A, the fluorescence of freshly purified CsgA mixed with 25 μm ThT was measured in 10-min intervals at 495 nm after excitation at 438 nm. B, circular dichroism analysis of 10 μm CsgA immediately after purification, 2 days after purification, 7 days after purification, and 15 days after purification. CsgA was incubated at room temperature without shaking after purification. C–E, TEM micrographs of 30 μm CsgA after incubation at room temperature for the indicated times. Scale bar, 500 nm.