Lipids in biological membranes are thought to be functionally organized, but few experimental tools can probe nanoscale membrane structure. Using brominated lipids as contrast probes for cryo-EM and a model ESCRT-III membrane-remodeling system composed of human CHMP1B and IST1, we observed leaflet-level and protein-localized structural lipid patterns within highly constricted and thinned membrane nanotubes. These nanotubes differed markedly from protein-free, flat bilayers in leaflet thickness, lipid diffusion rates and lipid compositional and conformational asymmetries. Simulations and cryo-EM imaging of brominated stearoyl-docosahexanenoyl-phosphocholine showed how a pair of phenylalanine residues scored the outer leaflet with a helical hydrophobic defect where polyunsaturated docosahexaenoyl tails accumulated at the bilayer surface. Combining cryo-EM of halogenated lipids with molecular dynamics thus enables new characterizations of the composition and structure of membranes on molecular length scales.

Cryo-electron microscopy (cryoEM) is a powerful tool for atomic- and molecular-resolution structure determination, while molecular dynamics (MD) simulations are similarly powerful tools for predicting molecular trajectories. Given the challenges in estimating biomolecule dynamics with cryoEM alone, MD simulations are employed to forecast molecular motions and to interpret cryoEM reconstructions. Few methods, however, can evaluate MD predictions directly. Here, we use multislice wave propagation to project sampled snapshots of MD trajectories, either coarse-grained (CG) or all-atom (AA), into simulated cryoEM 3D reconstructions. We compared simulated and experimental images of low- and high-curvature membranes to show that MD simulations qualitatively reflect the fluidity and thus the contrast of biological membranes observed by cryoEM. MD simulations also correctly predicted bilayer dimensions for single component flat bilayers observed in cryoEM images. However, Martini3 CG-MD simulations failed to predict changes in membrane thickness induced by high curvature and with heterogeneous lipid compositions. We pinpointed the misbehavior of polyunsaturated lipid tails and cholesterol in Martini3 simulations as the main error sources contributing to inaccurate bilayer thicknesses. Our comparisons also explain membrane structure discrepancies between cryoEM and small angle X-ray scattering (SAXS). Further testing of MD predictions by direct comparisons between simulated and experimental cryoEM images should lead to the development of more accurate MD force fields. Statement of Significance: Molecular dynamics (MD) simulations are frequently employed to predict the dynamics of biological macromolecules and assemblies, but these predictions remain difficult to validate experimentally. Cryo-electron microscopy (cryoEM) can be used to directly image the conformational ensemble of macromolecules, but images of Coulombic potential cannot be easily compared to snapshots of atoms from MD simulations. Here, we show that a physics-based multislice image projection algorithm accurately converts MD trajectories to simulated cryoEM 2D images and 3D reconstructions. Using this approach, we identify consistencies and discrepancies between MD simulations and cryoEM experiments. Notably, coarse-grained MD performs poorly compared to all-atom MD when simulating membranes composed of mixtures of lipids that include cholesterol and polyunsaturated lipids, providing observables for MD force field improvement.

EMPIAR, the Electron Microscopy Public Image Archive centered at EMBL-EBI, is a public resource for raw electron microscopy images related to EMDB, contains micrographs, particle sets and tilt-series.

Heritable thoracic aortic disease (HTAD) comprises genetic disorders that predispose to thoracic aortic aneurysm and dissection. Several also affect arteries beyond the aorta. This narrative review examines the burden, distribution, mechanisms, and screening implications of extra-aortic vascular disease in vascular Ehlers–Danlos syndrome (vEDS), Loeys–Dietz syndrome (LDS), Marfan syndrome (MFS), and nonsyndromic HTAD, alongside the related systemic arteriopathies spontaneous coronary artery dissection (SCAD) and fibromuscular dysplasia (FMD). Disease- and genotype-specific patterns emerge, although estimates differ with referral patterns, imaging coverage, and outcome definitions. In the Montalcino Aortic Consortium (MAC), COL3A1 carriers had the highest proportion of extra-aortic clinical arterial events, with prominent abdominopelvic and cervical involvement. LDS showed widespread arterial disease and head and neck involvement. MFS had fewer clinical arterial events, but imaging studies identified branch aneurysms, particularly in patients with advanced aortic disease. SCAD and FMD frequently involved additional vascular territories. Findings from broader nonsyndromic thoracic aortic disease cohorts should be distinguished from genetically confirmed HTAD. Imaging-detected aneurysm prevalence and clinical event proportions are not interchangeable. Guidelines and consensus support disease-specific vascular assessment, but anatomical coverage, surveillance intervals, and evidence strength vary. Comprehensive baseline imaging is supported in LDS, FMD, and SCAD; European guidance also recommends peripheral surveillance in vEDS and MFS. Additional assessment in nonsyndromic HTAD and cervical artery dissection depends on genotype and clinical features. We outline a practical framework integrating the presenting vascular lesion, molecular diagnosis, prior events, family history, and imaging-related burden, and discuss when an extra-aortic presentation should prompt aortic evaluation. Prospective studies are needed to establish whether increased detection and changes in management improve patient-important outcomes.