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Kleijn JM Barten D Stuart MA 《Langmuir : the ACS journal of surfaces and colloids》2004,20(22):9703-9713
Using an optical reflectometer with impinging-jet system, the adsorption from aqueous solution onto gold of three charged macromolecules has been studied: the strong linear-chain polyelectrolyte polyvinyl pyridine (PVP(+)), the fifth-generation poly(propylene imine) dendrimer DAB-64, which has a pH-dependent charge and a relatively fixed shape, and the protein lysozyme, of which both the charge and the structure-stability are dependent on solution composition. Experimental conditions that have been varied include the adsorbate concentration, electrolyte concentration, pH, and externally applied potential across the gold/solution interface. Making use of the earlier established dependency of the double layer potential of the gold substrate on solution conditions and externally applied potential, the results of measurements as a function of pH and as a function of external potential control are compared. The total set of results enables us to draw conclusions with respect to the relative importance of electrostatic interactions for the adsorption process. PVP(+) adsorption follows the electric potential of the gold/solution interface and is further determined by a rather strong nonelectrostatic affinity between segments and surface. The adsorption behavior of DAB-64 is not quite understood, but electrostatic interactions with the gold surface seem to play a minor role. For lysozyme, surface-induced conformational changes dominate the adsorption process. The extent of spreading of the molecules decreases with increasing polarity of the surface, resulting in a minimum in adsorbed amount around the point of zero potential of the gold. 相似文献
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Trimethylsilyl ethers of 2,3-hexadien-5-yn-1-ols (1) undergo carbocupration at the terminal triple bond, and this reaction has been used to prepare, among other species, the trimethylsilyl ethers of 8-trimethylsilyl-2,3,5-octatrien-7-yn-1-ols(6a and 7a). When the terminal triple bond of 1 is protected with a trimethylsilyl group SN2′-like displacements take place upon addition of RCu, with predominant formation of E-dienynes in which H is present instead of R, especially when s-BuCu is used. Only when R is methyl is the R group transferred. On the other hand, smooth formation of dienynes bearing the R group are observed upon reaction of methanesulfinates with RCu; in this case, however, the configuration of the dienynes is mainly Z. A mechanistic rationalization of the results is proposed. 相似文献
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The double-layer properties of colloidal RuO2, prepared by thermal decomposition of RuCl3 at 420°C, have been studied by potentiometric acid-base titrations in combination with electrophoretic mobility measurements. The point of zero charge (pzc) in KNO3 solutions was found to be pH 5.75 ± 0.05, and the isoelectric point (iep) is positioned at pH 5.8. From the total capacitance of the double layer at the pzc an electrochemical surface area of 21.5 m2/g has been found, which is equal to the BET surface area. The capacitance of the inner part of the double layer (Ci) is 300 μF/cm2, which is high compared to Ci on AgI and Hg, but of the same order as that commonly found for oxides. This subject is briefly discussed. The surface charge (σ0) as a function of pH could be fitted satisfactorily with a simple double-layer model. In the presence of KCl the pzc and the iep are shifted to higher and lower pH, respectively, indicating specific adsorption of Cl− ions. The ionic composition of the double layer as a function of σ0 and the specific adsorption of Cl− at the pzc have been calculated by a straightforward thermodynamic analysis combined with diffuse double-layer theory. Methylviologen (MV2+) also adsorbs specifically and at negative surface charges superequivalent adsorption can take place. In the presence of an excess of KNO3, specific adsorption of MV2+ is no longer noticeable. Some consequences for the catalytic reduction of water by RuO2 in the presence of MV2+ are considered. 相似文献
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The fluoride capacity of the Dowex 1-X4 anion exchange resin was measured by radiometric and elemental analysis. The capacity
data obtained by the two methods showed good agreement. 相似文献
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T B Vree A M Baars Y A Hekster E van der Kleijn W J O'Reilly 《Journal of chromatography. A》1979,162(4):605-614
9.
S. van Veldhuizen C. Vuik C.R. Kleijn 《Numerical Methods for Partial Differential Equations》2008,24(3):1037-1054
Two‐dimensional transient simulations are presented of the transport phenomena and multispecies, multireaction chemistry in chemical vapor deposition (CVD). The transient simulations are run until steady state, such that the steady state can be validated against the steady state solutions from literature. We compare various time integration methods in terms of efficiency and robustness. Besides stability, which is important due to the stiffness of the problem, preservation of non‐negativity is crucial. It appears that this latter condition on a time integration method is much more restrictive toward the time step size than stability. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008 相似文献
10.
Ring‐Closing and Cross‐Metathesis with Artificial Metalloenzymes Created by Covalent Active Site‐Directed Hybridization of a Lipase
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Dr. Manuel Basauri‐Molina Dide G. A. Verhoeven Arnoldus J. van Schaik Henk Kleijn Prof. Dr. Robertus J. M. Klein Gebbink 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15676-15685
A series of Grubbs‐type catalysts that contain lipase‐inhibiting phosphoester functionalities have been synthesized and reacted with the lipase cutinase, which leads to artificial metalloenzymes for olefin metathesis. The resulting hybrids comprise the organometallic fragment that is covalently bound to the active amino acid residue of the enzyme host in an orthogonal orientation. Differences in reactivity as well as accessibility of the active site by the functionalized inhibitor became evident through variation of the anchoring motif and substituents on the N‐heterocyclic carbene ligand. Such observations led to the design of a hybrid that is active in the ring‐closing metathesis and the cross‐metathesis of N,N‐diallyl‐p‐toluenesulfonamide and allylbenzene, respectively, the latter being the first example of its kind in the field of artificial metalloenzymes. 相似文献