Compositional effects on structure and transport properties in a polyelectrolyte gel

The copolymerization of lithium 2-acrylamido-2-methyl-1-propane sulfonate (LiAMPS) with N,N ′-dimethylacrylamide has yielded polyelectrolyte systems which can be gelled with an ethylene carbonate/N ′,N ′-dimethylacetamide solvent mixture and show high ionic conductivities. 7Li linewidth and relaxation times as well as 1H NMR diffusion coefficients have been used to investigate the effect of copolymer composition as well as copolymer concentration in the gel electrolyte with respect to ionic transport and polyelectrolyte structure. It appears that ion association is likely even in the case of low lithium salt concentration; however a rapid exchange exists between the associated and non-associated lithium species. Beyond 0.2 M of LiAMPS, both the conductivity and solvent diffusion reach a plateau, whilst lithium ion linewidth and spin-spin relaxation are suggestive, on average, of a less mobile species. The thermal analysis data is also supportive of this association effectively leading to a form of phase separation on the nanoscale, which gives a lower overall activity of lithium ions in the solvent rich regions beyond about 0.2 M of LiAMPS, thereby leading to an increase in the final liquidus temperature of the binary liquid solvent from –9 to +5°C.

Quantifying rubber degradation using NMR

Ageing can lead to the degradation of the tensile properties of natural rubber. The ageing process causes changes in the polymer segmental motion as well as the chemical structure, both of which can be monitored using nuclear magnetic resonance (NMR) spectroscopy. This work demonstrates that NMR can quantify rubber degradation due to ageing, and also that relatively simple NMR equipment can be used. This simpler equipment can be made portable and so could give a simple and fast indication of the condition of rubber in service. The 1H NMR transverse relaxation time, T2, and the 13C NMR spectrum using cross polarization and magic angle spinning (CP MAS) for samples taken at various levels of a degraded natural rubber liner were compared. These experiments showed that, as the level of degradation increased, the 1H NMR transverse relaxation time decreased. The 13C spectra showed considerable peak broadening, indicative of decreased mobility with increased level of degradation as well as the presence of degradation products. Further investigations using lower powered NMR equipment to measure the 1H NMR transverse relaxation times of two different series of natural rubbers were also performed. This work has shown that this simpler method is also sensitive to structural and mechanical property changes in the rubber. This method of monitoring rubber degradation could lead to the non-destructive use of NMR to determine the condition of a part in service.

N-Acetylcysteine infusion does not affect glucose disposal during prolonged moderate-intensity exercise in humans

There is evidence that reactive oxygen species (ROS) signalling is required for normal increases in glucose uptake during contraction of isolated mouse skeletal muscle, and that AMP-activated protein kinase (AMPK) is involved. The aim of this study was to determine whether ROS signalling is involved in the regulation of glucose disposal and AMPK activation during moderate-intensity exercise in humans. Nine healthy males completed 80 min of cycle ergometry at 62 ± 1 of peak oxygen consumption ( . A 6,6-2H-glucose tracer was infused at rest and during exercise, and in a double-blind randomised cross-over design, N-acetylcysteine (NAC) or saline (CON) was co-infused. NAC was infused at 125 mg kg?1h?1for 15 min and then at 25 mg kg?1h?1for 20 min before and throughout exercise. NAC infusion elevated plasma NAC and cysteine, and muscle NAC and cysteine concentrations during exercise. Although neither NAC infusion nor exercise significantly affected muscle reduced or oxidised glutathione (GSH or GSSG) concentration (P> 0.05), S-glutathionylation (an indicator of oxidative stress) of a protein band of ?270 kDa was increased ?3-fold with contraction and this increase was prevented by NAC infusion. Despite this, exercised-induced increases in tracer determined glucose disposal, plasma lactate, plasma non-esterified fatty acids (NEFAs), and decreases in plasma insulin were not affected by NAC infusion. In addition, skeletal muscle AMPK? and acetyl-CoA carboxylase-? (ACC?) phosphorylation increased during exercise by ?3- and ?6-fold (P< 0.05), respectively, and this was not affected by NAC infusion. Unlike findings in mouse muscle ex vivo, NAC does not attenuate skeletal muscle glucose disposal or AMPK activation during moderate-intensity exercise in humans.

Mechanisms of nitric oxide-mediated neurogenic,vasodilation in mesenteric resistance arteries of toad, Bufo marinus

This study determined the role of nitric oxide (NO) in neurogenic vasodilation in mesenteric resistance arteries of the toad Bufo marinus. NO synthase (NOS) was anatomically demonstrated in perivascular nerves, but not in the endothelium. ACh and nicotine caused TTX-sensitive neurogenic vasodilation of mesenteric arteries. The ACh-induced vasodilation was endothelium-independent and was mediated by the NO/soluble guanylyl cyclase signaling pathway, inasmuch as the vasodilation was blocked by the soluble guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one and the NOS inhibitors N^ω- nitro-L-arginine methyl ester and N^ω-nitro-L-arginine. Furthermore, the ACh-induced vasodilation was significantly decreased by the more selective neural NOS inhibitor N⁵-(1-imino-3-butenyl)-L-ornithine. The nicotine-induced vasodilation was endothelium-independent and mediated by NO and calcitonin gene-related peptide (CGRP), inasmuch as pretreatment of mesenteric arteries with a combination of N^ω-nitro-L-arginine and the CGRP receptor antagonist CGRP-(8–37) blocked the vasodilation. Clotrimazole significantly decreased the ACh-induced response, providing evidence that a component of the NO vasodilation involved Ca^2+-activated K⁺ or voltage-gated K⁺ channels. These data show that NO control of mesenteric resistance arteries of toad is provided by nitrergic nerves, rather than the endothelium, and implicate NO as a potentially important regulator of gut blood flow and peripheral blood pressure.

Extraction of copper(II) ions from aqueous solutions with a methimazole-based ionic liquid

The recently synthesized ionic liquid (IL) 2-butylthiolonium bis(trifluoromethanesulfonyl)amide, [mimSBu][NTf2], has been used for the extraction of copper(II) from aqueous solution. The pH of the aqueous phase decreases upon addition of [mimSBu]+, which is attributed to partial release of the hydrogen attached to the N(3) nitrogen atom of the imidazolium ring. The presence of sparingly soluble water in [mimSBu][NTf2] also is required in solvent extraction studies to promote the incorporation of Cu(II) into the [mimSBu][NTf2] ionic liquid phase. The labile copper(II) system formed by interacting with both the water and the IL cation component has been characterized by cyclic voltammetry as well as UV−vis, Raman, and 1H, 13C, and 15N NMR spectroscopies. The extraction process does not require the addition of a complexing agent or pH control of the aqueous phase. [mimSBu][NTf2] can be recovered from the labile copper−water−IL interacting system by washing with a strong acid. High selectivity of copper(II) extraction is achieved relative to that of other divalent cobalt(II), iron(II), and nickel(II) transition-metal cations. The course of microextraction of Cu2+ from aqueous media into the [mimSBu][NTf2] IL phase was monitored in situ by cyclic voltammetry using a well-defined process in which specific interaction with copper is believed to switch from the ionic liquid cation component, [mimSBu], to the [NTf2] anion during the course of electrochemical reduction from Cu(II) to Cu(I). The microextraction−voltammetry technique provides a fast and convenient method to determine whether an IL is able to extract electroactive metal ions from an aqueous solution.

Nonadditivity of Faradaic currents and modification of capacitance currents in the voltammetry of mixtures of ferrocene and the cobaltocenium cation in protic and aprotic ionic liquids

Unexpected nonadditivity of currents encountered in the electrochemistry of mixtures of ferrocene (Fc) and cobaltocenium cation (Cc+) as the PF6 - salt has been investigated by direct current (dc) and Fourier-transformed alternating current (ac) cyclic voltammetry in two aprotic (1-butyl-3-methylimidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium hexafluorophosphate) and three protic (triethylammonium formate, bis(2-hydroxyethyl)ammonium acetate, and triethylammonium acetate) ionic liquids (ILs). The voltammetry of the individual Fc0/+ and Cc+/0 couples always exhibits near-Nernstian behavior at glassy carbon and gold electrodes. As expected for an ideal process, the reversible formal potentials and diffusion coefficients at 23 ( 1 °C in each IL determined from measurement on individual Fc and Cc+ solutions were found to be independent of electrode material, concentration, and technique used for the measurement. However, when Fc and Cc+ were simultaneously present, the dc and ac peak currents per unit concentration for the Fc0/+ and Cc+/0 processes were found to be significantly enhanced in both aprotic and protic ILs. Thus, the apparent diffusion coefficient values calculated for Fc and Cc+ were respectively found to be about 25 and 35% larger than those determined individually in the aprotic ILs. A similar change in the Fc0/+ mass transport characteristics was observed upon addition of tetrabutylammonium hexafluorophosphate (Bu4NPF6), and the double layer capacitance also varied in distinctly different ways when Fc and Cc+ were present individually or in mixtures. Importantly, the nonadditivity of Faradaic current is not associated with a change in viscosity or from electron exchange as found when some solutes are added to ILs. The observation that the 1H NMR T1 relaxation times for the proton resonance in Cc+ also are modified in mixed systems implies that specific interaction with aggregates of the constituent IL ionic species giving rise to subtle structural changes plays an important role in modifying the mass transport, double layer characteristics, and dynamics when solutes of interest in this study are added to ILs. Analogous voltammetric changes were not observed in studies in organic solvent media containing 0.1 M added supporting electrolyte. Implications of the nonadditivity of Faradaic and capacitance terms in ILs are considered.

The effect of coordinating and non-coordinating additives on the transport properties in ionic liquid electrolytes for lithium batteries

In the present study we expand our analysis of using two contrasting organic solvent additives (toluene and THF) in an ionic liquid (IL)/Li NTf 2 electrolyte. Multinuclear Pulsed-Field Gradient (PFG) NMR, spin-lattice (T1) relaxation times and conductivity measurements over a wide temperature range are discussed in terms of transport properties and structuring of the liquid. The conductivity of both additive samples is enhanced the most at low temperatures, with THF slightly more effective than toluene. Both the anion and lithium self-diffusivity are enhanced in the same order by the additives (THF > toluene) while that of the pyrrolidinium cation is marginally enhanced. 1H spin-lattice relaxation times indicate a reasonable degree of structuring and anisotropic motion within all of the samples and both 19F and 7Li highlight the effectiveness of THF at influencing the lithium coordination within these systems.

Electrochemiluminescent monomers for solid support syntheses of Ru(II)-PNA bioconjugates : multimodal biosensing tools with enhanced duplex stability

The feasibility of devising a solid support mediated approach to multimodal Ru(II)-peptide nucleic acid (PNA) oligomers is explored. Three Ru(II)-PNA-like monomers, [Ru(bpy)2(Cpp-L-PNA-OH)]2+ (M1), [Ru(phen)2(Cpp-L-PNA-OH)]2+ (M2), and [Ru(dppz)2(Cpp-L-PNA-OH)]2+ (M3) (bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, dppz = dipyrido[3,2-a:2′,3′-c]phenazine, Cpp-L-PNA-OH = [2-(N-9-fluorenylmethoxycarbonyl)aminoethyl]-N-[6-(2-(pyridin-2yl)pyrimidine-4-carboxamido)hexanoyl]-glycine), have been synthesized as building blocks for Ru(II)-PNA oligomers and characterized by IR and 1H NMR spectroscopy, mass spectrometry, electrochemistry and elemental analysis. As a proof of principle, M1 was incorporated on the solid phase within the PNA sequences H-g-c-a-a-t-a-a-a-a-Lys-NH2 (PNA1) and H-P-K-K-K-R-K-V-g-c-a-a-t-a-a-a-a-lys-NH2 (PNA4) to give PNA2 (H-g-c-a-a-t-a-a-a-a-M1-lys-NH2) and PNA3 (H-P-K-K-K-R-K-V-g-c-a-a-t-a-a-a-a-M1-lys-NH2), respectively. The two Ru(II)-PNA oligomers, PNA2 and PNA3, displayed a metal to ligand charge transfer (MLCT) transition band centered around 445 nm and an emission maximum at about 680 nm following 450 nm excitation in aqueous solutions (10 mM PBS, pH 7.4). The absorption and emission response of the duplexes formed with the cDNA strand (DNA: 5′-T-T-T-T-T-T-T-A-T-T-G-C-T-T-T-3′) showed no major variations, suggesting that the electronic properties of the Ru(II) complexes are largely unaffected by hybridization. The thermal stability of the PNA·DNA duplexes, as evaluated from UV melting experiments, is enhanced compared to the corresponding nonmetalated duplexes. The melting temperature (Tm) was almost 8 °C higher for PNA2·DNA duplex, and 4 °C for PNA3·DNA duplex, with the stabilization attributed to the electrostatic interaction between the cationic residues (Ru(II) unit and positively charged lysine/arginine) and the polyanionic DNA backbone. In presence of tripropylamine (TPA) as co-reactant, PNA2, PNA3, PNA2·DNA and PNA3·DNA displayed strong electrochemiluminescence (ECL) signals even at submicromolar concentrations. Importantly, the combination of spectrochemical, thermal and ECL properties possessed by the Ru(II)-PNA sequences offer an elegant approach for the design of highly sensitive multimodal biosensing tools.

Physiological stress responses in the warm-water fish matrinxã (Brycon amazonicus) subjected to a sudden cold shock

The present work evaluated several aspects of the generalized stress response [endocrine (cortisol), metabolic (glucose), hematologic (hematocrit and hemoglobin) and cellular (HSP70)] in the Amazonian warm-water fish matrinxã (Brycon amazonicus ) subjected to an acute cold shock. This species farming has been done in South America, and growth and feed conversion rates have been interesting. However, in subtropical areas of Brazil, where the water temperature can rapidly change, high rates of matrinxã mortality have been associated with abrupt decrease in the water temperature. Thus, we subjected matrinxã to a sudden cold shock by transferring the fish directly to tanks in which the water temperature was 10oC below the initial conditions (cold shock from 28ºC to 18oC). After 1h the fish were returned to the original tanks (28ºC). The handling associated with tank transfer was also imposed on control groups (not exposed to cold shock). While exposure to cold shock did not alter the measured physiological conditions within 1h, fish returned to the ambient condition (water at 28º C) significantly increased plasma cortisol and glucose levels. Exposure to cold shock and return to the warm water did not affect HSP70 levels. The increased plasma cortisol and glucose levels after returning the fish to warm water suggest that matrinxã requires cortisol and glucose for adaptation to increased temperature.

Structure and transport properties of a plastic crystal ion conductor : Diethyl(methyl)(isobutyl)phosphonium hexafluorophosphate

Understanding the ion transport behavior of organic ionic plastic crystals (OIPCs) is crucial for their potential application as solid electrolytes in various electrochemical devices such as lithium batteries. In the present work, the ion transport mechanism is elucidated by analyzing experimental data (single-crystal XRD, multinuclear solid-state NMR, DSC, ionic conductivity, and SEM) as well as the theoretical simulations (second moment-based solid static NMR line width simulations) for the OIPC diethyl(methyl)(isobutyl)phosphonium hexafluorophosphate ([P1,2,2,4][PF6]). This material displays rich phase behavior and advantageous ionic conductivities, with three solid–solid phase transitions and a highly “plastic” and conductive final solid phase in which the conductivity reaches 10–3 S cm–1. The crystal structure shows unique channel-like packing of the cations, which may allow the anions to diffuse more easily than the cations at lower temperatures. The strongly phase-dependent static NMR line widths of the 1H, 19F, and 31P nuclei in this material have been well simulated by different levels of molecular motions in different phases. Thus, drawing together of the analytical and computational techniques has allowed the construction of a transport mechanism for [P1,2,2,4][PF6]. It is also anticipated that utilization of these techniques will allow a more detailed understanding of the transport mechanisms of other plastic crystal electrolyte materials.

Metabolite profiles in the anterior cingulate cortex of depressed patients differentiate those taking N-acetyl-cysteine versus placebo

Background: Increased oxidative stress is thought to contribute to the pathophysiology of major depressive disorder (MDD), which is in part due to diminished levels of glutathione, the primary anti-oxidant of the brain. Oral administration of N-acetyl-cysteine (NAC) replenishes glutathione and has therefore been shown to reduce depressive symptoms. Proton magnetic spectroscopy (1H-MRS) that allows quantification of brain metabolites pertinent to both MDD and oxidative biology may provide some novel insights into the neurobiological effects of NAC, and in particular metabolite concentrations within the anterior cingulate cortex (ACC) are likely to be important given the key role of this region in the regulation of affect.

Objective: The aim of this study was to determine whether the metabolite profile of the ACC in MDD patients predicts treatment with adjunctive NAC versus placebo.

Methods: This study was nested within a multicentre, randomized, double-blind, placebo-controlled study of MDD participants treated with adjunctive NAC. Participants (n = 76) from one site completed the spectroscopy component at the end of treatment (12 weeks). Spectra from a single-voxel in the ACC were acquired and absolute concentrations of glutamate (Glu), glutamate-glutamine (Glx), N-acetyl-aspartate (NAA) and myo-inositol (mI) were obtained. Binary logistic regression analysis was performed to determine whether metabolite profiles could predict NAC versus placebo group membership.

Results: When predicting group outcome (NAC or placebo), Glx, NAA and mI were a significant model, and had 75% accuracy, while controlling for depression severity and sex. However, the Glu, NAA and mI profile was only predictive at a trend level, with 68.3% accuracy. For both models, the log of the odds of a participant being in the NAC group was positively related to NAA, Glx and Glu levels and negatively related to mI levels.

Conclusion: The finding of higher Glx and NAA levels being predictive of the NAC group provides preliminary support for the putative anti-oxidative role of NAC in MDD.

Monitoring the early stage self-assembly of enzyme-assisted peptide hydrogels

The early stages of the self-assembly of peptide hydrogels largely determine their final material properties. Here we discuss experimental methodologies for monitoring the self-assembly kinetics which underpin peptide hydrogel formation. The early stage assembly of an enzyme-catalysed Fmoc-trileucine based self-assembled hydrogel was examined using spectroscopic techniques (circular dichroism, CD, and solution NMR) as well as chromatographic (HPLC) and mechanical (rheology) techniques. Optimal conditions for enzyme-assisted hydrogel formation were identified and the kinetics examined. A lag time associated with the formation and accumulation of the self-assembling peptide monomer was observed and a minimum hydrogelator concentration required for gelation was identified. Subsequent formation of well defined nano-and microscale structures lead to self-supporting hydrogels at a range of substrate and enzyme concentrations. 1H NMR monitoring of the early self-assembly process revealed trends that were well in agreement with those identified using traditional methods (i.e. HPLC, CD, rheology) demonstrating 1H NMR spectroscopy can be used to non-invasively monitor the self-assembly of peptide hydrogels without damaging or perturbing the system.

Polystyrene-b-poly(oligo(ethylene oxide) monomethyl ether methacrylate)-bpolystyrene triblock copolymers as potential carriers for hydrophobic drugs

A simple and effective method is introduced to synthesize a series of polystyrene-b-poly(oligo(ethylene oxide) monomethyl ether methacrylate)-b- polystyrene (PSt-b-POEOMA-b-PSt) triblock copolymers. The structures of PSt-b-POEOMA-b-PSt copolymers were characterized by Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H NMR) spectroscopy. The molecular weight and molecular weight distribution of the copolymer were measured by gel permeation chromatography (GPC). Furthermore£ the self-assembling and drug-loaded behaviours of three different ratios of PSt-b-POEOMA-b-PSt were studied. These copolymers could readily self-assemble into micelles in aqueous solution. The vitamin E-loaded copolymer micelles were produced by the dialysis method. The micelle size and core-shell structure of the block copolymer micelles and the drug-loaded micelles were confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The thermal properties of the copolymer micelles before and after drug-loaded were investigated by different scanning calorimetry (DSC). The results show that the micelle size is slightly increased with increasing the content of hydrophobic segments and the micelles are still core-shell spherical structures after drug-loaded. Moreover, the glass transition temperature (Tg) of polystyrene is reduced after the drug loaded. The drug loading content (DLC) of the copolymer micelles is 70%-80% by ultraviolet (UV) photolithography analysis. These properties indicate the micelles self-assembled from PSt-b- POEOMA-b- PSt copolymers would have potential as carriers for the encapsulation of hydrophobic drugs.

The role of infrequent and extraordinary deep dives in leatherback turtles (Dermochelys coriacea)

Infrequent and exceptional behaviours can provide insight into the ecology and physiology of a particular species. Here we examined extraordinarily deep (300–1250 m) and protracted (>1h) dives made by critically endangered leatherback turtles (Dermochelys coriacea) in the context of three previously suggested hypotheses: predator evasion, thermoregulation and exploration for gelatinous prey. Data were obtained via satellite relay data loggers attached to adult turtles at nesting beaches (N=11) and temperate foraging grounds (N=2), constituting a combined tracking period of 9.6 years (N=26,146 dives) and spanning the entire North Atlantic Ocean. Of the dives, 99.6% (N=26,051) were to depths <300 m with only 0.4% (N=95) extending to greater depths (subsequently termed `deep dives'). Analysis suggested that deep dives: (1) were normally distributed around midday; (2) may exceed the inferred aerobic dive limit for the species; (3) displayed slow vertical descent rates and protracted durations; (4) were much deeper than the thermocline; and (5) occurred predominantly during transit, yet ceased once seasonal residence on foraging grounds began. These findings support the hypothesis that deep dives are periodically employed to survey the water column for diurnally descending gelatinous prey. If a suitable patch is encountered then the turtle may cease transit and remain within that area, waiting for prey to approach the surface at night. If unsuccessful, then migration may continue until a more suitable site is encountered. Additional studies using a meta-analytical approach are nonetheless recommended to further resolve this matter.

Bis-thiourea macrocycles incorporating fused [n]polynorbornanes: binding of flexible versus rigid dicarboxylates

Two macrocyclic bis-thiourea hosts 5 and 6 were constructed and their interactions with two dicarboxylates of similar size (pimelate = flexible and terephthalate = rigid) were evaluated using 1H NMR titration techniques. In contrast to previous work with thiourea functionalised [n]polynorbornanes (where a notable increase in H:G affinity was noted for the rigid guest), the new macrocyclic hosts, in particular host 6, bind pimelate more strongly than terephthalate (for 6 binding pimelate log Ka = 4.7, terephthalate log Ka = 3.7). A binding arrangement in which the flexible dicarboxylate is ‘perched’ above the macrocycle is proposed to justify these results.