Heteronuclear cross-relaxation effect modulated by the dynamics of N-functional groups in the solid state under 15N DP-MAS DNP

• DOI: 10.1016/j.jmr.2020.106688
• Publication Date: 2020-01-16T16:41:25Z
• Authors: Heeyong Park; Boran Uluca-Yazgi; Saskia Heumann; Robert Schlögl; Josef Granwehr; Henrike Heise; P. Philipp M. Sch...
• Keywords: Heteronuclear molecule; Magnetization transfer; Magic angle spinning; Hyperpolarization; Gyromagnetic ratio; Nuclear Overhauser effect

In a typical magic-angle spinning (MAS) dynamic nuclear polarization (DNP) magnetic resonance (NMR) experiment, several mechanisms are simultaneously involved when transferring much larger of electron spins to NMR active nuclei interest. Recently, specific cross-relaxation enhancement by motions under DNP (SCREAM-DNP) [Daube et al. JACS 2016] has been reported as one these mechanisms. Thereby 13C with inverted sign was observed in direct (DP) MAS caused reorientation dynamics methyl that not frozen out at 100 K. Here, we report on the spontaneous transfer from hyperpolarized 1H both primary amine and ammonium nitrogens, resulting an additional positive signal 15N spectra during DP-MAS DNP. The induced (CRE) for is opposite compared due negative gyromagnetic ratio 15N. influence CRE efficiency variation radical solution composition temperature also investigated.