PMID- 22569748
OWN - NLM
STAT- MEDLINE
DCOM- 20120913
LR  - 20131121
IS  - 1463-9084 (Electronic)
IS  - 1463-9076 (Linking)
VI  - 14
IP  - 22
DP  - 2012 Jun 14
TI  - Nonadiabatic decay dynamics of 9H-guanine in aqueous solution.
PG  - 8137-46
LID - 10.1039/c2cp40300e [doi]
AB  - The nonadiabatic decay of the biologically relevant guanine tautomer (9H-guanine) 
      in aqueous solution has been investigated by trajectory surface hopping 
      simulations in a quantum mechanical-molecular mechanical (QM-MM) framework. The 
      QM part (9H-guanine) was treated at the semiempirical OM2/MRCI level, while the 
      MM part (water) was described by the TIP3P force field. The optimized geometries 
      for the relevant minima and conical intersections are qualitatively similar for 
      9H-guanine in the gas phase and in aqueous solution, while there are notable 
      solvent-induced shifts in the computed vertical excitation energies (up to about 
      0.4 eV). Overall, the results from the static OM2/MRCI-based calculations are in 
      reasonable agreement with the available ab initio and experimental data. The 
      dynamics simulations show ultrafast nonradiative decay for 9H-guanine in water 
      that is even slightly faster than in the gas phase, with time constants of 20 fs 
      and around 0.3 ps for the S(2)--> S(1) and S(1)--> S(0) internal conversions, 
      respectively. They predict a change in the S(1)--> S(0) decay mechanism when going 
      from the gas phase to aqueous solution: the major pathway for 9H-guanine in water 
      involves a conical intersection with an out-of-plane distortion of the carbonyl 
      oxygen atom, which does not play any significant role in the gas phase, where the 
      decay mainly proceeds via two other conical intersections characterized by ring 
      distortions and out-of-plane displacement of the amino group, respectively. 
      Possible reasons for this change in the mechanism are analyzed.
FAU - Heggen, Berit
AU  - Heggen B
AD  - Max-Planck-Institut fur Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mulheim an 
      der Ruhr, Germany.
FAU - Lan, Zhenggang
AU  - Lan Z
FAU - Thiel, Walter
AU  - Thiel W
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20120508
PL  - England
TA  - Phys Chem Chem Phys
JT  - Physical chemistry chemical physics : PCCP
JID - 100888160
RN  - 0 (Solutions)
RN  - 059QF0KO0R (Water)
RN  - 5Z93L87A1R (Guanine)
SB  - IM
MH  - Guanine/*chemistry
MH  - Models, Molecular
MH  - Molecular Conformation
MH  - Quantum Theory
MH  - Solutions
MH  - Water/*chemistry
EDAT- 2012/05/10 06:00
MHDA- 2012/09/14 06:00
CRDT- 2012/05/10 06:00
PHST- 2012/05/10 06:00 [entrez]
PHST- 2012/05/10 06:00 [pubmed]
PHST- 2012/09/14 06:00 [medline]
AID - 10.1039/c2cp40300e [doi]
PST - ppublish
SO  - Phys Chem Chem Phys. 2012 Jun 14;14(22):8137-46. doi: 10.1039/c2cp40300e. Epub 
      2012 May 8.