MALDI-TOF MS was carried out with a 4800 MALDI-TOF/TOF mass spectrometer from Applied Biosystems (Framingham, MA, USA). All mass spectra were obtained by averaging 2500 laser shots from each sample well in the positive-ion mode. The instrument was controlled using 4000 series Explorer software (version 3.6; Applied Biosystems). Data were processed by using Data Explorer software (version 4.8; Applied Biosystems). The calibration of the instrument in MS and MS/MS modes were carried out by using the ions derived from mixture of several synthetic peptides as described previously . Two MALDI-MS/MS spectra were acquired for all type 2 peptides with and without the CID gas (air). Peptides dissolved in water/acetonitrile/TFA solutions (0.5 μL) were mixed with the matrix solution (0.5 μL), (the supernatant of a 50 % acetonitrile solution saturated with α-cyano-4-hydroxycinnamic acid), and then air dried on the flat surface of a stainless-steel plate. The ions were generated by irradiating the sample area with the output of a Nd/YAG laser at a wavelength of 355 nm, and generated ions were accelerated at 20 kV potential in the ion source.