Figure 8. Time-resolved fluorescence anisotropy.

(Top) Time course of fluorescence decay after brief excitation at 337 nm. The samples were L-CaM in the absence of myo1c^IQ1-3 (left), L-CaM in the presence of myo1c^IQ1-3 and 1 mM EGTA (center), and L-CaM in the presence of myo1c^IQ1-3, 1.1 mM calcium, and 1 mM EGTA (right). The instrument response function (IRF) is the ~2 ns intensity spike near zero time. The upper red decay curve in each panel is I_VV and the lower blue decay curve is I_VH. Symbols are the recorded intensities and the lines are the convolutions of the IRF with a restricted rotational diffusion model. (Center) Plots of normalized residuals [(photon counts - fit)/fit]. (Bottom) Time-resolved anisotropies calculated with a restricted rotational diffusion model with r(0) and r(∞) values given in the text (solid black lines). A model assuming a single rotational decay for L-CaM in the absence of myo1c^IQ1-3 (blue line) gives identical results.