IGEM:Creative Proteomics/2009/Notebook/N-terminal sequencing service/Entry Base

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Although database search identification of proteins by mass spectrometry is well established, the method does not apply if the protein sequence does not exist in the current database. Therefore, de novo sequencing is the only method for identifying novel peptides, unsequenced organisms, and antibodies drugs, which database search methods were not able to detect. However, de novo sequencing poses more challenging than the traditional database search approach, such as, ambiguous assignments of fragment ions, insufficient product ions generated in incomplete fragmentation leading to low sequence coverage and difficulty in distinguishing ion series, notably N-terminal[1] from C-terminal MS/MS product ions (b ions from y ions).