Figure 2.

Schematic overview of the construction process of an RNA tetraloop hairpin molecular structure using the BCE approach proposed in the previous article in this issue (5). (A) A continuous and flexible thin rod, represented by a ribbon for better visibility, and shown in red is associated to a four nucleotides helical segment; (B and C) two helices of RNA are generated along helical lines, shown in yellow; (D) the flexible rod is bent smoothly into the capping elastic solution curve so that the tangents at its extremities, shown as blue and green arrows, match those of the two helices; helical segments and the capping rod are dissociated for clarity; (E) they are shown fully assembled; the complete molecular structure is the basic BCE molecular model and is computed after global deformation by keeping track of the translations and the rotations required to leave unchanged atoms in their nearest local reference frames along the helical segment.