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131.
Virus-ligand interactions: identification and characterization of ligand binding by NMR spectroscopy
Benie AJ Moser R Bäuml E Blaas D Peters T 《Journal of the American Chemical Society》2003,125(1):14-15
We demonstrate the detection and characterization of ligand binding to viruses via NMR. To illustrate the methodology, the interaction of an antiviral compound with human rhinovirus serotype 2 (HRV2) was investigated. Specific interaction of a capsid-binding inhibitor and native HRV2 was monitored utilizing saturation transfer difference (STD) NMR. STD NMR experiments at atomic resolution allowed those regions of the ligand that are involved in the interaction with the virus to be determined. The approach allows for (i) the fast and robust assessment of binding, (ii) the determination of the ligand binding epitope at atomic resolution without the necessity to crystallize virus-ligand complexes, and (iii) the reuse of the virus in subsequent assays. This methodology enables one to easily identify binding of drugs, peptides, and receptor or antibody fragments to the viral capsid. 相似文献
132.
Lutz-Werner Gross Rainer Moser Wilhelm P. Neumann Karl-Heinz Scherping 《Tetrahedron letters》1982,23(6):635-638
Thermally generated stannylenes R2Sn insert efficiently into Sn-X bonds (X Cl, 3r, SPh) as well as into electron deficient SnSn bonds e.g. in Me2(Hal)SnSn(Hal)Me2, but not into hexaalkyldistannanes R6Sn2 under the same conditions; stannylenes R2Sn always behave as nucleophiles here. 相似文献
133.
Dehydrohalogenation, or elimination of hydrogen-halide equivalents, remains one of the simplest methods for the installation of the biologically-important olefin functionality. However, this transformation often requires harsh, strongly-basic conditions, rare noble metals, or both, limiting its applicability in the synthesis of complex molecules. Nature has pursued a complementary approach in the novel vitamin B12-dependent photoreceptor CarH, where photolysis of a cobalt–carbon bond leads to selective olefin formation under mild, physiologically-relevant conditions. Herein we report a light-driven B12-based catalytic system that leverages this reactivity to convert alkyl electrophiles to olefins under incredibly mild conditions using only earth abundant elements. Further, this process exhibits a high level of regioselectivity, producing terminal olefins in moderate to excellent yield and exceptional selectivity. Finally, we are able to access a hitherto-unknown transformation, remote elimination, using two cobalt catalysts in tandem to produce subterminal olefins with excellent regioselectivity. Together, we show vitamin B12 to be a powerful platform for developing mild olefin-forming reactions.Terminal or subterminal olefins can be selectively formed from alkyl electrophiles via bio-inspired vitamin B12 photocatalysis. 相似文献
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Saturation of extrinsic photoconductivity in GaP:N(Zn, Te) diodes could be achieved by excitation with a TEA-CO2-laser. At wavelengths in the 10 m range intensities of several 100 kW/cm2 being near the damage threshold were applied. Carrier lifetimes of 60 ps at 4.2 K and 200 ps at 77 K could be estimated. The only conceivable mechanism explaining these short time constants is the capture of infrared excited holes by ionized shallow acceptors in the highly compensated p-side of the diode. 相似文献
136.
A peer-verified method is presented for the determination of percent moisture/solids and fat in dairy products by microwave drying and nuclear magnetic resonance (NMR) analysis. The method involves determining the moisture/solids content of dairy samples by microwave drying and using the dried sample to determine the fat content by NMR analysis. Both the submitting and peer laboratories analyzed various dairy products by using a CEM SMART system (moisture) and the SMART Trac (fat). The samples included milks, creams, ice cream mix, sour cream, yogurt, cream cheese, and mozzarella, Swiss, and cheddar cheeses. These samples represented a range of products that processors deal with in daily plant operations. The results were compared with moisture/solids and fat values derived from AOAC-approved methods. 相似文献
137.
Compressed pellets of partly crystalline, chemically synthesized, doped (Cl? and FeCl) polybithiophene (PBTd), poly(3-methylthiophene) (P3MTd), and their neutral (dedoped) forms (PBTn and P3MTn) were studied by wide-angle x-ray diffraction and positron annihilation lifetime spectroscopy. As synthesized, PBTd and P3MTd polymers have a helical syn conformation they crystallize in the hexagonal system. On dedoping, PBT macromolecules change their helical syn conformation in a rodlike anti conformation and crystallize in the orthorhombic or monoclinic system, whereas P3MT macromolecules retain their helical syn conformation. Chemical doping–dedoping cycles lead to amorphous PBT and P3MT in either doped or dedoped states. The P3MT helical macromolecule behaves like a spiral spring; by doping, it becomes axially compressed. The unit-cell volume of P3MTd is smaller than that of P3MTn. The positron lifetime spectra for all polymers were resolved, without constraint, into three components. The τ1 lifetime is attributed to free-positron annihilation events, the τ2 lifetime to positrons annihilating trapped in voids, and the τ3 lifetime to positrons annihilating as o-Ps trapped in cavities located inside the polymer grains for P3MTn and at the surface of the grains for PBTd, PBTn, and P3MTd. Most positrons annihilate when trapped in voids, both in doped and dedoped PBT and P3MT. The doping apparently increases the concentration of the voids and their mean diameter in P3MT, and probably also in PBT. Cavities anchored in the bulk are produced by dedoping. © 1993 John Wiley & Sons, Inc. 相似文献
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140.