1. Coadsorption of Complementary and Noncomplementary Bases Coadsorption of Complementary and Noncomplementary Bases on Au(111) A. P. M. Camargo, C. Donner Free University Berlin Institute of Physical and Theoretical Chemistry

2. 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 Problem * M. Orozco et al., J. Phys.Chem. B, 1998, 102, 5228 *

3. * (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 -0.9-0.6-0.30.00.30.6 -40 -20 0 20 chemisorbed phase physisorbed phase j /  Acm -2 E / V vs. Ag/Ag + Is it possible to obtain interaction of standard /nonstandard base pairs? to distinguish between the different interactions?Idea -Complementary base pair: Adenine / Thymine -Noncomplementary base pairs:Adenine / Bromouracil Guanine / BromouracilInvestigation Thymine Thymine - undergoes a phase transition at Au(111) - orientation of molecules depends on the potential Adsorption behaviour of DNA base at electrode

4.  Cell - Au(111)  Electrodes - Ag/Ag + - gold wire  Supporting Electrolyte: 0.1M NaClO 4 / + DNA bases, BrU  pH=2 Experimental Part

5. * Y.J.Xiao, Y.F.Chen, Spectrochemica Acta, Part A, 1999, 55, 1209. * Complementary Bases *

6.  Coadsorption Behaviour H+H+ Adenine-Dimers

7. Noncomplementary Bases * physisorbed phase chemisorbed phase

8.  Coadsorption Behaviour * F. Nart., Surface Science, 480, 2001, L383

9. Noncomplementary Bases *

10.  Coadsorption Behaviour

11. - We found attractive interactions between A-T complementary base pair 1, 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 electrodes 2 ) 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 Conclusions

12. Adenine Guanine Cytosine UracilTymine

13. Adenine