We utilized the density functional theory to study interactions in dopamine (DA)-graphene (G) systems. Graphene was modified with boron (B), nitrogen (N), calcium (Ca), and iron (Fe) atoms. Furthermore, an external electric field (E-field) between 0.005 and 0.020 au was applied between the DA and (Ca, Fe)doped G. The study revealed that interactions can be modulated between the DA and doped G (especially the Ca-and Fe-doped G) due to the formation of metal-O and O-metal-O covalent interactions. In addition, interactions are sensitive to the E-field applied to DA-Ca/Fe-G-lying models, there are the strongest interactions with the 0.015 au E-field. (C) 2017 Published by Elsevier B.V.