Cosolvents biologic effects

A potential limitation to the use of cosolvents may be the choice and amount of cosolvent needed. For pharmaceuticals there are relatively few organic cosolvents that are generally regarded as safe. Rubino in his article Cosolvent and Cosolvency has discussed the biological effects of many of the commonly utilized cosolvents such as ethanol, propylene glycol, glycerol, polyethylene glycols, and dimethylacetamide (DMA). 

In dilute aqueous solutions, biomolecules are completely covered by water molecules. The structure of water near a boundary essentially differs from the structure of bulk water (see Sections 2 and 5). Specific water structure is seen in one or two water layers near hydrophilic surfaces, whereas the rest of liquid water is bulk-like. This is also the case for the surfaces of biomolecules, which allow consideration of hydration water as a separate subsystem. Conformational transitions and aggregation of biomolecules occur in dilute solution due to variations of temperature and/or pressure and due to additions of some cosolvents. It is natural to expect that these biologically important processes are related to the changes in the state of hydration water shell. First, we consider the effect of heating on the state of hydration water shell and on the properties of biomolecules. Then, we discuss the dynamic transition of biomolecules and pressure-induced denaturation in relation with the liquid-liquid transitions of hydration water. 

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