Using isothermal microcalorimetry, the growth power-time
curves of three strains of Tetrahymena
were determined at 28C. Their Euclidean distances and cluster analysis
diagram were obtained by using two thermokinetic parameters (r
and Qlog), which
showed that T. thermophila BF1
and T. thermophila BF5
had a closer relationship. Compared with the single molecular biomarker (ITS1)
method, microcalorimetry wasmaybe a simpler, more sensitive andmore economic
technique in the phylogenetic studies of Tetrahymena
Occupational exposure to Cr(VI) causes various effects including deep skin ulcerations. Its action mechanisms are not fully
understood. In the present study, the evaluation of human dermal fibroblasts heat production was monitored, using microcalorimetry.
as part of Cr(VI) toxicity. In control cells, normal heat production was 15±5 pW/cell. Regardless of the Cr(VI) concentration
tested (0 to 500 μM), heat production was inhibited over time periods ranging from 3 to 25 h. These results could be correlated
with cell mortality and the IC50 for Cr(VI) was 29±4 μM. In the WST-1 bioassay, the IC50 was 35±5 μM (no statistical difference). Thus, Cr(VI) altered the metabolism of the fibroblasts, and led to cellular death.
Microcalorimetry can be a useful tool for determining the toxic effect of suspect compounds implicated in the occurrence of
The inhibitory effects of three berberine alkaloids (BAs) from Coptis chinensis Franch on Bifidobacterium adolescentis growth were investigated by microcalorimetry. The growth rate constant (k) and maximum heat-output power (Pmax) decreased and peak time of maximum heat-output power (tp) prolonged with the increase of BAs concentration. Half inhibitory ratios (IC50) BAs were respectively 790.3 (berberine),
339.6 (coptisine) and 229.8 μL−1 (palmatine), which indicated the sequence of their antimicrobial activity: berberine<coptisine<palmatine. Combined with previous
findings, the sequence which could show the bioactivity of Bacillus shigae and Escherichia coli was: berberine>coptisine>palmatine. The structure-function relationship of BAs indicated that the functional group methylenedioxy
or methoxyl at C2 and C3 might be the major group inducing the activities of BAs on E. coli and B. adolescentis. Meanwhile, the substituent groups at C2, C3, C9 and C10 almost had equal effect on B. shigae.
The use of isothermal microcalorimetry (MC) as a sensitive monitor for slow reactions is demonstrated in a number of examples.
In Example 1 the spontaneous decomposition of a nitrate ester propellant is studied and the absolute degradation rate estimated.
Example 2 illustrates how MC can be used for comparing the rate of oxidative ageing at different O2 concentrations. Synergetic effects between oxygen and moisture in accelerated ageing of nitrile rubber are evaluated from
a so-called 4-point test in Example 3. The last example shows a simple MC technique for rapid determination of moisture permeability
through a polymeric sealant.
The amorphous state of solids is characterized by a higher chemical and physical reactivity and a hygroscopic behaviour. Furthermore processing of amorphous powders is often difficult, because of the instability. Fast crystallizations, precipitations and milling favour the formation of the amorphous state. Galenical processes like granulation, drying, lyophilization, mixing, may also induce amorphous regions in the drug products.
This work is a ‘historical’
revision of the evolution of an experimental procedure developed by Prof.
Lisardo Nez and his research group TERBIPROMAT to study the
sustainability and the soil health state.
From the very beginning,
in 1993, the microbial activity was the main bioindicator selected to analyse
the ‘soil health state’. For this reason, a microcalorimetric
technique was used lately to analyse the influence of different human activities
such as reforestations, agricultural exploitation or pollution on the microbial
activity in different soils. Microcalorimetry is the main scientific technique
used in this research to follow the stimulation of the microbial activity
by addition of glucose. The data obtained were complemented by a study of
physical, chemical and biological parameters of soil and allowed to follow
the microbial activity in soils of Galicia (Spain) along the year.
The final results, still in revision, will be helpful in establishing
a data basis for real maps of the ‘health state’ of different
soils. Such maps could be used to design processes that help us to decide
how we should exploit soils ensuring their sustainability.
Both temperatures, TC, (TC —Curie temperature) and heat of the phase transition: ferroelectric-paraelectric, ΔH, in the BaxSr1−xTiO3 materials have been studied by means of the microcalorimetric method. The determined parameters were verified by either temperature
dependence of the dielectric permittivity (Curie-Weiss law) or thermodynamic method. The effect of strontium content on TC has been discussed. It was found that microcalorimetry is useful tool studying phase transition phenomena in ferroelectric
The action of three kinds of the selenomorpholine compounds on a strain ofEscherichia coli was studied by microcalorimetry. Differences in their capacities to affect the metabolism of this bacterium were observed.
The extent and duration of the effect on the metabolism as judged from the rate constant (k) of Escherichia coli (in log phase) varied with the different drugs. The kinetics show that selenomorpholine compounds had an effect on the metabolism
process of Escherichia coli. The k of Escherichia coli in the presence of the drugs increased with the increasing concentrations of the drugs (C) at low concentration; but at high concentration, the rate constant decreased with the increasing concentrations of the drugs.
The experimental results reveal that the sequence of antibiotic activity of selenomorpholines is: N-selenomorpholinemethyl
succinimide and its hydrochloride>N-(α-selenomorpholinebenzyl) succinimide.
Adsorption microcalorimetry has been employed to study the interaction of ethylene with the reduced and oxidized Pt-Ag/SiO2catalysts with different Ag contents to elucidate the modified effect of Ag towards the hydrocarbon processing on platinum
catalysts. In addition, microcalorimetric adsorption of H2, O2, CO and FTIR of CO adsorption were conducted to investigate the influence of Ag on the surface structure of Pt catalyst.
It is found from the microcalorimetric results of H2and O2adsorption that the addition of Ag to Pt/SiO2leads to the enrichment of Ag on the catalyst surface which decreases the size of Pt surface ensembles of Pt-Ag/SiO2catalysts. The microcalorimetry and FTIR of CO adsorption indicates that there still exist sites for linear and bridged CO
adsorption on the surface of platinum catalysts simultaneously although Ag was incorporated into Pt/SiO2. The ethylene microcalorimetric results show that the decrease of ensemble size of Pt surface sites suppresses the formation
of dissociative species (ethylidyne) upon the chemisorption of C2H4on Pt-Ag/SiO2. The differential heat vs. uptake plots for C2H4adsorption on the oxygen-preadsorbed Pt/SiO2and Pt-Ag/SiO2catalysts suggest that the incorporation of Ag to Pt/SiO2could decrease the ability for the oxidation of C2H4.
In recent years, microcalorimetry has been extensively used in studying the interaction between drugs and many kinds of microorganisms [ 1 – 6 ]. Being an universal, integral, nondestructive, and highly sensitive