The chloroperoxidase-catalyzed and horseradish peroxidase catalyzed oxidations of sulfides by tert-butyl and other peroxides have been investigated. The former metal enzyme afforded the corresponding sulfoxides having R absolute configuration in up to 92% enantiomeric excess (ee), whereas the latter gave racemic products. The various factors that control the enantioselectivity of the oxygenation have been examined.

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Polyamidoamines (PAAs) represent a family of degradable polymers carrying tert-amine groups in the polymer backbone, which behave as polyelectrolytes in aqueous solutions. Many relevant properties of PAAs, including the ability to interact with components of the biological environments, such as nucleic acids, proteins, and living cells, are strongly dependent on their acid-base properties, hence on their ionization state in different biological districts. In this article, the protonation constants of a series of PAAs have been precisely determined by electrochemical techniques in order to build up a homogeneous library containing both the protonation constants and the average distribution of the charged species, hence the net average charge as a function of pH. Moreover, correlations between chemical and cytotoxicity, have been attempted.

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A new amphoteric copolymer, PhenISA, has been obtained by copolymerization of 4-(4'-aminobutyl)-1,10-phenanthroline (BAP) with 2-methylpiperazine and bis(acrylamido)acetic acid (BAC) (6% of phenanthroline-containing repeating units). The copolymer showed excellent solubility in water, where it self-aggregated to give clear nanoparticle suspensions (hydrodynamic diameter = 21 ± 2 nm, by dynamic light scattering (DLS) analysis). The phenanthroline pendants of the polymer stably coordinated either Re(CO)(3)(+) or Ru(phen)(2)(2+) fragments, affording luminescent Re-PhenISA, Re-Py-PhenISA, and Ru-PhenISA polymer complexes, emitting from triplet metal-to-ligand charge transfer ((3)MLCT) excited states (with λ(em) = 608, 571, and 614 nm, respectively, and photoluminescence quantum yields Φ(em) = 0.7%, 4.8%, and 4.1%, in aerated water solution, respectively). DLS analyses indicated that the polymer complexes maintained the nanosize of PhenISA. All the complexes were stable under physiological conditions (pH 7.4, 0.15 M NaCl) in the presence of an excess of the ubiquitous competitor cysteine. In vitro viability assays showed no toxicity of Re-Py-PhenISA and Ru-PhenISA complexes, at concentrations in the range of 0.5-50 μM (calculated on the metal-containing unit), toward HEK-293 (human embryonic kidney) cells. A preliminary investigation of internalization in HEK-293 cells, by means of fluorescence confocal microscopy, showed that Ru-PhenISA enters cells via an endocytic pathway and, subsequently, homogeneously diffuse within the cytoplasm across the vesicle membranes.