In the case of polypeptide ladder, the signal is low because one peptide is split into several ladders. There is a limit to the sequencing. We try to improve the signal of polypeptide ladders through guanidination, which is known to enhance the signal of peptides. We are currently conducting an experiment to confirm the effect Protein De novo sequencing is a method to confirm peptide sequence without assistance of a sequence reference. Usually tandem mass spectrometry and Edman degradation are used to obtain protein sequence infromation. In tandem mass spectrometry, the sequence is determined using the mass difference between the two fragment ions to calculate the mass of the amino acid residue on the peptide backbone. The Edman degradation cleaves off the N-terminal amino acid of the protein. The sequence is determined by observing the separated amino acid. 

 Here we apply microwave-assisted weak acid hydrolysis to De novo sequencing. Proteins were made into polypeptide ladders using 1-hr microwave-assisted weak acid hydrolysis with a mixture of dilute HCl and 2% FA. C-terminals of aspartic acids are cleaved by 2 % FA and polypeptide ladders are generated by dilute HCl. Such as De novo sequencing using tandem mass spectrometry, the sequence information on both C-terminal and N-terminal can be identified using the mass difference between the two polypeptide ladders to calculate the mass of the amino acid residue on the peptide backbone.

 In the case of polypeptide ladder, the signal is low because one peptide is split into several ladders. There is a limit to the sequencing. We try to improve the signal of polypeptide ladders through guanidination, which is known to enhance the signal of peptides. We are currently conducting an experiment to confirm the effect of signal enhancement by guanidination using O-methylisourea.of signal enhancement by guanidination using O-methylisourea.