Immobilization of porphyrins in poly(hydroxymethylsiloxane)

Three tetracationic porphyrins differing in the position of charged nitrogen atoms on the peripheral substituents — 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP4), 5,10,15,20-tetrakis(N-methylpyridinium-2-yl)porphyrin (TMPyP2), 5,10,15,20-tetrakis(4-trimethylammoniophenyl) porphyrin (TMAPP), and hydrophobic 5,10,15,20-tetraphenylporphyrin (TPP), were immobilized by adsorption and encapsulation in poly(hydroxymethylsiloxane) (PHOMS). The so prepared porphyrin-PHOMS composites were characterized by porosimetry, scanning electron microscopy, fluorescence and diffuse reflectance UV-VIS spectroscopy. It was found that porphyrins are immobilized in the PHOMS matrix in the free base monomer form Their irradiation produced singlet oxygen O₂(¹Δ_g) with the lifetime of 10–30 μs.     

Synthesis and pharmacological evaluation of potential metabolites of the potassium-competitive acid blocker BYK 405879

Four potential metabolites of the potassium-competitive acid blocker BYK 405879 (1) were synthesized which might be formed in vivo by enzymatic oxidation of the pyran moiety or the methyl groups attached to the (hetero) aromatic system. In all cases, the oxidation of the parent compound 1 was accompanied by a significant loss of pharmacological activity and by a decrease in lipophilicity. The target compounds 6, 14, 20, and 21 constitute valuable tool substances for the investigation of the metabolic fate of BYK 405879 (1).     

Enhanced Catalytic Activity and Unexpected Products from the Oxidation of Cyclohexene by Organic Nanoparticles of 5,10,15,20‐Tetrakis‐(2,3,4,5,6‐pentafluorophenyl)porphyrinatoiron(III) in Water by Using O2

The catalytic oxidation of alkenes by most iron porphyrins using a variety of oxygen sources, but generally not dioxygen, yields the epoxide with minor quantities of other products. The turnover numbers for these catalysts are modest, ranging from a few hundred to a few thousand depending on the porphyrin structure, axial ligands, and other reaction conditions. Halogenation of substituents increases the activity of the metalloporphyrin catalyst and/or makes it more robust to oxidative degradation. Oxidation of cyclohexene by 5,10,15,20‐tetrakis‐(2,3,4,5,6‐pentafluorophenyl)porphyrinato iron(III), ([Fe^III(tppf₂₀)]) and H₂O₂ is typical of the latter: the epoxide is 99 % of the product and turnover numbers are about 350. 1 – 4 Herein, we report that dynamic organic nanoparticles (ONPs) of [Fe^III(tppf₂₀)] with a diameter of 10 nm, formed by host–guest solvent methods, catalytically oxidize cyclohexene with O₂ to yield only 2‐cyclohexene‐1‐one and 2‐cyclohexene‐1‐ol with approximately 10‐fold greater turnover numbers compared to the non‐aggregated metalloporphyrin in acetonitrile/methanol. These ONPs facilitate a greener reaction because the reaction solvent is 89 % water and O₂ is the oxidant in place of synthetic oxygen sources. This reactivity is unexpected because the metalloporphyrins are in close proximity and oxidative degradation of the catalyst should be enhanced, thus causing a significant decrease in catalytic turnovers. The allylic products suggest a different oxidative mechanism compared to that of the solvated metalloporphyrins. These results illustrate the unique properties of some ONPs relative to the component molecules or those attached to supports.     

Controlled/living radical polymerization of isoprene and butadiene in emulsion

A process for RAFT-controlled radical polymerization in emulsion [36] has been applied to the polymerizations of isoprene and of butadiene in emulsion systems, with the goal of producing latex particles containing block copolymers of acrylic acid (stabilizer and starting polymer), styrene (second polymer) and isoprene or butadiene (third polymer). The microstructure of the polymer chains was examined using dual-detection size-exclusion chromatography, and the nanostructure of the materials was investigated by differential scanning calorimetry and solid-state nuclear magnetic resonance. Reactions were always slow (although faster than the corresponding processes in solution), and exhibited limited reinitiation by isoprene when in emulsion. The materials containing isoprene exhibit a nanostructure with a phase separation into high-T_g polystyrene-rich domains and low-T_g polyisoprene-rich domains, revealed by DSC and NMR. This has the potential to lead to barrier materials with novel physical properties.     

Further Studies on Homo- and Copolymerization of Styrene through Metallocenic Initiator Systems

Summary: Binary metallocene-MAO and ternary diphenylzinc-metallocene-MAO initiator systems have been tested as initiators in the homopolymerization of styrene and also in its copolymerization with several diverse comonomers including substituted styrenes, styrene derivatives, α-olefins and dienes. Various titanocenes and zirconocenes and some exploratory experiment with hafnocene were carried out. The results indicate that titanocenes were more effective than zirconocenes in the homopolymerization of styrene while zirconocenes did better in α-olefin polymerization. It was found that titanocenes generated mainly syndiotactic polystyrene, s-PS, while zirconocenes yielded atactic polystyrene or, depending on the zirconocene, a low percentage of s-PS. For these types of initiators the polymerization process depends largely on the inductive effect of the substituents linked to the benzene ring of styrene and on its position (ortho, meta or para). Substituent multiplicity reduced markedly the effectiveness of these initiator systems. Styrene/isoprene polymerization was also studied using binary zirconocene-MAO initiator systems that yielded low conversions and also low molecular weight polymers.     

A Note on Toeplitz Operators in Schatten-Herz Classes Associated with Rearrangement-invariant Spaces

In recent papers, B. Choe, H. Koo, K. Na (see [3]) and Loaiza, M. Lopez-Garcia e S. Perez-Esteva (see [5]) studied conditions in order to a Toeplitz operator, acting on the harmonic Bergman space over the unit ball in and on analytic Bergman space on the unit disk in the complex plane, respectively, belong to the so-called Schaten-Herz class. The purpose of this note is to prove necessary and sufficient conditions in order to a Toeplitz operator T _μ with positive symbol, acting on the harmonic Bergman space on the unit ball in belong to a Schatten-Herz class S ^F _E , associated with a pair of rearrangement invariant sequence spaces E and F. The conditions involve the Berezin transform of its symbol and the average function. on some euclidian discs. The main point is the characterization of Toeplitz operators, that belong to Schatten ideals S _E associated with an arbitrary rearrangement invariant sequence space E.      

Asymptotic behaviour of a phase-field model with three coupled equations without uniqueness

We prove the existence of weak solutions for a phase-field model with three coupled equations with unknown uniqueness, and state several dynamical systems depending on the regularity of the initial data. Then, the existence of families of global attractors (level-set depending) for the corresponding multi-valued semiflows is established, applying an energy method. Finally, using the regularizing effect of the problem, we prove that these attractors are in fact the same.     

Deformation Techniques for Sparse Systems

We exhibit a probabilistic symbolic algorithm for solving zero-dimensional sparse systems. Our algorithm combines a symbolic homotopy procedure, based on a flat deformation of a certain morphism of affine varieties, with the polyhedral deformation of Huber and Sturmfels. The complexity of our algorithm is cubic in the size of the combinatorial structure of the input system. This size is mainly represented by the cardinality and mixed volume of Newton polytopes of the input polynomials and an arithmetic analogue of the mixed volume associated to the deformations under consideration. Research was partially supported by the following grants: UBACyT X112 (2004–2007), UBACyT X847 (2006–2009), PIP CONICET 2461, PIP CONICET 5852/05, ANPCyT PICT 2005 17-33018, UNGS 30/3005, MTM2004-01167 (2004–2007), MTM2007-62799 and CIC 2007–2008.     

Photodynamic treatment (ALA-PDT) suppresses the expression of the oncogenic Bcr-Abl kinase and affects the cytoskeleton organization in K562 cells

K562 is the chronic myelogenous leukemia (CML)-derived cell line that expresses high levels of chimeric oncoprotein Bcr-Abl. The deregulated (permanent) kinase activity of Bcr-Abl leads to continuous proliferation of K562 cells and their resistance to the apoptosis promotion by conventional drugs. The photodynamic treatment (PDT) based on the application of 5-aminolevulinic acid (ALA) and irradiation with blue light (ALA-PDT) resulted in the suppression of K562 cells proliferation. It was followed by a necrosis-like cell death [K. Kuzelová, D. Grebenová, M. Pluskalová, I. Marinov, Z. Hrkal, J. Photochem. Photobiol. B 73 (2004) 67-78]. ALA-PDT led to the perturbation of the Hsp90/p23 multichaperone complex of which the Bcr-Abl is the client protein. Bcr-Abl protein was suppressed whereas the bcr-abl mRNA level was not affected. Further on, we observed several changes in the cytoskeleton organization. We detected ALA-PDT-mediated disruption of filamental actin structure using FITC-Phalloidin staining. In connection with this we uncovered certain cytoskeleton organizing proteins involved in the cell response to the treatment. Among these proteins, Septin2, which plays a role in maintaining actin bundles, was suppressed. Another one, PDZ-LIM domain protein 1 (CLP36) was altered. This protein acts as an adaptor molecule for LIM-kinase which phosphorylates and thus inactivates cofilin. Cofilin was indeed dephosphorylated and could thus be activated and operate as an actin-depolymerizing factor. We propose the scheme of molecular response of K562 cells to ALA-PDT.