Dehydration
The amino acids asparagine
and glutamine have been shown to undergo dehydration
at elevated temperatures. This side reaction
involves the loss of a water molecule from
the side chain groups of these two amino acids.
With microwave peptide synthesis, the deprotection
and coupling reaction temperatures are elevated
and can cause dehydration of the side chains
of these two amino acids when they are exposed.
For this reason it is necessary to use side
chain protecting groups on these two amino
acids with microwave peptide synthesis. Both
of these amino acids are commonly available
with side chain protecting groups. Below are
the recommended side chain protecting groups
that will prevent dehydration during the peptide
chain assembly. These protecting groups will
be removed during the final acid cleavage of
the peptide; therefore, it is essential that
this reaction temperature be minimized. Experts
in the CEM peptide synthesis laboratory have
designed appropriate cleavage methods that
prevent dehydration.
When creating a new cleavage method for a particular peptide, an excessive
amount of power delivered to the peptide can increase the bulk temperature
of the reaction enough to cause dehydration of a peptide containing asparagine
or glutamine. For assistance with cleavage methods, contact the CEM peptide
application support group.
Recommended protection of Asparagine and Glutamine:
Fmoc-Asn(Trt)-OH
Fmoc-Gln(Trt)-OH |
