Protein labeling calculator (NHS activated ester chemistry)

1. Molecular weight of the protein is Da

Molecular weight of the protein. For IgG antibodies, MW is 150000.

2. Select label
or enter label molecular weight: Da

Molecular weight of the label can be obtained from the product page.

3. Molar excess of the label is

Molar excess of the label in the reaction. The more label is taken, the higher dye to protein ratio is achieved in the conjugate. The exact dependency is different for various labels and proteins, but generally 8-fold excess gives 1-3 labels per average protein.

4. My protein is

Select if your protein is in solid form, or already in a solution.

5. Protein mass is mg

Advanced options

Percent of co-solvent (DMF/DMSO) in the reaction mixture: %

Co-solvent should be present in the reaction mixture when a hydrophobic label is used, or when the label needs to be aliquoted (NHS esters and maleimides should not be stored in aqueous solutions). Some very sensitive proteins do not tolerate co-solvents, but many others are perfectly compatible with moderate DMSO percent. Up to 10% is fine for almost all proteins.

Protein concentration in reaction mixture: mg/mL

Choose the concentration of the protein in the labeling reaction. A good starting point is 10 mg/mL. Higher concentrations lead to more efficient use of the label, but some proteins are not sufficiently soluble to get concentrated solution.