why put NaOH and copper sulphate in protein solution to test for proteins?what reactions do these chemicals have with the protein solution that...

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.