Dear NMR Wiki'ers
I am identifying aminoacid residues or assignment of protein from following 3D NMR experments
HNCA/HNCOCA - Glycine (45 ppm )
CBCANH/CBCACONH - Alanine (52-CA , 19 - CB ), Serine,threonine - ( CA-58.57 , CB - 64 or 70 )
HBHACONH - Alanine , valine give (HB,HA all positives ) , glycine - (HA all negatives ) and serinie ,threinine - single postive on 700 vnmrj
apart from above aminioacid residues Could you please give any information about aminoacid residue identification by using 3d nmr experments .
If you are using the experiments you listed above to do sequence-specific resonance assignments, then you have already listed the "signpost" residues Ala, Gly, Ser, and Thr. Those four are really the only four residue types that are clearly obvious when simply visually inspecting the spectra. However, it is indeed possible to make an educated guess as to the residue type for other spin systems by using chemical shift statistics compiled for a large number of assigned proteins. You can find these chemical shift statistics on the BMRB webpage. The chemical shifts of H, N, and C crosspeaks in your spectra can be compared to the "average" chemical shift values for those atom types in a large number of proteins, and you can use the comparison to include or exclude possible residue types for a spin system. Note however that statistics, while generally helpful, are not a silver bullet. If you are unsure as to the residue type for a given spin system, the chemical shift statistics can be helpful, but you should really look for other experimental evidence to confirm or refute your best guess. Good luck!
answered May 19 '11 at 11:02