The Nature of the Hydrogen Bond in DNA
Matthias Bickelhaupt
Vrije Universiteit, Amsterdam
e-mail:bickel@chem.vu.nl
Jeudi 5 avril 2001, 14h30
In this presentation, the results are presented of a density functional
theoretical (DFT) investigation on the structure and nature of the
deoxyribonucleic acid (DNA) molecule, the carrier of the hereditary
information. Bonding analyses of the Watson-Crick base pairs
adenine-thymine (AT) and guanine-cytosine (GC) show that the present
conception of hydrogen bonds in DNA need to be substantially adjusted: they
are not plain electrostatic phenomena reinforced, as suggested by Gilli,
through resonance in the Pi-electronic system (the so-called Resonance
Assisted Hydrogen Bonding or RAHB). Instead, charge transfer, i.e.,
donor-acceptor orbital interactions appear to contribute considerably to
the strength of these hydrogen bonds. To understand and, in particular, to
reproduce correctly the experimental structures, the interaction of the DNA
base pairs with the molecular environment in the crystal (or under
physiological conditions) turns out to be of crucial importance. This
insight has led to the solution of a hitherto unresolved discrepancy
between experimental (X-ray) and theoretical (ab initio and DFT) structures
of AT (or AU) and GC.