NBO charge distribution of the nucleotide AT base pair. The (L-phosphate, R-phosphate) charges are (a) (0, 0), (b) (0, -1), (c) (-1, 0), (d) (0, -2), (e) (-2, 0), (f) (-1, -2), (g) (-2, -1), (h) (-2, -2) and (i) (-1, -1). The regions are divided into the AuL(R) electrode, the interfacial SL(R) atom, the phosphate PL(R) group, the ribose RL(R) group, and the L(R)-nucleobase M1(2) group, where the subscript L(R) denotes the left (L) and right (R) sides of the AT base pair.