Membrane Protein Explorer (MPEx) MPEx is a tool for explaining membrane proteins. The first version of MPEx was born to aid the studies of the role of peptide bonds in the energetics of transmembrane helix stability, but evolved over time to serve other research needs, such as studies of the relative contribution of hydrophobic moment to translocon recognition of transmembrane segments and peptide partitioning into membrane interfaces. MPEx is a now a highly refined implementation of the sliding-window method that utilizes primarily experiment-derived physical and biological hydrophobicity scales, although other scales can be us. MPEx is a tool that provides an extendable framework not only for physical and biological hydropathy analyses, but β-barrel identification screening as well. MPEx also calculates and displays hydrophobic moment ...