Fig. 2.

Coulombic (NLPB) results for an all-atom model of nucleic acid oligomers. NLPB results for the reduced coulombic free energy (G^coul/RT; panel A) and the thermodynamic extent of salt ion association (n^coul = −δ(G^coul/RT)/δln C; panel B), both at a 1 : 1 salt concentration C = 0.15 M, are plotted as a function of the number of charged residues (phosphates) ∣Z_D∣ on the oligomer. Calculations were performed for a duplex oligomer (solid dot symbol) built from 5 repeats of the 12-mer sequence 5′-CGATTAGATAGC-3′, for the individual stacked helical strands of this oligomer ss1 (diamond), ss2 (dash) as described in the text.