PubMed · 673270
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1978. Vitamin C and phagocyte function.. https://doi.org/10.1111/j.1753-4887.1978.tb03748.x
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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.
The reaction of ascorbate with recombinant hemoglobin (rHb1.1) in the presence of differing partial pressures of oxygen was studied. In the presence of 15 000 ppm (1.5%) residual oxygen, ascorbate/oxygen-mediated reactions resulted in an increased rate of autoxidation, modification of the beta-globin, increased oxygen affinity and decreased maximum Hill coefficient. One of the observed modifications to the beta-globin was a 72 Da addition to its N-terminus. Detailed characterization indicates the modification was an imidazolidinone type structure. Thorough deoxygenation of the hemoglobin solution to <150 ppm of oxygen prior to addition of ascorbate was required to prevent these modifications. Addition of ascorbate to the deoxy hemoglobin (deoxyHb) at pH 8 induced aggregation, eventually leading to precipitation. No such precipitation was observed at pH 7. Long-term storage of the hemoglobin was carried out by addition of ascorbate to deoxyHb at pH 7. The level of methemoglobin remained at <2% for up to 1 year at 4 degreesC, with no detectable precipitation of the protein. Modifications similar to those observed by the acute studies were observed over the 1-year period and correlated with disappearance of the added ascorbate.
A capillary zone electrophoresis (CZE) procedure for the determination of l-ascorbic acid (AA) and total ascorbic acid (TAA, as the sum of AA and dehydroascorbic acid) in vascular plants, lichens, bryophytes, and liverworts is described. The samples were frozen in liquid nitrogen and extracted with 2% metaphosphoric acid. To determine AA, an aliquot was directly injected in a fused-silica capillary. The determination of TAA was performed upon its reduction with dl-homocysteine at pH 7. The background electrolyte contained 60 mM sodium chloride, 60 mM sodium dihydrogen phosphate, 1 x 10(-4)% hexadimetrine bromide, and NaOH up to pH 7. The procedure was rapid and highly reproducible; the limit of detection was 0.2 microg ml-1, which corresponded to 0.4 mg/100 g of sample. The method was validated by comparison with an enzymatic assay. While the enzymatic assay failed to quantify AA in some plants owing to strong background UV absorption, CZE was successful in all the extracts assayed.