Odgaard L, Bak M, Jakobsen H J, Nielsen N C
Laboratory for Biomolecular NMR Spectroscopy, Department of Molecular and Structural Biology, University of Aarhus, DK-8000 Aarhus C, Denmark.
J Magn Reson. 2001 Feb;148(2):298-308. doi: 10.1006/jmre.2000.2262.
This work explores the utility of simple rotary resonance experiments for the determination of the magnitude and orientation of (13)C chemical shift tensors relative to one or more (13)C--(14)N internuclear axes from (13)C magic-angle-spinning NMR experiments. The experiment relies on simultaneous recoupling of the anisotropic (13)C chemical shift and (13)C--(14)N dipole--dipole coupling interactions using 2D rotary resonance NMR with RF irradiation on the (13)C spins only. The method is demonstrated by experiments and numerical simulations for the (13)C(alpha) spins in powder samples of L-alanine and glycine with (13)C in natural abundance. To investigate the potential of the experiment for determination of relative/absolute tensor orientations and backbone dihedral angles in peptides, the influence from long-range dipolar coupling to sequential (14)N spins in a peptide chain ((14)N(i)--(13)C(alpha)(i)--(14)N(i+1) and (14)N(i+1)--(13)C'(i)--(14)N(i) three-spin systems) as well as residual quadrupolar-dipolar coupling cross-terms is analyzed numerically.
本工作探索了简单旋转共振实验在确定相对于一个或多个来自¹³C魔角旋转核磁共振实验的¹³C–¹⁴N核间轴的¹³C化学位移张量的大小和方向方面的效用。该实验依赖于使用仅对¹³C自旋进行射频照射的二维旋转共振核磁共振，同时重新耦合各向异性¹³C化学位移和¹³C–¹⁴N偶极–偶极耦合相互作用。通过对天然丰度¹³C的L-丙氨酸和甘氨酸粉末样品中¹³C(α)自旋的实验和数值模拟，证明了该方法。为了研究该实验在确定肽中相对/绝对张量方向和主链二面角方面的潜力，对肽链中远程偶极耦合对连续¹⁴N自旋（¹⁴N(i)–¹³C(α)(i)–¹⁴N(i + 1)和¹⁴N(i + 1)–¹³C'(i)–¹⁴N(i)三自旋系统）的影响以及残余四极–偶极耦合交叉项进行了数值分析。
