>I have been attempting to set up a 1H/15N hmqc on a
>DRX-400 running xwinnmr 2.0. I did it by calling in
>the standard Bruker parameters for a 1H/13C hmqc and
>then using edasp to change the nucleus for the second
>dimension to 15N. The experiment worked but I ran
>into problems when I tried to calibrate the chemical
>shift scale for the 15N dimension. The SF value for
>the 15N dimension always sets itself back to 100MHz
>(the 13C frequency) even if I go into edp and explicitly
>set it 40.5MHz(the 15N frequency).
>Does anyone know how to work around this problem?
I seem to recall similar problems under UXNMR due to the 'intelligence' of
the software. 15N has a negative gyromagnetic ratio which makes it a little
harder for 'intelligent' software to adjust to. I seem to recall that under
UXNMR it is necessary to make sure that 15N and 15N parameters are
explicitly expressed everywhere, even where it does not seem necessary. Just
go through eda and edp completely with this in mind and it should work out.