The Ultrasonic Degradation of Thymine

Abstract

Chemical reactions that occur in liquids subjected to ultrasonic irradiation (insonation) of sufficient intensity to induce cavitation, have been attributed (1) to a number of processes; the reactive species produced in water and aqueous solutions during cavitation are hydroxyl radicals (2), hydrated electrons (3), hydroperoxyl radicals (4), and hydrogen atoms (5). These species are also produced during the radiolysis of water and in this paper we show that the sonolysis of thymine may be correlated with its radiolytic degradation.The radiolysis of aqueous thymine solutions has been the subject of numerous investigations and studies by Teoule and co-workers (6-11) identified more than 26 products formed during 60Co-y irradiation. Hydroxyl radicals produced by ionizing radiation react with thymine to give 6-hydroxy-5,6-dihydro-5-thyml and 5-hydroxy-5,6-dihydro-6-thymyl radicals; hydrogen atoms (or e,,-+ H,O+) react with thymine to give (5-uracyl)methyl, 5,6-dihydro-5-thyml, and 5,6-dihydro-6-thyml radicals (1 1). These radicals react. very rapidly with dissolved oxygen (e.g. K(TOH + 0,) = 1.5 x lo9 M -,l S-l (12) to produce hydroperoxide radicals which are reduced to the hydroperoxyhydroxydihydro products ( Fig. 1) (5 and 6) and the hydroperoxide products (7, 5-hydroperoxy-5,6-dihydrothymine, cis-and trans-6-hydroperoxy-5,6-dihydrothy-'For a preliminary communication see ref. 27. mine). The peroxide products are relatively unstable (11) and decompose to give various alcohols (cis-and trans-9, 8, 5-hydroxy-5,6-dihydrothymine, cis-and trans-6-hydroxy-5,6-dihydrothymine). In addition, the hydroxyhydroperoxides decompose to give 5-hydroxy-5-methylbarbituric acid and N-formyl-N'-pyruvylurea and the remaining products result from decomposition of N-formyl-N'-pyruvylurea to give pyruvylurea, urea, and formylurea.El'piner (1) was the first to investigate the effect of ultrasound on purine and pyrimidine bases. He insonated (500 kHz) aqueous solutions of the bases at an intensity of 5 W cm-2 in the presence of various gases. In the U.V. spectra of the insonated bases, the absorption maxima were reduced and the minima shifted to longer wavelengths. Uracil was found to be the most sensitive, adenine and guanine less so. In a later study, El'piner and Sokol'skaya (13) insonated aqueous solutions of cytosine, uracil, thymine, and adenine and investigated the products of sonolysis chromatographically but no degradation products were identified. The reduction in intensity of the U.V. absorption band of the various purines and pyrimidines was attributed to ring cleavage (1). Since the effect was considerably reduced in the presence of gases other than oxygen, it was suggested that molecular oxygen played an important role and a smaller oxidative role was assigned to hydroxyl radicals.This study was undertaken to reinvestigate the sonolysis of aerated aqueous thymine solutions Can. J. Chem. Downloaded from www.nrcresearchpress.com by 34.210.69.67 on 05/11/18For personal use only.

The sonolysis of cytosine and thymine

“…Ultrasonically induced chemical reactions of biologically important molecules related to RNA and DNA have been reported previously (1)(2)(3)(4). 2 In this paper we report the results of the sonolytic degradation of the pyrimidine bases cytosine and thymine.…”

“…2 In this paper we report the results of the sonolytic degradation of the pyrimidine bases cytosine and thymine. Results of such studies on thymine have been reported earlier (2); however, analyses of products were carried out using tlc techniques.…”

“…2 In this paper we report the results of the sonolytic degradation of the pyrimidine bases cytosine and thymine. Results of such studies on thymine have been reported earlier (2); however, analyses of products were carried out using tlc techniques. This study reports an attempt to determine whether gc-ms techniques cou!d reveal any additional compounds not observed in the previous work (2), and allows a direct comparison with the results obtained with cytosine.…”

Enzymatic Assisted Ultrasonic Pretreatment’s Effect on Poplar Pulp Properties

“…It has been proposed that the ultrasound-assisted reactions in aqueous solutions involve free-radical mechanisms because of the formation of hydroxyl radicals (HO·) with oxidation capabilities (Weissler 1959(Weissler , 1962Anbar and Pecht 1964;Reifsneider and Spurlock 1973;Mead et al 1975;McKee et al 1977). These proposals of free-radical formation have been confirmed via spin-trapping techniques (Makino et al 1982(Makino et al , 1983 Enzymatic treatments have gained recognition in the pulp and papermaking industry because they are stereo specific, nontoxic, environment friendly, and energy conserving alternatives (Madhu and Chakraborty 2017).…”

The sonolysis of uracil

“…reactions can be initiated by Aliquots (50 mL) of aqueous solutions were insonated in a glass Waves in liquids if the ~C O U S~~C intensity is sufficient with a Mylar 5 0 0~ plastic window (3,22). A gas inlet was to induce cavitation (1,2).…”