Gas-phase reactivity of peptide thiyl (RS•), perthiyl (RSS•), and sulfinyl (RSO•) radical ions formed from atmospheric pressure ion/radical reactions.
In this study, we demonstrated the formation of gas-phase peptide perthiyl (RSS•) and thiyl (RS•) radical ions besides sulfinyl radical (RSO•) ions from atmospheric pressure (AP) ion/radical reactions of peptides containing inter-chain disulfide bonds. The identity of perthiyl radical was verified from characteristic 65 Da (•SSH) loss in collision-induced dissociation (CID). This signature loss was further used to assess the purity of peptide perthiyl radical ions formed from AP ion/radical reactions. Ion/molecule reactions combined with CID were carried out to confirm the formation of thiyl radical. Transmission mode ion/molecule reactions in collision cell (q2) were developed as a fast means to estimate the population of peptide thiyl radical ions. The reactivity of peptide thiyl, perthiyl, and sulfinyl radical ions was evaluated based on ion/molecule reactions toward organic disulfides, allyl iodide, organic thiol, and oxygen, which followed in order of thiyl (RS•) > perthiyl (RSS•) > sulfinyl (RSO•). The gas-phase reactivity of these three types of sulfur-based radicals is consistent with literature reports from solution studies.
Department of Chemistry, Purdue University, West Lafayette, IN, USA.
Lei
L
Tan
Yu
Y
Xia
D001274:Atmospheric Pressure; D004220:Disulfides / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D005740:Gases / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods*; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013457:Sulfur Compounds / Q000737:chemistry*
D004220:Disulfides; D005609:Free Radicals; D005740:Gases; D007477:Ions; D010455:Peptides; D013438:Sulfhydryl Compounds; D013457:Sulfur Compounds