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961.
Jamin Huang Dean F. Bushey Michael D. Graves Brenda F. Johnson Dianne D. Singleton 《Journal of heterocyclic chemistry》1987,24(1):1-7
A series of 3-substituted-5-methoxy-1,3,4-oxadiazol-2-ones were prepared from aldehydes, ketones, phenylacetic acids, and 1,2- and 1,3-diketones. Conditions for the formation of these oxadiazolones from the precursor N-carbamoyl chlorides depended on the structure, and varied from spontaneous ring closure to those requiring bases. Variation in the N-3 substituents sometimes produced mixtures of isomers which were separated and identified. These molecules were prepared in order to study the effect of the N-3 substituent variation on the biological properties of oxadiazolones. 相似文献
962.
锆助剂对低温液相合成甲醇用铜铬硅催化剂性能的影响 总被引:3,自引:2,他引:3
考察了含锆的铜铬硅催化剂低温液相合成甲醇性能,并进行了BET、TPR-H2、TPD-H2、TPD-CO、XRD和XPS表征。结果表明,锆作为结构助剂及电子助剂对催化剂在低温液相合成甲醇反应中具有显著的促进作用,反应活性可提高32.25 %。锆助剂能有效提高催化剂的比表面积,促进催化剂中铜铬组分的分散及表面富集。ZrO2加入在催化剂表面产生的Cu+与催化活性的改善密切相关,Zr4+、Cr3+、Cu+可形成复合中心,为价态的稳定性提供微环境,在H2活化及C O键的断裂等反应步骤中起重要作用。 相似文献
963.
Shu-Liang Zang Qing-Guo Zhang Ming Huang Bin Wang Jia-Zhen Yang 《Fluid Phase Equilibria》2005,230(1-2):192-196
This paper reports that an ionic liquid (IL) has been prepared by directly mixing InCl3 and 1-methyl-3-ethylimidazolium chloride (EMIC) with molar ratio 1/1 under dry argon atmosphere. The densities, and surface tension of the pure IL were determined at temperature range of 293.15 to 343.15 ± 0.1 K. The volumetric properties and the properties of surface for ionic liquid based on group III were discussed by Glasser's theory and Yang's interstice model. 相似文献
964.
Designing proteins with novel protein/protein binding properties can be achieved by combining the tools that have been developed independently for protein docking and protein design. We describe here the sequence-independent generation of protein dimer orientations by protein docking for use as scaffolds in protein sequence design algorithms. To dock monomers into sequence-independent dimer conformations, we use a reduced representation in which the side chains are approximated by spheres with atomic radii derived from known C2 symmetry-related homodimers. The interfaces of C2-related homodimers are usually more hydrophobic and protein core-like than the interfaces of heterodimers; we parameterize the radii for docking against this feature to capture and recreate the spatial characteristics of a hydrophobic interface. A fast Fourier transform-based geometric recognition algorithm is used for docking the reduced representation protein models. The resulting docking algorithm successfully predicted the wild-type homodimer orientations in 65 out of 121 dimer test cases. The success rate increases to approximately 70% for the subset of molecules with large surface area burial in the interface relative to their chain length. Forty-five of the predictions exhibited less than 1 A C(alpha) RMSD compared to the native X-ray structures. The reduced protein representation therefore appears to be a reasonable approximation and can be used to position protein backbones in plausible orientations for homodimer design. 相似文献
965.
We perform molecular dynamics simulations of the hydrophobic collapse of two paraffin plates to examine how the collapse is mediated by realistic paraffin-water attractive van der Waals forces. We explore several aspects of the drying transition between the plates, including the critical separation for drying and the critical size of the vapor bubble required for the nucleation of the drying event. We also investigate the kinetics of hydrophobic collapse and find that the hydrophobic collapse occurs in about 100 ps. We compare these results with the simulations with the plate-water van der Waals attractions turned off and with recent results on the hydrophobic collapse of multidomain proteins. Last, we discuss the relationship among the dewetting transition critical distance, van der Waals potential well depth, and water contact angle on solute surface using a simple macroscopic theory. 相似文献
966.
IntroductionItiswellknownthatmetallocenesactivatedwithmethylaluminoxane (MAO)arehighlyactivehomogeneousZiegler Nattacatalyststhatproducepolyolefinwithcon trolledstereoregularityandnarrowmolecularweightdistri bution ,1 4 however,themolecularweightofthepolym… 相似文献
967.
968.
The photofragmentation of CH_3I at 249 nm has been investigated by means of our crossed laser-molecular beam apparatus with rotatable supersonic beam source. The measured I~*/I yield ratio is about 4/1. The C—I bond dissociation energy obtained is 56±1 kcal mol~(-1). The vibrational energy distribution of CH_3 fragments has been roughly estimated. 相似文献
969.
Nieh MP Raghunathan VA Kline SR Harroun TA Huang CY Pencer J Katsaras J 《Langmuir : the ACS journal of surfaces and colloids》2005,21(15):6656-6661
We observe the spontaneous formation of path-dependent monodisperse and polydisperse phospholipid unilamellar vesicles (ULV) from two different equilibrium morphologies specifically, disklike micelles and extended lamellae, respectively. On heating beyond a temperature Tc, low temperature disklike micelles, or so-called bicelles, transform into lamellae. Dilution of the lamellar phase, at a fixed temperature, results in a complete unbinding transition and the formation of polydisperse ULV, demonstrating the instability of the lamellar phase. On the other hand, heating of a dilute bicellar phase above Tc results in monodisperse ULV, which on cooling revert back to bicelles for lipid concentrations phi > or = 0.5 wt % and transform into oblate ellipsoids for phi = 0.1 wt %, a morphology not previously seen in "bicellar" lipid mixtures. Monodisperse ULV reform on heating of the oblate ellipsoids. 相似文献
970.
The hetero Diels-Alder reaction of 1-amino-3-siloxy-1,3-butadiene (1a) with a range of unactivated aldehydes proceeds readily under remarkably mild conditions: at room temperature and in the absence of Lewis acid catalysts. The cycloadducts are formed in good yields and can be converted directly to the corresponding dihydro-4-pyrones using acetyl chloride. Ketones and imines are also reactive in hetero Diels-Alder reactions with this diene. 相似文献