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71.
Wettability is one of the anisotropic surface properties of molecular crystals that exhibit the structural variance of chemical moieties on various growth faces. The divergence in liquid-solid interactions at different faces is thought to be related to the inherent responding capacity or sensitivity of a solid surface to the perturbation in electronic structures and atomic positions as a result of the contact by a liquid. Since the Fukui function, according to density functional theory (DFT), is a local function for describing such sensitivity to the structural perturbation and is directly related to local softness, it has been proposed and tested to use an integrated Fukui function over a crystallographic plane for describing the anisotropy of solid-liquid interactions. It is found that the contact angle of a polar solvent, such as water, on a crystal surface shows an intimate connection to the integrated Fukui functions of the surface, illustrating an extension of Pearson's HSAB (hard and soft acids and bases) to crystal systems. The concept of face-integrated Fukui function and the approach to apply the HSAB with the DFT-based concepts may provide a powerful means for describing anisotropic properties, including wettability of organic crystals. 相似文献
72.
73.
The closest packing ofx circles on the surface of a sphere is calculated in the same way that the stereochemical arrangement of atoms around a central atom is determined. A number of improved packings have been discovered for x = 19 to 80. A notable feature is that the structures are generally of low symmetry. The packing densityp, defined as the fraction of the spherical surface that is enclosed by the circles, increases only very slowly as the number of circles increases and the values remain substantially below that for a close packed plane, or for an octahedron or icosahedron. 相似文献
74.
Clare Ho 《Analytica chimica acta》2005,530(1):23-31
A sensitive and selective method using gas chromatography-electron capture negative ionization mass spectrometry (GC-ECNI-MS) for analysis of dimetridazole (DMZ) and metronidazole (MNZ) in poultry muscles, porcine kidney and liver, and chicken liver, was developed and validated for the purpose of food surveillance testing of the residues of these two nitroimidazoles in various types of animal tissues in the Hong Kong Special Administrative Region. Before homogenization and extraction with toluene, [2H3]dimetridazole-(DMZ-d3) and secnidazole (SNZ) were added to tissue samples as internal standards. The organic extracts were mixed with n-hexane and subject to solid-phase extraction cleanup by amine extraction columns. MNZ and SNZ were derivatized with BSA prior to GC-ECNI-MS determination. Good recovery and precision were obtained and the limit of detection was below parts per billion levels for poultry and porcine tissues. The method could also be applied for the detection of the hydroxylated metabolite of DMZ. 相似文献
75.
Barry CS Crosby SR Harding JR Hughes RA King CD Parker GD Willis CL 《Organic letters》2003,5(14):2429-2432
[reaction: see text] Reaction of homoallylic alcohols with aldehydes in the presence of TFA gives, after hydrolysis of the ester, 4-hydroxy-2,3,6-trisubstituted tetrahydropyrans with the creation of three new stereocenters in a single-pot process. By varying the aldehyde component, a variety of functionalized side chains are installed at C-2. The utility of this approach is extended to the enantioselective synthesis of tetrahydropyrans with >99% ee. 相似文献
76.
77.
Stephen L. De Wall Eric S. Meadows Clare L. Murray Hossein Shabany George W. Gokel 《Supramolecular chemistry》2013,25(1):13-22
Abstract A family of tris(macrocyclic) compounds of the form sidearm<N18N>Cn<N18N>Cn<N18N>sidearm, has been prepared, characterized chemically, and assayed by dynamic 23Na-NMR for the ability to transport sodium cations in a mixed phosphatidylglycerol/phosphatidylcholine vesicle system. A number of control experiments have been conducted that reinforce the hypothesis that cation transport occurs by a channel mechanism. The tris(macrocycle) channels proved to be functional at a level of 25–50% of that found for the natural pentadecapeptide channel gramicidin. Fluorescence data confirm the expected position of the channel within the bilayer. 相似文献
78.
PaulW. Finn Morwena Bandara Chris Butcher Angela Finn Ruth Hollinshead Nagma Khan Norman Law Sreenivasa Murthy Rosario Romero Clare Watkins Victor Andrianov RasmaM. Bokaldere Klara Dikovska Vija Gailite Einars Loza Irina Piskunova Igor Starchenkov Maxim Vorona Ivars Kalvinsh 《Helvetica chimica acta》2005,88(7):1630-1657
Inhibition of the enzyme histone deacetylase (HDAC) is emerging as a novel approach to the treatment of cancer. A series of novel sulfonamide derivatives were synthesized and evaluated for their ability to inhibit human HDAC. Compounds were identified which are potent enzyme inhibitors, with IC50 values in the low nanomolar range against enzyme obtained from HeLa cell extracts, and with antiproliferative effects in cell culture. Extensive characterization of the structure–activity relationships of this series identified key requirements for activity. These include the direction of the sulfonamide bond and substitution patterns on the central phenyl ring. The alkyl spacer between the aromatic head group and the sulfonamide functionality also influenced the HDAC inhibitory activity. One of these compounds, m 11.1 , also designated PXD101, has entered clinical trials for solid tumors and haematological malignancies. 相似文献
79.
Song F Carder EJ Kohler CC Koide K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(45):13500-13508
Residual metals in fine chemicals are currently detected by using inductively coupled plasma mass spectrometry, which requires expensive instrumentation and does not have high-throughput capabilities. Although fluorescent probes can be amenable to high-throughput analyses of metals, the utility of such analyses is limited due to the lack of generality. Herein, we report a significant improvement (≈19-fold) to our previously reported catalysis-based fluorescent probe for palladium. Specifically, we found that slightly elevated temperature dramatically improved the generality of the method and that the deallylation reaction of the nonfluorescent compound 1 was accelerated by phosphate ions in aqueous media. This method was capable of detecting 0.2 ppb palladium. We demonstrated reasonably accurate palladium detection in various active pharmaceutical ingredients and highly functionalized organic compounds. 相似文献
80.
Jordi Cabana Costana M. Ionica-Bousquet Clare P. Grey M. Rosa Palacín 《Electrochemistry communications》2010,12(2):315-318
The performance of Li7.9MnN3.2O1.6 and Li7MnN4 as electrode materials in lithium batteries was analyzed. At 1C rate, capacities of 180 and 230 mAh/g, respectively, were obtained after 50 cycles. If the first charge is done at 0.1C, outstanding capacities of 120–135 mAh/g are observed after 100 cycles at 5C. More lithium can be removed during the charge at 0.1C, leading to a large amount of lithium vacancies that enhance mobility and rate capability. It is proposed that incomplete filling of the vacancies occurs upon cycling, so that the mobility remains high. This performance compares well to that of Li4Ti5O12. 相似文献