S
1
Scanning Electrochemical Microscopy of
DNA Monolayers Modified with Nile Blue
Alon A. Gorodetsky
, William J. Hammond, Michael G. Hill, Krzysztof Slowinski,
and
Jacqueline K. Barton
Supporting
Figure
1
.
Schematic illustrat
ion of the
of the Nile Blue
modified uridine
.
S
2
Supporting Figure 2
. Cyclic voltammetry of DNA monolayers at various scan r
ates
modified with NB at the bottom (A) and top
(B) in pH =7.
1, 5 mM NaPi, 50 mM NaCl
buffer. The
corresponding plots of peak cu
rrent as a function of scan rate are shown on
the right.
The sequence was
5’
-
TGC GTG CTT TAT ATC
U
C
-
3’ (bottom NB)
and
5’
-
U
GC GTG CTT TAT ATC TC
-
3’ (top NB) where the italicized U indicates the location
of the NB moiety.
S
3
Supporting
Figure
3
.
Successiv
e cyclic voltammograms of ferricyanide at a bare Au
electrode in pH =7.1, 5 mM NaPi, 50 mM NaCl buffer before (red) and after (other
colors) addition of 1 mM 11
-
mercaptoundecylphosphoric acid to the buffer.
The
voltammograms correspond to different exposur
e times in the 11
-
mercaptoundecylphoshoric acid containing buffer.
Complete attenuation of the
ferricyanide signal is observed within 15 minutes.
S
4
Supporting Figure 4
:
SECM approach curves taken for Nile Blue
-
DNA monolayers
before (
C
, D
) and after (
A
,
B
)
addition of 1.5
μ
M Methylene Blue at substrate biases of 0
mV (
B
,
D
) and
-
300 mV (
A
,
C
). Approach curves were taken in pH= 7.2, 20 mM
Na
2
HPO
4
, 80 mM NaCl, and 5 mM K
4
Fe(CN)
6
buffer.
The sequence was
5’
-
U
GC GTG
CTT TAT ATC TC
-
3’
where the italicized U
indi
cates the location of the NB moiety.
Theoretical fits for positive and negative feedback are shown as solid lines for
comparison.