Spin Transport Modeling in The Small Tetraheme Cytochrome

Multi-heme cytochromes have attracted attention due to their conductive properties [1] and, more recently, their spin-selective properties [2]. The small tetraheme cytochrome (STC), a c-type cytochrome found in <i>S. oneidensis</i>, has been demonstrated experimentally to act as a spin filter [3], with the potential to be used in nano-scale spintronic devices. Building upon a spin-dependent transport model previously applied to related biomaterials and cytochromes [4], we investigated decoherent transport through the cytochrome and electron hopping between heme groups. This model incorporated spin-orbit coupling and a generalized spin model to explore non-collinear effects. Preliminary findings indicate that collinear effects, arising from electron exchange and spin state, predominantly influence the transport pathway while spin-orbit effects only cause minor shifts in orbital energies. Notably, the peptide backbone functions primarily as a structural scaffold facilitating heme-to-heme electron transport, rather than directly contributing to electron conduction. We also examined the impact of solvation within our model and identified its role in modulating the coupling between heme sites and the overall conductivity of the cytochrome.<br/><br/>The research was supported by National Science Foundation NSF Grant Number 2317843, NSF Future of Manufacturing Grant No. 2229131, and the NDSEG fellowship.<br/><br/>References:<br/>[1] Dahl, Peter J., et al. "A 300-fold conductivity increase in microbial cytochrome nanowires due to temperature-induced restructuring of hydrogen bonding networks." <i>Science advances</i> 8.19 (2022).<br/>[2] Mishra, Suryakant, et al. "Spin-dependent electron transport through bacterial cell surface multiheme electron conduits." <i>Journal of the American Chemical Society</i> 141.49 (2019): 19198-19202.<br/>[3] Niman, Christina M., et al. "Bacterial extracellular electron transfer components are spin selective." <i>The Journal of Chemical Physics</i> 159.14 (2023).<br/>[4] Livernois, William, and M. P. Anantram. "A Spin-Dependent Model for Multi-Heme Bacterial Nanowires." <i>ACS nano</i> 17.10 (2023): 9059-9068.