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51.
[formula: see text] S-Nitrosoglutathione oxidized 4-substituted Hantzsch 1,4-dihydropyridines in CH3CN/H2O or CH3CN/phosphate aqueous buffer solution to give aromatic products in various yields. 相似文献
52.
The reaction of fluorine-containing halides and acetamides with conjugated dienoic acids initiated by sodium dithionite gave halide-free 1,4-adducts in 40-80% yields, with the E configuration as the major products. 相似文献
53.
Lee KJ Mao S Sun C Gao C Blixt O Arrues S Hom LG Kaufmann GF Hoffman TZ Coyle AR Paulson J Felding-Habermann B Janda KD 《Journal of the American Chemical Society》2002,124(42):12439-12446
Overexpression of the cell-surface glycosphingolipid G(M3) is associated with a number of different cancers, including those of the skin, colon, breast, and lung. Antibodies against the G(M3) epitope have potential application as therapeutic agents in the treatment of these cancers. We describe the chemoenzymatic synthesis of two G(M3)-derived reagents and their use in the panning of a phage-displayed human single-chain Fv (scFv) antibody library derived from the blood of cancer patients. Three scFv-phage clones, GM3A6, GM3A8, and GM3A15, were selected for recombinant expression and were characterized using BIAcore and flow cytometry. BIAcore measurements using the purified, soluble scFvs yielded dissociation constants (K(d)) ranging from 4.2 x 10(-7) to 2.1 x 10(-5) M. Flow cytometry was used to evaluate the ability of each scFv to discriminate between normal human cells (human dermal fibroblast, HDFa), melanoma cells (HMV-1, M21, and C-8161), and breast cancer cells (BCM-1, BCM-2, and BMS). GM3A6 displayed cross-reactivity with normal cells, as well as tumor cells, and GM3A15 possessed little or no binding activity toward any of the cell lines tested. However, GM3A8 bound to five of the six tumor cell lines and showed no measurable reactivity against the HDFa cells. Hence, we have demonstrated that a synthetic G(M3) panning reagent can be used to isolate a fully human scFv that is highly specific for native G(M3) on the surface of tumor cells. The result is a significant step toward effective immunotherapies for the treatment of cancer. 相似文献
54.
相反转技术制备环氧树脂水基体系——相反转过程的流变行为研究 总被引:18,自引:0,他引:18
对高乳化剂浓度下的相反转发展过程的流变行为进行了应力扫描、动态频率扫描实验表征.结果表明,乳化剂浓度较高时,体系发生完全相反转;体系在相反转点前为W/O结构,其粘度几乎不随剪切应力的改变而改变,表现为牛顿流体行为;体系在相反转点后为O/W结构,具有很高的粘弹性,并且在较高剪切应力下表现为典型的假塑性.这是由于高分子水基微粒间通过其表面覆盖的表面活性剂与水形成氢键而产生了一种静态结构,此结构在较高剪切应力作用下破坏而导致假塑性. 相似文献
55.
A series of PCL/MDI/BDO segmented polyurethanes have been synthesized by two-step method in solution.The hard segment content ranges from 10% to 48% by weight, and the molecular weight of PCL diols is 1500. Hard segment spherulites have been observed in compression molded specimens of all of the samples except the one of the lowest hard segment content. The difficulty in sphernlite formation was explained as only in a small temperature range,the microphase separation rate may be faster than the crystallization rate and all these processes are very slow due to the hydrogen bonding between hard and soft segments and the interactions between hard segments themselves. PCL soft segments of molecular weight 1500 is still crystallizable and may form different crystalline superstructures. 相似文献
56.
57.
Vijaykumar D Mao W Kirschbaum KS Katzenellenbogen JA 《The Journal of organic chemistry》2002,67(14):4904-4910
Two different synthetic routes were explored for the synthesis of fluoro furanyl norprogesterone (FFNP) 1, a high-affinity ligand for the progesterone receptor (PgR) that is being developed as a PET imaging agent for PgR-positive breast cancer. Both approaches proceed through a key intermediate, triol 5. The first approach, starting from keto-ketal 2, employed a dioxenyl group as a synthon for installing a corticosteroid side chain in keto-alcohol 4. The second approach, starting from propargylic acetate 12b, involved the application of a two-step method, a Pd(II)-catalyzed oxidative rearrangement followed by a base-catalyzed acetate rearrangement of the intermediate unsaturated acetate 13b, to generate the requisite corticosteroid side chain in keto-acetate 14b. This intermediate was further elaborated to the final product 1 via efficient dihydroxylation with potassium permangnate, furan acetalization with scandium triflate, and mesylation and fluorination reactions. The palladium-catalyzed route is considerably more efficient than the dioxene approach for the synthesis of key intermediate triol 5, and the scandium triflate-catalyzed acetalization, in particular, led to a considerable improvement in the overall yield of the endo furan acetal alcohol 16a. This route provides a major improvement in the overall yield of the final progestin target, FFNP 1. 相似文献
58.
This study reports magnitudes and the orientation of the (13)C(alpha) chemical shift anisotropy (CSA) tensors of peptides obtained using quantum chemical calculations. The dependency of the CSA tensor parameters on the energy optimization of hydrogen atom positions and hydrogen bonding effects and the use of zwitterionic peptides in the calculations are examined. Our results indicate that the energy optimization of the hydrogen atom positions in crystal structures is necessary to obtain accurate CSA tensors. The inclusion of intermolecular effects such as hydrogen bonding in the calculations provided better agreement between the calculated and experimental values; however, the use of zwitterionic peptides in calculations, with or without the inclusion of hydrogen bonding, did not improve the results. In addition, our calculated values are in good agreement with tensor values obtained from solid-state NMR experiments on glycine-containing tripeptides. In the case of peptides containing an aromatic residue, calculations on an isolated peptide yielded more accurate isotropic shift values than the calculations on extended structures of the peptide. The calculations also suggested that the presence of an aromatic ring in the extended crystal peptide structure influences the magnitude of the delta(22) which the present level of ab initio calculations are unable to reproduce. 相似文献
59.
Weike Zhong Diandou Xu Zhifang Chai Xueying Mao 《Journal of Radioanalytical and Nuclear Chemistry》2004,259(3):485-488
Instrumental neutron activation analysis (INAA) has been used for the determination of extractable organohalogens (EOX) in
milk. The detection limits are 50 ng, 8 ng and 3.5 ng for Cl, Br and I, respectively. The EOX concentrations in milk samples
from various regions of China were determined. Meanwhile, organochlorine pesticides residues were detected by gas chromatography.
The concentrations of the EOX in the milk samples are decreasing in the order of EOCl >> EOBr > EOI, and EOCl accounts for
95% of the total EOX. The average concentration of EOCl in milk is 4.44 ·g/g expressed as fat weight basis, with the highest
value of 17.6 ·g/g from South China. The mean concentrations of total HCH and DDT are 0.038 ·g/g and 0.046 ·g/g, respectively.
Organochlorine pesticides account only for 1.6% of the EOCl, indicating the very high proportion of the unknown EOCl in the
milk sample.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
60.
The addition of gem-difluorinated alkyl iodides to alkynes initiated by AIBN neatly gave the corresponding difluoromethylene vinyl iodides among which the stereoselectivity of aromatic acetylenes was high. The further coupling reaction of E-phenyl difluoromethylene vinyl iodides with terminal alkynes in the presence of catalytic palladium afforded the substituted difluorinated enynes. 相似文献