In this project we will de novo sequence antibodies based on mass spectrometry. The method will be firstly tested on several monoclonal antibodies. Antibodies will be digested by multiple proteases to generate overlapping peptides. Moreover the peptides will be fragmented by both EThcD and stepped HCD fragmentation method. The experimental sequence will be validated by synthesis followed with western blot and ELISA. After we achieve high accuracy on the monoclonal antibodies, the method will be applied on more complicated samples, e.g. human sera. The target polyclonal antibodies will be purified by antigen specific binding and de novo sequenced.