Sensitive Morphological Characterization of Oriented High‐Density Lipoprotein Nanoparticles Using 31P NMR Spectroscopy

The biological function of high‐density lipoprotein (HDL) nanoparticles, the so‐called good cholesterol that is associated with a low risk of heart disease, depends on their composition, morphology, and size. The morphology of HDL particles composed of apolipoproteins, lipids and cholesterol is routinely visualised by transmission electron microscopy (TEM), but higher‐resolution tools are needed to observe more subtle structural differences between particles of different composition. Here, reconstituted HDL formulations are oriented on glass substrates and solid‐state 31P NMR spectroscopy is shown to be highly sensitive to the surface curvature of the lipid headgroups. The spectra report potentially functionally important differences in the morphology of different HDL preparations that are not detected by TEM. This method provides new morphological insights into HDL comprising a naturally occurring apolipoprotein A‐I mutant, which may be linked to its atheroprotective properties, and holds promise as a future research tool in the clinical analysis of plasma HDL. 31P NMR spectra are highly sensitive to the morphology of high‐density lipoprotein nanoparticles when oriented on glass surfaces. The spectra reveal new molecular insights that are relevant to the protective function of the lipoprotein nanoparticles against cardiovascular disease.