The top of the cover displays the molecular electrostatic potential of the acetic (ethanoic) acid anion (EA), a bioisostere of the 5-methyltetrazole anion (5MT), where the positive isosurface is shown in dark red, and the negative isosurfaces are in blue. There are four minima in the negative (blue) envelope of the EA that are almost identical in geometric disposition to those produced by the chemically unrelated 5MT, which explains their bioisosteric similarity. The bottom illustrates the electron density in the plane of a guanine–cytosine DNA base pair, showing the contours of the electron density, the quantum theory of atoms in molecules (QTAIM) partitioning of the density into separate atomic basins, the bond paths, and the gradient vector field lines. The background shows the localization/delocalization matrix (LDM) of the ethane molecule. LDMs are used in quantitative structure-to-activity relationships (QSAR) for the first time by Chérif F. Matta on page 1165 (DOI: 10.1002/jcc.23608).