Resolving atomic-level dynamics and interactions of high molecular weight hyaluronic acid by multidimensional solid-state NMR

High molecular weight (HMW) hyaluronic acid (HA) is a highly abundant natural polysaccharide and a fundamental component of the extracellular matrix (ECM). Its size and concentration regulate tissues’ macro- and microenvironments, and its upregulation is a hallmark feature of certain tumors. Yet, the conformational dynamics of HMW-HA and how it engages with components of the ECM microenvironment remain poorly understood on the molecular level. Probing the molecular structure and dynamics of HMW polysaccharides in a hydrated, physiological-like environment is crucial but also technically challenging. Here, we deploy advanced magic-angle-spinning (MAS) solid-state NMR (ssNMR) spectroscopy in combination with isotopic enrichment to enable an in-depth study of HMW-HA to address this challenge. This approach resolves multiple coexisting HA conformations and dynamics as a function of environmental conditions. By combining [13][1]C-labeled HA with unlabeled ECM components, we detect by MAS NMR HA-specific changes in global and local conformational dynamics as a consequence of hydration and ECM interactions. These measurements reveal atom-specific variations in dynamics and structure of the N-acetylglucosamine (GlcNAc) moiety of HA. We discuss possible implications for interactions that stabilize the structure of HMW-HA and facilitate its recognition by HA-binding proteins. The described methods apply similarly to studies of the molecular structure and dynamics of HA in tumor contexts and in other biological tissues, as well as HMW-HA hydrogels and nanoparticles used for biomedical and/or pharmaceutical applications. Synopsis Multidimensional solid-state NMR techniques unveil site-specific conformational heterogeneities within isotopically enriched high molecular weight HA hydrogels, elucidating its response to hydration levels and biomimetic ECM environments. ![Figure][2] Figure: For Table of contents only. ### Competing Interest Statement The authors have declared no competing interest. [1]: #ref-13 [2]: pending:yes