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Degree of Labeling (DOL) Calculator

The Degree of Labeling (DOL), sometimes called Degree of Substitution (DOS), is a particularly useful parameter for characterizing and optimizing bioconjugates, such as fluorophore-labeled proteins. It is expressed as a molar ratio in the form of label/protein. In general, conjugates with lower DOL values tend to have weaker fluorescence intensities. However, bioconjugates with very high DOL values (e.g. DOL > 6) may also experience reduced fluorescence. This often occurs as a result of self-quenching from the fluorophore. An accurate DOL value will allow a researcher to find the most optimal bioconjugation ratio for a given labeling as well as ensure reproducibility in conjugation results.

For antibodies, the optimal DOL usually falls between 2 to 10. A more precise value, however, will largely depend on the properties of the label and protein. This means that for many bioconjugations, the optimal DOL must be experimentally determined, often through several small-batch labelings. For AAT Bioquest's antibody labeling kits, the optimal DOL and reagent quantities have already been tested. For other bioconjugates, the tool below can be used to calculate the degree of labeling.

How to use this tool

1. Select a target from the drop down menu. After selecting a target, a list of labels will become available.

2. Select a label from the drop down menu.

3. Enter the maximum absorbance values for both the target and label. Note that the provided wavelengths are typical maximal wavelengths for the given compounds. However, for optimal results, use the maximal absorbances as determined by actual spectrophotometer readings.

4. Press the calculate button to display results.

Data Entry

Select target:

Select label:

Target absorbance:

Label absorbance:



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This online tool may be cited as follows


"Quest Calculate™ Degree of Labeling (DOL) Calculator." AAT Bioquest, Inc.6 Jul2022


AAT Bioquest, Inc. (2022July 6). Quest Calculate™ Degree of Labeling (DOL) Calculator. AAT Bioquest.

This online tool has been cited in 1 publications, including

Authors: H Hamouda, Ramzy and Mahmoud, Marwa F
Journal: Journal of Applied Veterinary Sciences (2020): 61--66