Fig. 3.
Temperature dependence of anisotropy AP(T) at atmospheric pressure. For EC RecA + ATP[γ-S] (□), AP(T) gradually decreases with T, followed up by a sharp transition to the anisotropy of bare DNA at T ≈ 42 °C. Upon further lowering the temperature in steps (*), the anisotropy does not increase to its original value, suggesting that heat inactivation is irreversible. The experiment run without RecA and just ATP[γ-S] is shown for comparison to the heat inactivation, indicating that no RecA is bound. For TT RecA + ATP[γ-S] (+), the anisotropy decreases gradually from low temperatures up to 60 °C. Much higher temperatures are required to observe the hypothetical sharp transition in anisotropy.