Surface thermodynamic properties and chromatographic and salting-out behavior of IgA and other serum proteins

Understanding the interaction of proteins to ion exchange chromatographic supports: A surface energetics approach

Ion exchange chromatography is one of the most widely used chromatographic technique for the separation and purification of important biological molecules. Due to its wide applicability in separation processes, a targeted approach is required to suggest the effective binding conditions during ion exchange chromatography. A surface energetics approach was used to study the interaction of proteins to different types of ion exchange chromatographic beads. The basic parameters used in this approach are derived from the contact angle, streaming potential, and zeta potential values. The interaction of few model proteins to different anionic and cationic exchanger, with different backbone chemistry i.e., agarose and methacrylate, was performed. Generally, under binding conditions, it was observed that proteins having negative surface charges showed strong to lose interaction (20 kT for Hannilase to 0.5 kT for IgG) with different anionic exchangers (having different positive surface charges). On the contrary, anionic exchangers showed almost no interaction (0 - 0.1 kT) with the positively charged proteins. An inverse behavior was observed for the interaction of proteins to cationic exchangers. The outcome from these theoretical calculations can predict the binding behavior of different proteins under real ion exchange chromatographic conditions. This will ultimately propose a better bioprocess design for protein separation. This article is protected by copyright. All rights reserved.

Comparative analysis of the methods used for finding surface energy to investigate protein interaction behavior on chromatographic supports

Hydrophobic interaction chromatography, an important and effective purification strategy, is generally used for the purification of variety of biomolecules. A basic understanding of the protein interaction behavior is required to effectively separate these biomolecules. A colloidal type extended Derjaguin, Landau, Verwey, and Overbeek calculations were utilized to study the interactions behavior of model proteins to commercially available hydrophobic chromatographic materials that is, Toyopearl Phenyl 650C and Toyopearl Butyl 650C. Physicochemical properties of selected model proteins were achieved by contact angle and zeta potential measurements. The contact angle of chromatographic materials used was achieved through sessile drop method on disrupted beads and capillary penetration method (CPM) on intact beads. The surface properties were further used to calculate the interactions of the proteins to chromatographic supports. The calculated secondary energy minimum of the proteins with the chromatographic materials (from the contact angle values determined through both methods can be correlated with the retention volumes from the real chromatography. The secondary energy minimum values are higher for each protein to the chromatographic materials calculated from the inputs derived through sessile drop method compared to CPM. For instance, immunoglobulin G has secondary energy minimum value of 0.17 kT compared to 0.11 kT, obtained through sessile drop method and CPM, respectively. Average relative values of the energy minimum calculated for all proteins are as 1.51 kT and 1.29 kT for Toyopearl Butyl 650C and Toyopearl Phenyl 650C, respectively, as a conversion factor for estimation of secondary energy minimum for both methods.

The role of ligands on protein retention in adsorption chromatography: a surface energetics approach

Protein adsorption onto hydrophobic chromatographic supports has been investigated using a colloid theory surface energetics approach. The surface properties of commercially available chromatographic beads, Toyopearl Phenyl 650-C, and Toyopearl Butyl 650-C, have been experimentally determined by contact angle and zeta potential measurements. The adsorption characteristics of these beads, which bear the same backbone matrix but harbor different ligands, have been studied toward selected model proteins, in the hydrated as well as dehydrated state. There were two prominent groups of proteins observed with respect to the chromatographic supports presented in this work: loosely retained proteins, which were expected to have lower average interaction energies, and the strongly retained proteins, which were expected to have higher average interaction energies. Results were also compared and contrasted with calculations derived from adsorbent surface energies determined by inverse liquid chromatography. These results showed a good qualitative agreement, and the interaction energy minima obtained from these extended Derjaguin, Landau, Verwey and Overbeek calculations were shown to correlate well with the experimentally determined adsorption behavior of each protein.

Nonequilibrium Phenomena Influencing the Wetting Behavior of Plant Fibers

It is examined whether useful information on plant fiber surfaces can be retrieved from wetting experiments such as dynamic contact angle (DCA) analysis by use of the Wilhelmy technique and the Lifshitz-van der Waals acid-base theory. It is argued from a theoretical point of view that plant fibers may give rise to various complex phenomena during wetting experiments, phenomena which are typically not found for synthetic fibers, and that these phenomena can be a source of invalidation of experimental techniques which are commonly thought to supply information on equilibrium (or quasi-equilibrium) properties of plant fiber surfaces or of surface-liquid interactions. The nonequilibrium phenomena are studied experimentally by DCA analysis of 10 sisal fibers, 10 coir fibers, and 5 polyacrylate-coated glass fibers. The fibers are immersed in deionized water at 10 different speeds ranging from 2 to 100 µm s(-1) and the relationship between immersion speed and contact angle is examined. In contrast to what is found for the coated glass fibers, the results indicate that the (aqueous) wetting behavior of sisal and coir fibers is qualitatively far from the behavior which should ensure the meaningful interpretation of the wetting data as (quasi-)equilibrium data. From both a theoretical and a practical basis it is hence concluded that nonequilibrium phenomena necessitate a more severe form of precaution toward surface energy component theories when these are used for interpreting plant fiber wetting than what is currently at issue. Copyright 2001 Academic Press.

Determination of interfacial tension from crystallization and dissolution data: a comparison with other methods

Methods for the determination of interfacial tension between a solid and a liquid are reviewed including solubility/particle size, crystallization and dissolution kinetics. The use of solubility as a function of particle size, originally put forward by Ostwald and later corrected by Freundlich, may be unjustified for determining interfacial tension at solid-liquid interfaces. The interfacial tension values between solutions and sparingly soluble minerals such as hydroxyapatite, fluorapatite, brushite, octacalcium phosphate, calcium oxalate monohydrate, barium sulfate, calcium sulfate, calcite, and divalent metal fluorides are discussed. A comparison of these results is made with contact angle or wetting measurements. The interfacial tension values obtained from constant composition reaction kinetics are of the same order of magnitude as those determined using a contact angle method involving thin layer wicking techniques.

Surface Tension of Biological Polyelectrolyte Solutions

Surface tensions, gamma, of biological polyelectrolytes in aqueous solutions are studied systematically as possible at the air-water interface by the Wilhelmy method. The polyelectrolytes measured are sodium chondroitin sulfates A (NaCRA) and C (NaCRC), sodium poly-alpha,l-glutamate (NaPGA), poly-l-lysine hydrobromide (PLL . HBr), deoxyribonucleic acid (DNA), lysozyme (LZ), and bovine serum albumin (BSA). Linear-type macroions such as NaCR, NaPGA, PLL . HBr, and DNA have no surface activity in a wide range of polymer concentrations below the critical polymer concentration, m*, and increases as the concentration increases above m*. Surface activity of the undissociated state of macroions is rather high in general. Globule-like macroions such as LZ and BSA show high surface activity at isoelectric point above m* accompanied with orientation of the molecules along the air-water interface. Separation into the hydrophobic and hydrophilic parts at the interface and balancing in their strength are important for appearance of surface activity. Copyright 1998 Academic Press.

Effects of temperature, flow rate and composition of binding buffer on adsorption of mouse monoclonal IgG1 antibodies to protein A Sepharose 4 Fast Flow

The binding capacity of protein A Sepharose 4 Fast Flow for mouse IgG1 monoclonal antibodies (mabs) appears to be highly dependent on the buffer composition with respect to both concentration and ion type. Depending on the particular mab dynamic binding capacities up to 20 mg mab per ml gel could be obtained, when these mabs were isolated from supernatants of protein free hollow fibre cell culture systems. Variation of linear flow rate from 10 up to 300 cm/h and temperature (4 degrees C versus 25 degrees C) had a slight effect on the dynamic binding capacity, when a high ionic strength buffer was used during adsorption. Applying optimum binding conditions, final IgG fractions with a purity of more than 95% monomeric IgG were obtained. However, as side effect of the use of binding buffers with high ionic strength, the binding of acid proteases was also promoted.

On the mechanism of the cold ethanol precipitation method of plasma protein fractionation

Given the negligible difference in the value of the dielectric constant of water at 20 degrees C and that of ethanol solutions at low temperatures, the often advanced explanation for the precipitation of plasma proteins by the cold ethanol process, as being due to a reduction of the dielectric constant and the resulting increase in interprotein charge interactions, is not tenable. It is shown by a surface-thermodynamic approach that, upon dehydration by ethanol, isoelectric serum albumin molecules as well as isoelectric serum gamma globulin molecules will attract each other to a sufficient degree by van der Waals forces to become insoluble in the ethanol-water mixtures used.

Monopolar surfaces

Following the development of a methodology for determining the apolar components as well as the electron donor and the electron acceptor parameters of the surface tension of polar surfaces, surfaces of a number of quite common materials were found to manifest virtually only electron donor properties and no, or hardly, any electron acceptor properties. Such materials may be called monopolar; they can strongly interact with bipolar materials (e.g., with polar liquids such as water); but one single polar parameter of a monopolar material cannot contribute to its energy of cohesion. Monopolar materials manifesting only electron acceptor properties also may exist, but they do not appear to occur in as great an abundance. Among the electron donor monopolar materials are: polymethylmethacrylate, polyvinylalcohol, polyethyleneglycol, proteins, many polysaccharides, phospholipids, nonionic surfactants, cellulose esters, etc. Strongly monopolar materials of the same sign repel each other when immersed or dissolved in water or other polar liquids. The interfacial tension between strongly monopolar surfaces and water has a negative value. This leads to a tendency for water to penetrate between facing surfaces of a monopolar substance and hence, to repulsion between the molecules or particles of such a monopolar material, when immersed in water, and thus to pronounced solubility or dispersibility. Monopolar repulsion energies can far outweigh Lifshitz-van der Waals attractions as well as electrostatic and "steric" repulsions. In aqueous systems the commonly observed stabilization effects, which usually are ascribed to "steric" stabilization, may in many instances be attributed to monopolar repulsion between nonionic stabilizing molecules. The repulsion between monopolar molecules of the same sign can also lead to phase separation in aqueous solutions (or suspensions), where not only two, but multiple phases are possible. Negative interfacial tensions between monopolar surfactants and the brine phase can be the driving force for the formation of microemulsions; such negative interfacial tensions ultimately decay and stabilize at a value very close to zero. Strongly monopolar macromolecules or particles surrounded by oriented water molecules of hydration can still repel each other, albeit to an attenuated degree. This repulsion was earlier perceived as caused by "hydration pressure". A few of the relevant colloid and surface phenomena are reviewed and re-examined in the light of the influence of surface monopolarity on these phenomena.

Mechanism of DNA (Southern) and protein (Western) blotting on cellulose nitrate and other membranes

The transfer of DNA fractions from hydrophilic gels to nitrocellulose membranes (Southern blotting) which was soon followed by the description of an analogous procedure for RNA (Northern blotting), and somewhat later for proteins (Western blotting), has rapidly become an important separation and characterization method in molecular biology, genetic engineering, and immunological detection. Surface tension measurements have shown that the interfacial attraction between DNA and cellulose esters (-delta G132) in aqueous media can be considerable. The weaker binding energy of proteins to cellulose nitrate and to cellulose acetate may be compared to hydrophobic interaction chromatography, as on account of the somewhat lower [-delta G132] values, it often is necessary to "fix" them more tightly onto nitrocellulose by using high salt concentrations. The binding energy of RNA to both cellulose esters also is rather low. In addition to the effect of high ionic strength, the effect of adding methanol, and the effects of denaturation, heating and drying on the energy of attachment of the biopolymers to cellulose esters, have been studied. Cationized nylon membranes have been advocated recently, especially for electrophoretic transfer of nucleic acids (in which process high salt concentrations cannot easily be used). With positively charged nylon membranes, the attachment mainly occurs through the electrostatic attraction between the strongly negatively charged nucleic acids (or proteins) and the positively charged membrane. Also, more apolar membranes (of polyvinyl difluoride) have been proposed, which manifest a strong interfacial (hydrophobic) attraction to all the above biopolymers (regardless of their electrostatic charge). However, with these two novel membrane types it is no longer possible to exploit the large difference in binding energy between DNA and RNA, which makes cellulose nitrate membranes so uniquely suited for RNA-DNA hybridization assays.