Global fitting of a, hp-GT DNA and b, hp-GU-20 RNA N1 and N3 RD profiles to 2-state algebraic equation (Eqn. 1, fit reduced χ2 shown in inset) and 3-state algebraic equation (Eqn. 2, fit reduced χ2 shown in inset). Numerical solutions to the Bloch-McConnell 3-state equations assuming no minor exchange and input exchange parameters obtained based on the 3-state algebraic fit are also shown to establish the validity of the 3-state expression under these exchange scenarios (Eqn. 2, see Methods). Sample conditions are indicated on each profile. Error bars represent experimental uncertainty (one s.d., see Methods).