Fig. 8.
Binding of 1-NPN to CcapOBP83a-2. The purified CcapOBP83a-2 was diluted in 20 mM Tris–HCl pH 7.4 with a final concentration of 2 μM. Aliquots of 1-NPN stock solution [1 mM] in methanol were added to a final concentration of 0.1, 0.2, 0.3, 0.5, 1, 1.5, 2, 2.5, 3, 5 and 10 μM. Excitation was set at 337 nm, the peak emission at 380–460 nm was recorded and plotted against 1-NPN concentrations. The curve was used to determine the dissociation constant (KD 2nd fraction: 0.617 ± 0.069 μM) by nonlinear regression curve fitting using GraphPad Prism 5, and transformed to Scatchard plot (insert).