I have a question just for curiosity, on which probably one of you has the
answer for me.
During the last two weeks I have done some sequencing work on
O-glycosylated peptides (at Thr as well as on Ser). The GalNAc-Ser
resulted in a peak with a fronting shoulder right before Asn, while
GalNac-Thr resulted in two peaks, one directly before (unglycosylated) Ser,
one between (unglycosylated) Thr and Gly (all work with fast standard
gradient using A3 and B2 on ABI 473A). So far, so good.
What I do not understand are several additional peaks I observe when
there's an unmodified Ser. While there's the PTH-Ser in agreement with the
standard, there is one peak directly in front of Arg (according to the
Standard gradient diagram on the Premix fact sheet, this is most likely
Ser') and two further peaks eluting between Tyr and Pro. The earlier one of
these two has approximately one third of the intensity of the later one and
their intensity is comparable to the Ser' signal. Does anybody of you have
an idea about their origin? Is it a side reaction of the Ser or Ser'? If it
is, is there a way to prevent this to get a more sensitive Ser detection?
Any hints will be greatly appreciated. Thanks in advance.
Yours sincerely,
Marcus Macht
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Dr. Marcus Macht
University of Cologne
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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