Exploring thermodynamic stability of the stalk fusion-intermediate with three-dimensional self-consistent field theory calculations

The prospects of compressible Self-Consistent Field (SCF) theory schemes for describing structures in amphiphilic membranes are illustrated by considering the thermodynamic stability of hourglass-shaped, hydrophobic connections (stalks) between apposed bilayers. The membranes are represented by a coarse-grained, solvent-free model. We represent the chain architecture by a Gaussian-thread representation of the chain architecture and capture the non-bonded interactions with a functional, which is of third-order in the densities of the hydrophilic and the hydrophobic segments. Using a three dimensional real-space scheme, we study the thermodynamic stability of the stalk with respect to two planar apposing bilayers as a function of membrane tension and molecular asymmetry. The structure and thermodynamics predicted by SCF theory agree very well with particle-based simulations, which include fluctuations. We discuss how the longer-range perturbations of the membrane induced by the stalk can affect thermodynamic properties.