Monomeric and Collective Deactivation Mechanisms in Photoexcited DNA Investigated by a Quantum Dynamical Approach. Fabrizio Santoroa aIstituto di Chimica dei Composti Organo Metallici del CNR, UOS di Pisa, Area della Ricerca del CNR, via Moruzzi 1 I-56124 Pisa. [email protected] Sunlight is essential to life but it is also a potential carcenogenic agent, and evolution has selected highly photostable molecules to encode the genomic information. Their photostability is ensured by highly efficient decay pathways that are able to transform the electronic excitation into vibrational energy and finally into heat. The deactivation mechanisms of the single nucleobases after the ??* excitation has been deeply investigated experimentally and show multi-exponential features ranging from fs to ps timescales [1]. Here we report the results of our recent static [2] and quantum dynamics investigation of the role of n?* in the decay of Uracil derivatives both in gas-phase [3] and in different solvents [4-5]. Potential energy surfaces have been characterized by TD-DFT, while solvent effect has been accounted by mixed atomistic/continuum models. The understanding of the dynamics of isolated nucleobases is the necessary pre-requisite for a full comprehension of the deactivation processes in the real bio-polymers, where nonetheless inter-bases interactions modify the efficiency of the single-base decays and open new competitive pathways. In fact long-living excited states, up to the nanosecond timescale have been identified in DNA oligomers, while they are absent in single nucleobeases [6]. Recently, we performed TD-DFT studies in water solution of the excited states of adenine stacked dimers [7], and of tetramers made up of adenine-thymine base-pairs [8]. From these data we derived a vibronic Hamiltonian to study, at quantum dynamical level, the interplay between excitonic and charge-transfer states in the decay mechanism, and we applied it to dimers and oligomers [9]. Quantum dynamical calculation have been carried through traditional Lanczos based propagation schemes and/or a self-made implementation of MCTDH method [10] [1] C. E. Crespo-Hernández, B. Cohen, P. M. Hare and B. Kohler , Chem. Rev. 104, 2004, 1977 [2] F. Santoro, V. Barone, T. Gustavsson R. Improta, J. Am. Chem. Soc. 128, 2006, 16312 [3] D. Picconi, V. Barone, A. Lami, F. Santoro, R. Improta Chem. Phys. Chem. 2011 DOI: 10.1002/cphc.201001080 [4] F. Santoro, V. Barone, R. Improta, Theor. Chem. Acc. 123, 2009, 273, [5] R. Improta, V. Barone, A. Lami, F. Santoro, J. Phys. Chem B 113, 2009, 14491 [6] Onidas, D.; Gustavsson, T.; Lazzarotto, E.; Markovitsi, D. J. Phys. Chem. B 111, 2007, 9644. [7] F. Santoro, V. Barone, and R. Improta, Proc Natl. Acad. of Science, USA 104, 2007, 9931 [8] F. Santoro, V. Barone, R. Improta, J. Am. Chem. Soc. 131, 2009, 15232 [9] R. Improta, F. Santoro, V. Barone, A. Lami, J. Phys. Chem. A, 113, 2009, 15346, [10] M. H. Beck, A. Jäckle, G. A. Worth, H.-D. Meyer, Physics Report 324, 2000, 1
Monomeric and collective deactivation mechanisms in photoexcited DNA investigated by a quantum dynamical approach
2011
Abstract
Monomeric and Collective Deactivation Mechanisms in Photoexcited DNA Investigated by a Quantum Dynamical Approach. Fabrizio Santoroa aIstituto di Chimica dei Composti Organo Metallici del CNR, UOS di Pisa, Area della Ricerca del CNR, via Moruzzi 1 I-56124 Pisa. [email protected] Sunlight is essential to life but it is also a potential carcenogenic agent, and evolution has selected highly photostable molecules to encode the genomic information. Their photostability is ensured by highly efficient decay pathways that are able to transform the electronic excitation into vibrational energy and finally into heat. The deactivation mechanisms of the single nucleobases after the ??* excitation has been deeply investigated experimentally and show multi-exponential features ranging from fs to ps timescales [1]. Here we report the results of our recent static [2] and quantum dynamics investigation of the role of n?* in the decay of Uracil derivatives both in gas-phase [3] and in different solvents [4-5]. Potential energy surfaces have been characterized by TD-DFT, while solvent effect has been accounted by mixed atomistic/continuum models. The understanding of the dynamics of isolated nucleobases is the necessary pre-requisite for a full comprehension of the deactivation processes in the real bio-polymers, where nonetheless inter-bases interactions modify the efficiency of the single-base decays and open new competitive pathways. In fact long-living excited states, up to the nanosecond timescale have been identified in DNA oligomers, while they are absent in single nucleobeases [6]. Recently, we performed TD-DFT studies in water solution of the excited states of adenine stacked dimers [7], and of tetramers made up of adenine-thymine base-pairs [8]. From these data we derived a vibronic Hamiltonian to study, at quantum dynamical level, the interplay between excitonic and charge-transfer states in the decay mechanism, and we applied it to dimers and oligomers [9]. Quantum dynamical calculation have been carried through traditional Lanczos based propagation schemes and/or a self-made implementation of MCTDH method [10] [1] C. E. Crespo-Hernández, B. Cohen, P. M. Hare and B. Kohler , Chem. Rev. 104, 2004, 1977 [2] F. Santoro, V. Barone, T. Gustavsson R. Improta, J. Am. Chem. Soc. 128, 2006, 16312 [3] D. Picconi, V. Barone, A. Lami, F. Santoro, R. Improta Chem. Phys. Chem. 2011 DOI: 10.1002/cphc.201001080 [4] F. Santoro, V. Barone, R. Improta, Theor. Chem. Acc. 123, 2009, 273, [5] R. Improta, V. Barone, A. Lami, F. Santoro, J. Phys. Chem B 113, 2009, 14491 [6] Onidas, D.; Gustavsson, T.; Lazzarotto, E.; Markovitsi, D. J. Phys. Chem. B 111, 2007, 9644. [7] F. Santoro, V. Barone, and R. Improta, Proc Natl. Acad. of Science, USA 104, 2007, 9931 [8] F. Santoro, V. Barone, R. Improta, J. Am. Chem. Soc. 131, 2009, 15232 [9] R. Improta, F. Santoro, V. Barone, A. Lami, J. Phys. Chem. A, 113, 2009, 15346, [10] M. H. Beck, A. Jäckle, G. A. Worth, H.-D. Meyer, Physics Report 324, 2000, 1I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
