Calorimetric Determination Research Articles

DNA-based assay for calorimetric determination of protein concentrations in pure or mixed solutions.

It was recently reported that values of the transition heat capacities, as measured by differential scanning calorimetry, for two globular proteins and a short DNA hairpin in NaCl buffer are essentially equivalent, at equal concentrations (mg/mL). To validate the broad applicability of this phenomenon, additional evidence for this equivalence is presented that reveals it does not depend on DNA sequence, buffer salt, or transition temperature (Tm). Based on the equivalence of transition heat capacities, a calorimetric method was devised to determine protein concentrations in pure and complex solutions. The scheme uses direct comparisons between the thermodynamic stability of a short DNA hairpin standard of known concentration, and thermodynamic stability of protein solutions of unknown concentrations. Sequences of two DNA hairpins were designed to confer a near 20°C difference in their Tm values. In all cases, evaluated protein concentrations determined from the DNA standard curves agreed with the UV-Vis concentration for monomeric proteins. For multimeric proteins evaluated concentrations were greater than determined by UV-Vis suggesting the calorimetric approach can also be an indicator of molecular stoichiometry.

Tailoring the Techno-Functional Properties of Fava Bean Protein Isolates: A Comparative Evaluation of Ultrasonication and Pulsed Electric Field Treatments

The fava bean protein isolate (FBPI) holds promise as a sustainable plant-based protein ingredient. However, native FBPIs exhibit limited functionality, including unsuitable emulsifying activities and a low solubility at a neutral pH, restricting their applications. This study is focused on the effect of ultrasonication (US) and pulsed electric fields (PEF) on modulating the techno-functional properties of FBPIs. Native FBPIs were treated with US at amplitudes of 60–90% for 30 min in 0.5 s on-and-off cycles and with PEF at an electric field intensity of 1.5 kV/cm with 1000–4000 pulses of 20 μs pulse widths. US caused a reduction in the size and charge of the FBPIs more prominently than the PEF. Protein characterization by means of SDS-PAGE illustrated that US and PEF caused severe-to-moderate changes in the molecular weight of the FBPIs. In addition, a spectroscopic analysis using Fourier-transform infrared (FTIR) and circular dichroism (CD) revealed that US and the PEF induced conformational changes through partial unfolding and secondary structure remodeling from an α-helix to a β-sheet. Crystallographic and calorimetric determinations indicated decreased crystallinity and lowered thermal transition temperatures of the US- and PEF-modified FBPIs. Overall, non-thermal processing provided an effective strategy for upgrading FBPIs’ functionality, with implications for developing competitive plant-based protein alternatives.

Calorimetric determination of wet snow liquid water content: The effect of test conditions on the calorimeter constant and its impact on the measurement uncertainty

The liquid water content (lwc) of wet snow is a fundamental parameter in determining snow properties like its strength and adhesion force to surfaces. Among the different methods available for the measurement of the lwc, this paper focuses on melting calorimetry: known masses of hot water and snow are mixed into a thermally insulated container, and the lwc is obtained from the difference between the initial hot water temperature and the final mixing temperature; it is a fast and easy to implement method that requires little equipment, making it suitable for both laboratory and field measurements. Tests with “equivalent” wet snow samples whose liquid water content was known in advance were carried out to assess the method, showing that the liquid water content was overestimated by a variable amount that seemed to depend on the test parameters. To account for the heat capacity of the calorimeter, which was found not to be negligible, a constant in terms of equivalent hot water mass (E) was introduced. However, its value also depended on the test conditions. Hence, a correlation between E and the test parameters was found, and the measurements were repeated using a container of a different material, showing a similar behavior. Eventually, a discussion about the effects of choosing different hot water masses and hot water-to-snow mass ratios on measurement accuracy is provided.

Introducing the 3R Program in Teaching Laboratories to Promote Sustainability Science through Miniaturization Studies on the Spectrophotometric Determination of Organic Carbon and Phosphorus in Soil

The general assembly meeting of the United Nations Educational, Scientific and Cultural Organization (UNESCO) in 2015 adopted the 17 Sustainable Development Goals (SDGs) aimed at achieving a better and more sustainable world by 2030. Incorporating sustainable values through a series of pedagogical strategies into university curricula to help future professionals enhance their understanding of sustainability and how they relate to it is one of the crucial steps to help achieve Sustainable Development Goals (SDGs) through education. Inspired by the principles of Green Analytical Chemistry (GAC) and the “3R” (reduce, recycle, and reuse) approach, a laboratory experiment has been developed to illustrate the basic concept of reaction miniaturization step by step. This article presents a novel experimental design consisting of 7 sessions, which includes all elements of the 3R approach. Herein, students miniaturize the conventional calorimetric determination of soil organic carbon (OC) and soil available phosphorus (P) utilizing recycled microtips and microcentrifuge tubes. Students apply their critical thinking abilities to compute and compare the waste generated, the analysis cost, and the time required for each test using the conventional approach (CA) and miniature approach (MA). They further assess the greenness of both approaches using the open-source Analytical GREEnness (AGREE) software. While students carry out these experiments, they acquire laboratory skills and reinforce their understanding of sustainability, Beer–Lambert law, how OC relates to the bioavailability of anionic nutrients such as PO43– phosphate species, and how such relationships can statistically vary based on the methods applied. Learning outcomes were assessed to evaluate the experimental design.

Molecular dynamics simulations, molecular docking, and kinetics study of kaempferol interaction on Jack bean urease: Comparison of extended solvation model.

Since the urease enzyme creates gastric cancer, peptic ulcer, hepatic coma, and urinary stones in millions of people worldwide, it is essential to find strong inhibitors to help patients. Natural products are well known for their beneficial effects on health and efforts are being made to isolate the ingredients, the so-called flavonoids. Flavonoids are now considered as an indispensable component in a variety of nutraceutical, pharmaceutical, and cosmetic applications. Kaempferol (KPF) is an antioxidant found in many fruits and vegetables. Many reports have explained the significant effects of dietary KPF in reducing the risk of chronic diseases such as cancer, ischemia, stroke, and Parkinson's. The current study aimed at investigating the inhibitory impact of KPF on Jack bean urease (JBU) using molecular dynamics (MD) simulations and molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) calculations to confirm the results obtained from isothermal titration calorimetry (ITC), extended solvation model, and docking software. In addition, UV-VIS spectrophotometry was used to study the kinetics of urease inhibition. Calorimetric and spectrophotometric determinations of the kinetic parameters of this inhibition indicate the occurrence of a reversible and noncompetitive mode. Also, the docking and MD results indicated that the urease had well adapted to the kaempferol in the binding pocket, thereby forming a stable complex. Kaempferol displayed low binding energy during MMPBSA calculations. The inhibitory potential of kaempferol was confirmed by experimental and simulation data, but in vivo investigations are also recommended to validate our results.

A tetrad effect in the glass transition of lanthanide‐doped sodium disilicate glasses

AbstractScanning calorimetric determination of the glass transition temperatures (Tg) of sodium disilicate doped individually with 25 wt.% of the oxides of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu reveals the presence of the so‐called “lanthanide tetrad effect” in their glass transition temperatures. This is to the best of our knowledge the first observation of a tetrad effect in the macroscopic properties of a high‐temperature silicate phase.

Elucidation of the sorbent role in sorption thermodynamics of uranium(VI) on goethite.

The sorption process of radionuclides, often conducted at ambient temperature, shows significant sensitivity to the surrounding temperature. Prediction of fate and transport in the environment, therefore, requires accurate thermodynamic data of their species defining sorption-desorption onto solid surfaces. Herein, we examined the thermodynamics of uranium(VI), U(VI), sorption onto goethite with particular emphasis on directly calculating the enthalpy of U(VI) surface species formed under slightly acidic pH conditions. To achieve this aim, a sorption study of U(VI) was carried out on goethite in the pH range 3-10 and modelled using a 2-pK single-site diffuse layer surface complexation model. A binuclear bidentate species of U(VI), (FeO)2UO2, reproduces the sorption profile at pH 3-5 while the sorption was under-estimated in the pH >5 region. Precipitation of schoeptite at pH 5-8 was attributed to the underestimation of the predicted sorption behaviour. The species complexation constant was employed in the analysis of heat consumed, measured using an isothermal titration calorimeter, in the titration of the goethite suspension with U(VI) at pH 4.5 ± 0.1. Enthalpy for the U(VI) species was found to be 41 ± 7 kJ mol-1, suggesting that sorption is an entropically driven process. Comparing thermodynamic data with that of similar U(VI)-iron oxide systems, binding energy of U(VI) surface species, surface hydration and hydrogen binding are suggested as main factors in the sorbent role towards the thermodynamics of the sorption process.

Variation of Nutrient Value in Selected Composted Farm Wastes

Smallholder farming is promoted for its environmental friendliness, assurance of food security sovereignty and conservation of indigenous knowledge. However, in actual practice, Smallholder farmers recycle farm plant waste to improve soil fertility. By so doing, they contribute to environmental pollution, emissions, and global warming. This situation is a Smallholder farmers’ challenge worldwide. One of these challenges is the inability to find cheaper sources of plant nutrients. These sources of nutrients are associated with environmental pollution, such as the release of Methane. This study focused on farm wastes (bean trash, maize trash, banana trash, cattle slurry, goat slurry, and pig slurry) commonly produced by smallholder farmers in two farming systems of Masaka and Lyantonde Districts to explore the effects of composting and surface decomposition on nutrients contained in farm wastes by specifically: estimating baseline nutrient contents in farm wastes before disposal, determining the variation of nutrients of farm wastes managed by composting and surface decomposition and the potential source of major nutrients among selected farm wastes. Through carbon analysis, Calorimetric determination of Nitrogen and Phosphorus analysis using a block digester and UV-Visible spectrometer, Carbon, Nitrogen, Potassium and Phosphorus were determined from bean trash, maize trash, banana trash, cattle slurry, goat slurry, and pig slurry. Results revealed that goat slurry, chicken waste, maize trash and pig slurry contained more and retained more P, K, C and N, respectively, as compared to other farm wastes. Significant volumes of N and P were retained in composted materials as compared to those managed by surface decomposition.

Determination of the thermodynamic potentials of metallic glasses and their relation to the defect structure

We performed calorimetric and shear modulus measurements on four bulk metallic glasses upon heating up to the temperature of the complete crystallization as well as in the fully crystallized state. On the basis of calorimetric experiments, we calculated the excess thermodynamic potentials with respect to the crystalline state—the enthalpy ΔH, entropy ΔS and Gibbs free energy ΔΦ—as functions of temperature. Using high-frequency shear modulus measurements we show that calorimetric determination of ΔH, ΔS and ΔΦ is consistent with the calculation of these potentials within the framework of the interstitialcy theory (IT) within a 15% uncertainty in the worst case for all MGs under investigation. It is concluded that the physical origin of the excess thermodynamic potentials in MGs can be related to a system of interstitial-type defects frozen-in from the liquid state upon melt quenching as suggested by the IT. The estimates of the defect formation enthalpy H f and entropy S f show that H f scales with the shear modulus while S f is quite large (10 k B to 20 k B), in line with the basic assumptions of the IT.

Calorimetric study of the giant magnetocaloric effect in (MnNiSi)0.56(FeNiGe)0.44

${(\mathrm{MnNiSi})}_{0.56}{(\mathrm{FeNiGe})}_{0.44}$ belongs to a new family of alloys, similar to MnAs, showing a magnetostructural first-order transition near room temperature with large latent heat and magnetocaloric effect (MCE). From isothermal magnetization, remarkable values of the entropy change have been reported, such as $|\mathrm{\ensuremath{\Delta}}{S}_{T}|=11.5$ J/kg K at 290 K for the small field change of 1 T, or $|\mathrm{\ensuremath{\Delta}}{S}_{T}|=70.1$ J/kg K for 5 T on a slightly different composition. Strangely, this last value almost doubles that obtained from the Clausius-Clapeyron equation. Therefore, a very detailed set of calorimetric determinations have been made including heat capacity by adiabatic and differential scanning calorimetry (DSC), and direct measurement of the heat absorbed on isothermal demagnetization for several magnetothermal histories of the sample. We found high values of $|\mathrm{\ensuremath{\Delta}}{S}_{T}|=45.7$ J/kg K at 289.4 K for a field change of 7 T, for a sample previously cooled to a low temperature and then heated under magnetic field to the target temperature. This value is high but very far from previously reported data, which happened to be nonphysical but obtained from a very frequently used, but incorrect, experimental protocol to determine $\mathrm{\ensuremath{\Delta}}{S}_{T}$ from magnetization, via the Maxwell relation. The spurious contribution has been analyzed and computed, explaining the nonphysical reported values. The strong thermal and magnetic hysteresis of 8.4 K and 8.3 T, respectively, make this alloy useless for magnetic refrigeration, but the results encourage searching for other derivatives with lower hysteresis which could have even higher $|\mathrm{\ensuremath{\Delta}}{S}_{T}|$.

Investigating the thermodynamics of conformational transitions in DNA oligomers

I first met Professor Wilhelm when I joined the Board of Directors of the North American Calorimetry Conference (CalCon) in 2009. Since that time, I have had the pleasure of seeing him every year at CalCon. Although I am formally trained in organic chemistry, my research has evolved to nucleic acid biophysics. None the less, I would attend Prof. Wilhelm’s lecture whenever possible at the CalCon meetings. The first lecture I attended focused on fugacity and afterwards, I thought to myself: “I could learn some physical chemistry from this man!” I am honored to contribute my story to this special issue of The Journal of Chemical Thermodynamics. The work reviewed below focuses on biophysical approaches by my research group to study conformational transitions in DNA using designed DNA oligomers and monitoring temperature or salt induced transition by optical melting and calorimetric determinations. Further, the influences on DNA sequence context and environmental conditions on these transitions are also discussed.

Evaluation of anticancer activity of Melaleuka Alternifolia. (i. e. tea tree oil) on Breast cancer cell line (MDA MB)- An in-vitro study

Introduction and Aims: According to Globocan 2012, India along with United States and China collectively accounts for almost one third of the global breast cancer burden. India is facing challenging situation due to 11.54% increases in incidence and 13.82% increase in mortality due to breast cancer during 2008–2012. The current treatment modality has issues of drug resistance and side effects. Many anticancer drugs currently used clinically have been isolated from plant species hence, investigation of plant species as a source of experimental therapeutic agents, in treating cancer is currently gaining a lot of importance. One such naturally available plant extract Melaleuka Alternifolia (TTO) which belongs to the family of essential oils is a very good antibacterial, antifungal, antiviral, antiprotozoal and anti-inflammatory agent. But currently there is a lot of importance has been given for its anticancer effect. Hence our aim is to evaluate anticancer activity of Melaleuka Alternifolia on Breast cancer cell line (MDA MB) by MTT assay an in vitro method. Material and Methods: Before the start of the study ethical clearance was obtained from Institutional Review Board. The cytotoxicity checked for Breast cancer cell line (MDA MB) and NIH 3T3 mouse fibroblasts which were used as a control in our current study. These cell lines were procured from NCCS Pune, India. 1. MTT solution preparation (stock solution): 5 mg in 1 ml of PBS. 2. Cell culture : The cell lines were maintained in 96 wells micro titer plate containing MEM media supplemented with 10% heat inactivated fetal calf serum (FCS), containing 5% of mixture of Gentamicin (10ug), Penicillin ( 100 Units/ ml) and Streptomycin (100µg/ml) in presence of 5% CO2 at 37oC for 48-72 hours. 3. Cytotoxicity Assay: In vitro growth inhibition effect of test compound was assessed by calorimetric or spectrophotometric determination of conversion of MTT into Formazan blue by living cells. Results: The results represent the mean of five readings. The IC50 value of tea tree oil for breast cancer cell line (MDA MB) after 48 hrs was 25µg/ml. Spearmans rho’s Correlation showed P value Conclusion: TTO has a promising anticancer property against Breast cancer cell line (MDA MB) with its IC50 value 25µg/ml. Hence this TTO with its greater efficacy related to its anticancer activity can be brought to the level of clinical trials in the coming future. Keywords: Cytotoxicity, MTT assay, MDAMB cell line, Tea tree oil.

Calorimetric Determination of the Formation Enthalpies of Cs Polymolybdates at 298.15 K and 0.1 MPa

Samples of cesium polymolybdates Cs2MonO3n+1 with n = 2, 3, 5, and 7 have been synthesized by melting and cooling stoichiometric mixtures of commercially available Cs2MoO4 and MoO3 powders. The sin...

Monte Carlo and water calorimetric determination of kilovoltage beam radiotherapy ionization chamber correction factors

The in-phantom calibration method for radiotherapy kilovoltage x-ray beams requires ionization chamber correction factors. The overall ionization chamber correction factor accounts for changes in the chamber response due to the displacement of water by the chamber cavity and wall, the presence of the stem and the change in incident photon energy and angular distribution in the phantom to that in air. A waterproof sheath, if required, is accounted for in a sheath correction factor. The aim of this study is to determine chamber correction factors through Monte Carlo (MC) simulations and water calorimetry measurements. Correction factors are determined for the PTW TM30013, NE2571, IBA FC65-G, IBA FC65-P and Exradin A12 ionization chambers. They are compared to experimental values obtained at the German national metrology institute Physikalisch-Technische Bundesanstalt (PTB) with their water calorimetry-based absorbed dose to water primary standard and at other national metrological institutes. An uncertainty analysis considers the contributions to the uncertainty on the chamber correction factors from the field size, photon cross sections, photon fluence spectra and chamber wall and central electrode dimensions. The MC calculated chamber correction factors are within 2.2% of unity with a standard uncertainty of 0.3%. For the 50 kV and 100 - 140 kV radiation beam qualities, the calculated correction factors deviate from the measured correction factors (with a standard uncertainty of 1%) by up to 2.6%. The calculated chamber correction factors for the PTW TM30013 and Exradin A12 are consistent with those derived from the BIPM kilovoltage primary standard. The inconsistencies between the calculated and experimental chamber correction factors indicate the need to further investigate the accuracy of kilovoltage absorbed dose to water primary standards and the use of MC simulations to determine kilovoltage beam chamber correction factors.

Thermodynamic Study of Barium Cerate (BaCeO3) by Knudsen Effusion Mass Spectrometry

The vaporization/decomposition of single-phase BaCeO3 samples was studied by the Knudsen Effusion Mass Spectrometry technique in the overall temperature range 1647–1923 K. The partial pressures of the gaseous species BaO(g), CeO2(g) and CeO(g) were monitored as a function of temperature. The formation of reduced form of cerium oxide as a product of the high temperature decomposition of BaCeO3 under the given experimental conditions was suggested by the low value of the measured CeO2(g)/CeO(g) pressure ratio and confirmed by the XRD spectra of the vaporization residues. The equilibrium data were tentatively processed according to various heterogeneous equilibria that may be established in the cell: (i) BaCeO3(s) = BaO(g) + CeO2(s); (ii) BaCeO3(s) + CeO(g) = BaO(g) + Ce2O3(s); (iii) BaCeO3(s) = BaO(g) + CeO2(g). The corresponding enthalpy changes were calculated by the third-law method and the enthalpy of formation of BaCeO3 derived thereafter. The thermodynamic analysis confirms that the decomposition process forming CeO2(s) is very unlikely to occur under the high temperature, high vacuum conditions used in the present study. The analysis of process BaCeO3(s) = BaO(g) + CeO2(g), not involving solid products, was selected as the most reliable and leads to a value for the enthalpy of formation of barium cerate (Δf$$H_{{298}}^{^\circ }$$ (BaCeO3) = –1688.7 ± 6.2 kJ/mol) in agreement with the available calorimetric determinations.

Calorimetric determination of the thermodynamics of alcohol-surfactant mixed micelle formation: Temperature and concentration effects

The thermodynamic parameters of surfactant/alcohol mixed micelles were determined in mixtures of sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) in a series of solvents composed of varying concentrations of n-propanol (C3OH), n-butanol (C4OH), and n-pentanol (C5OH). Conductivity studies were used to determine CMC values and the degrees of counterion binding. Isoperibol solution calorimetry was used to directly determine CMC values and enthalpy of micellization (ΔmicH). From these experimentally determined values, the Gibbs energy and entropy of micellization were calculated as a function of temperature and alcohol concentration. In general, CMC values decreased with increasing alcohol carbon chain length and concentration but increased with temperature. The effects of temperature, alcohol carbon chain length, and alcohol concentration on the energetics of these mixed micellar systems are explained in terms of the relative contributions to ΔmicH by alkyl chain interactions, hydrophobic effects, and electrostatic contributions.

Standard enthalpy of formation of selenium stannite Cu2FeSnSe4

The calorimetric determination of the standard enthalpy of formation of Cu2FeSnSe4 selenium stannite (CITSe) was carried out for the first time. This compound in its pure form does not occur in nature, but is a promising functional material (direct-gap semiconductor) and is used in photovoltaics to create solar cells as an alternative to silicon. The standard enthalpy of Cu2FeSnSe4 formation was obtained by measuring the heat of its formation from the elements in the calorimeter according to the reaction 2Cu + Fe + Sn + 4Se Cu2FeSnSe4. As a result, the standard enthalpy of formation is detrmined: ∆fH0298.15K(Cu2FeSnSe4) = (254.11 3.96) kJ/mol.

Thermometric analysis of blood metabolites in ICU patients

Real-time monitoring of patient’s blood metabolites, such as glucose and lactate, could potentially improve surgery and recovery outcomes for patients in surgical and intensive care units. Our enzyme thermometric biosensor which is based on flow injected calorimetric determination of immobilized enzyme reaction is capable of performing continuous, fast, and quantitative analysis of metabolites using whole blood. A key technical advantage the assay affords is the ability to use unpretreated whole blood. In this article, the enzyme thermometric biosensor was used, for the first time, to determine glucose and lactate concentrations in the blood of ICU patients. The linear detection range for glucose was 0.5–30 mM and 0.25–12 mM for lactate, using a 20 μL sample volume. A maximum sampling rate of 15 measurements per hour was achieved using venous blood samples, which corresponds to a 4-min measurement interval. In order to validate the accuracy of the results, a comparative analysis between the thermometric biosensor and the clinically applied instrument (LifeScan’s OneTouch®) which is based on disposable dry chemical reaction was performed using samples from 33 patients. The results showed a good correlation between the two methods for both glucose (r = 0.843, p < 0.0001) and lactate (r = 0.78, p = 0.0105). The ability to monitor metabolite levels and trends on a clinically relevant timescale of 5 min is critical for intensive monitoring of ICP and operative patients.

Thermochemistry of Surfactant-Templating of USY Zeolite.

With the aim of understanding the thermochemistry of the introduction of mesoporosity in zeolites by using surfactants, high temperature oxide melt solution calorimetry was used to determine the change in the enthalpy of formation of USY zeolite before and after the introduction of mesoporosity. Our results confirm that this process only slightly destabilizes the zeolite by the additional surface area. However, this can be overcome by the stabilizing effect of the interactions between the surfactant and the zeolite framework.

Comparative Study on Calorimetric Determination of Power Numbers in a Lab Scale Batch Reactor

Accurate measurement of power numbers on lab scale reactors can provide useful information about the needed energy to reduce mass transfer problems. Next, this knowledge can be used to avoid scale-up problems (Paul et al., 2004). In this study, the accuracy and applicability of four methods to determine the power number in a 1 L reactor are tested: calorimetry, torque measurement, computational fluid dynamics (CFD) and the Furukawa et al. correlation (Furukawa et al., 2012). Experiments with water and 2-octanol are performed with a 4-bladed 45 ° pitched blade turbine (4PBT) and 6-bladed Rushton turbine in baffled and unbaffled conditions. At low rotational speed, experimental techniques record higher power numbers compared to the theoretical techniques. The calorimetric method is only accurate at rotational speeds above 300 RPM due to insufficient heat flow at lower settings. Torque measurement is most accurate at low rotational speed, before the vortex reaches the stirrer and creates cavities that lead to inaccurate results. At rotational speeds higher than 300 RPM, differences between the four techniques are less than 30 %, confirming the accuracy of all methods. Therefore, literature correlations can be used for a quick estimation of the power number in lab scale reactor experiments at high rotational speed. However, experimental techniques are recommended for accurate power number measurements at low rotational speed and for specific reactor set-ups which are not described in literature.