Giraud Nicolas, Blackledge Martin, Goldman Maurice, Böckmann Anja, Lesage Anne, Penin François, Emsley Lyndon
Laboratoire de Chimie (UMR 5182 CNRS/ENS Lyon), Laboratoire de Recherche Conventionné du CEA (DSV 23V/DSM 0432), Ecole Normale Supérieure de Lyon, Lyon, France.
J Am Chem Soc. 2005 Dec 28;127(51):18190-201. doi: 10.1021/ja055182h.
A detailed analysis of nitrogen-15 longitudinal relaxation times in microcrystalline proteins is presented. A theoretical model to quantitatively interpret relaxation times is developed in terms of motional amplitude and characteristic time scale. Different averaging schemes are examined in order to propose an analysis of relaxation curves that takes into account the specificity of MAS experiments. In particular, it is shown that magic angle spinning averages the relaxation rate experienced by a single spin over one rotor period, resulting in individual relaxation curves that are dependent on the orientation of their corresponding carousel with respect to the rotor axis. Powder averaging thus leads to a nonexponential behavior in the observed decay curves. We extract dynamic information from experimental decay curves, using a diffusion in a cone model. We apply this study to the analysis of spin-lattice relaxation rates of the microcrystalline protein Crh at two different fields and determine differential dynamic parameters for several residues in the protein.
本文对微晶蛋白质中氮-15的纵向弛豫时间进行了详细分析。基于运动幅度和特征时间尺度，建立了一个定量解释弛豫时间的理论模型。研究了不同的平均方案，以提出一种考虑到魔角旋转（MAS）实验特殊性的弛豫曲线分析方法。特别地，研究表明魔角旋转在一个转子周期内对单个自旋所经历的弛豫率进行平均，导致单个弛豫曲线依赖于其相应样品盘相对于转子轴的取向。因此，粉末平均导致观察到的衰减曲线呈现非指数行为。我们使用圆锥模型中的扩散从实验衰减曲线中提取动态信息。我们将这项研究应用于分析微晶蛋白质Crh在两个不同场强下的自旋晶格弛豫率，并确定该蛋白质中几个残基的微分动力学参数。
