Enter your protein's pI (or paste its sequence), then set your solution pH, salt concentration, and temperature to get a Solubility Score for your protein under those conditions. You'll also see the ΔpH between your solution and the isoelectric point, an Aggregation Risk rating, and the Optimal pH Range to keep your protein happily in solution.
Solubility Score
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ΔpH (pH - pI)
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Aggregation Risk
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Optimal pH Range
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Protein solubility refers to the ability of a protein to dissolve in aqueous solution. It's crucial for protein purification, storage, and biological activity, as insoluble proteins can aggregate and lose function.
Protein solubility is typically lowest at its isoelectric point (pI) where net charge is zero. Moving the pH away from the pI increases net charge and usually improves solubility by reducing protein-protein interactions.
Salt affects protein solubility through ionic strength effects. Low salt can cause electrostatic repulsion, while high salt can shield charges and promote aggregation. Optimal salt concentrations typically range from 50-300 mM.
This calculator provides a heuristic estimate based on established biophysical principles. While useful for initial guidance, actual solubility can vary significantly due to protein-specific factors not captured in simple models.
Common additives include detergents (reduce hydrophobic interactions), reducing agents (prevent disulfide aggregation), glycerol (stabilizing agent), and various salts and buffers that can optimize solution conditions.
Lower temperatures generally improve protein stability and reduce aggregation. Most proteins are stored at 4°C for short-term use, though optimal temperature depends on the specific protein and application.
High aggregation risk indicates conditions favoring protein-protein interactions and precipitation. This typically occurs near the pI, at high concentrations, elevated temperatures, or inappropriate salt conditions.