Complementary (2D) NMR techniques provide new insights into the molecular structure of humin by-products.

Dynamic nuclear polarization (DNP) has become a powerful method to enhance spectroscopic sensitivity in the context of magnetic resonance imaging and nuclear magnetic resonance spectroscopy. We show that, compared to DNP at lower field (400 MHz/263 GHz), high field DNP (800 MHz/527 GHz) can significantly enhance spectral resolution and allows exploitation of the paramagnetic relaxation properties of DNP polarizing agents as direct structural probes under magic angle spinning conditions. Applied to a membrane-embedded K(+) channel, this approach allowed us to refine the membrane-embedded channel structure and revealed conformational substates that are present during two different stages of the channel gating cycle. High-field DNP thus offers atomic insight into the role of molecular plasticity during the course of biomolecular function in a complex cellular environment.

The efficiency of magnetization transfer between different spins S such as chemically inequivalent carbon-13 nuclei in solid samples that are spinning at high frequencies about the magic angle can be enhanced by a phase-alternated recoupling irradiation scheme (PARIS). Dipolar recoupling is assisted by a radio-frequency (rf) field applied to the abundant I (proton) spins. In contrast to rotary resonance-based recoupling schemes, the new method does not depend critically on the rf amplitude, which need not be matched with the spinning frequency. Modest rf amplitudes suffice to bring about efficient magnetization transfer even at high spinning speeds, thus avoiding excessive sample heating. The new method compensates efficiently for rf field inhomogeneity, so that the full sample volume is used more effectively.

The alarming rise of antimicrobial resistance requires antibiotics with unexploited mechanisms. Ideal templates could be antibiotics that target the peptidoglycan precursor lipid II, known as the bacterial Achilles heel, at an irreplaceable pyrophosphate group. Such antibiotics would kill multidrug-resistant pathogens at nanomolecular concentrations without causing antimicrobial resistance. However, due to the challenge of studying small membrane-embedded drug–receptor complexes in native conditions, the structural correlates of the pharmaceutically relevant binding modes are unknown. Here, using advanced highly sensitive solid-state NMR setups, we present a high-resolution approach to study lipid II-binding antibiotics directly in cell membranes. On the example of nisin, the preeminent lantibiotic, we show that the native antibiotic-binding mode strongly differs from previously published structures, and we demonstrate that functional hotspots correspond to plastic drug domains that are critical for the cellular adaptability of nisin. Thereby, our approach provides a foundation for an improved understanding of powerful antibiotics.