An NF-kB site in the 5'-untraslated leader region of the Human Immunodeficiency virus type 1 enhances the viral expression in response to NF-kB-activating stimuli.

The 5'-untranslated leader region of human immunodeficiency virus, type 1 (HIV-1), includes a complex array of putative regulatory elements whose role in the viral expression is not completely understood. Here we demonstrate the presence of an NF-κB-responsive element in the trans- activation response (TAR) region of HIV-1 that confers the full induction of HIV-1 long terminal repeat (LTR) in response to NF-κB-activating stimuli, such as DNA alkylating agents, phorbol 12-myristate 13-acetate, and tumor necrosis factor-α. The TAR NF-κB site GGGAGCTCTC spans from positions +31 to +40 and cooperates with the NF-κB enhancer upstream of the TATA box in the NF-κB-mediated induction of HIV-1 LTR. The conclusion stems from the following observations: (i) deletion of the two NF-κB sites upstream of the TATA box reduces, but does not abolish, the HIV-1 LTR activation by NF-κB inducers; (ii) deletion or base pair substitutions of the TAR NF-κB site significantly reduce the HIV-1 LTR activation by NF-κB inducers; (iii) deletions of both the NF-κB sites upstream of the TATA box and the TAR NF- κB site abolish the activation of HIV-1 LTR in response to NF-κB inducers. Moreover, the p50·p65 NF-κB complex binds to the TAR NF-κB sequence and trans-activates the TAR NF-κB-directed expression. The identification of an additional NF-κB site in the HIV-1 LTR points to the relevance of NF-κB factors in the HIV-1 life cycle

Perylenetetracarboxy-3,4:9,10-diimide derivatives with large two-photon absorption activity

Three new perylenetetracarboxy-3,4:9,10-diimides, bearing 2,6-diisopropylphenyl groups at the imide positions and 4-(R-ethynyl)phenoxy moieties (R = 4,7-di(2-thienyl)benzo[c][1,2,5]thiadiazole (P2), pyrene (P3) or pyrene-CH2OCH2 (P4)) at the four bay positions, were prepared, along with the known related derivative (R = phenyl (P1)), and well characterized. They have large two-photon absorption (TPA) cross-sections (sigma(2)), as determined by the Z-scan technique, the highest values being reached with P2 which bears a planar -delocalized donor moiety. P3 is characterized by higher sigma(2) values than both P1, as expected for the higher -conjugation of the donor pyrene moiety with respect to phenyl, and P4, due to the presence of the flexible and non-conjugated CH2OCH2 bridge between the pyrene and the ethynyl fragment in the latter compound. The molecular geometry of P1-P4 has been optimized by DFT modeling, showing that in P2 and P3 the bay substituents are stacked due to the - interactions of both pyrene and thiophene groups. The LUMO of P1-P4 lies at the same energy and is essentially delocalized on the perylene core whereas the HOMO and HOMO-1 of both P2 and P3 are degenerate and do not show contribution from the perylene core contrarily to that of P1 and P4. The HOMO-LUMO gap is therefore essentially influenced by the HOMO which reflects the electronic charge delocalization on the bay substituents, the lower gaps being observed for P2 and P3, which are characterized by the best TPA properties

An acido-triggered reversible luminescent and nonlinear optical switch based on a substituted styrylpyridine : EFISH measurements as an unusual method to reveal a protonation-deprotonation NLO contrast

Diphenyl-(4-{2-[4-(2-pyridin-4-yl-vinyl)-phenyl]-vinyl}-phenyl)-amine (DPVPA) constitutes a novel acido-triggered reversible luminescent and nonlinear optical switch. Remarkably, for the first time the Electric-Field Induced Second Harmonic generation (EFISH) technique is used to reveal a protonation-deprotonation NLO contrast

Novel N^C^N-cyclometallated platinum complexes with acetylide co-ligands as efficient phosphors for OLEDs

Two new cyclometallated platinum(ii) complexes have been prepared that incorporate a terdentate N^C^N-coordinating ligand and a monodentate acetylide co-ligand. The complexes, namely [PtL 3-CC-C 6H 3F 2] and [PtL 6-CC-C 6H 3F 2] (where HL 3 = 5-methyl-1,3-di(2-pyridyl) benzene; HL 6 = 5-mesityl-1,3-di(2-pyridyl)benzene; H-CC-C 6H 3F 2 = 3,5-difluorophenylacetylene), were prepared by ligand metathesis from the corresponding chloro complex PtL nCl. Both of the new complexes are intensely luminescent in solution, displaying quantum yields superior to PtL nCl. OLEDs have been prepared using the new compounds as phosphorescent emitters. Although both lead to efficient devices, the best electroluminescence quantum efficiencies are obtained with the derivative of HL 6, having the mesityl group on the cyclometallated phenyl ring. The superior performance with this complex can be rationalised in terms of the greater steric hindrance that serves to reduce aggregate-induced quenching

Bis(1,10-phenanthroline) copper complexes with tailored molecular architecture: from electrochemical features to application as redox mediators in dye-sensitized solar cells

In the last few years, copper coordination compounds turned out to be effective competitors of cobalt complexes as redox mediators in the formulation of iodine-free electrolytes for dye-sensitized solar cells (DSSCs). However, the lack of a clear correlation between electrochemical signatures of copper complexes (i.e. half-wave potential and heterogeneous electron transfer rate) and photoelectrochemical performance of solar devices makes difficult the optimization of their coordination sphere. Therefore, to partially fill this gap and to elucidate the intrinsic correlation between the molecular architecture of these complexes and their electrochemical features, we prepared four Cu+/2+redox couples in which the copper center is coordinated by two 1,10-phenanthrolines bearing various substituents in position 2. These complexes were well characterized, from both electrochemical and spectroscopic point of view, and tested as electron shuttles in lab-scale photoelectrochemical cells sensitized with two efficient \ucf\u80-extended benzothiadiazole dyes. It appeared that 2-aryl-1,10-phenanthrolines effectively combine suitable optical and electrochemical properties. While a fast electron transfer kinetics generally positively affects the dye regeneration process, an optimal balance between dye regeneration efficiency, mass transport and heterogeneous electron transfer at both the counter electrode and at the TiO2interface, must be achieved in order to optimize DSSC performance. Within our series, the top performer was [Cu(2-tolyl-1,10-phenanthroline)2]+/2+which achieved a relative 20% and 15% improvement in power conversion efficiency (under 100 mW s\ue2\u88\u921simulated AM 1.5G illumination) with respect to control cells filled with [Co(bpy)3]2+/3+(bpy = 2,2\ue2\u80\ub2-bipyridine) and I\ue2\u88\u92/I3\ue2\u88\u92electrolytes, respectively

Tuning the optical emission of MoS2 nanosheets using proximal photoswitchable azobenzene molecules

We report photoluminescence measurements performed on monolayer- and two-layer-MoS2 placed on two types of mixed self-assembled monolayers (mSAMs) of photoswitchable azobenzene molecules. The two mSAMs differ via the electronegative character of the azobenzene derivatives. Thin layers of a transition metal dichalcogenide - MoS2 - were mechanically exfoliated on mSAM to allow for direct interaction between the molecules and the MoS2 layers. When the MoS2 nanosheet is in contact with the electropositive azobenzene molecules in trans configuration, an emission side band at lower energies and at low excitation powers suggest n-type doping. The photoisomerization of the molecules from trans to cis configuration lowers the doping, quenching the side band and enhancing the overall PL efficiency by a factor of 3c3. Opposite results were observed with the chlorinated, more electronegative molecules, exhibiting a reversed trend in the PL efficiency between trans and cis, but with an overall larger intensity. The type of doping induced by the two types of mSAMs was determined by Kelvin probe force microscopy technique