I've used a final deprotection protocol for Fmoc Pept Synthesis for
several years and now, i'm having some problems in deprotecting PMC
group from Arg and some tBu from other aminoacids like Ser, Cys or
Thr, identified in Mass Spec.
I always used TFA: Anisol: EDT: Water at 85: 5: 3: 7 (and in
presence of Cys, i use TIS at 5%) for 6-8 hs (is that too long?),
then i extract it with ACOH 95%.
Have someone faced some problems like this also? How could i solve
it? Changing some scavengers or deprotection time, would help? Is it
some problem with some of the deprotection reagents?
another question:
i'm (still) not a peptide synthesizer expert, and i'm having a
"priviledge" to choose some peptides to synthesize. Actually i
received a big list of peptides (9-15 aa) to be done and i can
"eliminate" some of them that, by overlooking to the sequence, would
be "more difficult" to be synthesized. What sequences would you
eliminate first? I know that some sequences, changing the protocol
would make them "easier" to be done.
Anyways, when you look at a sequence of aminoacids, what sequences
makes you "scared"? For example, penta-alanines, long sequences of
hydrophobic aminoacids, presence of prolines etc.
For both questions, any sugestions, coments and critics will be very
welcomed. Thank you in advance,
Leo
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Leo Kei Iwai - Chemist
Dept of Biophysics
Escola Paulista de Medicina - EPM - UNIFESP
Lab of Transplant Immunology
Instituto do Coracao - Incor - FMUSP
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