Ab-initio Electronic Structure Calculations of Entire Metalloproteins

In this work we present a theoretical approach to deal with entire metalloproteins at quantum level. In particular we focus on single-Cu azurins and cytochrome c, which contains a heme group with its typical Fe-center. In this approach we consider the complete structure of these proteins as a whole rather than limiting our analysis to relevant fragments of coordination complexes. This is accomplished by combining fully ab-initio calculations based on density functional theory with atomic-scale molecular dynamics simulations. Beyond the main features arising from the metallic ions, our study reveals that the role played by the peripheral parts of the proteins could be of remarkable importance. More precisely, we find that oxygen atoms belonging to carboxyl groups of acidic amino acids, distributed all over the protein contribute to electronic states near the HOMO in the case of azurins. The contribution of the outer regions to the electronic structure of metalloproteins had so far been overlooked. Our results stress the need to investigate them thoroughly; this is especially important in prospect of understanding complex processes like the electronic transport through metal-metalloprotein junctions.