Electrostatic potentials mapped onto Nitrosamine molecules Physical chemists are becoming increasingly interested in understanding the differing potencies of toxic and carcinogenic groups of small molecules. Differing biological activities of similar molecules depend in part upon differences in electronic properties, and these may be calculated using quantum mechanics. However the enormous numerical output of such calculations does not lend itself readily to comprehension by the non-specialist. In collaboration with the Physical Chemistry Laboratory at Oxford University, computer graphics techniques are being developed to draw the results onto the space-filling representations of molecules which are familiar to chemists. This model shows the mapping of electrostatic potential onto two of a series of carcinogenic nitrosamine molecules. Two orthogonal views are shown of each molecule; the potential is shown as a scale from negative (red) through neutral (green) to positive (blue). Studying such molecular series, depicting a number of calculated quantum mechanical properties, allows the formulation of hypotheses to account for the observed activities.