Determination Of Melting Temperature Research Articles

Liquidus temperatures in the La2O3-SrO-TiO2-ZrO2-Fe2O3 system: Calculation and experiment

Ceramics based on the La2O3-SrO-TiO2-ZrO2-Fe2O3 system is of considerable interest for the development of the materials based on high-entropy oxides when their high-temperature endurance is required. However, limited information on its high-temperature behavior greatly limits its applications. In the present work, the potential of the geometric method for liquidus temperature calculation (GMLTC) in five-component oxide systems using data on the corresponding binary systems is verified for the first time with the example of the La2O3-SrO-TiO2-ZrO2-Fe2O3 system. The liquidus temperatures in the studied system calculated accordingly were experimentally confirmed by visual polythermal analysis within the limits not exceeding 10 % of the determined melting temperature. This allows us to recommend the proposed GMLTC approach for prediction of the position of liquidus curves in multicomponent oxide systems, which is particularly important for the calculations of liquidus temperatures of high-entropy oxides with unique physicochemical properties valuable for application at high temperatures up to 3000 K.

Probing Slipids Force Field for Phase Transitions in SOPC Lipid Bilayers with Various Cholesterol Concentrations

We explore the phase behavior of lipid bilayers containing SOPC (1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine) with various molar concentrations (0 mol%, 10 mol% and 30 mol%) of cholesterol. To this end, we performed extensive atomistic molecular dynamics simulations in conjunction with the Slipids force field with optimized parameters for the headgroups of phospholipids. We computed thermodynamic and structural quantities describing the ordering of the tails, the mobility of the heads and the arrangement of the lipids in the bilayers. We analyzed the behavior of the named quantities over the temperature range between 271 K and 283 K, where the experimentally determined melting temperature, Tm=279 K, lies, as well as at 400 K, which is used as a reference temperature. The obtained results are compared to available experimental data along with the outcome from molecular dynamics simulations of similar phospholipids containing different amounts of cholesterol. In the temperature interval of interest, we found evidence of the occurrence of a thermal-driven phase transition (melting) in both the pure system and the one with the lower concentration of cholesterol, while in the remaining system, the higher amount of cholesterol in the bilayer smears out the transitional behavior. Thus, we demonstrate the ability of the Slipids force field to predict the phase behavior of bilayers of SOPC and SOPC mixed with cholesterol.

RNA Complexes with Nicks and Gaps: Thermodynamic and Kinetic Effects of Coaxial Stacking and Dangling Ends.

Multiple RNA strands can interact in solution and assume a large variety of configurations dictated by their potential for base pairing. Although duplex formation from two complementary oligonucleotides has been studied in detail, we still lack a systematic characterization of the behavior of higher order complexes. Here, we focus on the thermodynamic and kinetic effects of an upstream oligonucleotide on the binding of a downstream oligonucleotide to a common template, as we vary the sequence and structure of the contact interface. We show that coaxial stacking in RNA is well correlated with but much more stabilizing than helix propagation over an analogous intact double helix step (median ΔΔG°37°C ≈ 1.7 kcal/mol). Consequently, approximating coaxial stacking in RNA with the helix propagation term leads to large discrepancies between predictions and our experimentally determined melting temperatures, with an offset of ≈10 °C. Our kinetic study reveals that the hybridization of the downstream probe oligonucleotide is impaired (lower kon) by the presence of the upstream oligonucleotide, with the thermodynamic stabilization coming entirely from an extended lifetime (lower koff) of the bound downstream oligonucleotide, which can increase from seconds to months. Surprisingly, we show that the effect of nicks is dependent on the length of the stacking oligonucleotides, and we discuss the binding of ultrashort (1-4 nt) oligonucleotides that are relevant in the context of the origin of life. The thermodynamic and kinetic data obtained in this work allow for the prediction of the formation and stability of higher-order multistranded complexes.

IMPATIENT-qPCR: monitoring SELEX success during in vitro aptamer evolution

SELEX (Systematic Evolution of Ligands by Exponential enrichment) processes aim on the evolution of high-affinity aptamers as binding entities in diagnostics and biosensing. Aptamers can represent game-changers as constituents of diagnostic assays for the management of instantly occurring infectious diseases or other health threats. Without in-process quality control measures SELEX suffers from low overall success rates. We present a quantitative PCR method for fast and easy quantification of aptamers bound to their targets. Simultaneous determination of melting temperatures (Tm) of each SELEX round delivers information on the evolutionary success via the correlation of increasing GC content and Tm alone with a round-wise increase of aptamer affinity to the respective target. Based on nine successful and published previous SELEX processes, in which the evolution/selection of aptamer affinity/specificity was demonstrated, we here show the functionality of the IMPATIENT-qPCR for polyclonal aptamer libraries and resulting individual aptamers. Based on the ease of this new evolution quality control, we hope to introduce it as a valuable tool to accelerate SELEX processes in general.IMPATIENT-qPCR SELEX success monitoring. Selection and evolution of high-affinity aptamers using SELEX technology with direct aptamer evolution monitoring using melting curve shifting analyses to higher Tm by quantitative PCR with fluorescence dye SYBR Green I.Key points• Fast and easy analysis.• Universal applicability shown for a series of real successful projects.Graphical

Immunoinformatic and molecular docking approaches: siRNA prediction to silence cell surface binding protein of monkeypox virus

BackgroundMonkeypox virus (MPV), an endemic pathogen in Africa, shares clinical similarities with smallpox. Recent reports indicate a concerning increase in the number of MPV cases detected outside its endemic region, highlighting the emergence of a multi-country outbreak. Given the importance of the cell surface-binding protein E8L in facilitating viral attachment to host cells, this study aimed to identify potential small interfering RNAs (siRNAs) capable of silencing E8L and thereby serving as a basis for therapeutic development.ResultssiRNAs have emerged as promising candidates for genetic therapies and antiviral and antibacterial treatments. In this investigation, we employed computational assays, including GC content analysis, binding free energy assessment, folding properties evaluation, melting temperature determination, and siRNA efficacy prediction. Our comprehensive analysis identified five siRNAs with high potential for effectively silencing the cell surface-binding protein of the monkeypox virus. Among these siRNAs, molecular docking revealed that “S8” (Guide-UUAUGGAUCCAAUCACUUGAU, Passenger-CAAGUGAUUGGAUCCAUAAUC) demonstrated the strongest affinity with the human argonaute-2 protein.ConclusionsThe siRNA “S8” represents a promising therapeutic target for developing treatments against monkeypox virus infection by specifically silencing the cell surface-binding protein E8L. Our research lays the foundation for future endeavors in genome-level therapies. It can potentially create chemically produced RNA molecules as effective antiviral drugs targeting Monkeypox virus infection. These findings contribute to advancing therapeutic strategies and offer new avenues for combating the spread of MPV, particularly in regions affected by the multi-country outbreak.

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

Theoretical investigation of size and shape dependent melting temperature of transition metal clusters

Recently, research on material properties has got lots of attention because of their promising technological applications. In this article, we report a theoretical investigation concerning the size and shape effect on the melting temperature of transition metal clusters. Within the thermo dynamical approach, we predict a structural melting temperature for spherical, regular tetrahedral, regular hexahedral and regular octahedral for the sizes around 0.2 nm, 0.5 nm, 1 nm, 1.5 nm and 2 nm respectively. The theoretical investigation of size and shape dependent melting temperature on transition metal clusters (Cr, W &Mo) using thermodynamic model, where the shape and size of clusters are considered by introducing a new parameter, i.e. the shape factor. Based on melting temperature estimations as a function of size and shape, we predict that certain transition metal clusters, such as small size, may be viable for nanoelectronics or nanophotonic devices or not, since the melting temperature is too close to, or in some cases even below, room temperature. The results are well consistent with theoretical and experimental values used in liquid drop model. According to the study, when the size of the cluster decrease the melting temperature of the cluster decrease. On the other hand, when the parameter (shape factor) increase the melting temperature of the cluster decrease or vice versa. In conclusion, both size and shape have big effect on the melting temperature determination of the clusters.

Oxidation induced emissivity variations of the Haynes 25 alloy at high temperatures

Haynes 25 alloy is used in the design of propulsion systems for spacecrafts and it can constitute a space debris at the end of life of the mission. All the thruster combustion chambers and nozzles are manufactured with Haynes 25 alloy and the thrusters used storable monopropellant hydrazine. During the atmospheric reentry of thruster pieces at high velocity, the Haynes 25 alloy is submitted to high temperatures in an extreme environment with atomic oxygen. This is why the high temperature oxidation of Haynes 25 was studied, in air plasma conditions in the temperature range 1000–1700 K. Moreover, as emissivity is an important parameter to know for the heat transfer, the spectral directional emissivity was measured on several samples surfaces: pristine, pre-oxidized in air plasma and in situ oxidized in air. The high temperature oxidation of Haynes 25 is moderate up to 1500 K and above an important mass loss occurred up to 1700 K (around 40 mg/cm2), that is the determined melting temperature. The emissivity of pristine Haynes 25 is vey low, around 0.20 at 1350 K and it increases with oxidation up to 0.85–0.90 at 1600 K.

Abstract 3844: A biophysical investigation into the binding interactions of novel anti-cancer inhibitors of atypical protein kinase C (aPKCs)

Abstract The aim of this study is to address the challenge of the expression of recombinant atypical protein kinase C (aPKCs) in a bacterial system and understand the binding interactions of novel anti-cancer inhibitors of aPKCs. The Protein kinase Cs (PKCs) expression at a high rate is a key indicator of cancer cell proliferation and survival. In particular, the over-expressions of aPKCs were found to be directly associated with various cancer cells in benign and malignant stages. Several cancer growth blockers (inhibitors) are available for targeted therapy. However, these inhibitors had to pass through rigorous in silico screening, in vitro, and in vivo assays before FDA approval. During the characterization studies of the protein, insights into binding interactions between aPKCs and drug molecules are crucial. For successive studies such as for biophysical characterization, the recombinant bioactive full-length PKC- ι (an aPKC) expression in the bacterial system is still a challenge. In addition, the binding interaction studies of aPKCs with inhibitors in physiological conditions providing structural details are limited to some X-ray crystallography structures and computational studies. Here we addressed these two challenges and report a protocol detailing the bioactive full-length and catalytic domain of PKC- ι expression and purification from the bacterial system. The further characterization of the recombinant protein by the determination of melting temperature, functional activity, and circular dichroism reported here provides important information on the characteristics of the protein in its native state. Moreover, we show the chemical interactions of five novel anti-cancer inhibitors ICA-1S (Nucleosidic homolog) 5-amino-1-((1R,2S,3S,4R)-2,3-dihydroxy-4-methylcyclopentyl)-1H-imidazole-4-carboxamide), ICA-1T (Phosphorylated nucleosidic homolog of ICA-1S, [4-(5-amino-4-carbamoylimidazol-1-yl)-2,3-dihydroxycyclopentyl] methyl dihydrogen phosphate), ACPD (2-acetyl-1,3-cyclopentanedione), DNDA (3,4-diaminonaphthalene-2,7-disulfonic acid) and ζ(ZETA)-Stat (8-hydroxy-1,3,6- naphthalenetrisulfonic acid) to locate their regions of binding on the catalytic domain of the aPKCs (PKC- ι and PKC- ζ). We have utilized the chemical shift changes obtained from various multi-dimensional Nuclear Magnetic Resonance (NMR) experiments. Moreover, we have applied the isothermal calorimetry method to understand the biophysical properties of the aPKCs in presence of these inhibitors. The observed biophysical properties of the protein and chemical shift perturbations in the amide backbone of the catalytic domain upon binding shed light on the molecular recognition process, binding characteristics, and atomic-level structural details of the aPKCs. Citation Format: Radwan Ebna Noor, Tracess B. Smalley, Mildred Acevedo-Duncan. A biophysical investigation into the binding interactions of novel anti-cancer inhibitors of atypical protein kinase C (aPKCs). [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3844.

Structural mechanism of Fab domain dissociation as a measure of interface stability

Therapeutic antibodies should not only recognize antigens specifically, but also need to be free from developability issues, such as poor stability. Thus, the mechanistic understanding and characterization of stability are critical determinants for rational antibody design. In this study, we use molecular dynamics simulations to investigate the melting process of 16 antigen binding fragments (Fabs). We describe the Fab dissociation mechanisms, showing a separation in the VH–VL and in the CH1–CL domains. We found that the depths of the minima in the free energy curve, corresponding to the bound states, correlate with the experimentally determined melting temperatures. Additionally, we provide a detailed structural description of the dissociation mechanism and identify key interactions in the CDR loops and in the CH1–CL interface that contribute to stabilization. The dissociation of the VH–VL or CH1–CL domains can be represented by conformational changes in the bend angles between the domains. Our findings elucidate the melting process of antigen binding fragments and highlight critical residues in both the variable and constant domains, which are also strongly germline dependent. Thus, our proposed mechanisms have broad implications in the development and design of new and more stable antigen binding fragments.

PH-dependent structural diversity of profilin allergens determines thermal stability.

The family of profilin allergens is a common class of proteins found in plants, viruses and various eukaryotes including mammals. Profilins are characterized by an evolutionary conserved structural fold, which is responsible for their cross-reactive nature of Immunoglobulin E (IgE) antibodies. Despite their high overall structural similarity, they exhibit substantial differences in their biophysical properties, such as thermal and pH stability. To understand the origin of these functional differences of Amb a 8, Art v 4 and Bet v 2, we performed constant pH molecular dynamics simulation in combination with Gaussian accelerated MD simulations. Depending on the respective protonation at different pH levels, we find distinct differences in conformational flexibility, which are consistent with experimentally determined melting temperatures. These variations in flexibility are accompanied by ensemble shifts in the conformational landscape and quantified and localized by residue-wise B-factors and dihedral entropies. These findings strengthen the link between flexibility of profilin allergens and their thermal stability. Thus, our results clearly show the importance of considering protonation dependent conformational ensembles in solution to elucidate biophysical differences between these structurally similar allergens.

Influence of DPPE surface undulations on melting temperature determination: UV/Vis spectroscopic and MD study

One of the most distinguished quantities that describes lipid main phase transition, i.e. the transition from the gel (Lβ(′)) to the fluid (Lα) phase, is its melting temperature (Tm). Because melting is accompanied by a large change in enthalpy the, Lβ(′) → Lα transition can be monitored by various calorimetric, structural and spectroscopic techniques and Tm should be the same regardless of the metric monitored or the technique employed. However, in the case of DPPE multilamellar aggregates there is a small but systematic deviation of Tm values determined by DSC and FTIR spectroscopy. The aim of this paper is to explain this discrepancy by combined UV/Vis spectroscopic and MD computational approach. Multivariate analysis performed on temperature-dependent UV/Vis spectra of DPPE suspensions demonstrated that at 55 ± 1 °C certain phenomenon causes a small but detectable change in suspension turbidity, whereas a dominant change in the latter is registered at 63.2 ± 0.4 °C that coincides with Tm value determined from DSC curve. If this effect should be ignored, the overall data give Tm value the same as FTIR spectra data (61.0 ± 0.4 °C). As the classical MD simulations suggest that about 10° below Tm certain undulations appear at the surface of DPPE bilayers, we concluded that certain discontinuities in curvature fluctuations arise at reported temperature which are to some extent coupled with lipid melting. Ultimately, such events and the associated changes in curvature affect Tm value measured by different techniques.

Origin of Historical Ba-Rich Slags Related to Pb-Ag Production from Jihlava Ore District (Czech Republic)

The aim of this study was to characterize historical slags which originated during silver production from the Jihlava ore district, Czech Republic. The area was among the head producers of silver within the Lands of the Czech Crown in 13th–14th centuries. The mined ores had complex composition, being formed mostly by pyrite, sphalerite, galena, chalcopyrite, and accessory silver-rich minerals such as silver-bearing tetrahedrite (freibergite) or pyrargyrite, with gangue represented by quartz and Mn-rich carbonates or baryte. Large volumes of slags with contrasting composition were generated during the Pb-Ag production. Altogether, two main types of slags were identified in the district. The first type is characterized by high BaO contents (up to 34.5 wt.%) and dominancy of glass, minor quartz, and accessory amounts of Ba-rich feldspar (up to 93 mol.% of Cls), metal-rich inclusions, Ba-Pb sulphates and only rare pyroxene, wollastonite and melilite. The composition of the second group belongs to fayalitic slags containing glass, Fe-rich olivine, accessory pyroxene, feldspar, quartz, and inclusions of various metallic phases. Fluxes were derived from gangue (quartz, carbonates, baryte) or local host rocks for both types of slag. The calculated viscosity indexes reflect (with minor exceptions) medium-to-high effectivity of metal separation. Smelting temperatures were estimated from a series of ternary plots; however, more reliable estimates for both types of slags were obtained only from experimental determination of melting temperature and calculations using bulk/glass compositions (~1100–1200 °C).

Determination of melting and solidification temperatures of Sn-Ag-Cu solder spheres by infrared thermography

This study introduces the application of infrared (IR) thermography for the determination of melting and solidification temperatures of Sn-Ag-Cu based solder materials commonly used for interconnects in electronic components and devices. The presented setup allows a fast and simultaneous analysis with heating and cooling rates of approx. 0.93 K/s and 0.74 K/s respectively. In order to prove feasibility, measurements were carried out on free standing solder spheres with a diameter of 270 µm which is a typical size for solder interconnects in electronic devices. Four Sn-Ag-Cu alloys (Sn-2.0Ag-0.5Cu, Sn-3.0Ag-0.25Cu, Sn-3.0Ag-0.7Cu, Sn-3.0Ag-0.5Cu) with 19 samples per alloy were investigated per experimental run, resulting in a total of 76 samples per measurement. The reproducible extraction of the respective onset temperatures for melting and solidification is demonstrated by the analysis of representative heating and cooling graphs. The onset temperature of melting, which represents the eutectic temperature of these alloys, was measured between 215.1 °C and 218.1 °C. This is less accurate but in good agreement with additionally conducted Differential Scanning Calorimetry (DSC) measurements (217.2 °C to 218.0 °C), as well as the eutectic temperature from the phase diagram (217.2 °C). The solidification temperature of these samples was statistically evaluated by four subsequent experimental runs (generating up to 76 values per alloy). The measured temperature range combined for all four alloys was between 127.2 °C and 196.4 °C. The DSC results (nine values per alloy; three samples; three runs) are comparable but yield a smaller range from 142.2 °C to 185.2 °C. Furthermore, the melting and solidification temperatures of small Sn-Ag FlipChip solder bumps (approx. ∅ 87 µm) were reproducibly analyzed by the IR thermography method and range from 220.3 °C to 220.5 °C and 176.3 °C to 196.7 °C respectively. The presented IR thermography method has proven a valuable alternative, especially for a statistical analysis of undercooling distributions in small samples, such as Sn-Ag-Cu solder joints.

Simulation-Assisted Determination of the Minimum Melting Temperature Composition of MgCl2–KCl–NaCl Salt Mixture for Next-Generation Molten Salt Thermal Energy Storage

Molten chloride mixtures such as MgCl2–KCl–NaCl are potential thermal energy storage (TES) materials and heat transfer fluids (HTFs) for next-generation concentrating solar power (CSP) systems due to their high operation temperatures (>700°C) and low costs. This ternary MgCl2–KCl–NaCl salt mixture with a low material cost (<0.35 $/kg) is a promising salt for high-temperature TES/HTF applications, for example, it could enable next-generation CSP plants to have significant power cycle efficiency and lower levelized cost of electricity (LCOE). In this study, the minimum melting temperature composition for the MgCl2–KCl–NaCl mixture was estimated by FactSage simulation, while the binary and ternary phase diagrams of the MgCl2–KCl–NaCl salt system, including their phase transitions, were studied. Five different eutectic compositions of the MgCl2–KCl–NaCl mixture from literature and simulations were selected to determine the minimum melting temperature composition by the differential scanning calorimetry technique. Results show agreement between experiments and simulations of the melting temperature and its composition. Hence, values of the exact and reliable minimum melting temperature and salt composition in mol% and wt% are given. Based on the determined melting temperature, the minimum operating temperature of MgCl2–KCl–NaCl is recommended according to the safety margin for CSP applications.

Comparative study on the curing kinetics and thermal properties of a new series of diglycidyl esters of bis(trimellitimide)s

AbstractThe non‐isothermal curing behavior of a new series of epoxy‐imide resins based on trimellitimide structures, synthesized in a three‐step procedure, were evaluated by differential scanning calorimetry. The chemical structures of the synthesized intermediates and their corresponding epoxy‐imide resins were characterized and confirmed by Fourier‐transform infrared spectroscopy and 1H‐NMR spectroscopy. The imide‐containing resins, also a medium molecular weight bisphenol‐A based epoxy (as reference) were cured by dicyandiamide. The variation of apparent activation energies (Eα) with conversion was then calculated by various differential, as well as integral isoconversional methods. Furthermore, the thermal stability of understudied systems was evaluated by thermogravimetric analysis (TGA). The results showed that the determined melting temperatures of epoxy‐imide resins were significantly higher than that of the reference one, but were still within the range of powder coating application temperatures. In contrast with the reference, the imide‐containing systems showed the dependency of Eα as a function of the curing conversion and the values of Eα at the onset of their curing reactions were considerably higher than that of another, ca. 111.6–155.4 kJ/mol against 50.7 kJ/mol, which approached the reference value at the end of the curing reactions. The evaluation of reaction mechanisms with the progress of the curing reactions by the methods of Friedman and Malek revealed the traits of autocatalytic behavior, despite the predominance of the nth‐order reaction mechanism. The TGA data also showed that the cured epoxy‐imide samples had lower degradation rates, extended stability windows, and enhanced flame retardancy compared with the reference resin.

Sequence Effect on the Activity of DNAzyme with Covalently Attached Hemin and Their Potential Bioanalytical Application.

In this work we investigated the effect of a DNA oligonucleotide sequence on the activity of a DNAzyme with covalently attached hemin. For this purpose, we synthesized seven DNA-hemin conjugates. All DNA-hemin conjugates as well as DNA/hemin complexes were characterized using circular dichroism, determination of melting temperatures and pKa of hemin. We observed that hemin conjugation in most cases led to the formation of parallel G-quadruplexes in the presence of potassium and increased thermal stability of all studied systems. Although the activity of DNA-hemin conjugates depended on the sequence used, the highest activity was observed for the DNA-hemin conjugate based on a human telomeric sequence. We used this DNAzyme for development of “sandwich” assay for detection of DNA sequence. For this assay, we used electric chip which could conduct electricity after silver deposition catalyzed by DNAzyme. This method was proved to be selective towards DNA oligonucleotides with mismatches and could be used for the detection of the target. To prove the versatility of our DNAzyme probe we also performed experiments with streptavidin-coated microplates. Our research proved that DNAzyme with covalently attached hemin can be used successfully in the development of heterogeneous assays.

Age at Glaucoma Diagnosis in Germline Myocilin Mutation Patients: Associations with Polymorphisms in Protein Stabilities.

Glaucoma is the leading cause of irreversible blindness worldwide, with elevated intraocular pressure (IOP) as the only known modifiable risk factor. Trabecular meshwork (TM)-inducible myocilin (the MYOC gene) was the first to be identified and linked to juvenile and primary open-angle glaucoma. It has been suggested that mutations in the MYOC gene and the aggregation of mutant myocilin in the endoplasmic reticulum (ER) of TM may cause ER stress, resulting in a reduced outflow of aqueous humor and an increase in IOP. We selected 20 MYOC mutations with experimentally determined melting temperatures of mutated myocilin proteins. We included 40 published studies with at least one glaucoma patient with one of these 20 MYOC mutations and information on age at glaucoma diagnosis. Based on data from 458 patients, we found that a statistically significant but weak correlation was present between age and melting temperature based on various assumptions for age. We therefore conclude that genetic analysis of MYOC mutations alone cannot be used to accurately predict age at glaucoma diagnosis. However, it might be an important prognostic factor combined with other clinical factors for critical and early detection of glaucoma.

Cooperative binding ensures the obligatory melibiose/Na+ cotransport in MelB.

MelB catalyzes the obligatory cotransport of melibiose with Na+, Li+, or H+. Crystal structure determination of the Salmonella typhimurium MelB (MelBSt) has revealed a typical major facilitator superfamily (MFS) fold at a periplasmic open conformation. Cooperative binding of Na+ and melibiose has been previously established. To determine why cotranslocation of sugar solute and cation is obligatory, we analyzed each binding in the thermodynamic cycle using three independent methods, including the determination of melting temperature by circular dichroism spectroscopy, heat capacity change (ΔCp), and regulatory phosphotransferase EIIAGlc binding with isothermal titration calorimetry (ITC). We found that MelBSt thermostability is increased by either substrate (Na+ or melibiose) and observed a cooperative effect of both substrates. ITC measurements showed that either binary formation yields a positive sign in the ΔCp, suggesting MelBSt hydration and a likely widening of the periplasmic cavity. Conversely, formation of a ternary complex yields negative values in ΔCp, suggesting MelBSt dehydration and cavity closure. Lastly, we observed that EIIAGlc, which has been suggested to trap MelBSt at an outward-open state, readily binds to the MelBSt apo state at an affinity similar to MelBSt/Na+. However, it has a suboptimal binding to the ternary state, implying that MelBSt in the ternary complex may be conformationally distant from the EIIAGlc-preferred outward-facing conformation. Our results consistently support the notion that binding of one substrate (Na+ or melibiose) favors MelBSt at open states, whereas the cooperative binding of both substrates triggers the alternating-access process, thus suggesting this conformational regulation could ensure the obligatory cotransport.

Spouted bed drying of milk–blackberry mixture: Material thermal properties and process energy aspects

AbstractThis work presents the determination of the thermal properties of a milk–blackberry pulp mixture (25–75%, vol/vol), and of the powder obtained by spouted bed drying. Based on the experimental data, polynomial and artificial neural networks (ANNs) correlations were proposed to predict the specific heat as a function of temperature. The effects of operating variables (air temperature, atomization pressure, and feed flow rate), on the energy efficiency (EE) and on the specific consumption of energy (ε) were evaluated using a 23‐factorial design. Afterward, the effects of feeding mode (atomization or dripping), on energy aspects were analyzed. The fusion of powder fat crystals occurred at 1°C and at 16°C, glass transition between 27°C and 34°C, and proteins denaturation starting at 87°C. The ANNs presented higher accuracy in the specific heat prediction, with mean deviation as low as 0.5%. The inlet air temperature and the feed flow rate have affected the energy parameters, but the atomization pressure and the interaction among these variables did not. The EE ranged from 7.3 to 23.2% and the ε from 10.6 to 33.8 MJ/kg. Besides the reuse of the outlet air, the drip‐feeding mode could be an alternative to decrease the net energy consumption of the drying process.Practical ApplicationsThis work presents the determination of melting and glass transition temperatures, melting enthalpy, and specific heat of the paste milk–blackberry pulp (25%:75%, vol/vol) and/or powder, which are important characteristics for equipment dimensioning, process control, product quality, and to determine storage conditions. We also proposed ANN‐based correlations to relate the specific heat of the paste and powder as a function of temperature. The ANNs equations showed high accuracy and were used in the analysis of the energy aspects of the spouted bed drying process. Statistical analysis of energy aspects as a function of operating variables was performed and two linear response models were obtained, allowing to predict the specific consumption of energy and energy efficiency of the process. Herein, we suggest the potential use of DSC analysis and ANN techniques as a powerful combination to obtain information about food products and process design.