温度对铽(Ⅲ)-转铁蛋白溶液构象的影响  

Effect of Temperature on the Conformation of Diterbium(Ⅲ) Transferrin

作　　者：杨斌盛[1] 白海静[1] 刘文[1] 丰九英[1] 

机构地区：[1]山西大学分子科学研究所,太原030006

出　　处：《化学学报》2002年第4期737-743,共7页Acta Chimica Sinica

基　　金：国家自然科学基金 (No .2 0 0 710 2 2 );山西省自然科学基金 (No .9910 13)资助项目

摘　　要：在pH 7.4,0 .0 1mol/LN 2 羟乙基哌嗪 N′ 2 乙磺酸 (Hepes)条件下 ,铽 (Ⅲ )与N ,N′ 二 (2 羟苄基 )乙二胺 N ,N′ 二乙酸 (HBED)结合并发生交换相互作用使铽 (Ⅲ )荧光增强 10 4 倍 ,通过监测铽 (Ⅲ ) 5 45nm荧光强度的变化测定了Tb HBED配合物的条件稳定常数是lgK =14.30± 0 .49;Tb HBED配合物中配体、铽 (Ⅲ )荧光强度均随着温度的升高而降低 .在pH 7.4,0 .0 1mol/LHepes条件下 ,TbN apoTf TbC 配合物中蛋白质的荧光强度随着温度的升高而降低 ,而能量受体铽 (Ⅲ )的荧光强度随着温度的升高而增强 ,主要源于铽 (Ⅲ )与螺旋 5色氨酸残基间的无辐射能量转移 ;当温度由 0℃上升到 5 5℃时 ,平均能量转移效率AE值增加了 2 9%,给体、受体间距离R有约 4.2 %的减小 ,温度变化引起TbN apoTf TbC 配合物大的构象变化 ;铽 (Ⅲ )与人血清脱铁转铁蛋白的结合使蛋白质的变性温度降低 .同样条件下 ,TbN apoOTf TbC 配合物与TbN apoTf TbC 配合物有所不同 ,虽然能量给体的荧光强度随着温度的增加而减小 ,但铽 (Ⅲ )荧光强度没有明显的增强 ;铽 (Ⅲ )对蛋白质的变性温度几乎没有影响 .In 0.01 mol/L N-(2-hydroxyethyl)-piperazine-N′-2-ethanesulfonic acid (Hepes), pH 7.4, the binding of N,N′-bis(2-hydroxybenzyl)ethylenedinitrilo-N,N′-diacetic acid (HBED) with Tb(Ⅲ) was monitored by fluorescence spectra. As the exchange interaction between HBED and Tb(Ⅲ), the Tb(Ⅲ) emission intensity at 545 nm is greatly enhanced. The conditional equilibrium constant for Tb-HBED is lgK=14.30±0.49. HBED emission intensity at 311 nm or Tb(Ⅲ) at 545 nm decreases as the temperature rises. For the complex of Tb(Ⅲ) ions with apotransferrin, Tb N-apoTf-Tb C, the protein emission intensity at 338 nm decreases as the temperature rises, while the Tb(Ⅲ) emission intensity at 549 nm increases gradually with increased temperature. The experimental phenomenon may be resulted from energy transfer between Tb(Ⅲ), the acceptor, and Trp residue in helix 5, the donor. According to Frster type dipole-dipole radiationless energy transfer, the average efficiency of energy transfer from Trp to Tb(Ⅲ) increases 29% over 55 ℃ temperature range, this represents a 4.2% decreases in donor-acceptor distance (R). The denaturation of the protein begins at 60 ℃ after Tb(Ⅲ) ions bind to apotransferrin. For the complex of Tb(Ⅲ) ions with apoovotransferrin, Tb N-apoOTf-Tb C, there is a decrease in protein emission intensity at 336 nm as temperature rises, but there is no significent increase in Tb(Ⅲ) emission intensity at 549 nm. Tb(Ⅲ) binding to apoovotransferrin has no effect on the denaturation point of the protein. It means that there is different conformational behavior for Tb N-apoTf-Tb C and Tb N-apoOTf-Tb C.

关 键 词：温度 铽(Ⅲ)离子 转铁蛋白 溶液构象 荧光光谱 荧光强度 

分 类 号：O641.4[理学—物理化学]