Electric properties of hydrated uracil: From micro- to macrohydration Tomáš Hrivnák a , Šimon Budzák b , Heribert Reis c , Robert Zaleśny d , Philippe Carbonnière e, ⁎, Miroslav Medveď b, ⁎ a Department of Physical and Theoretical Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina, Ilkovičova 6, SK-842 15 Bratislava, Slovakia b Department of Chemistry, Faculty of Natural Sciences, Matej Bel University, Tajovského 40, SK-97400 Banská Bystrica, Slovakia c Institute of Biology, Medicinal Chemistry and Biotechnology, National Hellenic Research Foundation, Vasileos Constantinou 48, GR-11635 Athens, Greece d Department of Physical and Quantum Chemistry, Faculty of Chemistry, Wroclaw University of Science and Technology, Wyb. Wyspiańskiego 27, PL-50370 Wrocław, Poland e Equipe de Chimie Physique, IPREM UMR 5254, Université de Pau et des Pays de L'Adour, 2 Avenue du président Angot, F-64000 Pau, France abstract article info Article history: Received 26 September 2018 Received in revised form 2 November 2018 Accepted 11 November 2018 Available online 15 November 2018 The accurate description of solvent effects on electric and optical properties of a solvated molecule is a complex task involving appropriate consideration of short-range as well as long-range intermolecular interactions having direct (local field induced) and indirect (solvent structure induced) impacts on the properties. In this study, we investigate the effects of hydration on dipole moment and dipole polarizability of uracil (U), focusing on the evo- lution of the properties from micro- to macrohydration regime. The microhydrated structures were generated by Global Search Algorithm of Minima (GSAM). Our results show a general increase in both induced dipole moment and isotropic polarizability with the cluster size, with a sudden decrease of the polarizability when passing from U(H 2 O) 5 to U(H 2 O) 6 . To explain the underlying effects, the variational-perturbational energy decomposition scheme (VP-EDS) was used. The interplay of hydrogen bonding between water molecules and the uracil mole- cule and hydrogen bonding between water molecules themselves is shown to be the driving force behind these trends. To represent the macrohydrated uracil, supermolecular (SM) and rigorous local field (RLF) methods were used, with representative structure generation performed by molecular dynamics (MD). The trends of in- duced electric properties with the cluster size are shown to be consistent between micro- and macrohydration regimes. While the induced dipole moment increases monotonically to a converged value of 1.305 ± 0.009 au, the induced isotropic polarizability, reaching maximum of 5.94 au for n = 8, slowly decreases again, and con- verges to the negative value (−1.21 ± 0.12 au), showing the decrease of the total polarizability of uracil in water. This study also clearly demonstrates that it is the electrostatic interaction which governs the significant property changes on going from micro- to macrohydration. © 2018 Elsevier B.V. All rights reserved. Keywords: Nucleobases Electric properties Solvent effects Intermolecular interactions Density functional theory Molecular dynamics 1. Introduction Theoretical studies of linear and nonlinear optical (NLO) properties of molecular systems are of interest both for a better understanding of underlying principles as well as for successful rational design of new materials with superior properties [1–3]. One important group of sys- tems studied for their NLO responses in recent years involves nucleic acid bases (NAB) [4–18], thanks to their biological functions [19–21] and potential application in nanobioelectronics [22–27]. Most of the cited computational studies on optical properties of NAB focused on ei- ther isolated molecules or interactions between NAB pairs, some of them including solvent effects [9,16–18] using the polarizable contin- uum approach (PCM). While the gas phase calculations help to eluci- date structure-property relationships for individual molecules, for practical applications it is also important to consider the changes of mo- lecular properties invoked by the environment in a condensed phase [28–30], liquid water being clearly the most relevant one for biomole- cules. From a computational point of view, these changes can be conve- niently described in terms of solvent-induced properties defined as the difference between the solute and gas phase property values: ΔP ¼ P solute −P gas ð1Þ The former can be calculated by using the differential shell approach (DSA) [31,32] as the difference between the total property and the property of the cluster without the solute molecule: P solute ¼ P total −P solvent ð2Þ The solute property can thus be obtained by performing two calcula- tions of the supersystem, one with and one without the solute molecule. It was shown that for water clusters the DSA scheme was in good Journal of Molecular Liquids 275 (2019) 338–346 ⁎ Corresponding authors. E-mail addresses: philippe.carbonniere@univ-pau.fr (P. Carbonnière), miroslav.medved@umb.sk (M. Medveď). https://doi.org/10.1016/j.molliq.2018.11.044 0167-7322/© 2018 Elsevier B.V. All rights reserved. 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