Monomer Molecular Weight Research Articles

Enzymatic synthesis of aromatic biobased polymers in green, low-boiling solvents

Given the urge to accelerate the substitution of petrol-derived solvents not only in more traditional fields like pharmaceuticals, personal care, or electronics but also in innovative research processes, this work focuses on the utilisation of four biobased solvents as media for the enzymatic synthesis of aliphatic-aromatic polyesters. As building blocks, the lignin-derived diethyl-2,4-pyridinedicarboxylate was selected as the potentially biobased, aromatic component while more classical diols such as 1,4-butanediol and 1,8-octanediol were used as the aliphatic portion. Results show that among the tested green solvents (cyclohexanone, phenetole, anisole and eucalyptol), the most suitable medium for lipase B from Candida antarctica-catalysed polycondensation reactions was eucalyptol that allowed reach monomer conversions >95 % and number average molecular weights up to 3500 g·mol−1. On the other hand, cyclohexanone led to the lowest monomer conversions (<80 %) and molecular weights (Mn<500 g·mol−1) confirming once again the unsuitability of ketone-containing solvents for enzymatic esterification and transesterification reactions. The lipase could be used up to three times, in eucalyptol as a solvent, without a significant decrease in monomer conversion or molecular weight.

Role of bacterial exopolysaccharides in edible films for food safety and sustainability. Current trends and future perspectives

Bacterial biopolymers are changing the concepts in the food industry as customer demands the addition of no artificial additives and want products “Clean labelled.” Exopolysaccharides (EPS) produced by some bacterial strains are the best replacements for these artificial additives. The monomeric composition, quality, quantity, structure, molecular weight, and charge on these bioparticles decide the qualities, that is, rheology, texture, shelf life, and physiochemical properties of the product. Exopolysaccharides are the best biothickeners and are being widely used in the food industry. They are widely used as coatings and edible films in food substances, especially fruits and vegetables. These consist of substances that are Generally Recognized as Safe. These coatings and edible films promise improved shelf life and better nutritional properties and act as a protective barrier for food items. Bacterial EPS are widely used in edible films, yogurt-like and plant-based beverages, the meat industry, and fermented low-fat meat, sourdoughs, and low-fat cheese. It interacts with other components and improves the texture, stabilization, viscosity, and mouthfeel of end products. The structural and functional properties of these substances still need to be explored. The main objective of this review is to focus on the importance of EPS produced by various strains, its structure and uses as edible coatings and films, functionality, and applications in various food products. Overall, the future of bacterial EPS in the food industry appears promising, with avenues for innovation and application across multiple facets of food production, including texture modification, nutritional enhancement, and sustainability.

Expression, characterization and cytotoxicity of recombinant l-asparaginase II from Salmonella paratyphi cloned in Escherichia coli

L-asparaginase is a remarkable antineoplastic enzyme used in medicine for the treatment of acute lymphoblastic leukemia (ALL) as well as in food industries. In this work, the L-asparaginase-II gene from Salmonella paratyphi was codon-optimized, cloned, and expressed in E. coli as a His-tag fusion protein. Then, using a two-step chromatographic procedure it was purified to homogeneity as confirmed by SDS-PAGE, which also showed its monomeric molecular weight to be 37 kDa. This recombinant L-asparaginase II from Salmonella paratyphi (recSalA) was optimally active at pH 7.0 and 40 °C temperature. It was highly specific for L-asparagine as a substrate, while its glutaminase activity was low. The specific activity was found to be 197 U/mg and the kinetics elements Km, Vmax, and kcat were determined to be 21 mM, 28 μM/min, and 39.6 S−1, respectively. Thermal stability was assessed using a spectrofluorometer and showed Tm value of 45 °C. The in-vitro effects of recombinant asparaginase on three different human cancerous cell lines (MCF7, A549 and Hep-2) by MTT assay showed remarkable anti-proliferative activity. Moreover, recSalA exhibited significant morphological changes in cancer cells and IC50 values ranged from 28 to 45.5 μg/ml for tested cell lines. To investigate the binding mechanism of SalA, both substrates L-asparagine and l-glutamine were docked with the protein and the binding energy was calculated to be −4.2 kcal mol−1 and − 4.4 kcal mol−1, respectively. In summary, recSalA has significant efficacy as an anticancer agent with potential implications in oncology while its in-vivo validation needs further investigation.

Amphiphilic block and random copolymers: aggregation and hydrophobic modification on metal-free tanned collagen fibers

Hydrophobicity enhancement of metal-free leather, which is crucial for improving its comprehensive performance, can be achieved by using amphiphilic copolymer retanning agents. However, the relationship between the sequential structure and the hydrophobic modification effect of amphiphilic copolymers remains unclear. Herein, an amphiphilic block copolymer was synthesized using stearyl methacrylate and 2-(dimethylamino)ethyl methacrylate via atom transfer radical polymerization, and the corresponding random copolymer with similar monomer compositions and molecular weights was prepared for comparison. The aggregation behavior of block and random copolymers was investigated. DLS and TEM results indicate that the block copolymer exhibits a larger aggregate size than the corresponding random copolymer. Molecular dynamics simulations suggest that the block copolymer aggregate exhibit a thicker hydrophilic shell and more concentrated distribution of cationic DMA block than the random copolymer aggregate. Subsequently, the block and random copolymers were used for the hydrophobic modification of metal-free tanned collagen fibers (CFs). The block copolymer shows superior binding capacity to CFs than the random one because of its larger size and more concentrated charge distribution. Hence, the block copolymer can form a dense and uniform hydrophobic film on the surface of collagen fibrils and endow CFs with higher hydrophobicity than the random one. This work provides theoretical guidance for modulating the hydrophobicity of CFs by tailoring the sequential structure of amphiphilic copolymers, which is expected to inspire the manufacturing of high-performance metal-free leather.Graphical

Polyvinyl alcohol (PVA)-based films: insights from crosslinking and plasticizer incorporation

The properties of polyvinyl alcohol (PVA) films are intricately influenced by factors such as polymer structure, fabrication method, the addition of plasticizers and the molecular weight of monomers. This research, investigates the implication of PVA films using a solution casting method for crosslinking with boric acid (H3BO4), glycerol (C3H8O3) and citric acid (C6H8O7). This approach is compared with pure PVA films, establishing a valuable benchmark. For the experiments, tensile strength tests, physicochemical property measurements, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were conducted to gain insights into the microstructure, surface characteristics and mineral composition of the films. This comprehensive approach aims to enhance our understanding of the intricate relationship between PVA, plasticizers and crosslinking agents, providing valuable insights for applications across diverse industries, including, construction and biomedical fields. The overarching objective of this research is to revolutionize the construction industry by developing polymer films that serve as the foundation for self-healing materials, fostering durability and innovation. The experiments revealed a significant influence of crosslinking agents on the properties of PVA films as measured.

Metal-Free, Photoinitiated Cationic Terpolymerization of Vinyl Ethers, Oxiranes, and Ketones: Simultaneous Control of Monomer Sequence and Molecular Weight by the Formation of Long-Lived Propagating Species

Metal-Free, Photoinitiated Cationic Terpolymerization of Vinyl Ethers, Oxiranes, and Ketones: Simultaneous Control of Monomer Sequence and Molecular Weight by the Formation of Long-Lived Propagating Species

Chemical Structure-Physicochemical Property Relationships of Copolymers Utilizable for Negative-Tone Photoimaging via Chemical Amplification.

We demonstrate an understanding of different physicochemical properties of copolymers induced by systematic changes in their structural parameters, i.e., the chemical structure of the comonomer unit, composition, molecular weight, and dispersity. The terpolymers were designed to be implemented in a chemically amplified resist (CAR) to form negative-tone patterns. With two basic repeating units of 4-hydroxystyrene and 2-ethyl-2-methacryloxyadamantane as monomers for conventional CARs, the pendant group of the third methacrylate comonomer was varied from aromatic, aliphatic lactone to lactone rings to modulate the interaction capability of the copolymer chains with n-butyl acetate, which is a negative-tone developer. Along with these structures, the monomer composition, molecular weight, and dispersity were also controlled. Physicochemical properties of the synthesized copolymers having controlled structures, i.e., dissolution behaviors and quantified Hansen solubility parameters, surface wetting characteristics, and surface roughness, which can be important properties affecting patterning capability in high-resolution lithography, were explored. Furthermore, the feasibility to use experimentally determined Hansen solubility parameters of the copolymers for the prediction of pattern formation using a coarse-grained model was assessed. Our comprehensive studies on the correlation of the structural parameters of the copolymers with final properties offer fundamental avenues to attain effective designs of the complex CAR system toward the lithographic process to achieve a sub-10 nm dimension, which is close to a single-chain dimension.

Dynamic Interfaces in Self-Healable Polymers.

It is well-established that interfaces play critical roles in biological and synthetic processes. Aside from significant practical applications, the most accessible and measurable quantity is interfacial tension, which represents a measure of the energy required to create or rejoin two surfaces. Owing to the fact that interfacial processes are critical in polymeric materials, this review outlines recent advances in dynamic interfacial processes involving physics and chemistry targeting self-healing. Entropic interfacial energies stored during damage participate in the recovery, and self-healing depends upon copolymer composition and monomer sequence, monomer molar ratios, molecular weight, and polymer dispersity. These properties ultimately impact chain flexibility, shape-memory recovery, and interfacial interactions. Self-healing is a localized process with global implications on mechanical and other properties. Selected examples driven by interfacial flow and shape memory effects are discussed in the context of covalent and supramolecular rebonding targeting self-healable materials development.

Stimuli-responsive self-assembled polymer nanoparticles for the oral delivery of antibodies

Currently, commercially available antibody therapies must be delivered via parenteral administration. Oral delivery of antibodies could increase patient compliance and improve quality of life, however there is currently no viable system for delivering antibodies orally. In this work, a self-assembled, pH-responsive nanoparticle delivery system was developed to load and deliver antibodies via the oral route. The nanoparticles were synthesized via nanoprecipitation using the pH-responsive copolymers based on poly(methacrylic acid-co-methyl methacrylate)-block-poly(ethylene glycol). The reversibly hydrophobic nature of this polymer allowed it to function as an antibody delivery system via self-assembly. Characteristics of the polymer, including monomer ratios and molecular weight, as well as parameters of the nanoprecipitation process were optimized using Design of Experiments to achieve nanoparticles with desired size, polydispersity, loading efficiency, and release characteristics. Ultimately, the synthesized and optimized nanoparticles exhibited a hydrodynamic size within a range that avoids premature clearance, a low polydispersity index, and high IgG loading efficiency. In in vitro antibody release studies at physiologically relevant pH values, the nanoparticles exhibit promising release profiles. The nanoparticles presented in this work show potential as oral delivery vehicles for therapeutic antibodies.

Molecular and thermo-mechanical assessment of long-chain branched polypropylene: Effect of irradiation dose, multifunctional monomer content and molecular weight

The influence of irradiation dose, trimetylolpropane trimethacrylate (TMPTMA) amount, as a three-functional monomer, and polypropylene (PP) molecular weight on the performance of irradiation technique to create long chain branched PP (LCB-PP) was investigated through molecular, rheological and thermo-mechanical characterizations. With increasing doses or amount of TMPTMA, a reduction in molar mass and an increment in long chain branches (LCBs) number as well as a change in the topology of LCBs from star to tree-like were found. PP grade with low molar mass had more branching ability and its LCBs topology was different. Irradiation declined the glass transition and melting temperature of PP, while it did not affect its crystallization temperature and its degree. Two opposing effects of molar mass reduction and LCBs formation controlled the tensile strength and toughness of irradiated PP samples.

Optimization of Affinity Chromatography Based on Sepharose 4B- chitin for Rapid Purification of Urtica dioica Agglutinin.

Today, numerous antimicrobial and anticancer properties have been reported for plant lectins due to their ability to bind to carbohydrates. The Urtica dioica agglutinin (UDA lectin) is a monomeric, small, and low molecular weight glycoprotein. It has attracted the attention of many researchers for identification, treatment, and other clinical purposes. The aim of this study is the optimization of the chitin affinity chromatography based on Sepharose 4B (CNBr-activated Sepharose 4B) for the rapid purification of UDA lectin from Urtica dioica rhizome. The chitin ligands were dissolved in 40% Trichloroacetic acid and attached to Sepharose 4B according to the Amersham-Biosciences instructions. The attachment of the ligand to the Sepharose 4B beads was investigated by Fourier transform infrared (FTIR) spectroscopy. An acidic crude extract of nettle rhizome passes from chromatographic columns in two sizes with dimensions: 24 x 0.51 cm and 8.44 x 0.86 cm. Quantity and quality of purified lectin were calculated by the Bradford microplate method: SDS-PAGE gel electrophoresis and human erythrocyte cell (RBC) hemagglutination, respectively. The analysis of FTIR spectrograms showed that major changes were observed in the fingerprint regions. Besides, due to the dissolution of Sepharose 4B and chitin in the aqueous phase, this difference was not significant in the Imine and Nitrile regions. On the other hand, the comparative results of purification chromatograms showed that increasing the column length causes a smaller half-width and increases the length of the purified peak. Also, it leads to high-quality purified UDA lectin, with a molecular weight of almost 12.5 kDa in gel electrophoresis. Hemagglutination activity on trypsinized red blood cells was displayed, and agglutination of purified UDA lectin started at least at 300 μg.mL-1 concentration. According to our findings, we suggested that dissolving chitin in the polar solvent of Trichloroacetic acid, using Sepharose 4B as the beads of a matrix, and increasing the column length might lead to a decrease in the half-width of the peak. These can increase the purity and concentration of purified UDA lectin, and speed up the purification process. These findings could be used by researchers to accelerate the purification of UDA lectin in other studies, dealing with drug delivery systems, ELISA techniques, and cell growth.

Release of Monomers from Dental Composite Materials into Saliva and the Possibility of Reducing the Toxic Risk for the Patient.

Background and Objectives: The objective of this study was (1) to measure the amount of monomers released into the saliva depending on the time elapsed after the hardening of the composite and on the type of monomer used; and (2) with the prolongation of the light-curing procedure, to publish information on whether it would be possible to influence the level of leached monomers. Materials and Methods: HPLC technique was used to monitor the levels of the unpolymerized monomers Bis-GMA, Bis/EMA, TEGDMA, and UDMA from the four commonly used composite materials, released into the saliva of a volunteer with intact dentition. The levels were monitored in 3 time periods during 24 h after composite hardening. From every composite material, 4 samples were formed and cured with an LED lamp for 10 s, 20 s, 40 s, and 60 s. After the light curing, the same polishing procedure was used and the samples were leached in blank saliva samples. Results: We observed that every monitored composite material eluted monomers into the saliva after its application. The amount of monomers depended on the time elapsed after the curing of the composite and on the type of composite used. A 40 s LED curing procedure can reduce the amount of leached monomers in comparison with the standard 20 s procedure, especially for monomers of higher molecular weight. Conclusions: Our study confirmed the hypothesis that the release of monomers gradually decreases with increasing time after the hardening of the composite filling.

Synthetic Star Nanoengineered Antimicrobial Polymers as Antibiofilm Agents: Bacterial Membrane Disruption and Cell Aggregation.

Antimicrobial resistance has become a worldwide issue, with multiresistant bacterial strains emerging at an alarming rate. Multivalent antimicrobial polymer architectures such as bottle brush or star polymers have shown great potential, as they could lead to enhanced binding and interaction with the bacterial cell membrane. In this study, a library of amphiphilic star copolymers and their linear copolymer equivalents, based on acrylamide monomers, were synthesized via RAFT polymerization. Their monomer distribution and molecular weight were varied. Subsequently, their antimicrobial activity toward a Gram-negative bacterium (Pseudomonas aeruginosa PA14) and a Gram-positive bacterium (Staphylococcus aureus USA300) and their hemocompatibility were investigated. The statistical star copolymer, S-SP25, showed an improved antimicrobial activity compared to its linear equivalent againstP. aeruginosaPA14. The star architecture enhanced its antimicrobial activity, causing bacterial cell aggregation, as revealed via electron microscopy. However, it also induced increased red blood cell aggregation compared to its linear equivalents. Changing/shifting the position of the cationic block to the core of the structure prevents the cell aggregation effect while maintaining a potent antimicrobial activity for the smallest star copolymer. Finally, this compound showed antibiofilm properties against a robust in vitro biofilm model.

Features of Methyl Methacrylate Polymerization Mediated by Methylene Blue and Ethyl 2-Bromoisobutyrate under Photoirradiation Conditions

Using methyl methacrylate polymerization as an example, the features of polymer synthesis in the presence of the catalytic system [methylene blue + ethyl 2-bromoisobutyrate] at room temperature under visible light irradiation are investigated. The effect of polymerization conditions, including the light irradiation wavelength and various structure activators, on the monomer conversion and molecular weight characteristics of polymers is estimated. It is shown that polymerization can proceed in the controlled mode under mild temperature conditions according to the atom transfer mechanism (Metal Free Atom Transfer Radical Polymerization) to high conversions at low photocatalyst concentrations.

Expression and characterisation of human glycerol kinase: the role of solubilising agents and molecular chaperones.

Glycerol kinase (GK; EC 2.7.1.30) facilitates the entry of glycerol into pathways of glucose and triglyceride metabolism and may play a potential role in Type 2 diabetes mellitus (T2DM). However, the detailed regulatory mechanisms and structure of the human GK are unknown. The human GK gene was cloned into the pET-24a(+) vector and over-expressed in Escherichia coli BL21 (DE3). Since the protein was expressed as inclusion bodies (IBs), various culture parameters and solubilising agents were used but they did not produce bioactive His-GK; however, co-expression of His-GK with molecular chaperones, specifically pKJE7, achieved expression of bioactive His-GK. The overexpressed bioactive His-GK was purified using coloumn chromatography and characterised using enzyme kinetics. The overexpressed bioactive His-GK was purified apparently to homogeneity (∼295-fold) and characterised. The native His-GK was a dimer with a monomeric molecular weight of ∼55 kDa. Optimal enzyme activity was observed in TEA buffer (50 mM) at 7.5 pH. K+ (40 mM) and Mg2+ (2.0 mM) emerged as prefered metal ions for His-GK activity with specific activity 0.780 U/mg protein. The purified His-GK obeyed standard Michaelis-Menten kinetics with Km value of 5.022 µM (R2=0.927) for its substrate glycerol; whereas, that for ATP and PEP was 0.767 mM (R2=0.928) and 0.223 mM (R2=0.967), respectively. Other optimal parameters for the substrate and co-factors were also determined. The present study demonstrates that co-expression of molecular chaperones assists with the expression of bioactive human GK for its characterisation.

Valorization of Grape Pomace as a Renewable Source of Techno-Functional and Antioxidant Pectins.

The food industry's increasing demand for new functional ingredients that meet both organoleptic and healthy requirements has driven the exploration of new sources of functional ingredients in agro-industrial by-products. The aim of this work was to valorize grape pomace (Vitis vinifera L. garnacha) as a source of pectins using food-grade extracting agents. Obtained pectins were evaluated for monomeric composition, methyl esterification, molecular weight, water retention, oil-holding capacity, and antioxidant properties. The relatively soft extraction conditions used permitted obtaining low methoxyl pectin (10-42%) enriched in homogalacturonan (38-45%) or rhamnogalacturonan (33-41%) with different branching degrees, molecular weight, and fewer impurities than those found in the scarce previous literature. The relationship between structure and functionality was studied. Among the different pectins obtained, the sample derived from the extraction with sodium citrate could resume the best characteristics, such as pectin purity and higher water retention and oil holding capacity. These results underscore the relevance of grape pomace as a viable alternative source of pectin.

Metal supported hydrotalcite catalytic depolymerization of lignin: Effects of reaction parameter on compounds distribution

In this study different metal (Ni, Co and Fe) supported hydrotalcite catalysts were synthesis and it was used for lignin depolymerization. Catalytic pyrolysis reactions have been carried out at reaction temperature range of 400 to 550 °C, reaction time 30 to 120 min. with the presence of different amount of metal supported catalysts. From product distribution, it has been found that reaction temperature 500 °C was the optimal temperature for the production of maximum bio-oil yield of 32.4 wt% at reaction time of 60 min reaction. With the addition of the catalysts in pyrolysis, bio-oil significantly increased and maximum bio-oil (47.4 wt%) was found with cobalt supported hydrotalcite catalyst (Co/MgAl2O4). Other catalysts for example Ni/MgAl2O4 and Fe/MgAl2O4 catalyst exhibited bio-oil yield of 42.1 and 43.2 wt%. Different metals on MgAl2O4 showed different properties, which is affecting the lignin depolymerization during the pyrolysis. Catalytic pyrolysis produced higher amount of G-types phenolic monomer with higher bio-oil yield. This is suggesting that Co supported MgAl2O4 catalyst effectively breakdown the ether bond (COC) in the lignin. Elemental analysis and GPC of bio-oil was specified that the macromolecules structure of lignin depolymerized effectively with the using of catalysts. breaking of lignin macromolecule into small monomers phenolic compounds. Co/MgAl2O4 and Fe/MgAl2O4 was effectively encouraged the breaking of raw lignin into low molecular weight monomers as compared to others catalyst. Higher Mw and PDI were obtained for the Fe/MgAl2O4 catalytic pyrolysis reactions due to the repolymerization of monomers are promoted during pyrolysis.

High-Resolution Single-Particle Cryo-EM Hydrated Structure of Streptococcus pyogenes Enolase Offers Insights into Its Function as a Plasminogen Receptor.

Cellular plasminogen (Pg) receptors (PgRs) are utilized to recruit Pg; stimulate its activation to the serine protease, plasmin (Pm); and sterically protect the surface Pm from inactivation by host inhibitors. One such PgR is the moonlighting enzyme, enolase, some of which leaves the cytoplasm and resides at the cell surface to potentially function as a PgR. Since microbes employ conscription of host Pg by PgRs as one virulence mechanism, we explored the structural basis of the ability of Streptococcus pyogenes enolase (Sen) to function in this manner. Employing single-particle cryo-electron microscopy (cryo-EM), recombinant Sen from S. pyogenes was modeled at 2.6 Å as a stable symmetrical doughnut-shaped homooctamer with point group 422 (D4) symmetry, with a monomeric subunit molecular weight of ∼49 kDa. Binding sites for hPg were reported in other studies to include an internal K252,255 and the COOH-terminal K434,435 residues of Sen. However, in native Sen, the latter are buried within the minor interfaces of the octamer and do not function as a Pg-binding epitope. Whereas Sen and hPg do not interact in solution, when Sen is bound to a surface, hPg interacts with Sen independently of K252,255,434,435. PgRs devoid of COOH-terminal lysine utilize lysine isosteres comprising a basic residue, "i", and an anionic residue at "i + 3" around one turn of an α-helix. We highlight a number of surface-exposed potential hPg-binding lysine isosteres and further conclude that while the octameric structure of Sen is critical for hPg binding, disruption of this octamer without dissociation exposes hPg-binding epitopes.

Photoresponsive Adhesives Based on Arylazoisoxazoles‐Containing Polymers

AbstractAdhesives exist in many forms and are essential in the daily life, in industrial processes, and in healthcare, calling for continuous improvements in terms of application fields, strength, biocompatibility, recyclability, and reversibility. Regarding the last two points, embedding photoresponsive molecules into the adhesive allows the use of light to attach or detach reversibly different surfaces. Photoresponsive adhesives can be removed without the use of high temperature or solvents, which is ideal for delicate environments. To date, azobenzenes are the most explored chromophore to prepare smart adhesive formulations. Here, the synthesis of polymer containing arylazoisoxazoles (AIZs) — azobenzene analogs containing a heterocycle — and their application as adhesives is described. Mechanical tests demonstrate an enhancement of the adhesion strength from 0.39 to 2.79 MPa, passing from low molecular weight monomer to selected AIZs acrylate polymer. Irradiation with UV induces the formation of the cis isomer with a consequent drop of more than 70% in the adhesion strength. The different compounds result as possible candidates as adhesives on the basis of the increased load that can be held, together with the possibility to obtain joints that can be either stable or detachable under light irradiation.

Conversion of Lignin into Phenolic Monomer and Low Molecular Weight Bio-oil in Different Supercritical Solvent System

Conversion of Lignin into Phenolic Monomer and Low Molecular Weight Bio-oil in Different Supercritical Solvent System