APPLICATIONS OF MOMENTUM-SPACE SIMILARITY

Momentum-space similarity indices were used in studies linking chemica l structure to observed activity. These included (a) the biological ac tivity of various molecules that are of interest due to their capacity for HIV inhibition; and (b) the hyperpolarisabilties of series of con jugated molecules. Study (a) included comparisons of the total valence densities of different molecules or the densities associated with par ticular molecular fragments. Study (b) involved, for each molecule, a comparison of the momentum-space densities of the highest occupied (HO MO) and lowest unoccupied (LUMO) molecular orbitals. The momentum-spac e approach, which is most sensitive to features of the long-range vale nce electron density, turned out to be particularly useful for cases s uch as these, in which the physical property or biological activity ha s no obvious dependence on the bonding topology of the molecules.