Salt-containing aqueous two-phase system shows predictable partition of proteins with surface amino acids residues.

Aqueous two-phase system (ATPS) containing salts has been used for protein purification and enrichment. However, it is unclear how proteins are partitioned in the top or bottom phases of the system. In this study, we demonstrate that the partition of proteins in salt-containing ATPS (SATPS) depends only on the relation between the protein-surface amino acids and the type of salt using SATPS.

Selective separation method of aggregates from IgG solution by aqueous two-phase system.

Aggregation of immunoglobulin G (IgG) is a serious concern that results in immunogenicity in pharmaceutical applications. Removal of the small and soluble aggregates in protein solutions through a simple method remains challenging. Here we show that an aqueous two-phase system (ATPS) can be used for the elimination of soluble aggregates from IgG solution.

Control of Aggregation, Coaggregation, and Liquid Droplet of Proteins Using Small Additives.

This review article presents the concepts of aggregates, coaggregates, and a liquid droplet of proteins and compares the concentrated states in the presence of small additives to control their formation and dissociation. The aggregates composed of single protein molecules result mainly from hydrophobic interactions between unfolded protein molecules. Thus, the aggregation of protein can be effectively suppressed by small additives that increase the solubility of hydrophobic solutes, typically arginine (Arg) and chaotropes.

Coacervates and coaggregates: Liquid-liquid and liquid-solid phase transitions by native and unfolded protein complexes.

Coacervates are self-assemblies formed by oppositely charged macromolecules in aqueous solution. Although coacervates usually take a homogeneous spherical shape with flowability, they have the potential to adopt unexpected macroscopic structures. In this study, we investigated the influence of the interaction mode and morphology on unfolded proteins constituting coacervates and coaggregates using ovalbumin (OVA) and lysozyme (LYZ) as the model systems.

Salt-dependent elution of uncharged aromatic solutes in ion-exchange chromatography.

Ion-exchange chromatography and multimodal ion-exchange chromatography are widely used for the separation of small molecules, peptides and proteins. Salts generally attenuate the electrostatic interactions between charged moieties of solutes and those of resins through electrostatic screening. However, little is known about how salts affect the interaction between the uncharged moieties of the solutes, such as aromatic moieties, and the charged moieties of the resins.

Viscosity Control of Protein Solution by Small Solutes: A Review.

Viscosity of protein solution is one of the most troublesome issues for the high-concentration formulation of protein drugs. In this review, we summarize the practical methods that suppress the viscosity of protein solution using small molecular additives. The small amount of salts decreases the viscosity that results from electrostatic repulsion and attraction.

Mechanism of co-aggregation in a protein mixture with small additives.

Co-aggregation plays an important role in processing protein-rich food materials under heterogeneous conditions. The main cause of co-aggregation is an electrostatic attraction between oppositely charged molecules. This study investigated thermal aggregation of β-lactoglobulin (BLG) (pI=5.

Arginine prevents thermal aggregation of hen egg white proteins.

The control of aggregation and solubilization of hen egg white protein (HEWP) is an important issue for industrial applications of one of the most familiar food protein sources. Here, we investigated the effects of edible amino acids on heat-induced aggregation of HEWP. The addition of 0.

Liquid Chromatographic Analysis of the Interaction between Amino Acids and Aromatic Surfaces Using Single-Wall Carbon Nanotubes.

Proteins have nonspecific adsorption capacities for solid surfaces. Although the nonspecific adsorption capacities are generally understood to be related to the hydrophobicity or charge density of the surfaces, little is known at the amino acid level about the interaction between proteins and polyaromatic surfaces such as carbon nanotubes, which have recently been used for biotechnology applications. In this study, we investigated the interaction between proteinogenic amino acids and carbon nanotubes using high-performance liquid chromatography on silica matrices coated by single-wall carbon nanotubes (SWCNTs).

Thermal aggregation of hen egg white proteins in the presence of salts.

Hen egg white contains more than 40 kinds of proteins with concentrations reaching 100 mg/mL. Highly concentrated protein mixtures are common in the food industry, but the effects of a crowded environment containing salts on protein stability and aggregation have only been investigated using pure protein solutions. Here, we investigated the thermal aggregation of hen egg white protein (EWP) at various concentrations in the presence of inorganic salts by solubility measurements and SDS-PAGE.