Thermostability assays were conducted in a buffer consisting of 50 mM Tris-HCl (pH 7.5) and 150 mM NaCl and with a JASCO FP-8300 fluorescence spectrometer (JASCO International Co. Ltd., Tokyo, Japan). One micromolar N protein was incubated either with the control buffer or each compound (10 μM) at 4 °C for 2 h. UV absorbance vs temperature profiles were acquired by ramping the temperature from 4–95 °C at a 1 °C min–1 and recording the absorbance at 280 nm every 0.5 min.