Hello,

I’ve discussed this with some colleagues (who know more about this than I do!) and it sounds like you are (or should) be looking at peak splittings, whereas that 3J H-HA Coupling dialog is for 3D HNHA data sets where you look at intensity ratios.

(If you want to measure splittings graphically then on a spectrum window if you hold the cursor over the first peak and hit the d key, the position indicator on the tool bar at the top then gives the position relative to that initial location, and you can turn this feature off with the D key.) 

Wayne

> On 15 Mar 2017, at 01:47, Ankur Jalan <[log in to unmask]> wrote:
> 
> Dear Users,
> 
> I have a 2D (z-TOCSY) NMR of my peptide (a 12-mer). I want to calculate the dihedral angles using the 3J H-Ha coupling values I found out from my 1D proton NMR.
> 
> I tried to create a new experiment H{[N]+[HA]} with my TOCSY uscf, and I copied all my assignments to this new experiment. 
> I tried to initialize root resonances and pick & assign from roots. I could not do it. It seems it need N15 2D NMR for that. Is that right? Why am I unable to pick peaks and derive a dihedral angle? I tried to read the posts on this forum and the explanation provided on the CCPNMR to calculate dihedral angles from 3J H-HA coupling, but it did not help. I am confused and a little frustrated with the problems I am encountering while trying to calculate the dihedrals.
> 
> Can anyone please help me? I think some of you must have used 2D proton Z-TOCSY spectra to derive the dihedral angles. It is very critical for me to calculate these dihedral angles to validate the dihedral angles I got through DANGLE in CYANA.
> 
> I will be extremely grateful to you all if you can reply back.
> 
> Best Regards,
> Ankur Jalan
> Graduate Student
> Organic Chemistry
> BYU, Provo, USA