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.