(a, c) The reference α-helical S4 model is simulated with varied electrode arrangements to mimic varied ionic strength of the baths (see Fig. 1). Labels in panel a indicate the internal//external ‘ionic strengths’ (H, high; L, low). (a, b) Charge-voltage relations, (c, d) translational energy profiles. (b, d) Simulations of the reference 310-helical S4 model.