The glutathione peroxidase homologous gene (Gpxh gene) in Chlamydomonas reinhardtii is up-regulated under oxidative stress conditions. The Gpxh gene showed a remarkably strong and fast induction by the singlet oxygen-generating photosensitizers neutral red, methylene blue and rose Bengal. The Gpxh mRNA levels strongly increased, albeit much more slowly, upon exposure to the organic hydroperoxides tert-butyl hydroperoxide (t-BOOH) and cumene hydroperoxide. In contrast, the Gpxh mRNA levels were only weakly induced by exposure to the superoxide-generating compound paraquat and by hydrogen peroxide. A comparison of the Gpxh mRNA levels with those of the heat shock protein HSP70A and the iron superoxide dismutase gene showed qualitative and quantitative differences for the three genes under oxidative stress conditions tested. The Gpxh gene is specifically induced by singlet-oxygen photosensitizers and the relative induction by other compounds is much weaker for Gpxh than for the other genes investigated. Using Gpxh promoter fusions with the arylsulfatase reporter gene, we have shown that the Gpxh was transcriptionally up-regulated by singlet-oxygen photosensitizers. It is also shown that the Gpxh promoter contains a region between 104 and 179 bp upstream of the transcription start that is responsible for the mRNA up-regulation upon exposure to 1O2 but not t-BOOH. Within this region a regulatory sequence homologous to the mammalian cAMP response element (CRE) and activator protein 1 (AP-1) binding site was identified within a 16 bp palindrome.
The topic 'Sulfa-Drugs in secondary school chemistry' has been developed in cooperation of three high schools (Kantonsschulen). Three essential aspects are covered that ideally complement each other: 1. The synthesis of sulfamethoxazole – an antibiotic 'without side effects' –
as a practical course in a school laboratory; 2. An introduction to the topic 'drug design' with the question of structure, effect and side effects of sulfonamides; 3. A detailed answer to the question of how side effects can be avoided by the design of drugs using molecular modelling. Teaching
materials on all topics can be downloaded free of charge from Swisseduc. ch (see box). The article discusses various possible approaches in high school chemistry along the lines of a well-established teaching unit on sulfonamides.
Photosynthesis or the storage of solar energy in chemical bonds is a process which, in its essence, goes far beyond a conversion of CO2 and water into dioxygen and glucose or other organic products. Photosynthesis is a process which comprises elementary features of most of the chemical reactions and some physical processes we are looking at in higher education; light absorption, proton transfer, redox reactions and making and breaking of bonds amongst others. Metals and main group elements are involved and the entire process is embedded in a biological environment that involves proteins and membranes. In this article, we will focus on two key aspects of natural photosynthesis, namely the absorption of light (photons) and the separation of the excitons into electrons and holes based on P680 along with the electrochemical energetics. Further, we will present an artificial light driven catalytic process which mimics PSI for the reduction of water to H2, the inorganic congener of nicotinamide adenine dinucleotide phosphate (NADPH). This light-driven reductive process shall show the mechanistic complexity of the 'easy' reaction 2H+ + 2e- → H2.
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