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Thylakoid membranes of photosynthetic plant chloroplasts are involved in a wide range of energy producing pathways. Their stacking can be employed in order to provide increased surface area for biocatalytic purposes. Here we probe the aggregate formation of higher plants' thylakoids using low-molecular poly-l-lysine as an electrostatic polymer linker in low ionic strength media. Microelectrophoresis, actinic light scattering, millisecond-delayed fluorescence and free radical production of thylakoid membranes are measured and analyzed in the presence of the cationic polypeptide to track its influence on the surface electrical properties, the electron-transport processes and the proton gradient accumulation across membranes. Enhanced proton gradient in polylysine-treated thylakoids is obtained upon illumination due to alterations of the proton intake across the membrane resulting from the non-specific electrostatic interactions of the cationic polypeptide with thylakoids. We report lower rates of lipid peroxidation in polylysine-treated thylakoids measured both in the dark and under illumination in salt-free medium. The gained insight on the effect of polycations on photosynthetic membranes may be used in future developments of thylakoid-based approaches for energy transfer applications.

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.

This study aims at establishing a correlation between the electrical charge of Moroccan stevensite particles and ionic dyes adsorption. The electrophoretic mobility, (Ue), of the stevensite particles in water, was measured at pH 2.5–12 by microelectrophoresis. At pH between 2.5 and 8, Ue remained constant (Ue = − 1.6 10− 8 m2/(V s)), as resulting from the permanent charge of the clay mineral planar surfaces. At pH > 8, the magnitude of electrophoretic mobility increased (Ue = − 2.7 10− 8 m2/(V s)) due to the deprotonation of silanol groups on the surfaces. The anionic Orange G adsorption at the clay mineral–water interface was negligible whereas the methylene blue cations were strongly adsorbed due to the electrostatic attraction.

This paper discusses the selective depression of pyrite from chalcopyrite and arsenopyrite by biomodulation using Acidithiobacillus ferrooxidans under natural conditions of pH. The effect of bacteria–mineral interaction on the surface charge of mineral and bacterial cell was studied by microelectrophoresis. Adhesion experiments were conducted to establish the relationship between cell adhesion to specific minerals and the electrokinetic behaviour of the minerals subsequent to interaction with cells. Effect of bacterial interaction on the xanthate-induced flotation of all the minerals was assessed. Adhesion of A. ferrooxidans on pyrite was rapid and tenacious and subsequent to interaction with cells, pyrite remained hydrophilic even in presence of xanthate collector. The collector, on the other hand, was able to render good flotability to chalcopyrite even after interaction with bacterial cells. Copper activated arsenopyrite was able to retain its hydrophobicity in presence of cells due to poor attachment kinetics of cells to the mineral surface. Thus, by suitably conditioning with the cells and collector, it was possible to effectively depress pyrite from chalcopyrite and arsenopyrite.

Publisher Summary This chapter compares the dependence of the electrophoretic mobility on the ionic strength of a fibrillated and a nonfibrillated oral streptococcal strain. It reports that a soft, ion-penetrable strain was fibrillated, while an electrophoretically harder strain was devoid of a proteinaceous fibrillar surface layer, demonstrable by electron microscopy after negative staining. The bald streptococcal strain had a diffusion coefficient, as measured by dynamic light scattering that was independent of ionic strength and composition of the suspending fluid. The fibrillar strain shows an almost twofold decrease in diffusion coefficient on increasing the suspension pH from 2 to 7. Direct probing of the softness of microbial cell surfaces has been described using atomic force microscopy and suggested that the mechanical softness of microbial cell surfaces related with the electrophoretic one and the dynamic nature of microbial cell surfaces upon changes of their ionic environment. Thus, particulate microelectrophoresis, dynamic light scattering, and atomic force microscopy have become valuable, partly complementary methods to assess the softness and related ion penetrability of microbial cell surfaces. Considering the implications of these dynamic properties of microbial cell surfaces for their adhesion to surfaces, the chapter describes the application of these three methods as geared toward the analysis of microbial cell surfaces.

Summary A methodology for elucidating the mechanism of adsorption on industrial oxidic supports of species containing catalytically active ions has been developed. This involves the correlation between the surface concentration corresponding to monolayer and the surface groups of oxidic supports, the combined use of potentiometric titrations and microelectrophoresis which allows the determination of the surface and electrokinetic charge densities, respectively as well as the mathematical analysis of the isotherms obtained. The methodology applied to the adsorption of molybdates and tungstates on y-alumina, to the adsorption of molybdates on titania and to the adsorption of Co 2+ and Ni 2+ ions on y-alumina led to the following conclusions: (I) Responsible for the creation of adsorption sites for negative (positive) species are, mainly, the protonated (deprotonated) surface hydroxyls of the oxidic supports.(II) These species are adsorbed on energetically equivalent sites of the Inner Helmholtz Plane of the double layer around the y-Al,O, particles suspended i n the aqueous medium. (III) Lateral interactions are operational between the adsorbed species, the magnitude of which depends on the nature of the support and the species to be adsorbed.

Publisher Summary This chapter describes the adsorption of surface active agents on polytetrafluoroethylene latex particle surfaces. In the method described in the chapter, the polytetrafluoroethylene (PTFE) lattices were prepared by dispersion polymerization and stored in an undialyzed state until required. The particle size distribution of the latex particles was obtained by electron microscopy using the sample preparation techniques. The surface charge density of latex DR2 was determined by conductimetric titration with sodium hydroxide solution in the presence of 10−3mol dm−3 sodium chloride. At low equilibrium concentrations of C12E6, the latex shows sensitized coagulation—that is, a lower concentration of magnesium sulfate—is needed to effect coagulation than in the complete absence of C12E6. This facilitates further adsorption via hydrocarbon–hydrocarbon cooperative association to provide a monolayer on the surface. The hydrocarbon chain is removed from the water on adsorption and lies flat on the surface of the hydrocarbon substrate. The preparation of the PTFE latex is carried out using disuccinic acid peroxide, a material which cleaves homolytically on heating to give two symmetrical free radicals. The presence of acidic groups on the surface of PTFE particles has been confirmed experimentally by both microelectrophoresis and titration with alkali.

A newly available instrument for automatically measuring mobility is described based on the principle of a “grating microelectrophoresis analyzer.” Performance advantages over the laser doppler method are cited. A description is provided of optionally available modules which can provide a variety of sophisticated research, clinical or industrial process control functions.

The electrokinetic properties of nickel hydroxide, prepared by slow hydrolysis from NiCl 2 solutions, were studied using microelectrophoresis and streaming potential techniques. The particles of a stable Ni(OH) 2 colloidal dispersion were found to be negatively charged throughout the pH range from 12 to 3 where electrophoretic mobility measurements were made. The isoelectric points (IEP) were determined by extrapolation of the mobility -pH curves. They were: 1.50 in HCl (variable ionic strength), 1.79 with NaCl, and 2.77 with CaCl 2 as background electrolytes (constant ionic strength). Experiments in the liotropic series of alkali chlorides showed decreasing mobilities at constant pH, and increasing values of the IEPs of 1.64, 1.77, 2.04, and 2.49 at constant, 10 −3 M/l of LiCl, NaCl, KCl, and CsCl, respectively. The IEP of precipitated, washed and dried (100°C in vacuo) Ni(OH) 2 was found shifted to alkaline region: 9.7 in NaCl and 9.4 in CaCl solutions. NiO, produced by thermal decomposition (250°C in vacuo) of these precipitates was found to have the IEP at pH 11.0 in 10 −3 M/l NaCl solutions. The interpretation suggests that the acidic surface OH groups are structural elements of Ni(OH) 2 . Successive dehydration results both in the aggregation of particles and in the appearance of hydrophobic parts of the surface.

One of the major problems in neurobiology is the isolation and identification of specific proteins in the nervous system and determination of their function. Nervous tissues are very rich in proteins and their exceedingly high turnover rate indicates their importance. Special protein species are characteristically associated with certain diseases, such as encephalitis, or with the developmental structure of the animal. Specific neuronal components like myelin, synaptosomes, neurofilaments, neurotubules are shown to contain certain characteristic proteins. Proteins are concerned with information processing or storage. This chapter discusses that one of the best procedures for analyzing brain proteins is that of polyacrylamide gel electrophoresis. This is because of the fact that gels can be prepared easily from analytically pure starting materials, and by varying the proportions of the starting materials, gels of different density and pore diameter can be prepared.

Publisher Summary The chapter discusses microelectrophoresis of enzymes in animal cell colonies. The starch gel microelectrophoresis includes potato starch gels that are extensively and successfully used as an anticonvection and molecular sieving matrix for the electrophoresis of many enzymes. The chapter presents an overview of the demonstration of microelectrophoresis, which was carried out as part of a human tumor cell line characterization project in the laboratory of Jorgen Fogh, Sloan-Kettering Institute, New York, N.Y. Thin strips of cellulose acetate in the nongel form and in the technically preferred gel form (Cellogel) are used for the electrophoresis of enzymes in macrosamples. The chapter discusses polyacrylamide gel microelectrophoresis and microelectrophoresis of single cells. Microelectrophoresis is more likely with microsamples having high concentrations of enzyme activity which can be achieved by harvesting cells in as small a volume as possible, storing samples at –20 to –80 o C until used, reducing the time required for electrophoresis by increasing voltages while maintaining adequate cooling, and increasing the sensitivity of the specific enzyme stains.

High-performance electrophoresis (HPE) has many features in common with high-performance liquid chromatography (HPLC), for instance high resolution and short run times for the separation of both low- and high-molecular weight substances on an analytical as well as a micropreparative scale. The experiments are performed in very narrow glass capillaries either in free solution or in a gel medium. The detection of the solute zones is based on instantaneous UV-measurements (no time-consuming post staining is thus required).

Publisher Summary This chapter discuses autoradiography and describes the application of the autoradiography technique in determining the site and the amount of radioactive substance in biological material. The techniques of detection and measurement of radioactive radiations are based upon the property of these radiations to ionize the medium they cross. The ionizing power varies directly with the square of the charge of the particle and inversely with the square of its velocity down to a certain minimum value after which the velocity is constant. The recording of the ionizing particles is performed by special photographic emulsions. The principle of the autoradiographic method by neutronic irradiation is different: stable atomic nuclei, when bombarded by nuclear particles, suffer distintegration. The products of this disintegration, if sufficiently energetic, can leave tracks in the photographic emulsion. The presence of a particular element can then be detected by its characteristic disintegration star after bombardment. Autoradiographic techniques can be combined with ultramicrobiochemical procedures such as microchromatography or microelectrophoresis on silk threads. By these techniques, the quantitative amounts of purines or pyrimidines extracted from single nerve cells are determined.

Publisher Summary The chapter discusses the differential distribution of 5-HT in various regions of the mammalian central nervous system (CNS) and the effects of the systemic administration of chemically related substances on behavior and psychological processes that have stimulated a great deal of research on the functions and mechanisms of actions of 5-HT in the CNS. Serotonin is administered locally to single neurons in the mammalian central nervous system by the technique of microelectrophoresis. When the effect of electrophoretically administered 5-HT is studied on heterogeneous neuronal populations in various brain regions, it is found that most sensitive neurons in telencephalon and diencephalon are depressed by 5-HT, although excitation is observed. Chemical and histochemical evidence for 5-HT pathways in the CNS, together with data on neuronal sensitivity to 5-HT strongly suggest that 5-HT may be a transmitter at central synapses; however, a transmitter function is not definitively demonstrated.

Publisher Summary Microelectrophoresis is employed for the determination of nucleic acid base composition. The technical basis of the electrophoretic separation of nucleic acid components in small amounts is the reduction in length, width, and thickness of the supporting medium, with the traditional basis for the evaluation of the individual compounds, ultraviolet light absorption, being retained. The increased sensitivity is obtained by measuring the absorption in smaller areas. Scaling down the electrophoretic procedure by reducing the dimensions must be accompanied by certain modifications in technique because of the resulting steepening of the concentration gradients of the migrating compounds. Microphoresis refers to electrophoresis in a scale involving bases and nucleotides in amounts of about 10 -10 gm. The methods, whereby RNA and DNA content are determined in microscopic tissue units may be considered as side products of the elaboration of the microphoretic technique. Microphoresis can also be used with advantage for the determination of the adenine: guanine quotient in DNA.