The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Jacob N Israelachvili - One of the best experts on this subject based on the ideXlab platform.
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impact of molecular architecture and adsorption density on adhesion of mussel inspired surface primers with catechol cation synergy
Journal of the American Chemical Society, 2019Co-Authors: George D Degen, Parker R Stow, Robert B Lewis, Roberto Andresen C Eguiluz, Eric Valois, Kai Kristiansen, Alison Butler, Jacob N IsraelachviliAbstract:Marine mussels secrete proteins rich in residues containing Catechols and cationic amines that displace hydration layers and adhere to charged surfaces under water via a cooperative binding effect known as catechol-cation synergy. Mussel-inspired adhesives containing paired catechol and cationic functionalities are a promising class of materials for biomedical applications, but few studies address the molecular adhesion mechanism(s) of these materials. To determine whether intramolecular adjacency of these functionalities is necessary for robust adhesion, a suite of siderophore analog surface primers was synthesized with systematic variations in intramolecular spacing between catechol and cationic functionalities. Adhesion measurements conducted with a surface forces apparatus (SFA) allow adhesive failure to be distinguished from cohesive failure and show that the failure mode depends critically on the siderophore analog adsorption density. The adhesion of these molecules to muscovite mica in an aqueous e...
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Surface-initiated self-healing of polymers in aqueous media
Nature Materials, 2014Co-Authors: Jacob N Israelachvili, J. Herbert WaiteAbstract:Synthetic polymers functionalized with mussel-inspired Catechols have been shown to exhibit self-healing and adhesive properties, mediated by metal chelation, that are much needed in biomedical and environmental applications. Now, a metal-free approach to complete polymer self-healing underwater mediated by extensive hydrogen bonding in catechol-functionalized polyacrylates is reported.
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Surface-initiated self-healing of polymers in aqueous media
Nature Materials, 2014Co-Authors: B. Kollbe Ahn, Dong Woog Lee, Jacob N Israelachvili, J. Herbert WaiteAbstract:Polymeric materials that intrinsically heal at damage sites under wet or moist conditions are urgently needed for biomedical and environmental applications. Although hydrogels with self-mending properties have been engineered by means of mussel-inspired metal-chelating catechol-functionalized polymer networks, biological self-healing in wet conditions, as occurs in self-assembled holdfast proteins in mussels and other marine organisms, is generally thought to involve more than reversible metal chelates. Here we demonstrate self-mending in metal-free water of synthetic polyacrylate and polymethacrylate materials that are surface-functionalized with mussel-inspired Catechols. Wet self-mending of scission in these polymers is initiated and accelerated by hydrogen bonding between interfacial catechol moieties, and consolidated by the recruitment of other non-covalent interactions contributed by subsurface moieties. The repaired and pristine samples show similar mechanical properties, suggesting that the triggering of complete self-healing is enabled underwater by the formation of extensive catechol-mediated interfacial hydrogen bonds.
J. Herbert Waite - One of the best experts on this subject based on the ideXlab platform.
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Surface-initiated self-healing of polymers in aqueous media
Nature Materials, 2014Co-Authors: Jacob N Israelachvili, J. Herbert WaiteAbstract:Synthetic polymers functionalized with mussel-inspired Catechols have been shown to exhibit self-healing and adhesive properties, mediated by metal chelation, that are much needed in biomedical and environmental applications. Now, a metal-free approach to complete polymer self-healing underwater mediated by extensive hydrogen bonding in catechol-functionalized polyacrylates is reported.
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Surface-initiated self-healing of polymers in aqueous media
Nature Materials, 2014Co-Authors: B. Kollbe Ahn, Dong Woog Lee, Jacob N Israelachvili, J. Herbert WaiteAbstract:Polymeric materials that intrinsically heal at damage sites under wet or moist conditions are urgently needed for biomedical and environmental applications. Although hydrogels with self-mending properties have been engineered by means of mussel-inspired metal-chelating catechol-functionalized polymer networks, biological self-healing in wet conditions, as occurs in self-assembled holdfast proteins in mussels and other marine organisms, is generally thought to involve more than reversible metal chelates. Here we demonstrate self-mending in metal-free water of synthetic polyacrylate and polymethacrylate materials that are surface-functionalized with mussel-inspired Catechols. Wet self-mending of scission in these polymers is initiated and accelerated by hydrogen bonding between interfacial catechol moieties, and consolidated by the recruitment of other non-covalent interactions contributed by subsurface moieties. The repaired and pristine samples show similar mechanical properties, suggesting that the triggering of complete self-healing is enabled underwater by the formation of extensive catechol-mediated interfacial hydrogen bonds.
Bernt Krebs - One of the best experts on this subject based on the ideXlab platform.
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The systematic influence of tripodal ligands on the catechol cleavingactivity of iron(III) containing model compounds for catechol 1,2-dioxygenases
Journal of The Chemical Society-dalton Transactions, 2020Co-Authors: Matthias Pascaly, Mark Duda, Florian Schweppe, Kristin Zurlinden, Felizitas K. Müller, Bernt KrebsAbstract:A series of mononuclear iron(III) complexes as functional and structural model compounds for intradiol cleaving catechol dioxygenases were synthesized. For all model compounds the iron(III) cores are in a distorted octahedral environment derived from tripodal tetradentate N4-donor ligands and a catechol. Model complexes for enzyme–substrate adducts were characterized by spectroscopic and electrochemical methods, and in four cases by single-crystal X-ray crystallography. The systematic variation of one ligand arm in the structurally characterized complexes yields a different steric shielding of the iron(III) center, significantly influencing the bonding of the catechol substrate and the subsequent reaction with dioxygen. The spectroscopic features and catechol cleaving activities of in situ generated complexes with the above ligands were probed. All complexes are highly reactive towards intradiol cleavage of various Catechols in the presence of air. The catechol 1,2-dioxygenase reaction depends on the redox potential of both the iron(III) complex and the catechol derivative as well as the steric demand of the tripodal ligand. Some complexes show high catalytic activities with yields up to 84% with respect to aerial cleavage of Catechols.
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purification and spectroscopic studies on catechol oxidases from lycopus europaeus and populus nigra evidence for a dinuclear copper center of type 3 and spectroscopic similarities to tyrosinase and hemocyanin
Journal of Biological Inorganic Chemistry, 1999Co-Authors: Annette Rompel, Helmut Fischer, Dirk Meiwes, Klaudia Buldtkarentzopoulos, Renee Dillinger, Herbert Witzel, Felix Tuczek, Bernt KrebsAbstract:We purified two catechol oxidases from Lycopus europaeus and Populus nigra which only catalyze the oxidation of Catechols to quinones without hydroxylating tyrosine. The molecular mass of the Lycopus enzyme was determined to 39 800 Da and the mass of the Populus enzyme was determined to 56 050 Da. Both catechol oxidases are inhibited by thiourea, N-phenylthiourea, dithiocarbamate, and cyanide, but show different pH behavior using catechol as substrate. Atomic absorption spectroscopic analysis found 1.5 copper atoms per protein molecule. Using EPR spectroscopy we determined 1.8 Cu per molecule catechol oxidase. Furthermore, EPR spectroscopy demonstrated that catechol oxidase is a copper enzyme of type 3. The lack of an EPR signal is due to strong antiferromagnetic coupling that requires a bridging ligand between the two copper ions in the met preparation. Addition of H2O2 to both enzymes leads to oxy catechol oxidase. In the UV/Vis spectrum two new absorption bands occur at 345 nm and 580 nm. In accordance with the oxy forms of hemocyanin and tyrosinase the absorption band at 345 nm is due to an O22– (πσ*)→Cu(II) (d x2–y2 ) charge transfer (CT) transition. The absorption band at 580 nm corresponds to the second O22– (πv*)→Cu(II) (d x2–y2 ) CT transition. The UV/Vis bands in combination with the resonance Raman spectra of oxy catechol oxidase indicate a μ-η2 : η2 binding mode for dioxygen. The intense resonance Raman peak at 277 cm–1, belonging to a Cu-N (axial His) stretching mode, suggests that catechol oxidase has six terminal His ligands, as known for molluscan and arthropodan hemocyanin.
Phillip B Messersmith - One of the best experts on this subject based on the ideXlab platform.
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ph dependent cross linking of Catechols through oxidation via fe3 and potential implications for mussel adhesion
RSC Advances, 2014Co-Authors: Dominic E Fullenkamp, Devin G Barrett, Dusty R Miller, Josh W Kurutz, Phillip B MessersmithAbstract:The mussel byssus is a remarkable attachment structure that is formed by injection molding and rapid in situ hardening of concentrated solutions of proteins enriched in the catecholic amino acid 3,4-dihydroxy-L-phenylalanine (DOPA). Fe3+, found in high concentrations in the byssus, has been speculated to participate in redox reactions with DOPA that lead to protein polymerization, however direct evidence to support this hypothesis has been lacking. Using small molecule Catechols, DOPA-containing peptides, and native mussel foot proteins, we report the first direct observation of catechol oxidation and polymerization accompanied by reduction of Fe3+ to Fe2+. In the case of the small molecule catechol, we identified two dominant dimer species and characterized their connectivities by nuclear magnetic resonance (NMR), with the C6–C6 and C5–C6 linked species as the major and minor products, respectively. For the DOPA-containing peptide, we studied the pH dependence of the reaction and demonstrated that catechol polymerization occurs readily at low pH, but is increasingly diminished in favor of metal–catechol coordination interactions at higher pH. Finally, we demonstrate that Fe3+ can induce cross-links in native byssal mussel proteins mefp-1 and mcfp-1 at acidic pH. Based on these findings, we discuss the potential implications to the chemistry of mussel adhesion.
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decoration of electrospun nanofibers with monomeric Catechols to facilitate cell adhesion
Macromolecular Bioscience, 2014Co-Authors: Ji Suk Choi, Phillip B MessersmithAbstract:: Monomeric Catechols are displayed on the surface of polymeric nanofibers by robust catechol-thiol interactions to enhance cell adhesion and migration. Dihydroxyphenyl propionic acid is chemically conjugated to primary amine groups of poly(ϵ-caprolactone)-poly(ethylene glycol)-amine (PCL-PEG) nanofibers to display catechol moieties on the surface. At basic pH, catecholized nanofibers incorporate thiol groups at a five-fold higher rate than at acidic pH, while catechol-coated surfaces do not show any pH-dependent binding. Live/dead cell staining indicates that the catecholized nanofibers do not exert any cytotoxic effects. Also, NIH 3T3 cells cultured on the catecholized nanofibers show increased attachment and migration that is proportional to the amount of the immobilized catechol moieties on the surface. These results clearly indicate that 6 nmol of monomeric Catechols on the surface of nanofiber can promote cell adhesion and migration by thiol-catehol interactions.
Yoon Sung Nam - One of the best experts on this subject based on the ideXlab platform.
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Mussel-inspired modification of dextran for protein-resistant coatings of titanium oxide.
Carbohydrate Polymers, 2013Co-Authors: Jae Yoon Park, Jee Seon Kim, Yoon Sung NamAbstract:Abstract Surface modification of inorganic materials to prevent non-specific protein adsorption is critically important for developing a biocompatible materials’ platform for medical implantation, diagnostics, and therapeutics. Here we report mussel-inspired chemical modification of dextran for anti-fouling coatings of metal oxide. Catechols are conjugated to dextran via a carbamate ester linkage, producing catechol-grafted dextran with a grafting density of 7.3 mol.%. Titanium dioxide (TiO 2 ) is coated with the catechol-grafted dextran, and the anti-fouling effect of dextran coatings is examined by using the adsorption of human serum albumin. The mussel-inspired dextran coatings show excellent resistance to non-specific protein adsorption: the adsorption equilibrium constant ( K ) is 0.69 L g −1 for dextran-coated TiO 2 while that for pristine TiO 2 surface is 3.53 L g −1 . This study suggests that catechol-grafted dextran is a promising material for effective anti-fouling coatings of implantable inorganic materials.
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Cell-repellant dextran coatings of porous titania using mussel adhesion chemistry
Macromolecular Bioscience, 2013Co-Authors: Jae Yoon Park, Jee Seon Kim, Jihyeon Yeom, Mihyun Lee, Haeshin Lee, Yoon Sung NamAbstract:The resistance of bioceramics against non-specific adsorption of serum proteins is critical for a wide range of biomedical applications. Some polysaccharides serve as natural protein-resistant molecules in extracellular matrices; however, the stable adhesion of polysaccharides to ceramic biomaterials in an aqueous solution is very challenging because chemical linkages at organic/inorganic interfaces are susceptible to hydrolytic degradation. Here, a catechol-grafted dextran, which strongly binds to titania (TiO2 ) in an aqueous milieu to effectively suppress cell adhesion through anti-fouling activity against non-specific protein adsorption, is introduced. Catechol is conjugated approximately to 6.7 mol% of glucose units of dextran via a carbamate ester linkage, corresponding to roughly three Catechols per dextran chain having an average molecular weight of 6 kDa. Multivalent interactions of Catechols with a titanium atom, enabled by the graft-type structure, provide a very stable coating of dextran on this inorganic surface. The adhesion of HeLa cells on the dextran-coated titania surface is reduced by 2.4-fold compared to that on a pristine titania surface. These results suggest that the graft-type incorporation of a small number of catechol moieties along a dextran backbone is an effective means of producing a stable anti-fouling interface on inorganic biomaterials in an aqueous environment.