Surface chemistry effects on the performance of an electrochemical DNA sensor

E-DNA sensors are a reagentless, electrochemical oligonucleotide sensing platform based on a redox-tag modified, electrode-bound probe DNA. Because E-DNA signaling is linked to hybridization-linked changes in the dynamics of this probe, sensor performance is likely dependent on the nature of the self-assembled monolayer coating the electrode. We have investigated this question by characterizing the gain, specificity, response time and shelf-life of E-DNA sensors fabricated using a range of co-adsorbates, including both charged and neutral alkane thiols. We find that, among the thiols tested, the positively charged cysteamine gives rise to the largest and most rapid response to target and leads to significantly improved storage stability. The best mismatch specificity, however, is achieved with mercaptoethanesulfonic and mercaptoundecanol, presumably due to the destabilizing effects of, respectively, the negative charge and steric bulk of these co-adsorbates. These results demonstrate that a careful choice of co-adsorbate chemistry can lead to significant improvements in the performance of this broad class of electrochemical DNA sensors.     

Quantitative proteomics by fluorescent labeling of cysteine residues using a set of two cyanine‐based or three rhodamine‐based dyes

Despite all remarkable progress in gel‐based proteomics in recent years, there is still need to further improve quantification by decreasing the detection limits and increasing the dynamic range. These criteria are achieved best by fluorescent dyes that specifically stain the proteins either by adsorption after gel electrophoresis (in‐gel staining) or covalent coupling prior to gel electrophoresis (in‐solution staining). Here we report a multiplex analysis of protein samples using maleimide‐activated cyanine‐based (Cy3 and Cy5) and rhodamine‐based dyes (Dy505, Dy535, and Dy635) to permanently label all thiol‐groups of cysteine‐containing proteins. The detection limits in SDS‐PAGE were about 10 ng per band and even 2 ng for BSA due to its high content of cysteine residues. Thus only 5 μg protein of a mouse brain homogenate were analyzed by 2‐DE. Both cyanine‐ and rhodamine‐based dyes also stained proteins that did not contain cysteines, probably by reaction with amino groups. This side reactivity did not limit the method and might even extend its general use to proteins missing cysteine residues, but at a lower sensitivity. The dynamic range was more than two orders of magnitude in SDS‐PAGE and the Dy‐fluorophores did not alter the mobility of the tested proteins. Thus, a mixture of Dy505‐, Dy555‐, and Dy635‐labeled Escherichia coli lysates were separated by 2‐DE in a single gel and the three spot patterns relatively quantified.     

基于CAN总线的楼宇温度检测系统

基于单片机实现传统温度检测技术的特点，提出了基于CAN总线的楼字温度检测系统方案．该系统方案的硬件平台主要包括温度检测模块和主控平台，并详细介绍了其硬件实现、软件设计思想及流程．实验表明：该系统可实现对楼宇温度的实时检测，并由LCD显示检测结果，对异常情况进行语音报警，从而实现对楼宇房间温度的有效监测．     

Plumbagin: A New Route to the Electroanalytical Determination of Cystine

The interaction between 5‐hydroxy‐1,4‐naphthoquinone and cysteine was found to give a clearly resolved voltammetric signature that could be used as an electrochemical assay for the thiol. A structure‐function study assessed the nature of the resulting voltammetric profile and the highly selective response to cysteine. The translation of the system as the basis of an assay for the determination of cystine was investigated using mercaptopropanol as the in situ reducing agent. The lack of response to the latter and high recovery performance of the label opens up a new direction for the one pot, mercury free determination of cystine.     

Polyadipates used as plasticizers in food contact: fraction below 1000 Da determined by size exclusion chromatography with evaporative light scattering detection and segmental response linearization or UV detection

Polyadipates might be a suitable replacement for conventional plasticizers in plastisols to produce lids for glass jars complying with legal limits for oily foods. For the characterization of polyadipates, the proportion of the material with a molecular mass below 1000 Da is important. Determination of the material < 1000 Da is also important for checking compliance with the specific legal limit. The analytical problems and the sources of uncertainty are investigated. Even when calibrated with constituents of polyadipates, preseparation at 1000 Da is of limited accuracy, since stretched and cyclic components of the same molecular mass have different retention times; a compromise must be found. UV detection leaves substantial uncertainty as the response particularly of the < 1000 Da components varies and tends to be below that of the higher molecular mass polyadipates. Evaporative light scattering detection has a nonlinear response for which a segmental correction (linearization of the integration raw data) is suggested: The raw data of the integration is linearized by an exponential function before the chromatogram is reconstructed.     

Regeneration of thiol-functionalized mesostructured silica adsorbents of mercury

The regeneration of thiol-functionalized SBA-15 adsorbents of mercury is presented in this article. The influence of temperature and pH on the adsorption process was studied. The effect due to the presence of complexing agents in aqueous solution on the desorption step was also evaluated. Hg(II) maximum adsorption capacities at different temperatures ranging from 20 °C to 60 °C were obtained and it was found that temperature does not affect the adsorption process. Mercury adsorption capacity was also determined in the presence of HNO₃ and HCl up to 3 M concentration. The comparison of the results showed that whereas hydrochloric acid exhibits an appreciable capacity to regenerate the thiol-functionalized SBA-15 adsorbent, the nitric acid results inefficient. The difference was attributed to the mercury complexing ability of chloride anion. Four complexing compounds, KBr, KSCN, (NH₂)₂CS, and HBr were tested for desorbing mercury in regeneration experiments. All agents were able to remove significant amounts of adsorbed mercury, being hydrobromic acid the complexing compound that yields the best results.     

Linear homobimetallic palladium complexes with end-capped SC(O)Me units

Rigid-rod structured homobimetallic palladium complexes of type [{trans-(Me(O)CS-4-C₆H₄-C₆H₄)(Ph₃P)₂Pd}₂(μ-N^∩N)](OTf)₂ (8a, μ-N^∩N = 4,4′-bipyridine, bpy; 8b, μ-N^∩N = C₅H₄N-CHN-NCH-C₅H₄N; 8c, μ-N^∩N = C₅H₄N-CHCH-C₆H₄-CHCH-C₅H₄N; 8d, μ-N^∩N = C₅H₄N-CHN-C₆H₄-NCH-C₅H₄N) were synthesized by the reaction of trans-[(Me(O)CS-4-C₆H₄-C₆H₄)(Ph₃P)₂Pd](OTf) (6) with 0.5 equivalents of N^∩N (7a, N^∩N = bpy; 7b, N^∩N = C₅H₄N-CHN-NCH-C₅H₄N; 7c, N^∩N = C₅H₄N-CHCH-C₆H₄-CHCH-C₅H₄N; 7d, N^∩N = C₅H₄N-CHN-C₆H₄-NCH-C₅H₄N) in high yield. Complex 6 was accessible by the subsequent reaction of I-4-C₆H₄-C₆H₄-4′-SC(O)Me (2) with [(PPh₃)₄Pd] (3) to produce trans-[(I)(Me(O)CS-4-C₆H₄-C₆H₄)(Ph₃P)₂Pd] (4) which further reacted with AgOTf (5) to give 6.The structures of 4 and 8c in the solid state are reported. Most characteristic for these systems is the square-planer coordination geometry of palladium with trans-positioned PPh₃ groups. This automatically positions the iodo ligand and the Me(O)CS-4-C₆H₄-C₆H₄ unit (complex 4) or the nitrogen donor atoms of the C₅H₄N-CHCH-C₆H₄-CHCH-C₅H₄N connectivity and the thio-acetyl group Me(O)CS-C₆H₄-C₆H₄ (complex 8c) trans to each other. In 8c a Pd-Pd separation of 20.156 Å is typical.The electrochemical redox behavior of 2, 4 and 8 is discussed.     

Mn(III) complex supported on Fe3O4 nanoparticles: magnetically separable nanocatalyst for selective oxidation of thiols to disulfides

A manganese(III) complex, [Mn(phox)₂(CH₃OH)₂]ClO₄ (phox?=?2-(2′-hydroxyphenyl)oxazoline), was immobilized on silica-coated magnetic Fe₃O₄ nanoparticles through the amino propyl linkage using a grafting process in dichloromethane. The resulting Fe₃O₄@SiO₂–NH₂@Mn(III) nanoparticles are used as efficient and recyclable catalysts for selective oxidation of thiols to disulfides using urea-hydrogen peroxide as the oxidant. The nanocatalyst was recycled several times. Leaching and recycling experiments revealed that the nanocatalyst can be recovered, recycled, and reused more than five times, without the loss of catalytic activity and magnetic properties. The recycling of the nanocatalyst in six consecutive runs afforded a total turnover number of more than 10,000. The heterogeneous Fe₃O₄@SiO₂–NH₂@Mn(III) nanoparticle shows more selectivity for the formation of disulfides in comparison with the homogeneous manganese complex.     

N-取代马来酰亚胺巯基荧光探针的研究进展

评述了测这含－SH生物活性物质和肽、蛋白质等的N－聚代马来酰亚胺荧光探针的种类、性能、原理、应用及其进展。