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Petra Fromme

Petra Fromme

Arizona State University, USA

Title: Dynamics of Biomolecules “In Action” Studied with X-ray Free Electron Lasers

Biography

Biography: Petra Fromme

Abstract

Biomolecules are highly dynamic; however, most structures only provide a static picture of the molecule. Serial Femtosecond Crystallography (SFX) provides a novel concept for structure determination, where X-ray diffraction “snapshots” are collected from a fully hydrated stream of nanocrystals, using femtosecond pulses from high energy X-ray free-electron lasers (XFELs), where diffraction is observed before destruction takes effect [1]. The first proof of concept of serial femtosecond crystallography was achieved using Photosystem I, a larger membrane protein complex involved in Photosynthesis as a model system [2]. The structure of non-damaged biomolecules can now be determined, unraveling their function at the atomic scale [3],[4] that include important human membrane-bound receptors [6], [8] [9]. SFX opens a new avenue for determination of protein dynamics, with the goal of molecular movies of biomolecules “in action”.  First experiments on the proof of principle for time resolved serial femtosecond nanocrystallography have been performed on proteins in Photosynthesis, where first snapshots of steps in water splitting reaction have been observed [10]. A new concept based on continuous X-ray diffraction extends resolution beyond Bragg diffraction and allows for direct phasing of X-ray diffraction data [11]. TR-SFX studies extend to atomic resolution where the first steps in photosensing were recently revealed at a time scale of femtoseconds using the photoactive yellow protein [12,13]. This pioneering work paves the way for the determination of molecular movies of the dynamics of membrane proteins "at work" in the future.

The talk will close with a progress report on the development of compact femto and attosecond X-ray Sources at DESY (AXSIS) and at ASU (CXLS and CXFEL) , which will provide unique new opportunities to study the ultrafast dynamics of reactions in photosynthesis with a combination of X-ray diffraction, X-ray spectroscopy and ultrafast optical spectroscopy [14].

References:

  1. Barty A, Caleman C, Aquila A, Timneanu N, Lomb L, et al. (2012) Self-terminating diffraction gates femtosecond X-ray nanocrystallography measurements. Nature Photonics 6: 35-40.
  2. Chapman HN, Fromme P, Barty A, White TA, Kirian RA, et al. (2011) Femtosecond X-ray protein nanocrystallography. Nature 470: 73-U81.
  3. Boutet S, Lomb L, Williams GJ, Barends TRM, Aquila A, et al. (2012) High-Resolution Protein Structure Determination by Serial Femtosecond Crystallography. Science 337: 362-364.
  4. Redecke L, Nass K, DePonte DP, White TA, Rehders D, et al. (2013) Natively Inhibited Trypanosoma brucei Cathepsin B Structure Determined by Using an X-ray Laser. Science 339: 227-230.
  5. Kang YY, Zhou XE, Gao X, He YZ, Liu W, et al. (2015) Crystal structure of rhodopsin bound to arrestin by femtosecond X-ray laser. Nature 523: 561-+.