Activation of Molecular Oxygen by Infrared Laser Radiation in Pigment-Free Aerobic Systems

A. A. Krasnovsky, Jr.^1*, N. N. Drozdova¹, A. V. Ivanov², and R. V. Ambartsumian³

¹Bach Institute of Biochemistry, Russian Academy of Sciences, Leninskii pr. 33, Moscow 119071, Russia; fax: (7-095) 954-2732; E-mail: phoal@mail.ru

²Blokhin Russian Cancer Center, Russian Academy of Medical Sciences, Kashirskoe Shosse 24, Moscow 115478, Russia

³Lebedev Physics Institute, Russian Academy of Sciences, Leninskii pr. 53, Moscow 119991, Russia

^* To whom correspondence should be addressed.

Received May 12, 2003; Revision received June 5, 2003

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With the goal of mimicking the mechanisms of the biological effects of low energy laser irradiation, we have shown that infrared low intensity laser radiation causes oxygenation of the chemical traps of singlet oxygen dissolved in organic media and water saturated by air at normal atmospheric pressure. The photooxygenation rate was directly proportional to the oxygen concentration and strongly inhibited by the singlet oxygen quenchers. The maximum of the photooxygenation action spectrum coincided with the maximum of the oxygen absorption band at 1270 nm. The data provide unambiguous evidence that photooxygenation is determined by the reactive singlet ¹Delta_g state formed as a result of direct laser excitation of molecular oxygen. Hence, activation of oxygen caused by its direct photoexcitation may occur in natural systems.

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KEY WORDS: singlet oxygen, oxygen photoactivation, infrared laser radiation

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