We report the binding energy of various nucleobases (guanine (G), adenine (A), thymine ( T) and cytosine ( C)) with (5,5) single-walled carbon nanotube(SWNT) calculated using first-principle Hartre-Fock method (HF) together with classical force field. The binding energy without including the solvation effects of water decreases in the order G > A > T > C. The inclusion of solvation energy changes the order of binding preference to be G > T > A > C. Using isothermal titration (micro) calorimetry experiments, we also show the relative binding affinity to be T > A > C, in agreement with our calculations. (c) 2008 Elsevier B. V. All rights reserved.