Other hybridization prediction algorithms are available on the Internet. However, when we compared the delta G predictions obtained from IDT Oligo Analyzer (http:// eu.idtdna.com/analyzer/Applications/OligoAnalyzer/), which uses a proprietary algorithm, with our experimental data, the correlation was poor (Supplementary Figure 2) . Although the exact experimental conditions (3M TMAC and 45 C) were not represented, this is not likely to have caused the low correlation.