  It has been recently shown that radical-ion pairs and their reactions are a
paradigm biological system manifesting non-trivial quantum effects, so far
invisible due to the phenomenological description of radical-ion-pair reactions
used until now. We here use the quantum-mechanically consistent master equation
describing magnetic-sensitive radical-ion-pair reactions to explain
experimental data [C. R. Timmel and K. B. Henbest, Phil. Trans. R. Soc. Lond. A
{\bf 362}, 2573 (2004); C. T. Rodgers, S. A. Norman, K. B. Henbest, C. R.
Timmel and P. J. Hore, J. Am. Chem. Soc. {\bf 129} 6746 (2007)] on the effect
of deuteration on the reaction yields. Anomalous behavior of radical-ion-pair
reactions after deuteration, i.e. data inconsistent with the predictions of the
phenomenological theory used so far, has been observed since the 70's and has
remained unexplained until now.
