Search Results
Abstract
The specific heat capacities (cp) for the brain and muscle equivalent liquids were determined with isothermal heat conduction microcalorimetry (IMC) and differential scanning calorimetry (DSC). IMC was found to afford an accurate technique to measure cp for solid and liquid samples, when an appropriate reference is employed. The accuracy of obtained cp values was estimated to be better than 0.7% with the equivalent liquids. Intercomparison with a conventional isoperibolic calorimeter showed an excellent agreement within the estimated uncertainty of the isoperibolic calorimeter (3%). Additionally, suitability of different kinds of IMC sample vessels was tested, and the standard electrical calibration procedure of IMC was evaluated through the determination of cp with and without a reference material.
Application of microcalorimetry and principal component analysis
Antibacterial evaluation of Benzoinum and Styrax on Staphylococcus aureus growth
Abstract
A useful microcalorimetric technique based on the bacterial heat production was applied to evaluate the antibacterial effects of Benzoinum and Styrax on the growth of Staphylococcus aureus (S. aureus). The thermogenic power-time curves of S. aureus growth in the presence of the two drugs were determined by a thermal activity monitor (TAM) air isothermal microcalorimeter, ampoule mode, at 310 K. Some quantitative metabolic parameters, such as growth rate constant k, the heat-flow power P, the appearance time for the heat power t, and the heat production Q were obtained from these curves. By analyzing these curves and some quantitative parameters using principal component analysis (PCA), the antibacterial effects of Benzoinum and Styrax on S. aureus growth were accurately evaluated from the change of the two main parameters, the heat-flow power for the second peaks P 2nd and total heat production Q t: the antibacterial effects of the two drugs at concentrations of 0–125 mg mL−1 were both enhanced with increasing the concentration, and Benzoinum with IC50 of 132.2 mg mL−1 had stronger antibacterial effect than Styrax with IC50 of 179.8 mg mL−1. This study provides some useful references for the application of Benzoinum and Styra as potential antibacterial agents. Microcalorimetry is a powerful analytical tool for the characterization of the microbial growth progress and the evaluation of the drugs’ efficiency.
Exploring antibiotic resistant mechanism by microcalorimetry
Determination of thermokinetic parameters of metallo-β-lactamase L1 catalyzing penicillin G hydrolysis
reported. The microcalorimetry is a powerful method to probe the pathway and mechanism of chemical reaction [ 13 ], and it is used in many fields [ 14 – 24 ]. With the microcalorimetry, recently, Kong et al. investigated the activity of berberine
Exploring antibiotic resistant mechanism by microcalorimetry II
Determination of thermokinetic parameters of imipenem hydrolysis with metallo-β-lactamase ImiS
active only in the monozinc form [ 8 ]. As of now, no clinically approved MβL inhibitor is available. Scheme 1 Imipenem hydrolysis catalyzed with MβLs The microcalorimetry is a
By using the LKB 2277 thermal activity monitor, it is demonstrated that both ampoule and flow-through modes can be used to monitor the reaction parameters for chemical reactions. Theoretical relationships applicable to first-order reactions are proposed and compared with those reported in the literature. Mathematical relationships applicable to second-order reactions are also proposed. The experimental results confirmed the validity of the theoretical relationships and showed that flow microcalorimetry is a rapid technique in kinetic studies.
Recent developments in instrumentation and working procedure in microcalorimetry have led to an increased interest in the direct measurements of heat production rates of living cells. Specific problems connected in particular with work on mammalian cells are briefly discussed and a system of microcalorimeters suitable for work on such cells is described. A few examples of its use in studies ofT-lymphoma cells are briefly discussed.
Abstract
In this work we report about the characterization of the acidic and redox properties of four different commercial tungstated zirconia catalysts with W loadings of about 12–13 mass%. The samples have been characterized in terms of their micro-structural and surface properties by BET, X-ray diffraction, temperature programmed reduction, elemental chemical analysis and adsorption microcalorimetry of NH3. Improved acidity has been detected upon addition of WO3 to zirconia and differences between the samples were pointed out thanks to the results obtained by the complementary physico-chemical techniques used in this study.
Abstract
A series of blends of dodecylbenzenesulfonic acid (DBSA)-doped polyaniline (PANDR) and PVC were synthesized by solution blending technique and investigated by heatflow microcalorimetry (HFC) for thermal and oxidative stability and for PVC–PANDR compatibility. FTIR results provided evidence for strong dipole–dipole interactions between PANDR and PVC. The energy of the oxidation is independent of the composition. The interaction energy and thermal stability increased with the increase of PANDR content in the blend. The activation energies calculated by using Arrhenius relationship can be employed for accelerated ageing of the synthesized blends. It has been observed that the average degradation of PANDR component is higher than that of PVC.
Abstract
The application of solution microcalorimetry was demonstrated on two model examples – inhibited oxidation of cumene and radical polymerization of styrene.From the experimental dependences of the rate of heat release on time, the rate constants k 7 of the interaction of an inhibitor with radicals of substrate (RO 2 . or R.) in oxidation or in polymerization were determined for the set of inhibitors of N-aryl N-(2-quinone) amine series. It was shown that these compounds are weak inhibitors of oxidation of cumene and rather efficient inhibitor of polymerization of styrene.
Abstract
Isothermal microcalorimetry is now established as a useful technique for the characterization of the microbial activity in soil. A brief summary of publications from this field and of instruments used in such work is presented. Several experimental parameters that can form important sources for systematic errors are discussed and it is suggested that further method work is made in this area. In most isothermal microcalorimetric investigations on the microbial activity in soil, the samples are amended with glucose. It is proposed that cellulose also will be used.
