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Wu Z.-Y.,Research Center for Analytical science | Fang F.,Research Center for Analytical science | Fang F.,Northeastern University China | He Y.-Q.,Research Center for Analytical science | And 3 more authors.
Analytical Chemistry | Year: 2012

Better understanding of the mechanism is important for exploring the potentials of a preconcentration method. In this work, we show for the first time that the HF etched porous junction on a fused silica capillary behaves not only as a filter but also as an integrated nanofluidic interface. This junction exhibits an obvious ion concentration polarization (CP) effect, with which highly efficient electrokinetic stacking (ES) inside the capillary can be achieved without molecular size or charge type limitation. Two major types of CP based ES were proposed, and an autostop etching principle was presented for avoiding overetching. The ES can be performed in a broad range of pH and buffer concentration. Over a billion times of concentration was demonstrated by a fluorescein probe with laser induced fluorescent (LIF) detection. ES of fluorescently labeled and native DNA and protein were characterized by charge-coupled device (CCD) imaging and online capillary gel electrophoresis (CGE) with ultraviolet (UV) absorption detections, respectively. With this junction, highly efficient ES can be performed easily by voltage manipulation without any mechanical operation. We may foresee that the performance of capillary-based conventional and chip electrophoresis could be greatly enhanced with this junction in the analysis of low abundance biomolecules. © 2012 American Chemical Society. Source

Ren H.-B.,Research Center for Analytical science | Wu B.-Y.,Research Center for Analytical science | Chen J.-T.,Nankai University | Yan X.-P.,Research Center for Analytical science
Analytical Chemistry | Year: 2011

Detection of intracellular Zn 2+ has gained great attention because of its biological significances. Here we show the fabrication of silica-coated S 2--enriched Mn-doped ZnS quantum dots (SiO 2-S-Mn-ZnS QDs) by enriching S 2- with a silica shell on the surface of Mn-doped ZnS QDs via a sol-gel process for imaging intracellular Zn 2+ ions. The developed probe gave a good linearity for the calibration plot (the recovered PL intensity of the SiO 2-S-Mn-ZnS QDs against the concentration of Zn 2+ from 0.3 to 15.0 μM), excellent reproducibility (1.2% relative standard deviation for 11 replicate measurements of Zn 2+ at 3 μM), and low detection limit (3s; 80 nM Zn 2+). The SiO 2-S-Mn-ZnS QDs showed negligible cytotoxicity, good sensitivity, and selectivity for Zn 2+ in a photoluminescence turn-on mode, being a promising probe for photoluminescence imaging of intracellular Zn 2+. © 2011 American Chemical Society. Source

Wang S.,Research Center for Analytical science | Wang S.,Nankai University | Liu P.,Nankai University | Cai W.,Research Center for Analytical science | And 2 more authors.
Gaodeng Xuexiao Huaxue Xuebao/Chemical Journal of Chinese Universities | Year: 2015

In order to investigate the hydrophobic effect of chain-like structures on shuttling in further, three similar rotaxanes are studied in this work. The rotaxanes are formed by an α-CD, two dodecamethylene chains (ALK) or two poly(ethylene glycol) (PEG) for stations, one bipyridinium moiety (PY) or one biphenyl moiety (PH) for linkers and large end groups at both sides. The shuttling of the rotaxanes was studied by means of molecular dynamics simulations (MD) combined with free-energy calculations in water and DMSO at room temperature. Two methods, the adaptive biasing force (ABF) method and the multiple walker ABF (MW-ABF) method, a modified version of ABF, are adopted for calculating the free-energy change characterizing the shuttling process. The potentials of mean force (PMFs) for the three rotaxanes are determined. The free-energy barriers of the PMFs for the PEG-rotaxane are lower than those for the the ALK-rotaxane both in water and DMSO. Furthermore, the barriers for the PEG-rotaxanes in DMSO are lower than that in water, which is in accordance with the ALK-rotaxanes. The barriers for the PH-rotaxanes are significantly lower than those for the PY-rotaxanes. Partitioning the PMFs into free-energy components suggests that change of the the charged group by an hydrophobic biphenyl moiety or decrease of the hydrophobicity of the chain-like structure in two stations from ALK to PEG reduces the free-energy barrier with respect to the stable states in the stations. In addition, comparison of the two free-energy calculation methods shows that the MW-ABF method can significantly improve the uniformity of sampling and hence increase the computational efficiency. © 2015, Higher Education Press. All right reserved. Source

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