Berlin 2024 – scientific programme

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BP: Fachverband Biologische Physik

BP 31: Protein Structure and Dynamics

BP 31.2: Talk

Thursday, March 21, 2024, 15:15–15:30, H 0112

Electric-field induced ultrafast protein changes — •Karsten Heyne, Clark Zahn, and Ramona Schlesinger — Freie Universität Berlin, Fachbereich Physik, Berlin, Deutschland

Light absorption activates photoreceptors and triggers a cascade of structural changes leading to the biological function. The time span of these processes ranges from femtoseconds to seconds. The fastest process is the absorption of a photon on a time-scale of a few fs. It is a long-standing debate whether excitation of the chromophore impacts the protein structure immediately or if the protein response is delayed until the photoproduct is formed. Here, we show direct response of the protein prior to chromophore isomerization. The vibrational fingerprint region of bacteriorhodopsin (bR) studied with polarization-resolved fs VIS-pump IR-probe spectroscopy reveals protein restructuration before and after photoisomerization. Transient protein signals were identified prior to and after photoisomerization with 500 fs. A proton continuum band, amide I band, and carboxylic acid groups, essential elements for the function of the bR proton pump, are altered by the excited chromophore. These groups have distances up to 10 Å to the chromophore. Therefore, we propose that an impulsive electric field change at the chromophore in the excited state perturbs polar groups throughout the protein. The ensuing reorganization prepares the protein for the down-stream processes.

Keywords: protein response; ultrafast dynamics; electric field interaction