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Concept: Buffer solution


Agricultural soils represent the main source of anthropogenic N2O emissions. Recently, interactions of black carbon with the nitrogen cycle have been recognized and the use of biochar is being investigated as a means to reduce N2O emissions. However, the mechanisms of reduction remain unclear. Here we demonstrate the significant impact of biochar on denitrification, with a consistent decrease in N2O emissions by 10-90% in 14 different agricultural soils. Using the (15)N gas-flux method we observed a consistent reduction of the N2O/(N2 + N2O) ratio, which demonstrates that biochar facilitates the last step of denitrification. Biochar acid buffer capacity was identified as an important aspect for mitigation that was not primarily caused by a pH shift in soil. We propose the function of biochar as an “electron shuttle” that facilitates the transfer of electrons to soil denitrifying microorganisms, which together with its liming effect would promote the reduction of N2O to N2.

Concepts: Carbon dioxide, Metabolism, Nitrogen, PH, Buffer solution, Bioremediation, Denitrification, Nitrogen cycle


The magnetic chitosan nanocomposites have been studied intensively and been used practically in various biomedical and biological applications including enzyme immobilization. However, the loading capacity and the remained activity of immobilized enzyme based on existing approaches are not satisfied. Simpler and more effective immobilization strategies are needed. Here we report a simple catechol modified protocol for preparing a novel catechol-chitosan (CCS)-iron oxide nanoparticles (IONPs) composites carrying adhesive moieties with strong surface affinity. The ω-transaminase (ω-TA) was immobilized onto this magnetic composite via nucleophilic reactions between catechol and ω-TA. Under optimal conditions, 87.5% of the available ω-TA was immobilized on the composite, yielding an enzyme loading capacity as high as 681.7 mg/g. Furthermore, the valuation of enzyme activity showed that ω-TA immobilized on CCS-IONPs displayed enhanced pH and thermal stability compared to free enzyme. Importantly, the immobilized ω-TA retained more than 50% of its initial activity after 15 repeated reaction cycles using magnetic separation and 61.5% of its initial activity after storage at 4°C in phosphate buffered saline (PBS) for 15 days. The results suggested that such adhesive magnetic composites may provide an improved platform technology for bio-macromolecules immobilized.

Concepts: Enzyme, PH, Composite material, Buffer solution, Enzymes, Immobilized enzyme, Epoxy, Composite video


Background and the purpose of the study: Rizatriptan is used effectively for the treatment of migraine headache. In this study, a simple, rapid and low cost spectrophotometric method based on the ion-pair complexation is proposed for the determination of rizatriptan in raw material and dosage forms. METHODS: The ion-pair complexation using bromocresol green as reagent was performed in a buffer solution and the absorbance was measured by a spectrophotometer. The ion-pair formation conditions were optimized and the accuracy and precision of the method were calculated.Results and major conclusion: Best results were achieved by using 6 ml of the bromocresol green reagent in the presence of phosphate buffer (pH 3.0). The stoichiometry of the resulted complex was 1:1. The within-day and between-day precision values were lower than 2.9 and 1.8 percent for the calibration range of 0.5–50 and 10–100 mug/ml, respectively. The proposed method was successfully used for the determination of rizatriptan in dosage forms without any interference.

Concepts: Spectroscopy, Chemical equilibrium, PH, Phosphate buffered saline, Accuracy and precision, Buffer solution, Equilibrium chemistry, Spectrophotometry


The International Society of Sports Nutrition (ISSN) provides an objective and critical review of the mechanisms and use of beta-alanine supplementation. Based on the current available literature, the conclusions of the ISSN are as follows: 1) Four weeks of beta-alanine supplementation (4-6 g daily) significantly augments muscle carnosine concentrations, thereby acting as an intracellular pH buffer; 2) Beta-alanine supplementation currently appears to be safe in healthy populations at recommended doses; 3) The only reported side effect is paraesthesia (tingling), but studies indicate this can be attenuated by using divided lower doses (1.6 g) or using a sustained-release formula; 4) Daily supplementation with 4 to 6 g of beta-alanine for at least 2 to 4 weeks has been shown to improve exercise performance, with more pronounced effects in open end-point tasks/time trials lasting 1 to 4 min in duration; 5) Beta-alanine attenuates neuromuscular fatigue, particularly in older subjects, and preliminary evidence indicates that beta-alanine may improve tactical performance; 6) Combining beta-alanine with other single or multi-ingredient supplements may be advantageous when supplementation of beta-alanine is high enough (4-6 g daily) and long enough (minimum 4 weeks); 7) More research is needed to determine the effects of beta-alanine on strength, endurance performance beyond 25 min in duration, and other health-related benefits associated with carnosine.

Concepts: Nutrition, Effect, Acid dissociation constant, PH, Paresthesia, Effects unit, Buffer solution, Buffering agent


Across diverse ecosystems, greater climatic variability tends to increase wildfire size, particularly in Australia, where alternating wet-dry cycles increase vegetation growth, only to leave a dry overgrown landscape highly susceptible to fire spread. Aboriginal Australian hunting fires have been hypothesized to buffer such variability, mitigating mortality on small-mammal populations, which have suffered declines and extinctions in the arid zone coincident with Aboriginal depopulation. We test the hypothesis that the relationship between climate and fire size is buffered through the maintenance of an anthropogenic, fine-grained fire regime by comparing the effect of climatic variability on landscapes dominated by Martu Aboriginal hunting fires with those dominated by lightning fires. We show that Aboriginal fires are smaller, more tightly clustered, and remain small even when climate variation causes huge fires in the lightning region. As these effects likely benefit threatened small-mammal species, Aboriginal hunters should be considered trophic facilitators, and policies aimed at reducing the risk of large fires should promote land-management strategies consistent with Aboriginal burning regimes.

Concepts: Climate, Weather, Climate change, Vegetation, Buffer solution, Buffer, Solar variation, Global warming


BACKGROUND:: Patients with Celiac Disease (CD) have a wide variety of symptoms, from being asymptomatic to having chronic diarrhea, abdominal pain and extra-intestinal symptoms. In the oral cavity, enamel defects and recurrent aphthous stomatitis are the most common symptoms. AIM:: To assess oral health, bacterial colonization and salivary buffering capacity of patients with CD at diagnosis were compared with CD patients on gluten free diet (GFD) and healthy children. METHODS:: Three groups were prospectively investigated: newly diagnosed celiac disease, celiac disease treated with GFD and a control group. All children were examined by pediatric dentists and saliva samples were collected for bacterial and pH analysis. RESULT:: Ninety children were enrolled in the study, thirty in each group. A higher prevalence of enamel hypoplasia (66%) was found in celiac children. Plaque Index was significantly lower in the celiac treated group, which correlated with oral health behavior: teeth brushing and frequency of eating between meals. Children on GFD brushed their teeth and used fluoride significantly more often than other children in the study. No difference between groups was found in snacks consumption, Mutans Streptococci and Lactobacilli counts in saliva, as well as pH and buffer capacity, CONCLUSIONS:: A lower degree of plaque was found in celiac children on GFD. This finding could not be explained by salivary properties or bacteria, but rather by better oral hygiene. The results should raise the awareness of pediatric gastroenterologists to oral health related issues in children with CD.

Concepts: Bacteria, Wheat, Crohn's disease, Buffer solution, Coeliac disease, Gluten, Aphthous ulcer, Gluten-free diet


A sensitive and reproducible high-performance liquid chromatography-fluorescence method was developed and validated for quantitative determination of indoxyl sulfate in plasma using methyl paraben as an internal standard. The separation was carried out on an OSD-2 C18 Spherisorb column by isocratic elusion with sodium acetate buffer (pH 4.5) and acetonitrile (10:90, v/v) as the mobile phase. The method was validated and found to be linear in the range of 2.5 to 50 µM. The limit of quantification was 2.0 µM. The variations for intra-day and inter-day precision were less than 10.1%, and the accuracy values were between 93.4 and 102.5%. The extraction recoveries were more than 89%.

Concepts: Scientific method, Measurement, Chromatography, Analytical chemistry, Acetic acid, Buffer solution, Conjugate acid, Sodium acetate


Based on the fact that hydrogen sulfide (H(2)S) possesses the smallest steric hindrance among thiols and the SH(-) group adds faster to an electron-poor C[double bond, length as m-dash]C double bond, we designed and synthesized a tricyanoethylene-derived colorimetric chemodosimeter 1 for the fast and highly selective assay of H(2)S. Chemodosimeter 1 exhibited excellent water-solubility due to the introduction of two hydrophilic hydroxyl groups. Upon the addition of Na(2)S, chemodosimeter 1 showed a fast (complete within 400 s) and robust decrease of the absorption intensity (>97%), accompanied by a color change from red to colorless. Additionally, a linear relationship between absorption intensity and the added Na(2)S concentrations (0-130 μM) was observed in aqueous buffer solution (pH 7.4, 20 mM PBS). Importantly, the proposed paradigm in this paper, adoption of the tricyanoethylene derivative as a recognition receptor to distinguish H(2)S from other thiols and analytes, provides a promising methodology for the design of colorimetric and fluorescent chemodosimeters for fast determination of H(2)S.

Concepts: Oxygen, Functional group, Concentration, Color, PH, Functional groups, Sulfur, Buffer solution


The Flinders Technology Australia (FTA) Elute Card is a commercial product that facilitates the collection, transport, archiving and processing of nucleic acids from a wide variety of biological samples at room temperature. While the cards have been designed so that sterile/deionized water can elute DNA easily, they are not suitable for some less stable RNAs. This study was undertaken to determine the optimal conditions such as the buffer type, buffer pH and incubation temperature for the elution of enteroviral RNA from FTA Elute Cards prior to quantitative analysis using real-time PCR (qPCR) or consensus degenerate hybrid oligonucleotide primer VP1 RT-semi nested PCR (CODEHOP VP1 RT-snPCR). TE-1 (pH 8.0), rather than sterile water, was the best buffer for high efficiency elution of enteroviral RNA at 95°C. However, as the estimated recovery rate of viral RNA eluted from the cards averaged to be only 6.1%, enterovirus assays using FTA elution should be considered qualitative, especially at low virus titers, and therefore the results of the assay should be interpreted carefully.

Concepts: DNA, Polymerase chain reaction, Molecular biology, Enzyme, Virus, RNA, Nucleic acid, Buffer solution


A stable, label-free optical biosensor based on a porous silicon-carbon (pSi-C) composite is demonstrated. The material is prepared by electrochemical anodization of crystalline Si in an HF-containing electrolyte to generate a porous Si template, followed by infiltration of poly(furfuryl) alcohol (PFA) and subsequent carbonization to generate the pSi-C composite as an optically smooth thin film. The pSi-C sensor is significantly more stable toward aqueous buffer solutions (pH 7.4 or 12) compared to thermally oxidized (in air, 800 °C), hydrosilylated (with undecylenic acid), or hydrocarbonized (with acetylene, 700 °C) porous Si samples prepared and tested under similar conditions. Aqueous stability of the pSi-C sensor is comparable to related optical biosensors based on porous TiO(2) or porous Al(2)O(3). Label-free optical interferometric biosensing with the pSi-C composite is demonstrated by detection of rabbit IgG on a protein-A-modified chip and confirmed with control experiments using chicken IgG (which shows no affinity for protein A). The pSi-C sensor binds significantly more of the protein A capture probe than porous TiO(2) or porous Al(2)O(3), and the sensitivity of the protein-A-modified pSi-C sensor to rabbit IgG is found to be ∼2× greater than label-free optical biosensors constructed from these other two materials.

Concepts: Acid, Optical fiber, Electrochemistry, Chemistry, Acid dissociation constant, PH, Buffer solution, Biosensor