二糖類水溶液の凍結と氷準安定相の形成(<特集>準安定相の形成と結晶成長) Freezing Process of Disaccharide Solutions with Cubic Ice Formation(<Special Issue>Formation and Crystal Growth of Metastable Phases)
Disaccharides are expected to be the natural cryoprotecting materials for living bodies and cells. However, since they are too large to permeate the biomembrane, the cryopreservation mechanism has not been revealed. The microscopic-scale observations on the freezing process of dissacharide solutions provided new insight of this mechanism. Two kinds of experiments, the transmission electron microscopic observations of freeze-fractured replica films and the powder x-ray diffraction measurements, on the quenched trehalose solutions revealed that the crystal growth of ice Ih crystallites was inhibited to grow by the non-crystalline trehalose phase. In addition, it was found that the quasi-stable phase of cubic ice (Ic) were formed in the large concentration samples. Since the stability of ice Ic was extended as high as approximately 243 K, it was considered that the meso-pore space stabilizing ice Ic was maintained until the trehalose molecules broke off their hydrogen-bonded network at the vitrification temperature. Based on the formation and anomalous stability of ice Ic, the compartment-like structure formed by the disaccaride molecules in the original solution would inhibit the growth of ice Ih, which results in the cryoprotective effect.
日本結晶成長学会誌 40(4), 238-243, 2014