We discuss effects of the adsorption of glycine, histidine, phenylalanine, and cysteine on the electronic structure of the metallic (3,3) carbon nanotube through calculations within density functional theory. Results show good nanotube electronic structure stability in the presence of the biomolecules. Molecule-nanotube band mixing and band degeneracy lifting are observed, though the limited extents to which these effects are manifested on the system electronics affirm the weak, noncovalent connection at their interface
