Chemistry Reference
In-Depth Information
In water, the lauryl and terpyridyl residues are expected to form hydrophobic clus-
ters (
6
) on the backbone of PEI. An active site consisting of two or more metal ions can
form in the cluster. Its structure depends on the contents of lauryl and terpyridyl re-
sidues. An active site obtained by combinatorial attachment of the pendants catalyzed
transesterification of HPNPP apparently by using adjacent metal centers (
7
). In this
work, we created the active site by self-assembly of hydrophobic pendants attached to
the backbone of PEI, taking advantage of the branched and flexible structure of the
polymer.
3.3
Heterogeneous Polymer Biocatalysts
3.3.1
Random Catalytic Adducts
Branched insoluble polymers have more rigid backbones and more hydrophobic mi-
crodomains than branched soluble polymers such as PEI, which can be advantageous
in designing some types of catalysts. In addition, such insoluble catalysts may be more
useful in practical applications.
An effective polymer catalyst with protease activity has been obtained simply by at-
taching imidazoles randomly to poly(chloromethylstyrene-co-divinylbenzene) (PCD).
This polymer is a cross-linked polystyrene (PS) with the styryl moiety being chloro-
methylated. Imidazole was attached to PCD through either C-2 or the N atom [44].
Unreacted chloro groups of PCD were blocked by treatment with methoxide. In
the best catalyst we obtained ([Im
C
]
22
PCD) imidazole was attached to PCD via C-2
and the content of imidazole was 22 residue mol%.
PCD: X = Cl
PAD: X = NH
2
