Myriad scientific domains concern themselves with biological electron transfer (ET) events that span across vast scales of rate and efficiency through a remarkably fine-tuned integration of amino acid (AA) sequences, electronic structure, dynamics, and environment interactions. Within this intricate scheme, many questions persist as to how proteins modulate electron-tunneling properties. To help elucidate these principles, we develop a model set of peptides representing the common ?-helix and ?-strand motifs including all natural AAs within implicit protein-environment solvation. Using an effective Hamiltonian strategy with density functional theory, we characterize the electronic coupling through these peptides, furthermore considering side-chain dynamics. For both motifs, predictions consistently show that backbone-mediated electronic coupling is distinctly sensitive to AA type (aliphatic, polar, aromatic, negatively charged and positively charged), and to side-chain orientation. Here, the unique properties of these residues may be employed to design activated, deactivated, or switch-like superexchange pathways. Electronic structure calculations and Green?s function analyses indicate that localized shifts in the electron density along the peptide play a role in modulating these pathways, and further substantiate the experimentally observed behavior of proline residues as superbridges.