Allen P D, St Pierre T G, Chua-anusorn W, Ström V, Rao K V
Department of Physics, The University of Western Australia, Nedlands, WA, Australia.
Biochim Biophys Acta. 2000 Feb 21;1500(2):186-96. doi: 10.1016/s0925-4439(99)00104-0.
Low-frequency low-field magnetic susceptibility measurements were made on four samples of mammalian tissue iron oxide deposits. The samples comprised: (1) horse spleen ferritin; (2) dugong liver hemosiderin; (3) thalassemic human spleen ferritin; and (4) crude thalassemic human spleen hemosiderin. These samples were chosen because Mössbauer spectroscopic measurements on the samples indicated that they exemplified the variation in magnetic and mineral structure found in mammalian tissue iron oxide deposits. The AC-magnetic susceptometry yielded information on the magnetization kinetics of the four samples indicating samples 1, 2, and 3 to be superparamagnetic with values of around 10(11) s(-1) for the pre-exponential frequency factor in the Néel-Arrhenius equation and values for characteristic magnetic anisotropy energy barriers in the range 250-400 K. Sample 4 was indicated to be paramagnetic at all temperatures above 1.3 K. The AC-magnetic susceptometry data also indicated a larger magnetic anisotropy energy distribution in the dugong liver sample compared with samples 1 and 3 in agreement with previous Mössbauer spectroscopic data on these samples. At temperatures below 200 K, samples 1-3 exhibited Curie-Weiss law behavior, indicating weak particle-particle interactions tending to favor antiparallel alignment of the particle magnetic moments. These interactions were strongest for the dugong liver hemosiderin, possibly reflecting the smaller separation between mineral particles in this sample. This is the first magnetic susceptometry study of hemosiderin iron deposits and demonstrates that the AC-magnetic susceptometry technique is a fast and informative method of studying such tissue iron oxide deposits.
对四个哺乳动物组织氧化铁沉积物样本进行了低频低场磁化率测量。这些样本包括：(1) 马脾铁蛋白；(2) 儒艮肝含铁血黄素；(3) 地中海贫血患者脾铁蛋白；以及 (4) 地中海贫血患者脾粗制含铁血黄素。选择这些样本是因为对样本进行的穆斯堡尔光谱测量表明，它们体现了哺乳动物组织氧化铁沉积物中发现的磁性和矿物结构变化。交流磁化率测量得出了这四个样本的磁化动力学信息，表明样本1、2和3为超顺磁性，在奈尔 - 阿雷尼乌斯方程中，指数前频率因子的值约为10(11) s(-1)，特征磁各向异性能垒的值在250 - 400 K范围内。样本4在高于1.3 K的所有温度下均表现为顺磁性。交流磁化率测量数据还表明，与样本1和3相比，儒艮肝样本中的磁各向异性能分布更大，这与之前对这些样本的穆斯堡尔光谱数据一致。在低于200 K的温度下，样本1 - 3表现出居里 - 外斯定律行为，表明弱的颗粒 - 颗粒相互作用倾向于使颗粒磁矩反平行排列。这些相互作用在儒艮肝含铁血黄素中最强，可能反映了该样本中矿物颗粒之间较小的间距。这是首次对含铁血黄素铁沉积物进行磁化率研究，并证明交流磁化率测量技术是研究此类组织氧化铁沉积物的一种快速且信息丰富的方法。
