MAGNETIC RELAXATION DISPERSION

磁弛豫色散

• 批准号: 6476558
• 负责人: Robert George Bryant
• 金额: $ 22.45万
• 依托单位: UNIVERSITY OF VIRGINIA
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-06-01 至 2003-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6476558
• 关键词: DNA; biomedical equipment development; calmodulin; diffusion; electrolytes; lysozyme; magnetic field; membrane activity; molecular dynamics; nuclear magnetic resonance spectroscopy; polymers; protein structure function; relaxation spectrometry; surface property; time resolved data

The magnetic field dependence of the nuclear spin-lattice relaxation rate provides the Magnetic Relaxation Dispersion profile (MRD). The MRD contains most of the molecular dynamical information that is available from a nuclear magnetic resonance experiment, and offers a very powerful as well as high resolution tool for defining both intra and intermolecular motions. We have constructed an instrument that circumvents the standard difficulties of low sensitivity and resolution in MRD experiments by pneumatically moving a sample between a high field polarization and detection magnet and a satellite relaxation magnet. By varying the field in the relaxation magnet, we may map the MRD. We have largely solved the problems of sample containment, shuttle time, and relaxation rate windows. We propose to address molecular dynamics directly using this spectrometer to map spectral density functions, which are Fourier transforms of autocorrelation functions that characterize the time fluctuations of intermoment distances and orientations. The time scale that may be investigated ranges from tenths of milliseconds to tenths of picoseconds. We will measure localized translational diffusion constants for ions in condensation or double layer regions of membranes and linear polyelectrolytes, DNA in particular. We will measure localized translational diffusion constants for other solutes of interest at membrane surfaces. We will measure spectral density functions associated with small-molecule structural fluctuations and compare them with spectral density functions computed from molecular dynamics simulations in the time range of tens of ps. We will develop further the methods to measure internal dynamics in proteins using selected spin pairs that may be spectrally isolated by isotropic labeling methods combined with standard spectral editing sequences. Using this approach we expect to define important hinge motion frequencies in proteins as well as other low and high frequency dynamics such as crucial active site motions of amino acid side chains. Initial protein experiments will be focused on calmodulin and T4 lysozyme; however, the approaches are general. We expect that understanding these dynamics will impact our understanding of function significantly.

核自旋-晶格弛豫速率的磁场依赖性提供了磁弛豫色散曲线（MRD）。 MRD包含了大部分的分子动力学信息，可从核磁共振实验，并提供了一个非常强大的，以及高分辨率的工具，用于定义内和分子间的运动。 我们已经构建了一个仪器，通过在高场极化和检测磁体与卫星弛豫磁体之间快速移动样品，规避了MRD实验中的低灵敏度和分辨率的标准困难。 通过改变弛豫磁体中的磁场，我们可以绘制MRD。 我们已经在很大程度上解决了样品容纳，穿梭时间和弛豫速率窗口的问题。 我们建议解决分子动力学直接使用该光谱仪映射谱密度函数，这是傅立叶变换的自相关函数，其特征的时刻间的距离和方向的时间波动。 可以研究的时间尺度范围从十分之一毫秒到十分之一皮秒。 我们将测量在膜和线性聚电解质，特别是DNA的凝聚或双层区域的离子的局部平移扩散常数。 我们将测量其他感兴趣的溶质在膜表面的局部平移扩散常数。 我们将测量与小分子结构波动相关的谱密度函数，并将其与数十ps时间范围内分子动力学模拟计算的谱密度函数进行比较。 我们将进一步开发的方法来测量内部动态的蛋白质使用选定的自旋对，可以通过各向同性标记方法结合标准的光谱编辑序列光谱隔离。 使用这种方法，我们希望定义重要的铰链运动频率的蛋白质以及其他低和高频率的动态，如氨基酸侧链的关键活性位点运动。 最初的蛋白质实验将集中在钙调素和T4溶菌酶;然而，这些方法是通用的。 我们期望理解这些动态将显著影响我们对功能的理解。