Biophysical Society Conference | Estes Park 2023

Membrane Budding and Fusion

Poster Abstracts

45-POS Board 15 REPULSIVE SURFACES FOR MODELING COMPLEX BIOMEMBRANE MORPHOLOGIES Meghdad Razizadeh 1 ; Khaled Khairy 1,2 ; 1 St. Jude Children's Research Hospital, Developmental Neurobiology, Memphis, TN, USA 2 St. Jude Children’s Research Hospital, Center for Bioimage Informatics, Memphis, TN, USA Lipid bilayers are essential components of biological membranes, playing a crucial role in maintaining the structural integrity of cells and organelles. The study of lipid bilayer vesicles, as models for biological membranes, has been an active area of research for the past four decades. The computational modeling of vesicles strives to relate morphology, membrane structure, and membrane energetics. The Canham-Helfrich energy functional and its variants represent a well established approach to computationally investigate the mechanics and dynamics of lipid bilayers in terms of local principal curvatures of the surface. However, even with the help of such powerful formulations, simulation of lipid vesicles, complex biomembranes, and realistic membrane-bound organelles such as Golgi, ER, or mitochondria, still pose significant computational challenges. For example, the evaluation of bending forces requires approximations of derivatives of surface coordinates up to the fourth order, which can lead to numerical challenges on discretized shapes. Importantly, published works on computational membrane modeling lack reliable mechanisms to prevent self-intersections, making it challenging to extend computational predictions of biomembrane shapes to more intricate highly convoluted forms. This issue is especially prevalent at high surface area to volume ratio shapes, observed for many cell organelles, where minimized shapes can become unphysical due to self intersections. In this study, we adopt a recently developed method for self-intersection prevention (repulsive surfaces), originally developed for computer graphics applications. We extend its application to model realistic biomembranes by adding a tangent point energy term to the Helfrich functional. Our method yields shape predictions, even at high surface-to-volume ratios, a regime that cannot be reliably explored without self-intersection treatments. Finally, our study demonstrates the ability of this model to predict complex biomembrane morphologies, where lipid bilayers are forced to form tubular or planar shapes; features commonly observed in cell organelles, for example, the ER and inner mitochondrial membrane.

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