Browsing by Author "Mao, J"

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    Grouper iridovirus GIV66 is a Bcl-2 protein that inhibits apoptosis by exclusively sequestering Bim
    (Society of Crystallographers in Australia and New Zealand, 2017-12-03) Banjara, S; Mao, J; Ryan, TM; Caria, S; Kvansakul, M
    Programmed cell death or apoptosis is a critical mechanism for the controlled removal of damaged or infected cells, and proteins of the Bcl-2 family are important arbiters of this process. Viruses have been shown to encode for functional and structural homologues of Bcl-2 to counter premature host cell apoptosis to ensure viral proliferation and/or survival. Grouper iridovirus (GIV) is a large DNA virus belonging to the iridoviridae family that harbours GIV66, a putative Bcl-2 like protein. GIV66 is a mitochondrially localised inhibitor of apoptosis, however, the molecular and structural basis of apoptosis inhibition is currently not understood. To gain insight into the mechanism of action we systematically evaluated the ability of GIV66 to bind peptides spanning the BH3 domain of proapoptotic Bcl-2 family members. Our data reveal that GIV66 harbours an unusually high level of specificity for pro-apoptotic Bcl-2, and only engages with Bim. We then determined crystal structures of both GIV66 on its own as well as bound to Bim BH3. Unexpectedly, GIV66 forms dimers via a novel interface that occludes access to the canonical Bcl-2 ligand binding groove, which break apart upon Bim binding. These data suggest that GIV66 dimerisation impacts on the ability of GIV66 to bind and select host pro-death Bcl-2 protein. Our findings provide a mechanistic understanding for the potent anti-apoptotic activity of GIV66 by identifying it as the first single specificity pro-survival Bcl2 protein, and demonstrating the pivotal role of Bim for GIV mediated inhibition of apoptosis.
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    An ordered P2/P3 composite layered oxide cathode with long cycle life in sodium-ion batteries
    (American Chemical Society, 2019-10-16) Rahman, MM; Mao, J; Kan, WH; Sun, CJ; Li, LX; Zhang, Y; Avdeev, M; Du, XW; Lin, F
    Developing stable cathode materials represents a crucial step toward long-life sodium-ion batteries. P2-type layered oxides are important as cathodes for their reversibility, but their long-term performance in full cells remains a key challenge. Herein, we report Na0.75Co0.125Cu0.125Fe0.125Ni0.125Mn0.5O2 with an intergrowth of ordered P2 and P3 phases, studied by neutron diffraction and Rietveld refinement. A stable electrochemical performance is achieved in Na half cells with 100% capacity retention at a rate of C/10 after 100 cycles (initial capacity of 90 mAh/g), 96% capacity retention at a rate of 1 C after 500 cycles (initial capacity of 70 mAh/g), and 85% capacity retention at a rate of 5 C after 1000 cycles (initial capacity of 55 mAh/g). Stable full cell performance is achieved with 84.2% capacity retention after 1000 cycles at a rate of 1 C. Synchrotron X-ray diffraction, spectroscopy, and imaging are applied to elucidate the relationship between chemical/structural evolution and battery performance. A reversible local and global structural evolution is observed during initial cycles. Meanwhile, the challenges with enabling prolonged cycling (beyond 1000 cycles) may be associated with Fe dissolution and formation of a copper oxide phase. This study implies that cathodes with complex chemical and structural formations may stabilize electrochemical performance and highlights the importance of decoupling the contribution of each transition metal to performance degradation. © 2019 American Chemical Society