On the Structure of Human Serum Low Density Lipoprotein

This 1972 biophysics paper used small-angle X-ray scattering to determine the molecular architecture of human low-density lipoprotein — an early structural investigation of the particle that would become central to cardiovascular medicine.

The investigators found that LDL particles are spherical and relatively homogeneous in size, with a lipid bilayer core surrounded by a protein coat organized with approximate icosahedral symmetry. Phospholipids and cholesterol esters were distributed on both sides of the bilayer; the protein subunits appeared to interact specifically with cholesterol esters on the particle surface.

This structural work is foundational to understanding why LDL behaves as it does in the circulation and arterial wall. The spherical, protein-coated particle architecture — with apoB-100 as the defining structural protein — is the platform for all subsequent work on LDL receptor recognition, LDL oxidation, and LDL retention in the arterial intima. The single apoB-100 per particle, confirmed by later work, is what makes LDL counting via apoB clinically precise.

We rate the evidence moderate. Historical structural biology of high methodological quality for its era; its clinical significance lies in establishing the physical basis for LDL’s behavior rather than directly informing clinical decisions.