  We report the results of our first-principles study based on density
functional theory on the interaction of the nucleic acid base molecules adenine
(A), cytosine (C), guanine (G), thymine (T), and uracil (U), with a
single-walled carbon nanotube (CNT). Specifically, the focus is on the
physisorption of base molecules on the outer wall of a (5,0) metallic CNT
possessing one of the smallest diameters possible. Compared to CNTs with large
diameters, the physisorption energy is found to be reduced in the
high-curvature case. The base molecules exhibit significantly different
interaction strengths, and the calculated binding energies follow the hierarchy
G > A > T > C > U, which appears to be independent of the tube curvature. The
stabilizing factor in the interaction between the base molecule and CNT is
dominated by the molecular polarizability that allows a weakly attractive
dispersion force to be induced between them. The present study provides an
improved understanding of the role of the base sequence in deoxyribonucleic
acid (DNA) or ribonucleic acid (RNA) on their interactions with carbon
nanotubes of varying diameters.
