Table 1.
Calculated and experimental pKa shifts of guanine, chemically modified guanine and Mg2+-guanine complexes. The calculated pKa shifts have been corrected for Mg2+-guanine binding affinity and Mg2+ concentration (0.01 M) using Eq. 2. Error estimates are not available because the method used to obtain those values are deterministic and do not involve sampling.
| Model | pKa shift (calc.) | pKa shift (expt.) |
|---|---|---|
| guanine (ref.) | – | – |
| inosine | −0.3 | −0.5 (90) |
| 3-deaza-guanine | 3.2 | 3.1 (91) |
| 7-deaza-guanine | 1.5 | 1.1 (91) |
| Mg2+-(H2O)5-guanine | −7.0 | – |
| Mg2+-(H2O)5-inosine | −7.0 | – |
| Mg2+-(H2O)5-3-deaza-guanine | −4.4 | – |
| HHR G12 | – | −1.2 (15) |