Electrochemical studies are reported on a series of peptides to determine the influence of different side-chains and backbone rigidity on electron transfer, to progress the field of molecular electronics. Specifically, these peptides share either a common helical or beta-strand conformation to cover a range of secondary structures, to fully investigate the influence of backbone rigidity. Two types of side-chain tethers, either triazole-containing or alkene-containing, are also compared to investigate these effects on electron transfer. Our results showed that the observed formal potentials (Eo) and electron transfer rate constants (ket) fall into two distinct groups. The peptides constrained via a side-chain tether exhibited high formal potentials and low electron transfer rate constants, whereas the linear peptides displayed low formal potentials and high electron transfer rate constants. This was found to occur irrespective of the backbone conformation, or the nature of the side-chain constraint. The vast formal potential shifts (as much as 482 mV) and the large disparity in the electron transfer rate constants (as much as 97%) between the constrained and linear peptides, provides two distinct states (i.e. on/off) with a sizeable differential, which is ideal for the design of molecular switches. (C) 2016 Elsevier Ltd. All rights reserved.