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首页> 外文期刊>Journal of magnetic resonance >Amide proton relaxation measurements employing a highly deuterated protein
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Amide proton relaxation measurements employing a highly deuterated protein

机译：使用高度氘化的蛋白质进行酰胺质子弛豫测量

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摘要

Proton NMR longitudinal and transverse relaxation rates of unlabelled proteins are generally dominated by the many ~1H-~1H dipolar interactions so that spin diffusion, rather than molecular or internal motions, governs longitudinal relaxation. Here, relaxation measurements of backbone amide proton (~1HN) magnetisations have been carried out employing the 99% ~2H, 98% ~(15)N labelled, small ~2F2 protein domain in 10%/90% H_2O/D_2O solution. Under these conditions, the longitudinal relaxation rates exhibit time constants, T_1~* = 1/R_1~* if described by a mono-exponential, within the range of 3.0 to 18.7 s-a wide range which indicates that the phenomenon of spin diffusion has been greatly reduced. The majority of ~1H~N nuclei in this sample (pH 4.0 and 5 ℃) exhibit chemical exchange with solvent that couples their longitudinal relaxation to that of the solvent. For the subset of ~1H~N nuclei not undergoing detectable solvent chemical exchange, the R_1~* rates correlate well with their individual ~1H~(N,O)/~2H~(N,O) structural environments. The correlation for corresponding transverse relaxation rates, R_2~* was found to be less good. Longitudinal relaxation measurements in 1%/99% H_2O/D_2O solution identify a further subset of ~1H~N nuclei which exhibit essentially indistinguishable R_1~* rates in both 1% and 10% H_2O, implying that averaging of rates from spin diffusion processes and different ~2F2 isotopomer populations are negligible for these ~1H~N sites. In addition to a high sensitivity to structural parameters, model calculations predict ~1H~N relaxation rates to exhibit pronounced sensitivity to internal dynamics.
机译：未标记蛋白的质子NMR纵向和横向弛豫速率通常受许多〜1H-〜1H偶极相互作用的支配，因此自旋扩散而不是分子或内部运动决定了纵向弛豫。在这里，已经在10％/ 90％H_2O / D_2O溶液中使用99％〜2H，98％〜（15）N标记的小〜2F2蛋白结构域进行了骨架酰胺质子（〜1HN）磁化强度的弛豫测量。在这些条件下，纵向弛豫速率表现出时间常数，T_1〜* = 1 / R_1〜*，如果用单指数表示，则在3.0至18.7 sa的宽范围内，这表明自旋扩散现象已经很大减少。该样品中大多数〜1H〜N核（pH 4.0和5℃）表现出与溶剂的化学交换，这使它们的纵向弛豫与溶剂的纵向弛豫耦合。对于〜1H〜N核子集未经历可检测的溶剂化学交换，R_1〜*速率与其各自的〜1H〜（N，O）/〜2H〜（N，O）结构环境密切相关。发现相应的横向弛豫速率R_2〜*的相关性较差。在1％/ 99％H_2O / D_2O溶液中的纵向弛豫测量结果确定了〜1H〜N原子核的另一子集，在1％和10％H_2O中均表现出基本不可区分的R_1〜*率，这意味着自旋扩散过程和对于这些〜1H〜N位点，不同的〜2F2同位异构体群体可以忽略不计。除了对结构参数具有很高的敏感性外，模型计算还可以预测〜1H〜N的弛豫速率，从而对内部动力学表现出明显的敏感性。

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