Identification and characterization of antibacterial compound(s) of cockroaches (Periplaneta americana).

Infectious diseases remain a significant threat to human health, contributing to more than 17 million deaths, annually. With the worsening trends of drug resistance, there is a need for newer and more powerful antimicrobial agents. We hypothesized that animals living in polluted environments are potential sources of antimicrobials. Under polluted milieus, organisms such as cockroaches encounter different types of microbes, including superbugs. Such creatures survive the onslaught of superbugs and are able to ward off disease by producing antimicrobial substances. Here, we characterized antibacterial properties in extracts of various body organs of cockroaches (Periplaneta americana) and showed potent antibacterial activity in crude brain extract against methicillin-resistant Staphylococcus aureus and neuropathogenic Escherichia coli K1. The size-exclusion spin columns revealed that the active compound(s) are less than 10 kDa in molecular mass. Using cytotoxicity assays, it was observed that pre-treatment of bacteria with lysates inhibited bacteria-mediated host cell cytotoxicity. Using spectra obtained with LC-MS on Agilent 1290 infinity liquid chromatograph, coupled with an Agilent 6460 triple quadruple mass spectrometer, tissues lysates were analysed. Among hundreds of compounds, only a few homologous compounds were identified that contained the isoquinoline group, chromene derivatives, thiazine groups, imidazoles, pyrrole-containing analogs, sulfonamides, furanones, and flavanones and known to possess broad-spectrum antimicrobial properties and anti-inflammatory, anti-tumour, and analgesic properties. Further identification, characterization, and functional studies using individual compounds can act as a breakthrough in developing novel therapeutics against various pathogens including superbugs.

Hybrid lipid-silica microcapsules engineered by phase coacervation of Pickering emulsions to enhance lipid hydrolysis.

We report on the fabrication of dry hybrid lipid-silica microcapsules for enhanced lipid hydrolysis using Pickering emulsion templates formed by interfacial nanoparticle-emulsifier electrostatic interaction. The microcapsules are produced by controlled precipitation of emulsion droplets by oppositely charged silica nanoparticles at room temperature. Microcapsule formation is driven by the interfacial structure of the initial Pickering emulsion, which is in turn controlled by the nanoparticle to lipid ratio. In the region of charge reversed, precipitated and aggregated droplets, droplet-nanoparticle networks have been identified by freeze-fracture SEM imaging. The microcapsules have diameters in the range 20-50 mum and contain approximately 65% oil distributed within an internal matrix structure composed of a labyrinth of interconnected pores approximately 20-100 nm. Pore distribution and diameters depend on the silica to nanoparticle ratio that in turn determines droplet coating and stability. The microcapsules facilitate enhanced lipid hydrolysis kinetics, i.e. their pseudo first-order rate constant for lipid hydrolysis is approximately 3 times greater than for equivalent submicron lipid droplets. This behaviour is attributed to the increased oil surface area within the microcapsule due to the specific porous structure that causes rapid release of submicron and micron size oil droplets. The simple route for fabrication of porous microcapsule morphologies may present new opportunities for applications in encapsulation, delivery, coatings, and catalysis.

Development of a facile fluorophosphonate-functionalised titanium surface for potential orthopaedic applications.

BACKGROUND: Aseptic loosening of total joint replacements (TJRs) continues to be the main cause of implant failures. The socioeconomic impact of surgical revisions is hugely significant; in the United Kingdom alone, it is estimated that £137 m is spent annually on revision arthroplasties. Enhancing the longevity of titanium implants will help reduce the incidence and overall cost of failed devices. METHODS: In realising the development of a superior titanium technology, we exploited the natural affinity of titanium for phosphonic acids and developed a facile means of coating the metal with (3S)1-fluoro-3-hydroxy-4-(oleoyloxy)butyl-1-phosphonate (FHBP), a phosphatase-resistant analogue of lysophosphatidic acid (LPA). Importantly LPA and selected LPA analogues like FHBP synergistically cooperate with calcitriol to promote human osteoblast formation and maturation. RESULTS: Herein, we provide evidence that simply immersing titanium in aqueous solutions of FHBP afforded a surface that was superior to unmodified metal at enhancing osteoblast maturation. Importantly, FHBP-functionalised titanium remained stable to 2 years of ambient storage, resisted ∼35 kGy of gamma irradiation and survived implantation into a bone substitute (Sawbone™) and irrigation. CONCLUSION: The facile step we have taken to modify titanium and the robustness of the final surface finish are appealing properties that are likely to attract the attention of implant manufacturers in the future. THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE: We have generated a functionalised titanium (Ti) surface by simply immersing Ti in aqueous solutions of a bioactive lipid. As a facile procedure it will have greater appeal to implant manufacturers compared to onerous and costly developmental processes.

fac-Aceto-nitrile-tricarbon-yl(di-methyl-carbamodi-thio-ato-κ2S,S')rhenium(I): crystal structure and Hirshfeld surface analysis.

The title compound, [Re(C3H6NS2)(C2H3N)(CO)3], features an octa-hedrally coordinated ReI atom within a C3NS2 donor set defined by three carbonyl ligands in a facial arrangement, an aceto-nitrile N atom and two S atoms derived from a symmetrically coordinating di-thio-carbamate ligand. In the crystal, di-thio-carbamate-methyl-H⋯O(carbon-yl) inter-actions lead to supra-molecular chains along [36-1]; both di-thio-carbamate S atoms participate in intra-molecular methyl-H⋯S inter-actions. Further but weaker aceto-nitrile-C-H⋯O(carbonyl) inter-actions assemble mol-ecules in the ab plane. The nature of the supra-molecular assembly was also probed by a Hirshfeld surface analysis. Despite their weak nature, the C-H⋯O contacts are predominant on the Hirshfeld surface and, indeed, on those of related [Re(CO)3(C3H6NS2)L] structures.

Examination of Surface Deposits on Oldbury Reactor Core Graphite to Determine the Concentration and Distribution of 14C.

Pile Grade A graphite was used as a moderator and reflector material in the first generation of UK Magnox nuclear power reactors. As all of these reactors are now shut down there is a need to examine the concentration and distribution of long lived radioisotopes, such as 14C, to aid in understanding their behaviour in a geological disposal facility. A selection of irradiated graphite samples from Oldbury reactor one were examined where it was observed that Raman spectroscopy can distinguish between underlying graphite and a surface deposit found on exposed channel wall surfaces. The concentration of 14C in this deposit was examined by sequentially oxidising the graphite samples in air at low temperatures (450°C and 600°C) to remove the deposit and then the underlying graphite. The gases produced were captured in a series of bubbler solutions that were analysed using liquid scintillation counting. It was observed that the surface deposit was relatively enriched with 14C, with samples originating lower in the reactor exhibiting a higher concentration of 14C. Oxidation at 600°C showed that the remaining graphite material consisted of two fractions of 14C, a surface associated fraction and a graphite lattice associated fraction. The results presented correlate well with previous studies on irradiated graphite that suggest there are up to three fractions of 14C; a readily releasable fraction (corresponding to that removed by oxidation at 450°C in this study), a slowly releasable fraction (removed early at 600°C in this study), and an unreleasable fraction (removed later at 600°C in this study).

[N,N-Bis(2-hy-droxy-eth-yl)di-thio-carbamato-κ2S,S']bis-(tri-phenyl-phosphane-κP)copper(I) chloro-form monosolvate: crystal structure, Hirshfeld surface analysis and solution NMR measurements.

The title compound, [Cu(C5H5NO2S2)(C18H15P)2]·CHCl3, features a tetra-hedrally coordinated CuI atom within a P2S2 donor set defined by two phosphane P atoms and by two S atoms derived from a symmetrically coordinating di-thio-carbamate ligand. Both intra- and inter-molecular hy-droxy-O-H⋯O(hydroxy) hydrogen bonding is observed: the former closes an eight-membered {⋯HOC2NC2O} ring, whereas the latter connects centrosymmetrically related mol-ecules into dimeric aggregates via eight-membered {⋯H-O⋯H-O}2 synthons. The complex mol-ecules are arranged to form channels along the c axis in which reside the chloro-form mol-ecules, being connected by Cl⋯π(arene) and short S⋯Cl [3.3488 (9) Å] inter-actions. The inter-molecular inter-actions have been investigated further by Hirshfeld surface analysis, which shows the conventional hydrogen bonding to be very localized with the main contributors to the surface, at nearly 60%, being H⋯H contacts. Solution NMR studies indicate that whilst the same basic mol-ecular structure is retained in solution, the tri-phenyl-phosphane ligands are highly labile, exchanging rapidly with free Ph3P at room temperature.

A Study of the Oxidation Behaviour of Pile Grade A (PGA) Nuclear Graphite Using Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM) and X-Ray Tomography (XRT).

Pile grade A (PGA) graphite was used as a material for moderating and reflecting neutrons in the UK's first generation Magnox nuclear power reactors. As all but one of these reactors are now shut down there is a need to understand the residual state of the material prior to decommissioning of the cores, in particular the location and concentration of key radio-contaminants such as 14C. The oxidation behaviour of unirradiated PGA graphite was studied, in the temperature range 600-1050°C, in air and nitrogen using thermogravimetric analysis, scanning electron microscopy and X-ray tomography to investigate the possibility of using thermal degradation techniques to examine 14C distribution within irradiated material. The thermal decomposition of PGA graphite was observed to follow the three oxidation regimes historically identified by previous workers with limited, uniform oxidation at temperatures below 600°C and substantial, external oxidation at higher temperatures. This work demonstrates that the different oxidation regimes of PGA graphite could be developed into a methodology to characterise the distribution and concentration of 14C in irradiated graphite by thermal treatment.

Investigating the role of microbes in mineral weathering: nanometre-scale characterisation of the cell-mineral interface using FIB and TEM.

Focused ion beam (FIB) sample preparation in combination with subsequent transmission electron microscopy (TEM) analysis are powerful tools for nanometre-scale examination of the cell-mineral interface in bio-geological samples. In this study, we used FIB-TEM to investigate the interaction between a cyanobacterium (Hassallia byssoidea) and a common sheet silicate mineral (biotite) following a laboratory-based bioweathering, incubation experiment. We discuss the FIB preparation of cross-sections of the cell mineral interface for TEM investigation. We also establish an electron fluence threshold (at 200keV) in biotite for the transition from scanning (S)TEM electron beam induced contamination build up on the surface of biotite thin sections to mass loss, or hole-drilling within the sections. Working below this threshold fluence nanometre-scale structural and elemental information has been obtained from biotite directly underneath cyanobacterial cells incubated on the biotite for 3 months. No physical alteration of the biotite was detected by TEM imaging and diffraction with little or no elemental alteration detected by STEM-energy dispersive X-ray (EDX) elemental line-scanning or by energy filtered TEM (EF-TEM) jump ratio elemental mapping. As such we present evidence that the cyanobacterial strain of H. byssoidea did not cause any measurable alteration of biotite, within the resolution limits of the analysis techniques used, after 3 months of incubation on its surface.

Dry hybrid lipid-silica microcapsules engineered from submicron lipid droplets and nanoparticles as a novel delivery system for poorly soluble drugs.

We report on the fabrication and characterization of dry hybrid lipid-silica nanoparticle based microcapsules with an internal porous matrix structure for encapsulation of poorly soluble drugs, and their delivery properties (in vitro release and lipolysis and in vivo pharmacokinetics demonstrated for indomethacin as a model drug). Microcapsules were prepared by spray drying of Pickering o/w emulsions containing either negatively or positively charged lipophilic surfactant in the oil phase and hydrophilic silica nanoparticles in the aqueous phase. Effective microcapsule formation is critically dependent on the interfacial structure of the nanoparticle containing emulsions, which are in turn controlled by the surfactant charge and the nanoparticle to lipid ratio. Microcapsules (containing 50-85% oil) can be prepared with 10 times fewer silica nanoparticles when a droplet-nanoparticle charge neutralizing mechanism is operative. Cross-sectional SEM imaging has confirmed the internal porous matrix structure and identified pore sizes in the range 20-100 nm, which is in agreement with BET average pore diameters determined from gas adsorption experiments. Differential scanning calorimetry and X-ray diffraction analysis have confirmed that the model drug indomethacin remains in a noncrystalline form during storage under accelerated conditions (40 degrees C, 75% RH). Dissolution studies revealed a 2-5-fold increase in dissolution efficiency and significantly reduced the time taken to achieve 50% of drug dissolution values (> or =2- or 10-fold) for indomethacin formulated as microcapsules in comparison to o/w submicron emulsions and pure drug, respectively. Orally dosed in vivo studies in rats have confirmed superior pharmacokinetics for the microcapsules. Specifically, the fasted state absolute bioavailability (F) was statistically higher (93.07 +/- 5.09%) (p < 0.05) than for aqueous suspension (53.54 +/- 2.91%) and o/w submicron emulsion (64.57 +/- 2.11%). The microcapsules also showed the highest maximum plasma concentration (C(max)) among the investigated formulations (p < 0.05). In vitro lipolysis showed statistically higher (p < 0.05) fasted digestion (75.8% after 5 min) and drug solubilization (98% after 5 min) in digestive products for microcapsules than o/w emulsions. The hybrid lipid-silica microcapsules improve oral absorption by enhancing lipolysis and drug dissolution.

Dynamic stereochemical rearrangements in chiral organometallic complexes.

Organometallic complexes have long been known to display a wide variety of dynamic stereochemical processes. Classic examples of such processes include the exchange of axial and equatorial environments in trigonal bipyramidal complexes, such as Fe(CO)(5), and the migration of the metal moiety round the periphery of the cyclopentadiene ring in eta(1)-bound Cp complexes. The systematic study of fluxional processes is of interest because it can not only help provide a detailed, quantitative 'picture' of the bonding between the metals and ligands involved, but it can also help to rationalise chemical reactivity patterns. The introduction of chirality into organometallic complexes, usually in the form of a non-racemic chiral ligand, has led to an explosion in the importance such species, particularly with regard to their applications in organic functional group transformations. The presence of a chiral centre can also provide an excellent spectroscopic handle on the complex in question, enabling both novel fluxional processes to be observed and new light to be shed on old (unresolved) problems. In this critical review (101 references) the literature on metal-centred fluxional rearrangements in chiral transition and main group organometallic complexes is reviewed, complementing the recent review by Faller (see reference 8).

Determination of the elemental composition of mature wheat grain using a modified secondary ion mass spectrometer (SIMS).

An imaging secondary ion mass spectrometry system has been developed that allows the distribution of elements or ions to be superimposed on an image of the plant cell or tissue generated by ion-induced secondary electrons. This system has been evaluated by analysing the aleurone and sub-aleurone cells of mature wheat grain, showing high spatial resolution (100-200 nm) images of O-, PO(2)-, Mg+, Ca+, Na+ and K+ within the phytate granules of the aleurone, with CN- being diagnostic for proteins and C(2)- being diagnostic for starch in the starchy endosperm cells. This system should provide improved localization of elements in a range of other plant systems.

A role for HKT1 in sodium uptake by wheat roots.

The high affinity potassium transporter, HKT1 from wheat was introduced into Florida wheat in sense and antisense orientation under control of a ubiquitin promoter. Ten transgenic lines expressing the transgene were identified and two of these showed strong down-regulation of the native HKT1 transcript. One line (271) was expressing the antisense construct and the other (223) was expressing a truncated sense construct. The two lines were examined further for phenotype relating to cation transport. Membrane depolarisations were measured in low (0.1 mm) K+ and high (100 mm) NaCl. Under these conditions there was no difference between line 271 and the control at low K+, but at high Na+ there was a rapid depolarisation that was significantly larger in control plants. 22Na uptake was measured in this line and there was a significant decrease in uptake at 100 mm NaCl in the transgenic line when compared with the control. The two transgenic lines were grown at high NaCl (200 mm) and analysed for growth and root sodium content. Lines 271 and 223 showed enhanced growth under salinity when compared with the control and had lower sodium in the root. Secondary ion mass spectrometry (SIMS) analysis of transverse sections of the root showed that Na+ and K+ were strongly localised to stelar regions when compared with other ions, and that the Na+ : K+ ratios were reduced in salt-stressed transgenic tissue when compared with the control.