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APC (Allophycocyanin) Concentration Calculator
The concentration of APC in solution can be determined by substituting the molecular weight, extinction coefficient and λ max into a derived form of the Beer - Lambert Law. A substance's λmax is the wavelength at which it experiences the strongest absorbance. For APC, this wavelength is 280 nm.
The absorbance at λmax can be measured using a spectrophotometer. There are some important things to keep in mind when measuring 280 absorbance:
  • The APC should be well-dissolved in solution. APC precipitation will cause inaccuracies in concentration calculations.
  • The absorbance reading should not exceed the maximum detection limit of the instrumentation. This can be identified by a plateau in the absorbance spectrum. If the absorbance spectrum plateaus, dilute the sample and try again.
  • This calculator assumes a 1 cm pathlength for instrumentation. Standard cuvettes for spectrophotometers are typically 1 cm. If a different pathlength is used, value should be corrected during data entry.
Protein
Absorbance at λmax
Dilution factor (optional)
Pathlength
 cm
Feedback
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References
This online resource may be cited as follows
MLA
"Quest Calculate™ APC (Allophycocyanin) Concentration Calculator." AAT Bioquest, Inc., 4 Nov. 2025, https://www.aatbio.com/tools/calculate-apc-concentration.
APA
AAT Bioquest, Inc. (2025, November 4). Quest Calculate™ APC (Allophycocyanin) Concentration Calculator. AAT Bioquest. https://www.aatbio.com/tools/calculate-apc-concentration.
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  • Select the protein type. Or select "custom sequence" to enter the sequence.
  • Enter the absorbance at λmax. Please use the maximum absorbance as indicated by the spectrophotometric reading (ie. highest peak).
  • If the absorbance is obtained with a diluted sample, enter the dilution factor in order to determine the concentration of the original sample.
  • If pathlength differs from 1 cm, enter corrected value into pathlength textbox.
  • Press calculate to display the concentration.