Undercooled water kinetics

The usefulness of undercooled water as a reaction medium has also been demonstrated in biochemical studies. Thus, the kinetics of biochemical reaction sequences can be sufficiently slowed down to become time resolved at subzero temperatures in the unfrozen state. Even more importantly, complex reaction pathways (mechanisms) are unaffected by undercooling, whereas the use of conventional cryoprotectants (glycerol, ethane diol, dimethylsulfoxide, etc.) alters the pathways, although not necessarily the nature of the end products. Finally, single cells or even cell clusters can be stored and kept intact for considerable periods in undercooled aqueous media. 

Apart from the dimensions of critical nuclei under varying conditions, it is also important to consider the kinetics of nucleation, especially relative to the kinetics of crystal growth. The nucleation rate (/) is commonly estimated by means of transition state theory. With the aid of the best available values for transport properties of undercooled water,it has been estimated that in the neighbourhood of —40°C, J increases rapidly with decreasing temperature, by about a factor 20 per degree nucleation is thus a well-defined event that is hardly affected by the rate of cooling. ... 

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