Fluorescence Measurements
Fluorescence assays were performed in a buffer consisting of 50 mM Tris-HCl (pH 8.3) and 150 mM NaCl. One micromolar N protein was incubated either with the control buffer or each compound (10 μM) at 4 °C for 1 h. Tryptophan fluorescence was acquired with a Jasco FP-8300 fluorescence spectrometer (JASCO International Co. Ltd., Tokyo, Japan) at an excitation wavelength of 280 nm and an emission wavelength range of 300–400 nm.