2017-09

Structure-based theory of light-harvesting in Photosystem II.

2017-09-29 14:00

rytoj, 2017 m. rugsėjo 29 d., penktadienį, 14.00 Fizikos Fakulteto 510-oje auditorijoje įvyks prof. Thomas Renger iš Johannes Kepler Universität Linz, Institute of Theoretical Physics, Department of Theoretical Biophysics seminaras.

Tema: Structure-based theory of light-harvesting in Photosystem II.

Santrauka:

Two challenges in the simulation of excitation energy transfer and optical spectra of pigment- protein complexes are the equal magnitude of the excitonic and the exciton-vibrational coupling and the structure-based parametrization of the Hamiltonian of the pigment-protein complex (for review see ref. 1). We have calculated optical transition energies of pigments in their binding site in the protein (site energies) and excitonic couplings of various subunits of photosystem II (PSII) cores [2-4] by using a combination of quantum chemical and electrostatic calculations, where the site energies have been refined from a calculation of optical spectra of these subunits.

The recent results on site energies for the CP43 and D1D2 subunits largely confirm our earlier predictions [5,6] that were solely based on fits of optical spectra. In case of CP47 the analysis of circularly polarized fluorescence spectra suggests that the lowest excited state of this subunit is localized on a

different Chl than was previously assumed [3]. This new assignment, however, does not change the transfer-to-the-trap limited characteristics of the light-harvesting dynamics in PSII core complexes, inferred earlier [5] from structure-based calculations. The first unambiguous experimental verification of this prediction was recently obtained from VIS/IR pump-probe spectroscopy on oriented single crystals of PSII core complexes [7]. The RC is found to be a very shallow trap of excitation energy that utilizes entropy (smaller number of pigments in the RC than in the antenna) for photoprotection.

For open reaction centers (RCs) the electron transfer is so fast that every exciton that reaches the reaction center is trapped by primary charge transfer, whereas for closed RCs the excitons can escape the RC and are quenched in the antenna. I will provide an overview of our attempts to model light-harvesting in photosystem II and present also a summary of recent theory developments in our group, concerning a non-equilibrium Modified Redfield theory of optical spectra [8], a multistate theory of hole-burning [9], and a theory of the non-conservative nature of excitonic CD spectra in the Qy spectral region [10].

References

[1] T. Renger, F. Müh (2013) Phys. Chem. Chem. Phys. 15, 3348.

[2] F. Müh, M. Plöckinger, H. Ortmayer, M. Schmidt am Busch, D.

Lindorfer, J. Adolphs, T. Renger (2015) J. Photochem. Photobiol. B.

152, 286.

[3] J. Hall, T. Renger, F. Müh, R. Picorel, E. Krausz (2016) Biochim.

Biophys. Acta 1857, 1580-1593.

[4] F. Müh, M. Plöckinger, T. Renger (2017) J. Phys. Chem. Lett. 8, 850.

[5] G. Raszewski, T. Renger (2008) J. Am. Chem. Soc. 130, 4431.

[6] Y. Shibata, S. Nishi, K. Kawakami, J. R. Shen, T. Renger (2013) J.

Am. Chem. Soc. 135,

6903.

[7] M. Kaucikas, K. Maghlaoui, J. Barber, T. Renger, J. van Thor (2016) Nature Comm. 7,

13977.

[8] T.-C. Dinh, T. Renger (2016) J. Chem. Phys. 142, 034104.

[9] J. Adolphs, M. Berrer, T. Renger (2016) J. Am. Chem. Soc. 138, 2993.

[10] D. Lindorfer, F. Müh, T. Renger (2017) Phys. Chem. Chem. Phys.

19, 7524.


Seminaras 2017 09 29

2017-09-25 14:22

2017 m. rugsėjo 29 d., penktadienį, 14.00 Fizikos Fakulteto 510-oje auditorijoje įvyks prof. Thomas Renger iš Johannes Kepler Universität Linz, Institute of Theoretical Physics, Department of Theoretical Biophysics seminaras.

Tema: Structure-based theory of light-harvesting in Photosystem II.

Santrauka:

Two challenges in the simulation of excitation energy transfer and optical spectra of pigment- protein complexes are the equal magnitude of the excitonic and the exciton-vibrational coupling and the structure-based parametrization of the Hamiltonian of the pigment-protein complex (for review see ref. 1). We have calculated optical transition energies of pigments in their binding site in the protein (site energies) and excitonic couplings of various subunits of photosystem II (PSII) cores [2-4] by using a combination of quantum chemical and electrostatic calculations, where the site energies have been refined from a calculation of optical spectra of these subunits. The recent results on site energies for the CP43 and D1D2 subunits largely confirm our earlier predictions [5,6] that were solely based on fits of optical spectra. In case of CP47 the analysis of circularly polarized fluorescence spectra suggests that the lowest excited state of this subunit is localized on a
different Chl than was previously assumed [3]. This new assignment, however, does not change the transfer-to-the-trap limited characteristics of the light-harvesting dynamics in PSII core complexes, inferred earlier [5] from structure-based calculations. The first unambiguous experimental verification of this prediction was recently obtained from VIS/IR pump-probe spectroscopy on oriented single crystals of PSII core complexes [7]. The RC is found to be a very shallow trap of excitation energy that utilizes entropy (smaller number of pigments in the RC than in the antenna) for photoprotection. For open reaction centers (RCs) the electron transfer is so fast that every exciton that reaches the reaction center is trapped by primary charge transfer, whereas for closed RCs the excitons can escape the RC and are quenched in the antenna. I will provide an overview of our attempts to model light-harvesting in photosystem II and present also a summary of recent theory developments in
our group, concerning a non-equilibrium Modified Redfield theory of optical spectra [8], a multistate theory of hole-burning [9], and a theory of the non-conservative nature of excitonic CD spectra in the Qy spectral region [10].

References

[1] T. Renger, F. Müh (2013) Phys. Chem. Chem. Phys. 15, 3348.

[2] F. Müh, M. Plöckinger, H. Ortmayer, M. Schmidt am Busch, D. Lindorfer, J. Adolphs, T. Renger (2015) J. Photochem. Photobiol. B. 152, 286.

[3] J. Hall, T. Renger, F. Müh, R. Picorel, E. Krausz (2016) Biochim. Biophys. Acta 1857, 1580-1593.

[4] F. Müh, M. Plöckinger, T. Renger (2017) J. Phys. Chem. Lett. 8, 850.

[5] G. Raszewski, T. Renger (2008) J. Am. Chem. Soc. 130, 4431.

[6] Y. Shibata, S. Nishi, K. Kawakami, J. R. Shen, T. Renger (2013) J. Am. Chem. Soc. 135,

6903.

[7] M. Kaucikas, K. Maghlaoui, J. Barber, T. Renger, J. van Thor (2016) Nature Comm. 7,

13977.

[8] T.-C. Dinh, T. Renger (2016) J. Chem. Phys. 142, 034104.

[9] J. Adolphs, M. Berrer, T. Renger (2016) J. Am. Chem. Soc. 138, 2993.

[10] D. Lindorfer, F. Müh, T. Renger (2017) Phys. Chem. Chem. Phys. 19, 7524.


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Darbotvarkėje:

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Darbotvarkėje:

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