Spectroscopic and redox properties of amine-functionalized K2[OsII(bpy)(CN)4] complexes

We report the first examples of amine-functionalized K(2)[Os(II)(bpy)(CN)(4)] (bpy = 2,2'-bipyridine) complexes. The tetracyanoosmate complexes were prepared by UV irradiation (λ = 254 nm) of K(4)[Os(II)(CN)(6)] and primary amine-functionalized bpy ligands in acidic aqueous media. The aqueous solution pH dependences of the spectroscopic and redox properties of 4,4'- and 5,5'-substituted complexes have been investigated. The pendant amine functional groups and coordinated cyanide ligands are basic sites that can be sequentially protonated, thereby allowing systematic tuning of electrochemical and optical spectroscopic properties.     

Chemical Perturbation of Oncogenic Protein Folding: from the Prediction of Locally Unstable Structures to the Design of Disruptors of Hsp90–Client Interactions

Protein folding quality control in cells requires the activity of a class of proteins known as molecular chaperones. Heat shock protein-90 (Hsp90), a multidomain ATP driven molecular machine, is a prime representative of this family of proteins. Interactions between Hsp90, its co-chaperones, and client proteins have been shown to be important in facilitating the correct folding and activation of clients. Hsp90 levels and functions are elevated in tumor cells. Here, we computationally predict the regions on the native structures of clients c-Abl, c-Src, Cdk4, B-Raf and Glucocorticoid Receptor, that have the highest probability of undergoing local unfolding, despite being ordered in their native structures. Such regions represent potential ideal interaction points with the Hsp90-system. We synthesize mimics spanning these regions and confirm their interaction with partners of the Hsp90 complex (Hsp90, Cdc37 and Aha1) by Nuclear Magnetic Resonance (NMR). Designed mimics selectively disrupt the association of their respective clients with the Hsp90 machinery, leaving unrelated clients unperturbed and causing apoptosis in cancer cells. Overall, selective targeting of Hsp90 protein–protein interactions is achieved without causing indiscriminate degradation of all clients, setting the stage for the development of therapeutics based on specific chaperone:client perturbation.     

Assessment of Bleached and Unbleached Nanofibers from Pistachio Shells for Nanopaper Making

Cellulose and lignocellulose nanofibrils were extracted from pistachio shells utilizing environmentally friendly pulping and totally chlorine-free bleaching. The extracted nanofibers were used to elaborate nanopaper, a continuous film made by gravimetric entanglement of the nanofibers and hot-pressed to enhance intramolecular bonding. The elaborated nanopapers were analyzed through their mechanical, optical, and surface properties to evaluate the influence of non-cellulosic macromolecules on the final properties of the nanopaper. Results have shown that the presence of lignin augmented the viscoelastic properties of the nanopapers by ≈25% compared with fully bleached nanopaper; moreover, the hydrophobicity of the lignocellulose nanopaper was achieved, as the surface free energy was diminished from 62.65 to 32.45 mNm⁻¹ with an almost non-polar component and a water contact angle of 93.52°. On the other hand, the presence of lignin had an apparent visual effect on the color of the nanopapers, with a ΔE of 51.33 and a ΔL of −44.91, meaning a substantial darkening of the film. However, in terms of ultraviolet transmittance, the presence of lignin resulted in a practically nonexistent transmission in the UV spectra, with low transmittance in the visible wavelengths. In general, the presence of lignin resulted in the enhancement of selected properties which are desirable for packaging materials, which makes pistachio shell nano-lignocellulose an attractive option for this field.     

High-Energy Long-Lived Emitting Mixed Excitons in Homopolymeric Adenine-Thymine DNA Duplexes

The publication deals with polymeric pA●pT and oligomeric A₂₀●T₂₀ DNA duplexes whose fluorescence is studied by time-correlated single photon counting. It is shown that their emission on the nanosecond timescale is largely dominated by high-energy components peaking at a wavelength shorter than 305 nm. Because of their anisotropy (0.02) and their sensitivity to base stacking, modulated by the duplex size and the ionic strength of the solution, these components are attributed to mixed ππ*/charge transfer excitons. As high-energy long-lived excited states may be responsible for photochemical reactions, their identification via theoretical studies is an important challenge.     

Effectively designed molecularly imprinted polymers for selective isolation of the antidiabetic drug metformin and its transformation product guanylurea from aqueous media

In the present study, two novel molecularly imprinted polymers (MIPs) with remarkable recognition properties for metformin and its transformation product, guanylurea, have been prepared for their selective, enrichment, isolation and removal from aqueous media. The prepared adsorbents were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and swelling experiments. The performance of the prepared MIPs was evaluated by various parameters including the influence of pH, contact time, temperature and initial compound concentration. The effects on the adsorption behavior of the removal process parameters were studied and the equilibrium data were fitted by the Langmuir and Freundlich models. Due to the imprinting effect, adsorption performance of MIPs was always superior to its corresponding NIP (non-imprinted polymer), with maximum adsorption capacity ∼80 mg g⁻¹ for both MIPs. Stability and reusability of the MIPs up to the 5th cycle meant that they could be applied repeatedly without losing substantial removal ability. In the next step, the prepared MIP nanoparticles were evaluated as sorbents in a dispersive solid phase extraction (D-SPE) configuration for selective enrichment and determination of metformin and guanylurea in different aqueous matrices. Under the working extraction conditions, the D-SPE method showed good linearity in the range of 50–1000 ng L⁻¹, repeatability of the extractions (RSD 2.1–5.1%, n = 3), and low limits of detection (1.5–3.4 ng L⁻¹). The expanded uncertainty of the data obtained was estimated following a bottom-up approach. The proposed method combined the advantages of MIPs and D-SPE, and it could become an alternative tool for analyzing the residues of METF and its transformation product GUA in complex water matrices, such as wastewaters.     

Corrosion processes of iron in acidic solutions associated with potential oscillations induced by chlorates and perchlorates

Potential oscillations appear under current-controlled conditions of the chlorate- and perchlorate-perturbed electrochemical Fe|H₂SO₄ system. The potential oscillates between the active and passive states of Fe. It is shown that this oscillatory phenomenon is associated with localized corrosion of Fe due to the generation of chlorides via the reduction of chlorates and perchlorates by ferrous ions. Ferrous ions are generated either during the active dissolution of bare Fe (low-potential state) or during the passivation of Fe (high-potential state) due to a H⁺-catalyzed chemical dissolution of the oxide. Potential oscillations can be utilized to detect and characterize pitting corrosion of Fe in acidic solutions because, under current-controlled conditions, the halide-free Fe|H₂SO₄ system does not exhibit any kind of oscillatory phenomena. Characterization of pitting corrosion becomes possible through the analysis of galvanodynamic and galvanostatic curves obtained at various concentrations of chlorates and perchlorates. The variation of the anion concentration and applied current influence the onset and features of the potential oscillations.     

Comparison of the thermal behavior and conformational changes in partially and fully hydrated dipalmitoylphosphatidylcholine systems

The temperature dependence of conformational changes for partially and fully hydrated DPPC systems through two physicochemical techniques, namely DSC and Raman spectroscopy, is studied. DSC experiments have shown a different thermal behavior between the two considered systems, indicating the effective role of water in the thermal behavior. A temperature resolution of inter- and intramolecular interactions during the main melting phase transition was achieved by using three different Raman intensity ratios, which confirm that the main phase transition represents a two-stage transition. Van’t Hoff plots for the C–C, C–H, C=O and C₄N⁺ stretching modes, in a temperature range just below the main transition temperature, have been used to compare the thermodynamic parameters extracted by the two physicochemical techniques. The significance of these results can be summarized as follows: (a) DSC and Raman spectroscopy have shown complementary results indicating that DPPC exists in partially or fully hydrated states; (b) thermodynamic parameters ΔΗ and ΔS calculated in both techniques for the two different hydration states of DPPC were in harmony; (c) water more significantly affects the thermal and dynamic properties of fully hydrated DPPC bilayers than of the partially hydrated DPPC; and (d) water disturbs the head-group packing, the alkyl chains interactions and the mesophase region. It appears that the amount of water plays a vital role in the bilayer structure. As more and more extensive studies appear in the literature on biomolecules or drug membrane interactions, this information will be valuable in understanding the role of water in these interactions.     

Synthesis of PhTAD-substituted dihydropyrrole derivatives via stereospecific C–H amination

Research on Chemical Intermediates - Stereospecific α-amination has been accomplished via addition of N-phenyltriazolinedione (PhTAD) to the allylic position of dihydropyrroles. The aim of...     

Charge controlled self-assembled quantum dots coupled to photonic crystal nanocavities

The system of charge controlled self-assembled quantum dots coupled to high-Q photonic crystal cavity modes is studied. The quantum dots are embedded in a p-i-n diode structure. Different designs of photonic crystal cavities are used, namely H1 and L3 and the Purcell effect is demonstrated. Furthermore, the fine tuning of the H1 cavity design is studied in order to achieve far field emission profiles that result in higher collection efficiency. An increase in the overall signal from the quantum dot when it is coupled to a cavity is observed, due to the Purcell effect and the improved collection efficiency. This together with the deterministic charging of the quantum dot that is demonstrated, can be used for a single electron spin measurement.     

Synthesis,characterization, crystal structure and antiproliferative activity of platinum(II) complexes with 2-acetylpyridine-4-cyclohexyl-thiosemicarbazone

New platinum complexes have been synthesized by the reaction of Na₂PtCl₄ with 2-acetylpyridine-4-cyclohexyl-thiosemicarbazone, HAc4CyclHexyl (1). The new complexes [Pt(Ac4CyclHexyl)Cl] (2) and [Pt(Ac4CyclHexyl)₂] (3) have been characterized by elemental analyses and spectroscopic studies. The crystal structure of the complex [Pt(Ac4CyclHexyl)Cl] · DMF has been solved by single-crystal X-ray diffraction. The anion of Ac4CyclHexyl coordinates in a planar conformation to the central platinum(II) through the pyridyl N, azomethine N and thiolato S atoms. The crystal packing is determined by double intermolecular hydrogen interactions, π–π, Pt–C and Pt–π contacts. The cytotoxic activities of 1–3 have been evaluated for antiproliferative activity in vitro against the cells of three human cancer cell lines: MCF-7 (human breast cancer cell line), T24 (bladder cancer cell line), A-549 (non-small cell lung carcinoma) and a mouse L-929 (a fibroblast-like cell line cloned from strain L). The compounds 1–3 display IC₅₀ values in a μM range better than that of the antitumor drug cisplatin and are considered as agents with potential antitumor activity candidates for further stages of screening in vitro and/or in vivo.