Spin concentration measurements of high-spin (g′=4.3) rhombic iron(III) ions in biological samples:: theory and application
Spin concentration measurements of high-spin (g′=4.3) rhombic iron(III) ions in biological samples:: theory and application
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DOI：
10.1007/s00775-007-0304-0
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发表时间：
2008-01-01
影响因子：
3
通讯作者：
Chasteen, N. Dennis
中科院分区：
文献类型：
--
作者：
Bou-Abdallah, Fadi;Chasteen, N. Dennis
由于单核高自旋（S = 5/2） Fe3+离子位于低对称性位点，在g' = 4.3处的电子顺磁共振（EPR）信号在生物样品中很常见。本研究旨在建立实验方法和合适的g′= 4.3强度标准，并准确量化产生这些信号的Fe3+的量。通过遵循Aasa和vangard （J. Magn.）的工作。原因19:308-315,1975)，我们提出了S = 5/2离子的EPR强度与EPR光谱中更常用的S = 1/2标准强度的关系式。在所测试的螯合物中，Fe3+-EDTA（1:3比例）在1:3甘油/水（v/v）， pH 2中被发现是77 K下冷冻溶液S = 5/2样品的优秀标准。Cu2+-EDTA和aqua VO2+的自旋浓度均为S = 1/2离子，Fe3+-转铁蛋白的自旋浓度均为S = 5/2离子，在此标准下进行了测量，结果与已知金属离子浓度的一致性在2.2%以内。三个样品的自旋浓度的相对标准偏差分别为+/- 3.6、+/- 5.3和+/- 2.9%。已知Fe3+浓度的Fe3+-去铁胺的自旋浓度异常低，表明溶液中存在epr沉默的多聚铁。
Electron paramagnetic resonance (EPR) signals at g' = 4.3 are commonly encountered in biological samples owing to mononuclear high-spin (S = 5/2) Fe3+ ions in sites of low symmetry. The present study was undertaken to develop the experimental method and a suitable g' = 4.3 intensity standard and for accurately quantifying the amount of Fe3+ responsible for such signals. By following the work of Aasa and Vanngard (J. Magn. Reson. 19:308-315, 1975), we present equations relating the EPR intensity of S = 5/2 ions to the intensities of S = 1/2 standards more commonly employed in EPR spectrometry. Of the chelates tested, Fe3+-EDTA (1:3 ratio) in 1:3 glycerol/water (v/v), pH 2, was found to be an excellent standard for frozen-solution S = 5/2 samples at 77 K. The spin concentrations of Cu2+-EDTA and aqua VO2+, both S = 1/2 ions, and of Fe3+-transferrin, an S = 5/2 ion, were measured against this standard and found to agree within 2.2% of their known metal ion concentrations. Relative standard deviations of +/- 3.6, +/- 5.3 and +/- 2.9% in spin concentration were obtained for the three samples, respectively. The spin concentration determined for Fe3+-desferrioxamine of known Fe3+ concentration was anomalously low suggesting the presence of EPR-silent multimeric iron species in solution.