Among the tools of structural biology, NMR spectroscopy is unique in that it not only derives a static three-dimensional structure, but also provides an atomic-level description of the local fluctuations and global dynamics around this static structure. A battery of NMR experiments is now available to probe the motions of proteins and nucleic acids over the whole biologically relevant timescale from picoseconds to hours. Here we focus on one of these methods, relaxation dispersion, which resolves dynamics on the micro- to millisecond timescale. Key biological processes that occur on this timescale include enzymatic catalysis, ligand binding, and local folding. In other words, relaxation-dispersion-resolved dynamics are often closely related to the function of the molecule and therefore highly interesting to the structural biochemist. With an astounding sensitivity of ∼0.5%, the method detects low-population excited states that are invisible to any other biophysical method. The kinetics of the exchange between the ground state and excited states are quantified in the form of the underlying exchange rate, while structural information about the invisible excited state is obtained in the form of its chemical shift. Lastly, the population of the excited state can be derived. This diversity in the information that can be obtained makes relaxation dispersion an excellent method to study the detailed mechanisms of conformational transitions and molecular interactions. Here we describe the two branches of relaxation dispersion, R2 and R1ρ, discussing their applicability, similarities, and differences, as well as recent developments in pulse sequence design and data processing.

中文翻译：

---

通过 R 2 和 R 1ρ 弛豫色散 NMR 解析生物分子运动和相互作用

在结构生物学的工具中，核磁共振光谱的独特之处在于它不仅可以推导出静态的三维结构，而且还提供了围绕该静态结构的局部波动和全局动力学的原子级描述。一系列 NMR 实验现在可用于对蛋白质和核酸在从皮秒到数小时的整个生物学相关时间尺度内的运动进行采样。在这里，我们专注于这些方法之一，弛豫分散，它解决了微到毫秒时间尺度上的动力学问题。在这个时间尺度上发生的关键生物过程包括酶催化、配体结合和局部折叠。换句话说，弛豫-弥散-分辨动力学通常与分子的功能密切相关，因此对结构生物化学家来说非常有趣。该方法具有约 0.5% 的惊人灵敏度，可检测到任何其他生物物理方法都看不到的低种群激发态。基态和激发态之间的交换动力学以潜在交换率的形式量化，而关于不可见激发态的结构信息以其化学位移的形式获得。最后，可以推导出激发态的布居数。这种可以获得的信息的多样性使得弛豫分散成为研究构象转变和分子相互作用的详细机制的极好方法。在这里，我们描述弛豫色散的两个分支 R2 和 R1ρ，讨论它们的适用性、相似性和差异性，以及脉冲序列设计和数据处理的最新进展。