Microwave-assisted synthesis of novel cyclodextrin–cucurbituril complexes

Microwave irradiation was successfully used in order to obtain stable supramolecular aggregates between cyclodextrins and cucurbiturils, without the participation of any long-chain common ‘molecular thread’ guest. These aggregates were characterised by means of various different techniques, namely NMR, thermogravimetry, polarimetry and ESI-MS. Cross-analysis of experimental data allowed us to obtain insights on the stoichiometries of the composites and their thermal stabilities. The possible structures of the composites are briefly discussed, as well as the actual nature of their intrinsic stability.     

Monohydrates of cuprous chloride and argentous chloride: H2O⋅⋅⋅CuCl and H2O⋅⋅⋅AgCl characterized by rotational spectroscopy and ab initio calculations

Pure rotational spectra of the ground vibrational states of ten isotopologues of each of H(2)O???CuCl and H(2)O???AgCl have been measured and analyzed to determine rotational constants and hyperfine coupling constants for each molecule. The molecular structure and spectroscopic parameters determined from the experimental data are presented alongside the results of calculations at the CCSD(T) level. Both experiment and theory are consistent with structures that are nonplanar at equilibrium. The heavy atoms are collinear while the local C(2) axis of the water molecule intersects the axis defined by the heavy atoms at an angle, φ = 40.9(13)° for Cu and φ = 37.4(16)° for Ag. In the zero-point state, each molecule is effectively planar, undergoing rapid inversion between two equivalent structures where φ has equal magnitude but opposite sign. The equilibrium geometry has C(s) symmetry, however. The ab initio calculations confirm that the timescale of this inversion is at least an order of magnitude faster than that of rotation of the molecule in the lowest rotational energy levels. The molecular geometries are rationalized using simple rules that invoke the electrostatic interactions within the complexes. Centrifugal distortion constants, Δ(J) and Δ(JK), nuclear quadrupole coupling constants, χ(aa)(Cu), χ(aa)(Cl), (χ(bb) - χ(cc))(Cu), and (χ(bb) - χ(cc))(Cl), and the nuclear spin-rotation constant of the copper atom, C(bb)(Cu)+C(cc)(Cu), are also presented.     

Anti-inflammatory and antimalarial meroterpenoids from the New Zealand ascidian Aplidium scabellum

Bioassay-directed fractionation of an extract of the New Zealand ascidian Aplidium scabellum has afforded the anti-inflammatory secondary metabolite 2-geranyl-6-methoxy-1,4-hydroquinone-4-sulfate (1) and a family of pseudodimeric meroterpenoids scabellones A (2)-D (5). The benzo[c]chromene-7,10-dione scaffold contained within scabellones A-D is particularly rare among natural products. The structures were elucidated by interpretation of NMR data. Scabellone B was also identified as a moderately potent, nontoxic inhibitor of Plasmodium falciparum.     

Monolayer-protected nanoparticle film assemblies as platforms for controlling interfacial and adsorption properties in protein monolayer electrochemistry

Assembled films of nonaqueous nanoparticles, known as monolayer-protected clusters (MPCs), are investigated as adsorption platforms in protein monolayer electrochemistry (PME), a strategy for studying the electron transfer (ET) of redox proteins. Modified electrodes featuring MPC films assembled with various linking methods, including both electrostatic and covalent mechanisms, are employed to immobilize cytochrome c (cyt c) for electrochemical analysis. The background signal (non-Faradaic current) of these systems is directly related to the structure and composition of the MPC films, including nanoparticle core size, protecting ligand properties, as well as the linking mechanism utilized during assembly. Dithiol-linked films of Au225(C6)75 are identified as optimal films for PME by sufficiently discriminating against detrimental background current and exhibiting interfacial properties that are readily engineered for cyt c adsorption and electroactivity (Faradaic current). Surface concentrations and denaturation rates of adsorbed cyt c are dictated by specific manipulation of the individual MPCs composing the outer layer of the film. The use of specially designed, hydrophilic MPCs as a terminal film layer results in near-ideal cyt c voltammetry, attributed to a high degree of molecular level control of the necessary interfacial interactions and flexibility needed to create a uniform and effective binding of protein across large areas of a substrate. The electrochemical properties of cyt c at MPC films, including ET rate constants that are unaffected by the large ET distance introduced by MPC assemblies, are compared to traditional strategies employing self-assembled monolayers to immobilize cyt c. The incorporation of nanoparticles as protein adsorption platforms has implications for biosensor engineering as well as fundamental biological ET studies.     

Quantum molecular dynamics study of water on TiO2(110) surface

The adsorption of water on perfect TiO(2)(110) surface is studied by quantum molecular dynamics simulation adopting a periodic model formed by five water molecules on a (5 x 1) surface unit cell of a five layer slab of TiO(2). The total simulation time is 3.2 ps. At about 1.3 ps, one water molecule dissociates with the help of other adsorbed waters and surface bridging oxygens. During the remaining 1.9 ps, the waters and OH groups vibrate, but no more dissociation or recombination is observed. By comparing recent experimental O1s photoemission (x-ray photoelectron spectroscopy) spectra of H(2)O/TiO(2)(110) to the computed spectrum of the adsorbate in the configurations supplied by the molecular dynamics simulation, the observed peaks can be attributed to different oxygen species. The proposed assignment of the main spectral features supports the occurrence of partial water dissociation (approximately 20%) also on a perfect TiO(2) surface.     

A low-cost and low-tech electrochemical flow system for the evaluation of total phenolic content and antioxidant power of tea infusions

A disposable, small scale and low-cost electrochemical "wall-jet" flow-cell was build up together with a graphite lead mounted onto a pencil holder able to modulate the current response by the control of the surface area of the electrode. The total phenolic content of different types of tea infusions was determined and compared with the conventional Folin-Ciocolteau method. An index of antioxidant power was also proposed and data were compared with those obtained by the DPPH* assay.     

A mass spectrometry-based workflow for the proteomic analysis of in vitro cultured cell subsets isolated by means of laser capture microdissection

This paper describes a microproteomic workflow that is useful for simultaneously identifying and quantifying proteins from a minimal number of morphotypically heterogeneous cultured adherent cells. The analytical strategy makes use of laser capture microdissection, an effective means of harvesting pure cell populations, and label-free mass spectrometry. We optimised the workflow with particular reference to cell fixation which is crucial for successful laser-based microdissection and also downstream molecular studies. In addition, we defined the minimum number of cells to be isolated and analysed for satisfactory proteome coverage. To set up this workflow, we choose human monocyte-derived macrophages spontaneously differentiated in vitro. These cells, under our culture conditions, show distinct morphotypes, reminiscent of the heterogeneity observed in tissues in various homeostatic and pathological states, e.g. atherosclerosis. This optimised workflow may provide new insights into biology and pathology of heterogeneous cell in culture, particularly when other cell selection approaches are not suitable.

New strategies for the synthesis of partially fluorinated acrylic polymers as possible materials for the protection of stone monuments

The conservation of the cultural heritage requires the development of new materials having specific characteristics that encompass particular attention to durability and efficacy. We approached this problem by synthesizing polyacrylic esters containing variable amounts of fluorine in the α-position of the main chain. These products were obtained from the copolymerisation of ammonium 2-fluoroacrylate and acrylic acid. The polyacrylic acids were esterified using different procedures. The polyester characteristics vary in relation to the polymerisation procedures and degree of esterification. The best esterification results, were obtained using a reaction catalyzed by BF₃ or TMSCl. These materials show good properties and are of potential interest for their use as protective agents for stone conservation.