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Sample records for enzyme action interfacial

  1. Activation of interfacial enzymes at membrane surfaces

    DEFF Research Database (Denmark)

    Mouritsen, Ole G.; Andresen, Thomas Lars; Halperin, Avi

    2006-01-01

    A host of water-soluble enzymes are active at membrane surfaces and in association with membranes. Some of these enzymes are involved in signalling and in modification and remodelling of the membranes. A special class of enzymes, the phospholipases, and in particular secretory phospholipase A2 (s...

  2. Steroid promiscuity: Diversity of enzyme action. Preface.

    Science.gov (United States)

    Lathe, Richard; Kotelevtsev, Yuri; Mason, J Ian

    2015-07-01

    This Special Issue on the topic of Steroid and Sterol Signaling: Promiscuity and Diversity, dwells on the growing realization that the 'one ligand, one binding site' and 'one enzyme, one reaction' concepts are out of date. Focusing on cytochromes P450 (CYP), hydroxysteroid dehydrogenases (HSDs), and related enzymes, the Special Issue highlights that a single enzyme can bind to diverse substrates, and in different conformations, and can catalyze multiple different conversions (and in different directions), thereby, generating an unexpectedly wide spectrum of ligands that can have subtly different biological actions. This article is part of a Special Issue entitled 'Steroid/Sterol Signaling' . Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Relation between various phospholipase actions on human red cell membranes and the interfacial phospholipid pressure in monolayers

    NARCIS (Netherlands)

    Demel, R.A.; Geurts van Kessel, W.S.M.; Zwaal, R.F.A.; Roelofsen, B.; Deenen, L.L.M. van

    1975-01-01

    The action of purified phospholipases on monomolecular films of various interfacial pressures is compared with the action on erythrocyte membranes. The phospholipases which cannot hydrolyse phospholipids of the intact erythrocyte membrane, phospholipase C from Bacillus cereus, phospholipase A2 from

  4. Morphology and interfacial action of nanocomposites formed from ethylene-vinyl acetate copolymers and organoclays.

    Science.gov (United States)

    Zhang, Qilu; Ma, Xiaoyan; Wang, Yifei; Kou, Kaichang

    2009-09-03

    The effect of the polarity of modifier and polymer matrixes on the morphology and interfacial action of nanocomposites was studied by molecular dynamics (MD) and inverse gas chromatography (IGC) based on ethylene-vinyl acetate (EVA) /organic montmorillonite (OMMT), where vinyl acetate (VA) concentrations are 9.3 and 18 wt %, respectively. It is found that EVA with higher VA concentration displays a higher surface energy than that with lower VA concentration. Modifier with two long alkyl tails will lower the surface energy of montmorillonite (MMT) more effectively. Combined with transmission electron microscopy (TEM) photography of EVA/OMMT nanocomposites, it is found that the surface energies of organic montmorillonite and EVAs make great contributions to the dispersion of the OMMT in polymer matrixes. OMMT modified by two long alkyl tails displays weaker acid and base properties which will have a better interaction with EVAs through acid-base interaction. Molecular simulation (MD) proved that nonpolar interaction determines the binding between EVAs and organoclays, otherwise electrostatic interaction in polar polymer/organoclay systems. Binding energies were calculated by MD, and the results show stronger interaction between 20A (organoclay made from two long alkyl tails surfactant) and EVA. Interfacial action between filler and polymer matrix should be accountable for the mechanical properties of the nanocomposite.

  5. Synergistic action of enzyme preparations towards recalcitrant corn silage polysaccharides

    NARCIS (Netherlands)

    Neumüller, K.G.; Streekstra, H.; Schols, H.A.; Gruppen, H.

    2014-01-01

    Corn silage, its water unextractable solids (WUS) and enzyme recalcitrant solids (ErCS) and an industrial corn silage-based anaerobic fermentation residue (AFR) represent corn substrates with different levels of recalcitrance. Compositional analysis reveals different levels of arabinoxylan

  6. Action of amylolytic and pullulytic enzymes from various anaerobic thermophiles on linear and branched glucose polymers

    Energy Technology Data Exchange (ETDEWEB)

    Koch, R. (Goettingen Univ. (Germany, F.R.). Inst. fuer Mikrobiologie); Antranikian, G. (Technische Univ. Hamburg-Harburg, Hamburg (Germany, F.R.). Arbeitsbereich Biotechnologie 1)

    1990-10-01

    A detailed study has been conducted on the action of starch hydrolyzing enzymes from thermophilic anaerobic bacteria belonging to the genera Clostridium, Thermoanaerobacter and Thermobacteroides. The appearance of multiple bands on polyacrylamide gels with amylolytic as well as pullulytic activities was shown to be a general feature of bacteria investigated. Analysis of the hydrolysis products of each protein band clearly demonstrated the capability of these organisms to hydrolyze {alpha}-1,4-glycosidic bonds in linear oligosaccharides and {alpha}-1,6-glycosidic linkages in pullulan. Furthermore, the enzyme system of thermophilic bacteria investigated was also capable of attacking in the {alpha}-1,6-linkages in branched oligosaccharides. Due to the action of these thermoactive enzymes with multiple specificity an almost complete hydrolysis of raw starch and maltodextrin could be achieved under the same conditions and in one step. (orig.).

  7. Inhibitory actions of Pseuderanthemum palatiferum (Nees Radlk. leaf ethanolic extract and its phytochemicals against carbohydrate-digesting enzymes

    Directory of Open Access Journals (Sweden)

    Pawitra Pulbutr

    2016-02-01

    Conclusions: These results indicate an inhibitory action against carbohydrate-digesting enzymes as the anti-diabetic mechanism of action of PPE. Nonetheless, further clinical study is required to justify its role in the treatment of diabetes.

  8. A coarse-grained model for synergistic action of multiple enzymes on cellulose

    Directory of Open Access Journals (Sweden)

    Asztalos Andrea

    2012-08-01

    Full Text Available Abstract Background Degradation of cellulose to glucose requires the cooperative action of three classes of enzymes, collectively known as cellulases. Endoglucanases randomly bind to cellulose surfaces and generate new chain ends by hydrolyzing β-1,4-D-glycosidic bonds. Exoglucanases bind to free chain ends and hydrolyze glycosidic bonds in a processive manner releasing cellobiose units. Then, β-glucosidases hydrolyze soluble cellobiose to glucose. Optimal synergistic action of these enzymes is essential for efficient digestion of cellulose. Experiments show that as hydrolysis proceeds and the cellulose substrate becomes more heterogeneous, the overall degradation slows down. As catalysis occurs on the surface of crystalline cellulose, several factors affect the overall hydrolysis. Therefore, spatial models of cellulose degradation must capture effects such as enzyme crowding and surface heterogeneity, which have been shown to lead to a reduction in hydrolysis rates. Results We present a coarse-grained stochastic model for capturing the key events associated with the enzymatic degradation of cellulose at the mesoscopic level. This functional model accounts for the mobility and action of a single cellulase enzyme as well as the synergy of multiple endo- and exo-cellulases on a cellulose surface. The quantitative description of cellulose degradation is calculated on a spatial model by including free and bound states of both endo- and exo-cellulases with explicit reactive surface terms (e.g., hydrogen bond breaking, covalent bond cleavages and corresponding reaction rates. The dynamical evolution of the system is simulated by including physical interactions between cellulases and cellulose. Conclusions Our coarse-grained model reproduces the qualitative behavior of endoglucanases and exoglucanases by accounting for the spatial heterogeneity of the cellulose surface as well as other spatial factors such as enzyme crowding. Importantly, it captures

  9. Enzyme

    Science.gov (United States)

    Enzymes are complex proteins that cause a specific chemical change in all parts of the body. For ... use them. Blood clotting is another example of enzymes at work. Enzymes are needed for all body ...

  10. The Secretion and Action of Brush Border Enzymes in the Mammalian Small Intestine.

    Science.gov (United States)

    Hooton, Diane; Lentle, Roger; Monro, John; Wickham, Martin; Simpson, Robert

    2015-01-01

    Microvilli are conventionally regarded as an extension of the small intestinal absorptive surface, but they are also, as latterly discovered, a launching pad for brush border digestive enzymes. Recent work has demonstrated that motor elements of the microvillus cytoskeleton operate to displace the apical membrane toward the apex of the microvillus, where it vesiculates and is shed into the periapical space. Catalytically active brush border digestive enzymes remain incorporated within the membranes of these vesicles, which shifts the site of BB digestion from the surface of the enterocyte to the periapical space. This process enables nutrient hydrolysis to occur adjacent to the membrane in a pre-absorptive step. The characterization of BB digestive enzymes is influenced by the way in which these enzymes are anchored to the apical membranes of microvilli, their subsequent shedding in membrane vesicles, and their differing susceptibilities to cleavage from the component membranes. In addition, the presence of active intracellular components of these enzymes complicates their quantitative assay and the elucidation of their dynamics. This review summarizes the ontogeny and regulation of BB digestive enzymes and what is known of their kinetics and their action in the peripheral and axial regions of the small intestinal lumen.

  11. NBT-PABA test to assess efficiency and kinetics of substituted proteolytic enzyme action in pancreatic duct ligated minipigs.

    Science.gov (United States)

    Mösseler, A; Bergemann, J; Becker, C; Stemme, K; Gregory, P C; Kamphues, J

    2008-06-01

    The NBT-PABA test is an established method for diagnosis of pancreatic exocrine insufficiency. In the present study the NBT-PABA test was used to test and compare the efficacy of two multienzyme preparations (product A and B) differing in galenic preparation in minipigs in which pancreatic exocrine insufficiency (PEI) was induced by pancreatic duct ligation. Without enzyme substitution no distinct increase in PABA was found in blood after oral administration of NBT-PABA. Administration of both enzyme preparations led to a clear dose dependent rise in PABA-concentrations in blood. Interestingly, the two preparations showed different time curves of serum PABA concentration, indicating differences in the kinetic of proteolytic enzyme action. It is concluded that the NBT-PABA test can be a very useful test for indirectly evaluating proteolytic enzyme efficacy in vivo, and also gives information about the kinetics of enzyme action, not only the end-result of enzyme action (like digestibility trials which were used traditionally). A single test is performed in a few hours and there is no need for fistulated animals.

  12. The Conservation of Structure and Mechanism of Catalytic Action in a Family of Thiamin Pyrophosphate (TPP)-dependent Enzymes

    Science.gov (United States)

    Dominiak, P.; Ciszak, Ewa

    2004-01-01

    Thiamin pyrophosphate (TPP)-dependent enzymes are a divergent family of TPP and metal ion binding proteins that perform a wide range of functions with the common decarboxylation steps of a -(O=)C-C(OH)- fragment of alpha-ketoacids and alpha- hydroxyaldehydes. To determine how structure and catalytic action are conserved in the context of large sequence differences existing within this family of enzymes, we have carried out an analysis of TPP-dependent enzymes of known structures. The common structure of TPP-dependent enzymes is formed at the interface of four alpha/beta domains from at least two subunits, which provide for two metal and TPP-binding sites. Residues around these catalytic sites are conserved for functional purpose, while those further away from TPP are conserved for structural reasons. Together they provide a network of contacts required for flip-flop catalytic action within TPP-dependent enzymes. Thus our analysis defines a TPP-action motif that is proposed for annotating TPP-dependent enzymes for advancing functional proteomics.

  13. Advancing lignocellulose bioconversion through direct assessment of enzyme action on insoluble substrates

    DEFF Research Database (Denmark)

    Goacher, Robyn E.; Selig, Michael J.; Master, Emma R.

    2014-01-01

    Microbial utilization of lignocellulose from plant cell walls is integral to carbon cycling on Earth. Correspondingly, secreted enzymes that initiate lignocellulose depolymerization serve a crucial step in the bioconversion of lignocellulosic biomass to fuels and chemicals. Genome and metagenome...... sequencing efforts that span the past decade reveal the diversity of enzymes that have evolved to transform lignocellulose from wood, herbaceous plants and grasses. Nevertheless, there are relatively few examples where ‘omic’ technologies have identified novel enzyme activities or combinations thereof...

  14. Phospholipase A(2) - An enzyme that is sensitive to the physics of its substrate

    DEFF Research Database (Denmark)

    Høyrup, Lise Pernille Kristine; Jørgensen, Kent; Mouritsen, O.G.

    2002-01-01

    A simple statistical mechanical model of lipid bilayers is proposed to account for the non-equilibrium action of the enzyme phospholipase A(2). The enzyme hydrolyses lipid-bilayer substrates and produces product molecules that lead to local variations in the bilayer interfacial pressure. Computer...... simulation of the model shows, in quantitative agreement with experimental data, that the enzyme activity is modulated by nano-scale lipid-domain formation in the lipid bilayer leading to a characteristic lag-burst behavior....

  15. Thermus thermophilus Glycoside Hydrolase Family 57 Branching Enzyme : Crystal Structure, Mechanism of Action, and Products Formed

    NARCIS (Netherlands)

    Palomo, Marta; Pijning, Tjaard; Booiman, Thijs; Dobruchowska, Justyna M.; Vlist, Jeroen van der; Kralj, Slavko; Planas, Antoni; Loos, Katja; Kamerling, Johannis P.; Dijkstra, Bauke W.; Maarel, Marc J.E.C. van der; Dijkhuizen, Lubbert; Leemhuis, Hans

    2011-01-01

    Branching enzyme (EC 2.4.1.18; glycogen branching enzyme; GBE) catalyzes the formation of alpha 1,6-branching points in glycogen. Until recently it was believed that all GBEs belong to glycoside hydrolase family 13 (GH13). Here we describe the cloning and expression of the Thermus thermophilus

  16. Characterization and mode of action of enzymes degrading galactan structures of arabinogalactans

    NARCIS (Netherlands)

    Vis, van de J.W.

    1994-01-01

    Agricultural biomass consisting mainly of cellulose, hemicellulose and lignin, is a renewable source of fuels and chemicals. An interesting option is enzymic conversion of biomass to readily usable material. To improve the overall economics of enzymic conversion of biomass not only

  17. Hormonal control of enzyme synthesis: on the mode of action of gibberellic Acid and abscisin in aleurone layers of barley.

    Science.gov (United States)

    Chrispeels, M J; Varner, J E

    1967-07-01

    Gibberellic acid (GA) enhances the synthesis of alpha-amylase and ribonuclease in isolated aleurone layers and this process is inhibited by abscisin. Removal of gibberellic acid in mid-course of alpha-amylase production results in a slowing down of alpha-amylase synthesis, suggesting a continued requirement of GA for enzyme synthesis. This is paralleled by a continuous requirement for RNA synthesis. Addition of 6-methylpurine or 8-azaguanine in mid-course results in an inhibition of alpha-amylase synthesis within 3 to 4 hours. However, actinomycin D added in mid-course is almost without effect. This is not due to its failure to enter the cells, because it does inhibit (14)C-uridine incorporation at this stage. Addition of abscisin to aleurone layers which are synthesizing alpha-amylase results in an inhibition of this synthesis within 2 to 3 hours. Cycloheximide on the other hand inhibits enzyme synthesis immediately upon its addition. These data are consistent with the hypothesis that the expression of the GA effect requires the synthesis of enzyme-specific RNA molecules. The similarity in the kinetics of inhibition between abscisin on the one hand and 8-azaguanine or 6-methylpurine on the other suggests that abscisin may exert its action by inhibiting the synthesis of these enzyme-specific RNA molecules or by preventing their incorporation into an active enzyme-synthesising unit.

  18. Synergistic action of recombinant accessory hemicellulolytic and pectinolytic enzymes to Trichoderma reesei cellulase on rice straw degradation.

    Science.gov (United States)

    Laothanachareon, Thanaporn; Bunterngsook, Benjarat; Suwannarangsee, Surisa; Eurwilaichitr, Lily; Champreda, Verawat

    2015-12-01

    Synergism between core cellulases and accessory hydrolytic/non-hydrolytic enzymes is the basis of efficient hydrolysis of lignocelluloses. In this study, the synergistic action of three recombinant accessory enzymes, namely GH62 α-l-arabinofuranosidase (ARA), CE8 pectin esterase (PET), and GH10 endo-1,4-beta-xylanase (XYL) from Aspergillus aculeatus expressed in Pichia pastoris to a commercial Trichoderma reesei cellulase (Accellerase® 1500; ACR) on hydrolysis of alkaline pretreated rice straw was studied using a mixture design approach. Applying the full cubic model, the optimal ratio of quaternary enzyme mixture was predicted to be ACR:ARA:PET:XYL of 0.171:0.079:0.100:0.150, which showed a glucose releasing efficiency of 0.173 gglc/FPU, higher than the binary ACR:XYL mixture (0.122 gglc/FPU) and ACR alone (0.081 gglc/FPU) leading to a 47.3% increase in glucose yield compared with that from ACR at the same cellulase dosage. The result demonstrates the varying degree of synergism of accessory enzymes to cellulases useful for developing tailor-made enzyme systems for bio-industry. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Cooperative action of cellulase enzyme and carboxymethyl cellulose on cotton fabric cleanability from a topographical standpoint

    NARCIS (Netherlands)

    Calvimontes, A.; Lant, N.J.; Dutschk, Victoria

    2011-01-01

    In this study, the effect of cotton treatment with cellulose and carboxymethyl cellulose on soil release of three different types of fabric: woven plain, woven twill and knitted were systematically studied. A recent study of the effect of a cleaning cellulase enzyme on cellulose films has proven

  20. An enzyme family reunion - similarities, differences and eccentricities in actions on alpha-glucans

    DEFF Research Database (Denmark)

    Seo, Eun-Seong; Christiansen, Camilla; Abou Hachem, Maher

    2008-01-01

    alpha-Glucans in general, including starch, glycogen and their derived oligosaccharides are processed by a host of more or less closely related enzymes that represent wide diversity in structure, mechanism, specificity and biological role. Sophisticated three-dimensional structures continue to em...

  1. Mechanism of action of clostridial glycine reductase: Isolation and characterization of a covalent acetyl enzyme intermediate

    Energy Technology Data Exchange (ETDEWEB)

    Arkowitz, R.A.; Abeles, R.H. (Brandeis Univ., Waltham, MA (USA))

    1991-04-23

    Clostridial glycine reductase consists of proteins A, B, and C and catalyzes the reaction glycine + P{sub i} + 2e{sup {minus}} {yields} acetyl phosphate + NH{sub 4}{sup +}. Evidence was previously obtained that is consistent with the involvement of an acyl enzyme intermediate in this reaction. The authors now demonstrate that protein C catalyzes exchange of ({sup 32}P)P{sub i} into acetyl phosphate, providing additional support for an acetyl enzyme intermediate on protein C. Furthermore, they have isolated acetyl protein C and shown that it is qualitatively, catalytically competent. Acetyl protein C can be obtained through the forward reaction from protein C and Se-(carboxymethyl)selenocysteine-protein A, which is generated by the reaction of glycine with proteins A and B. Acetyl protein C can also be generated through the reverse reaction by the addition of acetyl phosphate to protein C. Both procedures lead to the same acetyl enzyme. The acetyl enzyme reacts with P{sub i} to give acetyl phosphate. When ({sup 14}C)acetyl protein C is denaturated with TCA and redissolved with urea, radioactivity remained associated with the protein. Treatment with KBH{sub 4} removes all the radioactivity associated with protein C, resulting in the formation of ({sup 14}C)ethanol. They conclude that a thiol group on protein C is acetylated. Proteins A and C together catalyze the exchange of tritium atoms from ({sup 3}H)H{sub 2}O into acetyl phosphate. This exchange reaction supports the proposal that an enol of the acetyl enzyme is an intermediate in the reaction sequence.

  2. Structural Basis for Flip-Flop Action of Thiamin Pyrophosphate-Dependent Enzymes Revealed by Human Pyruvate Dehydrogenase

    Science.gov (United States)

    Dominiak, Paulina; Ciszak, Ewa M.; Korotchkina, Lioubov; Sidhu, Sukhdeep; Patel, Mulchand

    2003-01-01

    Thiamin pyrophosphate (TPP), the biologically active form of vitamin BI, is a cofactor of enzymes catalyzing reactions involving the cleavage of a carbon-carbon bond adjacent to an oxo group. TPP-dependent enzymes show a common mechanism of TPP activation by: (1) forming the ionic N-H...O(sup -) hydrogen bonding between the N1' atom of the aminopirymidine ring of the coenzyme and intrinsic gamma-carboxylate group of glutamate and (2) imposing an "active" V-conformation that brings the N4' atom of the aminopirymidine to the distance required for the intramolecular C-H.. .N hydrogen bonding with the thiazolium C2 atom. Within these two hydrogen bonds that rapidly exchange protons, protonation of the N1' atom is strictly coordinated with the deprotonation of the 4' -amino group and eventually abstraction of the proton from C2. The human pyruvate dehydrogenase Elp, component of human pyruvate dehydrogenase complex, catalyzes the irreversible decarboxylation of the pyruvate followed by the reductive acetylation of the lipoyl group of dihydrolipoyl acyltransferase. Elp is alpha(sub 2)beta(sub2)-heterotetrameric with a molecular mass of I54 kDa, which has two catalytic sites, each providing TPP and magnesium ion as cofactors and each formed on the interface between the PP and PYR domains. The dynamic nonequivalence of two otherwise chemically equivalent catalytic sites has been observed and the flip-flop mechanism was suggested, according to which two active sites affect each other and in which different steps of the catalytic reaction are performed in each of the sites at any given moment. Based on specific futures of human pyruvate dehydrogenase including rigid and flexible connections between domains that bind the cofactor we propose a mechanistic model for the flip-flop action of this enzyme. We postulate that the dynamic protein environment drives the exchange of tautomers in the 4' -aminopyrimidine ring of the cofactor through a concerted shuttl-like motion of

  3. Mechanism of action of clostridial glycine reductase: isolation and characterization of a covalent acetyl enzyme intermediate.

    Science.gov (United States)

    Arkowitz, R A; Abeles, R H

    1991-04-23

    Clostridial glycine reductase consists of proteins A, B, and C and catalyzes the reaction glycine + Pi + 2e(-)----acetyl phosphate + NH4+. Evidence was previously obtained that is consistent with the involvement of an acyl enzyme intermediate in this reaction. We now demonstrate that protein C catalyzes exchange of [32P]Pi into acetyl phosphate, providing additional support for an acetyl enzyme intermediate on protein C. Furthermore, we have isolated acetyl protein C and shown that it is qualitatively catalytically competent. Acetyl protein C can be obtained through the forward reaction from protein C and Se-(carboxymethyl)selenocysteine-protein A, which is generated by the reaction of glycine with proteins A and B [Arkowitz, R. A., & Abeles, R. H. (1990) J. Am. Chem. Soc. 112, 870-872]. Acetyl protein C can also be generated through the reverse reaction by the addition of acetyl phosphate to protein C. Both procedures lead to the same acetyl enzyme. The acetyl enzyme reacts with Pi to give acetyl phosphate. When [14C]acetyl protein C is denaturated with TCA and redissolved with urea, radioactivity remained associated with the protein. At pH 11.5 radioactivity was released with t1/2 = 57 min, comparable to the hydrolysis rate of thioesters. Exposure of 4 N neutralized NH2OH resulted in the complete release of radioactivity. Treatment with KBH4 removes all the radioactivity associated with protein C, resulting in the formation of [14C]ethanol. We conclude that a thiol group on protein C is acetylated. Proteins A and C together catalyze the exchange of tritium atoms from [3H]H2O into acetyl phosphate.(ABSTRACT TRUNCATED AT 250 WORDS)

  4. Differential scanning fluorometry signatures as indicators of enzyme inhibitor mode of action: case study of glutathione S-transferase.

    Directory of Open Access Journals (Sweden)

    Wendy A Lea

    Full Text Available Differential scanning fluorometry (DSF, also referred to as fluorescence thermal shift, is emerging as a convenient method to evaluate the stabilizing effect of small molecules on proteins of interest. However, its use in the mechanism of action studies has received far less attention. Herein, the ability of DSF to report on inhibitor mode of action was evaluated using glutathione S-transferase (GST as a model enzyme that utilizes two distinct substrates and is known to be subject to a range of inhibition modes. Detailed investigation of the propensity of small molecule inhibitors to protect GST from thermal denaturation revealed that compounds with different inhibition modes displayed distinct thermal shift signatures when tested in the presence or absence of the enzyme's native co-substrate glutathione (GSH. Glutathione-competitive inhibitors produced dose-dependent thermal shift trendlines that converged at high compound concentrations. Inhibitors acting via the formation of glutathione conjugates induced a very pronounced stabilizing effect toward the protein only when GSH was present. Lastly, compounds known to act as noncompetitive inhibitors exhibited parallel concentration-dependent trends. Similar effects were observed with human GST isozymes A1-1 and M1-1. The results illustrate the potential of DSF as a tool to differentiate diverse classes of inhibitors based on simple analysis of co-substrate dependency of protein stabilization.

  5. Nano-scale structure in membranes in relation to enzyme action - computer simulation vs. experiment

    DEFF Research Database (Denmark)

    Høyrup, P.; Jørgensen, Kent; Mouritsen, O.G.

    2002-01-01

    There is increasing theoretical and experimental evidence indicating that small-scale domain structure and dynamical heterogeneity develop in lipid membranes as a consequence of the the underlying phase transitions and the associated density and composition fluctuations. The relevant coherence le...... mixtures show that the enzyme activity is modulated by nano-scale lipid-domain formation in the lipid bilayer and lead to a characteristic lag-burst behavior. The simulations are found to be in semi-quantitative agreement with experimental data....

  6. Machine Learning and Molecular Dynamics Based Insights into Mode of Actions of Insulin Degrading Enzyme Modulators.

    Science.gov (United States)

    Jamal, Salma; Goyal, Sukriti; Shanker, Asheesh; Grover, Abhinav

    2017-01-01

    Alzheimer's disease (AD) is one of the most common lethal neurodegenerative disorders having impact on the lives of millions of people worldwide. The disease lacks effective treatment options and the unavailability of the drugs to cure the disease necessitates the development of effectual anti-Alzheimer drugs. Several mechanisms have been reported underlying the association of the two disorders, diabetes and dementia, one among which is the insulin-degrading enzyme (IDE) which is known to degrade insulin as well beta-amyloid peptides. The present study is aimed to generate accurate classification models using machine learning techniques, which could identify IDE modulators from a bioassay dataset consisting of IDE inhibitors as well as non-inhibitors. The identified compounds were subjected to docking and Molecular dynamics (MD) studies for an in-depth analysis of the binding modes along with the complex stability. This study proposes that the identified potential active compounds, STK026154 (PubChem ID: CID2927418) with Glide score of -7.70 kcal/mol and BAS05901102 (PubChem ID: CID3152845) with Glide score of -7.06 kcal/mol, could serve as promising leads for the development of novel drugs against AD. The present study shows that such in silico approaches can be effectively used to discover and select active compounds from unseen data for accelerated drug development process. The machine learning models generated in the present study were used to screen Traditional Chinese Medicine (TCM) database to identify the phytocompounds already been reported to have therapeutic effects against AD. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  7. Evasion of adaptive immunity by HIV through the action of host APOBEC3G/F enzymes.

    Science.gov (United States)

    Grant, Michael; Larijani, Mani

    2017-09-12

    APOBEC3G (A3G) and APOBEC3F (A3F) are DNA-mutating enzymes expressed in T cells, dendritic cells and macrophages. A3G/F have been considered innate immune host factors, based on reports that they lethally mutate the HIV genome in vitro. In vivo, A3G/F effectiveness is limited by viral proteins, entrapment in inactive complexes and filtration of mutations during viral life cycle. We hypothesized that the impact of sub-lethal A3G/F action could extend beyond the realm of innate immunity confined to the cytoplasm of infected cells. We measured recognition of wild type and A3G/F-mutated epitopes by cytotoxic T lymphocytes (CTL) from HIV-infected individuals and found that A3G/F-induced mutations overwhelmingly diminished CTL recognition of HIV peptides, in a human histocompatibility-linked leukocyte antigen (HLA)-dependent manner. Furthermore, we found corresponding enrichment of A3G/F-favored motifs in CTL epitope-encoding sequences within the HIV genome. These findings illustrate that A3G/F-mediated mutations mediate immune evasion by HIV in vivo. Therefore, we suggest that vaccine strategies target T cell or antibody epitopes that are not poised for mutation into escape variants by A3G/F action.

  8. The Action of Antidiabetic Plants of the Canadian James Bay Cree Traditional Pharmacopeia on Key Enzymes of Hepatic Glucose Homeostasis

    Directory of Open Access Journals (Sweden)

    Abir Nachar

    2013-01-01

    Full Text Available We determined the capacity of putative antidiabetic plants used by the Eastern James Bay Cree (Canada to modulate key enzymes of gluconeogenesis and glycogen synthesis and key regulating kinases. Glucose-6-phosphatase (G6Pase and glycogen synthase (GS activities were assessed in cultured hepatocytes treated with crude extracts of seventeen plant species. Phosphorylation of AMP-dependent protein kinase (AMPK, Akt, and Glycogen synthase kinase-3 (GSK-3 were probed by Western blot. Seven of the seventeen plant extracts significantly decreased G6Pase activity, Abies balsamea and Picea glauca, exerting an effect similar to insulin. This action involved both Akt and AMPK phosphorylation. On the other hand, several plant extracts activated GS, Larix laricina and A. balsamea, far exceeding the action of insulin. We also found a significant correlation between GS stimulation and GSK-3 phosphorylation induced by plant extract treatments. In summary, three Cree plants stand out for marked effects on hepatic glucose homeostasis. P. glauca affects glucose production whereas L. laricina rather acts on glucose storage. However, A. balsamea has the most promising profile, simultaneously and powerfully reducing G6Pase and stimulating GS. Our studies thus confirm that the reduction of hepatic glucose production likely contributes to the therapeutic potential of several antidiabetic Cree traditional medicines.

  9. Emulsions for interfacial filtration.

    Energy Technology Data Exchange (ETDEWEB)

    Grillet, Anne Mary; Bourdon, Christopher Jay; Souza, Caroline Ann; Welk, Margaret Ellen; Hartenberger, Joel David; Brooks, Carlton, F.

    2006-11-01

    We have investigated a novel emulsion interfacial filter that is applicable for a wide range of materials, from nano-particles to cells and bacteria. This technology uses the interface between the two immiscible phases as the active surface area for adsorption of targeted materials. We showed that emulsion interfaces can effectively collect and trap materials from aqueous solution. We tested two aqueous systems, a bovine serum albumin (BSA) solution and coal bed methane produced water (CBMPW). Using a pendant drop technique to monitor the interfacial tension, we demonstrated that materials in both samples were adsorbed to the liquid-liquid interface, and did not readily desorb. A prototype system was built to test the emulsion interfacial filter concept. For the BSA system, a protein assay showed a progressive decrease in the residual BSA concentration as the sample was processed. Based on the initial prototype operation, we propose an improved system design.

  10. Toward understanding interfacial activation of secretory phospholipase A2 (PLA2): membrane surface properties and membrane-induced structural changes in the enzyme contribute synergistically to PLA2 activation.

    OpenAIRE

    Tatulian, S A

    2001-01-01

    Phospholipase A2 (PLA2) hydrolyzes phospholipids to free fatty acids and lysolipids and thus initiates the biosynthesis of eicosanoids and platelet-activating factor, potent mediators of inflammation, allergy, apoptosis, and tumorigenesis. The relative contributions of the physical properties of membranes and the structural changes in PLA2 to the interfacial activation of PLA2, that is, a strong increase in the lipolytic activity upon binding to the surface of phospholipid membranes or micell...

  11. Identifying the Enzymatic Mode of Action for Cellulase Enzymes by Means of Docking Calculations and a Machine Learning Algorithm

    Directory of Open Access Journals (Sweden)

    Somisetti V. Sambasivarao

    2014-01-01

    Full Text Available Docking calculations have been conducted on 36 cellulase enzymes and the results were evaluated by a machine learning algorithm to determine the nature of the enzyme (i.e. endo- or exo- enzymatic activity. The docking calculations have also been used to identify crucial substrate-enzyme interactions, and establish structure-function relationships. The use of carboxymethyl cellulose as a docking substrate is found to correctly identify the endo- or exo- behavior of cellulase enzymes with 92% accuracy while cellobiose docking calculations resulted in an 86% predictive accuracy. The binding distributions for cellobiose have been classified into two distinct types; distributions with a single maximum or distributions with a bi-modal structure. It is found that the uni-modal distributions correspond to exo- type enzyme while a bi-modal substrate docking distribution corresponds to endo- type enzyme. These results indicate that the use of docking calculations and machine learning algorithms are a fast and computationally inexpensive method for predicting if a cellulase enzyme possesses primarily endo- or exo- type behavior, while also revealing critical enzyme-substrate interactions.

  12. Synthesis of branched polyglucans by the tandem action of potato phosphorylase and Deinococcus geothermalis glycogen branching enzyme

    NARCIS (Netherlands)

    van der Vlist, Jeroen; Reixach, Marta Palomo; van der Maarel, Marc; Dijkhuizen, Lubbert; Schouten, Arend Jan; Loos, Katja

    2008-01-01

    An enzymatic tandem reaction is described in which the enzymes phosphorylase and Deinococcus geothermalis glycogen branching enzyme (Dg GBE) catalyze the synthesis of branched polyglucans from glucose-1-phosphate (G-1-P). Phosphorylase consumes G-1-P and polymerizes linear amylose while DR GBE

  13. Hormonal Control of Enzyme Synthesis: On the Mode of Action of Gibberellic Acid and Abscisin in Aleurone Layers of Barley 1

    Science.gov (United States)

    Chrispeels, Maarten J.; Varner, J. E.

    1967-01-01

    Gibberellic acid (GA) enhances the synthesis of α-amylase and ribonuclease in isolated aleurone layers and this process is inhibited by abscisin. Removal of gibberellic acid in mid-course of α-amylase production results in a slowing down of α-amylase synthesis, suggesting a continued requirement of GA for enzyme synthesis. This is paralleled by a continuous requirement for RNA synthesis. Addition of 6-methylpurine or 8-azaguanine in mid-course results in an inhibition of α-amylase synthesis within 3 to 4 hours. However, actinomycin D added in mid-course is almost without effect. This is not due to its failure to enter the cells, because it does inhibit 14C-uridine incorporation at this stage. Addition of abscisin to aleurone layers which are synthesizing α-amylase results in an inhibition of this synthesis within 2 to 3 hours. Cycloheximide on the other hand inhibits enzyme synthesis immediately upon its addition. These data are consistent with the hypothesis that the expression of the GA effect requires the synthesis of enzyme-specific RNA molecules. The similarity in the kinetics of inhibition between abscisin on the one hand and 8-azaguanine or 6-methylpurine on the other suggests that abscisin may exert its action by inhibiting the synthesis of these enzyme-specific RNA molecules or by preventing their incorporation into an active enzyme-synthesising unit. PMID:16656590

  14. Lys98 substitution in human AP endonuclease 1 affects the kinetic mechanism of enzyme action in base excision and nucleotide incision repair pathways.

    Directory of Open Access Journals (Sweden)

    Nadezhda A Timofeyeva

    Full Text Available Human apurinic/apyrimidinic endonuclease 1 (APE1 is a key enzyme in the base excision repair (BER and nucleotide incision repair (NIR pathways. We recently analyzed the conformational dynamics and kinetic mechanism of wild-type (wt protein, in a stopped-flow fluorescence study. In this study, we investigated the mutant enzyme APE1K98A using the same approach. Lys98 was known to hydrogen bond to the carboxyl group of Asp70, a residue implicated in binding the divalent metal ion. Our data suggested that the conformational selection and induced fit occur during the enzyme action. We expanded upon the evidence that APE1 can pre-exist in two conformations. The isomerization of an enzyme-product complex in the BER process and the additional isomerization stage of enzyme-substrate complex in the NIR process were established for APE1K98A. These stages had not been registered for the wtAPE1. We found that the K98A substitution resulted in a 12-fold reduction of catalytic constant of 5'-phosphodiester bond hydrolysis in (3-hydroxytetrahydrofuran-2-ylmethyl phosphate (F, tetrahydrofuran containing substrate, and in 200-fold reduction in 5,6-dihydrouridine (DHU containing substrate. Thus, the K98A substitution influenced NIR more than BER. We demonstrated that the K98A mutation influenced the formation of primary unspecific enzyme-substrate complex in a complicated manner, depending on the Mg(2+ concentration and pH. This mutation obstructed the induced fit of enzyme in the complex with undamaged DNA and F-containing DNA and appreciably decreased the stability of primary complex upon interaction of enzyme with DNA, containing the natural apurinic/apyrimidinic (AP site. Furthermore, it significantly delayed the activation of the less active form of enzyme during NIR and slowed down the conformational conversion of the complex of enzyme with the cleavage product of DHU-substrate. Our data revealed that APE1 uses the same active site to catalyze the cleavage

  15. Action of Halowax 1051 on Enzymes of Phase I (CYP1A1 and Phase II (SULT1A and COMT Metabolism in the Pig Ovary

    Directory of Open Access Journals (Sweden)

    Justyna Barć

    2013-01-01

    Full Text Available Polychlorinated naphthalenes (PCNs are a group of organochlorinated compounds exhibiting dioxin-like properties. Previously published data showed the direct action of PCN-rich Halowax 1051 on ovarian follicular steroidogenesis. Taking into consideration that the observed biological effects of PCNs may be frequently side effects of metabolites generated by their detoxification, the aim of this study was to determine the activity and expression of enzymes involved in phase I (cytochrome P450, family 1 (CYP1A1 and phase II (sulfotransferase (SULT1A and catechol-O-methyltransferase (COMT detoxification metabolism. Cocultures of granulosa and theca interna cells collected from sexually mature pigs were exposed to 1 pg/mL to 10 ng/mL of Halowax 1051 for 1 to 48 hours, after which levels and activities of CYP1A1, SULT1A, and COMT were measured. Dose-dependent increases of CYP1A1 activity and expression were observed. High doses of Halowax 1051 were inhibitory to COMT and SULT1A activity and reduced their protein levels. In conclusion, fast activation of phase I enzymes with simultaneous inhibition of phase II enzymes indicates that the previously observed effect of Halowax 1051 on follicular steroidogenesis may partially result from metabolite action occurring locally in ovarian follicles.

  16. Mechanism of action of penicillin: triggering of the pneumococcal autolytic enzyme by inhibitors of cell wall synthesis.

    Science.gov (United States)

    Tomasz, A; Waks, S

    1975-10-01

    During penicillin treatment of an autolysin defective mutant pneumococcus we have observed three novel phenomena: (i) Growth of the mutant cultures is inhibited by the same concentrations of penicillin that induce lysis in the wild type. (ii) Mutant bacteria treated with the minimum growth inhibitory concentration of penicillin will lyse upon the addition of wild-type autolysin to the growth medium. Chloramphenicol and other inhibitors of protein synthesis protect the cells against lysis by exogenous enzyme. Sensitivity of the cells to exogenous autolysin requires treatment with penicillin or other inhibitors of cell wall synthesis (e.g., D-cycloserine or fosfonomycin) since exogenous autolysin alone has no effect on bacterial growth. (iii) Treatment with penicillin (or other inhibitors of cell wall synthesis) causes the escape into the medium of a choline-containing macromolecule that has properties suggesting that it contains pneumococcal lipoteichoic acid (Forssman antigen). Each one of these three phenomena (growth inhibition, sensitization to exogenous autolysin, and leakage of lipoteichoic acid) shows the same dose response as that of the penicillin-induced lysis of wild-type pneumococci. On the basis of these findings we propose a new hypothesis for the mechanism of penicillin-induced lysis of bacteria. It is suggested that inhibition of cell wall synthesis by any means triggers bacterial autolytic enzymes by destabilizing the endogenous complex of an autolysin inhibitor (lipoteichoic acid) and autolytic enzyme. Escape of lipoteichoic acid-like material to the growth medium is a consequence of this labilization. Chloramphenicol protects bacteria against penicillin-induced lysis by interfering with the activity of the autolytic enzyme, rather than by depleting the concentration of the enzyme at the cell surface.

  17. Effects of Interfacial Reaction on the Radial Displacement of Oil by Alkaline Solutions Effets des réactions interfaciales sur le déplacement radial de l'huile par les solutions alcalines

    Directory of Open Access Journals (Sweden)

    Nasr-El-Din H. A.

    2006-11-01

    Full Text Available Caustic flooding is frequently used to recover acidic oils in secondary and tertiary recovery modes. This study examines the secondary recovery of an acidic oil by alkaline solutions in a water-wet porous medium using a radial geometry. A model porous medium consisting of sintered glass beads sandwiched between two glass plates was employed to visualize the displacement process. The medium was originally saturated with the oil phase, namely paraffin oil (non-reacting system or paraffin oil doped with 1 wt% linoleic acid (reacting system. The effects of the injection flow rate and the NaOH concentration in the aqueous phase on the displacement pattern were studied experimentally. The volumetric oil recovery at the breakthrough condition was also measured. Dynamic interfacial tension (IFT measurements for the reacting system were measured in a spinning drop tensiometer. A drastic drop in the IFT occurred as a result of the chemical reaction at the interface between the linoleic acid in the oil phase and the NaOH in the aqueous phase. It was also found that the IFT behavior with respect to time was a function of NaOH concentration with a maximum interfacial activity (minimum IFT occurring at 0. 1 w% NaOH. Displacement runs showed a significant change in the displacement patterns during secondary recovery for the reacting system compared with those for the non-reacting one. A significant drop in the breakthrough recovery was obtained for the reacting systems, especially at high injection flow rates. The breakthrough recovery of the reacting system was found to be a function of NaOH concentration in the aqueous phase, with a minimum recovery at NaOH concentration of 0. 1 wt%. On a souvent recours à la submersion par des produits alcalins pour récupérer les acides gras dans les modes secondaire et tertiaire. Dans cette étude, on examine la récupération secondaire d'un acide gras par des solutions alcalines dans un milieu poreux imprégné d

  18. Possible mode of action of toltrazuril: studies on two Eimeria species and mammalian and Ascaris suum enzymes.

    Science.gov (United States)

    Harder, A; Haberkorn, A

    1989-01-01

    The anticoccidial properties of toltrazuril in Eimeria falciformis-infected mice were potentiated by the simultaneous application of pyrimethamine, trimethoprim, or sulfadimidine. The same drugs potentiate the effect of toltrazuril by killing E. tenella schizonts in chicken kidney-cell cultures. Activities of some enzymes of the respiratory chain, such as succinate-cytochrome C reductase and NADH oxidase and succinate oxidase from mouse liver, were reduced in the presence of toltrazuril. The same effects could be observed when the activities of NADH oxidase and fumarate reductase from the nematode Ascaris suum were determined in the presence of the drug. Vertebrate enzymes involved in pyrimidine synthesis, e.g., dihydrofolate reductase from chicken liver, were also affected by toltrazuril; however, this effect was 500 times weaker than that shown by pyrimethamine. Toltrazuril also showed an inhibitory effect on the dihydroorotate-cytochrome C reductase from mouse liver. Our results suggest that toltrazuril primarily affects the respiratory chain and secondarily, two enzymes involved in pyrimidine synthesis.

  19. [Molecular-kinetic parameters of thiamine enzymes and the mechanism of antivitamin action of hydroxythiamine in animal organisms].

    Science.gov (United States)

    Ostrovskiĭ KuM; Voskoboev, A I; Gorenshtenĭn, B I; Dosta, G A

    1979-09-01

    The molecula-kinetic parameters (Km, Ki) of three thiamine enzymes, e. g. thiamine pyrophosphokinase (EC 2.7.6.2), pyruvate dehydrogenase (EC 1.2.4.1) and transketolase (EC 2.2.1.1) with respect to the effects of the thiamine antimetabolite hydroxythiamine in the whole animal organism have been compared. It has been shown that only the first two enzymes, which interact competitively with the vitamin, antivitamin or their pyrophosphate ethers, obey the kinetic parameters obtained for the purified enzymes in vitro. The anticoenzymic effect of hydroxythiamine pyrophosphate with respect to transketolase is not observed in vivo at maximal concentration of the anticoenzyme in tissues due to the absence of competitive interactions with thiamine pyrophosphate. The incorporation of the true and false coenzymes into transketolase occurs only during de novo transketolase synthesis (the apoform is absent in tissues, with the exception of erythrocytes) and proceeds slowly with a half-life time equal to 24--30 hrs. After a single injection of hydroxythiamine at a large dose (70--400 mg/kg) the maximal inhibition of the transketolase activity in tissues (liver, heart, kidney, muscle, spleen, lungs adrenal grands) manifests itself by the 48th--72nd hour, when the concentration of free hydroxythiamine and its pyrophosphate is minimal and the whole anticoenzyme is tightly bound to the protein, forming the false holoenzyme. The use of hydroxythiamine for inhibition of pyruvate dehydrogenase or transketolase in animal organism is discussed.

  20. Effect of nanoscale patterned interfacial roughness on interfacial toughness.

    Energy Technology Data Exchange (ETDEWEB)

    Zimmerman, Jonathan A.; Moody, Neville Reid; Mook, William M. (University of Minnesota, Minneapolis, MN); Kennedy, Marian S. (Clemson University, Clemson, SC); Bahr, David F. (Washington State University, Pullman, WA); Zhou, Xiao Wang; Reedy, Earl David, Jr.

    2007-09-01

    The performance and the reliability of many devices are controlled by interfaces between thin films. In this study we investigated the use of patterned, nanoscale interfacial roughness as a way to increase the apparent interfacial toughness of brittle, thin-film material systems. The experimental portion of the study measured the interfacial toughness of a number of interfaces with nanoscale roughness. This included a silicon interface with a rectangular-toothed pattern of 60-nm wide by 90-nm deep channels fabricated using nanoimprint lithography techniques. Detailed finite element simulations were used to investigate the nature of interfacial crack growth when the interface is patterned. These simulations examined how geometric and material parameter choices affect the apparent toughness. Atomistic simulations were also performed with the aim of identifying possible modifications to the interfacial separation models currently used in nanoscale, finite element fracture analyses. The fundamental nature of atomistic traction separation for mixed mode loadings was investigated.

  1. Biconical bob oscillatory interfacial rheometer

    Energy Technology Data Exchange (ETDEWEB)

    Nagarajan, R.; Chung, S.I.; Wasan, D.T. [Illinois Inst. of Tech., Chicago, IL (United States). Dept. of Chemical Engineering

    1998-08-01

    This paper describes a biconical bob oscillatory interfacial rheometer designed to measure the dynamic viscoelastic response of a liquid-liquid interface subjected to a small amplitude oscillatory shear stress. This instrument is used to examine the rheological behavior of interfaces in the presence of surfactants, especially macromolecular types. Rheological parameters are calculated from a hydrodynamic analysis incorporating a linear viscoelastic interfacial rheological model. The general response of this instrument is compared with the oscillatory deep channel interfacial rheometer which is also capable of similar measurements. Measurements of interfacial viscoelasticity for the same liquid-liquid system with the two rheometers, the biconical bob and the deep channel rheometers, are shown to be comparable. This study demonstrates the intrinsic nature and, therefore, the instrument independent of these dynamic interfacial rheological properties. Accurate measurements of interfacial shear viscoelasticity can be carried out over a wide range of systems by combining measurements with the oscillatory interfacial rheometers. The limitations and regime of usefulness of these instruments are discussed.

  2. Biconical Bob Oscillatory Interfacial Rheometer.

    Science.gov (United States)

    Nagarajan; Chung; Wasan

    1998-08-01

    This paper describes a biconical bob oscillatory interfacial rheometer designed to measure the dynamic viscoelastic response of a liquid-liquid interface subjected to a small amplitude oscillatory shear stress. This instrument is used to examine the rheological behavior of interfaces in the presence of surfactants, especially macromolecular types. Rheological parameters are calculated from a hydrodynamic analysis incorporating a linear viscoelastic interfacial rheological model. The general response of this instrument is compared with the oscillatory deep channel interfacial rheometer which is also capable of similar measurements. Measurements of interfacial viscoelasticity for the same liquid-liquid system with the two rheometers, the biconical bob and the deep channel rheometers, are shown to be comparable. This study demonstrates the intrinsic nature and, therefore, the instrument independence of these dynamic interfacial rheological properties. Accurate measurements of interfacial shear viscoelasticity can be carried out over a wide range of systems by combining measurements with the oscillatory interfacial rheometers. The limitations and regime of usefulness of these instruments are discussed. Copyright 1998 Academic Press.

  3. Interfacial forces in aqueous media

    CERN Document Server

    van Oss, Carel J

    2006-01-01

    Thoroughly revised and reorganized, the second edition of Interfacial Forces in Aqueous Media examines the role of polar interfacial and noncovalent interactions among biological and nonbiological macromolecules as well as biopolymers, particles, surfaces, cells, and both polar and apolar polymers. The book encompasses Lifshitz-van der Waals and electrical double layer interactions, as well as Lewis acid-base interactions between colloidal entities in polar liquids such as water. New in this Edition: Four previously unpublished chapters comprising a new section on interfacial propertie

  4. Actions of p-synephrine on hepatic enzyme activities linked to carbohydrate metabolism and ATP levels in vivo and in the perfused rat liver.

    Science.gov (United States)

    Maldonado, Marcos Rodrigues; Bracht, Lívia; de Sá-Nakanishi, Anacharis Babeto; Corrêa, Rúbia Carvalho Gomes; Comar, Jurandir Fernando; Peralta, Rosane Marina; Bracht, Adelar

    2018-01-01

    p-Synephrine is one of the main active components of the fruit of Citrus aurantium (bitter orange). Extracts of the bitter orange and other preparations containing p-synephrine have been used worldwide to promote weight loss and for sports performance. The purpose of the study was to measure the action of p-synephrine on hepatic enzyme activities linked to carbohydrate and energy metabolism and the levels of adenine mononucleotides. Enzymes and adenine mononucleotides were measured in the isolated perfused rat liver and in vivo after oral administration of the drug (50 and 300 mg/kg) by using standard techniques. p-Synephrine increased the activity of glycogen phosphorylase in vivo and in the perfused liver. It decreased, however, the activities of pyruvate kinase and pyruvate dehydrogenase also in vivo and in the perfused liver. p-Synephrine increased the hepatic pools of adenosine diphosphate and adenosine triphosphate. Stimulation of glycogen phosphorylase is consistent with the reported increased glycogenolysis in the perfused liver and increased glycemia in rats. The decrease in the pyruvate dehydrogenase activity indicates that p-synephrine is potentially capable of inhibiting the transformation of carbohydrates into lipids. The capability of increasing the adenosine triphosphate-adenosine diphosphate pool indicates a beneficial effect of p-synephrine on the cellular energetics. Copyright © 2017 John Wiley & Sons, Ltd.

  5. Fundamental insights into interfacial catalysis.

    Science.gov (United States)

    Gong, Jinlong; Bao, Xinhe

    2017-04-03

    Surface and interfacial catalysis plays a vital role in chemical industries, electrochemistry and photochemical reactions. The challenges of modern chemistry are to optimize the chemical reaction processes and understand the detailed mechanism of chemical reactions. Since the early 1960s, the foundation of surface science systems has allowed the study of surface and interfacial phenomena on atomic/molecular level, and thus brought a number of significant developments to fundamental and technological processes, such as catalysis, material science and biochemistry, just to name a few. This themed issue describes the recent advances and developments in the fundamental understanding of surface and interfacial catalysis, encompassing areas of knowledge from metal to metal oxide, carbide, graphene, hexagonal boron nitride, and transition metal dichalcogenides under ultrahigh vacuum conditions, as well as under realistic reaction conditions.

  6. Interfacial activation, lysophospholipase and transacylase activity of group VI Ca2+-independent phospholipase A2.

    Science.gov (United States)

    Lio, Y C; Dennis, E A

    1998-06-15

    The Group VI 80-kDa Ca2+-independent phospholipase A2 (iPLA2) has been purified from murine P388D1 macrophages and Chinese hamster ovary (CHO) cells. The amino acid sequence of the iPLA2 has been determined and shown to contain a lipase consensus sequence and eight ankyrin repeats, which makes it distinct from Group I-V PLA2s. This enzyme appears to play a key role in mediating basal phospholipid remodeling. We now report that the Group VI iPLA2 displays interfacial activation toward short chain phospholipids, 1-octanoyl-2-heptanoyl-sn-glycero-3-phosphocholine, 1,2-diheptanoyl-sn-glycero-3-phosphocholine, and 1,2-dihexanoyl-sn-glycero-3-phosphocholine micelles. ATP protects the iPLA2 from a loss in activity as a result of prolonged incubation during the assay. Hence higher enzyme activity is observed in the presence than in the absence of ATP. Similar protection was obtained with glycerol. In addition, the iPLA2 exhibits multiple activities which are strongly dependent on substrate presentation. The lysophospholipase activity of this enzyme was diminished by Triton X-100 and stimulated by glycerol. With the combination of 50 microM Triton X-100 and 50% glycerol, the enzyme's lysophospholipase activity achieved equivalent activity to its PLA2 activity. The iPLA2 displayed both lysophospholipid/transacylase and phospholipid/transacylase activity, supporting the conclusion that the mechanism of action of iPLA2 proceeds through an acyl-enzyme intermediate as proposed for the Group IV cPLA2.

  7. Molecular Mechanism of Action of Antimalarial Benzoisothiazolones: Species-Selective Inhibitors of the Plasmodium spp. MEP Pathway enzyme, IspD

    Science.gov (United States)

    Price, Kathryn E.; Armstrong, Christopher M.; Imlay, Leah S.; Hodge, Dana M.; Pidathala, C.; Roberts, Natalie J.; Park, Jooyoung; Mikati, Marwa; Sharma, Raman; Lawrenson, Alexandre S.; Tolia, Niraj H.; Berry, Neil G.; O’Neill, Paul M.; John, Audrey R. Odom

    2016-01-01

    The methylerythritol phosphate (MEP) pathway is an essential metabolic pathway found in malaria parasites, but absent in mammals, making it a highly attractive target for the discovery of novel and selective antimalarial therapies. Using high-throughput screening, we have identified 2-phenyl benzo[d]isothiazol-3(2H)-ones as species-selective inhibitors of Plasmodium spp. 2-C-methyl-D-erythritol-4-phosphate cytidyltransferase (IspD), the third catalytic enzyme of the MEP pathway. 2-Phenyl benzo[d]isothiazol-3(2H)-ones display nanomolar inhibitory activity against P. falciparum and P. vivax IspD and prevent the growth of P. falciparum in culture, with EC50 values below 400 nM. In silico modeling, along with enzymatic, genetic and crystallographic studies, have established a mechanism-of-action involving initial non-covalent recognition of inhibitors at the IspD binding site, followed by disulfide bond formation through attack of an active site cysteine residue on the benzo[d]isothiazol-3(2H)-one core. The species-selective inhibitory activity of these small molecules against Plasmodium spp. IspD and cultured parasites suggests they have potential as lead compounds in the pursuit of novel drugs to treat malaria. PMID:27857147

  8. How a CCA sequence protects mature tRNAs and tRNA precursors from action of the processing enzyme RNase BN/RNase Z.

    Science.gov (United States)

    Dutta, Tanmay; Malhotra, Arun; Deutscher, Murray P

    2013-10-18

    In many organisms, 3' maturation of tRNAs is catalyzed by the endoribonuclease, RNase BN/RNase Z, which cleaves after the discriminator nucleotide to generate a substrate for addition of the universal CCA sequence. However, tRNAs or tRNA precursors that already contain a CCA sequence are not cleaved, thereby avoiding a futile cycle of removal and readdition of these essential residues. We show here that the adjacent C residues of the CCA sequence and an Arg residue within a highly conserved sequence motif in the channel leading to the RNase catalytic site are both required for the protective effect of the CCA sequence. When both of these determinants are present, CCA-containing RNAs in the channel are unable to move into the catalytic site; however, substitution of either of the C residues by A or U or mutation of Arg(274) to Ala allows RNA movement and catalysis to proceed. These data define a novel mechanism for how tRNAs are protected against the promiscuous action of a processing enzyme.

  9. How a CCA Sequence Protects Mature tRNAs and tRNA Precursors from Action of the Processing Enzyme RNase BN/RNase Z*

    Science.gov (United States)

    Dutta, Tanmay; Malhotra, Arun; Deutscher, Murray P.

    2013-01-01

    In many organisms, 3′ maturation of tRNAs is catalyzed by the endoribonuclease, RNase BN/RNase Z, which cleaves after the discriminator nucleotide to generate a substrate for addition of the universal CCA sequence. However, tRNAs or tRNA precursors that already contain a CCA sequence are not cleaved, thereby avoiding a futile cycle of removal and readdition of these essential residues. We show here that the adjacent C residues of the CCA sequence and an Arg residue within a highly conserved sequence motif in the channel leading to the RNase catalytic site are both required for the protective effect of the CCA sequence. When both of these determinants are present, CCA-containing RNAs in the channel are unable to move into the catalytic site; however, substitution of either of the C residues by A or U or mutation of Arg274 to Ala allows RNA movement and catalysis to proceed. These data define a novel mechanism for how tRNAs are protected against the promiscuous action of a processing enzyme. PMID:24022488

  10. Molecular Mechanism of Action of Antimalarial Benzoisothiazolones: Species-Selective Inhibitors of the Plasmodium spp. MEP Pathway enzyme, IspD.

    Science.gov (United States)

    Price, Kathryn E; Armstrong, Christopher M; Imlay, Leah S; Hodge, Dana M; Pidathala, C; Roberts, Natalie J; Park, Jooyoung; Mikati, Marwa; Sharma, Raman; Lawrenson, Alexandre S; Tolia, Niraj H; Berry, Neil G; O'Neill, Paul M; John, Audrey R Odom

    2016-11-18

    The methylerythritol phosphate (MEP) pathway is an essential metabolic pathway found in malaria parasites, but absent in mammals, making it a highly attractive target for the discovery of novel and selective antimalarial therapies. Using high-throughput screening, we have identified 2-phenyl benzo[d]isothiazol-3(2H)-ones as species-selective inhibitors of Plasmodium spp. 2-C-methyl-D-erythritol-4-phosphate cytidyltransferase (IspD), the third catalytic enzyme of the MEP pathway. 2-Phenyl benzo[d]isothiazol-3(2H)-ones display nanomolar inhibitory activity against P. falciparum and P. vivax IspD and prevent the growth of P. falciparum in culture, with EC50 values below 400 nM. In silico modeling, along with enzymatic, genetic and crystallographic studies, have established a mechanism-of-action involving initial non-covalent recognition of inhibitors at the IspD binding site, followed by disulfide bond formation through attack of an active site cysteine residue on the benzo[d]isothiazol-3(2H)-one core. The species-selective inhibitory activity of these small molecules against Plasmodium spp. IspD and cultured parasites suggests they have potential as lead compounds in the pursuit of novel drugs to treat malaria.

  11. Dentin-cement Interfacial Interaction

    Science.gov (United States)

    Atmeh, A.R.; Chong, E.Z.; Richard, G.; Festy, F.; Watson, T.F.

    2012-01-01

    The interfacial properties of a new calcium-silicate-based coronal restorative material (Biodentine™) and a glass-ionomer cement (GIC) with dentin have been studied by confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), micro-Raman spectroscopy, and two-photon auto-fluorescence and second-harmonic-generation (SHG) imaging. Results indicate the formation of tag-like structures alongside an interfacial layer called the “mineral infiltration zone”, where the alkaline caustic effect of the calcium silicate cement’s hydration products degrades the collagenous component of the interfacial dentin. This degradation leads to the formation of a porous structure which facilitates the permeation of high concentrations of Ca2+, OH-, and CO32- ions, leading to increased mineralization in this region. Comparison of the dentin-restorative interfaces shows that there is a dentin-mineral infiltration with the Biodentine, whereas polyacrylic and tartaric acids and their salts characterize the penetration of the GIC. A new type of interfacial interaction, “the mineral infiltration zone”, is suggested for these calcium-silicate-based cements. PMID:22436906

  12. Interfacial transport processes and rheology

    CERN Document Server

    Brenner, Howard

    1991-01-01

    This textbook is designed to provide the theory, methods of measurement, and principal applications of the expanding field of interfacial hydrodynamics. It is intended to serve the research needs of both academic and industrial scientists, including chemical or mechanical engineers, material and surface scientists, physical chemists, chemical and biophysicists, rheologists, physiochemical hydrodynamicists, and applied mathematicians (especially those with interests in viscous fluid mechanics and continuum mechanics).As a textbook it provides materials for a one- or two-semester graduate-level

  13. Enzyme catalysed tandem reactions

    OpenAIRE

    Oroz-Guinea, Isabel; García-Junceda, Eduardo

    2013-01-01

    To transfer to the laboratory, the excellent efficiency shown by enzymes in Nature, biocatalysis, had to mimic several synthetic strategies used by the living organisms. Biosynthetic pathways are examples of tandem catalysis and may be assimilated in the biocatalysis field for the use of isolated multi-enzyme systems in the homogeneous phase. The concurrent action of several enzymes that work sequentially presents extraordinary advantages from the synthetic point of view, since it permits a r...

  14. Metformin action in human hepatocytes: coactivation of atypical protein kinase C alters 5'-AMP-activated protein kinase effects on lipogenic and gluconeogenic enzyme expression.

    Science.gov (United States)

    Sajan, Mini P; Ivey, Robert A; Farese, Robert V

    2013-11-01

    Atypical protein kinase C (aPKC) levels and activity are elevated in hepatocytes of individuals with type 2 diabetes and cause excessive increases in the levels of lipogenic and gluconeogenic enzymes; aPKC inhibitors largely correct these aberrations. Metformin improves hepatic gluconeogenesis by activating 5'-AMP-activated protein kinase (AMPK). However, metformin also activates aPKC in certain tissues; in the liver, this activation could amplify diabetic aberrations and offset the positive effects of AMPK. In this study, we examined whether metformin activates aPKC in human hepatocytes and the metabolic consequences of any such activation. We compared protein kinase activities and alterations in lipogenic and gluconeogenic enzyme levels during activity of the AMPK activators metformin and AICAR, relative to those of an aPKC-ι inhibitor, in hepatocytes from non-diabetic and type 2 diabetic human organ donors. Metformin and 5-aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside (AICAR) activated aPKC at concentrations comparable with those required for AMPK activation. Moreover, both agents increased lipogenic enzyme levels by an aPKC-dependent mechanism. Thus, whereas insulin- and diabetes-dependent increases in lipogenic enzyme levels were reversed by aPKC inhibition, such levels were increased in hepatocytes from non-diabetic donors and remained elevated in hepatocytes from diabetic donors following metformin and AICAR treatment. In addition, whereas aPKC inhibition diminished gluconeogenic enzyme levels in the absence and presence of insulin in hepatocytes from both non-diabetic and diabetic donors, metformin and AICAR increased gluconeogenic enzyme levels in hepatocytes from non-diabetic individuals, but nevertheless diminished gluconeogenic enzyme levels in insulin-treated hepatocytes from diabetic donors. Metformin and AICAR activate aPKC together with AMPK in human hepatocytes. Activation of aPKC increases lipogenic enzyme levels and alters gluconeogenic

  15. Fundamental interfacial mechanisms underlying electrofreezing.

    Science.gov (United States)

    Acharya, Palash V; Bahadur, Vaibhav

    2017-12-08

    This article reviews the fundamental interfacial mechanisms underlying electrofreezing (promotion of ice nucleation via the application of an electric field). Electrofreezing has been an active research topic for many decades, with applications in food preservation, cryopreservation, cryogenics and ice formation. There is substantial literature detailing experimental and simulations-based studies, which aim to understand the complex mechanisms underlying accelerated ice nucleation in the presence of electric fields and electrical charge. This work provides a critical review of all such studies. It is noted that application-focused studies of electrofreezing are excluded from this review; such studies have been previously reviewed in literature. This review focuses only on fundamental studies, which analyze the physical mechanisms underlying electrofreezing. Topics reviewed include experimental studies on electrofreezing (DC and AC electric fields), pyroelectricity-based control of freezing, molecular dynamics simulations of electrofreezing, and thermodynamics-based explanations of electrofreezing. Overall, it is seen that electrofreezing can enable disruptive advancements in the control of liquid-to-solid phase change, and that our current understanding of the underlying mechanisms can be significantly improved through further studies of various interfacial effects coming into play. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Protein interfacial structure and nanotoxicology

    Science.gov (United States)

    White, John W.; Perriman, Adam W.; McGillivray, Duncan J.; Lin, Jhih-Min

    2009-02-01

    Here we briefly recapitulate the use of X-ray and neutron reflectometry at the air-water interface to find protein structures and thermodynamics at interfaces and test a possibility for understanding those interactions between nanoparticles and proteins which lead to nanoparticle toxicology through entry into living cells. Stable monomolecular protein films have been made at the air-water interface and, with a specially designed vessel, the substrate changed from that which the air-water interfacial film was deposited. This procedure allows interactions, both chemical and physical, between introduced species and the monomolecular film to be studied by reflectometry. The method is briefly illustrated here with some new results on protein-protein interaction between β-casein and κ-casein at the air-water interface using X-rays. These two proteins are an essential component of the structure of milk. In the experiments reported, specific and directional interactions appear to cause different interfacial structures if first, a β-casein monolayer is attacked by a κ-casein solution compared to the reverse. The additional contrast associated with neutrons will be an advantage here. We then show the first results of experiments on the interaction of a β-casein monolayer with a nanoparticle titanium oxide sol, foreshadowing the study of the nanoparticle "corona" thought to be important for nanoparticle-cell wall penetration.

  17. Sinusoidal Forcing of Interfacial Films

    Science.gov (United States)

    Rasheed, Fayaz; Raghunandan, Aditya; Hirsa, Amir; Lopez, Juan

    2015-11-01

    Fluid transport, in vivo, is accomplished via pumping mechanisms of the heart and lungs, which results in biological fluids being subjected to oscillatory shear. Flow is known to influence biological macromolecules, but predicting the effect of shear is incomplete without also accounting for the influence of complex interfaces ubiquitous throughout the body. Here, we investigated the oscillatory response of the structure of aqueous interfacial films using a cylindrical knife edge viscometer. Vitamin K1 was used as a model monolayer because its behaviour has been thoroughly quantified and it doesn't show any measurable hysteresis. The monolayer was subjected to sinusoidal forcing under varied conditions of surface concentrations, periodic frequencies, and knife edge amplitudes. Particle Image Velocimetry(PIV) data was collected using Brewster Angle Microscopy(BAM), revealing the influence of oscillatory interfacial shear stress on the monolayer. Insights were gained as to how the velocity profile dampens at specific distances from the knife edge contact depending on the amplitude, frequency, and concentration of Vitamin K1. Supported by NNX13AQ22G, National Aeronautics and Space Administration.

  18. Nanomechanical Sensing of Biological Interfacial Interactions

    Science.gov (United States)

    Du, Wenjian

    Cellulose is the most abundant biopolymer on earth. Cellulase is an enzyme capable of converting insoluble cellulose into soluble sugars. Cellulosic biofuel produced from such fermentable simple sugars is a promising substitute as an energy source. However, its economic feasibility is limited by the low efficiency of the enzymatic hydrolysis of cellulose by cellulase. Cellulose is insoluble and resistant to enzymatic degradation, not only because the beta-1,4-glycosidic bonds are strong covalent bonds, but also because cellulose microfibrils are packed into tightly bound, crystalline lattices. Enzymatic hydrolysis of cellulose by cellulase involves three steps--initial binding, decrystallization, and hydrolytic cleavage. Currently, the mechanism for the decrystallization has not yet been elucidated, though it is speculated to be the rate-limiting step of the overall enzymatic activity. The major technical challenge limiting the understanding of the decrystallization is the lack of an effective experimental approach capable of examining the decrystallization, an interfacial enzymatic activity on solid substrates. The work presented develops a nanomechanical sensing approach to investigate both the decrystallization and enzymatic hydrolytic cleavage of cellulose. The first experimental evidence of the decrystallization is obtained by comparing the results from native cellulase and non-hydrolytic cellulase. Surface topography has been applied to examine the activities of native cellulase and non-hydrolytic cellulase on cellulose substrate. The study demonstrates additional experimental evidence of the decrystallization in the hydrolysis of cellulose. By combining simulation and monitoring technology, the current study also investigates the structural changes of cellulose at a molecular level. In particular, the study employs cellulose nanoparticles with a bilayer structure on mica sheets. By comparing results from a molecular dynamic simulation and the distance

  19. Pancreatic Enzymes

    Science.gov (United States)

    ... NOW HONOR/MEMORIAL GENERAL DONATION MONTHLY PURPLESTRIDE Pancreatic enzymes Home Facing Pancreatic Cancer Living with Pancreatic Cancer ... and see a registered dietitian. What are pancreatic enzymes? Pancreatic enzymes help break down fats, proteins and ...

  20. Pectic enzymes

    NARCIS (Netherlands)

    Benen, J.A.E.; Voragen, A.G.J.; Visser, J.

    2003-01-01

    The pectic enzymes comprise a diverse group of enzymes. They consist of main-chain depolymerases and esterases active on methyl- and acetylesters of galacturonosyl uronic acid residues. The depolymerizing enzymes comprise hydrolases as wel as lyases

  1. [Antitumor enzyme L-lyzine-alpha-oxidase from Trichoderma harzianum Rifai F-180 and investigation of its action on L-lysine oxidation by capillar electrophoresis].

    Science.gov (United States)

    Smirnova, I P; Shkinev, V M; Rudnev, A V; Kuznetsova, O M; Karimova, E V; Orlova, V S

    2014-01-01

    Trichoderma harzianum Rifai F-180, an organism producing the antitumor enzyme L-lysine-alpha-oxidase was cultivated and the enzyme was isolated and purified under the manufacturing conditions. The effect of L-lysine-alpha-oxidase on oxidation of L-lysine was investigated for the first time by capillary electrophoresis and the procedure conditions were developed. The reaction of L-lysine oxidative deamination is described and location of the reaction components picks on the elecrophoregrams was identified. The average rate of the catalytic reaction of L-lysine oxidation equal to 0.46 RU/min (7.7 x 10(-3) RU/sec) was determined. The use of the antitumor enzyme L-lysine-alpha-oxidase is recommended as a drug for the treatment of superficial tumors and tissue relative oxygen excess.

  2. Proteolytic digestive enzymes and peritrophic membranes during the development of Plodia interpunctella (Lepidoptera: Piralidae): targets for the action of soybean trypsin inhibitor (SBTI) and chitin-binding vicilin (EvV).

    Science.gov (United States)

    Amorim, Ticiana M L; Macedo, Leonardo L P; Uchoa, Adriana F; Oliveira, Adeliana S; Pitanga, Joelma C M; Macedo, Francisco P; Santos, Elizeu A; de Sales, Mauricio P

    2008-09-10

    The digestive system of P. interpunctella was characterized during its larval development to determine possible targets for the action of proteinaceous enzyme inhibitors and chitin-binding proteins. High proteolytic activities using azocasein at pH 9.5 as substrate were found. These specific enzymatic activities (AU/mg protein) showed an increase in the homogenate of third instar larvae, and when analyzed by individual larvae (AU/gut), the increase was in sixth instar larvae. Zymograms showed two bands corresponding to those enzymatic activities, which were inhibited by TLCK and SBTI, indicating that the larvae mainly used serine proteinases at pH 9.5 in their digestive process. The presence of a peritrophic membrane in the larvae was confirmed by chemical testing and light microscopy. In a bioassay, P. interpunctella was not susceptible to the soybean trypsin inhibitor, which did not affect larval mass and mortality, likely due to the weak association with its target digestive enzyme. EvV (Erythrina velutina vicilin), when added to the diet, affected mortality (LD50 0.23%) and larval mass (ED50 0.27%). This effect was associated with EvV-binding to the peritrophic membrane, as seen by immunolocalization. EvV was susceptible to gut enzymes and after the digestion process, released an immunoreactive fragment that was bound to the peritrophic matrix, which probably was responsible for the action of EvV.

  3. Roles of multiple surface sites, long substrate binding clefts, and carbohydrate binding modules in the action of amylolytic enzymes on polysaccharide substrates

    DEFF Research Database (Denmark)

    Nielsen, Morten Munch; Seo, E.S.; Dilokpimol, Adiphol

    2008-01-01

    on the surface sites and varies for starch granules of different genotypes and botanical origin. The surface sites, moreover, are candidates for being involved in degradation of polysaccharides by a multiple attack mechanism. Future studies of the molecular nature of the multivalent enzyme-substrate interactions...

  4. The role of electrostatic interactions in protease surface diffusion and the consequence for interfacial biocatalysis.

    Science.gov (United States)

    Feller, Bob E; Kellis, James T; Cascão-Pereira, Luis G; Robertson, Channing R; Frank, Curtis W

    2010-12-21

    This study examines the influence of electrostatic interactions on enzyme surface diffusion and the contribution of diffusion to interfacial biocatalysis. Surface diffusion, adsorption, and reaction were investigated on an immobilized bovine serum albumin (BSA) multilayer substrate over a range of solution ionic strength values. Interfacial charge of the enzyme and substrate surface was maintained by performing the measurements at a fixed pH; therefore, electrostatic interactions were manipulated by changing the ionic strength. The interfacial processes were investigated using a combination of techniques: fluorescence recovery after photobleaching, surface plasmon resonance, and surface plasmon fluorescence spectroscopy. We used an enzyme charge ladder with a net charge ranging from -2 to +4 with respect to the parent to systematically probe the contribution of electrostatics in interfacial enzyme biocatalysis on a charged substrate. The correlation between reaction rate and adsorption was determined for each charge variant within the ladder, each of which displayed a maximum rate at an intermediate surface concentration. Both the maximum reaction rate and adsorption value at which this maximum rate occurs increased in magnitude for the more positive variants. In addition, the specific enzyme activity increased as the level of adsorption decreased, and for the lowest adsorption values, the specific enzyme activity was enhanced compared to the trend at higher surface concentrations. At a fixed level of adsorption, the specific enzyme activity increased with positive enzyme charge; however, this effect offers diminishing returns as the enzyme becomes more highly charged. We examined the effect of electrostatic interactions on surface diffusion. As the binding affinity was reduced by increasing the solution ionic strength, thus weakening electrostatic interaction, the rate of surface diffusion increased considerably. The enhancement in specific activity achieved at

  5. Hydrated interfacial ions and electrons.

    Science.gov (United States)

    Abel, Bernd

    2013-01-01

    Charged particles such as hydrated ions and transient hydrated electrons, the simplest anionic reducing agents in water, and the special hydronium and hydroxide ions at water interfaces play an important role in many fields of science, such as atmospheric chemistry, radiation chemistry, and biology, as well as biochemistry. This article focuses on these species near hydrophobic interfaces of water, such as the air or vacuum interface of water or water protein/membrane interfaces. Ions at interfaces as well as solvated electrons have been reviewed frequently during the past decade. Although all species have been known for some time with seemingly familiar features, recently the picture in all cases became increasingly diffuse rather than clearer. The current account gives a critical state-of-the art overview of what is known and what remains to be understood and investigated about hydrated interfacial ions and electrons.

  6. Regulation of Escherichia coli glutamine synthetase. Evidence for the action of some feedback modifiers at the active site of the unadenylylated enzyme.

    Science.gov (United States)

    Dahlquist, F W; Purich, D L

    1975-05-06

    The interaction of unadenylylated form of Escherichia coli glutamine synthetase with several substrates and effectors has been examined by magnetic resonance techniques. These studies show that two manganese ions bind per enzyme subunit. From the dramatic line broadening observed in the alanine spectra in the presence of manganese and enzyme, it is concluded that the binding of alanine occurs at a site nearer one of the two manganese sites. Electron spin resonance (ESR) titration experiments suggest apparent dissociation constants of 20 and 120 muM for manganese to these sites in the presence of 1.0 mM magnesium ion. The manganese concentration dependence of the broadening of alanine suggests an affinity of 30 muM for the manganese closest to the alanine binding site. This suggests that alanine binds closer to the more tightly bound manganese ion. Glutamate appears to displace the alanine and also appears to bind close to the strongly bound manganese ion. It is proposed that alanine and glutamine bind competitively and in the same site. The binding of alanine and ATP is shown to thermodynamically interact such that the presence of one ligand increases the affinity of the enzyme for the other ligand. The presence of ATP dramatically sharpens the alanine line width when manganese and glutamine synthetase are present. Addition of ADP or phosphate alone has little effect on the alanine line width but the addition of both ADP and phosphate shows the same dramatic sharpening as the addition of ATP alone, suggesting an induced fit conformational change in the enzyme induced by ATP or by both ADP and phosphate. A binding scheme is proposed in which all feedback inhibitors of the enzyme bind in a competitive fashion with substrates.

  7. Combined effect of hydrodynamic and interfacial flow parameters on lysozyme deactivation in a stirred tank bioreactor.

    Science.gov (United States)

    Ghadge, Rajaram S; Patwardhan, Ashwin W; Joshi, Jyeshtharaj B

    2006-01-01

    The dynamic environment within a bioreactor and in the purification equipment is known to affect the activity and yield of enzyme production. The present research focuses on the effect of hydrodynamic flow parameters (average energy dissipation rate, maximum energy dissipation rate, average shear rate, and average normal stress) and the interfacial flow parameters (specific interfacial area and mass transfer coefficient) on the activity of lysozyme. Flow parameters were estimated using CFD simulation based on the k-epsilon approach. Enzyme deactivation was investigated in 0.1, 0.3, 0.57, and 1 m i.d. vessels. Enzyme solution was subjected to hydrodynamic stress using various types of impellers and impeller combinations over a wide range of power consumption (0.03 mass transfer coefficient.

  8. Kunstige Enzymer

    DEFF Research Database (Denmark)

    Bols, Mikael; Bjerre, Jeannette; Marinescu, Lavinia

    2007-01-01

    Enzymer har en enestående evne til at accelerere kemiske processer. Der forskes målrettet i at optimere enzymer baseret på cyclodextrin.......Enzymer har en enestående evne til at accelerere kemiske processer. Der forskes målrettet i at optimere enzymer baseret på cyclodextrin....

  9. Potato Peroxidase for the Study of Enzyme Properties.

    Science.gov (United States)

    Shamaefsky, Brian R.

    1993-01-01

    Explains how the surface of a freshly sliced potato can be used for a variety of enzyme action experiments including the influence of pH on enzyme action, the enzyme denaturation potential of boiling water, the inhibition of enzymes by heavy metals, and the effects of salt concentration on enzyme effectiveness. (PR)

  10. The Impact of Enzyme Orientation and Electrode Topology on the Catalytic Activity of Adsorbed Redox Enzymes

    Science.gov (United States)

    McMillan, Duncan G. G.; Marritt, Sophie J.; Kemp, Gemma L.; Gordon-Brown, Piers; Butt, Julea N.; Jeuken, Lars J. C.

    2014-01-01

    It is well established that the structural details of electrodes and their interaction with adsorbed enzyme influences the interfacial electron transfer rate. However, for nanostructured electrodes, it is likely that the structure also impacts on substrate flux near the adsorbed enzymes and thus catalytic activity. Furthermore, for enzymes converting macro-molecular substrates it is possible that the enzyme orientation determines the nature of interactions between the adsorbed enzyme and substrate and therefore catalytic rates. In essence the electrode may impede substrate access to the active site of the enzyme. We have tested these possibilities through studies of the catalytic performance of two enzymes adsorbed on topologically distinct electrode materials. Escherichia coli NrfA, a nitrite reductase, was adsorbed on mesoporous, nanocrystalline SnO2 electrodes. CymA from Shewanella oneidensis MR-1 reduces menaquinone-7 within 200 nm sized liposomes and this reaction was studied with the enzyme adsorbed on SAM modified ultra-flat gold electrodes. PMID:24634538

  11. Recovery of small bioparticles by interfacial partitioning.

    Science.gov (United States)

    Jauregi, P; Hoeben, M A; van der Lans, R G J M; Kwant, G; van der Wielen, L A M

    2002-05-20

    In this article, a qualitative study of the recovery of small bioparticles by interfacial partitioning in liquid-liquid biphasic systems is presented. A range of crystallised biomolecules with varying polarities have been chosen such as glycine, phenylglycine and ampicillin. Liquid-liquid biphasic systems in a range of polarity differences were selected such as an aqueous two-phase system (ATPS), water-butanol and water-hexanol. The results indicate that interfacial partitioning of crystals occurs even when their density exceeds that of the individual liquid phases. Yet, not all crystals partition to the same extent to the interface to form a stable and thick interphase layer. This indicates some degree of selectivity. From the analysis of these results in relation to the physicochemical properties of the crystals and the liquid phases, a hypothetical mechanism for the interfacial partitioning is deduced. Overall these results support the potential of interfacial partitioning as a large scale separation technology. Copyright 2002 Wiley Periodicals, Inc.

  12. Modeling interfacial fracture in Sierra.

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Arthur A.; Ohashi, Yuki; Lu, Wei-Yang; Nelson, Stacy A. C.; Foulk, James W.,; Reedy, Earl David,; Austin, Kevin N.; Margolis, Stephen B.

    2013-09-01

    This report summarizes computational efforts to model interfacial fracture using cohesive zone models in the SIERRA/SolidMechanics (SIERRA/SM) finite element code. Cohesive surface elements were used to model crack initiation and propagation along predefined paths. Mesh convergence was observed with SIERRA/SM for numerous geometries. As the funding for this project came from the Advanced Simulation and Computing Verification and Validation (ASC V&V) focus area, considerable effort was spent performing verification and validation. Code verification was performed to compare code predictions to analytical solutions for simple three-element simulations as well as a higher-fidelity simulation of a double-cantilever beam. Parameter identification was conducted with Dakota using experimental results on asymmetric double-cantilever beam (ADCB) and end-notched-flexure (ENF) experiments conducted under Campaign-6 funding. Discretization convergence studies were also performed with respect to mesh size and time step and an optimization study was completed for mode II delamination using the ENF geometry. Throughout this verification process, numerous SIERRA/SM bugs were found and reported, all of which have been fixed, leading to over a 10-fold increase in convergence rates. Finally, mixed-mode flexure experiments were performed for validation. One of the unexplained issues encountered was material property variability for ostensibly the same composite material. Since the variability is not fully understood, it is difficult to accurately assess uncertainty when performing predictions.

  13. Interfacial area transport in bubbly flow

    Energy Technology Data Exchange (ETDEWEB)

    Ishii, M.; Wu, Q.; Revankar, S.T. [Purdue Univ., West Lafayette, IN (United States)] [and others

    1997-12-31

    In order to close the two-fluid model for two-phase flow analyses, the interfacial area concentration needs to be modeled as a constitutive relation. In this study, the focus was on the investigation of the interfacial area concentration transport phenomena, both theoretically and experimentally. The interfacial area concentration transport equation for air-water bubbly up-flow in a vertical pipe was developed, and the models for the source and sink terms were provided. The necessary parameters for the experimental studies were identified, including the local time-averaged void fraction, interfacial area concentration, bubble interfacial velocity, liquid velocity and turbulent intensity. Experiments were performed with air-water mixture at atmospheric pressure. Double-sensor conductivity probe and hot-film probe were employed to measure the identified parameters. With these experimental data, the preliminary model evaluation was carried out for the simplest form of the developed interfacial area transport equation, i.e., the one-dimensional transport equation.

  14. Enzyme assays

    OpenAIRE

    Bisswanger, Hans

    2014-01-01

    The essential requirements for enzyme assays are described and frequently occurring errors and pitfalls as well as their avoidance are discussed. The main factors, which must be considered for assaying enzymes, are temperature, pH, ionic strength and the proper concentrations of the essential components like substrates and enzymes. Standardization of these parameters would be desirable, but the diversity of the features of different enzymes prevents unification of assay conditions. Neverthele...

  15. Interfacial Engineering of Molecular Photovoltaics

    Science.gov (United States)

    Shelton, Steven Wade

    One of the most worthy pursuits in the field of organic solar cells is that of discovering ways to more effectively harvest charge generated by light absorption. The measure of the efficacy of this process is the external quantum efficiency (EQE). It is determined by the efficiency of incident light absorption, exciton diffusion, exciton splitting and charge transfer, and charge collection. Enhanced EQE can be realized by engineering interfaces between materials in the device to allow for smoother charge transfer throughout the extent of the device, which is usually between 10 and 200 nanometers. Improvements in charge transport are vitally important because the photogenerated excitons in electron donating polymers and small molecules typically only diffuse between 5 and 10 nanometers. These excitons must reach the interface between the electron donor and electron acceptor in order to be split so that the resulting electron and hole can be harvested at the cathode and anode, respectively. The aim of much of this dissertation is to describe a method by which the donor-acceptor interfacial area can be augmented using nanoimprint lithography, first with a single donor and then with multiple donors. Nanoimprint lithography is introduced as a simple embossing technique that can create features in a single component donor with dimensions as small as 20 nm. Solution-processable small molecules are of interest for their ease of synthesis and fabrication. I continue the discussion of nanoimprint lithography by offering candidates for a two-component donor combination. A two-component donor can extend the absorption range across a broader portion of the solar spectrum than just one donor to improve energy harvesting. After considering ways of optimizing the donor-acceptor interface, I describe the use of a charge selective layer for better charge transport and collection. When incorporated into a bilayer solar cell and an inverted solar cell, these two molecules markedly

  16. Interfacial phase-change memory.

    Science.gov (United States)

    Simpson, R E; Fons, P; Kolobov, A V; Fukaya, T; Krbal, M; Yagi, T; Tominaga, J

    2011-07-03

    Phase-change memory technology relies on the electrical and optical properties of certain materials changing substantially when the atomic structure of the material is altered by heating or some other excitation process. For example, switching the composite Ge(2)Sb(2)Te(5) (GST) alloy from its covalently bonded amorphous phase to its resonantly bonded metastable cubic crystalline phase decreases the resistivity by three orders of magnitude, and also increases reflectivity across the visible spectrum. Moreover, phase-change memory based on GST is scalable, and is therefore a candidate to replace Flash memory for non-volatile data storage applications. The energy needed to switch between the two phases depends on the intrinsic properties of the phase-change material and the device architecture; this energy is usually supplied by laser or electrical pulses. The switching energy for GST can be reduced by limiting the movement of the atoms to a single dimension, thus substantially reducing the entropic losses associated with the phase-change process. In particular, aligning the c-axis of a hexagonal Sb(2)Te(3) layer and the 〈111〉 direction of a cubic GeTe layer in a superlattice structure creates a material in which Ge atoms can switch between octahedral sites and lower-coordination sites at the interface of the superlattice layers. Here we demonstrate GeTe/Sb(2)Te(3) interfacial phase-change memory (IPCM) data storage devices with reduced switching energies, improved write-erase cycle lifetimes and faster switching speeds.

  17. Characterisation and applications of microcapsules obtained by interfacial polycondensation.

    Science.gov (United States)

    Zhang, Yufen; Rochefort, Dominic

    2012-01-01

    This review highlights the materials, mechanisms and applications of microencapsulation by interfacial polycondensation in different areas. This technology entraps active ingredients inside microcapsules/microspheres, having an average diameter ranging from nanosize to several 100 µ. Polycondensation reactions take place at the boundary of two phases to form the shells of microcapsules or matrix microspheres. The emulsion can be classified into three types: water-in-oil, oil-in-water and oil-in-oil. According to the hydrophilic-lipophilic property of core phase, different active substances, such as proteins, enzymes, insecticides, herbicides, vitamins, catalysts, drugs, essential oils, dyes and phase change materials, have been successfully incorporated into different microcapsules/microspheres. Based on the shell-forming materials, this technology is capable of preparing polyamine, polyurea, polyurethane, polythiourea, polyester, polyepoxide, polyacrylamide and polysiloxane microcapsules. Over the past two decades, microcapsules prepared by interfacial polycondensation have been widely used in carbonless paper, cosmetics, pharmacy, agriculture, energy storage/transfer, thermal insulation/regulation and information and magnetic recording.

  18. Interfacial and near interfacial crack growth phenomena in metal bonded alumina

    Energy Technology Data Exchange (ETDEWEB)

    Kruzic, Jamie Joseph [Univ. of California, Berkeley, CA (United States)

    2001-01-01

    Metal/ceramic interfaces can be found in many engineering applications including microelectronic packaging, multi-layered films, coatings, joints, and composite materials. In order to design reliable engineering systems that contain metal/ceramic interfaces, a comprehensive understanding of interfacial and near interfacial failure mechanisms is necessary.

  19. Interfacial area and interfacial transfer in two-phase systems. DOE final report

    Energy Technology Data Exchange (ETDEWEB)

    Ishii, Mamoru; Hibiki, T.; Revankar, S.T.; Kim, S.; Le Corre, J.M.

    2002-07-01

    In the two-fluid model, the field equations are expressed by the six conservation equations consisting of mass, momentum and energy equations for each phase. The existence of the interfacial transfer terms is one of the most important characteristics of the two-fluid model formulation. The interfacial transfer terms are strongly related to the interfacial area concentration and to the local transfer mechanisms such as the degree of turbulence near interfaces. This study focuses on the development of a closure relation for the interfacial area concentration. A brief summary of several problems of the current closure relation for the interfacial area concentration and a new concept to overcome the problem are given.

  20. In vitro effects of selected brominated flame retardants on the adreno cortical enzyme (CYP17). A novel endocrine mechanism of action?

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez Canton, R.; Sanderson, T.; Nijmeijer, S.; Berg, M. van den [Utrecht Univ. (NL). Inst. for Risk Assessment Sciences (IRAS); Berkman, Aa. [Stockholm Univ. (Sweden). Dept. of Environmental Chemistry and Analytical Chemistry

    2004-09-15

    Fire incidents have decreased over the last 20 years partly due to regulations requiring addition of flame retardants (FRs) to materials. These compounds can be divided into different chemical classes: inorganic, nitrogen, phosphorus and halogen containing flame retardants (usually brominated or chlorinated). Not surprisingly, the use of brominated flame retardants (BFRs) in a variety of commercial and household products has increased over the years due to their low cost and high effectiveness. Consequence of the high production of BFRs is that these compounds are now readily detectable in air, water, birds, fish, marine mammals, and in human adipose tissue and blood. The five major BFRs are hexabromocyclododecane (HBCD), tetrabromobisphenol-A (TBBPA) and three commercial mixtures of polybrominated diphenyl ethers (PBDEs) (penta, octa, deca), which are extensively used as FRs at high production volume levels. In addition, concentrations of PBDEs concentration have been rapidly increasing during the last 10 years in human breast milk from European and American women and a number of endocrine (in vitro) effects have been reported. Consequently, the concern about BFRs and their metabolites with respect to their potential as endocrine disruptors (EDs) has been growing. Studies in our laboratory are focused on potential interactions of a wide range of BFRs with sex hormone synthesis and metabolism. Previous results from our research group, showed inhibitory and inductive effects on aromatase (CYP19) (the key enzyme that converts androgens to estrogens) by certain BFRs, in particular the hydroxylated PBDEs and several bromophenols. In the present study, the effects of ten of these BFRs on CYP17 activity were investigated. This enzyme also catalyzes an important step in the sex steroidogenesis and is responsible for the biosynthesis of dehydroepiandrosterone (DHEA). DHEA, produced in the adrenal gland, is the most abundant sex steroid hormone in human blood and has been

  1. Enzyme Informatics

    Science.gov (United States)

    Alderson, Rosanna G.; Ferrari, Luna De; Mavridis, Lazaros; McDonagh, James L.; Mitchell, John B. O.; Nath, Neetika

    2012-01-01

    Over the last 50 years, sequencing, structural biology and bioinformatics have completely revolutionised biomolecular science, with millions of sequences and tens of thousands of three dimensional structures becoming available. The bioinformatics of enzymes is well served by, mostly free, online databases. BRENDA describes the chemistry, substrate specificity, kinetics, preparation and biological sources of enzymes, while KEGG is valuable for understanding enzymes and metabolic pathways. EzCatDB, SFLD and MACiE are key repositories for data on the chemical mechanisms by which enzymes operate. At the current rate of genome sequencing and manual annotation, human curation will never finish the functional annotation of the ever-expanding list of known enzymes. Hence there is an increasing need for automated annotation, though it is not yet widespread for enzyme data. In contrast, functional ontologies such as the Gene Ontology already profit from automation. Despite our growing understanding of enzyme structure and dynamics, we are only beginning to be able to design novel enzymes. One can now begin to trace the functional evolution of enzymes using phylogenetics. The ability of enzymes to perform secondary functions, albeit relatively inefficiently, gives clues as to how enzyme function evolves. Substrate promiscuity in enzymes is one example of imperfect specificity in protein-ligand interactions. Similarly, most drugs bind to more than one protein target. This may sometimes result in helpful polypharmacology as a drug modulates plural targets, but also often leads to adverse side-effects. Many cheminformatics approaches can be used to model the interactions between druglike molecules and proteins in silico. We can even use quantum chemical techniques like DFT and QM/MM to compute the structural and energetic course of enzyme catalysed chemical reaction mechanisms, including a full description of bond making and breaking. PMID:23116471

  2. Enzyme catalysed tandem reactions.

    Science.gov (United States)

    Oroz-Guinea, Isabel; García-Junceda, Eduardo

    2013-04-01

    To transfer to the laboratory, the excellent efficiency shown by enzymes in Nature, biocatalysis, had to mimic several synthetic strategies used by the living organisms. Biosynthetic pathways are examples of tandem catalysis and may be assimilated in the biocatalysis field for the use of isolated multi-enzyme systems in the homogeneous phase. The concurrent action of several enzymes that work sequentially presents extraordinary advantages from the synthetic point of view, since it permits a reversible process to become irreversible, to shift the equilibrium reaction in such a way that enantiopure compounds can be obtained from prochiral or racemic substrates, reduce or eliminate problems due to product inhibition or prevent the shortage of substrates by dilution or degradation in the bulk media, etc. In this review we want to illustrate the developments of recent studies involving in vitro multi-enzyme reactions for the synthesis of different classes of organic compounds. Copyright © 2013 Elsevier Ltd. All rights reserved.

  3. Multimodal mechanism of action for the Cdc34 acidic loop: a case study for why ubiquitin-conjugating enzymes have loops and tails.

    Science.gov (United States)

    Ziemba, Amy; Hill, Spencer; Sandoval, Daniella; Webb, Kristofor; Bennett, Eric J; Kleiger, Gary

    2013-11-29

    Together with ubiquitin ligases (E3), ubiquitin-conjugating enzymes (E2) are charged with the essential task of synthesizing ubiquitin chains onto protein substrates. Some 75% of the known E2s in the human proteome contain unique insertions in their primary sequences, yet it is largely unclear what effect these insertions impart on the ubiquitination reaction. Cdc34 is an important E2 with prominent roles in cell cycle regulation and signal transduction. The amino acid sequence of Cdc34 contains an insertion distal to the active site that is absent in most other E2s, yet this acidic loop (named for its four invariably conserved acidic residues) is critical for Cdc34 function both in vitro and in vivo. Here we have investigated how the acidic loop in human Cdc34 promotes ubiquitination, identifying two key molecular events during which the acidic loop exerts its influence. First, the acidic loop promotes the interaction between Cdc34 and its ubiquitin ligase partner, SCF. Second, two glutamic acid residues located on the distal side of the loop collaborate with an invariably conserved histidine on the proximal side of the loop to suppress the pKa of an ionizing species on ubiquitin or Cdc34 which greatly contributes to Cdc34 catalysis. These results demonstrate that insertions can guide E2s to their physiologically relevant ubiquitin ligases as well as provide essential modalities that promote catalysis.

  4. Etude comparative des coagulations du lait par actions de l'extrait des écorces de l'Ongokea gore et des enzymes coagulants bien connus

    Directory of Open Access Journals (Sweden)

    Libouga, DG.

    2008-01-01

    Full Text Available Milk Clotting Using Ongokea gore Bark Extract Compared to those Obtained to Well Known Milk Clotting Extracts. The evolution of firmness in curd obtained using plant extract (Ongokea gore barks and that using renounce coagulating enzymes (bovine pepsin, Endothia parasitica, porcine pepsin, Mucor pusillis, rennet were compared. The study was carried out using reconstituted milk (Berrigde substrate and a formagraph was used for the analysis of curd firmness. Variations in amplitude of the formagrammes were measured with time. It was noticed that at the same coagulation time, the curd firming rate of Ongokea gore extracts was higher than that of porcine pepsin but lower than those of Endothia parasitica, Mucor pusillis, bovine pepsin and rennet. The evolution of curd firmness with pH on one hand and the quantity of dissolved powder milk on the other hand showed some similarities in rennet and Ongokea gore extract curds: the effect of the pH of the milk substrate is less remarkable on the rate of curd firmness while this rate increases with the quantity of dissolved powder milk.

  5. Action of UV-A and blue light on enzymes activity and accumulation of lipid peroxidation products in attached and detached frog retinas

    Science.gov (United States)

    Lapina, Victoria A.; Doutsov, Alexander E.

    1994-07-01

    The effect of the UV-A and blue light on the accumulation of lipid peroxidation products and activities of succinate dehydrogenase and superoxide dismutase in the retina was examined in eye cup model of dark and light adapted frogs R. temporaria. Retinas were exposed to UV-A radiation (8 mW/cm2) and blue light (10 to 150 mW/cm2) for periods from 5 min to 1 hr. We have measured TBA-active products both in the retina homogenates and in the reaction media. Enzyme activities was measured in the retina homogenates only. The measurements revealed a significant increase in the endogenous and exogenous forms of lipid peroxidation products in the retina of dark adapted frog (1.6+/- 0.4; 1.4+/- 0.3 nmole TBA-active products per mg protein, respectively) compared to light adapted (0.85+/- 0.16; 0.32+/- 0.06 nmole TBA-active products per mg protein, respectively). In the same conditions succinate dehydrogenase activity was decline more than 50% but superoxide dismutase activity didn't decrease. Disorganized inner and outer segments were observed after 40 min exposures. No light microscopic changes were detected after 5 min exposures. Light damage was significantly higher in the retina of dark adapted frog. The results indicate that the retina from eye cup of dark adapted frog is more susceptible to UV-A and blue light damages.

  6. Enzyme Informatics

    OpenAIRE

    Alderson, Rosanna G.; De Ferrari, Luna; Mavridis, Lazaros; McDonagh, James L.; Mitchell, John B O; Nath, Neetika

    2012-01-01

    Over the last 50 years, sequencing, structural biology and bioinformatics have completely revolutionised biomolecular science, with millions of sequences and tens of thousands of three dimensional structures becoming available. The bioinformatics of enzymes is well served by, mostly free, online databases. BRENDA describes the chemistry, substrate specificity, kinetics, preparation and biological sources of enzymes, while KEGG is valuable for understanding enzymes and metabolic pathways. EzCa...

  7. Magneto-ionic control of interfacial magnetism.

    Science.gov (United States)

    Bauer, Uwe; Yao, Lide; Tan, Aik Jun; Agrawal, Parnika; Emori, Satoru; Tuller, Harry L; van Dijken, Sebastiaan; Beach, Geoffrey S D

    2015-02-01

    In metal/oxide heterostructures, rich chemical, electronic, magnetic and mechanical properties can emerge from interfacial chemistry and structure. The possibility to dynamically control interface characteristics with an electric field paves the way towards voltage control of these properties in solid-state devices. Here, we show that electrical switching of the interfacial oxidation state allows for voltage control of magnetic properties to an extent never before achieved through conventional magneto-electric coupling mechanisms. We directly observe in situ voltage-driven O(2-) migration in a Co/metal-oxide bilayer, which we use to toggle the interfacial magnetic anisotropy energy by >0.75 erg cm(-2) at just 2 V. We exploit the thermally activated nature of ion migration to markedly increase the switching efficiency and to demonstrate reversible patterning of magnetic properties through local activation of ionic migration. These results suggest a path towards voltage-programmable materials based on solid-state switching of interface oxygen chemistry.

  8. Interfacial properties of heat-treated ovalbumin.

    Science.gov (United States)

    Croguennec, Thomas; Renault, Anne; Beaufils, Sylvie; Dubois, Jean-Jacques; Pezennec, Stéphane

    2007-11-15

    The interfacial properties (kinetics of adsorption at the air/water interface, rheology of the interfacial layer) of ovalbumin molecules, unheated or previously heat-denatured in solution (10 g L(-1), pH 7, NaCl 50 mM) under controlled conditions (up to 40 min at 80 degrees C), were investigated. Heat treatments induced the formation of covalent aggregates which surface exhibits a higher hydrophobicity and an increased exposition of sulfhydryl groups when compared to native ovalbumin (unheated). Although they have a larger hydrodynamic size, aggregates adsorb as fast as native ovalbumin at the air/water interface. However, aggregates are able to established rapid contacts in the interfacial layer as shown by the fast increase of both surface pressure and shear elastic constant. In contrast, native ovalbumin needs longer time to developed intermolecular contacts and exhibits lower foam stability even if the shear elastic constant on aging reached higher value than for ovalbumin aggregates.

  9. Plant cell wall extensibility: connecting plant cell growth with cell wall structure, mechanics, and the action of wall-modifying enzymes

    Energy Technology Data Exchange (ETDEWEB)

    Cosgrove, Daniel J.

    2015-11-25

    The advent of user-friendly instruments for measuring force/deflection curves of plant surfaces at high spatial resolution has resulted in a recent outpouring of reports of the ‘Young's modulus’ of plant cell walls. The stimulus for these mechanical measurements comes from biomechanical models of morphogenesis of meristems and other tissues, as well as single cells, in which cell wall stress feeds back to regulate microtubule organization, auxin transport, cellulose deposition, and future growth directionality. In this article I review the differences between elastic modulus and wall extensibility in the context of cell growth. Some of the inherent complexities, assumptions, and potential pitfalls in the interpretation of indentation force/deflection curves are discussed. Reported values of elastic moduli from surface indentation measurements appear to be 10- to >1000-fold smaller than realistic tensile elastic moduli in the plane of plant cell walls. Potential reasons for this disparity are discussed, but further work is needed to make sense of the huge range in reported values. The significance of wall stress relaxation for growth is reviewed and connected to recent advances and remaining enigmas in our concepts of how cellulose, hemicellulose, and pectins are assembled to make an extensible cell wall. A comparison of the loosening action of α-expansin and Cel12A endoglucanase is used to illustrate two different ways in which cell walls may be made more extensible and the divergent effects on wall mechanics.

  10. Single-Molecule Interfacial Electron Transfer

    Energy Technology Data Exchange (ETDEWEB)

    Lu, H. Peter [Bowling Green State Univ., Bowling Green, OH (United States). Dept. of Chemistry and Center for Photochemical Sciences

    2017-11-28

    This project is focused on the use of single-molecule high spatial and temporal resolved techniques to study molecular dynamics in condensed phase and at interfaces, especially, the complex reaction dynamics associated with electron and energy transfer rate processes. The complexity and inhomogeneity of the interfacial ET dynamics often present a major challenge for a molecular level comprehension of the intrinsically complex systems, which calls for both higher spatial and temporal resolutions at ultimate single-molecule and single-particle sensitivities. Combined single-molecule spectroscopy and electrochemical atomic force microscopy approaches are unique for heterogeneous and complex interfacial electron transfer systems because the static and dynamic inhomogeneities can be identified and characterized by studying one molecule at a specific nanoscale surface site at a time. The goal of our project is to integrate and apply these spectroscopic imaging and topographic scanning techniques to measure the energy flow and electron flow between molecules and substrate surfaces as a function of surface site geometry and molecular structure. We have been primarily focusing on studying interfacial electron transfer under ambient condition and electrolyte solution involving both single crystal and colloidal TiO2 and related substrates. The resulting molecular level understanding of the fundamental interfacial electron transfer processes will be important for developing efficient light harvesting systems and broadly applicable to problems in fundamental chemistry and physics. We have made significant advancement on deciphering the underlying mechanism of the complex and inhomogeneous interfacial electron transfer dynamics in dyesensitized TiO2 nanoparticle systems that strongly involves with and regulated by molecule-surface interactions. We have studied interfacial electron transfer on TiO2 nanoparticle surfaces by using ultrafast single

  11. Interfacial rheology and emulsion stability in model systems

    CERN Document Server

    Pratt, G

    1998-01-01

    Measurements of thermodynamic interfacial tension sigma at a non-equilibrium surfactant adsorption have been made using a pulsed drop rheometer. The pulsed drop rheometer is based on an instantaneous expansion of a water droplet in oil. After perturbation an interfacial relaxation occurs, the interfacial pressure decay is followed as a function of time using a sensitive pressure transducer. The difference in pressure across a curved interface and the interfacial tension are directly related. Interfacial tension decays can be obtained above and below the surfactants CMC. The interfacial tension decays obtained were fitted to known relaxation mechanisms, and found generally to fit diffusional mechanisms. The funnel technique involves expansion of the interface through a funnel, the interfacial tension decays are followed directly. The results were found to be analogous to measurements made by the pulsed drop. Measurements have been made of the interfacial shear viscosity of a polymeric surfactant at the oil / w...

  12. The Constrained Vapor Bubble Experiment - Interfacial Flow Region

    Science.gov (United States)

    Kundan, Akshay; Wayner, Peter C., Jr.; Plawsky, Joel L.

    2015-01-01

    Internal heat transfer coefficient of the CVB correlated to the presence of the interfacial flow region. Competition between capillary and Marangoni flow caused Flooding and not a Dry-out region. Interfacial flow region growth is arrested at higher power inputs. 1D heat model confirms the presence of interfacial flow region. 1D heat model confirms the arresting phenomena of interfacial flow region Visual observations are essential to understanding.

  13. Surface and interfacial tension measurement, theory, and applications

    CERN Document Server

    Hartland, Stanley

    2004-01-01

    This edited volume offers complete coverage of the latest theoretical, experimental, and computer-based data as summarized by leading international researchers. It promotes full understanding of the physical phenomena and mechanisms at work in surface and interfacial tensions and gradients, their direct impact on interface shape and movement, and their significance to numerous applications. Assessing methods for the accurate measurement of surface tension, interfacial tension, and contact angles, Surface and Interfacial Tension presents modern simulations of complex interfacial motions, such a

  14. Gelation and interfacial behaviour of vegetable proteins

    NARCIS (Netherlands)

    Vliet, van T.; Martin, A.H.; Bos, M.A.

    2002-01-01

    Recent studies on gelation and interfacial properties of vegetable proteins are reviewed. Attention is focused on legume proteins, mainly soy proteins, and on wheat proteins. The rheological properties of vegetable protein gels as a function of heating time or temperature is discussed as well as the

  15. Interfacial properties of green leaf cellulosic particles

    NARCIS (Netherlands)

    Tamayo Tenorio, A.; Gieteling, J.; Nikiforidis, C.V.; Boom, R.M.; Goot, van der A.J.

    2017-01-01

    Cellulosic pulp from sugar beet leaves was fractionated and assessed on its interfacial properties. After pressing leaves to express the juice, the press cake was washed at alkaline pH (pH 9) to remove residual protein, dried, milled and air classified. The obtained cellulosic particles mainly

  16. Influence of interfacial layer on contact resistance

    NARCIS (Netherlands)

    Roy, D.; In 't Zand, M.A.A.; Delhounge, R.; Klootwijk, J.H.; Wolters, Robertus A.M.

    2008-01-01

    The contact resistance between two materials is dependent on the intrinsic properties of the materials in contact and the presence and properties of an interfacial layer at the contact. This article presents the difference in contact resistance measurements with and without the presence of a process

  17. Gelation and interfacial behaviour of vegetable proteins

    NARCIS (Netherlands)

    Vliet, T. van; Martin, A.H.; Bos, M.A.

    2002-01-01

    Recent studies on gelation and interfacial properties of vegetable protiens are reviewed. Attention is focused on legume proteins, mainly soy proteins, and on wheat proteins. The rheological properteis of vegetable protein gels as a function of heating time or temperature is discussed as well as the

  18. Current trends in interfacial polymerization chemistry

    NARCIS (Netherlands)

    Raaijmakers, Michiel; Benes, Nieck Edwin

    2016-01-01

    Interfacial polymerization is an enabling technique for the large-scale production of ultrathin layers, hollow nanospheres and nanofibers. The availability of a wide range of suitable monomer reactants allows for the synthesis of an impressive collection of polymers, including polyamides,

  19. Modeling interfacial dynamics using nonequilibrium thermodynamics frameworks

    NARCIS (Netherlands)

    Sagis, L.M.C.

    2013-01-01

    In recent years several nonequilibrium thermodynamic frameworks have been developed capable of describing the dynamics of multiphase systems with complex microstructured interfaces. In this paper we present an overview of these frameworks. We will discuss interfacial dynamics in the context of the

  20. Single-Molecule Interfacial Electron Transfer

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Wilson [University of California - Irvine

    2018-02-03

    Interfacial electron transfer (ET) plays an important role in many chemical and biological processes. Specifically, interfacial ET in TiO2-based systems is important to solar energy technology, catalysis, and environmental remediation technology. However, the microscopic mechanism of interfacial ET is not well understood with regard to atomic surface structure, molecular structure, bonding, orientation, and motion. In this project, we used two complementary methodologies; single-molecule fluorescence spectroscopy, and scanning-tunneling microscopy and spectroscopy (STM and STS) to address this scientific need. The goal of this project was to integrate these techniques and measure the molecular dependence of ET between adsorbed molecules and TiO2 semiconductor surfaces and the ET induced reactions such as the splitting of water. The scanning probe techniques, STM and STS, are capable of providing the highest spatial resolution but not easily time-resolved data. Single-molecule fluorescence spectroscopy is capable of good time resolution but requires further development to match the spatial resolution of the STM. The integrated approach involving Peter Lu at Bowling Green State University (BGSU) and Wilson Ho at the University of California, Irvine (UC Irvine) produced methods for time and spatially resolved chemical imaging of interfacial electron transfer dynamics and photocatalytic reactions. An integral aspect of the joint research was a significant exchange of graduate students to work at the two institutions. This project bridged complementary approaches to investigate a set of common problems by working with the same molecules on a variety of solid surfaces, but using appropriate techniques to probe under ambient (BGSU) and ultrahigh vacuum (UCI) conditions. The molecular level understanding of the fundamental interfacial electron transfer processes obtained in this joint project will be important for developing efficient light harvesting, solar energy

  1. Ordered mesoporous materials based on interfacial assembly and engineering.

    Science.gov (United States)

    Li, Wei; Yue, Qin; Deng, Yonghui; Zhao, Dongyuan

    2013-10-04

    Ordered mesoporous materials have inspired prominent research interest due to their unique properties and functionalities and potential applications in adsorption, separation, catalysis, sensors, drug delivery, energy conversion and storage, and so on. Thanks to continuous efforts over the past two decades, great achievements have been made in the synthesis and structural characterization of mesoporous materials. In this review, we summarize recent progresses in preparing ordered mesoporous materials from the viewpoint of interfacial assembly and engineering. Five interfacial assembly and synthesis are comprehensively highlighted, including liquid-solid interfacial assembly, gas-liquid interfacial assembly, liquid-liquid interfacial assembly, gas-solid interfacial synthesis, and solid-solid interfacial synthesis, basics about their synthesis pathways, princples and interface engineering strategies. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. A quenched-flow system for measuring heterogeneous enzyme kinetics with sub-second time resolution.

    Science.gov (United States)

    Olsen, Johan P; Kari, Jeppe; Borch, Kim; Westh, Peter

    2017-10-01

    Even though many enzyme processes occur at the interface of an insoluble substrate, these reactions are generally much less studied than homogenous enzyme reactions in the aqueous bulk. Interfacial (or heterogeneous) enzyme reactions involve several reaction steps, and the established experimental approach to elucidate multi-step reactions is transient (or pre steady-state) kinetics. A key requirement for pre steady-state measurements is good time resolution, and while this has been amply achieved in different commercial instruments, they are generally not applicable to precipitating suspensions of insoluble substrate. Perhaps for this reason, transient kinetics has rarely been reported for heterogeneous enzyme reactions. Here, we describe a quenched-flow system using peristaltic pumps and stirred substrate suspensions with a dead time below 100ms. The general performance was verified by alkali catalyzed hydrolysis of 2,4-dinitrophenyl acetate (DNPA), and the applicability to heterogeneous reactions was documented by two cellulases (Cel7A and Cel7B) acting on suspensions of microcrystalline cellulose (Avicel) at different loads up to 15g/l. The results showed distinctive differences between the two enzymes. In particular, we found that endo-lytic Cel7B combined very quickly with the substrate and reached the maximal activity within the dead-time of the instrument. Conversely, exo-lytic Cel7A showed a much slower initiation with maximal activity after 5-8s and a 10-fold lower turnover. We suggest that the instrument may provide an important tool in attempts to elucidate the mechanism of cellulases and other enzymes' action on insoluble substrate. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Interfacial Fluid Mechanics A Mathematical Modeling Approach

    CERN Document Server

    Ajaev, Vladimir S

    2012-01-01

    Interfacial Fluid Mechanics: A Mathematical Modeling Approach provides an introduction to mathematical models of viscous flow used in rapidly developing fields of microfluidics and microscale heat transfer. The basic physical effects are first introduced in the context of simple configurations and their relative importance in typical microscale applications is discussed. Then,several configurations of importance to microfluidics, most notably thin films/droplets on substrates and confined bubbles, are discussed in detail.  Topics from current research on electrokinetic phenomena, liquid flow near structured solid surfaces, evaporation/condensation, and surfactant phenomena are discussed in the later chapters. This book also:  Discusses mathematical models in the context of actual applications such as electrowetting Includes unique material on fluid flow near structured surfaces and phase change phenomena Shows readers how to solve modeling problems related to microscale multiphase flows Interfacial Fluid Me...

  4. Frontiers of interfacial water research :workshop report.

    Energy Technology Data Exchange (ETDEWEB)

    Cygan, Randall Timothy; Greathouse, Jeffery A.

    2005-10-01

    Water is the critical natural resource of the new century. Significant improvements in traditional water treatment processes require novel approaches based on a fundamental understanding of nanoscale and atomic interactions at interfaces between aqueous solution and materials. To better understand these critical issues and to promote an open dialog among leading international experts in water-related specialties, Sandia National Laboratories sponsored a workshop on April 24-26, 2005 in Santa Fe, New Mexico. The ''Frontiers of Interfacial Water Research Workshop'' provided attendees with a critical review of water technologies and emphasized the new advances in surface and interfacial microscopy, spectroscopy, diffraction, and computer simulation needed for the development of new materials for water treatment.

  5. Enzymes for Enhanced Oil Recovery (EOR)

    Energy Technology Data Exchange (ETDEWEB)

    Nasiri, Hamidreza

    2011-04-15

    Primary oil recovery by reservoir pressure depletion and secondary oil recovery by waterflooding usually result in poor displacement efficiency. As a consequence there is always some trapped oil remaining in oil reservoirs. Oil entrapment is a result of complex interactions between viscous, gravity and capillary forces. Improving recovery from hydrocarbon fields typically involves altering the relative importance of the viscous and capillary forces. The potential of many EOR methods depends on their influence on fluid/rock interactions related to wettability and fluid/fluid interactions reflected in IFT. If the method has the potential to change the interactions favorably, it may be considered for further investigation, i.e. core flooding experiment, pilot and reservoir implementation. Enzyme-proteins can be introduced as an enhanced oil recovery method to improve waterflood performance by affecting interactions at the oil-water-rock interfaces. An important part of this thesis was to investigate how selected enzymes may influence wettability and capillary forces in a crude oil-brine-rock system, and thus possibly contribute to enhanced oil recovery. To investigate further by which mechanisms selected enzyme-proteins may contribute to enhance oil recovery, groups of enzymes with different properties and catalytic functions, known to be interfacially active, were chosen to cover a wide range of possible effects. These groups include (1) Greenzyme (GZ) which is a commercial EOR enzyme and consists of enzymes and stabilizers (surfactants), (2) The Zonase group consists of two types of pure enzyme, Zonase1 and Zonase2 which are protease enzymes and whose catalytic functions are to hydrolyze (breakdown) peptide bonds, (3) The Novozyme (NZ) group consists of three types of pure enzyme, NZ2, NZ3 and NZ6 which are esterase enzymes and whose catalytic functions are to hydrolyze ester bonds, and (4) Alpha-Lactalbumin ( -La) which is an important whey protein. The effect of

  6. Facile Interfacial Electron Transfer of Hemoglobin

    Directory of Open Access Journals (Sweden)

    Chunhai Fan

    2005-12-01

    Full Text Available Abstract: We herein describe a method of depositing hemoglobin (Hb and sulfonated polyaniline (SPAN on GC electrodes that facilitate interfacial protein electron transfer. Well-defined, reproducible, chemically reversible peaks of Hb and SPAN can be obtained in our experiments. We also observed enhanced peroxidase activity of Hb in SPAN films. These results clearly showed that SPAN worked as molecular wires and effectively exchanged electrons between Hb and electrodes.Mediated by Conjugated Polymers

  7. Kinetics of Model Reactions for Interfacial Polymerization

    Directory of Open Access Journals (Sweden)

    Henry Hall

    2012-02-01

    Full Text Available To model the rates of interfacial polycondensations, the rates of reaction of benzoyl chloride and methyl chloroformate with various aliphatic monoamines in acetonitrile were determined at 25 °C. Buffering with picric acid slowed these extremely fast reactions so the rate constants could be determined from the rate of disappearance of picrate ion. The rates of the amine reactions correlated linearly with their Swain-Scott nucleophilicities.

  8. Kinetics of Model Reactions for Interfacial Polymerization

    OpenAIRE

    Henry Hall; Robert Bates (Harvard University); Jeffrey Robertson; Anne Padias; Trevor Centeno-Hall

    2012-01-01

    To model the rates of interfacial polycondensations, the rates of reaction of benzoyl chloride and methyl chloroformate with various aliphatic monoamines in acetonitrile were determined at 25 °C. Buffering with picric acid slowed these extremely fast reactions so the rate constants could be determined from the rate of disappearance of picrate ion. The rates of the amine reactions correlated linearly with their Swain-Scott nucleophilicities.

  9. Microstructural Evolution Based on Fundamental Interfacial Properties

    Energy Technology Data Exchange (ETDEWEB)

    A. D. Rollett; D. J. Srolovitz; A. Karma

    2003-07-11

    This first CMSN project has been operating since the summer of 1999. The main achievement of the project was to bring together a community of materials scientists, physicists and mathematicians who share a common interest in the properties of interfaces and the impact of those properties on microstructural evolution. Six full workshops were held at Carnegie Mellon (CMU), Northwestern (NWU), Santa Fe, Northeastern University (NEU), National Institute for Standards and Technology (NIST), Ames Laboratory, and at the University of California in San Diego (UCSD) respectively. Substantial scientific results were obtained through the sustained contact between the members of the project. A recent issue of Interface Science (volume 10, issue 2/3, July 2002) was dedicated to the output of the project. The results include: the development of methods for extracting anisotropic boundary energy and mobility from molecular dynamics simulations of solid/liquid interfaces in nickel; the extraction of anisotropic energies and mobilities in aluminum from similar MD simulations; the application of parallel computation to the calculation of interfacial properties; the development of a method to extract interfacial properties from the fluctuations in interface position through consideration of interfacial stiffness; the use of anisotropic interface properties in studies of abnormal grain growth; the discovery of abnormal grain growth from random distributions of orientation in subgrain networks; the direct comparison at the scale of individual grains between experimentally observed grain growth and simulations, which confirmed the importance of including anisotropic interfacial properties in the simulations; the classification of a rich variety of dendritic morphologies based on slight variations in the anisotropy of the solid-liquid interface; development of phase field methods that permit both solidification and grain growth to be simulated within the same framework.

  10. Facile Interfacial Electron Transfer of Hemoglobin

    OpenAIRE

    Chunhai Fan; Shiping Song; Haiping Wu; Lihua Wang; Xiaofang Hu; Runguang Sun; Bo Zhou

    2005-01-01

    Abstract: We herein describe a method of depositing hemoglobin (Hb) and sulfonated polyaniline (SPAN) on GC electrodes that facilitate interfacial protein electron transfer. Well-defined, reproducible, chemically reversible peaks of Hb and SPAN can be obtained in our experiments. We also observed enhanced peroxidase activity of Hb in SPAN films. These results clearly showed that SPAN worked as molecular wires and effectively exchanged electrons between Hb and electrodes.Mediated by Conjugated...

  11. Interfacial Functionalization and Engineering of Nanoparticles

    OpenAIRE

    Song, Yang

    2014-01-01

    The intense research interest in nanoscience and nanotechnology is largely fueled by the unique properties of nanoscale materials. In this dissertation, the research efforts are focused on surface functionalization and interfacial engineering of functional nanoparticles in the preparation of patchy nanoparticles (e.g., Janus nanoparticles and Neapolitan nanoparticles) such that the nanoparticle structures and properties may be manipulated to an unprecedented level of sophistication.Experiment...

  12. Interfacial phenomena and the ocular surface.

    Science.gov (United States)

    Yañez-Soto, Bernardo; Mannis, Mark J; Schwab, Ivan R; Li, Jennifer Y; Leonard, Brian C; Abbott, Nicholas L; Murphy, Christopher J

    2014-07-01

    Ocular surface disorders, such as dry eye disease, ocular rosacea, and allergic conjunctivitis, are a heterogeneous group of diseases that require an interdisciplinary approach to establish underlying causes and develop effective therapeutic strategies. These diverse disorders share a common thread in that they involve direct changes in ocular surface chemistry as well as the rheological properties of the tear film and topographical attributes of the cellular elements of the ocular surface. Knowledge of these properties is crucial to understand the formation and stability of the preocular tear film. The study of interfacial phenomena of the ocular surface flourished during the 1970s and 1980s, but after a series of lively debates in the literature concerning distinctions between the epithelial and the glandular origin of ocular surface disorders during the 1990s, research into this important topic has declined. In the meantime, new tools and techniques for the characterization and functionalization of biological surfaces have been developed. This review summarizes the available literature regarding the physicochemical attributes of the ocular surface, analyzes the role of interfacial phenomena in the pathobiology of ocular surface disease, identifies critical knowledge gaps concerning interfacial phenomena of the ocular surface, and discusses the opportunities for the exploitation of these phenomena to develop improved therapeutics for the treatment of ocular surface disorders. Copyright © 2014 Elsevier Inc. All rights reserved.

  13. Arresting dissolution by interfacial rheology design

    Science.gov (United States)

    Beltramo, Peter J.; Gupta, Manish; Alicke, Alexandra; Liascukiene, Irma; Gunes, Deniz Z.; Baroud, Charles N.; Vermant, Jan

    2017-09-01

    A strategy to halt dissolution of particle-coated air bubbles in water based on interfacial rheology design is presented. Whereas previously a dense monolayer was believed to be required for such an “armored bubble” to resist dissolution, in fact engineering a 2D yield stress interface suffices to achieve such performance at submonolayer particle coverages. We use a suite of interfacial rheology techniques to characterize spherical and ellipsoidal particles at an air-water interface as a function of surface coverage. Bubbles with varying particle coverages are made and their resistance to dissolution evaluated using a microfluidic technique. Whereas a bare bubble only has a single pressure at which a given radius is stable, we find a range of pressures over which bubble dissolution is arrested for armored bubbles. The link between interfacial rheology and macroscopic dissolution of ˜ 100 μm bubbles coated with ˜ 1 μm particles is presented and discussed. The generic design rationale is confirmed by using nonspherical particles, which develop significant yield stress at even lower surface coverages. Hence, it can be applied to successfully inhibit Ostwald ripening in a multitude of foam and emulsion applications.

  14. Increased enzyme binding to substrate is not necessary for more efficient cellulose hydrolysis

    Science.gov (United States)

    Gao, Dahai; Chundawat, Shishir P. S.; Sethi, Anurag; Balan, Venkatesh; Gnanakaran, S.; Dale, Bruce E.

    2013-01-01

    Substrate binding is typically one of the rate-limiting steps preceding enzyme catalytic action during homogeneous reactions. However, interfacial-based enzyme catalysis on insoluble crystalline substrates, like cellulose, has additional bottlenecks of individual biopolymer chain decrystallization from the substrate interface followed by its processive depolymerization to soluble sugars. This additional decrystallization step has ramifications on the role of enzyme–substrate binding and its relationship to overall catalytic efficiency. We found that altering the crystalline structure of cellulose from its native allomorph Iβ to IIII results in 40–50% lower binding partition coefficient for fungal cellulases, but surprisingly, it enhanced hydrolytic activity on the latter allomorph. We developed a comprehensive kinetic model for processive cellulases acting on insoluble substrates to explain this anomalous finding. Our model predicts that a reduction in the effective binding affinity to the substrate coupled with an increase in the decrystallization procession rate of individual cellulose chains from the substrate surface into the enzyme active site can reproduce our anomalous experimental findings. PMID:23784776

  15. Enzyme immunoassay

    DEFF Research Database (Denmark)

    Feldt-Rasmussen, B; Dinesen, B; Deckert, M

    1985-01-01

    An enzyme linked immunoadsorbent assay for urinary albumin using commercially available reagents is described. The assay range is 2.5-120 micrograms/l. When samples are analysed in two standard dilutions, the assayable albumin concentration range is 2.5-240 mg/l, covering the clinical range from...

  16. Food Enzymes

    Science.gov (United States)

    McBroom, Rachel; Oliver-Hoyo, Maria T.

    2007-01-01

    Many students view biology and chemistry as two unrelated, separate sciences; how these courses are generally taught in high schools may do little to change that impression. The study of enzymes provide a great opportunity for both biology and chemistry teachers to share with students the interdisciplinary nature of science. This article describes…

  17. Scaling of interfacial jump conditions; Escalamiento de condiciones de salto interfacial

    Energy Technology Data Exchange (ETDEWEB)

    Quezada G, S.; Vazquez R, A.; Espinosa P, G., E-mail: sequga@gmail.com [Universidad Autonoma Metropolitana, Unidad Iztapalapa, Area de Ingenieria en Recursos Energeticos, Apdo. Postal 55-535, 09340 Ciudad de Mexico (Mexico)

    2015-09-15

    To model the behavior of a nuclear reactor accurately is needed to have balance models that take into account the different phenomena occurring in the reactor. These balances have to be coupled together through boundary conditions. The boundary conditions have been studied and different treatments have been given to the interface. In this paper is a brief description of some of the interfacial jump conditions that have been proposed in recent years. Also, the scaling of an interfacial jump condition is proposed, for coupling the different materials that are in contact within a nuclear reactor. (Author)

  18. Enzyme Nanorings

    OpenAIRE

    Chou, Tsui-Fen; So, Christopher; White, Brian R.; Carlson, Jonathan C.T.; Sarikaya, Mehmet; Wagner, Carston

    2008-01-01

    We have demonstrated that nanostructures, and in particular nanorings incorporating a homodimeric enzyme, can be prepared by chemically induced self-assembly of dihydrofolate reductase (DHFR)-histidine triad nucleotide binding 1(Hint1) fusion proteins. The dimensions of the nanorings were found by static light scattering and atomic force microscopy studies to be dependent on the length and composition of the peptide linking the fusion proteins, ranging in size from 10 to 70 nm in diameter and...

  19. Enzyme technology: Key to selective biorefining

    DEFF Research Database (Denmark)

    Meyer, Anne S.

    2014-01-01

    their rational use in biorefinery processes requires an understanding of the basic features of enzymes and reaction traits with respect to specificity, kinetics, reaction optima, stability and structure-function relations – we are now at a stage where it is possible to use nature’s enzyme structures as starting...... point and then improve the functional traits by targeted mutation of the protein. The talk will display some of our recent hypotheses related to enzyme action, recently obtained results within knowledge-based enzyme improvements as well as cast light on research methods used in optimizing enzyme...... to the reaction is a unique trait of enzyme catalysis. Since enzyme selectivity means that a specific reaction is catalysed between particular species to produce definite products, enzymes are particularly fit for converting specific compounds in mixed biomass streams. Since enzymes are protein molecules...

  20. Interfacial Stress Transfer in an Aramid Reinforced Thermoplastic Elastomer

    OpenAIRE

    Coffey, Austin

    2007-01-01

    Abstract The interfacial micromechanics of Twaron 2200 aramid fibers in an engineering thermoplastic elastomer (Pebax 7033, polyether amide block co-polymer) has been investigated by determining the distribution of interfacial shear stress along fibers in single-fiber model composites using Raman spectroscopy. The effects of various fiber surface treatments on the interfacial shear stress and fragmentation of the aramid fibers are discussed. The fiber average stress in...

  1. Interfacial interaction between polypropylene and nanotube: A molecular dynamics simulation

    Science.gov (United States)

    Zhang, Danhui; Yang, Houbo; Liu, Zhongkui; Liu, Anmin; Li, Yunfang

    2017-09-01

    The interfacial interaction between polypropylene (PE) and single walled carbon nanotube (SWCNT) was studied using molecular dynamics (MD) simulations. The result showed that the PE chain could stabilize the SWCNT and then extended along the direction of SWCNT. The mechanism of interfacial interaction between PE and SWCNT was also discussed. Furthermore, the interfacial interaction between more PE and SWCNT was also investigated and the position also deeply influenced the interaction. This will be beneficial to understanding the interfacial interaction between polymer and CNT in solution, and also guiding the fabrication of high performance polymer/CNT nanocomposites.

  2. A Model for the Interfacial Kinetics of Phospholipase D Activity on Long-Chain Lipids

    Science.gov (United States)

    2013-07-01

    200 mLmin1 for 15 min; 3) removal of excess liposomes by flowing a solution of PLD buffer at 100 mL min1 for 20 min; 4), measuring the on rate of PLD...and 5), measuring the off rate of PLD from the lipid layer by introducing PLD buffer (without the enzyme) at 100 mL min1 for 30 min. Fig. S1in the... exocytosis , and migration (24–32). Only a limited number of studies have presented any analysis of the interfacial kinetics of PLD from mammalian (2,25,33

  3. Interfacial properties of semifluorinated alkane diblock copolymers

    Science.gov (United States)

    Pierce, Flint; Tsige, Mesfin; Borodin, Oleg; Perahia, Dvora; Grest, Gary S.

    2008-06-01

    The liquid-vapor interfacial properties of semifluorinated linear alkane diblock copolymers of the form F3C(CF2)n-1(CH2)m-1CH3 are studied by fully atomistic molecular dynamics simulations. The chemical composition and the conformation of the molecules at the interface are identified and correlated with the interfacial energies. A modified form of the Optimized Parameter for Liquid Simulation All-Atom (OPLS-AA) force field of Jorgensen and co-workers [J. Am. Chem. Soc. 106, 6638 (1984); 118, 11225 (1996); J. Phys. Chem. A 105, 4118 (2001)], which includes specific dihedral terms for H-F blocks-and corrections to the H-F nonbonded interaction, is used together with a new version of the exp-6 force field developed in this work. Both force fields yield good agreement with the available experimental liquid density and surface tension data as well as each other over significant temperature ranges and for a variety of chain lengths and compositions. The interfacial regions of semifluorinated alkanes are found to be rich in fluorinated groups compared to hydrogenated groups, an effect that decreases with increasing temperature but is independent of the fractional length of the fluorinated segments. The proliferation of fluorine at the surface substantially lowers the surface tension of the diblock copolymers, yielding values near those of perfluorinated alkanes and distinct from those of protonated alkanes of the same chain length. With decreasing temperatures within the liquid state, chains are found to preferentially align perpendicular to the interface, as previously seen.

  4. Interfacial properties of semiconducting transition metal chalcogenides

    Science.gov (United States)

    Jaegermann, W.; Tributsch, H.

    This review is aimed at the correlation of structural and electronic properies of semiconducting transition metal chalcogenides with molecular surface processes and mechanisms in photoelectrochemistry, (photo)catalysis, geochemistry and hydrometallurgy. Layer-type, pyrite structured and transition metal cluster containing chalcogenides are selected as model systems to explain the principles involved. Special emphasis is given to the discussion of materials which involve transition metal d- states in the interfacial reaction pathways of holes and electrons. Since they initiate and control heterogeneous coordination chemistry at the surfaces they may provide the possibility of tailoring selective and catalytically demanding reactions. Examples of such mechanisms are presented and discussed in relation to surface properties involved.

  5. Interfacial properties of bottle-brush polyelectrolytes

    DEFF Research Database (Denmark)

    Claesson, P. M.; Naderi, A.; Iruthayaraj, J.

    2007-01-01

    This article is focused on interfacial properties of bottle brush polyelectrolytes, where side-chains are attached along a polymer backbone. This class of polymer has been much less studied than block copolymers, which is particularly true for bottle brush polyelectrolytes with a high graft density...... whereas on silica both electrostatic forces and interactions between silica and ethylene oxide chains drive the adsorption. On silica the adsorbed amount is very sensitive to solution ionic strength and pH. We also report on surface interactions and frictional forces obtained between surfaces coated...

  6. Viscosity of interfacial water regulates ice nucleation

    Energy Technology Data Exchange (ETDEWEB)

    Li, Kaiyong; Chen, Jing; Zhang, Qiaolan; Zhang, Yifan [Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Green Printing, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xu, Shun; Zhou, Xin [School of Physics, University of Chinese Academy of Sciences, Beijing 100049 (China); Cui, Dapeng; Wang, Jianjun, E-mail: wangj220@iccas.ac.cn; Song, Yanlin [Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Green Printing, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

    2014-03-10

    Ice formation on solid surfaces is an important phenomenon in many fields, such as cloud formation and atmospheric icing, and a key factor for applications in preventing freezing. Here, we report temperature-dependent nucleation rates of ice for hydrophilic and hydrophobic surfaces. The results show that hydrophilic surface presents a lower ice nucleation rate. We develop a strategy to extract the thermodynamic parameters, J{sub 0} and Γ, in the context of classical nucleation theory. From the extracted J{sub 0} and Γ, we reveal the dominant role played by interfacial water. The results provide an insight into freezing mechanism on solid surfaces.

  7. Interfacial fluid dynamics and transport processes

    CERN Document Server

    Schwabe, Dietrich

    2003-01-01

    The present set of lectures and tutorial reviews deals with various topical aspects related to instabilities of interfacial processes and driven flows from both the theoretical and experimental point of views. New research has been spurred by the many demands for applications in material sciences (melting, solidification, electro deposition), biomedical engineering and processing in microgravity environments. This book is intended as both a modern source of reference for researchers in the field as well as an introduction to postgraduate students and non-specialists from related areas.

  8. Seeing & Feeling How Enzymes Work Using Tangible Models

    Science.gov (United States)

    Lau, Kwok-chi

    2013-01-01

    This article presents a tangible model used to help students tackle some misconceptions about enzyme actions, particularly the induced-fit model, enzyme-substrate complementarity, and enzyme inhibition. The model can simulate how substrates induce a change in the shape of the active site and the role of attraction force during enzyme-substrate…

  9. Interfacial Friction and Adhesion of Polymer Brushes

    KAUST Repository

    Landherr, Lucas J. T.

    2011-08-02

    A bead-probe lateral force microscopy (LFM) technique is used to characterize the interfacial friction and adhesion properties of polymer brushes. Our measurements attempt to relate the physical structure and chemical characteristics of the brush to their properties as thin-film, tethered lubricants. Brushes are synthesized at several chain lengths and surface coverages from polymer chains of polydimethylsiloxane (PDMS), polystyrene (PS), and a poly(propylene glycol)-poly(ethylene glycol) block copolymer (PPG/PEG). At high surface coverage, PDMS brushes manifest friction coefficients (COFs) that are among the lowest recorded for a dry lubricant film (μ ≈ 0.0024) and close to 1 order of magnitude lower than the COF of a bare silicon surface. Brushes synthesized from higher molar mass chains exhibit higher friction forces than those created using lower molar mass polymers. Increased grafting density of chains in the brush significantly reduces the COF by creating a uniform surface of stretched chains with a decreased surface viscosity. Brushes with lower surface tension and interfacial shear stresses manifest the lowest COF. In particular, PDMS chains exhibit COFs lower than PS by a factor of 3.7 and lower than PPG/PEG by a factor of 4.7. A scaling analysis conducted on the surface coverage (δ) in relation to the fraction (ε) of the friction force developing from adhesion predicts a universal relation ε ∼ δ4/3, which is supported by our experimental data. © 2011 American Chemical Society.

  10. Interfacial adsorption and aggregation of amphiphilic proteins

    Science.gov (United States)

    Cheung, David

    2012-02-01

    The adsorption and aggregation on liquid interfaces of proteins is important in many biological contexts, such as the formation of aerial structures, immune response, and catalysis. Likewise the adsorption of proteins onto interfaces has applications in food technology, drug delivery, and in personal care products. As such there has been much interest in the study of a wide range of biomolecules at liquid interfaces. One class of proteins that has attracted particular attention are hydrophobins, small, fungal proteins with a distinct, amphiphilic surface structure. This makes these proteins highly surface active and they recently attracted much interest. In order to understand their potential applications a microscopic description of their interfacial and self-assembly is necessary and molecular simulation provides a powerful tool for providing this. In this presentation I will describe some recent work using coarse-grained molecular dynamics simulations to study the interfacial and aggregation behaviour of hydrophobins. Specifically this will present the calculation of their adsorption strength at oil-water and air-water interfaces, investigate the stability of hydrophobin aggregates in solution and their interaction with surfactants.

  11. Interfacial adhesion of laser clad functionally graded materials

    NARCIS (Netherlands)

    Pei, Y. T.; Ocelik, V.; De Hosson, J. T. M.

    2003-01-01

    Specially designed samples of laser clad AlSi40 functionally graded materials (FGM) are made for evaluating the interfacial adhesion. To obtain the interfacial bond strength notches are made right at the interface of the FGMs. In-situ microstructural observations during straining in a field-emission

  12. Manipulation of interfacial instabilities by using a soft, deformable ...

    Indian Academy of Sciences (India)

    Abstract. Multilayer flows are oftensusceptible to interfacial instabilities caused due to jump in viscosity/elasticity across thefluid–fluid interface. It is frequently required to manipulate and control these interfacial instabilities in various applications such as coating processes or polymer coextrusion. We demonstrate here the ...

  13. Interfacial re-arrangement in initial microbial adhesion to surfaces

    NARCIS (Netherlands)

    Busscher, H.J.; Norde, W.; Sharma, P.K.; Mei, van der H.C.

    2010-01-01

    Upon initial microbial adhesion to a surface multiple events occur that include interfacial re-arrangements in the region between an adhering organism and a surface Application of physico-chemical mechanisms to explain microbial adhesion to surfaces requires better knowledge of the interfacial re

  14. Extraction of temperature dependent interfacial resistance of thermoelectric modules

    DEFF Research Database (Denmark)

    Chen, Min

    2011-01-01

    This article discusses an approach for extracting the temperature dependency of the electrical interfacial resistance associated with thermoelectric devices. The method combines a traditional module-level test rig and a nonlinear numerical model of thermoelectricity to minimize measurement errors...... on the interfacial resistance. The extracted results represent useful data to investigating the characteristics of thermoelectric module resistance and comparing performance of various modules....

  15. Manipulation of interfacial instabilities by using a soft, deformable ...

    Indian Academy of Sciences (India)

    Multilayer flows are oftensusceptible to interfacial instabilities caused due to jump in viscosity/elasticity across thefluid–fluid interface. It is frequently required to manipulate and control these interfacial instabilities in various applications such as coating processes or polymer coextrusion. We demonstrate here the possibility ...

  16. A toy quantum analog of enzymes

    CERN Document Server

    Svetlichny, George

    2015-01-01

    We present a quantum system incorporating qualitative aspects of enzyme action in which the possibility of quantum superposition of several conformations of the enzyme-substrate complex is investigated. We present numerical results showing quantum effects that transcend the case of a statistical mixture of conformations.

  17. Exogenous fibrolytic enzymes to unlock nutrients: Histological ...

    African Journals Online (AJOL)

    Exogenous fibrolytic enzymes to unlock nutrients: Histological investigation of its effects on fibre degradation in ruminants. ... There is a need for a better understanding of the mode-of-action of exogenous fibrolytic enzymes (EFE) used as additives in ruminant feeds. ... Keywords: Fibre digestion, histology, in vitro digestion ...

  18. Solid-liquid interfacial energy of aminomethylpropanediol

    Energy Technology Data Exchange (ETDEWEB)

    Ocak, Yavuz; Keslioglu, Kazim; Marasli, Necmettin [Department of Physics, Faculty of Arts and Sciences, Erciyes University, 38039 Kayseri (Turkey); Akbulut, Sezen [Department of Physics, Institute of Science and Technology, Erciyes University, 38039 Kayseri (Turkey)], E-mail: marasli@erciyes.edu.tr

    2008-03-21

    The grain boundary groove shapes for equilibrated solid aminomethylpropanediol, 2-amino-2 methyl-1.3 propanediol (AMPD) with its melt were directly observed by using a horizontal temperature gradient stage. From the observed grain boundary groove shapes, the Gibbs-Thomson coefficient ({gamma}), solid-liquid interfacial energy ({sigma}{sub SL}) and grain boundary energy ({sigma}{sub gb}) of AMPD have been determined to be (5.4 {+-} 0.5) x 10{sup -8} K m, (8.5 {+-} 1.3) x 10{sup -3} J m{sup -2} and (16.5 {+-} 2.8) x 10{sup -3} J m{sup -2}, respectively. The ratio of thermal conductivity of equilibrated liquid phase to solid phase for the AMPD has also been measured to be 1.12 at the melting temperature.

  19. Atrito interfacial em escoamento anular transicional

    OpenAIRE

    Marcos Heinzelmann Junqueira Pedras

    1993-01-01

    Resumo: o objetivo deste trabalho é estudar o atrito interfacial em escoamentos anulares co-correntes ascendentes na condição próxima da reversão de fluxo. O fenômeno foi experimentado em laboratório utilizando-se ar e água como fluidos de trabalho. Os resultados são apresentados e comparados com outros da literatura, validando assim os experimentos realizados. É proposta uma correlação para o cálculo da fração de vazio baseada no modelo de deslizamento. Também é proposta uma correlação para ...

  20. Liquid-liquid interfacial nanoparticle assemblies

    Science.gov (United States)

    Emrick, Todd S [South Deerfield, MA; Russell, Thomas P [Amherst, MA; Dinsmore, Anthony [Amherst, MA; Skaff, Habib [Amherst, MA; Lin, Yao [Amherst, MA

    2008-12-30

    Self-assembly of nanoparticles at the interface between two fluids, and methods to control such self-assembly process, e.g., the surface density of particles assembling at the interface; to utilize the assembled nanoparticles and their ligands in fabrication of capsules, where the elastic properties of the capsules can be varied from soft to tough; to develop capsules with well-defined porosities for ultimate use as delivery systems; and to develop chemistries whereby multiple ligands or ligands with multiple functionalities can be attached to the nanoparticles to promote the interfacial segregation and assembly of the nanoparticles. Certain embodiments use cadmium selenide (CdSe) nanoparticles, since the photoluminescence of the particles provides a convenient means by which the spatial location and organization of the particles can be probed. However, the systems and methodologies presented here are general and can, with suitable modification of the chemistries, be adapted to any type of nanoparticle.

  1. Interfacial dislocation motion and interactions in single-crystal superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Liu, B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Raabe, D. [Max Planck Inst. fur Eisenforshung. Dusseldorf (Germany); Roters, F. [Max Planck Inst. fur Eisenforshung. Dusseldorf (Germany); Arsenlis, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2014-10-01

    The early stage of high-temperature low-stress creep in single-crystal superalloys is characterized by the rapid development of interfacial dislocation networks. Although interfacial motion and dynamic recovery of these dislocation networks have long been expected to control the subsequent creep behavior, direct observation and hence in-depth understanding of such processes has not been achieved. Incorporating recent developments of discrete dislocation dynamics models, we simulate interfacial dislocation motion in the channel structures of single-crystal superalloys, and investigate how interfacial dislocation motion and dynamic recovery are affected by interfacial dislocation interactions and lattice misfit. Different types of dislocation interactions are considered: self, collinear, coplanar, Lomer junction, glissile junction, and Hirth junction. The simulation results show that strong dynamic recovery occurs due to the short-range reactions of collinear annihilation and Lomer junction formation. The misfit stress is found to induce and accelerate dynamic recovery of interfacial dislocation networks involving self-interaction and Hirth junction formation, but slow down the steady interfacial motion of coplanar and glissile junction forming dislocation networks. The insights gained from these simulations on high-temperature low-stress creep of single-crystal superalloys are also discussed.

  2. First-principles prediction of liquid/liquid interfacial tension

    DEFF Research Database (Denmark)

    Andersson, Martin Peter; Bennetzen, M.V.; Klamt, A.

    2014-01-01

    The interfacial tension between two liquids is the free energy per unit surface area required to create that interface. Interfacial tension is a determining factor for two-phase liquid behavior in a wide variety of systems ranging from water flooding in oil recovery processes and remediation...... of groundwater aquifers contaminated by chlorinated solvents to drug delivery and a host of industrial processes. Here, we present a model for predicting interfacial tension from first principles using density functional theory calculations. Our model requires no experimental input and is applicable to liquid...

  3. Oxidation-resistant interfacial coatings for continuous fiber ceramic composites

    Energy Technology Data Exchange (ETDEWEB)

    Stinton, D.P.; Besmann, T.M.; Bleier, A. [Oak Ridge National Lab., TN (United States); Shanmugham, S.; Liaw, P.K. [Univ. of Tennessee, Knoxville, TN (United States)

    1995-08-01

    Continuous fiber ceramic composites mechanical behavior are influenced by the bonding characteristics between the fiber and the matrix. Finite modeling studies suggest that a low-modulus interfacial coating material will be effective in reducing the residual thermal stresses that are generated upon cooling from processing temperatures. Nicalon{trademark}/SiC composites with carbon, alumina and mullite interfacial coatings were fabricated with the SiC matrix deposited using a forced-flow, thermal gradient chemical vapor infiltration process. Composites with mullite interfacial coatings exhibited considerable fiber pull-out even after oxidation and have potential as a composite system.

  4. Enzyme-based antifouling coatings: a review

    DEFF Research Database (Denmark)

    Olsen, Stefan Møller; Pedersen, Leif Toudal; Laursen, M.H.

    2007-01-01

    A systematic overview is presented of the literature that reports the antifouling (AF) protection of underwater structures via the action of enzymes. The overall aim of this review is to assess the state of the art of enzymatic AF technology, and to highlight the obstacles that have to be overcome...... for successful development of enzymatic AF coatings. The approaches described in the literature are divided into direct and indirect enzymatic AF, depending on the intended action of the enzymes. Direct antifouling is used when the enzymes themselves are active antifoulants. Indirect antifouling refers...... to the use of enzymes to release an active biocide with AF activity. For direct AF, several patents have been granted, and a commercial product has been launched. However, the achievement of an efficient broad-spectrum AF coating based on a single or a few enzymes has not yet been achieved. An indirect AF...

  5. The evolution of enzyme kinetic power.

    OpenAIRE

    Keleti, T.; Welch, G. R.

    1984-01-01

    Evolution of the kinetic potential of enzyme reactions is discussed. Quantitative assessment of the evolution of enzyme action has usually focused on optimization of the parametric ratio kcat./Km, which is the apparent second-order rate constant for the reaction of free substrate with free enzyme to give product. We propose that the general form kcat.[E]T/Km (where [E]T is total enzyme concentration), which is designated the 'kinetic power', is the real measure of kinetic/catalytic potential ...

  6. Final Project Report for "Interfacial Thermal Resistance of Carbon Nanotubes”

    Energy Technology Data Exchange (ETDEWEB)

    Cumings, John [Univ. of Maryland, College Park, MD (United States)

    2016-04-15

    This report describes an ongoing project to comprehensively study the interfacial thermal boundary resistance (Kapitza resistance) of carbon nanotubes. It includes a list of publications, personnel supported, the overall approach, accomplishments and future plans.

  7. Charles J. McMahon Interfacial Segregation and Embrittlement Symposium

    National Research Council Canada - National Science Library

    Vitek, Vaclav

    2003-01-01

    .... McMahon Interfacial Segregation and Embrittlement Symposium: Grain Boundary Segregation and Fracture in Steels was sponsored by ASM International, Materials Science Critical Technology Sector, Structural Materials Division, Materials Processing...

  8. Evanescent wave induced fluorescence. A tool for quantitative interfacial analysis

    CERN Document Server

    Byrne, C D

    2000-01-01

    Time-resolved angle-resolved evanescent wave induced fluorescence spectroscopy (EWIFS) has been used, for the first time, to determine interfacial concentration distributions of molecular species. Theoretical calculations demonstrate that in dynamic systems the non-radiative fluorescence decay coefficients of molecular species are effected only in a minor way by the presence of a dielectric interface. Consequently, measurements of interfacial fluorescence decay times are used to probe variations in molecular fluorescence quantum efficiencies, caused by the presence of an interface. The understanding of these variations is combined with angle-resolved evanescent wave theory. Examination of derived theoretical models using simulated data demonstrates that angle-resolved EWIFS is capable of measuring interfacial interactions on a nanometer scale. An evanescent wave induced fluorescence spectrometer is designed and fabricated to allow the measurement of the time-integrated and time-resolved interfacial emission. ...

  9. Enzyme detection by microfluidics

    DEFF Research Database (Denmark)

    2013-01-01

    Microfluidic-implemented methods of detecting an enzyme, in particular a DNA-modifying enzyme, are provided, as well as methods for detecting a cell, or a microorganism expressing said enzyme. The enzyme is detected by providing a nucleic acid substrate, which is specifically targeted by that enzyme......Microfluidic-implemented methods of detecting an enzyme, in particular a DNA-modifying enzyme, are provided, as well as methods for detecting a cell, or a microorganism expressing said enzyme. The enzyme is detected by providing a nucleic acid substrate, which is specifically targeted...

  10. Modeling interfacial liquid layers on environmental ices

    Directory of Open Access Journals (Sweden)

    M. H. Kuo

    2011-09-01

    Full Text Available Interfacial layers on ice significantly influence air-ice chemical interactions. In solute-containing aqueous systems, a liquid brine may form upon freezing due to the exclusion of impurities from the ice crystal lattice coupled with freezing point depression in the concentrated brine. The brine may be segregated to the air-ice interface where it creates a surface layer, in micropockets, or at grain boundaries or triple junctions.

    We present a model for brines and their associated liquid layers in environmental ice systems that is valid over a wide range of temperatures and solute concentrations. The model is derived from fundamental equlibrium thermodynamics and takes into account nonideal solution behavior in the brine, partitioning of the solute into the ice matrix, and equilibration between the brine and the gas phase for volatile solutes. We find that these phenomena are important to consider when modeling brines in environmental ices, especially at low temperatures. We demonstrate its application for environmentally important volatile and nonvolatile solutes including NaCl, HCl, and HNO3. The model is compared to existing models and experimental data from literature where available. We also identify environmentally relevant regimes where brine is not predicted to exist, but the QLL may significantly impact air-ice chemical interactions. This model can be used to improve the representation of air-ice chemical interactions in polar atmospheric chemistry models.

  11. Protein packing defects "heat up" interfacial water.

    Science.gov (United States)

    Sierra, María Belén; Accordino, Sebastián R; Rodriguez-Fris, J Ariel; Morini, Marcela A; Appignanesi, Gustavo A; Fernández Stigliano, Ariel

    2013-06-01

    Ligands must displace water molecules from their corresponding protein surface binding site during association. Thus, protein binding sites are expected to be surrounded by non-tightly-bound, easily removable water molecules. In turn, the existence of packing defects at protein binding sites has been also established. At such structural motifs, named dehydrons, the protein backbone is exposed to the solvent since the intramolecular interactions are incompletely wrapped by non-polar groups. Hence, dehydrons are sticky since they depend on additional intermolecular wrapping in order to properly protect the structure from water attack. Thus, a picture of protein binding is emerging wherein binding sites should be both dehydrons rich and surrounded by easily removable water. In this work we shall indeed confirm such a link between structure and dynamics by showing the existence of a firm correlation between the degree of underwrapping of the protein chain and the mobility of the corresponding hydration water molecules. In other words, we shall show that protein packing defects promote their local dehydration, thus producing a region of "hot" interfacial water which might be easily removed by a ligand upon association.

  12. Quantum interference in an interfacial superconductor.

    Science.gov (United States)

    Goswami, Srijit; Mulazimoglu, Emre; Monteiro, Ana M R V L; Wölbing, Roman; Koelle, Dieter; Kleiner, Reinhold; Blanter, Ya M; Vandersypen, Lieven M K; Caviglia, Andrea D

    2016-10-01

    The two-dimensional superconductor that forms at the interface between the complex oxides lanthanum aluminate (LAO) and strontium titanate (STO) has several intriguing properties that set it apart from conventional superconductors. Most notably, an electric field can be used to tune its critical temperature (T c ; ref. 7), revealing a dome-shaped phase diagram reminiscent of high-T c superconductors. So far, experiments with oxide interfaces have measured quantities that probe only the magnitude of the superconducting order parameter and are not sensitive to its phase. Here, we perform phase-sensitive measurements by realizing the first superconducting quantum interference devices (SQUIDs) at the LAO/STO interface. Furthermore, we develop a new paradigm for the creation of superconducting circuit elements, where local gates enable the in situ creation and control of Josephson junctions. These gate-defined SQUIDs are unique in that the entire device is made from a single superconductor with purely electrostatic interfaces between the superconducting reservoir and the weak link. We complement our experiments with numerical simulations and show that the low superfluid density of this interfacial superconductor results in a large, gate-controllable kinetic inductance of the SQUID. Our observation of robust quantum interference opens up a new pathway to understanding the nature of superconductivity at oxide interfaces.

  13. Interfacial functionalization and engineering of nanoparticles

    Science.gov (United States)

    Song, Yang

    The intense research interest in nanoscience and nanotechnology is largely fueled by the unique properties of nanoscale materials. In this dissertation, the research efforts are focused on surface functionalization and interfacial engineering of functional nanoparticles in the preparation of patchy nanoparticles (e.g., Janus nanoparticles and Neapolitan nanoparticles) such that the nanoparticle structures and properties may be manipulated to an unprecedented level of sophistication. Experimentally, Janus nanoparticles were prepared by an interfacial engineering method where one hemisphere of the originally hydrophobic nanoparticles was replaced with hydrophilic ligands at the air|liquid or solid|liquid interface. The amphiphilic surface characters of the Janus nanoparticles were verified by contact angle measurements, as compared to those of the bulk-exchange counterparts where the two types of ligands were distributed rather homogeneously on the nanoparticle surface. In a further study, a mercapto derivative of diacetylene was used as the hydrophilic ligands to prepare Janus nanoparticles by using hydrophobic hexanethiolate-protected gold nanoparticles as the starting materials. Exposure to UV irradiation led to effective covalent cross-linking between the diacetylene moieties of neighboring ligands and hence marked enhancement of the structural integrity of the Janus nanoparticles, which was attributable to the impeded surface diffusion of the thiol ligands on the nanoparticle surface, as manifested in fluorescence measurements of aged nanoparticles. More complicated bimetallic AgAu Janus nanoparticles were prepared by interfacial galvanic exchange reactions of a Langmuir-Blodgett monolayer of 1-hexanethiolate-passivated silver nanoparticles on a glass slide with gold(I)-mercaptopropanediol complex in a water/ethanol solution. The resulting nanoparticles exhibited an asymmetrical distribution not only of the organic capping ligands on the nanoparticle surface but

  14. Interfacial rheology: An overview of measuring techniques and its role in dispersions and electrospinning

    OpenAIRE

    Pelipenko, Jan; KRISTL, JULIJANA; Rošic, Romana; Baumgartner, Saša; KOCBEK, PETRA

    2012-01-01

    Interfacial rheological properties have yet to be thoroughly explored. Only recently, methods have been introduced that provide sufficient sensitivity to reliably determine viscoelastic interfacial properties. In general, interfacial rheology describes the relationship between the deformation of an interface and the stresses exerted on it. Due to the variety in deformations of the interfacial layer (shear and expansions or compressions), the field of interfacial rheology is divided into the s...

  15. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume IV. Chapters 15-19)

    Energy Technology Data Exchange (ETDEWEB)

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  16. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume III. Chapters 11-14)

    Energy Technology Data Exchange (ETDEWEB)

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  17. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume I. Chapters 1-5)

    Energy Technology Data Exchange (ETDEWEB)

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  18. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume II. Chapters 6-10)

    Energy Technology Data Exchange (ETDEWEB)

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  19. Elevated Liver Enzymes

    Science.gov (United States)

    Symptoms Elevated liver enzymes By Mayo Clinic Staff Elevated liver enzymes may indicate inflammation or damage to cells in the liver. Inflamed or ... than normal amounts of certain chemicals, including liver enzymes, into the bloodstream, which can result in elevated ...

  20. Computational approaches to modeling receptor flexibility upon ligand binding: Application to interfacially activated enzymes

    DEFF Research Database (Denmark)

    Wade, R.C.; Sobolev, V.; Ortiz, A.R. .

    1998-01-01

    Receptors generally undergo conformational change upon ligand binding. We describe how fairly simple techniques may be used in docking and design studies to account for some of the changes in the conformations of proteins on ligand binding. Simulations of protein-ligand interactions that give a m...

  1. Interfacial Behavior of Polymer Coated Nanoparticle

    Science.gov (United States)

    Qi, Luqing; Shamsijazeyi, Hadi; Mann, Jason; Verduzco, Rafael; Hirasaki, George; Rice University Team

    2015-03-01

    Oxidized carbon black (OCB) nanoparticle is functionalized with different coatings, i.e. alkyl group, polyvinyl alcohol (PVA) and partially sulfonated polyvinyl alcohol (sPVA). In oil and water systems, the functionalized nanoparticle is found to have a versatile dispersion i.e. in lower aqueous phase, in upper oil phase, or in middle phase microemulsion. Oil substitute n-octane and commercial oil IOSPAR have been test as oil phase; series of commercially available surfactant, C12-4,5 orthoxylene sulfonate(OXS), i-C13-(PO)7 -SO4Na (S13B), surfactant blend of anionic Alfoterra with nonionic Tergitol have been test as additive to help with the OCB dispersion. It is found that the OCB with sulfonated polyvinyl alcohol attachment (sPVA-OCB) stays in microemulsion; with the increase of salinity, it follows the microemulsion to go from lower phase, to middle phase, and to upper phase. The dispersion of sPVA and alkyl functionalized OCB (Cn-OCB-sPVA) is the balance of the length of alkyl and sPVA and the degree of sulfonation of PVA, depending on which, it can either disperse into microemulsion or form a separate layer. The sPVA-OCB also indicates a tolerance of high salinity; this is shown by the stable dispersion of it in blend surfactant solution of anionic Alfoterra and nonionic Tergitol at high salinity API brine(8% NaCl and 2% CaCl2). The study of different functionality on OCB dispersion can help design appropriate modified nanoparticle as additive for enhanced oil recovery either to reduce the interfacial tension between oil and water, or to stabilize microemulsion.

  2. Action semantics modulate action prediction.

    Science.gov (United States)

    Springer, Anne; Prinz, Wolfgang

    2010-11-01

    Previous studies have demonstrated that action prediction involves an internal action simulation that runs time-locked to the real action. The present study replicates and extends these findings by indicating a real-time simulation process (Graf et al., 2007), which can be differentiated from a similarity-based evaluation of internal action representations. Moreover, results showed that action semantics modulate action prediction accuracy. The semantic effect was specified by the processing of action verbs and concrete nouns (Experiment 1) and, more specifically, by the dynamics described by action verbs (Experiment 2) and the speed described by the verbs (e.g., "to catch" vs. "to grasp" vs. "to stretch"; Experiment 3). These results propose a linkage between action simulation and action semantics as two yet unrelated domains, a view that coincides with a recent notion of a close link between motor processes and the understanding of action language.

  3. Some Aspects of Interfacial Phenomena in Steelmaking and Refining

    Science.gov (United States)

    Wang, L. J.; Viswanathan, N. N.; Muhmood, L.; Kapilashrami, E.; Seetharaman, S.

    2016-08-01

    Unique experiments were designed to study the surface phenomena in steelmaking reactions. The concept of surface sulfide capacities and an understanding of the surface accumulation of surface-active species, based on experimental results, are presented. In order to understand the flow phenomenon at slag/metal interface, experiments were designed to measure the interfacial velocity of S on the surface of an iron drop immersed in an aluminosilicate slag using the X-ray sessile drop method. The oscillation of the iron drop in the slag due to the change in the surface concentration of sulfur at the slag-metal interface was monitored by X-ray imaging. From the observations, the interfacial velocity of sulfur was evaluated. Similar experiments were performed to measure the interfacial velocity of oxygen at the interface as well as the impact of oxygen potential on the interfacial velocity of sulfur. The interfacial shear viscosity and the dilatational modulus were also evaluated. In a study of the wetting of alumina base by iron drop at constant oxygen pressure under isothermal condition, the contact angle was found to be decreased with the progress of the reaction leading to the formation of hercynite as an intermediate layer creating non-wetting conditions. In the case of silica substrate, an intermediate liquid fayalite layer was formed.

  4. Modeling interfacial area transport in multi-fluid systems

    Energy Technology Data Exchange (ETDEWEB)

    Yarbro, Stephen Lee [Univ. of California, Berkeley, CA (United States)

    1996-11-01

    Many typical chemical engineering operations are multi-fluid systems. They are carried out in distillation columns (vapor/liquid), liquid-liquid contactors (liquid/liquid) and other similar devices. An important parameter is interfacial area concentration, which determines the rate of interfluid heat, mass and momentum transfer and ultimately, the overall performance of the equipment. In many cases, the models for determining interfacial area concentration are empirical and can only describe the cases for which there is experimental data. In an effort to understand multiphase reactors and the mixing process better, a multi-fluid model has been developed as part of a research effort to calculate interfacial area transport in several different types of in-line static mixers. For this work, the ensemble-averaged property conservation equations have been derived for each fluid and for the mixture. These equations were then combined to derive a transport equation for the interfacial area concentration. The final, one-dimensional model was compared to interfacial area concentration data from two sizes of Kenics in-line mixer, two sizes of concurrent jet and a Tee mixer. In all cases, the calculated and experimental data compared well with the highest scatter being with the Tee mixer comparison.

  5. Multiscale Modeling of Mesoscale and Interfacial Phenomena

    Science.gov (United States)

    Petsev, Nikolai Dimitrov

    With rapidly emerging technologies that feature interfaces modified at the nanoscale, traditional macroscopic models are pushed to their limits to explain phenomena where molecular processes can play a key role. Often, such problems appear to defy explanation when treated with coarse-grained continuum models alone, yet remain prohibitively expensive from a molecular simulation perspective. A prominent example is surface nanobubbles: nanoscopic gaseous domains typically found on hydrophobic surfaces that have puzzled researchers for over two decades due to their unusually long lifetimes. We show how an entirely macroscopic, non-equilibrium model explains many of their anomalous properties, including their stability and abnormally small gas-side contact angles. From this purely transport perspective, we investigate how factors such as temperature and saturation affect nanobubbles, providing numerous experimentally testable predictions. However, recent work also emphasizes the relevance of molecular-scale phenomena that cannot be described in terms of bulk phases or pristine interfaces. This is true for nanobubbles as well, whose nanoscale heights may require molecular detail to capture the relevant physics, in particular near the bubble three-phase contact line. Therefore, there is a clear need for general ways to link molecular granularity and behavior with large-scale continuum models in the treatment of many interfacial problems. In light of this, we have developed a general set of simulation strategies that couple mesoscale particle-based continuum models to molecular regions simulated through conventional molecular dynamics (MD). In addition, we derived a transport model for binary mixtures that opens the possibility for a wide range of applications in biological and drug delivery problems, and is readily reconciled with our hybrid MD-continuum techniques. Approaches that couple multiple length scales for fluid mixtures are largely absent in the literature, and

  6. Molecular determinants for interfacial binding and conformational change in a soluble diacylglycerol kinase.

    Science.gov (United States)

    Jerga, Agoston; Miller, Darcie J; White, Stephen W; Rock, Charles O

    2009-03-13

    DgkB is a soluble diacylglycerol (DAG) kinase that is essential for membrane lipid homeostasis in many Gram-positive pathogens. Anionic phospholipids, like phosphatidylglycerol (PtdGro), were required for DgkB to recognize diacylglycerol embedded in a phospholipid bilayer. An activity-independent vesicle binding assay was used to determine the role of specific residues in DgkB-PtdGro interactions. Lys15 and Lys165 were required for DgkB to dock with PtdGro vesicles and flank the entrance to the DgkB active site. Mg2+ was required for vesicle binding. The compromised vesicle binding by mutants in the key asparate residues forming the structural Mg2+-aspartate-water network within the substrate binding domain revealed that interfacial binding of DgkB required a Mg2+-dependent conformational change. DgkB interaction with phospholipid vesicles was not influenced by the presence of ATP, but anionic vesicles decreased the Km of the enzyme for ATP. Arg100 and Lys15 are two surface residues in the ATP binding domain that were necessary for high affinity ATP binding. The key residues responsible for the structural Mg2+ binding site, the conformational changes that increase ATP affinity, and interfacial recognition of anionic phospholipids were identical in DgkB and the mammalian diacylglycerol kinase catalytic cores. This sequence conservation suggests that the mammalian enzymes also require a structural divalent cation and surface positively charged residues to bind phospholipid bilayers and trigger conformational changes that accelerate catalysis.

  7. Molecular Determinants for Interfacial Binding and Conformational Change in a Soluble Diacylglycerol Kinase*

    Science.gov (United States)

    Jerga, Agoston; Miller, Darcie J.; White, Stephen W.; Rock, Charles O.

    2009-01-01

    DgkB is a soluble diacylglycerol (DAG) kinase that is essential for membrane lipid homeostasis in many Gram-positive pathogens. Anionic phospholipids, like phosphatidylglycerol (PtdGro), were required for DgkB to recognize diacylglycerol embedded in a phospholipid bilayer. An activity-independent vesicle binding assay was used to determine the role of specific residues in DgkB-PtdGro interactions. Lys15 and Lys165 were required for DgkB to dock with PtdGro vesicles and flank the entrance to the DgkB active site. Mg2+ was required for vesicle binding. The compromised vesicle binding by mutants in the key asparate residues forming the structural Mg2+-aspartate-water network within the substrate binding domain revealed that interfacial binding of DgkB required a Mg2+-dependent conformational change. DgkB interaction with phospholipid vesicles was not influenced by the presence of ATP, but anionic vesicles decreased the Km of the enzyme for ATP. Arg100 and Lys15 are two surface residues in the ATP binding domain that were necessary for high affinity ATP binding. The key residues responsible for the structural Mg2+ binding site, the conformational changes that increase ATP affinity, and interfacial recognition of anionic phospholipids were identical in DgkB and the mammalian diacylglycerol kinase catalytic cores. This sequence conservation suggests that the mammalian enzymes also require a structural divalent cation and surface positively charged residues to bind phospholipid bilayers and trigger conformational changes that accelerate catalysis. PMID:19112175

  8. Fundamentals of enzyme kinetics.

    Science.gov (United States)

    Seibert, Eleanore; Tracy, Timothy S

    2014-01-01

    This chapter provides a general introduction to the kinetics of enzyme-catalyzed reactions, with a focus on drug-metabolizing enzymes. A prerequisite to understanding enzyme kinetics is having a clear grasp of the meanings of "enzyme" and "catalysis." Catalysts are reagents that can increase the rate of a chemical reaction without being consumed in the reaction. Enzymes are proteins that form a subset of catalysts. These concepts are further explored below.

  9. Industrial enzyme applications.

    Science.gov (United States)

    Kirk, Ole; Borchert, Torben Vedel; Fuglsang, Claus Crone

    2002-08-01

    The effective catalytic properties of enzymes have already promoted their introduction into several industrial products and processes. Recent developments in biotechnology, particularly in areas such as protein engineering and directed evolution, have provided important tools for the efficient development of new enzymes. This has resulted in the development of enzymes with improved properties for established technical applications and in the production of new enzymes tailor-made for entirely new areas of application where enzymes have not previously been used.

  10. Interfacial characteristics of petroleum bitumens in contact with acid water

    Energy Technology Data Exchange (ETDEWEB)

    Salou, M.; Siffert, B.; Jada, A. [Institut de Chimie des Surfaces et Interfaces, Mulhouse (France)

    1998-03-01

    The chemical and interfacial properties of two bitumens were compared. The chemical properties were characterized by determining the asphaltene and resin contents of the bitumens. The interfacial properties were studied by wettability measurements and by determining the zeta potential of bitumen dispersions in acid water, with and without maturation of asphaltene dispersions in acid water and of bitumen dispersions in acid water containing asphaltenes. The study of the influence of the maturation at 80{degree}C for 7 h and of the addition of asphaltenes on the stability of the bitumen dispersion showed that the evolution of the interfacial properties of the bitumen depends on the resin content of the bitumen. Short communication. 15 refs., 1 figs., 2 tabs.

  11. Separation performance and interfacial properties of nanocomposite reverse osmosis membranes

    KAUST Repository

    Pendergast, MaryTheresa M.

    2013-01-01

    Four different types of nanocomposite reverse osmosis (RO) membranes were formed by interfacial polymerization of either polyamide (PA) or zeolite A-polyamide nanocomposite (ZA-PA) thin films over either pure polysulfone (PSf) or zeolite A-polysulfone nanocomposite (ZA-PSf) support membranes cast by wet phase inversion. All three nanocomposite membranes exhibited superior separation performance and interfacial properties relative to hand-cast TFC analogs including: (1) smoother, more hydrophilic surfaces (2) higher water permeability and salt rejection, and (3) improved resistance to physical compaction. Less compaction occurred for membranes with nanoparticles embedded in interfacially polymerized coating films, which adds further proof that flux decline associated with physical compaction is influenced by coating film properties in addition to support membrane properties. The new classes of nanocomposite membrane materials continue to offer promise of further improved RO membranes for use in desalination and advanced water purification. © 2011 Elsevier B.V.

  12. On Modulating Interfacial Structure towards Improved Anti-Icing Performance

    Directory of Open Access Journals (Sweden)

    Kshitij C. Jha

    2016-01-01

    Full Text Available The design of anti-icing surfaces presents an interface with high causal density that has been challenging to quantify in terms of individual contributions of various interactions and environmental factors. In this commentary, we highlight the role of interfacial water structure as uniquely expressing the physico-chemical aspects of ice accretion. Recent work on the topic that focuses on control of interfacial structure is discussed along with results by our research group on wettability of chemically modified surfaces and the role of ions in modulating interfacial structure. Suggestions for systematic studies to understand the fundamental interactions at play in ice adhesion at interfaces are made especially in the under-explored areas of cooperative hydrogen bonding and the role of solvated counterions. Insights expected from such studies would contribute to design of robust anti-icing hierarchies.

  13. Interfacial Fracture of Nanowire Electrodes of Lithium-Ion Batteries

    Science.gov (United States)

    Hardin, G. R.; Zhang, Y.; Fincher, C. D.; Pharr, M.

    2017-09-01

    Nanowires (NW) have emerged as a promising design for high power-density lithium-ion battery (LIB) electrodes. However, volume changes during cycling can lead to fracture of the NWs. In this paper, we investigate a particularly detrimental form of fracture: interfacial detachment of the NW from the current collector (CC). We perform finite element simulations to calculate the energy release rates of NWs during lithiation as a function of geometric parameters and mechanical properties. The simulations show that the energy release rate of a surface crack decreases as it propagates along the NW/CC interface toward the center of the NW. Moreover, this paper demonstrates that plastic deformation in the NWs drastically reduces stresses and thus crack-driving forces, thereby mitigating interfacial fracture. Overall, the results in this paper provide design guidelines for averting NW/CC interfacial fractures during operation of LIBs.

  14. Studies on the mechanism of action of imipenem (N-formimidoylthienamycin) in vitro: binding to the penicillin-binding proteins (PBPs) in Escherichia coli and Pseudomonas aeruginosa, and inhibition of enzyme activities due to the PBPs in E. coli.

    Science.gov (United States)

    Hashizume, T; Ishino, F; Nakagawa, J; Tamaki, S; Matsuhashi, M

    1984-04-01

    The binding affinities of imipenem (N- formimidoylthienamycin ) to penicillin-binding proteins ( PBSs ) of Escherichia coli and Pseudomonas aeruginosa were determined by two different methods in which competition with [14C]benzylpenicillin for the binding sites was measured. By both methods imipenem was shown to have very high binding affinities to PBPs-2 and -4 in E. coli and P. aeruginosa, and appreciable affinities to most of their other major PBPs. But higher concentrations of imipenem were required for binding to the PBPs-3 in these bacteria. More direct information about the antibacterial activity of imipenem was obtained by measuring its inhibition of the peptidoglycan-synthetic enzyme activities of E. coli PBPs. The results of enzyme inhibitions were compatible with those obtained in binding experiments. The antibiotic inhibited the transpeptidase activities of PBPs-1A, -1B and -2, and the D-alanine carboxypeptidase activities of PBPs-4 and -5. The antibiotic also seemed to cause strong inhibition of the transglycosylase activity of PBP-1A by some unknown mechanism. It inhibited the transpeptidase activity of PBP-3 only weakly, which is consistent with the findings that it had low binding affinity to PBP-3 and did not inhibit septum formation by the cells.

  15. Exploratory numerical experiments with a macroscopic theory of interfacial interactions

    Science.gov (United States)

    Giordano, D.; Solano-López, P.; Donoso, J. M.

    2017-09-01

    Phenomenological theories of interfacial interactions are founded on the core idea to model macroscopically the thin layer that forms between media in contact as a two-dimensional continuum (surface phase or interface) characterised by physical properties per unit area; the temporal evolution of the latter is governed by surface balance equations whose set acts as bridging channel in between the governing equations of the volume phases. These theories have targeted terrestrial applications since long time and their exploitation has inspired our research programme to build up, on the same core idea, a macroscopic theory of gas-surface interactions targeting the complex phenomenology of hypersonic reentry flows as alternative to standard methods in aerothermodynamics based on accommodation coefficients. The objective of this paper is the description of methods employed and results achieved in the exploratory study that kicked off our research programme, that is, the unsteady heat transfer between two solids in contact in planar and cylindrical configurations with and without interface. It is a simple numerical-demonstrator test case designed to facilitate quick numerical calculations but, at the same time, to bring forth already sufficiently meaningful aspects relevant to thermal protection due to the formation of the interface. The paper begins with a brief introduction on the subject matter and a review of relevant literature within an aerothermodynamics perspective. Then the case is considered in which the interface is absent. The importance of tension (force per unit area) continuity as boundary condition on the same footing of heat-flux continuity is recognised and the role of the former in governing the establishment of the temperature-difference distribution over the separation surface is explicitly shown. Evidence is given that the standard temperature-continuity boundary condition is just a particular case. Subsequently the case in which the interface is

  16. Complementary Actions

    Directory of Open Access Journals (Sweden)

    Luisa eSartori

    2015-05-01

    Full Text Available Complementary colors are color pairs which, when combined in the right proportions, produce white or black. Complementary actions refer here to forms of social interaction wherein individuals adapt their joint actions according to a common aim. Notably, complementary actions are incongruent actions. But being incongruent is not sufficient to be complementary (i.e., to complete the action of another person. Successful complementary interactions are founded on the abilities: (i to simulate another person’s movements, (ii to predict another person’s future action/s, (iii to produce an appropriate incongruent response which differ, while interacting, with observed ones, and (iv to complete the social interaction by integrating the predicted effects of one’s own action with those of another person. This definition clearly alludes to the functional importance of complementary actions in the perception–action cycle and prompts us to scrutinize what is taking place behind the scenes. Preliminary data on this topic have been provided by recent cutting-edge studies utilizing different research methods. This mini-review aims to provide an up-to-date overview of the processes and the specific activations underlying complementary actions.

  17. A Novel Thermodynamic Model for Obtaining Solid-Liquid Interfacial Energies

    Science.gov (United States)

    Zhang, Cong; Du, Yong

    2017-12-01

    The modeling of solid-liquid interfacial energies is developed in the present work. The total interfacial energy is separated into chemical and structure contributions, which are estimated by applying reported Gibbs energies, as well as correlated with molar interfacial area and melting temperature of solid phase. The present model is well validated with comprehensive datasets of measured solid-liquid interfacial energies, and it can provide key input parameters for microstructure simulations.

  18. Method for Computing the Anisotropy of the Solid-Liquid Interfacial Free Energy

    Energy Technology Data Exchange (ETDEWEB)

    Hoyt, J. J.; Asta, Mark; Karma, Alain

    2001-06-11

    We present a method to compute accurately the weak anisotropy of the solid-liquid interfacial free energy, a parameter which influences dendritic evolution in materials with atomically rough interfaces. The method is based on monitoring interfacial fluctuations during molecular dynamics simulation and extracting the interfacial stiffness which is an order of magnitude more anisotropic than the interfacial free energy. We present results for pure Ni with interatomic potentials derived from the embedded atom method.

  19. Method for Computing the Anisotropy of the Solid-Liquid Interfacial Free Energy

    Science.gov (United States)

    Hoyt, J. J.; Asta, Mark; Karma, Alain

    2001-06-01

    We present a method to compute accurately the weak anisotropy of the solid-liquid interfacial free energy, a parameter which influences dendritic evolution in materials with atomically rough interfaces. The method is based on monitoring interfacial fluctuations during molecular dynamics simulation and extracting the interfacial stiffness which is an order of magnitude more anisotropic than the interfacial free energy. We present results for pure Ni with interatomic potentials derived from the embedded atom method.

  20. Visualization and characterization of interfacial polymerization layer formation

    NARCIS (Netherlands)

    Zhang, Yali; Benes, Nieck Edwin; Lammertink, Rob G.H.

    2015-01-01

    We present a microfluidic platform to visualize the formation of free-standing films by interfacial polymerization. A microfluidic device is fabricated, with an array of micropillars to stabilize an aqueous–organic interface that allows a direct observation of the films formation process via optical

  1. Liquid metal actuation by electrical control of interfacial tension

    Science.gov (United States)

    Eaker, Collin B.; Dickey, Michael D.

    2016-09-01

    By combining metallic electrical conductivity with low viscosity, liquid metals and liquid metal alloys offer new and exciting opportunities to serve as reconfigurable components of electronic, microfluidic, and electromagnetic devices. Here, we review the physics and applications of techniques that utilize voltage to manipulate the interfacial tension of liquid metals; such techniques include electrocapillarity, continuous electrowetting, electrowetting-on-dielectric, and electrochemistry. These techniques lower the interfacial tension between liquid metals and a surrounding electrolyte by driving charged species (or in the case of electrochemistry, chemical species) to the interface. The techniques are useful for manipulating and actuating liquid metals at sub-mm length scales where interfacial forces dominate. We focus on metals and alloys that are liquid near or below room temperature (mercury, gallium, and gallium-based alloys). The review includes discussion of mercury—despite its toxicity—because it has been utilized in numerous applications and it offers a way of introducing several phenomena without the complications associated with the oxide layer that forms on gallium and its alloys. The review focuses on the advantages, applications, opportunities, challenges, and limitations of utilizing voltage to control interfacial tension as a method to manipulate liquid metals.

  2. Liquid-liquid interfacial tension of electrolyte solutions

    NARCIS (Netherlands)

    Bier, Markus; Zwanikken, J.W.; van Roij, R.H.H.G.

    2008-01-01

    It is theoretically shown that the excess liquid-liquid interfacial tension between two electrolyte solutions as a function of the ionic strength I behaves asymptotically as (-) for small I and as (±I) for large I. The former regime is dominated by the electrostatic potential due to an unequal

  3. Measurement of surface and interfacial tension using pendant drop tensiometry.

    Science.gov (United States)

    Berry, Joseph D; Neeson, Michael J; Dagastine, Raymond R; Chan, Derek Y C; Tabor, Rico F

    2015-09-15

    Pendant drop tensiometry offers a simple and elegant solution to determining surface and interfacial tension - a central parameter in many colloidal systems including emulsions, foams and wetting phenomena. The technique involves the acquisition of a silhouette of an axisymmetric fluid droplet, and iterative fitting of the Young-Laplace equation that balances gravitational deformation of the drop with the restorative interfacial tension. Since the advent of high-quality digital cameras and desktop computers, this process has been automated with high speed and precision. However, despite its beguiling simplicity, there are complications and limitations that accompany pendant drop tensiometry connected with both Bond number (the balance between interfacial tension and gravitational forces) and drop volume. Here, we discuss the process involved with going from a captured experimental image to a fitted interfacial tension value, highlighting pertinent features and limitations along the way. We introduce a new parameter, the Worthington number, Wo, to characterise the measurement precision. A fully functional, open-source acquisition and fitting software is provided to enable the reader to test and develop the technique further. Crown Copyright © 2015. Published by Elsevier Inc. All rights reserved.

  4. Phase transitions, interfacial fluctuations and hidden symmetries for ...

    Indian Academy of Sciences (India)

    Universidad de Sevilla, Apartado de Correos 1065, 41080 Sevilla, Spain. E-mail: a.o.parry@ic.ac.uk. Abstract. Fluids adsorbed at micro-patterned and geometrically structured substrates can exhibit novel phase transitions and interfacial fluctuation effects distinct from those characteristic of wetting at planar, homogeneous ...

  5. Limiting amplitudes of fully nonlinear interfacial tides and solitons

    NARCIS (Netherlands)

    Aguiar-González, B.; Gerkema, T.

    2016-01-01

    A new two-fluid layer model consisting of forcedrotation-modified Boussinesq equations is derived for studyingtidally generated fully nonlinear, weakly nonhydrostaticdispersive interfacial waves. This set is a generalization ofthe Choi–Camassa equations, extended here with forcingterms and Coriolis

  6. A comparative study regarding effects of interfacial ferroelectric ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 37; Issue 2. A comparative study regarding effects of interfacial ferroelectric Bi4Ti3O12 (BTO) layer on electrical characteristics of Au/-Si structures. M Yildirim M Gökçen. Electronic Supplementary Material Volume 37 Issue 2 April 2014 pp 257-262 ...

  7. Summer Research Institute Interfacial and Condensed Phase Chemical Physics

    Energy Technology Data Exchange (ETDEWEB)

    Barlow, Stephan E.

    2004-10-01

    Pacific Northwest National Laboratory (PNNL) hosted its first annual Summer Research Institute in Interfacial and Condensed Phase Chemical Physics from May through September 2004. During this period, fourteen PNNL scientists hosted sixteen young scientists from eleven different universities. Of the sixteen participants, fourteen were graduate students; one was transitioning to graduate school; and one was a university faculty member.

  8. Interfacial properties of immiscible Co-Cu alloys

    DEFF Research Database (Denmark)

    Egry, I.; Ratke, L.; Kolbe, M.

    2010-01-01

    Using electromagnetic levitation under microgravity conditions, the interfacial properties of an Cu75Co25 alloy have been investigated in the liquid phase. This alloy exhibits a metastable liquid miscibility gap and can be prepared and levitated in a configuration consisting of a liquid cobalt-ri...... experiment carried out on board the TEXUS 44 sounding rocket....

  9. Measurement of Interfacial Area Production and Permeability within Porous Media

    Energy Technology Data Exchange (ETDEWEB)

    Crandall, Dustin; Ahmadi, Goodarz; Smith, Duane H.

    2010-01-01

    An understanding of the pore-level interactions that affect multi-phase flow in porous media is important in many subsurface engineering applications, including enhanced oil recovery, remediation of dense non-aqueous liquid contaminated sites, and geologic CO2 sequestration. Standard models of two-phase flow in porous media have been shown to have several shortcomings, which might partially be overcome using a recently developed model based on thermodynamic principles that includes interfacial area as an additional parameter. A few static experimental studies have been previously performed, which allowed the determination of static parameters of the model, but no information exists concerning the interfacial area dynamic parameters. A new experimental porous flow cell that was constructed using stereolithography for two-phase gas-liquid flow studies was used in conjunction with an in-house analysis code to provide information on dynamic evolution of both fluid phases and gas-liquid interfaces. In this paper, we give a brief introduction to the new generalized model of two-phase flow model and describe how the stereolithography flow cell experimental setup was used to obtain the dynamic parameters for the interfacial area numerical model. In particular, the methods used to determine the interfacial area permeability and production terms are shown.

  10. Interfacial shear behavior of composite flanged concrete beams

    Directory of Open Access Journals (Sweden)

    Moataz Awry Mahmoud

    2014-08-01

    Full Text Available Composite concrete decks are commonly used in the construction of highway bridges due to their rapid constructability. The interfacial shear transfer between the top slab and the supporting beams is of great significance to the overall deck load carrying capacity and performance. Interfacial shear capacity is directly influenced by the distribution and the percentage of shear connectors. Research and design guidelines suggest the use of two different approaches to quantify the required interfacial shear strength, namely based on the maximum compressive forces in the flange at mid span or the maximum shear flow at the supports. This paper investigates the performance of flanged reinforced concrete composite beams with different shear connector’s distribution and reinforcing ratios. The study incorporated both experimental and analytical programs for beams. Key experimental findings suggest that concentrating the connectors at the vicinity of the supports enhances the ductility of the beam. The paper proposes a simple and straight forward approach to estimate the interfacial shear capacity that was proven to give good correlation with the experimental results and selected code provisions. The paper presents a method to predict the horizontal shear force between precast beams and cast in-situ slabs.

  11. Fluorescent probes used to monitor membrane interfacial polarity.

    NARCIS (Netherlands)

    Epand, R.M.; Kraayenhof, R.

    1999-01-01

    The polarity of the interface between a lipid bilayer membrane and bulk water is an important physical parameter of the membrane. It is likely that several membrane-dependent biological functions are modulated by this property. However, interfacial polarity can be difficult to define because of an

  12. High performance CNT point emitter with graphene interfacial layer.

    Science.gov (United States)

    Lee, Jeong Seok; Kim, Taewoo; Kim, Seul-Gi; Cho, Myung Rae; Seo, Dong Kyun; Lee, Minwoo; Kim, Seontae; Kim, Dae Weon; Park, Gun-Sik; Jeong, Dae Hong; Park, Yun Daniel; Yoo, Ji-Beom; Kang, Tae June; Kim, Yong Hyup

    2014-11-14

    Carbon nanotubes (CNTs) have great potential in the development of high-power electron beam sources. However, for such a high-performance electronic device, the electric and thermal contact problem between the metal and CNTs must be improved. Here, we report graphene as an interfacial layer between the metal and CNTs to improve the interfacial contact. The interfacial graphene layer results in a dramatic decrease of the electrical contact resistance by an order of 2 and an increase of the interfacial thermal conductivity by 16%. Such a high improvement in the electrical and thermal interface leads to superior field emission performance with a very low turn-on field of 1.49 V μm(-1) at 10 μA cm(-2) and a threshold field of 2.00 V μm(-1) at 10 mA cm(-2), as well as the maximum current of 16 mA (current density of 2300 A cm(-2)).

  13. Interfacial stresses in strengthened beam with shear cohesive zone ...

    Indian Academy of Sciences (India)

    The results of parametric study are compared with those of Smith and Teng. They confirm the accuracy of the proposed approach in predicting both interfacial shear and normal stresses. Author Affiliations. Zergua Abdesselam1. Department of Civil Engineering, University of Constantine 1, Constantine, Algeria. Dates.

  14. Interfacial microstructure and strength of diffusion brazed joint ...

    Indian Academy of Sciences (India)

    TECS

    Abstract. Joining of composite, Al2O3–TiC, with heat-resistant 9Cr1MoV steel, was carried out by diffusion brazing technology, using a combination of Ti, Cu and Ti as multi-interlayer. The interfacial strength was measured by shear testing and the result was explained by the fracture morphology. Microstructural charac-.

  15. Undergraduate Laboratory Experiment Modules for Probing Gold Nanoparticle Interfacial Phenomena

    Science.gov (United States)

    Karunanayake, Akila G.; Gunatilake, Sameera R.; Ameer, Fathima S.; Gadogbe, Manuel; Smith, Laura; Mlsna, Deb; Zhang, Dongmao

    2015-01-01

    Three gold-nanoparticle (AuNP) undergraduate experiment modules that are focused on nanoparticles interfacial phenomena have been developed. Modules 1 and 2 explore the synthesis and characterization of AuNPs of different sizes but with the same total gold mass. These experiments enable students to determine how particle size affects the AuNP…

  16. Perturbation theory for solid-liquid interfacial free energies

    Energy Technology Data Exchange (ETDEWEB)

    Warshavsky, Vadim B; Song Xueyu, E-mail: xsong@iastate.ed [Ames Laboratory and Department of Chemistry, Iowa State University, Ames, IA 50011 (United States)

    2010-09-15

    A perturbation theory is developed to calculate solid-liquid interfacial free energies, including anisotropy. The method is applied to systems with inverse-power and Lennard-Jones pair potentials as well as to metal systems with embedded-atom model potentials. The results are in reasonable agreement with the corresponding ones obtained from molecular dynamics simulations.

  17. Impact of Interfacial Layers in Perovskite Solar Cells.

    Science.gov (United States)

    Cho, An-Na; Park, Nam-Gyu

    2017-10-09

    Perovskite solar cells (PCSs) are composed of organic-inorganic lead halide perovskite as the light harvester. Since the first report on a long-term-durable, 9.7 % efficient, solid-state perovskite solar cell, organic-inorganic halide perovskites have received considerable attention because of their excellent optoelectronic properties. As a result, a power conversion efficiency (PCE) exceeding 22 % was certified. Controlling the grain size, grain boundary, morphology, and defects of the perovskite layer is important for achieving high efficiency. In addition, interfacial engineering is equally or more important to further improve the PCE through better charge collection and a reduction in charge recombination. In this Review, the type of interfacial layers and their impact on photovoltaic performance are investigated for both the normal and the inverted cell architectures. Four different interfaces of fluorine-doped tin oxide (FTO)/electron-transport layer (ETL), ETL/perovskite, perovskite/hole-transport layer (HTL), and HTL/metal are classified, and their roles are investigated. The effects of interfacial engineering with organic or inorganic materials on photovoltaic performance are described in detail. Grain-boundary engineering is also included because it is related to interfacial engineering and the grain boundary in the perovskite layer plays an important role in charge conduction, recombination, and chargecarrier life time. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Interfacial thermodynamics of water and six other liquid solvents.

    Science.gov (United States)

    Pascal, Tod A; Goddard, William A

    2014-06-05

    We examine the thermodynamics of the liquid-vapor interface by direct calculation of the surface entropy, enthalpy, and free energy from extensive molecular dynamics simulations using the two-phase thermodynamics (2PT) method. Results for water, acetonitrile, cyclohexane, dimethyl sulfoxide, hexanol, N-methyl acetamide, and toluene are presented. We validate our approach by predicting the interfacial surface tensions (IFT--excess surface free energy per unit area) in excellent agreement with the mechanical calculations using Kirkwood-Buff theory. Additionally, we evaluate the temperature dependence of the IFT of water as described by the TIP4P/2005, SPC/Ew, TIP3P, and mW classical water models. We find that the TIP4P/2005 and SPC/Ew water models do a reasonable job of describing the interfacial thermodynamics; however, the TIP3P and mW are quite poor. We find that the underprediction of the experimental IFT at 298 K by these water models results from understructured surface molecules whose binding energies are too weak. Finally, we performed depth profiles of the interfacial thermodynamics which revealed long tails that extend far into what would be considered bulk from standard Gibbs theory. In fact, we find a nonmonotonic interfacial free energy profile for water, a unique feature that could have important consequences for the absorption of ions and other small molecules.

  19. Enzyme inhibition by iminosugars

    DEFF Research Database (Denmark)

    López, Óscar; Qing, Feng-Ling; Pedersen, Christian Marcus

    2013-01-01

    Imino- and azasugar glycosidase inhibitors display pH dependant inhibition reflecting that both the inhibitor and the enzyme active site have groups that change protonation state with pH. With the enzyme having two acidic groups and the inhibitor one basic group, enzyme-inhibitor complexes...

  20. Studies on the disbonding initiation of interfacial cracks.

    Energy Technology Data Exchange (ETDEWEB)

    McAdams, Brian J. (Lehigh University, Bethlehem, PA); Pearson, Raymond A. (Lehigh University, Bethlehem, PA)

    2005-08-01

    With the continuing trend of decreasing feature sizes in flip-chip assemblies, the reliability tolerance to interfacial flaws is also decreasing. Small-scale disbonds will become more of a concern, pointing to the need for a better understanding of the initiation stage of interfacial delamination. With most accepted adhesion metric methodologies tailored to predict failure under the prior existence of a disbond, the study of the initiation phenomenon is open to development and standardization of new testing procedures. Traditional fracture mechanics approaches are not suitable, as the mathematics assume failure to originate at a disbond or crack tip. Disbond initiation is believed to first occur at free edges and corners, which act as high stress concentration sites and exhibit singular stresses similar to a crack tip, though less severe in intensity. As such, a 'fracture mechanics-like' approach may be employed which defines a material parameter--a critical stress intensity factor (K{sub c})--that can be used to predict when initiation of a disbond at an interface will occur. The factors affecting the adhesion of underfill/polyimide interfaces relevant to flip-chip assemblies were investigated in this study. The study consisted of two distinct parts: a comparison of the initiation and propagation phenomena and a comparison of the relationship between sub-critical and critical initiation of interfacial failure. The initiation of underfill interfacial failure was studied by characterizing failure at a free-edge with a critical stress intensity factor. In comparison with the interfacial fracture toughness testing, it was shown that a good correlation exists between the initiation and propagation of interfacial failures. Such a correlation justifies the continuing use of fracture mechanics to predict the reliability of flip-chip packages. The second aspect of the research involved fatigue testing of tensile butt joint specimens to determine lifetimes at sub

  1. Three-Dimensional Visualization of Interfacial Phenomena Using Confocal Microscopy

    Science.gov (United States)

    Shieh, Ian C.

    Surfactants play an integral role in numerous functions ranging from stabilizing the emulsion in a favorite salad dressing to organizing the cellular components that make life possible. We are interested in lung surfactant, which is a mixture of lipids and proteins essential for normal respiration because it modulates the surface tension of the air-liquid interface of the thin fluid lining in the lungs. Through this surface tension modulation, lung surfactant ensures effortless lung expansion and prevents lung collapse during exhalation, thereby effecting proper oxygenation of the bloodstream. The function of lung surfactant, as well as numerous interfacial lipid systems, is not solely dictated by the behavior of materials confined to the two-dimensional interface. Rather, the distributions of materials in the liquid subphase also greatly influence the performance of interfacial films of lung surfactant. Therefore, to better understand the behavior of lung surfactant and other interfacial lipid systems, we require a three-dimensional characterization technique. In this dissertation, we have developed a novel confocal microscopy methodology for investigating the interfacial phenomena of surfactants at the air-liquid interface of a Langmuir trough. Confocal microscopy provides the excellent combination of in situ, fast, three-dimensional visualization of multiple components of the lung surfactant system that other characterization techniques lack. We detail the solutions to the numerous challenges encountered when imaging a dynamic air-liquid interface with a high-resolution technique like confocal microscopy. We then use confocal microscopy to elucidate the distinct mechanisms by which a polyelectrolyte (chitosan) and nonadsorbing polymer (polyethylene glycol) restore the function of lung surfactant under inhibitory conditions mimicking the effects of lung trauma. Beyond this physiological model, we also investigate several one- and two-component interfacial films

  2. Strongly nonlinear steepening of long interfacial waves

    Directory of Open Access Journals (Sweden)

    N. Zahibo

    2007-06-01

    Full Text Available The transformation of nonlinear long internal waves in a two-layer fluid is studied in the Boussinesq and rigid-lid approximation. Explicit analytic formulation of the evolution equation in terms of the Riemann invariants allows us to obtain analytical results characterizing strongly nonlinear wave steepening, including the spectral evolution. Effects manifesting the action of high nonlinear corrections of the model are highlighted. It is shown, in particular, that the breaking points on the wave profile may shift from the zero-crossing level. The wave steepening happens in a different way if the density jump is placed near the middle of the water bulk: then the wave deformation is almost symmetrical and two phases appear where the wave breaks.

  3. Enzyme Kinetics: The Use of Amylose Azure.

    Science.gov (United States)

    Cusimano, Vincent J.

    1978-01-01

    Amylose azure can be used as a chromogenic substrate for alpha-amylase in studying the effects of temperature and pH enzyme action. This is a model system which students can use to measure the energy of activation using the Arrhenius plot. (Author/BB)

  4. Exogenous fibrolytic enzymes to unlock nutrients: Histological ...

    African Journals Online (AJOL)

    Useni , Alain

    2013-07-08

    Jul 8, 2013 ... Abstract. There is a need for a better understanding of the mode-of-action of exogenous fibrolytic enzymes. (EFE) used as additives in ruminant feeds. Four forages, treated with EFE, were evaluated in vitro and histologically, in an attempt to determine the effect of EFE on tissue degradation. Weeping love ...

  5. Probing Conformational Changes and Interfacial Recognition Site of Lipases With Surfactants and Inhibitors.

    Science.gov (United States)

    Mateos-Diaz, E; Amara, S; Roussel, A; Longhi, S; Cambillau, C; Carrière, F

    2017-01-01

    Structural studies on lipases by X-ray crystallography have revealed conformational changes occurring in the presence of surfactants/inhibitors and the pivotal role played by a molecular "lid" of variable size and structure depending on the enzyme. Besides controlling the access to the enzyme active site, the lid is involved in lipase activation, formation of the interfacial recognition site (IRS), and substrate docking within the active site. The combined use of surfactants and inhibitors has been critical for a better understanding of lipase structure-function relationships. An overview of crystal structures of lipases in complex with surfactants and inhibitors reveals common structural features and shows how surfactants monomers interact with the lid in its open conformation. The location of surfactants, inhibitors, and hydrophobic residues exposed upon lid opening provides insights into the IRS of lipases. The mechanism by which surfactants promote the lid opening can be further investigated in solution by site-directed spin labeling of lipase coupled to electron paramagnetic resonance spectroscopy. These experimental approaches are illustrated here by results obtained with mammalian digestive lipases, fungal lipases, and cutinases. © 2017 Elsevier Inc. All rights reserved.

  6. Improved Performance of Magnetic Cross-Linked Lipase Aggregates by Interfacial Activation: A Robust and Magnetically Recyclable Biocatalyst for Transesterification of Jatropha Oil.

    Science.gov (United States)

    Zhang, Weiwei; Yang, Huixia; Liu, Wanyi; Wang, Na; Yu, Xiaoqi

    2017-12-07

    Lipases are the most widely employed enzymes in commercial industries. The catalytic mechanism of most lipases involves a step called "interfacial activation". As interfacial activation can lead to a significant increase in catalytic activity, it is of profound importance in developing lipase immobilization methods. To obtain a potential biocatalyst for industrial biodiesel production, an effective strategy for enhancement of catalytic activity and stability of immobilized lipase was developed. This was performed through the combination of interfacial activation with hybrid magnetic cross-linked lipase aggregates. This biocatalyst was investigated for the immobilization of lipase from Rhizomucor miehei (RML). Under the optimal conditions, the activity recovery of the surfactant-activated magnetic RML cross-linked enzyme aggregates (CLEAs) was as high as 2058%, with a 20-fold improvement over the free RML. Moreover, the immobilized RML showed excellent catalytic performance for the biodiesel reaction at a yield of 93%, and more importantly, could be easily separated from the reaction mixture by simple magnetic decantation, and retained more than 84% of its initial activities after five instances of reuse. This study provides a new and versatile approach for designing and fabricating immobilized lipase with high activation and stability.

  7. Improved Performance of Magnetic Cross-Linked Lipase Aggregates by Interfacial Activation: A Robust and Magnetically Recyclable Biocatalyst for Transesterification of Jatropha Oil

    Directory of Open Access Journals (Sweden)

    Weiwei Zhang

    2017-12-01

    Full Text Available Lipases are the most widely employed enzymes in commercial industries. The catalytic mechanism of most lipases involves a step called “interfacial activation”. As interfacial activation can lead to a significant increase in catalytic activity, it is of profound importance in developing lipase immobilization methods. To obtain a potential biocatalyst for industrial biodiesel production, an effective strategy for enhancement of catalytic activity and stability of immobilized lipase was developed. This was performed through the combination of interfacial activation with hybrid magnetic cross-linked lipase aggregates. This biocatalyst was investigated for the immobilization of lipase from Rhizomucor miehei (RML. Under the optimal conditions, the activity recovery of the surfactant-activated magnetic RML cross-linked enzyme aggregates (CLEAs was as high as 2058%, with a 20-fold improvement over the free RML. Moreover, the immobilized RML showed excellent catalytic performance for the biodiesel reaction at a yield of 93%, and more importantly, could be easily separated from the reaction mixture by simple magnetic decantation, and retained more than 84% of its initial activities after five instances of reuse. This study provides a new and versatile approach for designing and fabricating immobilized lipase with high activation and stability.

  8. Electroluminescence and impedance analyses of organic light emitting diodes using anhydride materials as cathode interfacial layers

    Energy Technology Data Exchange (ETDEWEB)

    Nam, Eunkyoung [Department of Physics, Brain Korea 21 Physics Research Division, Institute of Basic Science, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Park, Hyungjun [School of Information and Communication Engineering, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Park, Keunhee; Moon, Mi Ran [Department of Physics, Brain Korea 21 Physics Research Division, Institute of Basic Science, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Sohn, Sunyoung [Korea Basic Science Institute, Dukjin Dong 664-14, Jeonju 561-756 (Korea, Republic of); Jung, Donggeun [Department of Physics, Brain Korea 21 Physics Research Division, Institute of Basic Science, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Yi, Junsin [School of Information and Communication Engineering, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Chae, Heeyeop [Department of Chemical Engineering, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Kim, Hyoungsub, E-mail: hsubkim@skku.ed [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of)

    2009-05-29

    Pyromellitic dianhydride (PMDA) and trimellitic anhydride (TMA) were tried as cathode interfacial layers between tris-(8-hydroxyquinoline) aluminum (Alq{sub 3}) and Al in organic light emitting diodes (OLEDs). Both ultra-thin anhydride cathode interfacial layers improved the electroluminescence characteristics of OLEDs compared to those without any interfacial layer, and the PMDA interfacial layer showed the most significant enhancement of the device performance. According to impedance measurements and equivalent circuit analysis, the PMDA interfacial layer decreased the impedance, probably due to the increase in the injection efficiency of electrons from the Al cathode.

  9. Glutathione transferase mimics : Micellar catalysis of an enzymic reaction

    NARCIS (Netherlands)

    Lindkvist, Björn; Weinander, Rolf; Engman, Lars; Koetse, Marc; Engberts, Jan B.F.N.; Morgenstern, Ralf

    1997-01-01

    Substances that mimic the enzyme action of glutathione transferases (which serve in detoxification) are described. These micellar catalysts enhance the reaction rate between thiols and activated halogenated nitroarenes as well as alpha,beta-unsaturated carbonyls. The nucleophilic aromatic

  10. Operating Conditions Effects Onenzyme Activity: Case Enzyme Protease

    OpenAIRE

    Adel Oueslati,; Mounirhaouala

    2014-01-01

    The Proteases an enzyme added to detergents to degrade the protein spots origin.Their action is manifested through its activity the middle of washing clothes. This activity depends on the operating conditions. In this article, the effects of temperature and pH of the reaction and the substrate concentration and time of washing medium on the enzyme activity were studied. There action mechanism has been shown. The activity measurements were made by absorption spectrometry

  11. Enzymes and muscle diseases

    Directory of Open Access Journals (Sweden)

    M. Plebani

    2011-09-01

    Full Text Available Skeletal muscle disorders may result in release of muscle enzymes into the circulation and give increased serum enzyme activity. A variety of enzymes routinely determined in the clinical laboratory may be elevated, but creatine kinase is the enzyme present in the highest concentration in muscle, and in every variety of muscle disease is the serum enzyme which shows the greatest incidence and degree of elevation. Aspartate aminotransferase is the enzyme associated most significantly with inflammation. A diagnostic algorithm based on the combined measurement of creatine kinase, aspartate aminotransferase and aldolase has been found to discriminate muscular distrophies from polymyositis and other myopathies. This combination of laboratory tests has diagnostic application and thus allows the clinician to better select patients who need to have a skeletal muscle biopsy as a diagnostic procedure.

  12. Enzymes for improved biomass conversion

    Science.gov (United States)

    Brunecky, Roman; Himmel, Michael E.

    2016-02-02

    Disclosed herein are enzymes and combinations of the enzymes useful for the hydrolysis of cellulose and the conversion of biomass. Methods of degrading cellulose and biomass using enzymes and cocktails of enzymes are also disclosed.

  13. Predicting Enzyme Adsorption to Lignin Films by Calculating Enzyme Surface Hydrophobicity*

    Science.gov (United States)

    Sammond, Deanne W.; Yarbrough, John M.; Mansfield, Elisabeth; Bomble, Yannick J.; Hobdey, Sarah E.; Decker, Stephen R.; Taylor, Larry E.; Resch, Michael G.; Bozell, Joseph J.; Himmel, Michael E.; Vinzant, Todd B.; Crowley, Michael F.

    2014-01-01

    The inhibitory action of lignin on cellulase cocktails is a major challenge to the biological saccharification of plant cell wall polysaccharides. Although the mechanism remains unclear, hydrophobic interactions between enzymes and lignin are hypothesized to drive adsorption. Here we evaluate the role of hydrophobic interactions in enzyme-lignin binding. The hydrophobicity of the enzyme surface was quantified using an estimation of the clustering of nonpolar atoms, identifying potential interaction sites. The adsorption of enzymes to lignin surfaces, measured using the quartz crystal microbalance, correlates to the hydrophobic cluster scores. Further, these results suggest a minimum hydrophobic cluster size for a protein to preferentially adsorb to lignin. The impact of electrostatic contribution was ruled out by comparing the isoelectric point (pI) values to the adsorption of proteins to lignin surfaces. These results demonstrate the ability to predict enzyme-lignin adsorption and could potentially be used to design improved cellulase cocktails, thus lowering the overall cost of biofuel production. PMID:24876380

  14. Profiling the orphan enzymes

    Science.gov (United States)

    2014-01-01

    The emergence of Next Generation Sequencing generates an incredible amount of sequence and great potential for new enzyme discovery. Despite this huge amount of data and the profusion of bioinformatic methods for function prediction, a large part of known enzyme activities is still lacking an associated protein sequence. These particular activities are called “orphan enzymes”. The present review proposes an update of previous surveys on orphan enzymes by mining the current content of public databases. While the percentage of orphan enzyme activities has decreased from 38% to 22% in ten years, there are still more than 1,000 orphans among the 5,000 entries of the Enzyme Commission (EC) classification. Taking into account all the reactions present in metabolic databases, this proportion dramatically increases to reach nearly 50% of orphans and many of them are not associated to a known pathway. We extended our survey to “local orphan enzymes” that are activities which have no representative sequence in a given clade, but have at least one in organisms belonging to other clades. We observe an important bias in Archaea and find that in general more than 30% of the EC activities have incomplete sequence information in at least one superkingdom. To estimate if candidate proteins for local orphans could be retrieved by homology search, we applied a simple strategy based on the PRIAM software and noticed that candidates may be proposed for an important fraction of local orphan enzymes. Finally, by studying relation between protein domains and catalyzed activities, it appears that newly discovered enzymes are mostly associated with already known enzyme domains. Thus, the exploration of the promiscuity and the multifunctional aspect of known enzyme families may solve part of the orphan enzyme issue. We conclude this review with a presentation of recent initiatives in finding proteins for orphan enzymes and in extending the enzyme world by the discovery of new

  15. Enzymes in animal nutrition

    OpenAIRE

    Scientific Committee on Animal Nutrition

    2011-01-01

    This report brings overview of endogenous as well as exogenous enzymes and their role and importance in animal nutrition. Enzymes for animal nutrition have been systematically developed since 1980´s. Phytase, xylanase and β-glucanase are used in poultry-rising, pig breeding, aquaculture and begin to push to the ruminant nutrition. Phytase increase availability of P, Ca, Zn, digestibility of proteins and fats. Its positive effect on the environment is well described – enzymes decrease the cont...

  16. Friction mechanisms and interfacial slip at fluid-solid interfaces

    CERN Document Server

    Leger, L

    2003-01-01

    We present series of experiments based on near field laser velocimetry, developed to characterize the friction mechanisms at fluid-solid interfaces. For polymers, entangled polymer melts are sheared against smooth solid surfaces, covered by surface attached polymer chains of the same chemical species, having a controlled surface density. Direct measurements of the interfacial velocity and of the shear force allow identification of the molecular mechanisms of friction. Depending on the value of the inverse of the shear rate experienced by the polymer compared to the reptation time, the transition between a regime of high and a regime of low friction observed when increasing the shear rate can be related to disentanglement or to the extraction of the surface chains from the bulk polymer. Surfaces with adjusted friction properties can thus be designed by choosing chain anchored length and surface density. For simple fluids, the direct measurements of the interfacial velocity show that, contrary to the usual hypo...

  17. Topology-generating interfacial pattern formation during liquid metal dealloying

    Science.gov (United States)

    Geslin, Pierre-Antoine; McCue, Ian; Gaskey, Bernard; Erlebacher, Jonah; Karma, Alain

    2015-11-01

    Liquid metal dealloying has emerged as a novel technique to produce topologically complex nanoporous and nanocomposite structures with ultra-high interfacial area and other unique properties relevant for diverse material applications. This process is empirically known to require the selective dissolution of one element of a multicomponent solid alloy into a liquid metal to obtain desirable structures. However, how structures form is not known. Here we demonstrate, using mesoscale phase-field modelling and experiments, that nano/microstructural pattern formation during dealloying results from the interplay of (i) interfacial spinodal decomposition, forming compositional domain structures enriched in the immiscible element, and (ii) diffusion-coupled growth of the enriched solid phase and the liquid phase into the alloy. We highlight how those two basic mechanisms interact to yield a rich variety of topologically disconnected and connected structures. Moreover, we deduce scaling laws governing microstructural length scales and dealloying kinetics.

  18. Quantification of interfacial segregation by analytical electron microscopy

    CERN Document Server

    Muellejans, H

    2003-01-01

    The quantification of interfacial segregation by spatial difference and one-dimensional profiling is presented in general where special attention is given to the random and systematic uncertainties. The method is demonstrated for an example of Al-Al sub 2 O sub 3 interfaces in a metal-ceramic composite material investigated by energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy in a dedicated scanning transmission electron microscope. The variation of segregation measured at different interfaces by both methods is within the uncertainties, indicating a constant segregation level and interfacial phase formation. The most important random uncertainty is the counting statistics of the impurity signal whereas the specimen thickness introduces systematic uncertainties (via k factor and effective scan width). The latter could be significantly reduced when the specimen thickness is determined explicitly. (orig.)

  19. The Interfacial-Area-Based Relative Permeability Function

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z. F.; Khaleel, Raziuddin

    2009-09-25

    CH2M Hill Plateau Remediation Company (CHPRC) requested the services of the Pacific Northwest National Laboratory (PNNL) to provide technical support for the Remediation Decision Support (RDS) activity within the Soil & Groundwater Remediation Project. A portion of the support provided in FY2009, was to extend the soil unsaturated hydraulic conductivity using an alternative approach. This alternative approach incorporates the Brooks and Corey (1964), van Genuchten (1980), and a modified van Genuchten water-retention models into the interfacial-area-based relative permeability model presented by Embid (1997). The general performance of the incorporated models is shown using typical hydraulic parameters. The relative permeability models for the wetting phase were further examined using data from literature. Results indicate that the interfacial-area-based model can describe the relative permeability of the wetting phase reasonably well.

  20. Mediated effect of ultrasound treated Diclofenac on mussel hemocytes: First evidence for the involvement of respiratory burst enzymes in the induction of DCF-mediated unspecific mode of action.

    Science.gov (United States)

    Toufexi, Eirini; Dailianis, Stefanos; Vlastos, Dimitris; Manariotis, Ioannis D

    2016-06-01

    The present study investigates the toxic behavior of diclofenac (DCF) before and after its ultrasound (US) treatment, as well as the involvement of intracellular target molecules, such as NADPH oxidase and NO synthase, in the DCF-induced adverse effects on hemocytes of mussel Mytilus galloprovincialis. In this context, appropriate volumes (350 and 500mL) of DCF solutions (at concentrations of 2, 2.5, 5 and 10mgL(-1)) were treated under different ultrasound operating conditions (frequency at 582 and 862kHz, electric power density at 133 and 167W) for assessing US method efficiency. In parallel, DCF and US DCF-mediated cytotoxic (in terms of cell viability measured with the use of neutral red uptake/NRU method), oxidative (in terms of superoxide anions/(.)O2(-), nitric oxides such as NO2(-) and lipid peroxidation products, such as malondialdehyde/MDA content) and genotoxic (DNA damage measured by the use of Comet assay method) effects were investigated in hemocytes exposed for 1h to 5, 10 and 100ngL(-1) and 1, 10 and 20μgL(-1) of DCF. The involvement of NADPH oxidase and NO synthase to the DCF-induced toxicity was further investigated by the use of 10μΜ L-NAME, a NO synthase inhibitor and 10μΜ DPI, a NADPH oxidase inhibitor. According to the results, 350mL of 2mgL(-1) DCF showed higher degradation (>50%) under 167W electric power density and frequency at 862kHz for 120min, compared to degradation in all other cases, followed by a significant elimination of its toxicity. Specifically, US DCF-treated hemocytes showed a significant attenuation of DCF-mediated cytotoxic, oxidative and genotoxic effects, which appeared to be caused by NADPH oxidase and NO synthase activation, since their inhibition was followed by a significant elimination of (.)O2(-) and NO2(-) generation and the concomitant oxidative damage within cells. The results of the present study showed for the first time that unspecific mode of action of DCF, associated with the induction of NADPH oxidase

  1. Food and feed enzymes.

    Science.gov (United States)

    Fraatz, Marco Alexander; Rühl, Martin; Zorn, Holger

    2014-01-01

    Humans have benefited from the unique catalytic properties of enzymes, in particular for food production, for thousands of years. Prominent examples include the production of fermented alcoholic beverages, such as beer and wine, as well as bakery and dairy products. The chapter reviews the historic background of the development of modern enzyme technology and provides an overview of the industrial food and feed enzymes currently available on the world market. The chapter highlights enzyme applications for the improvement of resource efficiency, the biopreservation of food, and the treatment of food intolerances. Further topics address the improvement of food safety and food quality.

  2. Enhanced esterification activity through interfacial activation and cross-linked immobilization mechanism of Rhizopus oryzae lipase in a nonaqueous medium.

    Science.gov (United States)

    Kartal, Funda

    2016-07-08

    Interfacial activation via surfactant (Tween 80, Triton X-100) treatment was conducted to improve the esterification activity of Rhizopus oryzae lipase that had undergone immobilization through cross-linked enzyme aggregates (CLEA®) technique. Surfactant pretreated immobilized enzymes exhibited better esterification activity compared to free and non-pretreated immobilized enzyme (Control CLEAs) since higher conversion rates were obtained within shorter times. The superiority of surfactant pretreated CLEAs, especially Tween 80 pretreated CLEAs (T 80 PT CLEAs), were clearly pronounced when longer alcohols were used as substrates. Conversion values exceeded 90% for octyl octanoate, oleyl octanoate and oleyl oleate synthesis with T 80 PT CLEAs whereas Control CLEAs and free enzyme showed no activity. Maximum conversions were achieved in the case equal molars of the substrates or in the case excess of the alcohol to acid in cyclohexane. In solvent free medium containing equal molars of substrates the conversion rates were 85% and 87% with T 80 PT CLEAs respectively for octyl octanoate and oleyl oleate within 2 hours. T 80 PT CLEAs showed 59% of its original activity after 7 consecutive usage for oleyl oleate synthesis. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:899-904, 2016. © 2016 American Institute of Chemical Engineers.

  3. The role of interfacial lipids in stabilizing membrane protein oligomers.

    Science.gov (United States)

    Gupta, Kallol; Donlan, Joseph A C; Hopper, Jonathan T S; Uzdavinys, Povilas; Landreh, Michael; Struwe, Weston B; Drew, David; Baldwin, Andrew J; Stansfeld, Phillip J; Robinson, Carol V

    2017-01-19

    Oligomerization of membrane proteins in response to lipid binding has a critical role in many cell-signalling pathways but is often difficult to define or predict. Here we report the development of a mass spectrometry platform to determine simultaneously the presence of interfacial lipids and oligomeric stability and to uncover how lipids act as key regulators of membrane-protein association. Evaluation of oligomeric strength for a dataset of 125 α-helical oligomeric membrane proteins reveals an absence of interfacial lipids in the mass spectra of 12 membrane proteins with high oligomeric stability. For the bacterial homologue of the eukaryotic biogenic transporters (LeuT, one of the proteins with the lowest oligomeric stability), we found a precise cohort of lipids within the dimer interface. Delipidation, mutation of lipid-binding sites or expression in cardiolipin-deficient Escherichia coli abrogated dimer formation. Molecular dynamics simulation revealed that cardiolipin acts as a bidentate ligand, bridging across subunits. Subsequently, we show that for the Vibrio splendidus sugar transporter SemiSWEET, another protein with low oligomeric stability, cardiolipin shifts the equilibrium from monomer to functional dimer. We hypothesized that lipids are essential for dimerization of the Na+/H+ antiporter NhaA from E. coli, which has the lowest oligomeric strength, but not for the substantially more stable homologous Thermus thermophilus protein NapA. We found that lipid binding is obligatory for dimerization of NhaA, whereas NapA has adapted to form an interface that is stable without lipids. Overall, by correlating interfacial strength with the presence of interfacial lipids, we provide a rationale for understanding the role of lipids in both transient and stable interactions within a range of α-helical membrane proteins, including G-protein-coupled receptors.

  4. Higher derivative free energy terms and interfacial curvatures

    OpenAIRE

    Mihailescu, M.

    2007-01-01

    High derivative terms do not play a major role in field theories because of the associated complexity and inherent difficulty in connecting these terms to physically measurable quantities. A role for higher derivative terms is analyzed for the case of field theories used to describe phase separated systems. In these theories, higher derivative terms are directly connected to an interfacial free energy which contains the mean and the Gaussian curvature and are shown to determine explicitly the...

  5. Shape Oscillations of Gas Bubbles With Newtonian Interfacial Rheological Properties

    Science.gov (United States)

    Nadim, Ali

    1996-01-01

    The oscillation frequency and damping rate for small-amplitude axisymmetric shape modes of a gas bubble in an ideal liquid are obtained, in the limit when the bubble interface possesses Newtonian interfacial rheology with constant surface shear and dilatational viscosities. Such results permit the latter surface properties to be measured by analyzing experimental data on frequency shift and damping rate of specific shape modes of suspended bubbles in the presence of surfactants.

  6. International Symposium on Interfacial Joining and Surface Technology (IJST2013)

    Science.gov (United States)

    Takahashi, Yasuo

    2014-08-01

    Interfacial joining (bonding) is a widely accepted welding process and one of the environmentally benign technologies used in industrial production. As the bonding temperature is lower than the melting point of the parent materials, melting of the latter is kept to a minimum. The process can be based on diffusion bonding, pressure welding, friction welding, ultrasonic bonding, or brazing-soldering, all of which offer many advantages over fusion welding. In addition, surface technologies such as surface modification, spraying, coating, plating, and thin-film formation are necessary for advanced manufacturing, fabrication, and electronics packaging. Together, interfacial joining and surface technology (IJST) will continue to be used in various industrial fields because IJST is a very significant form of environmentally conscious materials processing. The international symposium of IJST 2013 was held at Icho Kaikan, Osaka University, Japan from 27-29 November, 2013. A total of 138 participants came from around the world to attend 56 oral presentations and 36 posters presented at the symposium, and to discuss the latest research and developments on interfacial joining and surface technologies. This symposium was also held to commemorate the 30th anniversary of the Technical Commission on Interfacial Joining of the Japan Welding Society. On behalf of the chair of the symposium, it is my great pleasure to present this volume of IOP Conference Series: Materials Science and Engineering (MSE). Among the presentations, 43 papers are published here, and I believe all of the papers have provided the welding community with much useful information. I would like to thank the authors for their enthusiastic and excellent contributions. Finally, I would like to thank all members of the committees, secretariats, participants, and everyone who contributed to this symposium through their support and invaluable effort for the success of IJST 2013. Yasuo Takahashi Chair of IJST 2013

  7. Multiscale Random-Walk Algorithm for Simulating Interfacial Pattern Formation

    Energy Technology Data Exchange (ETDEWEB)

    Plapp, Mathis; Karma, Alain

    2000-02-21

    We present a novel computational method to simulate accurately a wide range of interfacial patterns whose growth is limited by a large-scale diffusion field. To illustrate the computational power of this method, we demonstrate that it can be used to simulate three-dimensional dendritic growth in a previously unreachable range of low undercoolings that is of direct experimental relevance. (c) 2000 The American Physical Society.

  8. Probing model tumor interfacial properties using piezoelectric cantilevers

    OpenAIRE

    Yegingil, Hakki; Shih, Wan Y.; Shih, Wei-Heng

    2010-01-01

    Invasive malignant breast cancers are typically branchy and benign breast tumors are typically smooth. It is of interest to characterize tumor branchiness (roughness) to differentiate invasive malignant breast cancer from noninvasive ones. In this study, we examined the shear modulus (G) to elastic modulus (E) ratio, G∕E, as a quantity to describe model tumor interfacial roughness using a piezoelectric cantilever capable of measuring both tissue elastic modulus and tissue shear modulus. The p...

  9. Bubble detachment assisted by electrowetting-driven interfacial wave

    Science.gov (United States)

    Xu, Haolun; Yan, Run; Wang, Sheng; Chen, Chung-Lung

    2017-10-01

    This article investigates both theoretically and numerically a novel mechanism of bubble detachment by an electrowetting-driven interfacial wave, inspired by droplet control and manipulation via electrowetting. Electrowetting-on-dielectric can be used to modulate the contact point movement at the water-air interface in a thin liquid film. Rapid oscillation of the contact line is achieved by a swift change of voltage under an AC signal. When disturbed with such contact angle changes, the interfacial wave between two immiscible fluids disrupts bubble dynamics. Numerical modeling reveals that an air bubble on a hydrophobic surface can be detached by the trough of such a wave. The frequency of the interfacial wave is twice the voltage frequency. A higher voltage frequency leads to a smaller amplitude and higher celerity of the wave, while a lower voltage frequency leads to a larger wave amplitude and lower celerity. The bubble can easily detach when the voltage frequency is 10 Hz. However, the bubble fails to detach when the voltage frequency is 100 Hz. This approach can be useful to improve two-phase cooling performance.

  10. Wettability controls slow immiscible displacement through local interfacial instabilities

    Science.gov (United States)

    Jung, Michael; Brinkmann, Martin; Seemann, Ralf; Hiller, Thomas; Sanchez de La Lama, Marta; Herminghaus, Stephan

    2016-11-01

    Immiscible fluid displacement with average front velocities in the capillary-dominated regime is studied in a transparent Hele-Shaw cell with cylindrical posts. Employing various combinations of fluids and wall materials allows us to cover a range of advancing contact angles 46∘≤θa≤180∘ of the invading fluid in our experiments. In parallel, we study the displacement process in particle-based simulations that account for wall wettability. Considering the same arrangement of posts in experiments and simulation, we find a consistent crossover between stable interfacial displacement at θa≲80∘ and capillary fingering at high contact angles θa≳120∘ . The position of the crossover is quantified through the evolution of the interface length and the final saturation of the displaced fluid. A statistical analysis of the local displacement processes demonstrates that the shape evolution of the fluid front is governed by local instabilities as proposed by Cieplak and Robbins for a quasistatic interfacial displacement [Cieplak and Robbins, Phys. Rev. Lett. 60, 2042 (1988), 10.1103/PhysRevLett.60.2042]. The regime of stable front advances coincides with a corresponding region of contact angles where cooperative interfacial instabilities prevail. Capillary fingering, however, is observed only for large θa, where noncooperative instabilities dominate the invasion process.

  11. Interfacial Materials for Organic Solar Cells: Recent Advances and Perspectives.

    Science.gov (United States)

    Yin, Zhigang; Wei, Jiajun; Zheng, Qingdong

    2016-08-01

    Organic solar cells (OSCs) have shown great promise as low-cost photovoltaic devices for solar energy conversion over the past decade. Interfacial engineering provides a powerful strategy to enhance efficiency and stability of OSCs. With the rapid advances of interface layer materials and active layer materials, power conversion efficiencies (PCEs) of both single-junction and tandem OSCs have exceeded a landmark value of 10%. This review summarizes the latest advances in interfacial layers for single-junction and tandem OSCs. Electron or hole transporting materials, including metal oxides, polymers/small-molecules, metals and metal salts/complexes, carbon-based materials, organic-inorganic hybrids/composites, and other emerging materials, are systemically presented as cathode and anode interface layers for high performance OSCs. Meanwhile, incorporating these electron-transporting and hole-transporting layer materials as building blocks, a variety of interconnecting layers for conventional or inverted tandem OSCs are comprehensively discussed, along with their functions to bridge the difference between adjacent subcells. By analyzing the structure-property relationships of various interfacial materials, the important design rules for such materials towards high efficiency and stable OSCs are highlighted. Finally, we present a brief summary as well as some perspectives to help researchers understand the current challenges and opportunities in this emerging area of research.

  12. Homocomposites of Polylactide (PLA) with Induced Interfacial Stereocomplex Crystallites.

    Science.gov (United States)

    Arias, Veluska; Odelius, Karin; Höglund, Anders; Albertsson, Ann-Christine

    2015-09-08

    The demand for "green" degradable composite materials increases with growing environmental awareness. The key challenge is achieving the preferred physical properties and maintaining their eco-attributes in terms of the degradability of the matrix and the filler. Herein, we have designed a series of "green" homocomposites materials based purely on polylactide (PLA) polymers with different structures. Film-extruded homocomposites were prepared by melt-blending PLA matrixes (which had different degrees of crystallinity) with PLLA and PLA stereocomplex (SC) particles. The PLLA and SC particles were spherical and with 300-500 nm size. Interfacial crystalline structures in the form of stereocomplexes were obtained for certain particulate-homocomposite formulations. These SC crystallites were found at the particle/matrix interface when adding PLLA particles to a PLA matrix with d-lactide units, as confirmed by XRD and DSC data analyses. For all homocomposites, the PLLA and SC particles acted as nucleating agents and enhanced the crystallization of the PLA matrixes. The SC particles were more rigid and had a higher Young's modulus compared with the PLLA particles. The mechanical properties of the homocomposites varied with particle size, rigidity, and the interfacial adhesion between the particles and the matrix. An improved tensile strength in the homocomposites was achieved from the interfacial stereocomplex formation. Hereafter, homocomposites with tunable crystalline arrangements and subsequently physical properties, are promising alternatives in strive for eco-composites and by this, creating materials that are completely degradable and sustainable.

  13. Homocomposites of Polylactide (PLA) with Induced Interfacial Stereocomplex Crystallites

    Science.gov (United States)

    2015-01-01

    The demand for “green” degradable composite materials increases with growing environmental awareness. The key challenge is achieving the preferred physical properties and maintaining their eco-attributes in terms of the degradability of the matrix and the filler. Herein, we have designed a series of “green” homocomposites materials based purely on polylactide (PLA) polymers with different structures. Film-extruded homocomposites were prepared by melt-blending PLA matrixes (which had different degrees of crystallinity) with PLLA and PLA stereocomplex (SC) particles. The PLLA and SC particles were spherical and with 300–500 nm size. Interfacial crystalline structures in the form of stereocomplexes were obtained for certain particulate-homocomposite formulations. These SC crystallites were found at the particle/matrix interface when adding PLLA particles to a PLA matrix with d-lactide units, as confirmed by XRD and DSC data analyses. For all homocomposites, the PLLA and SC particles acted as nucleating agents and enhanced the crystallization of the PLA matrixes. The SC particles were more rigid and had a higher Young’s modulus compared with the PLLA particles. The mechanical properties of the homocomposites varied with particle size, rigidity, and the interfacial adhesion between the particles and the matrix. An improved tensile strength in the homocomposites was achieved from the interfacial stereocomplex formation. Hereafter, homocomposites with tunable crystalline arrangements and subsequently physical properties, are promising alternatives in strive for eco-composites and by this, creating materials that are completely degradable and sustainable. PMID:26523245

  14. Modelling interfacial cracking with non-matching cohesive interface elements

    Science.gov (United States)

    Nguyen, Vinh Phu; Nguyen, Chi Thanh; Bordas, Stéphane; Heidarpour, Amin

    2016-11-01

    Interfacial cracking occurs in many engineering problems such as delamination in composite laminates, matrix/interface debonding in fibre reinforced composites etc. Computational modelling of these interfacial cracks usually employs compatible or matching cohesive interface elements. In this paper, incompatible or non-matching cohesive interface elements are proposed for interfacial fracture mechanics problems. They allow non-matching finite element discretisations of the opposite crack faces thus lifting the constraint on the compatible discretisation of the domains sharing the interface. The formulation is based on a discontinuous Galerkin method and works with both initially elastic and rigid cohesive laws. The proposed formulation has the following advantages compared to classical interface elements: (i) non-matching discretisations of the domains and (ii) no high dummy stiffness. Two and three dimensional quasi-static fracture simulations are conducted to demonstrate the method. Our method not only simplifies the meshing process but also it requires less computational demands, compared with standard interface elements, for problems that involve materials/solids having a large mismatch in stiffnesses.

  15. Polyaniline nanostructures tuning with oxidants in interfacial polymerization system

    Directory of Open Access Journals (Sweden)

    Fanxin Zeng

    2015-10-01

    Full Text Available Three kinds of nanostructured polyanilines (PANIs were prepared through interfacial polymerization by using ammonium persulfate (APS as a single oxidant, and APS/FeCl3, APS/K2Cr2O7 as composite oxidants, respectively. It is observed that faster formation process and higher yield of nanostructured PANIs could be achieved in the presence of FeCl3 and K2Cr2O7. The as-prepared PANIs were characterized by field emission scanning electron microscopy, ultraviolet–visible absorption spectroscopy, Fourier transform infrared and Raman spectroscopy, X-ray diffraction analysis and electrochemical measurements including cyclic voltammetry and galvanostatic charge/discharge measurement. The influence of composite oxidants on the morphology, microstructure, and electrical and electrochemical properties of PANIs was discussed. Interestingly, when APS/K2Cr2O7 was used as the composite oxidants, PANI exhibited petal-like structure with high yield of 57.35% instead of general nanofibrous morphology formed in interfacial polymerization. Compared with those nanofibrous PANIs obtained by using APS as a single oxidant or APS/FeCl3 as composite oxidants, petal-like PANIs exhibited the largest specific capacitance (692.4 F/g at scan rate of 5 mV/s and highest cycle stability among them. It provides a new insight into the control of PANI nanostructures with high yield and energy storage ability by simply selecting suitable composite oxidants in interfacial polymerization.

  16. Recent advances in interfacial engineering of perovskite solar cells

    Science.gov (United States)

    Ye, Meidan; He, Chunfeng; Iocozzia, James; Liu, Xueqin; Cui, Xun; Meng, Xiangtong; Rager, Matthew; Hong, Xiaodan; Liu, Xiangyang; Lin, Zhiqun

    2017-09-01

    Due to recent developments, organometallic halide perovskite solar cells (PSCs) have attracted even greater interest owing to their impressive photovoltaic properties and simple device manufacturing processes with the potential for commercial applications. The power conversion efficiencies (PCEs) of PSCs have surged from 3.8% for methyl ammonium lead halide-sensitized liquid solar cells, CH3NH3PbX3 (X  =  Cl, Br, I), in 2009, to more than 22% for all-solid-state solar cells in 2016. Over the past few years, significant effort has been dedicated to realizing PSCs with even higher performance. In this review, recent advances in the interfacial engineering of PSCs are addressed. The specific strategies for the interfacial engineering of PSCs fall into two categories: (1) solvent treatment and additives to improve the light-harvesting capabilities of perovskite films, and (2) the incorporation of various functional materials at the interfaces between the active layers (e.g. electron transporting layer, perovskite layer, and hole transporting layer). This review aims to provide a comprehensive overview of strategies for the interfacial engineering of PSCs with potential benefits including enhanced light harvesting, improved charge separation and transport, improved device stability, and elimination of photocurrent hysteresis.

  17. Action perception predicts action performance.

    Science.gov (United States)

    Bailey, Heather R; Kurby, Christopher A; Giovannetti, Tania; Zacks, Jeffrey M

    2013-09-01

    Everyday action impairments often are observed in demented older adults, and they are common potential barriers to functional independence. We evaluated whether the ability to segment and efficiently encode activities is related to the ability to execute activities. Further, we evaluated whether brain regions important for segmentation also were important for action performance. Cognitively healthy older adults and those with very mild or mild dementia of the Alzheimer's type watched and segmented movies of everyday activities and then completed the Naturalistic Action Test. Structural MRI was used to measure volume in the dorsolateral prefrontal cortex (DLPFC), medial temporal lobes (MTL), posterior cortex, and anterior cingulate cortex (ACC). Dementia status and the ability to segment everyday activities strongly predicted naturalistic action performance, and MTL volume largely accounted for this relationship. In addition, the current results supported the Omission-Commission Model: Different cognitive and neurological mechanisms predicted different types of action error. Segmentation, dementia severity, and MTL volume predicted everyday omission errors, DLPFC volume predicted commission errors, and ACC volume predicted action additions. These findings suggest that event segmentation may be critical for effective action production, and that the segmentation and production of activities may recruit the same event representation system. © 2013 Elsevier Ltd. All rights reserved.

  18. Nature and morphology of fumed oxides and features of interfacial phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Gun’ko, V.M., E-mail: vlad_gunko@ukr.net [Chuiko Institute of Surface Chemistry, 17 General Naumov Street, 03164 Kyiv (Ukraine); Zarko, V.I.; Goncharuk, O.V.; Matkovsky, A.K.; Remez, O.S. [Chuiko Institute of Surface Chemistry, 17 General Naumov Street, 03164 Kyiv (Ukraine); Skubiszewska-Zięba, J.; Wojcik, G. [Faculty of Chemistry, Maria Curie-Skłodowska University, 20-031 Lublin (Poland); Walusiak, B.; Blitz, J.P. [Eastern Illinois University, Department of Chemistry, Charleston, IL 61920 (United States)

    2016-03-15

    Graphical abstract: - Highlights: • Effects of oxide surface structure on interfacial behavior of nonpolar and polar adsorbates. • Confined space effects on freezing and melting temperatures of bound adsorbates. • Equilibrium adsorption and evaporation rate vs. structure of nanooxide adsorbents. - Abstract: Individual and complex fumed nanooxides were studied using high-resolution transmission electron microscopy, X-ray diffraction, ultraviolet-visible (UV–vis) spectroscopy, differential scanning calorimetry, nuclear magnetic resonance spectroscopy, adsorption, desorption (evaporation), and quantum chemical methods. For mixed nanooxides in contrast to simple and small nanoparticles of individual silica or titania, complex core–shell nanoparticles (50–200 nm in size) with titania or alumina cores and silica or alumina shells can be destroyed under high-pressure cryogelation (HPCG), mechnochemical activation (MCA) that also affect the structure of aggregates of nanoparticles and agglomerates of aggregates becoming more compacted. This is accompanied by changes in color from white to beige of different tints and changes in the UV–vis spectra in the 300–600 nm range, as well as changes in crystalline structure of alumina. Any treatment of ‘soft’ nanooxides affects the interfacial behavior of polar and nonpolar adsorbates. For some of them, the hysteresis loops become strongly open. Rearrangement of secondary particles affects the freezing-melting point depression. Clusterization of adsorbates bound in pores causes diminution of heat effects during phase transition (freezing, fusion). Freezing point depression and increasing melting point cause significant hysteresis freezing-melting effects for adsorbates bound to oxide nanoparticles. The study shows that complex nanooxides can be more sensitive to external actions than simple nanooxides such as silica.

  19. Interfacial phenomena at a surface of individual and complex fumed nanooxides.

    Science.gov (United States)

    Gun'ko, V M; Turov, V V; Zarko, V I; Goncharuk, O V; Pakhlov, E M; Skubiszewska-Zięba, J; Blitz, J P

    2016-09-01

    Investigations of interfacial and temperature behaviors of nonpolar and polar adsorbates interacting with individual and complex fumed metal or metalloid oxides (FMO), initial and subjected to various treatments or chemical functionalization and compared to such porous adsorbents as silica gels, precipitated silica, mesoporous ordered silicas, filled polymeric composites, were analyzed. Complex nanooxides include core-shell nanoparticles, CSNP (50-200nm in size) with titania or alumina cores and silica or alumina shells in contrast to simple and smaller nanoparticles of individual FMO. CSNP could be destroyed under high-pressure cryogelation (HPCG) or mechanochemical activation (MCA). These treatments affect the structure of aggregates of nanoparticles and agglomerates of aggregates, resulting in their becoming more compacted. The analysis shows that complex FMO could be more sensitive to external actions than simple nanooxides such as fumed silica. Any treatment of 'soft' FMO affects the interfacial and temperature behaviors of polar and nonpolar adsorbates. Rearrangement of secondary particles and surface functionalization affects the freezing-melting point depression of adsorbates. For some adsorbates, open hysteresis loops became readily apparent in adsorption-desorption isotherms. Clustering of adsorbates bound in textural pores in aggregates of nanoparticles (i.e., voids between nanoparticles in secondary structures) causes reduced changes in enthalpy during phase transitions (freezing, fusion, evaporation). Freezing point depression and melting point elevation cause significant hysteresis freezing-melting effects for adsorbates bound to FMO in the textural pores. Relaxation phenomena for both low- and high-molecular weight adsorbates or filled polymeric composites are affected by the morphology of primary particles, structural organization of secondary particles of differently treated or functionalized FMO, content of adsorbates, co-adsorption order, and

  20. Direct, Dynamic Measurement of Interfacial Area within Porous Media

    Energy Technology Data Exchange (ETDEWEB)

    Crandall, Dustin; Ahmadi, Goodarz; Smith, Duane H.; Bromhal, Grant

    2010-01-01

    Standard models of two-phase flow in porous media have been shown to exhibit several shortcomings that might be partially overcome with a recently developed model based on thermodynamic principles (Hassanizadeh and Gray, 1990). This alternative two-phase flow model contains a set of new and non-standard parameters, including specific interfacial area. By incorporating interfacial area production, destruction, and propagation into functional relationships that describe the capillary pressure and saturation, a more physical model has been developed. Niessner and Hassanizadeh (2008) have examined this model numerically and have shown that the model captures saturation hysteresis with drainage/imbibition cycles. Several static experimental studies have been performed to examine the validity of this new thermodynamically based approach; these allow the determination of static parameters of the model. To date, no experimental studies have obtained information about the dynamic parameters required for the model. A new experimental porous flow cell has been constructed using stereolithography to study two-phase flow phenomena (Crandall et al. 2008). A novel image analysis tool was developed for an examination of the evolution of flow patterns during displacement experiments (Crandall et al. 2009). This analysis tool enables the direct quantification of interfacial area between fluids by matching known geometrical properties of the constructed flow cell with locations identified as interfaces from images of flowing fluids. Numerous images were obtained from two-phase experiments within the flow cell. The dynamic evolution of the fluid distribution and the fluid-fluid interface locations were determined by analyzing these images. In this paper, we give a brief introduction to the thermodynamically based two-phase flow model, review the properties of the stereolithography flow cell, and show how the image analysis procedure has been used to obtain dynamic parameters for the

  1. INTERFACIAL AREA TRANSPORT AND REGIME TRANSITION IN COMBINATORIAL CHANNELS

    Energy Technology Data Exchange (ETDEWEB)

    Seugjin Kim

    2011-01-28

    . This study investigates the geometric effects of 90-degree vertical elbows and flow configurations in two-phase flow. The study shows that the elbows make a significant effect on the transport characteristics of two-phase flow, which includes the changes in interfacial structures, bubble interaction mechanisms and flow regime transition. The effect of the elbows is characterized for global and local two-phase flow parameters. The global two-phase flow parameters include two-phase pressure, interfacial structures and flow regime transition. In order to characterize the frictional pressure drop and minor loss across the vertical elbows, pressure measurements are obtained across the test section over a wide range of flow conditions in both single-phase and two-phase flow conditions. A two-phase pressure drop correlation analogous to Lockhart-Martinelli correlation is proposed to predict the minor loss across the elbows. A high speed camera is employed to perform extensive flow visualization studies across the elbows in vertical upward, horizontal and vertical downward sections and modified flow regime maps are proposed. It is found that modified flow regime maps immediately downstream of the vertical upward elbow deviate significantly from the conventional flow regime map. A qualitative assessment of the counter-current flow limitation characteristics specific to the current experimental facility is performed. A multi-sensor conductivity probe is used to measure local two-phase flow parameters such as: void fraction, bubble velocity, interfacial area concentration and bubble frequency. The local measurements are obtained for six different flow conditions at ten measurement locations along axial direction of the test section. Both the vertical-upward and vertical-downward elbows have a significant impact on bubble distribution, resulting in, a bimodal distribution along the horizontal radius of the tube cross-section and migration of bubbles towards the inside of the

  2. Determination of interfacial tension of binary mixtures from perturbative approaches

    Science.gov (United States)

    Martínez-Ruiz, F. J.; Blas, F. J.

    2015-05-01

    We determine the interfacial properties of mixtures of spherical Lennard-Jones molecules from direct simulation of the vapour-liquid interface. We consider mixtures with same molecular size but different dispersive energy parameter values. We use the extensions of the improved version of the inhomogeneous long-range corrections of Janeček, presented recently by MacDowell and Blas and Martínez-Ruiz et al., to deal with the interaction energy and microscopic components of the pressure tensor. We have performed Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of mixtures of Lennard-Jones molecules with a cut-off distance rc = 3σ in combination with the inhomogeneous long-range corrections. The pressure tensor is obtained using the mechanical (virial) and thermodynamic route. The vapour-liquid interfacial tension is also evaluated using three different procedures, the Irving-Kirkwood method, the difference between the macroscopic components of the pressure tensor, and the test-area methodology. This allows to check the validity of the recent extensions presented to deal with the contributions due to long-range corrections for intermolecular energy and pressure tensor in the case of binary mixtures. In addition to the pressure tensor and the surface tension, we also obtain density profiles, coexistence densities, and interfacial thickness as functions of pressure, at a given temperature. According to our results, the main effect of increasing the ratio between the dispersive energy parameters of the mixture, ε22/ε11, is to sharpen the vapour-liquid interface and to increase the width of the biphasic coexistence region. Particularly interesting is the presence of a relative maximum in the density profiles of the less volatile component at the interface. This maximum is related with adsorption or accumulation of these molecules at the interface, a direct consequence of stronger attractive interactions between these molecules in

  3. Enzymes in Fermented Fish.

    Science.gov (United States)

    Giyatmi; Irianto, H E

    Fermented fish products are very popular particularly in Southeast Asian countries. These products have unique characteristics, especially in terms of aroma, flavor, and texture developing during fermentation process. Proteolytic enzymes have a main role in hydrolyzing protein into simpler compounds. Fermentation process of fish relies both on naturally occurring enzymes (in the muscle or the intestinal tract) as well as bacteria. Fermented fish products processed using the whole fish show a different characteristic compared to those prepared from headed and gutted fish. Endogenous enzymes like trypsin, chymotrypsin, elastase, and aminopeptidase are the most involved in the fermentation process. Muscle tissue enzymes like cathepsins, peptidases, transaminases, amidases, amino acid decarboxylases, glutamic dehydrogenases, and related enzymes may also play a role in fish fermentation. Due to the decreased bacterial number during fermentation, contribution of microbial enzymes to proteolysis may be expected prior to salting of fish. Commercial enzymes are supplemented during processing for specific purposes, such as quality improvement and process acceleration. In the case of fish sauce, efforts to accelerate fermentation process and to improve product quality have been studied by addition of enzymes such as papain, bromelain, trypsin, pepsin, and chymotrypsin. © 2017 Elsevier Inc. All rights reserved.

  4. Amperometric enzyme electrodes

    OpenAIRE

    Calvo,E.J.; Danilowicz, C.

    1997-01-01

    Recent advances on amperometric enzyme electrodes are reviewed with particular emphasis on biosensors based on Glucose Oxidase and Horseradish Peroxidase. Redox mediation by artificial soluble and polymer attached redox mediators is discussed in terms of recent theoretical developments and experimental verification. The dependence of the amperometric response on substrate and mediator concentration, enzyme concentration, electrode potential and film thickness are analyzed. Possible applicatio...

  5. Enzyme Vs. Extremozyme -32 ...

    Indian Academy of Sciences (India)

    industries, while Taq polymerase T 4 lysozyme, ribonuclease and malate dehydrogenase are enzymes used in research laboratories. A major limitation of most enzymes used in the industries/ research .... pol 1 , (8) Small domain of Klentaq 1 and (C) Superimposed cluster of aromatic residues in K1entaq1. (thick lines) ...

  6. An interfacial shear term evaluation study for adiabatic dispersed air–water two-phase flow with the two-fluid model using CFD

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, S.L., E-mail: sharma55@purdue.edu [School of Nuclear Engineering, Purdue University, West Lafayette, IN (United States); Hibiki, T.; Ishii, M. [School of Nuclear Engineering, Purdue University, West Lafayette, IN (United States); Schlegel, J.P. [Department of Mining and Nuclear Engineering, Missouri University of Science and Technology, Rolla, MO (United States); Buchanan, J.R.; Hogan, K.J. [Bettis Laboratory, Naval Nuclear Laboratory, West Mifflin, PA (United States); Guilbert, P.W. [ANSYS UK Ltd, Oxfordshire (United Kingdom)

    2017-02-15

    Highlights: • Closure form of the interfacial shear term in three-dimensional form is investigated. • Assessment against adiabatic upward bubbly air–water flow data using CFD. • Effect of addition of the interfacial shear term on the phase distribution. - Abstract: In commercially available Computational Fluid Dynamics (CFD) codes such as ANSYS CFX and Fluent, the interfacial shear term is missing in the field momentum equations. The derivation of the two-fluid model (Ishii and Hibiki, 2011) indicates the presence of this term as a momentum source in the right hand side of the field momentum equation. The inclusion of this term is considered important for proper modeling of the interfacial momentum coupling between phases. For separated flows, such as annular flow, the importance of the shear term is understood in the one-dimensional (1-D) form as the major mechanism by which the wall shear is transferred to the gas phase (Ishii and Mishima, 1984). For gas dispersed two-phase flow CFD simulations, it is important to assess the significance of this term in the prediction of phase distributions. In the first part of this work, the closure of this term in three-dimensional (3-D) form in a CFD code is investigated. For dispersed gas–liquid flow, such as bubbly or churn-turbulent flow, bubbles are dispersed in the shear layer of the continuous phase. The continuous phase shear stress is mainly due to the presence of the wall and the modeling of turbulence through the Boussinesq hypothesis. In a 3-D simulation, the continuous phase shear stress can be calculated from the continuous fluid velocity gradient, so that the interfacial shear term can be closed using the local values of the volume fraction and the total stress of liquid phase. This form also assures that the term acts as an action-reaction force for multiple phases. In the second part of this work, the effect of this term on the volume fraction distribution is investigated. For testing the model two

  7. Effect of protein load on stability of immobilized enzymes.

    Science.gov (United States)

    Fernandez-Lopez, Laura; Pedrero, Sara G; Lopez-Carrobles, Nerea; Gorines, Beatriz C; Virgen-Ortíz, Jose J; Fernandez-Lafuente, Roberto

    2017-03-01

    Different lipases have been immobilized on octyl agarose beads at 1mg/g and at maximum loading, via physical interfacial activation versus the octyl layer on the support. The stability of the preparations was analyzed. Most biocatalysts had the expected result: the apparent stability increased using the highly loaded preparations, due to the diffusional limitations that reduced the initial observed activity. However, lipase B from Candida antarctica (CALB) was significantly more stable using the lowly loaded preparation than the maximum loaded one. This negative effect of the enzyme crowding on enzyme stability was found in inactivations at pH 5, 7 or 9, but not in inactivations in the presence of organic solvents. The immobilization using ethanol to reduce the immobilization rate had no effect on the stability of the lowly loaded preparation, while the highly loaded enzyme biocatalysts increased their stabilities, becoming very similar to that of the lowly loaded preparation. Results suggested that CALB molecules immobilized on octyl agarose may be closely packed together due to the high immobilization rate and this produced some negative interactions between immobilized enzyme molecules during enzyme thermal inactivation. Slowing-down the immobilization rate may be a solution for this unexpected problem. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. Maximising the Interfacial Fracture Toughness of Thin Coatings and Substrate through Optimisation of Defined Parameters

    OpenAIRE

    Khan, Zulfiqar Ahmad; Nazir, M.H.

    2015-01-01

    The influence of three parameters i.e. interfacial roughness, coating thickness and the size of impurity at the interface on interfacial fracture toughness has been investigated within the framework of two approaches i.e. thermodynamics and fracture mechanics. Mathematical relationship for both the approaches have been designed independently and then fused to form a governing law for evaluating the interfacial toughness. Simulation techniques founded on the experimental studies, have been dev...

  9. CELLULOSE DEGRADATION BY OXIDATIVE ENZYMES

    Directory of Open Access Journals (Sweden)

    Maria Dimarogona

    2012-09-01

    Full Text Available Enzymatic degradation of plant biomass has attracted intensive research interest for the production of economically viable biofuels. Here we present an overview of the recent findings on biocatalysts implicated in the oxidative cleavage of cellulose, including polysaccharide monooxygenases (PMOs or LPMOs which stands for lytic PMOs, cellobiose dehydrogenases (CDHs and members of carbohydrate-binding module family 33 (CBM33. PMOs, a novel class of enzymes previously termed GH61s, boost the efficiency of common cellulases resulting in increased hydrolysis yields while lowering the protein loading needed. They act on the crystalline part of cellulose by generating oxidized and non-oxidized chain ends. An external electron donor is required for boosting the activity of PMOs. We discuss recent findings concerning their mechanism of action and identify issues and questions to be addressed in the future.

  10. Cellulose degradation by oxidative enzymes

    Directory of Open Access Journals (Sweden)

    Maria Dimarogona

    2012-09-01

    Full Text Available Enzymatic degradation of plant biomass has attracted intensive research interest for the production of economically viable biofuels. Here we present an overview of the recent findings on biocatalysts implicated in the oxidative cleavage of cellulose, including polysaccharide monooxygenases (PMOs or LPMOs which stands for lytic PMOs, cellobiose dehydrogenases (CDHs and members of carbohydrate-binding module family 33 (CBM33. PMOs, a novel class of enzymes previously termed GH61s, boost the efficiency of common cellulases resulting in increased hydrolysis yields while lowering the protein loading needed. They act on the crystalline part of cellulose by generating oxidized and non-oxidized chain ends. An external electron donor is required for boosting the activity of PMOs. We discuss recent findings concerning their mechanism of action and identify issues and questions to be addressed in the future.

  11. Salinity Influence on Interfacial Area, Wettability, and NAPL Recovery

    Science.gov (United States)

    Zhong, L.; Valenta, M. M.

    2007-12-01

    Wettability, the tendency of rock or sediment particle surfaces to be preferentially wet by one fluid phase, has a strong influence on the distribution and flow of immiscible fluids in oil reservoirs or aquifers. The efficiency of oil and non-aqueous phase liquid (NAPL) recovery processes and the displacement and production of oil/NAPL by fluids injected into the reservoir or aquifer depend on the wetting properties of the rock/sediment particle surfaces. Effects of salinity on wettability and residual oil saturation during water flooding are of particular interest in the petroleum industry with some reservoirs. It was indicated that the residual oil saturation may be reduced significantly by flooding with low salinity water instead of seawater or brine. This observation may be also true in NAPL recovery from contaminated aquifers. NAPL recovery enhancement may be achieved by manipulating the salinity of the remedial fluid. Two sets of 8 core-flooding column experiments have been completed, using decane and Alaska North Slope (ANS) crude oil as surrogate NAPLs. Unconsolidated sand packs were used as representative porous media. NAPL removal was conducted by flushing column at residual NAPL saturation using water with salinity ranging from 0% to 8% wt of NaCl. The NAPL-water interfacial area (anw, cm-1) was measured and used as an indicator for the wettability characteristics of the packed sand. Sodium Dodecyl Benzene Sulfonate (SDBS) was used as an interfacial partitioning tracer and Pentafluoro Benzoic acid (PFBA) was used as a non-reactive and non-partitioning tracer. NAPL was imbibed into an initially water saturated column, using positive displacement methods. NAPL was then flushed out using water at certain salinity. When the column attained a residual NAPL saturation after each water flushing displacement, the partitioning and conservative tracer experiments were conducted separately, to characterize the specific NAPL-water interfacial areas, and the

  12. Action Refinement

    NARCIS (Netherlands)

    Gorrieri, R.; Rensink, Arend; Bergstra, J.A.; Ponse, A.; Smolka, S.A.

    2001-01-01

    In this chapter, we give a comprehensive overview of the research results in the field of action refinement during the past 12 years. The different approaches that have been followed are outlined in detail and contrasted to each other in a uniform framework. We use two running examples to discuss

  13. SH ultrasonic guided waves for the evaluation of interfacial adhesion.

    Science.gov (United States)

    Castaings, Michel

    2014-09-01

    Shear-Horizontally (SH) polarized, ultrasonic, guided wave modes are considered in order to infer changes in the adhesive properties at several interfaces located within an adhesive bond joining two metallic plates. Specific aluminium lap-joint samples were produced, with different adhesive properties at up to four interfaces when a glass-epoxy film is inserted into the adhesive bond. EMAT transducers were used to generate and detect the fundamental SH0 mode. This is launched from one plate and detected at the other plate, past the lap joint. Signals are picked up for different propagation paths along each sample, in order to check measurement reproducibility as well as the uniformity of the adhesively bonded zones. Signals measured for four samples are then compared, showing very good sensitivity of the SH0 mode to changes in the interfacial adhesive properties. In addition, a Finite Element-based model is used to simulate the experimental measurements. The model includes adhesive viscoelasticity, as well as spatial distributions of shear springs (with shear stiffness KT) at both metal-adhesive interfaces, and also at the adhesive-film interfaces when these are present. This model is solved in the frequency domain, but temporal excitation and inverse FFT procedure are implemented in order to simulate the measured time traces. Values of the interfacial adhesive parameters, KT, are determined by an optimization process so that best fit is obtained between both sets of measured and numerically predicted waveforms. Such agreement was also possible by adjusting the shear modulus of the adhesive component. This work suggests a promising use of SH-like guided modes for quantifying shear properties at adhesive interfaces, and shows that such waves can be used for inferring adhesive and cohesive properties of bonds separately. Finally, the paper considers improvements that could be made to the process, and its potential for testing the interfacial adhesion of adhesively

  14. Biomimetic construction of cellular shell by adjusting the interfacial energy.

    Science.gov (United States)

    Wang, Ben; Liu, Peng; Liu, Zhaoming; Pan, Haihua; Xu, Xurong; Tang, Ruikang

    2014-02-01

    Many unicellular organisms take their outer proteinaceous and lipidic membranes or carbonhydrate-rich cell walls as a template for biomineralization to synthesize a thin mineral layer as a functional covering. In nature most cells cannot be mineralized spontaneously in the normal states. Inspired by nature, we develop cytocompatible methods for cells encapsulated inside a mineral shell, called "cellular shellization." Using Layer-by-Layer (LbL) assembly, the precipitation of calcium minerals can be induced on the yeast cell surfaces. The effects of different synthetic polyelectrolytes on the calcifications of yeast, such as interfacial energy, zeta-potential, introduction time, and the affinity of mineral phase on the yeast cell surface have been studied by using constant composition method (CC) systemically and quantitatively. The results demonstrate that the effective adsorption of polyelectrolytes with carboxyl or sulfonate-rich groups on the yeast can enhance mineralization abilities of yeast cells readily, and the factor of interfacial energy plays a key role in the superficial mineralization of the cells. Furthermore, the influences of ion concentrations, as well as titration rates on the formation of inorganic shell, have also been examined. It is found that the biomimetic shell formation on the cell can also be achieved by using an appropriate selection of titration conditions rather than the pretreatment of LbL. Thus, the control of cellular biomineralization can become more feasible. In this study, we show that adjusting the interfacial energy is the key to cellular mineralization and suggest that these biomineralization treatments of single-cell may be applied as a potential and universal approach for cell-based sensing and therapy. © 2013 Wiley Periodicals, Inc.

  15. Indicators: Sediment Enzymes

    Science.gov (United States)

    Sediment enzymes are proteins that are produced by microorganisms living in the sediment or soil. They are indicators of key ecosystem processes and can help determine which nutrients are affecting the biological community of a waterbody.

  16. Starch Biorefinery Enzymes.

    Science.gov (United States)

    Läufer, Albrecht

    2017-03-07

    Nature uses enzymes to build and convert biomass; mankind uses the same enzymes and produces them on a large scale to make optimum use of biomass in biorefineries. Bacterial α-amylases and fungal glucoamylases have been the workhorses of starch biorefineries for many decades. Pullulanases were introduced in the 1980s. Proteases, cellulases, hemicellulases, and phytases have been on the market for a few years as process aids, improving yields, performance, and costs. Detailed studies of the complex chemical structures of biomass and of the physicochemical limitations of industrial biorefineries have led enzyme developers to produce novel tailor-made solutions for improving yield and profitability in the industry. This chapter reviews the development of enzyme applications in the major starch biorefining processes.

  17. Advances in enzyme immobilisation

    CSIR Research Space (South Africa)

    Brady, D

    2009-07-10

    Full Text Available substrate to fix the structure of cyclodextrin glycosyltransferases during rigidification by immobilisation, thereby enhancing the synthetic capability of the enzyme relative to its hydrolytic activity. In particular, modulation of enzyme... aggregates for enantioselective nitrile hydrolysis. Adv Synth Catal 349:2167- 2176 Kaulpiboon J, Pongsawasdi P, Zimmermann W (2007) Molecular imprinting of cyclodextrin glycosyltransferases from Paenibacillus sp. A11 and Bacillus macerans with γ-cyclodextrin...

  18. Overproduction of ligninolytic enzymes

    Science.gov (United States)

    Elisashvili, Vladimir; Kachlishvili, Eva; Torok, Tamas

    2014-06-17

    Methods, compositions, and systems for overproducing ligninolytic enzymes from the basidiomycetous fungus are described herein. As described, the method can include incubating a fungal strain of Cerrena unicolor IBB 303 in a fermentation system having growth medium which includes lignocellulosic material and then cultivating the fungal strain in the fermentation system under conditions wherein the fungus expresses the ligninolytic enzymes. In some cases, the lignocellulosic material is mandarin peel, ethanol production residue, walnut pericarp, wheat bran, wheat straw, or banana peel.

  19. Exploiting interfacial water properties for desalination and purification applications.

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Hongwu (Los Alamos National Laboratory, Los Alamos, NM); Varma, Sameer; Nyman, May Devan; Alam, Todd Michael; Thuermer, Konrad; Holland, Gregory P.; Leung, Kevin; Liu, Nanguo (University of New Mexico Albuquerque, NM); Xomeritakis, George K. (University of New Mexico Albuquerque, NM); Frankamp, Benjamin L.; Siepmann, J. Ilja (University of Minnesota, Minneapolis, MN); Cygan, Randall Timothy; Hartl, Monika A. (Los Alamos National Laboratory, Los Alamos, NM); Travesset, Alex (Iowa State University, Ames, IA); Anderson, Joshua A. (Iowa State University, Ames, IA); Huber, Dale L.; Kissel, David J. (University of New Mexico Albuquerque, NM); Bunker, Bruce Conrad; Lorenz, Christian Douglas; Major, Ryan C. (University of Minnesota, Minneapolis, MN); McGrath, Matthew J. (University of Minnesota, Minneapolis, MN); Farrow, Darcie; Cecchi, Joseph L. (University of New Mexico Albuquerque, NM); van Swol, Frank B.; Singh, Seema; Rempe, Susan B.; Brinker, C. Jeffrey; Clawson, Jacalyn S.; Feibelman, Peter Julian; Houston, Jack E.; Crozier, Paul Stewart; Criscenti, Louise Jacqueline; Chen, Zhu (University of New Mexico Albuquerque, NM); Zhu, Xiaoyang (University of Minnesota, Minneapolis, MN); Dunphy, Darren Robert (University of New Mexico Albuquerque, NM); Orendorff, Christopher J.; Pless, Jason D.; Daemen, Luke L. (Los Alamos National Laboratory, Los Alamos, NM); Gerung, Henry (University of New Mexico Albuquerque, NM); Ockwig, Nathan W.; Nenoff, Tina Maria; Jiang, Ying-Bing; Stevens, Mark Jackson

    2008-09-01

    A molecular-scale interpretation of interfacial processes is often downplayed in the analysis of traditional water treatment methods. However, such an approach is critical for the development of enhanced performance in traditional desalination and water treatments. Water confined between surfaces, within channels, or in pores is ubiquitous in technology and nature. Its physical and chemical properties in such environments are unpredictably different from bulk water. As a result, advances in water desalination and purification methods may be accomplished through an improved analysis of water behavior in these challenging environments using state-of-the-art microscopy, spectroscopy, experimental, and computational methods.

  20. Infiltration Kinetics and Interfacial Bond Strength of Metal Matrix Composites

    Science.gov (United States)

    1992-07-01

    in Surf. and Membrane Sci., 14 (1981), 353. 11. N. Erg, and A. W. Hennicke, "Ceramics in Advanced Enerrv Technologies", ed. H. Krockel et al...OLSON, G. P. MARTIN and GBR . Brazing Metallurgy a surface that is oxide-free, or with a very EDWARDS arer teCeterothin oxide layer which readily decom...JANAF Thermochemical Tables, 2nd ed., U.S. Dept. of Commerce, 1977, pp. 20-257. solid-vapor interfacial energy 6. Yu. Naidich: Prog. Surf. Membrane Sci

  1. A demonstration of enhancements in interfacial rheological characterisations

    DEFF Research Database (Denmark)

    Hodder, Peter; Baldursdottir, Stefania G.

    proteins can be studied as well as the typically used model proteins as bovine serum albumin (BSA) and lysozyme. Previously there was a need for high enough concentrations to produce a signal strong enough to be measured, a limitation of the technology to date. With the introduction of the new Discovery...... we have compared the performance of two models of the new Discovery Hybrid Rheometer and the AR G2 rheometer when studying the interfacial adsorption of lysozyme (from hen egg white, Sigma-Aldrich, Denmark) using the double wall ring geometry. The results show great improvement in the detection limit...

  2. Controlling Interdiffusion, Interfacial Composition, and Adhesion in Polymer Solar Cells

    KAUST Repository

    Dupont, Stephanie R.

    2014-07-10

    © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. NEXAFS spectroscopy is used to precisely quantify the interfacial composition and P3HT chain orientation at the weak P3HT:PCBM/PEDOT:PSS interface. An increase of P3HT:PCBM and PEDOT:PSS interdiffusion with post electrode deposition annealing time and temperature is found to be the underlying mechanism for effectively improving the interlayer adhesion, which is essential for the commercial realization of organic photovoltaic devices.

  3. POROUS MICROSTRUCTURE OF THE INTERFACIAL TRANSITION ZONE IN GEOPOLYMER COMPOSITES

    Directory of Open Access Journals (Sweden)

    Steinerová M.

    2013-12-01

    Full Text Available The study deals with a comparison of the differences in the structure, composition and micromechanical properties of a metakaolinite geopolymer composite matrix, inside and outside of the interfacial transition zone (ITZ with quartz grains of added silica sand. The microstructure is investigated by a measurement of the mercury porosimetry, microscopy and by a measurement in SEM and AFM, completed by Raman spectroscopy. Weaker mechanical properties, micropores in the ITZ, a higher concentration of Al atoms and hydroxyl groups than in the ambient matrix were detected. The water transport is probably the reason for the micropore formation, caused by disequilibrium in the course of solid-phase building from geopolymer dispersion.

  4. Interfacial nanobubbles produced by long-time preserved cold water

    Science.gov (United States)

    Zhou, Li-Min; Wang, Shuo; Qiu, Jie; Wang, Lei; Wang, Xing-Ya; Li, Bin; Zhang, Li-Juan; Hu, Jun

    2017-09-01

    Not Available Project supported by the Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, the Open Research Project of the Large Scientific Facility of the Chinese Academy of Sciences, the National Natural Science Foundation of China (Grant Nos. 11079050, 11290165, 11305252, 11575281, and U1532260), the National Key Basic Research Program of China (Grant Nos. 2012CB825705 and 2013CB932801), the National Natural Science Foundation for Outstanding Young Scientists, China (Grant No. 11225527), the Shanghai Academic Leadership Program, China (Grant No. 13XD1404400), and the Program of the Chinese Academy of Sciences (Grant Nos. KJCX2-EW-W09 and QYZDJ-SSW-SLH019)

  5. Theory of Interfacial Tension of Partially Miscible Liquids

    OpenAIRE

    Boudh-Hir, M. -E.; Mansoori, G. A.

    2017-01-01

    The aim of this work is to study the problem of the existence of a fundamental relation between the interfacial tension of a system of two partially miscible liquids and the surface tensions of the pure substances. It is shown that these properties cannot be correlated from the physical point of view. However, an accurate relation between them may be developed using a mathematical artifact. In the light of this work, the basis of the empirical formula of Girifalco and Good is examined. The we...

  6. Interfacial jetting phenomena induced by focused surface vibrations.

    Science.gov (United States)

    Tan, Ming K; Friend, James R; Yeo, Leslie Y

    2009-07-10

    We exploit large accelerations associated with surface acoustic waves to drive an extraordinary fluid jetting phenomena. Laterally focusing the acoustic energy to a small region beneath a drop placed on the surface causes rapid interfacial destabilization. Above a critical Weber number We, an elongated jet forms for drops with dimensions greater than the fluid sound wavelength. Further increases in We lead to single droplet pinch-off and subsequent axisymmetric breakup to form multiple droplets. A simple equation based on a momentum balance is derived to predict the jet velocity.

  7. Nanoscale and single-molecule interfacial electron transfer

    DEFF Research Database (Denmark)

    Hansen, Allan Glargaard; Wackerbarth, Hainer; Nielsen, Jens Ulrik

    2003-01-01

    Electrochemical science and technology in the 21st century have reached high levels of sophistication. A fundamental quantum mechanical theoretical frame for interfacial electrochemical electron transfer (ET) was introduced by Revaz Dogonadze. This frame has remained for four decades as a basis...... for comprehensive later theoretical work and data interpretation in many areas of chemistry, electrochemistry, and biology. We discuss here some new areas of theoretical electrochemical ET science, with focus on nanoscale electrochemical and bioelectrochemical sciences. Particular attention is given to in situ...

  8. Action of plant proteinase inhibitors on enzymes of physiopathological importance

    Directory of Open Access Journals (Sweden)

    Maria Luiza V. Oliva

    2009-09-01

    Full Text Available Obtained from leguminous seeds, various plant proteins inhibit animal proteinases, including human, and can be considered for the development of compounds with biological activity. Inhibitors from the Bowman-Birk and plant Kunitz-type family have been characterized by proteinase specificity, primary structure and reactive site. Our group mostly studies the genus Bauhinia, mainly the species bauhinioides, rufa, ungulata and variegata. In some species, more than one inhibitor was characterized, exhibiting different properties. Although proteins from this group share high structural similarity, they present differences in proteinase inhibition, explored in studies using diverse biological models.Obtidas de sementes leguminosas, várias proteínas inibem proteinases de origem animal, incluindo humanas, e podem ser consideradas para o desenvolvimento de compostos com atividade biológica. Inibidores da família Bowman-Birk e da família Kunitz vegetal tem sido caracterizados em relação a especificidade para proteinase, estrutura primária e sitio reativo. O nosso grupo majoritariamente vem estudando o gênero Bauhinia, principalmente as espécies bauhinioides, rufa, ungulatae variegata. Em algumas espécies, mais de um inibidor com propriedades diferentes foi caracterizado. Embora tais proteínas apresentem alta similaridade estrutural, diferem quanto à inibição de proteinases, e foram exploradas em estudos utilizando diversos modelos biológicos.

  9. Actionable Nuggets

    Science.gov (United States)

    McColl, Mary Ann; Aiken, Alice; Smith, Karen; McColl, Alexander; Green, Michael; Godwin, Marshall; Birtwhistle, Richard; Norman, Kathleen; Brankston, Gabrielle; Schaub, Michael

    2015-01-01

    Abstract Objective To present the results of a pilot study of an innovative methodology for translating best evidence about spinal cord injury (SCI) for family practice. Design Review of Canadian and international peer-reviewed literature to develop SCI Actionable Nuggets, and a mixed qualitative-quantitative evaluation to determine Nuggets’ effect on physician knowledge of and attitudes toward patients with SCI, as well as practice accessibility. Setting Ontario, Newfoundland, and Australia. Participants Forty-nine primary care physicians. Methods Twenty Actionable Nuggets (pertaining to key health issues associated with long-term SCI) were developed. Nugget postcards were mailed weekly for 20 weeks to participating physicians. Prior knowledge of SCI was self-rated by participants; they also completed an online posttest to assess the information they gained from the Nugget postcards. Participants’ opinions about practice accessibility and accommodations for patients with SCI, as well as the acceptability and usefulness of Nuggets, were assessed in interviews. Main findings With Actionable Nuggets, participants’ knowledge of the health needs of patients with SCI improved, as knowledge increased from a self-rating of fair (58%) to very good (75%) based on posttest quiz results. The mean overall score for accessibility and accommodations in physicians’ practices was 72%. Participants’ awareness of the need for screening and disease prevention among this population also increased. The usefulness and acceptability of SCI Nugget postcards were rated as excellent. Conclusion Actionable Nuggets are a knowledge translation tool designed to provide family physicians with concise, practical information about the most prevalent and pressing primary care needs of patients with SCI. This evidence-based resource has been shown to be an excellent fit with information consumption processes in primary care. They were updated and adapted for distribution by the Canadian

  10. Substrate-induced interfacial plasmonics for photovoltaic conversion

    Science.gov (United States)

    Li, Xinxi; Jia, Chuancheng; Ma, Bangjun; Wang, Wei; Fang, Zheyu; Zhang, Guoqing; Guo, Xuefeng

    2015-01-01

    Surface plasmon resonance (SPR) is widely used as light trapping schemes in solar cells, because it can concentrate light fields surrounding metal nanostructures and realize light management at the nanoscale. SPR in photovoltaics generally occurs at the metal/dielectric interfaces. A well-defined interface is therefore required to elucidate interfacial SPR processes. Here, we designed a photovoltaic device (PVD) with an atomically flat TiO2 dielectric/dye/graphene/metal nanoparticle (NP) interface for quantitatively studying the SPR enhancement of the photovoltaic conversion. Theoretical and experimental results indicated that the graphene monolayer was transparent to the electromagnetic field. This transparency led to significant substrate-induced plasmonic hybridization at the heterostructure interface. Combined with interparticle plasmonic coupling, the substrate-induced plasmonics concentrated light at the interface and enhanced the photo-excitation of dyes, thus improving the photoelectric conversion. Such a mechanistic understanding of interfacial plasmonic enhancement will further promote the development of efficient plasmon-enhanced solar cells and composite photocatalysts. PMID:26412576

  11. Friction mechanisms and interfacial slip at fluid-solid interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Leger, Liliane [Institut Universitaire de France, Laboratoire de Physique des Fluides Organises, UMR CNRS 7125, College de France, 11 Place Marcelin Berthelot, 75231 Paris (France)

    2003-01-15

    We present series of experiments based on near field laser velocimetry, developed to characterize the friction mechanisms at fluid-solid interfaces. For polymers, entangled polymer melts are sheared against smooth solid surfaces, covered by surface attached polymer chains of the same chemical species, having a controlled surface density. Direct measurements of the interfacial velocity and of the shear force allow identification of the molecular mechanisms of friction. Depending on the value of the inverse of the shear rate experienced by the polymer compared to the reptation time, the transition between a regime of high and a regime of low friction observed when increasing the shear rate can be related to disentanglement or to the extraction of the surface chains from the bulk polymer. Surfaces with adjusted friction properties can thus be designed by choosing chain anchored length and surface density. For simple fluids, the direct measurements of the interfacial velocity show that, contrary to the usual hypothesis of hydrodynamics, a simple fluid can exhibit slip at the wall. Both the surface roughness and the strength of the fluid-solid interactions fix the amplitude of wall slip, acting in an antagonistic way.

  12. Interfacial rheological properties of self-assembling biopolymer microcapsules.

    Science.gov (United States)

    Xie, Kaili; de Loubens, Clément; Dubreuil, Frédéric; Gunes, Deniz Z; Jaeger, Marc; Léonetti, Marc

    2017-09-20

    Tuning the mechanical properties of microcapsules through a cost-efficient route of fabrication is still a challenge. The traditional method of layer-by-layer assembly of microcapsules allows building a tailored composite multi-layer membrane but is technically complex as it requires numerous steps. The objective of this article is to characterize the interfacial rheological properties of self-assembling biopolymer microcapsules that were obtained in one single facile step. This thorough study provides new insights into the mechanics of these weakly cohesive membranes. Firstly, suspensions of water-in-oil microcapsules were formed in microfluidic junctions by self-assembly of two oppositely charged polyelectrolytes, namely chitosan (water soluble) and phosphatidic fatty acid (oil soluble). In this way, composite membranes of tunable thickness (between 40 and 900 nm measured by AFM) were formed at water/oil interfaces in a single step by changing the composition. Secondly, microcapsules were mechanically characterized by stretching them up to break-up in an extensional flow chamber which extends the relevance and convenience of the hydrodynamic method to weakly cohesive membranes. Finally, we show that the design of microcapsules can be 'engineered' in an extensive way since they present a wealth of interfacial rheological properties in terms of elasticity, plasticity and yield stress whose magnitudes can be controlled by the composition. These behaviors are explained by the variation of the membrane thickness with the physico-chemical parameters of the process.

  13. Influence of interfacial rheology on stabilization of the tear film

    Science.gov (United States)

    Bhamla, M. Saad; Fuller, Gerald G.

    2014-11-01

    The tear film that protecting the ocular surface is a complex, thin film comprised of a collection of proteins and lipids that come together to provide a number of important functions. Of particular interest in this presentation is meibum, an insoluble layer that is spread from glands lining our eyelids. Past work has focussed on the role of this layer in reducing evaporation, although conflicting evidence on its ability to reduce evaporative loss has been published. We present here the beneficial effects that are derived through the interfacial viscoelasticity of the meibomian lipid film. This is a duplex film is comprised of a rich mixture of phospholipids, long chain fatty esters, and cholesterol esters. Using interfacial rheology measurements, meibum has been shown to be highly viscoelastic. By measuring the drainage and dewetting dynamics of thin aqueous films from hemispherical surfaces where those films are laden with insoluble layers of lipids at controlled surface pressure, we offer evidence that these layers strongly stabilize the films because of their ability to support surface shearing stresses. This alternative view of the role of meibum can help explain the origin of meibomian gland dysfunction, or dry eye disease, where improper compositions of this lipid mixture do not offer the proper mechanical resistance to breakage and dewetting of the tear film.

  14. Limiting amplitudes of fully nonlinear interfacial tides and solitons

    Science.gov (United States)

    Aguiar-González, Borja; Gerkema, Theo

    2016-08-01

    A new two-fluid layer model consisting of forced rotation-modified Boussinesq equations is derived for studying tidally generated fully nonlinear, weakly nonhydrostatic dispersive interfacial waves. This set is a generalization of the Choi-Camassa equations, extended here with forcing terms and Coriolis effects. The forcing is represented by a horizontally oscillating sill, mimicking a barotropic tidal flow over topography. Solitons are generated by a disintegration of the interfacial tide. Because of strong nonlinearity, solitons may attain a limiting table-shaped form, in accordance with soliton theory. In addition, we use a quasi-linear version of the model (i.e. including barotropic advection but linear in the baroclinic fields) to investigate the role of the initial stages of the internal tide prior to its nonlinear disintegration. Numerical solutions reveal that the internal tide then reaches a limiting amplitude under increasing barotropic forcing. In the fully nonlinear regime, numerical experiments suggest that this limiting amplitude in the underlying internal tide extends to the nonlinear case in that internal solitons formed by a disintegration of the internal tide may not reach their table-shaped form with increased forcing, but appear limited well below that state.

  15. A nanoengine governor based on the end interfacial effect

    Science.gov (United States)

    Shi, Jiao; Cai, Kun; Qin, Qing-Hua

    2016-12-01

    A conceptual design is presented for a nanoengine governor based on the end interfacial effect of two rotary nanotubes. The governor contains a thermal-driven rotary nanomotor made from double-walled carbon nanotubes (DWCNTs) and a coaxially laid out rotary nanotube near one end of the nanomotor rotor. The rotation of the rotor in the nanomotor can be controlled by two features. One is the stator (the outer tube of DWCNTs) which has some end atoms with inward radial deviation (IRD) on the stator. The other is the relative rotation of the neighboring rotary tube of the rotor. As the configuration of the stator is fixed, the end interfacial interaction between the two rotors will govern the dynamic response of the rotor in the nanomotor system. The obtained results demonstrate that the relative rotational speed between the two rotors provides friction on the rotor in the nanomotor system. In particular, higher relative rotational speed will provide lower friction on rotor 1, which is opposite to that between neighboring shells in DWCNTs.

  16. Fibrillization kinetics of insulin solution in an interfacial shearing flow

    Science.gov (United States)

    Balaraj, Vignesh; McBride, Samantha; Hirsa, Amir; Lopez, Juan

    2015-11-01

    Although the association of fibril plaques with neurodegenerative diseases like Alzheimer's and Parkinson's is well established, in-depth understanding of the roles played by various physical factors in seeding and growth of fibrils is far from well known. Of the numerous factors affecting this complex phenomenon, the effect of fluid flow and shear at interfaces is paramount as it is ubiquitous and the most varying factor in vivo. Many amyloidogenic proteins have been found to denature upon contact at hydrophobic interfaces due to the self-assembling nature of protein in its monomeric state. Here, fibrillization kinetics of insulin solution is studied in an interfacial shearing flow. The transient surface rheological response of the insulin solution to the flow and its effect on the bulk fibrillization process has been quantified. Minute differences in hydrophobic characteristics between two variants of insulin- Human recombinant and Bovine insulin are found to result in very different responses. Results presented will be in the form of fibrillization assays, images of fibril plaques formed, and changes in surface rheological properties of the insulin solution. The interfacial velocity field, measured from images (via Brewster Angle Microscopy), is compared with computations. Supported by NNX13AQ22G, National Aeronautics and Space Administration.

  17. Characterization of interfacial waves in horizontal core-annular flow

    Science.gov (United States)

    Tripathi, Sumit; Bhattacharya, Amitabh; Singh, Ramesh; Tabor, Rico F.

    2016-11-01

    In this work, we characterize interfacial waves in horizontal core annular flow (CAF) of fuel-oil and water. Experimental studies on CAF were performed in an acrylic pipe of 15.5mm internal diameter, and the time evolution of the oil-water interface shape was recorded with a high speed camera for a range of different flow-rates of oil (Qo) and water (Qw). The power spectrum of the interface shape shows a range of notable features. First, there is negligible energy in wavenumbers larger than 2 π / a , where a is the thickness of the annulus. Second, for high Qo /Qw , there is no single dominant wavelength, as the flow in the confined annulus does not allow formation of a preferred mode. Third, for lower Qo /Qw , a dominant mode arises at a wavenumber of 2 π / a . We also observe that the power spectrum of the interface shape depends weakly on Qw, and strongly on Qo, perhaps because the net shear rate in the annulus appears to depend weakly on Qw as well. We also attempt to build a general empirical model for CAF by relating the interfacial stress (calculated via the mean pressure gradient) to the flow rate in the annulus, the annular thickness and the core velocity. Authors are thankful to Orica Mining Services (Australia) for the financial support.

  18. Interfacial Polymerization on Dynamic Complex Colloids: Creating Stabilized Janus Droplets.

    Science.gov (United States)

    He, Yuan; Savagatrup, Suchol; Zarzar, Lauren D; Swager, Timothy M

    2017-03-01

    Complex emulsions, including Janus droplets, are becoming increasingly important in pharmaceuticals and medical diagnostics, the fabrication of microcapsules for drug delivery, chemical sensing, E-paper display technologies, and optics. Because fluid Janus droplets are often sensitive to external perturbation, such as unexpected changes in the concentration of the surfactants or surface-active biomolecules in the environment, stabilizing their morphology is critical for many real-world applications. To endow Janus droplets with resistance to external chemical perturbations, we demonstrate a general and robust method of creating polymeric hemispherical shells via interfacial free-radical polymerization on the Janus droplets. The polymeric hemispherical shells were characterized by optical and fluorescence microscopy, scanning electron microscopy, and confocal laser scanning microscopy. By comparing phase diagrams of a regular Janus droplet and a Janus droplet with the hemispherical shell, we show that the formation of the hemispherical shell nearly doubles the range of the Janus morphology and maintains the Janus morphology upon a certain degree of external perturbation (e.g., adding hydrocarbon-water or fluorocarbon-water surfactants). We attribute the increased stability of the Janus droplets to (1) the surfactant nature of polymeric shell formed and (2) increase in interfacial tension between hydrocarbon and fluorocarbon due to polymer shell formation. This finding opens the door of utilizing these stabilized Janus droplets in a demanding environment.

  19. Linear interfacial polymerization: theory and simulations with dissipative particle dynamics.

    Science.gov (United States)

    Berezkin, Anatoly V; Kudryavtsev, Yaroslav V

    2014-11-21

    Step-growth alternating interfacial polymerization between two miscible or immiscible monomer melts is investigated theoretically and by dissipative particle dynamics simulations. In both cases the kinetics for an initially bilayer system passes from the reaction to diffusion control. The polymer composed of immiscible monomers precipitates at the interface forming a film of nearly uniform density. It is demonstrated that the reaction proceeds in a narrow zone, which expands much slower than the whole film, so that newly formed polymer is extruded from the reaction zone. This concept of "reactive extrusion" is used to analytically predict the degree of polymerization and distribution of all components (monomers, polymer, and end groups) within the film in close agreement with the simulations. Increasing the comonomer incompatibility leads to thinner and more uniform films with the higher average degree of polymerization. The final product is considerably more polydisperse than expected for the homogeneous step-growth polymerization. The results extend the previous theoretical reports on interfacial polymerization and provide new insights into the internal film structure and polymer characteristics, which are important for membrane preparation, microencapsulation, and 3D printing technologies. A systematic way of mapping the simulation data onto laboratory scales is discussed.

  20. Design rules for interfacial thermal conductance: Building better bridges

    Science.gov (United States)

    Polanco, Carlos A.; Rastgarkafshgarkolaei, Rouzbeh; Zhang, Jingjie; Le, Nam Q.; Norris, Pamela M.; Ghosh, Avik W.

    2017-05-01

    We study the thermal conductance across solid-solid interfaces as the composition of an intermediate matching layer is varied. In the absence of phonon-phonon interactions, an added layer can make the interfacial conductance increase or decrease depending on the interplay between (1) an increase in phonon transmission due to better bridging between the contacts and (2) a decrease in the number of available conduction channels that must conserve their momenta transverse to the interface. When phonon-phonon interactions are included, the added layer is seen to aid conductance when the decrease in resistances at the contact-layer boundaries compensate for the additional layer resistance. For the particular systems explored in this work, the maximum conductance happens when the layer mass is close to the geometric mean of the contact masses. The surprising result, usually associated with coherent antireflection coatings, follows from a monotonic increase in the boundary resistance with the interface mass ratio. This geometric mean condition readily extends to a compositionally graded interfacial layer with an exponentially varying mass that generates the thermal equivalent of a broadband impedance matching network.

  1. Interfacial crack behavior in the stationary temperature field conditions

    Directory of Open Access Journals (Sweden)

    Đoković Jelena M.

    2014-01-01

    Full Text Available The brittle coatings, made of different materials, when subjected to elevated temperatures and in the heat exchange conditions, are susceptible to delamination. Those coatings, as well as thin films, can be used for various thermo insulating deposits, e.g. in turbines of thermal power plants., In layers made of different materials, due to the environmental temperature change, thermal stresses appear as a consequence of a difference in their thermal expansion coefficients. In this paper driving forces were analyzed causing delamination of one layer from the other, i.e. the interfacial fracture in the two-layered, bimaterial sample. This analysis was limited to considering the sample behavior when exposed to the stationary temperature field. The energy release rate G, which is the driving force for this interfacial fracture, is changing with temperature and that variation is increasing with increase of the temperature difference between the environment and the sample. Analysis of this relation can be used to predict the maximal temperature difference, which the two-layered sample can be subjected to, without appearance of delamination between layers.

  2. Interfacial Symmetry Control of Emergent Ferromagnetism at the Nanoscale.

    Science.gov (United States)

    Grutter, A J; Vailionis, A; Borchers, J A; Kirby, B J; Flint, C L; He, C; Arenholz, E; Suzuki, Y

    2016-09-14

    The emergence of complex new ground states at interfaces has been identified as one of the most promising routes to highly tunable nanoscale materials. Despite recent progress, isolating and controlling the underlying mechanisms behind these emergent properties remains among the most challenging materials physics problems to date. In particular, generating ferromagnetism localized at the interface of two nonferromagnetic materials is of fundamental and technological interest. Moreover, the ability to turn the ferromagnetism on and off would shed light on the origin of such emergent phenomena and is promising for spintronic applications. We demonstrate that ferromagnetism confined within one unit cell at the interface of CaRuO3 and CaMnO3 can be switched on and off by changing the symmetry of the oxygen octahedra connectivity at the boundary. Interfaces that are symmetry-matched across the boundary exhibit interfacial CaMnO3 ferromagnetism while the ferromagnetism at symmetry-mismatched interfaces is suppressed. We attribute the suppression of ferromagnetic order to a reduction in charge transfer at symmetry-mismatched interfaces, where frustrated bonding weakens the orbital overlap. Thus, interfacial symmetry is a new route to control emergent ferromagnetism in materials such as CaMnO3 that exhibit antiferromagnetism in bulk form.

  3. Interfacial phenomena at a surface of partially silylated nanosilica.

    Science.gov (United States)

    Gun'ko, V M; Turov, V V; Myronyuk, I F; Goncharuk, O V; Pakhlov, E M; Bezruka, N A; Skwarek, E; Janusz, W; Blitz, J P

    2014-11-15

    Unmodified pyrogenic silica PS300 and partially silylated nanosilica samples at a degree of substitution of surface silanols by trimethylsilyl (TMS) groups Θ(TMS)=27.2% and 37.2% were studied to elucidate features of the interfacial behavior of water adsorbed alone, or co-adsorbed with methane, hydrogen, or trifluoroacetic acid (TFAA). In the aqueous suspension modified PS300 at Θ(TMS)=37.2% forms aggregates of 50-200 nm in size and can bind significant amounts of water (up to ∼5 g/g). Only 0.5 g/g of this water is strongly bound, while the major fraction of water is weakly bound. The presence of surface TMS groups causes the appearance of weakly associated water (WAW) at the interfaces. The adsorption of methane and hydrogen onto TMS-nanosilica with pre-adsorbed water (hydration degree h=0.05 or 0.005 g/g) increases with increasing temperature. In weakly polar CDCl3 medium, interfacial water exists in strongly (SAW, chemical shift δ(H)=4-5 ppm) and weakly (δ(H)=1-2 ppm) associated states, as well as strongly (changes in the Gibbs free energy -ΔG>0.5-0.8 kJ/mol) and weakly (-ΔGsurface can dissolve TFAA. Copyright © 2014 Elsevier Inc. All rights reserved.

  4. Interfacial pH during mussel adhesive plaque formation

    Science.gov (United States)

    Rodriguez, Nadine R. Martinez; Das, Saurabh; Kaufman, Yair; Israelachvili, Jacob N.; Waite, J. Herbert

    2015-01-01

    Mussel (Mytilus californianus) adhesion to marine surfaces involves an intricate and adaptive synergy of molecules and spatio-temporal processes. Although the molecules, such as mussel foot proteins (mfps), are well characterized, deposition details remain vague and speculative. Developing methods for the precise surveillance of conditions that apply during mfp deposition would aid both in understanding mussel adhesion and translating this adhesion into useful technologies. To probe the interfacial pH at which mussels buffer the local environment during mfp deposition, a lipid bilayer with tethered pH-sensitive fluorochromes was assembled on mica. The interfacial pH during foot contact with modified mica ranged from 2.2−3.3, which is well below the seawater pH of ~8. The acidic pH serves multiple functions: it limits mfp-Dopa oxidation, thereby enabling the catecholic functionalities to adsorb to surface oxides by H-bonding and metal ion coordination, and provides a solubility switch for mfps, most of which aggregate at pH ≥ 7-8. PMID:25875963

  5. Solar-Pumping Upconversion of Interfacial Coordination Nanoparticles

    Science.gov (United States)

    Ishii, Ayumi; Hasegawa, Miki

    2017-01-01

    An interfacial coordination nanoparticle successfully exhibited an upconversion blue emission excited by very low-power light irradiation, such as sunlight. The interfacial complex was composed of Yb ions and indigo dye, which formed a nano-ordered thin shell layer on a Tm2O3 nanoparticle. At the surface of the Tm2O3 particle, the indigo dye can be excited by non-laser excitation at 640 nm, following the intramolecular energy transfer from the indigo dye to the Yb ions. Additionally, the excitation energy of the Yb ion was upconverted to the blue emission of the Tm ion at 475 nm. This upconversion blue emission was achieved by excitation with a CW Xe lamp at an excitation power of 0.14 mW/cm2, which is significantly lower than the solar irradiation power of 1.4 mW/cm2 at 640 ± 5 nm.

  6. Visualization and characterization of interfacial polymerization layer formation.

    Science.gov (United States)

    Zhang, Yali; Benes, Nieck E; Lammertink, Rob G H

    2015-01-21

    We present a microfluidic platform to visualize the formation of free-standing films by interfacial polymerization. A microfluidic device is fabricated, with an array of micropillars to stabilize an aqueous-organic interface that allows a direct observation of the films formation process via optical microscopy. Three different amines are selected to react with trimesoyl chloride: piperazine, JEFFAMINE(®)D-230, and an ammonium functionalized polyhedral oligomeric silsesquioxane. Tracking the formation of the free-standing films in time reveals strong effects of the characteristics of the amine precursor on the morphological evolution of the films. Piperazine exhibits a rapid reaction with trimesoyl chloride, forming a film up to 20 μm thick within half a minute. JEFFAMINE(®)D-230 displays much slower film formation kinetics. The location of the polymerization reaction was initially in the aqueous phase and then shifted into the organic phase. Our in situ real-time observations provide information on the kinetics and the changing location of the polymerization. This provides insights with important implications for fine-tuning of interfacial polymerizations for various applications.

  7. Grafted Peptides for the Control of Interfacial Properties

    Science.gov (United States)

    Ducker, William; Mosse, Wade; Gras, Sally

    2010-03-01

    Peptide or protein polymers that are used to control interfacial properties are usually prepared by solid-state synthesis and then adsorbed to an interface. Such a method results in a low yield and places restrictions on polymer structure, because the peptide must be designed to adsorb, as well as to provide the interfacial control. The method of grafting peptides from surfaces is an alternate method that is potentially very useful because the peptide is covalently linked, and the sequence limitations related to adsorption are removed. To demonstrate this technique, we have used solid-phase peptide synthesis to graft a 15-residue peptide, EKEKEKEKEKEKEGG, containing a zwitterionic sequence of alternating lysine and glutamic acid residues from the surface of an aminosilanized silicon wafer by placing the silicon wafer within a commercial microwave peptide synthesizer. We confirmed the presence of this peptide layer on the surface by X-ray photoelectron spectroscopy (XPS) and ellipsometry. Atomic force microscopy (AFM) was then used to study the forces between the peptide-modified surface and a borosilicate glass sphere as a function of solution pH. We will also discuss the use of grafted peptides to control the stability of colloidal suspensions.

  8. Interfacial interactions between plastic particles in plastics flotation.

    Science.gov (United States)

    Wang, Chong-qing; Wang, Hui; Gu, Guo-hua; Fu, Jian-gang; Lin, Qing-quan; Liu, You-nian

    2015-12-01

    Plastics flotation used for recycling of plastic wastes receives increasing attention for its industrial application. In order to study the mechanism of plastics flotation, the interfacial interactions between plastic particles in flotation system were investigated through calculation of Lifshitz-van der Waals (LW) function, Lewis acid-base (AB) Gibbs function, and the extended Derjaguin-Landau-Verwey-Overbeek potential energy profiles. The results showed that van der Waals force between plastic particles is attraction force in flotation system. The large hydrophobic attraction, caused by the AB Gibbs function, is the dominant interparticle force. Wetting agents present significant effects on the interfacial interactions between plastic particles. It is found that adsorption of wetting agents promotes dispersion of plastic particles and decreases the floatability. Pneumatic flotation may improve the recovery and purity of separated plastics through selective adsorption of wetting agents on plastic surface. The relationships between hydrophobic attraction and surface properties were also examined. It is revealed that there exists a three-order polynomial relationship between the AB Gibbs function and Lewis base component. Our finding provides some insights into mechanism of plastics flotation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Regulation of mitochondrial malic enzyme synthesis in mouse brain.

    Science.gov (United States)

    Bernstine, E G; Koh, C; Lovelace, C C

    1979-12-01

    In a previous study [Bernstine, E.G. (1979) J. Biol. Chem. 254, 83-87] it was shown that inbred strains of mice fall into two classes based on the specific activity of mitochondrial malic enzyme [L-malate:NADP+ oxidoreductase (oxaloacetate-decarboxylating), EC 1.1.1.40] in brain. In this report we demonstrate differences between high- and low-activity strains in the development of enzyme activity levels in adult mice and show that the rate of enzyme synthesis quantitatively accounts for the inherited level of the brain enzyme. Genetic analysis has established that the locus controlling the amount of enzyme in brain (Mdr-1) is located on chromosome 7. Its linkage to Hbb and c places it in the same region of the chromosome as Mod-2, the structural gene for mitochondrial malic enzyme. By making use of deletions and a duplication that include Mod-2, evidence for cis action of Mdr-1 was obtained.

  10. Modifications Caused by Enzyme-Retting and Their Effect on Composite Performance

    Directory of Open Access Journals (Sweden)

    Jonn A. Foulk

    2011-01-01

    Full Text Available Bethune seed flax was collected from Canada with seed removed using a stripper header and straw pulled and left in field for several weeks. Unretted straw was decorticated providing a coarse fiber bundle feedstock for enzyme treatments. Enzyme treatments using a bacterial pectinolytic enzyme with lyase activity were conducted in lab-scale reactors. Four fiber specimens were created: no retting, minimal retting, moderate retting, and full retting. Fiber characterization tests: strength, elongation, diameter, metal content, wax content, and pH were conducted with significant differences between fibers. Thermosetting vinyl ester resin was used to produce composite panels via vacuum-assisted infusion. Composite performance was evaluated using fiber bundle pull-out, tensile, impact, and interlaminar shear tests. Composite tests indicate that composite panels are largely unchanged among fiber samples. Variation in composite performance might not be realized due to poor interfacial bonding being of larger impact than the more subtle changes incurred by the enzyme treatment.

  11. Indium tin oxide with zwitterionic interfacial design for biosensing applications in complex matrices

    Energy Technology Data Exchange (ETDEWEB)

    Darwish, Nadia T.; Alias, Yatimah; Khor, Sook Mei, E-mail: naomikhor@um.edu.my

    2015-01-15

    Graphical abstract: - Highlights: • The incorporation of a linker and antifouling molecules is an important interfacial design for both affinity and enzymatic biosensors. • The resistance to non-specific protein adsorptions of BSA–FITC and RBITC–Cyt c were determined by confocal laser scanning microscopy. • The antifouling interface allows detection of target analytes in highly complicated biological matrices. - Abstract: Biosensing interfaces consisting of linker molecules (COOH or NH{sub 2}) and charged, antifouling moieties ((-SO{sup 3−} and N{sup +}(Me){sub 3}) for biosensing applications were prepared for the first time by the in situ deposition of mixtures of aryl diazonium cations on indium tin oxide (ITO) electrodes. A linker molecule is required for the attachment of biorecognition molecules (e.g., antibodies, enzymes, DNA chains, and aptamers) close to the transducer surface. The attached molecules improve the biosensing sensitivity and also provide a short response time for analyte detection. Thus, the incorporation of a linker and antifouling molecules is an important interfacial design for both affinity and enzymatic biosensors. The reductive adsorption behavior and electrochemical measurement were studied for (1) an individual compound and (2) a mixture of antifouling zwitterionic molecules together with linker molecules [combination 1: 4-sulfophenyl (SP), 4-trimethylammoniophenyl (TMAP), and 1,4-phenylenediamine (PPD); combination 2: 4-sulfophenyl (SP), 4-trimethylammoniophenyl (TMAP), and 4-aminobenzoic acid (PABA)] of aryl diazonium cations grafted onto an ITO electrode. The mixture ratios of SP:TMAP:PPD and SP:TMAP:PABA that provided the greatest resistance to non-specific protein adsorptions of bovine serum albumin labeled with fluorescein isothiocyanate (BSA–FITC) and cytochrome c labeled with rhodamine B isothiocyanate (RBITC–Cyt c) were determined by confocal laser scanning microscopy (CLSM). For the surface antifouling study

  12. Random-walk enzymes

    Science.gov (United States)

    Mak, Chi H.; Pham, Phuong; Afif, Samir A.; Goodman, Myron F.

    2015-09-01

    Enzymes that rely on random walk to search for substrate targets in a heterogeneously dispersed medium can leave behind complex spatial profiles of their catalyzed conversions. The catalytic signatures of these random-walk enzymes are the result of two coupled stochastic processes: scanning and catalysis. Here we develop analytical models to understand the conversion profiles produced by these enzymes, comparing an intrusive model, in which scanning and catalysis are tightly coupled, against a loosely coupled passive model. Diagrammatic theory and path-integral solutions of these models revealed clearly distinct predictions. Comparison to experimental data from catalyzed deaminations deposited on single-stranded DNA by the enzyme activation-induced deoxycytidine deaminase (AID) demonstrates that catalysis and diffusion are strongly intertwined, where the chemical conversions give rise to new stochastic trajectories that were absent if the substrate DNA was homogeneous. The C →U deamination profiles in both analytical predictions and experiments exhibit a strong contextual dependence, where the conversion rate of each target site is strongly contingent on the identities of other surrounding targets, with the intrusive model showing an excellent fit to the data. These methods can be applied to deduce sequence-dependent catalytic signatures of other DNA modification enzymes, with potential applications to cancer, gene regulation, and epigenetics.

  13. Enzyme recycling in lignocellulosic biorefineries

    DEFF Research Database (Denmark)

    Jørgensen, Henning; Pinelo, Manuel

    2017-01-01

    platform. Cellulases are the most important enzymes required in this process, but the complex nature of lignocellulose requires several other enzymes (hemicellulases and auxiliary enzymes) for efficient hydrolysis. Enzyme recycling increases the catalytic productivity of the enzymes by reusing them...... upscaled and tested in industrial settings, mainly because of many difficulties with recycling of enzymes from the complex lignocellulose hydrolyzate at industrially relevant conditions, i.e., high solids loadings. The challenges are associated with the large number of different enzymes required...... for efficient hydrolysis, enzyme stability, and the detrimental interaction between enzyme and lignin. This review provides a comprehensive overview of the various methods for enzyme recovery and recycling, for example recycling of free enzymes, readsorption to fresh material, recycling of solids, membrane...

  14. Influence of small amounts of additives on gas hold-up, bubble size, and interfacial area

    NARCIS (Netherlands)

    Cents, A. H. G.; Jansen, D. J. W.; Brilman, D. W. F.; Versteeg, G. F.

    2005-01-01

    The gas-liquid interfacial area, which is determined by the gas hold-up and the Sauter mean bubble diameter, determines the production rate in many industrial processes. The effect of additives on this interfacial area is, especially in multiphase systems (gas-liquid-solid, gas-liquid-liquid), often

  15. Organic photovoltaic device with interfacial layer and method of fabricating same

    Science.gov (United States)

    Marks, Tobin J.; Hains, Alexander W.

    2013-03-19

    An organic photovoltaic device and method of forming same. In one embodiment, the organic photovoltaic device has an anode, a cathode, an active layer disposed between the anode and the cathode; and an interfacial layer disposed between the anode and the active layer, the interfacial layer comprising 5,5'-bis[(p-trichlorosilylpropylphenyl)phenylamino]-2,2'-bithiophene (PABTSi.sub.2).

  16. Interfacial Interactions of CO2-Water-Bentheimer Sandstone System - Dissolution and Contact Angle

    NARCIS (Netherlands)

    Shojaikaveh, N.; Rudolph, E.S.J.; Rossen, W.R.; Wolf, K-H.A.A.

    2014-01-01

    CO2 storage in deep saline aquifers and depleted gas reservoirs is largely controlled by interfacial phenomena among fluid phases and rock pore spaces. Reduction of the interfacial tension may result in the mobilization of connate water (capillary trapping). In addition, dissolving CO2 in formation

  17. Droplet coalescence: drainage, film rupture and neck growth in ultralow interfacial tension systems

    NARCIS (Netherlands)

    Aarts, D.G.A.L.; Lekkerkerker, H.N.W.|info:eu-repo/dai/nl/159054885

    2008-01-01

    We study the coalescence of a drop with its bulk phase in fluid–fluid demixing colloid–polymer mixtures. Such mixtures show behaviour analogous to molecular fluid–fluid systems, but the interfacial tension is between 105 to 107 times smaller than in the molecular case. Such an ultralow interfacial

  18. Effect of antiferromagnetic interfacial coupling on spin-wave resonance frequency of multi-layer film

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Rong-ke, E-mail: rkqiu@163.com; Cai, Wei

    2017-08-15

    Highlights: • A quantum approach is developed to study the SWR of a bicomponent multi-layer films. • The comparison of the SWR in films with FM and AFM interfacial coupling has been made. • The present results show the method to enhance and adjust the SWR frequency of films. - Abstract: We investigate the spin-wave resonance (SWR) frequency in a bicomponent bilayer and triple-layer films with antiferromagnetic or ferromagnetic interfacial couplings, as function of interfacial coupling, surface anisotropy, interface anisotropy, thickness and external magnetic field, using the linear spin-wave approximation and Green’s function technique. The microwave properties for multi-layer magnetic film with antiferromagnetic interfacial coupling is different from those for multi-layer magnetic film with ferromagnetic interfacial coupling. For the bilayer film with antiferromagnetic interfacial couplings, as the lower (upper) surface anisotropy increases, only the SWR frequencies of the odd (even) number modes increase. The lower (upper) surface anisotropy does not affect the SWR frequencies of the even (odd) number modes{sub .} For the multi-layer film with antiferromagnetic interfacial coupling, the SWR frequency of modes m = 1, 3 and 4 decreases while that of mode m = 2 increases with increasing thickness of the film within a proper parameter region. The present results could be useful in enhancing our fundamental understanding and show the method to enhance and adjust the SWR frequency of bicomponent multi-layer magnetic films with antiferromagnetic or ferromagnetic interfacial coupling.

  19. Artificial Enzymes, "Chemzymes"

    DEFF Research Database (Denmark)

    Bjerre, Jeannette; Rousseau, Cyril Andre Raphaël; Pedersen, Lavinia Georgeta M

    2008-01-01

    that successfully perform Michaelis-Menten catalysis under enzymatic conditions (i.e., aqueous medium, neutral pH, ambient temperature) and for those that do, very high rate accelerations are seldomly seen. This review will provide a brief summary of the recent developments in artificial enzymes, so called...... "Chemzymes", based on cyclodextrins and other molecules. Only the chemzymes that have shown enzyme-like activity that has been quantified by different methods will be mentioned. This review will summarize the work done in the field of artificial glycosidases, oxidases, epoxidases, and esterases, as well...

  20. Mechanics of finite cracks in dissimilar anisotropic elastic media considering interfacial elasticity

    Science.gov (United States)

    Juan, Pierre-Alexandre; Dingreville, Rémi

    2017-02-01

    Interfacial crack fields and singularities in bimaterial interfaces (i.e., grain boundaries or dissimilar materials interfaces) are considered through a general formulation for two-dimensional (2-D) anisotropic elasticity while accounting for the interfacial structure by means of an interfacial elasticity paradigm. The interfacial elasticity formulation introduces boundary conditions that are effectively equivalent to those for a weakly bounded interface. This formalism considers the 2-D crack-tip elastic fields using complex variable techniques. While the consideration of the interfacial elasticity does not affect the order of the singularity, it modifies the oscillatory effects associated with problems involving interface cracks. Constructive or destructive "interferences" are directly affected by the interface structure and its elastic response. This general formulation provides an insight on the physical significance and the obvious coupling between the interface structure and the associated mechanical fields in the vicinity of the crack tip.

  1. Cold welding of organic light emitting diode: Interfacial and contact models

    Directory of Open Access Journals (Sweden)

    J. Asare

    2016-06-01

    Full Text Available This paper presents the results of an analytical and computational study of the contacts and interfacial fracture associated with the cold welding of Organic Light Emitting diodes (OLEDs. The effects of impurities (within the possible interfaces are explored for contacts and interfacial fracture between layers that are relevant to model OLEDs. The models are used to study the effects of adhesion, pressure, thin film layer thickness and dust particle modulus (between the contacting surfaces on contact profiles around impurities between cold-welded thin films. The lift-off stage of thin films (during cold welding is then modeled as an interfacial fracture process. A combination of adhesion and interfacial fracture theories is used to provide new insights for the design of improved contact and interfacial separation during cold welding. The implications of the results are discussed for the design and fabrication of cold welded OLED structures.

  2. Control of protein particle formation during ultrafiltration/diafiltration through interfacial protection.

    Science.gov (United States)

    Callahan, Daniel J; Stanley, Bradford; Li, Yuling

    2014-03-01

    This study investigates the mechanism of protein particle formation during ultrafiltration/diafiltration (UF/DF), finding that agitation drives particle formation by promoting protein-interface adsorption and desorption. Low conductivity and the presence of surfactant reduced the level of particle formation in small-scale stirring studies, and the same trends were observed in pumping and UF/DF. Polysorbate 80 (PS80) and hydroxypropyl-β-cyclodextrin (HPβCD) reduced particle formation in UF/DF by factors of 15 and 4, respectively. Measurements of conformational stability, colloidal stability, and surface tension demonstrated that PS80 protects against particle formation by preventing protein-interface adsorption, low conductivity improves the colloidal stability of the protein, and the mechanism of action of HPβCD remains unclear. This work demonstrates that interfacial adsorption-desorption of the protein during UF/DF is the principal cause of particle formation, that the level of surfactant-free particle formation depends on the colloidal stability of the protein, and that the inclusion of surfactant greatly reduces in-process particle formation during UF/DF. © 2014 The Authors. Journal of Pharmaceutical Sciences published by Wiley Periodicals, Inc. and the American Pharmacists Association.

  3. Interfacial and foaming interactions between casein glycomacropeptide (CMP) and propylene glycol alginate.

    Science.gov (United States)

    Martinez, María J; Pizones Ruiz-Henestrosa, Víctor M; Carrera Sánchez, Cecilio; Rodríguez Patino, Juan M; Pilosof, Ana M R

    2012-06-15

    Proteins and polysaccharides are widely used in food formulation. While most of the proteins are surface active, only few polysaccharides can adsorb at the air-water interface; this is the case of propylene glycol alginates (PGA). It is known that casein glycomacropeptide (CMP), a bioactive polypeptide derived from κ-casein by the action of chymosin, presents a great foaming capacity but provides unstable foams. So, the objective of this work was to analyze the impact of mixing CMP and a commercial variety of PGA, Kelcoloid O (KO), on the interfacial and foaming properties at pH 7.0. It was determined the surface pressure isotherm, the dynamics of adsorption and the foaming properties for CMP, KO and the mixed system CMP-KO. CMP dominated the surface pressure of CMP-KO mixed system. The presence of KO synergistically improved the viscoelastic properties of surface film. The foaming capacity of CMP was altered by KO. KO foam presented a higher stability than CMP foam and it controlled the stability against drainage and the initial collapse in the mixed foam. Copyright © 2012 Elsevier B.V. All rights reserved.

  4. Nature and morphology of fumed oxides and features of interfacial phenomena

    Science.gov (United States)

    Gun'ko, V. M.; Zarko, V. I.; Goncharuk, O. V.; Matkovsky, A. K.; Remez, O. S.; Skubiszewska-Zięba, J.; Wojcik, G.; Walusiak, B.; Blitz, J. P.

    2016-03-01

    Individual and complex fumed nanooxides were studied using high-resolution transmission electron microscopy, X-ray diffraction, ultraviolet-visible (UV-vis) spectroscopy, differential scanning calorimetry, nuclear magnetic resonance spectroscopy, adsorption, desorption (evaporation), and quantum chemical methods. For mixed nanooxides in contrast to simple and small nanoparticles of individual silica or titania, complex core-shell nanoparticles (50-200 nm in size) with titania or alumina cores and silica or alumina shells can be destroyed under high-pressure cryogelation (HPCG), mechnochemical activation (MCA) that also affect the structure of aggregates of nanoparticles and agglomerates of aggregates becoming more compacted. This is accompanied by changes in color from white to beige of different tints and changes in the UV-vis spectra in the 300-600 nm range, as well as changes in crystalline structure of alumina. Any treatment of 'soft' nanooxides affects the interfacial behavior of polar and nonpolar adsorbates. For some of them, the hysteresis loops become strongly open. Rearrangement of secondary particles affects the freezing-melting point depression. Clusterization of adsorbates bound in pores causes diminution of heat effects during phase transition (freezing, fusion). Freezing point depression and increasing melting point cause significant hysteresis freezing-melting effects for adsorbates bound to oxide nanoparticles. The study shows that complex nanooxides can be more sensitive to external actions than simple nanooxides such as silica.

  5. Feed enzyme technology: present status and future developments.

    Science.gov (United States)

    Ravindran, Velmurugu; Son, Jang-Ho

    2011-05-01

    Exogenous enzymes are now well accepted as a class of feed additives in diet formulations for poultry and pigs to overcome the negative effects of anti-nutritional factors, and to improve digestion of dietary components and animal performance. An overview of the current status of feed enzyme technology, including the different type of enzymes and modes of action, is provided. Variable response to enzyme supplementation is an important reason limiting the widespread acceptance of feed enzymes. The major reasons contributing to these variable responses are discussed. Main features of the next generation of feed enzymes and the various trends that will drive the future use of enzymes are highlighted. The use of feed enzymes in poultry and pig feed formulations is expected to increase in the future and this will be driven by on-going changes in the world animal production. Aquaculture and ruminant industries are emerging markets for exogenous feed enzymes. The article presents some promising patents on feed enzyme technology.

  6. Bioinspired design and interfacial failure of biomedical systems

    Science.gov (United States)

    Rahbar, Nima

    The deformation mechanism of nacre as a model biological material is studied in this project. A numerical model is presented which consists of tensile pillars, shear pillars, asperities and aragonite platelets. It has been shown that the tensile pillars are the main elements that control the global stiffness of the nacre structure. Meanwhile, ultimate strength of the nacre structure is controlled by asperities and their behavior and the ratio of L/2D which is itself a function of the geometry of the platelets. Protein/shear pillars provide the glue which holds the assembly of entire system together, particularly in the direction normal to the platelets main axis. This dissertation also presents the results of a combined theoretical/computational and experimental effort to develop crack resistant dental multilayers that are inspired by the functionally graded dento-enamel junction (DEJ) structure that occurs between dentin and enamel in natural teeth. The complex structures of natural teeth and ceramic crowns are idealized using at layered configurations. The potential effects of occlusal contact are then modeled using finite element simulations of Hertzian contact. The resulting stress distributions are compared for a range of possible bioinspired, functionally graded architecture. The computed stress distributions show that the highest stress concentrations in the top ceramic layer of crown structures are reduced significantly by the use of bioinspired functionally graded architectures. The reduced stresses are shown to be associated with significant improvements (30%) in the pop-in loads over a wide range of clinically-relevant loading rates. The implications of the results are discussed for the design of bioinspired dental ceramic crown structures. The results of a combined experimental and computational study of mixed mode fracture in glass/cement and zirconia/cement interfaces that are relevant to dental restorations is also presented. The interfacial fracture

  7. Interfacial Tension Effect on Cell Partition in Aqueous Two-Phase Systems.

    Science.gov (United States)

    Atefi, Ehsan; Joshi, Ramila; Mann, Jay Adin; Tavana, Hossein

    2015-09-30

    Aqueous two-phase systems (ATPS) provide a mild environment for the partition and separation of cells. We report a combined experimental and theoretical study on the effect of interfacial tension of polymeric ATPS on the partitioning of cells between two phases and their interface. Two-phase systems are generated using polyethylene glycol and dextran of specific properties as phase-forming polymers and culture media as the solvent component. Ultralow interfacial tensions of the solutions are precisely measured using an axisymmetric drop shape analysis method. Partition experiments show that two-phase systems with an interfacial tension of 30 μJ/m(2) result in distribution of majority of cells to the bottom dextran phase. An increase in the interfacial tension results in a distribution of cells toward the interface. An independent cancer cell spheroid formation assay confirms these observations: a drop of the dextran phase containing cancer cells is dispensed into the immersion polyethylene glycol phase to form a cell-containing drop. Only at very small interfacial tensions do cells remain within the drop to aggregate into a spheroid. We perform a thermodynamic modeling of cell partition to determine variations of free energy associated with displacement of cells in ATPS with respect to the ultralow interfacial tensions. This modeling corroborates with the experimental results and demonstrates that at the smallest interfacial tension of 30 μJ/m(2), the free energy is a minimum with cells in the bottom phase. Increasing the interfacial tension shifts the minimum energy and partition of cells toward the interfacial region of the two aqueous phases. Examining differences in the partition behavior and minimum free energy modeling of A431.H9 cancer cells and mouse embryonic stem cells shows that the surface properties of cells further modulate partition in ATPS. This combined approach provides a fundamental understanding of interfacial tension role on cell partition in

  8. The surface science of enzymes

    DEFF Research Database (Denmark)

    Rod, Thomas Holm; Nørskov, Jens Kehlet

    2002-01-01

    One of the largest challenges to science in the coming years is to find the relation between enzyme structure and function. Can we predict which reactions an enzyme catalyzes from knowledge of its structure-or from its amino acid sequence? Can we use that knowledge to modify enzyme function......? To solve these problems we must understand in some detail how enzymes interact with reactants from its surroundings. These interactions take place at the surface of the enzyme and the question of enzyme function can be viewed as the surface science of enzymes. In this article we discuss how to describe...... catalysis by enzymes, and in particular the analogies between enzyme catalyzed reactions and surface catalyzed reactions. We do this by discussing two concrete examples of reactions catalyzed both in nature (by enzymes) and in industrial reactors (by inorganic materials), and show that although analogies...

  9. enzyme-linked

    African Journals Online (AJOL)

    SA MEDIESE TYDSKRIF DEEL 63 29 JANUARIE 1983. B surface antigen in donated screening and confirmation by immunosorbent assay. Hepatitis blood - enzyme-linked. M. O. BUBB, T. ... weeks at weekly intervals. After 6 weeks test blood samples were ... This assay normally takes 3 hours. Results. Fig. 1. Frequency ...

  10. Implantable enzyme amperometric biosensors.

    Science.gov (United States)

    Kotanen, Christian N; Moussy, Francis Gabriel; Carrara, Sandro; Guiseppi-Elie, Anthony

    2012-05-15

    The implantable enzyme amperometric biosensor continues as the dominant in vivo format for the detection, monitoring and reporting of biochemical analytes related to a wide range of pathologies. Widely used in animal studies, there is increasing emphasis on their use in diabetes care and management, the management of trauma-associated hemorrhage and in critical care monitoring by intensivists in the ICU. These frontier opportunities demand continuous indwelling performance for up to several years, well in excess of the currently approved seven days. This review outlines the many challenges to successful deployment of chronically implantable amperometric enzyme biosensors and emphasizes the emerging technological approaches in their continued development. The foreign body response plays a prominent role in implantable biotransducer failure. Topics considering the approaches to mitigate the inflammatory response, use of biomimetic chemistries, nanostructured topographies, drug eluting constructs, and tissue-to-device interface modulus matching are reviewed. Similarly, factors that influence biotransducer performance such as enzyme stability, substrate interference, mediator selection and calibration are reviewed. For the biosensor system, the opportunities and challenges of integration, guided by footprint requirements, the limitations of mixed signal electronics, and power requirements, has produced three systems approaches. The potential is great. However, integration along the multiple length scales needed to address fundamental issues and integration across the diverse disciplines needed to achieve success of these highly integrated systems, continues to be a challenge in the development and deployment of implantable amperometric enzyme biosensor systems. Copyright © 2012 Elsevier B.V. All rights reserved.

  11. Angiotensin-converting enzyme

    DEFF Research Database (Denmark)

    Sørensen, P G; Rømer, F K; Cortes, D

    1984-01-01

    In order to evaluate bleomycin-associated lung damage in humans, lung function parameters and serum levels of the endothelial-bound angiotensin-converting enzyme (ACE) were determined by serial measurements in 11 patients who were treated for testicular cancer. None developed clinical or radiolog...

  12. Enzymes and fungal virulence

    African Journals Online (AJOL)

    may be common across a variety of fungal pathogens. Most fungal pathogens and ... Fungi utilize the food substances in their immediate vicinity to .... digestion of the fungal secreted enzymes thereby denying access to the host cell. For a pathogen to be successful, it mttst be able to circumvent or overcome these antifungal ...

  13. [Elevated liver enzymes].

    Science.gov (United States)

    Holstege, Axel

    2016-10-01

    Elevated liver enzymes are a frequent finding in both symptomatic and asymptomatic patients necessitating further evaluation to clarify the underlying disease. Three different patterns of increased liver enzymes can be defined to allow for a more precise and rational further diagnostic approach. A predominant increase in transaminase activities reflects a disturbance of hepatocellular integrity which can be found in patients with viral hepatitis, genetic liver diseases like Wilson`s disease or hemochromatosis, and drug-induced liver diseases. A second pattern is characterized by high serum alkaline phosphatase and γ-glutamyltranspeptidase activities indicating cholestatic liver diseases. The next important diagnostic measure in this group is an ultrasound study discerning intra- from extrahepatic cholestasis. Intrahepatic cholestatic diseases include primary and secondary sclerosing cholangitis, genetic disturbances of canalicular membrane transporters or drug-induced liver dieseases. Extrahepatic cholestasis involves obstruction of the large bile ducts by gall stones or tumors. The third enzym pattern is defined by a predominant rise in γ-glutamyl transpeptidase which is observed in alcoholic or non-alcoholic fatty liver disease and infiltrating liver diseases. A rise in liver enzymes is not necessarily indicative of a primary hepatic origin. Extrahepatic diseases often cause similarly increased serum activities. In addition even higher values can be observed under normal conditions during pregnancy or in adolescens. Lower values in asymptomatic patients should only be controlled since more than 30% of elevated transaminases spontaneously normalize during follow-up. © Georg Thieme Verlag KG Stuttgart · New York.

  14. ISFET based enzyme sensors

    NARCIS (Netherlands)

    van der Schoot, Bart H.; Bergveld, Piet

    1987-01-01

    This paper reviews the results that have been reported on ISFET based enzyme sensors. The most important improvement that results from the application of ISFETs instead of glass membrane electrodes is in the method of fabrication. Problems with regard to the pH dependence of the response and the

  15. Enzymes and fungal virulence

    African Journals Online (AJOL)

    Plant pathogenic fungi secrete extracellular enlymes that are capable of degrading the cell walls of their host plants. These CWDES may be necessary for penetration ofthc cell wall harricr. as well as for generation of simple molecules that can he assimilated for growth. Most of these enzymes are substrawinducible and both ...

  16. Interfacial Properties of CZTS Thin Film Solar Cell

    Directory of Open Access Journals (Sweden)

    N. Muhunthan

    2014-01-01

    Full Text Available Cu-deficient CZTS (copper zinc tin sulfide thin films were grown on soda lime as well as molybdenum coated soda lime glass by reactive cosputtering. Polycrystalline CZTS film with kesterite structure was produced by annealing it at 500°C in Ar atmosphere. These films were characterized for compositional, structural, surface morphological, optical, and transport properties using energy dispersive X-ray analysis, glancing incidence X-ray diffraction, Raman spectroscopy, scanning electron microscopy, atomic force microscopy, UV-Vis spectroscopy, and Hall effect measurement. A CZTS solar cell device having conversion efficiency of ~0.11% has been made by depositing CdS, ZnO, ITO, and Al layers over the CZTS thin film deposited on Mo coated soda lime glass. The series resistance of the device was very high. The interfacial properties of device were characterized by cross-sectional SEM and cross-sectional HRTEM.

  17. Interfacial colloidal rod dynamics: Coefficients, simulations, and analysis

    Science.gov (United States)

    Yang, Yuguang; Bevan, Michael A.

    2017-08-01

    Colloidal rod diffusion near a wall is modeled and simulated based on a constrained Stokesian dynamic model of chains-of-spheres. By modeling colloidal rods as chains-of-spheres, complete diffusion tensors are computed for colloidal rods in bulk media and near interfaces, including hydrodynamic interactions, translation-rotation coupling, and all diffusion modes in the particle and lab frames. Simulated trajectories based on the chain-of-spheres diffusion tensor are quantified in terms of typical experimental quantities such as mean squared positional and angular displacements as well as autocorrelation functions. Theoretical expressions are reported to predict measured average diffusivities as well as the crossover from short-time anisotropic translational diffusion along the rod's major axis to isotropic diffusion. Diffusion modes are quantified in terms of closed form empirical fits to model results to aid their use in interpretation and prediction of experiments involving colloidal rod diffusion in interfacial and confined systems.

  18. Interfacial chemistry of zinc anodes for reinforced concrete structures

    Energy Technology Data Exchange (ETDEWEB)

    Covino, B.S. Jr.; Bullard, S.J.; Cramer, S.D.; Holcomb, G.R. [Dept. of Energy, Albany, OR (United States). Albany Research Center; McGill, G.E.; Cryer, C.B. [Oregon Dept. of Transportation, Salem, OR (United States); Stoneman, A. [International Lead Zinc Research Organization, Research Triangle Park, NC (United States); Carter, R.R. [California Dept. of Transportation, Sacramento, CA (United States)

    1997-12-01

    Thermally-sprayed zinc anodes are used in both galvanic and impressed current cathodic protection systems for reinforced concrete structures. The Albany Research Center, in collaboration with the Oregon Department of Transportation, has been studying the effect of electrochemical aging on the bond strength of zinc anodes for bridge cathodic protection systems. Changes in anode bond strength and other anode properties can be explained by the chemistry of the zinc-concrete interface. The chemistry of the zinc-concrete interface in laboratory electrochemical aging studies is compared with that of several bridges with thermal-sprayed zinc anodes and which have been in service for 5 to 10 years using both galvanic and impressed current cathodic protection systems. The bridges are the Cape Creek Bridge on the Oregon coast and the East Camino Undercrossing near Placerville, CA. Also reported are interfacial chemistry results for galvanized steel rebar from the 48 year old Longbird Bridge in Bermuda.

  19. Phase behavior and interfacial tension studies of surfactant systems

    Energy Technology Data Exchange (ETDEWEB)

    Franses, E.I.

    1979-01-01

    Parallel studies of isomerically pure sodium P(1-heptylnonyl) benzene sulfoante, Texas No. 1, its mixture with sodium dodecyl sulfate (SDS), and the petroleum sulfonate TRS 10-80 were made. Phase behavior in water, in decane, and in water-decane mixtures was studied by spectroturbidimetry, polarizing light microscopy, ultracentrifugation, ultrafiltration, densitometry, conductimetry, low-frequency, 0.2 to 20 kHz, dielectric relaxation, isopiestic vapor pressure, and nuclear magnetic resonance spectroscopy. It was deduced that ultralow tensions (less than 0.01 dyn/cm) arise from the dispersed microcrystallites which form a third, usually liquid crystalline, phase at the decane-brine interfacial region. It appears that neither molecular adsorption from solution for micelles have anything to do with ultralow tensions, which appear to be sensitive to the third phase microstructure. The implications of these results for the mechanism of ultralow tensions in surfactant flooding processes for enhanced petroleum recovery are discussed.

  20. Work function engineering using lanthanum oxide interfacial layers

    Science.gov (United States)

    Alshareef, H. N.; Quevedo-Lopez, M.; Wen, H. C.; Harris, R.; Kirsch, P.; Majhi, P.; Lee, B. H.; Jammy, R.; Lichtenwalner, D. J.; Jur, J. S.; Kingon, A. I.

    2006-12-01

    A La2O3 capping scheme has been developed to obtain n-type band-edge metal gates on Hf-based gate dielectrics. The viability of the technique is demonstrated using multiple metal gates that normally show midgap work function when deposited directly on HfSiO. The technique involves depositing a thin interfacial of La2O3 on a Hf-based gate dielectric prior to metal gate deposition. This process preserves the excellent device characteristic of Hf-based dielectrics, but also allows the realization of band-edge metal gates. The effectiveness of the technique is demonstrated by fabricating fully functional transistor devices. A model is proposed to explain the effect of La2O3 capping on metal gate work function.

  1. Type II DNA: When the interfacial energy becomes negative

    Science.gov (United States)

    Sadhukhan, Poulomi; Maji, Jaya; Bhattacharjee, Somendra M.

    2011-08-01

    An important step in transcription of a DNA base sequence to a protein is the initiation from the exact starting point, called promoter region. We propose a physical mechanism for identification of the promoter region, which relies on a new classification of DNAs into two types, Type I and Type II, like superconductors, depending on the sign of the energy of the interface separating the zipped and the unzipped phases. This is determined by the energies of helical ordering and stretching over two independent length scales. The negative interfacial energy in Type II DNA leads to domains of helically ordered state separated by defect regions, or blobs, enclosed by the interfaces. The defect blobs, pinned by non-coding promoter regions, would be physically distinct from all other types of bubbles. We also show that the order of the melting transition under a force is different for Type I and Type II.

  2. The Enzyme Function Initiative†

    Science.gov (United States)

    Gerlt, John A.; Allen, Karen N.; Almo, Steven C.; Armstrong, Richard N.; Babbitt, Patricia C.; Cronan, John E.; Dunaway-Mariano, Debra; Imker, Heidi J.; Jacobson, Matthew P.; Minor, Wladek; Poulter, C. Dale; Raushel, Frank M.; Sali, Andrej; Shoichet, Brian K.; Sweedler, Jonathan V.

    2011-01-01

    The Enzyme Function Initiative (EFI) was recently established to address the challenge of assigning reliable functions to enzymes discovered in bacterial genome projects; in this Current Topic we review the structure and operations of the EFI. The EFI includes the Superfamily/Genome, Protein, Structure, Computation, and Data/Dissemination Cores that provide the infrastructure for reliably predicting the in vitro functions of unknown enzymes. The initial targets for functional assignment are selected from five functionally diverse superfamilies (amidohydrolase, enolase, glutathione transferase, haloalkanoic acid dehalogenase, and isoprenoid synthase), with five superfamily-specific Bridging Projects experimentally testing the predicted in vitro enzymatic activities. The EFI also includes the Microbiology Core that evaluates the in vivo context of in vitro enzymatic functions and confirms the functional predictions of the EFI. The deliverables of the EFI to the scientific community include: 1) development of a large-scale, multidisciplinary sequence/structure-based strategy for functional assignment of unknown enzymes discovered in genome projects (target selection, protein production, structure determination, computation, experimental enzymology, microbiology, and structure-based annotation); 2) dissemination of the strategy to the community via publications, collaborations, workshops, and symposia; 3) computational and bioinformatic tools for using the strategy; 4) provision of experimental protocols and/or reagents for enzyme production and characterization; and 5) dissemination of data via the EFI’s website, enzymefunction.org. The realization of multidisciplinary strategies for functional assignment will begin to define the full metabolic diversity that exists in nature and will impact basic biochemical and evolutionary understanding, as well as a wide range of applications of central importance to industrial, medicinal and pharmaceutical efforts. PMID

  3. Monitoring enzyme kinetic behavior of enzyme-quantum dot bioconjugates

    Science.gov (United States)

    Claussen, Jonathan C.; Walper, Scott A.; Susumu, Kimihiro; Ancona, Mario G.; Medintz, Igor L.

    2014-05-01

    Luminescent semiconductor nanocrystals or quantum dots (QDs) hold tremendous promise for in vivo biosensing, cellular imaging, theranostics, and smart molecular sensing probes due to their small size and favorable photonic properties such as resistance to photobleaching, size-tunable PL, and large effective Stokes shifts. Herein, we demonstrate how QD-based bioconjugates can be used to enhance enzyme kinetics. Enzyme-substrate kinetics are analyzed for solutions containing both alkaline phosphatase enzymes and QDs with enzyme-to- QD molar ratios of 2, 12, and 24 as well as for a solution containing the same concentration of enzymes but without QDs. The enzyme kinetic paramters Vmax, KM, and Kcat/KM are extracted from the enzyme progress curves via the Lineweaver-Burk plot. Results demonstrate an approximate increase in enzyme efficiency of 5 - 8% for enzymes immobilized on the QD versus free in solution without QD immobilization.

  4. SIMS studies of interfacial effects in polystyrene thin films

    Science.gov (United States)

    Strzhemechny, Yuri

    Secondary Ion Mass Spectrometry was employed to examine polystyrene chain dynamics near attractive surfaces. Diffusion from a silicon surface and from a sputter- deposited carbon surface was compared in tri-layer sandwiches with a deuterated middle layer. The carbon surface serves as an analog for the carbon-black surface in nanocomposites. Strong segregation of the deuterated component was observed at the native silicon oxide surface, but was inhibited at the carbon surface. A finite element computer program was developed to fit the observed diffusion profiles. The diffusion coefficient D varies with depth superlinearly, scaling roughly as a 3/2-power. Importantly, D in the marker layer region is observed to decrease strongly with time at both the vacuum and solid wall surfaces. The effect of standard wet chemical wafer cleaning procedures on the polystyrene/silicon interface was investigated as well. Deuterated solutions were employed to allow detection of remnant moisture from the cleaning/etching steps, and to indicate the extent of hydrogen termination at the polystyrene/silicon interface. The SIMS data indicated that the surface is effectively terminated by approximately one monolayer of hydrogen after an HF etch step, and by a thin oxide layer after an HCl/peroxide etch. The use of implant standards and a calibrated polymer blend permitted a rough calibration of the deuterium and fluorine concentrations at the interface. Also, deuterium and oxygen were found to be stable under high temperature anneals. The lack of a CD interfacial peak indicated that deuterium is associated with the silicon interface and not with the polymer chains. Oxygen and fluorine contamination peaks were also stable during the anneals. Following exposure to the peroxide/HCl solution, the deuterium level was shown to be much reduced, and the oxygen level is increased, as expected. Despite the wet processes employed in sample preparation, there is no evidence of remnant moisture in the

  5. Numerical modeling of mineral dissolution - precipitation kinetics integrating interfacial processes

    Science.gov (United States)

    Azaroual, M. M.

    2016-12-01

    The mechanisms of mineral dissolution/precipitation are complex and interdependent. Within a same rock, the geochemical modelling may have to manage kinetic reactions with high ratios between the most reactive minerals (i.e., carbonates, sulfate salts, etc.) and less reactive minerals (i.e., silica, alumino-silicates, etc.). These ratios (higher than 10+6) induce numerical instabilities for calculating mass and energy transfers between minerals and aqueous phases at the appropriate scales of time and space. The current scientific debate includes: i) changes (or not) of the mineral reactive surface with the progress of the dissolution/precipitation reactions; ii) energy jumps (discontinuity) in the thermodynamic affinity function of some dissolution/precipitation reactions and iii) integration of processes at the "mineral - aqueous solution" interfaces for alumino-silicates, silica and carbonates. In recent works dealing with the specific case of amorphous silica, measurements were performed on nano-metric cross-sections indicating the presence of surface layer between the bulk solution and the mineral. This thin layer is composed by amorphous silica and hydrated silica "permeable" to the transfer of water and ionic chemical constituents. The boundary/interface between the initial mineral and the silica layer is characterized by a high concentration jump of chemical products at the nanoscale and some specific interfacial dissolution/precipitation processes.In this study, the results of numerical simulations dealing with different mechanisms of silicate and carbonate dissolution/precipitation reactions and integrating interfacial processes will be discussed. The application of this approach to silica precipitation is based on laboratory experiments and it highlights the significant role of the "titration" surface induced by surface complexation reactions in the determination of the kinetics of precipitation.

  6. Hafnium metallocene compounds used as cathode interfacial layers for enhanced electron transfer in organic solar cells.

    Science.gov (United States)

    Park, Keunhee; Oh, Seungsik; Jung, Donggeun; Chae, Heeyeop; Kim, Hyoungsub; Boo, Jin-Hyo

    2012-01-09

    We have used hafnium metallocene compounds as cathode interfacial layers for organic solar cells [OSCs]. A metallocene compound consists of a transition metal and two cyclopentadienyl ligands coordinated in a sandwich structure. For the fabrication of the OSCs, poly[3,4-ethylenedioxythiophene]:poly(styrene sulfonate), poly(3-hexylthiophene-2,5-diyl) + 66-phenyl C61 butyric acid methyl ester, bis-(ethylcyclopentadienyl)hafnium(IV) dichloride, and aluminum were deposited as a hole transport layer, an active layer, a cathode interfacial layer, and a cathode, respectively. The hafnium metallocene compound cathode interfacial layer improved the performance of OSCs compared to that of OSCs without the interfacial layer. The current density-voltage characteristics of OSCs with an interfacial layer thickness of 0.7 nm and of those without an interfacial layer showed power conversion efficiency [PCE] values of 2.96% and 2.34%, respectively, under an illumination condition of 100 mW/cm2 (AM 1.5). It is thought that a cathode interfacial layer of an appropriate thickness enhances the electron transfer between the active layer and the cathode, and thus increases the PCE of the OSCs.

  7. Use of the pendant drop method to measure interfacial tension between molten polymers

    Directory of Open Access Journals (Sweden)

    Emerson Y. Arashiro

    1999-01-01

    Full Text Available In this paper the pendant drop method to measure interfacial tension between molten polymers is reviewed. A typical pendant drop apparatus is presented. The algorithms used to infer interfacial tension from the geometrical profile of the pendant drop are described in details, in particular a new routine to evaluate correctly the value of the radius at the apex of the drop, necessary to the calculation of interfacial tension is presented. The method was evaluated for the possibility of measuring the interfacial tension between polyethylene and polystyrene. It is shown that the method is unsuitable for the measurement of interfacial tension between high density polyethylene and polystyrene due possibly to a too small difference of density between the two polymers. Values of interfacial tension between low density polyethylene (LDPE and polystyrene (PS as a function of the molecular weight of PS are presented. It was shown that the interfacial tension between LDPE and PS increased as a function of molecular weight of PS up to values of molecular weight of roughly 40,000 g/mol, value for which entanglements occur.

  8. Development of local interfacial strains and stresses in the formation of asymmetric particle-stabilized capsules

    Science.gov (United States)

    Anna, Shelley; Sharkey, Charles

    2017-11-01

    Particles adsorbed at fluid interfaces can stabilize bubbles and droplets against coalescence. However, the method of generating the interface strongly impacts interparticle interactions, and in turn, interfacial microstructure, rheology, and stability. By controlling the adsorbed concentration of particles via residence time in a long channel, we generate non-spherical capsules that retain their shape for at least tens of hours. The capsule shape is in part determined by the dynamics of the bubble as it exits the tube. In this talk, we use image analysis to examine the development of interfacial strains during capsule formation at the channel exit. Tracking the bubble radius profile as a function of time allows us to examine the evolution of interfacial area and bubble volume, as well as the dilation rate profile along the interface. These observations allow us to infer the development of interfacial dilational and buckling stresses that lead to the capsule shape stability. We compare the interfacial strain evolution for clean, surfactant, and particle-laden interfaces as a function of the composition of the interfacially active component. These observations provide a direct connection between colloidal and production factors, and interfacial mechanics and capsule stability. NSF CBET Grant No. 1511016.

  9. Interfacial behavior of alkaline protease at the air-water and oil-water interfaces

    Science.gov (United States)

    Zhang, Jian; Li, Yanyan; Wang, Jing; Zhang, Yue

    2018-03-01

    The interfacial behavior of alkaline protease at the air-water and n-hexane-water interfaces was investigated using interfacial tension, dilatational rheology and dynamic light scattering. Additionally, different adsorption models which are Langmuir, Frumkin, Reorientation-A and Reorientation-R were used to fitting the data of equilibrium interfacial tension for further understanding the interfacial behavior of alkaline protease. Data fitting of the equilibrium interfacial tension was achieved by IsoFit software. The results show that the molecules arrangement of the alkaline protease at the n-hexane-water interface is more tightly than at the air-water interface. The data were further analyzed to indicate that the hydrophobic chains of alkaline protease penetrate into oil phase deeper than the air phase. Also data indicate that the electrostatic interactions and hydrophobic interactions at the n-hexane-water interface are stronger than at the air-water interface within molecules of the alkaline protease. Based on comprehensive analysis of the adsorption kinetics and interfacial rheological properties, interfacial structures mechanism of alkaline protease at n-hexane-water and air-water interfaces was proposed.

  10. Interplay of drug metabolizing enzymes with cellular transporters.

    Science.gov (United States)

    Böhmdorfer, Michaela; Maier-Salamon, Alexandra; Riha, Juliane; Brenner, Stefan; Höferl, Martina; Jäger, Walter

    2014-11-01

    Many endogenous and xenobiotic substances and their metabolites are substrates for drug metabolizing enzymes and cellular transporters. These proteins may not only contribute to bioavailability of molecules but also to uptake into organs and, consequently, to overall elimination. The coordinated action of uptake transporters, metabolizing enzymes, and efflux pumps, therefore, is a precondition for detoxification and elimination of drugs. As the understanding of the underlying mechanisms is important to predict alterations in drug disposal, adverse drug reactions and, finally, drug-drug interactions, this review illustrates the interplay between selected uptake/efflux transporters and phase I/II metabolizing enzymes.

  11. Special Issue: Retroviral Enzymes

    Directory of Open Access Journals (Sweden)

    Luis Menéndez-Arias

    2010-05-01

    Full Text Available The retroviral RNA genome encodes for three enzymes essential for virus replication: (i the viral protease (PR, that converts the immature virion into a mature virus through the cleavage of precursor polypeptides; (ii the reverse transcriptase (RT, responsible for the conversion of the single-stranded genomic RNA into double-stranded proviral DNA; and (iii the integrase (IN that inserts the proviral DNA into the host cell genome. All of them are important targets for therapeutic intervention. This Special Issue provides authoritative reviews on the most recent research towards a better understanding of structure-function relationships in retroviral enzymes. The Issue includes three reviews on retroviral PRs, seven on RT and reverse transcription, and four dedicated to viral integration. [...

  12. Halophilic adaptation of enzymes.

    Science.gov (United States)

    Madern, D; Ebel, C; Zaccai, G

    2000-04-01

    It is now clear that the understanding of halophilic adaptation at a molecular level requires a strategy of complementary experiments, combining molecular biology, biochemistry, and cellular approaches with physical chemistry and thermodynamics. In this review, after a discussion of the definition and composition of halophilic enzymes, the effects of salt on their activity, solubility, and stability are reviewed. We then describe how thermodynamic observations, such as parameters pertaining to solvent-protein interactions or enzyme-unfolding kinetics, depend strongly on solvent composition and reveal the important role played by water and ion binding to halophilic proteins. The three high-resolution crystal structures now available for halophilic proteins are analyzed in terms of haloadaptation, and finally cellular response to salt stress is discussed briefly.

  13. Membrane Assisted Enzyme Fractionation

    DEFF Research Database (Denmark)

    Yuan, Linfeng

    Purification of proteins is an increasingly important process for the biotechnology industry. Separation of the desired high value protein from other proteins produced by the cell is usually attempted using a combination of different chromatographic techniques. These techniques separate mixtures...... of proteins on the basis of their charge, degree of hydrophobicity, affinity or size. Adequate purity is often not achieved unless several purification steps are combined thereby increasing cost and reducing product yield. Conventional fractionation of proteins using ultrafiltration membranes is limited....... In this thesis, separations using crossflow elecro-membrane filtration (EMF) of amino acids, bovine serum albumin (BSA) and industrial enzymes from Novozymes were performed. The main objective of this study was to investigate the technological feasibility of EMF in the application of industrial enzyme...

  14. Organic/inorganic electrochromic nanocomposites with various interfacial interactions: A review

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Shanxin, E-mail: xiongsx@xust.edu.cn; Yin, Siyuan; Wang, Yuyun; Kong, Zhenzhen; Lan, Jinpeng; Zhang, Runlan; Gong, Ming; Wu, Bohua; Chu, Jia; Wang, Xiaoqin

    2017-07-15

    Highlights: • We review the effects of interfacial interactions in electrochromic nanocomposites. • Interfacial interactions are useful for film fabrication and property-enhancement. • The strong interaction can enhance the electron conduction and structural strength. • The weak interactions exist widely between organic and inorganic phases. • Multiple weak interactions can provide various performance-adjusting approaches. - Abstract: Electrochromic properties of organic or inorganic materials can be improved through preparing organic/inorganic electrochromic nanocomposites. In electrochromic nanocomposites, the interfacial interactions between the organic and inorganic phases play three important roles in preparation and application of the nanocomposites. Firstly, the interfacial interactions result in stable molecular structures. Secondly, they also improve the electron conduction and ion transport process in the nanocomposites. Thirdly, they enhance the electrochemical and electrochromic properties of the nanocomposites. In this paper, we review the common interfacial interactions including covalent bond, coordination bond, electrostatic interaction, hydrogen bond and π-π stacking interaction between the organic and inorganic phases in the electrochromic nanocomposites. The preparation method, the relationship between the structure and properties, and the mechanism of modulation of electrochromic effect in the nanocomposites with various interfacial interactions are surveyed. The strong interfacial interaction, e.g., covalent bond, is helpful for obtaining electrochromic nanocomposites with high electron conduction and high structural strength. However it is very complicated to construct covalent bond between the organic and inorganic phases. Another strong interfacial interaction, the coordination bond is mainly confined to preparation of electrochromic complex of metal ion and pyridine derivative. While, the weak interfacial interactions, e

  15. Quorum quenching enzymes.

    Science.gov (United States)

    Fetzner, Susanne

    2015-05-10

    Bacteria use cell-to-cell communication systems based on chemical signal molecules to coordinate their behavior within the population. These quorum sensing systems are potential targets for antivirulence therapies, because many bacterial pathogens control the expression of virulence factors via quorum sensing networks. Since biofilm maturation is also usually influenced by quorum sensing, quenching these systems may contribute to combat biofouling. One possibility to interfere with quorum sensing is signal inactivation by enzymatic degradation or modification. Such quorum quenching enzymes are wide-spread in the bacterial world and have also been found in eukaryotes. Lactonases and acylases that hydrolyze N-acyl homoserine lactone (AHL) signaling molecules have been investigated most intensively, however, different oxidoreductases active toward AHLs or 2-alkyl-4(1H)-quinolone signals as well as other signal-converting enzymes have been described. Several approaches have been assessed which aim at alleviating virulence, or biofilm formation, by reducing the signal concentration in the bacterial environment. These involve the application or stimulation of signal-degrading bacteria as biocontrol agents in the protection of crop plants against soft-rot disease, the use of signal-degrading bacteria as probiotics in aquaculture, and the immobilization or entrapment of quorum quenching enzymes or bacteria to control biofouling in membrane bioreactors. While most approaches to use quorum quenching as antivirulence strategy are still in the research phase, the growing number of organisms and enzymes known to interfere with quorum sensing opens up new perspectives for the development of innovative antibacterial strategies. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. A Nonlinear Finite Element Method for Magnetoelectric Composite and the Study on the Influence of Interfacial Bonding

    Directory of Open Access Journals (Sweden)

    He-Ling Wang

    2013-01-01

    Full Text Available Magnetoelectric composite material is effective in transferring magnetic field into electric signal. In this paper, a nonlinear finite element method is present to model the magnetoelectric composite of ferroelectric and magnetostrictive material. In the method, the nonlinear and coupling behavior of magnetostrictive material such as Terfenol-D is considered. The nonuniform magnetic, electric, and mechanical field distributions are present. An interfacial transferring coefficient is defined to investigate the performance of interfacial mechanical coupling quantitatively, and the influence of the properties of interfacial bonding material and interfacial cracks on magnetoelectric coefficient is discussed. A new laminate ME composite of curved interface is proposed to overcome weak interfacial bonding.

  17. Crosstalk between the subunits of the homodimeric enzyme triosephosphate isomerase.

    Science.gov (United States)

    Zomosa-Signoret, Viviana; Aguirre-López, Beatriz; Hernández-Alcántara, Gloria; Pérez-Montfort, Ruy; de Gómez-Puyou, Marietta Tuena; Gómez-Puyou, Armando

    2007-04-01

    Homodimeric triosephosphate isomerase (TIM) from Trypanosoma cruzi (TcTIM) and T. brucei (TbTIM) are markedly similar in amino acid sequence and three-dimensional structure. In their dimer interfaces, each monomer has a Cys15 that is surrounded by loop3 of the adjoining subunit. Perturbation of Cys15 by methylmethane thiosulfonate (MMTS) induces abolition of catalysis and structural changes. In the two TIMs, the structural arrangements of their Cys15 are almost identical. Nevertheless, the susceptibility of TcTIM to MMTS is nearly 100-fold higher than in TbTIM. To ascertain the extent to which the characteristics of the interface Cys depend on the dynamics of its own monomer or on those of the adjacent monomer, we studied MMTS action on mutants of TcTIM that had the interface residues of TbTIM, and hybrids that have only one interfacial Cys15 (C15ATcTIM-wild type TbTIM). We found that the solvent exposure of the interfacial Cys depends predominantly on the characteristics of the adjoining monomer. The maximal inhibition of activity induced by perturbation of the sole interface Cys in the C15ATcTIM-TbTIM hybrid is around 60%. Hybrids formed with C15ATcTIM monomers and catalytically inert TbTIM monomers (E168DTbTIM) were also studied. Their activity drops by nearly 50% when the only interfacial Cys is perturbed. These results in conjunction with those on C15ATcTIM-wild type TbTIM hybrid indicate that about half of the activity of each monomer depends on the integrity of each of the two Cys15-loop3 portions of the interface. This could be another reason of why TIM is an obligatory dimer. (c) 2007 Wiley-Liss, Inc.

  18. Uronic polysaccharide degrading enzymes.

    Science.gov (United States)

    Garron, Marie-Line; Cygler, Miroslaw

    2014-10-01

    In the past several years progress has been made in the field of structure and function of polysaccharide lyases (PLs). The number of classified polysaccharide lyase families has increased to 23 and more detailed analysis has allowed the identification of more closely related subfamilies, leading to stronger correlation between each subfamily and a unique substrate. The number of as yet unclassified polysaccharide lyases has also increased and we expect that sequencing projects will allow many of these unclassified sequences to emerge as new families. The progress in structural analysis of PLs has led to having at least one representative structure for each of the families and for two unclassified enzymes. The newly determined structures have folds observed previously in other PL families and their catalytic mechanisms follow either metal-assisted or Tyr/His mechanisms characteristic for other PL enzymes. Comparison of PLs with glycoside hydrolases (GHs) shows several folds common to both classes but only for the β-helix fold is there strong indication of divergent evolution from a common ancestor. Analysis of bacterial genomes identified gene clusters containing multiple polysaccharide cleaving enzymes, the Polysaccharides Utilization Loci (PULs), and their gene complement suggests that they are organized to process completely a specific polysaccharide. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Ultrasonic Guided Waves in Piezoelectric Layered Composite with Different Interfacial Properties

    Directory of Open Access Journals (Sweden)

    Xiao Chen

    2011-01-01

    Full Text Available Combining the propagation model of guided waves in a multilayered piezoelectric composite with the interfacial model of rigid, slip, and weak interfaces, the generalized dispersion characteristic equations of guided waves propagating in a piezoelectric layered composite with different interfacial properties are derived. The effects of the slip, weak, and delamination interfaces in different depths on the dispersion properties of the lowest-order mode ultrasonic guided wave are analyzed. The theory would be used to characterize the interfacial properties of piezoelectric layered composite nondestructively.

  20. Relationship Between Casting Distortion, Mold Filling, and Interfacial Heat Transfer in Sand Molds

    Energy Technology Data Exchange (ETDEWEB)

    J. K. Parker; K. A. Woodbury; T. S. Piwonka; Y. Owusu

    1999-09-30

    This project sought to determine the relationship between casting dimensions and interfacial heat transfer in aluminum alloy sand castings. The program had four parts; measurement of interfacial heat transfer coefficients in resin bonded and green sand molds, the measurement of gap formation in these molds, the analysis of castings made in varying gatings, orientations and thicknesses, and the measurement of residual stresses in castings in the as-cast and gate removed condition. New values for interfacial heat transfer coefficients were measured, a novel method for gap formation was developed, and the variation of casting dimensions with casting method, gating, and casting orientation in the mold was documented.

  1. Calculation of alloy solid-liquid interfacial free energies from atomic-scale simulations

    Science.gov (United States)

    Asta, M.; Hoyt, J. J.; Karma, A.

    2002-09-01

    Solid-liquid interfacial free energies and associated crystalline anisotropies are calculated for a model Ni-Cu alloy system based upon the analysis of equilibrium capillary fluctuations in molecular-dynamics simulations. Alloying of Ni by Cu leads to a reduction in the magnitude of the calculated interfacial free energy, while having only a minor effect on computed anisotropies. The present study demonstrates the viability of applying the fluctuation method to simulation-based calculations of solid-liquid interfacial free energies in alloys.

  2. Effects of crystal-melt interfacial energy anisotropy on dendritic morphology and growth kinetics

    Science.gov (United States)

    Glicksman, M. E.; Singh, N. B.

    1989-01-01

    Morphological and kinetic studies of succinonitrile, a BCC crystal with a low (0.5 percent) anisotropy and pivalic acid, and FCC crystal with relatively large (5 percent) anisotropy in solid-liquid interfacial energy, show clearly that anisotropy in the solid-liquid interfacial energy does not affect the tip radius-velocity relationship, but has a profound influence on the tip region and the rate of amplification of branching waves. Anisotropy of the solid-liquid interfacial energy may be one of the key factors by which the microstructural characteristics of cast structures reflect individual material behavior, especially crystal symmetry.

  3. Ab initio investigation of Al/Mo2B interfacial adhesion

    OpenAIRE

    SI ABDELKADER, H.; Faraoun, H.I.

    2011-01-01

    First-principles calculations were performed to study the adhesion and the interfacial electronic structure of aluminum/molybdenum semi-boride (Al/Mo2B) interface. The work of adhesion (Wad) was calculated for both terminations of the Mo2B surface and it was found that Mo-terminated has larger Wad than the B-terminated one. It was shown that interfacial Al and B atoms form polar covalent bonds, while bonding of interfacial Al and Mo atoms mainly presents metallic character. Computational M...

  4. A study on interfacial tension between flexible polymer and liquid crystal.

    Science.gov (United States)

    Wu, Youjun; Yu, Wei; Zhou, Chixing

    2006-06-15

    The interfacial property in polymer-liquid crystal systems is quite different from flexible polymer-polymer mixtures due to the anisotropic properties of liquid crystals. The apparent interfacial tension between a liquid crystal and a flexible polymer was measured by deformed droplet retraction method. The deformation and recovery of a single liquid crystal droplet dispersed in a poly(dimethylsiloxane) matrix were realized by a transient shear flow and observed by polarized optical microscope. The apparent interfacial tension of polymer-liquid crystal system was found to be greatly dependent on the temperature, initial droplet deformation and liquid crystal droplet size.

  5. Estimation of interfacial tension for immiscible and partially miscible liquid systems by Dissipative Particle Dynamics

    Science.gov (United States)

    Goel, Himanshu; Chandran, P. Rakesh; Mitra, Kishalay; Majumdar, Saptarshi; Ray, Partha

    2014-04-01

    Dissipative Particle Dynamics (DPD) can calculate mesoscale properties like interfacial tension for liquid-liquid systems with much less computational rigor compared to Molecular Dynamics (MD). As of now, no general coarse graining protocol is available for estimating interfacial tension for large number of immiscible and partially miscible systems. In the present effort, a protocol has been formulated for coarse graining of liquid molecules based on underlying chemistry and physics of the individual components and the capability of DPD framework based on self-repulsive interaction parameters of each component to estimate interfacial tension for large number of liquid-liquid systems is tested.

  6. Enzyme synthesis in the regulation of hepatic `malic' enzyme activity

    Science.gov (United States)

    Murphy, Gillian; Walker, Deryck G.

    1974-01-01

    A homogeneous preparation of `malic' enzyme (EC 1.1.1.40) from livers of thyroxine-treated rats was used to prepare in rabbits an antiserum to the enzyme that reacts monospecifically with the `malic' enzyme in livers of rats in several physiological states. Changes in enzyme activity resulting from modification of the state of the animal are hence due to an altered amount of enzyme protein. The antiserum has been used to precipitate out `malic' enzyme from heat-treated supernatant preparations of livers from both adult and neonatal rats, in a number of physiological conditions, that had been injected 30min earlier with l-[4,5-3H]leucine. The low incorporations of radioactivity into the immunoprecipitable enzyme have permitted the qualitative conclusion that changed enzyme activity in adult rats arises mainly from alterations in the rate of enzyme synthesis. The marked increase in `malic' enzyme activity that occurs naturally or as a result of thyroxine treatment of the weanling rat is likewise due to a marked increase in the rate of enzyme synthesis possibly associated with a concurrent diminished rate of enzyme degradation. PMID:4462568

  7. Enzyme synthesis in the regulation of hepatic "malic" enzyme activity.

    Science.gov (United States)

    Murphy, G; Walker, D G

    1974-10-01

    A homogeneous preparation of ;malic' enzyme (EC 1.1.1.40) from livers of thyroxine-treated rats was used to prepare in rabbits an antiserum to the enzyme that reacts monospecifically with the ;malic' enzyme in livers of rats in several physiological states. Changes in enzyme activity resulting from modification of the state of the animal are hence due to an altered amount of enzyme protein. The antiserum has been used to precipitate out ;malic' enzyme from heat-treated supernatant preparations of livers from both adult and neonatal rats, in a number of physiological conditions, that had been injected 30min earlier with l-[4,5-(3)H]leucine. The low incorporations of radioactivity into the immunoprecipitable enzyme have permitted the qualitative conclusion that changed enzyme activity in adult rats arises mainly from alterations in the rate of enzyme synthesis. The marked increase in ;malic' enzyme activity that occurs naturally or as a result of thyroxine treatment of the weanling rat is likewise due to a marked increase in the rate of enzyme synthesis possibly associated with a concurrent diminished rate of enzyme degradation.

  8. Interfacial Behavior of Polymers: Using Interfaces to Manipulate Polymers

    Energy Technology Data Exchange (ETDEWEB)

    Russell, Thomas P. [Univ. of Massachusetts, Amherst, MA (United States). Dept. of Polymer Science and Engineering

    2015-02-26

    The self-assembly of block copolymers into arrays of nanoscopic domains with areal densities approaching 10 terbit/in2 offer tremendous promise for the fabrication of ultrahigh density storage devices, batteries and other energy relevant devices. Interfacial interactions play a key role in dictating the orientation and ordering of these self-assembling materials. We have investigated the use of preferential and neutral solvents to overcome interfacial interactions and to rapid accelerate the dynamics of these materials, since the high molecular weight of the polymers significantly slows diffusion processes. Using a tailor-made chamber, we have introduced solvent vapor annealing (SVA) where solvent with a well-defined vapor pressures sells the copolymer film, enabling control over the solvent content in the film and, therefore, the thermodynamics governing the microphase separation of the copolymer, the interactions with the substrate and air interfaces and the dynamics. This tailor-made chamber also allows us to perform in situ grazing incidence x-ray scattering studies where the copolymer films can be characterized on the nanoscopic level over macroscopic distances. The methodologies developed in our laboratories are now used in numerous laboratories world-wide. We have found that arrays of block copolymer microdomains with perfect orientational order can be achieved over macroscopic areas using the SVA processes but the translational order is perturbed during the film drying process. As the copolymer film is swollen, the confinement of the film to the substrate introduces a frustration to the ordering of the microdomains. After equilibrium is achieved, when the swollen films are brought very close to the ordering transition, near perfect ordering is achieved. However, upon removal of the solvent, the confinement of the film to the substrate introduces translational disorder. We have investigated the influence of the rate of solvent removal and have found that

  9. NRSA enzyme decomposition model data

    Data.gov (United States)

    U.S. Environmental Protection Agency — Microbial enzyme activities measured at more than 2000 US streams and rivers. These enzyme data were then used to predict organic matter decomposition and microbial...

  10. Reversible Immobilization of Lipases on Heterofunctional Octyl-Amino Agarose Beads Prevents Enzyme Desorption

    Directory of Open Access Journals (Sweden)

    Nazzoly Rueda

    2016-05-01

    Full Text Available Two different heterofunctional octyl-amino supports have been prepared using ethylenediamine and hexylendiamine (OCEDA and OCHDA and utilized to immobilize five lipases (lipases A (CALA and B (CALB from Candida antarctica, lipases from Thermomyces lanuginosus (TLL, from Rhizomucor miehei (RML and from Candida rugosa (CRL and the phospholipase Lecitase Ultra (LU. Using pH 5 and 50 mM sodium acetate, the immobilizations proceeded via interfacial activation on the octyl layer, after some ionic bridges were established. These supports did not release enzyme when incubated at Triton X-100 concentrations that released all enzyme molecules from the octyl support. The octyl support produced significant enzyme hyperactivation, except for CALB. However, the activities of the immobilized enzymes were usually slightly higher using the new supports than the octyl ones. Thermal and solvent stabilities of LU and TLL were significantly improved compared to the OC counterparts, while in the other enzymes the stability decreased in most cases (depending on the pH value. As a general rule, OCEDA had lower negative effects on the stability of the immobilized enzymes than OCHDA and while in solvent inactivation the enzyme molecules remained attached to the support using the new supports and were released using monofunctional octyl supports, in thermal inactivations this only occurred in certain cases.

  11. Extracting enzyme processivity from kinetic assays

    Energy Technology Data Exchange (ETDEWEB)

    Barel, Itay; Brown, Frank L. H. [Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106 (United States); Department of Physics, University of California, Santa Barbara, California 93106 (United States); Reich, Norbert O. [Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106 (United States)

    2015-12-14

    A steady-state analysis for the catalytic turnover of molecules containing two substrate sites is presented. A broad class of Markovian dynamic models, motivated by the action of DNA modifying enzymes and the rich variety of translocation mechanisms associated with these systems (e.g., sliding, hopping, intersegmental transfer, etc.), is considered. The modeling suggests an elementary and general method of data analysis, which enables the extraction of the enzyme’s processivity directly and unambiguously from experimental data. This analysis is not limited to the initial velocity regime. The predictions are validated both against detailed numerical models and by revisiting published experimental data for EcoRI endonuclease acting on DNA.

  12. Enzyme Promiscuity: Engine of Evolutionary Innovation*

    Science.gov (United States)

    Pandya, Chetanya; Farelli, Jeremiah D.; Dunaway-Mariano, Debra; Allen, Karen N.

    2014-01-01

    Catalytic promiscuity and substrate ambiguity are keys to evolvability, which in turn is pivotal to the successful acquisition of novel biological functions. Action on multiple substrates (substrate ambiguity) can be harnessed for performance of functions in the cell that supersede catalysis of a single metabolite. These functions include proofreading, scavenging of nutrients, removal of antimetabolites, balancing of metabolite pools, and establishing system redundancy. In this review, we present examples of enzymes that perform these cellular roles by leveraging substrate ambiguity and then present the structural features that support both specificity and ambiguity. We focus on the phosphatases of the haloalkanoate dehalogenase superfamily and the thioesterases of the hotdog fold superfamily. PMID:25210039

  13. The Catalytic Function of Enzymes.

    Science.gov (United States)

    Splittgerber, Allan G.

    1985-01-01

    Discusses: structure of the enzyme molecule; active site; reaction mechanism; transition state; factors affecting enzyme reaction rates, concentration of enzyme; concentration of substrate; product concentration; temperature effects and pH effects; factors causing a lowering of activation energy; proximity and orientation effects; substrate strain…

  14. Measuring Air-water Interfacial Area for Soils Using the Mass Balance Surfactant-tracer Method

    Science.gov (United States)

    Araujo, Juliana B.; Mainhagu, Jon; Brusseau, Mark L.

    2015-01-01

    There are several methods for conducting interfacial partitioning tracer tests to measure air-water interfacial area in porous media. One such approach is the mass balance surfactant tracer method. An advantage of the mass-balance method compared to other tracer-based methods is that a single test can produce multiple interfacial area measurements over a wide range of water saturations. The mass-balance method has been used to date only for glass beads or treated quartz sand. The purpose of this research is to investigate the effectiveness and implementability of the mass-balance method for application to more complex porous media. The results indicate that interfacial areas measured with the mass-balance method are consistent with values obtained with the miscible-displacement method. This includes results for a soil, for which solid-phase adsorption was a significant component of total tracer retention. PMID:25950136

  15. A biomimetic approach to enhancing interfacial interactions: polydopamine-coated clay as reinforcement for epoxy resin.

    Science.gov (United States)

    Yang, Liping; Phua, Si Lei; Teo, Jun Kai Herman; Toh, Cher Ling; Lau, Soo Khim; Ma, Jan; Lu, Xuehong

    2011-08-01

    A facile biomimetic method was developed to enhance the interfacial interaction in polymer-layered silicate nanocomposites. By mimicking mussel adhesive proteins, a monolayer of polydopamine was constructed on clay surface by a controllable coating method. The modified clay (D-clay) was incorporated into an epoxy resin, it is found that the strong interfacial interactions brought by the polydopamine benefits not only the dispersion of the D-clay in the epoxy but also the effective interfacial stress transfer, leading to greatly improved thermomechanical properties at very low inorganic loadings. Rheological and infrared spectroscopic studies show that the interfacial interactions between the D-clay and epoxy are dominated by the hydrogen bonds between the catechol-enriched polydopamine and the epoxy.

  16. Measuring air-water interfacial area for soils using the mass balance surfactant-tracer method.

    Science.gov (United States)

    Araujo, Juliana B; Mainhagu, Jon; Brusseau, Mark L

    2015-09-01

    There are several methods for conducting interfacial partitioning tracer tests to measure air-water interfacial area in porous media. One such approach is the mass balance surfactant tracer method. An advantage of the mass-balance method compared to other tracer-based methods is that a single test can produce multiple interfacial area measurements over a wide range of water saturations. The mass-balance method has been used to date only for glass beads or treated quartz sand. The purpose of this research is to investigate the effectiveness and implementability of the mass-balance method for application to more complex porous media. The results indicate that interfacial areas measured with the mass-balance method are consistent with values obtained with the miscible-displacement method. This includes results for a soil, for which solid-phase adsorption was a significant component of total tracer retention. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Sound-induced Interfacial Dynamics in a Microfluidic Two-phase Flow

    Science.gov (United States)

    Mak, Sze Yi; Shum, Ho Cheung

    2014-11-01

    Retrieving sound wave by a fluidic means is challenging due to the difficulty in visualizing the very minute sound-induced fluid motion. This work studies the interfacial response of multiphase systems towards fluctuation in the flow. We demonstrate a direct visualization of music in the form of ripples at a microfluidic aqueous-aqueous interface with an ultra-low interfacial tension. The interface shows a passive response to sound of different frequencies with sufficiently precise time resolution, enabling the recording of musical notes and even subsequent reconstruction with high fidelity. This suggests that sensing and transmitting vibrations as tiny as those induced by sound could be realized in low interfacial tension systems. The robust control of the interfacial dynamics could be adopted for droplet and complex-fiber generation.

  18. Interfacial fracture toughness of different resin cements bonded to a lithium disilicate glass ceramic

    National Research Council Canada - National Science Library

    Hooshmand, Tabassom; Rostami, Golriz; Behroozibakhsh, Marjan; Fatemi, Mostafa; Keshvad, Alireza; van Noort, Richard

    2012-01-01

    To evaluate the effect of HF acid etching and silane treatment on the interfacial fracture toughness of a self-adhesive and two conventional resin-based cements bonded to a lithium disilicate glass ceramic...

  19. The Mechanism of the Interfacial Charge and Mass Transfer during Intercalation of Alkali Metal Cations.

    Science.gov (United States)

    Ventosa, Edgar; Paulitsch, Bianca; Marzak, Philipp; Yun, Jeongsik; Schiegg, Florian; Quast, Thomas; Bandarenka, Aliaksandr S

    2016-12-01

    Intercalation of alkali metal cations, like Li+ or Na+, follows the same three-stage mechanism of the interfacial charge and mass transfer irrespective of the nature of the electrolyte, electrolyte composition or electrode material.

  20. Atomistic Modeling of Mechanical Characteristics of CNT-Polyethylene with Interfacial Covalent Interaction

    Directory of Open Access Journals (Sweden)

    Qi-lin Xiong

    2015-01-01

    Full Text Available The mechanical properties of carbon nanotube- (CNT- reinforced polyethylenes (PE with interfacial covalent bonded interaction are investigated using molecular dynamics simulations. A reactive force field for hydrocarbons (ReaxFF is used in the nanocomposite system. Through a series of the tensile and pullout tests of carbon nanotube-reinforced polyethylene, Young’s modulus and the interfacial shear stress of the nano-reinforced polyethylene are obtained. The comparisons between the MD results of this work and the relevant experimental data of the existing literature are made and the results show that the interfacial covalent bonded interaction between CNTs and the polymer matrix is indispensable. The bond interaction plays the main role in the load transfer of nanocomposites. In addition, the influences of carbon nanotube embedded length and diameter on the interfacial mechanical properties also are studied.

  1. Effect of interfacial shear strength on crack-fiber interaction behavior in ceramic matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Kumaria, S.; Singh, R.N. [Univ. of Cincinnati, OH (United States). Dept. of Materials Science and Engineering; Gupta, V. [Dartmouth Coll., Hanover, NH (United States). Thayer School of Engineering

    1996-01-01

    Zircon matrix composites uniaxially reinforced with SiC fibers were fabricated with different interfacial properties by changing the fiber coatings. The phenomenon of crack interaction with fibers and/or fiber coatings and its dependence on the interfacial properties were studied using a microindentation technique. The influence of the fiber orientation relative to the crack extension direction on the crack-fiber interaction was also investigated. Crack deflection was observed at the fiber-matrix interface in composites having low interfacial shear strength, and the crack deflection was mostly single-sided, but double-sided deflection was also observed. Crack penetration into the fiber occurred in composites with high values of the interfacial shear strength. These observations were in general agreement with the theoretical predictions of the crack deflection behavior based on the bimaterial interfaces in ceramic composites, but additional observations were made on crack deflection at multiple fiber-matrix interfaces.

  2. Manipulating the Interfacial Electrical and Optical Properties of Dissimilar Materials with Metallic Nanostructures

    Science.gov (United States)

    2016-07-30

    AFRL-AFOSR-VA-TR-2016-0281 MANIPULATING THE INTERFACIAL ELECTRIAL & OPTICAL PROPERTIES OF DISSIMILA Seth Bank UNIVERSITY OF TEXAS AT AUSTIN 101 EAST...From - To) 1 May 2010 - 30 Apr 2016 4. TITLE AND SUBTITLE Manipulating the Interfacial Electrical & Optical Properties of Dissimilar Materials with...NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) The University of Texas at Austin 101 E. 27th, Ste

  3. The Effects of Excipients on Protein Aggregation During Agitation: An Interfacial Shear Rheology Study

    OpenAIRE

    Liu, Lu; Qi, Wei; Schwartz, Daniel K.; Randolph, Theodore W.; Carpenter, John F.

    2013-01-01

    We investigated the effects of excipients in solutions of keratinocyte growth factor 2 (KGF-2) on protein aggregation during agitation as well as on interfacial shear rheology at the air-water interface. Samples were incubated with or without agitation, and in the presence or absence of the excipients heparin, sucrose or polysorbate 80 (PS80). The effect of excipients on the extent of protein aggregation was determined by UV spectroscopy and microflow imaging (MFI). Interfacial shear rheology...

  4. Interfacial Interactions in van der Waals Heterostructures of MoS2and Graphene.

    Science.gov (United States)

    Li, Hai; Wu, Jiang-Bin; Ran, Feirong; Lin, Miao-Ling; Liu, Xue-Lu; Zhao, Yanyuan; Lu, Xin; Xiong, Qihua; Zhang, Jun; Huang, Wei; Zhang, Hua; Tan, Ping-Heng

    2017-11-28

    Interfacial coupling between neighboring layers of van der Waals heterostructures (vdWHs), formed by vertically stacking more than two types of two-dimensional materials (2DMs), greatly affects their physical properties and device performance. Although high-resolution cross-sectional scanning tunneling electron microscopy can directly image the atomically sharp interfaces in the vdWHs, the interfacial coupling and lattice dynamics of vdWHs formed by two different types of 2DMs, such as semimetal and semiconductor, are not clear so far. Here, we report the ultralow-frequency Raman spectroscopy investigation on interfacial couplings in the vdWHs formed by graphene and MoS 2 flakes. Because of the significant interfacial layer-breathing couplings between MoS 2 and graphene flakes, a series of layer-breathing modes with frequencies dependent on their layer numbers are observed in the vdWHs, which can be described by the linear chain model. It is found that the interfacial layer-breathing force constant between MoS 2 and graphene, α 0 ⊥ (I) = 60 × 10 18 N/m 3 , is comparable with the layer-breathing force constant of multilayer MoS 2 and graphene. The results suggest that the interfacial layer-breathing couplings in the vdWHs formed by MoS 2 and graphene flakes are not sensitive to their stacking order and twist angle between the two constituents. Our results demonstrate that the interfacial interlayer coupling in vdWHs formed by two-dimensional semimetals and semiconductors can lead to new lattice vibration modes, which not only can be used to measure the interfacial interactions in vdWHs but also is beneficial to fundamentally understand the properties of vdWHs for further engineering the vdWHs-based electronic and photonic devices.

  5. Interfacial structure of poly-{alpha}-olefin laminate by using scanning thermal microscope

    Energy Technology Data Exchange (ETDEWEB)

    Kotera, Masaru, E-mail: kotera@kobe-u.ac.jp [Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, Rokko, Nada, Kobe 657-8501 (Japan); Urushihara, Yoshimasa [Hyogo Science and Technology Association, Kouto, Shingu, Tatsuno, Hyogo 679-5165 (Japan); Izumo, Daiki; Nishino, Takashi [Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, Rokko, Nada, Kobe 657-8501 (Japan)

    2012-03-10

    Highlights: Black-Right-Pointing-Pointer Interfacial structure of laminated PE/PP film was investigated by SThM. Black-Right-Pointing-Pointer Spatial resolution of SThM technique was estimated to be 1.5 {mu}m. Black-Right-Pointing-Pointer High-contrast image of apparent thermal conductivity could be observed at the interfacial region. Black-Right-Pointing-Pointer Interfacial thickness, which depends on the thermal treatment of the laminate film, was estimated to be in micrometer order. - Abstract: The interfacial structure of laminated poly-{alpha}-olefin, polyethylene (PE)/polypropylene (PP), film was investigated by scanning thermal microscope (SThM). Spatial resolution of this technique was estimated as 1.5 {mu}m. Notwithstanding the flatness of the sample as observed in the height image of an atomic force micrograph, micro-thermomechanical analysis could distinguish each polymer. By scanning the thermal probe at isothermal temperature over a cross-section of the laminate film, a high-contrast image of apparent thermal conductivity at the interfacial region was obtained. The interfacial thickness was estimated to be in the micrometer order depending on the thermal treatment of the laminate film. This result coincides with the results of synchrotron X-ray microbeam diffraction. Moreover, the peel strength of the PE/PP laminate was considered to be influenced by the interfacial thickness. It is concluded that this proposed thermal-probe method is as a powerful tool for investigating the interfacial region of the polymer composites.

  6. Interfacial characteristics of Biodentine and MTA with dentine in simulated body fluid.

    Science.gov (United States)

    Kim, Jong Ryul; Nosrat, Ali; Fouad, Ashraf F

    2015-02-01

    Newer tricalcium silicate cements (TSC) may offer biocompatibility with improved working properties. This study aimed to evaluate: (1) the occurrence of mineral deposition at the interface between dentine and two TSC (ProRoot(®) MTA and Biodentine(®)) in simulated body fluid, and (2) to investigate the nature of interfacial layer. Six root dentine segments of 1.5mm thickness were obtained from extracted human teeth and were instrumented with Gates-Glidden drills. The specimens were then randomly filled with either MTA or Biodentine. The specimens were placed in the simulated body fluid containing the same phosphate concentration as blood plasma. After 4 weeks, the specimens were examined with Scanning Electron Microscope (SEM) and Energy Disperse X-ray Spectroscopy (EDX) to measure the thickness of the interfacial layer and Ca/P ratio. Transmission Electron Microscope (TEM) and Selective Area Electron Diffraction (SAED) were conducted to examine the interface ultramicroscopically and to determine the nature of the crystalline structure within interfacial layer. The thickness of interfacial layer was significantly higher in the MTA group (14.5 μm vs 4.8 μm) (pBiodentine in Ca/P ratio of interfacial layer (4.1 vs 2.7) (p>0.05). From TEM examination, amorphous calcium phosphate (ACP) was observed in the interface along with the surface of dentine. As an alternative to MTA, Biodentine displayed bioactivity by producing an interfacial layer on the root canal dentine even though its thickness was significantly lower than MTA. ACP was observed in the interfacial layer of both biomaterials. Biodentine could be considered as an alternative to MTA due to comparable bioactivity which creates interfacial layer between root canal dentin and Biodentine. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Perturbation theory of solid-liquid interfacial free energies of bcc metals

    Energy Technology Data Exchange (ETDEWEB)

    Warshavsky, Vadim B.; Song, Xueyu

    2012-09-18

    A perturbation theory is used to calculate bcc solid-liquid interfacial free energies of metallic systems with embedded-atom model potentials. As a reference system for bcc crystals we used a single-occupancy cell, hard-sphere bcc system. Good agreements between the perturbation theory results and the corresponding results from simulations are found. The strategy to extract hard-sphere bcc solid-liquid interfacial free energies may have broader applications for other crystal lattices.

  8. Improving Cooling Rate During Solidification by Eliminating the Metal-Mold Interfacial Gap

    Science.gov (United States)

    Zeng, Long; Zhang, Wei; Ji, Yanliang; Huang, Yujin; Li, Jianguo

    2015-07-01

    A new solidification process called non-interfacial-gap permanent-mold casting (NIGPMC) is proposed to improve the cooling rate by eliminating the metal-mold interfacial gap. High-Cr steel ingots were prepared by this process and conventional permanent-mold casing (CPMC) separately. Comparing with CPMC, the primary dendrite arm spacing obtained by NIGPMC is greatly refined. It is demonstrated that the NIGPMC is a promising pathway to refine the microstructure of the large ingot.

  9. Interfacial tensions of binary mixtures of ethanol with octane, decane, dodecane, and tetradecane

    Energy Technology Data Exchange (ETDEWEB)

    Mejia, Andres, E-mail: amejia@udec.cl [Departamento de Ingenieria Quimica, Universidad de Concepcion, P.O. Box 160-C, Correo 3, Concepcion (Chile); Cartes, Marcela [Departamento de Ingenieria Quimica, Universidad de Concepcion, P.O. Box 160-C, Correo 3, Concepcion (Chile); Segura, Hugo, E-mail: hsegura@udec.cl [Departamento de Ingenieria Quimica, Universidad de Concepcion, P.O. Box 160-C, Correo 3, Concepcion (Chile)

    2011-09-15

    Highlights: > Experimental interfacial tensions in binary mixtures with aneotropic behavior. > Experimental interfacial tensions for ethanol + hydrocarbon mixtures. > Aneotropic displacement in ethanol mixtures. - Abstract: This contribution is devoted to the experimental characterization of interfacial tensions of a representative group of binary mixtures pertaining to the (ethanol + linear hydrocarbon) series (i.e. octane, decane, dodecane, and tetradecane). Experimental measurements were isothermically performed using a maximum differential bubble pressure technique, which was applied over the whole mole fraction range and over the temperature range 298.15 K < T/K < 318.15 K. Experimental results show that the interfacial tensions of (ethanol + octane or decane) negatively deviate from the linear behavior and that sharp minimum points on concentration, or aneotropes, are observed for each isotherm. The interfacial tensions of (ethanol + dodecane or tetradecane), in turn, are characterized by combined deviations from the linear behavior, and inflecting behavior observed on concentration for each isotherm. The experimental evidence also shows that these latter mixtures are close to exhibit aneotropy. For the case of (ethanol + octane or decane) mixtures, aneotropy was clearly induced by the similarity of the interfacial tension values of the constituents. The inflecting behavior of the interfacial tensions of (ethanol + dodecane or tetradecane), in turn, was observed in the vicinity of the coordinates of the critical point of these mixtures, thus pointing to the fact that the quasi-aneotropic singularity that affects these mixtures was provoked by the proximity of an immiscibility gap of the liquid phase. Finally, the experimental data of interfacial tensions were smoothed with the Scott-Myers expansion, from which it is possible to conclude that the observed aneotropic concentrations weakly depend on temperature for all the analyzed mixtures.

  10. The effect of interfacial intermixing on magnetization and anomalous Hall effect in Co/Pd multilayers

    KAUST Repository

    Guo, Zaibing

    2015-05-01

    The effect of interfacial intermixing on magnetization and anomalous Hall effect (AHE) in Co/Pd multilayers is studied by using rapid thermal annealing to enhance the interfacial diffusion. The dependence of saturation magnetization and coercivity on the temperature of rapid thermal annealing at 5 K is discussed. It is found that AHE is closely related to the relative thickness of the Co and Pd layers. Localized paramagnetism has been observed which destroys AHE, while AHE can be enhanced by annealing.

  11. Periodic traveling interfacial hydroelastic waves with or without mass

    Science.gov (United States)

    Akers, Benjamin F.; Ambrose, David M.; Sulon, David W.

    2017-12-01

    We study the motion of an interface between two irrotational, incompressible fluids, with elastic bending forces present; this is the hydroelastic wave problem. We prove a global bifurcation theorem for the existence of families of spatially periodic traveling waves on infinite depth. Our traveling wave formulation uses a parameterized curve, in which the waves are able to have multivalued height. This formulation and the presence of the elastic bending terms allow for the application of an abstract global bifurcation theorem of "identity plus compact" type. We furthermore perform numerical computations of these families of traveling waves, finding that, depending on the choice of parameters, the curves of traveling waves can either be unbounded, reconnect to trivial solutions, or end with a wave which has a self-intersection. Our analytical and computational methods are able to treat in a unified way the cases of positive or zero mass density along the sheet, the cases of single-valued or multivalued height, and the cases of single-fluid or interfacial waves.

  12. Interfacial assembly structures and nanotribological properties of saccharic acids.

    Science.gov (United States)

    Shi, Hongyu; Liu, Yuhong; Zeng, Qingdao; Yang, Yanlian; Wang, Chen; Lu, Xinchun

    2017-01-04

    Saccharides have been recognized as potential bio-lubricants because of their good hydration ability. However, the interfacial structures of saccharides and their derivatives are rarely studied and the molecular details of interaction mechanisms have not been well understood. In this paper, the supramolecular assembly structures of saccharic acids (including galactaric acid and lactobionic acid), mediated by hydrogen bonds O-HN and O-HO, were successfully constructed on a highly oriented pyrolytic graphite (HOPG) surface by introducing pyridine modulators and were explicitly revealed by using scanning tunneling microscopy (STM). Furthermore, friction forces were measured in the saccharic acid/pyridine co-assembled system by atomic force microscopy (AFM), revealing a larger value than a pristine saccharic acid system, which could be attributed to the stronger tip-assembled molecule interactions that lead to the higher potential energy barrier needed to overcome. The effort on saccharide-related supramolecular self-assembly and nanotribological behavior could provide a novel and promising pathway to explore the interaction mechanisms underlying friction and reveal the structure-property relationship at the molecular level.

  13. Three-Dimensional Tracking of Interfacial Hopping Diffusion

    Science.gov (United States)

    Wang, Dapeng; Wu, Haichao; Schwartz, Daniel K.

    2017-12-01

    Theoretical predictions have suggested that molecular motion at interfaces—which influences processes including heterogeneous catalysis, (bio)chemical sensing, lubrication and adhesion, and nanomaterial self-assembly—may be dominated by hypothetical "hops" through the adjacent liquid phase, where a diffusing molecule readsorbs after a given hop according to a probabilistic "sticking coefficient." Here, we use three-dimensional (3D) single-molecule tracking to explicitly visualize this process for human serum albumin at solid-liquid interfaces that exert varying electrostatic interactions on the biomacromolecule. Following desorption from the interface, a molecule experiences multiple unproductive surface encounters before readsorption. An average of approximately seven surface collisions is required for the repulsive surfaces, decreasing to approximately two and a half for surfaces that are more attractive. The hops themselves are also influenced by long-range interactions, with increased electrostatic repulsion causing hops of longer duration and distance. These findings explicitly demonstrate that interfacial diffusion is dominated by biased 3D Brownian motion involving bulk-surface coupling and that it can be controlled by influencing short- and long-range adsorbate-surface interactions.

  14. Phosphonic Acids for Interfacial Engineering of Transparent Conductive Oxides

    KAUST Repository

    Paniagua, Sergio A.

    2016-05-26

    Transparent conducting oxides (TCOs), such as indium tin oxide and zinc oxide, play an important role as electrode materials in organic-semiconductor devices. The properties of the inorganic-organic interface - the offset between the TCO Fermi level and the relevant transport level, the extent to which the organic semiconductor can wet the oxide surface, and the influence of the surface on semiconductor morphology - significantly affect device performance. This review surveys the literature on TCO modification with phosphonic acids (PAs), which has increasingly been used to engineer these interfacial properties. The first part outlines the relevance of TCO surface modification to organic electronics, surveys methods for the synthesis of PAs, discusses the modes by which they can bind to TCO surfaces, and compares PAs to alternative organic surface modifiers. The next section discusses methods of PA monolayer deposition, the kinetics of monolayer formation, and structural evidence regarding molecular orientation on TCOs. The next sections discuss TCO work-function modification using PAs, tuning of TCO surface energy using PAs, and initiation of polymerizations from TCO-tethered PAs. Finally, studies that examine the use of PA-modified TCOs in organic light-emitting diodes and organic photovoltaics are compared. © 2016 American Chemical Society.

  15. Interfacial Properties of Methylcelluloses: The Influence of Molar Mass

    Directory of Open Access Journals (Sweden)

    Pauline L. Nasatto

    2014-12-01

    Full Text Available The interfacial interactions of four methylcelluloses having the same average degree of substitution and distribution of methyl groups, but different molar masses, are studied at ambient temperature and at very low polymer concentrations. Firstly, the surface tension σ at the water/air interface is determined for the progressive addition of methylcellulose up to 100 mg/L; σ starts to decrease over 1 mg/L up to the critical aggregation concentration (CAC at 10 mg/L. The curves describing the influence of polymer concentration on σ are independent of the molar mass at equilibrium. Secondly, the adsorption of methylcellulose on silica particles is estimated from ζ-potential measurements. The data are interpreted in terms of an increase of the adsorbed layer thickness at the interface when the molar mass of methylcellulose increases. It is concluded that methylcellulose is adsorbed, forming trains and loops at the interface based on the equilibrium between surface free energy and solvent quality.

  16. Interfacial characterization and analytical applications of chemically-modified surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jianhong [Iowa State Univ., Ames, IA (United States)

    1998-02-23

    The goal of this work is to explore several new strategies and approaches to the surface modification and the microscopic characterization of interfaces in the areas mainly targeting sensor technologies that are of interest to environmental control or monitoring, and scanning probe microscopies techniques that can monitor interfacial chemical reactions in real time. Centered on the main theme, four specific topics are presented as four chapters in this dissertation following the general introduction. Chapter 1 describes the development of two immobilization schemes for covalently immobilizing fluoresceinamine at cellulose acetate and its application as a pH sensing film. Chapter 2 investigates the applicability of SFM to following the base-hydrolysis of a dithio-bis(succinimidylundecanoate) monolayer at gold in situ. Chapter 3 studies the mechanism for the accelerated rate of hydrolysis of the dithio-bis(succinimidylundecanoate) monolayer at Au(111) surface. Chapter 4 focuses on the development of an electrochemical approach to the elimination of chloride interference in Chemical Oxygen Demand (COD) analysis of waste water. The procedures, results and conclusions are described in each chapter. This report contains the introduction, references, and general conclusions. Chapters have been processed separately for inclusion on the data base. 95 refs.

  17. Effect of Local and General Anesthetics on Interfacial Water.

    Directory of Open Access Journals (Sweden)

    Nenad Kundacina

    Full Text Available Water undergoes structural change as it interfaces with hydrophilic surfaces, including the many hydrophilic surfaces within the cell. This interfacial water has become known as "Exclusion Zone (EZ water" or "fourth-phase water" [1].We tested the hypothesis that anesthetics diminish the amount of EZ water, and that this change may correlate with functional changes in anesthesia. By using the local anesthetics Lidocaine and Bupivacaine as well as a general inhalational anesthetic, Isoflurane, we tracked the EZ size as these anesthetics were introduced.All three anesthetics diminished EZ size in a concentration-dependent manner at concentrations of 0.18 mM and greater for Bupivacaine, 0.85 mM and greater for Lidocaine, and 0.2% for Isoflurane. At extremely low (micromolar concentrations, however, all three anesthetics increased EZ size.The sharp increase of EZ size associated with micromolar anesthetic concentrations follows a similar pattern to induction of general anesthesia, from the excitation stage (Stage II to the depression and overdose stages of surgical anesthesia (Stages III and IV. The results are consistent with the hypothesis that anesthetics may act on water, a fundamental organizational component common to all cells.

  18. Evolutionary design of interfacial phase change van der Waals heterostructures.

    Science.gov (United States)

    Kalikka, Janne; Zhou, Xilin; Behera, Jitendra; Nannicini, Giacomo; Simpson, Robert E

    2016-10-27

    We use an evolutionary algorithm to explore the design space of hexagonal Ge 2 Sb 2 Te 5 ; a van der Waals layered two dimensional crystal heterostructure. The Ge 2 Sb 2 Te 5 structure is more complicated than previously thought. Predominant features include layers of Ge 3 Sb 2 Te 6 and Ge 1 Sb 2 Te 4 two dimensional crystals that interact through Te-Te van der Waals bonds. Interestingly, (Ge/Sb)-Te-(Ge/Sb)-Te alternation is a common feature for the most stable structures of each generation's evolution. This emergent rule provides an important structural motif that must be included in the design of high performance Sb 2 Te 3 -GeTe van der Waals heterostructure superlattices with interfacial atomic switching capability. The structures predicted by the algorithm agree well with experimental measurements on highly oriented, and single crystal Ge 2 Sb 2 Te 5 samples. By analysing the evolutionary algorithm optimised structures, we show that diffusive atomic switching is probable by Ge atoms undergoing a transition at the van der Waals interface from layers of Ge 3 Sb 2 Te 6 to Ge 1 Sb 2 Te 4 thus producing two blocks of Ge 2 Sb 2 Te 5 . Evolutionary methods present an efficient approach to explore the enormous multi-dimensional design parameter space of van der Waals bonded heterostructure superlattices.

  19. Interfacial charging phenomena of aluminum (hydr)oxides

    Energy Technology Data Exchange (ETDEWEB)

    Hiemstra, T.; Yong, H.; Van Riemsdijk, W.H.

    1999-08-31

    The interfacial charging of Al(OH){sub 3} (gibbsite and bayerite) and Al{sub 2}O{sub 3} has been studied. For Al(OH){sub 3} it can be shown that the very strong variation in charging behavior for different preparations is related to the relative presence of differently reacting crystal planes. The edge faces of the hexagonal gibbsite crystals are proton reactive over the whole pH range, in contrast to the 001 plane, which is mainly uncharged below pH = 10. On this 001 face only doubly coordinated surface groups are found, in contrast to the edges which also have singly coordinated surface groups. The results are fully in agreement with the predictions of the Multi site complexation (MUSIC) model. The proton adsorption, electrolyte ion adsorption, and shift of the IEP of gibbsite and aluminum oxide have been modeled simultaneously. For gibbsite, the ion pair formation of Na is larger than that of Cl, as is evidenced by modeling the experimentally observed upward shift on the IEP and charge reversal at high electrolyte concentrations. All these experimental results can be satisfactorily modeled with the MUSIC model, including the experimental surface potential of aluminum oxide (ISFET).

  20. Interfacial assembly of dendritic microcapsules with host-guest chemistry

    Science.gov (United States)

    Zheng, Yu; Yu, Ziyi; Parker, Richard M.; Wu, Yuchao; Abell, Chris; Scherman, Oren A.

    2014-12-01

    The self-assembly of nanoscale materials to form hierarchically ordered structures promises new opportunities in drug delivery, as well as magnetic materials and devices. Herein, we report a simple means to promote the self-assembly of two polymers with functional groups at a water-chloroform interface using microfluidic technology. Two polymeric layers can be assembled and disassembled at the droplet interface using the efficiency of cucurbit[8]uril (CB[8]) host-guest supramolecular chemistry. The microcapsules produced are extremely monodisperse in size and can encapsulate target molecules in a robust, well-defined manner. In addition, we exploit a dendritic copolymer architecture to trap a small hydrophilic molecule in the microcapsule skin as cargo. This demonstrates not only the ability to encapsulate small molecules but also the ability to orthogonally store both hydrophilic and hydrophobic cargos within a single microcapsule. The interfacially assembled supramolecular microcapsules can benefit from the diversity of polymeric materials, allowing for fine control over the microcapsule properties.

  1. Interfacial Microstructure and Properties of Steel/Aluminum Powder Additive

    Directory of Open Access Journals (Sweden)

    YUAN Jiang

    2017-09-01

    Full Text Available Based on first-principles density functional theory, the Fe/Al interface model of steel/aluminum laser welding was constructed by layer technique. The Fe/Al interface was studied by metal atom X (X=Sn, Sr, Zr, Ce, La.The results show that Sn, Sr and Ce preferentially displace the Al atoms at the Fe/Al interface, while La and Zr preferentially displace the Fe atoms at the Fe/Al interface. Alloying promotes the transfer of Fe/Al interfacial electrons between different orbits, enhances the ionic bond properties of Fe-Al, improves the Fe/Al interface binding capacity, improves the brittle fracture of Fe/Al interface, and the alloying effect of Sn most notable. On the basis of this, the laser lap welding test of Sn and Zr powder was carried out on 1.4mm thick DC51D+ZF galvanized steel and 1.2mm thick 6016 aluminum alloy specimen. The results show that the addition of powder can promote the flowability of the molten bath and change the composition and microstructure of the joint interface. The tensile strength of the steel/aluminum joint is 327.41MPa and the elongation is 22.93% with the addition of Sn powder, which is obviously improved compared with the addition of Zr powder and without the addition of powder.

  2. Interfacial Polycondensation Synthesis of Optically Sensitive Polyurea Microcapsule

    Directory of Open Access Journals (Sweden)

    Weidong Lai

    2014-01-01

    Full Text Available TMPTA prepolymer resin and photoinitiators of ITX/TPO had been encapsulated in core-shell structured microcapsules as optical responding ingredients based on interfacial polycondensation method, and polyurea structured microcapsule shell had been formed on the sheared O/W interface. The synthesized microcapsule had regular core-shell structure with the diameter of about 0.455 μm and shell thickness of about 40 nm. UV-visible absorption spectra indicated that the encapsulated ITX and TPO photoinitiators could efficiently absorb UV irradiation. Under exposure, the C=C bonds absorbance of the microencapsulated TMPTA decreased rapidly and then nearly unchanged during further exposure after 30 s. This implied that the optical response was achieved by C=C bond cleavage of TMPTA monomer initiated by the photoinitiator radicals, to form network polymers in microcapsules. The relative crosslinking rate was about 50%. Due to core polymer formation, the thermal phase change temperature of exposed microcapsules was narrowed and ranged from 105 to 205°C, compared with that from 125 to 260°C of unexposed microcapsules. Furthermore, the image density decrease at longer irradiation time had also verified the optical responding function of the synthesized microcapsules in macroscopic viewpoint.

  3. Interfacial slip in entrained soap films containing associating hydrosoluble polymer.

    Science.gov (United States)

    Adelizzi, Eric A; Troian, Sandra M

    2004-08-31

    Frankel's law predicts that the thickness of a Newtonian soap film entrained at small capillary number scales as Ca2/3 provided the bounding surfaces are rigid. Previous studies have shown that soap films containing low concentrations of high molecular weight (Mw) polymer can exhibit strong deviations from this scaling at low Ca, especially for associating surfactant-polymer solutions. We report results of extensive measurements by laser interferometry of the entrained film thickness versus Ca for the associating pair SDS/PEO over a large range in polymer molecular weight. Comparison of our experimental results to predictions of hydrodynamic models based on viscoelastic behavior shows poor agreement. Modification of the Frankel derivation by an interfacial slip condition yields much improved agreement. These experiments also show that the slip length increases as where zeta = 0.58 +/- 0.07. This correlation is suggestive of the Tolstoi-Larsen prediction that the slip length increases in proportion to the characteristic size of the fluid constituent despite its original derivation for liquid-solid interfaces.

  4. Interfacial thermal degradation in inverted organic solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Greenbank, William; Hirsch, Lionel; Wantz, Guillaume; Chambon, Sylvain, E-mail: sylvain.chambon@ims-bordeaux.fr [University of Bordeaux, CNRS, Bordeaux INP, IMS, UMR 5218, F-33405 Talence (France)

    2015-12-28

    The efficiency of organic photovoltaic (OPV) solar cells is constantly improving; however, the lifetime of the devices still requires significant improvement if the potential of OPV is to be realised. In this study, several series of inverted OPV were fabricated and thermally aged in the dark in an inert atmosphere. It was demonstrated that all of the devices undergo short circuit current-driven degradation, which is assigned to morphology changes in the active layer. In addition, a previously unreported, open circuit voltage-driven degradation mechanism was observed that is highly material specific and interfacial in origin. This mechanism was specifically observed in devices containing MoO{sub 3} and silver as hole transporting layers and electrode materials, respectively. Devices with this combination were among the worst performing devices with respect to thermal ageing. The physical origins of this mechanism were explored by Rutherford backscattering spectrometry and atomic force microscopy and an increase in roughness with thermal ageing was observed that may be partially responsible for the ageing mechanism.

  5. Interfacial charge separation and trapping in composite photocatalysts

    Science.gov (United States)

    Chakarov, Dinko

    We explore the phenomena of interfacial charge separation and trapping in composite metal-semiconductor systems and the interaction (energy and charge exchange) between optically excited nanoparticles and the surrounding medium. Disc-shaped copper nanoparticles (Cu NPs) were fabricated by hole-mask colloidal lithography on bare and thin titania film covered fused silica substrates. The dynamics of Cu oxide formation around the NPs were studied in water by localized surface plasmon resonance (LSPR) spectroscopy. We found that the oxidation rate is strongly enhanced under UV irradiation when the NPs are on the surface of the titania film, in comparison to NPs deposited on an inert fused silica substrate. The reason is sought in the ability of TiO2 to create hydroxyl radicals with strong oxidative potential in water under UV irradiation and the charge transfer at the interface between the Cu NPs and the TiO2. The results demonstrate the potential of using LSPR spectroscopy to monitor the oxidation of Cu NPs in situ and in different environments. The work was financially supported by The Nordic Energy Research Council through Project N-I-S-F-D.

  6. Coupled Interfacial Tension and Phase Behavior Model Based on Micellar Curvatures

    KAUST Repository

    Torrealba, V. A.

    2017-11-08

    This article introduces a consistent and robust model that predicts interfacial tensions for all microemulsion Winsor types and overall compositions. The model incorporates film bending arguments and Huh\\'s equation and is coupled to phase behavior so that simultaneous tuning of both interfacial tension (IFT) and phase behavior is possible. The oil-water interfacial tension and characteristic length are shown to be related to each other through the hydrophilic-lipophilic deviation (HLD). The phase behavior is tied to the micelle curvatures, without the need for using the net average curvature (NAC). The interfacial tension model is related to solubilization ratios in order to introduce a coupled interfacial tension-phase behavior model for all phase environments. The approach predicts two- and three-phase interfacial tensions and phase behavior (i.e., tie lines and tie triangles) for changes in composition and HLD input parameters, such as temperature, pressure, surfactant structure, and oil equivalent alkane carbon number. Comparisons to experimental data show excellent fits and predictive capability.

  7. The molecular understanding of interfacial interactions of functionalized graphene and chitosan

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hong-ping, E-mail: zhp1006@126.com [Engineering Research Center of Biomass Materials, Ministry of Education, School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan 621010 (China); Luo, Xue-gang, E-mail: lxg@swust.edu.cn [Engineering Research Center of Biomass Materials, Ministry of Education, School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan 621010 (China); Lin, Xiao-yan, E-mail: linxiaoyan@swust.edu.cn [Engineering Research Center of Biomass Materials, Ministry of Education, School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan 621010 (China); Lu, Xiong, E-mail: luxiong@home.swjtu.edu.cn [Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Tang, Youhong, E-mail: youhong.tang@flinders.edu.au [Centre for NanoScale Science and Technology and School of Computer Science, Engineering and Mathematics, Flinders University, South Australia 5042 (Australia)

    2016-01-01

    Graphical abstract: The type of the functional groups can be used to modulating interactions between graphene sheet and chitosan. - Highlights: • Investigate interfacial interactions between chitosan and functionalized graphene by DFT. • Observe covalent linkages between COOH-modified graphene and chitosan units. • Multi-functionalized graphene regulates the interfacial interactions with chitosan. • It is useful for guiding the preparation of graphene/chitosan composites. - Abstract: Graphene-reinforced chitosan scaffolds have been extensively studied for several years as promising hard tissue replacements. However, the interfacial interactions between graphene and chitosan are strongly related to the solubility, processability, and mechanical properties of graphene-reinforced chitosan (G–C) composites. The functionalization of graphene is regarded as the most effective way to improve the abovementioned properties of the G–C composite. In this study, the interfacial interactions between chitosan and functionalized graphene sheets with carboxylization (COOH-), amination (NH{sub 2}-), and hydroxylation (OH-) groups were systematically studied at the electronic level using the method of ab initio simulations based on quantum mechanics theory and the observations were compared with reported experimental results. The covalent linkages between COOH-modified graphene and the chitosan units were demonstrated and the combination of multi-functionalization on graphene could regulate the interfacial interactions between graphene and the chitosan. The interfacial interactions between chitosan and properly functionalized graphene are critical for the preparation of G–C-based composites for tissue engineering scaffolds and other applications.

  8. Influence of enzymes and ascorbic acid on dough rheology and ...

    African Journals Online (AJOL)

    Cliente

    organoleptic qualities especially dough formation and bread crumb texture. The gluten network is responsible also for dough elasticity, resistance and stability, while carbon dioxide production is due to the action of enzymes and yeast on sugar (Enriquez et al., 2003; Aamodt et al.,. 2003). Thus, to improve the gluten network ...

  9. Metal-coordinated phenoxyl radicals: Models for the enzyme ...

    Indian Academy of Sciences (India)

    Administrator

    In recent years, studies on metal coordinated phenoxyl radicals have gained importance due to their biochemical significance. Such radicals are involved in the action of various enzymes like galactose oxidase, ribonucleotide reductase etc. The present report deals with the synthesis and characterization of new ligand ...

  10. Effects of different autotoxins on antioxidant enzymes and chemical ...

    African Journals Online (AJOL)

    Jane

    2011-07-25

    Jul 25, 2011 ... allelopathic agents and the mechanism of action of autotoxins in tea seedlings is still unknown. To investigate the mechanism between autotoxins and membrane lipid peroxidation, the objective of this study was to determine the effects of root exudates autotoxins on antioxidant enzymes activity and index ...

  11. An investigation into keratinolytic enzymes to enhance ungual drug delivery.

    Science.gov (United States)

    Mohorcic, M; Torkar, A; Friedrich, J; Kristl, J; Murdan, S

    2007-03-06

    The topical therapy of nail diseases is limited by the low permeability of drugs through the nail plate. To increase drug penetration, the integrity of the nail plate must be compromised to a certain extent. We hypothesised that keratinolytic enzymes might decrease the barrier properties of the nail plate by hydrolysing the nail keratins, and thereby enhance ungual drug permeation. To determine enzyme action on nail plates, nail clippings were incubated at 35 degrees C, in the presence of keratinase at optimal pH for 48h, after which the nail plates were examined using scanning electron microscopy. It was found that the enzyme acted on the intercellular matrix which holds nail cells together, such that corneocytes on the dorsal surface separated from one another and 'lifted off' the nail plate. In addition, the surface of the corneocytes was corroded. Permeation studies using modified Franz diffusion cells and bovine hoof membranes as a model for the nail plate showed that the enzyme enhanced drug permeation through the hoof membrane. The permeability and partition coefficients, and the drug flux were found to be significantly increased in the presence of the enzyme. We can conclude that the enzyme, via its hydrolytic action on nail plate proteins, could increase ungual drug delivery.

  12. Caffeine's Vascular Mechanisms of Action

    Directory of Open Access Journals (Sweden)

    Darío Echeverri

    2010-01-01

    Full Text Available Caffeine is the most widely consumed stimulating substance in the world. It is found in coffee, tea, soft drinks, chocolate, and many medications. Caffeine is a xanthine with various effects and mechanisms of action in vascular tissue. In endothelial cells, it increases intracellular calcium stimulating the production of nitric oxide through the expression of the endothelial nitric oxide synthase enzyme. Nitric oxide is diffused to the vascular smooth muscle cell to produce vasodilation. In vascular smooth muscle cells its effect is predominantly a competitive inhibition of phosphodiesterase, producing an accumulation of cAMP and vasodilation. In addition, it blocks the adenosine receptors present in the vascular tissue to produce vasoconstriction. In this paper the main mechanisms of action of caffeine on the vascular tissue are described, in which it is shown that caffeine has some cardiovascular properties and effects which could be considered beneficial.

  13. Wettability Improvement with Enzymes: Application to Enhanced Oil Recovery under Conditions of the North Sea Reservoirs

    DEFF Research Database (Denmark)

    Khusainova, Alsu; Shapiro, Alexander; Stenby, Erling Halfdan

    2012-01-01

    , proteases and oxidoreductases, provided by Novozymes, have been investigated. Two commercial mixtures containing enzymes: Apollo-GreenZyme™ and EOR-ZYMAX™ have also been applied. The North Sea dead oil and the synthetic sea water were used as test fluids. Internal surface of a carbonate rock has been...... interfacially active oil compounds. Application of the commercial product Apollo-GreenZyme™ has also resulted in positive wettability changes, but according to the observations the working mechanisms are different. In an attempt to assess validity of the proposed mechanisms, the reference experiments have been...

  14. Morphology and Kinetics of Interfacial Layer Formation during Continuous Hot-Dip Galvanizing and Galvannealing

    Science.gov (United States)

    Chen, L.; Fourmentin, R.; Mc Dermid, J. R.

    2008-09-01

    A galvanizing simulator with rapid spot cooling was used to obtain a well-characterized reaction times as short as 2 seconds in order to study the short-time microstructural development and kinetics of the galvanizing and galvannealing interfacial reaction layer. It was determined that the incubation and nucleation events of the interfacial layer formation were completed by the 2-second reaction time in all cases. For a 0.20 wt pct dissolved Al bath, FeAl3 nucleates and grows during the initial stages of interfacial layer formation followed by Fe2Al5Zn X formation by diffusion-controlled transformation and growth. The final microstructure of the interfacial layer consisted of Fe2Al5Zn X in a two-layer arrangement comprising a fine-grained, compact lower layer with a coarser, noncompact upper layer. The Al content of the interfacial layer increased with reaction time and reaction temperature. Both of the Fe-Al phases formed exhibited a strong preferential crystallographic orientation with respect to the substrate surface. The evolution of the interfacial layer formed in a 0.13 wt pct dissolved Al bath was the result of competing processes. Fe-Al phases formed and grew during the reaction times explored, per the preceding mechanism. However, Fe-Zn phases also nucleated and grew during the reaction times explored via the process of inhibition breakdown, with these phases dominating the interfacial layer microstructures at longer reaction times. In this case, the Al content of the interfacial layer increased for all reaction times explored, but decreased with increasing reaction temperature, due to the more rapid initiation of inhibition breakdown. A model to describe the interfacial layer growth kinetics as a function of reaction time, bath temperature, and inhibition layer microstructure for the case of the 0.20 wt pct dissolved Al bath was proposed. It indicated that the development of microstructure of the interfacial layer had significant influence on the

  15. Givental action and trivialisation of circle action

    NARCIS (Netherlands)

    Dotsenko, V.; Shadrin, S.; Vallette, B.

    2015-01-01

    In this paper, we show that the Givental group action on genus zero cohomological field theories, also known as formal Frobenius manifolds or hypercommutative algebras, naturally arises in the deformation theory of Batalin-Vilkovisky algebras. We prove that the Givental action is equal to an action

  16. Efficient Interfacially Driven Vehiculization of Corticosteroids by Pulmonary Surfactant.

    Science.gov (United States)

    Hidalgo, Alberto; Salomone, Fabrizio; Fresno, Nieves; Orellana, Guillermo; Cruz, Antonio; Perez-Gil, Jesus

    2017-08-15

    Pulmonary surfactant is a crucial system to stabilize the respiratory air-liquid interface. Furthermore, pulmonary surfactant has been proposed as an effective method for targeting drugs to the lungs. However, few studies have examined in detail the mechanisms of incorporation of drugs into surfactant, the impact of the presence of drugs on pulmonary surfactant performance at the interface under physiologically meaningful conditions, or the ability of pulmonary surfactant to use the air-liquid interface to vehiculise drugs to long distances. This study focuses on the ability of pulmonary surfactant to interfacially vehiculize corticosteroids such as beclomethasone dipropionate (BDP) or Budesonide (BUD) as model drugs. The main objectives have been to (a) characterize the incorporation of corticosteroids into natural and synthetic surfactants, (b) evaluate whether the presence of corticosteroids affects surfactant functionality, and (c) determine whether surfactant preparations enable the efficient spreading and distribution of BDP and BUD along the air-liquid interface. We have compared the performance of a purified surfactant from porcine lungs and two clinical surfactants: Poractant alfa, a natural surfactant of animal origin extensively used to treat premature babies, and CHF5633, a new synthetic surfactant preparation currently under clinical trials. Both, natural and clinical surfactants spontaneously incorporated corticosteroids up to at least 10% by mass with respect to phospholipid content. The presence of the drugs did not interfere with their ability to efficiently adsorb into air-liquid interfaces and form surface active films able to reach and sustain very low surface tensions (<2 mN/m) under compression-expansion cycling mimicking breathing dynamics. Furthermore, the combination of clinical surfactant with corticosteroids efficiently promoted the active diffusion of the drug to long distances along the air-liquid interface. This effect could not be

  17. A method for computing unsteady fully nonlinear interfacial waves

    Science.gov (United States)

    Grue, John; André Friis, Helmer; Palm, Enok; Olav Rusås, Per

    1997-11-01

    We derive a time-stepping method for unsteady fully nonlinear two-dimensional motion of a two-layer fluid. Essential parts of the method are: use of Taylor series expansions of the prognostic equations, application of spatial finite difference formulae of high order, and application of Cauchy's theorem to solve the Laplace equation, where the latter is found to be advantageous in avoiding instability. The method is computationally very efficient. The model is applied to investigate unsteady trans-critical two-layer flow over a bottom topography. We are able to simulate a set of laboratory experiments on this problem described by Melville & Helfrich (1987), finding a very good agreement between the fully nonlinear model and the experiments, where they reported bad agreement with weakly nonlinear Korteweg de Vries theories for interfacial waves. The unsteady transcritical regime is identified. In this regime, we find that an upstream undular bore is generated when the speed of the body is less than a certain value, which somewhat exceeds the critical speed. In the remaining regime, a train of solitary waves is generated upstream. In both cases a corresponding constant level of the interface behind the body is developed. We also perform a detailed investigation of upstream generation of solitary waves by a moving body, finding that wave trains with amplitude comparable to the thickness of the thinner layer are generated. The results indicate that weakly nonlinear theories in many cases have quite limited applications in modelling unsteady transcritical two-layer flows, and that a fully nonlinear method in general is required.

  18. Interfacial Characteristics and Cytocompatibility of Hydraulic Sealer Cements.

    Science.gov (United States)

    Kebudi Benezra, Mira; Schembri Wismayer, Pierre; Camilleri, Josette

    2018-02-02

    The stability and long-term success of root canal obturation depends on the choice of sealer because the sealer bonds to the dentin and stabilizes the solid cone. Furthermore, the sealer needs to be nontoxic because sealer toxicity will certainly lead to treatment failure. The aim of this study was to assess the sealer-dentin interface of 3 hydraulic root canal sealers and to evaluate their cytocompatibility compared with AH Plus (Dentsply DeTrey GmbH, Konstanz, Germany). Four dental root canal sealers were assessed. AH Plus, MTA Fillapex (Angelus, Londrina, Brazil), BioRoot RCS (Septodont, Saint-Maur-des-Fossés, France), and Endoseal (Maruchi, Wonju-si, Gangwon-do, South Korea) were characterized using scanning electron microscopy and energy-dispersive spectroscopy. The sealer-tooth interface was assessed by confocal microscopy and scanning electron microscopy, and biocompatibility was measured by assessing the cell metabolic function using direct contact assays and alkaline phosphatase activity. The tricalcium silicate-based sealers presented a different microstructure and elemental composition despite their similar chemistry and classification. BioRoot RCS was free of aluminum, and all sealers presented different radiopacifying elements. The sealer penetration in the dentinal tubules and interfacial characteristics were different. The migration of silicon was evident from sealer to tooth for all sealers containing tricalcium silicate. MTA Fillapex and BioRoot RCS exhibited the best cytocompatibility in both the direct contact test and alkaline phosphatase activity. The use of hydraulic calcium silicate-based sealers has introduced a different material type to endodontics. These materials are different than other sealers mostly because of their hydraulic nature and their interaction with the environment. Although the sealers tested had a similar chemistry, their cytocompatibility and bonding mechanisms were diverse. Copyright © 2017 American Association of

  19. Probing model tumor interfacial properties using piezoelectric cantilevers.

    Science.gov (United States)

    Yegingil, Hakki; Shih, Wan Y; Shih, Wei-Heng

    2010-09-01

    Invasive malignant breast cancers are typically branchy and benign breast tumors are typically smooth. It is of interest to characterize tumor branchiness (roughness) to differentiate invasive malignant breast cancer from noninvasive ones. In this study, we examined the shear modulus (G) to elastic modulus (E) ratio, G/E, as a quantity to describe model tumor interfacial roughness using a piezoelectric cantilever capable of measuring both tissue elastic modulus and tissue shear modulus. The piezoelectric cantilever used had two lead zirconate titanate layers to facilitate all-electrical elastic (shear) modulus measurements using one single device. We constructed model tissues with tumors by embedding one-dimensional (1D) corrugated inclusions and three-dimensional (3D) spiky-ball inclusions made of modeling clay in gelatin. We showed that for smooth inclusions, G/E was 0.3 regardless of the shear direction. In contrast, for a 1D corrugated rough inclusion G/E was 0.3 only when the shear was parallel to corrugation and G/E increased with an increasing angle between the shear direction and the corrugation. When the shear was perpendicular to corrugation, G/E became >0.7. For 3D isotropic spiky-ball inclusions we showed that the G/E depended on the degree of the roughness. Using the ratio s/r of the spike length (s) to the overall inclusion radius (r) as a roughness parameter, we showed that for inclusions with s/r larger than or equal to 0.28, the G/E ratio over the inclusions was larger than 0.7 whereas for inclusions with s/r less than 0.28, the G/E decreased with decreasing s/r to around 0.3 at s/r=0. In addition, we showed that the depth limit of the G/E measurement is twice the width of the probe area of the piezoelectric cantilever.

  20. Blind Prediction of Interfacial Water Positions in CAPRI

    Science.gov (United States)

    Moal, Iain H.; Bates, Paul A.; Kastritis, Panagiotis L.; Melquiond, Adrien S.J.; Karaca, Ezgi; Schmitz, Christophe; van Dijk, Marc; Bonvin, Alexandre M.J.J.; Eisenstein, Miriam; Jiménez-García, Brian; Grosdidier, Solène; Solernou, Albert; Pérez-Cano, Laura; Pallara, Chiara; Fernández-Recio, Juan; Xu, Jianqing; Muthu, Pravin; Kilambi, Krishna Praneeth; Gray, Jeffrey J.; Grudinin, Sergei; Derevyanko, Georgy; Mitchell, Julie C.; Wieting, John; Kanamori, Eiji; Tsuchiya, Yuko; Murakami, Yoichi; Sarmiento, Joy; Standley, Daron M.; Shirota, Matsuyuki; Kinoshita, Kengo; Nakamura, Haruki; Chavent, Matthieu; Ritchie, David W.; Park, Hahnbeom; Ko, Junsu; Lee, Hasup; Seok, Chaok; Shen, Yang; Kozakov, Dima; Vajda, Sandor; Kundrotas, Petras J.; Vakser, Ilya A.; Pierce, Brian G.; Hwang, Howook; Vreven, Thom; Weng, Zhiping; Buch, Idit; Farkash, Efrat; Wolfson, Haim J.; Zacharias, Martin; Qin, Sanbo; Zhou, Huan-Xiang; Huang, Shen-You; Zou, Xiaoqin; Wojdyla, Justyna A.; Kleanthous, Colin; Wodak, Shoshana J.

    2015-01-01

    We report the first assessment of blind predictions of water positions at protein-protein interfaces, performed as part of the CAPRI (Critical Assessment of Predicted Interactions) community-wide experiment. Groups submitting docking predictions for the complex of the DNase domain of colicin E2 and Im2 immunity protein (CAPRI target 47), were invited to predict the positions of interfacial water molecules using the method of their choice. The predictions – 20 groups submitted a total of 195 models – were assessed by measuring the recall fraction of water-mediated protein contacts. Of the 176 high or medium quality docking models – a very good docking performance per se – only 44% had a recall fraction above 0.3, and a mere 6% above 0.5. The actual water positions were in general predicted to an accuracy level no better than 1.5 Å, and even in good models about half of the contacts represented false positives. This notwithstanding, three hotspot interface water positions were quite well predicted, and so was one of the water positions that is believed to stabilize the loop that confers specificity in these complexes. Overall the best interface water predictions was achieved by groups that also produced high quality docking models, indicating that accurate modelling of the protein portion is a determinant factor. The use of established molecular mechanics force fields, coupled to sampling and optimization procedures also seemed to confer an advantage. Insights gained from this analysis should help improve the prediction of protein-water interactions and their role in stabilizing protein complexes. PMID:24155158

  1. Dynamically reconfigurable complex emulsions via tunable interfacial tensions.

    Science.gov (United States)

    Zarzar, Lauren D; Sresht, Vishnu; Sletten, Ellen M; Kalow, Julia A; Blankschtein, Daniel; Swager, Timothy M

    2015-02-26

    Emulsification is a powerful, well-known technique for mixing and dispersing immiscible components within a continuous liquid phase. Consequently, emulsions are central components of medicine, food and performance materials. Complex emulsions, including Janus droplets (that is, droplets with faces of differing chemistries) and multiple emulsions, are of increasing importance in pharmaceuticals and medical diagnostics, in the fabrication of microparticles and capsules for food, in chemical separations, in cosmetics, and in dynamic optics. Because complex emulsion properties and functions are related to the droplet geometry and composition, the development of rapid, simple fabrication approaches allowing precise control over the droplets' physical and chemical characteristics is critical. Significant advances in the fabrication of complex emulsions have been made using a number of procedures, ranging from large-scale, less precise techniques that give compositional heterogeneity using high-shear mixers and membranes, to small-volume but more precise microfluidic methods. However, such approaches have yet to create droplet morphologies that can be controllably altered after emulsification. Reconfigurable complex liquids potentially have great utility as dynamically tunable materials. Here we describe an approach to the one-step fabrication of three- and four-phase complex emulsions with highly controllable and reconfigurable morphologies. The fabrication makes use of the temperature-sensitive miscibility of hydrocarbon, silicone and fluorocarbon liquids, and is applied to both the microfluidic and the scalable batch production of complex droplets. We demonstrate that droplet geometries can be alternated between encapsulated and Janus configurations by varying the interfacial tensions using hydrocarbon and fluorinated surfactants including stimuli-responsive and cleavable surfactants. This yields a generalizable strategy for the fabrication of multiphase emulsions with

  2. Probing model tumor interfacial properties using piezoelectric cantilevers

    Science.gov (United States)

    Yegingil, Hakki; Shih, Wan Y.; Shih, Wei-Heng

    2010-09-01

    Invasive malignant breast cancers are typically branchy and benign breast tumors are typically smooth. It is of interest to characterize tumor branchiness (roughness) to differentiate invasive malignant breast cancer from noninvasive ones. In this study, we examined the shear modulus (G) to elastic modulus (E) ratio, G /E, as a quantity to describe model tumor interfacial roughness using a piezoelectric cantilever capable of measuring both tissue elastic modulus and tissue shear modulus. The piezoelectric cantilever used had two lead zirconate titanate layers to facilitate all-electrical elastic (shear) modulus measurements using one single device. We constructed model tissues with tumors by embedding one-dimensional (1D) corrugated inclusions and three-dimensional (3D) spiky-ball inclusions made of modeling clay in gelatin. We showed that for smooth inclusions, G /E was 0.3 regardless of the shear direction. In contrast, for a 1D corrugated rough inclusion G /E was 0.3 only when the shear was parallel to corrugation and G /E increased with an increasing angle between the shear direction and the corrugation. When the shear was perpendicular to corrugation, G /E became >0.7. For 3D isotropic spiky-ball inclusions we showed that the G /E depended on the degree of the roughness. Using the ratio s /r of the spike length (s) to the overall inclusion radius (r) as a roughness parameter, we showed that for inclusions with s /r larger than or equal to 0.28, the G /E ratio over the inclusions was larger than 0.7 whereas for inclusions with s /r less than 0.28, the G /E decreased with decreasing s /r to around 0.3 at s /r=0. In addition, we showed that the depth limit of the G /E measurement is twice the width of the probe area of the piezoelectric cantilever.

  3. Enzyme changes associated with mitochondrial malic enzyme deficiency in mice

    Energy Technology Data Exchange (ETDEWEB)

    Mohrenweiser, H.W.; Erickson, R.P.

    1979-01-01

    A genetically determined absence of mitochondrial malic enzyme (EC 1.1.1.40) in c/sup 3H//c/sup 6H/ mice is accompanied by a four-fold increase in liver glucose-6-phosphate dehydrogenase and a two-fold increase for 6-phosphogluconate dehydrogenase activity. Smaller increases in the activity of serine dehydratase and glutamic oxaloacetic transaminase are observed while the level of glutamic pyruvate transaminase activity is reduced in the liver of deficient mice. Unexpectedly, the level of activity of total malic enzyme in the livers of mitochrondrial malic enzyme-deficient mice is increased approximately 50% compared to littermate controls. No similar increase in solublle malic enzyme activity is observed in heart of kidney tissue of mutant mice and the levels of total malic enzyme in these tissues are in accord with expected levels of activity in mitochondrial malic enzyme-deficient mice. The divergence in levels of enzyme activity between mutant and wild-type mice begins at 19 to 21 days of age. Immunoinactivation experiments with monospecific antisera to the soluble malic enzyme and glucose-6-phosphate dehydrogenase demonstrate that the activity increases represent increases in the amount of enzyme protein. The alterations are not consistent with a single hormonal response.

  4. Extracting elastic properties of an atomically thin interfacial layer by time-domain analysis of femtosecond acoustics

    Science.gov (United States)

    Chen, H.-Y.; Huang, Y.-R.; Shih, H.-Y.; Chen, M.-J.; Sheu, J.-K.; Sun, C.-K.

    2017-11-01

    Modern devices adopting denser designs and complex 3D structures have created much more interfaces than before, where atomically thin interfacial layers could form. However, fundamental information such as the elastic property of the interfacial layers is hard to measure. The elastic property of the interfacial layer is of great importance in both thermal management and nano-engineering of modern devices. Appropriate techniques to probe the elastic properties of interfacial layers as thin as only several atoms are thus critically needed. In this work, we demonstrated the feasibility of utilizing the time-resolved femtosecond acoustics technique to extract the elastic properties and mass density of a 1.85-nm-thick interfacial layer, with the aid of transmission electron microscopy. We believe that this femtosecond acoustics approach will provide a strategy to measure the absolute elastic properties of atomically thin interfacial layers.

  5. Two-group modeling of interfacial area transport in large diameter channels

    Energy Technology Data Exchange (ETDEWEB)

    Schlegel, J.P., E-mail: schlegelj@mst.edu [Department of Mining and Nuclear Engineering, Missouri University of Science and Technology, 301 W 14th St., Rolla, MO 65409 (United States); Hibiki, T.; Ishii, M. [School of Nuclear Engineering, Purdue University, 400 Central Dr., West Lafayette, IN 47907 (United States)

    2015-11-15

    Highlights: • Implemented updated constitutive models and benchmarking method for IATE in large pipes. • New model and method with new data improved the overall IATE prediction for large pipes. • Not all conditions well predicted shows that further development is still required. - Abstract: A comparison of the existing two-group interfacial area transport equation source and sink terms for large diameter channels with recently collected interfacial area concentration measurements (Schlegel et al., 2012, 2014. Int. J. Heat Fluid Flow 47, 42) has indicated that the model does not perform well in predicting interfacial area transport outside of the range of flow conditions used in the original benchmarking effort. In order to reduce the error in the prediction of interfacial area concentration by the interfacial area transport equation, several constitutive relations have been updated including the turbulence model and relative velocity correlation. The transport equation utilizing these updated models has been modified by updating the inter-group transfer and Group 2 coalescence and disintegration kernels using an expanded range of experimental conditions extending to pipe sizes of 0.304 m [12 in.], gas velocities of up to nearly 11 m/s [36.1 ft/s] and liquid velocities of up to 2 m/s [6.56 ft/s], as well as conditions with both bubbly flow and cap-bubbly flow injection (Schlegel et al., 2012, 2014). The modifications to the transport equation have resulted in a decrease in the RMS error for void fraction and interfacial area concentration from 17.32% to 12.3% and 21.26% to 19.6%. The combined RMS error, for both void fraction and interfacial area concentration, is below 15% for most of the experiments used in the comparison, a distinct improvement over the previous version of the model.

  6. The effects of excipients on protein aggregation during agitation: an interfacial shear rheology study.

    Science.gov (United States)

    Liu, Lu; Qi, Wei; Schwartz, Daniel K; Randolph, Theodore W; Carpenter, John F

    2013-08-01

    We investigated the effects of excipients in solutions of keratinocyte growth factor 2 (KGF-2) on protein aggregation during agitation as well as on interfacial shear rheology at the air-water interface. Samples were incubated with or without agitation, and in the presence or absence of the excipients heparin, sucrose, or polysorbate 80 (PS80). The effect of excipients on the extent of protein aggregation was determined by UV-visible spectroscopy and micro-flow imaging. Interfacial shear rheology was used to detect the gelation time and strength of protein gels at the air-water interface. During incubation, protein particles of size ≥1 μm and insoluble aggregates formed faster for KGF-2 solutions subjected to agitation. Addition of either heparin or sucrose promoted protein aggregation during agitation. In contrast, PS80 substantially inhibited agitation-induced KGF-2 aggregation but facilitated protein particulate formation in quiescent solutions. The combination of PS80 and heparin or sucrose completely prevented protein aggregation during both nonagitated and agitated incubations. Interfacial rheological measurements showed that KGF-2 in buffer alone formed an interfacial gel within a few minutes. In the presence of heparin, KGF-2 interfacial gels formed too quickly for gelation time to be determined. KGF-2 formed gels in about 10 min in the presence of sucrose. The presence of PS80 in the formulation inhibited gelation of KGF-2. Furthermore, the interfacial gels formed by the protein in the absence of PS80 were reversible when PS80 was added to the samples after gelation. Therefore, there is a correspondence between formulations that exhibited interfacial gelation and formulations that exhibited agitation-induced aggregation. Copyright © 2013 Wiley Periodicals, Inc.

  7. Effect of Interfacial Molecular Orientation on Power Conversion Efficiency of Perovskite Solar Cells.

    Science.gov (United States)

    Xiao, Minyu; Joglekar, Suneel; Zhang, Xiaoxian; Jasensky, Joshua; Ma, Jialiu; Cui, Qingyu; Guo, L Jay; Chen, Zhan

    2017-03-08

    A wide variety of charge carrier dynamics, such as transport, separation, and extraction, occur at the interfaces of planar heterojunction solar cells. Such factors can affect the overall device performance. Therefore, understanding the buried interfacial molecular structure in various devices and the correlation between interfacial structure and function has become increasingly important. Current characterization techniques for thin films such as X-ray diffraction, cross section scanning electronmicroscopy, and UV-visible absorption spectroscopy are unable to provide the needed molecular structural information at buried interfaces. In this study, by controlling the structure of the hole transport layer (HTL) in a perovskite solar cell and applying a surface/interface-sensitive nonlinear vibrational spectroscopic technique (sum frequency generation vibrational spectroscopy (SFG)), we successfully probed the molecular structure at the buried interface and correlated its structural characteristics to solar cell performance. Here, an edge-on (normal to the interface) polythiophene (PT) interfacial molecular orientation at the buried perovskite (photoactive layer)/PT (HTL) interface showed more than two times the power conversion efficiency (PCE) of a lying down (tangential) PT interfacial orientation. The difference in interfacial molecular structure was achieved by altering the alkyl side chain length of the PT derivatives, where PT with a shorter alkyl side chain showed an edge-on interfacial orientation with a higher PCE than that of PT with a longer alkyl side chain. With similar band gap alignment and bulk structure within the PT layer, it is believed that the interfacial molecular structural variation (i.e., the orientation difference) of the various PT derivatives is the underlying cause of the difference in perovskite solar cell PCE.

  8. Assessment of measurement techniques to determine the interfacial properties of bilayer dental ceramics

    Science.gov (United States)

    Anunmana, Chuchai

    The clinical success of all-ceramic dental restorations depends on the quality of interfacial bonding between ceramic layers. In addition, the residual stress in the structure that developed during ceramic processing is one of the important factors that contributes to the quality of the bond. Because all-ceramic restorations are usually fabricated as bilayer or trilayer structures and failures of all-ceramic restorations have been frequently reported as chipping or delamination of the veneer layers, the interfacial quality of bilayer dental ceramic restorations was investigated. However, most of the published bond test data reflect strength values that are inversely related to cross-sectional areas and failure locations are frequently disregarded or bond strength values are misinterpreted. In addition, residual tensile stresses that develop in the structures because of thermal expansion/contraction mismatches may also adversely affect interfacial fracture resistance. The first objective of this study was to determine the interfacial toughness of bonded bilayer ceramics using two different approaches. The results indicate that the short-bar chevron-notch test and a controlled-flaw microtensile test can induce interfacial failure that represents true bonding quality. The second objective of this study was to test the hypothesis that residual stresses estimated from an indentation technique are not significantly different from residual stresses that are calculated based on fractography and flexural strength. The indentation technique may be useful as a simplified method to determine residual stresses in bilayer dental ceramics. The results of this study demonstrate that there is no significant difference in mean residual stresses determined from the two techniques. Because of relationship between residual stresses and apparent interfacial toughness, estimates of residual stresses can now be estimated more rapidly by measuring the apparent interfacial toughness of

  9. Force-field dependence on the interfacial structure of oil-water interfaces

    Science.gov (United States)

    Bresme, Fernando; Chacón, Enrique; Tarazona, Pedro

    2010-07-01

    We investigate the performance of different force-fields for alkanes, united (TraPPE) and all atom (OPLS-AA) models, and water (SPC/E and TIP4P-2005), in the prediction of the interfacial structure of alkane (n-octane, and n-dodecane)-water interfaces. We report an extensive comparison of the interfacial thermodynamic properties as well as the interfacial structure (translational and orientational). We use the recently introduced intrinsic sampling method, which removes the averaging effect of the interfacial capillary waves and provides a clear view of the interface structure. The alkane interfacial structure is sensitive to the environment, i.e. alkane-vapour or alkane-water interfaces, showing a stronger structure when it is in contact with the water phase. We find that this structure is fairly independent of the level of detail, full or united atom, employed to describe the alkane phase. The water surface properties show a small dependence on the water model. The dipole moment of the SPC/E model shows asymmetric fluctuations, with a tendency to point both towards the alkane and water phases. On the other hand the dipole moment of the TIP4P-2005 model shows a tendency to point towards the water phase only. Analysis of the intrinsic electrostatic field indicates that the surface water potential is confined to an interfacial region of about 8 Å. Overall we find that the intrinsic structure of alkane-water interfaces is a robust interfacial property, which is independent of the details of the force-field employed. Hence, it should provide a good reference to interpret experimental data.

  10. Enzyme activity in terrestrial soil in relation to exploration of the Martian surface

    Science.gov (United States)

    Mclaren, A. D.

    1974-01-01

    Sensitive tests for the detection of extracellular enzyme activity in Martian soil was investigated using simulated Martian soil. Enzyme action at solid-liquid water interfaces and at low humidity were studied, and a kinetic scheme was devised and tested based on the growth of microorganisms and the oxidation of ammonium nitrite.

  11. Enzyme actuated bioresponsive hydrogels

    Science.gov (United States)

    Wilson, Andrew Nolan

    Bioresponsive hydrogels are emerging with technological significance in targeted drug delivery, biosensors and regenerative medicine. Conferred with the ability to respond to specific biologically derived stimuli, the design challenge is in effectively linking the conferred biospecificity with an engineered response tailored to the needs of a particular application. Moreover, the fundamental phenomena governing the response must support an appropriate dynamic range and limit of detection. The design of these systems is inherently complicated due to the high interdependency of the governing phenomena that guide the sensing, transduction, and the actuation response of hydrogels. To investigate the dynamics of these materials, model systems may be used which seek to interrogate the system dynamics by uni-variable experimentation and limit confounding phenomena such as: polymer-solute interactions, polymer swelling dynamics and biomolecular reaction-diffusion concerns. To this end, a model system, alpha-chymotrypsin (Cht) (a protease) and a cleavable peptide-chromogen (pro-drug) covalently incorporated into a hydrogel, was investigated to understand the mechanisms of covalent loading and release by enzymatic cleavage in bio-responsive delivery systems. Using EDC and Sulfo-NHS, terminal carboxyl groups of N-succinyl-Ala-Ala-Pro-Phe p-nitroanilide, a cleavable chromogen, were conjugated to primary amines of a hydrated poly(HEMA)-based hydrogel. Hydrogel discs were incubated in buffered Cht causing enzyme-mediated cleavage of the peptide and concomitant release of the chromophore for monitoring. To investigate substrate loading and the effects of hydrogel morphology on the system, the concentration of the amino groups (5, 10, 20, and 30 mol%) and the cross-linked density (1, 5, 7, 9 and 12 mol%) were independently varied. Loading-Release Efficiency of the chromogen was shown to exhibit a positive relation to increasing amino groups (AEMA). The release rates demonstrated a

  12. Hydrolytic enzymes of "Streptococcus milleri".

    Science.gov (United States)

    Ruoff, K L; Ferraro, M J

    1987-01-01

    Seventy-two isolates classified as "Streptococcus milleri" were examined for the presence of various hydrolytic enzymes. While no protein or lipid-degrading activities were demonstrated, some isolates showed DNase and mucopolysaccharide-degrading activities. Beta-hemolytic isolates were more likely to produce these enzymes than were nonhemolytic strains. Isolates of one "S. milleri" biotype (mannitol fermentation positive) were uniformly devoid of all enzyme activities tested. PMID:2958496

  13. Enzymes From Rare Actinobacterial Strains.

    Science.gov (United States)

    Suriya, J; Bharathiraja, S; Manivasagan, P; Kim, S-K

    Actinobacteria constitute rich sources of novel biocatalysts and novel natural products for medical and industrial utilization. Although actinobacteria are potential source of economically important enzymes, the isolation and culturing are somewhat tough because of its extreme habitats. But now-a-days, the rate of discovery of novel compounds producing actinomycetes from soil, freshwater, and marine ecosystem has increased much through the developed culturing and genetic engineering techniques. Actinobacteria are well-known source of their bioactive compounds and they are the promising source of broad range of industrially important enzymes. The bacteria have the capability to degrade a range of pesticides, hydrocarbons, aromatic, and aliphatic compounds (Sambasiva Rao, Tripathy, Mahalaxmi, & Prakasham, 2012). Most of the enzymes are mainly derived from microorganisms because of their easy of growth, minimal nutritional requirements, and low-cost for downstream processing. The focus of this review is about the new, commercially useful enzymes from rare actinobacterial strains. Industrial requirements are now fulfilled by the novel actinobacterial enzymes which assist the effective production. Oxidative enzymes, lignocellulolytic enzymes, extremozymes, and clinically useful enzymes are often utilized in many industrial processes because of their ability to catalyze numerous reactions. Novel, extremophilic, oxidative, lignocellulolytic, and industrially important enzymes from rare Actinobacterial population are discussed in this chapter. © 2016 Elsevier Inc. All rights reserved.

  14. Enzyme Mimics: Advances and Applications.

    Science.gov (United States)

    Kuah, Evelyn; Toh, Seraphina; Yee, Jessica; Ma, Qian; Gao, Zhiqiang

    2016-06-13

    Enzyme mimics or artificial enzymes are a class of catalysts that have been actively pursued for decades and have heralded much interest as potentially viable alternatives to natural enzymes. Aside from having catalytic activities similar to their natural counterparts, enzyme mimics have the desired advantages of tunable structures and catalytic efficiencies, excellent tolerance to experimental conditions, lower cost, and purely synthetic routes to their preparation. Although still in the midst of development, impressive advances have already been made. Enzyme mimics have shown immense potential in the catalysis of a wide range of chemical and biological reactions, the development of chemical and biological sensing and anti-biofouling systems, and the production of pharmaceuticals and clean fuels. This Review concerns the development of various types of enzyme mimics, namely polymeric and dendrimeric, supramolecular, nanoparticulate and proteinic enzyme mimics, with an emphasis on their synthesis, catalytic properties and technical applications. It provides an introduction to enzyme mimics and a comprehensive summary of the advances and current standings of their applications, and seeks to inspire researchers to perfect the design and synthesis of enzyme mimics and to tailor their functionality for a much wider range of applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Significant NRC Enforcement Actions

    Data.gov (United States)

    Nuclear Regulatory Commission — This dataset provides a list of Nuclear Regulartory Commission (NRC) issued significant enforcement actions. These actions, referred to as "escalated", are issued by...

  16. Enzyme structure, enzyme function and allozyme diversity in ...

    African Journals Online (AJOL)

    In estimates of population genetic diversity based on allozyme heterozygosity, some enzymes are regularly more variable than others. Evolutionary theory suggests that functionally less important molecules, or parts of molecules, evolve more rapidly than more important ones; the latter enzymes should then theoretically be ...

  17. Experimental characterization of interfacial behaviors of hydrocarbon mixtures in high pressure systems

    Energy Technology Data Exchange (ETDEWEB)

    Nie, Hui

    2012-07-01

    The interfacial properties and behaviors of the hydrocarbon mixtures in high pressure systems were experimentally and numerically studied during this work. Simultaneously measurements of phase densities, vapor phase compositions, and interfacial tensions were performed using the High Pressure interfacial tension facility in the Statoil Research Center, Trondheim. Numerical computations of interfacial properties at the non-homogeneous flat vapor/liquid interface were carried out with the Gradient Theory model so as to evaluate the method for future simulations of interfacial characteristics of the real gas condensate. It was found that the accuracy of the Gradient Theory is superior to the Parachor Method, which has been traditionally used in the oil industry for its interfacial tension predictions. In the laboratory, the high pressure Anton Paar oscillation tube densitometer was employed for liquid and vapor phase density measurements, and the pendant drop method was used to generate the interfacial tension data. The Online Gas Chromatography (GC) cell was utilized to obtain the vapor phase compositions under high pressure conditions. In this study, the methane + ethane + n-pentane system is considered to be a synthetic condensate, which mimics the thermodynamic behavior of a real nature gas in high pressure gas/liquid separation systems. The experimental temperature is set to 294.15 K since it is close to the scrubber' normal working temperature. Both the phase densities and interfacial tensions of the methane + n-pentane, ethane + n-pentane and methane + ethane + n-pentane systems were measured in the interfacial tension rig. The experimental data is crucial for the understanding, experimental characterizing, and developing the thermodynamic model in predicting interfacial properties and the phase behaviors governing the high pressure vapor/liquid separation process, which is the main purpose of this research. The Gradient Theory method, combined with the

  18. [The rise of enzyme engineering in China].

    Science.gov (United States)

    Li, Gaoxiang

    2015-06-01

    Enzyme engineering is an important part of the modern biotechnology. Industrial biocatalysis is considered the third wave of biotechnology following pharmaceutical and agricultural waves. In 25 years, China has made a mighty advances in enzyme engineering research. This review focuses on enzyme genomics, enzyme proteomics, biosynthesis, microbial conversion and biosensors in the Chinese enzyme engineering symposiums and advances in enzyme preparation industry in China.

  19. Computational enzyme design: transitioning from catalytic proteins to enzymes.

    Science.gov (United States)

    Mak, Wai Shun; Siegel, Justin B

    2014-08-01

    The widespread interest in enzymes stem from their ability to catalyze chemical reactions under mild and ecologically friendly conditions with unparalleled catalytic proficiencies. While thousands of naturally occurring enzymes have been identified and characterized, there are still numerous important applications for which there are no biological catalysts capable of performing the desired chemical transformation. In order to engineer enzymes for which there is no natural starting point, efforts using a combination of quantum chemistry and force-field based protein molecular modeling have led to the design of novel proteins capable of catalyzing chemical reactions not catalyzed by naturally occurring enzymes. Here we discuss the current status and potential avenues to pursue as the field of computational enzyme design moves forward. Published by Elsevier Ltd.

  20. Highly tunable interfacial adhesion of glass fiber by hybrid multilayers of graphene oxide and aramid nanofiber.

    Science.gov (United States)

    Park, Byeongho; Lee, Wonoh; Lee, Eunhee; Min, Sa Hoon; Kim, Byeong-Su

    2015-02-11

    The performance of fiber-reinforced composites is governed not only by the nature of each individual component comprising the composite but also by the interfacial properties between the fiber and the matrix. We present a novel layer-by-layer (LbL) assembly for the surface modification of a glass fiber to enhance the interfacial properties between the glass fiber and the epoxy matrix. Solution-processable graphene oxide (GO) and an aramid nanofiber (ANF) were employed as active components for the LbL assembly onto the glass fiber, owing to their abundant functional groups and mechanical properties. We found that the interfacial properties of the glass fibers uniformly coated with GO and ANF multilayers, such as surface free energy and interfacial shear strength, were improved by 23.6% and 39.2%, respectively, compared with those of the bare glass fiber. In addition, the interfacial adhesion interactions between the glass fiber and the epoxy matrix were highly tunable simply by changing the composition and the architecture of layers, taking advantage of the versatility of the LbL assembly.

  1. Estimation of solid-liquid interfacial tension using curved surface of a soft solid.

    Science.gov (United States)

    Mondal, Subrata; Phukan, Monmee; Ghatak, Animangsu

    2015-10-13

    Unlike liquids, for crystalline solids the surface tension is known to be different from the surface energy. However, the same cannot be said conclusively for amorphous materials like soft cross-linked elastomers. To resolve this issue we have introduced here a direct method for measuring solid-liquid interfacial tension by using the curved surface of a solid. In essence, we have used the inner surface of tiny cylindrical channels embedded inside a soft elastomeric film for sensing the effect of the interfacial tension. When a liquid is inserted into the channel, because of wetting-induced alteration in interfacial tension, its thin wall deflects considerably; the deflection is measured with an optical profilometer and analyzed using the Föppl-von Kármán equation. We have used several liquids and cross-linked poly(dimethylsiloxane) as the solid to show that the estimated values of the solid-liquid interfacial tension matches with the corresponding solid-liquid interfacial energy reasonably well.

  2. Determination of interfacial heat transfer coefficient for TC11 titanium alloy hot forging

    Science.gov (United States)

    Lu, Baoshan; Wang, Leigang; Geng, Zhe; Huang, Yao

    2017-10-01

    In this paper, based on self-developed experimental apparatus, the upsetting test of TC11 titanium alloy on the hot flat die was conducted and Beck's nonlinear inverse estimation method was adopted to calculate the interfacial heat transfer coefficient (IHTC) and the change rules of IHTC following billet deformation rate, average interfacial temperature and holding time were investigated respectively. Experimental results indicate that IHTC increases with the increase of deformation rate as a whole, and the billet deformation heat and interfacial friction heat during forming that remarkably contribute to IHTC and the contributions by heat conduction to IHTC is differ from that by friction; the glass lubricant coated on the billet surface that weakens the heat transfer situation in the early stage of forging, however, this blocking effect of lubricant on IHTC soon vanishes with increasing deformation rate and it enhances the interface heat transfer later; the average interfacial temperature impacts on IHTC in many aspects and a high average interfacial temperature IHTC corresponds to a high IHTC when the deformation rate is certain, but this changing trend is not monotonous; the IHTC decreases with the increase of holding time due to oxidation. After certain holding time, the IHTC is only related to temperature and pressure in the absence of deformation rate, and the influence of pressure on IHTC is larger than that of temperature on it.

  3. Interfacial assembly at silver nanoparticle enhances the antibacterial efficacy of nisin.

    Science.gov (United States)

    Arakha, Manoranjan; Borah, Sapna M; Saleem, Mohammed; Jha, Anupam N; Jha, Suman

    2016-12-01

    Nisin is a well-recognised antimicrobial peptide (AMP) used in food industry. However, efficacy of the peptide has been compromised due to development of resistance in different bacterial strains. Here, efficacy of the peptide upon assembly at a silver nanoparticle (AgNP) interface has been characterized. To this end, experimental and simulation studies are done to characterize the interfacial assembly of nisin and underlie antibacterial mechanism. Being an AMP, efficacy of an intact nisin is explored against Gram-positive and Gram-negative bacteria, and compared with antibacterial propensity of the interfacially assembled nisin. Antibacterial propensity, upon the assembly, increases against both kinds of bacteria. Interestingly, the growth inhibition studies of the interfacially assembled nisin indicate that the originally nisin resistant Gram-negative bacteria become sensitive to the nanomolar nisin concentrations. Furthermore, reactive oxygen species (ROS) measurements together with confocal microscopy imaging indicate that the increase in interfacial and intracellular ROS production upon the treatment is underling mechanism of enhanced antibacterial propensity of the assembled nisin. Thus, the study observed that the interfacial assembly of nisin at AgNP interface enhances the efficacy of nisin against different spectrum of bacteria, where the intact nisin is largely ineffective for the studied concentrations. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. On-chip microfluidic generation of monodisperse bubbles for liquid interfacial tension measurement.

    Science.gov (United States)

    Wang, Chen; Cao, Jing; Zhou, Yue; Xia, Xing-Hua

    2018-01-01

    A novel microfluidic method for measuring liquid interfacial tension using monodisperse microbubbles generated in situ has been proposed. Instead of bulky gas supply used in traditional microfluidic devices, microbubbles are efficiently generated via water electrolysis in the devices. Since the bubble formation frequency is related to the interfacial tension of liquids used, thus, precisely measuring the interfacial tension of liquids in microfluidics can be achieved. In addition, it is found that during the microbubble formation, the electrochemical potential fluctuates regularly at controlled electrolysis current, and the fluctuating period depends on the microbubble generation rate. Therefore, the change in electrochemical potential can be directly used to monitor the bubble formation process, which avoids the use of an external optical detection system. As demonstration, the interfacial tension of isopentanol solutions with different concentrations was measured, and the results show good agreement with the ones obtained using the maximum bubble pressure method, confirming the accuracy of the present method. The proposed strategy offers a simple, low cost and accurate solution to measure the liquid interfacial tension confined in microfluidic channels. The present platform is easily constructed and facilely manipulated in common laboratories, which is expected to be widely used in microfluidic-based research and application fields. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Oscillating drop/bubble tensiometry: effect of viscous forces on the measurement of interfacial tension.

    Science.gov (United States)

    Freer, E M; Wong, H; Radke, C J

    2005-02-01

    The oscillating drop/bubble technique is increasingly popular for measuring the interfacial dilatational properties of surfactant/polymer-laden fluid/fluid interfaces. A caveat of this technique, however, is that viscous forces are important at higher oscillation frequencies or fluid viscosities; these can affect determination of the interfacial tension. Here, we experimentally quantify the effect of viscous forces on the interfacial-tension measurement by oscillating 100 and 200 cSt poly(dimethylsiloxane) (PDMS) droplets in water at small amplitudes and frequencies ranging between 0.01 and 1 Hz. Due to viscous forces, the measured interfacial tension oscillates sinusoidally with the same frequency as the oscillation of the drop volume. The tension oscillation precedes that of the drop volume, and the amplitude varies linearly with Capillary number, Ca=DeltamuomegaDeltaV/gammaa(2), where Deltamu=mu(D)-mu is the difference between the bulk Newtonian viscosities of the drop and surrounding continuous fluid, omega is the oscillation frequency of the drop, DeltaV is the amplitude of volume oscillation, gamma is the equilibrium interfacial tension between the PDMS drop and water, and a is the radius of the capillary. A simplified model of a freely suspended spherical oscillating-drop well explains these observations. Viscous forces distort the drop shape at Ca>0.002, although this criterion is apparatus dependent.

  6. Direct observation of interfacial Au atoms on TiO₂ in three dimensions.

    Science.gov (United States)

    Gao, Wenpei; Sivaramakrishnan, Shankar; Wen, Jianguo; Zuo, Jian-Min

    2015-04-08

    Interfacial atoms, which result from interactions between the metal nanoparticles and support, have a large impact on the physical and chemical properties of nanoparticles. However, they are difficult to observe; the lack of knowledge has been a major obstacle toward unraveling their role in chemical transformations. Here we report conclusive evidence of interfacial Au atoms formed on the rutile (TiO2) (110) surfaces by activation using high-temperature (∼500 °C) annealing in air. Three-dimensional imaging was performed using depth-sectioning enabled by aberration-corrected scanning transmission electron microscopy. Results show that the interface between Au nanocrystals and TiO2 (110) surfaces consists of a single atomic layer with Au atoms embedded inside Ti-O. The number of interfacial Au atoms is estimated from ∼1-8 in an interfacial atomic column. Direct impact of interfacial Au atoms is observed on an enhanced Au-TiO2 interaction and the reduction of surface TiO2; both are critical to Au catalysis.

  7. Finite-size effects on molecular dynamics interfacial thermal-resistance predictions

    Science.gov (United States)

    Liang, Zhi; Keblinski, Pawel

    2014-08-01

    Using molecular dynamics simulations, we study the role of finite size effects on the determination of interfacial thermal resistance between two solids characterized by high phonon mean free paths. In particular, we will show that a direct, heat source-sink method leads to strong size effect, associated with ballistic phonon transport to and from, and specular reflections at the simulation domain boundary. Lack of proper account for these effects can lead to incorrect predictions about the role of interfacial bonding and structure on interfacial thermal resistance. We also show that the finite size effect can be dramatically reduced by introduction of rough external boundaries leading to diffuse phonon scattering, as explicitly demonstrated by phonon wave-packet simulations. Finally, we demonstrate that when careful considerations are given to the effects associated with the finite heat capacity of the simulation domains and phonon scattering from the external surfaces, a size-independent interfacial resistance can be properly extracted from the time integral of the correlation function of heat power across the interface. Our work demonstrates that reliable and consistent values of the interfacial thermal resistance can be obtained by equilibrium and nonequilibrium methods with a relatively small computational cost.

  8. In Situ STEM-EELS Observation of Nanoscale Interfacial Phenomena in All-Solid-State Batteries.

    Science.gov (United States)

    Wang, Ziying; Santhanagopalan, Dhamodaran; Zhang, Wei; Wang, Feng; Xin, Huolin L; He, Kai; Li, Juchuan; Dudney, Nancy; Meng, Ying Shirley

    2016-06-08

    Behaviors of functional interfaces are crucial factors in the performance and safety of energy storage and conversion devices. Indeed, solid electrode-solid electrolyte interfacial impedance is now considered the main limiting factor in all-solid-state batteries rather than low ionic conductivity of the solid electrolyte. Here, we present a new approach to conducting in situ scanning transmission electron microscopy (STEM) coupled with electron energy loss spectroscopy (EELS) in order to uncover the unique interfacial phenomena related to lithium ion transport and its corresponding charge transfer. Our approach allowed quantitative spectroscopic characterization of a galvanostatically biased electrochemical system under in situ conditions. Using a LiCoO2/LiPON/Si thin film battery, an unexpected structurally disordered interfacial layer between LiCoO2 cathode and LiPON electrolyte was discovered to be inherent to this interface without cycling. During in situ charging, spectroscopic characterization revealed that this interfacial layer evolved to form highly oxidized Co ions species along with lithium oxide and lithium peroxide species. These findings suggest that the mechanism of interfacial impedance at the LiCoO2/LiPON interface is caused by chemical changes rather than space charge effects. Insights gained from this technique will shed light on important challenges of interfaces in all-solid-state energy storage and conversion systems and facilitate improved engineering of devices operated far from equilibrium.

  9. Ionic Liquids as the MOFs/Polymer Interfacial Binder for Efficient Membrane Separation.

    Science.gov (United States)

    Lin, Rijia; Ge, Lei; Diao, Hui; Rudolph, Victor; Zhu, Zhonghua

    2016-11-23

    Obtaining strong interfacial affinity between filler and polymer is critical to the preparation of mixed matrix membranes (MMMs) with high separation efficiency. However, it is still a challenge for micron-sized metal organic frameworks (MOFs) to achieve excellent compatibility and defect-free interface with polymer matrix. Thin layer of ionic liquid (IL) was immobilized on micron-sized HKUST-1 to eliminate the interfacial nonselective voids in MMMs with minimized free ionic liquid (IL) in polymer matrix, and then the obtained IL decorated HKUST-1 was incorporated into 4,4'-(hexafluoroisopropylidene)diphthalic anhydride-2,3,5,6-tetramethyl-1,3-phenyldiamine (6FDA-Durene) to fabricate MMMs. Acting as a filler/polymer interfacial binder, the favorable MOF/IL and IL/polymer interaction can facilitate the enhancement of MOF/polymer affinity. Compared to MMM with only HKUST-1 incorporation, MMM with IL decorated HKUST-1 succeeded in restricting the formation of nonselective interfacial voids, leading to an increment in CO2 selectivity. The IL decoration method can be an effective approach to eliminate interfacial voids in MMMs, extending the filler selection to a wide range of large-sized fillers.

  10. Interfacial Surface Modification via Nanoimprinting to Increase Open-Circuit Voltage of Organic Solar Cells

    Science.gov (United States)

    Emah, Joseph B.; George, Nyakno J.; Akpan, Usenobong B.

    2017-08-01

    The low-cost patterning of poly(3,4-ethylenedioxythiophene) poly(4-styrenesulfonate) (PEDOT:PSS) interfacial layers inserted between indium tin oxide and poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric acid ester blends leads to an improvement in organic photovoltaics (OPV) device performance. Significantly, improvements in all device parameters, including the open-circuit voltage, are achieved. The nanoimprinted devices improved further as the pattern period and imprinting depth was reduced from 727 nm and 42 nm to 340 nm and 10 nm, respectively. A residue of poly(dimethylsiloxane) (PDMS) is found on the interfacial PEDOT:PSS film following patterning and can be used to explain the increase in OPV performance. Ultraviolet photoelectron spectroscopy measurements of the PEDOT:PSS interfacial layer demonstrated a reduction of the work function of 0.4 eV following nanoimprinting which may originate from chemical modification of the PDMS residue or interfacial dipole formation supported by x-ray photoelectron spectroscopy analysis. Ultimately, we have demonstrated a 39% improvement in OPV device performance via a simple low-cost modification of the anode interfacial layer. This improvement can be assigned to two effects resulting from a PDMS residue on the PEDOT:PSS surface: (1) the reduction of the anode work function which in turn decreases the hole extraction barrier, and (2) the reduction of electron transfer from the highest occupied molecular orbital of PCBM to the anode.

  11. Effect of hygroscopic expansion of resin filling on interfacial gap and sealing: a confocal microscopy study.

    Science.gov (United States)

    Rosales-Leal, Juan I; Castillo-Salmerón, Ramón Del; Molino-Serrano, María A; González-Moreira, Humberto; Cabrerizo-Vílchez, Miguel A

    2013-10-01

    To measure dimensional changes due to hygroscopic expansion and their effect on interface gaps and sealing in four light-cured restorative materials using an original confocal microscopic methodology. The materials tested were an ormocer (Admira [Voco]), a compomer (Dyract AP [Dentsply]), a hybrid composite (Spectrum [Dentsply]), and a nanohybrid composite (Esthet·X [Dentsply]). Water sorption was evaluated by weighing material disks after immersion. Hygroscopic expansion was measured from volumetric variations of material fillings in cylindrical cavities in dentin slices; the interfacial gap size was obtained from the same cavities using a novel confocal microscopic method. Microleakage was evaluated in cavities prepared in extracted third molars. Measurements followed water immersion for 24 h, 1 week, 4 weeks, and 8 weeks. A factorial ANOVA, the Student Newman Keuls test for post-hoc comparisons, the Student's t-test, and the Pearson test were used for the statistical analysis (p hygroscopic expansion, and sealing. Hygroscopic expansion reduced post-polymerization interfacial gaps and improved cavity sealing. Dyract AP and Admira showed the highest water sorption, hygroscopic expansion, and gap size reduction. 1. The proposed methodology is valid to measure hygroscopic expansion and interfacial gap. 2. Water sorption and hygroscopic expansion are positively correlated, and hygroscopic expansion, gap size, and sealing are also positively correlated. 3. The adhesive influences the interfacial gap size and its variation after hygroscopic expansion. 4. Hygroscopic expansion reduces the interfacial gaps generated by polymerization shrinkage and improves cavity sealing.

  12. Temperature dependence of interfacial properties and viscosity of nanofluids for droplet-based microfluidics

    Energy Technology Data Exchange (ETDEWEB)

    Murshed, S M Sohel; Tan, Say-Hwa; Nguyen, Nam-Trung [School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Singapore)], E-mail: mntnguyen@ntu.edu.sg

    2008-04-21

    Interfacial tension and viscosity of a liquid play an important role in microfluidic systems. In this study, temperature dependence of surface tension, interfacial tension and viscosity of a nanofluid are investigated for its applicability in droplet-based microfluidics. Experimental results show that nanofluids having TiO{sub 2} nanoparticles of 15 nm diameter in deionized water exhibit substantially smaller surface tension and oil-based interfacial tension than those of the base fluid (i.e. deionized water). These surface and interfacial tensions of this nanofluid were found to decrease almost linearly with increasing temperature. The Brownian motion of nanoparticles in the base fluid was identified as a possible mechanism for reduced surface and interfacial tensions of the nanofluid. The measured effective viscosity of the nanofluid was found to be insignificantly higher than that of the base fluid and to decrease with increasing fluid temperature. The dependence on the temperature of the droplet formation at the T-junction of a microfluidic device is also studied and the nanofluid shows larger droplet size compared with its base fluid.

  13. Interfacial Chemistry of Moisture-Aged Class II Composite Restorations

    Science.gov (United States)

    Spencer, Paulette; Wang, Yong; Bohaty, Brenda

    2007-01-01

    Under in vivo conditions, the adhesive/dentin bond at the gingival margin of class II composite restorations can be the first defense against substances that may penetrate and ultimately undermine the composite restoration. Deterioration of this bond during aqueous aging is an area of intense investigation, but to date, the majority of our techniques have provided only an indirect assessment of the degrading components. The purpose of this study was to analyze the in situ molecular structure of adhesive/dentin interfaces in class II composite restorations, following aging in aqueous solutions. Class II preparations were cut from 12 unerupted human third molars, with a water-cooled, high-speed, dental handpiece. The prepared teeth were randomly selected for restoration with single bond (SB) and Z100 (3M). Teeth were restored, as per the manufacturer’s directions, under environmental conditions that simulated humidity and temperature characteristics of the oral cavity. Restored teeth were kept in sterile Delbecco’s phosphate saline for 48 h or 90 days. The samples were sectioned occlusogingivally and micro-Raman spectra were acquired at ~1.5 μm spatial resolution across the composite/adhesive/dentin interfaces at the gingival margins. Samples were wet throughout spectral acquisition. The relative intensity of bands associated with the adhesive in the interfacial region decreased dramatically after aqueous storage. This decrease in concert with the similar depth of dentin demineralization provides direct spectroscopic evidence of leaching of adhesive monomer from the interface during the 90 days of storage. SB adhesive infiltrated 4 –5 μm of 12-μm demineralized dentin at the gingival margin. After 90 days of aqueous storage, SB adhesive infiltration was reduced to ~2 μm, leaving ~10 μm of demineralized dentin collagen exposed at the gingival margin. The unprotected collagen at the gingival margin of the aged class II composite restorations was disorganized

  14. Determination of interfacial roughness using X-ray scattering

    Energy Technology Data Exchange (ETDEWEB)

    Munkholm, Anneli [Stanford Univ., CA (United States)

    1997-05-01

    Crystal truncation rod (CTR) scattering is shown to be a powerful technique for determining interfacial roughness non-destructively. By measuring the decay of scattering away from a Bragg reflection in the surface direction an rms roughness of the surface or interface can be extracted. The authors obtain rms roughness values with an accuracy of ± 0.1 Å. Sensitivity to lateral length scale roughness ranges from the wavelength of the x-rays to between 1,000--10,000 Å depending on the instrument function and the specific truncation rod. The influence of different cleans, as well as the thermal oxidation process, on the Si-SiO2 interface is investigated. A hot water treatment prior to the thermal oxidation is shown to roughen the Si-SiO2 interface. CTR scattering results also show a smoothing of the interface as a result of the oxidation process even for as little as 60 Å of thermal oxidation. Comparison between AFM and CTR scattering gives a consistent picture of the relative roughness of the wafers, although the absolute numbers do not agree. The differences in the absolute values can be explained by the lateral roughness scale that the two techniques measure, indicating that it is at periodicities below ~ 100 Å that the increased roughness observed by the x-ray is found. Crystal truncation rods are shown to be perpendicular to the surface and not along the crystallographic axes of a miscut crystal. It is shown that for a crystal terminated by a regular step array both an atomistic and a continuum description of CTR scattering give identical results. Furthermore, the atomistic approach is used to show that a diamond cubic surface with a miscut is inherently rough. Even for a small miscut the tilt of the CTR with respect to the crystallographic axes results in complications for measuring the rod intensity. The authors present schemes for determining the exact position of the CTR in reciprocal space and for measuring the miscut of a single

  15. Interfacial adhesion of dental ceramic-resin systems

    Science.gov (United States)

    Della Bona, Alvaro

    The clinical success of resin bonding procedures for indirect ceramic restorations and ceramic repairs depends on the quality and durability of the bond between the ceramic and the resin. The quality of this bond will depend upon the bonding mechanisms that are controlled in part by the surface treatment that promotes micromechanical and/or chemical bonding to the substrate. The objective of this study is to correlate interfacial toughness (K A) with fracture surface morphological parameters of the dental ceramic-resin systems as a function of ceramic surface treatment. The analytical procedures focused on characterizing the microstructure and fracture properties of EmpressRTM ceramics (a leucite-based core ceramic, two lithia disilicate-based core ceramics, and a glass veneer) and determining the ceramic-resin adhesion zone bond strength characteristics. Microstructure and composition are controlling factors in the development of micromechanical retention produced by etching. Silane treated ceramics negated the effect of surface roughening produced by etching, inducing lower surface energy of the ceramic and, reduced bonding effectiveness. There was a positive correlation between WA, tensile bond strength (a), and KA, i.e., higher mean WA value, and higher mean sigma and KA values. This study suggests that (1) the sigma and KA values for ceramic bonded to resin are affected by the ceramic microstructure and the ceramic surface treatments; (2) the definition of the adhesion zone is essential to classify the modes of failure, which should be an integral component of all failure analyses; (3) the microtensile test may be preferable to conventional shear or flexural tests as an indicator of composite-ceramic bond quality; and (4) careful microscopic analysis of fracture surfaces and an x-ray dot map can produce a more consistent and complete description of the fracture process and interpretation of the modes of failure. The mode of failure and fractographic analyses

  16. Large-eddy simulation of sheared interfacial flow

    Science.gov (United States)

    Reboux, S.; Sagaut, P.; Lakehal, D.

    2006-10-01

    Large-eddy simulations (LES) of a turbulent interfacial gas-liquid flows are described in this paper. The variational multiscale approach (VMS) introduced by Hughes for single-phase flows is systematically assessed against direct numerical simulation (DNS) data obtained at a shear Reynolds number Re⋆=171, and compared to LES results obtained with the Smagorinsky model, modified by a near-interface turbulence decay treatment. The models are incorporated in the same pseudospectral DNS solver built within the boundary fitting method used by Fulgosi et al. for air-water flow. The LES are performed for physical conditions allowing low interface deformations that fall in the range of capillary waves of wave slope ak =0.01. The LES results show that both the modified Smagorinsky model and the VMS are capable to predict the boundary layer structure in the gas side, including the decay process, and to cope with the anisotropy of turbulence in the liquid blockage layer underneath the interface. Higher-order turbulence statistics, including the transfer of energy between the normal stresses is also well predicted by both approaches, but qualitatively the VMS results remain overall better than the modified Smagorinsky model. The study has demonstrated that the key to the prediction of the energy transfer mechanism is in the proper prediction of the fluctuating pressure field, which has been found out of reach of any of the LES methodologies. The superiority of the VMS is demonstrated through the analysis of the subgrid transport and exchange terms in the resolved kinetic energy, where it is indeed shown to be self-adaptive with regard to the eddy viscosity. Although VMS is shown to be sensitive to filter scale partition and model constant, the optimal setting can be easily translated in the interface tracking/finite-volume context, which makes it very useful for practical purposes. An important point is that the VMS approach yields very satisfactory results without the need

  17. Laser Ablation Increases PEM/Catalyst Interfacial Area

    Science.gov (United States)

    Whitacre, Jay; Yalisove, Steve

    2009-01-01

    An investigational method of improving the performance of a fuel cell that contains a polymer-electrolyte membrane (PEM) is based on the concept of roughening the surface of the PEM, prior to deposition of a thin layer of catalyst, in order to increase the PEM/catalyst interfacial area and thereby increase the degree of utilization of the catalyst. The roughening is done by means of laser ablation under carefully controlled conditions. Next, the roughened membrane surface is coated with the thin layer of catalyst (which is typically platinum), then sandwiched between two electrode/catalyst structures to form a membrane/ele c t - rode assembly. The feasibility of the roughening technique was demonstrated in experiments in which proton-conducting membranes made of a perfluorosulfonic acid-based hydrophilic, protonconducting polymer were ablated by use of femtosecond laser pulses. It was found that when proper combinations of the pulse intensity, pulse-repetition rate, and number of repetitions was chosen, the initially flat, smooth membrane surfaces became roughened to such an extent as to be converted to networks of nodules interconnected by filaments (see Figure 1). In further experiments, electrochemical impedance spectroscopy (EIS) was performed on a pristine (smooth) membrane and on two laser-roughened membranes after the membranes were coated with platinum on both sides. Some preliminary EIS data were interpreted as showing that notwithstanding the potential for laser-induced damage, the bulk conductivities of the membranes were not diminished in the roughening process. Other preliminary EIS data (see Figure 2) were interpreted as signifying that the surface areas of the laser-roughened membranes were significantly greater than those of the smooth membrane. Moreover, elemental analyses showed that the sulfur-containing molecular groups necessary for proton conduction remained intact, even near the laser-roughened surfaces. These preliminary results can be taken

  18. Enzyme Kinetics? Elementary, my dear

    Indian Academy of Sciences (India)

    Suppose that, in the absence of an enzyme, the. Desirazu N Rao is at the. Department of. Biochemistry, Indian. Institute of Science,. Bangalore. His main research interests are in the ateas of protein-DNA interactions using restriction enzymes as model systems and in. DNA methylation. 1 When a carbon atom has four.

  19. Cellulase enzyme and biomass utilization

    African Journals Online (AJOL)

    STORAGESEVER

    2009-06-03

    Jun 3, 2009 ... Key words: Cellulose, cellulase enzyme, fuel ethanol, biomass. ... nearly all fuel ethanol is produced by fermentation of corn ... efficiency. This review will introduce some background knowledge of cellulase enzyme and its hydrolyzation mechanism, focus on its current status in research and application,.

  20. Positron emitter labeled enzyme inhibitors

    Science.gov (United States)

    Fowler, J.S.; MacGregor, R.R.; Wolf, A.P.

    1987-05-22

    This invention involved a new strategy for imaging and mapping enzyme activity in the living human and animal body using positron emitter-labeled suicide enzyme inactivators or inhibitors which become covalently bound to the enzyme as a result of enzymatic catalysis. Two such suicide in activators for monoamine oxidase have been labeled with carbon-11 and used to map the enzyme subtypes in the living human and animal body using PET. By using positron emission tomography to image the distribution of radioactivity produced by the body penetrating radiation emitted by carbon-11, a map of functionally active monoamine oxidase activity is obtained. Clorgyline and L-deprenyl are suicide enzyme inhibitors and irreversibly inhibit monoamine oxidase. When these inhibitors are labeled with carbon-11 they provide selective probes for monoamine oxidase localization and reactivity in vivo using positron emission tomography. 2 figs.

  1. Engineering Cellulase Enzymes for Bioenergy

    Science.gov (United States)

    Atreya, Meera Elizabeth

    Sustainable energy sources, such as biofuels, offer increasingly important alternatives to fossil fuels that contribute less to global climate change. The energy contained within cellulosic biofuels derives from sunlight energy stored in the form of carbon-carbon bonds comprising sugars such as glucose. Second-generation biofuels are produced from lignocellulosic biomass feedstocks, including agricultural waste products and non-food crops like Miscanthus, that contain lignin and the polysaccharides hemicellulose and cellulose. Cellulose is the most abundant biological material on Earth; it is a polymer of glucose and a structural component of plant cell walls. Accessing the sugar is challenging, as the crystalline structure of cellulose resists degradation; biochemical and thermochemical means can be used to depolymerize cellulose. Cellulase enzymes catalyze the biochemical depolymerization of cellulose into glucose. Glucose can be used as a carbon source for growth of a biofuel-producing microorganism. When it converts glucose to a hydrocarbon fuel, this microbe completes the biofuels process of transforming sunlight energy into accessible, chemical energy capable of replacing non-renewable transportation fuels. Due to strong intermolecular interactions between polymer chains, cellulose is significantly more challenging to depolymerize than starch, a more accessible polymer of glucose utilized in first-generation biofuels processes (often derived from corn). While most mammals cannot digest cellulose (dietary fiber), certain fungi and bacteria produce cellulase enzymes capable of hydrolyzing it. These organisms secrete a wide variety of glycoside hydrolase and other classes of enzymes that work in concert. Because cellulase enzymes are slow-acting and expensive to produce, my aim has been to improve the properties of these enzymes as a means to make a cellulosic biofuels process possible that is more efficient and, consequently, more economical than current

  2. Nanocaged enzymes with enhanced catalytic activity and increased stability against protease digestion

    Science.gov (United States)

    Zhao, Zhao; Fu, Jinglin; Dhakal, Soma; Johnson-Buck, Alexander; Liu, Minghui; Zhang, Ting; Woodbury, Neal W.; Liu, Yan; Walter, Nils G.; Yan, Hao

    2016-02-01

    Cells routinely compartmentalize enzymes for enhanced efficiency of their metabolic pathways. Here we report a general approach to construct DNA nanocaged enzymes for enhancing catalytic activity and stability. Nanocaged enzymes are realized by self-assembly into DNA nanocages with well-controlled stoichiometry and architecture that enabled a systematic study of the impact of both encapsulation and proximal polyanionic surfaces on a set of common metabolic enzymes. Activity assays at both bulk and single-molecule levels demonstrate increased substrate turnover numbers for DNA nanocage-encapsulated enzymes. Unexpectedly, we observe a significant inverse correlation between the size of a protein and its activity enhancement. This effect is consistent with a model wherein distal polyanionic surfaces of the nanocage enhance the stability of active enzyme conformations through the action of a strongly bound hydration layer. We further show that DNA nanocages protect encapsulated enzymes against proteases, demonstrating their practical utility in functional biomaterials and biotechnology.

  3. Nanocaged enzymes with enhanced catalytic activity and increased stability against protease digestion

    Science.gov (United States)

    Zhao, Zhao; Fu, Jinglin; Dhakal, Soma; Johnson-Buck, Alexander; Liu, Minghui; Zhang, Ting; Woodbury, Neal W.; Liu, Yan; Walter, Nils G.; Yan, Hao

    2016-01-01

    Cells routinely compartmentalize enzymes for enhanced efficiency of their metabolic pathways. Here we report a general approach to construct DNA nanocaged enzymes for enhancing catalytic activity and stability. Nanocaged enzymes are realized by self-assembly into DNA nanocages with well-controlled stoichiometry and architecture that enabled a systematic study of the impact of both encapsulation and proximal polyanionic surfaces on a set of common metabolic enzymes. Activity assays at both bulk and single-molecule levels demonstrate increased substrate turnover numbers for DNA nanocage-encapsulated enzymes. Unexpectedly, we observe a significant inverse correlation between the size of a protein and its activity enhancement. This effect is consistent with a model wherein distal polyanionic surfaces of the nanocage enhance the stability of active enzyme conformations through the action of a strongly bound hydration layer. We further show that DNA nanocages protect encapsulated enzymes against proteases, demonstrating their practical utility in functional biomaterials and biotechnology. PMID:26861509

  4. Phonon Transport at Crystalline Si/Ge Interfaces: The Role of Interfacial Modes of Vibration.

    Science.gov (United States)

    Gordiz, Kiarash; Henry, Asegun

    2016-03-16

    We studied the modal contributions to heat conduction at crystalline Si and crystalline Ge interfaces and found that more than 15% of the interface conductance arises from less than 0.1% of the modes in the structure. Using the recently developed interface conductance modal analysis (ICMA) method along with a new complimentary methodology, we mapped the correlations between modes, which revealed that a small group of interfacial modes, which exist between 12-13 THz, exhibit extremely strong correlation with other modes in the system. It is found that these interfacial modes (e.g., modes with large eigen vectors for interfacial atoms) are enabled by the degree of anharmonicity near the interface, which is higher than in the bulk, and therefore allows this small group of modes to couple to all others. The analysis sheds light on the nature of localized vibrations at interfaces and can be enlightening for other investigations of localization.

  5. Zinc oxide nanowire interphase for enhanced interfacial strength in lightweight polymer fiber composites.

    Science.gov (United States)

    Ehlert, Gregory J; Sodano, Henry A

    2009-08-01

    A novel functionalization method for aramid fibers is developed to enhance the bonding of a ZnO nanowire interphase grown on the fiber surface for interfacial strength enhancement. The nanowire interphase functionally grades the typically discrete interface and reduces the stress concentration between the fiber and matrix. The functionalization process is developed to improve the bonding between the ZnO nanowires and the aramid fiber and is validated through Fourier transform IR and X-ray photoelectron spectroscopy studies. Mechanical testing shows significant improvement in the interfacial shear strength with no decrease in the base fiber strength. This is the only technique found in the literature for the growth of a nanowire interphase on polymer fibers for structural enhancement without degrading the in-plane properties of the bulk composite. Furthermore, it is firmly shown that the functionalization process is a necessary condition for enhanced interfacial strength, demonstrating that ZnO nanowires strongly interact with carboxylic acid functional groups.

  6. The Dynamic Interfacial Oxygen Potential Between Iron-Carbon Droplets and Oxidizing Slag

    Science.gov (United States)

    Gu, Kezhuan; Dogan, Neslihan; Coley, Kenneth S.

    2017-10-01

    The dynamic nature of the interfacial oxygen potential during dephosphorization was investigated based on the concept that P_{{{O}2 }} at the interface between slag and liquid metal is determined by the balance between oxygen supply from reducible oxides in the slag and oxygen consumption by alloying elements in the metal. Combining this approach with the knowledge that at the phosphorus reversion point the interfacial oxygen potential can be determined from the bulk phosphorus partition ratio, the mass transfer coefficient for FeO, k FeO, was determined for different slags and found to increase with increasing FeO content. In foamy slags, k FeO was found to be a linear function of slag liquid fraction. Equating the mass transfer rate of FeO in the slag with decarburization rate, the dynamic interfacial oxygen potential was calculated over the course of the reaction, and its effect on the rate determining step for dephosphorization was evaluated.

  7. Atomic-scale characterization of the interfacial phonon in graphene/SiC

    Science.gov (United States)

    Minamitani, Emi; Arafune, Ryuichi; Frederiksen, Thomas; Suzuki, Tetsuya; Shahed, Syed Mohammad Fakruddin; Kobayashi, Tomohiro; Endo, Norifumi; Fukidome, Hirokazu; Watanabe, Satoshi; Komeda, Tadahiro

    2017-10-01

    Epitaxial graphene on SiC that provides wafer-scale and high-quality graphene sheets on an insulating substrate is a promising material to realize graphene-based nanodevices. The presence of the insulating substrate changes the physical properties of free-standing graphene through the interfacial phonon, e.g., limiting the mobility. Despite such known impacts on the material properties, a complete and microscopic picture is missing. Here, we report on atomically resolved inelastic electron tunneling spectroscopy (IETS) with a scanning tunneling microscope for epitaxial graphene grown on 4 H -SiC(0001). Our data reveal a strong spatial dependence in the IETS spectrum, which cannot be explained by intrinsic graphene properties. We show that this variation in the IETS spectrum originates from a localized low-energy vibration of the interfacial Si atom with a dangling bond via ab initio electronic and phononic state calculations. This insight may help advancing graphene device performance through interfacial control.

  8. Manipulating the quantum interference effect and magnetotransport of ZnO nanowires through interfacial doping.

    Science.gov (United States)

    Zhao, Siwen; Wu, Yiming; Zhang, Kaixuan; Ding, Huaiyi; Du, Dongxue; Zhao, Jiyin; Pan, Nan; Wang, Xiaoping

    2017-11-16

    We carefully prepared interfacial Al-doped (IAD) and interfacial natively-doped (IND) ZnO nanowires (NWs) by introducing atomic-layer interfacial Δ-doping between the two steps of CVD growth. Variable-temperature electron transport as well as magnetotransport behaviours of these NWs were systematically investigated. By virtue of the unique architecture and the quality-guaranteed growth technique, a series of quantum interference effects were clearly observed in the IAD ZnO NWs, including weak localization, universal conductance fluctuation and Altshuler-Aronov-Spivak oscillations. The phase-coherence length (L φ ) of electrons exceeds 100 nm in the IAD ZnO NWs, much longer than those in the IND ones and most conventionally doped ZnO NWs. This ability to efficiently manipulate a variety of quantum interference effects in ZnO NWs is very desirable for applications in nano-optoelectronics, nano- & quantum-electronics and solid-state quantum computing.

  9. What Controls Thermo-osmosis? Molecular Simulations Show the Critical Role of Interfacial Hydrodynamics

    Science.gov (United States)

    Fu, Li; Merabia, Samy; Joly, Laurent

    2017-11-01

    Thermo-osmotic and related thermophoretic phenomena can be found in many situations from biology to colloid science, but the underlying molecular mechanisms remain largely unexplored. Using molecular dynamics simulations, we measure the thermo-osmosis coefficient by both mechanocaloric and thermo-osmotic routes, for different solid-liquid interfacial energies. The simulations reveal, in particular, the crucial role of nanoscale interfacial hydrodynamics. For nonwetting surfaces, thermo-osmotic transport is largely amplified by hydrodynamic slip at the interface. For wetting surfaces, the position of the hydrodynamic shear plane plays a key role in determining the amplitude and sign of the thermo-osmosis coefficient. Finally, we measure a giant thermo-osmotic response of the water-graphene interface, which we relate to the very low interfacial friction displayed by this system. These results open new perspectives for the design of efficient functional interfaces for, e.g., waste-heat harvesting.

  10. Research on Interfacial Bond-Slip Constitutive Relation Between FRP and Concrete Based on Two Parameters

    Science.gov (United States)

    Yin, Yushi; Fan, Yingfang

    2018-01-01

    The paper is to quantify and assess the roughness of 108 concrete samples with 6 kinds of interface roughness to investigate the influence of surface roughness on the bond property of FRP-concrete interface. And in order to solve the problem of so many parameters in interfacial stress-slip constitutive relation between FRP and concrete that hard to practise for engineers, so adopting shear test to establish two parameters (f c0, fi ) constitutive relation which are more suitable for engineers’ construction design. Results shows that the compressive strength (f c0) and interfacial roughness (fi ) are the two keys who influence the interfacial bond strength; The closed-form solution of τm and sf can be solved by the two factors f c0, fi , this method supplies a new algorithm for the interface calculation, due to the theoretical value is less than the measured values, so there is a certain safety stock to construction.

  11. Interfacial behavior of water droplet on micro-nano structured surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kwak, Ho Jae; Yu, Dong In; Park, Hyun Sun; Moriyama, Kiyofumi [POSTECH, Pohang (Korea, Republic of); Kim, Moo Hwan [Korea Institute of Nuclear Safety, Deajeon (Korea, Republic of); Ahn, Ho Sun [Division of Mechanical System Engineering, Incheon National University, Incheon (Korea, Republic of); Kim, Dong Eok [Dept. of Mechanical Engineering, Kyungpook National University, Daegu (Korea, Republic of)

    2015-03-15

    Recently, surfaces with micro and nano structures are the focus of various research and engineering fields to enhance wetting characteristics of the surfaces. Hydrophilic surfaces with hierarchical structures are generally characterized by the interfacial behavior of water droplets. In this study, the interfacial behavior of water droplets is experimentally investigated considering the scale of structures. Using the dry etching and conventional lithography method, quantitative hierarchical structured surfaces are developed. The behavior of the liquid-vapor interface on the test sections is visualized using an automatic goniometer and a high-speed camera. On the basis of the visualized data, the interfacial behavior of water droplets is intensively investigated according to surface geometrical characteristics.

  12. Structural and dynamic heterogeneity of interfacial water on chemically modified polymer surfaces

    Science.gov (United States)

    Bekele, Selemon; Tsige, Mesfin

    Using molecular dynamics (MD) simulations, we investigate the structural and dynamical properties of water molecules in a slab of water in contact with atactic polystyrene surfaces of varying polarity. We find that the dynamics of water molecules in the interfacial region slows down with increasing polarity of the polystyrene surface. In addition, the interfacial water molecules exhibit structural and dynamic heterogeneity with respect to diffusion, hydrogen bond distribution and relaxation of the hydrogen bond network. The results obtained enhance our understanding of water structure and dynamics at the polymer/water interface with important implications for such desired functional properties as lubrication, adhesion and friction. Interfacial properties of water at hydrophobic and hydrophilic SAM (Self Assembled Monolayers) surfaces will also be presented for comparison. This work was supported by NSF Grant DMR1410290.

  13. Thickness dependence of the interfacial Dzyaloshinskii–Moriya interaction in inversion symmetry broken systems

    Science.gov (United States)

    Cho, Jaehun; Kim, Nam-Hui; Lee, Sukmock; Kim, June-Seo; Lavrijsen, Reinoud; Solignac, Aurelie; Yin, Yuxiang; Han, Dong-Soo; van Hoof, Niels J. J.; Swagten, Henk J. M.; Koopmans, Bert; You, Chun-Yeol

    2015-01-01

    In magnetic multilayer systems, a large spin-orbit coupling at the interface between heavy metals and ferromagnets can lead to intriguing phenomena such as the perpendicular magnetic anisotropy, the spin Hall effect, the Rashba effect, and especially the interfacial Dzyaloshinskii–Moriya (IDM) interaction. This interfacial nature of the IDM interaction has been recently revisited because of its scientific and technological potential. Here we demonstrate an experimental technique to straightforwardly observe the IDM interaction, namely Brillouin light scattering. The non-reciprocal spin wave dispersions, systematically measured by Brillouin light scattering, allow not only the determination of the IDM energy densities beyond the regime of perpendicular magnetization but also the revelation of the inverse proportionality with the thickness of the magnetic layer, which is a clear signature of the interfacial nature. Altogether, our experimental and theoretical approaches involving double time Green's function methods open up possibilities for exploring magnetic hybrid structures for engineering the IDM interaction. PMID:26154986

  14. Numerical Treatment of Two-phase Flow in Porous Media Including Specific Interfacial Area

    KAUST Repository

    El-Amin, Mohamed

    2015-06-01

    In this work, we present a numerical treatment for the model of two-phase flow in porous media including specific interfacial area. For numerical discretization we use the cell-centered finite difference (CCFD) method based on the shifting-matrices method which can reduce the time-consuming operations. A new iterative implicit algorithm has been developed to solve the problem under consideration. All advection and advection-like terms that appear in saturation equation and interfacial area equation are treated using upwind schemes. Selected simulation results such as pc–Sw–awn surface, capillary pressure, saturation and specific interfacial area with various values of model parameters have been introduced. The simulation results show a good agreement with those in the literature using either pore network modeling or Darcy scale modeling.

  15. Interfacial structures of confined air-water two-phase bubbly flow

    Energy Technology Data Exchange (ETDEWEB)

    Kim, S.; Ishii, M.; Wu, Q.; McCreary, D.; Beus, S.G.

    2000-08-01

    The interfacial structure of the two-phase flows is of great importance in view of theoretical modeling and practical applications. In the present study, the focus is made on obtaining detailed local two-phase parameters in the air-water bubbly flow in a rectangular vertical duct using the double-sensor conductivity probe. The characteristic wall-peak is observed in the profiles of the interracial area concentration and the void fraction. The development of the interfacial area concentration along the axial direction of the flow is studied in view of the interfacial area transport and bubble interactions. The experimental data is compared with the drift flux model with C{sub 0} = 1.35.

  16. Influence of interfacial reaction rates on the wetting driving force in metal/ceramic systems

    Science.gov (United States)

    Landry, K.; Rado, C.; Eustathopoulos, N.

    1996-10-01

    The wetting of copper-silicon alloys of various compositions on vitreous carbon substrates at 1423 K was studied by the sessile drop method. The morphology and chemistry of products of interfacial reactions between silicon and carbon were characterized by scanning electron microscopy (SEM), electron probe microanalysis, and high-resolution optical profilometry. In addition to measurements of contact angles and spreading kinetics in the reactive Cu-Si/Cv system, similar measurements were performed for the nonreactive Cu-Si/SiC system. It was found that the reaction rate has no effect on the final contact angle, which is nearly equal to the thermodynamic contact angle of the alloy on the reaction product. These findings appear to be valid for a wide range of interfacial reaction rates and for different types of interfacial reactions.

  17. Influence of interfacial reaction rates on the wetting driving force in metal/ceramic systems

    Energy Technology Data Exchange (ETDEWEB)

    Landry, K. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Materials Science and Engineering; Rado, C.; Eustathopoulos, N. [LTPCM-ENSEEG, Saint Martin d`Heres (France)

    1996-10-01

    The wetting of copper-silicon alloys of various compositions on vitreous carbon substrates at 1,423 K was studied by the sessile drop method. The morphology and chemistry of products of interfacial reactions between silicon and carbon were characterized by scanning electron microscopy (SEM), electron probe microanalysis, and high-resolution optical profilometry. In addition to measurements of contact angles and spreading kinetics in the reactive Cu-Si/Cv system, similar measurements were performed for the nonreactive Cu-Si/SiC system. It was found that the reaction rate has no effect on the final contact angle, which is nearly equal to the thermodynamic contact angle of the alloy on the reaction product. These findings appear to be valid for a wide range of interfacial reaction rates and for different types of interfacial reactions.

  18. [Retinoids: mechanisms of action].

    Science.gov (United States)

    Berbis, P

    2010-11-01

    Retinoids, vitamin A derivatives, are natural or synthetic molecules with pleiotropic effects, which regulate cell differentiation, proliferation and apoptosis. In target cell, the active natural metabolites retinoic acid (RA) and 9-cis-retinoic acid are synthetized from retinol by a two-step process with intermediate metabolite retinaldehyde. In 1987, the identification of the nuclear retinoic acid receptors that belong to the superfamily of nuclear receptors led to a significant progress in the comprehension of the mechanism of action of retinoids. There are two families of Retinoid Nuclear Receptors (RNR), the RA receptors (RAR), which natural ligand is RA, and the Retinoid X Receptors (RXR), which natural ligand is 9-cis-retinoic acid. Among synthetic retinoids, isotretinoin, acitretin, tazarotene and adapalene are ligands of the RAR, bexarotene is the first rexinoid (ligand of the RXR), alitretinoin the first panagonist (RAR+ RXR). For each family, there are 3 isotypes (α, β, γ), and for each isotype several isoforms. Each NRR is composed of 6 regions (A-F). 3 regions are of importance: the A/B region has a ligand-independent transcriptional activation function, the C region harbors the DNA binding domain, the E region harbors the ligand binding domain. To regulate the expression of target genes, NRR have to dimerize. RXR are obligatory in dimers (heterodimers RAR-RXR, homodimers RXR-RXR). Dimers binds specific sequences of DNA, present in the promoters of target genes. When the ligand, natural or synthetic, bind to RNR, coactivators are recruited and transcription factors are activated. In target cell, retinoids not utilized are degradated in polar metabolites by enzymes of cytochrome P450. Copyright © 2010 Elsevier Masson SAS. All rights reserved.

  19. X-ray Studies of Interfacial Strontium–Extractant Complexes in a Model Solvent Extraction System

    Energy Technology Data Exchange (ETDEWEB)

    Bu, Wei; Mihaylov, Miroslav; Amoanu, Daniel; Lin, Binhua; Meron, Mati; Kuzmenko, Ivan; Soderholm, L.; Schlossman, Mark L.

    2014-10-30

    The interfacial behavior of a model solvent extraction liquidliquid system, consisting of solutions of dihexadecyl phosphate (DHDP) in dodecane and SrCl2 in water, was studied to determine the structure of the interfacial ionextractant complex and its variation with pH. Previous experiments on a similar extraction system with ErCl3 demonstrated that the kinetics of the extraction process could be greatly retarded by cooling through an adsorption transition, thus providing a method to immobilize ionextractant complexes at the interface and further characterize them with X-ray interface-sensitive techniques. Here, we use this same method to study the SrCl2 system. X-ray reflectivity and fluorescence near total reflection measured the molecular-scale interfacial structure above and below the adsorption transition for a range of pH. Below the transition, DHDP molecules form a homogeneous monolayer at the interface with Sr2+ coverage increasing from zero to saturation (one Sr2+ per two DHDP) within a narrow range of pH. Experimental values of Sr2+ interfacial density determined from fluorescence measurements are larger than those from reflectivity measurements. Although both techniques probe Sr2+ bound to DHDP, only the fluorescence provides adequate sensitivity to Sr2+ in the diffuse double layer. A Stern equation determines the Sr2+ binding constant from the reflectivity measurements and the additional Sr2+ measured in the diffuse double layer is accounted for by GouyChapman theory. Above the transition temperature, a dilute concentration of DHDPSr complexes resides at the interface, even for temperatures far above the transition. A comparison is made of the structure of the interfacial ionextractant complex for this divalent metal ion to recent results on trivalent Er3+ metal ions, which provides insight into the role of metal ion charge on the structure of interfacial ionextractant complexes, as well as implications for extraction of these two differently charged

  20. Modeling the Effects of Interfacial Characteristics on Gas Permeation Behavior of Nanotube-Mixed Matrix Membranes.

    Science.gov (United States)

    Chehrazi, Ehsan; Sharif, Alireza; Omidkhah, Mohammadreza; Karimi, Mohammad

    2017-10-25

    Theoretical approaches that accurately predict the gas permeation behavior of nanotube-containing mixed matrix membranes (nanotube-MMMs) are scarce. This is mainly due to ignoring the effects of nanotube/matrix interfacial characteristics in the existing theories. In this paper, based on the analogy of thermal conduction in polymer composites containing nanotubes, we develop a model to describe gas permeation through nanotube-MMMs. Two new parameters, "interfacial thickness" (aint) and "interfacial permeation resistance" (Rint), are introduced to account for the role of nanotube/matrix interfacial interactions in the proposed model. The obtained values of aint, independent of the nature of the permeate gas, increased by increasing both the nanotubes aspect ratio and polymer-nanotube interfacial strength. An excellent correlation between the values of aint and polymer-nanotube interaction parameters, χ, helped to accurately reproduce the existing experimental data from the literature without the need to resort to any adjustable parameter. The data includes 10 sets of CO2/CH4 permeation, 12 sets of CO2/N2 permeation, 3 sets of CO2/O2 permeation, and 2 sets of CO2/H2 permeation through different nanotube-MMMs. Moreover, the average absolute relative errors between the experimental data and the predicted values of the proposed model are very small (less than 5%) in comparison with those of the existing models in the literature. To the best of our knowledge, this is the first study where such a systematic comparison between model predictions and such extensive experimental data is presented. Finally, the new way of assessing gas permeation data presented in the current work would be a simple alternative to complex approaches that are usually utilized to estimate interfacial thickness in polymer composites.

  1. Phospholipase D from Allium sativum bulbs: A highly active and thermal stable enzyme.

    Science.gov (United States)

    Khatoon, Hafeeza; Talat, Sariya; Younus, Hina

    2008-05-01

    This is the first report on the identification and partial characterization of phospholipase D (EC 3.1.4.4) from Allium sativum (garlic) bulbs (PLD(GB)). The enzyme shares the phenomenon of interfacial activation with other lipolytic enzymes, i.e. the hydrolytic rate increases when the substrate changes to a more aggregated state. The enzyme activity is highly temperature tolerant and the temperature optimum was measured to be 70 degrees C. PLD(GB) unlike many plant PLDs exhibited high thermal stability. It was activated further after exposure to high temperatures, i.e. 80 degrees C, indicating that the enzyme refolds better upon cooling back to room temperature after short exposure to thermal stress. The activity of PLD(GB) is optimum in 70mM calcium ion concentration and the enzyme is activated further in the presence of phosphatidyl-4,5-bisphosphate (PIP(2)). PLD(GB) exhibited both hydrolytic and transphosphatidylation activities, both of which appear to be higher than those of PLD from cabbage leaves (PLD(CL)).

  2. Actions of thrombin in the interstitium.

    Science.gov (United States)

    de Ridder, G G; Lundblad, R L; Pizzo, S V

    2016-01-01

    Thrombin is a pleiotropic enzyme best known for its contribution to fibrin formation and platelet aggregation during vascular hemostasis. There is increasing evidence to suggest a role for thrombin in the development of interstitial fibrosis, but interstitial thrombin has not been demonstrated by the direct determination of activity. Rather its presence is inferred by products of thrombin action such as fibrin and activated fibroblasts. This review will focus on possible mechanisms of thrombin formation in the interstitial space, the possible actions of thrombin, processes regulating thrombin activity in the interstitial space, and evidence supporting a role for thrombin in fibrosis. © 2015 International Society on Thrombosis and Haemostasis.

  3. Structures and ultrafast dynamics of interfacial water assemblies on smooth hydrophobic surfaces

    Science.gov (United States)

    Yang, Ding-Shyue; He, Xing

    2017-09-01

    Using time-averaged and ultrafast electron diffraction, structures and ultrafast dynamics of interfacial water assemblies on smooth hydrophobic surfaces are reported. The lack of hydrophilic interaction and topographical template effect from the support surface leads to the formation of small, mostly randomly-oriented, ice crystallites with the cubic structure. Dynamically, following the substrate photoexcitation, interfacial water assemblies undergo four stages of changes-ultrafast melting, nonequilibrium isotropic phase transformation, annealing, and restructuring-which are closely correlated with the substrate dynamics. The connectivity and cooperative nature of the hydrogen-bonded network is considered crucial for water assemblies to withstand large structural motions without sublimation on ultrashort times.

  4. Miscibility–dispersion, interfacial strength and nanoclay mobility relationships in polymer nanocomposites

    KAUST Repository

    Carretero-González, Javier

    2009-01-01

    Fully dispersed layered silicate nanoparticles (nanoclay) in a polymer matrix have provided a new class of multi-functional materials exhibiting several performance improvements over conventional composites. Yet the challenges of miscibility and interfacial strength might prevent nanocomposites from realizing their full potential. In this paper we demonstrate the effect of the chemical characteristics of the nanoclay on the miscibility and dispersion in the polymer matrix as well as on the interfacial strength of the bound polymer and the nanoclay mobility, all of which determine the macroscopic properties of the nanocomposite. © 2009 The Royal Society of Chemistry.

  5. Calculation of Interfacial Tensions of Hydrocarbon-water Systems under Reservoir Conditions

    DEFF Research Database (Denmark)

    Zuo, You-Xiang; Stenby, Erling Halfdan

    1998-01-01

    Assuming that the number densities of each component in a mixture are linearly distributed across the interface between the coexisting vapor-liquid or liquid-liquid phases, we developed in this research work a linear-gradient-theory (LGT) model for computing the interfacial tension of hydrocarbon......-water mixtures on the basis of the SRK equation of state. With this model, it is unnecessary to solve the time-consuming density-profile equations of the gradient-theory model. In addition, a correlation was developed for representing the effect of electrolytes on the interfacial tension of hydrocarbon...

  6. Fullerenes - how 25 years of charge transfer chemistry have shaped our understanding of (interfacial) interactions.

    Science.gov (United States)

    Zieleniewska, A; Lodermeyer, F; Roth, A; Guldi, D M

    2017-11-29

    In this review article, we highlight over 25 years of fullerene research in charge transfer chemistry. The major thrust of this work is to illustrate interfacial interactions between fullerenes and porphyrins in electron donor-acceptor conjugates as well as self-assembled associates and co-crystallites all the way to organic photovoltaics. Hereby, the analysis of the fundamental proceses, namely, energy transfer, charge shift, charge separation as well as charge recombination stand at the forefront. Our examples, illustrate on how fine-tuning the structure leads to substantial alteration of interfacial interactions.

  7. Relative viscosity of emulsions in simple shear flow: Temperature, shear rate, and interfacial tension dependence

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Se Bin; Lee, Joon Sang [Dept. of Mechanical Engineering, Yonsei Unversity, Seoul (Korea, Republic of)

    2015-08-15

    We simulate an emulsion system under simple shear rates to analyze its rheological characteristics using the lattice Boltzmann method (LBM). We calculate the relative viscosity of an emulsion under a simple shear flow along with changes in temperature, shear rate, and surfactant concentration. The relative viscosity of emulsions decreased with an increase in temperature. We observed the shear-thinning phenomena, which is responsible for the inverse proportion between the shear rate and viscosity. An increase in the interfacial tension caused a decrease in the relative viscosity of the decane-in-water emulsion because the increased deformation caused by the decreased interfacial tension significantly influenced the wall shear stress.

  8. The effect of interfacial layers on charge transport in organic solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Mbuyise, Xolani G.; Tonui, Patrick; Mola, Genene Tessema, E-mail: mola@ukzn.ac.za

    2016-09-01

    The effect of interfacial buffer layers in organic photovoltaic cell (OPV) whose active layer is composed of poly(3 hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend was studied. The electrical properties of OPV devices produced with and without interfacial layers are compared and discussed in terms of measured parameters of the cells. The charge transport properties showed significant difference on the mobility and activation factor between the two types of device structures. The life time measurements in the unprotected conditions are also presented and discussed.

  9. Determination of interfacial heat transfer coefficient and its application in high pressure die casting process

    Directory of Open Access Journals (Sweden)

    Cao Yongyou

    2014-07-01

    Full Text Available In this paper, the research progress of the interfacial heat transfer in high pressure die casting (HPDC is reviewed. Results including determination of the interfacial heat transfer coefficient (IHTC, influence of casting thickness, process parameters and casting alloys on the IHTC are summarized and discussed. A thermal boundary condition model was developed based on the two correlations: (a IHTC and casting solid fraction and (b IHTC peak value and initial die surface temperature. The boundary model was then applied during the determination of the temperature field in HPDC and excellent agreement was found.

  10. Are nanometric films of liquid undercooled interfacial water bio-relevant?

    Science.gov (United States)

    Möhlmann, Diedrich T F

    2009-06-01

    It is known that life processes below the melting point temperature can actively evolve and establish in micrometer-sized (and larger) veins and structures in ice and permafrost soil, filled with unfrozen water. Thermodynamic arguments and experimental results indicate the existence of much smaller nanometer sized thin films of undercooled liquid interfacial (ULI) water on surfaces of micrometer sized and larger mineral particles and microbes in icy environments far below the melting point temperature. This liquid interfacial water can be described in terms of a freezing point depression, which is due to the interfacial pressure of van der Waals forces. The physics behind the possibly also life supporting capability of nanometric films of undercooled liquid interfacial water, which also can "mantle" the surfaces of the much larger and micrometer-sized microbes, is discussed. As described, biological processes do not necessarily have to proceed in the "bulk" of the thin interfacial water, as in "vinical" water and in the micrometer sized veins e.g., but they can be supported or are even made possible already by covering thin mantles of liquid interfacial water. These can provide liquid water for metabolic processes and act as carrier for the necessary transport of nutrients and waste. ULI water supports two different and possibly biologically relevant transport processes: 2D molecular diffusion in the interfacial film, and flow-like due to regelation. ULI-water, which is "lost" by transport into microbes, e.g., will be refilled from the neighbouring ice. In this way, the nanometric liquid environment of microbes in ULI-water is comparable to that of microbes in bulk water. Another probably also biologically relevant property of ULI is, depending on the hydrophobic or hydrophilic character of the surfaces, that it is of lower density (LDL) or higher density (HDL) than bulk water. Furthermore, capillary effects and ions in ULI-water solutions can support, enhance, and

  11. Effects of oxygen plasma treatment on domestic aramid fiber III reinforced bismaleimide composite interfacial properties

    Science.gov (United States)

    Shi, Chen; Wang, Jing; Chen, Ping; Feng, Jiayue; Cui, Jinyuan; Yang, Faze

    2017-12-01

    Domestic Aramid Fiber III (DAF III) was modified by oxygen plasma treatment. The fiber surface characteristics was observed by Scanning Electron Microscopy. The results showed that oxygen plasma treatment changed surface morphologies. The effects of oxygen plasma treatment on DAF III reinforced bismaleimides (BMI) composite bending and interfacial properties were investigated, respectively. The ILSS value increased from 49.3 MPa to 56.0 MPa (by 13.5%) after oxygen plasma treatment. The bending strength changed a little. Furthermore, the composite rupture mode changed from interfacial rupture to fiber or resin bulk rupture.

  12. Interfacial tension in cooled heterogeneous liquid acetonitrile-ethyl acetate-isopropanol-water-phenol systems

    Science.gov (United States)

    Rudakov, O. B.; Khorokhordina, E. A.; Preobrazhenskii, M. A.

    2017-04-01

    It is found that the tension at the interfacial boundary of liquid phases formed by mixtures of acetonitrile-ethyl acetate-isopropanol (85 : 15 : 0 and 80 : 15 : 5 vol/vol/vol %) and water at 263 K falls exponentially as the concentration of phenols grows within 0-1 mg/mL. It is shown that the relatively low values of interfacial tension (11-32 mN/m) observed in cooled heterogeneous systems promote the redistribution of phenols between two liquid phases.

  13. Aquivion Perfluorosulfonic Superacid as an Efficient Pickering Interfacial Catalyst for the Hydrolysis of Triglycerides.

    Science.gov (United States)

    Shi, Hui; Fan, Zhaoyu; Hong, Bing; Pera-Titus, Marc

    2017-09-11

    Rational design of the surface properties of heterogeneous catalysts can boost the interfacial activity in biphasic reactions through the generation of Pickering emulsions. This concept, termed Pickering interfacial catalysis (PIC), has shown promising credentials in acid-catalyzed transesterification, ester hydrolysis, acetalization, etherification, and alkylation reactions. PIC has now been applied to the efficient, solvent-free hydrolysis of the triglyceride glyceryl trilaurate to lauric acid, catalyzed by Aquivion perfluorosulfonic superacid at mild conditions (100 °C and ambient pressure). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Testing temperature on interfacial shear strength measurements of epoxy resins at different mixing ratios

    DEFF Research Database (Denmark)

    Petersen, Helga Nørgaard; Thomason, James L.; Minty, Ross

    2015-01-01

    The interfacial properties as Interfacial Shear Stress (IFSS) in fibre reinforced polymers are essential for further understanding of the mechanical properties of the composite. In this work a single fibre testing method is used in combination with an epoxy matrix made from Araldite 506 epoxy resin...... and triethylenetetramine (TETA) hardener. The IFSS was measured by a microbond test developed for a Thermal Mechanical Analyzer. The preliminary results indicate that IFSS has an inverse dependency of both testing temperature and the mixing ratio of hardener and epoxy resin. Especially interesting was the decreasing...

  15. A shape identification problem in estimating simultaneously two interfacial configurations in a multiple region domain

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Cheng-Hung; Shih, Chen-Chung [National Cheng Kung University, Tainan (Taiwan). Department of Systems and Naval Mechatronic Engineering

    2006-01-15

    A two-dimensional shape identification problem, i.e. inverse geometry problem, of estimating simultaneously two interfacial configurations in a multiple (three) region domain is solved in this study by using the Conjugate Gradient Method (CGM) and Boundary Element Method (BEM)-based inverse algorithm. Two over-utilized conditions should be applied in determining two gradient equations; this differs from our previous relevant studies. Numerical experiments using different measurement errors and number of sensors were performed to justify the validity of the conjugate gradient method in solving this shape identification problem. Finally it is concluded that the present algorithm can estimate the accurate interfacial configurations. (author)

  16. BAKERY ENZYMES IN CEREAL TECHNOLOGIES

    Directory of Open Access Journals (Sweden)

    Václav Koman

    2012-10-01

    Full Text Available Normal 0 21 false false false SK X-NONE X-NONE Bread is the most common and traditional food in the world. For years, enzymes such as malt and fungal alpha-amylase have been used in bread making. Due to the changes in the baking industry and the ever-increasing demand for more natural products, enzymes have gained real importance in bread-making. If an enzyme is added, it is often destroyed by the heat during the baking process. For generations, enzymes have been used for the improvement of texture and appearance, enhancement of nutritional values and generation of appealing flavours and aromas. Enzymes used in bakery industry constitute nearly one third of the market. The bakery products have undergone radical improvements in quality over the past years in terms of flavour, texture and shelf-life. The the biggest contributor for these improvementsis the usage of enzymes. Present work seeks to systematically describe bakery enzymes, their classification, benefits, usage and chemical reactions in the bread making process.doi:10.5219/193

  17. The nature of the two scaling laws in interfacial fracture.

    Science.gov (United States)

    Stormo, Arne; Lengliné, Olivier; Schmittbuhl, Jean

    2014-05-01

    Since Mandelbrot in 1984 first began to study fracture in the language of fractals, the fracture surfaces have been found to be self-affine, i.e. that the height of the surface scales with the relation h(r) ~ Λζh(Λx). (1) h is the height of the surface above a reference point, x is the position, Λ is an arbitrary scaling factor and ζ is the roughness exponent. The fracture surface morphology of vastly different materials have been studied and have been found to have eerily similar roughness exponents. In refined studies by Ponson et al. they found that there were two regimes of behaviour, leading to different roughening of the surface, depending on length-scale and specimen properties. However, these experiments were done in three dimensions, and it could only describe the fracture post mortem. In order to study the developing fracture front, Måløy et al. introduced a two dimensional, optically transparent experiment where the fracture propagated through a weak heterogenous plane between two Plexi glass plates. In 2010, Santucci et al. found that also this interfacial fracture had two regimes of morphology. Later, Tallakstad et al. found that the front also displayed Family-Vicek scaling. The question that is emerging is: Why is there tho regimes of behaviour, and can we create a model that captures this transition? We present a numerical bottom-up model able to reproduce this change of morphology and scaling. Our model is a variant of the fiber bundle model presented by Batrouni et al. The model consists of a two dimensional set of fibers that are attached to two clamps with elastic response. As the clamps are torn apart, the fibers experience stress and, depending on a distributed stress threshold, will fail at some point. When this happens the rest of the fibers will have to carry the load dropped by the broken fiber. Depending on the elasticity of the clamps and the width of the threshold distribution, the failure of the fibers will be brittle or quasi

  18. DAPs: Deep Action Proposals for Action Understanding

    KAUST Repository

    Escorcia, Victor

    2016-09-17

    Object proposals have contributed significantly to recent advances in object understanding in images. Inspired by the success of this approach, we introduce Deep Action Proposals (DAPs), an effective and efficient algorithm for generating temporal action proposals from long videos. We show how to take advantage of the vast capacity of deep learning models and memory cells to retrieve from untrimmed videos temporal segments, which are likely to contain actions. A comprehensive evaluation indicates that our approach outperforms previous work on a large scale action benchmark, runs at 134 FPS making it practical for large-scale scenarios, and exhibits an appealing ability to generalize, i.e. to retrieve good quality temporal proposals of actions unseen in training.

  19. Experimental study of a cocurrent upflow packed bed bubble column reactor: pressure drop, holdup and interfacial area

    NARCIS (Netherlands)

    Molga, E.J.; Westerterp, K.R.

    1997-01-01

    Gas¿liquid interfacial areas have been determined by means of chemically enhanced absorption of CO2 into DEA in a packed bed bubble column reactor with an inner diameter of 156 mm. The influence of the gas velocity and particle diameter on the interfacial areas, pressure drops and liquid holdups has

  20. Ultralow Interfacial Tensions in an Aqueous Phase-Separated Gelatin/Dextran and Gelatin/Gum Arabic System: A Comparison

    NARCIS (Netherlands)

    Scholten, E.; Visser, J.E.; Sagis, L.M.C.; Linden, van der E.

    2004-01-01

    Many protein/polysaccharide mixtures phase separate when the concentrations of these biopolymers are sufficiently high. One of the properties involved in this phenomenon is the interfacial tension. Here we present measurements of the interfacial tension of two different protein/polysaccharide

  1. Effects of carbon fiber surface characteristics on interfacial bonding of epoxy resin composite subjected to hygrothermal treatments

    Science.gov (United States)

    Li, Min; Liu, Hongxin; Gu, Yizhuo; Li, Yanxia; Zhang, Zuoguang

    2014-01-01

    The changes of interfacial bonding of three types of carbon fibers/epoxy resin composite as well as their corresponding desized carbon fiber composites subjecting to hygrothermal conditions were investigated by means of single fiber fragmentation test. The interfacial fracture energy was obtained to evaluate the interfacial bonding before and after boiling water aging. The surface characteristics of the studied carbon fiber were characterized using X-ray photoelectron spectroscopy. The effects of activated carbon atoms and silicon element at carbon fiber surface on the interfacial hygrothermal resistance were further discussed. The results show that the three carbon fiber composites with the same resin matrix possess different hygrothermal resistances of interface and the interfacial fracture energy after water aging can not recovery to the level of raw dry sample (irreversible changes) for the carbon fiber composites containing silicon. Furthermore, the activated carbon atoms have little impact on the interfacial hygrothermal resistance. The irreversible variations of interfacial bonding and the differences among different carbon fiber composites are attributed to the silicon element on the carbon fiber bodies, which might result in hydrolyzation in boiling water treatment and degrade interfacial hygrothermal resistance.

  2. Interfacial Hydrogen Bonds and Their Influence Mechanism on Increasing the Thermal Stability of Nano-SiO2-Modified Meta-Aramid Fibres

    National Research Council Canada - National Science Library

    Chao Tang; Xu Li; Zhiwei Li; Jian Hao

    2017-01-01

    ... of nano-SiO2/meta-aramid fibre interfacial hydrogen bonds and the strengthening mechanism behind interfacial hydrogen bonds on the thermal stability of meta-aramid fibres using molecular dynamics...

  3. Development and validation of a measurement technique for interfacial velocity in liquid-gas separated flow using IR-PTV

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang Geun; Kim, Hyung Dae [Dept. of Nuclear Engineering, Kyung Hee University, Seoul (Korea, Republic of)

    2015-07-15

    A measurement technique of interfacial velocity in air-water separated flow by particle tracking velocimetry using an infrared camera (IR-PTV) was developed. As infrared light with wavelength in the range of 3-5 um could hardly penetrate water, IR-PTV can selectively visualize only the tracer particles existing in depths less than 20 um underneath the air-water interface. To validate the measurement accuracy of the IR-PTV technique, a measurement of the interfacial velocity of the air-water separated flow using Styrofoam particles floating in water was conducted. The interfacial velocity values obtained with the two different measurement techniques showed good agreement with errors less than 5%. It was found from the experimental results obtained using the developed technique that with increasing air velocity, the interfacial velocity proportionally increases, likely because of the increased interfacial stress.

  4. Interfacial Bioorthogonal Chemistry for Biomaterials Synthesis and Patterning and Development of Catalytic Method for "Turning-On" the Tetrazine Ligation

    Science.gov (United States)

    Zhang, Han

    photosensitizers were found to catalyze the oxidation of DHTz to Tz effieciently in the presence of light and air. Horseradish peroxidase (HRP) was found to catalyze the oxidation at nanomolar concentrations in absence of peroxide. These methods can provide a milder and more physiology-friendly way to "turn-on" rapid tetrazine ligation reactivity with great promise in extending to a wide range of applications in materials, cellular, and in vivo systems. Moreover, based on the previous bioorthogonal interfacial polymerization developed from our group, DHTz functionality can be successfully incorporated onto the copolymer fibers, which can be activated postsynthetically by either light or an HRP enzyme. Conjugations with small molecule fluorophores, cell-instructive peptide sequences and fluorescent proteins were accomplished, providing a new tool for modulating the cell adhesive properties of a biomaterial. TCO-tetrazine ligation has emerged as a multifaceted strategy in polymer and biomaterials discovery, bringing promising results and exhilarating progress. The versatile materials we developed here will prove useful and become indispensable elements in the tissue engineering toolbox.

  5. Enzymes of inorganic polyphosphate metabolism.

    Science.gov (United States)

    Kulakovskaya, Tatyana; Kulaev, Igor

    2013-01-01

    Inorganic polyphosphate (PolyP) is a linear polymer containing a few to several hundred orthophosphate residues linked by energy-rich phosphoanhydride bonds. Investigation of PolyP-metabolizing enzymes is important for medicine, because PolyPs perform numerous functions in the cells. In human organism, PolyPs are involved in the regulation of Ca(2+) uptake in mitochondria, bone tissue development, and blood coagulation. The essentiality of polyphosphate kinases in the virulence of pathogenic bacteria is a basis for the discovery of new antibiotics. The properties of the major enzymes of PolyP metabolism, first of all polyphosphate kinases and exopolyphosphatases, are described in the review. The main differences between the enzymes of PolyP biosynthesis and utilization of prokaryotic and eukaryotic cells, as well as the multiple functions of some enzymes of PolyP metabolism, are considered.

  6. Photosynthetic fuel for heterologous enzymes

    DEFF Research Database (Denmark)

    Mellor, Silas Busck; Vavitsas, Konstantinos; Nielsen, Agnieszka Janina Zygadlo

    2017-01-01

    of reducing power. Recent work on the metabolic engineering of photosynthetic organisms has shown that the electron carriers such as ferredoxin and flavodoxin can be used to couple heterologous enzymes to photosynthetic reducing power. Because these proteins have a plethora of interaction partners and rely...... on electrostatically steered complex formation, they form productive electron transfer complexes with non-native enzymes. A handful of examples demonstrate channeling of photosynthetic electrons to drive the activity of heterologous enzymes, and these focus mainly on hydrogenases and cytochrome P450s. However......, competition from native pathways and inefficient electron transfer rates present major obstacles, which limit the productivity of heterologous reactions coupled to photosynthesis. We discuss specific approaches to address these bottlenecks and ensure high productivity of such enzymes in a photosynthetic...

  7. GRE Enzymes for Vector Analysis

    Data.gov (United States)

    U.S. Environmental Protection Agency — Microbial enzyme data that were collected during the 2004-2006 EMAP-GRE program. These data were then used by Moorhead et al (2016) in their ecoenzyme vector...

  8. Hybrid Action Systems

    DEFF Research Database (Denmark)

    Rönnkö, M.; Ravn, Anders Peter; Sere, K.

    2003-01-01

    In this paper we investigate the use of action systems with differential actions in the specifcation of hybrid systems. As the main contribution we generalize the definition of a differential action, allowing the use of arbitrary relations over model variables and their time-derivatives in modell......In this paper we investigate the use of action systems with differential actions in the specifcation of hybrid systems. As the main contribution we generalize the definition of a differential action, allowing the use of arbitrary relations over model variables and their time......-derivatives in modelling continuous-time dynamics. The generalized differential action has an intuitively appealing predicate transformer semantics, which we show to be both conjunctive and monotonic. In addition, we show that differential actions blend smoothly with conventional actions in action systems, even under...... parallel composition. Moreover, as the strength of the action system formalism is the support for stepwise development by refinement, we investigate refinement involving a differential action. We show that, due to the predicate transformer semantics, standard action refinement techniques apply also...

  9. Enzymes: principles and biotechnological applications

    Science.gov (United States)

    Robinson, Peter K.

    2015-01-01

    Enzymes are biological catalysts (also known as biocatalysts) that speed up biochemical reactions in living organisms, and which can be extracted from cells and then used to catalyse a wide range of commercially important processes. This chapter covers the basic principles of enzymology, such as classification, structure, kinetics and inhibition, and also provides an overview of industrial applications. In addition, techniques for the purification of enzymes are discussed. PMID:26504249

  10. Multi-enzyme Process Modeling

    DEFF Research Database (Denmark)

    Andrade Santacoloma, Paloma de Gracia

    or potential process configurations operated under different conditions. In these cases, process engineering, enzyme immobilization and protein engineering are presented as fields that can offer feasible solutions for better process configurations or biocatalyst modification to enhance actual process...... proven to be useful for a fast model formulation of multi-enzyme processes. Additionally, programming codes were developed using MATLAB (The Mathworks, Natick, MA) which were also used as computational tools to support the implementation, solution and analysis of all the mathematical problems faced...

  11. Water-soluble conjugated polymers for fluorescent-enzyme assays.

    Science.gov (United States)

    Feng, Fude; Liu, Libing; Yang, Qiong; Wang, Shu

    2010-08-17

    Enzyme assays are receiving more and more research and application interest because of the rapidly increasing demands of clinical diagnosis, environmental analysis, drug discovery, and molecular biology. Water-soluble light-harvesting conjugated polymers (CPs) coordinate the action of a large number of absorbing units to afford an amplified fluorescence signal, which makes them useful as optical platforms in highly sensitive chemical and biological sensors. This Feature Article highlights recent developments of water-soluble CPs for fluorescent assays of enzymes. Different signal transduction mechanisms, such as electron transfer, fluorescence resonance energy transfer (FRET), and aggregation or conformation changes of CPs, are employed in these assays according to the dissimilar nature of enzymes. Potential challenges and future research directions in these approaches based on CPs are also discussed. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Environmental risk assessments for transgenic crops producing output trait enzymes.

    Science.gov (United States)

    Raybould, Alan; Tuttle, Ann; Shore, Scott; Stone, Terry

    2010-08-01

    The environmental risks from cultivating crops producing output trait enzymes can be rigorously assessed by testing conservative risk hypotheses of no harm to endpoints such as the abundance of wildlife, crop yield and the rate of degradation of crop residues in soil. These hypotheses can be tested with data from many sources, including evaluations of the agronomic performance and nutritional quality of the crop made during product development, and information from the scientific literature on the mode-of-action, taxonomic distribution and environmental fate of the enzyme. Few, if any, specific ecotoxicology or environmental fate studies are needed. The effective use of existing data means that regulatory decision-making, to which an environmental risk assessment provides essential information, is not unnecessarily complicated by evaluation of large amounts of new data that provide negligible improvement in the characterization of risk, and that may delay environmental benefits offered by transgenic crops containing output trait enzymes.

  13. Structure, inhibition, and regulation of essential lipid A enzymes.

    Science.gov (United States)

    Zhou, Pei; Zhao, Jinshi

    2017-11-01

    The Raetz pathway of lipid A biosynthesis plays a vital role in the survival and fitness of Gram-negative bacteria. Research efforts in the past three decades have identified individual enzymes of the pathway and have provided a mechanistic understanding of the action and regulation of these enzymes at the molecular level. This article reviews the discovery, biochemical and structural characterization, and regulation of the essential lipid A enzymes, as well as continued efforts to develop novel antibiotics against Gram-negative pathogens by targeting lipid A biosynthesis. This article is part of a Special Issue entitled: Bacterial Lipids edited by Russell E. Bishop. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Enzyme hydrolysis kinetics of micro-grinded maize straws.

    Science.gov (United States)

    Hu, Jianjun; Jing, Yanyan; Zhang, Quanguo; Guo, Jie; Lee, Duu-Jong

    2017-09-01

    This study applied micro-grinding to disintegrate the maize straws and then use the micro-grinded straws of particle sizes particle size 53-61, 80-96 or 150-180μm, for subsequent enzyme hydrolysis tests. The reducing sugar productivity was increased with reducing particle size. A kinetic model considering product inhibition was developed as follows t=aln[S]0[S]0-[P]+b[P], where S, P and t are the substrate, enzyme and hydrolysis time, respectively, and a and b are fitting parameters. The initial substrate concentration is proportional to the total exposed surface area. Additionally, the mechanical grinding can increase the biomass affinity for enzyme attack, suggesting the enhanced local action of shearing on the fiber matrix surfaces. The enhanced hydrolysis efficiency of the micro-grinded straws is welcomed by the subsequent refinery steps. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Spherical monovalent ions at aqueous liquid-vapor interfaces: interfacial stability and induced interface fluctuations.

    Science.gov (United States)

    Ou, Shuching; Hu, Yuan; Patel, Sandeep; Wan, Hongbin

    2013-10-03

    Ion-specific interfacial behaviors of monovalent halides impact processes such as protein denaturation, interfacial stability, and surface tension modulation, and as such, their molecular and thermodynamic underpinnings garner much attention. We use molecular dynamics simulations of monovalent anions in water to explore effects on distant interfaces. We observe long-ranged ion-induced perturbations of the aqueous environment, as suggested by experiment and theory. Surface stable ions, characterized as such by minima in potentials of mean force computed using umbrella sampling MD simulations, induce larger interfacial fluctuations compared to nonsurface active species, conferring more entropy approaching the interface. Smaller anions and cations show no interfacial potential of mean force minima. The difference is traced to hydration shell properties of the anions, and the coupling of these shells with distant solvent. The effects correlate with the positions of the anions in the Hofmeister series (acknowledging variations in force field ability to recapitulate essential underlying physics), suggesting how differences in induced, nonlocal perturbations of interfaces may be related to different specific-ion effects in dilute biophysical and nanomaterial systems.

  16. Interfacial rheological properties and conformational aspects of soy glycinin at the air/water interface

    NARCIS (Netherlands)

    Martin, A.H.; Bos, M.A.; Vliet, van T.

    2002-01-01

    Interfacial (rheological) properties of soy glycinin were studied at different pH. At acidic and high alkaline pH glycinin (11S form, Mw~350 kDa) dissociates into smaller subunits, the so called 3S form (Mw~44 kDa) and 7S form (Mw~175 kDa). This dissociation behaviour is expected to affect the

  17. 3D in situ observations of glass fibre/matrix interfacial debonding

    DEFF Research Database (Denmark)

    Martyniuk, Karolina; Sørensen, Bent F.; Modregger, Peter

    2013-01-01

    X-ray microtomography was used for 3D in situ observations of the evolution of fibre/matrix interfacial debonding. A specimen with a single fibre oriented perpendicular to the tensile direction was tested at a synchrotron facility using a special loading rig which allowed for applying a load...

  18. pH stable thin film composite polyamine nanofiltration membranes by interfacial polymerisation

    NARCIS (Netherlands)

    Lee, Kah Peng; Zheng, Jumeng; Bargeman, Gerrald; Kemperman, Antonius J.B.; Benes, Nieck Edwin

    2015-01-01

    In this work polyamine membranes are presented that are prepared by the interfacial polymerisation of polyethylenimine and cyanuric chloride on porous polyethersulfone supports. The thin film composite polyamine membranes have superior pH stability as compared to conventional polyamide membranes

  19. The role of interfacial rheological properties on Ostwald ripening in emusions

    NARCIS (Netherlands)

    Meinders, M.B.J.; Vliet, van T.

    2004-01-01

    The coarsening of emulsion droplets by Ostwald ripening is studied by means of numerical simulations in which time-dependent (elastic) interfacial behaviour is taken into account. Theoretical calculations on the dissolution of a single emulsion droplet in an infinite medium at saturated conditions

  20. Use of electrowetting to measure dynamic interfacial tensions of a microdrop

    NARCIS (Netherlands)

    de Ruiter, Riëlle; Wennink, P.; Banpurkar, A.G.; Duits, Michael H.G.; Mugele, Friedrich Gunther

    2012-01-01

    The adsorption of surface active species to liquid–liquid and to solid–liquid interfaces can have dramatic effects in microfluidics. In this paper we show how electrowetting on dielectric can be used to monitor a dynamic liquid–liquid interfacial tension (IFT) with a time resolution of O(1 s) using