# Gaussian curvature directs the distribution of spontaneous curvature on bilayer membrane necks

## TL;DR

This paper investigates how Gaussian curvature influences the distribution of spontaneous curvature in membrane necks, using an augmented Helfrich model and shape equations to understand membrane mechanics during fission and fusion.

## Contribution

It introduces a model linking Gaussian curvature to spontaneous curvature distribution on membrane necks, revealing how heterogeneities affect membrane shape and energetics.

## Key findings

- Gaussian curvature governs non-uniform spontaneous curvature distribution.
- Membrane energetics depend on spontaneous curvature boundary conditions.
- Heterogeneities in spontaneous curvature influence membrane neck geometry.

## Abstract

Formation of membrane necks is crucial for fission and fusion in lipid bilayers. In this work, we seek to answer the following fundamental question: what is the relationship between protein-induced spontaneous mean curvature and the Gaussian curvature at a membrane neck? Using an augmented Helfrich model for lipid bilayers to include membrane-protein interaction, we solve the shape equation on catenoids to find the field of spontaneous curvature that satisfies mechanical equilibrium of membrane necks. In this case, the shape equation reduces to a variable coefficient Helmholtz equation for spontaneous curvature, where the source term is proportional to the Gaussian curvature. We show how this latter quantity is responsible for non-uniform distribution of spontaneous curvature in minimal surfaces. We then explore the energetics of catenoids with different spontaneous curvature boundary conditions and geometric asymmetries to show how heterogeneities in spontaneous curvature distribution can couple with Gaussian curvature to result in membrane necks of different geometries.