The Experts below are selected from a list of 269361 Experts worldwide ranked by ideXlab platform
Tianzhong Yang - One of the best experts on this subject based on the ideXlab platform.
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morphology controlled growth of pt nanoparticles taking advantage of Smaller Molecule and inorganic salt
Acta Materialia, 2014Co-Authors: Ming Lei, Ce Liang, Qing Huan, Keiko Miyabayashi, Mikio Miyake, Tianzhong YangAbstract:Platinum nanoparticles (NPs) with controllable morphologies were synthesized in aqueous solution utilizing a new type of additive and capping agent. This strategy suggests for the first time that an oxysalt can serve as a shape modifier, and can control the morphologies of NPs more precisely because of its moderate adsorption on them. The employment of disodium succinate reveals the possibility that small Molecules can serve as a capping agent, thereby avoiding the problems caused by larger reagents such as polyvinylpyrrolidone. Furthermore, the selectivity of the as-synthesized tetrahedra is as high as 80%, and the sizes can be tuned from 3 to 13 nm with a narrow size distribution. This paper proposes that the mechanism underlying the growth of NPs involves competition between absorption and desorption of the additive and between absorption of different reagents. Cyclic voltammetry and oxygen reduction reaction results reveal the typical nature of the Pt NPs, indicating the success of utilizing C4H4Na2O4 and Na2SO4. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Julius Rebek - One of the best experts on this subject based on the ideXlab platform.
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experimental and computational probes of the space in a self assembled capsule
Proceedings of the National Academy of Sciences of the United States of America, 2006Co-Authors: Dariush Ajami, Tetsuo Iwasawa, Julius RebekAbstract:Self-assembled capsules are hosts that recognize and surround Smaller Molecule guests of appropriate size, shape, and chemical surfaces. The space available inside is a cage of fixed solvent Molecules, many of which are aromatic. These aromatics provide anisotropic shielding to guests, and a map of induced magnetic shielding for the inner space can be obtained through nucleus-independent chemical shift calculations. Experimental values of the magnetic environment can be determined by NMR spectra of the guests inside. We describe here the environment in a cylindrical capsule with tapered ends. A series of terminal acetylenes—the narrowest of organic structures—was synthesized and used to probe the magnetic shielding of the capsule’s ends. Their NMR spectra showed that the acetylenic hydrogen experiences deshielding as it is forced deeper into the tapered end of the capsule where four benzene rings converge. Modeling and density functional theory calculations provided excellent agreement with the experimental values and established a molecular ruler to explore steric and magnetic environments inside the capsule.
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formation of discrete functional assemblies and informational polymers through the hydrogen bonding preferences of calixarene aryl and sulfonyl tetraureas
Journal of the American Chemical Society, 1998Co-Authors: Ronald K Castellano, Julius RebekAbstract:Derivatives of the calix[4]arenes in the cone conformation featuring either aryl urea or sulfonyl urea functions on their larger (upper) rims dimerize through hydrogen bonding to give molecular capsules. The capsules act as hosts that reversibly bind Smaller Molecule guests in organic media. Heterodimers form when both aryl and sulfonyl ureas are present, and the heterodimers form exclusively with respect to the homodimers. The heterodimerization encodes information at the molecular level and allows the predictable formation of discrete aggregates of nanometer dimensions. Evidence for the reversible assembly of these structures is provided by 1H NMR, guest encapsulation studies, and gel permeation chromatography. Covalent attachment of these calixarene aryl and sulfonyl ureas at their Smaller (lower) rims leads to polymeric assemblies in which the informational content is preserved.
Ruud P M Dings - One of the best experts on this subject based on the ideXlab platform.
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Beta-sheet is the bioactive conformation of the anti-angiogenic anginex peptide.
The Biochemical journal, 2003Co-Authors: Ruud P M Dings, Monica M Arroyo, Nathan A Lockwood, Loes I Van Eijk, Judy R Haseman, Arjan W Griffioen, Kevin H. MayoAbstract:Anginex is a designed peptide 33mer that functions as a cytokine-like agent to inhibit angiogenesis. Although this short linear peptide has been shown by NMR and CD to form a nascent beta-sheet conformation in solution, the actual bioactive structure formed upon binding to its receptor on the surface of endothelial cells could be quite different. By using a series of double-cysteine disulphide-bridged analogues, we provide evidence in the present study that the beta-sheet is in fact the bioactive conformation of anginex. CD and NMR spectral analysis of the analogues indicate formation of a beta-sheet conformation. Three functional assays, endothelial cell proliferation, apoptosis and in vitro angiogenesis, were performed on all analogues. As long as the placement of disulphide bonds preserved the beta-strand alignment, as in the proposed bioactive conformation, bioactivities were preserved. Knowledge of the bioactive conformation of anginex will aid in the design of Smaller Molecule mimetics of this potent anti-angiogenic peptide.
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beta sheet is the bioactive conformation of the anti angiogenic anginex peptide
Biochemical Journal, 2003Co-Authors: Ruud P M Dings, Monica M Arroyo, Nathan A Lockwood, Loes I Van Eijk, Judy R Haseman, Arjan W Griffioen, Kevin H. MayoAbstract:Anginex is a designed peptide 33mer that functions as a cytokine-like agent to inhibit angiogenesis. Although this short linear peptide has been shown by NMR and CD to form a nascent β-sheet conformation in solution, the actual bioactive structure formed upon binding to its receptor on the surface of endothelial cells could be quite different. By using a series of double-cysteine disulphide-bridged analogues, we provide evidence in the present study that the β-sheet is in fact the bioactive conformation of anginex. CD and NMR spectral analysis of the analogues indicate formation of a β-sheet conformation. Three functional assays, endothelial cell proliferation, apoptosis and in vitro angiogenesis, were performed on all analogues. As long as the placement of disulphide bonds preserved the β-strand alignment, as in the proposed bioactive conformation, bioactivities were preserved. Knowledge of the bioactive conformation of anginex will aid in the design of Smaller Molecule mimetics of this potent anti-angiogenic peptide.
Kevin H. Mayo - One of the best experts on this subject based on the ideXlab platform.
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Beta-sheet is the bioactive conformation of the anti-angiogenic anginex peptide.
The Biochemical journal, 2003Co-Authors: Ruud P M Dings, Monica M Arroyo, Nathan A Lockwood, Loes I Van Eijk, Judy R Haseman, Arjan W Griffioen, Kevin H. MayoAbstract:Anginex is a designed peptide 33mer that functions as a cytokine-like agent to inhibit angiogenesis. Although this short linear peptide has been shown by NMR and CD to form a nascent beta-sheet conformation in solution, the actual bioactive structure formed upon binding to its receptor on the surface of endothelial cells could be quite different. By using a series of double-cysteine disulphide-bridged analogues, we provide evidence in the present study that the beta-sheet is in fact the bioactive conformation of anginex. CD and NMR spectral analysis of the analogues indicate formation of a beta-sheet conformation. Three functional assays, endothelial cell proliferation, apoptosis and in vitro angiogenesis, were performed on all analogues. As long as the placement of disulphide bonds preserved the beta-strand alignment, as in the proposed bioactive conformation, bioactivities were preserved. Knowledge of the bioactive conformation of anginex will aid in the design of Smaller Molecule mimetics of this potent anti-angiogenic peptide.
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beta sheet is the bioactive conformation of the anti angiogenic anginex peptide
Biochemical Journal, 2003Co-Authors: Ruud P M Dings, Monica M Arroyo, Nathan A Lockwood, Loes I Van Eijk, Judy R Haseman, Arjan W Griffioen, Kevin H. MayoAbstract:Anginex is a designed peptide 33mer that functions as a cytokine-like agent to inhibit angiogenesis. Although this short linear peptide has been shown by NMR and CD to form a nascent β-sheet conformation in solution, the actual bioactive structure formed upon binding to its receptor on the surface of endothelial cells could be quite different. By using a series of double-cysteine disulphide-bridged analogues, we provide evidence in the present study that the β-sheet is in fact the bioactive conformation of anginex. CD and NMR spectral analysis of the analogues indicate formation of a β-sheet conformation. Three functional assays, endothelial cell proliferation, apoptosis and in vitro angiogenesis, were performed on all analogues. As long as the placement of disulphide bonds preserved the β-strand alignment, as in the proposed bioactive conformation, bioactivities were preserved. Knowledge of the bioactive conformation of anginex will aid in the design of Smaller Molecule mimetics of this potent anti-angiogenic peptide.
Paul A Webley - One of the best experts on this subject based on the ideXlab platform.
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discriminative separation of gases by a molecular trapdoor mechanism in chabazite zeolites
Journal of the American Chemical Society, 2012Co-Authors: Jin Shang, Ranjeet Singh, Kate M Nairn, Timothy J Bastow, Nikhil V Medhekar, Cara M Doherty, Anita J Hill, Jefferson Zhe Liu, Paul A WebleyAbstract:Separation of Molecules based on molecular size in zeolites with appropriate pore aperture dimensions has given rise to the definition of “molecular sieves” and has been the basis for a variety of separation applications. We show here that for a class of chabazite zeolites, what appears to be “molecular sieving” based on dimension is actually separation based on a difference in ability of a guest Molecule to induce temporary and reversible cation deviation from the center of pore apertures, allowing for exclusive admission of certain Molecules. This new mechanism of discrimination permits “size-inverse” separation: we illustrate the case of admission of a larger Molecule (CO) in preference to a Smaller Molecule (N2). Through a combination of experimental and computational approaches, we have uncovered the underlying mechanism and show that it is similar to a “molecular trapdoor”. Our materials show the highest selectivity of CO2 over CH4 reported to date with important application to natural gas purification.