Abstract
For understanding physicochemical and biological implications of amphoteric ions, we investigated hydration of glycinebetaine (GB) by obtaining the water sorption isotherm, and freezing behaviour of the aqueous GB solution by the use of differential scanning calorimetry (DSC). It was found, as a result, that GB is very hygroscopic and easily deliquesces. In the DSC cooling trace, the aqueous GB solution did not show an exotherm due to eutectic separation. However, it appeared during the subsequent heating, followed by the melting endotherm at -26℃. The solid-liquid state diagram indicated that Tg'for the freeze-concentrated GB system was very low (ca. -98℃) with the amount of unfrozen water estimated from the Cg'being large (ca. 58wt%). From these results, amphoteric GB ions are considered to be stabilized by hydration, and viscosity of the GB solution might remain rather low as a result of hydration even when it is freeze-concentrated, causing the solution not to be readily vitrified. Characteristics of hydration of GB explained above probably are relevant to its functions in the life process.
