Table 1.
Kinetic parameters for distamycin binding to its 1∶1 and 2∶1 sites
| Site | Phase | k1 | Ea1, kcal⋅mol−1 | ΔS1, cal⋅K−1⋅mol−1 | k2, s−1 | Ea2, kcal⋅mol−1 | ΔS2, cal⋅K−1⋅mol−1 |
|---|---|---|---|---|---|---|---|
| 1∶1 | On | 66.4 (3.8) μm−1⋅s−1 | 2.3 | −16.6 | 15.1 (0.3) | 19.7 | 16 |
| Off | 3.1 (0.08) s−1 | 23.7 | 33.7 | — | — | — | |
| 2∶1 | On | 74.5 (3.3) μm−1⋅s−1 | — | — | 5.1 (0.2) | 19.5 | 11 |
| Off | 0.08 (0.004) s−1 | 23.2 | 9.4 | — | — | — |
Values of bimolecular association constant for both sites were derived from plots of apparent rate vs. [Dst] at 25°C. Figures in parentheses indicate SD about the mean. The values of Ea and ΔS were derived from Arrhenius plots with temperatures ranging from 10°C to 35°C. The values of k2 indicated were obtained at [DNA] = 5 μM and [Dst] = 10 μM for the 1∶1 site and [DNA] = 2.5 μM and [Dst] = 25 μM for the 2∶1 site.