Figure 2.

Nuclear and electronic structure of a protein on single-layer graphene. (a) cyt c adsorbed on graphene (red) is computed to be structurally similar to its crystal structure (blue, PDB ID 1HRC). The adsorbed cyt c structure when compared to its crystal structure possesses more “salt bridges” between the positively and negatively charged amino acid side chains. (b) Projected density of states (pDOS) calculations show strong overlap between cyt c and graphene electronic states, indicating an efficient path of molecule-to-surface electron/hole transfer. Comparatively, for hydrated cyt c, some unoccupied cyt c states do not overlap with water electronic states, indicating that electrons could be trapped in these states. (c) The positively charged cyt c attracts the graphene electrons into a pool underneath the protein (yellow density, isosurface 2 × 10^–3 e Å^–3) to establish charge–image charge interactions.