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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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Anjan K. Saha M. Mahmun Hossain Desiree S. Grubisha Dennis W. Bennett 《Journal of chemical crystallography》1995,25(7):383-387
Benzophenone azine crystallizes in the monoclinic space groupA2/a (No. 15) witha=16.303(3) Å,b=5.4864(2) Å,c=21.973(5) Å, =85.52(2)°,V=1959.4(8) Å3, andD
calc=1.22 g cm–3 forZ=4. The structure was solved by direct methods and refined againstF to a finalR value of 0.047. The unit cell contains four molecules of the title compound; the asymmetric unit consists of half a molecule. Despite the high crystallographic symmetry, the two halves of the molecule arenot related by a center of symmetry; instead, the molecule adopts C2 symmetry; the molecular C2 axis is coincident with the crystallographic twofold axis. The formation of benzophenone azine from the reaction of the iron-containing Lewis acid complex [(5-C5H5)Fe(CO)2(THF)]+ [BF4]– and diphenyldiazomethane provides strong evidence for an Fe(II) carbene intermediate. 相似文献
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Dr. Anzhela Galstyan Dr. Desiree Block Dr. Silke Niemann Dr. Malte C. Grüner Prof.Dr. Stefania Abbruzzetti Michele Oneto Dr. Constantin G. Daniliuc Dr. Sven Hermann Prof.Dr. Cristiano Viappiani Prof.Dr. Michael Schäfers Prof.Dr. Bettina Löffler Priv.‐Doz.Dr. Cristian A. Strassert Dr. Andreas Faust 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(27):9051-9051
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Jeffrey B. Weinrach Dale R. Meyer Joseph T. Guy Jr. Paul E. Michalski Kay L. Carter Desiree S. Grubisha Dennis W. Bennett 《Journal of chemical crystallography》1992,22(3):291-301
Raman spectroscopy on solid anhydrous sodium dithionite reveals that it exists in at least two forms in the solid state. MAS23Na NMR spectra and X-ray powder diffraction patterns of the solids indicate that sodium ions are in different environments in each form of the material. The results suggest that the dithionite anion is conformationally different in each lattice. A single crystal X-ray diffraction study of the recrystallized form of anhydrous sodium dithionite reveals an anion with C2 geometry and a 16° O-S-S-O torsional angle; nearly eclipsed. (Crystal Data for recrystallized Na2S2O4 area=6.539(1) Å,b=6.552(1) Å,c=6.578(1) Å,V=240.0(1) Å3,=121.61(1)°, space group=P2/c,Z=2). Raman spectra of sodium dithionite dihydrate reveal that the dithionite ion is in a different conformation than in either of the anhydrous materials. A single crystal X-ray diffraction study of Na2S2O4·2H2O reveals a dithionite anion with a substantially shorter S-S bond length than in the anhydrous structure and an O-S-S-O torsional angle of 56°; approximately gauche. (Crystal Data for Na2S2O4·2H2O area=8.134(1) Å,b=5.756(2) Å,c=14.528(5) Å,V=653.3(3) Å3,=106.20(2)°, space group=P21/n,Z=4). The structure of the dithionite anion is found to depend critically upon the nature of its external environment. 相似文献
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Saghatelian A Guckian KM Thayer DA Ghadiri MR 《Journal of the American Chemical Society》2003,125(2):344-345
Rapid, sensitive, and sequence-specific DNA detection can be achieved in one step using an engineered intrasterically regulated enzyme. The semi-synthetic inhibitor-DNA-enzyme (IDE) construct (left) rests in the inactive state but upon exposure to a complementary DNA sequence undergoes a DNA hybridization-triggered allosteric enzyme activation (right). The ensuing rapid substrate turnover provides the built-in signal amplification mechanism for detecting approximately 10 fmol DNA in less than 3 min under physiological conditions. 相似文献
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Jürgen Brüning Desiree Heintz Alke Meents Michael Bolte Martin U. Schmidt 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(9):o459-o462
Indigo and thioindigo pigments are used for a wide range of applications. The crystal structure of the mixed compound monothioindigo [systematic name: (E)‐2‐(3‐oxo‐2,3‐dihydro‐1‐benzothiophen‐2‐ylidene)‐2,3‐dihydro‐1H‐indol‐3‐one], C16H9NO2S, has been determined by microcrystal structure analysis from a crystal with a size of just 1 × 2 × 10 µm. The crystal structure of monothioindigo resembles those of indigo and thioindigo. The molecules show orientational disorder, with site‐occupation factors of 0.962 (2) and 0.038 (2) for the major and minor disorder components, respectively. The indigo fragment donates an intermolecular hydrogen bond, leading to a criss‐cross arrangement of molecules similar to that in indigo, whereas the thioindigo fragment exhibits only van der Waals interactions and molecular stacking, similar to that in thioindigo. 相似文献
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Oliver P. Williams Alyah F. Chmiel Myriam Mikhael Desiree M. Bates Charles S. Yeung Zachary K. Wickens 《Angewandte Chemie (International ed. in English)》2023,62(18):e202300178
Herein, we describe a practical protocol for the removal of alcohol functional groups through reductive cleavage of their benzoate ester analogs. This transformation requires a strong single electron transfer (SET) reductant and a means to accelerate slow fragmentation following substrate reduction. To accomplish this, we developed a photocatalytic system that generates a potent reductant from formate salts alongside Brønsted or Lewis acids that promote fragmentation of the reduced intermediate. This deoxygenation procedure is effective across structurally and electronically diverse alcohols and enables a variety of difficult net transformations. This protocol requires no precautions to exclude air or moisture and remains efficient on multigram scale. Finally, the system can be adapted to a one-pot benzoylation-deoxygenation sequence to enable direct alcohol deletion. Mechanistic studies validate that the role of acidic additives is to promote the key C(sp3)−O bond fragmentation step. 相似文献