SEQUENCING OF HYDROPHOBIC PEPTIDES AS LITHIATED ADDUCTS USING LIQUID SECONDARY-ION MASS-SPECTROMETRY WITHOUT TANDEM MASS-SPECTROMETRY

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 [a(n) + Li - H](+) and [d(n) + Li - H](+) ions together with limited C-terminal [y(pro) + Li + H](+) ions lead to an easy sequencing of the peptides studied, without the need for tandem mass spectrometry.