Figure 3: LC-MS/MS. The protein sample is fractionated by HPLC, then it is ionized and enters the mass analyzed, where a series of peaks are analyzed in MS mode and one of them (i.e.785.05) is verified for the charge state (doubly charged) and then selected for fragmentation and fragmented in the collision cell. The MS fragments are analyzed in a second analyzed (MS/MS) and then all MS and MS/MS peaks are interrogated by database search and data analysis.