时 间：2024年12月7日（周六）09:30
地 点：深圳大学粤海校区南区致原楼1214
报告人：Oleg VASYUTINSKII
Email: osv@pms.ioffe.ru
Ioffe Institute Russian Academy of Sciences, Russia
ABSTRACT
The lecture presents the review of recent studied that have been carried out in the Ioffe Institute, Russian Academy of Sciences in the field of photodynamics of photoseensitizers (PS) and biomolecules in solutions, living cells, and on organic surfaces by means of time-resolved fluorescence polarization spectroscopy and fluorescence lifetime imaging microscopy (FLIM).
Detailed investigations of the fluorescence of coenzymes NADH and FAD in water-alcohol mixtures (methanol, ethanol, propylene glycol) and of a photosensitizer Chlorin e6 that is now widely used for photodynamics therapy of oncology diseases and for photodynamic purification of organic surfaces have been carried out [1]. A significant increase of fluorescence quantum yield in NADH and FAD with increase of alcohol concentration was observed. A new model has been developed for elucidation of the effect observed. The model takes into consideration several possible energy transfer channels in the coenzyme excited states after excitation with ultrashort laser pulses. The model results to a new expression for time-dependent intensity of fluorescence from the lowest excited state of the coenzyme and allows for separation of the fast sub-nanosecond nonradiative relaxation processes from more slow nanosecond radiative and nonradiative relaxation processes. The mechanisms of these relaxation processes were analyzed for each type of coenzymes under study.
Fluorescence anisotropy of PS Chlorin e6 in various solutions and the dependence of the fluorescence decay time on microenvironmental conditions in solutions and living cells have been investigated. A significant difference between the fluorescence anisotropy under one- and two-photon laser excitation has been observed within wide excitation spectrum and possible reasons for the difference of the fluorescence anisotropies observed have been analyzed [2]. We also observed a significant gain of the Chlorin e6 fluorescence quantum yield and a non-monotonous increase of the fluorescence decay time in solution with pH in the range of 5-7 [3]. The effects observed were then applied for investigation of PS Chlorin e6 distribution with FLIM in living cells and for the mapping of pH distribution inside cells. A new effective method of singlet oxygen generation on organic surfaces has been developed [4]. The method is based on the excitation of a PS dissolved in an appropriate solution and pulverized on the surface by a gas spay. Singlet oxygen generation quantum yield and PS Chlorin e6 photobleaching on various organic and non-organic surfaces were under study. An intriguing decrease by several decades of the photobleaching rate of PS on organic surfaces with respect to non-organic surfaces has been observed. The investigation of the photobleaching rate allowed for understanding of the photobleaching mechanism. As was shown, the PS photobleaching on organic surfaces occurred mainly due to interaction with oxygen molecules.
REFERENCES
[1] I. Gorbunova et al, J. Photochem. Photobiol. A: Chemistry, 436, 114388, 2023.
[2] I. Gorbunova et al, Photonics, 10, 9, 2023.
[3] A. Belashov et al, J. Photochem. Photobiol. B: Biology, 243, 112699, 2023.
[4] A. Zhikhoreva et al, J. Photochem. Photobiol. B: Biology, 228, 112395, 2022.
Prof. Oleg S. Vasyutinskii is a renowned scholar in the fields of quantum chemistry and physics. He is a member of the honorary committee of the International Symposium on Quantum Systems Chemistry and Physics, and has participated in the work of several international scientific committees, including the Molecular Dynamics Conference and the conferences on photon, electron, and atomic collisions. He has served as a member of the Russian Academy of Sciences and as a member of the Research Council and the dissertation and postdoctoral thesis committees at the Ioffe Institute.
Some of Prof. Vasyutinskii's major achievements include: 1. Predicting and experimentally observing the spin polarization of atomic fragments produced in molecular photolysis, and developing related quantum mechanical theory. 2. Observing for the first time the extremely high depolarization cross section of the alkali metal atoms with spin orientation in collisions with alkali metal halide molecules. 3. Developing a quantum mechanical method for describing the angular momentum polarization of photo-fragmentation, and observing for the first time the angular distribution of the spin polarization of photo-fragments. 4. Proposing a new method for analyzing polarization in synchrotron radiation and experimentally verifying it in the ultraviolet spectrum range. In addition, he has given more than 50 invited talks at international conferences and organized several important international conferences, promoting research and cooperation in the fields of quantum chemistry and physics.
