Chemistry Reference
In-Depth Information
reactions of polymers). The chloromethyl moieties serve as the initiating sites for formation of the
polypeptides:
R
O
+
O
NO
O
H
CH
2
Cl
H
R
O
R
O
NO
O
H
N
O
H
O
H
A new amino acid with a protective group can now be added. The sequence of additions can be
controlled and repeated many times to build up the desired polypeptide chain. Unwanted by-products
of the syntheses are washed away or filtered off before each new step.
This method lends itself so well to automation that automatic peptide synthesizers are now
available commercially. One automatic peptide synthesizer was employed, for instance, in the
synthesis of ribonuclease, an enzyme. In another instance, an enzyme, ferredoxin that consists of
55 amino acid residues was synthesized [
26
].
Most recent approaches to protein syntheses include use of templates for spontaneous self-
assembly of multiple copies of a derivatized peptide [
70
]. The resultant structure, however, is not a
conventional linear-chain protein. Instead, oxime bonds are formed between amino-oxyacetyl groups
on the peptides and aldehyde groups on the template. The method is claimed to have many potential
applications.
Bode et al. [
70
] reported a new method for synthesis of peptide oligomers. The reaction creates
aide linkages between
-keto carboxylic acids and
N
-alkylhydroxylamines.
a
O
O
OH
HO
R'
R'
-H
2
O
- CO
2
R
N
RN
+
O
H
H
8.5.4 Chemical Modification of Proteins
Proteins have been utilized commercially from ancient times, either in their naturally occurring form
or modified in some manner. Use of silk and wool fibers, for instance, goes back a very long time.
Many animal glues, prepared from bones and hides of cattle or sheep, have also been around for a
very long time. Today such glues are being replaced rapidly by synthetic materials. Those that are still
