Desorption/Ionization of Subunit and Kinetics of Iron Release Revealed with Matrix-assisted Laser Desorption Ionization-Time of Flight Mass spectrometry and Electronic Spectrum in Liver Ferritin of Aplysia

Liver ferritin of Aplysia (ALF) with purity of mass spectrometry (MS) was identified using peptide mass fingerprint. Both the lasers emitted from the matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF-MS) and the matrix sinapic acid together decomposed ALF into molecular ion of the subunit for MS analysis, showing three molecular ions, such as single subunit with double [M + 2H]2+ and single [M + H]+ charges and dimeric subunit with single charge [2M + H]+. The ratio of mass to charge (m/z) in these ions were divided to be 9784.03, 19678.42 and 39387.80, respectively. The molecular weight of ALF was less than that of the ferritin in shark liver (SLF) to a certain extent. Under the condition of basic medium (pH 8.0), the experimental results used with electron spectral technology showed that ascorbic acid, as a half-order reaction, reduced the whole iron component within the ferritin core for releasing, which resulted in the release of iron by ALF as the first-order reaction rather than half-order reaction, showing two different rates of iron release. The results obtained in this article suggested that these novel phenomena to be tightly connected with the low iron content and the capacities of subunit regulation in ALF and with the evolution level in Aplysia.