Figure 6.

(A) Fluorescence anisotropy decay of a mixture of 60 μM OG-GSH and 30 μM GST-mC with 880 nm excitation and detection in the acceptor window (630–650 nm). The fixed dipole angle model cannot be fit to the data with χ_R² minimized at an unacceptable value of 3.05 with θ_DA ∼ 40°. (B) Predicted form of the intrinsic acceptor anisotropy by subtraction of the calculated donor bleed through from the composite anisotropy measured in (A). The initial rise, plateau, and decay imply a time-varying θ_DA consistent with the measured orientational freedom of both the donor and acceptor. (C) Schematic structure of the OG-GSH-GST-mC complex, the negative initial anisotropy recovered in (B) implies a close to 60° value for θ_DA.