Effects of Cationization and 6-Hydroxydopamine on the Reduced Iron Release Rates From Ferritin by Radio-Frequency Magnetic Fields

The rates of iron chelation from ferritin with ferrozine, an optical marker, are reduced by up to a factor 3 in proteins previously exposed to radio frequency (RF) magnetic fields of 1 MHz and 30 muT for several hours. This change has been attributed to the power loss by the inner superparamagnetic nanoparticle and it is dependent on the frequency-field product. Given the relatively small energy released by the nanoparticle, we attribute the molecular origin of the effect to changes in the charge configuration around the entry pore at the threefold symmetry point. To test this hypothesis, we have performed measurements in cationized proteins where the negative charge around the pore is neutralized. We have also used strong reducing agents (6-Hydroxydopamine) that eliminate the need for the iron chelator to go inside the peptidic cage. In the first case, the effect of the magnetic fields is reversed, and proteins exposed to the fields release more iron than control samples. In the second case, the reducing agent quenches the magnetic field effect. No change in the inner nanoparticle structure, as tested via fluorescence measurements, is observed.