Ravindranathan Sapna, Mallet Jean-Maurice, Sinay Pierre, Bodenhausen Geoffrey
Institut de Chimie Moléculaire et Biologique, Ecole Polytechnique Fédérale de Lausanne, BCH, 1015 Lausanne, Switzerland.
J Magn Reson. 2003 Aug;163(2):199-207. doi: 10.1016/s1090-7807(03)00156-3.
Exchange transferred effects in solution-state NMR experiments allow one to determine the conformation of ligands that are weakly bound to macromolecules. Exchange-transferred nuclear Overhauser effect spectroscopy ('TR-NOESY') provides information about internuclear distances in a ligand in the bound state. Recently the possibility of obtaining dihedral angle information from a ligand in the bound state by exchange-transferred cross-correlation spectroscopy ('TR-CCSY') has been reported. In both cases the analysis of the signal amplitudes is usually based on the assumption that rapid exchange occurs between the free and bound forms of the ligand. In this paper we show that the fast exchange condition is not easily attained for observing exchange-transferred cross-correlation effects even in systems where exchange-transferred NOE can be observed. Extensive simulations based on analytical expressions for signal intensities corresponding to fast, intermediate, and slow chemical exchange have been carried out on a test system to determine the exchange regimes in which the fast exchange condition can be fulfilled for successfully implementing TR-NOESY and TR-CCSY.
溶液态核磁共振实验中的交换转移效应能让人确定与大分子弱结合的配体的构象。交换转移核Overhauser效应光谱法（“TR - NOESY”）提供了关于处于结合态的配体中核间距离的信息。最近，有报道称可通过交换转移交叉相关光谱法（“TR - CCSY”）从处于结合态的配体中获取二面角信息。在这两种情况下，信号幅度的分析通常基于配体的游离态和结合态之间发生快速交换这一假设。在本文中我们表明，即使在能够观察到交换转移NOE的系统中，对于观察交换转移交叉相关效应而言，快速交换条件也不易实现。我们在一个测试系统上基于对应快速、中间和慢速化学交换的信号强度解析表达式进行了大量模拟，以确定在哪些交换机制下能够满足快速交换条件从而成功实施TR - NOESY和TR - CCSY。
