Fluorescence Studies of Nucleotides and Polynucleotides

Deazanebularin, a cytotoxic nucleoside, is fluorescent at ambient temperature and at neutral pH. Some of its fluorescence properties and those of its phosphorylated derivatives are reported here. Deazanebularin nucleotides are substrates for Escherichia coli polynucleotide phosphorylase and RNA polymerase. With RNA polymerase deazanebularin triphosphate acts as an ambiguous substrate in that it functions, with almost equal efficiency, as an analogue of either ATP or GTP. The relevance of this observation to the mechanism of base selection by RNA polymerase is discussed. The synthesis, characterization, and properties of polymers containing deazanebularin are also described. Some of these polymers form unique ordered structures with base pairs possessing only a single hydrogen bond; these permit an assessment of the contribution of hydrogen bonding to helix stability. These polymers also exhibit some unusual fluorescence properties, including excited state energy transfer.