CHARACTERIZATION OF FULLY 2'-MODIFIED OLIGORIBONUCLEOTIDE HETERODUPLEX AND HOMODUPLEX HYBRIDIZATION AND NUCLEASE SENSITIVITY

The nuclease stability and melting temperatures (T-m) were compared fo r fully modified oligoribonucleotide sequences containing 2'-fluoro, 2 '-O-methyl, 2'-O-propyl and 2'-O-pentyl nucleotides. Duplexes formed b etween 2' modified oligoribonucleotides and RNA have typical A-form ge ometry as observed by circular dichroism spectroscopy, Modifications, with the exception of 2'-O-pentyl, were observed to increase the T, of duplexes formed with complementary RNA, Modified homoduplexes showed significantly higher T(m)s, with the following T-m order: 2'-fluoro:2' fluoro > 2'-)-propyl:2'-O-propyl > 2'-O-methyl:2'-O-methyl > RNA:RNA > DNA:DNA, The nuclease stability of 2'-modified oligoribonucleotides w as examined using snake venom phosphodiesterase (SVPD) and nuclease S1 . The stability imparted by 2' modifications was observed to correlate with the size of the modification, An additional level of nuclease st ability was present in oligoribonucleotides having the potential for f orming secondary structure, but only for 2' modified oligoribonucleoti des and not for 2'-deoxy oligoribonucleotides.