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111.
[reaction: see text] A chemoenzymatic synthesis of ADP-D-glycero-beta-D-manno-heptose (ADP-D,D-Hep) is described in which D,D-Hep 7-phosphate is converted to ADP-D,D-Hep by two biosynthetic enzymes. This strategy allows access to the 6'-deuterated analogue, which upon incubation with the epimerase showed complete retention of the isotopic label at the 6'-position. This provides evidence for a direct oxidation mechanism in which the hydride initially transferred to the NADP+ cofactor is subsequently returned to the same carbon in a nonstereospecific manner. 相似文献
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Oligo(p-phenylene) rigid rod 10 is synthesized via a functional group-tolerant molecular doubling approach. Preparative chromatographic methods, protecting groups, boronic acid isolations, and Grignard or organolithium reagents are not used. The convenient synthesis of well-defined, polar-functionalized oligophenylene rigid rods could afford ready access to a variety of useful electronic organic materials. 相似文献
114.
Brian J. Read 《Nuclear Physics B》1974,74(3):482-492
Data from three coincidence experiments which measure the cross section for π+ electroproduction around threshold are compared. Application of the PCAC motivated pseudovector Born approximation model yields corresponding values of the nucleon axial vector form factor for spacelike momentum transfer up to 0.6 GeV2. Attention is paid to possible theoretical uncertainties and to the influence of the first pion-nucleon resonance. (Recent single arm SLAC results are also included.) 相似文献
115.
The intensity of the specular beam for low energy positron diffraction (LEPD) from the Cu(111) surface is calculated in the energy range 20–150 eV. Close agreement is found with the first experimental data for LEPD published recently. This result indicates that LEPD may be exploited as a technique for determining surface structures in the near future. It is suggested that LEPD may have advantages in surface structure analysis in comparison with low energy electron diffraction (LEED). 相似文献
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The simple Regge absorption model used previously for high-energy charged kaon photoproduction is here directly extended to electroproduction, thus providing a framework for theoretical discussion and interpretation of future experimental efforts. 相似文献
120.
John N.H. Brunt George C. King Frank H. Read 《Journal of Electron Spectroscopy and Related Phenomena》1977,12(3):221-228
The excitation by electron impact of levels of helium atoms that decay by emission of ultraviolet light has been studied as a function of incident energy up to approximately the first ionization energy. The width (FWHM) of the energy spread of the incident beam was less than 30 meV. A crossed-beam interaction region was used and UV photons emitted approximately normally to the electron and gas beam directions were detected by a channel electron multiplier. Precautions were taken to avoid detection of scattered electrons and metastable atoms by the photon detector. The onset position of the lowest excited level was used in calibrating the incident energy scale. The energies of resonance structures in the cross-sections could therefore be obtained and are compared with the results of experiments detecting other products of the interaction. 相似文献