When Water Matters: NMR of Molecular Structure and Dynamics under Native Hydration

Water, as a ubiquitous and highly interactive solvent, plays a central role in determining molecular conformations, mediating intermolecular forces, and modulating the thermodynamic stability of assemblies across a broad spectrum of materials. Therefore, careful attention must be given to sample preparation and environmental control when performing structural characterization. The choice of experimental method should consider not only resolution and sensitivity, but also how closely the measurement conditions mimic the system’s native environment. Characterization techniques that preserve natural hydration condition, particularly solid-state NMR spectroscopy, offer unique advantages in probing molecular behavior without perturbing the system’s intrinsic state. In this review, we provide an integrated summary of theoretical and computational studies elucidating how hydration shells affect noncovalent interactions, such as hydrogen bonding, electrostatics, and van der Waals forces, and how these effects translate into macroscopic changes in material behavior. Complementing this, we review experimental evidence demonstrating how variations in hydration level or solvent composition can alter molecular structure, flexibility, and functional properties. Finally, we highlight recent advancements in solid-state NMR methodology that aim to achieve genuine native-environment characterization, allowing the direct observation of molecular interactions and motions within complex hydrated systems. By synthesizing insights across disciplines, this review seeks to raise awareness of the environmental dependence of structural data and encourages researchers to contextualize their interpretations accordingly, ensuring that conclusions drawn from experimental results accurately reflect the system’s true physicochemical state.