Revealing properties for enhanced quantum sensing in engineered proteins

Protein-based quantum sensors provide atomic-level sensitivity and precise measurements of local environments, where quantum-enabled magnetic detection can be linked to an optical readout of flavin radical pair photochemistry. Yet, the structural basis for the differing magnetosensitivities of individual proteins is still unclear, particularly regarding the respective roles of charge separation termination, complex stability, and spin relaxation. In this work, we employ all-atom molecular dynamics, quantum chemical energy calculations, Marcus-type free energy profiles, and spin relaxation theory to connect structure, electrostatics, hydration, and dynamics in AsLOV2-derived variants. Molecular dynamics simulations show that the LOV2 fold and FMN-binding core are preserved in all constructs, with enhanced flexibility restricted to surface regions, pointing to local reorganization of the donor microenvironment rather than a global loss of structural integrity. Analysis of dipolar couplings indeed demonstrates variant-specific, anisotropic inter-spin arrangements and substantially slower dephasing of the dipolar tensor, with correlation times increasing from a few nanoseconds to tens of nanoseconds. Energy gap calculations indicate strongly exergonic back electron transfer in all variants, while geometric considerations influence the differences in recombination rates. Collectively, these findings establish first principles for mechanistic design rules of engineered robust protein-based quantum sensors.