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121.
122.
Isolation of lipase producer and its performance in enantioselective hydrolysis of glycidyl butyrate
A racemic glycidyl butyrate resolving strain, preliminarily identified as a Rhizopus sp., had been isolated from soil. Its extracellular lipase was found to enantioselectively hydrolyze the (S)-enantiomer of
the chiral ester, with optimal activities at pH 5.3 and 42°C. Higher en antioselectivity of theenzyme was observed at lower
temperatures, while the best anantioselectivity was obtained at pH 5.5–6.0, with an, E value (enantiomeric ratio) of 57. 相似文献
123.
Tian SX 《The journal of physical chemistry. A》2005,109(20):4428-4430
Dialane anions can be formed via a single three-center two-electron (3c-2e) or two-center one-electron (2c-1e) bond. The 2c-1e bonded anion Al(2)H(6)(-)(D(3)(d)) and the 3c-2e bonded anion Al(2)H(6)(-)(C(s)) have significant thermodynamic stabilities with respect to the neutral Al(2)H(6)(D(2)(h)) and correspond to 0.22 and 0.32 eV of the adiabatic electron affinities, respectively. In particular, the 2c-1e bond plays an essential role in stabilizing the Al(2)H(6)(-)(D(3)(d)) anion. 相似文献
124.
偏最小二乘及双波长K系数光度法同时测定矿物中钛,铁 总被引:3,自引:0,他引:3
本文运用化学计量学中的偏最小二乘法及双波长K系数法实现了Ti、Fe的同时测定,方法用于铝钒土及钛铁矿中Ti、Fe同时测定,结果满意。 相似文献
125.
Oxo complex [(1,5-COD)4Pt4(mu3-O)2Cl2](BF4)2 (1) reacts readily with ethylene and norbornylene. The ethylene reaction yields acetaldehyde and a 1:1 mixture of (1,5-COD)Pt(Cl)(CH2CH3) (2) and [(1,5-COD)Pt4(eta3-CH2CHCH(CH3))](BF4) (3), while the norbornylene reaction yields a platinaoxetane complex, the first metallaoxetane to be obtained from the reaction of an oxo complex and an alkene. 相似文献
126.
The synthesis of norvancomycin (NVan)-capped silver nanoparticles (Ag@NVan) and their notable in vitro antibacterial activities against E. coli, a Gram-negative bacterial strain (GNB), are reported here. Mercaptoacetic acid-stabilized spherical silver nanoparticles
with a diameter of 16±4 nm are prepared by a simple chemical reaction. The formation process of the silver nanoparticles is
investigated by UV-visible (UV-vis) spectroscopy and transmission electron microscopy (TEM). NVan is then grafted to the terminal
carboxyl of the mercaptoacetic acid in the presence of N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDAC). The TEM images of single bacteria treated with Ag@NVan show that plenty of Ag@NVan
aggregate in the cell wall of E. coli. A possible antibacterial mechanism is proposed that silver nanoparticles may help destroy the stability of the outer membrane
of E. coli, which makes NVan easier to bind to the nether part of the peptidoglycan structure. The antibacterial activities of silver
nanoparticles on their own, together with the rigid polyvalent interaction between Ag@NVan and cell wall, enables Ag@NVan
to be an effective inhibitor of GNB. This kind of bionanocomposites might be used as novel bactericidal materials and we also
provide an effective synthesis method for preparing functional bioconjugated nanoparticles here.
Supported by the National Natural Science Foundation of China (Grant No. 50373036) and Fok Ying Tung Education Foundation
(Grant No. J20040212) 相似文献
127.
A new thioether-rich ligand with a conjugated dienyne backbone and its fluorescent Ag(I) coordination networks have been synthesized and characterized by single crystal X-ray diffraction studies, which reveal that the supramolecular architectures of the networks contain assembled helicates with thioether sites. 相似文献
128.
A detailed singlet potential energy surface(PES) of [Si,C,O,O] system including a van der Waals (vdW) comples SiO……CO2,eight isomers,and twelve transiton states is investigated by MP2 and QCISD(T) (single-point)methods.At the final QCISD(T)/6-311 G(2df)//MP2/6-311G(d) level with zero-point energy included,the complex SiO……CO is found to be thermodynamically and kinetically the most stable species.Although eight ismoers are located as local energy minima,they are rather unstable toward isomerization to the dissociation fragments or comples.For the reaction of silocon atoms with carbon dioxide,two competitive reaction channels are found,and the primary pathway,which leads to the products of SiO and CO fragments,is the direct oxygen-abstraction process from carbon dioxide by silicon atom with a41.16 kJ/mol reaction barrier height.Our predications are in good agreement with previous experimental and theoretical studies. 相似文献
129.
测定了116例冠心病患者血清中钙、镁、镉、铅、铍的含量并与正常对照组比较。结果显示,常量元素钙、镁与微量元素镉、铅含量降低,而铍的含量升高。它们之间的差异有显著性或高度显著性,P〈0.05或P〈0.01。 相似文献
130.
Al3Ti1B1RE细化剂对罐用铝材的细化效果及稀土的作用 总被引:6,自引:0,他引:6
采用XRD,OM,SEM,EDAX等探讨了一种新型Al3Ti1B1RE中间合金细化剂对罐用铝材的细化效果及RE的作用。结果表明,该细化剂对罐用铝材的细化效果优于进口和国产Al3Ti1B,且具有长效性,达6h后仍未见明显衰退,明显提高了该材料的强度和塑性;其细化效果及稳定性好的主要原因是:RE可降低铝液的表面能,增加铝液对细化核心(如TiAl3,TiB2)的润湿性,既充分发挥了异质形核作用,又防止了TiB2聚集沉淀倾向;RE也极易在结晶前沿富集造成成分过冷,阻碍了α-Al晶粒生长,并促进其在细化核心上形核;此外RE还兼有一定的净化、细化和变质作用,尤其是净化作用提高了该细化剂的冶金质量。 相似文献