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. 2011 Oct 6;7(10):e1002166. doi: 10.1371/journal.pcbi.1002166

Figure 1. Schematic representation of physico-chemical parameters of metabolites (Materials and Methods), exemplified using 2-ketoglutarate.

Figure 1

(a) Purple - polar surface area (PSA, oxygen and nitrogen atoms that are able to form hydrogen bonds, including hydrogen atoms attached to them). Blue - non-polar surface area (NPSA) which contributes to the hydrophobic effect. Yellow trapezes represent hydrogen bonds that the molecule can form with the solvent or with other solute molecules (HBI - hydrogen bond inventory). Charges are marked by red ellipses (NCA – number of charged atoms). Curved, dashed grey arrows correspond to rotatable bonds (NRB – number of rotatable bonds). (b) LogP (left) is the logarithm of the equilibrium ratio of concentrations of a metabolite in the two phases of a mixture of octanol and water. LogS (right) is the logarithm of the water solubility. See Materials and Methods for details on the calculation of these parameters.