Chirality errors in nucleic acid structures

The prevalence of errors as opposed to true anomalies in protein structures was discussed in Correspondence last year. We have analysed the nucleic acid structures in the Brookhaven Protein Data Bank using a simple automatic procedure (program available at http://www.mbi.ucla.edu/people/peter/chiral.html) to determine the configurations at tetrahedral chiral centres. It appears that a number of structures containing significant “chirality errors that no-one would argue with” have made their way into the data bank.