Ultrafast MAS and Deuteration for High-Resolution Proton Detected Solid-State NMR of Intact Fungal Cell Walls

Glycans are the main components of the fungal cell wall and play a central role in fungal pathogenesis, making atomic-level structural and dynamic insight into these biopolymers essential for the development of new antifungal therapeutics. 1H-detected solid-state NMR (ssNMR) at fast magic-angle spinning (MAS) offers an unprecedented opportunity to study glycan site, specifically at atomic resolution in intact fungal cell walls. However, the 1H resolution and sensitivity in ssNMR are often limited for detailed studies, especially for rigid and highly heterogeneous samples, such as intact fungal cells. Here, we conducted a detailed study on 1H line width and 1H T'2 coherence times in the rigid core of the human pathogenic Candida albicans fungal glycans at 60-150 kHz MAS rates and partial fungal cell wall deuteration schemes. We showcased the possibilities and limitations of 1H-detected multidimensional 1H/13C chemical shift assignment experiments for rigid cell wall glycans. Furthermore, we probed dynamics using relaxation measurements, providing access to motions spanning from nanoseconds to microseconds. Overall, we demonstrated significant methodological advances in 1H-detected ssNMR spectroscopy, achieving unprecedented 1H resolution of rigid glycans in intact fungal cell walls. These developments could be applicable for ssNMR detailed studies of intact cell walls in other human pathogens.