Effect of hydration on the morphology of enzyme powder.

We report the first direct images of the hydration of protein powders. Using an environmental scanning electron microscope (ESEM) we have taken a series of micrographs of a region of the enzyme (subtilisin) power whilst hydrating the sample. In addition, the sample has been viewed during exposure to toluene vapors. The ESEM is a remarkable new instrument that will have wide applicability in imaging of biological materials in their native environments.