PubMed · 15394638
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J D ANDREW. 1949-12-03. Experimental ascorbic acid deficiency.. https://doi.org/10.1136/bmj.2.4639.1273-a
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Ascorbic acid (AsA) is an essential nutritional component and powerful antioxidant in vegetables, and in plants, AsA levels are regulated by light. AsA levels in the leaves of Chinese chive (Allium tuberosum Rottler ex Spr), a popular vegetable, are poorly understood. Thus, this study was performed to assess the influence of light on AsA biosynthesis in chive and select related genes (AtuGGP1 and AtuGME1); in addition, bioinformatic analyses and gene expression level assays were performed. The biological information obtained for AtuGGP1 and AtuGME1 was analysed with several tools, including NCBI, DNAMAN, and MEGA11. After different light treatments were performed, the Chive AsA content and AtuGGP1 and AtuGME1 expression levels were determined. These results suggest that 1) compared with natural light, continuous darkness inhibited AsA synthesis in chives. 2) The amino acid sequences of AtuGGP1 and AtuGME1 are very similar to those of other plants. 3) The trends observed for the expression levels of AtuGGP1 and AtuGME1 were consistent with the AsA content observed in chives. Hence, we speculated that light controls AsA biosynthesis in chives by regulating AtuGGP1 and AtuGME1 expression. This study provided impactful and informative evidence regarding the functions of GGP and GME in chives.
Recent measurements of the flux control exerted by cytochrome c oxidase on the respiratory activity in intact cells have led to a re-appraisal of its regulatory function. We have further extended this in vivo study in the framework of the Metabolic Control Analysis and evaluated the impact of the mitochondrial transmembrane electrochemical potential (Deltamu(H+)) on the control strength of the oxidase. The results indicate that, under conditions mimicking the mitochondrial State 4 of respiration, both the flux control coefficient and the threshold value of cytochrome oxidase are modified with respect to the uncoupled condition. The results obtained are consistent with a model based on changes in the assembly state of the oxidative phosphorylation enzyme complexes and possible implications in the understanding of exercise-intolerance of human neuromuscular degenerative diseases are discussed.
A positionable platinum microelectrode fabricated by electrochemical etching was used to monitor the concentration of ascorbic acid in fruits and vegetables. Studies carried out with ascorbate oxidase confirmed the suitability of the amperometric sensor to measure selectively the ascorbic acid content. The results obtained with the proposed method for ascorbic acid determination in orange juices compared well with those found by iodimetry with coulometrically generated iodine. The standard deviation calculated by measuring limiting current values in voltammograms was found to be 3% (n = 150). The sensor allowed the evaluation of the spatial distribution of ascorbic acid concentration in oranges by in-situ measurements. Ascorbic acid concentration maps show that in a perpendicular cut the concentration is higher near the peel to the center of the fruit. In a parallel cut, the concentration increases with the distance to the stem. A correlation between the ripening stage and the ascorbic acid concentration was also observed from electrochemical measurements, the content being higher in mature fruits.