Form factor determination of biological molecules with X-ray free electron laser small-angle scattering (XFEL-SAS)
Clément Blanchet, Adam Round, Haydyn D. T. Mertens, Kartik Ayyer, Melissa A. Graewert, Salah Awel, Daniel Franke, Katerina Dörner, S. Bajt, Richard Bean, Tânia F. Custódio, Raphaël de Wijn, E Juncheng, Alessandra Henkel, Andrey Gruzinov, Cy M. Jeffries, Yoonhee Kim, Henry Kirkwood, Marco Kloos, J. Knoška, Jayanath Koliyadu, Romain Letrun, Christian Löw, Jana Makroczyová, Abhishek Mall, Rob Meijers, Gisel E. Peña Murillo, Dominik Oberthür, Ekaterina Round, Carolin Seuring, Marcin Sikorski, Patrik Vagovič, Joana Valério, Tamme Wollweber, Yulong Zhuang, Joachim Schulz, Heinrich Haas, Henry N. Chapman, Adrian P. Mancuso⋈, Dmitri I. 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 have an influence on the structure and dynamics of molecules can be varied and their effect on conformational changes can be monitored in time-resolved XFEL and SAXS experiments. We report here 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 scattering contributions from the solvent and the instrument are separately measured and accurately subtracted. The experiment was done using 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 X-ray pulses.