Department of Chemistry,Sharif University of Technology
Abstract
Interaction of the DNA thymine base with Cu+ and Zn2+ was studied to explore: a) The
metal binding energy (MIA) of thymine with Cu+ and Zn2+ and b) The possible correlation between
charge transfer and MIAs. The gas-phase Cu+ and Zn2+ anities of thymine, as well as the Mulliken
charges, on the complexed metal cations were both determined at the same computational level, including
the density functional level and employing the hybrid B3LYP exchange correlation potential in connection
with the 6-311++G (d; p) basis set. All the molecular complexes were obtained by interaction between the
most stable tautomer of thymine and two transition mono and divalent (Cu+, Zn2+) metal ions. To probe
all possible binding sites, these two cations were placed around the thymine nucleobase and optimized. For
both Cu+ and Zn2+, the complexes of thymine with O4 are the most stable structure. For complexes of
thymine with mono cations (Li+, Na+, K+ and Cu+) and dications (Mg2+, Ca2+ and Zn2+), the results
indicate a linear correlation between the transferred charge and metal binding energy. The results also
indicate that the amount of charge transfer and bonding strength are the highest for the transion metal
ions Cu+ and Zn2+, respectively.
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