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Sample records for adhesive binding mechanism

  1. Regulative mechanisms of chondrocyte adhesion

    DEFF Research Database (Denmark)

    Schmal, Hagen; Mehlhorn, Alexander T; Fehrenbach, Miriam;

    2006-01-01

    -matrix interaction, as well as collagen type II expression in the cartilage graft after two weeks of in vitro cultivation. Basic fibroblast growth factor (bFGF) treated chondrocytes showed increased adhesion to collagen types I and II, fibronectin, and fibrinogen. Attachment to these investigated proteins......%) increased. A cartilage construct was developed based on a clinically established collagen type I scaffold. In this matrix, more than 80% of the cells could be immobilized by mechanisms of adhesion, filtration, and cell entrapment. Confocal laser microscopy revealed focal adhesion sites as points of cell...... significantly enhanced cell proliferation. Matrix design in cartilage engineering must meet the biological demands of amplified cells, because adhesion of chondrocytes depends on their differentiation status and is regulated by bFGF....

  2. Mechanisms of adhesion in geckos.

    Science.gov (United States)

    Autumn, Kellar; Peattie, Anne M

    2002-12-01

    The extraordinary adhesive capabilities of geckos have challenged explanation for millennia, since Aristotle first recorded his observations. We have discovered many of the secrets of gecko adhesion, yet the millions of dry, adhesive setae on the toes of geckos continue to generate puzzling new questions and valuable answers. Each epidermally-derived, keratinous seta ends in hundreds of 200 nm spatular tips, permitting intimate contact with rough and smooth surfaces alike. Prior studies suggested that adhesive force in gecko setae was directly proportional to the water droplet contact angle (θ) , an indicator of the free surface energy of a substrate. In contrast, new theory suggests that adhesion energy between a gecko seta and a surface (W(GS)) is in fact proportional to (1 + cosθ), and only for θ > 60°. A reanalysis of prior data, in combination with our recent study, support the van der Waals hypothesis of gecko adhesion, and contradict surface hydrophobicity as a predictor of adhesion force. Previously, we and our collaborators measured the force production of a single seta. Initial efforts to attach a seta failed because of improper 3D orientation. However, by simulating the dynamics of gecko limbs during climbing (based on force plate data) we discovered that, in single setae, a small normal preload, combined with a 5 μm displacement yielded a very large adhesive force of 200 microNewton (μN), 10 times that predicted by whole-animal measurements. 6.5 million setae of a single tokay gecko attached maximally could generate 130 kg force. This raises the question of how geckos manage to detach their feet in just 15 ms. We discovered that simply increasing the angle that the setal shaft makes with the substrate to 30° causes detachment. Understanding how simultaneous attachment and release of millions of setae are controlled will require an approach that integrates levels ranging from molecules to lizards.

  3. Using engineered single-chain antibodies to correlate molecular binding properties and nanoparticle adhesion dynamics.

    Science.gov (United States)

    Haun, Jered B; Pepper, Lauren R; Boder, Eric T; Hammer, Daniel A

    2011-11-15

    Elucidation of the relationship between targeting molecule binding properties and the adhesive behavior of therapeutic or diagnostic nanocarriers would aid in the design of optimized vectors and lead to improved efficacy. We measured the adhesion of 200-nm-diameter particles under fluid flow that was mediated by a diverse array of molecular interactions, including recombinant single-chain antibodies (scFvs), full antibodies, and the avidin/biotin interaction. Within the panel of scFvs, we used a family of mutants that display a spectrum of binding kinetics, allowing us to compare nanoparticle adhesion to bond chemistry. In addition, we explored the effect of molecular size by inserting a protein linker into the scFv fusion construct and by employing scFvs that are specific for targets with vastly different sizes. Using computational models, we extracted multivalent kinetic rate constants for particle attachment and detachment from the adhesion data and correlated the results to molecular binding properties. Our results indicate that the factors that increase encounter probability, such as adhesion molecule valency and size, directly enhance the rate of nanoparticle attachment. Bond kinetics had no influence on scFv-mediated nanoparticle attachment within the kinetic range tested, however, but did appear to affect antibody/antigen and avidin/biotin mediated adhesion. We attribute this finding to a combination of multivalent binding and differences in bond mechanical strength between recombinant scFvs and the other adhesion molecules. Nanoparticle detachment probability correlated directly with adhesion molecule valency and size, as well as the logarithm of the affinity for all molecules tested. On the basis of this work, scFvs can serve as viable targeting receptors for nanoparticles, but improvements to their bond mechanical strength would likely be required to fully exploit their tunable kinetic properties and maximize the adhesion efficiency of nanoparticles that

  4. Assessing the impact of modifications neoprene adhesives amine-containing compounds the mechanisms to improve adhesion

    OpenAIRE

    KABLOV V.F.; KEYBAL N.A.; S. N. Bondarenko; RUDENKO K.U.; Zaikov, G. E.

    2015-01-01

    Possible mechanisms for an increase in the adhesion parameters of neopren-based adhesive compositions modified with adhesion promoters on the basis of epoxy compounds and aniline derivatives are studied.

  5. Molecular Mechanisms of Mechanosensitivity in Focal Adhesions

    OpenAIRE

    2016-01-01

    Physical environment guides tissue regeneration and morphology in both health and disease. In the past three decades, several experiments illustrated that mechanical cues are captured and transduced to biochemical signals in the cellular level (mechanotransduction) mediated by cell adhesion. Cells adhere to their microenvironment through large protein assemblies known as focal adhesions that directly couple intra- and extra-cellular matrices and play a critical role in many vital cell functio...

  6. Ligand binding mechanics of maltose binding protein.

    Science.gov (United States)

    Bertz, Morten; Rief, Matthias

    2009-11-13

    In the past decade, single-molecule force spectroscopy has provided new insights into the key interactions stabilizing folded proteins. A few recent studies probing the effects of ligand binding on mechanical protein stability have come to quite different conclusions. While some proteins seem to be stabilized considerably by a bound ligand, others appear to be unaffected. Since force acts as a vector in space, it is conceivable that mechanical stabilization by ligand binding is dependent on the direction of force application. In this study, we vary the direction of the force to investigate the effect of ligand binding on the stability of maltose binding protein (MBP). MBP consists of two lobes connected by a hinge region that move from an open to a closed conformation when the ligand maltose binds. Previous mechanical experiments, where load was applied to the N and C termini, have demonstrated that MBP is built up of four building blocks (unfoldons) that sequentially detach from the folded structure. In this study, we design the pulling direction so that force application moves the two MBP lobes apart along the hinge axis. Mechanical unfolding in this geometry proceeds via an intermediate state whose boundaries coincide with previously reported MBP unfoldons. We find that in contrast to N-C-terminal pulling experiments, the mechanical stability of MBP is increased by ligand binding when load is applied to the two lobes and force breaks the protein-ligand interactions directly. Contour length measurements indicate that MBP is forced into an open conformation before unfolding even if ligand is bound. Using mutagenesis experiments, we demonstrate that the mechanical stabilization effect is due to only a few key interactions of the protein with its ligand. This work illustrates how varying the direction of the applied force allows revealing important details about the ligand binding mechanics of a large protein.

  7. Sulfated polymannuroguluronate inhibits Tat-induced SLK cell adhesion via a novel binding site, a KKR spatial triad

    Institute of Scientific and Technical Information of China (English)

    Yan-lin WU; Jing AI; Jing-ming ZHAO; Bing XIONG; Xiao-jie XIN; Mei-yu GENG; Xian-liang XIN; Han-dong JIANG

    2011-01-01

    Aim: Sulfated polymannuroguluronate (SPMG), a candidate anti-AIDS drug, inhibited HIV replication and interfered with HIV entry into host T lymphocytes. SPMG has high binding affinity for the transactivating factor of the HIV-1 virus (Tat) via its basic domain. However, deletion or substitution of the basic domain affected, but did not completely eliminated Tat-SPMG interactions. Here, we sought to identify other SPMG binding sites in addition to the basic domain.Methods: The potential SPMG binding sites were determined using molecular simulation and a surface plasmon resonance (SPR) based competitive inhibition assay. The effect of SPMG on Tat induced adhesion was evaluated using a cell adhesion assay. Results: The KKR domain, a novel high-affinity heparin binding site, was identified, which consisted of a triad of Lys12, Lys41, and Arg78. The KKR domain, spatially enclosed SPMG binding site on Tat, functions as another binding domain for SPMG. Further func- tional evaluation demonstrated that SPMG inhibits Tat-mediated SLK cell adhesion by directly binding to the KKR region.Conclusion: The KKR domain is a novel high-affinity binding domain for SPMG. Our findings provide important new insights into the molecular mechanisms of SPMG and a potential therapeutic intervention for Tat-induced cell adhesion.

  8. Binding Strength Between Cell Adhesion Proteoglycans Measured by Atomic Force Microscopy

    Science.gov (United States)

    Dammer, Ulrich; Popescu, Octavian; Wagner, Peter; Anselmetti, Dario; Guntherodt, Hans-Joachim; Misevic, Gradimir N.

    1995-02-01

    Measurement of binding forces intrinsic to adhesion molecules is necessary to assess their contribution to the maintenance of the anatomical integrity of multicellular organisms. Atomic force microscopy was used to measure the binding strength between cell adhesion proteoglycans from a marine sponge. Under physiological conditions, the adhesive force between two cell adhesion molecules was found to be up to 400 piconewtons. Thus a single pair of molecules could hold the weight of 1600 cells. High intermolecular binding forces are likely to form the basis for the integrity of the multicellular sponge organism.

  9. Controllable and switchable capillary adhesion mechanism for bio-adhesive pads: Effect of micro patterns

    Institute of Scientific and Technical Information of China (English)

    ZHANG XiangJun; LIU Yuan; LIU YongHe; AHMED S.I.-U.

    2009-01-01

    Some insects and animals, such as bugs, grasshoppers and tree frogs, realize their efficient adhesion mechanism to glass surface, wall and ceiling by injecting a wetting liquid thin film into the pad-substrate contact area. Their ability to control adhesion (attaching or detaching from a surface) is in many cases connected to the contact geometry and surface patterns of their attachment pads. This paper focuses on the dependence of the capillary adhesion (wet adhesion) on the micro patterns of the bio-adhesive pads. The objective is to reveal the possible mechanism for a bio-adhesive pad to control capillary force through adjusting its micro-scale surface pattern and topography. A capillary adhesion force model is built up taking account of the combined role of micro-dimple geometry as well as the wetting behavior of the confined liquid thin film. Calculated results of the apparent contact angle on the regularly micro-dimpled surfaces are compared with and in good agreement with the experimental measurements. Simulation of the capillary adhesion force reveals that it is controllable in a large mag-nitude by adjusting a dimensionless surface pattern parameter k defined as a/(a+b), where a is the dia-meter of micro dimple, and (a+b) is the side length of one pattern cell. When adjusting the parameter k more than 0.75, the capillary adhesion force could be switchable from attractive to repulsive. This effect of micro patterns on the interfacial capillary force is proved to be dominant when the pad-substrate clearance decreases to the nano/micrometer scale. These results indicate that a controllable and switchable capillary adhesive mechanism might be utilized by a living insect or animal to realize its stable adhesion and quick releasing movement through adjusting the micro-pattern topography of its bio-adhesive pad.

  10. Mechanisms of temporary adhesion in benthic animals

    NARCIS (Netherlands)

    Dodou, D.; Breedveld, P.; Winter, J.C.F.; Dankelman, J.; Leeuwen, van J.L.

    2011-01-01

    Adhesive systems are ubiquitous in benthic animals and play a key role in diverse functions such as locomotion, food capture, mating, burrow building, and defence. For benthic animals that release adhesives, surface and material properties and external morphology have received little attention compa

  11. Postsurgical intrapericardial adhesions: mechanisms of formation and prevention.

    Science.gov (United States)

    Cannata, Aldo; Petrella, Duccio; Russo, Claudio Francesco; Bruschi, Giuseppe; Fratto, Pasquale; Gambacorta, Marcello; Martinelli, Luigi

    2013-05-01

    Postsurgical intrapericardial adhesions are still considered an unavoidable consequence of cardiothoracic operations. They increase the technical difficulty and the risk of reoperations. The pathogenesis of postsurgical adhesions is a multistep process, and the main key players are (1) loss of mesothelial cells, (2) accumulation of fibrin in areas devoid of mesothelial cells, (3) loss of normal pericardial fibrinolysis, and (4) local inflammation. Today, very promising methods to reduce adhesions are available for clinical use. This report reviews the process of formation of adhesions and the methods to prevent them, classified according to the mechanism of action.

  12. Contact mechanics, friction and adhesion with application to quasicrystals

    DEFF Research Database (Denmark)

    Persson, Bo; Carbone, Giuseppe; Samoilov, Vladimir N.;

    2015-01-01

    We discuss the origin of friction and adhesion between hard solids such as quasicrystals. We emphasize the fundamental role of surface roughness in many contact mechanics problems, in particular for friction and adhesion between solid bodies. The most important property of rough surfaces is the s...

  13. Mechanisms of Staphylococcus epidermidis adhesion to model biomaterial surfaces: Establising a link between thrombosis and infection

    Science.gov (United States)

    Higashi, Julie Miyo

    Infections involving Staphylococcus epidermidis remain a life threatening complication associated with the use of polymer based cardiovascular devices. One of the critical steps in infection pathogenesis is the adhesion of the bacteria to the device surface. Currently, mechanisms of S. epidermidis adhesion are incompletely understood, but are thought to involve interactions between bacteria, device surface, and host blood elements in the form of adsorbed plasma proteins and surface adherent platelets. Our central hypothesis is that elements participating in thrombosis also promote S. epidermidis adhesion by specifically binding to the bacterial surface. The adhesion kinetics of S. epidermidis RP62A to host modified model biomaterial surface octadecyltrichlorosilane (OTS) under hydrodynamic shear conditions were characterized. Steady state adhesion to adsorbed proteins and surface adherent platelets was achieved at 90-120 minutes and 60-90 minutes, respectively. A dose response curve of S. epidermidis adhesion in the concentration range of 10sp7{-}10sp9 bac/mL resembled a multilayer adsorption isotherm. Increasing shear stress was found to LTA, and other LTA blocking agents significantly decreased S. epidermidis adhesion to the fibrin-platelet clots, suggesting that this interaction between S. epidermidis and fibrin-platelet clots is specific. Studies evaluated the adhesion of S. epidermidis to polymer immobilized heparin report conflicting results. Paulsson et al., showed that coagulase negative staphylococci adhered in comparable numbers to both immobilized heparin and nonheparinized surfaces, while exhibiting significantly greater adhesion to both surfaces than S. aureus. Preadsorption of the surfaces with specific heparin binding plasma proteins vitronectin, fibronectin, laminin, and collagen significantly increased adhesion. It was postulated that immobilized heparin contained binding sites for the plasma proteins, exposing bacteria binding domains of the

  14. Mechanisms and Functions of Vinculin Interactions with Phospholipids at Cell Adhesion Sites.

    Science.gov (United States)

    Izard, Tina; Brown, David T

    2016-02-05

    The cytoskeletal protein vinculin is a major regulator of cell adhesion and attaches to the cell surface by binding to specific phospholipids. Structural, biochemical, and biological studies provided much insight into how vinculin binds to membranes, what components it recognizes, and how lipid binding is regulated. Here we discuss the roles and mechanisms of phospholipids in regulating the structure and function of vinculin and of its muscle-specific metavinculin splice variant. A full appreciation of these processes is necessary for understanding how vinculin regulates cell motility, migration, and wound healing, and for understanding of its role in cancer and cardiovascular diseases.

  15. The Mechanisms of Adhesion of Enteromorpha Clathrata.

    Science.gov (United States)

    1982-08-24

    Requirement for calcium in adhesion of a fouling diatom to glass. Appl . Environ. Microbiol. 41:1378-1382. 21. Corpe, W.A., 1970. Attachment of marine...T. I. Mutula, F.L.A. Buckmire and R.A. MacLeod, 1967. Nutrition and Metabolism of marine bacteria. XVI. Formation of protoplasts , spheroplasts, and...Influence of substrate wettabLlity on the attachment of marine bacteria to various surfaces. Appl . Microbiol. 30:298-308. 32. Dodson, Jr., J.R. and J.H

  16. The morphology and adhesion mechanism of Octopus vulgaris suckers.

    Directory of Open Access Journals (Sweden)

    Francesca Tramacere

    Full Text Available The octopus sucker represents a fascinating natural system performing adhesion on different terrains and substrates. Octopuses use suckers to anchor the body to the substrate or to grasp, investigate and manipulate objects, just to mention a few of their functions. Our study focuses on the morphology and adhesion mechanism of suckers in Octopus vulgaris. We use three different techniques (MRI, ultrasonography, and histology and a 3D reconstruction approach to contribute knowledge on both morphology and functionality of the sucker structure in O. vulgaris. The results of our investigation are two-fold. First, we observe some morphological differences with respect to the octopus species previously studied (i.e., Octopus joubini, Octopus maya, Octopus bimaculoides/bimaculatus and Eledone cirrosa. In particular, in O. vulgaris the acetabular chamber, that is a hollow spherical cavity in other octopuses, shows an ellipsoidal cavity which roof has an important protuberance with surface roughness. Second, based on our findings, we propose a hypothesis on the sucker adhesion mechanism in O. vulgaris. We hypothesize that the process of continuous adhesion is achieved by sealing the orifice between acetabulum and infundibulum portions via the acetabular protuberance. We suggest this to take place while the infundibular part achieves a completely flat shape; and, by sustaining adhesion through preservation of sucker configuration. In vivo ultrasonographic recordings support our proposed adhesion model by showing the sucker in action. Such an underlying physical mechanism offers innovative potential cues for developing bioinspired artificial adhesion systems. Furthermore, we think that it could possibly represent a useful approach in order to investigate any potential difference in the ecology and in the performance of adhesion by different species.

  17. The morphology and adhesion mechanism of Octopus vulgaris suckers.

    Science.gov (United States)

    Tramacere, Francesca; Beccai, Lucia; Kuba, Michael; Gozzi, Alessandro; Bifone, Angelo; Mazzolai, Barbara

    2013-01-01

    The octopus sucker represents a fascinating natural system performing adhesion on different terrains and substrates. Octopuses use suckers to anchor the body to the substrate or to grasp, investigate and manipulate objects, just to mention a few of their functions. Our study focuses on the morphology and adhesion mechanism of suckers in Octopus vulgaris. We use three different techniques (MRI, ultrasonography, and histology) and a 3D reconstruction approach to contribute knowledge on both morphology and functionality of the sucker structure in O. vulgaris. The results of our investigation are two-fold. First, we observe some morphological differences with respect to the octopus species previously studied (i.e., Octopus joubini, Octopus maya, Octopus bimaculoides/bimaculatus and Eledone cirrosa). In particular, in O. vulgaris the acetabular chamber, that is a hollow spherical cavity in other octopuses, shows an ellipsoidal cavity which roof has an important protuberance with surface roughness. Second, based on our findings, we propose a hypothesis on the sucker adhesion mechanism in O. vulgaris. We hypothesize that the process of continuous adhesion is achieved by sealing the orifice between acetabulum and infundibulum portions via the acetabular protuberance. We suggest this to take place while the infundibular part achieves a completely flat shape; and, by sustaining adhesion through preservation of sucker configuration. In vivo ultrasonographic recordings support our proposed adhesion model by showing the sucker in action. Such an underlying physical mechanism offers innovative potential cues for developing bioinspired artificial adhesion systems. Furthermore, we think that it could possibly represent a useful approach in order to investigate any potential difference in the ecology and in the performance of adhesion by different species.

  18. Control of mesenchymal stem cell phenotype and differentiation depending on cell adhesion mechanism

    Directory of Open Access Journals (Sweden)

    J Kang

    2014-11-01

    Full Text Available Control of cell-matrix adhesion has become an important issue in the regulation of stem cell function. In this study, a maltose-binding protein (MBP-linked basic fibroblast growth factor (FGF2-immobilised polystyrene surface (PS-MBP-FGF2 was applied as an artificial matrix to regulate integrin-mediated signalling. We sought to characterise human mesenchymal-stem cell (hMSC behaviour in response to two different mechanisms of cell adhesion; (i FGF2-heparan sulphate proteoglycan (HSPG-mediated adhesion vs. (ii fibronectin (FN-integrin-mediated adhesion. Heparin inhibited hMSC adhesion to PS-MBP-FGF2 but not to FN-coated surface. The phosphorylation of focal adhesion kinase, cytoskeletal re-organisation, and cell proliferation were restricted in hMSCs adhering to PS-MBP-FGF2 compared to FN-coated surface. Expression of MSC markers, such as CD105, CD90 and CD166, decreased in hMSCs expanded on PS-MBP-FGF2 compared to expression in cells expanded on FN-coated surface. hMSCs that were expanded on FN-coated surface differentiated into osteogenic and adipogenic cells more readily than those that were expanded on PS-MBP-FGF2. Furthermore, we characterised the N-linked glycan structures of hMSCs depending on the cell adhesion mechanism using mass spectrometry (MS-based quantitative techniques. MS analysis revealed that 2,3-sialylated glycans, a potential marker of stem cell function, were more abundant on hMSCs expanded on FN-coated surface than on those expanded on PS-MBP-FGF2. Thus, the differentiation potential of hMSCs is controlled by the type of adhesion substrate that might provide an idea for the design of biomaterials to control stem cell fate. Elucidation of the glycan structure on the cell membrane may help characterise hMSC function.

  19. Control of mesenchymal stem cell phenotype and differentiation depending on cell adhesion mechanism.

    Science.gov (United States)

    Kang, J; Park, H M; Kim, Y W; Kim, Y H; Varghese, S; Seok, H K; Kim, Y G; Kim, S H

    2014-11-25

    Control of cell-matrix adhesion has become an important issue in the regulation of stem cell function. In this study, a maltose-binding protein (MBP)-linked basic fibroblast growth factor (FGF2)-immobilised polystyrene surface (PS-MBP-FGF2) was applied as an artificial matrix to regulate integrin-mediated signalling. We sought to characterise human mesenchymal-stem cell (hMSC) behaviour in response to two different mechanisms of cell adhesion; (i) FGF2-heparan sulphate proteoglycan (HSPG)-mediated adhesion vs. (ii) fibronectin (FN)-integrin-mediated adhesion. Heparin inhibited hMSC adhesion to PS-MBP-FGF2 but not to FN-coated surface. The phosphorylation of focal adhesion kinase, cytoskeletal re-organisation, and cell proliferation were restricted in hMSCs adhering to PS-MBP-FGF2 compared to FN-coated surface. Expression of MSC markers, such as CD105, CD90 and CD166, decreased in hMSCs expanded on PS-MBP-FGF2 compared to expression in cells expanded on FN-coated surface. hMSCs that were expanded on FN-coated surface differentiated into osteogenic and adipogenic cells more readily than those that were expanded on PS-MBP-FGF2. Furthermore, we characterised the N-linked glycan structures of hMSCs depending on the cell adhesion mechanism using mass spectrometry (MS)-based quantitative techniques. MS analysis revealed that 2,3-sialylated glycans, a potential marker of stem cell function, were more abundant on hMSCs expanded on FN-coated surface than on those expanded on PS-MBP-FGF2. Thus, the differentiation potential of hMSCs is controlled by the type of adhesion substrate that might provide an idea for the design of biomaterials to control stem cell fate. Elucidation of the glycan structure on the cell membrane may help characterise hMSC function.

  20. Possible mechanism of adhesion in a mica supported phospholipid bilayer

    Energy Technology Data Exchange (ETDEWEB)

    Pertsin, Alexander, E-mail: ig3@ix.urz.uni-heidelberg.de [Angewandte Physikalische Chemie, Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg (Germany); Institute of Organo-Element Compounds, Russian Academy of Sciences, Vavilov Str. 28, 117991 Moscow (Russian Federation); Grunze, Michael [Angewandte Physikalische Chemie, Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg (Germany); Institute for Functional Interfaces, Karlsruhe Institute of Technology, Hermann-von- Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2014-05-14

    Phospholipid bilayers supported on hydrophilic solids like silica and mica play a substantial role in fundamental studies and technological applications of phospholipid membranes. In both cases the molecular mechanism of adhesion between the bilayer and the support is of primary interest. Since the possibilities of experimental methods in this specific area are rather limited, the methods of computer simulation acquire great importance. In this paper we use the grand canonical Monte Carlo technique and an atomistic force field to simulate the behavior of a mica supported phospholipid bilayer in pure water as a function of the distance between the bilayer and the support. The simulation reveals a possible adhesion mechanism, where the adhesion is due to individual lipid molecules that protrude from the bilayer and form widely spaced links with the support. Simultaneously, the bilayer remains separated from the bilayer by a thin water interlayer which maintains the bilayer fluidity.

  1. Rolling adhesion of alphaL I domain mutants decorrelated from binding affinity.

    Science.gov (United States)

    Pepper, Lauren R; Hammer, Daniel A; Boder, Eric T

    2006-06-30

    Activated lymphocyte function-associated antigen-1 (LFA-1, alphaLbeta2 integrin) found on leukocytes facilitates firm adhesion to endothelial cell layers by binding to intercellular adhesion molecule-1 (ICAM-1), which is up-regulated on endothelial cells at sites of inflammation. Recent work has shown that LFA-1 in a pre-activation, low-affinity state may also be involved in the initial tethering and rolling phase of the adhesion cascade. The inserted (I) domain of LFA-1 contains the ligand-binding epitope of the molecule, and a conformational change in this region during activation increases ligand affinity. We have displayed wild-type I domain on the surface of yeast and validated expression using I domain specific antibodies and flow cytometry. Surface display of I domain supports yeast rolling on ICAM-1-coated surfaces under shear flow. Expression of a locked open, high-affinity I domain mutant supports firm adhesion of yeast, while yeast displaying intermediate-affinity I domain mutants exhibit a range of rolling phenotypes. We find that rolling behavior for these mutants fails to correlate with ligand binding affinity. These results indicate that unstressed binding affinity is not the only molecular property that determines adhesive behavior under shear flow.

  2. Mechanical Activation of a Multimeric Adhesive Protein through Domain Conformational Change

    Science.gov (United States)

    Wijeratne, Sithara S.; Botello, Eric; Yeh, Hui-Chun; Zhou, Zhou; Bergeron, Angela; Frey, Eric W.; Patel, Jay M.; Moake, Joel; Dong, Jing-fei; Kiang, Ching-Hwa

    2013-01-01

    The mechanical force-induced activation of the adhesive protein von Willebrand Factor (VWF), which experiences high hydrodynamic forces, is essential in initiating platelet adhesion. The importance of the mechanical force-induced functional change is manifested in the multimeric VWF’s crucial role in blood coagulation, when high fluid shear stress activates plasma VWF (pVWF) multimers to bind platelets. Here we showed that a pathological level of high shear stress exposure of pVWF multimers results in domain conformational changes, and the subsequent shifts in the unfolding force allow us to use force as a marker to track the dynamic states of multimeric VWF. We found that shear-activated pVWF multimers (spVWF) are more resistant to mechanical unfolding than non-sheared pVWF multimers, as indicated in the higher peak unfolding force. These results provide insight into the mechanism of shear-induced activation of pVWF multimers. PMID:23521301

  3. Mechanical behaviour of adhesive joint under tensile and shear loading

    NARCIS (Netherlands)

    Jiang, X.; Kolstein, M.H.; Bijlaard, F.S.K.

    2013-01-01

    Due to various advantages of Fibre-Reinforced Polymer (FRP) decks, the FRP to steel composite bridge system is being increasingly used in new bridge structures as well as rehabilitation projects for old bridges. This paper focuses on the mechanical behaviours and failure modes of the adhesively-bond

  4. Platelet-collagen adhesion enhances platelet aggregation induced by binding of VWF to platelets

    Energy Technology Data Exchange (ETDEWEB)

    Laduca, F.M.; Bell, W.R.; Bettigole, R.E. (Johns Hopkins Univ. School of Medicine, Baltimore, MD (USA) State Univ. of New York, Buffalo (USA))

    1987-11-01

    Ristocetin-induced platelet aggregation (RIPA) was evaluated in the presence of platelet-collagen adhesion. RIPA of normal donor platelet-rich plasma (PRP) demonstrated a primary wave of aggregation mediated by the binding of von Willebrand factor (VWF) to platelets and a secondary aggregation wave, due to a platelet-release reaction, initiated by VWF-platelet binding and inhibitable by acetylsalicylic acid (ASA). An enhanced RIPA was observed in PRP samples to which collagen had been previously added. These subthreshold concentrations of collagen, which by themselves were insufficient to induce aggregation, caused measurable platelet-collagen adhesion. Subthreshold collagen did not cause microplatelet aggregation, platelet release of ({sup 3}H)serotonin, or alter the dose-responsive binding of {sup 125}I-labeled VWF to platelets, which occurred with increasing ristocetin concentrations. However, ASA inhibition of the platelet release reaction prevented collagen-enhanced RIPA. These results demonstrate that platelet-collagen adhesion altered the platelet-release reaction induced by the binding of VWF to platelets causing a platelet-release reaction at a level of VWF-platelet binding not normally initiating a secondary aggregation. These findings suggest that platelet-collagen adhesion enhances platelet function mediated by VWF.

  5. Distinct biophysical mechanisms of focal adhesion kinase mechanoactivation by different extracellular matrix proteins.

    Science.gov (United States)

    Seong, Jihye; Tajik, Arash; Sun, Jie; Guan, Jun-Lin; Humphries, Martin J; Craig, Susan E; Shekaran, Asha; García, Andrés J; Lu, Shaoying; Lin, Michael Z; Wang, Ning; Wang, Yingxiao

    2013-11-26

    Matrix mechanics controls cell fate by modulating the bonds between integrins and extracellular matrix (ECM) proteins. However, it remains unclear how fibronectin (FN), type 1 collagen, and their receptor integrin subtypes distinctly control force transmission to regulate focal adhesion kinase (FAK) activity, a crucial molecular signal governing cell adhesion/migration. Here we showed, using a genetically encoded FAK biosensor based on fluorescence resonance energy transfer, that FN-mediated FAK activation is dependent on the mechanical tension, which may expose its otherwise hidden FN synergy site to integrin α5. In sharp contrast, the ligation between the constitutively exposed binding motif of type 1 collagen and its receptor integrin α2 was surprisingly tension-independent to induce sufficient FAK activation. Although integrin α subunit determines mechanosensitivity, the ligation between α subunit and the ECM proteins converges at the integrin β1 activation to induce FAK activation. We further discovered that the interaction of the N-terminal protein 4.1/ezrin/redixin/moesin basic patch with phosphatidylinositol 4,5-biphosphate is crucial during cell adhesion to maintain the FAK activation from the inhibitory effect of nearby protein 4.1/ezrin/redixin/moesin acidic sites. Therefore, different ECM proteins either can transmit or can shield from mechanical forces to regulate cellular functions, with the accessibility of ECM binding motifs by their specific integrin α subunits determining the biophysical mechanisms of FAK activation during mechanotransduction.

  6. Glass Fiber Reinforced Polypropylene Mechanical Properties Enhancement by Adhesion Improvement

    Directory of Open Access Journals (Sweden)

    Mariana Etcheverry

    2012-06-01

    Full Text Available Glass fibers (GF are the reinforcement agent most used in polypropylene (PP based composites, as they have good balance between properties and costs. However, their final properties are mainly determined by the strength and stability of the polymer-fiber interphase. Fibers do not act as an effective reinforcing material when the adhesion is weak. Also, the adhesion between phases can be easily degraded in aggressive environmental conditions such as high temperatures and/or elevated moisture, and by the stress fields to which the material may be exposed. Many efforts have been done to improve polymer-glass fiber adhesion by compatibility enhancement. The most used techniques include modifications in glass surface, polymer matrix and/or both. However, the results obtained do not show a good costs/properties improvement relationship. The aim of this work is to perform an accurate analysis regarding methods for GF/PP adhesion improvement and to propose a new route based on PP in-situ polymerization onto fibers. This route involves the modification of fibers with an aluminum alkyl and hydroxy-α-olefin and from there to enable the growth of the PP chains using direct metallocenic copolymerization. The adhesion improvements were further proved by fragmentation test, as well as by mechanical properties measurements. The strength and toughness increases three times and the interfacial strength duplicates in PP/GF composites prepared with in-situ polymerized fibers.

  7. Mechanism of mast cell adhesion to human tenocytes in vitro.

    Science.gov (United States)

    Behzad, Hayedeh; Tsai, Shu-Huei; Nassab, Paulina; Mousavizadeh, Rouhollah; McCormack, Robert G; Scott, Alex

    2015-01-01

    Mast cells and fibroblasts are two key players involved in many fibrotic and degenerative disorders. In the present study we examined the nature of binding interactions between human mast cells and tendon fibroblasts (tenocytes). In the mast cell-fibroblast co-culture model, mast cells were shown to spontaneously bind to tenocytes, in a process that was partially mediated by α5β1 integrin receptors. The same receptors on mast cells significantly mediated binding of these cells to tissue culture plates in the presence of tenocyte-conditioned media; the tenocyte-derived fibronectin in the media was shown to also play a major role in these binding activities. Upon binding to tenocytes or tissue culture plates, mast cells acquired an elongated phenotype, which was dependent on α5β1 integrin and tenocyte fibronectin. Additionally, tenocyte-derived fibronectin significantly enhanced mRNA expression of the adhesion molecule, THY1, by mast cells. Our data suggests that α5β1 integrin mediates binding of mast cells to human tenocyte and to tenocyte-derived ECM proteins, in particular fibronectin.

  8. The neural cell adhesion molecule binds to fibroblast growth factor receptor 2

    DEFF Research Database (Denmark)

    Christensen, Claus; Lauridsen, Jes B; Berezin, Vladimir;

    2006-01-01

    The neural cell adhesion molecule (NCAM) can bind to and activate fibroblast growth factor receptor 1 (FGFR1). However, there are four major FGFR isoforms (FGFR1-FGFR4), and it is not known whether NCAM also interacts directly with the other three FGFR isoforms. In this study, we show by surface...

  9. Adhesion properties of Lactobacillus rhamnosus mucus-binding factor to mucin and extracellular matrix proteins.

    Science.gov (United States)

    Nishiyama, Keita; Nakamata, Koichi; Ueno, Shintaro; Terao, Akari; Aryantini, Ni Putu Desy; Sujaya, I Nengah; Fukuda, Kenji; Urashima, Tadasu; Yamamoto, Yuji; Mukai, Takao

    2015-01-01

    We previously described potential probiotic Lactobacillus rhamnosus strains, isolated from fermented mare milk produced in Sumbawa Island, Indonesia, which showed high adhesion to porcine colonic mucin (PCM) and extracellular matrix (ECM) proteins. Recently, mucus-binding factor (MBF) was found in the GG strain of L. rhamnosus as a mucin-binding protein. In this study, we assessed the ability of recombinant MBF protein from the FSMM22 strain, one of the isolates of L. rhamnosus from fermented Sumbawa mare milk, to adhere to PCM and ECM proteins by overlay dot blot and Biacore assays. MBF bound to PCM, laminin, collagen IV, and fibronectin with submicromolar dissociation constants. Adhesion of the FSMM22 mbf mutant strain to PCM and ECM proteins was significantly less than that of the wild-type strain. Collectively, these results suggested that MBF contribute to L. rhamnosus host colonization via mucin and ECM protein binding.

  10. The Adhesion and Formation Mechanism of Blast Furnace Gunning Layer

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Basing on the study of the equilibrium relationship of interfacial tension among gunning particles, repaired surface and atmosphere, this test is in a position to draw a conclusion concerning the adhesion mechanism of the gunning refractory and the repaired surface, which illustrates the formation of the bottom gunning layer by moist fine gunning particles on the repaired surface. Also involved within the scope of discussion and probe are the patterns formed under this contacting effect and the formation mechanism of gunning layer. The analytic research regarding the behavior of gunning interface has ascribed the influence upon adhesion intensity to the quality of furnace gunning refractory, the state of the repaired surface and the gunning techniques.

  11. The role of focal adhesion kinase in the regulation of cellular mechanical properties

    Science.gov (United States)

    Mierke, Claudia Tanja

    2013-12-01

    The regulation of mechanical properties is necessary for cell invasion into connective tissue or intra- and extravasation through the endothelium of blood or lymph vessels. Cell invasion is important for the regulation of many healthy processes such as immune response reactions and wound healing. In addition, cell invasion plays a role in disease-related processes such as tumor metastasis and autoimmune responses. Until now the role of focal adhesion kinase (FAK) in regulating mechanical properties of cells and its impact on cell invasion efficiency is still not well known. Thus, this review focuses on mechanical properties regulated by FAK in comparison to the mechano-regulating protein vinculin. Moreover, it points out the connection between cancer cell invasion and metastasis and FAK by showing that FAK regulates cellular mechanical properties required for cellular motility. Furthermore, it sheds light on the indirect interaction of FAK with vinculin by binding to paxillin, which then impairs the binding of paxillin to vinculin. In addition, this review emphasizes whether FAK fulfills regulatory functions similar to vinculin. In particular, it discusses the differences and the similarities between FAK and vinculin in regulating the biomechanical properties of cells. Finally, this paper highlights that both focal adhesion proteins, vinculin and FAK, synergize their functions to regulate the mechanical properties of cells such as stiffness and contractile forces. Subsequently, these mechanical properties determine cellular invasiveness into tissues and provide a source sink for future drug developments to inhibit excessive cell invasion and hence, metastases formation.

  12. The emerin-binding transcription factor Lmo7 is regulated by association with p130Cas at focal adhesions

    Directory of Open Access Journals (Sweden)

    Michele A. Wozniak

    2013-08-01

    Full Text Available Loss of function mutations in the nuclear inner membrane protein, emerin, cause X-linked Emery-Dreifuss muscular dystrophy (X-EDMD. X-EDMD is characterized by contractures of major tendons, skeletal muscle weakening and wasting, and cardiac conduction system defects. The transcription factor Lmo7 regulates muscle- and heart-relevant genes and is inhibited by binding to emerin, suggesting Lmo7 misregulation contributes to EDMD disease. Lmo7 associates with cell adhesions and shuttles between the plasma membrane and nucleus, but the regulation and biological consequences of this dual localization were unknown. We report endogenous Lmo7 also associates with focal adhesions in cells, and both co-localizes and co-immunoprecipitates with p130Cas, a key signaling component of focal adhesions. Lmo7 nuclear localization and transcriptional activity increased significantly in p130Cas-null MEFs, suggesting Lmo7 is negatively regulated by p130Cas-dependent association with focal adhesions. These results support EDMD models in which Lmo7 is a downstream mediator of integrin-dependent signaling that allows tendon cells and muscles to adapt to and withstand mechanical stress.

  13. Structural Insight into the Mechanisms of Targeting and Signaling of Focal Adhesion Kinase

    OpenAIRE

    2002-01-01

    Focal adhesion kinase (FAK) is a nonreceptor tyrosine kinase whose focal adhesion targeting (FAT) domain interacts with other focal adhesion molecules in integrin-mediated signaling. Localization of activated FAK to focal adhesions is indispensable for its function. Here we describe a solution structure of the FAT domain bound to a peptide derived from paxillin, a FAK-binding partner. The FAT domain is composed of four helices that form a “right-turn” elongated bundle; the globular fold is ma...

  14. Failure mechanisms of fibrin-based surgical tissue adhesives

    Science.gov (United States)

    Sierra, David Hugh

    A series of studies was performed to investigate the potential impact of heterogeneity in the matrix of multiple-component fibrin-based tissue adhesives upon their mechanical and biomechanical properties both in vivo and in vitro. Investigations into the failure mechanisms by stereological techniques demonstrated that heterogeneity could be measured quantitatively and that the variation in heterogeneity could be altered both by the means of component mixing and delivery and by the formulation of the sealant. Ex vivo tensile adhesive strength was found to be inversely proportional to the amount of heterogeneity. In contrast, in vivo tensile wound-closure strength was found to be relatively unaffected by the degree of heterogeneity, while in vivo parenchymal organ hemostasis in rabbits was found to be affected: greater heterogeneity appeared to correlate with an increase in hemostasis time and amount of sealant necessary to effect hemostasis. Tensile testing of the bulk sealant showed that mechanical parameters were proportional to fibrin concentration and that the physical characteristics of the failure supported a ductile mechanism. Strain hardening as a function of percentage of strain, and strain rate was observed for both concentrations, and syneresis was observed at low strain rates for the lower fibrin concentration. Blister testing demonstrated that burst pressure and failure energy were proportional to fibrin concentration and decreased with increasing flow rate. Higher fibrin concentration demonstrated predominately compact morphology debonds with cohesive failure loci, demonstrating shear or viscous failure in a viscoelastic rubbery adhesive. The lower fibrin concentration sealant exhibited predominately fractal morphology debonds with cohesive failure loci, supporting an elastoviscous material condition. The failure mechanism for these was hypothesized and shown to be flow-induced ductile fracture. Based on these findings, the failure mechanism was

  15. [Topography and mechanisms of adhesion of uropathogenic Escherichia coli bacteria in the human kidney and renal pelvis].

    Science.gov (United States)

    Vierbuchen, M; Peters, G; Ortmann, M; Pulverer, G; Fischer, R

    1989-01-01

    The occurrence and significance of bacterial carbohydrate recognition proteins (bacterial lectins) and endogenous carbohydrate binding proteins (endogenous lectins) of human urothelium as well as kidney tubulus epithelium was analyzed with respect to the adhesion of urotoxogenic Escherichia coli bacteria. Using biotinylated neoglycoproteins, we demonstrated a wide spectrum of endogenous lectins with Galactose-, Mannose-, Fucose-, N-Acetylgalactosamine-, and N-Acetylglucosamine binding activities in the urothelium. In the kidney the distal nephron and especially the medullar collecting ducts exhibited a similar spectrum of endogenous carbohydrate binding activities as detected for the urothelium. Adhesion- as well as inhibition-experiments with selective blocking of either bacterial lectins or endogenous lectins of the target cells by different carbohydrates both reduced the bacterial adhesion. However, maximal inhibition of bacterial adhesion was achieved by simultanous blocking of microbial and target cell lectins with mannose or mannan. From these results it is reasonable to conclude that specific adhesion which may result in an organotropism (urotropism) of E. coli infection is due to a dual recognition mechanism which is accomplished by the combined interaction of the bachterial and host cell lectins with the corresponding carbohydrates of E. coli and that of the target cells respectively. Further studies showed that normal human serum possesses natural antiadhesins which are represented by the glycan parts of the serum-glycoproteins.

  16. Mechanical Strength and Inhibition of the Staphylococcus aureus Collagen-Binding Protein Cna

    Science.gov (United States)

    Herman-Bausier, Philippe; Valotteau, Claire; Pietrocola, Giampiero; Rindi, Simonetta; Alsteens, David; Foster, Timothy J.

    2016-01-01

    ABSTRACT The bacterial pathogen Staphylococcus aureus expresses a variety of cell surface adhesion proteins that bind to host extracellular matrix proteins. Among these, the collagen (Cn)-binding protein Cna plays important roles in bacterium-host adherence and in immune evasion. While it is well established that the A region of Cna mediates ligand binding, whether the repetitive B region has a dedicated function is not known. Here, we report the direct measurement of the mechanical strength of Cna-Cn bonds on living bacteria, and we quantify the antiadhesion activity of monoclonal antibodies (MAbs) targeting this interaction. We demonstrate that the strength of Cna-Cn bonds in vivo is very strong (~1.2 nN), consistent with the high-affinity “collagen hug” mechanism. The B region is required for strong ligand binding and has been found to function as a spring capable of sustaining high forces. This previously undescribed mechanical response of the B region is of biological significance as it provides a means to project the A region away from the bacterial surface and to maintain bacterial adhesion under conditions of high forces. We further quantified the antiadhesion activity of MAbs raised against the A region of Cna directly on living bacteria without the need for labeling or purification. Some MAbs are more efficient in blocking single-cell adhesion, suggesting that they act as competitive inhibitors that bind Cna residues directly involved in ligand binding. This report highlights the role of protein mechanics in activating the function of staphylococcal adhesion proteins and emphasizes the potential of antibodies to prevent staphylococcal adhesion and biofilm formation. PMID:27795393

  17. Mechanical Strength and Inhibition of the Staphylococcus aureus Collagen-Binding Protein Cna

    Directory of Open Access Journals (Sweden)

    Philippe Herman-Bausier

    2016-10-01

    Full Text Available The bacterial pathogen Staphylococcus aureus expresses a variety of cell surface adhesion proteins that bind to host extracellular matrix proteins. Among these, the collagen (Cn-binding protein Cna plays important roles in bacterium-host adherence and in immune evasion. While it is well established that the A region of Cna mediates ligand binding, whether the repetitive B region has a dedicated function is not known. Here, we report the direct measurement of the mechanical strength of Cna-Cn bonds on living bacteria, and we quantify the antiadhesion activity of monoclonal antibodies (MAbs targeting this interaction. We demonstrate that the strength of Cna-Cn bonds in vivo is very strong (~1.2 nN, consistent with the high-affinity “collagen hug” mechanism. The B region is required for strong ligand binding and has been found to function as a spring capable of sustaining high forces. This previously undescribed mechanical response of the B region is of biological significance as it provides a means to project the A region away from the bacterial surface and to maintain bacterial adhesion under conditions of high forces. We further quantified the antiadhesion activity of MAbs raised against the A region of Cna directly on living bacteria without the need for labeling or purification. Some MAbs are more efficient in blocking single-cell adhesion, suggesting that they act as competitive inhibitors that bind Cna residues directly involved in ligand binding. This report highlights the role of protein mechanics in activating the function of staphylococcal adhesion proteins and emphasizes the potential of antibodies to prevent staphylococcal adhesion and biofilm formation.

  18. Role of surface layer collagen binding protein from indigenous Lactobacillus plantarum 91 in adhesion and its anti-adhesion potential against gut pathogen.

    Science.gov (United States)

    Yadav, Ashok Kumar; Tyagi, Ashish; Kaushik, Jai Kumar; Saklani, Asha Chandola; Grover, Sunita; Batish, Virender Kumar

    2013-12-14

    Human feacal isolates were ascertain as genus Lactobacillus using specific primer LbLMA1/R16-1 and further identified as Lactobacillus plantarum with species specific primers Lpl-3/Lpl-2. 25 L. plantarum strains were further assessed for hydrophobicity following the microbial adhesion to hydrocarbons (MATH) method and colonization potentials based on their adherence to immobilized human collagen type-1. Surface proteins were isolated from selected L. plantarum 91(Lp91) strain. The purified collagen binding protein (Cbp) protein was assessed for its anti-adhesion activity against enteric Escherichia coli 0157:H7 pathogen on immobilized collagen. Four L. plantarum strains displayed high degree of hydrophobicity and significant adhesion to collagen. A 72 kDa protein was purified which reduced 59.71% adhesion of E. coli 0157:H7 on immobilized collagen as compared to control well during adhesion assay. Cbp protein is the major influencing factor in inhibition of E. coli 0157:H7 adhesion with extracellular matrix (ECM) components. Hydrophobicity and adhesion potential are closely linked attributes precipitating in better colonization potential of the lactobacillus strains. Cbp is substantiated as a crucial surface protein contributing in adhesion of lactobacillus strains. The study can very well be the platform for commercialization of indigenous probiotic strain once their functional attributes are clinically explored.

  19. Adhesive Contact in Animal: Morphology, Mechanism and Bio-Inspired Application

    Institute of Scientific and Technical Information of China (English)

    Aihong Ji; Longbao Han; Zhendong Dai

    2011-01-01

    Many animals possess adhesive pads on their feet,which are able to attach to various substrates while controlling adhesive forces during locomotion.This review article studies the morphology of adhesive devices in animals,and the physical mechanisms of wet adhesion and dry adhesion.The adhesive pads are either ‘smooth' or densely covered with special adhesive setae.Smooth pads adhere by wet adhesion,which is facilitated by fluid secreted from the pads,whereas hairy pads can adhere by dry adhesion or wet adhesion.Contact area,distance between pad and substrate,viscosity and surface tension of the liquid filling the gap between pad and substrate are the most important factors which determine the wet adhesion.Dry adhesion was found only in hairy pads,which occurs in geckos and spiders.It was demonstrated that van der Waals interaction is the dominant adhesive force in geckos' adhesion.The bio-inspired applications derived from adhesive pads are also reviewed.

  20. Rapid and Localized Mechanical Stimulation and Adhesion Assay: TRPM7 Involvement in Calcium Signaling and Cell Adhesion.

    Directory of Open Access Journals (Sweden)

    Wagner Shin Nishitani

    Full Text Available A cell mechanical stimulation equipment, based on cell substrate deformation, and a more sensitive method for measuring adhesion of cells were developed. A probe, precisely positioned close to the cell, was capable of a vertical localized mechanical stimulation with a temporal frequency of 207 Hz, and strain magnitude of 50%. This setup was characterized and used to probe the response of Human Umbilical Endothelial Vein Cells (HUVECs in terms of calcium signaling. The intracellular calcium ion concentration was measured by the genetically encoded Cameleon biosensor, with the Transient Receptor Potential cation channel, subfamily M, member 7 (TRPM7 expression inhibited. As TRPM7 expression also regulates adhesion, a relatively simple method for measuring adhesion of cells was also developed, tested and used to study the effect of adhesion alone. Three adhesion conditions of HUVECs on polyacrylamide gel dishes were compared. In the first condition, the substrate is fully treated with Sulfo-SANPAH crosslinking and fibronectin. The other two conditions had increasingly reduced adhesion: partially treated (only coated with fibronectin, with no use of Sulfo-SANPAH, at 5% of the normal amount and non-treated polyacrylamide gels. The cells showed adhesion and calcium response to the mechanical stimulation correlated to the degree of gel treatment: highest for fully treated gels and lowest for non-treated ones. TRPM7 inhibition by siRNA on HUVECs caused an increase in adhesion relative to control (no siRNA treatment and non-targeting siRNA, but a decrease to 80% of calcium response relative to non-targeting siRNA which confirms the important role of TRPM7 in mechanotransduction despite the increase in adhesion.

  1. Rapid and Localized Mechanical Stimulation and Adhesion Assay: TRPM7 Involvement in Calcium Signaling and Cell Adhesion.

    Science.gov (United States)

    Nishitani, Wagner Shin; Alencar, Adriano Mesquita; Wang, Yingxiao

    2015-01-01

    A cell mechanical stimulation equipment, based on cell substrate deformation, and a more sensitive method for measuring adhesion of cells were developed. A probe, precisely positioned close to the cell, was capable of a vertical localized mechanical stimulation with a temporal frequency of 207 Hz, and strain magnitude of 50%. This setup was characterized and used to probe the response of Human Umbilical Endothelial Vein Cells (HUVECs) in terms of calcium signaling. The intracellular calcium ion concentration was measured by the genetically encoded Cameleon biosensor, with the Transient Receptor Potential cation channel, subfamily M, member 7 (TRPM7) expression inhibited. As TRPM7 expression also regulates adhesion, a relatively simple method for measuring adhesion of cells was also developed, tested and used to study the effect of adhesion alone. Three adhesion conditions of HUVECs on polyacrylamide gel dishes were compared. In the first condition, the substrate is fully treated with Sulfo-SANPAH crosslinking and fibronectin. The other two conditions had increasingly reduced adhesion: partially treated (only coated with fibronectin, with no use of Sulfo-SANPAH, at 5% of the normal amount) and non-treated polyacrylamide gels. The cells showed adhesion and calcium response to the mechanical stimulation correlated to the degree of gel treatment: highest for fully treated gels and lowest for non-treated ones. TRPM7 inhibition by siRNA on HUVECs caused an increase in adhesion relative to control (no siRNA treatment) and non-targeting siRNA, but a decrease to 80% of calcium response relative to non-targeting siRNA which confirms the important role of TRPM7 in mechanotransduction despite the increase in adhesion.

  2. Mechanically functional amyloid fibrils in the adhesive of a marine invertebrate as revealed by Raman spectroscopy and atomic force microscopy.

    Science.gov (United States)

    S Mostaert, Anika; Crockett, Rowena; Kearn, Graham; Cherny, Izhack; Gazit, Ehud; C Serpell, Louise; P Jarvis, Suzanne

    2009-01-01

    Amyloid fibrils are primarily known in a pathogenic context for their association with a wide range of debilitating human diseases. Here we show a marine invertebrate (Entobdella soleae) utilizes functional amyloid fibrils comparable to those of a unicellular prokaryote (Escherichia coli). Thioflavin-T binding and Raman spectroscopy provided evidence for the presence of amyloid in the adhesive of Entobdella soleae. We elucidated that for these two very different organisms, amyloid fibrils provide adhesive and cohesive strength to their natural adhesives. Comparing the nanoscale mechanical responses of these fibrils with those of pathogenic amyloid by atomic force microscopy revealed that the molecular level origin of the cohesive strength was associated with the generic intermolecular β-sheet structure of amyloid fibrils. Functional adhesive residues were found only in the case of the functional amyloid. Atomic force microscopy provided a useful means to characterize the internal structural forces within individual amyloid fibrils and how these relate to the mechanical performance of both functional and pathogenic amyloid. The mechanistic link of amyloid-based cohesive and adhesive strength could be widespread amongst natural adhesives, irrespective of environment, providing a new strategy for biomimicry and a new source of materials for understanding the formation and stability of amyloid fibrils more generally.

  3. L1CAM Binds ErbB Receptors through Ig-Like Domains Coupling Cell Adhesion and Neuregulin Signalling

    Science.gov (United States)

    Grijota-Martinez, Carmen; Lakomá, Jarmila; Baars, Sigrid; Garcia-Alonso, Luis; Cabedo, Hugo

    2012-01-01

    During nervous system development different cell-to-cell communication mechanisms operate in parallel guiding migrating neurons and growing axons to generate complex arrays of neural circuits. How such a system works in coordination is not well understood. Cross-regulatory interactions between different signalling pathways and redundancy between them can increase precision and fidelity of guidance systems. Immunoglobulin superfamily proteins of the NCAM and L1 families couple specific substrate recognition and cell adhesion with the activation of receptor tyrosine kinases. Thus it has been shown that L1CAM-mediated cell adhesion promotes the activation of the EGFR (erbB1) from Drosophila to humans. Here we explore the specificity of the molecular interaction between L1CAM and the erbB receptor family. We show that L1CAM binds physically erbB receptors in both heterologous systems and the mammalian developing brain. Different Ig-like domains located in the extracellular part of L1CAM can support this interaction. Interestingly, binding of L1CAM to erbB enhances its response to neuregulins. During development this may synergize with the activation of erbB receptors through L1CAM homophilic interactions, conferring diffusible neuregulins specificity for cells or axons that interact with the substrate through L1CAM. PMID:22815787

  4. Fracture mechanics characterisation of medium-size adhesive joint specimens

    DEFF Research Database (Denmark)

    Sørensen, Bent F.; Jacobsen, T.K.

    2004-01-01

    Medium-size specimens (adhesive layer were tested in four point bending to determine their load carrying capacity. Specimens having different thickness were tested. Except for onespecimen, the cracking occurred as cracking...... along the adhesive layer; initially cracking occurred along the adhesive/laminate interface, but after some crack extension the cracking took place inside the laminate (for one specimen the later part of thecracking occurred unstably along the adhesive/ laminate interface). Crack bridging by fibres...

  5. Functional roles of mannose-binding protein in the adhesion, cytotoxicity and phagocytosis of Acanthamoeba castellanii.

    Science.gov (United States)

    Kim, Jong-Hyun; Matin, Abdul; Shin, Ho-Joon; Park, Hyun; Yoo, Kyung-Tae; Yuan, Xi-Zhe; Kim, Kwang Sik; Jung, Suk-Yul

    2012-10-01

    Acanthamoeba castellanii is a single-celled protozoan that is widely distributed in the environment and is a well-known of causing human keratitis, a vision-threatening infection. In this study, an ethyl methane sulfonate (EMS) and a selection of saccharide were applied to A. castellanii by chemical mutagenesis. To understand the functional roles of a mannose-binding protein (MBP). A. castellanii were treated with methyl-alpha-D-mannopyranoside abbreviated Man, with and without the EMS pre-treatment, and their adhesion and cytotoxicity were analyzed, using a human brain microvascular endothelial cell (HBMEC) as the target cell. Both EMS and Man mutants exhibited significantly decreased levels of MBP expression and cytotoxicity to HBMEC, but showed similar levels of binding to HBMEC, as compared with the wild type. Of interest was that the exogenous mannose inhibited amoebae (i.e., Man mutant) binding to the HBMEC by <20%. Only the mutant Man exhibited a significant decrease in bacterial uptake, as compared to the wild type, 0.020 vs 0.032 (p<0.05) and proteolytic activity. The results showed that MBP should be clearly provided as the pathogenic target candidate, to further target-based therapy, but EMS mutation should not be associated with initial adhesion and phagocytosis of A. castellanii.

  6. Molecular Dynamics Simulations of the Roller Nanoimprint Process: Adhesion and Other Mechanical Characteristics

    Directory of Open Access Journals (Sweden)

    Fang Te-Hua

    2009-01-01

    Full Text Available Abstract Molecular dynamics simulations using tight-binding many body potential are carried out to study the roller imprint process of a gold single crystal. The effect of the roller tooth’s taper angle, imprint depth, imprint temperature, and imprint direction on the imprint force, adhesion, stress distribution, and strain are investigated. A two-stage roller imprint process was obtained from an imprint force curve. The two-stage imprint process included the imprint forming with a rapid increase of imprint force and the unloading stage combined with the adhesion stage. The results show that the imprint force and adhesion rapidly increase with decreasing taper angle and increasing imprint depth. The magnitude of the maximum imprint force and the time at which this maximum occurs are proportional to the imprint depth, but independent of the taper angle. In a comparison of the imprint mechanisms with a vertical imprint case, while high stress and strain regions are concentrated below the mold for vertical imprint, they also occur around the mold in the case of roller imprint. The regions were only concentrated on the substrate atoms underneath the mold in vertical imprint. Plastic flow increased with increasing imprint temperature.

  7. Staphylococcus aureus-fibronectin interactions with and without fibronectin-binding proteins and their role in adhesion and desorption

    NARCIS (Netherlands)

    Xu, Chun; Boks, Niels P; de Vries, Jacob; Kaper, Harm; Norde, Willem; Busscher, Hendrik; van der Mei, Henderina

    2008-01-01

    Adhesion and residence-time-dependent desorption of two Staphylococcus aureus strains with and without fibronectin (Fn) binding proteins (FnBPs) on Fn-coated glass were compared under flow conditions. To obtain a better understanding of the role of Fn-FnBP binding, the adsorption enthalpies of Fn wi

  8. Staphylococcus aureus-Fibronectin Interactions with and without Fibronectin-Binding Proteins and Their Role in Adhesion and Desorption

    NARCIS (Netherlands)

    Xu, C.P.; Boks, N.P.; Vries, de J.; Kaper, H.J.; Norde, W.; Busscher, H.J.; Mei, van der H.C.

    2008-01-01

    Adhesion and residence-time-dependent desorption of two Staphylococcus aureus strains with and without fibronectin (Fn) binding proteins (FnBPs) on Fn-coated glass were compared under flow conditions. To obtain a better understanding of the role of Fn-FnBP binding, the adsorption enthalpies of Fn wi

  9. Fucan inhibits Chinese hamster ovary cell (CHO) adhesion to fibronectin by binding to the extracellular matrix.

    Science.gov (United States)

    Rocha, Hugo A; Franco, Célia R; Trindade, Edvaldo S; Veiga, Silvio S; Leite, Edda L; Nader, Helena B; Dietrich, Carl P

    2005-07-01

    In recent years, sulfated fucans have emerged as an important class of natural biopolymers. In this study, the anti-adhesive activity of a fucan from the brown seaweed Spatoglossum schröederi was analyzed using tumorigenic cells: wild-type Chinese hamster ovary cells (CHO-K1) and the mutant type deficient in xylosyltransferase (CHO-745). Fibronectin (FN) was used as substrate for cell attachment. For both cell types, this fucan has shown a dose-dependent anti-adhesive effect, reaching saturation at around 400 mug/mL. This effect was abolished by desulfation of the fucan. In addition, this polymer exhibited the highest inhibitory effect in comparison to other sulfated polysaccharides. The fucan was biotinylated and used as a probe to identify its action sites. Biotinylated fucan was detected in the extracellular matrix environment by confocal microscopy and flow cytometric analysis, but not at the cell surface. The results suggest that the fucan shows anti-adhesive activity by binding directly to FN, and blocking FN sites that are recognized by cell surface ligands, possibly the integrin family.

  10. Adhesive and migratory effects of phosphophoryn are modulated by flanking peptides of the integrin binding motif.

    Directory of Open Access Journals (Sweden)

    Shigeki Suzuki

    Full Text Available Phosphophoryn (PP is generated from the proteolytic cleavage of dentin sialophosphoprotein (DSPP. Gene duplications in the ancestor dentin matrix protein-1 (DMP-1 genomic sequence created the DSPP gene in toothed animals. PP and DMP-1 are phosphorylated extracellular matrix proteins that belong to the family of small integrin-binding ligand N-linked glycoproteins (SIBLINGs. Many SIBLING members have been shown to evoke various cell responses through the integrin-binding Arg-Gly-Asp (RGD domain; however, the RGD-dependent function of PP is not yet fully understood. We demonstrated that recombinant PP did not exhibit any obvious cell adhesion ability, whereas the simultaneously purified recombinant DMP-1 did. A cell adhesion inhibitory analysis was performed by pre-incubating human osteosarcoma MG63 cells with various PP peptides before seeding onto vitronectin. The results obtained revealed that the incorporation of more than one amino acid on both sides of the PP-RGD domain was unable to inhibit the adhesion of MG63 cells onto vitronectin. Furthermore, the inhibitory activity of a peptide containing the PP-RGD domain with an open carboxyl-terminal side (H-463SDESDTNSESANESGSRGDA482-OH was more potent than that of a peptide containing the RGD domain with an open amino-terminal side (H-478SRGDASYTSDESSDDDNDSDSH499-OH. This phenomenon was supported by the potent cell adhesion and migration abilities of the recombinant truncated PP, which terminated with Ala482. Furthermore, various point mutations in Ala482 and/or Ser483 converted recombinant PP into cell-adhesive proteins. Therefore, we concluded that the Ala482-Ser483 flanking sequence, which was detected in primates and mice, was the key peptide bond that allowed the PP-RGD domain to be sequestered. The differential abilities of PP and DMP-1 to act on integrin imply that DSPP was duplicated from DMP-1 to serve as a crucial extracellular protein for tooth development rather than as an integrin

  11. Scaffold-forming and Adhesive Contributions of Synthetic Laminin-binding Proteins to Basement Membrane Assembly.

    Science.gov (United States)

    McKee, Karen K; Capizzi, Stephanie; Yurchenco, Peter D

    2009-03-27

    Laminins that possess three short arms contribute to basement membrane assembly by anchoring to cell surfaces, polymerizing, and binding to nidogen and collagen IV. Although laminins containing the alpha4 and alpha5 subunits are expressed in alpha2-deficient congenital muscular dystrophy, they may be ineffective substitutes because they bind weakly to cell surfaces and/or because they lack the third arm needed for polymerization. We asked whether linker proteins engineered to bind to deficient laminins that provide such missing activities would promote basement membrane assembly in a Schwann cell model. A chimeric fusion protein (alphaLNNd) that adds a short arm terminus to laminin through the nidogen binding locus was generated and compared with the dystrophy-ameliorating protein miniagrin (mAgrin) that binds to the laminin coiled-coil dystroglycan and sulfatides. alphaLNNd was found to mediate laminin binding to collagen IV, to bind to galactosyl sulfatide, and to selectively convert alpha-short arm deletion-mutant laminins LmDeltaalphaLN and LmDeltaalphaLN-L4b into polymerizing laminins. This protein enabled polymerization-deficient laminin but not an adhesion-deficient laminin lacking LG domains (LmDeltaLG) to assemble an extracellular matrix on Schwann cell surfaces. mAgrin, on the other hand, enabled LmDeltaLG to form an extracellular matrix on cell surfaces without increasing accumulation of non-polymerizing laminins. These gain-of-function studies reveal distinct polymerization and anchorage contributions to basement membrane assembly in which the three different LN domains mediate the former, and the LG domains provide primary anchorage with secondary contributions from the alphaLN domain. These findings may be relevant for an understanding of the pathogenesis and treatment of laminin deficiency states.

  12. The mechanics of the adhesive locomotion of terrestrial gastropods.

    Science.gov (United States)

    Lai, Janice H; del Alamo, Juan C; Rodríguez-Rodríguez, Javier; Lasheras, Juan C

    2010-11-15

    Research on the adhesive locomotion of terrestrial gastropods is gaining renewed interest as it provides a source of guidance for the design of soft biomimetic robots that can perform functions currently not achievable by conventional rigid vehicles. The locomotion of terrestrial gastropods is driven by a train of periodic muscle contractions (pedal waves) and relaxations (interwaves) that propagate from their tails to their heads. These ventral waves interact with a thin layer of mucus secreted by the animal that transmits propulsive forces to the ground. The exact mechanism by which these propulsive forces are generated is still a matter of controversy. Specifically, the exact role played by the complex rheological and adhesive properties of the mucus is not clear. To provide quantitative data that could shed light on this question, we use a newly developed technique to measure, with high temporal and spatial resolution, the propulsive forces that terrestrial gastropods generate while crawling on smooth flat surfaces. The traction force measurements demonstrate the importance of the finite yield stress of the mucus in generating thrust and are consistent with the surface of the ventral foot being lifted with the passage of each pedal wave. We also show that a forward propulsive force is generated beneath each stationary interwave and that this net forward component is balanced by the resistance caused by the outer rim of the ventral foot, which slides at the speed of the center of mass of the animal. Simultaneously, the animal pulls the rim laterally inward. Analysis of the traction forces reveals that the kinematics of the pedal waves is far more complex than previously thought, showing significant spatial variation (acceleration/deceleration) as the waves move from the tail to the head of the animal.

  13. Hierarchical macroscopic fibrillar adhesives: in situ study of buckling and adhesion mechanisms on wavy substrates.

    Science.gov (United States)

    Bauer, Christina T; Kroner, Elmar; Fleck, Norman A; Arzt, Eduard

    2015-12-01

    Nature uses hierarchical fibrillar structures to mediate temporary adhesion to arbitrary substrates. Such structures provide high compliance such that the flat fibril tips can be better positioned with respect to asperities of a wavy rough substrate. We investigated the buckling and adhesion of hierarchically structured adhesives in contact with flat smooth, flat rough and wavy rough substrates. A macroscopic model for the structural adhesive was fabricated by molding polydimethylsiloxane into pillars of diameter in the range of 0.3-4.8 mm, with up to three different hierarchy levels. Both flat-ended and mushroom-shaped hierarchical samples buckled at preloads one quarter that of the single level structures. We explain this behavior by a change in the buckling mode; buckling leads to a loss of contact and diminishes adhesion. Our results indicate that hierarchical structures can have a strong influence on the degree of adhesion on both flat and wavy substrates. Strategies are discussed that achieve highly compliant substrates which adhere to rough substrates.

  14. Evaluation of adhesive bond Young's modulus during crosslinking using a mechanical method and an ultrasound method

    Science.gov (United States)

    Mascaro, B.; Budzik, M. K.; Castaings, M.; Jumel, J.; Shanahan, M. E. R.

    2012-03-01

    The strength and stability of adhesive bonded structures are related to polymer curing, when crosslinking occurs and leads to adhesive strength, stiffness and durability. Depending on the resin and curing agent used, cure time can vary from minutes to weeks. Methods based on dynamic mechanical analysis (DMA) or calorimetric techniques (DSC, DTA) are valuable for evaluating mechanical properties of adhesives, but are devoted specifically to the polymers alone, and not in situ in adhesive bonds. In this contribution, we have monitored - during crosslinking - the Young's modulus of a slow-curing DGEBA - PAMAM adhesive system, with two non-destructive, in situ, methods used for the characterisation of the adhesive in a bonded system. The first method is based on measurements obtained from strain gauges mounted on one bonded adherend. The second method uses an ultrasound technique based on the through-transmission. Both methods suggest the same curing kinetics.

  15. Adhesion functions in cell sorting by mechanically coupling the cortices of adhering cells.

    Science.gov (United States)

    Maître, Jean-Léon; Berthoumieux, Hélène; Krens, Simon Frederik Gabriel; Salbreux, Guillaume; Jülicher, Frank; Paluch, Ewa; Heisenberg, Carl-Philipp

    2012-10-12

    Differential cell adhesion and cortex tension are thought to drive cell sorting by controlling cell-cell contact formation. Here, we show that cell adhesion and cortex tension have different mechanical functions in controlling progenitor cell-cell contact formation and sorting during zebrafish gastrulation. Cortex tension controls cell-cell contact expansion by modulating interfacial tension at the contact. By contrast, adhesion has little direct function in contact expansion, but instead is needed to mechanically couple the cortices of adhering cells at their contacts, allowing cortex tension to control contact expansion. The coupling function of adhesion is mediated by E-cadherin and limited by the mechanical anchoring of E-cadherin to the cortex. Thus, cell adhesion provides the mechanical scaffold for cell cortex tension to drive cell sorting during gastrulation.

  16. Nano-mechanics of Tunable Adhesion using Non Covalent Forces

    Energy Technology Data Exchange (ETDEWEB)

    Kenneth Liechti

    2012-09-08

    The objective of this program was to examine, via experiment and atomistic and continuum analysis, coordinated noncovalent bonding over a range of length scales with a view to obtaining modulated, patterned and reversible bonding at the molecular level. The first step in this project was to develop processes for depositing self-assembled monolayers (SAMs) bearing carboxylic acid and amine moieties on Si (111) surfaces and probe tips of an interfacial force microscope (IFM). This allowed the adhesive portion of the interactions between functionalized surfaces to be fully captured in the force-displacement response (force profiles) that are measured by the IFM. The interactionswere extracted in the form of traction-separation laws using combined molecular and continuum stress analyses. In this approach, the results of molecular dynamics analyses of SAMs subjected to simple stress states are used to inform continuum models of their stress-strain behavior. Continuum analyses of the IFM experiment were then conducted, which incorporate the stress-strain behavior of the SAMs and traction-separation relations that represent the interactions between the tip and functionalized Si surface. Agreement between predicted and measured force profiles was taken to imply that the traction-separation relations have been properly extracted. Scale up to larger contact areas was considered by forming Si/SAM/Si sandwiches and then separating them via fracture experiments. The mode 1 traction-separation relations have been extracted using fracture mechanics concepts under mode 1 and mixed-mode conditions. Interesting differences were noted between the three sets of traction-separation relations.

  17. Lactobacillus Adhesion to Mucus

    Directory of Open Access Journals (Sweden)

    Maxwell L. Van Tassell

    2011-05-01

    Full Text Available Mucus provides protective functions in the gastrointestinal tract and plays an important role in the adhesion of microorganisms to host surfaces. Mucin glycoproteins polymerize, forming a framework to which certain microbial populations can adhere, including probiotic Lactobacillus species. Numerous mechanisms for adhesion to mucus have been discovered in lactobacilli, including partially characterized mucus binding proteins. These mechanisms vary in importance with the in vitro models studied, which could significantly affect the perceived probiotic potential of the organisms. Understanding the nature of mucus-microbe interactions could be the key to elucidating the mechanisms of probiotic adhesion within the host.

  18. Improvement of mechanical properties of polylactic acid adhesion joints with bio-based adhesives by using air atmospheric plasma treatment

    OpenAIRE

    Jordá Vilaplana, Amparo; Sánchez Nacher, Lourdes; Fombuena Borrás, Vicent; García García, Daniel; Carbonell Verdú, Alfredo

    2015-01-01

    The packaging industry generates a high volume of wastes; so that, there is a high demand of biodegradable materials, which do not damage the environment. Nowadays, there is an interesting consumption of polylactic acid (PLA) due to its biodegradable features. This work focuses on the improvement of mechanical properties of PLA adhesion joints for uses in the packaging industry. In order to achieve that purpose, atmospheric plasma treatment is used to selectively modify PLA surface properties...

  19. Biotin-conjugated anti-CD44 antibody-avidin binding system for the improvement of chondrocyte adhesion to scaffolds.

    Science.gov (United States)

    Lin, Hong; Zhou, Jian; Shen, Longxiang; Ruan, Yuhui; Dong, Jian; Guo, Changan; Chen, Zhengrong

    2014-04-01

    The clinical need for improved treatment options for patients with cartilage injuries has motivated tissue-engineering studies aimed at the in vitro generation of cell-based implants with functional properties. The success of tissue-engineered repair of cartilage may depend on the rapid and efficient adhesion of transplanted cells to the scaffold. In the present study, chondrocyte-scaffold constructs were engineered by planting porcine chondrocytes into nonporous chitosan membranes and 3D porous chitosan scaffolds that were treated with or without biotin-conjugated anti-CD44 antibody-avidin binding system and avidin-biotin binding system. The spreading area, cell exfoliation rates, cell proliferation rates, histological analysis, DNA and glycosaminoglycan (GAG) content, and mRNA expression were investigated to evaluate the efficiency of biotin-conjugated anti-CD44 antibody-avidin binding system for the improvement of cell adhesion to scaffolds in the cartilage tissue. The results showed that the biotin-conjugated anti-CD44 antibody-avidin binding system improved cell adhesion to scaffolds effectively. These studies suggest that this binding system has the potential to provide improved tissue-engineered cartilage for clinical applications.

  20. A synthetic peptide from the COOH-terminal heparin-binding domain of fibronectin promotes focal adhesion formation

    DEFF Research Database (Denmark)

    Woods, A; McCarthy, J B; Furcht, L T;

    1993-01-01

    of focal adhesion and stress fiber formation requires additional interactions. Heparin-binding fragments of fibronectin can provide this signal. The COOH-terminal heparin-binding domain of fibronectin contains five separate heparin-binding amino acid sequences. We show here that all five sequences...... PRARI. The biological response to this peptide and to the COOH-terminal fragment may be mediated through cell surface heparan sulfate proteoglycans because treatment of cells with heparinase II and III, or competition with heparin, reduces the response. Treatment with chondroitinase ABC or competition...

  1. The use of micromachined structures for the management of mechanical properties and adhesion of thin films

    Science.gov (United States)

    Mehregamy, Mehran; Allen, Mark G.; Senturia, Stephen D.

    The application of silicon micromachining to the measurement of mechanical properties of thin films such as intrinsic stress, Young's modulus, and adhesion is presented. The measurement is based on the deflection and subsequent peeling of suspended membrane sections of the film. The goal was to make a quantitatively reproducible adhesion test by applying micromachining techniques to the blister peel test described by Hinkley. The initial measurements demonstrated the importance of residual stress in the films, which resulted in an expanded emphasis on the basic mechanical properties of the membrane as a prelude to accurate adhesion measurements. The process for micromachining suspended membranes is discussed along with the theory leading to the determination of mechanical properties of the films, the results, and the present status of the adhesion work.

  2. Influence of the Hardener Proportion on Mechanical Properties of Adhesive Bonds Used in Agriculture

    Directory of Open Access Journals (Sweden)

    Valášek P.

    2015-01-01

    Full Text Available Joining materials by adhesive bonding is used across all industrial branches. The occurrence of adhesive bonds in machine constructions is still more frequent because of the development of adhesives which are able to meet various requirements of designers. This trend is observable also in agriculture - in the construction of agricultural machines. There even exists a cooperation between the companies developing the adhesives and the agricultural machines producers. The production process of machines and equipment must consider a required production tact. Adhesives and the process of their hardening have to meet these requirements. In the sphere of agriculture, epoxy resins hardening based either on hardeners or heating are used. Mechanical properties of two-component epoxy resins depending on variable amount of the hardener starting crosslinking of these reactoplastics are described.

  3. Mechanics of the Adhesive Properties of Ivy Nanoparticles

    Science.gov (United States)

    2013-11-21

    substrates, due to their inherent low viscosity. Driven by the water evaporation , ivy nanoparticles adjusted their shapes to form a film . Pectic...based adhesive secretion produced by ivy rootlets for surface affixing and climbing . Both experimental and theoretical studies will be conducted...rootlets for surface affixing and climbing . Both experimental and theoretical studies will be conducted. More generally, we aim to use insight from

  4. Mechanical Properties and Adhesion of a Micro Structured Polymer Blend

    Directory of Open Access Journals (Sweden)

    Brunero Cappella

    2011-07-01

    Full Text Available A 50:50 blend of polystyrene (PS and poly(n-butyl methacrylate (PnBMA has been characterized with an Atomic Force Microscope (AFM in Tapping Mode and with force-distance curves. The polymer solution has been spin-coated on a glass slide. PnBMA builds a uniform film on the glass substrate with a thickness of @200 nm. On top of it, the PS builds an approximately 100 nm thick film. The PS-film undergoes dewetting, leading to the formation of holes surrounded by about 2 µm large rims. In those regions of the sample, where the distance between the holes is larger than about 4 µm, light depressions in the PS film can be observed. Topography, dissipated energy, adhesion, stiffness and elastic modulus have been measured on these three regions (PnBMA, PS in the rims and PS in the depressions. The two polymers can be distinguished in all images, since PnBMA has a higher adhesion and a smaller stiffness than PS, and hence a higher dissipated energy. Moreover, the polystyrene in the depressions shows a very high adhesion (approximately as high as PnBMA and its stiffness is intermediate between that of PnBMA and that of PS in the rims. This is attributed to higher mobility of the PS chains in the depressions, which are precursors of new holes.

  5. Cell adhesion-dependent membrane trafficking of a binding partner for the ebolavirus glycoprotein is a determinant of viral entry.

    Science.gov (United States)

    Dube, Derek; Schornberg, Kathryn L; Shoemaker, Charles J; Delos, Sue E; Stantchev, Tzanko S; Clouse, Kathleen A; Broder, Christopher C; White, Judith M

    2010-09-21

    Ebolavirus is a hemorrhagic fever virus associated with high mortality. Although much has been learned about the viral lifecycle and pathogenesis, many questions remain about virus entry. We recently showed that binding of the receptor binding region (RBR) of the ebolavirus glycoprotein (GP) and infection by GP pseudovirions increase on cell adhesion independently of mRNA or protein synthesis. One model to explain these observations is that, on cell adhesion, an RBR binding partner translocates from an intracellular vesicle to the cell surface. Here, we provide evidence for this model by showing that suspension 293F cells contain an RBR binding site within a membrane-bound compartment associated with the trans-Golgi network and microtubule-organizing center. Consistently, trafficking of the RBR binding partner to the cell surface depends on microtubules, and the RBR binding partner is internalized when adherent cells are placed in suspension. Based on these observations, we reexamined the claim that lymphocytes, which are critical for ebolavirus pathogenesis, are refractory to infection because they lack an RBR binding partner. We found that both cultured and primary human lymphocytes (in suspension) contain an intracellular pool of an RBR binding partner. Moreover, we identified two adherent primate lymphocytic cell lines that bind RBR at their surface and strikingly, support GP-mediated entry and infection. In summary, our results reveal a mode of determining viral entry by a membrane-trafficking event that translocates an RBR binding partner to the cell surface, and they suggest that this process may be operative in cells important for ebolavirus pathogenesis (e.g., lymphocytes and macrophages).

  6. Rho-kinase regulates adhesive and mechanical mechanisms of pulmonary recruitment of neutrophils in abdominal sepsis.

    Science.gov (United States)

    Palani, Karzan; Rahman, Milladur; Hasan, Zirak; Zhang, Su; Qi, Zhongquan; Jeppsson, Bengt; Thorlacius, Henrik

    2012-05-05

    We hypothesized that Rho-kinase signaling plays a role in mechanical and adhesive mechanisms of neutrophil accumulation in lung. Male C57BL/6 mice were treated with the Rho-kinase inhibitor Y-27632 prior to cecal ligation and puncture (CLP). Lung levels of myeloperoxidase (MPO) and histological tissue damage were determined 6h and 24h after CLP. Expression of Mac-1 and F-actin formation in neutrophils were quantified by using flow cytometry 6h after CLP. Mac-1 expression and F-actin formation were also determined in isolated neutrophils up to 3h after stimulation with CXCL2. Labeled and activated neutrophils co-incubated with Y-27632, an anti-Mac-1 antibody and cytochalasin B were adoptively transferred to CLP mice. Y-27632 reduced the CLP-induced pulmonary injury and MPO activity as well as Mac-1 on neutrophils. Neutrophil F-actin formation peaked at 6h and returned to baseline levels 24h after CLP induction. Rho-kinase inhibition decreased CLP-provoked F-actin formation in neutrophils. CXCL2 rapidly increased Mac-1 expression and F-actin formation in neutrophils. Co-incubation with Y-27632 abolished CXCL2-induced Mac-1 up-regulation and formation of F-actin in neutrophils. Notably, co-incubation with cytochalasin B inhibited formation of F-actin but did not reduce Mac-1 expression on activated neutrophils. Adoptive transfer experiments revealed that co-incubation of neutrophils with the anti-Mac-1 antibody or cytochalasin B significantly decreased pulmonary accumulation of neutrophils in septic mice. Our data show that targeting Rho-kinase effectively reduces neutrophil recruitment and tissue damage in abdominal sepsis. Moreover, these findings demonstrate that Rho-kinase-dependent neutrophil accumulation in septic lung injury is regulated by both adhesive and mechanical mechanisms.

  7. Cellular and molecular investigations of the adhesion and mechanics of Listeria monocytogenes

    Science.gov (United States)

    Eskhan, Asma Omar

    Atomic force microscopy has been used to quantify the adherence and mechanical properties of an array of L. monocytogenes strains and their surface biopolymers. First, eight L. monocytogenes strains that represented the two major lineages of the species were compared for their adherence and mechanics at cellular and molecular levels. Our results indicated that strains of lineage' II were characterized by higher adhesion and Young's moduli, longer and more rigid surface biopolymers and lower specific and nonspecific forces when compared to lineage' I strains. Additionally, adherence and mechanical properties of eight L. monocytogenes epidemic and environmental strains were probed. Our results pointed to that environmental and epidemic strains representative of a given lineage were similar in their adherence and mechanical properties when investigated at a cellular level. However, when the molecular properties of the strains were considered, epidemic strains were characterized by higher specific and nonspecific forces, shorter, denser and more flexible biopolymers compared to environmental strains. Second, the role of environmental pH conditions of growth on the adhesion and mechanics of a pathogenic L. monocytogenes EGDe was investigated. Our results pointed to a transition in the adhesion energies for cells cultured at pH 7. In addition, when the types of molecular forces that govern the adhesion were quantified using Poisson statistical approach and using a new proposed method, specific hydrogen-bond energies dominated the bacterial adhesion process. Such a finding is instrumental to researchers designing methods to control bacterial adhesion. Similarly, bacterial cells underwent a transition in their mechanical properties. We have shown that cells cultured at pH 7 were the most rigid compared to those cultured in lower or higher pH conditions of growth. Due to transitions observed in adherence and mechanics when cells were cultured at pH 7, we hypothesized that

  8. A New Self-Loading Locomotion Mechanism for Wall Climbing Robots Employing Biomimetic Adhesives

    Institute of Scientific and Technical Information of China (English)

    Amirpasha Peyvandi; Parviz Soroushian; Jue Lu

    2013-01-01

    A versatile locomotion mechanism is introduced and experimentally verified.This mechanism comprises four rectangular wheels (legs) with rotational phase difference which enables the application of pressure to each contacting surface for securing it to the surface using bio-inspired or pressure-sensitive adhesives.In this mechanism,the adhesives are applied to two rigid plates attached to each wheel via hinges incorporating torsional springs.The springs force the plates back to their original position after the contact with the surface is lost in the course of locomotion.The wheels are made of low-modulus elastomers,and the pressure applied during contact is controlled by the elastic modulus,geometry and phase difference of wheels.This reliable adhesion system does not rely upon gravity for adhering to surfaces,and provides the locomotion mechanism with the ability to climb walls and transition from horizontal to vertical surfaces.

  9. The fibronectin-binding integrins alpha5beta1 and alphavbeta3 differentially modulate RhoA-GTP loading, organization of cell matrix adhesions, and fibronectin fibrillogenesis

    DEFF Research Database (Denmark)

    Danen, Erik H J; Sonneveld, Petra; Brakebusch, Cord

    2002-01-01

    We have studied the formation of different types of cell matrix adhesions in cells that bind to fibronectin via either alpha5beta1 or alphavbeta3. In both cases, cell adhesion to fibronectin leads to a rapid decrease in RhoA activity. However, alpha5beta1 but not alphavbeta3 supports high levels...... receptors expressed on a cell dictates the ability of fibronectin to stimulate RhoA-mediated organization of cell matrix adhesions....

  10. Biofilm formation and binding specificities of CFA/I, CFA/II and CS2 adhesions of Enterotoxigenic Escherichia coli and CfaE-R181A mutant

    Directory of Open Access Journals (Sweden)

    Iram Liaqat

    2012-09-01

    Full Text Available Enterotoxigenic Escherichia coli (ETEC strains are leading causes of childhood diarrhea in developing countries. Adhesion is the first step in pathogenesis of ETEC infections and ETEC pili designated colonization factor antigens (CFAs are believed to be important in the biofim formation, colonization and host cell adhesions. As a first step, we have determined the biofilm capability of ETEC expressing various types of pili (CFA/I, CfaE-R181A mutant/ CfaE tip mutant, CFA/II and CS2. Further, enzyme-linked immunosorbent assay (ELISA assay were developed to compare the binding specificity of CFA/I, CFA/II (CS1 - CS3 and CS2 of ETEC, using extracted pili and piliated bacteria. CFA/II strain (E24377a as well as extracted pili exhibited significantly higher binding both in biofilm and ELISA assays compared to non piliated wild type E24377a, CFA/I and CS2 strains. This indicates that co-expression of two or more CS2 in same strain is more efficient in increasing adherence. Significant decrease in binding specificity of DH5αF'lacIq/∆cotD (CS2 strain and MC4100/pEU2124 (CfaE-R181A mutant strain indicated the important contribution of tip proteins in adherence assays. However, CS2 tip mutant strain (DH5αF'lacIq/pEU5881 showed that this specific residue may not be important as adhesions in these strains. In summary, our data suggest that pili, their minor subunits are important for biofilm formation and adherence mechanisms. Overall, the functional reactivity of strains co expressing various antigens, particularly minor subunit antigen observed in this study suggest that fewer antibodies may be required to elicit immunity to ETEC expressing a wider array of related pili.

  11. Variation in one residue associated with the metal ion-dependent adhesion site regulates αIIbβ3 integrin ligand binding affinity.

    Directory of Open Access Journals (Sweden)

    Joel Raborn

    Full Text Available The Asp of the RGD motif of the ligand coordinates with the β I domain metal ion dependent adhesion site (MIDAS divalent cation, emphasizing the importance of the MIDAS in ligand binding. There appears to be two distinct groups of integrins that differ in their ligand binding affinity and adhesion ability. These differences may be due to a specific residue associated with the MIDAS, particularly the β3 residue Ala(252 and corresponding Ala in the β1 integrin compared to the analogous Asp residue in the β2 and β7 integrins. Interestingly, mutations in the adjacent to MIDAS (ADMIDAS of integrins α4β7 and αLβ2 increased the binding and adhesion abilities compared to the wild-type, while the same mutations in the α2β1, α5β1, αVβ3, and αIIbβ3 integrins demonstrated decreased ligand binding and adhesion. We introduced a mutation in the αIIbβ3 to convert this MIDAS associated Ala(252 to Asp. By combination of this mutant with mutations of one or two ADMIDAS residues, we studied the effects of this residue on ligand binding and adhesion. Then, we performed molecular dynamics simulations on the wild-type and mutant αIIbβ3 integrin β I domains, and investigated the dynamics of metal ion binding sites in different integrin-RGD complexes. We found that the tendency of calculated binding free energies was in excellent agreement with the experimental results, suggesting that the variation in this MIDAS associated residue accounts for the differences in ligand binding and adhesion among different integrins, and it accounts for the conflicting results of ADMIDAS mutations within different integrins. This study sheds more light on the role of the MIDAS associated residue pertaining to ligand binding and adhesion and suggests that this residue may play a pivotal role in integrin-mediated cell rolling and firm adhesion.

  12. Neuritogenic and survival-promoting effects of the P2 peptide derived from a homophilic binding site in the neural cell adhesion molecule

    DEFF Research Database (Denmark)

    Pedersen, Martin V; Køhler, Lene B; Ditlevsen, Dorte K

    2004-01-01

    The neural cell adhesion molecule (NCAM) plays a pivotal role in neural development, regeneration, and plasticity. NCAM mediates adhesion and subsequent signal transduction through NCAM-NCAM binding. Recently, a peptide ligand termed P2 corresponding to a 12-amino-acid sequence in the FG loop...

  13. A novel role for fibronectin type I domain in the regulation of human hematopoietic cell adhesiveness through binding to follistatin domains of FLRG and follistatin.

    Science.gov (United States)

    Maguer-Satta, Véronique; Forissier, Stéphanie; Bartholin, Laurent; Martel, Sylvie; Jeanpierre, Sandrine; Bachelard, Elodie; Rimokh, Ruth

    2006-02-15

    FLRG and follistatin belong to the family of follistatin proteins involved in the regulation of various biological effects, such as hematopoiesis, mediated by their binding to activin and BMP, both members of the TGFbeta family. To further characterize the function of FLRG, we searched for other possible functional partners using a yeast two-hybrid screen. We identified human fibronectin as a new partner for both FLRG and follistatin. We also demonstrated that their physical interaction is mediated by type I motifs of fibronectin and follistatin domains. We then analyzed the biological consequences of these protein interactions on the regulation of hematopoiesis. For the first time, we associated a biological effect with the regulation of human hematopoietic cell adhesiveness of both the type I motifs of fibronectin and the follistatin domains of FLRG and follistatin. Indeed, we observed a significant and specific dose-dependent increase of cell adhesion to fibronectin in the presence of FLRG or follistatin, using either a human hematopoietic cell line or primary cells. In particular, we observed a significantly increased adhesion of immature hematopoietic precursors (CFC, LTC-IC). Altogether these results highlight a new mechanism by which FLRG and follistatin regulate human hematopoiesis.

  14. Localized mechanics of dentin self-etching adhesive system

    Directory of Open Access Journals (Sweden)

    Rodolfo Bruniera Anchieta

    2007-08-01

    Full Text Available The bond strength of composite resins (CRs to dentin is influenced by the interfacial microstructure of the hybrid layer (HL and the resin tags (TAG. The contemporary self-etching primer adhesive systems overcame the inconvenient of the etch-and-rinse protocol. Studies, however, have demonstrated that HL thickness and TAG length vary according to the wetting time and additional use of acid-etching prior to self-etching primers. This study investigated the localized stress distribution in the HL and the dentin/adhesive interface. Two HL thicknesses (3 or 6 µm, two TAG lengths (13 or 17 µm and two loading conditions (perpendicular and oblique-25º were investigated by the finite element (FE analysis. Five two-dimensional FE models (M of a dentin specimen restored with CR (38 x 64 µm were constructed: M1 - no HL and no TAG; M2 - 3 µm of HL and 13 µm of TAG; M3 - 3 µm of HL and 17 µm of TAG; M4 - 6 µm of HL and 13 µm of TAG; and M5 - 6 µm of HL and 17 µm of TAG. Two distributed loadings (L (20N were applied on CR surface: L1 - perpendicular, and L2 - oblique (25º. Fixed interfacial conditions were assigned on the border of the dentin specimen. Ansys 10.0 (Ansys®, Houston, PA, USA software was used to calculate the stress fields. The peak of von Mises (sigmavM and maximum principal stress (sigmamax was higher in L2 than in L1. Microstructures (HL and TAG had no effect on local stresses for L1. Decreasing HL decreased sigmavM and sigmamax in all structures for L2, but the TAG length had influence only on the peributular dentin. The thickness of HL had more influence on the sigmavM and sigmamax than TAG length. The peritubular dentin and its adjacent structures showed the highest sigmavM and sigmamax, mainly in the oblique loading.

  15. Mechanical integrity and adhesion of thin films for applications in electronics packaging and cell biology

    Energy Technology Data Exchange (ETDEWEB)

    Duan Jin; Wan Kaitak; Chian Kermsin

    2003-01-22

    A new theoretical model was developed for a pull-off adhesion test using an axisymmetric flat punch and a rectangular flat punch adhered to a thin polymer film interface. An elastic solution was derived to portray the mechanical integrity of the thin film. A mechanical energy release rate was calculated numerically. As the punch was pulled away from the adhered film, the film deformed under mixed bending and stretching. Both stiffness and thickness of the film were allowed to vary. The derived solid-film 'pull-off' events sharply contrast with the abrupt pull-off in solid-solid adhesion as predicted by the classical JKR theory.

  16. Substrate, focal adhesions, and actin filaments: a mechanical unit with a weak spot for mechanosensitive proteins

    Science.gov (United States)

    Kirchenbüchler, David; Born, Simone; Kirchgeßner, Norbert; Houben, Sebastian; Hoffmann, Bernd; Merkel, Rudolf

    2010-05-01

    Mechanosensing is a vital prerequisite for dynamic remodeling of focal adhesions and cytoskeletal structures upon substrate deformation. For example, tissue formation, directed cell orientation or cell differentiation are regulated by such mechanosensing processes. Focal adhesions and the actin cytoskeleton are believed to be involved in these processes, but where mechanosensing molecules are located and how elastic substrate, focal adhesions and the cytoskeleton couple with each other upon substrate deformation still remains obscure. To approach these questions we have developed a sensitive method to apply defined spatially decaying deformation fields to cells cultivated on ultrasoft elastic substrates and to accurately quantify the resulting displacements of the actin cytoskeleton, focal adhesions, as well as the substrate. Displacement fields were recorded in live cell microscopy by tracking either signals from fluorescent proteins or marker particles in the substrate. As model cell type we used myofibroblasts. These cells are characterized by highly stable adhesion and force generating structures but are still able to detect mechanical signals with high sensitivity. We found a rigid connection between substrate and focal adhesions. Furthermore, stress fibers were found to be barely extendable almost over their whole lengths. Plastic deformation took place only at the very ends of actin filaments close to focal adhesions. As a result, this area became elongated without extension of existing actin filaments by polymerization. Both ends of the stress fibers were mechanically coupled with detectable plastic deformations on either site. Interestingly, traction force dependent substrate deformation fields remained mostly unaffected even when stress fiber elongations were released. These data argue for a location of mechanosensing proteins at the ends of actin stress fibers and describe, except for these domains, the whole system to be relatively rigid for tensile

  17. Engagement of major histocompatibility complex class I and class II molecules up-regulates intercellular adhesion of human B cells via a CD11/CD18-independent mechanism.

    Science.gov (United States)

    Alcover, A; Juillard, V; Acuto, O

    1992-02-01

    We have studied the role of major histocompatibility complex (MHC) molecules in the regulation of intercellular adhesion of human B cells. We found that molecules able to bind to MHC class II molecules, such as monoclonal antibodies or staphylococcal enterotoxins, induced rapid and sustained homotypic adhesion of Epstein-Barr virus (EBV)-transformed B cell lines as well as peripheral blood B lymphocytes. Moreover, anti-MHC class I monoclonal antibodies also stimulated intercellular adherence. Adhesion induced upon MHC engagement was faster and stronger than that triggered by phorbol esters. It needed active metabolism, but divalent cations were not required. Monoclonal antibodies directed against LFA-1 (CD11a/CD18) or its ligand ICAM-1 (CD54) did not inhibit MHC class II-induced homotypic adhesion of various EBV-transformed B cell lines, nor of a variant of the B cell line Raji expressing very low LFA-1 surface levels. Moreover, EBV-transformed B cells from a severe lymphocyte adhesion deficiency patient, lacking surface CD11/CD18, also aggregated in response to anti-MHC class I or class II monoclonal antibodies. Together these data indicate that engagement of MHC molecules may transduce signals to B cells resulting in up-regulation of intercellular adhesion, via an LFA-1-independent mechanism. This may play a role in the stabilization of T cell/antigen-presenting cell conjugates at the moment of antigen recognition.

  18. Photorhabdus adhesion modification protein (Pam) binds extracellular polysaccharide and alters bacterial attachment

    LENUS (Irish Health Repository)

    Jones, Robert T

    2010-05-12

    Abstract Background Photorhabdus are Gram-negative nematode-symbiotic and insect-pathogenic bacteria. The species Photorhabdus asymbiotica is able to infect humans as well as insects. We investigated the secreted proteome of a clinical isolate of P. asymbiotica at different temperatures in order to identify proteins relevant to the infection of the two different hosts. Results A comparison of the proteins secreted by a clinical isolate of P. asymbiotica at simulated insect (28°C) and human (37°C) temperatures led to the identification of a small and highly abundant protein, designated Pam, that is only secreted at the lower temperature. The pam gene is present in all Photorhabdus strains tested and shows a high level of conservation across the whole genus, suggesting it is both ancestral to the genus and probably important to the biology of the bacterium. The Pam protein shows limited sequence similarity to the 13.6 kDa component of a binary toxin of Bacillus thuringiensis. Nevertheless, injection or feeding of heterologously produced Pam showed no insecticidal activity to either Galleria mellonella or Manduca sexta larvae. In bacterial colonies, Pam is associated with an extracellular polysaccharide (EPS)-like matrix, and modifies the ability of wild-type cells to attach to an artificial surface. Interestingly, Surface Plasmon Resonance (SPR) binding studies revealed that the Pam protein itself has adhesive properties. Although Pam is produced throughout insect infection, genetic knockout does not affect either insect virulence or the ability of P. luminescens to form a symbiotic association with its host nematode, Heterorhabditis bacteriophora. Conclusions We studied a highly abundant protein, Pam, which is secreted in a temperature-dependent manner in P. asymbiotica. Our findings indicate that Pam plays an important role in enhancing surface attachment in insect blood. Its association with exopolysaccharide suggests it may exert its effect through mediation of

  19. Photorhabdus adhesion modification protein (Pam binds extracellular polysaccharide and alters bacterial attachment

    Directory of Open Access Journals (Sweden)

    Joyce Susan A

    2010-05-01

    Full Text Available Abstract Background Photorhabdus are Gram-negative nematode-symbiotic and insect-pathogenic bacteria. The species Photorhabdus asymbiotica is able to infect humans as well as insects. We investigated the secreted proteome of a clinical isolate of P. asymbiotica at different temperatures in order to identify proteins relevant to the infection of the two different hosts. Results A comparison of the proteins secreted by a clinical isolate of P. asymbiotica at simulated insect (28°C and human (37°C temperatures led to the identification of a small and highly abundant protein, designated Pam, that is only secreted at the lower temperature. The pam gene is present in all Photorhabdus strains tested and shows a high level of conservation across the whole genus, suggesting it is both ancestral to the genus and probably important to the biology of the bacterium. The Pam protein shows limited sequence similarity to the 13.6 kDa component of a binary toxin of Bacillus thuringiensis. Nevertheless, injection or feeding of heterologously produced Pam showed no insecticidal activity to either Galleria mellonella or Manduca sexta larvae. In bacterial colonies, Pam is associated with an extracellular polysaccharide (EPS-like matrix, and modifies the ability of wild-type cells to attach to an artificial surface. Interestingly, Surface Plasmon Resonance (SPR binding studies revealed that the Pam protein itself has adhesive properties. Although Pam is produced throughout insect infection, genetic knockout does not affect either insect virulence or the ability of P. luminescens to form a symbiotic association with its host nematode, Heterorhabditis bacteriophora. Conclusions We studied a highly abundant protein, Pam, which is secreted in a temperature-dependent manner in P. asymbiotica. Our findings indicate that Pam plays an important role in enhancing surface attachment in insect blood. Its association with exopolysaccharide suggests it may exert its effect

  20. Adhesion and anti-adhesion of viscous fluids on solid surfaces--a study of ink transfer mechanism in waterless offset printing.

    Science.gov (United States)

    Shen, Wei; Mao, Yu; Murray, Gerard; Tian, Junfei

    2008-02-15

    The transfer of a liquid under dynamic conditions onto a solid surface relies on wetting/adhesion under transient external forces. We found the phenomena associated with forced wetting and dewetting could not be explained by thermodynamic approaches which are based on surface energy and work of adhesion. This is because these approaches do not take account of the dynamic nature of the forced wetting and dewetting. This study uses ink transfer in waterless offset printing as an example to present a new understanding of adhesion and anti-adhesion of a liquid to a solid surface under dynamic conditions. We focus on the adhesion strength, instead of work of adhesion, at the ink-plate interface and experimentally quantified ink adhesion forces on the image and non-image areas of the printing plate. Based on adhesion force measurements we proposed that the formation of a weak boundary layer and/or the softening the non-image area due to solvent swelling are likely to be the mechanisms that causes ink refusal on the non-image area. AFM images are presented to show changes of the non-image surface before and after contacting with ink.

  1. Mechanics of load-drag-unload contact cleaning of gecko-inspired fibrillar adhesives.

    Science.gov (United States)

    Abusomwan, Uyiosa A; Sitti, Metin

    2014-10-14

    Contact self-cleaning of gecko-inspired synthetic adhesives with mushroom-shaped tips has been demonstrated recently using load-drag-unload cleaning procedures similar to that of the natural animal. However, the underlying mechanics of contact cleaning has yet to be fully understood. In this work, we present a detailed experiment of contact self-cleaning that shows that rolling is the dominant mechanism of cleaning for spherical microparticle contaminants, during the load-drag-unload procedure. We also study the effect of dragging rate and normal load on the particle rolling friction. A model of spherical particle rolling on an elastomer fibrillar adhesive interface is developed and agrees well with the experimental results. This study takes us closer to determining design parameters for achieving self-cleaning fibrillar adhesives.

  2. Mutation of the conserved calcium-binding motif in Neisseria gonorrhoeae PilC1 impacts adhesion but not piliation.

    Science.gov (United States)

    Cheng, Yuan; Johnson, Michael D L; Burillo-Kirch, Christine; Mocny, Jeffrey C; Anderson, James E; Garrett, Christopher K; Redinbo, Matthew R; Thomas, Christopher E

    2013-11-01

    Neisseria gonorrhoeae PilC1 is a member of the PilC family of type IV pilus-associated adhesins found in Neisseria species and other type IV pilus-producing genera. Previously, a calcium-binding domain was described in the C-terminal domains of PilY1 of Pseudomonas aeruginosa and in PilC1 and PilC2 of Kingella kingae. Genetic analysis of N. gonorrhoeae revealed a similar calcium-binding motif in PilC1. To evaluate the potential significance of this calcium-binding region in N. gonorrhoeae, we produced recombinant full-length PilC1 and a PilC1 C-terminal domain fragment. We show that, while alterations of the calcium-binding motif disrupted the ability of PilC1 to bind calcium, they did not grossly affect the secondary structure of the protein. Furthermore, we demonstrate that both full-length wild-type PilC1 and full-length calcium-binding-deficient PilC1 inhibited gonococcal adherence to cultured human cervical epithelial cells, unlike the truncated PilC1 C-terminal domain. Similar to PilC1 in K. kingae, but in contrast to the calcium-binding mutant of P. aeruginosa PilY1, an equivalent mutation in N. gonorrhoeae PilC1 produced normal amounts of pili. However, the N. gonorrhoeae PilC1 calcium-binding mutant still had partial defects in gonococcal adhesion to ME180 cells and genetic transformation, which are both essential virulence factors in this human pathogen. Thus, we conclude that calcium binding to PilC1 plays a critical role in pilus function in N. gonorrhoeae.

  3. Diversity of Cyclic Di-GMP-Binding Proteins and Mechanisms.

    Science.gov (United States)

    Chou, Shan-Ho; Galperin, Michael Y

    2016-01-01

    Cyclic di-GMP (c-di-GMP) synthetases and hydrolases (GGDEF, EAL, and HD-GYP domains) can be readily identified in bacterial genome sequences by using standard bioinformatic tools. In contrast, identification of c-di-GMP receptors remains a difficult task, and the current list of experimentally characterized c-di-GMP-binding proteins is likely incomplete. Several classes of c-di-GMP-binding proteins have been structurally characterized; for some others, the binding sites have been identified; and for several potential c-di-GMP receptors, the binding sites remain to be determined. We present here a comparative structural analysis of c-di-GMP-protein complexes that aims to discern the common themes in the binding mechanisms that allow c-di-GMP receptors to bind it with (sub)micromolar affinities despite the 1,000-fold excess of GTP. The available structures show that most receptors use their Arg and Asp/Glu residues to bind c-di-GMP monomers, dimers, or tetramers with stacked guanine bases. The only exception is the EAL domains that bind c-di-GMP monomers in an extended conformation. We show that in c-di-GMP-binding signature motifs, Arg residues bind to the O-6 and N-7 atoms at the Hoogsteen edge of the guanine base, while Asp/Glu residues bind the N-1 and N-2 atoms at its Watson-Crick edge. In addition, Arg residues participate in stacking interactions with the guanine bases of c-di-GMP and the aromatic rings of Tyr and Phe residues. This may account for the presence of Arg residues in the active sites of every receptor protein that binds stacked c-di-GMP. We also discuss the implications of these structural data for the improved understanding of the c-di-GMP signaling mechanisms.

  4. The effect of interlayer adhesion on the mechanical behaviors of macroscopic graphene oxide papers.

    Science.gov (United States)

    Gao, Yun; Liu, Lu-Qi; Zu, Sheng-Zhen; Peng, Ke; Zhou, Ding; Han, Bao-Hang; Zhang, Zhong

    2011-03-22

    High mechanical performances of macroscopic graphene oxide (GO) papers are attracting great interest owing to their merits of lightweight and multiple functionalities. However, the loading role of individual nanosheets and its effect on the mechanical properties of the macroscopic GO papers are not yet well understood. Herein, we effectively tailored the interlayer adhesions of the GO papers by introducing small molecules, that is, glutaraldehyde (GA) and water molecules, into the gallery regions. With the help of in situ Raman spectroscopy, we compared the varied load-reinforcing roles of nanosheets, and further predicted the Young's moduli of the GO papers. Systematic mechanical tests have proven that the enhancement of the tensile modulus and strength of the GA-treated GO paper arose from the improved load-bearing capability of the nanosheets. On the basis of Raman and macroscopic mechanical tests, the influences of interlayer adhesions on the fracture mechanisms of the strained GO papers were inferred.

  5. Adhesion mechanism of salmon to polymer-coated can walls

    NARCIS (Netherlands)

    Dommershuijzen, H.; Hviid, L.; Hartog, den H.; Vereijken, J.

    2005-01-01

    Minimization of the amount of salmon adhering to the can wall after emptying is one of the convenience requirements of consumers of canned salmon. In order to achieve this, the mechanism by which salmon adheres to cans needs to be understood. The aim of this study was to provide such knowledge for p

  6. Biophysical studies on calcium and carbohydrate binding to carbohydrate recognition domain of Gal/GalNAc lectin from Entamoeba histolytica: insights into host cell adhesion.

    Science.gov (United States)

    Yadav, Rupali; Verma, Kuldeep; Chandra, Mintu; Mukherjee, Madhumita; Datta, Sunando

    2016-09-01

    Entamoeba histolytica, an enteric parasite expresses a Gal/GalNAc-specific lectin that contributes to its virulence by establishing adhesion to host cell. In this study, carbohydrate recognition domain of Hgl (EhCRD) was purified and biophysical studies were conducted to understand the thermodynamic basis of its binding to carbohydrate and Ca(++) Here, we show that carbohydrate recognition domain (CRD) of the lectin binds to calcium through DPN motif. To decipher the role of calcium in carbohydrate binding and host cell adhesion, biophysical and cell-based studies were carried out. We demonstrated that the presence of the cation neither change the affinity of the lectin for carbohydrates nor alters its conformation. Mutation of the calcium-binding motif in EhCRD resulted in complete loss of ability to bind calcium but retained its affinity for carbohydrates. Purified EhCRD significantly diminished adhesion of the amebic trophozoites to Chinese Hamster Ovary (CHO) cells as well as triggered red blood cell agglutination. The calcium-binding defective mutant abrogated amebic adhesion to CHO cells similar to the wild-type protein, but it failed to agglutinate RBCs suggesting a differential role of the cation in these two processes. This study provides the first molecular description of the role of calcium in Gal/GalNAc mediated host cell adhesion.

  7. Adhesion to the yeast cell surface as a mechanism for trapping pathogenic bacteria by Saccharomyces probiotics.

    Science.gov (United States)

    Tiago, F C P; Martins, F S; Souza, E L S; Pimenta, P F P; Araujo, H R C; Castro, I M; Brandão, R L; Nicoli, Jacques R

    2012-09-01

    Recently, much attention has been given to the use of probiotics as an adjuvant for the prevention or treatment of gastrointestinal pathology. The great advantage of therapy with probiotics is that they have few side effects such as selection of resistant bacteria or disturbance of the intestinal microbiota, which occur when antibiotics are used. Adhesion of pathogenic bacteria onto the surface of probiotics instead of onto intestinal receptors could explain part of the probiotic effect. Thus, this study evaluated the adhesion of pathogenic bacteria onto the cell wall of Saccharomyces boulardii and Saccharomyces cerevisiae strains UFMG 905, W303 and BY4741. To understand the mechanism of adhesion of pathogens to yeast, cell-wall mutants of the parental strain of Saccharomyces cerevisiae BY4741 were used because of the difficulty of mutating polyploid yeast, as is the case for Saccharomyces cerevisiae and Saccharomyces boulardii. The tests of adhesion showed that, among 11 enteropathogenic bacteria tested, only Escherichia coli, Salmonella Typhimurium and Salmonella Typhi adhered to the surface of Saccharomyces boulardii, Saccharomyces cerevisiae UFMG 905 and Saccharomyces cerevisiae BY4741. The presence of mannose, and to some extent bile salts, inhibited this adhesion, which was not dependent on yeast viability. Among 44 cell-wall mutants of Saccharomyces cerevisiae BY4741, five lost the ability to fix the bacteria. Electron microscopy showed that the phenomenon of yeast-bacteria adhesion occurred both in vitro and in vivo (in the digestive tract of dixenic mice). In conclusion, some pathogenic bacteria were captured on the surface of Saccharomyces boulardii, Saccharomyces cerevisiae UFMG 905 and Saccharomyces cerevisiae BY4741, thus preventing their adhesion to specific receptors on the intestinal epithelium and their subsequent invasion of the host.

  8. Mechanical and water soaking properties of medium density fiberboard with wood fiber and soybean protein adhesive.

    Science.gov (United States)

    Li, Xin; Li, Yonghui; Zhong, Zhikai; Wang, Donghai; Ratto, Jo A; Sheng, Kuichuan; Sun, Xiuzhi Susan

    2009-07-01

    Soybean protein is a renewable and abundant material that offers an alternative to formaldehyde-based resins. In this study, soybean protein was modified with sodium dodecyl sulfate (SDS) as an adhesive for wood fiber medium density fiberboard (MDF) preparation. Second-order response surface regression models were used to study the effects and interactions of initial moisture content (IMC) of coated wood fiber, press time (PT) and temperature on mechanical and water soaking properties of MDF. Results showed that IMC of coated fiber was the dominant influencing factor. Mechanical and soaking properties improved as IMC increased and reached their highest point at an IMC of 35%. Press time and temperature also had a significant effect on mechanical and water soaking properties of MDF. Second-order regression results showed that there were strong relationships between mechanical and soaking properties of MDF and processing parameters. Properties of MDF made using soybean protein adhesive are similar to those of commercial board.

  9. Small-scale mechanical characterization of viscoelastic adhesive systems

    Science.gov (United States)

    Shean, T. A. V.

    Aero engine hot end components are often covered with ceramic Thermal Barrier Coatings (TBCs). Laser drilling in the TBC coated components can be a source of service life TBC degradation and spallation. The present study aims to understand the mechanisms of TBC delamination and develop techniques to drill holes without damaging the TBC, Nimonic 263 workpieces coated with TBC are used in the experiments. Microwave non-destructive testing (NDT) is employed to monitor the integrity of the coating /substrate interfaces of the post-laser drilled materials. A numerical modelling technique is used to investigate the role of melt ejection on TBC delamination. The model accounts for the vapour and the assist gas flow effects in the process. Broadly, melt ejection induced mechanical stresses for the TBC coating / bond coating and thermal effects for the bond coating / substrate interfaces are found the key delamination mechanisms. Experiments are carried out to validate the findings from the model. Various techniques that enable laser drilling without damaging the TBC are demonstrated. Twin jet assisted acute angle laser drilling is one successful technique that has been analysed using the melt ejection simulation. Optimisation of the twin jet assisted acute angle laser drilling process parameters is carried out using Design of Experiments (DoE) and statistical modelling approaches. Finally, an industrial case study to develop a high speed, high quality laser drilling system for combustor cans is described. Holes are drilled by percussion and trepan drilling in TBC coated and uncoated Haynes 230 workpieces. The production rate of percussion drilling is significantly higher than the trepan drilling, however metallurgical hole quality and reproducibility is poor. A number of process parameters are investigated to improve these characteristics. Gas type and gas pressure effects on various characteristics of the inclined laser drilled holes are investigated through theoretical

  10. Transient adhesion and conductance phenomena in initial nanoscale mechanical contacts between dissimilar metals.

    Science.gov (United States)

    Paul, William; Oliver, David; Miyahara, Yoichi; Grütter, Peter

    2013-11-29

    We report on transient adhesion and conductance phenomena associated with tip wetting in mechanical contacts produced by the indentation of a clean W(111) tip into a Au(111) surface. A combination of atomic force microscopy and scanning tunneling microscopy was used to carry out indentation and to image residual impressions in ultra-high vacuum. The ∼7 nm radii tips used in these experiments were prepared and characterized by field ion microscopy in the same instrument. The very first indentations of the tungsten tips show larger conductance and pull-off adhesive forces than subsequent indentations. After ∼30 indentations to a depth of ∼1.7 nm, the maximum conductance and adhesion forces reach steady state values approximately 12 ×  and 6 ×  smaller than their initial value. Indentation of W(111) tips into Cu(100) was also performed to investigate the universality of tip wetting phenomena with a different substrate. We propose a model from contact mechanics considerations which quantitatively reproduces the observed decay rate of the conductance and adhesion drops with a 1/e decay constant of 9-14 indentation cycles. The results show that the surface composition of an indenting tip plays an important role in defining the mechanical and electrical properties of indentation contacts.

  11. Theory of the mechanical response of focal adhesions to shear flow

    Energy Technology Data Exchange (ETDEWEB)

    Biton, Y Y; Safran, S A, E-mail: yoav.biton@weizmann.ac.i, E-mail: sam.safran@weizmann.ac.i [Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100 (Israel)

    2010-05-19

    The response of cells to shear flow is primarily determined by the asymmetry of the external forces and moments that are sensed by each member of a focal adhesion pair connected by a contractile stress fiber. In the theory presented here, we suggest a physical model in which each member of such a pair of focal adhesions is treated as an elastic body subject to both a myosin-activated contractile force and the shear stress induced by the external flow. The elastic response of a focal adhesion complex is much faster than the active cellular processes that determine the size of the associated focal adhesions and the direction of the complex relative to the imposed flow. Therefore, the complex attains its mechanical equilibrium configuration which may change because of the cellular activity. Our theory is based on the experimental observation that focal adhesions modulate their cross-sectional area in order to attain an optimal shear. Using this assumption, our elastic model shows that such a complex can passively change its orientation to align parallel to the direction of the flow.

  12. Theory of the mechanical response of focal adhesions to shear flow

    Science.gov (United States)

    Biton, Y. Y.; Safran, S. A.

    2010-05-01

    The response of cells to shear flow is primarily determined by the asymmetry of the external forces and moments that are sensed by each member of a focal adhesion pair connected by a contractile stress fiber. In the theory presented here, we suggest a physical model in which each member of such a pair of focal adhesions is treated as an elastic body subject to both a myosin-activated contractile force and the shear stress induced by the external flow. The elastic response of a focal adhesion complex is much faster than the active cellular processes that determine the size of the associated focal adhesions and the direction of the complex relative to the imposed flow. Therefore, the complex attains its mechanical equilibrium configuration which may change because of the cellular activity. Our theory is based on the experimental observation that focal adhesions modulate their cross-sectional area in order to attain an optimal shear. Using this assumption, our elastic model shows that such a complex can passively change its orientation to align parallel to the direction of the flow.

  13. Fullerenes as adhesive layers for mechanical peeling of metallic, molecular and polymer thin films.

    Science.gov (United States)

    Wieland, Maria B; Slater, Anna G; Mangham, Barry; Champness, Neil R; Beton, Peter H

    2014-01-01

    We show that thin films of C60 with a thickness ranging from 10 to 100 nm can promote adhesion between a Au thin film deposited on mica and a solution-deposited layer of the elastomer polymethyldisolaxane (PDMS). This molecular adhesion facilitates the removal of the gold film from the mica support by peeling and provides a new approach to template stripping which avoids the use of conventional adhesive layers. The fullerene adhesion layers may also be used to remove organic monolayers and thin films as well as two-dimensional polymers which are pre-formed on the gold surface and have monolayer thickness. Following the removal from the mica support the monolayers may be isolated and transferred to a dielectric surface by etching of the gold thin film, mechanical transfer and removal of the fullerene layer by annealing/dissolution. The use of this molecular adhesive layer provides a new route to transfer polymeric films from metal substrates to other surfaces as we demonstrate for an assembly of covalently-coupled porphyrins.

  14. Viscous-poroelastic interaction as mechanism to create adhesion in frogs' toe pads

    Science.gov (United States)

    Tulchinsky, A.; Gat, A. D.

    2015-07-01

    The toe pads of frogs consist of soft hexagonal structures and a viscous liquid contained between and within the hexagonal structures. It has been hypothesized that this configuration creates adhesion by allowing for long range capillary forces, or alternatively, by allowing for exit of the liquid and thus improving contact of the toe pad. In this work we suggest interaction between viscosity and elasticity as a mechanism to create temporary adhesion, even in the absence of capillary effects or van der Waals forces. We initially illustrate this concept experimentally by a simplified configuration consisting of two surfaces connected by a liquid bridge and elastic springs. We then utilize poroelastic mixture theory and model frog's toe pads as an elastic porous medium, immersed within a viscous liquid and pressed against a rigid rough surface. The flow between the surface and the toe pad is modeled by the lubrication approximation. Inertia is neglected and analysis of the elastic-viscous dynamics yields a governing partial differential equation describing the flow and stress within the porous medium. Several solutions of the governing equation are presented and show a temporary adhesion due to stress created at the contact surface between the solids. This work thus may explain how some frogs (such as the torrent frog) maintain adhesion underwater and the reason for the periodic repositioning of frogs' toe pads during adhesion to surfaces.

  15. A statistical mechanics handbook for protein-ligand binding simulation.

    Science.gov (United States)

    Rocchia, Walter; Bonella, Sara

    2013-01-01

    In this work, the fundamental elements of statistical mechanics underlying the simulation of the protein-ligand binding process, such as statistical ensembles and the concept of microscopic estimators of macroscopic observables and free energy, are summarized in a self consistent fashion. Particular attention is then devoted to the introduction of some mathematical tools that are used in atomistic simulations aimed at estimating binding affinities and free energy profiles, and to the illustration of the origins of the difficulties encountered in this endeavor.

  16. Molecular mechanisms underlying synergistic adhesion of sickle red blood cells by hypoxia and low nitric oxide bioavailability.

    Science.gov (United States)

    Gutsaeva, Diana R; Montero-Huerta, Pedro; Parkerson, James B; Yerigenahally, Shobha D; Ikuta, Tohru; Head, C Alvin

    2014-03-20

    The molecular mechanisms by which nitric oxide (NO) bioavailability modulates the clinical expression of sickle cell disease (SCD) remain elusive. We investigated the effect of hypoxia and NO bioavailability on sickle red blood cell (sRBC) adhesion using mice deficient for endothelial NO synthase (eNOS) because their NO metabolite levels are similar to those of SCD mice but without hypoxemia. Whereas sRBC adhesion to endothelial cells in eNOS-deficient mice was synergistically upregulated at the onset of hypoxia, leukocyte adhesion was unaffected. Restoring NO metabolite levels to physiological levels markedly reduced sRBC adhesion to levels seen under normoxia. These results indicate that sRBC adherence to endothelial cells increases in response to hypoxia prior to leukocyte adherence, and that low NO bioavailability synergistically upregulates sRBC adhesion under hypoxia. Although multiple adhesion molecules mediate sRBC adhesion, we found a central role for P-selectin in sRBC adhesion. Hypoxia and low NO bioavailability upregulated P-selectin expression in endothelial cells in an additive manner through p38 kinase pathways. These results demonstrate novel cellular and signaling mechanisms that regulate sRBC adhesion under hypoxia and low NO bioavailability. Importantly, these findings point us toward new molecular targets to inhibit cell adhesion in SCD.

  17. Nature's Mechanisms for Tough, Self-healing Polymers and Polymer Adhesives

    Science.gov (United States)

    Hansma, Paul

    2007-03-01

    Spider silk^2 and the natural polymer adhesives in abalone shells^3 and bone^4,5 can give us insights into nature's mechanisms for tough, self-healing polymers and polymer adhesives. The natural polymer adhesives in biomaterials have been optimized by evolution. An optimized polymer adhesive has five characteristics. 1) It holds together the strong elements of the composite. 2) It yields just before the strong elements would otherwise break. 3) It dissipates large amounts of energy as it yields. 4) It self heals after it yields. 5) It takes just a few percent by weight. Both natural polymer adhesives and silk rely on sacrificial bonds and hidden length for toughness and self-healing.^6 A relatively large energy, of order 100eV, is required to stretch a polymer molecule after a weak bond, a sacrificial bond, breaks and liberates hidden length, which was previously hidden, typically in a loop or folded domain, from whatever was stretching the polymer. The bond is called sacrificial if it breaks at forces well below the forces that could otherwise break the polymer backbone, typically greater than 1nN. In many biological cases, the breaking of sacrificial bonds has been found to be reversible, thereby also providing a ``self-healing'' property to the material.^2-4 Individual polymer adhesive molecules based on sacrificial bonds and hidden length can supply forces of order 300pN over distances of 100s of nanometers. Model calculations show that a few percent by weight of adhesives based on these principles could be optimized adhesives for high performance composite materials including nanotube and graphene sheet composites. ^2N. Becker, E. Oroudjev, S. Mutz et al., Nature Materials 2 (4), 278 (2003). ^3B. L. Smith, T. E. Schaffer, M. Viani et al., Nature 399 (6738), 761 (1999). ^4J. B. Thompson, J. H. Kindt, B. Drake et al., Nature 414 (6865), 773 (2001). ^5G. E. Fantner, T. Hassenkam, J. H. Kindt et al., Nature Materials 4, 612 (2005). ^6G. E. Fantner, E. Oroudjev, G

  18. A room temperature cured low dielectric hyperbranched epoxy adhesive with high mechanical strength

    Indian Academy of Sciences (India)

    Bibekananda De; Niranjan Karak

    2014-05-01

    A low dielectric constant hyperbranched epoxy thermoset with excellent adhesive and mechanical strength is the demand for advanced electronics and engineering applications. The present investigation provided a room temperature, curable hyperbranched epoxy, obtained by an A2 + B3 polycondensation reaction. The synthesized hyperbranched epoxy was cured by a combined hardener system consisting of a commercial poly(amido-amine) and a first generation aliphatic poly(amido-amine) dendrimer (PAD) prepared by Michael addition reaction of methyl acrylate and aliphatic amines. The thermoset exhibited high mechanical strength, excellent adhesive strength, low dielectric constant, good thermal stability and excellent weather resistance along with very good moisture resistance. The results showed the influence of the amount of PAD on the performance of the thermoset. Thus, the study revealed that the combined poly(amido-amine) cured hyperbranched epoxy has high potential in advanced electrical packaging and microelectronic devices.

  19. Tablet mechanics depend on nano and micro scale adhesion, lubrication and structure.

    Science.gov (United States)

    Badal Tejedor, Maria; Nordgren, Niklas; Schuleit, Michael; Rutland, Mark W; Millqvist-Fureby, Anna

    2015-01-01

    Tablets are the most convenient form for drug administration. However, despite the ease of manufacturing problems such as powder adhesion occur during the production process. This study presents surface and structural characterization of tablets formulated with commonly used excipients (microcrystalline cellulose (MCC), lactose, mannitol, magnesium (Mg) stearate) pressed under different compaction conditions. Tablet surface analyses were performed with scanning electron microscopy (SEM), profilometry and atomic force microscopy (AFM). The mechanical properties of the tablets were evaluated with a tablet hardness test. Local adhesion detected by AFM decreased when Mg stearate was present in the formulation. Moreover, the tablet strength of plastically deformable excipients such as MCC was significantly decreased after addition of Mg stearate. Combined these facts indicate that Mg stearate affects the particle-particle bonding and thus elastic recovery. The MCC excipient also displayed the highest hardness which is characteristic for a highly cohesive material. This is discussed in the view of the relatively high adhesion found between MCC and a hydrophilic probe at the nanoscale using AFM. In contrast, the tablet strength of brittle materials like lactose and mannitol is unaffected by Mg stearate. Thus fracture occurs within the excipient particles and not at particle boundaries, creating new surfaces not previously exposed to Mg stearate. Such uncoated surfaces may well promote adhesive interactions with tools during manufacture.

  20. Mechanics of leukocyte deformation and adhesion to endothelium in shear flow.

    Science.gov (United States)

    Dong, C; Cao, J; Struble, E J; Lipowsky, H H

    1999-01-01

    The mechanics of leukocyte [white blood cell (WBC)] deformation and adhesion to endothelial cells (EC) in shear flow has been investigated. Experimental data on transient WBC-EC adhesion were obtained from in vivo measurements. Microscopic images of WBC-EC contact during incipient WBC rolling revealed that for a given wall shear stress, the contact area increases with time as new bonds are formed at the leading edge, and then decreases with time as the trailing edge of the WBC membrane peels away from the EC. A two-dimensional model (2D) was developed consisting of an elastic ring adhered to a surface under fluid stresses. This ring represents an actin-rich WBC cortical layer and contains an incompressible fluid as the cell interior. All molecular bonds are modeled as elastic springs distributed in the WBC-EC contact region. Variations of the proportionality between wall shear stress (tau(w)) in the vicinity of the WBC and the resulting drag force (F(s)), i.e., F(s)/tau(w), reveal its decrease with WBC deformation and increasing vessel channel height (2D). The computations also find that the peeling zone between adherent WBC and EC may account for less than 5% of the total contact interface. Computational studies describe the WBC-EC adhesion and the extent of WBC deformation during the adhesive process.

  1. Binding Mechanisms in Selective Laser Sintering and Selective Laser Melting

    NARCIS (Netherlands)

    Kruth, J.-P.; Mercelis, P.; Van Vaerenbergh, J.; Froyen, L.; Rombouts, M.

    2005-01-01

    Purpose – This paper provides an overview of the different binding mechanisms in selective laser sintering (SLS) and selective laser melting (SLM), thus improving the understanding of these processes. Design/methodology/approach – A classification of SLS/SLM processes was developed, based on the bin

  2. Mechanical and Physical Properties and Adhesion Durability of Flowable Resin Composite

    OpenAIRE

    金丸, 充徳; カナマル, ミツノリ; Mitsunori, KANAMARU

    2004-01-01

    The purpose of this study was to examine the mechanical and physical properties and adhesion durability to bovine dentin of the flowable resin composites in comparison with those of conventional resin composites and glass ionomers. In this experiment, four flowable resin composites, two conventional resin composites and two glass ionomers were used. The consistency, thermal expansion coefficiency, compressive strength, diametral tensile strength, brittleness, Vickers hardness, elastic modulus...

  3. Binding Mechanisms of Intrinsically Disordered Proteins: Theory, Simulation, and Experiment

    Science.gov (United States)

    Mollica, Luca; Bessa, Luiza M.; Hanoulle, Xavier; Jensen, Malene Ringkjøbing; Blackledge, Martin; Schneider, Robert

    2016-01-01

    In recent years, protein science has been revolutionized by the discovery of intrinsically disordered proteins (IDPs). In contrast to the classical paradigm that a given protein sequence corresponds to a defined structure and an associated function, we now know that proteins can be functional in the absence of a stable three-dimensional structure. In many cases, disordered proteins or protein regions become structured, at least locally, upon interacting with their physiological partners. Many, sometimes conflicting, hypotheses have been put forward regarding the interaction mechanisms of IDPs and the potential advantages of disorder for protein-protein interactions. Whether disorder may increase, as proposed, e.g., in the “fly-casting” hypothesis, or decrease binding rates, increase or decrease binding specificity, or what role pre-formed structure might play in interactions involving IDPs (conformational selection vs. induced fit), are subjects of intense debate. Experimentally, these questions remain difficult to address. Here, we review experimental studies of binding mechanisms of IDPs using NMR spectroscopy and transient kinetic techniques, as well as the underlying theoretical concepts and numerical methods that can be applied to describe these interactions at the atomic level. The available literature suggests that the kinetic and thermodynamic parameters characterizing interactions involving IDPs can vary widely and that there may be no single common mechanism that can explain the different binding modes observed experimentally. Rather, disordered proteins appear to make combined use of features such as pre-formed structure and flexibility, depending on the individual system and the functional context. PMID:27668217

  4. Mechanical unfolding of ribose binding protein and its comparison with other periplasmic binding proteins.

    Science.gov (United States)

    Kotamarthi, Hema Chandra; Narayan, Satya; Ainavarapu, Sri Rama Koti

    2014-10-01

    Folding and unfolding studies on large, multidomain proteins are still rare despite their high abundance in genomes of prokaryotes and eukaryotes. Here, we investigate the unfolding properties of a 271 residue, two-domain ribose binding protein (RBP) from the bacterial periplasm using single-molecule force spectroscopy. We observe that RBP predominately unfolds via a two-state pathway with an unfolding force of ∼80 pN and an unfolding contour length of ∼95 nm. Only a small population (∼15%) of RBP follows three-state pathways. The ligand binding neither increases the mechanical stability nor influences the unfolding flux of RBP through different pathways. The kinetic partitioning between two-state and three-state pathways, which has been reported earlier for other periplasmic proteins, is also observed in RBP, albeit to a lesser extent. These results provide important insights into the mechanical stability and unfolding processes of large two-domain proteins and highlight the contrasting features upon ligand binding. Protein structural topology diagrams are used to explain the differences in the mechanical unfolding behavior of RBP with other periplasmic binding proteins.

  5. Effect of the regional variability of dentinal substrate and modes of application of adhesive systems on the mechanical properties of the adhesive layer

    Directory of Open Access Journals (Sweden)

    Yasmine Mendes Pupo

    2012-01-01

    Full Text Available Aim: This study assessed the effect of the dentin depth and the application mode on the hardness and elastic modulus of the adhesive layer. Materials and Methods: Occlusal surfaces of 48 caries-free human third molars were removed, at two levels: Superficial and deep dentin. For each type of surface, the test specimens were randomly divided into groups which underwent the application: A conventional two-step adhesive system (Adper™ Single Bond [SB] and self-etch adhesives system (Adper™ SE Plus [SE] and AdheSE® [AD]. The adhesives applied were active or passive. Composite build-ups were constructed incrementally. The teeth were sectioned, embedded, and polished. The nanoindentation test was performed in the adhesive layer. The results were analyzed by ANOVA and Tukey tests. Results: In the adhesive layer, the higher hardness (0.307 ± 0.006 GPa and elastic modulus (4.796 ± 0.165 GPa of SE were obtained in superficial dentin in passive application. The elastic modulus of SE (4.115 ± 0.098 GPa was lowest in active application in superficial dentin. The active application significantly increased the hardness of the SB in the deep dentin (0.011 ± 0.314 GPa compared the superficial dentin (0.280 ± 0.010 GPa. For the AD, only the mode of application was statistically significant (P=0.0041 for the hardness, active application (0.289 ± 0.015 GPa being higher than passive application (0.261 ± 0.013 GPa (P=0.0042 in deep dentin. Conclusion: The experimental results reveal that the mechanical properties were influenced for the application mode of adhesive systems and dentin depth.

  6. Staphylococcal SSL5 binding to human leukemia cells inhibits cell adhesion to endothelial cells and platelets

    NARCIS (Netherlands)

    Walenkamp, Annemiek M. E.; Bestebroer, Jovanka; Boer, Ingrid G. J.; Kruizinga, Roeline; Verheul, Henk M.; van Strijp, Jos A. G.; de Haas, Carla J. C.

    2010-01-01

    Bacterial proteins provide promising tools for novel anticancer therapies. Staphylococcal superantigen-like 5 (SSL5) was recently described to bind P-selectin glycoprotein ligand-1 (PSGL-1) on leukocytes and to inhibit neutrophil rolling on a P-selectin surface. As leukocytes and tumor cells share m

  7. Characterization of debond growth mechanism in adhesively bonded composites under mode II static and fatigue loadings

    Science.gov (United States)

    Mall, S.; Kochhar, N. K.

    1988-01-01

    An experimental investigation of adhesively bonded composite joint was conducted to characterize the debond growth mechanism under mode II static and fatigue loadings. For this purpose, end-notched flexure specimens of graphite/epoxy (T300/5208) adherends bonded with EC 3445 adhesive were tested. In all specimen tested, the fatigue failure occurred in the form of cyclic debonding. The present study confirmed the result of previous studies that total strain-energy-release rate is the driving parameter for cyclic debonding. Further, the debond growth resistance under cyclic loading with full shear reversal (i.e., stress ratio, R = -1) is drastically reduced in comparison to the case when subjected to cyclic shear loading with no shear reversal (i.e., R = 0.1).

  8. A unique bivalent binding and inhibition mechanism by the yatapoxvirus interleukin 18 binding protein.

    Directory of Open Access Journals (Sweden)

    Brian Krumm

    Full Text Available Interleukin 18 (IL18 is a cytokine that plays an important role in inflammation as well as host defense against microbes. Mammals encode a soluble inhibitor of IL18 termed IL18 binding protein (IL18BP that modulates IL18 activity through a negative feedback mechanism. Many poxviruses encode homologous IL18BPs, which contribute to virulence. Previous structural and functional studies on IL18 and IL18BPs revealed an essential binding hot spot involving a lysine on IL18 and two aromatic residues on IL18BPs. The aromatic residues are conserved among the very diverse mammalian and poxviruses IL18BPs with the notable exception of yatapoxvirus IL18BPs, which lack a critical phenylalanine residue. To understand the mechanism by which yatapoxvirus IL18BPs neutralize IL18, we solved the crystal structure of the Yaba-Like Disease Virus (YLDV IL18BP and IL18 complex at 1.75 Å resolution. YLDV-IL18BP forms a disulfide bonded homo-dimer engaging IL18 in a 2∶2 stoichiometry, in contrast to the 1∶1 complex of ectromelia virus (ECTV IL18BP and IL18. Disruption of the dimer interface resulted in a functional monomer, however with a 3-fold decrease in binding affinity. The overall architecture of the YLDV-IL18BP:IL18 complex is similar to that observed in the ECTV-IL18BP:IL18 complex, despite lacking the critical lysine-phenylalanine interaction. Through structural and mutagenesis studies, contact residues that are unique to the YLDV-IL18BP:IL18 binding interface were identified, including Q67, P116 of YLDV-IL18BP and Y1, S105 and D110 of IL18. Overall, our studies show that YLDV-IL18BP is unique among the diverse family of mammalian and poxvirus IL-18BPs in that it uses a bivalent binding mode and a unique set of interacting residues for binding IL18. However, despite this extensive divergence, YLDV-IL18BP binds to the same surface of IL18 used by other IL18BPs, suggesting that all IL18BPs use a conserved inhibitory mechanism by blocking a putative receptor-binding

  9. Adhesion and cohesion.

    Science.gov (United States)

    von Fraunhofer, J Anthony

    2012-01-01

    The phenomena of adhesion and cohesion are reviewed and discussed with particular reference to dentistry. This review considers the forces involved in cohesion and adhesion together with the mechanisms of adhesion and the underlying molecular processes involved in bonding of dissimilar materials. The forces involved in surface tension, surface wetting, chemical adhesion, dispersive adhesion, diffusive adhesion, and mechanical adhesion are reviewed in detail and examples relevant to adhesive dentistry and bonding are given. Substrate surface chemistry and its influence on adhesion, together with the properties of adhesive materials, are evaluated. The underlying mechanisms involved in adhesion failure are covered. The relevance of the adhesion zone and its importance with regard to adhesive dentistry and bonding to enamel and dentin is discussed.

  10. Adhesion and Cohesion

    Directory of Open Access Journals (Sweden)

    J. Anthony von Fraunhofer

    2012-01-01

    Full Text Available The phenomena of adhesion and cohesion are reviewed and discussed with particular reference to dentistry. This review considers the forces involved in cohesion and adhesion together with the mechanisms of adhesion and the underlying molecular processes involved in bonding of dissimilar materials. The forces involved in surface tension, surface wetting, chemical adhesion, dispersive adhesion, diffusive adhesion, and mechanical adhesion are reviewed in detail and examples relevant to adhesive dentistry and bonding are given. Substrate surface chemistry and its influence on adhesion, together with the properties of adhesive materials, are evaluated. The underlying mechanisms involved in adhesion failure are covered. The relevance of the adhesion zone and its importance with regard to adhesive dentistry and bonding to enamel and dentin is discussed.

  11. A peptide derived from a trans-homophilic binding site in neural cell adhesion molecule induces neurite outgrowth and neuronal survival

    DEFF Research Database (Denmark)

    Køhler, Lene B; Soroka, Vladislav; Korshunova, Irina

    2010-01-01

    The neural cell adhesion molecule (NCAM) plays a key role in neural development, regeneration, and synaptic plasticity. The crystal structure of a fragment of NCAM comprising the three N-terminal immunoglobulin (Ig)-like modules indicates that the first and second Ig modules bind to each other, t...

  12. Staphylococcal SSL5 Binding to Human Leukemia Cells Inhibits Cell Adhesion to Endothelial Cells and Platelets

    Directory of Open Access Journals (Sweden)

    Annemiek M. E. Walenkamp

    2010-01-01

    Full Text Available Bacterial proteins provide promising tools for novel anticancer therapies. Staphylococcal superantigen-like 5 (SSL5 was recently described to bind P-selectin glycoprotein ligand-1 (PSGL-1 on leukocytes and to inhibit neutrophil rolling on a P-selectin surface. As leukocytes and tumor cells share many characteristics in migration and dissemination, we explored the potential of SSL5 as an antagonist of malignant cell behavior. Previously, it was demonstrated that rolling of human HL-60 leukemia cells on activated endothelial cells was mediated by P-selectin. In this study, we show that SSL5 targets HL-60 cells. Binding of SSL5 was rapid and without observed toxicity. Competition of SSL5 with the binding of three anti-PSGL-1 antibodies and P-selectin to HL-60 cells identified PSGL-1 as the ligand on HL-60 cells. Presence of sialyl Lewis x epitopes on PSGL-1 was crucial for its interaction with SSL5. Importantly, SSL5 not only inhibited the interaction of HL-60 cells with activated endothelial cells but also with platelets, which both play an important role in growth and metastasis of cancers. These data support the concept that SSL5 could be a lead in the search for novel strategies against hematological malignancies.

  13. The binding mechanism of a peptidic cyclic serine protease inhibitor

    DEFF Research Database (Denmark)

    Jiang, Longguang; Svane, Anna S P; Sørensen, Hans Peter

    2011-01-01

    Serine proteases are classical objects for studies of catalytic and inhibitory mechanisms as well as interesting as therapeutic targets. Since small-molecule serine protease inhibitors generally suffer from specificity problems, peptidic inhibitors, isolated from phage-displayed peptide libraries...... inhibitory mechanism and an unusually high specificity. Using a number of modified variants of upain-1, we characterised the upain-1-urokinase-type plasminogen activator complex using X-ray crystal structure analysis, determined a model of the peptide in solution by NMR spectroscopy, and analysed binding...... kinetics and thermodynamics by surface plasmon resonance and isothermal titration calorimetry. We found that upain-1 changes both main-chain conformation and side-chain orientations as it binds to the protease, in particular its Trp3 residue and the surrounding backbone. The properties of upain-1...

  14. Dennexin peptides modeled after the homophilic binding sites of the neural cell adhesion molecule (NCAM) promote neuronal survival, modify cell adhesion and impair spatial learning

    DEFF Research Database (Denmark)

    Køhler, Lene B; Christensen, Claus; Rossetti, Clara

    2010-01-01

    Neural cell adhesion molecule (NCAM)-mediated cell adhesion results in activation of intracellular signaling cascades that lead to cellular responses such as neurite outgrowth, neuronal survival, and modulation of synaptic activity associated with cognitive processes. The crystal structure...... between Ig1 and Ig3 and between Ig2 and Ig2, respectively, observed in the crystal structure. Although the two dennexin peptides differed in amino acid sequence, they both modulated cell adhesion, reflected by inhibition of NCAM-mediated neurite outgrowth. Both dennexins also promoted neuronal survival...

  15. Role of Polysaccharides on Mechanical and Adhesion Properties of Flax Fibres in Flax/PLA Biocomposite

    Directory of Open Access Journals (Sweden)

    Gijo Raj

    2011-01-01

    Full Text Available The effect of alkali and enzymatic treatments on flax fibre morphology, mechanical, and adhesion properties was investigated. The multilength scale analysis allows for the correlation of the fibre's morphological changes induced by the treatments with mechanical properties to better explain the adherence properties between flax and PLA. The atomic force microscopy (AFM images revealed the removal of primary layers, upon treatments, down to cellulose microfibrils present in the secondary layers. The variation in mechanical properties was found to be dependent, apart from the crystalline content, on interaction between cellulose microfibrils and encrusting polysaccharides, pectins and hemicelluloses, in the secondary layers. Finally, microbond tests between the modified fibres and PLA emphasize the important role of the outer fibre's surface on the overall composite properties. It was observed here that gentle treatments of the fibres, down to the oriented microfibrils, are favourable to a better adherence with a PLA drop. This paper highlights the important role of amorphous polymers, hemicellulose and pectin, in the optimisation of the adhesion and mechanical properties of flax fibres in the biocomposite.

  16. Flexible polyacrylamide substrata for the analysis of mechanical interactions at cell-substratum adhesions

    Science.gov (United States)

    Beningo, Karen A.; Lo, Chun-Min; Wang, Yu-Li

    2002-01-01

    We have described a powerful tool for the study of mechanical interactions between cells and their physical environment. Although the approach has already been used in a variety of ways to measure traction forces and to characterize active and passive responses of cultured cells to mechanical stimulation, it can be extended easily and combined with other microscopic approaches, including fluorescent analog imaging (Beningo et al., 2001), photobleaching, calcium imaging, micromanipulation, and electrophysiology. This method will be particularly useful for studying the functions of various components at focal adhesions, and the effects of mechanical forces on focal adhesion-mediated signal transduction. In addition, the method can be extended to a 3D setting, e.g., by sandwiching cultured cells between two layers of polyacrylamide to create an environment mimicking that in the tissue of a multicellular organism. Whereas chemical interactions between cells and the environment have been investigated extensively, many important questions remain as to the role of physical forces in cellular functions and the interplay between chemical and physical mechanisms of communication. The present approach, as well as other approaches capable of probing physical interactions, should fill in this important gap in the near future.

  17. Viscous-elastic interaction as a mechanism to create adhesion in frogs' toe pads

    Science.gov (United States)

    Gat, Amir; Tulchinsky, Arie

    2013-11-01

    The toe pads of frogs consist of soft hexagonal structures and a network of channels between and within the soft structures, containing a viscous liquid. It has been hypothesized that this configuration creates adhesion by allowing for long range capillary forces, or alternatively, that the channel network allows for exit of the viscous liquid and thus improve contact of the toe pad. In this work we suggest interaction between viscous flow and elastic forces as a mechanism to create temporary adhesion, even in the absence of capillary or van der Waals forces. We study the dynamics of a solid body covered with an array of protruding elastic cylinders, immersed within a viscous liquid, and pressed against a flat surface. Inertia is neglected and the elastic-viscous dynamics yield the governing differential equation describing the relative motion between the body and the surface. The compressed elastic cylinders apply a force acting to separate the solid body from the surface. The relative motion between the body and the surface creates a viscous flow and pressure field resisting the elastic force and significantly reducing the speed of separation. We show that the viscous-elastic interaction can prevent motion tangential and normal to the surface and can create temporary adhesion.

  18. Poly(AAc-co-MBA) hydrogel films: adhesive and mechanical properties in aqueous medium.

    Science.gov (United States)

    Arunbabu, Dhamodaran; Shahsavan, Hamed; Zhang, Wei; Zhao, Boxin

    2013-01-10

    Poly(acrylic acid-co-N,N'-methylenebisacrylamide) hydrogel films were synthesized by copolymerizing acrylic acid (AAc) with N,N'-methylenebisacrylamide (MBA) as a cross-linker via photo polymerization in the spacing confined between two glass plates. NMR spectroscopy was utilized to determine the cross-linking density. We found that the cross-linking density determined by NMR is higher than that expected from the feed concentrations of cross-linkers, suggesting that MBA is more reactive than AAc and the heterogeneous nature of the cross-linking. In addition to the swelling tests, indentation tests were performed on the hydrogel films under water to investigate effects of the cross-linking density on the adhesion and mechanical properties of the hydrogel films in terms of adhesive pull-off force and Hertz-type elastic modulus. As the cross-linker concentration increased, the effective elastic modulus of the hydrogel films increased dramatically at low cross-linking densities and reached a high steady-state value at higher cross-linking densities. The pull-off force decreased with increasing cross-linker concentration and reached a lower force plateau at high cross-linking densities. An optimal "trade-off" cross-linking density was determined to be 0.02 mol fraction of MBA in the hydrogel, where balanced elastic modulus and adhesive pull-off force can be obtained.

  19. Insights into Coupled Folding and Binding Mechanisms from Kinetic Studies.

    Science.gov (United States)

    Shammas, Sarah L; Crabtree, Michael D; Dahal, Liza; Wicky, Basile I M; Clarke, Jane

    2016-03-25

    Intrinsically disordered proteins (IDPs) are characterized by a lack of persistent structure. Since their identification more than a decade ago, many questions regarding their functional relevance and interaction mechanisms remain unanswered. Although most experiments have taken equilibrium and structural perspectives, fewer studies have investigated the kinetics of their interactions. Here we review and highlight the type of information that can be gained from kinetic studies. In particular, we show how kinetic studies of coupled folding and binding reactions, an important class of signaling event, are needed to determine mechanisms.

  20. CD4 binding to major histocompatibility complex class II antigens induces LFA-1-dependent and -independent homotypic adhesion of B lymphocytes.

    Science.gov (United States)

    Kansas, G S; Cambier, J C; Tedder, T F

    1992-01-01

    T helper cells recognize processed antigen (Ag) in the context of major histocompatibility complex (MHC) class II antigens present on the surface of B cells and other Ag-presenting cells. This interaction is mediated through the T cell receptor complex with associate recognition of class II molecules by the CD4 molecule. In this study, the binding of a soluble recombinant CD4/Ig heavy chain fusion protein (CD4-gamma 3) or monoclonal antibody (mAb) to class II antigens on human B cells was shown to induce rapid and specific homotypic adhesion of B cells and most B lymphoblastoid cell lines. mAb reactive with CD4 inhibited CD4-gamma 3-induced adhesion and a mutant B lymphoblastoid cell line deficient in class II antigens failed to respond. Induction of homotypic adhesion was dependent on energy metabolism and a functional cytoskeleton, and class II+ pre-B cells did not exhibit adhesion in response to these stimuli, suggesting that cross-linking of class II molecules generated a transmembrane signal and did not simply aggregate cells. In addition, MHC class II-induced adhesion was Fc receptor independent, as 15 mAb of different Ig isotypes reactive with HLA-D or HLA-DQ gene products induced adhesion. Anti-class II mAb and CD4-gamma 3 were able to induce adhesion at concentrations as low as 10 ng/ml and 100 ng/ml, respectively. Suboptimal stimulation of B cell lines through HLA-D antigens induced homotypic adhesion that was dependent on the activation of LFA-1 (CD11a/CD18), and which could be blocked by specific mAb. However, at greater signal strengths, adhesion was not blocked by mAb against the known adhesion receptors, suggesting the induction of a novel adhesion pathway. Consistent with this, homotypic adhesion induced by engagement of MHC class II antigens was observed with LFA-1-deficient B cell lines, and was independent of CD49d or CD18 expression. Thus, the direct engagement of B cell class II antigens by CD4 is likely to generate transmembrane signals which

  1. Relationship between mechanical properties and bond durability of short fiber-reinforced resin composite with universal adhesive.

    Science.gov (United States)

    Tsujimoto, Akimasa; Barkmeier, Wayne W; Takamizawa, Toshiki; Watanabe, Hidehiko; Johnson, William W; Latta, Mark A; Miyazaki, Masashi

    2016-10-01

    The purpose of this study was to determine the relationship between mechanical properties and bond durability of short fiber-reinforced resin composite with universal adhesive. As controls, micro-hybrid and nano-hybrid resin composites were tested. The universal adhesives used were Scotchbond Universal, Adhese Universal, and G-Premio Bond. The fracture toughness and flexural properties of resin composites, and shear bond strength and shear fatigue strength of universal adhesive with resin composite using both total-etch and self-etch modes were determined. In the results, short fiber-reinforced resin composite showed significantly higher fracture toughness than did micro-hybrid and nano-hybrid resin composites. The flexural strength and modulus of short fiber-reinforced and nano-hybrid resin composites were significantly lower than were those of micro-hybrid resin composites. Regardless of etching mode, the shear bond strength of universal adhesives with short fiber-reinforced resin composite did not show any significant differences from micro-hybrid and nano-hybrid resin composites. The shear fatigue strength of universal adhesives with short fiber-reinforced resin composite and micro-hybrid resin composites were significantly higher than that of nano-hybrid resin composites. The results of this study suggest that the mechanical properties of short fiber-reinforced resin composite improve their bond durability with universal adhesive.

  2. Structure and function of ameloblastin as an extracellular matrix protein: adhesion, calcium binding, and CD63 interaction in human and mouse.

    Science.gov (United States)

    Zhang, Xu; Diekwisch, Thomas G H; Luan, Xianghong

    2011-12-01

    The functional significance of extracellular matrix proteins in the life of vertebrates is underscored by a high level of sequence variability in tandem with a substantial degree of conservation in terms of cell-cell and cell-matrix adhesion interactions. Many extracellular matrix proteins feature multiple adhesion domains for successful attachment to substrates, such as integrin, CD63, and heparin. Here we have used homology and ab initio modeling algorithms to compare mouse ameloblastin (mAMBN) and human ameloblastin (hABMN) isoforms and to analyze their potential for cell adhesion and interaction with other matrix molecules as well as calcium binding. Sequence comparison between mAMBN and hAMBN revealed a 26-amino-acid deletion in mAMBN, corresponding to a helix-loop-helix frameshift. The human AMBN domain (174Q-201G), homologous to the mAMBN 157E-178I helix-loop-helix region, formed a helix-loop motif with an extended loop, suggesting a higher degree of flexibility of hAMBN compared with mAMBN, as confirmed by molecular dynamics simulation. Heparin-binding domains, CD63-interaction domains, and calcium-binding sites in both hAMBN and mAMBN support the concept of AMBN as an extracellular matrix protein. The high level of conservation between AMBN functional domains related to adhesion and differentiation was remarkable when compared with only 61% amino acid sequence homology.

  3. Biophysically inspired model for functionalized nanocarrier adhesion to cell surface: roles of protein expression and mechanical factors

    Science.gov (United States)

    Ramakrishnan, N.; Tourdot, Richard W.; Eckmann, David M.; Ayyaswamy, Portonovo S.; Muzykantov, Vladimir R.; Radhakrishnan, Ravi

    2016-06-01

    In order to achieve selective targeting of affinity-ligand coated nanoparticles to the target tissue, it is essential to understand the key mechanisms that govern their capture by the target cell. Next-generation pharmacokinetic (PK) models that systematically account for proteomic and mechanical factors can accelerate the design, validation and translation of targeted nanocarriers (NCs) in the clinic. Towards this objective, we have developed a computational model to delineate the roles played by target protein expression and mechanical factors of the target cell membrane in determining the avidity of functionalized NCs to live cells. Model results show quantitative agreement with in vivo experiments when specific and non-specific contributions to NC binding are taken into account. The specific contributions are accounted for through extensive simulations of multivalent receptor-ligand interactions, membrane mechanics and entropic factors such as membrane undulations and receptor translation. The computed NC avidity is strongly dependent on ligand density, receptor expression, bending mechanics of the target cell membrane, as well as entropic factors associated with the membrane and the receptor motion. Our computational model can predict the in vivo targeting levels of the intracellular adhesion molecule-1 (ICAM1)-coated NCs targeted to the lung, heart, kidney, liver and spleen of mouse, when the contributions due to endothelial capture are accounted for. The effect of other cells (such as monocytes, etc.) do not improve the model predictions at steady state. We demonstrate the predictive utility of our model by predicting partitioning coefficients of functionalized NCs in mice and human tissues and report the statistical accuracy of our model predictions under different scenarios.

  4. EFFECT OF INTERFACIAL ADHESION ON CRYSTALLIZATION AND MECHANICAL PROPERTIES OF POLY (ETHYLENE TEREPHTHALATE)/GLASS BEAD COMPOSITES

    Institute of Scientific and Technical Information of China (English)

    OU Yuchun; YU Zhongzhen; ZHU Jin; LI Ge; ZHU Shanguang

    1996-01-01

    The interfacial adhesion between poly (ethylene terephthalate) (PET) and glass bead was investigated by scanning electron microscope and parallel-plate rheometer. Effect of interfacial adhesion on the crystallization and mechanical properties of PET/glass bead composites was also studied by differential scanning calorimeter and mechanical testers.The results obtained indicate that the glass bead has a heterogeneous nucleation effect on the PET crystallization. Although better interfacial adhesion is advantageous to the increase of the tensile strength of the composite, yet it is unfavorable to the crystallization of PET. It should be pointed out that the crystallization rate of filled PET is always higher than that of pure PET, regardless of the state of interfacial adhesion.

  5. Neural cell adhesion molecule-180-mediated homophilic binding induces epidermal growth factor receptor (EGFR) down-regulation and uncouples the inhibitory function of EGFR in neurite outgrowth

    DEFF Research Database (Denmark)

    Povlsen, Gro Klitgaard; Berezin, Vladimir; Bock, Elisabeth

    2008-01-01

    The neural cell adhesion molecule (NCAM) plays important roles in neuronal development, regeneration, and synaptic plasticity. NCAM homophilic binding mediates cell adhesion and induces intracellular signals, in which the fibroblast growth factor receptor plays a prominent role. Recent studies...... not require NCAM-mediated fibroblast growth factor receptor activation....... on axon guidance in Drosophila suggest that NCAM also regulates the epidermal growth factor receptor (EGFR) (Molecular and Cellular Neuroscience, 28, 2005, 141). A possible interaction between NCAM and EGFR in mammalian cells has not been investigated. The present study demonstrates for the first time...

  6. Novel antagonists of alcohol inhibition of l1-mediated cell adhesion: multiple mechanisms of action.

    Science.gov (United States)

    Wilkemeyer, Michael F; Menkari, Carrie E; Charness, Michael E

    2002-11-01

    1-Octanol antagonizes ethanol inhibition of L1-mediated cell adhesion and prevents ethanol teratogenesis in mouse whole embryo culture. Herein, we identify a new series of alcohol antagonists and study their mechanism of action. Cell aggregation assays were carried out in ethanol-sensitive, human L1-transfected NIH/3T3 cells in the absence and presence of 100 mM ethanol or 2 mM 1-butanol and candidate antagonists. Antagonist potency for 1-alcohols increased progressively over 5 log orders from 1-pentanol (C5) to 1-dodecanol (C12). Antagonist potency declined from 1-dodecanol (C12) to 1-tridecanol (C13), and 1-tetradecanol (C14) and 1-pentadecanol (C15) were inactive. The presence and position of a double bond in the 1-butanol molecule determined whether a compound was a full agonist (1-butanol), a mixed agonist-antagonist (2-buten-1-ol), or an antagonist (3-buten-1-ol). Increasing the concentration of agonist (1-butanol or ethanol) overcame the antagonism of 3-buten-1-ol, benzyl alcohol, cyclopentanol, and 3-pentanol, but not that of 4-methyl-1-pentanol, 2-methyl-2-pentanol, 1-pentanol, 2-pentanol, 1-octanol, and 2,6-di-isopropylphenol (propofol), suggesting that the mechanisms of antagonism may differ between these groups of compounds. These findings suggest that selective straight, branched, and cyclic alcohols may act at multiple, discrete sites to antagonize the actions of ethanol and 1-butanol on L1-mediated cell-cell adhesion.

  7. Coupling behavior between adhesive and abrasive wear mechanism of aero-hydraulic spool valves

    Institute of Scientific and Technical Information of China (English)

    Chen Yunxia; Gong Wenjun; Kang Rui

    2016-01-01

    Leakage due to wear is one of the main failure modes of aero-hydraulic spool valves. This paper established a practical coupling wear model for aero-hydraulic spool valves based on dynamic system modelling theory. Firstly, the experiment for wear mechanism verification proved that adhesive wear and abrasive wear did coexist during the working process of spool valves. Sec-ondly coupling behavior of each wear mechanism was characterized by analyzing actual time-variation of model parameters during wear evolution process. Meanwhile, Archard model and three-body abrasive wear model were utilized for adhesive wear and abrasive wear, respectively. Furthermore, their coupling wear model was established by calculating the actual wear volume. Finally, from the result of formal test, all the required parameters for our model were obtained. The relative error between model prediction and data of pre-test was also presented to verify the accuracy of model, which demonstrated that our model was useful for providing accurate prediction of spool valve’s wear life.

  8. A factor VIII-derived peptide enables von Willebrand factor (VWF)-binding of artificial platelet nanoconstructs without interfering with VWF-adhesion of natural platelets.

    Science.gov (United States)

    Haji-Valizadeh, Hassan; Modery-Pawlowski, Christa L; Sen Gupta, Anirban

    2014-05-01

    There is substantial clinical interest in synthetic platelet analogs for potential application in transfusion medicine. To this end, our research is focused on self-assembled peptide-lipid nanoconstructs that can undergo injury site-selective adhesion and subsequently promote site-directed active platelet aggregation, thus mimicking platelet's primary hemostatic actions. For injury site-selective adhesion, we have utilized a coagulation factor FVIII-derived VWF-binding peptide (VBP). FVIII binds to VWF's D'-D3 domain while natural platelet GPIbα binds to VWF's A1 domain. Therefore, we hypothesized that the VBP-decorated nanoconstructs will adhere to VWF without mutual competition with natural platelets. We further hypothesized that the adherent VBP-decorated constructs can enhance platelet aggregation when co-decorated with a fibrinogen-mimetic peptide (FMP). To test these hypotheses, we used glycocalicin to selectively block VWF's A1 domain and, using fluorescence microscopy, studied the binding of fluorescently labeled VBP-decorated nanoconstructs versus platelets to ristocetin-treated VWF. Subsequently, we co-decorated the nanoconstructs with VBP and FMP and incubated them with human platelets to study construct-mediated enhancement of platelet aggregation. Decoration with VBP resulted in substantial construct adhesion to ristocetin-treated VWF even if the A1-domain was blocked by glycocalicin. In comparison, such A1-blocking resulted in significant reduction of platelet adhesion. Without A1-blocking, the VBP-decorated constructs and natural platelets could adhere to VWF concomitantly. Furthermore, the constructs co-decorated with VBP and FMP enhanced active platelet aggregation. The results indicate significant promise in utilizing the FVIII-derived VBP in developing synthetic platelet analogs that do not interfere with VWF-binding of natural platelets but allow site-directed enhancement of platelet aggregation when combined with FMP.

  9. Flocculation protein structure and cell-cell adhesion mechanism in Saccharomyces cerevisiae.

    Science.gov (United States)

    Goossens, Katty; Willaert, Ronnie

    2010-11-01

    Cell-cell adhesion occurs in a broad spectrum of biological processes, of which yeast flocculation is an area of interest for evolutionary scientists to brewers and winemakers. The flocculation mechanism is based on a lectin-carbohydrate interaction but is not yet fully understood, although the first model dates back to the 1950s. This review will update the current understanding of the complex mechanism behind yeast flocculation. Moreover, modern technologies to measure the forces involved in single carbohydrate-lectin interactions, are discussed. The Flo1 protein has been extensively described as the protein responsible for strong flocculation. Recently, more research has been directed to the detailed analysis of this flocculin. Due to the advances in the field of bioinformatics, more information about Flo1p could be obtained via structurally or functionally related proteins. Here, we review the current knowledge of the Flo1 protein, with a strong emphasis towards its structure.

  10. Cell adhesion to fibrillin-1: identification of an Arg-Gly-Asp-dependent synergy region and a heparin-binding site that regulates focal adhesion formation

    DEFF Research Database (Denmark)

    Bax, Daniel V; Mahalingam, Yashithra; Cain, Stuart;

    2007-01-01

    We have defined the molecular basis of cell adhesion to fibrillin-1, the major structural component of extracellular microfibrils that are associated with elastic fibres. Using human dermal fibroblasts, and recombinant domain swap fragments containing the Arg-Gly-Asp motif, we have demonstrated a...

  11. Binding energy and mechanical stability of single- and multi-walled carbon nanotube serpentines

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Junhua, E-mail: junhua.zhao@163.com, E-mail: timon.rabczuk@uni-weimar.de [Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology, Jiangnan University, 214122 Wuxi (China); Institute of Structural Mechanics, Bauhaus University, 99423 Weimar (Germany); Lu, Lixin [Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology, Jiangnan University, 214122 Wuxi (China); Rabczuk, Timon, E-mail: junhua.zhao@163.com, E-mail: timon.rabczuk@uni-weimar.de [Institute of Structural Mechanics, Bauhaus University, 99423 Weimar (Germany)

    2014-05-28

    Recently, Geblinger et al. [Nat. Nanotechnol. 3, 195 (2008)] and Machado et al. [Phys. Rev. Lett. 110, 105502 (2013)] reported the experimental and molecular dynamics realization of S-like shaped single-walled carbon nanotubes (CNTs), the so-called CNT serpentines. We reported here results from continuum modeling of the binding energy γ between different single- and multi-walled CNT serpentines and substrates as well as the mechanical stability of the CNT serpentine formation. The critical length for the mechanical stability and adhesion of different CNT serpentines are determined in dependence of E{sub i}I{sub i}, d, and γ, where E{sub i}I{sub i} and d are the CNT bending stiffness and distance of the CNT translation period. Our continuum model is validated by comparing its solution to full-atom molecular dynamics calculations. The derived analytical solutions are of great importance for understanding the interaction mechanism between different single- and multi-walled CNT serpentines and substrates.

  12. Multiscale mechanics and physics of nature’s dry adhesion systems

    OpenAIRE

    Karlsson, Nils

    2012-01-01

    Dry adhesion systems adhere via physical bonds without any significant contribution from a liquid medium. In nature, these systems are found among the footpads of spiders, lizards and many other small animals, with high adhesion force, low detachment force and elfcleaning properties. These features are highly interesting for biomimetic man-made adhesives. Heavy animals have an adhesion force much higher than its muscle force, and to enable detachment, they have evolved a functional surface wi...

  13. Influence of nanofillers on the thermal and mechanical behavior of DGEBA-based adhesives for bonded-in timber connections

    Science.gov (United States)

    Ahmad, Z.; Ansell, M. P.; Smedley, D.

    2006-09-01

    Results of an experimental investigation into the thermal behavior and mechanical properties of a room-temperature-cured epoxy adhesive (diglycidyl ether of bisphenol A, DGEBA) cross-linked with polyetheramines and filled with different fillers, namely nanosilica, liquid rubber (CTBN), and clay, are reported. The nanosilica and liquid rubber increased the flexural strength and elastic modulus of the adhesive systems; the addition of clay particles raised the elastic modulus significantly, but embrittled the adhesive. Establishing a correct cure time is very important for bonded-in timber structures, as it will affect the bond strength. A study on the effect of cure time on the flexural strength was carried out, from which it follows that the adhesives should be cured for at least 20 days at room temperature. The damping characteristics and the glass-transition temperature of the adhesives were determined by using a dynamic mechanical thermal analysis. The results showed that the filled adhesives had a higher storage modulus, which was in agreement with the elastic moduli determined from static bending tests. The introduction of the fillers increased its glass-transition temperature considerably.

  14. Binding equilibrium and kinetics of membrane-anchored receptors and ligands in cell adhesion: Insights from computational model systems and theory.

    Science.gov (United States)

    Weikl, Thomas R; Hu, Jinglei; Xu, Guang-Kui; Lipowsky, Reinhard

    2016-09-02

    The adhesion of cell membranes is mediated by the binding of membrane-anchored receptor and ligand proteins. In this article, we review recent results from simulations and theory that lead to novel insights on how the binding equilibrium and kinetics of these proteins is affected by the membranes and by the membrane anchoring and molecular properties of the proteins. Simulations and theory both indicate that the binding equilibrium constant [Formula: see text] and the on- and off-rate constants of anchored receptors and ligands in their 2-dimensional (2D) membrane environment strongly depend on the membrane roughness from thermally excited shape fluctuations on nanoscales. Recent theory corroborated by simulations provides a general relation between [Formula: see text] and the binding constant [Formula: see text] of soluble variants of the receptors and ligands that lack the membrane anchors and are free to diffuse in 3 dimensions (3D).

  15. Mechanical characterization of selected adhesives and bulk materials at liquid nitrogen and room temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Fitzpatrick, C.M.; Stoddart, W.C.T.

    1977-01-01

    This paper presents the results of a series of mechanical tests on selected adhesives and bulk materials. The materials tested are of general interest to designers of magnets for cryogenic service and include several epoxies, a varnish, a B-stage glass cloth, insulation papers, and commercially available fiber-reinforced composites. These tests were performed at room temperature (293 K) and at liquid nitrogen temperature (77 K). The tests include both simple tension tests and lap shear tests with various adherends. The parameters critical to tensile or bond strength were varied as part of the test program. The procedures used to manufacture and test these specimens and the results of the tests are reported in this paper.

  16. Nano-hydroxyapatite/polyacrylamide composite hydrogels with high mechanical strengths and cell adhesion properties.

    Science.gov (United States)

    Li, Zhiyong; Mi, Wenying; Wang, Huiliang; Su, Yunlan; He, Changcheng

    2014-11-01

    Nano-hydroxyapatite/polyacrylamide composite hydrogels were successfully fabricated by physically mixing nano-hydroxyapatite (nHAp) particles into a peroxidized micelles initiated and cross-linked (pMIC) polyacrylamide (PAAm) hydrogel. The nanocomposite hydrogels exhibited excellent mechanical properties. The fracture tensile stresses of the gels were in the range of 0.21-0.86 MPa and the fracture tensile strains were up to 30 mm/mm, and the compressive strengths were up to 35.8 MPa. Meanwhile the introduction of nHAp endowed the composite hydrogels with good cell adhesion properties. This nHAp/PAAm nanocomposite hydrogel is expected to find potential applications in tissue engineering.

  17. Spectroscopic and Docking Studies on the Binding of Liquiritigenin with Hyaluronidase for Antiallergic Mechanism

    OpenAIRE

    Hua-jin Zeng; Ran Yang; Jing You; Ling-bo Qu; Yan-jun Sun

    2016-01-01

    The inhibitory effect of liquiritigenin on hyaluronidase and its binding mechanism were investigated systematically by UV-vis absorption, fluorescence, and molecular modeling approaches. These results indicated that liquiritigenin could interact with hyaluronidase to form a liquiritigenin-hyaluronidase complex. The binding constant, number of binding sites, and thermodynamic parameters were calculated, which indicated that liquiritigenin could spontaneously bind with hyaluronidase mainly thro...

  18. Mechanisms of splicing-dependent trans-synaptic adhesion by PTPδ-IL1RAPL1/IL-1RAcP for synaptic differentiation

    Science.gov (United States)

    Yamagata, Atsushi; Yoshida, Tomoyuki; Sato, Yusuke; Goto-Ito, Sakurako; Uemura, Takeshi; Maeda, Asami; Shiroshima, Tomoko; Iwasawa-Okamoto, Shiho; Mori, Hisashi; Mishina, Masayoshi; Fukai, Shuya

    2015-04-01

    Synapse formation is triggered through trans-synaptic interaction between pairs of pre- and postsynaptic adhesion molecules, the specificity of which depends on splice inserts known as `splice-insert signaling codes'. Receptor protein tyrosine phosphatase δ (PTPδ) can bidirectionally induce pre- and postsynaptic differentiation of neurons by trans-synaptically binding to interleukin-1 receptor accessory protein (IL-1RAcP) and IL-1RAcP-like-1 (IL1RAPL1) in a splicing-dependent manner. Here, we report crystal structures of PTPδ in complex with IL1RAPL1 and IL-1RAcP. The first immunoglobulin-like (Ig) domain of IL1RAPL1 directly recognizes the first splice insert, which is critical for binding to IL1RAPL1. The second splice insert functions as an adjustable linker that positions the Ig2 and Ig3 domains of PTPδ for simultaneously interacting with the Ig1 domain of IL1RAPL1 or IL-1RAcP. We further identified the IL1RAPL1-specific interaction, which appears coupled to the first-splice-insert-mediated interaction. Our results thus reveal the decoding mechanism of splice-insert signaling codes for synaptic differentiation induced by trans-synaptic adhesion between PTPδ and IL1RAPL1/IL-1RAcP.

  19. Characterization of the in vitro binding and inhibition kinetics of primary amine oxidase/vascular adhesion protein-1 by glucosamine.

    LENUS (Irish Health Repository)

    Olivieri, Aldo

    2012-04-01

    Primary-amine oxidase (PrAO) catalyzes the oxidative deamination of endogenous and exogenous primary amines and also functions, in some tissues, as an inflammation-inducible endothelial factor, known as vascular adhesion protein-1. VAP-1 mediates the slow rolling and adhesion of lymphocytes to endothelial cells in a number of inflammatory conditions, including inflammation of the synovium.

  20. Mechanical properties of metallic nanowires using tight-binding model

    Science.gov (United States)

    Aish, Mohammed; Starostenkov, Mikhail

    2016-01-01

    The mechanical properties of Nickel nanowires have been studied at different temperatures using molecular dynamics simulations. Molecular Dynamics (MD) simulations have been carried out on pure Nickel (Ni) crystal with face-centered cubic (FCC) lattice upon application of uniaxial tension at nanolevel with a speed of 20 m/s. The deformation corresponds to the direction . To the calculated block of crystal, free boundary conditions are applied in the directions , . A many body interatomic potential for Ni within the second moment approximation of the tight binding model (the Cleri-Rosato potentials) was employed to carry out three dimensional molecular dynamics simulations. MD simulation used to investigate the effect of temperature of Ni nanowire on the nature of deformation and fracture. Temperature effect on the extension property of metal nanowire is discussed in detail. The mechanical strengths and the mechanical strain of the nanowires decrease linearly with the increasing temperature. The feature of deformation energy can be divided into four regions: quasi-elastic, plastic, flow and failure. Experiments have shown that when the temperature increases the yielding stress decreases, the first stage of deformation was narrowed, and the second stage was widened. The results showed that breaking position depended on temperature.

  1. Differential MSC activation leads to distinct mononuclear leukocyte binding mechanisms

    Science.gov (United States)

    Kota, Daniel J.; Dicarlo, Bryan; Hetz, Robert A.; Smith, Philippa; Cox, Charles S.; Olson, Scott D.

    2014-04-01

    Advances in the field of Multipotent Mesenchymal Stromal cell (MSC) biology have demonstrated that MSCs can improve disease outcome when `activated' to exert immunomodulatory effects. However, the precise mechanisms modulating MSC-immune cells interactions remain largely elusive. In here, we activated MSC based on a recent polarization paradigm, in which MSCs can be polarized towards a pro- or anti-inflammatory phenotype depending on the Toll-like receptor stimulated, to dissect the mechanisms through which MSCs physically interact with and modulate leukocytes in this context. Our data show that MSCs activated through the Toll-like receptor (TLR) 4 pathway increased VCAM-1 and ICAM-1 dependent binding of leukocytes. On the other hand, TLR3 stimulation strongly increases leukocytes affinity to MSC comparatively, through the formation of cable-like hyaluronic acid structures. In addition, TLR4 activation elicited secretion of pro-inflammatory mediators by MSCs, whereas TLR3-activated MSCs displayed a milder pro-inflammatory phenotype, similar to inactivated MSCs. However, the differently activated MSCs maintained their ability to suppress leukocyte activation at similar levels in our in vitro model, and this immunomodulatory property was shown here to be partially mediated by prostaglandin. These results reinforce the concept that alternate activation profiles control MSC responses and may impact the therapeutic use of MSCs.

  2. A peptide motif from the second fibronectin module of the neural cell adhesion molecule, NCAM, NLIKQDDGGSPIRHY, is a binding site for the FGF receptor

    DEFF Research Database (Denmark)

    Jacobsen, Jacob Hedemand; Kiselyov, Vladislav; Bock, Elisabeth

    2008-01-01

    The mechanism of fibroblast growth factor receptor (FGFR) activation by the neural cell adhesion molecule (NCAM) is not well understood. A motif in the second NCAM fibronectin type III (FN3) module, termed FGL, has by means of nuclear magnetic resonance (NMR) and surface plasmon resonance (SPR) a...

  3. New insights into the molecular mechanism of E-cadherin-mediated cell adhesion by free energy calculations

    DEFF Research Database (Denmark)

    Doro, Fabio; Saladino, Giorgio; Belvisi, Laura

    2015-01-01

    swapping to mediate cell adhesion. However, despite its importance, the molecular mechanism of domain swapping is still debated. Here, we study the conformational changes that lead to activation and dimerization via domain swapping of E-cadherin. Using state-of-the-art enhanced sampling atomistic...

  4. Intracellular delivery of recombinant arginine deiminase (rADI) by heparin-binding hemagglutinin adhesion peptide restores sensitivity in rADI-resistant cancer cells.

    Science.gov (United States)

    Wu, Fe-Lin Lin; Yeh, Tzyy-Harn; Chen, Ying-Luen; Chiu, Yu-Chin; Cheng, Ju-Chen; Wei, Ming-Feng; Shen, Li-Jiuan

    2014-08-04

    Recombinant arginine deiminase (rADI) has been used in clinical trials for arginine-auxotrophic cancers. However, the emergence of rADI resistance, due to the overexpression of argininosuccinate synthetase (AS), has introduced an obstacle in its clinical application. Here, we have proposed a strategy for the intracellular delivery of rADI, which depletes both extracellular and intracellular arginine, to restore the sensitivity of rADI-resistant cancer cells. In this study, the C terminus of heparin-binding hemagglutinin adhesion protein from Mycobacterium tuberculosis (HBHAc), which contains 23 amino acids, was used to deliver rADI into rADI-resistant human breast adenocarcinoma cells (MCF-7). Chemical conjugates (l- and d-HBHAc-SPDP-rADI) and a recombinant fusion protein (rHBHAc-ADI) were produced. l- and d-HBHAc-SPDP-rADI showed a significantly higher cellular uptake of rADI by MCF-7 cells compared to that of rADI alone. Cell viability was significantly decreased in a dose-dependent manner in response to l- and d-HBHAc-SPDP-rADI treatments. In addition, the ratio of intracellular concentration of citrulline to arginine in cells treated with l- and d-HBHAc-SPDP-rADI was significantly increased by 1.4- and 1.7-fold, respectively, compared with that obtained in cells treated with rADI alone (p < 0.001). Similar results were obtained with the recombinant fusion protein rHBHAc-ADI. Our study demonstrates that the increased cellular uptake of rADI by HBHAc modification can restore the sensitivity of rADI treatment in MCF-7 cells. rHBHAc-ADI may represent a novel class of antitumor enzyme with an intracellular mechanism that is independent of AS expression.

  5. Regulation of Cell Adhesion Strength by Peripheral Focal Adhesion Distribution

    OpenAIRE

    2011-01-01

    Cell adhesion to extracellular matrices is a tightly regulated process that involves the complex interplay between biochemical and mechanical events at the cell-adhesive interface. Previous work established the spatiotemporal contributions of adhesive components to adhesion strength and identified a nonlinear dependence on cell spreading. This study was designed to investigate the regulation of cell-adhesion strength by the size and position of focal adhesions (FA). The cell-adhesive interfac...

  6. Hydrophobic recovery of UV/ozone treated poly(dimethylsiloxane): adhesion studies by contact mechanics and mechanism of surface modification

    Science.gov (United States)

    Oláh, Attila; Hillborg, Henrik; Vancso, G. Julius

    2005-01-01

    Silicone elastomers (Sylgard 184 and 170), based on poly(dimethylsiloxane) (PDMS), were surface treated by a combined exposure to UV and ozone. The effects of the treatments were analyzed as a function of time elapsed after stopping the treatments using different standard surface characterization techniques, such as water contact angle measurements, XPS and atomic force microscopy (AFM). However, the primary focus of this study was to apply the Johnson-Kendall-Roberts (JKR) contact mechanics approach to investigate PDMS samples prior to and following UV/ozone surface treatment. A gradual formation of a hydrophilic, silica-like surface layer with increasing modulus was observed with increasing UV/ozone exposure. A subsequent hydrophobic recovery after UV/ozone exposure was observed, as indicated by increasing contact angles. This supports the hypothesis that the hydrophobic recovery is mainly caused by the gradual coverage of a permanent silica-like structure with free siloxanes and/or reorientation of polar groups. PDMS containing a homogenously dispersed filler (Sylgard 184), exhibited a decreasing surface roughness (by AFM) when the oxidized surface region "collapsed" into a smooth SiO x layer (final surface roughness Sylgard 170), exhibited an increasing surface roughness with treatment dose, which was attributed to the "collapse" of the oxidized surface region thus exposing the contours of the underlying filler aggregates (final surface roughness ˜140 nm). A dedicated device was designed and built to study the contact mechanics behavior of PDMS prior to, and following surface treatment. The value of the combined elastic modulus obtained for PDMS lens and semi-infinite flat surface system showed an increase in full agreement with the formation of a silica-like layer exhibiting a high elastic modulus (compared with untreated PDMS). The work of adhesion observed in JKR experiments exhibited an increasing trend as a function of treatment done in agreement with

  7. Adhesion in microelectronics

    CERN Document Server

    Mittal, K L

    2014-01-01

    This comprehensive book will provide both fundamental and applied aspects of adhesion pertaining to microelectronics in a single and easily accessible source. Among the topics to be covered include; Various theories or mechanisms of adhesionSurface (physical or chemical) characterization of materials as it pertains to adhesionSurface cleaning as it pertains to adhesionWays to improve adhesionUnraveling of interfacial interactions using an array of pertinent techniquesCharacterization of interfaces / interphasesPolymer-polymer adhesionMetal-polymer adhesion  (metallized polymers)Polymer adhesi

  8. Leukocyte adhesion - a fundamental process in leukocyte physiology

    Directory of Open Access Journals (Sweden)

    Gahmberg C.G.

    1999-01-01

    Full Text Available Leukocyte adhesion is of pivotal functional importance. The adhesion involves several different adhesion molecules, the most important of which are the leukocyte ß2-integrins (CD11/CD18, the intercellular adhesion molecules, and the selectins. We and others have extensively studied the specificity and binding sites in the integrins and the intercellular adhesion molecules for their receptors and ligands. The integrins have to become activated to exert their functions but the possible mechanisms of activation remain poorly understood. Importantly, a few novel intercellular adhesion molecules have been recently described, which seem to function only in specific tissues. Furthermore, it is becoming increasingly apparent that changes in integrins and intercellular adhesion molecules are associated with a number of acute and chronic diseases.

  9. Personal electronics printing via tapping mode composite liquid metal ink delivery and adhesion mechanism

    Science.gov (United States)

    Zheng, Yi; He, Zhi-Zhu; Yang, Jun; Liu, Jing

    2014-04-01

    Printed electronics is becoming increasingly important in a variety of newly emerging areas. However, restricted to the rather limited conductive inks and available printing strategies, the current electronics manufacture is usually confined to industry level. Here, we show a highly cost-effective and entirely automatic printing way towards personal electronics making, through introducing a tapping-mode composite fluid delivery system. Fundamental mechanisms regarding the reliable printing, transfer and adhesion of the liquid metal inks on the substrate were disclosed through systematic theoretical interpretation and experimental measurements. With this liquid metal printer, a series of representative electronic patterns spanning from single wires to desired complex configurations such as integrated circuit (IC), printed-circuits-on-board (PCB), electronic paintings, or more do-it-yourself (DIY) devices, were demonstrated to be printed out with high precision in a moment. And the total machine cost already reached personally affordable price. This is hard to achieve by a conventional PCB technology which generally takes long time and is material, water and energy consuming, while the existing printed electronics is still far away from the real direct printing goal. The present work opens the way for large scale personal electronics manufacture and is expected to generate important value for the coming society.

  10. Personal electronics printing via tapping mode composite liquid metal ink delivery and adhesion mechanism.

    Science.gov (United States)

    Zheng, Yi; He, Zhi-Zhu; Yang, Jun; Liu, Jing

    2014-04-04

    Printed electronics is becoming increasingly important in a variety of newly emerging areas. However, restricted to the rather limited conductive inks and available printing strategies, the current electronics manufacture is usually confined to industry level. Here, we show a highly cost-effective and entirely automatic printing way towards personal electronics making, through introducing a tapping-mode composite fluid delivery system. Fundamental mechanisms regarding the reliable printing, transfer and adhesion of the liquid metal inks on the substrate were disclosed through systematic theoretical interpretation and experimental measurements. With this liquid metal printer, a series of representative electronic patterns spanning from single wires to desired complex configurations such as integrated circuit (IC), printed-circuits-on-board (PCB), electronic paintings, or more do-it-yourself (DIY) devices, were demonstrated to be printed out with high precision in a moment. And the total machine cost already reached personally affordable price. This is hard to achieve by a conventional PCB technology which generally takes long time and is material, water and energy consuming, while the existing printed electronics is still far away from the real direct printing goal. The present work opens the way for large scale personal electronics manufacture and is expected to generate important value for the coming society.

  11. Morphology and contact mechanics influence adhesive characteristics of Dung Beetle's bristle and Gecko's setae

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Geckos (Gekko gecko) use their hairy setae to adhere on various solid surfaces and dung beetles ( Copris ochus Motschulsky) use their hairy bristles to anti-adhere in sticky environments. We study why two hairy systems express a conflict in functions by using SEM, histological approaches and functional experiments. Adhesion models and various parameters were collected and analyzed. Based on the morphological data and functional experimental results carried out by natural and denatured gecko setae and beetle bristles, we first demonstrated that the stiffness along the hair is 1000 to 30000 times that perpendicular to the hair. This stiffness difference is the key factor leading to the two hairy systems' functional differences. Slope of gecko setae reduces contact stiffness, increases contact points and real contact area that results in amazing adhesive abilities. On the other hand, stiff bristles in a beetle have higher contact stiffness, which reduces the real contact area and decreases the adhesion between two contact surfaces. Deformation of gecko setae destroys the hierarchical structure, increases the contact stiffness and results in a decrease of adhesion forces. Similarly, deformation of beetle bristles destroys the erect structure of the hair, interconnects the separated bristles and thus decreases the anti-adhesive functions. These observations inspire us in designing anti-adhesive and adhesive biomimetic systems.

  12. Comparison of the Folding Mechanism of Highly Homologous Proteins in the Lipid-binding Protein Family

    Science.gov (United States)

    The folding mechanism of two closely related proteins in the intracellular lipid binding protein family, human bile acid binding protein (hBABP) and rat bile acid binding protein (rBABP) were examined. These proteins are 77% identical (93% similar) in sequence Both of these singl...

  13. Motion of an Adhesive Gel in a Swelling Gradient a Mechanism for Cell Locomotion

    CERN Document Server

    Joanny, J F; Prost, J; Joanny, Jean-Francois; Julicher, Frank; Prost, Jacques

    2003-01-01

    Motivated by the motion of nematode sperm cells, we present a model for the motion of an adhesive gel on a solid substrate. The gel polymerizes at the leading edge and depolymerizes at the rear. The motion results from a competition between a self-generated swelling gradient and the adhesion on the substrate. The resulting stress provokes the rupture of the adhesion points and allows for the motion. The model predicts an unusual force-velocity relation which depends in significant ways on the point of application of the force.

  14. Adhesion mechanisms of Vibrio fluvialis to skin mucus of Epinephelus awoara

    Institute of Scientific and Technical Information of China (English)

    鄢庆枇; 赵敏慧; 王晓露; 邹文政; 陈昌生

    2010-01-01

    Vibrio fluvialis incubated in trypticase soy broth(TSB)showed stronger adhesion to the skin mucus of Epinephelus awoara than V.fluvialis grown on trypticase soy agar(TSA),and this bacterial adhesion was assessed in terms of saturation kinetics.Treating bacteria with antibody against O-antigens resulted in significantly reduced bacterial adhesion.In the early growth stage,the adhering bacteria numbers increased with incubation time,peaked at 24 h,and then dropped sharply.Prior heat treatment of the mucus at ...

  15. The effect of cores and coating dispersion composition on the mechanical and adhesion properties of hydroxypropyl methylcellulose films.

    Science.gov (United States)

    Banovec, M; Planinsek, O; Vrecer, F

    2014-08-01

    The influence of different additives on the mechanical properties of hydroxypropyl methylcellulose (HPMC) free films was studied using tensile testing. Free films were prepared using the cast method and sliced into bands, and their tensile strength and maximal elongation at break was measured. The results showed that the addition of PEG 400 and polysorbate 80 into the coating formulation had the most influence on the films' mechanical properties compared to the HPMC film used as a control. Tablet cores composed of microcrystalline cellulose and lactose with and without Mg stearate and compressed at three different compression forces were tested for wettability with coating formulations containing PEG 400 and polysorbate 80. For formulations with no Mg stearate added, the contact angle decreased with increasing core hardness and it also coincided with greater adhesion force of the coating. The addition of Mg stearate in the core led to reduced adhesion of the film coating with PEG 400, whereas the influence on the adhesion force of the film coating containing polysorbate 80 was negligible. The results also show that the adhesion force, regardless of the tablet core formulation, is highest at medium core hardness.

  16. Adhesions due to peritoneal carcinomatosis caused by a renal carcinoma leading to mechanical gastric outlet obstruction: a case report

    Directory of Open Access Journals (Sweden)

    Gruttadauria Salvatore

    2011-07-01

    Full Text Available Abstract Introduction Gastric outlet obstruction is a clinical syndrome caused by a variety of mechanical obstructions. Peptic ulcer disease used to be responsible for most gastric outlet obstruction, but in the last 40 years the prevalence of malignant tumors has risen significantly. Adhesive disease is an infrequent and insidious cause of mechanical gastric outlet obstruction. Case presentation We report the case of a 78-year-old Caucasian man who had a clinical history of a right nephrectomy for malignancy three years earlier and who was admitted for a severe gastric outlet obstruction (score of 1 confirmed both by an upper endoscopy and by a fluoroscopic view after contrast injection. A computed tomography scan and a laparotomy, with omental biopsies, showed a peritoneal carcinomatosis with the development of abdominal adhesions that prompted an abnormal gastric rotation around the perpendicular axis of his antrum with a dislocation in the empty space of his right kidney. Symptoms disappeared after surgical bypass through a gastrojejunostomy. Conclusions Our patient experienced a very rare complication characterized by the development of adhesions due to peritoneal carcinomatosis caused by a renal carcinoma treated with nephrectomy. These adhesions prompted an abnormal dislocation of his antrum, as an internal hernia, in the empty space of his right kidney.

  17. Cellular adhesion responses to the heparin-binding (HepII) domain of fibronectin require heparan sulfate with specific properties

    DEFF Research Database (Denmark)

    Mahalingam, Yashithra; Gallagher, John T; Couchman, John R

    2006-01-01

    Cell surface heparan sulfate (HS) proteoglycans are required in development and postnatal repair. Important classes of ligands for HS include growth factors and extracellular matrix macromolecules. For example, the focal adhesion component syndecan-4 interacts with the III(12-14) region of fibron......Cell surface heparan sulfate (HS) proteoglycans are required in development and postnatal repair. Important classes of ligands for HS include growth factors and extracellular matrix macromolecules. For example, the focal adhesion component syndecan-4 interacts with the III(12-14) region...... trap mutation in one of the two major glucosaminoglycan polymerases (EXT1). Several separate, specific properties of cell surface HS are therefore required in cell adhesion responses to the fibronectin HepII domain....

  18. Mechanical switching and coupling between two dissociation pathways in a P-selectin adhesion bond

    Science.gov (United States)

    Evans, Evan; Leung, Andrew; Heinrich, Volkmar; Zhu, Cheng

    2004-08-01

    Many biomolecular bonds exhibit a mechanical strength that increases in proportion to the logarithm of the rate of force application. Consistent with exponential decrease in bond lifetime under rising force, this kinetically limited failure reflects dissociation along a single thermodynamic pathway impeded by a sharp free energy barrier. Using a sensitive force probe to test the leukocyte adhesion bond P-selectin glycoprotein ligand 1 (PSGL-1)-P-selectin, we observed a linear increase of bond strength with each 10-fold increase in the rate of force application from 300 to 30,000 pN/sec, implying a single pathway for failure. However, the strength and lifetime of PSGL-1-P-selectin bonds dropped anomalously when loaded below 300 pN/sec, demonstrating unexpectedly faster dissociation and a possible second pathway for failure. Remarkably, if first loaded by a "jump" in force to 20-30 pN, the bonds became strong when subjected to a force ramp as slow as 30 pN/sec and exhibited the same single-pathway kinetics under all force rates. Applied in this way, a new "jump/ramp" mode of force spectroscopy was used to show that the PSGL-1-P-selectin bond behaves as a mechanochemical switch where force history selects between two dissociation pathways with markedly different properties. Furthermore, replacing PSGL-1 by variants of its 19-aa N terminus and by the crucial tetrasaccharide sialyl LewisX produces dramatic changes in the failure kinetics, suggesting a structural basis for the two pathways. The two-pathway switch seems to provide a mechanism for the "catch bond" response observed recently with PSGL-1-P-selectin bonds subjected to small-constant forces.

  19. The Adhesion Mechanism of Marine Mussel Foot Protein: Adsorption of L-Dopa on α- and β-Cristobalite Silica Using Density Functional Theory

    Directory of Open Access Journals (Sweden)

    Shabeer Ahmad Mian

    2017-01-01

    Full Text Available Marine mussels strongly adhere to various surfaces and endure their attachment under a variety of conditions. In order to understand the basic mechanism involved, we study the adsorption of L-dopa molecule on hydrophilic geminal and terminal isolated silanols of silica (001 surface. High content of modified amino acid L-dopa is found in the glue-like material secreted by the mussels through which it sticks to various surfaces under water. To understand the adsorption behavior, we have made use of periodic Density Functional Theory (DFT study. The L-dopa molecule adheres to silica surfaces terminated with geminal and terminal silanols via its catechol part. In both cases, the adhesion is achieved through the formation of 4 H-bonds. A binding energy of 29.48 and 31.67 kcal/mol has been estimated, after the inclusion of dispersion energy, for geminal and terminal silanols of silica, respectively. These results suggest a relatively stronger adhesion of dopa molecule for surface with terminal isolated silanols.

  20. CD36 binds oxidized low density lipoprotein (LDL) in a mechanism dependent upon fatty acid binding.

    Science.gov (United States)

    Jay, Anthony G; Chen, Alexander N; Paz, Miguel A; Hung, Justin P; Hamilton, James A

    2015-02-20

    The association of unesterified fatty acid (FA) with the scavenger receptor CD36 has been actively researched, with focuses on FA and oxidized low density lipoprotein (oxLDL) uptake. CD36 has been shown to bind FA, but this interaction has been poorly characterized to date. To gain new insights into the physiological relevance of binding of FA to CD36, we characterized FA binding to the ectodomain of CD36 by the biophysical method surface plasmon resonance. Five structurally distinct FAs (saturated, monounsaturated (cis and trans), polyunsaturated, and oxidized) were pulsed across surface plasmon resonance channels, generating association and dissociation binding curves. Except for the oxidized FA HODE, all FAs bound to CD36, with rapid association and dissociation kinetics similar to HSA. Next, to elucidate the role that each FA might play in CD36-mediated oxLDL uptake, we used a fluorescent oxLDL (Dii-oxLDL) live cell assay with confocal microscopy imaging. CD36-mediated uptake in serum-free medium was very low but greatly increased when serum was present. The addition of exogenous FA in serum-free medium increased oxLDL binding and uptake to levels found with serum and affected CD36 plasma membrane distribution. Binding/uptake of oxLDL was dependent upon the FA dose, except for docosahexaenoic acid, which exhibited binding to CD36 but did not activate the uptake of oxLDL. HODE also did not affect oxLDL uptake. High affinity FA binding to CD36 and the effects of each FA on oxLDL uptake have important implications for protein conformation, binding of other ligands, functional properties of CD36, and high plasma FA levels in obesity and type 2 diabetes.

  1. Quantum mechanics/molecular mechanics study of oxygen binding in hemocyanin.

    Science.gov (United States)

    Saito, Toru; Thiel, Walter

    2014-05-15

    We report a combined quantum mechanics/molecular mechanics (QM/MM) study on the mechanism of reversible dioxygen binding in the active site of hemocyanin (Hc). The QM region is treated by broken-symmetry density functional theory (DFT) with spin projection corrections. The X-ray structures of deoxygenated (deoxyHc) and oxygenated (oxyHc) hemocyanin are well reproduced by QM/MM geometry optimizations. The computed relative energies strongly depend on the chosen density functional. They are consistent with the available thermodynamic data for oxygen binding in hemocyanin and in synthetic model complexes when the BH&HLYP hybrid functional with 50% Hartree-Fock exchange is used. According to the QM(BH&HLYP)/MM results, the reaction proceeds stepwise with two sequential electron transfer (ET) processes in the triplet state followed by an intersystem crossing to the singlet product. The first ET step leads to a nonbridged superoxo CuB(II)-O2(•-) intermediate via a low-barrier transition state. The second ET step is even more facile and yields a side-on oxyHc complex with the characteristic Cu2O2 butterfly core, accompanied by triplet-singlet intersystem crossing. The computed barriers are very small so that the two ET processes are expected to very rapid and nearly simultaneous.

  2. Amino acid sequences mediating vascular cell adhesion molecule 1 binding to integrin alpha 4: homologous DSP sequence found for JC polyoma VP1 coat protein

    Directory of Open Access Journals (Sweden)

    Michael Andrew Meyer

    2013-07-01

    Full Text Available The JC polyoma viral coat protein VP1 was analyzed for amino acid sequences homologies to the IDSP sequence which mediates binding of VLA-4 (integrin alpha 4 to vascular cell adhesion molecule 1. Although the full sequence was not found, a DSP sequence was located near the critical arginine residue linked to infectivity of the virus and binding to sialic acid containing molecules such as integrins (3. For the JC polyoma virus, a DSP sequence was found at residues 70, 71 and 72 with homology also noted for the mouse polyoma virus and SV40 virus. Three dimensional modeling of the VP1 molecule suggests that the DSP loop has an accessible site for interaction from the external side of the assembled viral capsid pentamer.

  3. Amino Acid Sequences Mediating Vascular Cell Adhesion Molecule 1 Binding to Integrin Alpha 4: Homologous DSP Sequence Found for JC Polyoma VP1 Coat Protein.

    Science.gov (United States)

    Meyer, Michael Andrew

    2013-01-01

    The JC polyoma viral coat protein VP1 was analyzed for amino acid sequences homologies to the IDSP sequence which mediates binding of VLA-4 (integrin alpha 4) to vascular cell adhesion molecule 1. Although the full sequence was not found, a DSP sequence was located near the critical arginine residue linked to infectivity of the virus and binding to sialic acid containing molecules such as integrins (3). For the JC polyoma virus, a DSP sequence was found at residues 70, 71 and 72 with homology also noted for the mouse polyoma virus and SV40 virus. Three dimensional modeling of the VP1 molecule suggests that the DSP loop has an accessible site for interaction from the external side of the assembled viral capsid pentamer.

  4. Analysis of adhesive binding forces between laminin-1 and C2C12 muscle cell membranes measured via high resolution force spectroscopy

    Science.gov (United States)

    Gluck, George; Gilbert, Richard; Ortiz, Christine

    2002-03-01

    Laminins are a family of glycoproteins that regulate cell differentiation, shape, and motility through interactions with various cell surface receptors. Here, we have directly measured the biomolecular adhesive binding forces between a cantilever / probe tip that was covalently attached with laminin-1 and membrane receptors on C2C12 muscle cells using the technique of high-resolution force spectroscopy (HRFS). On retraction of the probe tip away from the membrane surface, discrete, long-range adhesive unbinding events were always observed. Statistical analysis of the data revealed an initial broad distribution of heterogeneous unbinding events (occurring at separation distances, D=0-2µm from the point of maximum compression) of magnitude 92.23±37.87pN followed by a narrow distribution of homogeneous unbinding events (occurring at D > 2µm) of magnitude 38.16±9.10pN, which is suggestive of an individual biomolecular adhesive interaction. On-going studies include loading rate dependence and effect of dystroglycan mutation.

  5. Carbohydrate-based anti-adhesive inhibition of Vibrio cholerae toxin binding to GM1-OS immobilized into artificial planar lipid membranes.

    Science.gov (United States)

    Sinclair, Haydn R; Kemp, Fred; Slegte, Jaap de; Gibson, Glenn R; Rastall, Robert A

    2009-10-12

    We have studied 'food grade' sialyloligosaccharides (SOS) as anti-adhesive drugs or receptor analogues, since the terminal sialic acid residue has already been shown to contribute significantly to the adhesion and pathogenesis of the Vibrio cholerae toxin (Ctx). GM1-oligosaccharide (GM1-OS) was immobilized into a supporting POPC lipid bilayer onto a surface plasmon resonance (SPR) chip, and the interaction between uninhibited Ctx and GM1-OS-POPC was measured. SOS inhibited 94.7% of the Ctx binding to GM1-OS-POPC at 10mg/mL. The SOS EC(50) value of 5.521mg/mL is high compared with 0.2811microg/mL (182.5rhoM or 1.825x10(-10)M) for GM1-OS. The commercially available sialyloligosaccharide (SOS) mixture Sunsial E((R)) is impure, containing one monosialylated and two disialylated oligosaccharides in the ratio 9.6%, 6.5% and 17.5%, respectively, and 66.4% protein. However, these inexpensive food-grade molecules are derived from egg yolk and could be used to fortify conventional food additives, by way of emulsifiers, sweeteners and/or preservatives. The work further supports our hypothesis that SOS could be a promising natural anti-adhesive glycomimetic against Ctx and prevent subsequent onset of disease.

  6. A novel membrane-dependent on/off switch mechanism of talin FERM domain at sites of cell adhesion

    Institute of Scientific and Technical Information of China (English)

    Xianqiang Song; Jun Qin; Jun Yang; Jamila Hirbawi; Sheng Ye; H Dhanuja Perera; Esen Goksoy; Pallavi Dwivedi; Edward F Plow; Rongguang Zhang

    2012-01-01

    The activation of heterodimeric (α/β) integrin transmembrane receptors by cytosolic protein talin is crucial for regulating diverse cell-adhesion-dependent processes,including blood coagulation,tissue remodeling,and cancer metastasis.This process is triggered by the coincident binding of N-terminal FERM (four-point-one-protein/ezrin/radixin/moesin) domain of talin (talin-FERM) to the inner membrane surface and integrin β cytoplasmic tail,but how these binding events are spatiotemporally regulated remains obscure.Here we report the crystal structure of a dormant talin,revealing how a C-terminal talin rod segment (talin-RS) self-masks a key integrin-binding site on talin-FERM via a large interface.Unexpectedly,the structure also reveals a distinct negatively charged surface on talin-RS that electrostatically hinders the talin-FERM binding to the membrane.Such a dual inhibitory topology for talin is consistent with the biochemical and functional data,but differs significantly from a previous model.We show that upon enrichment with phosphotidylinositol-4,5-bisphosphate (PIP2) - a known talin activator,membrane strongly attracts a positively charged surface on talin-FERM and simultaneously repels the negatively charged surface on talin-RS.Such an electrostatic "pull-push" process promotes the relief of the dual inhibition of talin-FERM,which differs from the classic "steric clash" model for conventional PIP2-induced FERM domain activation.These data therefore unravel a new type of membrane-dependent FERM domain regulation and illustrate how it mediates the talin on/off switches to regulate integrin transmembrane signaling and cell adhesion.

  7. Effect of Fluoride-Releasing Adhesive Systems on the Mechanical Properties of Eroded Dentin.

    Science.gov (United States)

    Guedes, Ana Paula Albuquerque; Moda, Mariana Dias; Suzuki, Thaís Yumi Umeda; Godas, André Gustavo de Lima; Sundfeld, Renato Herman; Briso, André Luiz Fraga; Santos, Paulo Henrique dos

    2016-01-01

    The aim of the study was to evaluate the effect of erosive pH cycling with solutions that simulate dental erosion on Martens hardness (HMV) and elastic modulus (Eit) of dentin restored with fluoride-releasing adhesive systems. Twenty-seven bovine dentin slabs were restored with three adhesive systems: Adper Single Bond 2 total-etch adhesive system, One Up Bond F and Clearfil SE Protect fluoride-containing self-etching adhesive systems. The restorations were made with Filtek Z250. The HMV and Eit values at distances of 10, 30, 50 and 70 µm from the interface were evaluated using a dynamic ultra microhardness tester before and after immersion in deionized water, citric acid and hydrochloric acid (n=9). Data were submitted to repeated-measures ANOVA and Fisher's PLSD tests (=0.05). After erosive cycling, HMV values of dentin decreased in all groups. For dentin restored with Adper Single Bond 2, the lowest values were found closer to the hybrid layer, while for One Up Bond F and Clearfil SE Protect, the values remained unaltered at all distances. For dentin restored with fluoride-releasing adhesive systems, a decrease in Eit was found, but after 30 µm this difference was not significant. The acid substances were able to alter HMV and Eit of the underlying dentin. For fluoride-releasing adhesives, the greater the distance from bonded interface, the lower the Eit values. The fluoride in One Up Bond F and Clearfil SE Protect was able to protect the underlying dentin closer to the materials. In this way, the fluoride from adhesive systems could have some positive effect in the early stages of erosive lesions.

  8. Scaffold-forming and Adhesive Contributions of Synthetic Laminin-binding Proteins to Basement Membrane Assembly*S⃞

    OpenAIRE

    McKee, Karen K.; Capizzi, Stephanie; Yurchenco, Peter D.

    2009-01-01

    Laminins that possess three short arms contribute to basement membrane assembly by anchoring to cell surfaces, polymerizing, and binding to nidogen and collagen IV. Although laminins containing the α4 and α5 subunits are expressed in α2-deficient congenital muscular dystrophy, they may be ineffective substitutes because they bind weakly to cell surfaces and/or because they lack the third arm needed for polymerization. We asked whether linker proteins engineered to bind...

  9. Stage-specific adhesion of Leishmania promastigotes to sand fly midguts assessed using an improved comparative binding assay.

    Directory of Open Access Journals (Sweden)

    Raymond Wilson

    Full Text Available BACKGROUND: The binding of Leishmania promastigotes to the midgut epithelium is regarded as an essential part of the life-cycle in the sand fly vector, enabling the parasites to persist beyond the initial blood meal phase and establish the infection. However, the precise nature of the promastigote stage(s that mediate binding is not fully understood. METHODOLOGY/PRINCIPAL FINDINGS: To address this issue we have developed an in vitro gut binding assay in which two promastigote populations are labelled with different fluorescent dyes and compete for binding to dissected sand fly midguts. Binding of procyclic, nectomonad, leptomonad and metacyclic promastigotes of Leishmania infantum and L. mexicana to the midguts of blood-fed, female Lutzomyia longipalpis was investigated. The results show that procyclic and metacyclic promastigotes do not bind to the midgut epithelium in significant numbers, whereas nectomonad and leptomonad promastigotes both bind strongly and in similar numbers. The assay was then used to compare the binding of a range of different parasite species (L. infantum, L. mexicana, L. braziliensis, L. major, L. tropica to guts dissected from various sand flies (Lu. longipalpis, Phlebotomus papatasi, P. sergenti. The results of these comparisons were in many cases in line with expectations, the natural parasite binding most effectively to its natural vector, and no examples were found where a parasite was unable to bind to its natural vector. However, there were interesting exceptions: L. major and L. tropica being able to bind to Lu. longipalpis better than L. infantum; L. braziliensis was able to bind to P. papatasi as well as L. major; and significant binding of L. major to P. sergenti and L. tropica to P. papatasi was observed. CONCLUSIONS/SIGNIFICANCE: The results demonstrate that Leishmania gut binding is strictly stage-dependent, is a property of those forms found in the middle phase of development (nectomonad and leptomonad

  10. Molecular Mechanisms of Pharmaceutical Drug Binding into Calsequestrin

    Directory of Open Access Journals (Sweden)

    ChulHee Kang

    2012-11-01

    Full Text Available Calsequestrin (CASQ is a major Ca2+-storage/buffer protein present in the sarcoplasmic reticulum of both skeletal (CASQ1 and cardiac (CASQ2 muscles. CASQ has significant affinity for a number of pharmaceutical drugs with known muscular toxicities. Our approach, with in silico molecular docking, single crystal X-ray diffraction, and isothermal titration calorimetry (ITC, identified three distinct binding pockets on the surface of CASQ2, which overlap with 2-methyl-2,4-pentanediol (MPD binding sites observed in the crystal structure. Those three receptor sites based on canine CASQ1 crystal structure gave a high correlation (R2 = 0.80 to our ITC data. Daunomycin, doxorubicin, thioridazine, and trifluoperazine showed strong affinity to the S1 site, which is a central cavity formed between three domains of CASQ2. Some of the moderate-affinity drugs and some high-affinity drugs like amlodipine and verapamil displayed their binding into S2 sites, which are the thioredoxin-like fold present in each CASQ domain. Docking predictions combined with dissociation constants imply that presence of large aromatic cores and less flexible functional groups determines the strength of binding affinity to CASQ. In addition, the predicted binding pockets for both caffeine and epigallocatechin overlapped with the S1 and S2 sites, suggesting competitive inhibition by these natural compounds as a plausible explanation for their antagonistic effects on cardiotoxic side effects.

  11. A triad of lys12, lys41, arg78 spatial domain, a novel identified heparin binding site on tat protein, facilitates tat-driven cell adhesion.

    Directory of Open Access Journals (Sweden)

    Jing Ai

    Full Text Available Tat protein, released by HIV-infected cells, has a battery of important biological effects leading to distinct AIDS-associated pathologies. Cell surface heparan sulfate protoglycans (HSPGs have been accepted as endogenous Tat receptors, and the Tat basic domain has been identified as the heparin binding site. However, findings that deletion or substitution of the basic domain inhibits but does not completely eliminate Tat-heparin interactions suggest that the basic domain is not the sole Tat heparin binding site. In the current study, an approach integrating computational modeling, mutagenesis, biophysical and cell-based assays was used to elucidate a novel, high affinity heparin-binding site: a Lys12, Lys41, Arg78 (KKR spatial domain. This domain was also found to facilitate Tat-driven β1 integrin activation, producing subsequent SLK cell adhesion in an HSPG-dependent manner, but was not involved in Tat internalization. The identification of this new heparin binding site may foster further insight into the nature of Tat-heparin interactions and subsequent biological functions, facilitating the rational design of new therapeutics against Tat-mediated pathological events.

  12. A triad of lys12, lys41, arg78 spatial domain, a novel identified heparin binding site on tat protein, facilitates tat-driven cell adhesion.

    Science.gov (United States)

    Ai, Jing; Xin, Xianliang; Zheng, Mingyue; Wang, Shuai; Peng, Shuying; Li, Jing; Wang, Limei; Jiang, Hualiang; Geng, Meiyu

    2008-01-01

    Tat protein, released by HIV-infected cells, has a battery of important biological effects leading to distinct AIDS-associated pathologies. Cell surface heparan sulfate protoglycans (HSPGs) have been accepted as endogenous Tat receptors, and the Tat basic domain has been identified as the heparin binding site. However, findings that deletion or substitution of the basic domain inhibits but does not completely eliminate Tat-heparin interactions suggest that the basic domain is not the sole Tat heparin binding site. In the current study, an approach integrating computational modeling, mutagenesis, biophysical and cell-based assays was used to elucidate a novel, high affinity heparin-binding site: a Lys12, Lys41, Arg78 (KKR) spatial domain. This domain was also found to facilitate Tat-driven β1 integrin activation, producing subsequent SLK cell adhesion in an HSPG-dependent manner, but was not involved in Tat internalization. The identification of this new heparin binding site may foster further insight into the nature of Tat-heparin interactions and subsequent biological functions, facilitating the rational design of new therapeutics against Tat-mediated pathological events.

  13. [Adhesion of corynebacterium diphtheriae: the role of surface structures and formation mechanism].

    Science.gov (United States)

    Kharseeva, G G; Alieva, A A

    2014-01-01

    The paper is devoted to the study of surface structures including pili (fimbriae) 67-72p surface protein, DIP 1281 surface protein, lipoarabinomannan CdiLAM and their role in the adhesion and colonization of the mucous membrane of the throat by Corynebacterium diphtheriae. A description is offered for the main stages in the adhesion process of diphtheria causative agent and the ability of its adhesins to stimulate the effect of innate and acquired immunity factors. The paper stresses prospectiveness of the development of vaccines forming immunoprotection of the organism against adhesive activity of C. diphtheriae and also preventing their colonization and reproduction. That would facilitate a solution for the problem of diphtheria carrier state, which cannot be solved using the existing means of preventive vaccination.

  14. Polysaccharide structural features that are critical for the binding of sulfated fucans to bindin, the adhesive protein from sea urchin sperm.

    Science.gov (United States)

    DeAngelis, P L; Glabe, C G

    1987-10-15

    We have investigated the structural features of sulfated fucose-containing polysaccharides which are responsible for their selective binding to Strongylocentrotus purpuratus bindin. The data presented demonstrate that the sulfate esters and a molecular weight in excess of approximately 15,000 are required for high affinity binding of the fucans to bindin. Desulfation destroys the binding activity of the fucans, which can be fully restored by chemical resulfation. Fucan fragments of an average molecular weight of 15,000 were nearly as active as the starting material (Mr 10(6)). The observed IC50 value for fragments of Mr congruent to 10,000 and Mr congruent to 5,000 were 1 and 2 orders of magnitude higher, respectively. The binding of fucoidan to bindin is stable in high salt (50% at 1.2 M NaCl) whereas the binding of fucoidan to DEAE-cellulose or polylysine is inhibited by the concentrations of salt normally found in sea water (50% at 0.2 and 0.5 M NaCl, respectively). This result suggests that the binding mechanism is not a simple ionic interaction and that hydrogen bonding and cooperativity may also be important determinants of the binding mechanism. We also found that polyvinyl sulfate binds to bindin with high affinity and inhibits the bindin-mediated agglutination of sea urchin eggs. The results of these investigations suggest that the spatial orientation of the sulfate esters plays a critical role in determining the selectivity of sulfated polysaccharide binding and that the polysaccharide backbone does not play a direct role in the binding mechanism.

  15. Primary cilia utilize glycoprotein-dependent adhesion mechanisms to stabilize long-lasting cilia-cilia contacts

    Directory of Open Access Journals (Sweden)

    Ott Carolyn

    2012-04-01

    Full Text Available Abstract Background The central tenet of cilia function is sensing and transmitting information. The capacity to directly contact extracellular surfaces would empower primary cilia to probe the environment for information about the nature and location of nearby surfaces. It has been well established that flagella and other motile cilia perform diverse cellular functions through adhesion. We hypothesized that mammalian primary cilia also interact with the extracellular environment through direct physical contact. Methods We identified cilia in rod photoreceptors and cholangiocytes in fixed mouse tissues and examined the structures that these cilia contact in vivo. We then utilized an MDCK cell culture model to characterize the nature of the contacts we observed. Results In retina and liver tissue, we observed that cilia from nearby cells touch one another. Using MDCK cells, we found compelling evidence that these contacts are stable adhesions that form bridges between two cells, or networks between many cells. We examined the nature and duration of the cilia-cilia contacts and discovered primary cilia movements that facilitate cilia-cilia encounters. Stable adhesions form as the area of contact expands from a single point to a stretch of tightly bound, adjacent cilia membranes. The cilia-cilia contacts persisted for hours and were resistant to several harsh treatments such as proteases and DTT. Unlike many other cell adhesion mechanisms, calcium was not required for the formation or maintenance of cilia adhesion. However, swainsonine, which blocks maturation of N-linked glycoproteins, reduced contact formation. We propose that cellular control of adhesion maintenance is active because cilia adhesion did not prevent cell division; rather, contacts dissolved during mitosis as cilia were resorbed. Conclusions The demonstration that mammalian primary cilia formed prolonged, direct, physical contacts supports a novel paradigm: that mammalian primary

  16. Peritoneal Adhesions as a Cause of Mechanical Small Bowel Obstruction Based on Own Experience

    Directory of Open Access Journals (Sweden)

    Morawski Bartłomiej

    2015-02-01

    Full Text Available Bowel obstruction is a condition which has been known for many years. As time goes by, the problem is still often encountered at surgical emergency rooms. More than 20% of emergency surgical interventions are performed because of symptoms of digestive tract obstruction with the disease mostly situated in the small bowel. Rates of causative factors of the disease have changed over recent years and there have been increasingly more cases of small bowel obstruction caused by peritoneal adhesions, i.e., adhesive small bowel obstruction (ASBO.

  17. A fundamental approach to adhesion: Synthesis, surface analysis, thermodynamics and mechanics. [titanium alloys

    Science.gov (United States)

    Chen, W.; Dwight, D. W.; Wightman, J. P.

    1978-01-01

    Various surface preparations for titanium 6-4 alloy were studied. An anodizing method was investigated, and compared with the results of other chemical treatments, namely, phosphate/fluoride, Pasa-Jell and Turco. The relative durability of the different surface treatments was assessed by monitoring changes in surface chemistry and morphology occasioned by aging at 505 K (450 F). Basic electron spectroscopic data were collected for polyimide and polyphenylquinoxaline adhesives and synthetic precursors. Fractographic studies were completed for several combinations of adherend, adhesive, and testing conditions.

  18. Statistical Mechanics of Transcription-Factor Binding Site Discovery Using Hidden Markov Models.

    Science.gov (United States)

    Mehta, Pankaj; Schwab, David J; Sengupta, Anirvan M

    2011-04-01

    Hidden Markov Models (HMMs) are a commonly used tool for inference of transcription factor (TF) binding sites from DNA sequence data. We exploit the mathematical equivalence between HMMs for TF binding and the "inverse" statistical mechanics of hard rods in a one-dimensional disordered potential to investigate learning in HMMs. We derive analytic expressions for the Fisher information, a commonly employed measure of confidence in learned parameters, in the biologically relevant limit where the density of binding sites is low. We then use techniques from statistical mechanics to derive a scaling principle relating the specificity (binding energy) of a TF to the minimum amount of training data necessary to learn it.

  19. Mechanism of neuroinflammation: enhanced cytotoxicity and IL-17 production via CD46 binding.

    Science.gov (United States)

    Yao, Karen; Graham, Jhanelle; Akahata, Yoshimi; Oh, Unsong; Jacobson, Steven

    2010-09-01

    The membrane co-factor protein CD46 is the cellular receptor for a number of pathogens including the human herpesvirus 6 (HHV-6). In addition to its function as an inhibitory complement receptor, engagement of CD46 in the context of T-cell receptor (TCR) signaling influences T-cell activation. Simultaneous cross-linking of the CD3/CD46 molecules led to differentiation of a unique population of CD4+ T-cell subset characterized by enhanced expressions of IFN-gamma, IL-10, granzyme B, adhesion molecule MAdCAM-1 (alpha-4-beta-7), surface-bound cytokine LIGHT, and chemokine receptor CCR9. Multiple sclerosis is a chronic inflammatory neurodegenerative disorder of the central nervous system (CNS) with unknown etiology. The HHV-6 is a candidate pathogen in MS and uses the CD46 molecule as its receptor. We hypothesize that binding of the HHV-6 glycoprotein to CD46 may trigger a pro-inflammatory response that could contribute to CNS tissue damage. To address this question, we examined immunological parameters such as proliferation, cytokine production and cytotoxic functions in CD4+ T cells of healthy individuals and MS patients following CD3/CD46 co-engagement by using anti-CD3 and anti-CD46 monoclonal antibodies as surrogates to mimic T-cell receptor and CD46 signaling. Our results demonstrated that CD3/CD46 cross-linking induced expression of IL-1beta and IL-17A in multiple sclerosis patient T cells. Additionally, increase in transient surface expression of lysosomal associated protein CD107a suggested enhanced CD4+ T-cell cytotoxic functions following CD3/CD46 co-stimulation. Collectively, this study demonstrated evidence to suggest a potential mechanism of virus-induced neuroinflammation that may be involved in MS disease pathogenesis.

  20. Physical and Mechanical Evaluation of Silicone-Based Double-Layer Adhesive Patch Intended for Keloids and Scar Treatment Therapy

    Directory of Open Access Journals (Sweden)

    Barbara Mikolaszek

    2016-11-01

    Full Text Available Growing interest in silicone elastomers for pharmaceutical purposes is due to both their beneficial material effect for scar treatment and their potential as drug carriers. Regarding their morphological structure, silicone polymers possess unique properties, which enable a wide range of applicability possibilities. The present study focused on developing a double-layer adhesive silicone film (DLASil by evaluating its physical and mechanical properties, morphology, and stability. DLASil suitability for treatment of scars and keloids was evaluated by measurement of tensile strength, elasticity modulus, and elongation. The results indicated that mechanical and physical properties of the developed product were satisfying.

  1. Binding of complement inhibitor C4b-binding protein to a highly virulent Streptococcus pyogenes M1 strain is mediated by protein H and enhances adhesion to and invasion of endothelial cells.

    Science.gov (United States)

    Ermert, David; Weckel, Antonin; Agarwal, Vaibhav; Frick, Inga-Maria; Björck, Lars; Blom, Anna M

    2013-11-08

    Streptococcus pyogenes AP1, a strain of the highly virulent M1 serotype, uses exclusively protein H to bind the complement inhibitor C4b-binding protein (C4BP). We found a strong correlation between the ability of AP1 and its isogenic mutants lacking protein H to inhibit opsonization with complement C3b and binding of C4BP. C4BP bound to immobilized protein H or AP1 bacteria retained its cofactor activity for degradation of (125)I-C4b. Furthermore, C4b deposited from serum onto AP1 bacterial surfaces was processed into C4c/C4d fragments, which did not occur on strains unable to bind C4BP. Recombinant C4BP mutants, which (i) lack certain CCP domains or (ii) have mutations in single aa as well as (iii) mutants with additional aa between different CCP domains were used to determine that the binding is mainly mediated by a patch of positively charged amino acid residues at the interface of domains CCP1 and CCP2. Using recombinant protein H fragments, we narrowed down the binding site to the N-terminal domain A. With a peptide microarray, we identified one single 18-amino acid-long peptide comprising residues 92-109, which specifically bound C4BP. Biacore was used to determine KD = 6 × 10(-7) M between protein H and a single subunit of C4BP. C4BP binding also correlated with elevated levels of adhesion and invasion to endothelial cells. Taken together, we identified the molecular basis of C4BP-protein H interaction and found that it is not only important for decreased opsonization but also for invasion of endothelial cells by S. pyogenes.

  2. Mechanical stimulation of C2C12 cells increases m-calpain expression, focal adhesion plaque protein degradation

    DEFF Research Database (Denmark)

    Grossi, Alberto; Karlsson, Anders H; Lawson, Moira Ann

    2008-01-01

    reorganization due to the activity of the ubiquitous proteolytic enzymes, calpains, has been reported. Whether there is a link between stretch- or load-induced signaling and calpain expression and activation is not known. Using a magnetic bead stimulation assay and C2C12 mouse myoblasts cell population, we have...... demonstrated that mechanical stimulation via laminin receptors leads to an increase in m-calpain expression, but no increase in the expression of other calpain isoforms. Our study revealed that after a short period of stimulation, m-calpain relocates into focal adhesion complexes and is followed by a breakdown...... of specific focal adhesion proteins previously identified as substrates for this enzyme. We show that stimulation also leads to an increase in calpain activity in these cells. These data support the pivotal role for m-calpain in the control of muscle precursor cell differentiation and thus strengthen the idea...

  3. Pressure-Sensitive Adhesives under the Influence of Relative Humidity: Inner Structure and Failure Mechanisms.

    Science.gov (United States)

    Schindler, Markus; Koller, Manuel; Müller-Buschbaum, Peter

    2015-06-17

    Model pressure-sensitive adhesive (PSA) films of the statistical copolymer P(EHA-stat-20MMA), which comprises 80% ethylhexyl acrylate (EHA) and 20% methyl methacrylate (MMA), are studied. The PSA films are stored under different relative humidities from postproduction treatment, which also influence the tack performance. This finding is supported by tack measurements using punches with different roughness.

  4. Insights on Structural Characteristics and Ligand Binding Mechanisms of CDK2

    Science.gov (United States)

    Li, Yan; Zhang, Jingxiao; Gao, Weimin; Zhang, Lilei; Pan, Yanqiu; Zhang, Shuwei; Wang, Yonghua

    2015-01-01

    Cyclin-dependent kinase 2 (CDK2) is a crucial regulator of the eukaryotic cell cycle. However it is well established that monomeric CDK2 lacks regulatory activity, which needs to be aroused by its positive regulators, cyclins E and A, or be phosphorylated on the catalytic segment. Interestingly, these activation steps bring some dynamic changes on the 3D-structure of the kinase, especially the activation segment. Until now, in the monomeric CDK2 structure, three binding sites have been reported, including the adenosine triphosphate (ATP) binding site (Site I) and two non-competitive binding sites (Site II and III). In addition, when the kinase is subjected to the cyclin binding process, the resulting structural changes give rise to a variation of the ATP binding site, thus generating an allosteric binding site (Site IV). All the four sites are demonstrated as being targeted by corresponding inhibitors, as is illustrated by the allosteric binding one which is targeted by inhibitor ANS (fluorophore 8-anilino-1-naphthalene sulfonate). In the present work, the binding mechanisms and their fluctuations during the activation process attract our attention. Therefore, we carry out corresponding studies on the structural characterization of CDK2, which are expected to facilitate the understanding of the molecular mechanisms of kinase proteins. Besides, the binding mechanisms of CDK2 with its relevant inhibitors, as well as the changes of binding mechanisms following conformational variations of CDK2, are summarized and compared. The summary of the conformational characteristics and ligand binding mechanisms of CDK2 in the present work will improve our understanding of the molecular mechanisms regulating the bioactivities of CDK2. PMID:25918937

  5. Insights on Structural Characteristics and Ligand Binding Mechanisms of CDK2

    Directory of Open Access Journals (Sweden)

    Yan Li

    2015-04-01

    Full Text Available Cyclin-dependent kinase 2 (CDK2 is a crucial regulator of the eukaryotic cell cycle. However it is well established that monomeric CDK2 lacks regulatory activity, which needs to be aroused by its positive regulators, cyclins E and A, or be phosphorylated on the catalytic segment. Interestingly, these activation steps bring some dynamic changes on the 3D-structure of the kinase, especially the activation segment. Until now, in the monomeric CDK2 structure, three binding sites have been reported, including the adenosine triphosphate (ATP binding site (Site I and two non-competitive binding sites (Site II and III. In addition, when the kinase is subjected to the cyclin binding process, the resulting structural changes give rise to a variation of the ATP binding site, thus generating an allosteric binding site (Site IV. All the four sites are demonstrated as being targeted by corresponding inhibitors, as is illustrated by the allosteric binding one which is targeted by inhibitor ANS (fluorophore 8-anilino-1-naphthalene sulfonate. In the present work, the binding mechanisms and their fluctuations during the activation process attract our attention. Therefore, we carry out corresponding studies on the structural characterization of CDK2, which are expected to facilitate the understanding of the molecular mechanisms of kinase proteins. Besides, the binding mechanisms of CDK2 with its relevant inhibitors, as well as the changes of binding mechanisms following conformational variations of CDK2, are summarized and compared. The summary of the conformational characteristics and ligand binding mechanisms of CDK2 in the present work will improve our understanding of the molecular mechanisms regulating the bioactivities of CDK2.

  6. Particle adhesion and removal

    CERN Document Server

    Mittal, K L

    2015-01-01

    The book provides a comprehensive and easily accessible reference source covering all important aspects of particle adhesion and removal.  The core objective is to cover both fundamental and applied aspects of particle adhesion and removal with emphasis on recent developments.  Among the topics to be covered include: 1. Fundamentals of surface forces in particle adhesion and removal.2. Mechanisms of particle adhesion and removal.3. Experimental methods (e.g. AFM, SFA,SFM,IFM, etc.) to understand  particle-particle and particle-substrate interactions.4. Mechanics of adhesion of micro- and  n

  7. Therapeutic effects of tyroservatide on metastasis of lung cancer and its mechanism affecting integrin–focal adhesion kinase signal transduction

    Science.gov (United States)

    Huang, Yu-ting; Zhao, Lan; Fu, Zheng; Zhao, Meng; Song, Xiao-meng; Jia, Jing; Wang, Song; Li, Jin-ping; Zhu, Zhi-feng; Lin, Gang; Lu, Rong; Yao, Zhi

    2016-01-01

    Tyroservatide (YSV) can inhibit the growth and metastasis of mouse lung cancer significantly. This study investigated the therapeutic effects of tripeptide YSV on metastasis of human lung cancer cells and explored its possible mechanism that affects integrin–focal adhesion kinase (FAK) signal transduction in tumor cells. YSV significantly inhibited the adhesion and the invasion of highly metastatic human lung cancer cell lines 95D, A549, and NCI-H1299. In addition, YSV significantly inhibited phosphorylation of FAK Tyr397 and FAK Tyr576/577 in the 95D, A549, and NCI-H1299 human lung cancer cells in vitro. And the mRNA level and protein expression of FAK in these human lung cancer cells decreased at the same time. YSV also significantly inhibited mRNA and protein levels of integrin β1 and integrin β3 in the 95D, A549, and NCI-H1299 human lung cancer cells. Our research showed that YSV inhibited adhesion and invasion of human lung cancer cells and exhibited therapeutic effects on metastasis of lung cancer. PMID:27041993

  8. Signaling mechanisms of neurite outgrowth induced by the cell adhesion molecules NCAM and N-cadherin

    DEFF Research Database (Denmark)

    Hansen, S M; Berezin, V; Bock, E

    2008-01-01

    Formation of appropriate neural circuits depends on a complex interplay between extracellular guiding cues and intracellular signaling events that result in alterations of cytoskeletal dynamics and a neurite growth response. Surface-expressed cell adhesion molecules (CAMs) interact with the surro...... interaction between NCAM and N-cadherin with a number of intracellular partners, as well as on their interaction with the fibroblast growth factor receptor (FGFR)....

  9. Multiscale treatment of theoretical mechanisms for the protection of hydrogel surfaces from adhesive forces

    Science.gov (United States)

    Sokoloff, J. B.

    2014-09-01

    One role of a lubricant is to prevent wear of two surfaces in contact, which is likely to be the result of adhesive forces that cause a pair of asperities belonging to two surfaces in contact to stick together. Such adhesive sticking of asperities can occur both for sliding surfaces and for surfaces which are pressed together and then pulled apart. The latter situation, for example, is important for contact lenses, as prevention of sticking reduces possible damage to the cornea as the lenses are inserted and removed from the eye. Contact lenses are made from both neutral and polyelectrolyte hydrogels. It is demonstrated here that sticking of neutral hydrogels can be prevented by repulsive forces between asperities in contact, resulting from polymers attached to the gel surface but not linked with each other. For polyelectrolyte hydrogels, it is shown that osmotic pressure due to counterions, held at the interface between asperities in contact by the electrostatic attraction between the ions and the fixed charges in the gel, can provide a sufficiently strong repulsive force to prevent adhesive sticking of small-length-scale asperities.

  10. Chemical functionalization of ceramic tile surfaces by silane coupling agents: polymer modified mortar adhesion mechanism implications

    Directory of Open Access Journals (Sweden)

    Alexandra Ancelmo Piscitelli Mansur

    2008-09-01

    Full Text Available Adhesion between tiles and mortars are crucial to the stability of ceramic tile systems. From the chemical point of view, weak forces such as van der Waals forces and hydrophilic interactions are expected to be developed preferably at the tiles and polymer modified Portland cement mortar interface. The main goal of this paper was to use organosilanes as primers to modify ceramic tile hydrophilic properties to improve adhesion between ceramic tiles and polymer modified mortars. Glass tile surfaces were treated with several silane derivatives bearing specific functionalities. Contact angle measurements and Fourier Transform Infrared Spectroscopy (FTIR were used for evaluating the chemical changes on the tile surface. In addition, pull-off tests were conducted to assess the effect on adhesion properties between tile and poly(ethylene-co-vinyl acetate, EVA, modified mortar. The bond strength results have clearly shown the improvement of adherence at the tile-polymer modified mortar interface, reflecting the overall balance of silane, cement and polymer interactions.

  11. Both common and specialty mushrooms inhibit adhesion molecule expression and in vitro binding of monocytes to human aortic endothelial cells in a pro-inflammatory environment

    Directory of Open Access Journals (Sweden)

    Martin Keith R

    2010-07-01

    Full Text Available Abstract Background Cardiovascular disease (CVD is a leading cause of mortality in the United States as well as globally. Epidemiological studies show that regular fruit and vegetable consumption reduces CVD risk, in part, due to antioxidant activity and immunomodulation since oxidative stress and inflammation are features of atherogenesis. Accumulating evidence also shows that dietary fungi, viz., mushrooms, can protect against chronic disease by altering inflammatory environments such as those associated with CVD although most research has focused on specialty mushrooms. In this study, we tested the ability of both common and specialty mushrooms to inhibit cellular processes associated with CVD. Methods Human aortic endothelial cells (HAEC were incubated overnight with control media with dimethylsulfoxide (DMSO vehicle (1% v/v or containing DMSO extracts of whole dehydrated mushrooms (0.1 mg/mL, which included Agaricus bisporus (white button and crimini, Lentinula edodes (shiitake, Pleurotus ostreatus (oyster, and Grifola frondosa (maitake. Monolayers were subsequently washed and incubated with medium alone or containing the pro-inflammatory cytokine IL-1β (5 ng/mL for 6 h to upregulate pro-atherosclerotic adhesion molecules (AM. AM expression was assayed by ELISA and binding of U937 human monocytes pre-loaded with fluorescent dye was determined. Results White button mushrooms consistently reduced (p Conclusion These data provide evidence that dietary mushrooms can inhibit cellular processes such as adhesion molecule expression and ultimate binding of monocytes to the endothelium under pro-inflammatory conditions, which are associated with CVD. As a result, these findings support the notion that dietary mushrooms can be protective against CVD.

  12. Spectroscopic and Docking Studies on the Binding of Liquiritigenin with Hyaluronidase for Antiallergic Mechanism

    Directory of Open Access Journals (Sweden)

    Hua-jin Zeng

    2016-01-01

    Full Text Available The inhibitory effect of liquiritigenin on hyaluronidase and its binding mechanism were investigated systematically by UV-vis absorption, fluorescence, and molecular modeling approaches. These results indicated that liquiritigenin could interact with hyaluronidase to form a liquiritigenin-hyaluronidase complex. The binding constant, number of binding sites, and thermodynamic parameters were calculated, which indicated that liquiritigenin could spontaneously bind with hyaluronidase mainly through electrostatic and hydrophobic interactions with one binding site. Synchronous fluorescence, three-dimensional fluorescence, and molecular docking results revealed that liquiritigenin bound directly to the enzyme cavity site and this binding influenced the microenvironment of the hyaluronidase activity site, resulting in reduced hyaluronidase activity. The present study provides useful information for clinical applications of liquiritigenin as a hyaluronidase inhibitor.

  13. Effects of ligand binding on the mechanical properties of ankyrin repeat protein gankyrin.

    Directory of Open Access Journals (Sweden)

    Giovanni Settanni

    Full Text Available Ankyrin repeat proteins are elastic materials that unfold and refold sequentially, repeat by repeat, under force. Herein we use atomistic molecular dynamics to compare the mechanical properties of the 7-ankyrin-repeat oncoprotein Gankyrin in isolation and in complex with its binding partner S6-C. We show that the bound S6-C greatly increases the resistance of Gankyrin to mechanical stress. The effect is specific to those repeats of Gankyrin directly in contact with S6-C, and the mechanical 'hot spots' of the interaction map to the same repeats as the thermodynamic hot spots. A consequence of stepwise nature of unfolding and the localized nature of ligand binding is that it impacts on all aspects of the protein's mechanical behavior, including the order of repeat unfolding, the diversity of unfolding pathways accessed, the nature of partially unfolded intermediates, the forces required and the work transferred to the system to unfold the whole protein and its parts. Stepwise unfolding thus provides the means to buffer repeat proteins and their binding partners from mechanical stress in the cell. Our results illustrate how ligand binding can control the mechanical response of proteins. The data also point to a cellular mechano-switching mechanism whereby binding between two partner macromolecules is regulated by mechanical stress.

  14. Cadherin-11 localizes to focal adhesions and promotes cell–substrate adhesion

    Science.gov (United States)

    Langhe, Rahul P.; Gudzenko, Tetyana; Bachmann, Michael; Becker, Sarah F.; Gonnermann, Carina; Winter, Claudia; Abbruzzese, Genevieve; Alfandari, Dominique; Kratzer, Marie-Claire; Franz, Clemens M.; Kashef, Jubin

    2016-01-01

    Cadherin receptors have a well-established role in cell–cell adhesion, cell polarization and differentiation. However, some cadherins also promote cell and tissue movement during embryonic development and tumour progression. In particular, cadherin-11 is upregulated during tumour and inflammatory cell invasion, but the mechanisms underlying cadherin-11 stimulated cell migration are still incompletely understood. Here, we show that cadherin-11 localizes to focal adhesions and promotes adhesion to fibronectin in Xenopus neural crest, a highly migratory embryonic cell population. Transfected cadherin-11 also localizes to focal adhesions in different mammalian cell lines, while endogenous cadherin-11 shows focal adhesion localization in primary human fibroblasts. In focal adhesions, cadherin-11 co-localizes with β1-integrin and paxillin and physically interacts with the fibronectin-binding proteoglycan syndecan-4. Adhesion to fibronectin mediated by cadherin-11/syndecan-4 complexes requires both the extracellular domain of syndecan-4, and the transmembrane and cytoplasmic domains of cadherin-11. These results reveal an unexpected role of a classical cadherin in cell–matrix adhesion during cell migration. PMID:26952325

  15. Investigation into the Formation and Adhesion of Cyclopentane Hydrates on Mechanically Robust Vapor-Deposited Polymeric Coatings.

    Science.gov (United States)

    Sojoudi, Hossein; Walsh, Matthew R; Gleason, Karen K; McKinley, Gareth H

    2015-06-09

    Blockage of pipelines by formation and accumulation of clathrate hydrates of natural gases (also called gas hydrates) can compromise project safety and economics in oil and gas operations, particularly at high pressures and low temperatures such as those found in subsea or arctic environments. Cyclopentane (CyC5) hydrate has attracted interest as a model system for studying natural gas hydrates, because CyC5, like typical natural gas hydrate formers, is almost fully immiscible in water; and thus CyC5 hydrate formation is governed not only by thermodynamic phase considerations but also kinetic factors such as the hydrocarbon/water interfacial area, as well as mass and heat transfer constraints, as for natural gas hydrates. We present a macroscale investigation of the formation and adhesion strength of CyC5 hydrate deposits on bilayer polymer coatings with a range of wettabilities. The polymeric bilayer coatings are developed using initiated chemical vapor deposition (iCVD) of a mechanically robust and densely cross-linked polymeric base layer (polydivinylbenzene or pDVB) that is capped with a covalently attached thin hydrate-phobic fluorine-rich top layer (poly(perfluorodecyl acrylate) or pPFDA). The CyC5 hydrates are formed from CyC5-in-water emulsions, and differential scanning calorimetry (DSC) is used to confirm the thermal dissociation properties of the solid hydrate deposits. We also investigate the adhesion of the CyC5 hydrate deposits on bare and bilayer polymer-coated silicon and steel substrates. Goniometric measurements with drops of CyC5-in-water emulsions on the coated steel substrates exhibit advancing contact angles of 148.3 ± 4.5° and receding contact angles of 142.5 ± 9.8°, indicating the strongly emulsion-repelling nature of the iCVD coatings. The adhesion strength of the CyC5 hydrate deposits is reduced from 220 ± 45 kPa on rough steel substrates to 20 ± 17 kPa on the polymer-coated steel substrates. The measured strength of CyC5 hydrate

  16. Neural cell adhesion molecule induces intracellular signaling via multiple mechanisms of Ca2+ homeostasis

    DEFF Research Database (Denmark)

    Kiryushko, Darya; Korshunova, Irina; Berezin, Vladimir;

    2006-01-01

    The neural cell adhesion molecule (NCAM) plays a pivotal role in the development of the nervous system, promoting neuronal differentiation via homophilic (NCAM-NCAM) as well as heterophilic (NCAM-fibroblast growth factor receptor [FGFR]) interactions. NCAM-induced intracellular signaling has been....... The first pathway was associated with activation of FGFR, phospholipase Cgamma, and production of diacylglycerol, and the second pathway involved Src-family kinases. Moreover, NCAM-mediated Ca2+ entry required activation of nonselective cation and T-type voltage-gated Ca2+ channels. These channels, together...

  17. Neisserial outer membrane vesicles bind the coinhibitory receptor carcinoembryonic antigen-related cellular adhesion molecule 1 and suppress CD4+ T lymphocyte function.

    Science.gov (United States)

    Lee, Hannah S W; Boulton, Ian C; Reddin, Karen; Wong, Henry; Halliwell, Denise; Mandelboim, Ofer; Gorringe, Andrew R; Gray-Owen, Scott D

    2007-09-01

    Pathogenic Neisseria bacteria naturally liberate outer membrane "blebs," which are presumed to contribute to pathology, and the detergent-extracted outer membrane vesicles (OMVs) from Neisseria meningitidis are currently employed as meningococcal vaccines in humans. While the composition of these vesicles reflects the bacteria from which they are derived, the functions of many of their constituent proteins remain unexplored. The neisserial colony opacity-associated Opa proteins function as adhesins, the majority of which mediate bacterial attachment to human carcinoembryonic antigen-related cellular adhesion molecules (CEACAMs). Herein, we demonstrate that the Opa proteins within OMV preparations retain the capacity to bind the immunoreceptor tyrosine-based inhibitory motif-containing coinhibitory receptor CEACAM1. When CD4(+) T lymphocytes were exposed to OMVs from Opa-expressing bacteria, their activation and proliferation in response to a variety of stimuli were effectively halted. This potent immunosuppressive effect suggests that localized infection will generate a "zone of inhibition" resulting from the diffusion of membrane blebs into the surrounding tissues. Moreover, it demonstrates that OMV-based vaccines must be developed from strains that lack CEACAM1-binding Opa variants.

  18. MUC16 contributes to the metastasis of pancreatic ductal adenocarcinoma through focal adhesion mediated signaling mechanism

    Science.gov (United States)

    Chugh, Seema; Rachagani, Satyanarayana; Lakshmanan, Imayavaramban; Gupta, Suprit; Seshacharyulu, Parthasarathy; Smith, Lynette M.; Ponnusamy, Moorthy P.; Batra, Surinder K.

    2016-01-01

    MUC16, a heavily glycosylated type-I transmembrane mucin is overexpressed in several cancers including pancreatic ductal adenocarcinoma (PDAC). Previously, we have shown that MUC16 is significantly overexpressed in human PDAC tissues. However, the functional consequences and its role in PDAC is poorly understood. Here, we show that MUC16 knockdown decreases PDAC cell proliferation, colony formation and migration in vitro. Also, MUC16 knockdown decreases the tumor formation and metastasis in orthotopic xenograft mouse model. Mechanistically, immunoprecipitation and immunofluorescence analyses confirms MUC16 interaction with galectin-3 and mesothelin in PDAC cells. Adhesion assay displayed decreased cell attachment of MUC16 knockdown cells with recombinant galectin-1 and galectin-3 protein. Further, CRISPR/Cas9-mediated MUC16 knockout cells show decreased tumor-associated carbohydrate antigens (T and Tn) in PDAC cells. Importantly, carbohydrate antigens were decreased in the region that corresponds to MUC16 and suggests for the decreased MUC16-galectin interactions. Co-immunoprecipitation also revealed a novel interaction between MUC16 and FAK in PDAC cells. Interestingly, we observed decreased expression of mesenchymal and increased expression of epithelial markers in MUC16-silenced cells. Additionally, MUC16 loss showed a decreased FAK-mediated Akt and ERK/MAPK activation. Altogether, these findings suggest that MUC16-focal adhesion signaling may play a critical role in facilitating PDAC growth and metastasis. PMID:27382435

  19. Friction and adhesion of hierarchical carbon nanotube structures for biomimetic dry adhesives: multiscale modeling.

    Science.gov (United States)

    Hu, Shihao; Jiang, Haodan; Xia, Zhenhai; Gao, Xiaosheng

    2010-09-01

    With unique hierarchical fibrillar structures on their feet, gecko lizards can walk on vertical walls or even ceilings. Recent experiments have shown that strong binding along the shear direction and easy lifting in the normal direction can be achieved by forming unidirectional carbon nanotube array with laterally distributed tips similar to gecko's feet. In this study, a multiscale modeling approach was developed to analyze friction and adhesion behaviors of this hierarchical fibrillar system. Vertically aligned carbon nanotube array with laterally distributed segments at the end was simulated by coarse grained molecular dynamics. The effects of the laterally distributed segments on friction and adhesion strengths were analyzed, and further adopted as cohesive laws used in finite element analysis at device scale. The results show that the laterally distributed segments play an essential role in achieving high force anisotropy between normal and shear directions in the adhesives. Finite element analysis reveals a new friction-enhanced adhesion mechanism of the carbon nanotube array, which also exists in gecko adhesive system. The multiscale modeling provides an approach to bridge the microlevel structures of the carbon nanotube array with its macrolevel adhesive behaviors, and the predictions from this modeling give an insight into the mechanisms of gecko-mimicking dry adhesives.

  20. pH Responsive and Oxidation Resistant Wet Adhesive based on Reversible Catechol-Boronate Complexation.

    Science.gov (United States)

    Narkar, Ameya R; Barker, Brett; Clisch, Matthew; Jiang, Jingfeng; Lee, Bruce P

    2016-08-09

    A smart adhesive capable of binding to a wetted surface was prepared by copolymerizing dopamine methacrylamide (DMA) and 3-acrylamido phenylboronic acid (AAPBA). pH was used to control the oxidation state and the adhesive property of the catechol side chain of DMA and to trigger the catechol-boronate complexation. FTIR spectroscopy confirmed the formation of the complex at pH 9, which was not present at pH 3. The formation of the catechol-boronate complex increased the cross-linking density of the adhesive network. Most notably, the loss modulus values of the adhesive were more than an order of magnitude higher for adhesive incubated at pH 9 when compared to those measured at pH 3. This drastic increase in the viscous dissipation property is attributed to the introduction of reversible complexation into the adhesive network. Based on the Johnson Kendall Roberts (JKR) contact mechanics test, adhesive containing both DMA and AAPBA demonstrated strong interfacial binding properties (work of adhesion (Wadh) = 2000 mJ/m(2)) to borosilicate glass wetted with an acidic solution (pH 3). When the pH was increased to 9, Wadh values (180 mJ/m(2)) decreased by more than an order of magnitude. During successive contact cycles, the adhesive demonstrated the capability to transition reversibly between its adhesive and nonadhesive states with changing pH. Adhesive containing only DMA responded slowly to repeated changes in pH and became progressively oxidized without the protection of boronic acid. Although adhesive containing only AAPBA also demonstrated strong wet adhesion (Wadh ∼ 500 mJ/m(2)), its adhesive properties were not pH responsive. Both DMA and AAPBA are required to fabricate a smart adhesive with tunable and reversible adhesive properties.

  1. TIM-1 glycoprotein binds the adhesion receptor P-selectin and mediates T cell trafficking during inflammation and autoimmunity.

    Science.gov (United States)

    Angiari, Stefano; Donnarumma, Tiziano; Rossi, Barbara; Dusi, Silvia; Pietronigro, Enrica; Zenaro, Elena; Della Bianca, Vittorina; Toffali, Lara; Piacentino, Gennj; Budui, Simona; Rennert, Paul; Xiao, Sheng; Laudanna, Carlo; Casasnovas, Jose M; Kuchroo, Vijay K; Constantin, Gabriela

    2014-04-17

    Selectins play a central role in leukocyte trafficking by mediating tethering and rolling on vascular surfaces. Here we have reported that T cell immunoglobulin and mucin domain 1 (TIM-1) is a P-selectin ligand. We have shown that human and murine TIM-1 binds to P-selectin, and that TIM-1 mediates tethering and rolling of T helper 1 (Th1) and Th17, but not Th2 and regulatory T cells on P-selectin. Th1 and Th17 cells lacking the TIM-1 mucin domain showed reduced rolling in thrombin-activated mesenteric venules and inflamed brain microcirculation. Inhibition of TIM-1 had no effect on naive T cell homing, but it reduced T cell recruitment in a skin hypersensitivity model and blocked experimental autoimmune encephalomyelitis. Uniquely, the TIM-1 immunoglobulin variable domain was also required for P-selectin binding. Our data demonstrate that TIM-1 is a major P-selectin ligand with a specialized role in T cell trafficking during inflammatory responses and the induction of autoimmune disease.

  2. Simulation of Cell Adhesion using a Particle Transport Model

    Science.gov (United States)

    Chesnutt, Jennifer

    2005-11-01

    An efficient computational method for simulation of cell adhesion through protein binding forces is discussed. In this method, the cells are represented by deformable elastic particles, and the protein binding is represented by a rate equation. The method is first developed for collision and adhesion of two similar cells impacting on each other from opposite directions. The computational method is then applied in a particle-transport model for a cloud of interacting and colliding cells, each of which are represented by particles of finite size. One application might include red blood cells adhering together to form rouleaux, which are chains of red blood cells that are found in different parts of the circulatory system. Other potential applications include adhesion of platelets to a blood vessel wall or mechanical heart valve, which is a precursor of thrombosis formation, or adhesion of cancer cells to organ walls in the lymphatic, circulatory, digestive or pulmonary systems.

  3. Thickness influence in mechanical properties of polyurethane adhesive overlap joints; Influencia del espesor de adhesivo de poliuretano en la resistencia deuniones sometidas a cortadura

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Ledesma, R.; Onoro, J.; Amo, J. M.; Duran, M. C.; Duran, J.

    2005-07-01

    The thickness of adhesive layers in metallic bonded joints has direct influence in the performance and mechanical behaviour of these joints. The aim of this study was to analyse the strength and strain properties of steel overlap joints bonded with polyurethane adhesive layers with different thickness. The results show that the strength is maximum when the thickness of the adhesive layer is very thin, 0.1 mm. When the thickness growth to 1 mm the strength goes down rapidly. for layers from 1 to 1.5 mm the strength goes down slower and from 1.5 to 4 mm the strength is nearly constant. In other hand, the joint strain increase uniformly with adhesive layer thickness growth. (Author) 13 refs.

  4. INTERFACIAL ADHESION AND MECHANICAL PROPERTIES OF PMMA-COATED CaCO3 NANOPARTICLE-REINFORCED PVC COMPOSITES

    Institute of Scientific and Technical Information of China (English)

    Xuehua Chen; Chunzhong Li; Shoufang Xu; Ling Zhang; Wei Shao; H. L. Du

    2006-01-01

    Polymethyl methacrylate (PMMA)-coated nano-CaCO3 particles were prepared by in-situ emulsion polymerization. The mechanical properties of nano-CaCO3 particles-reinforced PVC were investigated using an AG-2000A universal testing machine and an XJU-2.75 izod impact tester; interfacial adhesion between CaCO3 nanoparticles and PVC matrix by SEM, and structure of PMMA coated on the surface of CaCO3 by FTIR and 1H-NMR. The results indicate that the PMMA coated on the nano CaCO3 particles consists mainly of syndiotactic structure, and their three tacticity contents were rr 52.8%, mm 7.3% and mr 39.9%, respectively. The interfacial adhesion between CaCO3 nanoparticles and PVC matrix was significantly improved when the CaCO3 nanoparticles were coated with PMMA, which led to increased Young's moduli and tensile strengths of the PMMA-coated CaCO3/PVC composites. The izod impact strengths of the composites were strongly affected by the PMMA coating thickness and increased significantly with increasing the volume fraction of CaCO3 filler in the composites.

  5. Spectroscopic and molecular modelling studies of binding mechanism of metformin with bovine serum albumin

    Science.gov (United States)

    Sharma, Deepti; Ojha, Himanshu; Pathak, Mallika; Singh, Bhawna; Sharma, Navneet; Singh, Anju; Kakkar, Rita; Sharma, Rakesh K.

    2016-08-01

    Metformin is a biguanide class of drug used for the treatment of diabetes mellitus. It is well known that serum protein-ligand binding interaction significantly influence the biodistribution of a drug. Current study was performed to characterize the binding mechanism of metformin with serum albumin. The binding interaction of the metformin with bovine serum albumin (BSA) was examined using UV-Vis absorption spectroscopy, fluorescence, circular dichroism, density functional theory and molecular docking studies. Absorption spectra and fluorescence emission spectra pointed out the weak binding of metformin with BSA as was apparent from the slight change in absorbance and fluorescence intensity of BSA in presence of metformin. Circular dichroism study implied the significant change in the conformation of BSA upon binding with metformin. Density functional theory calculations showed that metformin has non-planar geometry and has two energy states. The docking studies evidently signified that metformin could bind significantly to the three binding sites in BSA via hydrophobic, hydrogen bonding and electrostatic interactions. The data suggested the existence of non-covalent specific binding interaction in the complexation of metformin with BSA. The present study will certainly contribute to the development of metformin as a therapeutic molecule.

  6. Elucidation of binding mechanism and identification of binding site for an anti HIV drug, stavudine on human blood proteins.

    Science.gov (United States)

    Sandhya, B; Hegde, Ashwini H; Seetharamappa, J

    2013-05-01

    The binding of stavudine (STV) to two human blood proteins [human hemoglobin (HHb) and human serum albumin (HSA)] was studied in vitro under simulated physiological conditions by spectroscopic methods viz., fluorescence, UV absorption, resonance light scattering, synchronous fluorescence, circular dichroism (CD) and three-dimensional fluorescence. The binding parameters of STV-blood protein were determined from fluorescence quenching studies. Stern-Volmer plots indicated the presence of static quenching mechanism in the interaction of STV with blood proteins. The values of n close to unity indicated that one molecule of STV bound to one molecule of blood protein. The binding process was found to be spontaneous. Analysis of thermodynamic parameters revealed the presence of hydrogen bond and van der Waals forces between protein and STV. Displacement experiments indicated the binding of STV to Sudlow's site I on HSA. Secondary structures of blood proteins have undergone changes upon interaction with STV as evident from the reduction of α-helices (from 46.11% in free HHb to 38.34% in STV-HHb, and from 66.44% in free HSA to 52.26% in STV-HSA). Further, the alterations in secondary structures of proteins in the presence of STV were confirmed by synchronous and 3D-fluorescence spectral data. The distance between the blood protein (donor) and acceptor (STV) was found to be 5.211 and 5.402 nm for STV-HHb and STV-HSA, respectively based on Föster's non-radiative energy transfer theory. Effect of some metal ions was also investigated. The fraction of STV bound to HSA was found to be 87.8%.

  7. [Binding mechanism of traditional Chinese medicine active component 5-hydroxymethyl-furfural and HSA or BSA].

    Science.gov (United States)

    Guo, Ming; He, Ling; Lu, Xiao-Wang

    2012-03-01

    A combination of spectral experiment and molecular modeling techniques has been used to characterize the binding mechanism between an active component 5-hydroxymethyl-furfural (5-HMF) of traditional Chinese medicine and human serum albumin (HSA) or bovine serum albumin (BSA). The interaction mechanism of 5-HMF binding with HSA/BSA is analyzed. Although the drug can bind with HSA/BSA to form stable complexes, there are some differences in the bond strength. The values of binding distances (r) are different and low, which indicated the occurrence of energy transfer. The drug had conformational effect on HSA/BSA, which resulted in different changes of hydrophobic environment of the binding domain in HSA/BSA. The 'phase diagram' of fluorescence revealed that the changes on the conformational pattern of proteins have been affected by drug conformed to the "all-or-none" pattern. The interactions between drug and protein influenced by Co(II) were also discussed. Its effects acting on 5-HMF-HSA/BSA interactions are different. The computational modeling method was used to study the interaction between 5-HMF and HSA/BSA. The results of molecular model studies revealed that the binding modes for drug-serum albumin systems are mainly hydrophobic interactions and hydrogen bonding. These results are in accordance with spectral results. The research results have given a better theoretical reference for the study of pharmacological mechanism of 5-hydroxymethyl-furfural.

  8. Lipopolysaccharide Binding Protein, Soluble-Intercellular Adhesion Molecule-1, Procalcitonin, and Protein C Activity and Clinical Outcome in Systemic Inflammatory Response Syndrome (SIRS or Sepsis Patients

    Directory of Open Access Journals (Sweden)

    Dewi Muliaty

    2009-04-01

    Full Text Available BACKGROUND: Biochemical markers may be used in diagnosis, prognostic and monitoring treatment and therapy for sepsis patients. In this study we used Lipopolysacharide Binding Protein (LBP, serum-Intercellular Adhesion Molecule-1 (ICAM-1, Procalcitonin (PCT and protein C activity. LBP is related to lipopolysachharide or gram-negative bacterial endotoxin which bound to LBP and induced inflammatory response. ICAM-1 is associated with endothelial dysfunction in response to systemic inflammatory and septic condition. PCT increased in bacterial infection and in severe systemic inflammatory. Role of Protein C is protecting the intravascular system to systemic inflammation, sepsis and the concomitant intravascular coagulopathy. The aim of this study was to examine the associations between levels of serum LBP, sICAM-1, PCT, and protein C activity with the clinical outcome of SIRS or sepsis patients. METHODS: We included 19 post surgery patients with SIRS criteria from intensive care unit (ICU and evaluated the level of LBP serum with Chemiliuminescent Enzyme Immunoassay (Diagnostic Product Co., ICAM-1 with ELISA (R&D System, PCT with immunochromatography (BRAHMS, protein C activity with chromogenic method (Dade Behring. We performed the samples serially at the first admission of patients and after 72 hours. Data were analysed by non-parametric with Wilcoxon test and Mann-Whitney test. Correlation study between biomarkers calculated by Kendall’s tau and Spearman’s rho. RESULTS: Of 19 patients, 9 (47,4% died and 10 (52,6% surviving. The level of LBP serum decreased after 72 hours in surviving-sepsis patients, and increased in nonsurviving sepsis patients with significant different levels at 72 hours examination (p0.05. In all patients were found high level of PCT serum since the first admission examination, decreasing levels were occurred significantly in surviving patients after 72 hours (p0.05 both in surviving and non-surviving patients. CONCLUSIONS

  9. Physiochemical properties of Caulobacter crescentus holdfast: a localized bacterial adhesive.

    Science.gov (United States)

    Berne, Cécile; Ma, Xiang; Licata, Nicholas A; Neves, Bernardo R A; Setayeshgar, Sima; Brun, Yves V; Dragnea, Bogdan

    2013-09-12

    To colonize surfaces, the bacterium Caulobacter crescentus employs a polar polysaccharide, the holdfast, located at the end of a thin, long stalk protruding from the cell body. Unlike many other bacteria which adhere through an extended extracellular polymeric network, the holdfast footprint area is tens of thousands times smaller than that of the total bacterium cross-sectional surface, making for some very demanding adhesion requirements. At present, the mechanism of holdfast adhesion remains poorly understood. We explore it here along three lines of investigation: (a) the impact of environmental conditions on holdfast binding affinity, (b) adhesion kinetics by dynamic force spectroscopy, and (c) kinetic modeling of the attachment process to interpret the observed time-dependence of the adhesion force at short and long time scales. A picture emerged in which discrete molecular units called adhesins are responsible for initial holdfast adhesion, by acting in a cooperative manner.

  10. Quantum mechanics/molecular mechanics study on the oxygen binding and substrate hydroxylation step in AlkB repair enzymes.

    Science.gov (United States)

    Quesne, Matthew G; Latifi, Reza; Gonzalez-Ovalle, Luis E; Kumar, Devesh; de Visser, Sam P

    2014-01-07

    AlkB repair enzymes are important nonheme iron enzymes that catalyse the demethylation of alkylated DNA bases in humans, which is a vital reaction in the body that heals externally damaged DNA bases. Its mechanism is currently controversial and in order to resolve the catalytic mechanism of these enzymes, a quantum mechanics/molecular mechanics (QM/MM) study was performed on the demethylation of the N(1) -methyladenine fragment by AlkB repair enzymes. Firstly, the initial modelling identified the oxygen binding site of the enzyme. Secondly, the oxygen activation mechanism was investigated and a novel pathway was found, whereby the catalytically active iron(IV)-oxo intermediate in the catalytic cycle undergoes an initial isomerisation assisted by an Arg residue in the substrate binding pocket, which then brings the oxo group in close contact with the methyl group of the alkylated DNA base. This enables a subsequent rate-determining hydrogen-atom abstraction on competitive σ- and π-pathways on a quintet spin-state surface. These findings give evidence of different locations of the oxygen and substrate binding channels in the enzyme and the origin of the separation of the oxygen-bound intermediates in the catalytic cycle from substrate. Our studies are compared with small model complexes and the effect of protein and environment on the kinetics and mechanism is explained.

  11. Deciphering the combinatorial roles of geometric, mechanical, and adhesion cues in regulation of cell spreading.

    Directory of Open Access Journals (Sweden)

    Greg M Harris

    Full Text Available Significant effort has gone towards parsing out the effects of surrounding microenvironment on macroscopic behavior of stem cells. Many of the microenvironmental cues, however, are intertwined, and thus, further studies are warranted to identify the intricate interplay among the conflicting downstream signaling pathways that ultimately guide a cell response. In this contribution, by patterning adhesive PEG (polyethylene glycol hydrogels using Dip Pen Nanolithography (DPN, we demonstrate that substrate elasticity, subcellular elasticity, ligand density, and topography ultimately define mesenchymal stem cells (MSCs spreading and shape. Physical characteristics are parsed individually with 7 kilopascal (kPa hydrogel islands leading to smaller, spindle shaped cells and 105 kPa hydrogel islands leading to larger, polygonal cell shapes. In a parallel effort, a finite element model was constructed to characterize and confirm experimental findings and aid as a predictive tool in modeling cell microenvironments. Signaling pathway inhibition studies suggested that RhoA is a key regulator of cell response to the cooperative effect of the tunable substrate variables. These results are significant for the engineering of cell-extra cellular matrix interfaces and ultimately decoupling matrix bound cues presented to cells in a tissue microenvironment for regenerative medicine.

  12. 贻贝的黏着机制%Adhesion Mechanism of Mussel

    Institute of Scientific and Technical Information of China (English)

    王伯初; 周太刚; 陈双扣; 冯莹柱

    2007-01-01

    贻贝通过足丝(byssus)分泌的贻贝黏着蛋白质(mussel adhesive protein,MAP)能附着在海水中的任何有机物和无机物表面,目前认为贻贝黏着蛋白质中含高浓度特殊的氨基酸DOPA(3,4-二羟基苯丙氨酸)在贻贝黏附过程中扮演重要的角色.DOPA能直接与金属氧化物通过有机金属络合反应形成稳定的络合物,也能在氧化后与其同一多肽链上或不同多肽链上的其他残基形成稳定的交联结构,进而牢固黏附于物体表面.贻贝黏着蛋白质具有黏合范围广、速度快、耐腐蚀、强度高和生物亲和性良好等优点,被认为是极好的广谱生物胶黏剂而应用于医学和生物工程等领域.

  13. Pressure sensitive adhesives from renewable resources

    OpenAIRE

    Maaßen, Wiebke

    2015-01-01

    Pressure-sensitive adhesives (PSAs) represent an important segment of the adhesives market. In this work, novel insights into the adhesive performance of bio-based pressure sensitive adhesives are presented. Three different homopolymers based on fatty acids derived from native vegetable oils as renewable feedstock were characterized in terms of their mechanical and adhesive properties.

  14. Acoustic Imaging of Microstructure and Evaluation of the Adhesive's Physical, Mechanical and Chemical Properties Changes at Different Cure States

    Science.gov (United States)

    Severina, I. A.; Fabre, A. J.; Maeva, E. Yu.

    Epoxy thermoset adhesives transform during cure from liquid state into the highly cross-linked solid. Cure state of the material depends on condition of the reaction (temperature, pressure, time etc.) and resin/hardener ratio. It is known that the cure degree of the adhesive correlates with adhesion strength, which is critical for structural adhesives used in automotive, aerospace and marine industries. In this work, characterization of cure process of the adhesive with acoustic methods is presented. Evolution of the acoustic and elastic properties (attenuation, sound velocity, density, elastic moduli) during cure reaction was monitored in relation to the substantial physical and chemical changes of the material. These macro parameters of the adhesive were compared with the material's microstructure obtained by high-resolution acoustic microscopy technique in frequencies range of 50-400 MHz. Development of the microstructure of the adhesive as it cures at different conditions has been investigated. Appearance and development of the granular structure on the adhesive interface during cure reaction has been demonstrated. Acoustic images were analyzed by mathematical method to quantitatively characterize distribution of the adhesive's components. Statistical analysis of such images provides an accurate quantitative measure of the degree of cure of such samples. Research results presented in this paper can be useful as a basis for non-destructive evaluation of the adhesive materials

  15. Mechanism of Coupled Folding and Binding in the siRNA-PAZ Complex.

    Science.gov (United States)

    Chen, Hai-Feng

    2008-08-01

    The PAZ domain plays a key role in gene silencing pathway. The PAZ domain binds with siRNAs to form the multimeric RNA-induced silencing complex (RISC). RISC identifies mRNAs homologous to the siRNAs and promotes their degradation. It was found that binding with siRNA significantly enhances apo-PAZ folding. However, the mechanism by which folding is coupled to binding is poorly understood. Thus, the coupling relationship between binding and folding is very important for understanding the function of gene silencing. We have performed molecular dynamics (MD) of both bound and apo-PAZ to study the coupling mechanism between binding and folding in the siRNA-PAZ complex. Room-temperature MD simulations suggest that both PAZ and siRNA become more rigid and stable upon siRNA binding. Kinetic analysis of high-temperature MD simulations shows that both bound and apo-PAZ unfold via a two-state process. The unfolding pathways are different between bound and apo-PAZ: the order of helix III and helices I & II unfolding is switched. Furthermore, transition probability was used to determine the transition state ensemble for both bound and apo-PAZ. It was found that the transition state of bound PAZ is more compact than that of apo-PAZ. The predicted Φ-values suggest that the Φ-values of helix III and sheets of β3-β7 for bound PAZ are more native-like than those of apo-PAZ upon the binding of siRNA. The results can help us to understand the mechanism of gene silencing.

  16. Discriminating binding mechanisms of an intrinsically disordered protein via a multi-state coarse-grained model

    Energy Technology Data Exchange (ETDEWEB)

    Knott, Michael [Department of Chemistry, Cambridge University, Lensfield Road, Cambridge CB2 1EW (United Kingdom); Best, Robert B., E-mail: robertbe@helix.nih.gov [Department of Chemistry, Cambridge University, Lensfield Road, Cambridge CB2 1EW (United Kingdom); Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520 (United States)

    2014-05-07

    Many proteins undergo a conformational transition upon binding to their cognate binding partner, with intrinsically disordered proteins (IDPs) providing an extreme example in which a folding transition occurs. However, it is often not clear whether this occurs via an “induced fit” or “conformational selection” mechanism, or via some intermediate scenario. In the first case, transient encounters with the binding partner favour transitions to the bound structure before the two proteins dissociate, while in the second the bound structure must be selected from a subset of unbound structures which are in the correct state for binding, because transient encounters of the incorrect conformation with the binding partner are most likely to result in dissociation. A particularly interesting situation involves those intrinsically disordered proteins which can bind to different binding partners in different conformations. We have devised a multi-state coarse-grained simulation model which is able to capture the binding of IDPs in alternate conformations, and by applying it to the binding of nuclear coactivator binding domain (NCBD) to either ACTR or IRF-3 we are able to determine the binding mechanism. By all measures, the binding of NCBD to either binding partner appears to occur via an induced fit mechanism. Nonetheless, we also show how a scenario closer to conformational selection could arise by choosing an alternative non-binding structure for NCBD.

  17. Inhibition of Adhesion of Enteropathogenic Escherichia coli to HEp-2 Cells by Binding of a Novel Peptide to EspB Protein.

    Science.gov (United States)

    Li, Duoyun; Chen, Zhong; Cheng, Hang; Zheng, Jin-Xin; Pan, Wei-Guang; Yang, Wei-Zhi; Yu, Zhi-Jian; Deng, Qi-Wen

    2016-09-01

    Enteropathogenic Escherichia coli (EPEC) is a major cause of infantile diarrhea in developing countries. The translocator EspB is a key virulence factor in the process of the attaching and effacing effect of EPEC and plays a critical role in the pathogenesis of the bacteria. In this study, we aimed to select the peptides binding to EspB protein by phage display library and further investigate whether these peptides can decrease the extent of invasion and virulence of EPEC on host cells by targeting to EspB protein. The expression and purification of EspB protein from E. coli was demonstrated by Western blotting. The Ph.D. 12-mer peptide phage display library was used to screen the candidate peptides binding specifically to EspB protein. Furthermore, the affinity of these candidate peptides bound to EspB was identified by enzyme-linked immunosorbent assay (ELISA). Moreover, we investigated whether these screened peptides could decrease the adherence ratio of EPEC to HEp-2 cells with increasing concentration. Successful purification of EspB protein from pET21b-EspB-transformed E. coli was identified by Western blotting. Then, the candidate peptides including phages 6, 7, 8, and 12 were screened by the Ph.D. 12-mer peptide phage display library and ELISA test demonstrated that their affinity binding to EspB protein was high compared with the control. Functional analysis indicated that synthetic peptide-6 (YFPYSHTSPRQP) significantly decreased the adherence ratio of EPEC to HEp-2 cells with increasing concentration (P < 0.01). Peptide-6 (100 µg/mL) could lead to a 40 % decrease in the adherence ratio of EPEC to HEp-2 cells compared with control (P < 0.01). However, the other three peptides at different concentrations showed only a slight ability to block the adherence of EPEC to host cells. Our data provided a potential strategy to inhibit the adhesion of EPEC to epithelial cells by a candidate peptide targeted toward EspB protein.

  18. Statistical-mechanical lattice models for protein-DNA binding in chromatin

    CERN Document Server

    Teif, Vladimir B

    2010-01-01

    Statistical-mechanical lattice models for protein-DNA binding are well established as a method to describe complex ligand binding equilibriums measured in vitro with purified DNA and protein components. Recently, a new field of applications has opened up for this approach since it has become possible to experimentally quantify genome-wide protein occupancies in relation to the DNA sequence. In particular, the organization of the eukaryotic genome by histone proteins into a nucleoprotein complex termed chromatin has been recognized as a key parameter that controls the access of transcription factors to the DNA sequence. New approaches have to be developed to derive statistical mechanical lattice descriptions of chromatin-associated protein-DNA interactions. Here, we present the theoretical framework for lattice models of histone-DNA interactions in chromatin and investigate the (competitive) DNA binding of other chromosomal proteins and transcription factors. The results have a number of applications for quant...

  19. Monoclonal antibodies to human laminin α4 chain globular domain inhibit tumor cell adhesion and migration on laminins 411 and 421, and binding of α6β1 integrin and MCAM to α4-laminins.

    Science.gov (United States)

    Ishikawa, Taichi; Wondimu, Zenebech; Oikawa, Yuko; Ingerpuu, Sulev; Virtanen, Ismo; Patarroyo, Manuel

    2014-06-01

    α4-Laminins, such as laminins 411 and 421, are mesenchymal laminins expressed by vascular and lymphatic endothelial cells, leukocytes and other normal cell types. These laminins are recognized by α6β1 and α6β4 integrins and MCAM (CD146), and promote adhesion and migration of the cells. α4-Laminins are also expressed and secreted by some tumor cells and strongly promote tumor cell migration. Moreover, the abluminal side of blood and/or lymphatic vessels and the nerve perineurium, common tracks of tumor cell dissemination, express α4-laminins, and these laminin isoforms, when expressed in the stroma, may contribute to tumor invasion. In the present study, we examined ten mAbs to human laminin α4 chain for their reactivity with the isolated laminin α4 globular domain, their ability to inhibit tumor cell adhesion and migration on laminins 411 and 421, and their effect on the binding of α6β1 integrin and MCAM to both α4-laminins. Most of the mAbs reacted with the laminin α4 globular domain, but only two, mAbs FC10 and 084, significantly inhibited tumor cell adhesion and migration on laminin-411. When used in combination, these antibodies practically abolished the cell adhesion and migration on laminin-411 and significantly reduced the cellular responses on laminin-421. Accordingly, mAbs FC10 and 084 significantly inhibited the binding of purified α6β1 integrin and MCAM to laminins 411 and 421. These results indicate that mAbs to the laminin α4 globular domain are able to inhibit tumor cell adhesion and migration on laminins 411 and 421, and that α6β1 integrin and MCAM bind α4-laminins at very close sites on the globular domain. These reagents contribute to a better understanding of the biology of α4-laminins and may have a therapeutic potential in malignant and inflammatory diseases.

  20. Molecular mechanism of recombinant liver fatty acid binding protein's antioxidant activity

    OpenAIRE

    YAN, JING; Gong, Yuewen; She, Yi-Min; Wang, Guqi; Roberts, Michael S; Burczynski, Frank J.

    2009-01-01

    Hepatocytes expressing liver fatty acid binding protein (L-FABP) are known to be more resistant to oxidative stress than those devoid of this protein. The mechanism for the observed antioxidant activity is not known. We examined the antioxidant mechanism of a recombinant rat L-FABP in the presence of a hydrophilic (AAPH) or lipophilic (AMVN) free radical generator. Recombinant L-FABP amino acid sequence and its amino acid oxidative products following oxidation were identified by MALDI quadrup...

  1. Study of the Mechanism of Essential Garlic Oil Inhibiting Interleukin-1α-Induced Monocyte Adhesion to Endothelial Cells

    Institute of Scientific and Technical Information of China (English)

    葛璐璐; 张薇; 戴云; 臧燕; 黄纯洁

    2001-01-01

    To observe the effects of essential garlic oil (EGO) on vascular cell adhesive molecule-1 (VCAM-1) expression of endothelial cells and monocyte-endothelial cell adhesion rate induced by interleukin-1α (IL-1α). Methods: Human umbilical vein endothelial cells (HUVEC) were isolated by trypsin digestion method and co-cultured with IL-1α or EGO+IL-1α in the absence or presence of U937 monocyte. Monocyte-endothelial cell adhesion rate was examined with reverted microscope. VCAM-1 expression of endothelial cells was measured by ACAS 570 confocal microscope, and the data were presented as mean fluorescent intensity. Results: EGO significantly inhibited IL-1α-induced endothelial expression of VCAM-1, and thus markedly decreased monocyte-endothelial cell adhesion rate. Conclusion: EGO has the effect on antagonizing adhesion of monocyte and vascular endothelial cell, which might be due to its inhibition on adhesive molecular expression on the surface of endothelial cells.

  2. Analysis of the moisture effect on the mechanical behaviour of an adhesively bonded joint under proportional multi-axial loads

    OpenAIRE

    Arnaud, N.; Creac' Hcadec, R; Cognard, J. Y.; Davies, Peter; Le Gac, Pierre-Yves

    2015-01-01

    The objective of the study is to identify the 3D behaviour of an adhesive in an assembly, and to take into account the effect of ageing in a marine environment. To that end, three different tests were employed. Gravimetric analyses were used to determine the water diffusion kinetics in the adhesive. Bulk tensile tests were performed to highlight the effects of humid ageing on the adhesive behaviour. Modified Arcan tests were performed for several ageing times to obtain the experimental databa...

  3. Prediction of Peptide Binding to Major Histocompatibility II Receptors with Molecular Mechanics and Semi-Empirical Quantum Mechanics Methods

    Directory of Open Access Journals (Sweden)

    James A Platts

    2012-02-01

    Full Text Available Methods for prediction of the binding of peptides to major histocompatibility complex (MHC II receptors are examined, using literature values of IC50 as a benchmark. Two sets of IC50 data for closely structurally related peptides based on hen egg lysozyme (HEL and myelin basic protein (MBP are reported first. This shows that methods based on both molecular mechanics and semi-empirical quantum mechanics can predict binding with good-to-reasonable accuracy, as long as a suitable method for estimation of solvation effects is included. A more diverse set of 22 peptides bound to HLA-DR1 provides a tougher test of such methods, especially since no crystal structure is available for these peptide-MHC complexes. We therefore use sequence based methods such as SYFPEITHI and SVMHC to generate possible binding poses, using a consensus approach to determine the most likely anchor residues, which are then mapped onto the crystal structure of an unrelated peptide bound to the same receptor. This analysis shows that the MM/GBVI method performs particularly well, as does the AMBER94 forcefield with Born solvation model. Indeed, MM/GBVI can be used as an alternative to sequence based methods in generating binding poses, leading to still better accuracy.

  4. In vitro stereoselective covalent binding of carprofen glucuronides to human serum albumin: characterization of the mechanism.

    Science.gov (United States)

    Greige-Georges, Hélène; Buronfosse, Thierry; Netter, Patrcik; Magdalou, Jacques; Lapicque, Françoise

    2003-01-01

    The reactivity, in terms of covalent binding, of R- and S-carprofen acylglucuronides with human serum albumin (HSA) has been investigated in vitro. The irreversible binding of these metabolites to the HSA 580 mM occurred at pH 7.4 and 37 degrees C instantaneously and stereoselectively in favour of the R-enentiomer glucuronide. The amount of carprofen adducts remained stable with time up to 48 hr, and increased with the glucuronide concentration. It was not modified by addiction of imine-trapping reagents, suggesting that the reaction is not mediated by a Schiff base mechanism. Moreover the extreme rapidity of the covalent binding supports a mechanism of nucleophilic attack. Competition studies with ligands known to bind to different sites of HSA, indicated that carprofen glucuronides interacted mainly with site II. The extent of the binding of R-carprofen glucuronide increased with pH, thus suggesting the participation of an alkaline group in the process. The modification of HSA by amino-acid directed chemicals led to the conclusion that Tyr, Lys or Arg residues in site II were mainly involved.

  5. Two Escape Mechanisms of Influenza A Virus to a Broadly Neutralizing Stalk-Binding Antibody.

    Science.gov (United States)

    Chai, Ning; Swem, Lee R; Reichelt, Mike; Chen-Harris, Haiyin; Luis, Elizabeth; Park, Summer; Fouts, Ashley; Lupardus, Patrick; Wu, Thomas D; Li, Olga; McBride, Jacqueline; Lawrence, Michael; Xu, Min; Tan, Man-Wah

    2016-06-01

    Broadly neutralizing antibodies targeting the stalk region of influenza A virus (IAV) hemagglutinin (HA) are effective in blocking virus infection both in vitro and in vivo. The highly conserved epitopes recognized by these antibodies are critical for the membrane fusion function of HA and therefore less likely to be permissive for virus mutational escape. Here we report three resistant viruses of the A/Perth/16/2009 strain that were selected in the presence of a broadly neutralizing stalk-binding antibody. The three resistant viruses harbor three different mutations in the HA stalk: (1) Gln387Lys; (2) Asp391Tyr; (3) Asp391Gly. The Gln387Lys mutation completely abolishes binding of the antibody to the HA stalk epitope. The other two mutations, Asp391Tyr and Asp391Gly, do not affect antibody binding at neutral pH and only slightly reduce binding at low pH. Interestingly, they enhance the fusion ability of the HA, representing a novel mechanism that allows productive membrane fusion even in the presence of antibody and hence virus escape from antibody neutralization. Therefore, these mutations illustrate two different resistance mechanisms used by IAV to escape broadly neutralizing stalk-binding antibodies. Compared to the wild type virus, the resistant viruses release fewer progeny viral particles during replication and are more sensitive to Tamiflu, suggesting reduced viral fitness.

  6. A novel COX-independent mechanism of sulindac sulfide involves cleavage of epithelial cell adhesion molecule protein.

    Science.gov (United States)

    Liggett, Jason L; Min, Kyung-Won; Smolensky, Dmitriy; Baek, Seung Joon

    2014-08-01

    Non-steroidal anti-inflammatory drugs (NSAIDs) are extensively used over the counter to treat headaches and inflammation as well as clinically to prevent cancer among high-risk groups. The inhibition of cyclooxygenase (COX) activity by NSAIDs plays a role in their anti-tumorigenic properties. NSAIDs also have COX-independent activity which is not fully understood. In this study, we report a novel COX-independent mechanism of sulindac sulfide (SS), which facilitates a previously uncharacterized cleavage of epithelial cell adhesion molecule (EpCAM) protein. EpCAM is a type I transmembrane glycoprotein that has been implemented as an over-expressed oncogene in many cancers including colon, breast, pancreas, and prostate. We found EpCAM to be down-regulated by SS in a manner that is independent of COX activity, transcription regulation, de novo protein synthesis, and proteasomal degradation pathway. Our findings clearly demonstrate that SS drives cleavage of the extracellular portion of EpCAM near the N-terminus. This SS driven cleavage is blocked by a deleting amino acids 55-81 as well as simply mutating arginine residues at positions 80 and 81 to alanine of EpCAM. Proteolysis of EpCAM by SS may provide a novel mechanism by which NSAIDs affect anti-tumorigenesis at the post-translational level.

  7. Network Analysis Reveals the Recognition Mechanism for Mannose-binding Lectins

    Science.gov (United States)

    Zhao, Yunjie; Jian, Yiren; Zeng, Chen; Computational Biophysics Lab Team

    The specific carbohydrate binding of mannose-binding lectin (MBL) protein in plants makes it a very useful molecular tool for cancer cell detection and other applications. The biological states of most MBL proteins are dimeric. Using dynamics network analysis on molecular dynamics (MD) simulations on the model protein of MBL, we elucidate the short- and long-range driving forces behind the dimer formation. The results are further supported by sequence coevolution analysis. We propose a general framework for deciphering the recognition mechanism underlying protein-protein interactions that may have potential applications in signaling pathways.

  8. Control of ion selectivity in LeuT: two Na+ binding sites with two different mechanisms.

    Science.gov (United States)

    Noskov, Sergei Y; Roux, Benoît

    2008-03-28

    The x-ray structure of LeuT, a bacterial homologue of Na(+)/Cl(-)-dependent neurotransmitter transporters, provides a great opportunity to better understand the molecular basis of monovalent cation selectivity in ion-coupled transporters. LeuT possesses two ion binding sites, NA1 and NA2, which are highly selective for Na(+). Extensive all-atom free-energy molecular dynamics simulations of LeuT embedded in an explicit membrane are performed at different temperatures and various occupancy states of the binding sites to dissect the molecular mechanism of ion selectivity. The results show that the two binding sites display robust selectivity for Na(+) over K(+) or Li(+), the competing ions of most similar radii. Of particular interest, the mechanism primarily responsible for selectivity for each of the two binding sites appears to be different. In NA1, selectivity for Na(+) over K(+) arises predominantly from the strong electrostatic field arising from the negatively charged carboxylate group of the leucine substrate coordinating the ion directly. In NA2, which comprises only neutral ligands, selectivity for Na(+) is enforced by the local structural restraints arising from the hydrogen-bonding network and the covalent connectivity of the polypeptide chain surrounding the ion according to a "snug-fit" mechanism.

  9. Marginal Micro-leakage of Self-etch and All-in One Adhesives to Primary Teeth, with Mechanical or Chemo-Mechanical Caries Removal

    Directory of Open Access Journals (Sweden)

    Nouzari A

    2016-06-01

    Full Text Available Statement of Problem: Chemo-mechanical caries removal is an effective alternative to the traditional rotary drilling method. One of the factors that can influence micro-leakage is the method of caries removal. Objectives: To compare the micro-leakage of resin composite in primary dentition using self-etch and all-in one adhesives following conventional and chemo-mechanical caries removal. Materials and Methods: Sixty extracted human primary anterior teeth with class III carious lesions were collected. The selected teeth were divided randomly into two groups each consisting of 30 teeth. In group1 carious lesions were removed using Carisolv multi mix gel. In group 2, caries was removed using round steel burs in a slow–speed hand piece. Then, the specimens in each group were randomly divided into two subgroups (A and B of 15 and treated by either Clearfil SE Bond (CSEB or Scotch bond. All prepared cavities were filled with a resin composite (Estellite. All the specimens were stored in distilled water at 37ºC for 24 hours and then thermocycled in 5ºC and 55ºC water with a dwell time of 20 seconds for 1500 cycles. The specimens were immersed in 1% methylene blue solution for 24 hours, removed, washed and sectioned mesiodistally. The sectioned splits were examined under a stereomicroscope to determine the micro-leakage scores. The data were analyzed using Kruskal-Wallis Test in SPSS version 21. Results: There were no significant differences between micro-leakage scores among the four groups (p = 0.127. Score 0 of micro-leakage was detected for 60% of the specimens in group 1-A (Carisolv + CSEB, 73% of the group 2-A (hand piece + CSEB, 80% of the group 1-B (Carisolv + Scotch bond, and 93% of the group 2-B in which caries was removed using hand piece and bonded with Scotch bond . Conclusions: Although caries removal using hand piece bur along with using Scotch bond adhesive performed less micro-leakage, it would seems that the use of Carisolv

  10. Molecular mechanisms of gastric epithelial cell adhesion and injection of CagA by Helicobacter pylori

    LENUS (Irish Health Repository)

    Backert, Steffen

    2011-11-01

    Abstract Helicobacter pylori is a highly successful pathogen uniquely adapted to colonize humans. Gastric infections with this bacterium can induce pathology ranging from chronic gastritis and peptic ulcers to gastric cancer. More virulent H. pylori isolates harbour numerous well-known adhesins (BabA\\/B, SabA, AlpA\\/B, OipA and HopZ) and the cag (cytotoxin-associated genes) pathogenicity island encoding a type IV secretion system (T4SS). The adhesins establish tight bacterial contact with host target cells and the T4SS represents a needle-like pilus device for the delivery of effector proteins into host target cells such as CagA. BabA and SabA bind to blood group antigen and sialylated proteins respectively, and a series of T4SS components including CagI, CagL, CagY and CagA have been shown to target the integrin β1 receptor followed by injection of CagA across the host cell membrane. The interaction of CagA with membrane-anchored phosphatidylserine may also play a role in the delivery process. While substantial progress has been made in our current understanding of many of the above factors, the host cell receptors for OipA, HopZ and AlpA\\/B during infection are still unknown. Here we review the recent progress in characterizing the interactions of the various adhesins and structural T4SS proteins with host cell factors. The contribution of these interactions to H. pylori colonization and pathogenesis is discussed.

  11. Molecular mechanisms of gastric epithelial cell adhesion and injection of CagA by Helicobacter pylori

    Directory of Open Access Journals (Sweden)

    Backert Steffen

    2011-11-01

    Full Text Available Abstract Helicobacter pylori is a highly successful pathogen uniquely adapted to colonize humans. Gastric infections with this bacterium can induce pathology ranging from chronic gastritis and peptic ulcers to gastric cancer. More virulent H. pylori isolates harbour numerous well-known adhesins (BabA/B, SabA, AlpA/B, OipA and HopZ and the cag (cytotoxin-associated genes pathogenicity island encoding a type IV secretion system (T4SS. The adhesins establish tight bacterial contact with host target cells and the T4SS represents a needle-like pilus device for the delivery of effector proteins into host target cells such as CagA. BabA and SabA bind to blood group antigen and sialylated proteins respectively, and a series of T4SS components including CagI, CagL, CagY and CagA have been shown to target the integrin β1 receptor followed by injection of CagA across the host cell membrane. The interaction of CagA with membrane-anchored phosphatidylserine may also play a role in the delivery process. While substantial progress has been made in our current understanding of many of the above factors, the host cell receptors for OipA, HopZ and AlpA/B during infection are still unknown. Here we review the recent progress in characterizing the interactions of the various adhesins and structural T4SS proteins with host cell factors. The contribution of these interactions to H. pylori colonization and pathogenesis is discussed.

  12. Physiologically relevant binding affinity quantification of monoclonal antibody PF‐00547659 to mucosal addressin cell adhesion molecule for in vitro in vivo correlation

    Science.gov (United States)

    Wang, Mengmeng; Kussrow, Amanda K; Ocana, Mireia Fernandez; Chabot, Jeffrey R; Lepsy, Christopher S

    2016-01-01

    Background and Purpose A monoclonal antibody (PF‐00547659) against mucosal addressin cell adhesion molecule (MAdCAM), expressed as both soluble (sMAdCAM) and trans‐membrane (mMAdCAM) target forms, showed over 30‐fold difference in antibody‐target KD between in vitro (Biacore) and clinically derived (KD,in‐vivo) values. Back‐scattering interferometry (BSI) was applied to acquire physiologically relevant KD values which were used to establish in vitro and in vivo correlation (IVIVC). Experimental Approach BSI was applied to obtain KD values between PF‐00547659 and recombinant human MAdCAM in buffer or CHO cells and endogenous MAdCAM in human serum or colon tissue. CHO cells and tissue were minimally processed to yield homogenate containing membrane vesicles and soluble proteins. A series of binding affinities in serum with various dilution factors was used to estimate both KD,in‐vivo and target concentrations; MAdCAM concentrations were also measured using LC–MS/MS. Key Results BSI measurements revealed low KD values (higher affinity) for sMAdCAM in buffer and serum, yet a 20‐fold higher KD value (lower affinity) for mMAdCAM in CHO, mMAdCAM and sMAdCAM in tissue. BSI predicted KD,in‐vivo in serum was similar to clinically derived KD,in‐vivo, and the BSI‐estimated serum sMAdCAM concentration also matched the measured concentration by LC–MS/MS. Conclusions and Implications Our results successfully demonstrated that BSI measurements of physiologically relevant KD values can be used to establish IVIVC, for PF‐00547659 to MAdCAM despite the lack of correlation when using Biacore measured KD and accurately estimates endogenous target concentrations. The application of BSI would greatly enhance successful basic pharmacological research and drug development. PMID:27760281

  13. Syndecan proteoglycans and cell adhesion

    DEFF Research Database (Denmark)

    Woods, A; Oh, E S; Couchman, J R

    1998-01-01

    It is now becoming clear that a family of transmembrane proteoglycans, the syndecans, have important roles in cell adhesion. They participate through binding of matrix ligand to their glycosaminoglycan chains, clustering, and the induction of signaling cascades to modify the internal microfilament...... organization. Syndecans can modulate the type of adhesive responses induced by other matrix ligand-receptor interactions, such as those involving the integrins, and so contribute to the control of cell morphology, adhesion and migration....

  14. Biofilm formation by Escherichia coli is stimulated by synergistic interactions and co-adhesion mechanisms with adherence-proficient bacteria

    NARCIS (Netherlands)

    Castonguay, MH; van der Schaaf, S; Koester, W; Krooneman, J; Harmsen, H; Landini, P; van der Meer, W.

    2006-01-01

    Laboratory strains of Escherichia coli do not show significant ability to attach to solid surfaces and to form biofilms. We compared the adhesion properties of the E. coli PHL565 laboratory strain to eight environmental E. coli isolates: only four isolates displayed adhesion properties to glass sign

  15. Insights into the selective binding and toxic mechanism of microcystin to catalase

    Science.gov (United States)

    Hu, Yuandong; Da, Liangjun

    2014-03-01

    Microcystin is a sort of cyclic nonribosomal peptides produced by cyanobacteria. It is cyanotoxin, which can be very toxic for plants and animals including humans. The present study evaluated the interaction of microcystin and catalase, under physiological conditions by means of fluorescence, three-dimensional (3D) fluorescence, circular dichroism (CD), Fourier Transform infrared (FT-IR) spectroscopy, and enzymatic reactionkinetic techniques. The fluorescence data showed that microcystin could bind to catalase to form a complex. The binding process was a spontaneous molecular interaction procedure, in which electrostatic interactions played a major role. Energy transfer and fluorescence studies proved the existence of a static binding process. Additionally, as shown by the three-dimensional fluorescence, CD and FT-IR results, microcystin could lead to conformational and microenvironmental changes of the protein, which may affect the physiological functions of catalase. The work provides important insights into the toxicity mechanism of microcystin in vivo.

  16. Mechanism of sequence-specific template binding by the DNA primase of bacteriophage T7

    KAUST Repository

    Lee, Seung-Joo

    2010-03-28

    DNA primases catalyze the synthesis of the oligoribonucleotides required for the initiation of lagging strand DNA synthesis. Biochemical studies have elucidated the mechanism for the sequence-specific synthesis of primers. However, the physical interactions of the primase with the DNA template to explain the basis of specificity have not been demonstrated. Using a combination of surface plasmon resonance and biochemical assays, we show that T7 DNA primase has only a slightly higher affinity for DNA containing the primase recognition sequence (5\\'-TGGTC-3\\') than for DNA lacking the recognition site. However, this binding is drastically enhanced by the presence of the cognate Nucleoside triphosphates (NTPs), Adenosine triphosphate (ATP) and Cytosine triphosphate (CTP) that are incorporated into the primer, pppACCA. Formation of the dimer, pppAC, the initial step of sequence-specific primer synthesis, is not sufficient for the stable binding. Preformed primers exhibit significantly less selective binding than that observed with ATP and CTP. Alterations in subdomains of the primase result in loss of selective DNA binding. We present a model in which conformational changes induced during primer synthesis facilitate contact between the zinc-binding domain and the polymerase domain. The Author(s) 2010. Published by Oxford University Press.

  17. Exploring the binding mechanism of ondansetron hydrochloride to serum albumins: spectroscopic approach.

    Science.gov (United States)

    B, Sandhya; Hegde, Ashwini H; K C, Ramesh; J, Seetharamappa

    2012-02-01

    The mechanism of interaction of ondansetron hydrochloride (OND) to serum albumins [bovine serum albumin (BSA) and human serum albumin (HSA)] was studied for the first time employing fluorimetric, circular dichroism, FTIR and UV-vis absorption techniques under the simulated physiological conditions. Fluorimetric results were utilized to investigate the binding and conformational characteristics of protein upon interaction with varying concentrations of the drug. Higher binding constant values revealed the strong interaction between the drug and protein while the number of binding sites close to unity indicated single class of binding site for OND in protein. Thermodynamic results revealed that both hydrogen bond and hydrophobic interactions played a major role in stabilizing drug-protein complex. Site marker competitive experiments indicated that the OND bound to albumins at subdomin II A (Sudlow's site I). Further, the binding distance between OND and serum albumin was calculated based on the Förster's theory of non-radioactive energy transfer and found to be 2.30 and 3.41 nm, respectively for OND-BSA and OND-HSA. The circular dichroism data revealed that the presence of OND decreased the α-helix content of serum albumins. 3D-fluorescence results also indicated the conformational changes in protein upon interaction with OND. Further, the effects of some cations have been investigated in the interaction of drug to protein.

  18. Molecular mechanism of ATP binding and ion channel activation in P2X receptors

    Energy Technology Data Exchange (ETDEWEB)

    Hattori, Motoyuki; Gouaux, Eric (Oregon HSU)

    2012-10-24

    P2X receptors are trimeric ATP-activated ion channels permeable to Na{sup +}, K{sup +} and Ca{sup 2+}. The seven P2X receptor subtypes are implicated in physiological processes that include modulation of synaptic transmission, contraction of smooth muscle, secretion of chemical transmitters and regulation of immune responses. Despite the importance of P2X receptors in cellular physiology, the three-dimensional composition of the ATP-binding site, the structural mechanism of ATP-dependent ion channel gating and the architecture of the open ion channel pore are unknown. Here we report the crystal structure of the zebrafish P2X4 receptor in complex with ATP and a new structure of the apo receptor. The agonist-bound structure reveals a previously unseen ATP-binding motif and an open ion channel pore. ATP binding induces cleft closure of the nucleotide-binding pocket, flexing of the lower body {beta}-sheet and a radial expansion of the extracellular vestibule. The structural widening of the extracellular vestibule is directly coupled to the opening of the ion channel pore by way of an iris-like expansion of the transmembrane helices. The structural delineation of the ATP-binding site and the ion channel pore, together with the conformational changes associated with ion channel gating, will stimulate development of new pharmacological agents.

  19. POF and HP1 bind expressed exons, suggesting a balancing mechanism for gene regulation.

    Science.gov (United States)

    Johansson, Anna-Mia; Stenberg, Per; Pettersson, Fredrik; Larsson, Jan

    2007-11-01

    Two specific chromosome-targeting and gene regulatory systems are present in Drosophila melanogaster. The male X chromosome is targeted by the male-specific lethal complex believed to mediate the 2-fold up-regulation of the X-linked genes, and the highly heterochromatic fourth chromosome is specifically targeted by the Painting of Fourth (POF) protein, which, together with heterochromatin protein 1 (HP1), modulates the expression level of genes on the fourth chromosome. Here we use chromatin immunoprecipitation and tiling microarray analysis to map POF and HP1 on the fourth chromosome in S2 cells and salivary glands at high resolution. The enrichment profiles were complemented by transcript profiles to examine the link between binding and transcripts. The results show that POF specifically binds to genes, with a strong preference for exons, and the HP1 binding profile is a mirror image of POF, although HP1 displays an additional "peak" in the promoter regions of bound genes. HP1 binding within genes is much higher than the basal HP1 enrichment on Chromosome 4. Our results suggest a balancing mechanism for the regulation of the fourth chromosome where POF and HP1 competitively bind at increasing levels with increased transcriptional activity. In addition, our results contradict transposable elements as a major nucleation site for HP1 on the fourth chromosome.

  20. POF and HP1 bind expressed exons, suggesting a balancing mechanism for gene regulation.

    Directory of Open Access Journals (Sweden)

    Anna-Mia Johansson

    2007-11-01

    Full Text Available Two specific chromosome-targeting and gene regulatory systems are present in Drosophila melanogaster. The male X chromosome is targeted by the male-specific lethal complex believed to mediate the 2-fold up-regulation of the X-linked genes, and the highly heterochromatic fourth chromosome is specifically targeted by the Painting of Fourth (POF protein, which, together with heterochromatin protein 1 (HP1, modulates the expression level of genes on the fourth chromosome. Here we use chromatin immunoprecipitation and tiling microarray analysis to map POF and HP1 on the fourth chromosome in S2 cells and salivary glands at high resolution. The enrichment profiles were complemented by transcript profiles to examine the link between binding and transcripts. The results show that POF specifically binds to genes, with a strong preference for exons, and the HP1 binding profile is a mirror image of POF, although HP1 displays an additional "peak" in the promoter regions of bound genes. HP1 binding within genes is much higher than the basal HP1 enrichment on Chromosome 4. Our results suggest a balancing mechanism for the regulation of the fourth chromosome where POF and HP1 competitively bind at increasing levels with increased transcriptional activity. In addition, our results contradict transposable elements as a major nucleation site for HP1 on the fourth chromosome.

  1. Identifying Sequential Substrate Binding at the Single-Molecule Level by Enzyme Mechanical Stabilization

    Science.gov (United States)

    Rivas-Pardo, Jaime Andrés; Alegre-Cebollada, Jorge; Ramírez-Sarmiento, César A.; Fernandez, Julio M.; Guixé, Victoria

    2015-01-01

    Enzyme-substrate binding is a dynamic process intimately coupled to protein structural changes, which in turn changes the unfolding energy landscape. By the use of single molecule force spectroscopy (SMFS), we characterize the open-to-closed conformational transition experienced by the hyperthermophilic ADP-dependent glucokinase from Thermococcus litoralis triggered by the sequential binding of substrates. In the absence of substrates, the mechanical unfolding of TlGK shows an intermediate I, which is stabilized in the presence of Mg·ADP-, the first substrate to bind to the enzyme. However, in the presence of this substrate, an additional unfolding event is observed, intermediate-1*. Finally, in the presence of both substrates, the unfolding force of intermediates-1 and -1*, increases as a consequence of the domain closure. These results show that SMFS could be used as a powerful experimental tool to investigate binding mechanisms of different enzymes with more than one ligand, expanding the repertoire of protocols traditionally used in enzymology. PMID:25840594

  2. STARD6 on steroids: solution structure, multiple timescale backbone dynamics and ligand binding mechanism

    Science.gov (United States)

    Létourneau, Danny; Bédard, Mikaël; Cabana, Jérôme; Lefebvre, Andrée; Lehoux, Jean-Guy; Lavigne, Pierre

    2016-06-01

    START domain proteins are conserved α/β helix-grip fold that play a role in the non-vesicular and intracellular transport of lipids and sterols. The mechanism and conformational changes permitting the entry of the ligand into their buried binding sites is not well understood. Moreover, their functions and the identification of cognate ligands is still an active area of research. Here, we report the solution structure of STARD6 and the characterization of its backbone dynamics on multiple time-scales through 15N spin-relaxation and amide exchange studies. We reveal for the first time the presence of concerted fluctuations in the Ω1 loop and the C-terminal helix on the microsecond-millisecond time-scale that allows for the opening of the binding site and ligand entry. We also report that STARD6 binds specifically testosterone. Our work represents a milestone for the study of ligand binding mechanism by other START domains and the elucidation of the biological function of STARD6.

  3. Kinetic mechanism and energetics of binding of phosphoryl group acceptors to Mycobacterium tuberculosis cytidine monophosphate kinase.

    Science.gov (United States)

    Jaskulski, Léia; Rosado, Leonardo A; Rostirolla, Diana C; Timmers, Luis F S M; de Souza, Osmar N; Santos, Diogenes S; Basso, Luiz A

    2013-08-01

    Cytidine monophosphate kinase from Mycobacterium tuberculosis (MtCMK) likely plays a role in supplying precursors for nucleic acid synthesis. MtCMK catalyzes the ATP-dependent phosphoryl group transfer preferentially to CMP and dCMP. Initial velocity studies and Isothermal titration calorimetry (ITC) measurements showed that MtCMK follows a random-order mechanism of substrate (CMP and ATP) binding, and an ordered mechanism for product release, in which ADP is released first followed by CDP. The thermodynamic signatures of CMP and CDP binding to MtCMK showed favorable enthalpy and unfavorable entropy, and ATP binding was characterized by favorable changes in enthalpy and entropy. The contribution of linked protonation events to the energetics of MtCMK:phosphoryl group acceptor binary complex formation suggested a net gain of protons. Values for the pKa of a likely chemical group involved in proton exchange and for the intrinsic binding enthalpy were calculated. The Asp187 side chain of MtCMK is suggested as the likely candidate for the protonation event. Data on thermodynamics of binary complex formation were collected to evaluate the contribution of 2'-OH group to intermolecular interactions. The data are discussed in light of functional and structural comparisons between CMP/dCMP kinases and UMP/CMP ones.

  4. Adhesive Categories

    DEFF Research Database (Denmark)

    Lack, Stephen; Sobocinski, Pawel

    2003-01-01

    We introduce adhesive categories, which are categories with structure ensuring that pushouts along monomorphisms are well-behaved. Many types of graphical structures used in computer science are shown to be examples of adhesive categories. Double-pushout graph rewriting generalises well...... to rewriting on arbitrary adhesive categories....

  5. Kinetic behavior of the general modifier mechanism of Botts and Morales with non-equilibrium binding

    CERN Document Server

    Jia, Chen; Qian, Min-Ping; Jiang, Da-Quan; Zhang, Yu-Ping

    2010-01-01

    In this paper, we thoroughly investigate the kinetic behavior of the general modifier mechanism of Botts and Morales at both equilibrium steady state assuming equilibrium substrate- and modifier-binding steps and non-equilibrium steady state (NESS) without assuming equilibrium binding steps. We introduce the net flux into discussion and propose a method which gains a strong advantage over early approaches involving King-Atman method and even the numerical computations in dealing with the cyclic reaction systems. Using this new approach, the expression of product rate at NESS gives clear biophysical significance. Moreover, we classify the kinetic behavior of the modifier into three categories, namely hyperbolic behavior, bell-shaped behavior, and switching behavior. It turns out that a modifier cannot be regarded as overall activator or inhibitor when the reaction system is not at equilibrium. The switching-behaved modifier may convert between activator and inhibitor via the general modifier mechanism when the...

  6. A Study on Efficient Mobile IPv6 Fast Handover Scheme Using Reverse Binding Mechanism

    Science.gov (United States)

    Tolentino, Randy S.; Lee, Kijeong; Kim, Sung-Gyu; Kim, Miso; Park, Byungjoo

    This paper proposes a solution for solving the packet handover issues of MIPv6. We propose an efficient scheme that can support fast handover effectively in standard Mobile IPv6 (MIPv6) by optimizing the associated data and the flow of signal during handover. A new signaling message Reverse Packet Binding Mechanism is defined and utilized to hasten the handover procedure by adding a buffer in access point (AP) and home agent (HA).

  7. Switchable bio-inspired adhesives

    Science.gov (United States)

    Kroner, Elmar

    2015-03-01

    Geckos have astonishing climbing abilities. They can adhere to almost any surface and can run on walls and even stick to ceilings. The extraordinary adhesion performance is caused by a combination of a complex surface pattern on their toes and the biomechanics of its movement. These biological dry adhesives have been intensely investigated during recent years because of the unique combination of adhesive properties. They provide high adhesion, allow for easy detachment, can be removed residue-free, and have self-cleaning properties. Many aspects have been successfully mimicked, leading to artificial, bio-inspired, patterned dry adhesives, and were addressed and in some aspects they even outperform the adhesion capabilities of geckos. However, designing artificial patterned adhesion systems with switchable adhesion remains a big challenge; the gecko's adhesion system is based on a complex hierarchical surface structure and on advanced biomechanics, which are both difficult to mimic. In this paper, two approaches are presented to achieve switchable adhesion. The first approach is based on a patterned polydimethylsiloxane (PDMS) polymer, where adhesion can be switched on and off by applying a low and a high compressive preload. The switch in adhesion is caused by a reversible mechanical instability of the adhesive silicone structures. The second approach is based on a composite material consisting of a Nickel- Titanium (NiTi) shape memory alloy and a patterned adhesive PDMS layer. The NiTi alloy is trained to change its surface topography as a function of temperature, which results in a change of the contact area and of alignment of the adhesive pattern towards a substrate, leading to switchable adhesion. These examples show that the unique properties of bio-inspired adhesives can be greatly improved by new concepts such as mechanical instability or by the use of active materials which react to external stimuli.

  8. Amino acid analogues bind to carbon nanotube via π-π interactions: Comparison of molecular mechanical and quantum mechanical calculations

    Science.gov (United States)

    Yang, Zaixing; Wang, Zhigang; Tian, Xingling; Xiu, Peng; Zhou, Ruhong

    2012-01-01

    Understanding the interaction between carbon nanotubes (CNTs) and biomolecules is essential to the CNT-based nanotechnology and biotechnology. Some recent experiments have suggested that the π-π stacking interactions between protein's aromatic residues and CNTs might play a key role in their binding, which raises interest in large scale modeling of protein-CNT complexes and associated π-π interactions at atomic detail. However, there is concern on the accuracy of classical fixed-charge molecular force fields due to their classical treatments and lack of polarizability. Here, we study the binding of three aromatic residue analogues (mimicking phenylalanine, tyrosine, and tryptophan) and benzene to a single-walled CNT, and compare the molecular mechanical (MM) calculations using three popular fixed-charge force fields (OPLSAA, AMBER, and CHARMM), with quantum mechanical (QM) calculations using the density-functional tight-binding method with the inclusion of dispersion correction (DFTB-D). Two typical configurations commonly found in π-π interactions are used, one with the aromatic rings parallel to the CNT surface (flat), and the other perpendicular (edge). Our calculations reveal that compared to the QM results the MM approaches can appropriately reproduce the strength of π-π interactions for both configurations, and more importantly, the energy difference between them, indicating that the various contributions to π-π interactions have been implicitly included in the van der Waals parameters of the standard MM force fields. Meanwhile, these MM models are less accurate in predicting the exact structural binding patterns (matching surface), meaning there are still rooms to be improved. In addition, we have provided a comprehensive and reliable QM picture for the π-π interactions of aromatic molecules with CNTs in gas phase, which might be used as a benchmark for future force field developments.

  9. Systems Biology Reveals Cigarette Smoke-Induced Concentration-Dependent Direct and Indirect Mechanisms That Promote Monocyte-Endothelial Cell Adhesion.

    Science.gov (United States)

    Poussin, Carine; Laurent, Alexandra; Peitsch, Manuel C; Hoeng, Julia; De Leon, Hector

    2015-10-01

    Cigarette smoke (CS) affects the adhesion of monocytes to endothelial cells, a critical step in atherogenesis. Using an in vitro adhesion assay together with innovative computational systems biology approaches to analyze omics data, our study aimed at investigating CS-induced mechanisms by which monocyte-endothelial cell adhesion is promoted. Primary human coronary artery endothelial cells (HCAECs) were treated for 4 h with (1) conditioned media of human monocytic Mono Mac-6 (MM6) cells preincubated with low or high concentrations of aqueous CS extract (sbPBS) from reference cigarette 3R4F for 2 h (indirect treatment, I), (2) unconditioned media similarly prepared without MM6 cells (direct treatment, D), or (3) freshly generated sbPBS (fresh direct treatment, FD). sbPBS promoted MM6 cells-HCAECs adhesion following I and FD, but not D. In I, the effect was mediated at a low concentration through activation of vascular inflammation processes promoted in HCAECs by a paracrine effect of the soluble mediators secreted by sbPBS-treated MM6 cells. Tumor necrosis factor α (TNFα), a major inducer, was actually shed by unstable CS compound-activated TNFα-converting enzyme. In FD, the effect was triggered at a high concentration that also induced some toxicity. This effect was mediated through an yet unknown mechanism associated with a stress damage response promoted in HCAECs by unstable CS compounds present in freshly generated sbPBS, which had decayed in D unconditioned media. Aqueous CS extract directly and indirectly promotes monocytic cell-endothelial cell adhesion in vitro via distinct concentration-dependent mechanisms.

  10. DNA-Binding Kinetics Determines the Mechanism of Noise-Induced Switching in Gene Networks.

    Science.gov (United States)

    Tse, Margaret J; Chu, Brian K; Roy, Mahua; Read, Elizabeth L

    2015-10-20

    Gene regulatory networks are multistable dynamical systems in which attractor states represent cell phenotypes. Spontaneous, noise-induced transitions between these states are thought to underlie critical cellular processes, including cell developmental fate decisions, phenotypic plasticity in fluctuating environments, and carcinogenesis. As such, there is increasing interest in the development of theoretical and computational approaches that can shed light on the dynamics of these stochastic state transitions in multistable gene networks. We applied a numerical rare-event sampling algorithm to study transition paths of spontaneous noise-induced switching for a ubiquitous gene regulatory network motif, the bistable toggle switch, in which two mutually repressive genes compete for dominant expression. We find that the method can efficiently uncover detailed switching mechanisms that involve fluctuations both in occupancies of DNA regulatory sites and copy numbers of protein products. In addition, we show that the rate parameters governing binding and unbinding of regulatory proteins to DNA strongly influence the switching mechanism. In a regime of slow DNA-binding/unbinding kinetics, spontaneous switching occurs relatively frequently and is driven primarily by fluctuations in DNA-site occupancies. In contrast, in a regime of fast DNA-binding/unbinding kinetics, switching occurs rarely and is driven by fluctuations in levels of expressed protein. Our results demonstrate how spontaneous cell phenotype transitions involve collective behavior of both regulatory proteins and DNA. Computational approaches capable of simulating dynamics over many system variables are thus well suited to exploring dynamic mechanisms in gene networks.

  11. Design of protein-ligand binding based on the molecular-mechanics energy model.

    Science.gov (United States)

    Boas, F Edward; Harbury, Pehr B

    2008-07-04

    While the molecular-mechanics field has standardized on a few potential energy functions, computational protein design efforts are based on potentials that are unique to individual laboratories. Here we show that a standard molecular-mechanics potential energy function without any modifications can be used to engineer protein-ligand binding. A molecular-mechanics potential is used to reconstruct the coordinates of various binding sites with an average root-mean-square error of 0.61 A and to reproduce known ligand-induced side-chain conformational shifts. Within a series of 34 mutants, the calculation can always distinguish between weak (K(d)>1 mM) and tight (K(d)mechanics potential is used to redesign a ribose-binding site. Out of a search space of 2 x 10(12) sequences, the calculation selects a point mutant of the native protein as the top solution (experimental K(d)=17 microM) and the native protein as the second best solution (experimental K(d)=210 nM). The quality of the predictions depends on the accuracy of the generalized Born electrostatics model, treatment of protonation equilibria, high-resolution rotamer sampling, a final local energy minimization step, and explicit modeling of the bound, unbound, and unfolded states. The application of unmodified molecular-mechanics potentials to protein design links two fields in a mutually beneficial way. Design provides a new avenue for testing molecular-mechanics energy functions, and future improvements in these energy functions will presumably lead to more accurate design results.

  12. Electrochemical layer-by-layer approach to fabricate mechanically stable platinum black microelectrodes using a mussel-inspired polydopamine adhesive

    Science.gov (United States)

    Kim, Raeyoung; Nam, Yoonkey

    2015-04-01

    Objective. Platinum black (PtBK) has long been used for microelectrode fabrication owing to its high recording performance of neural signals. The porous structure of PtBK enlarges the surface area and lowers the impedance, which results in background noise reduction. However, the brittleness of PtBK has been a problem in practice. In this work, we report mechanically stable PtBK microelectrodes using a bioinspired adhesive film, polydopamine (pDA), while maintaining the low impedance of PtBK. Approach. The pDA layer was incorporated into the PtBK structure through electrochemical layer-by-layer deposition. Varying the number of layers and the order of materials, multi-layered pDA-PtBK hybrids were fabricated and the electrical properties, both impedance and charge injection limit, were evaluated. Main results. Multilayered pDA-PtBK hybrids had electrical impedances as low as PtBK controls and charge injection limit twice larger than controls. For the 30 min-ultrasonication agitation test, impedance levels rarely changed for some of the pDA-PtBK hybrids indicating that the pDA improved the mechanical property of the PtBK structures. The pDA-PtBK hybrid microelectrodes readily recorded neural signals of cultured hippocampal neurons, where background noise levels and signal-to-noise were 2.43 ∼ 3.23 μVrms and 28.4 ∼ 69.1, respectively. Significance. The developed pDA-PtBK hybrid microelectrodes are expected to be applicable to neural sensors for neural prosthetic studies.

  13. Co元素对硬质合金基底金刚石涂层膜基界面结合强度的影响∗%The Influence of Co binding phase on adhesive strength of diamond coating with cemented carbide substrate

    Institute of Scientific and Technical Information of China (English)

    简小刚; 陈军

    2015-01-01

    Diamond coating has many excellent properties as the same as those of the natural diamond, such as extreme hard-ness, high thermal conductivity, low thermal expansion coefficient, high chemical stability, and good abrasive resistance, which is considered as the best tool coating material applied to the high-silicon aluminum alloy cutting. We can use the hot filament chemical vapor deposition method (HFCVD) to deposit a 2—20 µm diamond coating on the cemented carbide tool to improve the cutting performance and increase the tool life significantly. Many experiments have proved that the existence of cobalt phase can weaken the adhesive strength of diamond coating. However, we still lack a perfect theory to explain why the Co element can reduce the adhesive strength of diamond coating is still lacking. What we can do now is only to improve the adhesive strength of diamond coating by doing testing many times in experiments. Compared with these traditional experiments, the first principles simulation based on quantum mechanics can describe the microstructure property and electron density of materials. It is successfully used to investigate the surface, interface, electron component, and so on etc. We can also use this method to study the interface problem at an atomic level. So the first principles based upon density functional theory (DFT) is used to investigate the influence of cobalt binding phase in cemented carbide substrate on adhesive strength of diamond coating. In this article, we uses Material Studios software to build WC/diamond and WC-Co/diamond interface models to evaluate the influence of cobalt phase on the adhesive strength of diamond coating with CASTEP program which can calculate the most stablest structure of film-substrate interface. We use PBE functional form to obtain the exchange potential and relevant potential, and to solve the self-consistent Kohn-Sham equations. We calculate the interfacial bonding energy, analyse the electron density of

  14. Regulation of cell adhesion strength by peripheral focal adhesion distribution.

    Science.gov (United States)

    Elineni, Kranthi Kumar; Gallant, Nathan D

    2011-12-21

    Cell adhesion to extracellular matrices is a tightly regulated process that involves the complex interplay between biochemical and mechanical events at the cell-adhesive interface. Previous work established the spatiotemporal contributions of adhesive components to adhesion strength and identified a nonlinear dependence on cell spreading. This study was designed to investigate the regulation of cell-adhesion strength by the size and position of focal adhesions (FA). The cell-adhesive interface was engineered to direct FA assembly to the periphery of the cell-spreading area to delineate the cell-adhesive area from the cell-spreading area. It was observed that redistributing the same adhesive area over a larger cell-spreading area significantly enhanced cell-adhesion strength, but only up to a threshold area. Moreover, the size of the peripheral FAs, which was interpreted as an adhesive patch, did not directly govern the adhesion strength. Interestingly, this is in contrast to the previously reported functional role of FAs in regulating cellular traction where sizes of the peripheral FAs play a critical role. These findings demonstrate, to our knowledge for the first time, that two spatial regimes in cell-spreading area exist that uniquely govern the structure-function role of FAs in regulating cell-adhesion strength.

  15. Focal Adhesion Induction at the Tip of a Functionalized Nanoelectrode.

    Science.gov (United States)

    Fuentes, Daniela E; Bae, Chilman; Butler, Peter J

    2011-12-01

    Cells dynamically interact with their physical micro-environment through the assembly of nascent focal contacts and focal adhesions. The dynamics and mechanics of these contact points are controlled by transmembrane integrins and an array of intracellular adaptor proteins. In order to study the mechanics and dynamics of focal adhesion assembly, we have developed a technique for the timed induction of a nascent focal adhesion. Bovine aortic endothelial cells were approached at the apical surface by a nanoelectrode whose position was controlled with a resolution of 10s of nanometers using changes in electrode current to monitor distance from the cell surface. Since this probe was functionalized with fibronectin, a focal contact formed at the contact location. Nascent focal adhesion assembly was confirmed using time-lapse confocal fluorescent images of red fluorescent protein (RFP) - tagged talin, an adapter protein that binds to activated integrins. Binding to the cell was verified by noting a lack of change of electrode current upon retraction of the electrode. This study demonstrates that functionalized nanoelectrodes can enable precisely-timed induction and 3-D mechanical manipulation of focal adhesions and the assay of the detailed molecular kinetics of their assembly.

  16. Hodgkin lymphoma cell lines bind to platelets. Incubation with platelets induces CD15 and P-selectin dependent adhesion of the cell lines to Human Umbilical Vein Endothelial cells (HUVEC).

    Science.gov (United States)

    Ohana, Ofra Malka; Ozer, Janet; Prinsloo, Isebrand; Benharroch, Daniel; Gopas, Jacob

    2015-01-01

    Hodgkin's lymphoma is believed to spread in an orderly fashion within the lymphatic compartment. In a minority of cases, after reaching the spleen, the neoplasm disseminates, reminiscent of metastasis. In the spleen, the Hodgkin-Reed-Sternberg tumor cells come across platelets in the blood vessels and mainly in the splenic red pulp. Based on this knowledge, we investigated the possibility of platelets inducing cell adhesion in Hodgkin's lymphoma cell lines. We showed that L428 and KMH-2 cells strongly adhere to thrombin-activated platelets. Cell adhesion to platelets is partially dependent on CD15 antigens (Lewis(X)), mainly sialyl-CD15, and P-selectin. KMH-2, as compared to L428 cells, showed increased binding due to its differential high expression of the sialyl-CD15. As a consequence of incubation with platelets, KMH-2 cells also produced increased amounts of tumor necrosis factors α (TNFα) followed by enhanced binding to human vascular endothelial cells (HUVEC). Incubation of both cell lines with activated platelets also induced activation of AP-1 transcription complex. Our findings are consistent with the concept that platelets play a critical role in the dissemination of HRS cells in HL, predominantly in the spleen, by increasing cell adhesion and thus promoting their proliferative and migratory properties beyond the lymphatic system.

  17. Mac-2 binding protein is a cell-adhesive protein of the extracellular matrix which self-assembles into ring-like structures and binds beta1 integrins, collagens and fibronectin

    DEFF Research Database (Denmark)

    Sasaki, T; Brakebusch, C; Engel, J

    1998-01-01

    in solid-phase assays to collagens IV, V and VI, fibronectin and nidogen, but not to fibrillar collagens I and III or other basement membrane proteins. The protein also mediated adhesion of cell lines at comparable strength with laminin. Adhesion to M2BP was inhibited by antibodies to integrin beta1...

  18. Behavioural evidence for separate mechanisms of audiovisual temporal binding as a function of leading sensory modality.

    Science.gov (United States)

    Cecere, Roberto; Gross, Joachim; Thut, Gregor

    2016-06-01

    The ability to integrate auditory and visual information is critical for effective perception and interaction with the environment, and is thought to be abnormal in some clinical populations. Several studies have investigated the time window over which audiovisual events are integrated, also called the temporal binding window, and revealed asymmetries depending on the order of audiovisual input (i.e. the leading sense). When judging audiovisual simultaneity, the binding window appears narrower and non-malleable for auditory-leading stimulus pairs and wider and trainable for visual-leading pairs. Here we specifically examined the level of independence of binding mechanisms when auditory-before-visual vs. visual-before-auditory input is bound. Three groups of healthy participants practiced audiovisual simultaneity detection with feedback, selectively training on auditory-leading stimulus pairs (group 1), visual-leading stimulus pairs (group 2) or both (group 3). Subsequently, we tested for learning transfer (crossover) from trained stimulus pairs to non-trained pairs with opposite audiovisual input. Our data confirmed the known asymmetry in size and trainability for auditory-visual vs. visual-auditory binding windows. More importantly, practicing one type of audiovisual integration (e.g. auditory-visual) did not affect the other type (e.g. visual-auditory), even if trainable by within-condition practice. Together, these results provide crucial evidence that audiovisual temporal binding for auditory-leading vs. visual-leading stimulus pairs are independent, possibly tapping into different circuits for audiovisual integration due to engagement of different multisensory sampling mechanisms depending on leading sense. Our results have implications for informing the study of multisensory interactions in healthy participants and clinical populations with dysfunctional multisensory integration.

  19. Cytotoxicity and comparative binding mechanism of piperine with human serum albumin and α-1-acid glycoprotein.

    Science.gov (United States)

    Yeggoni, Daniel Pushparaju; Rachamallu, Aparna; Kallubai, Monika; Subramanyam, Rajagopal

    2015-01-01

    Human serum albumin (HSA) and α-1-acid glycoprotein (AGP) (acute phase protein) are the plasma proteins in blood system which transports many drugs. To understand the pharmacological importance of piperine molecule, here, we studied the anti-inflammatory activity of piperine on mouse macrophages (RAW 264.7) cell lines, which reveals that piperine caused an increase in inhibition growth of inflammated macrophages. Further, the fluorescence maximum quenching of proteins were observed upon binding of piperine to HSA and AGP through a static quenching mechanism. The binding constants obtained from fluorescence emission were found to be K(piperine) = 5.7 ± .2 × 10(5) M(-1) and K(piperine) = 9.3± .25 × 10(4) M(-1) which correspond to the free energy of -7.8 and -6.71 kcal M(-1)at 25 °C for HSA and AGP, respectively. Further, circular dichrosim studies revealed that there is a marginal change in the secondary structural content of HSA due to partial destabilization of HSA-piperine complexes. Consequently, inference drawn from the site-specific markers (phenylbutazone, site I marker) studies to identify the binding site of HSA noticed that piperine binds at site I (IIA), which was further authenticated by molecular docking and molecular dynamic (MD) studies. The binding constants and free energy corresponding to experimental and computational analysis suggest that there are hydrophobic and hydrophilic interactions when piperine binds to HSA. Additionally, the MD studies have showed that HSA-piperine complex reaches equilibration state at around 3 ns, which prove that the HSA-piperine complex is stable in nature.

  20. Thinking outside the cell: how cadherins drive adhesion.

    Science.gov (United States)

    Brasch, Julia; Harrison, Oliver J; Honig, Barry; Shapiro, Lawrence

    2012-06-01

    Cadherins are a superfamily of cell surface glycoproteins whose ectodomains contain multiple repeats of β-sandwich extracellular cadherin (EC) domains that adopt a similar fold to immunoglobulin domains. The best characterized cadherins are the vertebrate 'classical' cadherins, which mediate adhesion via trans homodimerization between their membrane-distal EC1 domains that extend from apposed cells, and assemble intercellular adherens junctions through cis clustering. To form mature trans adhesive dimers, cadherin domains from apposed cells dimerize in a 'strand-swapped' conformation. This occurs in a two-step binding process involving a fast-binding intermediate called the 'X-dimer'. Trans dimers are less flexible than cadherin monomers, a factor that drives junction assembly following cell-cell contact by reducing the entropic cost associated with the formation of lateral cis oligomers. Cadherins outside the classical subfamily appear to have evolved distinct adhesive mechanisms that are only now beginning to be understood.

  1. Biological adhesion of Parthenocissus tricuspidata

    Directory of Open Access Journals (Sweden)

    He Tianxian

    2011-01-01

    Full Text Available Parthenocissus tricuspidata is a climbing plant of the grape family. It can climb with its adhesive discs on different substrates such as stone mountains, roadside stone banks, exterior walls of buildings, thereby withstanding strong winds and storms without detachment. The details about the adhesion process of Parthenocissus tricuspidata are not yet entirely understood. We studied the component-structure-property relationship of the adhesive discs in detail and propose a twostage model to describe the biological adhesion: (i structural contact and (ii adhesive action. These two stages and their variations play an important role for the attaching of the adhesive disc to different structural surfaces. We believe that in Parthenocissus tricuspidata different mechanisms work together to allow the adhesive disc to climb on various vertical substrates and reveal strong adhesive properties.

  2. Investigations of Takeout proteins' ligand binding and release mechanism using molecular dynamics simulation.

    Science.gov (United States)

    Zhang, Huijing; Yu, Hui; Zhao, Xi; Liu, Xiaoguang; Feng, Xianli; Huang, Xuri

    2016-07-29

    Takeout (To) proteins exist in a diverse range of insect species. They are involved in many important processes of insect physiology and behaviors. As the ligand carriers, To proteins can transport the small molecule to the target tissues. However, ligand release mechanism of To proteins is unclear so far. In this contribution, the process and pathway of the ligand binding and release are revealed by conventional molecular dynamics simulation, steered molecular dynamics simulation and umbrella sampling methods. Our results show that the α4-side of the protein is the unique gate for the ligand binding and release. The structural analysis confirms that the internal cavity of the protein has high rigidity, which is in accordance with the recent experimental results. By using the potential of mean force calculations in combination with residue cross correlation calculation, we concluded that the binding between the ligand and To proteins is a process of conformational selection. Furthermore, the conformational changes of To proteins and the hydrophobic interactions both are the key factors for ligand binding and release.

  3. Sliding mechanics of coated composite wires and the development of an engineering model for binding.

    Science.gov (United States)

    Zufall, S W; Kusy, R P

    2000-02-01

    A tribological (friction and wear) study, which was designed to simulate clinical sliding mechanics, was conducted as part of an effort to determine the suitability of poly(chloro-p-xylylene) coatings for composite orthodontic archwires. Prototype composite wires, having stiffnesses similar to those of current initial and intermediate alignment wires, were tested against stainless steel and ceramic brackets in the passive and active configurations (with and without angulation). Kinetic coefficient of friction values, which were determined to quantify sliding resistances as functions of the normal forces of ligation, had a mean that was 72% greater than uncoated wire couples at 0.43. To improve analysis of the active configuration, a mathematical model was developed that related bracket angulation, bracket width, interbracket distance, wire geometry, and wire elastic modulus to sliding resistance. From this model, kinetic coefficients of binding were determined to quantify sliding resistances as functions of the normal forces of binding. The mean binding coefficient was the same as that of uncoated wire couples at 0.42. Although penetrations through the coating were observed on many specimens, the glass-fiber reinforcement within the composite wires was undamaged for all conditions tested. This finding implies that the risk of glass fiber release during clinical use would be eliminated by the coating. In addition, the frictional and binding coefficients were still within the limits outlined by conventional orthodontic wire-bracket couples. Consequently, the coatings were regarded as an improvement to the clinical acceptability of composite orthodontic archwires.

  4. Structural and mutational analyses of the receptor binding domain of botulinum D/C mosaic neurotoxin: Insight into the ganglioside binding mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Nuemket, Nipawan [Graduate School of Life Sciences, Hokkaido University, Sapporo 060-0810 (Japan); Tanaka, Yoshikazu [Creative Research Institution ' Sousei,' Hokkaido University, Sapporo 001-0021 (Japan); Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810 (Japan); Tsukamoto, Kentaro; Tsuji, Takao [Department of Microbiology, Fujita Health University School of Medicine, Toyoake, Aichi 470-1192 (Japan); Nakamura, Keiji; Kozaki, Shunji [Department of Veterinary Science, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Osaka 598-8531 (Japan); Yao, Min [Graduate School of Life Sciences, Hokkaido University, Sapporo 060-0810 (Japan); Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810 (Japan); Tanaka, Isao, E-mail: tanaka@castor.sci.hokudai.ac.jp [Graduate School of Life Sciences, Hokkaido University, Sapporo 060-0810 (Japan); Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810 (Japan)

    2011-07-29

    Highlights: {yields} We determined the crystal structure of the receptor binding domain of BoNT in complex with 3'-sialyllactose. {yields} An electron density derived from the 3'-sialyllactose was confirmed at the cleft in the C-terminal subdomain. {yields} Alanine site-directed mutagenesis showed that GBS and GBL are important for ganglioside binding. {yields} A cell binding mechanism, which involves cooperative contribution of two sites, was proposed. -- Abstract: Clostridium botulinum type D strain OFD05, which produces the D/C mosaic neurotoxin, was isolated from cattle killed by the recent botulism outbreak in Japan. The D/C mosaic neurotoxin is the most toxic of the botulinum neurotoxins (BoNT) characterized to date. Here, we determined the crystal structure of the receptor binding domain of BoNT from strain OFD05 in complex with 3'-sialyllactose at a resolution of 3.0 A. In the structure, an electron density derived from the 3'-sialyllactose was confirmed at the cleft in the C-terminal subdomain. Alanine site-directed mutagenesis showed the significant contribution of the residues surrounding the cleft to ganglioside recognition. In addition, a loop adjoining the cleft also plays an important role in ganglioside recognition. In contrast, little effect was observed when the residues located around the surface previously identified as the protein receptor binding site in other BoNTs were substituted. The results of cell binding analysis of the mutants were significantly correlated with the ganglioside binding properties. Based on these observations, a cell binding mechanism of BoNT from strain OFD05 is proposed, which involves cooperative contribution of two ganglioside binding sites.

  5. Theory on the mechanisms of combinatorial binding of transcription factors with DNA

    CERN Document Server

    Murugan, R

    2016-01-01

    We develop a theoretical framework on the mechanism of combinatorial binding of transcription factors (TFs) with their specific binding sites on DNA. We consider three possible mechanisms viz. monomer, hetero-oligomer and coordinated recruitment pathways. In the monomer pathway, combinatorial TFs search for their targets in an independent manner and the protein-protein interactions among them will be insignificant. The protein-protein interactions are very strong so that the hetero-oligomer complex of TFs as a whole searches for the cognate sites in case of hetero-oligomer pathway. The TF which arrived first will recruit the adjacent TFs in a sequential manner in the recruitment pathway. The free energy released from the protein-protein interactions among TFs will be in turn utilized to stabilize the TFs-DNA complex. Such coordinated binding of TFs in fact emerges as the cooperative effect. Monomer and hetero-oligomer pathways are efficient only when few TFs are involved in the combinatorial regulation. Detai...

  6. Mechanical Stimulation of C2C12 Cells Increases m-Calpain Expression and Activity, Focal Adhesion Plaque Degradation and Cell Fusion

    DEFF Research Database (Denmark)

    Grossi, Alberto; Lawson, Moira Ann; Karlsson, Anders H

    Abstract Mechanical Stimulation of C2C12 Cells Increases m-calpain Expression and Activity, Focal Adhesion Plaque Degradation and Cell Fusion A. Grossi, A. H. Karlsson, M. A. Lawson; Department of Dairy and Food Science, Royal Veterinary and Agricultural University, Frederiksberg C, Denmark...... to the activity of ubiquitous proteolytic enzymes known as calpains has been reported. Whether there is a link between stretch- or load induced signaling and calpain expression and activation is not known. Using a magnetic bead stimulation assay and C2C12 mouse myoblasts cell population, we have demonstrated...... that mechanical stimulation via laminin receptors leads to an increase in m-calpain expression, but no increase in the expression of other calpain isoforms. Our study revealed that after a short period of stimulation, m-calpain relocates into focal adhesion complexes and is followed by a breakdown of specific...

  7. Mechanical properties of a waterborne pressure-sensitive adhesive with a percolating poly(acrylic acid)-based diblock copolymer network: effect of pH.

    Science.gov (United States)

    Gurney, Robert S; Morse, Andrew; Siband, Elodie; Dupin, Damien; Armes, Steven P; Keddie, Joseph L

    2015-06-15

    Copolymerizing an acrylic acid comonomer is often beneficial for the adhesive properties of waterborne pressure-sensitive adhesives (PSAs). Here, we demonstrate a new strategy in which poly(acrylic acid) (PAA) is distributed as a percolating network within a PSA film formed from a polymer colloid. A diblock copolymer composed of PAA and poly(n-butyl acrylate) (PBA) blocks was synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization and adsorbed onto soft acrylic latex particles prior to their film formation. The thin adsorbed shells on the particles create a percolating network that raises the elastic modulus, creep resistance and tensile strength of the final film. When the film formation occurs at pH 10, ionomeric crosslinking occurs, and high tack adhesion is obtained in combination with high creep resistance. The results show that the addition of an amphiphilic PAA-b-PBA diblock copolymer (2.0 wt.%) to a soft latex provides a simple yet effective means of adjusting the mechanical and adhesive properties of the resulting composite film.

  8. Simulative Calculation of Mechanical Property, Binding Energy and Detonation Property of TATB/Fluorine-polymer PBX

    Institute of Scientific and Technical Information of China (English)

    MA, Xiu-Fang; XIAO, Ji-Jun; HUANG, Hui; JU, Xue-Hai; LI, Jin-Shan; XIAO, He-Ming

    2006-01-01

    Molecular dynamics (MD) method was used to simulate 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) coated with fluorine containing polymers. The mechanical properties and binding energies of PBXs were obtained. It was found that when the number of chain monomers of fluorine containing polymers was the same, the elasticity of TATB/F2314 was increased more greatly than others and the binding energy of TATB/F2311 was the largest among four PBXs. Detonation heat and velocity of such four PBXs were calculated according to theoretical and empirical formulas. The results show that the order of detonation heat is TATB>TATB/PVDF>TATB/F2311 >TATB/F2314>TATB/PCTFE while the order of detonation velocity is TATB/PVDF<TATB/F2311 <TATB/F2314<TATB/PCTFE<TATB.

  9. Mechanisms of photoisomerization of polyenes in confined media: from organic glasses to protein binding cavities.

    Science.gov (United States)

    Liu, Robert S H; Yang, Lan-Ying; Liu, Jin

    2007-01-01

    Photochemical reactivities of model organic systems (stilbene and diphenylbutadiene) in organic glasses were first examined and compared with those in solution and in organized media. These observations were in turn compared with reactivities of polyene chromophores in protein binding cavities (specifically PYP, rhodopsin and bacteriorhodopsin). The obvious conclusion is that the preference for the most volume-conserving Hula-twist mechanism isomerization in organic glasses is because of the close interaction between the guest and the host molecules. In organized media (zeolites, crystals and protein binding cavities), the residual empty space coupled with any specific guest-host interactions that are characteristic of a given system, could lead to involvement of the more volume-demanding one-bond-flip (i.e. torsional relaxation) or bicycle-pedal or an extended HT process in photoisomerization.

  10. [Endothelial cell adhesion molecules].

    Science.gov (United States)

    Ivanov, A N; Norkin, I A; Puchin'ian, D M; Shirokov, V Iu; Zhdanova, O Iu

    2014-01-01

    The review presents current data concerning the functional role of endothelial cell adhesion molecules belonging to different structural families: integrins, selectins, cadherins, and the immunoglobulin super-family. In this manuscript the regulatory mechanisms and factors of adhesion molecules expression and distribution on the surface of endothelial cells are discussed. The data presented reveal the importance of adhesion molecules in the regulation of structural and functional state of endothelial cells in normal conditions and in pathology. Particular attention is paid to the importance of these molecules in the processes of physiological and pathological angiogenesis, regulation of permeability of the endothelial barrier and cell transmigration.

  11. The reaction mechanism of methyl-coenzyme M reductase: how an enzyme enforces strict binding order.

    Science.gov (United States)

    Wongnate, Thanyaporn; Ragsdale, Stephen W

    2015-04-10

    Methyl-coenzyme M reductase (MCR) is a nickel tetrahydrocorphinoid (coenzyme F430) containing enzyme involved in the biological synthesis and anaerobic oxidation of methane. MCR catalyzes the conversion of methyl-2-mercaptoethanesulfonate (methyl-SCoM) and N-7-mercaptoheptanoylthreonine phosphate (CoB7SH) to CH4 and the mixed disulfide CoBS-SCoM. In this study, the reaction of MCR from Methanothermobacter marburgensis, with its native substrates was investigated using static binding, chemical quench, and stopped-flow techniques. Rate constants were measured for each step in this strictly ordered ternary complex catalytic mechanism. Surprisingly, in the absence of the other substrate, MCR can bind either substrate; however, only one binary complex (MCR·methyl-SCoM) is productive whereas the other (MCR·CoB7SH) is inhibitory. Moreover, the kinetic data demonstrate that binding of methyl-SCoM to the inhibitory MCR·CoB7SH complex is highly disfavored (Kd = 56 mM). However, binding of CoB7SH to the productive MCR·methyl-SCoM complex to form the active ternary complex (CoB7SH·MCR(Ni(I))·CH3SCoM) is highly favored (Kd = 79 μM). Only then can the chemical reaction occur (kobs = 20 s(-1) at 25 °C), leading to rapid formation and dissociation of CH4 leaving the binary product complex (MCR(Ni(II))·CoB7S(-)·SCoM), which undergoes electron transfer to regenerate Ni(I) and the final product CoBS-SCoM. This first rapid kinetics study of MCR with its natural substrates describes how an enzyme can enforce a strictly ordered ternary complex mechanism and serves as a template for identification of the reaction intermediates.

  12. Two-component spin-coated Ag/CNT composite films based on a silver heterogeneous nucleation mechanism adhesion-enhanced by mechanical interlocking and chemical grafting

    Science.gov (United States)

    Zhang, Yang; Kang, Zhixin; Bessho, Takeshi

    2017-03-01

    In this paper, a new method for the synthesis of silver carbon nanotube (Ag/CNT) composite films as conductive connection units for flexible electronic devices is presented. This method is about a two-component solution process by spin coating with an after-treatment annealing process. In this method, multi-walled carbon nanotubes (MWCNTs) act as the core of silver heterogeneous nucleation, which can be observed and analyzed by a field-emission scanning electron microscope. With the effects of mechanical interlocking, chemical grafting, and annealing, the interfacial adhesive strength between films and PET sheets was enhanced to 12 N cm‑1. The tensile strength of the Ag/CNT composite films was observed to increase by 38% by adding 5 g l‑1 MWCNTs. In the four-probe method, the resistivity of Ag/CNT-5 declined by 78.2% compared with pristine Ag films. The anti-fatigue performance of the Ag/CNT composite films was monitored by cyclic bending deformation and the results revealed that the growth rate of electrical resistance during the deformation was obviously retarded. As for industrial application, this method provides an efficient low-cost way to prepare Ag/CNT composite films and can be further applied to other coating systems.

  13. From simple receptors to complex multimodal percepts: A first global picture on the mechanisms involved in perceptual binding

    Directory of Open Access Journals (Sweden)

    Rosemarie eVelik

    2012-07-01

    Full Text Available The binding problem in perception is concerned with answering the question how information from millions of sensory receptors, processed by millions of neurons working in parallel, can be merged into a unified percept. Binding in perception reaches from the lowest levels of feature binding up to the levels of multimodal binding of information coming from the different sensor modalities and also from other functional systems. The last 40 years of research have shown that the binding problem cannot be solved easily. Today, it is considered as one of the key questions to brain understanding. To date, various solutions have been suggested to the binding problem including: (1 combination coding, (2 binding by synchrony, (3 population coding, (4 binding by attention, (5 binding by knowledge, expectation, and memory, (6 hardwired versus on-demand binding, (7 bundling and binding of features, (8 the feature-integration theory of attention, (9 synchronization through top-down processes. Each of those hypotheses addresses important aspects of binding. However, each of them also suffers from certain weak points and can never give a complete explanation. This article gives a brief overview of the so far suggested solutions of perceptual binding and then shows that those are actually not mutually exclusive but can complement each other. A computationally verified model is presented which shows that, most likely, the different described mechanisms of binding act (1 at different hierarchical levels and (2 in different stages of perceptual knowledge acquisition. The model furthermore considers and explains a number of inhibitory filter mechanisms that suppress the activation of inappropriate or currently irrelevant information.

  14. Effects of ligand binding on the mechanical stability of protein GB1 studied by steered molecular dynamics simulation.

    Science.gov (United States)

    Su, Ji-Guo; Zhao, Shu-Xin; Wang, Xiao-Feng; Li, Chun-Hua; Li, Jing-Yuan

    2016-08-01

    Regulation of the mechanical properties of proteins plays an important role in many biological processes, and sheds light on the design of biomaterials comprised of protein. At present, strategies to regulate protein mechanical stability focus mainly on direct modulation of the force-bearing region of the protein. Interestingly, the mechanical stability of GB1 can be significantly enhanced by the binding of Fc fragments of human IgG antibody, where the binding site is distant from the force-bearing region of the protein. The mechanism of this long-range allosteric control of protein mechanics is still elusive. In this work, the impact of ligand binding on the mechanical stability of GB1 was investigated using steered molecular dynamics simulation, and a mechanism underlying the enhanced protein mechanical stability is proposed. We found that the external force causes deformation of both force-bearing region and ligand binding site. In other words, there is a long-range coupling between these two regions. The binding of ligand restricts the distortion of the binding site and reduces the deformation of the force-bearing region through a long-range allosteric communication, which thus improves the overall mechanical stability of the protein. The simulation results are very consistent with previous experimental observations. Our studies thus provide atomic-level insights into the mechanical unfolding process of GB1, and explain the impact of ligand binding on the mechanical properties of the protein through long-range allosteric regulation, which should facilitate effective modulation of protein mechanical properties.

  15. Structural mechanism of S-adenosyl methionine binding to catechol O-methyltransferase.

    Directory of Open Access Journals (Sweden)

    Douglas Tsao

    Full Text Available Methyltransferases possess a homologous domain that requires both a divalent metal cation and S-adenosyl-L-methionine (SAM to catalyze its reactions. The kinetics of several methyltransferases has been well characterized; however, the details regarding their structural mechanisms have remained unclear to date. Using catechol O-methyltransferase (COMT as a model, we perform discrete molecular dynamics and computational docking simulations to elucidate the initial stages of cofactor binding. We find that COMT binds SAM via an induced-fit mechanism, where SAM adopts a different docking pose in the absence of metal and substrate in comparison to the holoenzyme. Flexible modeling of the active site side-chains is essential for observing the lowest energy state in the apoenzyme; rigid docking tools are unable to recapitulate the pose unless the appropriate side-chain conformations are given a priori. From our docking results, we hypothesize that the metal reorients SAM in a conformation suitable for donating its methyl substituent to the recipient ligand. The proposed mechanism enables a general understanding of how divalent metal cations contribute to methyltransferase function.

  16. Small substrate transport and mechanism of a molybdate ATP binding cassette transporter in a lipid environment.

    Science.gov (United States)

    Rice, Austin J; Harrison, Alistair; Alvarez, Frances J D; Davidson, Amy L; Pinkett, Heather W

    2014-05-23

    Embedded in the plasma membrane of all bacteria, ATP binding cassette (ABC) importers facilitate the uptake of several vital nutrients and cofactors. The ABC transporter, MolBC-A, imports molybdate by passing substrate from the binding protein MolA to a membrane-spanning translocation pathway of MolB. To understand the mechanism of transport in the biological membrane as a whole, the effects of the lipid bilayer on transport needed to be addressed. Continuous wave-electron paramagnetic resonance and in vivo molybdate uptake studies were used to test the impact of the lipid environment on the mechanism and function of MolBC-A. Working with the bacterium Haemophilus influenzae, we found that MolBC-A functions as a low affinity molybdate transporter in its native environment. In periods of high extracellular molybdate concentration, H. influenzae makes use of parallel molybdate transport systems (MolBC-A and ModBC-A) to take up a greater amount of molybdate than a strain with ModBC-A alone. In addition, the movement of the translocation pathway in response to nucleotide binding and hydrolysis in a lipid environment is conserved when compared with in-detergent analysis. However, electron paramagnetic resonance spectroscopy indicates that a lipid environment restricts the flexibility of the MolBC translocation pathway. By combining continuous wave-electron paramagnetic resonance spectroscopy and substrate uptake studies, we reveal details of molybdate transport and the logistics of uptake systems that employ multiple transporters for the same substrate, offering insight into the mechanisms of nutrient uptake in bacteria.

  17. Investigation of adhesion and mechanical properties of human glioma cells by single cell force spectroscopy and atomic force microscopy.

    Science.gov (United States)

    Andolfi, Laura; Bourkoula, Eugenia; Migliorini, Elisa; Palma, Anita; Pucer, Anja; Skrap, Miran; Scoles, Giacinto; Beltrami, Antonio Paolo; Cesselli, Daniela; Lazzarino, Marco

    2014-01-01

    Active cell migration and invasion is a peculiar feature of glioma that makes this tumor able to rapidly infiltrate into the surrounding brain tissue. In our recent work, we identified a novel class of glioma-associated-stem cells (defined as GASC for high-grade glioma--HG--and Gasc for low-grade glioma--LG) that, although not tumorigenic, act supporting the biological aggressiveness of glioma-initiating stem cells (defined as GSC for HG and Gsc for LG) favoring also their motility. Migrating cancer cells undergo considerable molecular and cellular changes by remodeling their cytoskeleton and cell interactions with surrounding environment. To get a better understanding about the role of the glioma-associated-stem cells in tumor progression, cell deformability and interactions between glioma-initiating stem cells and glioma-associated-stem cells were investigated. Adhesion of HG/LG-cancer cells on HG/LG-glioma-associated stem cells was studied by time-lapse microscopy, while cell deformability and cell-cell adhesion strengths were quantified by indentation measurements by atomic force microscopy and single cell force spectroscopy. Our results demonstrate that for both HG and LG glioma, cancer-initiating-stem cells are softer than glioma-associated-stem cells, in agreement with their neoplastic features. The adhesion strength of GSC on GASC appears to be significantly lower than that observed for Gsc on Gasc. Whereas, GSC spread and firmly adhere on Gasc with an adhesion strength increased as compared to that obtained on GASC. These findings highlight that the grade of glioma-associated-stem cells plays an important role in modulating cancer cell adhesion, which could affect glioma cell migration, invasion and thus cancer aggressiveness. Moreover this work provides evidence about the importance of investigating cell adhesion and elasticity for new developments in disease diagnostics and therapeutics.

  18. Investigation of adhesion and mechanical properties of human glioma cells by single cell force spectroscopy and atomic force microscopy.

    Directory of Open Access Journals (Sweden)

    Laura Andolfi

    Full Text Available Active cell migration and invasion is a peculiar feature of glioma that makes this tumor able to rapidly infiltrate into the surrounding brain tissue. In our recent work, we identified a novel class of glioma-associated-stem cells (defined as GASC for high-grade glioma--HG--and Gasc for low-grade glioma--LG that, although not tumorigenic, act supporting the biological aggressiveness of glioma-initiating stem cells (defined as GSC for HG and Gsc for LG favoring also their motility. Migrating cancer cells undergo considerable molecular and cellular changes by remodeling their cytoskeleton and cell interactions with surrounding environment. To get a better understanding about the role of the glioma-associated-stem cells in tumor progression, cell deformability and interactions between glioma-initiating stem cells and glioma-associated-stem cells were investigated. Adhesion of HG/LG-cancer cells on HG/LG-glioma-associated stem cells was studied by time-lapse microscopy, while cell deformability and cell-cell adhesion strengths were quantified by indentation measurements by atomic force microscopy and single cell force spectroscopy. Our results demonstrate that for both HG and LG glioma, cancer-initiating-stem cells are softer than glioma-associated-stem cells, in agreement with their neoplastic features. The adhesion strength of GSC on GASC appears to be significantly lower than that observed for Gsc on Gasc. Whereas, GSC spread and firmly adhere on Gasc with an adhesion strength increased as compared to that obtained on GASC. These findings highlight that the grade of glioma-associated-stem cells plays an important role in modulating cancer cell adhesion, which could affect glioma cell migration, invasion and thus cancer aggressiveness. Moreover this work provides evidence about the importance of investigating cell adhesion and elasticity for new developments in disease diagnostics and therapeutics.

  19. 肾上皮细胞损伤使草酸钙晶体黏附增强的分子机制%Molecular Mechanism of Adhesion of Monohydrate and Dihydrate Calcium Oxalate Crystals on Injured Kidney Epithelial Cells

    Institute of Scientific and Technical Information of China (English)

    甘琼枝; 孙新园; 姚秀琼; 欧阳健明

    2016-01-01

    研究了非洲绿猴肾上皮细胞( Vero)在损伤前后与一水合草酸钙( COM)和二水合草酸钙( COD)晶体的黏附作用及其引起的细胞反应,探讨了肾结石形成机理。 COM和COD晶体与损伤细胞的黏附加重了细胞的过氧化损伤程度,导致损伤细胞的活力进一步降低,乳酸脱氢酶( LDH)释放量和活性氧( ROS)进一步增加,坏死细胞数量进一步增多,细胞体积缩小,并出现凋亡小体。 COM晶体对细胞的损伤能力显著大于COD晶体。扫描电子显微镜( SEM)观测结果表明,损伤组Vero与COM微晶的黏附作用显著强于对照组,且能促进COM微晶的聚集。共聚焦显微镜观测结果表明, Vero损伤后,其表面表达的晶体黏附分子透明质酸( HA)显著增加, HA分子是促进微晶黏附的重要原因。细胞表面草酸钙的黏附量和晶体聚集程度与细胞的损伤程度成正相关。本文结果从分子和细胞水平上提示,细胞损伤是导致草酸钙肾结石形成的重要因素。%Effects of cell injury on calcium oxalate monohydrate( COM) and calcium oxalate dihydrate( COD) microcrystalline adhesion and cellular response of calcium oxalate microcrystalline on African green monkey renal epithelial( Vero) cells after adhesion were evaluated. COM amd COD crystal adhesion to injured Vero cells increased oxidative damage degree, the LDH release amount, reactive oxygen species( ROS) and dead cells and decreased cell viability. The cells shrinked and apoptotic bodies appeared. COM crystals caused more serious damage to injured Vero cells than COD crystals. The results of scanning electron microscopy ( SEM) showed that the adhesive capacity of injured Vero cells to COM was significantly stronger than the con-trol group, which enhanced crystals adhesion and aggregation. Laser scanning confocal microscope showed that Vero cell injury increased the expression of crystal binding hyaluronic acid ( HA ) molecules which were

  20. Kinetic mechanism of phenylalanine hydroxylase: intrinsic binding and rate constants from single-turnover experiments.

    Science.gov (United States)

    Roberts, Kenneth M; Pavon, Jorge Alex; Fitzpatrick, Paul F

    2013-02-12

    Phenylalanine hydroxylase (PheH) catalyzes the key step in the catabolism of dietary phenylalanine, its hydroxylation to tyrosine using tetrahydrobiopterin (BH(4)) and O(2). A complete kinetic mechanism for PheH was determined by global analysis of single-turnover data in the reaction of PheHΔ117, a truncated form of the enzyme lacking the N-terminal regulatory domain. Formation of the productive PheHΔ117-BH(4)-phenylalanine complex begins with the rapid binding of BH(4) (K(d) = 65 μM). Subsequent addition of phenylalanine to the binary complex to form the productive ternary complex (K(d) = 130 μM) is approximately 10-fold slower. Both substrates can also bind to the free enzyme to form inhibitory binary complexes. O(2) rapidly binds to the productive ternary complex; this is followed by formation of an unidentified intermediate, which can be detected as a decrease in absorbance at 340 nm, with a rate constant of 140 s(-1). Formation of the 4a-hydroxypterin and Fe(IV)O intermediates is 10-fold slower and is followed by the rapid hydroxylation of the amino acid. Product release is the rate-determining step and largely determines k(cat). Similar reactions using 6-methyltetrahydropterin indicate a preference for the physiological pterin during hydroxylation.

  1. Charging effect in Au nanoparticle memory device with biomolecule binding mechanism.

    Science.gov (United States)

    Jung, Sung Mok; Kim, Hyung-Jun; Kim, Bong-Jin; Yoon, Tae-Sik; Kim, Yong-Sang; Lee, Hyun Ho

    2011-07-01

    Organic memory device having gold nanoparticle (Au NPs) has been introduced in the structure of metal-pentacene-insulator-silicon (MPIS) capacitor device, where the Au NPs layer was formed by a new bonding method. Biomolecule binding mechanism between streptavidin and biotin was used as a strong binding method for the formation of monolayered Au NPs on polymeric dielectric of poly vinyl alcohol (PVA). The self-assembled Au NPs was functioned to show storages of charge in the MPIS device. The binding by streptavidin and biotin was confirmed by AFM and UV-VIS. The UV-VIS absorption of the Au NPs was varied at 515 nm and 525 nm depending on the coating of streptavidin. The AFM image showed no formation of multi-stacked layers of the streptavidin-capped Au NPs on biotin-NHS layer. Capacitance-voltage (C-V) performance of the memory device was measured to investigate the charging effect from Au NPs. In addition, charge retention by the Au NPs storage was tested to show 10,000 s in the C-V curve.

  2. Adhesive Categories

    DEFF Research Database (Denmark)

    Lack, Stephen; Sobocinski, Pawel

    2004-01-01

    We introduce adhesive categories, which are categories with structure ensuring that pushouts along monomorphisms are well-behaved. Many types of graphical structures used in computer science are shown to be examples of adhesive categories. Double-pushout graph rewriting generalises well to rewrit...

  3. Cellulose as an adhesion agent for the synthesis of lignin aerogel with strong mechanical performance, Sound-absorption and thermal Insulation.

    Science.gov (United States)

    Wang, Chao; Xiong, Ye; Fan, Bitao; Yao, Qiufang; Wang, Hanwei; Jin, Chunde; Sun, Qingfeng

    2016-08-26

    The lignin aerogels that are both high porosity and compressibility would have promising implications for bioengineering field to sound-adsorption and damping materials; however, creating this aerogel had a challenge to adhesive lignin. Here we reported cellulose as green adhesion agent to synthesize the aerogels with strong mechanical performance. Our approach-straightforwardly dissolved in ionic liquids and simply regenerated in the deionized water-causes assembly of micro-and nanoscale and even molecule level of cellulose and lignin. The resulting lignin aerogels exhibit Young's modulus up to 25.1 MPa, high-efficiency sound-adsorption and excellent thermal insulativity. The successful synthesis of this aerogels developed a path for lignin to an advanced utilization.

  4. Study on the Mechanism of Adhesion Improvement Using Dry-Ice Blasting for Plasma-Sprayed Al2O3 Coatings

    Science.gov (United States)

    Dong, Shujuan; Song, Bo; Hansz, Bernard; Liao, Hanlin; Coddet, Christian

    2013-03-01

    The mechanisms of adhesion improvement of plasma-sprayed Al2O3 coatings using dry-ice blasting were investigated. In this study, the change of substrate surface characteristics in both the topography and the wettability due to the treatment of dry-ice blasting was mainly studied. The effect of dry-ice blasting on Al2O3 splat morphology with different treatment durations was also examined. The residual stress of plasma-sprayed Al2O3 coatings using dry-ice blasting was measured by curvature method and compared to that of coatings deposited with conventional air cooling. Based on these numerous assessment tests, it could be concluded that the adhesion improvement of Al2O3 coatings could be attributed to the cleaning effect of dry-ice blasting on different organic substances adsorbed on the substrates and the peening effect.

  5. Full-length recombinant Plasmodium falciparum VAR2CSA binds specifically to CSPG and induces potent parasite adhesion blocking antibodies

    DEFF Research Database (Denmark)

    Khunrae, Pongsak; Dahlbäck, Madeleine; Nielsen, Morten A;

    2010-01-01

    Plasmodium falciparum malaria remains one of the world's leading causes of human suffering and poverty. Each year, the disease takes 1-3 million lives, mainly in sub-Saharan Africa. The adhesion of parasite-infected erythrocytes to the vascular endothelium or the placenta is the key event...

  6. Surface-modified nanoparticles as a new, versatile, and mechanically robust nonadhesive coating: Suppression of protein adsorption and bacterial adhesion

    NARCIS (Netherlands)

    Holmes, P.F.; Currie, E.P.K.; Thies, J.C.; Mei, van der H.C.; Busscher, H.J.; Norde, W.

    2009-01-01

    The synthesis of surface-modified silica nanoparticles, chemically grafted with acrylate and poly(ethylene glycol) (PEG) groups, and the ability of the resulting crosslinked coatings to inhibit protein adsorption and bacterial adhesion are explored. Water contact angles, nanoindentation, and atomic

  7. Surface-modified nanoparticles as a new, versatile, and mechanically robust nonadhesive coating : Suppression of protein adsorption and bacterial adhesion

    NARCIS (Netherlands)

    Holmes, P. F.; Currie, E. P. K.; Thies, J. C.; van der Mei, H. C.; Busscher, H. J.; Norde, W.

    2009-01-01

    The synthesis of surface-modified silica nanoparticles, chemically grafted with acrylate and poly(ethylene glycol) (PEG) groups, and the ability of the resulting crosslinked coatings to inhibit protein adsorption and bacterial adhesion are explored. Water contact angles, nanoindentation, and atomic

  8. Study of adhesion and friction properties on a nanoparticle gradient surface: transition from JKR to DMT contact mechanics.

    Science.gov (United States)

    Ramakrishna, Shivaprakash N; Nalam, Prathima C; Clasohm, Lucy Y; Spencer, Nicholas D

    2013-01-01

    We have previously investigated the dependence of adhesion on nanometer-scale surface roughness by employing a roughness gradient. In this study, we correlate the obtained adhesion forces on nanometer-scale rough surfaces to their frictional properties. A roughness gradient with varying silica particle (diameter ≈ 12 nm) density was prepared, and adhesion and frictional forces were measured across the gradient surface in perfluorodecalin by means of atomic force microscopy with a polyethylene colloidal probe. Similarly to the pull-off measurements, the frictional forces initially showed a reduction with decreasing particle density and later an abrupt increase as the colloidal sphere began to touch the flat substrate beneath, at very low particle densities. The friction-load relation is found to depend on the real contact area (A(real)) between the colloid probe and the underlying particles. At high particle density, the colloidal sphere undergoes large deformations over several nanoparticles, and the contact adhesion (JKR type) dominates the frictional response. However, at low particle density (before the colloidal probe is in contact with the underlying surface), the colloidal sphere is suspended by a few particles only, resulting in local deformations of the colloid sphere, with the frictional response to the applied load being dominated by long-range, noncontact (DMT-type) interactions with the substrate beneath.

  9. Kinetic Mechanism of Uracil Phosphoribosyltransferase from Escherichia coli and Catalytic Importance of the Conserved Proline in the PRPP Binding Site

    DEFF Research Database (Denmark)

    Lundegaard, Claus; Jensen, Kaj Frank

    1999-01-01

    catalytic properties with the properties of the wild-type protein. We found that UPRTase of E. coli obeyed the kinetics of a sequential mechanism with the binding of PRPP preceding the binding of uracil. The basic kinetic constants were derived from initial velocity measurements, product inhibition......, and ligand binding assays. The change of Pro 131 to Asp caused a 50-60-fold reduction of the catalytic rate (kcat) in both directions of the reaction and approximately a 100-fold increase in the KM for uracil. The KM for PRPP was strongly diminished by the mutation, but kcat/KM,PRPP and the dissociation...... constant (KD,PRPP) were nearly unaffected. We conclude that the proline in the PRPP binding site of UPRTase is of only little importance for binding of PRPP to the free enzyme, but is critical for binding of uracil to the enzyme-PRPP complex and for the catalytic rate....

  10. Formation Mechanism and Binding Energy for Body-Centered Cubic Structure of He+9 Cluster

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jian-Ping; GOU Qing-Quan; LI Ping

    2004-01-01

    The formation mechanism for the body-centered cubic structure of He+9 cluster is proposed and its total energy curve is calculated by the method of a Modified Arrangement Channel Quantum Mechanics. The energy is the function of separation R between the nuclei at the center and an apex of the body-centered cubic structure. The result of the calculation shows that the curve has a minimal energy -25.6669 (a.u.) at R = 2.550ao. The binding energy of He+9 with respect to He+ + 8He was calculated to be 0.8857 a.u. This means that the cluster of He+9 may be formed in the body-centered cubic structure of R = 2.55a0.

  11. Mechanical Control of ATP Synthase Function: Activation Energy Difference between Tight and Loose Binding Sites

    KAUST Repository

    Beke-Somfai, Tamás

    2010-01-26

    Despite exhaustive chemical and crystal structure studies, the mechanistic details of how FoF1-ATP synthase can convert mechanical energy to chemical, producing ATP, are still not fully understood. On the basis of quantum mechanical calculations using a recent highresolution X-ray structure, we conclude that formation of the P-O bond may be achieved through a transition state (TS) with a planar PO3 - ion. Surprisingly, there is a more than 40 kJ/mol difference between barrier heights of the loose and tight binding sites of the enzyme. This indicates that even a relatively small change in active site conformation, induced by the γ-subunit rotation, may effectively block the back reaction in βTP and, thus, promote ATP. © 2009 American Chemical Society.

  12. The zebrafish galectins Drgal1-L2 and Drgal3-L1 bind in vitro to the infectious hematopoietic necrosis virus (IHNV) glycoprotein and reduce viral adhesion to fish epithelial cells.

    Science.gov (United States)

    Nita-Lazar, Mihai; Mancini, Justin; Feng, Chiguang; González-Montalbán, Núria; Ravindran, Chinnarajan; Jackson, Shawn; de las Heras-Sánchez, Ana; Giomarelli, Barbara; Ahmed, Hafiz; Haslam, Stuart M; Wu, Gang; Dell, Anne; Ammayappan, Arun; Vakharia, Vikram N; Vasta, Gerardo R

    2016-02-01

    The infectious hematopoietic necrosis virus (IHNV; Rhabdoviridae, Novirhabdovirus) infects teleost fish, such as salmon and trout, and is responsible for significant losses in the aquaculture industry and in wild fish populations. Although IHNV enters the host through the skin at the base of the fins, the viral adhesion and entry mechanisms are not fully understood. In recent years, evidence has accumulated in support of the key roles played by protein-carbohydrate interactions between host lectins secreted to the extracellular space and virion envelope glycoproteins in modulating viral adhesion and infectivity. In this study, we assessed in vitro the potential role(s) of zebrafish (Danio rerio) proto type galectin-1 (Drgal1-L2) and a chimera galectin-3 (Drgal3-L1) in IHNV adhesion to epithelial cells. Our results suggest that the extracellular Drgal1-L2 and Drgal3-L1 interact directly and in a carbohydrate-dependent manner with the IHNV glycosylated envelope and glycans on the epithelial cell surface, significantly reducing viral adhesion.

  13. A biophysical model of cell adhesion mediated by immunoadhesin drugs and antibodies.

    Directory of Open Access Journals (Sweden)

    Ryan N Gutenkunst

    Full Text Available A promising direction in drug development is to exploit the ability of natural killer cells to kill antibody-labeled target cells. Monoclonal antibodies and drugs designed to elicit this effect typically bind cell-surface epitopes that are overexpressed on target cells but also present on other cells. Thus it is important to understand adhesion of cells by antibodies and similar molecules. We present an equilibrium model of such adhesion, incorporating heterogeneity in target cell epitope density, nonspecific adhesion forces, and epitope immobility. We compare with experiments on the adhesion of Jurkat T cells to bilayers containing the relevant natural killer cell receptor, with adhesion mediated by the drug alefacept. We show that a model in which all target cell epitopes are mobile and available is inconsistent with the data, suggesting that more complex mechanisms are at work. We hypothesize that the immobile epitope fraction may change with cell adhesion, and we find that such a model is more consistent with the data, although discrepancies remain. We also quantitatively describe the parameter space in which binding occurs. Our model elaborates substantially on previous work, and our results offer guidance for the refinement of therapeutic immunoadhesins. Furthermore, our comparison with data from Jurkat T cells also points toward mechanisms relating epitope immobility to cell adhesion.

  14. Bacterial Adhesion of Streptococcus suis to Host Cells and Its Inhibition by Carbohydrate Ligands

    Directory of Open Access Journals (Sweden)

    Sauli Haataja

    2013-07-01

    Full Text Available Streptococcus suis is a Gram-positive bacterium, which causes sepsis and meningitis in pigs and humans. This review examines the role of known S. suis virulence factors in adhesion and S. suis carbohydrate-based adhesion mechanisms, as well as the inhibition of S. suis adhesion by anti-adhesion compounds in in vitro assays. Carbohydrate-binding specificities of S. suis have been identified, and these studies have shown that many strains recognize Galα1-4Gal-containing oligosaccharides present in host glycolipids. In the era of increasing antibiotic resistance, new means to treat infections are needed. Since microbial adhesion to carbohydrates is important to establish disease, compounds blocking adhesion could be an alternative to antibiotics. The use of oligosaccharides as drugs is generally hampered by their relatively low affinity (micromolar to compete with multivalent binding to host receptors. However, screening of a library of chemically modified Galα1-4Gal derivatives has identified compounds that inhibit S. suis adhesion in nanomolar range. Also, design of multivalent Galα1-4Gal-containing dendrimers has resulted in a significant increase of the inhibitory potency of the disaccharide. The S. suis adhesin binding to Galα1-4Gal-oligosaccharides, Streptococcal adhesin P (SadP, was recently identified. It has a Galα1-4Gal-binding N-terminal domain and a C-terminal LPNTG-motif for cell wall anchoring. The carbohydrate-binding domain has no homology to E. coli P fimbrial adhesin, which suggests that these Gram-positive and Gram-negative bacterial adhesins recognizing the same receptor have evolved by convergent evolution. SadP adhesin may represent a promising target for the design of anti-adhesion ligands for the prevention and treatment of S. suis infections.

  15. Evaluation of a sequential extraction process used for determining mercury binding mechanisms to coal combustion byproducts.

    Science.gov (United States)

    Noel, James D; Biswas, Pratim; Giammar, Daniel E

    2007-07-01

    Leaching of mercury from coal combustion byproducts is a concern because of the toxicity of mercury. Leachability of mercury can be assessed by using sequential extraction procedures. Sequential extraction procedures are commonly used to determine the speciation and mobility of trace metals in solid samples and are designed to differentiate among metals bound by different mechanisms and to different solid phases. This study evaluated the selectivity and effectiveness of a sequential extraction process used to determine mercury binding mechanisms to various materials. A six-step sequential extraction process was applied to laboratory-synthesized materials with known mercury concentrations and binding mechanisms. These materials were calcite, hematite, goethite, and titanium dioxide. Fly ash from a full-scale power plant was also investigated. The concentrations of mercury were measured using inductively coupled plasma (ICP) mass spectrometry, whereas the major elements were measured by ICP atomic emission spectrometry. The materials were characterized by X-ray powder diffraction and scanning electron microscopy with energy dispersive spectroscopy. The sequential extraction procedure provided information about the solid phases with which mercury was associated in the solid sample. The procedure effectively extracted mercury from the target phases. The procedure was generally selective in extracting mercury. However, some steps in the procedure extracted mercury from nontarget phases, and others resulted in mercury redistribution. Iron from hematite and goethite was only leached in the reducible and residual extraction steps. Some mercury associated with goethite was extracted in the ion exchangeable step, whereas mercury associated with hematite was extracted almost entirely in the residual step. Calcium in calcite and mercury associated with calcite were primarily removed in the acid-soluble extraction step. Titanium in titanium dioxide and mercury adsorbed onto

  16. Reactive calcium-phosphate-containing poly(ester-co-ether) methacrylate bone adhesives: chemical, mechanical and biological considerations.

    Science.gov (United States)

    Zhao, Xin; Olsen, Irwin; Li, Haoying; Gellynck, Kris; Buxton, Paul G; Knowles, Jonathan C; Salih, Vehid; Young, Anne M

    2010-03-01

    A poly(propylene glycol-co-lactide) dimethacrylate adhesive with monocalcium phosphate monohydrate (MCPM)/beta-tricalcium phosphate (beta-TCP) fillers in various levels has been investigated. Water sorption by the photo-polymerized materials catalyzed varying filler conversion to dicalcium phosphate (DCP). Polymer modulus was found to be enhanced upon raising total calcium phosphate content. With greater DCP levels, faster release of phosphate and calcium ions and improved buffering of polymer degradation products were observed. This could reduce the likelihood of pH-catalyzed bulk degradation and localized acid production and thereby may prevent adverse biological responses. Bone-like MG-63 cells were found to attach, spread and have normal morphology on both the polymer and composite surfaces. Moreover, composites implanted into chick embryo femurs became closely apposed to the host tissue and did not appear to induce adverse immunological reaction. The above results suggest that the new composite materials hold promise as clinical effective bone adhesives.

  17. Ultra-high aspect ratio Si nanowires fabricated with plasma etching: plasma processing, mechanical stability analysis against adhesion and capillary forces and oleophobicity

    Science.gov (United States)

    Zeniou, A.; Ellinas, K.; Olziersky, A.; Gogolides, E.

    2014-01-01

    Room-temperature deep Si etching using time-multiplexed deep reactive ion etching (DRIE) processes is investigated to fabricate ultra-high aspect ratio Si nanowires (SiNWs) perpendicular to the silicon substrate. Nanopatterning is achieved using either top-down techniques (e.g. electron beam lithography) or colloidal polystyrene (PS) sphere self-assembly. The latter is a faster and more economical method if imperfections in diameter and position can be tolerated. We demonstrate wire radii from below 100 nm to several micrometers, and aspect ratios (ARs) above 100:1 with etching rates above 1 μm min-1 using classical mass flow controllers with pulsing rise times of seconds. The mechanical stability of these nanowires is studied theoretically and experimentally against adhesion and capillary forces. It is shown that above ARs of the order of 50:1 for spacing 1 μm, SiNWs tend to bend due to adhesion forces between them. Such large adhesion forces are due to the high surface energy of silicon. Wetting the SiNWs with water and drying also gives rise to capillary forces. We find that capillary forces may be less important for SiNW collapse/bending compared to adhesion forces of dry SiNWs, contrary to what is observed for polymeric nanowires/nanopillars which have a much lower surface energy compared to silicon. Finally we show that SiNW arrays have oleophobic and superoleophobic properties, i.e. they exhibit excellent anti-wetting properties for a wide range of liquids and oils due to the re-entrant profile produced by the DRIE process and the well-designed spacing.

  18. Probing ligand-binding modes and binding mechanisms of benzoxazole-based amide inhibitors with soluble epoxide hydrolase by molecular docking and molecular dynamics simulation.

    Science.gov (United States)

    Chen, Hang; Zhang, Ying; Li, Liang; Han, Ju-Guang

    2012-08-30

    Soluble epoxide hydrolase (sEH) has become a new therapeutic target for treating a variety of human diseases. The inhibition of human sEH hydrolase activity was studied by molecular docking and molecular dynamics (MD) simulation techniques. A set of six benzoxazole-based amide inhibitors binding to sEH has been studied through molecular docking, MD simulation, free energy calculations, and energy decomposition analysis. On the basis of molecular mechanics-generalized Born/surface area (MM-GB/SA) computation and normal-mode analysis (NMA), the obtained results indicate that the rank of calculated binding free energies (ΔΔGTOT) of these inhibitors is in excellent agreement with that of experimental bioactivity data (IC50). The correlation coefficient (r(2)) between the predicted ΔΔGTOT and IC50 is 0.88. van der Waals energies are the largest component of the total energies, and the entropy changes play an indispensable role in determining the ΔΔGTOT. Rational binding modes were discussed and determined by the docking results and binding free energies. The free energy decomposition of each residue reveals that the residue Trp334 dominates the most binding free energies among all residues and that the activities for these molecules to the sEH are not decided by hydrogen bonds or a certain residue but by the common effect of multiple side chains in the active site.

  19. Neural Mechanisms of Context Effects on Face Recognition: Automatic Binding and Context Shift Decrements

    Science.gov (United States)

    Hayes, Scott M.; Baena, Elsa; Truong, Trong-Kha; Cabeza, Roberto

    2011-01-01

    Although people do not normally try to remember associations between faces and physical contexts, these associations are established automatically, as indicated by the difficulty of recognizing familiar faces in different contexts (“butcher-on-the-bus” phenomenon). The present functional MRI (fMRI) study investigated the automatic binding of faces and scenes. In the Face-Face (F-F) condition, faces were presented alone during both encoding and retrieval, whereas in the Face/Scene-Face (FS-F) condition, they were presented overlaid on scenes during encoding but alone during retrieval (context change). Although participants were instructed to focus only on the faces during both encoding and retrieval, recognition performance was worse in the FS-F than the F-F condition (“context shift decrement”—CSD), confirming automatic face-scene binding during encoding. This binding was mediated by the hippocampus as indicated by greater subsequent memory effects (remembered > forgotten) in this region for the FS-F than the F-F condition. Scene memory was mediated by the right parahippocampal cortex, which was reactivated during successful retrieval when the faces were associated with a scene during encoding (FS-F condition). Analyses using the CSD as a regressor yielded a clear hemispheric asymmetry in medial temporal lobe activity during encoding: left hippocampal and parahippocampal activity was associated with a smaller CSD, indicating more flexible memory representations immune to context changes, whereas right hippocampal/rhinal activity was associated with a larger CSD, indicating less flexible representations sensitive to context change. Taken together, the results clarify the neural mechanisms of context effects on face recognition. PMID:19925208

  20. Adhesion in hydrogel contacts

    Science.gov (United States)

    Torres, J. R.; Jay, G. D.; Kim, K.-S.; Bothun, G. D.

    2016-05-01

    A generalized thermomechanical model for adhesion was developed to elucidate the mechanisms of dissipation within the viscoelastic bulk of a hyperelastic hydrogel. Results show that in addition to the expected energy release rate of interface formation, as well as the viscous flow dissipation, the bulk composition exhibits dissipation due to phase inhomogeneity morphological changes. The mixing thermodynamics of the matrix and solvent determines the dynamics of the phase inhomogeneities, which can enhance or disrupt adhesion. The model also accounts for the time-dependent behaviour. A parameter is proposed to discern the dominant dissipation mechanism in hydrogel contact detachment.

  1. Amygdalin blocks the in vitro adhesion and invasion of renal cell carcinoma cells by an integrin-dependent mechanism.

    Science.gov (United States)

    Juengel, Eva; Afschar, Masud; Makarević, Jasmina; Rutz, Jochen; Tsaur, Igor; Mani, Jens; Nelson, Karen; Haferkamp, Axel; Blaheta, Roman A

    2016-03-01

    Information about the natural compound amygdalin, which is employed as an antitumor agent, is sparse and thus its efficacy remains controversial. In this study, to determine whether amygdalin exerts antitumor effects on renal cell carcinoma (RCC) cells, its impact on RCC metastatic activity was investigated. The RCC cell lines, Caki-1, KTC-26 and A498, were exposed to amygdalin from apricot kernels, and adhesion to human vascular endothelium, immobilized collagen or fibronectin was investigated. The influence of amygdalin on chemotactic and invasive activity was also determined, as was the influence of amygdalin on surface and total cellular α and β integrin expression, which are involved in metastasis. We noted that amygdalin caused significant reductions in chemotactic activity, invasion and adhesion to endothelium, collagen and fibronectin. Using FACScan analysis, we noted that amygdalin also induced reductions, particularly in integrins α5 and α6, in all three cell lines. Functional blocking of α5 resulted in significantly diminished adhesion of KTC-26 and A498 to collagen and also in decreased chemotactic behavior in all three cell lines. Blocking α6 integrin significantly reduced chemotactic activity in all three cell lines. Thus, we suggest that exposing RCC cells to amygdalin inhibits metastatic spread and is associated with downregulation of α5 and α6 integrins. Therefore, we posit that amygdalin exerts antitumor activity in vitro, and this may be linked to integrin regulation.

  2. Characterization of mechanics and cytocompatibility of fibrin-genipin annulus fibrosus sealant with the addition of cell adhesion molecules.

    Science.gov (United States)

    Guterl, Clare C; Torre, Olivia M; Purmessur, Devina; Dave, Khyati; Likhitpanichkul, Morakot; Hecht, Andrew C; Nicoll, Steven B; Iatridis, James C

    2014-09-01

    There is an unmet clinical need for a biomaterial sealant capable of repairing small annulus fibrosus (AF) defects. Causes of these defects include painful intervertebral disc herniations, microdiscectomy procedures, morbidity associated with needle puncture injury from discography, and future nucleus replacement procedures. This study describes the enhancements of a fibrin gel through genipin crosslinking (FibGen) and the addition of the cell adhesion molecules (CAMs), fibronectin and collagen. The gel's performance as a potential AF sealant is assessed using a series of in vitro tests. FibGen gels with CAMs had equivalent adhesive strength, gene expression, cytomorphology, and cell proliferation as fibrin alone. However, FibGen gels had enhanced material behaviors that were tunable to higher shear stiffness values and approximated human annulus tissue as compared with fibrin alone, were more dimensionally stable, and had a slower in vitro degradation rate. Cytomorphology of human AF cells cultured on FibGen gels exhibited increased elongation compared with fibrin alone, and the addition of CAMs to FibGen did not significantly affect elongation. This FibGen gel offers the promise of being used as a sealant material to repair small AF defects or to be used in combination with other biomaterials as an adhesive for larger defects.

  3. Towards full Quantum-Mechanics-based Protein-Ligand Binding Affinities.

    Science.gov (United States)

    Ehrlich, Stephan; Göller, Andreas H; Grimme, Stefan

    2017-01-29

    Computational methods play a key role in modern drug design in the pharmaceutical industry but are mostly based on force fields, which are limited in accuracy when describing non-classical binding effects, proton transfer, or metal coordination. Here, we propose a general fully quantum mechanical (QM) scheme for the computation of protein-ligand affinities. It works on a single protein cutout (of about 1000 atoms) and evaluates all contributions (interaction energy, solvation, thermostatistical) to absolute binding free energy on the highest feasible QM level. The methodology is tested on two different protein targets: activated serine protease factor X (FXa) and tyrosine-protein kinase 2 (TYK2). We demonstrate that the geometry of the model systems can be efficiently energy-minimized by using general purpose graphics processing units, resulting in structures that are close to the co-crystallized protein-ligand structures. Our best calculations at a hybrid DFT level (PBEh-3c composite method) for the FXa ligand set result in an overall mean absolute deviation as low as 2.1 kcal mol(-1) . Though very encouraging, an analysis of outliers indicates that the structure optimization level, conformational sampling, and solvation treatment require further improvement.

  4. Crystal Structure and Mechanism of Activation of TANK-Binding Kinase 1

    Directory of Open Access Journals (Sweden)

    Amede Larabi

    2013-03-01

    Full Text Available Tank-binding kinase I (TBK1 plays a key role in the innate immune system by integrating signals from pattern-recognition receptors. Here, we report the X-ray crystal structures of inhibitor-bound inactive and active TBK1 determined to 2.6 Å and 4.0 Å resolution, respectively. The structures reveal a compact dimer made up of trimodular subunits containing an N-terminal kinase domain (KD, a ubiquitin-like domain (ULD, and an α-helical scaffold dimerization domain (SDD. Activation rearranges the KD into an active conformation while maintaining the overall dimer conformation. Low-resolution SAXS studies reveal that the missing C-terminal domain (CTD extends away from the main body of the kinase dimer. Mutants that interfere with TBK1 dimerization show significantly reduced trans-autophosphorylation but retain the ability to bind adaptor proteins through the CTD. Our results provide detailed insights into the architecture of TBK1 and the molecular mechanism of activation.

  5. Molecular Mechanism of Mot1, a TATA-binding Protein (TBP)-DNA Dissociating Enzyme.

    Science.gov (United States)

    Viswanathan, Ramya; True, Jason D; Auble, David T

    2016-07-22

    The essential Saccharomyces cerevisiae ATPase Mot1 globally regulates transcription by impacting the genomic distribution and activity of the TATA-binding protein (TBP). In vitro, Mot1 forms a ternary complex with TBP and DNA and can use ATP hydrolysis to dissociate the TBP-DNA complex. Prior work suggested an interaction between the ATPase domain and a functionally important segment of DNA flanking the TATA sequence. However, how ATP hydrolysis facilitates removal of TBP from DNA is not well understood, and several models have been proposed. To gain insight into the Mot1 mechanism, we dissected the role of the flanking DNA segment by biochemical analysis of complexes formed using DNAs with short single-stranded gaps. In parallel, we used a DNA tethered cleavage approach to map regions of Mot1 in proximity to the DNA under different conditions. Our results define non-equivalent roles for bases within a broad segment of flanking DNA required for Mot1 action. Moreover, we present biochemical evidence for two distinct conformations of the Mot1 ATPase, the detection of which can be modulated by ATP analogs as well as DNA sequence flanking the TATA sequence. We also show using purified complexes that Mot1 dissociation of a stable, high affinity TBP-DNA interaction is surprisingly inefficient, suggesting how other transcription factors that bind to TBP may compete with Mot1. Taken together, these results suggest that TBP-DNA affinity as well as other aspects of promoter sequence influence Mot1 function in vivo.

  6. Structural models of antibody variable fragments: A method for investigating binding mechanisms

    Science.gov (United States)

    Petit, Samuel; Brard, Frédéric; Coquerel, Gérard; Perez, Guy; Tron, François

    1998-03-01

    The value of comparative molecular modeling for elucidating structure-function relationships was demonstrated by analyzing six anti-nucleosome autoantibody variable fragments. Structural models were built using the automated procedure developed in the COMPOSER software, subsequently minimized with the AMBER force field, and validated according to several standard geometric and chemical criteria. Canonical class assignment from Chothia and Lesk's [Chottin and Lesk, J. Mol. Biol., 196 (1987) 901; Chothia et al., Nature, 342 (1989) 877] work was used as a supplementary validation tool for five of the six hypervariable loops. The analysis, based on the hypothesis that antigen binding could occur through electrostatic interactions, reveals a diversity of possible binding mechanisms of anti-nucleosome or anti-histone antibodies to their cognate antigen. These results lead us to postulate that anti-nucleosome autoantibodies could have different origins. Since both anti-DNA and anti-nculeosome autoantibodies are produced during the course of systemic lupus erythematosus, a non-organ specific autoimmune disease, a comparative structural and electrostatic analysis of the two populations of autoantibodies may constitute a way to elucidate their origin and the role of the antigen in tolerance breakdown. The present study illustrates some interests, advantages and limits of a methodology based on the use of comparative modeling and analysis of molecular surface properties.

  7. Role of dystrophins and utrophins in platelet adhesion process.

    Science.gov (United States)

    Cerecedo, Doris; Mondragón, Ricardo; Cisneros, Bulmaro; Martínez-Pérez, Francisco; Martínez-Rojas, Dalila; Rendón, Alvaro

    2006-07-01

    Platelets are crucial at the site of vascular injury, adhering to the sub-endothelial matrix through receptors on their surface, leading to cell activation and aggregation to form a haemostatic plug. Platelets display focal adhesions as well as stress fibres to contract and facilitate expulsion of growth and pro-coagulant factors contained in the granules and to constrict the clot. The interaction of F-actin with different actin-binding proteins determines the properties and composition of the focal adhesions. Recently, we demonstrated the presence of dystrophin-associated protein complex corresponding to short dystrophin isoforms (Dp71d and Dp71) and the uthophin gene family (Up400 and Up71), which promote shape change, adhesion, aggregation, and granule centralisation. To elucidate participation of both complexes during the platelet adhesion process, their potential association with integrin beta-1 fraction and the focal adhesion system (alpha-actinin, vinculin and talin) was evaluated by immunofluorescence and immunoprecipitation assays. It was shown that the short dystrophin-associated protein complex participated in stress fibre assembly and in centralisation of cytoplasmic granules, while the utrophin-associated protein complex assembled and regulated focal adhesions. The simultaneous presence of dystrophin and utrophin complexes indicates complementary structural and signalling mechanisms to the actin network, improving the platelet haemostatic role.

  8. Heparin-binding hemagglutinin adhesion of Mycobacterium tuberculosis and tuberculosis%结核分枝杆菌肝素结合血凝黏附素与结核病

    Institute of Scientific and Technical Information of China (English)

    聂理会; 李传友

    2008-01-01

    结核分枝杆菌肝素结合血凝黏附素是一种表面蛋白,有3个功能结构域,其C末端在翻译后进行甲基化修饰,与其免疫特性相关.可结合硫酸化糖,可通过补体C3介导与巨噬细胞的结合,与上皮细胞结合在肺外结核发病中有重要作用.通过对其细胞免疫及体液免疫作用的研究发现,其在诊断中有较好的作用,在免疫预防及免疫治疗中有广阔的应用前景.%The heparin-binding hemagglutinin adhesion(HBHA) of Mycobacterium tuberculosis (MTB)is a surface-expressed protein,which has three functional domains.It experiences post'translationally modification of lysine,proline and alanine residues at its carboxyl-terminal that is relative with its immune properties.HBHA can bind with sulfated glycoconj ugates such as heparin,and attach to mononuclear phagocytes by binding to human component C3. Its adhesion to epithelial cells is important to extrapulmonary tuberculosis.HBHA plays a provital role in diagnosis of tuberculosis by cellular immune combining humoral immune assay,and is a viable candidate for tuberculosis vaccine and immune therapy.

  9. Dynamic mechanisms for pre-miRNA binding and export by Exportin-5.

    Science.gov (United States)

    Wang, Xia; Xu, Xue; Ma, Zhi; Huo, Yingqiu; Xiao, Zhengtao; Li, Yan; Wang, Yonghua

    2011-08-01

    The biogenesis and function of mature microRNAs (miRNAs) is dependent on the nuclear export of miRNA precursors (pre-miRNA) by Exportin-5 (Exp5). To characterize the molecular mechanisms of how pre-miRNA is recognized and transported by Exp5, we have performed 21 molecular dynamic (MD) simulations of RNA-bound Exp5 (Exp5-RanGTP-premiRNA, Exp5-RanGDP-premiRNA, Exp5-premiRNA), RNA-unbound Exp5 (Exp5-RanGTP, Exp5-RanGDP, apo-Exp5), and pre-miRNA. Our simulations with standard MD, steered molecular dynamics (SMD), and energy analysis have shown that (1) Free Exp5 undergoes extensive opening motion, and in this way facilitates the RanGTP binding. (2) RanGTP efficiently regulates the association/dissociation of pre-miRNA to its complex by inducing conformational changes in the HEAT-repeat helix stacking of Exp5. (3) The GTP hydrolysis prevents Ran from rebinding to Exp5 by regulating the hydrophobic interfaces and salt bridges between Ran and Exp5. (4) The transition from the A'-form to the A-form of the pre-miRNA modulates the structural complementarities between the protein and the pre-miRNA, thus promoting efficient assembly of the complex. (5) The base-flipping process (from the closed to the fully flipped state) of the 2-nt 3' overhang is a prerequisite for the pre-miRNA recognition by Exp5, which occurs in a sequence-independent manner as evidenced by the fact that different 2-nt 3' overhangs bind to Exp5 in essentially the same way. And finally, a plausible mechanism of the pre-miRNA export cycle has been proposed explaining how the protein-protein and protein-RNA interactions are coordinated in physiological conditions.

  10. Leveraging non-binding instruments for global health governance: reflections from the Global AIDS Reporting Mechanism for WHO reform.

    Science.gov (United States)

    Taylor, A L; Alfven, T; Hougendobler, D; Tanaka, S; Buse, K

    2014-02-01

    As countries contend with an increasingly complex global environment with direct implications for population health, the international community is seeking novel mechanisms to incentivize coordinated national and international action towards shared health goals. Binding legal instruments have garnered increasing attention since the World Health Organization adopted its first convention in 2003. This paper seeks to expand the discourse on future global health lawmaking by exploring the potential value of non-binding instruments in global health governance, drawing on the case of the 2001 United Nations General Assembly Special Session Declaration of Commitment on HIV/AIDS. In other realms of international concern ranging from the environment to human rights to arms control, non-binding instruments are increasingly used as effective instruments of international cooperation. The experience of the Global AIDS Reporting Mechanism, established pursuant to the Declaration, evidences that, at times, non-binding legal instruments can offer benefits over slower, more rigid binding legal approaches to governance. The global AIDS response has demonstrated that the use of a non-binding instrument can be remarkably effective in galvanizing increasingly deep commitments, action, reporting compliance and ultimately accountability for results. Based on this case, the authors argued that non-binding instruments deserve serious consideration by the international community for the future of global health governance, including in the context of WHO reform.

  11. Mechanisms of in vivo binding site selection of the hematopoietic master transcription factor PU.1.

    Science.gov (United States)

    Pham, Thu-Hang; Minderjahn, Julia; Schmidl, Christian; Hoffmeister, Helen; Schmidhofer, Sandra; Chen, Wei; Längst, Gernot; Benner, Christopher; Rehli, Michael

    2013-07-01

    The transcription factor PU.1 is crucial for the development of many hematopoietic lineages and its binding patterns significantly change during differentiation processes. However, the 'rules' for binding or not-binding of potential binding sites are only partially understood. To unveil basic characteristics of PU.1 binding site selection in different cell types, we studied the binding properties of PU.1 during human macrophage differentiation. Using in vivo and in vitro binding assays, as well as computational prediction, we show that PU.1 selects its binding sites primarily based on sequence affinity, which results in the frequent autonomous binding of high affinity sites in DNase I inaccessible regions (25-45% of all occupied sites). Increasing PU.1 concentrations and the availability of cooperative transcription factor interactions during lineage differentiation both decrease affinity thresholds for in vivo binding and fine-tune cell type-specific PU.1 binding, which seems to be largely independent of DNA methylation. Occupied sites were predominantly detected in active chromatin domains, which are characterized by higher densities of PU.1 recognition sites and neighboring motifs for cooperative transcription factors. Our study supports a model of PU.1 binding control that involves motif-binding affinity, PU.1 concentration, cooperativeness with neighboring transcription factor sites and chromatin domain accessibility, which likely applies to all PU.1 expressing cells.

  12. Molecular composition of the node of Ranvier: identification of ankyrin-binding cell adhesion molecules neurofascin (mucin+/third FNIII domain-) and NrCAM at nodal axon segments.

    Science.gov (United States)

    Davis, J Q; Lambert, S; Bennett, V

    1996-12-01

    Neurofascin, NrCAM, L1, and NgCAM are a family of Ig/FNIII cell adhesion molecules that share ankyrin-binding activity in their cytoplasmic domains, and are candidates to form membrane-spanning complexes with members of the ankyrin family of spectrin-binding proteins in a variety of cellular contexts in the nervous system. Specialized forms of ankyrin, 270 kD and/or 480 kD ankyrinG are components of the membrane undercoat of axons at the node of Ranvier. This paper focuses on definition of the isoforms of ankyrin-binding cell adhesion molecules localized with ankyrinG at the nodal axon segment. The exon usage of two major forms of neurofascin was determined by isolation of full-length cDNAs and used to prepare isoform-specific antibodies. An isoform of neurofascin containing a mucin-like domain and lacking the third FNIII domain was concentrated at axon initial segments and colocalized at nodes of Ranvier with ankyrinG and the voltage-dependent sodium channel. An alternative form of neurofascin lacking the mucin-like domain and containing the third FNIII domain was present in unmyelinated axons. The antibody initially raised against neurofascin was used to screen a rat brain cDNA expression library. In addition to neurofascin, this screen yielded a clone with 80% sequence identity to NrCAM from chicken. The sequences of two full-length cDNAs are presented. NrCAM is most closely related to neurofascin among the other members of the L1/neurofascin/NgCAM family, with over 70% identity between cytoplasmic domains. NrCAM, visualized with antibodies specific for the ecto-domain, also was found to be coexpressed with neurofascin at nodes of Ranvier and at axon initial segments. This is the first characterization of defined neuronal cell adhesion molecules localized to axonal membranes at the node of Ranvier of myelinated axons.

  13. Dual effects and mechanism of TiO2 nanotube arrays in reducing bacterial colonization and enhancing C3H10T1/2 cell adhesion

    Directory of Open Access Journals (Sweden)

    Peng Z

    2013-08-01

    Full Text Available Zhaoxiang Peng,1,2,* Jiahua Ni,3,* Kang Zheng,2 Yandong Shen,2 Xiaoqing Wang,1 Guo He,3 Sungho Jin,4 Tingting Tang1 1Shanghai Key Laboratory of Orthopaedic Implants, Department of Orthopaedic Surgery, Shanghai Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China; 2Department of Orthopaedic Surgery, Ningbo Medical Treatment Center Lihuili Hospital, Ningbo, People's Republic of China; 3State Key Lab of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, People's Republic of China; 4Materials Science and Engineering, University of California, San Diego, La Jolla, CA, USA *These authors contributed equally to this work Abstract: Competition occurs between the osteoblasts in regional microenvironments and pathogens introduced during surgery, on the surface of bone implants, such as joint prostheses. The aim of this study was to modulate bacterial and osteoblast adhesion on implant surfaces by using a nanotube array. Titanium oxide (TiO2 nanotube arrays, 30 nm or 80 nm in diameter, were prepared by a two-step anodization on titanium substrates. Mechanically polished and acid-etched titanium samples were also prepared to serve as control groups. The standard strains of Staphylococcus epidermidis (S. epidermidis, American Type Culture Collection [ATCC]35984 and mouse C3H10T1/2 cell lines with osteogenic potential were used to evaluate the different responses to the nanotube arrays, in bacteria and eukaryotic cells. We found that the initial adhesion and colonization of S. epidermidis on the surface of the TiO2 nanotube arrays were significantly reduced and that the adhesion of C3H10T1/2 cells on the surface of the TiO2 nanotube arrays was significantly enhanced when compared with the control samples. Based on a surface analysis of all four groups, we observed increased surface roughness, decreased water contact angles, and an enhanced

  14. Quantum mechanics/molecular mechanics modeling of photoelectron spectra: the carbon 1s core-electron binding energies of ethanol-water solutions.

    Science.gov (United States)

    Löytynoja, T; Niskanen, J; Jänkälä, K; Vahtras, O; Rinkevicius, Z; Ågren, H

    2014-11-20

    Using ethanol-water solutions as illustration, we demonstrate the capability of the hybrid quantum mechanics/molecular mechanics (QM/MM) paradigm to simulate core photoelectron spectroscopy: the binding energies and the chemical shifts. An integrated approach with QM/MM binding energy calculations coupled to preceding molecular dynamics sampling is adopted to generate binding energies averaged over the solute-solvent configurations available at a particular temperature and pressure and thus allowing for a statistical assessment with confidence levels for the final binding energies. The results are analyzed in terms of the contributions in the molecular mechanics model-electrostatic, polarization, and van der Waals-with atom or bond granulation of the corresponding MM charge and polarizability force-fields. The role of extramolecular charge transfer screening of the core-hole and explicit hydrogen bonding is studied by extending the QM core to cover the first solvation shell. The results are compared to those obtained from pure electrostatic and polarizable continuum models. Particularly, the dependence of the carbon 1s binding energies with respect to the ethanol concentration is studied. Our results indicate that QM/MM can be used as an all-encompassing model to study photoelectron binding energies and chemical shifts in solvent environments.

  15. Chemical characterization of a degradable polymeric bone adhesive containing hydrolysable fillers and interpretation of anomalous mechanical properties.

    Science.gov (United States)

    Young, Anne M; Man Ho, Sze; Abou Neel, Ensanya A; Ahmed, Ifty; Barralet, Jake E; Knowles, Jonathan C; Nazhat, Showan N

    2009-07-01

    An experimental, light-curable, degradable polyester-based bone adhesive reinforced with phosphate glass particles ((P(2)O(5))(0.45)(CaO)(x)(Na(2)O)(0.55-)(x), x=0.3 or 0.4mol) or calcium phosphate (monocalcium phosphate/beta-tricalcium phosphate (MCPM/beta-TCP)) has been characterized. Early water sorption (8wt.% at 1week) by the unfilled set adhesive catalysed subsequent bulk degradation (4wt.% at 2weeks) and substantial decline in both elastic and storage moduli. Addition of phosphate glass fillers substantially enhanced this water sorption, catalysed greater bulk mass loss (40-50 and 52-55wt.%, respectively) but enabled generation of a microporous scaffold within 2weeks. The high levels of acidic polymer degradation products (38-50wt.% of original polymer) were advantageously buffered by the filler, which initially released primarily sodium trimetaphosphate (P(3)O93-). Calcium phosphate addition raised polymer water sorption to a lesser extent (16wt.%) and promoted intermediate early bulk mass loss (12wt.%) but simultaneous anomalous increase in modulus. This was attributed to MCPM reacting with absorbed water and beta-TCP to form more homogeneously dispersed brushite (CaHPO(4)) throughout the polymer. Between 2 and 10weeks, linear erosion of both polymer (0.5wt.%week(-1)) and composites (0.7-1.2wt.%week(-1)) occurred, with all fillers providing long-term buffer action through calcium and orthophosphate (PO43-) release. In conclusion, both fillers can raise degradation of bone adhesives whilst simultaneously providing the buffering action and ions required for new bone formation. Through control of water sorption catalysed filler reactions, porous structures for cell support or substantially stiffer materials may be generated.

  16. PUR热熔胶和装订涂布系统%PUR Hot-melt Adhesive and Glueing System in Book Binding

    Institute of Scientific and Technical Information of China (English)

    季栋梁

    2011-01-01

    @@ PUR热熔胶(Poly Urethan Reactive Hotmelt Adhesive,聚氨酯反应型热熔胶)已经历了从第一代到第二、第三代的改进,现在正向UV热熔胶发展.为什么在书籍上要改用PUR热熔胶,它与EVA(乙烯一醋酸乙烯)热熔胶性能有何差异?如果对PUR热熔胶缺少正确的认识,装订出的书籍的质量与生产效率就会大打折扣.

  17. Decipher the mechanisms of protein conformational changes induced by nucleotide binding through free-energy landscape analysis: ATP binding to Hsp70.

    Directory of Open Access Journals (Sweden)

    Adrien Nicolaï

    Full Text Available ATP regulates the function of many proteins in the cell by transducing its binding and hydrolysis energies into protein conformational changes by mechanisms which are challenging to identify at the atomic scale. Based on molecular dynamics (MD simulations, a method is proposed to analyze the structural changes induced by ATP binding to a protein by computing the effective free-energy landscape (FEL of a subset of its coordinates along its amino-acid sequence. The method is applied to characterize the mechanism by which the binding of ATP to the nucleotide-binding domain (NBD of Hsp70 propagates a signal to its substrate-binding domain (SBD. Unbiased MD simulations were performed for Hsp70-DnaK chaperone in nucleotide-free, ADP-bound and ATP-bound states. The simulations revealed that the SBD does not interact with the NBD for DnaK in its nucleotide-free and ADP-bound states whereas the docking of the SBD was found in the ATP-bound state. The docked state induced by ATP binding found in MD is an intermediate state between the initial nucleotide-free and final ATP-bound states of Hsp70. The analysis of the FEL projected along the amino-acid sequence permitted to identify a subset of 27 protein internal coordinates corresponding to a network of 91 key residues involved in the conformational change induced by ATP binding. Among the 91 residues, 26 are identified for the first time, whereas the others were shown relevant for the allosteric communication of Hsp70 s in several experiments and bioinformatics analysis. The FEL analysis revealed also the origin of the ATP-induced structural modifications of the SBD recently measured by Electron Paramagnetic Resonance. The pathway between the nucleotide-free and the intermediate state of DnaK was extracted by applying principal component analysis to the subset of internal coordinates describing the transition. The methodology proposed is general and could be applied to analyze allosteric communication in

  18. 变异链球菌黏附机制的研究进展%Research progress on Streptococcus mutans adhesion mechanism

    Institute of Scientific and Technical Information of China (English)

    杨隆强; 周乔

    2011-01-01

    Streptococcus mutans (S.mutans) is one of the most important pathogens in dental caries. In recent years, the studies on the mechanism of S. mutans adhesion focused on the molecular and genetic level, laying the foundation for the further study of dental caries prevention and treatment. The paper mainly reviews mechanism of adhesion and associated regulating factors of S. mutans.%变异链球菌对牙面的黏附,是形成牙菌斑的前提和致龋的重要条件.分子生物学技术的不断进步使针对变异链球菌黏附机制的研究进入了分子水平,旨在更好地诠释变异链球菌在致龋过程中的作用,为龋病的防治奠定基础.本文就黏附、变异链球菌表面成分与黏附的关系、影响变异链球菌黏附的环境因素、变异链球菌黏附研究的前景展望等作一综述.

  19. Understanding the Mechanism of Solvent-Mediated Adhesion of Vacuum Deposited Au and Pt Thin Films onto PMMA Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Mo, Alan K [ORNL; Brown, Victoria L. [James Madison University; Rugg, Brandon K. [James Madison University; Devore, Prof. Thomas C. [James Madison University; Meyer III, Harry M [ORNL; Hu, Dr. Xiaofeng [James Madison University; Hughes, Prof. W. Christopher [James Madison University; Augustine, Prof. Brian H. [James Madison University

    2012-01-01

    The adhesion of 100 nm thick electron-beam deposited Au and Pt and magnetron sputtered Au thin films onto poly(methyl methacrylate) (PMMA) substrates can be significantly enhanced to over 90% adhesion by either spin-casting or vapor-exposure to hydrohalocarbon solvents prior to metal deposition compared to samples that are either cleaned in isopropyl alcohol or pre-treated with a remote O2 plasma. X-ray photoelectron spectroscopy (XPS) and evolved gas Fourier transform infrared spectroscopy (EGA-FTIR) reveal the presence of residual halogenated solvent molecules at the PMMA surface which chemically activates the surface to produce a stable chemical interaction between the noble metal film and the PMMA. Density functional theory (DFT) calculations show that the halogenated solvent molecules preferentially form a Lewis acid-base adduct with the oxygen atoms in the ester group in PMMA which is consistent with the measured enthalpy of desorption of chloroform (CHCl3) on PMMA determined by EGA-FTIR to be 36 kJ mol-1. The DFT model also supports the experimentally observed change in the high resolution XPS O 1s peak at 533.77 eV after metallization attributed to a change in the local bonding environment of the bridging O in the PMMA ester group. DFT also predicts that the deposited metal atom (M) inserts into the C-X bond where X is the halogen atom on either CHCl3 or bromoform (CHBr3) to form a O M X interaction that is observed by a M-X bond in the high resolution XPS Cl 2p3/2 peak at 198.03 eV and Br 3p3/2 peak at 182.06 eV. A range of solvents with differing polarities for PMMA pre-treatment have been used and it is proposed that non-complexing solvents result in significant metal adhesion improvement. The Gutmann acceptor number can be used to predict the effectiveness of solvent treatment for noble metal adhesion. A model is proposed in which the bond energy of the C-X bond of the solvent must be sufficiently low so that the C-X bond can be cleaved to form the M

  20. Proposed binding mechanism of galbanic acid extracted from Ferula assa-foetida to DNA.

    Science.gov (United States)

    Ahmadi, F; Shokoohinia, Y; Javaheri, Sh; Azizian, H

    2017-01-01

    Recently, galbanic acid (GA), a sesquiterpenoid coumarin, has been introduced as an apoptotic and geno/cytotoxicity agent. In the present study, GA has been extracted from Ferula assa-foetida, a native medicinal plant in Iran, and characterized by (1)H NMR, mass spectroscopy. Additionally, spectroscopic studies have been performed in order to investigate its DNA-interaction mode. The electrochemical behavior of GA has been studied by cyclic voltammetry (CV) in various scan rates. In neutral media (pH=7.3) one irreversible cathodic peak was obtained at -1.46 V, while in higher scan rates an irreversible one was determined at -1.67 V. According to the voltametric data GA can be easily reduced by 2e(-)/2H(+) mechanism at hanging mercury drop electrode (HMDE). The interaction of GA with ct-DNA was evaluated by CV, differential pulse voltammetry (DPV), enhancement fluorescence, UV-Vis, FT-IR spectroscopy and molecular docking. The molecular docking study shows that the GA interacts to DNA on partial intercalation mode via DNA groove binding and forms a complex by van der Waals and electroastatic interactions. In addition, the thermodynamic parameters of GA-DNA complex were investigated with ΔH°, ΔS° and ΔG° values of 15.81KJmol(-1), 133.95Jmol(-1) and -23.10KJmol(-1), respectively. All data revealed that the GA is binding to DNA by van der Waals and electrostatic interactions through the partial intercalations from the DNA's grooves.

  1. NMr studies of the AMP binding site and mechanism of adenylate kinase

    Energy Technology Data Exchange (ETDEWEB)

    Kuby, S.A.; Fry, D.C.; Mildvan, A.S.

    1986-05-01

    The authors recently located by NMR the MgATP binding site on adenylate kinase correcting the proposed location for this site based on X-ray studies of the binding of salicylate. To determine the conformation and location of the other substrate, they have determined distances from Cr/sup 3 +/ AMPPCP to 6 protons and to the phosphorus atom of AMP on adenylate kinase using the paramagnetic-probe-T/sub 1/ method. They have also used time-dependent NOEs to measure five interproton distances on AMP, permitting evaluation of the conformation of enzyme-bound AMP and its position with respect to metal-ATP. Enzyme-bound AMP exhibits a high-anti glycosyl torsional angle (X = 110/sup 0/), a 3'-endo sugar pucker (delta = 105/sup 0/), and a gauche-trans orientation about the C/sub 4/'-C/sub 5/' bond (..gamma.. = 180/sup 0/). The distance from Cr/sup 3 +/ to the phosphorus of AMP is 6.4 +/- 0.3 A, indicating a reaction coordinate distance of greater than or equal to A which is consistent with an associative SN2 mechanism for the phosphoryl transfer. Ten intermolecular NOEs, from protons of the enzyme to those of AMP were detected. These constraints, together with the conformation of AMP and the X-ray structure of the enzyme, suggest proximity (less than or equal to A) of AMP to leu 116, arg 171, val 173, gln 185, thr 188, and asp 191.

  2. Computational Study of the Binding Mechanism of Actin-Depolymerizing Factor 1 with Actin in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Juan Du

    Full Text Available Actin is a highly conserved protein. It plays important roles in cellular function and exists either in the monomeric (G-actin or polymeric form (F-actin. Members of the actin-depolymerizing factor (ADF/cofilin protein family bind to both G-actin and F-actin and play vital roles in actin dynamics by manipulating the rates of filament polymerization and depolymerization. It has been reported that the S6D and R98A/K100A mutants of actin-depolymerizing factor 1 (ADF1 in Arabidopsis thaliana decreased the binding affinity of ADF for the actin monomer. To investigate the binding mechanism and dynamic behavior of the ADF1-actin complex, we constructed a homology model of the AtADF1-actin complex based on the crystal structure of AtADF1 and the twinfilin C-terminal ADF-H domain in a complex with a mouse actin monomer. The model was then refined for subsequent molecular dynamics simulations. Increased binding energy of the mutated system was observed using the Molecular Mechanics Generalized Born Surface Area and Poisson-Boltzmann Surface Area (MM-GB/PBSA methods. To determine the residues that make decisive contributions to the ADF1 actin-binding affinity, per-residue decomposition and computational alanine scanning analyses were performed, which provided more detailed information on the binding mechanism. Root-mean-square fluctuation and principal component analyses confirmed that the S6D and R98A/K100A mutants induced an increased conformational flexibility. The comprehensive molecular insight gained from this study is of great importance for understanding the binding mechanism of ADF1 and G-actin.

  3. The formation mechanism and the binding energy of the body-centred regular tetrahedral structure of He+5

    Institute of Scientific and Technical Information of China (English)

    李萍; 熊勇; 芶清泉; 张建平

    2002-01-01

    We propose the formation mechanism of the body-centred regular tetrahedral structure of the He+5 cluster. The total energy curve for this structure has been calculated by using a modified arrangement channel quantum mechanics method. The result shows that a minimal energy of -13.9106 a.u. occurs at a separation of 1.14a0 between the nucleus at the centre and nuclei at the apexes. Therefore we obtain the binding energy of 0.5202 a.u. for this structure. This means that the He+5 cluster may be stable with a high binding energy in a body-centred regular tetrahedral structure.

  4. Mechanism of selective VEGF-A binding by neuropilin-1 reveals a basis for specific ligand inhibition.

    Directory of Open Access Journals (Sweden)

    Matthew W Parker

    Full Text Available Neuropilin (Nrp receptors function as essential cell surface receptors for the Vascular Endothelial Growth Factor (VEGF family of proangiogenic cytokines and the semaphorin 3 (Sema3 family of axon guidance molecules. There are two Nrp homologues, Nrp1 and Nrp2, which bind to both overlapping and distinct members of the VEGF and Sema3 family of molecules. Nrp1 specifically binds the VEGF-A(164/5 isoform, which is essential for developmental angiogenesis. We demonstrate that VEGF-A specific binding is governed by Nrp1 residues in the b1 coagulation factor domain surrounding the invariant Nrp C-terminal arginine binding pocket. Further, we show that Sema3F does not display the Nrp-specific binding to the b1 domain seen with VEGF-A. Engineered soluble Nrp receptor fragments that selectively sequester ligands from the active signaling complex are an attractive modality for selectively blocking the angiogenic and chemorepulsive functions of Nrp ligands. Utilizing the information on Nrp ligand binding specificity, we demonstrate Nrp constructs that specifically sequester Sema3 in the presence of VEGF-A. This establishes that unique mechanisms are used by Nrp receptors to mediate specific ligand binding and that these differences can be exploited to engineer soluble Nrp receptors with specificity for Sema3.

  5. Syndecan-4 and focal adhesion function

    DEFF Research Database (Denmark)

    Woods, A; Couchman, J R

    2001-01-01

    Two groups have now reported the viability of mice that lack syndecan-4. These mice have wound healing/angiogenesis problems, and fibroblasts from these animals differ in adhesion and migration from normal. This is consistent with recent in vitro data indicating a need for signaling via syndecan-4...... for focal adhesion formation, and reports that overexpression of proteins that bind syndecan-4 can modify cell adhesion and migration....

  6. Antimyeloperoxidase antibodies rapidly induce alpha-4-integrin-dependent glomerular neutrophil adhesion.

    Science.gov (United States)

    Kuligowski, Michael P; Kwan, Rain Y Q; Lo, Cecilia; Wong, Cyndi; James, Will G; Bourges, Dorothee; Ooi, Joshua D; Abeynaike, Latasha D; Hall, Pam; Kitching, A Richard; Hickey, Michael J

    2009-06-18

    Patients with antineutrophil cytoplasmic antibodies (ANCAs) frequently develop severe vasculitis and glomerulonephritis. Although ANCAs, particularly antimyeloperoxidase (anti-MPO), have been shown to promote leukocyte adhesion in postcapillary venules, their ability to promote adhesion in the glomerular vasculature is less clear. We used intravital microscopy to examine glomerular leukocyte adhesion induced by anti-MPO. In mice pretreated with LPS, 50 microg anti-MPO induced LFA-1-dependent adhesion in glomeruli. In concert with this finding, in mice pretreated with LPS, more than 80% of circulating neutrophils bound anti-MPO within 5 minutes of intravenous administration. However, even in the absence of LPS, more than 40% of circulating neutrophils bound anti-MPO in vivo, a response not seen in MPO(-/-) mice. In addition, a higher dose of anti-MPO (200 microg) induced robust glomerular leukocyte adhesion in the absence of LPS. The latter response was beta2-integrin independent, instead requiring the alpha4-integrin, which was up-regulated on neutrophils in response to anti-MPO. These data indicate that anti-MPO antibodies bind to circulating neutrophils, and can induce glomerular leukocyte adhesion via multiple pathways. Lower doses induce adhesion only after an infection-related stimulus, whereas higher doses are capable of inducing responses in the absence of an additional inflammatory stimulus, via alternative adhesion mechanisms.

  7. Platelet and endothelial adhesion on fluorosurfactant polymers designed for vascular graft modification.

    Science.gov (United States)

    Tang, Chad; Kligman, Faina; Larsen, Coby C; Kottke-Marchant, Kandice; Marchant, Roger E

    2009-02-01

    A prominent failure mechanism of small diameter expanded polytetrafluoroethylene (ePTFE) vascular grafts is platelet-mediated thrombosis. We have designed a surface modification for ePTFE consisting of a self-assembling fluorosurfactant polymer (FSP) bearing biologically active ligands, including adhesive peptides and polysaccharide moieties. The goal of this biomimetic construct is to improve graft hemocompatibility by promoting rapid surface endothelialization, whereas minimizing platelet adhesion. Here we present a direct comparison of platelet and endothelial cell (EC) adhesion to FSPs containing one of three cell-adhesion peptides: cyclic Arg-Gly-Asp-D-Phe-Glu (cRGD), cyclic *Cys-Arg-Arg-Glu-Thr-Ala-Trp-Ala-Cys* (cRRE, *denotes disulfide bond cyclization), linear Gly-Arg-Gly-Asp-Ser-Pro-Ala (RGD), or a polysaccharide moiety: oligomaltose (M-7), later designed to prevent nonspecific protein adhesion. Measurements of soluble peptide-integrin binding indicated that cRRE exhibits very low affinity for the alpha(IIb)beta(3) platelet fibrinogen receptor. Static and dynamic adhesion of washed, activated platelets on FSP-modified surfaces revealed that M-7 and cRRE promote significantly less platelet adhesion compared to RGD and cRGD FSPs, whereas EC adhesion was similar on all peptide FSPs and minimal on M-7 FSP. These results illustrate the potential for ligands presented in a FSP surface modification to selectively adhere ECs with limited platelet attachment.

  8. The mechanism of enterprise-university-esearch institute binding to promote higher education and protection measures --.For example Tianiin

    Institute of Scientific and Technical Information of China (English)

    Xu Zheng

    2012-01-01

    The Mechanism of Enterprise-university-research institute (EUR.I) Binding is a market-oriented strategic alliance as the government and industry associations and intermediary organs for auxiliary forces complement, in which enterprises play the leading role and which combines the efforts of enterprises, universities and research institutes. It is the advanced development of enterprise- university-research institute binding cooperation. The development of technology and social economy continue to offer new challenges for higher education. Under this situation, many universities in Tianjin area actively develop their superiority and cooperate with enterprise and research department, trying their best to explore various enterprise- university-research institute binding ways to quicken the pace of technology innovation and transfer in order to make the school's track wider and wider. According to the situation of Tianjin area, this text introduces the cases of mechanism of enterprise-university- research binding about this area' s universities and comes up with safeguard measures on the base of analyzing other areas' mechanism of enterprise-university-~esearch institute binding, combining with educational economy and management theory.

  9. Bacterial Adhesion & Blocking Bacterial Adhesion

    DEFF Research Database (Denmark)

    Vejborg, Rebecca Munk

    2008-01-01

    tract to the microbial flocs in waste water treatment facilities. Microbial biofilms may however also cause a wide range of industrial and medical problems, and have been implicated in a wide range of persistent infectious diseases, including implantassociated microbial infections. Bacterial adhesion...... is the first committing step in biofilm formation, and has therefore been intensely scrutinized. Much however, still remains elusive. Bacterial adhesion is a highly complex process, which is influenced by a variety of factors. In this thesis, a range of physico-chemical, molecular and environmental parameters......, which influence the transition from a planktonic lifestyle to a sessile lifestyle, have been studied. Protein conditioning film formation was found to influence bacterial adhesion and subsequent biofilm formation considerable, and an aqueous extract of fish muscle tissue was shown to significantly...

  10. Network analyses of sperm-egg recognition and binding: ready to rethink fertility mechanisms?

    Science.gov (United States)

    Bernabò, Nicola; Ordinelli, Alessandra; Di Agostino, Raffaele; Mattioli, Mauro; Barboni, Barbara

    2014-12-01

    The rapid growth of published literature makes biomedical text mining increasingly invaluable for unpacking implicit knowledge hidden in unstructured text. We employed biomedical text mining and biological networks analyses to research the process of sperm egg recognition and binding (SERB). We selected from the literature the molecules expressed either on spermatozoa or on oocytes thought to be involved in SERB and, using an automated literature search software (Agilent Literature Search), we realized a network, SERBN, characterized by a hierarchical scale free and a small world topology. We used an integrated approach, either based on selection of hubs or by a cluster analysis, to discern the key molecules of SERB. We found that in most cases some of them are not directly situated on spermatozoa and oocyte, but are dispersed in oviductal fluid or embedded in exosomes present in the perivitelline space. To confirm and validate our results, we performed further analyses using STRING and Reactome FI software. Our findings underscore that the fertility is not a property of gametes in isolation, but rather depends on the functional integrity of the entire reproductive system. These observations collectively underscore the importance of integrative biology in exploring biological systems and in rethinking of fertility mechanisms in the light of this innovative approach.

  11. 壁虎粘附微观力学机制的仿生研究进展%PROGRESS IN THE BIONIC STUDY ON GECKO'S MICRO-ADHESION MECHANISM

    Institute of Scientific and Technical Information of China (English)

    陈少华; 志龙

    2012-01-01

    A class of animals possesses special climbing abilities in nature, which attracts enormous academic interests. To investigate the macro- and micro-mechanisms of such animals' adhesion can not only develop relevant surface/interface mechanics, but also provide novel ideas for the design of advanced adhesive materials and appropriate adhesive system for a micro-climbing robot, and shed lights on solving methods for adhesive failure problems in MEMS/NEMS and AFM. Experiments have found that the adhesive system on gecko's foot is hierarchical, which will produce strong adhesion. There are millions of setae on a gecko's foot and each seta will branch into hundreds of spatulae. The spatula is the smallest adhesive structure in a gecko's foot, which is about 200nm in width and length, about 5nm in thickness. The adhesive behavior of a spatula on a surface looks like that of a finite-sized nano-film. The basic principle of the adhesion is due to Van Der Waals force between two surfaces. Plenty of spatulae will cause the adhesion force large enough to support the weight of a gecko. In the present paper, considering the real shape of the smallest adhesive structure, which is similar to a nano-film with a finite length, we present an overview of the main influence factors of the micro-adhesion mechanism of gecko's spatula, including the effects of adhesion length, thickness and peeling angles of a finite nano-film on the adhesion force, the effects of surface roughness and environmental humidity on surface/interface adhesion. Experimental investigations as well as theoretical and numerical studies are also reviewed. Finally, possible challenges and future development of the biomimetic adhesive mechanics are proposed and prospected.%本文针对壁虎粘附系统最小单元的真实形状, 类似于有限尺寸纳米薄膜的铲状纤维, 综述了对其微观粘附力学机制主要影响因素的多个研究, 主要考虑了有限尺寸纳米薄膜长度、厚度

  12. Evaluation of mechanism of non-thermal plasma effect on the surface of polypropylene films for enhancement of adhesive and hemo compatible properties

    Energy Technology Data Exchange (ETDEWEB)

    Navaneetha Pandiyaraj, K., E-mail: dr.knpr@gmail.com [Surface Engineering Laboratory, Department of Physics, Sri Shakthi Institute of Engineering and Technology, L& T by pass, Chinniyam Palayam (post), Coimbatore-641062 (India); Deshmukh, R.R. [Department of Physics, Institute of Chemical Technology, Matunga, Mumbai-400 019 (India); Arunkumar, A.; Ramkumar, M.C. [Surface Engineering Laboratory, Department of Physics, Sri Shakthi Institute of Engineering and Technology, L& T by pass, Chinniyam Palayam (post), Coimbatore-641062 (India); Ruzybayev, I.; Ismat Shah, S. [Department of Physics and Astronomy, Department of Materials Science and Engineering, University of Delaware, 208 Dupont Hall, Newark (United States); Su, Pi-Guey [Department of Chemistry, Chinese Culture University, Taipei 111, Taiwan (China); Periayah, Mercy Halleluyah; Halim, A.S. [School of Medical Sciences, Health Campus, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan (Malaysia)

    2015-08-30

    Highlights: • Investigated the mechanism of effect of various gaseous plasma treatments on the surface properties of Polypropylene (PP) films. • The improvement in surface energy is basically due to the incorporation of polar functional groups onto the PP films. • The extent of surface modification and hydrophobic recovery depends upon the type of plasma forming gas. • Due to the significant morphological and chemical changes induced by the gaseous plasma treatment, improved the blood compatibility as well as adhesive strength of the PP films. - Abstract: The hydro-carbon based polymers have attracted attention of scientists for its use in bio-medical field as various implants due to inherent flexibility. However, they have poor surface properties; particularly they have low surface energy (SE). Hence, blood components (platelets, blood proteins, etc.)-polymer surface interaction is the major concern when it comes in contact with blood. Thus, surface modification is required to develop the perfect antithrombogenic property without affecting the materials bulk. The present study describes the improvement in adhesive and blood compatible properties of polypropylene (PP) by low temperature (non-thermal) plasma of various gases such as Ar, O{sub 2}, air and Ar + O{sub 2} for biomedical applications. The changes in surface morphological, chemical and hydrophilic modification induced by the gaseous plasma treatment were analyzed by atomic force microscopy (AFM), X-ray photo electron spectroscopy (XPS), electron spin resonance (ESR) spectroscopy and contact angle measurements, respectively. Moreover, the stability of plasma effect was also studied for the different storage conditions. Variation in adhesive strength of the plasma treated PP film was studied by T-Peel and Lap-Shear strength tests. The blood compatibility of the surface modified PP films was investigated by in vitro analysis. It was found that gaseous plasma treatment improved the blood compatibility

  13. Injectable Dopamine-Modified Poly(ethylene glycol) Nanocomposite Hydrogel with Enhanced Adhesive Property and Bioactivity

    Science.gov (United States)

    2015-01-01

    A synthetic mimic of mussel adhesive protein, dopamine-modified four-armed poly(ethylene glycol) (PEG-D4), was combined with a synthetic nanosilicate, Laponite (Na0.7+(Mg5.5Li0.3Si8)O20(OH)4)0.7–), to form an injectable naoncomposite tissue adhesive hydrogel. Incorporation of up to 2 wt % Laponite significantly reduced the cure time while enhancing the bulk mechanical and adhesive properties of the adhesive due to strong interfacial binding between dopamine and Laponite. The addition of Laponite did not alter the degradation rate and cytocompatibility of PEG-D4 adhesive. On the basis of subcutaneous implantation in rat, PEG-D4 nanocomposite hydrogels elicited minimal inflammatory response and exhibited an enhanced level of cellular infiltration as compared to Laponite-free samples. The addition of Laponite is potentially a simple and effective method for promoting bioactivity in a bioinert, synthetic PEG-based adhesive while simultaneously enhancing its mechanical and adhesive properties. PMID:25222290

  14. NMR studies of the AMP-binding site and mechanism of adenylate kinase.

    Science.gov (United States)

    Fry, D C; Kuby, S A; Mildvan, A S

    1987-03-24

    NMR has previously been used to determine the conformation of enzyme-bound MgATP and to locate the MgATP-binding site on adenylate kinase [Fry, D. C., Kuby, S. A., & Mildvan, A. S. (1985) Biochemistry 24, 4680-4694]. To determine the conformation and location of the other substrate, AMP, distances have been measured from Cr3+AMPPCP, a linear competitive inhibitor with respect to MgATP, to six protons and to the phosphorus atom of AMP on adenylate kinase, with the paramagnetic probe-T1 method. Time-dependent nuclear Overhauser effects (NOEs) have been used to measure five interproton distances on enzyme-bound AMP. These distances were used to determine the conformation of bound AMP in addition to its position with respect to metal-ATP. Enzyme-bound AMP exhibits a high anti-glycosyl torsional angle (chi = 110 +/- 10 degrees), a 3'-endo,2'-exo ribose pucker (delta = 105 +/- 10 degrees), and gauche-trans orientations about the C4'-C5' bond (gamma = 180 +/- 10 degrees) and the C5'-O5' bond (beta = 170 +/- 20 degrees). The distance from Cr3+ to the phosphorus of AMP is 5.9 +/- 0.3 A, indicating a reaction coordinate distance of approximately 3 A, which is consistent with an associative SN2 mechanism for the phosphoryl transfer. Ten intermolecular NOEs, from protons of the enzyme to those of AMP, were detected, indicating the proximity of at least three hydrophobic amino acids to bound AMP. These constraints, together with the conformation of AMP and the intersubstrate distances, were used to position AMP into the X-ray structure of adenylate kinase. The AMP binding site is found to be near (less than or equal to 4 A from) Leu-116, Arg-171, Val-173, Val-182, and Leu-190; all of these residues have been found to be invariant in muscle-type rabbit, calf, human, porcine [Kuby, S. A., Palmieri, R. H., Frischat, A., Fischer, A. H., Wu, L. H., Maland, L., & Manship, M. (1984) Biochemistry 23, 2393-2399], and chicken adenylate kinase [Kishi, F., Maruyama, M., Tanizawa, Y

  15. Cell adhesion during bullet motion in capillaries.

    Science.gov (United States)

    Takeishi, Naoki; Imai, Yohsuke; Ishida, Shunichi; Omori, Toshihiro; Kamm, Roger D; Ishikawa, Takuji

    2016-08-01

    A numerical analysis is presented of cell adhesion in capillaries whose diameter is comparable to or smaller than that of the cell. In contrast to a large number of previous efforts on leukocyte and tumor cell rolling, much is still unknown about cell motion in capillaries. The solid and fluid mechanics of a cell in flow was coupled with a slip bond model of ligand-receptor interactions. When the size of a capillary was reduced, the cell always transitioned to "bullet-like" motion, with a consequent decrease in the velocity of the cell. A state diagram was obtained for various values of capillary diameter and receptor density. We found that bullet motion enables firm adhesion of a cell to the capillary wall even for a weak ligand-receptor binding. We also quantified effects of various parameters, including the dissociation rate constant, the spring constant, and the reactive compliance on the characteristics of cell motion. Our results suggest that even under the interaction between P-selectin glycoprotein ligand-1 (PSGL-1) and P-selectin, which is mainly responsible for leukocyte rolling, a cell is able to show firm adhesion in a small capillary. These findings may help in understanding such phenomena as leukocyte plugging and cancer metastasis.

  16. Development of a Surface Plasmon Resonance Assay for the Characterization of Small-Molecule Binding Kinetics and Mechanism of Binding to Kynurenine 3-Monooxygenase.

    Science.gov (United States)

    Poda, Suresh B; Kobayashi, Masakazu; Nachane, Ruta; Menon, Veena; Gandhi, Adarsh S; Budac, David P; Li, Guiying; Campbell, Brian M; Tagmose, Lena

    2015-10-01

    Kynurenine 3-monooxygenase (KMO), a pivotal enzyme in the kynurenine pathway, was identified as a potential therapeutic target for treating neurodegenerative and psychiatric disorders. In this article, we describe a surface plasmon resonance (SPR) assay that delivers both kinetics and the mechanism of binding (MoB) data, enabling a detailed characterization of KMO inhibitors for the enzyme in real time. SPR assay development included optimization of the protein construct and the buffer conditions. The stability and inhibitor binding activity of the immobilized KMO were significantly improved when the experiments were performed at 10°C using a buffer containing 0.05% n-dodecyl-β-d-maltoside (DDM) as the detergent. The KD values of the known KMO inhibitors (UPF648 and RO61-8048) from the SPR assay were in good accordance with the biochemical LC/MS/MS assay. Also, the SPR assay was able to differentiate the binding kinetics (k(a) and k(d)) of the selected unknown KMO inhibitors. For example, the inhibitors that showed comparable IC50 values in the LC/MS/MS assay displayed differences in their residence time (τ = 1/k(d)) in the SPR assay. To better define the MoB of the inhibitors to KMO, an SPR-based competition assay was developed, which demonstrated that both UPF648 and RO61-8048 bound to the substrate-binding site. These results demonstrate the potential of the SPR assay for characterizing the affinity, the kinetics, and the MoB profiles of the KMO inhibitors.

  17. Multifunctionality and mechanism of ligand binding in a mosquito antiinflammatory protein

    Energy Technology Data Exchange (ETDEWEB)

    Calvo, Eric; Mans, Ben J.; Ribeiro, José M.C.; Andersen, John F.; (NIH)

    2009-04-07

    The mosquito D7 salivary proteins are encoded by a multigene family related to the arthropod odorant-binding protein (OBP) superfamily. Forms having either one or two OBP domains are found in mosquito saliva. Four single-domain and one two-domain D7 proteins from Anopheles gambiae and Aedes aegypti (AeD7), respectively, were shown to bind biogenic amines with high affinity and with a stoichiometry of one ligand per protein molecule. Sequence comparisons indicated that only the C-terminal domain of AeD7 is homologous to the single-domain proteins from A. gambiae, suggesting that the N-terminal domain may bind a different class of ligands. Here, we describe the 3D structure of AeD7 and examine the ligand-binding characteristics of the N- and C-terminal domains. Isothermal titration calorimetry and ligand complex crystal structures show that the N-terminal domain binds cysteinyl leukotrienes (cysLTs) with high affinities (50-60 nM) whereas the C-terminal domain binds biogenic amines. The lipid chain of the cysLT binds in a hydrophobic pocket of the N-terminal domain, whereas binding of norepinephrine leads to an ordering of the C-terminal portion of the C-terminal domain into an alpha-helix that, along with rotations of Arg-176 and Glu-268 side chains, acts to bury the bound ligand.

  18. On the denaturation mechanisms of the ligand binding domain of thyroid hormone receptors

    NARCIS (Netherlands)

    Martínez, Leandro; Souza, Paulo C T; Garcia, Wanius; Batista, Fernanda A H; Portugal, Rodrigo V; Nascimento, Alessandro S; Nakahira, Marcel; Lima, Luis M T R; Polikarpov, Igor; Skaf, Munir S

    2010-01-01

    The ligand binding domain (LBD) of nuclear hormone receptors adopts a very compact, mostly alpha-helical structure that binds specific ligands with very high affinity. We use circular dichroism spectroscopy and high-temperature molecular dynamics simulations to investigate unfolding of the LBDs of t

  19. On the Denaturation Mechanisms of the Ligand Binding Domain of Thyroid Hormone Receptors

    NARCIS (Netherlands)

    Martínez, Leandro; Telles de Souza, P C; Garcia, Wanius; Batista, Fernanda A H; Portugal, Rodrigo V; Nascimento, Alessandro S; Nakahira, Marcel; Lima, Luis M T R; Polikarpov, Igor; Skaf, Munir S

    2010-01-01

    The ligand binding domain (LBD) of nuclear hormone receptors adopts a very compact, mostly alpha-helical structure that binds specific ligands with very high affinity. We use circular dichroism spectroscopy and high-temperature molecular dynamics Simulations to investigate unfolding of the LBDs of t

  20. Structure, mechanics, and binding mode heterogeneity of LEDGF/p75-DNA nucleoprotein complexes revealed by scanning force microscopy

    Science.gov (United States)

    Vanderlinden, Willem; Lipfert, Jan; Demeulemeester, Jonas; Debyser, Zeger; de Feyter, Steven

    2014-04-01

    LEDGF/p75 is a transcriptional coactivator implicated in the pathogenesis of AIDS and leukemia. In these contexts, LEDGF/p75 acts as a cofactor by tethering protein cargo to transcriptionally active regions in the human genome. Our study - based on scanning force microscopy (SFM) imaging - is the first to provide structural information on the interaction of LEDGF/p75 with DNA. Two novel approaches that allow obtaining insights into the DNA conformation inside nucleoprotein complexes revealed (1) that LEDGF/p75 can bind at least in three different binding modes, (2) how DNA topology and protein dimerization affect these binding modes, and (3) geometrical and mechanical aspects of the nucleoprotein complexes. These structural and mechanical details will help us to better understand the cellular mechanisms of LEDGF/p75 as a transcriptional coactivator and as a cofactor in disease.LEDGF/p75 is a transcriptional coactivator implicated in the pathogenesis of AIDS and leukemia. In these contexts, LEDGF/p75 acts as a cofactor by tethering protein cargo to transcriptionally active regions in the human genome. Our study - based on scanning force microscopy (SFM) imaging - is the first to provide structural information on the interaction of LEDGF/p75 with DNA. Two novel approaches that allow obtaining insights into the DNA conformation inside nucleoprotein complexes revealed (1) that LEDGF/p75 can bind at least in three different binding modes, (2) how DNA topology and protein dimerization affect these binding modes, and (3) geometrical and mechanical aspects of the nucleoprotein complexes. These structural and mechanical details will help us to better understand the cellular mechanisms of LEDGF/p75 as a transcriptional coactivator and as a cofactor in disease. Electronic supplementary information (ESI) available: SFM topographs of phage lambda DNA in situ, in the absence and presence of LEDGF/p75; model-independent tests for DNA chain equilibration in 2D; SFM topographs of

  1. PI3K{gamma} activation by CXCL12 regulates tumor cell adhesion and invasion

    Energy Technology Data Exchange (ETDEWEB)

    Monterrubio, Maria; Mellado, Mario; Carrera, Ana C. [Department of Immunology and Oncology, Centro Nacional de Biotecnologia/CSIC, Campus de Cantoblanco, E-28049 Madrid (Spain); Rodriguez-Frade, Jose Miguel, E-mail: jmrfrade@cnb.csic.es [Department of Immunology and Oncology, Centro Nacional de Biotecnologia/CSIC, Campus de Cantoblanco, E-28049 Madrid (Spain)

    2009-10-16

    Tumor dissemination is a complex process, in which certain steps resemble those in leukocyte homing. Specific chemokine/chemokine receptor pairs have important roles in both processes. CXCL12/CXCR4 is the most commonly expressed chemokine/chemokine receptor pair in human cancers, in which it regulates cell adhesion, extravasation, metastatic colonization, angiogenesis, and proliferation. All of these processes require activation of signaling pathways that include G proteins, phosphatidylinositol-3 kinase (PI3K), JAK kinases, Rho GTPases, and focal adhesion-associated proteins. We analyzed these pathways in a human melanoma cell line in response to CXCL12 stimulation, and found that PI3K{gamma} regulates tumor cell adhesion through mechanisms different from those involved in cell invasion. Our data indicate that, following CXCR4 activation after CXCL12 binding, the invasion and adhesion processes are regulated differently by distinct downstream events in these signaling cascades.

  2. Molecular mechanisms involved in TFF3 peptide-mediated modulation of the E-cadherin/catenin cell adhesion complex.

    Science.gov (United States)

    Meyer zum Büschenfelde, Dirk; Hoschützky, Heinz; Tauber, Rudolf; Huber, Otmar

    2004-05-01

    TFF3 is a member of the TFF-domain peptide family which is constitutively expressed in mucous epithelial tissues where it acts as a motogenic factor and plays an important role during epithelial restitution after wounding and during inflammation. In contrast to these beneficial functions, TFFs were also reported to be involved in cell scattering and tumor invasion. These changes in epithelial cell morphology and motility are associated with a modulation of cell contacts. In this respect, we here investigated the E-cadherin/catenin cell adhesion complex in FLAG-hTFF3-transfected HT29/B6 and MDCK cells. In hTFF3-transfected cells the amount of E-cadherin is reduced with a concomitant reduction of alpha- and beta-catenin levels. On one hand, E-cadherin expression is lowered at the transcriptional level as shown by multiplex RT-PCR analysis. This decrease does not depend on differences in the promoter methylation status as shown by methylation-specific PCR. On the other hand, pulse-chase experiments showed a reduction in the E-cadherin half-life in hTFF3-transfected cells reflecting increased E-cadherin degradation. In summary, hTFF3 induces transcriptional and posttranslational processes resulting in a modulation of E-cadherin-mediated cell-cell contacts that may play an important role in the paradoxical benefical and pathogenic function of TFF peptides.

  3. Mechanical stimuli on C2C12 myoblasts affect myoblast differentiation, focal adhesion kinase phosphorylation and galectin-1 expression

    DEFF Research Database (Denmark)

    Grossi, Alberto Blak; Lametsch, Rene; Karlsson, Anders H;

    2011-01-01

    to specific receptors on the cell surface. We showed that mechanical stimuli promote an increase of FAK phosphorylation. In order to further shed light in the process of myoblast induced differentiation by mechanical stimuli, we performed a proteomic analysis. Thirteen proteins were found to be affected...... by mechanical stimulation including Galectin-1, Annexin III, and RhoGDI. In this study we demonstrate how the combination of this method of mechanical stimuli and proteomic analysis can be a powerful tool to detect proteins that are potentially interacting in biochemical pathways or complex cellular mechanisms...... during the process of myoblast differentiation. We determined an increase in expression and changes in cellular localization of Galectin-1, in mechanically stimulated myoblasts. A potential involvement of Galectin-1 in myoblast differentiation is presented....

  4. Mechanical stimulation of C2C12 cells increases m-calpain expression, focal adhesion plaque protein degradation and cell differentiation

    DEFF Research Database (Denmark)

    Grossi, Alberto; Lawson, Moira Ann

    Abstract Mechanical stimulation of C2C12 cells increases m-calpain expression, focal adhesion plaque protein degradation and cell differentiation. A. Grossi, M. A. Lawson; Department of Food Science, Royal Veterinary and Agricultural University, Frederiksberg C, Denmark The process of muscle...... documented and has been shown to affect transcription of specific gene sequences, protein synthesis, the immune system and increase in Ca2+ influx. The past 10 years has seen a dramatic increase in the understanding of how proteolytic enzymes such as calpains can affect the growth of muscle. In vivo studies...... have shown that m-calpain is necessary for myoblast fusion leading to the formation of muscle fibers and that inhibition of this enzyme restricts myotube formation. Whether there is a link between stretchor load induced signaling and m-calpain expression and activation is not known. Using a magnetic...

  5. Sequential dimerization of human zipcode-binding protein IMP1 on RNA: a cooperative mechanism providing RNP stability

    DEFF Research Database (Denmark)

    Nielsen, J.; Kristensen, M. A.; Willemoes, Martin;

    2004-01-01

    zipcode-binding protein IMP1 on targets in the 3'-UTR from Igf-II mRNA and in H19 RNA. In both cases, two molecules of IMP1 bound to RNA by a sequential, cooperative mechanism, characterized by an initial fast step, followed by a slow second step. The first step created an obligatory assembly intermediate...... of low stability, whereas the second step was the discriminatory event that converted a putative RNA target into a ‘locked' stable RNP. The ability to dimerize was also observed between members of the IMP family of zipcode-binding proteins, providing a multitude of further interaction possibilities...

  6. Adhesive plasters

    Science.gov (United States)

    Holcombe, Jr., Cressie E.; Swain, Ronald L.; Banker, John G.; Edwards, Charlene C.

    1978-01-01

    Adhesive plaster compositions are provided by treating particles of Y.sub.2 O.sub.3, Eu.sub.2 O.sub.3, Gd.sub.2 O.sub.3 or Nd.sub.2 O.sub.3 with dilute acid solutions. The resulting compositions have been found to spontaneously harden into rigid reticulated masses resembling plaster of Paris. Upon heating, the hardened material is decomposed into the oxide, yet retains the reticulated rigid structure.

  7. Self-healing efficiency of cementitious materials containing microcapsules filled with healing adhesive: mechanical restoration and healing process monitored by water absorption.

    Directory of Open Access Journals (Sweden)

    Wenting Li

    Full Text Available Autonomous crack healing of cementitious composite, a construction material that is susceptible to cracking, is of great significance to improve the serviceability and to prolong the longevity of concrete structures. In this study, the St-DVB microcapsules enclosing epoxy resins as the adhesive agent were embedded in cement paste to achieve self-healing capability. The self-healing efficiency was firstly assessed by mechanical restoration of the damaging specimens after being matured. The flexural and compressive configurations were both used to stimulate the localized and distributed cracks respectively. The effects of some factors, including the content of microcapsules, the curing conditions and the degree of damage on the healing efficiency were investigated. Water absorption was innovatively proposed to monitor and characterize the evolution of crack networks during the healing process. The healing cracks were observed by SEM-EDS following. The results demonstrated that the capsule-containing cement paste can achieve the various mechanical restorations depending on the curing condition and the degree of damage. But the voids generated by the surfactants compromised the strength. Though no noticeable improved stiffness obtained, the increasing fracture energy was seen particularly for the specimen acquiring 60% pre-damage. The sorptivity and amount of water decreased with cracks healing by the adhesive, which contributed to cut off and block ingress of water. The micrographs by SEM-EDS also validated that the cracks were bridged by the hardened epoxy as the dominated elements of C and O accounted for 95% by mass in the nearby cracks.

  8. Identical phosphatase mechanisms achieved through distinct modes of binding phosphoprotein substrate

    Energy Technology Data Exchange (ETDEWEB)

    Pazy, Y.; Motaleb, M.A.; Guarnieri, M.T.; Charon, N.W.; Zhao, R.; Silversmith, R.E. (WVU); (UNC); (Colorado); (EC Uni.)

    2010-04-05

    Two-component signal transduction systems are widespread in prokaryotes and control numerous cellular processes. Extensive investigation of sensor kinase and response regulator proteins from many two-component systems has established conserved sequence, structural, and mechanistic features within each family. In contrast, the phosphatases which catalyze hydrolysis of the response regulator phosphoryl group to terminate signal transduction are poorly understood. Here we present structural and functional characterization of a representative of the CheC/CheX/FliY phosphatase family. The X-ray crystal structure of Borrelia burgdorferi CheX complexed with its CheY3 substrate and the phosphoryl analogue BeF{sub 3}{sup -} reveals a binding orientation between a response regulator and an auxiliary protein different from that shared by every previously characterized example. The surface of CheY3 containing the phosphoryl group interacts directly with a long helix of CheX which bears the conserved (E - X{sub 2} - N) motif. Conserved CheX residues Glu96 and Asn99, separated by a single helical turn, insert into the CheY3 active site. Structural and functional data indicate that CheX Asn99 and CheY3 Thr81 orient a water molecule for hydrolytic attack. The catalytic residues of the CheX-CheY3 complex are virtually superimposable on those of the Escherichia coli CheZ phosphatase complexed with CheY, even though the active site helices of CheX and CheZ are oriented nearly perpendicular to one other. Thus, evolution has found two structural solutions to achieve the same catalytic mechanism through different helical spacing and side chain lengths of the conserved acid/amide residues in CheX and CheZ.

  9. Conserved inhibitory mechanism and competent ATP binding mode for adenylyltransferases with Fic fold.

    Directory of Open Access Journals (Sweden)

    Arnaud Goepfert

    Full Text Available The ubiquitous FIC domain is evolutionarily conserved from bacteria to human and has been shown to catalyze AMP transfer onto protein side-chain hydroxyl groups. Recently, it was predicted that most catalytically competent Fic proteins are inhibited by the presence of an inhibitory helix αinh that is provided by a cognate anti-toxin (class I, or is part of the N- or C-terminal part of the Fic protein itself (classes II and III. In vitro, inhibition is relieved by mutation of a conserved glutamate of αinh to glycine. For the class III bacterial Fic protein NmFic from Neisseria meningitidis, the inhibitory mechanism has been elucidated. Here, we extend above study by including bacterial class I and II Fic proteins VbhT from Bartonella schoenbuchensis and SoFic from Shewanella oneidensis, respectively, and the respective E->G mutants. Comparative enzymatic and crystallographic analyses show that, in all three classes, the ATP substrate binds to the wild-type FIC domains, but with the α-phosphate in disparate and non-competent orientations. In the E->G mutants, however, the tri-phosphate moiety is found reorganized to the same tightly bound structure through a unique set of hydrogen bonds with Fic signature motif residues. The γ-phosphate adopts the location that is taken by the inhibitory glutamate in wild-type resulting in an α-phosphate orientation that can be attacked in-line by a target side-chain hydroxyl group. The latter is properly registered to the Fic active center by main-chain β-interactions with the β-hairpin flap. These data indicate that the active site motif and the exposed edge of the flap are both required to form an adenylylation-competent Fic protein.

  10. Characterization of Heparin-binding Site of Tissue Transglutaminase

    Science.gov (United States)

    Wang, Zhuo; Collighan, Russell J.; Pytel, Kamila; Rathbone, Daniel L.; Li, Xiaoling; Griffin, Martin

    2012-01-01

    Tissue transglutaminase (TG2) is a multifunctional Ca2+-activated protein cross-linking enzyme secreted into the extracellular matrix (ECM), where it is involved in wound healing and scarring, tissue fibrosis, celiac disease, and metastatic cancer. Extracellular TG2 can also facilitate cell adhesion important in wound healing through a nontransamidating mechanism via its association with fibronectin, heparan sulfates (HS), and integrins. Regulating the mechanism how TG2 is translocated into the ECM therefore provides a strategy for modulating these physiological and pathological functions of the enzyme. Here, through molecular modeling and mutagenesis, we have identified the HS-binding site of TG2 202KFLKNAGRDCSRRSSPVYVGR222. We demonstrate the requirement of this binding site for translocation of TG2 into the ECM through a mechanism involving cell surface shedding of HS. By synthesizing a peptide NPKFLKNAGRDCSRRSS corresponding to the HS-binding site within TG2, we also demonstrate how this mimicking peptide can in isolation compensate for the RGD-induced loss of cell adhesion on fibronectin via binding to syndecan-4, leading to activation of PKCα, pFAK-397, and ERK1/2 and the subsequent formation of focal adhesions and actin cytoskeleton organization. A novel regulatory mechanism for TG2 translocation into the extracellular compartment that depends upon TG2 conformation and the binding of HS is proposed. PMID:22298777

  11. Mechanism of quinine-dependent monoclonal antibody binding to platelet glycoprotein IIb/IIIa.

    Science.gov (United States)

    Bougie, Daniel W; Peterson, Julie; Rasmussen, Mark; Aster, Richard H

    2015-10-29

    Drug-dependent antibodies (DDAbs) that cause acute thrombocytopenia upon drug exposure are nonreactive in the absence of the drug but bind tightly to a platelet membrane glycoprotein, usually α(IIb)/β3 integrin (GPIIb/IIIa) when the drug is present. How a drug promotes binding of antibody to its target is unknown and is difficult to study with human DDAbs, which are poly-specific and in limited supply. We addressed this question using quinine-dependent murine monoclonal antibodies (mAbs), which, in vitro and in vivo, closely mimic antibodies that cause thrombocytopenia in patients sensitive to quinine. Using surface plasmon resonance (SPR) analysis, we found that quinine binds with very high affinity (K(D) ≈ 10⁻⁹ mol/L) to these mAbs at a molar ratio of ≈ 2:1 but does not bind detectably to an irrelevant mAb. Also using SPR analysis, GPIIb/IIIa was found to bind monovalently to immobilized mAb with low affinity in the absence of quinine and with fivefold greater affinity (K(D) ≈ 2.2 × 10⁻⁶) when quinine was present. Measurements of quinine-dependent binding of intact mAb and fragment antigen-binding (Fab) fragments to platelets showed that affinity is increased 10 000- to 100 000-fold by bivalent interaction between antibody and its target. Together, the findings indicate that the first step in drug-dependent binding of a DDAb is the interaction of the drug with antibody, rather than with antigen, as has been widely thought, where it induces structural changes that enhance the affinity/specificity of antibody for its target epitope. Bivalent binding may be essential for a DDAb to cause thrombocytopenia.

  12. Comparative binding mechanism of lupeol compounds with plasma proteins and its pharmacological importance.

    Science.gov (United States)

    Kallubai, Monika; Rachamallu, Aparna; Yeggoni, Daniel Pushparaju; Subramanyam, Rajagopal

    2015-04-01

    Lupeol, a triterpene, possesses beneficial effects like anti-inflammatory and anti-cancer properties. Binding of lupeol and its derivative (phytochemicals) to plasma proteins such as human serum albumin (HSA) and α-1-acid glycoprotein (AGP) is a major determinant in the disposition of drugs. Cytotoxic studies with mouse macrophages (RAW 246.7) and HeLa cell lines revealed anti-inflammatory and anti-cancer properties for both lupeol and lupeol derivative. Both molecules reduced the expression of pro-inflammatory cytokines in LPS induced macrophages. Further, apoptosis was observed in HeLa cell lines when they were incubated with these molecules for 24 h. The fluorescence quenching of HSA was observed upon titration with different concentrations of lupeol and lupeol derivative; their binding constants were found to be 3 ± 0.01 × 10(4) M(-1) and 6.2 ± 0.02 × 10(4) M(-1), with binding free energies of -6.59 kcal M(-1) and -7.2 kcal M(-1). With AGP, however, the lupeol and lupeol derivative showed binding constants of 0.9 ± 0.02 × 10(3) M(-1) and 2.7 ± 0.01 × 10(3) M(-1), with free energies of -4.6 kcal M(-1) and -5.1 kcal M(-1) respectively. Molecular displacement studies based on competition with site I-binding phenylbutazone (which binds site I of HSA) and ibuprofen (which binds site II) suggest that lupeol binds site II and the lupeol derivative site I. Molecular docking studies also confirmed that lupeol binds to the IIIA and the lupeol derivative to the IIA domain of HSA. Secondary structure changes were observed upon formation of HSA-lupeol/lupeol derivative complexes by circular dichroism spectroscopy. Molecular dynamics simulations support greater stability of HSA-lupeol and HSA-lupeol derivative complexes compared to that of HSA alone.

  13. Effects of interfacial adhesion on mechanical properties of filler reinforced composites%界面粘接对填充复合材料力学性能的影响

    Institute of Scientific and Technical Information of China (English)

    周兴平; 屈仁伟; 解孝林

    2001-01-01

    Polymethyl methacrylate(PMMA) coated talc was obtained by the in situ polymerization of MMA on the surface of talc.The composites containing PMMA adhesive layer was subsequently producted by filling the treated talc into PVC matrix.The polymer adhesive layer improves the mechanical proeperties of the composite for its interfacial adhesion similar to general adhesive agent.Since a mutual diffusion between adhesive layer and matrix and a innerstress on interfaces exist,there is a optimal thickness of adhesive layer in composites.%利用原位聚合的方法将聚甲基丙烯酸甲酯(PMMA)包覆在滑石粉的表面,制得了含PMMA粘接层的滑石粉/PVC复合材料。聚合物粘接层类似于粘接材料的粘接剂的作用,它很好地改善了复合材料的界面粘附性,提高了复合材料的机械强度。由于聚合物粘接层和基体聚合物的相互扩散以及界面内应力的存在,复合材料中存在一个最佳的聚合物粘接层。

  14. DNA structure, binding mechanism and biology functions of polypyridyl complexes in biomedicine

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    There is considerable research interest and vigorous debate about the DNA binding of polypyridyl complexes including the electron transfer involving DNA. In this review, based on the fluorescence quenching experiments, it was proposed that DNA might serve as a conductor. From the time-interval CD spectra, the different binding rates of D- and L-enantiomer to calf thymus DNA were observed. The factors influencing the DNA-binding of polypyridyl complexes, and the potential bio-functions of the complexes are also discussed.

  15. Synthesis, {sup 68}Ga labeling and preliminary evaluation of DOTA peptide binding vascular adhesion protein-1: a potential PET imaging agent for diagnosing osteomyelitis

    Energy Technology Data Exchange (ETDEWEB)

    Ujula, Tiina [Turku PET Center, Turku University Hospital, Turku (Finland); Salomaeki, Satu [Turku PET Center, Turku University Hospital, Turku (Finland); Department of Chemistry, University of Turku, Turku (Finland); Virsu, Pauliina [Turku PET Center, Turku University Hospital, Turku (Finland); Lankinen, Petteri; Maekinen, Tatu J. [Orthopedic Research Unit, University of Turku, Turku (Finland); Autio, Anu [Turku PET Center, Turku University Hospital, Turku (Finland); Yegutkin, Gennady G. [MediCity Research Laboratory, University of Turku, Turku (Finland); Knuuti, Juhani [Turku PET Center, Turku University Hospital, Turku (Finland); Jalkanen, Sirpa [MediCity Research Laboratory, University of Turku, Turku (Finland); National Public Health Institute, Turku (Finland); Roivainen, Anne [Turku PET Center, Turku University Hospital, Turku (Finland); Turku Center for Disease Modeling, University of Turku, Turku (Finland)], E-mail: anne.roivainen@utu.fi

    2009-08-15

    Introduction: Vascular adhesion protein-1 (VAP-1) is an infection/inflammation-inducible endothelial glycoprotein. Based on our previous studies, the most VAP-1-selective peptide (VAP-P1) was 1,4,7,10-tetraazacyclododecane-N',N'',N''',N,,,,-tetraacetic acid (DOTA)-conjugated, {sup 68}gallium ({sup 68}Ga)-labeled (named [{sup 68}Ga]DOTAVAP-P1) and evaluated preliminarily. Methods: Targeting was evaluated by using VAP-1-transfected cells. Biodistribution of [{sup 68}Ga]DOTAVAP-P1 was studied by positron emission tomography imaging of healthy rats and rats with bone inflammation caused by Staphylococcus aureus infection. Uptake of [{sup 68}Ga]DOTAVAP-P1 in osteomyelitis was compared with negative control peptide and competition with an excess of unlabeled DOTAVAP-P1. Results: [{sup 68}Ga]DOTAVAP-P1 bound more efficiently to VAP-1-transfected cells than to controls. In rats, [{sup 68}Ga]DOTAVAP-P1 cleared rapidly from blood circulation, excreted quickly in urine and showed an in vivo half-life of 26{+-}2.3 min. Imaging of osteomyelitis demonstrated modest target-to-background ratio. Studies with the negative control peptide and competitors revealed a significantly lower uptake at the infection site compared to [{sup 68}Ga]DOTAVAP-P1. Conclusions: The results represent a proof-of-concept that infection-induced VAP-1 can be targeted by [{sup 68}Ga]DOTA peptide. [{sup 68}Ga]DOTAVAP-P1 is just the first candidate peptide and an essential opening for developing VAP-1-specific imaging agents.

  16. Molecular modeling study on the allosteric inhibition mechanism of HIV-1 integrase by LEDGF/p75 binding site inhibitors.

    Directory of Open Access Journals (Sweden)

    Weiwei Xue

    Full Text Available HIV-1 integrase (IN is essential for the integration of viral DNA into the host genome and an attractive therapeutic target for developing antiretroviral inhibitors. LEDGINs are a class of allosteric inhibitors targeting LEDGF/p75 binding site of HIV-1 IN. Yet, the detailed binding mode and allosteric inhibition mechanism of LEDGINs to HIV-1 IN is only partially understood, which hinders the structure-based design of more potent anti-HIV agents. A molecular modeling study combining molecular docking, molecular dynamics simulation, and binding free energy calculation were performed to investigate the interaction details of HIV-1 IN catalytic core domain (CCD with two recently discovered LEDGINs BI-1001 and CX14442, as well as the LEDGF/p75 protein. Simulation results demonstrated the hydrophobic domain of BI-1001 and CX14442 engages one subunit of HIV-1 IN CCD dimer through hydrophobic interactions, and the hydrophilic group forms hydrogen bonds with HIV-1 IN CCD residues from other subunit. CX14442 has a larger tert-butyl group than the methyl of BI-1001, and forms better interactions with the highly hydrophobic binding pocket of HIV-1 IN CCD dimer interface, which can explain the stronger affinity of CX14442 than BI-1001. Analysis of the binding mode of LEDGF/p75 with HIV-1 IN CCD reveals that the LEDGF/p75 integrase binding domain residues Ile365, Asp366, Phe406 and Val408 have significant contributions to the binding of the LEDGF/p75 to HIV1-IN. Remarkably, we found that binding of BI-1001 and CX14442 to HIV-1 IN CCD induced the structural rearrangements of the 140 s loop and oration displacements of the side chains of the three conserved catalytic residues Asp64, Asp116, and Glu152 located at the active site. These results we obtained will be valuable not only for understanding the allosteric inhibition mechanism of LEDGINs but also for the rational design of allosteric inhibitors of HIV-1 IN targeting LEDGF/p75 binding site.

  17. Operating mechanism and molecular dynamics of pheromone-binding protein ASP1 as influenced by pH.

    Directory of Open Access Journals (Sweden)

    Lei Han

    Full Text Available Odorant binding protein (OBP is a vital component of the olfactory sensation system. It performs the specific role of ferrying odorant molecules to odorant receptors. OBP helps insects and types of animal to sense and transport stimuli molecules. However, the molecular details about how OBPs bind or release its odorant ligands are unclear. For some OBPs, the systems' pH level is reported to impact on the ligands' binding or unbinding capability. In this work we investigated the operating mechanism and molecular dynamics in bee antennal pheromone-binding protein ASP1 under varying pH conditions. We found that conformational flexibility is the key factor for regulating the interaction of ASP1 and its ligands, and the odorant binds to ASP1 at low pH conditions. Dynamics, once triggered by pH changes, play the key roles in coupling the global conformational changes with the odorant release. In ASP1, the C-terminus, the N-terminus, helix α2 and the region ranging from helices α4 to α5 form a cavity with a novel 'entrance' of binding. These are the major regions that respond to pH change and regulate the ligand release. Clearly there are processes of dynamics and hydrogen bond network propagation in ASP1 in response to pH stimuli. These findings lead to an understanding of the mechanism and dynamics of odorant-OBP interaction in OBP, and will benefit chemsensory-related biotech and agriculture research and development.

  18. Expression of adhesion molecules and collagen on rat chondrocyte seeded into alginate and hyaluronate based 3D biosystems. Influence of mechanical stresses.

    Science.gov (United States)

    Gigant-Huselstein, C; Hubert, P; Dumas, D; Dellacherie, E; Netter, P; Payan, E; Stoltz, J F

    2004-01-01

    Chondrocytes use mechanical signals, via interactions with their environment, to synthesize an extracellular matrix capable to withstanding high loads. Most chondrocyte-matrix interactions are mediated via transmembrane receptors such as integrins or non-integrins receptors (i.e. annexin V and CD44). The aim of this study was to analyze, by flow cytometry, the adhesion molecules (alpha5/beta1 integrins and CD44) on rat chondrocytes seeded into 3D biosystem made of alginate and hyaluronate. These biosystems were submitted to mechanical stress by knocking the biosystems between them for 48 hours. The expression of type I and type II collagen was also evaluated. The results of the current study showed that mechanical stress induced an increase of type II collagen production and weak variations of alpha5/beta1 receptors expression no matter what biosystems. Moreover, our results indicated that hyaluronan receptor CD44 expression depends on extracellular matrix modifications. Thus, these receptors were activated by signals resulted from cell environment variations (HA addition and modifications owing to mechanical stress). It suggested that this kind of receptor play a crucial role in extracellular matrix homeostasis. Finally, on day 24, no dedifferentiation of chondrocytes was noted either in biosystems or under mechanical stress. For all biosystems, the neosynthesized matrix contained an important level of collagen, which was type II, whatever biosystems. In conclusion, it appeared that the cells, under mechanical stress, maintained their phenotype. In addition, it seems that, on rat chondrocytes, alpha5/beta1 integrins did not act as the main mechanoreceptor (as described for human chondrocytes). In return, hyaluronan receptor CD44 seems to be in relation with matrix composition.

  19. Mechanism of Auxin Interaction with Auxin Binding Protein (ABP1): A Molecular Dynamics Simulation Study

    Science.gov (United States)

    Bertoša, Branimir; Kojić-Prodić, Biserka; Wade, Rebecca C.; Tomić, Sanja

    2008-01-01

    Auxin Binding Protein 1 (ABP1) is ubiquitous in green plants. It binds the phytohormone auxin with high specificity and affinity, but its role in auxin-induced processes is unknown. To understand the proposed receptor function of ABP1 we carried out a detailed molecular modeling study. Molecular dynamics simulations showed that ABP1 can adopt two conformations differing primarily in the position of the C-terminus and that one of them is stabilized by auxin binding. This is in agreement with experimental evidence that auxin induces changes at the ABP1 C-terminus. Simulations of ligand egress from ABP1 revealed three main routes by which an auxin molecule can enter or leave the ABP1 binding site. Assuming the previously proposed orientation of ABP1 to plant cell membranes, one of the routes leads to the membrane and the other two to ABP1's aqueous surroundings. A network of hydrogen-bonded water molecules leading from the bulk water to the zinc-coordinated ligands in the ABP1 binding site was formed in all simulations. Water entrance into the zinc coordination sphere occurred simultaneously with auxin egress. These results suggest that the hydrogen-bonded water molecules may assist in protonation and deprotonation of auxin molecules and their egress from the ABP1 binding site. PMID:17766341

  20. Insights into the mechanism of DNA recognition by the methylated LINE binding protein EhMLBP of Entamoeba histolytica.

    Science.gov (United States)

    Lavi, Tal; Siman-Tov, Rama; Ankri, Serge

    2009-08-01

    EhMLBP is an essential Entamoeba histolytica protein that binds preferentially to methylated long interspersed nuclear elements and rDNA. In an effort to identify more EhMLBP DNA substrates, we developed an affinity-based technique in which the C-terminal DNA binding domain of EhMLBP (GST-CterEhMLBP) was used as the ligand. Bioinformatic analysis of the DNA sequences that were isolated by this affinity method revealed the presence of a 29-nucleotide consensus motif that includes a stretch of ten adenines. Gel retardation analysis showed that EhMLBP binds to the consensus motif with a preference for its methylated form. Four DNA sequences, namely those that encoded either dihydrouridine synthetase, RAP GTPase activating protein, serine/threonine protein kinase or leucine-rich repeat containing protein (LRPP) were then selected for further analysis. In vivo binding of EhMLBP to these genes was confirmed by chromatin immunoprecipitation. The presence of methylated cytosines was detected in DNA encoding LRPP and to a lower extent in the other genes. EhMLBP binds preferentially to the methylated forms of these DNA targets. The ability of the consensus motif to compete with EhMLBP binding to its DNA substrates indicates that the adenine stretch is involved in the mechanism of DNA recognition. The results of this investigation extend our existing knowledge on the number of DNA sequences that are recognized by EhMLBP and reinforce the notion that this protein is an innate methylated DNA binding protein in E. histolytica.

  1. The asymmetric binding of PGC-1α to the ERRα and ERRγ nuclear receptor homodimers involves a similar recognition mechanism.

    Directory of Open Access Journals (Sweden)

    Maria Takacs

    Full Text Available BACKGROUND: PGC-1α is a crucial regulator of cellular metabolism and energy homeostasis that functionally acts together with the estrogen-related receptors (ERRα and ERRγ in the regulation of mitochondrial and metabolic gene networks. Dimerization of the ERRs is a pre-requisite for interactions with PGC-1α and other coactivators, eventually leading to transactivation. It was suggested recently (Devarakonda et al that PGC-1α binds in a strikingly different manner to ERRγ ligand-binding domains (LBDs compared to its mode of binding to ERRα and other nuclear receptors (NRs, where it interacts directly with the two ERRγ homodimer subunits. METHODS/PRINCIPAL FINDINGS: Here, we show that PGC-1α receptor interacting domain (RID binds in an almost identical manner to ERRα and ERRγ homodimers. Microscale thermophoresis demonstrated that the interactions between PGC-1α RID and ERR LBDs involve a single receptor subunit through high-affinity, ERR-specific L3 and low-affinity L2 interactions. NMR studies further defined the limits of PGC-1α RID that interacts with ERRs. Consistent with these findings, the solution structures of PGC-1α/ERRα LBDs and PGC-1α/ERRγ LBDs complexes share an identical architecture with an asymmetric binding of PGC-1α to homodimeric ERR. CONCLUSIONS/SIGNIFICANCE: These studies provide the molecular determinants for the specificity of interactions between PGC-1α and the ERRs, whereby negative cooperativity prevails in the binding of the coactivators to these receptors. Our work indicates that allosteric regulation may be a general mechanism controlling the binding of the coactivators to homodimers.

  2. Direct binding of ledipasvir to HCV NS5A: mechanism of resistance to an HCV antiviral agent.

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    Hyock Joo Kwon

    Full Text Available Ledipasvir, a direct acting antiviral agent (DAA targeting the Hepatitis C Virus NS5A protein, exhibits picomolar activity in replicon cells. While its mechanism of action is unclear, mutations that confer resistance to ledipasvir in HCV replicon cells are located in NS5A, suggesting that NS5A is the direct target of ledipasvir. To date co-precipitation and cross-linking experiments in replicon or NS5A transfected cells have not conclusively shown a direct, specific interaction between NS5A and ledipasvir. Using recombinant, full length NS5A, we show that ledipasvir binds directly, with high affinity and specificity, to NS5A. Ledipasvir binding to recombinant NS5A is saturable with a dissociation constant in the low nanomolar range. A mutant form of NS5A (Y93H that confers resistance to ledipasvir shows diminished binding to ledipasvir. The current study shows that ledipasvir inhibits NS5A through direct binding and that resistance to ledipasvir is the result of a reduction in binding affinity to NS5A mutants.

  3. Septin 9 interacts with kinesin KIF17 and interferes with the mechanism of NMDA receptor cargo binding and transport.

    Science.gov (United States)

    Bai, Xiaobo; Karasmanis, Eva P; Spiliotis, Elias T

    2016-03-15

    Intracellular transport involves the regulation of microtubule motor interactions with cargo, but the underlying mechanisms are not well understood. Septins are membrane- and microtubule-binding proteins that assemble into filamentous, scaffold-like structures. Septins are implicated in microtubule-dependent transport, but their roles are unknown. Here we describe a novel interaction between KIF17, a kinesin 2 family motor, and septin 9 (SEPT9). We show that SEPT9 associates directly with the C-terminal tail of KIF17 and interacts preferentially with the extended cargo-binding conformation of KIF17. In developing rat hippocampal neurons, SEPT9 partially colocalizes and comigrates with KIF17. We show that SEPT9 interacts with the KIF17 tail domain that associates with mLin-10/Mint1, a cargo adaptor/scaffold protein, which underlies the mechanism of KIF17 binding to the NMDA receptor subunit 2B (NR2B). Significantly, SEPT9 interferes with binding of the PDZ1 domain of mLin-10/Mint1 to KIF17 and thereby down-regulates NR2B transport into the dendrites of hippocampal neurons. Measurements of KIF17 motility in live neurons show that SEPT9 does not affect the microtubule-dependent motility of KIF17. These results provide the first evidence of an interaction between septins and a nonmitotic kinesin and suggest that SEPT9 modulates the interactions of KIF17 with membrane cargo.

  4. Theory on the mechanism of rapid binding of transcription factor proteins at specific-sites on DNA

    CERN Document Server

    Murugan, Rajamanickam

    2014-01-01

    We develop revised theoretical ideas on the mechanism by which the transcription factor proteins locate their specific binding sites on DNA faster than the three-dimensional (3D) diffusion controlled rate limit. We demonstrate that the 3D-diffusion controlled rate limit can be enhanced when the protein molecule reads several possible binding stretches of the template DNA via one-dimensional (1D) diffusion upon each 3D-diffusion mediated collision or nonspecific binding event. The overall enhancement of site-specific association rate is directly proportional to the maximum possible sliding length (LA, square root of (6Do/kr) where Do is the 1D-diffusion coefficient and kr is the dissociation rate constant associated with the nonspecific DNA-protein complex) associated with the 1D-diffusion of protein molecule along DNA. Upon considering several possible mechanisms we find that the DNA binding proteins can efficiently locate their cognate sites on DNA by switching across fast-moving, slow-moving and reading sta...

  5. Collecting variable-concentration isothermal titration calorimetry datasets in order to determine binding mechanisms.

    Science.gov (United States)

    Freiburger, Lee A; Mittermaier, Anthony K; Auclair, Karine

    2011-04-07

    Isothermal titration calorimetry (ITC) is commonly used to determine the thermodynamic parameters associated with the binding of a ligand to a host macromolecule. ITC has some advantages over common spectroscopic approaches for studying host/ligand interactions. For example, the heat released or absorbed when the two components interact is directly measured and does not require any exogenous reporters. Thus the binding enthalpy and the association constant (Ka) are directly obtained from ITC data, and can be used to compute the entropic contribution. Moreover, the shape of the isotherm is dependent on the c-value and the mechanistic model involved. The c-value is defined as c = n[P]tKa, where [P]t is the protein concentration, and n is the number of ligand binding sites within the host. In many cases, multiple binding sites for a given ligand are non-equivalent and ITC allows the characterization of the thermodynamic binding parameters for each individual binding site. This however requires that the correct binding model be used. This choice can be problematic if different models can fit the same experimental data. We have previously shown that this problem can be circumvented by performing experiments at several c-values. The multiple isotherms obtained at different c-values are fit simultaneously to separate models. The correct model is next identified based on the goodness of fit across the entire variable-c dataset. This process is applied here to the aminoglycoside resistance-causing enzyme aminoglycoside N-6'-acetyltransferase-Ii (AAC(6')-Ii). Although our methodology is applicable to any system, the necessity of this strategy is better demonstrated with a macromolecule-ligand system showing allostery or cooperativity, and when different binding models provide essentially identical fits to the same data. To our knowledge, there are no such systems commercially available. AAC(6')-Ii, is a homo-dimer containing two active sites, showing cooperativity between

  6. Combined quantum mechanics/molecular mechanics (QM/MM) simulations for protein-ligand complexes: free energies of binding of water molecules in influenza neuraminidase.

    Science.gov (United States)

    Woods, Christopher J; Shaw, Katherine E; Mulholland, Adrian J

    2015-01-22

    The applicability of combined quantum mechanics/molecular mechanics (QM/MM) methods for the calculation of absolute binding free energies of conserved water molecules in protein/ligand complexes is demonstrated. Here, we apply QM/MM Monte Carlo simulations to investigate binding of water molecules to influenza neuraminidase. We investigate five different complexes, including those with the drugs oseltamivir and peramivir. We investigate water molecules in two different environments, one more hydrophobic and one hydrophilic. We calculate the free-energy change for perturbation of a QM to MM representation of the bound water molecule. The calculations are performed at the BLYP/aVDZ (QM) and TIP4P (MM) levels of theory, which we have previously demonstrated to be consistent with one another for QM/MM modeling. The results show that the QM to MM perturbation is significant in both environments (greater than 1 kcal mol(-1)) and larger in the more hydrophilic site. Comparison with the same perturbation in bulk water shows that this makes a contribution to binding. The results quantify how electronic polarization differences in different environments affect binding affinity and also demonstrate that extensive, converged QM/MM free-energy simulations, with good levels of QM theory, are now practical for protein/ligand complexes.

  7. Antiphospholipid Antibodies Bind ATP: A putative Mechanism for the Pathogenesis of Neuronal Dysfunction

    Directory of Open Access Journals (Sweden)

    J. Chapman

    2005-01-01

    Full Text Available Antiphospholipid antibodies (aPL generated in experimental animals cross-react with ATP. We therefore examined the possibility that aPL IgG from human subjects bind to ATP by affinity column and an enzyme linked immunosorbent assay (ELISA. Sera with high levels of aPL IgG were collected from 12 patients with the antiphospholipid syndrome (APS. IgG fractions from 10 of 12 APS patients contained aPL that could be affinity-bound to an ATP column and completely eluted with NaCl 0.5 M. A significant (>50% inhibition of aPL IgG binding by ATP 5 mM was found in the majority. Similar inhibition was obtained with ADP but not with AMP or cAMP. All the affinity purified anti-ATP antibodies also bound β2-glycoprotein-I (β2-GPI, also known as apolipoprotein H suggesting that, similar to most pathogenic aPL, their binding depends on this serum cofactor. We further investigated this possibility and found that the binding of β2-GPI to the ATP column was similar to that of aPL IgG in that most was reversed by NaCl 0.5 M. Furthermore, addition of β2-GPI to aPL IgG significantly increased the amount of aPL binding to an ATP column. We conclude that aPL IgG bind ATP, probably through β2-GPI. This binding could interfere with the normal extracellular function of ATP and similar neurotransmitters.

  8. Raman, IR and DFT studies of mechanism of sodium binding to urea catalyst

    Science.gov (United States)

    Kundu, Partha P.; Kumari, Gayatri; Chittoory, Arjun K.; Rajaram, Sridhar; Narayana, Chandrabhas

    2015-12-01

    Bis-camphorsulfonyl urea, a newly developed hydrogen bonding catalyst, was evaluated in an enantioselective Friedel-Crafts reaction. We observed that complexation of the sulfonyl urea with a sodium cation enhanced the selectivity of reactions in comparison to reactions performed with urea alone. To understand the role of sodium cation, we performed Infrared and Raman spectroscopic studies. The detailed band assignment of the molecule was made by calculating spectra using Density Functional theory. Our studies suggest that the binding of the cation takes place through the oxygen atoms of carbonyl and sulfonyl groups. Natural Bond Orbital (NBO) analysis shows the expected charge distribution after sodium binding. The changes in the geometrical parameter and charge distribution are in line with the experimentally observed spectral changes. Based on these studies, we conclude that binding of the sodium cation changes the conformation of the sulfonyl urea to bring the chiral camphor groups closer to the incipient chiral center.

  9. Elucidation of the binding mechanism of coumarin derivatives with human serum albumin.

    Directory of Open Access Journals (Sweden)

    Archit Garg

    Full Text Available Coumarin is a benzopyrone which is widely used as an anti-coagulant, anti-oxidant, anti-cancer and also to cure arthritis, herpes, asthma and inflammation. Here, we studied the binding of synthesized coumarin derivatives with human serum albumin (HSA at physiological pH 7.2 by using fluorescence spectroscopy, circular dichroism spectroscopy, molecular docking and molecular dynamics simulation studies. By addition of coumarin derivatives to HSA the maximum fluorescence intensity was reduced due to quenching of intrinsic fluorescence upon binding of coumarin derivatives to HSA. The binding constant and free energy were found to be 1.957±0.01×10(5 M(-1, -7.175 Kcal M(-1 for coumarin derivative (CD enamide; 0.837±0.01×10(5 M(-1, -6.685 Kcal M(-1 for coumarin derivative (CD enoate, and 0.606±0.01×10(5 M(-1, -6.49 Kcal M(-1 for coumarin derivative methylprop (CDM enamide. The CD spectroscopy showed that the protein secondary structure was partially unfolded upon binding of coumarin derivatives. Further, the molecular docking studies showed that coumarin derivatives were binding to HSA at sub-domain IB with the hydrophobic interactions and also with hydrogen bond interactions. Additionally, the molecular dynamics simulations studies contributed in understanding the stability of protein-drug complex system in the aqueous solution and the conformational changes in HSA upon binding of coumarin derivatives. This study will provide insights into designing of the new inspired coumarin derivatives as therapeutic agents against many life threatening diseases.

  10. Ligand binding and activation mechanism og the glucagon-like peptide-1 receptor

    DEFF Research Database (Denmark)

    Underwood, Christina Rye

    molecule-mediated activation of GLP-1R (Study II). A fully functional, cysteine-deprived and Cterminally truncated GLP-1R is developed and characterised in Study III. In Study IV, a cAMP biosensor is used to investigate the cAMP kinetics of GLP-1R upon stimulation with different receptor agonists....... Collectively, the work has contributed to a more detailed understanding of GLP-1R pharmacology in a number of ways. A crystal structure elucidated the molecular details of GLP- 1 binding to the ECD of GLP-1R and supported the existence of different binding modes of GLP-1 and exendin-4. In addition, the work...

  11. Investigation of the interfacial adhesion of the transparent conductive oxide films to large-area flexible polymer substrates using laser-induced thermo-mechanical stresses

    Science.gov (United States)

    Park, Jin-Woo; Lee, Seung-Ho; Yang, Chan-Woo

    2013-08-01

    In this study, we investigated the interfacial adhesion strength (σint) of transparent conductive oxide (TCO) coatings on polymer substrates using a nanosecond Nd:YAG pulsed laser. We compared our results with those achieved using conventional testing methods such as bending and fragmentation tests as well as theoretical calculations. In the fragmentation and bending tests, mechanical compressive stress is induced in the film due to mismatches in Poisson's ratio and Young's modulus between the substrate and film. But, the incident laser makes the film under compression due to the mismatch in thermal expansion between the TCO and the polymer substrate. With a pulse incident to the substrate, the TCO rapidly expands by laser-induced instant heating while the transparent polymer does little, which causes the TCO to buckle and delaminate over the critical pulse energy. The critical compressive stress that scales with σint was calculated using simple equations, which agreed well with the results from previous theoretical calculations. Because the films preferentially delaminate at the defects and grain boundaries, this technique also provided useful information regarding the interface microstructures. Moreover, because the laser can scan over large areas, this method is suitable for flexible substrates that are produced by a roll-to-roll process. Nevertheless, the mechanical stress introduced by the bending and fragmentation tests causes the TCO to buckle without interfacial delamination. Hence, the stresses at the buckling disagreed with the results obtained from the laser test and the theoretical calculations.

  12. Polycystin-1 Induces Cell Migration by Regulating Phosphatidylinositol 3-kinase-dependent Cytoskeletal Rearrangements and GSK3β-dependent Cell–Cell Mechanical Adhesion

    Science.gov (United States)

    Boca, Manila; D'Amato, Lisa; Distefano, Gianfranco; Polishchuk, Roman S.; Germino, Gregory G.

    2007-01-01

    Polycystin-1 (PC-1) is a large plasma-membrane receptor encoded by the PKD1 gene mutated in autosomal dominant polycystic kidney disease (ADPKD). Although the disease is thought to be recessive on a molecular level, the precise mechanism of cystogenesis is unclear, although cytoarchitecture defects seem to be the most likely initiating events. Here we show that PC-1 regulates the actin cytoskeleton in renal epithelial cells (MDCK) and induces cell scattering and cell migration. All of these effects require phosphatidylinositol 3-kinase (PI3-K) activity. Consistent with these observations Pkd1−/− mouse embryonic fibroblasts (MEFs) have reduced capabilities to migrate compared with controls. PC-1 overexpressing MDCK cells are able to polarize normally with proper adherens and tight junctions formation, but show quick reabsorption of ZO-1, E-cadherin, and β-catenin upon wounding of a monolayer and a transient epithelial-to-mesenchymal transition (EMT) that favors a rapid closure of the wound and repolarization. Finally, we show that PC-1 is able to control the turnover of cytoskeletal-associated β-catenin through activation of GSK3β. Expression of a nondegradable form of β-catenin in PC-1 MDCK cells restores strong cell–cell mechanical adhesion. We propose that PC-1 might be a central regulator of epithelial plasticity and its loss results in impaired normal epithelial homeostasis. PMID:17671167

  13. EPSP synthase: binding studies using isothermal titration microcalorimetry and equilibrium dialysis and their implications for ligand recognition and kinetic mechanism.

    Science.gov (United States)

    Ream, J E; Yuen, H K; Frazier, R B; Sikorski, J A

    1992-06-23

    Isothermal titration calorimetry measurements are reported which give important new binding constant (Kd) information for various substrate and inhibitor complexes of Escherichia coli EPSP synthase (EPSPS). The validity of this technique was first verified by determining Kd's for the known binary complex with the substrate, shikimate 3-phosphate (S3P), as well as the herbicidal ternary complex with S3P and glyphosate (EPSPS.S3P.glyphosate). The observed Kd's agreed very well with those from previous independently determined kinetic and fluorescence binding measurements. Further applications unequivocally demonstrate for the first time a fairly tight interaction between phosphoenolpyruvate (PEP) and free enzyme (Kd = 390 microM) as well as a correspondingly weak affinity for glyphosate (Kd = 12 mM) alone with enzyme. The formation of the EPSPS.PEP binary complex was independently corroborated using equilibrium dialysis. These results strongly suggest that S3P synergizes glyphosate binding much more effectively than it does PEP binding. These observations add important new evidence to support the hypothesis that glyphosate acts as a transition-state analogue of PEP. However, the formation of a catalytically productive PEP binary complex is inconsistent with the previously reported compulsory binding order process required for catalysis and has led to new studies which completely revise the overall EPSPS kinetic mechanism. A previously postulated ternary complex between S3P and inorganic phosphate (EPSPS.S3P.Pi, Kd = 4 mM) was also detected for the first time. Quantitative binding enthalpies and entropies were also determined for each ligand complex from the microcalorimetry data. These values demonstrate a clear difference in thermodynamic parameters for recognition at the S3P site versus those observed for the PEP, Pi, and glyphosate sites.

  14. Investigation of the mechanism of the cell wall DD-carboxypeptidase reaction of penicillin-binding protein 5 of Escherichia coli by quantum mechanics/molecular mechanics calculations.

    Science.gov (United States)

    Shi, Qicun; Meroueh, Samy O; Fisher, Jed F; Mobashery, Shahriar

    2008-07-23

    Penicillin-binding protein 5 (PBP 5) of Escherichia coli hydrolyzes the terminal D-Ala-D-Ala peptide bond of the stem peptides of the cell wall peptidoglycan. The mechanism of PBP 5 catalysis of amide bond hydrolysis is initial acylation of an active site serine by the peptide substrate, followed by hydrolytic deacylation of this acyl-enzyme intermediate to complete the turnover. The microscopic events of both the acylation and deacylation half-reactions have not been studied. This absence is addressed here by the use of explicit-solvent molecular dynamics simulations and ONIOM quantum mechanics/molecular mechanics (QM/MM) calculations. The potential-energy surface for the acylation reaction, based on MP2/6-31+G(d) calculations, reveals that Lys47 acts as the general base for proton abstraction from Ser44 in the serine acylation step. A discrete potential-energy minimum for the tetrahedral species is not found. The absence of such a minimum implies a conformational change in the transition state, concomitant with serine addition to the amide carbonyl, so as to enable the nitrogen atom of the scissile bond to accept the proton that is necessary for progression to the acyl-enzyme intermediate. Molecular dynamics simulations indicate that transiently protonated Lys47 is the proton donor in tetrahedral intermediate collapse to the acyl-enzyme species. Two pathways for this proton transfer are observed. One is the direct migration of a proton from Lys47. The second pathway is proton transfer via an intermediary water molecule. Although the energy barriers for the two pathways are similar, more conformers sample the latter pathway. The same water molecule that mediates the Lys47 proton transfer to the nitrogen of the departing D-Ala is well positioned, with respect to the Lys47 amine, to act as the hydrolytic water in the deacylation step. Deacylation occurs with the formation of a tetrahedral intermediate over a 24 kcal x mol(-1) barrier. This barrier is approximately 2

  15. Gecko adhesion pad: a smart surface?

    Science.gov (United States)

    Pesika, Noshir S.; Zeng, Hongbo; Kristiansen, Kai; Zhao, Boxin; Tian, Yu; Autumn, Kellar; Israelachvili, Jacob

    2009-11-01

    Recently, it has been shown that humidity can increase the adhesion of the spatula pads that form the outermost (adhesive) surface of the tokay gecko feet by 50% relative to the main adhesion mechanism (i.e. van der Waals adhesive forces), although the mechanism by which the enhancement is realized is still not well understood. A change in the surface hydrophobicity of a gecko setal array is observed when the array, which supports the spatulae, is exposed to a water drop for more than 20 min, suggesting a change in the hydrophilic-lyophilic balance (HLB), and therefore of the conformation of the surface proteins. A surface force apparatus (SFA) was used to quantify these changes, i.e. in the adhesion and friction forces, while shearing the setal array against a silica surface under (i) dry conditions, (ii) 100% humidity and (iii) when fully immersed in water. The adhesion increased in the humid environment but greatly diminished in water. Although the adhesion forces changed significantly, the friction forces remained unaffected, indicating that the friction between these highly textured surfaces is 'load-controlled' rather than 'adhesion-controlled'. These results demonstrate that the gecko adhesive pads have the ability to exploit environmental conditions to maximize their adhesion and stabilize their friction forces. Future designs of synthetic dry adhesives inspired by the gecko can potentially include similar 'smart' surfaces that adapt to their environment.

  16. Gecko adhesion pad: a smart surface?

    Energy Technology Data Exchange (ETDEWEB)

    Pesika, Noshir S [Chemical and Biomolecular Engineering Department, Tulane University, New Orleans, LA 70118 (United States); Zeng Hongbo [Chemical and Materials Engineering Department, University of Alberta, Edmonton, AB, T6G 2V4 (Canada); Kristiansen, Kai; Israelachvili, Jacob [Chemical Engineering Department, University of California, Santa Barbara, CA 93117 (United States); Zhao, Boxin [Chemical Engineering Department and Waterloo Institute of Nanotechnology, University of Waterloo, Ontario, N2L 3G1 (Canada); Tian Yu [State Key Laboratory of Tribology, Department of Precision Instruments, Tsinghua University, Beijing 100084 (China); Autumn, Kellar, E-mail: npesika@tulane.ed [Department of Biology, Lewis and Clark College, Portland, OR 97219 (United States)

    2009-11-18

    Recently, it has been shown that humidity can increase the adhesion of the spatula pads that form the outermost (adhesive) surface of the tokay gecko feet by 50% relative to the main adhesion mechanism (i.e. van der Waals adhesive forces), although the mechanism by which the enhancement is realized is still not well understood. A change in the surface hydrophobicity of a gecko setal array is observed when the array, which supports the spatulae, is exposed to a water drop for more than 20 min, suggesting a change in the hydrophilic-lyophilic balance (HLB), and therefore of the conformation of the surface proteins. A surface force apparatus (SFA) was used to quantify these changes, i.e. in the adhesion and friction forces, while shearing the setal array against a silica surface under (i) dry conditions, (ii) 100% humidity and (iii) when fully immersed in water. The adhesion increased in the humid environment but greatly diminished in water. Although the adhesion forces changed significantly, the friction forces remained unaffected, indicating that the friction between these highly textured surfaces is 'load-controlled' rather than 'adhesion-controlled'. These results demonstrate that the gecko adhesive pads have the ability to exploit environmental conditions to maximize their adhesion and stabilize their friction forces. Future designs of synthetic dry adhesives inspired by the gecko can potentially include similar 'smart' surfaces that adapt to their environment.

  17. Experimental Studies on the Bonding Strength and Fracture Behavior of Incompatible Materials Bonded by Mechanical Adhesion in Multilayer Rotational Molding

    Directory of Open Access Journals (Sweden)

    Martin Löhner

    2016-01-01

    Full Text Available Rotational molding is a plastic processing method that allows for the production of seamless, hollow parts. Defined shaping of the polymeric material only takes place on the outer surface where contact to the tooling is given. The inner surface forms by surface tension effects. By sequential adding of materials, complex multilayer build-up is possible. Besides pure, single materials, filled, or multiphase systems can be processed as well. In this work, possibilities to generate bonding between supposedly incompatible materials by adding a mix-material interlayer are investigated. Interlock mechanisms on a microscale dimension occur and result in mechanical bonding between the used materials, polyethylene (PE and thermoplastic polyurethane (TPE-U. The bonding strength between the materials was investigated to reveal the correlations between processing parameters, resulting layer build-up, and bonding strength. The failure behavior was analyzed and inferences to the influence of the varied parameters were drawn.

  18. Curli mediate bacterial adhesion to fibronectin via tensile multiple bonds

    Science.gov (United States)

    Oh, Yoo Jin; Hubauer-Brenner, Michael; Gruber, Hermann J.; Cui, Yidan; Traxler, Lukas; Siligan, Christine; Park, Sungsu; Hinterdorfer, Peter

    2016-09-01

    Many enteric bacteria including pathogenic Escherichia coli and Salmonella strains produce curli fibers that bind to host surfaces, leading to bacterial internalization into host cells. By using a nanomechanical force-sensing approach, we obtained real-time information about the distribution of molecular bonds involved in the adhesion of curliated bacteria to fibronectin. We found that curliated E. coli and fibronectin formed dense quantized and multiple specific bonds with high tensile strength, resulting in tight bacterial binding. Nanomechanical recognition measurements revealed that approximately 10 bonds were disrupted either sequentially or simultaneously under force load. Thus the curli formation of bacterial surfaces leads to multi-bond structural components of fibrous nature, which may explain the strong mechanical binding of curliated bacteria to host cells and unveil the functions of these proteins in bacterial internalization and invasion.

  19. Differences in Binding and Monitoring Mechanisms Contribute to Lifespan Age Differences in False Memory

    Science.gov (United States)

    Fandakova, Yana; Shing, Yee Lee; Lindenberger, Ulman

    2013-01-01

    Based on a 2-component framework of episodic memory development across the lifespan (Shing & Lindenberger, 2011), we examined the contribution of memory-related binding and monitoring processes to false memory susceptibility in childhood and old age. We administered a repeated continuous recognition task to children (N = 20, 10-12 years),…

  20. Multidrug transport by ATP binding cassette transporters : a proposed two-cylinder engine mechanism

    NARCIS (Netherlands)

    van Veen, HW; Higgins, CF; Konings, WN

    2001-01-01

    The elevated expression of ATP binding cassette (ABC) multidrug transporters in multidrug-resistant cells interferes with the drug-based control of cancers and infectious pathogenic microorganisms. Multidrug transporters interact directly with the drug substrates. This review summarizes current insi

  1. Isolation and Characterization of Adhesive Secretion from Cuvierian Tubules of Sea Cucumber Holothuria forskåli (Echinodermata: Holothuroidea

    Directory of Open Access Journals (Sweden)

    Malgorzata Baranowska

    2011-01-01

    Full Text Available The sea cucumber Holothuria forskåli possesses a specialized system called Cuvierian tubules. During mechanical stimulation white filaments (tubules are expelled and become sticky upon contact with any object. We isolated a protein with adhesive properties from protein extracts of Cuvierian tubules from H. forskåli. This protein was identified by antibodies against recombinant precollagen D which is located in the byssal threads of the mussel Mytilus galloprovincialis. To find out the optimal procedure for extraction and purification, the identified protein was isolated by several methods, including electroelution, binding to glass beads, immunoprecipitation, and gel filtration. Antibodies raised against the isolated protein were used for localization of the adhesive protein in Cuvierian tubules. Immunostaining and immunogold electron microscopical studies revealed the strongest immunoreactivity in the mesothelium; this tissue layer is involved in adhesion. Adhesion of Cuvierian tubule extracts was measured on the surface of various materials. The extracted protein showed the strongest adhesion to Teflon surface. Increased adhesion was observed in the presence of potassium and EDTA, while cadmium caused a decrease in adhesion. Addition of antibodies and trypsin abolished the adhesive properties of the extract.

  2. Microtubules Inhibit E-Cadherin Adhesive Activity by Maintaining Phosphorylated p120-Catenin in a Colon Carcinoma Cell Model.

    Directory of Open Access Journals (Sweden)

    Stephanie L Maiden

    Full Text Available Tight regulation of cadherin-mediated intercellular adhesions is critical to both tissue morphogenesis during development and tissue homeostasis in adults. Cell surface expression of the cadherin-catenin complex is often directly correlated with the level of adhesion, however, examples exist where cadherin appears to be inactive and cells are completely non-adhesive. The state of p120-catenin phosphorylation has been implicated in regulating the adhesive activity of E-cadherin but the mechanism is currently unclear. We have found that destabilization of the microtubule cytoskeleton, independent of microtubule plus-end dynamics, dephosphorylates p120-catenin and activates E-cadherin adhesion in Colo 205 cells. Through chemical screening, we have also identified several kinases as potential regulators of E-cadherin adhesive activity. Analysis of several p120-catenin phosphomutants suggests that gross dephosphorylation of p120-catenin rather than that of specific amino acids may trigger E-cadherin adhesion. Uncoupling p120-catenin binding to E-cadherin at the membrane causes constitutive adhesion in Colo 205 cells, further supporting an inhibitory role of phosphorylated p120-catenin on E-cadherin activity.

  3. Microtubules Inhibit E-Cadherin Adhesive Activity by Maintaining Phosphorylated p120-Catenin in a Colon Carcinoma Cell Model.

    Science.gov (United States)

    Maiden, Stephanie L; Petrova, Yuliya I; Gumbiner, Barry M

    2016-01-01

    Tight regulation of cadherin-mediated intercellular adhesions is critical to both tissue morphogenesis during development and tissue homeostasis in adults. Cell surface expression of the cadherin-catenin complex is often directly correlated with the level of adhesion, however, examples exist where cadherin appears to be inactive and cells are completely non-adhesive. The state of p120-catenin phosphorylation has been implicated in regulating the adhesive activity of E-cadherin but the mechanism is currently unclear. We have found that destabilization of the microtubule cytoskeleton, independent of microtubule plus-end dynamics, dephosphorylates p120-catenin and activates E-cadherin adhesion in Colo 205 cells. Through chemical screening, we have also identified several kinases as potential regulators of E-cadherin adhesive activity. Analysis of several p120-catenin phosphomutants suggests that gross dephosphorylation of p120-catenin rather than that of specific amino acids may trigger E-cadherin adhesion. Uncoupling p120-catenin binding to E-cadherin at the membrane causes constitutive adhesion in Colo 205 cells, further supporting an inhibitory role of phosphorylated p120-catenin on E-cadherin activity.

  4. Studies on binding mechanism between carotenoids from sea buckthorn and thermally treated α-lactalbumin

    Science.gov (United States)

    Dumitraşcu, Loredana; Ursache, Florentina Mihaela; Stănciuc, Nicoleta; Aprodu, Iuliana

    2016-12-01

    Sea buckthorn is a natural food ingredient rich in bioactive compounds such as carotenoids, tocopherols, sterols, flavonoids, lipids, vitamins, tannins and minerals. Herein, fluorescence and UV-vis techniques were used to study the interaction of heat treated α-lactalbumin (α-LA) with carotenoids from sea buckthorn berries extract (CSB) and β-carotene. Further atomic level details on the interaction between α-LA and β-carotene were obtained by means of molecular modelling techniques. The quenching rate constants, binding constants, and number of binding sites were calculated in the presence of CSB. The emission spectral studies revealed that, CSB have the ability to bind α-LA and form a ground state complex via static quenching process. Maximum degree of quenching was reached at 100 °C, where β-carotene and CSB quenched the Trp fluorescence of α-LA by 56% and 47%, respectively. In order to reveal the interaction between CSB and α-LA, the thermodynamic parameters were determined from the van't Hoff plot based on the temperature dependence of the binding constant. In agreement with the in silico observations, the thermodynamic parameters enabled us to consider that the association between α-LA and β-carotene is a spontaneous process driven by enthalpy, dominated mainly by the van der Waals interaction, but hydrophobic interactions might also be considered. The interaction between CSB and α-LA was further confirmed by UV-vis absorption spectra, where a blue shift of position was noticed at higher temperature suggesting the complex formation. The results provided here supply a better understanding of the binding of CSB to α-LA, which can be further exploited in designing new healthy food applications.

  5. Substrate binding and catalytic mechanism in phospholipase C from Bacillus cereus. a molecular mechanics and molecular dynamics study

    DEFF Research Database (Denmark)

    da Graça Thrige, D; Buur, J R; Jørgensen, Flemming Steen

    1997-01-01

    For the first time a consistent catalytic mechanism of phospholipase C from Bacillus cereus is reported based on molecular mechanics calculations. We have identified the position of the nucleophilic water molecule, which is directly involved in the hydrolysis of the natural substrate phosphatidyl...

  6. Self-cleaning properties, mechanical stability, and adhesion strength of transparent photocatalytic TiO(2)-ZnO coatings on polycarbonate.

    Science.gov (United States)

    Fateh, Razan; Dillert, Ralf; Bahnemann, Detlef

    2014-02-26

    Transparent layers containing TiO2 have been intensively studied because of their interesting application potential including photocatalytically active and self-cleaning surfaces. In the present work, transparent TiO2-ZnO thin films on a SiO2 interlayer were successfully deposited on the surface of polycarbonate to provide polymeric sheets with a self-cleaning, superhydrophilic, and photocatalytically active surface layer. To ensure a good adhesion of the SiO2 interlayer, the polycarbonate sheets were first modified by irradiation with UV(C) light. The prepared films were characterized by UV/vis spectrophotometry, SEM, XRD, Raman spectroscopy, ellipsometry, and water contact-angle measurements. All prepared films are transparent, have thicknesses in the range between 120 and 250 nm, and possess superhydrophilic properties. Moreover, they exhibit good adhesion qualities as defined quantitatively by cross-cut tests. However, their mechanical strengths, checked by felt-abrasion tests, differ by changing the molar TiO2-ZnO ratio. The photocatalytic activity, expressed as photonic efficiency, of the coated surfaces was estimated from the kinetics of the photocatalytic degradation of methylene blue and methyl stearate. The combination between superhydrophilic properties and photocatalytic activity was determined by studying the change of water contact angle during the storage of the prepared films in the dark under an ambient atmosphere and under an atmosphere containing either acetone or isopropanol followed by UV(A) irradiation. In addition, self-cleaning properties were examined by determining the changes in the contact angle during the irradiation time after applying oleic acid to the surface. The results show that increasing the molar ratio of ZnO in TiO2 coatings up to 5% yields maximum photonic efficiency values of 0.023%, as assessed by the photocatalytic degradation of methylene blue. Moreover, the superhydrophilic coating with a molar TiO2-ZnO ratio of 1

  7. Elucidating the structures and cooperative binding mechanism of cesium salts to the multitopic ion-pair receptor through density functional theory calculations.

    Science.gov (United States)

    Sadhu, Biswajit; Sundararajan, Mahesh; Velmurugan, Gunasekaran; Venuvanalingam, Ponnambalam

    2015-09-21

    Designing new and innovative receptors for the selective binding of radionuclides is central to nuclear waste management processes. Recently, a new multi-topic ion-pair receptor was reported which binds a variety of cesium salts. Due to the large size of the receptor, quantum chemical calculations on the full ion-pair receptors are restricted, thus the binding mechanisms are not well understood at the molecular level. We have assessed the binding strengths of various cesium salts to the recently synthesized multi-topic ion-pair receptor molecule using density functional theory based calculations. Our calculations predict that the binding of cesium salts to the receptor predominantly occurs via the cooperative binding mechanism. Cesium and the anion synergistically assist each other to bind favorably inside the receptor. Energy decomposition analysis on the ion-pair complexes shows that the Cs salts are bound to the receptor mainly through electrostatic interactions with small contribution from covalent interactions for large ionic radius anions. Further, QTAIM analysis characterizes the importance of different inter-molecular interactions between the ions and the receptor inside the ion-pair complexes. The role of the crystallographic solvent molecule contributes significantly by ~10 kcal mol(-1) to the overall binding affinities which is quite significant. Further, unlike the recent molecular mechanics (MM) calculations, our calculated binding affinity trends for various Cs ion-pair complexes (CsF, CsCl and CsNO3) are now in excellent agreement with the experimental binding affinity trends.

  8. Advances in modeling and design of adhesively bonded systems

    CERN Document Server

    Kumar, S

    2013-01-01

    The book comprehensively charts a way for industry to employ adhesively bonded joints to make systems more efficient and cost-effective Adhesively bonded systems have found applications in a wide spectrum of industries (e.g., aerospace, electronics, construction, ship building, biomedical, etc.) for a variety of purposes. Emerging adhesive materials with improved mechanical properties have allowed adhesion strength approaching that of the bonded materials themselves. Due to advances in adhesive materials and the many potential merits that adhesive bonding offers, adhesive bonding has replac

  9. Surface binding sites (SBSs), mechanism and regulation of enzymes degrading amylopectin and α-limit dextrins

    DEFF Research Database (Denmark)

    Møller, Marie Sofie; Cockburn, Darrell; Nielsen, Jonas W.;

    2013-01-01

    Certain enzymes interact with polysaccharides at surface binding sites (SBSs) situated outside of their active sites. SBSs are not easily identified and their function has been discerned in relatively few cases. Starch degradation is a concerted action involving GH13 hydrolases. New insight...... into barley seed α-amylase 1 (AMY1) and limit dextrinase (LD) includes i. kinetics of bi-exponential amylopectin hydrolysis by AMY1, one reaction having low Km (8 μg/mL) and high kcat (57 s-1) and the other high Km (97 μg/mL) and low kcat (23 s-1). β-Cyclodextrin (β-CD) inhibits the first reaction by binding...

  10. Ritonavir binds to and downregulates estrogen receptors: Molecular mechanism of promoting early atherosclerosis

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, Jin [Ministry of Education Laboratory of Combinatorial Biosynthesis and Drug Discovery, School of Pharmaceutical Science, Wuhan University, Wuhan 430071 (China); Wang, Ying [Department of Pathophysiology, School of Medicine, Wuhan University, Wuhan 430071 (China); Su, Ke [Department of Nephrology, Renmin Hospital of Wuhan University, Wuhan 430060 (China); Liu, Min [Ministry of Education Laboratory of Combinatorial Biosynthesis and Drug Discovery, School of Pharmaceutical Science, Wuhan University, Wuhan 430071 (China); Hu, Peng-Chao [Department of Pathophysiology, School of Medicine, Wuhan University, Wuhan 430071 (China); Ma, Tian; Li, Jia-Xi [Ministry of Education Laboratory of Combinatorial Biosynthesis and Drug Discovery, School of Pharmaceutical Science, Wuhan University, Wuhan 430071 (China); Wei, Lei [Department of Pathophysiology, School of Medicine, Wuhan University, Wuhan 430071 (China); Zheng, Zhongliang, E-mail: biochem@whu.edu.cn [State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072 (China); Yang, Fang, E-mail: fang-yang@whu.edu.cn [Department of Physiology, School of Medicine, Wuhan University, Wuhan 430071 (China)

    2014-10-01

    Estrogenic actions are closely related to cardiovascular disease. Ritonavir (RTV), a human immunodeficiency virus (HIV) protease inhibitor, induces atherosclerosis in an estrogen-related manner. However, how RTV induce pathological phenotypes through estrogen pathway remains unclear. In this study, we found that RTV increases thickness of coronary artery walls of Sprague Dawley rats and plasma free fatty acids (FFA) levels. In addition, RTV could induce foam cell formation, downregulate both estrogen receptor α (ERα) and ERβ expression, upregulate G protein-coupled estrogen receptor (GPER) expression, and all of them could be partially blocked by 17β-estradiol (E2), suggesting RTV acts as an antagonist for E2. Computational modeling shows a similar interaction with ERα between RTV and 2-aryl indoles, which are highly subtype-selective ligands for ERα. We also found that RTV directly bound to ERα and selectively inhibited the nuclear localization of ERα, and residue Leu536 in the hydrophobic core of ligand binding domain (LBD) was essential for the interaction with RTV. In addition, RTV did not change the secondary structure of ERα-LBD like E2, which explained how ERα lost the capacity of nuclear translocation under the treatment of RTV. All of the evidences suggest that ritonavir acts as an antagonist for 17β-estradiol in regulating α subtype estrogen receptor function and early events of atherosclerosis. - Graphical abstract: RTV directly binds to ERα and Leu536 in the hydrophobic core of ligand binding domain is essential for the interaction. - Highlights: • RTV increases the thickness of rat coronary artery wall and foam cell formation. • RTV downregulates the expression of ERα and ERβ. • RTV inhibits ERα promoter activity. • RTV directly binds to ERα and the key amino acid is Leu536. • RTV inhibits the nuclear translocation of ERα and GPER.

  11. Kinetic mechanism and order of substrate binding for sn-glycerol-3-phosphate acyltransferase from squash (Cucurbita moschata).

    Science.gov (United States)

    Hayman, Matthew W; Fawcett, Tony; Slabas, Antoni R

    2002-03-13

    sn-Glycerol-3-phosphate acyltransferase (G3PAT, EC 2.3.1.15), a component of glycerolipid biosynthesis, is an important enzyme in chilling sensitivity in plants. The three-dimensional structure of the enzyme from squash (Cucurbita moschata), without bound substrate, has been determined [Turnbull et al. (2001) Acta Crystallogr. D 57, 451-453; Turnbull et al. (2001) Structure 9, 347-353]. Here we report the kinetic mechanism of plastidial G3PAT from squash and the order of substrate binding using acyl-acyl carrier protein (acyl-ACP) substrates. The reaction proceeds via a compulsory-ordered ternary complex with acyl-ACP binding before glycerol-3-phosphate. We have also determined that the reaction will proceed with C(4:0)-CoA, C(6:0)-CoA and C(12:0)-ACP substrates, allowing a wider choice of acyl groups for future co-crystallisation studies.

  12. C-terminal substitution of MDM2 interacting peptides modulates binding affinity by distinctive mechanisms.

    Directory of Open Access Journals (Sweden)

    Christopher J Brown

    Full Text Available The complex between the proteins MDM2 and p53 is a promising drug target for cancer therapy. The residues 19-26 of p53 have been biochemically and structurally demonstrated to be a most critical region to maintain the association of MDM2 and p53. Variation of the amino acid sequence in this range obviously alters the binding affinity. Surprisingly, suitable substitutions contiguous to this region of the p53 peptides can yield tightly binding peptides. The peptide variants may differ by a single residue that vary little in their structural conformations and yet are characterized by large differences in their binding affinities. In this study a systematic analysis into the role of single C-terminal mutations of a 12 residue fragment of the p53 transactivation domain (TD and an equivalent phage optimized peptide (12/1 were undertaken to elucidate their mechanistic and thermodynamic differences in interacting with the N-terminal of MDM2. The experimental results together with atomistically detailed dynamics simulations provide insight into the principles that govern peptide design protocols with regard to protein-protein interactions and peptidomimetic design.

  13. The mechanism by which influenza A virus nucleoprotein forms oligomers and binds RNA

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Qiaozhen; Krug, Robert M.; Tao, Yizhi Jane

    2006-12-06

    Influenza A viruses pose a serious threat to world public health, particularly the currently circulating avian H5N1 viruses. The influenza viral nucleoprotein forms the protein scaffold of the helical genomic ribonucleoprotein complexes, and has a critical role in viral RNA replication. Here we report a 3.2 Angstrom crystal structure of this nucleoprotein, the overall shape of which resembles a crescent with a head and a body domain, with a protein fold different compared with that of the rhabdovirus nucleoprotein. Oligomerization of the influenza virus nucleoprotein is mediated by a flexible tail loop that is inserted inside a neighboring molecule. This flexibility in the tail loop enables the nucleoprotein to form loose polymers as well as rigid helices, both of which are important for nucleoprotein functions. Single residue mutations in the tail loop result in the complete loss of nucleoprotein oligomerization. An RNA-binding groove, which is found between the head and body domains at the exterior of the nucleoprotein oligomer, is lined with highly conserved basic residues widely distributed in the primary sequence. The nucleoprotein structure shows that only one of two proposed nuclear localization signals are accessible, and suggests that the body domain of nucleoprotein contains the binding site for the viral polymerase. Our results identify the tail loop binding pocket as a potential target for antiviral development.

  14. A platinum complex that binds non-covalently to DNA and induces cell death via a different mechanism than cisplatin.

    Science.gov (United States)

    Suntharalingam, Kogularamanan; Mendoza, Oscar; Duarte, Alexandra A; Mann, David J; Vilar, Ramon

    2013-05-01

    Cisplatin and some of its derivatives have been shown to be very successful anticancer agents. Their main mode of action has been proposed to be via covalent binding to DNA. However, one of the limitations of these drugs is their poor activity against some tumours due to intrinsic or acquired resistance. Therefore, there is interest in developing complexes with different binding modes and mode of action. Herein we present a novel platinum(ii)-terpyridine complex (1) which interacts non-covalently with DNA and induces cell death via a different mechanism than cisplatin. The interaction of this complex with DNA was studied by UV/Vis spectroscopic titrations, fluorescent indicator displacement (FID) assays and circular dichroism (CD) titrations. In addition, computational docking studies were carried out with the aim of establishing the complex's binding mode. These experimental and computational studies showed the complex to have an affinity constant for DNA of ∼10(4) M(-1), a theoretical free energy of binding of -10.83 kcal mol(-1) and selectivity for the minor groove of DNA. Long-term studies indicated that 1 did not covalently bind (or nick) DNA. The cancer cell antiproliferative properties of this platinum(ii) complex were probed in vitro against human and murine cell lines. Encouragingly the platinum(ii) complex displayed selective toxicity for the cancerous (U2OS and SH-SY5Y) and proliferating NIH 3T3 cell lines. Further cell based studies were carried out to establish the mode of action. Cellular uptake studies demonstrated that the complex is able to penetrate the cell membrane and localize to the nucleus, implying that genomic DNA could be a cellular target. Detailed immunoblotting studies in combination with DNA-flow cytometry showed that the platinum(ii) complex induced cell death in a manner consistent with necrosis.

  15. Nanoscale adhesion, friction and wear of proteins on polystyrene.

    Science.gov (United States)

    Bhushan, Bharat; Utter, Jason

    2013-02-01

    Protein layers are routinely deployed on biomaterials and biological micro/nanoelectromechanical systems (bioMEMS/NEMS) as a functional layer allowing for specific molecular recognition, binding properties or to facilitate biocompatibility. In addition, uncoated biomaterial surfaces will have uncontrolled protein layers adsorbing to the surface within seconds of implantation, so a pre-defined protein layer will improve the host response. Implanted biomaterials also experience micromotion over time which may degrade any surface protein layers. Degradation of these protein layers may lead to system failure or an unwanted immune response. Therefore, it is important to characterize the interfacial properties of proteins on biomaterial surfaces. In this study, the nanoscale adhesion, friction and wear properties of proteins adsorbed to a spin coated polystyrene surface were measured using atomic force microscopy (AFM) in deionized (DI) water and phosphate buffered saline. Adhesion, friction and wear have been measured for bovine serum albumin (BSA), collagen, fibronectin and streptavidin (STA) in DI water and PBS as a function of protein concentration. These proteins were chosen due to their importance and widespread application in the biotechnology field. Adhesion and friction were also measured for BSA and STA at two different temperatures and different pH values to simulate a biological environment. Based on this study, adhesion, friction and wear mechanisms of the different proteins are discussed.

  16. Mechanism of the Association between Na+ Binding and Conformations at the Intracellular Gate in Neurotransmitter:Sodium Symporters.

    Science.gov (United States)

    Stolzenberg, Sebastian; Quick, Matthias; Zhao, Chunfeng; Gotfryd, Kamil; Khelashvili, George; Gether, Ulrik; Loland, Claus J; Javitch, Jonathan A; Noskov, Sergei; Weinstein, Harel; Shi, Lei

    2015-05-29

    Neurotransmitter:sodium symporters (NSSs) terminate neurotransmission by Na(+)-dependent reuptake of released neurotransmitters. Previous studies suggested that Na(+)-binding reconfigures dynamically coupled structural elements in an allosteric interaction network (AIN) responsible for function-related conformational changes, but the intramolecular pathway of this mechanism has remained uncharted. We describe a new approach for the modeling and analysis of intramolecular dynamics in the bacterial NSS homolog LeuT. From microsecond-scale molecular dynamics simulations and cognate experimental verifications in both LeuT and human dopamine transporter (hDAT), we apply the novel method to identify the composition and the dynamic properties of their conserved AIN. In LeuT, two different perturbations disrupting Na(+) binding and transport (i.e. replacing Na(+) with Li(+) or the Y268A mutation at the intracellular gate) affect the AIN in strikingly similar ways. In contrast, other mutations that affect the intracellular gate (i.e. R5A and D369A) do not significantly impair Na(+) cooperativity and transport. Our analysis shows these perturbations to have much lesser effects on the AIN, underscoring the sensitivity of this novel method to the mechanistic nature of the perturbation. Notably, this set of observations holds as well for hDAT, where the aligned Y335A, R60A, and D436A mutations also produce different impacts on Na(+) dependence. Thus, the detailed AIN generated from our method is shown to connect Na(+) binding with global conformational changes that are critical for the transport mechanism. That the AIN between the Na(+) binding sites and the intracellular gate in bacterial LeuT resembles that in eukaryotic hDAT highlights the conservation of allosteric pathways underlying NSS function.

  17. Dynamics of Actin Stress Fibers and Focal Adhesions during Slow Migration in Swiss 3T3 Fibroblasts: Intracellular Mechanism of Cell Turning

    Directory of Open Access Journals (Sweden)

    Michiko Sugawara

    2016-01-01

    Full Text Available To understand the mechanism regulating the spontaneous change in polarity that leads to cell turning, we quantitatively analyzed the dynamics of focal adhesions (FAs coupling with the self-assembling actin cytoskeletal structure in Swiss 3T3 fibroblasts. Fluorescent images were acquired from cells expressing GFP-actin and RFP-zyxin by laser confocal microscopy. On the basis of the maximum area, duration, and relocation distance of FAs extracted from the RFP-zyxin images, the cells could be divided into 3 regions: the front region, intermediate lateral region, and rear region. In the intermediate lateral region, FAs appeared close to the leading edge and were stabilized gradually as its area increased. Simultaneously, bundled actin stress fibers (SFs were observed vertically from the positions of these FAs, and they connected to the other SFs parallel to the leading edge. Finally, these connecting SFs fused to form a single SF with matured FAs at both ends. This change in SF organization with cell retraction in the first cycle of migration followed by a newly formed protrusion in the next cycle is assumed to lead to cell turning in migrating Swiss 3T3 fibroblasts.

  18. Indium gallium zinc oxide layer used to decrease optical reflection loss at intermediate adhesive region for fabricating mechanical stacked multijunction solar cells

    Science.gov (United States)

    Sameshima, Toshiyuki; Nimura, Takeshi; Sugawara, Takashi; Ogawa, Yoshihiro; Yoshidomi, Shinya; Kimura, Shunsuke; Hasumi, Masahiko

    2017-01-01

    Reduction of optical reflection loss is discussed in three mechanical stacked samples: top crystalline silicon and bottom crystalline germanium substrates, top crystalline GaAs and bottom crystalline silicon substrates, and top crystalline GaP and bottom crystalline silicon substrates using an epoxy-type adhesive with a reflective index of 1.47. Transparent conductive Indium gallium zinc oxide (IGZO) layers with a refractive index of 1.85 were used as antireflection layers. IGZO layers were formed on the bottom surface of the top substrate and the top surface of the bottom substrate of the three stacked samples with thicknesses of 188, 130, and 102 nm. The insertion of IGZO layers decreased the optical reflectivity of the stacked samples. The IGZO layers provided high effective optical absorbency of bottom substrates of 0.925, 0.943, and 0.931, respectively, for light wavelength regions for light in which the top substrates were transparent and the bottom substrates were opaque.

  19. Proteomic dataset of the sea urchin Paracentrotus lividus adhesive organs and secreted adhesive

    Directory of Open Access Journals (Sweden)

    Nicolas Lebesgue

    2016-06-01

    Full Text Available Sea urchins have specialized adhesive organs called tube feet, which mediate strong but reversible adhesion. Tube feet are composed by a disc, producing adhesive and de-adhesive secretions for substratum attachment, and a stem for movement. After detachment the secreted adhesive remains bound to the substratum as a footprint. Recently, a label-free quantitative proteomic approach coupled with the latest mass-spectrometry technology was used to analyze the differential proteome of Paracentrotus lividus adhesive organ, comparing protein expression levels in the tube feet adhesive part (the disc versus the non-adhesive part (the stem, and also to profile the proteome of the secreted adhesive (glue. This data article contains complementary figures and results related to the research article “Deciphering the molecular mechanisms underlying sea urchin reversible adhesion: a quantitative proteomics approach” (Lebesgue et al., 2016 [1]. Here we provide a dataset of 1384 non-redundant proteins, their fragmented peptides and expression levels, resultant from the analysis of the tube feet differential proteome. Of these, 163 highly over-expressed tube feet disc proteins (>3-fold, likely representing the most relevant proteins for sea urchin reversible adhesion, were further annotated in order to determine the potential functions. In addition, we provide a dataset of 611 non-redundant proteins identified in the secreted adhesive proteome, as well as their functional annotation and grouping in 5 major protein groups related with adhesive exocytosis, and microbial protection. This list was further analyzed to identify the most abundant protein groups and pinpoint putative adhesive proteins, such as Nectin, the most abundant adhesive protein in sea urchin glue. The obtained data uncover the key proteins involved in sea urchins reversible adhesion, representing a step forward to the development of new wet-effective bio-inspired adhesives.

  20. Advanced adhesives in electronics

    CERN Document Server

    Bailey, C

    2011-01-01

    Adhesives are widely used in the manufacture of electronic devices to act as passive and active components. Recently there has been considerable interest in the use of conductive adhesives. This book reviews key types of conductive adhesives, processing methods, properties and the way they can be modelled as well as potential applications.$bAdhesives for electronic applications serve important functional and structural purposes in electronic components and packaging, and have developed significantly over the last few decades. Advanced adhesives in electronics reviews recent developments in adhesive joining technology, processing and properties. The book opens with an introduction to adhesive joining technology for electronics. Part one goes on to cover different types of adhesive used in electronic systems, including thermally conductive adhesives, isotropic and anisotropic conductive adhesives and underfill adhesives for flip-chip applications. Part two focuses on the properties and processing of electronic ...

  1. Intrinsically disordered caldesmon binds calmodulin via the “buttons on a string” mechanism

    Directory of Open Access Journals (Sweden)

    Sergei E. Permyakov

    2015-09-01

    Full Text Available We show here that chicken gizzard caldesmon (CaD and its C-terminal domain (residues 636–771, CaD136 are intrinsically disordered proteins. The computational and experimental analyses of the wild type CaD136 and series of its single tryptophan mutants (W674A, W707A, and W737A and a double tryptophan mutant (W674A/W707A suggested that although the interaction of CaD136 with calmodulin (CaM can be driven by the non-specific electrostatic attraction between these oppositely charged molecules, the specificity of CaD136-CaM binding is likely to be determined by the specific packing of important CaD136 tryptophan residues at the CaD136-CaM interface. It is suggested that this interaction can be described as the “buttons on a charged string” model, where the electrostatic attraction between the intrinsically disordered CaD136 and the CaM is solidified in a “snapping buttons” manner by specific packing of the CaD136 “pliable buttons” (which are the short segments of fluctuating local structure condensed around the tryptophan residues at the CaD136-CaM interface. Our data also show that all three “buttons” are important for binding, since mutation of any of the tryptophans affects CaD136-CaM binding and since CaD136 remains CaM-buttoned even when two of the three tryptophans are mutated to alanines.

  2. Targeting of nucleotide-binding proteins by HAMLET--a conserved tumor cell death mechanism.

    Science.gov (United States)

    Ho, J C S; Nadeem, A; Rydström, A; Puthia, M; Svanborg, C

    2016-02-18

    HAMLET (Human Alpha-lactalbumin Made LEthal to Tumor cells) kills tumor cells broadly suggesting that conserved survival pathways are perturbed. We now identify nucleotide-binding proteins as HAMLET binding partners, accounting for about 35% of all HAMLET targets in a protein microarray comprising 8000 human proteins. Target kinases were present in all branches of the Kinome tree, including 26 tyrosine kinases, 10 tyrosine kinase-like kinases, 13 homologs of yeast sterile kinases, 4 casein kinase 1 kinases, 15 containing PKA, PKG, PKC family kinases, 15 calcium/calmodulin-dependent protein kinase kinases and 13 kinases from CDK, MAPK, GSK3, CLK families. HAMLET acted as a broad kinase inhibitor in vitro, as defined in a screen of 347 wild-type, 93 mutant, 19 atypical and 17 lipid kinases. Inhibition of phosphorylation was also detected in extracts from HAMLET-treated lung carcinoma cells. In addition, HAMLET recognized 24 Ras family proteins and bound to Ras, RasL11B and Rap1B on the cytoplasmic face of the plasma membrane. Direct cellular interactions between HAMLET and activated Ras family members including Braf were confirmed by co-immunoprecipitation. As a consequence, oncogenic Ras and Braf activity was inhibited and HAMLET and Braf inhibitors synergistically increased tumor cell death in response to HAMLET. Unlike most small molecule kinase inhibitors, HAMLET showed selectivity for tumor cells in vitro and in vivo. The results identify nucleotide-binding proteins as HAMLET targets and suggest that dysregulation of the ATPase/kinase/GTPase machinery contributes to cell death, following the initial, selective recognition of HAMLET by tumor cells. The findings thus provide a molecular basis for the conserved tumoricidal effect of HAMLET, through dysregulation of kinases and oncogenic GTPases, to which tumor cells are addicted.

  3. The non-equilibrium thermodynamics and kinetics of focal adhesion dynamics.

    Directory of Open Access Journals (Sweden)

    Joseph E Olberding

    Full Text Available BACKGROUND: We consider a focal adhesion to be made up of molecular complexes, each consisting of a ligand, an integrin molecule, and associated plaque proteins. Free energy changes drive the binding and unbinding of these complexes and thereby controls the focal adhesion's dynamic modes of growth, treadmilling and resorption. PRINCIPAL FINDINGS: We have identified a competition among four thermodynamic driving forces for focal adhesion dynamics: (i the work done during the addition of a single molecular complex of a certain size, (ii the chemical free energy change associated with the addition of a molecular complex, (iii the elastic free energy change associated with deformation of focal adhesions and the cell membrane, and (iv the work done on a molecular conformational change. We have developed a theoretical treatment of focal adhesion dynamics as a nonlinear rate process governed by a classical kinetic model. We also express the rates as being driven by out-of-equilibrium thermodynamic driving forces, and modulated by kinetics. The mechanisms governed by the above four effects allow focal adhesions to exhibit a rich variety of behavior without the need to introduce special constitutive assumptions for their response. For the reaction-limited case growth, treadmilling and resorption are all predicted by a very simple chemo-mechanical model. Treadmilling requires symmetry breaking between the ends of the focal adhesion, and is achieved by driving force (i above. In contrast, depending on its numerical value (ii causes symmetric growth, resorption or is neutral, (iii causes symmetric resorption, and (iv causes symmetric growth. These findings hold for a range of conditions: temporally-constant force or stress, and for spatially-uniform and non-uniform stress distribution over the FA. The symmetric growth mode dominates for temporally-constant stress, with a reduced treadmilling regime. SIGNIFICANCE: In addition to explaining focal adhesion

  4. A Novel DNA Binding Mechanism for maf Basic Region-Leucine Zipper Factors Inferred from a MafA-DNA Complex Structure and Binding Specificities

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Xun; Guanga, Gerald P; Wan, Cheng; Rose, Robert B [Z; (W Elec.); (NCSU)

    2012-11-13

    MafA is a proto-oncoprotein and is critical for insulin gene expression in pancreatic β-cells. Maf proteins belong to the AP1 superfamily of basic region-leucine zipper (bZIP) transcription factors. Residues in the basic helix and an ancillary N-terminal domain, the Extended Homology Region (EHR), endow maf proteins with unique DNA binding properties: binding a 13 bp consensus site consisting of a core AP1 site (TGACTCA) flanked by TGC sequences and binding DNA stably as monomers. To further characterize maf DNA binding, we determined the structure of a MafA–DNA complex. MafA forms base-specific hydrogen bonds with the flanking G–5C–4 and central C0/G0 bases, but not with the core-TGA bases. However, in vitro binding studies utilizing a pulse–chase electrophoretic mobility shift assay protocol revealed that mutating either the core-TGA or flanking-TGC bases dramatically increases the binding off rate. Comparing the known maf structures, we propose that DNA binding specificity results from positioning the basic helix through unique phosphate contacts. The EHR does not contact DNA directly but stabilizes DNA binding by contacting the basic helix. Collectively, these results suggest a novel multistep DNA binding process involving a conformational change from contacting the core-TGA to contacting the flanking-TGC bases.

  5. Crystal structures of starch binding domain from Rhizopus oryzae glucoamylase in complex with isomaltooligosaccharide: insights into polysaccharide binding mechanism of CBM21 family.

    Science.gov (United States)

    Chu, Chen-Hsi; Li, Kun-Mou; Lin, Shih-Wei; Chang, Margaret Dah-Tsyr; Jiang, Ting-Ying; Sun, Yuh-Ju

    2014-06-01

    Glucoamylases are responsible for hydrolysis of starch and polysaccharides to yield β-D-glucose. Rhizopus oryzae glucoamylase (RoGA) is composed of an N-terminal starch binding domain (SBD) and a C-terminal catalytic domain connected by an O-glycosylated linker. Two carbohydrate binding sites in RoSBD have been identified, site I is created by three highly conserved aromatic residues, Trp47, Tyr83, and Tyr94, and site II is built up by Tyr32 and Phe58. Here, the two crystal structures of RoSBD in complex with only α-(1,6)-linked isomaltotriose (RoSBD-isoG3) and isomaltotetraose (RoSBD-isoG4) have been determined at 1.2 and 1.3 Å, respectively. Interestingly, site II binding is observed in both complexes, while site I binding is only found in the RoSBD-isoG4 complex. Hence, site II acts as the recognition binding site for carbohydrate and site I accommodates site II to bind isoG4. Site I participates in sugar binding only when the number of glucosyl units of oligosaccharides is more than three. Taken together, two carbohydrate binding sites in RoSBD cooperate to reinforce binding mode of glucoamylase with polysaccharides as well as the starch.

  6. An intermolecular binding mechanism involving multiple LysM domains mediates carbohydrate recognition by an endopeptidase

    DEFF Research Database (Denmark)

    Wong, Jaslyn E M M; Midtgaard, Søren Roi; Gysel, Kira

    2015-01-01

    LysM domains, which are frequently present as repetitive entities in both bacterial and plant proteins, are known to interact with carbohydrates containing N-acetylglucosamine (GlcNAc) moieties, such as chitin and peptidoglycan. In bacteria, the functional significance of the involvement of multi......LysM domains, which are frequently present as repetitive entities in both bacterial and plant proteins, are known to interact with carbohydrates containing N-acetylglucosamine (GlcNAc) moieties, such as chitin and peptidoglycan. In bacteria, the functional significance of the involvement...... of multiple LysM domains in substrate binding has so far lacked support from high-resolution structures of ligand-bound complexes. Here, a structural study of the Thermus thermophilus NlpC/P60 endopeptidase containing two LysM domains is presented. The crystal structure and small-angle X-ray scattering...... solution studies of this endopeptidase revealed the presence of a homodimer. The structure of the two LysM domains co-crystallized with N-acetyl-chitohexaose revealed a new intermolecular binding mode that may explain the differential interaction between LysM domains and short or long chitin oligomers...

  7. An intermolecular binding mechanism involving multiple LysM domains mediates carbohydrate recognition by an endopeptidase

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Jaslyn E. M. M. [Aarhus University, Gustav Wieds Vej 10C, 8000 Aarhus (Denmark); Midtgaard, Søren Roi [University of Copenhagen, Universitetsparken 5, 2100 Copenhagen (Denmark); Gysel, Kira [Aarhus University, Gustav Wieds Vej 10C, 8000 Aarhus (Denmark); Thygesen, Mikkel B.; Sørensen, Kasper K.; Jensen, Knud J. [University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C (Denmark); Stougaard, Jens; Thirup, Søren; Blaise, Mickaël, E-mail: mickael.blaise@cpbs.cnrs.fr [Aarhus University, Gustav Wieds Vej 10C, 8000 Aarhus (Denmark)

    2015-03-01

    The crystal and solution structures of the T. thermophilus NlpC/P60 d, l-endopeptidase as well as the co-crystal structure of its N-terminal LysM domains bound to chitohexaose allow a proposal to be made regarding how the enzyme recognizes peptidoglycan. LysM domains, which are frequently present as repetitive entities in both bacterial and plant proteins, are known to interact with carbohydrates containing N-acetylglucosamine (GlcNAc) moieties, such as chitin and peptidoglycan. In bacteria, the functional significance of the involvement of multiple LysM domains in substrate binding has so far lacked support from high-resolution structures of ligand-bound complexes. Here, a structural study of the Thermus thermophilus NlpC/P60 endopeptidase containing two LysM domains is presented. The crystal structure and small-angle X-ray scattering solution studies of this endopeptidase revealed the presence of a homodimer. The structure of the two LysM domains co-crystallized with N-acetyl-chitohexaose revealed a new intermolecular binding mode that may explain the differential interaction between LysM domains and short or long chitin oligomers. By combining the structural information with the three-dimensional model of peptidoglycan, a model suggesting how protein dimerization enhances the recognition of peptidoglycan is proposed.

  8. NMR studies of the AMP-binding site and mechanism of adenylate kinase

    Energy Technology Data Exchange (ETDEWEB)

    Fry, D.C.; Kuby, S.A.; Mildvan, A.S.

    1987-03-24

    NMR has previously been used to determine the conformation of enzyme-bound MgATP and to locate the MgATP-binding site on adenylate kinase. To determine the conformation and location of the other substrate, AMP, distances have been measured from Cr/sup 3 +/AMPPCP, a linear competitive inhibitor with respect to MgATP, to six protons and to the phosphorus atom of AMP on adenylate kinase, with the paramagnetic probe-T/sub 1/ method. Time-dependent nuclear Overhauser effects (NOEs) have been used to measure five interproton distances on enzyme-bound AMP. These distances were used to determine the conformation of bound AMP in addition to its position with respect to metal-ATP. Ten intermolecular NOEs, from protons of the enzyme to those of AMP, were detected, indicating the proximity of at least three hydrophobic amino acids to bound AMP. These constraints, together with the conformation of AMP and the intersubstrate distances, were used to position AMP into the X-ray structure of adenylate kinase. The AMP binding site is found to be near Leu-116, Arg-171, Val-173, Val-182, and Leu-190; all of these residues have been found to be invariant in muscle-type rabbit, calf, human, porcine.

  9. Acanthamoeba castellanii Proteases are Capable of Degrading Iron-Binding Proteins as a Possible Mechanism of Pathogenicity.

    Science.gov (United States)

    Ramírez-Rico, Gerardo; Martínez-Castillo, Moisés; de la Garza, Mireya; Shibayama, Mineko; Serrano-Luna, Jesús

    2015-01-01

    Acanthamoeba castellanii, a free-living amoeba, is an amphizoic organism that can behave as an opportunistic pathogen, causing granulomatous amoebic encephalitis in immunocompromised patients or infecting immunocompetent individuals via cutaneous lesions, sinusoidal infections, or amoebic keratitis. Therefore, this amoeba could be in contact with different iron-binding proteins, such as lactoferrin in tears and mucosa and transferrin and hemoglobin in blood. Iron is a vital and necessary element for host metabolism but also for parasite survival. Accordingly, parasites have developed iron uptake mechanisms, one of which is the utilization of proteases to degrade host iron-binding proteins. In this work, we performed a partial biochemical characterization of A. castellanii proteases at different pHs and utilizing protease inhibitors with 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis and copolymerized with different iron-binding proteins. We describe for the first time the presence of several cysteine proteases in a total A. castellanii crude extract and in conditioned culture medium precipitated with ethanol. These amoebic peptidases degraded human holo-lactoferrin, holo-transferrin, hemoglobin, and horse spleen ferritin; some of these proteases were substrate specific, and others degraded multiple substrates. These proteases could be considered virulence factors that promote iron acquisition from the host.

  10. The role of the Zn(II binding domain in the mechanism of E. coli DNA topoisomerase I

    Directory of Open Access Journals (Sweden)

    Tse-Dinh Yuk-Ching

    2002-05-01

    Full Text Available Abstract Background Escherichia coli DNA topoisomerase I binds three Zn(II with three tetracysteine motifs which, together with the 14 kDa C-terminal region, form a 30 kDa DNA binding domain (ZD domain. The 67 kDa N-terminal domain (Top67 has the active site tyrosine for DNA cleavage but cannot relax negatively supercoiled DNA. We analyzed the role of the ZD domain in the enzyme mechanism. Results Addition of purified ZD domain to Top67 partially restored the relaxation activity, demonstrating that covalent linkage between the two domains is not necessary for removal of negative supercoils from DNA. The two domains had similar affinities to ssDNA. However, only Top67 could bind dsDNA with high affinity. DNA cleavage assays showed that the Top67 had the same sequence and structure selectivity for DNA cleavage as the intact enzyme. DNA rejoining also did not require the presence of the ZD domain. Conclusions We propose that during relaxation of negatively supercoiled DNA, Top67 by itself can position the active site tyrosine near the junction of double-stranded and single-stranded DNA for cleavage. However, the interaction of the ZD domain with the passing single-strand of DNA, coupled with enzyme conformational change, is needed for removal of negative supercoils.

  11. Biomechanics of cell rolling: shear flow, cell-surface adhesion, and cell deformability.

    Science.gov (United States)

    Dong, C; Lei, X X

    2000-01-01

    The mechanics of leukocyte (white blood cell; WBC) deformation and adhesion to endothelial cells (EC) has been investigated using a novel in vitro side-view flow assay. HL-60 cell rolling adhesion to surface-immobilized P-selectin was used to model the WBC-EC adhesion process. Changes in flow shear stress, cell deformability, or substrate ligand strength resulted in significant changes in the characteristic adhesion binding time, cell-surface contact and cell rolling velocity. A 2-D model indicated that cell-substrate contact area under a high wall shear stress (20 dyn/cm2) could be nearly twice of that under a low stress (0.5 dyn/cm2) due to shear flow-induced cell deformation. An increase in contact area resulted in more energy dissipation to both adhesion bonds and viscous cytoplasm, whereas the fluid energy that inputs to a cell decreased due to a flattened cell shape. The model also predicted a plateau of WBC rolling velocity as flow shear stresses further increased. Both experimental and computational studies have described how WBC deformation influences the WBC-EC adhesion process in shear flow.

  12. Syndecans in tumor cell adhesion and signaling

    Directory of Open Access Journals (Sweden)

    Rapraeger Alan C

    2004-01-01

    Full Text Available Abstract Anchorage of cells to "heparin" – binding domains that are prevalent in extracellular matrix (ECM components is thought to occur primarily through the syndecans, a four-member family of transmembrane heparan sulfate proteoglycans that communicate environmental cues from the ECM to the cytoskeleton and the signaling apparatus of the cell. Known activities of the syndecans trace to their highly conserved cytoplasmic domains and to their heparan sulfate chains, which can serve to regulate the signaling of growth factors and morphogens. However, several emerging studies point to critical roles for the syndecans' extracellular protein domains in tumor cell behavior to include cell adhesion and invasion. Although the mechanisms of these activities remain largely unknown, one possibility involves "co-receptor" interactions with integrins that may regulate integrin function and the cell adhesion-signaling phenotype. Thus, alterations in syndecan expression, leading to either overexpression or loss of expression, both of which take place in tumor cells, may have dramatic effects on tumor cell invasion.

  13. Detailed characterization of the cooperative mechanism of Ca(2+) binding and catalytic activation in the Ca(2+) transport (SERCA) ATPase.

    Science.gov (United States)

    Zhang, Z; Lewis, D; Strock, C; Inesi, G; Nakasako, M; Nomura, H; Toyoshima, C

    2000-08-01

    Expression of heterologous SERCA1a ATPase in Cos-1 cells was optimized to yield levels that account for 10-15% of the microsomal protein, as revealed by protein staining on electrophoretic gels. This high level of expression significantly improved our characterization of mutants, including direct measurements of Ca(2+) binding by the ATPase in the absence of ATP, and measurements of various enzyme functions in the presence of ATP or P(i). Mutational analysis distinguished two groups of amino acids within the transmembrane domain: The first group includes Glu771 (M5), Thr799 (M6), Asp800 (M6), and Glu908 (M8), whose individual mutations totally inhibit binding of the two Ca(2+) required for activation of one ATPase molecule. The second group includes Glu309 (M4) and Asn796 (M6), whose individual or combined mutations inhibit binding of only one and the same Ca(2+). The effects of mutations of these amino acids were interpreted in the light of recent information on the ATPase high-resolution structure, explaining the mechanism of Ca(2+) binding and catalytic activation in terms of two cooperative sites. The Glu771, Thr799, and Asp800 side chains contribute prominently to site 1, together with less prominent contributions by Asn768 and Glu908. The Glu309, Asn796, and Asp800 side chains, as well as the Ala305 (and possibly Val304 and Ile307) carbonyl oxygen, contribute to site 2. Sequential binding begins with Ca(2+) occupancy of site 1, followed by transition to a conformation (E') sensitive to Ca(2+) inhibition of enzyme phosphorylation by P(i), but still unable to utilize ATP. The E' conformation accepts the second Ca(2+) on site 2, producing then a conformation (E' ') which is able to utilize ATP. Mutations of residues (Asp813 and Asp818) in the M6/M7 loop reduce Ca(2+) affinity and catalytic turnover, suggesting a strong influence of this loop on the correct positioning of the M6 helix. Mutation of Asp351 (at the catalytic site within the cytosolic domain

  14. Fibrillar Adhesive for Climbing Robots

    Science.gov (United States)

    Pamess, Aaron; White, Victor E.

    2013-01-01

    A climbing robot needs to use its adhesive patches over and over again as it scales a slope. Replacing the adhesive at each step is generally impractical. If the adhesive or attachment mechanism cannot be used repeatedly, then the robot must carry an extra load of this adhesive to apply a fresh layer with each move. Common failure modes include tearing, contamination by dirt, plastic deformation of fibers, and damage from loading/ unloading. A gecko-like fibrillar adhesive has been developed that has been shown useful for climbing robots, and may later prove useful for grasping, anchoring, and medical applications. The material consists of a hierarchical fibrillar structure that currently contains two levels, but may be extended to three or four levels in continuing work. The contacting level has tens of thousands of microscopic fibers made from a rubberlike material that bend over and create intimate contact with a surface to achieve maximum van der Waals forces. By maximizing the real area of contact that these fibers make and minimizing the bending energy necessary to achieve that contact, the net amount of adhesion has been improved dramatically.

  15. Antiphospholipid antibodies promote leukocyte-endothelial cell adhesion and thrombosis in mice by antagonizing eNOS via beta 2GPI and apoER2

    NARCIS (Netherlands)

    Ramesh, Sangeetha; Morrell, Craig N.; Tarango, Cristina; Thomas, Gail D.; Yuhanna, Ivan S.; Girardi, Guillermina; Herz, Joachim; Urbanus, Rolf T.; de Groot, Philip G.; Thorpe, Philip E.; Salmon, Jane E.; Shaul, Philip W.; Mineo, Chieko

    2011-01-01

    In antiphospholipid syndrome (APS), antiphospholipid antibodies (aPL) binding to beta 2 glycoprotein I (beta 2GPI) induce endothelial cell-leukocyte adhesion and thrombus formation via unknown mechanisms Here we show that in mice both of these processes are caused by the inhibition of eNOS In studie

  16. Design and fabrication of polymer based dry adhesives inspired by the gecko adhesive system

    Science.gov (United States)

    Jin, Kejia

    There has been significant interest in developing dry adhesives mimicking the gecko adhesive system, which offers several advantages compared to conventional pressure sensitive adhesives. Specifically, gecko adhesive pads have anisotropic adhesion properties: the adhesive pads (spatulae) stick strongly when sheared in one direction but are non-adherent when sheared in the opposite direction. This anisotropy property is attributed to the complex topography of the array of fine tilted and curved columnar structures (setae) that bear the spatulae. In this thesis, easy, scalable methods, relying on conventional and unconventional techniques are presented to incorporate tilt in the fabrication of synthetic polymer-based dry adhesives mimicking the gecko adhesive system, which provide anisotropic adhesion properties. In the first part of the study, the anisotropic adhesion and friction properties of samples with various tilt angles to test the validity of a nanoscale tape-peeling model of spatular function are measured. Consistent with the Peel Zone model, samples with lower tilt angles yielded larger adhesion forces. Contact mechanics of the synthetic array were highly anisotropic, consistent with the frictional adhesion model and gecko-like. Based on the original design, a new design of gecko-like dry adhesives was developed which showed superior tribological properties and furthermore showed anisotropic adhesive properties without the need for tilt in the structures. These adhesives can be used to reversibly suspend weights from vertical surfaces (e.g., walls) and, for the first time to our knowledge, horizontal surfaces (e.g., ceilings) by simultaneously and judiciously activating anisotropic friction and adhesion forces. Furthermore, adhesion properties between artificial gecko-inspired dry adhesives and rough substrates with varying roughness are studied. The results suggest that both adhesion and friction forces on a rough substrate depends significantly on the

  17. In Pursuit of Fully Flexible Protein-Ligand Docking: Modeling the Bilateral Mechanism of Binding.

    Science.gov (United States)

    Henzler, Angela M; Rarey, Matthias

    2010-03-15

    Modern structure-based drug design aims at accounting for the intrinsic flexibility of therapeutic relevant targets. Over the last few years a considerable amount of docking approaches that encounter this challenging problem has emerged. Here we provide the readership with an overview of established methods for fully flexible protein-ligand docking and current developments in the field. All methods are based on one of two fundamental models which describe the dynamic behavior of proteins upon ligand binding. Methods for ensemble docking (ED) model the protein conformational change before the ligand is placed, whereas induced-fit docking (IFD) optimizes the protein structure afterwards. A third category of docking approaches is formed by recent approaches that follow both concepts. This categorization allows to comprehensively discover strengths and weaknesses of the individual processes and to extract information for their applicability in real world docking scenarios.

  18. Photoactivation mechanisms of flavin-binding photoreceptors revealed through ultrafast spectroscopy and global analysis methods.

    Science.gov (United States)

    Mathes, Tilo; van Stokkum, Ivo H M; Kennis, John T M

    2014-01-01

    Flavin-binding photoreceptor proteins use the isoalloxazine moiety of flavin cofactors to absorb light in the blue/UV-A wavelength region and subsequently translate it into biological information. The underlying photochemical reactions and protein structural dynamics are delicately tuned by the protein environment and represent fundamental reactions in biology and chemistry. Due to their photo-switchable nature, these proteins can be studied efficiently with laser-flash induced transient absorption and emission spectroscopy with temporal precision down to the femtosecond time domain. Here, we describe the application of both visible and mid-IR ultrafast transient absorption and time-resolved fluorescence methods in combination with sophisticated global analysis procedures to elucidate the photochemistry and signal transduction of BLUF (Blue light receptors using FAD) and LOV (Light oxygen voltage) photoreceptor domains.

  19. Quantum mechanical treatment of binding energy between DNA nucleobases and carbon nanotube: A DFT analysis

    Science.gov (United States)

    Chehel Amirani, Morteza; Tang, Tian; Cuervo, Javier

    2013-12-01

    The interactions between DNA and carbon nanotubes (CNTs) have been widely studied in recent years. The binding process of DNA with CNT as well as the electronic properties of DNA/CNT hybrids constitutes an interesting yet complicated problem. The binding energy (BE) of the hybridization is one of the most extensively studied parameters for the problem. In this work, density functional theory (DFT) was used to perform geometry optimization of neutral nucleobases including adenine, cytosine, guanine and thymine absorbed on a zigzag (7,0) single-walled CNT and to evaluate the basis set superposition error corrected BE of the optimized configuration. All DFT calculations were performed using the M05-2X functional. The 6-31G(d) basis set was used for the optimization step and single point energy calculations were done using the 6-31G(d,p) basis set. For each nucleobase, we examined the influence of the initial configuration (IC) on the BE value. In particular, we considered 24 different ICs for each nucleobase, and each IC was subjected to an independent optimization and BE calculation. Our results showed that different ICs result in very different BE values and can even change the order of the BE corresponding to different nucleobases. The difference in the BE for a particular nucleobase caused by changes in its IC can be comparable to the difference in the BE between different nucleobases at the same initial position relative to the CNT. This provides an explanation for the discrepancies that exist in the literature on the nucleobase/CNT BE, and suggests that the potential energy surface between the nucleobases and the CNT can have many local minima and care should be exercised in the calculation and interpretation of the BE.

  20. A combined binding mechanism of nonionic ethoxylated surfactants to bovine serum albumin revealed by fluorescence and circular dichroism.

    Science.gov (United States)

    Iovescu, Alina; Băran, Adriana; Stîngă, Gabriela; Cantemir-Leontieş, Anca Ruxandra; Maxim, Monica Elisabeta; Anghel, Dan Florin

    2015-12-01

    The study systematically investigates aqueous mixtures of fixed bovine serum albumin (BSA) and various ethoxylated nonionic surfactants belonging to a homologous series or not. Mono-disperse tetra-(C12E4), hexa-(C12E6) and octa-ethyleneglycol mono-n-dodecyl ether (C12E8), and poly-disperse eicosa-ethyleneglycol mono-n-tetradecyl ether (C14EO20) are respectively employed. Fluorescence and circular dichroism measurements are performed at surfactant/protein molar ratios (rm)s lower and higher than one. We aim to get new insights into the binding mechanism of these species and to differentiate among the interaction abilities of these surfactants. The relative magnitude of the binding thermodynamic parameters by fluorescence, and the increase of α-helix prove that hydrogen bonding drives the interaction next to the hydrophobic attraction. C12En (n=4,6,8) develop more H bonds with the albumin than C14EO20 owing to a zigzag conformation of their short ethyleneoxide chains. Among the homologous surfactants, C12E6 has a slightly stronger interaction with BSA due to a maximal number of H bonds at a minimal hindering. Static fluorescence and dynamic fluorescence indicate an inter-conversion between the tryptophan (Trp) rotamers which happens around the surfactants critical micellar concentration. For C14EO20, the meander conformation of the polar group determines a less evident conversion of the Trp rotamers and smaller α-helix rise. Binding isotherms of the homologous surfactants and the fluorescence quenching mechanism by C12E6 are also provided.

  1. Converging ligand-binding free energies obtained with free-energy perturbations at the quantum mechanical level.

    Science.gov (United States)

    Olsson, Martin A; Söderhjelm, Pär; Ryde, Ulf

    2016-06-30

    In this article, the convergence of quantum mechanical (QM) free-energy simulations based on molecular dynamics simulations at the molecular mechanics (MM) level has been investigated. We have estimated relative free energies for the binding of nine cyclic carboxylate ligands to the octa-acid deep-cavity host, including the host, the ligand, and all water molecules within 4.5 Å of the ligand in the QM calculations (158-224 atoms). We use single-step exponential averaging (ssEA) and the non-Boltzmann Bennett acceptance ratio (NBB) methods to estimate QM/MM free energy with the semi-empirical PM6-DH2X method, both based on interaction energies. We show that ssEA with cumulant expansion gives a better convergence and uses half as many QM calculations as NBB, although the two methods give consistent results. With 720,000 QM calculations per transformation, QM/MM free-energy estimates with a precision of 1 kJ/mol can be obtained for all eight relative energies with ssEA, showing that this approach can be used to calculate converged QM/MM binding free energies for realistic systems and large QM partitions. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.

  2. Insight into invertebrate defensin mechanism of action: oyster defensins inhibit peptidoglycan biosynthesis by binding to lipid II.

    Science.gov (United States)

    Schmitt, Paulina; Wilmes, Miriam; Pugnière, Martine; Aumelas, André; Bachère, Evelyne; Sahl, Hans-Georg; Schneider, Tanja; Destoumieux-Garzón, Delphine

    2010-09-17

    Three oyster defensin variants (Cg-Defh1, Cg-Defh2, and Cg-Defm) were produced as recombinant peptides and characterized in terms of activities and mechanism of action. In agreement with their spectrum of activity almost specifically directed against Gram-positive bacteria, oyster defensins were shown here to be specific inhibitors of a bacterial biosynthesis pathway rather than mere membrane-active agents. Indeed, at lethal concentrations, the three defensins did not compromise Staphylococcus aureus membrane integrity but inhibited the cell wall biosynthesis as indicated by the accumulation of the UDP-N-acetylmuramyl-pentapeptide cell wall precursor. In addition, a combination of antagonization assays, thin layer chromatography, and surface plasmon resonance measurements showed that oyster defensins bind almost irreversibly to the lipid II peptidoglycan precursor, thereby inhibiting the cell wall biosynthesis. To our knowledge, this is the first detailed analysis of the mechanism of action of antibacterial defensins produced by invertebrates. Interestingly, the three defensins, which were chosen as representative of the oyster defensin molecular diversity, bound differentially to lipid II. This correlated with their differential antibacterial activities. From our experimental data and the analysis of oyster defensin sequence diversity, we propose that oyster defensin activity results from selective forces that have conserved residues involved in lipid II binding and diversified residues at the surface of oyster defensins that could improve electrostatic interactions with the bacterial membranes.

  3. Quantum mechanics capacitance molecular mechanics modeling of core-electron binding energies of methanol and methyl nitrite on Ag(111) surface

    Science.gov (United States)

    Löytynoja, T.; Li, X.; Jänkälä, K.; Rinkevicius, Z.; Ågren, H.

    2016-07-01

    We study a newly devised quantum mechanics capacitance molecular mechanics (QMCMM) method for the calculation of core-electron binding energies in the case of molecules adsorbed on metal surfaces. This yet untested methodology is applied to systems with monolayer of methanol/methyl nitrite on an Ag(111) surface at 100 K temperature. It was found out that the studied C, N, and O 1s core-hole energies converge very slowly as a function of the radius of the metallic cluster, which was ascribed to build up of positive charge on the edge of the Ag slab. Further analysis revealed that an extrapolation process can be used to obtain binding energies that deviated less than 0.5 eV against experiments, except in the case of methanol O 1s where the difference was as large as 1.8 eV. Additional QM-cluster calculations suggest that the latter error can be connected to the lack of charge transfer over the QM-CMM boundary. Thus, the results indicate that the QMCMM and QM-cluster methods can complement each other in a holistic picture of molecule-adsorbate core-ionization studies, where all types of intermolecular interactions are considered.

  4. Quantum mechanics capacitance molecular mechanics modeling of core-electron binding energies of methanol and methyl nitrite on Ag(111) surface.

    Science.gov (United States)

    Löytynoja, T; Li, X; Jänkälä, K; Rinkevicius, Z; Ågren, H

    2016-07-14

    We study a newly devised quantum mechanics capacitance molecular mechanics (QMCMM) method for the calculation of core-electron binding energies in the case of molecules adsorbed on metal surfaces. This yet untested methodology is applied to systems with monolayer of methanol/methyl nitrite on an Ag(111) surface at 100 K temperature. It was found out that the studied C, N, and O 1s core-hole energies converge very slowly as a function of the radius of the metallic cluster, which was ascribed to build up of positive charge on the edge of the Ag slab. Further analysis revealed that an extrapolation process can be used to obtain binding energies that deviated less than 0.5 eV against experiments, except in the case of methanol O 1s where the difference was as large as 1.8 eV. Additional QM-cluster calculations suggest that the latter error can be connected to the lack of charge transfer over the QM-CMM boundary. Thus, the results indicate that the QMCMM and QM-cluster methods can complement each other in a holistic picture of molecule-adsorbate core-ionization studies, where all types of intermolecular interactions are considered.

  5. p38 signaling and receptor recycling events in a microfluidic endothelial cell adhesion assay.

    Directory of Open Access Journals (Sweden)

    Dwayne A L Vickers

    Full Text Available Adhesion-based microfluidic cell separation has proven to be very useful in applications ranging from cancer diagnostics to tissue engineering. This process involves functionalizing microchannel surfaces with a capture molecule. High specificity and purity capture can be achieved using this method. Despite these advances, little is known about the mechanisms that govern cell capture within these devices and their relationships to basic process parameters such as fluid shear stress and the presence of soluble factors. This work examines how the adhesion of human endothelial cells (ECs is influenced by a soluble tetrapeptide, Arg-Glu-Asp-Val (REDV and fluidic shear stress. The ability of these ECs to bind within microchannels coated with REDV is shown to be governed by shear- and soluble-factor mediated changes in p38 mitogen-activated protein kinase expression together with recycling of adhesion receptors from the endosome.

  6. Tuneable adhesion through novel binder technologies

    NARCIS (Netherlands)

    Wouters, M.E.L.; Burghoorn, M.M.A.; Ingenhut, B.; Timmer, K.; Rentrop, C.H.A.; Bots, T.L.; Oosterhuis, G.; Fischer, H.R.

    2011-01-01

    A reversible crosslinking mechanism enabling bonding and debonding of adhesives and coatings based on Diels-Alder chemistry is described. The Diels-Alder compounds form a covalently crosslinked network at low temperatures that break at elevated temperatures. As a result, the adhesive exhibits good s

  7. Focal adhesions and cell-matrix interactions

    DEFF Research Database (Denmark)

    Woods, A; Couchman, J R

    1988-01-01

    Focal adhesions are areas of cell surfaces where specializations of cytoskeletal, membrane and extracellular components combine to produce stable cell-matrix interactions. The morphology of these adhesions and the components identified in them are discussed together with possible mechanisms of th...

  8. Switchable adhesion by chemical functionality and topography

    NARCIS (Netherlands)

    Kamperman, M.M.G.; Synytska, A.

    2012-01-01

    Progress in adhesion technology over the last few decades has led to widespread replacement of mechanical fasteners with adhesive bonds. Despite the advances, it remains challenging to produce materials that are sticky on demand. In this feature article we highlight recent efforts to develop reversi

  9. Carbohydrate-binding specificities of potential probiotic Lactobacillus strains in porcine jejunal (IPEC-J2) cells and porcine mucin.

    Science.gov (United States)

    Valeriano, Valerie Diane; Bagon, Bernadette B; Balolong, Marilen P; Kang, Dae-Kyung

    2016-07-01

    Bacterial lectins are carbohydrate-binding adhesins that recognize glycoreceptors in the gut mucus and epithelium of hosts. In this study, the contribution of lectin-like activities to adhesion of Lactobacillus mucosae LM1 and Lactobacillus johnsonii PF01, which were isolated from swine intestine, were compared to those of the commercial probiotic Lactobacillus rhamnosus GG. Both LM1 and PF01 strains have been reported to have good adhesion ability to crude intestinal mucus of pigs. To confirm this, we quantified their adhesion to porcine gastric mucin and intestinal porcine enterocytes isolated from the jejunum of piglets (IPEC-J2). In addition, we examined their carbohydrate-binding specificities by suspending bacterial cells in carbohydrate solutions prior to adhesion assays. We found that the selected carbohydrates affected the adherences of LM1 to IPEC-J2 cells and of LGG to mucin. In addition, compared to adhesion to IPEC-J2 cells, adhesion to mucin by both LM1 and LGG was characterized by enhanced specific recognition of glycoreceptor components such as galactose, mannose, and N-acetylglucosamine. Hydrophobic interactions might make a greater contribution to adhesion of PF01. A similar adhesin profile between a probiotic and a pathogen, suggest a correlation between shared pathogen-probiotic glycoreceptor recognition and the ability to exclude enteropathogens such as Escherichia coli K88 and Salmonella Typhimurium KCCM 40253. These findings extend our understanding of the mechanisms of the intestinal adhesion and pathogen-inhibition abilities of probiotic Lactobacillus strains.

  10. Shear adhesion strength of aligned electrospun nanofibers.

    Science.gov (United States)

    Najem, Johnny F; Wong, Shing-Chung; Ji, Guang

    2014-09-01

    Inspiration from nature such as insects' foot hairs motivates scientists to fabricate nanoscale cylindrical solids that allow tens of millions of contact points per unit area with material substrates. In this paper, we present a simple yet robust method for fabricating directionally sensitive shear adhesive laminates. By using aligned electrospun nylon-6, we create dry adhesives, as a succession of our previous work on measuring adhesion energies between two single free-standing electrospun polymer fibers in cross-cylinder geometry, randomly oriented membranes and substrate, and peel forces between aligned fibers and substrate. The synthetic aligned cylindrical solids in this study are electrically insulating and show a maximal Mode II shear adhesion strength of 27 N/cm(2) on a glass slide. This measured value, for the purpose of comparison, is 270% of that reported from gecko feet. The Mode II shear adhesion strength, based on a commonly known "dead-weight" test, is 97-fold greater than the Mode I (normal) adhesion strength of the same. The data indicate a strong shear binding on and easy normal lifting off. Anisotropic adhesion (Mode II/Mode I) is pronounced. The size and surface boundary effects, crystallinity, and bending stiffness of fibers are used to understand these electrospun nanofibers, which vastly differ from otherwise known adhesive technologies. The anisotropic strength distribution is attributed to a decreasing fiber diameter and an optimized laminate thickness, which, in turn, influences the bending stiffness and solid-state "wettability" of points of contact between nanofibers and surface asperities.

  11. Novel gamete receptors that facilitate sperm adhesion to the egg coat.

    Science.gov (United States)

    Ensslin, Michael A; Lyng, Robert; Raymond, Adam; Copland, Susannah; Shur, Barry D

    2007-01-01

    Mammalian fertilization is initiated by species-specific binding of the sperm to the zona pellucida, or egg coat. Previous studies suggested that sperm adhesion to the egg coat is facilitated, at least in part, through the binding of sperm surface beta1 ,4-galactosyltransferase I (GaIT) to glycoside chains on the egg coat glycoprotein, ZP3. Binding of multiple ZP3 oligosaccharides induces aggregation of GaIT within the sperm membrane, triggering, directly or indirectly, a pertussis toxin sensitive G-protein cascade leading to induction of the acrosome reaction. Consistent with this, spermatozoa bearing targeted deletions in GaIT are unable to bind ZP3 or undergo ZP3-dependent acrosomal exocytosis; however, unexpectedly, GaIT-null sperm are still able to bind to the egg coat. This indicates that sperm-egg binding requires at least two independent binding mechanisms; a GaIT-ZP3-independent event that mediates initial adhesion, followed by a GaIT-ZP3 interaction that facilitates acrosomal exocytosis. Our recent efforts have focused on the identification and characterization of these novel gamete receptors. One recently identified sperm protein that is required for sperm adhesion to the egg coat is SED1. SED1 is a bimotif protein composed of two Notch-like EGF repeats and two discoidin/complement F5/8 domains. SED1 is secreted by the epididymal epithelium and coats spermatozoa as they progress through the epididymis. Spermatozoa null for SED1 fail to bind the egg coat, illustrating its requirement for gamete adhesion. Interestingly, SED1 is also expressed by a variety of other epithelial tissues, where it appears to be required for epithelial morphogenesis and/or maintenance. A second novel gamete receptor has recently been identified on the coat of ovulated oocytes. This ZP3-independent, egg coat component is a high molecular weight, wheat germ agglutinin (WGA)-reactive glycoprotein that is derived from oviduct secretions and appears to participate in initial sperm

  12. Structure of a Blm10 Complex Reveals Common Mechanisms for Proteasome Binding and Gate Opening

    Energy Technology Data Exchange (ETDEWEB)

    Sadre-Bazzaz, K.; Robinson, H.; Whitby, F. G.; Formosa, T.; Hill, C. P.

    2010-03-12

    The proteasome is an abundant protease that is critically important for numerous cellular pathways. Proteasomes are activated in vitro by three known classes of proteins/complexes, including Blm10/PA200. Here, we report a 3.4 {angstrom} resolution crystal structure of a proteasome-Blm10 complex, which reveals that Blm10 surrounds the proteasome entry pore in the 1.2 MDa complex to form a largely closed dome that is expected to restrict access of potential substrates. This architecture and the observation that Blm10 induces a disordered proteasome gate structure challenge the assumption that Blm10 functions as an activator of proteolysis in vivo. The Blm10 C terminus binds in the same manner as seen for 11S activators and inferred for 19S/PAN activators and indicates a unified model for gate opening. We also demonstrate that Blm10 acts to maintain mitochondrial function. Consistent with the structural data, the C-terminal residues of Blm10 are needed for this activity.

  13. Human climbing with efficiently scaled gecko-inspired dry adhesives.

    Science.gov (United States)

    Hawkes, Elliot W; Eason, Eric V; Christensen, David L; Cutkosky, Mark R

    2015-01-01

    Since the discovery of the mechanism of adhesion in geckos, many synthetic dry adhesives have been developed with desirable gecko-like properties such as reusability, directionality, self-cleaning ability, rough surface adhesion and high adhesive stress. However, fully exploiting these adhesives in practical applications at different length scales requires efficient scaling (i.e. with little loss in adhesion as area grows). Just as natural gecko adhesives have been used as a benchmark for synthetic materials, so can gecko adhesion systems provide a baseline for scaling efficiency. In the tokay gecko (Gekko gecko), a scaling power law has been reported relating the maximum shear stress σmax to the area A: σmax ∝ A(-1/4). We present a mechanical concept which improves upon the gecko's non-uniform load-sharing and results in a nearly even load distribution over multiple patches of gecko-inspired adhesive. We created a synthetic adhesion system incorporating this concept which shows efficient scaling across four orders of magnitude of area, yielding an improved scaling power law: σmax ∝ A(-1/50). Furthermore, we found that the synthetic adhesion system does not fail catastrophically when a simulated failure is induced on a portion of the adhesive. In a practical demonstration, the synthetic adhesion system enabled a 70 kg human to climb vertical glass with 140 cm(2) of adhesive per hand.

  14. Computational Chemistry of Adhesive Bonds

    Science.gov (United States)

    Phillips, Donald H.

    1999-01-01

    This investigation is intended to determine the electrical mechanical, and chemical properties of adhesive bonds at the molecular level. The initial determinations will be followed by investigations of the effects of environmental effects on the chemistry and properties of the bond layer.

  15. Human formyl peptide receptor ligand binding domain(s). Studies using an improved mutagenesis/expression vector reveal a novel mechanism for the regulation of receptor occupancy.

    Science.gov (United States)

    Perez, H D; Vilander, L; Andrews, W H; Holmes, R

    1994-09-09

    Recently, we reported the domain requirements for the binding of formyl peptide to its specific receptor. Based on experiments using receptor chimeras, we also postulated an importance for the amino-terminal domain of the receptor in ligand binding (Perez, H. D., Holmes, R., Vilander, L., Adams, R., Manzana, W., Jolley, D., and Andrews, W. H. (1993) J. Biol. Chem. 268, 2292-2295). We have begun to perform a detailed analysis of the regions within the formyl peptide receptor involved in ligand binding. To address the importance of the receptor amino-terminal domain, we substituted (or inserted) hydrophilic sequences within the amino-terminal domain, expressed the receptors, and determined their ability to bind ligand. A stretch of nine amino acids next to the initial methionine was identified as crucial for receptor occupancy. A peptide containing such a sequence specifically completed binding of the ligand to the receptor. Alanine screen mutagenesis of the second extracellular domain also identified amino acids involved in ligand binding as well as a disulfide bond (Cys98 to Cys176) crucial for maintaining the binding pocket. These studies provide evidence for a novel mechanism involved in regulation of receptor occupancy. Binding of the ligand induces conformational changes in the receptor that result in the apposition of the amino-terminal domain over the ligand, providing a lid to the binding pocket.

  16. Focal Adhesion-Independent Cell Migration.

    Science.gov (United States)

    Paluch, Ewa K; Aspalter, Irene M; Sixt, Michael

    2016-10-06

    Cell migration is central to a multitude of physiological processes, including embryonic development, immune surveillance, and wound healing, and deregulated migration is key to cancer dissemination. Decades of investigations have uncovered many of the molecular and physical mechanisms underlying cell migration. Together with protrusion extension and cell body retraction, adhesion to the substrate via specific focal adhesion points has long been considered an essential step in cell migration. Although this is true for cells moving on two-dimensional substrates, recent studies have demonstrated that focal adhesions are not required for cells moving in three dimensions, in which confinement is sufficient to maintain a cell in contact with its substrate. Here, we review the investigations that have led to challenging the requirement of specific adhesions for migration, discuss the physical mechanisms proposed for cell body translocation during focal adhesion-independent migration, and highlight the remaining open questions for the future.

  17. Silver nanoparticles-loaded activated carbon fibers using chitosan as binding agent: Preparation, mechanism, and their antibacterial activity

    Science.gov (United States)

    Tang, Chengli; Hu, Dongmei; Cao, Qianqian; Yan, Wei; Xing, Bo

    2017-02-01

    The effective and strong adherence of silver nanoparticles (AgNPs) to the substrate surface is pivotal to the practical application of those AgNPs-modified materials. In this work, AgNPs were synthesized through a green and facile hydrothermal method. Chitosan was introduced as the binding agent for the effective loading of AgNPs on activated carbon fibers (ACF) surface to fabricate the antibacterial material. Apart from conventional instrumental characterizations, i. e., scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), zeta potential and Brunauer-Emmett-Teller (BET) surface area measurement, molecular dynamics simulation method was also applied to explore the loading mechanism of AgNPs on the ACF surface. The AgNPs-loaded ACF material showed outstanding antibacterial activity for S. aureus and E. coli. The combination of experimental and theoretical calculation results proved chitosan to be a promising binding agent for the fabrication of AgNPs-loaded ACF material with excellent antibacterial activity.

  18. The function of the RNA-binding protein TEL1 in moss reveals ancient regulatory mechanisms of shoot development.

    Science.gov (United States)

    Vivancos, Julien; Spinner, Lara; Mazubert, Christelle; Charlot, Florence; Paquet, Nicolas; Thareau, Vincent; Dron, Michel; Nogué, Fabien; Charon, Céline

    2012-03-01

    The shoot represents the basic body plan in land plants. It consists of a repeated structure composed of stems and leaves. Whereas vascular plants generate a shoot in their diploid phase, non-vascular plants such as mosses form a shoot (called the gametophore) in their haploid generation. The evolution of regulatory mechanisms or genetic networks used in the development of these two kinds of shoots is unclear. TERMINAL EAR1-like genes have been involved in diploid shoot development in vascular plants. Here, we show that disruption of PpTEL1 from the moss Physcomitrella patens, causes reduced protonema growth and gametophore initiation, as well as defects in gametophore development. Leafy shoots formed on ΔTEL1 mutants exhibit shorter stems with more leaves per shoot, suggesting an accelerated leaf initiation (shortened plastochron), a phenotype shared with the Poaceae vascular plants TE1 and PLA2/LHD2 mutants. Moreover, the positive correlation between plastochron length and leaf size observed in ΔTEL1 mutants suggests a conserved compensatory mechanism correlating leaf growth and leaf initiation rate that would minimize overall changes in plant biomass. The RNA-binding protein encoded by PpTEL1 contains two N-terminus RNA-recognition motifs, and a third C-terminus non-canonical RRM, specific to TEL proteins. Removal of the PpTEL1 C-terminus (including this third RRM) or only 16-18 amino acids within it seriously impairs PpTEL1 function, suggesting a critical role for this third RRM. These results show a conserved function of the RNA-binding PpTEL1 protein in the regulation of shoot development, from early ancestors to vascular plants, that depends on the third TEL-specific RRM.

  19. Application of the quantum mechanical IEF/PCM-MST hydrophobic descriptors to selectivity in ligand binding.

    Science.gov (United States)

    Ginex, Tiziana; Muñoz-Muriedas, Jordi; Herrero, Enric; Gibert, Enric; Cozzini, Pietro; Luque, F Javier

    2016-06-01

    We have recently reported the development and validation of quantum mechanical (QM)-based hydrophobic descriptors derived from the parametrized IEF/PCM-MST continuum solvation model for 3D-QSAR studies within the framework of the Hydrophobic Pharmacophore (HyPhar) method. In this study we explore the applicability of these descriptors to the analysis of selectivity fields. To this end, we have examined a series of 88 compounds with inhibitory activities against thrombin, trypsin and factor Xa, and the HyPhar results have been compared with 3D-QSAR models reported in the literature. The quantitative models obtained by combining the electrostatic and non-electrostatic components of the octanol/water partition coefficient yield results that compare well with the predictive potential of standard CoMFA and CoMSIA techniques. The results also highlight the potential of HyPhar descriptors to discriminate the selectivity of the compounds against thrombin, trypsin, and factor Xa. Moreover, the graphical representation of the hydrophobic maps provides a direct linkage with the pattern of interactions found in crystallographic structures. Overall, the results support the usefulness of the QM/MST-based hydrophobic descriptors as a complementary approach for disclosing structure-activity relationships in drug design and for gaining insight into the molecular determinants of ligand selectivity. Graphical Abstract Quantum Mechanical continuum solvation calculations performed with the IEF/PCM-MST method are used to derived atomic hydrophobic descriptors, which are then used to discriminate the selectivity of ligands against thrombin, trypsin and factor Xa. The descriptors provide complementary view to standard 3D-QSAR analysis, leading to a more comprehensive understanding of ligand recognition.

  20. BIOLOGICAL ADHESIVES. Adaptive synergy between catechol and lysine promotes wet adhesion by surface salt displacement.

    Science.gov (United States)

    Maier, Greg P; Rapp, Michael V; Waite, J Herbert; Israelachvili, Jacob N; Butler, Alison

    2015-08-01

    In physiological fluids and seawater, adhesion of synthetic polymers to solid surfaces is severely limited by high salt, pH, and hydration, yet these conditions have not deterred the evolution of effective adhesion by mussels. Mussel foot proteins provide insights about adhesive adaptations: Notably, the abundance and proximity of catecholic Dopa (3,4-dihydroxyphenylalanine) and lysine residues hint at a synergistic interplay in adhesion. Certain siderophores—bacterial iron chelators—consist of paired catechol and lysine functionalities, thereby providing a convenient experimental platform to explore molecular synergies in bioadhesion. These siderophores and synthetic analogs exhibit robust adhesion energies (E(ad) ≥-15 millijoules per square meter) to mica in saline pH 3.5 to 7.5 and resist oxidation. The adjacent catechol-lysine placement provides a "one-two punch," whereby lysine evicts hydrated cations from the mineral surface, allowing catechol binding to underlying oxides.

  1. Using docking and alchemical free energy approach to determine the binding mechanism of eEF2K inhibitors and prioritizing the compound synthesis.

    Science.gov (United States)

    Wang, Qiantao; Edupuganti, Ramakrishna; Tavares, Clint D J; Dalby, Kevin N; Ren, Pengyu

    2015-01-01

    A-484954 is a known eEF2K inhibitor with submicromolar IC50 potency. However, the binding mechanism and the crystal structure of the kinase remains unknown. Here, we employ a homology eEF2K model, docking and alchemical free energy simulations to probe the binding mechanism of eEF2K, and in turn, guide the optimization of potential lead compounds. The inhibitor was docked into the ATP-binding site of a homology model first. Three different binding poses, hypothesis 1, 2, and 3, were obtained and subsequently applied to molecular dynamics (MD) based alchemical free energy simulations. The calculated relative binding free energy of the analogs of A-484954 using the binding pose of hypothesis 1 show a good correlation with the experimental IC50 values, yielding an r (2) coefficient of 0.96 after removing an outlier (compound 5). Calculations using another two poses show little correlation with experimental data, (r (2) of less than 0.5 with or without removing any outliers). Based on hypothesis 1, the calculated relative free energy suggests that bigger cyclic groups, at R1 e.g., cyclobutyl and cyclopentyl promote more favorable binding than smaller groups, such as cyclopropyl and hydrogen. Moreover, this study also demonstrates the ability of the alchemical free energy approach in combination with docking and homology modeling to prioritize compound synthesis. This can be an effective means of facilitating structure-based drug design when crystal structures are not available.

  2. Properties of Nano SiO2 Modified PVF Adhesive

    Institute of Scientific and Technical Information of China (English)

    CHEN He-sheng; SUN Zhen-ya; XUE Li-hui

    2004-01-01

    Some properties of nano SiO2 modified PVF adhesive were studied. The experimental results show that nano SiO2 can improve the properties of PVF adhesive very well. Meanwhile the modification mechanism of nano SiO2 to PVF adhesive and the applications of this adhesive in paper-plastic composite, concrete and fireproof paint were discussed by using IR and XRD determination.

  3. Adhesion of Plasmodium falciparum infected erythrocytes in ex vivo perfused placental tissue

    DEFF Research Database (Denmark)

    Pehrson, Caroline; Mathiesen, Line; Heno, Kristine K;

    2016-01-01

    BACKGROUND: Placental malaria occurs when Plasmodium falciparum infected erythrocytes sequester in the placenta. Placental parasite isolates bind to chondroitin sulphate A (CSA) by expression of VAR2CSA on the surface of infected erythrocytes, but may sequester by other VAR2CSA mediated mechanisms...... placental tissue. RESULTS: The ex vivo placental perfusion model was modified to study adhesion of infected erythrocytes binding to CSA, endothelial protein C receptor (EPCR) or a transgenic parasite where P. falciparum erythrocyte membrane protein 1 expression had been shut down. Infected erythrocytes...... expressing VAR2CSA accumulated in perfused placental tissue whereas the EPCR binding and the transgenic parasite did not. Soluble CSA and antibodies specific against VAR2CSA inhibited binding of infected erythrocytes. CONCLUSION: The ex vivo model provides a novel way of studying receptor-ligand interactions...

  4. Adhesive loose packings of small dry particles

    Science.gov (United States)

    Liu, Wenwei; Li, Shuiqing; Baule, Adrian; Makse, Hernán A.

    We explore adhesive loose packings of dry small spherical particles of micrometer size using 3D discrete-element simulations with adhesive contact mechanics. A dimensionless adhesion parameter ($Ad$) successfully combines the effects of particle velocities, sizes and the work of adhesion, identifying a universal regime of adhesive packings for $Ad>1$. The structural properties of the packings in this regime are well described by an ensemble approach based on a coarse-grained volume function that includes correlations between bulk and contact spheres. Our theoretical and numerical results predict: (i) An equation of state for adhesive loose packings that appears as a continuation from the frictionless random close packing (RCP) point in the jamming phase diagram; (ii) The existence of a maximal loose packing point at the coordination number $Z=2$ and packing fraction $\\phi=1/2^{3}$. Our results highlight that adhesion leads to a universal packing regime at packing fractions much smaller than the random loose packing, which can be described within a statistical mechanical framework. We present a general phase diagram of jammed matter comprising frictionless, frictional, adhesive as well as non-spherical particles, providing a classification of packings in terms of their continuation from the spherical frictionless RCP.

  5. Macromolecular depletion modulates the binding of red blood cells to activated endothelial cells.

    Science.gov (United States)

    Yang, Yang; Koo, Stephanie; Lin, Cheryl Shuyi; Neu, Björn

    2010-09-01

    Adhesion of red blood cells (RBCs) to endothelial cells (ECs) is usually insignificant but an enhanced adhesion has been observed in various diseases associated with vascular complications. This abnormal adhesion under pathological conditions such as sickle cell disease has been correlated with increased levels of various plasma proteins but the detailed underlying mechanism(s) remains unclear. Usually it is assumed that the proadhesive effects of plasma proteins originate from ligand interactions cross-linking receptors on adjacent cells, but explicit results detailing binding sites or receptors for some proteins (e.g., fibrinogen) on either RBC or EC surfaces that would support this model are missing. In this study, the authors tested whether there is an alternative mechanism. Their results demonstrate that dextran 2 MDa promotes the adhesion of normal RBCs to thrombin-activated ECs and that this effect becomes more pronounced with increasing thrombin concentration or with prolonged thrombin incubation time. It is concluded that depletion interaction originating from nonadsorbing macromolecules (i.e., dextran) can modulate the adhesion of red blood cells to thrombin-activated EC. This study thereby suggests macromolecular depletion as an alternative mechanism for the adhesion-promoting effects of nonadsorbing plasma proteins. These findings should not only aid in getting a better understanding of diseases associated with vascular complications but should also have many potential applications in biomedical or biotechnological areas that require the control of cell-cell or cell surface interactions.

  6. PH dependent adhesive peptides

    Science.gov (United States)

    Tomich, John; Iwamoto, Takeo; Shen, Xinchun; Sun, Xiuzhi Susan

    2010-06-29

    A novel peptide adhesive motif is described that requires no receptor or cross-links to achieve maximal adhesive strength. Several peptides with different degrees of adhesive strength have been designed and synthesized using solid phase chemistries. All peptides contain a common hydrophobic core sequence flanked by positively or negatively charged amino acids sequences.

  7. Binding, tuning and mechanical function of the 4-hydroxy-cinnamic acid chromophore in photoactive yellow protein

    NARCIS (Netherlands)

    Horst, M.A. van der; Arents, J.C.; Kort, R.; Hellingwerf, K.J.

    2007-01-01

    The bacterial photoreceptor protein photoactive yellow protein (PYP) covalently binds the chromophore 4-hydroxy coumaric acid, tuning (spectral) characteristics of this cofactor. Here, we study this binding and tuning using a combination of pointmutations and chromophore analogs. In all photosensor

  8. Short Peptides Enhance Single Cell Adhesion and Viability onMicroarrays

    Energy Technology Data Exchange (ETDEWEB)

    Veiseh, Mandana; Veiseh, Omid; Martin, Michael C.; Asphahani,Fareid; Zhang, Miqin

    2007-01-19

    Single cell patterning holds important implications forbiology, biochemistry, biotechnology, medicine, and bioinformatics. Thechallenge for single cell patterning is to produce small islands hostingonly single cells and retaining their viability for a prolonged period oftime. This study demonstrated a surface engineering approach that uses acovalently bound short peptide as a mediator to pattern cells withimproved single cell adhesion and prolonged cellular viabilityon goldpatterned SiO2 substrates. The underlying hypothesis is that celladhesion is regulated bythe type, availability, and stability ofeffective cell adhesion peptides, and thus covalently bound shortpeptides would promote cell spreading and, thus, single cell adhesion andviability. The effectiveness of this approach and the underlyingmechanism for the increased probability of single cell adhesion andprolonged cell viability by short peptides were studied by comparingcellular behavior of human umbilical cord vein endothelial cells on threemodelsurfaces whose gold electrodes were immobilized with fibronectin,physically adsorbed Arg-Glu-Asp-Val-Tyr, and covalently boundLys-Arg-Glu-Asp-Val-Tyr, respectively. The surface chemistry and bindingproperties were characterized by reflectance Fourier transform infraredspectroscopy. Both short peptides were superior to fibronectin inproducing adhesion of only single cells, whereas the covalently boundpeptide also reduced apoptosis and necrosisof adhered cells. Controllingcell spreading by peptide binding domains to regulate apoptosis andviability represents a fundamental mechanism in cell-materialsinteraction and provides an effective strategy in engineering arrays ofsingle cells.

  9. Adhesion of subsets of human blood mononuclear cells to porcine endothelial cells

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Cellular immune response is a major barrier to xenotransplantation, and cell adhesion is the first step in intercellular recognition. Flow-cytometric adhesion assay has been used to investigate the differential adhesions of monocyte (Mo), natural killer cell (NK) and T lymphocyte (T) present within human peripheral blood mononuclear cells (PBMC) to porcine aortic endothelial cells (PAEC), and to demonstrate the effect of human interferon-γ(hIFN-γ) or/and tumor necrosis factor-α (hTNF-α) pretreatment of PAEC on their adhesiveness for different PBMC subsets. The preferential sequence for PBMC subset binding to resting PAEC is Mo, NK and T cells, among which T cells show the slightest adherence; hTNF-α can act across the species, and augment Mo, NK and T cell adhesion ratios by 40%, 110% and 3 times, respectively. These results confirm at the cell level that host Mo and NK cells are major participants in the cellular xenograft rejection, thereby, providing a prerequisite for further studying the human Mo/NK-PAEC interactive mechanisms.

  10. RNA-Binding Proteins in Trichomonas vaginalis: Atypical Multifunctional Proteins Involved in a Posttranscriptional Iron Regulatory Mechanism

    Science.gov (United States)

    Figueroa-Angulo, Elisa E.; Calla-Choque, Jaeson S.; Mancilla-Olea, Maria Inocente; Arroyo, Rossana

    2015-01-01

    Iron homeostasis is highly regulated in vertebrates through a regulatory system mediated by RNA-protein interactions between the iron regulatory proteins (IRPs) that interact with an iron responsive element (IRE) located in certain mRNAs, dubbed the IRE-IRP regulatory system. Trichomonas vaginalis, the causal agent of trichomoniasis, presents high iron dependency to regulate its growth, metabolism, and virulence properties. Although T. vaginalis lacks IRPs or proteins with aconitase activity, possesses gene expression mechanisms of iron regulation at the transcriptional and posttranscriptional levels. However, only one gene with iron regulation at the transcriptional level has been described. Recently, our research group described an iron posttranscriptional regulatory mechanism in the T. vaginalis tvcp4 and tvcp12 cysteine proteinase mRNAs. The tvcp4 and tvcp12 mRNAs have a stem-loop structure in the 5'-coding region or in the 3'-UTR, respectively that interacts with T. vaginalis multifunctional proteins HSP70, α-Actinin, and Actin under iron starvation condition, causing translation inhibition or mRNA stabilization similar to the previously characterized IRE-IRP system in eukaryotes. Herein, we summarize recent progress and shed some light on atypical RNA-binding proteins that may participate in the iron posttranscriptional regulation in T. vaginalis. PMID:26703754

  11. Theoretical Characterization of the Spectral Density of the Water-Soluble Chlorophyll-Binding Protein from Combined Quantum Mechanics/Molecular Mechanics Molecular Dynamics Simulations.

    Science.gov (United States)

    Rosnik, Andreana M; Curutchet, Carles

    2015-12-08

    Over the past decade, both experimentalists and theorists have worked to develop methods to describe pigment-protein coupling in photosynthetic light-harvesting complexes in order to understand the molecular basis of quantum coherence effects observed in photosynthesis. Here we present an improved strategy based on the combination of quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) simulations and excited-state calculations to predict the spectral density of electronic-vibrational coupling. We study the water-soluble chlorophyll-binding protein (WSCP) reconstituted with Chl a or Chl b pigments as the system of interest and compare our work with data obtained by Pieper and co-workers from differential fluorescence line-narrowing spectra (Pieper et al. J. Phys. Chem. B 2011, 115 (14), 4042-4052). Our results demonstrate that the use of QM/MM MD simulations where the nuclear positions are still propagated at the classical level leads to a striking improvement of the predicted spectral densities in the middle- and high-frequency regions, where they nearly reach quantitative accuracy. This demonstrates that the so-called "geometry mismatch" problem related to the use of low-quality structures in QM calculations, not the quantum features of pigments high-frequency motions, causes the failure of previous studies relying on similar protocols. Thus, this work paves the way toward quantitative predictions of pigment-protein coupling and the comprehension of quantum coherence effects in photosynthesis.

  12. Understanding adhesive dentistry.

    Science.gov (United States)

    Burrow, Michael

    2010-03-01

    This review paper firstly provides an outline of the development of resin-based adhesives. A simple classification method is described based on whether an acid etching agent requiring a washing and drying step is used. These systems are called etch and rinse systems. The other adhesives that do not have the washing and drying steps are referred to as self-etching adhesives. The advantages and disadvantages of these groups of adhesives are discussed. Methods of adhering to the tooth surface are provided, especially where the resin-based adhesive reliability is difficult to control.

  13. Postoperative Complications Leading to Death after Coagulum Pyelolithotomy in a Tetraplegic Patient: Can We Prevent Prolonged Ileus, Recurrent Intestinal Obstruction due to Adhesions Requiring Laparotomies, Chest Infection Warranting Tracheostomy, and Mechanical Ventilation?

    Directory of Open Access Journals (Sweden)

    Subramanian Vaidyanathan

    2013-01-01

    Full Text Available A 22-year-old male sustained C-6 tetraplegia in 1992. In 1993, intravenous pyelography revealed normal kidneys. Suprapubic cystostomy was performed. He underwent open cystolithotomy in 2004 and 2008. In 2009, computed tomography revealed bilateral renal calculi. Coagulum pyelolithotomy of left kidney was performed. Pleura and peritoneum were opened. Peritoneum could not be closed. Following surgery, he developed pulmonary atelectasis; he required tracheostomy and mechanical ventilation. He did not tolerate nasogastric feeding. CT of abdomen revealed bilateral renal calculi and features of proximal small bowel obstruction. Laparotomy revealed small bowel obstruction due to dense inflammatory adhesions involving multiple small bowel loops which protruded through the defect in sigmoid mesocolon and fixed posteriorly over the area of previous intervention. All adhesions were divided. The wide defect in mesocolon was not closed. In 2010, this patient again developed vomiting and distension of abdomen. Laparotomy revealed multiple adhesions. He developed chest infection and required ventilatory support again. He developed pressure sores and depression. Later abdominal symptoms recurred. This patient’s general condition deteriorated and he expired in 2011. Conclusion. Risk of postoperative complications could have been reduced if minimally invasive surgery had been performed instead of open surgery to remove stones from left kidney. Suprapubic cystostomy predisposed to repeated occurrence of stones in urinary bladder and kidneys. Spinal cord physicians should try to establish intermittent catheterisation regime in tetraplegic patients.

  14. Mechanisms of recognition and binding of α-TTP to the plasma membrane by multi-scale molecular dynamics simulations

    Directory of Open Access Journals (Sweden)

    Christos eLamprakis

    2015-07-01

    Full Text Available We used multiple sets of simulations both at the atomistic and coarse-grained level of resolution, to investigate interaction and binding of α-tochoperol transfer protein (α-TTP to phosphatidylinositol phosphate lipids (PIPs. Our calculations indicate that enrichment of membranes with such lipids facilitate membrane anchoring. Atomistic models suggest that PIP can be incorporated into the binding cavity of α-TTP and therefore confirm that such protein can work as lipid exchanger between the endosome and the plasma membrane. Comparison of the atomistic models of the α-TTP / PIPs complex with membrane-bound α-TTP revealed different roles for the various basic residues composing the basic patch that is key for the protein / ligand interaction. Such residues are of critical importance as several point mutations at their position lead to severe forms of ataxia with vitamin E deficiency (AVED phenotypes. Specifically, R221 is main residue responsible for the stabilisation of the complex. R68 and R192 exchange strong interactions in the protein or in the membrane complex only, suggesting that the two residues alternate contact formation, thus facilitating lipid flipping from the membrane into the protein cavity during the lipid exchange process. Finally, R59 shows weaker interactions with PIPs anyway with a clear preference for specific phosphorylation positions, hinting a role in early membrane selectivity for the protein. Altogether, our simulations reveal significant aspects at the atomistic scale of interactions of α-TTP with the plasma membrane and with PIP, providing clarifications on the mechanism of intracellular vitamin E trafficking and helping establishing the role of key residue for the functionality of α-TTP.

  15. Adhesion of microchannel-based complementary surfaces.

    Science.gov (United States)

    Singh, Arun K; Bai, Ying; Nadermann, Nichole; Jagota, Anand; Hui, Chung-Yuen

    2012-03-06

    We show that highly enhanced and selective adhesion can be achieved between surfaces patterned with complementary microchannel structures. An elastic material, poly(dimethylsiloxane) (PDMS), was used to fabricate such surfaces by molding into a silicon master with microchannel profiles patterned by photolithography. We carried out adhesion tests on both complementary and mismatched microchannel/micropillar surfaces. Adhesion, as measured by the energy release rate required to propagate an interfacial crack, can be enhanced by up to 40 times by complementary interfaces, compared to a flat control, and slightly enhanced for some special noncomplementary samples, despite the nearly negligible adhesion for other mismatched surfaces. For each complementary surface, we observe defects in the form of visible striations, where pillars fail to insert fully into the channels. The adhesion between complementary microchannel surfaces is enhanced by a combination of a crack-trapping mechanism and friction between a pillar and channel and is attenuated by the presence of defects.

  16. Endotoxin/lipopolysaccharide activates NF-kappa B and enhances tumor cell adhesion and invasion through a beta 1 integrin-dependent mechanism.

    LENUS (Irish Health Repository)

    Wang, Jiang Huai

    2012-02-03

    Beta(1) integrins play a crucial role in supporting tumor cell attachment to and invasion into the extracellular matrix. Endotoxin\\/LPS introduced by surgery has been shown to enhance tumor metastasis in a murine model. Here we show the direct effect of LPS on tumor cell adhesion and invasion in extracellular matrix proteins through a beta(1) integrin-dependent pathway. The human colorectal tumor cell lines SW480 and SW620 constitutively expressed high levels of the beta(1) subunit, whereas various low levels of alpha(1), alpha(2), alpha(4), and alpha(6) expression were detected. SW480 and SW620 did not express membrane-bound CD14; however, LPS in the presence of soluble CD14 (sCD14) significantly up-regulated beta(1) integrin expression; enhanced tumor cell attachment to fibronectin, collagen I, and laminin; and strongly promoted tumor cell invasion through the Matrigel. Anti-beta(1) blocking mAbs (4B4 and 6S6) abrogated LPS- plus sCD14-induced tumor cell adhesion and invasion. Furthermore, LPS, when combined with sCD14, resulted in NF-kappaB activation in both SW480 and SW620 cells. Inhibition of the NF-kappaB pathway significantly attenuated LPS-induced up-regulation of beta(1) integrin expression and prevented tumor cell adhesion and invasion. These results provide direct evidence that although SW480 and SW620 cells do not express membrane-bound CD14, LPS in the presence of sCD14 can activate NF-kappaB, up-regulate beta(1) integrin expression, and subsequently promote tumor cell adhesion and invasion. Moreover, LPS-induced tumor cell attachment to and invasion through extracellular matrix proteins is beta(1) subunit-dependent.

  17. In silico analysis of molecular mechanisms of Galanthus nivalis agglutinin-related lectin-induced cancer cell death from carbohydrate-binding motif evolution hypothesis.

    Science.gov (United States)

    Yu, Qi-Jia; Li, Zi-Yue; Yao, Shun; Ming, Miao; Wang, Shu-Ya; Liu, Bo; Bao, Jin-Ku

    2011-10-01

    Galanthus nivalis agglutinin-related lectins, a superfamily of strictly mannose-binding-specific lectins widespread amongst monotyledonous plants, have drawn a rising attention for their remarkable anti-proliferative and apoptosis-inducing activities toward various types of cancer cells; however, the precise molecular mechanisms by which they induce tumor cell apoptosis are still only rudimentarily understood. Herein, we found that the three conserved motifs "QXDXNXVXY," the mannose-specific binding sites, could mutate at one or more amino acid sites, which might be a driving force for the sequential evolution and thus ultimately leading to the complete disappearance of the three conserved motifs. In addition, we found that the motif evolution could result in the diversification of sugar-binding types that G. nivalis agglutinin-related lectins could bind from specific mannose receptors to more types of sugar-containing receptors in cancer cells. Subsequently, we indicated that some sugar-containing receptors such as TNFR1, EGFR, Hsp90, and Hsp70 could block downstream anti-apoptotic or survival signaling pathways, which, in turn, resulted in tumor cell apoptosis. Taken together, our hypothesis that carbohydrate-binding motif evolution may impact the G. nivalis agglutinin-related lectin-induced survival or anti-apoptotic pathways would provide a new perspective for further elucidating the intricate relationships between the carbohydrate-binding specificities and complex molecular mechanisms by which G. nivalis agglutinin-related lectins induce cancer cell death.

  18. The O-glycosylated ectodomain of FXYD5 impairs adhesion by disrupting cell-cell trans-dimerization of Na,K-ATPase β1 subunits.

    Science.gov (United States)

    Tokhtaeva, Elmira; Sun, Haying; Deiss-Yehiely, Nimrod; Wen, Yi; Soni, Pritin N; Gabrielli, Nieves M; Marcus, Elizabeth A; Ridge, Karen M; Sachs, George; Vazquez-Levin, Mónica; Sznajder, Jacob I; Vagin, Olga; Dada, Laura A

    2016-06-15

    FXYD5 (also known as dysadherin), a regulatory subunit of the Na,K-ATPase, impairs intercellular adhesion by a poorly understood mechanism. Here, we determined whether FXYD5 disrupts the trans-dimerization of Na,K-ATPase molecules located in neighboring cells. Mutagenesis of the Na,K-ATPase β1 subunit identified four conserved residues, including Y199, that are crucial for the intercellular Na,K-ATPase trans-dimerization and adhesion. Modulation of expression of FXYD5 or of the β1 subunit with intact or mutated β1-β1 binding sites demonstrated that the anti-adhesive effect of FXYD5 depends on the presence of Y199 in the β1 subunit. Immunodetection of the plasma membrane FXYD5 was prevented by the presence of O-glycans. Partial FXYD5 deglycosylation enabled antibody binding and showed that the protein level and the degree of O-glycosylation were greater in cancer than in normal cells. FXYD5-induced impairment of adhesion was abolished by both genetic and pharmacological inhibition of FXYD5 O-glycosylation. Therefore, the extracellular O-glycosylated domain of FXYD5 impairs adhesion by interfering with intercellular β1-β1 interactions, suggesting that the ratio between FXYD5 and α1-β1 heterodimer determines whether the Na,K-ATPase acts as a positive or negative regulator of intercellular adhesion.

  19. Effects of nitric oxide-releasing nonsteroidal anti-inflammatory drugs (NONO-NSAIDs) on melanoma cell adhesion

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Huiwen [Edison Biotechnology Institute, Ohio University, Athens, OH 45701 (United States); Department of Chemistry and Biochemistry, Ohio University, Athens, OH 45701 (United States); Mollica, Molly Y.; Lee, Shin Hee [Edison Biotechnology Institute, Ohio University, Athens, OH 45701 (United States); Wang, Lei [Edison Biotechnology Institute, Ohio University, Athens, OH 45701 (United States); Department of Chemistry and Biochemistry, Ohio University, Athens, OH 45701 (United States); Velázquez-Martínez, Carlos A., E-mail: velazque@ualberta.ca [Chemistry Section, Laboratory of Comparative Carcinogenesis and Basic Research Program, SAIC-Frederick Inc., National Cancer Institute at Frederick, Frederick, MD 21702 (United States); Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton Alberta, Canada T6G 2N8 (Canada); Wu, Shiyong, E-mail: wus1@ohio.edu [Edison Biotechnology Institute, Ohio University, Athens, OH 45701 (United States); Department of Chemistry and Biochemistry, Ohio University, Athens, OH 45701 (United States)

    2012-10-15

    A new class of nitric oxide (NO•)-releasing nonsteroidal anti-inflammatory drugs (NONO-NSAIDs) were developed in recent years and have shown promising potential as NSAID substitutes due to their gentle nature on cardiovascular and gastrointestinal systems. Since nitric oxide plays a role in regulation of cell adhesion, we assessed the potential use of NONO-NSAIDs as anti-metastasis drugs. In this regard, we compared the effects of NONO-aspirin and a novel NONO-naproxen to those exerted by their respective parent NSAIDs on avidities of human melanoma M624 cells. Both NONO-NSAIDs, but not the corresponding parent NSAIDs, reduced M624 adhesion on vascular cellular adhesion molecule-1 (VCAM-1) by 20–30% and fibronectin by 25–44% under fluid flow conditions and static conditions, respectively. Only NONO-naproxen reduced (∼ 56%) the activity of β1 integrin, which binds to α4 integrin to form very late antigen-4 (VLA-4), the ligand of VCAM-1. These results indicate that the diazeniumdiolate (NO•)-donor moiety is critical for reducing the adhesion between VLA-4 and its ligands, while the NSAID moiety can impact the regulation mechanism of melanoma cell adhesion. -- Highlights: ► NONO-naproxen, a novel nitric oxide-releasing NSAID, was synthesized. ► NONO-NSAIDs, but not their parent NSAIDs, reduced melanoma adhesion. ► NONO-naproxen, but not NONO-aspirin and NSAIDs, reduced activity of β1 integrin.

  20. Microtubule-dependent modulation of adhesion complex composition.

    Science.gov (United States)

    Ng, Daniel H J; Humphries, Jonathan D; Byron, Adam; Millon-Frémillon, Angélique; Humphries, Martin J

    2014-01-01

    The microtubule network regulates the turnover of integrin-containing adhesion complexes to stimulate cell migration. Disruption of the microtubule network results in an enlargement of adhesion complex size due to increased RhoA-stimulated actomyosin contractility, and inhibition of adhesion complex turnover; however, the microtubule-dependent changes in adhesion complex composition have not been studied in a global, unbiased manner. Here we used label-free quantitative mass spectrometry-based proteomics to determine adhesion complex changes that occur upon microtubule disruption with nocodazole. Nocodazole-treated cells displayed an increased abundance of the majority of known adhesion complex components, but no change in the levels of the fibronectin-binding α5β1 integrin. Immunofluorescence analyses confirmed these findings, but revealed a change in localisation of adhesion complex components. Specifically, in untreated cells, α5-integrin co-localised with vinculin at peripherally located focal adhesions and with tensin at centrally located fibrillar adhesions. In nocodazole-treated cells, however, α5-integrin was found in both peripherally located and centrally located adhesion complexes that contained both vinculin and tensin, suggesting a switch in the maturation state of adhesion complexes to favour focal adhesions. Moreover, the switch to focal adhesions was confirmed to be force-dependent as inhibition of cell contractility with the Rho-associated protein kinase inhibitor, Y-27632, prevented the nocodazole-induced conversion. These results highlight a complex interplay between the microtubule cytoskeleton, adhesion complex maturation state and intracellular contractile force, and provide a resource for future adhesion signaling studies. The proteomics data have been deposited in the ProteomeXchange with identifier PXD001183.

  1. Adhesion beyond the interface: Molecular adaptations of the mussel byssus to the intertidal zone

    Science.gov (United States)

    MIller, Dusty Rose

    The California mussel, Mytilus californianus, adheres robustly in the high-energy and oxidizing intertidal zone with a fibrous holdfast called the byssus using 3,4-dihydroxyphenyl-L-alanine (Dopa)-containing adhesive mussel foot proteins (mfps). There are many supporting roles to mussel adhesion that are intimately linked and ultimately responsible for mussel byssus's durable and dynamic adhesion. This dissertation explores these supporting mechanisms, including delivery of materials underwater, iron binding, friction, and antioxidant activity. As the outermost covering of the byssus, the cuticle deserves particular attention for its supporting roles to adhesion including the high stiffness and extensibility of the M. californianus byssal cuticle, which make it one of the most energy tolerant materials known. The cuticle's matrix-granule composite structure contributes to its toughness by microcracking between its harder granules and softer matrix. We investigated delivery of cuticular material underwater, cohesion of cuticle proteins, and surface damage mitigation by cuticle protein-based coacervates. To investigate underwater material delivery, we made cuticle matrix mimics by coacervating a key cuticular protein, Mytilus californianus foot protein 1, mfp-1, with hyaluronic acid. These matrix mimics coacervated over a wide range of solution conditions, delivered concentrated material, settled on and coated surfaces underwater. Because the granules are composed of mfp-1 condensed with iron, we used the surface forces apparatus to investigate the effects of iron on the cohesion of mfp-1 from two different species of mussels and found that subtle sequence variations modulate cohesion. Using the coacervate matrix mimics and, modeling the granules as a hard surface (mica), we investigated the wear protection of coacervated mfp-1/HA to mica under frictional shear and found that preventing wear depends critically on the presence of Dopa groups. In addition to cuticle

  2. Fresh look at electron-transfer mechanisms via the donor/acceptor bindings in the critical encounter complex.

    Science.gov (United States)

    Rosokha, Sergiy V; Kochi, Jay K

    2008-05-01

    Seminal insights provided by the iconic R. S. Mulliken and his "charge-transfer" theory, H. Taube and his "outer/inner-sphere" mechanisms, R. A. Marcus and his "two-state non-adiabatic" theory, and N. S. Hush and his "intervalence" theory are each separately woven into the rich panoramic tapestry constituting chemical research into electron-transfer dynamics, and its mechanistic dominance for the past half century and more. In this Account, we illustrate how the simultaneous melding of all four key concepts allows sharp focus on the charge-transfer character of the critical encounter complex to evoke the latent facet of traditional electron-transfer mechanisms. To this end, we exploit the intervalence (electronic) transition that invariably accompanies the diffusive encounter of electron-rich organic donors (D) with electron-poor acceptors (A) as the experimental harbinger of the collision complex, which is then actually isolated and X-ray crystallographically established as loosely bound pi-stacked pairs of various aromatic and olefinic donor/acceptor dyads with uniform interplanar separations of r(DA) = 3.1 +/- 0.2 A. These X-ray structures, together with the spectral measurements of their intervalence transitions, lead to the pair of important electron-transfer parameters, H(DA) (electronic coupling element) versus lambdaT (reorganization energy), the ratio of which generally defines the odd-electron mobility within such an encounter complex in terms of the resonance stabilization of the donor/acceptor assembly [D, A] as opposed to the reorganization-energy penalty required for its interconversion to the electron-transfer state [D(+*), A(-*)]. We recognize the resonance-stabilization energy relative to the intrinsic activation barrier as the mechanistic binding factor, Q = 2H(DA)/lambdaT, to represent the quantitative measure of the highly variable continuum of inner-sphere/outer-sphere interactions that are possible within various types of precursor complexes

  3. Investigation on the Mechanics of Adhesion to the Selective Extracellular Matrix Coated Surfaces of Lung Cancer Cells%肺癌细胞与胞外基质选择裱衬表面粘附力学的研究

    Institute of Scientific and Technical Information of China (English)

    张婷; 屈谦; 薛亚梅; 吴泽志; 宋关斌; 蔡绍皙

    2001-01-01

    The adhesion properties of tumor cells with extracellular matrix(ECM) are closely associated with their invasion and metastasis.Our work reported here was intended reveal the relevant biomechanical and biorheological manifestations of human lung cancer. Using micropipette aspiration technique, we investigated quantitatively the adhesive mechanics properties of high metastatic human giant cell carcinoma(PG) cells as well as low metastatic adenocarcinoma(PAa) cells of lung based on cell culture in vitro. The results showed that the adhesion forces of PAa and PG cells to collagen Ⅳ were significantly higher than those to glass surfaces, but at the lower concentrations(1.00μg/ml and 2.00μg/ml) of collagen Ⅳ, the amplitude for the increase of adhesion forces of PG cells were less than the amplitude for that of PAa cells, and most of the adhesion force values of PAa cells to the coated surfaces of incorporation of laminin along with 2 μg/ml collagen Ⅳ were significantly greater than those of PG cells. At the lower concentrations(0.625μg/ml for PAa cells,and 0.625 μg/ml, 1. 25 μg/ml for PG cells) of laminin tested,the adhesion force values of PAa and PG cells all decreased, but the amplitude and level for the decreased values of adhesion forces of PG cells were greater than those for the PAa cells. In conclusion, the adhesive and proteolytic behaviour of cancer cells to extracellular matrix might be mediated mainly by tumor cell membrane receptors such as integrin receptors and laminin receptors, it might affect the biological characteristics and the metastasis of the tumor cells. The results may benefit to explain some questions in biomechanical views about how the highly metastatic PG cells are prone to migration and invasion.%肿瘤细胞与细胞外基质的粘附特性与肿瘤的侵袭转移密切相关,作者力图揭示人肺癌细胞相应的生物力学和生物流变学特征。采用微管吸吮技术定量测定体外培

  4. Mechanisms of extracellular signal-regulated kinase/cAMP response element-binding protein/brain-derived neurotrophic factor signaltransduction pathway in depressive disorder

    Institute of Scientific and Technical Information of China (English)

    Hongyan Wang; Yingquan Zhang; Mingqi Qiao

    2013-01-01

    The extracellular signal-regulated kinase/cAMP response element-binding protein/brain-derived neurotrophic factor signal transduction pathway plays an important role in the mechanism of action of antidepressant drugs and has dominated recent studies on the pathogenesis of depression. In the present review we summarize the known roles of extracellular signal-regulated kinase, cAMP response element-binding protein and brain-derived neurotrophic factor in the pathogenesis of depression and in the mechanism of action of antidepressant medicines. The extracellular signal-regulated kinase/cAMP response element-binding protein/brain-derived neurotrophic factor pathway has potential to be used as a biological index to help diagnose depression, and as such it is considered as an important new target in the treatment of depression.

  5. Mechanisms of extracellular signal-regulated kinase/cAMP response element-binding protein/brain-derived neurotrophic factor signal transduction pathway in depressive disorder.

    Science.gov (United States)

    Wang, Hongyan; Zhang, Yingquan; Qiao, Mingqi

    2013-03-25

    The extracellular signal-regulated kinase/cAMP response element-binding protein/brain-derived neurotrophic factor signal transduction pathway plays an important role in the mechanism of action of antidepressant drugs and has dominated recent studies on the pathogenesis of depression. In the present review we summarize the known roles of extracellular signal-regulated kinase, cAMP response element-binding protein and brain-derived neurotrophic factor in the pathogenesis of depression and in the mechanism of action of antidepressant medicines. The extracellular signal-regulated kinase/cAMP response element-binding protein/brain-derived neurotrophic factor pathway has potential to be used as a biological index to help diagnose depression, and as such it is considered as an important new target in the treatment of depression.

  6. Molecular mechanism of AMD3100 antagonism in the CXCR4 receptor: transfer of binding site to the CXCR3 receptor

    DEFF Research Database (Denmark)

    Rosenkilde, Mette M; Gerlach, Lars-Ole; Jakobsen, Janus S

    2004-01-01

    AMD3100 is a symmetric bicyclam, prototype non-peptide antagonist of the CXCR4 chemokine receptor. Mutational substitutions at 16 positions located in TM-III, -IV, -V, -VI, and -VII lining the main ligand-binding pocket of the CXCR4 receptor identified three acid residues: Asp(171) (AspIV:20), Asp......, respectively. Metal ion binding in the cyclam rings of AMD3100 increased its dependence on Asp(262) and provided a tighter molecular map of the binding site, where borderline mutational hits became clear hits for the Zn(II)-loaded analog. The proposed binding site for AMD3100 was confirmed by a gradual build...... that AMD3100 binds through interactions with essentially only three acidic anchor-point residues, two of which are located at one end and the third at the opposite end of the main ligand-binding pocket of the CXCR4 receptor. We suggest that non-peptide antagonists with, for example, improved oral...

  7. Prevention of peritoneal adhesions: A promising role for gene therapy

    Institute of Scientific and Technical Information of China (English)

    Hussein M Atta

    2011-01-01

    Adhesions are the most frequent complication of abdominopelvic surgery, yet the extent of the problem, and its serious consequences, has not been adequately recognized. Adhesions evolved as a life-saving mechanism to limit the spread of intraperitoneal inflammatory conditions. Three different pathophysiological mechanisms can independently trigger adhesion formation. Mesothelial cell injury and loss during operations, tissue hypoxia and inflammation each promotes adhesion formation separately, and potentiate the effect of each other. Studies have repeatedly demonstrated that interruption of a single pathway does not completely prevent adhesion formation. This review summarizes the pathogenesis of adhesion formation and the results of single gene therapy interventions. It explores the promising role of combinatorial gene therapy and vector modifications for the prevention of adhesion formation in order to stimulate new ideas and encourage rapid advancements in this field.

  8. Markov State Models Reveal a Two-Step Mechanism of miRNA Loading into the Human Argonaute Protein: Selective Binding followed by Structural Re-arrangement

    KAUST Repository

    Jiang, Hanlun

    2015-07-16

    Argonaute (Ago) proteins and microRNAs (miRNAs) are central components in RNA interference, which is a key cellular mechanism for sequence-specific gene silencing. Despite intensive studies, molecular mechanisms of how Ago recognizes miRNA remain largely elusive. In this study, we propose a two-step mechanism for this molecular recognition: selective binding followed by structural re-arrangement. Our model is based on the results of a combination of Markov State Models (MSMs), large-scale protein-RNA docking, and molecular dynamics (MD) simulations. Using MSMs, we identify an open state of apo human Ago-2 in fast equilibrium with partially open and closed states. Conformations in this open state are distinguished by their largely exposed binding grooves that can geometrically accommodate miRNA as indicated in our protein-RNA docking studies. miRNA may then selectively bind to these open conformations. Upon the initial binding, the complex may perform further structural re-arrangement as shown in our MD simulations and eventually reach the stable binary complex structure. Our results provide novel insights in Ago-miRNA recognition mechanisms and our methodology holds great potential to be widely applied in the studies of other important molecular recognition systems.

  9. Deciphering the kinetic binding mechanism of dimeric ligands using a potent plasma-stable dimeric inhibitor of postsynaptic density protein-95 as an example

    DEFF Research Database (Denmark)

    Chi, Celestine N; Bach, Anders; Gottschalk, Marie;

    2010-01-01

    addressed the kinetic mechanism of interaction of such bivalent ligands. We have investigated the binding interaction of a recently identified potent plasma-stable dimeric pentapeptide and PDZ1-2 of postsynaptic density protein-95 (PSD-95) using protein engineering in combination with fluorescence...

  10. Grey Target Optimization of Waterproof Adhesive Material for Concrete Bridge Deck Pavement Based on Mechanical Analysis%基于力学分析的桥面铺装防水粘结层材料灰靶优选

    Institute of Scientific and Technical Information of China (English)

    于新; 李英涛; 刘云

    2012-01-01

    为了优选与混凝土箱梁桥防水粘结层实际受力状态相匹配的材料,以沪杭高速公路拓宽改建工程高架桥为例,采用有限元法建立了全桥模型,在分析刹车、超载、随机动荷载等因素对防水粘结层力学响应的基础上,利用灰靶理论优选室内实测典型防水粘结层的相关技术参数.研究结果表明:刹车超载使防水粘结层产生的剪应力大于由桥面不平度引起的防水粘结层剪应力,最大可达0.397 MPa;橡胶沥青和SBS改性沥青防水粘结层综合性能较优,可作为混凝土桥防水粘结层材料.%In order to select the optimal waterproof adhesive material that meets the stress needs of concrete box girder bridge deck pavement, taking the viaduct in widening project of the Shanghai-Hangzhou Expressway as an example, a composite structure model of the whole bridge was established using the finite element method, and the influence of braking, overloading, random dynamic loading on the mechanical response of the waterproof adhesive layer was analyzed. The technique parameters of some typical materials for waterproof adhesive layer were tested in lab, and then analyzed by the grey target theory. The result shows that braking plus overloading has a larger effect on the shear stress of adhesive layer than the random dynamic loading caused by bridge deck roughness, and may produce a maximum shear stress of 0. 397 MPa. The rubber asphalt and SBS modified asphalt both have good performance, and can be used as the material of waterproof adhesive layer.

  11. Evaluation of mechanism of non-thermal plasma effect on the surface of polypropylene films for enhancement of adhesive and hemo compatible properties

    Science.gov (United States)

    Navaneetha Pandiyaraj, K.; Deshmukh, R. R.; Arunkumar, A.; Ramkumar, M. C.; Ruzybayev, I.; Ismat Shah, S.; Su, Pi-Guey; Periayah, Mercy Halleluyah; Halim, A. S.

    2015-08-01

    The hydro-carbon based polymers have attracted attention of scientists for its use in bio-medical field as various implants due to inherent flexibility. However, they have poor surface properties; particularly they have low surface energy (SE). Hence, blood components (platelets, blood proteins, etc.)-polymer surface interaction is the major concern when it comes in contact with blood. Thus, surface modification is required to develop the perfect antithrombogenic property without affecting the materials bulk. The present study describes the improvement in adhesive and blood compatible properties of polypropylene (PP) by low temperature (non-thermal) plasma of various gases such as Ar, O2, air and Ar + O2 for biomedical applications. The changes in surface morphological, chemical and hydrophilic modification induced by the gaseous plasma treatment were analyzed by atomic force microscopy (AFM), X-ray photo electron spectroscopy (XPS), electron spin resonance (ESR) spectroscopy and contact angle measurements, respectively. Moreover, the stability of plasma effect was also studied for the different storage conditions. Variation in adhesive strength of the plasma treated PP film was studied by T-Peel and Lap-Shear strength tests. The blood compatibility of the surface modified PP films was investigated by in vitro analysis. It was found that gaseous plasma treatment improved the blood compatibility as well as adhesive strength of the PP films without affecting materials bulk which may be due to the significant morphological and chemical changes induced by the gaseous plasma treatment. Among the various gaseous plasma treatments, Ar + O2 mixture has provided remarkable physico-chemical changes compared with other plasma treatments studied.

  12. Characterization of heparin-binding site of tissue transglutaminase: its importance in cell surface targeting, matrix deposition, and cell signaling.

    Science.gov (United States)

    Wang, Zhuo; Collighan, Russell J; Pytel, Kamila; Rathbone, Daniel L; Li, Xiaoling; Griffin, Martin

    2012-04-13

    Tissue transglutaminase (TG2) is a multifunctional Ca(2+)-activated protein cross-linking enzyme secreted into the extracellular matrix (ECM), where it is involved in wound healing and scarring, tissue fibrosis, celiac disease, and metastatic cancer. Extracellular TG2 can also facilitate cell adhesion important in wound healing through a nontransamidating mechanism via its association with fibronectin, heparan sulfates (HS), and integrins. Regulating the mechanism how TG2 is translocated into the ECM therefore provides a strategy for modulating these physiological and pathological functions of the enzyme. Here, through molecular modeling and mutagenesis, we have identified the HS-binding site of TG2 (202)KFLKNAGRDCSRRSSPVYVGR(222). We demonstrate the requirement of this binding site for translocation of TG2 into the ECM through a mechanism involving cell surface shedding of HS. By synthesizing a peptide NPKFLKNAGRDCSRRSS corresponding to the HS-binding