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Gas-Phase Reverse Micelles – Generation, Structure and Application
Jianbo Liu, Department of Chemistry and Biochemistry
Queens College and the Graduate Center of the City University of New York, Flushing, NY 11367
We present encapsulation of various amino acids into gas-phase multiply-charged sodium bis(2-ethylhexyl) sulfosuccinate
(NaAOT) reverse micelles (RMs). Hydrophilic amino acids are encapsulated into the micellar core through electrostatic
interactions; while hydrophobic amino acids adopt zwitterionic structures, and are incorporated at the interface through a
combination of electrostatic and hydrophobic interactions. We demonstrate that gas-phase RMs can act as “nanometersized vehicles” for selective encapsulation and transport of amino acids from solution to the gas phase.
1500
17+WH
2
a)
*
17+W
2
b)
16+WH
8 (16 ) 2 17
1 2
2
*
2
15
2
7 (14 ) * 21+WH
1 2
3
12+WH
2 13+WH
2
13 20+WH
3
2
15
2
6(12 )
1 2
21
3
7 14
20 1( 2 )
3
20
3
8
1
18+WH
6 12*
3
17+WH ( )
1 2
3
11
2
17
3
*
12+WH
2
13+WH
13
2
2
* 17+WH
3
14
93
2
2000
5(10, 15 )
1 2 3
6 (12 )
11
1 2
2
2500
8
9
12
13
10
14
11
15
n + mDH
=
z
17
16
3000
m/z
3500
4000
15
3
11+DH
3
20+W
3
20
12+DH
2
15
21
22
4000
z =1
16
23
17
24
25
10+DH
2
11+DH
2
z =2
26
z =3
21+DH
3
14+DH
2
21+2DH
3
14+2DH
25+DH
2
3
20+DH
17+DH
3
23+DH
24+DH
2
3
22+DH
3
26+DH
3
16+DH
3
15+DH
2
2
23+2DH 24+2DH
3
3
13+DH
2
14+DH
3
12+DH
3
18+2DH
3
15+2DH
3
18+W
3
11+WH
3
12+WH
3
11+2WH
2
14+2WH
3
23+WH
3
18+2WH 26+WH
3
4
22+WH
4
13+WH
3
14+WH
3
* precursor ions
18+WH
4
n+mW
z+
z =[(NaAOT)nNazTrpm]
2500
8
14
19
17+2DH
3
18+DH
3
15+DH
3
3
15+W
3
13
18
17+DH
3
3
17
3
*
7
12
16+DH
3
z+
* 17+W
n+mWH
=
z
z+
[(NaAOT)nNaz-mTrpHm]
3500
6
19+DH
3
[(NaAOT)nNaz-mAspHm]
18
3
17
3
16+WH 3 11+WH
2
3
6 (12 )
5 16 11
1 2
1 3 2
* 15+WH
14+WH
3
5
13+DH
3
*
14+WH
2
15
2
3000
15+W
2
* 21+W
15+WH
2
8
1
20+WH
19+WH *
3
12+WH 3
2
6 12 19
1( 2 ) 3
n=7
n=10 11
* 15+WH
2500
n=4
*
17
2
14
2 14+WH
2
5(10
1 2)
2000
3000
3500
17+WH
3
15+WH
3
11+WH
2
9+WH
2
10+WH
2
4000
m/z
Collision Induced Dissociation (CID) of amino acidencapsulating RMs: a) Exclusion of protonated Trp (WH) upon
CID resulted in collapse of micellar structure, proving WH was
hosted inside the core; b) CID stripped neutral Trp (W) and only
W off micelles, proving W was attached to the interface.
16+WH
3
17+2WH
3
12+WH
2
20+WH
3
13+2WH
2
19+WH
3
[(NaAOT)nNaz-mTrpHm]
z+
2000
14+WH
2
12+2WH
2
24+WH
3
14+2WH
2
13+WH
2
15+2WH
3
n + mWH
=
z
1500
18+WH
3
21+WH
3
21+2WH
3
15+WH
2
16+WH
2
17+WH
2
23+2WH
3
20+2WH
3
10+2WH
2
Preferential encapsulation
of Trp over Asp
2500
3000
3500
4000
m/z
Top) Mass Spectrum of solution containing NaAOT and Asp, showing
encapsulation of protonated Asp in gas-phase RMs; bottom) After adding
Trp to the solution, all Asp signals vanished; instead, only protonated Trp
was encapsulated, demonstrating the selectivity of gas-phase RMs.