MAS NMR experiments of corynebacterial cell walls: Complementary 1H- and CPMAS CryoProbe-enhanced 13C-detected experiments.

Bacterial cell walls are gigadalton-large cross-linked polymers with a wide range of motional amplitudes, including rather rigid as well as highly flexible parts. Magic-angle spinning NMR is a powerful method to obtain atomic-level information about intact cell walls. Here we investigate sensitivity and information content of different homonuclear 13C 13C and heteronuclear 1H 15N, 1H 13C and 15N 13C correlation experiments. We demonstrate that a CPMAS CryoProbe yields ca. 8-fold increased signal-to-noise over a room-temperature probe, or a ca. 3–4-fold larger per-mass sensitivity. The increased sensitivity allowed to obtain high-resolution spectra even on intact bacteria. Moreover, we compare resolution and sensitivity of 1H MAS experiments obtained at 100 kHz vs. 55 kHz. Our study provides useful hints for choosing experiments to extract atomic-level details on cell-wall samples. [Display omitted] • MAS NMR spectra of isolated corynebacterial cell walls and intact bacteria are obtained. • Quantitative comparison shows that a CPMAS CryoProbe yield ca. 8-fold improved sensitivity. • INEPT-hNH and hCH show a sensitivity advantage of 1.3 mm over 0.7 mm probes for similar line widths. • A purely INEPT-based pulse sequence is applied for recording N-C correlation spectra of cell walls. [ABSTRACT FROM AUTHOR]