Fig 2. Binding of different six-carbon chain soluble lipids to PZ.

Intrinsic tryptophan fluorescence intensities of 150 nM PZ in 50 mM Tris-HCl, pH 7.5, 175 mM NaCl, 5 mM CaCl₂, 0.6% PEG were measured as a function of added A. C6PA (○), B. C6PC (●), C. C6PG (Δ) and D. C6(D)PS (▼) to obtain binding constants. The apparent K_d values for binding are 165 ± 25 μM, 129 ± 32, 131± 39, for PA, PC and PG respectively. (D)-PS shows extremely weak binding with K_d~900 μM.