Water replacement hypothesis

The mechanism by which these solutes exert their influence on protein stability is uncertain. The phenomenon has been extensively studied by Timasheff and his colleagues and their conclusion is that all of the protein structure-stabilising compounds are preferentially excluded from contact with the surface of the protein (Timasheff, 1982). This explanation is rather different from that invoked in the water replacement hypothesis. 

Clegg, J. S., Seitz, P Seitz, W., Hazelwood, C. F. (1982). Cellular response to extreme water loss the water-replacement hypothesis. Cryobiology 19, 306-316. 

Clegg, J. S. (1986). The physical properties and metabolic status of Anemia cysts at low water contents The water replacement hypothesis. In Membrane, Metabolism and Dry Organisms (Leopold, A. C ed.), H>. 169-187, Cornell University Press, Ithaca, NY. 

Hydrophilic solutes like carbohydrates, i.e. glucose, sucrose, and trehalose also bind close to the charged headgroups, replacing hydration water, as laid down in the water-replacement hypothesis . They act as cryoprotectants and help to stabilize the bilayer in case of insufficient water. 

In Fig. 3 a transition of sorbitol protons from dissolved into solid state is observed in the water content range between 20 and 7 % suggesting that sorbitol becomes incorporated into the dry biomass and therefore confirming the water replacement hypothesis. 

J.H. Crowe, L.M. Crowe, and J.F. Carpenter, Preserving dry biomaterials The water replacement hypothesis, European Journal of Pharmaceutics and Biopharmaceutics, 6 (4), 28-37, 1993. 

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