Chirally-modified oligonucleotides and the control of gene expression - the case of L-DNAs and -RNAs

The affinity of L-DNAs, L-RNAs and L/D-DNAs for homopurine.homopyrimidine d.s. D-DNA and s.s. D-RNA was probed by gel electrophoresis and CD spectroscopy. It was found that the L-modified oligomers do not bind to d.s. DNA and to natural RNA that contains all four natural bases. Thus they cannot be used, in general, for the control of gene expression according to the antigene and antisense methodologies. Heterochiral complexes with 1:1 stoichiometry and low thermal stability are formed, instead, by homopurinic L-RNA or L/D-DNA and homopyrimidinic L-RNA with the W/C complementary natural RNA sequences.