Hello Enrico;
I too had a similiar problem with Arginine rich and Tryptophan containing
peptides using Arg(pbf) and Trp(Boc). Check the ABRF archives under
"origin and removal of +98 adducts" also a paper by same title Chowdhury
and Chait in JASMS. Suggestions ranged from sulfonation of Arginine, HBTU
adducts forming Tmg derivatives, and adding indole to the TFA cleavage
cocktail to mop up trifluoracetaldehyde. The only way I could remove the
+98 adducts was by loading the cleaved peptide onto a C18 SepPak and
washing well with 0.1% TFA and then eluting with 60% ACN. After
lyophilisation I then proceeded to clean up the peptide by HPLC. Putting
the crude cleavage product directly on a RP-HPLC did not remove the adduct.
I finally tracked the problem to a bad bottle of MeOH on my ABI 430A even
though it is used sparingly (or not at all?) for the FastMoc chemistry.
The MeOH had turned a yellow color when I dumped it from the brown reagent
bottle on the synthesiser.
Hope this helps.
Darryl
Hardie
Victoria Protein Microchemistry Centre
Department of Biochemistry and Microbiology
University of Victoria
Victoria B.C. CANADA
Phone: (250) 7218884
FAX (250) 7218855
Webpage http://www.proteincentre.com
Sandy Kielland
Victoria Protein Microchemistry Centre
Department of Biochemistry and Microbiology
University of Victoria
Victoria B.C. CANADA
phone: (250) 7218884
FAX (250) 7218855
Email Kielland@UVic.ca
Webpage http://www.proteincentre.com
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