Tashtoush B M, Traboulsi A A, Dittert L, Hussain A A
Jordan University of Science and Technology, College of Pharmacy, Irbid, Jordan.
Anal Biochem. 2001 Jan 1;288(1):16-21. doi: 10.1006/abio.2000.4832.
Chloramine-T (CAT) is commonly used in radiolabeling of bioactive molecules by halogenation. CAT is used to release radioactive elemental iodine by oxidation of its salts. Unfortunately, CAT is a strong oxidizing agent and can cause significant damage to peptides and proteins. This may lower the yield of the iodination reaction and may produce undesirable side products. Recently, it was found that the in situ formation of N-chlorosecondary amines, by the addition of secondary amines to CAT prior to exposure to the substrate, can reduce the oxidative damage caused by CAT. To simplify the method, we prepared penta-O-acetyl-N-chloro-N-methylglucamine (NCMGE) as a solid N-chlorosecondary amine. The chemical reactivity of NCMGE toward a model amino acid, 1-aminocyclohexane carboxylic acid, was compared with that of chloramine-T. In the presence of the model amino acid, CAT lost all its chlorine titer within 60 min while NCMGE retained 99% of its chlorine titer. NCMGE was compared to CAT for the iodination of l-tyrosine and leucine enkephalin. For both substrates, the NCMGE method produced larger or equal yields of the monoiodo and diiodo products and less decomposition. It is proposed that the method employing NCMGE to release diatomic iodine is more convenient and efficient for radiolabeling peptides and proteins than currently used methods.
氯胺-T（CAT）常用于通过卤化对生物活性分子进行放射性标记。CAT用于通过氧化其盐来释放放射性元素碘。不幸的是，CAT是一种强氧化剂，会对肽和蛋白质造成显著损害。这可能会降低碘化反应的产率，并可能产生不良副产物。最近发现，在将仲胺添加到CAT中并使其接触底物之前原位形成N-氯代仲胺，可以减少CAT引起的氧化损伤。为了简化该方法，我们制备了五-O-乙酰基-N-氯代-N-甲基葡糖胺（NCMGE）作为固体N-氯代仲胺。将NCMGE对模型氨基酸1-氨基环己烷羧酸的化学反应性与氯胺-T进行了比较。在存在模型氨基酸的情况下，CAT在60分钟内失去了所有氯含量，而NCMGE保留了其99%的氯含量。将NCMGE与CAT用于L-酪氨酸和亮氨酸脑啡肽的碘化反应进行了比较。对于这两种底物，NCMGE方法产生的单碘和二碘产物的产率更高或相等，且分解更少。有人提出，采用NCMGE释放双原子碘的方法比目前使用的方法更方便、高效地用于肽和蛋白质的放射性标记。
