Fruh Dominique, Chiarparin Elisabetta, Pelupessy Philippe, Bodenhausen Geoffrey
Institut de Chimie Moléculaire et Biologique, Ecole Polytechnique Fédérale de Lausanne, BCH, 1015 Lausanne, Switzerland.
J Am Chem Soc. 2002 Apr 17;124(15):4050-7. doi: 10.1021/ja011790v.
A method is described to determine long-range cross-correlations between the modulations of an anisotropic chemical shift (e.g., of a C' carbonyl carbon in a protein) and the fluctuations of a weak long-range dipolar interaction (e.g., in cross-correlation between the same C' carbonyl and the H(N) proton of the neighboring amide group). Such long-range correlations are difficult to measure because the corresponding long-range scalar couplings are so small that Redfield's secular approximation is often violated. The method, which combines features of single- and double-quantum NMR spectroscopy, allows one to cancel the effects of dominant short-range dipolar interactions (e.g., between the CSA of the amide nitrogen N and the dipolar coupling to its attached proton H(N)) and is designed so that the secular approximation is rescued even if the scalar coupling between the long-range dipolar coupling partners is very small. The cross-correlation rates thus determined in ubiquitin cover a wide range because of local motions and variations of the CSA tensors.
本文描述了一种方法，用于确定各向异性化学位移的调制（例如蛋白质中C'羰基碳的化学位移）与弱远程偶极相互作用的波动（例如同一C'羰基与相邻酰胺基团的H(N)质子之间的交叉相关性）之间的长程交叉相关性。由于相应的长程标量耦合非常小，以至于常常违反Redfield的久期近似，因此这种长程相关性很难测量。该方法结合了单量子和双量子核磁共振光谱的特点，能够消除主要的短程偶极相互作用的影响（例如酰胺氮N的化学位移各向异性与与其相连质子H(N)的偶极耦合之间的相互作用），并且设计成即使远程偶极耦合伙伴之间的标量耦合非常小，也能挽救久期近似。由于泛素中局部运动和化学位移各向异性张量的变化，由此确定的交叉相关率覆盖了很宽的范围。
