I am not sure if it is the same problem, but I already got 0% of the
desired product but instead a +96, and a +201 adduct and in my case, it
seemed it was TFA adduct and HMP/TFA adduct added to the two unprotected
trp that I had in my sequence. I synthesized it again with protected trp
and cleaved and deprotected using new bottles of reagent
(TFA/EDT/Thioanisole) and I got more than 85% of the desired product.
I hope this will help,
Sylvie
*****************
>I have made a peptide with an N-terminal
>serine. I left the Fmoc on and removed
>the protecing groups and resin. The
>LC/MS ( API-100 electrospray) shows a
>peak (about 90% pure) with a molecular
>ion showing the Fmoc on. I dissolved
>the peptide ~40mg in 2ml DMF and added
>500ul of piperidine. Shake for 5 minutes
>and precipitate and wash with
>t-butylmethyl ether. LC/MS now shows
>four peaks:
>1. about 35%-Correct mw wtih Fmoc
>removed.
>2. About 15% Mw +96 above the correct
>molecular weight.
>3. About 45% Mw +201 above the correct
>molecular weight.
>4. About 5% Mw +199 above the correct
>molecular weight.
>
>HELP!!
Sylvie Bourassa Ph.D.
Service de Sequence de Peptides de l'Est du Quebec (SSPEQ)
CHUL Research Center Room 9750
2705, Laurier blvd
Ste-Foy, Quebec
Canada G1V 4G2
phone 418 656-4141 ext 7088
fax 418 654-2159
Email: sspeq@crchul.ulaval.ca