Peptide–zinc oxide interaction: Finite element simulation using cohesive zone models based on molecular dynamics simulation I. Schäfer a,⇑ , G. Lasko a , T.A. Do b , J. Pleiss b , U. Weber a , S. Schmauder a a Institute for Materials Testing, Materials Science and Strength of Materials (IMWF), Pfaffenwaldring 32, D-70569 Stuttgart, Germany b Institute of Technical Biochemistry, Allmandring 31, D-70569 Stuttgart, Germany article info Article history: Received 16 August 2013 Received in revised form 16 July 2014 Accepted 18 July 2014 Keywords: Biomimetic Bio-inspired Zinc oxide (ZnO) Peptide Nano composite MD simulation FEM simulation Multiscale COD abstract In this study, a multiscale simulation approach of coupling molecular dynamics (MD) and finite element method (FEM) simulations was established to investigate the mechanical properties of a ZnO–peptide material. MD simulations of a single 6-mer peptide adsorbed on the polar ZnO(0001)–O surface were per- formed to calculate the adsorbed peptide conformations and their adsorption force parameters, which were used to estimate mechanical properties of the ZnO–peptide composite material in three point bend- ing tests using FEM simulations. The results from the multiscale simulations revealed that the influence of the Elastic modulus of the peptide on the material properties of the composite differs depending on the elastic properties of the cohesive zone. For developing a nanocomposite based on ZnO and a peptide, this dependency should be carefully considered and used to create stronger nanocomposites. Based on these simulation results, a set of binding affinities of the peptide and mechanical properties like the crack open- ing displacement of ZnO–peptide material could be predicted. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction In material science, especially for metals, multiscale simulations have been recently applied to use the results of molecular dynamics (MD) simulations as input data for other simulation tools like finite element method (FEM) simulation or phase field simulations. Molnar et al. reported on multiscale simulations on the coarsening of Cu-rich precipitates in a-Fe using kinetic Monte Carlo, molecular dynamics and phase-field simulations [1]. Similar multiscale simu- lations were also performed on metal/ceramic materials where frac- ture on the metal/ceramic interface was analyzed [2]. In the present work, a method is developed to combine MD simulations of peptide binding to a ceramic surface with FEM simulations. Coupling molecular dynamics simulations to FE simulations is important for bridging the gap between nanoscale and micro- or macroscale. MD simulations have been successfully applied to study atomistic effects in nanoscale of biological molecules [3,4], although they are usually limited to microsecond timescale simulations for typical systems (10 6 –10 5 atoms) [5], while FEM simulations in the frame- work of conventional continuum mechanics are used for macroscale material behavior [6]. A combination of the two simulation methods is able to predict mechanical properties of organic–inorganic nano- composites as shown in [7]. A virtual ceramic composite material which consists of zinc oxide (ZnO) and peptides with a high binding affinity for ZnO was examined for its mechanical properties. The molecular binding mechanism of peptides to ZnO was studied by MD simulations and the binding affinities were evaluated. The material properties of layered structures of peptides and zinc oxide are of high interest for the industry. The use of ZnO is based on its favorable properties making it well suited for many applications [8], which leads to the need to understand the mechanical properties of peptides adsorbed on the ZnO surface material. The use of ZnO includes construction of solar cells, luminescent materials and acoustic devices [8–11]. Within the last decade, many attempts have been made to study the adsorption of peptides to the ZnO surface to prepare nanostructured hybrid materials [12–17]. It was also demonstrated that ZnO-binding pep- tides could be used as bioactive layers for surface functionalization and modification [18] and that nano-sized structures of ZnO have unique material properties and a remarkable performance in electronics, optics, and photonics [19]. One major disadvantage of ZnO is that it is a relatively soft material [20]. A reinforcement of the mechanical properties of these nanomaterials could lead to longer life spans and an improved usability of these systems in http://dx.doi.org/10.1016/j.commatsci.2014.07.032 0927-0256/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +49 711 685 62734. E-mail address: Immanuel.Schaefer@imwf.uni-stuttgart.de (I. Schäfer). Computational Materials Science 95 (2014) 320–327 Contents lists available at ScienceDirect Computational Materials Science journal homepage: www.elsevier.com/locate/commatsci