Supporting information
Characterization of a DAPI-RIT-DAPI System for Gas-Phase
Ion/Molecule and Ion/Ion Reactions
Ziqing Lin1; Lei Tan2; Sandilya Garimella1; Linfan Li1; Tsung-Chi Chen1; Wei Xu1; Yu Xia2*; Zheng
Ouyang1*
1Weldon
School of Biomedical Engineering
of Chemistry
Purdue University, West Lafayette, IN, 47907, USA
2Department
Corresponding authors:
*To whom correspondence should be addressed.
Zheng Ouyang, Email: ouyang@purdue.edu. Phone: (765) 494-2214. Fax: (765) 496-1912.
Yu Xia, Email: yxia@purdue.edu. Phone (765) 494-1142. Fax: (765) 494-0239
1
The configuration of the DAPI-RIT-DAPI system and the pressure change during reaction
The 3D schematic in Figure S1a gives a direct view of the DAPI-RIT-DAPI system for gas phase reactions.
The ion gauge was placed closed to the RIT to monitoring the pressure change during the scan function.
Figure S1b shows the pressure change inside vacuum chamber of three duty circles. The pressure rose to
10-2 Torr when DAPI (I) opened to introduce ions, dropped back to 10-3 Torr after cooling and isolation,
rose again to 10-2 torr when DAPI (II) opened to introduce other reagents. MS analysis took place several
hundreds of milliseconds reaction/cooling time, when the pressure was around 10-3-10-4 Torr.
(a)
High Pressure Reaction
(b)
DAPI(II)
DAPI(I)
Figure S1.
MS scan
(a) 3D schematic of the DAPI-RIT-DAPI system; (b) pressure change during the scan
2
Ion/molecule reactions: thiyl radical ions react with allyl iodide molecules
+ ●CH2CH=CH2 (41 Da)
O
HOOC
S
HOOC
NH2
N
H
H
N
O
+
COOH + H
NH2
CH2=CHCH2I
+
COOH + H
m/z 348
O
I
O
m/z 307
HOOC
+ ●I (127 Da)
Figure S2.
H
N
N
H
●
O
S
NH2
S
N
H
H
N
O
+
COOH + H
m/z 434
Scheme of the reactions between glutathione thiyl radical ions (m/z 307) and allyl iodide
(CH2=CHCH2I)
3
Ion/ion reactions: triply charged Angiotensin I cations react with PCP anions
The scan function for ion/ion reactions was slightly different from that of ion/molecule reactions since ions
of both polarities need to be trapped in the RIT. We set the dc on the mesh electrodes to 0 V to avoid the
diminishment of anions. After the reaction, dc voltage was adjusted back to 10 V to acquire MS spectra
(Figure S3a). The MS spectra of Angiotensin I in positive polarity (without opening second DAPI),
isolated triply charged species blank control (DAPI (II) opening without introducing PCP negative ions)
and PCP in negative polarity (dc -10 V during MS analysis) using the same scan function were recorded in
Figure S3b, S3c and S3d.
(a)
3500
3000
2500
2500
[M+3H]3+
2000
1500
Intensity
3000
2000
1500
1000
1000
500
500
300
400
500
m/z
600
700
800
OH
[PCP-H]-
2500
Cl
2000
Cl
Cl
Cl
Cl
1500
[2PCP-H]-
1000
b4 +
y4+
500
0
0
0
(d)
(c) [M+3H]3+
[M+2H]2+
Intensity
Intensity
3000
3500
(b)
300
400
500
m/z
600
700
800
150
250
350
m/z
450
550
Figure S3. (a) Waveforms of the ion/ion reaction; (b) MS spectrum of Angiotensin I without opening the
second DAPI; (c) MS spectrum of isolated triply charged peptide ions with DAPI (II) opening but the
nanoESI source being turned off for anion production; and (d) MS spectrum of PCP using the same scan
function in the negative polarity (dc was set to -10 V during mass analysis).
4
CID efficiency at different pressures
A series of CID experiments (q = 0.30) with cocaine (m/z 304, 3 μM) were carried out to investigate the
MS/MS efficiency as a function of pressure. The activation time was set to 30 ms and the amplitude was
200 mV. In Figure S4, the CID efficiency increases dramatically from 3 x 10-3 Torr to 8 x 10-4 Torr, and
drops slowly when the pressure goes down to 2 x 10-5 Torr.
O
O
O
+
N
O
N
- C6H5COOH
+H
O
N
O
- CH3OH
CH
C
H
O
[M+H]+, m/z 304
3000
3.2 x10-3 Torr
304
m/z 150
m/z 182
3000
3000
1.3 x10-3 Torr
8 x10-4 Torr
182
Intensity
182
2000
2000
1000
1000
2000
304
1000
182
150
304
150
100
3000
Intensity
0
0
0
200
m/z
100
300
3000
m/z
200
m/z
3000
300
2 x10-5 Torr
2000
2000
182
100
300
2 x10-4 Torr
5 x10-4 Torr
2000
200
182
182
1000
1000
1000
304
304
304
150
150
150
0
0
0
100
200
m/z
300
100
200
m/z
100
300
200
m/z
300
Fragmentation Rate %
100
50
0
1.0E-02
1.0E-03
Pressure (Torr)
1.0E-04
1.0E-05
Figure S4. CID spectra and MS/MS efficiency of protonated cocaine m/z 304 at different pressures.
Activation time 30 ms, amplitude 200 mV.
5
Internal Energy distribution
MS spectra of five thermometer ions on DAPI system and 4000 QTRAP are shown in Figure S5.
4000
(a)
9.0E+05
*p-OCH3
3500
3000
6.0E+05
p-OCH3
2500
p-CH3
2000
p-NO2
1500
1000
p-Cl
*p-Cl
500
Intensity
Intensity
7.0E+05
p-CN
*p-CH3
p-NO2
(b)
8.0E+05
p-OCH3
5.0E+05
p-Cl
p-CH3
4.0E+05
3.0E+05
p-CN
2.0E+05
*p-OCH3
1.0E+05
0.0E+00
0
80
120
160
m/z
200
240
80
120
160
m/z
200
240
Figure S5. MS spectra of thermometer ions on (a) DAPI instrument and (b) 4000 QTRAP
6
Ion/molecule reactions involving thiyl radical ions
MS spectra of the reaction between glutathione thiyl radical ions (m/z 307) and dimethyl disulfides were
recorded in Figure S6 with different capillary 3 inner diameters and different DAPI (II) functions (opening
time and multiple injections). The reaction time, the duration between the neutral introduction and MS
scan, was fixed to 600 ms, while the cooling time between injections was 100 ms for multiple reagent
introductions. The yields were about the same. Stable N-terminal α-radicals were probably produced
during CID or neutral injections. Ac excitation as well as the CID of the precursor thiyl radical ions (with
additional 250 ms cooling time after ac excitation) was carried out in Figure S7 (capillary 3 i.d. 0.125 mm;
DAPI (II) opening time 25 ms). The activation decreased the reaction yield, which implies nonreactive
radical ions were produced.
3500
3500
3500
DAPI(II) 0.125 mm 10 ms
DAPI(II) 0.125 mm 10ms*2
3000
DAPI(II) 0.125 mm 10ms*3
3000
3000
2500
2500
2000
1500
Intensity
Intensity
Intensity
2500
2000
1500
2000
1500
1000
1000
500
500
1000
500
0
0
0
200
200
250
300
350
400
450
250
300
500
350
400
450
200
500
300
DAPI(II) 0.125 mm 25 ms
350
400
450
500
m/z
3500
3500
3500
3000
250
m/z
m/z
DAPI(II) 0.125 mm 25ms*2
3000
DAPI(II) 0.125 mm 25ms*3
3000
2500
Intensity
Intensity
2000
1500
Intensity
2500
2500
2000
1500
2000
1500
1000
1000
1000
500
500
500
0
0
0
300
350
400
450
200
200
500
250
300
400
450
DAPI(II) 0.25 mm 10 ms
3000
300
350
m/z
400
450
500
Yield
0.8
10 ms
1
1500
0
200
10ms*2
250
2000
500
250
300
350
m/z
3
4
400
450
5
6
200
500
10 ms
0
25ms*3
0
500
1000
25ms*2
500
25 ms
500
200
Intensity
1500
1000
450
DAPI(II) 0.25 mm 10ms*2
3000
2000
1000
400
2500
10ms*3
Intensity
2500
350
3500
2500
1500
300
m/z
DAPI(II) 0.25 mm 25 ms
3000
2000
250
500
3500
3500
Intensity
350
m/z
m/z
250
300
350
m/z
400
450
500
25ms*2
250
25 ms
200
0.6
0.4
0.2
0
1
2
Capillary 3 i.d. 0.125 mm
Figure S6.
7
8
9
i.d. 0.25 mm
Thiyl radical reaction for different capillary inner diameters and opening times
7
2500
2500
(a)
2000
307
2000
Intensity
Intensity
(b)
307
1500
354
1000
500
1500
1000
354
500
289
232
0
0
200
250
300
350
m/z
400
450
500
200
3000
3500
(c)
307
250
300
350
400
450
500
350
400
450
500
m/z
(d)
3000
2500
232 [b2-H] +•
2500
Intensity
Intensity
2000
1500
-H2O
289
2000
1500
1000
1000
307
354
500
500
289
232
0
0
200
250
300
350
m/z
400
450
500
200
250
300
m/z
Figure S7. MS spectra of thiyl radical reaction for activation with ac amplitude (a) 0.06 V; (b) 0.066 V;
(c) 0.07 V; and (d) CID spectrum of thiyl radical ions.
8
Simultaneous opening of DAPI (I) and (II) could also be used for carrying out reactions (dual DAPI
reaction mode). In dual DAPI reaction mode, two DAPIs opened synchronically, allowing the two gas
flows to collide inside the RIT, which is expected to have higher internal energy deposition than the
sequential injection mode. Previous simulation (Garimella, S., Xu, W., Ouyang, Z.: Simulation of Transient
Rarefied Gas Expansion for Discontinuous Atmospheric Pressure Interface (DAPI) Using Direct
Simulation Monte Carlo (DSMC). ASMS 60th Annual Conference Proceedings ThOF PM (2012)) implies
that a collision plane could be formed inside the RIT due to the gas flows coming from opposite directions.
Figure S8 shows a comparison of the reaction products of thiyl radical ion with dimethyl disulfide between
the sequential introduction mode without isolation or activation (Figure S8a and b) and the simultaneous
introduction mode (Figure S8c and d). A much higher reaction yield was observed for latter, which
indicates a higher energy condition associated with the confrontation of the two gas flows. More thiyl
radical ions could be generated from the protonated S-nitrosoglutathione and were immediately involved in
the reactions, which correspond to a higher efficiency with the higher collision frequencies, more energetic
collisions, and higher number densities of both reactant species.
(a)
(d)
3000
Simultaneous Injection Mode
1800
Reactant
307
1200
600
Product
354
1200
337
2400
Intensity
1500
Sequential Injection Mode
Intensity
(b)
(c)
Product
354
900
Reactant
307
600
337
289
300
0
0
200
250
300
m/z
350
400
450
200
250
300
m/z
350
400
450
Figure S8. Dual DAPI reaction of protonated S-nitrosoglutathione and dimethyl disulfide. (a) The scan
function and (b) reaction spectrum of sequential injections of the reactants without isolation or activation;
(c) The scan function and (d) spectrum of simultaneous injections of the reactants.
9