Chemistry Reference
In-Depth Information
R
R
=M
Si
R
O
R
R
=D
Si
O
O
R
O
=T
Si
O
O
O
O
=Q
Si
O
O
Fig. 3.2
Solid-state
29
Si NMR spectra of three amorphous silica gels produced using trypsin (
top
),
α-chymotrypsin (
middle
) and hydrochloric acid (
bottom
) [
22
]
OMe
OEt
OEt
EtO
OEt
Si
Si
Si
MeO
OMe
EtO
OEt
n
R
R=Me, Et, Allyl, Ph
n
=0,1
Fig. 3.3
The alkoxysilanes that were subjected to enzymatic hydrolysis by enzymes not naturally
evolved to process silicon-based substrates
In addition to trypsin and α-chymotrypsin, the combinations of pepsin or
bromelain with TEOS lead to the formation of silica monoliths. The other enzymes
did not appear to hydrolyze TEOS as well and produced only minute amounts of
precipitated silica. When these same seven enzymes were charged with the hydro-
lysis of phenyltrimethoxysilane (PTMS), only trypsin, α-chymotrypsin, and pepsin
produced organically modified silica.
Attempts at using enzymes to process bis(trialkoxysilyl)alkanes were not fruitful.
In fact analysis by
29
Si NMR could not confirm even a single hydrolysis event. The
lack of enzyme-mediated chemistry has been attributed to phase separation between
the hydrophobic bis(trialkoxysilyl)alkane and the aqueous enzyme solution.
