Two kinds of free‐standing electrodes, reduced graphene oxide (rGO)‐wrapped Fe‐doped MnO2 composite (G‐MFO) and rGO‐wrapped hierarchical porous carbon microspheres composite (G‐HPC) are fabricated using a frozen lake‐inspired, bubble‐assistance method. This configuration fully enables utilization of the synergistic effects from both components, endowing the materials to be excellent electrodes for flexible and lightweight electrochemical capacitors. Moreover, a nonaqueous HPC‐doped gel polymer electrolyte (GPE‐HPC) is employed to broad voltage window and improve heat resistance. A fabricated asymmetric supercapacitor based on G‐MFO cathode and G‐HPC anode with GPE‐HPC electrolyte achieves superior flexibility and reliability, enhanced energy/power density, and outstanding cycling stability. The ability to power light‐emitting diodes also indicates the feasibility for practical use. Therefore, it is believed that this novel design may hold great promise for future flexible electronic devices. 相似文献
The imbalance between excess reactive oxygen species (ROS) generation and insufficient antioxidant defenses contribute to a range of neurodegenerative diseases. High ROS levels damage cellular macromolecules such as DNA, proteins and lipids, leading to neuron vulnerability and eventual death. However, the underlying molecular mechanism of the ROS regulation is not fully elucidated. Recently, an increasing number of studies suggest that microRNAs (miRNAs) emerge as the targets in regulating oxidative stress. We recently reported the neuroprotective effect of miR-137-3p for brachial plexus avulsion-induced motoneuron death. The present study is sought to investigate whether miR-137-3p also could protect PC12 cells against hydrogen peroxide (H2O2) induced neurotoxicity. By using cell viability assay, ROS assay, gene and protein expression assay, we found that PC-12 cells exposed to H2O2 exhibited decreased cell viability, increased expression levels of calpain-2 and neuronal nitric oxide synthase (nNOS), whereas a decreased miR-137-3p expression. Importantly, restoring the miR-137-3p levels in H2O2 exposure robustly inhibited the elevated nNOS, calpain-2 and ROS expression levels, which subsequently improved the cell viability. Furthermore, the suppressive effect of miR-137-3p on the elevated ROS level under oxidative stress was considerably blunted when we mutated the binding site of calpain-2 targted by miR-137-3p, suggesting the critical role of calpain-2 involving the neuroprotective effect of miR-137-3p. Collectively, these findings highlight the neuroprotective role of miR-137-3p through down-regulating calpain and NOS activity, suggesting its potential role for combating oxidative stress insults in the neurodegenerative diseases.
Mitochondrial dysfunction plays a central role in glutamate-evoked neuronal excitotoxicity, and mitochondrial fission/fusion dynamics are essential for mitochondrial morphology and function. Here, we establish a novel mechanistic linker among glutamate excitotoxicity, mitochondrial dynamics, and mitochondrial dysfunction in spinal cord motor neurons. Ca2+-dependent activation of the cysteine protease calpain in response to glutamate results in the degradation of a key mitochondrial outer membrane fusion regulator, mitofusin 2 (MFN2), and leads to MFN2-mediated mitochondrial fragmentation preceding glutamate-induced neuronal death. MFN2 deficiency impairs mitochondrial function, induces motor neuronal death, and renders motor neurons vulnerable to glutamate excitotoxicity. Conversely, MFN2 overexpression blocks glutamate-induced mitochondrial fragmentation, mitochondrial dysfunction, and/or neuronal death in spinal cord motor neurons both in vitro and in mice. The inhibition of calpain activation also alleviates glutamate-induced excitotoxicity of mitochondria and neurons. Overall, these results suggest that glutamate excitotoxicity causes mitochondrial dysfunction by impairing mitochondrial dynamics via calpain-mediated MFN2 degradation in motor neurons and thus present a molecular mechanism coupling glutamate excitotoxicity and mitochondrial dysfunction. 相似文献
Protein tyrosine phosphorylation is regulated by both protein tyrosine kinases and protein tyrosine phosphatases (PTPases). Recently, the structures of a family of PTPases have been described. In order to study the structure-function relationships of receptor-linked PTPases, we analyzed the effects of deletion and point mutations within the cytoplasmic region of the receptor-linked PTPases, LCA and LAR. We show that the first of the two domains has enzyme activity by itself, and that one cysteine residue in the first domain of both LCA and LAR is absolutely required for activity. The second PTPase like domains do not have detectable catalytic activity using a variety of substrates, but sequences within the second domains influence substrate specificity. The functional significance of a stretch of 10 highly conserved amino acid residues surrounding the critical cysteine residue located in the first domain of LAR was assessed. At most positions, any substitution severely reduced enzyme activity, while missense mutations at the other positions tested could be tolerated to varying degrees depending on the amino acid substitution. It is suggested that this stretch of amino acids may be part of the catalytic center of PTPases. 相似文献