Shortest flexible atom-pair path. Exemplary visualization of an atom-pair of the marked atoms. The shortest topological path is depicted by the red and green dotted lines. A red line represents a rigid bond, whereas a green line marks a rotatable bond. The last bond of the path (bond from the heterocycle to the carbon of the carboxyl group) is treated as a rigid bond because a rotation of this bond has no influence on the geometric distance of the atom-pair.