Molecular dynamics (MD) simulations are another computational approach that can be used to complement experimental work and build comprehensive models of interactions on the level of molecules and atoms. MD simulations have already been used for several decades to study interactions between proteins in a membrane,(8-14) in particular also for NMR structure refinement.(15) More recently, the introduction of coarse grain (CG) models has made MD a standard approach for investigating the association of components in a membrane,(16, 17) allowing simulations of larger systems and larger time scales. These studies typically report binding to occur within one to several microseconds, after which the formed complexes are found to be stable for the remainder of the simulations, up to 25 μs.(9, 18-20) This observed stability may actually be a concern as it may reflect that the off-rate koff is just too low to allow sufficient sampling in simulations. Indeed, it is known that even simple dimers such as glycophorin A (GpA) take significant time to exchange(21) and long-term atomistic simulations performed on a dedicated machine have recently strengthened this view.(22