Heterointerfaces formed by the intimate connection of different materials with electromagnetic losses are expected to achieve stronger electromagnetic(EM)absorption.However,constructing composites with heterointerface...Heterointerfaces formed by the intimate connection of different materials with electromagnetic losses are expected to achieve stronger electromagnetic(EM)absorption.However,constructing composites with heterointerfaces still faces great challenges in facile preparation process,optimized impedance matching,high reflection loss(RL),and ultrathin matching thickness.In this work,we develop ZIF-8 functionalized MXene to produce hierarchical Ti_(3)C_(2)@C@ZnO composites with heterointerface to advance EM absorption enhancement.Modified with polydopamine(PDA),few-layer Ti_(3)C_(2)T_(x) MXene sheets enable adsorption of Zn^(2+)metal ions on Ti3C2Tx@PDA by electrostatic interaction for in-situ growth of ZIF-8.Ti_(3)C_(2)/C/ZnO heterointerface were obtained after heat treatment of Ti_(3)C_(2)T_(x)@PDA@ZIF-8 nanocomposites at various temperatures.The Ti_(3)C_(2)/C/ZnO-600℃ with 1.15 mm thickness have a RL of−50.241 dB and an effective absorption bandwidth of 3.50 GHz.In-depth studies on the electromagnetic loss mechanisms reveal that Ti3C2,carbon,and ZnO in nanocomposites generate multiple interfacial polarization losses beyond partial conductivity losses caused by Ti_(3)C_(2) and ZnO.Oxygen vacancy defects in ZnO form dipole losses with carbon.This work not only provides a simple and effective concept for preparing MXene@MOFs heterogeneous composites as an ultrathin and strong electromagnetic wave absorber,but also offers a vital guideline to fabricate various metal oxides derived from the MXene and metal-organic frameworks(MOFs)precursors.展开更多
Cytochrome c maturation(CCM),a posttranslational modification involving covalent attachment of heme to polypeptides(apocyt c),is essential for the activity and cellular function of cytochromes c.Here,we identify and s...Cytochrome c maturation(CCM),a posttranslational modification involving covalent attachment of heme to polypeptides(apocyt c),is essential for the activity and cellular function of cytochromes c.Here,we identify and substantiate CcmB as heme translocase in bacteria.When in excess,CcmB expels intracellular heme into the periplasm and thus is detrimental to the cell.We then show that complexation with CcmACD ensures heme translocated by CcmB to be used for CCM only.Moreover,structural analysis and atomistic molecular dynamics simulations reveal that CcmB absorbs heme from the membrane to a heme pocket formed in the dimer interface of the transmembrane helix-bundles.These data,collectively by providing detailed insights into the conformational landscape of CcmB during heme entry,fill in the missing link in our understanding of the heme translocation for CCM.展开更多
Heme is an important cofactor and a regulatory molecule involved in various physiological processes in virtually all living cellular organisms,and it can also serve as the primary iron source for many bacteria,particu...Heme is an important cofactor and a regulatory molecule involved in various physiological processes in virtually all living cellular organisms,and it can also serve as the primary iron source for many bacteria,particularly pathogens.However,excess heme is cytotoxic to cells.In order to meet physiological needs while preventing deleterious effects,bacteria have evolved sophisti-cated cellular mechanisms to maintain heme homeostasis.Recent advances in technologies have shaped our understanding of the molecular mechanisms that govern the biological processes crucial to heme homeostasis,including synthesis,acquisition,utilization,degradation,trafficking,and efflux,as well as their regulation.Central to these mechanisms is the regulation of the heme,by the heme,and for the heme.In this review,we present state-of-the-art findings covering the biochemical,physio-logical,and structural characterization of important,newly identified hemoproteins/systems involved in heme homeostasis.展开更多
基金The authors thank the financial support from the National Natural Science Foundation of China(No.52071270)the National Key Research and Development Program of China(No.2023YFE0206300)+2 种基金the Natural Science Foundation of Shaanxi Province(No.2024RS-CXTD-62)the Science Fund of Shandong Laboratory of Advanced Materials and Green Manufacturing(Yantai)(No.AMGM2023F03)the Research Fund of the State Key Laboratory of Solidification Processing(NPU)(No.2022-QZ04)。
文摘Heterointerfaces formed by the intimate connection of different materials with electromagnetic losses are expected to achieve stronger electromagnetic(EM)absorption.However,constructing composites with heterointerfaces still faces great challenges in facile preparation process,optimized impedance matching,high reflection loss(RL),and ultrathin matching thickness.In this work,we develop ZIF-8 functionalized MXene to produce hierarchical Ti_(3)C_(2)@C@ZnO composites with heterointerface to advance EM absorption enhancement.Modified with polydopamine(PDA),few-layer Ti_(3)C_(2)T_(x) MXene sheets enable adsorption of Zn^(2+)metal ions on Ti3C2Tx@PDA by electrostatic interaction for in-situ growth of ZIF-8.Ti_(3)C_(2)/C/ZnO heterointerface were obtained after heat treatment of Ti_(3)C_(2)T_(x)@PDA@ZIF-8 nanocomposites at various temperatures.The Ti_(3)C_(2)/C/ZnO-600℃ with 1.15 mm thickness have a RL of−50.241 dB and an effective absorption bandwidth of 3.50 GHz.In-depth studies on the electromagnetic loss mechanisms reveal that Ti3C2,carbon,and ZnO in nanocomposites generate multiple interfacial polarization losses beyond partial conductivity losses caused by Ti_(3)C_(2) and ZnO.Oxygen vacancy defects in ZnO form dipole losses with carbon.This work not only provides a simple and effective concept for preparing MXene@MOFs heterogeneous composites as an ultrathin and strong electromagnetic wave absorber,but also offers a vital guideline to fabricate various metal oxides derived from the MXene and metal-organic frameworks(MOFs)precursors.
基金supported by the National Natural Science Foundation of China(31930003 and 41976087)the National Key R&D Program of China(2018YFA0901300).
文摘Cytochrome c maturation(CCM),a posttranslational modification involving covalent attachment of heme to polypeptides(apocyt c),is essential for the activity and cellular function of cytochromes c.Here,we identify and substantiate CcmB as heme translocase in bacteria.When in excess,CcmB expels intracellular heme into the periplasm and thus is detrimental to the cell.We then show that complexation with CcmACD ensures heme translocated by CcmB to be used for CCM only.Moreover,structural analysis and atomistic molecular dynamics simulations reveal that CcmB absorbs heme from the membrane to a heme pocket formed in the dimer interface of the transmembrane helix-bundles.These data,collectively by providing detailed insights into the conformational landscape of CcmB during heme entry,fill in the missing link in our understanding of the heme translocation for CCM.
基金This work was supported by the National NaturalScience Foundation of China(Nos.31930003 and 41976087)。
文摘Heme is an important cofactor and a regulatory molecule involved in various physiological processes in virtually all living cellular organisms,and it can also serve as the primary iron source for many bacteria,particularly pathogens.However,excess heme is cytotoxic to cells.In order to meet physiological needs while preventing deleterious effects,bacteria have evolved sophisti-cated cellular mechanisms to maintain heme homeostasis.Recent advances in technologies have shaped our understanding of the molecular mechanisms that govern the biological processes crucial to heme homeostasis,including synthesis,acquisition,utilization,degradation,trafficking,and efflux,as well as their regulation.Central to these mechanisms is the regulation of the heme,by the heme,and for the heme.In this review,we present state-of-the-art findings covering the biochemical,physio-logical,and structural characterization of important,newly identified hemoproteins/systems involved in heme homeostasis.
