Sequencing of hydrophobic peptides as lithiated adducts using liquid secondary‐ion mass spectrometry without tandem mass spectrometry

Abstract
Lithium cationized hydrophobic peptides in the molecular weight range 1900–2650 Da have been studied by liquid secondary‐ion mass spectrometry. The mass spectra exhibit characteristic lithiated sequence ions. N‐terminal [an+LiH]+ and [dn+LiH]+ ions together with limited C‐terminal [ypro+Li+H]+ ions lead to an easy sequencing of the peptides studied, without the need for tandem mass spectrometry.