In the reverse system (GpAIpC), the K-means clustering analysis showed that 30.0% of the structures sampled canonical structure of the GpAIpC dinucleotide involving WC base pairing interaction with the complementary nucleotides on the templating strand which resembles the major con- ). An alternatively folded conformation of the GpAIpC dinucleotide is populated in 19.1% and is referred to as an O-stacked structure, due to its ring-like, circular arrangement (see Fig. ) and Fig. )). Consequently, the binding of the activated GpAIpC dinucleotide to the template is clearly less specific than for the CpAIpG dinucleotide discussed above.