Phosphate radicals

Free-radical intermediates in the oxidation of a series of quinol phosphates by permanganate at pH 11.7 have been characterised by an esr rapid-mixing technique . Clearly a one-equivalent oxidation step to give a semiquinone phosphate radical operates in this case. 

E.s.r. showed that, X. ray irradiation of tetraalkyldiphosphine diphosphides gave phosphoranyl radicals with t.b.p. structures (39).114 A structure has been assigned to phosphiny1hydrazy1s (40). The dimethy1 ami no radical was particularly persistent.115 The e.s.r. parameters of the electrogenerated pyrazine radical cations (41) have been recorded.116 The spectra of a stable furanyl phosphate radical adduct117 and a phenalene radical anion which involves injection of spin density into half an attached cyclophosphazene ring,11 are reported. 

Formation of products of rearrangement may be looked upon as occurring by way of loss of hydrogen from a carbon atom which is not adjacent to the carbon atom holding the phosphate radical. This results in the transitory formation of a cyclopropane or cyclobutane ring which then opens to yield the rearranged olefin. Thus, in the copolymerization of isobutylene with 2-butene, the intermediate ester may react in the following ways ... 

Hole transfer from guanine to sites of lower ionization potential such as intercalators occurs and is discussed later. ESR results also show that sugar and phosphate radicals are produced in smaller abundance [3, 9, 20-23] than expected from the 50% fraction of ionization that occurs on the sugar-phosphate backbone. This is evidence for hole transfer from the sugar ion-... 

Maruthamuthu, P. and Neta, P, Phosphate radicals spectra, acid-base equilibria, and reactions with inorganic compounds, /. Phys. Chem., 82, 710-713, 1978. 

Nakashima, M. and Hayon, E., Rates of reaction of inorganic phosphate radicals in solution, /. Phys. Chem., 74(17), 3290-3291, 1970. 

Marcus RA (1999) Electron transfer past and future. In Jortner J, Bixon M (eds) Electron transfer -from isolated molecules to biomolecules, part 1. Wiley, New York, pp 1-6 Martin RF, Anderson RF (1998) Pulse radiolysis studies indicate that electron transfer is involved in radioprotection by Floechst 33342 and methylproamine. Int J Radiat Oncol Biol Phys42 827-831 Maruthamuthu P (1980) Absolute rate constants for the reactions of sulfate, phosphate and hydroxyl radicals with monomers. Macromol Chem Rapid Commun 1 23-25 Maruthamuthu P, Neta P (1977) Reactions of phosphate radicals with organic compounds. J Phys Chem 81 1622-1625... 

The electrophilic S04, preferentially adds to an electron-rich position of the substrate, C(5) in the case of pyrimidines. This must also hold for the phosphate radical [reaction (16)]. Here, however, the radical observed by EPR is the C(61-adduct radical, and it has been concluded that a rapid 1,2-shift leads to this thermodynamically more stable radical [reaction (17) Behrens et al. 1988], At pH > 6.5, the transformation reaction (17) is sufficiently slow to be intercepted by a spin trap, and the adduct to the primary radical formed in reaction (16) is indeed observed (Hildenbrand 1995). 

The reason for the greater stability of the phosphate radical-adduct compared the sulfate radical-adduct is due to effects discussed in Chapter. 6.9. 

For a study on the reaction of pyrimidine bases with the phosphate radical in the presence of peroxodiphosphate see Kumar et al. (2000) Kumar and Adina-rayana (2001). 

Mundy CJ, Colvin ME, Quong AA (2002) Irradiated guanine a Car-Parinello molecular dynamics study of dehydrogenation in the presence of an OH radical. J Phys Chem A 106 10063-10071 Murata-Kamiya N, Kamiya H, Muraoka M, Kaji H, Kasai H (1998) Comparison of oxidation products from DNA components byy-irradiation and Fenton-type reactions. J Radiat Res 38 121-131 Nabben FJ, van der Stroom HA, Loman H (1983) Inactivation of biologically active DNA by isopropanol and formate radicals. Int J Radiat Biol 43 495-504 Nakashima M, Hayon E (1979) Rates of reaction of inorganic phosphate radicals in solution. J Phys Chem 74 3290-3291... 

Glycol phosphates have been found to eliminate either water or phosphate depending on the radical structure (Samuni and Neta, 1973b). For example hydrogen abstraction from glycerol-1-phosphate yields three different radicals which behave differently. The 3-phosphate radical eliminates water at a moderate rate with... 

These compounds inhibit the hydrolysis of the neurotransmitter acetylcholine by the enzyme acetylcholinesterase within the mammalian nervous system (Zwiener and Ginsburg, 1988). This inhibition causes acetylcholine levels to rise, thus causing cholinergic hyperstimulation at muscarinic and nicotinic receptors. There are important differences in the way carbamates and OPs bind to acetylcholinesterase as well as their abililty to affect the CNS. Carbamates are reversible inhibitors of cholinesterase enzymes. Carbamates create a reversible bond to the cholinesterase enzyme through carbamylation which can spontaneously hydrolyze, reversing toxicity. Carbamate poisoning produces toxicity similar to that of OPs however, the toxicity is usually of a shorter duration and less severe in nature (Lifshitz et al, 1994). In contrast, OPs inhibit cholinesterase via an irreversible bond of phosphate radicals... 

The symbol [i Ppo Ail needs to be explained further, since this mode of subscripting is used in the unit processes part of this book. First, [ ] is read as the concentration of The symbol sp stands for species and its first subscript, PO4, stands for the type of species, which is the PO4 radical. The second subscript, Al, stands for the reason for the existence of the type of species. In other words, the use of alum (the Al) is the reason for the existence of the phosphate radical, the type of species. 

Write the molar mass balance for the total molar concentration of the phosphate radical. 

From the previous equations, a molar mass balance on the phosphate radical may be performed. Let ippo Peiii represent the species in solution containing PO4 species, nsing a ferric salt as the precipitant. (Note the Felll as the second subscript, indicating that a ferric salt is used.) Therefore,... 

As described earlier, formation of substantially increased amounts of DNA-backbone-sugar and -phosphate radicals are observed in argon and oxygen ion-beam irradiated hydrated DNA samples relative to those found with low LET / irradiation.The usual mechanism suggested for formation of sugar radicals, i.e. hole deprotonation from direct ionization of the cannot explain the... 

Faster protonation rates were observed in the self-protonation of aromatic carboxylic radical anions (kprot > 10 m s ) [216] and (R)-(—)-l,l -biphenyl-2,2 -diyl hydrogen phosphate radical anion (kprot = 5.7 x 10 m s ) [217]. 

From these studies it is clear that damage to DNA is broader than initially expected from the two-component model since products on aU four bases and the sugar moiety have been proposed. These proposals include sugar and phosphate radicals despite early failures to detect radicals in the backbone of the DNA double helix. More work is requited in order to determine the exact identity of the radical products since structural information is difficult to obtain through the methods implemented thus far. 

Fructose-l,6-diphosphate (FDP) may also be converted into dihydroxyacetone phosphate (DHAP), which is also synthesized from glyceraldehyde-3-phosphate (GAP). The dihydroxyacetone phosphate (DHAP), thus obtained, is converted into glycerol-3-phosphate (G-3-P), in the presence of cytosolic NADH. The latter gives away one phosphate radical to ADP to generate ATP and glycerol (Chart 1). Thus in the above process, one mole of glucose is converted into two moles of pyruvate with a net gain of two moles of ATP [1],... 

Hydroxyl radical, phosphate radical anion, and sulfate radical anion add to the 5 position of oxazole <90JPC1887>. The hydroxyl radical adduct is stable at pH 5-9, but reacts further above or below that range to give a ring-opened product (Scheme 22). 

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