Causal relationship between the transitions in the core and the surface in porcine low-density lipoproteins.

Two independent parameters, two characteristic temperatures, one indicating the change in the molecular organization of the core, Tc, and the other in the surface layer, Ts, were measured for a number of natural and triglyceride-enriched porcine low-density lipoprotein (LDL1 (buoyant density 1.020--1.063 g/ml) and LDL2 (buoyant density 1.063--1.080 g/ml) samples. Tc was determined by differential scanning calorimetry (DSC), whereas Ts was measured by Mn(II) binding to the lipoprotein surface followed by electron spin resonance (ESR) spectroscopy. A significant causal relationship between Tc and Ts in both LDL subfractions demonstrates the surface-core interaction in LDL. The significance of that interaction is emphasized as a possible link in the chain diet----lipoprotein changes----atherosclerosis.