The periodicity of n dihedral angles of a molecular system inspires its description in an n-toroidial space, rather than in an equivalent n-Cartesian space. Thus, the 2-torus representation of the 2-Ramachandran map shows the correct continuity of both of the independent variables (e.g., phi, psi) related to its backbone potential energy surface (PES). Such a conversion of coordinate system is applied to the fold description of a typical peptide unit. In a 2-torus mode of representation any point of the PES becomes embedded in its true surrounding, no edges tumble the true topographic nature of the system. (C) 2012 Elsevier B.V. All rights reserved.