Formation of gas-phase peptide ions and their dissociation in MALDI: insights from kinetic and ion yield studies

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Title
Formation of gas-phase peptide ions and their dissociation in MALDI: insights from kinetic and ion yield studies
Author(s)
Jeong Hee Moon; S Yoon; Y J Bae; M S Kim
Bibliographic Citation
Mass Spectrometry Reviews, vol. 34, no. 2, pp. 94-115
Publication Year
2015
Abstract
Insights on mechanisms for the generation of gas-phase peptide ions and their dissociation in matrix-assisted laser desorption ionization (MALDI) gained from the kinetic and ion yield studies are presented. Even though the time-resolved photodissociation technique was initially used to determine the dissociation kinetics of peptide ions and their effective temperature, it was replaced by a simpler method utilizing dissociation yields from in-source decay (ISD) and post-source decay (PSD). The ion yields for a matrix and a peptide were measured by repeatedly irradiating a region on a sample and collecting ion signals until the sample in the region was completely depleted. Matrix- and peptide-derived gas-phase cations were found to be generated by pre-formed ion emission or by ion-pair emission followed by anion loss, but not by laser-induced ionization. The total number of ions, that is, matrix plus peptide, was found to be equal to the number of ions emitted from a pure matrix. A matrix plume was found to cool as it expanded, from around 800-1,000 K to 400-500 K. Dissociation of peptide ions along b/y channels was found to occur statistically, that is, following RRKM behavior. Small critical energy (E0=0.6-0.7 eV) and highly negative critical entropy (ΔS‡=-30 to -25 eu) suggested that the transition structure was stabilized by multiple intramolecular interactions.
Keyword
Expansion coolingIon yieldMALDIPeptide ion dissociationPeptide ion formationThermal model
ISSN
0277-7037
Publisher
Wiley
DOI
http://dx.doi.org/10.1002/mas.21427
Type
Article
Appears in Collections:
Division of Bio Technology Innovation > Core Research Facility & Analysis Center > 1. Journal Articles
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