Ernst Matthias, Samoson Ago, Meier Beat H
Physical Chemistry, ETH-Zürich, CH-8093 Zürich, Switzerland.
J Magn Reson. 2003 Aug;163(2):332-9. doi: 10.1016/s1090-7807(03)00155-1.
Low-power XiX proton decoupling under fast magic-angle spinning is introduced. The method is applicable if the MAS frequency exceeds the proton-proton interactions. For rigid organic solids this is the case for MAS frequencies above approximately 40 kHz. It is shown that the quality of the decoupling as well as the sensitivity to frequency offsets can be improved compared to low-power continuous-wave decoupling. The decoupling efficiency is somewhat reduced compared to optimized high-power decoupling: in a peptide sample investigated at an MAS frequency of 50 kHz a loss of about 10% in signal intensity for CH3 and CH groups, and of about 40% for CH2 groups was observed. Taking into consideration, that the rf amplitude in the low-power XiX was about 15 times lower than in high-power XiX decoupling, such a reduction in line intensity is sometimes tolerable.
介绍了在快速魔角旋转下的低功率XiX质子去耦。如果魔角旋转频率超过质子-质子相互作用，该方法适用。对于刚性有机固体，当魔角旋转频率高于约40 kHz时就是这种情况。结果表明，与低功率连续波去耦相比，去耦质量以及对频率偏移的灵敏度都可以得到提高。与优化的高功率去耦相比，去耦效率有所降低：在一个以50 kHz的魔角旋转频率研究的肽样品中，观察到CH3和CH基团的信号强度损失约10%，CH2基团的信号强度损失约40%。考虑到低功率XiX中的射频幅度比高功率XiX去耦中的低约15倍，这种线强度的降低有时是可以接受的。
