Collisional activation of peptide ions in FT‐ICR mass spectrometry

Abstract

In the last decade, the characterization of complex molecules, particularly biomolecules, became a focus of fundamental and applied research in mass spectrometry. Most of these studies utilize tandem mass spectrometry (MS/MS) to obtain structural information for complex molecules. Tandem mass spectrometry (MS/MS) typically involves the mass selection of a primary ion, its activation by collision or photon excitation, unimolecular decay into fragment ions characteristic of the ion structure and its internal excitation, and mass analysis of the fragment ions. Although the fundamental principles of tandem mass spectrometry of relatively small molecules are fairly well-understood, our understanding of the activation and fragmentation of large molecules is much more primitive. For small ions, a single energetic collision is sufficient to dissociate the ion; however, this is not the case for complex molecules. For large ions, two fundamental limits severely constrain fragmentation in tandem mass spectrometry. First, the center-of-mass collision energy-the absolute upper limit of energy transfer in a collision process-decreases with increasing mass of the projectile ion for fixed ion kinetic energy and neutral mass. Secondly, the dramatic increase in density of states with increasing internal degrees of freedom of the ion decreases the rate of dissociation by many orders of magnitude at a given internal energy. Consequently, most practical MS/MS experiments with complex ions involve multiple-collision activation (MCA-CID), multi-photon activation, or surface-induced dissociation (SID). This review is focused on what has been learned in recent research studies concerned with fundamental aspects of MCA-CID and SID of model peptides, with an emphasis on experiments carried out with Fourier transform ion cyclotron resonance mass spectrometers (FT-ICR MS). These studies provide the first quantitative comparison of gas-phase multiple-collision activation and SID of peptide ions. Combining collisional energy-resolved data with RRKM-based modeling revealed the effect of peptide size and identity on energy transfer in collisions-very important characteristics of ion activation from fundamental and the analytical perspectives. Finally, the combination of FT-ICR with SID was utilized to carry out the first time-resolved experiments that examine the kinetics of peptide fragmentation. This has lead to the discovery that the time-dependence of ion dissociation varies smoothly up to a certain collision energy, and then shifts dramatically to a time-independent, extensive dissociation. This near-instantaneous "shattering" of the ion generates a large number of relatively small fragment ions. Shattering of ions on surfaces opens up a variety of dissociation pathways that are not accessible with multiple-collision and multiphoton excitation.

Photodissociation of non-covalent peptide-crown ether complexes

“…T he ongoing need for improved methods for characterizing biological molecules is driving efforts to develop new ion activation and dissociation approaches in mass spectrometry (MS) [1,2]. Currently, collisional-activated dissociation (CAD) remains the most popular technique used to produce diagnostic fragment ions [3,4]. However, this MS/MS method is subject to a number of shortcomings such as insufficient or inefficient energy deposition.…”

“…Currently, collisional-activated dissociation (CAD) remains the most popular technique used to produce diagnostic fragment ions [3,4]. However, this MS/MS method is subject to a number of shortcomings such as insufficient or inefficient energy deposition.…”

Peptide and protein characterization by high‐rate electron capture dissociation Fourier transform ion cyclotron resonance mass spectrometry

“…Tsybin et al Conventionally, peptide and protein fragmentation techniques employed for MS/MS in FTICR-MS are based on vibrational excitation of precursor ions and belong to the family of 'slow-heating fragmentation techniques'. 13,14 In modern tandem FTICR-MS the slow-heating fragmentation techniques are represented by low-energy multiple collision-induced dissociation (CID), 15 ultraviolet photodissociation (UVPD), 16 infrared multiphoton dissociation (IRMPD), 17 -19 and blackbody infrared radiative dissociation (BIRD). 20 In spite of being widely used, these techniques have the common drawbacks of not preserving labile posttranslational modifications and producing selective cleavage of the peptide backbone.…”

Kinetics for tautomerizations and dissociations of triglycine radical cations

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[7,8], infrared multiphoton dissociation (IRMPD) [9], and blackbody radiation [10]. The mechanisms by which protonated peptides dissociate have, therefore, generated much interest [11,12].

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