Scavenging systems

Scavenging system required to allow self-starting. 

The use of phthaloyl dichlonde as a scavenger for potassium nitrite and/or potassium oxide [108, 109, III] significantly increases yields of aryl fluorides, m fluoronitrobenzene is obtained in 70% yield with sulfolane as a solvent at 200 °C after 72 h Addition of tetraphenylphosphonium bromide as a phase-transfer catalyst to the phthaloyl dichlonde scavenger system further increases the yield of m-fluoronitrobenzene to 89% under less forcing conditions 150-180 C, 5 h) [if 2] This optimized technique can be applied to give m-fluorobenzonitnle from in-m-trobenzonitnle in 86% yield [/i2]... 

Smirnoff, J. Colombe, S.V. (1988). Drought influences the activity of enzymes of the chloroplast hydrogen peroxide scavenging system. Journal of Experimental Botany, 39, 1097-1109. 

Roy, R.S. and McCord, J.M. (1983). Superoxide and ischaemia conversion of xanthine dehydrogenase to xanthine oxidase. In Oxyradicals and their Scavenging Systems , Vol. 2 (eds. K Greenwald and G. Cohen) pp. 145-153. Elsevier, New York. 

Asayama, K., Kooy, N.W. and Burr, I.M. (1986). Effect of vitamin E deficiency and selenium deficiency on insulin reserve and free radical scavenging systems in islets decrease of islet manganosuperoxide dismutase. J. Lab. Clin. Med. 107, 459-463. 

Perumal, A.S., Gopal, V.B., Tordzro, W.K., Cooper, T.B. and Cadet, J.L. (1992). Vitamin E attenuates the toxic effects of 6-hydrooxydopamine on free radical scavenging systems in rat brain. Brain Res. Bull. 29, 699-701. 

RL Arudi, MW Sutherland, BHJ Bielski. In Oxy Radicals and Their Scavenger Systems. Vol 1, G Cohen, RA Greenwald (Eds). Elsevier, Amsterdam, 1983. 

The dual role of these ruthenium complexes, as both an NO donor and scavenger, appears to lie strongly in the binding constant of NO to Ru(II) and the ligands present, which can facilitate NO dissociation. Clearly the investigative approach into these systems has just touched the surface and the future appears very promising in these potential NO source/scavenger systems. 

A method for the study of ET from a protein metal center to a surface ruthenium has been developed by Lieber [26]. In this method, Ru(bpy) " acts as an oxidant, selectively removing an electron from a surface a5Ru(IIXhistidine). A Ni/RBr scavenger system (Ni(II)hexamethyltetraaza-cyclododeeane and an alkyl bromide) oxidizes the Ru(bpy)3 before it can back react with the a5Ru(IIIXhistidine) complex. ET from the reduced protein metal center to the oxidized ruthenium can be monitored spectroscopically. 

Falahee, M. B., Park, S. F., and Adams, M. R. (2003). Detection and enumeration of Campylobacter jejuni and Campylobacter coli by indirect impedimetry with an oxygen scavenging system. /. Food Prot. 66,1724-1726. 

Cytochrome P-450 from rat or human liver microsome preparations is inactivated when incubated anaerobically with carbon tetrachloride in the presence of NADPH and an oxygen-scavenging system (Manno et al. 1988 1992). Inactivation involved destruction of the heme tetrapyrrolic structure, and followed pseudo first-order kinetics with fast and slow half lives of 4.0 and 29.8 minutes. When compared with rat liver microsomes, the human preparations were 6-7 times faster at metabolizing carbon tetrachloride, and only about one- eighth as susceptible to suicide inactivation (about 1 enzyme molecule lost for every 196 carbon tetrachloride molecules metabolized). 

Klug D, Rabani J, Fridovich I (1972) A direct demonstration of the catalytic action of superoxide dismutase through the use of pulse radiolysis. J Biol Chem 247 4839-4842 Koppenol WH (1983) Thermodynamic of the Fenton-driven Haber-Weiss and related reactions. In Cohen G, Greenwald RA (eds) Oxy radicals and their scavenger systems. Vol I Molecular aspects. Elsevier Biomedical, New York, pp 84-88... 

W.C. Stallings, C. Bull, J.A. Fee, M.S. Lah, and M.L. Ludwig, in Molecular Biology of Free Radical Scavenging Systems (J. Scandalios, Ed.) Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York, p. 193 (1992). 

Alternatively, the RNA can be immobilized on a shde, in which case single molecules can be studied for many seconds and conformational transitions observed. The time of observation is limited by photochemical effects on the fluorophores, but this can be extended with recently improved oxygen scavenging systems (Aitken et al., 2008 Rasnik et al., 2006). Again there are two choices. A wide-held approach can be used,... 

Aitken, C. E., Marshall, R. A., and Pughsi, J. D. (2008). An oxygen scavenging system for improvement of dye stability in single-molecule fluorescence experiments. Biophys.J. 94, 1826-1835. 

Cohen, G. and Greenwald, R.A. In "Oxy-Radicals in Their Scavenger Systems, Molecular Aspects" Elsevier New York,... 

---