Journal article

Publication year: 1999

Pages: 660-666

Journal: Analytical Chemistry

Volume number: 71

Issue number: 3

ISSN: 0003-2700

DOI Link: https://doi.org/10.1021/ac980841c

Publisher: American Chemical Society

Abstract: 
Dissected tissue pieces of the pituitary pars intermedia from the amphibian Xenopus laevis was directly subjected to matrix-assisted laser desorption/ionization (MALDI) mass analysis. The obtained MALDI peptide profile revealed both previously known and unexpected processing products of the proopiomelanocortin gene. Mass spectrometric peptide sequencing of a few of these neuropeptides was performed by employing MALDI combined with postsource decay (PSD) fragment ion mass analysis. The potential of MALDI-PSD for sequence analysis of peptides directly from unfractionated tissue samples was examined for the first time for the known desacetyl-alpha-MSH-NH2 and the presumed vasotocin neuropeptide. In addition, the sequence of an unknown peptide which was present in the pars intermedia tissue sample at mass 1392.7 u was determined. The MALDI-PSD mass spectrum of precursor ion 1392.7 u contained sufficient structural information to uniquely identify the sequence by searching protein sequence databases. The determined amino acid sequence corresponds to the vasotocin peptide with a C-terminal extension of Gly-Lys-Arg ("vasotocinyl-GKR"), indicating incomplete processing of the vasotocin precursor protein in the pituitary pars intermediate of X. laevis. Both vasotocin and vasotocinyl-GKR are nonlinear peptides containing a disulfide (S-S) bridge between two cysteine residues. Interpretation of the spectra of these two peptides reveals three different forms of characteristic fragment ions of the cysteine side chain: peptide-CH2-SH (regular mass of Cys-containing fragment ions), peptide -CH2-S-SH (regular mass + 32 u) and peptide=CH2 (regular mass - 34 u) due to cleavage on either side of the sulfur atoms.

Harvard Citation style: Jespersen, S., Chaurand, P., van Strien, F., Spengler, B. and van der Greef, J. (1999) Direct sequencing of neuropeptides in biological tissue by MALDI-PSD mass spectrometry, Analytical Chemistry, 71(3), pp. 660-666. https://doi.org/10.1021/ac980841c

APA Citation style: Jespersen, S., Chaurand, P., van Strien, F., Spengler, B., & van der Greef, J. (1999). Direct sequencing of neuropeptides in biological tissue by MALDI-PSD mass spectrometry. Analytical Chemistry. 71(3), 660-666. https://doi.org/10.1021/ac980841c