RESUMO
Trichorzin PA VI (Ac Aib1 Ser Ala Aib Iva Gln Aib Val Aib Gly10 Leu Aib Pro Leu Aib Aib Gln Pheol18) is one of the seven main peptaibols forming the natural antibiotic 18-residue peptide mixture biosynthesised by a Trichoderma harzianum strain. Trichorzins exhibit antimycoplasmic activity resulting from membrane permeability perturbations. The membrane permeabilisation process by trichorzin PA VI has been examined in egg yolk phosphatidylcholine large unilamellar vesicles (LUV) and under conditions of ionic equilibrium by 23Na- and 35Cl-NMR experiments conducted in the presence of a chemical shift reagent and a relaxation agent, respectively. In such conditions, trichorzin PA VI exchanges both cations and anions across the vesicle bilayers, indicating the absence of ion- and charge-selectivity, in contrast to antibiotic ionophores, such as monensin or nigericin; the Na+ exchange is not influenced by the ionic strength. The kinetics of the Na+ exchange have been found to be third to fourth order with respect to the peptide concentration. The permeabilisation process of liposomes has been shown to be due to the formation of aggregates of three to four helical peptide monomers arranged into a supramolecular complex including presumably lipid molecules and forming a badly-defined pore in the bilayer. The major mechanism by which ions may exchange through the bilayer involves a long-lasting opening of the pores allowing complete exchange of the internal and external media in an 'all or nothing mode'.
Assuntos
Antibacterianos/química , Antibacterianos/metabolismo , Ionóforos , Espectroscopia de Ressonância Magnética , Peptídeos , Sequência de Aminoácidos , Ânions , Cátions , Permeabilidade da Membrana Celular , Cloretos/metabolismo , Peptídeos e Proteínas de Sinalização Intercelular , Cinética , Bicamadas Lipídicas/metabolismo , Lipossomos/metabolismo , Dados de Sequência Molecular , Concentração Osmolar , Sódio/metabolismoRESUMO
A new neutral glycoside of myo-inositol was isolated from the pregnancy urine of a single donor. Its structure was investigated by 1H-NMR spectroscopy and mass spectroscopy. It was identified as 1-O-alpha-2-acetamido-2-deoxy-D-galactopyranosyl-myo-inositol. No such structure or sequence has previously been reported in either myo-inositol or glucose glycosides.
Assuntos
Dissacarídeos/urina , Gravidez , Feminino , Cromatografia Gasosa-Espectrometria de Massas , Humanos , Espectroscopia de Ressonância Magnética , Terceiro Trimestre da GravidezRESUMO
Robinia pseudoacacia seeds contain lectins which are closely related. Pronase digestion of the dimeric and tetrameric lectins, RPA1 and RPA3, gave glycopeptides. The structure of the oligosaccharide was determined by 1H NMR spectroscopy and carbohydrate determination as alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)]-[alpha-D-Manp+ ++-(1-->6)]-beta- D-Manp-(1-->4)-beta-D-GlcpNAc-(1-->4)-[alpha-L-Fucp-(1-->3)] -beta-D-GlcpNAc - (1-->4)-Asn. It appears that the 34-kDa constitutive polypeptide of RPA1 contains 4-5 carbohydrate chains whereas the 30.5-kDa and 29-kDa subunits of RPA3 contain two and one oligosaccharide chains, respectively.
Assuntos
Carboidratos/química , Glicopeptídeos/química , Lectinas/análise , Sementes/química , Sequência de Aminoácidos , Sequência de Carboidratos , Glicopeptídeos/isolamento & purificação , Espectroscopia de Ressonância Magnética , Dados de Sequência Molecular , Lectinas de Plantas , PrótonsRESUMO
A new acidic oligosaccharide, isolated from the urine of a pregnant woman by gel filtration and ion-exchange chromatography, was shown on the basis of sugar analysis, methylation analysis, exo-glycosidase digestion, e.i.-m.s., f.a.b.-m.s., and n.m.r. spectroscopy to have the following structure: (Formula: see text).
Assuntos
Gravidez , Fosfatos Açúcares/urina , Trissacarídeos/urina , Animais , Configuração de Carboidratos , Sequência de Carboidratos , Bovinos , Cromatografia em Papel , Epididimo/enzimologia , Feminino , Fucose/análise , Humanos , Espectroscopia de Ressonância Magnética , Masculino , Espectrometria de Massas , Metilação , Terceiro Trimestre da Gravidez , alfa-L-FucosidaseRESUMO
A new antibiotic peptide, trichorzianine A1, was isolated from a culture of Trichoderma harzianum. It contains 19 residues, the N terminus is blocked by an acetyl group and the C terminus is tryptophanol. As a first part of the structural study of this new peptide, we here present the analysis of the 1H NMR spectrum accomplished by 2 DJ resolved and spin echo correlated spectroscopy.