Reduction In Molecular Weight Research Articles

Unlocking the Potential: PEGylation and Molecular Weight Reduction of Ionenes for Enhanced Antifungal Activity and Biocompatibility.

Numerous synthetic polymers, imitating natural antimicrobial peptides, have demonstrated potent antimicrobial activity, positioning them as potential candidates for new antimicrobial drugs. However, the high activity of these molecules often comes at the cost of elevated toxicity against eukaryotic organisms. In this study, a series of cationic ionenes with varying molecular weights to assess the influence of polymer chain length on ionene activity is investigated. To enhance polymer antimicrobial activity and limit toxicity a PEG side chain is introduced into the repeating unit. The resulting molecules consistently exhibited high activity against three model organisms: E. coli, S. aureus and C. albicans. The incorporation of side PEG chain improves antifungal properties and biocompatibility, regardless of molecular weight. The most important finding of this work is that the reduction of polymer molecular mass led to increased antifungal activity and reduced cytotoxicity against HMF and MRC-5 cell lines simultaneously. As a result, the best-performing molecules reported herein displayed minimal inhibitory concentrations (MIC) as low as 2 and 0.0625µgmL1 for C. albicans and C. tropicalis respectively, demonstrating exceptional selectivity. It is plausible that some of described herein molecules can serve as potential lead candidates for new antifungal drugs.

Effect of silicon dioxide nanoparticles on the rheology properties of fresh and mechanically degraded hydrolyzed polyacrylamide polymer solutions

AbstractPartially hydrolyzed polyacrylamide is extensively utilized in enhanced oil recovery operations. However, its efficacy is compromised by mechanical degradation during transport through injection lines, valves, and reservoir, which leads to a reduction in the average molecular weight, diminishing the solution's viscosity and viscoelastic properties, critical for efficient oil displacement. In this investigation, we characterized the degree of mechanical degradation in HPAM solutions by evaluating shear and extensional rheological parameters preand post‐degradation. Mechanical degradation was induced by subjecting them to controlled flow through a valve featuring varying degrees of constriction and flow rates. Our results demonstrate a significant reduction in zero‐shear viscosity and high‐strain extensional viscosity of mechanically degraded solutions, with reductions of up to 64%. To mitigate this issue, we explored the incorporation of silica nanoparticles as a potential remedy for mechanical degradation. These nanoparticles strengthen the network structure of HPAM, thereby reducing its susceptibility to mechanical degradation. Our findings reveal that shear and extensional viscosities of mechanically degraded NPs‐HPAM solutions experienced only minimal reductions, dropping to 12% and 0%, respectively. This underscores the effectiveness of the nanoparticle‐enhanced HPAM solutions in preserving viscosity and viscoelasticity under mechanical stress, presenting a promising avenue for improving the robustness of EOR processes.

Development and mechanism research of hydrophobic associative polymer drag reducing agents

ABSTRACT The challenge of insufficient proppant transportation capacity in slick water remains unresolved. To tackle this concern, a hydrophobically associating water-soluble polymer (HAWP), characterized by a low molecular weight (MW) of 8.11 × 105 g/mol, was successfully synthesized via a photo-initiation method. The drag reduction mechanism of the material was characterized through nuclear magnetic resonance and rheological performance testing. The drag reduction mechanism of the material was characterized through nuclear magnetic resonance and rheological performance testing. The results show that in comparison to conventional drag reducers in slick water with an average MW of approximately 1 × 107 g/mol, HAWP demonstrates significantly reduced MW. The rheological test results indicate that upon addition of sodium dodecyl benzene sulfonate (SDS, 200 mg/L) to the HAWP solution (0.3 wt%), the storage modulus experienced a substantial increase from 0.14 Pa to 7.42 Pa, demonstrating enhanced mechanical properties. Meanwhile, drag reduction (DR) tests showed that the efficiency of drag reduction achieved by the polymer system (PS) drag reducer was comparable to that of conventional linear polymers. This research achievement effectively addresses the challenges of low molecular weight and resistance reduction encountered in previous endeavors.

Glycerol-driven adaptive evolution for the production of low-molecular-weight Welan gum: Characterization and activity evaluation

Through adaptive laboratory evolution (ALE) of Sphingomonas sp. ATCC 31555, fermentation for production of low-molecular-weight welan gum (LMW-WG) was performed using glycerol as sole carbon source. During ALE, GPC-MALS analysis revealed a gradual decrease in WG molecular weight with the increase of adaptation cycles, accompanied by changes in solution conformation. LMW-WG was purified and structurally analyzed using GPC-MALS, monosaccharide composition analysis, infrared spectroscopy, NMR analysis, atomic force microscopy, and scanning electron microscopy. Subsequently, LMW-WG obtains hydration, transparency, antioxidant activity, and rheological properties. Finally, an in vitro simulation colon reactor was used to evaluate potential prebiotic properties of LMW-WG as dietary fiber. Compared with WG produced using sucrose as substrate, LMW-WG exhibited a fourfold reduction in molecular weight while maintaining moderate viscosity. Structurally, L-Rha nearly completely replaced L-Man. Furthermore, LMW-WG demonstrated excellent hydration, antioxidant activity, and high transparency. It also exhibited resistance to saliva and gastrointestinal digestion, showcasing a favorable colonization effect on Bifidobacterium, making it a promising symbiotic agent.

Structure Identification of Ganoderma lucidum Spore Polysaccharides and Their Antitumor Activity In Vivo.

Ganoderma lucidum spore powder, valued for its nutritional and medicinal properties, contains polysaccharides crucial for its efficacy. However, the complex structural nature of these polysaccharides necessitates further investigation to fully realize their potential. This study aimed to investigate the effects of acid heat treatment on Ganoderma lucidum spore polysaccharides (GLSPs) to enhance their properties and application in antitumor activity. The GLSP was obtained via acid heat treatment, concentration, and centrifugal separation. This process led to a notable reduction in polysaccharide molecular weight, increasing water solubility and bioavailability. Analytical techniques including NMR spectroscopy and methylation analysis revealed a polysaccharide composition comprising four distinct monosaccharides, with molecular weights of 3291 Da (Mw) and 3216 Da (Mn). Six different linkage modes were identified, with a molar ratio of 1:5:2:3:4:3. In vivo experiments demonstrated the GLSP's significant inhibitory effect on the growth of four tumor models (sarcoma S180, Lewis lung cancer, liver cancer H22, and colon cancer C26) in mice, with no observed toxicity. These findings suggest the GLSP's potential as an antitumor therapeutic agent for clinical use.

Control of chain transfer and chain walking by tailored metal–π interactions in polymerization catalysis

Chain walking and chain transfer are pivotal processes that govern the microstructure and molecular weight of polyolefins synthesized via late transition metal-catalyzed ethylene (co)polymerization. In this study, we demonstrate that tailored metal–π interactions using heteroatomic dibenzosuberyl substituents can effectively modulate both chain transfer and chain walking in α-diimine nickel- and palladium-catalyzed systems. This modulation leads to significant reductions in the molecular weight and branching density of the resulting polyethylenes and copolymers. To achieve this, we designed, synthesized, and characterized a series of α-diimine Ni(II) and Pd(II) complexes bearing diverse heteroatomic dibenzosuberyl substituents. In nickel-catalyzed ethylene polymerization, the heteroatomic dibenzosuberyl Ni(II) catalysts showed lower catalytic activities and produced polyethylenes with fewer branches (21–48/1000C vs 83–90/1000C) and an order of magnitude lower molecular weight (2.3–6.5 kg/mol vs 54.6–89.1 kg/mol) than the non-heteroatomic dibenzosuberyl Ni(II) catalyst. Comparable trends were observed in palladium-catalyzed ethylene polymerization and ethylene-MA copolymerization, with sulfur-containing substituents exerting more pronounced effects. We propose a mechanism where the weak metal–π interactions between the dibenzosuberyl substituents and the metal center during polymerization catalysis suppress β-H elimination and promote synergistic chain transfer. This provides a rationale for the observed reductions in molecular weight and branching density, offering valuable insights for the rational design of catalysts for tailored polyolefin synthesis.

Biodegradation of low-density polyethylene film by two bacteria isolated from plastic debris in coastal beach

Low-density polyethylene (LDPE) conduces massive environmental accumulation due to its high production and recalcitrance to environment. In this study, We successfully enriched and isolated two strains, Nitratireductor sp. Z-1 and Gordonia sp. Z-2, from coastal plastic debris capable of degrading LDPE film. After a 30-day incubation at 30 ℃, strains Z-1 and Z-2 decreased the weight of branched-LDPE (BLDPE) film by 2.59 % and 10.27 % respectively. Furthermore, high temperature gel permeation chromatography (HT-GPC) analysis revealed molecular weight reductions of 7.69 % (Z-1) and 23.22 % (Z-2) in the BLDPE film. Scanning electron microscope (SEM) image showed the presence of microbial colonization and perforations on the film's surface. Fourier transform infrared spectroscopy (FTIR) analysis indicated novel functional groups, such as carbonyl and carbon-carbon double bonds in LDPE films. During LDPE degradation, both strains produced extracellular reactive oxygen species (ROS). GC-MS analysis revealed the degradation products included short-chain alkanes, alkanols, fatty acids, and esters. Genomic analysis identified numerous extracellular enzymes potentially involved in LDPE chain scission. A model was proposed suggesting a coordinated role between ROS and extracellular enzymes in the biodegradation of LDPE. This indicates strains Z-1 and Z-2 can degrade LDPE, providing a basis for deeper exploration of biodegradation mechanisms.

Characterization and prebiotic potential of polysaccharides from Rosa roxburghii Tratt pomace by ultrasound-assisted extraction

In this study, polysaccharides (RRTPs) were extracted from Rosa roxburghii Tratt pomace by hot water or ultrasound (US)-assisted extraction. The structural properties and potential prebiotic functions of RRTPs were investigated. Structural characterization was conducted through HPAEC, HPGPC, GC–MS, FT-IR and SEM. Chemical composition analysis revealed that RRTPs extracted by hot water (RRTP-HW) or US with shorter (RRTP-US-S) or longer duration (RRTP-US-L) all consisted of galacturonic acid, galactose, glucose, arabinose, rhamnose and glucuronic acid in various molar ratio. US extraction caused notable reduction in molecular weight of RRTPs but no significant changes in primary structures. Fecal fermentation showed RRTPs could reshape microbial composition toward a healthier balance, leading to a higher production of beneficial metabolites including total short-chain fatty acids, curcumin, noopept, spermidine, 3-feruloylquinic acid and citrulline. More beneficial shifts in bacterial population were observed in RRTP-HW group, while RRTP-US-S had stronger ability to stimulate bacterial short-chain fatty acids production. Additionally, metabolic profiles with the intervention of RRTP-HW, RRTP-US-S or RRTP-US-L were significantly different from each other. The results suggested RRTPs had potential prebiotic effects which could be modified by power US via molecular weight degradation.

Recycling of a commercial biodegradable polymer blend: Influence of reprocessing cycles on rheological and thermo-mechanical properties

Mechanical recycling is a viable option for reducing plastic waste, especially for post-consumer waste and scraps from production processes. Biodegradable polymers have gained attention as alternatives to conventional ones, and their potential for reprocessing using standard techniques before composting needs to be explored. This study focused on a commercial biodegradable polymer blend which underwent ten extrusion cycles to assess the effects of mechanical recycling on mechanical properties, rheological behavior, and thermal stability. The results indicated that the blend's mechanical properties were largely maintained across the extrusion cycles, with only a 53 % decrease in ductility. The thermal stability slightly declined by 2.3 % in T5% onset temperature. This can be attributed to a balance between molecular chain scission (resulting in an average molecular weight reduction of approximately 8.4 %) and crosslinking phenomenon (evidenced by an increase in complex viscosity throughout the extrusion cycles). Overall, the results suggest a suitable recycling attitude of this material.

The impact of mechanical recycling on the degradation of polyamide

There is currently no agreement on the degradation mechanisms for PA6 as a result of mechanical recycling. In this study, PA6 was extruded five times to simulate mechanical melt recycling process. Both virgin PA6 and the extruded PA6 were characterised to determine the predominant degradation mechanism. Melt flow rate (MFR) increases with increasing number of extrusion passes suggesting a reduction in melt viscosity due to mechanical processing. Gel permeation chromatography (GPC) results confirmed a reduction in molecular weight from 18,600 g/mol to 13,100 g/mol. Chain ends titration showed a decrease in the concentration of both the amine and carboxyl chain ends after the fifth extrusion. There were no changes to the chemical structure of the virgin PA6 and extruded PA6 observed from the Fourier transform infra-red (FTIR) and Nuclear magnetic resonance (NMR) spectra. X-ray photoelectron spectroscopy (XPS) showed a reduction in the C–N peak area supporting the scission of the N-alkylamide bond. The increase in the O=C–N peak area suggests that chain recombination via branching is possible. The shorter chains have higher mobility, and this gives rise to an increase in the crystallisation rate as seen from the differential scanning calorimeter (DSC) thermograms. The appearance of the γ phase after the fifth extrusion was identified in the DSC melting endotherms. The understanding of the degradation process of recycled PA6 will enable targeted modifications involving the incorporation of additives in the recycling process to ensure good mechanical properties in the recycled polymer.

Fractionation of Glycans from Hot‐Water Extracts with Ceramic Ultrafiltration Membranes

AbstractExtraction of hemicelluloses from biomass with pressurized hot‐water employs the mechanism of autohydrolysis for molecular weight reduction. In a pilot‐scale extraction of depectinized apple pomace, molecular weight was 30 kDa with a broad mass distribution including monomers and their degradation products. Ultrafiltration with sequential use of ceramic membranes with decreasing cut‐off yielded a suitable fraction with molecular weight of 9 kDa representing 10 % of the extracted hemicelluloses. Further autohydrolytic treatment of the extracted hemicellulose decreases molecular weight while increasing the mass of degradation products. For a series of hydrolysates sequential filtration through ceramic membranes was further tested for fractionation and purification. The efficiency of this fractionation was analyzed by size exclusion chromatography and a total mass balance of the ultrafiltration process is given as an evaluation for suitability of purifying and fraction glycans.

Enhancing the Hydrolytic Stability of Poly(lactic acid) Using Novel Stabilizer Combinations.

Commercially available poly(lactic acid) exhibits poor hydrolytic stability, which makes it impossible for use in durable applications. Therefore, a novel hydrolysis inhibitor based on an aziridine derivative as well as a novel stabilizer composition, containing an aziridine derivative and an acid scavenger, were investigated to improve the hydrolytic stability. To evaluate the stabilizing effect, the melt volume rate (MVR) and molecular weight were monitored during an accelerated hydrolytic aging in water at elevated temperatures. Temperatures were selected according to the glass transition temperature (~60 °C) of PLA. It was shown that the novel hydrolysis inhibitor as well as the novel stabilizer composition exhibited excellent performance during hydrolytic aging, exceeding commercially available alternatives, e.g., polymeric carbodiimides. A molecular weight analysis resulted in a molecular weight decrease of only 10% during approximately 850 h and up to 20% after 1200 h of hydrolytic aging, whereas poly(lactic acid) stabilized with a commercial polycarbodiimide revealed comparable molecular weight reductions after only 300 h. Furthermore, the stabilization mechanism of the aziridine derivative alone, as well as in the synergistic combination with the acid scavenger (calcium hydrotalcite), was investigated using nuclear magnetic resonance (NMR) spectroscopy. In addition to an improved hydrolytic stability, the thermal properties were also enhanced compared to polymeric carbodiimides.

Fast insights into chitosan-cleaving enzymes by simultaneous analysis of polymers and oligomers through size exclusion chromatography

The thorough characterization of chitosan-cleaving enzymes is crucial to unveil structure–function relationships of this promising class of biomolecules for both, enzymatic fingerprinting analyses and to use the enzymes as biotechnological tools to produce tailor-made chitosans for diverse applications. Analyzing polymeric substrates as well as oligomeric products has been established as an effective way to understand the actions of enzymes, but it currently requires separate, rather laborious methods to obtain the full picture. Here, we present ultra high performance size exclusion chromatography coupled to refractive index and mass spectrometry detection (UHPSEC-RI-MS) as a straightforward method for the semi-quantitative analysis of chitosan oligomers of up to ten monomers in length. Additionally, the method allows to determine the average molecular weight of the remaining polymers and its distribution. By sampling live from an ongoing enzymatic reaction, UHPSEC-RI-MS offers the unique opportunity to analyze polymers and oligomers simultaneously—i.e., to monitor the molecular weight reduction of the polymeric substrate over the course of the digestion, while at the same time analyzing the emerging oligomeric products in a semi-quantitative manner. In this way, a single simple analysis yields detailed insights into an enzyme’s action on a given substrate.

Dynamic changes in ferulic acid and diferulic acids in wheat flour doughs during the breadmaking process

Ferulic acid (FA), a phytochemical concentrated in wheat bran, influences structural characteristics of arabinoxylan (AX) and rheological properties of wheat dough. This study investigates the dynamic changes in FA and diferulic acids, closely associated with AX molecular weight, during the breadmaking process. FA predominantly exists in a tightly bound state within the arabinoxylan matrix, with a substantial increase in free FA content observed during the initial fermentation phase. Furthermore, this research identified four specific wheat-derived diferulic acids: 8–5′-DFA, 5–5′-DFA, 8-O-4′-DFA, and 8–5′-DFA (benzofuran form), tracking their variations throughout breadmaking. The notable upsurge in diferulic acid levels in the early fermentation stages suggests that the cleavage of ferulic acid moieties may not be the primary factor contributing to the reduction in AX molecular weight. Future investigations into the effects of FA and diferulic acids on arabinoxylan and wheat dough properties promise to enhance understanding of the intricacies of the breadmaking process.

Sample transformation in online separations: how chemical conversion advances analytical technology.

While the advent of modern analytical technology has allowed scientists to determine the complexity of mixtures, it also spurred the demand to understand these sophisticated mixtures better. Chemical transformation can be used to provide insights into properties of complex samples such as degradation pathways or molecular heterogeneity that are otherwise unaccessible. In this article, we explore how sample transformation is exploited across different application fields to empower analytical methods. Transformation mechanisms include molecular-weight reduction, controlled degradation, and derivatization. Both offline and online transformation methods have been explored. The covered studies show that sample transformation facilitates faster reactions (e.g. several hours to minutes), reduces sample complexity, unlocks new sample dimensions (e.g. functional groups), provides correlations between multiple sample dimensions, and improves detectability. The article highlights the state-of-the-art and future prospects, focusing in particular on the characterization of protein and nucleic-acid therapeutics, nanoparticles, synthetic polymers, and small molecules.

Structural, chemical and technofunctional properties pectin modification by green and novel intermediate frequency ultrasound procedure

The impact of intermediate frequency ultrasound (IFUS, 582, 864 and 1144 kHz), mode of operation (continue and pulsed) and ascorbic acid (Aa) addition on the structural, chemical and technofunctional properties of commercial citrus high methoxyl-grade pectin (HMP) was investigated. The chemical dosimetry of IFUS, monitored by the triiodide formation rate (I3−), demonstrated that the pulsed ratio (1900 ms on/100 ms off) at the three frequencies was similar to that of continue mode but IFUS1144 kHz produced more acoustic streaming demonstrated by the height liquid measured using image analysis. In presence of Aa, HMP presented higher fragmentation than in its absence. IFUS did not give rise any changes in the main functional groups of the HMP. In general, a reduction in molecular weight was observed, being the presence of Aa the most influencing factor. Regarding monosaccharides, IFUS modified the structure of homogalacturonan and rhamnogalacturonan-I and increased of GalA contents of the HMP in presence of Aa at the above three frequencies. A reducing of the consistency index (k) and increasing of the flow index (n) of HMP were showed by IFUS frequency and Aa addition. The emulsifying activity and stability index were increased for HMP treated by IFUS in continue mode at all frequencies and in presence of Aa. The results presented in this research shown the effectiveness of IFUS as tool to modify pectin into different structures with different functionalities.

Kinetic Phenomena in Mechanochemical Depolymerization of Poly(styrene)

Kinetic Phenomena in Mechanochemical Depolymerization of Poly(styrene)

Modification of pectin with high-pressure processing treatment of fresh orange peel before pectin extraction: Part I. The effects on pectin extraction and structural properties

The possibility of utilizing endogenous plant pectin methyl-esterase (PME) to modify pectin in source material prior to pectin extraction is proposed and explored in this study. This is based on the reports about activation of endogenous PME in plant-based foods by high-pressure processing (HPP) treatment. Fresh orange (Hamlin) peel from a local commercial juice plant was pretreated with HPP at different combinations of pressures and durations, followed by pectin extraction with a commercial method. The effects of HPP pretreatments on pectin yield and structural properties of the extracted pectins were determined. HPP pretreatment increased the yield of subsequent pectin extraction by 41.10 %. Crude extracts from HPP-treated peels showed higher PME activities than the untreated peel. Pectins extracted from HPP pretreated peel (Hp) had a lower degree of methyl-esterification (DM), accompanied by an increase in degree of blockiness (DB) of non-esterified galacturonic acid (GalA) than the control (pectin extracted from un-treated peel). GalA content and linearity of pectin (LP) were higher, while neutral sugar content and degree of branching (DBr) were lower in Hp. The reduction in weight average molecular weight of Hp was minor, and it was positively correlated with a reduction in neutral sugars, indicating an effect of pectin debranching without degradation of the pectin main chain. The effects of HPP on the pectin main chain, degree, and distribution of methyl-esterification in this study were similar to the reported effects of orange PME on extracted pectin. The identified pectin structural features were validated by Fourier Transform Infrared Spectroscopy analysis and a newly developed lateral flow assay. The study indicates that HPP modification of pectin structure in fresh orange peel before pectin extraction may be an efficient and economical way to generate pectin with desirable structural features and to increase pectin yield.

Viscosity, mixing regime and power consumption analysis during enzymatic hydrolysis of fish (Sardina pilchardus) processing by-products, through development of power number and Reynolds number correlations

The influence of processing conditions on fluid rheology and mixing regime is of considerable importance during enzymatic hydrolysis of fish processing by-products. Solids concentration ranging from 30 to 70 % (wet basis) and mixing speed from 100 to 400 rpm were investigated, with apparent viscosity, power consumption, power number (Np) and Reynolds number (Re) as response variables of interest. The fish processing by-products at different solids concentration showed power-law pseudoplastic behaviour. Apparent viscosity ranged from 4.35 to 8.51 mPa·s, and power consumption ranged from 53.0 to 492 W/m3. Np―Re curves showed the typical relationship where Np decreased from 20.4 to 1.99 when Re increased from 425 to 3 317. Poor mixing was observed at high solids concentration and low mixing speed, with cavern formation in the early stages of mixing. Liquefaction of solids led to the disappearance of caverns, resulting in good degree of mixing during the hydrolysis process. Contrary to expectations, our study indicated that liquefaction of solids and reduction in molecular weight of proteins had a significant effect on power consumption more than increase in soluble protein concentration, gel formation and/or emulsion. Liquefaction and molecular weight reduction caused a decrease in fluid viscosity while increase in protein concentration, gel formation and/or emulsion contributed to an increase in viscosity. The net result was a decrease in power consumption from 0 to 60 min of enzymatic hydrolysis. The practical implications of the results presented in this study are that one Np―Re curve can be used for any solids concentration between 30 and 50 %. Beyond 50 %, low degree of hydrolysis, protein recovery and significantly high power consumption are experienced.

Recyclability of a bio-based biocomposite under different reprocessing conditions

The present paper studies the effect of reprocessing, on both dry and wet reprocessing conditions, on the rheological and mechanical properties of a biocomposite made of a bio-based, biodegradable polymer with 40 wt% wood flour. The results show that the viscosity of the matrix decreases as the number of extrusions increases, with the greatest reduction for samples processed under wet conditions. The same behavior was observed for the biocomposite, but since the viscosity of the biocomposite is much higher than that of the matrix, this causes a greater reduction of molecular weight. Mechanical results show that properties such as tensile strength and elongation decrease as the number of extrusions increases for the matrix. In terms of maximum variations, the tensile strength experiences a decrease of approximately 18%, while the elongation at break shows a more significant reduction of about 40%. Conversely, the biocomposite shows an increase in tensile strength (about 30%) and elongation at break (about 90%) after the first extrusion and then a slight decrease, but with values of tensile strength and elongation higher than those of the virgin biocomposite.