Biophysical Society Thematic Meeting | Bucharest 2026

Biophysics of Membrane Reactions in Brian

Tuesday Speaker Abstracts

MEMBRANE TOPOGRAPHY VARIATIONS AND QUANTITATIVE BIOLOGY - PITFALLS AND SOLUTIONS Ingela Parmryd Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden To understand complex cellular processes in the plasma membrane, quantitation is essential. For the data interpretation to generate biological insights we need to acknowledge that across a range of length scales the plasma membrane is not flat. However, uncovering high-resolution membrane topography is very challenging and its importance is therefore frequently dismissed or ignored. In single particle tracking, movement is recorded with high lateral and temporal resolution, but the z-dimension is often absent. Simulations of Brownian motion on surfaces with pillars ridges, with movement in three dimensions but only recorded in two, consistently underreports the diffusion rates and can be misinterpreted as transient confinement or anomalous diffusion (PMID:20195248). Importantly, even 3D Euclidean distance measurements substantially underreport diffusion on non-flat surfaces because it is essential that membrane molecules remain in the membrane. The shortest within surface (geodesic) distance, is a solution for foldable but not deformed (unfoldable) surfaces because topographical features themselves can produce the appearance of anomalous diffusion (PMID:30652124). Membrane topography variations are not homogeneously distributed being smaller above the nucleus than other parts of the cell. Failing to appreciate this can mislead the interpretation of fluorescence correlation spectroscopy data and a remedy is to account for the amount of membrane in the detection volume using a membrane marker (PMID:32903922). Single-molecule localisation microscopy suggests that most plasma membrane proteins are organised in clusters but local membrane density differences exist and will make randomly distributed membrane molecules appear clustered. Differentiation between genuine and topography-variation-caused clusters requires including a membrane marker to map the local amount of membrane (PMID:38951588). Our findings suggest that clustering and non-Brownian motion are less common than the contemporary literature implies. In conclusion, acknowledging membrane topography radically improves the interpretation of experimental data and of the underlying biology.

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