We report on a method for simultaneous detection of the pathogens Vibrio parahaemolyticus and Salmonella typhimurium. It is based on dual fluorescence resonance energy transfer (FRET) from green-emitting quantum-dots (gQDs) and red-emitting quantum-dots (rQDs) as donors, and on novel amorphous carbon nanoparticles (CNPs) that act as acceptor. The gQDs were modified with an aptamer (Apt 1) recognizing V. parahaemolyticus, and the rQDs with an aptamer (Apt 2) recognizing S. typhimurium. The fluorescence of both QDs is strongly quenched in the presence of CNPs. However, on addition of the target analytes, the QDsaptamer-target complex is formed and quenching by CNPs is suppressed. The fluorescence of the QDs is linearly proportional to the concentration of the two pathogens in the range from 50 to 10 6 cfu·mL −1 , with detection limits as low as 25 cfu·mL −1 for V. parahaemolyticus, and of 35 cfu·mL −1 for S. typhimurium. The assay was applied to real food samples, and the results were consistent with the results obtained with plate counting methods. We presume that this strategy can be extended to the detection of other pathogenic bacteria and biomolecules by simply substituting the aptamer.
A series of novel chiral-bridged atropisomeric monophosphine ligands were synthesized via convenient and simple pathways. The prepared ligands, especially for ligand 7d, were found to be highly effective in the Pd-catalyzed Suzuki-Miyaura coupling reaction. The steric hindrance and electronic effect of substrates on the reactivity and enantioselectivity were explored preliminarily.
Ar apid construction of enantioenriched benzofused quinolizidines,i ndolizidines,a nd their analogues by ruthenium-catalyzed asymmetric cascade hydrogenation/ reductive amination of quinolinyl-and quinoxalinyl-containing ketones has been developed. This reaction proceeds under mild reaction conditions,a ffording chiral benzo-fused aliphatic N-heterocyclic compounds with structural diversity in good yields (up to 95 %) with excellent diastereoselectivity (up to > 20:1 dr) and enantioselectivity (up to > 99 %e e). Furthermore,t his catalytic protocol is applicable to the formal synthesis of (+ +)-gephyrotoxin.Scheme 1. Synthesis of quinolizidines, indolizidines, and their analogues via chemoselective asymmetric hydrogenation/intramolecular asymmetric reductive amination cascade process.
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