I'm not sure if this is a designed feature, but it caused me a lot of
frustration. For non-stereospecific assignments of prochiral Me-groups
of Val and Leu residues atom names are Cga, Cgb, Hga*,Hgb* or Cda*,
Cdb*, Hda*, Hdb*. My understanding is that Hga* is connected to Cga,
Hgb* is connected to Cgb and so on. So when I don't know the
stereospecific assignment I simply assign Hga*/Cga to one Me group and
Hgb*/Cgb to another. However this turned out to be impossible to do in
some cases because a and b are being swapped automatically depending on
the chemical shift. To give an example, I have a Val residue with Me
shifts 1.21 and 0.85 ppm. I want 1.21 ppm to be Hga* to match Cga, so I
pick the pick the peak at 1.21, create new resonance for the
contribution and assign it to Hga*. Then I pick the peak at 0.85 ppm,
create new resonance for the contribution and assign it to Hgb*. But as
soon as I click on Hgb* for the 0.85 contribution, the resonance
assignment is automatically swapped, so 0.85 is assigned to Hga* and
1.21 to Hgb*. If this is an intended behavior, I can't see how I can
pair Cga and Hga*, in which case having a and b seems useless. I can
arbitrary assign them to stereospec atoms, but this again makes a and b
redundant. Could anybody comment on the good way to deal with the
prochiral centres, please.
Cheers
Igor
--
Dr. Igor Barsukov
Biological NMR Centre,
University of Leicester
PO Box 138,
University Road,
Henry Wellcome Building,
Leicester LE1 9HN
UK
E-mail: [log in to unmask]
Tel: +44 (0)116 229 7098
FAX: +44 (0)116 229 7053
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