Effects of soil metal(loid)s pollution on microbial activities and environmental risks in an abandoned chemical smelting site

Abandoned chemical smelting sites containing toxic substances can seriously threaten and pose a risk to the surrounding ecological environment. Soil samples were collected from different depths (0 to 13 m) and analyzed for metal(loid)s content and fractionation, as well as microbial activities. The potential ecological risk indices for the different soil depths (ordered from high to low) were: 1 m (D-1) > surface (S-0) > 5 m (D-5) > 13 m (D-13) > 9 m (D-9), ranging between 1840.65-13,089.62, and representing extremely high environmental risks, of which Cd (and probably not arsenic) contributed to the highest environmental risk. A modified combined pollution risk index (MCR) combining total content and mobile proportion of metal(loid)s, and relative toxicities, was used to evaluate the degree of contamination and potential environmental risks. For the near-surface samples (S-0 and D-1 layers), the MCR considered that As, Cd, Pb, Sb, and Zn achieved high and alarming degrees of contamination, whereas Fe, Mn, and Ti were negligible or low to moderate pollution degrees. Combined microcalorimetry and enzymatic activity measurements of contaminated soil samples were used to assess the microbial metabolic activity characteristics. Correlation analysis elucidated the relationship between metal(loid)s exchangeable fraction or content and microbial activity characteristics (p < 0.05). The microbial metabolic activity in the D-1 layer was low presumably due to heavy metal stress. Enzyme activity indicators and microcalorimetric growth rate (k) measurements were considered sensitive indicators to reflect the soil microbial activities in abandoned chemical smelting sites.

Use of Isothermal Microcalorimetry to Measure Cellular Heat Production in Thermogenic Adipocytes

Induction of thermogenesis in brown and brite adipocytes has recently emerged as a therapeutic target for novel anti obesogenic therapies necessitating the development of methods that can accurately measure heat production in these cells. Modern isothermal microcalorimetric techniques allow for the high throughput quantitative measurement of cellular heat production with limited sample material. Here, we describe the application of this technique for the measurement of thermogenesis in both floating and adherent adipocytes from various murine depots and human cell lines.

Evaluation of electroactive denitrifiers at different potentials, temperatures and buffers based on microcalorimetry

Electroactive denitrifiers contribute to the nitrate removal in a bioelectrochemical system, but their metabolism and growth parameters remain vague. In this study, microcalorimetry as a suitable method was used to evaluate the metabolism and growth parameters of electroactive denitrifiers at different cathode potentials, temperatures and buffer solutions. The suitable cathode potential and temperature for electroactive denitrifiers were deemed as -100 mV and 30 °C, respectively. The suitable buffer was found to be phosphate buffer solution but can be replaced by bicarbonate buffer solution. When cultivated with bicarbonate buffer solution at -100 mV and 30 °C, electroactive denitrifiers achieved a specific nitrate removal rate of 2.20 ± 0.08 × 10^-10 mg NO₃^--N·(min·cell)^-1 and two growth rate constants (k₁ = 0.0051 ± 0.0004 min^-1, k₂ = 0.0030 ± 0.0004 min^-1), with gaseous nitrogen as the end product. The bioelectrochemical denitrification behaved as a two-step process, in which the nitrite reduction to gaseous nitrogen was the rate-limiting step.

Relationships between microbial activity, enzyme activities and metal(loid) form in NiCu tailings area

Here we combined microcalorimetry, enzyme activity measurements, and characterization of metal form in order to evaluate the effect of metal(loid)s on the activity of microbial community inhabiting tailings area with high toxic metal(loid)s concentration. Chromium (Cr), nickel (Ni), copper (Cu) and manganese (Mn) were the main pollutants. The exchangeable fractions (bioavailability) of Cu, Ni and Mn were higher in the tailings sample (Site Z), indicating a higher environmental risk. The total heat Q_total (17,726.87 J/g), peak power P_peak (541.42 μW/g) and growth rate constant k (0.11 h^-1) of Site Z were higher than that of the polluted soil around tailings (Site Y). Such observation may be explained by physiological changes within the microbial community in response to high levels of heavy metal stress, thereby increasing respiration and improving microbial activity. In contrast, enzyme activities and enzyme activities index (GmeA) of Site Z were lower than the Site Y, which is strongly influenced by changes on physical-chemical properties (TN and TOC) and the presence of Cr, Mn, and Ni. Correlation coefficient and principal component analysis (PCA) indicate that GmeA is significantly correlated (p < 0.05 or p < 0.01) with environmental factors (EC, TOC and TN), Mn and Ni concentration, Ni bioavailability, and peak time (T_peak). Therefore, GmeA represents a potential biological indicator for reporting the pollution degree in tailings area. Our results provide a theoretical basis for the prevention and control of pollution in non-ferrous metal(loid) tailings area.

5-Substituted 3, 3', 4', 7-tetramethoxyflavonoids - A novel class of potent DNA triplex specific binding ligands

Herein, we present a class of potent triplex DNA binding ligands derived from the natural product quercetin, which is the first of its kind that has ever been reported in the literature. The binding of 5-substituted quercetin derivatives (3, 3', 4', 7-tetramethoxyflavonoids) to triplex and duplex DNA was investigated using several biophysical tools, including thermal denaturation monitored by UV, circular dichroism, differential scanning calorimetry, and isothermal titration calorimetry. Experimental data reveal that several 5-substituted 3, 3', 4', 7-tetramethoxyflavonoids have remarkable effects on binding to DNA triple helices, and they do not influence the double-helical DNA structures. A few derivatives such as compounds 5 and 7 have comparable (if not better) binding affinities to neomycin, a well-known DNA triplex binding ligand, under the same conditions. The amino-containing side chains at the 5-position of 3, 3', 4', 7-tetramethoxyflavonoids are crucial for the observed binding affinity and specificity.

A spectrum-effect based method for screening antibacterial constituents in Niuhuang Shangqing Pill using comprehensive two-dimensional liquid chromatography

To investigate and screen the active antibacterial constituents of Niuhuang Shangqing Pill (NSP), the current study developed a two-dimensional liquid chromatography (2DLC) method combining microcalorimetry technique. 60% ethanol extracts from 10 batches of different commercial NSP samples were analyzed and their chemical fingerprint were developed by the comprehensive 2DLC system of Shimadzu Nexera X2. Anti-streptococcus pneumoniae (SP) constituents were determined by microcalorimetry. Thermal kinetic parameters of the SP thermogram affected by 60% ethanol extracts from 10 NSP samples were analyzed by principal component analysis. Spectrum-effect correlation between comprehensive 2DLC fingerprint and the antibacterial activity were analyzed by orthogonal partial least squares (OPLS) and orthogonal partial least squares discriminant analysis (OPLS-DA). Findings showed that peak X1 (unknown), X9 (aloe-emodin), X10 (baicalein), X11 (unknown), X14 (wogonin), X15 (glycyrrhizic acid) and X17 (unknown) are the relevant components that are in positive correlation with inhibitory rate. Regarding inhibitory rate, X17 is the most powerful one, followed by X14, X15, X10, X11, X1 and X9, suggesting that compound X17, wogonin, glycyrrhizic acid and baicalein are the major active antibacterial components of NSP. The current method employing 2DLC with microcalorimetry technique proposes a new insight for screening and identifying antibacterial components in complex herbal formula.

Effect of methotrexate and its photodegradation products on the temperature induced denaturation of human serum albumin

Effect of the photodegradation of chemotherapeutic agent methotrexate on the denaturation of human serum albumin has been studied by differential scanning calorimetry and fluorimetric measurements. Photoluminescence studies highlighted entropy driven binding of both methotrexate molecules and its degradation products to the albumin molecules. The calorimetric measurements evaluated by the Kissinger method show elevated activation energy in the presence of methotrexate. Similar but moderated enhancement of the activation energy was obtained in the presence of the photodegradation products of methotrexate. These results highlight stabilization of the human serum albumin by the methotrexate drug which finding may contribute to fine tuning of methotrexate applications in therapy.

Measurements of Protein-DNA Complexes Interactions by Isothermal Titration Calorimetry (ITC) and Microscale Thermophoresis (MST)

Interactions between protein complexes and DNA are central regulators of the cell life. They control the activation and inactivation of a large set of nuclear processes including transcription, replication, recombination, repair, and chromosome structures. In the literature, protein-DNA interactions are characterized by highly complementary approaches including large-scale studies and analyses in cells. Biophysical approaches with purified materials help to evaluate if these interactions are direct or not. They provide quantitative information on the strength and specificity of the interactions between proteins or protein complexes and their DNA substrates. Isothermal titration calorimetry (ITC) and microscale thermophoresis (MST) are widely used and are complementary methods to characterize nucleo-protein complexes and quantitatively measure protein-DNA interactions. We present here protocols to analyze the interactions between a DNA repair complex, Ku70-Ku80 (Ku) (154 kDa), and DNA substrates. ITC is a label-free method performed with both partners in solution. It serves to determine the dissociation constant (K_d), the enthalpy (ΔH), and the stoichiometry N of an interaction. MST is used to measure the K_d between the protein or the DNA labeled with a fluorescent probe. We report the data obtained on Ku-DNA interactions with ITC and MST and discuss advantages and drawbacks of both the methods.

Antibacterial and probiotic promotion potential of a new soluble soybean polysaccharide‑iron(III) complex

In this study soluble soybean polysaccharide‑iron(III) (SSPS-Fe(III)) was synthesized to investigate the effects on the growth of Escherichia coli, Staphylococcus aureus and Bacillus licheniformis. Two new detection methods of real-time fluorescence quantitative polymerase chain reaction (qRT-PCR) and microcalorimetry were used to evaluate the effects of different concentrations of SSPS-Fe(III) on the growth of three bacteria. The copy numbers of three bacteria showed that SSPS-Fe(III) had different impacts on the growth of E. coli, S. aureus and B. licheniformis. E. coli growth was inhibited by SSPS-Fe(III) in the higher concentration range and S. aureus growth was inhibited at any concentration, however B. licheniformis growth was promoted. The thermogenic curves for growth metabolism of E. coli and S. aureus presented peak shapes while those of B. licheniformis did platform shapes. As SSPS-Fe(III) concentration increased, the peak heights lowered for E. coli and S. aureus, and the time reaching stationary phase advanced for B. licheniformis. These findings demonstrate that SSPS-Fe(III) has an inhibitory effect on the foodborne pathogens of E. coli and S. aureus, and an enhancement on the probiotics of B. licheniformis.

Liquid crystalline nanoparticles for drug delivery: The role of gradient and block copolymers on the morphology, internal organisation and release profile

Amphiphilic polymers represent one of the main class of stabilizers for non-lamellar lyotropic liquid crystalline nanoparticles, being essential for their formation and stability. In the present study, poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL) block copolymers and poly(2-methyl-2-oxazoline)-grad-poly(2-phenyl-2-oxazoline) (MPOx) gradient copolymers were incorporated as stabilizers in liquid crystalline nanoparticles prepared from glyceryl monooleate. The polymers were chosen according to their high biocompatibility and promising stealth properties, in order to develop safe and efficient drug delivery nanosystems. The physicochemical characteristics and fractal dimension of the resultant nanosystems were obtained from light scattering techniques, while their micropolarity and microfluidity from fluorescence spectroscopy. The effect of temperature, serum proteins and ionic strength on the physicochemical behavior was monitored. Their morphology was assessed by cryo-TEM, while their thermal behavior by microcalorimetry and high-resolution ultrasound spectroscopy. Their properties were dependent on the stabilizer chemistry and topology (block/gradient copolymer) and its concentration. Subsequently, resveratrol, as model hydrophobic drug, was loaded into the nanosystems, the entrapment efficiency was calculated and in vitro release studies were carried out, highlighting how the different stabilizer can differentiate the drug release profile. In conclusion, the proposed copolymers broaden the toolbox of polymeric stabilizers for the development of liquid crystalline nanoparticles intended for drug delivery applications.

Effect of perfluorooctanoic acid on microbial activity in wheat soil under different fertilization conditions

Perfluorooctanoic acid (PFOA) is an emerging persistent organic pollutant which has been identified at significant levels in soils. Existed ecotoxicological studies have mainly employed earthworms to evaluate the toxicity of PFOA. However, little information do we know about the toxicity of PFOA regarding soil microorganisms. Accordingly, the adverse effects of PFOA on microbial activity in a wheat soil under four fertilization treatments were investigated in this study. The microcalorimetric results revealed that the toxicity of PFOA on soil microbial activity in four treatments followed a descending sequence: Control (no fertilization), NK (no P fertilizer, but N and K fertilizers were used), PK (no N fertilizer, but P and K fertilizers were used), and NPK (N, P and K fertilizers were used). The soil sample with higher available P content had higher resistant to PFOA. There were significant differences in urease activity and alkaline phosphatase activity among the four fertilization treated soils. Molecular modeling studies clearly demonstrated that the binding of PFOA with alkaline phosphatase was more stable than with urease through electrostatic interaction, van der Waals force, and hydrogen bonds. These results are expected to provide more comprehensive information in toxicity of PFOA in soil environment.

Thermogenic diagnosis of periprosthetic joint infection by microcalorimetry of synovial fluid

Background

Synovial fluid culture is the standard investigation for the preoperative diagnosis of periprosthetic joint infection (PJI). However, the culture has limited sensitivity and requires several days until result. We evaluated the value of isothermal microcalorimetry for real-time diagnosis of PJI based on heat produced by microbial growth in synovial fluid.

Methods

Patients undergoing aspiration of prosthetic hip or knee joint before revision surgery were prospectively included between 2014 and 2015. The performance of microcalorimetry was compared to synovial fluid culture using McNemar’s chi-squared test. Pearson’s correlation coefficient was calculated for synovial fluid leukocyte count and microcalorimetric heat.

Results

Of 107 included patients (58 knee and 49 hip prosthesis), PJI was diagnosed in 46 patients (43%) and aseptic failure in 61 patients (57%) according to institutional criteria. In 26 PJI cases (56%) the pathogen grew in synovial fluid and intra-operative cultures. The sensitivity of synovial fluid culture and microcalorimetry was both 39% and the results were concordant in 98 patients (92%). In patients with PJI, microcalorimetry missed 4 pathogens which grew in synovial fluid culture, whereas culture missed 4 pathogens detected by microcalorimetry. A linear correlation (r = 0.366) was found between leukocyte count and microcalorimetric heat in synovial fluid (p < 0.001). The median time to positivity of microcalorimetry was 9 h (range, 1–64 h) vs. 3 days for cultures (range, 1–14 days).

Conclusion

Microcalorimetry of synovial fluid allows thermogenic diagnosis of periprosthetic joint infection in synovial fluid. The diagnostic performance of synovial fluid microcalorimetry is comparable to culture and delivers results considerably faster.

Trial registration

This prospective study was registered on August 21, 2015 with the public clinical trial identification NCT02530229.

LecB, a High Affinity Soluble Fucose-Binding Lectin from Pseudomonas aeruginosa

LecB/PA-IIL (Pfam PF07472) from bacterium Pseudomonas aeruginosa is a fucose-binding lectin with unusual high affinity for glycans. The occurrence of LecB and related proteins is limited to few opportunistic bacterial species, some of them being responsible for severe infections in immune-compromised patients. This lectin is therefore of interest as a target for the design of anti-infectious compounds, but can also be used for research and biotechnology. LecB is a small protein that can be produced in good quantity in recombinant system and purified by affinity chromatography.

Fatty acid transfer between serum albumins and shungite carbon nanoparticles and its effect on protein aggregation and association

The bioactivity of the natural ultrafine carbon form shungite nanocarbon (ShC) is of particular interest both for biomedical applications of such nanomaterials and their negative impact on the aquatic environmental. Here we studied the interaction of serum albumin (SA) with ShC nanoparticles in aqueous dispersion with respect to its structural-dynamic, thermodynamic, and hydrodynamic effects. Electron spin resonance (EPR) with a 5-DOXYL-stearic acid spin probe (5DSA) demonstrates that ShC can affect fatty acid (FA) binding by SA, protein conformation in the stearic FA spin probe binding region, and protein aggregation due to the partial transfer of FA to the ShC nanoparticles. The ratio of SA fractions changes in the presence of ShC in favor of the fraction that is less saturated with FA as shown by differential scanning calorimetry (DSC). The stability of interaction with ShC is significantly higher for aggregates of SA molecules that carry physiological amounts of FA, compared to aggregates of the FA-free protein, as studied by dynamic light scattering (DLS) analysis. Generally, the mixed dispersion of SA and ShC nanoparticles is more homogeneous than the SA solution alone. This is manifested both in the size of the molecular associates and in the microenvironment of the protein-bound FA. The formation of the SA-ShC interface is likely to result in a greater uniformity of the FA binding sites and a decrease in protein fractions and "hot patches" on the protein surface responsible for the supramolecular heterogeneity of the protein in solution.

Toxicity of perfluorinated compounds to soil microbial activity: Effect of carbon chain length, functional group and soil properties

Perfluorinated compounds (PFCs) have been detected at various concentrations in different environment compartments due to their widespread usage. Nowadays, soil environment has become a prominent sink of PFCs from surface runoff and penetration, but few researches have been conducted in the toxicity of PFCs to soil microorganisms. To address the issue, microcalorimetry was applied to investigate the toxicity of six PFCs with different carbon chain length (4, 8, and 10) and functional group (carboxylic and sulfonic) to microbial activities in three Chinese soils varying widely in soil properties. Adsorption of PFCs by soil matrix was a key factor in controlling the toxicity of PFCs to soil microorganisms. The differences of carbon chain length and functional groups of PFCs have different impacts on soil microbial activity while affecting adsorption progress. Particularly, the sulfonic PFCs expressed higher toxicity than the carboxylic. It is also identified that the longer the chain length, the greater the toxicity of PFCs. Soil pH was another relevant factor of soil adsorption, and with the increase of pH, adsorption capability increased. Soil available P, N and K were essential nutrients in soil, and suggested to improve microbial activity under PFCs stress.

Electronic spectroscopic characterization of the formation of iron(III) metal complexes: The 8-HydroxyQuinoline as ligand case study

Synthetic siderophores derivated from 8-HydroxyQuinoline (HQ) present various biological and pharmacological activities, such as anti-neurodegenerative or anti-oxydative. However, their affinity towards iron(III) seems to depend on the position (i.e., 7 or 2) of the HQ substitution by an electron withdrawing group. Two ester-derivatives of HQ at 2- and 7-position are synthesized and their respective iron-complexation is characterized by a joined experimental and theoretical work. By investigating the stability of all the possible accessible spin states of the iron(III) complexes at density-functional theory (DFT) level, we demonstrate that the high-spin (HS) state is the most stable one, and leads to a UV/vis absorption spectrum in perfect match with experiments. From this DFT protocol, and in agreement with the experimental results, we show that the ester functionalization of HQ in 2-position weakens the formation of the iron(III) complex while its substitution in 7-position allows a salicylate coordination of the metal very close to the ideal octahedral environment.

Antibacterial evaluation of plants extracts against ampicillin-resistant Escherichia coli (E. coli) by microcalorimetry and principal component analysis

Antibiotics abuse has caused increased bacterial resistance, which severely limits the application of antibiotics to the treatment of bacterial infections. Therefore, it is urgent to develop new antibacterial drugs through other sources. Dracontomelon dao (Blanco) Merr. & Rolfe (Ren Mianzi in Chinese) is a traditional medicinal material derived from Anacardiaceae with a long history of treating various infectious diseases, such as decubitus and skin ulcers. Recent research has indicated that different extracts from the leaves of D. dao, especially the ethyl acetate (EtOAc) fraction containing flavonoids and phenolic acids, exhibit potent antibacterial activities. In this research, the combined anti-drug-resistant bacterial activities of these active ingredients were investigated. Six samples (S1-S6) were obtained from the EtOAc fraction of D. dao leaves. Microcalorimetric measurements and principal component analysis were performed on the in vitro samples. The results showed that all six samples had notable antibacterial activities. Specifically, sample S6 exhibited a prominent antibacterial effect, with an IC50 value of 84.3 μg mL-1, which was significantly lower than that of other samples. The relative contents of main flavonoids and phenolic acids in S6 sample were confirmed by UPLC/Q-TOF-MS. In conclusion, sample S6 from the EtOAc fraction of D. dao leaves could be used as a potential antimicrobial resource in the treatment of infectious diseases. This work provides an insight into the effect of traditional Chinese medicine on drug-resistant bacteria. Moreover, the purification and characterization of the chemical compounds from the sample S6 deserve further analysis.

Microbial activity and biodiversity responding to contamination of metal(loid) in heterogeneous nonferrous mining and smelting areas

The combined contamination of nonferrous metal(loid) mining and smelting areas is a global issue, in need of urgent management. To our knowledge, this is the first report of microbial activities by microcalorimetry in specific nonferrous metal(loid) tailings with oligonutrition and high contents of toxic metal(loid)s. Dynamics of bacterial diversity were also characterized. Here we show that tailings had low microbial activities (P_max = 64.1-331 μW g^-1), which were accelerated by the presence of dipotassium phosphate (P_max = 346-856 μW g^-1), as measured by microcalorimetry. Frequent detection of S- and metal-resistant related genera and differences of Thiobacillus and Acidithiobacillus abundances indicated that the tailings were in an early stage of acidification. It has been further confirmed by the presence of a weak acid environment and secondary sulfur associated minerals, such as Sb₂S₃, FeAsS, FeS₂, and CuFeS₂. During the acidification process, phosphate, metal(loid)s, and microbial activity were correlated to the bacterial communities. It is suggested that the bacterial communities have metabolic capacities with a high potential for the use in management processes of multi-contaminated nonferrous metalliferous tailings.

Effect of the concentration process on unloaded and doxorubicin loaded liposomal dispersions

Liposomes are lamellar nanovesicles made of phospholipids of a great interest as drug delivery carriers, able to encapsulate both hydrophilic and lipophilic compounds. Some liposomal formulations have reached the market, including the doxorubicin loaded PEGylated liposomal dispersion Doxil^®. The aim of the work was to investigate the possibility of concentrating liposomes through the ultrafiltration process under nitrogen pressure, using Doxil^® formulation as a model. The concentrated liposomal dispersions (4x and 8x) obtained from Doxil^® were characterised in terms of size evolution (dynamic light scattering), morphology (cryo-TEM) and thermal behaviour (microcalorimetry, mDSC and high-resolution ultrasonic spectroscopy, HR-US) and compared to the unloaded liposomes of the same composition. The ultrafiltration process resulted to be effective in concentrating both loaded and unloaded liposomal dispersions, which showed a particle size and thermal properties comparable to those of the non concentrated ones. Moreover, all liposomal dispersions did not show any remarkable variation in term of particle size distribution and morphology for at least 8 weeks after concentration. Altogether, results demonstrated the effectiveness in using ultrafiltration as a methodology to concentrate both loaded and unloaded liposomes without affecting the quality of the processed product.

Microcalorimetric and microscopic studies of the effect of chitosan quaternary ammonium salt on mitochondria

Chitosan quaternary ammonium salt (HACC) has been regarded as an effective biomedical carrier with good application because of its good water-solubility, high cationic potential and strong cell adhesion. Mitochondria are important organelle involved in ATP production and are the center of energy metabolism. In this work, we firstly investigated the effect of HACC on the thermogenic curve of isolated mitochondrial metabolism by microcalorimetry. The results showed that different concentration of HACC had great influence on the mitochondrial energy metabolism. Specifically, low level of HACC stimulated the metabolic activity of mitochondria and the inhibition was found with high concentration of HACC. Then, the effect of HACC on mitochondrial respiratory chain was studied, which was consistent with the results of microcalorimetry. Finally, the alteration of mitochondrial structure induced by HACC was observed and it showed that the membrane of mitochondria was dramatically damaged. These new findings can help us deeply understand the influence and action mechanism of HACC in the metabolic process and provide theoretical and practical foundation for the biosafety of HACC as a medical carrier.

Isothermal microcalorimetry - A quantitative method to monitor Trypanosoma congolense growth and growth inhibition by trypanocidal drugs in real time

Trypanosoma congolense is a protozoan parasite that is transmitted by tsetse flies, causing African Animal Trypanosomiasis, also known as Nagana, in sub-Saharan Africa. Nagana is a fatal disease of livestock that causes severe economic losses. Two drugs are available, diminazene and isometamidium, yet successful treatment is jeopardized by drug resistant T. congolense. Isothermal microcalorimetry is a highly sensitive tool that can be used to study growth of the extracellular T. congolense parasites or to study parasite growth inhibition after the addition of antitrypanosomal drugs. Time of drug action and time to kill can be quantified in a simple way by real time heat flow measurements. We established a robust protocol for the microcalorimetric studies of T. congolense and developed mathematical computations in R to calculate different parameters related to growth and the kinetics of drug action. We demonstrate the feasibility and benefit of the method exemplary with the two standard drugs, diminazene aceturate and isometamidium chloride. The method and the mathematical approach can be translated to study other pathogenic or non-pathogenic cells if they are metabolically active and grow under axenic conditions.

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Isothermal microcalorimetry enables heat flow measurement of T. congolense in real-time.

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Heat flow measurements correlate with number of viable cells.

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Growth and drug-induced growth inhibition can be deducted from heat flow curves.

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Pharmacodynamic drug action parameters can be computed from heat flow curves.

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This method is a valuable tool in the drug discovery process against T. congolense.

Isolation of lead-resistant Arthrobactor strain GQ-9 and its biosorption mechanism

In this study, lead-resistant bacterium Arthrobacter sp. GQ-9 with a resistant capability to cadmium, zinc, and copper was isolated from a heavy metal polluted soil. Microcalorimetry analysis was applied to assess the strain's microbial activity under Pb(II) stress and suggested that GQ-9's microbial activities under Pb(II) stress were stronger than a non-resistant strain. Biosorption batch experiments revealed that the optimal condition for adsorption of Pb(II) by GQ-9 was pH 5.5, a biomass dosage of 1.2 g L^-1, and an initial Pb(II) concentration of 100 mg L^-1 with a maximum biosorption capacity of 17.56 mg g^-1.Adsorption-desorption experiments and Fourier transform infrared spectroscopy (FTIR) analysis were applied to elucidate the biosorption mechanisms. Adsorption-desorption analysis showed that GQ-9 cells could sequester 56.60% of the adsorbed Pb(II) ions on the cell wall. FTIR analysis suggested that hydroxyl, carboxyl, amino, nitrile, and sulfhydryl groups and amide I, amide II bands on the GQ-9 cell wall participated in the complexation of Pb(II) ions. The present study illustrates that the lead-resistant bacteria GQ-9 has the potential for further development of an effective and ecofriendly adsorbent for heavy metal bioremediation.

Antibacterial evaluation of Salvia miltiorrhizae on Escherichia coli by microcalorimetry coupled with chemometrics

For seeking novel antibacterial agents with high efficacy and low toxicity to deal with drug resistance, the effects of Salvia miltiorrhizae from various sources on Escherichia coli were evaluated by microcalorimetry coupled with chemometrics. Firstly, the heat-flow power-time curves of E. coli growth affected by different S. miltiorrhizae samples were recorded. Then, some crucial quantitative thermo-kinetic parameters including growth rate constant, heat-flow power and heat output, etc. were obtained from theses curves and were further investigated by some powerful chemometric techniques including similarity analysis, multivariate analysis of variance, hierarchical clustering analysis and principle component analysis. By analyzing the principle parameters, growth rate constant of the second exponential phase (k 2) and the heat-flow output powers of the second highest peak (P 2), together with the derived parameter inhibitory ratio (I,  %), it could be quickly concluded that the tested S. miltiorrhizae samples from different sources in China exhibited strong antibacterial effects on E. coli and the samples from Beijing city exhibited the strongest anti-E. coli effects, which might be used as novel and underlying antibacterial candidates for the resistance of E. coli to the existing drugs in practice. This study provides a useful tool and helpful idea to accurately and rapidly evaluate the antibacterial effects of some complex matrices, offering some references for exploring new antibacterial agents.

Heating treatments affect the thermal behaviour of doxorubicin loaded in PEGylated liposomes

Doxil^® is a stealth marketed PEGylated liposomal formulation, containing the anticancer drug doxorubicin. After loading via a pH gradient, fibrillar supramolecular structures of doxorubicin sulfate originates inside the core of the liposomes. Recently, the crystallinity of doxorubicin sulfate has been confirmed by high-resolution calorimetry. However, no detailed information are available on the nature of doxorubicin sulfate nanocrystals and on the effect of different thermal treatments. Thus, the aim of this work was to characterize the thermal behaviour of Doxil^® in comparison to the unloaded liposomes using microcalorimetry, dynamic light scattering and high-resolution ultrasound spectroscopy (HR-US). Different thermal programmes were applied with the aim to highlight the effect of the treatments on the formulation. The used techniques confirmed the ordered state of doxorubicin nanocrystals inside PEGylated liposomes. Particularly, microcalorimetry and HR-US highlighted the changes in the thermal behaviour of the drug under different heating programmes. Doxorubicin nanocrystals were found to be stable after heating up to 80°C, but an irreversible thermal behaviour was observed after a prolonged heating at elevated temperature (2h at 80°C). The non-reversibility could be related to the formation of a different ordered structure and enhanced by the slight leakage of the drug occurring after a prolonged heating.

Application of phosphate solubilizing bacteria in immobilization of Pb and Cd in soil

In the present study, heavy metal (HM)-tolerant phosphate solubilizing bacteria (PSB) were isolated and their performance during the remediation of Pb and Cd in contaminated soil was studied. A total of 16 bacterial strains and one consortium were isolated, and the consortium had the highest phosphate solubilizing ability and HM tolerance. Great variations between the Fourier transform infrared (FTIR) spectra of consortium cells before and after adsorption of Pb²⁺ and Cd²⁺ revealed that amide I/amide II bonds and carboxyl on the cell surface were involved in binding of metal ions. High-throughput sequencing technique revealed that the consortium was composed of Enterobacter spp., Bacillus spp., and Lactococcus spp. The consortium was added into contaminated soil, and its potential ability in dissolution of phosphate from Ca₃(PO₄)₂ and subsequent immobilization of HMs was tested. Results showed that when Ca₃(PO₄)₂ was applied at 10.60 mg/g soil, PSB addition significantly increased soil available phosphate content from 12.28 to 17.30 mg/kg, thereby enhancing the immobilization rate of Pb and Cd from 69.95 to 80.76% and from 28.38 to 30.81%, respectively. Microcalorimetric analysis revealed that PSB addition significantly improved soil microbial activity, which was possibly related with the decreased HMs availability and the nutrient effect of the solubilized phosphate. The present study can provide a cost-effective and environmental-friendly strategy to remediate multiple HM-contaminated soils.

Chemical and Biophysical Approaches for Complete Characterization of Lectin-Carbohydrate Interactions

Lectins are carbohydrate-binding proteins unrelated to antibodies or enzymes. While carbohydrates are present on all cells and pathogens, lectins are also ubiquitous in nature and their interactions with glycans mediate countless biological and physical interactions. Due to the multivalency found in both lectins and their glycan-binding partners, complete characterization of these interactions can be complex and typically requires the use of multiple complimentary techniques. In this chapter, we provide a general strategy and protocols for chemical and biophysical approaches that can be used to characterize carbohydrate-mediated interactions in the context of individual oligosaccharides, as part of a glycoprotein, and ending with visualization of interactions with whole virions.

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.

Spectroscopic, Polarographic, and Microcalorimetric Studies on Mitochondrial Dysfunction Induced by Ethanol

Liver mitochondria are involved in several important life processes; mitochondrial dysfunction and disorders are implicated in several human diseases. Alcohol permeates all tissues of the body and exerts some intrinsic hepatotoxicity. In this work, our results demonstrated that ethanol caused a series of mitochondria permeability transition pore (MPTP) opening factors such as mitochondrial swelling, increased permeability of H⁺ and K⁺, collapsed membrane potential, and increased membrane fluidity. Furthermore, mitochondrial ultrastructure alternation observed clearly by transmission electron microscopy and the release of Cytochrome c could explain the MPTP opening from another aspect. Moreover, ethanol damaged the mitochondrial respiration system and induced disturbance of mitochondrial energy metabolism which was monitored by polarographic and microcalorimetric methods, respectively. Considered together, these damages may promote both apoptotic and necrotic cell death and contribute to the onset or progression alcohol-induced liver diseases.

Fluoranthene degradation and binding mechanism study based on the active-site structure of ring-hydroxylating dioxygenase in Microbacterium paraoxydans JPM1

In this study, a gram-positive fluoranthene-degrading bacterial strain was isolated from crude oil in Dagang Oilfield and identified as Microbacterium paraoxydans JPM1 by the analysis of 16S rDNA sequence. After 25 days of incubation, the strain JPM1 could degrade 91.78 % of the initial amount of fluoranthene. Moreover, four metabolites 9-fluorenone-1-carboxylic acid, 9-fluorenone, phthalic acid, and benzoic acid were detected in the culture solution. The gene sequence encoding the aromatic-ring-hydroxylating dioxygenase was amplified in the strain JPM1 by PCR. Based on the translated protein sequence, a homology modeling method was applied to build the crystal structure of dioxygenase. Subsequently, the interaction mechanism between fluoranthene and the active site of dioxygenase was simulated and analyzed by molecular docking. Consequently, a feasible degrading pathway of fluoranthene in the strain JPM1 was proposed based on the metabolites and the interaction analyses. Additionally, the thermodynamic analysis showed that the strain JPM1 had high tolerance for fluoranthene, and the influence of fluoranthene for the bacterial growth activity was negligible under 100 to 400 mg L^-1 concentrations. Taken together, this study indicates that the strain JPM1 has high potential for further study in bioremediation of polycyclic aromatic hydrocarbon (PAH)-contaminated sites.

Toxic effect of two kinds of mineral collectors on soil microbial richness and activity: analysis by microcalorimetry, microbial count, and enzyme activity assay

Flotation reagents are hugely and increasingly used in mining and other industrial and economic activities from which an important part is discharged into the environment. China could be the most affected country by the resulting pollution. However, their ecotoxicological dimension is still less addressed and understood. This study aimed to analyze the toxic effect of sodium isobutyl xanthate (SIBX) and sodium isopropyl xanthate (SIPX) to soil microbial richness and activity and to make a comparison between the two compounds in regard to their effects on soil microbial and enzymes activities. Different methods, including microcalorimetry, viable cell counts, cell density, and catalase and fluorescein diacetate (FDA) hydrololase activities measurement, were applied. The two chemicals exhibited a significant inhibitory effect (P < 0.05 or P < 0.01) to all parameters, SIPX being more adverse than SIBX. As the doses of SIBX and SIPX increased from 5 to 300 μg g^-1 soil, their inhibitory ratio ranged from 4.84 to 45.16 % and from 16.13 to 69.68 %, respectively. All parameters fluctuated with the incubation time (10-day period). FDA hydrolysis was more directly affected but was relatively more resilient than catalase activity. Potential changes of those chemicals in the experimental media and complementarity between experimental techniques were justified.

Microcalorimetric studies on the energy release of isolated rat mitochondria under different concentrations of gadolinium (III)

Gadolinium-based compounds are most widely utilized for paramagnetic contrast agents, but, the toxicological mechanism of gadolinium (Gd) had not been fully elucidated since the first report about Gd anomaly. In this work, we analyzed the effect of Gd(3+) on mitochondria in vitro by microcalorimetry. Microcalorimetry can provide detailed kinetic and thermodynamic information from thermogenic curve. At the tested concentration, Gd(3+) induced the increase of growth rate constant (k1). At high concentration (100-500 μM), the maximum power output time (tm), the decline rate constant (-k2) and the time of activity recovery phase (tR) decreased with the addition of Gd(3+) and the maximum power output (Pm) increased. At low concentration (0-100 μM), the changes were different from high concentration. From the results we concluded that the effect of different concentrations of Gd(3+) had a relationship with time, high concentration of Gd(3+) induced mitochondrial energy metabolism disturb however low concentration may promote mitochondrial adaption to physiological stresses. The effect of low concentration of Gd(3+) need more work to elucidate the mechanism. The results of total heat output (Q) and mitochondrial respiratory activities suggested high concentrations of Gd(3+) could accelerate adenosine triphosphate (ATP) consumption under respiratory system damaged.

Microcalorimetry studies of the antimicrobial actions of Aconitum alkaloids

The metabolic activity of organisms can be measured by recording the heat output using microcalorimetry. In this paper, the total alkaloids in the traditional Chinese medicine Radix Aconiti Lateralis were extracted and applied to Escherichia coli and Staphylococcus aureus. The effect of alkaloids on bacteria growth was studied by microcalorimetry. The power-time curves were plotted with a thermal activity monitor (TAM) air isothermal microcalorimeter and parameters such as growth rate constant (μ), peak-time (Tm), inhibitory ratio (I), and enhancement ratio (E) were calculated. The relationships between the concentration of Aconitum alkaloids and μ of E. coli or S. aureus were discussed. The results showed that Aconitum alkaloids had little effect on E. coli and had a potentially inhibitory effect on the growth of S. aureus.

Effect of three typical sulfide mineral flotation collectors on soil microbial activity

The sulfide mineral flotation collectors are wildly used in China, whereas their toxic effect on soil microbial activity remains largely unexplored. In this study, isothermal microcalorimetric technique and soil enzyme assay techniques were employed to investigate the toxic effect of typical sulfide mineral flotation collectors on soil microbial activity. Soil samples were treated with different concentrations (0-100 μg•g - 1 soil) of butyl xanthate, butyl dithiophosphate, and sodium diethyldithiocarbamate. Results showed a significant adverse effect of butyl xanthate (p < 0.05), butyl dithiophosphate, and sodium diethyldithiocarbamate (p < 0.01) on soil microbial activity. The growth rate constants k decreased along with the increase of flotation collectors concentration from 20.0 to 100.0 μg•g(-1). However, the adverse effects of these three floatation collectors showed significant difference. The IC 20 of the investigated flotation reagents followed such an order: IC 20 (butyl xanthate) > IC 20 (sodium diethyldithiocarbamate) > IC 20 (butyl dithiophosphate) with their respective inhibitory concentration as 47.03, 38.36, and 33.34 μg•g(-1). Besides, soil enzyme activities revealed that these three flotation collectors had an obvious effect on fluorescein diacetate hydrolysis (FDA) enzyme and catalase (CAT) enzyme. The proposed methods can provide meaningful toxicological information of flotation reagents to soil microbes in the view of metabolism and biochemistry, which are consistent and correlated to each other.

Different responses of soil microbial metabolic activity to silver and iron oxide nanoparticles

The knowledge regarding the effects of metal or metal oxide nanoparticles on soil microbial metabolic activity and key ecological functions is limited, relative to the information about their species diversity. For this reason, the responses of soil microbial metabolic activity to silver (AgNPs) and iron oxide (FeONPs) nanoparticles, along concentration gradients of each, were evaluated by microcalorimetry and soil nitrification potential. The changes in abundances of bacteria, eukaryotes and ammonia-oxidizing bacteria were measured by real time quantitative PCR. It was found that AgNP (at 0.1, 1 and 10 mg kg(-1) soil) amendments decreased soil microbial metabolic activity, nitrification potential and the abundances of bacteria and ammonia-oxidizing bacteria; on the contrary, FeONPs had the positive effects on soil microbial metabolic activity (at 1 and 10 mg kg(-1) soil) and soil nitrification potential (at 0.1 and 1 mg kg(-1) soil). Specific microbial metabolic activity and specific nitrification potential further revealed that metal or metal oxide nanoparticles could change the C and N cycles of the agricultural soil through influencing soil microbial metabolism. These findings could deepen the understanding of the influence of NPs on soil microorganisms and their driven soil ecology process.

Muscle heat: a window into the thermodynamics of a molecular machine

The contraction of muscle is characterized by the development of force and movement (mechanics) together with the generation of heat (metabolism). Heat represents that component of the enthalpy of ATP hydrolysis that is not captured by the microscopic machinery of the cell for the performance of work. It arises from two conceptually and temporally distinct sources: initial metabolism and recovery metabolism. Initial metabolism comprises the hydrolysis of ATP and its rapid regeneration by hydrolysis of phosphocreatine (PCr) in the processes underlying excitation-contraction coupling and subsequent cross-bridge cycling and sliding of the contractile filaments. Recovery metabolism describes those process, both aerobic (mitochondrial) and anaerobic (cytoplasmic), that produce ATP, thereby allowing the regeneration of PCr from its hydrolysis products. An equivalent partitioning of muscle heat production is often invoked by muscle physiologists. In this formulation, total enthalpy expenditure is separated into external mechanical work (W) and heat (Q). Heat is again partitioned into three conceptually distinct components: basal, activation, and force dependent. In the following mini-review, we trace the development of these ideas in parallel with the development of measurement techniques for separating the various thermal components.

Susceptibility testing of Mycobacterium abscessus by isothermal microcalorimetry

We evaluated a new method for susceptibility testing of a rapidly growing mycobacterium using real-time measurement of heat (microcalorimetry). MICs of 2 clinical Mycobacterium abscessus isolates were determined by microbroth dilution and E-test. For microcalorimetry, Middlebrook-7H10 agar+10% oleic acid-albumin-dextrose-catalase, containing amikacin, clarithromycin, linezolid, and ciprofloxacin was inoculated with ~10(5)CFU/mL. Heat production was measured at 37°C for 72h. Minimal heat inhibition concentration (MHIC) was defined as the lowest antibiotic concentration inhibiting growth-related heat production. Growth of M. abscessus was detected after a median of 16.5h (range, 8.5-26.9h). Heat detection was proportionally delayed with increasing concentration of antibiotics. MHICs for the tested strains were 16 to >16mg/L for amikacin, >8mg/L for clarithromycin, 4 to >16mg/L for ciprofloxacin, 24 to >32mg/L for linezolid. MHICs were in agreement within two 2-fold dilutions with conventional MICs. Microcalorimetry may accelerate antimicrobial susceptibility testing in mycobacteria and provide additional real-time information on the drug effect.

Anthranoyl-CoA monooxygenase/reductase from Azoarcus evansii possesses both FMN and FAD in two distinct and independent active sites

Anthranoyl-CoA monooxygenase/reductase (ACMR) participates in an unusual pathway for the degradation of aromatic compounds in Azoarcus evansii. It catalyzes the monooxygenation of anthranoyl-CoA to 5-hydroxyl-2-aminobenzoyl-CoA and the subsequent reduction to the dearomatized product 2-amino-5-oxo-cyclohex-1-ene-1-carbonyl-CoA. The two reactions occur in separate domains, termed the monooxygenase and reductase domain. Both domains were reported to utilize FAD as a cofactor for hydroxylation and reduction, respectively. We have heterologously expressed ACMR in Escherichia coli BL21 and found that the monooxygenase domain contains FAD. However, the reductase domain utilizes FMN and not FAD for the reduction of the intermediate 5-hydroxyl-2-aminobenzoyl-CoA. A homology model for the reductase domain predicted a topology similar to the Old Yellow Enzyme family, which exclusively bind FMN, in accordance with our results. Binding studies with 2-aminobenzoyl-CoA (AbCoA) and p-hydroxybenzaldehyde (pHB) as probes for the monooxygenase and reductase domain, respectively, indicated that two functionally distinct and independent active sites exist. Given the homodimeric quartenary structure of ACMR and the compact shape of the dimer as determined by small-angle X-ray scattering experiments we propose that the monooxygenase and reductase domain of opposite peptide chains are involved in the transformation of anthranoyl-CoA to 2-amino-5-oxo-cyclohex-1-ene-1-carbonyl-CoA.

The toxicity of binary mixture of Cu (II) ion and phenols on Tetrahymena thermophila

The toxicity of binary mixture of Cu(2+) and phenols (phenol; o-nitrophenol; m-nitrophenol; p-nitrophenol) was evaluated using Tetrahymena thermophila as the model organism, by microcalorimetry, optical density, field emission scanning electron microscope (FESEM) and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR). The growth curves and metabolic properties of Tetrahymena exposed to Cu(2+) and phenols were monitored by microcalorimetry. Binary mixture toxicity changed with the concentration of Cu(2+)/phenols and the order of toxicity was Cu(2+)/phenol<Cu(2+)/m-nitrophenol<Cu(2+)/o-nitrophenol<Cu(2+)/p-nitrophenol. The results of FESEM and ATR-FTIR also indicated that Cu(2+)/phenols had a great effect on cell cortex and flagellum. A synergistic effect was noted between Cu(2+) and phenols on Tetrahymena.

Activity of bone cement loaded with daptomycin alone or in combination with gentamicin or PEG600 against Staphylococcus epidermidis biofilms

Daptomycin is a promising candidate for local treatment of bone infection due to its activity against multi-resistant staphylococci. We investigated the activity of antibiotic-loaded PMMA against Staphylococcus epidermidis biofilms using an ultra-sensitive method bacterial heat detection method (microcalorimetry). PMMA cylinders loaded with daptomycin alone or in combination with gentamicin or PEG600, vancomycin and gentamicin were incubated with S. epidermidis-RP62A in tryptic soy broth (TSB) for 72 h. Cylinders were thereafter washed and transferred in microcalorimetry ampoules pre-filled with TSB. Bacterial heat production, proportional to the quantity of biofilm on the PMMA, was measured by isothermal microcalorimetry at 37 °C. Heat detection time was considered time to reach 20 μW. Experiments were performed in duplicate. The heat detection time was 5.7-7.0 h for PMMA without antibiotics. When loaded with 5% of daptomycin, vancomycin or gentamicin, detection times were 5.6-16.4 h, 16.8-35.7 h and 4.7-6.2 h, respectively. No heat was detected when 5% gentamicin or 0.5% PEG600 was added to the daptomycin-loaded PMMA. The study showed that vancomycin was superior to daptomycin and gentamicin in inhbiting staphylococcal adherence in vitro. However, PMMA loaded with daptomycin combined with gentamicin or PEG600 completely inhibited S. epidermidis-biofilm formation. PMMA loaded with these combinations may represent effective strategies for local treatment in the presence of multi-resistant staphylococci.

The adsorption of pharmaceutically active compounds from aqueous solutions onto activated carbons

In this study, the adsorption of pharmaceutically active compounds - salicylic acid, acetylsalicylic acid, atenolol and diclofenac-Na onto activated carbons has been studied. Three different commercial activated carbons, possessing ∼650, 900 or 1500m(2)g(-1) surface areas were used as solid adsorbents. These materials were fully characterized - their textural, surface features and points of zero charge have been determined. The adsorption was studied from aqueous solutions at 303K using batch adsorption experiments and titration microcalorimetry, which was employed in order to obtain the heats evolved as a result of adsorption. The maximal adsorption capacities of investigated solids for all target pharmaceuticals are in the range of 10(-4)molg(-1). The obtained maximal retention capacities are correlated with the textural properties of applied activated carbon. The roles of acid/base features of activated carbons and of molecular structures of adsorbate molecules have been discussed. The obtained results enabled to estimate the possibility to use the activated carbons in the removal of pharmaceuticals by adsorption.

Comparison of anti-bacterial activity of three types of di-O-caffeoylquinic acids in Lonicera japonica flowers based on microcalorimetry

The anti-bacterial activities of three types of di-O-caffeoylquinic acids (diCQAs) in Lonicera japonica flowers, a traditional Chinese medicine (TCM), on Bacillus shigae growth were investigated and compared by microcalorimetry. The three types of diCQAs were 3, 4-di-O-caffeoylquinic acid (3, 4-diCQA), 3, 5-di-O-caffeoylquinic acid (3, 5-diCQA), and 4, 5-di-O-caffeoylquinic acid (4, 5-diCQA). Some qualitative and quantitative information of the effects of the three diCQAs on metabolic power-time curves, growth rate constant k, maximum heat-output power Pm, and the generation time tG, total heat output Qt, and growth inhibitory ratio I of B. shigae were calculated. In accordance with a thermo-kinetic model, the corresponding quantitative relationships of k, Pm, Qt, I and c were established. Also, the half-inhibitory concentrations of the drugs (IC50) were obtained by quantitative analysis. Based on the quantity-activity relationships and the IC50 values, the sequence of inhibitory activity was 3, 5-diCQA > 4, 5-diCQA > 3, 4-diCQA. The results illustrate the possibility that the caffeoyl ester group at C-5 is the principal group that has a higher affinity for the bacterial cell, and that the intramolecular distance of the two caffeoyl ester groups also has an important influence on the anti-bacterial activities of the diCQAs.

The interactions between CdSe quantum dots and yeast Saccharomyces cerevisiae: adhesion of quantum dots to the cell surface and the protection effect of ZnS shell

The interactions between quantum dots (QDs) and biological systems have attracted increasing attention due to concerns on possible toxicity of the nanoscale materials. The biological effects of CdSe QDs and CdSe/ZnS QDs with nearly identical hydrodynamic size on Saccharomyces cerevisiae were investigated via microcalorimetric, spectroscopic and microscopic methods, demonstrating a toxic order CdSe>CdSe/ZnS QDs. CdSe QDs damaged yeast cell wall and reduced the mitochondrial membrane potential. Noteworthy, adhesion of QDs to the yeast cell surface renders this work a good example of interaction site at cell surface, and the epitaxial coating of ZnS could greatly reduce the toxicity of Cd-containing QDs. These results will contribute to the safety evaluation of quantum dots, and provide valuable information for design of nanomaterials.

Structure and stability of an unusual zinc-binding protein from Bacteroides thetaiotaomicron

The crystal structure of a putative protease from Bacteroides thetaiotaomicron (ppBat) suggested the presence of a zinc ion in each protomer of the dimer as well as a flavin in the dimer interface. Since the chemical identity of the flavin and the exact mode of binding remained unclear, we have determined the crystal structure of ppBat in complex with riboflavin. The obtained structure revealed that the isoalloxazine ring is sandwiched between two tryptophan residues (Trp164) from both chains and adopts two alternate orientations with the N(10)-ribityl side chain protruding from the binding site in opposite directions. In order to characterize the zinc-binding site, we generated two single variants and one double variant in which the two coordinating cysteine residues (Cys74 and Cys111) were replaced by alanine. All three variants were unable to bind zinc demonstrating that both cysteine residues are essential for binding. Moreover, the lack of zinc binding also resulted in drastically reduced thermal stability (11-15°C). A similar effect was obtained when wild-type protein was incubated with EDTA supporting the conclusion that the zinc-binding site plays an important structural role in ppBat. On the other hand, attempts to identify proteolytic activity failed suggesting that the zinc may not act as a catalytic center in ppBat. Structurally similar zinc binding motives in other proteins were also found to play a structural rather than catalytic role and hence it appears that neither the flavin nor the zinc binding sites possess a catalytic function in ppBat.

Biodegradation and utilization of 4-n-nonylphenol by Aspergillus versicolor as a sole carbon and energy source

4-n-Nonylphenol (4-n-NP) is an environmental pollutant with endocrine-disrupting activities that is formed during the degradation of nonylphenol polyethoxylates, which are widely used as surfactants. Utilization of 4-n-NP by the filamentous fungus Aspergillus versicolor as the sole carbon and energy source was investigated. By means of gas chromatography-mass spectrometry, we showed that in the absence of any carbon source other than 4-n-NP in the medium, A. versicolor completely removed the xenobiotic (100 mg L(-1)) after 3 d of cultivation. Moreover, mass spectrometric analysis of intracellular extracts led to the identification of eight intermediates. The mineralization of the xenobiotic in cultures supplemented with 4-n-NP [ring-(14)C(U)] as a growth substrate was also assessed. After 3 d of incubation, approximately 50% of the initially applied radioactivity was recovered in the form of (14)CO2, proving that this xenobiotic was completely metabolized and utilized by A. versicolor as a carbon source. Based on microscopic analysis, A. versicolor is capable of germinating spores under such conditions. To confirm these observations, a microcalorimetric method was used. The results show that even the highest amount of 4-n-NP initiates heat production in the fungal samples, proving that metabolic processes were affected by the use of 4-n-NP as an energetic substrate.

Necrotizing fasciitis after breast augmentation: rapid microbiologic detection by using sonication of removed implants and microcalorimetry

OBJECTIVES

To describe the use of sonication and microcalorimetry in diagnosing necrotizing fasciitis in a 27-year-old woman with bilateral breast implants.

METHODS

The removed breast implants were subjected to sonication and microcalorimetry. The microcalorimetry findings were correlated with conventional microbiologic methods. The time to detection of infection was noted.

RESULTS

The patient had painful cellulitis of the right breast that enlarged within hours. Her C-reactive protein level was increased. Chest radiograph showed gas formation in the soft tissue lateral of the right breast. Surgery was performed: 300 mL (right breast) and 100 mL (left breast) of serous-purulent fluid were evacuated. Streptococcus pyogenes was cultured from the fluid 1 day after clinical presentation. Infection was diagnosed by microcalorimetry of sonication fluid in 1 hour and 21 minutes. The microcalorimetry curve from the right implant reached the peak earlier than did the left implant.

CONCLUSION

Microcalorimetry will have a benefit in conditions in which rapid diagnosis of infection is important.

Joint toxicity of heavy metals and chlorobenzenes to pyriformis Tetrahymena

Chlorobenzens and heavy metals are frequently detected in the environment, but few studies have assessed the joint toxicity of organic and inorganic contaminants. The joint toxicity of heavy metals and chlorobenzenes was evaluated in the present study. Growth metabolism of the joint toxicity was studied by microcalorimetry at 28°C, the growth constant (k) and inhibitory ratio (I) were calculated. Toxic unit (TU) and additional index (AI) were introduced to determine the outcome in combined tests, and the coexistence of Cu, Cd, Cr(III) and p-chlorobenzene was antagonism, and the effect of Cu, Cd, Cr(III) and o-chlorobenzene, Cu and 1,2,4-trichlorobenzene were synergism. In addition, micro-situation of the cell membrane surface of pyriformis Tetrahymena was observed by SEM. The cells suffered serious damage after sufficient acting time. ATR-FTIR spectra revealed that amide groups and PO2(-) of the phospholipid phospho-diester, both in the hydrophobic end exposed to the outer layer, were the easiest to be damaged.

Spectrum-effect relationships between UPLC fingerprints and bioactivities of crude secondary roots of Aconitum carmichaelii Debeaux (Fuzi) and its three processed products on mitochondrial growth coupled with canonical correlation analysis

ETHNOPHARMACOLOGICAL RELEVANCE

The crude secondary roots of Aconitum carmichaelii Debeaux (Fuzi), together with its processed products, including Yanfuzi, Heishunpian and Paofupian, are commonly applied in clinic using for thousands of years, such as collapse, syncope, rheumatic fever, painful joints and various tumors.

AIM OF THE STUDY

To explore the different effects of Fuzi and its processed products on energy metabolism, with mitochondria as the model with the aim of guiding the clinical use of Fuzi and its products. fingerprints of Fuzi, Yanfuzi, Heishunpian and Paofupian were established by Ultra-high Performance Liquid Chromatography (UPLC) and effects of Fuzi and its processed products on rat's liver׳s mitochondrial metabolism were studied by microcalorimetry. Spectrum-effect relationships between UPLC fingerprints and energy metabolism of mitochondria were investigated using canonical correlation analysis (CCA).

RESULTS

Because of their inherent differences in chemical compositions, the main activities of energy metabolism of mitochondria were different among Fuzi and its processed products. The potential bioactivity sequence of the tested products was Fuzi>Heishunpian>Paofupian>Yanfuzi. RESULTS of CCA showed that compounds mesaconitine, benzoylaconitine, and benzoylhypacoitine might be the principal active components.

CONCLUSION

Altogether, this work provides a general model of combination of UPLC and microcalorimetry to study the spectrum-effect relationships of Fuzi and its processed products which can offer some references for detecting principal components of traditional Chinese medicine on bioactivity to mitochondrial growth.

Microcalorimetric investigation of the effect of non-ionic surfactant on biodegradation of pyrene by PAH-degrading bacteria Burkholderia cepacia

Polycyclic aromatic hydrocarbons (PAHs) are widespread in various ecosystems and are pollutants of great concern due to their potential toxicity, mutagenecity and carcinogenicity. Surfactant has become a hot topic for its wide application in the bioremediation of PAHs. The aim of this work is to explore a microcalorimetric method to determine the toxic effect of pyrene on Bacillus subtilis (B. subtilis) and the PAH-degrading bacteria Burkholderia cepacia (B. cepacia) and to evaluate the effect of Tween 80 on biodegradation of pyrene. Power-time curves were studied and calorimetric parameters including the growth rate constant (k), half inhibitory concentration (IC₅₀), and total thermal effect (Q(T)) were determined. B. subtilis, B. cepacia and B. cepacia with Tween 80 were completely inhibited when the concentration of pyrene were 200, 800 and 1600 µg mL⁻¹, respectively. B. cepacia shows better tolerance to pyrene than B. subtilis. Tween 80 significantly improves the biodegradation of pyrene by increasing the bioavailability of pyrene. In addition, the expression of catechol 2,3-dioxygenase (C23O) in B. cepacia is responsible for the degradation of pyrene and plays an important role in improving the biodegradation of pyrene. Moreover, the activity of C23O increases with the application of Tween 80. The enhanced bioavailability and biodegradation of pyrene by Tween 80 shows the potential use of Tween 80 in the PAHs bioremediation.

Microcalorimetry: a powerful and original tool for tracking the toxicity of a xenobiotic on Tetrahymena pyriformis

Fighting against water pollution requires the ability to evaluate the toxicity of pollutants such as herbicides. Tetrahymena pyriformis are ubiquitous ciliated protozoans commonly used in ecotoxicological research. Microcalorimetry can be used in many biological investigations as a universal, non-destructive and highly sensitive tool that provides a continuous real-time monitoring of the metabolic activity. This technique based on the thermal power output was applied to evaluate the influence of herbicide diuron on cultures of T. pyriformis. The heat flux produced upon addition of 0, 3.5, 7.0, 14.0, 28.0, and 56.0 µg mL⁻¹ of diuron was monitored. The biomass change during the growth was also determined by flow cytometry. The results confirmed that the growth of T. pyriformis is progressively inhibited as the concentration of diuron increases and revealed that the state of the living system is severely altered at a concentration of 56.0 µg mL⁻¹. The IC₅₀ was estimated at 13.8 µg mL⁻¹ by microcalorimetry and at 18.6 µg mL⁻¹ by flow cytometry. It was shown that microcalorimetry is not only a very effective tool for the determination of the growth rate constant but that it is also a valuable probe for a rapid detection of the metabolic perturbations and, in ultimate cases, of the critical alterations of the living system under the action of a toxic agent.

Toxicity of perfluorooctanoic acid to Pseudomonas putida in the aquatic environment

Perfluorinated compounds are potential persistent organic pollutants which attracted much concerns in recent years. Thus relevant toxicity data of perfluorooctanoic acid (PFOA) are vitally important for identification of possible risk in the aquatic environment. In the present study, the acute toxic effect of PFOA in the absence and presence of either chromium (III) or tetra butyl ammonium (TBA) towards Pseudomonas putida in the aquatic environment was investigated by microcalorimetry. The thermokinetic parameters including growth rate constant (k), inhibitory ratio, and half inhibitory concentration, were calculated and compared using the data obtained from the power-time curves. Our work revealed the toxicity of PFOA under three experimental conditions in a descending sequence: PFOA, PFOA+Cr(3+), and PFOA+TBA. The results highlighted that the presence of un-ionized NH3 in the test solutions could not be a potential significant contributor to the observed toxicity of PFOA. In addition, PFOA interacted antagonistically with Cr(3+) and TBA. TBA was found to substantially enhance the surface pressure of PFOA which could be related with the toxicity of PFOA. The higher surface pressure caused for the reduction in toxicity. Thus the results highlighted the potential toxicological risk associated with this surfactant in the aquatic ecosystems.