Time-resolved small-angle X-ray scattering system development for the biological macromolecules at SACLA: A pilot study.

A time-resolved small-angle X-ray scattering (SAXS) system for protein solution samples using an X-ray free-electron laser (XFEL) was established by developing a SAXS diffractometer by integrating a helium path into the DAPHNIS system initially designed for Serial Femtosecond Crystallography (SFX) experiments at BL2 of SACLA. This modification enabled us to successfully capture the SAXS profiles of ovalbumin under conditions without any reaction trigger, using both the newly developed system and the sample solution flow device that was originally designed for SFX experiments. Furthermore, we conducted acid denaturation experiments on cytochrome c, using a T-junction-type solution mixing flow system, and observed the denaturation-induced changes in the SAXS profiles.