This proposal presents a novel methodology to explore the mechanisms of different electron pathways in redox bio-molecular architectures at the single-molecule level. Single-molecule contacts have been shown to be experimentally realizable at room temperature. Scanning Probe Microscopies are the most employed techniques for creating contacts due to the high spatial resolution. A huge variety of molecular systems has been already explored bringing a more robust understanding of the critical parameters required to build and measure charge transport through single-molecule devices; stable molecule-electrode chemical binding, univocal detection of a single-molecule contact formation or the elucidation of the effect on charge transport by different chemical groups. Single-molecule junctions with more complex bio-molecular systems are less explored but their feasibility has been already demonstrated on well-know structures like DNA or alpha-helices. Sulfur-content chemical groups are targeted in these systems to allow long-lived electrical contacts to the metal electrodes. Here we propose to use the above methodologies to achieve a complete picture of the electron pathways on an individual bio-molecular redox structure. Different electron pathways can be selected by forming single-molecule junctions at different positions of the outer shell of the protein structure. Site-directed mutagenesis can be used for creating the specific sites. A step further in this project will be to explore the dominant parameters involved in the sequential-step hopping electron transfer (ET). Such a study will provide clues for the understanding of the structural effects on the long-range ET in living organisms. This proposal assures a novel pioneering research particularly designed for the present host institution specialized in Biochemistry to be led by an expert researcher in the field of Molecular Electronics.