It's probably best to look at the structure separately - using the structural restraints derived from the NMR data - NOE', J-couplings, etc. The 13C shift of glutamate C-delta atoms alone won't give the answer.

It's probably best to look at the structure separately - using the structural restraints derived from the NMR data - NOE', J-couplings, etc. The 13C shift of glutamate C-delta atoms alone won't give the answer.

Maybe it is possible to change the pH, while monitoring NOEs and couplings?

As glutamate becomes protonated, the structural changes may happen as well.well - so it may be both.