Biocatalysis in low-water media: understanding effects of reaction conditions.

The key role played by counter-ions with enzymes in low-water systems has become better appreciated with, for example, large effects on enantioselectivity. In low-dielectric media, counter-ions will associate strongly with charges in the protein or its substrates. Studies of temperature dependence have shown that hard-to-model entropies have a significant effect on behaviour, including enantioselectivity. Evidence has been presented that the supramolecular organisation of enzyme molecules can have important effects on behaviour, for example collapse of microstructure in cross-linked crystals.