Protein Conformation Governs Spin-Selective Electron Transmission.

The chiral induced spin selectivity (CISS) effect results in spin-dependent electron transmission through chiral systems. In biological systems such as proteins, chirality appears in both primary and secondary structures, namely, in the existence of asymmetric carbon atoms and in the chiral configuration of oligopeptide subunits. An important question is what contribution each type of chirality makes to this effect. Here we present the impact of denaturation on spin polarization using d-glucose oxidase (GOx) as a model system. Employing Hall-effect and magnetoresistance (MR) measurements, we compared the spin selective behavior of GOx in its native and thermally denatured states. Our results show that the native protein, characterized by a well-defined helical structure and intact flavin adenine dinucleotide (FAD) cofactor, exhibits strong spin polarization. Upon denaturation at elevated temperatures (65 and 95 °C), a marked reduction in both Hall voltage slope and MR values indicates a significant loss in spin polarization capability. This behavior is attributed to the disruption of the protein's secondary structure, which is essential for maintaining chiral potential landscapes for spin selectivity. These findings highlight the importance of secondary structure in maintaining a high spin polarization in proteins. We also demonstrate that the spin-related structural properties of the protein are retained, even when the protein is imbedded in a solid-state device.