Highly sensitive and selective detection of silver(I) in aqueous solution with silver(I)-specific DNA and Sybr Green I.

We report a label-free fluorescence turn-on approach for the sensitive and selective sensing of silver ion Ag(+) based on Ag(+) induced conformational change of cytosine-rich single-stranded DNA. A silver specific oligonucleotide (SSO) undergoes a structural transition from single-stranded DNA (ssDNA) to a C-Ag(+)-C mediated hairpin structure, which can be recognized by a double-stranded DNA (dsDNA) intercalator Sybr Green I (SG). The linear response range for Ag(+) detection was from 1 nM to 100 nM. The method presented here is highly sensitive and a limit of detection of 1 nM was obtained. More importantly, this optical method was successfully used to identify complex sample mixtures.

A graphene-based platform for fluorescent detection of SNPs.

A novel fluorescent single nucleotide polymorphism (SNP) assay was developed by using Graphene Oxide (GO), which provides a fast, sensitive and simple method for SNP detection. The strategy was based on the single base extension reaction and different absorption capacity of fluorescein labeled dGTP (dGTP-Fl) and double-stranded DNA (dsDNA) to GO. dGTP-Fl is incorporated into the probe by extension reaction for the mutant target but not for the wild target, which leads to recovered fluorescence for the mutant target because of weak interaction between dsDNA and GO and weak fluorescence for the wild target because of the quenched fluorescence of dGTP-Fl by GO. The method shows a linear range for the mutant-type target from 3 nM to 50 nM and 3 nM is the detection limit. It was noted that as low as 10% mutant-type target could be detected in the presence of the wild-type target, in which the concentration is 9 times higher than that of the mutant-type target.

UiO-66 derived ZrO2@C catalysts for the double-bond isomerization reaction of 2-butene.

1-Butene, as one of the widely used chemical raw materials, can be produced by the double bond isomerization of 2-butene. However, the current yield of the isomerization reaction is only up to 20% or so. It is therefore an urgent issue to develop novel catalysts with higher performances. In this work, a high-activity ZrO2@C catalyst that is derived from UiO-66(Zr) is fabricated. The catalyst is prepared by calcining the precursor UiO-66(Zr) at high temperature in nitrogen, and characterized by XRD, TG, BET, SEM/TEM, XPS and NH3-TPD. The results demonstrate that the calcination temperature has significant influences on the catalyst structure and performance. Regarding the catalyst ZrO2@C-500, the selectivity and yield of 1-butene are 94.0% and 35.1%, respectively. The high performance is due to multiple aspects, including the inherited octahedral morphology from parent UiO-66(Zr), suitable medium-strong acidic active sites and high surface area. The present work will lead to a better understanding of the ZrO2@C catalyst and guide the rational design of high-activity catalysts for the double bond isomerization of 2-butene to 1-butene.

A hemicyanine-based near-infrared fluorescent probe for vapor-phase hydrazine detection and bioimaging in a complete aqueous media.

A novel near-infrared fluorescent probe CyOE based on hemicyanine dye containing acetyl as a recognition site is reported. The probe CyOE shows high selectivity and sensitivity (LOD = 82 nM, 2.58 ppb), as well as good water solubility and quantitative detectability of hydrazine in the concentration range of 0-75 µM (R2 = 0.993). Moreover, CyOE has a significant increase in fluorescence at 735 nm with the addition of N2H4, which provides a rapid, colorimetric and gas-phase detection method for N2H4 in both aqueous solution and real water samples. In addition, CyOE is successfully utilized to visualize hydrazine in cells with low cytotoxicity and high cell permeability.

Recombinant Expression And Indirect ELISA For COWP And HSP70 Proteins From Cryptosporidium andersoni.

Cryptosporidium spp. infect cattle at a high rates, and reduce milk production. Cryptosporidiosis has caused economic losses for the dairy industry. Studies in Western countries have shown that Cryptosporidium can also infect humans. Therefore, the development of methods for the early detection of Cryptosporidium is an important public health objective. Total RNA isolated from C. andersoni was used as template for generating cDNA encoding the COWP and HSP70 proteins. The recombinant plasmid, pET-32a(+)-COWP-HSP70, was constructed by double digestion and subcloning. The expression of the three recombinant proteins was induced in Escherichia coli BL21 using isopropyl-ß-D-thiogalactopyranoside. The antigenicity of the recombinant proteins was examined using western blotting and indirect ELISA. The identities of the COWP fusion protein (CFP), HSP70 fusion protein (HFP), and COWP-HSP70 fusion protein (CHFP) were confirmed by BLAST searches of known sequences in GenBank respectively. The ELISA and western blot analyses indicated that all three of the proteins were highly immunogenic and antigenic. An indirect ELISA method was developed using the three recombinant proteins as coating antigens for the analysis of 40 clinical samples. The results showed that CHFP was the best candidate antigen for clinical testing, with a detection rate of 100%, compared with general parasitological screening. Above of all, the recombinant CHFP protein represents the best candidate antigen among three ones for detecting anti-Cryptosporidium antibodies in clinical samples. The development of the indirect ELISA lays the foundation for further research in immunodiagnosis and disease prevention of cryptosporidiosis.