Human Plasma Very Low-Density Lipoproteins Are Stabilized by Electrostatic Interactions and Destabilized by Acidic pH
Figure 5
Effects of millimolar concentrations of Na phosphate on the structural stability of VLDL assessed in the melting experiments. VLDL solutions containing 1–25 mM Na phosphate (as indicated) at pH 7.6 were heated at a constant rate of 11°C/h. The turbidity (dynode voltage) and CD melting data, V 320(T) and Θ320(T), were recorded simultaneously at 320 nm. (a) Turbidity was used to monitor increase in the particle size due to fusion and coalescence into lipid droplets, and (b) CD was used to monitor repacking of apolar core lipids upon VLDL rupture and coalescence into lipid droplets [20, 33]. (c) The apparent melting temperature Tm, which was determined from the peak position in the 1st derivative of the turbidity melting data such as those in (a), is plotted as a function of Na phosphate concentration. Data fitting with a monoexponential decay function (solid line, mM-1) is characteristic of the ionic screening effect [34], with providing a measure of macromolecular sensitivity to ionic screening. A similar effect of salt was observed in human HDL [24].
