RESUMEN
By using scanning tunneling microscopy we found that the surface reconstruction of Ge/Si(001) epilayers evolves from (M x N) to (2 x N), and eventually to (2 x 1), during exposure to a Si flux. This sequence appears to be just the inverse of that observed during the growth of Ge or SiGe alloys on Si(001). However, molecular dynamics simulations supported by ab initio calculations allow us to interpret this morphological evolution in terms of Si migration through the epilayer and complex Si-Ge intermixing below the top Ge layer.
RESUMEN
Naphthalene dioxygenase, a key enzyme in the dihydroxylation of naphthalene, is encoded by the plasmid pN3, responsible for naphthalene metabolism in Pseudomonas fluorescens N3. The naphthalene dioxygenase, including all the sequences for its expression and the regulatory region, has been localized on the 4.3-kb HindIII-ClaI fragment and on the 3.5-kb HindIII fragment of the plasmid pN3, by Southern analysis using as probes nahA and nahR genes, the homologous genes of the plasmid NAH7 from Pseudomonas putida G7. We cloned in Escherichia coli JM109 the dioxygenase gene and its regulatory region and developed an efficient bacterial system inducible by salicylic acid, able to produce dihydrodiols. E. coli containing recombinant plasmids carrying the dioxygenase gene were analysed for their potential as a biocatalytic tool to produce dihydrodiols from different naphthalenes with the substituent on the aromatic ring at the alpha or beta position. The dihydrodiols, identified by HPLC (high-performance liquid chromatography) and 1H-NMR (nuclear magnetic resonance) were produced with yields ranging from 50 to 94%. The degree of bioconversion efficiency depends on the nature and the position of the substituent and indicates the broad substrate specificity of this dioxygenase and its potential for the production of a wide variety of fine chemicals.
Asunto(s)
Escherichia coli/genética , Complejos Multienzimáticos/metabolismo , Naftoles/metabolismo , Oxigenasas/metabolismo , Pseudomonas fluorescens/enzimología , Proteínas Bacterianas/genética , Biotransformación , Clonación Molecular , Dioxigenasas , Regulación Bacteriana de la Expresión Génica/efectos de los fármacos , Regulación Bacteriana de la Expresión Génica/genética , Genes Bacterianos/genética , Complejos Multienzimáticos/genética , Naftalenos/metabolismo , Oxigenasas/genética , Plásmidos/genética , Regiones Promotoras Genéticas/genética , Pseudomonas fluorescens/genética , Mapeo Restrictivo , Ácido Salicílico/farmacología , Factores de Transcripción/genéticaRESUMEN
A case of malabsorption syndrome (organic wasting, hypokaliaemia, metabolic acidosis, diarrhoea, hypochromic anaemia) following removal of 4 m of ileus for thrombophlebitis of the mesentery is described. In the first seven months, the patient was hospitalised five times to correct these imbalances by means of PA, with repeated venous incannulation. PA was continued at home each evening, together with heparin therapy (25,000 U calcic heparin/day). The patient later died following the appearance of serious venous thrombosis. The question of this complication and its prevention is discussed.
Asunto(s)
Síndromes de Malabsorción/terapia , Nutrición Parenteral/efectos adversos , Síndrome del Intestino Corto/terapia , HumanosRESUMEN
Intravenous administration of 400-600 mg/day potassium canrenoate normalised plasma osmolarity and permitted rapid re-establishment of the metabolic picture in 9/12 patients with hyperosmolarity admitted to a resuscitation department for complex physiopathological pictures. The soundness of the drug in this sense is affirmed, as well as its permission of the recommencement of parenteral nutrition.