N²-Substituted-2′-deoxyguanosine 5′-Triphosphates as Substrates forE. coliDNA Polymerase I

Several N2-alkyl and N2-phenyl 2′-deoxyguanosine 5′-triphosphates and 2-bromo-2′-deoxyinosine 5′-triphosphate were synthesized and tested as substrates for E. coli DNA polymerase I with a template: primer system requiring incorporation of 85 nucleotides. N2-Methyl-dGTP and N2-ethyl-dGTP were found to be efficiently incorporated in place of dGTP to give full length product. N2-n-Hexyl-dGTP supported limited full length synthesis at high concentration, but N2-phenyl- and N2-(p-n-butylphenyl)-dGTP were poor substrates. 2-Bromo-2′-deoxyinosine 5′-triphosphate was a good substrate for pol I, and it was a replacement only for dGTP. Melting temperatures of oligodeoxyribonucleotides containing N2-alkyl-dG residues, annealed to complementary single stranded DNA, were lower than that of the normal oligomer.