Biomolecular NMR spectroscopy has greatly benefited from the development of TROSY-type pulse sequences, in pair with specific labeling. The selection of spin operators with favorable relaxation properties has led to an increase in the resolution and sensitivity of spectra of large biomolecules. However, nuclei with a large chemical shift anisotropy (CSA) contribution to relaxation can still suffer from large linewidths at conventional magnetic fields (higher than 9 T). Here, we introduce the concept of two-field TROSY (2F-TROSY) where the chemical shifts of nuclei with large CSA is labeled at low fields (ca. 2 T) dramatically reducing the contribution of CSA to relaxation. Signal detection is performed at high field (> 9 T) on a nucleus with efficient TROSY interference to yield high resolution and sensitivity. We use comprehensive numerical simulations to demonstrate the power of this approach on aromatic ¹³C-¹⁹F spin pairs for which a TROSY pulse sequence has recently been published. We predict that the 2F-TROSY experiment shall yield good quality spectra for large proteins (global tumbling correlation times as high as 100 ns) with one order of magnitude higher sensitivity than the single-field experiment.

TROSY型脉冲序列与特定标记相结合，极大地受益于生物分子NMR光谱学。具有良好弛豫特性的自旋算子的选择导致大生物分子光谱的分辨率和灵敏度增加。但是，在常规磁场（大于9 T）下，具有较大化学位移各向异性（CSA）的核仍会遭受较大的线宽。在这里，我们介绍两场TROSY（2F-TROSY）的概念，其中具有大CSA的原子核的化学位移被标记在低场（ca.2 T）大大降低了CSA对松弛的贡献。信号检测是在高磁场（> 9 T）的原子核上进行的，并具有有效的TROSY干扰，以产生高分辨率和灵敏度。我们使用全面的数值模拟来证明此方法对最近发布了TROSY脉冲序列的芳族¹³ C- ¹⁹ F自旋对的作用。我们预测2F-TROSY实验将产生高质量的大蛋白质谱图（全局翻转相关时间高达100 ns），其灵敏度比单场实验高一个数量级。