Bo Göran Jönsson

Lund University | LU · Department of Theoretical Chemistry

We study the aggregation of calcium silicate hydrate nanoplatelets on a surface by means of Monte Carlo and Molecular Dynamics simulations at thermodynamic equilibrium. Calcium silicate hydrate (C-S-H) is the main component formed in cement and is responsible for the strength of the material. The hydrate is formed in early cement paste and grows to...

We analyze the classical problem of the interaction between two charged surfaces separated by a solution containing neutralizing counter-ions. The focus is on obtaining a description where the solvent is treated explicitly rather than through a dielectric approximation as is conventionally done. We summarize the results of three papers where we hav...

The dissolution and swelling properties of montmorillonite at different pH have been studied, using small angle X-ray scattering (SAXS), imaging and osmotic stress methods combined with Monte Carlo simulations. The acidity of montmorillonite dispersions has been varied as well as the counterions to the net negatively charged platelets. At low pH, N...

Montmorillonite is a key ingredient in a number of technical applications. However, little is known regarding the microstructure and the forces between silicate platelets. The size of montmorillonite platelets from different natural sources can vary significantly. This has an influence on their swelling behavior in water as well as in salt solution...

Growth models of charged nanoplatelets are investigated with Monte Carlo simulations and simple theory. In a first model, 2-dimensional simulations in the Canonical Ensemble are used to demonstrate that the growth of a single weakly charged platelet could be limited by its own internal repulsion. The short range attractive interaction in the crysta...

The influence of the charge anisotropy and platelet size on the formation of gel and glass states and nematic phases in suspensions of plate-like particles is investigated using Monte Carlo simulations in the canonical ensemble. The platelets are modeled as discs with charged sites distributed on a hexagonal lattice. The edge sites can carry a posi...

Proteins and other biomolecules contain acidic and basic titratable groups that give rise to intricate charge distributions and control electrostatic interactions. 'Charge regulation' concerns how the proton equilibria of these sites are perturbed when approached by alien molecular matter such as other proteins, surfaces and membranes, DNA, polyele...

The free energy of interaction between parallel charged platelets with divalent counterions has been calculated using Monte Carlo simulations to investigate the electrostatic effects on aggregation. The platelets are primarily intended to represent clay particles. With divalent counterions, the free energy for two platelets or two tactoids (cluster...

Monte Carlo simulations show that charge-regulation alone can cause highly charged zirconium nanoparticles to adsorb to a similarly charged or neutral silica particle and thereby stabilizing the latter. This mechanism, referred to as halo stabilization, is quite general and applicable in a range of systems provided that pH, van der Waals forces, an...

Aqueous dispersions of Ca montmorillonite contain small clusters of clay platelets, often named “tactoids”. In these tactoids, the platelets are arranged parallel to each other with a constant spacing of 1 nm. We have used small-angle X-ray scattering (SAXS) to determine the average number of platelets per tactoid, N. We found that this number depe...

We present a theoretical investigation of a model clay dispersion in 1-1 salt solutions by varying the particle volume fraction and ionic strength as well as the charge distribution on the clay platelets. The platelets are modeled as discs with charged sites distributed on a hexagonal lattice. The edge sites can be positively charged while the rema...

Anisotropic interactions in colloidal suspensions have recently emerged as a route for the design of new soft materials. Nonisotropic particles can form nematic, smectic, hexatic, and columnar liquid crystals. Although the formation of these phases is well rationalized when excluded volume is solely at play, the role of electrostatic interactions s...

Aqueous dispersions of pure sodium and calcium smectite clays with platelet sizes on the order of a few hundred nanometers were characterized using a combination of cryo-transmission electron microscopy (cryo-TEM) and small-angle X-ray scattering (SAXS). With monovalent sodium counterions the clay is dispersed as individual platelets, as seen by cr...

Effective pair potentials between charged colloids, obtained from Monte Carlo simulations of two single colloids in a closed cell at the primitive model level, are shown to reproduce accurately the structure of aqueous salt-free colloidal dispersions, as determined from full primitive model simulations by Linse et al. (Linse, P.; Lobaskin, V. Elect...

We analyze, using Monte Carlo simulations, how a dielectric medium, modeled as a Stockmayer fluid, modulates the force between two similarly charged surfaces. A major objective is to provide a basis for understanding the strengths and weaknesses of the primitive model. The system studied has uniformly charged walls separated by counterions and solv...

We present a comparison of experimentally and theoretically determined osmotic pressures for various colloidal dispersions. Experimental data is collected from several different silica and polystyrene dispersions. The theoretical pressure determinations are based on the primitive model combined with the cell model, and the physical quantities are c...

The surface charge density of C-S-H particles appears to be one of the key parameters for predicting the cohesion strength, understanding the ion retention, the pollutant leakage, and admixture adsorption in hydrated cement pastes.This paper presents a Monte Carlo simulation of the surface-ions interactions that permits the prediction of surface ch...

This paper studies the possibility for improving the ductility of cement based materials by means of oligocationic additives. Actually, the setting of cement is due to ionic correlation forces between highly negatively charged C–S–H nanoparticles throughout a calcium rich solution. The main drawback of this strong attraction is its very short range...

Cement paste is a complex heterogeneous, polyphasic and reactive material with a relatively low stability range of the different phases. The pH and ionic concentrations of the pore solution are high or very high, circumstances that have made it difficult to set up accurate experiments at the nanometric scale. The nanometric dimensions of the main h...

Among the hydrates constituting a cement paste, C-S-H is the main component, it represents at least 60 % of the fully hydrated paste. C-S-H has a lamellar structure similar to that of a rare mineral, tobermorite. The germination and growth of the C-S-H particles result in increasing mechanical resistance (strength, cohesion). Mechanical experiments...

Ca/Na montmorillonite and natural Wyoming bentonite (MX-80) have been studied experimentally and theoretically. For a clay system in equilibrium with pure water, Monte Carlo simulations predict a large swelling when the clay counterions are monovalent, while in presence of divalent counterions a limited swelling is obtained with an aqueous layer be...

Interaction forces between charged interfaces in the presence of oppositely charged dendrimers are studied by experiment and simulation. The experiments involve direct force measurements with an atomic force microscope (AFM) between two negatively charged colloidal particles in the presence of adsorbed, positively charged globular dendrimers. The s...

We study the association of the cationic protein lysozyme with several almost neutral protein fragments but with highly uneven charge distributions. Using mesoscopic protein models, we show how electrostatic interactions can align or steer protein complexes into specific constellations dictated by the specific charge distributions of the interactin...

The interplay between the biocolloidal characteristics (especially size and charge), pH, salt concentration and the thermal energy results in a unique collection of mesoscopic forces of importance to the molecular organization and function in biological systems. By means of Monte Carlo simulations and semi-quantitative analysis in terms of perturba...

In this work, we present Monte Carlo simulations of mixtures containing negatively charged latex particles and positively charged dendrimers. We focus on the interaction between two latex particles as salt concentration, dendrimer dose, and generation number are varied. Interaction free energies and corresponding stability ratios are calculated. Mi...

Confronting grand canonical titration Monte Carlo simulations (MC) with recently published titration and charge reversal (CR) experiments on silica surfaces by Dove and Craven (Dove, P. M.; Craven, C. M. Geochim. Cosmochim. Acta 2005, 69, 4963-4970) and van der Heyden et al. (van der Heyden, F. H. J.; Stein, D.; Besteman, K.; Lemay, S. G.; Dekker,...

Attractive interactions between like-charged aggregates (macromolecules, colloidal particles, or micelles) in solution due to electrostatic correlation effects are revisited. The associated phenomenon of phase separation in a colloidal solution of highly charged particles is directly observed in Monte Carlo simulations. We start with a simple, yet...

We have performed Monte Carlo simulations for two like-charged infinite plates with counterions and solvent in between. The solvent is described at the primitive model (PM) level and also as a Stockmayer fluid. Both descriptions share the same qualitative ion correlation picture. At sufficiently high coupling, the pressure between the plates shows...

We have recently reported Monte Carlo simulations for a system of two infinite like-charged plates in a dipolar fluid solvent (Pegado et al 2008 J. Chem. Phys. at press). The pressure as a function of plate separation qualitatively reproduces the ion–ion correlation attraction picture seen in primitive model studies, where the solvent only enters t...

The free energy of interaction between two nanometric clay platelets immersed in an electrolyte solution has been calculated using Monte Carlo simulations as well as direct integration of the configurational integral. Each platelet has been modeled as a collection of charged spheres carrying a unit charge the face of a platelet contains negative ch...

We have used Monte Carlo simulations to study the interaction of two uniformly charged colloidal particles with adsorbed oppositely charged polyelectrolytes. A predominantly attractive net force is found. The force consists of an attractive term due to bridging and electrostatic correlations and a repulsive term of direct entropic origin. At large...

We have studied the equilibrium between a lamellar phase and crystalline salts in a four-component system containing both a cationic and an anionic surfactant in water. The chemical potentials for the different components have been derived from a thermodynamic model for the free energy. In our model system there are four salts that can precipitate...

The interaction of two oppositely charged surfaces has been investigated using Monte Carlo simulations and approximate analytical methods. When immersed in an aqueous electrolyte containing only monovalent ions, two such surfaces will generally show an attraction at large and intermediate separations. However, if the electrolyte solution contains d...

Using Monte Carlo (MC) simulation, mean-field and scaling arguments we investigate forces between charged spherical aggregates conferred by an oppositely charged polymeric chain. At interaggregate separations comparable to the length of the chain the force is attractive due to a special type of long-range bridging attraction mediated by the polyele...

The cohesion of cement grains is caused by surface forces acting between calcium silicate hydrate (C-S-H) nanoparticles in interstitial electrolytic solution. The influence of pH, cations valency and concentration on the stability of the final concrete construction is investigated both through Grand Canonical Monte Carlo (GCMC) simulations and forc...

Solvation of protein surface charges plays an important role for the protonation states of titratable surface groups and is routinely incorporated in low dielectric protein models using surface accessible areas. For many-body protein simulations, however, such dielectric boundary methods are rarely tractable and a greater level of simplification is...

Electrokinetic measurements such as electrophoresis may show an inversion of the effective surface charge of colloidal particle called overcharging. This phenomenon has been studied by various theoretical approaches but up to now very few attempts of confrontation between theory and experiment have been conducted. In this work we report electrophor...

We have used Monte Carlo simulations and an extended mean field theory to study the interaction between two uniformly charged surfaces with an interstitial, neutralising solution of counterions, consisting of flexible polyelectrolytes. The latter are modelled as charged monomers bonded via harmonic potentials. The monotonic repulsion between surfac...

An overview of the interaction between charged macromolecules in aqueous so-lution is presented. The starting point is the dielectric continuum model and the Debye-Hückel equation. The usefulness of the simple theory is empha-sized in particular for biological macromolecules, whose net charge or surface charge density often is low. With more highly...

Within the primitive model of electrolytes, partitioning the system free energy into contributions from entropy and energy requires an explicit description of the temperature dependence of the dielectric constant εr. Taking this into account, the authors find that the ion-ion correlation attraction between like charged macroions is governed by entr...

In answer to recent experimental force measurements between oppositely charged surfaces we here reproduce the repulsion in the presence of multivalent salt using Monte Carlo simulations within the primitive model. Our osmotic pressure curves are in good agreement with experimental results. In contrast with Poisson-Boltzmann calculations, both repul...

Electrokinetic measurements such as electrophoresis may show an inversion of the effective surface charge of colloidal particle called overcharging. This phenomenon has been studied by various theoretical approaches but up to now very few attempts of confrontation between theory and experiment have been conducted. In this work we report electrophor...

The charge state of molecules and solid/liquid interfaces is of paramount importance in the understanding of the reactivity and the physico-chemical properties of many systems. In this work, we propose a new Monte Carlo method in the grand canonical ensemble using the primitive model, which allows us to simulate the titration behavior of molecules...

In this paper, we are concerned with the charging and electrokinetic behavior of colloidal particles exhibiting a high surface charge in the alkaline pH range. For such particles, a theoretical approach has been developed in the framework of the primitive model. The charging and electrokinetic behavior of the particles are determined by the use of...

Calmodulin (CaM) operates as a Ca(2+) sensor and is known to interact with and regulate hundreds of proteins involved in a great many aspects of cellular function. It is of considerable interest to understand the balance of forces in complex formation of CaM with its target proteins. Here we have studied the importance of electrostatic interactions...

Both natural and synthetic polyelectrolytes form strong complexes with a variety of proteins. One peculiar phenomenon is that association can take place even when the protein and the polyelectrolyte carry the same charge. This has been interpreted as if the ion-dipole interaction can overcome the repulsive ion-ion interaction. On the basis of Monte...

The main source of cohesion in cement paste is the nanoparticles of calcium silicate hydrate (C-S-H), which are formed upon the dissolution of the original tricalcium silicate (C(3)S). The interaction between highly charged C-S-H particles in the presence of divalent calcium counterions is strongly attractive because of ion-ion correlations and a n...

When a protein molecule approaches a charged surface, its protonation state can undergo dramatic changes due to the imposed electric potential. This has a large impact on adsorption strengths that may be enhanced by several kT. Using mesoscopic simulation techniques as well as analytical theories, we have investigated this regulation mechanism and...

The generalized hole corrected Debye–Hückel theory (Penfold et al J. Stat. Mech. (2005) P06009) is implemented. Predictions of thermodynamic functions and simple structural properties compare favourably with results from closure of the Ornstein–Zernike integral equation in the mean spherical approximation, and with Monte Carlo simulation of the cha...

It is known that the overall charge of a protein can change as the molecule approaches a charged object like another protein or a cell membrane. We have formalized this mechanism using a statistical mechanical framework and show how this rather overlooked interaction increases the attraction between protein molecules. From the theory, we can identi...

Although interactions in biological systems occur in the presence of a large number of charged species, the binding of charged ligands to different biomolecules is often analyzed in a simplified model focusing only upon the receptor, ligand, and added salt. Here we demonstrate that the presence of charged macromolecules can affect binding to the re...

The complex between calmodulin and the calmodulin-binding portion of smMLCKp has been studied. Electrostatic interactions have been anticipated to be important in this system where a strongly negative protein binds a peptide with high positive charge. Electrostatic interactions were probed by varying the pH in the range from 4 to 11 and by charge d...

A molecular dynamics program for arbitrary molecular mixtures is presented. All intramolecular degrees of freedom are treated explicitly, which means that the program is based on central forces only. A double time step technique has been devised in order to separate rapidly varying, covalent forces from slowly varying ones. Typically, the ratio bet...

It is generally agreed that the cohesion of cement paste occurs through the formation of a network of nanoparticles of a calcium-silicate-hydrate ("C-S-H"). However, the mechanism by which these particles develop this cohesion has not been established. Here we propose a dielectric continuum model which includes all ionic interactions within a dispe...

The coexistence of two lamellar liquid crystalline phases has been investigated by means of Monte Carlo simulations. The surfaces of the negatively charged bilayers formed by the surfactant molecules are modeled as planar infinite walls with a uniform surface charge density. Water is treated as a dielectric continuum, and only electrostatic interac...

Ion–ion correlations play an important role in liquid dispersion with strong electrostatic interactions. Examples can be found in very diverse areas with the setting of cement paste as one extreme and the compactation of DNA as another. One particularly spectacular effect of ion–ion correlations is that the traditional double layer repulsion someti...

A polymer density functional theory is evaluated in terms of its ability to predict interactions between large surfaces in a polymer fluid. Comparisons are made with results from simulations in an expanded isotension ensemble. The variation of the net surface-surface interaction with adsorption strength is examined. Cases where the monomers interac...

Protein self-association may be detrimental in biological systems, but can be utilized in a controlled fashion for protein crystallization. It is hence of considerable interest to understand how factors like solution conditions prevent or promote aggregation. Here we present a computational model describing interactions between protein molecules in...

Monte Carlo simulations and density functional calculations have been performed for charged macromolecules confined to planar slits. The force between the confining walls has been evaluated as a function of separation, while keeping the chemical potential of the macromolecules constant. Highly charged spherical particles and flexible polyelectrolyt...

The behavior of polyampholytes (PAs) in electric fields is investigated by Monte Carlo simulations. In bulk it is found that the response of the PA depends on the charge sequence. For small repeating units of positive and negative charges the response is linear, while bigger units results in a nonlinear response in both the induced dipole moment an...

Different Amphiphile SystemsSurfactants Start to Form Micelles at the CMCCMC Depends on Chemical StructureTemperature and Cosolutes Affect the CMCThe Solubility of Surfactants May be Strongly Temperature DependentDriving Forces of Micelle Formation and Thermodynamic ModelsThe Association Process and Counterion Binding Can be Monitored by NMR Spectr...

Microemulsions Can be Used as Minireactors for Chemical ReactionsSurface Active Reagents May be Subject to Micellar CatalysisMicroemulsions are Good Solvents for Organic SynthesisMicroemulsions are Useful as Media for Enzymatic ReactionsMicroemulsions Can be Used to Prepare Nanosized LatticesNanosized Inorganic Particles Can be Prepared in Microemu...

The Term Microemulsion is MisleadingPhase Behaviour of Oil–Water–Surfactant Systems Can be Illustrated by Phase DiagramsThe Choice of Surfactant is DecisiveTernary Phase Diagrams Can be ComplexHow to Approach Microstructure?Molecular Self-diffusion Can be MeasuredConfinement, Obstruction and Solvation Determine Solvent Self-diffusion in Microemulsi...

Surfactants Adsorb at InterfacesSurfactants Aggregate in SolutionSurfactants are AmphiphilicSurface Active Compounds are Plentiful in NatureSurfactant Raw Materials May be Based on Petrochemicals or OleochemicalsSurfactants are Classified by the Polar Head GroupDermatological Aspects of Surfactants are Vital IssuesThe Ecological Impact of Surfactan...

Liquids Spread at InterfacesThe Critical Surface Tension of a Solid is a Useful ConceptThe Critical Surface Tension Can be Applied to CoatingsSurface Active Agents Can Promote or Prevent Wetting and SpreadingMeasuring Contact AnglesBibliography

The Adsorbed Amount Depends on Polymer Molecular WeightThe Solvent Has a Profound Influence on the AdsorptionElectrostatic Interactions Affect the AdsorptionPolyelectrolyte Adsorption Can be Modelled TheoreticallyPolyelectrolytes Change the Double-layer RepulsionPolymer Adsorption is Practically IrreversibleThe Acid–Base Concept Can be Applied to P...

Systems of Surfactants with Similar Head Groups Require No Net InteractionGeneral Treatment of Surfactant Mixtures Requires a Net InteractionThe Concept of Mixed Micelles Can Also be Applied to Amphiphiles Not Forming MicellesMixed Surfactant Systems at Higher Concentrations Show Interesting FeaturesMixed Surfactant Systems are Used TechnicallyAppe...

Polyoxyethylene Chains Make Up the Hydrophilic Part of Many Surfactants and PolymersCMC and Micellar Size of Polyoxyethylene-based Surfactants are Strongly Temperature DependentTemperature Dependence Can be Studied Using Phase DiagramsThe L3 or ‘Sponge’ PhaseSequence of Self-assembly Structures as a Function of TemperatureThe Critical Packing Param...

Proteins are AmphiphilicSurfactant–Protein Interactions Have a Broad RelevanceSurface Tension and Solubilization Give Evidence for Surfactant Binding to ProteinsThe Binding Isotherms are ComplexProtein–Surfactant Solutions May Have High ViscositiesProtein–Surfactant Solutions May Give Rise to Phase SeparationSurfactants May Induce Denaturation of P...

Gemini Surfactants Have an Unusual StructureCleavable Surfactants are Environmentally Attractive But are of Interest for Other Reasons As WellPolymerizable Surfactants are of Particular Interest for Coatings ApplicationsPolymeric Surfactants Constitute a Chapter of Their OwnSpecial Surfactants Give Extreme Surface Tension ReductionBibliography

Pair Potentials Act between Two Molecules in a VacuumThe Intermolecular Interaction Can be PartitionedEffective Pair Potentials Act between Two Molecules in a MediumBibliography

Surfactant Adsorption is Governed Both by the Nature of the Surfactant and the SurfaceModel Surfaces and Methods to Determine AdsorptionAnalysis of Surfactant Adsorption is Frequently Carried Out in Terms of the Langmuir EquationSurfactants Adsorb on Hydrophobic SurfacesSurfactants Adsorb on Hydrophilic SurfacesCompetitive Adsorption is a Common Ph...

Surface Tension is Due to Asymmetric Cohesive Forces at a SurfaceSolutes Affect Surface TensionDynamic Surface Tension is ImportantThe Surface Tension is Related to AdsorptionSurfactant Adsorption at the Liquid–Air Surface is Related to the Critical Packing ParameterPolymer Adsorption Can be MisinterpretedMeasurement of Surface TensionThe Surface a...

Surfactant-based Cleaning Formulations May Act by in situ Formation of a Microemulsion (Detergency)Microemulsion-based Cleaning Formulations are EfficientMicroemulsions were Once Believed to be the Solution to Enhanced Oil RecoveryBibliography

A “complex salt” of cetyltrimethylammonium (CTA+) with short (30 repeating units) polyacrylate (PA-) counterions has been synthesized. The phase diagrams of its aqueous mixtures with either the surfactant cetyltrimethylammonium acetate (CTAAc), or the polyelectrolyte NaPA, have been studied by visual inspection through crossed polarizers and by sma...

A new approach to the estimation of activity coefficients in sea water has been established using statistical mechanics. The distribution of particles (ions and nonelectrolytes) are simulated with a Monte Carlo method combined with a particle insertion technique that allows calculation of the activity coefficients. The simulations are based on the...

The force between two planar charged surfaces in the presence of polyampholytes (PAs) is investigated as a function of the surface separation. The model system contains PA molecules with zero net charge adsorbing onto the charged surfaces from a dilute surrounding solution without salt. We compare the results obtained on three levels of approximati...

The titration properties of a fatty acid solubilized in different types of micelles, cationic, anionic and nonionic, have been investigated experimentally and theoretically. The solution containing micelles, counterions, and added salt was treated as a dielectric continuum in the Monte Carlo simulations. The dielectric permittivity of the interior...

The polarizabilities of polyampholytes have been calculated in Monte Carlo simulations. For chains with random charge topologies, the polarizability increases with the chain length and the chain flexibility. For block copolymers, the polarizability initially increases with the block size to a maximum and then decreases. The polarizability is used t...

The stability of a colloidal solution consisting of a mixture of charged spherical aggregates and polyampholytes is investigated by means of Monte Carlo simulations. The double-layer repulsion between the charged macroions is reduced upon addition of neutral polyampholyte and for sufficiently highly charged colloids it is converted into a net attra...

The binding of calcium ions by EF-hand proteins depends strongly on the electrostatic interactions between Ca(2+) ions and negatively charged residues of these proteins. We have investigated the pH dependence of the binding of Ca(2+) ions by calbindin D(9k). This protein offers a unique possibility for interpretation of such data since the pK(a) va...

Monte Carlo simulations are used to assess the adequacy of the Tanford-Kirkwood prescription for electrostatic interactions in macromolecules. Within a continuum dielectric framework, the approach accurately describes salt screening of electrostatic interactions for moderately charged systems consistent with common proteins at physiological conditi...

Biological functions for a large class of calmodulin-related proteins, such as target protein activation and Ca(2+) buffering, are based on fine-tuned binding and release of Ca(2+) ions by pairs of coupled EF-hand metal binding sites. These are abundantly filled with acidic residues of so far unknown ionization characteristics, but assumed to be es...

The adsorption of flexible polyampholytes to charged surfaces has been investigated. The electrostatic interactions are included in a mean-field manner, while the chain connectivity is treated by Metropolis Monte Carlo (MC) simulations. For large enough surface charge densities, adsorption is found both for neutral polyampholytes and for polyamphol...

Colloidal particles, biopolymers and membranes all carry charges in an aqueous environment. The molecular source of these charges can be cova-lently bound ionic groups like phosphates, sulfates, carboxylates, quarte-nary ammoniums or protonated amines. The carboxylates and amines can titrate in response to pH changes, while the other groups remain...

Binding of ions to various materials, such as small molecules, proteins, polymers, colloid particles, and membranes, represents a central theme in basic and applied chemistry. Particularly, the case of proton binding to these substances (i.e., their acid-base behavior) has been a focus of research in many branches of chemistry since the turn of the...

A new Monte Carlo simulation method designed for polymer solutions confined to planar slits is presented. The slit is in equilibrium with a surrounding bulk solution and the method allows a variation of the slit width while maintaining the polymer chemical potential constant. This is achieved by changing the tangential pressure as a function of sli...

The interaction between two charged walls neutralized by grafted polyelectrolytes and mobile counterions is studied using a simplified model system, in which the charged monomers of the polyelectrolyte are replaced by “grafted” ions that interact with the grafting wall via a one-dimensional potential. Using a mean-field approximation, the model is...

Centrifugation can be used to remove the continuous aqueous phase of an oil-in-water emulsion. The cream that remains after most of the water has been removed has the structure of a biliquid foam; it can be redispersed in water. Examination of this cream through electron microscopy shows polyhedral oil cells separated by thin films. The thickness o...

Fatty acids are found in many solutions treated in ultrafiltration plants, for example, in dairy products, fermentation broth, oily waste water and bleach plant effluents from pulp mills. The influence of fatty acids on the fouling of membranes is often ignored because their concentration is rather low. However, during recent years the significant...

A modular software package for computational steering and visualiza-tion of molecular simulations is presented. The package, GISMOS, builds on in-strumentation of existing Fortran programs to accomplish data extraction for vi-sualization as well as run time input of control parameters for steering. A set of template files for instrumentation is pro...

The condensation of a single DNA can be induced by multivalent counterions and is thought to be due to ion−ion correlations. Both Monte Carlo simulations and fluorescence microscopy experiments confirm this picture. The effect is less pronounced for chain counterions (polyamines) than for simple spherical counterions with the same charge. When simp...

The ionization state of seven glutamate residues, one aspartate, and the C-terminal alpha-COOH group in bovine apo calbindin D(9k) has been studied by measurement and modeling of the pH titration curves and apparent pK(a) values. The observed pK(a) ranged from 3.0 to 6.5. Most of the observed acidic groups were half-ionized at lower pH values than...