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Updated: Aug 9, 2026

LERLIC-MS/MS for In-depth Characterization and Quantification of Glutamine and Asparagine Deamidation in Shotgun Proteomics
Published on: April 9, 2017
NQ-Flipper: validation and correction of asparagine/glutamine amide rotamers in protein crystal structures
Christian X Weichenberger1, Manfred J Sippl
1Center of Applied Molecular Engineering, University of Salzburg, Jakob Haringerstrasse 5, 5020 Salzburg, Austria.
Abstract:
The error rate of asparagine (Asn) and glutamine (Gln) amide rotamers in protein crystal structures is in the order of 20% and as a consequence the current Protein Database (PDB) contains approximately half a million incorrect Asn and Gln side-chain rotamers. Here we present NQ-Flipper, a web service based on knowledge-based potentials of mean force to automatically detect and correct erroneous rotamers. We achieve excellent agreement with expert curated data.
