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Ермакова, Л. Э.; Kiprianova, A. A.; Sidorova, M. P.; Gribanova, E. V.; Savina, I. A.; Тимофеев, С. В.

doi:10.1023/a:1013263601704

Cited by 5 publications

(2 citation statements)

References 2 publications

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“…In addition, the voltage-current characteristics were monitored while the potential difference ranging from -800 to 800 mV was applied stepwise to the membrane. When studying the dependence of the conductance of a single conical pore on pH, we found a minimum of conductance at pH 3.86, which agreed with data on the isoelectric point for track PET membranes for pH values of 3.7-3.8 [6,7]. To demonstrate the cation selectivity of the pores obtained by etching the PET membranes, we determined transfer numbers ( t + ) in multipore membranes using a tenfold concentration gradient (0.1 M/0.01 M) KCl at pH 8 for all solutions used.…”

Section: Biochemistry Biophysics and Molecular Biologysupporting

confidence: 85%

The Use of Synthetic Nanometer Pores for Modeling the Conduction Block of Cation-Selective Channels of Cell Membranes by Ruthenium Red

Apel

et al. 2005

Dokl Biochem Biophys

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The mechanisms of blocking ion channels of cell membranes are interesting from both theoretical and practical viewpoints; knowing these mechanisms is necessary for targeted selection of some therapeutic agents, as well local and general anesthetics. To date, many cell-membrane ion channels varying in functional characteristics have been described. Although ion channels are very diverse, they may be divided into two large classes-the cation-conducting and anionconductingchannels. If the density of fixed negative charges on the walls of the ion-conducting space of the channels is large enough, cation conduction may be accounted for by the so-called cation surface conduction, which must contribute much to the pore conduction, because cell ion channels are narrow. Neutralization of the negative charges fixed on the channel walls and, hence, partial or complete suppression of surface conduction must block the cation permeability of the ion channel.At present, it is generally believed that ion channels have special "portal" structures determining ion conduction or block of conduction. Change in ion conductivity is attributed to either a "mechanical" obstruction of the ion-conducting space of the pores or (which is more plausible) the appearance of an electric potential, local or spread throughout the pore. The results of a recent series of studies on nanometer pores in polymeric membranes [1-4] demonstrated that it was possible to detect discrete currents that were similar to the currents of single ion channels of cell membranes with respect to several characteristics, including a high cation selectivity. The model pores of synthetic membranes cannot be assumed to have special portal mechanisms capable of mechanically obstructing the conduction; however, conduction blockage in the form of the suppression of discrete currents may be accounted for by a decrease in the dominating surface conduction in the nanometer pore.The experimental data reported below, obtained with the use of a completely synthetic model of nanometer pores, demonstrate the possibility of such a blocking mechanism based on neutralizing the negative charges fixed on the pore surface. The ion-conductive space in calcium and sodium channels of cell membranes was demonstrated to be conical [5]. We used a system of nanometer pores in a polyethylene teraphthalate (PET) membrane as a model for proving the aforementioned notions on the mechanism of conduction block in cation-selective ion channels of cell membranes. To make nanometer pores, PET membranes 12 µ m in thickness were irradiated with heavy ions, such as xenon, krypton, and gold ones, with energies about 250 MeV by means of a linear accelerator in the Institute of GSI (The Society for Studying Heavy Ions) (Darmstadt, Germany). The resultant tracks were then etched with alkaline solutions. The formation of a single pore in PET membranes differed from the formation of multiple pores. A single track was formed if the membrane was so irradiated that the flow of heavy ions deviated when the passage dete...

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Section: Biochemistry Biophysics and Molecular Biologysupporting

confidence: 85%

The Use of Synthetic Nanometer Pores for Modeling the Conduction Block of Cation-Selective Channels of Cell Membranes by Ruthenium Red

Apel

et al. 2005

Dokl Biochem Biophys

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“…The ion exchange capacity and water content also provide values for the membrane hydration number ( n m , mol H 2 O/mol -SO 3 − ) [ 63 ], which is the average number of water molecules per functional group. The n m is calculated according to the formula [ 63 , 65 ]:

where M w is the molar weight of water (18 g mol −1 ).…”

Section: Methodsmentioning

confidence: 99%

Structural Characterization and Physicochemical Properties of Functionally Porous Proton-Exchange Membrane Based on PVDF-SPA Graft Copolymers

Ponomar,

Ruleva,

Sarapulova

et al. 2024

IJMS

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Fluorinated proton-exchange membranes (PEMs) based on graft copolymers of dehydrofluorinated polyvinylidene fluoride (D-PVDF), 3-sulfopropyl acrylate (SPA), and 1H, 1H, 2H-perfluoro-1-hexene (PFH) were prepared via free radical copolymerization and characterized for fuel cell application. The membrane morphology and physical properties were studied via small-(SAXS) and wide-angle X-ray scattering (WAXS), SEM, and DSC. It was found that the crystallinity degree is 17% for PEM-RCF (co-polymer with SPA) and 16% for PEM-RCF-2 (copolymer with SPA and PFH). The designed membranes possess crystallite grains of 5–6 nm in diameter. SEM images reveal a structure with open pores on the surface of diameters from 20 to 140 nm. Their transport and electrochemical characterization shows that the lowest membrane area resistance (0.9 Ωcm2) is comparable to perfluorosulfonic acid PEMs (such as Nafion®) and polyvinylidene fluoride (PVDF) based CJMC cation-exchange membranes (ChemJoy Polymer Materials, China). Key transport and physicochemical properties of new and commercial membranes were compared. The PEM-RCF permeability to NaCl diffusion is rather high, which is due to a relatively low concentration of fixed sulfonate groups. Voltammetry confers that the electrochemical behavior of new PEM correlates to that of commercial cation-exchange membranes, while the ionic conductivity reveals an impact of the extended pores, as in track-etched membranes.

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Physical carbon‐sequestration mechanisms under special consideration of soil wettability

Bachmann

Guggenberger

Baumgartl

et al. 2008

Z. Pflanzenernähr. Bodenk.

157

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The protective impact of aggregation on microbial degradation through separation has been described frequently, especially for biotically formed aggregates. However, to date little information exists on the effects of organic‐matter (OM) quantity and OM quality on physical protection, i.e., reduced degradability by microorganisms caused by physical factors. In the present paper, we hypothesize that soil wettability, which is significantly influenced by OM, may act as a key factor for OM stabilization as it controls the microbial accessibility for water, nutrients, and oxygen in three‐phase systems like soil. Based on this hypothesis, the first objective is to evaluate new findings on the organization of organo‐mineral complexes at the nanoscale as one of the processes creating water‐repellent coatings on mineral surfaces. The second objective is to quantify the degree of alteration of coated surfaces with regard to water repellence. We introduce a recently developed trial that combines FTIR spectra with contact‐angle data as the link between chemical composition of OM and the physical wetting behavior of soil particles. In addition to characterizing the wetting properties of OM coatings, we discuss the implications of water‐repellent surfaces for different physical protection mechanisms of OM. For typical minerals, the OM loading on mineral surfaces is patchy, whereas OM forms nanoscaled micro‐aggregates together with metal oxides and hydroxides and with layered clay minerals. Such small aggregates may efficiently stabilize OM against microbial decomposition. However, despite the patchy structure of OM coating, we observed a relation between the chemical composition of OM and wettability. A higher hydrophobicity of the OM appears to stabilize the organic C in soil, either caused by a specific reduced biodegradability of OM or indirectly caused by increased aggregate stability. In partly saturated nonaggregated soil, the specific distribution of the pore water appears to further affect the mineralization of OM as a function of wettability. We conclude that the wettability of OM, quantified by the contact angle, links the chemical structure of OM with a bundle of physical soil properties and that reduced wettability results in the stabilization of OM in soils.

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Cited by 5 publications

References 2 publications

The Use of Synthetic Nanometer Pores for Modeling the Conduction Block of Cation-Selective Channels of Cell Membranes by Ruthenium Red

The Use of Synthetic Nanometer Pores for Modeling the Conduction Block of Cation-Selective Channels of Cell Membranes by Ruthenium Red

Structural Characterization and Physicochemical Properties of Functionally Porous Proton-Exchange Membrane Based on PVDF-SPA Graft Copolymers

Physical carbon‐sequestration mechanisms under special consideration of soil wettability

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