Protein monolayer-based MpD preparation frequently yields short-circuited junctions. This problem decreases as protein layers are added, allowing reasonable yields (~60 %) of functional junctions of the protein tri/tetra layer, over the layer thickness >15 nm. However, the first protein layers that self-assemble on the bottom electrode leave substantial voids (Figure ). During top electrode evaporation, these voids can facilitate filamentous growth of the top electrode, leading to electrically shorted junctions. The larger the protein size, in terms of its footprint on the substrate, the lower the packing density, i.e., the more of the bottom substrate remains exposed, i.e., the higher the probability of short circuits. In this study, a single bilayer of bacteriorhodopsin (bR; only bR bilayers yield reasonable coverage) left a higher fraction of voids over the covered area than those of monolayers made of the smaller human serum albumin (HSA) (Figure ). Consistently transport-active (non-shorted) junctions were achieved using a quality protein bilayers or thicker multilayers without any direct exposure to the bottom electrode. Here we demonstrate the MpD configuration with junctions, containing ~16 nm HSA tetralayers and ~23 nm bR triple bilayers.