Physics Department & Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai 200062, China.
J Magn Reson. 2012 Oct;223:107-19. doi: 10.1016/j.jmr.2012.07.013. Epub 2012 Jul 27.
We demonstrate that inter-residue (13)C-(13)C proximities (of about 380 pm) in uniformly (13)C-labeled proteins can be probed by applying robust first-order recoupling during several milliseconds in single-quantum single-quantum dipolar homo-nuclear correlation (SQ-SQ D-HOMCOR) 2D experiments. We show that the intensity of medium-range homo-nuclear correlations in these experiments is enhanced using broadband first-order finite-pulse radio-frequency-driven recoupling (fp-RFDR) NMR sequence with a nested (XY8)4(1) super-cycling. The robustness and the efficiency of the fp-RFDR-(XY8)4(1) method is demonstrated at high magnetic field (21.1T) and high Magic-Angle Spinning (MAS) speeds (up to 60 kHz). The introduced super-cycling, formed by combining phase inversion and a global four-quantum phase cycle, improves the robustness of fp-RFDR to (i) chemical shift anisotropy (CSA), (ii) spread in isotropic chemical shifts, (iii) rf-inhomogeneity and (iv) hetero-nuclear dipolar couplings for long recoupling times. We show that fp-RFDR-(XY8)4(1) is efficient sans (1)H decoupling, which is beneficial for temperature-sensitive biomolecules. The efficiency and the robustness of fp-RFDR-(XY8)4(1) is investigated by spin dynamics numerical simulations as well as solid-state NMR experiments on [U-(13)C]-L-histidine·HCl, a tetra-peptide (Fmoc-[U-(13)C,(15)N]-Val-[U-(13)C,(15)N]-Ala-[U-(13)C,(15)N]-Phe-Gly-t-Boc) and Al(PO(3))(3).
我们证明，在均匀（13）C 标记的蛋白质中，通过在单量子单量子偶极同核相关（SQ-SQ D-HOMCOR）2D 实验中应用稳健的一阶重聚，可探测残基间（13）C-（13）C 近邻（约 380 pm）。我们表明，在这些实验中，使用宽带一阶有限脉冲射频驱动重聚（fp-RFDR）NMR 序列（具有嵌套（XY8）4（1）超循环），可以增强中程同核相关的强度。在高磁场（21.1T）和高魔角旋转（MAS）速度（高达 60 kHz）下，证明了 fp-RFDR-（XY8）4（1）方法的稳健性和效率。所引入的超循环通过组合相反转和全局四量子相位循环形成，提高了 fp-RFDR 对（i）化学位移各向异性（CSA）、（ii）各向同性化学位移的分散、（iii）射频不均匀性和（iv）长重聚时间的异核偶极耦合的稳健性。我们表明，fp-RFDR-（XY8）4（1）在没有（1）H 去耦的情况下是有效的，这对温度敏感的生物分子有益。通过自旋动力学数值模拟以及[U-（13）C]-L-组氨酸·HCl、四肽（Fmoc-[U-（13）C，（15）N]-Val-[U-（13）C，（15）N]-Ala-[U-（13）C，（15）N]-Phe-Gly-t-Boc）和 Al（PO（3））（3）的固态 NMR 实验，研究了 fp-RFDR-（XY8）4（1）的效率和稳健性。
