title: Synthesis and biological properties of 5-azido-2'-deoxyuridine 5'-triphosphate, a photoactive nucleotide suitable for making light-sensitive DNA.
abstract: A photoactive nucleotide analogue of dUTP, 5-azido-2'-deoxyuridine 5'-triphosphate (5-N3dUTP), was synthesized from dUMP in five steps. The key reaction in the synthesis of 5-N3dUTP is the nitration of dUMP in 98% yield in 5 min at 25 degrees C using an excess of nitrosonium tetrafluoroborate in anhydrous dimethylformamide. Reduction of the resulting 5-nitro compound with zinc and 20 mM HCl gave 5-aminodeoxyuridine monophosphate (5-NH2dUMP). Diazotization of 5-NH2dUMP with HNO2 followed by the addition of NaN3 to the acidic diazonium salt solution gave a photoactive nucleotide derivative in 80-90% yield. The monophosphate product was identified as 5-N3dUMP by proton NMR, UV, IR, and chromatographic analysis as well as by the mode of synthesis and its photosensitivity. After formation of 5-N3dUTP through a chemical coupling of pyrophosphate to 5-N3dUMP, the triphosphate form of the nucleotide was found to support DNA synthesis by Escherichia coli DNA polymerase I at a rate indistinguishable from that supported by dTTP. When UMP was used as the starting compound, 5-N3UTP was formed in an analogous fashion with similar yields and produced a photoactive nucleotide which is a substrate for E. coli RNA polymerase. To prepare [gamma-32P]-5-N3dUTP for use as an active-site-directed photoaffinity labeling reagent, a simple method of preparing gamma-32P-labeled pyrimidine nucleotides was developed. [gamma-32P]-5-N3dUTP is an effective photoaffinity labeling reagent for DNA polymerase I and was found to bind to the active site with a 2-fold higher affinity than dTTP.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000345:Affinity Labels / Q000138:chemical synthesis*; D001386:Azides / Q000138:chemical synthesis* / Q000378:metabolism; D004247:DNA / Q000138:chemical synthesis* / Q000528:radiation effects; D004256:DNA Polymerase I / Q000378:metabolism; D003856:Deoxyuracil Nucleotides / Q000138:chemical synthesis* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D007202:Indicators and Reagents; D008027:Light; D013053:Spectrophotometry
chemical_list: D000345:Affinity Labels; D001386:Azides; D003856:Deoxyuracil Nucleotides; D007202:Indicators and Reagents; C048865:5-azido-2'-deoxyuridine 5'-triphosphate; D004247:DNA; D004256:DNA Polymerase I