The fast growing application of inorganic nanostructures for biomedical purposes has led to an increasing demand for further studies to obtain deeper understanding on the interactions between biomolecules and nanostructures at the atomic level. In this regard, a group of amino acids (AA) are the subject of the present study; in which density functional theory (DFT) is employed to investigate the interaction between aromatic amino acids (AAs) and Zinc oxide single walled nanotubes (SWNT) to identify the effective parameters for the biomedical applications. The structural changes and site specific binding nature of the bio-conjugated system are examined in detail. The results show that nanotube’s curvature is an effective factor in the magnitude of binding energy, since by decrease of nanotubes’ curvature the binding energy increases. Examination of the interactions between ZnO SWNTs and different binding sites of aromatic AAs indicates that the charge-solvent structure involving aromatic ring site of AAs is energetically more favorable. In this configuration the bonding is mediated by hybridization of π orbitals in aromatic ring and the d orbitals of Zinc atoms. The results of this study support the possible capability of ZnO SWNTs in detection of amino acids which shows the promising application of ZnO SWNTs in biosensing purposes.

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