Kuwata K, Brooks D, Yang H, Schleich T
Sinsheimer Laboratories, Department of Chemistry and Biochemistry, University of California, Santa Cruz 95064.
J Magn Reson B. 1994 May;104(1):11-25. doi: 10.1006/jmrb.1994.1049.
The derivation of a generalized relaxation matrix equation for the off-resonance rotating-frame spin-lattice experiment, representing N macromolecular components, is presented. The applicability of the derived formalism was demonstrated using water proton off-resonance rotating-frame spin-lattice relaxation data obtained for calf lens cortical and nuclear homogenates, a tissue system characterized by the presence of both mobile and solid-like protein domains, whose relative amounts vary in a protein-concentration-dependent manner. Protein concentration and temperature were utilized as variables in the magnetization-transfer experiments. Curve fitting to obtain the relevant magnetization-transfer parameters was accomplished by simulated annealing and the method of steepest descents. In all cases, the best fit, as reflected by the smallest root-mean-square deviation, was obtained by assuming the presence of three components representing bulk-water and mobile and solid-like macromolecular components, characterized by Lorentzian (water and mobile protein) and Gaussian proton resonance lineshapes (solid-like protein). A two-component relaxation model gave unsatisfactory fits. Dilution of nuclear homogenate resulted in physically realistic changes in the derived magnetization-transfer parameters, which included a decrease in the fraction of solid-like protein, in agreement with previously published 13C NMR studies. Changes in magnetization-transfer parameters occurred as a result of the cold cataract phase transition in nuclear homogenate. The utility and limitations of the derived formalism are discussed.
本文推导了用于非共振旋转坐标系自旋晶格实验的广义弛豫矩阵方程，该实验涉及N个大分子成分。通过使用从小牛晶状体皮质和核匀浆获得的水质子非共振旋转坐标系自旋晶格弛豫数据，证明了所推导形式体系的适用性。该组织系统的特征是同时存在移动性和类固体蛋白结构域，其相对含量随蛋白质浓度的变化而变化。在磁化转移实验中，将蛋白质浓度和温度用作变量。通过模拟退火和最速下降法完成曲线拟合以获得相关的磁化转移参数。在所有情况下，通过假设存在代表大量水以及移动性和类固体大分子成分的三个成分，以洛伦兹（水和移动性蛋白质）和高斯质子共振线形（类固体蛋白质）为特征，获得了最小均方根偏差所反映的最佳拟合。双组分弛豫模型的拟合效果不理想。核匀浆的稀释导致所推导的磁化转移参数发生符合物理实际的变化，其中包括类固体蛋白质比例的降低，这与先前发表的13C NMR研究结果一致。核匀浆中的冷白内障相变导致了磁化转移参数的变化。讨论了所推导形式体系的实用性和局限性。
