Journal of Biomolecular NMR

, Volume 44, Issue 4, pp 213–223 | Cite as

TALOS+: a hybrid method for predicting protein backbone torsion angles from NMR chemical shifts

  • Yang Shen
  • Frank Delaglio
  • Gabriel Cornilescu
  • Ad BaxEmail author


NMR chemical shifts in proteins depend strongly on local structure. The program TALOS establishes an empirical relation between 13C, 15N and 1H chemical shifts and backbone torsion angles ϕ and ψ (Cornilescu et al. J Biomol NMR 13 289–302, 1999). Extension of the original 20-protein database to 200 proteins increased the fraction of residues for which backbone angles could be predicted from 65 to 74%, while reducing the error rate from 3 to 2.5%. Addition of a two-layer neural network filter to the database fragment selection process forms the basis for a new program, TALOS+, which further enhances the prediction rate to 88.5%, without increasing the error rate. Excluding the 2.5% of residues for which TALOS+ makes predictions that strongly differ from those observed in the crystalline state, the accuracy of predicted ϕ and ψ angles, equals ±13°. Large discrepancies between predictions and crystal structures are primarily limited to loop regions, and for the few cases where multiple X-ray structures are available such residues are often found in different states in the different structures. The TALOS+ output includes predictions for individual residues with missing chemical shifts, and the neural network component of the program also predicts secondary structure with good accuracy.


Heteronuclear chemical shift Secondary structure Order parameter Dynamics TALOS 



We thank Alex Grishaev for carrying out the MSG calculation with the new TALOS+ backbone angle restraints. This work was funded by the Intramural Research Program of the NIDDK, NIH. G.C. was supported by NIH grants P41RR02301 (BRTP/NCRR) and P41GM66326 (NIGMS)

Supplementary material

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Copyright information

© US Government 2009

Authors and Affiliations

  • Yang Shen
    • 1
  • Frank Delaglio
    • 1
  • Gabriel Cornilescu
    • 2
  • Ad Bax
    • 1
    Email author
  1. 1.Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney DiseasesNational Institutes of HealthBethesdaUSA
  2. 2.National Magnetic Resonance FacilityMadisonUSA

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