Quantum Spin Dynamics in Biology

Weak Magnetic Field and Isotope Effects from Microtubules to Genome Regulation

Monthly Seminar in Physical Genomics (CPG), Northwestern University, August 2025 (Virtual)

Presenter:

Travis Craddock, Associate Professor (Biology), University of Waterloo; Tier 1 Canada Research Chair in Quantum Neurobiology

Weak magnetic fields and magnetic isotopes can alter biological function, even though their interaction energies are far below the thermal noise limit, a challenge for classical biochemical explanations. Quantum biology offers an alternative framework, particularly through spin-dependent reaction pathways such as the radical pair mechanism. This talk will begin with an overview of weak field and isotope effects in biology and an introduction to the principles of quantum biology. Dr. Craddock will present theoretical proposals and experimental evidence for quantum spin dynamics as a regulator of biomolecular processes, focusing on microtubules, dynamic cytoskeletal polymers that shape neuronal structure and plasticity, drive intracellular transport, and contribute to chromatin organization and genome stability.

The findings, consistent with a radical pair mechanism driven by the nuclear spin of ²⁵Mg, establish a direct link between quantum spin dynamics and cytoskeletal function. The presentation will conclude by exploring how this spin-sensitive chemistry could extend to other magnesium-dependent processes, including DNA replication and repair, epigenetic remodelling, and mitochondrial bioenergetics. Such mechanisms may offer new biophysical strategies to modulate chromatin dynamics and maintain cellular homeostasis, with potential applications in precision diagnostics and targeted therapies for neurodegeneration, cancer, and infectious disease.