Protein Solubility Calculator

Calculate the percentage of protein in solution after centrifugation. Enter the total protein mass and the mass of soluble protein to determine solubility and concentration.

Mass of protein in sample

Total volume of solution

Mass of protein in supernatant after centrifugation

Molecular weight of protein in kilodaltons

Protein Solubility Formula: Solubility (%) = (Soluble Mass / Total Mass) × 100 Concentration Calculations: Total Concentration (mg/mL) = Total Mass (mg) / Volume (mL) Soluble Concentration (mg/mL) = Soluble Mass (mg) / Volume (mL) Molarity Calculation: Molarity (M) = (Mass in g) / (MW in g/mol) / Volume (L) = (Mass in mg / 1000) / (MW in kDa × 1000) / Volume (L) = (Mass in mg) / (MW × Volume) × 10⁻⁶
Example 1 (High Solubility): Total Protein = 50 mg Volume = 10 mL Soluble = 45 mg Solubility = (45/50) × 100 = 90% Interpretation: Highly Soluble Example 2 (Moderate Solubility): Total Protein = 100 mg Volume = 5 mL Soluble = 55 mg Solubility = 55% Total Conc. = 100/5 = 20 mg/mL Example 3 (With Molarity): Total = 25 mg, Volume = 2 mL MW = 66.5 kDa Soluble = 22 mg Solubility = 88% Molarity = (25/1000) / 66.5 / 0.002 = 0.188 mM Soluble Molarity = 0.166 mM Example 4 (Low Solubility): Total = 10 mg, Volume = 1 mL Soluble = 2 mg Solubility = 20% Interpretation: Poorly Soluble

How is protein solubility calculated?

Protein solubility is calculated as the percentage of protein that remains soluble after centrifugation. Divide the soluble protein mass by the total protein mass and multiply by 100. For example, if 35 mg dissolves out of 50 mg total, solubility = (35/50) × 100 = 70%.

What is a good solubility for proteins?

Most recombinant proteins should have solubility above 70% for downstream applications. Above 90% is excellent, 70-90% is good, 50-70% is moderate, and below 50% indicates potential issues with aggregation or misfolding that may require optimization.

Why is protein solubility important?

Protein solubility is critical for purification, storage, and functional studies. Insoluble proteins (inclusion bodies) cannot be easily purified or characterized. Soluble proteins maintain their native structure and biological activity, essential for crystallography, enzymology, and structural studies.

What affects protein solubility?

Protein solubility depends on temperature, pH, ionic strength, solvent composition, and the presence of chaotropes or stabilizers. The amino acid sequence (hydrophobic vs hydrophilic residues), post-translational modifications, and tag presence also significantly influence solubility.

What is the difference between total and soluble protein?

Total protein is the entire amount in the sample. Soluble protein is the fraction that remains in the supernatant after centrifugation, representing properly folded, functional protein. The pellet contains insoluble aggregates, misfolded protein, and debris.

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