Lei Tan, Yu Xia Department of Chemistry Purdue University

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1 Lei Tan, Yu Xia Department of Chemistry Purdue University 1

2 Sulfinyl radical (-) Introduction Photolysis of sulfoxide (sulfur cycle) (CH 3 ) 2 SO hv CH 3 CH 3 H CH 3 Ar Observed in protein system Glycyl Inactivation of Pyruvate Formate-Lyase (PFL) Enzyme with Radical Storage site: Glycyl radical Active site: Thiyl radical Oxygen ESR of protein sulfinyl radical 2 Cysteine Darmanyan A.P. et al, J. Phys. Chem. A. 1997, 101(37), Gauld J.W.; J. Am. Chem. Soc. 2000, 122,

3 New Way to Form Sulfinyl Radical Ion HV: 1-2 kv 2-3 kv AC 30 khz NanoESI AP Plasma Helium H 2 O e - OH H e - O H 2 O 2 OH MS inlet x5 [M2H] [17] 2 [16] C I E L L Q A R C [MHNa] H 2 N radical rxns (e.g. OH) SH C nh CO 2 H C nh SO Peptide Sulfinyl Radical n n CID HS C H 2 N H b m C SO O y n CO 2 H nh n Xia Y.; Anal. Chem.; 2010, 82(7), Ma X.X.; J. Am. Soc. Mass Spectr. 2011, 22(5),

4 Formation of Site-Specific Sulfinyl Radical H 2 N H 2 N Chain A Chain B COOH COOH Inter-chain disulfide linked peptide ESI radical rxns (e.g. OH ) H 2 N H 2 N Chain A/B COOH /- /- COOH Site-Specific Peptide Sulfinyl Radical Ion Easy to determine the site of sulfinyl radical Change the polarity of ions easily. 4

5 Experiment Setup Ion/Radical Reaction Q0 Q1 Q2 Q QTRAP 1. Helium Atmospheric Pressure (AP) Low Temperature Plasma 2. Low Pressure Hg Lamp 185 nm, 248 nm 20 ma NanoESI AI foil MS inlet 5 Wed. Poster WP 760 Craig Stinson

6 Formation of Site-Specific Peptide Sulfinyl Radical Ions 6

7 Formation of Site-Specific Peptide Sulfinyl Ion Positive mode [B SH H] [B H] [M2H] [MNaH] 2 [MKH] 2 [A SH H] [ CLPTRH ] SH HMAC CLPTR Chain A: Chain B: [A SH H] [A H] [A H] [ CLPTRH ] Sulfinyl Radical 7

8 Formation of Site-Specific Peptide Sulfinyl Ion Positive mode [B SH H] [B H] [M2H] [MNaH] 2 [MKH] 2 HMAC CLPTR Chain A: Chain B: [A SH H] [A H] Negative mode [B SH -H] [B -H] [M-2H] [A SH -H] [A -H]

9 Formation of Sulfinyl Radical Ion Higher Helium Flow Rate [ CLPTRH ] SH [ CLPTRH ] More Intense Plasma Higher Radical Density Consecutive oxidation c) b) a) Increasing Flow Rate 9

10 Structure of Cysteine Sulfinyl Radical Ions Cys-, 137 Chasity Love Joe Francisco Tue. Poster: TP 761 Cys- Spin densities Neutral S: O: Protonated at NH 2 S: O: Protonation NH 2 C=O Energy 0 kj/mol kj/mol Protonated at C=O S: O: *All calculation was carried out using Gaussian, MP2/6-31G* andb3lyp/6-31g* 10

11 Collisional Induced Dissociation (CID) of Peptide Sulfinyl Radical Ions - Radical v.s. Charge Driven Dissociation 11

12 Rel. Int. (%) (a) 0 Ion trap CID of Peptide Sulfinyl Cation [ CLPTRH ] - 62Da (CH 2 SO) -56Da (L) Da (CH 2 SO) Da (CH 2 SO) (c) [ HMACH ] b 2-74Da (M) -47Da (M) -18Da Da -HSO (b) [ GCGKH ] HSO -49Da

13 Loss of 62 Da (CH 2 SO) Radical Directed Dissociation 2 Sulfinyl Radical H N CH O CID C Glycyl Radical 62 Da 2 Accurate Mass Da Activation energy: 38.7 ± 1.4 kcal/mol * Calculation based on neutral cysteine sulfinyl radical Activation energy for amide bond cleavage: kcal/mol 13 Lioe H.; J. Am. Soc. Mass Spectr. 2007, 18,

14 Rel. Int. (%) Ion trap CID of Peptide Sulfinyl Cation - 62Da (CH 2 SO) Da (CH 2 SO) Da (CH 2 SO) (a) 0 [ CLPTRH ] -56Da (L) (c) [ HMACH ] b 2-74Da (M) -47Da (M) -18Da Da -HSO (b) (d) [ GCGKH ] a b HSO -49Da [ TLCH ] -62Da (CH 2 SO)

15 100 Radical v.s. Charge Directed Dissociation - Charge States [ C G A I L R H ] Radical Directed 50 Dissociation - 62Da (CH 2 SO) [MH] -56Da(I or L) Charge Directed 50 Dissociation [M2H] 2 y Da o b 4 y 3 o b 3 y 1 0 y [ C G A I L R 2H ] 2 Loss of CH 2 SO ~ 39 kcal/mol Amide bond cleavage kcal/mol 15

16 [ C G N K R H ] N-terminal Acetylation - 62Da (CH 2 SO) [ CH 3 -CO-C G N K R H ] 42 Da - 49Da (HSO) CH 2 SO Acetylation can promote 49Da (HSO) loss! 16

17 [ GGCK H ] Charge/Radical Location -71Da (K) Da (CH 2 SO) Da (HSO) [ GCGK H ] CH 2 SO HSO [ CGGK H ] -71Da (K) -CH 2 SO

18 Loss of 49Da (H) [ G G C K - HSO H ] *y y dehydroalanine But somehow affected by charge 18

19 Charge Polarity [ CSR H ] - 62Da (CH 2 SO) [ CSR - H ] Da (HSO)

20 Reactivity of Sulfinyl Radical - The fate of sulfinyl radical - Ion/molecular reaction 20

21 Experiment Setup Ion-molecule reaction Ion/Radical Reaction Q0 Q1 Q2 CAD gas line Q3 Neutral 5.0 m Torr 0.05 mtorr 4000 QTRAP 21

22 Ion-Molecule Rxns of Peptide Sulfinyl Radical Ions Trapping 3s with ally iodide [ CLPTR H ] CH 2 -CH=CH 2 (41 Da) CH 2 -CH=CH I 22

23 Ion-Molecule Rxns of Peptide Sulfinyl Radical Ions Trapping 3s with dimethyl disulfide [ CLPTR H ] Da SCH 3 (47 Da)

24 10% 5% Ion-Molecule Rxns: Sulfinyl v.s. Thiyl Trapping 3 s with CH 3 -S-S-Ph Da (SCH 3 ) [ CLPTR H ] 0% % 5% Da (SCH 3 ) [ CLPTR H ] 0% S 123 Da (SPh)

25 Formation of Site-Specific Glycyl Radical 2 H N CH O CID C Glycyl Radical 62 Da 2 Sulfinyl Radical 25

26 [GGGK H] [GGGK H] [GGGK H] Tracking Radical Migration y (K) y y (K) -30 y y Sulfinyl Radical CID Glycyl Radical CID CH 2 =CH(CH 2 ) 2 NH 2 71 Da y (K)

27 Summary H 2 N COOH ESI H 2 N /- COOH H 2 N COOH radical rxns (e.g. OH ) Sulfinyl Radical Ion-molecule reaction CID S S CH 2 =CH CH 2 I Low reactivity H N CH O C Glycyl Radical -CH 2 SO Basic amino acid Charge state Charge location Charge polarity 27

28 Acknowledgement Dr. Larry Campbell Dr. Jim Hager Dr. Joe Francisco 28