Small Molecular Weight Research Articles

Comparison of the in-vitro effect of five prebiotics with different structure on gut microbiome and metabolome

This study aimed to compare the effects of sodium alginate (SA), galactooligosaccharides (GOS), lactulose (LC), polydextrose (PDX), and inulin (IN) on gut microbiome and metabolome using stable in vitro human gut fermentation model. The five prebiotics with different structure were effective in promoting beneficial bacteria, such as increased Bifidobacterium, Enterococcus, and Ruminococcaceae_UCG_014 in the GOS group, and Parabacteroides and Phascolarctobacterium in the PDX group. Also, prebiotics promoted total short chain fatty acids (SCFAs) production, especially the butyric acid increased by SA with the largest molecular weight and high content of ManA. Most prebiotics affected carbohydrate metabolism, amino acid metabolism, and lipid metabolism pathways. The changed metabolic pathways were similar between the LC and GOS with the smallest molecular weight, and IN and PDX with analogous molecular weight and monosaccharide composition were strongly associated with energy metabolism pathways. This paper could promote the application and development of prebiotics in food industry.

Simultaneous determination of multiple urine biomarkers for kidney injury using SPE combined with LC-MS/MS

Background and ObjectivesUrinary biomarkers such as low molecular weight proteins and small molecular weight metabolites are crucial in the diagnosis of kidney injury. The objective of this study was to develop and preliminarily validate a sensitive and specific method using solid-phase extraction (SPE) in conjunction with liquid chromatography–tandem mass spectrometry (LC-MS/MS) for the simultaneous measurement of these biomarkers in human urine. MethodThis study presents the development of a solid-phase extraction method integrated with LC-MS/MS analyzing biomarkers including creatinine, urea, β2-microglobulin, α1-microglobulin, and cystatin C in human urine. An enhanced solid-phase cartridge technique was employed for peptide purification and dilution of small molecule metabolites during sample preparation. ResultsThe developed LC-MS/MS method achieved satisfactory separation of the five analytes within 15 min. Accuracy levels ranged from −8.6% to 13.6%. Both intra-assay and inter-assay imprecision rates were maintained below 7.9% for all analytes. ConclusionsThe established LC-MS/MS method effectively quantifies creatinine, urea, β2-microglobulin, α1-microglobulin and cystatin C concurrently. This offers a viable alternative for the detection of kidney injury biomarkers in human urine, demonstrating potential for clinical application in kidney injury diagnosis.

Fucoidan from brown seaweed Tubinaria decurrens: Structure and structure - anticancer activity relationship

The aims of this study are to determine the structure of a fucoidan from brown seaweed Turbinaria decurrens, to investigate its anticancer activity and structure–activity relationship. SEC-MALLS, IR, ESI-MS and NMR spectra analysis indicated that dominant structure of the fucoidan, with a Mw 122.6 KDa, has a backbone of (1 → 3)– and (1 → 4)–α–L–Fucp residues, branched at C–4, sulfate groups are attached at C–2, C–3 and C–4; branches are (1 → 4)–β–D–Galp residues and sulfated at C–2. The fucoidan was hydrolyzed by HCl aqueous solution to obtain hydrolyzed fucoidans. It is assumed that native and hydrolyzed fucoidans have a rod-like conformation in solution with cross–sectional radius of gyration (Rgc) ranged from 0.53 to 1.52 nm as estimated from SAXS measurements. The fucoidans show great anticancer activity against HT29 human colon cancer cell line with IC50 ranging from 5.41 ± 0.36 to 73.52 ± 2.54 μg/mL. Anticancer activity of the fucoidan could be significantly improved by lowering molecular weight, furthermore, fucoidan required small molecular weight, small molecular weight distribution and rod–like structure with a short branch length for high anticancer activity.

Study on the formation mechanism of pea protein nanofibrils and the changes of structural properties of fibril under different pH and temperature

The functional performance of plant proteins can be enhanced by converting them into nanofibrils using controlled acid-heat treatments. Initially, the impact of heating time on the morphology and properties of nanofibrils prepared from pea proteins was assessed. The pea protein nanofibrils (PPF) were formed by heating at 85 °C and pH 2.0 for different times (0–24 h). Multiple analytical methods were then used to characterize the properties of the nanofibrils, including transmission electron microscopy (TEM), gel electrophoresis (SDS-PAGE), thioflavin T (ThT) fluorescence spectroscopy, molecular flexibility, and surface hydrophobicity. With increasing heating time, the protein molecules were gradually decomposed into small molecular weight peptides, which then assembled into nanofibrils. Initially, the length of the PPFs increased with heating time, but then it decreased, which was attributed to fibril fragmentation. In the food processing industry, pH and temperature are important factors affecting food preparation. For this reason, the effects of pH (2–9) and temperature (55, 85, 100 °C) on the properties of the nanofibrils were explored. These environmental conditions had a strong influence on the morphology and properties of PPFs. For instance, their flexibility increased with increasing pH, whereas their surface hydrophobicity decreased with increasing pH and temperature. Moreover, their charge went from positive to negative as the pH was ascended from below to above their isoelectric point. The findings of the structural properties of protein nanofibrils could provide some new insights into the wider application of nanofibrils in the food industry.

Speeding-up the Determination of Protein-Ligand Affinities by STD NMR: The Reduced Data Set STD NMR Approach (rd-STD NMR).

STD NMR spectroscopy is a powerful ligand-observed NMR tool for screening and characterizing the interactions of small molecules and low molecular weight fragments with a given macromolecule, identifying the main intermolecular contacts in the bound state. It is also a powerful analytical technique for the accurate determination of protein-ligand dissociation constants (KD) of medium-to-weak affinity, of interest in the pharmaceutical industry. However, accurate KD determination and epitope mapping requires a long series of experiments at increasing saturation times to carry out a full analysis using the so-called STD NMR build-up curve approach and apply the "initial slopes approximation". Here, we have developed a new protocol to bypass this important limitation, which allows us to obtain initial slopes by using just two saturation times and, hence, to very quickly determine precise protein-ligand dissociation constants by STD NMR.

Color characteristics and pyrolysis volatile properties of main colored fractions from the Maillard reaction models of glucose with three amino acids

The effects of hydrosoluble colored fractions generated in the Maillard reaction models on the volatiles of pyrolytic Maillard reaction products was investigated. The hydrosoluble colored fractions obtained by reaction of glucose with glycine (Gly-Glc), proline (Pro-Glc) and phenylalanine (Phe-Glc) respectively at 125 °C were separated using Sephadex LH-20 Gel column. The colored fraction with large molecular weight had a higher contribution to the overall color and more glucose residue structures in main skeleton than that with small molecular weight in the same model. Gel permeation chromatography analysis indicated that these colored fractions had continuous relative molecular weight distribution (1000–80000 Da). Pyrolysis - gas chromatography - mass spectrometry determination (pyrolysis temperature: 160∼900 °C) suggested that furans and pyrroles were the main volatiles of two Gly-Glc fractions after pyrolysis, and the key pyrolysis volatiles of Pro-Glc fraction were furans, pyrroles, pyran, indole and cyclopentenes, which gave a freshly baked bread, nutty, coffee-like and sweet caramel-like odor. Especially phenyl-containing compounds seemed typical indicators of Phe-Glc fraction pyrolysis products, exhibiting a benzene-like, tallowy, sweet, balsamic and floral odor. The hydrosoluble colored fractions produced by different Maillard reactions had different pyrolytic volatile properties and were suitable for the development of bakery food improver with different color and flavor requirements.

Impact of Lactiplantibacillus plantarum and casein fortification on angiotensin converting enzyme inhibitory peptides in yogurt: identification and in silico analysis.

In this study, the effects of Lactiplantibacillus plantarum M11 (Lb. plantarum M11) in conjunction with sodium caseinate on the characteristics and angiotensin converting enzyme (ACE) inhibitory activity of yogurt were investigated. ACE inhibitory peptides (ACEIPs) in yogurt were identified by nano-LC-MS/MS and potential ACEIPs were predicted by in silico and molecular docking methods. The results showed that the ACE-inhibitory activity of yogurt was significantly enhanced (p < 0.05), while maintaining the quality characteristics of the yogurt. Thirteen ACEIPs in the improved yogurt (883 + M11-CS group) were identified, which were more abundant than the other yogurt groups (control 883 group, 883 + M11 group and 883-CS group). Two novel peptides with potential ACE inhibitory activity, YPFPGPIH and NILRFF, were screened. The two peptides showed PeptideRanker scores above 0.8, small molecular weight and strong hydrophobicity, and were non-toxic after prediction. Molecular docking results showed that binding energies with ACE were -9.4 kcal mol-1 and -10.7 kcal mol-1, respectively, and could bind to the active site of ACE. These results indicated that yogurt with Lb. plantarum M11 and sodium caseinate has the potential to be utilized as a functional food with antihypertensive properties. The combination of ACEIP-producing strains and casein fortification could be an effective method to promote the release of ACEIPs from yogurt.

A novel biomimetic probe for galectin‐3 recognition: Chemical synthesis and structural characterization of a β‐galactose branched sodium hyaluronate

AbstractSodium hyaluronate (HA), a derivative of hyaluronan, is a natural and biocompatible polysaccharide that interacts with cluster of differentiation‐44 receptor to promote fine‐tuning of inflammation, fibrosis, and tissue remodeling. HA has a smaller molecular weight than hyaluronan and is overall more stable being less prone to oxidation. In this study, we report a novel lactose‐functionalized sodium hyaluronate, named HYLACH®. Functionalization with multiple β‐galactose residues facilitates its interaction with galectin‐3, a β‐galactose binding lectin implicated in various pathological processes including inflammation, host defense, and fibrosis, especially critical in idiopathic pulmonary fibrosis (IPF). Our strategy was to modify HA, to varying extents, at carboxyl sites with 1‐amino‐1‐deoxy‐lactitol, in the presence of 4‐(4,6‐dimethoxy‐1,3,5‐triazin‐2‐yl)‐4‐methyl morpholinium chloride in aqueous media. We characterized the chemical structure, molecular weight, and degree of substitution of HYLACH® using NMR spectroscopy and size exclusion chromatography. We further determined several key parameters including its stability toward enzymatic degradation and the binding affinity and conformational changes of galectin‐3 interaction with HYLACH®. Collectively, the generation of a novel functionalized HA with an ability to bind and suppress galectin‐3 function, in combination with safety and biocompatibility, offers the opportunity to test this compound in therapeutic trials of devastating fibrotic diseases such as IPF.

Removal of urea in ultrapure water system by urease-coated reverse osmosis membrane

Among the various substances found in the feed source for the production of ultrapure water (UPW), urea is challenging to remove because it is a small molecular weight molecule that is not easily oxidized and does not carry a charge under neutral pH conditions. Urease enzyme, found in various organisms such as plants and bacteria, catalyze the hydrolysis of urea into carbon dioxide and ammonia. In this study, urease was immobilized on the polyamide layer of a reverse osmosis (RO) membrane to remove urea in UPW systems. The removal efficiency of urea by urease-coated RO membrane showed up to 27.9 % higher urea removal efficiency compared to the pristine membrane. This increase in urea removal can be attributed to both physical and biological effects from the urease coating on the membrane. Firstly, urease on the membrane surface can act as an additional physical barrier for urea to pass through. Secondly, urea can be hydrolyzed by the enzyme when it passes through the urease-coated RO membrane. In a two-pass RO system typical for UPW production, the removal of urea by a urease-coated membrane would be enhanced by twofold. This overall method can significantly increase the removal efficiency of urea in UPW systems, especially when considering the compounded removal by the urease coating, rejection by RO, and additional reactions by other treatment processes. Moreover, urea in UPW systems can be removed without the installment of additional processes by simply coating urease on the existing RO membranes.

Next-Generation Sequencing and Proteomics-Enabled Approach for Rapid and High-Throughput Isolation of Virus-Neutralizing Nanobodies.

Compared with traditional antibodies, nanobodies from camelids have various advantages, including small molecular weight, high affinity, low immunogenicity, convenient production through genetic engineering, etc. Here we combined next-generation sequencing (NGS) with proteomics technology based on affinity purification-mass spectrometry (AP-MS) and bioinformatics analysis to high-throughput screen monoclonal nanobodies from camels immunized with surface glycoprotein (glycoprotein N, Gn) of severe fever with thrombocytopenia syndrome virus and fulfilled production of the screened anti-Gn monoclonal nanobody with high affinity by genetic engineering. The innovative high-throughput technical route developed here could also be expanded to the production of neutralizing nanobodies specific for Rift Valley fever virus.

THE MECHANISM AND BIOCHEMISTRY IN OXIDATIVE STRESS A BRIEF OVERVIEW

This article provides a comprehensive overview of oxidative stress, emphasizing its pivotal role in human health and disease progression. Oxidative stress, characterized by an imbalance between reactive oxygen species (ROS) and antioxidative defense, leads to cellular damage and exacerbates chronic diseases. Initially perceived solely as harmful, recent studies reveal ROS's dual role in cellular signaling and metabolic regulation. This shift in perspective underlines the nuanced nature of redox biology, where ROS can be both beneficial and detrimental. The article highlights the importance of antioxidative strategies, including enzymes like SOD, catalase, glutathione peroxidase, and small molecular weight antioxidants such as vitamins E and C. Advancements in redox signaling and sensor understanding have redefined oxidative stress, focusing on the need for precise diagnostic and therapeutic strategies. The paper underscores the necessity for ongoing research to characterize redox biomarkers and establish robust clinical and epidemiological reference values.

Vasoprotective Effect of Sulodexide in Diabetic Retinopathy

Diabetes is a group of metabolic diseases, considered a lifestyle disease. Diabetic retinopathy is the leading cause of blindness in working-age adults worldwide. Pathogenetically, due to the changed anionic charge, collagen gradually replaces glycosaminoglycans (GAG) in the basement membrane of retinal capillaries, affecting vascular permeability. Clinically, these changes cause leakage from the retinal capillaries, which leads to the development of microaneurysms and, consequently, the formation of hard effusions (HE). Sulodexide is a glycosaminoglycan containing 80% of small molecular weight, fast moving heparin fraction (FMH) and 20% of dermatan sulfate. An important target of sulodexide's action are vascular endothelial cells, and its protective effect is partially related to the preservation and reconstruction of the glycocalyx structure on the surface of the endothelial layer cells. Additionally, sulodexide has been documented to strengthen the glycocalyx of retinal arterioles in people with diabetes. These findings suggest that sulodexide holds promise as a potential therapeutic agent for the treatment of diabetic retinopathy.

Structure, physicochemical properties, and biological activities of protein hydrolysates from Zanthoxylum seed.

Zanthoxylum seed, as a low-cost and easily accessible plant protein resource, has good potential in the food industry. But protein and its hydrolysates from Zanthoxylum seed are underutilized due to the dearth of studies on them. This study aimed to investigate the structure and physicochemical and biological activities of Zanthoxylum seed protein (ZSP) hydrolysates prepared using Protamex®, Alcalase®, Neutrase®, trypsin, or pepsin. Hydrolysis using each of the five enzymes diminished average particle size and molecular weight of ZSP but increased random coil content. ZSP hydrolysate prepared using pepsin had the highest degree of hydrolysis (24.07%) and the smallest molecular weight (<13 kDa) and average particle size (129.80 nm) with the highest solubility (98.9%). In contrast, ZSP hydrolysate prepared using Alcalase had the highest surface hydrophobicity and foaming capacity (88.89%), as well as the lowest foam stability (45.00%). Moreover, ZSP hydrolysate prepared using Alcalase exhibited the best hydroxyl-radical scavenging (half maximal inhibitory concentration (IC50 ) 1.94 mg mL-1 ) and ferrous-ion chelating (IC50 0.61 mg mL-1 ) activities. Additionally, ZSP hydrolysate prepared using pepsin displayed the highest angiotensin-converting enzyme inhibition activity (IC50 0.54 mg mL-1 ). These data showed that enzyme hydrolysis improved the physicochemical properties of ZSP, and enzymatic hydrolysates of ZSP exhibited significant biological activity. These results provided validation for application of ZSP enzymatic hydrolysates as antioxidants and antihypertensive agents in the food or medicinal industries. © 2023 Society of Chemical Industry.

Novel fluorescence nano-orbital biosensor for highly sensitive microRNA detection

BackgroundMicroRNAs play an important role in regulating cell function and gene expression. Early prevention and clinical diagnosis of diseases have high requirements for high-sensitivity detection of microRNAs. Due to the limitations of tedious operation and large sample size, miRNA with small molecular weight and low expression abundance cannot be accurately detected in traditional miRNA detection. To improve the sensitivity and accuracy of detection, we established a novel biosensor based on nucleic acid circuit of signal amplification, which converted miRNA recognition into a fluorescence signal for amplification. ResultsWe designed a biosensor based on an exponential amplification reaction with cascaded HCR and DNAzyme nucleic acid circuit (named E-NOF biosensor) by amplicon sub-fragments to trigger the construction of fluorescence nano-orbitals (NOF), which could be used to detect miRNA ultrasensitively. By modifying two fluorophores (Cy3 and Cy5) on the chain of constructing nano-orbitals, when the amplicon triggered the construction of nano-orbitals, fluorescence resonance energy transfer (FRET) occurred between Cy3 and Cy5, and then two fluorescence signals with different trends could be observed. Therefore, through the ratio of the two signals, we could quantitatively and quickly detect the miRNA from 1 fM to 100 nM, and the E-NOF biosensor detection limit was as low as 0.129 fM. Furthermore, the HCR nucleic acid circuit cascaded with DNAzyme could enrich the fluorophores on the nano-orbitals and significantly enhance the fluorescence signal by accelerating the reaction rate. SignificanceAccording to our understanding, the E-NOF biosensor is the first strategy to cascade EXPAR with HCR and DNAzyme nucleic acid circuit for miRNA-1246 detection. Accurate results can be obtained in only 120 min. Compared with the traditional HCR system, the sensitivity of the new E-NOF biosensor is increased by 1 × 109 times. Furthermore, the biosensor can also detect biomarkers in human serum samples. It has great potential in miRNA detection and identification.

Synergistic effects of dry-brush compatibility and shear stress on rapid alignment of lamellar microstructures for block copolymer reflectors

Because of the high viscosity of severe chain entanglements, a time-consuming process of aligning microstructural orientation in high molecular-weight (Mw) block copolymer photonic crystal films imposed limitations on efficient mass production. In this study, the effective alignment of the block copolymer microstructures in the film state can be carried out within approximately a few minutes. This achievement was realized through the synergistic localized compatibility of dry brush and shear stress during the spin-casting process. The orientation and orderliness of the microphase-separated lamellar structure in as-spun poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP) films can be meticulously controlled by introducing blends with PS homopolymer (hPS) of varying Mws (Mw,hPS) and cholesteric liquid crystal mesogen (Chol). Within the ternary blended films of hPS/PS-b-P4VP(Chol), the wet-brush miscibility by blending low-Mw hPS with a small molecular weight ratio (α) of Mw,hPS to Mw,bPS (Mw of the PS block chain) of α <1 results in the formation of disoriented lamellar structures, whereas dry-brush localization by introducing high-Mw hPS with α∼0.9 yields highly parallel-aligned lamellar structures to the substrate after spin casting, even with a massive quantity of additive hPS (∼59 wt%). The dry-brush compatibility can be demonstrated by morphological observation in the ternary blended film after extraction of the hPS. As a result, without any further efforts, such as additional solvent or thermal annealing treatments, the as-spun ternary blended film can exhibit visible structural colorations with controlled wavelengths by alternating the quantity of hPS. This provides an accessible solution for rapidly producing flexible photonic crystals featuring tunable photonic band gaps.

Effect of ultrasound and thermal pretreatments on antioxidant activity of egg white hydrolysate.

The use of ultrasonic (US) treatment of egg white prior to enzymatic hydrolysis to produce hydrolysate with antioxidant activity was investigated. The state of egg white (raw vs. cooked form) along with two levels of Alcalase (1% and 10% (w/w) protein) was applied. Hydrolysis and antioxidant activity of hydrolysate increased by US pretreatment at intensity of 41.53W/cm2 . The hydrolysate prepared from US treatment on raw egg white hydrolyzed by 1% Alcalase (US-R1%) showed the lowest degree of hydrolysis (DH); however, its 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging and ferric reducing antioxidant power activities were the highest. In contrast, the highest cytoprotective effect and intracellular reactive oxygen species scavenging activity were more notable in the hydrolysate prepared from US treatment of boiled egg white hydrolyzed by 10% Alcalase (US-B10%), which also exhibited the highest DH and metal chelation ability. The hydrolysate possessing cellular antioxidant activity (CAA) showed the highest proportion of small molecular weight peptides (<200Da). Fourier-transform infrared spectroscopy revealed an increase of N- and C-terminal ends at 1500 and 1400cm-1 , respectively, in concomitant with a decrease of amide I. Principal component analysis showed clear differentiation of spectra from different levels of enzyme according to their DH, C-terminal ends, and antioxidant activity. Our findings suggested that cooked egg white followed by US pretreatment was beneficial to produce hydrolysate containing high CAA.

Preparation and identification of hypoglycemic bioactive peptide from Amygdalus communis L. by multienzyme hydrolysis

Amygdalus communis L. is rich in high-quality protein and its natural peptides have potential in controlling and preventing diseases. The objective of this study was to evaluate the hypoglycemic activity of bioactive peptides obtained from Amygdalus communis L. protein by synergistic hydrolysis of trypsin and protamex. After ultrafiltration and purification, active peptide B4 with small molecular weight in four hypoglycemic active peptides showed the best inhibitory activities on α-amylase and α-glucosidase. Moreover, insulin resistance model was established with HepG2 cells to study the hypoglycemic mechanism of active peptide B4. The experimental results confirmed that the active peptide B4 was able to up-regulate GYS1 gene mRNA expression and down-regulate PEPCK, G6Pase and GP gene mRNA expression. Meanwhile, active peptide B4 significantly increased the glucose consumption and glycogen synthesis in IR-HepG2. This research enhances the additional value of nut proteins and contributes to the development of potential functional products to expand their application in the food field.

SuperDopa (SD), SuperDopa amide (SDA) and Thioredoxin-mimetic peptides protect ARPE-19 cells from photic- and non-photic stress

Oxidative stress and inflammation in the retinal pigment epithelium (RPE) cells have been identified as significant risk factors in the development and progression of retinal associated diseases including age-related macular degeneration (AMD). In addition, AMD and myopia have been associated with impaired dopamine activity. Treatment of RPE cells with antioxidants or high concentrations of l-DOPA (levodopa), which down-regulates vascular endothelial growth factor (VEGF) via a G-protein-coupled receptor GPR143, slow AMD progression. To develop a targeted and effective treatment aimed at improving the viability of RPE cells we examined small molecular weight thiol-based and levodopa containing molecules. These include the N-acetylcysteine amide (AD4/NACA), SuperDopa-Amide (SDA), and members of the thioredoxin mimetic (TXM) family of peptides, TXM-CB13, TXM-CB30, and SuperDopa (SD). We show that these antioxidant/anti-inflammatory reagents protect ARPE-19 cells from photic stress mediated by rose Bengal (rB) and rhodopsin-rich POS, and from non-photic stress induced by oxidation with sodium iodate. Protection is correlated with a reduction in DPPH radical and singlet-oxygen quenching. Compared to GSH the bimolecular rate-constants of singlet oxygen quenching in aqueous solution by the levodopa derivatives SD and SDA were two-fold higher. Inhibition of auranofin-induced activation of the mitogen-activation-kinases (MAPK's) JNK1/2 and ERK1/2 confirmed the antioxidant/anti-inflammatory activity of the thiol-levodopa derivatives. The antioxidant and radical scavenging activities of TXM-CB13 and TXM-CB30, or SD and SDA, which combine redox activity with elevating cellular levodopa, might offer an efficient protection of RPE cells. These retino-protective peptides are potential drug candidates destined for slowing the onset and/or progression of RPE-related disorders.

Synergistic Stabilization of Nanoemulsion Using Nonionic Surfactants and Salt-Sensitive Cellulose Nanocrystals.

Soybean stover is a lignocellulose biomass that is rich in cellulose. In the present study, soybean cellulose nanocrystals (CNCs) were prepared from soybean stover by alkaline treatment, bleaching treatment, acid hydrolysis, dialysis and ultrasonication. The as-prepared soybean CNC was characterized by transmission electron microscopy (TEM), zetasizer and rheometer. The effects of NaCl on the particle size, zeta potential, and viscosity of soybean CNC was studied. Soybean CNC was explored as an emulsion stabilizer for lemongrass-essential-oil-loaded emulsions. Soybean CNCs could stabilize the oil-in-water emulsion against coalescence but not flocculation. The addition of NaCl reduced the creaming index and enhanced the encapsulation efficiency and freeze-thaw stability of the CNC-stabilized emulsion. Salted CNC (i.e., CNC in the presence of NaCl) enhanced the thermodynamic stability (i.e., heating-cooling and freeze-thaw stability) of Tween 80 stabilized emulsion, while unsalted CNC did not. Synergistic effects existed between Tween 80 and salted CNC in stabilizing oil-in-water emulsions. The nanoemulsion stabilized with Tween 80 and salted CNC had a mean particle size of ~70 nm, and it was stable against all thermodynamic stability tests. This is the first study to report the synergistic interaction between salted CNC and small molecular weight surfactants (e.g., Tween 80) to improve the thermodynamic stability of nanoemulsion.

Preparation of the modified chitosan flocculant introduced acryloyloxyethyl trimethyl ammonium chloride and 2-acrylamido-2-methyl propane sulfonic acid for the treatment of papermaking wastewater

To solve the shortcomings of poor solubility, low cationic strength, and small molecular weight of chitosan (CTS), acryloyloxyethyl trimethyl ammonium chloride (DAC) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) were introduced into the amino group of chitosan by graft copolymerization, and the modified chitosan flocculant CTS-DAC-AMPS was successfully prepared. The performance of CTS-DAC-AMPS in the treatment of papermaking wastewater was investigated, and the mechanism of the flocculation process was analyzed. The results showed that the crystal habit of CTS-DAC-AMPS was reduced, and the solubility range was broadened compared with CTS due to the introduction of DAC and AMPS. In addition, CTS-DAC-AMPS with quaternary ammonium and sulfonic groups prompted its cationic strength stronger than CTS. In addition to high thermal stability, CTS-DAC-AMPS, composed of two CTS molecules, one DAC molecule, and one AMPS molecule, had a long molecular chain. The results of flocculation experiments showed that the performance of CTS-DAC-AMPS in treating papermaking wastewater was better than that of unmodified CTS and commercially available flocculants. Based on the experimental results, the mechanism of CTS-DAC-AMPS treatment of papermaking wastewater was mainly charge neutralization.