The reference-probe model for a robust and optimal radical-pair-based magnetic compass sensor

Area of Science:

• * Quantum biology
• * Spin chemistry
• * Biophysics

Background:

• * Radical-pair reactions are proposed mechanisms for magnetoreception in animals.
• * Sensitivity to weak magnetic fields is crucial for biological compasses.
• * The reference-probe model guides the design of radical pairs for directional magnetic sensitivity.

Purpose of the Study:

• * To investigate the role of the reference radical in radical-pair reactions.
• * To determine parameters for optimal directional sensitivity to magnetic fields.
• * To assess the robustness of directional effects against magnetic field variations.

Main Methods:

• * Analytical and numerical calculations of a simple radical-pair model.
• * Evaluation of a single axially anisotropic hyperfine interaction.
• * Investigation of radical pairs with multiple hyperfine interactions.

Main Results:

• * Derived a general expression for radical-pair reaction yield, offering insights into directional effects.
• * Confirmed that reference character enhances directional sensitivity to magnetic fields.
• * Demonstrated that reference character contributes to robustness against Earth-strength magnetic fields.

Conclusions:

• * The reference radical plays a significant role in optimizing directional sensitivity in radical-pair reactions.
• * Reference character is important for robust magnetic compass mechanisms.
• * Understanding reference radical properties is essential for designing advanced bioinspired magnetic sensors.