Heteronuclear Cross-Relaxation under Dynamic Nuclear Polarization in Nicotine and Caffeine

Abstract

Dynamic nuclear polarization (DNP) is a technique in magic-angle spinning (MAS) nuclear magnetic resonance (NMR) which leads to sensitivity enhancement and helps to overcome the issue of low polarization in detected nuclei. Recent research showed, that methyl groups, which show active reorientation dynamics and cause heteronuclear cross relaxation at typical DNP temperatures around 100 K, may be used as a pinpoint source of polarization for selective and site-specific probing. In this study, we investigated the cross-relaxation behavior of methyl groups in nicotine and caffeine under DNP. These effects could be useful for investigating receptor/ligand binding.

Dynamic Nuclear Polarization for Sensitivity Enhancement in Biomolecular Solid-State NMR

“…Further studies have identified small drug molecules as potential SCREAM-DNP sources in order to probe their interactions with their respective receptors . Recently, SCREAM-DNP has been investigated by Sergeyev et al in HIV-1 CA assemblies where the authors analyzed the CP-based indirect DNP, direct DNP, as well as SCREAM-DNP pathways providing an overview of their dependence on the PA .…”

“…218 Further studies have identified small drug molecules as potential SCREAM-DNP sources in order to probe their interactions with their respective receptors. 433 Recently, SCREAM-DNP has been investigated by Sergeyev et al in HIV-1 CA assemblies where the authors analyzed the CPbased indirect DNP, direct DNP, as well as SCREAM-DNP pathways providing an overview of their dependence on the PA. 160 Furthermore, SCREAM-DNP was used for characterization of regioselectivity in two cellulose methyl ethers with a well-defined molecular structure in terms of overall degree of substitution with methyl groups. 434 Besides methyl groups, Park et al have proven that similar dynamics in primary amine and ammonium groups support the indirect polarization transfer from hyperpolarized 1 H to their nitrogen under direct 15 N DNP.…”

Specific Signal Enhancement on an RNA‐Protein Interface by Dynamic Nuclear Polarization

“…[18] Thus, this effect has been named specific cross relaxation enhancement by active motions under DNP (SCREAM-DNP). [19] In contrast to a typical hetNOE experiment, the polarization transferred to methyl- 13 C is not originating from the saturated Zeeman polarization of 1 H, but is based on the strongly hyperpolarized 1 H reservoir due to DNP. Consequentially, Equation (2) may be rewritten in Equation (3) as…”

“…In 2016 it has been shown that hyperpolarized 1 H can spontaneously induce a similar hetNOE‐like transfer within dynamical functional groups during DNP [18] . Thus, this effect has been named specific cross relaxation enhancement by active motions under DNP (SCREAM‐DNP) [19] . In contrast to a typical hetNOE experiment, the polarization transferred to methyl‐ 13 C is not originating from the saturated Zeeman polarization of 1 H, but is based on the strongly hyperpolarized 1 H reservoir due to DNP.…”

Serial Polarization Transfer by Combination of Cross‐Relaxation and Rotational Resonance for Sensitivity‐Enhanced Solid‐State NMR

“…Note that the presence of chemical shift anisotropy introduces a further time dependence of the Hamiltonian in the toggling frame, such that Eq. (1) has to be rewritten as: (5) Expansion of Eq. ( 5) into a Fourier series, (6) finally results in the extension of the R 2 matching condition, such that also higher spinning sidebands can contribute to the effective recoupling if Dw iso ¼ nw r with n = � 1, � 2, � 3,…:…”