Table 2.
Thermodynamic parameters for ligand binding to the THF riboswitch at 25 °C.
| RNA | Ligand | MgCl2 [mM] |
KD (μM) |
ΔH, (kcal mol−1) |
TΔS (kcal mol−1) |
n1 |
|---|---|---|---|---|---|---|
| wt | folinic acid | 6 | 18 ± 1 | 15 ± 1 | 8.0 ± 0.2 | 2.1 ± 0.1 |
| wt | folinic acid | 0.5 | 22 ± 2 | −15 ± 1 | −9.1 ± 0.1 | 2.0 ± 0.1 |
| wt | 7-deazaG | 6 | 24 ± 1 | −20 ± 1 | −14 ± 1 | 2.0 ±0.1 |
| wt | 7-deazaG | 2.5 | 26 ± 2 | −19 ± 1 | −13 ± 1 | 2.0 ± 0.1 |
| wt | 7-deazaG | 0.5 | 38 ± 1 | −30 ± 1 | −24 ± 1 | 2.1 ± 0.1 |
| U7C | folinic acid | 6 | 23 ± 2 | −20 ± 1 | −13 ± 1 | 1.1 ± 0.1 |
| U25C | folinic acid | 6 | 18 ± 1 | −11 ± 1 | −4.1 ± 0.2 | 1.3 ± 0.1 |
| U7C/U25C | folinic acid | 6 | n.d.2 | n.d. | n.d. | n.d. |
| U7C | folinic acid | 0.5 | 140 ± 7 | −30 ± 1 | −25 ± 1 | 1.1 ± 0.1 |
| U25C | folinic acid | 0.5 | 340 ± 10 | −19 ± 1 | −14 ± 1 | 1.2 ± 0.1 |
| U7C/U25C | folinic acid | 0.5 | n.d. | n.d. | n.d. | n.d. |
1
n is a fitted parameter that reflects the number of ligand binding sites.
2
n.d. no detectable binding.