In our tests, using either Martini 2 or Martini 3 versions, none of the expected coiled coil dimers formed correctly (Figure ) when compared to the experimentally obtained structures. With Martini 2, dimers did form stably, but incorrectly: the 1ZIK dimer formed in an antiparallel orientation, contrary to the parallel X-ray structure; the 1U0I dimer formed roughly as frequently in either orientation, with some of the replicate trajectories exhibiting a transition between the two states, but even when correctly parallel the peptides dimerized along a shifted and rotated interface (see the mismatch between the experimental and simulated contacts in Figures and). Martini 2 dimers may have also been overstabilized in that no dissociation was observed in any of the replicates.