Intra-ionic interactions in electrosprayed peptide ions

130

138

This article provides a perspective on collisions of ions with surfaces, including surfaceinduced dissociation (SID) and reactive ion scattering spectrometry (RISS). The content is organized into sections on surface-induced dissociation of small ions, surface characterization of organic thin films by collision of well-characterized ions into surfaces, the use of SID to probe peptide fragmentation, and the dissociation of large non-covalent complexes by SID. Examples are given from the literature with a focus on experiments from the authors' laboratory. The article is not a comprehensive review but is designed to provide the reader with an overview of the types of results possible by collisions of ions into surfaces. (J Am Soc Mass Spectrom 2008, 19, 190 -208) © 2008 American Society for Mass Spectrometry T andem mass spectrometry (MS/MS) is an essential tool for elucidating ion structure. The MS/MS experiment involves mass selection of a precursor ion followed by ion activation and subsequent dissociation. The ion activation step is commonly accomplished via collision-induced dissociation (CID) in which the initial kinetic energy of a projectile ion is converted into internal energy through inelastic collisions with a neutral gas. Several alternative activation methods have been used in tandem mass spectrometry, one of which is surfaceinduced dissociation (SID). SID is analogous to CID, except that a surface replaces the neutral gas as the collision target. A typical ion-surface collision event is illustrated in Figure 1.The incorporation of a surface into a mass spectrometer for ion activation was pioneered in the laboratory of R. Graham Cooks in the mid-1970s and early 1980s [1][2][3]. Since that time, collisions of lowenergy (eV) organic ions with surfaces within the tandem mass spectrometer have been valuable for analyzing surface composition, characterizing reactions between organic projectile ions and surface adsorbates, chemically modifying surfaces, and determining projectile ion structure. A major motivation for development of SID is that energy transfer to ionic projectiles can be improved by increasing the mass of the collision target. The total available energy for transfer into the internal modes of the projectile ion is defined by the center-of-mass energy (E COM ) described by eq 1:where E LAB is the laboratory collision energy and M ION and M N are the masses of the projectile ion and neutral, respectively. Energy transfer in CID is limited by the mass of the collision partner, typically inert gases such as helium, argon, or xenon. In SID, if one assumes that the surface is an infinitely large collision partner, E COM becomes independent of mass and approaches the laboratory collision energy. The assumption that the entire surface can be viewed as the collision partner is not always valid, however, and there are instances where the mass of the terminal groups on the surface influence the amount of energy transfer [4,5]. Nonetheless, the use of a massive surface target should, in theory, provide ...

Section: The Role Of Sid In Developing the Mobile Proton Model And Elmentioning

confidence: 99%

Surface-induced dissociation of small molecules, peptides, and non-covalent protein complexes

Wysocki

Joyce

Jones

et al. 2008

130

138

“…The "mobile proton" model [13,14] has been devised to explain this. In the high-energy CAD [10], which is usually done with sector and time-of-flight (TOF) mass spectrometers, a peptide ion gains more internal energy than the above through electronic excitation.…”

mentioning

confidence: 99%

Time-resolved photodissociation of singly protonated peptides with an arginine at the N-terminus: A statistical interpretation

Yoon

Chung

Kim

2008

Time-evolution of product ion signals in ultraviolet photodissociation (UV-PD) of singly protonated peptides with an arginine at the N-terminus was investigated by using a tandem time-of-flight mass spectrometer equipped with a cell floated at high voltage. Observation of different time-evolution patterns for different product ion types-an apparently nonstatistical behavior-could be explained within the statistical framework by invoking consecutive formation of some product ions and broad internal energy distributions for precursor ions. a n ϩ 1 and b n ions were taken as the primary product ions from this type of peptide ions. Spectral characteristics in post-source decay, UV-PD, and collisionally activated dissociation at low and high kinetic energies could be explained via rough statistical calculation of rate constants. Specifically, the striking characteristics in high-energy CAD and UV-PD-dominance of a n and d n formed via a n ϩ 1-were not due to the peculiarity of the excitation processes themselves, but due to quenching of the b n channels caused by the presence of arginine. ( T andem mass spectrometry has been widely used for identification and sequence determination of polypeptides and proteins [1][2][3]. In spite of extensive studies made so far, fundamental understanding on the dissociation of activated peptide ions observed by tandem mass spectrometry is still lacking. This is in contrast with the case of the dissociation of small polyatomic ions, for which nearly quantitative theoretical description and even prediction are possible [4]. The main reasons for such a lack of fundamental understanding are experimental and computational difficulties to get structural, mechanistic, and kinetic data for large polyatomic systems consisting of more than 100 atoms. In this regard, it is to be mentioned that we recently developed a systematic method to calculate sequence-specific statistical (Rice-Ramsperger-KasselMarcus, RRKM) rate constants for dissociations of peptide and protein ions [5][6][7].The most popular method to activate a peptide ion and hence to induce its dissociation is the collisionally activated dissociation (CAD) [8 -12]. The kinetic energy of a peptide ion is an important factor affecting the CAD spectral pattern. Hence, CAD of a peptide ion is classified into two categories, low (around 100 eV) and high (higher than 1 keV) energy regimes. In the lowenergy CAD [11], which is typically done with triple quadrupole ion trap and ion cyclotron resonance mass spectrometers, a peptide ion gains sufficient energy for dissociation usually via multiple collisions, each collision supplying rather small amounts of internal energy through vibrational excitation. Most of the product ions are b and y types (see Scheme 1) formed via rearrangement reactions.Presence of arginine, proline and aspartic acid residues and the charge state of a peptide ion are known to affect the relative intensities of these product ions. The "mobile proton" model [13,14] has been devised to explain this. In the high-energy CA...

“…With the charge on the guanidine functionality of the Arg ϩ side chain, the acidic side chain of aspartic acid can induce selective fragmentation through interaction with the peptide backbone. This common dissociation pathway has been described mechanistically in a number of studies [65][66][67][68][69][70][71]. According to one frequently proposed charge-remote fragmentation mechanism involving Asp residues, the hydroxyl hydrogen of the aspartic acid side chain can hydrogen bond with the carbonyl oxygen of the peptide backbone promoting a cis-1,2-elimination reaction leading to backbone cleavage C-terminal to the acidic side-chain [66 -68, 71].…”

Section: Fragmentation Pathwaysmentioning

confidence: 99%

“…In this mechanism, the Asp residue plays no part in the solvation of the charge sequestered on the Arg sidechain (Scheme 1a). Alternatively, others have proposed that the selective fragmentation C-terminal to aspartic acid is driven by the formation of a salt bridge between the protonated Arg residue and the Asp side chain [66,69,70]. This mechanism is still charge-remote with the proton sequestered at the guanidine of the Arg ϩ residue, however, the charge is solvated by the Asp side chain resulting in an intramolecular salt-bridge intermediate (Scheme 1b).…”

Section: Fragmentation Pathwaysmentioning

confidence: 99%

Fragmentation mechanisms of oxidized peptides elucidated by SID, RRKM modeling, and molecular dynamics

Spraggins

Lloyd

Johnston

et al. 2009

The gas-phase fragmentation reactions of singly charged angiotensin II (AngII, DR ϩ VYIHPF) and the ozonolysis products AngIIϩO (DR ϩ VY*IHPF), AngIIϩ3O (DR ϩ VYIH*PF), and AngIIϩ4O (DR ϩ VY*IH*PF) were studied using SID FT-ICR mass spectrometry, RRKM modeling, and molecular dynamics. Oxidation of Tyr (AngIIϩO) leads to a low-energy charge-remote selective fragmentation channel resulting in the b 4 ϩO fragment ion. Modification of His (AngIIϩ3O and AngIIϩ4O) leads to a series of new selective dissociation channels. For AngIIϩ3O and AngIIϩ4O, the formation of [MH؉3O] ؉ ؊45 and [MH؉3O] ؉ ؊71 are driven by charge-remote processes while it is suggested that b 5 and [MH؉3O] ؉ ؊88 fragments are a result of charge-directed reactions. Energy-resolved SID experiments and RRKM modeling provide threshold energies and activation entropies for the lowest energy fragmentation channel for each of the parent ions. Fragmentation of the ozonolysis products was found to be controlled by entropic effects. Mechanisms are proposed for each of the new dissociation pathways based on the energies and entropies of activation and parent ion conformations sampled using molecular dynamics. (J Am Soc Mass