1,721,006 research outputs found
Correlation between oxygen availability, energy charge, and protein synthesis in squash cotyledons isolated from germinating seeds
No full textThe influence of O(2) availability on the rate of protein synthesis, the levels of RNA and of adenylates, and the value of the energy charge in squash (Cucurbita maxima) cotyledons isolated from seeds germinated for 15 or 28 hours at different O(2) concentration (3% or 20% O(2)) has been investigated.The rate of protein synthesis is five times lower in cotyledons maintained in 3% O(2) than in those maintained in 20% O(2). Also net RNA synthesis is almost blocked in 3% O(2), while in 20% O(2) it proceeds almost linearly for 48 hours.The different RNA contents cannot explain the different rates of protein synthesis.The results of shift experiments (cotyledons shifted from 20% to 3% O(2) or vice versa) show that the rate of protein synthesis is strictly correlated with actual O(2) availability and is largely independent of the one in the previous period. O(2) controls the development of the adenylate pool and particularly the increase of ATP level. Thus, both the adenylate pool and the values of the energy charge ratio are lower in cotyledons grown in 3% than in 20% O(2).The shifts of O(2) availability induce rapid changes of ATP, ADP, and AMP levels and thus of the values of the energy charge, which are about 0.7 at 3% O(2) and higher than 0.8 at 20% O(2), independent of previous O(2) availability.The rate of protein synthesis appears to be largely independent of the levels of the single nucleotides and better correlated to the energy charge values
Analisi di imminostilbeni (carbamazepina e oxcarbazepina) e metaboliti in fluidi biologici mediante HPLC-DAD
No full textEvidence for an electrogenic ATPase in microsomal vesicles from pea internodes
No full textThe transmembrane electropotential of microsomal vesicles from pea internode segments, monitored by equilibrium distribution of the permeant anion SCN-, is strongly hyperpolarized when ATP is present in the incubation medium. The stimulation of SCN- uptake by ATP is rather specific with respect to the other nucleoside di- and triphosphates tested: ADP, GTP, CTP and UTP. ATP-stimulated SCN- uptake is strongly inhibited by ATPase inhibitors such as p-chloromercuribenzenesulphonate and N,N'-dicyclohexylcarbodiimide and by 2.5% toluene/ethanol (1 : 4, v/v), the latter being a treatment which makes the vesicles permeable. On the contrary, oligomycin is almost ineffective in influencing ATP-induced SCN- uptake. The proton conductor carbonyl cyanide p-trifluoromethoxyphenylhydrazone strongly inhibits ATP-stimulated SCN- uptake. The effect of ATP on SCN- uptake depends on the pH of the medium, the maximum being reached at about pH 7.0. These data support the view that microsomal fractions from pea internodes contain membrane vesicles endowed with a membrane-bound ATPase coupling ATP hydrolysis to electrogenic transport of ions, probably H+
Plant membrane transport: the current position : proceedings of the 8. International Workshop on Plant Membrane, Venice, Italy, 25-30 June, 1989
No full textOn the inhibiting effect of oligomycin on Mg: ATP-dependent ΔpH and Δψ in microsomal vesicles from radish
No full textThe kinetics of inhibition by oligomycin of the mitochondrial ATPase and the Mg: ATP-dependent electrogenic transport of protons were compared in membrane preparations from radish seedlings.
Oligomycin blocks the phosphohydrolyzing activity of mitochondrial ATPase (measured at pH 8.5) at 1 μg × mg−1 prot and the ATP-synthase one (measured at pH 6.6) at 3 μg × mg−1 prot.
Oligomycin at these concentrations does not influence Mg: ATP-dependent proton transport and Mg: ATP-dependent hyperpolarization of transmembrane electric potential difference (PD) in microsomal vesicles. However, an inhibiting effect of the drug becomes apparent at concentrations higher than 10 μg × mg−1 prot, increasing with the increase of oligomycin concentration at least up to 240 μg × mg−1 prot. Both the vanadate and the NO3−-sensitive systems of Mg: ATP-dependent electrogenic transport of protons show similar sensitivity to oligomycin
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