(very smelly, but not as smelly as with EDT). TIS is a great scavenger
for Trt and Boc carbocations, but I'm not sure it would be very effective
with Pbf. I have had good luck with the mixture above, cleaving not only
Pbf, but also Pmc, even with multiple Arginines in a sequence. The thio-
anisole/thiocresol combination is also supposed to prevent sulfate from
being attached to Arg or other residues (happens when there is cleavage
at the sulfur of the sulfonyl part of Pbf or Pmc).
Hope this helps.
Angela C. Murphy
On Fri, 30 Jul 1999, Jane Nagel wrote:
> Hello all,
>
> 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
> !
!
> !
>
>
>
*******************************************
Angela C. Murphy, Chemist
Lab. of Cell Biology, NHLBI, NIH
3 Center Drive, MSC 0301, Rm. B1-22
9000 Rockville Pike
Bethesda, MD 20892-0301 USA
tel.: (301) 496-2324
fax: (301) 402-1519
email: acmurphy@helix.nih.gov
*******************************************