Quantifying conformational dynamics using solid-state R1ρ experiments
Quantifying conformational dynamics using solid-state R1ρ experiments
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DOI：
10.1016/j.jmr.2012.05.014
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发表时间：
2012-09-01
影响因子：
2.2
通讯作者：
McDermott, Ann E.
中科院分区：
文献类型：
--
作者：
Quinn, Caitlin M.;McDermott, Ann E.
我们证明了定量率的分子在固体状态下的旋转框架（R-1 ρ）弛豫测量的测定。碳化学位移各向异性（CSA）张量的重取向被用来探测模型系统d（6）-二甲基砜（d（6）-DMS）中的位点特异性构象交换。CSA作为交换探针的优点是，当没有偶极机制（即没有质子附着到感兴趣的位点）时，它仍然可以被利用。其他作品提出了R-1 ρ测量作为动力学的一般指标，但本研究提取定量的R-1 ρ值的分子重定向率。这种技术的一些挑战包括精确了解样品温度和确定R-2（0）对观察到的弛豫速率的贡献，所述弛豫速率来自除分子重新取向之外的相互作用，例如残余偶极耦合或快速时标动力学;由于2项之间的协方差，必须确定该项以量化交换速率。低温实验测得的R-2（0）值为1.8 +/- 0.2 s（-1）。考虑到额外的弛豫项（R-2（0）），其被建模为温度依赖性和温度无关性，在四个不同温度下从依赖于场强的R-1 rho测量中提取分子重取向速率，并从这些交换速率确定活化能。对于温度无关和温度相关的R-2（0）模型，所确定的活化能分别为74.7 +/- 4.3 kJ/mol和71.7 +/- 2.9 kJ/mol，与文献值非常吻合。这项研究的结果表明，该方法的应用程序更复杂的系统，如蛋白质，如氘化样品的重要性和需要作出假设的R-2（0）的松弛的贡献的重要方法考虑。(C)2012 Elsevier Inc. All rights reserved.
We demonstrate the determination of quantitative rates of molecular reorientation in the solid state with rotating frame (R-1 rho) relaxation measurements. Reorientation of the carbon chemical shift anisotropy (CSA) tensor was used to probe site-specific conformational exchange in a model system, d(6)-dimethyl sulfone (d(6)-DMS). The CSA as a probe of exchange has the advantage that it can still be utilized when there is no dipolar mechanism (i.e. no protons attached to the site of interest). Other works have presented R-1 rho measurements as a general indicator of dynamics, but this study extracts quantitative rates of molecular reorientation from the R-1 rho values. Some challenges of this technique include precise knowledge of sample temperature and determining the R-2(0) contribution to the observed relaxation rate from interactions other than molecular reorientation, such as residual dipolar couplings or fast timescale dynamics; determination of this term is necessary in order to quantify the exchange rate due to covariance between the 2 terms. Low-temperature experiments measured an R-2(0) value of 1.8 +/- 0.2 s(-1) Allowing for an additional relaxation term (R-2(0)), which was modeled as both temperature-dependent and temperature-independent, rates of molecular reorientation were extracted from field strength-dependent R-1 rho measurements at four different temperatures and the activation energy was determined from these exchange rates. The activation energies determined were 74.7 +/- 4.3 kJ/mol and 71.7 +/- 2.9 kJ/mol for the temperature-independent and temperature-dependent R-2(0) models respectively, in excellent agreement with literature values. The results of this study suggest important methodological considerations for the application of the method to more complicated systems such as proteins, such as the importance of deuterating samples and the need to make assumptions regarding the R-2(0) contribution to relaxation. (C) 2012 Elsevier Inc. All rights reserved.