Change In Melting Temperature Research Articles

DSC Derived (Ea & ΔG) Energetics and Aggregation Predictions for mAbs

The Arrhenius energy of activation of unfolding Ea unfolding and Gibbs free energy of unfolding ΔG unfolding have been calculated utilizing DSC differential scanning calorimetry for 4 mAbs (1 biosimilar) in 3 formulations. DSC derived ΔTm melting temperature changes for each mAb domain (CH2, Fab, CH3) at calorimetric scan rates at 60 °C, 90 °C, 150 °C and 200 °C / hr. were utilized to calculate the kinetic Eaunfolding. The DSC derived Ea trend with observed aggregate formation and can be used to predict%HMW formation post 9-month storage at 5 °C and 40 °C for all formulations analyzed. Additionally, thermodynamic ΔG unfolding energies were also derived (Tm, ΔCp and ΔH measurements) for each mAb at every scan rate to observe scan rate dependence of ΔG and for extrapolation to 0 °C/hr. (to report ΔG at true equilibrium conditions). Both derived thermodynamic ΔG and kinetic Ea energies were combined to build full energetic landscapes for mAb unfolding and aggregation. Statistical multivariate analysis of kinetic (Ea CH2, Ea Fab, Ea CH3) energies, thermodynamic (ΔG5 °C and ΔG40 °C) energies and in-silico modeled surface properties was also performed. Analysis revealed key significant parameters contributing to aggregation. These parameters were utilized to build predictive aggregation models for 25 mg/mL mAb formulations stored 9-months at 5 °C and 40 °C.

Elucidation of inhibitory effects of bioactive anthraquinones towards formation of DNA advanced glycation end products (DNA-AGEs)

DNA is essential in biological processes as it directs transcription and translation assisting in RNA and protein synthesis. Extended periods of elevated blood glucose levels cause non-enzymatic DNA glycation, which results in the formation of DNA-AGEs and the production of free radicals, causing structural perturbation of DNA. In this work, we have investigated the glycation of calf thymus (ct-DNA) DNA and examined its inhibition by two anthraquinone derivatives, purpurin and aloin. Ribose sugar served as the glycating agent inducing non-enzymatic glycation of DNA and subsequent DNA-AGEs formation. UV–vis and fluorescence spectroscopic methods were utilized to characterize DNA-AGE formation in vitro. Circular dichroism (CD) spectroscopy was used to observe the structural disruption of DNA caused by glycation. The changes in AGEs fluorescence intensity and melting temperature (Tm) were measured to assess the inhibition of glycation process by aloin and purpurin. These derivatives demonstrated inhibitory effects via binding to glycating sites of ct-DNA or by scavenging free radicals generated during glycation. The current study elucidates the inhibitory actions of aloin and purpurin on DNA glycation, suggesting their possible applications in mitigating the adverse consequences linked to increased ribose concentrations.

The unique salt bridge network in GlacPETase: a key to its stability.

The extensive accumulation of polyethylene terephthalate (PET) has become a critical environmental issue. PET hydrolases can break down PET into its building blocks. Recently, we identified a glacial PET hydrolase GlacPETase sharing less than 31% amino acid identity with any known PET hydrolases. In this study, the crystal structure of GlacPETase was determined at 1.8 Å resolution, revealing unique structural features including a distinctive N-terminal disulfide bond and a specific salt bridge network. Site-directed mutagenesis demonstrated that the disruption of the N-terminal disulfide bond did not reduce GlacPETase's thermostability or its catalytic activity on PET. However, mutations in the salt bridges resulted in changes in melting temperature ranging from -8°C to +2°C and the activity on PET ranging from 17.5% to 145.5% compared to the wild type. Molecular dynamics simulations revealed that these salt bridges stabilized the GlacPETase's structure by maintaining their surrounding structure. Phylogenetic analysis indicated that GlacPETase represented a distinct branch within PET hydrolases-like proteins, with the salt bridges and disulfide bonds in this branch being relatively conserved. This research contributed to the improvement of our comprehension of the structural mechanisms that dictate the thermostability of PET hydrolases, highlighting the diverse characteristics and adaptability observed within PET hydrolases.IMPORTANCEThe pervasive problem of polyethylene terephthalate (PET) pollution in various terrestrial and marine environments is widely acknowledged and continues to escalate. PET hydrolases, such as GlacPETase in this study, offered a solution for breaking down PET. Its unique origin and less than 31% identity with any known PET hydrolases have driven us to resolve its structure. Here, we report the correlation between its unique structure and biochemical properties, focusing on an N-terminal disulfide bond and specific salt bridges. Through site-directed mutagenesis experiments and molecular dynamics simulations, the roles of the N-terminal disulfide bond and salt bridges were elucidated in GlacPETase. This research enhanced our understanding of the role of salt bridges in the thermostability of PET hydrolases, providing a valuable reference for the future engineering of PET hydrolases.

Verification Method for Determination of Melting Temperature and Enthalpy Changes (∆H) Using Differential Scanning Calorimeter

Verification of measurement method for determination of melting temperature and enthalpy changes using Differential Scanning Calorimeter has been carried out. This study was done to ensure that the method used can be applied in the laboratory with valid results and uncertainty. The verification method in this research consists of accuracy and precision. Accuracy was done by comparing measurement results with reference values using the t-student test. Precision can be seen in its repeatability and reproducibility. In this study, method verification of melting temperature measurement was carried out by thermal analysis using Differential Scanning Calorimeter (DSC) based on ISO 11357-3: 2018 method concerning determining temperature and enthalpy changes in melting and crystallization. The results showed that the method used to determine melting temperature and enthalpy changes (∆H) had met the repeatability and reproducibility requirements. The RSD (Relative Standard Deviation) value was less than 2%, and the accuracy met the acceptance requirements with a t-count smaller than the t-table in a 95% confidence level. It means that the results are not significantly different from reference values, so the method can be used in the laboratory. Keyword: verification method, melting temperature, differential scanning calorimetry

Experimental study of a latent heat thermal energy storage system using erythritol for medium temperature applications

Using solar energy and waste heat for medium-temperature thermal applications depends on efficient and economical heat storage development. Developing a compact thermal energy storage system is essential to use excess thermal energy from a source in a process or to shift the utilisation time of solar thermal energy or recovered waste heat. Phase change materials are commonly used for energy storage applications globally. In this work, a latent heat thermal energy storage (LHTES) system with 2.37 kg of Erythritol as the phase change material (PCM) has been studied. A shell and tube heat storage system is selected due to its effectiveness in heat transfer. Synthetic silicone oil Hi-Tech Therm-60 was used as heat transfer fluid. Thermal stability tests in a differential scanning calorimeter (DSC) for a small sample mass and a specifically designed experiment for a larger sample mass were performed to assess the stability of the PCM. The time-dependent temperature distribution inside the storage system and the effect of heat transfer fluid (HTF) inlet temperature on the charging behaviour were studied during the charging process. Charging time and melt fraction have been calculated. No significant change in melting temperature and a 10% reduction in latent heat of PCM was observed in the thermal stability test for a small sample mass in DSC. The charging time of the storage device was observed to be 91–97 min and 195 min for 140 °C and 130 °C HTF inlet temperatures, respectively. The total stored energy in the system was 922 kJ with a Stefan number of 0.59. Temperature variation during the charging process inside the storage also suggests a buoyancy effect, leading to increased natural convection during the melting process.

Deciphering the binding mechanism of an anti-cancer phytochemical plumbagin with calf thymus DNA using biophysical and in silico techniques.

Plumbagin (PLM), a plant derivative, is well known for a wide range of therapeutic effects in humans including anti-cancer, anti-inflammatory, anti-oxidant, and anti-microbial. Cytotoxic and genotoxic potential of this phytochemical has been studied which demands further insight. DNA being a major target for several drugs was taken to study against PLM to understand its effects on the cellular system. UV-Vis spectroscopy has indicated the binding of PLM to ctDNA and dye displacement assays have confirmed the formation of PLM-ctDNA complex. The insignificant changes in circular dichroism spectra suggested that PLM is not affecting the structural makeup of the ctDNA, hence the binding could be peripheral and not intercalating. Further, the relative viscosity and minimal change in melting temperature upon the complex formation supported this finding and confirmed the groove binding of PLM. Molecular docking analysis and simulation studies also show PLM as a minor groove binder to DNA and provide details on the interaction dynamics of PLM-DNA complex. Docking followed by a 100ns simulation reveals the negative Gibbs free energy change (∆G = -6.6kcalmol-1), and the formation of a stable complex. The PLM- DNA complex with stable dynamics was further supported by different parameters including RMSD, RMSF, SASA, Rg, and the energy profile of interaction. This study provides an insight into the cytotoxic and genotoxic mechanism of PLM which can be a crucial step forward to exploit its therapeutic potential against several diseases including cancer.

Platinum (II) complex of isopentyl glycine ligand: DNA binding, molecular dynamic, and anticancer activity against breast cancer

In this paper, we performed thorough experimental and theoretical calculations to examine the interaction between Pt derivative, as an anticancer, and ct-DNA. The mode of DNA binding with [Pt(NH3)2(Isopentylgly)]NO3, where Isopentylgly is Isopentyl glycine, was evaluated by various spectroscopic methods, docking, and molecular dynamics simulation studies. UV-Vis and fluorescence spectroscopic titration results and CD spectra of DNA-drug showed this interaction is via groove binding. Also, thermal stability studies or DNA melting temperature changes (ΔTm), as well as the quenching emissions monitoring proved it. Also, the thermodynamic parameter and binding constant displayed that complex-DNA formation is a spontaneous process, and H-binding and also groove binding were found to be the main forces. Theoretical studies stated [Pt(NH3)2(Isopentylgly)]NO3-DNA formation occurs on C-G center on DNA, along with rising DNA-compound stability. IC50 value against the human breast cell line probably is due to the Isopentyl glycine ligand in the structure of the Pt compound, and it was obtained more than cisplatin and less than carboplatin against the MCF7 cell. Communicated by Ramaswamy H. Sarma

Microcalorimetry reveals multi-state thermal denaturation of G. stearothermophilus tryptophanyl-tRNA synthetase.

Mechanistic studies of Geobacillus stearothermophilus tryptophanyl-tRNA synthetase (TrpRS) afford an unusually detailed description-the escapement mechanism-for the distinct steps coupling catalysis to domain motion, efficiently converting the free energy of ATP hydrolysis into biologically useful alternative forms of information and work. Further elucidation of the escapement mechanism requires understanding thermodynamic linkages between domain configuration and conformational stability. To that end, we compare experimental thermal melting of fully liganded and apo TrpRS with a computational simulation of the melting of its fully liganded form. The simulation also provides important structural cameos at successively higher temperatures, enabling more confident interpretation. Experimental and simulated melting both proceed through a succession of three transitions at successively higher temperature. The low-temperature transition occurs at approximately the growth temperature of the organism and so may be functionally relevant but remains too subtle to characterize structurally. Structural metrics from the simulation imply that the two higher-temperature transitions entail forming a molten globular state followed by unfolding of secondary structures. Ligands that stabilize the enzyme in a pre-transition (PreTS) state compress the temperature range over which these transitions occur and sharpen the transitions to the molten globule and fully denatured states, while broadening the low-temperature transition. The experimental enthalpy changes provide a key parameter necessary to convert changes in melting temperature of combinatorial mutants into mutationally induced conformational free energy changes. The TrpRS urzyme, an excerpted model representing an early ancestral form, containing virtually the entire catalytic apparatus, remains largely intact at the highest simulated temperatures.

Investigation of numerical and experimental assessment of melting behavior of phase change material in U tube heat exchanger

This study analyzes the melting process and temperature changes of a phase change material (PCM) in a U-tube heat exchanger, both experimentally and numerically. In the study, PCM was placed in a U-tube heat exchanger body and hot water was sent to the heat exchanger with a flow rate of 1.75 l/min and a temperature of 60 °C. In the study, the equations valid for continuity, momentum and energy were solved numerically by considering the phase change effects. The melting process was simulated and the melting percentages of the PCM at different time intervals were calculated to show the transition zones from the solid phase to the liquid phase. The PCM was initially subjected to hot water at 333 K at 300 K. In the experimental study, the PCM temperature reaches 306 K between the first 700–1200 min and melting is observed. This temperature is 303 K for numerical operation. After 3800 min, the PCM was observed to have completely melted for experimental and numerical study. The hardest and slowest melting part of the PCM is the area farthest from the center of the heat exchanger. In the comparison, approximately 4% error rate was determined between the measured and calculated values.

Probing protein stability: towards a computational atomistic, reliable, affordable, and improvable model.

We present an improved application of a recently proposed computational method designed to evaluate the change of free energy as a function of the average value of a suitably chosen collective variable in proteins. The method is based on a full atomistic description of the protein and its environment. The goal is to understand how the protein melting temperature changes upon single-point mutations, because the sign of the temperature variation will allow us to discriminate stabilizing vs. destabilizing mutations in protein sequences. In this refined application the method is based on altruistic well-tempered metadynamics, a variant of multiple-walkers metadynamics. The resulting metastatistics is then modulated by the maximal constrained entropy principle. The latter turns out to be especially helpful in free-energy calculations as it is able to alleviate the severe limitations of metadynamics in properly sampling folded and unfolded configurations. In this work we apply the computational strategy outlined above in the case of the bovine pancreatic trypsin inhibitor, a well-studied small protein, which is a reference for computer simulations since decades. We compute the variation of the melting temperature characterizing the folding-unfolding process between the wild-type protein and two of its single-point mutations that are seen to have opposite effect on the free energy changes. The same approach is used for free energy difference calculations between a truncated form of frataxin and a set of five of its variants. Simulation data are compared to in vitro experiments. In all cases the sign of the change of melting temperature is reproduced, under the further approximation of using an empirical effective mean-field to average out protein-solvent interactions.

Effect of Alkali Treatment and Fibre Composition on the Performance of Pineapple Leaf Fiber-Polyvinyl Alcohol Composites

This paper studied the properties of composites based on polyvinyl alcohol reinforced with pineapple leaf fibres (PALF/PVA). The surface of pineapple leaf fibres (PALF) has been previously treated with 6% sodium hydroxide solution. The influence of fibre loading and fibre surface treatment were examined. Analysis by Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) displayed physico-chemical changes on treated PALF/PVA composites compared to untreated PALF/PVA composites. The results from thermogravimetric analysis (TGA) showed that the introduction of untreated PALF into the composites enhanced the thermal stability of the composites. Progressive improvement of thermal stability was discovered by associating treated PALF with the composites. The treated PALF composites produced also improved mechanical properties with increasing fibre content. Differential scanning calorimetric (DSC) analyses showed no significant changes in melting temperatures upon incorporating untreated PALF into the PALF/PVA composites. The best improvement in tensile strength value was obtained for treated PALF composite having 3 wt% of fibre loading, with enhancements of about 11% and 54%, compared to untreated PALF composites and plain PVA matrix, respectively.

Effect of Melting Temperature and Flux on Slag Percentage in Die Casting Process of Zamak3 Alloy

This research aims to identify the optimal condition of the zinc Zamak3 alloys' melting process using 2k full factorial design and its optimizer in Minitab 18 software. The evaluation results of the ANOVA test with a first-order model revealed that the change in both independent variables simultaneously resulted in a statistically significant alteration of the percentage of slag. The independent parameters also had an effect individually on the response. Additionally, the slag percentage reduction was increased significantly due to an elevation of the temperature. However, the change of flux type resulted in an overall alteration of the slag percentage more than the change of melting temperature. The response optimizer demonstrated that the optimal condition was the melting temperature of 500°C coupled with the ZinCrex EP7119 flux achieving the lowest slag percentage of 1.672%, with the 95% confidence interval ranging from 0.643% to 2.701%.

Extended investigation of an abrupt crystal diameter change during Czochralski silicon growth with transverse magnetic field

An investigation about the phenomenon of an abrupt diameter deviation during Czochralski crystal growth, a characteristic when using a transverse magnet, has been carried out both experimentally and computationally. 300-mm silicon crystals have been pulled under certain conditions and the diameter deviations have been recorded in these processes. Three-dimensional calculations of the melt flow have been performed using CGSim Flow Module 3D, accounting for distribution of the actual non-uniform magnetic field, to accurately simulate the heat transfer and melt flow for selected growth stages along the entire process. The sudden change of melt temperature near the triple point that leads to the diameter deviation, is attributed to the evolution of melt flow pattern, which can be altered by positioning the magnet at a different height. The discovery of such melt flow behavior proposes an effective solution to eventually eliminate the abrupt diameter deviation during body growth. The visualization of the melt flow transformation by 3-D simulation offers another adjustability to the process of modern industrial crystal growth with transverse magnet. The mechanism of how the magnet position impacts the melt flow is also discussed.

Effect of CaO/Al2O3 Ratio on Physical Properties of Lime-Alumina-Based Mould Powders

High-aluminium steels contain a significant amount of aluminium. The reaction between Al in the liquid steel and SiO2 in lime-silica-based mould powders during the continuous casting process of high Al steel causes chemical compositional changes in the mould powders, subsequently affecting the surface quality of slabs. In order to solve the aforementioned problem, lime-alumina-based mould powders have been developed, which can lead to an increase in the surface quality of cast slabs by inhibiting steel/slag interaction. However, the mould slag tends to crystallise easily, which leads to a deterioration of the mould lubrication. In view of this aspect, it is important to develop and optimize lime-alumina-based mould powders to meet the requirements of continuous casting of high-aluminium steels. In this study, the changes in crystallinity, viscosity and melting temperature of lime-alumina-based mould powders with the effects of increasing the CaO/Al2O3 ratio have been observed through STA (Simultaneous Thermal Analysis), HSM (Hot Stage Microscopy), XRD (X-ray Diffraction), IPT (Inclined Plate Test) and rotational viscometer. The crystallisation behaviour of these mould powders was evaluated by generating CCT (continuous cooling transformation) diagrams. Additionally, the changes in steel chemistry have also been analysed using XRF (X-ray fluorescence) and ICP (Inductively Coupled Plasma Mass Spectrometer). The results of these analyses demonstrated that crystallinity of lime-alumina-based mould powder is increased while the initial crystallisation temperature and viscosity are decreased by CaO/Al2O3 additions. However, the degree of steel/slag interaction decreases with an increase in Al2O3 content.

Feasibility assessment of injection molding online monitoring based on oil pressure/nozzle pressure/cavity pressure

Abstract This study produced a box-like product through injection molding, and pressure sensors were installed at the nozzle in the injection molding machine and mold cavity. Injection molding experiments were conducted with various process parameters to understand the correlations between the pressure of the cavity, nozzle, and oil pump. A high correlation (R > 0.95) between oil pressure and nozzle pressure could be found in the study. The oil pressure in the injection molding machine could fully describe the pressure variation of the molten plastic at the nozzle. However, the correlation between nozzle pressure and cavity pressure was slightly reduced due to changes in injection speed, melting temperature, and packing time. Thus, a suitable molding window can improve the correlation between oil pressure, nozzle pressure, and cavity pressure. This study provides a correlation between the three pressures and a reference for the future selection of process variables, an essential pretreatment for online monitoring.

Effect of gamma irradiation on shape memory, thermal and mechanical properties of polycaprolactone

In the present study, the effect of gamma irradiation on the shape memory, thermal and mechanical properties of polycaprolactone (PCL) was investigated. Triallylisocyanurate (TAIC) was used as crosslinker. It was found that gamma irradiation influence the shape memory and mechanical properties of PCL by introducing crosslinking in its network. The degree of crosslinking was analysed by gel content. Gel content up to 50% was obtained with 50 kGy irradiation dose. With the incorporation of crosslinking via irradiation, shape memory property was generated in PCL. Shape recovery up to 95% was observed with 25 kGy radiation dose. Thermal analysis by DSC showed no significant change in melting and crystallization temperature after irradiation. XRD analysis revealed that the crystallized domains of PCL remain intact after irradiation. Mechanical properties viz. tensile strength and Young's modulus increases with irradiation, meanwhile a decrease in elongation was observed. The findings revealed that crosslinking introduced through gamma irradiation along with TAIC is effective in tailoring the shape memory, thermal and mechanical properties of polycaprolactone for different applications.

Food-Package-Processing relationships in emerging technologies: Ultrasound effects on polyamide multilayer packaging in contact with different food simulants

In this study, the effect of ultrasound processing on the properties of two packages widely used in food products was evaluated: polyamide (PA) and polyethylene (PE) multilayer packaging. Packages composed of PE/PA/PE (Film A) and PE/PA/PE/PA/PE (Film B) were filled with aqueous and fatty food simulants and treated in an ultrasound water bath (frequency 25 kHz, volumetric power of 9.74 W/L, temperature of 25 °C, and time of 30 and 60 min). Materials were evaluated in term of structure and performance properties. Ultrasound did not or induced small changes in chemical groups, crystallinity, melting temperature, and tensile strength of the films. Film A showed a reduction in heat sealing tensile strength of 25% in the machine direction and 22% in the transverse direction. Film B showed a 20% increase of water vapor transmission rate after ultrasound processing. Although ultrasound had little impact on the properties of the evaluated materials, these modifications do not compromise the use of these packages for applications in ultrasound-processed foods. Therefore, the results indicate that ultrasound can be used as a food processing technology in multilayer PA and PE packaging.

Real-Time Nondestructive Evaluation of Additive Manufacturing Using a Laser Vibrometer and Shock Tube

Abstract Additive manufacturing (AM) parts retain a certain degree of individuality and could suffer from a combination of different defect types, and therefore the nondestructive evaluation on AM parts remains a challenging task. Engineering non-contact and nondestructive real-time inspection and in situ quality assurance of AM parts would be a net improvement compared to current quality control methods that are conducted post-production. Here, the authors propose to combine the use of a laser vibrometer with a compression-driven shock tube to assess the quality of AM parts through the evaluation of the vibration spectra of the part. An AM of a cylindrical part was selected for the study, along with different defect types and sizes. These defects include internal voids of different sizes at different locations, local changes in thickness (infill), and local changes in melting temperatures. A numerical model was created and validated using experimental data to conduct model-assisted probability of detection (MAPOD). Results were analyzed by evaluating correlation matrices between different models. Results showed that vibration spectra induced by a shock wave were sensitive to different types and sizes of defects under the studied geometry. The defect index yielded an approximately linear relationship with respect to defect void severity. MAPOD curve studies revealed a minimum detectable void defect of 0.039% of the AM part’s volume.

On‐line melt temperature measurements for polymer injection molding through an instrumented annular duct

AbstractPolymer processing requires reliable monitoring equipment to ensure product quality, improve energy efficiency and apply advanced control strategies. This work tests an instrumented annular duct as a nozzle on the downstream side of the screw‐barrel to analyze the thermal behavior of the polymer flow in an injection molding machine. The plasticization step is first studied, and then virtual injection molding cycles are performed. The measurements via the instrumented annular duct show that the melt temperature decreases during fast production, due to the lack of residence time in the barrel for the material to be sufficiently heated by conduction. The instrumented annular duct also enables detection of changes in melt temperature over time during a single injection. Moreover, the experiments prove the robustness of the temperature measurements in an annular geometry for process monitoring.

Low‐Temperature Melting and Glass Formation of the Zeolitic Imidazolate Frameworks ZIF‐62 and ZIF‐76 through Ionic Liquid Incorporation

AbstractHybrid glass formation offers a potential route for processing metal‐organic frameworks (MOFs) in bulk shapes, however, only a small number of MOFs have proven to be meltable. For the non‐meltable zeolitic imidazolate framework ZIF‐8, ionic liquid (IL) incorporation has recently been found to reduce the melting temperature to below the thermal decomposition temperature, thus, enabling the formation of IL@ZIF‐8 glasses. Here, the effect of IL incorporation on the enthalpic response of some zeolitic imidazolate frameworks (ZIFs) and other MOFs upon heating is reported. For ZIF‐62, ZIF‐67, ZIF‐76, and MIL‐68, the accessibility of the metal site and MOF porosity govern the meltability of IL@MOF composites. IL incorporation enables the formation of ZIF‐76 glasses, and significantly reduces the melting temperature of ZIF‐62 but does not seem to facilitate the melting of ZIF‐67 or MIL‐68 (before thermal decomposition). Although the thermal stability limit of the IL plays an important role in governing the melting window of the IL@MOF composite, by careful selection of the melting temperature, thermal decomposition and compositional changes upon melting can be avoided to a greater extent. IL incorporation seems to offer a more universal route for melting MOFs, but requires careful adaption to the specific MOF architecture.