x 10 5 M -1 for the E isomer, whilst the affinity of the Z isomer for the same G4 was 25-fold lower, Ka = 0.08 x 10 5 M -1 (Figure ). Whilst the affinity of the active E isomer 1 is lower than for the stiff-stilbene analogue (Ka = 25 and 0.1 x 10 5 M -1 for E and Z isomers, respectively)