S 1
Supporting Information
Coupling
Into the Base Pair Stack is Necessary for DNA
-mediated
Electrochemistry
Alon A. Gorodetsky, Omar Green, Eylon Yavin,
and Jacqueline K. Barton*
Division of Chemistry and Chemical Engineering
California Institute of Techn
ology,
Pasadena, California 91125
*to whom correspondence should be addressed
S 2
500
400
300
200
100
0
500
400
300
200
100
0
nm
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
nm
Figure
S1
. AFM characterization of DNA
-modified and bare HOPG
. Data were
collected
in
5 mM sodium
phosphate
, 50 mM NaCl, pH 7.1
(tapping mode). Typical
AFM
image of A:
well matched
DNA on HOPG, B: DNA featuring an acetylene
-
TEMPO modified uridine, and C: unmodified HOPG. Sequences for A are pyrene
-
(CH
2
)
3
CONH(CH
2
)
6
NHCO
-5’-CTA
CAG
TCGT-
3’ plus well matched
complement and
for B are pyrene
-(CH
2
)
3
CONH(CH
2
)
6
NHCO
-5’-CTACAG
TCGT-
3’ plus TEMPO
modified complement.
S 3
10
20
30
40
50
60
70
80
90
0.36
0.37
0.38
0.39
0.40
0.41
0.42
0.43
0.44
Absorption (A.U.)
Temperature (deg C)
10
20
30
40
50
60
70
80
90
100
0.195
0.200
0.205
0.210
0.215
0.220
0.225
0.230
0.235
Absorption (A.U.)
Temperature (deg C)
Figure
S2
. Melting temperature determinations of DNA modified by AQ through an
acetylene linkage (top) and unmodified DNA with the same sequence (bottom). The
melting temperature was determined through a
pplication of a sigmoidal fit (red),
revealing a melting point of 55°C for AQ modified DNA, and 5
1°C for unmodified
DNA. Data were collected in 5 mM sodium
phosphate
, 50 mM NaCl, pH 7.1
.
S 4
0
100
200
0
200
400
600
800
1000
Scan Rate (mV/s)
Current (nA)
Figure
S3
. Scan rate dependence of DNA modified by AQ through an
acetylene linkage.
Data were collected in
5 mM sodium
phosphate
, 50 mM NaCl, pH 7.1.
0
25
50
-2
-1.5
-1
-0.5
0
Log (
)
Epc
10 s-1
30 s-1
50 s-1
Experimental Data
Figure
S4
. Plot of peak splitting
E
pc
(
E
pc
= E
pc
-E°) versus log (
) (where
= scan
rate) for DNA modified by AQ through an acetylene linkage. Simulated curves
corresponding to k
s
values of 10 s
-1
(blue), 30 s
-1
(green) and 50 s
-1
(red) are shown for
comparison.
1
1
Tender, L., Carter, M
.T., Murray, R.W.,
Anal. Chem.
,
1994
,
66
, 3173-
3181
S 5
0
100
200
300
0.2
0.6
1.0
Potential (V vs. NHE)
Peak Current (nA)
Figure
S5
. Square wave voltammetry of a
DNA
-modified
surface featuring well
matched DNA (black) and DNA with a CA mismatch above the TEMPO label (red). The
sequence was
pyrene
-(CH
2
)
3
CONH(CH
2
)
6
NH
CO
-5’-CTA C
A
G
T
CG T-
3’ plus TEMPO
modified complement The italicized base indicates the location of the TEMPO, and the
bold base indicates the location of the mismatch.