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3D HSQC-TOCSY-NOESY-HSQC experiment [1] designed for 15N labeled proteins with poor dispersion of 1H chemical shifts and correlates chemical shifts of amide 15N with those of 1H and 15N atoms of nearby (most often sequential residue's) amide group.

Coherence follows the following pathway: H15N -- inept --> H15N (ω1) -- inept --> H15N -- TOCSY --> Hα -- NOE --> H15N -- inept --> H15N (ω2) -- inept --> H (ω3)15N

Two of the three dimensions record 15N chemical shift which can still be well dispersed when 1H chemical shift is not. HSQC-TOCSY-NOESY-HSQC works best with β-sheet proteins where TOCSY transfer H-N-Ca-Ha is more efficient.

Zhang et. al [1] used this experiment to aid sequential assigment of partially unfolded state of 59-residue drk SH3 domain. About 40% of residues of those that displayed sequential connectivities in the folded state did so in the unfolded state. Experiment was recorded for 65 hours using 1 mM sample where protein about equally populated the folded and partially unfolded state.

3D hsqc-tocsy-noesy-hsqc nmr experiment


  1. Zhang, O and Kay, LE and Olivier, JP and Forman-Kay, JD. Backbone 1 H and 15 N resonance assignments of the N-terminal SH3 domain of drk in folded and unfolded states using enhanced-sensitivity pulsed field gradient NMR techniques. Journal of Biomolecular NMR 4(6):845--858, 1994. BibTeX [zhang94]
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