1,721,051 research outputs found
Visita University Chemical Laboratory . Cambridge (UK) 1984/85
No full textStudi sulla biosintesi della vitamina B12: sintesi chimica degli ipotetici precursori con marcatura isotopica ed esperimenti della loro incorporazione enzimatica nell'acido cobirinico. Ruolo degli acidi 5'- e 15'-norcobirinici.si
Visita University Chemical Laboratory, Cambridge (UK) 1985/86
No full textStudi sulla biosintesi della vitamina B12: sintesi chimica degli ipotetici precursori biosintetici marcati con isotopi
(radioattivi o stabili) ed esperimenti della loro incorporazione enzimatica nell'acido cobirinico. Caratterizzazione del prodotto della prima C-metilazione dell'uroporfirinogeno III, precorrina I.
Sintesi e cristallizzazione dell'eptametil-estere dell'acido diciano 15'- norcobirinicosi
Visita University Chemical Laboratory, Cambrigde (UK), 1987
No full textStudi sulla vitamina B12: Sintesi e cristallizzazione dell'eptametilestere dell'acido diciano 15'-norcobirinicosi
Reaction of 3-halomethyl-2-cephem derivatives with phenols
No full text2-cephem allylic bromides are important, versatile intermediates for the derivatization of C-3’ position in cephalosporines. We showed that they can react smoothly with phenols, yielding the C-3’ cephem derivatives by C-alkylation of phenols
Studies on the biosynthesis of syringomycin E and syringopeptin 22A
No full textFeeding radioactive putative precursors to the bacterial cultures of Pseudomonas syingae pv. syringae in the presence of a protein synthesis inhibitor allowed the formation of radiolabelled syringomycin and syringopeptin. The result indicates that a nonribosomal mechanism of peptide synthesis is operating in the formation of these peptide metabolites
Evidence of the non ribosomal biosynthetic mechanism in the formation of syringomycin and syringopeptin, bioative lipodepsipeptides of the phytopathogenic bacterium Pseudomonas syringae pv. syringae
No full textSyringomycin and syringopeptins are lipodepsipeptide metabolites produced by the phytopathogenic bacterium Pseudomonas syringae pv. syringae. Radioactively labelled lipopeptides were produced in whole cell cultures supplemented with radioactively labelled putative biosynthetic precursors in the presence of the protein synthesis inhibitor, chloramphenicol. The results indicate that these lipopeptides are formed by a nonribosomal mechanism of peptide synthesis
Lipopeptide secondary metabolites from the phytopathogenic bacterium Pseudomonas syringae.
No full textOver the past twenty years or so, significant advances have been made in the study of the secondary metabolism of the widespread phytopathogenic Gram-negative bacterium Pseudomonas syringae. Interdisciplinary approach, which required the expertise of plant pathologists, chemists, biochemists and molecular biologists, led to the discovery of a new family of bioactive peptide secondary metabolites. The determination of their structures was pivotal for the investigations on their biosynthetic pathways, their relevance in the development of plant disease, and for the understanding of the molecular bases of their biological activities in plant, microbial and animal cells. In particular, the antibiotic activities of some of these compounds appear very interesting in the perspective of their utilization both in medicine and in agriculture. The goal of this chapter is to summarize the present knowledge in various areas of research on P. syringae peptide metabolites
Biosynthetic origin of four modified aminoacidic residues in bioactive lipodepsipeptides prom Pseudomonas syringae pv. syringae
No full textThe modified amino acids 2,4-diaminobutyric acid, (2,4 Dab) 2,3-dehydroaminobutyric acid (2,3 Dhb) are present in lipopeptides syringopeptins and lipodespinonapeptides (LDNPs) produced by the phytopathogenic bacterium Pseudomonas syringae pv. syringae. LDNPs contain also 3-hydroxy-aspartic acid (3-OH)Asp and 4-chlorothreonine (4-Cl) Thr. Feeding 14CThr and 14CAsp to chloramphenicol containing bacterial cultures produced radioactively labelled lipopeptide metabolites. Degradation studies showed that Thr is the biosynthetic precursor of (4-Cl)Thr and 2,3-Dhb, while Asp, besides labelling the above residues, is also incorporated in (3-OH)Asp and 2,4-Dab
A convenient synthesis of secondary amines
No full textA general simple method for the synthesis of pure secondary amines , starting from the primary amines is reported. The method provides a procedure for the preparation of symmetrical secondary amines free of tertiary amines
Biosintesi della vitamina B12: studi sulle ultime reazioni
No full textDue ipotetici precursori dell’acido cobirinico, macrociclo tetrapirrolico della vitamina B12, acidi 5’-normetil e 15’-normetil cobirinici sono stati sintetizzati in forma marcata con trizio. Esperimenti di incorporazione enzimatica nell’acido cobirinico hanno mostrato che di questi composti non sono i precursori biosintetici della vitamina B12
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