flbarroso's virial [29 articles]

Abstract

Experimental data at 25°C are reported for osmotic pressures of aqueous solutions containing lysozyme and any one of the following salts: ammonium sulfate, ammonium oxalate, and ammonium phosphate at ionic strength 1 or 3 M. Data were obtained using a Wescor colloid membrane osmometer at lysozyme concentrations from about 4 to 20 g/l at pH 4, 7, or 8. Osmotic second virial coefficients for lysozyme were calculated from the osmotic-pressure data. All coefficients were negative, increasing in magnitude with ionic strength. ...

Abstract

We study the penetrable sphere (alias square mound) model in the fluid phase by means of the virial expansion, molecular dynamics simulations, and Ornstein-Zernike integral equation. The virial coefficients up to B8 are expressed as polynomials in the Boltzmann factor with the coefficients calculated by a Monte Carlo integration. New data for pressure and internal energy are obtained by molecular dynamics simulations with attention paid to finite-size errors and properties of the Andersen thermostat. The data and virial coefficients are correlated ...

Abstract

A very simple and accurate approach is proposed to predict the high-order virial coefficients of hard spheres and hard disks. In the approach, the nth virial coefficient Bn is expressed as the sum of nD-1 and a remainder, where D is the spatial dimension of the system. When n[greater-than-or-equal] 3, the remainders of the virials can be accurately expressed with Pade-type functions of n. The maximum deviations of predicted B5-B10 for the two systems are only 0.0209%-0.0044% and 0.0390%-0.0525%, respectively, which ...

Abstract

We report values of the virial coefficients <i>B</i>_<i>n</i> of the Lennard-Jones (LJ) model, as computed by the Mayer Sampling Monte Carlo method. For <i>n</i> = 4 and 5, values are reported for 103 temperatures <i>T</i> = 0.62 to 40.0 (in LJ units); for <i>n</i> = 6, 31 values are reported for <i>T</i> = 0.625 to 20.0; for <i>n</i> = 7, 15 values are reported from <i>T</i> = 0.625 to 10; and for <i>n</i> = 8, four values are reported from <i>T</i> ...

Abstract

PMID: 17266364 The osmotic virial equation was used to predict osmolalities of solutions of interest in biology. The second osmotic virial coefficients, Bi, account for the interactions between identical solute molecules. For multisolute solutions, the second osmotic virial cross coefficient, Bij, describes the interaction between two different solutes. We propose to use as a mixing rule for the cross coefficient the arithmetic average of the second osmotic virial coefficients of the pure species, so that only binary solution measurements are required ...

Abstract

Weak protein interactions are often characterized in terms of the osmotic second virial coefficient (B22), which has been shown to correlate with protein phase behavior, such as crystallization. Traditional methods for measuring B22, such as static light scattering, are too expensive in terms of both time and protein to allow extensive exploration of the effects of solution conditions on B22. In this work we have measured protein interactions using self-interaction chromatography, in which protein is immobilized on chromatographic particles and the ...

Abstract

We describe a thermodynamic approach that supports the adoption of a simplified procedure for the determination of protein second virial coefficients ( B 2 ) by self-interaction chromatography. Its major advantage over the original method is a decrease in the number of parameters to which magnitudes must be assigned for the determination of B 2 . Improved correlation of virial coefficients obtained by the chromatographic procedure with those obtained by light scattering is achieved by taking into account the twofold ...

Abstract

The importance of weak protein interactions, such as protein self-association, is widely recognized in a variety of biological and technological processes. Although protein self-association has been studied extensively, much less attention has been devoted to weak protein cross-association, mainly due to the difficulties in measuring weak interactions between different proteins in solution. Here a framework is presented for quantifying the osmotic second virial cross coefficient directly using a modified form of self-interaction chromatography called cross-interaction chromatography. A theoretical relationship is developed ...

Abstract

A previous method of the author to calculate the second cross virial coefficients is re-considered to improve the reliability of the predictions and to reduce the number of empirical rules. The method is based on the reduced second cross coefficient at the normal boiling temperature, inlMMLBox , whose value is always assumed equal to unity. This value is then extrapolated to the experimental temperatures using only two empirical constants: K 1 , a corrective multiplying factor of inlMMLBox ...

Abstract

Light scattering measurements were carried out on several standard polystyrenes and their binary mixtures in benzene and in 2-butanone. Their second virial coefficients, B2, were determined as a function of the polymer composition. It was revealed that for some pairs of mixtures whose components differ greatly in size, a minimum in B2 is observed, whereas a maximum is expected theoretically. The reasons for this phenomenon are discussed and interpreted in terms of the characteristics of the samples in solution and by ...

Abstract

Previously Vilker et al. ( J. Colloid Interface Sci. 79(2), (1981)) reported the osmotic pressure of concentrated bovine serum albumin (BSA) up to 475 g/L in 0.15 M sodium chloride at pH 4.5, 5.4, and 7.4. The authors used a semiempirical model based on Donnan theory to predict the osmotic pressure with good agreement. However, the formal application of a three-term virial expansion with the coefficients determined from the potential energy of interaction between BSA molecules resulted in poor agreement with ...

Abstract

The challenge of crystallizing proteins has led to a significant amount of research in understanding protein self-association and assembly. Arguably the most influential finding in this field in the past decade has been that weakly attractive protein interactions, characterized in terms of the osmotic second virial coefficient, correlate with solution conditions that are conducive to crystallization. Recent work in this area has focused on the development of more efficient techniques for measuring the second virial coefficient, as traditional characterization methods suffer ...

Abstract

A method is proposed for the measurement of the B 22 value of proteins in aqueous solutions in flow-mode that utilizes a novel fabricated dual-detector cell, which simultaneously measures protein concentration and the corresponding scattered light intensity at 90°, after the protein elutes from a size-exclusion column. Each data point on the chromatograms obtained from the light scattering detector and the concentration (ultraviolet) detector is converted to Rayleigh’s ratio, R θ , and concentration, c , respectively. ...

Abstract

The second osmotic virial coefficient ( B ) is a measure of solution nonideality that is useful for predicting conditions favorable for protein crystallization and for inhibition of aggregation. Static light scattering is the technique most commonly used to determine B values, typically using protein concentrations less than 5 mg/mL. During static light scattering experiments at low protein concentrations, frequently the protein is assumed to exist either as a single nonassociating species or as a combination of assembly states ...

Abstract

A correlation between the osmotic second virial coefficient and the solubility of proteins is derived from classical thermodynamics to support an empirical relation previously found by Wilson and co-workers (1). The model is based on the equality of fugacities of the protein in the equilibrium phases, with the details of the model depending on the standard state used. The parameters in this model have been fitted to data for several systems, mainly with lysozyme as the protein. The model is found ...

Abstract

The goal of this review is to examine the effect of salts and organic additives on the solubility of proteins in aqueous mixed solvents. The focus is on the correlation between the aqueous protein solubility and the osmotic second virial coefficient or the preferential binding parameter. First, several approaches which connect the solubility and the osmotic second virial coefficient are presented. Most of the experimental and theoretical results correlate the solubility and the osmotic second virial coefficient in the presence of ...

Abstract

The effects of ammonium sulphate concentration on the osmotic second virial coefficient ( B AA  /  M A ) for equine serum albumin (pH 5.6, 20 °C) have been examined by sedimentation equilibrium. After an initial steep decrease with increasing ammonium sulphate concentration, B AA  /  M A assumes an essentially concentration-independent magnitude of 8–9 ml/g. Such behaviour conforms with the statistical–mechanical prediction that a sufficient increase in ionic strength should effectively eliminate the contributions of charge interactions to ...

Abstract

Experimental data for ovalbumin and lysozyme are presented to highlight the nonequivalence of second virial coefficients obtained for proteins by sedimentation equilibrium and light scattering. Theoretical considerations confirm that the quantity deduced from sedimentation equilibrium distributions is B(22), the osmotic second virial coefficient describing thermodynamic nonideality arising solely from protein self-interaction. On the other hand, the virial coefficient determined by light scattering is shown to reflect the combined contributions of protein-protein and protein-buffer interactions to thermodynamic nonideality of the protein solution. ...

Abstract

Protein self-interaction is important in protein crystal growth, solubilization, and aggregation, both in vitro and in vivo, as with protein misfolding diseases, such as Alzheimer's. Although second virial coefficient studies can supply invaluable quantitative information, their emergence as a systematic approach to evaluating protein self-interaction has been slowed by the limitations of traditional measurement methods, such as static light scattering. Comparatively, self-interaction chromatography is an inexpensive, high-throughput method of evaluating the osmotic second virial coefficient (B) of proteins in solution. In ...

Abstract

It has been shown for several years that the second virial coefficient, A(2), can be helpfully used to describe the thermodynamic behavior of biological macromolecules in solution prior to crystallization. The coefficient, which reflects either repulsive or attractive interactions between particles, can allow a rapid determination of crystallization conditions. Different biological systems, from 14 kDa to 4600 kDa, were studied by small angle X-ray scattering. With large macromolecules, the A(2) values were found at the low end of the crystallization slot ...

Abstract

The osmotic second virial coefficient, B(22), has become the quantity most widely used in developing a rational understanding of protein crystallization. In this work a novel method of measuring B22 using self-interaction chromatography (SIC) is presented that is at least an order of magnitude more efficient than traditional characterization methods, such as static light scattering. It is shown that SIC measurements of second virial coefficients for BSA are in quantitative agreement with static light scattering results. The measured virial coefficient for ...

Abstract

There has been an increasing awareness that proteins, like other biopolymers, are large enough to exhibit colloidal behavior in aqueous solution. Net attractive or repulsive forces have been found to govern important physical properties, such as solubility and aggregation. The extent of intermolecular interactions, usually expressed in terms of the osmotic second virial coefficient, B, is most often measured using static light scattering. More recently, self-interaction chromatography (SIC) has emerged as a method for rapid determination of B in actual formulations, ...

Abstract

The second osmotic virial coefficients of seven proteins-ovalbumin, ribonuclease A, bovine serum albumin, alpha-lactalbumin, myoglobin, cytochrome c, and catalase-were measured in salt solutions. Comparison of the interaction trends in terms of the dimensionless second virial coefficient b(2) shows that, at low salt concentrations, protein-protein interactions can be either attractive or repulsive, possibly due to the anisotropy of the protein charge distribution. At high salt concentrations, the behavior depends on the salt: In sodium chloride, protein interactions generally show little salt dependence ...

Abstract

Important progress has been made in recent years toward developing a molecular-level understanding of protein phase behavior in terms of the osmotic second virial coefficient, a thermodynamic parameter that characterizes pairwise protein interactions. Yet there has been little practical application of this knowledge to the field of protein crystallization, largely because of the difficult and time-consuming nature of traditional techniques for characterizing protein interactions. Self-interaction chromatography has recently been proposed as a highly efficient method for measuring the osmotic second virial ...

Abstract

Interactions between proteins are often sufficiently weak that their study through the use of conventional structural techniques becomes problematic. Of the few techniques capable of providing experimental measures of weak protein-protein interactions, perhaps the most useful is the second virial coefficient, B 22 , which quantifies a protein solution's deviations from ideal behavior. It has long been known that B 22 can in principle be computed, but only very recently has it been demonstrated that such calculations can be performed ...

Abstract

The paper presents a method for interpolation of the temperature dependence of the coefficients appearing in the virial equation of state. Regression of available data for a virial coefficient at high and low temperatures is used to formulate an approximant that captures the order-of-magnitude behaviour in these extremes. This behaviour is factored out of the data, and the resulting residual is subject to spline interpolation. The value of the virial coefficient at an interpolated temperature is recovered by multiplying by the ...

Abstract

We have calculated the direct correlation function, <i>c</i>(1, 2), via a high-order virial expansion, for systems of hard spheres and spheroids, in both the isotropic and nematic phases. For hard spheres, we find that truncation at sixth order in density gives good agreement with simulation data. Close to freezing, the virial series still appears to converge to the simulation results, but there are significant discrepancies, particularly at very small separations. In the non-overlap region, the virial theory begins to capture the ...