Increase In Melting Temperature Research Articles

Clean and Complete Protein Digestion with an Autolysis Resistant Trypsin for Peptide Mapping.

Peptide mapping requires cleavage of proteins in a predictable fashion so that target protein-specific peptides can be reliably identified and quantified. Trypsin, a commonly used protease in this process, can also undergo self-cleavage or autolysis, thereby reducing the effectivity and even cleavage specificity at lysine and arginine residues. Here, we report highly efficient and reproducible peptide mapping of biotherapeutic monoclonal antibodies. We highlight the properties of a homogeneous chemically modified trypsin on thermal stability, a 54% increase in melting temperature with an 84% increase in energy required for unfolding, an indication of more thermally stable trypsin, >90% retained intact mass peak area after exposure to digestion conditions confirming autolysis resistance, 10× more intensity for intact enzyme compared to trypsin of similar source and narrower molecular weight distribution with LC-MS indicative of low degradation compared to 3 other types of trypsin. Finally, we show the utility of this autolysis-resistant trypsin in characterizing biotherapeutic monoclonal antibodies consistently and reliably showing a >30% reduction in missed cleavage for a short-duration protein digestion time of 30 min compared to heterogeneously modified trypsin of a similar source.

The microstructural development and erosion mechanism of BaZrO3/Al2O3 double ceramics by Ti–46Al–8Nb alloy melt

In this study, the erosion of BaZrO3/Al2O3 double ceramics by Ti–46Al–8Nb alloy melt was investigated at different melting temperatures (1833 K, 1873 K and 1913 K) and time (1800 s, 3600 s, 5400 s and 7200 s). The microstructure of erosion layer and the alloy ingot were analyzed as well as the oxygen content of the alloy ingot. The erosion mechanism was clarified in the kinetic perspectives. The results showed that the new oxide BaAl2O4 production was attached on the ingot surface, and two kinds of inclusions, i.e., (Ti, Zr)5(Si, Al)3 and YAlO3, were formed in the ingot matrix. The thickness of erosion layer, the oxygen content of ingot, and the volume fraction of inclusions increased with increasing melting temperatures and time. In addition, these three phenomena were controlled by the kinetics of dissolution, and the time exponents were approximately equaled to 0.5, indicating that the erosion mechanism was dissolution controlled by mutual diffusion between the double ceramics and alloy melts. The activation energies of three phenomena were determined by Arrhenius equation, and three kinetic models were further established.

Computer-Aided Site-Specific PEGylation of PET Hydrolases for Enhanced PET Degradation.

The enormous accumulation of poly(ethylene terephthalate) (PET) waste has posed a serious threat to the environment and human health, and biodegradation with PET hydrolase (PETase) can be a possible solution. Herein, we propose site-specifically modifying PETase with amphiphilic polymers to improve the enzyme performance at ambient temperature. For this purpose, we devise a computer-aided strategy to prioritize the conjugation site, and polyethylene glycol (PEG) preparations of 0.55 to 10 kDa are site-specifically conjugated to PETase. The most active conjugate PETase-PEG 5k (PETase-5K) shows an increase of melting temperature (3.88 °C) and significantly improves PET degradation performance (3.5- and 3.1-fold increases at 30 and 40 °C, respectively). Experimental investigation and molecular dynamics simulations reveal that the site-specific PEGylation increases the hydrophobic solvent-accessible surface area and the binding capability to the PET surface, thickens the hydration layer, increases the intramolecular hydrogen bonding, reduces the interactions between water and the conjugated enzyme surface, and rigidifies the enzyme structure via hydrogen bonding and hydrophobic interactions between the polymer and the enzyme, thus leading to improved enzymatic performance of PETase-5K. We further validate the versatility of the site-specific PEGylation in one of the most evolved variants of PETase, FAST-PETase, by 1.8-fold improvement in PET degradation at 30 °C. The presented computer-aided site-specific conjugation strategy has opened a new avenue to enhancing PETase performance at ambient temperature, and the contribution of PEGylation to PETase unraveled in this work laid a foundation for the rational engineering of PET hydrolases.

Insights into the Main Protease of SARS-CoV-2: Thermodynamic Analysis, Structural Characterization, and the Impact of Inhibitors.

The main protease (Mpro) of SARS-CoV-2 is an essential enzyme for coronaviral maturation and is the target of Paxlovid, which is currently the standard-of-care treatment for COVID-19. There remains a need to identify new inhibitors of Mpro as viral resistance to Paxlovid emerges. Here, we report the use of native mass spectrometry coupled with 193 nm ultraviolet photodissociation (UVPD) and integrated with other biophysical tools to structurally characterize Mpro and its interactions with potential covalent inhibitors. The overall energy landscape was obtained using variable temperature nanoelectrospray ionization (vT-nESI), thus providing quantitative evaluation of inhibitor binding on the stability of Mpro. Thermodynamic parameters extracted from van't Hoff plots revealed that the dimeric complexes containing each inhibitor showed enhanced stability through increased melting temperatures as well as overall lower average charge states, giving insight into the basis for inhibition mechanisms.

Boosting Fructosyl Transferase's Thermostability and Catalytic Performance for Highly Efficient Fructooligosaccharides (FOS) Production.

Achieving enzymatic food processing at high substrate concentrations can significantly enhance production efficiency; however, related studies are notably insufficient. This study focused on the enzymatic synthesis of fructooligosaccharides (FOS) at high temperature and high substrate concentration. Results revealed that increased viscosity and limited substrate solubility in high-concentration systems could be alleviated by raising the reaction temperature, provided it aligned with the enzyme's thermostability. Further analysis of enzyme thermostability in real sucrose solutions demonstrates that the enzyme's thermostability was remarkedly improved at higher sucrose concentrations, evidenced by a 10.3 °C increase in melting temperature (Tm) in an 800 g/L sucrose solution. Building upon these findings, we developed a novel method for enzymatic FOS synthesis at elevated temperatures and high sucrose concentrations. Compared to existing commercial methods, the initial transglycosylation rate and volumetric productivity for FOS synthesis increased by 155.9% and 113.5%, respectively, at 65 °C in an 800 g/L sucrose solution. This study underscores the pivotal role of substrate concentration, incubation temperature, and the enzyme's actual status in advancing enzyme-catalyzed processes and demonstrates the potential of enzymatic applications in enhancing food processing technologies, providing innovative strategies for the food industry.

Stereoregular Poly(Phenyl Glycidyl Ethers): In Situ Formation of a Polyether Stereocomplex from a Racemic Monomer Mixture

Polymer stereocomplex formation represents a promising research area as it can improve thermal and mechanical properties of co‐crystallized polymer strands of opposite chirality. Polymers that form stereocomplexes commonly feature high stereoregularity and usually require sourcing from enantiopure monomer building blocks. Herein, we report the in situ polyether stereo­complex formation from racemic epoxide monomers, i.e., substituted methyl phenyl glycidyl ethers. The bio‐renewable glycidyl ethers were explored in both enantio‐ and isoselective ring‐opening polymerizations (ROPs), resulting in isotactic poly(phenyl glycidyl ether). While the enantio­selective ROP selectively resolves a single enantiomeric, isotactic polyether stereoisomer ([mm]P ≥ 78%), the isoselective ROP leads to the concurrent formation of both isotactic (R)‐ and (S)‐poly(phenyl glycidyl ether) stereoisomers ([mm]P ≥ 92%) and thus results directly in a stereoisomer blend, which forms a stereocomplex. This is one of only a few polymer stereocomplexes generated directly during polymerization from a racemic monomer mixture. Stereo­complexes of the different poly(phenyl glycidyl ether)s show an increase in melting temperature of up to 76 °C, relative to the enantiopure parent polymers. The position of the methyl group at the phenyl ring determines both stereocomplex formation and the thermal properties of the resulting materials.

Stereoregular Poly(Phenyl Glycidyl Ethers): In Situ Formation of a Polyether Stereocomplex from a Racemic Monomer Mixture.

Polymer stereocomplex formation represents a promising research area as it can improve thermal and mechanical properties of co-crystallized polymer strands of opposite chirality. Polymers that form stereocomplexes commonly feature high stereoregularity and usually require sourcing from enantiopure monomer building blocks. Herein, we report the in situ polyether stereo-complex formation from racemic epoxide monomers, i.e., substituted methyl phenyl glycidyl ethers. The bio-renewable glycidyl ethers were explored in both enantio- and isoselective ring-opening polymerizations (ROPs), resulting in isotactic poly(phenyl glycidyl ether). While the enantio-selective ROP selectively resolves a single enantiomeric, isotactic polyether stereoisomer ([mm]P ≥ 78%), the isoselective ROP leads to the concurrent formation of both isotactic (R)- and (S)-poly(phenyl glycidyl ether) stereoisomers ([mm]P ≥ 92%) and thus results directly in a stereoisomer blend, which forms a stereocomplex. This is one of only a few polymer stereocomplexes generated directly during polymerization from a racemic monomer mixture. Stereo-complexes of the different poly(phenyl glycidyl ether)s show an increase in melting temperature of up to 76 °C, relative to the enantiopure parent polymers. The position of the methyl group at the phenyl ring determines both stereocomplex formation and the thermal properties of the resulting materials.

Disulfide Bond Engineering of Soluble ACE2 for Thermal Stability Enhancement.

Although the primary pandemic of SARS-CoV-2 is over, there are concerns about the resurgence of the next wave of related viruses, including a wide range of variant viruses. The soluble ACE2 (sACE2) inhibits the SARS-CoV-2 spike protein ACE2 interaction and has potential as a variant-independent therapeutic against SARS-CoV-2. Here, we introduce novel disulfide bonds in the wild-type sACE2-Fc by structure-guided mutagenesis, aiming to improve its stability. The stability of each mutant was assessed by a thermal shift assay to screen mutants with increased thermal stability. As a result, we identified a mutant sACE2-Fc with a significantly increased melting temperature. X-ray crystal structure determination of the sACE2 mutant confirmed the correct formation of the designed disulfide bond, and there were no significant structural disturbances. We also proved that the thermostable sACE2-Fc preserved the spike protein binding affinity comparable to the wild-type sACE2-Fc in both molecular and cellular environments, suggesting its therapeutic potential.

Effect of carboxymethyl cellulose incorporation to gelatin‐sunflower oil bigel on the physicochemical and structural properties

AbstractBigels are innovative and appealing heterogeneous matrices composed of two structured‐gel (hydrogel and oleogel) phases, which suitable for the entrapment of both hydrophilic and lipophilic active agents. As structuring the bigel phases using convenient materials can enhance the main characteristics, this study aimed to develop bigel system based on a hybrid hydrogel consisting of gelatin and carboxymethylcellulose (CMC). The impact of incorporating various concentrations of CMC (0, 0.5, 1, 2, and 3% w/w) into gelatin‐based hydrogel at a constant organogel/hydrogel ratio of 60:40 was investigated on bigel properties. The integration of gelatin and CMC significantly affected the solvent holding capacity (SHC), microstructure, rheology, thermal, and textural properties. The results showed that bigel samples containing gelatin‐CMC had lower SHC compared to gelatin‐based samples. The integration of CMC to bigel formulation resulted in a significant decrease in hardness, cohesiveness, and adhesiveness also smooth texture. Differential scanning calorimeter (DSC) analysis of the bigels showed a descending trend in melting point from 99.07 to 98.60°C for bigel samples as the CMC concentration increased from 0% to 2%. This was followed by an increase in melting temperature (100.95°C) in the bigel containing 3% CMC. Particle size distribution data indicated that the droplet sizes of the bigels increased with the incorporation of CMC into the hydrogel phase, without displaying a distinct concentration‐dependent trend. The rheological characteristics of strain sweep, frequency sweep, and loss factor affected by gelatin/CMC concentration. Overall obtained results highlight that CMC incorporation to gelatin plays a crucial role in bigel offering different textural, rheological and thermal properties. So that carefully selection and optimization of gelatin and CMC concentrations in hydrogel phase are essential for tailoring the mechanical strength and stability of bigels for various applications such as drug delivery, cosmetic, and food industries. Regarding the desired properties of CMC, it could be recommend to use by combination with gelatin to create a structure–function aimed bigels.

Influence of synthetic carbon grade on the metabolic flux of polyhydroxyalkanoate monomeric constitution synthesized by Bacillus cereus AAR-1

Carbon substrate is a pivotal factor influencing polyhydroxyalkanoate (PHA) properties of varied industrial importance. Three synthetic sucrose samples with varying manufacturing purity levels were selected as carbon substrates to synthesize diverse PHAs using a wild-type Bacillus cereus AAR-1. Comparative monomeric analyses of the extracted biopolymers revealed Poly (3-hydroxytetradecanoate) (P3HTD), Poly(3-hydroxybutyrate-co-2-hydroxytetradecanoate) [P(3HB-co-2HTD)], and Poly(3-hydroxybutyrate) (P3HB) with carbon elemental contents that ranged from 39 to 53 % and no nitrogen detected. The decomposition temperature of [P(3HB-co-2HTD)] was 279 °C, indicating higher thermal stability than the individual monomeric units. Notably, the homopolymer P3HTD exhibited an increased melting temperature of 172.4 °C and a reduced crystallinity percentage (Xc % = 20.7 %), crucial properties for bioplastics and medical sector applications. All the biopolymers displayed a low specific heat capacity ranging between 0.03 and 0.05 J/g°C, suitable for applications such as thermal storage materials and temperature-regulating textiles. The results suggest that different carbon purity grades influenced homopolymer accumulated in Bacillus cereus AAR-1.

Biochemical characterization of naturally occurring mutations in SARS-CoV-2 RNA-dependent RNA polymerase.

Since the emergence of SARS-CoV-2, mutations in all subunits of the RNA-dependent RNA polymerase (RdRp) of the virus have been repeatedly reported. Although RdRp represents a primary target for antiviral drugs, experimental studies exploring the phenotypic effect of these mutations have been limited. This study focuses on the phenotypic effects of substitutions in the three RdRp subunits: nsp7, nsp8, and nsp12, selected based on their occurrence rate and potential impact. We employed nano-differential scanning fluorimetry and microscale thermophoresis to examine the impact of these mutations on protein stability and RdRp complex assembly. We observed diverse impacts; notably, a single mutation in nsp8 significantly increased its stability as evidenced by a 13°C increase in melting temperature, whereas certain mutations in nsp7 and nsp8 reduced their binding affinity to nsp12 during RdRp complex formation. Using a fluorometric enzymatic assay, we assessed the overall effect on RNA polymerase activity. We found that most of the examined mutations altered the polymerase activity, often as a direct result of changes in stability or affinity to the other components of the RdRp complex. Intriguingly, a combination of nsp8 A21V and nsp12 P323L mutations resulted in a 50% increase in polymerase activity. To our knowledge, this is the first biochemical study to demonstrate the impact of amino acid mutations across all components constituting the RdRp complex in emerging SARS-CoV-2 subvariants.

Enhancing monoclonal antibody stability during protein a chromatography using 2-methyl imidazolium dihydrogen phosphate

This study investigates the impact of 2-methyl imidazolium dihydrogen phosphate (2-MIDHP) on monoclonal antibody (mAb) aggregation during the Protein A purification stage, at a low pH (pH 3.0), and the viral inactivation phase. Size-exclusion high-performance liquid chromatography (SE-HPLC) and dynamic light scattering (DLS) were used to assess the mAb aggregation. Additionally, the influence of 2-MIDHP on mAb recovery, host cell protein (HCP) clearance, and Protein A leaching was investigated. Thermal stability of mAb, eluted in buffers containing 5 % to 25 % 2-MIDHP was analysed, using differential scanning calorimetry (DSC). Structural insights were obtained via circular dichroism (CD) and fluorescence spectroscopy. Our findings indicated that 2-MIDHP exerted a concentration-dependent protective effect against mAb aggregation, at the pH of 3.0. As the concentration of 2-MIDHP was increased from 0 % to 25 %, the aggregation was significantly reduced from 3.8 ± 0.01 % to 0.56 ± 0.002 %, as analysed by SE-HPLC. Addition of 2-MIDHP did not significantly impact the mAb recovery, HCP clearance, or Protein A leaching. DSC data supported these results, with higher 2-MIDHP concentrations leading to increased melting temperatures of mAb. CD and fluorescence spectroscopy revealed no significant changes in the secondary structure or aromatic residue environment in 2-MIDHP-treated samples, despite the observed reduction in aggregation. The results suggested that 2-MIDHP mitigated mAb aggregation during Protein A purification, possibly by stabilizing the protein structure under acidic stress conditions. These findings offer valuable insights for improving the robustness of mAb purification processes, enhancing product quality and yield.

Explore the fascinating realm of comparing metal melting curves by applying the equation of state and Lindemann's law

Our research, which is not just theoretical but also has practical implications, is a comprehensive study that aims to find the equation of state needed to calculate the pressure-dependent melting curves of metals. We have introduced a unique model for the melting curve, utilizing equations of state such as those proposed by Srivastava-Pandey and Kholiya. This model has been compared with Lindemann's model and available experimental data. It establishes the relationship between pressure, bulk modulus, pressure derivative of bulk modulus, and volume compression. Our findings show that a significant increase in melting temperature is directly linked to a substantial rise in bulk modulus and a gradual decrease in the first-order pressure derivative of bulk modulus. This study provides insights into understanding the effect of pressure on melting temperature. The present study finds that the equation of state of Srivastava-Pandey is more suitable for describing the melting temperature of metals, which could have significant implications for material science and engineering.

Sustainable lignin-based powder coatings doped with ZnO displayed excellent UV resistance properties

Lignin with increased polyhydroxyl content (LOH) was prepared via a one-pot synthesis using enzymatically hydrolyzed lignin (EHL) as the raw material. The modified structure and hydroxyl content of LOH were analyzed using FT-IR, 1H NMR, and 31P NMR. LOH was blended with zinc oxide (ZnO), polyester resin and hydroxyl alkyl amide (HAA) to prepare polyester powder coatings. The anti-UV properties of the coating were significantly enhanced by the addition of LOH and ZnO. The coating exhibits exceptional adhesion, rating at level 0, and achieves a pencil hardness of 7H. The gel time for the coating is 195 s, and it has a 5-degree Celsius increase in melting temperature, which greatly enhances its storage stability. Considering a range of factors, the formula LOH7.5 % has been identified as the optimal composition. The results of this study demonstrate an easy approach to developing sustainable lignin-based powder coatings with excellent properties.

Synergistic Effects of Heated Walnut Shell Powder and Reduced Graphene Oxide in Paraffin Wax Composites for Marine Thermal Applications

The study focuses on creating and analyzing paraffin wax composites enriched with heated walnut shell powder and reduced graphene oxide nanoparticles. Experimental procedures include careful blending of materials to form homogeneous mixtures, followed by analysis using techniques such as thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The composites show improved thermal properties compared to pure paraffin wax, with increased melting temperatures, heat of fusion, and thermal conductivity. The study also examines density and thermal diffusivity, providing insights into thermal behavior. Additionally, it ensures the corrosion resistance of nano-enhanced bio-based phase change materials (PCMs) for marine engineering through thorough material selection, corrosion testing, and long-term exposure studies simulating seawater conditions. The study evaluates environmental impacts, toxicity, and compliance with standards and proposes mitigation strategies like protective coatings and encapsulation techniques. Overall, the research contributes to developing environmentally sustainable PCM materials for marine applications and offers insights into their thermal behavior for thermal energy storage and management.

Lipid composition affects the thermal stability of cytochrome P450 3A4 in nanodiscs

Nanodiscs (NDs), self-assembled lipid bilayers encircled by membrane scaffold proteins (MSPs), offer a versatile platform for the reconstitution of membrane proteins for structural and biochemical investigations. Saturated, isoprenoid lipids are commonly found in thermophiles and have been associated with thermotolerance. To test whether these lipids confer additional stability on ND-incorporated membrane proteins, this study focuses on the thermal stability of human cytochrome P450 3A4 (CYP3A4) inside NDs composed of different phosphocholine lipids: 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), and 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC). NDs were characterized using size-exclusion chromatography coupled with multi-angle light scattering (SEC-MALS) and densitometric SDS-PAGE. CYP3A4-DPhPC-NDs were found to comprise three MSP copies instead of the canonical dimer, as reported before for the empty NDs. Rapid, thermally induced unfolding of CYP3A4 inside NDs measured using circular dichroism and differential scanning fluorimetry (nanoDSF) revealed that the CYP3A4 melting temperature was dependent on ND composition. In POPC and DMPC-CYP3A4-NDs the melting temperature was comparable to CYP3A4 without NDs (59 °C). CYP3A4 in DPhPC-NDs showed an increase in melting temperature of 4 °C. Decline in CYP3A4 integrity as well as ND aggregation and disintegration occur at similar rates for all membrane types when subjected to exposure at 37 °C for several hours. The POPC and DMPC- CYP3A4-NDs show significant lipid loss over time, which is not observed for DPhPC-NDs. The results demonstrate that thermally induced denaturation of protein-NDs is a complex, multifaceted process, which is not represented well by rapid thermal unfolding experiments.

Electrospun O-quaternary ammonium chitosan/polyvinyl alcohol nanofibrous film by application of Box–Behnken design response surface method for eliminating pathogenic bacteria

In this study, O-quaternary ammonium chitosan (O-HTCC) containing bicationic antibacterial active groups was synthesized to develop an O-HTCC/PVA porous nanofibrous film to enhance antibacterial activity, leveraging surface modification and nano-porous structure design. Uniform and smooth nanofibrous structures (average diameter: 72–294 nm) were successfully obtained using a simple and feasible electrospinning method. A response surface model via Box-Behnken design (BBD) was used to clarify the interaction relationship between O-HTCC fiber diameter and three critical electrospinning parameters (O-HTCC concentration, applied voltage, feed flow rate), predicting that the minimum O-HTCC fiber diameter (174 nm) could be achieved with 7 wt% of O-HTCC concentration, 14 kV of voltage, and 0.11 mL/h of feed flow rate. Linear regression (R2 = 0.9736, Radj2 = 0.9716) and the Anderson Darling test demonstrated the excellent fit of the RSM-BBD model. Compared to N-HTCC/PVA nanofibrous film, the O-HTCC/PVA version showed increased growth inhibition and more effective antibacterial efficacies against Escherichia coli (E. coli) (~;86.34 %) and Staphylococcus aureus (S. aureus) (~;99.99 %). DSC revealed improved thermal stability with an increased melting temperature (238 °C) and endothermic enthalpy (157.7 J/g). This study holds potential for further development of antibacterial packaging to extend food shelf-life to reduce bacterial infection.

A pH-sensitive film based on chitosan/gelatin and anthocyanin from Zingiber striolatum Diels for monitoring fish freshness

As a new type of packaging method, the anthocyanin-based pH-sensitive indicator film has gained much attention owing to low cost, small size, and visually informative property. In this study, an intelligent film based on chitosan/gelatin (CG) matrix with Zingiber striolatum Diels (ZSD) anthocyanin for fish freshness monitoring was developed. The film properties, including thickness, moisture content, color, mechanical properties, UV–vis light barrier property, as well as pH and ammonia sensitivity, were evaluated. The CG-ZSD films exhibited a more compact structure when compared with the CG film. The CG-ZSD20 film showed the highest elongation at break (6.33 ± 0.62%) and lowest tensile strength (20.0 ± 0.58 MPa). FTIR spectra revealed the strong hydrogen bond interactions between ZSD and polymer matrix. Film incorporated with 15% anthocyanin extract has increased melting temperature at 118.9 °C, and a lower weight loss (13.8%) at melting temperature. In pH 1–14 buffer, the color of CG-ZSD films underwent a significant change from red to yellow-green. The CG-ZSD15 film was utilized for monitoring fish freshness and showed visible color changes from deep purple to brown. The total volatile basic nitrogen content and pH value changes of fish were closely related to the visual color changes in film. This demonstrated that the film was a highly pH-sensitive film for quantifying fish freshness in real-time.

Synthesis and properties of biodegradable PBAT prepared from PBT chemically recycled resources

The production of synthetic polymer materials has engendered substantial environmental hazards stemming from waste generation. Employing chemical recycling methods constitutes a viable approach for attaining sustained recycling of synthetic raw materials. In the present study, bishydroxybutyl terephthalate (BHBT), a precursor for the synthesis of poly(butylene adipate-co-terephthalate) (PBAT), was created by chemically alcoholyzing polybutylene terephthalate (PBT). Further, bis(4-hydroxybutyl) adipate (BHAT), which was produced via esterification with adipic acid (AA) and 1,4-butanediol (BDO), and BHBT condensation polymerization were combined to create biodegradable PBAT. Additionally, the effects of the recycled BHBT and BHAT segment ratio on the structures and properties of biodegradable PBAT were investigated. The results indicate that the synthesis of repolymerized PBAT was accomplished successfully. As the proportion of butylene terephthalate (BT) segments increased, several notable improvements were observed: an increase in melting temperature, enhanced thermal stability, elevated tensile strength, and a reduction in the rate of biodegradation. The melting point was 139.51 °C, the tensile strength was 22.62 MPa, and the 30-day biodegradation rate was 23.32 % when the percentage of BT segments was 60 %. In the present study, a method for producing biodegradable polyesters through the process of alcoholysis and repolymerization of recalcitrant polyester waste was proposed. It provides a new solution for the efficient recycling of waste polymer materials.

Effect of alkyl chain length on the thermal properties and toxicity of n-alkyl-ammonium nitrate ionic liquids (n = 2, 3, 4, 5, 6, 8) for energy applications

AbstractThe most currently used ionic liquids (ILs) are protic ionic liquids (PILs), subject to extensive investigation regarding their physical properties. These compounds along with their mixtures with other substances such as salts and solvents, serve as electrolytes in next generation electrochemical smart devices, and emerge as viable candidates to replace conventional Heat Transfer Fluids (HTFs) in various energy applications. Despite the extensive number of studies, important information about this kind of compounds is still unknown, such as the effect of alkyl chain length on thermal and thermophysical properties, as well as toxicity. This work, extending previous studies of our group, summarizes the liquid range, heat capacity and acute toxicity level of six ammonium ILs: specifically, n-alkyl-ammonium nitrate ILs with increasing alkyl chain length (n = 2, 3, 4, 5, 6, 8). For this study, the synthesis of the three ILs with the longest alkyl chain was performed, along with DSC, TGA and toxicity measurements. It was observed that an increase in alkyl chain length resulted in a decrease in short-term thermal stability and an increase in melting temperature, indicating a reduction in the liquid range. A compensation effect between enthalpy and entropy of melting was observed for the studied chain lengths. The isobaric specific and molar heat capacities increase with temperature for all the compounds studied here, and good correlations were obtained between molar heat capacity and the number of carbon atoms in the alkyl chain for every temperature. Finally, most of the ILs are non-toxic, although toxicity increases with alkyl chain length.