Pulse radiolysis free radical reactions with

Adams, G.E. and Redpath, J.L. (1974). Selective free-radical reactions with proteins and enzymes pulse radiolysis and inactivation studies on papain. Int. J. Badiat. Biol. 25, 129-136. 

R.H. Bisby, R.B. Cundall, G.E. Adams, and M.L. Posener FREE RADICAL REACTIONS WITH PEPSIN STUDIED BY PULSE RADIOLYSIS... 

The technique of pulse radiolysis (1) has found extensive application in the study of fast free radical reactions with compounds of biological interest (2), The high energy, electron pulse of short duration (typically 0.2 ys) produced by a microwave linear accelerator forms products, including free radical species, from the radiolysis of water ... 

Advances in pulse radiolysis studies in the gas phase have been summarized in several review papers. In a comprehensive review by Sauer [4], a review presented by Firestone and Dorfman [5] in 1971 was referred to as the first review on gas-phase pulse radiolysis. Experimental techniques and results obtained were summarized by one of the present authors [6], with emphasis on an important contribution of pulse radiolysis to gas-phase reaction dynamics studies. Examples were chosen by Sauer [7] from the literature prior to 1981 to show the types of species that were investigated in the gas phase using pulse radiolysis technique. Armstrong [8] reviewed experimental data obtained from gas-phase pulse radiolysis together with those from ordinary steady-state radiolysis. Advances in gas-phase pulse radiolysis studies since 1981 were also briefly reviewed by Jonah et al. [9], with emphasis on an important contribution of this technique to free radical reaction studies. One of the present authors reviewed comprehensively the gas-phase collision dynamics studies of low-energy electrons, ions, excited atoms and molecules, and free radicals by means of pulse radiolysis method [1-3]. An important contribution of pulse radiolysis to electron attachment, recombination, and Penning collision studies was also reviewed in Refs. 10-15. 

Visscher KJ, de Haas MP, Loman H, Vojnovic B, Warman JM (1987) Fast protonation of adenosine and of its radical anion formed by hydrated electron attack a nanosecond optical and dc-conduc-tivity pulse radiolysis study. Int J Radiat Biol 52 745-753 Visscher KJ, Spoelder HJW, Loman H, Hummel A, Horn ML (1988) Kinetics and mechanism of electron transfer between purines and pyrimidines, their dinucleotides and polynucleotides after reaction with hydrated electrons a pulse radiolysis study. Int J Radiat Biol 54 787-802 von Sonntag C (1980) Free radical reactions of carbohydrates as studied by radiation techniques. Adv Carbohydr Chem Biochem 37 7-77... 

In many cases the product S is itself a free radical (S ), or a hyper-reduced metal ion, which in turn reacts in one-electron gain or loss processes. It is not surprising, then, that radiation-chemical methods are widely used in the study of electron-transfer processes. Of particular value is the technique of pulse radiolysis which permits reactions to be studied on timescales ranging from seconds down to picoseconds, so that even the most reaetive speeies ean be studied. It is this technique and its applications that form the subject matter of this chapter which begins with an outline of the radiation chemistry of water and other solvents. Next there is a historical view of pulse radiolysis, some of the landmark discoveries are discussed, followed by a description of the principal features of a pulse radiolysis facility and the various methods of detecting and measuring transient speeies. The chapter ends with some examples of data capture and analysis, and methods of sample preparation. 

The free-radical reactions of carbohydrates as studied by radiation techniques have been reviewed.The nature of the reactions of carbohydrates with hydroxy-radicals and hydrated electrons formed by pulse radiolysis has been investigated. Simple monosaccharides are unreactive towards the solvated electron but readily give unstable species with hydroxy-radicals. Aryl glycosides react readily with both in the manner of nucleophile and electrophile, respec-... 

Pulse radiolysis results (74) have led other workers to conclude that adsorbed OH radicals (surface trapped holes) are the principal oxidants, whereas free hydroxyl radicals probably play a minor role, if any. Because the OH radical reacts with HO2 at a diffusion controlled rate, the reverse reaction, that is desorption of OH to the solution, seems highly unlikely. The surface trapped hole, as defined by equation 18, accounts for most of the observations which had previously led to the suggestion of OH radical oxidation. The formation of H2O2 and the observations of hydroxylated intermediate products could all occur via... 

Epr is most effective for detecting free radicals that may occur as intermediates in oxidation and reduction reactions involving transition metal ions. Since these transients are invariably quite labile, epr is combined with continuous flow, (more conveniently) stopped-flow, flash photolysis, and pulse radiolysis. 

The fates of the G(-H) radicals in DNA are mostly determined by reactions with other substrates. Here, we consider the reactions of the G(-H) radicals with types of free radicals that are generated in vivo under conditions of oxidative stress. One of these radicals is the nitrogen dioxide radical, NO2. This radical can be generated in vivo by the oxidation of nitrite, N02, a process that can be mediated by myeloperoxidase [111, 112] as well as by other cellular oxidants [113, 114]. An alternative pathway of the generation of NO2 is the homolysis of peroxynitrite [102, 115] or nitrosoperoxycarbonate formed by the reaction of peroxynitrite with carbon dioxide [99-101]. The redox potential, E°( NO2/NO2")=1.04 V vs NHE [116] is less than that of guanine, E7[G(-H)7G] = 1.29 V vs NHE [8]. Pulse radiolysis [117] and laser flash photolysis [109] experiments have shown that, in agreement with these redox potentials, N02 radicals do not react with intact DNA. However, N02 radicals can oxidize 8-oxo-dG that has a lower redox potential ( 7=0.74 vs NHE [56]) than any of the normal nucleobases [109]. 

Mieden OJ, von Sonntag C (1989) Peptide free-radicals the reactions of OH radicals with glycine anhydride and its methyl derivatives sarcosine and alanine anhydride. A pulse radiolysis and product study. Z Naturforsch 44b 959-974... 

Tripathi GNR (1998) Electron-transfer component in hydroxyl radical reactions observed by time resolved resonance Raman spectroscopy. J Am Chem Soc 120 4161-4166 TsaiT, Strauss R, Rosen GM (1999) Evaluation of various spin traps for the in vivo in situ detection of hydroxyl radical. J Chem Soc Perkin Trans 2 1759-1763 Tsay L-Y, Lee K-T, Liu T-Z (1998) Evidence for accelerated generation of OH radicals in experimental obstructive jaundice of rats. Free Rad Biol Med 24 732-737 Ulanski P, von Sonntag C (2000) Stability constants and decay of aqua-copper(lll) - a study by pulse radiolysis with conductometric detection. Eur J Inorg Chem 1211-1217 Veltwisch D, Janata E, Asmus K-D (1980) Primary processes in the reactions of OH radicals with sul-phoxides. J Chem Soc Perkin Trans 2 146-153... 

Most of the pKd values of free radicals have been determined by pulse radiolysis, and it is therefore useful to recall, how fast pK equilibria become established. In general, the reaction of H+ with an acid anion is practically diffusion-controlled [reaction (2) k ranging between 5 x 109 dm3 mol1 s1 and 5 X 1010 dm3 mol"1 s 1 (Eigen et al. 1964 Perrin et al. 1981)]. The same holds for the deprotonation of an acid by OH [reaction (3)]. The rates of reaction (4) can be calculated from the pKa value taking into account that Kw = [H+] x [OH ] = 1014 mol2 dm 6. 

Freiberg M, Meyerstein D (1980) Reactions of aliphatic free radicals with copper cations in aqueous solution, part 2. Reactions with cupric ions a pulse radiolysis study. J Chem Soc Faraday Trans 176 1825-1837... 

Schuchmann H-P, von Sonntag C (1988) The oxidation of methanol and 2-propanol by potassium peroxodisulphate in aqueous solution free-radical chain mechanisms elucidated by radiation-chemical techniques. Radiat Phys Chem 32 149-156 Schuchmann H-P, Wagner R, von Sonntag C (1986) The reactions of the hydroxymethyl radical with 1,3-dimethyluracil and 1,3-dimethylthymine. Int J Radiat Biol 50 1051-1068 Schuchmann MN, von Sonntag C (1982) Determination of the rate constants of the reactions C02 + OH" -> HC03 and barbituric acid —> barbiturate anion + H+ using the pulse radiolysis technique. Z Naturforsch 37b 1184-1186... 

Deeble DJ, von Sonntag C (1992) Decarboxylation of 3,4-dihydroxymandelic acid induced by the superoxide radical anion a chain reaction. Int J Radiat Biol 62 105 Deeble DJ, Parsons BJ, Phillips GO (1987) Evidence for the addition of the superoxide anion to the anti- oxidant -propyl gallate in aqueous solution. Free Rad Res Commun 2 351-358 Deeble DJ, Parsons BJ, Phillips GO, Schuchmann H-P, von Sonntag C (1988) Superoxide radical reactions in aqueous solutions of pyrogallol and n-propyl gallate the involvement of phenoxyl radicals. A pulse radiolysis study. Int J Radiat Biol 54 179-193 Denisov ET, Denisova TG (1993) The polar effect in the reaction of alkoxy and peroxy radicals with alcohols. Kinet Catal 34 738-744... 

Han P, Bartels DM (1994) Encounters of H and D atoms with 02 in water relative diffusion and reaction rates. In Gauduel Y, Rossky P (eds) AIP conference proceedings 298. "Ultrafast reaction dynamics and solvent effects." AIP Press, New York, 72 pp Hasegawa K, Patterson LK (1978) Pulse radiolysis studies in model lipid systems formation and behavior of peroxy radicals in fatty acids. Photochem Photobiol 28 817-823 Herdener M, Heigold S, Saran M, Bauer G (2000) Target cell-derived superoxide anions cause efficiency and selectivity of intercellular induction of apoptosis. Free Rad Biol Med 29 1260-1271 Hildenbrand K, Schulte-Frohlinde D (1997) Time-resolved EPR studies on the reaction rates of peroxyl radicals of polyfacrylic acid) and of calf thymus DNA with glutathione. Re-examination of a rate constant for DNA. Int J Radiat Biol 71 377-385 Howard JA (1978) Self-reactions of alkylperoxy radicals in solution (1). In Pryor WA(ed) Organic free radicals. ACS Symp Ser 69 413-432... 

Jonsson M, Lind J, Reitberger T, Eriksen TE, Merenyi G (1993) Free radical combination reactions involving phenoxyl radicals. J Phys Chem 97 8229-8233 Kapoor SK, Gopinathan C (1992) Reactions of halogenated organic peroxyl radicals with various purine derivatives, tyrosine, and thymine a pulse radiolysis study. Int J Chem Kinet 24 1035-1042 Khaikin Gl, Neta P (1995) Formation and reactivity of vinylperoxyl radicals in aqueous solutions. J Phys Chem 99 4549-4553... 

Sway Ml, Waddington DJ (1982) Reactions of oxygenated radicals in the gas phase, part 11. Reaction of isopropylperoxyl radicals with 2,3-dimethylbut-2-ene. J Chem Soc Perkin Trans 2 999-1003 Tamba M, Simone G, Quintiliani M (1986) Interactions of thiyl free radicals with oxygen a pulse radiolysis study. Int J Radiat Biol 50 595-600... 

The reduction and oxidation of radicals are discussed in Chapter. 6.3-6.5. That in the case of radicals derived from charged polymers the special effect of repulsion can play a dramatic role was mentioned above, when the reduction of poly(U)-derived base radicals by thiols was discussed. Beyond the common oxidation and reduction of radicals by transition metal ions, an unexpected effect of very low concentrations of iron ions was observed in the case of poly(acrylic acid) (Ulanski et al. 1996c). Radical-induced chain scission yields were poorly reproducible, but when the glass ware had been washed with EDTA to eliminate traces of transition metal ions, notably iron, from its surface, results became reproducible. In fact, the addition of 1 x 10 6 mol dm3 Fe2+ reduces in a pulse radiolysis experiment the amplitude of conductivity increase (a measure of the yield of chain scission Chap. 13.3) more than tenfold and also causes a significant increase in the rate of the chain-breaking process. In further experiments, this dramatic effect of low iron concentrations was confirmed by measuring the chain scission yields by a different method. At present, the underlying reactions are not yet understood. These data are, however, of some potential relevance to DNA free-radical chemistry, since the presence of adventitious transition metal ions is difficult to avoid. 

Schuchmann MN, Bothe E, von Sonntag J, von Sonntag C(1998) Reaction of OH radicals with benzo-quinone in aqueous solutions. A pulse radiolysis study. J Chem Soc Perkin Trans 2 791-796 Schuchmann MN, Schuchmann H-P, Knolle W, von Sonntag J, Naumov S, Wang W-F, von Sonntag C (2000) Free-radical chemistry of thiourea in aqueous solution, induced by OH radical, H atom, cx-hydroxyalkyl radicals, photoexcited maleimide.and the solvated electron. Nukleonika 45 55-62... 

Schuchmann MN, Naumov S, Schuchmann H-P, von Sonntag J, von Sonntag C (2005) 4-Amino-3Ff-pyrimidin-2-one ("isocytosine") is a short-lived non-radical intermediate formed in the pulse radiolysis of cytosine in aqueous solution. Radiat Phys Chem 72 243-250 Schulte-Frohlinde D, Hildenbrand K (1989) Electron spin resonance studies of the reactions of OH and SO4 radicals with DNA, polynucleotides and single base model compounds. In Minisci F (ed) Free radicals in synthesis and biology. Kluwer, Dordrecht, pp 335-359 Schulte-Frohlinde D, Behrens G, Onal A (1986) Lifetime of peroxyl radicals of poly(U), poly(A) and single- and double-stranded DNA and the rate of their reaction with thiols. Int J Radiat Biol 50 103-110... 

In the present chapter, it will be shown that in the polynucleotides reactions take place that are not apparent on the nucleotide level (Chap. 10). The increasing number of reactions available to polymer-derived radicals (Chap 9) renders the free-radical chemistry of polynucleotides and ODNs more complex than that of the corresponding nucleotides. Nevertheless, our understanding of mechanistic details is not on a much lower level, because with polymers the pulse radiolysis technique (Chap. 13.3) provides additional information. 

Hankiewicz E (1995) Hydroxyl radical-induced reactions in polyadenylic acid as studied by pulse radiolysis II. Reactions of primary radicals with oxidants. Bull Pol Acad Sci Chem 43 41-49 Hankiewicz E (1996) Hydroxyl radical-induced reactions in polyadenylic acid as studied by pulse radiolysis - Part III. Consecutive reactions. Radiat Phys Chem 47 61-65 Hankiewicz E (1998) Hydroxyl radical-induced reactions in polyadenylic acid as studied by pulse radiolysis. IV. Reactions of primary radicals with reductants. Bull Pol Acad Sci Chem 46 455-464 Hankiewicz E, Bothe E, Schulte-Frohlinde D (1992) Hydroxyl radical-induced reactions in polyadenylic acid as studied by pulse radiolysis, part. I. Transformation reactions of two isomeric OH-adducts. Free Rad Res Commun 16 391-400... 

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