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Femtosecond molecular dynamics of tautomerization in model base pairs

Douhal, A. and Kim, S. K. and Zewail, A. H. (1995) Femtosecond molecular dynamics of tautomerization in model base pairs. Nature, 378 (6554). pp. 260-263. ISSN 0028-0836. doi:10.1038/378260a0.

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Hydrogen bonds commonly lend robustness and directionality to molecular recognition processes and supramolecular structures. In particular, the two or three hydrogen bonds in Watson–Crick base pairs bind the double-stranded DNA helix and determine the complementarity of the pairing. Watson and Crick pointed out, however, that the possible tautomers of base pairs, in which hydrogen atoms become attached to the donor atom of the hydrogen bond, might disturb the genetic code, as the tautomer is capable of pairing with different partners. But the dynamics of hydrogen bonds in general, and of this tautomerization process in particular, are not well understood. Here we report observations of the femtosecond dynamics of tautomerization in model base pairs (7-azaindole dimers) containing two hydrogen bonds. Because of the femtosecond resolution of proton motions, we are able to examine the cooperativity of formation of the tautomer (in which the protons on each base are shifted sequentially to the other base), and to determine the characteristic timescales of the motions in a solvent-free environment. We find that the first step occurs on a timescale of a few hundred femtoseconds, whereas the second step, to form the full tautomer, is much slower, taking place within several picoseconds; the timescales are changed significantly by replacing hydrogen with deuterium. These results establish the molecular basis of the dynamics and the role of quantum tunnelling.

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Additional Information:© 1995 Nature Publishing Group. Received 7 September; accepted 25 October 1995. A. Douhal is on leave from the Universidad de Castilla-La Mancha (Spain), and thanks that university and the California Institute of Technology (USA) for support and for making possible a fruitful stay at Caltech. We thank S. Pedersen for his help with Fig. 1. This work was supported by the US Air Force Office of Scientific Research and the US NSF.
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Air Force Office of Scientific Research (AFOSR)UNSPECIFIED
Issue or Number:6554
Record Number:CaltechAUTHORS:20150605-100727261
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58035
Deposited By: Tony Diaz
Deposited On:05 Jun 2015 17:51
Last Modified:10 Nov 2021 21:58

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