Aromatic carbon materials (ACM), such as graphene, carbon nanotubes, activated carbon, and others, have a wide range of biological and environmental applications. They are known to interact strongly with proteins, but mechanistic understanding of amino acid-specific interactions with ACM is limited. Such knowledge is needed in order to a priori predict the strength of protein adsorption to ACM. The interactions between amino acids (the building blocks of proteins) and graphene (a model ACM) have been modelled with molecular dynamics using nonpolarizable biomolecular force fields to describe graphene. However, accurate descriptions of protein-water-ACM interactions may require explicit incorporation of the polarizability of ACM surfaces, especially for amino acids with charged or aromatic side chains where cation-π and π-π interactions are important. Furthermore, while electrolytes are known to impact protein adsorption to surfaces, the effects of electrolytes on amino acid-ACM interactions in aqueous solutions has not been modelled. This study aims to quantify the free energies of adsorption of twenty natural amino acids to polarizable, triple-layer graphene through molecular dynamics simulations using an umbrella sampling approach. Simulations will be performed under neutral conditions and with varying concentrations of NaCl, KCl, MgCl2, and CaCl2 in order to assess amino acid adsorption to graphitic surfaces under varying ionic compositions. An aromaphilicity index characterizing the strength of the amino acids’ adsorption to graphene will also be determined. These results will improve understanding of protein-ACM interactions under more biologically and environmentally relevant conditions.

Exploring the effects of electrolytes on adsorption of amino acids to aromatic carbon materials

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