I have seen similiar things happen (unusually low resin weight gains) when I
use "old" DMF (>2-3 months) to prepare the HBTU/HOBT solution. Preparing
the HBTU/HOBT solution using a newly opened bottle of DMF makes the problem
go away (I don't use ABI's HOBT/DMF solution, I make up my own). Maybe the
organic chemistry gurus can out there can verify this, but I believe that as
DMF ages, it can degrade into formaldehyde, which could then cap the resin
during the coupling step.
Russ
--On Mon, Sep 27, 1999 10:18 AM -0400 "Jeni Lauer-Fields"
<jlauer@ACC.FAU.EDU> wrote:
> Hello,
>
> I have some questions for the synthetic experts out there. The last two
peptides
> we've made have totally bombed. We're seeing an incredible amount of resin
> capping. I blamed the first failure on the presence of water in the
HOBt/HBTU
> bottle or the DIEA bottle (both were changed just prior to synthesis). I
remade
> the solutions with new dry bottles and the second synthesis was even
worse. The
> good news is that we're incorporating a Lys(Dnp) residue so I can tell by
> looking at the resin that something went awry (not yellow enough). The bad
news
> is that I can't tell from the monitor trace that there is a problem. A
very
> small portion of the resin is synthesized to completion (as verified by
MS).
>
> My questions are:
> 1) Am I wrong in thinking that water did this? Could it be something else?
> 2) We've opened no new reagents lately, so my guess is that something has
gone
> bad. What is the most likely culprit? Our HOBt is the oldest, with HBTU
second.
> The pip and DIEA are turned over so often they're never more than a month
or two
> old.
>
> Thanks in advance for your assistance.
>
> Jeni
>
>
> Janelle Lauer-Fields
> Department of Chemistry & Biochemistry
> Florida Atlantic University
> 777 Glades Road
> Boca Raton, Florida 33431
> 561-297-2094/Fax 561-297-2759
>