title: Evaluation of a novel approach for peptide sequencing: laser-induced acoustic desorption combined with P(OCH(3))(2)(+) chemical ionization and collision-activated dissociation in a Fourier transform ion cyclotron resonance mass spectrometer.
abstract: A novel mass spectrometric method has been developed for obtaining sequence information on small peptides. The peptides are desorbed as intact neutral molecules into a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR) by means of laser-induced acoustic desorption (LIAD). Reactions of the neutral peptides with the dimethoxyphosphenium ion, P(OCH(3))(2)(+), occur predominantly by addition of the peptide to P(OCH(3))(2)(+) followed by the loss of two methanol molecules, thus yielding product ions with the composition (peptide + P - 2H)(+). Upon sustained off-resonance irradiation for collision-activated dissociation (SORI-CAD), the (peptide + P - 2H)(+) ions undergo successive losses of CO and NHCHR or H(2)O, CO, and NHCHR to yield sequence-related fragment ions in addition to the regular a(n)- and b(n)-type ions. Under the same conditions, SORI-CAD of the analogous protonated peptides predominantly yields the regular a(n)- and b(n)-type ions. The mechanisms of the reactions of peptides with P(OCH(3))(2)(+) and the dissociation of the (peptide + P - 2H)(+) ions were examined by using model peptides and molecular orbital calculations.
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Jayalakshmi
authors.initials: J
authors.lastname: Somuramasami
authors.forename: Hilkka I
authors.initials: HI
authors.lastname: Kenttämaa
mesh_terms: D017357:Cyclotrons; D005069:Evaluation Studies as Topic; D005583:Fourier Analysis; D007477:Ions / Q000737:chemistry*; D007834:Lasers; D013058:Mass Spectrometry; D015394:Molecular Structure; D010455:Peptides / Q000032:analysis*; D020033:Protein Isoforms / Q000737:chemistry; D020539:Sequence Analysis, Protein / Q000379:methods*
chemical_list: D007477:Ions; D010455:Peptides; D020033:Protein Isoforms