AMINO ACID LABELING FOR LARGER PROTEINS METHYL GROUP LABELING

正如我们在最初的提案中所讨论的那样， 是对较大蛋白质进行核磁共振结构研究的关键。 有 质子的化学位移范围有相当大的重叠 氨基酸中甲基的共振， 甲基质子很难。 此外，只有脆弱的分配， 可以制备缬氨酸和亮氨酸残基中的前手性甲基， 没有同位素歧视。 虽然差异“C-标记的 缬氨酸前手性甲基可用于指定 为了达到这个目的，碳维度上的化学位移分散使得 希望用13 C标记缬氨酸和/或亮氨酸中的甲基。 因此，我们的计划是用13 C标记所有的甲基基团， ，并通过引入 差异氘标记。 我们已经制定了一个计划， 手性甲基标记缬氨酸的合成。 差异 氘代碘甲烷已经以克的数量生产。 的 缬氨酸的异丙基侧链立体选择性地使用 Oppolzer sultam手性助剂。 我们现在正处于 制备标记的缬氨酸并将其掺入Trp 抑制剂很快。 此外，还取得了重大进展 这条路由将允许差分 咪唑氮的标记和手性诱导 α-氨基。

As discussed in our original proposal methyl groups in proteins are pivotal for NMR structural studies on larger proteins. There is considerable overlap in the chemical shift range of the proton resonances of methyl groups in amino acids making resolution of the methyl protons difficult. In addition, only tenuous assignments of the prochiral methyls in valine and leucine residues can be made without isotopic discrimination. While differential "C-labeling of the prochiral methyls of valine has been useful for assignment purposes, the chemical shift dispersion in the carbon dimension makes it desirable to label both methyls in valine and/or leucine with 13C . Therefore, we our plan was to label all of the methyl groups with 13C , and distinguish the prochiral methyl groups by introducing differential deuterium labels. We have developed the a scheme for the synthesis of the chiral methyl labeling in valine. Differentially deuterated methyl iodides have been produced in gram quantities. The isopropyl side chain of valine is produced stereoselectively using the Oppolzer sultam chiral auxiliary. We are now in the final stages of preparing the labeled valine and will incorporate it into the Trp repressor soon. In addition, significant progress has been made toward a new route to labeled This route will allow differential labeling of the imidazole nitrogens and chiral induction of the a-amino group.