Table 1.
Thermodynamic parameters obtained by isothermal titration calorimetry for PDC-109 binding to phsophotidylcholine and phosphatidylglycerol unilamellar vesicles.
Figure 1.
PDC-109 induced solubilization of phospholipid multilamellar vesicles.
Solubilization was monitored by turbidimetry by measuring optical density at 333 nm. The phospholipids used are: DMPC (○), DMPG (•) and DMPE (Δ). See text for details.
Figure 2.
Calorimetric titrations for the binding of PDC-109 to DMPC membranes in the gel phase in the absence and presence of cholesterol.
ITC profiles corresponding to the binding of PDC-109 to unilamellar vesicles of DMPC (A, B) and DMPC/cholesterol (3∶1; mol/mol) (C, D) at 20°C are shown. Upper panels (A & C) show the raw data for the titration of phospholipid vesicles with protein and lower panels (B & D) show the integrated heats of binding obtained from the raw data, after subtracting the heat of dilution. The solid lines in the bottom panels represent the best curve fits to the experimental data, using the one set of sites model from MicroCal Origin. See text for further details.
Figure 3.
Titration calorimetry for PDC-109 binding to DMPG vesicles.
Injection of PDC-109 (250 µM) to the phospholipid vesicles (∼90 µM) at 20°C, yielded an endothermic binding isotherm (A). Lower panel (B) shows the integrated data obtained from the raw data, after subtracting the heat of dilution. Experimental data were fitted by using the one set of sites model from MicroCal Origin.
Table 2.
Thermodynamic parameters obtained by isothermal titration calorimetry for the binding of PDC-109 to DMPC/cholesterol (3∶1; mol/mol) mixture.
Figure 4.
Binding of PDC-109 with Lyso-PC micelles.
A) Raw data for the titration of 450 µM protein with 10.88 mM Lyso-PC at 25°C. B) Integrated heats of binding obtained from the raw data, after subtracting the heat of dilution. The solid line in B represents the best curve fit to the experimental data, using the two sets of sites model from MicroCal Origin.
Table 3.
Effect of pH on thermodynamic parameters obtained by isothermal titration calorimetry for PDC-109 binding to DMPC unilamellar vesicles.
Figure 5.
Enthalpy-entropy compensation plot.
Data are shown for the interaction of PDC-109 with phospholipid vesicles made up of DMPC (•), DPPC (□), DMPC/cholesterol (O) and DMPG (▾). The straight line corresponds to a linear least squares fit (slope = 0.69).