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

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: univie.ac.at/columbus

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

A TOOL-KIT: FROM POTENTIAL SURFACES TO PHOTODYNAMICS

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

Ultrafast decay of DNA/RNA bases Canuel et al. JCP 122, (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?

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] delay time / fs [1] Ullrich et al. JACS 126, 2262 (2004) [2] Canuel et al. JCP 122, (2005) [3] Kang et al. JACS 124, (2002) [4] Perun et al. JACS 127, 6257 (2005) [5] Serrano-Andrés et al. PNAS 103, 8691 (2006)

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, (2005) Perun, Sobolewski and Domcke, JACS 127, 6257 (2005) Serrano-Andrés, Merchán and Borin, PNAS 103, 8691 (2006)

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

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

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)

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)

9-H Adenine MXS Structures

Adenine Dynamics

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

Single trajectory

All trajectories

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

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

COLUMBUS Photos OSU May 2000

ANL July 2001

Seattle, July 2001

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