Chemical etiology of nucleic acid structure: Comparing pentopyranosyl-(2 '-> 4 ') oligonucleotides with RNA

All four members of the family of pentopyranosyl-(2'-->4') oligonucleotide systems that contain beta-ribo-, beta-xylo-, alpha-lyxo-, or alpha-arabinop yranosyl units as repeating sugar building blocks are found to be much stro nger Watson-Crick base-pairing systems than RNA. The alpha-arabinopyranosyl system is the strongest of ali and in fact belongs to the strongest oligon ucleotide base-pairing systems known, Whatever the chemical determinants by which nature selected RNA as a genetic system, maximization of base-pairin g strengths within the domain of pentose-derived oligonucleotide systems wa s not the critical selection criterion.