A fluorescence study of apolipoprotein localization in relation to lipids in serum low density lipoproteins.

Fluorescence energy transfer studies were carried out on low density lipoproteins (LDL) containing pyrene, in order to investigate their structure. The results indicate that almost all of the LDL tryptophan residues are located in the same surroundings near the surface of the particle and are immersed in the lipid phase 10-20 A below the lipid/water interface. The data do not support a model of protein spikes protruding from the particle surface. Such spikes have been observed in LDL preparations only after long-term storage.