Kupce Eriks, Freeman Ray
Varian Ltd., 6 Mead Road, Yarnton, Oxford, UK.
J Magn Reson. 2007 Aug;187(2):258-65. doi: 10.1016/j.jmr.2007.05.009. Epub 2007 May 17.
When adiabatic fast passage is used to flip nuclear spins, sites with different chemical shifts are inverted at different times, causing refocusing errors. By mapping the phase evolution diagrams, we show that these effects can be accurately compensated with matched pairs of adiabatic pulses, either opposed or in the same sense, depending on the application. Applied to well-known heteronuclear polarization transfer experiments such as INEPT and HSQC, the requisite evolution of J-vectors is achieved irrespective of chemical shift or the duration of the adiabatic sweeps. By replacing conventional 180 degrees pulses, these new adiabatic sequences offer an order of magnitude improvement in effective bandwidth for the X-spins. Alternatively the experiments can be carried out with significantly reduced radiofrequency power. One- and two-dimensional spectra of (13)C in 13-cis-retinal at 600MHz have been used to demonstrate these advantages.
当使用绝热快速通道翻转核自旋时，具有不同化学位移的位点会在不同时间发生反转，从而导致重聚焦误差。通过绘制相位演化图，我们表明，根据应用情况，这些效应可以用一对匹配的绝热脉冲精确补偿，这对脉冲可以是反向的，也可以是同向的。应用于诸如INEPT和HSQC等著名的异核极化转移实验时，无论化学位移或绝热扫描的持续时间如何，都能实现J矢量的必要演化。通过取代传统的180度脉冲，这些新的绝热序列使X自旋的有效带宽提高了一个数量级。或者，实验可以在显著降低射频功率的情况下进行。已使用600MHz下13 - 顺式视黄醛中(13)C的一维和二维光谱来证明这些优点。
