title: 2'-Deoxy-2'-fluoro-beta-D-arabinonucleosides and oligonucleotides (2'F-ANA): synthesis and physicochemical studies.
abstract: Recently, hybrids of RNA and D-arabinonucleic acids (ANA) as well as the 2'-deoxy-2'-fluoro-D-arabinonucleic acid analog (2'F-ANA) were shown to be substrates of RNase H. This enzyme is believed to be involved in the primary mechanism by which antisense oligonucleotides cause a reduction in target RNA levels in vivo. To gain a better understanding of the properties of arabinose based oligonucleotides, we have prepared a series of 2'F-ANA sequences of homopolymeric (A and T) and mixed base composition (A, T, G and C). UV thermal melting and circular dichroic (CD) studies were used to ascertain the thermodynamic stability and helical conformation of 2'F-ANA/RNA and 2'F-ANA/DNA hybrids. It is shown that 2'F-ANA has enhanced RNA affinity relative to that of DNA and phosphorothioate DNA. The 2'-fluoroarabino modification showed favorable pairing to single-stranded DNA also. This is in sharp contrast to ANA, which forms weak ANA/DNA hybrids at best. According to the measured thermodynamic parameters for duplex formation, the increased stability of hybrids formed by 2'F-ANA (e.g., 2'F-ANA/RNA) appears to originate from conformational pre-organization of the fluorinated sugars and a favorable enthalpy of hybridization. In addition, NMR spectroscopy revealed a five-bond coupling between the 2'F and the base protons (H6/H8) of 2'-deoxy-2'-fluoro-beta-D-arabinonucleosides. This observation is suggestive of a through-space interaction between 2'F and H6/H8 atoms. CD experiments indicate that 2'F-ANA/RNA hybrids adopt an 'A-like' structure and show more resemblance to DNA/RNA hybrids than to the pure RNA/RNA duplex. This feature is believed to be an important factor in the mechanism that allows RNase H to discriminate between 2'F-ANA/RNA (or DNA/RNA) and RNA/RNA duplexes.
authors.affiliation: Department of Chemistry, Otto Maass Chemistry Building, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 2K6, Canada.
authors.forename: C J
authors.initials: CJ
authors.lastname: Wilds
authors.forename: M J
authors.initials: MJ
authors.lastname: Damha
mesh_terms: D001089:Arabinose / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D020029:Base Pairing; D002942:Circular Dichroism; D009691:Nucleic Acid Denaturation; D009693:Nucleic Acid Hybridization; D009841:Oligonucleotides / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D012313:RNA / Q000737:chemistry*; D016914:Ribonuclease H / Q000378:metabolism; D013379:Substrate Specificity; D013816:Thermodynamics; D014466:Ultraviolet Rays
chemical_list: C118537:2'-deoxy-2'-fluoroarabinose; D009841:Oligonucleotides; D012313:RNA; D001089:Arabinose; D016914:Ribonuclease H