Supporting information
The Dehydration Dynamics of Model Cell Membrane Induced by
Cholesterol Analogue 6-Ketocholestanol Investigated Using Sum Frequency
Generation Vibrational Spectroscopy
Sulan Ma,1 Kangzhen Tian1,2, Shuji Ye,1,2*
1
Hefei National Laboratory for Physical Sciences at the Microscale, and Department of
Chemical Physics, University of Science and Technology of China, Hefei, Anhui, P.R.China
230026; 2Synergetic Innovation Center of Quantum Information & Quantum Physics,
University of Science and Technology of China, Hefei, Anhui 230026, China
1. Fitting of SFG-VS Signal
As described in detail elsewhere, the intensity of the SFG light is related to the square of
( 2)
the sample's second-order nonlinear susceptibility  eff
, and the intensity of the two input
fields I ( IR ) and I ( vis ) , see eq. (1), which vanishes when a material has inversion
symmetry [1-6].
2
( 2)
I ( SFG )   eff
I 1 ( vis ) I 2 ( IR )
(S1)
where  SFG   IR  vis . As the IR beam frequency is tuned over the vibrational resonance of
surface/interface molecules, the effective surface nonlinear susceptibility  R( 2) can be
( 2)
enhanced. The frequency dependence of  eff
is described by
( 2)
( 2)
 eff
( )   NR


A
(S2)
    i
where A ,  , and  are the strength, resonant frequency, and damping coefficient of the
vibrational mode(), respectively. A could be either positive or negative depending on the
S1
phase of the vibrational mode. The plot of SFG signal vs. the IR input frequency shows a
polarized vibrational spectrum of the molecules at surface or interface. A ,  , and  can
be extracted by fitting the spectrum.
2. Figure S1-Figure S6
a)
b)
c)
d)
Figure S1. Molecular structure of a) 6-ketocholestanol; b) DMPC; c) DMPG d) DMEPC.
S2
A
Surface pressure (mN/m)
Surface pressure (mN/m)
50
KCL
KBr
KNO3
40
B
DMPC:6-KC=12： 20
DMPC:6-KC=12： 15
DMPC:6-KC=12： 10
DMPC:6-KC=12： 5
DMPC:6-KC=12： 1
DMPC
50
Water
K2SO4
KI
KSCN
30
20
40
30
20
10
10
0
0.2
0.4
0.6
0.8
2
1.0
0
0.2
1.2
Mean molecular area(nm /molecule)
0.4
0.6
0.8
1.0
2
1.2
1.4
Mean molecular area(nm /molecule)
Figure S2. The surface pressure-area (-A) isotherms of A)DMPC at air/ different salt
solution
(100 mM); B) The mixture of DMPC and 6-KC with different DMPC/6-KC ratios
Intensity
at air/water interface.
1.2
0.8
0.4
0.0
1.0
0.5
0.0
1.2
0.6
0.0
0.8
0.4
0.0
0.4
0.0
a)
b)
c)
d)
e)
f)
0.3
0.0
0.2
g)
0.0
0
200
400
600
Time(min)
Figure S3 Time dependence of ssp SFG intensity at different wave numbers collected from
S3
d-DMPC bilayer/water interface at different time after adding 3L 6- ketocholestanol solution
at t = 0 min: a). 3000 cm-1; b). 3100 cm-1; c). 3200 cm-1; d). 3300 cm-1; e). 3400 cm-1; f). 3500
cm-1; g). 3600 cm-1.
SFG Intensity
2
a)
0
4
2
0
6
3
0
4
2
0
2
0
2
0
1
0
b)
c)
d)
e)
f)
g)
0
100 200 300 400 500 600
Time(min)
Figure S4 Time dependence of the ssp SFG intensity at different wave numbers collected
from DMEPC bilayer/water interface at different time after adding 10 L 6-ketocholestanol
solution: a). 3000 cm-1; b). 3100 cm-1; c). 3200 cm-1; d). 3300 cm-1; e). 3400 cm-1; f). 3500
cm-1; g). 3600 cm-1.
S4
0.4
SFG intensity
1.2
0.3
0.2
ssp
0.1
(2)
psp SFG Intensity
A
B
0.9
0.6
0.3
0.0
1.2
C
0.9
0.6
0.3
0.0
0.0
0
50
100
150
0
200
Time(min)
40
80
120
160
Time(min)
Figure S5. (A) Time dependent psp spectra intensity at 2935 cm-1 after injecting
6-ketocholestanol into DMEPC bilayer at t=0; (B) Time dependent ssp intensity at 1710
cm-1; (C) Time dependent fitting amplitude of 1710 cm-1 peak in the ssp spectra.
0.15
a
0.10
0.05
SFG Intensity
0.00
b
0.10
0.05
0.00
0.10
c
0.05
0.00
0.10
d
0.05
0.00
2800
2900
3000
3100
-1
Wavenumber(cm )
Figure S6. The psp spectra of 6-ketocholestanol after injecting 10 L 6-ketocholestanol
S5
solution into the mixed DMPC/DMPG bilayer/water subphase. a) DMPC/DMPG=75/25; b)
DMPC/DMPG=50/50; b) DMPC/DMPG=25/75; b) DMPC/DMPG=0/100.
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S6