Completion of a programmable DNA-binding small molecule library

Hairpin pyrrole-imidazole (Py-Im) polyamides are programmable oligomers that bind the DNA minor groove in a sequence-specific manner with affinities comparable to those of natural DNA-binding proteins. These cell-permeable small molecules have been shown to enter the nuclei of live cells and downregulate endogenous gene expression. We complete here a library of 27 hairpin Py-Im polyamides, which bind seven-base-pair sequences of the general form 5′-WWGNNNW-3′ (where W=A or T, N=W, G, or C). Their equilibrium association constants (Ka) range from Ka=1×108 to 4×1010 M−1 with good sequence specificity. A table of binding affinities and sequence contexts for this completed 27-member library has been assembled for the benefit of the chemical biology community interested in molecular control of transcription.