ascorbic-acid and syringaldazine

The contribution of antioxidant defence systems in different tolerance to direct and bicarbonate-induced Fe deficiency was evaluated in two pea cultivars (Kelvedon, tolerant and Lincoln, susceptible). Fe deficiency enhanced lipid peroxidation and H2 O2 concentration in roots of both cultivars, particularly in the sensitive one grown under bicarbonate supply. The results obtained on antioxidant activities (SOD, CAT, POD) suggest that H2 O2 accumulation could be due to an overproduction of this ROS and, at the same time, to a poor capacity to detoxify it. Moreover, under bicarbonate supply the activity of POD isoforms was reduced only in the sensitive cultivar, while in the tolerant one a new isoform was detected, suggesting that POD activity might be an important contributor to pea tolerance to Fe deficiency. The presence of bicarbonate also resulted in stimulation of GR, MDHAR and DHAR activities, part of the ASC-GSH pathway, which was higher in the tolerant cultivar than in the sensitive one. Overall, while in the absence of Fe only slight differences were reported between the two cultivars, the adaptation of Kelvedon to the presence of bicarbonate seems to be related to its greater ability to enhance the antioxidant response at the root level.

Topics: Antioxidants; Ascorbic Acid; Catalase; Glutathione; Hydrazones; Hydrogen Peroxide; Iron; Iron Deficiencies; Isoenzymes; Lipid Peroxidation; Malondialdehyde; Peroxidase; Pisum sativum; Plant Roots; Substrate Specificity; Superoxide Dismutase

A gas-phase oxygen biosensor based on blue copper-containing oxidases was developed. Blue-oxidase enzymes, including laccase and ascorbate oxidase, have a blue chromophore prosthetic group, type 1 Cu+2, which can be reduced and decolorized with reducing substrates. When the enzyme is reoxidized with molecular oxygen, there is a concomitant return of the blue color. The oxygen biosensor consisted of the Rhus vernicifera laccase and ascorbate as substrate enclosed in pouches of low-density polyethylene under nitrogen gas. Operational stability of the biosensor was established by exposing it to different oxygen/nitrogen gas mixtures at 5 degrees C. Gas-phase oxygen concentrations were measured by keeping it under nitrogen gas and subsequently recording the rate of reappearance of the enzyme blue color, both visually and spectrophotometrically at 610 nm. The oxygen biosensor was able to detect a wide range of oxygen concentrations. The time required to recover the blue color, namely the biosensor response time, at the optimized assay conditions of 5 degrees C and a high-water activity level, was determined. This research describes the development of an oxygen biosensor with adequate activity and stability to measure gas-phase oxygen concentrations at 5 degrees C and high-water activity levels. The oxygen biosensor could be used to indicate oxygen concentrations above acceptable levels in headspace oxygen concentration which could affect the quality and safety of products packaged under initial low levels of oxygen concentration.

Topics: Ascorbate Oxidase; Ascorbic Acid; Biosensing Techniques; Enzyme Stability; Hydrazones; Indicators and Reagents; Kinetics; Laccase; Oxidation-Reduction; Oxidoreductases; Oxygen; Plants, Toxic; Spectrophotometry; Toxicodendron