I have synthesized a peptide with the sequence CDGSVWAQSESFPELK. The HPLC
shows two major peaks adjacent to each other with the major peak being a
dehydrated (-18) species of the peptide as shown by mass spec. I suspect
pyroglu. formation, but I'm not sure where. Can anyone comment on what
might have happened here and what I can do to prevent this if I need to
resynthesize??
Thanks in advance!
Mary
Mary Bower
Instrument Specialist
Purdue University
Department of Biochemistry
West Lafayette, IN 47907
Dear Mary
You are almost certainly seeing aspartimide formation across the DG residues.
Aspartimide can occur across any DX residue but is most frequent when X is
Gly. There are several ways to avoid this. One is to use the Hmb protected
amino acids available from Nova Biochem. Another way, which I routinely
use is to add 0.1M HOBt to the piperidine solution. I find this minimises
aspartimide in most cases and in the very worst, where it would normally
be 80% or more, lowers it to 30% and the product is nearly always
purifiable by LC unless it is a very long sequence.
Dr Graham Bloomberg
Dept Biochemistry
Medical School
University of Bristol
Bristol
BS8 1TD
G.B.Bloomberg@bristol.ac.uk