Synthesis and structure-activity relationship studies of MI-2 analogues as MALT1 inhibitors.

Recent studies revealed that MALT1 is a promising therapeutic target for the treatment of ABC-DLBCL. Among several reported MALT1 inhibitors, MI-2 as an irreversible inhibitor represents a new class of ABC-DLBCL therapeutics. Due to its inherent potential cross-reactivity, further structure-activity relationship (SAR) study is imperative. In this work, five focused compound libraries based on the chemical structure of MI-2 are designed and synthesized. The systematic SARs revealed that the side chain of 2-methoxyethoxy has little impact on the activity and can be replaced by other functionalized groups, providing new MI-2 analogues with retained or enhanced potency. Compounds 81-83 with terminal hydroxyl group as side chain displayed enhanced activities against MALT1. Replacement of triazole core with pyrazole is also tolerant, while structural modifications on other sites are detrimental. These findings will facilitate further development of small-molecule MALT1 inhibitors.

An ultrasensitive conformation-dependent colorimetric probe for the detection of mercury(II) using exonuclease III-assisted target recycling and gold nanoparticles.

An ultrasensitive conformation-dependent colorimetric assay has been developed for the detection of mercury(II) ions. It is based on the use of exonuclease III (Exo III)-assisted target recycling and gold nanoparticles (AuNPs). In the absence of Hg(II), the hairpin-shaped DNA probe (H-DNA) binds to AuNPs and stabilizes them in solutions of high ionic strength. In the presence of Hg(II), on the other hand, the sticky termini of the H-DNA form a rigid DNA duplex stem with a blunt 3'-terminus. Thus, Exo III is activated as a biocatalyst for selective and stepwise removal of mononucleotides from the 3'-terminus of the H-DNA. As a result, Hg(II) is released from the T-Hg(II)-T complexes. The guanine-rich sequences released from the H-DNA are then self-assembled with potassium ion to form a stable G-quadruplex conformation. In solutions of high ionic strength, this results in aggregation of AuNPs and a color change from red to blue which can be seen with bare eyes. The method is highly sensitive and selective. It has a linear response in the 10 pM to 100 nM Hg(II) concentration range, and the detection limit is as low as 3.2 pM (at an S/N ratio of 3). The relative standard deviation at a level of 0.5 nM of Hg(II) is 4.9% (for n = 10). The method was applied to the detection of Hg(II) in spiked environment water samples, with recoveries ranging from 92% to 106%. Graphical abstract A conformation-dependent colorimetric system was fabricated for label-free detection of mercury(II) by utilizing exonuclease III(Exo III)-assisted target recycling and gold nanoparticles (AuNPs).