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131.
Mi Jung Lee 《Tetrahedron》2006,62(13):3128-3136
A new and regioselective [4+2] benzannulation protocol toward polysubstituted benzenes was developed. A nitroalkane derivative, which was prepared from Baylis-Hillman adduct, served as the four-carbon unit and a Michael acceptor as a two-carbon unit. Vinyltriphenylphosphonium salt could also be used as a Michael acceptor efficiently. 相似文献
132.
Corn silk induces nitric oxide synthase in murine macrophages 总被引:1,自引:0,他引:1
Corn silk has been purified as an anticoagulant previously and the active component is a polysaccharide with a molecular mass of 135 kDa. It activates murine macrophages to induce nitric oxide synthase (NOS) and generate substantial amounts of NO in time and dose-dependent manners. It was detectable first at 15 h after stimulation by corn silk, peaked at 24 h, and undetectable by 48 h. Induction of NOS is inhibited by pyrolidine dithiocarbamate (PDTC) and genistein, an inhibitor of nuclear factor kappa B (NF-kappaB) and tyrosine kinase, respectively, indicating that iNOS stimulated by corn silk is associated with tyrosine kinase and NF-kappaB signaling pathways. IkappaB-alpha degradation was detectible at 10 min, and the level was restored at 120 min after treatment of corn silk. Corn silk induced nuclear translocation of NF-kappaB by phosphorylation and degradation of IkappaB-alpha. 相似文献
133.
Lee HJ Kim JH Jung HJ Kim KY Kim EJ Choi YS Yoon CJ 《Journal of computational chemistry》2004,25(2):169-178
The effect of thioamide substitution on the conformational stability of an azaglycine-containing peptide, For-AzaGly-NH2 (1), was investigated for the sake of finding possible applications by using ab initio and DFT methods. As model compounds, For-[psiCSNH]-AzaGly-NH2 (2), For-AzaGly-[psiCSNH]-NH2 (3), and For-[psiCSNH]-AzaGly-[psiCSNH]-NH2 (4) were used. Two-dimensional phi-psi potential energy surfaces (PESs) for 2-4 were calculated at the B3LYP/6-31G*//HF/6-31G* level in gas (epsilon = 1.0) and in water (epsilon = 78.4) by applying the isodensity polarizable continuum model (IPCM) method. On the basis of these PESs, the minimum energy conformations for 2-4 were characterized at the B3LYP level with 6-31G*, 6-311G**, and 6-31+G** basis sets. The remarkable structural effect of thioamide substitution for 2-4 is that beta-strand structure is observed as a global or local minimum. The minima of 2-4 are also compared with those for glycine and thioamide-containing glycine peptides. Our theoretical results demonstrate that compounds 2-4 would be used to design controllable secondary structures. 相似文献
134.
(+)-Monomorine has been synthesized under mild hydrogenation conditions initiating deprotection followed by intramolecular, sequential reductive amination reactions. The precursors could be prepared concisely using B-alkyl Suzuki cross coupling of a chiral homoallylamine and a vinyl iodide or an iodofuran derivative. 相似文献
135.
Structural transitions as determinants of the action of the calcium-dependent antibiotic daptomycin 总被引:14,自引:0,他引:14
Daptomycin is a cyclic anionic lipopeptide antibiotic recently approved for the treatment of complicated skin infections (Cubicin). Its function is dependent on calcium (as Ca2+). Circular dichroism spectroscopy indicated that daptomycin experienced two structural transitions: a transition upon interaction of daptomycin with Ca2+, and a further transition upon interaction with Ca2+ and the bacterial acidic phospholipid, phosphatidyl glycerol. The Ca2+-dependent insertion of daptomycin into model membranes promoted mild and more pronounced perturbations as assessed by the increase of lipid flip-flop and membrane leakage, respectively. The NMR structure of daptomycin indicated that Ca2+ induced a conformational change in daptomycin that increased its amphipathicity. These results are consistent with the hypothesis that the association of Ca2+ with daptomycin permits it to interact with bacterial membranes with effects that are similar to those of the cationic antimicrobial peptides. 相似文献
136.
Beltrami I Bylsma BG DeBonte R Gan KK Koltick D Loeffler FJ Low EH McIlwain RL Miller DH Ng CR Ong PP Rangan LK Shibata EI Wilson RJ Derrick M Fernandez E Fries R Hyman L Kooijman P Loos JS Musgrave B Price LE Schlereth J Sugano K Weiss JM Wood DE Baranko G Baringer P Blockus D Brabson B Forden GE Gray SW Jung C Neal H Ogren H Rust DR Valdata-Nappi M Akerlof C Bonvicini G Chapman J Errede D Harnew N Kesten P Kooijman S Meyer DI Nitz D Rubin D Seidl AA Thun R Trinko T Willutzky W Cork B Keller L 《Physical review letters》1985,54(16):1775-1778
137.
Alkauskas A Ramoino L Schintke S von Arx M Baratoff A Güntherodt HJ Jung TA 《The journal of physical chemistry. B》2005,109(49):23558-23563
We studied the electronic structure of copper-octaethylporphyrin (CuEOP) adsorbed on three metal surfaces--Ag(001), Ag(111), and Cu(111)--by means of ultraviolet photoelectron spectroscopy (UPS). The adsorption-induced work function shifts saturate roughly beyond two monolayers. The saturation values are substrate dependent, negative, and range from -1.30 to -0.85 eV. This shift is larger than that for tetraphenylporphyrins. The two highest occupied molecular orbitals (HOMO and HOMO-1) of the organic are clearly resolved in the UPS spectra. The origin of the negative work function shift is discussed. 相似文献
138.
J. Jung J. H. Yoon H. H. Chung M. J. Lee 《Journal of Radioanalytical and Nuclear Chemistry》2002,252(3):451-454
Gamma-ray treatment in the presence of ozone (O3) and titanium dioxide (TiO2) showed an efficient removal of trichloroethylene (TCE) and perchloroethylene (PCE). Without gamma-irradiation, TCE and PCE were not sufficiently decomposed to comply with the water quality limit of groundwater. However, near 100% of TCE and PCE were removed at a dose of 300 Gy in the presence of O3 and TiO2, where TiO2 showed an explicit enhancement of decomposition. Cytotoxicity test using Chinese hamster V79 cells showed no toxicity of the TCE and PCE decomposition products. 相似文献
139.
[formula: see text] The synthesis of all four diastereomers of bis(propionates), 3,5-dialkoxy-2,4-dimethylalkanals, by non-aldol aldol chemistry is described. The epoxy alcohols (3, 4) were converted into the mesylates (9, 11) which were cleanly rearranged to the desired 3,5-bis(oxygenated)-2,4-dimethylalkanals (10, 12) in high yield. The epoxy mesylates (13, 16) gave the desired products (14, 17) in good yield on treatment with TMSOTf and a hindered base. 相似文献
140.