Protein solubility is a thermodynamic parameter defined as the concentration of protein in a saturated solution that is in equilibrium with a solid phase, crystalline or amorphous, under a given set of conditions. Solubility of proteins in aqueous solutions ranges from almost completely insoluble to hundreds of milligrams per milliliter. The solubility is usually affected by a number of external factors, including pH, ionic strength, temperature, and the presence of various solvent additives. The intrinsic factors affecting protein solubility are mainly defined by the amino acids on the protein surface, and other factors are protein concentration, conformation, quaternary structure and location. Solubility plays a key role in protein homeostasis. Insoluble regions in proteins tend to aggregate, and aggregation as the flip side of low protein solubility has also been implicated in a number of human diseases.
Protein therapies are fast growing in the pharmaceutical industry. In order to obtain an effective protein dose using a smaller injection volume, clinically approved protein drugs usually have higher concentrations. The physical stability of proteins at high concentrations is a key issue because of the possible immune response to protein aggregates. Therefore, solubility and stability are key variables that must be considered when developing protein therapies. Preparing concentrated, soluble, and stable proteins is often a difficult task because proteins often aggregate, precipitate, or denature. Suitable solutions are needed to effectively evaluate the solubility of target proteins and to identify and optimize the solubility conditions. Amerigo Scientific offers solubility screening kits designed to assist in the identification of solution conditions that promote protein solubility and minimize protein aggregation, and these kits are also available for excipients screening.
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