Amyloid nanofiber coatings formed by TLC-M at 4 or 25°C were scraped and resuspended in deionized water. Mature nanofibers formed by TDP43 LC were pelleted by centrifugation at 10,000g, followed by washing several times with copious amounts of deionized water to remove remaining salts. The nanofiber pellets were then suspended in deionized water. Two microliters of suspensions were pipetted between two fire-polished glass rods and dried for several hours. The diffraction data were collected on a Rigaku MicroMax 007 x-ray generator and an R-AXIS IV++ area detector. Data are presented in Fig. 2A and fig. S4A.