Rovnyak David, Kennedy Paul E
Bucknell University, Department of Chemistry, Moore Avenue, Lewisburg, PA 17837, USA.
J Magn Reson. 2009 Feb;196(2):191-9. doi: 10.1016/j.jmr.2008.11.005. Epub 2008 Nov 18.
Competition between nutation (r.f. driven) and adiabatic (rotor-driven) multi-quantum coherence transfer mechanisms in spin 3/2 systems results in diminished performance of rotation induced adiabatic coherence transfer (RIACT) in isotropic multiple-quantum magic-angle spinning (MQMAS) experiments for small e(2)qQ/h (<2 MHz) and high radio-frequency powers. We present a simple shaped RIACT pulse consisting of a truncated sine wave (spanning 0-0.8pi) that corrects the sensitivity losses, phase twist and relative intensity errors that can arise in MQMAS spectra utilizing constant-amplitude RIACT pulses. The shaped RIACT pulse may enhance the study of metals in biomolecules where quadrupole couplings of S=3/2 nuclei such as (23)Na tend to be small.
在自旋3/2系统中，章动（射频驱动）和绝热（转子驱动）多量子相干转移机制之间的竞争导致在小e(2)qQ/h（<2 MHz）和高射频功率的各向同性多量子魔角旋转（MQMAS）实验中，旋转诱导绝热相干转移（RIACT）的性能下降。我们提出了一种简单的成形RIACT脉冲，它由一个截断的正弦波（跨越0 - 0.8π）组成，可校正利用恒定幅度RIACT脉冲的MQMAS谱中可能出现的灵敏度损失、相位扭曲和相对强度误差。这种成形RIACT脉冲可能会增强对生物分子中金属的研究，其中诸如(23)Na等S = 3/2核的四极耦合往往较小。
