T-1 and T-2 of ferritin solutions: Effect of loading factor
T-1 and T-2 of ferritin solutions: Effect of loading factor
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DOI：
10.1002/mrm.1910360111
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发表时间：
1996-07-01
影响因子：
3.3
通讯作者：
Brooks, RA
中科院分区：
文献类型：
--
作者：
Vymazal, J;Zak, O;Brooks, RA
质子磁弛豫时间T-1和T-2是在磁场强度为0.05 T至1.5 T的铁蛋白溶液中测量的，其中负载因子为每分子90至3600个铁原子，如先前观察到的，1/T-2随磁场强度线性增加，并且每单位铁的斜率在所有样品中大致相同，这后一发现表明，T-2的场依赖性可以用作铁蛋白结合铁的量度，而不管加载因子如何。基于铁蛋白核心的假定反铁磁结构和1/T-2对核心磁化的线性依赖性，提出了一种可能的解释，对1/T-1的贡献和对1/T-2的贡献均随加载因子的增加而线性增加;这些效应表示水质子通过核表面上的铁原子或通过铁芯本身的量子力学偶极-偶极弛豫。最后，对于1/T-1和1/T-2，在LF = 0处的外推截距表明来自结合到蛋白质壳的少量铁离子的贡献。这些结果可能有助于使用MRI来测量脑铁和可能甚至铁蛋白负载因子。
Proton magnetic relaxation times T-1 and T-2 were measured at field strengths from 0.05 T to 1.5 T in solutions of ferritin with loading factors from 90 to 3600 iron atoms per molecule, 1/T-2 increased linearly with field strength, as previously observed, and the slope per unit iron was approximately the same in all samples, This latter finding indicates that the field dependence of T-2 may be used as a measure of ferritin-bound iron, regardless of loading factor, A possible explanation is presented, based on the presumed antiferromagnetic structure of the ferritin core and the linear dependence of 1/T-2 on core magnetization, A nonzero contribution to 1/T-2 in the limit of tow field and a contribution to 1/T-1 were also found, both of which increase linearly with loading factor for constant protein concentration; these effects represent quantum mechanical dipole-dipole relaxation of water protons either by iron atoms on the surface of the core or by the iron core itself, Finally, the extrapolated intercept at LF = 0 for both 1/T-1, and 1/T-2 indicates a contribution from a small number of iron ions bound to the protein shell, These results may help in the use of MRI to measure brain iron and possibly even ferritin loading factor.