Fig. 2

Extent of biochemical space. Fraction (Y axis) of Fragments derived from the space of all possible chemicals that are not found in actual metabolites, compared to the fraction that would be expected not to be found in the same number of chemicals sampled at random from the chemical space of possible metabolites, plotted as a function of fragment size (N – X axis). Blue squares – fraction of fragments not found in actual metabolites. Red circles – fraction not found in an equivalent size collection of random molecules. Panel a: fragments not found in the ‘core metabolism’ of 611 molecules represented in the ExPasy metabolic map. Panel b: Fragments not found in the ~45,000 unique molecules listed in the Dictionary of Natural Products [11]