FIGURE 2.

Steady-state fluorescence spectra of Dpo4 labeled at LF domain K329C at 20 °C. Alexa Fluor 488-labeled DNA (100 nm; solid black line) was excited at 493 nm. The sequential addition of Alexa Fluor 594-labeled Dpo4 (600 nm) and dTTP (1 mm) produced the dotted gray and dashed black lines, respectively. Spectra were normalized to one by using the donor in the absence of the acceptor as a reference. Emission spectra are shown for both O-2 (A) and O-3 (B) DNA substrates (Table 1).