why put NaOH  and copper sulphate in protein solution to test for proteins?what reactions do these chemicals have with the protein solution that would promt you to use them to test for proteins?

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william1941 | College Teacher | (Level 3) Valedictorian

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To test for proteins a BCA assay can be used. This test is performed with a stock BCA solution which contains Bicinchoninic acid, salts of sodium and Cupric sulfate pentahydrate in a solution with a high alkalinity.

During this test, when the BCA solution is added to proteins the peptide bonds in the proteins reduces the Cu 2+ ions to Cu 1+ ions. This reduction is dependent on the amount of protein in the solution. Following this, two molecules of bicinchoninic acid chelate with each of the Cu1+ ions, and form a purple-colored product which strongly absorbs light at a wavelength of 562 nm.

Looking at the absorption spectra after the chelation and comparing it with solutions with a known protein concentration allows us to determine the protein concentration in the solution being tested.

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