Dear Justin,
Ideally min ppm and max ppm would be set when you first enter the spectrum
and never changed. This requires knowing if you can actually have aliased
peaks and in what region, so the user would have to enter it explicitly.
But to make it easier, Analysis calculates a default settiing for you.
Then, if you pick a peak (or alias one) outside the allowed region,
Analysis automatically expands the allowed region. The user is always
right, if the user says there is a peak there it has to be allowed. In
your case you maybe picked a peak outside the allowed area, or somehow
unaliased or moved one there. Maybe you picked a peak in the TOCSY-HSQC
when you thought is was the 2D TOCSY. That would have the effect you saw.
Or, of course, it could be that picking peaks in the 2D TOCSY or some
other innocuous activity had this as an undesirable side effect. Tim would
be the only one to have an opinion there. These things can go wrong - what
we are trying to do is to get the right settings for you instead of
forcing the users to enter them by hand for every spectrum, and that is
simply not easy.
Yours,
Rasmus
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Dr. Rasmus H. Fogh Email: [log in to unmask]
Dept. of Biochemistry, University of Cambridge,
80 Tennis Court Road, Cambridge CB2 1GA, UK. FAX (01223)766002
On Thu, 20 Oct 2005, Justin T Douglas wrote:
>
> > Are you sure you are seeing a mirror image and not a
> > displaced image?
>
> You are correct. I misspoke. I observe displaced
> images, NOT mirror images.
>
> > Then go to 'Edit Spectra', click 'Referencing', and
> > look under
> > 'Minimum aliased Frequency' and 'Maximum aliased
> > frequency'. for the HNHN> dimension of your
> HSHSQCOTOCSYIf you have no peaks
> > outside the acquired
> > region, reset the frequency limits so that they
> > correspond to the limits
> > of what you have asascuiredYour ghost peaks should
> > then disappear.
>
> Once again you are correct. Resetting min. ppm fixed
> the problem.
>
> I do have one question. Why did Analysis miscalculate
> min ppm for me? Referencing, number of points and
> sweep width were all set correctly.
>
>
>
>
>
>
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