Thomas,
The back of the Novabiochem catalog (an excellent
reference source) recommends a cocktail of TFA:
Water:EDT:TIPS in a ratio of 94.5:2.5:2.5:1
respectively. TIPS is Triisopropylsilane (aka TIS).
See pgs P14-P15 of their Y2K catalog.
Not as skunky as reagent K.
Regards,
Steven R. Johnson, B.S. Chem
Research Associate, Chemistry/Chemical Development
Biomeasure, Inc. Milford, Massachusetts
--- "Carter, Mark" <MCarter@axcellbio.com> wrote:
> Thomas,
>
> Purple is most likely the color of the carbocations
> liberated by your Trt
> blocker. But that should fade to pale yellow when
> you add ether or water.
> Of course the color could also be from degradation
> of your Trp to indole,
> but that shouldn't run with your peptide on HPLC.
> Do you have MS or AAA
> data on your peak.
>
> I'm guessing you've got the wrong cleavage reagent.
> You'll have to remind
> me what's in Reagent B, since I always use Reagent R
> for cleavage
> (TFA:anisole:thioanisole:EDT). You might try using
> tBoc protected Trp, or
> indole as a scavenger. But offhand I suggest using
> stinky Reagent K or R
> for your cleavage. In a fume hood they smell just
> fine ;)
>
> Mark
>
> -----Original Message-----
> From: Thomas Weber [mailto:thomas.weber@mssm.edu]
> Sent: Wednesday, May 09, 2001 9:37 AM
> To: Recipients of ABRF List
> Subject: PepSyn
>
> I synthesized the following peptide with Fastmoc
> chemistry on rink amide
> resin:
>
> H W Y D S F V P W G H Q C
>
> H, Q, C were protected as Trt
> D,S,Y as tBu
>
> when I deprotect in reagent B (50mg 500ul reagent B,
> r.t.) the solution
> turns dark yellow to brown and the resin purple.
> After evaporation of
> the cleavage mixture and precipitation with ether a
> purple precipitate
> remains. HPLC shows mostly one peak, but the purple
> color comigrates
> with this. The problem gets worse on prolonged
> deprotection (>2hrs).
>
> 1) Does anyone know what the purple color is ?
> 2) any suggestions how to fix this, preferably
> without using noxious
> reagents like reagent K ?
>
> thanks
>
>
> Thomas
>
> --
> Dr. Thomas Weber
> Institute for Gene Therapy and Molecular Medicine
> Box 1496
> Mount Sinai School of Medicine
> 1425 Madison Avenue
> New York, NY 10029-6574
> United States of America
>
> Phone (office): (212) 659 8293
> Phone (lab): (212) 659 8299
> Fax: (212) 849 2437
> e-mail: thomas.weber@mssm.edu
>
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