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991.
Herein, a novel sensitive pseudobienzyme electrocatalytic DNA biosensor was proposed for mercury ion (Hg2+) detection by using autonomously assembled hemin/G-quadruplex DNAzyme nanowires for signal amplification. Thiol functionalized capture DNA was firstly immobilized on a nano-Au modified glass carbon electrode (GCE). In presence of Hg2+, the specific coordination between Hg2+ and T could result in the assembly of primer DNA on the electrode, which successfully triggered the HCR to form the hemin/G-quadruplex DNAzyme nanowires with substantial redox probe thionine (Thi). In the electrolyte of PBS containing NADH, the hemin/G-quadruplex nanowires firstly acted as an NADH oxidase to assist the concomitant formation of H2O2 in the presence of dissolved O2. Then, with the redox probe Thi as electron mediator, the hemin/G-quadruplex nanowires acted as an HRP-mimicking DNAzyme that quickly bioelectrocatalyzed the reduction of produced H2O2, which finally led to a dramatically amplified electrochemical signal. This method has demonstrated a high sensitivity of Hg2+ detection with the dynamic concentration range spanning from 1.0 ng L−1 to 10 mg L−1 Hg2+ and a detection limit of 0.5 ng L−1 (2.5 pM) at the 3Sblank level, and it also demonstrated excellent selectivity against other interferential metal ions. 相似文献
992.
Using a cascade signal amplification strategy, an ultrasensitive electrochemical biosensor for specific detection of DNA based on molecular beacon (MB) mediated circular strand displacement polymerization (CSDP) and hyperbranched rolling circle amplification (HRCA) was proposed. The hybridization of MB probe to target DNA resulted in a conformational change of the MB and triggered the CSDP in the presence of bio-primer and Klenow fragment (KF exo−), leading to multiple biotin-tagged DNA duplex. Furthermore, the HRCA was implemented to product amounts of double-stranded DNA (ds-DNA) fragments using phi29 DNA polymerase via biotin-streptavidin interaction. After the product of HRCA binded numerous biotinylated detection probes, an ultrasensitive electrochemical readout by further employing the streptavidin-alkaline phosphatase. The proposed biosensor exhibited excellent detection sensitivity and specificity with a log-linear response to target DNA from 0.01 fM to 10 pM as low as 8.9 aM. The proposed method allowed DNA detection with simplicity, rapidness, low cost and high specificity, which might have the potential for application in clinical molecular diagnostics and environmental monitoring. 相似文献
993.
A. A. Shutov 《Fluid Dynamics》2006,41(6):901-915
The shape of a charged jet is determined in the approximation of a strong electric field. The stability of the jet with respect to both axisymmetric and nonaxisymmetric perturbations of the sinusoidal type is investigated in the linear approximation. The domains of predominance of the axisymmetric and bending modes and the longitudinal partition mode are determined. Experimental data on the longitudinal partition of a polymeric jet into several daughter jets are given. 相似文献
994.
995.
A set of original, analytical equations useful for theoretical calculation of the electron paramagnetic resonance (EPR) signal intensity are presented for the multitude of sample shapes, which range from point-like, line-like, planar, rectangular, cubical, circular, cylindrical, spherical to an irregularly shaped sample. The samples can be situated at any available position within the prescribed part of the microwave cavity (a central cylinder of diameter 11 mm and length 23.5 mm, in either a Bruker single TE102 or double TE104 rectangular cavity, with the modulation coils situated in the left and right side cavity walls, which is connected to a X-band, field-modulated CW Bruker EPR spectrometer). The theoretical computations of EPR signal intensity can be used in the computer simulations in which: (i) the EPR signal intensity profiles are constructed; (ii) the optimal sample positions in the cavity to give a maximum value of signal intensity are found; (iii) the errors associated with sample positioning within the cavity when compared to a second sample of a different size, shape or position are studied. 相似文献
996.
Chorng-Shyan?ChernEmail author Cheng-Kang?Lee Chia-Jung?Chang 《Colloid and polymer science》2004,283(3):257-264
The electrostatic interactions between amphoteric polymethyl methacrylate latex particles and proteins with different pI values were investigated. These latex particles possess a net positive charge at low pH, but they become negatively charged at high pH. The nature and degree of interactions between these polymer particles and proteins are primarily controlled by the electrostatic characteristics of the particles and proteins under the experimental conditions. The self-promoting adsorption process from the charge neutralization of latex particles by the proteins, which have the opposite net charge to that of the particles, leads to a rapid reduction in the zeta potential of the particles (in other words colloidal stability), and so strong flocculation occurs. On the other hand, the electrostatic repulsion forces between similarly charged latex particles and the proteins retard the adsorption of protein molecules onto the surfaces of the particles. Therefore, latex particles exhibit excellent colloidal stability over a wide range of protein concentrations. A transition from net negative charge to net positive charge, and vice versa (charge reversal), was observed when the particle surface charge density was not high enough to be predominant in the protein adsorption process. 相似文献
997.
998.
Toshiharu Okui Yuriko Saito Tatsuya Okubo Masayoshi Sadakata 《Journal of Sol-Gel Science and Technology》1995,5(2):127-134
Selective gas permeation of porous organic/inorganic hybrid membranes via sol-gel route and its thermal stability are described. Separation performance of the hybrid membrane was improved compared with porous membranes governed by the Knudsen flow, and gas permeability was still much higher than that through nonporous membranes. Additionally, it was shown that these membranes were applicable at higher temperatures than organic membranes.SEM observation demonstrated that the thin membrane was crack-free. Nitrogen physisorption isotherms showed the pore size was in the range of nanometers. Gas permeability through this membrane including phenyl group was in the range of 10–8 [cc(STP) cm/(cm2 s cmHg)] at 25°C. The ratios of O2/N2 and CO2/N2 were 1.5 and 6.0, respectively, showing the permeation was not governed by the Knudsen flow. The permeability decreased as the temperature increased. Furthermore, the specific affinity between gas molecules and surface was observed not only in the permeation data of the hybrid membranes but in the physisorption data. These results suggested that the gas permeation through the hybrid membrane was governed by the surface flow mechanism.Thermal analysis indicated that these functional groups were still stable at higher temperatures. The phenyl group especially remained undamaged even at 400°C. 相似文献
999.
A new dicarboxylic acid monomer containing the N-methylcarbazole and imide structures, 3,6-bis(trimellitimido)-N-methylcarbazole (I), was prepared from the condensation of 3,6-diamino-N-methylcarbazole (c) and trimellitic anhydride. The diamine c was synthesized in three steps starting from the methylation of carbazole, followed by nitration and catalytic hydrazine
reduction. A series of N-methylcarbazole-containing poly(amide–imide)s were synthesized by direct polycondensation from the diimide–diacid I with various aromatic diamines. These poly(amide–imide)s had inherent viscosities of 0.66–1.47 dl/g and were readily soluble
in a variety of organic solvents, including N-methyl-2-pyrrolidone and N,N-dimethylacetamide (DMAc). Transparent, flexible, and tough films of these polymers could be cast from DMAc solutions, and
these films exhibited excellent mechanical strength. The glass-transition temperatures of these poly(amide–imide)s were in
the range 317–362 °C. All the poly (amide–imide) did not degrade noticeably below 480 °C in nitrogen, and the 10% weight loss
temperatures and char yields at 800 °C were above 520 °C and 60% in nitrogen, respectively, indicating high thermal stability.
Received: 8 February 2000/Accepted: 23 March 2000 相似文献
1000.
A new complex [Pb(phen)2(4-NBA)]2·2(NO3)·H2O(phen = 1,10-phenanthroline,4-NBA = 4-nitrobenzoate) has been hydrothermally synthesized and structurally determined by single-crystal X-ray diffraction,elemental analyses and IR spectroscopy.The complex crystallizes in monoclinic,space group P21/c with a = 13.416(3),b = 14.065(3),c = 16.845(3) ,β = 110.55(3)o,V = 2976.5(10)3,Z = 2,Dc = 1.796 g/cm3,F(000) = 1564,GOOF = 0.962,the final R = 0.0686 and wR = 0.1746.The crystal structure shows that the lead ion is coordinated with two carboxylate O atoms from the 4-NBA anion,and four N atoms from two phen molecules,forming a slightly distorted pentagonalbipyramidal coordination geometry.It is further extended by various supramo-lecular interactions to form a three-dimensional supramolecular network.The TG analysis result shows that this complex begins decomposing at 30 ℃ and decompounding completely at 733 ℃. 相似文献