Structure of the protein BPTI derived with NOESY in supercooled water: Validation and refinement of solution structures

(Chemical Equation Presented) Fidelity without frostbite: Refinement of an NMR solution structure of 6-kDa protein BPTI determined at 36°C (see picture, red) with NOE distance constraints measured in supercooled water at -15°C increased precision of backbone and core side-chain coordinates about twofold (blue). In contrast to cryogenic X-ray crystallography (-150°C), supercooling to about -15°C hardly affects the conformation of flexibly disordered surface side chains.