Microcalorimetric Study Research Articles

Microcalorimetric Study of the Effect of CeIII on Metabolic Activity of Mitochondria Isolated from Indice Rice 9311

Rare earth elements (REEs) have beneficial influence on plant growth and are widely used in agriculture practice, but little is known about behavior of the REEs on mitochondria in plant cells. Thermogenic metabolic curves were determined by the ampoule method at 303 K using a TAM air isothermal microcalorimeter in mitochondria isolated from indice rice 9311 (Oryza sativa L.), and the effect of Ce(III) on mitochondrial metabolism was investigated. By analyzing the obtained heat flux curves, the crucial parameters such as activity recovery rate constant (k) and maximum heat power (P(m)) were investigated. Application of Ce3+ in concentrations ranging from 0 to 120 microg/ml significantly increased k and P(m) values, with the maximum reaching 261 and 180% of the control, respectively. Concentrations from 140 to 150 microg/ml had the opposite effect. These results were consistent with previous reports on the effects of REEs on plant growth. It was concluded that the Ce(III)-induced change of mitochondrial metabolic activity is a possible mechanism by which Ce(III) influenced indice rice 9311 growth.

A Microcalorimetric Study of the Heat Effects of Sorption of Imino Acids on KU-2 × 8 H-Sulfocation Exchanger

The thermokinetic characteristics of sorption of proline and hydroxyproline on H-sulfocation exchanger were determined. The absorption of dipolar imino acid ions by the cation exchanger was found to be an exothermic process accompanied by a decrease in the enthalpy component of sorption. The enthalpy character of sorption was to a greater extent characteristic of hydroxyproline.

Microcalorimetric Study on Effect of Chromium(III) and Chromium(VI) Species on the Growth ofEscherichia coli

AbstractThe effects of Cr(III) and Cr(VI) species (Cr2O72−, CrO42−and Cr3+) on the growth ofEscherichia coli(E. coli) have been investigated in detail by microcalorimetry at 37 °C. Parameters including the growth rate constant (k), inhibitory ratio (I), half‐inhibitory concentration (IC50), total heat output (Qtotal), time of the maximum heat production (tlog) in the log phase have been obtained. The results showed that Cr(VI) and Cr(III) had the inhibition effect on the growth ofE. coliin aquatic environment; however, the inhibitory ratio of Cr(III) toE. coliwas smaller than that of Cr(VI). Thekvalues ofE. coliin the presence of Cr(VI) and at high concentrations of Cr(III) were decreased with increasing the concentrations of these chromium species. Among the three chromium species investigated, Cr2O72−was found to be the most poisonous species againstE. coliwith an IC50value of 35.52 µg·mL−1. CrO42−exhibited moderate toxicity onE. coliwith an IC50of 50.24 µg·mL−1, and Cr3+had the lowest toxicity with an IC50of 84.30 µg·mL−1. Microcalorimetry can provide a convenient, sensitive and reliable method to study the effect of various metal species on the growth of bacteria or other microorganisms.

Thermal stability of acrylic bone cement powder under shelf storage conditions: An isothermal microcalorimetric study

Heat-conduction isothermal microcalorimetry was used to measure the exothermic heat flow rate (Q) from the powder of a widely used commercially-available acrylic bone cement, Palacos R, when it interacted with ambient laboratory air, as a function of time, t, in the calorimeter, for up to 200 h. Four variants of the powder were used, these being unsterilized, sterilized using ethylene oxide gas, gamma-irradiated, in ambient air, with a minimum dosage of 2.5 Mrad, and gamma-irradiated, in ambient air, with a minimum dosage of 4.5 Mrad. In each case, the powder variant was tested after being stored on the shelf, under ambient conditions, for 2 days, 3 weeks and 9 months immediately following sterilization. Best-fit correlations between Q and t for each powder variant were determined. Then, this relationship was integrated over the period 14 h< or =t< or =200 h to give an estimate of the "effective" heat flow, Q(eff). For powder variants tested 2 days after being sterilized, the difference in their thermal stabilities (Qeff ranged from 0.19+/-0.01 to 0.62+/-0.03 microJ/g, respectively) was significant in the case of some pairs and not for others. However, for powders tested either 3 weeks or 9 months following sterilization, there was no significant difference between the means of Qeff (they ranged from 0.18+/-0.01 to 0.31+/-0.07 microJ/g) for any pair. These results suggest that an acrylic bone cement in which the powder is EtO-sterilized may be mixed with the liquid monomer for use in cemented arthroplasties after any length of time of shelf storage of the powder, under ambient conditions, whereas, for powders that are gamma-irradiated and then stored under the same conditions, at least 3 weeks should elapse before they are used in these procedures.

Microcalorimetric Study of the Influence of Alcohols on the Critical Micelle Concentration and Thermodynamic Functions of Nonaqueous Micelle Solutions at 298.15 K

The power-time curves of the micellization process were determined for two kinds of anionic surfactants [sodium laurate (SLA) and sodium dodecyl sulfate (SDS)] and a kind of nonaqueous solvent [N,N-dimethyl formamide (DMF)] with mixed alcohols by titration microcalorimetry. From the data of the lowest point and the area of the power-time curves, the critical micelle concentration (CMC) and ΔH 0 m were obtained. ΔG 0 m and ΔS 0 m were also calculated according to the thermodynamic theory. For different surfactants, cosurfactants, and solvents, the relationships between the alcohol's carbon number, concentration, and CMC and the thermodynamic functions are discussed. For an identical alcohol concentration at the same temperature, the values of CMC, ΔH 0 m , ΔG 0 m , and ΔS 0 m decrease with an increase in the carbon number of the alcohol. For each alcohol at the same temperature, the CMC and ΔG 0 m increase, while ΔH 0 m and ΔS 0 m decrease with an increase in the alcohol concentration.

Microcalorimetric study of the inhibition of butyrylcholinesterase by carbamates

The inhibition of horse serum butyrylcholinesterase (EC 3.1.1.8) by three carbamates (eserine, neostigmine, and rivastigmine) was studied by flow microcalorimetry at 37 °C in Tris buffer (pH 7.5). The kinetics of carbamylation was studied in the absence or presence of the substrate, butyrylcholine, using an extension of the model described by Stojan and coworkers (FEBS Lett. 440 (1998) 85–88). The model was fitted to the data by a nonlinear regression procedure using simulated annealing followed by Marquardt’s method. The affinity of the carbamates for the free enzyme increased in the order neostigmine < eserine < rivastigmine, whereas the carbamylation rates followed an inverse order. In the case of rivastigmine, the results suggested that an acyl-enzyme–inhibitor complex could be formed either by reversible binding of the carbamate to the acyl-enzyme or by acylation of the enzyme–inhibitor complex. This work confirms the usefulness of microcalorimetry to study irreversible or progressive inhibitors and emphasizes the need to investigate the binding of such compounds to intermediate enzyme forms.

Thermodynamics of Hydrophobic Interactions: Entropic Recognition of a Hydrophobic Moiety by Poly(Ethylene Oxide)–Zinc Porphyrin Conjugates

The recognition of 4-alkylpyridines by water-soluble poly(ethylene oxide)-zinc porphyrin conjugates was studied with a focus on the thermodynamic parameters of binding. Microcalorimetric studies indicated that binding of the alkyl group of the guest in water is driven by the entropic term (delta DeltaH0 = DeltaH0(4-pentylpyridine) - DeltaH0(4-methylpyridine) = +1.7 kJ mol(-1), deltaT DeltaS0 = TDeltaS0(4-pentylpyridine) - TDeltaS0(4-methylpyridine) = +11.8 kJ mol(-1) at 298 K), thus showing the significance of water reorganization during host-guest interaction. The enthalpy-entropy compensation temperature of binding of 4-alkylpyridines was as low as 38 K; only below this temperature could the enthalpic term be a driving force. The binding affinity was modulated by the addition of cations and by varying the degree of polymerization of poly(ethylene oxide), which suggests that guest binding is coupled with polymer conformation.

Estimation of vitamin E in plant oils by microcalorimetry

Microcalorimetric studies were performed to estimate the content of vitamin E (tocopherols) in natural plant oils. The approach used was a kinetic method of estimating vitamin E and was based on the ability of tocopherols to inhibit a liquid-phase free-radical oxidation reaction. A model reaction consisting of the initiation of cumene (isopropylbenzene) oxidation showed that fatty oils inhibit the free-radical reaction with an induction period proportional to the content of tocopherols in oils. Tocopherol contents measured here were in good agreement with values reported in the literature. Experimental curves were used to calculate oxidation inhibition rate constants; all the oils tested (cameline seed, wintercress, rapeseed, and cedar) had essentially identical values, at k 7 = (1.4–6.8) × 104 mol/liter · sec.

Microcalorimetric study the toxic effect of hexavalent chromium on microbial activity of Wuhan brown sandy soil: An in vitro approach

A multi-channel thermal activity monitor was applied to study soil microbial activity in Wuhan brown sandy soil in the presence of different concentrations of hexavalent chromium ( K 2 Cr 2 O 7 ) . In order to stimulate the soil microbial activity, 5.0 mg of glucose and 5.0 mg of ammonium sulfate were added to a 1.20-g soil sample under a controlled humidity of 35%. The results show that the poisonous species of K 2 Cr 2 O 7 at an half inhibitory concentration ( IC 50 ) value of 4.27 μ g mL - 1 against soil microbe, and an increase of the amount of hexavalent chromium is associated to a decrease in the microbial activity of the soil, probably due to an increase in the toxicity of hexavalent chromium, affecting strongly the life in this soil microbial environment. Our work also suggests that microcalorimetry is a fast, simple and more sensitive method that can be easily performed to study the toxicity of different species of heavy metals on microorganism compared to other biological methods.

Microcalorimetric study on the bacteriostatic activity of isoquinoline alkaloids

The isoquinoline alkaloids were isolated from traditional Chinese drugs of Phellodendri Cortex, Radix Stephaniae Tetrandrae, Corydalis Yanhusuo and Corydalis Bungeana. The power-time curves of growth of E. coli at different concentrations of isoquinoline alkaloid at 37°C were determined by a 2277 Thermal Activity Monitor. The rate constant of bacteriostastic activity was calculated. The relationship between growth rate constant and concentration was established. The optimum bacteriostastic concentration was determined. Experimental results have indicated that all the isoquinoline alkaloids isolated from the four kinds of traditional Chinese drugs have bacteriostastic activity and the order is Phellodendri Cortex>Radix Stephaniae Tetrandrae>Corydalis Yanhusuo>Corydalis Bungeana.

Complexation and transport of transition and heavy metal cations by p-tert-butyldihomooxacalix[4]arene tetraketones and X-ray crystal structure of the tert-butyl ketone derivative

The binding properties of three p-tert-butyldihomooxacalix[4]arene tetraketone derivatives (tert-butyl 2b, adamantyl 2c and phenyl 2d) in the cone conformation and one derivative (methyl 2a) in a partial cone conformation, towards transition (Mn2+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+) and heavy (Ag+, Cd2+, Hg2+ and Pb2+) metal cations have been established by extraction studies of metal picrates from water into dichloromethane, transport experiments with the same salts through a dichloromethane membrane and stability constant measurements in methanol and acetonitrile. Results concerning the microcalorimetric study of Cu2+, Ag+ and Pb2+ complexes in methanol are presented. The affinity of the ligands for some cations (Zn2+, Ag+, Pb2+ and Hg2+) has also been investigated by proton NMR spectrometry. The X-ray crystal structure of tert-butylketone 2b was determined. Towards transition metal cations, ketones 2b, 2c and 2d are reasonable binders, showing in general preference for Cu2+. Methylketone 2a is a poor binder for these cations, due to its partial cone conformation. The three ligands in the cone conformation present a high affinity for the heavy metal cations, with selectivities for Ag+ and Pb2+. This series of cations is even fairly well complexed by methylketone 2a, which presents high stability constants for Hg2+ and Pb2+. The cases studied by 1H NMR titrations confirm the formation of 1 : 1 complexes between the ketones and the cations, also indicating that they should be located inside the cavity defined by the phenoxy and carbonyl oxygen atoms. Ketones 2b, 2c and 2d show transport rate sequences that follow, in general, the same trends observed in extraction and complexation for transition cations, but they are reversed for the heavy metal cations.

Kinetic, Thermodynamic, and Mechanistic Patterns for Free (Unbound) Cytochrome c at Au/SAM Junctions: Impact of Electronic Coupling, Hydrostatic Pressure, and Stabilizing/Denaturing Additives

Combined kinetic (electrochemical) and thermodynamic (calorimetric) investigations were performed for an unbound (intact native-like) cytochrome c (CytC) freely diffusing to and from gold electrodes modified by hydroxyl-terminated self-assembled monolayer films (SAMs), under a unique broad range of experimental conditions. Our approach included: 1) fine-tuning of the charge-transfer (CT) distance by using the extended set of Au-deposited hydroxyl-terminated alkanethiol SAMs [-S-(CH(2))(n)-OH] of variable thickness (n=2, 3, 4, 6, 11); 2) application of a high-pressure (up to 150 MPa) kinetic strategy toward the representative Au/SAM/CytC assemblies (n=3, 4, 6); 3) complementary electrochemical and microcalorimetric studies on the impact of some stabilizing and denaturing additives. We report for the first time a mechanistic changeover detected for "free" CytC by three independent kinetic methods, manifested through 1) the abrupt change in the dependence of the shape of the electron exchange standard rate constant (k(o)) versus the SAM thickness (resulting in a variation of estimated actual CT range within ca. 15 to 25 A including ca. 11 A of an "effective" heme-to-omega-hydroxyl distance). The corresponding values of the electronic coupling matrix element vary within the range from ca. 3 to 0.02 cm(-1); 2) the change in activation volume from +6.7 (n=3), to approximately 0 (n=4), and -5.5 (n=6) cm(3) mol(-1) (disclosing at n=3 a direct pressure effect on the protein's internal viscosity); 3) a "full" Kramers-type viscosity dependence for k(o) at n=2 and 3 (demonstrating control of an intraglobular friction through the external dynamic properties), and its gradual transformation to the viscosity independent (nonadiabatic) regime at n=6 and 11. Multilateral cross-testing of "free" CytC in a native-like, glucose-stabilized and urea-destabilized (molten-globule-like) states revealed novel intrinsic links between local/global structural and functional characteristics. Importantly, our results on the high-pressure and solution-viscosity effects, together with matching literature data, strongly support the concept of "dynamic slaving", which implies that fluctuations involving "small" solution components control the proteins' intrinsic dynamics and function in a highly cooperative manner as far as CT processes under adiabatic conditions are concerned.

Microcalorimetric study on the growth and metabolism of microencapsulated microbial cell culture

The rate of heat output is one of the suitable measurements of metabolic activity of the organism or its parts, down to the cellular or even the sub-cellular levels. In this paper, microcalorimetry was first applied to study the metabolic activity of microbial in both alginate–polylysine–alginate and alginate–chitosan–alginate microencapsulated cultures as well as in free non-encapsulated culture. The organisms used for the measurements were Escherichia coli and Saccharomyces cerevisiae. As a result of this work, it was found that, despite E. coli cell in free non-encapsulated culture has the highest metabolic rate due to the highest value of heat output, the proliferation of the cells terminates quickly with a lowest biomass formed. And we found also an obviously longer stationary phase in microencapsulated culture. As far as S. cerevisiae was concerned, it was found that there was also the highest value of heat output in free non-encapsulated culture, but the cell density was lower than that in microencapsulated culture. On account of the microcalorimetric and metabolic measurements, it can be concluded that more substrate can be used to convert to biomass in microencapsulated culture which means a higher biomass yield existed.

Microcalorimetric Study on the Effect of Sodium Arsenite on Metabolic Activity of Mitochondria Isolated fromCarassius auratus Liver Tissue

Metabolic thermogenic curves of mitochondria isolated from liver tissue of Carassius auratus and the effect of different concentration of NaAsO2 on it were investigated by TAM air isothermal microcalorimeter, ampoule method, at 28.00 °C. From the thermogenic curves, activity recovery rate constants k, the maximum heat production rate (Pmax) and the total heat produced (Q) were obtained. The values of k and Pmax decline gradually with the increase of the concentration of NaAsO2, and both of the values of Pmax and k are highly correlated to the concentration of NaAsO2. When concentration of NaAsO2 reached 16.0 µg/mL, the maximum heat production rate dropped to 70.8% of the control group, and the corresponding percentage of k was 71.4% of the control group. This experimental result indicates that the addition of NaAsO2 has restrained the metabolic activities of mitochondria in vitro.

Detailed in Situ XRD and Calorimetric Study of the Formation of Silicate/Mixed Surfactant Mesophases under Alkaline Conditions. Influence of Surfactant Chain Length and Synthesis Temperature

The formation of mesoscopically ordered silica/surfactant composites under alkaline synthesis conditions has been studied by time-resolved in situ small-angle X-ray diffraction with synchrotron radiation. Alkyltrimethylammoniumbromide surfactants, C(n)()TAB, of different chain lengths (n = 14, 16, and 18) as well as mixtures thereof were used as structure directing agents and the measurements were carried out at two different temperatures. A linear relationship between the mean surfactant chain length and the d spacing of the hexagonal phase was observed, suggesting an ideal mixing of the surfactants in the supramolecular surfactant aggregates. It is shown that the formation of the hexagonal phase is kinetically controlled mainly by the rate of silicate condensation, while the effect of changes in the surfactant chain length on the kinetics is small under the studied conditions. Two concominant, albeit partly interlinked, processes, suggested being intra- and intermicellar condensation, followed by aggregate-aggregate condensation, govern the nucleation and growth of the hexagonal phase. The two-step mechanism is confirmed by a microcalorimetric study where the heat evolved during the hydrolysis-condensation reactions is followed as a function of time.

Microcalorimetric Study on Interaction between PEO‐PPO‐PEO Triblock Copolymers and Sodium Dodecyl Trioxyethylenated Sulfonate in Aqueous Solutions

Interactions between three triblock copolymers of poly (ethylene oxide)‐poly (propylene oxide)‐poly (ethylene oxide), EOmPOnEOm, and the ionic surfactant sodium dodecyl trioxyethylenated sulfonate, C12E3S, in aqueous solutions were investigated with titration microcalorimetry at 293.15 K. Values of enthalpies, entropies, and free energies of interaction have been derived. The thermodynamic data indicate that interactions between EOmPOnEOm and C12E3S decrease with the increase of m/n.

Flow microcalorimetric study of butyrylcholinesterase kinetics and inhibition

The enzymatic hydrolysis of butyrylcholine, catalyzed by horse serum butyrylcholinesterase (EC 3.1.1.8), was studied at 37 °C in Tris buffer (pH 7.5) by flow microcalorimetry. A convolution procedure, using the Gamma distribution to represent the impulse response of the calorimeter, was developed to analyze the microcalorimetric curves. After correction for buffer protonation, the hydrolysis reaction was found to be slightly endothermic, with Δ H = +9.8 kJ mol −1. Enzyme kinetics was studied with both the differential and integrated forms of the Michaelis equation with equivalent results: Michaelis constant K m = 3.3 mM, catalytic constant k cat = 1.7 × 10 3 s −1, bimolecular rate constant k s = 5.1 × 10 5 M −1 s −1. The reaction product, choline, was found to be a competitive inhibitor with a dissociation constant K i = 9.1 mM. Betaine had a slightly higher affinity for the enzyme, but the inhibition was only partial. This study confirms the usefulness of microcalorimetry for the kinetic study of enzymes and their inhibitors.

Microcalorimetric studies on the adsorption of DNA by soil colloidal particles

This study applied TAM air isothermal calorimeter to measure the adsorption enthalpies of DNA on eight colloidal fractions from permanent-charge and variable-charge soils. The adsorption of DNA on soil colloids was also examined by equilibrium adsorption analysis. The data evaluated from isotherms fitted by Langmuirean model revealed that the affinity of DNA for variable-charge soil colloids was higher than that for permanent-charge soil colloids. More tightly bound DNA molecules were observed on coarse clays and inorganic clays than on fine clays and organic clays, respectively. The adsorption enthalpies of DNA on permanent-charge soil colloids were higher than those on variable-charge soil colloids. DNA adsorption on organic clays is endothermic, whereas that on inorganic clays is exothermic. Dehydration and electrostatic repulsion were considered to cause the higher adsorption enthalpies of DNA with organic clays, while hydrogen bonding, ligand exchange and electrostatic attraction result in the lower DNA adsorption enthalpies on inorganic clays. The thermodynamic parameters presented in this study have important implication for providing further insight into mechanisms of the adsorption of DNA on soil particles.

Microcalorimetric study of sorption of water and ethanol in zeolites 3A and 5A

Sorption of water and ethanol in zeolites 3A and 5A was investigated using gas flow-through microcalorimetry in view of finding differences in these materials performance as potential sorbents in the process of drying of ethanol. In microcalorimetric experiments, both zeolites show comparable properties for the sorption of water, but they differ profoundly in their sorption of ethanol, which was negligible small in zeolite 3A compared to zeolite 5A, in spite of the much larger enthalpy of sorption of ethanol in zeolite 3A. The difference can be explained in terms of a steric hindrance preventing the ethanol molecules from entering the narrow pores of the 3A structure, with the 5A structure remaining easily accessible for both the water and ethanol molecules alike. We propose to use a size selectivity index, defined as the ratio of sorption capacity of water and ethanol, to characterise the applicability of a zeolite as sorbent for drying of ethanol. The thermal effects of sorption of water in zeolite 3A was found to be a function of the nature of carrier gas, He or N 2, used in microcalorimetric measurements.

Microcalorimetric Study of Energy Metabolism of HSV‐2 and FMDV Infection Processes

AbstractThe metabolic thermogenic power data of the HSV‐2 infected HeLa cells and the FMDV infected BHK‐21 cells were determined by LKB‐2277 bioactivity monitor. The aim of the study was to investigate the difference of the cell metabolism under the action of two different viruses and the effects of hyperthermia and drugs on it. The results illustrated that the metabolic thermogenic power of infected cells was larger than the uninfected ones and there was a significant difference between the metabolism heat released by the two types of infected cells. From the maximal thermal power and total metabolism heat, the infection process was observed to be thermosensitive and could be inhibited by interferon. Our experiments also revealed that 6 month storage of FMDV could attenuate its virulence and infectivity. The study shows that microcalorimetry is a potent tool to investigate the metabolism of virus infection process.