1. Multireference-Ab Initio Dynamics Simulations of the Photostability of DNA Bases Hans Lischka Institute for Theoretical Chemistry

2. COLUMBUS Program System Focus: multireference calculations on ground and excited states Methods: MCSCF, MR-CISD, MR-ACPF/AQCC, Spin- orbit CI Analytic MR-CI gradients, nonadiabatic couplings, parallel CI Authors: R. Shepard, I. Shavitt, R. M. Pitzer, H.Lischka –Vienna: M. Barbatti, M. Ruckenbauer, J. Szymczak, B. Sellner –Budapest: P. G. Szalay –Jülich: Th. Müller –Columbus/Ohio S. Brozell, … Web page: http://www. univie.ac.at/columbus

3. Photodynamics Input includes the energy surfaces, energy gradients and nonadiabatic coupling vectors What kind of dynamics – quantum (wavepacket) or surface-hopping? Restricted set of internal coordinates vs. on- the-fly approach with full set of internal coordinates? Development of the surface-hopping program NEWTON-X

4. A TOOL-KIT: FROM POTENTIAL SURFACES TO PHOTODYNAMICS

5. Available QC codes COLUMBUS (MR-CISD, State-averaged CASSCF) TURBOMOLE (RI-CC2, TDDFT: adiabatic dynamics) MOPAC Coming: ACES II (EOM-CCSD, nonadiabatic couplings (P. G. Szalay, A. Tajti) Installation in progress: DFTB (TD-DFTB, adiabatic dynamics) In development: QM/MM for solvation based on COLUMBUS

6. Ultrafast decay of DNA/RNA bases Canuel et al. JCP 122, 074316 (2005) UV solar radiation Fast deactivation times for the DNA/RNA bases  Photostability of DNA/RNA under the UV solar radiation? Relevance for prebiotic evolution?

7. Lifetime: Between 750 fs [1] and 1.1 ps [2] Mechanism: Single-exponential decay [3] Double-exponential decay [2] 1: 100 fs– relaxation into S 1 [4] 2: 1 ps– relaxation into S 0 1: 100 fs– relaxation into S 0 (  *)[5] 2: 1 ps– relaxation into S 0 (n  *) Triple-exponential decay [1] 07501500 delay time / fs [1] Ullrich et al. JACS 126, 2262 (2004) [2] Canuel et al. JCP 122, 074316 (2005) [3] Kang et al. JACS 124, 12958 (2002) [4] Perun et al. JACS 127, 6257 (2005) [5] Serrano-Andrés et al. PNAS 103, 8691 (2006)

8. Photodynamics of DNA bases Hydrogen detachment  */S 0 crossing 9H-adenine, Sobolewski and Domcke, Eur. Phys. J. D 20, 369 (2002) Adenine: Ring puckering  */S 0 crossing Marian, JCP 122, 104314 (2005) Perun, Sobolewski and Domcke, JACS 127, 6257 (2005) Serrano-Andrés, Merchán and Borin, PNAS 103, 8691 (2006)

9. Three-state model Serrano-Andrés, Merchán and Borin, Chem. Eur. J. 12, 6559 (2006) 100 fs 1 ps

10. Aminopyrimidine  9H Adenine Ring puckering vs. NH 2 out-of-plane motion CASSCF(8el,7orb), state-averaging over 2 and 3 states 6-31G* basis

11. Cremer-Pople parameters Any puckered N-membered ring is described by a special subset of N-3 coordinates Cremer and Pople [1] gave an useful prescription using the deviations from the average ring plane For 6-memberd rings, these coordinates are: Q – degree of puckering  and  – type of puckering [1] Cremer and Pople, JACS 97, 1358 (1975)

12. Q   Boat Chair Envelope Twisted-chair Screw-boat Example: 1 S 6 = Screw-boat with atoms 1 above the plane and 6 below Boeyers, J. Cryst. Mol. Struct. 8, 317 (1978)

13. 9-H Adenine MXS Structures

14. Adenine Dynamics

15. Lifetime S1:S1:  1 : 22 fs,  2 : 538 fs, exp: ~0.1/1 ps

16. Single trajectory

17. All trajectories

18. Aminopyrimidine/Adenine dynamics Ring puckering is the main mechanism at picosecond level First step: Fast relaxation S 3  S 2  S 1 (22 fs) Second step: S 1  S 0 relaxation (0.5 ps) After relaxation in to S 1 : trapping close to 2 E structure Deactivation almost exclusively at 2 E Deactivation via NH 2 out-of-plane motion not observed

19. Outlook Photodynamics in solution – QM/MM Base pairs – ultrafast deactivation by proton transfer? Energy trapping due to stacking interaction of bases MRCI, CAS Force field

20. COLUMBUS Photos OSU May 2000

21. ANL July 2001

22. Seattle, July 2001

23. Acknowledgments Vienna: Mario Barbatti, Adélia Aquino, Daniel Tunega, Jaroslaw Szymczak, Matthias Ruckenbauer, B. Sellner, H. Pašalić Pisa: Maurizio Persico, Giovanni Granucci Berlin/Prague: V.Bonačić-Koutecký,J. Pittner Argonne/USA: R. Shepard Budapest: P. Szalay Munich: R. de Vivie-Riedle, E. Riedle Zagreb: Z. Maksić, M. Eckert-Maksić, M. Vazdar and I. Antol Sofia: I. Georgieva and N. Trendafilova Bratislava: V. Lukeš São Paulo: S. Canuto and K. Coutinho Rio de Janeiro: M. A. C. Nascimento, I. Borges, Jr. Ribeirão Preto: S. E. Galembeck Prag: P. Hobza Austrian Science Fund