Ozone degradation of biological macromolecules: Proteins, hemoglobin, RNA, and DNA

The reactions of ozone with a series of biological macromolecules are reviewed. With proteins, ozone causes the oxidation or the ozonolysis of certain amino acid residues, for instance, tryptophan, tyrosine and cysteine. As a result of this attack the protein molecules undergo changes in their usual folding and binding ability and are denaturated as shown by polarimetric or chirooptical measurements and by the inhibition of their biological activity. In any case viscosimetric measurements show that the amide bond of proteins is resistant to the ozone attack and no chain scission phenomena occur as in the case of radiolysis of proteins. A special protein is hemoglobin which is characterized by a complex tetrameric structure where each of the 4 polypeptide chains binds a prosthetic haeme group having a porphyn structure. It is shown by a series of systematic studies on model molecules, on the isolated prosthetic groups, on isolated hemoglobin (methemoglobin) and on whole blood that the action of ozone is specifically directed toward the prosthetic haeme groups of this protein causing their fission into oxidized degradation products. Therefore, ozone is selectively bound by haeme groups of hemoglobin. RNA and DNA are very reactive with ozone in comparison to proteins. The ozone attack is directed mainly toward the nucleic acids. The stoichiometric ratio between ozone and RNA monomeric unit has been determined both polarimetrically and iodometrically. The complete collapse of RNA supramolecular structure occurs at a RNA/O-3 molar ratio between 2.0 and 1.5. Also DNA appears to be highly reactive with ozone, reactivity which is similar to RNA in all aspects.