DNA-Mediated Charge Transport Requires Conformational Motion of the DNA Bases:
Elimination of Charge Transport in Rigid Glasses at 77 K
Melanie A. O’Neill, and Jacqueline K. Barton
Division of Chemistry and Chemical Engineering, California Institute of Technology,
Pasadena, California 91125
Supporting Information
Figure S-1.
Reproducibility (a) and stability (b) of 10 M aqueous LiCl glasses, as monitored by
the fluorescence emission of photoexcited 2-aminopurine (Ap*, 25
μ
M,
λ
ex = 325 nm). Shown
in (a) are the emission spectra of obtained in three independently prepared glassy matrices at 77
K. These emission spectra are very stable over periods of at least several hours. Shown in (b) is
the variation in emission intensity Ap* (monitored at
λ
max = 360 nm) in a LiCl glass at 77 K as
a function of time (total time of 30 minutes). The expanded plot (inset) reveals intensity
fluctuation of < 5 %. Similar results were observed for Ap-DNA samples.
0
500
1000
1500
2000
2500
0
500
1000
1500
Intensity (a.u.)
Time (s)
2280
2300
2320
2340
2360
2380
0
500
1000
1500
Intensity
(a.u.)
Time (s)
(b)
350
400
450
500
550
Intensity (a.u.)
Wavelength (nm)
(a)
Figure S-2.
Fluorescence excitation spectra (
λ
em = 370 nm) of 2.5
μ
M ApA4I in 100 mM
sodium phosphate pH 7 (closed circles) and 10 M LiCl pH 7 (open circles) at ambient
temperature (~ 298 K) The lower duplex concentration is necessary due to the strong absorption
of the natural DNA bases at
λ
< 300 nm.
220
240
260
280
300
320
340
Normalized Intensity (a.u.)
Wavelength (nm)
Table S-1.
A comparison of the photophysical properties of Ap-DNA assemblies, and yield of
charge transport between Ap* and G in 10 M LiCl pH 7 versus 100 mM sodium phosphate pH 7
(NaP) at ambient temperature (~ 298 K).
Sample
a
Φ
rel
Y=I
b
Anisotropy Y=I
c
Fq (298 K)
d
NaP
LiCl
NaP
LiCl
NaP
LiCl
ApY
0.1
0.1
0.25
0.26
0.87
0.,68
ApAY
0.06
0.1
0.23
0.25
0.47
0.47
ApA2Y
0.04
0.06
0.25
0.24
0.20
0.23
ApA3Y
0.03
0.05
0.26
0.23
0.24
0.18
ApA4Y
0.04
0.07
0.23
0.23
0.14
0.14
a
25
μ
M Ap in 35-mer DNA duplexes, 5’-GAT TAT AGA CAT ATT IAp(A)
n
YIT ATT AAG
TAC ATT AC-3’, Y=I,G, in 10 M LiCl, pH 7 or 100 mM sodium phosphate pH 7 at ~ 298 K.
b
Fluorescence yields relative to Ap in respective solution (
λ
ex
= 325 nm).
c
Monitored at 370 nm.
d
Evaluated as Fq = 1 –
Φ
G
/
Φ
I
, relative uncertainties ± 10 %.