To investigate the mechanism of action of hydration environment affecting the oxidative stability of myoglobin (Mb) in the presence of a magnetic field, and to provide a basis for improving the oxidative stability of Mb.

Two magnetic field environments of low intensity (3 mT) and high intensity (12 mT) were set up at 4 ℃, the magnetic field treated Mb aqueous solution, Mb powder, and deionized water (the magnetic field treated deionized water and then dissolved Mb), respectively, and the magnetic field treatment time was 1 h. The Mb aqueous solution without magnetic field treatment was used as the control. The oxidative stability properties of Mb were analyzed by the relative content of high iron myoglobin, heme iron content and the variation of UV absorption bands, while the changes of Mb secondary structure, tertiary structure and porphyrin iron structure were analyzed by circular dichroism, and Raman spectroscopy and fluorescence spectroscopy techniques were employed to investigate the mechanism of the effect of magnetic field on the oxidative stability of Mb.

Both magnetic field treatment of Mb powder directly and magnetic field treatment of solvent water followed by dissolution of Mb had no significant effect (P>0.05) on the relative content of methemoglobin, while both 3 mT and 12 mT magnetic field treatment of Mb aqueous solution significantly increased the relative content of methemoglobin. The results of heme iron content and heme Shore band UV absorption showed that the heme porphyrin ring structure was sensitive to the magnetic field environment, and the magnetic field of different intensities had significant damage to the Mb heme structure, while the high intensity magnetic field environment had relatively greater damage to the porphyrin ring structure. Mb tertiary and secondary structure results showed that both 3 mT magnetic field treatment of solvent water before dissolving Mb, and 3 mT and 12 mT magnetic field treatment of Mb aqueous solution significantly promoted the unfolding of Mb secondary structure and oxidative damage of tryptophan and tyrosine residues of side chain groups. Raman spectroscopy results showed that 12 mT magnetic field treatment of Mb aqueous solution induced the cross-linking of Mb through disulfide bonds.

Hydration in Mb aqueous solution directly affected the effect of magnetic field on the oxidative properties of myoglobin, and magnetic field treatment promoted the oxidation of Mb central iron as well as heme porphyrin ring, probably because the magnetic field changes the physical properties of water molecules, such as dielectricity and degree of ionization, as well as the hydrogen bonding state between Mb and water, which further affected the structure of Mb with the unfolding of α-helix structure and the exposure of side chain groups, accelerating the destruction of heme structure and loss of heme iron, and promoting the oxidation of central iron.