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In this work, we report a facile, sensitive, selective, and reproducible DNA impedimetric sensor device. We demonstrate that, combined with exonuclease III, the easily prepared electrochemically reduced graphene oxide (rGO) could be a desirable platform to amplify signals in electrochemical impedance spectroscopy for ultrasensitive DNA detection. Guided by enzyme assisted target recycling, efficient interfacial tuning can be obtained, from the situation with high impedance caused by single-stranded DNA probes directly adsorbed onto rGO to the one with low impedance due to the continuous desorption of target–probe DNA hybrids and the consequent digestion of DNA probes. Just a few DNA targets can specifically trigger the enzymatic digestion of a large number of DNA probes. It is the excellent electrical conductivity of rGO that further enlarges the changes of electron transfer resistance after the removal of DNA probes. As a result of synergistically combining both enzymatic and electrical amplification, the enlarged changes of impedimetric signals can be measured to sensitively report DNA targets. The specificity has been guaranteed by the intrinsic recognition of hybrids through both rGO and exonuclease III. A limit of detection as low as 10 aM target DNA in the matrix of cell culture medium, as well as a wide linear range and good discrimination of mismatched sequences even at the one-base level, suggests its great application prospect in biosensing and biomedical analysis. It also has other advantages including easy operation, low cost, and convenient regeneration, with more competitive performance in developing impedimetric biosensors. [ABSTRACT FROM AUTHOR]

Lately, polymers as electrochemical catalysts have attracted intense interest. As two promising candidates, herein, electrochemically deposited polyaniline and poly(aspartic acid) thin film materials have been fabricated on glassy carbon electrodes. Through multiple characterizations, including attenuated total reflection Fourier transform infrared spectrophotometry, cyclic voltammetry, electrochemical impedance spectroscopy, and proton nuclear magnetic resonance, essential properties of these two electro-synthesized polymers, especially the capacity in electrochemically catalyzing the oxidation of electro-active isomers of hydroquinone and catechol, have been investigated. The polymer-modified electrodes present improved conductivity, and diffusion-dominated redox behaviors of hydroquinone and catechol at both modified glassy carbon electrodes are observed. In addition, quantitative proton nuclear magnetic resonance spectra provide the evident information on the electrochemically induced molecular transformation, which confirms the better electrochemical activity of poly(aspartic acid). [ABSTRACT FROM AUTHOR]

The 19F NMR chemical shieldings of MF2 (M=Zn, Cd, Pb), MF3 (M=Al, Ga, In), and SnF4 were studied by the GIAO-B3LYP method. The aug-cc-pVTZ basis set was used for the inspected fluorine atom, and LanL2DZ for the remaining fluorine atoms. The 3-21G(2d) basis set was utilized for the Al atom, and CRENBL and/or DZVP for the other metal atoms. When appropriate cluster models were employed, the theoretical shieldings agree well with experimental ones. The relativistic and electron correlation effects have greater influence on the calculated results of fluorides containing heavy or transition metal atoms. [Copyright &y& Elsevier]

In many ultrafast imaging applications, the reduced field-of-view (rFOV) technique is often used to enhance the spatial resolution and field inhomogeneity immunity of the images. The stationary-phase characteristic of the spatiotemporally-encoded (SPEN) method offers an inherent applicability to rFOV imaging. In this study, a flexible rFOV imaging method is presented and the superiority of the SPEN approach in rFOV imaging is demonstrated. The proposed method is validated with phantom and in vivo rat experiments, including cardiac imaging and contrast-enhanced perfusion imaging. For comparison, the echo planar imaging (EPI) experiments with orthogonal RF excitation are also performed. The results show that the signal-to-noise ratios of the images acquired by the proposed method can be higher than those obtained with the rFOV EPI. Moreover, the proposed method shows better performance in the cardiac imaging and perfusion imaging of rat kidney, and it can scan one or more regions of interest (ROIs) with high spatial resolution in a single shot. It might be a favorable solution to ultrafast imaging applications in cases with severe susceptibility heterogeneities, such as cardiac imaging and perfusion imaging. Furthermore, it might be promising in applications with separate ROIs, such as mammary and limb imaging. [ABSTRACT FROM AUTHOR]