The shortage of high quantum yield (QY) organic fluorophores in the second near‐infrared window (NIR‐II) has become a bottleneck in bioimaging field. Now, a simple strategy is proposed to address this: constitutional isomerization on the basis of the molecular design philosophy of aggregation‐induced emission. With the combination of backbone distortion and rotor twisting, the resultant NIR‐II fluorophore 2TT‐oC6B displays an emission peak at 1030 nm and a QY of 11% in nanoparticles, one of the highest reported so far. Control molecules confirm that the distorted backbone and twisted rotors play equally important roles in determining the fluorescence properties of the NIR‐II fluorophores. To allow for the targeting ability to reach deeply located diseases, neutrophils (NEs) are used to penetrate the brain tissues and accumulate in the inflammation site. Herein, it is shown that NEs carrying 2TT‐oC6B nanoparticles can penetrate the blood‐brain‐barrier and visualize the deeply located inflammation through an intact scalp and skull. Notably, the bright 2TT‐oC6B contributes to a significantly enhanced signal‐to‐background ratio of 30.6 in the brain inflammation site.
An amended kinetic model for the self-assembly of empty capsids of brome mosaic virus is proposed. The model has been modified to account for a new feature in the assembly kinetics revealed by timecourse light scattering experiments at higher temporal resolution than previously attempted. To be able to simulate the sharp takeoff from the initial lag phase to the growth phase in the kinetic curves, a monomer activation step was proposed.
Weak association energy can lead to uniform nanostructures: defects can anneal due to subunit lability. What happens when strong association energy leads to particles where defects are trapped? Alphaviruses are enveloped viruses whose icosahedral nucleocapsid core can assemble independently. We used a simplest case system to study Ross River virus (RRV) core-like particle (CLP) self-assembly using purified capsid protein and a short DNA oligomer. We find that capsid protein binds the oligomer with high affinity to form an assembly-competent unit (U). Subsequently, U assembles with concentration dependence into CLPs. We determined that U-U pairwise interactions are very strong (ca. −6 kcal/mol) compared to other virus assembly systems. Nonetheless, assembled RRV CLPs appeared morphologically uniform and cryo-EM image reconstruction with imposed icosahedral symmetry yielded a T=4 structure. However, 2D class averages of the CLPs show that virtually every class had disordered regions. These results suggested that irregular cores may be present in RRV virions. To test this hypothesis, we determined 2D class averages of RRV virions using authentic virions or only the core from intact virions isolated by computational masking. Virion-based class averages were symmetrical, geometric, and corresponded well to projections of image reconstructions. In core-based class averages, cores and envelope proteins in many classes were disordered. These results suggest that partly-disordered components are common even in ostensibly well-ordered viruses, a biological realization of a patchy particle. Biological advantages of partly-disordered complexes may arise from their ease of dissociation and asymmetry.
A series of cobalt and heteroatom (N and/or S) doped carbon materials were prepared and explored as electrocatalysts for hydrogen evolution reaction (HER). The most active catalyst is a Co-, N-, and S-tridoped carbon (CoNS-C), which was prepared through heat treatment of nitrogen- and sulfur-enriched poly(m-aminobenzenesulfonic acid) and cobalt(II) nitrate, followed by acid leaching. The presence of cobalt-heteroatom complexes in CoNS-C is confirmed and identified as highly active molecule catalytic centers for HER. The overpotential of CoNS-C is 180 mV at 10 mA cm(-2) in 0.5 M aqueous H2SO4. Besides the high HER activity, the CoNS-C also shows excellent durability and can be produced readily in large quantities. This work may have provided a new and simple route in the design and batch-synthesis of highly active and durable carbonaceous electrocatalysts for HER.
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