论文标题
使用Presto或偶极介导的重新聚焦方法，从质子从质子转移到固态NMR中的四极核转移
Magnetization transfer from protons to quadrupolar nuclei in solid-state NMR using PRESTO or dipolar-mediated refocused INEPT methods
论文作者
论文摘要
We compare here the performances of two approaches to achieve such transfer: PRESTO (Phase-shifted Recoupling Effects a Smooth Transfer of Order), which is currently the method of choice to achieve the magnetization transfer from protons to quadrupolar nuclei and which has been shown to supersede Cross-Polarization under Magic-Angle Spinning (MAS) for quadrupolar nuclei and D-RINEPT (Dipolar-mediated Refocused Insensitive Nuclei Enhanced by极化转移）使用基于对称的SR4 $ {} _ 1 {}^2 $重新耦合，已经采用了以相反的方式将磁化物从半级数四极性旋转转移到质子。我们还使用R16 $ {} _ 7 {}^6 $使用270 $ {} _ 0 $ 90 $ {} _ 180 $复合$π$ -pulses作为反转元素来测试Presto序列。这种重耦方案尚未用于重新引入与质子的偶性耦合。使用（i）使用（i）平均哈密顿理论，（ii）旋转动力学的数值模拟，以及（iii）实验$ {}^1 $ h $ \ rightarrow {}^{27} $ al and} $ {1} $ {1} $ {1} $ {1} $ {1} $ {1} $ {1} $ {1} $ {1分别以ASSYNTHESIDAL ALPO4-14和$ {}^{17} $ O-o-o-labelled Fumed Silica进行转移。实验和模拟是在两个磁场（9.4和18.8 T）和几个旋转速度（15、18-24和60 kHz）上进行的。 This analysis indicates that owing to its $γ$-encoded character, PRESTO yields the highest transfer efficiency at low magnetic fields and MAS frequencies, whereas owing to its higher robustness to rf-field inhomogeneity and chemical shifts, D-RINEPT is more sensitive at high fields and MAS frequencies, notably for protons exhibiting large offset or CSA, such as those involved in hydrogen bonds.
We compare here the performances of two approaches to achieve such transfer: PRESTO (Phase-shifted Recoupling Effects a Smooth Transfer of Order), which is currently the method of choice to achieve the magnetization transfer from protons to quadrupolar nuclei and which has been shown to supersede Cross-Polarization under Magic-Angle Spinning (MAS) for quadrupolar nuclei and D-RINEPT (Dipolar-mediated Refocused Insensitive Nuclei Enhanced by Polarization Transfer) using symmetry-based SR4${}_1{}^2$ recoupling, which has already been employed to transfer the magnetization in the reverse way from half-integer quadrupolar spin to protons. We also test the PRESTO sequence with R16${}_7{}^6$ recoupling using 270${}_0$90${}_180$ composite $π$-pulses as inversion elements. This recoupling scheme has not so far been employed to reintroduce dipolar couplings with protons. These various techniques to transfer the magnetization from protons to quadrupolar nuclei are analyzed using (i) an average Hamiltonian theory, (ii) numerical simulations of spin dynamics, and (iii) experimental ${}^1$H $\rightarrow {}^{27}$Al and ${}^{1}$H $\rightarrow {}^{17}$O transfers in as-synthesized AlPO4-14 and ${}^{17}$O-labelled fumed silica, respectively. The experiments and simulations are done at two magnetic fields (9.4 and 18.8 T) and several spinning speeds (15, 18-24 and 60 kHz). This analysis indicates that owing to its $γ$-encoded character, PRESTO yields the highest transfer efficiency at low magnetic fields and MAS frequencies, whereas owing to its higher robustness to rf-field inhomogeneity and chemical shifts, D-RINEPT is more sensitive at high fields and MAS frequencies, notably for protons exhibiting large offset or CSA, such as those involved in hydrogen bonds.
