REVIEW: Primary Mechanisms of Photoactivation of Molecular Oxygen. History of Development and the Modern Status of Research

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A. A. Krasnovsky, Jr.^1,2

¹Bach Institute of Biochemistry, Russian Academy of Sciences, Leninskii pr. 33, 119071 Moscow, Russia

²Biological Faculty, Lomonosov Moscow State University, 119899 Moscow, Russia; E-mail: phoal@mail.ru

Received June 1, 2007

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This review starts from a brief historical account devoted to the principles of the Bach-Engler peroxidation theory and experiments and ideas which led A. N. Bach to its creation. Then, the discovery of photodynamic action is described, which was shown to result from pigment photosensitized activation of molecular oxygen. The dramatic history of mechanistic studies of oxygen photoactivation is reviewed starting from the Bach-Engler peroxidation theory to the hypothesis of moloxide, discovery of singlet oxygen and free radicals and, then, to modern views on the primary photoactivation processes. The origin of widely used division of photodynamic processes into type I and type II and the relation of these processes to the nature of the primary photochemical reactions of photosensitizers are discussed. New definitions of these reactions are proposed on the basis of the mechanisms of oxygen photoactivation. Photographs of the scientists who greatly contributed to the development of this field of research are presented.

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KEY WORDS: peroxidation of organic compounds, photodynamic action, singlet oxygen, free radicals, oxygen dimols, triplet state, oxygen activation

DOI: 10.1134/S0006297907100057

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