chlorophyll-a and glycolaldehyde

CO(2) fixation in mosses saturates at moderate irradiances. Relative electron transport rate (RETR) inferred from chlorophyll fluorescence saturates at similar irradiance in shade species (e.g. Plagiomnium undulatum, Trichocolea tomentella), but many species of unshaded habitats (e.g. Andreaea rothii, Schistidium apocarpum, Sphagnum spp. and Frullania dilatata) show non-saturating RETR at high irradiance, with high non-photochemical quenching (NPQ). In P. undulatum and S. apocarpum, experiments in different gas mixtures showed O(2) and CO(2) as interchangeable electron sinks. Nitrogen + saturating CO(2) gave high RETR and depressed NPQ. In S. apocarpum, glycolaldehyde (inhibiting photosynthesis and photorespiration) depressed RETR in air more at low than at high irradiance; in CO(2) -free air RETR was maintained at all irradiances. Non-saturating electron flow was not suppressed in ambient CO(2) with 1% O(2) . The results indicate high capacity for oxygen photoreduction when CO(2) assimilation is limited. Non-saturating light-dependent H(2) O(2) production, insensitive to glycolaldehyde, suggests that electron transport is supported by oxygen photoreduction, perhaps via the Mehler-peroxidase reaction. Consistent with this, mosses were highly tolerant to paraquat, which generates superoxide at photosystem I (PSI). Protection against excess excitation energy in mosses involves high capacity for photosynthetic electron transport to oxygen and high NPQ, activated at high irradiance, alongside high reactive oxygen species (ROS) tolerance.

Topics: Acetaldehyde; Bryophyta; Carbon Dioxide; Chlorophyll; Oxidation-Reduction; Oxygen; Photochemistry; Photosynthesis; Reactive Oxygen Species

Sealed Chlamydomonas reinhardtii cultures evolve significant amounts of hydrogen gas under conditions of sulfur depletion. However, the eukaryotic green alga goes through drastic metabolic changes during this nutritional stress resulting in cell growth inhibition and eventually cell death. This study aimed at isolating C. reinhardtii transformants which produce hydrogen under normal growth conditions to allow a continuous hydrogen metabolism without the stressful impact of nutrient deprivation.. To achieve a steady photobiological hydrogen production, a screening protocol was designed to identify C. reinhardtii DNA insertional mutagenesis transformants with an attenuated photosynthesis to respiration capacity ratio (P/R ratio). The screening protocol entails a new and fast method for mutant strain selection altered in their oxygen production/consumption balance. Out of 9000 transformants, four strains with P/R ratios varying from virtually zero to three were isolated. Strain apr1 was found to have a slightly higher respiration rate and a significantly lower photosynthesis rate than the wild type. Sealed cultures of apr1 became anaerobic in normal growth medium (TAP) under moderate light conditions and induced [FeFe]-hydrogenase activity, yet without significant hydrogen gas evolution. However, Calvin-Benson cycle inactivation of anaerobically adapted apr1 cells in the light led to a 2-3-fold higher in vivo hydrogen production than previously reported for the sulfur-deprived C. reinhardtii wild type.. Attenuated P/R capacity ratio in microalgal mutants constitutes a platform for achieving steady state photobiological hydrogen production. Using this platform, algal hydrogen metabolism can be analyzed without applying nutritional stress. Furthermore, these strains promise to be useful for biotechnological hydrogen generation, since high in vivo hydrogen production rates are achievable under normal growth conditions, when the photosynthesis to respiration capacity ratio is lowered in parallel to down regulated assimilative pathways.

Topics: Acetaldehyde; Anaerobiosis; Animals; Autotrophic Processes; Chlamydomonas reinhardtii; Chlorophyll; Hydrogen; Hydrogenase; Iron-Sulfur Proteins; Mutagenesis, Insertional; Oxygen Consumption; Photosynthesis; Sulfur; Transformation, Genetic

Horseradish peroxidase (EC 1.11.1.7) is shown to catalyze the aerobic oxidation of lysozyme, bovine serum albumin, and protamine adducts with glycolaldehyde at physiological pH. This reaction is accompanied by light emission, which is attributed to the generation of triplet species. The intensity of chemiluminescence is enhanced by addition of chlorophyll alpha solubilized in Brij 35. A role of electronically excited species in deleterious and pathological processes associated with formation of Schiff-type adducts is suggested, with emphasis on the case of alcohol-induced liver injury.

Topics: Acetaldehyde; Chlorophyll; Chlorophyll A; Horseradish Peroxidase; Kinetics; Luminescent Measurements; Muramidase; Oxidation-Reduction; Oxygen; Peroxidases; Polidocanol; Polyethylene Glycols; Protamines; Proteins; Serum Albumin, Bovine; Spectrophotometry