Size and Surface Effects Related to Phase Transitions in Human Plasma Low Density Lipoprotein

Abstract

Size and surface effects on liquid crystal transitions are studied by absorbing samples in porous silica (Porasil) and observing the phase transitions by differential scanning calorimetry. The transitions are depressed and broadened and the transition enthalpy decreases. The smectic-cholesteric-isotropic transitions of cholesteryl oleate absorbed in 150 Å porous silica are measured. These transitions are compared with previously reported liquid crystal transitions in human plasma low density lipoproteins (LDL). We show that the broad transition and its low enthalpy observed in LDL can be explained, at least partially, in terms of size effect phenomena.