E(Z) Depth Potential Position Finder

Calculate the energy minimum of a sequence in standard alpha-helix conformation using the Ez potential.
Reference: Senes A, Chadi DC, Law PB, Walters RF, Nanda V, Degrado WF "E(z), a depth-dependent potential for assessing the energies of insertion of amino acid side-chains into membranes: derivation and applications to determining the orientation of transmembrane and interfacial helices.", Journal of Molecular Biology (2007) 366(2), 436-48 [PDF reprint]