Crystal structure of phenanthrenide salts stabilized by 15-crown-5 and 18-crown-6

Potassium 15-crown-5 phenanthrenide and potassium 18-crown-6 phenanthrenide were synthesized and characterized by powder X-ray diffraction and 39K solid state NMR spectroscopy. While the radical carbanion is very reactive in solution, the crystals are stable and storable under inert atmosphere. For 15-crown-5, a sandwich-like complex of potassium is formed with two molecules of crown ether per potassium resulting in a coordination number of 10. For the larger 18-crown-6 ligand, a 1:1 complex is obtained and a coordination number of 6 for the potassium cation. In neither crystal structure solvent molecules are incorporated. The 15-crown-5 compound crystallizes faster and is less soluble in THF as compared to the 18-crown-6 compound. Both compounds form solid phenanthrenide that is easy to handle and can be applied for reduction reactions.

Soil Organic Carbon in Forest and Other Land Use Types at Bengkulu City, Indonesia

Conversion of natural forest into agricultural land uses has decreased soil organic carbon (SOC) and increased carbon emission into the atmosphere, but proper management of agricultural land can sequester carbon from the atmosphere and increase the SOC. This study was conducted to estimate the SOC content and storage in a forest, agroforestry land, oil palm plantation, and agricultural experimental field and to analyze the correlation between the SOC and other soil characteristics at Bengkulu City, Indonesia. Soil were sampled from the following depths: 0–10 cm, 10–20 cm, and 20–30 cm. The biomass of litter and ground cover was also sampled. This study found that the forest had the highest average SOC content from the three depths, and 0–30 cm depth SOC storage, while the agroforestry system had the lowest of both SOC content and storage. The 0–10 cm depth had the highest SOC content and storage, while the 20–30 cm depth had the lowest of both variables. The SOC was positively correlated with litter biomass, field capacity, exchangeable potassium, cation exchange capacity, and negatively correlated with bulk density and exchangeable calcium, but not correlated with total nitrogen and available phosphorus. High litter biomass input is the key to the maintenance of high SOC.

Novel Coordination Mode in the Potassium Mefenamate Trihydrate Polymeric Structure

As a result of the synthesis of mefenamic acid with potassium hydroxide, a salt with a polymeric structure is formed. The one-dimensional polymeric structure was studied by single crystal X-ray diffraction. The potassium cation is coordinated to one oxygen atom of the carboxylate group and six water oxygen atoms. Potassium ions are bridged by oxygen atoms of water molecules. The crystal structure was used as an input to QTAIM and NCI approaches to investigate the K-O interactions linking the cation with the water oxygen and carboxylate groups. The weak K-O interactions of the potassium cation and water oxygen atoms were strong enough to form a polymeric structure. The flexibility of the weak interactions is responsible for a novel coordination mode in the potassium mefenamate trihydrate.

Prediction of hERG inhibition of drug discovery compounds using biomimetic HPLC measurements

The major causes of failure of drug discovery compounds in clinics are the lack of efficacy and toxicity. To reduce late-stage failures in the drug discovery process, it is essential to estimate early the probability of adverse effects and potential toxicity. Cardiotoxicity is one of the most often observed problems related to a compound's inhibition of the hERG channel responsible for the potassium cation flux. Biomimetic HPLC methods can be used for the early screening of a compound's lipophilicity, protein binding and phospholipid partition. Based on the published hERG pIC50 data of 90 marketed drugs and their measured biomimetic properties, a model has been developed to predict the hERG inhibition using the measured binding of compounds to alpha-1-acid-glycoprotein (AGP) and immobilised artificial membrane (IAM). A representative test set of 16 compounds was carefully selected. The training set, involving the remaining compounds, served to establish the linear model. The mechanistic model supports the hypothesis that compounds have to traverse the cell membrane and bind to the hERG ion channel to cause the inhibition. The AGP and the hERG ion channel show structural similarity, as both bind positively charged compounds with strong shape selectivity. In contrast, a good IAM partition is a prerequisite for cell membrane traversal. For reasons of comparison, a corresponding model was derived by replacing the measured biomimetic properties with calculated physicochemical properties. The model established with the measured biomimetic binding properties proved to be superior and can explain over 70% of the variance of the hERG pIC50 values. ©2021 by the authors. This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/4.0/).

Characterization and identification of contemporary diagnostic (B) horizons of some soils in Ideato North local government area of Imo state Southeastern Nigeria

Most soils in Nigeria have not been characterized and classified based on diagnostic B horizon and identification of diagnostic B horizon is essential in the study of soils. As a result, this study was carried out to characterize and classify these soils with special emphasis on the identification of diagnostic B- horizons. A free survey method was employed to locate the representative profiles. Ten profile pits were dug, studied macromorphologically, georeferenced and sampled based on identified horizons. Results were presented using descriptive statistics. Soil textural classes consisted of sand, loamy sand, sandy loam and sandy clay loam. Soil bulk density was low to high ranging from 1.23g/cm3 to 1.94g/cm3. Soil pH values were extremely acidic (pH 4.4) to slightly acidic (pH 6.1). Exchangeable calcium and magnesium were low to high, ranging from 0.20cmol/kg to 6.20cmol/kg for calcium and from trace to 30.20cmol/kg for magnesium while that of sodium and potassium were very low ranging from 0.005 to 0.052cmol/kg for sodium and from 0.003cmol/kg to 0.016cmol kg-1 for potassium. Cation exchange capacity was low to high ranging from 5.20cmol kg-1 to 51.20cmol kg-1. Exchangeable acidity was trace to low; soil organic matter was low to high ranging from 0.07 g/kg to 5.00 g/kg. Percentage base saturation was low to very high ranging from 2.32% to 82.20%. Effective cation exchange capacity were low (1.457cmol kg-1) to high (35.56cmol kg-1). The available phosphorus is low ranging from 0.004cmol/kg to 0.013cmol/kg. Water dispersible clay values range d from 4.32% - 20.32%. The diagnostic criteria such as clay coatings/cutans, subsurface to surface clay ratio of 1.2, lithologic discontinuity, abrupt textural changes, artefacts, CEC. ECEC, etc. were identified. The two diagnostic B- horizons identified in the study areas were Kandic horizon and Argillic horizon (USDA) which correlate with Argic horizon (FAO/UNESCO (WRB).

Crystal structure of Z-DNA in complex with the polyamine putrescine and potassium cations at ultra-high resolution

The X-ray crystal structure of the d(CGCGCG)2/putrescine(2+)/K+ complex has been determined at 0.60 Å resolution. Stereochemical restraints were used only for the putrescinium dication, and 23 bonds and 18 angles of the Z-DNA nucleotides with dual conformation. The N atoms of the putrescine(2+) dication form three direct hydrogen bonds with the N7_G atoms of three different Z-DNA molecules, plus three water-mediated hydrogen bonds with cytosine, guanine and phosphate acceptors. A unique potassium cation was also unambiguously identified in the structure, albeit at a ∼0.5 occupation site shared with a water molecule, providing the first example of such a complex with Z-DNA. The K+ cation has coordination number of eight and an irregular coordination sphere, formed by four water molecules and four O atoms from two phosphate groups of the Z-DNA, including ligands present at fractional occupancy. The structural disorder of the Z-DNA duplex is manifested by the presence of alternate conformations along the DNA backbone. Comparison of the position and interactions of putrescine(2+) in the present structure with other ultra-high-resolution structures of Z-DNA in complexes with Mn2+ and Zn2+ ions shows that the dicationic putrescinium moiety can effectively substitute these metal ions for stabilization of Z-type DNA duplexes. Furthermore, this comparison also suggests that the spermine(4+) tetracation has a higher affinity for Z-DNA than K+.

Study of the effect of alcoholic fermentation on the formation of crystal stability of base wines

Изменение химического состава сусла и мезги в ходе спиртового брожения приводит к нарушению равновесия, отражающегося на значениях интегральных показателей. Цель - изучение превращений компонентов сусла и мезги в ходе спиртового брожения с точки зрения кристаллической стабильности вин. Динамику показателей исследовали в условиях сбраживания мезги и сусла из винограда сорта Каберне-Совиньон. Определяли содержания сахаров, этилового спирта, титруемых и органических кислот (лимонной, яблочной, винной), ионов калия, интегральные показатели (рН, электропроводность, буферная емкость). Склонность к кристаллообразованию определяли по температуре насыщения битартратом калия. Содержание молекулярной и диссоциированных форм яблочной и винной кислот рассчитывали в зависимости от значений рН. Установлен двухфазный характер процесса брожения сусла и мезги. На I фазе сбраживания сахаров происходит повышение содержания титруемых кислот, обусловленное диссоциацией органических кислот по I ступени как следствие обогащения среды ионами водорода. Массовая концентрация винной и яблочной кислот, катиона калия при сбраживании сусла снижается более значительно, чем при брожении мезги, что сопровождается уменьшением значения температуры насыщения среды битартратом калия. II фаза брожения характеризуется меньшими изменениями физико-химических показателей, чем I: уменьшилась скорость сбраживания и накопления этанола, снижается содержание титруемых кислот, в том числе органических, а также катиона калия. Значения некоторых компонентов изменяются независимо от фазы брожения: величина рН повышается; электропроводности, катиона калия - снижается. Температура насыщения битартратом калия бродящих сред (мезги и сусла) проявляет тенденцию к снижению, что позволяет сделать вывод о стабилизирующем характере процесса брожения. Changes in the chemical composition of the must and pomace in the process of alcoholic fermentation lead to an imbalance, reflected in the values ??of integral indicators. The aim is to study the transformations of components of the must and pomace in the process of alcoholic fermentation from the point of view of the crystal stability of wines. The dynamics of indicators was investigated in conditions of fermentation of the pomace and must made of 'Cabernet-Sauvignon' grape variety. The contents of sugars, ethyl alcohol, titratable and organic acids (citric, malic and tartaric), potassium ions, integral indicators (pH, electrical conductivity, buffer capacity) were determined. The tendency to crystal formation was determined by the temperature of saturation with potassium bitartrate. The content of molecular and dissociated forms of malic and tartaric acids was calculated depending on the pH values. The two-phase character of the must and pomace fermentation process was established. On the 1st phase of sugar fermentation an increase in the content of titratable acids results due to the dissociation of organic acids along the 1st stage on the back of the enrichment of the medium with hydrogen ions. Mass concentration of tartaric and malic acids and potassium cation during the must fermentation decreases more significantly than during the pomace fermentation, accompanied by a decrease in the temperature of saturation of the medium with potassium bitartrate. The 2nd phase of fermentation is characterized by less change in physicochemical parameters than the 1st: the rate of fermentation and accumulation of ethanol has decreased as well as the content of titratable, including organic, acids and the potassium cation. Ranges ??of some components change regardless the phase of fermentation: the pH value rises; values of electrical conductivity and potassium cation - decrease. Saturation temperature of fermenting media (pomace and must) with potassium bitartrate tends to decrease, allowing to make a conclusion about the stabilizing character of fermentation process.

Biosensor Technology in Diagnostics and Mechanistic Studies of Epilepsy

Epilepsy is represented by a set of neurological disorders that result in recurring seizures and convulsions. Although several types of the condition have been characterized, the underlying cause for these remains largely unknown. A number of molecular biomarkers for epilepsy have been identified including glutamate, γ-aminobutyric acid, and miRNAs. In addition, a special role appears to be played by the potassium cation. Detection of these species is anticipated to assist in both diagnosis and fundamental understanding of the condition. This review details the application of a number of biosensor devices that have been designed specifically for the detection of both molecular biomarkers and the K+ cation in proximity to an animal cortex. These devices offer considerable potential not only for diagnostic goals, but also for study of the cause and spread of the epileptic seizure, especially if such biosensors can detect analytes in a multiplexed, real-time manner.