We are trying to detect the number of NH signals in a molecule through HSQC in DMSO-d6 where little amount of water also exists. Suppose if the NH protons are exchanging continiously - we could hardly detect through 1D NMR - is it possible to detect the attached less sensitive nuclei like 15N? OR If the NH proton is appering at the same region where aromatic protons also exist, HSQC is observeable?
If the NH is in fast exchange you will not be able to observe. If the NH are slowly exchanging but appear among the aromatic signals the you will be able to observe as protons bound to C12 or C13 will not be observed.
Thank you Aditya Jyoti Basak When a proton is labile it's difficult to see INEPT, that makes sense.
Why don't you try to add a lot of H2O and run 1H-15N HSQC-WET (or smth)?. The chemical balance will shift to NH, and you'll see corresponding cross-peaks
Thank you Andrii Kozytskyi This I wasn't aware. I'll attempt.
Dear Vijayakumar, what we often do to shift the equilibrium of exchangeable H's to one side is to add a drop (2 ul) of TFA to DMSO. This of course does not work if you have a very acid-labile compound.....
Good Luck
Alfred
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