FIGURE 3.

Interaction of RecQ with DNA molecules of different length. A, stopped-flow Trp fluorescence traces recorded upon rapidly mixing RecQ (0.5 μm) with dT₁₈ (black), dT₅₄ (dark gray), dT₉₀ (gray), and poly(dT) (light gray; all DNA ligands applied at 81 μm, nt). Triple exponential fits are shown as lines. (The slowest phase arose from photobleaching; see “Results.”) Fluorescence levels were normalized to that of the DNA-free state. B, DNA concentration dependence of k_obs values of the first (k_rapid; main panel) and second (k_slow; inset) phases of transients recorded as in A (dT₁₈ (squares), dT₅₄ (circles), dT₉₀ (triangles), and poly(dT) (inverted triangles)) alongside linear fits (lines). C, DNA concentration dependence of total (main panel) and rapid phase (inset) amplitudes of transients recorded as in A (symbols as in B) alongside hyperbolic fits (lines). Data were recorded at 5 °C. Parameters derived from fits are shown in Table 2.