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11.
Andrew S. Rowan Thomas S. Moody Roger M. Howard Toby J. Underwood Iain R. Miskelly Yanan He Bo Wang 《Tetrahedron: Asymmetry》2013,24(21-22):1369-1381
Libraries of highly enantioenriched secondary alcohols in both enantiomeric forms were synthesised by enzymatic reduction of their parent ketones using selectAZyme? carbonyl reductase (CRED) technology. Commercially available CREDs were able to reduce a range of substrate classes efficiently and with very high enantioselectivity. Matching substrate classes to small subsets of CREDs enabled the fast development of preparative bioreductions and the rapid generation of 100–1500 mg samples of chiral alcohols in typically >95% ee and the majority in ?99.0% ee. The conditions for small scale synthesis were then scaled up to 0.5 kg to deliver one of the chiral alcohols, (S)-1-(4-bromophenyl)-2-chloroethanol, in 99.8% ee and 91% isolated yield. 相似文献
12.
Maria Lorna A. De Leoz Shuai Wu John S. Strum Milady R. Niñonuevo Stephanie C. Gaerlan Majid Mirmiran J. Bruce German David A. Mills Carlito B. Lebrilla Mark A. Underwood 《Analytical and bioanalytical chemistry》2013,405(12):4089-4105
Human milk oligosaccharides (HMOs), though non-nutritive to the infant, shape the intestinal microbiota and protect against pathogens during early growth and development. Infant formulas with added galacto-oligosaccharides have been developed to mimic the beneficial effects of HMOs. Premature infants have an immature immune system and a leaky gut and are thus highly susceptible to opportunistic infections. A method employing nanoflow liquid chromatography time-of-flight mass spectrometry (MS) is presented to simultaneously identify and quantify HMOs in the feces and urine of infants, of which 75 HMOs have previously been fully structurally elucidated. Matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance MS was employed for high-resolution and rapid compositional profiling. To demonstrate this novel method, samples from mother–infant dyads as well as samples from infants receiving infant formula fortified with dietary galacto-oligosaccharides or probiotic bifidobacteria were analyzed. Ingested oligosaccharides are demonstrated in high abundance in the infant feces and urine. While the method was developed to examine specimens from preterm infants, it is of general utility and can be used to monitor oligosaccharide consumption and utilization in term infants, children, and adults. This method may therefore provide diagnostic and therapeutic opportunities. Figure
Quantification of human milk oligosacchairdes in the milk, feces, and urine of a mother-infant dyad by MALDI FT-ICR (spectra) and nano-LC MS (pie charts) 相似文献
13.
Appropriate oxygen-18 labeling experiments demonstrate that N,O-diarylhydroxylamines do not undergo solvolysis the reversible formation of ion pairs. This is in total conflict with the conclusions from previous indirect kinetic studies of these ultimate carcinogen models. 相似文献
14.
Excited state intramolecular proton transfer in 1-chloroacetylaminoanthraquinone is investigated from the perspective of the solvent. Using a new two-dimensional nonlinear optical spectroscopy the solvent response is probed directly as the proton transfer takes place. The measurements indicate that solvent reorganization controls the proton transfer in acetonitrile by dynamically shifting the position of equilibrium in the excited state, even on subpicosecond time scales. 相似文献
15.
16.
Ball-indentation experiment ware performed with A723 steel of 100- to 1200-MPa ultimate strength. Results are compared with
conventional tension tests and with an elastic-plastic finite-element model of the ball indentation. Finite-element analysis
shows the ball-indentation process to be insensitive to friction effects. Comparison of indentation and conventional tests
shows that slip-line field analysis closely predicts the ball contact stress. The indentation tests gave an accurate measure
of ultimate tensile strength because of the following test procedures: using a large ball size and a fixed ratio of indentation
depth to ball size; accounting for directional material properties; accounting for extraneous system deflections. 相似文献
17.
18.
D. Kapolnek R. D. Underwood B. P. Keller S. Keller S. P. Denbaars U. K. Mishra 《Journal of Crystal Growth》1997,170(1-4):340-343
Selective area epitaxy of GaN by MOCVD has been used to fabricate arrays of hexagonal pyramid structures for electron field emission devices. The reactor temperature and pressure have been found to strongly affect the resulting pyramid morphology. Growth at 76 Torr results in improved pyramid shape and uniformity compared to growth at atmospheric pressure. Optimized arrays of pyramids produced emission currents of 80 μA at 1100 V, when biased across 0.5 mm in UHV. 相似文献
19.
Two new cesium thorium fluorides and three new rubidium thorium fluorides have been synthesized hydrothermally and structurally characterized. The structures of two polymorphs of CsTh(3)F(13) are described in space group P6/mmm with a = 8.2608(14) and c = 8.6519(17) and space group Pmc2(1) with a = 8.1830(16), b = 7.5780(15), and c = 8.6244(17). The analogous orthorhombic compound RbTh(3)F(13), with a = 8.1805(16), b = 7.4378(15), and c = 8.6594(17) in space group Pmc2(1), is also reported. Two other rubidium thorium fluorides are also described: RbTh(2)F(9) crystallizes in the space group Pnma where a = 8.9101(18), b = 11.829(2), and c = 7.4048(15), and Rb(7)Th(6)F(31) crystallizes in the space group R3 where a = 15.609(2) and c = 10.823(2). Comparison of these materials was made on the basis of their structures and synthesis conditions. The formation of these species in hydrothermal fluids appears to be dependent upon the concentration of the alkali fluoride mineralizer solution and, thus, the ratio of alkali ions to thorium in the system. 相似文献
20.
Summary This paper introduces a novel, highly effective method of producing packed capillaries for use in capillary electrochromatography
(CEC) or microbore HPLC. It is our opinion that CEC offers significant advantages for future separation systems particularly
with MS detection and these methods will assist the development of the capillary production technology. 相似文献