1,721,017 research outputs found
13C and 31P NMR studies of glucose and 2-deoxyglucose metabolism in normal and enzyme-deficient human erythrocytes. Ferretti A, Bozzi A, Di Vito M, Podo F, Strom R.
No full textThe flux of 13C-labeled glucose through the Embden-Meyerhof and pentose phosphate pathways was studied by 13C NMR in intact erythrocytes isolated from normal subjects or from patients suffering of glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49) deficiency. Similar rates of glucose catabolism and similar fluxes of the 13C-label into 2,3-bisphosphoglycerate and lactate were found, under basal conditions, in normal and in G6PD-deficient erythrocytes incubated in the presence of either [1-13C]- or D[6-13C]glucose. Exposure to oxidative stress by preincubation with tert-butylhydroperoxide induced in normal, but not in G6PD-deficient erythrocytes, a significant enhancement of glucose consumption, as well as a substantial reduction in 13C-label transfer from C1-glucose into lactate. It was also possible, by 31P NMR, to evaluate the conversion of 2-deoxyglucose to its phosphate-containing metabolites. The oxidation and subsequent decarboxylation of 2-deoxyglucose-6-phosphate was assessed in reconstituted systems and could subsequently be evidenced also in ethanolic extracts from normal (but not from G6PD-deficient) erythrocytes which had been exposed to oxidative stress. The results indicate that, in terms of glucose flux through the glycolytic pathway, there is little or no difference between normal and G6PD-deficient erythrocytes, regardless of previous exposure to oxidative stress. Faster consumption of either glucose or 2-deoxyglucose is induced, only in normal cells, by treatment with tert-butylhydroperoxide, essentially as a consequence of the activation of the pentose-phosphate pathway
Proton magnetic resonance studies on the structure and hydratatin of non-ionic detergent inverted micelles
No full text31P Nuclear Magnetic resonance study of growth and dimorphic transition in Candida albicans.
No full textA 31P NMR study of the fungal pathogen Candida albicans was carried out. Yeast-form cells at
different phases of growth, as well as germ tubes and hyphae were examined. In all cases, the
NMR spectra showed well separated resonance peaks arising from phosphorus-containing
metabolites, the most prominent being attributable to inorganic phosphate (P,) polyphosphates,
sugar phosphates and mononucleotides, NAD, ADP and ATP. Relevant signals were also
detected in the phosphodiester region. The intensity of most signals, as measured relative to that
of PI, was clearly modulated both at the different phases of growth and during yeast-to-mycelium
conversion, suggesting significant changes in the intracellular concentration of the corresponding
metabolites. In particular, the intensity of the polyphosphate signal was high in
exponentially growing, yeast-form cells, then progressively declined in the stationary phase, was
very low in germ tubes and, finally, undetectable in hyphae.
NMR spectral analysis of the PI region showed that from early-stationary phase, P, was
present in two different cellular compartments, probably corresponding to the cytoplasm and
the vacuole. From the chemical shift of Pi, the pH values of these two compartments could be
evaluated. The cytoplasmic pH was generally slightly lower than neutrality (6.74-8), whereas
the vacuolar pH was always markedly more acidic
1H NMR detection of 1H-13C bonds by double 13C editing. Application to the doscrimination of glucose metabolites
No full textTemperature dependence of intracellular pH in higher plant cells. 31P-Nuclear Magnetic Resonance study on maize root tips.
No full textThe recent introduction of 31P nuclear magnetic resonance spectroscopy offers a new approach to the problem of obtaining a simultaneous and direct evaluation of both the cytoplasmic and vacuolar pH in higher plant cells (J. K. M. Roberts, P.M.Ray,N.Waderlardetzky and O. Sardetzky, 1980, Nature 283, 870–872; 1981, Planta 152, 74–78). Using this method we have been able to detect a selective pH decrease of about 0.5 units at the level of the cytoplasmic compartment of maize root tips when the temperature was increased from 4 to 28°C. This effect was completely reversible with temperature. No pH variation could be detected at the level of the vacuolar compartment
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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