The volume of overlapping peaks

I have a lot of peaks in NOESY that overlap and form piles. When I try to get the volume using “Estimate current peak volume”, it counts the volume of the entire pile.

I would really appreciate it if someone could help me figure out how to solve this.


it depends a bit what you mean with “overlap” and “piles”.

If you have several peaks directly on top of each other, then you simply calculate the volume of that whole peak, but assign it to the multiple atom pairs which contribute towards that peak. Your structure calculation program will then try to work out how much of that volume belongs to each contributing pair of atoms.

If you have several peaks which are not directly on top of each other, but fairly close, so they form shoulders of one another or just merge a bit, then things start to become more complicated. If it is clear that there are simply two or three peaks which are slightly merged, you can place three peaks and then fit them together using right-mouse menu / Refit Peak Group (shortcut RG). It’s always worth having a look at how good the fit it, by setting the Peak Symbol to Filled Linewidths (either cycle through the different PeakSymbols using shorcut PS) or set it directly in the SpectrumDisplay Settings (gear icon in the top left corner). Sometimes, it is worth doing RG multiple times till you get a good fit, as the starting position does affect the fit.

If, however, you have lots of peaks that are merged into one large pancake, then it may be impossible to get accurate volumes (or even peak positions). In that case you may need to consider whether you can use these peaks in your structure calculation at all - and sometimes you can’t. Alternatively, you can try to doing the structure calculation using peak heights rather than volumes (you then have to do that for all peaks, not just some!).
Otherwise, you could try to process your spectra differently or get higher resolution data so that you can start to identify the peak positions and volumes correctly.