Precise Subnanometer Plasmonic Junctions for SERS within Gold Nanoparticle Assemblies Using Cucurbit[n]uril "Glue"

Cucurbit[n]urils (CB[n]) are macrocyclic host molecules with subnanometer dimensions capable of binding to gold surfaces. Aggregation of gold nanoparticles with CB[n] produces a repeatable, fixed, and rigid interparticle separation of 0.9 nm, and thus such assemblies possess distinct and exquisitely sensitive plasmonics. Understanding the plasmonic evolution is key to their use as powerful SERS substrates. Furthermore, this unique spatial control permits fast nanoscale probing of the plasmonics of the aggregates "glued" together by CBs within different kinetic regimes using simultaneous extinction and SERS measurements. The kinetic rates determine the topology of the aggregates including the constituent structural motifs and allow the identification of discrete plasmon modes which are attributed to disordered chains of increasing lengths by theoretical simulations. The CBs directly report the near-field strength of the nanojunctions they create via their own SERS, allowing calibration of the enhancement. Owing to the unique barrel-shaped geometry of CB[n] and their ability to bind "guest" molecules, the aggregates afford a new type of in situ self-calibrated and reliable SERS substrate where molecules can be selectively trapped by the CB[n] and exposed to the nanojunction plasmonic field. Using this concept, a powerful molecular-recognition-based SERS assay is demonstrated by selective cucurbit[n]uril host-guest complexation.

Anthelmintic resistance in Northern Ireland (II): Variations in nematode control practices between lowland and upland sheep flocks

A questionnaire to obtain information on nematode control practices and sheep management was sent to over 1000 farmers in Northern Ireland. Replies were received from 305 flock owners, and data from 252 of them were analysed. Farms were divided into lowland and upland areas. Sizes of pasture and stocking rates on lowland and upland farms were 59.5 hectares, 6.99 sheep/hectare and 62.9 hectares and 10.01 sheep/hectare, respectively. Mean drenching rates for lambs and adults were 2.33 and 2.44, respectively, in lowland flocks and 2.73 and 2.71, respectively, in upland flocks. Between 2008 and 2011, the most frequently identified compounds in use were benzimidazoles and moxidectin in lowland flocks, and benzimidazoles and avermectins in upland flocks. Over the same period the most frequently identified commercial formulations were Tramazole (R), Panacur (R) and Allverm (R) (white drench), Levacide (R) (yellow drench), Oramec (R) (clear drench; avermectin), Cydectin (R) (clear drench; moxidectin) and Monepantel (R) (orange drench).

Most respondents (56.35%) treated their lambs at weaning and the most common time to treat ewes was identified to be pre-mating (67.86% of respondents).

The results of the questionnaire survey revealed that lowland annual drench frequency was 233 and 2.44 in lambs and ewes, respectively, although drench frequencies were higher in upland flocks: 2.73 and 2.71 for lambs and ewes, respectively.

Annual drench rotation was practiced by 43.96% of flock owners, but whether this was true rotation or pseudo-rotation (i.e., substitution of one anthelmintic product by another product belonging to the same chemical group of anthelmintics) could not be explicitly determined. (C) 2012 Elsevier B.V. All rights reserved.

Marine-derived quorum-sensing inhibitory activities enhance the antibacterial efficacy of tobramycin against Pseudomonas aeruginosa

Bacterial epiphytes isolated from marine eukaryotes were screened for the production of quorum sensing inhibitory compounds (QSIs). Marine isolate KS8, identified as a Pseudoalteromonas sp., was found to display strong quorum sensing inhibitory (QSI) activity against acyl homoserine lactone (AHL)-based reporter strains Chromobacterium violaceum ATCC 12472 and CV026. KS8 supernatant significantly reduced biofilm biomass during biofilm formation (−63%) and in pre-established, mature P. aeruginosa PAO1 biofilms (−33%). KS8 supernatant also caused a 0.97-log reduction (−89%) and a 2-log reduction (−99%) in PAO1 biofilm viable counts in the biofilm formation assay and the biofilm eradication assay respectively. The crude organic extract of KS8 had a minimum inhibitory concentration (MIC) of 2 mg/mL against PAO1 but no minimum bactericidal concentration (MBC) was observed over the concentration range tested (MBC > 16 mg/mL). Sub-MIC concentrations (1 mg/mL) of KS8 crude organic extract significantly reduced the quorum sensing (QS)-dependent production of both pyoverdin and pyocyanin in P. aeruginosa PAO1 without affecting growth. A combinatorial approach using tobramycin and the crude organic extract at 1 mg/mL against planktonic P. aeruginosa PAO1 was found to increase the efficacy of tobramycin ten-fold, decreasing the MIC from 0.75 to 0.075 µg/mL. These data support the validity of approaches combining conventional antibiotic therapy with non-antibiotic compounds to improve the efficacy of current treatments.

Permeation of bioactive constituents from Arnica montana preparations through human skin in-vitro

This study investigated and characterised transdermal permeation of bioactive agents from a topically applied Arnica montana tincture. Permeation experiments conducted over 48 h used polydimethylsiloxane (silastic) and human epidermal membranes mounted in Franz-type diffusion cells with a methanol-water (50:50 v/v) receptor fluid. A commercially available tincture of A. montana L. derived from dried Spanish flower heads was a donor solution. Further donor solutions prepared from this stock tincture concentrated the tincture constituents 1, 2 and 10 fold and its sesquiterpene lactones 10 fold. Permeants were assayed using a high-performance liquid chromatography method. Five components permeated through silastic membranes providing peaks with relative retention factors to an internal standard (santonin) of 0.28, 1.18, 1.45, 1.98 and 2.76, respectively. No permeant was detected within 12 h of applying the Arnica tincture onto human epidermal membranes. However, after 12 h, the first two of these components were detected. These were shown by Zimmermann reagent reaction to be sesquiterpene lactones and liquid chromatography/diode array detection/mass spectrometry indicated that these two permeants were 11,13-dihydrohelenalin (DH) analogues (methacrylate and tiglate esters). The same two components were also detected within 3 h of topical application of the 10-fold concentrated tincture and the concentrated sesquiterpene lactone extract.

Non-thermal Plasma Exposure Rapidly Attenuates Bacterial AHL-Dependent Quorum Sensing and Virulence.

The antimicrobial activity of atmospheric pressure non-thermal plasma has been exhaustively characterised, however elucidation of the interactions between biomolecules produced and utilised by bacteria and short plasma exposures are required for optimisation and clinical translation of cold plasma technology. This study characterizes the effects of non-thermal plasma exposure on acyl homoserine lactone (AHL)-dependent quorum sensing (QS). Plasma exposure of AHLs reduced the ability of such molecules to elicit a QS response in bacterial reporter strains in a dose-dependent manner. Short exposures (30-60 s) produce of a series of secondary compounds capable of eliciting a QS response, followed by the complete loss of AHL-dependent signalling following longer exposures. UPLC-MS analysis confirmed the time-dependent degradation of AHL molecules and their conversion into a series of by-products. FT-IR analysis of plasma-exposed AHLs highlighted the appearance of an OH group. In vivo assessment of the exposure of AHLs to plasma was examined using a standard in vivo model. Lettuce leaves injected with the rhlI/lasI mutant PAO-MW1 alongside plasma treated N-butyryl-homoserine lactone and n-(3-oxo-dodecanoyl)-homoserine lactone, exhibited marked attenuation of virulence. This study highlights the capacity of atmospheric pressure non-thermal plasma to modify and degrade AHL autoinducers thereby attenuating QS-dependent virulence in P. aeruginosa.

Molecular Recognition in Biomimetic Receptors

This book commemorates the 25th anniversary of the International Izatt-Christensen Award in Macrocyclic and Supramolecular Chemistry. The award, one of the most prestigious of small awards in chemistry, recognizes excellence in the developing field of macrocyclic and supramolecular chemistry

Macrocyclic and Supramolecular Chemistry: How Izatt-Christensen Award Winners Shaped the Field features chapters written by the award recipients who provide unique perspectives on the spectacular growth in these expanding and vibrant fields of chemistry over the past half century, and on the role of these awardees in shaping this growth. During this time there has been an upsurge of interest in the design, synthesis and characterization of increasingly more complex macrocyclic ligands and in the application of this knowledge to understanding molecular recognition processes in host-guest chemistry in ways that were scarcely envisioned decades earlier.

Rotary moulding of ceramic hollow wares

A novel processing method for the fast and economic production of hollow ceramic components has been developed by combining in situ coagulation moulding with a modified version of the technique of rotary moulding[Binner, J. G. P., Al-Dawery, I. A., Tari, G. and Yan, Y., Rotary casting technique. UK Patent application No. 0506349.0, March 2005], the latter being adapted from the polymer industry. The process was found to require a high solids content suspension, hence development work was performed in this direction though in the end a new, commercial suspension was utilised. Of the three forming routes of gel casting, direct coagulation casting and in situ coagulation moulding, the latter was found to be the most promising for the new process of rotary moulding of ceramics. Due to the low value of clay-based ceramics, a new low cost coagulant was identified and the effect of lactone concentration and temperature on setting time determined. Following substantial optimisation work, it was found that a two-speed approach to multi-axial rotation was the most successful; medium sized cream jugs could be produced in just 7 min. With respect to mould materials, the porous resin normally used for pressure casting of sanitary ware was found to be the best option, though since this is quite expensive conventional plaster-of-paris moulds were found to be a suitable material to enable companies, particularly SMEs, to become familiar with the technology whilst avoiding high costs for trials. The processed articles could be successfully fired and glazed using gas-fired kilns with no sign of any black cores. Major advantages of the process include the ability to precisely calculate the amount of ceramic slip required, eliminating either slip wastage or the need to pour used slip back into the virgin material as currently happens with slip casting. In addition, since the precursor suspension has a very high solids content, the time and energy required to dry the green product and associated moulds has been considerably reduced. © 2008 Elsevier Ltd. All rights reserved.