Matrix assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS) was employed for analysis of HPLC-purified peptides. Typically, a 0.8 ml sample was mixed 1:1 with sample matrix (15% w/v a-cyano-4-hydroxycinnamic acid dissolved in 50% ACN+0.1% TFA), spotted and dried on the MALDI-TOF MS sample plate. In some cases, samples were first purified using C18 Zip Tips (Millipore) as recommended by the manufacturer. MALDI-TOF MS was performed on a Microflex LRF MALDI-TOF system (Bruker Daltonics) [46] .