MALDI-TOF MS和电子光谱技术研究海兔肝铁蛋白亚基电离和释放铁动力学特性

选用肽质量指纹谱(peptide mass fingerprint,PMF)技术鉴定质谱纯海兔肝铁蛋白(liver ferritin ofAplysia,ALF)。来源于基质辅助激光解吸电离飞行时间质谱(MALDI-TOF MS)仪中的激光和基质芥子酸协同解吸海兔肝铁蛋白(ALF)为带双电荷、单电荷M H] 和二聚体的亚基离子,并可供质谱分析。ALF亚基的质荷比m/z分别为9784.03M 2H]2 、19678.42M H] 和39387.802M H] ,其中亚基分子量M H] 略小于鲨鱼肝铁蛋白(liver ferritin of shark,SLF)。在弱碱介质(pH8.0)条件下,电子光谱技术研究指出,抗坏血酸以1/2级反应方式参与ALF释放铁全过程,同时又使ALF以一级反应动力学方式释放铁,呈现两种不同的速率。推测这一异常现象可能与ALF含低铁量、亚基调节能力和海兔的进化地位有关。

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.