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71.
Martina Havlikova Zuzana Bosakova Gabor Benkovics Jindrich Jindrich Martin Popr Pavel Coufal 《Chemical Papers》2016,70(9):1144-1154
This study details the use of two permanently positively charged mono-substituted β-cyclodextrin derivatives, 6I -deoxy-6I-(N,N N′,N′,Nt’-pentamethyl-ethylene-1,2-diammonio)-cyclomaltoheptose dichloride (PEMEDA-β-CD) and the newly synthesised 6I-deoxy-6I-(N,N,N′,N′,N′-pentamethyl-propylene-1,3-diammonio)-cyclomaltoheptose (PEMPDA-β-CD) as chiral selectors in capillary electrophoresis. Cyclodextrin (CD) derivatives were tested as additives in various buffers at various pH values with the optional addition of an organic modifier. Fourteen anionogenic analytes were tested, including native amino acids, N-blocked amino acids and profens, which were detected using a UV-VIS detector at optimal wavelengths of 214 nm, 254 nm or 280 nm. A borate buffer (15 mmol L?1) at pH 9.5 without the addition of an organic modifier was chosen as a suitable background electrolyte. In addition, the effect of the concentration of the chiral selector on the separation and enantioseparation of selected analytes was monitored. The additions of cyclodextrin derivatives varied within the concentration range of 0.0–5.0 mmol L?1. Both chiral selectors were suitable for the enantioseparation of N-Boc-d,l-tryptophan, which was already separated on the baseline at 0.5 mmol L?1 concentration of the chiral selector. 相似文献
72.
Kim S Yin Y Alivisatos AP Somorjai GA Yates JT 《Journal of the American Chemical Society》2007,129(30):9510-9513
FTIR spectroscopy has been used to monitor the transport of CO to the Pt cores of Pt@CoO nanoparticles forming CO/Pt species. It was found that external Pt sites are not present on the outer surfaces of the approximately 10 nm diameter nanostructures and that CO transports to Pt adsorption sites by an activated surface diffusion process through the CoO shells surrounding approximately 2 nm diameter Pt cores. The CO transport process is not due to gas-phase transport below 300 K. The weakly bound adsorbed CO/CoO species responsible for transport was directly observed at approximately 2147 cm(-1) during transport through the CoO shells. 相似文献
73.
Balazs G Cloke FG Harrison A Hitchcock PB Green J Summerscales OT 《Chemical communications (Cambridge, England)》2007,(8):873-875
Structural, magnetic and theoretical studies show that the bimetallic pentalene complex, Mn(2)(C(8)H(4)(1,4-Si(i)Pr(3)))(2), contains both high and low spin Mn(ii) in two very different sites. 相似文献
74.
Krishnakumar V Keresztury G Sundius T Seshadri S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,68(3):845-850
The FT-IR and FT-Raman spectra of 1-methyl-4-piperidone was recorded and the observed bands were interpreted with the aid of normal coordinate analysis following a full structure optimization and force field calculation based on the density functional theory (DFT) using the standard B3LYP/6-311G** method and basis set combinations. A very good agreement obtained between the simulated and experimental spectra was established and unambiguous vibrational assignments of various modes were proposed based on the results of potential energy distribution (PED) calculations. 相似文献
75.
Gabor Toth 《Transactions of the American Mathematical Society》1999,351(4):1423-1443
The purpose of this paper is to give lower estimates on the range dimension of spherical minimal immersions in various settings. The estimates are obtained by showing that infinitesimal isometric deformations (with respect to a compact Lie group acting transitively on the domain) of spherical minimal immersions give rise to a contraction on the moduli space of the immersions and a suitable power of the contraction brings all boundary points into the interior of the moduli space.
76.
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78.
Journal of Theoretical Probability - We study a multi-group version of the mean-field Ising model, also called Curie–Weiss model. It is known that, in the high-temperature regime of this... 相似文献
79.
Numerous forms of the neurotransmitter GnRH have been discovered in vertebrates and invertebrates. Methods used for identification of these peptides are laborious and often require the application of multiple, confirmatory techniques. In this study, we investigate whether HPLC-MS/MS and de novo sequencing techniques applied to whole peptide analysis can provide a simpler approach to GnRH characterization. Experiments were performed with six GnRH forms (chicken I, chicken II, lamprey III, mammalian, salmon and seabream) to determine whether MS/MS spectra would be dominated by proline-directed fragmentation to the detriment of obtaining sufficient fragmentation for sequencing. While the expected b8 fragment was prominent, sufficient ion series were obtained for the six GnRH peptides to provide sequence identification. On the basis of the patterns observed for six model peptides, similar fragmentation patterns are expected for other GnRH forms. To confirm the applicability of the method, extracts from Sprague-Dawley rat brains were examined. These experiments confirm the presence of mammalian GnRH and a posttranslationally modified form of mammalian GnRH, hydroxyproline9 GnRH, in Sprague-Dawley rat brains and demonstrate that ESI-MS/MS techniques provide a valuable addition to existing qualitative methods. 相似文献
80.
Padar P Bokros A Paragi G Forgó P Kele Z Howarth NM Kovacs L 《The Journal of organic chemistry》2006,71(22):8669-8672
8-Benzyloxymethyl-3,4,5-tribenzoyloxy-9-oxa-1-azabicyclo[4.2.1]nonane has been prepared as the single diastereoisomer 8 from an intramolecular 1,3-dipolar cycloaddition involving 2-(benzyloxy)acetaldehyde and omega-unsaturated hydroxylamine 7 derived from methyl alpha-D-glucopyranoside. The analogous 8-methoxycarbonyl 9-oxa-1-azabicyclo[4.2.1]nonane was afforded in a similar manner, from methyl D-galactopyranoside and methyl glyoxylate, as a 3:1 mixture of diastereoisomers 15 and 16. When conducted in achiral ionic liquid 17 this ratio increased to 8:1, and in chiral ionic liquid 18, compound 15 was formed exclusively. 相似文献