Met methyl assignment with NOESY

Met Methyl Resonance Assignment

Usually, the Met methyl resonance assignment can be obtained from NOESY, however, in a different manner as described above. The Met methyl group has unique chemical shifts with 1H around 2.0ppm and 13C as 17ppm. Therefore, the best way to identify Met methyl is starting from the 13C aliphatic HSQC. It is also recommended to obtain aliphatic side-chain assignment before pursuing the following approach.

1. Same as above, process the simultaneous NOESY, make a 2D 13C HSQC project plane for the NOESY, generate a starting simultaneous NOESY PeakList from a AtomList with Met methy chemical shifts.
2. In XEASY, load the 3D NOESY PeakList to the 2D 13C aliphatic HSQC or the 2D 13C HSQC projection plane, type in the dimention names as below in the pop-up window.
   <img src="%ATTACHURLPATH%/3d2d.jpg" alt="3d2d.jpg" width='389' height='147' />
   use pp to manually pick the possible Met methyl peaks in the 2D spectrum, use wr write the update NOESY PeakList.
3. In XEASY, load the two copies of 3D NOESY and the updated 3D PeakList; use sp, es, se, gs to create and display strips from Met residues in two orthogonal views; use sp, se to create addtional strips for these manually unassigned peaks. Note: All the other peaks from the NOESY are simulated and assigned; type in n= and =n when the window below pop up.
   <img src="%ATTACHURLPATH%/strip1.jpg" alt="strip1.jpg" width='388' height='120' />
   
4. In XEASY, use cd, cc to identify these unassigned peaks to the corresponding Met methyl group, use mr to adjust the simulated Met methyl peaks to the assign position, use dp to delete the manually picked peaks that are aready indentified.
5. In XEASY, use aa, ac, wc and wp to save updated AtomList and PeakList.

-- Main.GaohuaLiu - 30 Jan 2008