RESUMO
Isatin in a solution of dry N,N-dimethylformamide/NaClO4 is electroreduced in the presence of CH3I. N-methylisatin (NMI) is obtained in quantitative molar yield and high current efficiency by controlled potential electrolysis (CPE). NMI and N-methylisatoic anhydride are the reaction products when CPE is performed in the absence of CH3I, but adding it once the CPE was completed. The water effect on the identity and yield of the reaction product(s) is investigated. Reaction pathways are proposed.
RESUMO
Pseudocercospora griseola is the causal agent of Angular Leaf Spot (ALS), a disease of common bean. Due to its coevolution with beans, two major groups have been defined, "Andean" (P. griseola f. griseola) and "Mesoamerican" (P. griseola f. mesoamericana). The aim of this study was to characterize the dark pigment, melanin, synthetized by a selected isolate of each genic group of P. griseola when grown on Potato-dextrose broth. P. griseola f. griseola isolate S3b and P. griseola f. mesoamericana isolate T4 produced 1.7⯱â¯0.6 and 4.1⯱â¯0.9â¯mg of melanin per g of dry biomass, respectively. Although both melanins possessed similar UV-visible absorption spectroscopic pattern, P. griseola f. mesoamericana isolate T4 melanin had a lower UV-visible absorption, higher reducing activity and metal chelating ability than melanin from P. griseola f. griseola isolate S3b. However, when the size of the sample was 10â¯mg S3b melanin had a higher content of free phenolic groups. Furthermore, cell wall polysaccharides modified in melanin the availability of active phenolic groups, which was dependent on the fungal isolate and the size of the sample. Therefore, the amount and chemical features of melanin as well as its deposition in mycelium walls within isolates is different, which might explain the different pigmentation and physiological behaviours of these representatives of the two groups of P. griseola.
Assuntos
Ascomicetos/metabolismo , Melaninas/química , Antioxidantes/química , Ascomicetos/crescimento & desenvolvimento , Ascomicetos/isolamento & purificação , Biomassa , Espectroscopia de Ressonância de Spin Eletrônica , Melaninas/metabolismo , Oxirredução , Phaseolus/microbiologia , Doenças das Plantas/microbiologia , Espectrofotometria Ultravioleta , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
We use electron paramagnetic resonance (EPR) with liposoluble spin labels in order to study the lipid structures obtained after Triton X-100 extraction of erythrocyte membranes. The apparent order profile in these detergent resistant membranes (DRM) is very similar to that of the parent membrane, although with higher absolute values, consistent with a liquid-ordered state. DRM could also be obtained from erythrocytes previously depleted in a 40% of their membrane cholesterol, in apparent opposition to the phenomenon of raft disruption reported by other authors. However, the protein profile of these samples showed important differences with that of DRM from untreated cells. The analysis of our results suggests that the effect of Triton X-100 on cholesterol depleted erythrocytes is limited to the solubilization of raft proteins, without disrupting the lipid matrix of DRM.