I have been cursed with a peptide which has some residual Pbf protecting group left on an Arg residue (it is a 21-mer). The peptide synthesizes beautifully, one peak on HPLC and usually one peak on MALDI-TOF but the removal of the Pbf is somewhat hit and miss. I have never encountered a problem with its removal before so I have been surprised to see it on this peptide. I make a bunch of this stuff and the cleavage either goes to completion or it gives me this portion of still Pbf protected peptide even when batches are cleaved side by side.
As it happens, the Pbf protected bits elute at roughly the same % as the clean stuff so I had hoped to try a rescue measure and re-cleave the already cleaved peptide. I looked through the ABRF archive and could not find any instance of this being attempted before so here I am, asking for your assistance. I have had excellent results removing residual Trt from cleaved peptides by stirring them in 99% TFA and 1% TIS, anyone have any experience with Pbf removal in the same general fashion? I was thinking of using 95% TFA + 2.5% EDT + 2.5% TIS.
Your input would be much appreciated!
Thanks in advance,
Jane
Jane A. Nagel MSc
Genetics Institute
Cambridge, MA
1 888 577 1500 x 8597
jnagel@genetics.com
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