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  1. The kinetochore scaffold 1 (KNL1) protein recruits spindle assembly checkpoint (SAC) proteins to ensure accurate chromosome segregation during mitosis. Despite such a conserved function among eukaryotic organisms, its molecular architectures have rapidly evolved so that the functional mode of plant KNL1 is largely unknown. To understand how SAC signaling is regulated at kinetochores, we characterized the function of theKNL1gene inArabidopsis thaliana. The KNL1 protein was detected at kinetochores throughout the mitotic cell cycle, and nullknl1mutants were viable and fertile but exhibited severe vegetative and reproductive defects. The mutant cells showed serious impairments of chromosome congression and segregation, that resulted in the formation of micronuclei. In the absence of KNL1, core SAC proteins were no longer detected at the kinetochores, and the SAC was not activated by unattached or misaligned chromosomes. Arabidopsis KNL1 interacted with SAC essential proteins BUB3.3 and BMF3 through specific regions that were not found in known KNL1 proteins of other species, and recruited them independently to kinetochores. Furthermore, we demonstrated that upon ectopic expression, the KNL1 homolog from the dicot tomato was able to functionally substitute KNL1 inA.thaliana, while others from the monocot rice or moss associated with kinetochores but were not functional, as reflected by sequence variations of the kinetochore proteins in different plant lineages. Our results brought insights into understanding the rapid evolution and lineage-specific connection between KNL1 and the SAC signaling molecules.

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    Free, publicly-accessible full text available January 9, 2025
  2. Free, publicly-accessible full text available July 1, 2024
  3. A new class of stable four-coordinated benzotriazole-borane compounds was developed via gold-catalyzed alkyne hydroboration. The application of polymeric (BH 2 CN) n reagent gave the formation of cyano-amine-boranes (CAB) complexes with less basic N-heterocyclic amines and anilines. Various new CABs were investigated in catalytic hydroboration to synthesize N–B cycles. The 1,2,3-benzotriazoles were identified as the only feasible N-source, giving the four coordinated borane N–B cycles (BTAB) in excellent yields (up to 90%) with good functional group tolerability. This new class of polycyclic N–B compounds showed excellent stability toward acid, base, high temperature, and photo-irradiation. The facile synthesis, excellent stability, strong and tunable fluorescence emission make BTAB interesting new fluorescent probes for future chemical and biological applications. 
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    Systematic investigations were performed with various substituted groups at C8 purine and ribose. A series of isoG analogs, C8-phenyl substituted isoG were synthesized and applied for Cs + coordination. The structural proximity between purine and ribose limited pentaplex formation for C8-phenyl substituted isoG derivatives. Based on this observation, deoxy isoG derivative with modification on ribose ( tert -butyldimethylsilyl ether) was applied to assemble with the Cs + cation. Critical solvent (CDCl 3 and CD 3 CN) and anion (BPh 4 − , BARF − , and PF 6 − ) effects were revealed, leading to the controllable formation of various stable isoG pentaplexes, including singly charged decamer, doubly charged decamer, and 15-mer, etc. Finally, the X-ray crystal structure of [isoG 20 Cs 3 ] 3+ (BARF − ) 3 was successfully obtained, which is the first example of multiple-layer deoxy isoG binding with the Cs + cation, providing solid evidence of this new isoG ionophore beyond two-layer sandwich self-assembly. 
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    Axially chiral enamides bearing a N–C axis have been recently studied and were proposed to be valuable chiral building blocks, but a stereoselective synthesis has not been achieved. Here, we report the first enantioselective synthesis of axially chiral enamides via a highly efficient, catalytic approach. In this approach, C(sp 2 )–N bond formation is achieved through an iridium-catalyzed asymmetric allylation, and then in situ isomerization of the initial products through an organic base promoted 1,3-H transfer, leading to the enamide products with excellent central-to-axial transfer of chirality. Computational and experimental studies revealed that the 1,3-H transfer occurs via a stepwise deprotonation/re-protonation pathway with a chiral ion-pair intermediate. Hydrogen bonding interactions with the enamide carbonyl play a significant role in promoting both the reactivity and stereospecificity of the stepwise 1,3-H transfer. The mild and operationally simple formal N -vinylation reaction delivered a series of configurationally stable axially chiral enamides with good to excellent yields and enantioselectivities. 
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