Effects of low frequency magnetic field on myoglobin oxidation stability.

• Total sulfhydryl and free amino groups increased at 9 and 12 mT (magnetic field). • 3–12 mT treatments inhibited Mb (myoglobin) central iron atom oxidation. • More uniform Mb particle size distribution appeared at 3, 9 and 12 mT. • Increased zeta potential at 3, 6 and 12 mT improved Mb stability. • Mb clusters and β-turn or β-sheet structures unfolded at 9 or 12 mT. The effects of low frequency magnetic field on myoglobin (Mb) oxidation stability were evaluated by treatments at 0, 3, 6, 9, 12 mT and storage for 10 h. The results showed that Mb oxidation was inhibited under all magnetic field treatments, due to the increase of total sulfhydryl and free amino groups (9 or 12 mT) from unfolding of Mb clusters (3, 9, 12 mT) as well as β-turn and β-sheet structures (9 or 12 mT). The unfolding also induced (i) the destruction or burial of iron porphyrin and tyrosine residues; (ii) the exposure of tryptophan; (iii) more uniform Mb particle size distribution (3, 9, 12 mT) and increased zeta potential (3, 6, 12 mT). Overall, magnetic field promoted exposed active groups as the preferred oxidation target, thus decreasing the oxidation rate of central iron atoms. It also promoted Mb stability by redistributing particle size and increasing zeta potential. [ABSTRACT FROM AUTHOR]