All 30 bicyclic systems were subsequently subjected to pair-wise comparisons using a range of standard 2D similarity measures, together with the 3D-based ESP-Sim measure. A summary of the results obtained from each method is reported in Table . For completeness, the results using four different anchor fragments (hexazine, carboxylic acid, piperidine and iodine) are shown in Figure . The heat-maps are essentially the same indicating that the method is not dependent on the choice of anchor fragment.