Microcalorimetry is a sensitive method for studying the effect of nucleotide mutation on promoter activity

Toxicity of nickel to soil microbial community with and without the presence of its mineral collectors-a calorimetric approach

The toxicity of nickel and three of its main collectors, sodium isopropyl xanthate (SIPX), sodium ethyl xanthate (SEX), and potassium ethyl xanthate (PEX) to soil microbial activity, was analyzed, individually and as a binary combination of nickel and each of the collectors. The investigation was performed through the microcalorimetric analysis method. For the single chemicals, all power-time curves exhibited lag, exponential, stationary, and death phases of microbial growth. Different parameters exhibited a significant adverse effect of the analyzed chemicals on soil microbial activity, with a positive relationship between the inhibitory ratio and the chemical dose (p < 0.05 or p < 0.01). A peak power reduction level of 24.23% was noted for 50 μg g^-1 soil in the case of Ni while for the mineral collectors, only 5 μg g^-1 soil and 50 μg g^-1 soil induced a peak power reduction level of over 35 and 50%, respectively, in general. The inhibitory ratio ranged in the following order: PEX > SEX > SIPX > Ni. Similar behavior was observed with the mixture toxicity whose inhibitory ratio substantially decreased (maximum decrease of 38.35%) and slightly increased (maximum increase of 15.34%), in comparison with the single toxicity of mineral collectors and nickel, respectively. The inhibitory ratio of the mixture toxicity was positively correlated (p < 0.05 or p < 0.01) with the total dose of the mixture. In general, the lesser and higher toxic effects are those of mixtures containing SIPX and PEX, respectively.

Microcalorimetric, spectroscopic and microscopic investigation on the toxic effects of CdTe quantum dots on Halobacterium halobium R1

The biological effect of CdTe quantum dots (QDs) on Halobacterium halobium R1 (H. halobium R1) growth was analyzed by a microcalorimetric technique. By using a TAM air eight channels microcalorimeter, the thermogenic curves of H. halobium R1 growth were obtained at 37 °C. To analyze the results, the maximum heat power (P(m)) and the growth rate constants (k) were determined, which showed that they were correlated to the concentration of QDs. The addition of quantum dots caused a gradual increase of P(m) and k at low concentrations of QDs, and a conspicuous decrease at high concentrations. For confirmation, the turbidity (OD(600)) and respiratory rate at different concentrations of QDs were studied. The morphology of H. halobium R1 cells both in the absence and presence of QDs was examined by transmission electron microscopy (TEM). The results of these studies were corroborated with ones derived from microcalorimetry. In this work, the mechanism of cytotoxicity of QDs was explored through fluorescence spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS) and microcalorimetry. It was clear that metabolic mechanism of H. halobium R1 growth was changed by the addition of QDs. To the best of our knowledge, the thermokinetics and toxicology of CdTe QDs against H. halobium R1 were obtained for the first time by microcalorimetry.

Spectrum-effect relationships between ultra performance liquid chromatography fingerprints and anti-bacterial activities of Rhizoma coptidis

The fingerprints of Rhizoma coptidis from various sources were established by ultra performance liquid chromatography (UPLC) and the anti-bacterial activities of R. coptidis on Escherichia coli (E. coli) growth was studied by microcalarimetry. The UPLC fingerprints were evaluated using similarity analysis (SA) and hierarchical clustering analysis (HCA). Some quantitative parameters obtained from the thermo-genic curves of E. coli growth affected by R. coptidis were analyzed using principal component analysis (PCA). The spectrum-effect relationships between UPLC fingerprints and anti-bacterial activities were investigated using canonical correlation analysis (CCA). The results showed that close correlation existed between the spectrum-effect relationships. Berberine, jateorrhizine and palmatine in the UPLC fingerprints might be the main anti-bacterial components. The anti-bacterial activities of R. coptidis were related with the main active constituents, along with the production place and the harvesting time of this herb, the latitude and longitude of the place. This work provides a general model of the combination of UPLC and microcalorimetry to study the spectrum-effect relationships of R. coptidis, which can be used to discover principle components of it on bioactivity.

Thermochemical studies on the quantity-antibacterial effect relationship of four organic acids from Radix Isatidis on Escherichia coli growth

In this report, we have investigated the inhibitory action of four organic acids from Radix Isatidis on Escherichia coli growth was investigated at 37 degrees C by using a microcalorimeter. The four organic acids were: syringic acid, 2-amino-benzoic acid, salicylic acid, benzoic acid. In accordance with thermokinetic model, the pertaining relationships of the drugs, such as growth inhibitory ratio vs. concentration, maximal power-output vs. growth rate constant, growth rate constant vs. concentration, were obtained. Half-inhibitory concentration of the drugs, IC(50), was obtained by quantitative analysis. From the view of thermodynamics and molecular structure, the relationship between quantity and effect of the four organic acids has been discussed. The functional groups on phenyl ring had important influence on the antibacterial activities. Our work suggests that microcalorimetry is a fast, simple and more sensitive method that can be easily performed and applied to study the anti-bacterial activities of organic acids from Radix Isatidis on microorganism compared to other biological methods.

Microcalorimetric study on the effect of Ce3+ on Halobacterium halobium R1

A microcalorimeric technique was used to evaluate the influence of rare earths Ce3+ on Halobacterium halobium R1 growth. By means of TAM air Thermal Activity Monitor, the thermogenic curves of H. halobium R1 growth were obtained. To analyze the results, the growth rate constant k and IC50 were calculated, indicating that the values of k are linked to the concentration of Ce3+. The growth rate constant k of H. halobium R1 decreased gradually in the low concentration; thus, rare earths restrained the growth of H. halobium R1. On the contrary, as the concentration of Ce3+ became higher, the value of k for H. halobium R1 increased gradually, which showed Ce3+ stimulated the growth of H. halobium R1. When the concentration of rare earths became much higher, the value of k for H. halobium R1 also decreased, and the growth of H. halobium R1 was restrained totally in the end. By using transmission electron microscopy (TEM), it was observed that the transforming of H. halobium R1 in the different concentrations of Ce3+ confirmed the results derived from microcalorimetry. According to the thermogenic curves and TEM photos of H. halobium R1 under various conditions, it showed that there was some special effect about the interaction between rare earths and H. halobium R1 growth.