RCDI/eRCDI: a web-server to estimate codon usage deoptimization

BACKGROUND: The Relative Codon Deoptimization Index (RCDI) was developed by Mueller et al. (2006) as measure of codon deoptimization by comparing how similar is the codon usage of a gene and the codon usage of a reference genome. FINDINGS: RCDI/eRCDI is a web application server that calculates the Relative Codon Deoptimization Index and a new expected value for the RCDI (eRCDI). The RCDI is used to estimate the similarity of the codon frequencies of a specific gene in comparison to a given reference genome. The eRCDI is determined by generating random sequences with similar G+C and amino acid composition to the input sequences and may be used as an indicator of the significance of the RCDI values. RCDI/eRCDI is freely available at http://genomes.urv.cat/CAIcal/RCDI. CONCLUSIONS: This web server will be a useful tool for genome analysis, to understand host-virus phylogenetic relationships or to infer the potential host range of a virus and its replication strategy, as well as in experimental virology to ease the step of gene design for heterologous protein expression.