Bradford assay performed on BMG LABTECH microplate readers

Franka Gankse, E.J. Dell BMG LABTECH 08/2007

With the help of the standard curve the MARS data analysis software calculates the protein concentration for unknown samples automatically. If the option “path length correction” is used, the measured data is multiplied by a factor that depends on the type of microplate and volume used. With the help of this calculation, the data are normalized to a path length of  1 cm, thereby allowing a comparison to be made  between absolute data obtained from a microplate reader with data obtained from a cuvette-based spectrometer.




The Bradford assay was successfully performed on the BMG LABTECH microplate reader. According to the manufacturers protocol this protein assay is linear in the range of 0.1 – 1.4 mg/ml. Because of its homogeneous and fast nature, the assay is a preferred method to determine the protein concentration of samples.

BMG LABTECH microplate readers offer entirely new possibilities with its spectrometer tool. A whole absorbance spectrum can be read in about 1 sec per well. Furthermore, the new MARS data analysis  software allows for the absorbance maximum or minimum to be recognized at once after clicking on the spectral curve. Any wavelength can be selected to give the values for the optical density in any well. The speed of the spectrometer and the easy work-up in  the software provide users with unmatched flexibility that can be used to optimize absorbance settings for  all experiments.

Different colorimetric assays have been developed to determine the protein concentration of samples. The most commonly used methods are the Bradford assay, the Lowry assay and the BCA assay. In this application note we demonstrate how to determine the protein concentration of samples using the Bradford assay and a BMG LABTECH microplate reader. The Bradford assay is based on the binding of protein to Coomassie® Brilliant Blue G-250, a dye that shifts its absorbance maximum upon protein binding. A calibration curve of protein solutions with known concentration is required to calculate protein concentrations of unknown samples.


Spectrometer-based microplate readers by BMG LABTECH quantified protein solutions in the range of 0.1-1.4 mg/ml. The MARS Data Analysis Software provided one-click calculation of sample concentrations, completing the combination of assay and reader to ensure an easy and quick protein measurement.

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