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The hybrid quantum/classical (QM/MM) calculations of the aqueous solvent effect on adenine with respect to the [super 1]H and [super 15]N NMR resonance lines and their solvent shifts are presented. The results have indicated that the proper incorporation of electrostatic effects is very important for a correct assignment of the experimental NMR resonances and that the QM/MM scheme is suitable for a reliable description for such effects.

The density functional theory (DFT) is used to study the binding of clusters of gold atoms (Au) with the guanine-cytosine (GC) and adenine-thymine (AT) Watson-Crick DNA base pairs. The analysis has shown that guanine and adenine have high affinity for Au clusters and the calculated adiabatic electron affinities (AEAs) of the GC-[Au.sub.n] complexes (n = 4, 8) are found to be much larger than those of the isolated base pairs.

An experimental and computational study of hydrogen atom adducts to adenine is conducted. The result shows that the relative free energies of adenine radicals in aqueous solution point to the C-8 adducted as the most stable tautomer, which is predicted to be the predominating product at thermal equilibrium in solution at 298 K.

A new form of the uracil-adenine dimer anion [AU (super -)] is considered where the two monomers are connected by an excess electron suspended between them. An AU(super -) anion of this kind can be formed in the gas phase by an attachment of an adenine molecule to a dipole-bound electron of uracil.

A configurational change was predicted for the adenine-imidazole complex upon dipole-bound attachment of an excess electron to this system. The presence of the electron reverses the stability order of the two lowest energy configurations of the complex.

A density functional theory (DFT) study are performed in order to explore the influences of oxygen at the C8 position on the intramolecular proton transfer between the 6-oxo form and 6-hydro form of C8 -oxidative adenine. The 8-oxo form with the oxygen at the C8 position is found to be energetically favored by the purines.

A multiphotone ionization investigation was carried out on hydrated clusters of DNA base adenine in supersonic molecular beams. It is concluded that the change of solvent to those of less proton-donating or even proton-accepting character systematically reduces the tendency of fragmentation.

The high-resolution scanning tunneling microscopy (STM) used to study the self-assembly of the DNA base molecule adenine (A) revealed two coexisting distinct (homo- and heterochiral) domain of adenine formed at the liquid/solid interface. The STM findings were validated and confirmed by using ab initio density functional theory (DFT) calculations.