Reactions of hydroxyl radical (˙OH) and oxide radical anion (O˙) with 2-aminopurine in aqueous medium

Manoj, P. ; Mohan, H. ; Manoj, V. M. ; Mittal, J. P. ; Aravindakumar, C. T. (2006) Reactions of hydroxyl radical (˙OH) and oxide radical anion (O˙) with 2-aminopurine in aqueous medium Research on Chemical Intermediates, 32 (9). pp. 817-826. ISSN 0922-6168

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Official URL: http://www.ingentaconnect.com/content/vsp/rci/2006...

Related URL: http://dx.doi.org/10.1163/156856706778938446

Abstract

Pulse radiolysis has been used to investigate the reaction of hydroxyl radical (·OH) and oxide radical anion (O·-) with 2-aminopurine (2AP), a fluorescent analogue of adenine, in aqueous medium. The second-order rate constant for the reaction of ·OH with 2AP was determined to be 3 × 109 dm3 mol-1s-1 and for the reaction of O·- it was 7.1 × 108 dm3 mol-1s-1. The transient absorption spectrum obtained in the reaction of ·OH at pH 7 has absorption maxima at 370 and 470 nm. The spectrum undergoes a time-dependent transformation at higher time-scale. The intermediate species was found to react with N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD). The yield of TMPD·+ was calculated in terms of G(TMPD·+) to be 3.3 × 10-7 mol J-1 at pH 7. The ·OH reactions were also carried out at pH 10 and the transient absorption spectra have λmax at 400 and 480 nm. The transient spectra obtained in the reaction of O·- at pH ≈14 have maxima at 400 and 480 nm. The transient intermediate species at pH 7 are assigned to the formation of 2AP-4-OH· (54%), 2AP-5-OH· (7%) and 2AP-8-OH· (39%) based on the spectral evidence and TMPD·+ build-up. Both 2AP-4-OH· and 2AP-5-OH· undergo OH- elimination to form a radical cation. At higher pH (pH 10), the dehydration reaction of these OH-adducts leads to a N-centered radical (2AP-N(9)·, 71%). Formation of 2AP-8-OH· (29%) is also proposed at this pH. In the reaction of O·- with 2AP, it is proposed that a similar nitrogen centered 2AP-N(9)· radical is formed by an electron-transfer reaction at N(9).

Item Type:Article
Source:Copyright of this article belongs to Springer.
Keywords:Pulse Radiolysis; Radicals; 2-aminopurine; Reaction Kinetics
ID Code:84966
Deposited On:28 Feb 2012 11:59
Last Modified:28 Feb 2012 11:59

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