MAGNETIC RELAXATION DISPERSION

磁弛豫色散

• 批准号: 6329764
• 负责人: Robert George Bryant
• 金额: $ 21.82万
• 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/6329764
• 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.

核自旋晶格弛豫率的磁场依赖性提供了磁弛豫色散分布（MRD）。 MRD 包含可从核磁共振实验中获得的大部分分子动力学信息，并为定义分子内和分子间运动提供了非常强大且高分辨率的工具。 我们构建了一种仪器，通过在高场极化和检测磁体与卫星弛豫磁体之间气动移动样品，规避了 MRD 实验中低灵敏度和分辨率的标准困难。 通过改变弛豫磁铁的磁场，我们可以绘制 MRD 图。 我们已经很大程度上解决了样品遏制、穿梭时间和弛豫率窗口的问题。 我们建议直接使用该光谱仪来映射光谱密度函数来解决分子动力学问题，这些函数是自相关函数的傅立叶变换，表征瞬间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。 我们将测量膜和线性聚电解质（特别是 DNA）的凝结或双层区域中离子的局部平移扩散常数。 我们将测量膜表面其他感兴趣溶质的局部平移扩散常数。 我们将测量与小分子结构涨落相关的谱密度函数，并将其与数十皮秒时间范围内的分子动力学模拟计算出的谱密度函数进行比较。 我们将进一步开发使用选定的自旋对测量蛋白质内部动力学的方法，这些自旋对可以通过各向同性标记方法结合标准光谱编辑序列进行光谱分离。 使用这种方法，我们期望定义蛋白质中重要的铰链运动频率以及其他低频和高频动力学，例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于钙调蛋白和 T4 溶菌酶；然而，这些方法都是通用的。 我们期望理解这些动态将显着影响我们对功能的理解。