Oligomeric Fraction Research Articles

On the fractionation of lignin oligomers by stepwise gradient reversed-phase liquid chromatography

With the increased interest in lignin valorization, the analytical challenge to separate a complex mixture of a vast number of phenolics has made chromatography an indispensable step in lignin analysis. High-resolution separations, such as gas chromatography, reversed-phase liquid chromatography and supercritical fluid chromatography have typically been targeting low-molecular-weight compounds, while larger lignin oligomers have received less attention. These compounds have proven to be difficult to separate due to the inherent complexity of the high-molecular-weight fraction of lignins, in fact, even high-resolving linear reversed-phase gradients elute them as one wide zone. To tackle this, in this study we show that a crude fractionation of lignin oligomers can be achieved by applying stepwise reversed-phase gradients. A commonly employed reversed-phase system with water:acetonitrile mobile phase is evaluated for this task. Special attention was devoted to uncovering the molecular level explanation of the retention phenomenon. Our results indicate that separation is mainly governed by reversed-phase retention phenomena without any major exclusion or viscosity-related effects, shown by great fits to linear retention models (R2avg=0.9599 for five different oligomers) and apparent differences in retentivity between different stationary phases. The influence of the gradient shape was demonstrated by the comparison of stepwise gradients with different number and frequency of steps, leading to the conclusion that gradients with a low number of steps yield fewer, but better resolved fractions, while finer multi-step gradients can be used to distinguish more fractions.

Structural Analyses of Polysaccharides Extracted from Cyanobacterial Extracellular Gels and Oriented Liquid Crystalline Microfiber Processing by Poly(vinyl alcohol)-Assisted Electrospinning.

Sacran is a supergiant cyanobacterial polysaccharide that forms mesogenic supercoil rods that exhibit liquid crystalline (LC) gels at deficient concentrations of around 0.5 wt%, and has several bioactive stimuli-responsive functions. Here, we attempted to form oriented microfibers of sacran by electrospinning, following structural analyses of the sacran rods. A heterogeneous acid-hydrolysis method using a protonated cation-exchange resin was adopted to examine the short-time exposition of concentrated acid to sacran rods. From the supernatant, the oligomeric fraction that was soluble in water and methanol was isolated. The oligomeric fraction had a main sugar ratio of α-Glc:β-Glc:α-Xyl:β-Xyl:α-Rha of 2:5:1.5:1.5:4 (Glc:Xyl:Rha = 7 (=4 + 3):3:4), and it was speculated that the sacran structure includes rhamnoglucan and xyloglucan (4:3), which are generally rigid enough to exhibit LC. To make oriented microfibers of LC sacran, solubility testing was performed on sacran to find good new solvents of polyhydroxy alcohols such as ethylene glycol, 1,2-propanediol, and glycerol. The oriented film was prepared from a sacran aqueous solution where calcium compound particles deposited on the film are different from polyhydroxy alcohol solutions. Although sacran could not form microfibers by itself, polymer composite microfibers of sacran with poly(vinyl alcohol) were prepared by electrospinning. Cross-polarizing microscopy revealed the molecular orientation of the microfibers.

Diffusion and Oligomerization States of the Muscarinic M1 Receptor in Live Cells─The Impact of Ligands and Membrane Disruptors.

G protein-coupled receptors (GPCRs) are a major gateway to cellular signaling, which respond to ligands binding at extracellular sites through allosteric conformational changes that modulate their interactions with G proteins and arrestins at intracellular sites. High-resolution structures in different ligand states, together with spectroscopic studies and molecular dynamics simulations, have revealed a rich conformational landscape of GPCRs. However, their supramolecular structure and spatiotemporal distribution is also thought to play a significant role in receptor activation and signaling bias within the native cell membrane environment. Here, we applied single-molecule fluorescence techniques, including single-particle tracking, single-molecule photobleaching, and fluorescence correlation spectroscopy, to characterize the diffusion and oligomerization behavior of the muscarinic M1 receptor (M1R) in live cells. Control samples included the monomeric protein CD86 and fixed cells, and experiments performed in the presence of different orthosteric M1R ligands and of several compounds known to change the fluidity and organization of the lipid bilayer. M1 receptors exhibit Brownian diffusion characterized by three diffusion constants: confined/immobile (∼0.01 μm2/s), slow (∼0.04 μm2/s), and fast (∼0.14 μm2/s), whose populations were found to be modulated by both orthosteric ligands and membrane disruptors. The lipid raft disruptor C6 ceramide led to significant changes for CD86, while the diffusion of M1R remained unchanged, indicating that M1 receptors do not partition in lipid rafts. The extent of receptor oligomerization was found to be promoted by increasing the level of expression and the binding of orthosteric ligands; in particular, the agonist carbachol elicited a large increase in the fraction of M1R oligomers. This study provides new insights into the balance between conformational and environmental factors that define the movement and oligomerization states of GPCRs in live cells under close-to-native conditions.

Glucosamine conjugated gold nanoparticles modulate protein aggregation induced autophagic neuronal cell death via regulation of intracellular Parkin homeostasis

Recent studies have suggested that ∼ 25% of the brain glycogen is composed of glucosamine (Gln), though its role in maintaining the balance in nervous system is yet to be fully understood. Here, we have reported the synthesis and protective effect of glucosamine conjugated gold nanoparticles (Gln@CA-AuNP) on the oligomeric and fibrillar fraction of hen egg white lysozyme (HEWL). The synthesized Gln@CA-AuNP (∼ 30.1±3.7 nm) was characterized by different spectroscopy and microscopy techniques. The corresponding biophysical studies suggested that Gln@CA-AuNP could effectively inhibit the HEWLO formation and simultaneously, could restrict the nucleation step of protein aggregation. Studies carried out with human neuroblastoma cells (SH-SY5Y) suggested that Gln@CA-AuNP alleviated protein aggregation induced cell death via inhibition of oligomer formation (∼ 2.4 times), reduction of intracellular oxidative stress (∼ 3.6 times) by uplifting the mitochondrial health. The intracellular delivery of Gln was found to modulate cytosolic Parkin oxidation and restrict autophagic neuronal cell death as confirmed by western blot studies. Further, Gln@CA-AuNP has been found to enhance sulfated glycosaminoglycans (sGAGs) production which suggested its role in protecting the extracellular matrix (ECM) during protein aggregation induced toxicity. Also, neuronal synapse of the in vivo Caenorhabditis elegans model could be preserved with the pre-treatment of Gln@CA-AuNP. Overall, we predict that this approach of neuroprotection via simultaneous targeting of early and late aggregates may serve as a better therapeutic strategy for the treatment of neurodegenerative diseases.

Characterizing Styrene Monomer and Oligomers by SEC/MALS/VISC/DRI

Worldwide polystyrene (PS) production in 2020 was approximately 27 million metric tons, distributed among many nations, making it one of the most heavily imported and exported chemicals. Commercially produced PS usually possesses a broad molar mass distribution, often with a substantial oligomeric component. The latter can significantly affect processing and end-use, in addition to having potentially hazardous health effects and to impacting the polymer’s export classification by regulatory agencies. Quantitation of the oligomeric region of polymers by size-exclusion chromatography with concentration-sensitive and/or static light scattering detection is complicated by the non-constancy of the specific refractive index increment (∂n/∂c) in this region, which affects the calculated amount (mass fraction) of oligomer in a polymer, molar mass averages, and related conclusions regarding macromolecular properties. Here, a multi-detector SEC approach including differential refractometry, multi-angle static light scattering, and differential viscometry has been applied to determining the ∂n/∂c of n-butyl terminated styrene oligomers at each degree of polymerization from monomer to hexamer, and also of a hexadecamer. Large changes in this parameter from one degree of polymerization to the next are observed, including but not restricted to the fact that the ∂n/∂c of the monomer is less than half that of PS polymer at identical experimental conditions. As part of this study, the individual effects of injection volume, flow rate, and temperature on chromatographic resolution were examined. Incorporation of the on-line viscometer allowed for accurate determination of the intrinsic viscosity and viscometric radius of the monomer and oligomers.

Altered properties of amyloidogenic prion protein in genetic Creutzfeldt-Jakob disease with PRNP V180I mutation in response to pentosan polysulfate.

Genetic Creutzfeldt-Jakob disease (gCJD) with V180I prion protein gene (PRNP) mutation shows weaker prion protein (PrP) deposition histologically compared with sporadic CJD, and it is more difficult to detect protease-resistant prion protein in immunoblotting. However, we previously reported the autopsy case of a patient with V180I gCJD who was treated with pentosan polysulfate sodium (PPS); this case had increased protease-resistant PrP deposition. It has been suggested that PPS might reduce protease-resistant PrP; however, the detailed pharmacological and histopathological effects of PPS in humans remain unknown. We examined autopsied human brain tissue from four cases with V180I gCJD that were added to our archives between 2011 and 2021: two cases treated with PPS and two cases without PPS. We conducted a neuropathological assessment, including immunohistochemistry for PrP. We also performed immunoblotting for PrP on homogenate samples from each brain to detect protease-resistant PrP using both a conventional procedure and size-exclusion gel chromatography for the purification of oligomeric PrP. Both PPS-treated cases showed long survival time over 5 years from onset and increased PrP deposition with a characteristic pattern of coarse granular depositions and congophilic PrP microspheres, whereas the cases without PPS showed around 1-year survival from onset and relatively mild neuronal loss and synaptic PrP deposition. Although cortical gliosis seemed similar among all cases, aquaporin 4-expression as a hallmark of astrocytic function was increased predominantly in PPS cases. Immunoblotting of non-PPS cases revealed protease-resistant PrP in the oligomeric fraction only, whereas the PPS-treated cases showed clear signals using conventional procedures and in the oligomeric fraction. These unique biochemical and histopathological changes may reflect the progression of V180I gCJD and its modification by PPS, suggesting the possible existence of toxic PrP-oligomer in the pathophysiology of V180I gCJD and beneficial effects of PPS toward the aggregation and detoxication of toxic PrP-oligomer.

<i>In vitro</i> and <i>in vivo</i> Immunoadjuvant Effects of the Enzymatically Modified Fucoidan

Objectives. No sulfated polysaccharides (fucoidans) has been declared as the pharmaceutical substances, adjuvants, etc., which is associated with the problems of obtaining the structurally characterized and homogeneous samples or their oligomeric fractions that retain high biological activity. The highly purified fucoidan with regular reproducible structural characteristics (F1) was obtained by enzymatic hydrolysis of native fucoidan (F2). Aim. The comparative study of fucoidans from the brown alga Fucus evanescens (F1 and F2) effects on the effector functions of innate and adaptive immunity cells loaded with ovalbumin (OVA) in vitro and in vivo. Material and methods. Fucoidan F1 — the enzymatically modified product of native fucoidan; F2 — the native fucoidan. The fucoidans effects on the expression level of the main immunophenotypic markers of innate and adaptive immunity (neutrophils, monocytes, natural killers, lymphocytes) cells in vitro were studied by methods of flow cytometry. The fucoidans effects on the production of serum OVA-specific antibodies (IgG, IgG1, IgG2а) and cytokines (IFNγ, IL-2, IL-10, IL-12) were detected in BALB/c mice immunized with OVA. Results. The tested fucoidans activate the effector functions of innate and adaptive immunity cells loaded with OVA in vitro and act as adjuvants, stimulating both Th1 (IgG2а, INFγ, IL-2) and Th2 (IgG1, IL-10) immune response to OVA in vivo. Conclusions. The immunoadjuvant effect of the enzymatically modified fucoidan (F1) on effector functions of innate and adaptive immunity cells are comparable to those of the native fucoidan (F2). The findings determine the possibility of F1 use as an adjuvant for a wide range of prophylactic and therapeutic vaccines.

I-Shaped Dimers of a Plant Chloroplast FOF1-ATP Synthase in Response to Changes in Ionic Strength

F-type ATP synthases play a key role in oxidative and photophosphorylation processes generating adenosine triphosphate (ATP) for most biochemical reactions in living organisms. In contrast to the mitochondrial FOF1-ATP synthases, those of chloroplasts are known to be mostly monomers with approx. 15% fraction of oligomers interacting presumably non-specifically in a thylakoid membrane. To shed light on the nature of this difference we studied interactions of the chloroplast ATP synthases using small-angle X-ray scattering (SAXS) method. Here, we report evidence of I-shaped dimerization of solubilized FOF1-ATP synthases from spinach chloroplasts at different ionic strengths. The structural data were obtained by SAXS and demonstrated dimerization in response to ionic strength. The best model describing SAXS data was two ATP-synthases connected through F1/F1′ parts, presumably via their δ-subunits, forming “I” shape dimers. Such I-shaped dimers might possibly connect the neighboring lamellae in thylakoid stacks assuming that the FOF1 monomers comprising such dimers are embedded in parallel opposing stacked thylakoid membrane areas. If this type of dimerization exists in nature, it might be one of the pathways of inhibition of chloroplast FOF1-ATP synthase for preventing ATP hydrolysis in the dark, when ionic strength in plant chloroplasts is rising. Together with a redox switch inserted into a γ-subunit of chloroplast FOF1 and lateral oligomerization, an I-shaped dimerization might comprise a subtle regulatory process of ATP synthesis and stabilize the structure of thylakoid stacks in chloroplasts.

Single particle mass photometry provides size distributions of tau oligomers in CSF samples revealing strong differences between samples from Alzheimer’s patients and healthy controls

AbstractBackgroundTau oligomers are considered toxic species in neurodegenerative disorders and their abundance correlate well with the disease onset and pathology. Assays used for detection of these toxic tau oligomer species fail to detect their low levels and to differentiate between various oligomers. This limitation reduces the potential for early diagnosis and for possible intervention. A label‐free approach that can detect these biomarkers at low concentrations while also revealing their size distribution will be ideal.MethodHere, we use a combination of tau oligomer‐specific immunoprecipitation from human CSF samples and single‐molecule mass analysis based on so‐called mass photometry to determine the size of thousands of individual oligomeric species in solution in a label‐free manner.ResultSingle‐oligomer mass analysis makes it possible to determine the number of tau monomers in thousands of individual oligomer particles in CSF samples from human patients and control subjects. The method reveals a dramatic difference in the size distribution of tau oligomer species from Alzheimer’s patients compared to control subjects. In particular, samples from AD patients contain a significant fraction of trimeric tau oligomers, which are completely absent in the control samples.ConclusionSingle‐particle mass analysis of tau protein oligomers enables discrimination of samples from patients with AD from those of age‐matched control subjects. Furthermore, single‐particle based analysis of the size distribution of oligomeric species will help to shed light on the toxicity of various oligomers species.

Evaluation of electro-synthesized oligothiophenes as donor materials in vacuum-processed organic photovoltaic devices

2,2′:5′,2″-terthiophene (3Th) was utilized as a precursor in the electro-synthesis of oligothiophenes and their further evaluation as donor materials in the active layer of vacuum-processed organic photovoltaic (OPV) devices. Electro-polymerization conditions were optimized to obtain a controlled fraction of polydisperse oligomers, as demonstrated by size exclusion chromatography (SEC). The polydispersity of the material was further decreased during thermal evaporation, where a reduced fraction of the oligomer was deposited, as observed by SEC, absorption spectroscopy, and the characterization of the fabricated devices. Our results demonstrate for the first time the potential of the electro-synthesis of oligothiophenes as active materials for their application in bulk heterojunction for OPV devices.

Epsilon-Caprolactam- and Nylon Oligomer-Degrading Bacterium Brevibacterium epidermidis BS3: Characterization and Potential Use in Bioremediation.

epsilon-Caprolactam (Caprolactam, CAP), a monomer of the synthetic non-degradable polymer nylon-6, is the major wastewater component in the production of caprolactam and nylon-6. Biological treatment of CAP, using microbes could be a potent alternative to the current waste utilization techniques. This work focuses on the characterization and potential use of caprolactam-degrading bacterial strain BS3 isolated from soils polluted by CAP production wastes. The strain was identified as Brevibacterium epidermidis based on the studies of its morphological, physiological, and biochemical properties and 16S rRNA gene sequence analysis. This study is the first to report the ability of Brevibacterium to utilize CAP. Strain BS3 is an alcalo- and halotolerant organism, that grows within a broad range of CAP concentrations, from 0.5 up to 22.0 g/L, optimally at 1.0-2.0 g/L. A caprolactam biodegradation experiment using gas chromatography showed BS3 to degrade 1.0 g/L CAP over 160 h. In contrast to earlier characterized narrow-specific CAP-degrading bacteria, strain BS3 is also capable of utilizing linear nylon oligomers (oligomers of 6-aminohexanoic acid), CAP polymerization by-products, as sole sources of carbon and energy. The broad range of utilized toxic pollutants, the tolerance for high CAP concentrations, as well as the physiological properties of B. epidermidis BS3, determine the prospects of its use for the biological cleanup of CAP and nylon-6 production wastes that contain CAP, 6-aminohexanoic acid, and low molecular weight oligomer fractions.

Depolymerised lignin oil: A promising building block towards thermoplasticity in polyurethanes

The use of lignin as building block in the preparation of lignin-based thermoplastics has been a great challenge for the scientific community. Indeed, both the heterogeneous branched structure and the high hydroxyl functionality of lignin favours crosslinking reactions leading to the formation of thermosetting chemical structures. Some attempts have been made to circumvent these limitations, although the approaches required labour-intensive and time-consuming modifications of lignin and used only a relatively low amount in the materials. To tackle this problem, the present work employs lignin hydrogenolysis oil (LHO) which contains a low hydroxyl functionality oligomeric fraction suitable for the synthesis of thermoplastic polyurethanes (TPUs) via a two-step polymerization process. A series of TPUs were synthesized to investigate the impact of lignin content as well as soft segment molar mass on the chemical and thermo-mechanical properties of the materials. The study demonstrates that the use of high lignin content (38–46 wt. %) and high molar mass of the polyol (polypropylene glycol, PPG, Mn=4 kg mol−1) enhanced the mechanical properties of the obtained TPUs compared to counterpart polymers synthesized with lower molar mass of PPG. Additionally, LHO-based TPUs were applied as hot-melt adhesives for wood and their bonding strengths were evaluated by single lap shear tests. The lap shear adhesiveness was found to increase with increasing LHO concentration and decreasing molar mass of PPG. The developed methodology could lead to the preparation of robust thermoplastic lignin-based polyurethanes with a wide range of desired properties.

Fabrication of ultraviolet resistant and anti-bacterial non-isocyanate polyurethanes using the oligomers from the reductive catalytic fractionated lignin oil

Under the ‘green chemistry’ concept, lignin oligomers obtained from the reductive catalytic fractionation process was utilized as the renewable polyol substitute for non-isocyanate polyurethane (NIPU) films. After fractionation and characterization, the lignin oligomers underwent oxypropylation and were subsequently prepared as o-chlorohydrin resins. Then, the obtained cyclic carbonate (CC) was reacted with amines-based molecules for the fabrication of NIPUs. Owing to the low molecular weight, high hydroxyl group content, and good solubility, the obtained NIPUs substituted with the RCF lignin oligomers derived CC exhibited satisfactory mechanical properties and thermal stability. More attractively, the NIPUs possessed excellent UV resistant property and antibacterial activity, revealing that the RCF lignin-based NIPUs can be potentially applied as the antibacterial coating, protective coating, and anti-ultraviolet materials. These findings opening a new approach for valorization of the low valuable oligomer fractions in the RCF oil, which improving the overall economic feasibility of the lignin-first biorefineries.

A protein aggregation platform that distinguishes oligomers from amyloid fibrils.

Deposition of aggregated proteins is a pathological feature in many neurodegenerative disorders such as Alzheimer's and Parkinson's. In addition to insoluble amyloid fibrils, protein aggregation leads to the formation of soluble oligomers, which are more toxic and pathogenic than fibrils. However, it is challenging to screen for inhibitors targeting oligomers due to the overlapping processes of oligomerization and fibrillization. Here we report a protein aggregation platform that uses intact and split TEM-1 β-lactamase proteins as reporters of protein aggregation. The intact β-lactamase fused with an amyloid protein can report the overall protein aggregation, which leads to loss of lactamase activity. On the other hand, reconstitution of active β-lactamase from the split lactamase construct requires the formation of amyloid oligomers, making the split lactamase system sensitive to oligomerization. Using Aβ, a protein that forms amyloid plaques in Alzheimer's disease, we show that the growth curves of bacterial cells expressing either intact or split lactamase-Aβ fusion proteins can report changes in the Aβ aggregation. The cell lysate lactamase activity assays show that the oligomer fraction accounts for 20% of total activity for the split lactamase-Aβ construct, but only 3% of total activity for the intact lactamase-Aβ construct, confirming the sensitivity of the split lactamase to oligomerization. The combination of the intact and split lactamase constructs allows the distinction of aggregation modulators targeting oligomerization from those targeting overall aggregation. These low-cost bacterial cell-based and biochemical assays are suitable for high-throughput screening of aggregation inhibitors targeting oligomers of various amyloid proteins.

Preparation and Fractionation of Heterogeneous Aβ42 Oligomers with Different Aggregation Properties.

Deposition of amyloid-β (Aβ) aggregates in the form of amyloid plaques is a central feature of Alzheimer's disease. The end products of Aβ aggregation are amyloid fibrils. Soluble Aβ aggregates called oligomers are also formed either on or off the pathway of fibril formation. The amyloid fibrils from different clinical subtypes of Alzheimer's disease have been found to adopt different structures, a phenomenon called fibril polymorphism. Meanwhile, different types of Aβ oligomers have also been found. Recently, it has been shown that different types of Aβ42 oligomers may form fibrils of different structures, linking oligomer heterogeneity to fibril polymorphism. In this chapter, we describe methods to prepare heterogeneous Aβ42 oligomers and to quantify the concentration of these oligomers at a low micromolar range using a fluorescamine method. Fractionation of these oligomers by size using ultrafiltration filters allows for the formation of Aβ42 fibrils with different structural properties.

Effects of enzymatically depolymerised fucoidan on effector functions of innate and adaptive immunity cells

The use of sulfated polysaccharides (fucoidans) as active pharmaceutical ingredients or adjuvants poses the challenge of obtaining structurally characterised and homogeneous samples or their oligomeric fractions maintaining high biological activity. The authors obtained a highly purified enzymatic hydrolysate of fucoidan from the brown alga Fucus evanescens and compared its biological activity with that of a native sample. The aim of the study was to compare, in vitro and in vivo, the effects of depolymerised fucoidan from the brown alga F. evanescens and native fucoidan on the effector functions of innate and adaptive immunity cells loaded with ovalbumin (OVA). Materials and methods: the effects of the fucoidan samples (depolymerised and native) on the expression of the main immunophenotypic markers by innate and adaptive immunity cells (neutrophils, monocytes, natural killers, and lymphocytes) were studied in vitro using flow cytometry. The levels of serum OVA-specific antibodies (IgG, IgG1, IgG2а) and cytokines (IFN-γ, IL-2, IL-10, IL-12) were studied in vivo using BALB/c mice immunised with OVA. The statistical analysis of the data obtained was performed using the Statistica 10 software package. Results: in vitro, both fucoidan samples altered the expression of the main immunophenotypic markers by innate and adaptive immunity cells, indicating their activation. In vivo, mice treated with the fucoidan samples demonstrated an increase in the levels of OVA-specific antibodies (IgG, IgG1 and IgG2a) and in the production of cytokines (IFN-γ, IL-2, IL-10). Conclusions: the effects of enzymatically depolymerised fucoidan on functional activity of innate and adaptive immunity cells are comparable to those of native fucoidan. The findings indicate the possibility of using enzymatic hydrolysis products of fucoidan as adjuvants for a wide range of prophylactic and therapeutic vaccines.

Safety assessment of the active substances cyclooctene homopolymer and cobalt stearate in combination for use in active food contact materials.

The EFSA Panel on Food Contact Materials, Enzymes and Processing Aids (CEP) assessed the safety of the combined use of cyclooctene homopolymer (PCOE) and cobalt stearate (CoS) intended as a oxygen scavenger in the packaging of all kinds of food stored at room temperature or below for up to 6 months. The CoS is the oxidation catalyst and the PCOE is intentionally oxidised for the oxygen scavenging function. They are incorporated into a plastic layer that is intended to be either in direct or indirect contact with the food. The potential migration of cobalt and cyclooctene monomer were below their respective specific migration limit (SML). The potential migration of PCOE non‐oxidised oligomeric low molecular weight fraction (LMWF) < 1,000 Da was estimated to be up to ■■■■■ The Panel concluded that this fraction does not raise concern for genotoxicity potential and that the no observed adverse effect level (NOAEL) derived from a subchronic toxicity study would ensure a margin of exposure large enough to not raise a safety concern. However, the Panel considered the analysis of the oxidised PCOE LMWF not sufficiently comprehensive, i.e. that additional oxidation products of different nature may be formed, and that the limit of detection corresponding to ca. ■■■■■ for individual substances is too high. The oxidised PCOE LMWF was not covered by the genotoxicity tests or the 90‐day study on the PCOE oligomers. The assessment of the identified potential oxidised migrants was considered conclusive, but not that of the migrants having remained undetected. Therefore, the CEP Panel was not able to conclude on the safety of the proposed use of cyclooctene homopolymer and cobalt stearate together as active substances in a layer for scavenging oxygen, either in direct contact with the food or separated from the food by a passive layer of polymer.

Synergistic autoinhibition and activation mechanisms control kinesin-1 motor activity.

SUMMARYKinesin-1 activity is regulated by autoinhibition. Intramolecular interactions within the kinesin heavy chain (KHC) are proposed to be one facet of motor regulation. The KHC also binds to the kinesin light chain (KLC), which has been implicated in both autoinhibition and activation of the motor. We show that the KLC inhibits the kinesin-microtubule interaction independently from the proposed intramolecular interaction within KHC. Cargo-adaptor proteins that bind the KLC stimulated processive movement, but the landing rate of activated kinesin complexes remained low. Microtubule-associated protein 7 (MAP7) enhanced motility by increasing the landing rate and run length of the activated kinesin motors. Our results support a model whereby the motor activity of the kinesin is regulated by synergistic inhibition mechanisms and that cargo-adaptor binding to the KLC releases both mechanisms. However, a non-motor MAP is required for robust microtubule association of the activated motor. Thus, human kinesin is regulated by synergistic autoinhibition and activation mechanisms.

Influence of oligomer content on viscosity and dynamic mechanical properties of epoxy asphalt binders

The impact of oligomer content on the viscosity, dynamic mechanical properties and mechanical behaviors of hot-mix epoxy asphalt binders was investigated by Brookfield viscometer, dynamic mechanical analysis and universal testing machine. The viscosity of epoxy asphalt binders during curing decreased in the oligomer content. However, the allowable construction time increased with the oligomer content. The storage modulus of epoxy asphalt binders at the glassy stage decreased in the oligomer content, whereas an opposite trend appeared at the rubbery stage. Epoxy asphalt binders exhibited two glass transition temperatures (Tgs) for both epoxy resin and asphalt, and increased in the epoxy oligomer content. The Tg of epoxy of epoxy asphalt binder increased from 30.9 to 42.4 °C when the mass fraction of oligomer increased from 23.5 % to 25.5 %. The damping properties and tensile strength of epoxy asphalt binders increased in the oligomer content, while the elongation at break and toughness showed a contrary trend. The tensile strength of epoxy asphalt binder with 23.5 % oligomer was only 0.89 MPa, which was much lower than the specification required.

Catalytic oligomerization and polymerization of ethylene with complexes of iron triad metals: influence of metal nature and new prospects

In the last five years the field of catalytic oligomerization and polymerization of olefins using complexes of late transition metals has been the most intensively developing area of post-metallocene catalysis. This review is devoted to detailed analysis of the influence of metal nature on the catalytic properties of systems based on complexes of iron triad metals. Some novel and developing areas of application of such complexes in olefin oligomerization and polymerization (ethylene trimerization, production of olefins with an odd number of carbon atoms and polyethylene waxes, targeted synthesis of heavy fractions of ethylene oligomers) are surveyed. Different approaches to the heterogenization of catalysts on various solid supports are considered.The bibliography includes 225 references.