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4The 30th International Conference on Advanced Laser Technologies B-I-6
ALT'23
Time-resolved measurements of singlet oxygen phosphorescence in the solvents lacking hydrogen atoms. Application to the study of biologically important compounds
A. Krasnovsky, Jr.*, A. Benditkis
FRC of biotechnology RAS, Leninskii pr., 33, bld. 2, Moscow, 199071, Russia
*phoal@mail.ru
In solvents, molecules of which do not contain hydrogen atoms, the lifetime of singlet oxygen is known to reach several tens of milliseconds. Therefore, the use of these solvents is exceptionally efficient for studying the properties of singlet oxygen and measuring the intrinsic IR phosphorescence of singlet oxygen at 1270 nm, which is known to be the most reliable method for singlet oxygen detection. However, for phosphorescence measurements in these solvents, one needs a special equipment that allows recording slowly decaying phosphorescence under a very low rate of generation of singlet oxygen. We have recently succeeded in constructing such spectrometers for steady-state and time-resolved phosphorescence measurements that are based on the use of cw and pulsed diode lasers and LEDs [1]. For kinetic measrements, the methods of time-resolved photon counting and time-correlated single photon counting were apllied with the accumulation and averaging of a phosphorescence signal after hundreds of thousands of exciting laser (LED) flashes. These set-ups open up new amazing research opportnities, some of which will be presented in our talk. For instance, the lifetimes of singlet oxygen have been measured in a range of solvents, in which hydrogen atoms are replaced by clorine, fluorine or iodine. It was shown that in aerated solvents of this type singlet oxygen is quenched by dissolved triplet oxygen molecules and the quenching rate constants were determined. The spectrometers are very efficient for excitation of photosensitizers absorbing light in violet, blue and near ultraviolet regions. In particular, this allowed us to reveal the ability of phytofluene, which is the universal precursor of all natural colored carotenoids, to efficiently generate singlet oxygen. It was found that colored C40 carot-enoids that are usually considered as strong quenchers of singlet oxygen, photosensitize its formation upon photoexcitation.
Application of these spectrometers to studies of chlorophylls and bacteriochrorophylls, which are rapidly destroyed under light will also be discussed.
This work was partially supported by the Russian Science Foundation, Project # 23-65-10005.
[1] A. Krasnovsky, A. Benditkis, A. Kozlov. Biochemistry (Moscow), vol. 84, pp. 153-163 (2019) doi: 10.1134/S0006297919020068
[2] A. Ashikhmin, A. Benditkis, A. Moskalenko, A. Krasnovsky, Biochemistry (Moscow), vol. 85, pp. 773-780 (2020) doi: 10.31857/S0320972520070052
[3] A. Benditkis, A., Kozlov, S. Goncharov, A. Krasnovsky, J. Opt. Soc. Am. B, vol. 38, 3410-3416 (2021); doi.org/10.1364/JOSAB.432684
[4] A. Ashikhmin, A. Benditkis, A. Moskalenko, A. Krasnovsky, Biochemistry (Moscow), vol. 87, pp. 1169-1178. doi: 10.1134/S0006297922100108
[5] A. Benditkis A., Ashikhmin, A. Moskalenko, A. Krasnovsky, Photosynth. Res., submitted
