We encountered this problem some time ago in our lab as well using BigDye
chemistry. As far as we could figure out, it seems to be sample related
because we had particular samples with virtually no T's inside (while all
other bases were o.k.) in the direct neighbourhood of samples which looked
fine. It also seems to be related to signal intensity because we observed
it primarily with weak signal samples (signal intensity approx. below 70).
We still could not figure out where it originated from. We also contacted
PE, Qiagen and Macherey-Nagel if they have any idea about its origin (all
afflicted samples had been prepared with PlasmidPrep-kits of the latter two
vendors while samples worked up by precipitation methods seemed to be
o.k.), but they all have never heard of this problem before.
Fortunately, the problem disappeared after a short while by itself a didn't
show up again yet.
Since I know the problem and can't give an answer about its origin and how
to solve it, I would also be interested if it was observed by other groups
as well and if so, if anybody could bring some more light into the dark.
Yours sincerely,
Marcus Macht
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Dr. Marcus Macht
Centre for molecular medicine - Service laboratory
Joseph-Stelzmann-Str. 52
50931 Cologne, Germany
Tel.: +49 221 478-6995
Fax: +49 221 478-6977
e-mail: Marcus.Macht@uni-koeln.de
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