Radical pair based magnetic field effects in cells: the importance of photoexcitation conditions and single cell measurements

A recent publication1on the bioRxiv preprint server aims to replicate our observation of magnetic field effects on the autofluorescence of HeLa cells2, but is unable to reproduce the effects described in our original work. Here we examine this new study and demonstrate, based on a model of the reaction photocycle, why the differences in the measurement conditions used render the experiment unlikely to be able to observe the originally reported effect. In addition, we highlight substantial problems in the quality of the data in the replicate study and reiterate the advantages of the direct modulation, single cell measurement approach presented in the original work over a more standard statistical approach.