Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Chemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Hospital for Sick Children, Program in Molecular Medicine, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada.
Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Chemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
J Magn Reson. 2023 Apr;349:107412. doi: 10.1016/j.jmr.2023.107412. Epub 2023 Mar 2.
The measurement of spin relaxation rates provides a unique avenue for quantifying dynamic processes in biomolecules. In order to simplify analysis of the measurements so that a few key intuitive parameters can be extracted, it is often the case that experiments are designed to eliminate interference effects between different classes of spin relaxation. One example emerges in the measurement of amide proton (H) transverse relaxation rates in N labeled proteins, where N inversion pulses are applied during a relaxation element to eliminate cross-correlated spin relaxation between H-N dipole-H CSA interactions. We show that unless these pulses are essentially perfect, significant oscillations in magnetization decay profiles can be obtained, due to the excitation of multiple-quantum coherences, leading potentially to errors in measured R rates. With the recent development of experiments for quantifying electrostatic potentials via amide proton relaxation rates, the need for highly accurate measurement schemes becomes critical. Straightforward modifications to existing pulse sequences are suggested to achieve this goal.
自旋弛豫率的测量为定量研究生物分子中的动态过程提供了一条独特的途径。为了简化测量分析，以便提取少数几个关键的直观参数，通常会设计实验来消除不同类自旋弛豫之间的干扰效应。在 N 标记蛋白质中酰胺质子（H）横向弛豫率的测量中，就出现了一个例子，在弛豫单元期间施加 N 反转脉冲，以消除 H-N 偶极子-H CSA 相互作用之间的交叉相关自旋弛豫。我们表明，除非这些脉冲是完美的，否则由于多量子相干的激发，可能会得到磁化衰减曲线的显著振荡，从而导致测量的 R 率出现误差。随着通过酰胺质子弛豫率定量测量静电势的实验的最新发展，对高精度测量方案的需求变得至关重要。建议对现有脉冲序列进行简单修改以实现这一目标。
