The NQ-Flipper page V2.7

Welcome to CAME's NQ-Flipper home page. NQ-Flipper recognizes unfavorable rotamers of Asn and Gln residues in protein structures. This service is applicable to structures obtained from X-ray crystallography, NMR or modeling studies. The method is based on knowledge-based potentials of mean force compiled from a database of known protein structures determined by X-ray crystallography. The potentials are then refined by several cycles of rotamer correction and recompilation of potentials. The refined potentials are used here to validate or correct asparagine and glutamine amide rotamers.
To identify and correct improper rotamers, enter the PDB four letter code (e.g. 1ra9) or upload your own PDB formatted file. Hitting the "Validate Structure" button executes the program, displays the structure and highlights the residues that need to be corrected. (Please have Java and JavaScript enabled in your web browser.)
Usually, there is no need to change any of the parameters. However, if you want to explore your structure in more detail, please find a detailed description of the parameters here.
NQ-Flipper V2.7 has quadrupled in speed and finally displays interactions to crystal neighbors. You also benefit from this on your own machine, simply download the program.
PDB code: File name:
Model number: Altloc indicator:
Consider Asparagine (ASN)
Glutamine (GLN)
Histidine (HIS) [This feature is under development.]


Weichenberger, C. X., Byzia, P., and Sippl, M. J. (2008) Visualization of unfavorable interactions in protein folds.
Bioinformatics., 24, 1206-1207. [Abstract (HTML)] [pdf]
Weichenberger, C. X., and Sippl, M. J. (2007) Recognition and Correction of Erroneous Asparagine and Glutamine Side Chain Rotamers in Protein Structures.
Nucleic Acids Res., 35(Web Server issue), W403-406. [Abstract (HTML)] [pdf]
Weichenberger, C. X., and Sippl, M. J. (2006) NQ-Flipper: Validation and Correction of Asparagine/Glutamine Amide Rotamers in Protein Crystal Structures.
Bioinformatics, 22, 1397-1398. [Abstract (HTML)] [pdf]
Weichenberger, C. X., and Sippl, M. J. (2006) Self-consistent Assignment of Asparagine and Glutamine Amide Rotamers in Protein Crystal Structures.
Structure, 14, 967-972. [Abstract (HTML)] [pdf]

This site is maintained by Chris Weichenberger. Please send comments and suggestions to:
Flipper-address Valid HTML 4.01 Transitional