The experiment is to determine the protein content of the solution. I followed the procedure of the Bradford assay but the reagent needed is unavailable and so we use an alternative by using cold pure ethanol. Since ethanol precipitates the protein can I still determine the protein content of my sample using UV Vis at 260nm absorbance? or the protein content can be measured by its precipitate using a different method?

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    $\begingroup$ How do you want to measure the concentration of a solution when part of the dissolved content is not in the solution anymore? $\endgroup$
    – Chris
    Nov 20, 2020 at 10:47
  • $\begingroup$ ohh.... Even if the pure ethanol is at low temperature, still it cannot measure the protein content of the solution? $\endgroup$ Nov 20, 2020 at 11:19
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    $\begingroup$ How do you know how much precipitated? $\endgroup$
    – Chris
    Nov 20, 2020 at 12:52
  • $\begingroup$ From what I know protein binds with ethanol forming a precipitate but I don't know if the temperature affects the precipitation because I also don't know if I can still read the protein content of the sample solution at 260nm using the UV Vis spectrophotometer. Some are saying that it can still be read when cold ethanol is used but I don't know if its true because most of the solutions that are subjected to UV vis are usually clear solution or clear colored solutions. that's why I'm asking. $\endgroup$ Nov 20, 2020 at 13:28
  • $\begingroup$ How would precipitating (some of) the protein with ethanol or any other method help you to measure the A280 of a protein solution? The Bradford or Coomassie dye is to measure absorbance around 600 nm. $\endgroup$
    – MattDMo
    Nov 21, 2020 at 1:35


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