Abstract
Environmental exposure to electromagnetic fields is potentially carcinogenic. The radical pair mechanism is considered the most feasible mechanism of interaction between weak magnetic fields encountered in our environment and biochemical systems. Radicals are abundant in biology, both as free radicals and reaction intermediates in enzyme mechanisms. The catalytic cycles of some flavin-dependent enzymes are either known or potentially involve radical pairs. Here, we have investigated the magnetic field sensitivity of a number of flavoenzymes with important cellular roles. We also investigated the magnetic field sensitivity of a model system involving stepwise reduction of a flavin analogue by a nicotinamide analogue—a reaction known to proceed via a radical pair. Under the experimental conditions used, magnetic field sensitivity was not observed in the reaction kinetics from stopped-flow measurements in any of the systems studied. Although widely implicated in radical pair chemistry, we conclude that thermally driven, flavoenzyme-catalysed reactions are unlikely to be influenced by exposure to external magnetic fields.
Highlights
There is continued public concern over the possible impact of environmental exposure to electromagnetic fields on human health [1]
In 2011, the International Agency for Research on Cancer (IARC) published a review of the evidence on health risks of magnetic field effects (MFEs) concluding that current evidence is inadequate to confirm the existence of health consequences from exposure to low level environmental magnetic fields (MFs) [9]
Expression constructs for the targeted enzymes were either available in our laboratories or obtained by commercial gene synthesis at Eurofins MWG Operon applying codon optimization for E. coli expression
Summary
There is continued public concern over the possible impact of environmental exposure to electromagnetic fields on human health [1]. We have targeted systems (table 1) where ‘hydride’ transfer might reasonably proceed via the RP intermediates proposed in figure 1a,b These include mammalian flavoprotein enzymes that impact important physiological processes and where we can measure accurately the pre-steady-state kinetics of the reductive half-reaction in the presence of an applied MF. It might be tempting to consider diflavin enzyme systems where stable, very long-lived (ms –s) radicals are produced [34,35] In such cases, the overall reaction rate might not be limited by the spin chemistry but by some influence of the protein (e.g. domain motions) [36]. A C4a-hydroperoxyflavin intermediate is formed which decays into fully oxidized flavin and H2O2 [30]
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