Although both lead to the gap-opening effect, CPCM and level shifting modify orbital energies differently. Level-shifting applies the same shift to all virtual orbitals regardless of their local electrostatic environment (Eq (10)). In contrast, the change of orbital energy caused by CPCM, 𝛥𝜖 ; %&%' , depends on the shape of the orbital 𝜑 ; (𝑟 ⃗) and the distribution of the solvent polarization charges, as detailed in our theoretical analysis in Section II. To verify this, we investigated the change of HOMO and LUMO energies and orbital shapes as functions of CPCM dielectric constant, ε, for a representative zwitterionic peptide, 3ftr. As shown in Figure , The HOMO is mainly localized at the negatively charged C-terminal and therefore is expected to get electrostatically stabilized by surrounding positive CPCM polarization charges. In contrast, the LUMO is closer to the positively charged N- G .