Kb. Green-church et Pa. Limbach, Matrix-assisted laser desorption/ionization mass spectrometry of hydrophobic peptides, ANALYT CHEM, 70(24), 1998, pp. 5322-5325
Hydrophobic peptides, especially those with acid-labile protecting groups,
are difficult to characterize using mass spectrometric methods. We have dev
eloped a new procedure for matrix-assisted laser desorption/ionization time
-of-flight (MALDI-TCF) mass spectrometric analysis of such samples. Hydroph
obic peptides, which are insoluble in aqueous solutions, are dissolved in c
hloroform and combined with matrixes prepared in chloroform or chloroform/m
ethanol solutions. The use of a common solvent for the matrix and the analy
te improves the analyte isolation step in MALDI mass spectrometry, The lack
of acidic solutions previously used for electrospray ionization or MALDI m
ass spectrometry of hydrophobic peptides extends this methodology to cyclic
or protected hydrophobic peptides. Conventional peptide matrixes, such as
2,5-dihydroxybenzoic acid and sinapinic acid, as well as 3-indoleacrylic ac
id are shown to be suitable for hydrophobic peptides. Cyclic hydrophobic pe
ptides and linear hydrophobic peptides with blocked termini are detected as
the cation-adducted pseudomolecular ion due to the lack of suitable sites
of protonation on the analyte.