Observation of a single protein by ultrafast X-ray diffraction

The idea of using ultrashort X-ray pulses to obtain images of single proteins frozen in time has fascinated and inspired many. It was one of the arguments for building X-ray free-electron lasers. According to theory, the extremely intense pulses provide sufficient signal to dispense with using crystals as an amplifier, and the ultrashort duration of the pulse means that any motion of the molecules is inevitably exploited. This has enabled us to transform and biologically study objects of picometre resolution, providing a way to probe the smallest sample that can be imaged. The ability to capture snapshots on the timescale of atomic vibrations, while keeping the sample at room temperature, may allow probing the entire conformational phase space of macromolecules. Here we show the first observation of an X-ray diffraction pattern from a single protein, that of Escherichia coli GroEL with a 14 nm in diameter is the smallest biological sample ever imaged by X-rays, and demonstrate that the concept of diffraction before destruction extends to single proteins. From the pattern, it is possible to determine the approximate orientation of the protein. Our experiment demonstrates the feasibility of ultrafast imaging of single proteins, opening the way to single-molecule time-resolved studies on the femtosecond timescale.

Tomas Ekeberg, Dameli Assalaoua, Johan Bielecki, Rebecca Boll, Benedikt J. Dauer, Lutz A. Eichacker, Linda E. Franken, Davide E. Galli, Luca Geisler, Lars Gumpricht, Laura H. Günther, Janos Hajdu, Robert Hartmann, Dirk Hasse, Alexandr Ignatenko, Jayanath Koliyadu, Olena Kulyk, Ruslan Kuras, Markus Kuster, Wolfgang Lugmayr, Jannik Lübke, Adrian P. Mancuso, Tommaso Mazza, Carl Nettelblad, Yevheniy Ovcharenko, Daniel E. Rivas, Max Rose, Amit K. Samanta, Philipp Schmidt, Egor Sobolev, Nicusor Timneanu, Sergey Usenko, Daniel Westphal, Tamme Wollweber, Lena Wrobs, Paul Lorouda Xavier, Hazem Yousef, Kartik Ayyer, Henry N. Chapman, Jonas A. Sellberg, Caroll Seuring, Ivan A. Vartanyants, Jochen Küpper, Michael Meyer, Filipe R. N. C. Maia