Citraconylation--a simple method for high protein sequence coverage in MALDI-TOF mass spectrometry

Lysine epsilon -amino group reacts with citraconic anhydride forming a derivative, which is stable on terms for trypsin cleavage. This modification changes the spectrum of peptides formed by the trypsin action; as the number of trypsin-sensitive sites is reduced, the peptides with higher molecular mass can survive in the digest. The various studies of proteins by MALDI-TOF mass spectrometry are often complicated by the low sequence coverage of the peptide chain. This paper demonstrates that the modification of proteins by citraconylation before trypsin cleavage represents a simple experimental technique, which allows a significant increase of sequence coverage in MALDI-TOF mass spectrometry. This improvement is caused both by change of trypsin fragmentation pattern and by disturbance of the protein's native tertiary structure.