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31.
单分散磁性纳米颗粒的制备及生物高分子在其上的组装 总被引:3,自引:0,他引:3
磁性纳米颗粒因其潜在的生物医学应用价值而成为纳米生物材料领域研究的前沿。本文综述了单分散磁性纳米颗粒的制备方法以及生物高分子在磁性纳米颗粒上的组装的研究进展。 相似文献
32.
1,7-Enynes 1, connected through an aromatic ring and bearing a leaving methoxy group at the 4-position, underwent the PtBr(2)-catalyzed enyne metathesis followed by aromatization in one pot to afford vinyl naphthalenes 3 in good to acceptable yields. The cyclobutene intermediate 11a and another intermediate 2a were isolated, indicating that PtBr(2) acts as a dual role catalyst: (1) as a transition metal catalyst, it induces the enyne metathesis to produce 11a starting from 1a, and (2) as a Lewis acid catalyst, it facilitates elimination of MeOH from 2a to give the aromatized product 3a. 相似文献
33.
This paper reports a new method for detection of ROS scavengers including superoxide dismutase, ascorbic acid and glutathione based on a 'probe' of peroxidase-oxidase biochemical oscillator. The oscillation period and amplitude change with different concentrations of scavengers. The linear ranges of superoxide dismutase, ascorbic acid and glutathione are respectively 1.56 x 10(-4)-1.56 x 10(-3) mg mL(-1), 1.75 x 10(-7)-1.75 x 10(-5) mol L(-1) and 9.38 x 10(-7)-7.5 x 10(-5) mol L(-1). The selectivity, linearity and precision for superoxide dismutase, ascorbic acid, and glutathione are presented and discussed. The results compared well with other standard methods for determination of superoxide dismutase, ascorbic acid and glutathione. Some possible steps in the overall reaction mechanisms are discussed. 相似文献
34.
Denote by *
n
the set of all k
*-cycle resonant hexagonal chains with n hexagons. For any B
n
*
n
, let m(B
n
) and i(B
n
) be the numbers of matchings (=the Hosoya index) and the number of independent sets (=the Merrifield–Simmons index) of B
n
, respectively. In this paper, we give a characterization of the k
*-cycle resonant hexagonal chains, and show that for any B
n
*
n
, m(H
n
)m(B
n
) and i(H
n
)i(B
n
), where H
n
is the helicene chain. Moreover, equalities hold only if B
n
=H
n
. 相似文献
35.
An organopalladium complex containing ortho-metalated (S)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary has been used to promote the asymmetric hydrophosphination reactions between diphenylphosphine and (E)- or (Z)-diphenyl-1-propenylphosphine in high regio- and stereoselectivities under mild conditions. Hydrophosphination of (Z)-diphenyl-1-propenylphosphine with diphenylphosphine gave (S)-(-)-prophos as the major product. Using the same chiral metal template, the corresponding hydrophosphination reaction with (E)-diphenyl-1-propenylphosphine gave (R)-(+)-prophos predominantly. The hydrophosphination reactions generated the asymmetric diphosphines as bidentate chelates on the chiral naphthylamine palladium templates. The template products obtained undergo cis-trans isomerization in solution to form an equilibrium mixture of regioisomers. X-ray analysis of the major template products obtained from the hydrophosphination of (Z)-diphenyl-1-propenylphosphine reveals that the two regioisomers are cocrystallized in a 1:1 ratio. The naphthylamine auxiliary could be removed chemoselectively from the template products by treatment with concentrated hydrochloric acid to form the corresponding optically pure neutral complexes [(R)- or (S)-(prophos)PdCl(2)]. Subsequently, the (R)- and (S)-dichloro complexes undergo ligand displacement with aqueous cyanide to generate the corresponding optically pure diphosphine ligands in high yields. Mechanistic pathways explaining the stereoselectivity of the chiral organopalladium template promoted hydrophosphination reactions are also proposed. 相似文献
36.
Determination of tetracyclines in ovine milk by high-performance liquid chromatography with a coulometric electrode array system 总被引:1,自引:0,他引:1
A method has been developed to analyze residual tetracyclines (TCs) (oxytetracycline (OTC), tetracycline (TC), chlortetracycline (CTC), methacycline (MTC), doxycycline (DC)) in ovine milk, using high-performance liquid chromatography (HPLC) with a coulometric electrode array system. The samples were pretreated, using liquid-liquid extraction based on hexane. The chromatography was performed, using a C18 column (150 mm x 4 mm i.d. and 5 microm) with a mobile phase: sodium phosphate monobasic dihydrate (pH 2.2, 0.05 M)-acetonitrile (78:22, v/v). The flow rate of mobile phase was kept constantly at 1ml/min. The residues were monitored by an ESA electrochemical detector. Potentials of four electrodes in series were set at 400, 660, 680 and 700 mV, respectively. The first electrode was set to remove those interfering substances that may co-elute with TCs and the other three electrodes were used for quantification. The maximal potential of our detection was 700 mV. Calibration curve showed good linearity and the detection limit of TCs was 12.5, 20, 25, 10 and 25 ng/ml, respectively. Optimization of the pH of the mobile phase, the proportion of acetonitrile and the pH of the pretreatment were also performed. Recoveries of TCs from spiked samples were more than 88% and the relative standard deviations were less than 4.3%. This method was reliable, sensitive, economical and suited for routine monitoring of TC residues in ovine dairy milk. 相似文献
37.
A novel method for the determination of trace amounts of Al(III) based on resonance Rayleigh scattering (RRS) has been developed. In the presence of some surfactants, Al(III) can react with morin and form an Al(III)-morin-surfactant complex, which results in the enhancement of RRS intensity and the appearance of the corresponding RRS spectral characteristics. Their maximum scatter peaks are at 476 nm for the cetyltrimethylammonium bromide (CTAB) system, 489 nm for the cetylpyridinium chloride (CPC) system, 474 nm for the Triton X-100 system, and 473 nm for the Tween-20 system. The enhanced RRS intensity is directly proportional to the concentration of Al(III). The detection limits are in the range of (0.50-1.2)×10−7 mol l−1 depending on the surfactant. The characteristics of RRS spectra of the complexes, the optimum conditions of these reactions and the influencing factors have been investigated. The method has high selectivity, and was successfully applied to the determination of Al(III) in natural and biological samples. Furthermore, according to different complexation capacity of Al(III)-morin-CTAB system under two pH conditions, speciation analysis of Al(III) in natural waters was explored. The labile monomeric Al fraction (mainly inorganic Al, Ali) is determined at acidic pH and the total monomeric Al fraction (Ala) is determined at alkaline pH. The results are in agreement with those obtained by Driscoll’s 8-hydroxyquinoline extraction-ion exchange method. 相似文献
38.
Huang S Xiao Z Wang F Zhou J Yuan G Zhang S Chen Z Thiel W von Ragué Schleyer P Zhang X Hu X Chen B Gan L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(18):5449-5456
[60]Fullerene mixed peroxides C60(O)(OOtBu)4 exhibit chemo- and regioselective reactions under mild conditions. The epoxy moiety is opened by ferric chloride to form vicinal hydroxy chloride C60Cl(OH)(OOtBu)4. BF3 is also effective in opening the epoxy moiety. The O-O bond of the fullerene mixed peroxide is cleaved by aluminum chloride to form both [5,6]- and [6,6]-fullerene hemiketals (oxohomo[60]fullerenes). A Hock-type rearrangement is proposed for the formation of the hemiketals, in which a fullerene C-C bond is cleaved. Lewis acids and/or visible light can initiate isomerization of the hemiketal isomers. Single-crystal X-ray analysis and theoretical calculations confirmed the results. 相似文献
39.
高效液相色谱分离与质谱稳定同位素稀释法联合测定地质样品中钐及钕 总被引:1,自引:0,他引:1
本文报道了用高效液相色谱分离,制取高纯度的Sm及Nd。再与质谱稳定同位素稀释法联合测定几种岩石矿物中的Sm与Nd。 相似文献
40.
Edwards KW Ogg M Bellerive A Britton DI Hyatt ER MacFarlane DB Patel PM Spaan B Sadoff AJ Ammar R Baringer P Bean A Besson D Coppage D Copty N Davis R Hancock N Kelly M Kotov S Kravchenko I Kwak N Lam H Kubota Y Lattery M Momayezi M Nelson JK Patton S Poling R Savinov V Schrenk S Wang R Alam MS Kim IJ Ling Z Mahmood AH O'Neill JJ Severini H Sun CR Wappler F Crawford G Daubenmier CM Fulton R Fujino D Gan KK Honscheid K Kagan H Kass R Lee J Sung M White C Wolf A Zoeller MM Butler F Fu X Nemati B 《Physical review letters》1995,74(17):3331-3335