Coadsorption of Complementary and Noncomplementary Bases Coadsorption of Complementary and Noncomplementary Bases on Au(111) A. P. M. Camargo, C. Donner.
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Coadsorption of Complementary and Coadsorption of Complementary and Noncomplementary Bases Noncomplementary Bases on Au(111)
A. P. M. Camargo, C. Donner
Free University Berlin
Institute of Physical and Theoretical Chemistry
F
F
F
F
F
F
D
D
D
D
D
D
A T
C
F
F
D
D
C
T A
FF
D
D
C
DeoxyribosePhosphate group
Nitrogened bases
Nonstandard base pair
Mutagenicity Cancer Therapy
How does it work?
- Mutagenicity: one DNA base (thymine) is replaced by a nonstandard base (BrU)
- Cancer Therapy: substitution of one base by BrU at DNA leads to a greater sensitivity to ionising radiation
ProblemProblem
* M. Orozco et al., J. Phys.Chem. B, 1998, 102, 5228
*
D
D
D
D
A T
CG
D
A
Br
U
* (a) W.Haiss et al., J. Electroanal. Chem., 1998, 454, 107; (b) B. Roelfs, H. Baumgärtel, Ber. Bunsenges Phy. Chem., 1995, 99, 677
*
40
Thymine 20mM
-0.9 -0.6 -0.3 0.0 0.3 0.6
-40
-20
0
20
chemisorbed phasephysisorbed phasej /
Acm
-2
E / V vs. Ag/Ag+
Is it possible• to obtain interaction of standard /nonstandard base pairs?• to distinguish between the different interactions?
IdeaIdea-Complementary base pair: Adenine / Thymine
-Noncomplementary base pairs:Adenine / Bromouracil Guanine / Bromouracil
InvestigationInvestigation
ThymineThymine - undergoes a phase transition at Au(111) - orientation of molecules depends on the potential
Adsorption behaviour of DNA base at electrodeAdsorption behaviour of DNA base at electrode
Cell
- Au(111)
Electrodes - Ag/Ag+
- gold wire
Supporting Electrolyte: 0.1M NaClO4 / + DNA bases, BrU
pH=2
Experimental PartExperimental Part
* Y.J.Xiao, Y.F.Chen, Spectrochemica Acta, Part A, 1999, 55, 1209.
*
Complementary BasesComplementary Bases
-0.9 -0.6 -0.3 0.0 0.3 0.6
-40
-20
0
20
40
Thymine 20mM
chemisorbed phasephysisorbed
phase
j / A
cm
-2
E / V vs. Ag/Ag+
*
-0.9 -0.6 -0.3 0.0 0.3 0.6
-5
0
5
10
A'1
A'2
A'3
A3
A2
A1
Adenine 2mM
chemisorbed
phase
physisorbed phase
E / V vs. Ag/Ag+
Coadsorption Behaviour
-0.9 -0.6 -0.3 0.0 0.3 0.6
-10
-5
0
5
10
Thymine 20mM + Adenine 3mMAT'1
AT'2
T'2/3
T2/3
AT2
AT1
j / A
cm-2
H+Adenine-Dimers
-0.9 -0.6 -0.3 0.0 0.3 0.6
-10
-5
0
5
10
AT'1
AT'2
T'2/3
T2/3
AT2
AT1
Tymine 20mM + Adenine 0.4mM
-0.9 -0.6 -0.3 0.0 0.3 0.6
-10
-5
0
5
10
j / A
cm-2
T'1
T1
E / V vs. Ag/Ag+
Tymine 20mM + Adenine 0.08mM
-0.9 -0.6 -0.3 0.0 0.3 0.6
-15
-10
-5
0
5
10
15
20
25
E / V vs. Ag/Ag+
Tymine 20mM + Adenine 0.008mM
Noncomplementary BasesNoncomplementary Bases
-0.9 -0.6 -0.3 0.0 0.3 0.6
-10
-5
0
5
10
15
Bromouracil 5mM
j / A
cm
-2
E / V vs Ag/Ag+
*
physisorbed phase
chemisorbed phase
-0.9 -0.6 -0.3 0.0 0.3 0.6
-5
0
5
10
A'1
A'2
A'3
A3
A2
A1
Adenine 2mM
chemisorbed
phase
physisorbed phase
E / V vs. Ag/Ag+
Coadsorption Behaviour
-0.9 -0.6 -0.3 0.0 0.3 0.6
-20
-10
0
10
E / V vs Ag/Ag+
j / A
cm
-2
BrU 5mM+Adenine 0.0001mM
BrU 5mM
-0.9 -0.6 -0.3 0.0 0.3 0.6
-20
-10
0
10
BrU 5mM+Adenine 0.001mM
-0.9 -0.6 -0.3 0.0 0.3 0.6
-20
-10
0
10
E / V vs Ag/Ag+
j / A
cm
-2
BrU 5mM+Adenine 0.01mM
-0.9 -0.6 -0.3 0.0 0.3 0.6
-20
-10
0
10
BrU 5mM+Adenine 0.1mM
Adenine 2mM
*F. Nart., Surface Science, 480, 2001, L383
Noncomplementary Bases Noncomplementary Bases
*
-0.9 -0.6 -0.3 0.0 0.3 0.6
-5
0
5
10
A'1
A'2
A'3
A3
A2
A1
Adenine 2mM
chemisorbed
phase
physisorbed phase
E / V vs. Ag/Ag+
-0.9 -0.6 -0.3 0.0 0.3 0.6
-10
-5
0
5
10
15
chemisorbed
phasephysisorbed
phase
Bromouracil 5mM
j / A
cm
-2
E / V vs Ag/Ag+ -0.9 -0.6 -0.3 0.0 0.3
-10
-5
0
5
10
15
Guanine 0.1mM
physisorbed
phase
chemisorbed
phase
E / V vs Ag/Ag+
Coadsorption Behaviour
-0.9 -0.6 -0.3 0.0 0.3 0.6
-20
-10
0
10
BrU 5mM + Guanine 0.005mM
-0.9 -0.6 -0.3 0.0 0.3 0.6
-20
-10
0
10
BrU 5mM + Guanine 0.05mM
j /
Ac
m-2
E / V vs Ag/Ag+
-0.9 -0.6 -0.3 0.0 0.3 0.6
-20
-10
0
10
E / V vs Ag/Ag+
BrU 5mM + Guanine 0.1mM
Guanine 0.1mM
-0.9 -0.6 -0.3 0.0 0.3 0.6
-20
-10
0
10
BrU 5mM+Guanine 0.0005mM
BrU 5mM
j /
Ac
m-2
- We found attractive interactions between A-T complementary base pair1, whereby adenine was chemisorbed at the thymine physisorbed phase
- For the noncomplementary base pairs BrU-A and BrU-G we did not find any indication for attractive interactions
- The phase transition in a physisorbed condensed film for noncomplementary pairs vanishes if coadsorption takes place, it means that the interaction between them is weaker than between the bases alone (according to A-T on Hg electrodes2)
1- A.P.M. Camargo, H. Baumgärtel, C. Donner, Phys. Chem. Chem. Phys., 5, 2003, 1657
2- S. Kirste, C. Donner, Phys. Chem. Chem. Phys., 3, 2001, 4384
ConclusionsConclusions
1
2
34
5
8
67
9
N
CH
N
C
C
C
NH
HC
N
H2NAdenine Guanine
C
N
C
NH
CH
CH
O
NH2
45
2
3
16
Cytosine Uracil
45
2
3
16
NH
C
NH
C
C
C
O
O
H3C
Tymine
45
2
3
16
NH
C
NH
HC
HC
C
O
O
1
2
34
5
8
67
9
NH
C
N
C
C
C
NH
C
N
O
NH2
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