Trisubstituted olefin synthesis via Ni-catalyzed hydroalkylation of internal alkynes with non-activated alkyl halides.

The stereoselective synthesis of tri-substituted alkenes is challenging. Herein, we report a Ni-catalyzed regio- and stereo-selective hydroalkylation of internal alkynes with non-activated alkyl halides. This method does not use any sensitive organometallic reagents and shows good functional group compatibility, which enables the efficient synthesis of many tri-substituted olefins from readily available coupling partners. It also provides a straightforward method for the modification of bioactive organic molecules.

A label-free fluorescence assay for trypsin based on the electron transfer between oligonucleotide-stabilized Ag nanoclusters and cytochrome c.

A label-free fluorescent assay for the detection of trypsin by using oligonucleotide-templated silver nanoclusters (Ag NCs) and cytochrome c (Cyt c) has been demonstrated. When negatively charged Ag NCs and positively charged Cyt c are mixed, they tend to form a hybrid complex, and then lead the fluorescence of Ag NCs to be quenched significantly due to electron transfer between Ag NCs and the heme cofactor of Cyt c. In the presence of trypsin, it catalyzes the hydrolytic cleavage of Cyt c to small peptide fragments, and releases the heme moiety from the Ag NCs/Cyt c complex; the quenched fluorescence restores therewith. By virtue of this specific response, the fluorescent biosensor has a linear range of from 0.7 to 4 µg mL(-1) and from 9 to 120 µg mL(-1) with a detection limit of 58.7 ng mL(-1). Aside from the easy manufacture aspect, our method also possesses a high signal-to-background ratio (~11), excellent selectivity and good biocompatibility, which makes it a promising bioanalysis for a trypsin activity assay.

A cytosine-rich DNA decorated gold nanoparticles surface enhanced Raman-scattering platform for sensitive and selective detection of silver ions.

In this work, we developed a label-free, homogeneous surface-enhanced Raman-scattering (SERS) platform for the rapid, simple and sensitive detection of Ag(+) by using the unmodified gold nanoparticles (AuNPs). It utilizes the different absorption properties of single-strand DNA (ssDNA) and double-strand DNA (dsDNA) on citrate-coated AuNPs and specific interactions between Ag(+) and cytosine-cytosine pairs. In the presence of Ag(+), the structure of ssDNA containing rich cytosine will form a duplex, resulting in the salt-induced aggregation of gold nanoparticles; the corresponding SERS signal transduction can be observed due to the plasmonic coupling of metallic nanoparticles. The assay possesses a superior signal-to-background ratio as high as ∼35.8 with a detection limit of 15 nM. This approach is not only rapid and convenient in operation, but also shows excellent selectivity, which makes it possible to detect Ag(+) in actual samples.