RESUMEN
A combined theoretical and experimental study was performed to elucidate the photocatalytic potential of tenorite, CuO (1 1 0) and to assess the evolution pathway of carbon dioxide (CO2) evolution pathway. The calculations were performed with density functional theory (DFT) at a DFT + U + J0 and spin polarized level. The CuO was experimentally synthesized and characterized with structural and optical methodologies. The band structure and density of states revealed the rise of band gaps at 1.24 and 1.03 eV with direct and indirect band gap nature, respectively. These values are in accordance with the experimental evidence at 1.28 and 0.96 eV; respectively, which were obtained by UV-Vis DRS. Such a behavior could be related to enhanced photocatalytic activity among copper oxide materials. Experimental evidence such as SEM images and work function measurements were also performed to evaluate the oxide. The redox potential suggests a catalytic character of tenorite (1 1 0) for the CO2 transformation through aldehydes (methanal) intermediate formation. Furthermore, a route through methylene glycol CH2(OH)2 was also explored with the theoretical methodology. The reaction path exhibits an immediate reduction of Image 1 into a â¢OH radical and an [OH]- anion, in the first step. This â¢OH radical attacks a double bond (C = O) of Image 2 to form bicarbonate ([Image 3]-) and subsequently, carbonic acid (Image 4). The carbonic acid reacts with other â¢OH radical to finally form orthocarbonic acid (Image 5).
RESUMEN
Preparations of purified full-length fusion (F) protein of human respiratory syncytial virus (HRSV) expressed in recombinant vaccinia-F infected cells, or of an anchorless mutant (F(TM(-))) lacking the C-terminal 50 amino acids secreted from vaccinia-F(TM(-))-infected cells contain a minor polypeptide that is an intermediate product of proteolytic processing of the F protein precursor F0. N-terminal sequencing of the intermediate demonstrated that it is generated by cleavage at a furin-motif, residues 106-109 of the F sequence. By contrast, the F1 N terminus derives from cleavage at residue 137 of F0 which is also C-terminal to a furin recognition site at residues 131-136. Site-directed mutagenesis indicates that processing of F0 protein involves independent cleavage at both sites. Both cleavages are required for the F protein to be active in membrane fusion as judged by syncytia formation, and they allow changes in F structure from cone- to lollipop-shaped spikes and the formation of rosettes by anchorless F.
Asunto(s)
Fusión de Membrana/fisiología , Precursores de Proteínas/metabolismo , Procesamiento Proteico-Postraduccional , Virus Sincitiales Respiratorios/fisiología , Proteínas Virales de Fusión/fisiología , Proteínas Virales/fisiología , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Animales , Línea Celular , Cricetinae , Efecto Citopatogénico Viral , Endopeptidasas/metabolismo , Células Gigantes , Humanos , Riñón , Mesocricetus , Microscopía Electrónica , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Conformación Proteica , Precursores de Proteínas/química , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/fisiología , Virus Sincitiales Respiratorios/genética , Relación Estructura-Actividad , Proteínas Virales de Fusión/química , Proteínas Virales de Fusión/genética , Proteínas Virales de Fusión/ultraestructura , Proteínas Virales/química , Proteínas Virales/genética , Proteínas Virales/ultraestructuraRESUMEN
Full-length fusion (F) glycoprotein of human respiratory syncytial virus (HRSV) and a truncated anchorless mutant lacking the C-terminal 50 amino acids were expressed from vaccinia recombinants and purified by immunoaffinity chromatography and sucrose gradient centrifugation. Electron microscopy of full-length F protein in the absence of detergents revealed micelles, (i.e., rosettes) containing two distinct types of protein rods, one cone-shaped and the other lollipop-shaped. Analysis of membrane anchorless F molecules indicated that they were similar to the cone-shaped rods and that rosettes, which they formed on storage, were made up of lollipop-shaped rods. The two forms of F protein may represent different structures that the molecule may adopt before and after activation for its role in membrane fusion. Studies of complexes of these structures with monoclonal antibodies of known specificity provide information on the three-dimensional organization of antigenic sites on the F protein and confirm the oligomeric structure, possibly trimeric, of both full-length F and membrane anchorless F.