Water unfreezeable

The introduction of solvent into molecular dynamics simulations of proteins produces complex changes in motional properties (Brooks and Karplus, 1986) and generally decreases the time constants of atom and group motions (Ahlstroem et al., 1987 Levitt and Sharon, 1988). This is in qualitative agreement with experiments, in that addition of water unfreezes both surface and internal motions of groups of atoms. 

Fig. 1.51. Unfreezable water (UFW) in a 0.57 % ovalbumin solution as a function of the freezing temperature with different CPAs (Fig. 4. from [1.36]).

Table 1.13 Tg data, related UFW (unfreezable water, %) 7 and Tc data (7T- and UFW data from [3.6] Tr and Tc data from [1.113]).

Duckworth, R. B. Differential thermal analysis of frozen food systems. I. The determination of unfreezable water. Joum. Food Technol. 6, p. 317-327, 1971... 

As shown in the following table (from [3.6]) the selection of the excipient also defines Tg- and the amount of unfreezable water (UFW) in the glass phase. 

Other research using NMR techniques to study mobility in starch systems includes Li et al. (1998), who investigated the mobility of unfreezable and freezable water in waxy cornstarch using H and 2H NMR Choi and Kerr... 

ESR spectroscopy can be used with adsorbed paramagnetic ions to study the liquid associated with mineral surfaces. Cu(II) and Mn(II) have been used in his type of investigation, although difficulties are encountered with observing a resonance from Mn(II) in distorted environments. Measurements of Cu(II) on silica at room temperature and above have shown that adsorbed water behaves in the same manner as bulk water, but at lower temperatures it experiences a decreased mobility (61). On freezing two types of water are found one which is freezable and undergoes crystallization and the other which is unfreezable, in which the ice structure cannot be formed because of the surface interaction. NMR, IR and differential thermal... 

Calorimetric data on native DNA shows similar hydration properties like on collagen188. Up to 0.6 g water/g dry DNA water is unfreezable. The amount of bound water corresponds to 11.6 mole water/molecule nucleotide. Similar amounts are found by NMR technique1811. Addition of 0.15 mole/1 NaQ reduces the bound water content to 10.5 — With calorimetric studies on denaturated calf thymus DNA was found181,201, a dependence of the unfrozen water on the additions of cations ... 

The unfreezable water may have more than a theoretical meaning. Adding more water than the total of the unfreezable to biopolymers, small amounts of freezable water are observed but the freezing point is reduced (see Figs. 16 and 20 in 181 ). So in fish (cod) muscle water freezes at —10 °C 208. Feeney has found a special anti-... 

Table 1.1.1 shows the unfreezable water (UFW) in various foods. The reasons and the consequences are described in Sections 1.1.3 and 1.1.4. In comparing these data with other publications, e.g. [1.3], smaller values may be found. This can depend not only on the different raw materials and the history of the probe until measurement, but also on the methods of measurement. 

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