Pisum arvense plants were subjected to 5 days of nitrogen deprivation. Then, in the conditions that increased or decreased the root glutamine and asparagine pools, the uptake rates of 0.5 mM NH₄⁺ and 0.5 mM K⁺ were examined. The plants supplied with 1 mM glutamine or asparagine took up ammonium and potassium at rates lower than those for the control plants. The uptake rates of NH₄⁺ and K⁺ were not affected by 1 mM glutamate. When the plants were pre-treated with 100 µM methionine sulphoximine, an inhibitor of glutamine synthesis, the efflux of NH₄⁺ from roots to ambient solution was enhanced. On the other hand, exposure of plants to methionine sulphoximine led to an increase in potassium uptake rate. The addition of asparagine, glutamine or glutamate into the incubation medium caused a decline in the rate of NH₄⁺ uptake by plasma membrane vesicles isolated from roots of Pisum arvense, whereas on addition of methionine sulphoximine increased ammonium uptake. The results indicate that both NH₄⁺ and K⁺ uptake appear to be similarly affected by glutamine and asparagine status in root cells.
The presence of highly toxic acrylamide in food products such as fried potatoes and chips was confirmed by Swedish scientists from the Stockholm University. Neurotoxicity of this compound and its metabolites imposes a duty to control it by qualitative and quantitative assays. Recent findings showed that acrylamide is formed in heat-treated foods rich in asparagine and reducing sugars such as glucose. Exposing acrylamide to pH extremes results in its hydrolysis to acrylic acid and ammonia. The main objective of the work presented is the development of a new electrochemical sensor for the determination of acrylic acid in the presence of asparagine and acrylamide. We report on an intramolecular ion-channel sensor using self-assembled monolayers deposited onto gold electrodes. Macrocyclic polyamine molecules with long alkyl chains were adsorbed into the monolayer of 1-dodecanethiol on the gold surface. The signal generated due to the formation of a supramolecular complex between host and acrylic acid guest at the electrode interface was measured by Osteryoung square wave voltammetry (OSWV) with [Ru(NH3)6]3+ as an electroactive marker.
In Penicilium isariiforme there occur two endogenous rhythms: the growth-“wave” rhythm and sporulation rhythm in the form of coremia-bearing zonations. The growth rhythm of wave type occurring in P. isariiforme in light and in darkness is an endogenous spontaneous rhythm, whereas the sporulation rhythm manifested by the formation of spore-bearing coremia zonations represents an analogue induced rhythm. For this rhythm to occur a light impulse is necessary. The growth-wave rhythm has a long period 120 h, the sporulation rhythm has a 30 h period. Asparagine seems to regulate the sporulation rhythm; but it does not exert any greater influence on the wave rhythm in cultures grown in light nor in darkness. An addition of asparagine shortened the period of first zonation by a few hours, and the successive sporulation periods followed within very short time. Inhibitors such as: avidin. chloramphenicol, cycloheximide and puromycine controlled the length of the period of the sporulation rhythm.
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