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991.
Li Y Zhao M Wang J Liu K Cai C 《Langmuir : the ACS journal of surfaces and colloids》2011,27(8):4848-4856
We have developed a general method combining photochemical grafting and copper-catalyzed click chemistry for biofunctionalization of titanium substrates. The UV-activated grafting of an α,ω-alkenyne onto TiO(2)/Ti substrates provided a "clickable" thin film platform. The selective attachment of the vinyl end of the molecule to the surface was achieved by masking the alkynyl end with a trimethylgermanyl (TMG) protecting group. Subsequently, various oligo(ethylene glycol) (OEG) derivatives terminated with an azido group were attached to the TMG-alkynyl modified titanium surface via a one-pot deprotection/click reaction. The films were characterized by X-ray photoelectron spectroscopy (XPS), contact angle goniometry, ellipsometry, and atomic force microscopy (AFM). We showed that the titanium surface presenting click-immobilized OEG substantially suppressed the nonspecific attachment of protein and cells as compared to the unmodified titanium substrate. Furthermore, glycine-arginine-glycine-aspartate (GRGD), a cell adhesion peptide, was coimmobilized with OEG on the platform. We demonstrated that the resultant GRGD-presenting thin film on Ti substrates can promote the specific adhesion and spreading of AsPC-1 cells. 相似文献
992.
Linghao HeLu Yao Jing SunWei Wu Jie YangLifang Cai Rui Song Yongmei HaoZhi Ma Wei Huang 《Polymer Degradation and Stability》2011,96(7):1187-1193
The aim of this investigation is to obtain a polymer-based hybrid material with biodegradability, biocompatibility, and good mechanical properties and this object was realized via. in-situ introduction of the unmodified calcium carbonate (CaCO3) into a poly(l-lactic acid) (PLLA) matrix. As verified by the measurements from scanning electron microscopy (SEM), optical microscopy, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), the hybrid films which possesses a uniform dispersion of calcium carbonate CaCO3 in nano-meter scale, mechanically robustness and thermal stability could be fabricated by a mineralization-alike process. For example, the storage modulus increases from 441 MPa of neat PLLA to 1034 MPa of hybrid film containing 2% (w/w) CaCO3. In addition, the hybrid films display a significant improvement in its UV-exposure resistance. 相似文献
993.
Dong‐Cai Zhao Geng‐Jie Xiao Ni Ren Zhan‐Ji Ma Sheng‐Hu Wu 《Surface and interface analysis : SIA》2011,43(11):1392-1396
The composites, such as CFRP and GFRP, have been widely applied in spaceflight, for their low specific gravity, low cost, and additional structural stability. However, the high resistivity of the composites severely inhibits their further applications. Therefore, Cr/Al films with low resistivity and high adhesion were deposited on composites by cathodic arc technique. The films were characterized by pull test, Dektak 8 Stylus Profilometer, SEM, XPS, XRD and Z‐82 standard four probes. Results show that the aluminum film of fcc structure is compact and uniform, with resistivity as low as bulk Al. The adhesion between Cr buffer layer and composite substrate was greatly enhanced because of the formation of the chemical bonds, such as Cr? C, Cr? O and Cr? N, at the Cr/composite interface. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
994.
Tunable synthesis of propylene glycol ether from methanol and propylene oxide under ambient pressure
A series of basic and acidic ionic liquids, 1-butyl-3-methylimidazolium hydroxide (BMIMOH), 1-acetyl-3-methylimidazolium chloride
(AcMIMCl) and AcMIMCl-FeCl3, or analogues of AcMIMCl, namely 1-potassium acetate-3-methylimidazolium chloride (KAcMIMCl), 1-potassium (sodium, ammonium)
acetate-3-methylimidazolium hydroxides (KAcMIMOH, NaAcMIMOH and NH4AcMIMOH), were prepared and used as catalysts for catalytic synthesis of propylene glycol ether via reaction of propylene
oxide (PO) with methanol under mild reaction conditions. KAcMIMOH exhibited outstanding catalytic performance with 94.2% of
conversion of PO and 99.1% of selectivity to 1-methoxy-2-propanol (MP-2) at 60°C and ambient pressure for 4 h. However, AcMIMCl-FeCl3 showed a good catalysis performance with high selectivity to 2-methoxy-1-propanol (MP-1). The tunable synthesis of MP-2 or
MP-1 catalyzed by basic compound KAcMIMOH or acidic ionic liquid AcMIMCl-FeCl3 was realized. 相似文献
995.
Yin YingZhuo Chai Hai-Feng WangPeng Li Chang-Wu ZhengGang Zhao Yue-Peng Cai 《Tetrahedron》2011,67(19):3337-3342
A highly enantioselective [4+2] cycloaddition reaction of β,γ-unsaturated α-keto esters with oxazolones was realized with readily available cinchona alkaloids as the catalysts. Using this reaction, a series of highly functionalized δ-lactones with adjacent α-quaternary-β-tertiary stereocenters were obtained in high yields (up to 97%) and with good-to-excellent enantioselectivities (up to 97% ee). 相似文献
996.
The great performance of a fibrous bed bioreactor (FBB) is mainly dependent on the cell adhesion and immobilization into the
fibrous matrix. Therefore, understanding the mechanism and factors controling cell adhesion in the fibrous matrix is necessary
to optimize the FBB setup and further improve the fermentability. The adhesion behavior of a strain of Clostridium tyrobutyricum isolated from an FBB was studied, which was proven to be affected by the different environmental conditions, such as growth
phase of cells, pH, ionic strength, ionic species, and composition of media. Our results also suggested that electrostatic
interactions played an important role on bacteria adhesion into the fibrous matrix. This study demonstrated that the compositions
of fermentation broth would have a significant effect on cell adhesion. Consequently, a two-stage glucose supply control strategy
was developed to improve the performance of FBB with higher viable cell density in the operation of the FBB setup. 相似文献
997.
Bromobenzoquinones (BBQs) represent a class of reactive metabolites of various aromatic contaminants with bromine-containing substituents, including bromobenzene, bromophenols, polybrominated diphenyl ethers (PBDEs). Recently, 2,6-dibromobenzoquinone also has been detected directly from drinking water. The alternation of the genome caused by covalent binding of chemicals or their metabolites to DNA provides a viable mechanism for carcinogenicity. In the present study, electrospray ionization coupled with ion trap mass spectrometry (ITMS), triple quadrupole MS or quadrupole time-of-flight MS was applied for the analysis of DNA adducts formed by BBQs. The study demonstrated 2-monobromobenzoquinone and 2,6-dibromobenzoquinone could covalently bind to deoxyguanosine (dG) and DNA in vitro. The chemical structures of the DNA adducts were confirmed by accurate mass values, collision-induced fragmentation tandem mass spectra as well as isotopic patterns. Generally, the reaction mechanism for the DNA adduction involved Michael addition between the electron-deficient carbon from the quinone and the nucleophilic exocyclic nitrogen from the dG followed by reductive cyclization with loss of a small molecule such as H(2)O, or HBrO. It was of particular interest to note that some adducts were generated from the reaction of one dG molecule with two BBQ molecules. The obtained results provided new information for assessing the potential cancer risk associated with bromobenzene, bromophenols, PBDEs and BBQs. 相似文献
998.
Cai Y Liu X Li J Chen W Wang W Lin L Feng X 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(52):14916-14921
Highly diastereo‐ and enantioselective iodoamination of chalcones, 4‐aryl‐4‐oxobutenoates, and a trifluoro‐substituted enone has been accomplished in the presence of a chiral N,N′‐dioxide/[Sc(OTf)3] complex (0.5–2 mol %), delivering the desired vicinal anti‐α‐iodo‐β‐amino carbonyl compounds regioselectively in high yields (up to 97 %) and with excellent diastereoselectivities (>99:1 d.r.) and enantioselectivities (up to 99 % ee). Enantiopure syn‐α‐iodo‐β‐amino products could also be obtained from the isomerization of particular iodo compounds. TsNHX species (X=Cl, Br, I), generated from the reactions between the halo sources and TsNH2, were further confirmed as the active species in the haloamination reactions involved in the formation of the key halonium ion intermediates. A typical haloamination dependency was observed, with reactivity decreasing in the order NBS>NIS?NCS. 相似文献
999.
Cai H Huang ZH Shi L Zhao YF Kunz H Li YM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(23):6396-6406
The membrane‐bound tumor‐associated glycoprotein MUC1 is aberrantly glycosylated in cancer cells compared with normal cells, and is therefore considered an attractive target for cancer immunotherapy. However, tumor‐associated glycopeptides from MUC1 do not elicit a sufficiently robust immune response. Therefore, antitumor vaccines were developed, which consist of MUC1 glycopeptides as the B epitopes and immune‐stimulating toll‐like receptor 2 (TLR 2) lipopeptide ligands. These fully synthetic vaccine candidates were prepared by solid‐phase synthesis of the MUC1 glycopeptides. The Pam3Cys lipopeptide, also synthesized on solid‐phase, was C‐terminally coupled to oligovalent lysine cores, which N‐terminally incorporate O‐propargyl oligoethylene glycol acyl side chains. The MUC1 glycopeptides and lipopeptide lysine constructs were then conjugated by click chemistry to give oligovalent synthetic vaccines. Oligovalent glycopeptide–lipopeptide conjugates are considered more immunogenic than their monovalent analogues. 相似文献
1000.
In this work, we propose a simple, sensitive and reliable assay for melamine in raw milk with dopamine-stabilized silver nanoparticles (AgNPs) as a colorimetric reader. Dopamine can reduce Ag(+) and functionalize the produced AgNPs to form monodispersed AgNPs. The coexisting melamine in reaction solution could bind dopamine through Michael addition and Schiff base reactions, which leads to the aggregation of AgNPs and induces a colorimetric response. The one-step assay is simple, rapid and highly sensitive. The color-change is quantitatively correlated with the concentration of melamine in the range of 10 ppb to 1.26 ppm, which is below the safety limit in China (1.0 ppm) and EU (2.0 ppm). The coexisting substances including phenylalanine, dl-leucine, l-glutamate, sulfanilic acid, Mg(2+), galactose, lysine, urea and glucose do not affect the determination of melamine. The colorimetric sensor can be used for rapid monitoring of raw milk quality. 相似文献