Microcalorimetric Technique Research Articles

Study on the toxic effects of diphenol compounds on soil microbial activity by a combination of methods

Microcalorimetric technique based on heat-output measurement, direct microorganism counting and enzymatic activity determination, have been explored to evaluate the toxic effects of diphenol species (catechol, resorcinol, and hydroquinone) on soil microbial activity. The thermokinetic parameters including growth rate constant ( k), inhibitory ratio, half inhibitory concentration and total thermal effect ( Q total), were calculated and compared using the data obtained from the power–time curves of the microcalorimeter. It was found that addition of high concentrations of diphenol compounds to the soil samples resulted in low microorganism counts. The trend of the number of cultivable microorganisms with increasing concentration of diphenols was similar to specific growth rate k. It appeared that the higher the water soluble carbon (WSC) content, the higher the Q total value. The low dehydrogenase and β-glucosidase found in the soils treated by catechol and hydroquinone was possibly due to their low WSC concentration and high inhibitory effects, respectively. The results reveal the toxicity of the three diphenols in a descending sequence: hydroquinone, resorcinol and catechol. The combination of the three methods is a more comprehensive toxicological investigation of a complex microbiological system. Microcalorimetry is for studying the metabolic growth of microorganisms, the plate counting method is for quantifying the real microbial growth, and the soil enzyme activity is for assessing the intracellular and extracellular activity of microbial biomass. Our proposed methods can provide toxicological information of diphenols to soil microbes from the metabolic, microbial and biochemical point of views which are consistent with and correlated to each other.

Thermodynamic study of proton transfer reactions of Re(V) trans-dioxocomplexes in aqueous solution

The thermodynamics of protonation of trans-[Re(V)O(2)L(2)](+) (L = aliphatic di and polyamines) complexes in aqueous solution was studied by using experimental and theoretical approaches. The complexes containing diamines undergo protonation on the oxo ligands, whereas those containing polydentate amines protonate on uncoordinated amino groups. The protonation reactions were studied experimentally by microcalorimetric techniques, in all cases exothermic with |DeltaH degrees | ranging from 7 to 50 kJ/mol. For complexes containing diamines, the exothermicity was in concordance with the basicities in some cases, while in others no systematic behaviour was found. For complexes with polydentate amines, the enthalpy dominates with a modest influence on the entropy. Theoretically, Density Functional Theory (DFT) methods were employed in the gas phase, and bulk solvent effects were treated by means of the Polarizable Continuum Model. Direct solute-solvent effects were considered adding explicit water molecules. The enthalpy change calculated in the gas phase was in marked disagreement with the experimental results due to the relevancy of solvation/desolvation processes. The explicit inclusion of water molecules led to a good improvement. A discrete-continuum model was also employed, for which DeltaG degrees was overestimated in all cases. Further investigations, both experimental and theoretical are necessary to get a more complete picture of the proton transfer reactions of these complexes. The experimental values herein determined constitute the first step to construct a set of data to which it is possible to benchmark new theoretical approaches to compute the thermodynamics of proton transfer reactions of metal complexes in aqueous solution.

The toxic effect of cadmium on pure microbes using a microcalorimetric method and a biosensor technique

A microcalorimetric technique based on microbes heat-output was explored to evaluate the effect of Cd (II) on Bacillus subtilis and Candida humicola. The power-time curves of the growth metabolism of Bacillus subtilis and Candida humicola and the effect of Cd (II) on it were studied by using a TAM III microcalorimeter, ampoules method at 28°C. For the evaluation of toxic effect on pure micro-organisms, the maximum peak-heat output power (P max) in the growth phase, the growth rate constants (k), the log phase heat effects (Q log), and the total heat effect (Q T) for Bacillus subtilis and Candida humicola were determined. Dissolved oxygen and biochemical oxygen demand (BOD) were evaluated by a biosensor. Cadmium has been regarded as the essential biological trace element. Cd (II) solutions of different concentration have different effects on Bacillus subtilis and Candida humicola growth metabolism. The higher concentrations of Cd (II) inhibit the growth of Candida humicola (1600–3200 μ g·mL−1), Bacillus subtilis (240–480 μg·mL−1); the lower concentrations can promote the growth of both micro-organism. The values of cell dry weight is also showed in conformity in the cell dry weight changes to the micro-organisms' growth time. Comparison of growth curves of two micro-organisms showed that both the trends of biochemical oxygen demand were exhibiting regressive changes with the passage of time during their generation times (t G). Results from ultraviolet spectrophotometer and precision pH meter all showed that the control growth curves were visioning same trends with the thermodynamic curves of micro-organisms measured by microcalorimeter.

Predicting relative low-temperature tolerance of non-acclimatized buffalograss using calorimetric data

No information is available regarding the usefulness of calorimetry in assessing freeze tolerance, cold hardiness and associated mechanisms in turfgrass. In this study, isothermal and scanning microcalorimetric techniques were used to determine relative low-temperature tolerance and freezing points of leaf and root segments of three, non-acclimatized buffalograss ( Buchloe dactyloides (Nutt.) Engelm.) genotypes. Based on isothermal microcalorimetric data, genotype NE91-118 (cultivar now known as ‘Prestige’) was less affected by low temperatures than either genotype 609 or UCD 95 in the −5 to −15 °C range suggesting greater cold hardiness for ‘Prestige’. Among the three genotypes tested, leaf and root segments of ‘Prestige’ froze at the lowest temperature, 609 was intermediate, and UCD 95 froze at the highest temperature. Scanning microcalorimetry showed that the freezing points of root segments were 7.5–8.8 °C higher than leaf segments for all three genotypes. Our results suggested that the lower freezing temperatures and the greater ability to maintain metabolic stability after exposure to low temperatures contributed to the higher degree of freezing tolerance of ‘Prestige’. Results indicated that calorimetry was an effective tool for determining low-temperature tolerance.

Toxic Effect of Inorganic Arsenite [As(III)] on Metabolic Activity of Bacillus subtilis by Combined Methods

In this study, microcalorimetry and measurement of culture turbidity were applied to evaluate the As(III) toxic effect on the metabolic growth of Bacillus subtilis. Using a multichannel thermal activity monitor, the power-time curves of the metabolic activity of B. subtilis during growth in the absence and presence of various concentrations of As(III) were obtained and studied. The turbidity changes during B. subtilis growth with As(III) were investigated by ultraviolet-visible spectrophotometry and the data agree with the results obtained by microcalorimetry. As(III) of various concentrations has different effects on the metabolic growth of B. subtilis with biphasic dose-response relationships called hormesis [i.e., low-concentration stimulation (10 microg/mL) and high-concentration inhibition (20-160 microg/mL). Typical J-shapes of the relationship between the growth rate constant (k) and c, and toxicity at the half-inhibitory concentration (IC(50)) of 98.82 +/- 7.32 microg/mL were obtained. The similarity between the two methods corroborates the validity and sensitivity of the microcalorimetric technique to investigate the toxic effect of As(III) on microorganisms.

Bamberger rearrangement on solid acids

Bamberger rearrangement of phenylhydroxylamine (PHA) to para-aminophenol (PAP) is investigated at 353 K, with water as solvent, on a series of solid acid catalysts. The catalysts are characterized by a micro-calorimetric technique using the adsorption of ammonia for acid strength. The solid acid catalysts under study include beta zeolite, K10 clay, sulphonated silica, and sulphated zirconias, obtained by different procedures. Both activity and selectivity are affected by the choice of the catalyst. The selectivity towards PAP is found to be 17% for K10 clay, 70% for sulphonated silica, 84% for beta zeolite and >90% for sulphated zirconia, respectively. The reaction obeys a first-order rate law and the rate constant shows a linear dependence on the number of acid sites. On sulphated zirconia calcined at 973 K, a quantitative reaction is obtained, and the catalyst can be recycled, giving the first example of selective Bamberger rearrangement catalysed by solids.

Standard molar enthalpy of formation of 1-cyano-acetylpiperidine

The standard (p0=0.1 MPa) molar enthalpy of formation of 1-cyanoacetylpiperidine, in the crystalline state, at T=298.15 K, has been derived from measurements of its standard massic energy of combustion, by static bomb combustion calorimetry, as ΔfHm0=−217.1±1.4 kJ mol−1. The standard molar enthalpy of sublimation was measured, at T=298.15 K, by the microcalorimetric sublimation technique as ΔcrgHm0=103.5±1.9 kJ mol−1.

Microcalorimetric measurements of the microbial activities of single- and mixed-species with trivalent iron in soil

A microcalorimetric technique was applied to a series of experiments to follow the toxic effect caused by the trivalent iron on the single and mixed microbes in sterilized soil that was inoculated with the single Bacillus subtilis (B. subtilis) (prokaryotic bacterium), single Candida humicola (C. humicola) (eukaryotic fungus) and the mixed-species. The microbial activity was stimulated by the addition of 5.0mg glucose and 5.0mg ammonium sulfate under a 35% controlled humidity in the studied soil samples of 1.2g. The power–time curves from every experiment were analyzed, and from these analyses characteristic parameters, such as growth rate constant (k) and total thermal effect (Q) which can reflect the biochemical reactions were determined. The mixed-species have moderate tolerance to the iron overload, comparing with single species, and exhibit synergistic interaction in exponential growth phase (0–400.0μgmL−1). Meanwhile, there is no much difference in the thermal effect (Q) per gram soil sample for the single and mixed culture. This also validates that the nutrient substances in natural environment determine the organisms’ metabolic activities. Ultraviolet–visible spectrophotometry and dissolved oxygen sensor also were successfully applied to reflect the activities of B. subtilis and C. humicola in the pure culture. The investigation could provide insight into the microbial ecology of bacteria and fungi in ecological niches.

Inhibitory Effect of Copper Complex of Indomethacin on Bacteria Studied by Microcalorimetry

A microcalorimetric technique based on the bacterial heat output was explored to evaluate the effect of copper-indomethacin complex on Staphylococcus aureus and Escherichia coli. The extent and duration of the inhibitory effect on the metabolism as judged from the rate constant (k) in log phase, half inhibitory ratio (IC50). The rate constant of bacteria in the presence of the drugs decreased with increasing concentrations of the drugs. The copper complex exhibited higher antibacterial activity than the parent drug whose IC50 value was 1.5 and 2.3 times lower than that of indomethacin to S. aureus and E. coli, respectively. It was indicated that when the copper ion is coupled with indomethacin, the drug is more potent as a bacteriostatic.

Calorimetric studies of the interaction between sodium alginate and sodium dodecyl sulfate in dilute solutions at different pH values

Interactions between the polyelectrolyte sodium alginate (NaAlg) and the anionic surfactant sodium dodecyl sulfate (SDS) have been investigated by microcalorimetric techniques. The polymer–surfactant interactions were observed between NaAlg and SDS at different pH values in dilute solution. The thermodynamic parameters for their interaction process are evaluated from the results of the observed dilution enthalpy curves. As the pH value of the solution decreases from 7 to 6, NaAlg polymers have an obvious effect on the cmc of SDS as a simple salt, which indicates no association between SDS and NaAlg owing to electrostatic repulsion. With the progressive decrease of pH value from 5 to 3, the hydrophobic segments in the alginate chains are increasing and the hydrophilic segments decreasing, and the aggregation between SDS and alginate due to hydrophobic interactions is observed.

Thermoelectric Sensors as Microcalorimeter Load

Thermoelectric power sensors can now be used as transfer standards, instead of bolometers, in the microcalorimeter technique. This alternative has the technical advantages to be less sensitive to absolute temperature and not downward frequency limited. At INRiM the high frequency power standards are now based on coaxial thermocouples from dc to 34 GHz. Modified commercial thermocouple mounts in 7 mm and 3.5 mm coaxial line are used to realize the national power standard with an accuracy ranging from 0.03 % to 1 % in the mentioned frequency range.

Microcalorimetric Investigation of Influence of Fungicide SYP‐L190 on Growth Metabolism of Tetrahymena thermophila and Bacillus thuringiensis

AbstractFlumorph (SYP‐L190) is a new systemic fungicide with good protective, curative and antisporulant activities but no phytotoxicity to certain plants. Its performance on the environmental ecosystem is unknown. Tetrahymena thermophila and Bacillus thuringiensis are two of biological indicators for the aquatic and soil environmental ecosystem respectively. Microcalorimetric technique based on the heat output was applied to evaluate the influence of fungicide flumorph (SYP‐L190) on the two microorganisms. The thermogenic curves and corresponding thermodynamic and thermokinetic parameters were obtained. SYP‐L190 at a concentration of 50–100 µg·mL−1 had 5% –10% inhibitory ratios aganist Tetrahymena thermophila and was used as a protection reagent, while at a concentration of 100–200 µg·mL−1 SYP‐L190 had 10% –20% inhibitory ratios and was used as a therapy reagent. The metabolic thermogenic curves of Bacillus thuringiensis contained bacterial growth phase and sporulation phase. The SYP‐L190 at a concentration of 0–200 µg·mL−1 had no influence on bacterial growth phase, but led to a little lag of the sporulation phase with a constant heat output. Hormesis was obviously observed in present study.

Microcalorimetric Studies of the Biological Effect of Holmium (III) on Halobacterium halobium R1 Growth

The biological effect of Ho3+ on Halobacterium halobium R1 growth was analyzed by a microcalorimetric technique. By means of LKB-2277 Bioactivity Monitor, ampoule method at 37 degrees C, we obtained the thermogenic curves of H. halobium R1 growth. To analyze the results, the maximum power (Pm) and the growth rate constants (k) were determined, which show that values of Pm and k are linked to the concentration of Ho3+. In all, the addition of Ho3+ causes a decrease of the maximum heat production and growth rate constants. For comparison, we observed the shapes of H. halobium R1 cell by means of transmission electron microscope (TEM). According to the thermogenic curves and TEM photos of H. halobium R1 under different conditions, it is clear that metabolic mechanism of H. halobium R1 growth has been changed with the addition of Ho3+.

A MICROCALORIMETRIC METHOD TO STUDY THE EFFECT OF KANAMYCIN ON THE METABOLISM OF RECOMBINANT ESCHERICHIA COLI

A microcalorimetric technique based on the metabolic heat production from cultured cells was used to investigate the effect of kanamycin on the growth and metabolism of recombinant Escherichia coli. Power-time curves of growing recombinant Escherichia coli cell suspensions treated with different kanamycin doses were recorded and were described very accurately by the generalized logistic equation. The rate constant (k) is kanamycin concentration-dependent and the relationship between k and C (kanamycin dose) is nearly linear. The 50% inhibitory concentration IC50 was 88.49 µg/mL. The experimental results revealed that high doses of kanamycin inhibited the growth of recombinant E. coli during the log phase and promoted growth during the stationary phase. These results are important for deciding the optimum kanamycin dose for the maximal synthesis of human-like collagen.

A microcalorimetric method for studying the toxic effect of different diphenol species on the growth of Escherichia coli

A microcalorimetric technique based on bacterial heat-output was explored to evaluate the toxic effect of different diphenol species on the growth of Escherichia coli (E. coli). Power-time curves of the growth metabolism for E. coli in the presence of different diphenol species were studied using a multi-channel microcalorimetric system with an ampoule method at 37°C. The growth rate constant (k), generation time (t G), inhibitory ratio (I), half-inhibitory concentration (IC 50) and the total thermal effect (Q T) for E. coli were obtained. The results show that catechol and hydroquinone are more toxic to E. coli than resorcinol. In all cases, the growth rate constants of E. coli (in log phase) decreased as the concentrations of these diphenols increased. Among these diphenols species, catechol was found to be the most poisonous species at an IC 50 of 323.5 μ g/mL against E. coli. Hydroquinone exhibited moderate virulence with an IC 50 of 1196 μ g/mL and resorcinol had the lowest toxicity with an IC 50 of 2113 μ g/mL. The microcalorimetric bioassay can be a quantitative, inexpensive, and versatile method for acute cellular toxicity study.

XPS and 1H NMR Study of Thermally Stabilized Rh/CeO2 Catalysts Submitted to Reduction/Oxidation Treatments

Rh/CeO2 catalysts submitted to different H2 reduction, Ar+ sputtering, and oxidation treatments have been studied by X-ray photoelectron (XPS) and 1H nuclear magnetic resonance (NMR) spectroscopies. Depending on the reduction temperature, two stages have been identified in the reduction of the catalyst: below 473 K, reduction increases the amount of OH and Ce3+ species; above this temperature, reduction produces oxygen vacancies at the surface of the support. Volumetric and microcalorimetric techniques have been used to study hydrogen adsorption on the catalyst, and 1H NMR spectroscopy was used to differentiate hydrogen adsorbed on the metal from that adsorbed on the support. From 1H NMR and TEM results, the main metal particle size (38 A) in the Rh/CeO2 catalyst has been estimated. The influence of the support reduction on the metal adsorption capacity has also been investigated, showing that formation of oxygen vacancies at the metal-support interface enhances the electronic perturbation and decreases the hydrogen adsorption on metal particles. The comparison of data reported on catalysts of high and low surface area supports has shown that both processes are shifted to higher temperatures in the Rh/CeO2 catalyst of lower surface area.

Microcalorimetric investigation on the metabolic activity of Bacillus thuringiensis as influenced by kaolinite, montmorillonite and goethite

The metabolic activity of microorganisms in soil is influenced by various colloidal soil particles especially clay minerals or iron oxide. The knowledge of the impacts of soil minerals on microorganisms is essential in understanding microbially mediated processes in soil. However, to date, the available information on this regard is scarce. Based on microcalorimetric techniques, a powerful tool for monitoring the activity of microorganisms, the metabolic activity of Bacillus thuringiensis in the presence of goethite, kaolinite and montmorillonite was investigated. The clay minerals and iron oxide stimulated the exponential growth of B. thuringiensis, whereas the sporulation of B. thuringiensis was somewhat inhibited by kaolinite and montmorillonite. Goethite significantly depressed the sporulation and the total metabolic activity of the bacterium . The surface interaction between microbial cell and soil mineral probably account for the effect of these minerals on the metabolic activity of B. thuringiensis.

Microcalorimetric Investigation of the Toxic Effect of Iron Species on Escherichia coli

ABSTRACTA microcalorimetric technique based on bacterial heat output was explored to evaluate the toxic effect of iron species on Escherichia coli. Power–time curves of the growth metabolism of E. coli and the effect of different iron species on it were studied using the TAM III multichannel microcalorimetric system, isothermal mode, at 37°C. The differences in shape of the power–time curves and the thermodynamic and kinetic characteristics of E. coli growth have been compared. The thermodynamic parameters, that is, growth rate constant (k), inhibitory ratio (I), half-inhibitory concentration (IC50), Pmax, and Qtotal, have been calculated. The experimental results reveal that the sequence of antibiotic activity of the different iron species (three forms) on E. coli growth is Fe3+ (ferric citrate) > Fe2+ (ferrous chloride) > Fe3+ (ferric chloride). These results are important to further studies of the physiology and pharmacology of iron species as antibacterial agents.

Influence of agricultural practices on soil microbial activity measured by microcalorimetry

To investigate the influence of different agricultural practices and vegetations on soil microbial activity and diversity, soil samples from different habitats were studied with their microbial activities measured by the microcalorimetric technique. Seven soil samples were collected in Wuhan, China from different locations with primary and regeneration forest, nursery and crop land, and uncultivated land. The number of microorganisms in soils was measured by viable count, and some physicochemical parameters were determined. Power–time curves were recorded for soil samples supplemented with glucose and ammonium sulphate, and the total heat changes of the microbial growth reaction, Q total (Jg −1) and the microbial growth rate constant, k (min −1) were calculated from the curves. All power–time curves presented typical changes of microbial activity. The curves of soil samples could be divided into two groups differing in agricultural practices and vegetations. The same grouping could also be reached according to the values of peak time ( t max). The most soil samples showed a higher correlation between the values of k and the counted bacterial numbers. The Q total correlated well with vegetation abundance and probably with microbial diversity. In conclusion, microbial activity of the soil samples determined by microcalorimetry reflected differences in soil vegetation and agricultural management.

Study on interaction between antibiotics and Escherichia coli DH5α by microcalorimetric method

A microcalorimetric technique based on the bacterial heat output was applied to evaluate the influence of antibiotics PIP (Piperacillin Sodium) and composite preparation of PIP and SBT (Sulbactam Sodium) on the growth of E. coli DH5α. The power–time curves of the growth metabolism of E. coli DH5α were studied using a TAM Air Isothermal Microcalorimeter at 37°C. By analyzing the power–time curves, the parameters such as growth rate constants (k), inhibitory ratio (I), the maximum heat power (Pm) and the time of the maximum heat power (tm) were obtained. The results show that different concentrations of antibiotics affect the growth metabolism of E. coli DH5α. The PIP in the concentration range of 0–0.05 µg mL–1 has a stimulatory effect on the E. coli DH5α growth, while the PIP of higher concentrations (0.05 –0.25 µg mL–1) can inhibit its growth. It seems that the composite preparation composed of PIP and SBT cannot improve the inhibitory effect on E. coli DH5α as compared with the PIP.