MODELING, SYNTHESIS, AND HYBRIDIZATION PROPERTIES OF (L)-RIBONUCLEIC ACID

Calculations suggest that nucleic acids based on (L)-ribose may hybridize with natural configuration DNA and RNA if a loosely wound, parallel-stranded A-like formation can be adopted. The tendency of RNA to adopt A-form helices suggest that (L)-nucleic acids may bind more tightly to natural RNA than to natural DNA. Oligomers of (L)-dU and (L)-rU have been synthesized to test these models. Neither [(L)-dU]12 nor [(L)-rU]12 mixed with natural poly(dA) shows hyperchromicity indicative of hybridization, nor does a mixture of [(L)-dU]12 with poly(rA). Hybridization is observed between [(L)-dU]20 and poly(rA) (T(m) = 31-degrees-C in 10 mM Mg2+), although this is substantially weaker than that observed between [(D)-dU]20 and poly(rA) (T(m) = 42-degrees-C in 10 mM Mg2+). Mixtures of [(L)-rU]12 and poly(rA) show strong hybridization (T(m) = 38-degrees-C in 1.0 M NaCl), comparable to that observed between [(D)-rU]12 and poly(rA) (T(m) = 40-degrees-C in 1.0 M NaCl). Both RNA:RNA systems form triplex structures. (L)-RNA is resistant to both purified ribonuclease A and total cell extracts of L-cells.