Mou Yun, Tsai Tim W T, Chan Jerry C C
Department of Chemistry, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei, Taiwan.
Solid State Nucl Magn Reson. 2007 Apr;31(2):72-81. doi: 10.1016/j.ssnmr.2007.01.003. Epub 2007 Jan 26.
We demonstrate that the backbone torsion psi angle of a uniformly labeled residue can be determined accurately by correlating the chemical shift anisotropy of the carbonyl carbon and the 13C-1H heteronuclear dipole-dipole interaction of the alpha carbon. To obtain the highest sensitivity for the psi angle determination, the following conditions are desired: (i) the recoupling pulse sequences for the CSA and the heteronuclear dipolar interactions are gamma encoded, in which the spatial parts of m=2 are selected; (ii) the homonuclear polarization transfer is based on the scalar spin-spin coupling. Experimental data were obtained for [U-13C, 15N]-alanine and N-acetyl-[U-13C, 15N]-d,l-valine under magic-angle spinning at 25kHz. Only three data points are required for the measurements and the dihedral angles determined are in excellent agreement with the diffraction data.
我们证明，通过关联羰基碳的化学位移各向异性和α碳的13C-1H异核偶极-偶极相互作用，可以准确测定均匀标记残基的主链扭转ψ角。为了获得用于ψ角测定的最高灵敏度，需要满足以下条件：（i）用于CSA和异核偶极相互作用的再耦合脉冲序列采用γ编码，其中选择m = 2的空间部分；（ii）同核极化转移基于标量自旋-自旋耦合。在25kHz魔角旋转条件下，获得了[U-13C, 15N]-丙氨酸和N-乙酰-[U-13C, 15N]-d,l-缬氨酸的实验数据。测量仅需三个数据点，所确定的二面角与衍射数据高度吻合。
