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991.
The nano-palpation technique,i.e.,nanometer-scale elastic and viscoelastic measurements based on atomic force microscope,is introduced.It is demonstrated to be very useful in analyzing nanometer-scale materials properties for the surfaces and interfaces of various types of soft materials.It enables us to obtain not only structural information but also mechanical information about a material at the same place and at the same time. 相似文献
992.
993.
Psychotriasine was isolated from the leaves of Psychotria calocarpa (Rubiaceae). The structure was established by spectroscopic methods including 2D‐NMR analysis. To the best of our knowledge, psychotriasine is the first example of a dimeric tryptamine‐related alkaloid that contains a free Nα‐methyltryptamine unit in the molecule. 相似文献
994.
Bo Ding Wei‐Wei Ma Yi Dai Hao Gao Yang Yu Ye Tao Yi Zhong Xin‐Sheng Yao 《Helvetica chimica acta》2010,93(12):2488-2494
Two new iridoids, 10‐O‐benzoyl‐6′‐O‐α‐L ‐arabino(1→6)‐β‐D ‐glucopyranosylgeniposidic acid ( 1 ), deacetyl‐6‐ethoxyasperulosidic acid methyl ester ( 2 ), along with 14 other known iridoids, were isolated from the whole plant of Hedyotis diffusa Willd. Their structures were determined on the basis of spectroscopic analysis. The short‐term‐memory‐enhancement activities of compounds 1, 7 – 9, 11 , and 13 were evaluated on an Aβ transgenic drosophila model. 相似文献
995.
Phat L. Tran Jessica R. Gamboa David J. You Jeong-Yeol Yoon 《Analytical and bioanalytical chemistry》2010,398(2):759-768
An alternative approach for fabricating a protein array at nanoscale is suggested with a capability of characterization and/or
localization of multiple components on a nanoarray. Fluorescent micro- and nanobeads each conjugated with different antibodies
are assembled by size-dependent self-assembly (SDSA) onto nanometer wells that were created on a polymethyl methacrylate (PMMA)
substrate by electron beam lithography (EBL). Antibody-conjugated beads of different diameters are added serially and electrostatically
attached to corresponding wells through electrostatic attraction between the charged beads (confirmed by zeta potential analysis)
and exposed p-doped silicon substrate underneath the PMMA layer. This SDSA method is enhanced by vibrated-wire-guide manipulation
of droplets on the PMMA surface containing nanometer wells. Saturation rates of antibody-conjugated beads to the nanometer
patterns are up to 97% under one component and 58–70% under two components nanoarrays. High-density arrays (up to 40,000 wells)
could be fabricated, which can also be multi-component. Target detection utilizes fluorescence resonance energy transfer (FRET)
from fluorescent beads to fluorescent-tagged secondary antibodies to Octamer-4 (Oct4), which eliminates the need for multiple
steps of rinsing. The 100 nm green beads are covalently conjugated with anti-Oct4 to capture Oct4 peptides (39 kDa); where
the secondary anti-Oct4 and F(ab)2 fragment of anti-gIgG tagged with phycoerythrin are then added to function as an indicator of Oct4 detection. FRET signals
are detected through confocal microscopes, and further confirmed by Fluorolog3 spectrofluorometer. The success rates of detecting
Oct4 are 32% and 14% of the beads in right place under one and two component nanoarrays, respectively. Ratiometric FRET is
used to quantify the amount of Oct4 peptides per each bead, which is estimated about 2 molecules per bead. 相似文献
996.
Wei-Long Zhang Chen-Sheng Lin Ye-Yu Li Hao Zhang Wen-Dan Cheng 《Journal of solid state chemistry》2010,183(5):1108-1113
Two members of MIII2BP3O12 borophosphates, namely Fe2BP3O12 and In2BP3O12, were synthesized by the solid-state method and characterized by the X-ray single crystal diffraction, the powder diffraction and the electron microscopy. They both crystallize in the hexagonal system, space group P6(3)/m (no. 176) and feature 3D architectures, build up of the M2O9 units and B(PO4)3 groups via sharing the corners; however, they are not isomorphic for the different crystallographically distinct atomic positions. Optical property measurements of both compounds and magnetic susceptibility measurements of Fe2BP3O12 also have been performed. Moreover, in order to gain further insights into the relationship between physical properties and band structure of the MIII2BP3O12 borophosphates, theoretical calculations based on density functional theory (DFT) were performed using the total-energy code CASTEP. 相似文献
997.
A series of Fe(III), Co(II) and Cu(II) complexes of 8‐quinolinol were encapsulated into the supercages of zeolite? Y and characterized by X‐ray diffraction, SEM, N2 adsorption/desorption, FT‐IR, UV–vis spectroscopy, elemental analysis, ICP‐AES and TG/DSC measurements. The encapsulation was achieved by a flexible ligand method in which the transition metal cations were first ion‐exchanged into zeolite Y and then complexed with 8‐quinolinol ligand. The metal‐exchanged zeolites, metal complexes encapsulated in zeolite–Y plus non‐encapsulated homogeneous counterparts were all screened as catalysts for the aerobic oxidation of styrene under mild conditions. It was found that the encapsulated complexes always showed better activity than their respective non‐encapsulated counterparts. Moreover, the encapsulated iron complex showed good recoverability without significant loss of activity and selectivity within successive runs. Heterogeneity test for this catalyst confirmed its high stability against leaching of active complex species into solution. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
998.
Yi-Bin Zhao Quan-Shui Fan Gui-Li Xu Zi-Liang Feng Xiao-Jiang Hao 《Journal of carbohydrate chemistry》2013,32(7):401-410
Three new carbohydrates were isolated from the acidic hydrolysis part of the ethyl acetate extract of Cynanchum otophyllum Schneid (Asclepiadaceae) and one new carbohydrate from the ethyl acetate extract of Cynanchum paniculatum Kitagawa. Their structures were determined as methyl 2,6-dideoxy-3-O-methyl-α-D-arabino-hexopyranosyl-(1 → 4)-2,6-deoxy-3-O-methyl-β-D-arabino-hexopyranosyl-(1 → 4)-2,6-dideoxy-3-O-methyl-α-D-arabino-hexopyranoside (1), ethyl 2,6-dideoxy-3-O-methyl-β-D-ribo-hexopyranosyl-(1 → 4)-2,6-dideoxy-3-O-methyl-α-l-lyxo-hexopyranoside (2), met hyl 2,6-dideoxy-3-O-methyl-α-l-ribo-hexopyranosyl-(1 → 4)-2,6-dideoxy-3-O-methyl-β-D-lyxo-hexopyranosyl-(1 → 4)-2,6-dideoxy-3-O-methyl-α-D-arabino-hexopyranoside (3), and 2,6-dideoxy-3-O-methyl-β-D-ribo-hexopyranosyl-(1 → 4)-2,6-dideoxy-3-O-methyl-α-d-arabino-hexopyranosyl-(1 → 4)-2,6-dideoxy-3-O-methyl-α -d-arabino-hexopyranose (4), respectively, by spectral methods. 相似文献
999.
Hao Guo Xingliang Zheng Xiaoyu Huang 《Journal of polymer science. Part A, Polymer chemistry》2013,51(5):1091-1098
A well‐defined amphiphilic graft copolymer, consisting of hydrophobic polyallene‐based backbone and hydrophilic poly(N‐isopropylacrylamide) (PNIPAM) side chains, was prepared by the combination of living coordination polymerization, single electron transfer‐living radical polymerization (SET‐LRP), and the grafting‐from strategy. First, the double‐bond‐containing backbone was prepared by [(η3‐allyl)NiOCOCF3]2‐initiated living coordination polymerization of 6‐methyl‐1,2‐heptadiene‐4‐ol (MHDO). Next, the pendant hydroxyls in every repeating unit of poly(6‐methyl‐1,2‐heptadiene‐4‐ol) (PMHDO) homopolymer were treated with 2‐chloropropionyl chloride to give PMHDO‐Cl macroinitiator. Finally, PNIPAM side chains were grown from PMHDO backbone via SET‐LRP of N‐isopropylacrylamide initiated by PMHDO‐Cl macroinitiator in N,N‐dimethylformamide/2‐propanol using copper(I) chloride/tris(2‐(dimethylamino)ethyl)amine as catalytic system to afford PMHDO‐g‐PNIPAM graft copolymers with a narrow molecular weight distribution (Mw/Mn = 1.19). The critical micelle concentration (cmc) in water was determined by fluorescence probe technique and the effects of pH and salinity on the cmc of PMHDO‐g‐PNIPAM were also investigated. The micellar morphology was found to be spheres using transmission electron microscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
1000.
Jessica E. Coughlin Andreas Reisch Marie Z. Markarian Joseph B. Schlenoff 《Journal of polymer science. Part A, Polymer chemistry》2013,51(11):2416-2424
Sulfonation of narrow polydispersity polystyrene, PS, standards remains the method of choice for generating polystyrene sulfonate, PSS, samples with defined composition. Although a variety of sulfonation techniques have been described, relatively little is reported on the material obtained, which is used for so many studies on the fundamental behavior of polyelectrolytes. Here, we show that powdered polystyrene treated with concentrated sulfuric acid (96%) at 90 °C without catalyst yields fully sulfonated PSS. Extensive characterization with 1H and 13C NMR as well as size exclusion chromatography coupled with static and dynamic light scattering shows no evidence of sulfone crosslinking or chain degradation under the conditions used. Though mono‐sulfonated as soon as it dissolves in the acid, the PSS contains about 6% meta substitution. Sulfonation kinetics for this heterogeneous reaction depend strongly on particle size, sulfuric acid content and temperature. For preparing perdeuterated PSS from the corresponding PS it is essential to employ D2SO4, as about half of the aromatic units undergo H/D exchange during sulfonation. The remaining ortho H/D may be exchanged with extended exposure to the concentrated sulfuric acid, but the meta site is deactivated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2416–2624 相似文献