Table 3. Dissociation Constants for XPA Binding to Y-Shaped ssDNA–dsDNA Junction Substratea.
| treatment | Kd (μM) |
|---|---|
| unmodified | 0.30 ± 0.03 |
| DMSO | 0.31 ± 0.03 |
| adenine propenal | 1 ± 0.1 |
| NHS–biotin | n.d. |
a
Dissociation constants (Kd) were determined by fitting fluorescence anisotropy data to a simple two-state binding model. Kd values represent the mean ± SD of at least three titrations. The biotin-modification of XPA causes such a large loss of DNA-binding affinity that there is no significant change in fluorescence anisotropy; hence, a Kd value could not be determined.