Nickel modification by spontaneous deposition of transition metals such as Ag and Cu is shown as an economic and simple alternative for the activation of hydrogen evolution reaction（HER） on cathodes in alkaline medi...Nickel modification by spontaneous deposition of transition metals such as Ag and Cu is shown as an economic and simple alternative for the activation of hydrogen evolution reaction（HER） on cathodes in alkaline media. The kinetics of HER is studied on Ni/Ag and Ni/Cu catalysts by cyclic voltammetry and electrochemical impedance spectroscopy（EIS） using a rotating disk electrode（RDE）. Freshly synthesized catalysts, as well as catalysts subjected to a short chronoamperometric ageing procedure, are analyzed and the kinetic and thermodynamic parameters of the HER are obtained. The nickel surface modified with transition metals with an outer shell electronic configuration [xd;（x+1）s;], such as Cu(3d;4s;)and Ag(4d;5s;), shows an improved activity for the HER compared to bare nickel. Furthermore, the Ni/Cu catalyst presents a decreased onset potential. The hydrogen evolution rate, measured as current density at –1.5 V（vs. SCE）, is similar on Ni/Cu and Ni/Ag electrodes.展开更多
Extensins （EXTs） are highly repetitive plant O-glycoproteins that require several post-translational modifi- cations （PTMs） to become functional in plant cell walls. First, they are hydroxylated on contiguous prol...Extensins （EXTs） are highly repetitive plant O-glycoproteins that require several post-translational modifi- cations （PTMs） to become functional in plant cell walls. First, they are hydroxylated on contiguous proline residues; then they are O-glycosylated on hydroxyproline and serine. After secretion into the apoplast, O-glycosylated EXTs form a tridimensional network organized by inter- and intra-Tyr linkages. Recent studies have made significant progress in the identification of the enzymatic machinery required to process EXTs, which includes prolyl 4-hydroxylases, glycosyltransferases, papain-type cysteine endopeptidases, and peroxidases. EXTs are abundant in plant tissues and are particularly important in rapidly expanding root hairs and pollen tubes, which grow in a polar manner. Small changes in EXT PTMs affect fastgrowing cells, although the molecular mechanisms underlying this regulation are unknown. In this review, we highlight recent advances in our understanding of EXT modifications throughout the secretory pathway, EXT assembly in cell walls, and possible sensing mechanisms involving the Catharanthus roseus cell surface sensor receptor-like kinases located at the interface between the apoplast and the cytoplasmic side of the plasma membrane.展开更多
基金financial support from Agencia Nacional de Promoción Científica y Tecnológica(PICT 1818)CONICET(PIP 00095)
文摘Nickel modification by spontaneous deposition of transition metals such as Ag and Cu is shown as an economic and simple alternative for the activation of hydrogen evolution reaction（HER） on cathodes in alkaline media. The kinetics of HER is studied on Ni/Ag and Ni/Cu catalysts by cyclic voltammetry and electrochemical impedance spectroscopy（EIS） using a rotating disk electrode（RDE）. Freshly synthesized catalysts, as well as catalysts subjected to a short chronoamperometric ageing procedure, are analyzed and the kinetic and thermodynamic parameters of the HER are obtained. The nickel surface modified with transition metals with an outer shell electronic configuration [xd;（x+1）s;], such as Cu(3d;4s;)and Ag(4d;5s;), shows an improved activity for the HER compared to bare nickel. Furthermore, the Ni/Cu catalyst presents a decreased onset potential. The hydrogen evolution rate, measured as current density at –1.5 V（vs. SCE）, is similar on Ni/Cu and Ni/Ag electrodes.
文摘Extensins （EXTs） are highly repetitive plant O-glycoproteins that require several post-translational modifi- cations （PTMs） to become functional in plant cell walls. First, they are hydroxylated on contiguous proline residues; then they are O-glycosylated on hydroxyproline and serine. After secretion into the apoplast, O-glycosylated EXTs form a tridimensional network organized by inter- and intra-Tyr linkages. Recent studies have made significant progress in the identification of the enzymatic machinery required to process EXTs, which includes prolyl 4-hydroxylases, glycosyltransferases, papain-type cysteine endopeptidases, and peroxidases. EXTs are abundant in plant tissues and are particularly important in rapidly expanding root hairs and pollen tubes, which grow in a polar manner. Small changes in EXT PTMs affect fastgrowing cells, although the molecular mechanisms underlying this regulation are unknown. In this review, we highlight recent advances in our understanding of EXT modifications throughout the secretory pathway, EXT assembly in cell walls, and possible sensing mechanisms involving the Catharanthus roseus cell surface sensor receptor-like kinases located at the interface between the apoplast and the cytoplasmic side of the plasma membrane.
