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271.
Convenient and selective preparations of ω-cyano-alkyl methacrylic esters are described using either PTC conditions or acetone cyanohydrin. The scope and limitations of the two methods are compared. 相似文献
272.
Pavel Vlad Elena Gorincioi Aculina Aricu Alic Barba Ada Manzocchi Enzo Santaniello 《Tetrahedron: Asymmetry》2010,21(17):2108-2116
The asymmetric dihydroxylation of drim-7-en-11-ol was studied in detail and diastereomerically pure driman-7α,8α,11- and driman-7β,8β,11-triols were prepared. Further elaboration of driman-7α,8α,11-triol afforded 14,15-bisnorlabd-7α,8α-isopropylidenedioxy-11,13-dione from which a novel chlorinated bisnorlabdanic compound (14,15-bisnorlabd-12-ene-12-chloro-8α,13-epoxy-7α-ol-11-one) and an unusual dichloro-derivative, 13,14,15,16-tetranorlabd-12-dichloro-7α-acetoxy-8α-ol-11-one, were obtained. 相似文献
273.
274.
Sílvia Barrabs Ariadna Sarrats Esther Fort Rafael De Llorens Pauline M. Rudd Rosa Peracaula 《Electrophoresis》2010,31(17):2903-2912
2‐DE is broadly used for quantitative analysis of differential protein expression in complex mixtures such as serum samples or cell lysates. PTMs directly influence the 2‐DE pattern, and knowledge of the rules of protein separation is required in order to understand the protein distribution in a 2‐DE gel. Glycosylation is the most common PTM and can modify both the molecular weight and the pI of a protein. In particular, the effect of charged monosaccharides (mainly sialic acids, SAs) on the 2‐DE pattern of a protein is of major interest since changes in sialylation are regularly observed in comparative studies. Little is known about the pI shift of a glycoprotein induced by the presence of SAs, or whether this shift is the same for all glycoproteins. To address this issue, this study examined the influence of SA on the 2‐DE pattern of three serum glycoproteins (haptoglobin, α1‐antitrypsin and ribonuclease 1), which N‐glycan chains had been previously characterised, and reviewed existing bibliographic data. The SA content of the different glycoforms of a glycoprotein showed a negative linear correlation with the pI, although the slope varied among the studied glycoproteins. We also described a positive correlation between the protein pI and the pI decrease per SA molecule. 相似文献
275.
We provide a condition in terms of a supermartingale property for a functional of the Markov process, which implies (a) f-ergodicity of strong Markov processes at a subgeometric rate, and (b) a moderate deviation principle for an integral (bounded) functional. An equivalent condition in terms of a drift inequality on the extended generator is also given. Results related to (f,r)-regularity of the process, of some skeleton chains and of the resolvent chain are also derived. Applications to specific processes are considered, including elliptic stochastic differential equations, Langevin diffusions, hypoelliptic stochastic damping Hamiltonian systems and storage models. 相似文献
276.
We consider a form of state-dependent drift condition for a general Markov chain, whereby the chain subsampled at some deterministic time satisfies a geometric Foster–Lyapunov condition. We present sufficient criteria for such a drift condition to exist, and use these to partially answer a question posed in Connor and Kendall (2007) [2] concerning the existence of so-called ‘tame’ Markov chains. Furthermore, we show that our ‘subsampled drift condition’ implies the existence of finite moments for the return time to a small set. 相似文献
277.
278.
Bagaria HG Ada ET Shamsuzzoha M Nikles DE Johnson DT 《Langmuir : the ACS journal of surfaces and colloids》2006,22(18):7732-7737
Tailoring the surface of nanoparticles is essential for biological applications of magnetic nanoparticles. FePt nanoparticles are interesting candidates owing to their high magnetic moment. Established procedures to make FePt nanoparticles use oleic acid and oleylamine as the surfactants, which make them dispersed in nonpolar solvents such as hexane. As a model study to demonstrate the modification of the surface chemistry, stable aqueous dispersions of FePt nanoparticles were synthesized after ligand exchange with mercaptoalkanoic acids. This report focuses on understanding the surface chemistry of FePt upon ligand exchange with mercapto compounds by conducting X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) studies. It was found that the mercapto end displaces oleylamine on the Pt atoms and the carboxylic acid end displaces the oleic acid on the Fe atoms, thus exposing carboxylate and thiolate groups on the surface that provide the necessary electrostatic repulsion to form stable aqueous dispersions of FePt nanoparticles. 相似文献
279.
Barsu C Fortrie R Nowika K Baldeck PL Vial JC Barsella A Fort A Hissler M Bretonnière Y Maury O Andraud C 《Chemical communications (Cambridge, England)》2006,(45):4744-4746
The design of new chromophores presenting simultaneous SHG and TPEF properties is reported. 相似文献
280.
Desmarets C Champagne B Walcarius A Bellouard C Omar-Amrani R Ahajji A Fort Y Schneider R 《The Journal of organic chemistry》2006,71(4):1351-1361
Naphthidines 2 were prepared by nickel-catalyzed amination of 1-chloronaphthalene followed by oxidative homocoupling of 1-naphthalene amines 1 using titanium(IV) tetrachloride. The electronic and magnetic properties of materials 2 were investigated by cyclic voltammetry and other electrochemical techniques, EPR and UV-visible spectroscopies, and magnetic susceptibility. It was demonstrated that compounds 2 could be easily and reversibly oxidized via a two-electron-transfer reaction into their bis(radical cation) 2(2.2+), which displays a substantial stability at room temperature (the half-life of 2(2.2+) estimated by EPR at 25 degrees C was 10 days). B3LYP/6-31G optimized structures of N,N'-bis(4-methoxyphenyl)-(1,1'-binaphthyl)-4,4'-diamine 2g shows significant differences in the torsion angle between the naphthalene moieties depending on its oxidation state. Twisted structures are preferred for neutral compounds, whereas more planar are favored for the oxidized forms 2g*+ and 2g(2.2+) to realize spin and/or charge delocalizations over the whole pi-system. Such conformation changes concerted with the electron transfers contribute to explain the unusual two-electron process observed in the electrochemical behavior of 2g instead of the two single-electron transfers that would have been expected in the case of two successive oxidations. It is finally shown that the oxidation of 2g in CH2Cl2 with thianthrenium perchlorate (ThClO4) generates the dication 2g(2.2+) with singlet spin-multiplicity. 相似文献