Question

What problems might one encounter performing a biuret test for protein on intact red blood cells?

Answer 1

This test is based on the interaction between the copper ions of the Biuret reagent and the amino groups of the peptide bonds of the amino acids that make up proteins. When there is a reaction, the color changes blue to violet.
Due to it is not very sensitive compared to the lowry method and requires 2 to 4mg of protein per test, opalescence may occur if the sample has high levels of lipids and carbohydrates.

Answer 2

The biuret test refers to a chemical examination done to determine the existence of peptide bonds. In the presence of peptides, a violet color coordination complexes are formed by copper ions in an alkaline solution.  

The intact red blood cells comprise pigment hemoglobin and hemoglobin also exhibits the same color as of biuret test result color. Thus, one of the prime issue, which can take place at the time of biuret test is the hemolysis of the red blood cells that can ultimately affect the result.  

Therefore, one of the solution to overcome the issue is to remove the hemoglobin from the cells prior to performing the analysis.