High Molecular Weight Fraction Research Articles

How weathering might intensify the toxicity of spilled crude oil in marine environments.

Crude oils are highly complex mixtures containing many toxic compounds for organisms. While their level of toxicity in a marine environment depends on many parameters, one of the main factors is their composition. After oil spills, their compositions are significantly changed, so it changes the toxicity. In this study, different weathering processes such as evaporation, photooxidation, and biodegradation were applied to crude oil to understand how composition changed over time and how this affects its toxicity on phytoplankton. In laboratory settings, three distinct water-accommodated fraction samples of crude oil were prepared, unweathered, evaporated, and weathered and were exposed to phytoplankton communities at different dilution levels. After 3days, evaporation reduced the crude oil concentration by 47%, and the concentration of the crude oil affected by photooxidation, biodegradation, and evaporation reduced by 81%. This study also showed that even though the weathering reduced the overall amount of crude oil substantially, its toxicity increased significantly. In the microcosm experiments, 7-day EC50 values of the unweathered oil, the evaporated oil and the weathered oil were 49.07, 21.09, and 7.16µg/L, respectively. Different processes altered the crude oil composition, and weathered crude oil ended up with a higher fraction of high molecular weight (HMW) polycyclic aromatic hydrocarbons (PAHs). A promising relation between the increasing toxicity and HMW PAH fraction indicates that increasing the fraction of HMW PAHs might be one of the main reasons for the weathering process to cause higher crude oil toxicity. These results could be used as a diagnostic tool to estimate the extent of weathering and toxicity of crude oil after spills.

Sialylation and Sulfation of Anionic Glycoconjugates Are Common in the Extracellular Polymeric Substances of Both Aerobic and Anaerobic Granular Sludges.

Anaerobic and aerobic granular sludge processes are widely applied in wastewater treatment. In these systems, microorganisms grow in dense aggregates due to the production of extracellular polymeric substances (EPS). This study investigates the sialylation and sulfation of anionic glyconconjugates in anaerobic and aerobic granular sludges collected from full-scale wastewater treatment processes. Size exclusion chromatography revealed a wide molecular weight distribution (3.5 to >5500 kDa) of the alkaline-extracted EPS. The high-molecular weight fraction (>5500 kDa), comprising 16.9-27.4% of EPS, was dominant with glycoconjugates. Mass spectrometry analysis and quantification assays identified nonulosonic acids (NulOs, e.g., bacterial sialic acids) and sulfated groups contributing to the negative charge in all EPS fractions. NulOs were predominantly present in the high-molecular weight fraction (47.2-84.3% of all detected NulOs), while sulfated glycoconjugates were distributed across the molecular weight fractions. Microorganisms, closely related to genera found in the granular sludge communities, contained genes responsible for NulO and sulfate group synthesis or transfer. The similar distribution patterns of sialylation and sulfation of the anionic glycoconjugates in the EPS samples indicate that these two glycoconjugate modifications commonly occur in the EPS of aerobic and anaerobic granular sludges.

Schistosoma mansoni egg-derived thioredoxin and Sm14 drive the development of IL-10 producing regulatory B cells.

During chronic schistosome infections, a complex regulatory network is induced to regulate the host immune system, in which IL-10-producing regulatory B (Breg) cells play a significant role. Schistosoma mansoni soluble egg antigens (SEA) are bound and internalized by B cells and induce both human and mouse IL-10 producing Breg cells. To identify Breg-inducing proteins in SEA, we fractionated SEA by size exclusion chromatography and found 6 fractions able to induce IL-10 production by B cells (out of 18) in the high, medium and low molecular weight (MW) range. The high MW fractions were rich in heavily glycosylated molecules, including multi-fucosylated proteins. Using SEA glycoproteins purified by affinity chromatography and synthetic glycans coupled to gold nanoparticles, we investigated the role of these glycan structures in inducing IL-10 production by B cells. Then, we performed proteomics analysis on active low MW fractions and identified a number of proteins with putative immunomodulatory properties, notably thioredoxin (SmTrx1) and the fatty acid binding protein Sm14. Subsequent splenic murine B cell stimulations and hock immunizations with recombinant SmTrx1 and Sm14 showed their ability to dose-dependently induce IL-10 production by B cells both in vitro and in vivo. Identification of unique Breg cells-inducing molecules may pave the way to innovative therapeutic strategies for inflammatory and auto-immune diseases.

Comprehensive study on particle size distribution, MAH and PAH profiles during alkylbenzene pyrolysis

The 5 linear alkylbenzenes, i.e., toluene, ethylbenzene, n-propylbenzene, n-butylbenzene, and n-pentylbenzene as fuels underwent pyrolysis at temperatures from 950 to 1450 °C in a flow reactor. Measurements of particle number size distribution, 11 monocyclic aromatic hydrocarbons, and 3 groups of polycyclic aromatic hydrocarbons (20 unsubstituted PAHs, 5 aliphatic-bridged PAHs, and 10 methyl PAHs) during the pyrolysis of linear alkylbenzenes were conducted. Results showed that the increase in side chain length suppressed the formation of particles, but ethylbenzene produced the highest particle mass and most extensive particle number size distribution. Total particle peak number concentrations exhibited a rise-then-fall trend (peaking at a critical temperature of 1050 °C) with increasing temperature regardless of the side chain length, indicating that high temperature promoted a transition from nucleation to agglomeration and coagulation. Total PAH mass concentrations were ranked in the same order with the variation of side-chain length as particle mass and peak number concentrations, indicating that soot nucleation was highly related to total PAH mass concentrations. Unsubstituted PAHs accounted for most PAHs while substituted·PAHs, including aliphatic-bridged PAHs and methyl PAHs presented 1–2 orders of magnitude less than the corresponding unsubstituted PAHs, probably distinct thermal stability and reactivity led to different growth routes between unsubstituted and substituted PAHs. Increasing the temperature from 950 to 1250 °C, the formation of high molecular weight PAHs was promoted. while a drop of high molecular weight fractions was observed above 1350 °C, which is attributed to the suppression of the formation, as well as their conversions of high molecular weight PAHs to heavier unidentified PAHs or soot. Among the test alkylbenzene fuels, the fuels with a long side chain benefit from the reduction of particles and PAHs. Furthermore, carbon atoms in aromatic rings are dominant sources of large PAHs and particles, while the carbon atoms in aliphatic side chains mainly form gas species.

Past to Future: Application of Gel Permeation Chromatography from Petroleomics and Metallopetroleomics to New Energies Applications: A Minireview

In the field of petroleomics and metallopetroleomics, the gel permeation chromatography (GPC) technique coupled with high-resolution detection technologies has made significant contributions as an analytical and preparative tool for over five decades. This bibliographic minireview highlights the study of the supramolecular and structural behavior of heavy crude oil and its fractions, as well as their reactivity to various processes by use of GPC. The preferred mobile phase is tetrahydrofuran (THF), whereas the stationary phase is polystyrene–divinylbenzene copolymer to avoid compound retention in the column. Other techniques such as HPTLC, RPLC, and NPHPLC have been used to provide multidimensional separations complementary to GPC. The high molecular weight (HMW) fraction, due to its greater polarity, reactivity to polymerization, and resistance to hydrodemetallization processes, has been the focus of interest for years. GPC coupled with high-resolution techniques has proven to be reliable for the detection of organic and inorganic species in bio-oils, making it a valuable tool for researchers and industry professionals in the context of feedstocks changes and new energy production.

Insights into the formation and stability of soil aggregates in relation to the structural properties of dissolved organic matter from various organic amendments

Organic matter is an important determinant of soil aggregate formation and stability. However, the role of its structure, especially that of dissolved organic matter (DOM) from organic amendments (OAs), in the aggregation process remains imprecise. The purpose of this study was to understand the relationship between the chemical structure of water-extractable organic matter (WEOM), potential source of DOM from OAs, and their aggregate formation/stability functionality through model experiment. The WEOM samples were prepared from bark compost (BC), coffee residue compost (CRC), cattle manure compost (CMC), sewage sludge compost (SSC), fish cake (FC), and rapeseed oil cake (ROC) and characterized using high-performance size exclusion chromatography and 13C nuclear magnetic resonance and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopies. An upland field soil was packed in glass columns and each WEOM solution or ultrapure water (Control) was applied repeatedly during a 30-day period. Aggregate size distribution (>2000, 500–2000, 250–500, 53–250, and <53 µm) was then measured and aggregate stability indices, mean weight diameter (MWD), and geometric mean diameter (GMD) were calculated. The addition of WEOM increased the distributions of soil mass and soil organic carbon (C) into the > 2000 µm aggregate fraction compared to Control treatment, and the ROC-, CRC-, and SSC-WEOM treatments resulted in greater MWD and GMD than Control and/or the other WEOM treatments. The % O-alkyl C (29–59% of total C) and the relative abundance of high-molecular-weight (HMW) fraction (>10 kDa; 2.3–7.1% of total) in WEOM correlated positively with the proportion of > 2000 µm aggregate fraction. The relative abundance of HMW fraction also correlated positively with MWD. These findings suggest that the high amounts of polysaccharides, suggested by % O-alkyl C and supported by DRIFT spectra, and/or other HMW components are desirable structural characteristics of WEOM for promoting macroaggregate formation and aggregate stability.

Molecular Weight Distribution of Humic Acids Isolated from Buried Soils and Yedoma Sediments

The soils of cold regions store up to 60% of all organic carbon on the planet. As a result of climate change, this organic matter can be biodegraded by microorganisms and thereby make an additional contribution to carbon balance. Nowadays, there are fragmentary data on organic C stocks in high-latitude soils and single works on the analysis of the quality of buried organic matter. This paper presents the first data on the molecular weight distributions of humic acids (HAs) extracted from soils and sediments in Yedoma. Molecular weight distributions of HAs preparations were obtained on an AKTAbasic 10 UPS chromatographic system (Amersham Biosciences, Sweden) using a SuperdexTM 200 10/300 GL column (with cross-linked dextran gel, fractionation range for globular proteins 10–600 kDa). As a result of the study, it was found that the buried soil horizons are characterized by the highest content of low molecular weight fraction (with molecular mass (Mr) 1.4–1.9 kDa and molar fraction in the range of 54.3–67.1%). The high molecular weight fraction is concentrated mainly in the superficial horizons and decreases with depth (with Mr 299–346 kDa and molar fraction in the range of 3.4–9.8%). In the Yedoma sediments, the maximum content of the medium-molecular fraction is observed (with Mr 24.6 kDa and 39.6% of the molar fraction), which may indicate a low rate of organic matter transformation in the permafrost. The data obtained serve as a database of analysis in terms of modeling the global carbon cycle in the cold regions of the planet.

Low- and high-molecular weight fractions of geological ambers detected by evolved gas analysis-mass spectrometry

We used evolved gas analysis-mass spectrometry (EGA-MS) to characterize a pool of ambers belonging to different geological varieties, with the aim of obtaining information on both their non-polymeric and polymeric components. Small molecular components can be trapped in amber during the fossilization process. Their characterization can provide insights into the maturation process of amber and help in determining its age and botanical origin. Most of the analyzed ambers showed two gas evolution regions, corresponding to the desorption of low-molecular weight compounds at low temperature, and to the pyrolysis of the macromolecular matrix at high temperature. We established characteristic m/z signals of the non-polymeric and polymeric fractions, and we were able to classify most of the samples in agreement with the available literature. We also performed principal component analysis of diterpenoid ambers using their average mass spectra. This allowed us to differentiate between succinite and rumanite ambers, which showed very similar spectra. The results demonstrate that EGA-MS constitutes a reliable technique to obtain information on the molecular composition of ambers, and on their relative content of low- and high-molecular weight fractions.

Exposure Order to Photoaging and Humic Acids Significantly Modifies the Aggregation and Transformation of Nanoplastics in Aqueous Solutions.

The colloidal stability of nanoplastics in aqueous solutions is greatly regulated by photoaging and dissolved organic matter (DOM). However, how the exposure order to sunlight and DOM modifies the environmental behavior of nanoplastics is seldomly determined. Here, with two different exposure orders, we investigated the impact of molecular-weight (MW)-fractionated humic acids (HAs) derived from biochar and the Suwannee River, respectively, on the aggregation of poly(ethylene terephthalate) nanoplastics (PET-NPs) in mono- and divalent electrolyte solutions. For exposure pattern (i) (photoaging followed by HA coating), photoaged PET-NPs had more oxidized surfaces and exhibited 22-320% higher binding affinity to HAs (especially the higher MW fractions) than the pristine counterparts, which greatly improved the dispersion of PET-NPs. For exposure pattern (ii) (HA coating followed by photoaging), HA-PET assemblies were formed, the dispersion of which increased with increasing irradiation time and was significantly higher than that of the samples in the exposure pattern (i) at the end of the experiment. This high dispersion of photoaged HA-PET assemblies was ascribed to the extra oxidation of PET by reactive oxygen species generated in the PET-HA interfaces during photoaging. These findings highlight the "active nature" of HA-PET assemblies, which provide new insight into the reaction of HA with nanoplastics beyond adsorption in the natural environment.

Cerebrospinal fluid lipoproteins inhibit α-synuclein aggregation by interacting with oligomeric species in seed amplification assays

BackgroundAggregation of α-synuclein (α-syn) is a prominent feature of Parkinson’s disease (PD) and other synucleinopathies. Currently, α-syn seed amplification assays (SAAs) using cerebrospinal fluid (CSF) represent the most promising diagnostic tools for synucleinopathies. However, CSF itself contains several compounds that can modulate the aggregation of α-syn in a patient-dependent manner, potentially undermining unoptimized α-syn SAAs and preventing seed quantification.MethodsIn this study, we characterized the inhibitory effect of CSF milieu on detection of α-syn aggregates by means of CSF fractionation, mass spectrometry, immunoassays, transmission electron microscopy, solution nuclear magnetic resonance spectroscopy, a highly accurate and standardized diagnostic SAA, and different in vitro aggregation conditions to evaluate spontaneous aggregation of α-syn.ResultsWe found the high-molecular weight fraction of CSF (> 100,000 Da) to be highly inhibitory on α-syn aggregation and identified lipoproteins to be the main drivers of this effect. Direct interaction between lipoproteins and monomeric α-syn was not detected by solution nuclear magnetic resonance spectroscopy, on the other hand we observed lipoprotein-α-syn complexes by transmission electron microscopy. These observations are compatible with hypothesizing an interaction between lipoproteins and oligomeric/proto-fibrillary α-syn intermediates. We observed significantly slower amplification of α-syn seeds in PD CSF when lipoproteins were added to the reaction mix of diagnostic SAA. Additionally, we observed a decreased inhibition capacity of CSF on α-syn aggregation after immunodepleting ApoA1 and ApoE. Finally, we observed that CSF ApoA1 and ApoE levels significantly correlated with SAA kinetic parameters in n = 31 SAA-negative control CSF samples spiked with preformed α-syn aggregates.ConclusionsOur results describe a novel interaction between lipoproteins and α-syn aggregates that inhibits the formation of α-syn fibrils and could have relevant implications. Indeed, the donor-specific inhibition of CSF on α-syn aggregation explains the lack of quantitative results from analysis of SAA-derived kinetic parameters to date. Furthermore, our data show that lipoproteins are the main inhibitory components of CSF, suggesting that lipoprotein concentration measurements could be incorporated into data analysis models to eliminate the confounding effects of CSF milieu on α-syn quantification efforts.

Physical and Oxidative Stabilization of Oil-In-Water Emulsions by Roasted Coffee Fractions: Interface- and Continuous Phase-Related Effects.

Emulsions fortified with polyunsaturated fatty acids are highly relevant from a nutritional perspective; however, such products are prone to lipid oxidation. In the current work, this is mitigated by the use of natural antioxidants occurring in coffee. Coffee fractions with different molecular weights were extracted from roasted coffee beans. These components were positioned either at the interface or in the continuous phase of emulsions where they contributed to emulsion stability via different pathways. Coffee brew as a whole, and its high-molecular-weight fraction (HMWF), was able to form emulsions with good physical stability and excellent oxidative stability. When added post-homogenization to the continuous phase of dairy protein-stabilized emulsions, all coffee fractions were able to slow down lipid oxidation considerably without altering the physical stability of emulsions, though HMWF was more effective in retarding lipid oxidation than whole coffee brew or low-molecular-weight fraction. This is caused by various effects, such as the antioxidant properties of coffee extracts, the partitioning of components in the emulsions, and the nature of the phenolic compounds. Our research shows that coffee extracts can be used effectively as multifunctional stabilizers in dispersed systems leading to emulsion products with high chemical and physical stability.

Perspectives in the Application of High, Medium, and Low Molecular Weight Oat β-d-Glucans in Dietary Nutrition and Food Technology—A Short Overview

For centuries human civilization has cultivated oats, and now they are consumed in various forms of food, from instant breakfasts to beverages. They are a nutrient-rich food containing linear mixed-linkage (1 → 3) (1 → 4)-β-d-glucans, which are relatively well soluble in water and responsible for various biological effects: the regulation of the blood cholesterol level, as well as being anti-inflammatory, prebiotic, antioxidant, and tumor-preventing. Numerous studies, especially in the last two decades, highlight the differences in the biological properties of the oat β-d-glucan fractions of low, medium, and high molecular weight. These fractions differ in their features due to variations in bioavailability related to the rheological properties of these polysaccharides, and their association with food matrices, purity, and mode of preparation or modification. There is strong evidence that, under different conditions, the molecular weight may determine the potency of oat-extracted β-d-glucans. In this review, we intend to give a concise overview of the properties and studies of the biological activities of oat β-d-glucan preparations depending on their molecular weight and how they represent a prospective ingredient of functional food with the potential to prevent or modulate various pathological conditions.

Differences in the spectral characteristics of dissolved organic matter binding to Cu(II) in wetland soils with moisture gradients

The environmental behavior of heavy metals in soil is significantly regulated by their binding with dissolved organic matter (DOM), which is affected by soil moisture contents. However, the mechanism of this interaction in soils with varying moisture is still not well understood. Using a combination of ultrafiltration, Cu(II) titration, and multispectral (ultraviolet-visible absorption, 3D fluorescence, Fourier transform infrared) analysis techniques, we studied the differences in the spectral characteristics and Cu(II) binding properties of soil dissolved organic matter (DOM) and its different molecular weight (MW) fractions with moisture gradients. We found that the abundance and spectral characters of soil DOM changed with increasing soil moisture, i.e., the increase in abundance while the decrease in aromaticity and humification index. The components of DOM, shown by Fluorescence region-integration (FRI) analysis, also changed, with an increase in the proportion of protein-like substances and a decrease of humic-like and fulvic-like substances. The overall Cu(II) binding potential of soil DOM diminished with increasing soil moisture, as indicated by the fluorescence parallel factor (PARAFAC) analysis. This is aligns with the changes in DOM composition, as the humic-like and fulvic-like fractions exhibited higher Cu(II) binding potential compared to the protein-like fractions. The low MW fraction of the MW-fractionated samples showed a stronger binding potential for Cu(II) compared to the high MW fraction. Finally, the active binding site of Cu(II) in DOM, as revealed by UV-difference spectroscopy and 2D-FTIR-COS analysis, decreased with increasing soil moisture, with the order of preferentially functional groups shifting from OH, NH, and CO to CN and CO. This study emphasizes the impact of moisture variations on the characteristics of DOM and its interaction with Cu(II), providing insight into the environmental fate of heavy metal contaminants in soil in areas with alternating land and water conditions.

Identification of Antioxidative Peptides Derived from Arthrospira maxima in the Biorefinery Process after Extraction of C-Phycocyanin and Lipids.

Arthrospira maxima has been identified as a sustainable source of rich proteins with diverse functionalities and bioactivities. After extracting C-phycocyanin (C-PC) and lipids in a biorefinery process, the spent biomass still contains a large proportion of proteins with potential for biopeptide production. In this study, the residue was digested using Papain, Alcalase, Trypsin, Protamex 1.6, and Alcalase 2.4 L at different time intervals. The resulting hydrolyzed product with the highest antioxidative activity, evaluated through their scavenging capability of hydroxyl radicals, superoxide anion, 2,2-diphenyl-1-picrylhydrazyl (DPPH), and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS), was selected for further fractionation and purification to isolate and identify biopeptides. Alcalase 2.4 L was found to produce the highest antioxidative hydrolysate product after four-hour hydrolysis. Fractionating this bioactive product using ultrafiltration obtained two fractions with different molecular weights (MW) and antioxidative activity. The low-molecular-weight fraction (LMWF) with MW <3 kDa had higher DPPH scavenging activity with the IC50 value of 2.97 ± 0.33 compared to 3.76 ± 0.15 mg/mL of the high-molecular-weight fraction (HMWF) with MW >3 kDa. Two stronger antioxidative fractions (F-A and F-B) with the respective significant lower IC50 values of 0.83 ± 0.22 and 1.52 ± 0.29 mg/mL were isolated from the LMWF using gel filtration with a Sephadex G-25 column. Based on LC-MS/MS analysis of the F-A, 230 peptides derived from 108 A. maxima proteins were determined. Notably, different antioxidative peptides possessing various bioactivities, including antioxidation, were detected with high predicted scores together with in silico analyses on their stability and toxicity. This study established knowledge and technology to further value-add to the spent A. maxima biomass by optimizing hydrolysis and fraction processes to produce antioxidative peptides with Alcalase 2.4 L after two products already produced in a biorefinery. These bioactive peptides have potential applications in food and nutraceutical products.

Exopolysaccharide-producing Lacticaseibacillus paracasei strains isolated from kefir as starter for functional dairy products.

Exopolysaccharides (EPS) produced by lactic acid bacteria are molecules of great interest for the dairy food industry. Lacticaseibacillus paracasei CIDCA 8339, CIDCA 83123, and CIDCA 83124 are potentially probiotic strains isolated from kefir grains whose EPS-production on MRS broth is dependent on incubation temperature. The aim of the present work is to evaluate the effect of fermentation temperature on the characteristics of EPS produced in milk by L. paracasei strains and the consequent impact on the rheological properties of the fermented products. Additionally, the protective effect of these EPS against Salmonella infection was evaluated in vitro. Acid gels with each strain were obtained by milk fermentation at 20°C, 30°C, and 37°C evidencing for all the strains a reduction in growth and acidification rate at lower temperature. Lacticaseibacillus paracasei CIDCA 83123 showed low fermentation rate at all temperatures requiring between 3 and 8 days to obtain acids gels, whereas CIDCA 8339 and 83124 needed between 24 and 48 h even when the temperature was 20°C. Fermentation temperature led to changes in crude EPS characteristics of the three strains, observing an increase in the relative amount of the high molecular weight fraction when the fermentation temperature diminished. Additionally, EPS83124 and EPS83123 presented modifications in monosaccharide composition, with a reduction of rhamnose and an increase of amino-sugars as temperature rise. These changes in the structure of EPS83124 resulted in an increase of the apparent viscosity of milks fermented at 20°C (223 mPa.s) and 30°C (217 mPa.s) with respect to acid gels obtained at 37°C (167 mPa.s). In order to deepen the knowledge on EPS characteristics, monosaccharide composition of low and high molecular weight EPS fractions were evaluated. Finally, it was evidenced that the preincubation of intestinal epithelial cells Caco-2/TC-7 with EPS8339 and EPS83124 partially inhibit the association and invasion of Salmonella. In light of these results, it can be concluded that the selection of the EPS-producing strain along with the appropriate fermentation conditions could be an interesting strategy to improve the technological properties of these L. paracasei fermented milks with potential protective effects against intestinal pathogens.

Molecular Characterization of Aged Bitumen with Selective and Nonselective Ionization Methods by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. 3. Investigation on Molecular Fractions Obtained by Gel Permeation Chromatography

Long-term aging of bitumen causes formation of oxidation products that can be associated with polar and strongly interacting functional groups leading to a tremendous influence on bitumen properties. This can lead to an aggregation of the most polar molecules in the asphaltene fraction. Other types of aggregation have also been described in the literature, with larger and more aliphatic compounds through wax interactions. These aggregate phases can be studied using gel permeation chromatography (GPC) for the separation of heavy petroleum products based on their molecular weight. Three molecular weight fractions of native bitumen and its aged state by a long-term pressure aging vessel (PAV-72h) were obtained with low molecular weight (LMW), medium molecular weight (MMW), and high molecular weight (HMW) fractions. To characterize oxidative aging on each fraction at the molecular level, Fourier transform ion cyclotron resonance (FTICR) was used. Indeed, the ultrahigh resolution and mass accuracy of this analyzer allow to attribute molecular formulas to each signal of complex matrices unambiguously. An electrospray ionization (ESI) source was used to selectively ionize acid molecules, while atmospheric pressure photoionization source (APPI) was used to have a nonselective ionization of low polarity molecules from bitumen. With both ionization sources, the LMW fraction exhibited the most aromatic and heteroelement-enriched molecules. In terms of variation with aging, the LMW fraction showed the most pronounced variations. Molecular maps evidenced the occurrence of low DBE oxidation markers for Oz and OzSy families. Low variations were observed on distributions of MMW and HMW fractions. Concerning HMW, these unexpected results, obtained by ESI and APPI ionization sources, may be due to a protection of the molecules against oxidation within aggregates. In addition, APPI results underlined that the higher molecular weight distribution containing most of the aggregate molecules was mainly composed of large aliphatic molecules. Overall, this study demonstrated that oxidation products corresponded to small and aliphatic molecules majorly found in the LMW fraction and that aggregated molecules form HMW fraction were relatively protected from oxidation.

Different-sized extracellular vesicles derived from stored red blood cells package diverse cargoes and cause distinct cellular effects.

The formation of extracellular vesicles (EVs) occurs during cold storage of RBCs. Transfusion of EVs may contribute to adverse responses in recipients receiving RBCs. However, EVs are poorly characterized with limited data on whether distinct vesicles are formed, their composition, and potential biological effects. Stored RBC-derived EVs were purified using protocols that separate larger microvesicle-like EVs (LEVs) from smaller exosome-like vesicles (SEVs). Vesicles were analyzed by electron microscopy, content of hemoglobin, heme, and proteins (by mass spectrometry), and the potential to mediate lipid peroxidation and endothelial cell permeability in vitro. SEVs were characterized by having an electron-dense double membrane whereas LEVs had more uniform electron density across the particles. No differences in hemoglobin nor heme levels per particle were observed, however, due to smaller volumes, SEVs had higher concentrations of oxyHb and heme. Both particles contained antioxidant proteins peroxiredoxin-2 and copper/zinc superoxide dismutase, these were present in higher molecular weight fractions in SEVs suggesting either oxidized proteins are preferentially packaged into smaller vesicles and/or that the environment associated with SEVs is more pro-oxidative. Furthermore, total glutathione (GSH + GSSG) levels were lower in SEVs. Both EVs mediated oxidation of liposomes that were prevented by hemopexin, identifying heme as the pro-oxidant effector. Addition of SEVs, but not LEVs, induced endothelial permeability in a process also prevented by hemopexin. These data show that distinct EVs are formed during cold storage of RBCs with smaller particles being more likely to mediate pro-oxidant and inflammatory effects associated with heme.

Surface-enhanced Raman spectroscopy of centrifuged blood serum samples of diabetic type II patients by using 50KDa filter devices

Blood serum contains essential biochemical information which are used for early disease diagnosis. Blood serum consisted of higher molecular weight fractions (HMWF) and lower molecular weight fractions (LMWF). The disease biomarkers are lower molecular weight fraction proteins, and their contribution to disease diagnosis is suppressed due to higher molecular weight fraction proteins. To diagnose diabetes in early stages are difficult because of the presence of huge amount of these HMWF. In the current study, surface-enhanced Raman spectroscopy (SERS) are employed to diagnose diabetes after centrifugation of serum samples using Amicon ultra filter devices of 50 kDa which produced two fractions of whole blood serum of filtrate, low molecular weight fraction, and residue, high molecular weight fraction. Furthermore SERS is employed to study the LMW fractions of healthy and diseased samples. Some prominent SERS bands are observed at 725 cm−1, 842 cm−1, 1025 cm−1, 959 cm−1, and 1447 cm−1 due to small molecular weight proteins, and these biomarkers helped to diagnose the disease early stage. Moreover, chemometric techniques such as principal component analysis (PCA) and partial least square discriminant analysis (PLS-DA) are employed to check the potential of surface-enhanced Raman spectroscopy for the differentiation and classifications of the blood serum samples. SERS can be employed for the early diagnosis and screening of biochemical changes during type II diabetes.

Role of lake dissolved organic matter in cyanobacteria removal by cationic polyacrylamide flocculation and screen filtration

Prompt removal of densely accumulated cyanobacteria is a straightforward method to alleviate the harm of cyanobacterial blooms to lakes. In this study, a cyanobacteria harvesting ship based on flocculation and filtration was used for the removal of cyanobacteria in a bay of Dianchi Lake (Yunnan Province, China), in which the fate and influence of lake dissolved organic matter (DOM) were investigated. After flocculation with 1–3 mg/L cationic polyacrylamide (CPAM) and filtration with the 100-µm-pore-sized screens of a rotary drum filter (RDF), >90 % of cyanobacteria was removed and the DOM was slightly reduced from 7.83 mg/L to 4.61 ∼ 6.49 mg/L. Tryptophan protein-like and high molecular weight (MW) DOM was selectively removed, increasing the humification index and decreasing the biological index in the treated water. Lake DOM, especially the high MW fractions of lake DOM, played an important role in CPAM flocculation. Cyanobacteria could not be effectively flocculated in Milli-Q water while the removal efficiency increased to over 90 % when 1–3 mg/L high MW DOM of Dianchi Lake was added. Three lakes in Yunnan Province were also plagued by cyanobacterial blooms, including Erhai Lake, Qilu Lake, and Xingyun Lake. The high MW DOM (1.7–2.7 mg/L) in the lakes could also deduce the effective flocculation of cyanobacteria with CPAM. The flocculation mechanism could function by the interactions of quaternary ammonium groups of CPAM and carboxylate groups of high MW DOM that form net-like polyelectrolyte complexes (PECs), and coexisting cyanobacteria cells were encapsulated into the PECs, leading to the formation of large flocs under stirring conditions. In the lakes with high densities of cyanobacteria, there might be enough high-MW DOM to promote the flocculation of CPAM, and after flocculation-filtration treatment, both cyanobacteria and cyanobacteria-deprived DOM were effectively removed.

Relating algal-derived extracellular and intracellular dissolved organic nitrogen with nitrogenous disinfection by-product formation

The dissolved organic nitrogen (DON) pool from algal-derived extracellular and intracellular organic matter (EOM and IOM) comprises proteins, peptides, free amino acids and carbohydrates, of which, proteins can contribute up to 100% of the DON. Previous reports of algal-derived DON character have focused on bulk properties including concentration, molecular weight and hydrophobicity. However, these can be similar between algal species and between the EOM and IOM even when the inherent molecular structures vary. A focus on bulk character presents challenges to the research on algal-derived nitrogenous-disinfection by-product (N-DBP) formation as N-DBP formation is sensitive to the changes in molecular structure. Hence, the main aim of this study was to characterize algal EOM and IOM-derived DON, specifically proteinaceous-DON, using a combination of bulk and molecular characterization techniques to enable a more detailed exploration of the relationship between the character of algal-derived proteins and the N-DBP formation potential. DON from the EOM and IOM of four commonly found algae and cyanobacteria in natural waters were evaluated, namely Chlorella vulgaris, Microcystis aeruginosa, Dolichospermum circinale, and Cylindrospermopsis raciborskii. It was observed that 77-96% of total DON in all EOM and IOM samples was of proteinaceous origin. In the proteins, DON concentrations were highest in the high molecular weight fraction of IOM-derived bulk proteins (0.13–0.75 mg N L−1) and low to medium molecular weight fraction of EOM-derived bulk proteins (0.15–0.63 mg N L−1) in all species. Similar observations were also made via sodium dodecyl sulphate polyacrylamide gel electrophoresis and liquid chromatography-high resolution mass spectrometry. Solid-state 15N nuclear magnetic resonance (NMR) spectroscopy of the EOM and IOM revealed the existence of common aliphatic and heterocyclic N-groups in all samples, including a dominant 2° amide peak. Species dependent variability was also observed in the spectra, particularly in the EOM; e.g. nitro signals were found only in the Cylindrospermopsis raciborskii EOM. Dichloroacetonitrile (DCAN) and N-nitrosamine concentrations from the EOM of the species evaluated in this study were lower than the guideline limits set by regulatory agencies. It is proposed that the dominant 2° amide in all samples decreased N-DBP formation upon chlorination. For chloramination, the presence of nitro groups and aliphatic and heterocyclic N-DBP precursors could cause variable N-nitrosamine formation. Compared to non-algal impacted waters, algae-laden waters are characterised by low organic carbon: organic nitrogen ratios of ∼7–14 and elevated DON and protein concentrations. Hence, relying only on bulk characterization increases the perceived risk of N-DBP formation from algae-laden waters.