Re: ProtSeq: Additional Peaks for Ser?
Ricardo Bastos Cunha (rbcunha@unb.br)
Wed, 08 Sep 1999 15:10:02 -0300
Marcus Macht wrote:
> 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.
I've seen the two Ser peaks eluting between Tyr and Pro. I don't know
what side reaction is, but the cycle was undoubtedly a Ser cycle.
According to the costumer, the protein was not glycosylated. But we
never know...
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Prof. Ricardo B. Cunha
Brazilian Center for Protein Research and Services - CBSP
Laboratory of Protein Chemistry and Biochemistry
Departament of Cell Biology
University of Brasilia
Brasilia - DF Brazil
CEP 70910-900
Tel: 55-21-61-307-2142
Fax: 55-21-61-272-4548
mailto:rbcunha@unb.br
http://www.lbqp.unb.br/ricardo
http://www.unb.br/cbsp
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