Gel Permeation Chromatography Research Articles

Thermoresponsive block-copolymer brush-modified interfaces for effective fabrication of hepatocyte sheets

Hepatic tissue engineering has been investigated for the treatment of liver disease. One promising tissue is the hepatocyte sheet, cultured in temperature-responsive cell culture dishes. However, the preparation of hepatocyte sheets requires precoating of the dish with fetal bovine serum (FBS), which is not desirable for clinical applications. To overcome this issue, we developed a thermoresponsive polymer-modified glass with an affinity for hepatocytes. Poly(N-p-vinylbenzyl-O-β-d-galactopyranosyl-(1→4)-d-guliconamide)-b-poly(N-isopropylacrylamide) (PVLA-b-PNIPAAm) was prepared through two steps of atom transfer radical polymerization (ATRP). The prepared copolymer brushes were characterized using X-ray photoelectron spectroscopy, atomic force microscopy, gel permeation chromatography, contact angle measurements, and fluorescence labeled-fibronectin and -lectin adsorption assays. These characterizations showed that the smooth block copolymer layer was successfully modified by ATRP. The feasibility of using the prepared polymer brush-grafted glass as a hepatocyte sheet fabrication dish was investigated using primary rat hepatocytes. The PVLA-b-PNIPAAm brushes exhibited hepatocyte adhesion and proliferation without FBS precoating. By reducing the temperature from 37 °C to 20 °C, the hepatocyte sheet was recovered from the copolymer brush. These results indicated that the prepared PVLA-b-PNIPAAm brushes can be utilized for effective hepatocyte sheet fabrication without the need for FBS precoating.

Self-healing performance and rheological properties of styrene-butadiene-styrene block copolymer modified asphalt promoted by polyurea elastomers containing disulfide bonds

Self-healing asphalt is considered as one of the desirable methods to extend the service life of asphalt pavement. This research prepared a polyurea elastomer containing dynamic disulfide bonds (PUA)/styrene butadiene styrene block copolymer (SBS) composite modified asphalt. Moreover, a new asphalt self-healing performance evaluation method based on the damage process and results has been proposed. Subsequently, the self-healing ability of PUA, the distribution of modifier, the functional group and molecular weight of composite modified asphalt were characterized by fluorescence microscope, Fourier transform infrared spectroscopy (FTIR) and Gel permeation chromatography (GPC). The self-healing potential and limits of PUA/SBS composite modified asphalt was investigated through the proposed healing linear amplitude scanning (HLAS) test. Results show that the SBS content and fatigue load level are the main factors affecting the self-healing promotion effect of PUA. The critical point of healing fatigue strain (HFS) can indirectly characterize the threshold at which healing promoters exert their effects. Next, the addition of fillers will reduce the self-healing performance of PUA/SBS composite modified asphalt, but it still improves by at least 61.318% compared with SBS modified asphalt. Finally, the addition of self-healing elastomers (PUA) improves the permanent deformation resistance at high temperature and low-temperature crack resistance of SBS modified asphalt. The dynamic recombination of disulfide bonds can increase the fatigue cycle number of 4%SBS modified asphalt by 93.52% at a 5% load strain level.

Gastroprotective activity and physicochemical analysis of carboxymethylated gum from Anadenanthera colubrina

Biotechnological advancements require the physicochemical alteration of molecules to enhance their biological efficacy for the effective treatment of gastric ulcers. The study aimed to produce a polyelectrolytic compound from red angico gum (AG) by carboxymethylation, evaluate its physicochemical characteristics and investigate gastric protection against ethanol-induced ulcers. AG and carboxymethylated angico gum (CAG) were characterized by Fourier transform infrared spectroscopy, determination of the degree of substitution and gel permeation chromatography (GPC) and 13C NMR techniques. The results demonstrated that the modification of the polymer was satisfactory, presenting conformational changes e improving the interaction with the gastric mucosa. AG and CAG reduced macroscopic and microscopic damage such as edema, hemorrhage and cell loss caused by exposure of the mucosa to alcohol. Both demonstrated antioxidant activity in vitro, and in vivo, pretreatment with gums led to the restoration of superoxide dismutase and glutathione levels compared to the injured group. Concurrently, the levels of malondialdehyde and nitrite decreased. Atomic force microscopy showed that CAG presented better conformational properties of affinity and protection with the gastric mucosa compared to AG in the acidic pH. Based on our findings, it is suggested that this compound holds promise as a prospective product for future biotechnological applications.

Structural Analysis and Novel Mechanism of Enteromorpha prolifera Sulfated Polysaccharide in Preventing Type 2 Diabetes Mellitus.

A water-soluble polysaccharide (EP) was purified from edible algae Enteromorpha prolifera. Gel permeation chromatography (GPC), ion chromatography (IC), and fourier transform infrared (FT-IR) were performed to characterize its structure. EP was defined as a low molecular weight (6625Da) composed of rhamnose, glucose, glucuronic acid, xylose, galactose, arabinose, and mannose. Moreover, it was a sulfated polysaccharide with a degree of substitution (DS) of 1.48. Then, the high-fat diet/streptozotocin (HFD/STZ) induced diabetic mouse model was established to support evidence for a novel hypoglycemic mechanism. Results showed that blood glucose (47.32%), liver index (7.65%), epididymal fat index (16.86%), serum total cholesterol (26.78%) and triglyceride (37.61%) in the high-dose EP (HEP) group were significantly lower than those in the HFD group. Noticeably, the content of liver glycogen in the HEP group was significantly higher (62.62%) than that in the HFD group, indicating the promotion of glycogen synthesis. These beneficial effects were attributed to significantly increased protein kinase B (AKT) phosphorylation and its downstream signaling response. Further studies showed that diabetic mice exhibited excessive O-GlcNAcylation level and high expression of O-linked β-D-N-acetylglucosamine transferase (OGT), which were decreased by 62.21 and 30.43% in the HEP group. This result suggested that EP had a similar effect to OGT inhibitors, which restored AKT phosphorylation and prevented pathoglycemia. This work reveals a novel hypoglycemic mechanism of EP, providing a theoretical basis for further studies on its pharmacological properties in improvement of T2DM.

High‐temperature resistant copolymer oil well cement retarder: Synthesis, assessment of performance, and mechanism of retardation

AbstractThis work used aqueous solution free radical polymerization to create polymers of 2‐acrylamide‐2‐methylpropane sulfonic acid, itaconic acid, and allyl polyoxyethylene ether as a high‐temperature resistant retarder (APMS/IA/APEG, from now on referred to as AIA). Gel permeation chromatography, fourier transform infrared (FTIR), proton nuclear magnetic resonance (1HNMR), and thermo‐gravimetric analysis (TG) were used to characterize their molecular structure and characteristics. Tests were conducted on the thickening time, rheological characteristics, and compressive strength of AIA in cement slurries. The cement slurry thickened for 276 min at 180°C during the test, and the cement stone's 24‐h compressive strength was consistently more than 20 MPa. The hydration products were analyzed using x‐ray diffractometer and scanning electron microscopy methods, which were then coupled with molecular dynamics simulations to elucidate the AIA retarding mechanism. When AIA is added to a cement slurry, it forms a chelate structure with Ca2+ and a strong adsorption layer on the surfaces of the cement particles. This stops the cement from hydrating. The AIA side chain, APEG, can wrap the active group in AIA at low temperatures. AIA exposes more adsorption groups because of the APEG chains stretching at higher temperatures. AIA can, therefore, be used for deep well operations at high temperatures.

Synthesis of terpolymer from Helianthus annuus (natural oil) and evaluation as pour point depressant and viscosity reducer on Indian crude oil

Pour Point Depressant is introduced to crude oil at ppm level to overcome transportation problem of crude oil because of its complex chemical structure. Synthesized PPDs improve flow property, viscosity and also improve its numerous parameters to improve performance of crude oil. Low molecular weight and high molecular weight, copolymer having better PPD types. In present work, synthesized Terpolymer, from natural source, was formed from the reaction with Helianthus annuus oil and ester of Erucic Acid with various fatty alcohol. It was evaluated for its properties on Indian waxy crude oils, i.e., From Limbodra well. Structure and molecular weight of synthesized polymer was confirmed by Spectral data and Gel permeation chromatography (GPC). Also its effect on crude oil was evaluated by Rheological studies, SARA Analysis, Pour point depressant effect. Cross–polarizing microscopic studies were performed to study changes in morphology of wax crystals in crude oil with and without additive. A zero friction advanced Rheometer AR-500 was used to determine the viscosity by applying Bingham plastic-flow model.

Multiple Force-Triggered Downconverted and Upconverted Emission in Polymers Containing Diels-Alder Adducts.

Fluorescent mechanophores can indicate the deformation or damage in polymers. The development of mechanophores with multi-triggered response is of great interest. Herein, Diels-Alder (DA) adducts are incorporated into linear poly(methyl acrylate) PMA-BA and network poly(hexyl methacrylate) (PHMA) as mechanophores to detect the stress caused by ultrasound, freezing, and compression. The DA mechanophores undergo retro-DA reaction to release 9-styrylanthracene chromophore upon applying force, resulting in cyan fluorescence. The dissociation ratio of the DA mechanophore after pulsed ultrasonication of PMA-BA solution for 240 minutes is estimated to be 52 % by absorption spectra and 1H NMR. Additionally, the rate constant of mechanical cleavage is calculated to be 1.2×10-4 min-1⋅kDa-1 with the decrease in molecular weight from 69 to 22 kDa measured by gel permeation chromatography. Freezing of PHMA gels as well as compression of PHMA bulk samples turn-on the DA mechanophores, revealing the microscale fracture. Photon upconversion responses toward various force stimuli are also achieved in both polymer solutions and bulk samples by doping platinum octaethylporphyrin (PtOEP) or palladium meso-tetraphenyltetrabenzoporphyrin (PdTPTBP) sensitizers with multiple excitation wavelengths.

Azobenzene‐containing liquid crystalline poly(methacrylates) with different spacer length as media for holographic grating recording

AbstractLiquid crystalline (LC) poly(methacrylates) with azobenzene moieties in their side chains have been synthesized and their chemical structure has been confirmed with nuclear magnetic resonance spectroscopy and gel permeation chromatography. Azobenzene moieties are linked to polymer backbone via an alkyl spacer with length from 2 to 10 methylene units. Photooptical processes in thin amorphized polymer films are examined through measurements of optical anisotropy and holographic grating recording. Birefringence values induced with a linearly polarized green (532 nm) laser beam has strongly depended from the spacer length. Irradiation with two circularly polarized green laser beams leads to the formation of polarization and surface relief gratings, which have been visualized with polarized optical and atomic force microscopy, respectively. Diffraction efficiency of the recorded gratings is in correlation with the spacer length, namely, the shorter the spacer, the higher diffraction efficiency can be achieved. For polymers with short spacers polarization gratings can be easily erased by circularly polarized light, but only partial erasing of surface relief gratings is observed. The results presented offer the possibility of tailoring the chemical structure of azobenzene‐containing polymers for designing high‐efficiency media for the holographic recording.

Influence of various pretreatments on molecular and rheological properties of a linear and a long-chain branched polypropylene

The influence of a mechanical or a thermal pretreatment of a linear (L-PP) and a long-chain branched polypropylene (LCB-PP) in the molten state was studied. The molar mass distributions and the branching structure were determined by high-temperature gel permeation chromatography HT-GPC coupled with laser-light scattering. The samples were extruded through long or short capillaries of various geometries corresponding to a predominant shear or elongational deformation. As a rheological probe, the extrudate swell at low stresses was measured for the differently pretreated samples. For the L-PP, neither molecular nor rheological changes were observed. However, the extrudate swell of the LCB-PP was found to decrease with increasing volume throughput. It was more strongly affected by shear in the capillary than by molecule stretching in the entry region. The smaller extrudate swell was accompanied by a decrease of the high molar mass tail of the LCB-PP, which could be the reason for the decay of swell, in principle. However, a comparable degradation of the high molar mass tail was obtained by a pure thermal treatment that was shown to leave the extrudate swell unchanged. This result and the unaffected branching structures found by high-temperature gel permeation chromatography (HT-GPC) support the hypothesis of a change of the branching topography by the mechanical pretreatment.

Synthesis of L-Lactide from Lactic Acid and Production of PLA Pellets: Full-Cycle Laboratory-Scale Technology.

Lactide is one of the most popular and promising monomers for the synthesis of biocompatible and biodegradable polylactide and its copolymers. The goal of this work was to carry out a full cycle of polylactide production from lactic acid. Process conditions and ratios of reagents were optimized, and the key properties of the synthesized polymers were investigated. The influence of synthesis conditions and the molecular weight of lactic acid oligomers on the yield of lactide was studied. Lactide polymerization was first carried out in a 500 mL flask and then scaled up and carried out in a 2000 mL laboratory reactor setup with a combined extruder. Initially, the lactic acid solution was concentrated to remove free water; then, the oligomerization and synthesis of lactide were carried out in one flask in the presence of various concentrations of tin octoate catalyst at temperatures from 150 to 210 °C. The yield of lactide was 67-69%. The resulting raw lactide was purified by recrystallization in solvents. The yield of lactide after recrystallization in butyl acetate (selected as the optimal solvent for laboratory purification) was 41.4%. Further, the polymerization of lactide was carried out in a reactor unit at a tin octoate catalyst concentration of 500 ppm. Conversion was 95%; Mw = 228 kDa; and PDI = 1.94. The resulting products were studied by differential scanning calorimetry, NMR spectroscopy and gel permeation chromatography. The resulting polylactide in the form of pellets was obtained using an extruder and a pelletizer.

Performance and mechanism of amphiphilic polymeric chelator for enhanced removal of high concentrations of Cu(II) from wastewater.

An amphiphilic polymeric chelator (APC16-g-SX) grafted with sodium xanthate (SX) groups was successfully prepared for the efficient removal of high concentrations of Cu(II) from wastewater. The ordinary polymeric chelator (PAM-g-SX) based on linear polyacrylamide (PAM) was also prepared for comparative studies. The polymeric chelators were characterized by Fourier transform infrared spectroscopy (FT-IR), solid-state nuclear magnetic resonance (13C-NMR), gel permeation chromatography (GPC), elemental analyzer, and scanning electron microscope (SEM). The chelating performance of these polymeric chelators was investigated, and the mechanism of APC16-g-SX for enhanced removal of Cu(II) from wastewater was proposed based on fluorescence spectroscopy, cryo-scanning electron microscope (Cryo-SEM), energy-dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS) tests. The results show that as the initial Cu(II) concentration in the wastewater increases, APC16-g-SX shows more excellent chelating performance than ordinary PAM-g-SX. For the wastewater with an initial Cu(II) concentration of 200mg/L, the removal rate of Cu(II) was 99.82% and 89.34% for both 500mg/L APC16-g-SX and PAM-g-SX, respectively. The pH of the system has a very great influence on the chelating performance of the polymeric chelators, and the increase in pH of the system helps to improve the chelating performance. The results of EDS and XPS tests also show that N, O, and S atoms in APC16-g-SX were involved in the chelation of Cu(II). The mechanism of enhanced removal of Cu(II) by APC16-g-SX can be attributed to the spatial network structure constructed by the self-association of hydrophobic groups that enhances the utilization of chelation sites.

Synthesis and Morphology Characteristics of New Highly Branched Polycaprolactone PCL.

A simple and efficient method for the synthesis of biodegradable, highly branched polycaprolactone (PCL) is presented. The solvent-free (bulk) reaction was carried out via ring opening polymerization (ROP), catalyzed by tin octanoate Sn(Oct)2, and it employed hyperbranched polyamide (HPPA) as a macro-initiator. The core-shell structure of the obtained products (PCL-HPPA), with the hyperbranched HPPA core and linear PCL chains as shell, was in the focus of the product characterization. 1H nuclear magnetic resonance (1H NMR) and elemental analysis confirmed the covalent incorporation of the HPPA in the products, as well as a high degree of grafting conversion of its amino functional groups. Confocal Raman Micro spectroscopy, and especially Time-of-Flight Secondary Ion Mass Spectrometry, further supported the existence of a core-shell structure in the products. Direct observation of macromolecules by means of cryogenic transmission electron microscopy, as well as gel permeation chromatography (GPC), suggested the existence of a minor 'aggregated' product fraction with multiple HPPA cores, which was attributed to transesterification reactions. Differential scanning calorimetry, as well as X-ray diffraction, demonstrated that the PCL-HPPA polymers displayed a similar degree of crystallinity to linear neat PCL, but that the branched products possessed smaller and less regular crystallites.

Directly using H2S to Synthesize Crystalline Poly(thioether‐ester)s via Organocatalysis

AbstractThe direct utilization of H2S in polymerization is rarely reported. Here step polymerization of H2S and diacrylates using commercially available organic bases as the catalysts is reported. Poly(thioether‐ester)s are successfully synthesized in an atom‐economical way, as confirmed by 1H NMR spectra, and the molecular weights of these poly(thioether‐ester)s can be up to 64.7 kDa as determined by the gel permeation chromatography, which also shows the polymerization of H2S with diacrylates is stepwise manner. The calculation results show that H2S is first deprotonated by organic base, and the generated HS‐ attacks the double bond of diacrylates through anionic Michael addition, to form the intermediate with double bond and ─SH ends or two ─SH ends (slight excess H2S used). The continuous self‐Michael addition of the polymer species with double bond and ─SH ends is the main manner for chain growth. The resultant polymers exhibit tensile strength and elongation at breaks of as high as 21.6 MPa and 1031%, respectively and can be chemically recycled. This work provides a facile and atom‐economical method to produce sulfur‐containing polymers by directly using commercially available H2S.

Structural Elucidation of a Polysaccharide from Flammulina velutipes and Its Lipid-Lowering and Immunomodulation Activities.

FVPT1, a novel heteropolysaccharide, was purified from the fruiting body of Flammulina velutipes using magnetic-field-assisted three-phase partitioning and gel permeation chromatography. The structure was characterized using monosaccharide composition and methylation analysis, infrared spectroscopy and nuclear magnetic resonance (NMR). The FVPT1 (~1.64 × 104 Da) was composed of L-fucose, D-galactose, D-glucose and D-mannose at a molar ratio of 1.0:3.5:1.0:1.4. The polysaccharide repeating unit of FVPT1 was established with methylation analyses and NMR spectroscopy. Moreover, a zebrafish larva hyperlipidemia model test demonstrated that FVPT1 can show appreciable lipid-lowering effects. In addition, the FVPT1 exhibited remarkable immunoregulatory activity by increasing nitric oxide, interleukin (IL)-1β and IL-1 secretion in macrophages. Therefore, these results suggest that FVPT1 has the potential to be developed into a new immune or hypolipidemic health product.

Current State of Alkyd Resin Synthesis and Characterization, Extracted from Vegetable Oils

Alkyd resins' high film-forming capacity, excellent adhesion, and durability to a variety of environmental conditions have led to its major attention in the field of industrial coatings and paint applications. The purpose of this work is to present a thorough overview of the synthesis and characterization of alkyd resins for these particular uses. Thirty-eight (38) vegetable oils were reviewed from 2001 to 2023 whose data were derived from online sources, not excluding google scholar, ScienceDirect and Semantics scholar. Alkyd resins are made by reacting polyols (like glycerol or pentaerythritol) with dicarboxylic acids (like phthalic anhydride), then modifying the mixture with fatty acids or drying oils. The qualities of the resulting alkyd resins are significantly influenced by process variables, including catalysts, reaction conditions, and raw material selection. Numerous methods are used in the characterization of alkyd resins, such as nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and thermal analysis (TGA/DSC).
 These methods offer important insights into the alkyd resins' molecular weight distribution, thermal stability, and chemical structure. Gaining knowledge about the synthesis and characterization of alkyd resins helps to optimize their formulation for use in paint and industrial coatings, improving their performance and durability.

Chitosan–fucoidan encapsulating cinnamaldehyde composite coating films: Preparation, pH-responsive release, antibacterial activity and preservation for litchi

In this study, an edible composite film with pH-responsive release was prepared by the formation of Schiff-base imine bonds between chitosan (CS) and oxidized fucoidan (CS–FU) and encapsulating cinnamaldehyde (CA). Fourier-transform infrared, 1H nuclear magnetic resonance, X-ray photoelectron spectroscopy and gel permeation chromatography confirmed the formation of CS–FU. The result showed that, oxidation degree of FU, degrees of substitution, average molecular weight and yield of CS–FU were 25.57 %, 10.48 %, 23.3094 kDa and 45.63 ± 0.64 %, respectively. Scanning electron microscopy revealed that CA was encapsulated within the CS–FU matrix. Increasing the CA content could improve the mechanical properties and ultraviolet and visible-light resistances of the CS–FU coating films but enhance their water vapor permeabilities. The release of CA increased as the pH decreased, and the antibacterial rate at pH 5 was 2.3-fold higher than that at pH 7, indicating good pH-responsive release and antibacterial properties in mildly acidic environments. Owing to their excellent properties, the CA/CS–FU-0.1 coating films maintained the appearance and quality indices of litchis for at least eight days. Hence, multifunctional composite coating films are prospective eco-friendly and intelligently responsive controlled-release packaging materials for fruit preservation.

Preparation of a low-temperature poly (amino acids) demulsifier and its demulsification mechanism

To improve the universality and efficiency of polymer demulsifiers at low temperatures, a unique type of biodegradable poly (ε-carbobenzyloxy-L-lysine) -block-poly (L-phenylalanine) (PZLL-b-PPA) demulsifier with stronger polarity and higher aromaticity was developed. The molecular structure and weight of PZLL-b-PPA were determined using Fourier transform infrared (FT-IR) spectroscopy, 1H nuclear magnetic resonance hydrogen spectra (NMR) and gel permeation chromatography (GPC). A bottle test was used to evaluate the demulsification performance of PZLL-b-PPA with different block ratios, structure and interfacial activity. Numerous critical variables, such as demulsifier structure and dosage, pH levels, emulsion salinity, oil content and oil type, were carefully examined. The demulsification results showed that PZLL5-b-PPA25 has excellent low-temperature demulsification capability and can effectively separate oil from water emulsions with different pH values (4.0 ∼ 11.0) and oil contents ranging from 1.0 ∼ 20.0 wt% within 2 min at room temperature. The best demulsification efficiency reached 99.98 %, with only 6.0 mg/L of residual oil in the separated water. The analysis of interfacial self-assembly behavior revealed that PZLL-b-PPA has a strong affinity for aromatic molecules and exhibits high interfacial activity. The quantum chemical calculation indicated that the main chain polyamide skeleton of PZLL-b-PPA has a stronger interaction for asphaltene, resin and naphthenic acid molecules than conventional oxygen-containing skeleton polymers. Furthermore, the microscopy analysis indicated that PZLL-b-PPA has excellent capacity for flocculation and coalescence of oil droplets in an O/W emulsion. As a result, when PZLL-b-PPA is added to the emulsion, it can quickly migrate to the oil-water interface and interact with and displace the emulsion's stabilizers (asphaltenes and resins), promoting oil droplet coalescence and separation from water at low temperature.

Research on the performances of VPEG macromonomer grafted different functional groups to prepare polycarboxylate superplasticizers

AbstractThe advent of novel polyether macromonomer has garnered significant attention within the industrial domain. In this study, a range of polycarboxylate superplasticizers (PCEs) was produced via free radical polymerization, employing a new polyether monomer, 4‐hydroxybutyl vinyl polyethylene glycol ether (VPEG). This monomer served as the predominant component and was grafted with various functional monomers on its main chain. The molecular configuration of the resultant PCEs was discerned through Fourier infrared spectroscopy and gel permeation chromatography, while the surface tension underwent assessment via a surface tension meter. Both the initial and subsequent fluidity of cement paste and mortar were leveraged to ascertain the dispersion and retention efficacy of the synthetic PCEs. The ramifications of diverse functional group grafts of the new polyether monomer on the cement hydration procedure and strength attributes were elucidated via setting time, hydration heat assays of cement paste, SEM analysis, and compressive strength evaluations of mortar. Observations reveal that the carboxylic acid group significantly reduces surface tension, whereas the sulfonic acid group's effect remains minimal. The incorporation of both the amide and sulfonic acid groups marginally impacts the preliminary dispersion efficacy of PCEs but notably affects dispersion retention. Furthermore, these functional groups facilitate cement hydration, expedite the primary setting time of the cement paste, and bolster the initial compressive strength of the mortar. Specifically, the grafted of sodium methacrylsulfonate (SMAS) yields the most noticeable results. Finally, the working mechanism of PCEs with varying molecular structures has been explained in light both theoretical and experimental results. This research offers valuable insights for subsequent investigations into the fabrication of polycarboxylate superplasticizers using the VPEG macromonomer.

Antioxidant and cytotoxic properties of water‐soluble crude polysaccharides from two edible mushroom species of Ramaria

AbstractWater‐soluble crude polysaccharides (WSCPs) were isolated from the fruiting bodies of Ramaria flava (Schaeff.) Quél. (RFCP) and Ramaria cf. aurea (Schaeff.) Quél. (RACP). Species of Ramaria were collected in Boyacá‐Colombia. WSCPs were obtained by hot‐water extraction, ethanol precipitation, and dialysis and characterized using UV‐Vis spectroscopy, gel permeation chromatography, high‐performance liquid chromatography‐diode array detector, fourier transform infrared and nuclear magnetic resonance spectroscopy. Different assays evaluated the antioxidant capacity, and the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT)‐assay was used to determine cytotoxic effects. Chemical compositional analysis revealed that RFCP and RACP are heteropolysaccharides with molecular weights of 407 and 818 kDa, respectively compose mainly of glucose, mannose, galactose, fucose, and glucuronic acid with small amounts of protein and polyphenols. The backbone of RFCP and RACP is composed of β‐D‐Glcp‐(4→,→3)‐β‐D‐Glcp‐(1→,→2,6)‐α‐D‐Galp‐(1→,→3,6)‐α‐D‐Manp‐(1→. Antioxidant capacity demonstrated that both crude polysaccharides exhibit reducing power, radical scavenging ability, and a protective effect on lipid‐peroxidation. MTT assay showed that RFCP and RACP inhibited the growth of cancer cells HCT 116‐(colorectal) and MG‐63‐(bone) in a concentration‐dependent manner. Compared with RFCP, RACP showed better antioxidant capacity and cytotoxic effects due to differences in composition, molecular weight, and triple‐helical conformation. Overall, WSCPs exhibited a promising biological effect, highlighting the cultural, nutritional, and medicinal value of wild mushrooms.

Unveiling the Nanocluster Conversion Pathway for Highly Monodisperse InAs Colloidal Quantum Dots.

Colloidal quantum dots (CQDs) have garnered significant attention in nanoscience and technology, with a particular emphasis on achieving high monodispersity in their synthesis. Recent advances in understanding the chemistry of reaction intermediates such as magic-sized nanoclusters (MSC) have paved the way for innovative synthetic strategies. Notably, monodisperse CQDs of various compositions, including indium phosphide, indium arsenide, and cadmium chalcogenide, have been successfully prepared using nanocluster intermediates as single-source precursors. Still, the early stage conversion chemistry of these nanoclusters preceding CQD formation has not been fully unveiled yet. Herein, we report the first-order conversion of amorphous nanoclusters (AMCs) to InAs MSCs prior to the formation of CQDs. We find that MSC, isolated via gel-permeation chromatography, is more stable than purified AMCs, as demonstrated in various chemical and thermolytic reactions. While the surface of InAs AMCs and MSC is similarly bound with carboxylate ligands, detailed structural analyses employing synchrotron X-ray scattering and X-ray absorption spectroscopy unveil subtle distinctions arising from the distinct surface properties and structural disorder characteristics of InAs nanoclusters. We propose that InAs AMCs undergo a surface reduction and structural ordering process, resulting in the formation of an InAs MSC in a thermodynamically local minimum state. Furthermore, we demonstrate that both types of nanoclusters serve as viable precursors, providing a similar monomer supply rate at elevated temperatures of around 300 °C. This study offers invaluable insights into the interplay of structure and chemical stability in binary nanoclusters, enhancing our ability to design these nanoclusters as precursors for highly monodisperse CQDs.