A colorimetric competitive displacement assay for the evaluation of catalytic peptidesElectronic supplementary information (ESI) available: Experimental procedures, NMR and MS spectra. See DOI: 10.1039/c7ob02032e

An indicator displacement assay has been adapted to detect the diol products of the aldol reaction between 4-nitrobenzaldehyde and hydroxyacetone in crude reaction mixtures. This provides a rapid colorimetric method of detecting product formation and thus evaluating potential catalysts, which is demonstrated using multiple catalytic peptides. An assay based on competitive dye displacement was adapted to detect the formation of aldol product in crude reaction mixtures, and was used to evaluate minimal peptide aldol catalysts.