This paper demonstrates the importance of calculating both the reduction and oxidation electrode potential-dependent activation energy curves, E-a(U), and then evaluating the respective derived E-a(U) curves from them when using constrained variation theory for electron transfer to a local reaction center, an approach developed in this lab. A structure parameter averaging is introduced for calculating improved results if the calculated and derived results are not in satisfactory agreement. This averaging technique is used to improve upon a previous study of the first step of O-2 reduction to hydrogen peroxide or water when bonded to platinum and to show the role that twisting of Pt-O-O-H+ can play by increasing its electron affinity and lowering the activation energy. By the same token, oxidation of peroxide proceeds with a higher barrier when the molecule is allowed to be twisted, which is its stable structure. © 2005 Elsevier B.V. All rights reserved.