TY  - GEN
A1  - Maximowitsch, Egle
N2  - Most organisms on earth are able to sense light, to which they adapt their behavior by using photoreceptor proteins containing light-absorbing chromophores. Phytochrome photoreceptors contain a covalently-attached tetrapyrrole chromophore and switch between two thermally stable forms, a red-absorbing (Pr) and a far-red-absorbing (Pfr) state. Although phytochromes have been studied for more than fifty years, the molecular mechanisms defining their photoinduced properties are not fully understood, hampering the efficient engineering of phytochrome-based molecular tools. The computational study presented in this thesis combines quantum chemical calculations and molecular dynamics simulations in order to elucidate the molecular mechanisms of spectral tuning and excited-state decay in phytochromes. The calculations have demonstrated that the spectral red shift of the Pfr state is induced by the hydrogen bond formation between the chromophore and a highly conserved aspartate. Here it is also shown how the formation of this hydrogen bond is coupled to dynamics of other active-site interactions. In addition, the chromophore deprotonation by a protein residue is proposed to contribute to the absorption at the Q-band blue shoulder in the Pr-state spectrum. For the first time, the photoinduced electron transfer coupled to proton transfer was characterized in phytochromes. These charge transfer pathways may contribute to the excited-state decay by quenching fluorescence and influencing photoproduct formation. The discoveries provided in this thesis will facilitate further phytochrome investigations and the rational design of phytochrome-based fluorescent markers and optogenetic tools.
ID  - heidok26412
TI  - Molecular mechanisms of spectral tuning and excited-state decay in phytochrome photoreceptors
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/26412/
AV  - public
Y1  - 2020///
ER  -