3q61

</td></tr><tr id='NonStdRes'><td class="sblockLbl"><b>[[Non-Standard_Residue|NonStd Res:]]</b></td><td class="sblockDat"><scene name='pdbligand=F3H:1,5-ANHYDRO-2,3-DIDEOXY-3-FLUORO-2-(5-METHYL-2,4-DIOXO-3,4-DIHYDROPYRIMIDIN-1(2H)-YL)-6-O-PHOSPHONO-D-ALTRITOL'>F3H</scene></td></tr>

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== Publication Abstract from PubMed ==

The synthesis, biophysical, structural, and biological properties of both isomers of 3'-fluoro hexitol nucleic acid (FHNA and Ara-FHNA) modified oligonucleotides are reported. Synthesis of the FHNA and Ara-FHNA thymine phosphoramidites was efficiently accomplished starting from known sugar precursors. Optimal RNA affinities were observed with a 3'-fluorine atom and nucleobase in a trans-diaxial orientation. The Ara-FHNA analog with an equatorial fluorine was found to be destabilizing. However, the magnitude of destabilization was sequence-dependent. Thus, the loss of stability is sharply reduced when Ara-FHNA residues were inserted at pyrimidine-purine (Py-Pu) steps compared to placement within a stretch of pyrimidines (Py-Py). Crystal structures of A-type DNA duplexes modified with either monomer provide a rationalization for the opposing stability effects and point to a steric origin of the destabilization caused by the Ara-FHNA analog. The sequence dependent effect can be explained by the formation of an internucleotide C-F...H-C pseudo hydrogen bond between F3' of Ara-FHNA and C8-H of the nucleobase from the 3'-adjacent adenosine that is absent at Py-Py steps. In animal experiments, FHNA-modified antisense oligonucleotides formulated in saline showed a potent downregulation of gene expression in liver tissue without producing hepatotoxicity. Our data establish FHNA as a useful modification for antisense therapeutics and also confirm the stabilizing influence of F(Py)...H-C(Pu) pseudo hydrogen bonds in nucleic acid structures.

Synthesis, improved antisense activity and structural rationale for the divergent RNA affinities of 3'-fluoro hexitol nucleic acid (FHNA and Ara-FHNA) modified oligonucleotides.,Egli M, Pallan PS, Allerson CR, Prakash TP, Berdeja A, Yu J, Lee S, Watt A, Gaus H, Bhat B, Swayze EE, Seth PP J Am Chem Soc. 2011 Oct 19;133(41):16642-9. Epub 2011 Sep 22. PMID:21919455<ref>PMID:21919455</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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== References ==

<references/>

[[Category: Allerson, C R]]

[[Category: Berdeja, A]]

[[Category: Bhat, B]]

[[Category: Egli, M]]

[[Category: Gaus, H]]

[[Category: Pallan, P S]]

[[Category: Prakash, T P]]

[[Category: Seth, P R]]

[[Category: Siwkowski, A]]

[[Category: Swayze, E E]]

[[Category: Watt, A T]]

[[Category: Yu, J]]

[[Category: Fhna]]