Structure of serum low-density lipoprotein. II. A freeze-etching electron microscopy study.

Normal human and diet-induced hyperlipidemic Rhesus monkey serum low-density lipoprotein structure was investigated by freeze-etching electron microscopy employing a novel rapid freezing technique. Using turnip yellow mosaic virus as a standard, the technique was shown to be capable of providing information regarding the general architecture of particles in solution. Human and monkey serum low-density lipoprotein particle morphology appeared to deviate markedly from that of a perfect sphere. Instead, the outer layer of the particles appeared to consist of a small number of globules. The number and dimensions of these globules as well as their arrangement are in remarkable agreement with the tetrahedral model proposed by Luzzati et al. (1979) in the preceding paper for the low temperature form of the Rhesus monkey low-density lipoprotein.