Halomethanes in tri-n-octylamine and squalane mixtures at infinite dilution

The retention behavior of eight halomethanes and four saturated hydrocarbons was measured in gas chromatographic stationary phases consisting in tri-n-octylamine (TOA), squalane (SQ) and six TOA+SQ mixtures, at 55.0, 58.5, 62.5 and 65.0°C. Equlibrium constants for complex formation were extracted from experimental data by using a lattice model developed by Martire. The results may be interpreted in terms of the formation of weak hydrogen-bonded complexes, with sociation constants of about 0.13 L-mol^–1 for haloforms and 0.07 L-mol^–1 for dihalomethanes at 60°C.     

Janus Gold Nanostars–Mesoporous Silica Nanoparticles for NIR-Light-Triggered Drug Delivery

Janus gold nanostar–mesoporous silica nanoparticle ( AuNSt–MSNP ) nanodevices able to release an entrapped payload upon irradiation with near infrared (NIR) light were prepared and characterized. The AuNSt surface was functionalized with a thiolated photolabile molecule ( 5 ), whereas the mesoporous silica face was loaded with a model drug (doxorubicin) and capped with proton-responsive benzimidazole-β-cyclodextrin supramolecular gatekeepers ( N 1 ). Upon irradiation with NIR-light, the photolabile compound 5 photodissociated, resulting in the formation of succinic acid, which induced the opening of the gatekeeper and cargo delivery. In the overall mechanism, the gold surface acts as a photochemical transducer capable of transforming the NIR-light input into a chemical messenger (succinic acid) that opens the supramolecular nanovalve. The prepared hybrid nanoparticles were non-cytotoxic to HeLa cells, until they were irradiated with a NIR laser, which led to intracellular doxorubicin release and hyperthermia. This induced a remarkable reduction in HeLa cells viability.     

Large‐Scale Synthesis of Helicene‐Like Molecules for the Design of Enantiopure Thin Films with Strong Chiroptical Activity

Helicenes are fascinating molecules owing to their unusual properties and applications in many fields from catalysis to organic electronics. Herein, we report a straightforward pathway for the synthesis of helicene‐like molecules on a gram scale in an enantiopure form. Thin‐film materials with good propagating optical properties and very high chiroptical responses have been grown by using pulsed laser ablation without altering the structure or the enantiopurity of the molecules. Moreover, electronic and vibrational circular dichroism spectroscopies coupled with theoretical calculations enabled some dependences of the chiroptical properties with the structure to be highlighted, for example, effects of rigidification, aromatization, or the state of matter (liquid versus solid).     

An inorganic iron complex that inhibits wild-type and an isoniazid-resistant mutant 2-trans-enoyl-ACP (CoA) reductase from Mycobacterium tuberculosis

The in vitro kinetics of inactivation of both wild-type and I21V InhA enzymes by [FeII(CN)5(INH)]3- indicate that this process requires no activation by KatG, and no need for the presence of NADH. This inorganic complex may represent a new class of lead compounds to the development of anti-tubercular agents aiming at inhibition of a validated target.     

Heparin Binding by Murine Recombinant Prion Protein Leads to Transient Aggregation and Formation of RNA-Resistant Species

The conversion of cellular prion protein (PrP(C)) into the pathological conformer PrP(Sc) requires contact between both isoforms and probably also requires a cellular factor, such as a nucleic acid or a glycosaminoglycan (GAG). Little is known about the structural features implicit in the GAG-PrP interaction. In the present work, light scattering, fluorescence, circular dichroism, and nuclear magnetic resonance (NMR) spectroscopy were used to describe the chemical and physical properties of the murine recombinant PrP 23-231 interaction with low molecular weight heparin (LMWHep) at pH 7.4 and 5.5. LMWHep interacts with rPrP 23-231, thereby inducing transient aggregation. The interaction between murine rPrP and heparin at pH 5.5 had a stoichiometry of 2:1 (LMWHep:rPrP 23-231), in contrast to a 1:1 binding ratio at pH 7.4. At binding equilibrium, NMR spectra showed that rPrP complexed with LMWHep had the same general fold as that of the free protein, even though the binding can be indicated by significant changes in few residues of the C-terminal domain, especially at pH 5.5. Notably, the soluble LMWHep:rPrP complex prevented RNA-induced aggregation. We also investigated the interaction between LMWHep and the deletion mutants rPrP Δ51-90 and Δ32-121. Heparin did not bind these constructs at pH 7.4 but was able to interact at pH 5.5, indicating that this glycosaminoglycan binds the octapeptide repeat region at pH 7.4 but can also bind other regions of the protein at pH 5.5. The interaction at pH 5.5 was dependent on histidine residues of the murine rPrP 23-231. Depending on the cellular milieu, the PrP may expose different regions that can bind GAG. These results shed light on the role of GAGs in PrP conversion. The transient aggregation of PrP may explain why some GAGs have been reported to induce the conversion into the misfolded, scrapie conformation, whereas others are thought to protect against conversion. The acquired resistance of the complex against RNA-induced aggregation explains some of the unique properties of the PrP interaction with GAGs.     

Immobilization of Xanthine Oxidase on Carbon Nanotubes Through Double Supramolecular Junctions for Biosensor Construction

A novel approach for the noncovalent functionalization of single‐walled carbon nanotubes with enzymes, using a β‐cyclodextrin‐modified pyrene derivative, mono‐6‐ethylenediamino‐(2‐pyrene carboxamido)‐6‐deoxy‐β‐cyclodextrin (Pyr‐βCD), as a molecular bridge for the construction of a supramolecular assembly between the nanotube surface and an adamantane‐modified enzyme, is reported. The Pyr‐βCD derivative was synthesized and its stacking to SWNT through π–π interactions accomplished. The functionalized nanotubes showed low capacity for the nonspecific adsorption of proteins, but were able to immobilize adamantane‐modified xanthine oxidase via host‐guest associations. This double supramolecular junctions‐based approach was employed to modify a glassy carbon electrode with the enzyme/nanotubes complex for designing a biosensor device toward xanthine. The biosensor showed fast electroanalytical response (10 s), high sensitivity (5.9 mA/M cm²) low detection limit (2 µM) and high stability.     

Interpretation of the cytostatic properties of sodium morpholyldithiocarbamate,a chelating agent

Summary The antioxidant properties of sodium morpholyldithiocarbamate (MorDTC) were studied in order to contribute to the interpretation of its antitumor activity and synergetic effect overcis-platinum.MorDTC inhibits pyrogallol autooxidation better than vitamin C but does not dismutate the superoxide radical generated by the xanthine — xanthine oxidase system. Nevertheless, the complexes formedin situ betweenMorDTC and Mn(II), Co(II), Ni(II), and Cu(II) do dismutate the superoxide radical with a SOD-like activity (SOD=superoxide dismutase), expressed in terms of IC₅₀ values within the range of 3.2 to 62 µM. The highest activity corresponds to Mn(II) and Cu(II) complexes. The possible inhibitory action ofMorDTC on erythrocyte SOD was also studiedin vitro; however, the results were negative. Therefore,MorDTC should dismulate the superoxide radical after chelating metals without inhibiting SOD, the enzyme playing this rolein vivo.

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Interpretation der cytostatischen Eigenschaften von Natriummorpholyldithiocarbamat, einem komplexbildenden Reagens

Zusammenfassung Die antioxidativen Eigenschaften von Natriummorpholyldithiocarbamat (MorDTC) wurden im Hinblick auf seine Wirkung gegen Tumore und seinem synergistischen Effekt im Zusammenhang mitcis-Platin untersucht.MorDTC hemmt die Autoxidation von Pyrogallol besser als Vitamin C, greift aber das vom System Xanthin-Xanthinoxidase gebildete Superoxidradikal nicht an. Dieses wird jedoch von demin situ ausMorDTC und Mn(II), Co(II), Ni(II) und Cu(II) gebildeten Komplexen mit einer SOD-vergleichbaren Aktivität umgesetzt (SOD=Superoxiddismutase; IC₅₀ im Bereich von 3.2 bis 62 µM). Die höchste Aktivität wurde für Mn(II)- und Cu(II)-Komplexe gefunden. Die hemmende Wirkung vonMorDTC auf erythrocytische SOD wurdein vitro untersucht. Die Ergebnisse waren negativ.MorDTC ist daher nach der Komplexierung mit Metallen in der Lage, das Superoxidradikal anzugreifen, ohne SOD, das Enzym, das Enzym, das diese Aufgabein vivo übernimmt, zu hemmen.

     

Supramolecular immobilization of redox enzymes on cyclodextrin-coated magnetic nanoparticles for biosensing applications

Mono-6-formyl-β-cyclodextrin moieties were attached to (3-aminopropyl)triethoxysilane-coated superparamagnetic Fe(3)O(4) nanoparticles by reductive alkylation with NaBH(3)CN. The oligosaccharide-capped core-shell nanoparticles were employed as support for the supramolecular immobilization of two different adamantane-modified enzymes, tyrosinase and xanthine oxidase, through host-guest interactions. The enzyme-modified nanomaterial was further used to magnetically modify carbon paste electrodes for constructing amperometric biosensors toward cathecol and xanthine. The tyrosinase and xanthine oxidase based biosensors showed excellent electroanalytical behaviours, with linear ranges of 100nM-12μM cathecol and 5.0-120μM xanthine, sensitivities of 12mA/M and 130mA/M, and low detection limits of 22nM and 2.0μM, respectively. The supramolecular nature of the immobilization approach was confirmed by electroanalytical methods.     

Infinite dilution activity coefficents of hydrocarbons in tetra-n-alkyltin solvents between 40 and 60°C measured by gas-liquid chromatography

Infinite dilution activity coefficients for twenty-three hydrocarbons in tetra-n-amyltin (TAT) and in tetra-n-lauryltin (TLT) at several temperatures between 40 and 60°C were measured by gas liquid chromatography. The results, together with those obtained in an earlier paper in tetra-n-octyltin (TOT), are compared and discussed in terms of the equation of state theory of Flory and of the lattice fluid theory of Sanchez and Lacombe.