Journal of Lipids / 2011 / Article / Fig 7

Research Article

Human Plasma Very Low-Density Lipoproteins Are Stabilized by Electrostatic Interactions and Destabilized by Acidic pH

Figure 7

Effects of Na salts on thermal stability of VLDL. VLDL solutions (0.1 mg/mL protein concentration, 5 mM Na phosphate buffer, pH 7.6) containing buffer alone (black) or together with 10 mM NaCl (grey) or Na2SO4 (light grey) were subjected to melting (a) or kinetic experiments ((b) and (c)). The melting data were recorded by turbidity during sample heating at a constant rate of 11°C/h (a). The kinetic data were recorded in T-jumps from 25°C to higher temperatures, such as 85°C (b). Arrhenius analysis of the T-jump data shows that, similar to Na phosphate (Figure 6(b)), increasing the NaCl or Na2SO4 concentration leads to a decrease in the slope of the Arrhenius plot, indicating a decrease in the activation energy . Linear extrapolation of the Arrhenius plots suggests that the kinetic stability of VLDL at 37°C decreases by about 2 kcal/mol upon addition of 10 mM NaCl and by about 2.5 kcal/moL upon addition of 10 mM Na2SO4 (double arrows).

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