we used N-terminomics approach to identify the N-terminal sequences of SEPs in Hep3B cells. Three SEPs enrichment methods (HCl precipitation, heating precipitation and ACN precipitation), three chemical derivatization methods (dimethylation, acetylation and guanidylation) and three N-terminal peptides enrichment materials (hexadecaldehyde, CNBr activated agarose and NHS activated agarose) were tested in this experiment. We also determined the start codons of SEPs with their N-terminal information.