Secondary ion mass spectra of the neuropeptides leucine-enkephalin and methionine-enkephalin

Abstract

Positive and negative secondary ion mass spectra obtained by bombardment of thin films of leucine-enkephalin and methionine-enkephalin with a pulsed beam of Cs' ions of energy 5-15 keV were recorded using a time-of-flight mass spectrometer. Many of the secondary ions are metastable. The spectra contain a wealth of information, including the following important features: (i) ions characteristic of the intact molecule, from which the molecular weight may be deduced; (ii) ions diagnostic of the amino acid composition of the peptide; (iii) ions diagnostic of the sequence of amino acids in the peptide.

Secondary ion mass spectrometry of protected diribonucleoside monophosphates with a time-of-flight mass spectrometer

“…As yet there have been no spectra of protected nucleotides reported for fast atom bombardment. However, judging from the similar fragmentation observed for unprotected nucleotides (20)(21)(22)(23)(24)(25) and for peptides (24,35) and from the probable common mechanism of the two processes (36), we should expect results similar to ours to be obtainable with this technique. Likewise, no protected nucleotides have been examined by laser desorption, but the similarity of the spectra of unprotected nucleotides observed for this method and for fission fragment bombardment (13) would argue that similar spectra might again be obtained for this technique.…”

Desorption/ionization mass spectrometric technique for the analysis of thermally labile compounds based on thermionic emission materials

“…The thermal lability of the peptides has required extensive derivatization before a mass spectrometric analysis can be performed. Ionization methods requiring no derivatization have therefore been of considerable interest (39,40). Pyrolysis processes of amino acids have been studied and are well understood (41).…”

Californium-252 plasma-desorption mass spectrometry of polymethylenediamine-linked enkephalin peptides

“…In elucidating fragmentation pathways, it is always desirable to know whether or not one or more hydrogen atoms have been transferred at the point of scission. As mentioned above, such determinations are not easy from low resolution data, but even -0.18 to 0.07 M + Na -C7HsO -0.35 (10) -H n3-c7h8 -0.29 (04) -H with the higher resolution spectrometers using fast atom bombardment (12, 13) relatively abundant ions appear at masses adjacent to the major fragment ions. It may be that ubiquitous and complex hydrogen transfer processes will make assignment of mass to the nearest unit in fragment ions somewhat unrewarding in all such methods, especially at higher masses.…”

“…Recent applications of this method to peptides include a comparison of synthetic and natural alamethicins (5), a variety of small peptides (6,7), (3-endorphin (8), gramicidin-A, (6) glutathione (6), and, more recently, insulin, (9). Closely related studies include secondary ion mass spectra of enkephalins (10), bradykinin (11), and fast atom bombardment analysis of ACTH and insulin (12) and somatostatin, substance P, and other peptides (13).…”