Khaneja Navin, Kumar Ashutosh
Department of Electrical Engineering, IIT Bombay, Powai 400076, India.
Department of Biosciences and Bioengineering, IIT Bombay, Powai 400076, India.
J Magn Reson. 2017 Aug;281:162-171. doi: 10.1016/j.jmr.2017.06.004.
The paper describes a family of novel recoupling pulse sequences in magic angle spinning (MAS) solid state NMR, called two pulse recoupling. These pulse sequences can be employed for both homonuclear and heteronuclear recoupling experiments and are robust to dispersion in chemical shifts and rf-inhomogeneity. The homonuclear pulse sequence consists of a building block (π)(π) where ϕ=π4n, and n is number of blocks in a rotor period. The recoupling block is made robust to rf-inhomogeneity by extending it to (π)(π)(π)(π). The heteronuclear recoupling pulse sequence consists of a building block [Formula: see text] and [Formula: see text] on channel I and S, where ϕ=3π8n,ϕ=π8n and n is number of blocks in a rotor period. The recoupling block is made robust to rf-inhomogeneity by extending it to [Formula: see text] and [Formula: see text] on two channels respectively. The recoupling pulse sequences mix the z magnetization. Experimental quantification of this method is shown forC-CO homonuclear recoupling in a sample of Glycine and N-C heteronuclear recoupling in Alanine. Application of this method is demonstrated on a sample of tripeptide N-formyl-[U-C,N]-Met-Leu-Phe-OH (MLF). Compared to R-sequences (Levitt, 2002), these sequences are more robust to rf-inhomogeneity and give better sensitivity, as shown in Fig. 3.
本文描述了一类用于魔角旋转（MAS）固态核磁共振的新型重耦合脉冲序列，称为双脉冲重耦合。这些脉冲序列可用于同核和异核重耦合实验，并且对化学位移分散和射频不均匀性具有鲁棒性。同核脉冲序列由一个构建块(π)(π)组成，其中ϕ = π4n，n是转子周期内的块数。通过将其扩展为(π)(π)(π)(π)，重耦合块对射频不均匀性具有鲁棒性。异核重耦合脉冲序列由通道I和S上的构建块[公式：见正文]和[公式：见正文]组成，其中ϕ = 3π8n，ϕ = π8n，n是转子周期内的块数。通过分别在两个通道上扩展为[公式：见正文]和[公式：见正文]，重耦合块对射频不均匀性具有鲁棒性。重耦合脉冲序列混合z磁化强度。在甘氨酸样品中的C - CO同核重耦合和丙氨酸中的N - C异核重耦合实验中展示了该方法的定量结果。在三肽N - 甲酰基 - [U - C,N] - 蛋氨酸 - 亮氨酸 - 苯丙氨酸 - OH（MLF）样品上展示了该方法的应用。如图3所示，与R序列（Levitt，2002）相比，这些序列对射频不均匀性更具鲁棒性且灵敏度更高。
