Melting Temperature Measurements Research Articles

Synthesis and study of arginine-containing iodine chelates

Synthesis conditions have been established and arginine (Arg) containing iodine chelate compounds with the general formula: IXArgY·mH2O (where x = y = 1 or 2; m=1 ÷3) have been synthesized. The synthesized chelates have been studied using a number of physical and chemical research methods. Composition has been determined by means of trace element analysis, while individuality – via melting temperature measurement and diffractographic method. It has been established via study of qualitative solubility in different solvents that chelates are highly soluble in water and poorly soluble in organic solvents. Using the conductometric method there has been calculated the dissociation constant for solutions containing chelate compounds. As a results of studies, conducted under production conditions it has been established that addition of chelate form of microelement (iodine) to broiler feed has a positive impact on all zootechnical parameters (live weight, daily weight gain, survival and feed consumption).

Biocompatible DNA hydrogel composed of minimized Takumi-shaped DNA nanostructure exhibits sustained retention after in vivo administration

Our previous studies showed that DNA hydrogels containing unmethylated CpG motifs effectively induced antigen-specific immune responses when combined with the appropriate antigens. A potential drawback of existing DNA hydrogels for further applications is the need for many oligodeoxynucleotide (ODN) types. Therefore, in this study, we attempted to optimize and minimize the nanostructured DNA units for DNA hydrogels to reduce the preparation cost, design difficulty, and possible risk of sequence-dependent off-target effects, and prepare DNA hydrogels with sustained retention ability. A Takumi-shaped unit with a stem and four flanking cohesive parts was constructed using one type of ODN with a palindromic sequence. A DNA hydrogel was prepared by mixing two Takumi-shaped units with complementary cohesive parts. The required length of the cohesive part was first examined using ODNs with 14 or 18 bases of stem length. Electrophoresis, melting temperature measurements, and viscoelastic analysis showed that the properties of the cohesive part determined the hydrogel properties. ODNs with a cohesive part consisting of GC-rich 5′-ccgcaagacg-3′ efficiently formed a hydrogel with sustained retention in mice after administration. Several ODNs with optimized cohesive sequences and different stem lengths and sequences were designed. Analyses showed that a stem of 10 bases or longer was required for efficient hydrogel formation, and ODNs with a 12-base stem part exhibited the most prolonged retention after subcutaneous injection into mice. Thus, the present study demonstrated the requirements of minimal DNA units for preparing DNA hydrogels with sustained retention ability.

Highly phosphorescent N^C^N platinum(II)-peptide nucleic acid conjugates: synthesis, photophysical studies and hybridization behaviour.

The synthesis of novel highly phosphorescent N^C^N tridentate platinum(II)-complex-peptide nucleic acid (PNA) bioconjugates was accomplished through the solid-phase approach. Melting temperature measurements and circular dichroism spectroscopy studies demonstrated that these conjugates maintain the PNA ability to recognize complementary ssDNA and ssRNA, though the length of the spacer between the metal center and the PNA sequence affects their hybridization properties. Noteworthy, the conjugation of PNA to this family of Pt(II) complexes significantly enhanced the luminescent features of the organometallic moiety, leading to increased quantum yields (82.8%, 10-5 M), even in the presence of oxygen (48.6%, 10-5 M). An in vitro cytotoxicity study of Pt(II)-PNA conjugates on HeLa cells showed no significative effect on cell growth in the dark (1 μM for 72 h).

Data-driven clustering learning modeling for semiconductor silicon single crystal growth process based on fuzzy C-means and DBN

The optimal operation of the semiconductor silicon single crystal (SSC) growth in an industrial single crystal furnace is contingent upon the precise measurement of both the crystal diameter and melt temperature. The Czochralski (CZ) silicon single crystal growth process (CZ-SSCGP) is a phase transition process from solid to liquid that takes place in a high-temperature, enclosed furnace designed for single crystal growth. The direct measurement of crystal diameter and melt temperature using sensors can pose a challenge due to the physical limitations of the furnace. This study introduces a novel approach for modeling clustering based on data that integrate fuzzy C-means (FCM) and deep belief network (DBN) techniques. The proposed method aims to estimate the online crystal diameter and melt temperature. The objective of this approach is to efficiently and precisely derive the CZ-SSCGP model. In order to address the negative impact of nonequilibrium properties of data on the model, it is advisable to employ FCM to produce numerous subsets of data that exhibit comparable operating conditions. This is especially important because data change over time and are different in different working situations. In order to enhance the precision of the fitting process for crystal diameter and melt temperature, we amalgamate the output outcomes of DBN that have been constructed for each individual subset. It is imperative to address the nonlinear and time-varying features manifested by the engineering data. Industrial data are utilized for conducting diverse data experiments and comparative analyses. The process takes into account the data’s susceptibility to contamination by outliers. The findings suggest that the method put forth exhibits superior precision and enhanced resilience in predicting crystal diameter and melt temperature compared to alternative modeling approaches.

L-DNA-Based Melt Analysis Enables Within-Sample Validation of PCR Products.

The melt analysis feature in most real-time polymerase chain reaction (PCR) instruments is a simple method for determining if expected or unexpected products are present. High-resolution melt (HRM) analysis seeks to improve the precision of melt temperature measurements for better PCR product sequence characterization. In the area of tuberculosis (TB) drug susceptibility screening, sequencing has shown that a single base change can be sufficient to make a first-line TB drug ineffective. In this study, a reagent-based calibration strategy based on synthetic left-handed (L)-DNA, designated LHRM, was developed to confirm validation of a PCR product with single base resolution. To test this approach, a constant amount of a double-stranded L-DNA melt comparator was added to each sample and used as a within-sample melt standard. The performance of LHRM and standard HRM was used to classify PCR products as drug-susceptible or not drug-susceptible with a test bed of nine synthetic katG variants, each containing single or multiple base mutations that are known to confer resistance to the first-line TB drug isoniazid (INH). LHRM achieved comparable classification to standard HRM relying only on within-sample melt differences between L-DNA and the unknown PCR product. Using a state-of-the-art calibrated instrument and multiple sample classification analysis, standard HRM was performed at 66.7% sensitivity and 98.8% specificity. Single sample analysis incorporating L-DNA for reagent-based calibration into every sample maintained high performance at 77.8% sensitivity and 98.7% specificity. LHRM shows promise as a high-resolution single sample method for validating PCR products in applications where the expected sequence is known.

Synthesis and study of Arginin-containing copper and chrome chelates

Synthesis conditions have been established and arginin (Arg)-containing copper and chrome chelate compounds with the following general formulas: CuArgn(CH3COO)2·mH2O and CrArgn(CH3COO)3·mH2O (where n =1÷3; m=2 or 4) have been synthesized. Synthesized chelates have been studied using a number of physical and chemical research methods. In particular, their composition has been established via trace element analysis, while the individuality has been identified through melting temperature measurement and diffractographic method. Through study of qualitative solubility in different solvents there has been established that chelates are highly soluble in water and poorly soluble in organic solvents. Using the conductometric research method there has been calculated a dissociation constant of chelate compounds-containing solutions. Based on the preliminary trial tests carried out in order to study the biological activity, there is expressed an opinion that entry of arginin-containing copper and chrome chelates into composition of combined feed premixes of egg-laying (oviparous) poultry has had a positive impact on egg-laying intensity and poultry survival rate. There is given an opinion on the expediency of basic test conduct in order to determine the optimum doses of arginin-containing copper and chrome chelate compounds for egg-laying birds.

Enhancing Binding Affinity to CGG/CGG Triad: Optimizing Naphthyridine Carbamate Dimer Derivatives with Varied Linker Lengths.

This study examines the binding properties of six naphthyridine carbamate dimer (NCD) derivatives with varying linker lengths to the CGG/CGG triad, a non-canonical DNA structure linked to repeat expansion disorders. By altering the linker length from 2 to 4 methylene groups, we found changes in thermal stability of the ligand-bound complexes while maintaining a consistent 2 : 1 binding stoichiometry. Among the derivatives, CC23 showed superior binding affinity compared to the parent molecule CC33 (NCD). Spectroscopic analyses revealed that linker length influences the conformational equilibrium of NCD derivatives. Thermal melting temperature measurements demonstrated CC23's enhanced thermal stability over CC33. These findings underscore the potential of optimized NCD derivatives, like CC23, as tools to modulate CGG repeat structures, offering insights for therapeutic strategies targeting repeat expansion disorders.

Elasticity and Thermal Stability are Key Determinants of Hearing Rescue by Mini-Protocadherin-15 Proteins.

Protocadherin-15 is a core protein component of inner-ear hair-cell tip links pulling on transduction channels essential for hearing and balance. Protocadherin-15 defects can result in non-syndromic deafness or Usher syndrome type 1F (USH1F) with hearing loss, balance deficits, and progressive blindness. Three rationally engineered shortened versions of protocadherin-15 (mini-PCDH15s) amenable for gene therapy have been used to rescue function in USH1F mouse models. Two can successfully or partially rescue hearing, while another one fails. Here we show that despite varying levels of hearing rescue, all three mini-PCDH15 versions can rescue hair-cell mechanotransduction. Negative-stain electron microscopy shows that all three versions form dimers like the wild-type protein, while crystal structures of some engineered fragments show that these can properly fold and bind calcium ions essential for function. In contrast, simulations predict distinct elasticities and nano differential scanning fluorimetry shows differences in melting temperature measurements. Our data suggest that elasticity and thermal stability are key determinants of sustained hearing rescue by mini-PCDH15s.

Influence of TiO2/SiO2 and BaO/CaO ratios on viscosity, crystallization and structure of high-TiO2 mold slags for casting of high-Ti steel

In the current study, the influence of TiO2/SiO2 and BaO/CaO ratios on viscosity, crystallization and structure of high-TiO2 mold slags was discussed through the measurement of viscosity-temperature relationship, melting temperature, crystallization temperature, crystallization rate and phases, and Raman spectrum. With the substitution of SiO2 by TiO2 in slags from 0 % to 12 %, the viscosity at 1300 °C, the melting temperature and break temperature decreased and then increased, while those of slags with the substitution of CaO by BaO from 4 % to 16 % decreased. With the substitution of SiO2 by TiO2 from 0 % to 10 %, crystallization phases gradually changed from cuspidine (Ca4Si2F2O7) to perovskite (CaTiO3), the initial and complete crystallization temperatures had the tendency to increase from 918 °C to 1260 °C and from 857 °C to 1139 °C, respectively, and the overall crystallization ability of slags increased. With the substitution of CaO by BaO from 4 % to 16 %, the initial and complete crystallization temperature of these slags decreased, and the overall crystalline ability decreased. With the substitution of SiO2 by TiO2 from 0 % to 10 %, structural units changed from the simple units to complex units, but the transition was opposite with the substitution from 10 % to 12 %, which was related to the transition of TiO2 from basic oxide to amphoteric oxide. With the substitution of CaO by BaO from 4 % to 16 %, the degree of polymerization and the viscosity of theses slags decreased, which was related to the supplement of more active O2− ion from BaO. Hence, the excessive substitution of SiO2 by TiO2 under the steel-slag reaction would cause the increase of the slag viscosity and crystallization ability, while the substitution of CaO by BaO could weaken the variation of slag viscosity and crystallization ability.

Development of Allosteric Ribozymes for ATP and l-Histidine Based on the R3C Ligase Ribozyme.

During the evolution of the RNA, short RNAs are thought to have joined together to form long RNAs, enhancing their function as ribozymes. Previously, the artificial R3C ligase ribozyme (73 nucleotides) was successfully reduced to 46 nucleotides; however, its activity decreased significantly. Therefore, we aimed to develop allosteric ribozymes, whose activities could be regulated by effector compounds, based on the reduced R3C ligase ribozyme (R3C-A). Among the variants prepared by fusing an ATP-binding aptamer RNA with R3C-A, one mutant showed increased ligation activity in an ATP-dependent manner. Melting temperature measurements of the two RNA mutants suggested that the region around the aptamer site was stabilized by the addition of ATP. This resulted in a suitable conformation for the reaction at the ligation site. Another ribozyme was prepared by fusing R3C-A with a l-histidine-binding aptamer RNA, and the ligase activity increased with increasing l-histidine concentrations. Both ATP and l-histidine play prominent roles in current molecular biology and the interaction of RNAs and these molecules could be a key step in the evolution of the world of RNAs. Our results suggest promise in the development of general allosteric ribozymes that are independent of the type of effector molecule and provide important clues to the evolution of the RNA world.

Machine-Learned Potential Energy Surfaces for Free Sodium Clusters with Density Functional Accuracy: Applications to Melting

Gaussian Process Regression based Gaussian Approximation Potential has been used to develop machine learned interatomic potentials having density functional accuracy, for free sodium clusters. The training data was generated from a large sample of over 100,000 data points computed for clusters in the size range of N = 40–200, where N denotes the number of atoms in the cluster, using the density functional method as implemented in the VASP code. Two models have been developed, model M1 using data for N = 55 only, and model M2 using additional data from larger clusters. The models are intended for computing thermodynamic properties using molecular dynamics. Hence, particular attention has been paid to improve the fitting of the forces. Although it was possible to obtain a good fit using the data of Na55 only, additional data points from larger clusters were needed to get better accuracies in energies and forces for larger sizes. Surprisingly, the model M1 could be significantly improved by adding about 50 data points per cluster from the larger sizes. Thus, it turns out that the best fit can be obtained by carefully selecting a small number of data points viz. 1,900 and 1,300 configurations for the two models M1 and M2, respectively. These two models have been deployed to compute the heat capacities of Na55. The heat capacities of Na147 and about 40 isomers for larger clusters of sizes N = 147, 200, 201, and 252, have been obtained using the final model M2. There is an excellent agreement between the computed and experimentally measured melting temperatures. The geometries of these isomers have been further optimized by density functional theory. The mean absolute error with respect to DFT energies is found to be about 7 meV/atom or less. The errors in the lowest interatomic bond lengths are below 2% in almost all the cases.

A high-throughput differential scanning fluorimetry method for rapid detection of thermal stability and iron saturation in lactoferrin

Thermal stability and iron saturation of lactoferrin (LF) are of great significance not only for the evaluation of the biological activities of LF but also for the optimization of the isolation and drying process parameters. Differential scanning calorimetry (DSC) is a well-established and efficient method for thermal stability and iron saturation detection in LF. However, multiple DSC measurements are typically performed sequentially, thus time-consuming and low throughput. Herein, we introduced the differential scanning fluorimetry (DSF) approach to overcome such limitations. The DSF can monitor LF thermal unfolding with a commonly available real-time PCR instrument and a fluorescent dye (SYPRO orange or Glomelt), and the measured melting temperature of LF is consistent with that determined by DSC. On the basis of that, a new quantification method was established for determination of iron saturation levels using the linear correlation of the degree of ion saturation of LF with DSF measurements. Such DSF method is simple, inexpensive, rapid (<15 min), and high throughput (>96 samples per experiment), and provides a valuable alternative tool for thermal stability detection of LF and other whey proteins.

Evaporation and its Effects on Physico-Chemical Properties of PbO-containing Slag

PbO as well as other volatiles will evaporate at high temperature. In the measure of relevant slag property, the slag will be kept at high temperature for a long time (even several hours). The continuous evaporation will result in uncertainty of the measured results. In another point of view, that means the measured result is no longer in consistent with the pre-determined slag composition, but a new one changed obviously. For high or medium PbO content slag, the weight loss can reach to 20∼40 % at high temperature. The effect is not negligible. In this work, the evaporation and physicochemical property (melting point and viscosity) measurement of typical PbO-containing slag were jointly analyzed based on calculation, TG-DSC, melting temperature and viscosity measurement. A deviation method based on traditional measurement ways was suggested and practiced. It is proved that to take physicochemical property value with traditional method and the get the in-time composition to match the measured values is feasible. how obtain in-time composition is also discussed and tried. The work will be of extensive reference significance to other slag system with higher volatiles.

Numerical modelling of heating and melting of metal in a mini industrial direct current electrical arc furnace

PurposeThe purpose of this paper is the study of the electro-vortex flow (EVF) as well as heating and melting processes for mini industrial direct current electric arc furnace (DC EAF).Design/methodology/approachA mini DC EAF was designed, manufactured and installed to study the industrial processes of heating and melting a small amount of melt, being 4.6 kg of steel in the case under study. Numerical modelling of metal melting was performed using the enthalpy and porosity approach at equal values and non-equal values of the solidus and liquidus temperatures of the metal. The EVF of the liquid phase of metal was computed using the large eddy simulation model of turbulence. Melt temperature measurements were made using an infrared camera and a probe with a thermocouple sensor. The melt speed was estimated by observing the movement of particles at the top surface of melt.FindingsThe thermal flux for metal heating and melting, which is supplied through an arc spot at the top surface of metal, is estimated using the thermal balance of the furnace at melting point. The melting time was estimated using numerical modelling of heating and melting of metal. The process started at room temperature and finished once whole volume of metal was molten. The evolution of the solid/melt phase boundary as well as evolution of EVF patterns of the melt was studied.Originality/valueNumerical studies of heating and melting processes in metal were performed in the case of intensive liquid phase turbulent circulation due to the Lorentz force in the melt, which results from the interaction of electrical current with a self-magnetic field.

Design of stable circular permutants of the GroEL chaperone apical domain

Enhancing protein stability holds paramount significance in biotechnology, therapeutics, and the food industry. Circular permutations offer a distinctive avenue for manipulating protein stability while keeping intra-protein interactions intact. Amidst the creation of circular permutants, determining the optimal placement of the new N- and C-termini stands as a pivotal, albeit largely unexplored, endeavor. In this study, we employed PONDR-FIT’s predictions of disorder propensity to guide the design of circular permutants for the GroEL apical domain (residues 191–345). Our underlying hypothesis posited that a higher predicted disorder value would correspond to reduced stability in the circular permutants, owing to the increased likelihood of fluctuations in the novel N- and C-termini. To substantiate this hypothesis, we engineered six circular permutants, positioning glycines within the loops as locations for the new N- and C-termini. We demonstrated the validity of our hypothesis along the set of the designed circular permutants, as supported by measurements of melting temperatures by circular dichroism and differential scanning microcalorimetry. Consequently, we propose a novel computational methodology that rationalizes the design of circular permutants with projected stability.8ghBPrif1HpKfHNvAL1G2xVideo

Synthesis and study of Arginin-containing iron and cobalt chelates

Synthesis conditions have been established and arginin-containing iron and cobalt chelate compounds with general formula: Me(Arg)n(CH3COO)2·mH2O, where Me = Fe, Co; Arg – neutral arginin molecule, n = 1÷3; m = 1÷4 have been synthesized. Synthesized chelates have been studied using a number of physical and chemical methods. In particular, the content has been established via trace element analysis, while individuality has been identified using melting temperature measurement and diffractographic method. According to study of qualitative solubility chelates are well soluble in water, though they are poorly soluble in organic solvents. Using the conductometric method there has been calculated the dissociation constant of chelate compound containing solutions. On the basis of preliminary trial tests conducted with a purpose of biological activity study, there has been expressed an opinion that entry of arginin-containing iron and cobalt chelates into composition of broilers’ combined feed premixes has had a positive impact on poultry live weight gain and poultry survival rate. An opinion on the reasonability of basic tests conduction has been given in order to determine the doses of arginin-containing iron and cobalt chelate compounds optimal for broilers.

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 on the sintering characteristics of biomass ash

The alkaline metal content in biomass is high, which leads to a low initial sintering temperature. Therefore, during the process of direct biomass combustion for power generation, there are serious problems such as ash deposition and slagging on the heating surface, which has become a technical bottleneck for the safe, stable and long-term operation of boilers. In industry, the melting characteristics of ash are commonly used to guide boiler design and operation. However, traditional measurement of ash melting temperature has a large subjective error, and the releasing of alkaline metals during the measurement process results bit higher value, which affects the accuracy of the measured characteristic temperature. Comparingly, the initial sintering temperature is lower than the deformation temperature of the ash. This article provides a device for measuring the sintering temperature of biomass ash by using the pressure drop method. A novel two ash chamber system was invented, in which the alkali element released from the first ash chamber was captured by the downstream second ash chamber to compensate the escaping of alkali element. The initial sintering temperature of the second ash chamber has more accuracy with lower value than that measured by the traditional single sample chamber. XRD was used to analyze the mineral composition and causes of sintering of the ash samples before and after sintering. The results show that the sintering mechanisms of different types of biomass are different. In addition, combined with SEM analysis of rice husk, fruit core, rapeseed straw, and corn straw, the results show that the initial sintering temperature of the ash samples measured by the double chamber measurement method is more accurate than that measured by the single chamber measurement method, further validating the reliability of the two ash column system.

The 2.4 Å structure of Zymomonas mobilis pyruvate kinase: Implications for stability and regulation

Human liver pyruvate kinase (hlPYK) catalyzes the final step in glycolysis, the formation of pyruvate (PYR) and ATP from phosphoenolpyruvate (PEP) and ADP. Fructose 1,6-bisphosphate (FBP), a pathway intermediate of glycolysis, serves as an allosteric activator of hlPYK. Zymomonas mobilis pyruvate kinase (ZmPYK) performs the final step of the Entner-Doudoroff pathway, which is similar to glycolysis in that energy is harvested from glucose and pyruvate is generated. The Entner-Doudoroff pathway does not have FBP as a pathway intermediate, and ZmPYK is not allosterically activated. In this work, we solved the 2.4 Å X-ray crystallographic structure of ZmPYK. The protein is dimeric in solution as determined by gel filtration chromatography, but crystallizes as a tetramer. The buried surface area of the ZmPYK tetramerization interface is significantly smaller than that of hlPYK, and yet tetramerization using the standard interfaces from higher organisms provides an accessible low energy crystallization pathway. Interestingly, the ZmPYK structure showed a phosphate ion in the analogous location to the 6-phosphate binding site of FBP in hlPYK. Circular Dichroism (CD) was used to measure melting temperatures of hlPYK and ZmPYK in the absence and presence of substrates and effectors. The only significant difference was an additional phase of small amplitude for the ZmPYK melting curves. We conclude that the phosphate ion plays neither a structural or allosteric role in ZmPYK under the conditions tested. We hypothesize that ZmPYK does not have sufficient protein stability for activity to be tuned by allosteric effectors as described for rheostat positions in the allosteric homologues.

Odd–even disparity in the population of slipped hairpins in RNA repeat sequences with implications for phase separation

Low-complexity nucleotide repeat sequences, which are implicated in several neurological disorders, undergo liquid-liquid phase separation (LLPS) provided the number of repeat units, n, exceeds a critical value. Here, we establish a link between the folding landscapes of the monomers of trinucleotide repeats and their propensity to self-associate. Simulations using a coarse-grained Self-Organized Polymer (SOP) model for (CAG)n repeats in monovalent salt solutions reproduce experimentally measured melting temperatures, which are available only for small n. By extending the simulations to large n, we show that the free-energy gap, ΔGS, between the ground state (GS) and slipped hairpin (SH) states is a predictor of aggregation propensity. The GS for even n is a perfect hairpin (PH), whereas it is a SH when n is odd. The value of ΔGS (zero for odd n) is larger for even n than for odd n. As a result, the rate of dimer formation is slower in (CAG)30 relative to (CAG)31, thus linking ΔGS to RNA-RNA association. The yield of the dimer decreases dramatically, compared to the wild type, in mutant sequences in which the population of the SH decreases substantially. Association between RNA chains is preceded by a transition to the SH even if the GS is a PH. The finding that the excitation spectrum-which depends on the exact sequence, n, and ionic conditions-is a predictor of self-association should also hold for other RNAs (mRNA for example) that undergo LLPS.