Adenine, density functional theory studies

Nowak, M. J., L. Lapinski, J. S. Kwiatkowski, and J. Leszczynski. 1996. Molecular Structure and Infrared Spectra of Adenine—Experimental Matrix Isolation and Density Functional Theory Study of Adenine N-15 Isotopomers. J. Phys. Chem. 100, 3527. 

A recent study employing ESR spectroscopy and density functional theory calculations has shown that the adenine cation radical (A +) in aqueous glassy solutions of dAdo and of the DNA oligomer (dA) is stabilized by base stacking interactions. The pK of the adenine cation radical in isolated dAdo in aqueous solutions is ca. 1 and, therefore, A " readily deprotonates from its exocylic amine group, nevertheless, these researchers find that the pK of the adenine cation radical in stacked systems to be ca. 8 at 150 K. It appears that the hole delocalizes over several bases, which stabilize it by charge resonance interactions. Calculations show that in the... 

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