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Journal archive > 2009 > N 3 May-June

SPIN-CATALYSIS IN THE PROCESSES OF PHOTO- AND BIOACTIVATION OF MOLECULAR OXYGEN

B. F. Minaev

Bohdan Khmelnytsky National University, Cherkasy, Ukraine;
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Rational explanation of the mechanisms of bioactivation of molecular oxygen by enzymes is impossible without understanding more simple mechanisms of the O2 photoactivation in collision complexes of gases and solvents. Production of peroxides in oxidases and more complicated oxidation processes by molecular oxygen are spin forbidden reactions and bioactivation of dioxygen is connected with enzymatic spin-catalysis by acceleration of the triplet-singlet (T-S) quantum transitions. Internal magnetic perturbations in the free oxygen molecule and in O2 complexes with solvents or with coenzyme in biopolymers bear characteristic entirely similar features and removal of spin prohibition on T-S transitions is quantified by some common physical mechanisms. An account of specific spin-orbit coupling (SOC) in the open ?g-shell of dioxygen permits to explain the T S transitions intensity of the red atmospheric band in the O2 molecule and the selective enhancement of the radiative а1?g?Х3?-g transition intensity in various solvents (P). Charge transfer contribution Р+ О2- leads to increase of SOC between the Т-S oxygen states that enhances the О2(а1?g) quenching. Similar T-S transitions mechanisms and SOC enhancement is realized upon dioxygen activation by enzymes of the glucoseoxidase type. Three electronic mechanisms of reductive bioactivation of O2 by oxidases coenzymes are considered on the basis of physical mechanisms of the O2 photoactivation. They include intermediate stages of the superoxide and peroxide ion formation. Study of the O2 activation mechanisms by T-S transitions in enzymatic complexes of dioxygen binding open new potentialities in biotechnology and medicine.

Key words: singlet oxygen, spin-orbit coupling, exchange interaction, superoxide ion, glucose oxidase, copper amine oxidases, cytochromoxidases, hemoglobin, myoglobin, photodynamic therapy.

The original article in Russian is available for download in PDF format.

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