A carbon dioxide biosensor based on hemoglobin incorporated in metal supported bilayer lipid membranes (BLMs): Investigations for enhancement of response characteristics by using platelet‐activating factor

Hydration of carbon dioxide in water solution is the rate limiting step for the CO2 mineralization process, a process which is at the base of many carbon capture and utilization (CCU) technologies aiming to convert carbon dioxide to added-value products and mitigate climate change. Here, we present a combined experimental and computational study to clarify the effectiveness and molecular mechanism by which nickel nanoparticles, NiNPs, may enhance CO2 hydration in aqueous solutions. Contrary to previous literature, our kinetic experiments recording changes of pHs, conductivity, and dissolved carbon dioxide in solution reveal a minimal effect of the NiNPs in catalyzing CO2 hydration. Our atomistic simulations indicate that the Ni metal surface can coordinate only a limited number of water molecules, leaving uncoordinated metal sites for the binding of carbon dioxide or other cations in solution. This deactivates the catalyst and limits the continuous re-formation of a hydroxyl-decorated surface, which was a key chemical step in the previously suggested Ni-catalyzed hydration mechanism of carbon dioxide in aqueous solutions. At our experimental conditions, which expand the investigation of NiNP applicability toward a wider range of scenarios for CCU, NiNPs show a limited catalytic effect on the rate of CO2 hydration. Our study also highlights the importance of the solvation regime: while Ni surfaces may accelerate carbon dioxide hydration in water restricted environments, it may not be the case in fully hydrated conditions.

A POLAROGRAPHIC depolarization effect due to carbon dioxide in aqueous solutions occurring at − 2.2 V. (from the normal calomel electrode) has been described by Van Rysselberghe1 and v. Stackelberg2. This effect is, however, indistinct. When using absolute (99.8 per cent) ethyl alcohol with 0.3 M tetramethyl ammonium chloride in electrolysis with the dropping mercury cathode, a well-defined wave with a maximum at − 2V. (Fig. 1) is formed on the current-voltage curve. The behaviour shows it to be due to the evolution of hydrogen from carbonic acid, the carbon dioxide molecule being regarded as not reducible. Here nitrogen containing 4 vol. per cent of carbon dioxide was bubbled through the solution for 3–4 min. at room temperature. The equilibrium concentration of carbon dioxide dissolved under its pressure in the gaseous phase is attained very quickly (in about 2 min.). The ensuing limiting current is strictly proportional to the partial pressure of carbon dioxide.

CHAPTER 26 - SOME BIOLOGICAL ANALYTICAL METHODS

The solvation of carbon dioxide in solution represents a key step for the capture and fixation CO2 in nature, which may be further influenced by the formation of (bi)carbonate species and/or the formation of CO2 clusters in solution. The latter processes are strongly dependent on the exact environment of the liquid state (e.g., pH value, solvated ions, etc.) and may interfere with the experimental determination of structural, dynamical, and thermodynamic properties. In this work a hybrid quantum mechanical/molecular mechanical (QM/MM) simulation approach at correlated ab initio level of theory resolution-of-identity second-order Møller-Plesset Perturbation Theory (RI-MP2) has been applied in the framework of thermodynamic integration (TI) to study structure, dynamics, and the hydration free energy of a single carbon dioxide molecule in aqueous solution. A detailed analysis of the individual QM/MM potential energy contributions demonstrate that the overall potential remains highly consistent over the entire sampling phase and that no artificial contributions are influencing the determination of the hydration free energy. The latter value of 0.01 ± 0.92 kcal/mol was found in very good agreement with the values of 0.06 and 0.24 kcal/mol obtained via quasi-chemical theory and experimental measurements, respectively. In order to obtain detailed information about the C- and O C-water interaction, conically restricted regions with respect to the main axis of the CO2 molecule have been employed in structural analysis. The presented data not only provide detailed information about the hydration properties of CO2 but act as a critical validation of the simulation technique, which will be beneficial in the study of nonaqueous solvents such as pure and aqueous NH3 solutions, which have been suggested as potential candidates to capture CO2 from anthropogenic sources.

The chemical absorption of carbon dioxide by a laminar jet of ethylenediamine has been studied at 25.5°C under pseudo‐first‐order kinetic conditions. The reaction was found to be second‐order with a rate constant of 1.0 x 105 1/g. mole sec. Equilibrium calculations at 18°C indicate that the partial pressure of carbon dioxide is very low, even over highly carbonated ethylenediamine solutions. The effects of amine concentration and carbonation ratio on the physical solubility and diffusivity of carbon dioxide in solution were inferred from corresponding results for nitrous oxide

IN an earlier publication1 the discovery was reported of a substance extractable by water from red beetroot and capable of inhibiting the active accumulation of manganese by slices of storage tissue. It was suspected at the time that the substance might be produced by the dark fixation of respiratory carbon dioxide which, as Burton2 showed for potatoes, may reach concentrations of about 7 per cent in bulky storage organs. I have now shown that the presence of carbon dioxide in solutions from which beetroot tissue slices are absorbing manganese reduces the rate of absorption. The reduction in rate is proportional to the concentration of carbon dioxide up to about 40 per cent, at which the rate appears to be minimal.

The photostability and fluorescence of hydroxycoumarins in aprotic solvents

Methane hydrate exists in huge amounts in certain locations, in sea sediments and the geological structures below them, at low temperature and high pressure. Production methods are in development to produce the methane to a floating platform. There it can be reformed to produce hydrogen and carbon dioxide, in an endothermic process. Some of the methane can be burned to provide heat energy to develop all needed power on the platform and to support the reforming process. After separation, the hydrogen is the valuable and transportable product. All carbon dioxide produced on the platform can be separated from other gases and then sequestered in the sea as carbon dioxide hydrate. In this way, hydrogen is made available without the release of carbon dioxide to the atmosphere, and the hydrogen could be an enabling step toward a world hydrogen economy.

This work investigates the interactions of atrazine with bilayer lipid membranes (BLMs) that can be used for the direct electrochemical sensing of this herbicide. Egg phosphatidylcholine (PC) and dipalmitoylphosphatidic acid (DPPA) were used for the formation of solventless BLMs. The interactions of atrazine with these membranes were found to be electrochemically transduced by BLMs in the form of a transient current signal with a duration of seconds, which reproducibly appeared within 1 min after exposure of the membranes to atrazine. The sensitivity of the response was maximized by use of BLMs composed of 35% (w./w.) DPPA, and by alteration of the phase distribution within membranes by the introduction of calcium ions in bulk solution. The mechanism of signal generation was related to the adsorption of atrazine with a consequent rapid reorganization of the membrane electrostatics due to atrazine aggregation at the surface of BLMs. Hydrogen bonding between atrazine and the carbonyl group of the lipid was explored by addition of platelet‐activating factor (PAF; an ether analog of PC) in BLMs composed of PC. Differential scanning calorimetry of vesicles composed of 15% DPPA was used to study the aggregation of atrazine in membrane domains enriched in the charged lipid. The magnitude of the transient current signal was linearly related to the concentration of atrazine in bulk solution with sub‐micromolar detection limits. This electrochemical transduction of atrazine interactions with BLMs holds prospects for flow injection monitoring of triazine herbicides.

This work describes the use of filter‐supported stabilized bilayer lipid membranes (BLMs) for the rapid electrochemical monitoring of an immunological reaction in flowing solution streams. BLMs were prepared from egg phosphatidylcholine (egg PC) and dipalmitoyl phosphatidic acid (DPPA) and the ultrafiltration membranes used were composed of glass microfibers. Thyroxin (T4)/anti‐rabbit T4 was used as a representative immunological reaction for these studies. Antibody was incorporated into a floating lipid matrix at an air–electrolyte interface, and then a casting procedure was used to deliver the lipid onto the filter supports for BLM formation. Injections of antigen were made into flowing streams of a carrier electrolyte solution. Experiments were done in a stopped‐flow mode using lipid mixtures containing 15% (w/w) DPPA to provide only a single transient current signal with a magnitude related to the antigen concentration. Differential scanning calorimetric experiments provided evidence that the antibody‐lipid interactions at the BLMs occurred through electrostatic interactions. BLMs containing 35% DPPA were used to examine regeneration of the active sites of antibody after complex formation by washing with the carrier electrolyte solution. Repetitive cycles of injection of antigen followed by regeneration of antibody binding activity have shown that the maximum number of cycles is about 5, followed by a degradation of signal for a larger number of injections. However, the sensor can also be easily regenerated by recasting of the existing lipid/antibody film at the air–electrolyte interface to form fresh BLMs.

1. Sprout growth is inhibited at 10°C by a concentration of 15 per cent of carbon dioxide in the storage atmosphere, decreased by lower concentrations, and stimulated by still lower concentrations. The optimum concentration for growth need not necessarily be the same in all cases; but appears to be about 2–4 per cent, which would give a concentration in the cell sap of some 0.04–0.05 ml carbon dioxide per ml sap. 2. In agreement with reports by other workers, sprout growth was found to be stimulated by reducing the concentration of oxygen in the storage atmosphere to 5 per cent, which would give a concentration of oxygen in the cell sap of about 0.006 ml oxygen per ml sap. 3. A reduced oxygen tension causes augmented growth either by means of an increase in the number of sprouts or in the number of cells in individual sprouts. A raised carbon dioxide tension causes an increase in the number of cells in the sprouts and also marked cell elongation. 4. Over the range 10–25 C the effect of temperature upon respiration and upon the solubility of gases — and hence upon the concentrations in the cell sap of dissolved oxygen and, more particularly, carbon dioxide —could be an important factor contributing to the effect of temperature upon sprout growth. In some cases the increased sprout growth after some time at a higher temperature may be no more than would be expected as a result of the increased carbon dioxide in solution. 5. Discussion of the results in the light of other work suggests several mechanisms through which changes in the carbon dioxide or oxygen concentrations may influence sprout growth. Such suggestions must be very tentative pending more detailed investigation of the systems involved.

Irradiation of a polycrystalline silver electrode with near-u.v./visible light in solutions containing either dissolved carbon dioxide or nitrate ions produces strong enhancement of the cathodic current. Maximum photocurrent efficiency is observed for the photon energies of about 3.5 eV characteristic of surface plasmons on silver. In the presence of carbon dioxide in solution, the electrode illumination not only increases the rate of CO2 to CO reduction but also shifts the onset of the CO production by about 0.5 V to less cathodic potentials.

Emission from the tris(1,10-phenanthroline)ruthenium(II) complex (Ru(phen)32+) bearing a (dimesityl)boryldurylethynyl (DBDE) charge transfer unit at the 4-position of one of the three phen ligands ([Ru(phen)2(4-DBDE-phen)] = 4BRu2+) was quenched by carbon dioxide in solution with the rate constant of ∼106 M−1 s−1.

Electrochemical investigation of interactions of bilayer lipid membranes (BLMs) with incorporated resorcin[4]arene receptor with ephedrine for the development of a stabilized lipid film biosensor for ephedrine

Observations made hitherto by different workers on the relation between concentration of carbon dioxide and the rate of its assimilation by plants are not entirely harmonious, and it seems possible that much of the apparent disagreement may be due to the differences in the experimental conditions which have been used. In recent work on aquatic plants, bicarbonate solutions have been freely utilised as method of supplying carbon dioxide, instead of the carbon dioxide solutions of earlier workers. For these methods to be directly comparable with one another it must be assumed that only carbon dioxide present in the free form is assimilable by the plant, and that HCO 3 ions and undissociated salts (NaHCO 3 , etc.) are not available. This assumption has been supported by Nathansohn, 1907 (13), Benecke, 1921 (3), and wilmott, 1921 (23), but opposed by Angelstein, 1911 (1), Osterhout and Haas, 1918 (14), and Ruttner, 1921 (16). The present paper records an attempt to reinvestigate this problem by means of a method which allows direct comparisons to be made between these two types of solutions. Each solutions has been investigated over a range of concentrations, and using varying intensities of light. Attention has been given to the rate of flow of the solutions over the assimilating plant. In this way a collection of assimilation values under precisely defined conditions has been built up, which helps a closer understanding of the interaction of factors in this process, and enables us to get a clearer picture of the essential differences between carbon dioxide and bicarbonate solutions as media for assimilation.