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. 2016 Oct;271:75-82. doi: 10.1016/j.jmr.2016.08.011. Epub 2016 Aug 23.
The paper studies a family of recoupling pulse sequences in magic angle spinning (MAS) solid state NMR, that are characterized by constant phase increments at regular intervals. 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 [Formula: see text] , where ϕ(p)=p(n-1)πn, where n is number of blocks in a rotor period and p=0,1,2,…. The pulse sequence repeats itself every rotor period when n is odd and every two rotor period when n is even. The heteronuclear recoupling pulse sequence consists of a building block [Formula: see text] and [Formula: see text] on channel I and S, where ϕ1(p)=p(2n-3)π2n,ϕ2(p)=p(2n-1)π2n and n is number of blocks in a rotor period. The recoupling pulse sequences mix the z magnetization. Experimental quantification of this method is shown for (13)Cα-(13)CO, homonuclear recoupling in a sample of Glycine and (15)N-(13)Cα, heteronuclear recoupling in Alanine. Application of this method is demonstrated on a sample of tripeptide N-formyl-[U-(13)C,(15)N]- Met-Leu-Phe-OH (MLF).
本文研究了魔角旋转（MAS）固态核磁共振中的一类重新耦合脉冲序列，其特征是在固定间隔处有恒定的相位增量。这些脉冲序列可用于同核和异核重新耦合实验，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模块[公式：见正文]组成，其中ϕ(p)=p(n - 1)π/n，其中n是转子周期中的模块数，p = 0,1,2,…。当n为奇数时，脉冲序列每转子周期重复一次；当n为偶数时，每两个转子周期重复一次。异核重新耦合脉冲序列由通道I和S上的构建模块[公式：见正文]和[公式：见正文]组成，其中ϕ1(p)=p(2n - 3)π/2n，ϕ2(p)=p(2n - 1)π/2n，n是转子周期中的模块数。重新耦合脉冲序列混合z磁化强度。展示了该方法对(13)Cα-(13)CO的实验定量，甘氨酸样品中的同核重新耦合以及丙氨酸中的(15)N-(13)Cα异核重新耦合。该方法在三肽N-甲酰基-[U-(13)C,(15)N]-Met-Leu-Phe-OH（MLF）样品上的应用也得到了证明。
