Mixed lineage kinase domain-like protein (MLKL) was identified to function downstream of receptor interacting protein 3 (RIP3) in tumor necrosis factor-α (TNF)-induced necrosis (also called necroptosis). However, how MLKL functions to mediate necroptosis is unknown. By reconstitution of MLKL function in MLKL-knockout cells, we showed that the N-terminus of MLKL is required for its function in necroptosis. The oligomerization of MLKL in TNF-treated cells is essential for necroptosis, as artificially forcing MLKL together by using the hormone-binding domain (HBD*) triggers necroptosis. Notably, forcing together the N-terminal domain (ND) but not the C-terminal kinase domain of MLKL causes necroptosis. Further deletion analysis showed that the four-α-helix bundle of MLKL (1-130 amino acids) is sufficient to trigger necroptosis. Both the HBD*-mediated and TNF-induced complexes of MLKL(ND) or MLKL are tetramers, and translocation of these complexes to lipid rafts of the plasma membrane precedes cell death. The homo-oligomerization is required for MLKL translocation and the signal sequence for plasma membrane location is located in the junction of the first and second α-helices of MLKL. The plasma membrane translocation of MLKL or MLKL(ND) leads to sodium influx, and depletion of sodium from the cell culture medium inhibits necroptosis. All of the above phenomena were not seen in apoptosis. Thus, the MLKL oligomerization leads to translocation of MLKL to lipid rafts of plasma membrane, and the plasma membrane MLKL complex acts either by itself or via other proteins to increase the sodium influx, which increases osmotic pressure, eventually leading to membrane rupture.

Transition metal nitrides (TMNs) are considered as potential electrode materials for high‐performance energy storage devices. However, the structural instability during the electrochemical reaction process severely hinders their wide application. A general strategy to overcome this obstacle is to fabricate nanocomposite TMNs on the conducting substrate. Herein, the honeycomb‐like CoN‐Ni3N/N‐C nanosheets are in situ grown on a flexible carbon cloth (CC) via a mild solvothermal method with post‐nitrogenizing treatment. As an integrated electrode for the supercapacitor, the optimized CoN‐Ni3N/N‐C/CC achieves remarkable electrochemical performance due to the enhanced intrinsic conductivity and increased concentration of the active sites. In particular, the flexible quasi‐solid‐state asymmetric supercapacitor assembled with CoN‐Ni3N/N‐C/CC cathode and VN/CC anode delivers an excellent energy density of 106 μWh cm−2, maximum power density of 40 mW cm−2, along with an outstanding cycle stability. This study provides a neoteric perspective on construction of high‐performance flexible energy storage devices with novel metallic nitrides.

Electronic and ionic conductivities are two key parameters in determining the electrochemical performance of lithium/sodium ion batteries, and element-doping is an effective way to regulate the conductivity of an active material. In this work, we attempt to modify the electronic and ionic conductivities of Na3V2(PO4)3/C cathode through a proper content of Zr-doping and the two kinds of conductivities are distinguished by an ion-blocking measurement method. All Zr-doped samples display significant increase of the electronic conductivity and the x = 0.1 sample possesses the highest value of the electronic conductivity. The ionic conductivity shows a similar variation trend, but the variation value is far smaller than that of the electronic conductivity. The increase of the electronic conductivity is about one order larger than that of the ionic conductivity as x increases from 0 to 0.1. The enhanced electronic and ionic conductivities can considerably improve the cycling and rate performance of the sodium ion batteries using Na3V2(PO4)3/C cathode, especially the rate performance. The x = 0.1 electrode exhibits a much higher capacity in the whole cycling process after 1000 cycles at 10 C rate and its capacity at 50 C is about 5 times larger than that of the pristine sample.