Secondary Structure Analysis

The secondary structure of the peptide was determined by use of circular dichroism spectrometry (JASCO J-815 CD spectrometer, Jasco, Essex, United Kingdom) as described in a previous study (Gao et al., 2016; Wu et al., 2016). Peptides were dissolved in 10 mM ammonium acetate buffer or 50% TFE in 10 mM ammonium acetate buffer at a final concentration of 100 μM. The percentage of the α-helix structure was predicted by the online tool K2D3 (Louis-Jeune et al., 2012). Peptide samples were measured within the range of 190–250 nm at 20°C. The parameters were set as: 200 nm/min scanning speed, a bandwidth of 1 nm, and 0.5 nm data pitch.