Radiation Chemistry of Ethylene Glycol, Meso‐Erythritol, 2‐Deoxy‐D‐Ribose and Alkyl Phosphates as DNA Model Compounds

Abstract

The γ‐radiolysis of ethylene glycol, meso‐erythritol, 2‐deoxy‐ribose, and alkyl phosphates has been studied in diluted (10−2 M), N2 O‐saturated, deoxygenated aqueous solutions. Products and their G values have been determined. Reaction schemes were derived from complete material balances. In the polyols the primary attack of the radiolytically formed OH radicals and H atoms leads to α, β‐dihydroxyalkyl radicals (A) which eliminate water to give substituted α‐carbonyl‐methyl radicals: (B) Disproportionation reactions of the radicals A and B yield products having the structural units COCHOH and COCH2 —. In ethylene glycol a chain reaction is induced, radical B abstracts a hydrogen from ethylene glycol to give acetaldehyde and radical A. In 2‐deoxy‐ribose the major attack is at C‐1. Products from this radical are 2‐deoxy‐ribonic acid and 2,5‐dideoxy‐ribonic acid. In the formation of the latter a rearrangement is involved. With trimethyl phosphate, the reaction of the solvated electron is only small (2 × 10s 1/mole sec), as shown by pulse radiolysis. Dimethyl and methyl phosphates do not react with the solvated electron to a measurable extent. The attack of the OH radical apparently leads to a cleavage of the alkyl phosphate linkage.

A Mechanistic Study of the Effects of Antioxidants on the Formation of Malondialdehyde‐Like Products in the Reaction of Hydroxyl Radicals with Deoxyribose

“…If the radicals CDR* react also with the MDA-like products this will explain partially the deviation from a linear dependence of the yield on the dose. The G value of 2-hydroxy-oxa-cyclohexan-4-one reported earlier is 1.15 [21] whereas we measured a G value of 0.70 of MDA-like products at the same, 8 mm, DR concentration. The only difference between these experiments is that the literature value was measured in a g source with a dose rate of 4500 Gy h À1 whereas the present measurements used a g source with a dose rate of 180 Gy h À1 .…”

“…Adapted from ref. [21], [22]: 1) In the product of Reaction i) a hydrogen atom was deleted from the product which was clearly a typo in the original scheme as one carbon atom had five bonds. 2) Radical IX, formed in Reaction t), was radical VI in the original scheme, but it differs from radical VI formed in Reaction h)).…”

“…The yield of MDA formed in Reaction (7) is less than 2 %. [21] On the other hand the yield of 2-hydroxy-oxa-cyclohexan-4-one and 2,5-dihydroxy-oxa-cyclohexan-4-one are 19 and < 3 %, respectively. Both these compounds form MDA-like products via ring opening.…”

“…Both these compounds form MDA-like products via ring opening. Schulte-Frohlinde and von Sonntag suggested the following reaction scheme (see Scheme 1) to explain the product yields observed when COH radicals are formed in a solution containing 8 mm DR. [21,22] The MDA-like products 2-hydroxy-oxa-cyclohexan-4-one (6) and 2,5-dihydroxy-oxa-cyclohexan-4-one (3) in Scheme 1 are formed via the abstraction of the H atom from C3 of DR.…”

Food irradiation‐chemistry and applications∗

“…During irradiation, in the presence of water, carbohydrates are attacked by .OH radicals. They abstract hydrogen of the C-H bond forming a-hydroxyl (i) and a,/3-dihydroxy (ii) radicals (39,40).…”