Kim Jihyun, Grün J Tassilo, Novakovic Mihajlo, Kupce Eriks, Rosenzweig Rina, Frydman Lucio
Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel.
Current address: BASF SE, RGA/AS-B 009, 67056, Ludwigshafen am Rhein, Germany.
Angew Chem Int Ed Engl. 2023 Aug 28;62(35):e202304900. doi: 10.1002/anie.202304900. Epub 2023 Jul 18.
INEPT-based experiments are widely used for H→ N transfers, but often fail when involving labile protons due to solvent exchanges. J-based cross polarization (CP) strategies offer a more efficient alternative to perform such transfers, particularly when leveraging the H H exchange process to boost the H→ N transfer process. This leveraging, however, demands the simultaneous spin-locking of both H and H protons by a strong H RF field, while fulfilling the γ B =γ B Hartmann-Hahn matching condition. Given the low value of γ /γ , however, these demands are often incompatible-particularly when experiments are executed by the power-limited cryogenic probes used in contemporary high field NMR. The present manuscript discusses CP alternatives that can alleviate this limitation, and evaluates their performance on urea, amino acids, and intrinsically disordered proteins. These alternatives include new CP variants based on frequency-swept and phase-modulated pulses, designed to simultaneously fulfill the aforementioned conflicting conditions. Their performances vis-à-vis current options are theoretically analyzed with Liouville-space simulations, and experimentally tested with double and triple resonance transfer experiments.
基于INEPT的实验广泛用于H→N转移，但由于溶剂交换，在涉及不稳定质子时常常失败。基于J的交叉极化（CP）策略为执行此类转移提供了一种更有效的替代方法，特别是在利用H-H交换过程来促进H→N转移过程时。然而，这种利用需要通过强H射频场同时对H和H质子进行自旋锁定，同时满足γB =γB哈特曼-哈恩匹配条件。然而，鉴于γ/γ的值较低，这些要求往往相互矛盾，特别是当实验由当代高场核磁共振中使用的功率受限低温探头执行时。本手稿讨论了可以缓解这一限制的CP替代方法，并评估了它们在尿素、氨基酸和内在无序蛋白质上的性能。这些替代方法包括基于频率扫描和相位调制脉冲的新CP变体，旨在同时满足上述相互冲突的条件。通过刘维尔空间模拟对它们相对于当前选项的性能进行了理论分析，并通过双共振和三共振转移实验进行了实验测试。
