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A two-step strategy is developed to synthesize a NixSy (Ni3S4 and NiS2)/MoS2 hybrid nanomaterial, which is utilized as a high performance electrode. The best loose structure of this hybrid nanomaterial benefits ion diffusion. Utilized as an electrode, the as-synthesized electrode delivers a high specific capacity (169.44 mAh g-1 at 1 A g-1) and excellent cycling stability (~88.24% capacity retention after 8000 charge-discharge tests). Most significantly, an asymmetric supercapacitor (ASC) device was constructed from this efficient electrode material, which could also reach an excellent energy density (306 W h kg-1 at a power density of 12.24 KW kg-1) and outstanding cycling stability (~92.31% capacity retention even after 10?000 cycles). The high power density and energy density could facilitate fast charge and discharge, as expected, and the combined two ASC devices in series could power four red light-emitting diode (LED) bulbs for 16 min, and subsequently light one red LED bulb for 5 min, confirming its possible practical application. This general method provides a simple and cost-effective way to design the metal sulfides hybrid electrode, which could be applied in the field of energy storage. [ABSTRACT FROM AUTHOR]

The anaerobic global regulator FNR from Escherichia coli is a [4Fe-4S]2+ duster-containing dimer that is inactivated by O2 through disruption of the Fe-S duster and conversion to the monomeric apoprotein. It was shown that apo-FNR is subject to ClpXP proteolysis, and two recognition sites, amino acids 5-11 and amino acids 249 and 250, are responsible for targeting PNR to the protease. However, how the exposure of these sites is mediated such that only apo-FNR is recognized by the ClpXP protease and is degraded in a regulated manner so that a sufficient and similar FNR level is maintained in both anaerobic and aerobic conditions is unknown. To investigate this, we performed three-alanine scanning on amino acids 2-19 and 236-250 that are in the proximity of the two ClpXP recognition sites, and their functions remain unknown. We found that three-alanine substitution of residues 239-241 (LAQ239-241A3) and 242-244 (LAG242-244A3) caused reduced FNR protein levels, transcription activities, and growth rates under anaerobic conditions. Lu vivo degradation assays demonstrated that these mutants were degraded significantly faster than the wild type (WT), and either deletion of clpXP or blocking the ClpXP recognition Site of amino acids 249 and 250 stabilizes these proteins. Circular dichroism analysis revealed that introduction of LAQ239-241A3 caused conformational changes with a significant loss of secondary structures in both WT and an O2 stable FNR dimer, FNR D 154A. We propose that the region of amino acids 239-244 plays a negative role in the proteolysis of FNR by promoting a structural fold that limits the exposure of the proximal ClpXP site to the protease. [ABSTRACT FROM AUTHOR]