Knock Down of Heat Shock Protein 27 (HspB1) Induces Degradation of Several Putative Client Proteins

Hsp27 belongs to the heat shock protein family and displays chaperone properties in stress conditions by holding unfolded polypeptides, hence avoiding their inclination to aggregate. Hsp27 is often referenced as an anti-cancer therapeutic target, but apart from its well-described ability to interfere with different stresses and apoptotic processes, its role in non-stressed conditions is still not well defined. In the present study we report that three polypeptides (histone deacetylase HDAC6, transcription factor STAT2 and procaspase-3) were degraded in human cancerous cells displaying genetically decreased levels of Hsp27. In addition, these proteins interacted with Hsp27 complexes of different native size. Altogether, these findings suggest that HDAC6, STAT2 and procaspase-3 are client proteins of Hsp27. Hence, in non stressed cancerous cells, the structural organization of Hsp27 appears to be a key parameter in the regulation by this chaperone of the level of specific polypeptides through client-chaperone type of interactions

Reaction of organic and metallorganic π-cation Radicals: Electrical and electrochemical properties of polymeric materials obtained by oxidation of pyrrole and Tetraaza[14]annulenic nickel(II) complexes

The reactions between π-cation radicals generated by electrochemical or chemical oxidation of pyrrole and metallorganic complexes, i.e. tetramethyldibenzo[b,i] tetraaza[14]annulenenickel(II), Nitmdbtaa, and tetramethyldinaphtho[b,i]tetraaza[14] annulenenickel(II), Nitmdntaa, were investigated. There is voltammetric evidence that pyrrolyl units insert as organic spacers between nickel-macrocycle molecules when solutions containing controlled amounts of Nitmdbtaa and pyrrole are cycled in the range + 1.4 to −0.5 V (vs SCE). Thin conducting films of [(Nitmdbtaa)(Py)0.95(BF4)0.75]n grow over platinum, gold and glassy carbon surfaces. Solutions of Nitmdbtaa and pyrrole in CH2Cl2, upon chemical oxidation, show an unusual behaviour of the absorbance measured at λmax = 605 and 585 nm vs time. This is interpreted as due to a co-polymerization process and gives indications on the nature of the reaction intermediates. Layers of (Nitmdbtaa)n cannot be grown over polypyrrole (Ppy) by electrochemical methods. In its turn, Nitmdntaa is not found to co-polymerize with pyrrole but polymeric films of the complex can be generated on Ppy galvanostatically, by constant potential electrolysis at +1.4 V or by cycling from +1.4 to −0.5 V (vs SCE). These overlapped films show rectifying properties in the 0.0 to + 1.4 V potential range

New Investigations of Geometric, Electronic, and Spectroscopic Properties of Tetrapyrrolic Macrocycles by a TD-DFT Approach. Carbon, Nitrogen, and Chalcogen (O, S, Se) Peripheral Substitution Effects on Ni(II) Porphyrazinato Complexes.

The electronic structure of five complexes [M(oXHpz)] [M = Ni2+; oXHpz2- = 2,3,7,8,12,13,17,18-octakis-substituted (X = CH2, NH, O, S, Se)-5,10,15,20-tetraazaporphyrinate dianion] has been investigated using a d. functional approach. All the geometries have been obtained minimizing the total intramol. energy using a nonlocal hybrid functional (B3LYP) at the 6-31g* level. The electronic configuration of Ni2+ is (dx2-y2)0(dxy)2(dxz,dyz)4(dz2)2. Optimized geometries exhibit a planar conformation and are all above the threshold for ruffling, which is described by a Ni-Np bond distance of 1.85-1.87 Å for sterically unhindered porphyrazines. Indeed, the smallest bond distance is 1.880 Å for Ni(oOHpz). Peripheral substituents yield modifications to the "core" of the macrocycle and to the energy levels, changing σ and π interactions. Furthermore, within a time-dependent d. functional theory approach, excited states of Ni(oXHpz) [X = CH2, NH, O, S, Se,] complexes have been studied and compared with available exptl. UV-vis spectra. [on SciFinder(R)

Effects of fluorine atoms on the optical nonlinear response of stilbene derivatives.

The effect of fluorine atoms on the second-order optical nonlinear response of 4-nitro-4'-methoxy-trans-stilbene and polyene derivs. contg. up to three double bonds (n = 1, 2, 3) has been investigated within a semiempirical context (PM3 Hamiltonian). Exptl. data reported in literature indicate a βvec(SHG) value of 34, 47 and 76 (× 10-30 esu) for n = 1, 2, 3, resp., at 0.65 eV in CHCl3 solns. Our calcns. show that fluorinating the nitrophenyl group the βvec(SHG) is doubled. Further increase in the second-order nonlinear response can be obtained fluorinating the C:C bond linkers between the arom. moieties.Besides, the effect of different donor-acceptor pairs has been studied and the results interpreted in the two-state model context.Some results concerning the third-harmonic generation (THG), γ (THG), are presented, and a possible interpretation proposed. [on SciFinder(R)

Monolayers and Langmuir-Blodgett films of a new lutetium(III)-bis-octakis(alkylthio)tetraazaporphyrin

We studied the properties of the monolayers and deposition behaviour of a new member of the group of bis-porphyrin complexes of rare earth metals, namely the newly fabricated lutetium(III) bis-2,3,7,8,12,13,17,18-octakis(butylthio) tetraazaporphyrinato, as a pure compound and in mixture with cadmium stearate, in the light of their magnetic, semiconducting and gas sensing properties. In both cases the molecules assumed a tilted edge-on orientation at the liquid-air interface, with the molecular rings perpendicular to the water surface, as deduced from π−A isotherms. Multilayer Langmuir-Blodgett (LB) films were successfully built up only when the bis-porphyrin molecules were mixed with cadmium stearate. Electronic absorption spectra using plane-polarized light indicated isotropy in the plane of the film, i.e. the axes of the molecules were randomly oriented in this plane. The peak width at half-height for the Q band increased on passing from the chloroform solution to the LB films of pure and mixed compounds, indicating different degrees of molecular packing. A single electron spin resonance line was given by the chloroform solution of the molecule and it was also maintained in the mixed LB film

Inter-ring interactions and peripheral tail effects on the discotic mesomorphism of 'free-base' and Co(II), Ni(II) and Cu(II) alkenyl(sulfanyl) porphyrazines

The self-organizing capability of a family of newly synthesized ‘free-base', H2(OASPz), and metal porphyrazines, M(OASPz) (OASPz2− = 2,3,7,8,12,13,17,18-octakis(alkenylthio)-5,10,15,20-tetraazaporphyrinato dianion, n = 4, 5, 6, 8; M = Co, Ni, Cu), into columnar, discotic liquid crystals, has been investigated by differential scanning calorimetry (DSC), optical microscopy and X-ray diffraction. It is found that of the metal-free porphyrazines only those with n = 4 or 5 show, as indicated by X-ray and optical microscopy studies, characteristic stable and discotic nematic mesophases. All the metallated porphyrazines show a discotic liquid crystalline behavior and those with the largest values of n present, consistent with the X-ray results, hexagonal columnar packing. Comparing the mesomorphic behavior of these compounds with those of the parent compounds peripherally substituted with saturated alkyl(sulfanyl)-chains it is seen that the effect of the increased stiffness at the periphery of the chains, induced in the title tetrapyrroles by the terminal double bonds, results in a decrease of the clearing temperature, Ti, and also of the mesophase temperature stability range, ΔT. This effect is larger in H2 and Ni than in Cu and especially in Co porphyrazines, where the axial coordinating capability of the Co seems to counterbalance the effect of this perturbation