Bradford Assay Lab

Question

Milk diluted 1:50 gives a reading of 0.224 absorbance units, which gives a concentration M mg/mL. The final concentration of milk is M x 50 = ? mg/mL.

Answer 1

First off, here's a useful resource for the principle behind the assay https://www.bio-rad.com/webroot/web/pdf/lsr/literature/4110065A.pdf (vendor sites are a really good resource for these kinds of things generally!)

You generally use a protein standard with a known concentration (the protocol here recommends BSA or g-globulin). The assay assumes a linear relationship between concentration and absorbance, but at high protein concentrations the detection reagent becomes saturated and you will lose that linear relationship (some protein isn't being detected) so you want to ensure that you're within the linear range and your calculations are accurate.

I've never done a Bradford without a standard, but if this is for a class maybe you were given a standard curve along with the assignment? If that's the case, you should have an equation defining a line y=mx+b where y = the concentration and x = the absorbance (m and b should be defined, you generally get these from your standard curve with BSA or a standard protein).

If you have already been given the equation, what you want to do is calculate y = m (0.224) + B to get the concentration of your 1:50 dilution, then multiply that number by 50 to obtain your actual concentration.