Water sample showing pink/purple color is an error.
Explanation:
Biuret is a blue color reagent that changes its color to pink/purple whenever it detects protein in a sample. Water don't contain proteins so it should not show pink/purple color instead it should maintain the blue color. Food items generally contain proteins so it show pink/purple color but it showed blue color.
Error might have caused by wrong marking of the samples, test tube marked with Water might contain a mystery food while Mystery food tube might contain water.
The
Thymocyte progenitors enter the subcapsular region of the thymus as
double-negative cd3- t cells where the double negative refers to lack of
cluster determinants CD4 and CD8. Double-negative cd3- t cells exist as small population
that is 1%-5% of lymphocytes in the lymphoid organs and peripheral blood of
humans and normal rodents.