Synthesis and DNA binding properties of 1-(3-aminopropyl)-imidazole-containing triamide f-Im*PyIm: a novel diamino polyamide designed to target 5'-ACGCGT-3'.

A novel diamino/dicationic polyamide f-Im()PyIm (5) that contains an orthogonally positioned aminopropyl chain on an imidazole (Im()) moiety was designed to target 5'-ACGCGT-3'. The DNA binding properties of the diamino polyamide 5, determined by CD, ΔT(M), DNase I footprinting, SPR, and ITC studies, were compared with those of its monoamino/monocationic counterpart f-ImPyIm (1) and its diamino/dicationic isomer f-ImPy()Im (2), which has the aminopropyl group attached to the central pyrrole unit (Py()). The results gave evidence for the minor groove binding and selectivity of polyamide 5 for the cognate sequence 5'-ACGCGT-3', and with strong affinity (K(eq)=2.3×10(7) M(-1)). However, the binding affinities varied according to the order: f-ImPy()Im (2)>f-ImPyIm (1)≥f-Im()PyIm (5) confirming that the second amino group can improve affinity, but its position within the polyamide can affect affinity.