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Polymer nanoparticles of 40-400 nm diameter with spiropyran-merocyanine dyes incorporated into their hydrophobic cavities are prepared, and in contrast to their virtually nonfluorescent character in most environments, the merocyanine forms of the encapsulated dyes are highly fluorescent. To evaluate the potential for biological tagging, these optically addressable nanoparticles are delivered into living cells and imaged with liquid nitrogen-cooled CCD.

Amide-linked spiropyran-anthraquinone (SP-AQ) conjugates were mediated to ZnTPPS(super 4-) photosensitized transmembrane reduction of occluded Co(bpy)(sub 3)(super 3+) within unilamellar phosphatidylcholine vesicles by external EDTA. Examination revealed low quantum yields due to unproductive quenching of ZnTPPS(super 4-) by spiropyran (SP) and merocyanine (MC) groups on the dye and back-electron transfer between semiquinone and ZnTPPS(super 3-).

Repetitive mass spectrometric measurement of the istopic distribution of O2 formed in reactions catalyzed by (sub 18)O-labeled catalyst established the existence of two reaction pathways characterized by products containing either one atom each from a ruthenyl O and solvent H2O or both O atoms from solvent molecules.

Pyrylium and thiipyrylium ions were found to mediate cyclic transmembrane charge transport.

The kinetic models for the reactions between peroxynitrite and membrane lipids and for transmembrane oxidations in the inner aqueous cores indicate that peroxynitrous acid and nitric oxide permeation of the bilayer is rapid. The permeability coefficients are much higher that those reported for other polar nonelectrolytes.

Resonance Raman and optical spectroscopic characterizations of a water oxidation catalyst were made.

The triplet-triplet annihilation reactions of meso-tetra(N-methyl-4-pyridyl)porphine cations on the anionic surfaces of dihexadecyl phophate in small unilamellar surface are studied. It is shown that the diffusion coefficient undergoes a discontinuous change at the major phase-transition temperature of the vesicles, demonstrating Arrhenius activation energies of 31 kJ/mol under 62 degrees centigrade and 7.9 kJ/mol over 62 degrees Centigrade.

A comparison of the yields of O2 formed during decomposition of peroxynitrous acid (ONOOH) under a wide variety of medium conditions with predictions provides strong support for decomposition via homolysis of the ONOOH peroxo bond. Results show that the reactivity of the oxidizing intermediate cannot be distinguished from that of *OH. Moreover, the reaction scheme accurately accounts for the complex medium-dependent effect of NO(sub 2)(super -) and other *OH scavengers upon the dynamics of the system.

A number of solvents and phosphatidylcholine liposomes were examined to investigate the photochromic behavior of several spirooxazines with phenanthrene or phenanthroline moieties in the oxazine part of molecules. An intersite movement was observed in transient spectroscopic data, with the merocyanine (MC) forms of these dyes located at relatively nonpolar sites within the bilayer membrane when first formed by photoexcitation. However, they later moved to a more polar environment to the aqueous-organic interface. Destabilization of the MC form also took place upon coordination to a Ru(bpy)(sub 2)(super 2+) group, as gleaned from a shift in the thermal equilibrium position toward the spirooxazine form and a substantial rise in the thermal rate constant for ring-closing.

A study was conducted to analyze the dynamics of photoinduced charge separation on the surface of dihexydecylphosphate vesicles. N-Alkyl-4-cyanopyridinium ions were prepared from 4-cyanopyridine and an alkyl halide. Laser flash photolysis was carried out to determine the absorption spectra and decay kinetics of reaction intermediates. Results indicated that the photoexcitation of the complete system accommodated a reduction of entrapped Co(bpy)3(super 3+) to Co(bpy)3(super 2+).

A study was conducted to analyze N-alkyl-4-cyanopyridinium-mediated photoinduced charge separation across dihexadecyl phosphate vesicle membranes. 4-Cyanopyridine was purified by ethanol-based recrystallization. A 1.5 kW xenon lamp was utilized to carry out continuous photolysis. Experimental results indicated net photoinduced transmembrane reductions in vectorially structured systems supporting oxidants within the inner aqueous phase of the vesicles.

Research was conducted to examine the CO2-catalyzed one-electron oxidations by peroxynitrite and the properties of the reactive intermediate. Measurements for reactions with NO2-, Fe(CN)6(super -4) and Mo(CN)8(super 4-) showed that they were all oxidized by a common intermediate. Based on the reactivity properties that were revealed, it is suggested that the intermediate is a carbonate radical formed by homolytic decomposition of an ONO2CO2- adduct.

A quantitative mechanistic study was conducted on CO2-catalyzed oxidation of tyrosine to obtain knowledge on the modulation of peroxynitrite ion (ONO2-) reactivity by CO2. Findings are in quantitative agreement with a mechanism in which the initial reaction step is one-electron oxidation of tyrosine generating tyrosyl and .NO2 radicals, followed by reaction between these radicals, producing 3-nitrotyrosine, and by tyrosine radical dimerization, forming 3,3'-dityrosine.

Resonance Raman (RR) and EPR spectroscopic studies help characterize species formed on oxidation of the (Ru(bpy)2OH2)2O(4+)(3,3)Mu-oxo ion with Ce4+. Spin-localized Ru-O-Ru symmetric stretching mode accounts for a band in the Raman spectrum. Addition of further Ce4+ leads to the appearance of more signals. RR and EPR techniques reveal the formation of different species, (3-4), (4,5) and (5,5) under highly oxidizing conditions.

Experiments on bipyridinium ion mobilities across-dihexadecyl phosphate bilayer membranes validate the concept that short-chain viologens function as mobile charge relays. The long chain congeners perform electron transfers through electron tunneling. The N-alkyl-N'-methyl-4,4'-bipyridinium dications and the N-methyl-4, 4'-bipyridinium do not permeate the membrane.

The (bpy 2 Ru OH2)2O(super 4+) ion was prepared from cis-Ru(bpy)2Cl2 and isolated as the perchlorate salt. Resonance Raman spectra of the ion and its congeners in III-IV, IV-V and V-V oxidation states were principally single bands at 370 to 403 centimeters(super -1). One pathway of water oxidation involves solvent nucleophilic attack of a terminal oxo atom as the O-O bond forming step. The bridging oxygen atom activates the reactant H2O by formation of a strong hydrogen bond. Another pathway involves both oxygen atoms derived from a solvent.

A class of polymer nanoparticles containing both fluorescent dyes and photoswitchable chromophores within the hydrophobic core are described as new tools for live-cell imaging. Photoswitchable spiropyran dyes can be integrated with fluorescent perylene diimide into the hydrophobic core of hydrophilic polymer nanoparticles to produce high photoluminescence and superior resistance to photo bleaching.

Two major pathways have involved concerted addition of H and OH fragments derived from [H.sub.2]O to the complexes in their four-electron-oxidized states, generating bound peroxy intermediates that decay with the evolution of [O.sub.2]. A photosensitized system is developed for catalyzed water oxidation, which has assessed the catalytic efficiencies of the complex ions under neutral and alkaline conditions.

The article explains the detection and the mechanistic importance of the various transient ligand radicals that are formed during the [[Ru[(bpy).sub.2]([OH.sub.2])].sub.2][O.sup.4+]-catalyzed water oxidation.

The study examines various macrophage cell lines that are used for oxidant production at different times after the activation. The generation of new pathways for an intracellular development of oxidants and tyrosine nitration by these cell lines is also described.

A hard-and-soft hybrid nanosystem whose fluorescence intensity can be reversibly modulated using specific bandwidths of light is reported. These studies show that the optical modulation of nanoparticle fluorescence is possible, suggesting potential application to optically addressable devices.

Electroporation was conducted to transform Escherichia coli to introduce a plasmid harboring a green fluorescent protein (GFP) gene-containing vector. The results obtained by the study imply that sufficient HOCl was formed within the neutrophil phagosome to kill the microbe.

Research has been conducted on peroxynitrite decay in weakly alkaline media. The authors demonstrate that this decay occurs via the concurrent sets of pathways distinguished by their reaction products.

Measurement of labilization of the cis-coordinated aqua ligand is presented by Mu-oxo group in cis, cis-[(bpy)(sub 2)Ru(OH2)][(sub 2)O(super 4+)]. This is done with relevance to its capacity to function as catalyst for oxidation of water to O2 and other reactions involving oxidation of coordinated ligands.

A report on the pressure dependence of the peroxynitrite anion reactions is presented. Peroxynitirite is a pathogenic agent in human diseases.