Marsden P J, Smith F A, Evans R W
Department of Medical Electronics and Physics, St Bartholomew's Medical College, London, England.
Int J Rad Appl Instrum A. 1989;40(8):715-22. doi: 10.1016/0883-2889(89)90084-1.
Samples of monoferric human serum transferrin have been prepared in which the iron occupies predominantly the N-site (sample A) and the C-site (sample B). 111In was then added in concentrations small enough to ensure that there was always an excess of specific binding sites. Because of the presence of apo-transferrin in both the samples, the occupancy by 111In in the two sites was only 75-78% C-site in sample A and only 61-65% N-site in sample B. Time differential PAC spectra showed a transition in the quadrupole frequency which took place at different temperatures, approximately 275 K in sample A and between 290 and 305 K in sample B. Debye and Arrhenius plots of the temperature dependence of the correlation time associated with molecular reorientation indicated an effective molecular volume about 50% larger than that of the hydrated diferric molecule determined by "biochemical" methods, and an activation energy for re-orientation of approximately 0.065 eV.
已制备出单铁人血清转铁蛋白样品，其中铁主要占据N位点（样品A）和C位点（样品B）。然后加入浓度足够低的¹¹¹In，以确保始终存在过量的特异性结合位点。由于两个样品中都存在脱铁转铁蛋白，¹¹¹In在两个位点的占有率在样品A中仅为C位点的75 - 78%，在样品B中仅为N位点的61 - 65%。时间微分PAC谱显示四极频率发生了转变，该转变在不同温度下发生，样品A中约为275 K，样品B中在290至305 K之间。与分子重排相关的相关时间对温度依赖性的德拜和阿累尼乌斯图表明，有效分子体积比通过“生化”方法测定的水合双铁分子的有效分子体积大约50%，重排的活化能约为0.065 eV。
