A synthetic oligonucleotide duplex containing the chemotherapeutic and mutagenic agent 5-fluorouracil paired with guanine has been studied in solution by proton and fluorine NMR. The 7-mer duplex containing a central FU · G base pair adopts a normal right-handed configuration. At low pH, the predominant base-paired structure is wobble, whereas at higher pH an ionized structure in Watson-Crick geometry is observed. The two structures are in a pH-dependent equilibrium with one another with an apparent pK of 8.3 at 23°C. This is the first demonstration of an equilibrium between two distinct base pairing schemes and the first demonstration of a negatively charged base pair in DNA.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Biological Chemistry|
|State||Published - 1988|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology