The recently-released Martini 3 model tackles the limitations of the prior Martini 2 model by introducing several new particle types, with explicitly different interaction sizes to account for 3-to-1 and 2-to-1 mappings. With this new approach proteins in solution, transmembrane (TM) pores, and helical membrane-bound oligomers have been successfully simulated without undergoing excessive protein aggregation as was likely under Martini 2 . With over-aggregation out of the way, we set out in this work to gauge the accuracy of more subtle aspects of Martini 3 protein interactions. We focus on two types of biologically relevant systems: i) coiledcoil dimers with well-defined parallel structures (PDB ids 1ZIK and 1U0I) to test Martini 3 recognition of heptad repeats -an aspect strongly dependent on steric matching and hydrophobicity/hydrophilicity discrimination ; and ii) the WALP (tryptophan-alanine-leucine) series of peptides, which are single-pass TM alpha-helices with a well described tilting behavior in response to membrane thinning . The study of the latter systems was prompted by recent observations that transmembranar behavior might be somewhat unstable under Martini 3 .