How can you explain that Biurets reaction with amino acids as compared to other protein substances?
This is an excellent source
http://www.clinchem.org/cgi/content/abstract/51/8/1411
To explain the difference between Biuret's reaction with amino acids compared to other protein substances, we need to understand the principles behind Biuret's test and how it specifically reacts with proteins.
Biuret's test is a biochemical test used to detect the presence of proteins in a sample. It relies on the ability of proteins to form a violet or purple-colored complex with copper ions in an alkaline medium. The reaction occurs due to the structure of proteins, specifically the presence of peptide bonds.
Amino acids are the building blocks of proteins. They contain both amine (-NH2) and carboxyl (-COOH) functional groups, along with a side chain (R-group). When Biuret's reagent (usually a solution of copper sulfate in sodium hydroxide) is added to a solution containing amino acids, they form a complex with the copper ions, resulting in a purple color change.
However, not all protein substances react the same way with Biuret's reagent. Other non-protein substances, such as peptides or certain small molecules, may also give a positive reaction due to the presence of peptide bonds or similar functional groups. This is because Biuret's test primarily detects the presence of peptide bonds, which are characteristic of proteins, but can also be found in other compounds.
To specifically differentiate between the Biuret's reaction of amino acids and other protein substances, additional tests or techniques may be required. For example:
1. Quantitative analysis: Comparing the intensity of the color change can provide a rough estimation of protein concentration. Since different proteins have different amino acid compositions, the absorbance or color intensity can differ, which may help differentiate them.
2. Specificity tests: Performing complementary tests, such as the Bradford assay or SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis), can help identify and separate various protein substances based on their specific properties, such as molecular weight or binding ability to certain dyes.
3. Enzymatic tests: Certain enzymes can be used to specifically target and break down proteins into their constituent amino acids. By subjecting the protein substance to enzyme hydrolysis, followed by Biuret's test, one can confirm the presence and composition of amino acids.
In summary, while Biuret's test can provide an initial indication of the presence of proteins in a sample, it does not specifically differentiate between amino acids and other protein substances. Additional tests and techniques are necessary to obtain a more precise and detailed understanding of the composition and identity of the protein substances present.