Revealing essential properties for enhanced quantum sensing in engineered AsLOV2 proteins

Genetically encoded flavoproteins have emerged as optically readable radical pair quantum sensors, but the molecular basis of the differing magnetic responses of closely related variants remains unresolved. Here, we analyse parental AsLOV2 and three evolved MagLOV variants using molecular dynamics, quantum chemical hyperfine calculations, Marcus electron transfer theory, and trajectory-based spin relaxation analysis. The mutations preserve the LOV fold and FMN-binding core but progressively reshape the conformational landscape of the W89 electron donor, with broader rigid-body libration yet increasingly restricted internal torsional motion and predominant occupation of a single rotameric basin in MagLOV2f. These distinct motions have different magnetic consequences: dipolar coupling modulation increases strongly in the later variants, whereas hyperfine modulation rates vary non-monotonically and decrease from MagLOV2 to MagLOV2f. The mutations also alter the radical pair free energy landscape and donor-acceptor orientation, producing variant-dependent back electron transfer rates, with MagLOV2f combining comparatively fast calculated recombination with reduced hyperfine relaxation relative to MagLOV2. Thus, directed evolution redistributes competing recombination and relaxation pathways rather than optimising a single kinetic parameter. This molecular picture rationalises the distinct magnetic-response amplitudes and saturation dynamics of closely related MagLOV proteins and identifies donor conformational control as a practical design variable for protein-based radical pair quantum sensors.