Fast atom bombardment (FAB) mass spectrometry: A mass spectral investigation of some of the insulins

Abstract

Mass measurements of the protonated molecules [M + H]+ of four insulins are presented. In addition, structurally significant fragment ions are observed in the mass spectrum and metastable scanning has been used to link these ions to the protonated molecule.

In situ reduction suitable for matrix‐assisted laser desorption/ionization and liquid secondary ionization using tris(2‐carboxyethyl)phosphine

“…21 We did not observe any indication of reduction of insulin (in the absence of reducing agents) even after extended analysis, in contrast to Barber et aZ. *l The absence of reduction ma be inappropriate redox potentials25 of the matrix and the sample.…”

Peptide mixture sequencing by tandem Fourier-transform mass spectrometry.

“…Tandem mass spectrometry (MS/MS) offers a possible solution to both problems (17,25,26,30). In MS/MS the molecular ion species of a mixture component can be separated by MS-I, fragmented by collisionally activated dissociation (CAD) (17) or laser photodissociation (18,19) to produce fragments measured in MS-II indicating the peptide sequence (7, 8, 17-21, 25, 26, 30).However, the few examples in which MS/MS has been applied to larger peptides (ionized by FAB) gave only limited sequence information of poor resolution (peak widths, >3 daltons), sensitivity (nmol samples), and mass accuracy (7,8,17,25,26). This arises because primary ion dissociations are accompanied by translational energy release, causing both broadening and shifting of peaks in magnetic sector instruments (17).…”

“…For oligopeptides, MS can utilize picomole samples, determine exact molecular weights, identify unusual amino acids or terminal groups (1)(2)(3)(4), and detect frameshift errors in Maxam-Gilbert sequencing of the gene encoding an enzyme (5). MS characterization of larger peptides is now possible by using powerful methods for the ionization of nonvolatile molecules, such as fast atom bombardment (FAB) (2,(6)(7)(8)(9)(10), laser desorption (LD) (11)(12)(13)(14), and particle-induced desorption (15,16). The latter has recently been used to measure molecular ions of 23,406 ± 140 daltons from porcine trypsin (16).…”

“…However, the few examples in which MS/MS has been applied to larger peptides (ionized by FAB) gave only limited sequence information of poor resolution (peak widths, >3 daltons), sensitivity (nmol samples), and mass accuracy (7,8,17,25,26). This arises because primary ion dissociations are accompanied by translational energy release, causing both broadening and shifting of peaks in magnetic sector instruments (17).…”

Identification of fragmentation in matrix-assisted laser desorption mass spectrometry using a voltage labelling technique

“…Fragmentation of bovine insulin negative ions in this manner has previously been reported using plasma desorption mass spectrometry 19 and fast atom bombardment. 20 Details of the mass calibration used in the present case will be given in a subsequent publication.…”