, Ningbo University, Ningbo, Zhejiang 315211 (China); Zhang, Zheng [Key Laboratory of E& M (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014 (China); Chai, Guozhong, E-mail: chaigz@zjut.edu.cn [Key Laboratory of E& M (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014 (China)

2016-09-30

Highlights: • Apparent contact angle equation of all wetting states on dual-scale rough surfaces is derived. • Structured sidewalls can improve superhydrophobicity than smooth sidewalls. • Structured sidewalls can enlarge ACA than smooth sidewalls. • Structured sidewalls present an advantage over smooth sidewalls in terms of enhancing superhydrophobic stability. - Abstract: The superhydrophobicity of biological surfaces with dual-scale roughness has recently received considerable attention because of the unique wettability of such surfaces. Based on this, artificial micro/nano hierarchical structures with structured sidewalls and smooth sidewalls were designed and the influences of sidewall configurations (i.e., structured and smooth) on the wetting state of micro/nano hierarchical structures were systematically investigated based on thermodynamics and the principle of minimum free energy. Wetting transition and superhydrophobic stability were then analyzed for a droplet on dual-scale rough surfaces with structured and smooth sidewalls. Theoretical analysis results show that dual-scale rough surfaces with structured sidewalls have a larger “stable superhydrophobic region” than those with smooth sidewalls. The dual-scale rough surfaces with smooth sidewalls can enlarge the apparent contact angle (ACA) without improvement in the superhydrophobic stability. By contrast, dual-scale rough surfaces with structured sidewalls present an advantage over those with smooth sidewalls in terms of enlarging ACA and enhancing superhydrophobic stability. The proposed thermodynamic model is valid when compared with previous experimental data and numerical analysis results, which is helpful for designing and understanding the wetting states and superhydrophobic stability of surfaces with dual-scale roughness.

The Effects of Molecular Crowding on the Structure and Stability of G-Quadruplexes with an Abasic Site

Science.gov (United States)

Fujimoto, Takeshi; Nakano, Shu-ichi; Miyoshi, Daisuke; Sugimoto, Naoki

2011-01-01

Both cellular environmental factors and chemical modifications critically affect the properties of nucleic acids. However, the structure and stability of DNA containing abasic sites under cell-mimicking molecular crowding conditions remain unclear. Here, we investigated the molecular crowding effects on the structure and stability of the G-quadruplexes including a single abasic site. Structural analysis by circular dichroism showed that molecular crowding by PEG200 did not affect the topology of the G-quadruplex structure with or without an abasic site. Thermodynamic analysis further demonstrated that the degree of stabilization of the G-quadruplex by molecular crowding decreased with substitution of an abasic site for a single guanine. Notably, we found that the molecular crowding effects on the enthalpy change for G-quadruplex formation had a linear relationship with the abasic site effects depending on its position. These results are useful for predicting the structure and stability of G-quadruplexes with abasic sites in the cell-mimicking conditions. PMID:21949901

Metabolic Regulation of Manganese Superoxide Dismutase Expression via Essential Amino Acid Deprivation*

Science.gov (United States)

Aiken, Kimberly J.; Bickford, Justin S.; Kilberg, Michael S.; Nick, Harry S.

2008-01-01

Organisms respond to available nutrient levels by rapidly adjusting metabolic flux, in part through changes in gene expression. A consequence of adaptations in metabolic rate is the production of mitochondria-derived reactive oxygen species. Therefore, we hypothesized that nutrient sensing could regulate the synthesis of the primary defense of the cell against superoxide radicals, manganese superoxide dismutase. Our data establish a novel nutrient-sensing pathway for manganese superoxide dismutase expression mediated through essential amino acid depletion concurrent with an increase in cellular viability. Most relevantly, our results are divergent from current mechanisms governing amino acid-dependent gene regulation. This pathway requires the presence of glutamine, signaling via the tricarboxylic acid cycle/electron transport chain, an intact mitochondrial membrane potential, and the activity of both the MEK/ERK and mammalian target of rapamycin kinases. Our results provide evidence for convergence of metabolic cues with nutrient control of antioxidant gene regulation, revealing a potential signaling strategy that impacts free radical-mediated mutations with implications in cancer and aging. PMID:18187411

Critical Role of Crystalline Anisotropy in the Stability of Cellular Array Structures in Directional Solidification

International Nuclear Information System (INIS)

Kopczynski, P.; Rappel, W.; Karma, A.

1996-01-01

We calculate numerically the full Floquet-Bloch stability spectrum of cellular array structures in a symmetric model of directional solidification. Our results demonstrate that crystalline anisotropy critically influences the stability of these structures. Without anisotropy, the stability balloon of cells in the plane of wave number and velocity closes near the onset of morphological instability. With a finite, but even small, amount of anisotropy this balloon remains open and a band of stable solutions persists for higher velocities into a deep cell regime. The width of the balloon depends critically on the anisotropy strength. copyright 1996 The American Physical Society

Transgenic mice with increased Cu/Zn-superoxide dismutase activity: animal model of dosage effects in Down syndrome

International Nuclear Information System (INIS)

Epstein, C.J.; Avraham, K.B.; Lovett, M.; Smith, S.; Elroy-Stein, O.; Rotman, G.; Bry, C.; Groner, Y.

1987-01-01

Down syndrome, the phenotypic expression of human trisomy 21, is presumed to result from a 1.5-fold increase in the expression of the genes on human chromosome 21. As an approach to the development of an animal model for Down syndrome, several strains of transgenic mice that carry the human Cu/Zn-superoxide dismutase gene have been prepared. The animals express the transgene in a manner similar to that of humans, with 0.9- and 0.7-kilobase transcripts in a 1:4 ratio, and synthesize the human enzyme in an active form capable of forming human-mouse enzyme heterodimers. Cu/Zn-superoxide dismutase activity is increased from 1.6- to 6.0-fold in the brains of four transgenic strains and to an equal or lesser extent in several other tissues. These animals provide a unique system for studying the consequences of increased dosage of the Cu/Zn-superoxide dismutase gene in Down syndrome and the role of this enzyme in a variety of other pathological processes

Superoxide dismutase: an industrial perspective.

Science.gov (United States)

Bafana, Amit; Dutt, Som; Kumar, Sanjay; Ahuja, Paramvir S

2011-03-01

The application of enzyme technologies to industrial research, development, and manufacturing has become a very important field. Since the production of crude rennet in 1874, several enzymes have been commercialized, and used for therapeutic, supplementary, and other applications. Recent advancements in biotechnology now allow companies to produce safer and less expensive enzymes with enhanced potency and specificity. Antioxidant enzymes are emerging as a new addition to the pool of industrial enzymes and are surpassing all other enzymes in terms of the volume of research and production. In the 1990s, an antioxidant enzyme--superoxide dismutase (SOD)--was introduced into the market. Although the enzyme initially showed great promise in therapeutic applications, it did not perform up to expectations. Consequently, its use was limited to non-drug applications in humans and drug applications in animals. This review summarizes the rise and fall of SOD at the industrial level, the reasons for this, and potential future thrust areas that need to be addressed. The review also focuses on other industrially relevant aspects of SOD such as industrial importance, enzyme engineering, production processes, and process optimization and scale-up.

Structure and Stability of Pt-Y Alloy Particles for Oxygen Reduction Studied by Electron Microscopy

DEFF Research Database (Denmark)

Deiana, Davide; Wagner, Jakob Birkedal; Hansen, Thomas Willum

2015-01-01

Platinum-yttrium alloy nanoparticles show both a high activity and stability for the oxygen reduction reaction. The catalysts were prepared by magnetron sputter aggregation and mass filtration providing a model catalyst system with a narrow size distribution. The structure and stability of nanost...... the catalyst after reaction and after aging tests shows the development of a core-shell type structure after being exposed to reaction conditions....

Polyhedral Lyapunov functions structurally ensure global asymptotic stability of dynamical networks iff the Jacobian is non-singular

NARCIS (Netherlands)

Blanchini, Franco; Giordano, G.

2017-01-01

For a vast class of dynamical networks, including chemical reaction networks (CRNs) with monotonic reaction rates, the existence of a polyhedral Lyapunov function (PLF) implies structural (i.e., parameter-free) local stability. Global structural stability is ensured under the additional

Nonlinear Stability and Structure of Compressible Reacting Mixing Layers

Science.gov (United States)

Day, M. J.; Mansour, N. N.; Reynolds, W. C.

2000-01-01

The parabolized stability equations (PSE) are used to investigate issues of nonlinear flow development and mixing in compressible reacting shear layers. Particular interest is placed on investigating the change in flow structure that occurs when compressibility and heat release are added to the flow. These conditions allow the 'outer' instability modes- one associated with each of the fast and slow streams-to dominate over the 'central', Kelvin-Helmholtz mode that unaccompanied in incompressible nonreacting mixing layers. Analysis of scalar probability density functions in flows with dominant outer modes demonstrates the ineffective, one-sided nature of mixing that accompany these flow structures. Colayer conditions, where two modes have equal growth rate and the mixing layer is formed by two sets of vortices, offer some opportunity for mixing enhancement. Their extent, however, is found to be limited in the mixing layer's parameter space. Extensive validation of the PSE technique also provides a unique perspective on central- mode vortex pairing, further supporting the view that pairing is primarily governed perspective sheds insight on how linear stability theory is able to provide such an accurate prediction of experimentally-observed, fully nonlinear flow phenomenon.

Two-phase flow stability structure in a natural circulation system

Energy Technology Data Exchange (ETDEWEB)

Zhou, Zhiwei [Nuclear Engineering Laboratory Zurich (Switzerland)

1995-09-01

The present study reports a numerical analysis of two-phase flow stability structures in a natural circulation system with two parallel, heated channels. The numerical model is derived, based on the Galerkin moving nodal method. This analysis is related to some design options applicable to integral heating reactors with a slightly-boiling operation mode, and is also of general interest to similar facilities. The options include: (1) Symmetric heating and throttling; (2) Asymmetric heating and symmetric throttling; (3) Asymmetric heating and throttling. The oscillation modes for these variants are discussed. Comparisons with the data from the INET two-phase flow stability experiment have qualitatively validated the present analysis.

Interactive effects of body-size structure and adaptive foraging on food-web stability.

Science.gov (United States)

Heckmann, Lotta; Drossel, Barbara; Brose, Ulrich; Guill, Christian

2012-03-01

Body-size structure of food webs and adaptive foraging of consumers are two of the dominant concepts of our understanding how natural ecosystems maintain their stability and diversity. The interplay of these two processes, however, is a critically important yet unresolved issue. To fill this gap in our knowledge of ecosystem stability, we investigate dynamic random and niche model food webs to evaluate the proportion of persistent species. We show that stronger body-size structures and faster adaptation stabilise these food webs. Body-size structures yield stabilising configurations of interaction strength distributions across food webs, and adaptive foraging emphasises links to resources closer to the base. Moreover, both mechanisms combined have a cumulative effect. Most importantly, unstructured random webs evolve via adaptive foraging into stable size-structured food webs. This offers a mechanistic explanation of how size structure adaptively emerges in complex food webs, thus building a novel bridge between these two important stabilising mechanisms. © 2012 Blackwell Publishing Ltd/CNRS.

Inhibitory effect of alliin from Allium sativum on the glycation of superoxide dismutase.

Science.gov (United States)

Anwar, Shehwaz; Younus, Hina

2017-10-01

Inhibition of glycation is an important approach for alleviating diabetic complications. Alliin, the most abundant sulphur compound in garlic has been demonstrated to possess antidiabetic activity. However, there is no scientific evidence supporting its antiglycating activity. The objective of this study was to determine the inhibitory effect of alliin on glucose and methyglyoxal (MG)-induced glycation of an important antioxidant enzyme, superoxide dismutase (SOD). Glycation of SOD resulted in a decrease in enzyme activity, fragmentation/cross-linking, reduced cross-reactivity with anti-SOD antibodies, both tertiary and secondary structural changes, and formation of AGEs and fibrils. Alliin offered protection against glucose or MG induced glycation of SOD. The antiglycating potential of alliin appears to be comparable with that of quercetin which is reported to be a potent natural inhibitor of glycation. Alliin has a good antiglycating effect and hence is expected to have therapeutic potential in the prevention of glycation-mediated diabetic complications. Copyright © 2017 Elsevier B.V. All rights reserved.

Oxygen-dependent radiosensitivity of Escherichia coli and mitigation in lethality by superoxide dismutase

International Nuclear Information System (INIS)

Niwa, Taeko; Yamaguchi, Hikoyuki; Yano, Keiji

1978-01-01

Oxygen-dependent radiosensitivity of Escherichia coli W3623 his - was confirmed. Regarding cellular superoxide dismutase (SOD), cells grown oxically gained higher activity than those anoxically, however, the reinforced enzyme level could not compensate the oxygen effect, i.e., the enhanced lethal effect of oxic γ-irradiation. Rather, the enhancement of oxygen effect was found in cells grown oxically compared with those anoxically. Oxygen enhanced lethality was mitigated to the extent by the amount of added SOD into the cell suspension to be irradiated. The results supported a proposal that superoxide anion, O 2 - , is involved in the oxygen effect, with the most likely site of the damage in the outer structure of cell but not in the cell matrix. Reverse oxygen effect could be found with lambda phage DNA in transfecting ability. Added SOD protected phage DNA somewhat in oxic irradiation. While considerable protections were found in anoxic one with the added SOD even autoclaved but their function was still unknown. (auth.)

Myocardial capillary permeability after regional ischemia and reperfusion in the in vivo canine heart. Effect of superoxide dismutase

DEFF Research Database (Denmark)

Svendsen, J H; Bjerrum, P J; Haunsø, S

1991-01-01

This study assesses the effect of the superoxide anion scavenger superoxide dismutase on myocardial capillary permeability-surface area (PS) products for small hydrophilic molecules after ischemia and reperfusion. Open-chest dogs underwent a 20-minute occlusion of the left anterior descending...... the start of reperfusion. In 13 dogs, no scavenger treatment was given (nonprotected control group), whereas eight dogs were treated systemically with 15,000 units/kg superoxide dismutase during 1 hour, starting 20 minutes before ischemia. In the control group, three dogs developed reperfusion ventricular...

Phase stabilities at a glance: Stability diagrams of nickel dipnictides

International Nuclear Information System (INIS)

Bachhuber, F.; Rothballer, J.; Weihrich, R.; Söhnel, T.

2013-01-01

In the course of the recent advances in chemical structure prediction, a straightforward type of diagram to evaluate phase stabilities is presented based on an expedient example. Crystal structures and energetic stabilities of dipnictides NiPn 2 (Pn = N, P, As, Sb, Bi) are systematically investigated by first principles calculations within the framework of density functional theory using the generalized gradient approximation to treat exchange and correlation. These dipnictides show remarkable polymorphism that is not yet understood systematically and offers room for the discovery of new phases. Relationships between the concerned structures including the marcasite, the pyrite, the arsenopyrite/CoSb 2 , and the NiAs 2 types are highlighted by means of common structural fragments. Electronic stabilities of experimentally known and related AB 2 structure types are presented graphically in so-called stability diagrams. Additionally, competing binary phases are taken into consideration in the diagrams to evaluate the stabilities of the title compounds with respect to decomposition. The main purpose of the stability diagrams is the introduction of an image that enables the estimation of phase stabilities at a single glance. Beyond that, some of the energetically favored structure types can be identified as potential new phases

Parasitization by Scleroderma guani influences expression of superoxide dismutase genes in Tenebrio molitor

Science.gov (United States)

Superoxide dismutase (SOD) is an antioxidant enzyme involved in detoxifying reactive oxygen species. In this study, we identified genes encoding the extracellular and intracellular copper-zinc SODs (ecCuZnSOD and icCuZnSOD) and a manganese SOD (MnSOD) in the yellow mealworm beetle, Tenebrio molitor....

Vane coupling rings: a simple technique for stabilizing a four-vane radiofrequency quadrupole structure

International Nuclear Information System (INIS)

Howard, D.; Lancaster, H.

1982-11-01

The benefits of stabilized accelerating structures, with regard to the manufacture and operation, have been well documented. The four-vane radiofrequency quadrupoles (RFQ) presently being designed and constructed in many laboratories are not stabilized because of the weak electromagnetic coupling between the quadrant resonators. This paper presents a simple technique developed at the Lawrence Berkeley Laboratory using vane coupling rings (VCR's) which azimuthally stabilize the RFQ structure and greatly enhance its use as a practical accelerator. In particular, the VCR's: completely eliminate the dipole modes in the frequency range of interest; provide adequate quadrant balance with an initial precision mechanical alignment of the vanes; and enhance axial balance and simplify end tuners. Experimental verification tests on a scale model are discussed

Vane coupling rings: a simple technique for stabilizing a four-vane radiofrequency quadrupole structure

International Nuclear Information System (INIS)

Howard, D.; Lancaster, H.

1983-01-01

The benefits of stabilized accelerating structures, with regard to the manufacture and operation, have been well documented. The four-vane radiofrequency quadrupoles (RFQ) presently being designed and constructed in many laboratories are not stabilized because of the weak electromagnetic coupling between the quadrant resonators. This paper presents a simple technique developed at the Lawrence Berkeley Laboratory using vane coupling rings (VCR's) which azimuthally stabilize the RFQ structure and greatly enhance its use as a practical accelerator. In particular, the VCR's: Completely eliminate the dipole modes in the frequency range of interest; Provide adequate quadrant balance with an initial precision mechanical alignment of the vanes; Enhance axial balance and simplify end tuners. Experimental verification tests on a scale model will be discussed

Theoretical study of stability geometrical and electronic structure of (BeHsub(2))sub(n) oligomers

Energy Technology Data Exchange (ETDEWEB)

Sukhanov, L P; Boldyrev, A I; Charkin, O P [AN SSSR, Moscow. Inst. Novykh Khimicheskikh Problem

1983-01-01

The Hartree-Fock-Ruthane method with the Roos-Siegbahn two-exponent basis is used to calculate stability, geometrical and electronic structures of (BeHsub(2))sub(n) oligomers, where n=1, 2, 3, 4 and 6. It is shown that with the growth of oligomerization degree n stability of linear band structure is increased as compared with other configurations including high-coordination volumetric ones. Tendencies in formation with n growth of geometrical, energetic characteristics, electronic structure of (BeHsub(2))sub(n) oligomers of band type are analysed.

New insights into transcription fidelity: thermal stability of non-canonical structures in template DNA regulates transcriptional arrest, pause, and slippage.

Science.gov (United States)

Tateishi-Karimata, Hisae; Isono, Noburu; Sugimoto, Naoki

2014-01-01

The thermal stability and topology of non-canonical structures of G-quadruplexes and hairpins in template DNA were investigated, and the effect of non-canonical structures on transcription fidelity was evaluated quantitatively. We designed ten template DNAs: A linear sequence that does not have significant higher-order structure, three sequences that form hairpin structures, and six sequences that form G-quadruplex structures with different stabilities. Templates with non-canonical structures induced the production of an arrested, a slipped, and a full-length transcript, whereas the linear sequence produced only a full-length transcript. The efficiency of production for run-off transcripts (full-length and slipped transcripts) from templates that formed the non-canonical structures was lower than that from the linear. G-quadruplex structures were more effective inhibitors of full-length product formation than were hairpin structure even when the stability of the G-quadruplex in an aqueous solution was the same as that of the hairpin. We considered that intra-polymerase conditions may differentially affect the stability of non-canonical structures. The values of transcription efficiencies of run-off or arrest transcripts were correlated with stabilities of non-canonical structures in the intra-polymerase condition mimicked by 20 wt% polyethylene glycol (PEG). Transcriptional arrest was induced when the stability of the G-quadruplex structure (-ΔG°37) in the presence of 20 wt% PEG was more than 8.2 kcal mol(-1). Thus, values of stability in the presence of 20 wt% PEG are an important indicator of transcription perturbation. Our results further our understanding of the impact of template structure on the transcription process and may guide logical design of transcription-regulating drugs.

Manganese superoxide dismutase and breast cancer recurrence

DEFF Research Database (Denmark)

Cronin-Fenton, Deirdre P; Christensen, Mariann; Lash, Timothy L

2014-01-01

BACKGROUND: Manganese superoxide dismutase (MnSOD) inhibits oxidative damage and cancer therapy effectiveness. A polymorphism in its encoding gene (SOD2: Val16Ala rs4880) may confer poorer breast cancer survival, but data are inconsistent. We examined the association of SOD2 genotype and breast......-metastatic breast cancer from 1990-2001, received adjuvant Cyclo, and were registered in the Danish Breast Cancer Cooperative Group. We identified 118 patients with BCR and 213 matched breast cancer controls. We genotyped SOD2 and used conditional logistic regression to compute the odds ratio (OR) and associated 95...... cancer recurrence (BCR) among patients treated with cyclophosphamide-based chemotherapy (Cyclo). We compared our findings with published studies using meta-analyses. METHODS: We conducted a population-based case-control study of BCR among women in Jutland, Denmark. Subjects were diagnosed with non...

Bounds of thermal stability of infinite cylindrical structures with non-uniform internal heat generation

International Nuclear Information System (INIS)

Gadalla, M.A.

1992-01-01

This paper presents an overview analyses of the thermal instability or thermal viability of infinite cylindrical structures with non-linear and non-uniform internal heat generation. The structure may be subjected to different and combined boundary conditions. An analytical solution is obtained for the generalized problem in spite of the non-linearity and the non-homogeneity of the source term. Four case studies with different boundary conditions are presented. The analyses show that the critical parameter for thermal stability may be though of as an altitude of surface below which the cylindrical structure will be thermally stable and performance worthy. The results also show that the bounds of thermal stability of a cylindrical structure system (solid or hollow) is eminently determined by the boundary conditions to which the system is subjected and can significantly alter the life-span of the structure

Stability of the octameric structure affects plasminogen-binding capacity of streptococcal enolase.

Directory of Open Access Journals (Sweden)

Amanda J Cork

Full Text Available Group A Streptococcus (GAS is a human pathogen that has the potential to cause invasive disease by binding and activating human plasmin(ogen. Streptococcal surface enolase (SEN is an octameric α-enolase that is localized at the GAS cell surface. In addition to its glycolytic role inside the cell, SEN functions as a receptor for plasmin(ogen on the bacterial surface, but the understanding of the molecular basis of plasmin(ogen binding is limited. In this study, we determined the crystal and solution structures of GAS SEN and characterized the increased plasminogen binding by two SEN mutants. The plasminogen binding ability of SENK312A and SENK362A is ~2- and ~3.4-fold greater than for the wild-type protein. A combination of thermal stability assays, native mass spectrometry and X-ray crystallography approaches shows that increased plasminogen binding ability correlates with decreased stability of the octamer. We propose that decreased stability of the octameric structure facilitates the access of plasmin(ogen to its binding sites, leading to more efficient plasmin(ogen binding and activation.

Structure and stability insights into tumour suppressor p53 evolutionary related proteins.

Directory of Open Access Journals (Sweden)

Bruno Pagano

Full Text Available The p53 family of genes and their protein products, namely, p53, p63 and p73, have over one billion years of evolutionary history. Advances in computational biology and genomics are enabling studies of the complexities of the molecular evolution of p53 protein family to decipher the underpinnings of key biological conditions spanning from cancer through to various metabolic and developmental disorders and facilitate the design of personalised medicines. However, a complete understanding of the inherent nature of the thermodynamic and structural stability of the p53 protein family is still lacking. This is due, to a degree, to the lack of comprehensive structural information for a large number of homologous proteins and to an incomplete knowledge of the intrinsic factors responsible for their stability and how these might influence function. Here we investigate the thermal stability, secondary structure and folding properties of the DNA-binding domains (DBDs of a range of proteins from the p53 family using biophysical methods. While the N- and the C-terminal domains of the p53 family show sequence diversity and are normally targets for post-translational modifications and alternative splicing, the central DBD is highly conserved. Together with data obtained from Molecular Dynamics simulations in solution and with structure based homology modelling, our results provide further insights into the molecular properties of evolutionary related p53 proteins. We identify some marked structural differences within the p53 family, which could account for the divergence in biological functions as well as the subtleties manifested in the oligomerization properties of this family.

The stability of gabion walls for earth retaining structures

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Mahyuddin Ramli

2013-12-01

Full Text Available The stability of earth retaining structures in flood prone areas has become a serious problem in many countries. The two most basic causes of failure arising from flooding are scouring and erosion of the foundation of the superstructure. Hence, a number of structures like bridges employ scour-arresting devices, e.g., gabions to acting on the piers and abutments during flooding. Research was therefore undertaken to improve gabion resistance against lateral movement by means of an interlocking configuration instead of the conventional stack-and-pair system. This involved simulating lateral thrusts against two dimensionally identical retaining wall systems configured according to the rectangular and hexagonal gabion type. The evolution of deformation observed suggested that the interlocking design exhibits better structural integrity than the conventional box gabion-based wall in resisting lateral movement and therefore warrants consideration for use as an appropriate scour-arresting device for earth retaining structures.

High order quaternary arrangement confers increased structural stability to Brucella Spp. lumazine synthase

Energy Technology Data Exchange (ETDEWEB)

Zylberman, V.; Craig, P.O.; Klinke, S.; Cauerhff, A.; Goldbaum, F.A. [Instituto Leloir, Buenos Aires (Argentina); Braden, B.C. [Bowie State Univ., Maryland (United States)

2004-07-01

The penultimate step in the pathway of riboflavin biosynthesis is catalyzed by the enzyme lumazine synthase (LS). One of the most distinctive characteristics of this enzyme is the structural quaternary divergence found in different species. The protein exists as pentameric and icosahedral forms, built from practically the same structural monomeric unit. The pentameric structure is formed by five 18 kDa monomers, each extensively contacting neighboring monomers. The icosahedral structure consists of 60 LS monomers arranged as twelve pentamers giving rise to a capsid exhibiting icosahedral 532 symmetry. In all lumazine synthases studied, the topologically equivalent active sites are located at the interfaces between adjacent subunits in the pentameric modules. The Brucella spp. lumazine synthase (BLS) sequence clearly diverges from pentameric and icosahedral enzymes. This unusual divergence prompted to further investigate on its quaternary arrangement. In the present work, we demonstrate by means of solution Light Scattering and X-ray structural analyses that BLS assembles as a very stable dimer of pentamers representing a third category of quaternary assembly for lumazine synthases. We also describe by spectroscopic studies the thermodynamic stability of this oligomeric protein, and postulate a mechanism for dissociation/unfolding of this macromolecular assembly. The higher molecular order of BLS increases its stability 20 deg C compared to pentameric lumazine synthases. The decameric arrangement described in this work highlights the importance of quaternary interactions in the stabilization of proteins. (author)

High order quaternary arrangement confers increased structural stability to Brucella Spp. lumazine synthase

International Nuclear Information System (INIS)

Zylberman, V.; Craig, P.O.; Klinke, S.; Cauerhff, A.; Goldbaum, F.A.; Braden, B.C.

2004-01-01

The penultimate step in the pathway of riboflavin biosynthesis is catalyzed by the enzyme lumazine synthase (LS). One of the most distinctive characteristics of this enzyme is the structural quaternary divergence found in different species. The protein exists as pentameric and icosahedral forms, built from practically the same structural monomeric unit. The pentameric structure is formed by five 18 kDa monomers, each extensively contacting neighboring monomers. The icosahedral structure consists of 60 LS monomers arranged as twelve pentamers giving rise to a capsid exhibiting icosahedral 532 symmetry. In all lumazine synthases studied, the topologically equivalent active sites are located at the interfaces between adjacent subunits in the pentameric modules. The Brucella spp. lumazine synthase (BLS) sequence clearly diverges from pentameric and icosahedral enzymes. This unusual divergence prompted to further investigate on its quaternary arrangement. In the present work, we demonstrate by means of solution Light Scattering and X-ray structural analyses that BLS assembles as a very stable dimer of pentamers representing a third category of quaternary assembly for lumazine synthases. We also describe by spectroscopic studies the thermodynamic stability of this oligomeric protein, and postulate a mechanism for dissociation/unfolding of this macromolecular assembly. The higher molecular order of BLS increases its stability 20 deg C compared to pentameric lumazine synthases. The decameric arrangement described in this work highlights the importance of quaternary interactions in the stabilization of proteins. (author)

Physical modeling of river spanning rock structures: Evaluating interstitial flow, local hydraulics, downstream scour development, and structure stability

Science.gov (United States)

Collins, K.L.; Thornton, C.I.; Mefford, B.; Holmquist-Johnson, C. L.

2009-01-01

Rock weir and ramp structures uniquely serve a necessary role in river management: to meet water deliveries in an ecologically sound manner. Uses include functioning as low head diversion dams, permitting fish passage, creating habitat diversity, and stabilizing stream banks and profiles. Existing information on design and performance of in-stream rock structures does not provide the guidance necessary to implement repeatable and sustainable construction and retrofit techniques. As widespread use of rock structures increases, the need for reliable design methods with a broad range of applicability at individual sites grows as well. Rigorous laboratory testing programs were implemented at the U.S. Bureau of Reclamation (Reclamation) and at Colorado State University (CSU) as part of a multifaceted research project focused on expanding the current knowledge base and developing design methods to improve the success rate of river spanning rock structures in meeting project goals. Physical modeling at Reclamation is being used to measure, predict, and reduce interstitial flow through rock ramps. CSU is using physical testing to quantify and predict scour development downstream of rock weirs and its impact on the stability of rock structures. ?? 2009 ASCE.

Superoxide dismutase from Trichuris ovis, inhibiton by benzimidazoles and pyrimidine derivatives

OpenAIRE

Sanchez-Moreno, M.; Garcia-Rejon, L.; Salas, I.; Osuna, A.; Monteoliva, M.

1992-01-01

Three superoxide dismutase isoenzymes of different cellular location were detected in an homogenate of Thrichuris ovis. Each of these molecular forms was purified by differential centrifugation and precipitation with ammonium sulphate, followed by chromatography on DEAE-cellulose and Sephadex G-75 columns. The activity levels of the two molecular forms detected in the mitochondrial (one cyanide sensitive Cu-Zn-SOD and the other cyanide intensitive Mn-Sod were higher than that of the superoxid...

Structure and stability of triglyceride monolayers on water and mica surfaces

NARCIS (Netherlands)

Zdravkova, A.N.; van der Eerden, J.P.J.M.

2007-01-01

The structure and the stability of tripalmitin (PPP), tristearin (SSS), and triarachidin (AAA) monolayers at the air-water interface are investigated with the Langmuir method. The Langmuir-Blodgett (LB) layers obtained by deposition on mica were investigated with atomic force microscopy (AFM). Our

Relative Stabilities of Conserved and Non-Conserved Structures in the OB-Fold Superfamily

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Andrei T. Alexandrescu

2009-05-01

Full Text Available The OB-fold is a diverse structure superfamily based on a β-barrel motif that is often supplemented with additional non-conserved secondary structures. Previous deletion mutagenesis and NMR hydrogen exchange studies of three OB-fold proteins showed that the structural stabilities of sites within the conserved β-barrels were larger than sites in non-conserved segments. In this work we examined a database of 80 representative domain structures currently classified as OB-folds, to establish the basis of this effect. Residue-specific values were obtained for the number of Cα-Cα distance contacts, sequence hydrophobicities, crystallographic B-factors, and theoretical B-factors calculated from a Gaussian Network Model. All four parameters point to a larger average flexibility for the non-conserved structures compared to the conserved β-barrels. The theoretical B-factors and contact densities show the highest sensitivity.Our results suggest a model of protein structure evolution in which novel structural features develop at the periphery of conserved motifs. Core residues are more resistant to structural changes during evolution since their substitution would disrupt a larger number of interactions. Similar factors are likely to account for the differences in stability to unfolding between conserved and non-conserved structures.

A Subset of Autism-Associated Genes Regulate the Structural Stability of Neurons

Science.gov (United States)

Lin, Yu-Chih; Frei, Jeannine A.; Kilander, Michaela B. C.; Shen, Wenjuan; Blatt, Gene J.

2016-01-01

Autism spectrum disorder (ASD) comprises a range of neurological conditions that affect individuals’ ability to communicate and interact with others. People with ASD often exhibit marked qualitative difficulties in social interaction, communication, and behavior. Alterations in neurite arborization and dendritic spine morphology, including size, shape, and number, are hallmarks of almost all neurological conditions, including ASD. As experimental evidence emerges in recent years, it becomes clear that although there is broad heterogeneity of identified autism risk genes, many of them converge into similar cellular pathways, including those regulating neurite outgrowth, synapse formation and spine stability, and synaptic plasticity. These mechanisms together regulate the structural stability of neurons and are vulnerable targets in ASD. In this review, we discuss the current understanding of those autism risk genes that affect the structural connectivity of neurons. We sub-categorize them into (1) cytoskeletal regulators, e.g., motors and small RhoGTPase regulators; (2) adhesion molecules, e.g., cadherins, NCAM, and neurexin superfamily; (3) cell surface receptors, e.g., glutamatergic receptors and receptor tyrosine kinases; (4) signaling molecules, e.g., protein kinases and phosphatases; and (5) synaptic proteins, e.g., vesicle and scaffolding proteins. Although the roles of some of these genes in maintaining neuronal structural stability are well studied, how mutations contribute to the autism phenotype is still largely unknown. Investigating whether and how the neuronal structure and function are affected when these genes are mutated will provide insights toward developing effective interventions aimed at improving the lives of people with autism and their families. PMID:27909399

Superoxide dismutase amplifies organismal sensitivity to ionizing radiation

International Nuclear Information System (INIS)

Scott, M.D.; Meshnick, S.R.; Eaton, J.W.

1989-01-01

Although increased superoxide dismutase (SOD) activity is often associated with enhanced resistance of cells and organisms to oxidant challenges, few direct tests of the antioxidant importance of this enzyme have been carried out. To assess the importance of SOD in defending against gamma-radiation, we employed Escherichia coli with deficient, normal, and super-normal enzyme activities. Surprisingly, the radiation sensitivity of E. coli actually increases as bacterial SOD activity increases. Elevated intracellular SOD activity sensitizes E. coli to radiation-induced mortality, whereas SOD-deficient bacteria show normal or decreased radiosensitivity. Toxic effects of activated oxygen species are involved in this phenomenon; bacterial SOD activity has no effect on radiation sensitivity under anaerobic conditions or on the lethality of other, non-oxygen-dependent, toxins such as ultraviolet radiation

Reduced superoxide dismutase activity in xeroderma pigmentosum fibroblasts

International Nuclear Information System (INIS)

Nishigori, C.; Miyachi, Y.; Imamura, S.; Takebe, H.

1989-01-01

This study was performed in order to assess the possible protective effect of superoxide dismutase (SOD) on ultraviolet (UV) damage in xeroderma pigmentosum (XP) fibroblasts. SOD activity in fibroblasts originating from seven xeroderma pigmentosum (XP) patients was significantly lower than that in normal cells (p less than 0.005). Average SOD activity in XP cells belonging to complementation group A was 3.68 +/- 0.54 (n = 7) and that in normal human cells was 5.79 +/- 1.59 (n = 6). Addition of SOD before and during UV irradiation (UVB and UVC) to the cells caused no change in the amount of unscheduled DNA synthesis and UV survival. A possible involvement of reduced SOD in XP and a possible protective effect by SOD on UV damage is discussed

Colloidal stability of suspended and agglomerate structures of settled carbon nanotubes in different aqueous matrices.

Science.gov (United States)

Schwyzer, Irène; Kaegi, Ralf; Sigg, Laura; Nowack, Bernd

2013-08-01

Carbon nanotubes (CNTs) are often processed in suspended form and therefore a release of CNT-suspensions into the aquatic environment is plausible. In this study, the behaviour of two physico-chemically very different CNT types in the presence of varying, environmentally relevant calcium-containing media was investigated, including the long-term colloidal stability and the sedimentary structures of settled CNTs. Calcium induced CNT flocculation, however, the stability of the CNTs in the medium did not monotonously decrease with increasing calcium concentration. At intermediate calcium concentrations (0.5-1.5 mM Ca) pre-dispersed CNTs were stabilized in humic acid medium to similar, temporarily even to higher degree than in the absence of calcium. Between pH 5 and 8 only at the highest pH an influence on CNT stability was observed by either promoting flocculation or stabilisation depending on the CNT type. Humic acid stabilized CNTs much better than fulvic acid. Generally, the colloidal stability of the long, thick CNTs with higher surface oxygen content was less affected by the media composition. An investigation of the settled CNT material using analytical electron microscopy revealed the presence of spheroidal, bundle-like and net like CNT-agglomerate structures. Calcium possibly acted as bridging agent linking CNTs in a network like manner, temporarily increasing the CNT concentrations stabilized in the supernatants due to the low density of these structures. With increasing settling time the CNTs formed a fluffy sediment layer at the bottom of the reaction vessels. Bundle-like CNT agglomerates were also observed within that layer of settled CNTs, possibly caused by calcium neutralizing the surface charges. Furthermore, the CNT suspensions contained spheroidal CNT agglomerates, most likely residues from the original dry powder that were not disaggregated. The analysis of settled CNT material is a novelty and illustrates CNT agglomerate structures possibly

Structural stability and elastic properties of L12 Co3(Ga,W) precipitate from first-principle calculations

International Nuclear Information System (INIS)

Yao Qiang; Zhu Yuhong; Wang Yan

2011-01-01

Ultrasoft pseudopotential within a generalized gradient approximation was employed to study the structural stability, electronic structure, and elastic properties of ternary Co 3 (Ga,W) precipitate. The Young's and shear moduli of the polycrystals containing the Co 3 (Ga,W) precipitate were calculated using the Voigt-Reuss-Hill averaging scheme. Results show that the stable ternary Co 3 (Ga,W) compound has the L1 2 structure, and is ductile in nature. The structural stability of the Co 3 (Ga,W) compound is discussed together with the calculated electronic structure.

Superoxide dismutases in chronic gastritis.

Science.gov (United States)

Švagelj, Dražen; Terzić, Velimir; Dovhanj, Jasna; Švagelj, Marija; Cvrković, Mirta; Švagelj, Ivan

2016-04-01

Human gastric diseases have shown significant changes in the activity and expression of superoxide dismutase (SOD) isoforms. The aim of this study was to detect Mn-SOD activity and expression in the tissue of gastric mucosa, primarily in chronic gastritis (immunohistochemical Helicobacter pylori-negative gastritis, without other pathohistological changes) and to evaluate their possible connection with pathohistological diagnosis. We examined 51 consecutive outpatients undergoing endoscopy for upper gastrointestinal symptoms. Patients were classified based on their histopathological examinations and divided into three groups: 51 patients (archive samples between 2004-2009) with chronic immunohistochemical Helicobacter pylori-negative gastritis (mononuclear cells infiltration were graded as absent, moderate, severe) divided into three groups. Severity of gastritis was graded according to the updated Sydney system. Gastric tissue samples were used to determine the expression of Mn-SOD with anti-Mn-SOD Ab immunohistochemically. The Mn-SOD expression was more frequently present in specimens with severe and moderate inflammation of gastric mucosa than in those with normal mucosa. In patients with normal histological finding, positive immunoreactivity of Mn-SOD was not found. Our results determine the changes in Mn-SOD expression occurring in the normal gastric mucosa that had undergone changes in the intensity of chronic inflammatory infiltrates in the lamina propria. © 2016 APMIS. Published by John Wiley & Sons Ltd.

Cloning, Expression, Characterization, and Computational Approach for Cross-Reactivity Prediction of Manganese Superoxide Dismutase Allergen from Pistachio Nut

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Reihaneh Noorbakhsh

Full Text Available ABSTRACT: Background: Tree nut allergy is one of the common potentially life-threatening food allergies in children and adults. Recombinant food allergens offer new perspectives to solve problems of clinical and molecular allergology in diagnosis, research, and therapy of food allergies. So far, superoxide dismutase (s has been identified as a panallergen and studied in different allergenic sources. Manganese Superoxide Dismutase (MnSOD has also been reported in pistachio that may cause allergic reactions in atopic subjects. The aim of this study was to describe the cloning, expression, and purification of MnSOD from pistachio nut. Methods: The pistachio MnSOD was cloned and expressed in E. coli BL21 (DE3 using a vector pET-32b (+. A recombinant protein was purified by metal precipitation. The protein immunoreactivity was evaluated using patients' IgE binding by means of ELISA and immunoblotting assays. Results: The MnSOD gene from pistachio was successfully cloned and expressed in E. coli. The purified pistachio MnSOD was recognized by IgE in 10 (40% out of the 25 sera tested. Our results also showed that this protein might trigger some cross-reactions toward IgE antibodies and thus could be considered as a panallergen. Conclusions: For the first time recombinant manganese superoxide dismutase from nut source was expressed as a possible allergen. This pistachio allergen could be a possible basis for cross-reactivity with MnSOD from other sources. KEY WORDS: cloning, cross-reaction, Manganese Superoxide Dismutase (MnSOD, pistachio (Pistacia vera, recombinant allergen

Paroxysmal atrial fibrillation: dynamics of the main antioxidant enzymes--superoxide dismutase and catalase.

Science.gov (United States)

Negreva, Mariya N; Penev, Atanas P; Georgiev, Svetoslav Zh; Aleksandrova, Albena A

2014-01-01

Researchers have a particularly strong interest in the mechanisms implicated in the clinical manifestation of atrial fibrillation. To examine dynamically the activity of the antioxidant enzymes, superoxide dismutase and catalase in patients with paroxysmal atrial fibrillation (duration enzyme activity was determined by a spectrophotometric method. The average duration of atrial fibrillation episodes until the time of hospitalization was 8.14 hours (from 2 to 24 hours). During patient hospitalization the activity of superoxide dismutase and catalase was considerably higher compared to that of the controls (8.46 +/- 0.26 vs 5.81 +/- 0.14 U/mg Hb; 7.36 +/- 0.25 vs 4.76 +/- 0.12 E240/min/mg Hb; P catalase remained increased (5.11 +/- 0.08 vs 4.76 +/- 0.12 E240/min/mg Hb, p catalase even in the early hours of clinical manifestation of the disorder, which then slowly decreased with the restoration of sinus rhythm. Therefore, we can conclude that changes in oxidative status are closely related to the disease and are probably a part of the intimate mechanisms related to its initiation and clinical course.

The role of a topologically conserved isoleucine in glutathione transferase structure, stability and function

International Nuclear Information System (INIS)

Achilonu, Ikechukwu; Gildenhuys, Samantha; Fisher, Loren; Burke, Jonathan; Fanucchi, Sylvia; Sewell, B. Trevor; Fernandes, Manuel; Dirr, Heini W.

2010-01-01

The role of a topologically conserved isoleucine in the structure of glutathione transferase was investigated by replacing the Ile71 residue in human GSTA1-1 by alanine or valine. The common fold shared by members of the glutathione-transferase (GST) family has a topologically conserved isoleucine residue at the N-terminus of helix 3 which is involved in the packing of helix 3 against two β-strands in domain 1. The role of the isoleucine residue in the structure, function and stability of GST was investigated by replacing the Ile71 residue in human GSTA1-1 by alanine or valine. The X-ray structures of the I71A and I71V mutants resolved at 1.75 and 2.51 Å, respectively, revealed that the mutations do not alter the overall structure of the protein compared with the wild type. Urea-induced equilibrium unfolding studies using circular dichroism and tryptophan fluorescence suggest that the mutation of Ile71 to alanine or valine reduces the stability of the protein. A functional assay with 1-chloro-2,4-dinitrobenzene shows that the mutation does not significantly alter the function of the protein relative to the wild type. Overall, the results suggest that conservation of the topologically conserved Ile71 maintains the structural stability of the protein but does not play a significant role in catalysis and substrate binding

The concentration of extracellular superoxide dismutase in plasma is maintained by LRP-mediated endocytosis

DEFF Research Database (Denmark)

Petersen, Steen V; Thøgersen, Ida B; Valnickova, Zuzana

2010-01-01

In this study, we show that human extracellular superoxide dismutase (EC-SOD) binds to low-density lipoprotein receptor-related protein (LRP). This interaction is most likely responsible for the removal of EC-SOD from the blood circulation via LRP expressed in liver tissue. The receptor recognition...

Stabilization of Si_60 Cage Structure: The Agony and the Ecstasy

Science.gov (United States)

Kawazoe, Y.; Sun, Q.; Wang, Q.; Rao, B. K.; Jena, P.

2003-03-01

The unique role of silicon in the micro-electronics industry has motivated many researchers to find ways to stabilize Si_60 with fullerene structure. In spite of numerous experimental attempts, synthesis of a theoretically predicted C_60-supported Si_60 cluster (C_60@Si_60) has not been possible. Using a state-of-the-art theoretical method, we provide the first answer for this long-standing contradiction between the experimental observation and the theoretical prediction. The flaws in earlier theoretical works are pointed out, and Si_60 is shown to be unstable in the fullerene structure either on its own or when supported on a C_60 fullerene (C_60@Si_60). On the other hand, we show that Si_60 cage can be stabilized by using magic clusters such as Al_12X (X = Si, Ge, Sn, Pb) as endohedral units, which have been identified in recent experiment as stable clusters and as suitable building blocks for cluster-assembled materials.

Preparation, structure and thermal stability of Cu/LDPE nanocomposites

International Nuclear Information System (INIS)

Xia Xianping; Cai Shuizhou; Xie Changsheng

2006-01-01

Copper/low-density-polyethylene (Cu/LDPE) nanocomposites have been prepared using a melt-blending technique in a single-screw extruder. Their structure and thermal characteristics are characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results of XRD, SEM and SEM-EDS Cu-mapping show that the nanocomposites are a hybrid of the polymer and the copper nanoparticles, and the copper nanoparticles aggregates were distributed uniformly in general. The results also show that the nanocomposites and the base resin, the pure LDPE, have a different crystalline structure and the same oriented characteristics owing to the presence of copper nanoparticles and the same cooling condition. The results of DSC show that the incorporation of copper nanoparticles can decrease the melting temperatures but increase the crystallization temperatures, and can lower the crystallinity degree of the matrix of the composites. The results of TGA show that the presence of copper nanoparticles can improve the thermal stability of the nanocomposites, a maximum increment of 18 deg. C is obtained comparing with the pure LDPE in this experiment. The results of TGA also show that the influence of the incorporation of the copper nanoparticles on the thermal stability of the Cu/LDPE nanocomposites is different from that of the non-metal nanoparticles on the polymer/non-metal nanocomposites and the copper microparticles on the Cu/LDPE microcomposites. The increase of the thermal stability of the Cu/LDPE nanocomposites will decrease when the content of the copper nanoparticles is more than 2 wt.%. The difference might be caused by the fact that the activity of the metal nanoparticles is much more higher than that of the non-metal nanoparticles, and the different size effect the different copper particles has

Axial ratio dependence of the stability of self-interstitials in HCP structures

International Nuclear Information System (INIS)

Peng, Qing; Ji, Wei; Huang, Hanchen; De, Suvranu

2013-01-01

We investigate the effect of the axial ratio (c/a) on the stability of self-interstitial atoms (SIAs) in hexagonal close-packed crystal structures, using hcp-zirconium as a prototype, through density functional theory based ab initio calculations. The axial ratio is found to dominate the relative stability of SIAs over volumetric strains. We observe that below the ideal value of 1.633, the basal octahedral configuration is the most stable. Above the ideal value, the off-plane SIAs are more stable than in-plane ones

Structure and phase stability of a Pu-0.32 wt% Ga alloy

Energy Technology Data Exchange (ETDEWEB)

Wheeler, D.W., E-mail: David.Wheeler@awe.co.uk; Ennaceur, S.M.; Matthews, M.B.; Roussel, P.; Bayer, P.D.

2016-08-01

In plutonium-gallium (Pu-Ga) alloys that have a Ga content of 0.3–0.4 wt%, their readiness to transform to α′ renders them of particular interest in efforts to understand the tenuous nature of δ phase stability. The present study is a comprehensive examination of the structure and phase stability of a cast Pu-0.32 wt% Ga alloy, the Ga content being close to the minimum amount needed to retain the δ phase to ambient temperature. The alloy was characterised in both the as-cast condition as well as following a homogenising heat treatment. The 250-h heat treatment at 450 °C was shown to achieve an apparently stable δ-Pu phase. However, the stability of the δ-Pu phase was shown to be marginal: partial transformation to α′-Pu was observed when the alloy was subjected to hydrostatic compression. Similar transformation was also apparent during metallographic preparation as well as during hardness indentation. The results provide new understanding of the nature of δ phase stability. - Highlights: • New insights into the delta phase stability of a Pu-0.32 wt% Ga alloy. • Density and DSC of as-cast alloy both show α-Pu contents of approximately 30%. • The heat-treated alloy has a largely δ-Pu structure at ambient temperature. • Heat-treated alloy susceptible to δ → α transformation during hardness indentation.

Evaluation of the Structure Stability of a Plate Girder Bridge Using MIDAS Structure Analysis

Energy Technology Data Exchange (ETDEWEB)

Kim, Eui Soo; Kim, Jong Hyuk [National Forensic Service, Wonju (Korea, Republic of)

2014-04-15

Recently, as a means of resolving the issue of legal liability in the event of an accident or a disaster, a wide variety of simulation techniques, such as structural and structure-fluid interaction analysis, have been used in the field of forensic engineering. The plate girder bridge discussed in this paper was being constructed between a pier and an abutment to expand an existing bridge, but an accident whereby the bridge overturned occurred at the end of the concrete laying process for a protective wall. This accident was caused by additional loads not being considered at the time of the design as well as the actual construction being different from the design. The additional loads ultimately generated a negative support force. In this study, we determined the cause of the accident by comparing the structural stability of the original design with that of the additional, non-conforming construction using MIDAS structural analysis.

Evaluation of the Structure Stability of a Plate Girder Bridge Using MIDAS Structure Analysis

International Nuclear Information System (INIS)

Kim, Eui Soo; Kim, Jong Hyuk

2014-01-01

Recently, as a means of resolving the issue of legal liability in the event of an accident or a disaster, a wide variety of simulation techniques, such as structural and structure-fluid interaction analysis, have been used in the field of forensic engineering. The plate girder bridge discussed in this paper was being constructed between a pier and an abutment to expand an existing bridge, but an accident whereby the bridge overturned occurred at the end of the concrete laying process for a protective wall. This accident was caused by additional loads not being considered at the time of the design as well as the actual construction being different from the design. The additional loads ultimately generated a negative support force. In this study, we determined the cause of the accident by comparing the structural stability of the original design with that of the additional, non-conforming construction using MIDAS structural analysis

Lattice stability of metastable AlN and wurtzite-to-rock-salt structural transformation by CALPHAD modeling

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yanhui, E-mail: yanhui.z@hotmail.com [Karlsruhe Institute of Technology (KIT), Institute for Applied Materials-Applied Materials Physics (IAM-AWP), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); High-performance Ceramics Division, Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 110016, Shenyang (China); Franke, Peter; Li, Dajian; Seifert, Hans Jürgen [Karlsruhe Institute of Technology (KIT), Institute for Applied Materials-Applied Materials Physics (IAM-AWP), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

2016-12-01

Reliable lattice stability of cubic AlN with rock-salt structure (rs-AlN) is the prerequisite of accurate thermodynamic modeling of cubic (M, Al)N solid solutions (M = Ti, Zr, Cr etc.). In order to derive the Gibbs energy of metastable rs-AlN, and then its lattice stability, we did the pressure-temperature (P-T) assessment of AlN phases by equations-of-state modeling. Meanwhile, the molar volumes and the heat capacities of wurtzite and rock-salt AlN, as well as the wurtzite-to-rock-salt structural transition at high P&T were successfully incorporated in CALPHAD-type database by integrating thermodynamic data from experiments and ab-initio calculations. These results promise subsequent investigations on phase stabilities and transitions of solid solutions with AlN component and the development of novel multicomponent coatings. - Highlights: • Phase stability investigation for novel multi-component metastable coatings. • Structural transition at high temperature and high pressure. • Integrating thermodynamic data from ab-initio calculations and experiments. • Thermal expansion, isothermal compressibility and heat capacity of w-AlN and rs-AlN.

The relationship between dental implant stability and trabecular bone structure using cone-beam computed tomography

Science.gov (United States)

2016-01-01

Purpose The objective of this study was to investigate the relationships between primary implant stability as measured by impact response frequency and the structural parameters of trabecular bone using cone-beam computed tomography(CBCT), excluding the effect of cortical bone thickness. Methods We measured the impact response of a dental implant placed into swine bone specimens composed of only trabecular bone without the cortical bone layer using an inductive sensor. The peak frequency of the impact response spectrum was determined as an implant stability criterion (SPF). The 3D microstructural parameters were calculated from CT images of the bone specimens obtained using both micro-CT and CBCT. Results SPF had significant positive correlations with trabecular bone structural parameters (BV/TV, BV, BS, BSD, Tb.Th, Tb.N, FD, and BS/BV) (Pmicro-CT and CBCT (Pimplant stability prediction by combining BV/TV and SMI in the stepwise forward regression analysis. Bone with high volume density and low surface density shows high implant stability. Well-connected thick bone with small marrow spaces also shows high implant stability. The combination of bone density and architectural parameters measured using CBCT can predict the implant stability more accurately than the density alone in clinical diagnoses. PMID:27127692

Molecular Cloning and Expression of Sequence Variants of Manganese Superoxide Dismutase Genes from Wheat

Science.gov (United States)

Reactive oxygen species (ROS) are very harmful to living organisms due to the potential oxidation of membrane lipids, DNA, proteins, and carbohydrates. Transformed E.coli strain QC 871, superoxide dismutase (SOD) double-mutant, with three sequence variant MnSOD1, MnSOD2, and MnSOD3 manganese supero...

Inclusions of amyotrophic lateral sclerosis-linked superoxide dismutase in ventral horns, liver, and kidney

DEFF Research Database (Denmark)

Jonsson, P.A.; Bergemalm, D.; Andersen, P.M.

2008-01-01

Mutant superoxide dismutases type 1 (SOD1s) cause amyotrophic lateral sclerosis by an unidentified toxic property. In a patient carrying the G127X truncation mutation, minute amounts of SOD1 were found in ventral horns using a mutant-specific antibody. Still, both absolute levels and ratios versus...

Low activity of superoxide dismutase and high activity of glutathione reductase in erythrocytes from centenarians

DEFF Research Database (Denmark)

Andersen, Helle Raun; Jeune, B; Nybo, H

1998-01-01

aged between 60 and 79 years. MEASUREMENTS: enzyme activities of superoxide dismutase (CuZn-SOD), glutathione peroxidase, catalase and glutathione reductase (GR) in erythrocytes. Functional capacity among the centenarians was evaluated by Katz' index of activities of daily living, the Physical...

Hydrodynamic stability theory of double ablation front structures in inertial confinement fusion

International Nuclear Information System (INIS)

Yanez Vico, C.

2012-11-01

For moderate-Z materials, the hydrodynamic structure of the ablation region formed by the irradiation of high intensity laser beams differs from that of low-Z materials (hydrogenic ablators). In particular, the role played by the radiative energy flux becomes non-negligible for increasing atomic number material and ended up forming a second ablation front. This structure of two separated ablation fronts, called double ablation (DA) front, was confirmed in the simulations carried out by Fujioka et al. In this work a linear stability theory of DA fronts is developed for direct-drive inertial confinement fusion targets. Two models are proposed. First, a sharp boundary model where the thin front approximation is assumed for both ablation fronts. The information about the corona region that permits to close the sharp boundary model is obtained from a prior self-consistent analysis of the electronic-radiative ablation (ERA) front. Numerical results are presented as well as an analytical approach for the radiation dominated regime of very steep double ablation front structure. Second, a self-consistent numerical method where the finite length of the ablation fronts is considered. Accurate hydrodynamic profiles are taken into account in the theoretical model by means of a fitting parameters method using one-dimensional simulation results. Numerical dispersion relation is compared to the analytical sharp boundary model showing an excellent agreement for the radiation dominated regime, and the stabilization due to smooth profiles. 2D simulations are presented to validate the linear stability theory

Epothilones as lead structures for the synthesis-based discovery of new chemotypes for microtubule stabilization.

Science.gov (United States)

Feyen, Fabian; Cachoux, Frédéric; Gertsch, Jürg; Wartmann, Markus; Altmann, Karl-Heinz

2008-01-01

Epothilones are macrocyclic bacterial natural products with potent microtubule-stabilizing and antiproliferative activity. They have served as successful lead structures for the development of several clinical candidates for anticancer therapy. However, the structural diversity of this group of clinical compounds is rather limited, as their structures show little divergence from the original natural product leads. Our own research has explored the question of whether epothilones can serve as a basis for the development of new structural scaffolds, or chemotypes, for microtubule stabilization that might serve as a basis for the discovery of new generations of anticancer drugs. We have elaborated a series of epothilone-derived macrolactones whose overall structural features significantly deviate from those of the natural epothilone scaffold and thus define new structural families of microtubule-stabilizing agents. Key elements of our hypermodification strategy are the change of the natural epoxide geometry from cis to trans, the incorporation of a conformationally constrained side chain, the removal of the C3-hydroxyl group, and the replacement of C12 with nitrogen. So far, this approach has yielded analogs 30 and 40 that are the most advanced, the most rigorously modified, structures, both of which are potent antiproliferative agents with low nanomolar activity against several human cancer cell lines in vitro. The synthesis was achieved through a macrolactone-based strategy or a high-yielding RCM reaction. The 12-aza-epothilone ("azathilone" 40) may be considered a "non-natural" natural product that still retains most of the overall structural characteristics of a true natural product but is structurally unique, because it lies outside of the general scope of Nature's biosynthetic machinery for polyketide synthesis. Like natural epothilones, both 30 and 40 promote tubulin polymerization in vitro and at the cellular level induce cell cycle arrest in mitosis. These

On dependence of stability of lanthanum complexes with aminopolycarboxylic acids on the complex structure

International Nuclear Information System (INIS)

Poluehktov, N.S.; Meshkova, S.B.; Danilkovich, M.M.; Topilova, Z.M.

1985-01-01

Regularities in changes of stability constants of lanthanum complexes with aminopolycarboxylic acids (APA) versus their structure are studied, The stability of lathanum-APA complexes depends mainly on the number of carboxyl groups in a ligand molecule. At that, the highest stability constant is characteristic of a complex with a ligand, containing 3 nitrogen atoms and 5 carboxyl groups, in the presenoe of which the lanthanum ion coordination sphere gets satupated. The oxyethy group introduction into a ligand molecule also improves the lanthanum complex stability but to a lesser degree than during the introduction of a carboxyl group. The number of nitrogen atoms in a ligand polecule affects insignificantly the complex stability constant value, and the elongation of a chain of CH 2 groups, separating nitrogen atoms, reduces the constant to a -0.6 power

Dynamics and stability of radiation-driven double ablation front structures

International Nuclear Information System (INIS)

Drean, V.; Olazabal-Loume, M.; Tikhonchuk, V. T.; Sanz, J.

2010-01-01

The dynamics of double ablation front (DAF) structures is studied for planar targets with moderate atomic number ablators. These structures are obtained in hydrodynamic simulations for various materials and laser intensities and are qualitatively characterized during the acceleration stage of the target. The importance of the radiative transport for the DAF dynamics is then demonstrated. Simulated hydrodynamic profiles are compared with a theoretical model, showing the consistency of the model and the relevant parameters for the dynamics description. The stability of DAF structures with respect to two-dimensional perturbations is studied using two different approaches: one considers the assumptions of the theoretical model and the other one a more complete physics. The numerical simulations performed with both approaches demonstrate good agreement of dispersion curves.

Infusing sodium bicarbonate suppresses hydrogen peroxide accumulation and superoxide dismutase activity in hypoxic-reoxygenated newborn piglets.

Directory of Open Access Journals (Sweden)

Jiang-Qin Liu

Full Text Available The effectiveness of sodium bicarbonate (SB has recently been questioned although it is often used to correct metabolic acidosis of neonates. The aim of the present study was to examine its effect on hemodynamic changes and hydrogen peroxide (H(2O(2 generation in the resuscitation of hypoxic newborn animals with severe acidosis.Newborn piglets were block-randomized into a sham-operated control group without hypoxia (n = 6 and two hypoxia-reoxygenation groups (2 h normocapnic alveolar hypoxia followed by 4 h room-air reoxygenation, n = 8/group. At 10 min after reoxygenation, piglets were given either i.v. SB (2 mEq/kg, or saline (hypoxia-reoxygenation controls in a blinded, randomized fashion. Hemodynamic data and blood gas were collected at specific time points and cerebral cortical H(2O(2 production was continuously monitored throughout experimental period. Plasma superoxide dismutase and catalase and brain tissue glutathione, superoxide dismutase, catalase, nitrotyrosine and lactate levels were assayed.Two hours of normocapnic alveolar hypoxia caused cardiogenic shock with metabolic acidosis (PH: 6.99 ± 0.07, HCO(3(-: 8.5 ± 1.6 mmol/L. Upon resuscitation, systemic hemodynamics immediately recovered and then gradually deteriorated with normalization of acid-base imbalance over 4 h of reoxygenation. SB administration significantly enhanced the recovery of both pH and HCO(3- recovery within the first hour of reoxygenation but did not cause any significant effect in the acid-base at 4 h of reoxygenation and the temporal hemodynamic changes. SB administration significantly suppressed the increase in H(2O(2 accumulation in the brain with inhibition of superoxide dismutase, but not catalase, activity during hypoxia-reoxygenation as compared to those of saline-treated controls.Despite enhancing the normalization of acid-base imbalance, SB administration during resuscitation did not provide any beneficial effects on hemodynamic recovery in

Assessment of structural stability of a degraded sandy clay loam soil ...

African Journals Online (AJOL)

The effects of bare, two legumes and four grasses cover treatments on the structural stability of a sandy clay loam Ultisol were studied within a two year period. The experiment was of a randomised complete block design with seven treatments. The legume treatments were Centrosema pubescens (Ce) and Pueraria ...

Comparative study of copper(II)-curcumin complexes as superoxide dismutase mimics and free radical scavengers.

Science.gov (United States)

Barik, Atanu; Mishra, Beena; Kunwar, Amit; Kadam, Ramakant M; Shen, Liang; Dutta, Sabari; Padhye, Subhash; Satpati, Ashis K; Zhang, Hong-Yu; Indira Priyadarsini, K

2007-04-01

Two stoichiometrically different copper(II) complexes of curcumin (stoichiometry, 1:1 and 1:2 for copper:curcumin), were examined for their superoxide dismutase (SOD) activity, free radical-scavenging ability and antioxidant potential. Both the complexes are soluble in lipids and DMSO. The formation constants of the complexes were determined by voltammetry. EPR spectra of the complexes in DMSO at 77K showed that the 1:2 Cu(II)-curcumin complex is square planar and the 1:1 Cu(II)-curcumin complex is distorted orthorhombic. Cu(II)-curcumin complex (1:1) with larger distortion from square planar structure shows higher SOD activity. These complexes inhibit gamma-radiation induced lipid peroxidation in liposomes and react with DPPH acting as free radical scavengers. One-electron oxidation of the two complexes by radiolytically generated azide radicals in Tx-100 micellar solutions produced phenoxyl radicals, indicating that the phenolic moiety of curcumin in the complexes participates in free radical reactions. Depending on the structure, these two complexes possess different SOD activities, free radical neutralizing abilities and antioxidant potentials. In addition, quantum chemical calculations with density functional theory have been performed to support the experimental observations.

The stabilities and electron structures of Al-Mg clusters with 18 and 20 valence electrons

Science.gov (United States)

Yang, Huihui; Chen, Hongshan

2017-07-01

The spherical jellium model predicts that metal clusters having 18 and 20 valence electrons correspond to the magic numbers and will show specific stabilities. We explore in detail the geometric structures, stabilities and electronic structures of Al-Mg clusters containing 18 and 20 valence electrons by using genetic algorithm combined with density functional theories. The stabilities of the clusters are governed by the electronic configurations and Mg/Al ratios. The clusters with lower Mg/Al ratios are more stable. The molecular orbitals accord with the shell structures predicted by the jellium model but the 2S level interweaves with the 1D levels and the 2S and 1D orbitals form a subgroup. The clusters having 20 valence electrons form closed 1S21P61D102S2 shells and show enhanced stability. The Al-Mg clusters with a valence electron count of 18 do not form closed shells because one 1D orbital is unoccupied. The ionization potential and electron affinity are closely related to the electronic configurations; their values are determined by the subgroups the HOMO or LUMO belong to. Supplementary material in the form of one pdf file available from the Journal web page at http://https://doi.org/10.1140/epjd/e2017-80042-9

Enhancing the crumb rubber modified asphalt’s storage stability through the control of its internal network structure

Directory of Open Access Journals (Sweden)

Mohyeldin Ragab

2018-01-01

Full Text Available The current research investigated the effect of the internal network structure developed in the crumb rubber modified asphalt (CRMA on its storage stability. The authors investigated the influence of asphalt-crumb rubber modifier (CRM interaction parameters (interaction time, interaction speed, and interaction temperature on the development of the internal network structure in CRMA. The authors found that the existence of three dimensional (3D network structures in the CRMA enhanced its storage stability. Fourier Transform Infrared (FTIR Spectroscopy was utilized to determine the nature of CRM components responsible for the development of 3D network structure in the liquid phase of CRMA. This was achieved by monitoring the changes of the IR distinctive peaks in the CRMA liquid phase. Dissolution tests and thermo gravimetric analysis (TGA were carried out on the extracted CRM after interaction with asphalt to determine the role of CRM dissolved amounts and released components on the development of 3D network structure in CRMA. The asphalt-CRM interaction parameters were found to be essential to induce the formation of the 3D network structure within the liquid phase of the CRMA through controlling the swelling, dissolution and release of CRM components into the asphalt liquid phase. The existence of 3D network structure in the CRMA had determinant impact on the enhancement of its storage stability. Keywords: Storage stability, Three dimensional (3D network, Crumb rubber modified asphalt

Structural Design Optimization of a Tiltrotor Aircraft Composite Wing to Enhance Whirl Flutter Stability

DEFF Research Database (Denmark)

Kim, Taeseong; Kim, Jaehoon; Shin, Sang Joon

2013-01-01

In order to enhance the aeroelastic stability of a tiltrotor aircraft, a structural optimization framework is developed by applying a multi-level optimization approach. Each optimization level is designed to achieve a different purpose; therefore, relevant optimization schemes are selected for each...... level. Enhancement of the aeroelastic stability is selected as an objective in the upper-level optimization. This is achieved by seeking the optimal structural properties of a composite wing, including its mass, vertical, chordwise, and torsional stiffness. In the upper-level optimization, the response...... surface method (RSM), is selected. On the other hand, lower-level optimization seeks to determine the local detailed cross-sectional parameters, such as the ply orientation angles and ply thickness, which are relevant to the wing structural properties obtained at the upper-level. To avoid manufacturing...

Metalloantibiotic Mn(II)-bacitracin complex mimicking manganese superoxide dismutase

International Nuclear Information System (INIS)

Piacham, Theeraphon; Isarankura-Na-Ayudhya, Chartchalerm; Nantasenamat, Chanin; Yainoy, Sakda; Ye Lei; Buelow, Leif; Prachayasittikul, Virapong

2006-01-01

Superoxide dismutase (SOD) activities of various metallobacitracin complexes were evaluated using the riboflavin-methionine-nitro blue tetrazolium assay. The radical scavenging activity of various metallobacitracin complexes was shown to be higher than those of the negative controls, e.g., free transition metal ions and metal-free bacitracin. The SOD activity of the complex was found to be in the order of Mn(II) > Cu(II) > Co(II) > Ni(II). Furthermore, the effect of bacitracin and their complexation to metals on various microorganisms was assessed by antibiotic susceptibility testing. Moreover, molecular modeling and quantum chemical calculation of the metallobacitracin complex was performed to evaluate the correlation of electrostatic charge of transition metal ions on the SOD activity

Differential Effects of Superoxide Dismutase Mimetics after Mechanical Overload of Articular Cartilage

Directory of Open Access Journals (Sweden)

Mitchell C. Coleman

2017-11-01

Full Text Available Post-traumatic osteoarthritis can develop as a result of the initial mechanical impact causing the injury and also as a result of chronic changes in mechanical loading of the joint. Aberrant mechanical loading initiates excessive production of reactive oxygen species, oxidative damage, and stress that appears to damage mitochondria in the surviving chondrocytes. To probe the benefits of increasing superoxide removal with small molecular weight superoxide dismutase mimetics under severe loads, we applied both impact and overload injury scenarios to bovine osteochondral explants using characterized mechanical platforms with and without GC4403, MnTE-2-PyP, and MnTnBuOE-2-PyP. In impact scenarios, each of these mimetics provides some dose-dependent protection from cell death and loss of mitochondrial content while in repeated overloading scenarios only MnTnBuOE-2-PyP provided a clear benefit to chondrocytes. These results support the hypothesis that superoxide is generated in excess after impact injuries and suggest that superoxide production within the lipid compartment may be a critical mediator of responses to chronic overload. This is an important nuance distinguishing roles of superoxide, and thus superoxide dismutases, in mediating damage to cellular machinery in hyper-acute impact scenarios compared to chronic scenarios.

Accuracy Enhanced Stability and Structure Preserving Model Reduction Technique for Dynamical Systems with Second Order Structure

DEFF Research Database (Denmark)

Tahavori, Maryamsadat; Shaker, Hamid Reza

A method for model reduction of dynamical systems with the second order structure is proposed in this paper. The proposed technique preserves the second order structure of the system, and also preserves the stability of the original systems. The method uses the controllability and observability...... gramians within the time interval to build the appropriate Petrov-Galerkin projection for dynamical systems within the time interval of interest. The bound on approximation error is also derived. The numerical results are compared with the counterparts from other techniques. The results confirm...

Vertically aligned carbon nanotubes/diamond double-layered structure for improved field electron emission stability

Energy Technology Data Exchange (ETDEWEB)

Yang, L., E-mail: qiaoqin.yang@mail.usask.ca; Yang, Q.; Zhang, C.; Li, Y.S.

2013-12-31

A double-layered nanostructure consisting of a layer of vertically aligned Carbon Nanotubes (CNTs) and a layer of diamond beneath has been synthesized on silicon substrate by Hot Filament Chemical Vapor Deposition. The synthesis was achieved by first depositing a layer of diamond on silicon and then depositing a top layer of vertically aligned CNTs by applying a negative bias on the substrate holder. The growth of CNTs was catalyzed by a thin layer of spin-coated iron nitride. The surface morphology and structure of the CNTs/diamond double-layered structure were characterized by Scanning Electron Microscope, Energy Dispersive X-ray spectrum, and Raman Spectroscopy. Their field electron emission (FEE) properties were measured by KEITHLEY 237 high voltage measurement unit, showing much higher FEE current stability than single layered CNTs. - Highlights: • A new double-layered nanostructure consisting of a layer of vertically aligned CNTs and a layer of diamond beneath has been synthesized by hot filament chemical vapor deposition. • This double-layered structure exhibits superior field electron emission stability. • The improvement of emission stability is due to the combination of the unique properties of diamond and CNTs.

Effects of sorbitol and glycerol on the structure, dynamics, and stability of Mycobacterium tuberculosis pyrazinamidase

Directory of Open Access Journals (Sweden)

Mehrnoosh Khajehzadeh

2016-01-01

Conclusion: It can be concluded that the native conformation of the enzyme was stabilized in the sorbitol and glycerol and tend to exclude from the PZase surface, forcing the enzyme to keep it in the compactly folded conformation. The glycerol molecules stabilized PZase by decreasing the loops flexibility and then compacting the enzyme structure. It appears that more stability of PZase in glycerol solution correlates with its amphiphilic orientation, which decreases the unfavorable interactions of hydrophobic regions.

Structure and stability of the spinach aquaporin SoPIP2;1 in detergent micelles and lipid membranes.

Directory of Open Access Journals (Sweden)

Inés Plasencia

Full Text Available BACKGROUND: SoPIP2;1 constitutes one of the major integral proteins in spinach leaf plasma membranes and belongs to the aquaporin family. SoPIP2;1 is a highly permeable and selective water channel that has been successfully overexpressed and purified with high yields. In order to optimize reconstitution of the purified protein into biomimetic systems, we have here for the first time characterized the structural stability of SoPIP2;1. METHODOLOGY/PRINCIPAL FINDING: We have characterized the protein structural stability after purification and after reconstitution into detergent micelles and proteoliposomes using circular dichroism and fluorescence spectroscopy techniques. The structure of SoPIP2;1 was analyzed either with the protein solubilized with octyl-β-D-glucopyranoside (OG or reconstituted into lipid membranes formed by E. coli lipids, diphytanoylphosphatidylcholine (DPhPC, or reconstituted into lipid membranes formed from mixtures of 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPE, 1-palmitoyl-2oleoyl-phosphatidylethanolamine (POPE, 1-palmitoyl-2-oleoyl-phosphatidylserine (POPS, and ergosterol. Generally, SoPIP2;1 secondary structure was found to be predominantly α-helical in accordance with crystallographic data. The protein has a high thermal structural stability in detergent solutions, with an irreversible thermal unfolding occurring at a melting temperature of 58°C. Incorporation of the protein into lipid membranes increases the structural stability as evidenced by an increased melting temperature of up to 70°C. CONCLUSION/SIGNIFICANCE: The results of this study provide insights into SoPIP2;1 stability in various host membranes and suggest suitable choices of detergent and lipid composition for reconstitution of SoPIP2;1 into biomimetic membranes for biotechnological applications.

The effect of structured triglycerides on the kinetic stability of total nutrient admixtures.

Science.gov (United States)

Balogh, Judit; Bubenik, Júlia; Dredán, Judit; Csempesz, Ferenc; Kiss, Dorottya; Zelkó, Romána

2005-10-05

The physical stability of two types of total parenteral nutrient (TPN) admixtures was studied as a function of storage time and temperature. One of them contained only structured triglycerides and the other exclusively long-chain triglycerides as lipid components. Droplet size of the mixtures was followed by photon correlation spectroscopy for 10 days. Zeta potential and dynamic surface tension measurements were carried out to evaluate the possible changes in the charge and interfacial surface tension of the emulsion droplets during the storage. pH values were monitored in order to follow the possible decomposition processes in the course of storage. Droplet size of emulsions prepared with lipids containing exclusively long-chain triglycerides showed remarkable increase after 4 days of storage in contrast with that of the mixtures containing structured lipids. The obtained results indicate that besides the advantageous metabolic effects of structured triglycerides, their application is recommended to improve the physical stability of TPN admixtures.

The cytoplasmic Cu,Zn superoxide dismutase of saccharomyces cerevisiae is required for resistance to freeze-thaw stress. Generation of free radicals during freezing and thawing

DEFF Research Database (Denmark)

Park, J I; Grant, C M; Davies, Michael Jonathan

1998-01-01

The involvement of oxidative stress in freeze-thaw injury to yeast cells was analyzed using mutants defective in a range of antioxidant functions, including Cu,Zn superoxide dismutase (encoded by SOD1), Mn superoxide dismutase (SOD2), catalase A, catalase T, glutathione reductase, gamma...

The effect of exchange-correlation on change and stability of crystal structure

International Nuclear Information System (INIS)

Yazdani, A.; Niazi, M.; Alimardan, V.

2007-01-01

Since exchange interaction energy has effect on band structure via polarization of spin of free electron, then can directly effects formation crystal structure. Therefore exchange-correlation is able to have an effect on determination of crystal structure or its change and stability. This energy is subject to fluctuation range of electrons between conduction band and valance band or density of electrons which due to increase the entropy of system, via Gibss Energy .We investigated these factors: 1) Size of ions 2) Density of States 3) Range of inter atomic and pair-potential.

A pulse-radiolysis study of the manganese-containing superoxide dismutase from Bacillus stearothermophilus

International Nuclear Information System (INIS)

McAdam, M.E.; Fox, R.A.; Lavelle, F.; Fielden, E.M.

1977-01-01

The enzymic reaction mechanism of a manganese-containing superoxide dismutase from Bacillus stearothermophilus was studied by using pulse radiolysis. During catalysis (pH 8.9; 25 0 C), changes occurring in the kinetics of substrate disappearance and in the visible absorption of the enzyme at 480 nm established that the simple two-step mechanism found for copper- and iron-containing superoxide dismutases was not involved. At a low ratio ( 2 sup(-.) was close to exponential, whereas at much higher ratios (> 100) the observed decay was predominantly zero-order. The simplest interpretation of the results invokes a rapid one-electron oxidation-reduction cycle ('the fast cycle') and, concurrently, a slower reaction giving a form of the enzyme that is essentially unreactive towards O 2 sup(-.) but which undergoes a first-order decay to yield fully active native enzyme ('the slow cycle'). The fast cycle involved the native enzyme Esub(A) and a form of the enzyme Esub(B) which could be obtained also be treating the form Esub(A) with H 2 O 2 . Computer calculations made with such a simple model predicted behaviour in excellent agreement with the observed results. (author)

Temperature stability of Poly-[hemoglobin-superoxide dismutase-catalase-carbonic anhydrase] in the form of a solution or in the lyophilized form during storage at -80 °C, 4 °C, 25 °C and 37 °C or pasteurization at 70 °C.

Science.gov (United States)

Bian, Y Z; Guo, C; Chang, T M S

2016-01-01

Polyhemoglobin-superoxide dismutase-catalase-carbonic anhydrase (Poly-[Hb-SOD-CAT-CA]) contains all three major functions of red blood cells (RBCs) at an enhanced level. It transports oxygen, removes oxygen radicals and transports carbon dioxide. Our previous studies in a 90-min 30 mm Hg Mean Arterial Pressure (MAP) sustained hemorrhagic shock rat model shows that it is more effective than blood in the lowering of elevated intracellular pCO2, recovery of ST-elevation and histology of the heart and intestine. This paper is to analyze the storage and temperature stability. Allowable storage time for RBC is about 1 d at room temperature and 42 d at 4 °C. Also, RBC cannot be pasteurized to remove infective agents like HIV and Ebola. PolyHb can be heat sterilized and can be stored for 1 year even at room temperature. However, Poly-[Hb-SOD-CAT-CA] contains both Hb and enzymes and enzymes are particularly sensitive to storage and heat. We thus carried out studies to analyze its storage stability at different temperatures and heat pasteurization stability. Results of storage stability show that lyophilization extends the storage time to 1 year at 4 °C and 40 d at room temperature (compared to respectively, 42 d and 1 d for RBC). After the freeze-dry process, the enzyme activities of Poly-[SFHb-SOD-CAT-CA] was 100 ± 2% for CA, 100 ± 2% for SOD and 93 ± 3.5% for CAT. After heat pasteurization at 70 °C for 2 h, lyophilized Poly-[Hb-SOD-CAT-CA] retained good enzyme activities of CA 97 ± 4%, SOD 100 ± 2.5% and CAT 63.8 ± 4%. More CAT can be added during the crosslinking process to maintain the same enzyme ratio after heat pasteurization. Heat pasteurization is possible only for the lyophilized form of Poly-[Hb-SOD-CAT-CA] and not for the solution. It can be easily reconstituted by dissolving in suitable solutions that continues to have good storage stability though less than that for the lyophilized form. According to the P50 value, Poly-[SFHb-SOD-CAT-CA] retains its

A New Bioinspired Perchlorate Reduction Catalyst with Significantly Enhanced Stability via Rational Tuning of Rhenium Coordination Chemistry and Heterogeneous Reaction Pathway.

Science.gov (United States)

Liu, Jinyong; Han, Mengwei; Wu, Dimao; Chen, Xi; Choe, Jong Kwon; Werth, Charles J; Strathmann, Timothy J

2016-06-07

Rapid reduction of aqueous ClO4(-) to Cl(-) by H2 has been realized by a heterogeneous Re(hoz)2-Pd/C catalyst integrating Re(O)(hoz)2Cl complex (hoz = oxazolinyl-phenolato bidentate ligand) and Pd nanoparticles on carbon support, but ClOx(-) intermediates formed during reactions with concentrated ClO4(-) promote irreversible Re complex decomposition and catalyst deactivation. The original catalyst design mimics the microbial ClO4(-) reductase, which integrates Mo(MGD)2 complex (MGD = molybdopterin guanine dinucleotide) for oxygen atom transfer (OAT). Perchlorate-reducing microorganisms employ a separate enzyme, chlorite dismutase, to prevent accumulation of the destructive ClO2(-) intermediate. The structural intricacy of MGD ligand and the two-enzyme mechanism for microbial ClO4(-) reduction inspired us to improve catalyst stability by rationally tuning Re ligand structure and adding a ClOx(-) scavenger. Two new Re complexes, Re(O)(htz)2Cl and Re(O)(hoz)(htz)Cl (htz = thiazolinyl-phenolato bidentate ligand), significantly mitigate Re complex decomposition by slightly lowering the OAT activity when immobilized in Pd/C. Further stability enhancement is then obtained by switching the nanoparticles from Pd to Rh, which exhibits high reactivity with ClOx(-) intermediates and thus prevents their deactivating reaction with the Re complex. Compared to Re(hoz)2-Pd/C, the new Re(hoz)(htz)-Rh/C catalyst exhibits similar ClO4(-) reduction activity but superior stability, evidenced by a decrease of Re leaching from 37% to 0.25% and stability of surface Re speciation following the treatment of a concentrated "challenge" solution containing 1000 ppm of ClO4(-). This work demonstrates the pivotal roles of coordination chemistry control and tuning of individual catalyst components for achieving both high activity and stability in environmental catalyst applications.

Valence electron structure and properties of stabilized ZrO2

Institute of Scientific and Technical Information of China (English)

LI JinPing; HAN JieOai; MENG SongHe; ZHANG XingHong

2008-01-01

To reveal the properties of stabilizers in ZrO2 on nanoscopic levels,the valence elec-tron structures of four stable ZrO2 phases and c-ZrO2 were analyzed on the basis of the empirical electron theory of solids and molecules.The results showed that the hybridization levels of Zr atoms in c-ZrO2 doped with Ca and Mg dropped from B17 to B13,the hybridization levels of Zr atoms in c-ZrO2 doped with Y and Ce dropped from B17 to B15,and that the four stabilizing atoms all made the hybridization levels of O atoms drop from level 4 to level 2.The numbers of covalent electrons in the strongest covalent bond in the descending order are c-ZrO2>ZrCeO2>ZrYOZrMgO>ZrCaO.The bond energies of the strongest covalent bond and the melting points of the solid solutions in the descending order are ZrCeO2>c-ZrO2>ZrYO>ZrMgO>ZrCaO.The percent-ages of the total number of covalent electrons in the descending order arec-ZrO2>ZrYO> ZrCeO2>ZrMgO> ZrCaO.From the above analysis,it can be concluded that the stabilizing degrees of the four stabilizers in the descending order are CaO> MgO>Y2O3>CeO2.

Study on the Protective Effect of a New Manganese Superoxide Dismutase on the Microvilli of Rabbit Eyes Exposed to UV Radiation

OpenAIRE

Grumetto, Lucia; Del Prete, Antonio; Ortosecco, Giovanni; Barbato, Francesco; Del Prete, Salvatore; Borrelli, Antonella; Schiattarella, Antonella; Mancini, Roberto; Mancini, Aldo

2015-01-01

We present a study on the protective effects against UV radiation of a gel formulation containing a new recombinant form of manganese superoxide dismutase on the conjunctiva and corneal epithelia of rabbit eyes. The integrity of the microvilli of both ocular tissues has been considered as an indicator of the health of the tissues. Samples, collected by impression cytology technique, were added of 80??L of a gel formulation containing superoxide dismutase (2.0??g/mL) and irradiated with UV ray...

Flexible Structure Control Scheme of a UAVs Formation to Improve the Formation Stability During Maneuvers

Directory of Open Access Journals (Sweden)

Kownacki Cezary

2017-09-01

Full Text Available One of the issues related to formation flights, which requires to be still discussed, is the stability of formation flight in turns, where the aerodynamic conditions can be substantially different for outer vehicles due to varying bank angles. Therefore, this paper proposes a decentralized control algorithm based on a leader as the reference point for followers, i.e. other UAVs and two flocking behaviors responsible for local position control, i.e. cohesion and repulsion. But opposite to other research in this area, the structure of the formation becomes flexible (structure is being reshaped and bent according to actual turn radius of the leader. During turns the structure is bent basing on concentred circles with different radiuses corresponding to relative locations of vehicles in the structure. Simultaneously, UAVs' air-speeds must be modified according to the length of turn radius to achieve the stability of the structure. The effectiveness of the algorithm is verified by the results of simulated flights of five UAVs.

Phase structures of the black Dp-D(p+4)-brane system in various ensembles II: electrical and thermodynamic stability

International Nuclear Information System (INIS)

Xiao, Zhiguang; Zhou, Da

2015-01-01

By incorporating the electrical stability condition into the discussion, we continue the study on the thermodynamic phase structures of the Dp-D(p+4) black brane in GG, GC, CG, CC ensembles defined in our previous paper http://dx.doi.org/10.1007/JHEP07(2015)134. We find that including the electrical stability conditions in addition to the thermal stability conditions does not modify the phase structure of the GG ensemble but puts more constraints on the parameter space where black branes can stably exist in GC, CG, CC ensembles. In particular, the van der Waals-like phase structure which was supposed to be present in these ensembles when only thermal stability condition is considered would no longer be visible, since the phase of the small black brane is unstable under electrical fluctuations. However, the symmetry of the phase structure by interchanging the two kinds of brane charges and potentials is still preserved, which is argued to be the result of T-duality.

Relationship between the structural stability with the types and land uses in southeastern Spain

International Nuclear Information System (INIS)

Marin Sanleandro, P.; Sanchez Navarro, A.; Delgado Iniesta, M. J.; Fernandez-Delgado Juarez, M.

2009-01-01

Structural stability is one of the most important physical properties and is proposed as an indicator of quality. The aim of this study is to see the possible relationship between this property with soil types and uses of them. In this paper we have selected the Mazarron area based on their environmental characteristics and has taken forty-one topsoil samples, after analysis and study of the relationship between its structural stability with soil types and uses of same, we find a closer relationship in the case of uses that type, so that the natural soil as the percentage of stable aggregates close to 75%, while in soils anthropized this value reaches 44 %. (Author) 6 refs

Extended X-ray absorption fine structure investigation of nitrogen stabilized expanded austenite

DEFF Research Database (Denmark)

Oddershede, Jette; Christiansen, Thomas; Ståhl, Kenny

2010-01-01

As-delivered austenitic stainless steel and nitrogen stabilized expanded austenite, both fully nitrided and denitrided (in H2), were investigated with Cr, Fe and Ni extended X-ray absorption fine structure. The data shows pronounced short-range ordering of Cr and N. For the denitrided specimen...

The flow field structure of highly stabilized partially premixed flames in a concentric flow conical nozzle burner with coflow

KAUST Repository

Elbaz, Ayman M.; Zayed, M.F.; Samy, M.; Roberts, William L.; Mansour, Mohy S.

2015-01-01

The stability limits, the stabilization mechanism, and the flow field structure of highly stabilized partially premixed methane flames in a concentric flow conical nozzle burner with air co-flow have been investigated and presented in this work

First-principle study of structure and stability of nickel carbides

Energy Technology Data Exchange (ETDEWEB)

Gibson, Josh S; Uddin, Jamal; Cundari, Thomas R; Bodiford, Nelli K; Wilson, Angela K [Center for Advanced Scientific Computing and Modeling, University of North Texas, Denton, TX 76203 (United States); Department of Chemistry, University of North Texas, 1155 Union Circle 305070, Denton, TX 76203 (United States)

2010-10-10

Computational studies of nickel carbides, particularly Ni{sub 2}C, are scarce. A systematic density functional theory study is reported for Ni{sub 2}C, along with NiC and Ni{sub 3}C, to understand the stability and electronic structure of nickel carbides of varying stoichiometry. A comprehensive study was executed that involved 28 trial structures of varying space group symmetry for Ni{sub 2}C. An analysis of the electronic structure, geometry and thermodynamics of Ni{sub 2}C is performed, and compared with that for Ni{sub 3}C and NiC as well as several defect structures of varying composition. It is found that the most stable ground state arrangement of Ni{sub 2}C exists within a simple orthorhombic lattice and that it has metallic character. The calculated formation energies (kcal mol{sup -1}) of NiC, Ni{sub 2}C, and Ni{sub 3}C are 48.6, 7.9 and 6.4, respectively.

Contribution of simple saccharides to the stabilization of amyloid structure

International Nuclear Information System (INIS)

Fung, Justin; Darabie, Audrey A.; McLaurin, JoAnne

2005-01-01

The use of osmolytes or chaperones to stabilize proteins/peptides that misfold in neurodegenerative diseases is an attractive concept for drug development. We have investigated the role of a series of small carbohydrates for protection of the natively structured Alzheimer's amyloid-β peptides (Aβ). Using circular dichroism spectroscopy to follow the β-structural transitions and electron microscopy to examine tertiary structural characteristics, we demonstrate that the hydrogen bonding capacity of the carbohydrate determines the inhibition or promotion of fibrillogenesis. Three sugar molecules that vary only in their distribution of potential H-bonding partners promote various structural changes in Aβ. Two of these sugar molecules are excluded from Aβ during aggregation and promote mature fibre growth, while the other binds Aβ promoting nucleation and the accumulation of protofibrils. Our studies suggest that utilization of a combinatorial strategy to alter H-bonding capacity across a simple carbohydrate molecule may represent a novel drug design strategy

Seismic stability of a standalone glove box structure

Energy Technology Data Exchange (ETDEWEB)

Saraswat, A., E-mail: anupams@barc.gov.in [Bhabha Atomic Research Centre, Mumbai (India); Reddy, G.R. [Bhabha Atomic Research Centre, Mumbai (India); Ghosh, S. [Indian Institute of Technology Bombay, Mumbai (India); Ghosh, A.K.; Kumar, Arun [Bhabha Atomic Research Centre, Mumbai (India)

2014-09-15

Highlights: • Glove box is a leak tight, safety related structure used for handling radiotoxic materials. • To study the seismic performance of a freestanding glove box, extensive shake table testing has been carried out. • Glove box maintained structural integrity and leak tightness up to design basis earthquake loading. • Detailed three-dimensional finite element model of the structure is developed and analyzed by using direct time integration methods. • Simplified numerical method is proposed and successfully applied, to quickly estimate sliding displacement and determine upper bounds for it. - Abstract: In a nuclear fuel cycle facility, radiotoxic materials are being handled in freestanding leak tight enclosures called glove boxes (GBs). These glove boxes act as a primary confinement for the radiotoxic materials. Glove boxes are designed as per codal requirements for class I component. They are designed to withstand extreme level of earthquake loading with a return period of 10,000 years. To evaluate seismic performance of the glove box, there is a need to check the stability (sliding and overturning), structural integrity (stresses and strains) and leak tightness under earthquake loading. Extensive shake table experiments were conducted on a single standalone glove box. Actual laboratory conditions were simulated during testing to check the response. After extensive shake table testing, glove box structure was also analyzed using finite element (FE) software. Detailed three-dimensional model of glove box structure was developed and analyzed using nonlinear time history method. It was observed that finite element methods could be utilized to accurately predict dynamic response of glove box structure. This paper discusses the details and results of shake table testing and methodology used for modelling and analysing freestanding glove box structure under seismic loading. In addition, simplified numerical procedure, developed using energy conservation

Seismic stability of a standalone glove box structure

International Nuclear Information System (INIS)

Saraswat, A.; Reddy, G.R.; Ghosh, S.; Ghosh, A.K.; Kumar, Arun

2014-01-01

Highlights: • Glove box is a leak tight, safety related structure used for handling radiotoxic materials. • To study the seismic performance of a freestanding glove box, extensive shake table testing has been carried out. • Glove box maintained structural integrity and leak tightness up to design basis earthquake loading. • Detailed three-dimensional finite element model of the structure is developed and analyzed by using direct time integration methods. • Simplified numerical method is proposed and successfully applied, to quickly estimate sliding displacement and determine upper bounds for it. - Abstract: In a nuclear fuel cycle facility, radiotoxic materials are being handled in freestanding leak tight enclosures called glove boxes (GBs). These glove boxes act as a primary confinement for the radiotoxic materials. Glove boxes are designed as per codal requirements for class I component. They are designed to withstand extreme level of earthquake loading with a return period of 10,000 years. To evaluate seismic performance of the glove box, there is a need to check the stability (sliding and overturning), structural integrity (stresses and strains) and leak tightness under earthquake loading. Extensive shake table experiments were conducted on a single standalone glove box. Actual laboratory conditions were simulated during testing to check the response. After extensive shake table testing, glove box structure was also analyzed using finite element (FE) software. Detailed three-dimensional model of glove box structure was developed and analyzed using nonlinear time history method. It was observed that finite element methods could be utilized to accurately predict dynamic response of glove box structure. This paper discusses the details and results of shake table testing and methodology used for modelling and analysing freestanding glove box structure under seismic loading. In addition, simplified numerical procedure, developed using energy conservation

Designing of new structure PID controller of boost converter for solar photovoltaic stability

Science.gov (United States)

Shabrina, Hanifati Nur; Setiawan, Eko Adhi; Sabirin, Chip Rinaldi

2017-03-01

Nowadays, the utilization of renewable energy as the source on distributed generation system is increasing. It aims to reduce reliance and power losses from utility grid and improve power stability in near loads. One example of renewable energy technology that have been highly proven on the market is solar photovoltaic (PV). This technology converts photon from sunlight into electricity. However, the fluctuation of solar radiation that often occurs become the main problem for this system. Due to this condition, the power conversion is needed to convert the change frequently in photovoltaic panel into a stable voltage to the system. Developing control of boost converter has important role to keep ability of system stabilization. A conventional PID (Proportional, Integral, Derivative) control is mostly used to achieve this goal. In this research, a design of new structure PID controller of boost converter is offered to better optimize system stability comparing to the conventional PID. Parameters obtained from this PID structure have been successfully yield a stable boost converter output at 200 V with 10% overshoot, 1.5 seconds of settling time, and 1.5% of steady-state error.

Prediction and analysis of structure, stability and unfolding of thermolysin-like proteases

Science.gov (United States)

Vriend, Gert; Eijsink, Vincent

1993-08-01

Bacillus neutral proteases (NPs) form a group of well-characterized homologous enzymes, that exhibit large differences in thermostability. The three-dimensional (3D) structures of several of these enzymes have been modelled on the basis of the crystal structures of the NPs of B. thermoproteolyticus (thermolysin) and B. cercus. Several new techniques have been developed to improve the model-building procedures. Also a model-building by mutagenesis' strategy was used, in which mutants were designed just to shed light on parts of the structures that were particularly hard to model. The NP models have been used for the prediction of site-directed mutations aimed at improving the thermostability of the enzymes. Predictions were made using several novel computational techniques, such as position-specific rotamer searching, packing quality analysis and property-profile database searches. Many stabilizing mutations were predicted and produced: improvement of hydrogen bonding, exclusion of buried water molecules, capping helices, improvement of hydrophobic interactions and entropic stabilization have been applied successfully. At elevated temperatures NPs are irreversibly inactivated as a result of autolysis. It has been shown that this denaturation process is independent of the protease activity and concentration and that the inactivation follows first-order kinetics. From this it has been conjectured that local unfolding of (surface) loops, which renders the protein susceptible to autolysis, is the rate-limiting step. Despite the particular nature of the thermal denaturation process, normal rules for protein stability can be applied to NPs. However, rather than stabilizing the whole protein against global unfolding, only a small region has to be protected against local unfolding. In contrast to proteins in general, mutational effects in proteases are not additive and their magnitude is strongly dependent on the location of the mutation. Mutations that alter the stability

Oxidative stability of milk drinks containing structured lipids produced from sunflower oil and caprylic acid

DEFF Research Database (Denmark)

Timm Heinrich, Maike; Xu, Xuebing; Nielsen, Nina Skall

2003-01-01

Milk drinks containing 5% traditional sunflower oil (SO), randomized lipid (RL) or specific structured lipid (SL) (both produced from SO and tricaprylin/caprylic acid) were compared with respect to their particle size, viscosity and oxidative stability during storage. Furthermore, the effect...... drink could not be ascribed was most likely influenced by the structure of the lipid and to a single factor, differences in the process applied to produce and purify the lipids. EDTA was a strong antioxidant, while gallic acid did not exert a distinct antioxidative effect in the milk drink based on SL....... of adding potential antioxidants EDTA or gallic acid to the milk drink based on SL was investigated. The lipid type significantly affected the oxidative stability of the milk drinks: Milk drink based on SL oxidized faster than milk drink based on RL or SO. The reduced oxidative stability in the SL milk...

Straightforward and accurate technique for post-coupler stabilization in drift tube linac structures

Directory of Open Access Journals (Sweden)

Mohammad Reza Khalvati

2016-04-01

Full Text Available The axial electric field of Alvarez drift tube linacs (DTLs is known to be susceptible to variations due to static and dynamic effects like manufacturing tolerances and beam loading. Post-couplers are used to stabilize the accelerating fields of DTLs against tuning errors. Tilt sensitivity and its slope have been introduced as measures for the stability right from the invention of post-couplers but since then the actual stabilization has mostly been done by tedious iteration. In the present article, the local tilt-sensitivity slope TS_{n}^{′} is established as the principal measure for stabilization instead of tilt sensitivity or some visual slope, and its significance is developed on the basis of an equivalent-circuit diagram of the DTL. Experimental and 3D simulation results are used to analyze its behavior and to define a technique for stabilization that allows finding the best post-coupler settings with just four tilt-sensitivity measurements. CERN’s Linac4 DTL Tank 2 and Tank 3 have been stabilized successfully using this technique. The final tilt-sensitivity error has been reduced from ±100%/MHz down to ±3%/MHz for Tank 2 and down to ±1%/MHz for Tank 3. Finally, an accurate procedure for tuning the structure using slug tuners is discussed.

Straightforward and accurate technique for post-coupler stabilization in drift tube linac structures

Science.gov (United States)

Khalvati, Mohammad Reza; Ramberger, Suitbert

2016-04-01

The axial electric field of Alvarez drift tube linacs (DTLs) is known to be susceptible to variations due to static and dynamic effects like manufacturing tolerances and beam loading. Post-couplers are used to stabilize the accelerating fields of DTLs against tuning errors. Tilt sensitivity and its slope have been introduced as measures for the stability right from the invention of post-couplers but since then the actual stabilization has mostly been done by tedious iteration. In the present article, the local tilt-sensitivity slope TSn' is established as the principal measure for stabilization instead of tilt sensitivity or some visual slope, and its significance is developed on the basis of an equivalent-circuit diagram of the DTL. Experimental and 3D simulation results are used to analyze its behavior and to define a technique for stabilization that allows finding the best post-coupler settings with just four tilt-sensitivity measurements. CERN's Linac4 DTL Tank 2 and Tank 3 have been stabilized successfully using this technique. The final tilt-sensitivity error has been reduced from ±100 %/MHz down to ±3 %/MHz for Tank 2 and down to ±1 %/MHz for Tank 3. Finally, an accurate procedure for tuning the structure using slug tuners is discussed.

Effect of ionic liquid on activity, stability, and structure of enzymes: a review.

Science.gov (United States)

Naushad, Mu; Alothman, Zied Abdullah; Khan, Abbul Bashar; Ali, Maroof

2012-11-01

Ionic liquids have shown their potential as a solvent media for many enzymatic reactions as well as protein preservation, because of their unusual characteristics. It is also observed that change in cation or anion alters the physiochemical properties of the ionic liquids, which in turn influence the enzymatic reactions by altering the structure, activity, enatioselectivity, and stability of the enzymes. Thus, it is utmost need of the researchers to have full understanding of these influences created by ionic liquids before choosing or developing an ionic liquid to serve as solvent media for enzymatic reaction or protein preservation. So, in the present review, we try to shed light on effects of ionic liquids chemistry on structure, stability, and activity of enzymes, which will be helpful for the researchers in various biocatalytic applications. Copyright © 2012. Published by Elsevier B.V.

Resveratrol suppresses ethanol stress in winery and bottom brewery yeast by affecting superoxide dismutase, lipid peroxidation and fatty acid profile.

Science.gov (United States)

Gharwalova, Lucia; Sigler, Karel; Dolezalova, Jana; Masak, Jan; Rezanka, Tomas; Kolouchova, Irena

2017-11-03

Mid-exponential cultures of two traditional biotechnological yeast species, winery Saccharomyces cerevisiae and the less ethanol tolerant bottom-fermenting brewery Saccharomyces pastorianus, were exposed to different concentrations of added ethanol (3, 5 and 8%) The degree of ethanol-induced cell stress was assessed by measuring the cellular activity of superoxide dismutase (SOD), level of lipid peroxidation products, changes in cell lipid content and fatty acid profile. The resveratrol as an antioxidant was found to decrease the ethanol-induced rise of SOD activity and suppress the ethanol-induced decrease in cell lipids. A lower resveratrol concentration (0.5 mg/l) even reduced the extent of lipid peroxidation in cells. Resveratrol also alleviated ethanol-induced changes in cell lipid composition in both species by strongly enhancing the proportion of saturated fatty acids and contributing thereby to membrane stabilization. Lower resveratrol concentrations could thus diminish the negative effects of ethanol stress on yeast cells and improve their physiological state. These effects may be utilized to enhance yeast vitality in high-ethanol-producing fermentations or to increase the number of yeast generations in brewery.

Structure, elastic properties and phase stability of Cr1-xAlxN

International Nuclear Information System (INIS)

Mayrhofer, P.H.; Music, D.; Reeswinkel, Th.; Fuss, H.-G.; Schneider, J.M.

2008-01-01

The effect of composition and metal sublattice population on the phase stability, structure and elastic properties of cubic (c), hexagonal (h) and orthorhombic spin-polarized Cr 1-x Al x N was studied using ab initio calculations. Excellent correlation between ab initio and experimentally obtained lattice parameters and elastic constants was obtained. The energy of formation suggests that the cubic phase can be stabilized for x in the range 0.48-0.75, depending on the metal sublattice population. The broad range of x, which is also observed in experiments, can be understood by considering the Al distribution induced changes in the configurational contribution to the total energy

Breaking Dense Structures: Proving Stability of Densely Structured Hybrid Systems

Directory of Open Access Journals (Sweden)

Eike Möhlmann

2015-06-01

Full Text Available Abstraction and refinement is widely used in software development. Such techniques are valuable since they allow to handle even more complex systems. One key point is the ability to decompose a large system into subsystems, analyze those subsystems and deduce properties of the larger system. As cyber-physical systems tend to become more and more complex, such techniques become more appealing. In 2009, Oehlerking and Theel presented a (de-composition technique for hybrid systems. This technique is graph-based and constructs a Lyapunov function for hybrid systems having a complex discrete state space. The technique consists of (1 decomposing the underlying graph of the hybrid system into subgraphs, (2 computing multiple local Lyapunov functions for the subgraphs, and finally (3 composing the local Lyapunov functions into a piecewise Lyapunov function. A Lyapunov function can serve multiple purposes, e.g., it certifies stability or termination of a system or allows to construct invariant sets, which in turn may be used to certify safety and security. In this paper, we propose an improvement to the decomposing technique, which relaxes the graph structure before applying the decomposition technique. Our relaxation significantly reduces the connectivity of the graph by exploiting super-dense switching. The relaxation makes the decomposition technique more efficient on one hand and on the other allows to decompose a wider range of graph structures.

First Principles Prediction of Structure, Structure Selectivity, and Thermodynamic Stability under Realistic Conditions

Energy Technology Data Exchange (ETDEWEB)

Ceder, Gerbrand [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Dept. of Materials and Engineering

2018-01-28

Novel materials are often the enabler for new energy technologies. In ab-initio computational materials science, method are developed to predict the behavior of materials starting from the laws of physics, so that properties can be predicted before compounds have to be synthesized and tested. As such, a virtual materials laboratory can be constructed, saving time and money. The objectives of this program were to develop first-principles theory to predict the structure and thermodynamic stability of materials. Since its inception the program focused on the development of the cluster expansion to deal with the increased complexity of complex oxides. This research led to the incorporation of vibrational degrees of freedom in ab-initio thermodynamics, developed methods for multi-component cluster expansions, included the explicit configurational degrees of freedom of localized electrons, developed the formalism for stability in aqueous environments, and culminated in the first ever approach to produce exact ground state predictions of the cluster expansion. Many of these methods have been disseminated to the larger theory community through the Materials Project, pymatgen software, or individual codes. We summarize three of the main accomplishments.

Synthesis, Structure and Reactivity of a Borylene Cation [(NHSi)2B(CO)]+ Stabilized by Three Neutral Ligands.

Science.gov (United States)

Wang, Hao; Wu, Linlin; Lin, Zhenyang; Xie, Zuowei

2017-10-04

A borylene cation stabilized by bis(silylene) and carbon monoxide was prepared and structurally characterized via the reaction of bis(silylene)-stabilized bromoborylene with W(CO) 6 . This is the first example of a borylene cation coordinated by three neutral ligands, which can be viewed as a cationic form of a long-sought Lewis base-stabilized zerovalent boron compound. This cation can cleave dihydrogen.

PWL approximation of nonlinear dynamical systems, part I: structural stability

International Nuclear Information System (INIS)

Storace, M; De Feo, O

2005-01-01

This paper and its companion address the problem of the approximation/identification of nonlinear dynamical systems depending on parameters, with a view to their circuit implementation. The proposed method is based on a piecewise-linear approximation technique. In particular, this paper describes the approximation method and applies it to some particularly significant dynamical systems (topological normal forms). The structural stability of the PWL approximations of such systems is investigated through a bifurcation analysis (via continuation methods)

Stability study of MMC tubes and advanced assemblies for telescope structures

Science.gov (United States)

Nivet-Lutz, Martine; Pommatau, Gilles

2017-11-01

This paper presents new advances concerning the development of an Aluminum Matrix Composite for dimensionally stable satellite structures. Feasibility of thermally stable thin-walled tubes have been acquired through microstructure observation and Coefficient of Thermal Expansion measurement. In order to fit the thermo-mechanical stability domain of tubes on specifications, 3 thermal cycles have been tested, regarding to relaxation of internal stress and changes in macroscopic thermo-mechanical properties. Experimental expansion curves and microstructure observation show that thermal treatments permitts such a good fitting. For a better understanding of physical internal phenomena, internal stress has been measured by neutron diffraction on tube samples after each thermal treatment. Results show a significant decrease of stress due to cycling in cold temperature. In order to decrease the absolute value of CTE of assemblies, a new concept of thermo-mechanical stable linkage has been developped, which consists in a common alumlinum infiltration of superposed carbon preforms. Structural bonding, which usually affects stability properties and impose surface treatments and polymerization, can so be avoided. The study has been achieved through CNES (Centre National d'Etudes Spatiales) and French Ministry of Defense (DGA) supports.

STRUCTURAL STABILITY OF HIGH NITROGEN AUSTENITIC STAINLESS STEELS

Directory of Open Access Journals (Sweden)

Jana Bakajová

2011-05-01

Full Text Available This paper deals with the structural stability of an austenitic stainless steel with high nitrogen content. The investigated steel was heat treated at 800°C using different annealing times. Investigation was carried out using light microscopy, transmission electron microscopy and thermodynamic calculations. Three phases were identified by electron diffraction: Cr2N, sigma – phase and M23C6. The thermodynamic prediction is in good agreement with the experimental result. The only is the M23C6 carbide phase which is not thermodynamically predicted. Cr2N is the majority secondary phase and occurs in the form of discrete particles or cells (lamellas of Cr2N and austenite.

Hydrolytic catalysis and structural stabilization in a designed metalloprotein

Science.gov (United States)

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

2011-01-01

Metal ions are an important part of many natural proteins, providing structural, catalytic and electron transfer functions. Reproducing these functions in a designed protein is the ultimate challenge to our understanding of them. Here, we present an artificial metallohydrolase, which has been shown by X-ray crystallography to contain two different metal ions – a Zn(II) ion which is important for catalytic activity and a Hg(II) ion which provides structural stability. This metallohydrolase displays catalytic activity that compares well with several characteristic reactions of natural enzymes. It catalyses p-nitrophenyl acetate hydrolysis (pNPA) to within ~100-fold of the efficiency of human carbonic anhydrase (CA)II and is at least 550-fold better than comparable synthetic complexes. Similarly, CO2 hydration occurs with an efficiency within ~500-fold of CAII. While histidine residues in the absence of Zn(II) exhibit pNPA hydrolysis, miniscule apopeptide activity is observed for CO2 hydration. The kinetic and structural analysis of this first de novo designed hydrolytic metalloenzyme uncovers necessary design features for future metalloenzymes containing one or more metals. PMID:22270627

Pathological Roles of Wild-Type Cu, Zn-Superoxide Dismutase in Amyotrophic Lateral Sclerosis

Directory of Open Access Journals (Sweden)

Yoshiaki Furukawa

2012-01-01

Full Text Available Dominant mutations in a Cu, Zn-superoxide dismutase (SOD1 gene cause a familial form of amyotrophic lateral sclerosis (ALS. While it remains controversial how SOD1 mutations lead to onset and progression of the disease, many in vitro and in vivo studies have supported a gain-of-toxicity mechanism where pathogenic mutations contribute to destabilizing a native structure of SOD1 and thus facilitate misfolding and aggregation. Indeed, abnormal accumulation of SOD1-positive inclusions in spinal motor neurons is a pathological hallmark in SOD1-related familial ALS. Furthermore, similarities in clinical phenotypes and neuropathology of ALS cases with and without mutations in sod1 gene have implied a disease mechanism involving SOD1 common to all ALS cases. Although pathogenic roles of wild-type SOD1 in sporadic ALS remain controversial, recent developments of novel SOD1 antibodies have made it possible to characterize wild-type SOD1 under pathological conditions of ALS. Here, I have briefly reviewed recent progress on biochemical and immunohistochemical characterization of wild-type SOD1 in sporadic ALS cases and discussed possible involvement of wild-type SOD1 in a pathomechanism of ALS.

113Cd-NMR investigation of a cadmium-substituted copper, zinc-containing superoxide dismutase from yeast

DEFF Research Database (Denmark)

Kofod, Pauli; Bauer, Rogert; Danielsen, Eva

1991-01-01

113Cd nuclear magnetic resonance spectroscopy has been used to investigate the metal binding sites of cadmium-substituted copper,zinc-containing superoxide dismutase from baker's yeast. NMR signals were obtained for 113Cd(II) at the Cu site as well as for 113Cd(II) at the Zn site. The two subunits...

Effects of superoxide dismutase, dithiothreitol and formate ion on the inactivation of papain by hydroxyl and superoxide radicals in aerated solutions

International Nuclear Information System (INIS)

Lin, W.S.; Armstrong, D.A.

1978-01-01

Losses in enzyme activity and sulphydryl content have been studied in aerated papain solutions containing formate, superoxide dismutase and dithiothreitol. Both formate and dithiothreitol converted .OH to .0 2 -, whereas superoxide dismutase completely suppressed the inactivation by .0 2 -. Using results from all systems, the fraction of .0 2 - reactions with papain that caused inactivation of the enzyme was 0.33+-0.07. The results also showed that the fraction of .OH reactions, which cause inactivation of papain, is significantly higher in aerated than in oxygen-free solutions. (author)

Leaching of concrete : the leaching process : extrapolation of deterioration : effect on the structural stability

OpenAIRE

Fagerlund, Göran

2000-01-01

The leaching process when water attacks concrete, and the effect of leaching on the strength and durability of a concrete structure, is analysed theoretically. Technique for prediction of the future leaching and structural stability is outlined. The analysis is to a certain extent supported by data from literature. The leaching process is divided in five different types: 1: Pure surface leaching 2: Surface leaching involving erosion 3: Homogeneous leaching over the entire structure 4...

A first principles study of structural stability, electronic structure and mechanical properties of beryllium alanate BeAlH{sub 5}

Energy Technology Data Exchange (ETDEWEB)

Santhosh, M.; Rajeswarapalanichamy, R., E-mail: rajeswarapalanichamy@gmail.com; Priyanga, G. Sudha; Cinthia, A. Jemmy [Department of physics, N.M.S.S.V.N college, Madurai, Tamilnadu-625019 (India); Kanagaprabha, S. [Department of Physics, Kamaraj College, Tuticorin, Tamil Nadu 628003 (India); Iyakutti, K. [Department of Physics and Nanotechnology, SRM University, Chennai, Tamilnadu-603203 (India)

2015-06-24

Ab initio calculations are performed to investigate the structural stability, electronic structure and mechanical properties of BeAlH{sub 5} for monoclinic crystal structures with two different types of space group namely P2{sub 1} and C{sub 2}/c. Among the considered structures monoclinic (P2{sub 1}) phase is found to be the most stable at ambient condition. The structural phase transition from monoclinic (P2{sub 1}) to monoclinic (C{sub 2}/c) phase is observed in BeAlH{sub 5}. The electronic structure reveals that this compound is insulator. The calculated elastic constants indicate that this material is mechanically stable at ambient condition.

Formation and thermodynamic stability of (polymer + porphyrin) supramolecular structures in aqueous solutions

International Nuclear Information System (INIS)

Costa, Viviana C.P. da; Hwang, Barrington J.; Eggen, Spencer E.; Wallace, Megan J.; Annunziata, Onofrio

2014-01-01

Highlights: • Thermodynamic stability of a (polymer + porphyrin) supramolecular structure was characterized. • Isothermal titration calorimetry provided two ways to determine reaction enthalpies. • Exothermic (polymer + porphyrin) binding competes with porphyrin self-association. • (Polymer + porphyrin) binding is entropically favored with respect to porphyrin self-association. • Spectral shifts show importance of porphyrin central hydrogens in polymer binding. - Abstract: Optical properties of porphyrins can be tuned through (polymer + porphyrin) (host + guest) binding in solution. This gives rise to the formation of supramolecular structures. In this paper, the formation, thermodynamic stability and spectroscopic properties of (polymer + porphyrin) supramolecular structures and their competition with porphyrin self-association were investigated by both isothermal titration calorimetry (ITC) and absorption spectroscopy. Specifically, reaction enthalpies and equilibrium constants were measured for meso-tetrakis(4-sulfonatophenyl) porphyrin (TPPS) self-association and TPPS binding to the polymer poly(vinylpyrrolidone) (PVP, 40 kg/mol) in aqueous solutions at pH 7 and three different temperatures (12, 25 and 37 °C). ITC, compared to spectroscopic techniques, provides two independent means to determine reaction enthalpies: direct measurements and Van’t Hoff plot. This was used as a criterion to assess that (1) self-association of TPPS is limited to the formation of dimers and (2) TPPS binds to PVP in its monomeric state only. The formation of TPPS dimers and (PVP + TPPS) supramolecular structures are both enthalpically driven. However, (polymer + porphyrin) binding was found to be entropically favored compared to dimerization. Furthermore, the reaction enthalpies of these two processes significantly depend on temperature. This behavior was attributed to hydrophobic interactions. Finally, the limiting absorption spectra of monomeric, dimeric and polymer

Structure of the Nanobody-Stabilized Active State of the Kappa Opioid Receptor.

Science.gov (United States)

Che, Tao; Majumdar, Susruta; Zaidi, Saheem A; Ondachi, Pauline; McCorvy, John D; Wang, Sheng; Mosier, Philip D; Uprety, Rajendra; Vardy, Eyal; Krumm, Brian E; Han, Gye Won; Lee, Ming-Yue; Pardon, Els; Steyaert, Jan; Huang, Xi-Ping; Strachan, Ryan T; Tribo, Alexandra R; Pasternak, Gavril W; Carroll, F Ivy; Stevens, Raymond C; Cherezov, Vadim; Katritch, Vsevolod; Wacker, Daniel; Roth, Bryan L

2018-01-11

The κ-opioid receptor (KOP) mediates the actions of opioids with hallucinogenic, dysphoric, and analgesic activities. The design of KOP analgesics devoid of hallucinatory and dysphoric effects has been hindered by an incomplete structural and mechanistic understanding of KOP agonist actions. Here, we provide a crystal structure of human KOP in complex with the potent epoxymorphinan opioid agonist MP1104 and an active-state-stabilizing nanobody. Comparisons between inactive- and active-state opioid receptor structures reveal substantial conformational changes in the binding pocket and intracellular and extracellular regions. Extensive structural analysis and experimental validation illuminate key residues that propagate larger-scale structural rearrangements and transducer binding that, collectively, elucidate the structural determinants of KOP pharmacology, function, and biased signaling. These molecular insights promise to accelerate the structure-guided design of safer and more effective κ-opioid receptor therapeutics. Copyright © 2017 Elsevier Inc. All rights reserved.

Unusual Growth Phase and Oxygen Tension Regulation of Oxidative Stress Protection Enzymes, Catalase and Superoxide Dismutase, in the Phytopathogen Xanthomonas oryzae pv. oryzae

OpenAIRE

Chamnongpol, S.; Mongkolsuk, S.; Vattanaviboon, P.; Fuangthong, M.

1995-01-01

The enzymes catalase and superoxide dismutase play major roles in protecting phytopathogenic bacteria from oxidative stress. In Xanthomonas species, these enzymes are regulated by both growth phase and oxygen tension. The highest enzyme levels were detected within 1 h of growth. Continued growth resulted in a decline of both enzyme activities. High oxygen tension was an inducing signal for both enzyme activities. An 80,000-Da monofunctional catalase and a manganese superoxide dismutase were t...

Optical properties and thermal stability of germanium oxide (GeO2) nanocrystals with α-quartz structure

International Nuclear Information System (INIS)

Ramana, C.V.; Carbajal-Franco, G.; Vemuri, R.S.; Troitskaia, I.B.; Gromilov, S.A.; Atuchin, V.V.

2010-01-01

Germanium dioxide (GeO 2 ) crystals were prepared by a chemical precipitation method at a relatively low-temperature (100 o C). The grown crystals were characterized by studying their microstructure, optical properties and thermal stability. The results indicate that the grown GeO 2 crystals exhibit α-quartz type crystal structure. The lattice parameters obtained from XRD were a = 4.987(4) A and c = 5.652(5) A. Electron microscopy analysis indicates a high structural quality of GeO 2 crystals grown using the present approach. Optical absorption measurements indicate a direct bandgap of 5.72 eV without any additional bands arising from localized or defect states. Thermogravimetric measurements indicate the temperature stability of the grown GeO 2 nanocrystals. Microscopic analysis coupled with energy dispersive X-ray spectroscopy of the GeO 2 crystals with α-quartz type crystal structure indicates their stability in chemical composition up to a temperature of 400 deg. C. The surface morphology of GeO 2 crystals, however, found to be changing with the increase in temperature.

Electronic structure effects on stability and quantum conductance in 2D gold nanowires

International Nuclear Information System (INIS)

Kashid, Vikas; Shah, Vaishali; Salunke, H. G.

2011-01-01

In this study, we have investigated the stability and conductivity of unsupported, two-dimensional infinite gold nanowires using ab initio density functional theory (DFT). Two-dimensional ribbon-like nanowires with 1–5 rows of gold atoms in the non-periodic direction and with different possible structures have been considered. The nanowires with >2 rows of atoms exhibit dimerization, similar to finite wires, along the non-periodic direction. Our results show that in these zero thickness nanowires, the parallelogram motif is the most stable. A comparison between parallelogram- and rectangular-shaped nanowires of increasing width indicates that zero thickness (111) oriented wires have a higher stability over (100). A detailed analysis of the electronic structure, reveals that the (111) oriented structures show increased delocalization of s and p electrons in addition to a stronger delocalization of the d electrons and hence are the most stable. The density of states show that the nanowires are metallic and conducting except for the double zigzag structure, which is semiconducting. Conductance calculations show transmission for a wide range of energies in all the stable nanowires with more than two rows of atoms. The conductance channels are not purely s and have strong contributions from the d levels, and weak contributions from the p levels.

The Role of Superoxide Dismutase in Inducing of Wheat Seedlings Tolerance to Osmotic Shock

Directory of Open Access Journals (Sweden)

Oboznyi A.I.

2013-08-01

Full Text Available Influence of short-term hardening osmotic exposure (immersion in 1 M sucrose solution with subsequent transferring to distilled water for 20 min on the hydrogen peroxide generation and superoxide dismutase activity in wheat (Triticum aestivum L., cv. Elegiya seedlings and their tolerance to osmotic shock were investigated. During the initial 30 min after osmotic exposure, the increasing of hydrogen peroxide amount in roots and shoots (to a lesser extent was observed, but the resistance of the seedlings and superoxide dismutase (SOD activity decreased. Sometime later the decrease in hydrogen peroxide amount and the increase of seedlings tolerance to osmotic shock took place. SOD activity increased in 10 min after hardening osmotic exposure. Transient accumulation of hydrogen peroxide induced in this way was suppressed by the treatment of seedlings with sodium diethyldithiocarbamate (DDC, SOD inhibitor. DDC and hydrogen peroxide scavenger dimethylthiourea decreased positive hardening effect of osmotic exposure on the development of seedlings tolerance. It was concluded that SOD providing the generation of signal hydrogen peroxide pool took part in the induction of seedlings tolerance to osmotic shock development caused by preliminary hardening effect.

Correlation of structural stability with functional remodeling of high-density lipoproteins: the importance of being disordered.

Science.gov (United States)

Guha, Madhumita; Gao, Xuan; Jayaraman, Shobini; Gursky, Olga

2008-11-04

High-density lipoproteins (HDLs) are protein-lipid assemblies that remove excess cell cholesterol and prevent atherosclerosis. HDLs are stabilized by kinetic barriers that decelerate protein dissociation and lipoprotein fusion. We propose that similar barriers modulate metabolic remodeling of plasma HDLs; hence, changes in particle composition that destabilize HDLs and accelerate their denaturation may accelerate their metabolic remodeling. To test this notion, we correlate existing reports on HDL-mediated cell cholesterol efflux and esterification, which are obligatory early steps in cholesterol removal, with our kinetic studies of HDL stability. The results support our hypothesis and show that factors accelerating cholesterol efflux and esterification in model discoidal lipoproteins (including reduced protein size, reduced fatty acyl chain length, and/or increased level of cis unsaturation) destabilize lipoproteins and accelerate their fusion and apolipoprotein dissociation. Oxidation studies of plasma spherical HDLs show a similar trend: mild oxidation by Cu(2+) or OCl(-) accelerates cell cholesterol efflux, protein dissociation, and HDL fusion, while extensive oxidation inhibits these reactions. Consequently, moderate destabilization may be beneficial for HDL functions by facilitating insertion of cholesterol and lipophilic enzymes, promoting dissociation of lipid-poor apolipoproteins, which are primary acceptors of cell cholesterol, and thereby accelerating HDL metabolism. Therefore, HDL stability must be delicately balanced to maintain the structural integrity of the lipoprotein assembly and ensure structural specificity necessary for interactions of HDL with its metabolic partners, while facilitating rapid HDL remodeling and turnover at key junctures of cholesterol transport. The inverse correlation between HDL stability and remodeling illustrates the functional importance of structural disorder in macromolecular assemblies stabilized by kinetic barriers.

The study of the structural stability of the spiral laser beams propagation through inhomogeneous phase medium

Science.gov (United States)

Zinchik, Alexander A.; Muzychenko, Yana B.

2015-06-01

This paper discusses theoretical and experimental results of the investigation of light beams that retain their intensity structure during propagation and focusing. Spiral laser beams are a family of laser beams that preserve the structural stability up to scale and rotation with the propagation. Properties of spiral beams are of practical interest for laser technology, medicine and biotechnology. Researchers use a spiral beams for movement and manipulation of microparticles. Functionality laser manipulators can be significantly enhanced by using spiral beams whose intensity remains invariable. It is well known, that these beams has non-zero orbital angular momentum. Spiral beams have a complicated phase distribution in cross section. In this paper we investigate the structural stability of the laser beams having a spiral phase structure by passing them through an inhomogeneous phase medium. Laser beam is passed through a medium is characterized by a random distribution of phase in the range 0..2π. The modeling was performed using VirtualLab 5.0 (manufacturer LightTrans GmbH). Compared the intensity distribution of the spiral and ordinary laser beam after the passage of the inhomogeneous medium. It is shown that the spiral beams exhibit a significantly better structural stability during the passage phase heterogeneous environments than conventional laser beams. The results obtained in the simulation are tested experimentally. Experimental results show good agreement with the theoretical results.

A first-principles study on hydrogen in ZnS: Structure, stability and diffusion

Energy Technology Data Exchange (ETDEWEB)

Sun, Yu [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Xie, Sheng-Yi, E-mail: ayikongjian@gmail.com [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Meng, Xing, E-mail: mengxingjlu@163.com [College of Physics, Jilin University, Changchun 130012 (China)

2015-02-20

Based on first-principles calculations, the local structures and their energetic stability for impurity hydrogen (H) in semiconductor ZnS are investigated. H is most favorable to dwell in the bond center (BC) site in ZnS. The antibonding site of Zn (AB{sub Zn}) has close energy with BC. The antibonding site of S (AB{sub S}) and interstitial (I{sub H}) site have 0.19 eV and 0.44 eV energy cost, separately. The bond strength with S and Zn determines the stability of impurity H in ZnS. Meanwhile, H is highly moveable in ZnS. At the room temperature, H can overcome the barrier to diffuse through the neighboring BC site. - Highlights: • Local structures for hydrogen in ZnS are investigated. • Impurity level of hydrogen is modulated by bonding with S or Zn. • Hydrogen is highly moveable in ZnS.

Do Superoxide Dismutase (SOD) and Catalase (CAT) protect Cells from DNA Damage Induced by Active Arsenicals?

Science.gov (United States)

Superoxide dismutase (SOD) catalyzes the conversion of superoxide to hydrogen peroxide, which can be converted to water and oxygen through the action of catalase. Heterozygous mice of strain B6: 129S7-SodltmlLeb/J were obtained from Jackson Laboratories and bred to produce offspr...

First-principles study of structural stability and elastic property of pre-perovskite PbTiO3

International Nuclear Information System (INIS)

Liu Yong; Ni Li-Hong; Ren Zhao-Hui; Xu Gang; Li Xiang; Song Chen-Lu; Han Gao-Rong

2012-01-01

The structural stability and the elastic properties of a novel structure of lead titanate, which is named pre- perovskite PbTiO 3 (PP-PTO) and is constructed with TiO 6 octahedral columns arranged in a one-dimensional manner, are investigated by using first-principles calculations. PP-PTO is energetically unstable compared with conventional perovskite phases, however it is mechanically stable. The equilibrium transition pressures for changing from pre- perovskite to cubic and tetragonal phases are −0.5 GPa and −1.4 GPa, respectively, with first-order characteristics. Further, the differences in elastic properties between pre-perovskite and conventional perovskite phases are discussed for the covalent bonding network, which shows a highly anisotropic character in PP-PTO. This study provides a crucial insight into the structural stabilities of PP-PTO and conventional perovskite. (condensed matter: structural, mechanical, and thermal properties)

Effect of intradermal human recombinant copper-zinc superoxide dismutase on random pattern flaps in rats.

Science.gov (United States)

Schein, Ophir; Westreich, Melvyn; Shalom, Avshalom

2013-09-01

Studies have focused on enhancing flap viability using superoxide dismutase (SOD), but only a few used SOD from human origin, and most gave the compound systemically. We evaluated the ability of SOD to improve random skin flap survival using human recombinant copper-zinc superoxide dismutase (Hr-CuZnSOD) in variable doses, injected intradermally into the flap. Seventy male Sprague Dawley rats were randomly assigned into 4 groups. Cephalic random pattern flaps were elevated on their backs and intradermal injections of different dosages of Hr-CuZnSOD were given 15 minutes before surgery. Flap survival was evaluated by fluorescein fluorescence. Analysis of variance (ANOVA) and t test statistical analyses were performed. Flap survival in all treated groups was significantly better than in the controls. The beneficial effect of HR-CuZnSOD on flap survival is attained when it is given intradermally into the flap tissue. Theoretically, Hr-CuZnSOD delivered with local anesthetics used in flap elevation may be a valuable clinical tool. Copyright © 2012 Wiley Periodicals, Inc.

Magnet Cycles and Stability Periods of the CMS Structures from 2008 to 2013 as Observed by the Link Alignment System

International Nuclear Information System (INIS)

Arce, P.; Barcala, J.M.; Calvo, E.; Ferrando, A.; Josa, M.I.; Molinero, A.; Navarrete, J.; Oller, J.C.

2015-01-01

In this document Magnet Cycles and Stability Periods of the CMS Experiment are studied with the recorded Alignment Link System data along the 2008 to 2013 years of operation. The motions of the mechanical structures due to the magnetic field forces are studied including an in-depth analysis of the relative distance between the endcap structures and the central Tracker body during the Stability Periods to verify the mechanical stability of the detector during the physics data taking.

Status of Serum and Salivary Levels of Superoxide Dismutase in Type 2 Diabetes Mellitus with Oral Manifestations: A Case Control Study.

Science.gov (United States)

Madi, Medhini; Babu, Subhas; Kumari, Suchetha; Shetty, Shishir; Achalli, Sonika; Madiyal, Ananya; Bhat, Manohar

2016-11-01

Type 2 Diabetes Mellitus is a very well known metabolic disorder that has reached epidemic proportions worldwide. Evidence suggests that oxidative stress increases in Diabetes Mellitus because of the excessive production of reactive oxygen species and an impaired antioxidant defence mechanism. This study estimated, compared and correlated the serum and salivary Superoxide dismutase levels in healthy subjects and subjects with Type 2 Diabetes Mellitus having oral manifestations. In this study, serum and salivary Superoxide dismutase levels were estimated in 45 healthy subjects and 45 patients with Type 2 Diabetes Mellitus with oral manifestations. The mean serum and salivary Superoxide dismutase levels were significantly decreased in subjects with Type 2 Diabetes Mellitus with oral manifestations compared to the healthy subjects. Positive correlation in both healthy and diabetics was observed between serum and salivary samples. This study highlights that the abnormally high levels of oxidative stress in diabetics coupled with simultaneous decline in antioxidant defence mechanism results in complications in Diabetes mellitus. Thus exploring saliva for antioxidant markers that accurately reflect the redox status of the body is worthwhile.

Higher order structural effects stabilizing the reverse watson-crick guanine-cytosine base pair in functional RNAs

KAUST Repository

Chawla, Mohit

2013-10-10

The G:C reverse Watson-Crick (W:W trans) base pair, also known as Levitt base pair in the context of tRNAs, is a structurally and functionally important base pair that contributes to tertiary interactions joining distant domains in functional RNA molecules and also participates in metabolite binding in riboswitches. We previously indicated that the isolated G:C W:W trans base pair is a rather unstable geometry, and that dicationic metal binding to the Guanine base or posttranscriptional modification of the Guanine can increase its stability. Herein, we extend our survey and report on other H-bonding interactions that can increase the stability of this base pair. To this aim, we performed a bioinformatics search of the PDB to locate all the occurencies of G:C trans base pairs. Interestingly, 66% of the G:C trans base pairs in the PDB are engaged in additional H-bonding interactions with other bases, the RNA backbone or structured water molecules. High level quantum mechanical calculations on a data set of representative crystal structures were performed to shed light on the structural stability and energetics of the various crystallographic motifs. This analysis was extended to the binding of the preQ1 metabolite to a preQ1-II riboswitch. 2013 The Author(s).

Evaluation of the effect of non-B DNA structures on plasmid integrity via accelerated stability studies.

Science.gov (United States)

Ribeiro, S C; Monteiro, G A; Prazeres, D M F

2009-04-01

Plasmid biopharmaceuticals are a new class of medicines with an enormous potential. Attempts to increase the physical stability of highly purified supercoiled (SC) plasmid DNA in pharmaceutical aqueous solutions have relied on: (i) changing the DNA sequence, (ii) improving manufacturing to reduce deleterious impurities and initial DNA damage, and (iii) controlling the storage medium characteristics. In this work we analyzed the role of secondary structures on the degradation of plasmid molecules. Accelerated stability experiments were performed with SC, open circular (OC) and linear (L) isoforms of three plasmids which differed only in the "single-strandlike" content of their polyadenylation (poly A) signals. We have proved that the presence of more altered or interrupted (non-B) DNA secondary structures did not directly translate into an easier strand scission of the SC isoforms. Rather, those unusual structures imposed a lower degree of SC in the plasmids, leading to an increase in their resistance to thermal degradation. However, this behavior was reversed when the relaxed or L isoforms were tested, in which case the absence of SC rendered the plasmids essentially double-stranded. Overall, this work suggests that plasmid DNA sequence and secondary structures should be taken into account in future investigations of plasmid stability during prolonged storage.

Micromagnetic study of skyrmion stability in confined magnetic structures with perpendicular anisotropy

Science.gov (United States)

Novak, R. L.; Garcia, F.; Novais, E. R. P.; Sinnecker, J. P.; Guimarães, A. P.

2018-04-01

Skyrmions are emerging topological spin structures that are potentially revolutionary for future data storage and spintronics applications. The existence and stability of skyrmions in magnetic materials is usually associated to the presence of the Dzyaloshinskii-Moriya interaction (DMI) in bulk magnets or in magnetic thin films lacking inversion symmetry. While some methods have already been proposed to generate isolated skyrmions in thin films with DMI, a thorough study of the conditions under which the skyrmions will remain stable in order to be manipulated in an integrated spintronic device are still an open problem. The stability of such structures is believed to be a result of ideal combinations of perpendicular magnetic anisotropy (PMA), DMI and the interplay between geometry and magnetostatics. In the present work we show some micromagnetic results supporting previous experimental observations of magnetic skyrmions in spin-valve stacks with a wide range of DMI values. Using micromagnetic simulations of cobalt-based disks, we obtain the magnetic ground state configuration for several values of PMA, DMI and geometric parameters. Skyrmion numbers, corresponding to the topological charge, are calculated in all cases and confirm the occurrence of isolated, stable, axially symmetric skyrmions for several combinations of DMI and anisotropy constant. The stability of the skyrmions in disks is then investigated under magnetic field and spin-polarized current, in finite temperature, highlighting the limits of applicability of these spin textures in spintronic devices.

First principles study of structural stability and site preference in Co3 (W,X

Directory of Open Access Journals (Sweden)

Joshi Sri Raghunath

2014-01-01

Full Text Available Since the discovery [1] of γ′ precipitate (L12 – Co3(Al, W in the Co-Al-W ternary system, there has been an increased interest in Co-based superalloys. Since these alloys have two phase microstructures (γ + γ′ similar to Ni-based superalloys [2], they are viable candidates in high temperature applications, particularly in land-based turbines. The role of alloying on stability of the γ′ phase has been an active area of research. In this study, electronic structure calculations were done to probe the effect of alloying in Co3W with L12 structure. Compositions of type Co3(W,X, (where X/Y = Mn, Fe, Ni, Pt, Cr , Al, Si, V, W, Ta, Ti, Nb, Hf, Zr and Mo were studied. Effect of alloying on equilibrium lattice parameters and ground state energies was used to calculate Vegard's coefficients and site preference related data. The effect of alloying on the stability of the L12 structure vis a vis other geometrically close packed ordered structures was also studied for a range of Co3X compounds. Results suggest that the penchant of element for the W sublattice can be predicted by comparing heats of formation of Co3X in different structures.

Oxidative stability of mayonnaise and milk drink produced with structured lipids based on fish oil and caprylic acid

DEFF Research Database (Denmark)

Timm Heinrich, Maike; Xu, Xuebing; Nielsen, Nina Skall

2004-01-01

The oxidative stabilities of traditional fish oil (FO), randomized lipids (RFO), or specific structured lipids (SFO) produced from fish oil were compared when incorporated into either milk drink or mayonnaise. Furthermore, the effect of adding the potential antioxidants EDTA (240 mg...... not be ascribed to a single factor, but was most likely influenced by the structure of the lipids and differences in the processes used to produce and purify the lipids. In milk drinks based on SFO, EDTA slightly reduced oxidation, while lactoferrin did not exert a distinct antioxidative effect....../kg) or lactoferrin (1000 mg/kg) to the milk drink based on SFO was investigated. The lipid type significantly affected the oxidative stability of both mayonnaises and milk drinks: The oxidative stability decreased in the order RFO>FO>SFO. The reduced oxidative stability in the SFO food emulsions could...

Structure and Stability of Deflagrations in Porous Energetic Materials

Energy Technology Data Exchange (ETDEWEB)

stephen B. Margolis; Forman A. Williams

1999-03-01

Theoretical two-phase-flow analyses have recently been developed to describe the structure and stability of multi-phase deflagrations in porous energetic materials, in both confined and unconfined geometries. The results of these studies are reviewed, with an emphasis on the fundamental differences that emerge with respect to the two types of geometries. In particular, pressure gradients are usually negligible in unconfined systems, whereas the confined problem is generally characterized by a significant gas-phase pressure difference, or overpressure, between the burned and unburned regions. The latter leads to a strong convective influence on the burning rate arising from the pressure-driven permeation of hot gases into the solid/gas region and the consequent preheating of the unburned material. It is also shown how asymptotic models that are suitable for analyzing stability may be derived based on the largeness of an overall activation-energy parameter. From an analysis of such models, it is shown that the effects of porosity and two-phase flow are generally destabilizing, suggesting that degraded propellants, which exhibit greater porosity than their pristine counterparts, may be more readily subject to combustion instability and nonsteady deflagration.

Stability of cosmic structures in scalar-tensor theories of gravity

Energy Technology Data Exchange (ETDEWEB)

Panotopoulos, Grigoris [Universidade de Lisboa, Centro Multidisciplinar de Astrofisica, Instituto Superior Tecnico, Lisbon (Portugal); Rincon, Angel [Pontificia Universidad Catolica de Chile, Instituto de Fisica, Santiago (Chile)

2018-01-15

In the present work we study a concrete model of scalar-tensor theory of gravity characterized by two free parameters, and we compare its predictions to observational data and constraints coming from supernovae, solar system tests and the stability of cosmic structures. First an exact analytical solution at the background level is obtained. Using that solution the expression for the turnaround radius is computed. Finally we show graphically how current data and limits put bounds on the parameters of the model at hand. (orig.)

Covalent-bond stabilization of the Si(111)-(3 1 -1 1)-Pb structure

DEFF Research Database (Denmark)

Kumpf, C.; Nielsen, M.; Feidenhans'l, R.

2001-01-01

by codeposition of Pb and Sn. Our surface X-ray diffraction measurements prove that the alloy structure is closely related to the low-temperature reconstruction. The interatomic distances reveal the nature of the chemical bonding in the surface layer and provide insight into the mechanism stabilizing...

Molecular and biochemical characterization of a unique mutation in CCS, the human copper chaperone to superoxide dismutase

DEFF Research Database (Denmark)

Huppke, Peter; Brendel, Cornelia; Korenke, Georg Christoph

2012-01-01

chaperone mutations have been described to date. We describe a child from a consanguineous family who inherited homozygous mutations in the SLC33A1, encoding an acetyl CoA transporter, and in CCS, encoding the Cu chaperone for superoxide dismutase. The CCS mutation, p.Arg163Trp, predicts substitution...... of a highly conserved arginine residue at position 163, with tryptophan in domain II of CCS, which interacts directly with superoxide dismutase 1 (SOD1). Biochemical analyses of the patient's fibroblasts, mammalian cell transfections, immunoprecipitation assays, and Lys7Δ (CCS homolog) yeast complementation...... support the pathogenicity of the mutation. Expression of CCS was reduced and binding of CCS to SOD1 impaired. As a result, this mutation causes reduced SOD1 activity and may impair other mechanisms important for normal Cu homeostasis. CCS-Arg163Trp represents the primary example of a human mutation...

Structural stability analysis considerations in fusion reactor plasma chamber design

International Nuclear Information System (INIS)

Delaney, M.J.; Cramer, B.A.

1978-01-01

This paper presents an approach to analyzing a toroidal plasma chamber for the prevention of both static and dynamic buckling. Results of stability analyses performed for the doublet shaped plasma chamber of the General Atomic 3.8 meter radius TNS ignition test reactor are presented. Load conditions are the static external atmospheric pressure load and the dynamic plasma disruption pulse load. Methods for analysis of plasma chamber structures are presented for both types of load. Analysis for static buckling is based on idealizing the plasma chamber into standard structural shapes and applying classical cylinder and circular torus buckling equations. Results are verified using the Buckling of Shells of Revolution (BOSOR4) finite difference computer code. Analysis for the dynamic loading is based on a pulse buckling analysis method for circular cylinders

Dissecting the structure of surface stabilizer on the dispersion of inorganic nanoparticles in aqueous medium

Energy Technology Data Exchange (ETDEWEB)

Ding, Yong; Yu, Zongzhi; Zheng, Junping, E-mail: jpzheng@tju.edu.cn [Tianjin University, Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering (China)

2017-03-15

Dispersing inorganic nanoparticles in aqueous solutions is a key requirement for a great variety of products and processes, including carriers in drug delivery or fillers in polymers. To be highly functional in the final product, inorganic particles are required to be finely dispersed in nanoscale. In this study, silica was selected as a representative inorganic particle. Surface stabilizers with different chain length and charged group were designed to reveal the influence of electrostatic and van der Waals forces between silica and stabilizer on the dispersion of silica particles in aqueous medium. Results showed surface stabilizer with longer alkyl chain and charged group exerted best ability to deaggregate silica, leading to a hydrodynamic size of 51.1 nm. Surface stabilizer designing with rational structure is a promising solution for deagglomerating and reducing process time and energy. Giving the designability and adaptability of surface stabilizer, this method is of potential for dispersion of other inorganic nanoparticles.

Dissecting the structure of surface stabilizer on the dispersion of inorganic nanoparticles in aqueous medium

Science.gov (United States)

Ding, Yong; Yu, Zongzhi; Zheng, Junping

2017-03-01

Dispersing inorganic nanoparticles in aqueous solutions is a key requirement for a great variety of products and processes, including carriers in drug delivery or fillers in polymers. To be highly functional in the final product, inorganic particles are required to be finely dispersed in nanoscale. In this study, silica was selected as a representative inorganic particle. Surface stabilizers with different chain length and charged group were designed to reveal the influence of electrostatic and van der Waals forces between silica and stabilizer on the dispersion of silica particles in aqueous medium. Results showed surface stabilizer with longer alkyl chain and charged group exerted best ability to deaggregate silica, leading to a hydrodynamic size of 51.1 nm. Surface stabilizer designing with rational structure is a promising solution for deagglomerating and reducing process time and energy. Giving the designability and adaptability of surface stabilizer, this method is of potential for dispersion of other inorganic nanoparticles.

Extracellular superoxide dismutase is necessary to maintain renal blood flow during sepsis development.

Science.gov (United States)

Constantino, Larissa; Galant, Letícia Selinger; Vuolo, Francieli; Guarido, Karla Lorena; Kist, Luiza Wilges; de Oliveira, Giovanna Medeiros Tavares; Pasquali, Matheus Augusto de Bittencourt; de Souza, Cláudio Teodoro; da Silva-Santos, José Eduardo; Bogo, Maurício Reis; Moreira, José Cláudio Fonseca; Ritter, Cristiane; Dal-Pizzol, Felipe

2017-12-01

Extracellular superoxide dismutase (ECSOD) protects nitric oxide (NO) bioavailability by decreasing superoxide levels and preventing peroxynitrite generation, which is important in maintaining renal blood flow and in preventing acute kidney injury. However, the profile of ECSOD expression after sepsis is not fully understood. Therefore, we intended to evaluate the content and gene expression of superoxide dismutase (SOD) isoforms in the renal artery and their relation to renal blood flow. Sepsis was induced in Wistar rats by caecal ligation and perforation. Several times after sepsis induction, renal blood flow (12, 24 and 48 h); the renal arterial content of SOD isoforms, nitrotyrosine, endothelial and inducible nitric oxide synthase (e-NOS and i-NOS), and phosphorylated vasodilator-stimulated phosphoprotein (pVASP); and SOD activity (3, 6 and 12 h) were measured. The influence of a SOD inhibitor was also evaluated. An increase in ECSOD content was associated with decreased 3-nitrotyrosine levels. These events were associated with an increase in pVASP content and maintenance of renal blood flow. Moreover, previous treatment with a SOD inhibitor increased nitrotyrosine content and reduced renal blood flow. ECSOD appears to have a major role in decreasing peroxynitrite formation in the renal artery during the early stages of sepsis development, and its application can be important in renal blood flow control and maintenance during septic insult.

Structural stabilities and electronic properties of Mg28-nAln clusters: A first-principles study

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Bao-Juan Lu

2017-09-01

Full Text Available In this paper, we have constructed the alloy configurations of Mg28-nAln by replacing atoms at various possible positions, starting from the stable structures of Mg28 and Al28 clusters. According to the symmetry of the cluster structure, the isomers of these initial structures have been screened with the congruence check, which would reduce computational hours and improve efficiency. Using the first-principles method, the structural evolution, mixing behavior and electronic properties of Mg28-nAln clusters are investigated for all compositions. We conclude that Al atoms prefer to reside in the central positions of Mg−Al clusters and Mg atoms tend to occupy the peripheral location. The negative mixing enthalpies imply the stabilities of these Mg-Al clusters and thus possible applications in catalysis and hydrogen storage materials. Among Mg28-nAln clusters, Mg24Al4, Mg21Al7, Mg14Al14, Mg26Al2 and Mg27Al1 present relatively high thermodynamic stabilities, and the electronic properties of these stable structures are discussed with the charge distributions around the Fermi level.

Cloning and characterization of iron-superoxide dismutase in Antarctic yeast strain Rhodotorula mucilaginosa AN5.

Science.gov (United States)

Kan, Guangfeng; Wen, Hua; Wang, Xiaofei; Zhou, Ting; Shi, Cuijuan

2017-08-01

A novel superoxide dismutase gene from Antarctic yeast Rhodotorula mucilaginosa AN5 was cloned, sequenced, and then expressed in Escherichia coli. The R. mucilaginosa AN5 SOD (RmFeSOD) gene was 639 bp open reading frame in length, which encoded a protein of 212 amino acids with a deduced molecular mass of 23.5 kDa and a pI of 7.89. RmFeSOD was identified as iron SOD type with a natural status of homodimer. The recombinant RmFeSOD showed good pH stability in the pH 1.0-9.0 after 1 h incubation. Meanwhile, it was found to behave relatively high thermostability, and maintained more than 80% activity at 50 °C for 1 h. By addition of 1 mM metal ions, the enzyme activity increased by Zn 2+ , Cu 2+ , Mn 2+ , and Fe 3+ , and inhibited only by Mg 2+ . RmFeSOD showed relatively low tolerance to some compounds, such as PMSF, SDS, Tween-80, Triton X-100, DMSO, β-ME, and urea. However, DTT showed no inhibition to enzyme activity. Using copper stress experiment, the RmFeSOD recombinant E. coli exhibited better growth than non-recombinant bacteria, which revealed that RmFeSOD might play an important role in the adaptability of heavy metals. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analysis on complex structure stability under different bar angle with BIM technology

Directory of Open Access Journals (Sweden)

Wang Xiongjue

2016-03-01

Full Text Available Sun Valley, the landmark building of World Expo in Shanghai, which has free surface with single-layer reticulated shell structure, is a typical complex structure. CAD/CAM integrated information system to design is used for the complex structure; however, it is a very rigorous process to be used widely. The relevant technology of the Sun Valley is not open to the public at present, so we try to use BIM technology to model the Sun Valley, including architecture modelling and structure analysis. By analysis of the Sun Valley structure using this method, it is proved that the problems in modelling may be solved by writing some script codes in Rhino software and the stability of the model can also be analyzed. The new approach is viable and effective in combination with different softwares such as Rhino, Revit, and Midas in solution of the complex shaped surfaces’ structure for modelling and calculation.

Assessment of Slope Stability and Interference of Structures Considering Seismity in Complex Engineering-Geological Conditions Using the Method of Finite Elements

International Nuclear Information System (INIS)

Menabdishvili, Papuna; Eremadze, Nelly

2008-01-01

There is elaborated the calculation model of slope deformation mode stability and the methodic of calculation considering the interference of structures to be built on it using the method of finite elements. There is examined the task of slope stability using the soil physically nonlinear finite element considering the seismicity 8. The deformation mode and field of coefficients of stability are obtained and slope supposed sliding curve is determined. The elaborated calculation methodic allows to determine the slope deformation mode, stability and select the optimum version of structure foundation at any slant and composition of slope layers

Protein secondary structure and stability determined by combining exoproteolysis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Science.gov (United States)

Villanueva, Josep; Villegas, Virtudes; Querol, Enrique; Avilés, Francesc X; Serrano, Luis

2002-09-01

In the post-genomic era, several projects focused on the massive experimental resolution of the three-dimensional structures of all the proteins of different organisms have been initiated. Simultaneously, significant progress has been made in the ab initio prediction of protein three-dimensional structure. One of the keys to the success of such a prediction is the use of local information (i.e. secondary structure). Here we describe a new limited proteolysis methodology, based on the use of unspecific exoproteases coupled with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), to map quickly secondary structure elements of a protein from both ends, the N- and C-termini. We show that the proteolytic patterns (mass spectra series) obtained can be interpreted in the light of the conformation and local stability of the analyzed proteins, a direct correlation being observed between the predicted and the experimentally derived protein secondary structure. Further, this methodology can be easily applied to check rapidly the folding state of a protein and characterize mutational effects on protein conformation and stability. Moreover, given global stability information, this methodology allows one to locate the protein regions of increased or decreased conformational stability. All of this can be done with a small fraction of the amount of protein required by most of the other methods for conformational analysis. Thus limited exoproteolysis, together with MALDI-TOF MS, can be a useful tool to achieve quickly the elucidation of protein structure and stability. Copyright 2002 John Wiley & Sons, Ltd.

Correlating the Impact of Well-Defined Oligosaccharide Structures on Physical Stability Profiles of IgG1-Fc Glycoforms.

Science.gov (United States)

More, Apurva S; Toprani, Vishal M; Okbazghi, Solomon Z; Kim, Jae H; Joshi, Sangeeta B; Middaugh, C Russell; Tolbert, Thomas J; Volkin, David B

2016-02-01

As part of a series of articles in this special issue describing 4 well-defined IgG1-Fc glycoforms as a model system for biosimilarity analysis (high mannose-Fc, Man5-Fc, GlcNAc-Fc and N297Q-Fc aglycosylated), the focus of this work is comparisons of their physical properties. A trend of decreasing apparent solubility (thermodynamic activity) by polyethylene glycol precipitation (pH 4.5, 6.0) and lower conformational stability by differential scanning calorimetry (pH 4.5) was observed with reducing size of the N297-linked oligosaccharide structures. Using multiple high-throughput biophysical techniques, the physical stability of the Fc glycoproteins was then measured in 2 formulations (NaCl and sucrose) across a wide range of temperatures (10°C-90°C) and pH (4.0-7.5) conditions. The data sets were used to construct 3-index empirical phase diagrams and radar charts to visualize the regions of protein structural stability. Each glycoform showed improved stability in the sucrose (vs. salt) formulation. The HM-Fc and Man5-Fc displayed the highest relative stability, followed by GlcNAc-Fc, with N297Q-Fc being the least stable. Thus, the overall physical stability profiles of the 4 IgG1-Fc glycoforms also show a correlation with oligosaccharide structure. These data sets are used to develop a mathematical model for biosimilarity analysis (as described in a companion article by Kim et al. in this issue). Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Thermodynamic Stability of Structure H Hydrates Based on the Molecular Properties of Large Guest Molecules

OpenAIRE

Tezuka, Kyoichi; Taguchi, Tatsuhiko; Alavi, Saman; Sum, Amadeu K.; Ohmura, Ryo

2012-01-01

This paper report analyses of thermodynamic stability of structure-H clathrate hydrates formed with methane and large guest molecules in terms of their gas phase molecular sizes and molar masses for the selection of a large guest molecule providing better hydrate stability. We investigated the correlation among the gas phase molecular sizes, the molar masses of large molecule guest substances, and the equilibrium pressures. The results suggest that there exists a molecular-size value for the ...

Myocardial capillary permeability after regional ischemia and reperfusion in the in vivo canine heart. Effect of superoxide dismutase

DEFF Research Database (Denmark)

Svendsen, Jesper Hastrup; Bjerrum, P J; Haunsø, S

1991-01-01

coronary artery followed by 1 hour of reperfusion. Myocardial plasma flow rate and capillary extraction of chromium 51-labeled EDTA or technetium 99m-labeled diethylenetriaminepentaacetic acid were measured by the single-injection, residue-detection method before ischemia and 5 and 60 minutes after...... fibrillation in contrast to none in the superoxide dismutase group. Before ischemia, plasma flow rate, myocardial capillary extraction fraction, and PS values were similar in the two groups. Five minutes after the start of reperfusion, plasma flow rate increased significantly (p less than 0.01) in both groups....... In the control group, capillary extraction fraction increased by 12% (p = NS) in spite of the higher plasma flow; these increases in capillary extraction fraction and plasma flow induced a 69% increase in PS (p less than 0.01). In the superoxide dismutase-treated group, capillary extraction fraction decreased...

An experimental model of acute encephalopathy after total body irradiation in the rat: effect of liposome-entrapped Cu/Zn superoxide dismutase

International Nuclear Information System (INIS)

Lamproglou, Ioannis; Magdelenat, Henri; Boisserie, Gilbert; Baillet, Francois; Mayo, Willy; Fessi, Hatem; Puisieux, Francis; Perderau, Bernard; Colas-Linhart, Nicole; Delattre, Jean-Yves

1998-01-01

Purpose: To develop an experimental model of acute encephalopathy following total body irradiation in rats and to define the therapeutic effect of liposome-entrapped Cu/Zn superoxide dismutase. Methods and Materials: A total of 120 4-month-old rats received 4.5 Gy total body irradiation (TBI) while 120 rats received sham irradiation. A behavioral study based on a conditioning test of negative reinforcement, the one-way avoidance test, was performed 5 hours before irradiation and repeated the following days. Subcutaneous treatment was started 1 hour after irradiation and repeated daily for 2 weeks. In both the irradiated and sham group, three subgroups were defined according to the treatment received: liposome-entrapped Cu/Zn superoxide dismutase (0.5 mg/kg), liposomes only, normal saline. Results: This work comprised two consecutive studies. In study A (90 rats) the one-way avoidance test was administered daily from day 0 to day 4 with a recall session at day 14. In study B (validation phase in 150 rats) the behavioral test was performed only from day 0 to day 6. Before irradiation, all rats showed a similar behavioral response. Study A (6 groups of 15 rats): Following TBI, irradiated rats treated with liposomes only or saline demonstrated a significant delay in learning the one-way avoidance test in comparison with sham-irradiated rats (0.05 < p <0.001 depending upon the day of evaluation and the subgroup type). In contrast, irradiated rats treated with liposome-entrapped Cu/Zn superoxide dismutase did not differ from sham-irradiated rats. Study B (6 groups of 25 rats): The results were the same as those in study A, demonstrating a significant delay in the learning of the test in the liposome and saline-treated irradiated rats in comparison with sham-irradiated rats (0.02 < p < 0.001). The irradiated rats, treated with liposome-entrapped Cu/Zn superoxide dismutase did not differ from the sham-irradiated controls. Conclusion: This study indicates that a relatively

Manganese Superoxide Dismutase Gene Expression Is Induced by Nanog and Oct4, Essential Pluripotent Stem Cells’ Transcription Factors

Science.gov (United States)

Solari, Claudia; Vázquez Echegaray, Camila; Cosentino, María Soledad; Petrone, María Victoria; Waisman, Ariel; Luzzani, Carlos; Francia, Marcos; Villodre, Emilly; Lenz, Guido; Miriuka, Santiago; Barañao, Lino; Guberman, Alejandra

2015-01-01

Pluripotent stem cells possess complex systems that protect them from oxidative stress and ensure genomic stability, vital for their role in development. Even though it has been reported that antioxidant activity diminishes along stem cell differentiation, little is known about the transcriptional regulation of the involved genes. The reported modulation of some of these genes led us to hypothesize that some of them could be regulated by the transcription factors critical for self-renewal and pluripotency in embryonic stem cells (ESCs) and in induced pluripotent stem cells (iPSCs). In this work, we studied the expression profile of multiple genes involved in antioxidant defense systems in both ESCs and iPSCs. We found that Manganese superoxide dismutase gene (Mn-Sod/Sod2) was repressed during diverse differentiation protocols showing an expression pattern similar to Nanog gene. Moreover, Sod2 promoter activity was induced by Oct4 and Nanog when we performed a transactivation assay using two different reporter constructions. Finally, we studied Sod2 gene regulation by modulating the expression of Oct4 and Nanog in ESCs by shRNAs and found that downregulation of any of them reduced Sod2 expression. Our results indicate that pluripotency transcription factors positively modulate Sod2 gene transcription. PMID:26642061

Targeting of superoxide dismutase to the liver results in anti-inflammatory effects in rats with fibrotic livers

NARCIS (Netherlands)

Swart, P J; Hirano, T; Kuipers, M E; Ito, Y; Smit, C; Hashida, M; Nishikawa, M; Beljaars, L; Meijer, D K; Poelstra, K

1999-01-01

Background/Aims: The rapid clearance from plasma and the limited uptake of superoxide dismutase (SOD) in the liver hampers the effectiveness of this enzyme in liver diseases. We therefore compared the pharmacokinetics and in vivo efficacy of SOD with two modified forms of this protein: SOD coupled

Dynamical stability in fluid-structure interaction

International Nuclear Information System (INIS)

Planchard, J.; Thomas, B.

1991-01-01

The aim of the paper is to investigate the dynamical stability of a group of elastic tubes placed in a cross-flow which obeys to the Navier-Stokes equations. The stability of this coupled system is deduced from the study of a quadratic eigenvalue problem arising in the linearized equations. The instability occurs when the real part of one of the eigenvalues becomes positive; the steady state is then replaced by a time-periodic state which is stable (Hopf bifurcation phenomenon). Some numerical methods for solving the quadratic eigenvalue problem are described [fr

The Grading Entropy-based Criteria for Structural Stability of Granular Materials and Filters

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Janos Lőrincz

2015-05-01

Full Text Available This paper deals with three grading entropy-based rules that describe different soil structure stability phenomena: an internal stability rule, a filtering rule and a segregation rule. These rules are elaborated on the basis of a large amount of laboratory testing and from existing knowledge in the field. Use is made of the theory of grading entropy to derive parameters which incorporate all of the information of the grading curve into a pair of entropy-based parameters that allow soils with common behaviours to be grouped into domains on an entropy diagram. Applications of the derived entropy-based rules are presented by examining the reason of a dam failure, by testing against the existing filter rules from the literature, and by giving some examples for the design of non-segregating grading curves (discrete particle size distributions by dry weight. A physical basis for the internal stability rule is established, wherein the higher values of base entropy required for granular stability are shown to reflect the closeness between the mean and maximum grain diameters, which explains how there are sufficient coarser grains to achieve a stable grain skeleton.

Parasitization by Scleroderma guani influences expression of superoxide dismutase genes in Tenebrio molitor.

Science.gov (United States)

Zhu, Jia-Ying; Ze, Sang-Zi; Stanley, David W; Yang, Bin

2014-09-01

Superoxide dismutase (SOD) is an antioxidant enzyme involved in detoxifying reactive oxygen species. In this study, we identified genes encoding the extracellular and intracellular copper-zinc SODs (ecCuZnSOD and icCuZnSOD) and a manganese SOD (MnSOD) in the yellow mealworm beetle, Tenebrio molitor. The cDNAs for ecCuZnSOD, icCuZnSOD, and MnSOD, respectively, encode 24.55, 15.81, and 23.14 kDa polypeptides, which possess structural features typical of other insect SODs. They showed 20-94% identity to other known SOD sequences from Bombyx mori, Musca domestica, Nasonia vitripennis, Pediculus humanus corporis, and Tribolium castaneum. Expression of these genes was analyzed in selected tissues and developmental stages, and following exposure to Escherichia coli and parasitization by Scleroderma guani. We recorded expression of all three SODs in cuticle, fat body, and hemocytes and in the major developmental stages. Relatively higher expressions were detected in late-instar larvae and pupae, compared to other developmental stages. Transcriptional levels were upregulated following bacterial infection. Analysis of pupae parasitized by S. guani revealed that expression of T. molitor SOD genes was significantly induced following parasitization. We infer that these genes act in immune response and in host-parasitoid interactions. © 2014 Wiley Periodicals, Inc.

Molecular Characterization of a Recombinant Manganese Superoxide Dismutase from Lactococcus lactis M4

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Boon Hooi Tan

2014-01-01

Full Text Available A superoxide dismutase (SOD gene of Lactococcus lactis M4 was cloned and expressed in a prokaryotic system. Sequence analysis revealed an open reading frame of 621 bp which codes for 206 amino acid residues. Expression of sodA under T7 promoter exhibited a specific activity of 4967 U/mg when induced with 1 mM of isopropyl-β-D-thiogalactopyranoside. The recombinant SOD was purified to homogeneity by immobilised metal affinity chromatography and Superose 12 gel filtration chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western blot analyses of the recombinant SOD detected a molecular mass of approximately 27 kDa. However, the SOD was in dimer form as revealed by gel filtration chromatography. The purified recombinant enzyme had a pI of 4.5 and exhibited maximal activity at 25°C and pH 7.2. It was stable up to 45°C. The insensitivity of this lactococcal SOD to cyanide and hydrogen peroxide established that it was a MnSOD. Although it has 98% homology to SOD of L. lactis IL1403, this is the first elucidated structure of lactococcal SOD revealing active sites containing the catalytic manganese coordinated by four ligands (H-27, H-82, D-168, and H-172.

Metal Hydride Nanoparticles with Ultrahigh Structural Stability and Hydrogen Storage Activity Derived from Microencapsulated Nanoconfinement.

Science.gov (United States)

Zhang, Jiguang; Zhu, Yunfeng; Lin, Huaijun; Liu, Yana; Zhang, Yao; Li, Shenyang; Ma, Zhongliang; Li, Liquan

2017-06-01

Metal hydrides (MHs) have recently been designed for hydrogen sensors, switchable mirrors, rechargeable batteries, and other energy-storage and conversion-related applications. The demands of MHs, particular fast hydrogen absorption/desorption kinetics, have brought their sizes to nanoscale. However, the nanostructured MHs generally suffer from surface passivation and low aggregation-resisting structural stability upon absorption/desorption. This study reports a novel strategy named microencapsulated nanoconfinement to realize local synthesis of nano-MHs, which possess ultrahigh structural stability and superior desorption kinetics. Monodispersed Mg 2 NiH 4 single crystal nanoparticles (NPs) are in situ encapsulated on the surface of graphene sheets (GS) through facile gas-solid reactions. This well-defined MgO coating layer with a thickness of ≈3 nm efficiently separates the NPs from each other to prevent aggregation during hydrogen absorption/desorption cycles, leading to excellent thermal and mechanical stability. More interestingly, the MgO layer shows superior gas-selective permeability to prevent further oxidation of Mg 2 NiH 4 meanwhile accessible for hydrogen absorption/desorption. As a result, an extremely low activation energy (31.2 kJ mol -1 ) for the dehydrogenation reaction is achieved. This study provides alternative insights into designing nanosized MHs with both excellent hydrogen storage activity and thermal/mechanical stability exempting surface modification by agents. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enzyme stability, thermodynamics and secondary structures of α-amylase as probed by the CD spectroscopy.

Science.gov (United States)

Kikani, B A; Singh, S P

2015-11-01

An amylase of a thermophilic bacterium, Bacillus sp. TSSC-3 (GenBank Number, EU710557) isolated from the Tulsi Shyam hot spring reservoir (Gujarat, India) was purified to the homogeneity in a single step on phenyl sepharose 6FF. The molecular weight of the enzyme was 25kD, while the temperature and pH optima for the enzyme catalysis were 80°C and 7, respectively. The purified enzyme was highly thermostable with broad pH stability and displayed remarkable resistance against surfactants, chelators, urea, guanidine HCl and various solvents as well. The stability and changes in the secondary structure of the enzyme under various extreme conditions were determined by the circular dichroism (CD) spectroscopy. The stability trends and the changes in the α-helices and β-sheets were analyzed by Mean Residual Ellipticity (MRE) and K2D3. The CD data confirmed the structural stability of the enzyme under various harsh conditions, yet it indicated reduced α-helix content and increased β-sheets upon denaturation. The thermodynamic parameters; deactivation rate constant, half-life, changes in entropy, enthalpy, activation energy and Gibb's free energy indicated that the enzyme-substrate reactions were highly stable. The overall profile of the enzyme: high thermostability, alkalitolerance, calcium independent nature, dextrose equivalent values and resistance against chemical denaturants, solvents and surfactants suggest its commercial applications. Copyright © 2015 Elsevier B.V. All rights reserved.

Stability, electrochemical behaviors and electronic structures of iron hydroxyl-phosphate

International Nuclear Information System (INIS)

Wang Zhongli; Sun Shaorui; Li Fan; Chen Ge; Xia Dingguo; Zhao Ting; Chu Wangsheng; Wu Ziyu

2010-01-01

Iron hydroxyl-phosphate with a uniform spherical particle size of around 1 μm, a compound of the type Fe 2-y □ y (PO 4 )(OH) 3-3y (H 2 O) 3y-2 (where □ represents a vacancy), has been synthesized by hydrothermal methods. The particles are composed of spheres of diameter -1 and 120 mAh g -1 at current densities of 170 mA g -1 and 680 mA g -1 , respectively. The stability of crystal structure of this material was studied by TGA and XRD which show that the material remains stable at least up to the temperature 200 deg. C. Investigation of the electronic structure of the iron hydroxyl-phosphate by GGA + U calculation has indicated that it has a better electronic conductivity than LiFePO 4 .

Atomistic structural ensemble refinement reveals non-native structure stabilizes a sub-millisecond folding intermediate of CheY

International Nuclear Information System (INIS)

Shi, Jade; Schwantes, Christian; Bilsel, Osman

2017-01-01

The dynamics of globular proteins can be described in terms of transitions between a folded native state and less-populated intermediates, or excited states, which can play critical roles in both protein folding and function. Excited states are by definition transient species, and therefore are difficult to characterize using current experimental techniques. We report an atomistic model of the excited state ensemble of a stabilized mutant of an extensively studied flavodoxin fold protein CheY. We employed a hybrid simulation and experimental approach in which an aggregate 42 milliseconds of all-atom molecular dynamics were used as an informative prior for the structure of the excited state ensemble. The resulting prior was then refined against small-angle X-ray scattering (SAXS) data employing an established method (EROS). The most striking feature of the resulting excited state ensemble was an unstructured N-terminus stabilized by non-native contacts in a conformation that is topologically simpler than the native state. We then predict incisive single molecule FRET experiments, using these results, as a means of model validation. Our study demonstrates the paradigm of uniting simulation and experiment in a statistical model to study the structure of protein excited states and rationally design validating experiments.

Development of a Cloud Computing-Based Pier Type Port Structure Stability Evaluation Platform Using Fiber Bragg Grating Sensors.

Science.gov (United States)

Jo, Byung Wan; Jo, Jun Ho; Khan, Rana Muhammad Asad; Kim, Jung Hoon; Lee, Yun Sung

2018-05-23

Structure Health Monitoring is a topic of great interest in port structures due to the ageing of structures and the limitations of evaluating structures. This paper presents a cloud computing-based stability evaluation platform for a pier type port structure using Fiber Bragg Grating (FBG) sensors in a system consisting of a FBG strain sensor, FBG displacement gauge, FBG angle meter, gateway, and cloud computing-based web server. The sensors were installed on core components of the structure and measurements were taken to evaluate the structures. The measurement values were transmitted to the web server via the gateway to analyze and visualize them. All data were analyzed and visualized in the web server to evaluate the structure based on the safety evaluation index (SEI). The stability evaluation platform for pier type port structures involves the efficient monitoring of the structures which can be carried out easily anytime and anywhere by converging new technologies such as cloud computing and FBG sensors. In addition, the platform has been successfully implemented at “Maryang Harbor” situated in Maryang-Meyon of Korea to test its durability.

Superoxide Dismutase 2 is dispensable for platelet function.

Science.gov (United States)

Fidler, Trevor P; Rowley, Jesse W; Araujo, Claudia; Boudreau, Luc H; Marti, Alex; Souvenir, Rhonda; Dale, Kali; Boilard, Eric; Weyrich, Andrew S; Abel, E Dale

2017-10-05

Increased intracellular reactive oxygen species (ROS) promote platelet activation. The sources of platelet-derived ROS are diverse and whether or not mitochondrial derived ROS, modulates platelet function is incompletely understood. Studies of platelets from patients with sickle cell disease, and diabetes suggest a correlation between mitochondrial ROS and platelet dysfunction. Therefore, we generated mice with a platelet specific knockout of superoxide dismutase 2 (SOD2-KO) to determine if increased mitochondrial ROS increases platelet activation. SOD2-KO platelets demonstrated decreased SOD2 activity and increased mitochondrial ROS, however total platelet ROS was unchanged. Mitochondrial function and content were maintained in non-stimulated platelets. However SOD2-KO platelets demonstrated decreased mitochondrial function following thrombin stimulation. In vitro platelet activation and spreading was normal and in vivo, deletion of SOD2 did not change tail-bleeding or arterial thrombosis indices. In pathophysiological models mediated by platelet-dependent immune mechanisms such as sepsis and autoimmune inflammatory arthritis, SOD2-KO mice were phenotypically identical to wildtype controls. These data demonstrate that increased mitochondrial ROS does not result in platelet dysfunction.

Distinguishing Active Site Characteristics of Chlorite Dismutases with Their Cyanide Complexes.

Science.gov (United States)

Geeraerts, Zachary; Celis, Arianna I; Mayfield, Jeffery A; Lorenz, Megan; Rodgers, Kenton R; DuBois, Jennifer L; Lukat-Rodgers, Gudrun S

2018-03-06

O 2 -evolving chlorite dismutases (Clds) efficiently convert chlorite (ClO 2 - ) to O 2 and Cl - . Dechloromonas aromatica Cld ( DaCld) is a highly active chlorite-decomposing homopentameric enzyme, typical of Clds found in perchlorate- and chlorate-respiring bacteria. The Gram-negative, human pathogen Klebsiella pneumoniae contains a homodimeric Cld ( KpCld) that also decomposes ClO 2 - , albeit with an activity 10-fold lower and a turnover number lower than those of DaCld. The interactions between the distal pocket and heme ligand of the DaCld and KpCld active sites have been probed via kinetic, thermodynamic, and spectroscopic behaviors of their cyanide complexes for insight into active site characteristics that are deterministic for chlorite decomposition. At 4.7 × 10 -9 M, the K D for the KpCld-CN - complex is 2 orders of magnitude smaller than that of DaCld-CN - and indicates an affinity for CN - that is greater than that of most heme proteins. The difference in CN - affinity between Kp- and DaClds is predominantly due to differences in k off . The kinetics of binding of cyanide to DaCld, DaCld(R183Q), and KpCld between pH 4 and 8.5 corroborate the importance of distal Arg183 and a p K a of ∼7 in stabilizing complexes of anionic ligands, including the substrate. The Fe-C stretching and FeCN bending modes of the DaCld-CN - (ν Fe-C , 441 cm -1 ; δ FeCN , 396 cm -1 ) and KpCld-CN - (ν Fe-C , 441 cm -1 ; δ FeCN , 356 cm -1 ) complexes reveal differences in their FeCN angle, which suggest different distal pocket interactions with their bound cyanide. Conformational differences in their catalytic sites are also reported by the single ferrous KpCld carbonyl complex, which is in contrast to the two conformers observed for DaCld-CO.

Evaluation of liquid fragility and thermal stability of Al-based metallic glasses by equivalent structure parameter

International Nuclear Information System (INIS)

Li Xuelian; Bian Xiufang; Hu Lina

2010-01-01

Based on extended Ideal-Atomic-Packing model, we propose an equivalent structure parameter '6x+11y' to evaluate fragility and thermal stability of Al-TM-RE metallic glasses, where x and y are composition concentrations of transition metal (TM) and rare earth (RE), respectively. Experimental results show that glass forming compositions with '6x+11y' near 100 have the smallest fragility parameter and best structure stability. In addition, '6x+11y' parameter has a positive relationship with onset-crystallization temperature, T x . Al-TM-RE glassy alloys with (6x+11y)≤100 undergo primary crystallization of fcc-Al nanocrystals, while alloys with (6x+11y)>100 exhibit nanoglassy or glassy crystallization behavior.

Identification of Manganese Superoxide Dismutase from Sphingobacterium sp. T2 as a Novel Bacterial Enzyme for Lignin Oxidation.

Science.gov (United States)

Rashid, Goran M M; Taylor, Charles R; Liu, Yangqingxue; Zhang, Xiaoyang; Rea, Dean; Fülöp, Vilmos; Bugg, Timothy D H

2015-10-16

The valorization of aromatic heteropolymer lignin is an important unsolved problem in the development of a biomass-based biorefinery, for which novel high-activity biocatalysts are needed. Sequencing of the genomic DNA of lignin-degrading bacterial strain Sphingobacterium sp. T2 revealed no matches to known lignin-degrading genes. Proteomic matches for two manganese superoxide dismutase proteins were found in partially purified extracellular fractions. Recombinant MnSOD1 and MnSOD2 were both found to show high activity for oxidation of Organosolv and Kraft lignin, and lignin model compounds, generating multiple oxidation products. Structure determination revealed that the products result from aryl-Cα and Cα-Cβ bond oxidative cleavage and O-demethylation. The crystal structure of MnSOD1 was determined to 1.35 Å resolution, revealing a typical MnSOD homodimer harboring a five-coordinate trigonal bipyramidal Mn(II) center ligated by three His, one Asp, and a water/hydroxide in each active site. We propose that the lignin oxidation reactivity of these enzymes is due to the production of a hydroxyl radical, a highly reactive oxidant. This is the first demonstration that MnSOD is a microbial lignin-oxidizing enzyme.

A study on superoxide dismutase activity of some model compounds.

Science.gov (United States)

Liao, Z; Liu, W; Liu, J; Jiang, Y; Shi, J; Liu, C

1994-08-15

The synthesis and characteristics of a binuclear ligand N,N,N',N'-tetrakis (2'-benzimidazolyl methyl)-1,4-diethylene amino glycol ether (EGTB) and its series of coordination compounds containing copper(II), iron(III), and manganese(II) with and without exogenous bridging ligand which was imidazolate ion (Im-), bipyridine (bpy), or 1,10-phenanthroline (phen) are reported. Depending on the redox potentials by cyclic voltammetry, the coordination compounds can act as catalysts for the dismutation of superoxide radicals (O2-). The detection of the rate constant of the reaction of superoxide ion with nitroblue tetrazolium (NBT) which is inhibited by superoxide dismutase (SOD) and its model compounds of the EGTB system has been performed by a modified illumination method. The rate constants kQ of the catalytic dismutation have been obtained.

Superoxide dismutase in radioresistant PC-3 human prostate carcinoma cells

International Nuclear Information System (INIS)

Prokopovic, J.; Adzic M; Niciforovic, A.; Vucic, V.; Zaric, B.; Radojcic, M. B.

2006-01-01

The molecular mechanism of gamma-ionizing radiation (IR) resistance of human prostate cancer cells PC-3 is not known. Since low-LET-IR effects are primarily achieved through generation of reactive oxygen species (ROS), IR-induced expression of ROS-metabolizing antioxidant enzymes, Mn- and CuZn-superoxide dismutase (Mn- and CuZnSOD) and catalase (CAT), and their upstream regulator transcription factor NFκB was followed. Significant elevation of both SODs was found in cells irradiated with 10- and 20 Gy, while CAT and NFκB expression was unchanged. Since, such conditions lead to accumulation of H 2 O 2 , it is concluded that radioresistance of PC-3 cells may emerge from positive feed-forward vicious circle established between H 2 O 2 activation of NFκB and elevated MnSOD activity. (author)

Polyhydroxy surfactants for the formulation of lipid nanoparticles (SLN and NLC): effects on size, physical stability and particle matrix structure.

Science.gov (United States)

Kovacevic, A; Savic, S; Vuleta, G; Müller, R H; Keck, C M

2011-03-15

The two polyhydroxy surfactants polyglycerol 6-distearate (Plurol(®)Stearique WL1009 - (PS)) and caprylyl/capryl glucoside (Plantacare(®) 810 - (PL)) are a class of PEG-free stabilizers, made from renewable resources. They were investigated for stabilization of aqueous solid lipid nanoparticle (SLN) and nanostructured lipid carrier (NLC) dispersions. Production was performed by high pressure homogenization, analysis by photon correlation spectroscopy (PCS), laser diffraction (LD), zeta potential measurements and differential scanning calorimetry (DSC). Particles were made from Cutina CP as solid lipid only (SLN) and its blends with Miglyol 812 (NLC, the blends containing increasing amounts of oil from 20% to 60%). The obtained particle sizes were identical for both surfactants, about 200 nm with polydispersity indices below 0.20 (PCS), and unimodal size distribution (LD). All dispersions with both surfactants were physically stable for 3 months at room temperature, but Plantacare (PL) showing a superior stability. The melting behaviour and crystallinity of bulk lipids/lipid blends were compared to the nanoparticles. Both were lower for the nanoparticles. The crystallinity of dispersions stabilized with PS was higher, the zeta potential decreased with storage time associated with this higher crystallinity, and leading to a few, but negligible larger particles. The lower crystallinity particles stabilized with PL remained unchanged in zeta potential (about -50 mV) and in size. These data show that surfactants have a distinct influence on the particle matrix structure (and related stability and drug loading), to which too little attention was given by now. Despite being from the same surfactant class, the differences on the structure are pronounced. They are attributed to the hydrophobic-lipophilic tail structure with one-point anchoring in the interface (PL), and the loop conformation of PS with two hydrophobic anchor points, i.e. their molecular structure and its

BOMB STABILIZING STRUCTURE

Science.gov (United States)

Kelley, J.L.; Runyan, C.E.

1963-12-10

A stabilizinig structure capable of minimizing deviations of a falling body such as a bomb from desired trajectory is described. The structure comprises a fin or shroud arrangement of double-wedge configuration, the feeding portion being of narrow wedge shape and the after portion being of a wider wedge shape. The structure provides a force component for keeping the body on essentially desired trajectory throughout its fall. (AEC)

Structure, stability, and thermodynamics of a short intermolecular purine-purine-pyrimidine triple helix

International Nuclear Information System (INIS)

Pilch, D.S.; Shafer, R.H.; Levenson, C.

1991-01-01

The authors have investigated the structure and physical chemistry of the d(C 3 T 4 C 3 )·2[d(G 3 A 4 G 3 )] triple helix by polyacrylamide gel electrophoresis (PAGE), 1 H NMR, and ultraviolet (UV) absorption spectroscopy. The triplex was stabilized with MgCl 2 at neutral pH. PAGE studies verify the stoichiometry of the strands comprising the triplex and indicate that the orientation of the third strand in purine-purine-pyrimidine (pur-pur-pyr) triplexes is antiparallel with respect to the purine strand of the underlying duplex. Imino proton NMR spectra provide evidence for the existence of new purine-purine (pur·pur) hydrogen bonds, in addition to those of the Watson-Crick (W-C) base pairs, in the triplex structure. These new hydrogen bonds are likely to correspond to the interaction between third-strand guanine NH1 imino protons and the N7 atoms of guanine residues on the puring strand of the underlying duplex. Thermal denaturation of the triplex proceeds to single strands in one step, under the conditions used in this study. Binding of the third strand appears to enhance the thermal stability of the duplex by 1-3 C, depending on the DNA concentration. This marked enhancement in stability, coupled with the lack of an acidic pH requirement, suggests that pur-pur-pyr triplexes are appealing choices for use in applications involving oligonucleotide targeting of duplex DNA in vitro and in vivo

Structurally stabilized organosilane-templated thermostable mesoporous titania.

Science.gov (United States)

Amoli, Vipin; Tiwari, Rashmi; Dutta, Arghya; Bhaumik, Asim; Sinha, Anil Kumar

2014-01-13

Structurally thermostable mesoporous anatase TiO2 (m-TiO2) nanoparticles, uniquely decorated with atomically dispersed SiO2, is reported for the first time. The inorganic Si portion of the novel organosilane template, used as a mesopores-directing agent, is found to be incorporated in the pore walls of the titania aggregates, mainly as isolated sites. This is evident by transmission electron microscopy and high-angle annular dark field scanning transmission electron microscopy, combined with electron dispersive X-ray spectroscopy. This type of unique structure provides exceptional stability to this new material against thermal collapse of the mesoporous structure, which is reflected in its high surface area (the highest known for anatase titania), even after high-temperature (550 °C) calcination. Control of crystallite size, pore diameter, and surface area is achieved by varying the molar ratios of the titanium precursor and the template during synthesis. These mesoporous materials retain their porosity and high surface area after template removal and further NaOH/HCl treatment to remove silica. We investigate their performance for dye-sensitized solar cells (DSSCs) with bilayer TiO2 electrodes, which are prepared by applying a coating of m-TiO2 onto a commercial titania (P25) film. The high surface area of the upper mesoporous layer in the P25-m-TiO2 DSSC significantly increases the dye loading ability of the photoanode. The photocurrent and fill factor for the DSSC with the bilayer TiO2 electrode are greatly improved. The large increase in photocurrent current (ca. 56%) in the P25-m-TiO2 DSSC is believed to play a significant role in achieving a remarkable increase in the photovoltaic efficiency (60%) of the device, compared to DSSCs with a monolayer of P25 as the electrode. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The global stability of a delayed predator-prey system with two stage-structure

International Nuclear Information System (INIS)

Wang Fengyan; Pang Guoping

2009-01-01

Based on the classical delayed stage-structured model and Lotka-Volterra predator-prey model, we introduce and study a delayed predator-prey system, where prey and predator have two stages, an immature stage and a mature stage. The time delays are the time lengths between the immature's birth and maturity of prey and predator species. Results on global asymptotic stability of nonnegative equilibria of the delay system are given, which generalize and suggest that good continuity exists between the predator-prey system and its corresponding stage-structured system.

Manganese Superoxide Dismutase: Guardian of the Powerhouse

Directory of Open Access Journals (Sweden)

Daret K. St. Clair

2011-10-01

Full Text Available The mitochondrion is vital for many metabolic pathways in the cell, contributing all or important constituent enzymes for diverse functions such as β-oxidation of fatty acids, the urea cycle, the citric acid cycle, and ATP synthesis. The mitochondrion is also a major site of reactive oxygen species (ROS production in the cell. Aberrant production of mitochondrial ROS can have dramatic effects on cellular function, in part, due to oxidative modification of key metabolic proteins localized in the mitochondrion. The cell is equipped with myriad antioxidant enzyme systems to combat deleterious ROS production in mitochondria, with the mitochondrial antioxidant enzyme manganese superoxide dismutase (MnSOD acting as the chief ROS scavenging enzyme in the cell. Factors that affect the expression and/or the activity of MnSOD, resulting in diminished antioxidant capacity of the cell, can have extraordinary consequences on the overall health of the cell by altering mitochondrial metabolic function, leading to the development and progression of numerous diseases. A better understanding of the mechanisms by which MnSOD protects cells from the harmful effects of overproduction of ROS, in particular, the effects of ROS on mitochondrial metabolic enzymes, may contribute to the development of novel treatments for various diseases in which ROS are an important component.

Study on thermal stability and chemical structure of polyamide blended with small amount of Cu

International Nuclear Information System (INIS)

Arai, Tsuyoshi; Ueno, Tomonaga; Kajiya, Takafumi; Ishikawa, Tomoyuki; Takeda, Kunihiko

2007-01-01

The thermal stability and the chemical structure of Polyamide 66 (PA66) blended with a small amount of copper have been studied. The thermal degradation of the blend with 35 ppm or more of copper was restrained and no strong influence of the concentration of copper was observed. The molecular weight of PA66 decreased by the thermal aging process but the amount of decrease of the blend was smaller than that of the non-blend. The water uptake of the blend increased. The chemical structure, which was observed by IR and NMR, changed slightly by blending with copper after aging at higher temperatures. Multiple items influenced the thermal stability of PA66 blended with a small amount of copper instead of just one. Namely, the main chain of PA66 is cut by heat and the degree of the cut is restrained by the copper. The diffusion time of copper atoms that disperse uniformly in the PA66 matrix is short enough to cover the individual amide groups and the effect enlarges the entire configuration of the PA66 chain to enhance the thermal stability. (author)

Internet Addiction: Stability and Change

Science.gov (United States)

Huang, Chiungjung

2010-01-01

This longitudinal study examined five indices of stability and change in Internet addiction: structural stability, mean-level stability, differential stability, individual-level stability, and ipsative stability. The study sample was 351 undergraduate students from end of freshman year to end of junior year. Convergent findings revealed stability…

The effects of the sulfonylurea glyburide on glutathione peroxidase, superoxide dismutase and catalase activities in the heart tissue of streptozotocin-induced diabetic rat.

Science.gov (United States)

Bukan, N; Sancak, B; Bilgihan, A; Kosova, F; Buğdayci, G; Altan, N

2004-09-01

Oxygen free radicals have been suggested to be a contributory factor in diabetes complications. The aim of this study was to examine the effects of glyburide on the antioxidant enzyme activities in the heart tissue of diabetic rats. We investigated the activities of antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase) in the hearts of both control and streptozotocin-induced diabetic rats. In the heart of diabetic rats, the activity of total superoxide dismutase decreased significantly (p < 0.005), whereas the activity of catalase and glutathione peroxidase increased to a large extent (p < 0.0001 and p = 0.05, respectively) at the end of the fourth week compared with the control group. Glyburide treatment of diabetic rats for 4 weeks corrected the changes observed in diabetic heart. In addition, blood glucose levels of untreated diabetic rats decreased following the glyburide treatment. These results demonstrate that the sulfonylurea glyburide is capable of exerting direct insulin-like effect on heart superoxide dismutase, catalase and glutathione peroxidase activities of diabetic rats in vivo.

Structure and Stability of the Spinach Aquaporin SoPIP2;1 in Detergent Micelles and Lipid Membranes

DEFF Research Database (Denmark)

Plasencia, Ines; Survery, Sabeen; Ibragimova, Sania

2011-01-01

Background: SoPIP2;1 constitutes one of the major integral proteins in spinach leaf plasma membranes and belongs to the aquaporin family. SoPIP2;1 is a highly permeable and selective water channel that has been successfully overexpressed and purified with high yields. In order to optimize...... reconstitution of the purified protein into biomimetic systems, we have here for the first time characterized the structural stability of SoPIP2;1. Methodology/Principal Finding: We have characterized the protein structural stability after purification and after reconstitution into detergent micelles...... and proteoliposomes using circular dichroism and fluorescence spectroscopy techniques. The structure of SoPIP2;1 was analyzed either with the protein solubilized with octyl-beta-D-glucopyranoside (OG) or reconstituted into lipid membranes formed by E. coli lipids, diphytanoylphosphatidylcholine (DPh...

Superoxide dismutase of human platelets

International Nuclear Information System (INIS)

Kimura, Akiro; Fujimura, Kingo; Kuramoto, Atsushi

1979-01-01

Superoxide dismutase (S.O.D.) is the enzyme to protect from destructive effect of superoxide (O 2 -) produced in many metabolic pathways related to oxygen. The purpose of this study was to investigate the possibility that S.O.D. may play an important role in the platelet function. The cytoplasmic and mitochondrial S.O.D. has been investigated spectrophotometrically and gel electrophoretically in human platelets from eleven patients of chronic myelogenous leukemia (CML) and three patients of primary thrombocythemia (P.Th.). Neither deficiency nor abnormality of cytoplasmic and mitochondrial S.O.D. has been found electrophoretically in any case compared to normal platelets. However, the total activity from three of the CML patients and one of the P.Th. patients were above 3 unit/mg platelet protein (normal subject: 2.11 - 2.70 unit/mg protein), suggesting the possibility either that more O 2 -production occurs in the platelets or that rather little O 2 -production due to much O 2 -deprivation by the increased S.O.D. The S.O.D. activity of human platelets has been also investigated in several conditions, where much O 2 -generation might occur in platelets. Sodium fluoride (2 mM), which increases platelet O 2 -production about 3 fold, had no effect on platelet S.O.D. The aggregated platelets induced by ADP (10 -5 M), epinephrin (50 μg/ml), ristocetin (1.5 mg/ml) or collagen (1 - 20 μg/ml) had no increase of S.O.D. activity compared to that from non aggregated platelets. X-ray irradiation (1,000 - 20,000R) had not induced its activity increase or decrease. These findings indicated the induction of platelet S.O.D. was not brought about under these conditions. (author)

Silicon/Wolfram Carbide@Graphene composite: enhancing conductivity and structure stability in amorphous-silicon for high lithium storage performance

International Nuclear Information System (INIS)

Sun, Wei; Hu, Renzong; Liu, Hui; Zhang, Hanying; Liu, Jiangwen; Yang, Lichun; Wang, Haihui; Zhu, Min

2016-01-01

Highlights: • Two-step ball milling was used to produce an amorphous-Si/WC@Graphene(SW@G) composite. • Concrete-like core-shell structure with high stability was designed. • Multiscale WC particle strengthen the inside structure. • Graphene coating outside much enhanced the cycling stability and conductivity. • The SW@G anode exhibited long cycle life and superior volumetric capacity. - Abstract: Improving the electron conductivity and lithiated structure stability for Si anodes can result in high stable capacity in cells. A Silicon/Wolfram Carbide@Graphene (SW@G) composite anode is designed and produced by a simple two-step ball milling the mixture of coarse-grained Si with good conductive wolfram carbide (WC) and graphite. The SW@G composite consists of multiple-scale WC particles, which are uniformly distributed in amorphous Si matrices, and wrapped by graphene nanosheets (GNs) on the outside. Owing to the unique concrete-like core-shell structure, the wrapping of GNs on the Si improves the conductivity and structural stability of the composite. The inner WC particles which tightly connect the Si and graphene act as the cornerstone to resist large volumetric expansion of Si during charge/discharge, and in particular serve as the high-speed channels of electrons as well as provide more interface paths for Li + to accelerate their transfer inside the Si. These contribute to the excellent electrochemical properties of SW@G composite anode, including high volumetric capacity (three times higher than that of graphite), superior rate capability, and long-life stable cycleability. The synthetic method developed in this work paves the way for large-scale manufacturing of high performance Li storage anodes using commercially available materials and technologies.

Effects of topical vitamin E on corneal superoxide dismutase, glutathione peroxidase activities and polymorphonuclear leucocyte infiltration after photorefractive keratectomy.

Science.gov (United States)

Bilgihan, Ayse; Bilgihan, Kamil; Yis, Ozgür; Sezer, Cem; Akyol, Gülen; Hasanreisoglu, Berati

2003-04-01

Photorefractive keratectomy (PRK) induces free radical formation and polymorphonuclear (PMN) cell infiltration in the cornea. Vitamin E is a free radical scavenger and protects the cells from reactive oxygen species. We investigated the effects of topical vitamin E on corneal PMN cell infiltration and corneal antioxidant enzyme activities after PRK. We studied four groups, each consisting of seven eyes. Group 1 were control eyes. In group 2 the corneal epithelium was removed by a blunt spatula (epithelial scrape). In group 3, corneal photoablation (59 micro m, 5 dioptres) was performed after epithelial removal (traditional PRK). In group 4 we tested the effects of topical Vitamin E after traditional PRK. Corneal tissues were removed and studied with enzymatic analysis (measurement of corneal superoxide dismutase and glutathione peroxidase activities) and histologically. Stromal PMN leucocyte counts were significantly higher after mechanical epithelial removal and traditional PRK (p < 0.05). Corneal superoxide dismutase and glutathione peroxidase activities decreased significantly after mechanical epithelial removal and traditional PRK (p < 0.05). In group 4, treated with vitamin E, corneal superoxide dismutase activity did not differ significantly from that in the medically non-treated groups, nor did corneal PMN cell infiltration after traditional PRK. The reduction of corneal glutathione peroxidase activity after PRK was reduced significantly after topical vitamin E treatment. Topical vitamin E treatment may be useful for reducing the harmful effects of reactive oxygen radical after epithelial scraping and PRK in that it increases corneal glutathione peroxidase activity.

Insights on the structure and stability of Licanantase: a trimeric acid-stable coiled-coil lipoprotein from Acidithiobacillus thiooxidans

Directory of Open Access Journals (Sweden)

Fernando Abarca

2014-08-01

Full Text Available Licanantase (Lic is the major component of the secretome of Acidithiobacillus thiooxidans when grown in elemental sulphur. When used as an additive, Lic improves copper recovery from bioleaching processes. However, this recovery enhancement is not fully understood. In this context, our aim is to predict the 3D structure of Lic, to shed light on its structure-function relationships. Bioinformatics analyses on the amino acid sequence of Lic showed a great similarity with Lpp, an Escherichia coli Lipoprotein that can form stable trimers in solution. Lic and Lpp share the secretion motif, intracellular processing and alpha helix structure, as well as the distribution of hydrophobic residues in heptads forming a hydrophobic core, typical of coiled-coil structures. Cross-linking experiments showed the presence of Lic trimers, supporting our predictions. Taking the in vitro and in silico evidence as a whole, we propose that the most probable structure for Lic is a trimeric coiled-coil. According to this prediction, a suitable model for Lic was produced using the de novo algorithm “Rosetta Fold-and-Dock”. To assess the structural stability of our model, Molecular Dynamics (MD and Replica Exchange MD simulations were performed using the structure of Lpp and a 14-alanine Lpp mutant as controls, at both acidic and neutral pH. Our results suggest that Lic was the most stable structure among the studied proteins in both pH conditions. This increased stability can be explained by a higher number of both intermonomer hydrophobic contacts and hydrogen bonds, key elements for the stability of Lic’s secondary and tertiary structure.

Periplasmic Cu,Zn superoxide dismutase and cytoplasmic Dps concur in protecting Salmonella enterica serovar Typhimurium from extracellular reactive oxygen species.

Science.gov (United States)

Pacello, Francesca; Ceci, Pierpaolo; Ammendola, Serena; Pasquali, Paolo; Chiancone, Emilia; Battistoni, Andrea

2008-02-01

Several bacteria possess periplasmic Cu,Zn superoxide dismutases which can confer protection from extracellular reactive oxygen species. Thus, deletion of the sodC1 gene reduces Salmonella enterica serovar Typhimurium ability to colonize the spleens of wild type mice, but enhances virulence in p47phox mutant mice. To look into the role of periplamic Cu,Zn superoxide dismutase and into possible additive effects of the ferritin-like Dps protein involved in hydrogen peroxide detoxification, we have analyzed bacterial survival in response to extracellular sources of superoxide and/or hydrogen peroxide. Exposure to extracellular superoxide of Salmonella Typhimurium mutant strains lacking the sodC1 and sodC2 genes and/or the dps gene does not cause direct killing of bacteria, indicating that extracellular superoxide is poorly bactericidal. In contrast, all mutant strains display a sharp hydrogen peroxide-dependent loss of viability, the dps,sodC1,sodC2 mutant being less resistant than the dps or the sodC1,sodC2 mutants. These findings suggest that the role of Cu,Zn superoxide dismutase in bacteria is to remove rapidly superoxide from the periplasm to prevent its reaction with other reactive molecules. Moreover, the nearly additive effect of the sodC and dps mutations suggests that localization of antioxidant enzymes in different cellular compartments is required for bacterial resistance to extracytoplasmic oxidative attack.

Study on the Protective Effect of a New Manganese Superoxide Dismutase on the Microvilli of Rabbit Eyes Exposed to UV Radiation

Directory of Open Access Journals (Sweden)

Lucia Grumetto

2015-01-01

Full Text Available We present a study on the protective effects against UV radiation of a gel formulation containing a new recombinant form of manganese superoxide dismutase on the conjunctiva and corneal epithelia of rabbit eyes. The integrity of the microvilli of both ocular tissues has been considered as an indicator of the health of the tissues. Samples, collected by impression cytology technique, were added of 80 µL of a gel formulation containing superoxide dismutase (2.0 µg/mL and irradiated with UV rays for 30 minutes and were evaluated with scanning electron microscopy. Wilcoxon test was used to verify the possible occurrence of statistically significant differences between damage for treated and nontreated tissues. Application of gel produces a significant reduction of damage by UV irradiation of ocular epithelia; both epithelia present a significant reduction of damaged microvilli number if treated with the superoxide dismutase gel formulation: the p values (differences between damage found for treated and nontreated both ocular tissues for conjunctiva and cornea samples were p≪0.01 and p≪0.0001, respectively, at confidence level of 95%. The administration of this gel formulation before UV exposure plays a considerable protective role in ocular tissues of rabbit eye with a significant reduction of the damage.

Study on the Protective Effect of a New Manganese Superoxide Dismutase on the Microvilli of Rabbit Eyes Exposed to UV Radiation.

Science.gov (United States)

Grumetto, Lucia; Del Prete, Antonio; Ortosecco, Giovanni; Barbato, Francesco; Del Prete, Salvatore; Borrelli, Antonella; Schiattarella, Antonella; Mancini, Roberto; Mancini, Aldo

2015-01-01

We present a study on the protective effects against UV radiation of a gel formulation containing a new recombinant form of manganese superoxide dismutase on the conjunctiva and corneal epithelia of rabbit eyes. The integrity of the microvilli of both ocular tissues has been considered as an indicator of the health of the tissues. Samples, collected by impression cytology technique, were added of 80 µL of a gel formulation containing superoxide dismutase (2.0 µg/mL) and irradiated with UV rays for 30 minutes and were evaluated with scanning electron microscopy. Wilcoxon test was used to verify the possible occurrence of statistically significant differences between damage for treated and nontreated tissues. Application of gel produces a significant reduction of damage by UV irradiation of ocular epithelia; both epithelia present a significant reduction of damaged microvilli number if treated with the superoxide dismutase gel formulation: the p values (differences between damage found for treated and nontreated both ocular tissues) for conjunctiva and cornea samples were p ≪ 0.01 and p ≪ 0.0001, respectively, at confidence level of 95%. The administration of this gel formulation before UV exposure plays a considerable protective role in ocular tissues of rabbit eye with a significant reduction of the damage.

STABILITY AND DYNAMICS OF SPATIO-TEMPORAL STRUCTURES

Energy Technology Data Exchange (ETDEWEB)

Hermann Riecke

2005-10-21

This document constitutes the final report for the grant. It provides a complete list of publications and presentations that arose from the project as well as a brief description of the highlights of the research results. The research funded by this grant has provided insights into the spontaneous formation of structures of increasing complexity in systems driven far from thermodynamic equilibrium. A classic example of such a system is thermally driven convection in a horizontal fluid layer. Highlights of the research are: (1) explanation of the localized traveling wave pulses observed in binary-mixture convection, (2) explanation of the localized waves in electroconvection, (3) introduction of a new diagnostics for spatially and temporally chaotic states, which is based on the statistics of defect trajectories, (4) prediction of complex states in thermally driven convection in rotating systems. Additional contributions provided insight into the localization mechanism for oscillons, the prediction of a new localization mechanism for traveling waves based on a resonant periodic forcing, and an analysis of the stability of quasi-periodic patterns.

Virial theorem analysis of the structure and stability of magnetized clouds

International Nuclear Information System (INIS)

Zweibel, E.G.

1990-01-01

The tensor virial theorem is used to analyze the structure and stability of self-gravitating, magnetized spheroids surrounded by a low-density medium with pressure and magnetic field. Analytical expressions are developed for the effect of a weak field and calculate critical states when the effect of the field is arbitrarily strong, comparing the results with full magnetohydrostatic calculations. This analysis suggests that a magnetic field may prevent gravitational collapse but may also be destabilizing, depending on its degree of concentration within the cloud. 34 refs

An Enhanced Asymptotic Expansion for the Stability of Nonlinear Elastic Structures

DEFF Research Database (Denmark)

Christensen, Claus Dencker; Byskov, Esben

2010-01-01

A new, enhanced asymptotic expansion applicable to stability of structures made of nonlinear elastic materials is established. The method utilizes “hyperbolic” terms instead of the conventional polynomial terms, covers full kinematic nonlinearity and is applied to nonlinear elastic Euler columns...... with two different types of cross-section. Comparison with numerical results show that our expansion provides more accurate predictions of the behavior than usual expansions. The method is based on an extended version of the principle of virtual displacements that covers cases with auxiliary conditions...

The pH dependence of the spectral and anion binding properties of iron containing superoxide dismutase from E. coli B

International Nuclear Information System (INIS)

Fee, J.A.; McClune, G.J.; Lees, A.C.; Zidovetzki, R.; Pecht, I.

1981-01-01

Examination of the optical and EPR properties of the ferric form of the iron containing superoxide dismutase from E.coli B, at pH values ranging from 4.5 to 10.9, has revealed two reversible structural transitions affecting the Fe 3+ ion. The apparent pKsub(a) values of these transitions are 5.1+-0.3 and 9.O+-0.3. The binding of azide has been studied over the pH range 4.5 to 10.7; the affinity of the Fe 3+ for N 3 - is independent of pH from 4.5 to approximately 7.5, after which the dissociation constant decreased by a factor of 10 per unit increase in pH. The apparent pKsub(a) which affects N 3 - binding to the iron is 8.6+-0.2. The association of N 3 - with the iron has been examined using the temperature-jump method at pH 7.4 and 9.3. The kinetics of ligand association were shown to conform to the minimal mechanism: P-Fe 3+ + N 3 - reversible K 1 N 3 - - P-Fe 3+ reversible K 2 P-Fe 3+ - N 3 - . K 1 was found to be essentially unaffected by pH whereas K 2 was much lower at pH 9.3 than at 7.4. The value of K 1 at pH 7.4 (100 M -1 ) corresponds very closely to that obtained for the inhibition constant of azide, 10mM. A scheme is presented in which N 3 - inhibits the iron containing dismutase by competing with O 2 - for an anion binding site near, but not on the Fe 3+ . (author)

Effects of mannose, fructose, and fucose on the structure, stability, and hydration of lysozyme in aqueous solution

DEFF Research Database (Denmark)

Rahim, Abdoul; Peters, Günther H.J.; Jalkanen, Karl J.

2013-01-01

The bio-protective properties of monosaccharaides, namely mannose, fructose and fucose, on the stability and dynamical properties of the NMR determined hen egg-white lysozyme structure have been investigated by means of molecular dynamics simulations at room temperature in aqueous solution and in...... of the solvent and sugar distributions around lysozyme was used to investigate the interfacial solvent and sugar structure near the protein surface.......The bio-protective properties of monosaccharaides, namely mannose, fructose and fucose, on the stability and dynamical properties of the NMR determined hen egg-white lysozyme structure have been investigated by means of molecular dynamics simulations at room temperature in aqueous solution and in 7...... and 13 wt % concentrations of the three sugars. Results are discussed in the framework of the bio-protective phenomena. The three sugars show similar bio-protective behaviours at room temperature (300 K) in the concentration range studied as shown by the small RMSDs of the resulting MD structures from...

Analysis of the structural stability of the smectite submitted to high pressures and temperatures

International Nuclear Information System (INIS)

Alabarse, Frederico Gil

2009-10-01

The thermal stability of bentonite is of particular interest for containment barrier in nuclear waste disposal facilities. However, very little is known about the stability of smectite (principal component of bentonite) under high-pressure and high-temperature conditions (HPHT). The objective of this work was to investigate the stability of the smectite structure under HP-HT conditions. The HP-HT experiments were performed on toroidal chambers (TC) with pressure up 7.7 GPa and temperatures of 1000 deg C. The samples were characterized by X-ray diffraction after the HP-HT processing. Furthermore, one sample from the original material was analyzed using Fourier transformed infra-red (FTIR) in situ measurements on a diamond anvil cell (DAC) in experiments up to 12 GPa. The original sample of bentonite, calcium dioctahedral montmorillonite with small fraction of quartz, was characterized by FTIR, XRD, X-ray fluorescence (XRF), scanning electron microscopy (SEM), surface area, thermogravimetric analysis (TGA) and differential thermal analysis (DTA). In the experiment performed using the DAC up to 12 GPa, the FTIR in situ measurements analysis showed that the smectite structure is stable with a reversible deformation in the Si-O bond and that the smectite did not loose water. Experiments performed in TC at 7.7 GPa of pressure and 250 deg C of temperature, during 3.5 h showed, after analysis by XRD and FTIR, that the smectite structure is stable and did not loose water. Experiments performed in TC at 7.7 GPa of pressure and 1000 deg C of temperature, during 3.5 h showed, after analysis by XRD and SEM, the transformation of bentonite to the mineral assemblage: Coesite, Quartz, Kyanite and Pyrope. (author)

Functional and structural stability of the epidermal growth factor receptor in detergent micelles and phospholipid nanodiscs

DEFF Research Database (Denmark)

Mi, Li-Zhi; Grey, Michael J; Nishida, Noritaka

2008-01-01

Cellular signaling mediated by the epidermal growth factor receptor (EGFR or ErbB) family of receptor tyrosine kinases plays an important role in regulating normal and oncogenic cellular physiology. While structures of isolated EGFR extracellular domains and intracellular protein tyrosine kinase...... differential functional stability in Triton X-100 versus dodecyl maltoside. Furthermore, the kinase activity can be significantly stabilized by reconstituting purified EGF-bound EGFR dimers in phospholipid nanodiscs or vesicles, suggesting that the environment around the hydrophobic transmembrane...

Stability and electronic structure of superlattices (IIIV)n/(IV2)n

International Nuclear Information System (INIS)

Casagrande, D.; Ferraz, A.C.

1996-01-01

Theoretical investigations of atomic relaxation and electronic states have been made for ultrathin superlattices (GaP) n /(Ge 2 ) n , (GaP) n /(Si 2 ) n , (In P) n /(Ge 2 ) n and (In P) n /(Si 2 ) n with period n ≤ 3 in growth directions (001) and (110). The calculations were performed within the momentum-space formalism of the self-consistent ab-initio pseudopotential method and the molecular dynamics approach as proposed by Car and Parrinello. The structures were found to be unstable with respect to the phase separation into the constituent bulk materials. The results for the enthalpy show a metastability as increasing the superlattice period n. The density of nonoctet wrong-bonds play an important role to determine the stability of the structures. (author). 13 refs., 2 figs., 3 tabs

Stabilization of crystal and magnetic structure of Gd2Al1-xInx

International Nuclear Information System (INIS)

Niazi, M.; Yazdani, A.

2006-01-01

A random mixture of two compounds with different type of crystal structure and magnetic characteristic which can lead to a new phase, is studied to find out the critical point at which both of them stabilized. such an interesting random system can be found by; 1) Gd 2 Al with two different magnetic phase transition on which T c is unstable 2) Gd 2 In which is also shows two magnetic phase transition, but completely different with Gd 2 Al on which T N is unstable. The stabilized point which is consider experimentally by X-Ray diffraction and theoretically by WIEN2K is suggested to be at x=0.3 where it is a good agreement between these two methods.

Valence electron structure and properties of stabilized ZrO2

Institute of Scientific and Technical Information of China (English)

2008-01-01

To reveal the properties of stabilizers in ZrO2 on nanoscopic levels, the valence electron structures of four stable ZrO2 phases and c-ZrO2 were analyzed on the basis of the empirical electron theory of solids and molecules. The results showed that the hybridization levels of Zr atoms in c-ZrO2 doped with Ca and Mg dropped from B17 to B13, the hybridization levels of Zr atoms in c-ZrO2 doped with Y and Ce dropped from B17 to B15, and that the four stabilizing atoms all made the hybridization levels of O atoms drop from level 4 to level 2. The numbers of covalent electrons in the strongest covalent bond in the descending order are c-ZrO2>Zr0.82Ce0.18O2> Zr0.82Y0.18O1.91>Zr0.82Mg0.18O1.82>Zr0.82Ca0.18O1.82. The bond energies of the strongest covalent bond and the melting points of the solid solutions in the descending order are Zr0.82Ce0.18O2> c-ZrO2>Zr0.82Y0.18O1.91>Zr0.82Mg0.18O1.82>Zr0.82Ca0.18O1.82. The percent-ages of the total number of covalent electrons in the descending order are c-ZrO2>Zr0.82Y0.18O1.91> Zr0.82Ce0.18O2>Zr0.82Mg0.18O1.82> Zr0.82Ca0.18O1.82. From the above analysis, it can be concluded that the stabilizing degrees of the four stabilizers in the descending order are CaO> MgO>Y2O3>CeO2.

Evaluation of the influence of fluoroquinolone chemical structure on stability: forced degradation and in silico studies

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André Valle de Bairros

2018-05-01

Full Text Available ABSTRACT Fluoroquinolones are a known antibacterial class commonly used around the world. These compounds present relative stability and they may show some adverse effects according their distinct chemical structures. The chemical hydrolysis of five fluoroquinolones was studied using alkaline and photolytic degradation aiming to observe the differences in molecular reactivity. DFT/B3LYP-6.31G* was used to assist with understanding the chemical structure degradation. Gemifloxacin underwent degradation in alkaline medium. Gemifloxacin and danofloxacin showed more degradation perceptual indices in comparison with ciprofloxacin, enrofloxacin and norfloxacin in photolytic conditions. Some structural features were observed which may influence degradation, such as the presence of five member rings attached to the quinolone ring and the electrostatic positive charges, showed in maps of potential electrostatic charges. These measurements may be used in the design of effective and more stable fluoroquinolones as well as the investigation of degradation products from stress stability assays.

The influence of boundary conditions on domain structure stability in spin wave approximation

International Nuclear Information System (INIS)

Wachinewski, A.

1974-01-01

Instead of the usually used Born-Karman cyclic conditions, boundary conditions which take into account the situation of the boundary lattice sites lying on the crystal's surface are assumed. It is shown that the particular choice of the boundary conditions secures the stability of domain structure in ferromagnet (positive spin wave energies), without including the Winter term in Hamiltonian. (author)

Analysis of eddy current loss in high-Tc superconducting power cables with respect to various structure of stabilizer

International Nuclear Information System (INIS)

Choi, S. J.; Song, M. K.; Lee, S. J.; Cho, J. W.; Sim, K. D.

2005-01-01

The High-Tc superconducting power cable consists of a multi-layer high-Tc superconducting cable core and a stabilizer which is used to bypass the current at fault time. Eddy current loss is generated in the stabilizer in normal operating condition and affects the whole system. In this paper, the eddy current losses are analyzed with respect to various structure of stabilizer by using opera-3d. Moreover, optimal conditions of the stabilizer are derived to minimize the eddy current losses from the analyzed results. The obtained results could be applied to the design and manufacture of the high-Tc superconducting power cable system.

Aeroelastic impact of above-rated wave-induced structural motions on the near-wake stability of a floating offshore wind turbine rotor

Science.gov (United States)

Rodriguez, Steven; Jaworski, Justin

2017-11-01

The impact of above-rated wave-induced motions on the stability of floating offshore wind turbine near-wakes is studied numerically. The rotor near-wake is generated using a lifting-line free vortex wake method, which is strongly coupled to a finite element solver for kinematically nonlinear blade deformations. A synthetic time series of relatively high-amplitude/high-frequency representative of above-rated conditions of the NREL 5MW referece wind turbine is imposed on the rotor structure. To evaluate the impact of these above-rated conditions, a linear stability analysis is first performed on the near wake generated by a fixed-tower wind turbine configuration at above-rated inflow conditions. The platform motion is then introduced via synthetic time series, and a stability analysis is performed on the wake generated by the floating offshore wind turbine at the same above-rated inflow conditions. The stability trends (disturbance modes versus the divergence rate of vortex structures) of the two analyses are compared to identify the impact that above-rated wave-induced structural motions have on the stability of the floating offshore wind turbine wake.

Effect of the mixing fields on the stability and structure of turbulent partially premixed flames in a concentric flow conical nozzle burner

KAUST Repository

Mansour, Mohy S.

2016-10-22

The mixing field is known to be one of the key parameters that affect the stability and structure of partially premixed flames. Data in these flames are now available covering the effects of turbulence, combustion system geometry, level of partially premixing and fuel type. However, quantitative analyses of the flame structure based on the mixing field are not yet available. The aim of this work is to present a comprehensive study of the effects of the mixing fields on the structure and stability of partially premixed methane flames. The mixing field in a concentric flow conical nozzle (CFCN) burner with well-controlled mechanism of the mixing is investigated using Rayleigh scattering technique. The flame stability, structure and flow field of some selected cases are presented using LIF of OH and PIV. The experimental data of the mixing field cover wide ranges of Reynolds number, equivalence ratio and mixing length. The data show that the mixing field is significantly affected by the mixing length and the ratio of the air-to-fuel velocities. The Reynolds number has a minimum effect on the mixing field in high turbulent flow regime and the stability is significantly affected by the turbulence level. The temporal fluctuations of the range of mixture fraction within the mixing field correlate with the flame stability. The highest point of stability occurs at recess distances where fluid mixtures near the jet exit plane are mostly within the flammability limits. This paper provides some correlations between the stability range in mixture fraction space and the turbulence level for different equivalence ratios.

Preliminary neutron diffraction analysis of challenging human manganese superoxide dismutase crystals.

Science.gov (United States)

Azadmanesh, Jahaun; Trickel, Scott R; Weiss, Kevin L; Coates, Leighton; Borgstahl, Gloria E O

2017-04-01

Superoxide dismutases (SODs) are enzymes that protect against oxidative stress by dismutation of superoxide into oxygen and hydrogen peroxide through cyclic reduction and oxidation of the active-site metal. The complete enzymatic mechanisms of SODs are unknown since data on the positions of hydrogen are limited. Here, methods are presented for large crystal growth and neutron data collection of human manganese SOD (MnSOD) using perdeuteration and the MaNDi beamline at Oak Ridge National Laboratory. The crystal from which the human MnSOD data set was obtained is the crystal with the largest unit-cell edge (240 Å) from which data have been collected via neutron diffraction to sufficient resolution (2.30 Å) where hydrogen positions can be observed.

Role of tryptophan 95 in substrate specificity and structural stability of Sulfolobus solfataricus alcohol dehydrogenase.

Science.gov (United States)

Pennacchio, Angela; Esposito, Luciana; Zagari, Adriana; Rossi, Mosè; Raia, Carlo A

2009-09-01

A mutant of the thermostable NAD(+)-dependent (S)-stereospecific alcohol dehydrogenase from Sulfolobus solfataricus (SsADH) which has a single substitution, Trp95Leu, located at the substrate binding pocket, was fully characterized to ascertain the role of Trp95 in discriminating between chiral secondary alcohols suggested by the wild-type SsADH crystallographic structure. The Trp95Leu mutant displays no apparent activity with short-chain primary and secondary alcohols and poor activity with aromatic substrates and coenzyme. Moreover, the Trp --> Leu substitution affects the structural stability of the archaeal ADH, decreasing its thermal stability without relevant changes in secondary structure. The double mutant Trp95Leu/Asn249Tyr was also purified to assist in crystallographic analysis. This mutant exhibits higher activity but decreased affinity toward aliphatic alcohols, aldehydes as well as NAD(+) and NADH compared to the wild-type enzyme. The crystal structure of the Trp95Leu/Asn249Tyr mutant apo form, determined at 2.0 A resolution, reveals a large local rearrangement of the substrate site with dramatic consequences. The Leu95 side-chain conformation points away from the catalytic metal center and the widening of the substrate site is partially counteracted by a concomitant change of Trp117 side chain conformation. Structural changes at the active site are consistent with the reduced activity on substrates and decreased coenzyme binding.

Extraction of superoxide dismutase, catalase, and carbonic anhydrase from stroma-free red blood cell hemolysate for the preparation of the nanobiotechnological complex of polyhemoglobin-superoxide dismutase-catalase-carbonic anhydrase.

Science.gov (United States)

Guo, C; Gynn, M; Chang, T M S

2015-06-01

We report a novel method to simultaneously extract superoxide dismutase (SOD), catalase (CAT), and carbonic anhydrase (CA) from the same sample of red blood cells (RBCs). This avoids the need to use expensive commercial enzymes, thus enabling a cost-effective process for large-scale production of a nanobiotechnological polyHb-SOD-CAT-CA complex, with enhancement of all three red blood cell functions. An optimal concentration of phosphate buffer for ethanol-chloroform treatment results in good recovery of CAT, SOD, and CA after extraction. Different concentrations of the enzymes can be used to enhance the activity of polyHb-SOD-CAT-CA to 2, 4, or 6 times that of RBC.

Atomistic Origins of High Capacity and High Structural Stability of Polymer-Derived SiOC Anode Materials.

Science.gov (United States)

Sun, Hong; Zhao, Kejie

2017-10-11

Capacity and structural stability are often mutually exclusive properties of electrodes in Li-ion batteries (LIBs): a gain in capacity is usually accompanied by the undesired large volumetric change of the host material upon lithiation. Polymer-derived ceramics, such as silicon oxycarbide (SiOC) of hybrid Si-O-C bonds, show an exceptional combination of high capacity and superior structural stability. We investigate the atomistic origins of the unique chemomechanical performance of carbon-rich SiOC using the first-principles theoretical approach. The atomic model of SiOC is composed of continuous Si-O-C units caged by a graphene-like cellular network and percolated nanovoids. The segregated sp 2 carbon network serves as the backbone to maintain the structural stability of the lattice. Li insertion is first absorbed at the nanovoid sites, and then it is accommodated by the SiOC tetrahedral units, excess C atoms, and topological defects at the edge of or within the segregated carbon network. SiOC expands up to 22% in volumetric strain at the fully lithiated capacity of 1230 mA h/g. We examine in great detail the evolution of the microscopic features of the SiOC molecule in the course of Li reactions. The first-principles modeling provides a fundamental understanding of the physicochemical properties of Si-based glass ceramics for their application in LIBs.

Stability, electrochemical behaviors and electronic structures of iron hydroxyl-phosphate

Energy Technology Data Exchange (ETDEWEB)

Wang Zhongli; Sun Shaorui; Li Fan; Chen Ge [College of Environmental and Energy Engineering, Beijing University of Technology, Pingleyuan 100, Chaoyang District, Beijing 100022 (China); Xia Dingguo, E-mail: dgxia@bjut.edu.cn [College of Environmental and Energy Engineering, Beijing University of Technology, Pingleyuan 100, Chaoyang District, Beijing 100022 (China); Zhao Ting; Chu Wangsheng [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); University of Science and Technology of China, Hefei 230026 (China); Wu Ziyu, E-mail: wuzy@ihep.ac.cn [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); University of Science and Technology of China, Hefei 230026 (China)

2010-09-01

Iron hydroxyl-phosphate with a uniform spherical particle size of around 1 {mu}m, a compound of the type Fe{sub 2-y}{open_square}{sub y}(PO{sub 4})(OH){sub 3-3y}(H{sub 2}O){sub 3y-2} (where {open_square} represents a vacancy), has been synthesized by hydrothermal methods. The particles are composed of spheres of diameter <100 nm. The compound exhibits good electrochemical performance, with reversible capacities of around 150 mAh g{sup -1} and 120 mAh g{sup -1} at current densities of 170 mA g{sup -1} and 680 mA g{sup -1}, respectively. The stability of crystal structure of this material was studied by TGA and XRD which show that the material remains stable at least up to the temperature 200 deg. C. Investigation of the electronic structure of the iron hydroxyl-phosphate by GGA + U calculation has indicated that it has a better electronic conductivity than LiFePO{sub 4}.

Integrated optimization on aerodynamics-structure coupling and flight stability of a large airplane in preliminary design

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Xiaozhe WANG

2018-06-01

Full Text Available The preliminary phase is significant during the whole design process of a large airplane because of its enormous potential in enhancing the overall performance. However, classical sequential designs can hardly adapt to modern airplanes, due to their repeated iterations, long periods, and massive computational burdens. Multidisciplinary analysis and optimization demonstrates the capability to tackle such complex design issues. In this paper, an integrated optimization method for the preliminary design of a large airplane is proposed, accounting for aerodynamics, structure, and stability. Aeroelastic responses are computed by a rapid three-dimensional flight load analysis method combining the high-order panel method and the structural elasticity correction. The flow field is determined by the viscous/inviscid iteration method, and the cruise stability is evaluated by the linear small-disturbance theory. Parametric optimization is carried out using genetic algorithm to seek the minimal weight of a simplified plate-beam wing structure in the cruise trim condition subject to aeroelastic, aerodynamic, and stability constraints, and the optimal wing geometry shape, front/rear spar positions, and structural sizes are obtained simultaneously. To reduce the computational burden of the static aeroelasticity analysis in the optimization process, the Kriging method is employed to predict aerodynamic influence coefficient matrices of different aerodynamic shapes. The multidisciplinary analyses guarantee computational accuracy and efficiency, and the integrated optimization considers the coupling effect sufficiently between different disciplines to improve the overall performance, avoiding the limitations of sequential approaches utilized currently. Keywords: Aeroelasticity, Integrated optimization, Multidisciplinary analysis, Large airplane, Preliminary design

Computational analysis of histidine mutations on the structural stability of human tyrosinases leading to albinism insurgence.

Science.gov (United States)

Hassan, Mubashir; Abbas, Qamar; Raza, Hussain; Moustafa, Ahmed A; Seo, Sung-Yum

2017-07-25

Misfolding and structural alteration in proteins lead to serious malfunctions and cause various diseases in humans. Mutations at the active binding site in tyrosinase impair structural stability and cause lethal albinism by abolishing copper binding. To evaluate the histidine mutational effect, all mutated structures were built using homology modelling. The protein sequence was retrieved from the UniProt database, and 3D models of original and mutated human tyrosinase sequences were predicted by changing the residual positions within the target sequence separately. Structural and mutational analyses were performed to interpret the significance of mutated residues (N 180 , R 202 , Q 202 , R 211 , Y 363 , R 367 , Y 367 and D 390 ) at the active binding site of tyrosinases. CSpritz analysis depicted that 23.25% residues actively participate in the instability of tyrosinase. The accuracy of predicted models was confirmed through online servers ProSA-web, ERRAT score and VERIFY 3D values. The theoretical pI and GRAVY generated results also showed the accuracy of the predicted models. The CCA negative correlation results depicted that the replacement of mutated residues at His within the active binding site disturbs the structural stability of tyrosinases. The predicted CCA scores of Tyr 367 (-0.079) and Q/R 202 (0.032) revealed that both mutations have more potential to disturb the structural stability. MD simulation analyses of all predicted models justified that Gln 202 , Arg 202 , Tyr 367 and D 390 replacement made the protein structures more susceptible to destabilization. Mutational results showed that the replacement of His with Q/R 202 and Y/R 363 has a lethal effect and may cause melanin associated diseases such as OCA1. Taken together, our computational analysis depicts that the mutated residues such as Q/R 202 and Y/R 363 actively participate in instability and misfolding of tyrosinases, which may govern OCA1 through disturbing the melanin biosynthetic pathway.

Deficiency of superoxide dismutase promotes cerebral vascular hypertrophy and vascular dysfunction in hyperhomocysteinemia.

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Sanjana Dayal

Full Text Available There is an emerging consensus that hyperhomocysteinemia is an independent risk factor for cerebral vascular disease and that homocysteine-lowering therapy protects from ischemic stroke. However, the mechanisms by which hyperhomocysteinemia produces abnormalities of cerebral vascular structure and function remain largely undefined. Our objective in this study was to define the mechanistic role of superoxide in hyperhomocysteinemia-induced cerebral vascular dysfunction and hypertrophy. Unlike previous studies, our experimental design included a genetic approach to alter superoxide levels by using superoxide dismutase 1 (SOD1-deficient mice fed a high methionine/low folate diet to produce hyperhomocysteinemia. In wild-type mice, the hyperhomocysteinemic diet caused elevated superoxide levels and impaired responses to endothelium-dependent vasodilators in cerebral arterioles, and SOD1 deficiency compounded the severity of these effects. The cross-sectional area of the pial arteriolar wall was markedly increased in mice with SOD1 deficiency, and the hyperhomocysteinemic diet sensitized SOD1-deficient mice to this hypertrophic effect. Analysis of individual components of the vascular wall demonstrated a significant increase in the content of smooth muscle and elastin. We conclude that superoxide is a key driver of both cerebral vascular hypertrophy and vasomotor dysfunction in this model of dietary hyperhomocysteinemia. These findings provide insight into the mechanisms by which hyperhomocysteinemia promotes cerebral vascular disease and ischemic stroke.

A Manganese Superoxide Dismutase (SOD2 Gene Polymorphism in Insulin-Dependent Diabetes Mellitus

Directory of Open Access Journals (Sweden)

Flemming Pociot

1993-01-01

Full Text Available Interleukin I (lL-I is selectively cytotoxic to the insulin producing beta cell of pancreatic islets. This effect may be due to IL-I induced generation of reactive oxygen species and nitric oxide. Since beta cells contain low amounts of the superoxide radical scavenger enzyme manganese superoxide dismutase (MnSOD, this may leave beta cells more susceptible to IL-I than other cell types. Genetic variation in the MnSOD locus could reflect differences in scavenger potential. We, therefore, studied possible restriction fragment length polymorphisms (RFLPs of this locus in patients with insulin-dependent diabetes mellitus (100M (n= 154 and control individuals (n=178, Taql revealed a double diallelic RFLP in patients as well as in controls. No overall difference in allelic or genotype frequencies were observed between 100M patients and control individuals (p=0.11 and no significant association of any particular RFLP pattern with 100M was found. Structurally polymorphic MnSOD protein variants with altered activities have been reported. If genetic variation results in MnSOD variants with reduced activities, the MnSOD locus may still be a candidate gene for 100M susceptibility. Whether the RFLPs reported in this study reflects differences in gene expression level, protein level and/or specific activity of the protein is yet to be studied.

Polymer stabilized Ni-Ag and Ni-Fe alloy nanoclusters: Structural and magnetic properties

Energy Technology Data Exchange (ETDEWEB)

Kabir, L.; Mandal, A.R. [Department of Physics, Visva-Bharati, Santiniketan-731 235 (India); Mandal, S.K., E-mail: sk_mandal@hotmail.co [Department of Physics, Visva-Bharati, Santiniketan-731 235 (India)

2010-04-15

We report here the structural and magnetic behaviors of nickel-silver (Ni-Ag) and nickel-iron (Ni-Fe) nanoclusters stabilized with polymer (polypyrrole). High resolution transmission electron microscopy (HRTEM) indicates Ni-Ag nanoclusters to stabilize in core-shell configuration while that of Ni-Fe nanoclusters in a mixed type of geometry. Structural characterizations by X-ray diffraction (XRD) reveal the possibility of alloying in such bimetallic nanoclusters to some extent even at temperatures much lower than that of bulk alloying. Electron paramagnetic resonance (EPR) spectra clearly reveal two different absorption behaviors: one is ascribed to non-isolated Ni{sup 2+} clusters surrounded by either silver or iron giving rise to a broad signal, other (very narrow signal) being due to the isolated superparamagnetic Ni{sup 2+} clusters or bimetallic alloy nanoclusters. Results obtained for Ni-Ag and Ni-Fe nanoclusters have been further compared with the behavior exhibited by pure Ni nanoclusters in polypyrrole host. Temperature dependent studies (at 300 and 77 K) of EPR parameters, e.g. linewidth, g-value, line shape and signal intensity indicating the significant influence of surrounding paramagnetic silver or ferromagnetic iron within polymer host on the EPR spectra have been presented.

Polymer stabilized Ni-Ag and Ni-Fe alloy nanoclusters: Structural and magnetic properties

Science.gov (United States)

Kabir, L.; Mandal, A. R.; Mandal, S. K.

2010-04-01

We report here the structural and magnetic behaviors of nickel-silver (Ni-Ag) and nickel-iron (Ni-Fe) nanoclusters stabilized with polymer (polypyrrole). High resolution transmission electron microscopy (HRTEM) indicates Ni-Ag nanoclusters to stabilize in core-shell configuration while that of Ni-Fe nanoclusters in a mixed type of geometry. Structural characterizations by X-ray diffraction (XRD) reveal the possibility of alloying in such bimetallic nanoclusters to some extent even at temperatures much lower than that of bulk alloying. Electron paramagnetic resonance (EPR) spectra clearly reveal two different absorption behaviors: one is ascribed to non-isolated Ni 2+ clusters surrounded by either silver or iron giving rise to a broad signal, other (very narrow signal) being due to the isolated superparamagnetic Ni 2+ clusters or bimetallic alloy nanoclusters. Results obtained for Ni-Ag and Ni-Fe nanoclusters have been further compared with the behavior exhibited by pure Ni nanoclusters in polypyrrole host. Temperature dependent studies (at 300 and 77 K) of EPR parameters, e.g. linewidth, g-value, line shape and signal intensity indicating the significant influence of surrounding paramagnetic silver or ferromagnetic iron within polymer host on the EPR spectra have been presented.

Polymer stabilized Ni-Ag and Ni-Fe alloy nanoclusters: Structural and magnetic properties

International Nuclear Information System (INIS)

Kabir, L.; Mandal, A.R.; Mandal, S.K.

2010-01-01

We report here the structural and magnetic behaviors of nickel-silver (Ni-Ag) and nickel-iron (Ni-Fe) nanoclusters stabilized with polymer (polypyrrole). High resolution transmission electron microscopy (HRTEM) indicates Ni-Ag nanoclusters to stabilize in core-shell configuration while that of Ni-Fe nanoclusters in a mixed type of geometry. Structural characterizations by X-ray diffraction (XRD) reveal the possibility of alloying in such bimetallic nanoclusters to some extent even at temperatures much lower than that of bulk alloying. Electron paramagnetic resonance (EPR) spectra clearly reveal two different absorption behaviors: one is ascribed to non-isolated Ni 2+ clusters surrounded by either silver or iron giving rise to a broad signal, other (very narrow signal) being due to the isolated superparamagnetic Ni 2+ clusters or bimetallic alloy nanoclusters. Results obtained for Ni-Ag and Ni-Fe nanoclusters have been further compared with the behavior exhibited by pure Ni nanoclusters in polypyrrole host. Temperature dependent studies (at 300 and 77 K) of EPR parameters, e.g. linewidth, g-value, line shape and signal intensity indicating the significant influence of surrounding paramagnetic silver or ferromagnetic iron within polymer host on the EPR spectra have been presented.

Ab initio study on stacking sequences, free energy, dynamical stability and potential energy surfaces of graphite structures

International Nuclear Information System (INIS)

Anees, P; Valsakumar, M C; Chandra, Sharat; Panigrahi, B K

2014-01-01

Ab initio simulations have been performed to study the structure, energetics and stability of several plausible stacking sequences in graphite. These calculations suggest that in addition to the standard structures, graphite can also exist in AA-simple hexagonal, AB-orthorhombic and ABC-hexagonal type stacking. The free energy difference between these structures is very small (∼1 meV/atom), and hence all the structures can coexist from purely energetic considerations. Calculated x-ray diffraction patterns are similar to those of the standard structures for 2θ ⩽ 70°. Shear elastic constant C 44 is negative in AA-simple hexagonal, AB-orthorhombic and ABC-hexagonal structures, suggesting that these structures are mechanically unstable. Phonon dispersions show that the frequencies of some modes along the Γ–A direction in the Brillouin zone are imaginary in all of the new structures, implying that these structures are dynamically unstable. Incorporation of zero point vibrational energy via the quasi-harmonic approximation does not result in the restoration of dynamical stability. Potential energy surfaces for the unstable normal modes are seen to have the topography of a potential hill for all the new structures, confirming that all of the new structures are inherently unstable. The fact that the potential energy surface is not in the form of a double well implies that the structures are linearly as well as globally unstable. (paper)

COMPARISON OF SELECTIVE AND NON SELECTIVE CYCLO-OXYGENASE 2 INHIBITORS IN EXPERIMENTAL COLITIS EXACERBATION: role of leukotriene B4 and superoxide dismutase

Directory of Open Access Journals (Sweden)

José Wander BREGANÓ

2014-09-01

Full Text Available Context Nonsteroidal anti-inflammatory drugs are considered one of the most important causes of reactivation of inflammatory bowel disease. With regard to selective cyclo-oxygenase 2 inhibitors, the results are controversial in experimental colitis as well as in human studies. Objectives The aim this study is to compare nonsteroidal anti-inflammatory drugs effects, selective and non selective cyclo-oxygenase 2 inhibitors, in experimental colitis and contribute to the understanding of the mechanisms which nonsteroidal anti-inflammatory drugs provoke colitis exacerbation. Methods Six groups of rats: without colitis, with colitis, and colitis treated with celecoxib, ketoprofen, indometacin or diclofenac. Survival rates, hemoglobin, plasmatic albumin, colonic tissue of interleukin-1ß, interleukin-6, tumor necrosis factor alpha, prostaglandin E2, catalase, superoxide dismutase, thiobarbituric acid-reactive substances, chemiluminescence induced by tert-butil hydroperoxides, and tissue and plasmatic leukotriene B4 were determined. Results The groups treated with diclofenac or indometacin presented lower survival rates, hemoglobin and albumin, higher tissue and plasmatic leukotriene B4 and tissue superoxide dismutase than the group treated with celecoxib. Ketoprofen presented an intermediary behavior between diclofenac/indometacin and celecoxib, concerning to survival rate and albumin. The groups without colitis, with colitis and with colitis treated with celecoxib showed leukotriene B4 and superoxide dismutase lower levels than the groups treated with nonselective cyclo-oxygenase 2 inhibitors. Conclusions Diclofenac and indometacin presented the highest degree of induced colitis exacerbation with nonsteroidal anti-inflammatory drugs, celecoxib did not show colitis exacerbation, and ketoprofen presented an intermediary behavior between diclofenac/indometacin and celecoxib. These results suggest that leukotriene B4 and superoxide dismutase can be

Hepatoprotective effects of Poly-[hemoglobin-superoxide dismutase-catalase-carbonic anhydrase] on alcohol-damaged primary rat hepatocyte culture in vitro.

Science.gov (United States)

Jiang, Wenhua; Bian, Yuzhu; Wang, Zhenghui; Chang, Thomas Ming Swi

2017-02-01

We have prepared a novel nanobiotherapeutic, Poly-[hemoglobin-superoxide dismutase-catalase-carbonic anhydrase], which not only transports both oxygen and carbon dioxide but also a therapeutic antioxidant. Our previous study in a severe sustained 90 min hemorrhagic shock rat model shows that it has a hepatoprotective effect. We investigate its hepatoprotective effect further in this present report using an alcohol-damaged primary hepatocyte culture model. Results show that it significantly reduced ethanol-induced AST release, lipid peroxidation, and ROS production in rat primary hepatocytes culture. It also significantly enhanced the viability of ethanol-treated hepatocytes. Thus, the result shows that Poly-[hemoglobin-superoxide dismutase-catalase-carbonic anhydrase] also has some hepatoprotective effects against alcohol-induced injury in in vitro rat primary hepatocytes cell culture. This collaborate our previous observation of its hepatoprotective effect in a severe sustained 90-min hemorrhagic shock rat model.

DFT investigations on mechanical stability, electronic structure and magnetism in Co2TaZ (Z = Al, Ga, In) heusler alloys

Science.gov (United States)

Khandy, Shakeel Ahmad; Gupta, Dinesh C.

2017-12-01

Ferromagnetic Heusler compounds have vast and imminent applications for novel devices, smart materials thanks to density functional theory (DFT) based simulations, which have scored out a new approach to study these materials. We forecast the structural stability of Co2TaZ alloys on the basis of total energy calculations and mechanical stability criteria. The elastic constants, robust spin-polarized ferromagnetism and electron densities in these half-metallic alloys are also discussed. The observed structural aspects calculated to predict the stability and equilibrium lattice parameters agree well with the experimental results. The elastic parameters like elastic constants, bulk, Young’s and shear moduli, poison’s and Pugh ratios, melting temperatures, etc have been put together to establish their mechanical properties. The elaborated electronic band structures along with indirect band gaps and spin polarization favour the application of these materials in spintronics and memory device technology.

Structuring detergents for extracting and stabilizing functional membrane proteins.

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Rima Matar-Merheb

Full Text Available BACKGROUND: Membrane proteins are privileged pharmaceutical targets for which the development of structure-based drug design is challenging. One underlying reason is the fact that detergents do not stabilize membrane domains as efficiently as natural lipids in membranes, often leading to a partial to complete loss of activity/stability during protein extraction and purification and preventing crystallization in an active conformation. METHODOLOGY/PRINCIPAL FINDINGS: Anionic calix[4]arene based detergents (C4Cn, n=1-12 were designed to structure the membrane domains through hydrophobic interactions and a network of salt bridges with the basic residues found at the cytosol-membrane interface of membrane proteins. These compounds behave as surfactants, forming micelles of 5-24 nm, with the critical micellar concentration (CMC being as expected sensitive to pH ranging from 0.05 to 1.5 mM. Both by 1H NMR titration and Surface Tension titration experiments, the interaction of these molecules with the basic amino acids was confirmed. They extract membrane proteins from different origins behaving as mild detergents, leading to partial extraction in some cases. They also retain protein functionality, as shown for BmrA (Bacillus multidrug resistance ATP protein, a membrane multidrug-transporting ATPase, which is particularly sensitive to detergent extraction. These new detergents allow BmrA to bind daunorubicin with a Kd of 12 µM, a value similar to that observed after purification using dodecyl maltoside (DDM. They preserve the ATPase activity of BmrA (which resets the protein to its initial state after drug efflux much more efficiently than SDS (sodium dodecyl sulphate, FC12 (Foscholine 12 or DDM. They also maintain in a functional state the C4Cn-extracted protein upon detergent exchange with FC12. Finally, they promote 3D-crystallization of the membrane protein. CONCLUSION/SIGNIFICANCE: These compounds seem promising to extract in a functional state

Effect of homogenization and pasteurization on the structure and stability of whey protein in milk.

Science.gov (United States)

Qi, Phoebe X; Ren, Daxi; Xiao, Yingping; Tomasula, Peggy M

2015-05-01

The effect of homogenization alone or in combination with high-temperature, short-time (HTST) pasteurization or UHT processing on the whey fraction of milk was investigated using highly sensitive spectroscopic techniques. In pilot plant trials, 1-L quantities of whole milk were homogenized in a 2-stage homogenizer at 35°C (6.9 MPa/10.3 MPa) and, along with skim milk, were subjected to HTST pasteurization (72°C for 15 s) or UHT processing (135°C for 2 s). Other whole milk samples were processed using homogenization followed by either HTST pasteurization or UHT processing. The processed skim and whole milk samples were centrifuged further to remove fat and then acidified to pH 4.6 to isolate the corresponding whey fractions, and centrifuged again. The whey fractions were then purified using dialysis and investigated using the circular dichroism, Fourier transform infrared, and Trp intrinsic fluorescence spectroscopic techniques. Results demonstrated that homogenization combined with UHT processing of milk caused not only changes in protein composition but also significant secondary structural loss, particularly in the amounts of apparent antiparallel β-sheet and α-helix, as well as diminished tertiary structural contact. In both cases of homogenization alone and followed by HTST treatments, neither caused appreciable chemical changes, nor remarkable secondary structural reduction. But disruption was evident in the tertiary structural environment of the whey proteins due to homogenization of whole milk as shown by both the near-UV circular dichroism and Trp intrinsic fluorescence. In-depth structural stability analyses revealed that even though processing of milk imposed little impairment on the secondary structural stability, the tertiary structural stability of whey protein was altered significantly. The following order was derived based on these studies: raw whole>HTST, homogenized, homogenized and pasteurized>skimmed and pasteurized, and skimmed UHT

Antioxidant therapy attenuates myocardial telomerase activity reduction in superoxide dismutase-deficient mice.

Science.gov (United States)

Makino, Naoki; Maeda, Toyoki; Oyama, Jun-ichi; Sasaki, Makoto; Higuchi, Yoshihiro; Mimori, Koji; Shimizu, Takahiko

2011-04-01

Oxidative stress plays a pathological role in the development of heart failure. This study examined telomere biology in heart/muscle-specific manganese superoxide dismutase-deficient mice (H/M-SOD2(-/-)), which develop progressive congestive heart failure and exhibit pathology typical of dilated cardiomyopathy. EUK-8 (25mg/kg/day), a superoxide dismutase and catalase mimetic, was administered to H/M-SOD2(-/-) mice for four weeks beginning at 8 weeks of age. Telomere length, telomerase activity, telomere-associated proteins, and cell death signals were assessed in hearts from control wild-type mice (H/M-Sod2 (lox/ lox)) and H/M-SOD2(-/-) mice either treated or untreated with EUK-8. While cardiac function was unchanged in these experimental mice, the end-diastolic dimension in H/M-SOD2(-/-) mice was notably dilated and could be significantly reduced by EUK-8 treatment. At the end of the study, no shortening of telomere length was observed in heart tissues from all mice tested, but telomerase activity was decreased in heart tissue from H/M-SOD2(-/-) mice compared to control mice. Protein expression for telomerase reverse transcriptase and telomere repeat binding factor 2 was also downregulated in H/M-SOD2(-/-) heart tissue as was expression of phospho-Akt, insulin-like growth factor, and endothelial nitric oxide synthase. Expression levels of Sirt1, a lifespan modulator, were enhanced while FoxO3a was depressed in H/M-SOD2(-/-) hearts. All of the changes seen in H/M-SOD2(-/-) heart tissue could be inhibited by EUK-8 treatment. Taken together, the results suggest that oxidant stress might affect myocardial telomerase activity and telomere-associated proteins. Telomerase may therefore play a pivotal role in antioxidant defense mechanisms, and may be useful as a novel therapeutic tool for treating human heart failure. Copyright © 2010 Elsevier Ltd. All rights reserved.

Structural aspects of magnetic fluid stabilization in aqueous agarose solutions

Energy Technology Data Exchange (ETDEWEB)

Nagornyi, A.V. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Taras Shevchenko National University of Kyiv, Kyiv (Ukraine); Petrenko, V.I., E-mail: vip@nf.jinr.ru [Joint Institute for Nuclear Research, Dubna (Russian Federation); Taras Shevchenko National University of Kyiv, Kyiv (Ukraine); Avdeev, M.V. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Yelenich, O.V.; Solopan, S.O.; Belous, A.G. [V.I.Vernadsky Institute of General and Inorganic Chemistry of the Ukrainian NAS, Kyiv (Ukraine); Gruzinov, A.Yu. [National Research Centre “Kurchatov Institute”, Moscow (Russian Federation); Ivankov, O.I. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Institute for Safety Problems of Nuclear Power Plants of the Ukrainian NAS, Kyiv (Ukraine); Bulavin, L.A. [Taras Shevchenko National University of Kyiv, Kyiv (Ukraine); Institute for Safety Problems of Nuclear Power Plants of the Ukrainian NAS, Kyiv (Ukraine)

2017-06-01

Structure characterization of magnetic fluids (MFs) synthesized by three different methods in aqueous solutions of agarose was done by means of small-angle neutron (SANS) and synchrotron X-ray scattering (SAXS). The differences in the complex aggregation observed in the studied magnetic fluids were related to different stabilizing procedures of the three kinds of MFs. The results of the analysis of the scattering (mean size of single polydisperse magnetic particles, fractal dimensions of the aggregates) are consistent with the data of transmission electron microscopy (TEM). - Highlights: • MFs synthesized by three different methods in agarose solution were studied. • all MFs are agglomerated colloidal systems whose structures are nevertheless stable in time. • differences in the complex aggregation were observed in the studied magnetic fluids. • results of the SAXS and SANS analysis are consistent with TEM data.

Structure of anti-FLAG M2 Fab domain and its use in the stabilization of engineered membrane proteins

International Nuclear Information System (INIS)

Roosild, Tarmo P.; Castronovo, Samantha; Choe, Senyon

2006-01-01

The X-ray crystallographic analysis of anti-FLAG M2 Fab is reported and the implications of the structure on FLAG epitope binding are described as a first step in the development of a tool for the structural and biophysical study of membrane proteins. The inherent difficulties of stabilizing detergent-solubilized integral membrane proteins for biophysical or structural analysis demand the development of new methodologies to improve success rates. One proven strategy is the use of antibody fragments to increase the ‘soluble’ portion of any membrane protein, but this approach is limited by the difficulties and expense associated with producing monoclonal antibodies to an appropriate exposed epitope on the target protein. Here, the stabilization of a detergent-solubilized K + channel protein, KvPae, by engineering a FLAG-binding epitope into a known loop region of the protein and creating a complex with Fab fragments from commercially available anti-FLAG M2 monoclonal antibodies is reported. Although well diffracting crystals of the complex have not yet been obtained, during the course of crystallization trials the structure of the anti-FLAG M2 Fab domain was solved to 1.86 Å resolution. This structure, which should aid future structure-determination efforts using this approach by facilitating molecular-replacement phasing, reveals that the binding pocket appears to be specific only for the first four amino acids of the traditional FLAG epitope, namely DYKD. Thus, the use of antibody fragments for improving the stability of target proteins can be rapidly applied to the study of membrane-protein structure by placing the short DKYD motif within a predicted peripheral loop of that protein and utilizing commercially available anti-FLAG M2 antibody fragments

Effects of stabilizer ratio on photoluminescence properties of sol-gel ZnO nano-structured thin films

International Nuclear Information System (INIS)

Boudjouan, F.; Chelouche, A.; Touam, T.; Djouadi, D.; Khodja, S.; Tazerout, M.; Ouerdane, Y.; Hadjoub, Z.

2015-01-01

Nanostructured ZnO thin films with different molar ratios of MEA to zinc acetate (0.5, 1.0, 1.5 and 2.0) have been deposited on glass substrates by a sol–gel dip coating technique. X-ray diffraction, Scanning Electron Microscopy, UV–visible spectrophotometry and photoluminescence spectroscopy have been employed to investigate the effect of MEA stabilizer ratio on structural, morphological, absorbance and emission properties of the ZnO thin films. Diffraction patterns have shown that all the films are polycrystalline and exhibit a wurtzite hexagonal structure. The c axis orientation has been enhanced with increasing stabilizer ratio. SEM micrographs have revealed that the morphology of the ZnO films depend on stabilizer ratio. The UV–visible absorption spectra have demonstrated that the optical absorption is affected by stabilizer ratio. The photoluminescence spectra have indicated one ultraviolet and two visible emission bands (green and red), while band intensities are found to be dependent on stabilizer ratio. ZnO thin films deposited at MEA ratio of 1.0 show the highest UV emission while the minimum UV emission intensity is observed in thin films deposited at ratio of 0.5 and the maximum green has been recorded for films deposited at MEA ratio of 2.0. - Highlight: • c axis orientation increases with increasing MEA ratio. • The increase of MEA ration from 0.5 to 1.0 enhances greatly the UV emission. • The larger I UV /I visible is obtained for the MEA to Zn ratio of 1:1. • The MEA ratio of 0.5 favors the formation of large density of V zn . • The MEA ratio of 2.0 increases the V o density

Structure, stability, and thermomechanical properties of Ca-substituted Pr2NiO4 + δ

Science.gov (United States)

Pikalova, E. Yu.; Medvedev, D. A.; Khasanov, A. F.

2017-04-01

Ca-substituted layered nickelates with a general Pr2- x Ca x NiO4 + δ composition ( x = 0-0.7, Δ x = 0.1) were prepared in the present work and their structural and physic-chemical properties were investigated in order to select the most optimal materials, which can be used as cathodes for solid oxide fuel cells. With an increase in Ca content in Pr2- x Ca x NiO4 + δ the following tendencies were observed: (i) a decrease in the concentration of nonstoichiometric oxygen (δ), (ii) a decrease in the unit cell parameters and volume, (iii) stabilization of the tetragonal structure, (iv) a decrease of the thermal expansion coefficients, and (v) enchancement of thermodynamic stability and compatibility with selected oxygen- and proton-conducting electrolytes. The Pr1.9Ca0.1NiO4 + δ material, having highest δ value, departs from the general "properties-composition" dependences ascertained. This indicates that oxygen non-stoichiometry has determining influence on the functional properties of layered nickelates.

Stability, structure, and evolution of cool loops

International Nuclear Information System (INIS)

Cally, P.S.; Robb, T.D.

1991-01-01

The criteria for the existence and stability of cool loops are reexamined. It is found that the stability of the loops strongly depends on the form of the heating and radiative loss functions and that if the Ly-alpha peak which appears in most calculations of the radiative loss function is real, cool loops are almost certainly unstable. Removing the hydrogen contribution from the recent loss function Q(T) by Cook et al. (1989) does not produce the much-used result, Q proportional to T-cubed, which is so favorable to cool loop stability. Even using the probably unrealistically favorable loss function Q1 of Cook et al. with the hydrogen contribution removed, the maximum temperature attainable in stable cool loops is a factor of 2-3 too small to account for the excess emission observed in lower transition region lines. Dynamical simulations of cool loop instabilities reveal that the final state of such a model is the hot loop equilibrium. 26 refs

Influence of Surfactant Structure on the Stability of Water-in-Oil Emulsions under High-Temperature High-Salinity Conditions

Directory of Open Access Journals (Sweden)

Abdelhalim I. A. Mohamed

2017-01-01

Full Text Available Emulsified water-in-oil (W/O systems are extensively used in the oil industry for water control and acid stimulation. Emulsifiers are commonly utilized to emulsify a water-soluble material to form W/O emulsion. The selection of a particular surfactant for such jobs is critical and certainly expensive. In this work, the impact of surfactant structure on the stability of W/O emulsions is investigated using the hydrophilic-lipophilic balance (HLB of the surfactant. Different commercial surfactants were evaluated for use as emulsifiers for W/O systems at high-temperature (up to 120°C high-salinity (221,673 ppm HTHS conditions. Diverse surfactants were examined including ethoxylates, polyethylene glycols, fluorinated surfactants, and amides. Both commercial Diesel and waste oil are used for the oleic phase to prepare the emulsified system. Waste oil has shown higher stability (less separation in comparison with Diesel. This work has successfully identified stable emulsified W/O systems that can tolerate HTHS environments using HLB approach. Amine Acetate family shows higher stability in comparison with Glycol Ether family and at even lower concentration. New insights into structure-surfactant stability relationship, beyond the HLB approach, are provided for surfactant selection.

Oxidative stability of mayonnaise containing structured lipids produced from sunflower oil and caprylic acid

DEFF Research Database (Denmark)

Jacobsen, Charlotte; Xu, Xuebing; Nielsen, Nina Skall

2003-01-01

Mayonnaise based on enzymatically produced specific structured lipid (SL) from sunflower oil and caprylic acid was compared with mayonnaise based on traditional sunflower oil (SO) or chemically randomized lipid (RL) with respect to their oxidative stability, sensory and rheological properties......, but was most likely influenced by the structure of the lipid, the lower tocopherol content and the higher initial levels of lipid hydroperoxides and secondary volatile oxidation compounds in the SL itself compared with the RL and traditional sunflower oil employed. EDTA was a strong antioxidant, while propyl...

Improving stability and strength characteristics of framed structures with nonlinear behavior

Science.gov (United States)

Pezeshk, Shahram

1990-01-01

In this paper an optimal design procedure is introduced to improve the overall performance of nonlinear framed structures. The design methodology presented here is a multiple-objective optimization procedure whose objective functions involve the buckling eigenvalues and eigenvectors of the structure. A constant volume with bounds on the design variables is used in conjunction with an optimality criterion approach. The method provides a general tool for solving complex design problems and generally leads to structures with better limit strength and stability. Many algorithms have been developed to improve the limit strength of structures. In most applications geometrically linear analysis is employed with the consequence that overall strength of the design is overestimated. Directly optimizing the limit load of the structure would require a full nonlinear analysis at each iteration which would be prohibitively expensive. The objective of this paper is to develop an algorithm that can improve the limit-load of geometrically nonlinear framed structures while avoiding the nonlinear analysis. One of the novelties of the new design methodology is its ability to efficiently model and design structures under multiple loading conditions. These loading conditions can be different factored loads or any kind of loads that can be applied to the structure simultaneously or independently. Attention is focused on optimal design of space framed structures. Three-dimensional design problems are more complicated to carry out, but they yield insight into real behavior of the structure and can help avoiding some of the problems that might appear in planar design procedure such as the need for out-of-plane buckling constraint. Although researchers in the field of structural engineering generally agree that optimum design of three-dimension building frames especially in the seismic regions would be beneficial, methods have been slow to emerge. Most of the research in this area has dealt

Disulfide scrambling in superoxide dismutase 1 reduces its cytotoxic effect in cultured cells and promotes protein aggregation.

Directory of Open Access Journals (Sweden)

Lina Leinartaitė

Full Text Available Mutations in the gene coding for superoxide dismutase 1 (SOD1 are associated with familiar forms of the neurodegenerative disease amyotrophic lateral sclerosis (ALS. These mutations are believed to result in a "gain of toxic function", leading to neuronal degeneration. The exact mechanism is still unknown, but misfolding/aggregation events are generally acknowledged as important pathological events in this process. Recently, we observed that demetallated apoSOD1, with cysteine 6 and 111 substituted for alanine, is toxic to cultured neuroblastoma cells. This toxicity depended on an intact, high affinity Zn(2+ site. It was therefor contradictory to discover that wild-type apoSOD1 was not toxic, despite of its high affinity for Zn(2+. This inconsistency was hypothesized to originate from erroneous disulfide formation involving C6 and C111. Using high resolution non-reducing SDS-PAGE, we have in this study demonstrated that the inability of wild-type apoSOD1 to cause cell death stems from formation of non-native intra-molecular disulfides. Moreover, monomeric apoSOD1 variants capable of such disulfide scrambling aggregated into ThT positive oligomers under physiological conditions without agitation. The oligomers were stabilized by inter-molecular disulfides and morphologically resembled what has in other neurodegenerative diseases been termed protofibrils. Disulfide scrambling thus appears to be an important event for misfolding and aggregation of SOD1, but may also be significant for protein function involving cysteines, e.g. mitochondrial import and copper loading.

Structure stability of HKUST-1 towards water and ethanol and their effect on its CO2 capture properties.

Science.gov (United States)

Álvarez, J Raziel; Sánchez-González, Elí; Pérez, Eric; Schneider-Revueltas, Emilia; Martínez, Ana; Tejeda-Cruz, Adriana; Islas-Jácome, Alejandro; González-Zamora, Eduardo; Ibarra, Ilich A

2017-07-18

Water and ethanol stabilities of the crystal structure of the Cu-based metal-organic framework (MOF) HKUST-1 have been investigated. Vapour (water and ethanol) sorption isotherms and cyclability were measured by a dynamic strategy. The ethanol sorption capacity of HKUST-1 at 303 K remained unchanged contrasting water sorption (which decreased along with the sorption experiment time). Considering the binding energy of each sorbate with the open Cu(ii) sites, obtained by the use of diffusion coefficients, we showed the superior crystal stability of the HKUST-1 framework towards ethanol. Finally, a small quantity of ethanol (pre-adsorbed) slightly enhanced CO 2 capture without crystal structure degradation.

Evidence for the long-term stability of uranium mill tailings: survivability of ancient man-made earthern structures

International Nuclear Information System (INIS)

Lindsey, C.G.; Mishima, J.

1982-09-01

Pacific Northwest Laboratory (PNL), as part of a study for the Nuclear Regulatory Commission (NRC), is investigating long-term stabilization techniques for uranium mill tailings piles. Part of this invetigation involves the design of a rock armoring blanket to mitigate wind and water erosion of the underlying soil cover, which, in turn, prevents exposure of the tailings to the environment. However, the need for the armoring blanket, as well as this blanket's effectiveness, depends on the stability of the underlying soil cap (radon suppression cover) and on the tailings themselves. Compelling evidence in archaeological records suggests that large man-made earthen structures can remain sound and intact for time periods comparable to those required for the tailings piles. In this paper we present archaeological evidence of the existence and survivability of man-made earthen and rock structures through specific examples of such structures around the world. We also review factors contributing to the survival or destruction of these structures. Archaeological evidence suggests that whereas natural erosional forces have affected these structures, man's activities (e.g., agriculture, looting) have been the most damaging. The influence of climate, building materials, and construction techniques on survivability is addressed in this paper

Dromion-like structures and stability analysis in the variable coefficients complex Ginzburg–Landau equation

International Nuclear Information System (INIS)

Wong, Pring; Pang, Li-Hui; Huang, Long-Gang; Li, Yan-Qing; Lei, Ming; Liu, Wen-Jun

2015-01-01

The study of the complex Ginzburg–Landau equation, which can describe the fiber laser system, is of significance for ultra-fast laser. In this paper, dromion-like structures for the complex Ginzburg–Landau equation are considered due to their abundant nonlinear dynamics. Via the modified Hirota method and simplified assumption, the analytic dromion-like solution is obtained. The partial asymmetry of structure is particularly discussed, which arises from asymmetry of nonlinear and dispersion terms. Furthermore, the stability of dromion-like structures is analyzed. Oscillation structure emerges to exhibit strong interference when the dispersion loss is perturbed. Through the appropriate modulation of modified exponent parameter, the oscillation structure is transformed into two dromion-like structures. It indicates that the dromion-like structure is unstable, and the coherence intensity is affected by the modified exponent parameter. Results in this paper may be useful in accounting for some nonlinear phenomena in fiber laser systems, and understanding the essential role of modified Hirota method

The Use of Polymerized Genipin for the Stabilization of the Collagen Structure of Animal Hides

Science.gov (United States)

Animal hides are the major byproduct of meat industry and the collagen fibers is the main constituent. Crosslinkers play a key role in stabilizing the collagen structure for useful applications. Genipin is widely used as an ideal biological protein crosslinking agent due to its low toxicity compare...

111Cd TDPAC investigation of metal sites in superoxide dismutase: A comparison with X-ray diffraction data

DEFF Research Database (Denmark)

Bauer, R.; Bjerrum, M.J.; Danielsen, E.

1990-01-01

111Cd Time Differential Ferturbed γ-γ Angular Correlation (TDPAC) has been used to investigate the Zn-site in Cu2, Zn2-superoxide dismutase. These experiments show a clear difference between Cu(II)2 Cd2 SOD and Cu(I)2Cd2SOD. The result of Cu(II)2, Cd2-SOD agrees with the Angular Overlap Model (AO...

Effect of liposome entrapped Cu/Zn bovine superoxide dismutase in rat after total body (neutron-gamma) irradiation

International Nuclear Information System (INIS)

Lamproglou, I.; Martin, S.; Lambert, F.; Fontanille, P.; Fessi, H.; Puisieux, F.; Colas-Linhart, N.; Bok, B.; Fatome, M.; Martin, C.

1998-01-01

Our purpose was, to study in rat the effects of (neutron-gamma) exposure and of LIPSOD treatment (liposomal Cu/Zn super-oxide dismutase) on cognitive functions. Our data demonstrate that whole-body irradiation induces in Sprague-Dawley rats some cognitive dysfunction. Treatment using LIPSOD corrects in a significantly way this trend. Moreover, in sham-irradiated rats, this treatment shows an inhibitory effect. (authors)

Chemical structure and radiation stability of solid crystalline antibiotics: thiamphenicol and chloramphenicol

International Nuclear Information System (INIS)

Varshney, Lalit; Soe Nwe

1997-01-01

Antibiotics in solid state show significant radiation resistance and some of them are exposed to gamma or electron beam irradiation for sterilization. Even small radiation degradation in solid state antibiotics is not desirable. Two antibiotics namely thiamphenicol (TPL) and chloramphenicol (CPL) having similar chemical and solid state structure were irradiated at different graded radiation doses to study their stability. Differential scanning calorimetry (DSC) was used to evaluate purity, entropy of radiation processing, heat of fusion and melting point. (author). 3 refs., 1 tab

Effect of Juglone foliar injection on Superoxide dismutases antioxidant system in two Musa spp cultivars

Directory of Open Access Journals (Sweden)

Michel Leiva Mora

2004-04-01

Full Text Available Some diseases in higher plants cause formation of reactive oxygen species (ROS which acts like mediator on tolerance to oxidative stress. Several phytotoxins produced by plant pathogen fungus induce ROS by different mechanisms which damage plant cell tissues. This paper was focused to determine juglone impact (Psedocercospora fijiensis toxin on Superoxide dismutases antioxidant system in Fougamou (ABB and Grande naine (AAA by native Poliacrylamide gel electrophoresis (PAGE 10%. Samples of proteins were collected at 2, 4, 6, 8 and 48h after juglone injection on both Musa cultivar and 65 μl of them (120 μg of total protein were applied to gels. Gels were incubated in staining solution (25 mg.ml-1 de Nitrobluetetrazolium (NTB and 0.1 mg.ml-1 de riboflavin and were exposured to fluorescent light. In both cultivars it was observed changes in expression patterns of superoxide dismutases between injected and not injected plants. On Grande naine (AAA 4 h after injection an isoform of SOD disappeared respect to control. Nevertheless on Fougamou (ABB, 2 h after injection it was activated a new isoform which was observed until 48 h. In the present work it was observed a correspondence between protein patterns expression of SOD isoforms and tolerance to oxidative stress caused by the effect of juglone on Musa spp. Key words: antioxidant enzymes, Mycosphaerella fijiensis,oxidative stress, toxins

Beam Stability in the Drive-Beam Decelerator of CLIC Using Structures of High-Order Symmetry

CERN Document Server

Millich, Antonio; Schulte, Daniel

1999-01-01

The RF power necessary to accelerate the main beam of the Compact Linear Collider (CLIC) is produced by decelerating a high-current drive beam in Power Extraction and Transfer Structures (PETS). The reference structure is not cylindrically symmetric but has longitudinal waveguides carved into the inner surface. This gives rise to a transverse component of the main longitudinal mode which can not be damped, in contrast to the transverse dipole wake- field. The field is non-linear and couples the motion of the particles in the two planes. Limits of the stability of the decelerated beam are investigated for different structures.

Strategies to curb structural changes of lithium/transition metal oxide cathode materials & the changes’ effects on thermal & cycling stability

Science.gov (United States)

Xiqian, Yu; Enyuan, Hu; Seongmin, Bak; Yong-Ning, Zhou; Xiao-Qing, Yang

2016-01-01

Structural transformation behaviors of several typical oxide cathode materials during a heating process are reviewed in detail to provide in-depth understanding of the key factors governing the thermal stability of these materials. We also discuss applying the information about heat induced structural evolution in the study of electrochemically induced structural changes. All these discussions are expected to provide valuable insights for designing oxide cathode materials with significantly improved structural stability for safe, long-life lithium ion batteries, as the safety of lithium-ion batteries is a critical issue; it is widely accepted that the thermal instability of the cathodes is one of the most critical factors in thermal runaway and related safety problems. Project supported by the U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies (Grant No. DE-SC0012704).

Innovative Ingredients and Emerging Technologies for Controlling Ice Recrystallization, Texture, and Structure Stability in Frozen Dairy Desserts: A Review.

Science.gov (United States)

Soukoulis, Christos; Fisk, Ian

2016-11-17

Over the past decade, ice cream manufacturers have developed a strong understanding of the functionality of key ingredients and processing, developing effective explanations for the link between structure forming agents, stability mechanisms, and perceived quality. Increasing demand for products perceived as healthier/more natural with minimal processing has identified a number of new tools to improve quality and storage stability of frozen dairy desserts. Ingredients such as dietary fiber, polysaccharides, prebiotics, alternate sweeteners, fat sources rich in unsaturated fatty acids and ice strucsturing proteins (ISP) have been successfully applied as cryoprotective, texturizing, and structuring agents. Emerging minimal processing technologies including hydrostatic pressure processing, ultrasonic or high pressure assisted freezing, low temperature extrusion and enzymatically induced biopolymers crosslinking have been evaluated for their ability to improve colloidal stability, texture and sensory quality. It is therefore timely for a comprehensive review.

Screening of drugs inhibiting in vitro oligomerization of Cu/Zn-superoxide dismutase with a mutation causing amyotrophic lateral sclerosis

Directory of Open Access Journals (Sweden)

Itsuki Anzai

2016-08-01

Full Text Available Dominant mutations in Cu/Zn-superoxide dismutase (SOD1 gene have been shown to cause a familial form of amyotrophic lateral sclerosis (SOD1-ALS. A major pathological hallmark of this disease is abnormal accumulation of mutant SOD1 oligomers in the affected spinal motor neurons. While no effective therapeutics for SOD1-ALS is currently available, SOD1 oligomerization will be a good target for developing cures of this disease. Recently, we have reproduced the formation of SOD1 oligomers abnormally cross-linked via disulfide bonds in a test tube. Using our in vitro model of SOD1 oligomerization, therefore, we screened 640 FDA-approved drugs for inhibiting the oligomerization of SOD1 proteins, and three effective classes of chemical compounds were identified. Those hit compounds will provide valuable information on the chemical structures for developing a novel drug candidate suppressing the abnormal oligomerization of mutant SOD1 and possibly curing the disease.

Stability and electronic structure of carbon capsules with superior gas storage properties: A theoretical study

International Nuclear Information System (INIS)

Manna, Arun K.; Pati, Swapan K.

2013-01-01

Highlights: • Stability and electronic structure of various carbon capsules are studied. • Effects of capsule’s sizes on electronic and optical properties are explored. • Changes in cohesive and formation energy and electronic gap are discussed. • Capsule’s gas storage propensity is addressed using DFT and ab initio MD. • Capsule’s optical absorptions are discussed with and without stored gas molecules. - Abstract: Structures, electronic and optical properties of carbon nanocapsules of varying sizes (length and diameter) are studied using first-principles density functional theory. Based on calculated cohesive energy, formation energy, electronic gap and extent of orbital delocalization, we examine structural stability and changes in low-energy physics of these carbon capsules. We find that both cohesive and formation energy decrease with increase in capsule’s sizes, indicating their greater structural rigidity and favorable formation feasibility. The electronic gap also decreases with increase in capsule’s sizes due to the larger electronic delocalization. The simulated optical absorption spectra show lowering of low-energy peak positions with increase in the capsule’s dimensions, consistent with the reduction in electronic gap. Additionally, we also provide an estimate of gas storage capacity for the larger carbon capsule (C 460 ) considered. We find 7.69 wt.% and 28.08 wt.% storage propensity for hydrogen and carbon dioxide gases, respectively, which clearly suggests their potential use as light storage materials

Structure-based stabilization of HIV-1 gp120 enhances humoral immune responses to the induced co-receptor binding site.

Directory of Open Access Journals (Sweden)

Barna Dey

2009-05-01

Full Text Available The human immunodeficiency virus type 1 (HIV-1 exterior envelope glycoprotein, gp120, possesses conserved binding sites for interaction with the primary virus receptor, CD4, and also for the co-receptor, generally CCR5. Although gp120 is a major target for virus-specific neutralizing antibodies, the gp120 variable elements and its malleable nature contribute to evasion of effective host-neutralizing antibodies. To understand the conformational character and immunogenicity of the gp120 receptor binding sites as potential vaccine targets, we introduced structure-based modifications to stabilize gp120 core proteins (deleted of the gp120 major variable regions into the conformation recognized by both receptors. Thermodynamic analysis of the re-engineered core with selected ligands revealed significant stabilization of the receptor-binding regions. Stabilization of the co-receptor-binding region was associated with a marked increase in on-rate of ligand binding to this site as determined by surface plasmon resonance. Rabbit immunization studies showed that the conformational stabilization of core proteins, along with increased ligand affinity, was associated with strikingly enhanced humoral immune responses against the co-receptor-binding site. These results demonstrate that structure-based approaches can be exploited to stabilize a conformational site in a large functional protein to enhance immunogenic responses specific for that region.

Structure and stability of semiconductor tip apexes for atomic force microscopy

International Nuclear Information System (INIS)

Pou, P; Perez, R; Ghasemi, S A; Goedecker, S; Jelinek, P; Lenosky, T

2009-01-01

The short range force between the tip and the surface atoms, that is responsible for atomic-scale contrast in atomic force microscopy (AFM), is mainly controlled by the tip apex. Thus, the ability to image, manipulate and chemically identify single atoms in semiconductor surfaces is ultimately determined by the apex structure and its composition. Here we present a detailed and systematic study of the most common structures that can be expected at the apex of the Si tips used in experiments. We tackle the determination of the structure and stability of Si tips with three different approaches: (i) first principles simulations of small tip apexes; (ii) simulated annealing of a Si cluster; and (iii) a minima hopping study of large Si tips. We have probed the tip apexes by making atomic contacts between the tips and then compared force-distance curves with the experimental short range forces obtained with dynamic force spectroscopy. The main conclusion is that although there are multiple stable solutions for the atomically sharp tip apexes, they can be grouped into a few types with characteristic atomic structures and properties. We also show that the structure of the last atomic layers in a tip apex can be both crystalline and amorphous. We corroborate that the atomically sharp tips are thermodynamically stable and that the tip-surface interaction helps to produce the atomic protrusion needed to get atomic resolution.

Micro-ring structures stabilize microdroplets to enable long term spheroid culture in 384 hanging drop array plates.

Science.gov (United States)

Hsiao, Amy Y; Tung, Yi-Chung; Kuo, Chuan-Hsien; Mosadegh, Bobak; Bedenis, Rachel; Pienta, Kenneth J; Takayama, Shuichi

2012-04-01

Using stereolithography, 20 different structural variations comprised of millimeter diameter holes surrounded by trenches, plateaus, or micro-ring structures were prepared and tested for their ability to stably hold arrays of microliter sized droplets within the structures over an extended period of time. The micro-ring structures were the most effective in stabilizing droplets against mechanical and chemical perturbations. After confirming the importance of micro-ring structures using rapid prototyping, we developed an injection molding tool for mass production of polystyrene 3D cell culture plates with an array of 384 such micro-ring surrounded through-hole structures. These newly designed and injection molded polystyrene 384 hanging drop array plates with micro-rings were stable and robust against mechanical perturbations as well as surface fouling-facilitated droplet spreading making them capable of long term cell spheroid culture of up to 22 days within the droplet array. This is a significant improvement over previously reported 384 hanging drop array plates which are susceptible to small mechanical shocks and could not reliably maintain hanging drops for longer than a few days. With enhanced droplet stability, the hanging drop array plates with micro-ring structures provide better platforms and open up new opportunities for high-throughput preparation of microscale 3D cell constructs for drug screening and cell analysis.

A Method to Predict the Structure and Stability of RNA/RNA Complexes.

Science.gov (United States)

Xu, Xiaojun; Chen, Shi-Jie

2016-01-01

RNA/RNA interactions are essential for genomic RNA dimerization and regulation of gene expression. Intermolecular loop-loop base pairing is a widespread and functionally important tertiary structure motif in RNA machinery. However, computational prediction of intermolecular loop-loop base pairing is challenged by the entropy and free energy calculation due to the conformational constraint and the intermolecular interactions. In this chapter, we describe a recently developed statistical mechanics-based method for the prediction of RNA/RNA complex structures and stabilities. The method is based on the virtual bond RNA folding model (Vfold). The main emphasis in the method is placed on the evaluation of the entropy and free energy for the loops, especially tertiary kissing loops. The method also uses recursive partition function calculations and two-step screening algorithm for large, complicated structures of RNA/RNA complexes. As case studies, we use the HIV-1 Mal dimer and the siRNA/HIV-1 mutant (T4) to illustrate the method.

Probing the 3-D Structure, Dynamics, and Stability of Bacterial Collagenase Collagen Binding Domain (apo- versus holo-) by Limited Proteolysis MALDI-TOF MS

Science.gov (United States)

Sides, Cynthia R.; Liyanage, Rohana; Lay, Jackson O.; Philominathan, Sagaya Theresa Leena; Matsushita, Osamu; Sakon, Joshua

2012-03-01

Pairing limited proteolysis and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) to probe clostridial collagenase collagen binding domain (CBD) reveals the solution dynamics and stability of the protein, as these factors are crucial to CBD effectiveness as a drug-delivery vehicle. MS analysis of proteolytic digests indicates initial cleavage sites, thereby specifying the less stable and highly accessible regions of CBD. Modulation of protein structure and stability upon metal binding is shown through MS analysis of calcium-bound and cobalt-bound CBD proteolytic digests. Previously determined X-ray crystal structures illustrate that calcium binding induces secondary structure transformation in the highly mobile N-terminal arm and increases protein stability. MS-based detection of exposed residues confirms protein flexibility, accentuates N-terminal dynamics, and demonstrates increased global protein stability exported by calcium binding. Additionally, apo- and calcium-bound CBD proteolysis sites correlate well with crystallographic B-factors, accessibility, and enzyme specificity. MS-observed cleavage sites with no clear correlations are explained either by crystal contacts of the X-ray crystal structures or by observed differences between Molecules A and B in the X-ray crystal structures. The study newly reveals the absence of the βA strand and thus the very dynamic N-terminal linker, as corroborated by the solution X-ray scattering results. Cobalt binding has a regional effect on the solution phase stability of CBD, as limited proteolysis data implies the capture of an intermediate-CBD solution structure when cobalt is bound.

Influence of flocculating agents and structural vehicles on the physical stability and rheological behavior of nitrofurantoin suspension.

Science.gov (United States)

Moghimipour, Eskandar; Salimi, Anayatollah; Rezaee, Saeed; Balack, Maryam; Handali, Somayeh

2014-05-01

Nitrofurantoin is a nitrofuran antibiotic that has been used for treatment of urinary tract against positive and negative bacteria. The aim of this study was to evaluate the effect of structural vehicles and flocculating agents on physical stability and rheological behavior of nitrofurantoin suspension. To formulate the suspensions, the effect of glycerin and polysorbate 80 as wetting agents was evaluated and their particle sizes were determined using the sieve method. Then to achieve controlled flocculation, sodium citrate and aluminum chloride were added. After choosing the suitable wetting and flocculating agents, structural vehicles such as sodium carboxyl methyl cellulose and Veegum were evaluated individually and in combination. In addition, the effect of sorbitol on density of continuous phase and some physical stability parameters such as sedimentation volume, degree of flocculation and ease of redispersion of the suspensions were evaluated. After incorporation of structural vehicles, the rheological properties of formulations were also determined to find their flow behavior. According to the results, glycerin (0.2%) and sodium citrate (0.3%) had the best effect on the suspension stability as wetting and flocculating agents, respectively. Rheological properties of formulations showed pseudoplastic behavior with some degree of thixotropy. In conclusion, the suspension containing Veegum 1%, sodium carboxy methyl cellulose 1%, glycerine 0.2%, sodium citrate 0.3% and sorbitol 20 % was chosen as the most physically stable formulation.

Modeling and simulation of adaptive Neuro-fuzzy based intelligent system for predictive stabilization in structured overlay networks

Directory of Open Access Journals (Sweden)

Ramanpreet Kaur

2017-02-01

Full Text Available Intelligent prediction of neighboring node (k well defined neighbors as specified by the dht protocol dynamism is helpful to improve the resilience and can reduce the overhead associated with topology maintenance of structured overlay networks. The dynamic behavior of overlay nodes depends on many factors such as underlying user’s online behavior, geographical position, time of the day, day of the week etc. as reported in many applications. We can exploit these characteristics for efficient maintenance of structured overlay networks by implementing an intelligent predictive framework for setting stabilization parameters appropriately. Considering the fact that human driven behavior usually goes beyond intermittent availability patterns, we use a hybrid Neuro-fuzzy based predictor to enhance the accuracy of the predictions. In this paper, we discuss our predictive stabilization approach, implement Neuro-fuzzy based prediction in MATLAB simulation and apply this predictive stabilization model in a chord based overlay network using OverSim as a simulation tool. The MATLAB simulation results present that the behavior of neighboring nodes is predictable to a large extent as indicated by the very small RMSE. The OverSim based simulation results also observe significant improvements in the performance of chord based overlay network in terms of lookup success ratio, lookup hop count and maintenance overhead as compared to periodic stabilization approach.

Strategies to curb structural changes of lithium/transition metal oxide cathode materials and the changes’ effects on thermal and cycling stability

International Nuclear Information System (INIS)

Yu Xiqian; Hu Enyuan; Bak, Seongmin; Zhou Yong-Ning; Yang Xiao-Qing

2016-01-01

Structural transformation behaviors of several typical oxide cathode materials during a heating process are reviewed in detail to provide in-depth understanding of the key factors governing the thermal stability of these materials. We also discuss applying the information about heat induced structural evolution in the study of electrochemically induced structural changes. All these discussions are expected to provide valuable insights for designing oxide cathode materials with significantly improved structural stability for safe, long-life lithium ion batteries, as the safety of lithium-ion batteries is a critical issue; it is widely accepted that the thermal instability of the cathodes is one of the most critical factors in thermal runaway and related safety problems. (topical review)

Constraint Network Analysis (CNA): a Python software package for efficiently linking biomacromolecular structure, flexibility, (thermo-)stability, and function.

Science.gov (United States)

Pfleger, Christopher; Rathi, Prakash Chandra; Klein, Doris L; Radestock, Sebastian; Gohlke, Holger

2013-04-22

For deriving maximal advantage from information on biomacromolecular flexibility and rigidity, results from rigidity analyses must be linked to biologically relevant characteristics of a structure. Here, we describe the Python-based software package Constraint Network Analysis (CNA) developed for this task. CNA functions as a front- and backend to the graph-based rigidity analysis software FIRST. CNA goes beyond the mere identification of flexible and rigid regions in a biomacromolecule in that it (I) provides a refined modeling of thermal unfolding simulations that also considers the temperature-dependence of hydrophobic tethers, (II) allows performing rigidity analyses on ensembles of network topologies, either generated from structural ensembles or by using the concept of fuzzy noncovalent constraints, and (III) computes a set of global and local indices for quantifying biomacromolecular stability. This leads to more robust results from rigidity analyses and extends the application domain of rigidity analyses in that phase transition points ("melting points") and unfolding nuclei ("structural weak spots") are determined automatically. Furthermore, CNA robustly handles small-molecule ligands in general. Such advancements are important for applying rigidity analysis to data-driven protein engineering and for estimating the influence of ligand molecules on biomacromolecular stability. CNA maintains the efficiency of FIRST such that the analysis of a single protein structure takes a few seconds for systems of several hundred residues on a single core. These features make CNA an interesting tool for linking biomacromolecular structure, flexibility, (thermo-)stability, and function. CNA is available from http://cpclab.uni-duesseldorf.de/software for nonprofit organizations.

Theoretical Investigation of the Structural Stabilities of Ceria Surfaces and Supported Metal Nanocluster in Vapor and Aqueous Phases

Energy Technology Data Exchange (ETDEWEB)

Ren, Zhibo [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China; Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Liu, Ning [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China; Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Chen, Biaohua [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China; Li, Jianwei [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China; Mei, Donghai [Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States

2018-01-25

Understanding the structural stability and dynamics at the interface between the solid metal oxide and aqueous phase is significant in a variety of industrial applications including heterogeneous catalysis and environmental remediation. In the present work, the stabilities of three low-index ceria (CeO2) surfaces, i.e., (111), (110) and (100) in vapor and aqueous phases were studied using ab initio molecular dynamics simulations and density functional theory (DFT) calculations. Gibbs surface free energies as a function of temperature, water partial pressure, and water coverages were calculated using DFT based atomistic thermodynamic approach. On the basis of surface free energies, the morphology and exposed surface structures of the CeO2 nanoparticle were predicted using Wulff construction principle. It is found that the partially hydroxylated (111) and (100) are two major surface structures of CeO2 nanoparticles in vapor phase at ambient temperature (300 K). As the temperature increases, the fully dehydrated (111) surface gradually becomes the most dominant surface structure. While in aqueous phase, the exposed surface of the CeO2 nanoparticle is dominated by the hydroxylated (110) structure at 393 K. Finally, the morphology and stability of a cuboctahedron Pt13 nanocluster supported on CeO2 surfaces in both gas and aqueous phases were investigated. In gas phase, the supported Pt13 nanocluster has the tendency to wetting the CeO2 surface due to the strong metal-support interaction. The calculated interaction energies suggest the CeO2(110) surface provides the best stability for the Pt13 nanocluster. The CeO2 supported Pt13 nanoclusters are oxidized. Compared to the gas phase, the morphology of the CeO2 supported Pt13 nanocluster is less distorted due to the solvation effect provided by surrounding water molecules in aqueous phase. More electrons are transferred from the Pt13 nanocluster to the CeO2 support, implying the supported Pt13 nanocluster is further

Synchronisation and stability in river metapopulation networks.

Science.gov (United States)

Yeakel, J D; Moore, J W; Guimarães, P R; de Aguiar, M A M

2014-03-01

Spatial structure in landscapes impacts population stability. Two linked components of stability have large consequences for persistence: first, statistical stability as the lack of temporal fluctuations; second, synchronisation as an aspect of dynamic stability, which erodes metapopulation rescue effects. Here, we determine the influence of river network structure on the stability of riverine metapopulations. We introduce an approach that converts river networks to metapopulation networks, and analytically show how fluctuation magnitude is influenced by interaction structure. We show that river metapopulation complexity (in terms of branching prevalence) has nonlinear dampening effects on population fluctuations, and can also buffer against synchronisation. We conclude by showing that river transects generally increase synchronisation, while the spatial scale of interaction has nonlinear effects on synchronised dynamics. Our results indicate that this dual stability - conferred by fluctuation and synchronisation dampening - emerges from interaction structure in rivers, and this may strongly influence the persistence of river metapopulations. © 2013 John Wiley & Sons Ltd/CNRS.

Mononuclear nonheme iron(III) complexes that show superoxide dismutase-like activity and antioxidant effects against menadione-mediated oxidative stress.

Science.gov (United States)

Hitomi, Yutaka; Iwamoto, Yuji; Kashida, Akihiro; Kodera, Masahito

2015-05-21

This communication describes the superoxide dismutase (SOD)-like activity of mononuclear iron(III) complexes with pentadentate monocarboxylamido ligands. The SOD activity can be controlled by the electronic nature of the substituent group on the ligand. The nitro-substituted complex showed clear cytoprotective activity against menadione-mediated oxidative stress in cultured cells.

Photocatalytic property and structural stability of CuAl-based layered double hydroxides

International Nuclear Information System (INIS)

Lv, Ming; Liu, Haiqiang

2015-01-01

Three types of CuMAl layered double hydroxides (LDHs, M=Mg, Zn, Ni) were successfully synthesized by coprecipitation. Powder X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometry (ICP-AES) and UV–Vis diffuse reflectance spectrum (UV–vis) were used to confirm the formation of as-synthesized solids with good crystal structure. The photocatalytic activity of those LDH materials for CO 2 reduction under visible light was investigated. The experimental results show that CuNiAl-LDHs with narrowest band gap and largest surface areas behave highest efficiency for methanol generation under visible light compared with CuMgAl-LDHs and CuZnAl-LDHs. The CuNiAL-LDH showed high yield for methanol production i.e. 0.210 mmol/g h, which was high efficient. In addition, the influence of the different M 2+ on the structures and stability of the CuMAl-LDHs was also investigated by analyzing the geometric parameters, electronic arrangement, charge populations, hydrogen-bonding, and binding energies by density functional theory (DFT) analysis. The theoretical calculation results show that the chemical stability of LDH materials followed the order of CuMgAl-LDHs>CuZnAl-LDHs>CuNiAl-LDHs, which is just opposite with the photocatalytic activity and band gaps of three materials. - Graphical abstract: The host–guest calculation models and XRD patterns of CuMAl-LDHs: CuMgAl-LDHs (a), CuZnAl-LDHs (b) and CuNiAl-LDHs (c). - Highlights: • Three types of CuMAl layered double hydroxides (LDHs, M=Mg, Zn, Ni) has been synthesized. • CuMgNi shows narrower band gap and more excellent textural properties than other LDHs. • The band gap: CuMgAlstability and lowest photocatalytic activity, while CuNiAl just opposite

Cloning, Characterization and Expression Pattern Analysis of a Cytosolic Copper/Zinc Superoxide Dismutase (SaCSD1 in a Highly Salt Tolerant Mangrove (Sonneratia alba

Directory of Open Access Journals (Sweden)

Enze Yang

2015-12-01

Full Text Available Mangroves are critical marine resources for their remarkable ability to tolerate seawater. Antioxidant enzymes play an especially significant role in eliminating reactive oxygen species and conferring abiotic stress tolerance. In this study, a cytosolic copper/zinc superoxide dismutase (SaCSD1 cDNA of Sonneratia alba, a mangrove species with high salt tolerance, was successfully cloned and then expressed in Escherichia coli Rosetta-gami (designated as SaCSD1. SaCSD1 comprised a complete open reading frame (ORF of 459 bp which encoded a protein of 152 amino acids. Its mature protein is predicted to be 15.32 kDa and the deduced isoelectric point is 5.78. SaCSD1 has high sequence similarity (85%–90% with the superoxide dismutase (CSD of some other plant species. SaCSD1 was expressed with 30.6% yield regarding total protein content after being introduced into the pET-15b (Sma I vector for expression in Rosetta-gami and being induced with IPTG. After affinity chromatography on Ni-NTA, recombinant SaCSD1 was obtained with 3.2-fold purification and a specific activity of 2200 U/mg. SaCSD1 showed good activity as well as stability in the ranges of pH between 3 and 7 and temperature between 25 and 55 °C. The activity of recombinant SaCSD1 was stable in 0.25 M NaCl, Dimethyl Sulphoxide (DMSO, glycerol, and chloroform, and was reduced to a great extent in β-mercaptoethanol, sodium dodecyl sulfate (SDS, H2O2, and phenol. Moreover, the SaCSD1 protein was very susceptive to pepsin digestion. Real-time Quantitative Polymerase Chain Reaction (PCR assay demonstrated that SaCSD1 was expressed in leaf, stem, flower, and fruit organs, with the highest expression in fruits. Under 0.25 M and 0.5 M salt stress, the expression of SaCSD1 was down-regulated in roots, but up-regulated in leaves.

Multivariate stability of force-reflecting teleoperation: Structures of finite and infinite zeros

International Nuclear Information System (INIS)

Daniel, R.W.; McAree, P.R.

2000-01-01

This paper presents a stability analysis of force-position teleoperation under general end-effector contact. The analysis is based on the finite and infinite zero structure of the multivariable root-locus resulting from modulation of the environment stiffness. The starting point is an analysis of the stability of robot force control, motivated by the observation that the human-operator in a force reflection loop acts as a force servo, generating position commands in response to reflected force. Asymptotic root loci properties are used to establish passivity conditions on force feedback to give root locus interpretations of the well-known results that (1) feedback via the inverse joint Jacobian can lead to (kinematic) instability and that (2) passivity is preserved by kinematically proper force feedback through the transpose of the joint angle Jacobian. It is demonstrated that a fully constrained force-position teleoperation loop has an identical infinite zero structure to that of a slave manipulation under kinematically proper force control and that the dominant vibration modes of a force-position loop are fully described by a multivariable analogue of the single-input single-output pseudo-system investigated in a study by Daniel and McAree. Extension of the analysis to cover partial end-effector constraint provides a design tool for teleoperation control and serves to aid selection of teleoperation slate-arms. The paper concludes by giving a passivity condition for multiple-input multiple-output force-position teleoperation for stable contact against all environments

Hydrogen peroxide induce modifications of human extracellular superoxide dismutase that results in enzyme inhibition

Directory of Open Access Journals (Sweden)

Randi H. Gottfredsen

2013-01-01

Full Text Available Superoxide dismutase (EC-SOD controls the level of superoxide in the extracellular space by catalyzing the dismutation of superoxide into hydrogen peroxide and molecular oxygen. In addition, the enzyme reacts with hydrogen peroxide in a peroxidase reaction which is known to disrupt enzymatic activity. Here, we show that the peroxidase reaction supports a site-specific bond cleavage. Analyses by peptide mapping and mass spectrometry shows that oxidation of Pro112 supports the cleavage of the Pro112–His113 peptide bond. Substitution of Ala for Pro112 did not inhibit fragmentation, indicating that the oxidative fragmentation at this position is dictated by spatial organization and not by side-chain specificity. The major part of EC-SOD inhibited by the peroxidase reaction was not fragmented but found to encompass oxidations of histidine residues involved in the coordination of copper (His98 and His163. These oxidations are likely to support the dissociation of copper from the active site and thus loss of enzymatic activity. Homologous modifications have also been described for the intracellular isozyme, Cu/Zn-SOD, reflecting the almost identical structures of the active site within these enzymes. We speculate that the inactivation of EC-SOD by peroxidase activity plays a role in regulating SOD activity in vivo, as even low levels of superoxide will allow for the peroxidase reaction to occur.

Superhydrophobicity of biological and technical surfaces under moisture condensation: stability in relation to surface structure.

Science.gov (United States)

Mockenhaupt, Bernd; Ensikat, Hans-Jürgen; Spaeth, Manuel; Barthlott, Wilhelm

2008-12-02

The stability of superhydrophobic properties of eight plants and four technical surfaces in respect to water condensation has been compared. Contact and sliding angles were measured after application of water drops of ambient temperature (20 degrees C) onto cooled surfaces. Water evaporating from the drops condensed, due to the temperature difference between the drops and the surface, on the cooled samples, forming "satellite droplets" in the vicinity of the drops. Surface cooling to 15, 10, and 5 degrees C showed a gradual decrease of superhydrophobicity. The decrease was dependent on the specific surface architecture of the sample. The least decrease was found on hierarchically structured surfaces with a combination of a coarse microstructure and submicrometer-sized structures, similar to that of the Lotus leaf. Control experiments with glycerol droplets, which show no evaporation, and thus no condensation, were carried out to verify that the effects with water were caused by condensation from the drop (secondary condensation). Furthermore, the superhydrophobic properties after condensation on cooled surfaces from a humid environment for 10 min were examined. After this period, the surfaces were covered with spherical water droplets, but most samples retained their superhydrophobicity. Again, the best stability of the water-repellent properties was found on hierarchically structured surfaces similar to that of the Lotus leaf.

Improving the apo-state detergent stability of NTS1 with CHESS for pharmacological and structural studies.

Science.gov (United States)

Scott, Daniel J; Kummer, Lutz; Egloff, Pascal; Bathgate, Ross A D; Plückthun, Andreas

2014-11-01

The largest single class of drug targets is the G protein-coupled receptor (GPCR) family. Modern high-throughput methods for drug discovery require working with pure protein, but this has been a challenge for GPCRs, and thus the success of screening campaigns targeting soluble, catalytic protein domains has not yet been realized for GPCRs. Therefore, most GPCR drug screening has been cell-based, whereas the strategy of choice for drug discovery against soluble proteins is HTS using purified proteins coupled to structure-based drug design. While recent developments are increasing the chances of obtaining GPCR crystal structures, the feasibility of screening directly against purified GPCRs in the unbound state (apo-state) remains low. GPCRs exhibit low stability in detergent micelles, especially in the apo-state, over the time periods required for performing large screens. Recent methods for generating detergent-stable GPCRs, however, offer the potential for researchers to manipulate GPCRs almost like soluble enzymes, opening up new avenues for drug discovery. Here we apply cellular high-throughput encapsulation, solubilization and screening (CHESS) to the neurotensin receptor 1 (NTS1) to generate a variant that is stable in the apo-state when solubilized in detergents. This high stability facilitated the crystal structure determination of this receptor and also allowed us to probe the pharmacology of detergent-solubilized, apo-state NTS1 using robotic ligand binding assays. NTS1 is a target for the development of novel antipsychotics, and thus CHESS-stabilized receptors represent exciting tools for drug discovery. Copyright © 2014 Elsevier B.V. All rights reserved.

Black Carbon (Biochar) In Water/Soil Environments: Molecular Structure, Sorption, Stability, and Potential Risk.

Science.gov (United States)

Lian, Fei; Xing, Baoshan

2017-12-05

Black carbon (BC) is ubiquitous in the environments and participates in various biogeochemical processes. Both positive and negative effects of BC (especially biochar) on the ecosystem have been identified, which are mainly derived from its diverse physicochemical properties. Nevertheless, few studies systematically examined the linkage between the evolution of BC molecular structure with the resulted BC properties, environmental functions as well as potential risk, which is critical for understanding the BC environmental behavior and utilization as a multifunctional product. Thus, this review highlights the molecular structure evolution of BC during pyrolysis and the impact of BC physicochemical properties on its sorption behavior, stability, and potential risk in terrestrial and aqueous ecosystems. Given the wide application of BC and its important role in biogeochemical processes, future research should focus on the following: (1) establishing methodology to more precisely predict and design BC properties on the basis of pyrolysis and phase transformation of biomass; (2) developing an assessment system to evaluate the long-term effect of BC on stabilization and bioavailability of contaminants, agrochemicals, and nutrient elements in soils; and (3) elucidating the interaction mechanisms of BC with plant roots, microorganisms, and soil components.

Enhanced structural stability of DNA origami nanostructures by graphene encapsulation

International Nuclear Information System (INIS)

Matković, Aleksandar; Vasić, Borislav; Pešić, Jelena; Gajić, Radoš; Prinz, Julia; Bald, Ilko; Milosavljević, Aleksandar R

2016-01-01

We demonstrate that a single-layer graphene replicates the shape of DNA origami nanostructures very well. It can be employed as a protective layer for the enhancement of structural stability of DNA origami nanostructures. Using the AFM based manipulation, we show that the normal force required to damage graphene encapsulated DNA origami nanostructures is over an order of magnitude greater than for the unprotected ones. In addition, we show that graphene encapsulation offers protection to the DNA origami nanostructures against prolonged exposure to deionized water, and multiple immersions. Through these results we demonstrate that graphene encapsulated DNA origami nanostructures are strong enough to sustain various solution phase processing, lithography and transfer steps, thus extending the limits of DNA-mediated bottom-up fabrication. (paper)

Studies on electronic structure of interfaces between Ag and gelatin for stabilization of Ag nanoparticles

International Nuclear Information System (INIS)

Tani, Tadaaki; Uchida, Takayuki

2015-01-01

Extremely high stability of Ag nanoparticles in photographic materials has forced us to study the electronic structures of the interfaces between thin layers of Ag, Au, and Pt and their surface membranes in ambient atmosphere by photoelectron yield spectroscopy in air and Kelvin probe method. Owing to the Fermi level equalization between a metal layer and a membrane coming from air, the electron transfer took place from the membrane to Pt and Au layers and from an Ag layer to the membrane, giving the reason for poor stability of Ag nanoparticles in air. The control of the Fermi level of an Ag layer with respect to that of a gelatin membrane in air could be widely made according to Nernst's equation by changing the pH and pAg values of an aqueous gelatin solution used to form the membrane, and thus available to stabilize Ag nanoparticles in a gelatin matrix. (author)

The flow field structure of highly stabilized partially premixed flames in a concentric flow conical nozzle burner with coflow

KAUST Repository

Elbaz, Ayman M.

2015-08-29

The stability limits, the stabilization mechanism, and the flow field structure of highly stabilized partially premixed methane flames in a concentric flow conical nozzle burner with air co-flow have been investigated and presented in this work. The stability map of partial premixed flames illustrates that the flames are stable between two extinction limits. A low extinction limit when partial premixed flames approach non-premixed flame conditions, and a high extinction limit, with the partial premixed flames approach fully premixed flame conditions. These two limits showed that the most stable flame conditions are achieved at a certain degree of partial premixed. The stability is improved by adding air co-flow. As the air co-flow velocity increases the most stable flames are those that approach fully premixed. The turbulent flow field of three flames at 0, 5, 10 m/s co-flow velocity are investigated using Stereo Particle Image Velocimetry (SPIV) in order to explore the improvement of the flame stability due to the use of air co-flow. The three flames are all at a jet equivalence ratio (Φj) of 2, fixed level of partial premixing and jet Reynolds number (Rej) of 10,000. The use of co-flow results in the formation of two vortices at the cone exit. These vortices act like stabilization anchors for the flames to the nozzle tip. With these vortices in the flow field, the reaction zone shifts toward the reduced turbulence intensity at the nozzle rim of the cone. Interesting information about the structure of the flow field with and without co-flow are identified and reported in this work.

Microencapsulation structures based on protein-coated liposomes obtained through electrospraying for the stabilization and improved bioaccessibility of curcumin.

Science.gov (United States)

Gómez-Mascaraque, Laura G; Casagrande Sipoli, Caroline; de La Torre, Lucimara Gaziola; López-Rubio, Amparo

2017-10-15

Novel food-grade hybrid encapsulation structures based on the entrapment of phosphatidylcholine liposomes, within a WPC matrix through electrospraying, were developed and used as delivery vehicles for curcumin. The loading capacity and encapsulation efficiency of the proposed system was studied, and the suitability of the approach to stabilize curcumin and increase its bioaccessibility was assessed. Results showed that the maximum loading capacity of the liposomes was around 1.5% of curcumin, although the loading capacity of the hybrid microencapsulation structures increased with the curcumin content by incorporation of curcumin microcrystals upon electrospraying. Microencapsulation of curcumin within the proposed hybrid structures significantly increased its bioaccessibility (∼1.7-fold) compared to the free compound, and could successfully stabilize it against degradation in PBS (pH=7.4). The proposed approach thus proved to be a promising alternative to produce powder-like functional ingredients. Copyright © 2017 Elsevier Ltd. All rights reserved.

A plastic stabilizer dibutyltin dilaurate induces subchronic neurotoxicity in rats☆

Science.gov (United States)

Jin, Minghua; Song, Peilin; Li, Na; Li, Xuejun; Chen, Jiajun

2012-01-01

Dibutyltin dilaurate functions as a stabilizer for polyvinyl chloride. In this study, experimental rats were intragastrically administered 5, 10, or 20 mg/kg dibutyltin dilaurate to model sub-chronic poisoning. After exposure, our results showed the activities of superoxide dismutase and glutathione peroxidase decreased in rat brain tissue, while the malondialdehyde and nitric oxide content, as well as nitric oxide synthase activity in rat brain tissue increased. The cell cycle in the right parietal cortex was disordered and the rate of apoptosis increased. DNA damage was aggravated in the cerebral cortex, and the ultrastructure of the right parietal cortex tissues was altered. The above changes became more apparent with exposure to increasing doses of dibutyltin dilaurate. Our experimental findings confirmed the neurotoxicity of dibutyltin dilaurate in rat brain tissues, and demonstrated that the poisoning was dose-dependent. PMID:25538742

Influence of pea protein aggregates on the structure and stability of pea protein/soybean polysaccharide complex emulsions.

Science.gov (United States)

Yin, Baoru; Zhang, Rujing; Yao, Ping

2015-03-20

The applications of plant proteins in the food and beverage industry have been hampered by their precipitation in acidic solution. In this study, pea protein isolate (PPI) with poor dispersibility in acidic solution was used to form complexes with soybean soluble polysaccharide (SSPS), and the effects of PPI aggregates on the structure and stability of PPI/SSPS complex emulsions were investigated. Under acidic conditions, high pressure homogenization disrupts the PPI aggregates and the electrostatic attraction between PPI and SSPS facilitates the formation of dispersible PPI/SSPS complexes. The PPI/SSPS complex emulsions prepared from the PPI containing aggregates prove to possess similar droplet structure and similar stability compared with the PPI/SSPS emulsions produced from the PPI in which the aggregates have been previously removed by centrifugation. The oil droplets are protected by PPI/SSPS complex interfacial films and SSPS surfaces. The emulsions show long-term stability against pH and NaCl concentration changes. This study demonstrates that PPI aggregates can also be used to produce stable complex emulsions, which may promote the applications of plant proteins in the food and beverage industry.

Influence of Pea Protein Aggregates on the Structure and Stability of Pea Protein/Soybean Polysaccharide Complex Emulsions

Directory of Open Access Journals (Sweden)

Baoru Yin

2015-03-01

Full Text Available The applications of plant proteins in the food and beverage industry have been hampered by their precipitation in acidic solution. In this study, pea protein isolate (PPI with poor dispersibility in acidic solution was used to form complexes with soybean soluble polysaccharide (SSPS, and the effects of PPI aggregates on the structure and stability of PPI/SSPS complex emulsions were investigated. Under acidic conditions, high pressure homogenization disrupts the PPI aggregates and the electrostatic attraction between PPI and SSPS facilitates the formation of dispersible PPI/SSPS complexes. The PPI/SSPS complex emulsions prepared from the PPI containing aggregates prove to possess similar droplet structure and similar stability compared with the PPI/SSPS emulsions produced from the PPI in which the aggregates have been previously removed by centrifugation. The oil droplets are protected by PPI/SSPS complex interfacial films and SSPS surfaces. The emulsions show long-term stability against pH and NaCl concentration changes. This study demonstrates that PPI aggregates can also be used to produce stable complex emulsions, which may promote the applications of plant proteins in the food and beverage industry.

Effects of lysine residues on structural characteristics and stability of tau proteins

International Nuclear Information System (INIS)

Lee, Myeongsang; Baek, Inchul; Choi, Hyunsung; Kim, Jae In; Na, Sungsoo

2015-01-01

Pathological amyloid proteins have been implicated in neuro-degenerative diseases, specifically Alzheimer's, Parkinson's, Lewy-body diseases and prion related diseases. In prion related diseases, functional tau proteins can be transformed into pathological agents by environmental factors, including oxidative stress, inflammation, Aβ-mediated toxicity and covalent modification. These pathological agents are stable under physiological conditions and are not easily degraded. This un-degradable characteristic of tau proteins enables their utilization as functional materials to capturing the carbon dioxides. For the proper utilization of amyloid proteins as functional materials efficiently, a basic study regarding their structural characteristic is necessary. Here, we investigated the basic tau protein structure of wild-type (WT) and tau proteins with lysine residues mutation at glutamic residue (Q2K) on tau protein at atomistic scale. We also reported the size effect of both the WT and Q2K structures, which allowed us to identify the stability of those amyloid structures. - Highlights: • Lysine mutation effect alters the structure conformation and characteristic of tau. • Over the 15 layers both WT and Q2K models, both tau proteins undergo fractions. • Lysine mutation causes the increment of non-bonded energy and solvent accessible surface area. • Structural instability of Q2K model was proved by the number of hydrogen bonds analysis.

Effects of lysine residues on structural characteristics and stability of tau proteins

Energy Technology Data Exchange (ETDEWEB)

Lee, Myeongsang; Baek, Inchul; Choi, Hyunsung; Kim, Jae In; Na, Sungsoo, E-mail: nass@korea.ac.kr

2015-10-23

Pathological amyloid proteins have been implicated in neuro-degenerative diseases, specifically Alzheimer's, Parkinson's, Lewy-body diseases and prion related diseases. In prion related diseases, functional tau proteins can be transformed into pathological agents by environmental factors, including oxidative stress, inflammation, Aβ-mediated toxicity and covalent modification. These pathological agents are stable under physiological conditions and are not easily degraded. This un-degradable characteristic of tau proteins enables their utilization as functional materials to capturing the carbon dioxides. For the proper utilization of amyloid proteins as functional materials efficiently, a basic study regarding their structural characteristic is necessary. Here, we investigated the basic tau protein structure of wild-type (WT) and tau proteins with lysine residues mutation at glutamic residue (Q2K) on tau protein at atomistic scale. We also reported the size effect of both the WT and Q2K structures, which allowed us to identify the stability of those amyloid structures. - Highlights: • Lysine mutation effect alters the structure conformation and characteristic of tau. • Over the 15 layers both WT and Q2K models, both tau proteins undergo fractions. • Lysine mutation causes the increment of non-bonded energy and solvent accessible surface area. • Structural instability of Q2K model was proved by the number of hydrogen bonds analysis.

Chemical cross-linked polyvinyl alcohol/cellulose nanocrystal composite films with high structural stability by spraying Fenton reagent as initiator.

Science.gov (United States)

Song, Meili; Yu, Houyong; Gu, Jiping; Ye, Shounuan; Zhou, Yuwei

2018-07-01

Cross-linked polyvinyl alcohol (PVA) composite films with high structural stability were prepared by free radical copolymerization between cellulose nanocrystal (CNC) and maleic anhydride (MAH) modified PVA through spraying Fenton free radical as initiator. The influence of chemical cross-linked and physical network structure on mechanical, thermal and water absorption properties of the composite films were investigated. Compared to PVA and PVA/CNC composite film, significant improvements in the mechanical, thermal and water uptake properties of the cross-linked composite film were found. The tensile strength of the cross-linked composite film was enhanced from 23.1MPa (neat PVA film) and 32.6MPa (PVA/CNC-10%) to 42.5MPa, and the maximum thermal degradation temperature was increased from 266.8°C and 281.2°C to 366.7°C (cross-linked composite film). Besides, the water absorption was reduced from 385.9% and 220.6% to 175.7% for cross-linked composite film. It indicates that compared with physical network structure in PVA/CNC composite film, the multiple cross-linked networks showed excellent thermal stability, resistance of water swelling and structural stability at the same CNC loading level. Thus, the PVA/CNC composite film with the multiple cross-linked network shows greater property reinforcements. Copyright © 2018 Elsevier B.V. All rights reserved.

Lyapunov stability and poisson structure of the thermal TDHF and RPA equations

International Nuclear Information System (INIS)

Balian, R.; Veneroni, M.

1989-01-01

The thermal TDHF equation is analyzed in the Liouville representation of quantum mechanics, where the matrix elements of the single-particle (s.p) density ρ behave as classical dynamical variables. By introducing the Lie--Poisson bracket associated with the unitary group of the s.p. Hilbert space, we show that TDHF has a Hamiltonian, but non-canonical, classical form. Within this Poisson structure, either the s.p. energy or the s.p. grand potential Ω(ρ) act as a Hamilton function. The Lyapunov stability of both the TDHF and RPA equations around a HF state then follows, since the HF approximation for thermal equilibrium is determined by minimizing Ω(ρ). The RPA matrix in the Liouville space is expressed as the product of the Poisson tensor with the HF stability matrix, interpreted as a metric tensor generated by the entropy. This factorization displays the roles of the energy and entropy terms arising from Ω(ρ) in the RPA dynamics, and it helps to construct the RPA modes. Several extensions are considered. copyright 1989 Academic Press, Inc

Lyapunov stability and Poisson structure of the thermal TDHF and RPA equations

International Nuclear Information System (INIS)

Veneroni, M.; Balian, R.

1989-01-01

The thermal TDHF equation is analyzed in the Liouville representation of quantum mechanics, where the matrix elements of the single-particle (s.p.) density ρ behave as classical dynamical variables. By introducing the Lie-Poisson bracket associated with the unitary group of the s.p. Hilbert space, we show that TDHF has a hamiltonian, but non-canonical, classical form. Within this Poisson structure, either the s.p. energy or the s.p. grand potential Ω(ρ) act as a Hamilton function. The Lyapunov stability of both the TDHF and RPA equations around a HF state then follows, since the HF approximation for thermal equilibrium is determined by minimizing Ω(ρ). The RPA matrix in the Liouville space is expressed as the product of the Poisson tensor with the HF stability matrix, interpreted as a metric tensor generated by the entropy. This factorization displays the roles of the energy and entropy terms arising from Ω(ρ) in the RPA dynamics, and it helps to construct the RPA modes. Several extensions are considered

Accurate prediction of stability changes in protein mutants by combining machine learning with structure based computational mutagenesis.

Science.gov (United States)

Masso, Majid; Vaisman, Iosif I

2008-09-15

Accurate predictive models for the impact of single amino acid substitutions on protein stability provide insight into protein structure and function. Such models are also valuable for the design and engineering of new proteins. Previously described methods have utilized properties of protein sequence or structure to predict the free energy change of mutants due to thermal (DeltaDeltaG) and denaturant (DeltaDeltaG(H2O)) denaturations, as well as mutant thermal stability (DeltaT(m)), through the application of either computational energy-based approaches or machine learning techniques. However, accuracy associated with applying these methods separately is frequently far from optimal. We detail a computational mutagenesis technique based on a four-body, knowledge-based, statistical contact potential. For any mutation due to a single amino acid replacement in a protein, the method provides an empirical normalized measure of the ensuing environmental perturbation occurring at every residue position. A feature vector is generated for the mutant by considering perturbations at the mutated position and it's ordered six nearest neighbors in the 3-dimensional (3D) protein structure. These predictors of stability change are evaluated by applying machine learning tools to large training sets of mutants derived from diverse proteins that have been experimentally studied and described. Predictive models based on our combined approach are either comparable to, or in many cases significantly outperform, previously published results. A web server with supporting documentation is available at http://proteins.gmu.edu/automute.

Effect of dysprosia doping on structural and electrical property of stabilized zirconia for intermediate- temperature SOFCs

International Nuclear Information System (INIS)

Pastor, M.; Maiti, S.; Pandey, A.; Biswas, K.; Manna, I.

2011-01-01

Present work deals with structural, micro-structural and electrical properties of dysprosia stabilized zirconia electrolyte, which have been evaluated by means of X-ray diffraction (XRD) and scanning (SEM), and complex impedance analysis respectively. The amount of dysprosia was varied from 2 to 12 mol% in zirconia. The addition of dysprosia (8-12 mol%) stabilized the cubic zirconia phase, which was analyzed from XRD analysis. SEM micrographs clearly showed the improvement in sinterability with increase in dysprosia concentration up to 6 mol% disprosia. Complex impedance analysis was performed in the temperature range from 250 to 600 deg. C. The results indicated a gradual decrease in impedance of both bulk and grain boundary and increase in conductivity with dysprosia doping up to 6 mol% and thereafter showing a reverse trend. The activation energies for oxygen ion migration were also found to decrease with increase in dysprosia doping which was in the range of 0.99 - 1.28 eV. The average thermal expansion coefficient increases linearly.

Isolation and sequence of complementary DNA encoding human extracellular superoxide dismutase

International Nuclear Information System (INIS)

Hjalmarsson, K.; Marklund, S.L.; Engstroem, A.; Edlund, T.

1987-01-01

A complementary DNA (cDNA) clone from a human placenta cDNA library encoding extracellular superoxide dismutase has been isolated and the nucleotide sequence determined. The cDNA has a very high G + C content. EC-SOD is synthesized with a putative 18-amino acid signal peptide, preceding the 222 amino acids in the mature enzyme, indicating that the enzyme is a secretory protein. The first 95 amino acids of the mature enzyme show no sequence homology with other sequenced proteins and there is one possible N-glycosylation site (Asn-89). The amino acid sequence from residues 96-193 shows strong homology (∼ 50%) with the final two-thirds of the sequences of all know eukaryotic CuZn SODs, whereas the homology with the P. leiognathi CuZn SOD is clearly lower. The ligands to Cu and Zn, the cysteines forming the intrasubunit disulfide bridge in the CuZn SODs, and the arginine found in all CuZn SODs in the entrance to the active site can all be identified in EC-SOD. A comparison with bovine CuZn SOD, the three-dimensional structure of which is known, reveals that the homologies occur in the active site and the divergencies are in the part constituting the subunit contact area in CuZn SOD. Amino acid sequence 194-222 in the carboxyl-terminal end of EC-SOD is strongly hydrophilic and contains nine amino acids with a positive charge. This sequence probably confers the affinity of EC-SOD for heparin and heparan sulfate. An analysis of the amino acid sequence homologies with CuZn SODs from various species indicates that the EC-SODs may have evolved form the CuZn SODs before the evolution of fungi and plants

Metal-free ALS variants of dimeric human Cu,Zn-superoxide dismutase have enhanced populations of monomeric species.

Directory of Open Access Journals (Sweden)

Anna-Karin E Svensson

2010-04-01

Full Text Available Amino acid replacements at dozens of positions in the dimeric protein human, Cu,Zn superoxide dismutase (SOD1 can cause amyotrophic lateral sclerosis (ALS. Although it has long been hypothesized that these mutations might enhance the populations of marginally-stable aggregation-prone species responsible for cellular toxicity, there has been little quantitative evidence to support this notion. Perturbations of the folding free energy landscapes of metal-free versions of five ALS-inducing variants, A4V, L38V, G93A, L106V and S134N SOD1, were determined with a global analysis of kinetic and thermodynamic folding data for dimeric and stable monomeric versions of these variants. Utilizing this global analysis approach, the perturbations on the global stability in response to mutation can be partitioned between the monomer folding and association steps, and the effects of mutation on the populations of the folded and unfolded monomeric states can be determined. The 2- to 10-fold increase in the population of the folded monomeric state for A4V, L38V and L106V and the 80- to 480-fold increase in the population of the unfolded monomeric states for all but S134N would dramatically increase their propensity for aggregation through high-order nucleation reactions. The wild-type-like populations of these states for the metal-binding region S134N variant suggest that even wild-type SOD1 may also be prone to aggregation in the absence of metals.

Isolation and in silico analysis of Fe-superoxide dismutase in the cyanobacterium Nostoc commune.

Science.gov (United States)

Kesheri, Minu; Kanchan, Swarna; Richa; Sinha, Rajeshwar P

2014-12-15

Cyanobacteria are known to endure various stress conditions due to the inbuilt potential for oxidative stress alleviation owing to the presence of an array of antioxidants. The present study shows that Antarctic cyanobacterium Nostoc commune possesses two antioxidative enzymes viz., superoxide dismutase (SOD) and catalase that jointly cope with environmental stresses prevailing at its natural habitat. Native-PAGE analysis illustrates the presence of a single prominent isoform recognized as Fe-SOD and three distinct isoforms of catalase. The protein sequence of Fe-SOD in N. commune retrieved from NCBI protein sequence database was used for in silico analysis. 3D structure of N. commune was predicted by comparative modeling using MODELLER 9v11. Further, this model was validated for its quality by Ramachandran plot, ERRAT, Verify 3D and ProSA-web which revealed good structure quality of the model. Multiple sequence alignment showed high conservation in N and C-terminal domain regions along with all metal binding positions in Fe-SOD which were also found to be highly conserved in all 28 cyanobacterial species under study, including N. commune. In silico prediction of isoelectric point and molecular weight of Fe-SOD was found to be 5.48 and 22,342.98Da respectively. The phylogenetic tree revealed that among 28 cyanobacterial species, Fe-SOD in N. commune was the closest evolutionary homolog of Fe-SOD in Nostoc punctiforme as evident by strong bootstrap value. Thus, N. commune may serve as a good biological model for studies related to survival of life under extreme conditions prevailing at the Antarctic region. Moreover cyanobacteria may be exploited for biochemical and biotechnological applications of enzymatic antioxidants. Copyright © 2014 Elsevier B.V. All rights reserved.

Kinetic stability and membrane structure of liposomes during in vitro infant intestinal digestion: Effect of cholesterol and lactoferrin.

Science.gov (United States)

Liu, Weilin; Wei, Fuqiang; Ye, Aiqian; Tian, Mengmeng; Han, Jianzhong

2017-09-01

The effects of cholesterol and lactoferrin on the kinetic stability and membrane structural integrity of negatively charged liposomes under in vitro infant intestinal digestion conditions were elucidated using dynamic light scattering, pH-stat titration, Fourier transform infrared spectroscopy, and pyrene steady state fluorescence probes. The liposomes had a smaller particle diameter, a wider size distribution, and a greater negative charge after digestion. The incorporation of cholesterol into the phospholipid bilayers resulted in a more ordered conformation in the aliphatic tail region and reduced micropolarity, indicating that cholesterol can improve the structural stability of liposomal membranes against intestinal environmental stress. Lactoferrin coverage facilitated the release of free fatty acids and increased the microfluidity of the bilayers, reducing the structural integrity of the liposomes. This study provides useful information on the design of liposomes and other microcapsules with improved and controlled release properties during digestion for particular groups of people. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of spin-orbit interactions on the structural stability, thermodynamic properties, and transport properties of lead under pressure

Science.gov (United States)

Smirnov, N. A.

2018-03-01

The paper investigates the role of spin-orbit interaction in the prediction of structural stability, lattice dynamics, elasticity, thermodynamic and transport properties (electrical resistivity and thermal conductivity) of lead under pressure with the FP-LMTO (full-potential linear-muffin-tin orbital) method for the first-principles band structure calculations. Our calculations were carried out for three polymorphous lead modifications (fcc, hcp, and bcc) in generalized gradient approximation with the exchange-correlation functional PBEsol. They suggest that compared to the scalar-relativistic calculation, the account for the SO effects insignificantly influences the compressibility of Pb. At the same time, in the calculation of phonon spectra and transport properties, the role of SO interaction is important, at least, for P ≲150 GPa. At higher pressures, the contribution from SO interaction reduces but not vanishes. As for the relative structural stability, our studies show that SO effects influence weakly the pressure of the fcc →hcp transition and much higher the pressure of the hcp →bcc transition.

Molecular and biochemical characterization of a unique mutation in CCS, the human copper chaperone to superoxide dismutase.

Science.gov (United States)

Huppke, Peter; Brendel, Cornelia; Korenke, Georg Christoph; Marquardt, Iris; Donsante, Anthony; Yi, Ling; Hicks, Julia D; Steinbach, Peter J; Wilson, Callum; Elpeleg, Orly; Møller, Lisbeth Birk; Christodoulou, John; Kaler, Stephen G; Gärtner, Jutta

2012-08-01

Copper (Cu) is a trace metal that readily gains and donates electrons, a property that renders it desirable as an enzyme cofactor but dangerous as a source of free radicals. To regulate cellular Cu metabolism, an elaborate system of chaperones and transporters has evolved, although no human Cu chaperone mutations have been described to date. We describe a child from a consanguineous family who inherited homozygous mutations in the SLC33A1, encoding an acetyl CoA transporter, and in CCS, encoding the Cu chaperone for superoxide dismutase. The CCS mutation, p.Arg163Trp, predicts substitution of a highly conserved arginine residue at position 163, with tryptophan in domain II of CCS, which interacts directly with superoxide dismutase 1 (SOD1). Biochemical analyses of the patient's fibroblasts, mammalian cell transfections, immunoprecipitation assays, and Lys7Δ (CCS homolog) yeast complementation support the pathogenicity of the mutation. Expression of CCS was reduced and binding of CCS to SOD1 impaired. As a result, this mutation causes reduced SOD1 activity and may impair other mechanisms important for normal Cu homeostasis. CCS-Arg163Trp represents the primary example of a human mutation in a gene coding for a Cu chaperone. © 2012 Wiley Periodicals, Inc.

Structural Stability and Performance of Noble Metal-Free SnO2-Based Gas Sensors

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Antonio Tricoli

2012-05-01

Full Text Available The structural stability of pure SnO2 nanoparticles and highly sensitive SnO2-SiO2 nanocomposites (0–15 SiO2 wt% has been investigated for conditions relevant to their utilization as chemoresistive gas sensors. Thermal stabilization by SiO2 co-synthesis has been investigated at up to 600 °C determining regimes of crystal size stability as a function of SiO2-content. For operation up to 400 °C, thermally stable crystal sizes of ca. 24 and 11 nm were identified for SnO2 nanoparticles and 1.4 wt% SnO2-SiO2 nanocomposites, respectively. The effect of crystal growth during operation (TO = 320 °C on the sensor response to ethanol has been reported, revealing possible long-term destabilization mechanisms. In particular, crystal growth and sintering-neck formation were discussed with respect to their potential to change the sensor response and calibration. Furthermore, the effect of SiO2 cosynthesis on the cross-sensitivity to humidity of these noble metal-free SnO2-based gas sensors was assessed.

Influence of protic ionic liquids on the structure and stability of succinylated Con A.

Science.gov (United States)

Attri, Pankaj; Venkatesu, Pannuru

2012-01-01

We report the synthesis of a series of ionic liquids (ILs) from various ions having different kosmotropicity including dihydrogen phosphate (H(2)PO(4)(-)), hydrogen sulfate (HSO(4)(-)) and acetate (CH(3)COO(-)) as anions and chaotropic cation such as trialkylammonium cation. To characterize the biomolecular interactions of ILs with protein, we have explored the stability of succinylated Con A (S Con A) in the presence of these aqueous ILs, which are varied combinations of kosmotropic anion with chaotropic cation such as triethylammonium dihydrogen phosphate [(CH(3)CH(2))(3)NH][H(2)PO(4)] (TEAP), trimethylammonium acetate [(CH(3))(3)NH][CH(3)COO] (TMAA), trimethylammonium dihydrogen phosphate [(CH(3))(3)NH][H(2)PO(4)] (TMAP) and trimethylammonium hydrogen sulfate [(CH(3))(3)NH][HSO(4)] (TMAS). Circular dichroism (CD) and fluorescence experiments have been used to characterize the stability of S Con A by ILs. Our data distinctly demonstrate that the long alkyl chain IL TEAP is a strong stabilizer for S Con A. Further, our experimental results reveal that TEAP is an effective refolding enhancer for S Con A from a thermally denatured protein structure. Copyright © 2012 Elsevier B.V. All rights reserved.

Stability and electronic structure of Zr-based ternary metallic glasses and relevant compounds

International Nuclear Information System (INIS)

Hasegawa, M.; Soda, K.; Sato, H.; Suzuki, T.; Taketomi, T.; Takeuchi, T.; Kato, H.; Mizutani, U.

2007-01-01

The electronic structure of the Zr-based metallic glasses has been investigated by theoretical and experimental approaches. One approach is band calculations of the Zr 2 Ni (Zr 66.7 Ni 33.3 ) compound to investigate the electronic structure of the Zr 66.7 Ni 33.3 metallic glass (ΔT x = 0 K) of which the local atomic structure is similar to that of the Zr 2 Ni compound. The other is photoemission spectroscopy of the Zr 50 Cu 35 Al 15 bulk metallic glass (BMG) (ΔT x = 69 K). Here ΔT x = T x - T g where T x and T g are crystallization and glass transition temperature, respectively. Both results and previous ones on the Zr 55 Cu 30 Ni 5 Al 10 BMG indicate that there is a pseudogap at the Fermi level in the electronic structure of these Zr-based metallic glasses, independent of the value of the ΔT x . This implies that the pseudogap at the Fermi level is one of the factors that stabilize the glass phase of Zr-based metallic glasses

Structure and stability of small H clusters on graphene

DEFF Research Database (Denmark)

Sljivancanin, Zeljko; Andersen, Mie; Hammer, Bjørk

2011-01-01

The structure and stability of small hydrogen clusters adsorbed on graphene is studied by means of density functional theory (DFT) calculations. Clusters containing up to six H atoms are investigated systematically, with the clusters having either all H atoms on one side of the graphene sheet (cis......-clusters) or having the H atoms on both sides in an alternating manner (trans-clusters). The most stable cis-clusters found have H atoms in ortho- and para-positions with respect to each other (two H’s on neighboring or diagonally opposite carbon positions within one carbon hexagon), while the most stable trans......-clusters found have H atoms in ortho-trans-positions with respect to each other (two H’s on neighboring carbon positions, but on opposite sides of the graphene). Very stable trans-clusters with 13–22 H atoms were identified by optimizing the number of H atoms in ortho-trans-positions and thereby the number...

Structure and Stability of Molecular Crystals with Many-Body Dispersion-Inclusive Density Functional Tight Binding.

Science.gov (United States)

Mortazavi, Majid; Brandenburg, Jan Gerit; Maurer, Reinhard J; Tkatchenko, Alexandre

2018-01-18

Accurate prediction of structure and stability of molecular crystals is crucial in materials science and requires reliable modeling of long-range dispersion interactions. Semiempirical electronic structure methods are computationally more efficient than their ab initio counterparts, allowing structure sampling with significant speedups. We combine the Tkatchenko-Scheffler van der Waals method (TS) and the many-body dispersion method (MBD) with third-order density functional tight-binding (DFTB3) via a charge population-based method. We find an overall good performance for the X23 benchmark database of molecular crystals, despite an underestimation of crystal volume that can be traced to the DFTB parametrization. We achieve accurate lattice energy predictions with DFT+MBD energetics on top of vdW-inclusive DFTB3 structures, resulting in a speedup of up to 3000 times compared with a full DFT treatment. This suggests that vdW-inclusive DFTB3 can serve as a viable structural prescreening tool in crystal structure prediction.

Piper betle shows antioxidant activities, inhibits MCF-7 cell proliferation and increases activities of catalase and superoxide dismutase

Directory of Open Access Journals (Sweden)

Abrahim Noor

2012-11-01

Full Text Available Abstract Background Breast cancer is the most common form of cancer and the focus on finding chemotherapeutic agents have recently shifted to natural products. Piper betle is a medicinal plant with various biological activities. However, not much data is available on the anti-cancer effects of P. betle on breast cancer. Due to the current interest in the potential effects of antioxidants from natural products in breast cancer treatment, we investigated the antioxidant activities of the leaves of P. betle and its inhibitory effect on the proliferation of the breast cancer cell line, MCF-7. Methods The leaves of P. betle were extracted with solvents of varying polarities (water, methanol, ethyl acetate and hexane and their phenolic and flavonoid content were determined using colorimetric assays. Phenolic composition was characterized using HPLC. Antioxidant activities were measured using FRAP, DPPH, superoxide anion, nitric oxide and hyroxyl radical scavenging assays. Biological activities of the extracts were analysed using MTT assay and antioxidant enzyme (catalase, superoxide dismutase, glutathione peroxidase assays in MCF-7 cells. Results Overall, the ethyl acetate extract showed the highest ferric reducing activity and radical scavenging activities against DPPH, superoxide anion and nitric oxide radicals. This extract also contained the highest phenolic content implying the potential contribution of phenolics towards the antioxidant activities. HPLC analyses revealed the presence of catechin, morin and quercetin in the leaves. The ethyl acetate extract also showed the highest inhibitory effect against the proliferation of MCF-7 cells (IC50=65 μg/ml. Treatment of MCF-7 cells with the plant extract increased activities of catalase and superoxide dismutase. Conclusions Ethyl acetate is the optimal solvent for the extraction of compounds with antioxidant and anti-proliferative activities. The increased activities of catalase and superoxide

Piper betle shows antioxidant activities, inhibits MCF-7 cell proliferation and increases activities of catalase and superoxide dismutase.

Science.gov (United States)

Abrahim, Noor Nazirahanie; Kanthimathi, M S; Abdul-Aziz, Azlina

2012-11-15

Breast cancer is the most common form of cancer and the focus on finding chemotherapeutic agents have recently shifted to natural products. Piper betle is a medicinal plant with various biological activities. However, not much data is available on the anti-cancer effects of P. betle on breast cancer. Due to the current interest in the potential effects of antioxidants from natural products in breast cancer treatment, we investigated the antioxidant activities of the leaves of P. betle and its inhibitory effect on the proliferation of the breast cancer cell line, MCF-7. The leaves of P. betle were extracted with solvents of varying polarities (water, methanol, ethyl acetate and hexane) and their phenolic and flavonoid content were determined using colorimetric assays. Phenolic composition was characterized using HPLC. Antioxidant activities were measured using FRAP, DPPH, superoxide anion, nitric oxide and hyroxyl radical scavenging assays. Biological activities of the extracts were analysed using MTT assay and antioxidant enzyme (catalase, superoxide dismutase, glutathione peroxidase) assays in MCF-7 cells. Overall, the ethyl acetate extract showed the highest ferric reducing activity and radical scavenging activities against DPPH, superoxide anion and nitric oxide radicals. This extract also contained the highest phenolic content implying the potential contribution of phenolics towards the antioxidant activities. HPLC analyses revealed the presence of catechin, morin and quercetin in the leaves. The ethyl acetate extract also showed the highest inhibitory effect against the proliferation of MCF-7 cells (IC50=65 μg/ml). Treatment of MCF-7 cells with the plant extract increased activities of catalase and superoxide dismutase. Ethyl acetate is the optimal solvent for the extraction of compounds with antioxidant and anti-proliferative activities. The increased activities of catalase and superoxide dismutase in the treated cells could alter the antioxidant defense

COMPREHENSIVE ANALYSIS ON SEEPAGE AND STRUCTURAL STABILITY OF EARTH-ROCK DAM: A CASE STUDY OF XIQUANYAN DAM IN CHINA

Directory of Open Access Journals (Sweden)

Qingqing GUO

2016-07-01

Full Text Available Earth-rock dam is commonly used in the high-dam engineering around the world. It has been widely accepted that the analysis on structural and seepage stability plays a very important role, and it is necessary to take into account while designing the earth-rock dam. In performing the analysis of structural and seepage stability, many remarkable methods are available at current stage. However, there are still some important issues remaining unsolved, including: (1 Finite element methods (FEMs is a means of solutions to analysis seepage process, but it is often a difficult task to determine the so-called seepage coefficient, because the common-used water injection test is limited in the practical work due to the high cost and complex procedure. (2 It has long been discussed that the key parameters for structural stability analysis show a significant spatial and temporal variations. It may be partly explained by the inhomogeneous dam-filling during construction work and the developing seepage process. The consequence is that one constant value of the parameter cannot represent the above variations. In this context, we solve the above issues and introduce the solution with a practical earth-rock dam project. For determining the seepage coefficient, the data from the piezo metric tube is used to calculate the potential value, based on which the seepage coefficient can be back-analysed. Then the seepage field, as well as the seepage stability are numerically analysed using the FEM-based SEEP/W program. As to the structural safety, we take into account the spatial and temporal variations of the key parameters, and incorporate the Monte-Carlo simulation method into the commonly used M-P method to calculate the frequency distribution of the obtained structural safety factor. In this way, the structural and seepage safety can be well analysed. This study is also beneficial to provide a mature method and a theoretical insight into the earth-rock dam design

Structural properties, deformation behavior and thermal stability of martensitic Ti-Nb alloys

Energy Technology Data Exchange (ETDEWEB)

Boenisch, Matthias

2016-06-10

Ti-Nb alloys are characterized by a diverse metallurgy which allows obtaining a wide palette of microstructural configurations and physical properties via careful selection of chemical composition, heat treatment and mechanical processing routes. The present work aims to expand the current state of knowledge about martensite forming Ti-Nb alloys by studying 15 binary Ti-c{sub Nb}Nb (9 wt.% ≤ c{sub Nb} ≤ 44.5 wt.%) alloy formulations in terms of their structural and mechanical properties, as well as their thermal stability. The crystal structures of the martensitic phases, α{sup '} and α'', and the influence of the Nb content on the lattice (Bain) strain and on the volume change related to the β → α{sup '}/α'' martensitic transformations are analyzed on the basis of Rietveld-refinements. The magnitude of the shuffle component of the β → α{sup '}/α'' martensitic transformations is quantified in relation to the chemical composition. The largest transformation lattice strains are operative in Nb-lean alloys. Depending on the composition, both a volume dilatation and contraction are encountered and the volume change may influence whether hexagonal martensite α{sup '} or orthorhombic martensite α'' forms from β upon quenching. The mechanical properties and the deformation behavior of martensitic Ti-Nb alloys are studied by complementary methods including monotonic and cyclic uniaxial compression, nanoindentation, microhardness and impulse excitation technique. The results show that the Nb content strongly influences the mechanical properties of martensitic Ti-Nb alloys. The elastic moduli, hardness and strength are minimal in the vicinity of the limiting compositions bounding the interval in which orthorhombic martensite α'' forms by quenching. Uniaxial cyclic compressive testing demonstrates that the elastic properties of strained samples are different than those of unstrained ones

Effects of time delays on stability and Hopf bifurcation in a fractional ring-structured network with arbitrary neurons

Science.gov (United States)

Huang, Chengdai; Cao, Jinde; Xiao, Min; Alsaedi, Ahmed; Hayat, Tasawar

2018-04-01

This paper is comprehensively concerned with the dynamics of a class of high-dimension fractional ring-structured neural networks with multiple time delays. Based on the associated characteristic equation, the sum of time delays is regarded as the bifurcation parameter, and some explicit conditions for describing delay-dependent stability and emergence of Hopf bifurcation of such networks are derived. It reveals that the stability and bifurcation heavily relies on the sum of time delays for the proposed networks, and the stability performance of such networks can be markedly improved by selecting carefully the sum of time delays. Moreover, it is further displayed that both the order and the number of neurons can extremely influence the stability and bifurcation of such networks. The obtained criteria enormously generalize and improve the existing work. Finally, numerical examples are presented to verify the efficiency of the theoretical results.

First-principles calculations of BC{sub 4}N nanostructures: stability and electronic structure

Energy Technology Data Exchange (ETDEWEB)

Freitas, A.; Azevedo, S. [Universidade Federal da Paraiba, CCEN, Departamento de Fisica, Joao Pessoa, PB (Brazil); Machado, M. [Universidade Federal de Pelotas, Departamento de Fisica, Pelotas, RS (Brazil); Kaschny, J.R. [Instituto Federal da Bahia-Campus Vitoria da Conquista, Vitoria da Conquista, BA (Brazil)

2012-07-15

In this work, we apply first-principles methods to investigate the stability and electronic structure of BC{sub 4}N nanostructures which were constructed from hexagonal graphite layers where substitutional nitrogen and boron atoms are placed at specific sites. These layers were rolled up to form zigzag and armchair nanotubes, with diameters varying from 7 to 12 A, or cut and bent to form nanocones, with 60 and 120 disclination angles. The calculation results indicate that the most stable structures are the ones which maximize the number of B-N and C-C bonds. It is found that the zigzag nanotubes are more stable than the armchair ones, where the strain energy decreases with increasing tube diameter D, following a 1/D {sup 2} law. The results show that the 60 disclination nanocones are the most stable ones. Additionally, the calculated electronic properties indicate a semiconducting behavior for all calculated structures, which is intermediate to the typical behaviors found for hexagonal boron nitride and graphene. (orig.)

Temporal stability in the genetic structure of Sarcoptes scabiei under the host-taxon law: empirical evidences from wildlife-derived Sarcoptes mite in Asturias, Spain

Directory of Open Access Journals (Sweden)

Rossi Luca

2011-07-01

Full Text Available Abstract Background Implicitly, parasite molecular studies assume temporal genetic stability. In this study we tested, for the first time to our knowledge, the extent of changes in genetic diversity and structure of Sarcoptes mite populations from Pyrenean chamois (Rupicapra pyrenaica in Asturias (Spain, using one multiplex of 9 microsatellite markers and Sarcoptes samples from sympatric Pyrenean chamois, red deer (Cervus elaphus, roe deer (Capreolus capreolus and red fox (Vulpes vulpes. Results The analysis of an 11-years interval period found little change in the genetic diversity (allelic diversity, and observed and expected heterozygosity. The temporal stability in the genetic diversity was confirmed by population structure analysis, which was not significantly variable over time. Population structure analysis revealed temporal stability in the genetic diversity of Sarcoptes mite under the host-taxon law (herbivore derived- and carnivore derived-Sarcoptes mite among the sympatric wild animals from Asturias. Conclusions The confirmation of parasite temporal genetic stability is of vital interest to allow generalizations to be made, which have further implications regarding the genetic structure, epidemiology and monitoring protocols of the ubiquitous Sarcoptes mite. This could eventually be applied to other parasite species.

Exogenous melatonin suppresses dark-induced leaf senescence by activating the superoxide dismutase-catalase antioxidant pathway and down-regulating chlorophyll degradation in excised leaves of perennial ryegrass (Lolium perenne L.

Directory of Open Access Journals (Sweden)

Jing Zhang

2016-10-01

Full Text Available Leaf senescence is a typical symptom in plants exposed to dark and may be regulated by plant growth regulators. The objective of this study was to determine whether exogenous application of melatonin (N-acetyl-5-methoxytryptamine suppresses dark-induced leaf senescence and the effects of melatonin on reactive oxygen species (ROS scavenging system and chlorophyll degradation pathway in perennial grass species. Mature perennial ryegrass (Lolium perenne L. cv. ‘Pinnacle’ leaves were excised and incubated in 3 mM 2-(N-morpholino ethanesulfonic buffer (pH 5.8 supplemented with melatonin or water (control and exposed to dark treatment for 8 d. Leaves treated with melatonin maintained significantly higher endogenous melatonin level, chlorophyll content, photochemical efficiency, and cell membrane stability expressed by lower electrolyte leakage and malondialdehyde (MDA content compared to the control. Exogenous melatonin treatment also reduced the transcript level of chlorophyll degradation-associated genes and senescence marker genes (LpSAG12.1, Lph36, and Lpl69 during the dark treatment. The endogenous O2- production rate and H2O2 content were significantly lower in these excised leaves treated with melatonin compared to the water control. Exogenous melatonin treatment caused increases in enzymatic activity and transcript levels of superoxide dismutase and catalase but had no significant effects on ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase, and monohydroascorbate reductase. The content of non-enzymatic antioxidants, such as ascorbate and dehydroascorbate, were decreased by melatonin treatment, while the content of glutathione and oxidized glutathione was not affected by melatonin. These results suggest that the suppression of dark-induced leaf senescence by exogenous melatonin may be associated with its roles in regulating ROS scavenging through activating the superoxide dismutase-catalase enzymatic antioxidant

Importance of interlayer H bonding structure to the stability of layered minerals

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Conroy, Michele; Soltis, Jennifer A.; Wittman, Rick S.; Smith, Frances N.; Chatterjee, Sayandev; Zhang, Xin; Ilton, Eugene S.; Buck, Edgar C.

2017-10-16

The exact atomic structures of layered minerals have been difficult to characterize because the layers often possess out-of-plane hydrogen atoms that cannot be detected by many analytical techniques. However, the ordering of these bonds are thought to play a fundamental role in the structural stability and solubility of layered minerals. We report a new strategy of using the intense radiation field of a focused electron beam to probe the effect of differences in hydrogen bonding networks on mineral solubility while simultaneously imaging the dissolution behavior in real time via liquid cell electron microscopy. We show the loss in hydrogens from interlayers of boehmite (γ-AlOOH) resulted in 2D nanosheets exfoliating from the bulk that subsequently and rapidly dissolved. However gibbsite (γ-Al(OH)3), with its higher concentration of OH terminating groups, was more accommodating to the deprotonation and stable under the beam.

Study of Local and Distortional Stability of Thin-Walled Structures

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Imene Mahi

2018-01-01

Full Text Available Thin-walled structures have an increasingly large and growing field of application in the engineering sector, the goal behind using this type of structure is efficiency in terms of resistance and cost, however the stability of its components (the thin walls remains the first aspect of the behavior, and a primordial factor in the design process. The hot rolled sections are known by a consequent post-buckling reserve, cold-formed steel sections which are thin-walled elements also benefit, in this case, it seems essential to take into account the favorable effects of this reserve in to the verification procedure of the resistance with respect to the three modes of failures of this type of structure. The design method that takes into account this reserve of resistance is inevitably the effective width method. The direct strength method has been developed to improve the speed and efficiency of the design of thin-walled profiles. The latter mainly uses the buckling loads (for Local, Distortional and Global mode obtained from a numerical analysis and the resistance curves calibrated experimentally to predict the ultimate load of the profile. Among those, the behavior of a set of Cshaped profiles (highly industrialized is studied, this type of section is assumed to be very prone to modes of local and distortional instability. The outcome of this investigation revealed very relevant conclusions both scientifically and practically.

Adaptation of Staphylococcus aureus to Airway Environments in Patients With Cystic Fibrosis by Upregulation of Superoxide Dismutase M and Iron-Scavenging Proteins.

Science.gov (United States)

Treffon, Janina; Block, Desiree; Moche, Martin; Reiss, Swantje; Fuchs, Stephan; Engelmann, Susanne; Becher, Dörte; Langhanki, Lars; Mellmann, Alexander; Peters, Georg; Kahl, Barbara C

2018-04-11

Adaptation of S. aureus to the hostile environment of CF airways resulted in changed abundance of proteins involved in energy metabolism, cellular processes, transport and binding, but most importantly in an iron-scavenging phenotype and increased activity of superoxide dismutase M.

Influence of encapsulated functional lipids on crystal structure and chemical stability in solid lipid nanoparticles: Towards bioactive-based design of delivery systems.

Science.gov (United States)

Salminen, Hanna; Gömmel, Christina; Leuenberger, Bruno H; Weiss, Jochen

2016-01-01

We investigated the influence of physicochemical properties of encapsulated functional lipids--vitamin A, β-carotene and ω-3 fish oil--on the structural arrangement of solid lipid nanoparticles (SLN). The relationship between the crystal structure and chemical stability of the incorporated bioactive lipids was evaluated with different emulsifier compositions of a saponin-rich, food-grade Quillaja extract alone or combined with high-melting or low-melting lecithins. The major factors influencing the structural arrangement and chemical stability of functional lipids in solid lipid dispersions were their solubility in the aqueous phase and their crystallization temperature in relation to that of the carrier lipid. The results showed that the stabilization of the α-subcell crystals in the lattice of the carrier lipid is a key parameter for forming stable solid lipid dispersions. This study contributes to a better understanding of SLN as a function of the bioactive lipid. Copyright © 2015 Elsevier Ltd. All rights reserved.

High beta and second stability region transport and stability analysis

International Nuclear Information System (INIS)

1991-01-01

This document describes ideal and resistive MHD studies of high-beta plasmas and of the second stability region. Significant progress is reported on the resistive stability properties of high beta poloidal ''supershot'' discharges. For these studies initial profiles were taken from the TRANSP code which is used extensively to analyze experimental data. When an ad hoc method of removing the finite pressure stabilization of tearing modes is implemented it is shown that there is substantial agreement between MHD stability computation and experiment. In particular, the mode structures observed experimentally are consistent with the predictions of the resistive MHD model. We also report on resistive stability near the transition to the second region in TFTR. Tearing modes associated with a nearby infernal mode may explain the increase in MHD activity seen in high beta supershots and which impede the realization of Q∼1. We also report on a collaborative study with PPPL involving sawtooth stabilization with ICRF

Many-body effects on the structures and stability of Ba{sup 2+}Xe{sub n} (n = 1–39, 54) clusters

Energy Technology Data Exchange (ETDEWEB)

Abdessalem, Kawther, E-mail: kawtherabdessalem@yahoo.fr; Habli, Héla; Ghalla, Houcine [Laboratoire de Physique Quantique, Faculté des Sciences de Monastir, Université de Monastir, Avenue de l’Environnement, 5019 Monastir (Tunisia); Yaghmour, Saud Jamil [Physics Department, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia); Calvo, Florent [University of Grenoble Alpes, LIPHY, F-38000 Grenoble, France and CNRS, LIPHY, F-38000 Grenoble (France); Oujia, Brahim [Laboratoire de Physique Quantique, Faculté des Sciences de Monastir, Université de Monastir, Avenue de l’Environnement, 5019 Monastir (Tunisia); Physics Department, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia)

2014-10-21

The structures and relative stabilities of mixed Ba{sup 2+}Xe{sub n} (n = 1–39, 54) clusters have been theoretically studied using basin-hopping global optimization. Analytical potential energy surfaces were constructed from ab initio or experimental data, assuming either purely additive interactions or including many-body polarization effects and the mutual contribution of self-consistent induced dipoles. For both models the stable structures are characterized by the barium cation being coated by a shell of xenon atoms, as expected from simple energetic arguments. Icosahedral packing is dominantly found, the exceptional stability of the icosahedral motif at n = 12 being further manifested at the size n = 32 where the basic icosahedron is surrounded by a dodecahedral cage, and at n = 54 where the transition to multilayer Mackay icosahedra has occurred. Interactions between induced dipoles generally tend to decrease the Xe-Xe binding, leading to different solvation patterns at small sizes but also favoring polyicosahedral growth. Besides attenuating relative energetic stability, many-body effects affect the structures by expanding the clusters by a few percents and allowing them to deform more.

An engineering approach for examining crack growth and stability in flawed structures

International Nuclear Information System (INIS)

Shih, C.F.; German, M.D.; Kumar, V.

1981-01-01

Progress made in two research programmes, sponsored by the Electric Power Research Institute (EPRI), to identify viable parameters for characterising crack initiation and continued extension are summarised. An engineering/design methodology, based on these parameters, for the assessment of crack growth and instability in engineering structures which are stressed beyond the regime of applicability of linear elastic fracture mechanics is developed. The ultimate goal in the development of such a methodology is to establish an improved basis for analysing the effect of flaws (postulated or detected) on the safety margins of pressure boundary components of light water-cooled type nuclear steam supply systems. The methodology can also be employed for structural integrity analyses of other engineering components. Extensive experimental and analytical investigations undertaken to evaluate potential criteria for crack initiation and growth and the selection of the final criteria for analysing crack growth and stability in flawed structures are summarised. The experimental and analytical results obtained to date suggest that parameters based on the J-integral and the crack tip opening displacement, delta, are the most promising. This is not surprising since, from a theoretical basis, the two approaches are similar if certain conditions are met. An engineering/design approach for the assessment of crack growth and instability in flawed structures is outlined. (author)

Development of tantalum oxynitride thin films produced by PVD: Study of structural stability

Energy Technology Data Exchange (ETDEWEB)

Cristea, D. [Centro de Física, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Department of Materials Science, Transylvania University, 500036 Brasov (Romania); Crisan, A. [Department of Materials Science, Transylvania University, 500036 Brasov (Romania); Barradas, N.P.; Alves, E. [Instituto Superior Técnico, Universidade Técnica de Lisboa Estrada Nacional 10, ao km 139,7 2695-066, Bobadela LRS (Portugal); Moura, C.; Vaz, F. [Centro de Física, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Cunha, L., E-mail: lcunha@fisica.uminho.pt [Centro de Física, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal)

2013-11-15

The purpose of this work is to study the evolution of the structure and of the thermal stability of a group of tantalum oxynitride thin films, prepared by magnetron sputtering, under the influence of vacuum annealing, up to a temperature of 800 °C. When varying the partial pressure of the reactive gases (P{sub O{sub 2+N{sub 2}}}), during the deposition process, the films change from a structure with a combination of poorly developed crystallites of the tetragonal β-Ta and of the face centred cubic (fcc) Ta(O,N) phases, for the films deposited with low P{sub O2+N2}, to a quasi-amorphous structure, for the films deposited with highest pressures. For intermediate pressures, the films reveal the presence of the fcc-Ta(O,N) structure. This structure corresponds to O atoms substituting some of the N atoms on the fcc-TaN structure and/or N atoms substituting O atoms of the fcc-γ-TaO structure. When subjected to the thermal annealing at 700 °C or higher, the film produced with lowest partial pressure revealed a remarkable structural change. New diffraction peaks appear and can only be attributed to a sub-stoichiometric hexagonal tantalum nitride structure. The film did not reveal any signs of delamination or cracks after all annealing temperatures. The two films produced with highest partial pressure proved to be the most stable. Structurally, they maintain the amorphous structure after all the annealing treatments and, in addition, no cracks or delamination were detected.

A cross-cultural investigation into the dimensional structure and stability of the Barriers to Research and Utilization Scale (BARRIERS Scale).

Science.gov (United States)

Williams, Brett; Brown, Ted; Costello, Shane

2015-10-24

It is important that scales exhibit strong measurement properties including those related to the investigation of issues that impact evidence-based practice. The validity of the Barriers to Research Utilization Scale (BARRIERS Scale) has recently been questioned in a systematic review. This study investigated the dimensional structure and stability of the 28 item BARRIERS Scale when completed by three groups of participants from three different cross-cultural environments. Data from the BARRIERS Scale completed by 696 occupational therapists from Australia (n = 137), Taiwan (n = 413), and the United Kingdom (n = 144) were analysed using principal components analysis, followed by Procrustes Transformation. Poorly fitting items were identified by low communalities, cross-loading, and theoretically inconsistent primary loadings, and were systematically removed until good fit was achieved. The cross-cultural stability of the component structure of the BARRIERS Scale was examined. A four component, 19 item version of the BARRIERS Scale emerged that demonstrated an improved dimensional fit and stability across the three participant groups. The resulting four components were consistent with the BARRIERS Scale as originally conceptualised. Findings from the study suggest that the four component, 19 item version of the BARRIERS Scale is a robust and valid measure for identifying barriers to research utilization for occupational therapists in paediatric health care settings across Australia, United Kingdom, and Taiwan. The four component 19 item version of the BARRIERS Scale exhibited good dimensional structure, internal consistency, and stability.

Phase stability in yttria-stabilized zirconia from first principles

Energy Technology Data Exchange (ETDEWEB)

Carbogno, Christian; Scheffler, Matthias [Materials Department, University of California, Santa Barbara, CA (United States); Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin (Germany); Levi, Carlos G.; Van de Walle, Chris G. [Materials Department, University of California, Santa Barbara, CA (United States)

2012-07-01

Zirconia based ceramics are of pivotal importance for a variety of industrial technologies, e.g., for thermal barrier coatings in gas and airplane turbines. Naturally, the stability of such coatings at elevated temperatures plays a critical role in these applications. It is well known that an aliovalent doping of tetragonal ZrO{sub 2} with yttria, which induces oxygen vacancies due to charge conservation, increases its thermodynamic stability. However, the atomistic mechanisms that determine the phase stability of such yttria-stabilized Zirconia (YSZ) coatings are not yet fully understood. In this work, we use density functional theory calculations to assess the electronic structure of the different YSZ polymorphs at various levels of doping. With the help of population analysis schemes, we are able to unravel the intrinsic mechanisms that govern the interaction in YSZ and that can so explain the relative stabilities of the various polymorphs. We critically compare our results to experimental measurements and discuss the implications of our findings with respect to other oxides.

Direct reactions in inverse kinematics for nuclear structure studies far off stability at low incident energies

International Nuclear Information System (INIS)

Egelhof, P.

1997-02-01

The investigation of light-ion induced direct reactions with exotic beams in inverse kinematics gives access to a wide field of nuclear structure studies in the region far off stability. The present contribution will focus on the investigation of few-nucleon transfer reactions, which turn out to be most favourably studied with good-quality low-energy radioactive beams, as provided by the new generation of radioactive beam facilities presently planned or under construction at Caen, Grenoble, Munich, and elsewhere. An overview on the physics motivation, basically concerning nuclear structure and nuclear astrophysics questions, is given. Of particular interest are the nuclear shell model in the region far off stability, the two-body residual interaction in nuclei, the structure of halo nuclei, as well as the understanding of the r-process scenario. The experimental conditions, along with the experimental concept, for such measurements are discussed with particular emphasis on the kinematical conditions, the observables, as well as the appropriate detection schemes. The concept of a large solid angle TPC ionization chamber as an active target for experiments with low-energy radioactive beams is presented. It turns out to be a highly effective detection scheme, well suited for the present experimental conditions, at least for light exotic beams up to Z∼20. (orig.)

A study on aseismic performance estimation of a nuclear facility from a viewpoint of structural stability

International Nuclear Information System (INIS)

En, Koshiro; Imazuka, Yoshikatsu; Okutani, Tetsuya; Akita, Shodo; Kawasato, Takeshi

2004-01-01

In estimating aseismic performance of a nuclear facility, structural stability is quantified in terms of ''contact ratio'' of a base considering dynamic soil-structure interaction. However, the maximum response in the time-domain non-linear analysis may strongly depend on the phase characteristics of input motions. The stochastic properties of the overturning moment and ''contact ratio'' are investigated through Monte Carlo simulation using 100 artificial seismic waves synthesized for the multi-damping design response spectra. The fragility curve is also proposed based on random vibration theory and its dependence on both geometric proportion of the structure and the amplitude of input motions is illustrated. (author)

Felder-Soloman's Index of Learning Styles: internal consistency, temporal stability, and factor structure.

Science.gov (United States)

Hosford, Charles C; Siders, William A

2010-10-01

Strategies to facilitate learning include using knowledge of students' learning style preferences to inform students and their teachers. Aims of this study were to evaluate the factor structure, internal consistency, and temporal stability of medical student responses to the Index of Learning Styles (ILS) and determine its appropriateness as an instrument for medical education. The ILS assesses preferences on four dimensions: sensing/intuitive information perceiving, visual/verbal information receiving, active/reflective information processing, and sequential/global information understanding. Students entering the 2002-2007 classes completed the ILS; some completed the ILS again after 2 and 4 years. Analyses of responses supported the ILS's intended structure and moderate reliability. Students had moderate preferences for sensing and visual learning. This study provides evidence supporting the appropriateness of the ILS for assessing learning style preferences in medical students.

"Choice" and destiny: the substrate composition and mechanical stability of settlement structures can mediate coral recruit fate in post-bleached reefs

Science.gov (United States)

Yadav, Shreya; Rathod, Pooja; Alcoverro, Teresa; Arthur, Rohan

2016-03-01

Increasingly frequent and intense ocean warming events seriously test the buffer and recovery capacities of tropical coral reefs. Post-disturbance, available settlement structures on a reef (often dead coral skeletons) vary considerably in their mechanical stability and substrate composition, critically influencing coral recruit settlement choice and fate. In the wake of a coral mass mortality in the Lakshadweep archipelago, we examine (1) the relative availability of recruit settlement structures (from stable to unstable: reef platform, dead massive coral, consolidated rubble, dead corymbose coral, dead tabular coral, and unconsolidated rubble) in 12 recovering reefs across three atolls in the archipelago, (2) the substrate composition [crustose coralline algae (CCA), mixed turf, macroalgae] of these structural forms, and (3) whether the choice and fate of young coral are mediated by the substrate and stability of different structural forms. For this, we measured the abundance and distribution of recruit (<1 cm), juvenile (1-5 cm), and young adult (5-10) corals of 24 common coral genera. Four years after the mass mortality, reefs differed considerably in composition of settlement structures. The structures themselves varied significantly in substrate cover with dead tables largely covered in CCA [60 ± 6.05 % (SE)] and dead corymbose coral dominated by mixed turf (61.83 ± 3.8 %). The youngest visible recruits (<1 cm) clearly preferred CCA-rich structures such as dead massives and tables. However, older size classes were rarely found on unstable structures (strongly "avoiding" tables, Ivlev's electivity index, E = -0.5). Our results indicate that while substrate cover might mediate coral choice, the mechanical stability of settlement structures is critical in determining post-settlement coral survival. The composition and availability of settlement structures on a reef may serve as a characteristic signature of its recovery potential, aiding in assessments of reef

Structures and related properties of helical, disulfide-stabilized peptides

Energy Technology Data Exchange (ETDEWEB)