Abstract
AbstractDynamic 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.
Highlights
The study of ligand binding with magic-angle spinning (MAS) nuclear magnetic resonance (NMR) is challenging, as biomolecules made of same building blocks suffer from spectral overlap
If the missing ΔDPsat signal at 155 K is due to broadening beyond detectability or inefficient SCREAM-Dynamic nuclear polarization (DNP) transfer
All three methyl groups of caffeine show no significant broadening in cross polarization (CP) and provide a strong SCREAM-DNP signal (ΔDPsat) with a build-up constant of 3.3 s at 110 K
Summary
The study of ligand binding with magic-angle spinning (MAS) NMR is challenging, as biomolecules made of same building blocks suffer from spectral overlap. NMR has the issue of very low sensitivity as a result of low thermal spin polarization. DNP is a technique that allows overcoming the sensitivity problem (Lilly Thankamony, et al, 2017). The effect of spontaneous 1H–13C polarization transfer via heteronuclear cross-relaxation due to fast reorientation dynamics in a 13C or 15N MAS direct polarization experiment under DNP was discovered (Daube et al, 2016; Hoffmann et al, 2017a, 2017b; Park et al, 2020).
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