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

Are UV-VIS and luminescence spectra of Alq3 [Aluminium tris (8-hydroxy-quinolinate)] delta-phase compatible with the presence of the fac-Alq3 isomer? A TD-DFT investigation

Recently a new crystalline phase of aluminium tris(8-hydroxyquinolinate) (Alq3) called d-phase has been reported. On the basis of luminescence data, the presence of the facial isomer has been suggested. Using time dependent density functional theory calculations we compared the spectral features of meridianal and facial Alq3. Comparisons between the two isomers have been used to confirm the presence of facial Alq3 in d-phase crystals. The interpretation of some characteristics of the more studied meridianal isomer has been suggested. 2002 Published by Elsevier Science B.V

Atomistic Simulation of Discotic Liquid Crystals: Transition from Isotropic to Columnar Phase Example

Molecular dynamics simulations at atomistic level have been performed on a metal-porphyrazine complex. Starting from an isotropic state, the system was cooled until transition from isotropic to columnar phase was observed; no nematic phase was encountered. Many tools were utilized to follow the system evolution: order parameter, g(r), g(parallel to)(r(parallel to)), g(c)(r(parallel to)), g(perpendicular to)(r(perpendicular to)), g(2)(r), also density and energy changes. Very long runs were required to get reliable results, times greater than 40 ns of simulation. The structure of columnar phase was analyzed and the organization of molecules in the columns was investigated, along with the role of conformation of side chains. We found that in columnar phase the molecules are tilted versus the column axis and the conformation of side chains changes during the phase transition to allow this kind of organization; moreover the direction of columns axes is different from that of the director

Synthesis and physico-chemical properties of the bis(2,3,7,8,12,13,17,18-octakis-(octhylthio)-5,10,15,20-tetraazaporphyrinato)lutetium(III) complex

The synthesis and the physico-chemical properties of the bis(2,3,7,8,12,13,17,18-octakis-(octhylthio)-5,10,15,20-tetraazaporphyrinato)lutetium(III) double-decker complex, Lu(OOTTAP)2, are described, ESR, 1H and 13C NMR, UV-visible and NIR studies show that radical nature of this compound and suggest that the unpaired electron cannot be assigned to a specific tetra-azaporphyrinic ring on the time scales available. Some relevant UV-visible spectroscopic and redox features of Lu(OOTTAP)2 resemble closely those of diphthalocyanine complexes, while the intensity and vibrational structure of the NIR spectra are rather reminiscent of those of bis-porphyrin systems

Mono- and multilayer films of discotic metal-(alkythio)tetraazaporphyrins

We report on the use of a copper compound of 2,3,7,8,12,13,17,18-octakis(octylthio)-5,10,15,20-tetraazaporphyrin for the fabrication of a spreading monolayer and Langmuir-Blodgett films. This compound, as a free ligand or metal substituted, gives mesogenic material with a discotic, columnar structure. Its structural and magnetic properties have been characterized by optical and ESR spectroscopies. The spreading monolayer was not homogeneous and use of a typical film-forming amphiphile, such as stearic acid, was necessary for obtaining stable, reproducible surface films, which were easily transferred onto quartz plates treated with dimethyldichlorosilane. The properties of the film were also analyzed with both UV-vis and ESR spectroscopies. The film did not show orientation order, and the discotic material maintained a columnar aggregate structure

Monolayers and Langmuir-Blodgett Films of a Newly Synthesized Asymmetric Tetraazaporphyrin Derivative

Molecular assemblies such as monolayers at the water-air interface and Langmuir-Blodgett films of 2,3- bis(N-(3-thiopropy1)phtha1imido)-7,8,12,13,17,18-hexakis(octy1thio)-5,10,15,20-tetraazaporphyrinato ( TAP) copper(II) and nickel(II) derivatives were studied for the first time. Monolayers at the water-air interface both of the pure macrocyclic derivative and of its mixture with stearic acid were investigated. The degree of order within Langmuir-Blodgett films was established with the aid of UV-vis and ESR spectroscopies. The surface behavior of the above unsymmetrically substituted TAP, in the form of metal derivatives, has been compared with that of the corresponding symmetrically substituted compounds (Bonosi; et al. J. Phys. Chem. 1993, 97, 9181), which give disordered films. We report here on the improved ordering in the LB film fabrication reached with the unsymmetrical substitution as being due to the presence of the hydrophilic phthalimide moieties in two of the eight long chains around the TAP skeleton, which favor an edge-on orientation of the macrocycle at the air-water interface

Monolayers and Langmuir-Blodgett films of nickel(II) tetraaza[14]annulene complexes

The surface and the aggregation properties of the nickel(II) compounds with the dibenzo- and dinaphtho-tetraazal[14]annulene (TAA) macrocycles have been investigated by their spreading isotherms and electronic spectra. The possibility to form LB films was checked for both compounds. Homogeneous, reproducible LB films were obtained with the dibenzo-TAA derivatives, whereas the high surface viscosity prevented a good multilayer overlapping with the dinaphtho-compound