PDF《peptides†》

1 The conversion of the amino acid residue arginine (left) to citrulline (right). a School of Dentistry, Periodontal Research Group, University of Birmingham, St Chads Queensway, Birmingham, B4 6NN, UK b School of Biosciences, University of Birmingham, Birmingham, B15 2TT, UK. E-mail: [email protected] ? Electronic supplementary information (ESI) available: The m/z values and ion intensities for all informative fragments from MS/MS spectra in ?gure

1 are shown in table S1. See DOI: 10.1039/c0ay00414f This journal is ? The Royal Society of Chemistry

2011 Anal. Methods, 2011, 3, 259C266 |

259 PAPER www.rsc.org/methods | Analytical Methods preferential loss of post-translational modi?cations at the expense of sequence fragments. This occurrence can hinder both peptide identi?cation and localisation of the site of the modi?- cation. Electron transfer dissociation (ETD) is a tandem mass spectrometry technique, analogous to electron capture dissocia- tion (ECD),28 developed by Syka et al. in 2004.29 Both ETD and ECD involve radical ion chemistry and result in the cleavage of the NCCa peptide bond, producing c and zc ions. There are signi?cant advantages gained by fragmentation of peptides with ETD or ECD: fragmentation is random and relatively non- selective, the only exception being cleavage N-terminal to proline,30 hence the extent of peptide sequence coverage is often greater than for CID.31,32 Furthermore, in ET/CD, labile post- translational modi?cations (PTMs) are retained on the peptide backbone fragments. The site of modi?cation can therefore be localised: g-carboxyglutamic acid,33 phosphorylation (S, T and Y),34C37 N and O glycosylation,38C40 acylation,41 sulf........