The geometry of all terminal nucleotides is more variable and fluctuates throughout the simulation, as demonstrated in Fig. for GpAIpG. The averaged value of the considered dihedral angle for this system oscillates around 0 deg throughout the simulation, indicating no evident preference for one conformation over the other (Fig. ). Higher population the C3 ′ -endo conformation among different terminal nucleotides was observed only for the activated CpAIpC and CpAIpG dinucleotides with the latter system reaching the population of nearly 70%. We observed the opposite preference for the population of the C2 ′ -endo arrangement of the terminal nucleotide for GpAIpC and UpAIpU dinucleotides (59.5% and 64.9 %). The remaining four systems maintain an almost equal population of both sugar forms in the terminal nucleotide (48 -49%). Overall, the studied dinucleotide intermediates do not retain well C3 ′ -endo conformations associated with the canonical A-RNA structure, when bound near the 5 ′ -end of the template. This is also consistent with previous experimental works, which showed that downstream helper oligonucleotides facilitate efficient nonenzymatic RNA template copying, which was assigned to stabilization of the A-RNA structure . Finally, to better understand how the conformation of the three key ribose rings affects the O3 ′ • • • P distance between the 3 ′ -end of the primer and the adjacent nucleotide, we plotted three correlation plots for each dinucleotide system (see Fig. and the SI for more details on other systems). The parent GpAIpG system demonstrate a strong correlation of the C3 ′ -endo conformation of the adjacent ribose ring with a possibly short O3 ′ • • • P distance, that below 4.0 Å. Similar trend can be observed for the activated dinucleotides GpAIpC, CpAIpG IpAIpA and ApAIpA on the tUtU template, all of which exhibit at least a considerable population of the C3 ′ -endo conformation within the adjacent nucleotide. In contrast, stronger preference for the C2 ′ -endo arrangement of the adjacent nucleotide found for the CpAIpC, UpAIpU and ApAIpA (UU template) dinucleotides results O3 ′ • • • P distances often exceeding 4.0 Å(see Fig. ). This ca be very clearly illustrated based on the correlation plot for the bound GpAIpC dinucleotide, which maintains a good balance between both C3 ′ -endo and C2 ′endo ribose conformations. When the adjacent guanosine of GpAIpC adopts the C3 ′ -endo conformation, the O3 ′ • • • P distances center around ∼3.8 Å, whereas population of C2 ′endo sugar arrangement leads to a diffused population of O3 ′ • • • P distances ranging from 3.8 Åup to 8.0 Åand beyond. Overall, this analysis further demonstrates that retention of the A-RNA conformation of the primer end and the adjacent activated nucleotide could facilitate the formation of a new phosphodiester linkage in nonenzymatic RNA selfreplication . Importantly, the ribose conformation within the terminal nucleotide exhibits little or no direct correlation with the with the monitored O3 ′ • • • P distance.