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. Author manuscript; available in PMC: 2009 Jun 1.
Published in final edited form as: Arch Biochem Biophys. 2008 Mar 25;474(1):198–204. doi: 10.1016/j.abb.2008.03.017

Figure 1.

Figure 1

A. Fluorescence of increasing concentrations of Nile Red in the presence of 1 µM wtCYP3A4. The signal shifts from a λem of ~620 nm at low ligand concetrations to a λem of ~660 nm at high concentrations. B. The fluorescence of 2 µM Nile Red in the presence and absence of 1 µM CYP3A4. Both ‘blue’ (~620 nm) and ‘red’ (~660 nm) spectral components are enhanced by binding to CYP3A4. C. Absorbance spectroscopy of the Type I spin shift induced by Nile Red binding wtCYP3A4. The binding isotherm fits well (solid line) to a two-site sequential model with KD values of 0.05 ± 0.1 µM and 2.3 ± 0.35 µM, with the first Nile Red molecule having 13% of the effect on the spin state that the second molecule does.