A Compass at Weak Magnetic Fields Using Thymine Dimer Repair
Related Experiment Video
Updated: Feb 12, 2026

Chemical Dimerization-Induced Protein Condensates on Telomeres
Published on: April 12, 2021
Theodore J Zwang1, Edmund C M Tse1, Dongping Zhong2
1Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States.
Abstract:
How birds sense the variations in Earth's magnetic field for navigation is poorly understood, although cryptochromes, proteins homologous to photolyases, have been proposed to participate in this magnetic sensing. Here, in electrochemical studies with an applied magnetic field, we monitor the repair of cyclobutane pyrimidine dimer lesions in duplex DNA by photolyase, mutants of photolyase, and a modified cryptochrome. We find that the yield of dimer repair is dependent on the strength and angle of the applied magnetic field even when using magnetic fields weaker than 1 gauss. This high sensitivity to weak magnetic fields depends upon a fast radical pair reaction on the thymines leading to repair. These data illustrate chemically how cyclobutane pyrimidine dimer repair may be used in a biological compass informed by variations in Earth's magnetic field.
Related Concept Videos
Compass
Magnetic Fields
A magnetic field is defined by the force that a charged particle experiences...
Weak Base Solutions
Magnetic Field of a Solenoid
Consider a solenoid with 100 turns wrapped around a cylinder of...
Magnetic Field Lines
Magnetic field lines follow several hard-and-fast rules:
Energy In A Magnetic Field
Take an ideal inductor with zero resistance. Although it's practically impossible, assume that the coil's resistance is so small that it is practically negligible. The loss of the field's energy to dissipate thermal energy (or heat) is thus...

