Long-chain Components Research Articles

Molecular simulation of nanoparticles composed of mono- and bi-dispersed poly(ethylene oxide).

Monte Carlo simulation of coarse-grained poly(ethylene oxide) (PEO) models on high-coordination lattice was employed to investigate structural properties of nanoparticles composed of mono- and bi-dispersed molecular weight PEO with diameters ranging from 7.4 to 16.4 times the radius of gyration of polymers. For mono-dispersed chains, with an increasing PEO molecular weight, the bulk density increases and nanoparticle diameter is decreased. For nanoparticles with mixed molecular weights, shorter chains tend to segregate near the surface while the longer chains have more tendency to locate near the center of the particle. There is a higher degree of parallel orientation of the chains and bonds at the surface and this bond orientation pertains to a broader region. Compared to mono-dispersed nanoparticles, bond and chain orientations for both short- and long-chain components have no noticeable difference which is in contrast to the situation in polymer thin films and nanofibers where anisotropic orientation of short chain is enhanced in the presence of longer chains in mixed molecular weight systems.

Organic geochemistry of the Upper Miocene-Lower Pliocene sedimentary rocks in the Hellenic Fold and Thrust Belt, NW Corfu island, Ionian sea, NW Greece

Abstract The northwestern margin of the Hellenic Fold and Thrust Belt situated along the southern edge of the Dinarides – Albanides - Hellenides continental convergent zone, has been studied in terms of its hydrocarbon generating potential. More than a hundred (100) samples of the Upper Miocene-Lower Pliocene sedimentary rocks from several sites in Corfu Island were analyzed using Rock-Eval VI pyrolysis, while a selected representative group was further analyzed using bitumen extraction, open column chromatography and gas chromatography-mass spectrometry. Results of this investigation revealed units with sufficient organic material of good enough quality and quantity to be considered as potential source rocks. A general Type III kerogen was identified, indicating terrestrial origin of the organic matter. Tmax and Production Index values further indicate that the most promising parts of the sediments are immature with respect to oil generation and have not experienced high temperature during burial. n-alkanes distribution for selected samples of the Northern Miocene to Pliocene mudstones present dominance of the long-chain components. Immaturity of the organic matter is also evident by the low Pr/Ph and 20S/(20S + 20R) steranes ratios.

Yeast Mpo1 Is a Novel Dioxygenase That Catalyzes the α-Oxidation of a 2-Hydroxy Fatty Acid in an Fe2+-Dependent Manner.

Phytosphingosine (PHS) is the major long-chain base component of sphingolipids in Saccharomyces cerevisiae The PHS metabolic pathway includes a fatty acid (FA) α-oxidation reaction. Recently, we identified the novel protein Mpo1, which is involved in PHS metabolism. However, the details of the FA α-oxidation reaction and the role of Mpo1 in PHS metabolism remained unclear. In the present study, we revealed that Mpo1 is involved in the α-oxidation of 2-hydroxy (2-OH) palmitic acid (C16:0-COOH) in the PHS metabolic pathway. Our in vitro assay revealed that not only the Mpo1-containing membrane fraction but also the soluble fraction was required for the α-oxidation of 2-OH C16:0-COOH. The addition of Fe2+ eliminated the need for the soluble fraction. Purified Mpo1 converted 2-OH C16:0-COOH to C15:0-COOH in the presence of Fe2+, indicating that Mpo1 is the enzyme body responsible for catalyzing the FA α-oxidation reaction. This reaction was also found to require an oxygen molecule. Our findings indicate that Mpo1 catalyzes the FA α-oxidation reaction as 2-OH fatty acid dioxygenase, mediated by iron(IV) peroxide. Although numerous Mpo1 homologs exist in bacteria, fungi, protozoa, and plants, their functions had not yet been clarified. However, our findings suggest that these family members function as dioxygenases.

Effects of Amphipathic Polypeptides on Membrane Organization Inferred from Studies Using Bicellar Lipid Mixtures

SP-B63-78, a lung surfactant protein fragment, and magainin 2, an antimicrobial peptide, are amphipathic peptides with the same overall charge but different biological functions. Deuterium nuclear magnetic resonance has been used to compare the interactions of these peptides with dispersions of 1,2-dimyristoyl- sn-glycero-3-phophocholine (DMPC)/1,2-dihexanoyl- sn-glycero-3-phophocholine (DHPC) (4:1) and DMPC/1,2-dimyristoyl- sn-glycero-3-phopho-(1'-rac-glycerol) (DMPG)/DHPC (3:1:1), two mixtures of long-chain and short-chain lipids that display bicellar behavior. This study exploited the sensitivity of a bicellar system structural organization to factors that modify partitioning of their lipid components between different environments. In small bicelle particles formed at low temperatures, short-chain components preferentially occupy curved rim environments around bilayer disks of the long-chain components. Changes in chain order and lipid mixing, on heating, can drive transitions to more extended assemblies including a magnetically orientable phase at intermediate temperature. In this work, neither peptide had a substantial effect on the behavior of the zwitterionic DMPC/DHPC mixture. For bicellar mixtures containing the anionic lipid DMPG, the peptide SP-B63-78 lowered the temperature at which magnetically orientable particles coalesced into more extended lamellar structures. SP-B63-78 did not promote partitioning of the zwitterionic and anionic long-chain lipid components into different environments. Magainin 2, on the other hand, was found to promote separation of the anionic lipid, DMPG, and the zwitterionic lipid, DMPC, into different environments for temperatures above 34 °C. The contrast between the effects of these two peptides on the lipid mixtures studied appears to be consistent with their functional roles in biological systems.

Nanosegregation and Structuring in the Bulk and at the Surface of Ionic-Liquid Mixtures

Ionic-liquid (IL) mixtures hold great promise, as they allow liquids with a wide range of properties to be formed by mixing two common components rather than by synthesizing a large array of pure ILs with different chemical structures. In addition, these mixtures can exhibit a range of properties and structural organization that depend on their composition, which opens up new possibilities for the composition-dependent control of IL properties for particular applications. However, the fundamental properties, structure, and dynamics of IL mixtures are currently poorly understood, which limits their more widespread application. This article presents the first comprehensive investigation into the bulk and surface properties of IL mixtures formed from two commonly encountered ILs: 1-ethyl-3-methylimidazolium and 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][Tf2N] and [C12mim][Tf2N]). Physical property measurements (viscosity, conductivity, and density) reveal that these IL mixtures are not well described by simple mixing laws, implying that their structure and dynamics are strongly composition dependent. Small-angle X-ray and neutron scattering measurements, alongside molecular dynamics (MD) simulations, show that at low mole fractions of [C12mim][Tf2N], the bulk of the IL is composed of small aggregates of [C12mim]+ ions in a [C2mim][Tf2N] matrix, which is driven by nanosegregation of the long alkyl chains and the polar parts of the IL. As the proportion of [C12mim][Tf2N] in the mixtures increases, the size and number of aggregates increases until the C12 alkyl chains percolate through the system and a bicontinuous network of polar and nonpolar domains is formed. Reactive atom scattering-laser-induced fluorescence experiments, also supported by MD simulations, have been used to probe the surface structure of these mixtures. It is found that the vacuum-IL interface is enriched significantly in C12 alkyl chains, even in mixtures low in the long-chain component. These data show, in contrast to previous suggestions, that the [C12mim]+ ion is surface active in this binary IL mixture. However, the surface does not become saturated in C12 chains as its proportion in the mixtures increases and remains unsaturated in pure [C12mim][Tf2N].

Effect of an Anionic Lipid on the Barotropic Behavior of a Ternary Bicellar Mixture.

Dispersions of lipid mixtures comprising long- and short-chain phospholipids (bicellar mixtures) can form small isotropically reorienting particles (bilayered micelles), magnetically orientable stuctures, or unorientable lamellar structures. Application of hydrostatic pressure can also induce interdigitation of the long-chain lipid components. In this work, variable-pressure 2H NMR was used to study the effect of head group charge on the barotropic behavior of bicellar mixtures. Observations at pressures up to 152 MPa and temperatures up to 64 °C were combined with earlier observations at lower pressure and lower temperature to obtain a pressure-temperature phase diagram for DMPC-d54/DMPG/DHPC (3:1:1). In this phase diagram, a region corresponding to small, isotropically reorienting particles at lower temperature and higher pressure is separated from a region corresponding to unorientable lamellar organization, at higher temperature and lower pressure, by a band in which the magnetically orientable phase is stable below ∼100 MPa and in which an interdigitated gel phase is stable above ∼120 MPa. From ∼46 to ∼52 °C, the dispersion transforms directly from the unorientable lamellar to isotropically reorienting particle phases upon isothermal pressurization. The extent to which this behavior reflects the presence of anionic lipid in the long-chain fraction of this mixture is illustrated by comparison with spectral series obtained during isothermal pressurization of DMPC-d54/DHPC (4:1) and DMPC-d54/DMPG/DHPC (2.7:1.3:1) at selected temperatures. These observations show how electrostatic interactions at a bilayer surface can affect the balance between hydrophobic and hydrophilic interactions that is reflected by a dispersion's barotropic phase behavior.

Evaluation of the Activity of the Essential Oil from an Ornamental Flower against Aedes aegypti: Electrophysiology, Molecular Dynamics and Behavioral Assays.

Dengue fever has spread worldwide and affects millions of people every year in tropical and subtropical regions of Africa, Asia, Europe and America. Since there is no effective vaccine against the dengue virus, prevention of disease transmission depends entirely on regulating the vector (Aedes aegypti) or interrupting human-vector contact. The aim of this study was to assess the oviposition deterrent activity of essential oils of three cultivars of torch ginger (Etlingera elatior, Zingiberaceae) against the dengue mosquito. Analysis of the oils by gas chromatography (GC)—mass spectrometry revealed the presence of 43 constituents, of which α-pinene, dodecanal and n-dodecanol were the major components in all cultivars. Solutions containing 100 ppm of the oils exhibited oviposition deterrent activities against gravid Ae. aegypti females. GC analysis with electroantennographic detection indicated that the oil constituents n-decanol, 2-undecanone, undecanal, dodecanal, trans-caryophyllene, (E)-β-farnesene, α-humulene, n-dodecanol, isodaucene and dodecanoic acid were able to trigger antennal depolarization in Ae. aegypti females. Bioassays confirmed that solutions containing 50 ppm of n-dodecanol or dodecanal exhibited oviposition deterrent activities, while a solution containing the alcohol and aldehyde in admixture at concentrations representative of the oil presented an activity similar to that of the 100 ppm oil solution. Docking and molecular dynamics simulations verified that the interaction energies of the long-chain oil components and Ae. aegypti odorant binding protein 1 were quite favorable, indicating that the protein is a possible oviposition deterrent receptor in the antenna of Ae. aegypti.

Comparison study of sedimentary humic substances isolated from contrasting coastal marine environments by chemical and spectroscopic analysis

To gain a better understanding of the chemical structural composition and reactivity of sedimentary organic matter in coastal environments, the properties of sedimentary humic substances (HSs) isolated from contrasting coastal marine environments (i.e., salt marsh estuary, continental shelf, and continental slope) in China were investigated and compared. The complementary analytical approaches employed included elemental analysis, cross polarization magic angle spinning (CP/MAS)-13C nuclear magnetic resonance, pyrolysis-gas chromatography–mass spectrometry, and potentiometric titrations. The results indicate that HSs isolated from the salt marsh site in the Changjiang Estuary, which is strongly influenced by terrestrial river inputs, had the highest content of lignin-derived components, such as phenols and alkyl phenols, and acidic functional groups; HSs from the continental slope site in the South China Sea, which mainly originated from the inputs of marine algae and planktons, contained the highest level of aliphatic compounds, carbohydrates, and nitrogen-containing compounds; however, HSs from the continental shelf site in the East China Sea presented a mixture of both land and marine properties due to the influence of the two sources. Humic acids were found to contain comparatively more highly branched, long-chain aliphatic components but fewer oxygen-containing functional groups, such as carboxyl groups, and fewer sulfur-containing compounds than their fulvic acid counterparts. The total concentrations of proton binding sites and the structural characteristics of the studied HSs may provide insights into the migration and fate of HS-bound contaminants, such as heavy metals and organic pollutants, in coastal marine systems.

Role of Stably Entangled Chain Network Density in Shish-Kebab Formation in Polyethylene under an Intense Flow Field

The physically entangled chain networks, formed by a long-chain polymer component, have been demonstrated to be very effective for shish-kebab formation in a flow field. However, an open question still remains whether there is an optimal content of entangled chain networks. The answer is crucial in the academic and industrial fields but faces a challenge since physically entangled chain networks are not stable, which tend to disentangle during flow. In the current work, we utilized lightly cross-linked chain networks, which can be considered as stably entangled chain networks (SECN), to study the role of SECN density in shish-kebab formation under an intense flow field. The SECN density was adjusted by adding various contents of lightly cross-linked polyethylene (PEX) in short-chain polyethylene, and the intense flow field was applied by a modified injection molding machine, so-called oscillation shear injection molding (OSIM). The results show that the structure in the core layer of the OSIM samples coul...

Understanding the Growth Rates of Polymer Cocrystallization in the Binary Mixtures of Different Chain Lengths: Revisited.

Polymers often contain a polydispersity of chain lengths, which brings a complicated influence on crystallization behaviors. In our previous publication (J. Phys. Chem. B 2008, 112, 7370), we reported dynamic Monte Carlo simulations of cocrystallization in the binary mixtures of long (32-mer) and short (16-mer) homologue chains. We observed a linear dependence of crystal growth rates on the volume fractions of the long-chain component at low temperatures. In this article, with new confirming data, we further observed that the mole fractions also give linear dependence to the crystal growth rates, but split into two regimes. We attributed the phenomenon of two regimes to the variation between two thicknesses of lamellar crystals. The small thickness in the regime of low mole fractions is dominated by the metastable integer-number folding of 16-mers, which causes the "self-poisoning" effect on the crystal growth rates.

Intracellular Delivery System for Antibody–Peptide Drug Conjugates

Antibodies armed with biologic drugs could greatly expand the therapeutic potential of antibody-drug conjugates for cancer therapy, broadening their application to disease targets currently limited by intracellular delivery barriers. Additional selectivity and new therapeutic approaches could be realized with intracellular protein drugs that more specifically target dysregulated pathways in hematologic cancers and other malignancies. A multifunctional polymeric delivery system for enhanced cytosolic delivery of protein drugs has been developed that incorporates endosomal-releasing activity, antibody targeting, and a biocompatible long-chain ethylene glycol component for optimized safety, pharmacokinetics, and tumor biodistribution. The pH-responsive polymeric micelle carrier, with an internalizing anti-CD22 monoclonal targeting antibody, effectively delivered a proapoptotic Bcl-2 interacting mediator (BIM) peptide drug that suppressed tumor growth for the duration of treatment and prolonged survival in a xenograft mouse model of human B-cell lymphoma. Antitumor drug activity was correlated with a mechanistic induction of the Bcl-2 pathway biomarker cleaved caspase-3 and a marked decrease in the Ki-67 proliferation biomarker. Broadening the intracellular target space by more effective delivery of protein/peptide drugs could expand the repertoire of antibody-drug conjugates to currently undruggable disease-specific targets and permit tailored drug strategies to stratified subpopulations and personalized medicines.

Geochemistry of Upper Miocene–Lower Pliocene source rocks in the Hellenic Fold and Thrust Belt, Zakynthos Island, Ionian Sea, western Greece

The southwestern margin of the Hellenic Fold and Thrust Belt, situated along the southern edge of the Dinarides-Albanides-Hellenides continental convergent zone, has been studied in terms of its hydrocarbon generating potential. The Upper Miocene–Lower Pliocene (Tortonian to Zanclean) clastic sedimentary succession at Zakynthos Island provides an excellent opportunity to evaluate the source rock potential of such a system. Twenty seven mudstone samples were analyzed using organic geochemical techniques such as, Rock-Eval pyrolysis, bitumen extraction, open-column chromatography and gas chromatography–mass spectrometry. The obtained data indicate that the sedimentary sequence contains units with sufficient organic material of good enough quality to be considered as potential source rocks. The input of terrestrial organic material and associated gaseous generating potential is indicated by: (1) Rock-Eval pyrolytic yields and calculated values of hydrogen and oxygen indices, (2) n-alkane distribution with dominant long-chain components, (3) high terrigenous to aquatic organic material ratios, (4) odd to even predominance values, (5) low sulfur content and (6) occurrence of gammacerane. The kerogen is immature as evidenced by: (1) Tmax and production index values, (2) odd to even predominance values, (3) low diasterane to sterane and Pr/Ph ratios, (4) low 20S/(20S + 20R) and ββ/(ββ + αα) sterane ratios and (5) presence of gammacerane.

When Schwann Cells Conspire with Mitochondria, Neighboring Axons Are under Attack by Glia-Derived Neurotoxic Lipids

In this issue of Neuron, Viader etal. (2013) report on the production of toxic lipids by Schwann cells deficient in mitochondrial respiration, which are capable of destroying neighboring axons. This may have implications for understanding the neurobiology and treatment of mitochondrial neuropathies.

The sensitive to freezing3 mutation of Arabidopsis thaliana is a cold-sensitive allele of homomeric acetyl-CoA carboxylase that results in cold-induced cuticle deficiencies

The sfr3 mutation causes freezing sensitivity in Arabidopsis thaliana. Mapping, sequencing, and transgenic complementation showed sfr3 to be a missense mutation in ACC1, an essential gene encoding homomeric (multifunctional) acetyl-CoA carboxylase. Cuticle permeability was compromised in the sfr3 mutant when plants were grown in the cold but not in the warm. Wax deposition on the inflorescence stem of cold-grown sfr3 plants was inhibited and the long-chain components of their leaf cuticular wax were reduced compared with wild-type plants. Thus, freezing sensitivity of sfr3 appears, from these results, to be due to cuticular deficiencies that develop during cold acclimation. These observations demonstrated the essential role of the cuticle in tolerance to freezing and drought.

Quantifying the anthropogenic fraction of fatty alcohols in a terrestrial environment

Fatty alcohols are naturally produced hydrocarbons present in all living organisms. They are also used in detergent and cosmetic formulations, may be sourced from either petroleum or biological materials, and are typically disposed of down the drain. This study was conducted on the Luray catchment, Virginia, USA, where sales data indicate that approximately 2 kg of fatty alcohols from detergent enter the wastewater every day. Reconstructing fatty alcohols in the influent on the basis of sales data indicated a mix of odd and even chain compounds, with C(12) being dominant. This profile was influenced strongly by liquid laundry detergents (69%). Sediment and soil samples from the catchment were analyzed by gas chromatography-mass spectrometry and by stable isotope ratio mass spectrometry to determine the δ(13)C and δ(2)H signatures. The long-chain components in agricultural soils and river sediments were distinguishable clearly from the algal fatty alcohols produced within the river system. The wastewater was a mixture of fecal and detergent sources of fatty alcohols in a ratio of 75:25%. The fatty alcohols in the effluent had different stable isotopic signatures and chain-length profiles from the influent, indicating that these compounds are not the same as those that entered the treatment plant. The total quantity of fatty alcohols leaving the treatment plant through the effluent pipe was low compared with the input. Analysis of the contributions based on the stable isotopes and profiles suggests that of the fatty alcohols present in the river system downstream of the treatment plant, 84% were derived from terrestrial plant production, 15% came from in situ algal synthesis, and 1% were derived from the effluent.

Characterization of wildfire effects on soil organic matter using analytical pyrolysis

The effectiveness of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) as a rapid analytical technique to get insight in wildfire-induced molecular alterations of the soil organic matter in Mediterranean Leptosols was examined. To this end, the topsoil of two slopes with adjacent patches of burnt and unburnt Maritime Pine (Pinus pinaster) and eucalypt plantations (Eucalyptus globulus) were sampled in the Serra de Lousã, central Portugal. Several differences were found between the neighbouring burnt and unburnt soils, both in thermal desorption and pyrolysis behaviour. Thermal desorption results showed large amounts of aliphatic compounds (both alkyl and carbohydrate-derived compounds), which may indicate the incorporation of fresh plant material or low wildfire severity. Pyrolysis at 500°C revealed an increase of low molecular weight molecules for certain homologous series in fire-affected soils, suggesting the occurrence of thermal breakdown and cracking of long-chain components. In addition, the presence of several thermo-labile markers pointed to the low severity of the wildfire. Elemental analysis indicated marked fire-induced increases in TOC and TN for the pine stand as opposed to noticeable decreases for the eucalypt stands. Probably, this contrast between the two sites is not due to differences in direct fire effects (especially fire severity) but to indirect fire effects i.e. in particular needle/leaf fall from affected canopies.

Egg discrimination by workers in Diacamma sp. from Japan

In eusocial Hymenoptera, workers usually cannot mate but can lay male-destined haploid eggs. In contrast, in many species, worker reproduction is regulated by means of worker policing, which consists of two behavioral categories: aggression towards workers that have developed ovaries, and the destruction of worker-laid eggs. We focused on the latter behavior in the ant Diacamma sp. from Japan, in which a mated worker (gamergate) serves as the functional queen in each colony. An experiment in which we introduced both worker-laid eggs and gamergate-laid eggs from foreign colonies showed that workers preferentially destroyed the worker-laid eggs. This indicates that workers can discriminate worker-laid eggs from gamergate-laid eggs. In contrast, gamergates destroyed all introduced eggs that they discovered. Our chemical analysis of egg surface substances revealed that the worker-laid eggs clearly differed from gamergate-laid eggs in their surface hydrocarbons (SHCs), with the former containing more long-chain components. However, a bioassay to test whether specific components of the SHCs trigger the observed discrimination behavior by workers remains to be done.

The long-chain dynamics in a model homopolymer blend under strong flow: small-angle neutron scattering and theory

We use small-angle neutron scattering (SANS) measurements to provide a detailed picture of the non-linear dynamics of the long chains in a model polystyrene blend. By a weighted subtraction of SANS measurements from two otherwise identical blends with different deuteration fractions, we isolate the single-chain form factor of the long-chain component of a model blend flowing through a 4 : 1 contraction–expansion flow. Complementary flow-birefringence also provides a measure of chain deformation on finer length-scales. In addition, higher flow Weissenberg numbers than in previous studies on monodisperse melts were achieved, leading to greater anisotropy in the measured single-chain structure factor. The short residence time inside the slit means that the chains are still oriented in the flow direction as they enter the contraction exit, leading to a rapid reversing flow. We compare these data to a simple generalisation of a non-linear tube model. Our model predictions are entirely ab initio, with all model parameters being determined from independent equilibrium measurements. The model shows very good agreement with the experimental data across the full range of length-scales for the contraction entrance and subsequent relaxation within the slit. However, there is conspicuous disagreement between theory and experiments at the contraction exit, in both the SANS and birefringence predictions, which we attribute to the reversing flow that occurs in this region.

A constitutive analysis of transient and steady-state elongational viscosities of bidisperse polystyrene blends

The transient and steady-state elongational viscosity data of three bidisperse polystyrene blends were investigated recently by Nielsen et al. [J. Rheol. 50, 453–476 (2006)]. The blends contain a monodisperse high molar mass component (ML=390kg∕mol) in a matrix of a monodisperse small molar mass component (either MS=103kg∕mol or MS=52kg∕mol at two different weight fractions). The experimental data are analyzed in the framework of the molecular stress function model of Wagner et al. [J. Rheol. 49, 1317–1327 (2005)], which is based on the assumption of a strain-dependent tube diameter and the interchain pressure term of Marrucci and Ianniruberto [Macromolecules 37, 3934–3942 (2004)]. The dilution of the long chains in the matrix of the short chains is identified as the origin of a drastic increase in the tube-diameter relaxation time of the long chains, leading to a large stretching potential of the long-chain component and an increasing steady-state elongational viscosity with increasing strain rate. In ad...

The Distribution and Conformation of Very Long-Chain Plant Wax Components in a Lipid Bilayer

Plant wax contains long-chain alkanes and related components which are transported to the surface of the plant by specialized ABC transporter proteins. Here, we determine the distribution and conformation of three wax components, nonacosane, nonacosan-15-one, and nonacosan-15-ol, using unbiased and umbrella sampling molecular dynamics simulations. The molecules all partitioned to the center of the bilayer, with a free-energy difference of -70 kJ/mol between bulk water and the center of the bilayer for the alkane and -55 kJ/mol for the two more-polar molecules. All of the wax molecules were highly mobile in the bilayer, freely moving between opposite leaflets on a time scale of a few nanoseconds. Nonacosan-15-one and nonacosan-15-ol folded double to expose their hydrophilic group to the solvent, whereas nonacosane alternated between orientations spanning the full bilayer and orientations in the center of the bilayer.