Polynucleotides. LVI. Synthesis and properties of poly(2-deoxy-2'-fluoroinosinic acid).

Poly (2'-deoxy-2'-fluoroinosinic acid) [ poly(If)] was synthesized by polymerization of 2'-deoxy-2'-fluoroinosine 5'-diphosphate catalyzed by Escherichia coli polynucleotide phosphorylase. Although the UV absorption properties of poly(If) closely resembled those of poly(I), thermal melting curves at Na+ concentrations of 0.15M and 0.75M suggested two ordered structures for poly(If) neutral form. CD psectra taken at 0.15M Na+ concentration showed rather larger amplitudes in both a peak at 273 nm and a trough at 246 nm, suggesting rather strong vertical stacking of bases. When complexed with poly(C), poly(If) forms a double-stranded complex, poly(If).poly(C) which has Tm's higher by 10-20 degrees than those of poly(If).poly(C) measured under the same conditions. The CD spectrum of this complex resembled that of poly(I).poly(C). The effect of the fluorine atom at the 2'-position on thermal stability of polynucleotides is discussed.