Isomeric Composition Research Articles

High‐pressure Raman spectroscopy of nanoparticle polyacetylene in a poly(vinyl‐butyral) matrix

AbstractThe pressure‐induced Raman shifts of six vibrational bands of 20% and 50% trans‐polyacetylene nanoparticles in poly(vinyl‐butyral) matrix films (NPA/PVB) were studied from 0 to 45 kbar using a diamond anvil cell (DAC). The Raman shifts did not depend on the thickness of the two samples studied. Two of the vibrational bands displayed peak positions that depended on the isomeric compositions, with the 20% trans‐NPA/PVB bands being slightly blue‐shifted relative to the 50% trans‐NPA/PVB bands over the 45 kbar pressure range. The Raman bands of NPA/PVB associated with the trans form initially exhibited a relatively large shift at low pressures (P < 10 kbar) along with a drastic change in their band profile. In order to investigate the relative shielding of the vibrational modes studied, a Grüneisen analysis of the pressure‐induced shifts was conducted by estimating the parameters of the Murnaghan equation of state for solid polyacetylene (PA). Four of the six vibrational modes were found to be sensitive to compression of the interchain void space, while the other two modes were insensitive, indicating that they are relatively shielded from the compression of the sample. Copyright © 2011 John Wiley & Sons, Ltd.

Environmental levels and distribution of structural isomers of perfluoroalkyl acids after aqueous fire-fighting foam (AFFF) contamination

Environmental contextPerfluoroalkyl acids are used in many products and have spread into the environment where their persistence and potential toxicity pose a threat to humans and wildlife. The present study describes environmental contamination from usage of aqueous film forming foams, and investigates the distribution of structural isomers of perfluoroalkyl acids from a point source to the surrounding environment. Isomer patterns might be used to track contamination sources since isomer composition differs in the various products containing perfluoroalkyl acids. The environmental behaviour of these structural isomers is described, and limitations of their use to track contamination sources are identified. AbstractThe environment (soil, water, sediment, fish, crab and mussel) around a training facility using aqueous film forming foams (AFFFs) was studied with respect to perfluorinated alkyl acids (PFAAs) and 6 : 2 fluorotelomer sulfonate (FTS) and their structural isomers. High levels of many PFAAs and 6 : 2 FTS were detected in soil, seepage water, sediment and fish liver. Structural isomers were found for sulfonates, except PFBuS, and for PFOA. Quantification using authentic standards revealed an isomer pattern of 63% linear PFOS (L-PFOS) and 80% linear PFOA (L-PFOA) in the soil at the contamination site, which indicated a source produced by electrochemical fluorination (ECF). The 6 : 2 FTS was 100% linear in all compartments thus coming from a telomerisation product. Enrichment of the linear structure of PFOS and PFOA in soil was seen with increasing distance from the training centre, and an enrichment of branched isomers for both compounds could be found in the seepage water. Sorption to sediment and accumulation in fish liver led to an enrichment of L-PFOS whereas all PFOA remained in the water body.

Incremental effects of feeding a rumen-inert MUFA supplement to dairy cows on milk trans fatty acid isomer composition

Incremental effects of feeding a rumen-inert MUFA supplement to dairy cows on milk <i>trans</i> fatty acid isomer composition

CLA TAG rich in cis ‐9, trans ‐11‐CLA is stable beyond 2 years of proper storage

We analyzed a triacylgylcerol esterified CLA preparation characteristically rich in c9,t11-CLA and free of t10,c12-CLA three times within a period of 2½ years by GC and silver ion-HPLC. For the first time, we present data on the long-term stability of this preparation with regard to the fatty acid profile and the isomeric composition of CLA under certain storage conditions, providing useful information for the planning of long-term trials.

Glass-transition temperature and microstructure of polybutadienes

DSC and NMR are employed to determine the glass-transition temperatures and the structural features of polybutadienes with widely varying configuration isomeric compositions. The dependences of the glass-transition temperature on the contents of cis-1,4-, trans-1,4, and 1,2-units in polybutadiene chains are plotted and discussed. An analysis of the experimental results and the published data suggests that, in the study of the glass-transition-structure relationship, simplified approaches are inapplicable and it is necessary to consider the configurational and conformational geometry of polybutadiene chains.

Recent and Upcoming Innovation in the Technology of Hip Arthroscopy

The advancements in our understanding of hip anatomy and pathology have stimulated the innovation of new products and technologies in hip arthroscopy. Specialized patient-positioning systems can help optimize the limb distraction and joint access that is critical for accessing the hip joint. Guiding systems have been developed to reduce the risk of iatrogenic damage and improve the efficiency and safety by which the secondary portals are established. Suture anchors now commonly contain polylactic acid with varying isomer compositions that help control the rate with which these anchors are reabsorbed. The addition of composite anchors may potentially offer improved anchor-osseus fixation and degradation characteristics. Knotless anchors are now becoming available and hold the potential to improve the ease and speed of achieving stable anchor fixation. Specialized instruments, including flexible and maneuverable thermal probes, extra-long cannulas, and extra-long shavers, burs, drills, implants, and loose body retrieval devices have improved access to the hip joint and have expanded the spectrum of indications for arthroscopy of the hip. These aforementioned products and technologies are representative of an exciting period of growth and innovation in the armamentarium of tools available to surgeons versed in hip arthroscopy. This work explores some of the new products and technologies that have recently come to market in hip arthroscopy that have and potentially will continue to improve our ability to arthroscopically treat hip pathology.

Determinations of hexabromocyclododecane (HBCD) isomers in channel catfish, crayfish, hen eggs and fish feeds from China by isotopic dilution LC–MS/MS

HBCD is widely used brominated flame retardant, which is increasingly reported in the environment. A new isotopic dilution LC–MS/MS method was developed to determine three HBCD isomers, α-, β- and γ-HBCD in channel catfish, crayfish, hen eggs and fish feeds in this study, and especially for the first time HBCD isomers composition in crayfish, hen eggs and fish feeds. Soxhlet extractor and GPC cleanup were used, some important steps and crucial parameters were modified and intensified compared with other literatures, and LC and MS/MS conditions were optimized. The limits of quantitation values of 0.01, 0.005 and 0.005 ng g −1 wet weight in channel catfish and crayfish were calculated for three HBCD isomers, respectively; so did 0.1, 0.05 and 0.05 ng g −1 wet weight in eggs and 0.2, 0.1, 0.1 ng g −1 wet weight in fish feeds. Recoveries of α-HBCD, β-HBCD and γ-HBCD were ranged between 75% and 105% for these productions at medium and high-level spiked samples, and between 60% and 85% at low-level spiked samples. The established methods were therefore suitable for the determinations of three HBCD isomers in these productions at trace contamination levels. Moreover, thirty commercial channel catfish, crayfish, hen eggs and fish feeds samples collected from local markets, and thirty home-produced hen eggs from private owners in Hubei province of China, were analyzed to determine whether these productions were contaminated by HBCD. Using the established methods, HBCD emerged in 4 of 30 fish feeds and 3 of 30 home-produced eggs, and in low-ng g −1 wet weight.

Isomer‐specific accumulation of perfluorooctane sulfonate in the liver of chicken embryos exposed in ovo to a technical mixture

Prior to its recent phaseout, perfluorooctane sulfonate (PFOS) was produced by electrochemical fluorination processes, which yielded technical mixtures composed of linear isomer (∼65-79%) and several branched isomers (∼21-35%). Because PFOS can biomagnify in wildlife, birds that occupy higher trophic levels are at increased risk of exposure. We hypothesized that the pharmacokinetic properties of PFOS are isomer-specific in developing chicken (Gallus gallus domesticus) embryos exposed to technical grade PFOS (T-PFOS). In the present study, T-PFOS was composed of 62.7% linear isomer (L-PFOS), and 37.3% branched isomer, including six mono(trifluoromethyl)-branched isomers and four bis(trifluoromethyl)-branched isomers. Concentrations of 0.1, 5, or 100 µg/g of T-PFOS were injected into the air cell of chicken eggs prior to incubation. After pipping, compared with T-PFOS, the PFOS isomer profile in embryonic liver tissue for the 0.1 µg/g dose group showed 21% enrichment in the proportion of L-PFOS with a corresponding decrease in the proportion of branched isomers. Not all branched isomers were discriminated against at equal rates. The proportion of two mono(trifluoromethyl)-branched isomers and three bis(trifluoromethyl)-branched isomers decreased to a greater degree than other branched isomers. In contrast, the mono-branched isomer, P6MHpS, was overrepresented in the low-dose group. In the higher dose groups, L-PFOS was still enriched but only by approximately 10%, which indicated a dose-dependent change in isomer composition relative to T-PFOS. These results show that accumulation of PFOS in chicken embryo livers is dependent on the presence and position of branches on the alkyl backbone. This supports the hypothesis that the pharmacokinetics of PFOS are isomer-specific in biota, and may help explain why wildlife PFOS burdens are dominated by L-PFOS relative to T-PFOS mixtures.

Regulation of adiponectin production by insulin: interactions with tumor necrosis factor-α and interleukin-6

Obesity is often associated with insulin resistance, low-grade systemic inflammation, and reduced plasma adiponectin. Inflammation is also increased in adipose tissue, but it is not clear whether the reductions of adiponectin levels are related to dysregulation of insulin activity and/or increased proinflammatory mediators. In this study, we investigated the interactions of insulin, tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6) in the regulation of adiponectin production using in vivo and in vitro approaches. Plasma adiponectin and parameters of insulin resistance and inflammation were assessed in a cohort of lean and obese insulin-resistant subjects. In addition, the effect of insulin was examined in vivo using the hyperinsulinemic-euglycemic clamp, and in adipose tissue (AT) cultures. Compared with lean subjects, the levels of total adiponectin, and especially the high-molecular-weight (HMW) isomer, were abnormally low in obese insulin-resistant subjects. The hyperinsulinemic clamp data confirmed the insulin-resistant state in the obese patients and showed that insulin infusion significantly increased the plasma adiponectin in lean but not obese subjects (P < 0.01). Similarly, insulin increased total adiponectin release from AT explants of lean and not obese subjects. Moreover, expression and secretion of TNF-α and IL-6 increased significantly in AT of obese subjects and were negatively associated with expression and secretion of adiponectin. In 3T3-L1 and human adipocyte cultures, insulin strongly enhanced adiponectin expression (2-fold) and secretion (3-fold). TNF-α, and not IL-6, strongly opposed the stimulatory effects of insulin. Intriguingly, the inhibitory effect of TNF-α was especially directed toward the HMW isomer of adiponectin. In conclusion, these studies show that insulin upregulates adiponectin expression and release, and that TNF-α opposes the stimulatory effects of insulin. A combination of insulin resistance and increased TNF-α production could explain the decline of adiponectin levels and alterations of isomer composition in plasma of obese insulin-resistant subjects.

Synthesis and Properties of Novel Melt Processable Isomeric Polythioetherimides

A series of 3,3’,4,4’-diphenylthioethertetracarboxylic dianhydride (s-TDPA), 2,3,3’,4’ -diphenylthioethertetracarboxylic dianhydride (a-TDPA), and 2,2’,3,3’-diphenylthioethertetracarboxylic dianhydride (i-TDPA) isomer mixtures were synthesized from 3- and 4-chlorophthalic anhydrides. Copolythioetherimides derived from TDPAs with different ratios of the isomers and 4,4’-oxydianiline (ODA) were prepared by a two-step polycondensation procedure. Solubility, thermal properties, mechanical properties and melt processability of copolythioetherimides were investigated and compared with corresponding homopolyimides. The dependence of these properties on the composition of TDPA isomers and the effects of molecular structures were discussed in this work in order to obtain an indication for the molecular design of high performance melt-processable polyimides.

Selected Organochlorine Pesticides in the Atmosphere of Major Indian Cities: Levels, Regional versus Local Variations, and Sources

India has extensive production and usage of organochlorine pesticides (OCPs) for agriculture and vector control. Despite this, few data are available on the levels and distribution of OCPs in the urban atmosphere of India. Passive and active air sampling was therefore conducted between Dec 2006 and March 2007 in 7 metropolitan cities: New Delhi, Kolkata, Mumbai, Chennai, Bangalore, Goa, and Agra. Concentrations (pg·m(-3)) were as follows: HCHs 890-17000 (mean: 5400 ± 4110); DDTs 250-6110 (1470 ± 1010); chlordanes 290-5260 (1530 ± 790); endosulfans 240-4650 (1040 ± 610); and hexachlorobenzene 120-2890 (790 ± 510). HCHs observed in India appear to be the highest reported across the globe. Chlordanes and endosulfans are lower than levels reported from southern China. Passive sampling enabled within- and between-city variations to be assessed. As expected, paired-sample t-test analysis revealed higher regional than local variation. Comparisons with the limited data available from studies conducted in 1989 suggest general declines of HCHs and DDTs for most regions. γ-HCH dominated the HCH signal, reflecting widespread use of Lindane in India, although the isomeric composition in Kolkata suggests potential technical HCH use. High o,p'-/p,p'-DDT ratios in northern India indicate recent DDT usage. High HCB levels in the industrial areas of New Delhi and Kolkata indicate ongoing sources. Correlation between trans- and cis-chlordane implies ongoing usage. Endosulfan sulfate generally dominated the endosulfan signal, but high values of α/β-endosulfan at Chennai, Mumbai and Goa suggest ongoing usage. Backward trajectories were computed using the NOAA HYSPLIT model to trace the air mass history. Result shows local/regional sources of OCPs within India.

Applicability of Corbicula as a bioindicator for monitoring organochlorine pesticides in fresh and brackish waters

The applicability of Corbicula as a bioindicator for monitoring organochlorine pesticides (OCPs) in fresh and brackish waters is presented here. Differences in isomer compositions and OCP bioaccumulation levels were analyzed in western Japan and the Pearl River Delta (PRD) in China. Isomer compositions of DDTs, chlordanes, and HCHs were significantly different between the two areas because of their different historical uses and property of the chemicals. This is represented by the (DDE + DDD)/DDT ratio in Corbicula, ranging 4.9-39 in western Japan and 1.1-2.4 in the PRD. However, isomer compositions in Corbicula reflected those in water, and the different patterns in Corbicula likely reflected the usage history. Concentrations of dissolved oxygen, suspended solids, and volatile suspended solids in water, and the difference in species did not influence OCP bioaccumulative levels in Corbicula when conducting biomonitoring. These levels are likely similar to those in Mytilus galloprovincialis. Therefore, Corbicula could be an appropriate bioindicator for monitoring OCPs in fresh and brackish waters.

Thermodynamics and mesoscopic organisation in Langmuir monolayers of an azobenzene derivative

We have carried out the analysis of liquid crystalline Langmuir monolayers at the air-water interface composed of the amphiphilic azobenzene derivative 8Az5COOH. By varying the temperature and the isomeric (trans-cis) composition, the monolayer behaviour has been studied in comparison with a shorter homologue, 8Az3COOH, by measuring the surface pressure-area isotherms along with Brewster angle microscopy (BAM). Our data with the pure trans isomer enable a posterior thermodynamic analysis, which was not feasible with the shorter homologue. For the mixed trans-cis monolayers, BAM observations reveal a phase segregation with trans enriched domains surrounded by a cis enriched matrix. Line tension between the two phases is lower than in the shorter homologue. The organisation of the rodlike molecules inside the trans domains results in highly symmetric textures that make the quantitative analysis of the BAM images possible, and a better understanding of the microscopic structure of the monolayer can be achieved.

Organochlorine Pesticides (OCPs) in Soils Along the Eastern Slope of the Tibetan Plateau

Soil samples collected from several sites along an altitudinal transect on the eastern slope of the Tibetan Plateau were analyzed for hexachlorobenzenes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs). The results showed that HCHs and DDTs were found in the soil samples from the remote high altitude areas away from source regions, which confirmed the long-range atmospheric transport phenomenon of these organochlorine pesticides (OCPs) insecticides. The OCP concentrations in the soils had a significant negative correlation with altitude; they showed a trend to increase with decreasing altitude, but the increase was not continuous, being interrupted at some moderate-altitude sites on the transect. The distances from the source region, landforms, soil properties, and physical-chemical properties of OCPs were more important than total organic carbon content to the distribution of OCPs in soils disturbed by human activities. An analysis of the compositions of HCH isomers and DDTs revealed predominantly low ratios of CK-HCH to 7-HCH, ranging from 0.06 to 4.79, which suggested current lindane inputs. On the other hand, low p,p'-DDT/ p,p'-DDE and o,p'-DDT/ p,p'-DDT ratios were observed, indicating mainly aged historical DDT residues in the study area.

Dynamic simulation of cardiolipin remodeling: greasing the wheels for an interpretative approach to lipidomics

Cardiolipin is a class of mitochondrial specific phospholipid, which is intricately involved in mitochondrial functionality. Differences in cardiolipin species exist in a variety of tissues and diseases. It has been demonstrated that the cardiolipin profile is a key modulator of the functions of many mitochondrial proteins. However, the chemical mechanism(s) leading to normal and/or pathological distribution of cardiolipin species remain elusive. Herein, we describe a novel approach for investigating the molecular mechanism of cardiolipin remodeling through a dynamic simulation. This approach applied data from shotgun lipidomic analyses of the heart, liver, brain, and lung mitochondrial lipidomes to model cardiolipin remodeling, including relative content, regiospecificity, and isomeric composition of cardiolipin species. Generated cardiolipin profiles were nearly identical to those determined by shotgun lipidomics. Importantly, the simulated isomeric compositions of cardiolipin species were further substantiated through product ion analysis. Finally, unique enzymatic activities involved in cardiolipin remodeling were assessed from the parameters used in the dynamic simulation of cardiolipin profiles. Collectively, we described, verified, and demonstrated a novel approach by integrating both lipidomic analysis and dynamic simulation to study cardiolipin biology. We believe this study provides a foundation to investigate cardiolipin metabolism and bioenergetic homeostasis in normal and disease states.

Enantiomer-specific analysis of hexabromocyclododecane in fish from Etnefjorden (Norway)

High-performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS) was applied to sterospecifically quantify the content of α-, β-, and γ-hexabromocyclododecane (HBCD) in six fish species from the Norwegian Etnefjorden. A combination of a β-PM cyclodextrin and an achiral column enabled the paired chromatographic separation of the stereoisomers in the order (−)-α-, (+)-α-, (−)-β-, (+)-β-, (+)-γ- and, (−)-γ-HBCD. The limits of detection were in the range of 6–21 pg g −1 depending on the stereoisomer and the concentrations of α-, β-, and γ-HBCD in fillets ranged from <5.4 ng g −1 to 11.1 μg g −1 lipid weight. α-HBCD enantiomers were throughout dominating, and in most cases the accumulation of the respective first eluted enantiomers ((−)-α-, (−)-β- and (+)-γ-HBCD) was observed. Deviations from the racemic EF-value were considered to be significant if it was outside of the expanded uncertainty range for each of the racemic HBCD-ratios. The composition of HBCD isomers varied between the investigated fish species and the relative high values for the γ-HBCD concentrations for the bottom-dwellers flounder and thorny skate seems to echo the HBCD pattern of ocean sediments.

Bound forms, compositional features, major sources and diagenesis of long chain, alkyl mid-chain diols in Lake Baikal sediments over the past 28,000 years

To elucidate the possibility of long chain, alkyl mid-chain diols (hereafter, mid-chain diols) in Lake Baikal sediments over the past 28 ka being paleoproxies, we studied their: (i) bound forms and compositional features, (ii) major sources and (iii) diagenesis during sedimentation. Of the seven bound forms investigated, i.e. free form (free type), three base-hydrolysable types (base-1, base-2, and base-3) and acid-hydrolysable type (acid-1 type) in solvent extractable lipids and base hydrolysable (NB) and acid hydrolysable (NA) types in non-solvent extractable (NONEX) lipids, only three, viz. free, NB, and base-3 types, were found. The relative compositions of the three types were 70–100%, 0–30% and 0–8%, respectively. The most abundant component of the free-type diols was the C 32 1,15-diol, whereas that of the base-3 and NB types was the C 30 1,13-diol. The average chain length, ratio of total amount of even chain lengths to that of odd chain lengths, the relative composition of positional isomers for each carbon number, and the diol index, obtained using the equation [C 30 1,15-diol]/([C 30 1,15-diol] + [C 32 1,15-diol]) × 100, hardly responded to reported major paleoenvironmental changes around the Lake Baikal region over the last 28 ka. Comparison of mid-chain diol compositions and their bound forms with those in possible sources suggested that the major biological source of all mid-chain diols in the sediments might be the Eustigmatophyceae class of algae. In the alga, the occurrence of mid-chain diols in the five bound forms, free, base-3, acid-1, NB and NA types, was suggested, while the acid-1 and NA types were not found in the sediments. Under the oxic depositional conditions of Lake Baikal, most of the acid-1 and NA type diols and part of the base-3 and NB type diols might be degraded and/or released free-type diols. In the anoxic sediments of the lake, the base-3 and NB diols seem to be resistant to diagenesis. All investigated parameters for the free, base-3 and NB diols in the sediments did not provide any information on paleoenvironments around the lake. On the other hand, among the fluxes of the three diol types, the base-3 type diol flux seems to have responded to the climatic events around the lake, especially over the last 15 ka. Hence, this flux might be a potential paleoproxy for the productivity of the biological source(s) and associated environmental factors.

Molecular structure of polybutadienes synthesized with a lithium-containing initiation system

With the use of high-resolution NMR spectroscopy (600 MHz) and gel-permeation chromatography, the products of anionic polymerization of butadiene initiated by n-butyllithium modified with sodium and magnesium alcoholates are studied. It is shown that a change in synthesis conditions makes it possible to vary the configuration and isomeric composition and molecular parameters of polybutadienes. The distribution of 1,2-, cis-1,4-, and trans-1,4-units in a chain has a pronounced statistical character and depends on the composition of the initiation system.

Tautomerism of anthraquinones: XI. 1-amino-4-hydroxyanthraquinone

The disperse dye red 2C regarded as 1-amino-4-hydroxy-9,10-anthraquinone is not a 9,10-anthraquinone derivative. It is characterized by a keto-enol and amino-imine tautomerism, and it consists of equilibrium mixtures of tautomers and conformers containing 4-amino-9-hydroxy-1,10-, 9 amino-4-hydroxy-1,10-, 9 amino-10-hydroxy-1,4-anthraquinones, 9 hydroxy-1,10-anthraquinone 10-imine, and also their conformers with a single intramolecular hydrogen bond. The significant differences in the absorption spectra known for this dye originate from the dissimilar isomeric composition of the samples of this dye prepared or purified by various procedures

A perspective on MALDI alternatives—total solvent‐free analysis and electron transfer dissociation of highly charged ions by laserspray ionization

Progress in research is hindered by analytical limitations, especially in biological areas in which sensitivity and dynamic range are critical to success. Inherent difficulties of characterization associated with complexity arising from heterogeneity of various materials including topologies (isomeric composition) and insolubility also limit progress. For this reason, we are developing methods for total solvent-free analysis by mass spectrometry consisting of solvent-free ionization followed by solvent-free gas-phase separation. We also recently constructed a novel matrix-assisted laser desorption ionization (MALDI) source that provides a simple, practical and sensitive way of producing highly charged ions by laserspray ionization (LSI) or singly charged ions commonly observed with MALDI by choice of matrix or matrix preparation. This is the first ionization source with such freedom-an extremely powerful analytical 'switch'. Multiply charged LSI ions allow molecules exceeding the mass-to-charge range of the instrument to be observed and permit for the first time electron transfer dissociation fragment ion analysis.