Organophosphorus pesticides (OPs) can inhibit the activity of acetylcholinesterase (AChE) to induce neurological diseases. It is significant to exploit a rapid and sensitive strategy to monitor OPs. Here, a metal–organic framework (MOF) acted as a carrier to encapsulate AuNCs, which can limit the molecular motion of AuNCs, trigger the aggregation-induced emission (AIE) effect, and exhibit a strong fluorescence with a fluorescence lifetime and quantum yield of 6.83 μs and 4.63%, respectively. Then, the marriage of fluorescence and colorimetric signals was realized on the basis of the dual function of the enzymolysis product from AChE and choline oxidase (CHO) on AuNCs@ZIF-8. First, it can decompose ZIF-8 to weaken the restraint on AuNCs, and thus the fluorescence receded. Second, it can be used as a substrate for the peroxidase mimics of the released AuNCs to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) and a visible blue appeared. Thus, on the basis of the inhibition of AChE activity by OPs, a fluorescence–colorimetric dual-signal biosensor was established. In addition, colorimetric paper strips were exploited to realize a visual semiquantitative detection, and a smartphone APP was developed to make the visualization results more precise and realize real-time supervision of pesticide contamination.

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TAL (transcriptional activator-like) effectors (TALEs) are DNA-binding proteins, containing a modular central domain that recognizes specific DNA sequences. Recently, the crystallographic studies of TALEs revealed the structure of DNA-recognition domain. In this article, molecular dynamics (MD) simulations are employed to study two crystal structures of an 11.5-repeat TALE, in the presence and absence of DNA, respectively. The simulated results indicate that the specific binding of RVDs (repeat-variable diresidues) with DNA leads to the markedly reduced fluctuations of tandem repeats, especially at the two ends. In the DNA-bound TALE system, the base-specific interaction is formed mainly by the residue at position 13 within a TAL repeat. Tandem repeats with weak RVDs are unfavorable for the TALE-DNA binding. These observations are consistent with experimental studies. By using principal component analysis (PCA), the dominant motions are open-close movements between the two ends of the superhelical structure in both DNA-free and DNA-bound TALE systems. The open-close movements are found to be critical for the recognition and binding of TALE-DNA based on the analysis of free energy landscape (FEL). The conformational analysis of DNA indicates that the 5′ end of DNA target sequence has more remarkable structural deformability than the other sites. Meanwhile, the conformational change of DNA is likely associated with the specific interaction of TALE-DNA. We further suggest that the arrangement of N-terminal repeats with strong RVDs may help in the design of efficient TALEs. This study provides some new insights into the understanding of the TALE-DNA recognition mechanism.

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The major facilitator superfamily (MFS) is an important and widespread family of secondary membrane transporters. Recently, an outward-open structure of MFS, the fucose/H + symporter FucP was determined by X-ray crystallography. In this article, the outward-open form of FucP is analyzed by elastic network models. It is found that the periplasmic half region has remarkable fluctuation, and the closure of the periplasmic half is the most dominant conformational change for outward-open conformation of FucP. To ascertain the process of transport, an adaptive anisotropic network model is applied to explore the allosteric transitions of FucP. In particular, our simulation not only yields the intermediate states similar to that seen in the EmrD crystal structure, but also exhibits the whole transport process of FucP. On the basis of the coarse-grained analyses, we propose a new working model of how FucP mediates the symport of L-fucose and a proton. The allosteric and transport knowledge of FucP revealed in this work can provide some insights into the mechanism studies of MFS and other transport proteins.