Figure 5.

Dependence of the exchange and dipolar interactions in a radical pair on the center-to-center separation of the two radicals. The shaded area corresponds to log[|J₀/μT|exp(−βr)] with 8 × 10¹² μT ≤ |J₀| ≤ 8 × 10¹⁴ μT and β = 14 nm⁻¹. The dashed lines represent log|(D(r)/3)/μT and log|(D(r)/6)/μT|, calculated using the point-dipole approximation. The vertical lines indicate the separations of the radicals in the primary, secondary, and tertiary FAD-tryptophan radical pairs. The horizontal line drawn at 50 μT is the approximate strength of the Earth's magnetic field.