Fig. 7.

An example of positive design operator. Here we consider a two-target design. In this example, a parent sequence, target structures 1 and 2, a selected predicted structure, and a child sequence are denoted by Parent, Target1, Target2, Predict1, Child, respectively. First, the Parent sequence is copied to the Child sequence; Step 1) we scan Predict1 from the left to the right to find a target base pair which is missing in Predict1 (denoted by a red base pair); Step 2) we change the shadowed A in Parent to the shadowed G in Child. Then, to repair the base complementarity, the shadowed U is changed to the shadowed C; Step 3) in addition, since the changed position forms a base pair in Target2, the shadowed A is changed to the shadowed G