2,6-Diaminopurine and 5-chloro-uracil 2'-deoxynucleoside 5'-triphosphates were synthesized from their 2'-deoxynucleosides. Using a method of creating oligonucleotides by enzymatic primer extension, dodecanucleotides representing an XbaI/SalI site and the complementary SalI/XbaI site were generated containing these base modifications. Their duplex stability was quantitatively compared by thin-layer chromatography to oligomers containing 2'-deoxyadenosine and 2'-deoxythymidine. The two unmodified oligomers already showed significant differences in dissociation temperature and binding equilibrium. Substitution with 5-chloro-2'-deoxyuridine did not affect the dissociation temperature of either oligomer, the 2,6-diaminopurine, however, led to an increase of 1.8°C or 1.5°C per modified base, respectively. While in the XbaI/SalI oligomer both base modifications changed the binding equilibrium, the 2,6-diaminopurine by a factor of 1.32, the 5-chloro-uracil by 0.65, no such effect was found with the complementary oligomer. © 1990.
Hoheisel, J. D., & Lehrach, H. (1990). Quantitative measurements on the duplex stability of 2,6-diaminopurine and 5-chloro-uracil nucleotides using enzymatically synthesized oligomers. FEBS Letters, 274(1–2), 103–106. https://doi.org/10.1016/0014-5793(90)81340-T