home contents changes options help

Heteronuclear Sidechain assignment

We will assume a partially or fully mapped backbone assignment (HN,N,CA,CB) as detailed in the "Heteronuclear Backbone Assignment Tutorials":HeteronuclearBackboneAssignment

Working with HCCH-type spectra: HC(C)H-TOCSY, (H)CCH-COSY etc...

You need to generate the anchors HA-CA and HB-CB: Open the !15N-resolved -[1H,1H]-NOESY or -[1H,1H]-TOCSY or a HNHA or HNHB with PolyScope and pick prospective HA and HB spins in the H-N towers. This will generate HA-CA and HB-CB anchors in the PolyScope(HSQC13C). Check whether they appear at locations that have signals. You can use "gr" or "gs" to jump to the correlations for the residue in question.

Now that you have anchors HA-CA and HB-CB, you can use SystemScope to extend into the sidechain.

Pick and assign new spins in SystemScope, as described on SystemScope's page.

You can open in parallel additional windows, e.g. a second SystemScope in which you display a (H)CCH-COSY. As soon as you assign a HA in the first window, the new anchor HA/CA becomes available in the second one, and you can use it to determine additional 13C shifts. Then switch back to the HC(C)H-TOCSY again to get the HB.

A second SystemScopeRotated? in which you display a (H)CCH-COSY oriented so that the 13C,13C-anchors are avaliable and the 1H dimension along the strip axis is an alternative to the HC(C)H-TOCSY for getting 1H assignments.

Use HomoScope to check and adjust your assignments in HSQC-spectra. Furthermore, it will allow you to complete spin pairs and find unpicked systems.

Working with HCCONH-type spectra: (H)CCONH, H(C)CONH etc...

Peak pick the sidechain spins of each H-N strip in PolyScope (offset -1: e.g. CG-1, CD-1 ...). Use the chemical shift statistics for the expected preceeding residue to make educated guesses.

After you have picked all the sidechain spins, copy the projected spins (e.g. CG-1) to their origin system (CG) using the script CreateOriginSystemsFromProjectedSpins.lua. This will create the predecessor systems if they don't exist yet, and copy all the spins to their origin system. Check your guesses by using "gr" or "gs" in HomoScope(HSQC13C). You should see resonances there!

BACK: HeteronuclearBackboneAssignment

NEXT: HomonuclearAssignment