Form factor determination of biological molecules with X-ray free electron laser small-angle scattering (XFEL-SAS)

Authors

Clement E. Blanchet, Adam Round, Haydyn D.T. Mertens, Kartik Ayyer, Melissa Graewert, Salah Awel, Daniel Franke, Katerina Dörner, Saša Bajt, Richard Bean, Tânia F. Custódio, Raphael de Wijn, E. Juncheng, Alessandra Henkel, Andrey Gruzinov, Cy M. Jeffries, Yoonhee Kim, Henry Kirkwood, Marco Kloos, Juraj Knoška, Jayanath Koliyadu, Romain Letrun, Christian Löw, Jana Makroczyova, Abhishek Mall, Rob Meijers, Gisel Esperanza Pena Murillo, Dominik Oberthür, Ekaterina Round, Carolin Seuring, Marcin Sikorski, Patrik Vagovic, Joana Valerio, Tamme Wollweber, Yulong Zhuang, Joachim Schulz, Heinrich Haas, Henry N. Chapman, Adrian P. Mancuso and Dmitri Svergun

Abstract

Free-electron lasers (FEL) are revolutionizing X-ray-based structural biology methods. While protein crystallography is already routinely performed at FELs, Small Angle X-ray Scattering (SAXS) studies of biological macromolecules are not as prevalent. SAXS allows the study of the shape and overall structure of proteins and nucleic acids in solution, in a quasi-native environment. In solution, chemical and biophysical parameters that influence structure and dynamics can be varied and their effect on conformational changes monitored in time-resolved XFEL-SAXS experiments. We report the collection of scattering form factors of proteins in solution using FEL X-rays. The form factors correspond to the scattering signal of the protein ensemble alone; the contributions from solvent and instrument are separately measured and accurately subtracted. The experiment used a liquid jet for sample delivery. These results pave the way for time-resolved studies and measurements from dilute samples, capitalizing on the intense and short FEL pulses.