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New complexes of neptunyl(V) isothiocyanate with 4'-aryl-substituted 2,2':6',2″-terpyridines (Terpy) and N,N-dimethylacetamide (DMA) were obtained: [(NpO2)(4'-Ph-Terpy)(DMA)(NCS)]·DMA, [(NpO2)(4'-(4-(CF3)C6H4)-Terpy)(DMA)(NCS)]·2H2O·DMA, [(NpO2)(4'-(3-BrC6H4)-Terpy)(DMA)(NCS)]·DMA, and [(NpO2)(4'-(2-(COOH)C6H4)-Terpy)(DMA)(NCS)]·DMA. The structures of the compounds were determined with X-ray diffraction analysis. The neptunium coordination polyhedra were found to be pentagonal bipyramids with O atoms of the NpO2 groups in the apical positions and the equatorial planes formed by three N atoms of the terpyridine ligand, a N atom of the isothiocyanate anion, and an O atom of DMA. The influence of the substituents of the Ar group on the crystal structure is discussed. The IR spectra contain well-resolved bands of characteristic vibrations of all groups in the complex. The electronic absorption spectra are typical for neptunium(V) complexes and contain an intense narrow absorption band belonging to an f-f transition with a maximum of 988 nm and several long-wave satellites of lower intensity. The substituted terpyridines were shown to be efficient for the extraction of various valence forms of neptunium from the isothiocyanate solutions.

The synthesis of new zinc porphyrin oligomers linked by a triazole bridge was carried out via "click" reaction. A split in the porphyrin oligomer B-band was observed. It was considered as evidence of exciton-excitonic coupling. The relaxation of excited states in Q-band porphyrin oligomers was studied by the femtosecond laser spectroscopy technique with a 20 fs pump pulse. The transient oscillations of two B-band excitonic peaks have a π-radian shift. For explanation of the coherent oscillation, a theoretical model was developed. The model considered the combination of the exciton-excitonic coupling between porphyrin rings in dimer and weak exciton-vibronic coupling in one porphyrin ring. By varying the values of the structural parameters of porphyrins (the strength values of this couplings and measure of symmetry breaking), we obtained correspondence between the experimental data (phase shift and amplitudes of the spectrum oscillations) and the predictions of the model developed here.

While opto-genetics has proven to have tremendous value in revealing the functions of the macromolecular machinery in cells, it is not amenable to exploration of small molecules such as phospholipids (PLs). Here, we describe a redox opto-lipidomics approach based on a combination of high affinity light-sensitive ligands to specific PLs in mitochondria with LC-MS based redox lipidomics/bioinformatics analysis for the characterization of pro-apoptotic lipid signals. We identified the formation of mono-oxygenated derivatives of C18:2-containing cardiolipins (CLs) in mitochondria after the exposure of 10-nonylacridine orange bromide (NAO)-loaded cells to light. We ascertained that these signals emerge as an immediate opto-lipidomics response, but they decay long before the commencement of apoptotic cell death. We found that a protonophoric uncoupler caused depolarization of mitochondria and prevented the mitochondrial accumulation of NAO, inhibited the formation of C18:2-CL oxidation product,s and protected cells from death. Redox opto-lipidomics extends the power of opto-biologic protocols to studies of small PL molecules resilient to opto-genetic manipulations.

Ca2+-independent lipoprotein-associated phospholipase A2 (Lp-PLA2) is a member of the phospholipase A2 superfamily with a distinguishing characteristic of high specificity for oxidatively modified sn-2 fatty acid residues in phospholipids that has been especially well characterized for peroxidized species of phosphatidylcholines (PC). The ability of Lp-PLA2 to hydrolyze peroxidized species of phosphatidylserine (PS), acting as a recognition signal for clearance of apoptotic cells by professional phagocytes, as well as the products of the reaction has not been investigated. We performed liquid chromatography–electrospray ionization mass spectrometry-based structural characterization of oxygenated, hydrolyzed molecular species of PS-containing linoleic acid in either the sn-2 position (C18:0/C18:2) or in both sn-1 and sn-2 positions (C18:2/C18:2), formed in the cytochrome c- and H2O2-driven enzymatic oxidation reaction. Cytochrome c has been chosen as a catalyst of peroxidation reactions because of its like...

Ionizing radiation triggers mitochondrial overproduction of H(2)O(2) with concomitant induction of intrinsic apoptosis, whereby clearance of H(2)O(2) upon overexpression of mitochondrial catalase increases radioresistance in vitro and in vivo. As an alternative to gene therapy, we tested the potential of Mn((III))-porphyrin complexes to clear mitochondrial H(2)O(2). We report that triphenyl-[(2E)-2-[4-[(1Z,4Z,9Z,15Z)-10,15,20-tris(4-aminophenyl)-21,23-dihydroporphyrin-5-yl]phenyl]iminoethyl]phosphonium-Mn((III)) compartmentalizes preferentially into mitochondria of mouse embryonic cells, reacts with H(2)O(2), impedes γ-ray-induced mitochondrial apoptosis, and increases the survival of mice exposed to whole body irradiation with γ-rays.

Interaction of a mitochondria-specific anionic phospholipid, cardiolipin (CL), with an intermembrane protein, cytochrome c (cyt c), yields a peroxidase complex. During apoptosis, the complex induces accumulation of CL oxidation products that are essential for detachment of cyt c from the mitochondrial membrane, induction of permeability transition, and release of proapoptotic factors into the cytosol. Therefore, suppression of the peroxidase activity and prevention of CL oxidation may lead to discovery of new antiapoptotic drugs. Here, we report a new approach to regulate the cyt c peroxidase activity by using modified CL with an oxidizable and fluorescent 7-nitro-2,1,3-benzoxadiazole (NBD) moiety (NBD-CL). We demonstrate that NBD-CL forms high-affinity complexes with cyt c and blocks cyt c-catalyzed oxidation of several peroxidase substrates, cyt c self-oxidation, and, most importantly, inhibits cyt c-dependent oxidation of polyunsaturated tetralinoleoyl CL (TLCL) and accumulation of TLCL hydroperoxides. Electrospray ionization mass spectrometry and fluorescence analysis revealed that oxidation and cleavage of the NBD moiety of NBD-CL underlie the inhibition mechanism. We conclude that modified CL combining a nonoxidizable monounsaturated trioleoyl CL with a C(12)-NBD fragment undergoes a regiospecific oxidation thereby representing a novel inhibitor of cyt c peroxidase activity.

During apoptosis, cytochrome c (cyt c) is released from intermembrane space of mitochondria into the cytosol where it triggers the caspase-dependent machinery. We discovered that cyt c plays another critical role in early apoptosis as a cardiolipin (CL)-specific oxygenase to produce CL hydroperoxides required for release of pro-apoptotic factors [Kagan, V. E., et al. (2005) Nat. Chem. Biol. 1, 223-232]. We quantitatively characterized the activation of peroxidase activity of cyt c by CL and hydrogen peroxide. At low ionic strength and high CL/cyt c ratios, peroxidase activity of the CL/cyt c complex was increased >50 times. This catalytic activity correlated with partial unfolding of cyt c monitored by Trp(59) fluorescence and absorbance at 695 nm (Fe-S(Met(80)) band). The peroxidase activity increase preceded the loss of protein tertiary structure. Monounsaturated tetraoleoyl-CL (TOCL) induced peroxidase activity and unfolding of cyt c more effectively than saturated tetramyristoyl-CL (TMCL). TOCL/cyt c complex was found more resistant to dissociation by high salt concentration. These findings suggest that electrostatic CL/cyt c interactions are central to the initiation of the peroxidase activity, while hydrophobic interactions are involved when cyt c's tertiary structure is lost. In the presence of CL, cyt c peroxidase activity is activated at lower H(2)O(2) concentrations than for isolated cyt c molecules. This suggests that redistribution of CL in the mitochondrial membranes combined with increased production of H(2)O(2) can switch on the peroxidase activity of cyt c and CL oxidation in mitochondria-a required step in execution of apoptosis.

Palladium nanoparticles stabilized in micelles formed by polystyrene-co-poly(ethylene oxide) and cetylpyridinium chloride as a surfactant were investigated as a catalyst in the following reactions: the Heck reaction of 2-ethylhexyl acrylate with iodobenzene and p-bromoacetophenone and heterocyclization of N-methylsulfonyl-o-iodoaniline with phenylacetylene and of methyl o-iodobenzoate with diphenylacetylene leading to formation of substituted indole and isocoumarin, respectively. The activity of the colloidal palladium catalytic system is comparable to that of the low-molecular-weight palladium complexes, whereas the stability of the colloidal palladium system is much higher. The reuse of the catalyst was demonstrated in the experiments with fresh starts as well as by thermomorphous separation of the catalyst from products.

The nitrosation of cellular thiols has attracted much interest as a regulatory mechanism that mediates some of the pathophysiological effects of nitric oxide (NO). In cells, virtually all enzymes contain cysteine residues that can be subjected to S-nitrosation, whereby this process often acts as an activity switch. Nitrosation of biological thiols is believed to be mediated by N2O3, metal-nitrosyl complexes, and peroxynitrite. To date, however, enzymatic pathways for S-denitrosation of proteins have not been identified. Herein, we present experimental evidence that two ubiquitous cellular dithiols, thioredoxin and dihydrolipoic acid, catalyze the denitrosation of S-nitrosoglutathione, S-nitrosocaspase 3, S-nitrosoalbumin, and S-nitrosometallothionenin to their reduced state with concomitant generation of nitroxyl (HNO), the one-electron reduction product of NO. In these reactions, formation of NO and HNO was assessed by ESR spectrometry, potentiometric measurements, and quantification of hydroxylamine and sodium nitrite as end reaction products. Nitrosation and denitrosation of caspase 3 was correlated with its proteolytic activity. We also report that thioredoxin-deficient HeLa cells with mutated thioredoxin reductase denitrosate S-nitrosothiols less efficiently. We conclude that both thioredoxin and dihydrolipoic acid may be involved in the regulation of cellular S-nitrosothiols.

Oxidative stress in biological membranes can regulate various aspects of apoptosis, including phosphatidylserine (PS) externalization. It is not known, however, if the targets for these effects are lipids or proteins. Nitric oxide (NO), a bifunctional modulator of apoptosis, has both antioxidant and prooxidant potential. We report here that the NO donor PAPANONOate completely protected all phospholipids, including PS, from oxidation in HL-60 cells treated with 2,2'-azobis(2,4-dimethylisovaleronitrile) (AMVN), presumably via the ability of NO to react with lipid-derived peroxyl radicals and terminate the propagation of lipid peroxidation. PAPANONOate, however, had no effect on PS externalization or other markers of apoptosis following AMVN. Therefore, PS oxidation is not required for PS externalization during AMVN-induced apoptosis. PS externalization was accompanied by inhibition of aminophospholipid translocase (APT). NO potentiated AMVN inhibition of APT. Treatment with PAPANONOate alone produced modest (20%) inhibition of APT without PS externalization. NO did not reverse AMVN-induced oxidation of glutathione and protein thiols. We speculate that APT was sensitive to AMVN and/or NO via modification of protein thiols critical for functional activity. Therefore, the lipoprotective effects of NO were insufficient to prevent PS externalization and apoptosis following oxidative stress. Other targets such as protein thiols may be important redox-sensitive regulators of apoptosis initiation and execution. Thus, in the absence of significant peroxynitrite formation, NO's antioxidant effects are restricted to protection of lipids, while modification of protein substrates continues to occur.