Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne, EPFL, Batochime, 1015 Lausanne, Switzerland.
Chemphyschem. 2011 Oct 24;12(15):2729-34. doi: 10.1002/cphc.201100365. Epub 2011 Aug 31.
The relaxation of long-lived states (LLS) corresponds to the slow return to statistical thermal equilibrium between symmetric and antisymmetric proton spin states. This process is remarkably sensitive to the presence of external spins and can be used to obtain information about partial unfolding of proteins. We detected the appearance of a destabilized conformer of ubiquitin when urea is added to the protein in its native state. This conformer shows increased mobility in the C-terminus, which significantly extends the lifetimes of proton LLS magnetisation in Ser-65. These changes could not be detected by conventional measurements of T(1) and T(2) relaxation times of protons, and would hardly be sensed by carbon-13 or nitrogen-15 relaxation measurements. Conformers with similar dynamic and structural features, as revealed by LLS relaxation times, could be observed, in the absence of urea, in two ubiquitin mutants, L67S and L69S.
长寿命状态（LLS）的弛豫对应于对称和反对称质子自旋态之间缓慢返回统计热平衡的过程。这个过程对外部自旋的存在非常敏感，可以用来获取关于蛋白质部分展开的信息。当脲素被添加到天然状态的蛋白质中时，我们检测到泛素的不稳定构象体的出现。这种构象体在 C 末端表现出更高的迁移率，这显著延长了 Ser-65 质子 LLS 磁化的寿命。这些变化不能通过质子 T(1)和 T(2)弛豫时间的常规测量来检测，而且用碳-13 或氮-15 弛豫测量也很难感知到。在没有脲素的情况下，通过 LLS 弛豫时间可以观察到具有类似动态和结构特征的构象体，在两种泛素突变体 L67S 和 L69S 中可以观察到。
