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101.
Using quartz crystal microbalance (QCM) as an immunosensor, this work investigates the contribution of a cyclic voltammetry (CV) on the proper immobilization of antibodies with the aim of enhancing its target recognition and binding ability. Primarily, CV in the range of −0.1 to 0.9 V was applied to form a layer of poly-(2-cyano-ethylpyrrole) (PCEPy) on gold quartz crystal electrode. Then the efficiencies of antibodies (anti-IgG, AIgG) immobilized electrochemically with CV applied in 0-0.65 V were compared to those immobilized via physical adsorption, by observing relative affinity towards AIgG-Fab and AIgG-Fc fragments. The results showed antibody-AIgG-Fab interaction could be enhanced about 4 times when CV is applied (11.2 ± 1.3 vs 41.6 ± 3.4 relative fluorescence unit). On the contrary, physisorbed antibodies showed a higher degree of affinity towards AIgG-Fc indicating inappropriate orientations of physisorbed antibodies. AIgG immobilized PCEPy-gold QC electrode was characterized further for its sensitivity towards a new target bovine albumin with both a QCM and fluorescence measurement. Such electrode exhibited a good sensitivity as well as a large linear dynamic range, from 0.4 μg/ml to 1.0 μg/ml and from 0.5 μg/ml to 10.0 μg/ml, at QCM and fluorescence measurement, respectively. 相似文献
102.
Pseudo-first-order rate constants (k(obsd)) for reactions of 4-nitrophenyl salicylate (7) with alkali metal ethoxides (EtOM, M = K, Na, and Li) in anhydrous ethanol have been measured spectrophotometrically. Interestingly, the k(obsd) value decreases significantly as the concentration of EtOM increases. Because the phenolic moiety of substrate 7 would be deprotonated and exist as an anionic form (i.e., 7(-)) under kinetic conditions, the ground-state stabilization of 7(-) through formation of a six-membered cyclic complex with M(+) (i.e., 8) is proposed to be responsible for the decreasing k(obsd) trend. The k(obsd) value at a given concentration of EtOK increases steeply upon addition of [18]crown-6 ether (18C6) up to [18C6]/[EtOK] = 1 in the reaction mixture and then remains relatively constant thereafter. In contrast, k(obsd) decreases upon addition of salts (e.g., LiClO(4) or KSCN) to the reaction mixture, which indicates that M(+) ions inhibit the reaction. However, in the presence of 18C6, the k(obsd) value is independent of the concentration of EtOK but remains constant, which indicates that the reaction proceeds through a unimolecular mechanism in the presence of the complexing agent. Although two conceivable unimolecular pathways (formation of ketene 9 and lactone 10) can account for the kinetic results, the reaction has been concluded to proceed via formation of ketene 9 as the reactive intermediate on the basis of theoretical calculations. 相似文献
103.
Jung A Um Young-Geun Choi Dong-Kyu Lee Yun Sun Lee Chang Ju Lim Young A Youn Hwa Dong Lee Hi Jae Cho Jeong Hill Park Young Bae Seo Hsun-chih Kuo Johan Lim Tae-Jin Yang Sung Won Kwon Jeongmi Lee 《Analytical and bioanalytical chemistry》2013,405(23):7523-7534
Sixty peony root training samples of the same age were collected from various regions in Korea and China, and their genetic diversity was investigated for 23 chloroplast intergenic space regions. All samples were genetically indistinguishable, indicating that the DNA-based techniques employed were not appropriate for determining the samples’ regions of origin. In contrast, 1H-nuclear magnetic resonance (1H-NMR) spectroscopy-based metabolomics coupled with multivariate statistical analysis revealed a clear difference between the metabolic profiles of the Korean and Chinese samples. Orthogonal projections on the latent structure-discrimination analysis allowed the identification of potential metabolite markers, including γ-aminobutyric acid, arginine, alanine, paeoniflorin, and albiflorin, that could be useful for classifying the samples’ regions of origin. The validity of the discrimination model was tested using the response permutation test and blind prediction test for internal and external validations, respectively. Metabolomic data of 21 blended samples consisting of Korean and Chinese samples mixed at various proportions were also acquired by 1H-NMR analysis. After data preprocessing which was designed to eliminate uncontrolled deviations in the spectral data between the testing and training sets, a new statistical procedure for estimating the mixing proportions of blended samples was established using the constrained least squares method for the first time. The predictive procedure exhibited relatively good predictability (adjusted R 2?=?0.7669), and thus has the potential to be used in the quality control of peony root by providing correct indications for a sample’s geographical origins. Figure
1H-NMR spectroscopy-based metabolomics allowed the discrimination between genetically identical peony roots from different regions of origin and the estimation of the mixing proportions of blended samples 相似文献
104.
We introduce an energy-momentum density vector which is independent of the affine structure of the manifold and whose conservation is linked to observers. Integrating this quantity over time-like surfaces we can define Hamiltonian and momentum for the system which coincide with the corresponding ADM definitions for the case of irrotational Riemannian manifolds. As a consequence of our formalism, a Weak Equivalence Principle version for manifolds with torsion appears as the natural extension to non-Riemannian geometries from the Equivalence Principle of General Relativity. 相似文献
105.
106.
Alkali‐Metal Ion Catalysis and Inhibition in SNAr Displacement: Relative Stabilization of Ground State and Transition State Determines Catalysis and Inhibition in SNAr Reactivity
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Prof. Ik‐Hwan Um Hyo‐Jin Cho Min‐Young Kim Prof. Erwin Buncel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13337-13344
We report here the first observation of alkali‐metal ion catalysis and inhibition in SNAr reactions. The plot of kobsd versus [alkali‐metal ethoxide] exhibits downward curvature for the reactions of 1‐(4‐nitrophenoxy)‐2,4‐dinitrobenzene with EtOLi, EtONa, and EtOK, but upward curvature for the corresponding reaction with EtOK in the presence of 18‐crown‐6‐ether (18C6). Dissection of kobsd into the second‐order rate constants for the reactions with the dissociated EtO? and the ion‐paired EtOM (i.e., k and kEtOM, respectively) has revealed that the reactivity increases in the order EtOLi<EtONa<EtOK<EtO?<EtOK/18C6. This indicates that the reaction is inhibited by Li+, Na+, and K+ ions but is catalyzed by 18C6 K+ ion. The reactions of 1‐(Y‐substituted‐phenoxy)‐2,4‐dinitrobenzenes have been proposed to proceed through a stepwise mechanism, in which expulsion of the leaving group occurs after the rate‐determining step based on the kinetic result that σo constants exhibit a much better Hammett correlation than σ? constants. Alkali‐metal ion catalysis or inhibition has been discussed in terms of differential stabilization of ground‐state and transition‐state complexes through a qualitative energy profile. A π‐complexed transition‐state structure is proposed to account for the kinetic results. 相似文献
107.
In this study, we investigated the enlargement of liquid crystal (LC) blue-phase (BP) temperature range using the rod-like low-molecular-weight cyano phenyl-type chiral nematic LC with various core group and chiral dopant concentrations. Also, the electro-optic response time was investigated for them. We found that the BP temperature range was strongly dependent upon the core structure and the chiral dopant concentration for the chiral nematic LC mixtures having the same terminal group. Also, we found a stable BP with a wide temperature range (more than 6 K), including a BP-isotropic coexistence state over 13.5 K upon heating and cooling processes and very fast response time (less than 1 ms), by using the cyano phenyl-type chiral nematic LC mixture with a high molecular aspect ratio and a high chiral dopant concentration. 相似文献
108.
Sun-Mi Lee Min Ok Cho Youngsoon Um Byoung-In Sang 《Applied biochemistry and biotechnology》2010,161(1-8):75-83
Degeneration is one of the limiting factors in butanol fermentation, and it must be monitored and prevented for stable butanol production. In Clostridium acetobutylicum ATCC 824, the most well-known butanol-producing microorganism, degeneration is caused by the loss of the pSOL1 plasmid that carries essential genes involved in solvent production. In this study, we designed two specific primer and probe sets for real-time qPCR (RT-qPCR) detection of C. acetobutylicum ATCC 824 (the C. aceto set) and pSOL1-possessing C. acetobutylicum ATCC 824 (the DGS set). Specific primer and probe sets were designed on the basis of the 16S rDNA sequence and pSOL1 sequence. The number of degenerated C. acetobutylicum could be quantified by subtracting the number of C. acetobutylicum ATCC 824 containing pSOL1 from the total number of C. acetobutylicum ATCC 824. The primer and probe sets permitted the specific detection and quantification of degenerated C. acetobutylicum and total butanol-producing C. acetobutylicum by RT-qPCR. 相似文献
109.
110.
The effect of an electric field on the local stoichiometry of front waves in an ionic chemical system 总被引:2,自引:0,他引:2
A model based on an autocatalytic, two-step reaction mechanismincluding two ionic components (of the same charge) and twonon-ionic components, where both reactions are of second orderoverall, is considered when an electric field is applied tothe system. The model is motivated by experimental observationson the iodate-arsenous acid system. The travelling wave equationsare examined first and conditions obtained for the existenceand form of these waves. These conditions are then used to interpretthe results obtained from numerical simulations of the fullsystem. These results display all the main features observedexperimentally, the change in the local stoichiometry and thepossible wave annihilation for sufficiently strong fields. Themodel provides a clear explanation for these features as wellas predicting new features not reported from the experiments.The main one of which is the occurrence of an internal wavepropagating in the reacted part of the system in the directioninduced by the applied field. 相似文献