Supplementary information for he5572

To confirm that the sample box is anaerobic we performed a methyl viologen (MV) colorimetric assay. We prepared and aliquoted an MV solution (violet in color) into a 96-well plate under anaerobic conditions, sealed it with an aluminum sealing film, and placed it on the robot tray platform. We then pierced one well with the robot needle, leaving the MV solution exposed to the atmosphere, and the second MV sample was then loaded into the SAXS sample cell contained within the helium-purged sample box. Over the course of 5 minutes there was no change in the violet color of the solution in the sample cell while the solution exposed to atmosphere quickly became clear. This is more than sufficient time to collect a complete SAXS dataset. In addition we have recently added an oxygen sensor (model 201RSP, Advanced Micro Instruments, Huntington Beach, CA ) which has indicated the oxygen concentration to be below 0.01\% (the detection limit of the instrument).