On Wed, 3 May 2006, Vicky Higman wrote:
> I seem to have several Leucines where both delta carbon resonances are called
> Cda although they have different chemical shifts. I tried de-assigning and
> then re-assigning them to Cda and Cdb, but they still both end up as Cda. I
> then tried de-assigning the H atoms as well, but I still end up with being
> able to assign the H atoms as Hda and Hdb, but the carbon atoms both being
> Cda.
> Does anyone have any suggestions as to what may be going wrong?
It could be down to how your experimental prototypes are set up for the
experiments you're making the assignments in. By default, things like the
HCCH_TOCSY prototype do not necessarily associate the right dimensions of
your experiment with the appropriate dimensions of the experimental
prototype. The information about which atoms are only one bond apart (and
should therefore have their a or b ness determined by the H chemical
shift) is then not correctly communicated to the program and the situation
you see arises. Look carefully at the Main:Experiment->Experiment Types
popup for the experiment where you are making the assignment (and possibly
Experiment Prototypes).
For a typical HCCH_TOCSY recorded the way I've seen most often
H(t1,3)->C(t2,2)-TOCSY->C()->H(acquisition,1)
with dims in AZARA order indicated by the number after the comma.
The full type should be HC_cH.TOCSY but the Reference Dimensions bit needs
to be adjusted so that Exp Dim 1 -> Ref Exp Dim 3 (Ref Measurement 4). The
other dims should sort themselves out.
There are several types of experiments where this type of mapping becomes
an issue, so it is worth paying a little attention to how you attribute
experiment prototypes as you load a spectrum, HcccoNH comes to mind.
Because of the different numbering strategies, careful thought about the
Experiment Prototype and the dimension ordering are initially required not
to end up with a fried brain, but once you get it it's simple.
Brian
--
Dr. Brian O. Smith ---------------------- B Smith at bio gla ac uk
Division of Biochemistry & Molecular Biology,
Institute Biomedical & Life Sciences,
Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, UK.
Tel: 0141 330 5167/6459/3089 Fax: 0141 330 8640
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