Negative‐ion electrospray tandem mass spectrometry of peptides derivatized with 4‐aminonaphthalenesulphonic acid

The value of derivatizing peptides at the C-terminus with 4-aminonaphthalenesulphonic acid (ansa) to aid in the de novo sequencing of peptides by mass spectrometry was assessed. Negative-ion electrospray of peptides is enhanced by derivatization witb ansa. The derivatizing group also has the effect of increasing the mass of the peptides by 205 Da, often shifting their deprotonated molecules to regions of the mass spectrum with reduced chemical noise. Collision-induced dissociation of naphthalenesulphonated peptide [M-H] - ions results in abundant fragment ions formed by charge-remote fragmentations. The resulting fragmentation patterns are less complex than those of the underivatized analogues and are easier to interpret. Peptides were successfully derivatized at the low picomole level and sequenced on the hundred femtomole level using nano-electrospray tandem mass spectrometry.