title: Amino acid sequence determination of phosphoenkephalins using liquid secondary ionization mass spectrometry.
abstract: Liquid secondary ionization mass spectrometry (LSIMS) operating in the positive- and negative-ion modes was used to study fragmentation profiles and to obtain the amino acid sequences of a set of seven phosphoenkephalin peptides. The use of glycerol as the liquid matrix led to increase in fragmentation of phosphopeptides. The prominent amino acid sequence-determining ions in the positive-ion mode are y-type C-terminal ions; the N-terminal sequence-specific ions are observed sporadically. The most dominant ions in those mass spectra, however, are the immonium ions and a few low-mass side-chain cleavage products. The mass spectra in the negative-ion mode are more information-rich, and provide data complementary to that from the positive-ion mode. The phosphate group marker ions, m/z 79 (PO-3) and 97 (H2PO-4), are prominent and both N- and C-termini sequence ions are formed with equal facility in this mode of analysis. Both positive- and negative-ion mass spectral data are useful in determining the amino acid sequence of all the seven phosphoenkephalins. Thus, LSIMS alone can be a viable option to the tandem mass spectrometry approach when sufficient quantities (> 50 nmol) of phosphopeptides are available.
authors.affiliation: Department of Chemistry, University of Memphis, TN 38152, USA.
authors.forename: C
authors.initials: C
authors.lastname: Dass
authors.forename: P
authors.initials: P
authors.lastname: Mahalakshmi
mesh_terms: D000595:Amino Acid Sequence; D004745:Enkephalins / Q000737:chemistry*; D008969:Molecular Sequence Data; D010748:Phosphopeptides / Q000737:chemistry*; D018629:Spectrometry, Mass, Secondary Ion
chemical_list: D004745:Enkephalins; D010748:Phosphopeptides