Amino Acid Analogue-Conjugated BN Nanomaterials in a Solvated Phase: First Principles Study of Topology-Dependent Interactions with a Monolayer and a (5,0) Nanotube

Using density functional theory and an implicit solvation model, the relationship between the topology of boron nitride (BN) nanomaterials and the protonated/deprotonated states of amino acid analogues is investigated. In the solvated phase, the calculated results show distinct “physisorbed versus chemisorbed” conditions for the analogues of arginine (Arg)and aspartic acid (Asp)-conjugated BN nanomaterials, including a monolayer (ML) and a small-diameter zigzag nanotube (NT). Such a distinction does not depend on the functional groups of amino acids but rather depends on the curvature-induced interactions associated with the tubular configuration. Arg and Asp interact with the BNML to form physisorbed complexes irrespective of the state of the amino acids in the solvated phase. For the NT, Arg and Asp form chemisorbed complexes, and the distinct nature of bonds between the donor electron moieties of N(Arg) and O(Asp) and the boron of the tubular surface is revealed by the natural bond orbital analysis; stronger s-type bonds for the deprotonated conjugated complexes and slightly weaker p-type dominated bonds for the protonated conjugated complexes. The interaction of neutral Trp with BN nanomaterials results in physisorbed configurations through π-stacking interactions with the indole ring of the Trp and BN nanomaterials. The calculated results form the basis for a theoretical study of more complex protein macromolecules interacting with nanomaterials under physiological conditions.