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This study aimed to investigate the effect of selected compounds from the group of triterpene sapogenins on model phosphatidylcholine membranes. Two types of biological membrane model systems were used in the work, i.e., liposomes (microelectrophoresis method) and spherical bilayers (interfacial tension method). Each model was modified with the tested sapogenin compounds, and the change in their physicochemical and electrical parameters was analyzed. Parameters characterizing the equilibrium in the membrane of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)-oleanolic acid (OA) and DPPC-asiatic acid (AA) were determined). Based on the Young-Laplace equation, the interfacial tensions of spherical lipid bilayers were measured. The formation of 1:1 complexes was assumed in the DPPC-OA and DPPC-AA membrane systems, and the parameters characterizing the interactions in the formed complexes were calculated. Microelectrophoresis was used to study the surface charge density of lipid membranes. These values were obtained from electrophoretic mobility data using Smoluchowsky's equation. The influence of pH on the electrolyte solution and the composition of the membranes was investigated. The results indicate that modifying DPPC membranes with selected triterpene sapogenins, both OA and AA, causes changes in the surface charge density and shifts of the isoelectric point. Data presented in this work, obtained through mathematical derivation and confirmed experimentally, are of great importance for interpreting phenomena occurring in lipid membranes. A quantitative description of equilibria between phosphatidylcholine and sapogenins lets us understand the processes on the membrane surface. The equilibria are particularly significant from the standpoint of cell functioning. Phosphatidylcholine-sapogenin interactions modulate a range of physicochemical properties of membranes, and they are important in the course of the multiple processes involving membranes in the living cell (e.g., transport mechanism). [ABSTRACT FROM AUTHOR]

Abstract This study aimed to investigate the effect of selected compounds from the group of triterpene sapogenins on model phosphatidylcholine membranes. Two types of biological membrane model systems were used in the work, i.e., liposomes (microelectrophoresis method) and spherical bilayers (interfacial tension method). Each model was modified with the tested sapogenin compounds, and the change in their physicochemical and electrical parameters was analyzed. Parameters characterizing the equilibrium in the membrane of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)-oleanolic acid (OA) and DPPC-asiatic acid (AA) were determined). Based on the Young-Laplace equation, the interfacial tensions of spherical lipid bilayers were measured. The formation of 1:1 complexes was assumed in the DPPC-OA and DPPC-AA membrane systems, and the parameters characterizing the interactions in the formed complexes were calculated. Microelectrophoresis was used to study the surface charge density of lipid membranes. These values were obtained from electrophoretic mobility data using Smoluchowsky’s equation. The influence of pH on the electrolyte solution and the composition of the membranes was investigated. The results indicate that modifying DPPC membranes with selected triterpene sapogenins, both OA and AA, causes changes in the surface charge density and shifts of the isoelectric point. Data presented in this work, obtained through mathematical derivation and confirmed experimentally, are of great importance for interpreting phenomena occurring in lipid membranes. A quantitative description of equilibria between phosphatidylcholine and sapogenins lets us understand the processes on the membrane surface. The equilibria are particularly significant from the standpoint of cell functioning. Phosphatidylcholine-sapogenin interactions modulate a range of physicochemical properties of membranes, and they are important in the course of the multiple processes involving membranes in the living cell (e.g., transport mechanism).

Introduction: The current understanding of the biological impacts of a static magnetic field (SMF) is restricted to the direct interactions of the magnetic field with biological membranes. The electrokinetic (zeta) potential is an electrochemical property of erythrocyte surfaces which was negatively charged in physiological media after SMF exposure (0.1‒2.0 T).Methods: The novel data about electrokinetic parameters of the erythrocytes is determined by microelectrophoresis after SMF-exposure in norm and heterozygous β-thalassemia. The methods of light scattering, lipid peroxidation, fluorescence microscopy are used.Results: The electrokinetic potential of erythrocytes in norm is increased after SMF intensities due to enhanced negatively exposed charges on the outer surface of the membrane accompanied by an increase in light scattering where changes in cell morphology are observed. Conversely, a decrease in the zeta potential of β-thalassemia erythrocytes upon SMF-treatment was determined because of the reduction in the surface electrical charge of the membranes, where a significant decrease in light scattering at 1.5 T and 2.0 T was recorded. Exposure to SMF (0.5–2.0 T) was associated with an increase in the malondialdehyde content in erythrocytes. Biophysical studies regarding the influence of SMF on the electrostatic free energy of cells shows an increase in negative values in healthy erythrocytes, which corresponds to the implementation of a spontaneous process. This is also the process in β-thalassemia cells after SMF exposure with lower negative values of free electrostatic energy than erythrocytes in norm.Discussion: The effect of static magnetic field (SMF 0.1–2.0 T) on the electrokinetic and morphological characteristics of erythrocytes in norm and β-thalassemia is determined and correlated with the increase/reduction in surface charge and shrinkage/swelling of the cells, respectively. Lipid peroxidation of healthy and β-thalassemia erythrocytes caused an enhancement of lipid peroxidation because of the higher concentrations of TBARS products in cellular suspension. SMF (0.1‒2.0 T) altered the spontaneous chemical processes with negative values of electrostatic free energy of erythrocytes in norm and β-thalassemia accompanied by a lower FITC-Concanavalin A binding affinity to membrane receptors (SMF 2.0 T). The electrokinetic properties of human erythrocytes in norm and β-thalassemia upon SMF treatment and their interrelationship with the structural-functional state of the membrane were reported. The presented work would have future fundamental applications in biomedicine.

Montmorillonite (MM) colloid nanoplates have high adsorption capacity due to their large size/thickness ratio, which allows them to be used as carriers for drug delivery. Upon adsorption of the mitochondrial protein cytochrome c (cytC) onto MM plates, the composite cytC–MM particles acquire anticancer properties because of the ability of cancer cells to phagocytize submicron particles (in contrast to the normal cells). In this way, exogenous cytC can be introduced into tumor cells, thereby triggering apoptosis—an irreversible cascade of biochemical reactions leading to cell death. In the present study, we investigated the physicochemical properties of cytC–MM particles as a function of the cytC concentration in the suspension, namely, the electrophoretic mobility, the mass increment of MM monoplates upon cytC adsorption, the ratio of the adsorbed to the free cytC in the bulk, the protein density on the MM's surface, the number of cytC globules adsorbed on an MM monoplate, the concentration of cytC–MM composite particles in the suspension, and the dependence of cytotoxicity on the cytC–MM particle concentration. For this purpose, we used microelectrophoresis, static and electric light scattering, and a colon cancer cell culture to test the cytotoxic effects of the cytC–MM suspensions. The results show that the cytotoxicity depends linearly on the logarithm of the particle concentration in the cytC–MM suspension reaching 97%. [ABSTRACT FROM AUTHOR]

The influence of kaempferol (K), myricetin (M) and lipoic acid (LA) on the properties of natural erythrocytes, isolated from animal blood and biological membrane models (monolayers and liposomes) made of phosphatidylcholine (PC), cholesterol (CHOL), and sphingomyelin (SM), CHOL in a ratio of 10:9, was investigated. The Langmuir method, Brewster angle microscopy (BAM) and microelectrophoresis were used. The presented results showed that modification of liposomes with kaempferol, myricetin and lipoic acid caused changes in the surface charge density and the isoelectric point value. Comparing the tested systems, several conclusions were made. (1) The isoelectric point for the DPPC:Chol:M (~2.2) had lower pH values compared to lipoic acid (pH~2.5) and kaempferol (pH~2.6). (2) The isoelectric point for the SM-Chol with myricetin (~3.0) had lower pH values compared to kaempferol (pH~3.4) and lipoic acid (pH~4.7). (3) The surface charge density values for the DPPC:Chol:M system in the range of pH 2–9 showed values from 0.2 to −2.5 × 10−2 C m−2. Meanwhile, for the DPPC:Chol:K and DPPC:Chol:LA systems, these values were higher at pH~2 (0.7 × 10−2 C m−2 and 0.8 × 10−2 C m−2) and lower at pH~9 (−2.1 × 10−2 C m−2 and −1.8 × 10−2 C m−2), respectively. (4) The surface charge density values for the SM:Chol:M system in the range of pH 2–9 showed values from 0.5 to −2.3 × 10−2 C m−2. Meanwhile, for the DPPC:Chol:K and DPPC:Chol:LA systems, these values were higher at pH~2 (0.8 × 10−2 C m−2), and lower at pH~9 (−1.0 × 10−2 C m−2 and −1.8 × 10−2 C m−2), respectively. (5) The surface charge density values for the erythrocytes with myricetin in the range of pH 2–9 showed values from 1.0 to −1.8 × 10−2 C m−2. Meanwhile, for the erythrocytes:K and erythrocytes:LA systems, these values, at pH~2, were 1.3 × 10−2 C m−2 and 0.8 × 10−2 C m−2 and, at pH~9, −1.7 × 10−2 C m−2 and −1.0 × 10−2 C m−2, respectively. [ABSTRACT FROM AUTHOR]

Abstract Background The apoptosis (a cascade of biochemical reactions leading to suicide of damaged biological cells) is blocked in the cancer cells because of impossibility of cytochrome c (cytC) go out from the mitochondria. However, the apoptosis can be started by introducing of exogenous cytC into cytoplasm using colloid particles as a protein carrier due to ability of the cancer cells to phagocytize extracellular particles with submicron size. Results The clay mineral montmorillonite (MM) were used to prepare aqueous suspension of protein/mineral composite particles by electrostatic adsorption of the positively charged cytC globules on the negatively charged MM colloid plates, and then added to colon cancel culture. The results shows out that separately cytC and MM have no effect but the composite cytC-MM particles kill 95% of the cancer cells after 96 h treatment using equine cytC which is 97% structurally identical with the human cytC. To reach this high cytotoxicity we have formulated requirements to: (a) bare colloid particles (electric charge, form and size), (b) conditions for protein adsorption (concentrations, pH, ionic strength), and (c) suspension with the composite particles (positive total charge and optimal concentration). Due to satisfying these requirements we have reached cytotoxicity which is 1/3 higher than the reached by other authors using different artificial particles. The cytotoxicity rapidly increases with concentration of the cytC-MM particles but further it shows tendency to saturation. Methods The optimal pH 6.5 and the 10:3 mg/mg cytC/MM concentration ratio at adsorption were found out by employing computer (protein electrostatics) and physicochemical methods (microelectrophoresis and colloid electrooptics) to prepare cytC-MM suspension. The anticancer capability of cytC-MM nanoplates were investigated using cell culture of metastasizing colon cancer. Conclusion The in vitro experiments with colon cancer cell culture disclose that cytC-MM composite particles have potential for application in anticancer therapy of superficial neoplasms of the skin and the alimentary system (mouth cavity, esophagus, stomach, jejunum and colon). Graphic abstract

The characteristics of the wetting process of the porous surface of silica gel when penetrated by base liquids (water and n-octane), ethanol and stable drug systems (naproxen, ibuprofen and cyclosporine A), as biologically active substances in two ethanol concentrations, were determined by the wetting rate vs. time. The tests were performed for contacted and non-contacted plates with the vapours of the wetting liquid. Thin-layer liquid chromatography was used to determine the penetration rate of the SiO2-coated plates, taking into account the linear dependence consistent with the Washburn equation. Additionally, the changes in the adhesive tension ΔG were determined for the tested drugs. Drug stability tests were conducted using the dynamic light scattering technique and microelectrophoresis. The penetration time of the plate depends on the properties and structure of the wetting liquid droplets. The types of interactions (dispersive, electrostatic and hydrogen bonding) formed between the silanol surface groups of the silica gel and the groups contained in the adsorbate particles are also very important factors. The greater the impact force, the slower the wetting process due to the strong penetration of the liquid into the pores of the substrate. The characteristics of the drug wetting/stability process may contribute to the development of their new forms, creating delivery systems with greater efficiency and lower side effects. [ABSTRACT FROM AUTHOR]

Pooled Immunoglobulin G (IgG), hematin and the membrane-disruptive amphipathic peptide melittin have received attention as powerful biomacromolecules for biomedical and pharmacology applications. Their action on surface properties, oxidation status and epifluorescence properties measured in vitro provide useful information about the functional activity of upper biomacromolecules in erythrocytes in vivo. The hemolysis of erythrocyte membranes, as well as changes in hematocrit and the morphology of erythrocytes, was investigated here via fluorescence microscopy using FITC-concanavalin A binding to cells. The effect of melittin on the membrane capacitance and resistance of model lipid bilayers was probed via electrochemical impedance spectroscopy. Lipid bilayer capacitance was higher in the presence of 0.10 g/L melittin compared to that in the control, which is likely related to bilayer thinning and alterations of the dielectric permittivity of melittin-treated membranes. The biomolecule interactions with red blood cells were probed in physiological media in which the surface of erythrocyte membranes was negatively charged. Surface parameters of erythrocytes are reported upon IgG/hematin and IgG/melittin treatment. Pooled IgG in the presence of melittin, preincubated IgG/hematin preparations promoted a significant decrease in the electrokinetic potential of erythrocytes (Rh-positive). A malondialdehyde (MDA) assay revealed a high rate of lipid peroxidation in erythrocytes treated with IgG/hematin or IgG/melittin preparations. This finding might be a result of pooled IgG interactions with the hematin molecule and the subsequent conformational changes in the protein molecule altering the electrokinetic properties of the erythrocyte membrane related to the Rh group type of erythrocytes. The pooled IgG and hematin are reported to have important consequences for the biophysical understanding of the immunopathological mechanisms of inflammatory, autoimmune and antibody-mediated pathological processes.

Montmorillonite (MM) colloid nanoplates have high adsorption capacity due to their large size/thickness ratio, which allows them to be used as carriers for drug delivery. Upon adsorption of the mitochondrial protein cytochrome c (cytC) onto MM plates, the composite cytC–MM particles acquire anticancer properties because of the ability of cancer cells to phagocytize submicron particles (in contrast to the normal cells). In this way, exogenous cytC can be introduced into tumor cells, thereby triggering apoptosis—an irreversible cascade of biochemical reactions leading to cell death. In the present study, we investigated the physicochemical properties of cytC–MM particles as a function of the cytC concentration in the suspension, namely, the electrophoretic mobility, the mass increment of MM monoplates upon cytC adsorption, the ratio of the adsorbed to the free cytC in the bulk, the protein density on the MM’s surface, the number of cytC globules adsorbed on an MM monoplate, the concentration of cytC–MM composite particles in the suspension, and the dependence of cytotoxicity on the cytC–MM particle concentration. For this purpose, we used microelectrophoresis, static and electric light scattering, and a colon cancer cell culture to test the cytotoxic effects of the cytC–MM suspensions. The results show that the cytotoxicity depends linearly on the logarithm of the particle concentration in the cytC–MM suspension reaching 97%.

We present a novel approach for label-free concentration measurement of a specific protein in a solution. The technique combines optical tweezers and microelectrophoresis to establish the electrophoretic mobility of a single microparticle suspended in the solution. From this mobility measurement, the amount of adsorbed protein on the particle is derived. Using this method, we determine the concentration of avidin in a buffer solution. After calibration of the setup, which accounts for electro-osmotic flow in the measurement device, the mobilities of both bare and biotinylated microspheres are measured as a function of the avidin concentration in the mixture. Two types of surface adsorption are identified: the biotinylated particles show specific adsorption, resulting from the binding of avidin molecules with biotin, at low avidin concentrations (below 0.04 μg/ml) while at concentrations of several μg/ml non-specific on both types of particles is observed. These two adsorption mechanisms are incorporated in a theoretical model describing the relation between the measured mobility and the avidin concentration in the mixture. This model describes the electrophoretic mobility of these particles accurately over four orders of magnitude of the avidin concentration. [ABSTRACT FROM AUTHOR]

Background: The apoptosis (a cascade of biochemical reactions leading to suicide of damaged biological cells) is blocked in the cancer cells because of impossibility of cytochrome c (cytC) go out from the mitochondria. However, the apoptosis can be started by introducing of exogenous cytC into cytoplasm using colloid particles as a protein carrier due to ability of the cancer cells to phagocytize extracellular particles with submicron size. Results: The clay mineral montmorillonite (MM) were used to prepare aqueous suspension of protein/mineral composite particles by electrostatic adsorption of the positively charged cytC globules on the negatively charged MM colloid plates, and then added to colon cancel culture. The results shows out that separately cytC and MM have no effect but the composite cytC-MM particles kill 95% of the cancer cells after 96 h treatment using equine cytC which is 97% structurally identical with the human cytC. To reach this high cytotoxicity we have formulated requirements to: (a) bare colloid particles (electric charge, form and size), (b) conditions for protein adsorption (concentrations, pH, ionic strength), and (c) suspension with the composite particles (positive total charge and optimal concentration). Due to satisfying these requirements we have reached cytotoxicity which is 1/3 higher than the reached by other authors using different artificial particles. The cytotoxicity rapidly increases with concentration of the cytC-MM particles but further it shows tendency to saturation. Methods: The optimal pH 6.5 and the 10:3 mg/mg cytC/MM concentration ratio at adsorption were found out by employing computer (protein electrostatics) and physicochemical methods (microelectrophoresis and colloid electrooptics) to prepare cytC-MM suspension. The anticancer capability of cytC-MM nanoplates were investigated using cell culture of metastasizing colon cancer. Conclusion: The in vitro experiments with colon cancer cell culture disclose that cytC-MM composite particles have potential for application in anticancer therapy of superficial neoplasms of the skin and the alimentary system (mouth cavity, esophagus, stomach, jejunum and colon). [ABSTRACT FROM AUTHOR]

Investigation of protein-ligand interactions in physiological conditions is crucial for better understanding of biochemistry because the binding stoichiometry and conformations of complexes in biological processes, such as various types of regulation and transportation, could reveal key pathways in organisms. Nanoelectrospray ionization mass spectrometry is widely used in studies of biological processes and systems biology. However, non-volatile salts in biological fluid may adversely interfere with nanoelectrospray ionization mass spectrometry. In this study, the previously developed method of induced nanoelectrospray ionization was used to facilitate in situ desalting of protein in solutions with high concentrations of non-volatile salts, and direct investigation of protein-ligand interactions for the first time. In situ desalting occurred at the tip of emitters within a short period lasting for a few to tens of milliseconds, enabling the maintenance of nativelike conditions compatible with mass spectrometry measurements. Induced nanoelectrospray ionization was driven by pulsed potential and exhibited microelectrophoresis effect in each spray cycle, which is not observed in conventional nanoelectrospray ionization because the continuous spray procedure is driven by direct current. Microelectrophoresis caused desalting through micron-sized spray emitters (1–20 μ m), as confirmed experimentally with proteins in 100 mM NaCl solution. The method developed in this study has been further illustrated as a potential option for fast and direct identification of protein-ligand (small molecules or metal ions) interactions in complex samples. The results of this study demonstrate that the newly developed method may represent a reliable approach for investigations of proteins and protein complexes in biological samples. Induced nanoelectrospray ionization with micron-sized spray emitter was employed to realize direct investigation of protein-ligand interactions in highly concentrated salt solutions. Image 1 • The ability to directly investigate the protein-ligand interactions in highly concentrated salt solutions. • In situ detachment of proteins and non-volatile salts via microelectrophoresis by induced nanoelectrospray ionization. • Directly desalting within micron-sized spray emitters without additional separation process. • The capacity to desalt protein in mimic physiological environment. [ABSTRACT FROM AUTHOR]

The characteristics of the wetting process of the porous surface of silica gel when penetrated by base liquids (water and n-octane), ethanol and stable drug systems (naproxen, ibuprofen and cyclosporine A), as biologically active substances in two ethanol concentrations, were determined by the wetting rate vs. time. The tests were performed for contacted and non-contacted plates with the vapours of the wetting liquid. Thin-layer liquid chromatography was used to determine the penetration rate of the SiO2-coated plates, taking into account the linear dependence consistent with the Washburn equation. Additionally, the changes in the adhesive tension ΔG were determined for the tested drugs. Drug stability tests were conducted using the dynamic light scattering technique and microelectrophoresis. The penetration time of the plate depends on the properties and structure of the wetting liquid droplets. The types of interactions (dispersive, electrostatic and hydrogen bonding) formed between the silanol surface groups of the silica gel and the groups contained in the adsorbate particles are also very important factors. The greater the impact force, the slower the wetting process due to the strong penetration of the liquid into the pores of the substrate. The characteristics of the drug wetting/stability process may contribute to the development of their new forms, creating delivery systems with greater efficiency and lower side effects.

Rationale: Modern cell diagnostic methods are in high demand during the development of new approaches in personalized medicine. Coherent phase interferometry and cell microelectrophoresis are among such methods that are being actively introduced into the diagnostic process in medical institutions.Aim: To substantiate the potential use of biophysical and morphodensitometrical erythrocytes parameters as criteria of treatment efcacy and course of adaptation process in patients with gastrointestinal tract disorders.Materials and methods: The study included 25 patients aged from 40 to 54 years (11 males and 14 females), among them 9 (36%) with gastric peptic ulcer, 3 (12%) with duodenal ulcer, 8 (32%) with acute gastritis, and 5 (20%) with acute pancreatitis. Biophysical and morphological particulars of peripheral blood erythrocytes were assessed before and after treatment using cell diagnostic techniques, such as microelectrophoresis and laser modulation interference microscopy. Also, we evaluated changes over time in routine clinical laboratory tests, such as red and white blood cell counts, hemoglobin levels, and erythrocyte sedimentation rate (ESR), and differential leukocyte counts. The control group included 10 healthy donors aged from 36 to 52 years. In vitro experiments were performed to assess the erythrocyte electrophoretic mobility (EEPM) and morphology of erythrocytes treated with epinephrine or cortisol.Results: After the treatment, the patients demonstrated a decrease in their leukocyte counts (by 27%), a 2-fold increase in monocyte counts and an ESR decrease (by 10%), compared to the corresponding baseline values before treatment (p < 0.05 for all comparisons). EEPM increased by 12% (1.37 vs. 1.22 mcm × cm/V × s, p < 0.05). The erythrocyte pool of the patients before treatment, had a decreased proportion of discocytes, compared to that in the control group (85.2 vs. 95.4%, р < 0.05), increased proportions of echinocytes, stomatocytes and degenerative forms (11, 2.8 and 1%, respectively, р < 0.05). After the treatment, the discocytes counts increased virtually up to their physiological normal range (91.3%). However, the surface of the discoid cells remained heterogeneous with multiple microspicules; this resulted in changes of electrokinetic and morphological properties of erythrocyte response to stress reaction occurring in the body. The impact of the stress effectors was confrmed in in vitro experiments assessing the effects of epinephrine (1 × 10-9 g/mL) and cortisol (5 × 10-7 g/mL) on erythrocytes. At 120 minutes of the experiment, epinephrine decreased EEPM (1.14 vs. 1.24 mcm × cm/V × s at baseline, р < 0.05) and increased cell sphericity. On the contrary, cortisol increased EEPM (1.72 vs. 1.36 mcm × cm/V × s, р < 0.05), with non-signifcant echinocytic transformation.Conclusion: Biophysical and morphodensitometric parameters of red blood cells obtained with the use of current express methods of cell microelectrophoresis and coherent interference microscopy help to objectivize the intensity of stress response during a pathological process and activation of adaptation mechanisms during the treatment.

Low-level laser therapy (LLLT) is widely used in clinical practice for treatment of various pathologies. It is assumed that LLLT impact on microcirculation is among the mechanisms underlying its therapeutic effect. The microcirculation disorder is observed in the pathogenesis of any inflammatory process and is significantly influenced by red blood cells (RBCs). On this point, studying the RBCs morphology under the influence of LLLT on alterated organism is of scientific interest and practical importance. The aim of the present study was to analyze the LLLT effect on morphokinetic parameters of RBCs in hyperadrenalinemia. The LLLT effect was analyzed on rats intraperitoneally injected with adrenaline hydrochloride solution (0.1 mg/kg). As the comparison groups, the effects of LLLT, adrenaline, or saline injection as well as the parameters of intact animals were studied. LLLT was applied on the occipital region of rats for 10 min. The light irradiation with pulse frequency 415 Hz at 890 nm wavelength and average power density in the plane of the output window at 193 μW/cm2 was used. The dynamics of morphological characteristics of RBCs was studied by phase interference microscopy; the RBC electrophoretic mobility was tested by microelectrophoresis technique; photometric analyses of the RBCs amount, hemoglobin content, and osmotic fragility were performed. The adrenaline injection resulted in a significant increase in the amount of RBC pathological forms and a decrease in discocytes and normocytes by more than 50%. An increase in the optical density of RBC phase portraits, a decline in osmotic resistance, and electronegativity of RBC membranes and a reduction of their number in peripheral blood were also registered. The revealed effects persisted for 1 week after the adrenaline administration. LLLT did not significantly impact on the RBC parameters 1 h after adrenaline injection. However, a day later, LLLT reduced the severity of the adrenaline effect on RBSs, which was manifested in a decreased amount of the pathological forms of RBCs, restored RBC phase portraits, higher electrophoretic mobility and osmotic resistance, and RBSs amount in peripheral blood restored up to the level of intact animals. We suppose that the mechanism of LLLT action is realized both at cellular level through the laser radiation effect on RBC membranes, and at systemic level through the activation of stress-realizing systems of the organism with subsequent limitation of inflammatory response. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Adsorption of cytochrome c (cytC) on montmorillonite (MM) colloid particles. • Employed methods: electric light scattering and micro-electrophoresis. • Minimum of the electric polarizability coincide with zero electrophoretic mobility. Abstract The purpose is to study the capability of the electric light scattering to determine the point of zero charge of native protein macromolecules adsorbed on colloid particles at low ionic strength and without using buffers. The chosen protein and particles are cytochrome c (cytC, globular haemoproteid) and montmorillonite (MM, negatively charged plate-like crystal). The pH-dependence of the electric polarizability γ(pH) in the range pH 6–11 shows minimum which coincides with the isoelectric point determined by measuring the electrophoretic mobility μ(pH) of the cytC-MM particles. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Adsorption of cytochrome c (cytC) on montmorillonite (MM) colloid particles. • Employed methods: micro-electrophoresis, isoelectric focusing, protein electrostatics. • Isoelectric point of cytC-MM particles coincide with that of free cytC. • There are no reliable techniques for isoelectric point of free proteins. • The isoelectric point of cytochrome c in literature has inaccuracy of 1.7 pH-units. Abstract The purpose is to determine the isoelectric point (IEP) pI μ of cytochrome c (cytC, a globular haemoproteid) adsorbed on montmorillonite (MM, plate-like colloid particles) by microelectrophoresis and to compare the pI μ value with pI f 9.44 measured by isoelectric focusing in gel with covalently linked ampholytes, and with pI nz 10.0–10.6 of free cytC globule calculated by three programs for pH-dependent net charge nz using the crystallographic structure of cytC. The pH-dependence of the electrophoretic mobility μ(pH) in the range pH 6–11 shows out that IEP of cytC-MM particles appears at pH 9.35. The near courses of μ(pH) and nz (pH) reveal that the pH-independent negative charge of the MM substrate is hydrodynamically shielded by the adsorbed protein globules. The nearness of IEP and pI f allows attributing IEP value of cytC-MM particles to the isoelectric point pI μ of cytC. A short survey for pI of cytC reported in the literature since 1941 shows out that pI is dispersed in the range pH 9.0–10.65 although cytC is used now as pI f marker with well known IEP; the reason for that and the imperfections of the employed methods are discussed. [ABSTRACT FROM AUTHOR]

We propose herein a theoretical model describing the effect of fatal ethanol poisoning on the equilibria between cell membranes and the surrounding ions. Using this model, we determined the parameters characterizing the interaction between the electrolyte solution’s ions and the functional groups on the blood cells’ surface. Via the application of mathematical equations, we calculated the total surface concentrations of the acidic and basic groups, cA and cB, and their association constants with solution ions, KAH and KBOH. Using the determined parameters and mathematical equations’ values, we calculated the theoretical surface charge density values. We verified the proposed model by comparing these values with experimental data, which were selected based on measurements of the electrophoretic mobility of erythrocyte and thrombocyte membranes. Compatibility of the experimental and theoretical surface charge density values was observed in the range of pH 2–8, while deviations were observed at higher pH values.

Introduction: The current understanding of the biological impacts of a static magnetic field (SMF) is restricted to the direct interactions of the magnetic field with biological membranes. The electrokinetic (zeta) potential is an electrochemical property of erythrocyte surfaces which was negatively charged in physiological media after SMF exposure (0.1‒2.0 T). Methods: The novel data about electrokinetic parameters of the erythrocytes is determined by microelectrophoresis after SMF-exposure in norm and heterozygous β-thalassemia. The methods of light scattering, lipid peroxidation, fluorescence microscopy are used. Results: The electrokinetic potential of erythrocytes in norm is increased after SMF intensities due to enhanced negatively exposed charges on the outer surface of the membrane accompanied by an increase in light scattering where changes in cell morphology are observed. Conversely, a decrease in the zeta potential of β-thalassemia erythrocytes upon SMF-treatment was determined because of the reduction in the surface electrical charge of the membranes, where a significant decrease in light scattering at 1.5 T and 2.0 T was recorded. Exposure to SMF (0.5-2.0 T) was associated with an increase in the malondialdehyde content in erythrocytes. Biophysical studies regarding the influence of SMF on the electrostatic free energy of cells shows an increase in negative values in healthy erythrocytes, which corresponds to the implementation of a spontaneous process. This is also the process in β-thalassemia cells after SMF exposure with lower negative values of free electrostatic energy than erythrocytes in norm. Discussion: The effect of static magnetic field (SMF 0.1-2.0 T) on the electrokinetic and morphological characteristics of erythrocytes in norm and β-thalassemia is determined and correlated with the increase/reduction in surface charge and shrinkage/swelling of the cells, respectively. Lipid peroxidation of healthy and β-thalassemia erythrocytes caused an enhancement of lipid peroxidation because of the higher concentrations of TBARS products in cellular suspension. SMF (0.1‒2.0 T) altered the spontaneous chemical processes with negative values of electrostatic free energy of erythrocytes in norm and β-thalassemia accompanied by a lower FITC-Concanavalin A binding affinity to membrane receptors (SMF 2.0 T). The electrokinetic properties of human erythrocytes in norm and β-thalassemia upon SMF treatment and their interrelationship with the structural-functional state of the membrane were reported. The presented work would have future fundamental applications in biomedicine., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Doltchinkova, Lozanova, Rukova, Nikolov, Ivanova and Roumenin.)

Coupled electrokinetic protective reactive barriers (PRB) are considered as a perspective technology for the treatment of contaminated groundwater. Design of PRB is directly connected with a problem of barrier material choice. Clays can be considered as an appropriate material due to high adsorptive properties and relative cheapness. The barrier internals are formed by clay surface charge properties. We revealed that acidic and alkaline treatment of clay is an effective way to affect its protective properties so that clay can be used to treat various pollutants. Surface charge and electrokinetic properties of clays were characterized by point of zero charge (p.z.c.), point of zero net proton charge (p.z.n.p.c.) and ζ-potential at different pH. Suspensions of 3 main clay types were studied by microelectrophoresis and potentiometric titration methods. At pH > p.z.n.p.c. clayey barrier adsorbs predominantly cationic toxicants and at pH < p.z.c. – anionic ones. The barrier is seemed to be the least effective in pH range between p.z.c. and p.z.n.p.c. Given the physicochemical and electrokinetic parameters, the most efficient clays for barrier design are Cambrian illite and all montmorillonite clays. [ABSTRACT FROM AUTHOR]

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Vitamin B12 wastewater, as a pharmaceutical wastewater, is difficult to treat due to its high concentrations of bioresistant organic matters, salinity, chromaticity, and poor biodegradability. A laboratory-scale microelectrolysis (ME) process with aeration device was designed to treat this wastewater. Our results suggested that, under obtained optimal condition of hydraulic retention time of 80 min, initial pH of 3, and air/water ratio of 100:1, the removal efficiency of chemical oxygen demand, ammonia nitrogen (NH3-N), and chromaticity in the wastewater by ME process was achieved by 43.9%, 7.9%, and 82.6%, respectively. Organic matter with benzene ring was largely removed or degraded and, therefore, C = C and C = O bonds were destroyed, and substituents of aromatic rings contained more aliphatic chains after treatment by ME process. All wastewater samples were divided into three parallel factor analysis components: one protein-like (component 1 [C1]) and two humic-like components (component 2 [C2] and component 3 [C3]). Fluorescence analysis results demonstrated that humic-like and fulvic-like substances with macromolecular weight and complex structure were decomposed or degraded into smaller molecular weight substances by ME process, in addition to those easily degradable protein-like components. We further demonstrated that biodegradability of vitamin B12 wastewater after treatment by ME process was increased using biodegradability index, suggesting that the ME process can greatly improve the removal efficiency of contaminants in wastewater by subsequent treatment process. [ABSTRACT FROM AUTHOR]

Natural mordenite originated from volcanic soils in Greek islands was treated with sulfuric acid aqueous solutions of different concentrations and solid mass/solution volumes. The samples were characterized using various techniques (N 2 -physisorption, XRD, ATR-FTIR, SEM-EDS, TEM, Microelectrophoresis, Equilibrium pH) and tested in the transformation of limonene into p -cymene in the presence of atmospheric air at various temperatures and reaction times. The acid treatment is causing the removal of sodium oxide located inside the framework micropores and the small inter-fiber mesopores. This, in turn, increases drastically the BET specific surface area and unmasks negatively charged surface sites which are transformed into acid sites by adsorbing H + /H 2 O + ions. The relatively low extent removal of Al 3+ ions does not disturb the framework of natural mordenite nor its fibrous morphology. The development of micropores and small mesopores surface area and surface acid sites are transforming the catalytically inactive natural mordenite into very active catalysts. The increase in the conversion and the yield of p -cymene follows the increase in the BET specific surface area. A novel mechanism was experimentally established involving a catalytic step followed by a non catalytic one. The first step involves adsorption of limonene on acid sites via the exocyclic double bond to form the more stable tertiary carbenium ion from which terpinolenes, terpinenes and “polymeric species” are formed. The “transition state shape selectivity” manifested by the catalysts studied does not allow the formation of intermediate disproportionation products. In the second step, catalyst-free aromatization and “polymerization” of terpinolenes and terpinenes were found to occur. The aromatization was proposed to proceed by abstraction of an allylic hydrogen resulting to free radical (R ) followed by combination with O 2 and radical chain propagation to yield allylic peroxides ([ROO ]) which by elimination of (HOO ) lead to the production of p -cymene. Moreover, high molecular weight compounds may be formed as radicals are combined to alkyl and peroxyl dimmers that may be polymerized. The experimental parameters concerning the acid treatment and reaction conditions were optimized for maximizing the amount of the produced p -cymene keeping as low as possible the amount of the produced polymeric species. [ABSTRACT FROM AUTHOR]

As a bioactive and functional polysaccharide, sea cucumber fucoidan has received increasing attention. Chain conformation and physicochemical properties of fucoidan extracted from Thelenota ananas (Ta-FUC) was investigated by utilizing HPSEC-MALLS-Visc-RI, microelectrophoresis and steady shear measurements. The conformation parameter α s (0.61 ± 0.02), the Mark-Houwink-Kuhn-Sakurada exponent α η (0.92 ± 0.01), α h (0.64 ± 0.01) and the Smidsrød-Haug stiffness parameter B (0.036 ± 0.010) consistently manifested that Ta-FUC adopted a semi-flexible coil conformation in NaCl solution. Based on a wormlike cylinder model, stiffness parameters, including persistence length q (13.27 ± 0.80 nm) and cylinder diameter d (0.79 nm), were calculated. This polysaccharide demonstrated shear-thinning rheological behaviour, and critical concentration from dilute to semidilute concentration regime was determined as 3.6 mg/ml. Ta-FUC exhibited as a negative polyelectrolyte in wide pH and ionic strength ranges. These molecular characteristics and physicochemical properties would facilitate further application of Ta-FUC as a functional ingredient in food. [ABSTRACT FROM AUTHOR]

The influence of the counterion condensation on the colloid stability of alumina suspension with added carboxymethylcellulose (CMC) is investigated by electric light scattering and microelectrophoresis. The electrophoretic mobility μ and the interface ion polarizability γ are used as criteria for the effective charge of CMC-alumina particles. The light scattering intensity I 0 and the field-strength dependence τ( E 2 ) of the relaxation time τ are used as criteria for aggregation. The polymer-concentration dependences μ( C CMC ), γ( C CMC ) and I 0 ( C CMC ) under and above the recharging point are measured at different degrees of proton dissociation α and fraction φ of counterions condensed on the adsorbed polyelectrolyte chains: α ≈ 1/2, φ = 0 at pH 4.5, and α ≈ 1, φ ≈ 1/3 at pH 6.0. The results show out that the colloid stability is conditioned by the effective charge of CMC-alumina particles determined by the surface charge, the dissociated carboxylic groups of CMC chains and the condensed counterions. The particle aggregation about the recharging point (at 1:50 CMC/alumina) is explained with hetero-coagulation by polyelectrolyte chain bridging conditioned by the reduced total charge, surface charge-patches, low surface occupation and the high rigidity of CMC chains. [ABSTRACT FROM AUTHOR]

We carry out frequency-dependent solvent impedance measurements and alternating current (ac) colloid microelectrophoresis experiments in partially polar solvents in the low-frequency regime (0.25 Hz ≤ f ≤ 10 Hz). Solvent electrode polarization effects are quantified first in partially polar solvent mixtures containing bromocyclohexane (CHB). We find that the polarization capacitance from electrode polarization exhibits a clear power law behavior C p = C p0 f -m with power law exponent m = 0.25 ± 0.04. Once we account for electrode polarization effects, we are able to obtain quantitative mobilities in the low-frequency regime from our ac microelectrophoresis measurements; for these measurements, we use poly(methyl methacrylate colloids that are gravitationally confined to a plane while suspended in a low-polar solvent mixture of cis-trans decahydronapthalene and CHB. We find that the dimensionless electrophoretic mobility is constant, consistent with expectations for frequencies below the ion-diffusion frequency, and has a value E = 1.6 ± 0.4. [ABSTRACT FROM AUTHOR]

Interactions of alkali metal cations (Li, Na, K, Cs) with phosphatidylcholine (PC) liposomal membranes were investigated through experimental studies and theoretical considerations. Using a microelectrophoresis technique, charge densities of experimental membrane surfaces were measured as a function of the pH of electrolyte solutions. Equilibria between the PC liposomal membranes and monovalent ions were mathematically analyzed and described quantitatively through a previously proposed theoretical model. Association constants between functional groups of PC and the studied ions were determined and used to define theoretical curves of membrane surface charge density versus pH. Theoretical and experimental data were compared to verify the model. The PC membrane was found to have the highest affinity for lithium ions, among the ions tested. [ABSTRACT FROM AUTHOR]

This study investigates the potential of the comet and micronucleus assays of fish DNA as a means of screening the toxicity of aquatic environments. Catla catla and Cirrhinus mrigala collected from the River Chenab in Pakistan were used as a case study for the application of comet and micronucleus techniques. Comet and micronucleus assays were used to compare DNA damage in C. catla and C. mrigala collected from polluted areas of the River Chenab and farmed fish. Atomic absorption spectrophotometry showed an acute level of toxicity from Cd, Cu, Mn, Zn, Pb, Cr, Sn, and Hg in river water. Comet assay showed significant ( p < 0.05) DNA damage in C. catla representing 17.33 ± 2.42, 11.53 ± 2.14, and 14.17% DNA in the comet tail, averaged from three sites of the polluted area of the river. Tail moment was observed as 10.06 ± 2.71, 3.11 ± 0.74, and 14.70 ± 1.89, while olive moment was 8.85 ± 1.84, 3.83 ± 0.76, and 7.11 ± 0.73, respectively. Highly significant ( p < 0.01) damage was reported in C. mrigala as 37.29 ± 2.51, 34.96 ± 2.53, and 38.80 ± 2.42% DNA in comet tail, tail moment was 23.48 ± 3.90, 19.78 ± 4.26, and 14.30 ± 1.82, and olive moment was 16.22 ± 2.04, 13.83 ± 1.96, and10.99 ± 0.90. Significant ( p < 0.05) differences were observed in genotoxicity between farmed and polluted area fish. Micronucleus assay showed a similar picture of significant difference in respect to single and double micronucleus induction: i.e., 23.20 ± 4.19 and 2.80 ± 1.07‰ in C. catla and 44.80 ± 3.73 and 06.20 ± 0.97‰, respectively, in C. mrigala. Nuclear abnormalities were found as 6.00 ± 0.84 and 09.60 ± 1.72/thousand cells, respectively, in both species. The results of this study suggest that these novel fish DNA damage assays can be used as an expedient toxicity screening for aquatic environments. [ABSTRACT FROM AUTHOR]

The electrophoretic mobility and the zeta potential (ζ) of fluorescently labeled colloidal silica rods, with an aspect ratio of 3.8 and 6.1, were determined with microelectrophoresis measurements using confocal microscopy. In the case where the colloidal particles all move at the same speed parallel to the direction of the electric field, we record a xyz-stack over the whole depth of the capillary. This method is faster and more robust compared to taking xyt-series at different depths inside the capillary to obtain the parabolic flow profile, as was done in previous work from our group. In some cases, rodlike particles do not move all at the same speed in the electric field, but exhibit a velocity that depends on the angle between the long axis of the rod and the electric field. We measured the orientation-dependent velocity of individual silica rods during electrophoresis as a function of κa, where κ-1 is the double layer thickness and a is the radius of the rod associated with the diameter. Thus, we determined the anisotropic electrophoretic mobility of the silica rods with different sized double layers. The size of the double layer was tuned by suspending silica rods in different solvents at different electrolyte concentrations. We compared these results with theoretical predictions. We show that even at already relatively high κa when the Smoluchowski limiting law is assumed to be valid (κa > 10), an orientation dependent velocity was measured. Furthermore, we observed that at decreasing values of κa the anisotropy in the electrophoretic mobility of the rods increases. However, in low polar solvents with κa < 1, this trend was reversed: the anisotropy in the electrophoretic mobility of the rods decreased. We argue that this decrease is due to end effects, which was already predicted theoretically. When end effects are not taken into account, this will lead to strong underestimation of the experimentally determined zeta potential. [ABSTRACT FROM AUTHOR]

In this paper, we examined the effect of adsorbed monovalent ions on the surface charge of liposomal membranes formed from neutral (sphingomyelin), anionic (phosphatidylinositol) lipids mixed in various ratios. The surface charge density of the membrane was determined from electrophoretic mobility measurements at various pHs of solution. A four-quilibria model describing adsorption of ions on the sphingomyelin (SM) membrane and a two-equilibria model describing adsorption of ions on the phosphatidylinositol (PI) membrane was presented. We proposed a mathematical model for characterizing these equilibria. Using these models, together with experimental data of the membrane surface charge density, we determined association constants characterizing the equilibria. The correctness of the proposed model was proven by comparing the theoretical charge variation curves for SM and PI membranes with the experimental date. [ABSTRACT FROM AUTHOR]

Graphical abstract A number of new membrane anchors based on water-soluble aminoglycerides with geraniol fragments have been synthesized. A biomimetic approach was used based on the design of meroterpenes structurally similar to archaeal lipids. Turbidimetry and laser Doppler microelectrophoresis showed that the synthesized compounds were incorporated into unilamellar dipalmitoylphosphatidylcholine (DPPC) vesicles. [ABSTRACT FROM AUTHOR]

The viability of the probiotic strain Lactobacillus plantarum subsp. plantarum, after its passage through simulated gastric and pancreatic juices, was evaluated as function of its pre-growth in a medium containing the known prebiotics pectin or inulin, and was compared to glucose used as control. The presence of pectin or inulin did not markedly affect the growth (10.07 log10 colony forming units/mL and 10.28 log10 colony forming units/mL for pectin and inulin respectively versus 10.42 log10 colony forming units/mL obtained for glucose). Pectin and inulin, in contrast to glucose, induced cell stress resistance against gastrointestinal juices (D log101.5 and 2.4 colony forming units/mL respectively, versus D log10 4.0 for glucose). The data were corroborated by the analysis of the protein pattern following stress treatments which, in the case of microbial cells grown with glucose, revealed a more marked protein degradation after the double passage through simulated gastric and intestinal juices. Inulin stimulated the production of the relevant healthy bio-molecule butyrate, which amount was 30% higher respect of growth in the presence of glucose. Inulin and pectin improved cell DPPH scavenging activity, and an impressive hydrophobicity (35.28% and 34.81%, respectively) was observed with respect to the microbial growth in presence of glucose (3.39%).

The charged nature of a cellulosic fiber surface is expected to play major roles in such phenomena as fiber dispersion, flocculation, adhesion, and adsorption of polyelectrolytes. This review focuses on the evaluation of such charges by means of electrokinetic measurements, with emphasis on the fiber-pad streaming potential technique. Results of recent experiments suggest that a continuous network or networks of pores below the outer surface of a kraft fiber can significantly contribute to observed streaming potential data. At present it is not clear whether the main subsurface contributions to the observed electrokinetic effects come from fibrillar layers on the fiber surfaces or from systems of nanopores within the cell walls of fibers. Based on the literature it is possible to suggest two conceptual models to account for the fact that the streaming potential of polymer-treated fibers can change in sign, dependent on the concentration of salt. Additional research is needed to clarify various theoretical and practical points. There may be opportunities to make more effective use of streaming potential tests in the future by carrying out such tests at reduced salt levels.

The importance of fungicides uses to maintain healthy crops and reliable, high-quality yields poses environmental issues due to the water and soil contaminations. The montmorillonite is known as efficient adsorbent for many pesticides, while the organo modification enabled to use them in wider range of applications. In this study, the fungicide fludioxonil (FDX) was adsorbed on raw and organo-modified Patagonian montmorillonite. The effects of the organo treatment as well as the FDX adsorption on the surface properties were investigated by X-ray diffraction, microelectrophoresis and inverse gas chromatography. The importance of the organo treatment was revealed both for the changes in the surface properties (dispersive component of the surface energy, nanoroughness and surface acidity as well as zeta-potential) and for the adsorption of FDX as it enabled increase two times respect to the pristine montmorillonite. [ABSTRACT FROM AUTHOR]

Purpose: The sperm membrane undergoes extensive surface remodeling as it matures in the epididymis. During this process, the sperm is encapsulated in an extensive glycocalyx layer, which provides the membrane with its characteristic negative electrostatic charge. In this study, we develop a method of microelectrophoresis and standardize the protocol to isolate sperm with high negative membrane charge. Methods: Under an electric field, the percentage of positively charged sperm (PCS), negatively charged sperm (NCS), and neutrally charged sperm was determined for each ejaculate prior to and following density gradient centrifugation (DGC), and evaluated for sperm DNA damage, and histone retention. Subsequently, PCS, NCS, and neutrally charged sperm were selected using an ICSI needle and directly analyzed for DNA damage. Results: When raw semen was analyzed using microelectrophoresis, 94 % were NCS. In contrast, DGC completely or partially stripped the negative membrane charge from sperm resulting PCS and neutrally charged sperm, while the charged sperm populations are increased with an increase in electrophoretic current. Following DGC, high sperm DNA damage and abnormal histone retention were inversely correlated with percentage NCS and directly correlated with percentage PCS. NCS exhibited significantly lower DNA damage when compared with control ( P < 0.05) and PCS ( P < 0.05). When the charged sperm population was corrected for neutrally charged sperm, sperm DNA damage was strongly associated with NCS at a lower electrophoretic current. Conclusion: The results suggest that selection of NCS at lower current may be an important biomarker to select healthy sperm for assisted reproductive treatment. [ABSTRACT FROM AUTHOR]

Equilibria between the membranes of erythrocytes as well as thrombocytes and solution ions in fatal accidental hypothermia were analyzed using a theoretical four-equilibria model. The model was developed to determinate parameters characterizing cell membrane-surrounding ion interactions: the total surface concentrations of both acidic and basic groups C A, C B, and association constants K AH, K BOH. Knowledge of these parameters was necessary to calculate the theoretical values of surface charge density. The model was validated by curve-fitting the experimental data points to simulated data generated by the model. The experimental and theoretical surface charge density values agree at pH 2-8, at higher pH the deviation was observed. [ABSTRACT FROM AUTHOR]

Following systemic administration, liposomes are covered by a ‘corona’ of proteins, and preserving the surface functionality is challenging. Coating the liposome surface with polyethylene glycol (PEG) is the most widely used anti-opsonization strategy, but it cannot fully preclude protein adsorption. To date, protein binding has been studied following in vitro incubation to predict the fate of liposomes in vivo, while dynamic incubation mimicking in vivo conditions remains largely unexplored. The main aim of this investigation was to determine whether shear stress, produced by physiologically relevant dynamic flow, could influence the liposome-protein corona. The corona of circulating PEGylated liposome was thoroughly compared with that formed by incubation in vitro. Systematic comparison in terms of size, surface charge and quantitative composition was made by dynamic light scattering, microelectrophoresis and nano-liquid chromatography tandem mass spectrometry (nanoLC-MS/MS). Size of coronas formed under static vs. dynamic incubation did not appreciably differ from each other. On the other side, the corona of circulating liposomes was more negatively charged than its static counterpart. Of note, the variety of protein species in the corona formed in a dynamic flow was significantly wider. Collectively, these results demonstrated that the corona of circulating PEGylated liposomes can be considerably different from that formed in a static fluid. This seems to be a key factor to predict the biological activity of a liposomal formulation in a physiological environment. [ABSTRACT FROM AUTHOR]

Clinoptilolite, an abundant and low cost natural zeolite, activated by sulphuric acid has been shown to be useful for treating coal seam gas (CSG) co-produced saline water. This paper aims to further examine the effect of the acid activation on changes in physicochemical properties of clinoptilolite which underpin the treatment of CSG saline water by clinoptilolite. Microelectrophoresis was applied to measure surface (zeta) potential of clinoptilolite particles before and after the acid activation as function of pH. The change in the surface potential was theoretically analysed applying the theory on the electrical double layers at solid-solution interfaces. The proton donor–acceptor reactions occurring simultaneously on amphoteric alumina and silica sites of clinoptilolite were considered. The mass balances were applied to link the zeolite active sites with the zeolite charge and potential. Comparing the model with the experimental data reveals the important role of the dealumination process occurred by the acid activation. The dealumination is the main reason for the increase in the surface charge and cation exchange capacity of clinoptilolite after the acid activation due to the increased defects in the crystal structure/lattice, which result in increasing numbers of charge vacancies. These results support our previous findings on the effectiveness of the acid activation of clinoptilolite in treating saline CSG co-produced water. [ABSTRACT FROM AUTHOR]

Reported values for the acid dissociation constant (p K a) of the saturated fatty acids show a wide range, depending on their method of measurement. Although the p K a values of the shorter chain saturated fatty acids are generally recognised to be approximately 4.5–5.0, p K a values for the longer chain fatty acids have been reported to be much higher, up to pH 10. It is the purpose of this study to investigate the values of p K a measured using microelectrophoresis for saturated fatty acids with chain lengths between C10 and C18. This returned an average p K a value of 4.0 for these saturated fatty acids. By the method of measurement, this value should be considered as the surface p K a value as opposed to bulk p K a values. The graphs of mobility vs. pH showed isoelectric points between 2 and 3, with the existence of positive surfaces on the particles of fatty acids confirmed. Some examples of the relevance of p K a values for saturated fatty acids in the flotation of non-sulphide minerals have also been given. [ABSTRACT FROM AUTHOR]