Reply to: Re: peptide synt: deprotection problems
Roger,
I just want to point out that "Reagent K" was developed by David King at =
UC, Berkeley not Gregg Fields (the "K" stands for King). So, please give =
credit where credit is due.
Mike Brasseur
Tularik Inc.
brasseur@tularik.com
Roger Murphy wrote:
>Dear Leo,
>
>I have used Greg Fields' "Reagent K" for many years with great success
>(ref. King et al., Int. J. Pept. Prot. Res., 36, 255-266, 1990), except
>where only tBu groups need to be removed, in which case straight 95% TFA/=
5%
>water works fine.
>
>With regard to your sequences, you should get a copy of a program like
>Peptide Companion (from CoshiSoft, San Diego), which has a predictive
>algorithm for looking for possible problem sequences. I've always found =
it
>to be a useful guide. Generally, long stretches of hydrophobic residues
>will cause aggregation problems, particulalrly multi-Ala sequences. =
These
>problems usually are most pronounced 5-15 residues into the synthesis. =
The
>Pro residues can actually be helpful in breaking up hydrophobic
>interactions by putting a kink into the growing peptide chains, but too
>many Pros will be a problem in themselves.
>
>If you haven't got a copy already, I would suggest you ask your local
>Novabiochem agent for a copy of their Catalogue & Peptide Synthesis
>Handbook - it has a great section of technical notes on synthesis, and it'=
s
>free!
>
>Hope all this helps - if you're really desperate you could send me the
>sequences you've been asked to look at, and I'll run them through Peptide
>Companion myself. That's not a general invitation to everyone to do so
>though!
>
>Good luck and best wishes,
>
>Roger
>
>
>At 08:45 AM 16-07-98 -0300, you wrote:
>>Dear all,
>>
>> 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
>>
>>----------------------------------------------------------
>>Leo Kei Iwai - Chemist
>>Dept of Biophysics
>>Escola Paulista de Medicina - EPM - UNIFESP
>>Lab of Transplant Immunology
>>Instituto do Coracao - Incor - FMUSP
>>----------------------------------------------------------
>> =
>
>
>Roger Murphy, Ph.D.
>Biological Production Facility
>Ludwig Institute for Cancer Research
>Austin & Repatriation Medical Centre
>Studley Road,
>Heidelberg, Vic. 3084
>Australia.
>
>Tel 61-3-94965463
>Fax 61-3-94965436
>Email murphy_r@licre.ludwig.edu.au
>
>
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>Old-To: "Leo Kei Iwai" <leo.biof@infar.epm.br>
>From: Roger Murphy <murphy_r@licre.ludwig.edu.au>
>Subject: Re: peptide synt: deprotection problems
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Reply to: Re: peptide synt: deprotection problems
Roger,