Vol.:(0123456789) 1 3 Theoretical Chemistry Accounts (2020) 139:92 https://doi.org/10.1007/s00214-020-02609-9 REGULAR ARTICLE Infuence of explicit water molecules on the charge migration dynamics of peptidomimetics: a DFT study Sherin Joy 1  · Ganga Periyasamy 1 Received: 20 November 2019 / Accepted: 6 May 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract Peptidomimetics are the synthetic analogous of the natural peptides that can act as signal transductors and transfer electrons through intra- and inter-molecular H-bonding interactions. The explicit interaction of the mimetics with aqueous media has been studied using density functional theoretical methods. Along with the complete solvation environment, the local solvation has been considered to understand the importance of weak interactions at each functional unit labeled as donor, acceptor or bridge based on the population analysis. The computations show that among the locally solvated models, linear ureidopep- tides show a variation in the electronic structure, stabilization energies, charge distribution, charge transfer after excitation and hole migration after ionization which is dependent on the location of water molecules either at amino, carboxylate ends or on the alkyl bridge. The time scale for hole migration is faster if the water molecules interact with the amino end wherein the contribution of water is evident from the plots. It is also perceived that the peptides under a complete solvation environ- ment mimic the characteristics of a local solvation at the amino or donor end. Keywords Peptidomimetics · Water molecule · Charge transfer · Hole migration 1 Introduction Water is pervasive and a ubiquitous part of living sys- tem which is an inevitable source of life that governs the structure, stability, dynamics and function of most of the biological processes [1–3]. Thus, water has been treated as an integral component of biomolecular systems [4, 5]. The interaction between water and bio-entities is crucial to understand their function which can fnd its applications in physical, chemical and biological processes involved in drug design, synthesis of macromolecules like proteins [6–8]. Water has been found to carry out its role depending upon the nature of bio-entities [9]. Base pairing of DNA is sup- ported by water molecules acting as a dielectric medium to stabilize their structure by neutralizing the charge on the phosphate groups thereby reducing the repulsion [10]. Intercellular migration of diferent ions is also drawn by the diference in the concentration and pH of the surrounding aqueous medium [9, 11]. Water is found to be a part of the mechanism of numerous reactions governing enzymatic catalysis [12]. Further, it is an energy and charge carrier that plays multiple roles in biological electron transfer triggering almost all reactions [11, 13]. The degree of interaction of water molecules with nat- ural entities is mediated by the covalent or non-covalent (H-bonding, electrostatic interactions) bonding [14, 15]. Specifcally, non-covalence is attributed to the simultane- ous hydrogen bond donating and accepting capacity of water that can afect the kinetics and dynamics of charge transfer through it [16]. Further, water can mediate the tunneling of electrons through proteins spontaneously by changing the pathway or decreasing the energy barrier [17, 18]. Thus, a small number of water molecules can form water-mediated hydrogen bonds to link the redox groups and enhance the electronic coupling of donor and acceptor. The mechanism of water-mediated charge transfer between Cys and Tyr residues in proteins has been investigated by Chen et al. [17]. The properties of proteins like folding and emission are also infuenced by water that can be applied as control Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00214-020-02609-9) contains supplementary material, which is available to authorized users. * Ganga Periyasamy ganga.periyasamy@gmail.com 1 Department of Chemistry, Bangalore University, Bangalore 560 056, India