Ozone degradation of ribonucleic acid (RNA)

RNA (ribonucleic acid) from Torula utilis was subjected to ozonization both in aqueous solution and in the solid state. The ozonization in aqueous solution was followed by spectrophotometry and polarimetry. The latter technique was extremely useful in following the RNA degradation as function of the amount Of 03 added to the solution. The RNA specific optical rotation drops to zero following a linear relationship with the amount Of 03 added to the solution. The loss in the chirooptical properties of RNA and the reduction of the specific viscosity of the solution were interpreted in terms of denaturation of the RNA macromolecule and in terms of oxidation of the purine and pyrimidine bases which are the pendent groups of RNA macromolecule. The polarimetric measurement of the reaction between O-3 and RNA has also allowed the measurement of the stoichiometric molar ratio at which the RNA optical rotation vanishes completely. This RNA/O-3 molar ratio was found to lie in the range of 2.0-1.5, suggesting that the RNA denaturation is complete when at least 50 % of the RNA monomeric units have reacted with O-3. The RNA/O-3 molar ratio was also checked iodometrically and found about 1.3. The differences between the polarimetric and iodometric stoichiometry are discussed. RNA ozonized in powder form in the solid state was found to be significantly less reactive than in the case of the aqueous solution. After 24 h ozonization in the solid state, RNA shows a certain reduction in the specific optical rotation (much less compared to RNA ozonized in aqueous solution at the equivalent nominal molar ratio) suggesting the occurrence of a certain degree of denaturation. The FT-IR spectra of the ozonized RNA are discussed in comparison to the reference pristine RNA spectrum. (c) 2005 Elsevier Ltd. All rights reserved.