Table 3. Dissociation constants for complexes of ribonucleotides binding to the terminus of RNA hairpins, as determined by fitting NMR dataa.
| Ribonucleotide | Templating base | Hairpin | pH | Kd [mM] | |
|---|---|---|---|---|---|
| UMP | (4u) | A | (8a) | 7.0 | > 500 |
| OAt-UMP | (5u) | A | (8a) | 7.0 | 43b |
| MeIm-UMP | (6u) | A | (8a) | 7.0 | > 500 |
| GMP | (4g) | C | (8c) | 7.0 | 27 (± 9)d |
| OAt-GMP | (5g) | C | (8c) | 7.0 | 11b |
| MeIm-GMP | (6g) | C | (8c) | 7.0 | 23 |
| CMP | (4c) | G | (8g) | 7.0 | 19c |
| OAt-CMP | (5c) | G | (8g) | 7.0 | n.d. |
| MeIm-CMP | (6c) | G | (8g) | 7.0 | (27)c |
| AMP | (4a) | U | (8u) | 7.0 | 90 |
| OAt-AMP | (5a) | U | (8u) | 7.0 | 14 |
| MeIm-AMP | (6a) | U | (8u) | 7.0 | 42 |
aConditions: 0.5 mM RNA hairpin in D2O and phosphate buffer (200 mM), NaCl (400 mM), MgCl2 (80 mM) at pH 7.0 (uncorrected values for deuterium effect) and 20°C.
bAverage value from 2 titrations.
cTitrations with CMP (4c) and MeIm-CMP (6c) were performed in D2O, without buffer salts, to avoid broadening of hairpin signals.
dAverage of two measurements done in this work and the value reported in (30), with standard deviation in parentheses.