Mechanistic insights into central spindle assembly mediated by the centralspindlin complex

The central spindle spatially and temporally regulates the formation of division plane during cytokinesis in animal cells. The heterotetrameric centralspindlin complex bundles microtubules to assemble the central spindle, the mechanism of which is poorly understood. Here, we determined the crystal structures of the molecular backbone of ZEN-4/CYK-4 centralspindlin from Caenorhabditis elegans, which revealed the detailed mechanism of complex formation. The molecular backbone of centralspindlin has the intrinsic propensity to undergo liquid–liquid phase separation. The condensation of centralspindlin requires two patches of basic residues at ZEN-4 and multiple acidic residues at the intrinsically disordered region of CYK-4, explaining the synergy of the two subunits for the function. These complementary charged residues were critical for the microtubule bundling activity of centralspindlin in vitro and for the assembly of the central spindle in vivo. Together, our findings provide insights into the mechanism of central spindle assembly mediated by centralspindlin through charge-driven macromolecular condensation.

The natural history of defences

Hosts can avoid infections by behavioural changes and by body walls. After infection, hosts can change their behaviours to reduce the effects of parasitism. Immune defences have different arms (humoral or cellular), and organization (innate, adaptive). Innate immunity consists of a collection of different systems that are evolutionarily very old. Adaptive immunity, based on expansion of specific lymphocytes, evolved in the higher vertebrates. Immune defences are regulated tightly and based on receptors that can recognize parasites (or their activity). This triggers a complex signalling cascade that results in the production of further signalling compounds and effectors. Important protein families, e.g. the immunoglobulins, form the molecular backbone. A key to efficient defences is the diversification of receptors, such as the highly evolved somatic diversification processes of advanced adaptive immunity. The microbiota adds to defences in many ways. Immune memory and priming occur throughout the tree of life.

The Effects of Molecular Packing Behavior of Small-Molecule Acceptors in Ternary Organic Solar Cells

Herein, two diketopyrrolopyrrole (DPP)-based, small-molecule isomers, o- and p-DPP-PhCN, were introduced as acceptors in ternary organic solar cells (OSCs). The isomers have the same molecular backbone but differ in the positions of the cyanide (CN) substituents (ortho and para), which greatly affects their packing behavior. Ternary solar cells composed of poly(3-hexylthiophene) (P3HT):DPP-PhCN:phenyl-C61-butyric acid methyl ester (PCBM) were fabricated, and the effects of the different packing behaviors of the third component on the device performance and the working mechanism of the ternary cells were investigated. The addition of o-DPP-PhCN with a relatively high-lying lowest unoccupied molecular orbital energy level resulted in an increase in the open-circuit voltage (VOC) in the ternary devices, demonstrating the alloy-like structure of the two acceptors (o-DPP-PhCN and PCBM) in the ternary system. However, the p-DPP-PhCN-based ternary cells exhibited VOC values similar to that of a P3HT:PCBM binary cell, irrespective of the addition of p-DPP-PhCN, indicating a cascade energy-level structure in the ternary system and an effective charge transfer from the P3HT to the PCBM. Importantly, by increasing the addition of p-DPP-PhCN, the short-circuit current density increased substantially, resulting in pronounced shoulder peaks in the external quantum efficiency responses in the long-wavelength region, corresponding to the contribution of the photocurrent generated by the light absorption of p-DPP-PhCN. Despite sharing the same molecular backbone, the two DPP-PhCNs exhibited substantially different packing behaviors according to the position of their CN substituents, which also greatly affected the working mechanism of the ternary devices fabricated using the DPP-PhCNs as the third component.

Cyclohexyl-substituted Non-fullerene Small-molecule Acceptors for Organic Solar Cells

In this paper, two cyclohexyl-substituted non-fullerene small molecules, T2-Cy6MRH and T2-Cy6PRH, are designed to have the same molecular backbone of a bithiophene (T2) core and rhodanine (RH) end groups. T2-Cy6MRH...