synthesis with pyro-glu: +111 mass

Michael Pereckas (msp@ace.biochem.mcw.edu)
Thu, 27 May 1999 15:11:37 -0500

I synthesized a 10 amino acid peptide with pyroglutamic acid on the
N-terminus which I added as unprotected Pyr-OH in the synthesis,
which was done on a PerSeptive 9050 using HATU activation. RP-HPLC of
the product shows two peaks, the major peak with the expected
molecular mass and a not-so-minor peak (60% of the area of the major
peak) with a mass 111.1 mass units greater. This is the mass of a
pyro-glu. Has anyone seen multiple additions of pyro-glu during a
synthesis? 

-- 
Michael Pereckas  //  msp@mcw.edu  //  Michael.Pereckas@mixcom.com
Protein and Nucleic Acid Shared Facility, Medical College of Wisconsin
Research Technologist and sysadmin/webmaster of www.biochem.mcw.edu