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Updated: Jul 16, 2026

Optimized Negative Staining: a High-throughput Protocol for Examining Small and Asymmetric Protein Structure by Electron Microscopy
Published on: August 15, 2014
Apolipoprotein E*dipalmitoylphosphatidylcholine particles are ellipsoidal in solution
Clare A Peters-Libeu1, Yvonne Newhouse, Steven C Hall
1Gladstone Institute of Neurological Disease, Biomolecular Resource Center Mass Spectrometry Facility, Department of Cell and Tissue Biology, University of California, San Francisco, CA 94158, USA.
Apolipoprotein E (apoE) forms quasi-spheroidal particles with phospholipids. New research suggests these apoE-phospholipid complexes adopt an ellipsoidal shape with a twisted-bilayer core, challenging previous models.
Area of Science:
- Biochemistry
- Structural Biology
- Neuroscience
Background:
- Apolipoprotein E (apoE) is crucial for lipid transport in the brain and plasma.
- ApoE genetic variations are linked to Alzheimer's disease and cardiovascular conditions.
- ApoE requires lipoprotein binding for its biological functions.
Purpose of the Study:
- To investigate the structural model of apolipoprotein E (apoE) bound to dipalmitoylphosphatidylcholine (DPPC) in solution.
- To reconcile conflicting structural data from X-ray diffraction and solution studies.
- To propose a new structural model for apoE-phospholipid complexes.
Main Methods:
- Small-angle X-ray scattering (SAXS) to determine particle shape in solution.
- Mass spectrometry of limited proteolysis products to analyze protein structure.
- Comparison with existing X-ray diffraction data.
Main Results:
- ApoE*DPPC particles in solution are ellipsoidal, not quasi-spheroidal.
- The phospholipid core's shape is consistent with a twisted-bilayer model.
- Proteolysis analysis supports an alpha-helical hairpin structure for exposed apoE regions.
Conclusions:
- The study proposes a twisted-bilayer model for the apoE*DPPC particle core.
- This model better explains SAXS data and proteolysis results than previous micelle-like or discoidal models.
- The findings provide new insights into the structure and function of apoE-lipid complexes in biological systems.
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