We report polyamorphism of supercooled bulk water and water in confined geometry. Anomalous behaviors of water in supercooled state are accounted for in terms of a liquid-liquid phase transition and the associated second critical point. It is found that water confined in two planar hydrophobic walls separated by less than 1 nm shows novel crystalline and amorphous structures. It is also shown that a urea molecule does not act as a structure breaker of water structure in dilute solution and that urea molecules aggregate to a significant extent in higher concentration.

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A kind of Hofmeister Series for hydrogel swelling was investigated with a special attention to ion effects on the hydrogen-bonding hydration at polar groups on polymer. On the basis of experimental observations for several polymer gels, we proposed a model mechanism for the ion-specific gel swelling. According to the model, the hydrogen-bonding hydration on the polar groups is stabilized or destabilized by ions through ionic hydration since anion and cation change water s abilities for electron pair donation (EPD) and acceptance (EPA), respectively.

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Effect of hydration on various functions of proteins and food properties was analyzed in consideration of water potential (water activity). From the thermodynamic analysis, the stabilizing effects of sugars in the thermal unfolding of lysozyme and α-chymotripsinogen A were explained by the indirect effect of water potential while the destabilizing effects of urea and formamide were explained only by the direct interaction of these solutes to the protein. Similar phenomena were observed in the effects of solutes on protein thermal stability, enzyme-substrate complex formation, and sol-gel transition, suggesting the existence of a common mechanism among these processes through the hydration of proteins.

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Water, the most abundant compound in living systems, can accounts for more than 85% of the fresh weight of biological tissues. In the study of biological systems using ^1H-NMR, water is an important probe for looking into the fluctuation of biological activities. MRI detects free water in tissues and creates anatomical images of the tissues. Since the quality and mobility of cell-associated water is closely related to the condition of cells, MR images represent physiological condition of the tissue. In this paper, we show some aspects of diffusion imaging in plant science.

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The glass transition temperatures (T_gs) of various food polymers were measured by some thermal analysis, to investigate whether the T_gs of food polymers can be controlled. As the result, the followings were suggested: 1) the T_g of starch tended to increase as its crystallinity by the retrogradation increased, 2) the T_g of galactan increased with hydrophobicity, 3) the steric change by transglutaminase treatment affected the T_g of food protein. These results show that the T_gs of the food polymers could be controlled by considering their structures.

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A mathematical model has been developed to determine the thermal conductivity and permeability for the dried layer of food samples undergoing sublimation dehydration. An automatic measurement system has developed for the data acquisition as well as determination of these transport properties by applying the drying data to the model. The values of transport property were presented for several food materials indicating the critical processing factors for the drying rate of each material. Some structural models were developed for predicting the permeability of water vapor flowing through the dried layer. In a cellular food model, the resistance of a cell membrane to the molecular transfer of water vapor was determined from both value of permeability and microscopic observation of the dried layer. The model was considered to play an important role in predicting optimum heating program for the surface temperature of materials. A micro-slicer image processing system (MSIPS) has been developed for measuring the three-dimensional (3-D) structure and distribution of ice crystals formed in frozen food materials. The system has functions to reconstruct the 3-D image based on the image data of exposed cross sections obtained by multi-slicing of a frozen sample with the minimum thickness of 1 μm and display the internal structure as well as an arbitrary cross section of the sample choosing observation angles. The effects of freezing conditions on the morphology and distribution of ice crystals were demonstrated quantitatively from the observations of raw beef and model solution systems stained by fluorescent indicator. A technical cooperation project has been carried out between university and industries for optimizing the design and operation of industrial freeze-dryer to produce egg soups. In the project a new heating program was developed to shorten the drying time for the batch-type freeze dryers in industrial scale.

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Residual water in lyophilized formulation acts as (l) a reactant, (2) plasticizer and/or (3) medium and affects storage stability of the formulations. The effects of residual water as a reactant and plasticizer on the storage stability of lyophilized formulations were examined for hydrolysis of cephalothin and acetyl transfer reaction between aspirin and sulfadiazine in lyophilized formulations.

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For successsful cryopreservation of animal cells, a control of water content in cells during freezing and thawing is critical. Since the finding of cryoprotective effect of glycerol and dimethyl sulfoxide in middle 1940's, numerous animal cells have been successfully cryopreserved. Placental/umbilical cord blood is enriched with hematopoeitic stem/progenitor cells, and that is now considered as a new source of hematopoietic cells to treat leukemia, lymphoma and other congenital diseases. We have cryopreserved cord blood with a mixture of penetrating and nonpenetrating cryoprotectants, i.e., 10% dimethyl sulfoxide, 1 % dextran and 0.8% hydroxyethyl starch with stepwise addition. With the cryoprotectant, the concentrated cord blood stem/progenitor cells were frozen at 2℃/min to -50℃ and plunged in LN_2 in a BioArchive System. This optimal freezing condition was determined by the analyses of differential scanning calorimeter. The cord blood units were transplanted to HLA matched patients and the number of transplantation has increased more than 120. About half of the patients received cord blood units washed out dimethyl sulfoxide after cryopreservation to avoid cell damage caused by rapid entry of water into the cells. The clinical outcome of these patients is as good as that of bone marrow transplantation, which was the major treatment for these difficult diseases.

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Seasonal changes in water distribution in xylem of trees were visualized at the cellular level using cryo-scanning electron microscopy (cryo-SEM). In a ring-porous tree (Fraxinus mandshurica var. japonica), the large earlywood vessel lumina of the outermost annual ring had maintained water during the period from May to September and disappeared water during the period from October to November. The earlywood vessel lumina of the outermost annual ring had no water during the next growing season. In two diffuse-porous trees (Betula platyphylla var. japonica and Salix sachalinensis), water in the vessel lumina of the outer three annual rings gradually disappeared during the period from January to March. In April, before the leaves had expanded, the lumina of most vessels of both species were refilled with water. Many vessel lumina of both species were filled with water during the period from the subsequent growth season to the beginning of the next winter. In three conifers (Larix kaempferi, Abies sachalinensis, and Picea jezoensis), all tracheid lumina of the outermost annual ring were filled with water during the period from May to August. In September, many tracheid lumina in the transition zone from earlywood to latewood had no water. Some earlywood tracheid lumina of the outermost annual ring lost water during the period from January to March. The second and third annual rings from the bark had a similar water distribution, except that the third annual ring had more cavitated tracheids than the second annual ring. In these two annual rings, most tracheid lumina in the transition zone from earlywood to latewood had no water, and latewood near the annual boundary and many earlywood tracheids kept water in their lumina. The results of this study suggest that the water transport pathway and seasonal changes in water distribution are depending on the xylem structure of the tree species.

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