Issue 37, 2018

Replacing H+ by Na+ or K+ in phosphopeptide anions and cations prevents electron capture dissociation

Abstract

By successively replacing H+ by Na+ or K+ in phosphopeptide anions and cations, we show that the efficiency of fragmentation into c and z˙ or c˙ and z fragments from N–Cα backbone bond cleavage by negative ion electron capture dissociation (niECD) and electron capture dissociation (ECD) substantially decreases with increasing number of alkali ions attached. In proton-deficient phosphopeptide ions with a net charge of 2−, we observed an exponential decrease in electron capture efficiency with increasing number of Na+ or K+ ions attached, suggesting that electrons are preferentially captured at protonated sites. In proton-abundant phosphopeptide ions with a net charge of 3+, the electron capture efficiency was not affected by replacing up to four H+ ions with Na+ or K+ ions, but the yield of c, z˙ and c˙, z fragments from N–Cα backbone bond cleavage generally decreased next to Na+ or K+ binding sites. We interpret the site-specific decrease in fragmentation efficiency as Na+ or K+ binding to backbone amide oxygen in competition with interactions of protonated sites that would otherwise lead to backbone cleavage into c, z˙ or c˙, z fragments. Our findings seriously challenge the hypothesis that the positive charge responsible for ECD into c, z˙ or c˙, z fragments can generally be a sodium or other metal ion instead of a proton.

Graphical abstract: Replacing H+ by Na+ or K+ in phosphopeptide anions and cations prevents electron capture dissociation

Supplementary files

Article information

Article type
Edge Article
Submitted
05 jun 2018
Accepted
07 jul 2018
First published
26 jul 2018
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2018,9, 7338-7353

Replacing H+ by Na+ or K+ in phosphopeptide anions and cations prevents electron capture dissociation

E. Schneeberger and K. Breuker, Chem. Sci., 2018, 9, 7338 DOI: 10.1039/C8SC02470G

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