(2,2':6',2"-terpyridine)platinum(II) complexes possess pronounced cytostatic activities against trypanosomes and leishmania. As shown here, the complexes are irreversible inhibitors of trypanothione reductase (TR) from Trypanosoma cruzi, the causative agent of Chagas' disease. The most effective derivatives are the (4'-chloro-2, 2':6',2"-terpyridine)platinum(II) ammine and the (4-picoline)(4'-p-bromophenyl-2,2':6',2" -terpyridine)platinum(II) complexes which in the presence of NADPH inhibit TR with second-order rate constants of about 1.3 x 10(4) M(-1) s(-1). The modified enzyme species possess increased oxidase activities. The inhibition is not reversed upon dialysis or treatment with low-molecular-mass thiols. Kinetic and spectroscopic data suggest that Cys52 in the active site has been specifically altered. Inhibition of this key enzyme of parasite thiol metabolism probably contributes to the antitrypanosomal activity of the compounds. In contrast to the parasite enzyme, most (terpyridine)platinum complexes interact only reversibly with human glutathione reductase and an initial inhibition is completely abolished during the course of the assay.

A novel approach of photoinduced phase separation has been demonstrated with a photolabile anionic surfactant, mixed with an inert nonionic surfactant in the presence of salting-out electrolyte. Breakdown of the photolyzable surfactant results in hydrophobic photoproducts, which are emulsified by the remaining inert surfactant; added electrolyte resolves the emulsion into macroscopic oily and aqueous phases. The initial micellar systems can disperse an insoluble additive marker dye (shown), which may be spatially segregated from the aqueous environment by the action of UV light.