Dissociation pathways of alkali-cationized peptides: opportunities for C-terminal peptide sequencing.
Dissociation pathways of alkali-cationized peptides have been studied using multiple stages of mass spectrometry (MSx) with a quadrupole ion trap mass spectrometer. Over 100 peptide ions ranging from 2 to 10 residues in length and containing each of the 20 common amino acids have been examined. The formation of the [b(n-1) + Na + OH]+ product ion is the predominant dissociation pathway for the majority of the common amino acids. This product corresponds to a sodium-cationized peptide one residue shorter in length than the original peptide. In a few cases, product ions such as [b(n-1) + Na - H]+ and those formed by loss, or partial loss, of a sidechain are observed. Both [b(n-1) + Na + OH]+ and [b(n-1) + Na - H]+ product ions can be selected as parent ions for a subsequent stage of tandem mass spectrometry (MS/MS). It is shown that these dissociation patterns provide opportunities for peptide sequencing by successive dissociation from the C-terminus of alkali-cationized peptides. Up to seven stages of MS/MS have been performed on a series of [b + Na + OH]+ ions to provide sequence information from the C-terminus. This method is analogous to Edman degradation except that the cleavage occurs from the C-terminus instead of the N-terminus, making it more attractive for N-terminal blocked peptides. The isomers leucine and isoleucine cannot be differentiated by this method but the isobars lysine and glutamine can.
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Department of Chemistry, University of North Carolina, Chapel Hill 27599-3290, USA.
Payne
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AH
Glish
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GL
D000468:Alkalies / Q000737:chemistry*; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D005973:Glutamine / Q000737:chemistry; D007532:Isoleucine / Q000737:chemistry; D007536:Isomerism; D007930:Leucine / Q000737:chemistry; D008239:Lysine / Q000737:chemistry; D013058:Mass Spectrometry; D009842:Oligopeptides / Q000737:chemistry*; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D012964:Sodium / Q000737:chemistry*; D013329:Structure-Activity Relationship
D000468:Alkalies; D000596:Amino Acids; D009842:Oligopeptides; D007532:Isoleucine; D005973:Glutamine; D012964:Sodium; D007930:Leucine; D008239:Lysine