Published October 24, 2024 | Published
Journal Article Open

Probing Bioinorganic Electron Spin Decoherence Mechanisms with an Fe₂S₂ Metalloprotein

  • 1. ROR icon California Institute of Technology

Abstract

Recent efforts have sought to develop paramagnetic molecular quantum bits (qubits) as a means to store and manipulate quantum information. Emerging structure–property relationships have shed light on electron spin decoherence mechanisms. While insights within molecular quantum information science have derived from synthetic systems, biomolecular platforms would allow for the study of decoherence phenomena in more complex chemical environments and further leverage molecular biology and protein engineering approaches. Here we have employed the exchange-coupled ST = 1/2 Fe2S2 active site of putidaredoxin, an electron transfer metalloprotein, as a platform for fundamental mechanistic studies of electron spin decoherence toward spin-based biological quantum sensing. At low temperatures, decoherence rates were anisotropic, reflecting a hyperfine-dominated decoherence mechanism, standing in contrast to the anisotropy of molecular systems observed previously. This mechanism provided a pathway for probing spatial effects on decoherence, such as protein vs solvent contributions. Furthermore, we demonstrated spatial sensitivity to single point mutations via site-directed mutagenesis and temporal sensitivity for monitoring solvent isotope exchange. Thus, this study demonstrates a step toward the design and construction of biomolecular quantum sensors.

Copyright and License

Copyright © 2024 The Authors. Published by American Chemical Society. This publication is licensed under CC-BY 4.0 .

Acknowledgement

The authors thank the Beckman Institute Laser Resource Center for instrument access. C.A.T. acknowledges partial funding support from the Biotechnology Leadership Pre-Doctoral Training Program (BLP) in The Donna and Benjamin M. Rosen Bioengineering Center of the Division of Chemistry and Chemical Engineering at Caltech, as well as a Roy T. Eddleman Graduate Fellowship. The Caltech EPR facility acknowledges support from the Beckman Institute and the Dow Next Generation Educator Fund. Support from Caltech and the Dow Next Generation Educator fund, as well as the National Science Foundation, Division of Molecular & Cellular Biosciences (BIO/MCB), award number: 2236609 is gratefully acknowledged.

Supplemental Material

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.jpcb.4c06186.

  • Instruments, procedures, methodology for data analysis, expressions for fitting and approximations, continuous-wave EPR spectra, tabulated spin Hamiltonian parameters, pulse EPR traces with fits, ESEEM, HYSCORE, UV–Vis electronic absorption spectra, CD spectra, tabulated Tm values, and additional plots (PDF)

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Additional details

Created:
December 4, 2024
Modified:
December 4, 2024