Trypsin trimethylethoxysilane

In the presence of trypsin, trimethylethoxysilane was hydrolyzed (100%) and condensed (84%) during the formation of HMDS in a neutral medium at 25°C over three hours (Figure 3). Since the relative rate of condensation decreased at temperatures < 2S°C (25), a time study of the trimethylethoxysilane reaction was conducted at 10°C for defined periods of time over three hours. The reaction products were isolated and quantitatively analyzed by GC (Figure... 

Figure 4. Trypsin-catalyzed hydrolysis and condensation of trimethylethoxysilane at 10° C.

Figure 5. Turnover numbers of the trypsin-catalyzed hydrolysis of trimethylethoxysilane and condensation of trimethylsilanol at 10 C.

Inhibition Study. A proteinaceous inhibition study was conducted to study the role of the enzymatic active site in the hydrolysis and condensation of trimethylethoxysilane. Prior to reaction, trypsin was independently inhibited with an excess amount of the Bowman-Birk inhibitor (34) (4 1 BBI to trypsin mole ratio) and die Popcorn inhibitor (35) (2 1 PCI to trypsin mole ratio) in stirred neutral media for two hours. Based on standard enzymatic activity assays (36), trypsin was fully inhibited by the BBI (98%) and PCI (91%). The reactions were formulated with an 1000 1 trimethylethoxysilane to trypsin mole ratio and conducted at 25°C for three hours. The reaction products were isolated and quantitatively analyzed by GC (Table II). Although the treated enzymes were observed to catalyze the hydrolysis of trimethylethoxysilane, the condensation of trimethylsilanol was conqiletely inhibited in conq>arison to the control reactions. Notably, the rate of hydrolysis decreased in the presence of the BBI- and PCI-inhibited trypsin. Following thermal denaturation, tiie activity of trypsin was comparable to the proteinaceous inhibition experiments. Based on a standard enzymatic activity assay (36), the relative decrease in the rate of silanol condensation correlated with the enhanced stability of trypsin at higher protein concentrations (25). Consequently, it appears that non-specific interactions with trypsin including the active site promoted the hydrolysis of trimethylethoxysilane. Therefore, the active site of trypsin was determined to selectively catalyze the in vitro condensation of trimethylsilanol imder mild conditions. 

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