新型磁共振靶向对比剂Gd-DTPA-链霉亲和素的制备及其反应条件的实验研究

目的探讨制备Gd3 标记的二乙三胺五乙酸-链霉亲和素(Gd-DTPA-SA)的最佳反应条件。方法选择不同pH值的反应体系(pH值分别为5、6、7、8)及不同DTPA-SA的摩尔比率(1000、500、200、100),测定不同反应条件下的每个SA分子所结合的Gd3 数目及Gd-DTPA-SA的结合活性。结果随着反应体系pH值的增高,每个SA分子所结合的Gd3 数目增高;当DTPA-SA摩尔比率低于500时,DTPA-SA联结Gd的数目随着DTPA-SA摩尔比的增高而增高;而当摩尔比率为1 000时,则出现下降。各实验组Gd-DTPA-SA复合物的生物素结合活性无明显差异。结论SA分子所结合的Gd3 数目依赖于反应体系的pH值及DTPA环酐-蛋白的摩尔比值,而Gd-DTPA-SA的生物素结合活性与反应条件无关。

Preparation of a novel targeted MR contrast agent Gd-DTPA-streptavidin and exploration of its reaction conditions

Objective To explore the optimal reaction condition of D TP A-coupled streptavidin labeled with gadolinium ion. Methods The number streptav idin-coupled of gadolinium ions and maximum biotin-binding capacity of Gd-DTPA-S A complex were analyzed at different DTPA-to-SA molar ratios (1000, 500, 200, 1 00) and in buffer solutions of different pH values (pH 5, 6, 7, and 8, respectiv ely). Results The number of streptavidin-coupled gadolinium ions increased with the pH value of the reaction system. When the DTPA-to-SA molar ratio was below 500, the number of gadolinium ions that SA-DTPA coupled increased with the DTPA -to-SA molar ratio, but tended to decrease when the ratio was 1 000. No signific ant difference in the maximum biotin-binding capacity of Gd-DTPA-SA complex was noted between the groups. Conclusion The number of gadolinium ions that s treptavidin coupled depends on the pH value of the reaction system and DTPA-to-S A molar ratio, but the maximum biotin-binding capacity of Gd-DTPA-SA complex is not affected by the reaction conditions.