Water-in-silicone oil emulsions were prepared using either silicone surfactants containing pendant polyethylene oxide (PEO) side chains (DC3225C) or terminal Si(OEt)_3 groups. The aqueous solutions contained either the enzymes α-chymotrypsin or alkaline phosphatase (DC3225C emulsions) or the surface active protein human serum albumin (TES-PDMS emulsions). Labelled albumin was shown to reside almost exclusively at the oil/water interface in the emulsion. The activity of the enzymes was followed over time by first breaking the emulsion and then performing standard enzyme assays on the aqueous phase. The enzymes were observed to undergo denaturation, as measured by reduced enzymatic activity, as a result of the mechanical energy used to make and break the emulsion. However, the rate of enzyme denaturation in the emulsions was lower than that observed for the aqueous control which had not been exposed to silicone. These results are consistent with favorable interactions between PEO or Si(OEt)_3 groups (or hydrolytic byproducts in the latter case) and the proteins that not only stabilize the interface of a water-in-oil emulsion, but also the protein, which normally would otherwise undergo efficient denaturation in the presence of silicone oil.
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