Novel spectral representation of RNA secondary structure without loss of information

Recently Liao et al. have shown that graphical representations of the secondary structures of RNA based on eight symbols (A, C, G, U, A′, C′, G′, U′) are accompanied with loss of information. We outline here graphical representation of RNA secondary structure, which is based on twelve symbols (A, C, G, U, A′, C′, G′, U′, A″, C″, G″, U″), in which we discriminate between X–Y and Y–X hydrogen bonds along of RNA sequence, X, Y standing for A, C, G, U.