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- Nilsson Lill, Sten O., 1970, et al.
(författare)
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Application of Q2MM to Stereoselective Reactions
- 2010
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Ingår i: Current Organic Chemistry. - : Wiley. - 1385-2728. ; 14:15, s. 1629-1645
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Tidskriftsartikel (refereegranskat)abstract
- Q2MM is a method designed to allow application of molecular mechanics calculations to transition states in chemical reactions. It is one of the few methods available that allow determination of a complete set of low-energy transition states for medium-sized systems, and thereby gives a unique opportunity to investigate kinetic selectivity, in particular stereoselectivity. The current review will give an outline of the procedure, an overview of the types of reactions that have been studied using this method, and summarize the factors affecting the accuracy of the results.
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| 4. |
- O'Mahony, Gavin, et al.
(författare)
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Synthesis of 2-([1,2,3]Triazol-1-yl)-2-deoxyadenosines
- 2008
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Ingår i: ChemInform. - : Wiley. - 0931-7597 .- 1522-2667. ; 27:5, s. 449-459
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Tidskriftsartikel (refereegranskat)abstract
- ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a Full Text option. The original article is trackable via the References option.
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| 6. |
- Tsybin, Youri O., et al.
(författare)
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Peptide and Protein Characterization by High Rate Electron Capture Dissociation Fourier Transform Ion Cyclotron Resonance Mass Spectrometry
- 2004
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 39:7, s. 719-729
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Tidskriftsartikel (refereegranskat)abstract
- The analytical utility of the electron capture dissociation (ECD) technique, developed by McLafferty and co-workers, has substantially improved peptide and protein characterization using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The limitations of the first ECD implementations on commercial instruments were eliminated by the employment of low-energy electron-injection systems based on indirectly heated dispenser cathodes. In particular, the ECD rate and reliability were greatly increased, enabling the combination of ECD/FTICR-MS with on-line liquid separation techniques. Further technique development allowed the combination of two rapid fragmentation techniques, high-rate ECD and infrared multiphoton dissociation (IRMPD), in a single experimental configuration. Simultaneous and consecutive irradiations of trapped ions with electrons and photons extended the possibilities for ion activation/dissociation and led to improved peptide and protein characterization. The application of high-rate ECD/FTICR-MS has demonstrated its power and unique capabilities in top-down sequencing of peptides and proteins, including characterization of post-translational modifications, improved sequencing of peptides with multiple disulfide bridges and secondary fragmentation (w-ion formation). Analysis of peptide mixtures has been accomplished using high-rate ECD in bottom-up mass spectrometry based on mixture separation by liquid chromatography and capillary electrophoresis. This paper summarizes the current impact of high-rate ECD/FTICR-MS for top-down and bottom-up mass spectrometry of peptides and proteins.
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- Tyutyunnik, A P, et al.
(författare)
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Synthesis, superconducting properties and structural (including electron diffraction) studies of Na chi NbO2 and Li chi NbO2
- 1996
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Ingår i: European Journal of Solid State and Inorganic Chemistry. - : Wiley. - 0992-4361 .- 1873-3751. ; 33, s. 53-65
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Tidskriftsartikel (refereegranskat)abstract
- Monophasic NaxNbO2 (x = 0.5 - 0.6), T-c approximate to 4.1 K was prepared by solid state reaction between Na3NbO4 and Nb. X-ray powder diffraction data from a monophasic sample were used for a refinement of the structure of Na0.5NbO2 (R(p) = 7.4 % and R(I) = 5.3 %), using the Rietveld method. At low x-values a closely related second phase can occur. Rietveld refinement using X-ray powder diffraction data showed this phase to be isostructural with NaNbO2 but with the chemical formula Na0.1NbO2. Transmission electron microscopy studies of NaxNbO2 and LixNbO2 revealed the presence of superstructures in some crystallites. The electron diffraction patterns resemble to some extent those reported for transformations among tantalum chalcogenides.
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- Wenska, Małgorzata, et al.
(författare)
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Synthesis of Conformationally Constrained 2'-N,4'-C-Ethylene-Bridged Adenosine (aza-ENA-A)
- 2007
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Ingår i: Heterocycles. - : Wiley. - 0385-5414 .- 1881-0942. ; 73:1, s. 303-324
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of conformationally constrained 2'-N,4'-C-ethylene-bridged adenosine(aza-ENA-A), in which the pentose-sugar is cis-fused with the piperidino skeleton at C2' and C4' centres of the sugar ring, is reported. The corresponding phosphoramidite building block will be used for incorporation into oligo-DNA and -RNA by solid phase synthesis to examine their nuclease stability as well as their application in blocking the translation of the target RNA using the antisense and siRNA approach. 2-Aza-6-oxabicyclo[3.2.1]octane skeleton is assembled through multi-step synthetic manipulation of appropriately protected D-arabinose based sugar precursor. The conversion of appropriate arabino precursor to ribo counterpart was achieved by direct nucleophilic displacement of "ara" positioned 2-(trifluoromethanesulfonyloxy) group in the sugar precursor 8. A high regio- and enhanced stereoselectivity with preferential formation of beta anomer in glycosylation reaction was achieved using Vorbruggen conditions in the absence of any 2-participating group. Coupling step was performed using 1-O-acetyl-3,5-di-O-benzyl-(2-deoxy-2-azido)-4-C-(p-toluoyloxyetliyl)-D- ribofur anose (10) as a glycosyl donor and persilylated N-6-benzoyladenine. Finally, the ring-closure giving the North-type conformationally constrained cis-fused bicyclic aza-ENA-A have been confirmed unambiguously by the long range H-1-C-13 NMR correlation (HMBC), TOCSY, COSY and nOe experiments.
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| 9. |
- Xiao, Zhaohua, 1962, et al.
(författare)
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Good selectivity between a NiCr mask and GaAs and AlGaAs by chemically assisted ion beam etching with Cl2 gas
- 1991
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Ingår i: Journal of the Electrochemical Society. - : Wiley. - 1945-7111 .- 0013-4651. ; 138, s. 3086-9
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Tidskriftsartikel (refereegranskat)abstract
- The authors report highly selective etching rates between a Ni-Cr mask and GaAs and AlGaAs layers as well as highly anisotropic profiles in these materials at a nanometer scale using the Ni-Cr mask and chemical assisted ion beam etching. The etching rates of Ni-Cr, GaAs, and AlGaAs depend on Cl2 gas flux. ion beam energy, and ion beam current density. Selectivities of the order of 40:1 and 8:1 between GaAs, respectively. Al0.29Ga0.71As and Ni0.7Cr0.3, were obtained at an ion beam energy of 500 eV, beam current density of 0.2 mA/cm2, and a Cl2 flow of 4.2 ml/min
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