Stabilization energies of DNA base pairs and aminoacid pairs: WFT, DFT and DFTB
calculations

Pavel Hobza, pavel.hobza@uochb.cas.cz, Center for Biomolecules and Complex
Molecular Systems, Institute of Organic Chemistry and Biochemistry, Flemingovo
nam. 2, 166 10 Prague, Czech Republic

Structures and stabilization energies of noncovalently bound molecular clusters
playing a role in biodisciplines are investigated. Specifically, we consider
H-bonded and stacked structures of DNA base pairs and amino acid
pairs. Structure of pairs is either optimized or is taken from
experiment. Benchmark stabilization energies of complexes studied are determined
as the Complete Basis Set (CBS) limit of the CCSD(T) calculations. The role of
CCSDT level is also discussed. Resulting stabilization energies of H-bonded and
stacked pairs are very larger, much larger than considered before. This is
especially true about stacked DNA base pairs and amino acid pairs. Stabilization
energy of these structures originates exclusively in London dispersion energy
and only high-level wave function theories can be applied. The use of density
functional theories including the recently introduced hybrid meta GGA
functionals is discussed. Surprisingly accurate stabilization energies for all
complexes investigated were obtained from SCC-DFTB-D calculations which
empirically cover the London dispersion energy. The method which allows to study
complexes with several thousand of atoms was successfully applied also to other
extended biomolecular complexes containing DNA.