title: Transition path from two apposed membranes to a stalk obtained by a combination of particle simulations and string method.
abstract: The formation of an hourglass-shaped passage (stalk) connecting two apposed membranes is an essential initial step in membrane fusion. The most probable transition path from two separate membranes to a stalk, i.e., the minimum free-energy path (MFEP), is constructed using a combination of particle simulations and string method. For the reversible transition path in the coarse-grained membrane model, a collective order parameter, m, can be identified as the local difference of hydrophilic and hydrophobic densities. In particle simulations, the free energy F[m] as a functional of m is not readily available. This difficulty is overcome by an equation-free approach, where the morphology and the excess free energy along the MFEP are obtained by an on-the-fly string method. The transition state is confirmed by diagonalization of order-parameter fluctuations and by the probability of reaching either stalk or bilayer morphology from different positions along the MFEP.
authors.affiliation: Institut für Theoretische Physik, Georg-August-Universität, 37077 Göttingen, Germany. mmueller@theorie.physik.uni-goettingen.de
authors.forename: Marcus
authors.initials: M
authors.lastname: Müller
authors.forename: Yuliya G
authors.initials: YG
authors.lastname: Smirnova
authors.forename: Giovanni
authors.initials: G
authors.lastname: Marelli
authors.forename: Marc
authors.initials: M
authors.lastname: Fuhrmans
authors.forename: An-Chang
authors.initials: AC
authors.lastname: Shi
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D003198:Computer Simulation; D008561:Membrane Fusion / Q000502:physiology*; D008954:Models, Biological; D013816:Thermodynamics