Czech and Slovak young brown coals in environmental applications

In recent time, various kinds of young brown (low-rank) coals are utilized increasingly not only as fuels, but also as valuable materials in advanced environmental applications. It should be noted in this context that significant deposits of the young brown coals can be found both in the Czech Republic as well as in Slovakia. For their effective applications e.g. in wastewater treatment or in soil remediation, the properties of the coals should be studied in more details and numerous physico-chemical characteristics should be measured. As a part of a common Czech-Slovak project, a series of various kinds of coals was collected, including North-Bohemian oxihumolites, lignite from South Moravia and several lignites from Slovakia (Baňa Zahorie). Basic properties were measured, such as acid-base titration curves, contents of main functional groups and sorption capability towards heavy metal cations (Cu2+, Zn2+, Co2+) and some organic pollutants. The contents of humic substances – main active constituents of the young coals – were also determined. Selected environmental applications of the brown coals will be mentioned further, e.g. for the removal of metal cations from waters or in phytoremediation of contaminated soils.

An Original Approach to Measure Ligand/receptor Binding Affinity in Non-purified Samples

Several biochemical and biophysical methods are available to determine dissociation constants between a biological target and its ligands. Most of them require purification, labelling or surface immobilisation. However, these measurements remain challenging concerning membrane proteins because purification requires their extraction from the native lipid environment using different approaches, a process that may impact receptor conformation and functionality. We have developed a novel experimental procedure to determine binding affinities of a ligand to a membrane protein, the dopamine D2 receptor (D2R), directly from cell membrane fragments, using microscale thermophoresis (MST). Two main challenges had to be overcome: to determine the concentration of dopamine D2R in the crude sample; to find ways to minimize or account for non-specific binding of the ligand to cell fragments. Using MST, we were able to determine the D2R concentration in cell membrane fragments to be about 36.8 ± 2.6 pmol/mg. Then titration curves allowed the determination of a KD about 5.3 ± 1.7 nM, that is very close to the reported value. Important details of the experimental procedure are detailed to allow the transposition of this novel method to various membrane proteins.

The Measurement of Mixed Potentials Using Platinum Decorated Nanoporous Gold Electrodes

Potentiometric redox sensing in solutions containing multiple redox molecules was evaluated using in-house constructed nanoporous gold (NPG)-platinum (Pt) and unmodified NPG electrodes. The NPG-Pt electrode was fabricated by electrodepositing Pt into the nanoporous framework of a chemically dealloyed NPG electrode. By varying the concentration of the Pt salt and the electrodeposition time, different amounts of Pt were introduced. Characterization by SEM shows the pore morphology doesn’t change with the addition of Pt and XPS indicates the electrodes contain ∼2.5–24 wt% Pt. Open-circuit potential (OCP) measurements in buffer and solutions containing ascorbic acid, cysteine, and/or uric acid show that the OCP shifts positive with the addition of Pt. These results are explained by an increase in the rate of the oxygen reduction reaction with the addition of Pt. The overall shape of the potentiometric titration curves generated from solutions containing one or more bioreagents is also highly dependent on the amount of Pt in the nanoporous electrode. Furthermore, the generation of OCP vs Log [bioreagent] from the results of the potentiometric experiments shows an ∼2-fold increase in sensitivity can result with the addition of Pt. These results indicate the promise that these electrodes have in potentiometric redox sensing.

Ionic Equilibria and pH

Ionic Equilibria and pH reviews the quantitative aspects of aqueous acid-base chemistry. Definitions and concepts are presented and appropriate worked examples illustrate calculations of concentration, pH and ionization constants. Acid-base properties of salts (salt hydrolysis) is introduced and explained along with the common-ion effect and calculation of hydrolysis constants. Equilibria of acid-base buffers with respect to buffer preparation, calculating the pH of a buffer solution and application of the Henderson-Hasselbalch equation, buffer range and buffer capacity is discussed. Determining the pH during acid-base titrations, selecting the appropriate acid-base indicators, and generating pH titration curves are explained.

Titration of chelating fibrous sorbent in the presence of complex-forming divalent cations

Titration curves of H-forms of the fibrous chelating sorbent with iminodiacetic groups based on industrial polyacrylonitrile fiber Nitron with potassium hydroxide in 1M KCl solution in the presence of Ni2+, Co2+, Cu2+ and Ca2+ chlorides were obtained. The method used made it possible to simultaneously measure the pH of the solution and the concentration of the divalent cation at each point of the titration curve. From these data, the dependences of their sorption values on the pH of the equilibrium solution were calculated. The curves of direct and back titration practically coincided in all cases. As the pH changed during titration, precipitation was observed at pH values of precipitation of the corresponding hydroxides. In this case, the increase in pH was suspended or greatly slowed down by adding alkali to the titration cell. The formation of a precipitate occurred mainly in a solution for Co2+ and Ni2+ (pH 8), when the ion exchanger was saturated with a metal ion. In the case of Cu2+ (precipitate formation pH 4), Cu2+ sorption occurs at both lower and higher pH due to ionization of carboxyl groups and partial dissolution of the precipitate. In all cases, the maximum sorption of Ni2+, Co2+, Cu2+, Ca2+ corresponded to the formation of sorption complexes of the R–N(CH2COO-)2Me2+ type.

BUFFER SYSTEMS BASED ON AMINOMETANESULPHONATE AND MONOETHANOLAMMONIUM N-ALKYLAMINOMETHANESULPHONATES

The limits of the pH buffering action (pHbuff) of YNHCH2SO3H – NH2CH2CH2OH –H2O (Y = H, CH3, HOCH2CH2, t-С4H9 and C6H5CH2) were determined and their buffer capacity (p) for monoethanolamine (MEA) was estimated in the temperature range 293–313 K. For systems with aminomethanesulfonic acid (AMSA), its N‑methyl, N‑hydroxyethyl (HEAMSA) and N‑benzyl (BzAMSA) derivatives, an increase in temperature leads to a decrease in the pH values of the lower limit of the buffering action of their solutions with monoethanolamine; in the case of N‑tert-butylaminomethanesulfonic acid (t-BuAMSA) – to an increase in the specified characteristic. An increase in temperature for systems with the most hydrophobic t-BuAMSA and BzAMSA (in comparison with other studied aminomethanesulfonic acids) leads to a decrease in the pH values of the upper limit of the buffer action. A decrease in the YNHCH2SO3H and NH2CH2CH2OH concentration leads to a shift in the boundaries of the pH of the buffering action to a more acidic region. The nature of the influence of the empirical function, combining their acid-base properties and lipophilicity (рKа + lgPow), on the concentration dependence of the buffer capacity according to MEA was revealed. It is shown that the buffering effect of the studied systems is due to the presence, in addition to the systems N‑alkylammoniummethanesulfonate – N‑alkylaminomethanesulfonate and 2-hydroxyethylammonium – monoethanolamine, ionic associates (pairs and triples). The position of the extrema on the graphical π=f(CMEA)/QYAMSA) dependencies for systems with hydrophilic AMSA and HEAMSA coincides with the position of the first minima on the differential titration curves dpH/dV = f(CMEA)/QYAMSA). Substitution of MEA to potassium aminomethanesulfonate leads to a shift in the pH buffering action to a more acidic region and increases the buffer capacity of the resulting systems.

KD determination from time-resolved experiments on live cells with LigandTracer and reconciliation with end-point flow cytometry measurements

Design of next-generation therapeutics comes with new challenges and emulates technology and methods to meet them. Characterizing the binding of either natural ligands or therapeutic proteins to cell-surface receptors, for which relevant recombinant versions may not exist, represents one of these challenges. Here we report the characterization of the interaction of five different antibody therapeutics (Trastuzumab, Rituximab, Panitumumab, Pertuzumab, and Cetuximab) with their cognate target receptors using LigandTracer. The method offers the advantage of being performed on live cells, alleviating the need for a recombinant source of the receptor. Furthermore, time-resolved measurements, in addition to allowing the determination of the affinity of the studied drug to its target, give access to the binding kinetics thereby providing a full characterization of the system. In this study, we also compared time-resolved LigandTracer data with end-point KD determination from flow cytometry experiments and hypothesize that discrepancies between these two approaches, when they exist, generally come from flow cytometry titration curves being acquired prior to full equilibration of the system. Our data, however, show that knowledge of the kinetics of the interaction allows to reconcile the data obtained by flow cytometry and LigandTracer and demonstrate the complementarity of these two methods.

A novel assay based on pre-equilibrium titration curves for the determination of enzyme inhibitor binding kinetics

Selection of pharmacological agents based on potency measurements performed at equilibrium fail to incorporate the kinetic aspects of the drug–target interaction. Here we describe a method for screening or characterization of enzyme inhibitors that allows the concomitant determination of the equilibrium inhibition constant in unison with rates of complex formation and dissociation. The assay is distinct from conventional enzymatic assays and is based on the analysis of inhibition curves recorded prior to full equilibration of the system. The methodology is illustrated using bicyclic peptide inhibitors of the serine protease plasma kallikrein.

COMPARATIVE ANALYSIS OF THE PHYSICOCHEMICAL PROPERTIES OF VARIETAL RED WINES RESEARCHED BY DIFFERENT METHODS

Проведен сравнительный анализ вида кривых титрования, оптических спектров, содержания органических кислот и катионов щелочных и щелочноземельных металлов красных сортовых вин с нахождением критериальных маркеров. Объекты исследования – красные сортовые вина, произведенные по одной технологии из выращенного в центральной зоне Краснодарского края винограда сортов Каберне Совиньон, Мерло, Саперави, Изабелла. Установлено, что кривые титрования индивидуальны, позволяют дать качественную оценку подлинности винодельческой продукции по начальной величине рН (обусловлена содержанием калия), виду кривых титрования до начала скачка (обусловлен содержанием винной и яблочной кислот). Определено количественное содержание титруемых кислот, а также маркерные значения, подтверждающие подлинность вин: рНо, tk, dpH/dt. Оптические свойства вин не позволяют дать количественную оценку фенольных веществ, но расширяют возможности применения данного метода в качестве интегральной характеристики сортовых красных вин по виду оптического спектра и значению оптической плотности D и длине волны λ. Отношение катионов щелочных и щелочноземельных металлов между собой можно применять в качестве дополнительного маркера сортовых вин, произведенных из винограда вида Vitis vinifera или Vitis labrusca. Показано, что отличие форм кривых титрования разных вин, а также оптических спектров и различия содержания органических кислот и катионов щелочных и щелочноземельных металлов можно использовать как графические образы винодельческой продукции конкретного наименования в рамках национальной системы защиты вин, обладающих особыми качествами. A comparative analysis of the type of titration curves, optical spectra, the content of organic acids and cations of alkaline and alkaline earth metals of red varietal wines with the search for criteria markers was carried out. The objects of the study are red varietal wines produced using the same technology from grapes grown in the central zone of the Krasnodar Territory, the variety: Cabernet Sauvignon, Merlot, Saperavi, Isabella. It is established that the titration curves are individual, allowing us to give a qualitative assessment of the authenticity of wine products by the initial pH value (due to the potassium content), by the type of titration curves before the jump (due to the content of tartaric and malic acids). The quantitative content of titrated acids was determined, as well as marker values confirming the authenticity of the wines: pH, tk, dpH/dt. The optical properties of wines do not allow us to give a quantitative assessment of phenolic substances, but they expand the possibilities of using this method as an integral characteristic of varietal red wines by the type of optical spectrum and the value of the optical density D and the wavelength λ. The ratio of cations of alkali and alkaline earth metals to each other can be used as an additional marker of varietal wines produced from grapes of the Vitis vinifera or Vitis labrusca species. It is shown that the difference in the shapes of the titration curves of different wines, as well as the optical spectra and differences in the content of organic acids and cations of alkaline and alkaline earth metals can be used as graphic images of wine products of a specific denomination within the framework of the national system for the protection of wines with special qualities.

Potentiometric Surfactant Sensor Based on 1,3-Dihexadecyl-1H-benzo[d]imidazol-3-ium for Anionic Surfactants in Detergents and Household Care Products

A 1,3-dihexadecyl-1H-benzo[d]imidazol-3-ium-tetraphenylborate (DHBI-TPB) ion-pair implemented in DHBI-TPB surfactant sensor was used for the potentiometric quantification of anionic surfactants in detergents and commercial household care products. The DHBI-TPB ion-pair was characterized by FTIR spectroscopy and computational analysis which revealed a crucial contribution of the C–H∙∙∙π contacts for the optimal complex formation. The DHBI-TPB sensor potentiometric response showed excellent analytical properties and Nernstian slope for SDS (60.1 mV/decade) with LOD 3.2 × 10−7 M; and DBS (58.4 mV/decade) with LOD 6.1 × 10−7 M was obtained. The sensor possesses exceptional resistance to different organic and inorganic interferences in broad pH (2–10) range. DMIC used as a titrant demonstrated superior analytical performances for potentiometric titrations of SDS, compared to other tested cationic surfactants (DMIC > CTAB > CPC > Hyamine 1622). The combination of DHBI-TPB sensor and DMIC was successfully employed to perform titrations of the highly soluble alkane sulfonate homologues. Nonionic surfactants (increased concentration and number of EO groups) had a negative impact on anionic surfactant titration curves and a signal change. The DHBI-TPB sensor was effectively employed for the determination of technical grade anionic surfactants presenting the recoveries from 99.5 to 101.3%. The sensor was applied on twelve powered samples as well as liquid-gel and handwashing home care detergents containing anionic surfactants. The obtained results showed good agreement compared to the outcomes measured by ISE surfactant sensor and a two-phase titration method. The developed DHBI-TPB surfactant sensor could be used for quality control in industry and has great potential in environmental monitoring.