Re: Repeat of Mystery peak question
Dan Brune (DBrune@asu.edu)
Tue, 05 May 1998 18:26:19 -0700 (MST)
Dear Sandie,
In view of the lack of response to your question about the mystery
peak, I thought I might reply with a few suggestions, even though I do not
have any definite answer. Occasionally, I have seen a peak with the
retention time of Thr when the main peak is due to Met, and therefore
suspect that methionine sulfoxide has the same retention time as Thr. From
your comment that the problem is sample-independent, I doubt that this is
causing the problem. Another possibility that occurs to me is that when
the sequencer first starts running, there might be oxidized impurities of
some sort in the teflon lines, since teflon is highly permeable to oxygen.
Still, I have not seen this problem with my Beckman (Porton) sequencer.
Another possiblity might be that one of the delivery valves downstream from
S1 (ethyl acetate) has a torn diaphragm, and allows some impurity to
accumulate there and undergo some type of side reaction while the
instrument is standing idle. Thus, you might want to inspect the R3, R2,
and R1 delivery valves to see that they are in good shape if you haven't
done so already. I suppose that by the same logic, problems with the
valves for delivering R4 or S2 could also be at fault. Again, I have not
seen the problem that you described with my instrument, even with a bad
valve, and I would be curious to learn what actually solves the mystery
peak problem once you manage to figure it out.
Good luck,
Dan Brune
>Here's a repeat of the question for those of you who missed it.
>
>Dear Members,
>
>We have been getting a junk peak at the same time as Thr in our
>Porton/Beckman LF3000. It is largest in the first amino acid cycle and
>quickly decreases in subsequent cycles. Any ideas what might be causing
>it?
>
>P. S. It is a good shaped peak(to Mark Crankshaw)
>
>Sandie Smith
>Protein Microanalysis Facility,
>Institute for Cellular and Molecular Biology
>University of Texas, Austin, Texas 78712
>Email: sandie@mail.utexas.edu
>Phone: 512 471-3741, Fax: 512 471-2149