No abstract

Besides genome editing, CRISPR-Cas12a has recently been used for DNA detection applications with attomolar sensitivity but, to our knowledge, it has not been used for the detection of small molecules. Bacterial allosteric transcription factors (aTFs) have evolved to sense and respond sensitively to a variety of small molecules to benefit bacterial survival. By combining the single-stranded DNA cleavage ability of CRISPR-Cas12a and the competitive binding activities of aTFs for small molecules and double-stranded DNA, here we develop a simple, supersensitive, fast and high-throughput platform for the detection of small molecules, designated CaT-SMelor ( C RISPR-Cas12a- and aT F-mediated s mall m ol e cu l e detect or ). CaT-SMelor is successfully evaluated by detecting nanomolar levels of various small molecules, including uric acid and p -hydroxybenzoic acid among their structurally similar analogues. We also demonstrate that our CaT-SMelor directly measured the uric acid concentration in clinical human blood samples, indicating a great potential of CaT-SMelor in the detection of small molecules.

Sub 10 nm Pd core @Pt shell nanocrystals (NCs) were prepared by a facile and green reduction method in aqueous solutions using commercially available and nontoxic poly(ethylene oxide)−poly(propylene oxide)−poly-(ethylene oxide) amphiphilic triblock copolymers as the reductant, stabilizer, and capping agent. The growth mode and morphology of the Pt shell on the Pd surface can be adjusted simply by the Pt/Pd molar ratio. The activity of carbonsupported Pd@Pt NCs toward oxygen reduction reaction exhibited a Pt shell morphology dependence, with Pd 2 @Pt 1 (Pt/Pd molar ratio 1/2) having the highest mass activity and Pd 1 @Pt 2 (Pt/Pd molar ratio 2/1) having the best areaspecific activity, and both of them were significantly enhanced in comparison with that of commercial Pt/C catalysts. Moreover, single-fuel-cell testing indicated superior activity and durability of Pd 2 @Pt 1 NCs, which made Pd 2 @Pt 1 NCs promising cathode catalysts for fuel cell applications.