Some proline substituent effects in the tandem mass spectrum of protonated pentaalanine

Probing the mechanism of electron capture dissociation on variously modified model peptide polycations has resulted in discovering many ways to prevent or reduce N À C ! bond fragmentation. Here we report on a rare finding of how to increase the backbone bond dissociation rate. In a number of model peptides, amide-to-ester backbone bond substitution increased the frequency of O À C ! bond cleavage (an analogue of N À C ! bonds in normal peptides) by several times, at the expense of reduced frequency of cleavages of the neighboring N À C ! bonds. In contrast, the ester linkage was only marginally broken in collisional dissociation. These results further highlight the complementarity of the reaction mechanisms in electron capture dissociation (ECD) and collision-activated dissociation (CAD). It is proposed that the effects of amide-to-ester bond substitution on fragmentation are mainly due to the differences in product ion stability (ECD, CAD) as well as proton affinity (CAD). This proposal is substantiated by calculations using density functional theory. The implications of these results in relation to the current understanding of the mechanisms of electron capture dissociation and electron transfer dissociation are discussed.

Section: Cad Results Are Best Explained By Differences In Proton Affimentioning

confidence: 99%

Effects of Peptide Backbone Amide-to-Ester Bond Substitution on the Cleavage Frequency in Electron Capture Dissociation and Collision-Activated Dissociation

Kjeldsen

Zubarev

2011

“…Note that the b-chain of bovine insulin with five basic sites is quintuply protonated [30]. Presumably the close proximity of the two arginine residues (amino acid 17 and 18) in glucagon prevents the protonation of both of them.…”

Section: Native Glucagonmentioning

confidence: 99%

“…Four different charge states (ϩ2, ϩ3, ϩ4, ϩ5) have been investigated ( Figure 6) and compared with the obtained sequence information (Figure 9). Note that Pro 27 is known to have a major influence on the dissociation behavior under ESI-CID conditions [30].…”

Section: B-chain Of Bovine Insulinmentioning

confidence: 99%

Investigation of the influence of charge derivatization on the fragmentation of multiply protonated peptides

Sonsmann¹,

Römer²,

Schomburg³

2002

The fragmentation of the multiply charged peptides b-chain of bovine insulin and glucagon have been investigated under low energy collision induced dissociation (CID) conditions using an electrospray ion trap mass spectrometer. The influence of charge state, specific amino acids such as aspartate or proline, the location of basic sites, and the derivatization on the fragmentation behavior has been the focus of interest. As a basis for understanding the fragmentation process, the concept of the mobile proton was applied. A set of different derivatives was used to manipulate the sites of protonation of the peptides in order to control and improve the fragmentation behavior. These results can be applied for de novo sequencing, although the sequence-specific fragmentation processes have significant influence on the dissociation behavior of the peptides. (J Am Soc Mass Spectrom 2002, 13, 47-58)

“…Proline residues enhance dissociation Nterminally, at the Xxx-Pro amide bond, often yielding intense y-type ions, and has been observed for the dissociation of small, singly-charged peptides as well as multiply-charged proteins [32,44]. This site-specific cleavage was first attributed to the high gas-phase basicity of the proline residue [45], but has also been theorized to be due to unfavorable ring strain of a proposed bicyclic structure of the b-type ion that would be formed upon cleavage C-terminal to the proline [46].…”

mentioning

confidence: 98%

Impact of proline and aspartic acid residues on the dissociation of intermolecularly crosslinked peptides

Gardner

Brodbelt

2008

The dissociation of intermolecularly crosslinked peptides was evaluated for a series of peptides with proline or aspartic acid residues positioned adjacent to the crosslinking sites (lysine residues). The peptides were crosslinked with either disuccinimidyl suberate (DSS) or disuccinimidyl L-tartrate (DST), and the influence of proline and aspartic acid residues on the fragmentation patterns were investigated for precursor ions with and without a mobile proton. Collisionally activated dissociation (CAD) spectra of aspartic acid-containing crosslinked peptide ions, doublycharged with both protons sequestered, were dominated by cleavage C-terminal to the Asp residue, similar to that of unmodified peptides. The proline-containing crosslinked peptides exhibited a high degree of internal ion formation, with the resulting product ions having an N-terminal proline residue. Upon dissociation of the doubly-charged crosslinked peptides, twenty to fifty percent of the fragment ion abundance was accounted for by multiple cleavage products. Crosslinked peptides possessing a mobile proton yielded almost a full series of b-and y-type fragment ions, with only proline-directed fragments still observed at high abundances. Interestingly, the crosslinked peptides exhibited a tendency to dissociate at the amide bond C-terminal to the crosslinked lysine residue, relative to the N-terminal side. One could envision updating computer algorithms to include these crosslinker specific product ions-particularly for precursor ions with localized protons-that provide complementary and confirmatory information, to offer more confident identification of both the crosslinked peptides and the location of the crosslink, as well as affording predictive guidelines for interpretation of the product-ion spectra of crosslinked peptides. (J