Pyrene-Modified quartz crystal microbalance for the detection of polynitroaromatic compounds

The synthesis of a dithiol-functionalized pyrene derivative is reported, together with studies of interactions between this receptor (and other related pyrenes) and nitroaromatic compounds (NACs), in both solution and in the solid state. Spectroscopic analysis in solution and X-ray crystallographic analysis of cocrystals of pyrene and NACs in the solid state indicate that supramolecular interactions lead to the formation of defined pi-pi stacked complexes. The dithiolfunctionalized pyrene derivative can be used to modify the surface of a gold quartz crystal microbalance (QCM) to create a unique π-electron rich surface, which is able to interact with electron poor aromatic compounds. For example, exposure of the modified QCM surface to the nitroaromatic compound 2,4-dinitrotoluene (DNT) in solution results in a reduction in the resonant frequency of the QCM as a result of supramolecular interactions between the electron-rich pyrenyl surface layer and the electron-poor DNT molecules. These results suggest the potential use of such modified QCM surfaces for the detection of explosive NACs.

Enhanced viability of corneal epithelial cells for efficient transport/storage using a structurally-modified calcium alginate hydrogel

Aims: Therapeutic limbal epithelial stem cells could be managed more efficiently if clinically validated batches were transported for ‘on-demand’ use. Materials & methods: In this study, corneal epithelial cell viability in calcium alginate hydrogels was examined under cell culture, ambient and chilled conditions for up to 7 days. Results: Cell viability improved as gel internal pore size increased, and was further enhanced with modification of the gel from a mass to a thin disc. Ambient storage conditions were optimal for supporting cell viability in gel discs. Cell viability in gel discs was significantly enhanced with increases in pore size mediated by hydroxyethyl cellulose. Conclusion: Our novel methodology of controlling alginate gel shape and pore size together provides a more practical and economical alternative to established corneal tissue/cell storage methods.

The study of chiral adsorption systems using synchrotron- based structural and spectroscopic techniques: stereospecific adsorption of serine on Au-modified chiral Cu{531} surfaces

We apply modern synchrotron-based structural techniques to the study of serine adsorbed on the pure andAumodified intrinsically chiral Cu{531} surface. XPS and NEXAFS data in combination with DFT show that on the pure surface both enantiomers adsorb in l4 geometries (with de-protonated b-OH groups) at low coverage and in l3 geometries at saturation coverage. Significantly larger enantiomeric differences are seen for the l4 geometries, which involve substrate bonds of three side groups of the chiral center, i.e. a three-point interaction. The l3 adsorption geometry, where only the carboxylate and amino groups form substrate bonds, leads to smaller but still significant enantiomeric differences, both in geometry and the decomposition behavior. When Cu{531} is modified by the deposition of 1 and 2ML Au the orientations of serine at saturation coverage are significantly different from those on the clean surface. In all cases, however, a l3 bond coordination is found at saturation involving different numbers of Au atoms, which leads to relatively small enantiomeric differences.

Fibrils and nanotubes assembled from a modified amyloid-β peptide fragment differ in the packing of the same β-sheet building blocks

The peptide AAKLVFF assembles into fibrils in water and nanotubes in methanol. Solid-state NMR data are consistent with fibrils constructed from β-sheet bilayers and nanotubes bounded by a wall of offset β-sheet monolayers. Remarkably distinct morphologies are thus traced to subtle differences in the arrangement of the same fundamental building blocks.

Control of DNA conformation using 3'-S-phosphorothiolate-modified linkages

An in-depth study into the incorporation of multiple 3'-S-phosphorothiolate modifications into oligodeoxynucleotides (ODNs) and their subsequent effect on ODN/DNA and ODN/RNA duplex stability. 3'-S-Phosphorothiolate linkages increase the stability of ODN/RNA duplexes and decrease the stability of ODN/DNA duplexes.

Comment on “A modified leapfrog scheme for shallow water equations” by Wen-Yih Sun and Oliver M.T. Sun

A recent paper published in this journal considers the numerical integration of the shallow-water equations using the leapfrog time-stepping scheme [Sun Wen-Yih, Sun Oliver MT. A modified leapfrog scheme for shallow water equations. Comput Fluids 2011;52:69–72]. The authors of that paper propose using the time-averaged height in the numerical calculation of the pressure-gradient force, instead of the instantaneous height at the middle time step. The authors show that this modification doubles the maximum Courant number (and hence the maximum time step) at which the integrations are stable, doubling the computational efficiency. Unfortunately, the pressure-averaging technique proposed by the authors is not original. It was devised and published by Shuman [5] and has been widely used in the atmosphere and ocean modelling community for over 40 years.

Effects of modified atmosphere packaging on quality of ‘Alphonso’ Mangoes

Postharvest quality of Alphonso mangoes (Mangifera indica L) is vital to ensure proper ripening and good quality. 500 g mature green mangoes, were subjected to three pre- packaging hot water dips (20, 30 & 40°C) for 40 min, two packaging films (OPP unperforated and perforated), using three levels of gas concentrations of 25,50 and 75% v/v CO2 treatments (balance N2) and stored at 10°C for 21 days. During the storage period headspace gas composition, weight loss, ascorbic acid, pulp firmness, external fruit colour and overall quality score were measured to determine optimum storage conditions. The most effective postharvest condition was found to be dipping in water maintained at 40°C for 40 min, followed by packaging under 50% CO2 in bags made of unperforated film when compared to mangoes packed under 25 and 75% CO2 which showed deteriorated quality including spoilage and mould. Good keeping quality of at least 21 days was achieved under these conditions, which was much superior to the control samples that showed deterioration after 12 days of storage.

A modified rapid enzymatic microtiter plate assay for the quantification of intracellular γ-aminobutyric acid and succinate semialdehyde in bacterial cells

The GABase assay is widely used to rapidly and accurately quantify levels of extracellular γ-aminobutyric acid (GABA). Here we demonstrate a modification of this assay that enables quantification of intracellular GABA in bacterial cells. Cells are lysed by boiling and ethanolamine-O-sulphate, a GABA transaminase inhibitor is used to distinguish between GABA and succinate semialdehyde.

Salts responsive nanovesicles through π-stacking induced self-assembly of backbone modified tripeptides

A set of backbone modified peptides of general formula Boc-Xx-m-ABA-Yy-OMe where m-ABA is meta-aminobenzoic acid and Xx and Yy are natural amino acids such as Phe, Gly, Pro, Leu, Ile, Tyr and Trp etc., are found to self-assemble into soft nanovesicular structures in methanol-water solution (9:1 by v/v). At higher concentration the peptides generate larger vesicles which are formed through fusion of smaller vesicles. The formation of vesicles has been facilitated through the participation of various noncovalent interactions such as aromatic pi-stacking, hydrogen bonding and hydrophobic interactions. Model study indicates that the pi-stacking induced self-assembly, mediated by m-ABA is essential for well structured vesicles formation. The presence of conformationally rigid m-ABA in the backbone of the peptides also helps to form vesicular structures by restricting the conformational entropy. The vesicular structures get disrupted in presence of various salts such as KCl, CaCl(2), N(n-Bu)(4)Br and (NH(4))(2)SO(4) in methanol-water solution. Fluorescence microscopy and UV studies reveal that the soft nanovesicles encapsulate organic dye molecules such as Rhodamine B and Acridine Orange which could be released through salts induced disruption of vesicles.

Changing European storm loss potentials under modified climate conditions according to ensemble simulations of the ECHAM5/MPI-OM1 GMC

A simple storm loss model is applied to an ensemble of ECHAM5/MPI-OM1 GCM simulations in order to estimate changes of insured loss potentials over Europe in the 21st century. Losses are computed based on the daily maximum wind speed for each grid point. The calibration of the loss model is performed using wind data from the ERA40-Reanalysis and German loss data. The obtained annual losses for the present climate conditions (20C, three realisations) reproduce the statistical features of the historical insurance loss data for Germany. The climate change experiments correspond to the SRES-Scenarios A1B and A2, and for each of them three realisations are considered. On average, insured loss potentials increase for all analysed European regions at the end of the 21st century. Changes are largest for Germany and France, and lowest for Portugal/Spain. Additionally, the spread between the single realisations is large, ranging e.g. for Germany from −4% to +43% in terms of mean annual loss. Moreover, almost all simulations show an increasing interannual variability of storm damage. This assessment is even more pronounced if no adaptation of building structure to climate change is considered. The increased loss potentials are linked with enhanced values for the high percentiles of surface wind maxima over Western and Central Europe, which in turn are associated with an enhanced number and increased intensity of extreme cyclones over the British Isles and the North Sea.