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Dear ABRFers,
A student of ours is working on a peptide with two cysteines, with which
we would like to make parallel and antiparallel homodimers. At the
moment we have made two versions of the peptide: peptide1 with a free
Cys towards the N-terminal and an Acm protected Cys towards the
C-terminal, and peptide2 which is vice-versa.
For the parallel dimer we thought of air oxidation of peptide one, to
form a first intermoloecular S-S bridge via the free cysteines, followed
by removal of Acm and second bridge formation. I am told oxidation in
the presence of DMSO is most efficient, but I suppose it must then be
removed someway before the Acm can be removed from the remaining two
cysteines. We thought of using iodine.
For the antiparallel peptide we need to initially form an S-S bridge
between Peptide1 and Peptide2 via the free cysteines. I suppose that to
do this we need to preactivate the free cys on one peptide before we add
it to the other peptide. I have read that Ellman's reagent can be used
for this but have not been able to find a good protocol. We could then
form the second S-S bridge by removing Acm.
One problem is that we have only a few mg of each peptide. Any
suggestions would be very welcome. If you feel that alternative
protection schemes requiring resynthesis would be better we would also
welcome these suggetsions.
Thanks , Alex Tossi
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Dr. Alessandro Tossi
Antiinfective peptides group
Dept. of Biochemistry, Biophysics and Macromolecular Chemistry
University of Trieste
Phone -- 39 40 6763673; Fax -- 39 40 6763691
email: tossi@univ.trieste.it
tossi@icgeb.trieste.it
http://www.univ.trieste.it:80/~nirdbbcm/antimic.html
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