Fluorescent guanosine-nucleotide analogs suitable for photoaffinity-labeling experiments

The synthesis and properties of strongly fluorescent derivative of inosine and its nucleotides are described. Reaction of 2-chloro-inosinic acid with sodium azide leads to a product bearing the tetrazole ring between position 2 and 3. Methylation at N1 was effected with dimethyl sulfate. The corresponding nucleosides and their 5'-triphosphates were also prepared. Only the non-methylated series is at equilibrium with small concentrations of their azido forms, and can be photolyzed by wavelengths above 300 nm. Both series are strongly fluorescent, their emission and excitation fluorescence spectra, as well as their quantum yields were measured. The nucleoside 5'-triphosphates are able to initiate and sustain polymerization of porcine brain tubulin.