High Molecular Weight Aggregates Research Articles

NT4X-167; Novel N-terminal Aβ specific antibody, prevents in vitro and in vivo toxicity of highly toxic Aβ4-42 species

Objectives: The novel monoclonal antibody (NT4X-167) specifically reacts with N-truncated Aβ at position 4 of Aβ. It binds N-truncated Aβ under native and denaturing conditions but only rescues in vitro toxicity of Aβ4-42 and not that of pyroglutamate AβpE3–42. One objective was to determine whether the NT4X-167 antibody and its respective Fab fragment could prevent behavioral deficits (Y-Maze), caused by Aβ4-42 injection in wildtype mice. Another was to determine if the antibody and its respective Fab could rescue the in vivo toxicity of Aβ4-42 in the Tg4-42 mouse model, by using passive immunization. Methods: Cell toxicity assay, in vivo toxicity, Y-Maze, mAB antibody production, immunostaining, passive immunization. Results: The novel Aβ4-x immunoreactive antibody NT4X-167 detected high molecular weight aggregates derived from N-truncated Aβ species. Phenylalanine at position four of Aβ was imperative for antibody binding. Both full-length and the Fab fragment of the antibody were able to prevent the in vitro toxicity caused by Aβ4-42 in rat primary cortical neuron cultures. Aβ4-42 IntraCerebroVentricular injection into wildtype mice induced a behavioral deficit, shown as a reduction in alteration rate in a Y-Maze, which was prevented using the NT4X-167. The Fab fragment of the antibody, at a higher dosage, was also able to prevent the behavioral deficit in a replicate experiment. The passive immunization was able to rescue both spatial memory deficits and significantly mitigate neuron loss. Conclusions: NT4X-167 and Fab demonstrate binding and prevention of Aβ4-42 toxicity in vitro and in vivo. NT4X full length antibody and Fab prevent Aβ4-42 induced behavioral deficits in wildtype mice. Functionally, the full length antibody and its respective Fab fragment exhibit the same profile. It would thus be of great interest to study the structural binding characteristics of the NT4X-167, represented by its Fab fragment, to the highly toxic N-truncated Aβ4-x species.

Aspartic acid functions as carbonyl trapper to inhibit the formation of advanced glycation end products by chemical chaperone activity

Advanced glycation end products (AGEs) were implicated in pathology of numerous diseases. In this study, we present the bioactivity of aspartic acid (Asp) to inhibit the AGEs. Hemoglobin and bovine serum albumin (BSA) were glycated with glucose, fructose, and ribose in the presence and absence of Asp (100–200 μM). HbA1c inhibition was investigated using human blood and characterized by micro-column ion exchange chromatography. The effect of methyl glyoxal (MG) on hemoglobin and BSA was evaluated by fluorescence spectroscopy and gel electrophoresis. The effect of MG on red blood cells morphology was characterized by scanning electron micrographs. Molecular docking was performed on BSA with Asp. Asp is capable of inhibiting the formation of fluorescent AGEs by reacting with the reducing sugars. The presence of Asp as supplement in whole blood reduced the HbA1c% from 8.8 to 6.1. The presence of MG showed an increase in fluorescence and the presence of Asp inhibited the glycation thereby the fluorescence was quenched. MG also affected the electrophoretic mobility of hemoglobin and BSA by forming high molecular weight aggregates. Normal RBCs showed typical biconcave shape. MG modified RBCs showed twisted and elongated shape whereas the presence of ASP tends to protect RBC from twisting. Asp interacted with arginine residues of bovine serum albumin particularly ARG 194, ARG 198, and ARG 217 thereby stabilized the protein complex. We conclude that Asp has dual functions as a chemical chaperone to stabilize protein and as a dicarbonyl trapper, and thereby it can prevent the complications caused by glycation.

Activation of Mitochondrial Complex II-Dependent Respiration Is Beneficial for α-Synucleinopathies

Parkinson’s disease and dementia with Lewy bodies are major challenges in research and clinical medicine world-wide and contribute to the most common neurodegenerative disorders. Previously, specific mitochondrial polymorphisms have been found to enhance clearance of amyloid-β from the brain of APP-transgenic mice leading to beneficial clinical outcome. It has been discussed whether specific mitochondrial alterations contribute to disease progression or even prevent toxic peptide deposition, as seen in many neurodegenerative diseases. Here, we investigated α-synuclein-transgenic C57BL/6J mice with the A30P mutation, and a novel A30P C57BL/6J mouse model with three mitochondrial DNA polymorphisms in the ND3, COX3 and mtRNAArg genes, as found in the inbred NOD/LtJ mouse strain. We were able to detect that the new model has increased mitochondrial complex II-respiration which occurs in parallel to neuronal loss and improved motor performance, although it exhibits higher amounts of high molecular weight species of α-synuclein. High molecular weight aggregates of different peptides are controversially discussed in the light of neurodegeneration. A favourable hypothesis states that high molecular weight species are protective and of minor importance for the pathogenesis of neurodegenerative disorders as compared to the extreme neurotoxic monomers and oligomers. Summarising, our results point to a potentially protective and beneficial effect of specific mitochondrial polymorphisms which cause improved mitochondrial complex II-respiration in α-synucleinopathies, an effect that could be exploited further for pharmaceutical interventions.Electronic supplementary materialThe online version of this article (doi:10.1007/s12035-015-9399-4) contains supplementary material, which is available to authorized users.

Mechanism-Based Inactivation of Human Cytochrome P450 2B6 by Chlorpyrifos.

Chlorpyrifos (CPS) is a commonly used pesticide which is metabolized by P450s into the toxic metabolite chlorpyrifos-oxon (CPO). Metabolism also results in the release of sulfur, which has been suggested to be involved in mechanism-based inactivation (MBI) of P450s. CYP2B6 was previously determined to have the greatest catalytic efficiency for CPO formation in vitro. Therefore, we characterized the MBI of CYP2B6 by CPS. CPS inactivated CYP2B6 in a time- and concentration-dependent manner with a kinact of 1.97 min(-1), a KI of 0.47 μM, and a partition ratio of 17.7. We further evaluated the ability of other organophosphate pesticides including chorpyrifos-methyl, diazinon, parathion-methyl, and azinophos-methyl to inactivate CYP2B6. These organophosphate pesticides were also potent MBIs of CYP2B6 characterized by similar kinact and KI values. The inactivation of CYP2B6 by CPS was accompanied by the loss of P450 detectable in the CO reduced spectrum and loss of detectable heme. High molecular weight aggregates were observed when inactivated CYP2B6 was run on SDS-PAGE gels indicating protein aggregation. Interestingly, we found that the rat homologue of CYP2B6, CYP2B1, was not inactivated by CPS despite forming CPO to a similar extent. On the basis of the locations of the Cys residues in the two proteins which could react with released sulfur during the metabolism of CPS, we investigated whether the C475 in CYP2B6, which is not conserved in CYP2B1, was the critical residue for inactivation by mutating it to a Ser. CYP2B6 C475S was inactivated to a similar extent as wild type CYP2B6 indicating that C475 is not likely the key difference between CYP2B1 and CYP2B6 with respect to inactivation. These results indicate that CPS and other organophosphate pesticides are potent MBIs of CYP2B6 which may have implications for the toxicity of these pesticides as well as the potential for pesticide-drug interactions.

Assessment of the Effects of Glycosylation on the Pattern and Kinetics of Degradation of Lenograstim in Comparison to Filgrastim Using a Stability-Indicating Orthogonal Testing Protocol

In the biopharmaceutical industry, protein aggregation and/or degradation has profound pathological implications and is encountered routinely during production, shipping, storage and administration. Lenograstim (glycosylated recombinant human granulocyte colony-stimulating factor) was subjected to stress conditions, namely, oxidation, pH, temperature, agitation and repeated freeze–thaw to generate all possible degradation products. An orthogonal stability-indicating testing protocol (RP-HPLC, SE-HPLC, ELISA and SDS-PAGE) was developed and validated for assessment of the pattern and kinetics of aggregation/degradation, under the studied experimental conditions. Results indicated clearly that Lenograstim is susceptible to degradation induced by the studied stress conditions. However, Lenograstim was found relatively more stable than Filgrastim (non-glycosylated recombinant human granulocyte colony-stimulating factor) which was attributed to the effect of glycosylation. Oxidized forms and high molecular weight aggregates of Lenograstim and Filgrastim were detected in all samples subjected to stress conditions to different degrees. ELISA assay and SDS-PAGE results were generally in agreement to those obtained using SE-HPLC assay which confirmed its selectivity to the intact drug. However, formation of soluble aggregates of both drugs was found to occur via physical adsorption and formation of intermolecular disulfide bonds. Results confirmed the need for an orthogonal testing protocol since it was impossible to reveal all types of degradation products using a single technique. Results raised a concern about the efficacy and safety of such sensitive products and highlighted the need for simple tools to inspect biologics for soluble aggregates and sub-visible particles before administration.

Purification of TNFR-Fc produced in recombinant CHO cells: Characterization of product-related impurities

Because of its large size and structural complexity, preparations of the cysteine-rich tumor necrosis factor receptor-Fc (TNFR-Fc) that are produced using recombinant CHO cells contain many undesirable impurities. In this study, to purify TNFR-Fc, cell culture supernatant was first clarified using a pre-filter and sterilization filter and then subjected to a series of purification steps consisting of protein A affinity column chromatography, anion exchange chromatography, and hydrophobic interaction chromatography (HIC). To characterize the presence of TNFR-Fc-related impurities after the HIC step, the HIC eluates were further fractionated using analytical HIC and then separated by size exclusion chromatography (SEC). Several product-related impurities were detected during SEC, including low molecular weight (LMW) species, high molecular weight aggregates, and species with a size equivalent to authentic TNFR-Fc. N-terminal sequence analysis of the LMW species indicated that N-terminal amino acids had been partially deleted from the protein sequence at amino acid positions 1–185 or 1–223. Peptide mapping analysis followed by quadrupole time-of-flight mass spectrometry (Q-TOF-MS) and MS/MS indicated that the species that was equivalent in size to authentic TNFR-Fc contained scrambled disulfide bonds linked as Cys98-Cys115 or Cys104-Cys112. These product-related impurities, which led to a marked reduction in TNF-α neutralizing activity during cytotoxicity neutralization assays in L929 cells, should be removed from the final product during purification.

Dynasore enhances the formation of mitochondrial antiviral signalling aggregates and endocytosis-independent NF-κB activation.

Dynasore has been used extensively as an inhibitor of clathrin-mediated endocytosis. While studying the role of endocytosis in LPS-induced signalling events, we discovered that dynasore itself induced activation of NF-κB, independently of its effects on endocytosis and without involving the Toll-like receptor 4 signalling pathways. The purpose of this study was to characterize this novel effect and to explore the underlying mechanism of action. We utilized gel electrophoresis, microscopy, gene knockdown and luciferase-based promoter activity to evaluate the effect of dynasore on cell signalling pathways and to delineate the mechanisms involved in its effects, Dynasore activated the NF-κB and IFN-β pathways by activating mitochondrial antiviral signalling protein (MAVS). We showed that MAVS is activated by NOX/Rac and forms high molecular weight aggregates, similar to that observed in response to viral infection. We also demonstrated that dynasore-induced activation of JNK occurs downstream of MAVS and is required for activation of NF-κB and IFN-β. These findings demonstrate a novel effect of dynasore on cell signalling. We describe a novel Rac1-, ROS- and MAVS-mediated signalling cascade through which dynasore dramatically activates NF-κB, mimicking the viral induction of this key inflammatory signalling pathway. Our results call attention to the need for a broader interpretation of results when dynasore is used in its traditional fashion as an inhibitor of clathrin-mediated endocytosis. These results suggest the intriguing possibility that dynasore or one of its analogues might be of value as an antiviral therapeutic strategy or vaccine adjuvant.

Engineered bacterial hydrophobic oligopeptide repeats in a synthetic yeast prion, [REP-PSI (+)

The yeast translation termination factor Sup35p, by aggregating as the [PSI+] prion, enables ribosomes to read-through stop codons, thus expanding the diversity of the Saccharomyces cerevisiae proteome. Yeast prions are functional amyloids that replicate by templating their conformation on native protein molecules, then assembling as large aggregates and fibers. Prions propagate epigenetically from mother to daughter cells by fragmentation of such assemblies. In the N-terminal prion-forming domain, Sup35p has glutamine/asparagine-rich oligopeptide repeats (OPRs), which enable propagation through chaperone-elicited shearing. We have engineered chimeras by replacing the polar OPRs in Sup35p by up to five repeats of a hydrophobic amyloidogenic sequence from the synthetic bacterial prionoid RepA-WH1. The resulting hybrid, [REP-PSI+], (i) was functional in a stop codon read-through assay in S. cerevisiae; (ii) generates weak phenotypic variants upon both its expression or transformation into [psi-] cells; (iii) these variants correlated with high molecular weight aggregates resistant to SDS during electrophoresis; and (iv) according to fluorescence microscopy, the fusion of the prion domains from the engineered chimeras to the reporter protein mCherry generated perivacuolar aggregate foci in yeast cells. All these are signatures of bona fide yeast prions. As assessed through biophysical approaches, the chimeras assembled as oligomers rather than as the fibers characteristic of [PSI+]. These results suggest that it is the balance between polar and hydrophobic residues in OPRs what determines prion conformational dynamics. In addition, our findings illustrate the feasibility of enabling new propagation traits in yeast prions by engineering OPRs with heterologous amyloidogenic sequence repeats.

Steric minimization towards high planarity and molecular weight for aggregation and photovoltaic studies

A steric minimization strategy is proposed to design a donor–acceptor polymer with high planarity, molecular weight and strong aggregation characteristics.

Effect of globular pea proteins fractionation on their heat-induced aggregation and acid cold-set gelation

This report focuses on cold-set gelation of pea (Pisum sativum L.) proteins and related globulin fractions, namely Vicilin 7S and Legumin 11S. Protein thermal denaturation and aggregation were investigated using differential scanning calorimetry (DSC) sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis, and sulfhydryl (S−)/disulfide (S–S) bond assessment. While the denaturation temperature (Td) of pea proteins increased from about 69 to 77 °C with increasing legumin content, the disulfide-linked acidic (α) and basic (β) legumin subunits (56–58 kDa) denatured and aggregated in a temperature range of 75–85 °C. Dissociation of legumin oligomers and their rearrangements via hydrophobic interactions and sulfhydryl/disulfide bonds exchange reactions would occur concomitantly during the heat-treatment, giving rise mainly to high-molecular weight aggregates of random structure. However thermal denaturation and aggregation of vicilin molecules would involve solely non-covalent interactions. Then glucono-δ-lactone (GDL) acid-induced gelation of protein thermal aggregates was evaluated by means of G′ and G″ moduli. The preheated mixed pea globulins and vicilin-enriched samples gave rise to increased final moduli values of the acid gels, while legumin-enriched samples displayed low gelling properties. Improving functional properties of pea proteins would help to promote their application in plant-based gelled products such as tofu, alternatively to their soy counterparts.

Effect of high intensity ultrasound on physicochemical and functional properties of aggregated soybean β-conglycinin and glycinin

The effects of high intensity ultrasound treatment (HUS; 20 kHz at 400 W for 5, 20 or 40 min) on aggregated soybean β-conglycinin (7S) and glycinin (11S) fractions were investigated in this study. HUS decreased turbidity and particle size of 7S in 0.05 M Tris–HCl buffer at pH 7.0, while it increased surface hydrophobicity (H0), solubility, emulsifying activity (EAI) and emulsion stability (ESI). Similarly, HUS of soybean 11S decreased turbidity while increasing EAI but it had minimal effects on particle size and ESI. The SH groups of both 7S and 11S fractions decreased after HUS. HUS did not change 7S or 11S secondary structure, but it slightly increased the percentage of high molecular-weight aggregates under non-reducing SDS-PAGE, and changed the microenvironment of aromatic and aliphatic side chains as observed by Raman spectroscopy of freeze-dried samples. These findings on physicochemical changes of 11S and especially of 7S proteins induced by HUS treatment may contribute to improved applications of soy proteins in food products.

Determination of supplier-to-supplier and lot-to-lot variability in glycation of recombinant human serum albumin expressed in Oryza sativa.

The use of different expression systems to produce the same recombinant human protein can result in expression-dependent chemical modifications (CMs) leading to variability of structure, stability and immunogenicity. Of particular interest are recombinant human proteins expressed in plant-based systems, which have shown particularly high CM variability. In studies presented here, recombinant human serum albumins (rHSA) produced in Oryza sativa (Asian rice) (OsrHSA) from a number of suppliers have been extensively characterized and compared to plasma-derived HSA (pHSA) and rHSA expressed in yeast (Pichia pastoris and Saccharomyces cerevisiae). The heterogeneity of each sample was evaluated using size exclusion chromatography (SEC), reversed-phase high-performance liquid chromatography (RP-HPLC) and capillary electrophoresis (CE). Modifications of the samples were identified by liquid chromatography-mass spectrometry (LC-MS). The secondary and tertiary structure of the albumin samples were assessed with far U/V circular dichroism spectropolarimetry (far U/V CD) and fluorescence spectroscopy, respectively. Far U/V CD and fluorescence analyses were also used to assess thermal stability and drug binding. High molecular weight aggregates in OsrHSA samples were detected with SEC and supplier-to-supplier variability and, more critically, lot-to-lot variability in one manufactures supplied products were identified. LC-MS analysis identified a greater number of hexose-glycated arginine and lysine residues on OsrHSA compared to pHSA or rHSA expressed in yeast. This analysis also showed supplier-to-supplier and lot-to-lot variability in the degree of glycation at specific lysine and arginine residues for OsrHSA. Both the number of glycated residues and the degree of glycation correlated positively with the quantity of non-monomeric species and the chromatographic profiles of the samples. Tertiary structural changes were observed for most OsrHSA samples which correlated well with the degree of arginine/lysine glycation. The extensive glycation of OsrHSA from multiple suppliers may have further implications for the use of OsrHSA as a therapeutic product.

In vitro and in vivo analysis of indocyanine green-labeled panitumumab for optical imaging-a cautionary tale.

Indocyanine green (IC-Green), the only FDA approved near-infrared (NIR) fluorophore for clinical use, is attractive to researchers for the development of targeted optical imaging agents by modification of its structure and conjugation to monoclonal antibodies (mAbs) or their fragments. IC-Green derivative, ICG-sulfo-OSu (ICG-sOSu), is frequently used for antibody conjugation. However, ICG-sOSu is amphiphilic and readily facilitates aggregation of mAbs that is not easily separable from the desired immunoconjugates. Complications originating from this behavior are frequently overlooked by researchers. This study examined detailed chemical and biological characteristics of an ICG-sOSu-labeled mAb, panitumumab, and provided a clinically applicable strategy to deliver a pure conjugation product. Size-exclusion high-performance liquid chromatography (SE-HPLC) analysis of conjugation reactions, performed at molar reaction ratios of ICG-sOSu: mAb of 5, 10, or 20, resulted in isolable desired ICG-sOSu-panitumumab conjugation product in 72%, 53%, and 19% yields, respectively, with the remainder consisting of high molecular weight aggregates (>150 kDa) 14%, 30%, and 51%, respectively. The HPLC-purified ICG-sOSu-panitumumab products were analyzed by native and SDS polyacrylamide gel electrophoresis (PAGE) followed by optical imaging. Results indicated that the interaction between ICG-sOSu and panitumumab was due to both covalent and noncovalent binding of the ICG-sOSu to the protein. Noncovalently bound dye in the ICG-sOSu-panitumumab conjugate products was removed by extraction with ethyl acetate to further purify the HPLC-isolated conjugation products. With conserved immunoreactivity, excellent target-specific uptake of the doubly purified bioconjugates was observed with minimal liver retention in athymic nude mice bearing HER1-expressing tumor xenografts. In summary, the preparation of well-defined bioconjugate products labeled with commercial ICG-sOSu dye is not a simple process and control of the conjugation reaction ratio and conditions is crucial. Furthermore, absolute purification and characterization of the products is necessitated prior to in vivo optical imaging. Use of validated and characterized dye conjugate products should facilitate the development of clinically viable and reproducible IC-Green derivative and other NIR dye mAb conjugates for optical imaging applications.

A central role for intermolecular dityrosine cross-linking of fibrinogen in high molecular weight advanced oxidation protein product (AOPP) formation

BackgroundAdvanced oxidation protein products (AOPPs) are dityrosine cross-linked and carbonyl-containing protein products formed by the reaction of plasma proteins with chlorinated oxidants, such as hypochlorous acid (HOCl). Most studies consider human serum albumin (HSA) as the main protein responsible for AOPP formation, although the molecular composition of AOPPs has not yet been elucidated. Here, we investigated the relative contribution of HSA and fibrinogen to generation of AOPPs. MethodsAOPP formation was explored by SDS-PAGE, under both reducing and non-reducing conditions, as well as by analytical gel filtration HPLC coupled to fluorescence detection to determine dityrosine and pentosidine formation. ResultsFollowing exposure to different concentrations of HOCl, HSA resulted to be carbonylated but did not form dityrosine cross-linked high molecular weight aggregates. Differently, incubation of fibrinogen or HSA/fibrinogen mixtures with HOCl at concentrations higher than 150μM induced the formation of pentosidine and high molecular weight (HMW)-AOPPs (>200kDa), resulting from intermolecular dityrosine cross-linking. Dityrosine fluorescence increased in parallel with increasing HMW-AOPP formation and increasing fibrinogen concentration in HSA/fibrinogen mixtures exposed to HOCl. This conclusion is corroborated by experiments where dityrosine fluorescence was measured in HOCl-treated human plasma samples containing physiological or supra-physiological fibrinogen concentrations or selectively depleted of fibrinogen, which highlighted that fibrinogen is responsible for the highest fluorescence from dityrosine. ConclusionsA central role for intermolecular dityrosine cross-linking of fibrinogen in HMW-AOPP formation is shown. General significanceThese results highlight that oxidized fibrinogen, instead of HSA, is the key protein for intermolecular dityrosine formation in human plasma.

NMR approaches in structure-based lead discovery: Recent developments and new frontiers for targeting multi-protein complexes

Nuclear magnetic resonance (NMR) spectroscopy is a pivotal method for structure-based and fragment-based lead discovery because it is one of the most robust techniques to provide information on protein structure, dynamics and interaction at an atomic level in solution. Nowadays, in most ligand screening cascades, NMR-based methods are applied to identify and structurally validate small molecule binding. These can be high-throughput and are often used synergistically with other biophysical assays. Here, we describe current state-of-the-art in the portfolio of available NMR-based experiments that are used to aid early-stage lead discovery. We then focus on multi-protein complexes as targets and how NMR spectroscopy allows studying of interactions within the high molecular weight assemblies that make up a vast fraction of the yet untargeted proteome. Finally, we give our perspective on how currently available methods could build an improved strategy for drug discovery against such challenging targets.

Probing structurally altered and aggregated states of therapeutically relevant proteins using GroEL coupled to bio-layer interferometry.

The ability of a GroEL-based bio-layer interferometry (BLI) assay to detect structurally altered and/or aggregated species of pharmaceutically relevant proteins is demonstrated. Assay development included optimizing biotinylated-GroEL immobilization to streptavidin biosensors, combined with biophysical and activity measurements showing native and biotinylated GroEL are both stable and active. First, acidic fibroblast growth factor (FGF-1) was incubated under conditions known to promote (40°C) and inhibit (heparin addition) molten globule formation. Heat exposed (40°C) FGF-1 exhibited binding to GroEL-biosensors, which was significantly diminished in the presence of heparin. Second, a polyclonal human IgG solution containing 6-8% non-native dimer showed an increase in higher molecular weight aggregates upon heating by size exclusion chromatography (SEC). The poly IgG solution displayed binding to GroEL-biosensors initially with progressively increased binding upon heating. Enriched preparations of the IgG dimers or monomers showed significant binding to GroEL-biosensors. Finally, a thermally treated IgG1 monoclonal antibody (mAb) solution also demonstrated increased GroEL-biosensor binding, but with different kinetics. The bound complexes could be partially to fully dissociated after ATP addition (i.e., specific GroEL binding) depending on the protein, environmental stress, and the assay's experimental conditions. Transmission electron microscopy (TEM) images of GroEL-mAb complexes, released from the biosensor, also confirmed interaction of bound complexes at the GroEL binding site with heat-stressed mAb. Results indicate that the GroEL-biosensor-BLI method can detect conformationally altered and/or early aggregation states of proteins, and may potentially be useful as a rapid, stability-indicating biosensor assay for monitoring the structural integrity and physical stability of therapeutic protein candidates.

Tunable thermal and flame response of phosphonated oligoallylamines layer by layer assemblies on cotton

In the present paper we have demonstrated how the change of the layer by layer deposition parameters can influence the final properties of cotton fabrics in terms of coating morphology, thermal stability and flammability. To this aim, novel synthetized oligoallylamines and phosphonated oligoallylamines have been assembled on the surface of cotton exploiting different molecular weights and pH conditions. Low molecular weights have yielded an incomplete “island growth” coating while high molecular weight resulted in a homogeneous coating which thickness was controlled by the adopted pH. Both low and high molecular weight assemblies induced a reduction of the cellulose decomposition temperatures that was, conversely, delayed by coatings assembled at pH=10. All assemblies were able to improve cotton flammability by suppressing the afterglow phenomenon; the best results in terms of flame spread and final residue have been achieved by high molecular weight assemblies.

Study of the Size Distribution of Sulfur, Vanadium, and Nickel Compounds in Four Crude Oils and Their Distillation Cuts by Gel Permeation Chromatography Inductively Coupled Plasma High-Resolution Mass Spectrometry

The size distribution of sulfur, vanadium, and nickel was determined for four crude oils and their distillation cuts using gel permeation chromatography (GPC) coupled to inductively coupled plasma high-resolution mass spectrometry (ICP HR MS). The results show a trimodal distribution of vanadium and nickel compounds in the crude oils, the atmospheric residues, and the vacuum residues and, for sulfur compounds, either a mono- or bimodal distribution depending upon the distillation cut considered. A correlation exists between the sulfur fraction retention times and the temperature cuts of the distillation for a temperature below 560 °C and also between the viscosity of the crude oils and the proportion of trapped sulfur compounds in a higher boiling temperature fraction. The thermic treatment applied for the distillation increases the aggregation of low- and medium-molecular-weight compounds of vanadium and nickel into higher molecular weight aggregates between the crude oil on the one hand and the atmospheric residue and vacuum residue on the other hand, especially when the crude oil has a high total sulfur content.

Effects of UV induced photo-oxidation on the physicochemical properties of milk protein concentrate

The objective of this study was to investigate the effects of UV induced photo-oxidation on protein modification and corresponding changes in color and solubility of milk protein concentrate powder (MPC70) stored at 25 or 40°C and at 11, 33 or 75% relative humidity (RH), respectively. Protein modifications in the soluble fractions were determined using liquid chromatography–mass spectrometry (LC–MS) and those in insoluble fractions using gel electrophoresis. The results showed that photo-oxidation caused significant decreases in L⁎ value. Moreover, the solubility of photo-oxidized MPC70 decreased significantly, while the MPC70 samples without UV exposure retained their solubility, except at 40°C and 75% RH. For the soluble fractions of photo-oxidized MPC70, the MS spectra showed multiple additional fractions besides the un- and lactosylated intact protein fractions compared to control suggesting that the photo-oxidation induced further modifications of the proteins, which coincided with the formation of carbonyl groups in the protein. At low RH, photo-oxidation promoted lactosylation of β-lactoglobulin. The insoluble fractions of photo-oxidized MPC70 were mainly caseins as well as high molecular weight aggregates, resulting mainly from non-disulfide covalent crosslinks induced by photo-oxidation. The results suggested that photo-oxidation could induce the modification of protein that eventually contributed to the solubility loss and discoloration of MPC70.

Isolation and Characterization of Protein Fractions Isolated from Camelina Meal

<abstract><title><italic>Abstract.</italic></title> <bold> </bold>Camelina is a new oil crop in North America. Camelina meal, a by-product of the camelina oil extraction process, typically contains 10% to 15% residual oil and 40% crude protein. As camelina oil demand increases, utilization of camelina protein for value-added products is critical to food and biotechnology industries; however, few studies have been conducted on camelina proteins.<bold> </bold>In this study, camelina protein fractions (albumin, globulins, and glutelins) were isolated from camelina meal based on their solubility using three different sequences: method 0 (S0), method 1 (S1), and method 2 (S2). The proteins’ physicochemical properties, including solubility, amino acid profiles, molecular weight, and thermal and morphological properties, were also characterized. Results showed that S1 harvested more protein (88.20%) than S0 (84.05%) and S2 (76.52%). Glutelin was the major fraction (64.64%) in camelina, followed by globulin (17.67%), and albumin (10.54%). Essential amino acids accounted for approximately 40% of the total amino acids in camelina protein. High molecular weight aggregates stabilized by covalent bonds in the glutelin and albumin fractions, as shown in size-exclusion chromatography (SEC), are closely related to larger-size protein aggregates observed in TEM images.