铽(Ⅲ)与人血清脱铁转铁蛋白结合的荧光光谱研究

Fluorescent Study on the Binding of Terbium Ion with Apotransferrin

在ｐＨ７．４０．１ｍｏｌ／ＬＨｅｐｅｓ及室温条件下，使用荧光光谱进行了Ｔｂ３＋对人血清脱铁转铁蛋白的滴定．结果表明Ｔｂ３＋与人血清脱铁转铁蛋白结合后，其５４９ｎｍ处的荧光强度增强约１０５倍．在５４９ｎｍ处Ｔｂ３＋－脱铁转铁蛋白络合物的摩尔荧光强度是（９．６５±０．０５）×１０４ｍｏｌ－１Ｌ，Ｔｂ３＋可占据脱铁转铁蛋白的两个金属离子结合部位，优先占据脱铁转铁蛋白的Ｃ端结合部位，条件平衡常数是ｌｇＫＣ＝９．９６±０．２０，ｌｇＫＮ＝６．３７±０．１６．Ｔｂ３＋与Ｒ３＋Ｅ（ＲＥ＝Ｎｄ、Ｓｍ。

The binding of Tb 3+ to human serum apotransferrin had been studied by monitoring the fluorescent intensity of Tb 3+ at 549 nm.Conditional equilibrium constants for the complex of Tb 3+ by human serum apotransferrin in 0.1 mol/L hepes,pH7.4 and room temperature were measured.The successive macroscopic binding constants were lg K C=9 96±0 20 and lg K N=6 37±0 16.The molar fluorescent enhancement of Tb apotransferrin comples was (9.65±.05)×10 4 mol -1 ·L.Titration of both C and N terminal monoferric transferrin with Tb 3+ indicated that Tb 3+ binding was stronger at the C terminal binding site than at the N terminal binding site.Linear free energy relationships for Tb 3+ and R 3+ E(R E=Nd,Sm,Eu and Gd)were established.There was a size restriction for the binding of lanthanide ions at the C terminal binding site of apotransferrin.