Supplemental Information
Transformation of [M+2H]2+ Peptide Cations to [M-H]+, [M+H+O]+, and M+• Cations via Ion/Ion Reactions:
Reagent Anions Derived from Persulfate
Alice L. Pilo, Jiexun Bu and Scott A. McLuckey*
Department of Chemistry
Purdue University
West Lafayette, IN 47907-2084
Running title: Generation of Oxidized and Radical Peptide Cations via Ion/Ion Reactions
*Address reprint requests to:
Dr. S. A. McLuckey
560 Oval Drive
Department of Chemistry
Purdue University
West Lafayette, IN 47907-2084, USA
Phone: (765) 494-5270
Fax: (765) 494-0239
E-mail:
Supplemental Information
Supplemental Figure S-1. Structures of (a) intact persulfate mono-anion (HS2O8-), (b) peroxymonosulfate anion (HSO5-), and (c) sulfate radical anion (SO4-•). Spectra derived from negative nESI of an aqueous solution of sodium persulfate using a nozzle-skimmer voltage difference of (d) 25 V and (e) 75 V.
Supplemental Figure S-2. Oxidation of KAKAKAA via ion/ion reactions with peroxymonosulfate and intact persulfate. Activation of (a) the complex between doubly protonated KAKAKAA and peroxymonosulfate anion, (b) [M+H+O]+, (c) the complex between doubly protonated KAKAKAA and intact persulfate anion, and (d) [M-H]+.
Supplemental Figure S-3. Control spectrum illustrating CID of ARAAAKA [M+H]+ showing dominant production of the b6 ion.
Supplemental Figure S-4. Ion/ion reactions between HSO5- and the [M+2H]2+ species of (a) ARAMAKA, and (b) RPPGFSPFR. The diamond (è) indicates the formation of an ion/ion complex between the [M+2H]2+ species and NaSO4-, present as a contaminant in the isolation of HSO5-.
Supplemental Figure S-5. Reaction between doubly protonated ARAMAKA and intact persulfate anion and subsequent CID of the H2SO5 loss peak, nominally represented as [M+H+SO3]+ to produce the proton transfer species, [M+H]+.
Supplemental Figure S-6. Comparison of activation of the [M+H+O]+ species produced via the ion/ion reaction between doubly protonated ARAMAKA and persulfate anion. Activation of the [M+H+O]+ species produced from (a) SO3 loss and (b) H2SO4 loss pathways. Asterisks (*) indicate ammonia losses, degree signs (°) indicate water losses, and the lightning bolt (~) indicates species subjected to CID.
Supplemental Figure S-7. Comparison of species nominally corresponding to [M-H]+ produced via the ion/ion reaction between doubly protonated ARAMAKA and intact persulfate anion. Activation of (a) the ion/ion complex and (b) water loss from the oxidized species. Asterisks (*) indicate ammonia losses, degree signs (°) indicate water losses, and the lightning bolt (~) indicates species subjected to CID.
Supplemental Figure S-8. Activation of ion/ion complexes between persulfate anions and (a) doubly protonated GAILAGAILR, (b) doubly protonated KGAILAGAILR, and (c) triply protonated KGAILAGAILR. Asterisks (*) indicate ammonia losses and the lightning bolt (~) indicates species subjected to CID.
Supplemental Figure S-9. Reaction between doubly protonated GAGGMGAGGRL and intact persulfate anion and subsequent CID of the complex, viz., [M+2H+HS2O8-]+.
Supplemental Scheme S-1. Alternative mechanism for oxidation of lysine with intact persulfate anion.
Supplemental Table S-1. List of mass-to-charge ratios with their assignments for each of the figures. When several peaks were present, the five most abundant peaks not corresponding to water or ammonia losses were chosen.
Figure / Mass-to-charge (Th) / Assignment1(a) / 1461.8 / [M+2H+HSO5-]+
1363.8 / [M+H+O]+
1(b) / 1541.8 / [M+2H+HS2O8-]+
1461.7 / [M+2H+HSO5-]+
1443.7 / [M+H+SO4]+
1427.6 / [M+H+SO3]+
1363.8 / [M+H+O]+
1345.8 / [M-H]+
1333.8 / [M+H+O-CH2O]+
1301.9 / [M-H-CO2]+
1110.8 / y9+O
1094.9 / y9
1(c) / 1444.7 / [M+2H+SO4-•]+
1383.7 / [M+2H+SO4-•-C2H5S•]+
1370.7 / [M+2H+SO4-•-C3H6S]+
1346.8 / [M]+•
1285.9 / [M+•-C2H5S•]+
1272.8 / [M+•-C3H6S•]+
2(a) / 772.0 / [M+2H+HSO5-]+
658.2 / [M+H]+
329.6 / [M+2H]2+
2(b) / 772.0 / [M+2H+HSO5-]+
674.2 / [M+H+O]+
658.2 / [M+H]+
2(c) / 674.2 / [M+H+O]+
657.2 / [M+H+O-NH3]+
639.2 / [M+H+O-NH3-H2O]+
585.2 / b6+O
2(d) / 585.2 / b6+O
457.2 / b5+O
315.1 / b3+O
244.2 / b2+O
211.2 / b2+O-NH2OH
3(a) / 832.1 / [M+2H+HSO5-]+
734.1 / [M+H+O]+
3(b) / 734.1 / [M+H+O]+
670.2 / [M+H+O-CH3SOH]+
645.2 / b6+O
581.3 / b6+O-CH3SOH
3(c) / 1173.7 / [M+2H+HSO5-]+
1075.9 / [M+H+O]+
1059.9 / [M+H]+
3(d) / 1075.9 / [M+H+O]+
919.9 / y8+O
903.9 / y8
807.0 / y7
755.1 / b7+O
710.1 / y6
651.1 / y5+O-H2O
270.1 / b2+O
4(a) / 911.7 / [M+2H+HS2O8-]+
831.9 / [M+2H+HSO5-]+
813.9 / [M+H+SO4]+
797.9 / [M+H+SO3]+
734.1 / [M+H+O]+
718.1 / [M+H]+
716.1 / [M-H]+
359.6 / [M+2H]2+
4(b) / 911.7 / [M+2H+HS2O8-]+
831.9 / [M+2H+HSO5-]+
813.9 / [M+H+SO4]+
797.9 / [M+H+SO3]+
734.1 / [M+H+O]+
716.1 / [M-H]+
704.1 / [M+H+O-CH2O]+
518.2 / c5
501.2 / b5
245.2 / c2
4(c) / 831.9 / [M+2H+HSO5-]+
734.1 / [M+H+O]+
4(d) / 813.9 / [M+H+SO4]+
734.1 / [M+H+O]+
716.1 / [M-H]+
704.1 / [M+H+O-CH2O]+
645.2 / b6+O
615.2 / b6+O-CH2O
5(a) / 1027.7 / [M+2H+SO4-•]+
930.0 / [M]+•
886.1 / [M]+•-CO2
824.0 / [M]+•-106
780.1 / [M]+•-CO2-106
641.3 / a5
5(b) / 930.0 / [M]+•
886.1 / [M]+•-CO2
844.0 / [M]+•-C3H8N3•
824.1 / [M]+•-106
780.1 / [M]+•-CO2-106
641.3 / a5
5(c) / 931.0 / [M+H]+
784.1 / b6+H2O
676.2 / y5
669.2 / b5
641.3 / a5
414.1 / YIH
6(a) / 1568.7 / [M+5H+3SO4-•]2+
1013.9 / [M+5H+2SO4-•]3+
736.7 / [M+5H+SO4-•]4+
570.1 / [M+5H]5+
6(b) / 1568.7 / [M+5H+3SO4-•]2+
1519.4 / [M+5H+3SO4-•-H2SO4]2+
1470.7 / [M+5H+3SO4-•-2H2SO4]2+
1421.8 / [M+5H+3SO4-•-3H2SO4]2+
6(c) / 1421.8 / [M-H]2+•••
1413.9 / [M-H]2+•••-NH2•
1407.0 / [M-H]2+•••-C2H5•
1399.9 / [M-H]2+•••-C3H7•
1392.5 / [M-H]2+•••-NH2COCH2•/C3H8N•