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Measuring transverse relaxation in highly paramagnetic systems.
Journal of Biomolecular NMR ( IF 2.7 ) Pub Date : 2020-07-24 , DOI: 10.1007/s10858-020-00334-w
Michele Invernici 1, 2 , Inês B Trindade 3 , Francesca Cantini 1, 2 , Ricardo O Louro 3 , Mario Piccioli 1, 2
Affiliation  

The enhancement of nuclear relaxation rates due to the interaction with a paramagnetic center (known as Paramagnetic Relaxation Enhancement) is a powerful source of structural and dynamics information, widely used in structural biology. However, many signals affected by the hyperfine interaction relax faster than the evolution periods of common NMR experiments and therefore they are broadened beyond detection. This gives rise to a so-called blind sphere around the paramagnetic center, which is a major limitation in the use of PREs. Reducing the blind sphere is extremely important in paramagnetic metalloproteins. The identification, characterization, and proper structural restraining of the first coordination sphere of the metal ion(s) and its immediate neighboring regions is key to understand their biological function. The novel HSQC scheme we propose here, that we termed R2-weighted, HSQC-AP, achieves this aim by detecting signals that escaped detection in a conventional HSQC experiment and provides fully reliable R2 values in the range of 1H R2 rates ca. 50–400 s−1. Independently on the type of paramagnetic center and on the size of the molecule, this experiment decreases the radius of the blind sphere and increases the number of detectable PREs. Here, we report the validation of this approach for the case of PioC, a small protein containing a high potential 4Fe-4S cluster in the reduced [Fe4S4]2+ form. The blind sphere was contracted to a minimal extent, enabling the measurement of R2 rates for the cluster coordinating residues.



中文翻译:

测量高顺磁系统中的横向弛豫。

由于与顺磁中心相互作用而导致的核弛豫率增强(称为顺磁弛豫增强)是结构和动力学信息的强大来源,广泛应用于结构生物学。然而,许多受超精细相互作用影响的信号弛豫速度比普通核磁共振实验的演化周期更快,因此它们的范围扩大到无法检测。这会在顺磁中心周围产生所谓的盲球,这是 PRE 使用的主要限制。减少盲球对于顺磁性金属蛋白极其重要。金属离子第一配位层及其紧邻区域的识别、表征和适当的结构限制是了解其生物学功能的关键。我们在这里提出的新颖的 HSQC 方案,我们称之为R 2加权 HSQC-AP,通过检测在传统 HSQC 实验中逃脱检测的信号来实现这一目标,并在1 H R 2速率范围内提供完全可靠的R 2值约 50–400秒-1。与顺磁中心的类型和分子的大小无关,该实验减小了盲球的半径并增加了可检测的 PRE 的数量。在这里,我们报告了这种方法在 PioC 情况下的验证,PioC 是一种小蛋白质,含有还原的 [Fe 4 S 4 ] 2+形式的高潜力 4Fe-4S 簇。盲球收缩到最小程度,从而能够测量簇配位残基的R 2速率。

更新日期:2020-07-25
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