Sweet neutron crystallography.

Extremely sweet proteins isolated from tropical fruit extracts are promising healthy alternatives to sugar and synthetic sweeteners. Sweetness and taste in general are, however, still poorly understood. The engineering of stable sweet proteins with tailored properties is made difficult by the lack of supporting high-resolution structural data. Experimental information on charge distribution, protonation states and solvent structure are vital for an understanding of the mechanism through which sweet proteins interact with taste receptors. Neutron studies of the crystal structures of sweet proteins allow a detailed study of these biophysical properties, as illustrated by a neutron study on the native protein thaumatin in which deuterium labelling was used to improve data quality.