Coadsorption of Complementary and Noncomplementary Bases on Au(111)
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Coadsorption of Coadsorption of Complementary and Complementary and Noncomplementary Bases Noncomplementary Bases on Au(111) A. P. M. Camargo, C. Donner Free University Berlin Institute of Physical and Theoretical
description
Coadsorption of Complementary and Noncomplementary Bases on Au(111) A. P. M. Camargo, C. Donner Free University Berlin Institute of Physical and Theoretical Chemistry. Nonstandard base pair Mutagenicity Cancer Therapy How does it work? - Mutagenicity: one DNA - PowerPoint PPT Presentation
Transcript of Coadsorption of Complementary and Noncomplementary Bases on Au(111)
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
Tymine
Adenine
